JP2005240025A - Thick foam molded article and method for producing the same - Google Patents

Abstract

【Task】
The present invention provides a thick foamed molded article obtained by in-mold molding of crystalline thermoplastic resin foamed particles, and a method for producing the same, which is excellent in the fusibility of the foamed particles up to the inside of the molded body. Is.
[Solution]
The present invention relates to a foamed molded product having a size capable of cutting out a sphere having a diameter of 200 mm obtained by in-mold molding of foamed particles of a thermoplastic resin, wherein the foamed particles are in a foamed state made of a crystalline thermoplastic resin. The Vicat softening temperature is 15 ° C. or more lower than the Vicat softening temperature of the core layer and the crystalline polyolefin polymer whose melting point is 15 ° C. or more lower than the melting point of the thermoplastic resin constituting the core layer or the thermoplastic resin constituting the core layer. A thick foam characterized by comprising a substantially non-foamed coating layer made of an amorphous polyolefin polymer and having a fusion rate of the foamed particles in the foamed molded product of 50% or more The present invention relates to a molded body and a manufacturing method thereof.
[Selection] Figure 1

Description

  The present invention relates to a thick foam molded article having excellent internal fusion properties obtained by in-mold molding foamed particles of a crystalline thermoplastic resin, and a method for producing the same.

  Crystalline thermoplastic resin foams, such as polyethylene resins and polypropylene resins, that exhibit a clear endothermic peak in heat flux differential scanning calorimetry, have excellent chemical resistance, buffering properties, and are difficult to chip in brittleness. It is preferably used as a cushioning material.

  A foam molded body obtained by a method called in-mold molding (hereinafter simply referred to as in-mold molding) in which foamed particles of a crystalline thermoplastic resin are filled in a cavity of a molding die and the foamed particles are heated by steam and fused together. Until now, the thickness of the “molded body” may be 150 to 200 mm. The reason is that the fusion between the expanded particles is remarkably reduced inside the expanded molded body as the thickness is increased. When the cross section of such a thick molded body is observed, the expanded particles are sufficiently fused only to a depth of about 70 to 80 mm from the outer surface. This is considered to be due to insufficient supply of steam to the center of the molded body and insufficient heating. Therefore, when higher pressure steam is used to improve the fusibility of the expanded particles, the dent (so-called hourglass shrinkage) at the center of the outer surface of the molded body immediately after molding increases, and the molded body is molded after in-mold molding. Only a deformed molded body whose shape cannot be recovered even after curing in a room set at about 50 to 80 ° C. can be obtained. In order to suppress this deformation, there is a method in which the foam particles are impregnated with air to increase the internal pressure of the foam particles. However, in that method, the foamed particles expand before reaching a temperature at which the foamed particles are sufficiently fused during molding in the mold, so that steam is not sufficiently supplied to the central portion in the cavity, and the surface layer of the molded body Foamed particles existing only in the thickness of several millimeters are sufficiently fused together, and the foamed particles inside are not fused together (so-called pomegranate phenomenon).

  As described above, in the in-mold molding of the foamed particles of the crystalline thermoplastic resin, it is impossible to obtain a thick molded body excellent in internal fusion properties. In the molded body used, a highly productive board production method such as a method of slicing a thick molded body of a block-like polystyrene resin foam to produce a board has been a concern in the industry.

  As a method for obtaining a thick foamed molded article by in-mold molding of polyolefin resin foamed particles, for example, in Patent Document 1, after introducing foamed particles into a mold, a predetermined preheating temperature within a range where fusion does not proceed is reached. After the caulking, the method for producing a thick molded body is disclosed in which the introduction of steam is stopped or introduced and left to steam for a predetermined time at a predetermined temperature, and then heated and molded. In this method, a specific preheating step and a steaming step are adopted in the molding process to improve the fusion property between the foamed particles inside the molded body, and in the in-mold molding of polyolefin resin foamed particles, It discloses that molding is possible.

However, the molding method described in the above-mentioned patent is not a heating method based on steam pressure control that is performed in advance by molding in a general molding machine, but a temperature sensor on the inner surface of the mold in the preheating process. In the method of controlling the steam pressure by detecting a temperature of the molded body itself by installing a plurality of temperature detection sensors of the molded body inside 3 to 50 mm from the inner surfaces of the male and female molds, There is a problem that a special control mechanism is required and a general molding machine for polyolefin foam particles cannot be used as it is.
In addition, when trying to obtain a foam having a high expansion ratio such that the expansion ratio of the obtained molded body exceeds 30 times (the apparent density is less than 30 g / L), the expanded particles having an increased internal pressure are molded in the mold. In this case, since the expansion of the foamed particles in the surface layer portion of the molded body is extremely advanced, the fusion rate of the foamed particles inside the molded body and the molded body with a thickness exceeding 200 mm (hereinafter, It was sometimes described as “internal fusion rate”.

  Patent Document 2 discloses a specific example in which a foamed core layer made of a crystalline thermoplastic resin and foamed particles are composed of an ethylene polymer and a substantially non-foamed coating layer. Expanded particles having a structure have been proposed. However, the foamed molded body specifically shown in this patent is only a thin molded body having a length of 200 mm, a width of 300 mm, and a thickness of 25 mm, and a thick molded body having excellent internal fusion properties is not disclosed. Absent.

Japanese Patent No. 3146004 JP-A-10-77359

In view of the above-described problems of the prior art, the present invention provides a foamed molded product obtained by in-mold molding of crystalline thermoplastic resin foamed particles, and has excellent fusion properties between the foamed particles up to the inside of the thick molded product. An object of the present invention is to provide a thick foam molded article and a method for producing the same.
More specifically, the present invention relates to a method in which foamed particles composed of a foamed core layer and a substantially non-foamed coating layer are molded in-mold, and the foamed particles are fused to each other inside the foamed molded product. The present invention provides a thick foam molded article having excellent properties.

  That is, the present invention relates to (1) a foamed molded product having a size capable of cutting a sphere having a diameter of 200 mm obtained by in-mold molding of thermoplastic resin foamed particles, wherein the foamed particles are made of a crystalline thermoplastic resin. The vitrified softening temperature is higher than the vicat softening temperature of the foamed core layer and the crystalline polyolefin polymer having a melting point of 15 ° C. lower than the melting point of the thermoplastic resin constituting the core layer or the thermoplastic resin constituting the core layer. It is composed of a substantially non-foamed coating layer made of a non-crystalline polyolefin polymer having a low temperature of 15 ° C. or more, and the fusion rate of the foamed particles inside the foamed molded product is 50% or more. The present invention relates to a thick foam molded article.

  Preferably, (2) the foamed molded article according to (1) above, wherein the foamed molded article is a cube or a rectangular parallelepiped having an apparent density of 10 g / L or more and less than 30 g / L and a minimum thickness of 300 to 1000 mm. (3) The thick foam molded article according to (1) or (2), wherein the crystalline thermoplastic resin constituting the core layer of the foamed particles is a polyolefin resin, (4) The thick foamed molded article according to (1) or (2) above, wherein the crystalline thermoplastic resin constituting the core layer of the foamed particles is a polypropylene resin.

  The present invention also provides (5) a foamed molded article having a size capable of cutting out a sphere having a diameter of 200 mm by filling foamed particles of a thermoplastic resin into a cavity, heating the foamed particles with steam and fusing them together. In the production method, the foamed particles comprise a foamed core layer made of a crystalline thermoplastic resin, and a crystalline polyolefin polymer or core having a melting point lower by 15 ° C. or more than the melting point of the thermoplastic resin constituting the core layer A meat characterized by comprising a substantially non-foamed coating layer comprising an amorphous polyolefin polymer having a Vicat softening temperature of 15 ° C. or more lower than the Vicat softening temperature of the thermoplastic resin constituting the layer The present invention relates to a method for producing a thick foam molded article.

Preferably, (6) the foamed particles have a bulk density of 10 to 300 g / L and an internal pressure of 0.005 MPa (G) or more, and the method for producing a thick foamed molded article according to (5) above, (7) Fill the foamed particles in the cavity, preheat the foamed particles at a steam pressure of 0.05 MPa or more lower than the steam pressure during the main heating, and then perform the main heating with high-pressure steam to fuse the foamed particles together. A method for producing a thick foam molded article according to (5) or (6), characterized in that
Is a summary.

  The foamed molded product of the present invention is a thick foamed molded product capable of cutting out a sphere having a diameter of 200 mm, and has a high internal fusion rate, so it has excellent workability such as slicing and cutting, and is processed during processing. The product does not break or break, and the beads are not easily chipped. When cutting out into a plate shape and using it as a cushioning material, etc., even when the plate-like product is punched and used as a cushioning material, etc., it is used up to the center of the foamed molded product be able to.

  Moreover, when using a foaming molding as it is, even if it uses it in the state where a big load is applied locally or a bending load is applied, it is hard to produce a fracture | rupture.

  According to the present invention, as described above, by using the foamed particles having a composite structure composed of a specific core layer and a coating layer, the fusion property between the foamed particles in the entire foamed molded product is extremely good. In addition, even if in-mold molding is performed using expanded particles with an increased internal pressure, the internal fusion rate does not drop significantly, so the excellent fusion property between the expanded particles inside the molded product is excellent. A thick foamed molded article having an expansion ratio can be produced.

  The thick foam molded article of the present invention is a foam molded article having a size capable of cutting a sphere having a diameter of 200 mm. The reason why the thick foam molded body is expressed as a foam molded body having a size capable of cutting out a sphere having a diameter of 200 mm in the present invention is as follows. When expressed by the minimum dimension or thickness, the expression may not be suitable for a spherical shape or a special shape having irregularities. On the other hand, in a sphere shaped body having a diameter of 200 mm and a cuboid shaped body having a side of 200 mm, the difficulty for achieving sufficient fusion of the expanded particles near the center of the shaped body is substantially the same. For example, in the case of a cylindrical molded body having an outer diameter of 250 mm, an inner diameter of 200 mm, and a height of 250 mm, it is an apparently thick molded body, but the substantial thickness is 50 mm. The difficulty for achieving sufficient fusion between the expanded particles is not high. In addition, a sphere having a diameter of 200 mm cannot be cut out with this shape. Based on the above, as a representative of a thick foamed molded article in which it is difficult to increase the internal fusion rate, it was expressed as a foamed molded article having a size capable of cutting a sphere having a diameter of 200 mm.

