JP6484206B2 - Foamed particles, foamed molded products, fiber reinforced composites, and automotive parts - Google Patents

Description

  The present invention relates to expanded particles, expanded molded articles, fiber reinforced composites, and automotive parts. More specifically, the present invention relates to foamed particles that can provide a foamed molded article having improved mechanical properties, and a foamed molded article, a fiber reinforced composite, and an automotive part obtained from the foamed particle.

In recent years, vehicles such as aircraft, automobiles, and ships have been required to improve fuel efficiency in order to reduce the burden on the global environment, and the metal materials that make up these vehicles have been changed to resin materials to achieve significant weight savings. The flow is getting stronger. Examples of these resin materials include fiber reinforced plastics, and it has been studied to further reduce weight and increase rigidity by using a lightweight core material in part. Polystyrene foam having high compressive strength has been studied as a material used as a lightweight core material.
For example, Japanese Patent Application Laid-Open No. 2012-214751 (Patent Document 1) describes a foamable particle containing a foaming agent composed of a hydrocarbon having 6 or less carbon atoms in a polystyrene resin particle. Expandable particles in which the organic compound having 7 or more carbon atoms is uniformly contained, and the solubility parameter (A) of the organic compound has a specific relationship with the solubility parameter (B) of the foaming agent, and A foamed molding obtained from expandable particles is described.

JP 2012-214751 A

  However, since the foamed molded article of Patent Document 1 is obtained from expandable particles made of polystyrene resin having a low glass transition temperature, mechanical properties such as heat resistance are not sufficient. Therefore, it has been desired to provide a foamed molded article having improved mechanical properties and foamed particles capable of producing the foamed molded article.

  The inventors of the present invention repeated the test under the idea that mechanical properties would be improved if other types of resins were used instead of polystyrene-based resins, and aromatic vinyl, (meth) It has been found that the mechanical properties of the foamed molded product can be improved to some extent by using a copolymer of an acrylate ester and an unsaturated dicarboxylic acid as a base resin for the foamed particles. Therefore, the inventors further studied, and surprisingly, by using this base resin, by controlling the size of the bubbles constituting the expanded particles and the total area of the bubbles, it is surprising that the mechanical properties can be greatly improved. As a result, the present invention has been achieved.

Thus, according to the present invention, the expanded particles are composed of a base resin containing a copolymer of aromatic vinyl, (meth) acrylic acid ester, and unsaturated dicarboxylic acid, and the expanded particles are 300 times larger. In a cross-sectional photograph of an area of 0.13 mm ² , a small bubble having a bubble diameter of 5 μm or more and less than 30 μm and a large bubble having a bubble diameter of 30 to 100 μm are provided, and the small bubble has a total area of the large bubble. Expanded particles are provided that exhibit a total area of 1 to 50 times.

Moreover, according to the present invention, there is provided a foamed molded article composed of a base resin containing a copolymer of aromatic vinyl, (meth) acrylic acid ester, and unsaturated dicarboxylic acid, and the foamed particles are: In a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times, a small bubble having a bubble diameter of 5 μm or more and less than 30 μm and a large bubble having a bubble diameter of 30 to 100 μm are included, and the small bubbles are the sum of the large bubbles There is provided a foamed molded article having a total area of 0.5 to 50 times the area.

Furthermore, according to the present invention, there is provided a fiber reinforced composite comprising the above foam molded body and a fiber reinforced plastic layer laminated and integrated on the surface of the foam molded body.
Moreover, according to this invention, the components for motor vehicles comprised from said foaming molding or a fiber reinforced composite are provided.

ADVANTAGE OF THE INVENTION According to this invention, the foaming molding which can manufacture the foaming molding which shows the outstanding mechanical property, and the foaming molding can be provided.
Moreover, in any of the following cases, a foamed molded article exhibiting more excellent mechanical properties and foamed particles capable of producing the foamed molded article can be provided.
(1) small bubbles, in a cross section photograph of an area of 0.13 mm ² in 300 times, present at 1 to 300 times the number of the number of large bubbles.
(2) In the cross-sectional photograph in which the expanded particle or the expanded molded body is photographed with an area of 0.13 mm ² at 300 times, it includes bubbles in the vicinity of the surface showing an interface aspect ratio of 0.2 to 0.8.
(3) Aromatic vinyl is a styrenic monomer, (meth) acrylic acid ester is (meth) acrylic acid alkyl ester (the alkyl group has 1 to 5 carbon atoms), and unsaturated dicarboxylic acid is 2 to 6 carbon atoms. An aliphatic unsaturated dicarboxylic acid, and the copolymer is aromatic when the total of units derived from three of vinyl aromatic, (meth) acrylic acid ester and unsaturated dicarboxylic acid is 100 parts by weight. 30 to 80 parts by weight of units derived from vinyl, 8 to 35 parts by weight of units derived from (meth) acrylic acid ester, and 10 to 50 parts by weight of units derived from unsaturated dicarboxylic acid.

2 is a cross-sectional photograph of expanded particles of Example 1. FIG. 2 is a cross-sectional photograph of expanded particles of Example 2. FIG. 4 is a cross-sectional photograph of expanded particles of Example 3. 4 is a cross-sectional photograph of expanded particles of Example 4. 6 is a cross-sectional photograph of expanded particles of Example 5. 6 is a cross-sectional photograph of expanded particles of Example 6. 2 is a cross-sectional photograph of expanded particles of Comparative Example 1. 4 is a cross-sectional photograph of expanded particles of Comparative Example 2. 2 is a cross-sectional photograph of the foam molded article of Example 1. FIG. 2 is a cross-sectional photograph of a foamed molded product of Example 2. 2 is a cross-sectional photograph of a foamed molded article of Comparative Example 1. 4 is a cross-sectional photograph of a foamed molded article of Comparative Example 2. 6 is a cross-sectional photograph of expanded particles of Example 7. 6 is a cross-sectional photograph of expanded particles of Example 8. 6 is a cross-sectional photograph of expanded particles of Example 9. It is a cross-sectional photograph of the foamed molded product of Example 7. It is a cross-sectional photograph of the foamed molded product of Example 8. It is a cross-sectional photograph of the foamed molded product of Example 9.

(Foamed particles)
(1) Base resin The foamed particles are composed of a base resin containing a copolymer of aromatic vinyl, (meth) acrylic acid ester, and unsaturated dicarboxylic acid. The proportion of the copolymer in the base resin is preferably 70% by weight or more, more preferably 85% by weight or more, and may be 100% by weight. The copolymer preferably has a glass transition temperature Tg of 115 to 160 ° C. When Tg is lower than 115 ° C., lamination and integration of the skin material on the surface of the foamed molded product produced using the foamed particles may be insufficient, and mechanical properties may be lowered. When the temperature is higher than 160 ° C., the foamability of the foamed particles is lowered, and the heat fusion integration between the foamed particles is insufficient, and the mechanical properties of the foamed molded product may be lowered. A more preferable Tg is 120 to 150 ° C.

(A) Aromatic vinyl Aromatic vinyl is an aromatic compound having a substituent composed of a vinyl group. The number of vinyl groups and the number of carbon atoms of the aromatic compound are not particularly limited. Specific aromatic vinyls include styrene monofunctional monomers such as styrene, α-methyl styrene, vinyl toluene, ethyl styrene, i-propyl styrene, t-butyl styrene, dimethyl styrene, bromostyrene, chlorostyrene, Divinylbenzene, trivinylbenzene, divinyltoluene, divinylxylene, bis (vinylphenyl) methane, bis (vinylphenyl) ethane, bis (vinylphenyl) propane, bis (vinylphenyl) butane, divinylnaphthalene, divinylanthracene, divinylbiphenyl, Examples thereof include bisphenol A ethylene oxide adduct di (meth) acrylate and bisphenol A propylene oxide adduct di (meth) acrylate. Aromatic vinyl may be used independently or 2 or more types may be used together. Of these, styrene is preferred from the viewpoint of availability.

(B) (Meth) acrylic acid ester The (meth) acrylic acid ester is not particularly limited, and examples thereof include (meth) acrylic acid alkyl esters. The carbon number of the alkyl group in the (meth) acrylic acid alkyl ester can be 1 to 5. Specific examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate. (Meth) acrylic acid ester may be used independently, or 2 or more types may be used together. From the viewpoint of improving the mechanical properties of the foam molded article, methyl (meth) acrylate is preferred, and methyl methacrylate is more preferred.

