WO2008069013A1

WO2008069013A1 - Resin foam suitable as energy absorption material

Info

Publication number: WO2008069013A1
Application number: PCT/JP2007/072249
Authority: WO
Inventors: Mitsuharu Korogi; Takeshi Sugiyama; Hidekazu Oohara; Takeshi Sato
Original assignee: Kaneka Corporation
Priority date: 2006-12-05
Filing date: 2007-11-16
Publication date: 2008-06-12
Also published as: JPWO2008069013A1

Abstract

Disclosed is a form which has the same level of impact absorption property as that of a hard polyurethane foam, shows a little increase in volume when absorbs moisture, and is suitable as an energy absorption material such as a bumper core and a side impact material. Specifically disclosed is a thermoplastic resin foam, which is characterized by having a ratio between a load at 70% deformation (F70%) and a load at 20% deformation (F20%) (i.e., a (F70%)/(F20%) ratio) as determined by a dynamic compression test of 0.70 to 1.30 inclusive, and more preferably having an anisotropy ratio for each cell of 1.1 to 3.0 inclusive.

Description

Specification

Resin foam suitable for energy absorber

Technical field

[0001] The present invention relates to a resin foam suitable for an energy absorbing material.

Background art

[0002] Automotive energy absorbers are used in various applications such as bumper cores and side bumps, and are required to be lighter in terms of improving fuel consumption and reducing costs.

[0003] When an energy absorber receives an impact, it absorbs the impact energy by partial destruction or deformation of itself, so the protected object does not receive an impact directly, but a load is still generated by the impact. . If this load is too large, the object to be protected will be destroyed and its function will be lost. Therefore, an energy absorber that minimizes the maximum load that can be generated is desirable.

[0004] On the other hand, the energy absorption amount is an integration of the impact load and the amount of deformation of the energy absorbing material, and a larger impact load can absorb more energy. From these two conflicting events, the most important performance required for energy absorbers is to absorb more energy by maintaining a constant load while keeping the maximum load generated. .

[0005] Furthermore, foamed plastics are often used as energy absorbing materials for automobiles from the viewpoint of lightness. Rigid polyurethane foam is widely known as a foamed plastic having such characteristics. Rigid polyurethane worms exhibit an almost constant compressive stress from 20% to 70% in the dynamic compression test due to the longitudinal characteristics of the cells and the characteristics of the resin, which tends to cause brittle fracture. Since it has such characteristics, the impact absorption performance of rigid polyurethane foam is good, but it is expensive and the volume increase due to moisture absorption is large, so it is not suitable as a core material for automobile bumpers exposed to the outside air.

In Patent Document 1, a plurality of thermoplastic extruded strand foams are combined to obtain a foam having higher compressive strength in one direction than in the other direction. It is disclosed that an impact is applied in the direction of higher strength to absorb the impact. This foam has been shown to have a higher compressive strength at 25% strain than a foam of the same material and density. However, only the foams made of polyolefin are disclosed in the literature. Polyolefins have the disadvantage that they cannot exhibit sufficient shock absorbing properties at high temperatures in automobiles where the temperature dependence of their mechanical properties is large and the temperature is relatively high. In addition, polyolefin has poor resin brittleness, so it cannot exhibit the same energy absorption characteristics as rigid polyurethane foam.

[0007] Patent Document 2 discloses a foam having a bending stiffness of 6000 to 14,000 kgf / cm ² , and the foam diameter in the direction in which the bubble diameter in the thickness direction of the foam is perpendicular to the thickness direction. A foam having an elliptical shape that is larger than the bubble diameter is disclosed. However, for the reasons described above, foams made of polyolefin cannot be expected to have the same energy absorption characteristics as rigid polyurethane foam.

[0008] On the other hand, expandable polystyrene resin is inexpensive and easily obtains an in-mold foam-molded product. Although the volume increase due to water absorption is small, it is not suitable for an energy absorbing material in an automobile at a relatively high temperature. In addition, since the load when subjected to an impact increases as the amount of deformation of the material increases, there is a drawback that the impact of the protected object increases.

[0009] Patent Document 3 discloses that a foam molded article having excellent impact absorption has a weight average molecular weight of 450,000 to 120,000 and a compression strain of 5% in a compression test defined by JIS-K7220. A polystyrene foam is disclosed in which the ratio Y / X of the compressive stress X and the compressive stress Y when the compressive strain is 50% is 2.0 or less. This is not disclosed for absorbing a large amount of energy by maintaining a constant stress S, which indicates that the impact stress is small at the beginning of impact. In general, in polystyrene foam, the stress during compression when the compressive strain exceeds 50% greatly increases. Therefore, it cannot be said that it exhibits good shock absorption in applications where compressive strain is further generated. V absorbs a lot of energy, and even shock absorbers are required to exhibit almost constant stress from about 20% to 70% compressive strain.