  The expanded particles used in the present invention have a composite structure composed of a foamed core layer and a substantially non-foamed coating layer. The core layer is made of a crystalline thermoplastic resin. In the present invention, the crystalline thermoplastic resin employs “when melting temperature is measured after performing a certain heat treatment” described in JIS K7121 (1987) (in addition, heating in condition adjustment of the test piece) Use a heat flux differential scanning calorimeter (hereinafter referred to as “DSC device”) and draw a DSC curve at a heating rate of 10 ° C./min. It means a thermoplastic resin that exhibits an endothermic peak accompanying melting of the thermoplastic resin in the obtained DSC curve.

  Examples of the crystalline thermoplastic resin constituting the core layer of the expanded particles used in the present invention include polyolefin resins such as polypropylene resin, polyethylene resin, polybutene resin, and polymethylpentene resin, crystalline polystyrene resin, and thermal resin. Plastic polyester resins, polyamide resins, fluororesins, and the like are mentioned. Propylene homopolymers, polypropylene random copolymers and polypropylene block copolymers obtained from propylene and α-olefins other than propylene and / or ethylene preferable.

  The polyolefin resin exemplified above means a resin in which the structural unit obtained from the olefin is 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%. Similarly, the polypropylene resin means a resin in which the structural unit obtained from propylene is 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%. Specific examples of preferred polypropylene resins include propylene homopolymers, copolymers of propylene and other monomers, or mixtures of two or more thereof. Similarly, for example, a polyethylene resin means a resin in which a structural unit obtained from ethylene is 50 mol% or more, preferably 60 mol% or more, more preferably 80 mol% to 100 mol%.

  In the present invention, another thermoplastic polymer may be mixed with the polyolefin resin such as polypropylene resin and polyethylene resin. The addition amount of the other thermoplastic polymer is preferably 100 parts by weight or less, more preferably 50 parts by weight or less, still more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight with respect to 100 parts by weight of the polyolefin resin. Hereinafter, it is most preferably mixed in the range of 5 parts by weight or less.

  In the present invention, the resin constituting the core layer may contain additives such as a catalyst neutralizing agent, a lubricant and a crystal nucleating agent. However, it is desirable that the amount be as small as possible within the range not impairing the object of the present invention. The addition amount of the additive is preferably 40 parts by weight or less, more preferably 30 parts by weight or less with respect to 100 parts by weight of the crystalline thermoplastic resin, although it depends on the kind of additive and the purpose of use. Yes, more preferably 0.001 to 15 parts by weight.

  The crystalline thermoplastic resin preferably has a melting point (Tm) of 100 ° C. to 250 ° C., and 110 ° C. to 170 ° C. in view of thermal processability and heat resistance in in-mold molding with high-pressure steam of expanded particles. The thing of 120 degreeC is still more preferable, and the thing of 120 to 165 degreeC is especially preferable. The crystalline thermoplastic resin preferably has a Vicat softening temperature of 70 ° C to 200 ° C, more preferably 90 ° C to 160 ° C, and particularly preferably 110 ° C to 150 ° C.

  In this specification, as the melting point (Tm), “when melting temperature is measured after performing a certain heat treatment” described in JIS K7121 (1987) is adopted (in addition, the heating rate in adjusting the condition of the test piece) The cooling rate is 10 ° C./min in all cases.) A DSC curve is drawn at a heating rate of 10 ° C./min using a DSC apparatus, and the endothermic peak accompanying melting of the resin on the obtained DSC curve. It is a value calculated as the apex temperature of. In addition, when a plurality of endothermic peaks are observed on the DSC curve, the peak temperature of the endothermic peak having the highest peak height of the endothermic peak with respect to the high temperature side baseline is defined as the melting point. Moreover, when there are a plurality of endothermic peaks showing the highest apex height, the arithmetic average value of the apex temperatures of these endothermic peaks is taken as the melting point.

  In this specification, the Vicat softening temperature is a Vicat softening temperature measured by the A50 method based on JIS K7206 (1999).

  In the foamed particles used in the present invention, the polyolefin polymer that forms the coating layer is a crystal that forms the core layer in the case of a crystalline polymer that exhibits a clear endothermic peak by the melting point measurement method described above. The melting point of the polyolefin polymer is required to be 15 ° C. or more lower than the melting point of the thermoplastic resin. In the case where the polyolefin polymer is an amorphous polymer that does not show a clear endothermic peak in the above melting point measurement method, from the Vicat softening temperature of the crystalline thermoplastic resin forming the core layer, The Vicat softening temperature of the polyolefin polymer is required to be 15 ° C. or lower.

In this way, foamed particles having a composite structure in which the melting point or Vicat softening temperature of the polyolefin polymer forming the coating layer is 15 ° C. lower than the melting point or Vicat softening temperature of the crystalline thermoplastic resin forming the core layer are used. In addition, by producing a foam molded body having a size capable of cutting out a sphere having a diameter of 200 mm by an in-mold molding method, a thick foam molded body having excellent fusion property between the expanded particles is obtained up to the central portion inside the molded body. be able to.
This is considered to be because the expanded particles used in the present invention can suppress the expansion of the expanded particles at a heating temperature at which the expanded particles can be fused together.

  Therefore, in the foamed particles used in the present invention, when the polyolefin polymer forming the coating layer is a crystalline polymer, the melting point is higher than the melting point of the crystalline thermoplastic resin forming the core layer. Is required to be as low as 15 ° C. or higher, and the melting point is preferably as low as 20 ° C. or lower, more preferably 20 ° C. to 60 ° C. lower, and particularly preferably 20 ° C. to 40 ° C. lower. Further, when the polyolefin polymer forming the coating layer is an amorphous polymer, the Vicat softening temperature may be 15 ° C. or more lower than the Vicat softening temperature of the crystalline thermoplastic resin forming the core layer. The Vicat softening temperature is preferably 20 ° C. or more lower, more preferably 20 ° C. to 60 ° C. lower, and particularly preferably 20 ° C. to 40 ° C. lower.

  On the other hand, when considering the heat resistance of the foamed molded article, the melting point of the crystalline polyolefin polymer forming the coating layer is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, 90 ° C. The above is particularly preferable. Further, the Vicat softening temperature of the amorphous polyolefin polymer forming the coating layer is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, still more preferably 70 ° C. or higher, and particularly preferably 80 ° C. or higher.

  In the present specification, unless otherwise distinguished, the crystalline polyolefin polymer and the amorphous polyolefin polymer are collectively referred to as “polyolefin polymer”.

  When the difference between the melting point or Vicat softening temperature of the crystalline thermoplastic resin forming the core layer of the foamed particle and the melting point or Vicat softening temperature of the polyolefin polymer forming the coating layer is less than 15 ° C, During in-mold molding, it becomes difficult to obtain surface-melting type foam particles that can suppress the expansion of the foam particles at a heating temperature at which the foam particles can be fused together, and the expansion of the foam particles precedes the surface melting of the foam particles. Resulting in. As a result, when trying to obtain a thick foam molded article by in-mold molding, there is almost no gap between the foam particles near the mold surface, and there is sufficient steam inside the foam molded article. It is not perfect, and the fusion of foamed particles tends to occur in the thick molded body. Furthermore, when the difference between the melting points of the two is small, or when the difference between the Vicat softening temperatures is small, a large number of cell structures are easily formed in the coating layer when the foamed particles are produced, and the coating layer is substantially non-exposed. There is a possibility that it becomes difficult to obtain a foamed state. In the case of foamed particles in which the coating layer is in a foamed state, when a foamed molded product is produced, there is a concern that the fusion force between the foamed particles may be reduced.

In the present invention, the substantially non-foamed state includes not only the case where no bubbles are present (including the case where bubbles are once formed but melted and destroyed), as well as a few minute bubbles. The case where it exists in is also included. If there are a few minute bubbles, these bubbles may be those that do not communicate with each other, or those that break and communicate with each other. It is preferable that the maximum length of the bubble observed with a microscope does not exceed 10 μm. When bubbles having a maximum length of 10 μm or less are present, the number of bubbles is preferably 3 or less and more preferably 2 or less per 500 μm ² of the cut surface of the coating layer.

As described above, the polyolefin polymer forming the coating layer of the expanded particles of the present invention includes those showing a melting point and those showing no melting point.
Examples of the crystalline polyolefin polymer having a melting point include, for example, high-pressure low-density polyethylene resin, linear low-density polyethylene resin, linear ultra-low-density polyethylene resin, vinyl acetate, unsaturated carboxylic acid ester, unsaturated Examples thereof include a polyethylene copolymer obtained from a monomer such as carboxylic acid and vinyl alcohol and ethylene. The crystalline polyolefin polymer may be a polypropylene resin or a polybutene resin as long as it satisfies the condition that the melting point is 15 ° C. or more lower than the melting point of the crystalline thermoplastic resin forming the core layer. Also good.

Examples of the amorphous polyolefin polymer that does not exhibit a melting point include polyethylene-based rubbers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-acrylic rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, and polyolefin. Examples thereof include elastomers and amorphous polyolefin resins.
Among the above polyolefin polymers, a high-pressure low-density polyethylene resin and a linear low-density polyethylene resin are preferable. As a linear low density polyethylene resin, for example, a linear low density polyethylene resin polymerized using a metallocene polymerization catalyst (hereinafter referred to as MeLLDPE) is preferable.
In addition, said polyolefin polymer is used independently, and 2 or more types can be mixed and used for it.

