JP2003340859A - Method for producing polypropylene resin in-mold foam molded body and in-mold foam molded body - Google Patents

Abstract

(57) [PROBLEMS] To provide a high quality, easy-to-manufacture, small difference in cooling shrinkage between parts having different properties in a polypropylene resin in-mold foam molded product having portions having different properties. A molded body and a method for producing the molded body are provided. SOLUTION: Two or more unit molded products having different characteristics are obtained by dividing a mold into two or more compartments, filling each compartment with polypropylene resin expanded particles, and then molding the polypropylene resin expanded particles in the mold. In a method for producing a polypropylene resin-in-mold foam-molded product having a part integrally formed adjacent to each other, a polypropylene resin or a polypropylene resin in which at least one of the compartments has a foamed particle having a tensile elastic modulus of 1200 MPa or more A foamed resin-based in-mold foam characterized by comprising a resin composition and having a relationship between an apparent density D1 (g / L) and a high-temperature peak heat quantity E1 (g / J) satisfying the following formula: Manufacturing method of a molded object. Formula (1): 20−0.014 × D1 ≦ E1 ≦ 65−0.072 × D1 Formula (2): 10 ≦ D1 ≦ 700

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polypropylene resin in-mold foam molded article having different characteristic regions and an in-mold foam molded article thereof.

[0002]

2. Description of the Related Art Polypropylene-based resin in-mold foamed molded articles can be produced without impairing the excellent properties of propylene such as mechanical strength, heat resistance, chemical resistance, and easy recyclability.
It is used in a wide range of industrial fields such as packaging materials and building materials because it can add properties such as cushioning and heat insulation. In particular, pre-expanded particles are made from polypropylene resin,
The so-called bead method in-mold foam molded product, which was filled in an openable mold and heated and fused by steam, has excellent cushioning properties and moldability, and is used as an automobile bumper core material,
Widely used as a shock absorber for door pads.
In recent years, lighter and more rigid shock absorbers have been demanded from the viewpoints of stricter collision safety standards and improved fuel efficiency.

As a product that meets the demand, a desired portion requiring strength is constituted by a high-density in-mold foam molded article, and a portion not requiring relatively strength is in-mold foam-molding having a lower density. There is a so-called dual density molded product that is made of a body and is of a different density to reduce the overall weight. In addition, for shock absorbers for automobiles, there is a demand for higher functionality in consideration of offset collision and pedestrian protection, but the dual density molded product is a product that can meet this demand. As such a dual density molded product, for example, a mold whose inside is divided into three compartments is used to form a molded body with relatively high density on both sides, and a central portion sandwiched between them is relatively low. Some consist of compacts of density. In order to obtain a dual-density molded product having such a configuration, the first and third compartments corresponding to both sides are filled with relatively high density expanded particles, and the second compartment corresponding to the central portion is filled.
Fill the relatively low-density foamed particles in the compartments of the mold, heat the foamed particles in the mold to integrate the foamed particles in each compartment and the foamed particles in each compartment, and then cool the mold. The method of taking out from the inside, so-called integral simultaneous molding method is preferable from the viewpoint of cost. These integral simultaneous molding methods are described in detail in Patent Documents 1 to 4, for example.

However, an in-mold molded article made of expanded particles usually becomes larger (expands) than the shape of the mold space when cooling immediately after heating is insufficient during molding, and conversely is excessively cooled. It is smaller than the shape of the mold space (it shrinks so much that it cannot be expected to recover sufficiently). As described above, the degree of expansion and the degree of contraction of the in-mold molded body differ depending on the degree of cooling. Also, its expansion and contraction
When the apparent density of the obtained molded product is large and when it is small, different tendencies are shown. Specifically, when the degree of cooling is the same, the low-density molded body portion tends to shift from expansion to contraction earlier. Usually, the expanded molded body is often disliked in comparison with the shape of the mold space, so cooling is performed so that the high-density molded body portion does not expand. As a result, a relatively low-density molded body portion is in a state of being greatly shrunk, so that it has been difficult to obtain a high quality product in the past.

[0005]

[Patent Document 1] Japanese Patent Laid-Open No. 11-334501

[Patent Document 2] Japanese Patent Laid-Open No. 2001-150471

[Patent Document 3] Japanese Utility Model Publication No. 62-22352

[Patent Document 4] US Pat. No. 5,164,257

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for easily producing a high-quality polypropylene resin in-mold foam molded article having portions having mutually different properties, and an in-mold foam molded article thereof. Let's take that issue.

[0007]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, the following method for producing a polypropylene resin in-mold foam molded article and the in-mold foam molded article are provided. (1) By partitioning the mold into two or more compartments, filling each compartment with polypropylene-based resin foamed particles, and then molding the polypropylene-based resin foamed particles in the mold, two or more unit molded bodies having different characteristics are obtained. In a method for producing a polypropylene-based resin in-mold foam molded article having adjacent and integrally molded portions, the foamed particles to be filled in at least one of the compartments are polypropylene-based resin or polypropylene-based resin having a tensile elastic modulus of 1200 MPa or more. It consists of a composition and has an apparent density D1 (g / L) and a high temperature peak calorie E1.
A method for producing a polypropylene resin in-mold foam molded article, characterized in that the expanded particles satisfy the following expressions (1) and (2) in relation to (g / J). Formula (1): 20-0.014 x D1 ≤ E1 ≤ 65-0.072 x D1 Formula (2): 10 ≤ D1 ≤ 700 (2) Polypropylene resin or polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more. The relationship between the heat quantity of the endothermic curve peak (ΔH _s ) at which the expanded particles composed of the object exist on the high temperature side of the surface layer portion and the heat quantity of the endothermic curve peak (ΔH _i ) at the high temperature side of the internal foamed layer of the expanded particles is ΔH _s <
ΔH _i × 0.86, The method for producing a polypropylene-based resin in-mold foam molded article according to (1) above. (3) A structure in which a plurality of unit moldings made of an in-mold foam molding of polypropylene resin foamed particles are adjacent and heat-sealed together, and (i) the density of two adjacent unit moldings. Are different from each other, (ii) the base resin of the expanded particles constituting at least one unit molded body (F) is a polypropylene resin or a polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more, (iii) The unit molded body has an endothermic curve peak on the higher temperature side than the intrinsic endothermic curve peak derived from the heat of fusion in the DSC curve by differential scanning calorimetry, (iv) in unit molded body (F) The density D2 (g / L) and the heat of fusion E2 (J / g) of the peak of the endothermic curve on the high temperature side of the polypropylene resin foam constituting the unit molded body (F) are expressed by the following formulas (3) and (4). (3): 20-0.020 × D2 ≦ E2 ≦ 65-0.100 × D2 Formula (4): 10 ≦ D2 ≦ 500 Foam molding. (4) The heat quantity (ΔH _s ) of the endothermic curve peak in which the expanded particles made of polypropylene resin or polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more exist on the high temperature side of the surface layer portion and the internal expanded layer of the expanded particles. The relationship with the heat quantity (ΔH _i ) of the endothermic curve peak existing on the high temperature side is ΔH _s <
ΔH _i × 0.86, The polypropylene-based resin in-mold foam molded article according to (3) above. (5) One of the adjacent two unit molded bodies is a high-density unit molded body having a density of 30 to 450 g / L,
The other unit molded body is a low density unit molded body having a density of 15 to 90 g / L and a density lower than that of the high density unit molded body, (3) or (4) The polypropylene-based resin in-mold expansion-molded article according to [4]. (6) The polypropylene resin in-mold molded article according to (5), wherein the density of the high-density unit molded body is 1.2 to 25 times the density of the low-density unit molded body.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A polypropylene-based resin in-mold foamed product (hereinafter sometimes referred to as "EPP molded product") of the present invention comprises a plurality of unit molded products, and two adjacent unit molded products are: It has a structure that is heat-sealed to each other. The polypropylene resin or polypropylene resin composition forming the polypropylene resin expanded particles used for forming this unit molded product contains a polypropylene homopolymer or a propylene component in an amount of 70 mol% or more (preferably a propylene component). Of 80% by mole or more) and a mixture of two or more kinds selected from these resins.

Examples of copolymers of propylene containing 70 mol% or more of propylene component with other comonomers include ethylene-propylene random copolymers, ethylene-propylene block copolymers, propylene-butene random copolymers, ethylene-propylene-butene. Examples thereof include random copolymers.

In the present invention, the polypropylene resin composition may contain a synthetic resin and / or an elastomer other than the polypropylene resin within a range not impairing the intended effect of the present invention. The addition amount of other synthetic resin or / and elastomer other than polypropylene resin is at most 60 parts by weight or less per 100 parts by weight of polypropylene resin, but preferably at most 35 parts by weight, It is more preferably 20 parts by weight, even more preferably at most 10 parts by weight, and most preferably at most 5 parts by weight.

Examples of synthetic resins other than the above polypropylene resins include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene,
Ethylene resin such as linear ultra-low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, or polystyrene, styrene-maleic anhydride copolymer, etc. Examples include styrene resins.

Examples of the elastomer include ethylene-propylene rubber, ethylene-1-butene rubber, propylene-1-butene rubber, styrene-butadiene rubber and hydrogenated products thereof, isoprene rubber, neoprene rubber, nitrile rubber, or styrene-butadiene block. Examples of the elastomer include copolymer elastomers and hydrogenated products thereof.

In the present invention, the polypropylene resin composition may contain various additives as desired. Such additives include, for example, antioxidants, UV inhibitors, antistatic agents, flame retardants,
Examples thereof include metal deactivators, pigments, dyes, nucleating agents, and bubble control agents. Examples of the cell regulator include inorganic powders such as zinc borate, talc, calcium carbonate, borax and aluminum hydroxide. These additives are preferably used in an amount of 20 parts by weight or less, and more preferably 5 parts by weight or less, per 100 parts by weight of the base resin. These additives are usually
Used in the minimum necessary amount. Further, these additives may be used, for example, in the extruder when the polypropylene resin particles used in the present invention (hereinafter sometimes referred to as “the present resin particles”) are produced by cutting the strand extruded by the extruder. It can be contained in the present resin particles by adding and kneading to the polypropylene-based resin or polypropylene-based resin composition melted in (1).

In the method of the present invention, the foamed particles for partitioning the mold into two or more compartments and filling at least one compartment have a polypropylene resin or polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more (hereinafter collectively referred to as "main group"). It is sometimes called a material resin ”). If the tensile elastic modulus of the base resin is less than 1200 MPa, the final molded body does not expand even if the molded body is cooled immediately after heating during molding for a short period of time, which will be described later. Even if it becomes excessive, there is no shrinkage or there is almost no shrinkage. "Therefore, the effect of the present invention cannot be sufficiently brought out, so that the object of the present invention cannot be achieved. According to the production method of the present invention, the expanded particles to be filled in at least one of the compartments are made of the base resin of the present invention, and the apparent density D of the expanded particles described later is obtained.
Immediately after heating at the time of molding, since the relationship between 1 and the high temperature peak calorie E1 of the expanded particles is expanded particles satisfying the formula (1) and the formula (2) described later (hereinafter sometimes referred to as specific expanded particles). Even if the molded body is cooled for a short time, expansion of the final molded body does not occur, and even if cooling is excessive, there is little or no shrinkage. Therefore, even if integrally molded so as to include a unit molded body part manufactured with specific foamed particles and a unit molded body part manufactured with foamed particles other than the specific foamed particles, foaming other than the specific foamed particles is performed. If the cooling during molding is adjusted so as not to cause convex bulges on the outside and concave sinks (shrinkage) on the inner side of the unit molded body portion manufactured by particles, as a whole,
It is possible to easily obtain an in-mold molded body that has a small amount of convex bulging outside and a concave shape inside of the molded body (shrinkage). Furthermore, in the case where all the unit molded bodies are manufactured from this specific expanded particle, it is easier to obtain an in-mold molded body with less bulging that is convex on the outside and concave that is concave on the inside of the resulting molded body. To be Further, since the molded product using the specific expanded particles has high rigidity such as compressive strength, an in-mold molded product excellent in lightness can be easily obtained.

The tensile modulus of the base resin is 1200 MPa.
To achieve the above, as the polypropylene resin to be used, a polypropylene homopolymer or a copolymer of propylene and another comonomer having a small amount of the other comonomer component may be used.

The above tensile elastic modulus is preferably 1250 MPa or more in order to enhance the effect of the present invention, and is preferably 1300 MPa.
More than a is more preferable. There is no particular upper limit, but 250
It is about 0 MPa.

The above-mentioned tensile modulus is based on the JI
It is a value obtained by measurement under the following conditions according to SK7161 (1994). -Test piece: Test piece 1A type described in JIS K 7162 (1994) (direct injection molding) -Test speed 1 mm / min

When the base resin is a polypropylene resin composition to which a synthetic resin other than the above-mentioned polypropylene resin, an elastomer, various additives, etc. are added,
Depending on the type and amount of these additives, the tensile modulus of the base resin may decrease. In the present invention, in order not to impair the initial effect of the present invention, the tensile elastic modulus of the present base resin (the same measuring method as the tensile elastic modulus of the present base resin)
Is not less than 1200 MPa, preferably 12
Most preferably 130, not less than 50 MPa
The above additives are added so as not to fall below 0 MPa.