[0010] Patent Document 4 includes a polycarbonate resin foam molded article, and a value obtained by dividing the energy absorption amount of the molded article at 50% compression at 80 ° C by the density of the molded article is 30 (kg ' cm/ An automotive energy absorber that is greater than or equal to cm ³ ) / (g / cm ³ ) is disclosed! However, this document only shows that the amount of energy absorbed per unit mass of the compact is large, and does not mention compressive stress. Therefore, even if the absorbed energy is large, the impact received by the protected object at the same time. The load can be very large.

[0011] Patent Document 5 discloses a structure in which a foamed molded product is destroyed when subjected to a large impact by dispersing the polyolefin resin foamed particles (B) in a foamed product (A) made of polystyrene resin. In the dynamic compression test, there is disclosed a thermoplastic resin foam molded article having a ratio of impact load at 20% strain to impact load at 60% strain of 1.6 or less. This document shows a performance close to that of polyurethane foam in a dynamic compression test, but only discloses that a constant load is maintained from 20% strain to 60% strain. Furthermore, it is required to maintain a constant load for a longer time!

[0012] Further, Patent Document 6 describes at least one thermoplastic resin foamed particle having a three-dimensional network structure, and one or more thermoplastic resins that do not melt at least partially with the thermoplastic resin foamed particles. There is disclosed an energy absorbing material comprising a composite resin molded body composed of particles and a space in which the composite resin molded body can be scattered during energy absorption. Such a document discloses an energy absorbing material that exhibits a substantially constant compressive stress from 10% strain to 60% strain in a dynamic compression test. In this document, since the composite resin molded body and the space where the composite resin molded body can be scattered are formed, it is necessary to design the shape including the cutting, drilling, joining process, or scattered space of the composite resin molded body. There is a demand for a material that exhibits good shock absorbing performance as a foamed molded product itself without adding such post-processing and shape design.

[0013] Patent Document 1: Japanese Translation of Special Publication 2002-511917

Patent Document 2: Japanese Patent Laid-Open No. 10-219017

Patent Document 3: Japanese Patent Laid-Open No. 2002-212322

Patent Document 4: JP-A-11 287277

Patent Document 5: Japanese Unexamined Patent Application Publication No. 2004 142260

Patent Document 6: Japanese Unexamined Patent Publication No. 2006-68905

Disclosure of the invention Problems to be solved by the invention

[0014] An object of the present invention is to provide a foam suitable for an energy absorbing material such as a bumper core and a side impact material that has a shock absorbing property equivalent to that of a rigid polyurethane foam and has a small volume increase due to moisture absorption. There is.

Means for solving the problem

That is, the present invention relates to a load at 70% strain (F) based on a dynamic compression test and a strain at 20% strain.

70%

The load ratio (F) / (¥) of load (F) is 0 · 70 or more and 1 · 30 or less.

20% 70% 20%

The present invention relates to a thermoplastic resin foam having a volume increase rate of 5% or less when immersed in time.

[0016] As a preferred embodiment,

(1) Cell shape anisotropy ratio is 1.1 or more and 3.0 or less,

(2) Copolymer comprising aromatic bur, unsaturated dicarboxylic anhydride and N-alkyl-substituted maleimide (A) 80-30 wt% and aromatic bul cyanide bur copolymer (B) 2 0-70 wt % Of a foamed thermoplastic resin composition formed by mixing

(3) The aromatic bullet is styrene,

(4) The unsaturated dicarboxylic acid anhydride is maleic anhydride,

(5) N-alkyl-substituted maleimide force N-phenylmaleimide,

(6) The cyanide bur is acrylonitrile,

(7) The thermoplastic resin foam is produced by an extrusion foam molding method,

It relates to the thermoplastic resin foam described above.

[0017] Another aspect of the present invention is the thermoplastic resin foam described above.

(1) Automotive bumper core,

(2) It relates to a side impact pad for automobiles.

The invention's effect

[0018] According to the present invention, it is possible to obtain a thermoplastic resin foam that is low in cost, excellent in energy absorption characteristics, and small in volume change due to water absorption.

BEST MODE FOR CARRYING OUT THE INVENTION [0019] The thermoplastic resin foam of the present invention has a load ratio between a load at 70% strain (hereinafter referred to as F) and a load at 20% strain (hereinafter referred to as F) based on a dynamic compression test. (F) / {\

70% 20% 70% 20%

The value of) is between 0.70 and 1.30. In order to absorb the energy while suppressing the maximum generated load as much as possible, it is preferably 0.75 or more and 1.20 or less.