In the present invention, a polymer composition obtained by mixing a polyolefin polymer with the same crystalline thermoplastic resin as that of the core layer can also be suitably used as the coating layer. According to such a polymer composition, when the core layer and the coating layer are difficult to thermally bond to each other, there is an advantage that the adhesion between the core layer and the coating layer is improved.
The blending ratio of the same crystalline thermoplastic resin as that of the core layer mixed in the coating layer is 1 to 100 parts by weight and 2 to 80 parts by weight with respect to 100 parts by weight of the polyolefin polymer. The amount is preferably 5 to 50 parts by weight. In the polymer composition, if the blending ratio of the same crystalline thermoplastic resin as the core layer is too large, the crystalline thermoplastic resin tends to form a continuous phase (sea phase). There is a possibility that it cannot be a surface-melting type foamed particle. In the above polymer composition, if the blending ratio of the same crystalline thermoplastic resin as the core layer is too small, the core layer and the coating layer are difficult to be thermally bonded to each other. The adhesive strength of the coating layer is lowered, and as a result, the fusion property between the foamed particles inside the thick foamed molded article is deteriorated.

In the coating layer forming the foamed particles, in addition to the polyolefin polymer, other thermoplastic polymers may be added as necessary, in addition to additives such as a catalyst neutralizing agent, a lubricant, and a crystal nucleating agent. it can. However, it is desirable that other thermoplastic polymers and additives be as small as possible within the range not impairing the object of the present invention.
The amount of the other thermoplastic polymer added is preferably 100 parts by weight or less with respect to 100 parts by weight of the polyolefin polymer. More preferably, it is 50 parts by weight or less, further preferably 30 parts by weight or less, particularly preferably 15 parts by weight or less, and most preferably 5 parts by weight or less.
Moreover, although the addition amount of the said additive is based also on the kind of additive, 40 weight part or less is preferable with respect to 100 weight part of polyolefin polymers, More preferably, it is 30 weight part or less, Most preferably, it is 0. 0.001 to 15 parts by weight.

In the present invention, a foamed core layer made of a polypropylene resin having a melting point of 120 ° C. to 165 ° C. and polyethylene having a melting point of 125 ° C. or less, preferably 80 ° C. to 125 ° C., more preferably 90 ° C. to 120 ° C. A combination in which a polymer is a coating layer is particularly desirable (however, in this case, the polyethylene polymer needs to have a melting point 15 ° C. or more lower than the melting point of the polypropylene resin). In this case, MeLLDPE is preferable as the polyethylene polymer for forming the coating layer. Usually, a polyethylene polymer tends to be hard to be thermally bonded to a polypropylene resin, but MeLLDPE has excellent thermal adhesiveness to a polypropylene resin. Therefore, when producing the foamed particles by foaming the composite resin particles having a multilayer structure, an excellent effect is obtained that peeling is hardly caused between the core layer and the coating layer. In addition, MeLLDPE has an advantage that a phenomenon in which foamed particles are thermally fused during production of foamed particles is less likely to occur. Although these reasons are not certain, it is presumed that the sharpness of the molecular weight distribution by the metallocene-based polymerization catalyst (particularly, there is no or almost no low molecular weight component) contributes. The density of MeLLDPE will usually be in a range of 0.890~0.935g / cm ^3, preferably in the range of 0.898~0.920g / cm ^3.

In the present invention, in particular, as the polypropylene resin forming the core layer, a structural unit obtained from propylene (100 to 85 mol%, ethylene and / or a C 4-20 α-olefin) (comonomer) Is preferably a homopolymer of propylene or a polypropylene copolymer in which 0 to 15 mol% of the structural unit) is present. Moreover, it is a propylene copolymer containing 85 to 98 mol% of a structural unit obtained from propylene in the polypropylene resin, and is a structural unit obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms (comonomer structure). It is more preferable that the unit is contained in a proportion of 2 to 15 mol% because both mechanical properties and foamability are excellent.
Specific examples of ethylene and / or α-olefin having 4 to 20 carbon atoms in the polypropylene copolymer include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 4-methyl-1. -Butene etc. can be mentioned.

In addition, the polypropylene resin has a ratio of position irregular units based on 2,1-insertion of propylene monomer units in all propylene insertions measured by ¹³ C-NMR of 0.5 to 2.0%, and propylene The ratio of the position irregular unit based on 1,3-insertion of the monomer unit is preferably 0.005 to 0.4%.

  When the ratio of the position irregular unit based on the 2,1-insertion is 0.5% or more, or when the ratio of the position irregular unit based on the 1,3-insertion is 0.005% or more, the polypropylene When foamed particles having a foamed body made of resin as a core layer are molded in a mold, the compression set of the foamed molded body obtained is reduced. On the other hand, when the ratio of the position irregular unit based on the 2,1-insertion is 2.0% or less, or the ratio of the position irregular unit based on the 1,3-insertion is 0.4% or less, The mechanical properties of the polypropylene resin, such as a decrease in bending strength and tensile strength, are small, and the strength of the foamed particles and the foamed molded product obtained therefrom is sufficient.

Both the position irregular unit based on the 2,1-insertion and the position irregular unit based on the 1,3-insertion act to reduce the crystallinity of the polypropylene resin containing these units in the structure. To do. Specifically, these position irregular units have an action of lowering the melting point and an action of lowering the crystallinity of the polypropylene resin.
These two actions show the effect of increasing the foaming suitability when the polypropylene resin is used as a base resin for foaming, and the effect of reducing the compression set of the obtained molded product. Therefore, a foam molded article obtained by in-mold molding of foam particles having a foam made of polypropylene resin having the above-mentioned position irregular unit as a core layer has a small compression set.

Here, a fraction of structural units obtained from propylene in the polypropylene resin, a fraction of structural units obtained from ethylene and / or an α-olefin having 4 to 20 carbon atoms, and an isotactic triad fraction described later. Is a value measured using a ¹³ C-NMR method.
The measurement method of ¹³ C-NMR spectrum is, for example, as follows.
That is, a sample of about 350 to 500 mg was placed in an NMR sample tube having a diameter of 10 mmφ, and completely dissolved using about 2.0 ml of o-dichlorobenzene as a solvent and about 0.5 ml of deuterated benzene for locking. Thereafter, measurement was performed at 130 ° C. under the complete proton decoupling condition.
As measurement conditions, a flip angle of 65 deg and a pulse interval of 5T1 or more (where T1 is the longest value of the spin lattice relaxation time of the methyl group) were selected. In the polypropylene resin, since the spin lattice relaxation time of the methylene group and methine group is shorter than that of the methyl group, the recovery of the magnetization of all the carbons is 99% or more under these measurement conditions.
Note that the detection sensitivity of the position irregular unit in the ¹³ C-NMR method is usually about 0.01%, but it can be increased by increasing the number of integrations.

In addition, the chemical shift in the above measurement was set such that the peak of the methyl group of the third unit of the 5-unit propylene unit having a head-to-tail bond and the same methyl branching direction was set to 21.8 ppm. The chemical shifts of other carbon peaks were set as
Using this criterion, the peak based on the methyl group of the second unit in the propylene unit 3 chain represented by PPP [mm] in the structural formula (Chemical Formula 1) shown below is 21.3 to 22.2 ppm. The peak based on the methyl group of the second unit in the three propylene unit chains represented by PPP [mr] is in the range of 20.5 to 21.3 ppm in the three propylene unit chain represented by PPP [rr]. The peak of the second unit based on the methyl group appears in the range of 19.7 to 20.5 ppm.
Here, PPP [mm], PPP [mr], and PPP [rr] are each represented by the following structural formula.

  The polypropylene resin containing a position irregular unit based on 2,1-insertion and 1,3-insertion of propylene contains a specific amount of partial structures (Ι) and (ΙΙ) of the following formula.

Such a partial structure is considered to be caused by positional irregularities that occur during polymerization when, for example, a polymerization reaction is performed using a metallocene polymerization catalyst.
That is, the propylene monomer usually reacts with a so-called “1,2-insertion” in which the methylene side is bonded to the metal component in the catalyst, but in rare cases, “2,1-insertion” or “1,3 -"Insert" may occur. “2,1-insertion” is a reaction mode in which the addition direction is opposite to “1,2-insertion”, and forms a structural unit represented by the above partial structure (構造) in the polymer chain.
Further, “1,3-insertion” means that propylene monomers C-1 and C-3 are incorporated into a polymer chain, and as a result, a linear structural unit, that is, the above partial structure ( Ii).

  The polypropylene resin in which the proportion of each position irregular unit is in a specific range can be obtained by selecting an appropriate catalyst. Specifically, it can be obtained using, for example, a metallocene polymerization catalyst having a hydroazurenyl group as a ligand. Here, the metallocene polymerization catalyst comprises a transition metal compound component having a metallocene structure and a promoter component. The proportion of each position irregular unit varies depending on the chemical structure of the metal complex component of the catalyst used in the polymerization, but generally the higher the polymerization temperature, the higher the tendency. In the present invention, in order to bring the ratio of each position irregular unit of the polypropylene resin into a specific range, it is preferable to employ 0 to 80 ° C. as the polymerization temperature.

The metal complex component can be used as a catalyst component as it is, but it is used as a solid catalyst in which the metal complex component is supported on a particulate carrier that is an inorganic or organic granular or particulate solid. May be.
When the metal complex component is supported on the fine particle carrier, the metal complex component is preferably 0.001 to 10 mmol, more preferably 0.001 to 5 mmol, per 1 g of the carrier.

Among the metallocene polymerization catalysts having the hydroazurenyl group as a ligand, a catalyst using titanium, zirconium, or hafnium as a metal atom is preferable, and a complex containing zirconium is particularly preferable because of high polymerization activity.
Among the metallocene polymerization catalysts, zirconium dichloride type complexes are preferably used, and among them, a cross-linked complex is particularly preferable. Specifically, methylenebis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride, methylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazulenyl)} zirconium dichloride. , Methylenebis {1,1 ′-(4-phenyldihydroazurenyl)} zirconium dichloride, methylenebis {1,1 ′-(4-naphthyldihydroazurenyl)} zirconium dichloride, ethylenebis {1,1 ′-(2- Methyl-4-phenyldihydroazurenyl)} zirconium dichloride, ethylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazurenyl)} zirconium dichloride, ethylenebis {1,1 ′-(4-phenyldihydro) Azulenyl)} zirconium dichloride, ethylenebis {1,1 ′-(4 Naphthyldihydroazurenyl)} zirconium dichloride, isopropylidenebis {1,1 ′-(2-methyl-4-phenyldihydroazurenyl)} zirconium dichloride, isopropylidenebis {1,1 ′-(2-ethyl-4-) Phenyldihydroazurenyl)} zirconium dichloride, isopropylidenebis {1,1 ′-(4-phenyldihydroazurenyl)} zirconium dichloride, isopropylidenebis {1,1 ′-(4-naphthyldihydroazurenyl)} zirconium dichloride Dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride, dimethylsilylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazurenyl)} zirconium dichloride , Dimethylsilylene bis {1,1 ′-(4-phenyldihydroazurenyl)} zirconium dichloride, dimethylsilylenebis {1,1 ′-(4-naphthyldihydroazurenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(2 -Methyl-4-phenyldihydroazurenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(2-ethyl-4-phenyldihydroazurenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(4 -Phenyldihydroazurenyl)} zirconium dichloride, diphenylsilylenebis {1,1 ′-(4-naphthyldihydroazurenyl)} zirconium dichloride, and the like.