(C) Unsaturated dicarboxylic acid Although unsaturated dicarboxylic acid is not specifically limited, C2-C6 aliphatic unsaturated dicarboxylic acid is mentioned. Specific examples of the unsaturated dicarboxylic acid include maleic acid, itaconic acid, citraconic acid, aconitic acid, and anhydrides thereof. Unsaturated dicarboxylic acid may be used independently or 2 or more types may be used together.

(D) Ratio of units derived from aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid The total number of units derived from aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid is 100. Assuming parts by weight, 30 to 80 parts by weight of units derived from aromatic vinyl, 8 to 35 parts by weight of units derived from (meth) acrylic acid ester, and 10 to 50 parts by weight of units derived from unsaturated dicarboxylic acid It is preferable to contain.
When the proportion of units derived from aromatic vinyl is less than 30 parts by weight, the foamability of the foamed particles is reduced during foam molding, and the heat fusion integration between the foamed particles becomes insufficient, and Mechanical properties may deteriorate. When this ratio is larger than 80 parts by weight, the heat resistance of the foamed molded product may be lowered. This ratio is more preferably 40 to 75 parts by weight, and still more preferably 45 to 70 parts by weight.

When the proportion of units derived from (meth) acrylic acid ester is less than 8 parts by weight, the mechanical properties of the foamed molded product may be lowered. When this ratio is larger than 35 parts by weight, the foamability of the foamed particles may be reduced during foam molding, and the heat fusion integration between the foamed particles may be insufficient and the mechanical properties of the foamed molded product may be degraded. is there. This ratio is more preferably 10 to 33 parts by weight, and still more preferably 15 to 30 parts by weight.
When the ratio which the unit derived from unsaturated dicarboxylic acid accounts is less than 10 weight part, the heat resistance of a foaming molding may fall. When this ratio is larger than 50 parts by weight, the foamability of the foamed particles may be reduced during foam molding, and the heat-fusion integration between the foamed particles may be insufficient, and the mechanical properties of the foamed molded product may be degraded. is there. This ratio is more preferably 15 to 40 parts by weight, and still more preferably 20 to 35 parts by weight.
In addition, the usage-amount of a monomer and content of the unit derived from the monomer are substantially in agreement.

Each component ratio, that is, the proportion of units derived from aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid, and further the units derived from other monomers and other resins described below is ¹ It can be defined by the peak height of H-NMR or the area ratio of FT-IR. A specific measurement method will be described in Examples.

(E) Other monomer The base resin may be a further copolymer with components derived from other monomers as long as the properties of the present invention are not impaired in addition to the above three monomers. Examples of other monomers include (meth) acrylonitrile, dimethyl maleate, diethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, (meth) acrylic acid, and the like.
The proportion of units derived from other monomers in the base resin is preferably 30% by weight or less, and may be 0% by weight.

(F) Other resin Other resin may be mixed with the base resin. Other resins include polyolefin-based resins such as polyethylene and polypropylene, rubber-modified resistances added with diene rubber-like polymers such as polybutadiene, styrene-butadiene copolymers, and ethylene-propylene-nonconjugated diene three-dimensional copolymers. Impact polystyrene resin, polycarbonate resin, polyester resin, polyamide resin, polyphenylene ether, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polymethyl methacrylate, styrene- (meth) acrylic acid copolymer Styrene- (meth) acrylic acid ester copolymer, aromatic vinyl-unsaturated dicarboxylic acid-unsaturated dicarboxylic imide copolymer, and the like.

  Of the other resins, the expanded particles preferably contain polymethyl methacrylate. By containing poly (methyl methacrylate), the heat-fusibility of the foamed particles is improved, and the foamed particles are more strongly heat-fused and integrated with each other. Can be obtained. The content of polymethyl methacrylate in the expanded particles is preferably 10 to 500 parts by weight, more preferably 20 to 450 parts by weight, and particularly preferably 30 to 400 parts by weight with respect to 100 parts by weight of the copolymer.

  The foamed particles preferably contain an acrylic resin as a processing aid. By containing a processing aid, the foam tension of the foamed particles is suppressed by making the melt tension (viscoelasticity) at the time of foaming of the resin constituting the foamed particles suitable for foaming. Thus, it is possible to produce a foamed molded article having improved mechanical properties, further strengthening the thermal fusion between the foamed particles, and having excellent mechanical properties. The content of the processing aid in the expanded particles is preferably 0.5 to 5 parts by weight, more preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the copolymer.

  The acrylic resin as a processing aid is not particularly limited, and contains 50% by weight or more of a homopolymer of an acrylic monomer or a copolymer composed of two or more of these, and an acrylic monomer. Examples thereof include a copolymer of an acrylic monomer and a vinyl monomer copolymerizable therewith. Examples of the acrylic monomer include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like. Examples of the vinyl monomer copolymerizable with the acrylic monomer include α-methylstyrene and acrylonitrile. The weight average molecular weight of the acrylic resin is preferably 1.5 million to 6 million, more preferably 2 million to 4.5 million, and particularly preferably 2.5 million to 4 million. Even if the weight average molecular weight of the acrylic resin is too low or too high, it is difficult to sufficiently adjust the melt tension (viscoelasticity) during foam molding of the resin constituting the foamed particles to that suitable for foaming. The foamability of the particles may not be improved.

(G) Aromatic vinyl-unsaturated dicarboxylic acid-unsaturated dicarboxylic imide copolymer As the above (f) other resin, an aromatic vinyl-unsaturated dicarboxylic acid-unsaturated dicarboxylic imide copolymer is used. It is preferable from the viewpoint of improving the heat resistance of the foam molded article.
Although it does not specifically limit as aromatic vinyl, The compound illustrated to said (a) is mentioned. Aromatic vinyl may be used independently or 2 or more types may be used together. Of these, styrene is preferred from the viewpoint of availability.
Although it does not specifically limit as unsaturated dicarboxylic acid, The compound illustrated in said (c) is mentioned. Unsaturated dicarboxylic acid may be used independently or 2 or more types may be used together. From the viewpoint of improving the mechanical properties of the foam molded article, maleic anhydride is preferable.

  The unsaturated dicarboxylic acid imide is not particularly limited, and examples thereof include maleimide monomers such as maleimide, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, and N-naphthylmaleimide. . An unsaturated dicarboxylic imide derivative may be used independently or 2 or more types may be used together. From the viewpoint of improving the heat resistance of the foam molded article, N-phenylmaleimide is preferred.

The proportion of units derived from aromatic vinyl, unsaturated dicarboxylic acid and unsaturated dicarboxylic imide is 20 to 80 parts by weight of units derived from aromatic vinyl, assuming that the total of the units derived from 3 is 100 parts by weight. It is preferable that 2 to 30 parts by weight of units derived from unsaturated dicarboxylic acid and 20 to 80 parts by weight of units derived from unsaturated dicarboxylic imide are included.
When the proportion of units derived from aromatic vinyl is less than 20 parts by weight, the foamability of the foamed particles is reduced during foam molding, and the thermal fusion integration between the foamed particles becomes insufficient, and Mechanical properties may deteriorate. When this ratio is larger than 80 parts by weight, the heat resistance of the foamed molded product may be lowered. This ratio is more preferably 30 to 75 parts by weight, and still more preferably 50 to 70 parts by weight.

(H) Additive The base resin may contain an additive in addition to the resin, if necessary. Additives include plasticizers, flame retardants, flame retardant aids, antistatic agents, spreading agents, bubble regulators, fillers, colorants, weathering agents, anti-aging agents, lubricants, antifogging agents, fragrances, etc. Can be mentioned.