[0020] Load ratio of load F at 70% strain and load F at 20% strain based on dynamic compression test (F

70% 20% 70%

) / (F) is an index of shock absorption characteristics.

20%

It means that it has good energy absorption performance that absorbs large energy while suppressing it. In the present invention, 70% load at strain (F) and 20% based on the dynamic compression test.

The load at 70% strain (F) is obtained as follows.

20%

[0021] The dynamic compression test is performed according to JIS-K7134. The equipment is a vertical drop tester with a guide, and the shape of the test sample is 100 mm long × 100 mm wide × 50 mm thick, and left in a constant temperature room at 23 ± 2 ° C and 50 ± 10% humidity for 24 hours. Is a test sample.

[0022] The dynamic compression test is performed in a constant temperature room at 23 ± 2 ° C and a humidity of 50 ± 10%. The fall height and the weight of the cone are determined so that the strain of the test sample is 80% or more. Free fall of the heavy cone on the test sample, measure the acceleration a generated in the heavy cone with an accelerometer attached to the heavy cone of the test equipment, and record it as a time function.

[0023] The load F [kN] is given by the following equation as the product of the acceleration a [G] and the heavy cone mass M [kg].

F [kN] = (a X M X 9.8) / 1000

[0024] Measure the height H of the pyramid while the test sample is compressed by the cone, and record it as a function of time. The amount of deformation of the sample is the difference between the height of the heavy cone H0 and H when the bottom surface of the heavy cone touches the top surface of the sample (deformation amount [mm] = H0—H). Strain is expressed as a percentage.

Strain [%] = (Deformation amount / Initial thickness of test sample) X 100

[0025] As described above, the load at 70% strain (F) and the load at 20% strain (F) can be obtained.

70% 20%

come. The load ratio is calculated from these values according to the following formula.

Load ratio = (F) / (F)

70% 20%

[0026] The volume increase rate when the thermoplastic resin foam of the present invention is immersed in water for 24 hours is 5% or less. If the volume increase rate was greater than 5%, resin foam was used for the bumper core. In this case, the bumper face may be deformed when the vehicle body is covered with water. The volume increase rate is calculated by measuring the dimensions of each side of the resin foam cut into a cubic shape, and then measuring the dimensions of each side by immersing the resin foam in water for 24 hours. The volume is calculated and the increase in volume is divided by the volume of the original resin foam.

[0027] In the present invention, as the thermoplastic resin constituting the thermoplastic resin foam, specifically, a polyethylene naphthalate resin, a polycarbonate resin, a polyether ether ketone resin, a phenylene ether And a mixture of the resin and the styrene resin. Also, a copolymer of the monomer constituting the resin and maleic anhydride, N-analkyl substituted maleimide, etc., a copolymer of aromatic bur and maleic anhydride, N alkynole-substituted maleimide, etc., aromatic vinyl cyanide Examples thereof include a bull copolymer and a resin composition made of these resins. Among them, a thermoplastic resin composition obtained by mixing a copolymer of an aromatic bule, an unsaturated dicarboxylic anhydride and an N-alkyl-substituted maleimide and an aromatic burcyanide bur copolymer is preferable. Among such thermoplastic resins, a thermoplastic resin having a bending fracture strain of 0.1% to 2.5% is preferable.

[0028] These thermoplastic resins preferably have heat resistance. The thermoplastic resin foam of the present invention has a heat resistance of 120 ° C., preferably a heating dimensional change rate of 3% or less when exposed to a hot air circulating dryer maintained at 100 ° C. for 168 hours. It is more preferable that the rate of change in heating dimension is 3% or less when exposed to a hot air circulating dryer for 168 hours.

[0029] The cell anisotropy ratio of the thermoplastic resin foam of the present invention is preferably 1.1 or more and 3.0 or less. The cell anisotropy ratio is defined by (cell vertical width) / (cell horizontal width). In the present invention, the compression direction of the foam is the vertical direction, and the direction orthogonal to the vertical direction is the horizontal direction. That is, when the cell is compressed in the longitudinal direction, good energy characteristics can be exhibited. When the vertical direction is determined, there are a plurality of horizontal directions perpendicular to it, and the cell width differs depending on which horizontal direction the width is taken, and the anisotropy ratio may be different. In such a case, the anisotropy ratio is calculated by adopting the width in the direction in which the lateral width becomes the smallest.

[0030] A thermoplastic resin having a bending fracture strain of 0.1% or more and 2.5% or less is subjected to bending deformation. In this case, breakage tends to occur while the deformation is small. Further, a foam having a vertically long shape with a cell anisotropy ratio of 1.1 to 3.0 is liable to cause cell destruction. When compressive deformation is applied to such a foam, a fracture zone occurs in the plane perpendicular to the compression direction, and as the compression strain increases, a fracture zone is created in sequence, so that a constant compressive stress is sustained and good. It is considered that it exhibits excellent energy absorption characteristics.