  Among these, in particular, dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyldihydroazulenyl)} zirconium dichloride and dimethylsilylene bis {1,1 ′-(2-ethyl-4-phenyldihydroazule) Nil)} zirconium dichloride is preferably used. In this case, the proportion of each position irregular unit can be easily controlled within the scope of the present invention, and a polypropylene resin having an isotactic triad fraction described later of 97% or more can be easily obtained. be able to.

  Examples of the promoter component include aluminoxanes such as methylaluminoxane, isobutylaluminoxane, methylisobutylaluminoxane, Lewis acids such as triphenylborane, tris (pentafluorophenyl) borane, magnesium chloride, dimethylanilinium tetrakis (pentafluorophenyl). ) An ionic compound such as borate can be exemplified. These promoter components can also be used in the presence of other organoaluminum compounds such as trialkylaluminum such as trimethylaluminum, triethylaluminum and triisobutylaluminum.

  The isotactic triad fraction in the entire polymer chain of the polypropylene resin is represented by the following formula (Equation 1). In the partial structure (ΙΙ), as a result of 1,3-insertion, only one methyl group derived from the propylene monomer has disappeared.

In this formula, ΣΙCH ₃ represents the area of all methyl groups (all peaks at 19-22 ppm of chemical shift). A <1>, A <2>, A <3>, A <4>, A <5>, A <6>, A <7>, A <8> and A <9> are respectively 42.3 ppm, 35.9 ppm, 38.6 ppm, 30.6 ppm, 36.0 ppm, 31.5 ppm, 31.0 ppm, 37.2 ppm, 27.4 ppm peak area, part in the above formula (Formula 2) The abundance ratio of carbon shown in the structures (Ι) and (ΙΙ) is shown.
Further, the ratio of 2,1-inserted propylene and the ratio of 1,3-inserted propylene with respect to the total propylene insertion were calculated by the following formula (Formula 2).

Further, in the present invention, the polypropylene resin, the melting point of the polypropylene resin when the Tm (° C.), the water vapor permeability in the case of molding the polypropylene resin film ^{Y (g / m 2 / 24hr} ), It is preferable that Tm and Y satisfy the following relational expression (2).

(Equation 3)
(−0.20) · Tm + 35 ≦ Y ≦ (−0.33) · Tm + 60 (2)

  The water vapor permeability can be measured according to JIS K7129 (1992) “Test method for water vapor permeability of plastic films and sheets”. In this measurement, an infrared sensor method is employed as a test method, and a test temperature of 40 ± 0.5 ° C. and a relative humidity of 90 ± 2% are employed as test conditions.

  The polypropylene resin within the range of the above formula (2) exhibits moderate water vapor permeability. Appropriate water vapor permeability facilitates the penetration of the steam used for molding into the foamed particles (in the core layer) during molding, thereby increasing the secondary foamability of the foamed particles. It is easy to produce a foamed molded article having no or few voids.

  In addition, as a method for producing foamed particles, a method in which resin particles are dispersed in water and impregnated with a foaming agent and then released from high temperature and pressure to low pressure to form foamed particles. The appropriate water vapor permeability facilitates the penetration of water and the foaming agent into the resin particles. As a result, water and the foaming agent are uniformly dispersed in the resin particles, the average cell diameter of the obtained foamed particles can be made uniform, and the expansion ratio can be improved.

The water vapor permeability (Y) is expressed in relation to the melting point (Tm) of the polypropylene resin. Generally, the foaming temperature during the production of the foamed particles and the saturated steam temperature during the in-mold molding are based on This is based on the fact that the higher the melting point (Tm) of the polypropylene resin as the material resin, the higher the melting point (Tm), and the lower the melting point (Tm).
When the water vapor transmission rate (Y) satisfies the relationship of the above formula (2), it shows appropriate permeability of the steam or blowing agent to the polypropylene resin constituting the core layer, and the average cell diameter of the obtained expanded particles is It becomes uniform, and finally exhibits a sufficient compressive strength, resulting in an excellent foamed molded article having a small compression set.

  A polypropylene resin in which the melting point (Tm) and the water vapor permeability (Y) satisfy the relationship of the above formula (2) can be obtained by selecting an appropriate catalyst when producing the polypropylene resin. Specifically, for example, among the above metallocene polymerization catalysts, it can be suitably obtained by using bridged bis {1,1 ′-(4-hydroazurenyl)} zirconium dichloride as a metal complex component. Examples of such metal complex components are as described above.

Next, the polypropylene resin preferably has an isotactic triad fraction (hereinafter referred to as mm fraction) measured by ¹³ C-NMR of 97% or more, more preferably mm. The fraction is preferably 98% or more. When the mm fraction is 97% or more, the mechanical properties of the polypropylene resin become higher. Therefore, the foamed particles having the foam made of the polypropylene resin as the core layer can be obtained by molding the foamed particles in a mold to obtain a foamed molded product having further excellent mechanical properties.

  The polypropylene resin forming the core layer preferably further has a melt flow rate (MFR) of 0.5 to 100 g / 10 minutes. In this case, expanded particles can be produced while maintaining industrially useful high production efficiency, and the mechanical properties of the expanded molded article made of the expanded particles can be improved. The MFR of the polypropylene resin is preferably 1.0 to 50 g / 10 minutes, more preferably 1.0 to 30 g / 10 minutes. The said MFR means the melt mass flow rate measured according to the conditions described in Table 3 of JIS K6921-2 (1997).

The expanded particles used in the present invention can be obtained as follows.
That is, it is usually obtained by foaming resin particles made of a composite composed of a non-foamed core layer and a non-foamed coating layer.
Resin particles composed of such composites use, for example, co-extrusion dies described in Japanese Patent Publication Nos. 41-16125, 43-23858, 44-29522, and JP-A-60-185816. Can be manufactured.
In this case, two extruders are used. One extruder melts and kneads a crystalline thermoplastic resin for forming a core layer, and the other extruder melts a polyolefin polymer constituting the coating layer. After kneading, each molten resin is introduced into a co-extrusion die and laminated and merged to form a sheath-core type composite consisting of a non-foamed core layer and a non-foamed coating layer and extruded into a string shape. . Subsequently, it is preferable to obtain a substantially columnar resin particle comprising a core layer and a coating layer which are not substantially foamed by cutting into a predetermined weight or size with a cutting machine equipped with a take-up machine.
The thinner the coating layer of the resin particles, the more difficult it is to form bubbles in the coating layer when the composite resin particles are foamed. However, if the coating layer is too thin, sufficient coating of the core layer is possible. It becomes difficult. Moreover, when the thickness of the coating layer of the resin particles becomes too thick, bubbles are generated in the coating layer when the resin particles are foamed, which may eventually lead to a decrease in mechanical properties of the foamed molded product.
Therefore, the thickness of the coating layer is preferably 5 to 500 μm for resin particles, more preferably 10 to 100 μm, preferably 0.1 to 200 μm for foamed particles, and 0.5 to 50 μm. More preferably. As described above, the coating layer in the expanded particles is substantially in an unexpanded state.

When the above composite is extruded into a string shape, a foaming agent is contained in the core layer forming resin, and a sheath core type composite comprising a foamed core layer and a substantially non-foamed coating layer. It is possible to extrude and foam the resin in a string shape, but usually the core layer forming resin is also extruded in a substantially non-foamed state.
In general, the normal weight of one resin particle is 0.1 to 20 mg. In particular, if the average weight of one resin particle is in the range of 0.2 to 10 mg and the variation in the weight of each individual particle is small, the production of the expanded particle is facilitated, and the bulk density of the obtained expanded particle is uneven. And the filling property of the expanded particles into the mold is improved.

  As a method of obtaining foamed particles from the resin particles, a method of foaming by impregnating a physical foaming agent into the resin particles produced as described above, specifically, Japanese Patent Publication Nos. 49-2183 and 56-1344. No. 1, West German Patent No. 1285722, No. 2107683, and the like can be used.

  Examples of the physical foaming agent include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, and halogenated hydrocarbons such as trichlorofluoromethane, dichlorodifluoromethane, tetrachlorodifluoroethane, dichloromethane, difluoroethane, and tetrafluoroethane. Inorganic gases such as nitrogen, air and carbon dioxide can be used alone or in admixture of two or more.

Among the above-mentioned methods of impregnating the resin particles with a foaming agent and foaming, the resin particles are put together with a physical foaming agent and a dispersion medium in a pressure vessel that can be sealed and opened, and heated to a temperature higher than the softening temperature of the core layer of the resin particles. In order to obtain expanded particles, a method in which a physical foaming agent is impregnated and then the contents in the sealed container are discharged from the sealed container into a low-pressure atmosphere to foam the resin particles and then dried is obtained.
In addition, it is preferable to use water, alcohol, etc. as said dispersion medium. Furthermore, in order to uniformly disperse the resin particles in the dispersion medium, poorly water-soluble inorganic substances such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide and kaolin, and high water solubility such as polyvinyl pyrrolidone, polyvinyl alcohol, and methyl cellulose. It is preferable to use an anionic surfactant such as molecular protective colloid agent, sodium dodecylbenzenesulfonate, sodium alkanesulfonate, or a mixture of two or more.
In addition, when releasing resin particles into a low-pressure atmosphere, in order to facilitate the release, a pressurized gas similar to that of the physical foaming agent is supplied into the sealed container to keep the pressure in the sealed container constant. It is preferable to hold.