(2) Configuration Expanded particles are provided with small bubbles having a bubble diameter of 5 μm or more and less than 30 μm and large bubbles having a bubble diameter of 30 to 100 μm in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. Moreover, a small bubble shows the total area of 1-50 times the total area of a large bubble. By providing bubbles having different bubble diameters at a specific area ratio, it is possible to provide expanded particles that give a foamed molded article having improved mechanical properties. If the total area of the small bubbles is less than 1 times the total area of the large bubbles, the increase in the number of large bubbles will increase the bubble film length between adjacent bubbles, making it easier for the bubbles to buckle. May decrease. If it is larger than 50 times, the bubbles may become too fine and the foamability may decrease. The total area of the small bubbles is preferably 3 to 30 times, more preferably 5 to 20 times the total area of the large bubbles.
The sum of the total area of the small bubbles and the large bubbles is preferably 80% or more of the total area of all the bubbles.

Moreover, it is preferable that the small bubbles are present in the number of 1 to 300 times the number of large bubbles in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. By providing the bubbles having different bubble diameters at a specific number ratio, it is possible to provide expanded particles that give a foamed molded article having improved mechanical properties. When the number of small bubbles is less than 1 times the number of large bubbles, the increase in the number of large bubbles increases the bubble film length between adjacent bubbles, making it easier for the bubbles to buckle. May decrease. If it is larger than 300 times, the bubbles may become too fine and foamability may be reduced. The number of small bubbles is preferably 10 to 200 times the number of large bubbles, and more preferably 20 to 100 times.
The total number of small bubbles and large bubbles is preferably 80% or more of the total number of bubbles.

Furthermore, it is preferable that the bubbles near the surface of the expanded particles show an interface aspect ratio of 0.2 to 0.8 (upper limit is a circle) in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. . By exhibiting a specific interface aspect ratio, it is possible to provide foamed particles that give a foamed molded article having improved mechanical properties. When the interface aspect ratio is less than 0.2, the mechanical properties may be deteriorated because bubbles tend to buckle. If it is larger than 0.8, it may be a brittle layer that is too hard and has reduced toughness. In addition, the bubble of the surface vicinity is restricted to the bubble which can be visually observed with a cross-sectional photograph of 300 times, and includes a small bubble and a large bubble. Here, the interface aspect ratio of the large bubbles in the expanded particles is preferably 0.4 or more, and more preferably 0.5 or more. On the other hand, the interface aspect ratio of the small bubbles is preferably 0.3 or more, and more preferably 0.4 or more.

Furthermore, it is preferable that there is a difference of 40 μm or more between the average bubble diameter of small bubbles and the average bubble diameter of large bubbles. Due to this difference, it is possible to provide foamed particles that give a foamed molded article having improved mechanical properties. A more preferable difference is 40 to 60 μm. Here, it is preferable that the average bubble diameter of a small bubble exists in the range of 5-20 micrometers, and it is preferable that the average bubble diameter of a large bubble exists in the range of 40-80 micrometers. The variation coefficient (CV value) of the average bubble diameter of the small bubbles and the CV value of the average bubble diameter of the large bubbles are preferably 20 to 50% and 5 to 40%, respectively, 20 to 30% and 10 to 20%. It is more preferable that
The average particle diameter of the expanded particles is preferably 500 to 5000 μm, and more preferably 1000 to 3000 μm.
The outer shape of the expanded particles is not particularly limited as long as the expanded molded body can be produced, and examples thereof include a spherical shape, a substantially spherical shape, and a cylindrical shape. The expanded particles preferably have an outer shape represented by an average aspect ratio of 0.8 or more (the upper limit is a true sphere).

The expanded particles preferably have a bulk multiple of 20 to 1.4 times. When the bulk factor is larger than 20 times, the open cell ratio of the foamed particles is increased, and the foamability of the foamed particles may be lowered during foaming of foam molding. When the ratio is less than 1.4 times, the foamed particles have non-uniform air bubbles, and the foamability of the foamed particles during foam molding may be insufficient. The bulk multiple is more preferably 14 to 1.6 times, and particularly preferably 12.5 to 2 times.
The expanded particles preferably exhibit an open cell ratio of 40% or less. When the open cell ratio is higher than 40%, the foaming pressure of the foamed particles is insufficient at the time of foam molding, and the heat physical integration between the foamed particles is insufficient, and the mechanical properties of the foamed molded product may be lowered. . The open cell ratio is more preferably 35% or less.

(3) Manufacturing method As a manufacturing method of a foamed particle, the resin particle is impregnated with a foaming agent in a gas phase to obtain foamable particles, and the foamable particles are foamed.
First, as a method for producing resin particles,
(I) A method of manufacturing by melting and kneading a raw material resin (mixture of constituent resins of a base resin) in an extruder, and cutting and cooling the kneaded product through a nozzle mold attached to the extruder, (ii) ) Method of manufacturing by melting and kneading the raw material resin in an extruder, extruding the kneaded product from a nozzle mold attached to the extruder, cooling to obtain a strand, and cutting this strand at predetermined intervals,
(Iii) A method in which a raw material resin is melt-kneaded in an extruder, the kneaded product is extruded from an annular die or a T-die attached to the extruder to produce a sheet, and the sheet is cut to produce the method. In addition, it is preferable that a bubble regulator is supplied to an extruder. Examples of the air conditioner include polytetrafluoroethylene powder, polytetrafluoroethylene powder modified with an acrylic resin, and talc. As for the quantity of a bubble regulator, 0.01-5 weight part is preferable with respect to 100 weight part of resin compositions. When the amount of the bubble adjusting agent is less than 0.01 weight, the bubbles of the foamed particles become coarse and the appearance of the obtained foamed molded product may be deteriorated. When the amount is more than 5 parts by weight, the closed cell ratio of the foamed particles may decrease due to bubble breakage. The amount of the bubble regulator is more preferably 0.05 to 3 parts by weight, particularly preferably 0.1 to 2 parts by weight.

  Next, as a method for producing expandable particles, a method in which a foaming agent is impregnated in a gas phase with a foaming agent in a hermetically sealed container can be mentioned. Examples of the blowing agent include propane, normal butane, isobutane, normal pentane, isopentane, hexane and other saturated aliphatic hydrocarbons, ethers such as dimethyl ether, methyl chloride, 1,1,1,2-tetrafluoroethane, 1, Examples thereof include chlorofluorocarbons such as 1-difluoroethane and monochlorodifluoromethane, and inorganic gases such as carbon dioxide and nitrogen. Among these, dimethyl ether, propane, normal butane, isobutane and carbon dioxide are preferable, propane, normal butane and isobutane are more preferable, and normal butane and isobutane are particularly preferable. In addition, a foaming agent may be used independently or 2 or more types may be used together.

If the amount of the foaming agent charged into the container is too small, the foamed particles may not be foamed to a desired expansion ratio. If the amount of the foaming agent is too large, the foaming agent acts as a plasticizer, so that the viscoelasticity of the base resin is excessively lowered, the foamability is lowered, and good foamed particles may not be obtained. Therefore, the amount of the foaming agent is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 4 parts by weight, and particularly preferably 0.3 to 3 parts by weight with respect to 100 parts by weight of the raw material resin.
Furthermore, as a manufacturing method of expanded particle, the method of heating with a heating medium like water vapor | steam in the container which can be sealed is mentioned. Examples of the heating conditions include a gauge pressure of 0.3 to 0.5 MPa, a temperature of 120 to 159 ° C., and 10 to 180 seconds.
The particle diameter of the expanded particles can be changed by changing the diameter of a multi-nozzle mold attached to the front end of the extruder.

(Foamed molded product)
(1) Base resin The base resin which comprises a foaming molding is the same as the base resin of the said foaming particle.
(2) Physical properties The foamed molded article is provided with small bubbles having a bubble diameter of 5 μm or more and less than 30 μm and large bubbles having a bubble diameter of 30 to 100 μm in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. . Moreover, a small bubble shows the total area 0.5 to 50 times the total area of a large bubble. By providing the bubbles having different bubble diameters at a specific area ratio, it is possible to provide a foamed molded article having improved mechanical properties. When the total area of the small bubbles is less than 0.5 times the total area of the large bubbles, the larger the number of large bubbles, the longer the bubble film length between adjacent bubbles and the easier it is for the bubbles to buckle. Physical properties may deteriorate. If it is larger than 50 times, the bubbles may become too fine and the foamability may decrease. The total area of the small bubbles is preferably 0.5 to 30 times, more preferably 3 to 20 times the total area of the large bubbles.
The sum of the total area of the small bubbles and the large bubbles is preferably 80% or more of the total area of all the bubbles.

