JP2006291067A - Thermoplastic resin foam-molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foam-molded article having a high energy absorption efficiency by using a polyolefin-based resin excellent in heat resistance, chemical resistance and recycling property. <P>SOLUTION: This thermoplastic resin foam-molded article consisting of thermoplastic resin pre-expansion particles obtained by using a resin containing 100 pts.wt. resin composition consisting of (A) a polyolefin-based resin and (B) a functional group-containing modified polyolefin-based resin and (C) ≥0.5 and ≤20 pts.wt. layered compound organized by an nonionic compound as an inorganic weight, as a base resin is characterized by having ≤1.6 ratio (P50%)/(P5%) of a compression stress at 5% compression set (P5%) to a compression stress at 50% compression set (P50%) in a compression test as prescribed by the NDZ0504. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an energy absorbing material having high energy absorption efficiency, which is preferably used for a buffer packaging material, an automobile bumper core material, and the like. Further, the present invention relates to a thermoplastic resin foam-molded article comprising a polyolefin resin, a functional group-containing modified polyolefin resin, and a resin to which an organic layered compound is added, and having excellent heat resistance, chemical resistance and recyclability.

  The energy absorbing material is used for a buffer packaging material of a precision machine or a bumper core material of an automobile. The shock-absorbing packaging material absorbs shocks such as dropping and vibration during transportation, and the automobile bumper core material prevents excessive damage to cars and people in the event of an accident.

  In recent years, there has been an increasing demand for pedestrian protection in automobile accidents, and it has become necessary to reduce the impact generated by accidents to a lower level. On the other hand, there is an increasing demand for improvement in the design of automobiles and a larger room space in automobiles, and the capacity for using energy absorbing materials tends to decrease. In order to meet these contradictory requirements, an energy absorbing material that can efficiently absorb energy with a small capacity is eagerly desired.

  A hard urethane foam is often used as an energy absorbing material having high energy absorption efficiency. Rigid urethane foam has a very high energy absorption performance in the compressive deformation behavior of the material, with a constant load generated from low strain to high strain. However, rigid urethane foam is inferior in recyclability and has the disadvantages of being easily hydrolyzed.

  On the other hand, there are thermoplastic resin foam moldings as materials with excellent recyclability and high processability, but these have low compressive load at low strain and high compressive deformation behavior at high strain. Absorption performance is not always at a satisfactory level.

  Development of energy-absorbing materials that satisfy energy-absorbing performance, recyclability, and workability has been studied. For example, Patent Document 1 discloses that a foam molded product using expanded styrene resin particles having a weight average molecular weight of 45,000 or more and 120,000 or less has a compression strain of 5% in a compression test defined in JIS K7220. It is shown that the value of Y / X is 2.0 or less when the compressive stress at the time is X and the compressive stress at the time of 50% is Y. However, the foamed styrenic resin has low chemical resistance, heat resistance and the like, and is difficult to use in applications where these are required, for example, automobile members.

  Further, in Patent Document 2, when a polypropylene homopolymer having a melt flow rate measured in accordance with ASTM D790 of 20-100 g / 10 min is used, the cell structure is destroyed at the time of compression in static compression, and even at high strain. It is shown that the increase in stress is suppressed and the energy absorption efficiency is good. However, in this technique, a polypropylene homopolymer having a high resin melting point is used, and it is necessary to increase a molding heating pressure for obtaining an in-mold foam molded product.

  Furthermore, Patent Document 3 shows that when a thermoplastic resin foam molded article in which polyolefin resin foam particles are dispersed in a foam made of polystyrene resin is used, the energy absorption efficiency is high in a dynamic compression test. Yes. However, since this technique uses two kinds of resins, it is necessary to separate the resin when it is recycled.

  Furthermore, Patent Document 4 shows that a lattice-shaped energy absorber made of an elastic body improves energy absorption efficiency by utilizing compression and buckling. However, the method of this document has a drawback that the shape is limited.

  As described above, there is no technology that satisfies all of heat resistance, chemical resistance, recyclability, and easy processability in the thermoplastic resin foam molded article used for energy absorbing materials.

  On the other hand, polyolefin-based resins, especially polypropylene-based resins, are materials with excellent balance such as mechanical strength, heat resistance, chemical resistance, molding processability, and low-cost availability of raw materials. Foam materials, injection molding materials, films It is used in various fields such as materials. In particular, in the field of foamed molded products using polyolefin-based resins, it is excellent in environmental compatibility such as recyclability, so the amount used is increasing year by year in the fields of automotive parts, packaging materials, building materials, heat insulating materials, food trays, etc. It is increasing.