In addition, when obtaining foamed particles having a foam made of polypropylene resin as a core layer by the above method, the foamed particles include a DSC curve obtained by heat flux differential scanning calorimetry (provided that 2 to 4 mg of foamed particles are heat flux differentials). It is preferable that two or more endothermic peaks appear in the DSC curve obtained when the temperature is increased from room temperature (20 ° C. to 45 ° C.) to 220 ° C. at a temperature increase rate of 10 ° C./min by a scanning calorimeter. This is manifested by the formation of a crystalline portion exhibiting an endothermic peak inherent to the propylene resin constituting the core layer and a crystalline portion exhibiting an endothermic peak on the higher temperature side.
Foamed particles in which two or more endothermic peaks appear in the DSC curve are excellent in secondary foaming properties, and the resulting foamed molded article has excellent mechanical strength and appearance. In addition, such foamed particles, for example, as described in JP-A-2002-200355, etc., conditions when foaming the resin particles, specifically, the holding temperature in the pressure vessel, the holding time, It can be obtained by controlling the temperature, pressure, time, etc. when discharging into a low-pressure atmosphere.

Next, the manufacturing method of the foaming molding of this invention is demonstrated.
The method for producing a foamed molded article of the present invention is described in detail above as the foamed particles of a thermoplastic resin in the method of producing a foamed molded article in which foamed particles of a thermoplastic resin are filled in a cavity and molded in a mold. A foamed core layer made of a crystalline thermoplastic resin, and a polyolefin polymer having a melting point or Vicat softening temperature at least 15 ° C. lower than the melting point or Vicat softening temperature of the thermoplastic resin constituting the core layer. Using foamed particles composed of a non-foamed coating layer, manufacturing a thick foamed molded product with a size capable of cutting out a sphere with a diameter of 200 mm with excellent fusion between the foamed particles inside the molded product To do.

  In the above manufacturing method, as the mold for filling the expanded particles, a mold having a cavity of a size capable of accommodating a sphere having a diameter exceeding 200 m in order to obtain a foam molded body having a size capable of cutting a sphere having a diameter of 200 mm. A type is used.

  In addition, the steam pressure supplied to the mold in the in-mold molding, that is, the steam pressure during the main heating for expanding the foamed particles and firmly fusing the foamed particles together to obtain a good foamed molded product, Although it depends on the type of thermoplastic resin constituting the expanded particles, the amount of heat at the endothermic peak on the high temperature side, the size of the bulk density of the expanded particles, and the height of the internal pressure of the expanded particles, A saturated steam pressure corresponding to a temperature not lower than [melting point−30 ° C.] of the crystalline thermoplastic resin constituting the layer and not higher than [melting point + 10 ° C.] of the crystalline thermoplastic resin constituting the core layer, It is preferably a saturated steam pressure corresponding to a temperature not lower than the melting point of the crystalline thermoplastic resin constituting the core layer and not higher than the melting point of the crystalline thermoplastic resin constituting the core layer. Crystalline thermoplastic Mp -21 ° C.] of the resin or higher, more preferably a saturated steam pressure corresponding to the melting point of -5 ° C.] temperature below the crystalline thermoplastic resin constituting the core layer.

Furthermore, as a steam heating condition in the method for producing a foamed molded article of the present invention, it is preferable to perform preheating before the main heating.
That is, by heating the foamed particles with low-pressure steam having a pressure lower by 0.05 MPa or more than the steam pressure during the main heating, the air between the foamed particles is exhausted and the foamed particles are melted without expanding the foamed particles. Preheating is performed to heat to a temperature at which it can be worn. Subsequently, the foamed particles are heated with high-pressure steam for main heating to expand the foamed particles and firmly fuse the foamed particles together.
In this way, by sequentially performing the preheating and the main heating, the air between the foamed particles can be replaced with steam while suppressing the expansion of the foamed particles during the preheating, so that the foamed particles at the center of the cavity are heated well. In addition, since the surface of the foamed particles is heated to a temperature at which the foamed particles can be fused, the fusion between the foamed particles proceeds, and the main fusion rate of the molded body is increased by performing the main heating to continuously expand the foamed particles from that state. Is very expensive. That is, even if it is a thick foam molded body, a product having a high internal fusion rate is obtained, for example, a cube or cuboid having a high foaming ratio of an apparent density of 10 to 28 g / L and a thickness of 300 to 1000 mm. Even if it is a thick foaming molding, what has a high internal fusion rate is obtained.

As described above, the steam pressure during the preliminary heating of the foamed particles is preferably 0.05 MPa or more lower than the steam pressure during the main heating, but is 0.05 to 0 lower than the steam pressure during the main heating. More preferably, the pressure is 3 MPa lower. However, the steam pressure during preheating is preferably 0.01 MPa (G) or more, and more preferably 0.02 MPa (G) or more.
In addition, all the said steam pressures are gauge pressures measured before the drain valve chamber side of the drain pipe connected to the chamber of the side which introduces steam.

  The foamed particles used in the method for producing a foamed molded product of the present invention generally have a bulk density in the range of 8 to 450 g / L, preferably in the range of 10 to 300 g / L, The thing of the range of 30 g / L is more preferable. The bulk density of the foamed particles is the random accumulation of the foamed particles immediately before molding, and they are naturally deposited while removing static electricity in a 1 L graduated cylinder in a room under an atmospheric pressure with an air temperature of 23 ° C. and a relative humidity of 50%. A large number of expanded particles can be accommodated to a scale of 1 L so as to be in a state, and then the weight of the accommodated expanded particles can be measured.

The foam molded article obtained by the method for producing a foam molded article of the present invention has an apparent density of approximately 8 to 600 g / L, and preferably has an apparent density of 10 g / L or more and less than 30 g / L. More preferred is ˜28 g / L. When producing a foamed molded article having an apparent density of less than 30 g / L, an in-mold molding method using foamed particles having an increased internal pressure is usually forced. Generally, when a thick molded body is obtained using expanded particles whose internal pressure is increased, the fusion property inside the molded body is extremely deteriorated. This is because it is difficult for the steam to reach the inside due to the expansion of the expanded particles located near the mold surface. However, in the method for producing a foamed molded article of the present invention by using a composite structure foamed particle composed of the specific core layer and the coating layer, the fusion pressure between the foamed particles is extremely good. Even if a foamed molded article having a wall thickness with an apparent density of less than 30 g / L is produced by using expanded particles having an increased squeezing property, the fusion property inside the molded article is excellent. Therefore, in the method for producing a foamed molded article of the present invention, the fusion density inside the molded article tends to be lowered, so that the apparent density is 30 g / h using foamed particles with high difficulty in molding and increased internal pressure. It is very effective in the molding of a foamed molded product having a wall thickness of less than L. The internal pressure of the expanded particles is preferably 0.005 MPa (G) or more, and more preferably 0.05 to 0.5 MPa (G). The upper limit of the internal pressure of the expanded particles is approximately 0.98 MPa (G).
In addition, the apparent density of the said foaming molding means the apparent whole density defined by JISK7222 (1999). Moreover, the internal pressure of the said foaming particle is calculated | required by the method described in Unexamined-Japanese-Patent No. 2003-201361.

The foamed molded product of the present invention can be produced by various in-mold molding methods.
For example, as described in Japanese Examined Patent Publication No. 46-38359, after filling foamed particles into a cavity formed by a pair of concave and convex portions under atmospheric pressure or reduced pressure, the cavity volume is reduced to 5 to 70%. There is a molding method in which compression is performed so as to decrease, and then a heating medium such as steam is introduced into the cavity to heat-fuse the expanded particles.
Further, as described in Japanese Patent Publication No. 51-22951, after filling the foamed particles whose internal pressure is increased by impregnating the foamed particles with a physical foaming agent, steam is introduced into the mold cavity. There may also be mentioned a molding method in which the expanded particles are fused together.
In addition, as described in Japanese Patent Publication No. 4-46217, a cavity pressurized to a pressure higher than the atmospheric pressure with a compressed gas is pressurized and filled with foamed particles at a pressure higher than the pressure in the cavity, There is also a molding method in which steam is introduced and the expanded particles are fused to each other.
Further, as described in Japanese Patent Application Laid-Open No. 9-104026, a molding method in which foamed particles are fused to each other by being heated while being transported in a molding region with the foamed particles sandwiched between upper and lower belts that travel endlessly. Also mentioned.
Further, as described in Japanese Patent Publication No. 6-22919, molding can be performed by appropriately combining the above methods.
Depending on the type and apparent density of the crystalline thermoplastic resin that forms the core layer, the foamed molded product obtained as described above may start shrinking immediately after release, in which case By performing curing at an early stage in an atmosphere of about 50 to 85 ° C., the dimensions can be recovered to substantially the same size as the molding space.

The thick foam molded body obtained by in-mold molding of the foamed particles having a specific composite structure of the present invention has a fusion rate of the foamed particles in the molded body of 50% or more. Nevertheless, it has excellent fusion properties between the expanded particles. Therefore, in the foamed molded article of the present invention, when slicing, cutting, etc., the processed product is hardly cracked or broken during processing, the chipped foam particles are hardly generated, and the defective rate of the processed product is extremely high. small. Further, even when a thick foam molded body is used as it is, breakage hardly occurs even if it is used in a state where a large load is applied locally or a bending load is applied. In addition, it is preferable that the fusion rate of the foamed particle in the inside of the said foaming molding is 60% or more, and it is more preferable that it is 70% or more.
In the foamed molded article having a thick wall as in the present invention, the fusibility between the foamed particles tends to decrease as it approaches the center of the foamed molded article. By measuring the adhesion rate, the portion with the lowest fusion property between the expanded particles is measured. Therefore, a foamed molded product having a foamed particle fusion rate of 50% or more inside the foamed molded product exhibits a foamed particle fusion rate of 50% or more in the whole foamed molded product.