The melting point of the base resin is 145 ° C. or higher in order to increase the heat resistance of the final in-mold foamed molded product (EPP molded product) and / or to increase the compressive strength. Is preferable, 155 ° C. or higher is more preferable, and 160 ° C. or higher is further preferable.
The upper limit of the melting point is usually about 170 ° C.

In order to increase the compression strength of the final EPP molded product, the tensile yield strength of the base resin is 31MP.
It is preferably a or more, and more preferably 32 MPa or more. The upper limit of the tensile yield strength is not particularly specified, but it is usually at most 45 MPa. In addition, in order to prevent bubble breakage of bubbles during bubble formation in the production of foamed particles, and further to prevent bubble breakage of bubbles in foamed particles during heating during in-mold molding, Tensile breaking elongation is preferably 20% or more, but 100%
More preferably, it is more preferably 200 to 1000%. The above-mentioned tensile yield strength and tensile breaking elongation are both JIS K 6758 (1981).
Year) based on the measurement method described.

Further, the base resin of the present invention has a molecular weight distribution (Mw / Mn) of 4 even in the case of expanded particles made of the base resin having a high melting point, in order to further lower the molding steam temperature during in-mold molding. It is preferably 0.4 or more, and more preferably 4.5 to 10. This molecular weight distribution is a value calculated from the polystyrene-equivalent weight average molecular weight Mw and number average molecular weight Mn measured by the GPC method using the following apparatus and conditions. <GPC measurement device> Device: WATERS 150C Column: TOSO GMHHR-H (S) HT Detector: RI detector for liquid chromatogram <Measurement conditions> Solvent: 1,2,4-trichlorobenzene Measurement temperature: 145 ° C Flow velocity: 1.0 ml / min Sample concentration: 2.2 mg / ml Injection volume: 160 microliter Calibration curve: Universal Calibration Analysis program: HT-GPC (Ver.1.0)

Further, the base resin is a melt flow rate abbreviated as MFR (JIS K6758 (1981)
Year)) is preferably 1 g / 10 minutes or more and 100 g / 10 minutes or less. If the MFR is less than 1 g / 10 minutes, the effect of lowering the molding steam temperature during in-mold molding may be insufficient. Also, its MFR is 100g
If it exceeds / 10 minutes, the obtained in-mold molded article may become brittle. From such a viewpoint, M of the base resin
FR is more preferably 10 g / 10 minutes or more and 70 g / 10 minutes or less.

The polypropylene resin used in the present invention having the above-mentioned characteristics is one of those sold as a polypropylene resin, and can be easily obtained on the market. Further, the polypropylene resin having the above-mentioned properties used in the present invention can be produced by various methods, and particularly, a slurry polymerization process or a bulk polymerization process is adopted, or a slurry polymerization process or a bulk polymerization process is included. By adopting a multi-stage polymerization process (for example, a multi-stage polymerization process of gas phase polymerization and bulk polymerization), the isotactic index (the ratio of insoluble components after extraction of boiling normal heptane) is 85% by weight or more, by ¹³ C-NMR analysis. The mmmm pentad% is 85 to 97.5%, and the weight average molecular weight is 200,000 or more (preferably 200,000).
To 550000) and a number average molecular weight of 20,000 or more (preferably 20000 to 53000) (including post-treatment such as removal of atactic content), and easily obtained. So that the content ratio of the propylene component of 99% by weight,
If the (co) polymerization conditions are selected, the production can be performed more easily. Further, a slurry-based polymerization process or a bulk-polymerized process, or a polypropylene-based resin obtained through a multi-staged polymerization process including a slurry-polymerized process or a bulk-polymerized process is more than a polypropylene-based resin obtained through another polymerization process. It is preferably used in the invention. Examples of usable polymerization catalysts include homogeneous catalysts such as metallocene catalysts and heterogeneous catalysts such as Ziegler-Natta type catalysts, but slurry polymerization process or bulk polymerization process, or slurry polymerization process or bulk polymerization process is used. Ziegler-Natta type catalysts are preferred for the multi-stage polymerization process involving.

The present resin particles were obtained by quenching the strands immediately after extrusion when the present base resin was melted in an extruder and the extruded strands were cut to produce the present resin particles. Those are preferable. With the resin particles thus rapidly cooled, the surface modification described later can be efficiently performed. The quenching of the strand immediately after its extrusion is carried out immediately after the strand is extruded, preferably at 50
It can be carried out by putting it in water adjusted to a temperature of 0 ° C or lower, more preferably in water adjusted to a temperature of 40 ° C or lower, and most preferably in water adjusted to a temperature of 30 ° C or lower. Then, the sufficiently cooled strand is pulled out from water and cut into an appropriate length to obtain the resin particles of a desired size. The resin particles are usually adjusted to have a length / diameter ratio of 0.5 to 2.0, preferably 0.8 to 1.3, and an average weight per one (randomly selected. The average value of 200 pieces simultaneously measured) is adjusted to 0.1 to 20 mg, preferably 0.2 to 10 mg.

The expanded particles of the present resin particles (hereinafter referred to as "main expanded particles") used as the raw material for the in-mold expanded molded article of the present invention (hereinafter referred to as "main expanded particles") are impregnated with a foaming agent and then expanded into particles. It is manufactured by

The expanded beads used in the present invention are preferably expanded particles whose surface has been modified as described below. The expanded particles whose surface has been modified can be molded in the mold at a lower temperature than the expanded particles which have not been surface modified.

The foamed particles having a modified surface that can be molded at a low temperature are obtained by dispersing the resin particles in a dispersion medium in which an organic peroxide is present, and by using the obtained dispersion (hereinafter, also referred to as a dispersion liquid). The surface of the resin particles is modified by decomposing the organic peroxide by maintaining the temperature at a temperature lower than the melting point of the base resin of the resin particles and substantially decomposing the organic peroxide. It can be manufactured by obtaining the surface-modified particles (hereinafter sometimes referred to as “surface-modified particles”) that have been formed and then expanding the surface-modified particles into particles. The foamed particles having a modified surface thus obtained have excellent heat-sealing properties, and the steam-cooling at low temperature allows the foamed particles to be fused to each other.

The dispersion medium used in the production of the above surface-modified particles is generally an aqueous medium, preferably water, more preferably ion-exchanged water, but not limited to water, the base resin It is possible to use any solvent or liquid that does not dissolve the resin and can disperse the resin particles. Examples of the dispersion medium other than water include ethylene glycol, glycerin, methanol, ethanol and the like. The aqueous medium includes a mixed solution of water and an organic solvent such as the alcohol.

As the organic peroxide, various conventionally known organic peroxides such as isobutyl peroxide [50 ° C. /
85 ° C], cumyl peroxy neodecanoate [55 ° C
/ 94 ° C], α, α'-bis (neodecanoylperoxy) diisopropylbenzene [54 ° C / 82 ° C], di-
n-propyl peroxydicarbonate [58 ° C / 94
° C], diisopropyl peroxydicarbonate [56
° C / 88 ° C], 1-cyclohexyl-1-methylethylperoxy neodecanoate [59 ° C / 94 ° C], 1,
1,3,3-Tetramethylbutylperoxy neodecanoate [58 ° C / 92 ° C], bis (4-t-butylcyclohexyl) peroxydicarbonate [58 ° C / 92
C], di-2-ethoxyethyl peroxydicarbonate [59 ° C / 92 ° C], di (2-ethylhexylperoxy) dicarbonate [59 ° C / 91 ° C], t-hexylperoxy neodecanoate [63]. ° C / 101 ° C],
Dimethoxybutyl peroxydicarbonate [64 ° C /
102 ° C.], di (3-methyl-3-methoxybutylperoxy) dicarbonate [65 ° C./103° C.], t-butyl peroxy neodecanoate [65 ° C./104
° C], 2,4-dichlorobenzoyl peroxide [74
° C / 119 ° C], t-hexylperoxypivalate [71 ° C / 109 ° C], t-butylperoxypivalate [73 ° C / 110 ° C], 3,5,5-trimethylhexanoyl peroxide [77 ° C] / 113 ° C], octanoyl peroxide [80 ° C / 117 ° C], lauroyl peroxide [80 ° C / 116 ° C], stearoyl peroxide [80 ° C / 117 ° C], 1,1,3,3-tetramethylbutyl Peroxy 2-ethylhexanoate [8
4 ° C / 124 ° C], succinic peroxide [87 ° C
/ 132 ° C], 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane [83 ° C / 11
9 ° C.], 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate [90 ° C./138
C], t-hexylperoxy-2-ethylhexanoate [90 ° C / 133 ° C], t-butylperoxy-2.
-Ethyl hexanoate [92 ° C / 134 ° C], m-toluoyl benzoyl peroxide [92 ° C / 131
° C], benzoyl peroxide [92 ° C / 130 ° C],
t-butyl peroxyisobutyrate [96 ° C / 136
° C], 1,1-bis (t-butylperoxy) -2-methylcyclohexane [102 ° C / 142 ° C], 1,1-
Bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane [106 ° C / 147 ° C], 1,1-
Bis (t-hexylperoxy) cyclohexane [10
7 ° C / 149 ° C], 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane [109
C./149° C.], 1,1-bis (t-butylperoxy) cyclohexane [111 ° C./154° C.], 2,2-
Bis (4,4-dibutylperoxycyclohexyl) propane [114 ° C / 154 ° C], 1,1-bis (t-butylperoxy) cyclododecane [114 ° C / 153
° C], t-hexylperoxyisopropyl monocarbonate [115 ° C / 155 ° C], t-butylperoxymaleic acid [119 ° C / 168 ° C], t-butylperoxy-3,5,5-trimethylhexanoate. [119
[Deg.] C / 166 [deg.] C], t-butyl peroxylaurate [1
18 ° C./159° C.], 2,5-dimethyl-2,5-di (m-toluoylperoxy) hexane [117 ° C./1
56 ° C], t-butylperoxyisopropyl monocarbonate [118 ° C / 159 ° C], t-butylperoxy-2-ethylhexyl monocarbonate [119 ° C /
161 ° C.], t-hexyl peroxybenzoate [1
19 ° C / 160 ° C], 2,5-dimethyl-2,5-di (benzoylperoxy) hexane [119 ° C / 158
° C] etc. are illustrated. The temperature on the left side in [] immediately behind each of the organic peroxides is the 1-hour half-life temperature described later, and the temperature on the right side is the 1-minute half-life temperature described later. The organic peroxide may be used alone or in combination of two or more, and is generally 0.01 per 100 parts by weight of the resin particles.
It is necessary to add 10 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight in the dispersion medium.

In the dispersion composed of the organic peroxide, the resin particles and the dispersion medium, if the weight ratio of the resin particles / dispersion medium becomes too large, it may not be possible to perform uniform surface modification on the resin particles. There is. In that case, the surface-modified particles include particles that have undergone excessive modification, which causes a large number of the modified resin particles to fuse together in the closed container during the subsequent foaming process. As a result, it may become a large lump, and it may not be possible to discharge it outside the closed container. From such a viewpoint, the weight ratio of the present resin particles / dispersion medium is preferably 1.3 or less.
2 or less, more preferably 1.1 or less,
Most preferably, it is 1.0 or less. However, if the weight ratio is too small, effective low-temperature moldability may not be imparted to the obtained expanded particles unless the amount of the organic peroxide used for the resin particles is increased. An increase in the amount of organic peroxide used leads to an increase in cost. In order to reduce the amount of the organic peroxide used, the weight ratio of the resin particles / dispersion medium is preferably 0.6 or more,
It is more preferably 0.7 or more.

The organic peroxide is substantially decomposed at a temperature lower than the melting point of the base resin. Therefore, the 1-hour half-life temperature of the organic peroxide (the constant temperature when the amount of active oxygen becomes half the initial amount in 1 hour when the organic oxide is decomposed at the constant temperature) is Vicat softening point of resin (JIS
K 6747-1981, the same shall apply hereinafter). When the 1-hour half-life temperature of the organic peroxide used exceeds the Vicat softening point of the base resin, a temperature higher than the melting point of the base resin is required to quickly decompose the peroxide. Is not preferable, and in some cases, it is not possible to substantially decompose at a temperature lower than the melting point of the present base resin, which is not preferable. When the peroxide is substantially decomposed at a temperature higher than the melting point of the base resin, the peroxide is decomposed in a state of penetrating deep into the resin particles, and thus the base group constituting the resin particles is formed. Since the material resin is largely decomposed on the surface and inside, there is a possibility that only expanded particles that cannot be used for molding can be obtained, and even if molding is possible, it is finally obtained. There is a possibility that the mechanical properties of the EPP molded body may be significantly reduced.