[0031] The thermoplastic resin foam of the present invention comprises a copolymer (A) comprising 80% to 30% by weight of an aromatic bull, an unsaturated dicarboxylic acid anhydride, and an N-alkyl-substituted maleimide, and an aromatic vinyl lucyanated bull copolymer. The polymer (B) is preferably a foamed thermoplastic resin composition obtained by mixing 20 to 70% by weight.

[0032] The aromatic bur constituting the copolymer (A) comprising an aromatic bule, an unsaturated dicarboxylic acid anhydride and an N-alkyl-substituted maleimide includes styrene, α-methylstyrene, ethynole styrene, isopropino styrene, dimethino. Examples include restyrene, bromostyrene, chlorostyrene, butyltoluene, and butylxylene.

[0033] Of these, styrene and α-methylstyrene are preferred from the viewpoint of compatibility with the aromatic bulcyanated bulene copolymer (Β) and ease of polymerization, and are also inexpensive. Some styrene is optimal.

[0034] Examples of the unsaturated dicarboxylic acid anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride, and the like. From the viewpoint of compatibility with the copolymer (Β), ease of polymerization, and low cost. Hydrous maleic acid is preferred.

[0035] Examples of アルキル -alkyl-substituted maleimide include メチル methyl maleimide, ブチル butyl maleimide, シクロ cyclohexyl maleimide, Ν phenyl maleimide, Ν-4-diphenyl maleimide, Ν-2 kurono phenolemaleimide, Ν- 4 Bromophenylalemaleimide, N-1-naphthalemaleimide, and the like. Among them, Νphenylmaleimide is most suitable from the viewpoint of compatibility with the copolymer (Β), ease of polymerization, and low cost.

[0036] Sum of aromatic bur, unsaturated dicarboxylic anhydride and Ν-alkyl-substituted maleimide monomers in copolymer (Α) consisting of aromatic bur, unsaturated dicarboxylic anhydride and アルキル alkyl-substituted maleimide When the amount is 100% by weight, it is preferable that the alkyl-substituted maleimide is 40% by weight or more from the viewpoint of imparting heat resistance. In view of water absorption and moisture absorption resistance, the unsaturated dicarboxylic acid anhydride is preferably 5% or less.

[0037] Further, the copolymer (B) used in the present invention also has an aromatic bull force and a cyanide bull force. As the aromatic bullet, as described above, styrene and α-methylstyrene are preferable from the viewpoint of compatibility with the copolymer (A) and ease of polymerization, and styrene is also inexpensive. Is the best.

[0038] Further, examples of cyanuric bur include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and the like. From the viewpoint of compatibility with the copolymer (Α) and ease of polymerization, acrylonitrile is preferred. Is preferred. In view of compatibility with the copolymer (ニトリル), ease of polymerization, and low cost, a copolymer of styrene and acrylonitrile is preferred.

[0039] The thermoplastic resin composition of the present invention comprises the copolymer (Α) and the copolymer.

(Β) is mixed.

[0040] The weight ratio of the copolymer (Α) to the copolymer (Β) in the resin composition is such that the copolymer (Α) is 30 to 80% by weight and the copolymer (Β) is 70 to 20% by weight. % Of the preferred copolymer (Α) is 35 to 70% by weight and the copolymer (Β) is more preferably 65 to 30% by weight of the copolymer (Α) and 40 to 65% by weight. The polymer (60) is more preferably 60 to 35% by weight.

[0041] In the present invention, as required for the thermoplastic resin composition, a nucleating agent, a stabilizer, a lubricant, a flame retardant, an antistatic agent, a plasticizer, a water absorbing agent, a radiation inhibitor, and the like. Additives may be added.

[0042] The thermoplastic resin foam of the present invention can be obtained by a known foaming method.

[0043] As a foaming method for obtaining the thermoplastic resin foam of the present invention, a thermoplastic resin is melt-kneaded in an extruder, a foaming agent is injected and kneaded, and the foamed molded body is extruded into the atmosphere from a die. There is an extrusion foaming method of obtaining

[0044] In the case of the extrusion foam molding method, when a slit-shaped die is used to form a plate-like extruded foam, the cell expands in the thickness direction when the resin is extruded. It is possible to obtain a foam having an anisotropy ratio larger than 1.1. In order to greatly increase the cell anisotropy ratio in the thickness direction, the thickness expansion ratio when foaming the molten resin into the atmosphere during extrusion foaming is increased. As a method of increasing the thickness expansion rate, a slit die is used as the die. There are a method of increasing the back pressure during extrusion by reducing the slit thickness, a method of increasing the elasticity at the time of melting the resin, or a method of increasing the die swell by changing the die flow path. Alternatively, there is a method of increasing the molding resistance during molding. In order to increase the molding resistance, there are a method of reducing the speed of the molding roll and a method of increasing the frictional resistance between the molding die and the foam.