The fusion rate of the expanded particles inside the expanded molded body is measured by the measuring apparatus shown in FIG. 3 as follows. 3A is a front view of the measuring device, and FIG. 3B is a plan view of the measuring device.
The foamed molded article to be measured is dried and then left for 120 hours in a room under an atmospheric pressure of 23 ° C. and a relative humidity of 50%. The subsequent work is carried out in a room maintained in this state.
First, the center of the thickness direction of the thickest part in the thickness direction of the foam molded body (usually the direction that coincides with the mold opening / closing direction) is included (in the case of a rectangular parallelepiped shape or a cubic shape, the molded body A rectangular solid foam having a thickness of 25 mm, a length of 180 mm, and a width of 50 mm is cut out from the foamed molded article. Further, the cutting position of the rectangular parallelepiped foam will be described in detail. The rectangular foam is cut out so that the center thereof substantially coincides with the center of the largest sphere that can be cut out from the foam molded body. Note that substantially matching means that the positional deviation between the center of the sphere and the center of the rectangular parallelepiped foam is 20 mm or less. Next, in the cut rectangular parallelepiped foam, a 2 mm deep cut is placed on one surface (one surface of length 180 mm, width 50 mm) at the center in the length direction so as to cross the entire width. This is a test piece.

As shown in FIGS. 3A and 3B, a rigid body having a height of 100 mm, a width of 60 mm, and a thickness of 10 mm, which is erected in parallel so that the distance between the centers is 70 mm and whose upper end is rounded to a radius of 5 mm. The test piece 1 is placed on the two support plates 2 and 2, and the surface provided with the notch 5 is directed downward, and the length direction of the test piece 1 is orthogonal to the support plates 2 and 2. So that they are evenly straddled.
Next, in the pressing plate 3 made of a rigid body having a height of 60 mm, a width of 60 mm, and a thickness of 10 mm, the tip of which is rounded to a radius of 5 mm, the center portion in the thickness direction of the pressing plate 3 and the notch 5 of the test piece are matched. And the three-point bending test is performed from the opposite side of the notch 5 of the test piece 1 at a pressing speed of the pressing plate 3 of 200 mm / min until the test piece 1 breaks or the test piece 1 is the support plate 2, 2. Press until it comes off from above 2 and completely enters between the support plates 2 and 2.
Next, the fracture surface of the test piece 1 is observed, and the fusion rate is calculated from the number of broken foam particles (GN) and the number of foam particles peeled between the foam particles (PN) by the following formula (3). Find (BR). As a matter of course, any foamed particles present on the initial 2 mm incision are not counted. In addition, when focusing on one expanded particle on the fracture surface of the test piece 1 and including both a broken portion and a portion peeled between the expanded particles, the area of the broken portion is considered in consideration of the area. Is 50% or more, it is counted as the number of broken parts, and when the area of the broken part is less than 50%, it is counted as the number of peeled particles between the expanded particles.

(Equation 4)
BR (%) = GN × 100 / (GN + PN) (3)

  As a result of this test, if the test piece was not completely broken, it was considered that all the non-broken portions were broken, and the non-broken portion was cut vertically (in the thickness direction of the test piece) with a knife. The number of foam particles present on the cut surface is counted as the number of destroyed, the number of broken foam particles (GN) and the number of foam particles peeled between the foam particles (PN) are counted, the same as above The fusion rate (BR) is measured by a calculation formula.

  The foamed molded article of the present invention is preferably a cube or a rectangular parallelepiped having an apparent density of 10 g / L or more and less than 30 g / L and a minimum thickness of 300 to 1000 mm. In addition, the minimum thickness in a cubic or rectangular parallelepiped foamed molded product means the smallest value among the thicknesses in the three directions of length, width, and height. This foamed molded body is a cubic or cuboid foamed molded body that has been conventionally difficult to manufacture, has a high foaming ratio, is very thick, and has an excellent internal fusion rate. When used as a material, furthermore, even if it is a case where the plate-like product is used as a cushioning material by punching, etc., it can be used without problems up to the part reaching the center of the foam molded article, A processed product can be provided at low cost without waste.

  A foamed molded article having an apparent density of 10 g / L or more, less than 30 g / L, and further 10 to 28 g / L is suitable as a buffer packaging material or the like. The thickness of the foamed molded product is preferable because the thicker one can increase the productivity when cut into a plate shape and used as a buffer material, but if it is too thick, a foamed molded product with high internal fusion property may not be obtained. There is. Accordingly, the minimum thickness is preferably 300 to 1000 mm, more preferably 400 to 600 mm.

Next, examples of the present invention will be described.
In this embodiment, a foamed particle having a composite structure composed of a foamed core layer made of polypropylene resin as a base resin and a coating layer made of a polyethylene polymer, and foamed by molding this in-mold A molded body is produced.

[Production of polypropylene resin]
First, a polypropylene resin as a base resin for forming the core layer was synthesized by the method shown in the following Production Examples 1 and 2.

Production Example 1
(I) Synthesis of [dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride] The following reactions are all carried out in an inert gas atmosphere. A dried and purified solvent was used.

(A) Synthesis of racemic / meso mixture 2.22 g of 2-methylazulene synthesized according to the method described in JP-A-62-207232 was dissolved in 30 mL of hexane, and 15.6 mL of cyclohexane-diethyl ether solution of phenyllithium ( 1.0 equivalent) was added in small portions at 0 ° C.
The solution was stirred at room temperature for 1 hour, cooled to −78 ° C., and 30 mL of tetrahydrofuran was added.
Subsequently, after adding 0.95 mL of dimethyldichlorosilane, it heated up to room temperature, and also heated at 50 degreeC for 90 minutes. Thereafter, a saturated aqueous solution of ammonium chloride was added, the organic layer was separated and dried over sodium sulfate, and the solvent was distilled off under reduced pressure.
By purifying the obtained crude product by silica gel column chromatography (developing solvent; hexane: dichloromethane = 5: 1 (weight ratio)), bis {1,1 ′-(2-methyl-4-phenyl-1) , 4-Dihydroazurenyl) dimethylsilane 1.48 g was obtained.
786 mg of the bis {1,1 ′-(2-methyl-4-phenyl-1,4-dihydroazurenyl) dimethylsilane obtained above was dissolved in 15 mL of diethyl ether, and hexane of n-butyllithium was added at −78 ° C. 1.98 mL of the solution (1.68 mol / L) was added dropwise, the temperature was gradually raised to room temperature, and then the mixture was stirred at room temperature for 12 hours. The solid obtained by distilling off the solvent under reduced pressure was washed with hexane and dried under reduced pressure.
Furthermore, 20 mL of a toluene-diethyl ether mixed solvent (40: 1 (weight ratio)) was added, 325 mg of zirconium tetrachloride was added at −60 ° C., the temperature was gradually raised, and the mixture was stirred at room temperature for 15 minutes.
The obtained solution was concentrated under reduced pressure, and reprecipitated by adding hexane, thereby forming a racemic product composed of dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride. -150 mg of meso mixture was obtained.

(B) Separation of racemic body 887 mg of the racemic / meso mixture obtained by repeating the above reaction was put in a glass container, dissolved in 30 mL of dichloromethane, and irradiated with a high pressure mercury lamp for 30 minutes. Thereafter, dichloromethane was distilled off under reduced pressure to obtain a yellow solid.
7 mL of toluene was added to this solid and stirred, and then allowed to stand to precipitate and separate a yellow solid. The supernatant was removed, and the solid was dried under reduced pressure to obtain 437 mg of a racemate consisting of dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride.

(Ii) Catalyst synthesis (a) Treatment of catalyst carrier 135 mL of demineralized water and 16 g of magnesium sulfate were placed in a glass container and stirred to obtain a solution. After adding 22.2 g of montmorillonite (trade name “Kunipia-F”, manufactured by Kunimine Kogyo Co., Ltd.) to this solution, the temperature was raised and kept at 80 ° C. for 1 hour.
Next, after adding 300 mL of demineralized water, the solid content was separated by filtration. After adding 46 mL of demineralized water, 23.4 g of sulfuric acid and 29.2 g of magnesium sulfate to this solid content, the temperature was raised and the mixture was heated and refluxed for 2 hours, and then 200 mL of demineralized water was added and filtered.
Further, 400 mL of demineralized water was added and filtration was performed twice. Thereafter, the solid was dried at 100 ° C. to obtain chemically treated montmorillonite as a catalyst carrier.

(B) Preparation of catalyst component After the inside of a stirred autoclave having an internal volume of 1 liter was sufficiently substituted with propylene, 230 mL of dehydrated heptane was introduced, and the temperature inside the autoclave was maintained at 40 ° C.
10 g of chemically treated montmorillonite as the catalyst carrier prepared above was suspended in 200 mL of toluene and added thereto.
Furthermore, a racemic body (0.15 mmol) of dimethylsilylenebis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride prepared in a separate container in (b) of (i) above. A mixture of triisobutylaluminum (3 mmol) in toluene (total 20 mL) was added to the autoclave.
Thereafter, propylene was introduced at a rate of 10 g / hr for 120 minutes, and then the polymerization reaction was continued for 120 minutes. Thereafter, the solvent was distilled off under a nitrogen atmosphere and dried to obtain a solid catalyst component. This solid catalyst component contained 1.9 g of a polymer (polypropylene) per 1 g of the solid component. The solid component is a chemically treated montmorillonite, a racemic dimethylsilylene bis {1,1 ′-(2-methyl-4-phenyl-4-hydroazurenyl)} zirconium dichloride supported thereon, and further supported thereon. It is composed of three components of triisobutylaluminum.