Moreover, it is preferable that the small bubbles are present in the number of 1 to 300 times the number of large bubbles in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. By providing the bubbles having different bubble diameters at a specific number ratio, it is possible to provide expanded particles that give a foamed molded article having improved mechanical properties. When the number of small bubbles is less than 1 times the number of large bubbles, the increase in the number of large bubbles increases the bubble film length between adjacent bubbles, making it easier for the bubbles to buckle. May decrease. If it is larger than 300 times, the bubbles may become too fine and foamability may be reduced. The number of small bubbles is preferably 10 to 200 times the number of large bubbles, and more preferably 20 to 100 times.
The total number of small bubbles and large bubbles is preferably 80% or more of the total number of bubbles.

Further, the bubbles near the surface of the expanded particles preferably show an interface aspect ratio of 0.37 to 0.8 (upper limit is a circle of 1) in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. . By exhibiting a specific interface aspect ratio, it is possible to provide foamed particles that give a foamed molded article having improved mechanical properties. When the interface aspect ratio is less than 0.37, the mechanical properties may be deteriorated because bubbles tend to buckle. If it is larger than 0.8, it may be a brittle layer that is too hard and has reduced toughness. In addition, the bubble of the surface vicinity is restricted to the bubble which can be visually observed with a cross-sectional photograph of 300 times, and includes a small bubble and a large bubble. Here, the interface aspect ratio of the large bubbles in the expanded particles is preferably 0.4 or more, and more preferably 0.5 or more. On the other hand, the interface aspect ratio of the small bubbles is preferably 0.3 or more, and more preferably 0.4 or more.

Furthermore, it is preferable that there is a difference of 40 μm or more between the average bubble diameter of small bubbles and the average bubble diameter of large bubbles. Due to this difference, it is possible to provide foamed particles that give a foamed molded article having improved mechanical properties. A more preferable difference is 40 to 60 μm. Here, it is preferable that the average bubble diameter of a small bubble exists in the range of 5-20 micrometers, and it is preferable that the average bubble diameter of a large bubble exists in the range of 40-80 micrometers. The variation coefficient (CV value) of the average bubble diameter of the small bubbles and the CV value of the average bubble diameter of the large bubbles are preferably 20 to 50% and 5 to 40%, respectively, 20 to 30% and 10 to 20%. It is more preferable that
The average particle diameter of the fused expanded particles constituting the expanded molded body is preferably 600 to 6000 μm, and more preferably 1200 to 3600 μm.
The outer shape of the fused expanded particles is not particularly limited as long as the expanded molded body can be maintained.

The foamed molded article preferably has a multiple of 20 to 1.4 times. When the multiple is larger than 20 times, mechanical properties may be insufficient. If it is less than 1.4 times, the weight may increase and the advantage of foaming may be reduced. The multiple is more preferably 14 to 1.6 times, and particularly preferably 12.5 to 2 times.
The foamed molded product preferably exhibits an open cell ratio of 40% or less. When the open cell ratio is higher than 40%, the mechanical properties of the foamed molded product may be deteriorated. The open cell ratio is more preferably 35% or less.
The heating dimensional change rate at 120 ° C. of the foamed molded product is preferably −1 to 1%. A foaming molding can be conveniently used also for the use in a high temperature environment because the heating dimensional change rate is -1 to 1%.
The flexural modulus per unit density in the foam molded article is preferably 600 MPa / (g / cm ³ ) or more. If the flexural modulus is too small, the foamed molded product may be deformed by pressure applied when a skin material such as fiber reinforced plastic is laminated and integrated on the surface of the foamed molded product.

(3) Manufacturing method As a manufacturing method of a foaming molding, the foam particle was filled in the cavity of a metal mold, the heating medium was supplied in the cavity, the foam particle was heated and re-foamed, and re-foamed. There is a method of obtaining a foamed molded article by thermally fusing the foamed particles with each other by these foaming pressures. Examples of the heating medium include water vapor, hot air, hot water and the like, and water vapor is preferable.

(4) Applications The foamed molded article is excellent in light weight, heat resistance and mechanical properties, and particularly excellent in load resistance in a high temperature environment. Therefore, for example, it can be suitably used for parts of transportation equipment such as automobiles, airplanes, railway vehicles, and ships. Examples of automobile parts include parts used in the vicinity of the engine and exterior materials.

  According to the present invention, there is provided an automotive part composed of the foamed molded article of the present invention. Examples of the automotive part include a floor panel, a roof, a bonnet, a fender, an under cover, a wheel, a steering wheel, and a container. (Housing), hood panel, suspension arm, bumper, sun visor, trunk lid, luggage box, seat, door, etc.

  A skin material may be laminated and integrated on the surface of the foamed molded product to be used as a reinforced composite. When the foamed molded body is a foamed sheet, it is not necessary to be laminated and integrated on both surfaces of the foamed molded body, and the skin material only needs to be laminated and integrated on at least one surface of both surfaces of the foamed molded body. The lamination of the skin material may be determined according to the use of the reinforced composite. Among these, in consideration of the surface hardness and mechanical strength of the reinforced composite, it is preferable that the skin material is laminated and integrated on each of both surfaces in the thickness direction of the foamed molded product.

The skin material is not particularly limited, and examples thereof include fiber reinforced plastics, metal sheets, and synthetic resin films. Of these, fiber reinforced plastic is preferred. A reinforced composite using a fiber reinforced plastic as a skin material is referred to as a fiber reinforced composite.
The reinforcing fibers constituting the fiber reinforced plastic include glass fibers, carbon fibers, silicon carbide fibers, alumina fibers, Tyranno fibers, basalt fibers, ceramic fibers and other inorganic fibers; stainless steel fibers, steel fibers and other metal fibers; aramid Organic fibers such as fibers, polyethylene fibers, polyparaphenylene benzoxador (PBO) fibers; and boron fibers. Reinforcing fibers may be used alone or in combination of two or more. Among these, carbon fiber, glass fiber, and aramid fiber are preferable, and carbon fiber is more preferable. These reinforcing fibers have excellent mechanical properties despite being lightweight.

The reinforcing fiber is preferably used as a reinforcing fiber substrate processed into a desired shape. Examples of the reinforcing fiber base material include woven fabrics, knitted fabrics, non-woven fabrics, and face materials obtained by binding (stitching) fiber bundles (strands) obtained by aligning reinforcing fibers in one direction with yarns. . Examples of the weaving method include plain weave, twill weave and satin weave. Examples of the yarn include a synthetic resin yarn such as a polyamide resin yarn and a polyester resin yarn, and a stitch yarn such as a glass fiber yarn.
The reinforcing fiber substrate may be used without laminating only one reinforcing fiber substrate, or a plurality of reinforcing fiber substrates may be laminated and used as a laminated reinforcing fiber substrate. As a laminated reinforcing fiber base material in which a plurality of reinforcing fiber base materials are laminated, (1) a plurality of reinforcing fiber base materials of only one kind are prepared, and a laminated reinforcing fiber base material in which these reinforcing fiber base materials are laminated, 2) A plurality of types of reinforcing fiber base materials are prepared, a laminated reinforcing fiber base material obtained by laminating these reinforcing fiber base materials, and (3) a fiber bundle (strand) in which the reinforcing fibers are aligned in one direction is bound with a thread ( A plurality of reinforcing fiber base materials prepared by stitching) are prepared, and these reinforcing fiber base materials are superposed so that the fiber directions of the fiber bundles are different from each other. For example, a laminated reinforcing fiber base material integrated (stitched) with is used.

The fiber reinforced plastic is obtained by impregnating a reinforced fiber with a synthetic resin. The reinforcing fibers are bonded and integrated by the impregnated synthetic resin.
The method of impregnating the reinforcing fiber with the synthetic resin is not particularly limited, and examples thereof include (1) a method of immersing the reinforcing fiber in the synthetic resin, and (2) a method of applying the synthetic resin to the reinforcing fiber.
As the synthetic resin impregnated into the reinforcing fiber, either a thermoplastic resin or a thermosetting resin can be used, and a thermosetting resin is preferably used. The thermosetting resin impregnated into the reinforcing fiber is not particularly limited, and is an epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, polyurethane resin, silicone resin, maleimide resin, vinyl ester resin, cyanate ester resin, maleimide. Examples thereof include a resin obtained by prepolymerizing a resin and a cyanate ester resin, and an epoxy resin and a vinyl ester resin are preferable because they are excellent in heat resistance, shock absorption or chemical resistance. The thermosetting resin may contain additives such as a curing agent and a curing accelerator. In addition, a thermosetting resin may be used independently and 2 or more types may be used together.