Considering the above, it is preferable that the organic peroxide used has a one-hour half-life temperature of 20 ° C. or more lower than the Vicat softening point of the base resin. It is more preferable that the temperature is 30 ° C. or more lower than the Vicat softening point. The 1-hour half-life temperature is preferably equal to or higher than the glass transition temperature of the base resin, more preferably 40 to 100 ° C., and 50 to 90 ° C. in consideration of handleability and the like. Is more preferable. The glass transition temperature is JIS K 7121-1.
987 means the midpoint glass transition temperature determined by the heat flux DSC according to 987 (For the condition adjustment of the test piece at this time, “when measuring the glass transition temperature after performing a constant heat treatment” is adopted). Further, it is preferable that the peroxide is substantially decomposed at a temperature below the Vicat softening point of the present base resin in a dispersion medium in which the present resin particles are present, and is 20 ° C. higher than the Vicat softening point of the present base resin. It is more preferable that the resin is substantially decomposed at a low temperature as described above, and it is further preferable that the resin is substantially decomposed at a temperature of 30 ° C. or more lower than the Vicat softening point of the base resin. The organic peroxide has a 1-minute half-life temperature of the organic peroxide (the temperature at which the amount of active oxygen becomes half of the initial amount in 1 minute when the organic oxide is decomposed at a constant temperature) ± It is particularly preferable to maintain the temperature range of 30 ° C. for 10 minutes or more to substantially decompose it. When attempting to decompose at a temperature lower than [1 minute half-life temperature −30 ° C.], it takes a long time to decompose, resulting in poor efficiency. On the contrary, if the decomposition is attempted at a temperature higher than [1 minute half-life temperature + 30 ° C.], the decomposition may be rapid and the efficiency of surface modification may be deteriorated. Further, when the half-life temperature of 1 minute ± 30 ° C. is maintained for 10 minutes or more, it becomes easy to substantially decompose the organic peroxide. The holding time in the range of the one-minute half-life temperature ± 30 ° C. allows the organic peroxide to be more reliably decomposed as the holding time becomes longer, but it is no longer necessary for a certain time or longer. A longer time than necessary will lead to a decrease in production efficiency. The holding time in the above temperature range should normally be no longer than 60 minutes. To decompose the organic peroxide, first prepare the dispersion adjusted to a temperature at which the organic peroxide is difficult to decompose, and then heat the dispersion to the decomposition temperature of the organic peroxide. Good. At this time, 1-minute half-life temperature ± 3
The temperature rise rate may be selected so that the temperature is maintained in the range of 0 ° C for 10 minutes or longer, but it should be stopped at any temperature within the range of 1 minute half-life temperature ± 30 ° C and held at that temperature for 5 minutes or longer. Is more preferable. As the arbitrary temperature at that time, a temperature within a range of 1 minute half-life temperature ± 5 ° C. is most preferable.

Further, “substantially decomposing” means decomposing until the active oxygen amount of the peroxide used becomes 50% or less of the initial amount.
It is preferable to decompose it to 0% or less, more preferable to decompose it to 20% or less of the initial amount of active oxygen, and further to decompose it to 5% or less of the initial amount of active oxygen. preferable. The half-life temperature of the organic peroxide is adjusted with a 0.1 mol / L concentration of an organic peroxide solution by using a solution relatively inactive to radicals (such as benzene and mineral spirits). Then, it is sealed in a glass tube that has been purged with nitrogen, immersed in a constant temperature bath set to a predetermined temperature, and thermally decomposed for measurement.

The present resin particles, surface-modified particles, expanded particles having a modified surface that can be molded at low temperature, and EP obtained therefrom.
It is preferable that all the P molded bodies are substantially non-crosslinked. When the surface-modified particles are produced, no crosslinking agent or the like is used in combination, so that crosslinking does not substantially proceed.
The term "substantially non-crosslinked" is defined as follows. That is, regardless of the present base resin, the present resin particles, surface modified particles, expanded particles, and EPP molded body, each was used as a sample (use 1 g of sample per 100 g of xylene), and after immersing this in boiling xylene for 8 hours, It is rapidly filtered through a wire mesh having a mesh of 74 μm defined in JIS Z 8801 (1966) which defines a standard mesh sieve, and the weight of the boiling xylene insoluble matter remaining on the wire mesh is measured. The case where the proportion of the insoluble matter is 10% by weight or less of the sample is referred to as substantially non-crosslinking, but the proportion of the insoluble matter is preferably 5% by weight or less of the sample, and is preferably 3% by weight or less. More preferably, it is most preferably 1% by weight or less. The smaller the proportion of the insoluble matter, the easier it is to reuse. The insoluble content P (%) is expressed by the following formula. P (%) = (M ÷ L) × 100 where M is the weight (g) of the insoluble matter and L is the weight (g) of the sample.

The expanded particles having a modified surface that can be molded at a low temperature used in the present invention are obtained by heating the surface-modified particles in a dispersion medium in a closed container in the presence of a foaming agent while heating and under heating conditions. After the step of impregnating the modified particles with the foaming agent (foaming agent impregnation step), the resin particles or surface-modified particles and the dispersion medium are released into the low-pressure zone at a temperature at which expanded particles are generated when the pressure is released. It is preferable to manufacture by a foaming method (hereinafter referred to as a "dispersion medium releasing foaming method") including a step of obtaining expanded particles (resin particle foaming step).

The surface modification step of forming the surface modified particles and the foaming step of obtaining expanded particles from the surface modified particles (foaming agent impregnation step + resin particle foaming step) are performed by different devices. Although it is possible to carry out at a certain time, the organic peroxide having an appropriate decomposition temperature is added to the dispersion medium in a predetermined amount in the dispersion medium to perform the surface modification step, and then the surface is treated in the same container. It is also possible to obtain expanded particles from the surface-modified particles by impregnating the modified particles with a foaming agent and performing a foaming step by a usual dispersion medium releasing foaming method. In the foaming step, from the viewpoint of preventing fusion of the surface-modified particles in the closed container, the weight ratio of the surface-modified particles / the dispersion medium is 0.5 or less, preferably 0.5 to 0.1. Preferably. In the case where the weight ratio of the present resin particles / the dispersion medium in the surface modification step is 0.6 to 1.3 and the surface modification step and the foaming step are carried out in the same container, In order to set the weight ratio of the surface-modified particles / the dispersion medium in the foaming step to 0.5 or less, the dispersion medium may be added in the container after the surface-modification step.

In the surface-modified particles, the expanded particles having a modified surface which can be molded at a low temperature and the EPP molded article obtained from the surface-modified particles, an alcohol having a molecular weight of 50 or more produced by the decomposition of the peroxide is contained. Is several hundred ppm to several thousand pp
It may be contained in the order of m. As such alcohol,
If bis (4-t-butylcyclohexyl) peroxydicarbonate as shown in the examples below is used, Pt-butylcyclohexanol may be included in the surface modified particles of the present invention. . Other alcohols may be included if other peroxides are used. Examples of such alcohol include, for example, isopropanol, S
-Butanol, 3-methoxybutanol, 2-ethylhexylbutanol, and t-butanol are exemplified.

In the above dispersion medium releasing foaming method, it is preferable to add a dispersant to the dispersion medium so that the surface-modified particles in the container under heating are not fused with each other. As such a dispersant, any dispersant may be used as long as it can prevent fusion of the surface-modified particles in the container, and it can be used regardless of whether it is organic or inorganic. Inorganic substances are preferred. For example, natural or synthetic clay minerals such as amsnite, kaolin, mica, and clay, and aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, iron oxide, etc., in one kind or in a combination of several kinds. Can be used.

Further, in the above dispersion medium releasing foaming method, the dispersive power of the dispersant is strengthened (the fusion of the surface-modified particles is prevented in the container even if the addition amount of the dispersant is reduced).
It is preferable to add a dispersion strengthener to the dispersion medium. Such a dispersion enhancer is an inorganic compound which can dissolve at least 1 mg or more in 100 cc of water at 40 ° C.,
An inorganic substance in which at least one of an anion and a cation of the compound is divalent or trivalent. Examples of such inorganic substances include magnesium chloride, magnesium nitrate, magnesium sulfate, aluminum chloride, aluminum nitrate, aluminum sulfate, iron chloride, iron sulfate, iron nitrate and the like.

Usually, the present resin particles or surface-modified particles 100
The dispersant is used in an amount of about 0.001 to 5 parts by weight, and the dispersion strengthener is used in an amount of about 0.0001 to 1 part by weight per part by weight.

Examples of the foaming agent used in the production of expanded particles include aliphatic hydrocarbons such as propane, butane, hexane and heptane, cycloaliphatic hydrocarbons such as cyclobutane and cyclohexane, chlorofluoromethane and trifluoromethane. Organic physical foaming agents such as methane, 1,2-difluoroethane, 1,2,2,2-tetrafluoroethane, halogenated hydrocarbons such as methyl chloride, ethyl chloride and methylene chloride, nitrogen, oxygen, air and dioxide. carbon,
A so-called inorganic physical foaming agent such as water is exemplified. It is also possible to use an organic physical foaming agent and an inorganic physical foaming agent in combination. In the present invention, those containing, as a main component, one or more inorganic physical foaming agents selected from the group of nitrogen, oxygen, air, carbon dioxide and water are particularly preferably used. Of these, nitrogen and air are preferable in consideration of the stability of the apparent density of the expanded particles, environmental load, cost, and the like. As the water used as the foaming agent, water (including ion-exchanged water) used as a dispersion medium for dispersing the surface-modified particles in the closed container may be used as it is.

In the above dispersion medium releasing foaming method, the filling amount of the physical foaming agent into the container is appropriately selected according to the kind of the foaming agent used, the foaming temperature and the apparent density of the foamed particles to be aimed at. For example, when nitrogen is used as the foaming agent and water is used as the dispersion medium, the pressure in the closed container in a stable state immediately before the start of foaming, that is, the pressure in the space inside the closed container (gauge pressure) But 0.6-6MP
It is preferable to select so as to be a. Usually, it is desirable that the smaller the apparent density of the target foamed particles, the higher the pressure in the space within the container, and the lower the apparent density of the target foamed particles, the lower the pressure in the space. There is a tendency.

The expanded particles for producing at least one unit molded article for producing the EPP molded article of the present invention are composed of the present base resin. Further, the foamed particles have an apex of a specific endothermic curve peak (specific peak) derived from the heat of fusion of the base resin in a DSC curve by differential scanning calorimetry of the expanded particles (heat flux differential scanning calorimetry, the same applies hereinafter). In the expanded particles having an apex of the endothermic curve peak (high temperature peak) on the higher temperature side, the relationship between the apparent density D1 of the expanded particles and the heat amount E1 of the high temperature peak of the expanded particles is expressed by the following equation (1), ( It satisfies 2). Formula (1): 20-0.014 x D1 ≤ E1 ≤ 65-0.072 x D1 Formula (2): 10 ≤ D1 ≤ 700 In the formula (1), D1 is displayed in g / L unit. It is the numerical value of the apparent density of the expanded beads, and E1 is the numerical value of the high temperature peak calorific value of the expanded particles used for molding, which is expressed in J / g. If D1 is less than 10 g / L, the proportion of open cells increases, which may make molding difficult. Further, if D1 exceeds 700 g / L, the foaming power for filling the voids between the foamed particles during molding may be poor. On the other hand, when E1 is less than [20-0.014 × D1], shrinkage of the obtained molded article tends to be large, and the object of the present invention cannot be sufficiently achieved. Also, E1 is [65-0.0
72 × D1], the foaming power to fill the voids between the foamed particles during molding may be poor. E having a unit molded body composed of such specific expanded particles
The PP molded body does not expand in the final molded body even if the portion of the unit molded body is cooled immediately after heating during molding for a short time, and further shrinks even if cooling is excessive. Since there is little or no such property, it is possible to obtain a high quality EPP molded product in which two or more unit molded products having mutually different properties are adjacently integrated. Also, the above E
1 is 10 to 6 with respect to the total amount of heat of E1 and the characteristic peak.
It is preferably 0%, more preferably 20 to 50%. The heat quantity E1 at the high temperature peak and the heat quantity at the specific peak in the present specification both mean the heat absorption quantity, and the numerical values are expressed as absolute values. When the base resin is the same, the expanded particles of polypropylene-based resin tend to have a larger shrinkage in the obtained molded product as the expansion ratio becomes higher. This is because the amount of resin per unit volume is smaller than that of a low expansion ratio. Further, the smaller the high-temperature peak calorie (E1) of the expanded particles, the larger the shrinkage of the obtained molded article. On the contrary, the larger the high temperature peak calorific value of the expanded particles, the smaller the shrinkage of the obtained molded article. However, as the high-temperature peak calorific value of the expanded beads increases, it tends to be less likely to be melted by heating during molding (the expanded particles are less likely to be fused to each other during heating during molding) and the expansive force of the expanded particles tends to be poor. It is based on the above viewpoint that E1 in the above formula (1) is expressed by the relational expression of the apparent density of the expanded particles. Formula (1) above
Is experimentally determined under these viewpoints and in relation to the tensile elastic modulus of the base resin. Further, the above formula (2) is preferably 20 ≦ D1 ≦ 200, more preferably 30 ≦ D1 ≦ 150, in order to make the obtained in-mold molded article lighter and have higher rigidity.