(Iii) Preparation of polypropylene resin After the inside of a stirred autoclave with an internal volume of 200 L is sufficiently substituted with propylene, 60 L of purified n-heptane is introduced, and 500 mL (0.12 mol) of a hexane solution of triisobutylaluminum is added, The temperature inside the autoclave was raised to 70 ° C. Thereafter, 9.0 g of the above solid catalyst component was added, and a mixed gas of propylene and ethylene (propylene: ethylene = 97.5: 2.5 (weight ratio)) was introduced so that the pressure became 0.7 MPa, and polymerization was performed. The polymerization reaction was carried out for 3 hours under these conditions.
Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the residual gas component was purged to obtain 9.3 kg of polymer. This polymer has MFR = 8 g / 10 min, structural unit obtained from propylene is 97.6 mol%, structural unit obtained from ethylene is 2.4 mol%, and isotactic triad fraction is 99.2%. The melting point (Tm) was 141 ° C., the ratio of position irregular units based on 2,1-insertion was 1.06%, and the ratio of position irregular units based on 1,3-insertion was 0.17%.
Hereinafter, the polypropylene resin (propylene-ethylene random copolymer) obtained here is referred to as “polymer 1”.

Production Example 2
After thoroughly replacing the inside of the stirred autoclave with an internal volume of 200 L with propylene, 60 L of purified n-heptane is introduced, 500 mL (0.12 mol) of hexane solution of triisobutylaluminum is added, and the inside of the autoclave is raised to 70 ° C. Warm up. Thereafter, 6.0 g of the same solid catalyst component as in Production Example 1 was added, and a mixed gas of propylene and ethylene (propylene: ethylene = 96.5: 3.5 (weight ratio)) was adjusted to a pressure of 0.7 MPa. The polymerization was initiated to initiate polymerization, and the polymerization reaction was carried out for 3 hours under these conditions.
Thereafter, 100 mL of ethanol was injected into the reaction system to stop the reaction, and the remaining gas component was purged to obtain 8.8 kg of a polymer as a propylene polymer for the core layer.
This polymer is obtained from ethylene with MFR = 8 g / 10 min, isotactic triad fraction of 99.2%, melting point (Tm) of 125 ° C., structural unit obtained from propylene, 95.3 mol%. The structural unit was 4.7 mol%, the ratio of the position irregular unit based on 2,1-insertion was 0.95%, and the ratio of the position irregular unit based on 1,3-insertion was 0.11%. .
Hereinafter, the polypropylene resin (propylene-ethylene random copolymer) obtained here is referred to as “polymer 2”.

[Polypropylene resin using Ziegler catalyst]
In addition, as a polypropylene resin using a Ziegler-based catalyst, trade name “Novatech PP MB3B” (hereinafter referred to as polymer 3) and Idemitsu Kosan Co., Ltd., which are propylene-butene-1 random copolymers manufactured by Nippon Polychem Co., Ltd. The product name “J532MZV” (hereinafter referred to as polymer 4), which is a propylene-ethylene random copolymer manufactured by the Company, was obtained.

Table 1 shows the physical properties of the polymers 1 to 4.
(Table 1)

Next, production examples of foamed particles using the above polymers 1 to 4 and production examples of foamed molded articles using these foamed particles will be described.
In the following examples, each physical property was obtained as follows.
The melting point was measured by the above method using a heat flux differential scanning calorimeter “DSC-50” manufactured by Shimadzu Corporation.
The water vapor permeability was measured by the method described above by preparing a 25-micron-thick film from the above polymers 1 to 4.

Example 1
Using a 65 mm diameter single screw extruder, the polypropylene resin (Polymer 1) obtained in Production Example 1 was added with an antioxidant (0.05% by weight, “Yoshinox BHT” manufactured by Yoshitomi Pharmaceutical Co., Ltd.), and a product manufactured by Ciba Geigy Co., Ltd. The name “Irganox 1010” (0.10 wt%) was added and kneaded at 230 ° C., and the molten resin was added to the core introduction nozzle of the co-extrusion die at 150 kg / cm ² so that the extrusion amount was 46 kg / hr. Injected with pressure.
Furthermore, using a single screw extruder with a diameter of 30 mmφ, a low-density polyethylene having a density of 0.907 g / cm ³ and a melting point of 100 ° C. (trade name “Kernel KF270” manufactured by Nippon Polychem Co., Ltd.) with an antioxidant ( Yoshitomi Pharmaceutical Co., Ltd. trade name “Yoshinox BHT” 0.05% by weight and Ciba Geigy Co., Ltd. trade name “Irganox 1010” 0.10% by weight) were added and kneaded at 220 ° C., 8 kg / hr. Molten resin was injected into the coating part introduction nozzle of the co-pressing die at a pressure of 130 kg / cm ² so as to obtain an extrusion amount.
Next, from the orifice of the die having a diameter of 1.5 mm, the kneaded product of the polymer 1 and the antioxidant is used as a non-foamed core layer, and the linear low-density polyethylene is used as a non-foamed coating layer. As a strand.
The strand was cooled through a water tank and cut so that the weight of one strand was 1.0 mg to obtain resin particles made of a composite. When the resin particles are observed with a phase contrast microscope, the coating layer made of a linear low density polyethylene resin having a thickness of 47 microns has a structure in which a non-foamed core layer made of polypropylene resin is covered in a cylindrical shape. It was.

Next, in order to make the resin particles into expanded particles, 1000 g of resin particles are 2500 g of water, 200 g of tricalcium phosphate (however, 10 wt% aqueous dispersion), 30.0 g of sodium dodecylbenzenesulfonate (2 wt% aqueous solution). At the same time, it was put into an autoclave having an internal volume of 5 liters, and isobutane was further added in the amount shown in Table 2. The temperature was raised to the foaming temperature shown in Table 2 over 60 minutes, and then kept at this temperature for 30 minutes.
Thereafter, in order to maintain the pressure in the autoclave at the foaming pressure shown in Table 2, while the compressed nitrogen gas was added from the outside, the valve at the bottom of the autoclave was opened and the contents were released to atmospheric pressure at room temperature.
After the foamed particles obtained by the above operation were dried, the bulk density was measured and found to be 18 g / L. Further, the bubbles of the expanded particles were very uniform with an average cell diameter of 190 μm.
In addition, the average cell diameter of the above-mentioned expanded particles is a micrograph obtained by observing a section of the expanded particles cut through almost the center of the randomly selected expanded particles with a microscope, or this section on the screen. In the projected image, the maximum diameter of each bubble was measured for 50 random bubbles, and the average value was shown.

Next, the manufacturing method of a foaming molding is demonstrated based on FIG.1 and FIG.2.
FIG. 1 is a cross-sectional view showing an example of a molding die. FIG. 2 is an explanatory diagram of a steam supply process when manufacturing a foam molded article. The solid arrows indicate the steam supply and discharge directions, and the dotted lines indicate the steam flow.

First, the foamed particles obtained as described above are accommodated in pressurized air at 23 ° C. and a gauge pressure of 0.5 MPa (G: gauge), and the foamed particles are impregnated with air, whereby the internal pressure of the foamed particles is increased. To increase. Next, when the foamed particles exhibit the internal pressure shown in Table 2, aluminum molding having chambers A, B, C, drain valves D1, D2, D3, and steam valves S1, S2, S3 configured as shown in FIG. Fill the mold cavity E (cavity dimensions 2000 mm long, 1000 mm wide, 500 mm thick). First, as shown in FIG. 2 (1), all drain valves D 1, D 2, D 3 are opened, and steam valves S 1, By opening S2 and S3, steam was introduced into the chambers A, B and C for 5 seconds, and the air in the chamber and between the foamed particles was exhausted.
Subsequently, as shown in FIG. 2 (2), by closing the drain valve D1 and opening only the steam valve S1 while D2 and D3 are open, the steam is passed from the chamber A to the chambers B and C, and foamed. In order to further exhaust the air between the particles and preheat the foamed particles, the gauge pressure steam shown in Table 2 was introduced for the time shown in Table 2 (Preheating 1).
Immediately after that, as shown in FIG. 2 (3), the drain valve D3 is closed, D1 is opened while D2 is opened, and only the steam valve S3 is opened, so that steam is transferred from the chamber B to the chambers A and C. In order to further exhaust the air between the expanded particles by passing them through and to further preheat the expanded particles, steam at a gauge pressure shown in Table 2 was introduced for the time shown in Table 2 (Preheating 2).
Further, immediately after that, as shown in FIG. 2 (4), the drain valve D2 is closed, D3 is opened while D1 is opened, and only the steam valve S2 is opened, so that the chamber C moves toward the chambers A and B. In order to further exhaust the air between the expanded particles through the steam and further preheat the expanded particles, steam having a gauge pressure shown in Table 2 was introduced for the time shown in Table 2 (preheating 3).
Immediately thereafter, as shown in FIG. 2 (5), in order to expand the expanded particles to fill the gaps between the expanded particles and to firmly fuse the expanded particles, the drain valves D1 to D3 are closed, and the steam is closed. By opening all of the valves S1 to S3, steam of gauge pressure shown in Table 2 was introduced for the time shown in Table 2 to perform main heating. In addition, the steam pressure of preheating 1, 2, and 3 was made into a pressure 0.1 MPa lower than the steam pressure at the time of this heating.

Next, after cooling the mold with water for the time shown in Table 2, the foamed molded product was taken out from the mold. The foamed molded product after release was immediately transferred to a room at 70 ° C. and allowed to stand for 24 hours for drying and dimensional recovery. Subsequently, the foamed molded product was left in a room at 23 ° C. and a relative humidity of 50% for 5 days to complete curing.
The molded foam after curing has an apparent density of 20 g / L, a shrinkage ratio of 2.5% with respect to the mold dimensions, a small number of gaps between the foam particles on the outer surface of the molded body, and no irregularities on the entire outer surface of the molded body. The molded product was excellent in appearance. The internal fusion rate of the foamed molded product was 90%.

Moreover, the external appearance of the molded body in Table 2 was visually determined according to the following criteria.
○: The surface of the molded body in the mold is smooth and there is no gap between particles or is not noticeable.
Δ: The surface of the in-mold molded product is smooth, but the gaps between the particles are conspicuous.
X: The surface of the in-mold molded product lacks smoothness, and the gaps between the particles are conspicuous.