The thermoplastic resin impregnated into the reinforcing fiber is not particularly limited, and examples thereof include olefin resins, polyester resins, thermoplastic epoxy resins, amide resins, thermoplastic polyurethane resins, sulfide resins, acrylic resins, and the like. Polyester resins and thermoplastic epoxy resins are preferred because they are excellent in adhesiveness with the foamed molded article or adhesiveness between the reinforcing fibers constituting the fiber reinforced plastic. In addition, a thermoplastic resin may be used independently and 2 or more types may be used together.
The thermoplastic epoxy resin may be a polymer or copolymer of epoxy compounds having a linear structure, or a copolymer of an epoxy compound and a monomer that can be polymerized with the epoxy compound. And a copolymer having a linear structure. Specifically, as the thermoplastic epoxy resin, for example, bisphenol A type epoxy resin, bisphenol fluorene type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, cyclic aliphatic type epoxy resin, long chain aliphatic type An epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin and the like can be mentioned, and a bisphenol A type epoxy resin and a bisphenol fluorene type epoxy resin are preferable. In addition, a thermoplastic epoxy resin may be used independently and 2 or more types may be used together.

Examples of the thermoplastic polyurethane resin include a polymer having a linear structure obtained by polymerizing diol and diisocyanate. Examples of the diol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, and the like. Diols may be used alone or in combination of two or more. Examples of the diisocyanate include aromatic diisocyanate, aliphatic diisocyanate, and alicyclic diisocyanate. Diisocyanate may be used independently or 2 or more types may be used together. In addition, a thermoplastic polyurethane resin may be used independently and 2 or more types may be used together.
The content of the synthetic resin in the fiber reinforced plastic is preferably 20 to 70% by weight. When the oil content is less than 20% by weight, the binding property between the reinforcing fibers and the adhesion between the fiber reinforced plastic and the foamed molded article are insufficient, and the mechanical properties of the fiber reinforced plastic and the mechanical strength of the fiber reinforced composite are obtained. May not be sufficiently improved. When the amount is more than 70% by weight, the mechanical properties of the fiber reinforced plastic may be deteriorated, and the mechanical strength of the fiber reinforced composite may not be sufficiently improved. The content is more preferably 30 to 60% by weight.

The thickness of the fiber reinforced plastic is preferably 0.02 to 2 mm, and more preferably 0.05 to 1 mm. A fiber reinforced plastic having a thickness within this range is excellent in mechanical properties despite being lightweight.
Basis weight of the fiber reinforced plastic is preferably ^{50~4000g / m 2, 100~1000g / m} 2 is more preferable. A fiber reinforced plastic having a basis weight within this range is excellent in mechanical properties despite being lightweight.

  Next, a method for producing a reinforced composite will be described. The method for producing a reinforced composite by laminating and integrating the skin material on the surface of the foam molded body is not particularly limited. For example, (1) the skin material is laminated and integrated on the surface of the foam molded body via an adhesive. (2) A foam-molded article obtained by laminating a fiber-reinforced plastic forming material in which a reinforcing fiber is impregnated with a thermoplastic resin on the surface of the foam-molded article, and using the thermoplastic resin impregnated in the reinforcing fiber as a binder (3) Laminating a fiber reinforced plastic forming material in which a reinforcing fiber is impregnated with an uncured thermosetting resin on the surface of the foam molded body And a method of laminating and integrating the fiber reinforced plastic formed by curing the thermosetting resin with the thermosetting resin impregnated in the reinforcing fiber on the surface of the foam molded body (4) A skin material that is heated and softened is disposed on the surface of the foam molded body, and the skin material is deformed along the surface of the foam molded body as necessary by pressing the skin material against the surface of the foam molded body. However, a method of laminating and integrating on the surface of the foamed molded product, (5) a method generally applied in molding of fiber reinforced plastics, and the like can be mentioned. From the viewpoint that the foamed molded article is excellent in mechanical properties such as load resistance under a high temperature environment, the method (4) can also be suitably used.

  Examples of the method used for molding the fiber reinforced plastic include an autoclave method, a hand lay-up method, a spray-up method, a PCM (Prepre Compression Molding) method, an RTM (Resin Transfer Molding) method, a VaRTM (Vacuum Assisted Resin Transfer Transfer). Law.

The fiber reinforced composite thus obtained is excellent in heat resistance, mechanical strength and lightness. Therefore, it can be used in a wide range of applications such as the field of transportation equipment such as automobiles, airplanes, railway vehicles, ships, etc., the household appliances field, the information terminal field, and the furniture field.
For example, the fiber reinforced composite is composed of parts for transportation equipment, parts for transportation equipment including structural parts constituting the main body of transportation equipment (particularly parts for automobiles), windmill blades, robot arms, cushioning materials for helmets, It can be suitably used as an agricultural product box, a transport container such as a thermal insulation container, a rotor blade of an industrial helicopter, or a component packing material.

  According to the present invention, there is provided an automotive part composed of the fiber-reinforced composite of the present invention. Examples of the automotive part include a floor panel, a roof, a bonnet, a fender, an under cover, a wheel, a steering wheel, Examples include containers (housings), hood panels, suspension arms, bumpers, sun visors, trunk lids, luggage boxes, seats, doors, and other parts.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples. First, measurement methods and evaluation methods in Examples and Comparative Examples will be described.
(Bubble area ratio)
The cell area ratio of the expanded particles and the bubbles in the expanded molded body is measured as follows. First, an area of 0.13 mm ² is photographed at 300 times with a scanning electron microscope on the cut surface. The photographed image is printed on A4 paper, and the average bubble diameter is calculated for all bubbles. The bubble diameter is a value obtained by measuring the major and minor diameters of the bubble cross section and calculating the arithmetic mean value of the minor and major diameters. Specifically, two arbitrary points having the maximum mutual distance are selected on the outer contour line of the bubble cross section, and the distance between the two points is defined as “the major diameter of the bubble”. Also, any two points where the mutual distance is maximum are selected from any two points where the straight line perpendicular to the major axis of the bubble and the outer contour line of the bubble cross section intersect, and the distance between the two points is expressed as “ The short diameter of the bubble ”. A small bubble having an average bubble diameter of 5 μm or more and less than 30 μm and a large bubble having a bubble diameter of 30 to 100 μm are cut out from the paper along the bubble film with scissors, and the weight of the paper is measured. The paper weight is measured and the weight ratio (small bubble / large bubble) is calculated. The expanded particles and the expanded molded body are cut in the same manner as described above to obtain enlarged photographs, and the weight ratio of (small bubbles / large bubbles) is calculated in the same manner as described above based on these enlarged photographs. In 10 magnified photographs, the arithmetic average value of the weight ratio of (small bubbles / large bubbles) is defined as the bubble area ratio.

(Bubble number ratio)
The ratio of the number of bubbles in the expanded particles and the expanded molded body is measured as follows. First, an area of 0.13 mm ² is photographed at 300 times with a scanning electron microscope on the cut surface. The photographed image is printed on A4 paper, and the average bubble diameter is calculated for all bubbles. The bubble diameter is a value obtained by measuring the major and minor diameters of the bubble cross section and calculating the arithmetic mean value of the minor and major diameters. Specifically, two arbitrary points having the maximum mutual distance are selected on the outer contour line of the bubble cross section, and the distance between the two points is defined as “the major diameter of the bubble”. Also, any two points where the mutual distance is maximum are selected from any two points where the straight line perpendicular to the major axis of the bubble and the outer contour line of the bubble cross section intersect, and the distance between the two points is expressed as “ The short diameter of the bubble ”. The number of bubbles on the paper is counted for small bubbles having an average bubble diameter of 5 μm or more and less than 30 μm and large bubbles having a bubble diameter of 30 to 100 μm. In the counted number of bubbles, a quantity ratio of (number of small bubbles / number of large bubbles) is calculated. The expanded particles and the molded foam are cut in the same manner as described above to obtain enlarged photographs. Based on these enlarged photographs, the number ratio of (number of small bubbles / number of large bubbles) in the same manner as described above. Is calculated. In 10 enlarged photographs, the arithmetic average value of the number ratio of (number of small bubbles / number of large bubbles) is defined as the bubble area ratio.