The E1 of the expanded particles is 2 to 10 mg of expanded particles.
Under a nitrogen atmosphere by a differential scanning calorimeter at room temperature (1
Peculiar endothermic curve peak (specific peak) derived from the heat of fusion of the base resin observed in the first DSC curve shown in FIG. 1 obtained when the temperature is increased from 0 to 40 ° C.) to 220 ° C. at 10 ° C./min. ) The heat quantity (endothermic quantity) of an endothermic curve peak (high temperature peak) b in which the peak appears on the higher temperature side than the temperature at which the peak of a appears, which corresponds to the area of this high temperature peak b. You can ask in this way. First, a straight line (α-β) connecting a point α on the DSC curve corresponding to 80 ° C. and a point β on the DSC curve corresponding to the melting end temperature T of the expanded particles is drawn. Next, a straight line parallel to the vertical axis of the graph is drawn from the point γ on the DSC curve corresponding to the valley between the above-mentioned intrinsic peak a and high temperature peak b, and the straight line (α-β) is obtained.
Let σ be the point that intersects with. The area of high temperature peak b is DSC
The curve of the high temperature peak b of the curve, and the line segment (σ−β),
This is the area of the portion surrounded by the line segment (γ-σ) (the hatched portion in FIG. 1), and this corresponds to the heat quantity of the high temperature peak. The melting end temperature T is the intersection of the DSC curve on the high temperature side of the high temperature peak b and the high temperature side baseline. Further, the sum of the heat quantity of the high temperature peak and the heat quantity of the specific peak corresponds to the area of the portion surrounded by the straight line (α-β) and the DSC curve. When the specific peak and the high temperature peak of the expanded particles are measured by the differential scanning calorimeter as described above, the weight per expanded particle is 2%.
When the amount is less than mg, a plurality of expanded particles having a total weight of 2 mg to 10 mg may be used as they are for measurement, and when the weight per expanded particle is 2 mg to 10 mg, one expanded particle is used. Is used for the measurement as it is, and when the weight per expanded particle is more than 10 mg, a cut sample obtained by cutting one expanded particle into a plurality of pieces has a weight of 2 to 10 mg. One may be used for measurement. However, this cut sample was obtained by cutting one foamed particle using a cutter or the like, but at the time of cutting, the surface of the foamed particle originally held was not cut and left as it was, and each cut sample was cut. It is preferable to cut evenly so that the shape is as uniform as possible and in each cut sample so that the area of the surface of the expanded particles left without being cut out is the same as much as possible. For example, when the weight per expanded particle is 18 mg, if the expanded particles oriented in any direction are cut horizontally from the center in the vertical direction, two cut samples of approximately 9 mg having substantially the same shape are obtained, In each cut sample, the surface of the expanded particles that it originally has is left as it is, and the surface area of each cut sample is almost the same. One of the two cut samples thus obtained may be used for measuring the intrinsic peak and the high temperature peak as described above. In the present specification, when simply expressed as “high temperature peak calorific value of expanded particles”, the calorific value of the high temperature peak obtained by the above measurement, that is, E1 is referred to, which will be described later. In Eq. (3), the heat quantity of the high temperature peak for the surface layer portion of the expanded particles and the heat quantity of the high temperature peak for the internal foam layer are distinguished.

The above-mentioned high temperature peak b is recognized in the first DSC curve measured as described above, but after obtaining the first DSC curve, 220 ° C to 40 ° C once at 220 ° C / min. Lower the temperature to near (40-50 ° C), then again 10 ° C
Second D obtained when the temperature was raised to 220 ° C./min
It is not observed in the SC curve, and only the specific peak a corresponding to the endotherm when the base resin is melted as shown in FIG. 2 is observed. The temperature of the apex of the peculiar peak a appearing in the first DSC curve of the expanded particles is usually [Tm-5 ° C] to [Tm + 5 ° C] with reference to the melting point (Tm) of the base resin.
Appears in the range (most commonly [Tm-4 ° C] to [Tm
m + 4 ° C]). Further, the temperature at the apex of the high temperature peak b appearing in the first DSC curve of the expanded particles is
Based on the melting point (Tm) of the base resin, it is usually [Tm
It appears in the range of + 5 ° C. to [Tm + 15 ° C.] (most commonly, it appears in the range of [Tm + 6 ° C.] to [Tm + 14 ° C.]. In addition, the temperature at the apex of the unique peak a (temperature corresponding to the melting point of the base resin) observed in the second DSC curve of the expanded particles is usually [based on the melting point (Tm) of the base resin] It appears in the range of Tm-2 ° C] to [Tm + 2 ° C].

The expanded particles used in the present invention are as described above.
Some DSC measurements have a crystal structure in which a high temperature peak appears in the first DSC curve, but the heat quantity of this high temperature peak is strongly affected by the difference between the melting point of the resin and the foaming temperature. The high temperature peak calorific value of the expanded particles acts as a factor that determines the minimum fusing temperature, particularly with respect to the fusion of the expanded particles to each other. The minimum fusing temperature as used herein means the temperature that gives the lowest saturated steam pressure required for the expanded particles to fuse together in the mold. The high temperature peak calorific value is closely related to this minimum fusion temperature, and when the same base resin is used, the smaller the high temperature peak calorific value is, the smaller the minimum fusion temperature is when the high temperature peak calorific value is larger. It tends to be low. The value of this high temperature peak calorific value is strongly influenced by the high and low foaming temperature given to the resin at the stage of manufacturing expanded particles,
When the same base resin is used, the high-temperature peak calorific value tends to be smaller when the foaming temperature is higher than when the foaming temperature is low.

However, when an EPP molded product is obtained by using expanded particles having a small amount of high temperature peak heat, the minimum fusion temperature tends to be relatively low, but the strength properties such as the compression strength (rigidity) of the EPP molded product, etc. Tends to decrease relatively. On the other hand, when an EPP molded product is obtained by using expanded particles having a large amount of high-temperature peak heat, the minimum fusion temperature becomes relatively high although the strength properties such as the compression strength of the EPP molded product tend to be relatively high. As described above, there arises a problem that steam of high pressure may be required when manufacturing the EPP molded body. That is, the most preferable expanded particles are expanded particles having contradictory properties such that the minimum fusion temperature is low and the strength properties such as compressive strength of the EPP molded product are relatively high. The expanded particles having a modified surface that can be molded at a low temperature are those in which the minimum fusing temperature is effectively reduced, and E particles are produced using such expanded particles.
When manufacturing a PP molded body, an EPP molded body having excellent mechanical properties such as compressive strength can be obtained.

In order to obtain expanded particles having a high temperature peak in the DSC curve, when the surface-modified particles are dispersed in a dispersion medium and heated in a closed container, the melting end temperature (Te) or more of the base resin is not less than The temperature (Ta) is sufficient to stop at any temperature (Ta) within the range of not lower than 20 ° C. lower than the melting point (Tm) of the base resin and lower than the melting end temperature (Te) without increasing the temperature. For about 10 to 60 minutes, and then adjust to any temperature (Tb) in the range of 15 ° C lower than the melting point (Tm) to the melting end temperature (Te) + 10 ° C, and stop at that temperature. , If necessary, at that temperature for a sufficient time, preferably about 10 to 60 minutes,
It can be obtained by a method in which the surface-modified particles are held and then discharged from the closed container under a low pressure to foam. The melting point (Tm) means the differential scanning calorimetry of the resin particles in the same manner as the DSC curve of the expanded particles as described above using 2 to 4 mg of the resin particles as a sample. This is the temperature at the apex of the endothermic curve peak a peculiar to the base resin observed in the second DSC curve (an example of which is shown in FIG. 2) obtained by this, and the melting end temperature (Te) is the peculiarity of the peculiarity. DSC on the high temperature side of endothermic curve peak a
The intersection (β) between the curve and the high temperature side baseline ( _BL ). The endothermic curve peak that appears in the second DSC curve for the present resin particles usually appears as one endothermic curve peak, assuming that it is a peak based on the melting of the polypropylene resin. However, when it is composed of a mixture of two or more polypropylene resins, it is rare
The above endothermic peaks may be observed. In that case, a straight line that passes through the apex of each peak and is parallel to the vertical axis of the graph (orthogonal to the horizontal axis) is drawn, and the length from the apex of the peak to the baseline B _L is measured on each straight line, The apex of the peak on the longest straight line is the above T
m. However, when there are two or more straight lines of the same length, the peak of the highest temperature side among them is the above T
m.

The amount of heat of the above-mentioned high temperature peak in the expanded beads mainly depends on the temperature Ta and the holding time at the temperature and the temperature Tb and the holding time at the temperature and the rising time with respect to the resin particles during the production of the expanded particles. Depends on temperature rate. The calorific value of the high temperature peak of the expanded beads tends to increase as the temperature Ta or Tb falls within the above temperature range and as the holding time increases. Normal,
The heating rate during heating (average heating rate from the start of heating to the start of temperature maintenance) is 0.5 to 5 ° C./min. By repeating the preliminary experiment in consideration of these points, it is possible to easily know the production conditions of the expanded beads exhibiting the desired high-temperature peak calorific value.

The temperature range described above is an appropriate temperature range when an inorganic physical foaming agent is used as the foaming agent. When the organic physical foaming agent is used in combination, the appropriate temperature range shifts to the lower temperature side than the above temperature range depending on the type and the amount used.

The apparent density (g / L) of the expanded beads is
The weight (g) of the expanded particles is expressed by the apparent volume (L) of the expanded particles.
It is calculated by dividing. The apparent volume of expanded particles is
Foamed particles left at 23 ° C and atmospheric pressure for more than 48 hours
5 g of water at 23 ° C 100 cm ³Mescillin containing
From the excluded volume when submerged in the water in the dar, the expanded particles
Apparent volume of (cm³) And read this
It can be obtained by converting to rank. Foamed particles for this measurement
0.5000 to 10.0000 g, and expanded particles
Apparent volume of 50-90 cm³The amount of
Foam particles are used.

Incidentally, obtained from the above-mentioned surface-modified particles,
It has been found from the measurement results that the expanded particles having a modified surface that can be molded at a low temperature (hereinafter referred to as “surface modified expanded particles”) have the following structural specificity.

As a result of the DSC measurement of the expanded particles, the surface-modified expanded particles show a tendency different from that of the expanded particles obtained by the conventional method. When the melting point was measured by dividing the surface layer portion of the expanded particles and the inner foam layer not including the surface layer, the melting point of the conventional expanded particles (Tm _s ) was found to be the melting point of the internal foam layer (Tm). _While the surface-modified expanded particles had a melting point (Tm _s ) lower than the melting point (Tm _i ) of the internal foamed layer, the surface-modified expanded beads had a property that the melting point was always higher than that of _i ). It was observed that Therefore, as the surface-modified expanded particles, Tm _s is preferably lower than Tm _i by 0.05 ° C. or more, more preferably 0.1 ° C. or more, still more preferably 0.3 ° C. or more.

The melting point (Tm _s ) of the surface layer of the expanded particles is
The surface layer portion of the expanded beads was cut out, 2 to 4 mg were collected, and this was used as a sample. Means temperature. In addition, the melting point (Tm _i ) of the internal foam layer of the expanded particles was determined by cutting out from the inside of the expanded particles so that the surface layer portion was not included, collecting 2 to 4 mg, and using this as a sample, It means the temperature at the apex of the unique peak a of the second DSC curve obtained by performing the same operation as the measurement.

Further, when the high temperature peak calorific value was measured by dividing the surface layer portion of the expanded particles and the internal foam layer not including the surface layer portion, the conventional expanded particles had a high temperature peak calorie (ΔH _s ) at the surface layer portion of the expanded particles. The relationship with the amount of heat at the high temperature peak (ΔH _i ) of the internal foam layer was such that ΔH _s ≧ ΔH _i × 0.87, whereas in the case of the surface-modified expanded particles, ΔH s was
It was observed that _s <ΔH _i × 0.86. Therefore,
The surface-modified expanded particles are preferably ΔH _s <ΔH _i × 0.86, more preferably ΔH _s <ΔH _i × 0.80, and ΔH _s <ΔH _i × 0.75. Is more preferable, ΔH _s <ΔH _i × 0.70 is particularly preferable, and ΔH _s <ΔH _i × 0.60 is most preferable. Further, ΔH _s is ΔH _s ≧ ΔH _i × 0.25
Is preferred. The surface-modified expanded particles have a ΔH _s <
With ΔH _i × 0.86, in-mold molding can be performed at a lower temperature than that of the expanded particles that have not been surface-modified, and ΔH _s
The smaller the value, the greater the effect. This enables in-mold molding with low-temperature steam without lowering the rigidity of the unit molded body made of the surface-modified expanded particles. still,
ΔH _s is preferably 1.7 J / g to 60 J / g, more preferably 2 J / g to 50 J / g, further preferably 3 J / g to 45 J / g,
Most preferably, it is 4 J / g to 40 J / g.

The high temperature peak calorific value of the surface layer portion of the expanded particles is
It can be determined by performing the same operation as in the measurement of the high-temperature peak calorific value of the expanded particles, except that the surface layer portion of the expanded particles is cut out and 2 to 4 mg are collected and used as a sample. Also,
The high-temperature peak calorific value of the internal foam layer of the expanded particles is 2 to 4 m when cut out from the inside of the expanded particles so as not to include the surface layer portion.
It can be determined by performing the same operation as the above-mentioned measurement of the high temperature peak calorific value of the expanded particles except that g is collected and used as a sample.