In recent years, as disclosed in Patent Document 5, a resin composition is obtained by blending a thermoplastic resin with a compound obtained by organizing a layered compound with a cationic surfactant represented by a quaternary ammonium salt. Technologies for dramatically improving the strength characteristics of these are disclosed, and Patent Document 6 and Patent Document 7 are disclosed as examples of development of foams using these technologies. However, although these techniques are said to improve the strength, they have not been studied at all from the viewpoint of energy absorbing materials.
JP 2002-212332 A Japanese Patent Laid-Open No. 10-45939 JP 2004-142260 A JP 7-228144 A Japanese Patent Laid-Open No. 10-182892 JP 2002-30181 A JP 2002-356574 A

  An object of the present invention is to obtain a foam molded article having high energy absorption efficiency by using a polyolefin resin excellent in heat resistance, chemical resistance and recyclability.

  As a result of intensive studies, the inventors of the present invention contain a predetermined amount of a layered compound organized with a nonionic compound with respect to 100 parts by weight of a resin composition comprising a polyolefin resin and a functional group-containing modified polyolefin resin. The present inventors have found that a foamed molded body having high energy absorption efficiency can be obtained by forming a molded body using thermoplastic resin pre-foamed particles having a resin as a base resin, and the present invention has been completed.

  That is, the present invention relates to (A) a layered compound organized with a nonionic compound for 100 parts by weight of a resin composition comprising (A) a polyolefin resin and (B) a functional group-containing modified polyolefin resin. It is composed of thermoplastic resin pre-expanded particles whose base resin is 0.5 to 20 parts by weight of an inorganic resin, and compression when the compression strain is 5% in the compression test defined by NDZ0504 The ratio (P50%) / (P5%) of the stress (P5%) and the compressive stress (P50%) when the compressive strain is 50% is 1.6 or less. .

As a preferred embodiment,
(1) (A) The polyolefin resin is 30 wt% or more and 85 wt% or less, and (B) the functional group-containing modified polyolefin resin is 15 wt% or more and 70 wt% or less,
(2) The nonionic compound is a polyether compound,
(3) (C) A layered compound organized with a nonionic compound is obtained by mixing a nonionic compound and a layered compound in water or a polar solvent containing water. ,
(4) The layered compound is a layered silicate.
(5) (A) The polyolefin resin is a polypropylene resin,
The present invention relates to the thermoplastic resin foam molded article described above.

  With respect to 100 parts by weight of a resin composition comprising (A) a polyolefin-based resin and (B) a functional group-containing modified polyolefin-based resin, (C) a layered compound organized with a nonionic compound is used as an inorganic weight. It consists of thermoplastic resin pre-expanded particles with a resin containing 5 parts by weight or more and 20 parts by weight or less as a base resin. In the compression test defined by NDZ0504, the compression stress (P5%) when the compression strain is 5% Since the ratio (P50%) / (P5%) of the compressive stress (P50%) when the compressive strain is 50% is 1.6 or less, it is a foamed molded article that can efficiently absorb energy even with a small amount of use. . In addition, an energy absorbing material suitable for heat resistance, chemical resistance and recyclability can be obtained, which is industrially useful for automobile materials, packaging materials, building materials, and the like.

  The (A) polyolefin resin used in the present invention is not particularly limited, and a known polyolefin resin can be used. Specific examples thereof include homopolymers of α-olefins represented by low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, polybutene, polypentene, and the like, and ethylene-propylene random copolymers. , 1-butene-propylene random copolymer, ethylene-1-butene-propylene random terpolymer, copolymer of two or more α-olefins represented by ethylene-propylene block copolymer (random) Olefin elastomers represented by ethylene-propylene rubber, ethylene-butene rubber, ethylene-hexene rubber, ethylene-octene rubber, and the like. . These may be used alone or in combination of two or more. Among these, polypropylene resins such as ethylene-propylene random copolymers, 1-butene-propylene random copolymers, ethylene-1-butene-propylene random terpolymers, and homopolypropylene make thermoplastic resin foam molded articles easy. It is preferably used in that it can be obtained.