[0045] Further, when foamable resin particles impregnated with a foaming agent are produced, the foamable resin particles are heated to be prefoamed to produce prefoamed particles, and the prefoamed particles are subjected to in-mold foam molding, Method and resin particles are placed in a pressure-resistant container with a dispersant, an aqueous dispersion containing a surfactant, and a volatile foaming agent. The temperature is raised and the resin particles are impregnated with the foaming agent, and then released under a low-pressure atmosphere. Then, pre-expanded particles are prepared, and when the pre-expanded particles are molded in a mold, there are the re-coating method and the V, bead method.

[0046] In the bead method in-mold molding method, as a method of adjusting the cell anisotropy ratio to a desired range, pre-expanded particles are filled in a mold and heated to fuse the pre-expanded particles together. After expanding to form a foam that has no gaps between the particles, one mold is moved, and the foam is further expanded in that direction, so that the cell shape is elongated in the moving direction. A molded product can be obtained.

[0047] As the foaming agent for obtaining the thermoplastic resin foam of the present invention, one type selected from the group consisting of a physical type foaming agent and a chemical type foaming agent, or a mixture of two or more types may be used. Can do.

[0048] Specific examples of the physical blowing agent include hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, neopentane, and cyclopentane; —Gifnole talented Yutan, 1, 1, 1 卜 Lifnore talented Routan, 1, 1, 2— 卜 Lifnore talented Loetan, 1, 1, 1, 2—Teraf Nooret Roetan, 1, 1, 2, 2, —Te卜 Rafnorée Roetan, 1, 1, 1, 2, 2-Fluorinated hydrocarbons such as pentafluoroethane, difluoromethane, trifluoromethane; inorganic gases such as carbon dioxide, nitrogen, water, argon, helium; dimethyl ether And ethers such as Nore, Jetinoreethenore, Methinoleetinoreetenore, Isopropinoreetenore, _n- Pinoleete, and Diisoamylether. These can be used alone or in admixture of two or more. [0049] Specific examples of the chemical foaming agent include, for example, N, N'-dinitrosopentamethylenetetramine, p, p, monooxybisbenzenesulfonyl hydrazide, hydrazodicarbonamide, sodium carbonate, and azodicarbon. Examples include amide, terephthalazide, 5-phenyltetrazole, p-toluenesulfonyl semicarbazide and the like. These can be used alone or in admixture of two or more.

[0050] The density of the thermoplastic resin foam of the present invention is preferably 1 lkg / m ³ or more and 110 kg / m ³ or less from the viewpoint of obtaining good energy absorption characteristics. Within this range, the density can be adjusted according to the desired impact load.

[0051] The foamed molded product obtained by the molding method of the present invention is a side impact pad for automobiles and a bumper core material.

It is preferably used for (core) and the like.

Example

[0052] Hereinafter, the thermoplastic resin foam of the present invention will be described in detail by way of specific examples, but the present invention is not limited to only these examples. In the following, “part” and “%” are based on weight unless otherwise specified.

[0053] (Test method)

[Dynamic compression test]

Cut the resin foam into a rectangular parallelepiped shape with a length of 100 mm, width of 100 mm, and thickness of 50 mm so as not to include the surface skin layer, and leave it in a temperature-controlled room at a temperature of 23 ° C ± 2 ° C and a humidity of 50 ± 10% for 24 hours. A test piece for a dynamic compression test was obtained.

[0054] The dynamic compression test was carried out in a constant temperature room at a temperature of 23 ± 2 ° C and a humidity of 50 ± 10%, using a shock impact tester CST-320S for shock absorbers manufactured by Yoshida Seiki Co., Ltd. The energy given to the test piece in the dynamic compression test is determined by the product of the drop height and the weight of the heavy cone. The fall height and weight of the cone in the present invention were determined so that the strain of the evaluation sample was 80% or more.

[0055] An acceleration transducer AS-500HA manufactured by Kyowa Denki Co., Ltd. was fixed to the heavy cone of the test machine, and the force and acceleration G measured on the heavy truncated cone were measured. The load F [N] generated by impact is given by the following equation as the product of acceleration a [G] and the weight of the heavy cone M [kg].