The method for measuring the melting point and high-temperature peak calorie by dividing the above-mentioned expanded particles into the surface layer portion and the inner foam layer not containing the surface layer portion is as follows. As for the surface layer portion of the expanded beads, the surface layer portion may be sliced with a cutter knife, a microtome or the like, and the surface layer portion may be collected and used for the measurement.
However, the surface of the foamed particles is always present on the entire surface of the surface layer portion of the sliced foamed particles, but on the back surface of the surface layer portion of the sliced foamed particles, the surface of the foamed particles faces from the center of gravity of the foamed particles. Randomly selected on the surface of the expanded particles so that the area exceeding 200 μm is not included 1
Sliced from one or more locations. When the back surface of the surface layer portion of the sliced foamed particles includes a portion exceeding 200 μm from the surface of the foamed particle toward the center of gravity of the foamed particle, a large amount of the internal foamed layer is contained, and the melting point of the surface layer portion and There is a possibility that the high temperature peak heat quantity cannot be accurately measured. When the surface layer portion obtained from one expanded particle is less than 2 to 4 mg, the above operation may be repeated using a plurality of expanded particles to collect a required amount of the surface layer portion. On the other hand, the inner foam layer that does not include the surface layer portion of the foamed particles has the entire surface of the foamed particles so that the surface of the foamed particles and the portion between the surface of the foamed particles and 200 μm toward the center of gravity of the foamed particles are not included. The one obtained by cutting off the surface layer may be used for the measurement of the melting point and the high-temperature peak calorific value. However, when the size of the foamed particles is too small and the internal foamed layer disappears when the portion of 200 μm from the above surface is cut off, the surface of the foamed particles and the surface of the foamed particles go to the center of gravity of the foamed particles. When the surface layer is cut off from the entire surface of the expanded particles so that the area between 100 μm and 100 μm is not used as the internal expanded layer, and when the internal expanded layer is still lost, the surface of the expanded particles is The surface layer part cut off from the entire surface of the expanded particle is used as the internal expanded layer so that the part between the surface of the expanded particle and the center of gravity of the expanded particle does not include 50 μm. When the internal foam layer obtained from one expanded particle is less than 2 to 4 mg, the above operation may be repeated using a plurality of expanded particles to collect a required amount of the internal foam layer.

Further, when the MFR was measured, it was observed that the MFR value of the surface-modified foamed particles was the same as the MFR value of the present resin particles before the surface modification, but showed a larger value. . The MFR value of the surface-modified foamed particles is preferably 1.2 times or more, more preferably 1.5 times or more, the MFR value of the resin particles before surface modification. Most preferably, it is 8-3.5 times.
The MFR value of the surface-modified foamed particles is determined by considering the heat resistance of the EPP molded product and the foaming efficiency at the time of manufacturing the foamed particles.
It is preferably 0.5 g / 10 min to 150 g / 10 min, more preferably 1 g / 10 min to 100 g / 10 min, and more preferably 10 g / 10 min to 8
It is even more preferable to set it to 0 g / 10 minutes.

The MFR of the expanded particles means that the expanded particles are 2
A press sheet having a thickness of 0.2 mm to 1 mm was prepared with a heating press machine whose temperature was adjusted to 00 ° C., and a sample was cut into pellets or rods from the sheet, and the sample was used to prepare the MFR It is a value measured by the same method as the measurement. Incidentally, in measuring the MFR of the expanded particles, it is necessary to avoid inclusion of bubbles or the like in the sample in order to obtain an accurate measurement value. When air bubbles are unavoidable, the same sample can be repeated up to three times to prepare a press sheet for defoaming with a heating press machine.

Further, the surface-modified expanded particles are subjected to a surface-modifying step.
In particular, an oxygen radical is particularly used as the organic peroxide.
If the generated organic peroxide is used, the addition of organic peroxide
A modified surface containing a small amount of oxygen is formed by the action.
Be done. This is due to the surface of the surface-modified expanded particles and
It is clear from the analysis of the surface of the EPP molded product manufactured by
ing. Specifically, it is manufactured from surface-modified expanded particles.
The surface of the EPP molded article (that is, the surface of the surface-modified expanded particles and
(Substantially the same) as conventional non-surface-modified foam granules
AT each of the surface of the EPP molded body manufactured from the child
Surface modification as a result of comparison by R measurement (total reflection absorption measurement method)
On the surface of the EPP molded product manufactured from expanded particles, new
To 1033 cm^-1Check that there is a difference in absorption in the vicinity
Oxygen, or addition of oxygen-containing functional groups.
It was confirmed that there were changes such as rui or insertion. concrete
Is 1166 cm^-1Height of both peaks in absorption of
The height of the absorption peak from the surface-modified expanded particles to the molded product and
Assuming that the absorption peak height for conventional molded products is the same
First, the surface of the molded body obtained from the surface-modified expanded particles
33 cm ^-1The height of the absorption peak near the
1033 cm of surface^-1Higher than the height of absorption peaks in the vicinity
Has become. Furthermore, as a surface observation of the expanded particles, EDS (E
The result of elemental analysis by the energy dispersive analyzer
Regarding the ratio of oxygen to carbon, in the case of surface-modified expanded particles,
Although it was 0.2 (mol / mol),
In the case of foam particles, it was 0.09 (mol / mol).
From the above, some amount may be obtained due to the addition effect of organic peroxide.
Is clearly forming a modified surface containing
It The formation of such a modified surface allows the penetration of steam during molding.
It is thought to be advantageous to transitivity. From this perspective, the table
The surface-modified expanded particles are added to the EDS on the expanded particle surface.
It is preferable that the ratio of oxygen to carbon is 0.15 or more.
Good

The surface-modified foamed particles are those whose minimum fusion temperature is effectively reduced by lowering the high temperature peak calorific value of the surface layer portion of the foamed particles or / and lowering the melting start temperature of the surface of the foamed particles. Presumed to be.

The expanded beads used in the present invention are aged under atmospheric pressure, and if necessary, the internal pressure of the bubbles is increased and then heated with steam or hot air to obtain expanded beads having a higher expansion ratio. It is possible.

The polypropylene resin in-mold foam molded product (EPP molded product) according to the present invention is a mold capable of heating, cooling, opening, closing and closing the foamed particles after increasing the internal pressure of the bubbles as necessary. It can be manufactured by adopting a batch-type molding method in which the inside of the mold is filled and saturated steam is supplied to heat and expand the expanded particles in the mold so that they are mutually fused and then cooled and taken out from the mold. . As a molding machine used in the batch type molding method, a large number of molding machines already exist all over the world, and the pressure resistance thereof is 0.41 MPa (G) or 0.45 MPa (G), although it varies slightly depending on the country.
There are many things. Therefore, the pressure of the saturated steam at the time of expanding and melting the foamed particles is 0.45 MPa.
(G) is preferably less than or equal to, and 0.41M
More preferably, it is less than or equal to Pa (G).
In addition, when increasing the bubble internal pressure of the foamed particles, put the foamed particles in a closed container, and leave it for a suitable time while supplying pressurized air into the container to allow the compressed air to penetrate into the foamed particles. Good. The gas supplied under pressure can be used without any problem as long as the main component is an inorganic gas that does not liquefy or solidify under the required pressure, but is further selected from the group consisting of nitrogen, oxygen, air, carbon dioxide, and argon. Alternatively, those containing two or more inorganic gases as main components are particularly preferably used, and among them, nitrogen and air are preferable in consideration of environmental load and cost.

The internal pressure P (MP
a) is measured by the following operation. Here, an example is shown in which air is used to increase the internal pressure of the polypropylene resin expanded particles (EPP particles). First, the expanded particles used for molding are put in a closed container, and pressurized air (usually, the air pressure in the container is 0.98-9.
The internal pressure of the expanded beads is increased by allowing the air to penetrate into the expanded beads by leaving them for a suitable period of time while being supplied (so as to maintain the range of 8 MPa). The expanded particles having a sufficiently increased internal pressure are supplied into the mold of the molding machine. The internal pressure of the foamed particles is obtained by performing the following operation using a part of the foamed particles (hereinafter referred to as a foamed particle group) immediately before in-mold molding.

Within 60 seconds after taking out the expanded particle group immediately before in-mold molding with the increased internal pressure from the pressure tank, a large number of needle holes of a size that does not allow the expanded particles to pass but allows air to freely pass are formed. Stored in a polyethylene bag measuring 70 mm x 100 mm, the temperature is 23 ° C and the relative humidity is 50.
Move to a temperature-controlled room under the atmospheric pressure of. Then, it is placed on a scale in the temperature-controlled room and the weight is read. The weight is measured after the foamed particle group is taken out of the pressure tank by 120.
Seconds later. The weight at this time is defined as Q (g). Then, the bag is left in the same temperature-controlled room for 48 hours. Since the pressurized air in the expanded particles permeates the bubble film and escapes to the outside with the passage of time, the weight of the expanded particle group decreases accordingly.
After the time, the equilibrium is reached and the weight is substantially stable. After 48 hours, weigh the bag again,
The weight at this time is U (g). Immediately thereafter, all the foamed particle groups are taken out of the bag in the same constant temperature chamber and the weight of only the bag is read. Let the weight be Z (g). Any of the above weights shall be read up to 0.0001 g.
Using the difference between Q (g) and U (g) as the increased air amount W (g), the internal pressure P (MPa) of the expanded particles is calculated from the following equation. still,
This internal pressure P corresponds to a gauge pressure.

P = (W ÷ M) × R × T ÷ V However, in the above equation, M is the molecular weight of air, and here, 2
A constant of 8.8 (g / mol) is adopted. R is a gas constant, and is 0.0083 (MPa · L / (K · mo
l)) constant is adopted. T means absolute temperature, 23
Since the atmosphere of ℃ is adopted, it is 296 here.
It is a constant of (K). V means a volume (L) obtained by subtracting the volume of the base resin in the expanded particle group from the apparent volume of the expanded particle group.

The apparent volume (L) of the expanded particle group is 4
From the scale when the total amount of the expanded particle group taken out from the bag after 8 hours was immediately submerged in the water in the graduated cylinder containing 100 cm ³ of water at 23 ° C. in the constant temperature chamber,
It is determined by calculating the volume Y (cm ³ ) of the expanded particle group and converting this to the unit of liter (L). The apparent expansion ratio of the expanded particle group is the density of the base resin (g / c
It is determined by dividing m ³ ) by the apparent density (g / cm ³ ) of the expanded particle group. Also, the apparent density of the expanded particles (g
/ Cm ³ ) is the weight of the expanded particle group (U (g) and Z
It is obtained by dividing (difference from (g)) by the volume Y (cm ³ ). In the above measurement, the expanded particle group weight (difference between U (g) and Z (g)) was 0.5000 to 1.
A plurality of expanded particle groups are used in an amount of 0.0000 g and a volume Y of 50 to 90 cm ³ .

The internal pressure in the bubbles of the expanded particles is 0 to 0.
98 MPa is preferable, 0 to 0.69 MPa is more preferable, 0 to 0.49 MPa is particularly preferable, and 0 to 0.
Most preferred is 1 MPa. If the internal pressure of the bubbles becomes too high, the secondary foaming force at the time of molding becomes excessive, which hinders the saturated steam from penetrating into the molded body, resulting in insufficient heating of the center of the molded body, and mutual fusion of the foamed particles. Is likely to be defective.

In general, an in-mold foam molded article obtained by molding polypropylene resin foamed particles in a mold usually becomes larger than the shape of the mold space when cooling immediately after heating is insufficient during molding ( If it is excessively cooled, it will be smaller than the shape of the mold space (contract will be so large that sufficient recovery cannot be expected). The degree of expansion and the degree of contraction differ depending on the degree of cooling. Further, the expansion and contraction thereof show different tendencies when the apparent density of the obtained molded article is high and when it is low. Specifically, when the degree of cooling is the same, the low-density molded body portion tends to shift from expansion to contraction earlier. Usually, the expanded molded body is often disliked in comparison with the shape of the mold space, so cooling is performed so that the high-density molded body portion does not expand. As a result, immediately after being taken out from the mold (mold release), the relatively low-density molded body portion is in a state of being greatly contracted. When the shrinkage is relatively small, the shrinkage is usually recovered by placing the molded body in a heating atmosphere of about 50 to 100 ° C. for about 24 hours at an early stage after release,
When a large amount of shrinkage occurs, it hardly recovers even under such a heating atmosphere, so that it is difficult to obtain a high quality product. On the other hand, the in-mold foam molded article formed from the specific foamed particles described above does not cause expansion in the final molded article even if the cooling for the molded article performed immediately after heating during molding is short. Moreover, even if cooling is excessive, there is little or no shrinkage. Therefore, even if integrally molded so as to include a unit molded body part manufactured with specific foamed particles and a unit molded body part manufactured with foamed particles other than the specific foamed particles, foaming other than the specific foamed particles is performed. If the cooling during molding is adjusted so as not to cause convex bulges on the outside and concave sinks (shrinkage) on the inner side of the unit molded body portion manufactured by particles, as a whole,
It is possible to easily obtain an in-mold molded body with little bulging that becomes convex on the outside of the molded body and shrinkage that shrinks to the inside.
A high quality product that does not cause damage to the heat fusion interface between the unit molded bodies. Furthermore, when all the unit molded bodies are manufactured from this specific expanded particle, it is easier to obtain an in-mold molded body with few bulges that form a convex shape on the outside and concave marks that form a concave shape on the inside. In addition, the cooling time after heating during molding can be further shortened. This is a surprising fact found by the present inventors for the first time.