  The (B) functional group-containing modified polyolefin resin used in the present invention is added for the purpose of improving the affinity between the polyolefin resin and the layered compound and enhancing the dispersibility of the layered compound. Specific examples of the functional group in the main chain of the polyolefin resin include functional groups such as a hydroxyl group, a carboxyl group, a carbonyl group, a methacryl group, a maleic acid group, a maleimide group, a urethane group, a thiol group, and an epoxy group. It is done. Examples of such functional group-containing modified polyolefin include ethylene-maleic anhydride copolymer, maleic anhydride graft-modified polyethylene, ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer, propylene-maleic anhydride. Examples thereof include a copolymer, an ethylene-propylene maleic anhydride copolymer, a maleic anhydride graft-modified polypropylene, and a maleic anhydride graft-modified propylene-ethylene random copolymer. These may be used alone or in combination of two or more. Among these, for example, when a polypropylene resin is used as the polyolefin resin (A), a propylene-maleic anhydride copolymer, a maleic anhydride graft-modified polypropylene, a maleic anhydride graft-modified propylene-ethylene random copolymer, and the like. A functional group-containing modified polypropylene resin is more preferably used than the compatibility with the base resin.

  The molecular weight of the functional group-containing modified polyolefin resin is not particularly limited, but is preferably 10,000 to 100,000 in terms of weight average molecular weight. If it is less than 10,000, the melt characteristics of the functional group-containing modified polyolefin resin itself are lowered, so that good expanded particles tend not to be obtained. On the other hand, if it exceeds 100,000, the compatibility between the base resin and the functional group-containing modified polyolefin resin is lowered, so that the dispersibility of the layered compound is lowered and the mechanical strength of the foam tends to be lowered.

  Moreover, it is preferable that it is 0.5 to 10 weight% with respect to base-material resin about the addition amount of the functional group of functional group containing modified polyolefin resin. If the amount is less than 0.5% by weight, the effect for dispersing the layered compound tends to be low. Conversely, if the amount exceeds 10% by weight, the cost of the product tends to increase and the workability during foam molding tends to decrease.

  The composition ratio of (A) polyolefin resin and (B) functional group-containing modified polyolefin resin used in the present invention is not particularly limited, but preferably (A) is 30 wt% to 85 wt%, and (B) is It is 15 weight% or more and 70 weight% or less. Although the optimum value varies depending on the types of (A) and (B) used, when (A) is 85% by weight or less, that is, when (B) is 15% by weight or more, the energy absorption efficiency of the obtained in-mold foam molded product Tend to be higher. On the other hand, when (B) is 70% by weight or less, that is, (A) is 30% by weight or more, the resin tends to disperse well when pre-expanded particles are produced using water as a dispersion medium in a pressure resistant container. In addition, a good molded product tends to be obtained at the time of in-mold foam molding using pre-expanded particles.

  The layered compound constituting the layered compound organized in (C) nonionic compound used in the present invention is a silicate, a phosphate such as zirconium phosphate, a titanate such as potassium titanate, tungstic acid Examples thereof include tungstates such as sodium, uranates such as sodium uranate, vanadates such as potassium vanadate, molybdates such as magnesium molybdate, niobates such as potassium niobate, and graphite. A layered silicate is preferably used from the viewpoint of easy availability and handling.

  The layered silicate is formed mainly from a tetrahedral sheet of silicon oxide and an octahedral sheet of metal hydroxide, and examples thereof include smectite clay and swellable mica.

The smectite clay is represented by the following general formula (1):
^{_{X 1 0.2 ~ 0.6 Y 1 2}} ~ 3 Z 1 4 O 10 (OH) 2 · nH 2 O (1)
(In the formula, X ¹ is at least one selected from the group consisting of K, Na, 1 / 2Ca, and 1 / 2Mg, and Y ¹ is Mg, Fe, Mn, Ni, Zn, Li, Al, and Cr. Z ¹ is one or more selected from the group consisting of Si and Al, and H ₂ O represents a water molecule bonded to an interlayer ion, n is naturally or synthetically represented by) which varies significantly with interlayer ions and relative humidity. Specific examples of the smectite group clay include, for example, montmorillonite, beidellite, nontronite, saponite, iron saponite, hectorite, soconite, stevensite, bentonite, and the like, or substitution products, derivatives, or mixtures thereof. . The distance between the bottom surfaces of the smectite group clay in the initial aggregated state is about 100 to 170 nm, and the average particle size of the smectite group clay in the aggregated state is about 10 μm to 5 mm.
The swelling mica is represented by the following general formula (2):
X ² _0.5 to _1.0 Y ² ₂ to ₃ (Z ² ₄ O ₁₀ ) (F, OH) ₂ (2)
(Wherein X ² is at least one selected from the group consisting of Li, Na, K, Rb, Ca, Ba, and Sr, and Y ² is composed of Mg, Fe, Ni, Mn, Al, and Li. One or more selected from the group, and Z ² is one or more selected from the group consisting of Si, Ge, Al, Fe, and B). These are water, a polar solvent that is compatible with water at an arbitrary ratio, and a material that swells in a mixed solvent of water and the polar solvent. For example, lithium-type teniolite, sodium-type teniolite, lithium-type four Examples thereof include silicon mica and sodium-type tetrasilicon mica, or substituted products, derivatives, or mixtures thereof. The bottom surface interval in the initial aggregated state of the swellable mica is approximately 100 to 170 nm, and the average particle size of the swellable mica in the aggregated state is approximately 10 μm to 5 mm.