(Interface aspect ratio)
The interface aspect ratio of the foamed particles and the bubbles in the foamed molded product is measured as follows. First, the expanded particles and the expanded molded article are cut, and the cut surface is photographed with a scanning electron microscope at an magnification of 300 × 0.13 mm ² . The interface is between the surface of the expanded particle (in the case of the expanded molded product, the fused surface of the expanded particle) and a depth of 2.5% of the thickness of the expanded particle (expanded molded product) in a direction perpendicular to the surface. Let it be a part (near the surface). Next, the aspect ratio is measured for 30 bubbles included in the photographed image thus obtained, and the arithmetic average value is defined as the interface aspect ratio. The aspect ratio is a value obtained by measuring the major axis and minor axis of the bubble cross section and dividing the minor axis by the major axis. Specifically, two arbitrary points having the maximum mutual distance are selected on the outer contour line of the bubble cross section, and the distance between the two points is defined as “the major diameter of the bubble”. Also, any two points where the mutual distance is maximum are selected from any two points where the straight line perpendicular to the major axis of the bubble and the outer contour line of the bubble cross section intersect, and the distance between the two points is expressed as “ The short diameter of the bubble ”.
In addition, when the bubble which the cross section has exposed in a picked-up image exists, such a bubble is excluded from the measuring object of an aspect ratio. For example, when the unfoamed skin is cut and removed from the foam, there is a possibility that air bubbles having a cross-section exposed on the surface of the foam.

(Glass-transition temperature)
The glass transition temperature is measured by the method described in JIS K7121: 1987 "Method for measuring plastic transition temperature". However, the sampling method and temperature conditions are as follows.
Using a differential scanning calorimeter device DSC 6220 (manufactured by SII Nano Technology), about 6 mg of the sample is filled so that there is no gap at the bottom of the aluminum measurement container. The sample is heated from 30 ° C. to 220 ° C. at a temperature increase rate of 20 ° C./min under a nitrogen gas flow rate of 20 mL / min. From the DSC curve obtained when the sample was quickly removed after being held for 10 minutes, allowed to cool in an environment of 25 ± 10 ° C., and then heated from 30 ° C. to 220 ° C. at a temperature increase rate of 20 ° C./min. The glass transition temperature (starting point) is calculated. At this time, alumina is used as a reference material. The glass transition start temperature is determined from the standard (9.3 “How to determine the glass transition temperature”).

(Bulk density and bulk multiple)
The bulk density is measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. That is, it measures using the apparent density measuring device based on JISK6911, and measures bulk density based on a following formula.
Bulk density of expanded particles (g / cm ³ ) = [Weight of graduated cylinder with sample (g) −Weight of graduated cylinder (g)] / [Capacity of graduated cylinder (cm ³ )]
The bulk multiple is a value obtained by adding the resin density to the reciprocal of the bulk density.

(Density and multiple)
Measure the weight (a) and volume (b) of a test piece (ex. 75 x 300 x 30 mm) cut out from the foamed molded product so that each of them is at least 3 significant figures, and foam according to the formula (a) / (b). The density (g / cm ³ ) of the compact is determined.
The multiple is a value obtained by adding the resin density to the reciprocal of the density.

(Open cell ratio)
The open cell ratio is measured as follows.
First, a sample cup of a volumetric air comparison type hydrometer is prepared, and the total weight A (g) of foamed particles (or foamed molded product) in an amount satisfying about 80% of the sample cup is measured. Next, the volume B (cm ³ ) of the entire expanded particle (or expanded molded body) is measured by a 1-1 / 2-atm method using a hydrometer. In addition, the product name “1000 type” of Tokyo Science Co., Ltd. is used for the volumetric air comparison type hydrometer.
Subsequently, a wire mesh container is prepared, the wire mesh container is immersed in water, and the weight C (g) of the wire mesh container in the state immersed in the water is measured. Next, after all of the foam particles (or foamed molded product) are put in the wire mesh container, the wire mesh container is immersed in water, and the wire mesh container and the wire mesh made in the water are immersed in the water. The combined weight D (g) of the foamed particles (or foamed molded product) in the container is measured.
Then, to calculate the apparent volume E of the expanded beads according to the following equation (cm ³⁾ (or the foamed molded volume E (cm ^3)), based on the volume E and the whole foam particle volume B (cm ³⁾ Then, the open cell ratio of the foamed particles for foam molding is calculated by the following formula. The volume of 1 g of water is 1 cm ³ .
E = A + (CD)
Open cell ratio (%) = 100 × (EB) / E

(Heating dimensional change rate)
The heating dimensional change rate is measured by the method B described in JIS K6767: 1999 “Foamed plastics-polyethylene test method”. Specifically, a test piece having a square shape with a planar shape of 150 mm on a side and a thickness of the foam molded body is cut out from the foam molded body.
Three 100 mm straight lines are written at 50 mm intervals in the center of the test piece in parallel to each other in the vertical and horizontal directions. The lengths of three straight lines are measured in the vertical and horizontal directions, respectively, and the arithmetic average value L ₀ is set as the initial dimension. Thereafter, the test piece is left in a 120 ° C. hot air circulating drier for 168 hours to conduct a heating test, and then taken out, and the test piece is left at 25 ° C. for 1 hour. Next, the lengths of three straight lines in the vertical and horizontal directions written on the surface of the test piece are measured, and the arithmetic average value L ₁ thereof is taken as the dimension after heating. The heating dimensional change rate is calculated based on the following formula.
Heating dimensional change rate (%) = 100 × (L ₁ −L ₀ ) / L ₀

(Flexural modulus)
The flexural modulus is measured by a method in accordance with JIS K7221-1: 2006 “Rigid Foamed Plastics—Bending Test—Part 1: Determination of Flexural Properties”. That is, a rectangular parallelepiped test piece having a length of 20 mm, a width of 25 mm, and a height of 130 mm is cut out from the foam molded article. For the measurement, a Tensilon universal testing machine ("UCT-10T" manufactured by Orientec Co., Ltd.) is used. The flexural modulus is calculated using a universal testing machine data processing system ("UTPS-237S Ver, 1.00" manufactured by Soft Brain). The number of specimens shall be 5 or more, and the same as JIS K 7100: 1999 symbol “23/50” (temperature 23 ° C., relative humidity 50%) after adjusting the condition for 16 hours under a second grade standard atmosphere. Measure under standard atmosphere. The arithmetic mean value of the compression elastic modulus of each test piece is taken as the bending elastic modulus of the foamed molded product.
The flexural modulus is calculated by the following equation using the first linear portion of the load-deformation curve.
E = Δσ / Δε
E: Flexural modulus (MPa)
Δσ: Stress difference between two points on the straight line (MPa)
Δε: Difference in deformation between the same two points (%)
The flexural modulus per unit density is calculated by dividing the flexural modulus by the density of the foamed molded product.

(Maximum bending stress)
For the fiber reinforced composite, a strip-shaped test piece having a lateral dimension of 25 mm and a depth dimension of 130 mm is cut out and subjected to a bending test to obtain a bending strength. For the measurement, a Tensilon universal testing machine ("UCT-10T" manufactured by Orientec Co., Ltd.) is used. The bending maximum point stress of bending strength is calculated using a universal testing machine data processing system (“UTPS-237S Ver, 1.00” manufactured by Soft Brain).
A strip-shaped test piece is placed on a support, and the bending maximum point stress is measured under the conditions of a load cell 1000N, a test speed of 10 mm / min, a tip jig 10R of the support, and an opening width of 100 mm. The number of specimens shall be 5 or more, and the same as JIS K 7100: 1999 symbol “23/50” (temperature 23 ° C., relative humidity 50%) after adjusting the condition for 16 hours under a second grade standard atmosphere. Measure under standard atmosphere. The arithmetic mean value of the bending maximum point stress of each test piece is defined as the bending maximum point stress of the fiber reinforced composite.