F [kN] = (a X M X 9.8) / 1000

[0056] The deformation amount of the evaluation test piece was measured using a laser displacement meter manufactured by Keyence Corporation. in front Attach the displacement meter to the tester and measure the distance H between it and the displacement meter. The method of calculating the deformation of the evaluation specimen is calculated from the distance HO at which the output of the accelerometer is obtained, that is, when the drop jig and the evaluation specimen are in contact with each other. Deformation amount [mm] = HO— H

[0057] The strain based on the dynamic compression test is expressed as a percentage by dividing the amount of deformation by the thickness of the test piece as represented by the following equation.

Strain [%] = (Deformation amount / Evaluation sample thickness) X 100

[0058] The load F at 70% strain and the load F at 20% strain based on the dynamic compression test are

70% 20% When the strain is specified as described above, it is defined by the load measured at the time of the strain. The load ratio was calculated from these values according to the following formula.

Load ratio = (F) / (F)

70% 20%

[0059] [Bending fracture strain]

Bending fracture strain is measured according to JIS K7171. The foam base resin is molded into a strip-shaped test piece with a thickness of 6 mm, a width of 15 mm, and a length of 120 mm, and left in a constant temperature room at 23 ° C ± 1 ° C for 24 hours. Obtained. A three-point bending test was performed using a tensile compression tester manufactured by Minebea Co., Ltd. The distance between fulcrums was 90 mm, and the test speed (indenter descent speed) was 2 mm / min. The strain at break ε [%] is the deflection at break s [mm] and the thickness h of the specimen.

b b

It is given by the following equation from [mm] and the distance between supporting points L [mm].

ε = (6 X h X s X 100) / (L ² )

b b

[0060] [Cell anisotropy ratio]

A line was drawn vertically / horizontally in the foam cross-sectional photograph, the number of cells crossing the line was counted, and the width per cell was calculated by dividing the line length by the number of cells. The cell anisotropy ratio was calculated according to the following formula. The foam thickness direction was vertical and the direction perpendicular thereto was horizontal.

Cell anisotropy ratio = (cell height) / (cell width)

[0061] [Volume change test by water absorption]

Cut the resin foam into a cube shape 25 mm long, 25 mm wide, and 25 mm high so that it does not include the surface skin layer, and leave it in a constant temperature room at 23 ° C ± 1 ° C for 24 hours. A specimen was obtained. The length, width, and height of the test piece were measured, and the volume V of the test piece was calculated from the following equation. v _{i =} vertical X horizontal X height

[0062] After completely immersing the resin foam in water and leaving it in a constant temperature room at 23 ° C ± 1 ° C for 24 hours, measure the length, width, and height of the test piece. Calculate the volume of the specimen after immersion in

V = vertical X horizontal X height

2

[0063] The volume increase rate was calculated by the following formula.

Volume increase rate [%] = {(V -V) / V} X 100

2 1 1

[0064] [Heat resistance test]

The heating dimensional change rate was measured according to JIS-K6767. Write three straight lines that are parallel to each other in the vertical and horizontal directions on a flat plate of length 100mm, width 100mm, and thickness 25mm. The dimension of was measured and used as the dimension before heating (L1). Next, the foam was placed horizontally in a hot air circulating dryer maintained at 120 ° C, heated for 168 hours, then taken out, measured for the dimensions of the sample, and set to the dimension after heating (L2). The heating dimensional change rate was calculated from the following equation.

Heating dimensional change rate (%) = ((L2-L1) / L1) X 100

The same test was conducted with the temperature of the hot air circulating dryer set at 100 ° C, and the heating dimensional change rate at 100 ° C was calculated using the same formula.

[Example 1]

Copolymer (A) made by Denki Kagaku Kogyo Co., Ltd., which is a copolymer of styrene 49% N-phenylmaleimide 50% and maleic anhydride 1%, trade name: Denka IP MS-NA, copolymer ( As B), AS—XGS made by Denki Kagaku Kogyo Co., Ltd., which is a copolymer of 25% acrylonitrile and 75% styrene, is used. 80% / 20% of copolymer (A) / copolymer (B) is used. Thus, a thermoplastic resin composition was prepared. The thermoplastic resin composition was molded and subjected to a bending test. As a result, the bending fracture strain was 0.32%.

[0066] To 100 parts of this resin composition, 0.5 parts of talc (trade name: Talcan powder, manufactured by Hayashi Kasei Co., Ltd.) as a nucleating agent was dry blended, and the resulting resin composition was To a two-stage connection type extruder with a 65mm diameter first stage extruder and a 90mm diameter second stage extruder connected in series 5 It was supplied at a rate of Okg / hour. The resin composition supplied to the 65 mm diameter extruder is melted and kneaded by heating to about 280 ° C., and then 2.5 parts of dimethyl ether and n-butane as a blowing agent near the tip of the first stage extruder. 5 parts were press-fitted into the molten thermoplastic resin composition.