Some of the swellable mica have a structure similar to that of vermiculite (hereinafter sometimes referred to as “vermiculite equivalent”), and such vermiculite equivalent can also be used. The vermiculite-equivalent products include three octahedron type and two octahedron type, and the following general formula (3):
_{(Mg, Fe, Al) 2} ~ 3 (Si 4-x Al x) O 10 (OH) 2 · (M +, M 2+ 1/2) x · nH 2 O (3)
(Wherein M is an exchangeable cation of an alkali or alkaline earth metal such as Na and Mg, x = 0.6 to 0.9, and n = 3.5 to 5). It is done. The bottom surface interval in the initial aggregated state of the vermiculite equivalent is approximately 100 to 170 nm, and the average particle size in the aggregated state is approximately 10 μm to 5 mm.

  The crystal structure of the layered silicate is preferably one in which the layers are regularly stacked in the c-axis direction. However, a so-called mixed layer mineral in which the crystal period is disturbed and plural kinds of crystal structures are mixed can also be used.

  A layered silicate may be used independently and may be used in combination of 2 or more type. Among the layered compounds, montmorillonite, bentonite, hectorite, and swellable mica having sodium ions between the layers are obtained. From the point of view, it is preferable.

Although it does not specifically limit with the nonionic compound of the layered compound organized by the (C) nonionic compound used by this invention, The hydrophilic group part which consists of a polyether structure shown by following General formula (4) In the molecule (hereinafter sometimes referred to as “polyether compound”) can be suitably used.
-(-R-O-) _n- (4)
(In the formula, each R is a divalent hydrocarbon group having 1 to 5 carbon atoms, and they may be the same or different, and R may contain a hydroxyl group.) ≦ n ≦ 1000.)
As the polyether structure, polyoxyalkylene compounds such as polyoxyethylene, polyoxyethylene-polyoxypropylene copolymer, and polyoxypropylene are preferably used because they are highly hydrophilic and easy to produce. . Furthermore, since the polyether compound contains an aromatic hydrocarbon group in the molecule, the dispersibility of the layered compound tends to be further improved. The aromatic hydrocarbon group is, for example, a phenyl group, a naphthyl group, an anthracenyl group, and a substituted aromatic hydrocarbon group in which one or more hydrogens of these aromatic hydrocarbons are substituted with a hydrocarbon substituent. Etc. The composition ratio of the substituents in the polyether compound is not particularly limited, but it is desirable that the polyether compound is soluble in water or a polar solvent containing water. Specifically, for example, the solubility in 100 g of water at room temperature is preferably 1 g or more. More preferably, it is 2g or more, More preferably, it is 5g or more.

  The amount of the nonionic compound used is the affinity between the layered compound and the polyolefin resin and the functional group-containing modified polyolefin resin, and the dispersibility of the layered compound in the layered compound and the polyolefin resin and the functional group-containing modified polyolefin resin. Can be set to be sufficiently high. If necessary, a plurality of nonionic compounds having different functional groups can be used in combination. Accordingly, the amount of the nonionic compound used is not generally limited by numerical values, but the lower limit of the amount of the layered compound to 100 parts by weight of the layered compound is preferably 10 parts by weight. More preferably, it is 15 weight part, More preferably, it is 20 weight part. The upper limit of the compounding amount of the nonionic compound with respect to 100 parts by weight of the layered compound is preferably 150 parts by weight. More preferably, it is 100 weight part, More preferably, it is 70 weight part. If the lower limit of the nonionic compound is less than 10 parts by weight, the effect of finely dispersing the layered compound tends to be insufficient. Even if the upper limit of the nonionic compound exceeds 150 parts by weight, the fine dispersion effect of the layered compound tends not to change.