Next, the present invention will be described in detail with reference to the drawings. FIG. 3 is a structural explanatory view of one embodiment of the EPP molded body of the present invention. In FIG. 3, 1, 2 and 3
Indicates a unit molded body, 4 indicates a fusion bonding interface between two adjacent unit moldings 1 and 2, and 5 indicates a fusion bonding interface between two adjacent unit moldings 2 and 3. 6 shows an EPP molded product according to the present invention. Each of the unit molded bodies 1, 2, and 3 is an in-mold foam molded body obtained by molding a specific foamed particle.

The EPP molded body 6 of the present invention shown in FIG. 3 is a fused body in which the unit molded bodies 1, 2 and 3 are integrated with each other at the time of molding, and the characteristics of the two adjacent unit molded bodies. Are different from each other. The characteristics differing from each other in the present invention mean at least different apparent densities, different base resins, different colors, or different mechanical properties such as compressive strength. Specifically, the higher the apparent density, the higher the compressive strength. For example, in the case of the EPP molded body shown in FIG. 3, the apparent density D2 _{1 of} the unit molded body ₁ , the apparent density D2 ₂ of the unit molded body ₂ and the apparent density D of the unit molded body 3 are shown.
The relationship between 2 ₃ is expressed by the following equations (5) and (6). Formula (5): D2 ₂ > D2 ₁ Formula (6): D2 ₂ > D2 ₃ That is, the density D2 ₂ of the unit molded body ₂ is calculated from the apparent densities D2 ₁ and D2 ₃ of the other unit molded bodies ₁ and ₃ . High density.
The apparent densities D21 and D23 of the low-density unit molded bodies ₁ and ₃ may be the same or different. In the case of the present invention,
Density D2 ₂ units molding 2 of high density, from 1.2 to 25 times the apparent density D2 _1, D2 ₃ units moldings 1,3 the low density is preferred, 1.2 to 20 times is more preferable. Such an in-mold molded article is made lighter as a whole by increasing the rigidity of a necessary portion.

In each of the unit compacts 1, 2, and 3 constituting the EPP compact 6 of the present invention shown in FIG.
2 (g / L) and the high-temperature peak calorie E2 (J / g) of each foam constituting the unit molded bodies 1, 2, and 3 satisfy the following formulas (3) and (4), respectively. Have a relationship. Formula (3): 20-0.020 x D2 ≤ E2 ≤ 65-0.100 x D2 Formula (4): 10 ≤ D2 ≤ 500 In the above formulas (3) and (4), D2 is from the base resin. Apparent density of the test pieces cut out from each of the unit molded bodies 1, 2, and 3 composed of the expanded particles, that is, D2 ₁ , D
Indicates 2 ₂ or D2 _3, E2 is the high temperature side endothermic curve peak fusion heat value of the test pieces cut from each of the unit molded bodies 1, 2 and 3 molded from specific expanded beads (2-4 mg) (E2 ₁ , E2 ₂ or E2 ₃ ) is shown. A more preferable relationship between D2 and E2 is as shown in the following formulas (7) and (8). Formula (7): 25-0.020 x D2 ≤ E2 ≤ 55-0.100 x D2 Formula (8): 15 ≤ D2 ≤ 450 In the high-density unit molded body 2, the apparent density D
2 ₂ is preferably 30~450g / L, low apparent density D2 ₁ Density unit molded bodies 1, 3, D2 ₃ is a preferably 15~90g / L and the dense unit molded body 2
Is lower than the apparent density D2 ₂ . As a result, the required parts are densified to increase the rigidity, and the overall weight of the in-mold molded product is reduced. When D2 is less than 10 g / L, the mechanical properties are remarkably deteriorated.
Is more than 500 g / L, the effect of foaming (lightness, etc.) is almost lost, and thus both are not preferable. Further, in the above formula (3), when E2 is less than [20−0.020 × D2], there is a possibility that a large shrinkage may remain in the molded body if excessive cooling occurs during molding,
On the other hand, when E2 exceeds [65-0.100 × D2], the obtained molded article tends to be inferior in the fusion strength between the expanded particles. The reason why E2 is expressed by the relational expression of D2 is the same as the relation between E1 and D1 of the above formula (1), but the numerical values are the same in the apparent density in the above formulas (1) and (3). The reason for the difference is that the expanded particles expand to fill the voids between the expanded particles during molding, and as a result, the apparent density of the molded body becomes smaller than the apparent density of the expanded particles used for molding. There is.

In order to produce a unit molded body satisfying the above formulas (3) and (4), the above-mentioned specific expanded particles may be used for molding.

FIG. 4 is a structural explanatory view of another embodiment of the EPP molded body of the present invention. In FIG. 4, 1 indicates a high-density unit compact and 2 indicates a low-density unit compact. Four
Indicates the fused interface between the two.

FIG. 5 is a structural explanatory view of still another embodiment of the EPP molded body of the present invention. In FIG.
Reference numerals 11 to 15 denote unit molded bodies, and 16 to 19 denote fusion bonding interfaces of two adjacent unit molded bodies. In FIG.
Apparent densities of the unit molded bodies 11 to ₁₅ D2 _{11 to} D2 ₁₅
Is expressed by the following equations (9) and (10). Formula (9): D2 ₁₃ > D2 ₁₂ > D2 ₁₁ Formula (10): D2 ₁₃ > D2 ₁₄ > D2 ₁₅

In the EPP molded product of the present invention, the two adjacent unit molded products were directly fused to each other without interposing any other member at the interface, as shown in FIGS. 3, 4 and 5. Although it may have a structure, in some cases, it may have a fusion structure in which an insert material is interposed at the fusion interface. Regarding the method for producing an EPP molded body having a structure in which two adjacent unit constituents are directly fused, for example, JP-A-11-334501 and JP-A-200345
0-16205, JP 2001-63496 A, JP 2001-150471 A, JP 2002 A
-172642, JP-B-62-22352, U.S. Pat. No. 5,164,257 and the like. Further, FIG. 6 shows a structural explanatory view of an EPP molded body when an insert material is interposed at a fusion bonding interface between two adjacent unit molded bodies. In FIG. 6, a shows one of two adjacent unit molded bodies, b shows the other, and c shows an insert material interposed at the fusion interface.

The insert material c preferably has a large number of through holes on its surface. This insert material c is used as a partitioning member when partitioning the inside of the mold into a plurality of partitions by partitioning members and filling each partition with foamed particles in the manufacturing process of the in-mold foam molded article. . When the foamed particles are filled in a plurality of compartments partitioned by the insert material (partitioning member) c and heated by steam to fuse the foamed particles together, the insert material c
The foamed particles present on both sides of the are heat-sealed through the through holes of the insert material c. When this heat-sealed body is taken out of the mold as a product of the in-mold foam molded body, the insert material c remains at the heat-sealed interface of each unit molded body. still,
In the case where the insert material has thermal adhesiveness capable of being integrated with the unit molded body with sufficient strength by heating when molding the foamed particles, the insert material does not necessarily have to be provided with the through hole, but the unit molded body is not necessarily formed at the time of molding. They can be integrated with each other via an insert material. However, when such inserts do not have such thermal adhesiveness, if the through holes are formed in the insert material, the unit molded bodies can be integrated through the through holes during molding.

The insert material c having the through holes may be a wire net, a metal plate or a ceramic plate (glass plate) having a large number of through holes, a plastic plate, or a cardboard having a large number of through holes. it can. The shape of the through hole in the insert material c can be various shapes such as a groove shape (slit shape) as well as a circular shape. The size of this through hole is
At the time of integrally heat-sealing the expanded particles filled on both sides of the insert material c via the insert material c, the size may be such that the fusion of the expanded particles is not hindered,
The size may be such that at least one of the expanded particles a and b filled on both sides of the insert material c cannot pass through.
Generally, the through hole of the insert material c has an area S
¹ is 0.2 to 0.9 times, preferably 0.5 times the central cross-sectional area S ² = πr ² (r: minimum radius of the expanded particles) of the expanded particles.
The size is about 0.8 times. The thickness of the insert material c is about 1 to 10 mm, preferably about 2 to 8 mm, but is not particularly limited.

The number of through holes formed on the surface of the insert material c may be any number as long as the two unit molded bodies a and b can be fused with sufficient strength. Generally, the ratio of total through-hole area to surface area of insert material is 25-90%, preferably 50.
It is a number such that it is about 80%.

The EPP molded product of the present invention is manufactured by a continuous molding method (for example, JP-A-9-104026 and JP-A-9-104).
No. 027 and Japanese Patent Application Laid-Open No. 10-180888) and the like, and a partitioning material may be added for the production. In the continuous molding method, foamed particles having an increased bubble internal pressure are continuously supplied between belts that continuously move along the upper and lower sides of a passage to obtain a saturated steam supply region (heating region). ) By expanding and fusion-bonding the expanded particles to each other, then passing through a cooling region to cool, then taking out the obtained molded body from the road, and sequentially cutting it to an appropriate length, An EPP molded body is manufactured.

Further, a reinforcing material and / or a surface decoration material can be laminated and integrated on at least a part of the surface of the EPP molded product. Such a laminating method is described in US Pat.
92876, U.S. Patent No. 6,096,417, U.S. Patent No. 6,033,770, U.S. Patent No. 5,474,841, European Patent No. 477476, WO98 / 34770.
No., WO98 / 00287, Japanese Patent No. 309222.
It is described in detail in each publication such as No. 7. Further, in the EPP molded body of the present invention, other insert materials are wholly or partially embedded in the molded body without using the partition material / insert material or together with the partition material / insert material. In this way, the other insert material can be integrated and composite. A method of manufacturing such an insert composite type EPP molded body is described in "US Patent No. 60337".
70, U.S. Pat. No. 5,474,841, Japanese Unexamined Patent Publication No. 59-127714, Japanese Patent No. 3092227, and the like. The overall apparent density of the EPP molded product of the present invention produced by the above method can be arbitrarily selected depending on the purpose, but is usually 10 g / L to 600 g.
The range is / L. The overall apparent density of the EPP molded product is the apparent overall density according to JIS K 7222 (1999). However, the volume of the molded body used to calculate the apparent overall density is the volume calculated from the outer dimensions, but if the shape is complicated and calculation from the outer dimensions is difficult, submerge the molded body in water. The excluded volume is used. Also, the apparent density of each unit molded body is determined by cutting each unit molded body at the central portion of the fusion interface between the unit molded bodies and then using each of the cut unit molded bodies to determine the overall appearance of the EPP molded body. It is measured in the same way as density. The EPP molded product of the present invention is the same as ASTM D in any unit molded product.
The open cell rate based on Procedure C of 2856-70 is preferably 40% or less, more preferably 30% or less, and most preferably 25% or less. The smaller the open cell ratio, the better the mechanical strength.

FIG. 7 shows an explanatory view of one embodiment of the molding apparatus for manufacturing the EPP molded body of the present invention. This device is used for manufacturing a bumper core material for an automobile. As shown in FIG. 7, the apparatus 8 has a male frame 10a and a female frame 10b, which form a cavity corresponding to the shape of a bumper core member, are attached to mold frames 9a and 9b. The male mold 10a is a mold for the vehicle body side of the bumper core material, and is also a mold for forming the backup beam mounting surface side. The female die 10b is a die for forming the outer surface of the vehicle. Further, the molding device 8 includes a partition plate 11 that divides the longitudinal direction into a plurality of cavity spaces. The partition plate 11 is connected to the cylinder rod 13 of the air cylinder 12 for each partition plate, and is formed so as to be able to advance and retreat into the cavity space. The cylinder 12 for advancing and retracting the partition plate 11 is attached to the frame 9a on the beam side, and the partition plate 11 is formed so as to be able to enter the mold through an insertion hole 14 provided in the beam side male mold 10a. Also,
On the female die 10b side on the outer side of the vehicle body, a filling machine 16 for filling the foamed particles into the respective cavities partitioned by the partition plate 11 is provided for each of the partitioned cavities.