(Ratio of resin component of base resin)
⁽¹ H-NMR)
Measurement is performed under the following conditions using an ECX400P nuclear magnetic resonance apparatus manufactured by JEOL.
<Measurement conditions>
・ Measurement mode Single pulse ・ Pulse width 45 ° (6.05μsec)
・ Number of points 32k
・ Repetition time: 7.0 seconds ・ Number of integrations: 128 times ・ Measurement solvent: Deuterated chloroform ・ Sample concentration: about 20 mg / 0.6 mL
・ Measurement temperature 50 ℃
・ Chemical shift standard Chloroform: 7.24ppm
・ Measurement range 20ppm (-5ppm to 15ppm)
・ Window function exponnential (BF: 0.12 Hz)
The composition ratio of the base resin is calculated from the integral intensity ratio of each signal of the spectrum obtained from ¹ H-NMR measurement. In addition, when the signal estimated to be derived from impurities is observed in each signal region, these contributions are ignored in the calculation.

(FT-IR)
The absorbance ratio (D1780 / D698, D1720 / D698) of the base resin is measured as follows.
About 10 resin particles selected at random, surface analysis is performed by an infrared spectroscopic analysis ATR measurement method to obtain an infrared absorption spectrum. In this analysis, an infrared absorption spectrum in the depth range from the sample surface to several μm (about 2 μm) is obtained. The absorbance ratio (D1780 / D698, D1720 / D698) is calculated from each infrared absorption spectrum, and the arithmetic average of the calculated absorbance ratio is defined as the absorbance ratio.
Absorbances D1780, D1720, and D698 are connected to Thermo SCIENTIFIC's “Smart-iTR” as an ATR accessory connected to a measuring device sold under the trade name “Fourier transform infrared spectrophotometer Nicolet iS10” by Thermo SCIENTIFIC. taking measurement. Infrared spectroscopy ATR measurement is performed under the following conditions.

<Measurement conditions>
Measurement apparatus: Fourier transform infrared spectrophotometer Nicolet iS10 (manufactured by Thermo SCIENTIFIC) and single reflection type horizontal ATR Smart-iTR (manufactured by Thermo SCIENTIFIC)
ATR crystal: Diamond with ZnSe lens, angle = 42 °
・ Measuring method: Single ATR method ・ Measured wave number range: 4000 cm ^{−1 to} 650 cm ⁻¹
-Wavelength dependence of measurement depth: No correction-Detector: Deuterated triglycine sulfate (DTGS) detector and KBr beam splitter-Resolution: 4 cm ^-1
・ Number of integration: 16 times (same for background measurement)
In the ATR method, the intensity of the infrared absorption spectrum obtained by the measurement changes depending on the degree of adhesion between the sample and the high refractive index crystal, so the degree of adhesion is almost uniform by applying the maximum load that can be applied with the “Smart-iTR” of the ATR accessory. And measure.

The infrared absorption spectrum obtained under the above conditions is subjected to peak processing as follows to obtain D1780, D1720, and D698, respectively.
The absorbance D1780 at 1780 cm ⁻¹ obtained from the infrared absorption spectrum is the absorbance corresponding to the absorption spectrum derived from the antisymmetric stretching vibration due to C═O of the two carbonyl groups in maleic anhydride.
In this absorbance measurement, peak separation is not performed even if other absorption spectra overlap at 1780 cm ⁻¹ . Absorbance D1780 is a straight line connecting the 1920Cm ^-1 and 1620 cm ^-1 as a baseline, means the maximum absorbance between 1810 cm ^-1 and 1745 cm ^-1.

Further, the absorbance D1720 at 1720 cm ⁻¹ is an absorbance corresponding to an absorption spectrum derived from an antisymmetric stretching vibration caused by a carbonyl group C═O contained in methyl methacrylate.
In this measurement of absorbance, peak separation is not performed even if other absorption spectra overlap at 1720 cm ⁻¹ . Absorbance D1720 is a straight line connecting the 1920Cm ^-1 and 1620 cm ^-1 as a baseline, means the maximum absorbance between 1745 cm ^-1 and 1690 cm ^-1.

Absorbance D698 at 698 cm ⁻¹ is an absorbance corresponding to an absorption spectrum derived from an out-of-plane bending vibration of C—H in a monosubstituted benzene ring in styrene.
In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 698 cm ⁻¹ . Absorbance D698 is a straight line connecting the 1510 cm ^-1 and 810 cm ^-1 as a baseline, means the maximum absorbance between 720 cm ^-1 and 660 cm ^-1.

The ratio of styrene, methyl methacrylate and maleic anhydride (% by mass) is calculated from the absorbance ratio (D1780 / D698, D1720 / D698) based on the calibration curve described later. In addition, the peak processing method uses the method similar to the above-mentioned resin particle.
As a method for obtaining the composition ratio of styrene and methyl methacrylate from the absorbance ratio, a plurality of types of standard samples are prepared by uniformly mixing styrene resin and methyl methacrylate resin in a predetermined composition ratio.
Specifically, monomers measured by weight ratio of methyl methacrylate and styrene at weight ratios of 0/100, 20/80, 40/60, 50/50 and 60/40, respectively, were placed in a 10 ml screw vial, where 10 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) is added to 100 parts by weight of the monomer to dissolve the monomer. The obtained liquid mixture is transferred to a 2 ml sample tube (φ7 mm × 122 mm × 190 mm), purged with nitrogen and sealed. Next, this is put into a water bath set at 65 ° C. and heated for 10 hours to complete the polymerization, and the polymer taken out from the ampoule is used as a standard sample.
After obtaining an infrared absorption spectrum for each standard sample by the infrared spectroscopic analysis ATR method, an absorbance ratio (D1780 / D698) is calculated. The calibration curve is drawn by taking the composition ratio (styrene resin ratio in the standard sample = mass%) on the vertical axis and the absorbance ratio (D1780 / D698) on the horizontal axis. Based on this calibration curve, the composition ratio of the styrene resin and the methyl methacrylate resin can be determined.

Standard samples of styrene resin and maleic anhydride resin include 1/1 copolymer of styrene and maleic anhydride (trade name SMA1000 (P) manufactured by CRAY VALLEY) and 3/1 of styrene and maleic anhydride. A polymer (SMA3000 (P) CRAY VALLEY) is used.
After obtaining an infrared absorption spectrum for each standard sample by the infrared spectroscopic analysis ATR method, an absorbance ratio (D1720 / D698) is calculated. A calibration curve is drawn by taking the composition ratio (styrene resin ratio in the standard sample = mass%) on the vertical axis and the absorbance ratio (D1720 / D698) on the horizontal axis. Based on this calibration curve, the composition ratio of the styrene resin and the maleic anhydride resin can be determined.

The composition ratio of styrene and methyl methacrylate and styrene and maleic anhydride is determined from the calibration curve. From the respective composition ratios, the composition ratios of the three components of styrene, methyl methacrylate and maleic anhydride in the resin are determined by the following procedure.
Here, the ratio of each standard sample is set as follows.
Methyl methacrylate: styrene = A: B [1]
Styrene: maleic anhydride = C: D [2]
Since styrene is a common term, the styrene ratio C in [2] is matched with the styrene ratio B in [1].
From [2] Styrene: Maleic anhydride = C: D
= C x (B / C): D x (B / C)
= B: D × (B / C) [3]
From [3], since the ratio of styrene is equal to [1], the abundance ratio of methyl methacrylate, styrene, and maleic anhydride is as follows from [1] and [3].
Methyl methacrylate: styrene: maleic anhydride = A: B: D × (B / C) [4]
From the abundance ratio of [4], the ratio of each component is as follows.
Methyl methacrylate = {A / ((A + B + D × (B / C))} × 100
Styrene = {B / ((A + B + D × (B / C))} × 100
Maleic anhydride = {D × (B / C) / ((A + B + D × (B / C))} × 100

Example 1
(Resin particle manufacturing process)
Styrene-methyl methacrylate-maleic anhydride copolymer (trade name “DENKA RESISFY R-200”, manufactured by Denki Kagaku Kogyo Co., Ltd., styrene: 53 parts by weight, methyl methacrylate: 30 parts by weight, maleic anhydride: 17 parts by weight , Density 1.16 g / cm ³ ) 100 parts by weight and 1 part by weight of a resin composition containing talc were supplied to a twin screw extruder having a diameter of 30 mm and melt-kneaded at 240 ° C. Subsequently, the resin composition was extruded from each nozzle of a multi-nozzle mold (20 nozzles having a diameter of 1.0 mm arranged in a circle) attached to the front end of the twin-screw extruder. The extruded resin was immediately cooled in a cooling water bath. The cooled strand-shaped resin was sufficiently drained and then cut into small particles using a pelletizer to produce resin particles. The obtained resin particles had a particle length L of 1.3 to 1.8 mm and a particle diameter D of 1.0 to 1.2 mm.