  In the present invention, the method for treating a layered compound with a nonionic compound is not particularly limited. For example, it can be performed by the following method.

  First, the layered compound and the dispersion medium are mixed with stirring. Examples of the dispersion medium include water and polar solvents containing water. Examples of the polar solvent include alcohols such as methanol, ethanol and isopropanol, glycols such as ethylene glycol, propylene glycol and 1,4-butanediol, ketones such as acetone and methyl ethyl ketone, ethers such as diethyl ether, and dimethylformaldehyde. And amides. Especially, water is preferable at the point which processing is easy in the process of drying a dispersion medium.

  The method of stirring and mixing the layered compound and the dispersion medium is not particularly limited. For example, it is carried out using a conventionally known wet stirring mixer. For example, examples of the wet stirrer include a high-speed stirrer in which a stirring blade rotates at a high speed, and wet mills that wet-grind a sample in a gap between a rotor and a stator that are subjected to a high shear rate. Other mixing methods include mechanical wet pulverizers that use hard media, wet collision pulverizers that collide samples at high speed with jet nozzles, etc., and wet ultrasonic pulverizers that use ultrasonic waves. sell.

  For example, when wet mills are used, if more efficient mixing is desired, the speed is set to 1000 rpm or higher, preferably 1500 rpm or higher, more preferably 2000 rpm or higher. The upper limit of the rotational speed is 25000 rpm. Even if the rotational speed exceeds 25000 rpm, the effect of stirring tends not to change. Mixing can be performed efficiently by setting the shear rate to 500 (1 / s) or more, preferably 1000 (1 / s) or more, more preferably 1500 (1 / s) or more. The upper limit of the shear rate is about 500,000 (1 / s). Even if the shear rate exceeds 500,000 (1 / s), the effect of stirring tends not to change. The time required for mixing is 1 to 10 minutes. Next, the nonionic compound is added and stirring is continued for another 5 to 60 minutes, followed by thorough mixing. After that, it is heat-dried or freeze-dried and pulverized as necessary. As another method, a method of spraying and drying is also preferably used.

  The amount of the layered compound organized with such a nonionic compound is 0.5 parts by weight or more as an inorganic weight with respect to 100 parts by weight of the resin composition comprising the polyolefin resin and the functional group-containing modified polyolefin resin. 20 parts by weight or less. Preferably, it is 1.0 part by weight or more and 15 parts by weight or less, more preferably 1.5 parts by weight or more and 10 parts by weight or less. When the amount of the organically layered compound is less than 0.5 parts by weight, an expected in-mold foam molded product with high energy absorption efficiency cannot be obtained. When the amount exceeds 20 parts by weight, workability in foaming and surface appearance are deteriorated. And this leads to an increase in cost as a final product.

  The method for producing the resin composition comprising the polyolefin resin and the functional group-containing polyolefin resin of the present invention by dispersing a layered compound organized with a nonionic compound is not particularly limited. For example, a method of melt kneading using various general kneaders can be mentioned. Examples of the kneader include a single screw extruder, a twin screw extruder, a roll, a Banbury mixer, a kneader, and the like, and a kneader with high shear efficiency is particularly preferable. For polyolefin resins and functional group-containing polyolefin resins, layered compounds organized with nonionic compounds may be charged into the kneader and melt-kneaded, or a polyolefin-based polyolefin previously melted A layered compound organized with the nonionic compound of the present invention may be added to the resin and the functional group-containing polyolefin-based resin and melt-kneaded.

  Moreover, in order to produce the thermoplastic resin foam molded article of the present invention, in addition to blending a polyolefin compound resin and a functional group-containing polyolefin resin with a layered compound organized with a nonionic compound, depending on the purpose In addition, additives such as pigments and dyes, heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, lubricants, plasticizers, flame retardants, and antistatic agents can be added.