The periphery of the insertion hole 14 of the male die 10a is formed as a convex portion 15 protruding toward the inside of the cavity. The male protrusions forming the protrusions 15 are 0.7 to 25.0 mm on both sides of the insertion hole 14 in the longitudinal direction.
It is preferable that the width is formed. The width of the protruding portion is 0.
If it is less than 7 mm, the strength is insufficient and there is a risk of deformation or damage. The height of the convex portion 15 from the molding surface is appropriately determined according to the shape of the bumper core material 1 at the tip on the vehicle outer surface side, the presence or absence of a concave portion, etc., but is 1.0 to 50.0 m.
It is preferable to form m. Since the partition plate is generally formed to have a thickness of 0.5 to 10.0 mm, it is preferable that the width of the convex portion 15 is 2.0 to 62.0 mm as a whole. More preferably, it is formed to be about 30 mm. If the width of the convex portion 15 is less than 2.0 mm, the strength is insufficient, and if it exceeds 62.0 mm, the energy absorption efficiency of the obtained bumper core material may decrease. Further, the width (thickness) of the partition plate 11 is preferably 10 to 85% of the width of the convex portion 15.

As shown in FIG. 8A, the partition plate 11 is preferably formed so that the upper edge and the lower edge thereof are parallel to the method of moving the partition plate. In this case, the part of the female die 10b that contacts the upper and lower edges of the partition plate is formed in a shape corresponding to the upper and lower shapes of the partition plate 11. That is, the shape of the periphery of the part of the female die 10b that contacts the upper end edge 11a and the lower end edge 11b of the partition plate 11 is formed in parallel to the moving direction of the partition plate, like the partition plate 11, and the part of the female die 10b is It is formed in a shape projecting to the inside of the cavity rather than the surrounding portion.

When the peripheral shape of the portion of the partition plate 11 of the female die 10b which contacts the upper end edge 11a and the lower end edge 11b is formed so as to project more toward the inside of the cavity than the peripheral portion, the protrusions 15a and 15b The width is preferably the same as the width of the convex portion 15 around the insertion hole of the partition plate 11.

In order to manufacture a bumper core material using the molding apparatus 8 shown in FIG. 7, first, the partition plate 11 is advanced into the cavities and partitioned into cavities. Next, each of the filling machines 16 fills the cavity with a predetermined expanded particle. The partition plate is ejected after being filled with the expanded particles or while being filled. When each partition in the cavity is completely filled with foamed particles and the partition plate is removed from the inside of the cavity, the cavity is heated by steam etc. and the foamed particles are fused to form a plurality of regions integrally formed. A particle compact is obtained. Then, the foamed particle molded body is taken out from the cavity to obtain the bumper core material A shown in FIG. At this time, as shown in FIG. 9, burrs are generated on the bumper core material A at the top and bottom and in the center, but the burrs remain in the recesses 2 and do not project outward from the beam mounting surface.

To fill the foamed particles into the cavity,
A so-called cracking filling method in which a cavity is provided in the mold and the expanded particles are filled in the cavity with air or the like can be used. With this method, both high-density regions and low-density regions having different properties can be filled at the same time. Alternatively, a so-called compression filling method may be used in which the foamed particles are pressurized to reduce the volume and a pressure difference is provided between the inside of the mold cavity and the tank of the foamed particles. In this case, usually, in order to prevent the foamed particles in the low density region from being compressed and changing the apparent density, the high density region is first filled and then the low density region is filled.

The foamed particles of the raw material with which the cavities are filled may be foamed particles having the same apparent density, particle weight, base resin or the like, or may be different foamed particles. For example, in order to form unit molded bodies with different apparent densities using the same expanded particles, when filling the expanded particles in the respective cavities partitioned by the partition plate, the cavities formed as high density regions are filled. In the case of a method of increasing the amount of pressure applied to the expanded particles more than other methods or by cracking filling, the expanded particles are first filled in the cavity formed as a high density region, and then the gap in the mold is narrowed and then the low density A method of filling foamed particles in the cavity formed as the region may be used.

When the partition plate 11 is retracted from the cavity, it is preferable to retract it until the tip of the partition plate 11 is outside the protruding surface of the convex portion 15 of the male die 10a. That is, when molding is performed with the tip of the partition plate 11 entering the cavity more than the protruding surface of the convex portion 15 of the cavity, the partition plate portion is formed as a concave groove in the concave portion 2 of the obtained bumper core material. . If there is a small groove like the mark of the partition plate on the backup beam mounting surface of the bumper core material,
There is a risk that the shock absorption characteristics will deteriorate when a shock is applied. At this time, burrs are generated in the concave portion, but as described above, the burrs may be processed so that they do not project outward from the beam mounting surface, or even if they do, they do not project.

In the case where the above-mentioned impact absorbing material is composed of two types, a unit molded body composed of specific expanded particles and a unit molded body composed of polypropylene resin expanded particles other than the specific expanded particles, The weight (d1: g) of the unit molded body composed of the specific expanded particles, the high temperature peak heat quantity (C1: J / g) of the expanded particles, and the polypropylene resin expanded particles other than the specific expanded particles When the relationship between the weight of the unit molded body (d2: g) and the expanded particle heat quantity (C2: J / g) of the foamed unit is set so that the following equation (11) is established, the unit is lightweight and has an impact. It becomes highly absorbent. Formula (11): (C1 × d1) / (d1 + d2) + (C2 × d2) / (d1 + d2)> 22 where 22 in the formula is the high-temperature peak calorific value (J /
g).

The EPP molded product of the present invention is preferably used as a shock absorbing material for automobile bumper core materials, helmet core materials and the like.

FIG. 9 is a perspective view showing the external appearance of the main part of the automobile bumper core material A obtained as described above. 10 is a front view of the bumper core material A as seen from the beam side. Further, FIG. 11 shows a vertical sectional view taken along line III-III of FIG. In these figures, 1a is a high-density unit compact, 1b is a low-density unit compact, 2 is a concave portion, and 3 is a heat fusion interface between the high-density unit compact and the low-density unit compact. The automobile bumper core material obtained as described above is a combination of regions having different characteristics and the like (regions having different energy absorption ability, unit molded bodies) formed by partitioning the longitudinal direction into a plurality of predetermined lengths. Therefore, it has excellent impact characteristics, is light in weight and low in cost, and has a concave portion around the boundary of each unit molded body having different characteristics such as the backup beam mounting surface of the core material. Regardless, the burr on the beam surface side of the bumper core material is generated in the recess, so even if it protrudes significantly, it is easy to remove the burr and productivity is not reduced, and a protrusion that obstructs the beam surface of the bumper core material. It is easy to attach to the beam because there is no

[0093]

EXAMPLES The present invention will be described below with reference to examples and comparative examples.

Production Examples of Expanded Particles 1 to 4, 8 and 9 Polypropylene homopolymer resin 10 selected from Table 1
Zinc borate powder (cell adjuster) 0.05 per part by weight
After adding parts by weight and melt-kneading in the extruder, the mixture is extruded into strands from the extruder and the strands are immediately added to 25
Put it in water adjusted to ℃, take it out while quenching it, cool it sufficiently, then pull it up from water, cut the strands so that the length / diameter ratio becomes about 1.0, and average weight per particle. To obtain 2 mg of polypropylene resin particles. Then, in a 400 liter autoclave, 100 kg of the above resin particles, 120 kg of ion-exchanged water at 25 ° C. as a dispersion medium (resin particle / dispersion medium weight ratio 0.83),
Sodium dodecylbenzene sulfonate (surfactant)
0.002 kg and kaolin (dispersant) 0.4 kg, powdered aluminum sulfate (dispersion aid) 0.013 kg, and bis (4-t-butylcyclohexyl) peroxydicarbonate (organic oxide) 0.32 kg were charged, The temperature was raised to 90 ° C. (average heating rate 5 ° C./min) with stirring, and the temperature of 90 ° C. was maintained for 10 minutes. Next, 100 kg of ion-exchanged water and carbon dioxide (foaming agent) are added at 0.4 at equilibrium pressure.
After press-fitting to 9 MPa (G), the temperature was raised to 5 ° C. lower than the foaming temperature in Table 1 with stirring (average heating rate 4 ° C./min), and then with stirring, the foaming temperature in Table 1 was exceeded. The temperature was raised to a temperature lower by 1 ° C (average heating rate 0.16 ° C /
Minutes). After that, carbon dioxide gas (foaming agent) was introduced under pressure so as to have the pressure shown in Table 1, and the temperature was raised to 0.029 ° C./minute to raise the temperature to the foaming temperature. Then, one end of the autoclave was opened to release the contents of the autoclave under atmospheric pressure to obtain expanded particles. Note that carbon dioxide gas was supplied into the autoclave so that the internal pressure of the autoclave during the release of the resin particles from the autoclave was maintained at the internal pressure of the autoclave immediately before the release. The obtained expanded particles were washed with water, subjected to a centrifuge, and then allowed to stand at room temperature under atmospheric pressure of 23 ° C. for 24 hours for curing, followed by high temperature peak calorific value of one expanded particle and high temperature peak of surface layer (surface layer portion). The heat quantity, the high-temperature peak heat quantity of the inside (inner foam layer), and the apparent density of the expanded particles were measured. The results are shown in Table 1. The expanded beads obtained in this Production Example were substantially non-crosslinked (the boiling xylene insoluble content was 0 in all cases). Production Examples 5 to 7 of Expanded Particles Polypropylene resin particles were obtained in the same manner as in Production Example 1 of expanded particles. Then, in a 400 liter autoclave, 100 kg of the above resin particles, 220 kg of ion-exchanged water, sodium dodecylbenzenesulfonate (surfactant) 0.1.
005 kg and kaolin (dispersant) 0.3 kg powdered aluminum sulfate (dispersion aid) 0.01 kg were charged, and then carbon dioxide (foaming agent) was added at equilibrium pressure of 0.49 MPa.
After press-fitting so as to obtain (G), the temperature was raised to 5 ° C lower than the foaming temperature in Table 1 with stirring (average heating rate 4 ° C).
Then, the temperature was raised to 1 ° C. lower than the foaming temperature shown in Table 1 (average heating rate 0.16 ° C./min) with stirring. After that, carbon dioxide gas (foaming agent) was introduced under pressure so as to have the pressure shown in Table 1, and the temperature was raised to 0.029 ° C./minute to raise the temperature to the foaming temperature. Next, one end of the autoclave was opened and the contents of the autoclave were discharged into the space under atmospheric pressure to obtain expanded particles. Note that carbon dioxide gas was supplied into the autoclave so that the internal pressure of the autoclave during the release of the resin particles from the autoclave was maintained at the internal pressure of the autoclave immediately before the release. The obtained expanded particles were washed with water and subjected to a centrifuge, and then allowed to stand at atmospheric pressure for 24 hours for curing. layer)
The high-temperature peak calorific value and apparent density were measured. The results are shown in Table 1. The expanded beads obtained in this Production Example were substantially non-crosslinked (the boiling xylene insoluble content was 0 in all cases).

Examples 1 to 5 and Comparative Examples 1 to 5 In a molding apparatus, length 700 mm × width 200 mm × thickness 50
A molding apparatus equipped with a mold (comprising a male mold and a female mold) having a molding space of mm was prepared. This molding apparatus is provided with a partition member made of stainless steel that can move back and forth in the entire mold at a position 150 mm from each end in the length direction of the mold. These two partition materials partition the molding space into three compartments when the expanded particles are filled in the mold, and in the present example and comparative example, after the expanded particles were filled and before the heating. It is to be exited from the molding space. Using the above molding apparatus, as shown in Table 2 for each of the expanded particles obtained in the above-mentioned expanded particle production example, while filling the high-density particles A in the compartments at both ends in the molding space partitioned by the partition material, Low-density particles B were filled in the central compartment, and molding was performed as follows. When filling the foamed particles, a slight gap (about 10 mm) was opened without closing the mold completely (thickness 5
After filling the 0 mm direction with 60 mm) and then completely clamping the mold, the air in the mold is exhausted with steam,
The steam adjusted to 0.8 MPa (G) was introduced from the male mold side until the pressure reached 0.04 MPa (G) lower than the molding pressure in Table 2 (one-side heating), and then the pressure was formed in the table. After introducing steam from the female mold side until the pressure reaches 0.02 MPa (G) lower than the pressure (reverse one-side heating), steam is introduced from both male and female mold sides to reach the molding pressure in Table 2 and then the pressure. After 20 seconds of holding and heating (main heating), molding was performed (Comparative Examples 1 to 3 did not hold the molding and started cooling immediately after reaching the molding pressure). Meanwhile, the time from the start of heating on the one hand to the molding pressure in Table 2 was measured, and the pressurization rate calculated based on this was shown in Table 2. After molding, after water cooling until the surface pressure of the molded body in the mold reaches 0.059 MPa (G), the molded body is taken out of the mold and kept at 60 ° C. for 2 hours.
After drying for 4 hours, the molded body is 23 ° C., relative humidity 50%
Moved to my room.