[0067] Thereafter, the resin temperature is cooled to 200 ° C with an extruder having a diameter of 90 mm connected to the extruder, and the air is released from the die lip of the rectangular slit die provided at the tip of the extruder having a diameter of 90 mm. Extrusion foam having a density of 42 kg / cm ³ was obtained by extrusion. Table 1 shows the anisotropy ratio of the cells calculated by observing the cell structure of the foam obtained by a microscope. The obtained foam was subjected to a dynamic compression test, and the calculated load ratio = (F) / (F) is shown in Table 1. further,

70% 20%

Table 1 shows the measurement results of the volume change rate of the obtained foam when immersed in water and the heating dimensional change rate at 100 ° C and 120 ° C.

[Example 2]

The mixing ratio of copolymer (A) / copolymer (B) was changed to 60% / 40%, and the heat-kneading temperature in an extruder with a diameter of 65 mm was 260 ° C and the extruder with a diameter of 90 mm. Extruded foam having a density of 39 kg / cm ³ was obtained under the same conditions as in Example 1 except that the cooling temperature was changed to 180 ° C. Table 1 shows the anisotropic ratio of the cells calculated by observing the cell structure of the foam obtained by the microscope. The resulting foam was subjected to a dynamic compression test and the calculated load ratio = (F

70

) / (F) is shown in Table 1. Further, the volume change rate of the obtained foam when immersed in water, and

% 20%

Table 1 shows the measurement results of the rate of change in dimensional heating at 100 ° C and 120 ° C. As a result of molding the thermoplastic resin composition used in Example 2 (copolymer (A) / copolymer (B) mixing ratio 60% / 40%) and performing a bending test, The bending fracture strain was 0.49%.

[0069] (Example 3)

The mixing ratio of copolymer (A) / copolymer (B) was changed to 30% / 70%, and the heating and kneading temperature in an extruder with a diameter of 65 mm was 240 ° C and the extruder with a diameter of 90 mm Extruded foam having a density of 28 kg / cm ³ was obtained under the same conditions as in Example 1 except that the cooling temperature was changed to 140 ° C. Table 1 shows the anisotropic ratio of the cells calculated by observing the cell structure of the foam obtained by the microscope. The resulting foam was subjected to a dynamic compression test and the calculated load ratio = (F

70

) / (F) is shown in Table 1. Further, the volume change rate of the obtained foam when immersed in water, and Table 1 shows the measurement results of the rate of change in dimensional heating at 100 ° C and 120 ° C. As a result of molding the thermoplastic resin composition used in Example 3 (copolymer (A) / copolymer (B) mixing ratio is 30% / 70%) and conducting a bending test, The bending fracture strain was 0.74%.

[0070] (Example 4)

Except that PS Japan Co., Ltd. polystyrene G9401 was changed to Example 1 except that the heating and kneading temperature in an extruder with a diameter of 65 mm was changed to 200 ° C and the cooling temperature in an extruder with a diameter of 90 mm was changed to 120 ° C. An extruded foam having a density of 31 kg / cm ³ was obtained under the same conditions. Table 1 shows the anisotropy ratio of the cells calculated by observing the cell structure of the foam obtained by the microscope. The obtained foam was subjected to a dynamic compression test, and the calculated load ratio = (F) / (F) is shown in Table 1. further

70% 20%

Table 1 shows the measurement results of the volume change rate of the obtained foam when immersed in water and the heat dimensional change rate at 100 ° C and 120 ° C. In addition, as a result of carrying out a bending test after molding the thermoplastic resin (PS Japan Co., Ltd., polystyrene G9401) used in Example 4, the bending fracture strain was 0.92%.

[0071] (Comparative Example 1)

A test piece was cut so that the extruded foam obtained by the same method as in Example 1 was compressed in the extrusion direction, that is, in the direction perpendicular to the thickness direction, and a dynamic compression test was performed. The cell anisotropy ratio was calculated with the extrusion direction as the longitudinal direction. The results are shown in Table 1. The obtained foam was subjected to a dynamic compression test, and the calculated load ratio = (F) / (F) is shown in Table 1. In addition,

70% 20%

Table 1 shows the measurement results of the volume change rate of the obtained foam when immersed in water and the heating dimensional change rate at 100 ° C and 120 ° C. In addition, as a result of molding the thermoplastic resin composition used in Comparative Example 1 and conducting a bending test, the bending fracture strain was 0.49%.

[0072] (Comparative Example 2)

100 parts by weight of the thermoplastic resin composition obtained by the same method as in Example 2 was supplied to a single screw extruder and melt kneaded to obtain 0.8 mg of resin particles per grain.