  A conventionally known method is used as a method for producing the thermoplastic resin pre-expanded particles, which is a raw material of the thermoplastic resin foam molded article of the present invention. For example, a method can be mentioned in which resin pellets are dispersed in water while being stirred in a pressure vessel, heated to a predetermined foaming temperature under pressure, impregnated with a foaming agent, and the aqueous dispersion is discharged to a low pressure region. . The foaming temperature is usually selected from the range of the melting point of the thermoplastic resin from −20 ° C. to the melting point + 10 ° C. depending on the kind of the thermoplastic resin, the amount of foaming agent used, the target expansion ratio of the pre-expanded particles, and the like. The foaming pressure is usually selected from the range of about 1 to 10 MPa depending on the type of thermoplastic resin, the amount of foaming agent used, the target foaming ratio of the pre-foamed particles, and the like.

  Examples of the foaming agent impregnated into the resin pellet include aliphatic hydrocarbons such as propane, butane, pentane and hexane; aliphatic cyclized hydrogens such as cyclopentane and cyclobutane; inorganic gases such as air, nitrogen and carbon dioxide Kind; water, etc. are raised. These foaming agents may be used alone or in combination of two or more. The amount used is not limited, and may be appropriately used according to the desired expansion ratio of the thermoplastic resin pre-expanded particles. The amount used is usually 5 parts by weight or more and 60 parts by weight with respect to 100 parts by weight of the resin pellets. It is as follows. Preferable foaming agents include water and butane that enables foaming at a higher magnification.

  In preparing the aqueous dispersion, for example, tricalcium phosphate, basic magnesium carbonate, calcium carbonate or the like can be used as a dispersant, and a small amount of surfactant such as sodium dodecylbenzenesulfonate, n-paraffin sulfone. Acid soda, α-olefin sulfonic acid soda and the like can be used together as a dispersion aid.

  Such dispersants and surfactants vary depending on the type and type of thermoplastic resin used and the amount used, but usually 0.2 parts by weight or more and 3 parts by weight or less in the case of a dispersant with respect to 100 parts by weight of water. In the case of the surfactant, 0.001 part by weight and 0.2 part by weight or less are preferable.

  The resin pellet containing the foaming agent is usually preferably added in an amount of 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of water in order to improve dispersibility in water.

  The aqueous dispersion thus prepared is heated under pressure, and then discharged to a low pressure region through, for example, an opening orifice of 2 to 10 mmφ, and the resin pellets are prefoamed to obtain the thermoplastic resin prefoamed particles of the present invention. It is done.

  The pressure vessel is not particularly limited, and any pressure vessel can be used as long as it can withstand the pressure and temperature. As a specific example of such a pressure vessel, for example, an autoclave type pressure vessel can be mentioned.

  The method of obtaining the thermoplastic resin foam molded article of the present invention is based on a method of in-mold foam molding of thermoplastic resin pre-expanded particles. The in-mold foam molding methods are as follows: a) a method in which pre-expanded particles are used as they are, b) a method in which an inorganic gas such as air is press-fitted into the pre-expanded particles in advance to impart foaming ability, and c) the pre-expanded particles are compressed Conventionally known methods such as filling in a mold and molding can be used.

  As a method of molding an in-mold foam molded body from the thermoplastic resin pre-foamed particles of the present invention, for example, the pre-foamed particles are preliminarily air-pressed in a pressure-resistant container, and air is injected into the particles to give foaming ability. The mold is filled in a mold that can be closed but cannot be sealed, and is molded by heating with a steam pressure of about 0.06 to 0.60 MPa and a heating time of about 3 to 30 seconds using water vapor as a heating medium. The resin pre-expanded particles are fused together, and then the mold is cooled by water cooling to such an extent that the deformation of the in-mold foam molding after taking out from the mold can be suppressed, and then the mold is opened and in-mold foam molding is performed. The method of obtaining a body is mentioned.

  The thermoplastic resin foam molded article obtained as described above has a compressive stress when the compressive strain is 5% (P5%) and a compressive stress when the compressive strain is 50% in the compression test defined by NDZ0504. The ratio (P50%) / (P5%) of (P50%) is 1.6 or less, preferably 1.5 or less.

  The compression test defined by NDZ0504 used in the present invention uses a sample having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm and receives a load obtained as a reaction force when compressed at a speed of 10 mm / min in the thickness direction ( The value divided by (vertical dimension × horizontal dimension) is obtained as compressive stress, while the value obtained by dividing the displacement in the thickness direction by the original thickness of the sample is obtained as strain.