Examples 2-3 and Comparative Example 1
In Example 2, resin particles were obtained in the same manner as in Example 1 except that the polymer 1 was changed to the polymer 2 as the resin for forming the core layer. Moreover, in Example 3, resin particles were obtained in the same manner as in Example 1 except that the polymer 1 was changed to the polymer 3 as the resin for forming the core layer. Further, in Comparative Example 1, resin particles were obtained in the same manner as in Example 1 except that the resin of the coating layer was changed to that shown in Table 3. The obtained resin particles were carried out in the same manner as in Example 1 except that the production conditions of the expanded particles shown in Table 2 or Table 3 were adopted, and expanded particles were obtained. Next, using these foamed particles, a foamed molded article was produced in the same manner as in Example 1 except that the steam heating conditions were changed to the conditions shown in Table 2 or Table 3. The obtained foamed particles and foamed molded product were evaluated in the same manner as in Example 1. The results are shown in Table 2 for Examples 2 to 3 and in Table 3 for Comparative Example 1.

Example 4
In Example 4, the expanded particles obtained in Example 2 were used, and the steam pressure of preheating 1, 2, and 3 was changed to the same pressure as the steam pressure at the time of main heating. A foamed molded product was prepared by the operation. The obtained foamed molded article was evaluated in the same manner as in Example 2, and the results are shown in Table 2.

Example 5
Resin particles were obtained in the same manner as in Example 1 except that the polymer 1 was changed to polymer 4 as the resin for forming the core layer. The obtained resin particles were carried out in the same manner as in Example 1 except that the production conditions for the expanded particles shown in Table 2 were adopted, and expanded particles were obtained. Next, a foamed molded article was produced in the same manner as in Example 1 except that the steam heating conditions were changed to the conditions shown in Table 2 using the foamed particles. The obtained foamed particles and foamed molded product were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Examples 2-3
In this comparative example, polypropylene resin expanded particles without a coating layer were produced, and a foamed molded article was produced using the expanded particles.
First, the polymer 1 (Comparative Example 2) or the polymer 3 (Comparative Example 3) is kneaded using a single screw extruder having an inner diameter of 30 mmφ and cut so that the weight of one is 1.0 mg. Obtained.
Next, 1000 g of resin particles were placed in an autoclave having an internal volume of 5 liters together with 3000 g of water, 200 g of tribasic calcium phosphate (however, 10 wt% aqueous dispersion) and 25.0 g of sodium dodecylbenzenesulfonate (2 wt% aqueous solution), Isobutane was added in the amount shown in Table 3, and the temperature was raised to the foaming temperature shown in Table 3 over 60 minutes, and then maintained at this temperature for 30 minutes. Thereafter, in order to maintain the pressure in the autoclave at the foaming pressure shown in Table 3, while adding compressed nitrogen gas from the outside, the valve at the bottom of the autoclave was opened, and the contents were released to atmospheric pressure at room temperature.
Table 3 shows the results of measuring the bulk density after drying the expanded particles obtained by the above operation.
Next, a foamed molded product was produced by the same operation as in Example 1 using the foamed particles. The obtained foamed particles and foamed molded article were evaluated in the same manner as in Example 1, and the results are shown in Table 3.

＊１ 無作為に選んだ１００個の樹脂粒子より計算される１個当たりの平均重量
＊２ 日本ポリケム株式会社の高密度ポリエチレン 商品名「ノバテックHD HY450」
注 比較例１は芯層と被覆層の融点差が１５℃未満（６℃）の比較例
比較例２と３は被覆層が無い比較例
(Table 3)

* 1 Average weight calculated from 100 randomly selected resin particles * 2 High-density polyethylene from Nippon Polychem Co., Ltd. Product name “NOVATEC HD HY450”
Note: Comparative Example 1 is a comparative example in which the melting point difference between the core layer and the coating layer is less than 15 ° C (6 ° C)
Comparative examples 2 and 3 are comparative examples without a coating layer

  As shown in Table 2, in Examples 1 to 3 and 5 according to the method of the present invention, both are foamed molded products having a rectangular parallelepiped shape with a minimum thickness of 500 mm and an apparent density of less than 30 g / L. Although the foamed molded body is manufactured by a pressure-controlled steam heating method that does not require a special control mechanism, a foamed core layer made of a crystalline thermoplastic resin and a core layer are formed as foamed particles. By using foamed particles composed of a substantially non-foamed coating layer made of a crystalline polyolefin polymer having a melting point of 15 ° C. or more lower than the melting point of the thermoplastic resin constituting the foamed molded article, The internal fusing property was very high of 80 to 90%. Further, in Examples 1 to 3 and 5, even though a foamed molded body having a minimum thickness of 500 mm and an apparent density of less than 30 g / L was produced using foamed particles having an increased internal pressure, It is surprising that the internal fusion rate was 80-90%.

  In comparison between Example 2 and Example 4, Example 2 shows an example in which a preliminary heating step of allowing steam to pass between the expanded particles at a pressure lower by 0.05 MPa or more than the steam pressure during main heating is shown. On the other hand, Example 4 shows an example in which the preheating step is performed at the same pressure as the steam pressure during the main heating. From these comparisons, the example of the preheating process in which the steam is allowed to pass between the expanded particles at a pressure lower by 0.05 MPa or more than the steam pressure at the time of the main heating is compared with the example in which the process is not performed. You can see that the rate is high. In order to increase the internal fusion rate to 60% or more under the in-mold molding conditions of Example 4, it is necessary to reduce the thickness of the foamed molded product to about 300 mm. From this point also, the specific preheating is performed. The superiority of is recognized. Note that Example 4 had an internal fusion rate of 50%, which was inferior to Example 2, but far superior to Comparative Examples 1 to 3.

  Comparative Example 1 compared with Example 1 shows an example in which the difference between the melting point of the thermoplastic resin constituting the core layer and the melting point of the polyolefin polymer constituting the coating layer was less than 15 ° C. as expanded particles. Therefore, in spite of preheating as in Example 1, the fusion between the foamed particles at the center of the molded body was remarkably inferior. In Comparative Example 1, the fusion of the molded body surface layer is good, but the tendency of the fusion to decrease toward the center of the molded body is observed, and the foam particles near the surface layer of the molded body foam first, and the fusion is completed. Therefore, as a result of insufficient steam reaching the center of the molded body, the internal fusion rate was low.

  Comparative Examples 2 and 3 are respectively contrasted with Examples 1 and 3 and show examples having no coating layer. The foamed molded products obtained in Comparative Examples 2 and 3 were remarkably inferior in internal fusion property, and the foamed particles were not fused at the center. This result shows the excellence of Examples 1 and 3.

  Example 3 and Example 5 are polypropylene resins in which the resin constituting the core layer has specific position irregular units based on 2,1 insertion and 1,3 insertion of propylene monomer units as in Examples 1 and 2. It is a result which shows that the outstanding effect of this invention is achieved also with polypropylene resins other than this.

  Further, Example 1 in which the proportion of position irregular units based on 2,1 insertion and 1,3 insertion of propylene monomer units is a specific amount of polypropylene resin, and the proportion of position irregular units is 0. Compared to Example 3 in which polypropylene resin is used as the core layer resin, Example 1 is superior in in-mold moldability at low temperatures even when the difference in melting point between both core layers is taken into consideration.

  In the foam molded body molding process of this example, exhaust and preheating 1, 2, and 3 were performed, but the exhaust and / or preheating were omitted as long as the internal fusion rate of the molded body was satisfactory. Is possible. In addition, in order to make the surface state of each part of the molded body surface and the fusion state of each part of the molded body uniform, the A, B, C chambers may be further divided to partially adjust the steam pressure. Is possible.

It is sectional drawing which shows an example of the metal mold | die for manufacturing the foaming molding of this invention. It is explanatory drawing of the steam supply process at the time of manufacturing the foaming molding of this invention. It is a conceptual diagram of the measuring apparatus which measures the internal fusion rate of a foaming molding, (a) is a front view, (b) shows a top view.

Explanation of symbols

S1, S2, S3 Steam valve D1, D2, D3 Drain valve A, B, C Chamber E Cavity 1 Specimen 2 Support base 3 Press plate 4 Mounting base 5 Cutting

Claims (7)

  In a foamed molded product having a size capable of cutting out a sphere having a diameter of 200 mm obtained by in-mold molding of foamed particles of a thermoplastic resin, the foamed particles are a foamed core layer made of a crystalline thermoplastic resin, and A crystalline polyolefin polymer whose melting point is 15 ° C. or more lower than the melting point of the thermoplastic resin constituting the core layer, or an amorphous polyolefin whose Vicat softening temperature is 15 ° C. or more lower than the Vicat softening temperature of the thermoplastic resin constituting the core layer A thick foam molded article comprising a substantially non-foamed coating layer made of a polymer and having a fusion rate of foamed particles of 50% or more inside the foam molded article.   The thick foamed molded product according to claim 1, wherein the foamed molded product is a cube or a rectangular parallelepiped having an apparent density of 10 g / L or more, less than 30 g / L, and a minimum thickness of 300 to 1000 mm.   The thick foamed molded article according to claim 1 or 2, wherein the crystalline thermoplastic resin constituting the core layer of the foamed particles is a polyolefin resin.   The thick foamed molded article according to claim 1 or 2, wherein the crystalline thermoplastic resin constituting the core layer of the expanded particles is a polypropylene resin.   In the method for producing a foamed molded article having a size capable of cutting out a sphere having a diameter of 200 mm by filling a foamed particle of a thermoplastic resin into a cavity, and heating the foamed particle with steam to fuse each other, Of a foamed core layer made of a crystalline thermoplastic resin, and a crystalline polyolefin polymer or a thermoplastic resin constituting the core layer whose melting point is 15 ° C. or lower than the melting point of the thermoplastic resin constituting the core layer. A method for producing a thick foam molded article, comprising: a substantially non-foamed coating layer comprising an amorphous polyolefin polymer having a Vicat softening temperature lower by 15 ° C or more than the Vicat softening temperature.   The method for producing a thick foam molded article according to claim 5, wherein the foamed particles have a bulk density of 10 to 300 g / L and an internal pressure of 0.005 MPa (G) or more. Filling the foamed particles in the cavity, preheating the foamed particles with a steam pressure of 0.05 MPa or more lower than the steam pressure during the main heating, and then performing the main heating with high-pressure steam to fuse the foamed particles to each other. The manufacturing method of the thick foaming molding of Claim 5 or 6 characterized by the above-mentioned.

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