[0073] A 6L autoclave equipped with a stirrer was charged with 100 parts of the obtained thermoplastic resin particles, 100 parts of water, 0.2 part of calcium phosphate, and 0.006 part of α-olefin sulfonate. Next, 10 parts of normal butane was added, the temperature was raised to 125 ° C. while stirring, and the temperature was maintained for 9.5 hours to impregnate the thermoplastic resin particles with a foaming agent to obtain expandable thermoplastic resin particles. The [0074] Heating was performed for 2 minutes and 40 seconds with 190 ° C steam generated by a heated steam generator to obtain pre-expanded particles having a bulk ratio of 25 times. The obtained pre-expanded particles were filled in a mold of 450mm in length X 350mm in width X 40mm in thickness, molded by heating with 0.38MPa steam for 10 seconds, cooled and cooled to a density of 45kg / m ³ The foamed molded product was obtained. Table 1 shows the anisotropy ratio of the cells calculated by observing the cell structure of the obtained foam with a microscope. The obtained foam was subjected to a dynamic compression test, and the calculated load ratio = (F) / (F) is shown in Table 1. further,

70% 20%

Table 1 shows the measurement results of the volume change rate of the obtained foam when immersed in water and the heating dimensional change rate at 100 ° C and 120 ° C. The thermoplastic resin composition used in Comparative Example 2 was molded and subjected to a bending test. As a result, the bending fracture strain was 0.49%.

[0075] (Comparative Example 3)

A dynamic compression test was conducted on rigid polyurethane foam with a density of 58 kg / cm ^{3 using} 1,4'-diisocyanate and polypropylene glycol as raw materials, and the calculated load ratio = (F) / (¥) Table 1 shows. Cell structure of foam obtained by microscope

70% 20%

Table 1 shows the anisotropy ratio of the cells calculated by observation. Furthermore, Table 1 shows the measurement results of the volume change rate of the obtained foam when immersed in water, and the heating dimensional change rate at 100 ° C and 120 ° C.

[0076] (Comparative Example 4)

A dynamic compression test was performed on a rigid polyurethane foam with a density of 79 kg / cm ^{3 using} diphenylmethane 4,4'-diisocyanate and polypropylene glycol as raw materials, and the calculated load ratio = (F) / (¥) Shown in 1. Cell structure of foam obtained by microscope

70% 20%

[0077] [Table 1] Dimensional change rate during heating (%) Volume anisotropy ratio when immersed in water ( ^r 70 ° /.) Z (F ₂ .

100 ° C 120 ° C Increase (%) Example 1 2.0 1.16 -0.04 -0.10 0.1 Example 2 2.0 1.01 0.10 -0.37 2.5 Example 3 1.9 1.19 -0.21 -20 0,3 Example 4 1.9 1.07 One 45- 68 1.0 Comparative Example 1 0.66 2.20 -0.11 -0.38 2.3 Comparative Example 2 1.0 2.50 -0.09 -0.35 2.4 Comparative Example 3 1.4 0.88 0.42 3.0 8.3 Comparative Example 4 1.4 0.84 0.40 2.9 8.2

Claims

The scope of the claims

[1] Load ratio of 70% strain load (F) and 20% strain load (F) based on dynamic compression test (F)

70% 20%

F) / (¥) value is 0.70 or more and 1.30 or less, and volume increase when immersed in water for 24 hours

70% 20%

Thermoplastic resin foam having an addition rate of 5% or less.

[2] The thermoplastic resin foam according to claim 1, wherein the cell-shaped anisotropy ratio is 1.1 or more and 3.0 or less.

[3] A copolymer consisting of an aromatic bur, an unsaturated dicarboxylic acid anhydride and an N-alkyl-substituted maleimide (A) 80 to 30% by weight and an aromatic bulcyanated bulene copolymer (B) 20 to 70% by weight The thermoplastic resin foam according to claim 1 or 2, wherein a thermoplastic resin composition obtained by mixing is foamed.

4. The thermoplastic resin foam according to claim 3, wherein the aromatic bullet is styrene.

[5] The unsaturated dicarboxylic acid anhydride is maleic anhydride.

3. The thermoplastic resin foam according to 3.

6. The thermoplastic resin foam according to claim 3, wherein the N alkyl-substituted maleimide force is N phenylmaleimide.

7. The thermoplastic resin foam according to claim 3, wherein the cyanide bur is acrylonitrile.

8. The thermoplastic resin foam according to any one of claims 1 to 7, wherein the thermoplastic resin foam is produced by an extrusion foam molding method.

[9] An automobile bumper core comprising the thermoplastic resin foam according to any one of claims 1 to 8.

[10] An automobile side bump pad comprising the thermoplastic resin foam according to any one of claims 1 to 8.