  The ratio of compressive stress defined in the present invention (P50%) / (P5%) is determined by adjusting the sample at a test temperature of 23 ° C. ± 2 ° C. for 24 hours or more before the test, and then subjecting the sample to a compression test. The compressive stress at 5% is calculated and obtained as the ratio thereof.

The ratio of the compressive stress is a numerical value indicating the performance of the energy absorbing material. The performance of the energy absorbing material is that the generated impact is low and the amount of absorbed energy per unit volume is large. In other words, the difference between the compressive stress when the strain is small and the compressive stress when the strain is large is small. The compression stress ratio defined in the present invention is most preferably 1. However, since the in-mold foam molded body obtained from the thermoplastic resin pre-expanded particles has a closed cell structure, the compression stress increases as the strain increases. Tend.
When the ratio of compressive stress is 1.6 or less, it means a foamed molded article with high energy absorption efficiency.

  In the case of the pre-expanded particles of the present invention, the layered compound organized with a nonionic compound is uniformly and finely dispersed in the resin, and is also dispersed in the cell film constituting the expanded cell. The elastic modulus of the cell membrane is increased by the dispersed layer compound, and as a result, the elastic modulus of the foam is increased. As a result, the compressive stress at the time of low strain of the foam is increased. On the other hand, the dispersed layered compound is a foreign substance to the resin in the cell membrane. For this reason, when a certain strain or more is applied, the layer film is cracked and the cell film is broken. The destruction of the cell membrane leads to the dissipation of the internal air, and the increase in the compressive stress at the time of high strain, which is seen in the case of the closed cell structure, can be suppressed. As a result, the compressive stress at the time of high strain becomes low. The effect of suppressing the increase in compressive stress at the time of high strain is a remarkable effect when treated with a nonionic compound. Due to these two kinds of effects, when the pre-expanded particles of the present invention are used, a foamed molded article having high energy absorption efficiency can be obtained in which the compressive stress at low strain is high and the compressive stress at high strain is not high.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The main raw materials used in Examples and Comparative Examples are summarized below. Hereinafter, “part” and “%” are based on weight unless otherwise specified.

(material)
(A) Polyolefin resin A-1) Ethylene-propylene random copolymer (melting point 145 ° C. MFR 5 g / 10 min)
A-2) Homopolypropylene (melting point 165 ° C. MFR 20 g / 10 min)
(B) Functional group-containing modified polyolefin resin B-1) Modified polypropylene having a maleic anhydride conversion rate of 5 wt% (molecular weight 40,000)
B-2) Modified polypropylene having a maleic anhydride conversion rate of 2 wt% (molecular weight 80,000)
(Layered compound)
Co-op Chemical Co., Ltd. swelling mica Product name: Somasif ME100
(Polyether compound)
Polyoxyethylene octyl phenyl ether manufactured by Nippon Oil & Fats Co., Ltd. Product name: Nonion HS-206
(Layered compounds organized with cationic surfactants)
C-2) Coop Chemical Co., Ltd. swelling mica Product name: Somasif MAE120
A product obtained by adding 61 parts by weight of a cationic surfactant to 100 parts by weight of Somasif ME100. By adding 8.8 parts by weight to 100 parts by weight of the resin, the final inorganic weight becomes 5%.
(Example of production of a layered compound organized with a nonionic compound)
Ion-exchanged water and the layered compound Somasif ME100 were mixed for 5 minutes with a wet mill (colloid mill, Nippon Seiki Co., Ltd., rotational speed 3000-5000 rpm, shear rate 2000-3000 (1 / s)) to form a slurry. Next, 40 parts by weight of the polyether compound nonion HS-206 was added to 100 parts by weight of the layered compound, and the mixture was processed for 15 to 30 minutes. After that, it was dried and pulverized to obtain a layered compound (C-1) organized with a polyether compound. By adding 7.5 parts by weight to 100 parts by weight of the resin, the final inorganic weight becomes 5%.