The molding pressure in Table 2 is 24 after the molded body after drying is moved to a room at 23 ° C. and a relative humidity of 50%.
After a lapse of time, after making a cut of about 10 mm in the thickness direction of the molded body so as to divide the length of each unit molded body into two parts with a cutter knife on one surface of the surface of 700 mm long × 200 mm wide In a test of bending and breaking the molded body from the cut portion, the ratio (b /) of the number (n) of the expanded particles present in the fracture surface and the number (b) of the expanded particles that have been material-broken
The value of n) is 0.
It means the saturated steam pressure required for molding when it becomes 50 or more. Incidentally, Comparative Example 4 has the same pressure resistance of the molding machine of 0.4
The value of (b / n) was less than 0.50 even when molded at a molding pressure of 4 MPa (G). The number (n) of the expanded particles is the sum of the number of the expanded particles separated between the expanded particles and the number (b) of the expanded particles whose material is destroyed in the expanded particles. Further, the larger the value of (b / n), the larger the bending strength and the tensile strength of the molded body, which is preferable. Further, the melting point in Table 1, E1 and E2 in Table 2 were measured using a Shimadzu Corporation heat flux differential scanning calorimeter “DSC-50” manufactured by Shimadzu Corporation.

The evaluation methods and evaluation criteria for the properties of the molded products shown in Table 2 are as follows. (1) Evaluating whether the (b / n) ratio described above is 0.50 or more using a molding machine having a fusion resistance pressure resistance of 0.44 MPa (G). 0.50 or more × (b / n) ratio is less than 0.50 (2) There are few gaps between the foamed particles such as irregularities on the surface of the surface molding,
Visual evaluation of whether the appearance is good ○: Good ×: Poor (3) Shape stability After the molded body after drying was moved to a room at 23 ° C and a relative humidity of 50% and left for 24 hours. While measuring the length in the thickness direction (thickness) at each central portion of the high-density unit molded bodies located at both ends of the molded body (the central portion in the length direction and the central portion in the width direction of each unit molded body), The length in the thickness direction (thickness) is measured at the center of the low-density unit molded body located between the two high-density unit molded bodies (the center in the length direction and the center in the width direction of each unit molded body), It was evaluated as follows. ◎ The size of the measurement point of the unit molded body is 49.0 mm
It is in the range of up to 50.0 mm. ○: The size of the measurement point of the unit molded body is 48.0 mm
It is in the range of up to 51.0 mm. However, the case where it corresponds to ◎ is excluded. △: The dimension of the measurement point of the unit molded body is 47.0 mm
It is in the range of up to 52.0 mm. However, it is excluded when it corresponds to ◎ or ○. X: The dimension of the measurement point of the unit molded body is 47.0 mm
Below or above 52.0 mm. (4) Compressive strength Compressive strength means the molded body after drying at 23 ° C and relative humidity of 50
% After moving to a room of 14%, a test piece (one whose entire surface has been cut) obtained by cutting each unit molded body to have a length of 50 mm, a width of 50 mm and a thickness of 25 mm is used. , JIS Z 0234 (1976) A
According to the method, a compression test is performed until the strain reaches 55% under the conditions of a test piece temperature of 23 ° C. and a load speed of 10 mm / min, the stress at 50% strain is read from the obtained stress-strain diagram, and the compressive strength And

From the above results, the following can be understood. Examples 1 to 4 show examples in which both the high-density unit molded body and the low-density unit molded body were produced from the specific expanded particles of the present invention, but the shape stability of all unit molded bodies was remarkably excellent. There is. Example 5 is an example in which a high-density unit molded body is manufactured with expanded particles obtained by using a polypropylene resin having a small tensile modulus, and a low-density unit molded body is manufactured with the specific expanded particles of the present invention. Show. By adjusting the cooling of the molded body immediately after molding to the high density unit molded body side, it is possible to make the shape stability of the high density unit molded body side excellent,
The shape stability of the low-density unit molded body produced from the specific expanded particles of the present invention was remarkably excellent. Comparative Examples 1 to 3 show examples in which both the high-density unit molded body and the low-density unit molded body were manufactured from polypropylene resin expanded particles having a small tensile elastic modulus other than the specific expanded particles of the present invention. Comparative Examples 1 to 3 were molded under the same conditions except that the cooling time immediately after molding was different. In Comparative Example 1 in which the cooling time is short, the shape stability of the high-density unit compact is remarkably inferior. Comparative Example 1
In Comparative Examples 2 and 3 in which the cooling time was extended, the shape stability of the low-density unit compact was poor. That is, it can be seen that it is difficult to improve the shape stability of both the high-density unit molded body and the low-density unit molded body unless the unit molded body manufactured from the specific expanded particles of the present invention is present. . Comparative Example 4
A high-density unit molded product is produced from polypropylene resin expanded particles having a high high-temperature peak calorific value other than the specific expanded particles of the present invention, and a low-density unit molded product having a small tensile elastic modulus other than the specific expanded particles of the present invention is polypropylene. An example manufactured with expanded resin particles is shown. As a result, although the high-density unit molded body was molded by a steam pressure which was the same as the pressure resistance of the molding machine, the fused particles and the surface properties between the expanded particles were poor. Further, the low-density unit molded body had a markedly poor shape stability. In Comparative Example 5, a high-density unit molded body was produced from polypropylene-based resin foamed particles having a small tensile elastic modulus other than the specific foamed particles of the present invention, and the low-density unit molded body was manufactured at a high temperature other than the specific foamed particles of the present invention. An example of production with expanded polypropylene resin particles having a small peak calorie is shown. Although the cooling of the molded body immediately after molding was adjusted to the side of the high-density unit molded body having a low resin strength, the low-density unit molded body was remarkably inferior in shape stability.

[0099]

[Table 1]

[0100]

[Table 2]

[0101]

According to the manufacturing method of the present invention, the inside of the mold is divided into two or more compartments, each compartment is filled with the polypropylene resin expanded particles, and then the polypropylene resin expanded particles are molded in the mold. In the method for producing a polypropylene-based resin in-mold foam molded article having a portion in which two or more unit molded articles having different characteristics are adjacently integrally molded,
The expanded particles to be filled in at least one of the compartments are made of polypropylene resin having a tensile elastic modulus of 1200 MPa or more, and the relationship between the apparent density D1 (g / L) and the high temperature peak heat quantity E1 (g / J) is as described above. Formulas (1) and (2)
Since the expanded particles satisfy the above condition, expansion of the final molded product does not occur even if the molded product is cooled immediately after heating during molding for a short time, and there is no shrinkage even if cooling is excessive. Almost never. Therefore, even if integrally molded so as to include a unit molded body part made of specific expanded particles and a unit molded body part made of expanded particles other than the specific expanded particles, foaming other than the specific expanded particles If the cooling during molding is adjusted so that convex bulges on the outside and concave sinks (contraction) on the inside of the unit molded body made of particles do not occur, the entire molded body will be convex to the outside. It is possible to easily obtain an in-mold molded body having a small bulge and a concave shape (contraction) that is concave inside. Furthermore, in the case where all the unit molded bodies are manufactured from this specific expanded particle, it is easier to obtain an in-mold molded body with less bulging that is convex on the outside and concave that is concave on the inside of the resulting molded body. To be Further, since the molded product using the specific expanded particles has high rigidity such as compressive strength, an in-mold molded product excellent in lightness can be easily obtained. Furthermore, the amount of heat of the high temperature peak of the foamed particles (Δ
If the relationship between H _s ) and the heat quantity (ΔH _i ) of the high temperature peak of the internal foam layer of the expanded particles is ΔH _s <ΔH _i × 0.86, the rigidity of the molded body part made of the expanded particles is reduced. In-mold molding is possible with low-temperature steam without doing so. Also,
The in-mold molded body of the present invention has two adjacent unit molded bodies,
It is of high quality with little or no irregularities such as swelling and sink marks and poor appearance. The foamed molded product obtained by the present invention is suitable for use as a bumper core material for automobiles, a shock absorbing material arranged in the door of an automobile, a container, a helmet core material and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a chart of a first DSC curve of expanded polypropylene resin particles having a high temperature peak.

FIG. 2 Second DSC of polypropylene resin particles
It is a figure which shows an example of the chart of a curve.

FIG. 3 is a structural explanatory view of one example of the in-mold foam molded article of the present invention.

FIG. 4 is a structural explanatory view of another embodiment of the in-mold foam molded article of the present invention.

FIG. 5 is a structural explanatory view of still another embodiment of the in-mold foam molded article of the present invention.

FIG. 6 is an explanatory diagram of a fusion bonding interface when a porous member is present at the fusion bonding interface between two adjacent unit molded bodies.

FIG. 7 is an explanatory view of a bumper core forming device.

8A and 8B are views for explaining the action of the partition plate of the molding die of FIG. 7, where FIG. 8A shows a state where the partition plate has entered the cavity, and FIG. 8B shows that the partition plate has withdrawn from the cavity. Indicates the status.

FIG. 9 is a perspective view showing an external appearance of a main part of a bumper core material for an automobile.

FIG. 10 is a front view of the bumper core member of FIG. 9 seen from the vehicle body mounting side.

11 is a vertical cross-sectional view taken along the line III-III in FIG.

[Explanation of symbols]

(Figs. 3 to 6) 1-3 unit compacts 11 to 15 unit compacts a, b unit compact 4, 5, c Fusion interface between unit compacts 16-19 Units Fusion interface between unit compacts (Figs. 7 to 11) A car bumper core material 1a High density area 1b Low density area 2 recess 3 Border between high density area and low density area 8 molding equipment 9a, 9b Mold frame 10a male type 10b female 11 Partition plate (partition material) 12 air cylinders 13 cylinder rod 14 insertion holes 15 convex

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hidehiro Sasaki             10-3 Satsukicho, Kanuma City, Tochigi Prefecture             KSP Kanuma Research Institute F-term (reference) 4F074 AA24 AD08 AF03 AG20 BA32                       CA34 CC03X CC04X CC04Y                       DA02 DA08 DA24 DA33                 4F212 AA11 AE07 AG20 AH24 UA02                       UC06 UK03

Claims (8)

[Claims] 1. Two or more unit moldings having different characteristics by partitioning a mold into two or more compartments, filling each compartment with polypropylene-based resin foamed particles, and then molding the polypropylene-based resin foamed particles in a mold. In a method for producing a polypropylene-based resin in-mold foam molded article having a body adjacently and integrally molded, the foamed particles to be filled in at least one of the compartments are polypropylene-based resin or polypropylene having a tensile elastic modulus of 1200 MPa or more. It is composed of a resin composition, and the relationship between the apparent density D1 (g / L) and the high temperature peak heat quantity E1 (g / J) is expressed by the following equations (1) and (2).
A method for producing a polypropylene-based in-mold foam molded article, characterized in that the expanded particles satisfy the above requirements. Formula (1): 20-0.014 × D1 ≦ E1 ≦ 65-0.072 × D1 Formula (2): 10 ≦ D1 ≦ 700 2. A heat quantity (ΔH _s ) at an endothermic curve peak of a foamed particle made of a polypropylene resin or a polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more on the high temperature side of a surface layer portion and internal foaming of the foamed particle. The polypropylene resin in-mold foamed molded product according to claim 1, wherein the relationship with the heat quantity (ΔH _i ) of the endothermic curve peak existing on the high temperature side of the layer is ΔH _s <ΔH _i × 0.86. Manufacturing method. 3. A structure comprising a plurality of unit moldings made of an in-mold foam molding of polypropylene-based resin foamed particles, wherein a plurality of unit moldings are heat-sealed, and (i) the characteristics of the two adjacent unit moldings are (Ii) the expanded particles constituting at least one unit molded body (F) have a tensile elastic modulus of 12;
It is a polypropylene-based resin or polypropylene-based resin composition having a pressure of 00 MPa or more, and (iii) the unit molded body has an endothermic curve on a higher temperature side than an intrinsic endothermic curve peak derived from heat of fusion in a DSC curve by differential scanning calorimetry. The presence of a peak, (iv) in the unit molded body (F), its apparent density D2 (g / L) and the melting of the endothermic curve peak at the high temperature side of the polypropylene resin foam constituting the unit molded body (F) The amount of heat E2 (J / g) has a relationship satisfying the following formulas (3) and (4), formula (3): 20-0.020 × D2 ≦ E2 ≦ 65-0.100 × D2 formula (4): A polypropylene-based resin in-mold foam molded article characterized by 10 ≦ D2 ≦ 500. 4. An endothermic curve peak calorific value (ΔH _s ) of a foamed particle made of a polypropylene resin or a polypropylene resin composition having a tensile elastic modulus of 1200 MPa or more on the high temperature side of the surface layer portion and internal foaming of the foamed particle. The polypropylene resin in-mold foam molded article according to claim 3, wherein the relationship with the heat quantity (ΔH _i ) of the endothermic curve peak existing on the high temperature side of the layer is ΔH _s <ΔH _i × 0.86. . 5. One of the two adjacent unit molded bodies is a high density unit molded body having an apparent density of 30 to 450 g / L, and the other unit molded body has an apparent density of 15 to
The polypropylene resin in-mold foam molding according to claim 3 or 4, which is a low-density unit molded body having an apparent density of 90 g / L and lower than the apparent density of the high-density unit molded body. body. 6. The polypropylene resin mold according to claim 5, wherein the apparent density of the high-density unit molded body is 1.2 to 25 times the apparent density of the low-density unit molded body. Molded body. 7. The polypropylene resin in-mold foam molded article according to claim 3, wherein the in-mold foam molded article is an impact absorbing material. 8. The polypropylene resin in-mold foam molded article according to claim 7, wherein the impact absorbing material is a bumper core material for automobiles.