Example 1
(Pelletization by extrusion kneading)
In a weight ratio shown in Table 1, (A) a polyolefin-based resin, (B) a functional group-containing polyolefin-based resin, and (C-1) a layered compound organized with a nonionic compound obtained in Production Example were blended, Resin pellets having a particle weight of 1.8 mg were obtained by melt-kneading using a twin screw extruder (manufactured by Nippon Steel Works, TEX30HSS-25.5PW-2V).
(Production of foam)
100 parts of the resin pellets, 300 parts of powdered basic tricalcium phosphate as a dispersing agent, 300 parts of an aqueous dispersion medium containing 0.01 part of sodium n-paraffin sulfonate as a dispersing aid, and 6 to 12 parts of isobutane as a blowing agent Was charged into a pressure-resistant container having an internal volume of 10 L, heated while stirring and held for 10 minutes, and then isobutane was additionally injected and adjusted to a predetermined pressure, and held for 30 minutes. Thereafter, while isobutane is injected and the internal temperature and pressure are kept constant, the valve at the bottom of the pressure vessel is opened, and the aqueous dispersion medium is released under atmospheric pressure through an orifice plate having a hole diameter of 4.0 mmφ. Plastic resin pre-expanded particles were obtained. Next, a molded body was produced using the pre-expanded particles obtained. Further, the obtained molded body was dried at 75 ° C. for 16 hours, then cured at 23 ° C. for 24 hours, and used for measurement of compressive stress.
(Evaluation of compressive stress of foam)
A test piece having a length of 50 mm, a width of 50 mm, and a thickness of 25 mm is cut out from the foamed molded article, and compressed at a rate of 10 mm / min in accordance with NDZ-Z0504, and a compression stress at 50% compression and a compression stress at 5% compression. And the compression stress ratio was evaluated.
Hereafter, about Examples 2-8 and Comparative Examples 1-7, the sample was produced similarly to Example 1 and evaluated.

実施例１〜８については、得られる型内発泡成形体は圧縮応力比が１．６以下であり、高いエネルギー吸収効率を示している。

About Examples 1-8, the in-mold foam molding obtained has a compressive stress ratio of 1.6 or less, indicating high energy absorption efficiency.

比較例１〜４は、ポリオレフィン系樹脂のみで予備発泡粒子、及びこれを用いた型内発泡成形体を作製しており、得られる圧縮応力の比は１．６を超えている。比較例５は、非イオン性化合物ではなく、特開２００２−３０１８１号公報や特開２００２−３５６５７４号公報に記載のカチオン系界面活性剤で有機化した層状化合物を用いた発泡体についての実験例であるが、この場合も圧縮応力比が１．６を越えている。比較例７は、過剰に非イオン性化合物で有機化した層状化合物を配合しているので、熱可塑性樹脂発泡成形体の作製が困難となり評価ができなかった。

In Comparative Examples 1 to 4, pre-foamed particles and in-mold foam-molded articles using the same are produced using only a polyolefin-based resin, and the resulting compression stress ratio exceeds 1.6. Comparative Example 5 is not a nonionic compound, but an experimental example of a foam using a layered compound organized with a cationic surfactant described in JP-A Nos. 2002-30181 and 2002-356574 However, also in this case, the compressive stress ratio exceeds 1.6. Since Comparative Example 7 contains a layered compound that has been excessively organized with a nonionic compound, it was difficult to produce a thermoplastic resin foam molded article, and evaluation could not be performed.

It is the graph showing the compressive stress with respect to the distortion amount of Example 2 and Comparative Example 2 of the present invention.

Claims (6)

  With respect to 100 parts by weight of a resin composition comprising (A) a polyolefin-based resin and (B) a functional group-containing modified polyolefin-based resin, (C) a layered compound organized with a nonionic compound is used as an inorganic weight. It consists of thermoplastic resin pre-expanded particles with a resin containing 5 parts by weight or more and 20 parts by weight or less as a base resin. In the compression test defined by NDZ0504, the compression stress (P5%) when the compression strain is 5% A thermoplastic resin foam molded article having a ratio (P50%) / (P5%) of compressive stress (P50%) when the compressive strain is 50% is 1.6 or less.   2. The thermoplastic resin according to claim 1, wherein (A) the polyolefin resin is 30 wt% or more and 85 wt% or less, and (B) the functional group-containing modified polyolefin resin is 15 wt% or more and 70 wt% or less. Foam molded body.   The thermoplastic resin foam molded article according to claim 1 or 2, wherein the nonionic compound is a polyether compound.   (C) A layered compound organized with a nonionic compound is obtained by mixing a nonionic compound and a layered compound in water or a polar solvent containing water. The thermoplastic resin foam molded article according to any one of to 3.   The thermoplastic resin foam molded article according to any one of claims 1 to 4, wherein the layered compound is a layered silicate.   (A) Polyolefin resin is polypropylene resin, The thermoplastic resin foam molded object of any one of Claims 1-5 characterized by the above-mentioned.

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