(Impregnation process)
After 100 parts by weight of the resin particles were sealed in a pressure vessel and the inside of the pressure vessel was replaced with carbon dioxide, carbon dioxide was injected to an impregnation pressure of 0.5 MPa. After leaving still at 20 degreeC environment and 24 hours of impregnation time passed, the pressure vessel was pressure-removed slowly over 5 minutes. In this way, resin particles were impregnated with carbon dioxide gas to obtain expandable particles.
(Foaming process)
Immediately after the pressure removal in the impregnation step, the foamable particles were taken out from the pressure vessel, and 0.08 part by weight of calcium carbonate was added and mixed. Thereafter, the impregnated product was foamed with water vapor in a high-pressure foaming tank while being stirred with water vapor at a foaming temperature of 128 ° C. for 120 seconds. After foaming, the particles were taken out from the high-pressure foaming tank, and after removing calcium carbonate with an aqueous hydrogen chloride solution, drying was performed with an air dryer to obtain foamed particles. When the bulk density of the obtained foamed particles was measured by the method described above, it was 0.12 g / cm ³ .

(Molding process)
The obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day and then sealed in a pressure vessel. After the inside of the pressure vessel was replaced with carbon dioxide, the carbon dioxide was added to an impregnation pressure (gauge pressure) of 0.4 MPa. Press-fitted. It left still in a 20 degreeC environment, and pressure curing was implemented for 8 hours. After taking out, it is filled in a mold of 30 mm × 300 mm × 400 mm, heated with water vapor of 0.30 MPa for 60 seconds, and then cooled until the maximum surface pressure of the foamed molded product is reduced to 0.01 MPa. Thus, a foamed molded product was obtained.

(Example 2)
In the foaming step, foamed particles and a foamed molded article were obtained in the same manner as in Example 1 except that foaming was performed while stirring at a foaming temperature of 128 ° C. for 150 seconds.
(Example 3)
In the foaming step, foamed particles and a foamed molded article were obtained in the same manner as in Example 1 except that foaming was performed while stirring at a foaming temperature of 130 ° C. for 120 seconds.
Example 4
In the foaming step, foamed particles and a foamed molded article were obtained in the same manner as in Example 1 except that foaming was performed while stirring at a foaming temperature of 130 ° C. for 150 seconds.
(Example 5)
In the foaming step, foamed particles and a foamed molded article were obtained in the same manner as in Example 1 except that foaming was performed while stirring at a foaming temperature of 134 ° C. for 120 seconds.

(Example 6)
(Resin particle manufacturing process)
Styrene-methyl methacrylate-maleic anhydride copolymer (trade name “DENKA RESISFY KX-406”, manufactured by Denki Kagaku Kogyo Co., Ltd., styrene: 70 parts by weight, methyl methacrylate: 9 parts by weight, maleic anhydride: 21 parts by weight , Density 1.15 g / cm ³ ) 100 parts by weight and 1 part by weight of a resin composition containing talc were supplied to a twin screw extruder having a diameter of 30 mm and melt-kneaded at 254 ° C. Subsequently, the resin composition was extruded from each nozzle of a multi-nozzle mold (20 nozzles having a diameter of 1.0 mm arranged in a circle) attached to the front end of the twin-screw extruder. The extruded resin was immediately cooled in a cooling water bath. The cooled strand-shaped resin was sufficiently drained and then cut into small particles using a pelletizer to produce resin particles. The obtained resin particles had a particle length L of 1.3 to 1.8 mm and a particle diameter D of 1.0 to 1.2 mm.

(Impregnation process)
After sealing 100 parts by weight of the resin particles in a pressure vessel and replacing the inside of the pressure vessel with carbon dioxide, the carbon dioxide was press-fitted to an impregnation pressure of 1.0 MPa. After leaving still at 20 degreeC environment and 24 hours of impregnation time passed, the pressure vessel was pressure-removed slowly over 5 minutes. In this way, resin particles were impregnated with carbon dioxide gas to obtain expandable particles.
(Foaming process)
Immediately after the pressure removal in the impregnation step, the foamable particles were taken out from the pressure vessel, and 0.08 part by weight of calcium carbonate was added and mixed. Thereafter, the impregnated product was foamed with water vapor in a high-pressure foaming tank while stirring for 150 seconds at a foaming temperature of 136 ° C. using water vapor. After foaming, the particles were taken out from the high-pressure foaming tank, and after removing calcium carbonate with an aqueous hydrogen chloride solution, drying was performed with an air dryer to obtain foamed particles. When the bulk density of the obtained foamed particles was measured by the method described above, it was 0.12 g / cm ³ .

(Molding process)
The obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day and then sealed in a pressure vessel. After the inside of the pressure vessel was replaced with carbon dioxide, the carbon dioxide was added to an impregnation pressure (gauge pressure) of 0.4 MPa. Press-fitted. It left still in a 20 degreeC environment, and pressure curing was implemented for 8 hours. After taking out, it is filled in a 30 mm × 300 mm × 400 mm molding die, heated with 0.42 MPa steam for 60 seconds, and then cooled until the maximum surface pressure of the foamed molded product decreases to 0.01 MPa. Thus, a foamed molded product was obtained.

(Comparative Example 1)
(Foaming process)
Styrene-methyl methacrylate-maleic anhydride copolymer (trade name “DENKA RESISFY R-200”, manufactured by Denki Kagaku Kogyo Co., Ltd., styrene: 53 parts by weight, methyl methacrylate: 30 parts by weight, maleic anhydride: 17 parts by weight ) 100 parts by weight and a resin composition containing 1 part by weight of a resin composition containing talc and a resin composition containing talc in a tandem type extruder in which a first extruder having a screw diameter of 50 mm and a second extruder having a screw diameter of 65 mm are connected. The mixture was supplied and melt kneaded at 280 ° C.
Next, in the middle of the first single-screw extruder, the molten resin composition is 1.8 parts by weight of butane containing 35% by weight of isobutane and 65% by weight of normal butane with respect to 100 parts by weight of the resin. And was uniformly dispersed in the resin composition.

Thereafter, at the front end portion of the second extruder, the molten resin composition was cooled to 175 ° C., and then the resin composition was extruded and foamed from the nozzle of a multi-nozzle mold attached to the front end of the extruder. The multi-nozzle mold had a nozzle having a diameter of 1 mm at the outlet.
Then, the resin extrudate extruded and foamed from the outlet portion of the nozzle of the multi-nozzle mold was cut with a rotary blade and immediately cooled to produce expanded particles having substantially spherical re-expandability. The resin extrudate consisted of an unfoamed portion immediately after being extruded from the nozzle of the multi-nozzle mold, and a foamed portion in the process of foaming continuous with the unfoamed portion. The resin extrudate was cut at the open end of the outlet portion of the nozzle, and the resin extrudate was cut at the unfoamed portion.
(Molding process)
The obtained foamed particles are filled into a molding die of 30 mm × 300 mm × 400 mm, heated with 0.42 MPa of water vapor for 60 seconds, and then the maximum surface pressure of the foamed molded product is reduced to 0.01 MPa. The foamed molded product was obtained by cooling to 1.

(Comparative Example 2)
From the middle of the first single-screw extruder, butane containing 35% by weight of isobutane and 65% by weight of normal butane was pressed into the molten resin composition so as to be 2.5 parts by weight with respect to 100 parts by weight of the resin. In the same manner as in Example 1 except that the resin composition was uniformly dispersed, foamed particles and a foamed molded article were produced.
Table 1 summarizes the types of foaming agent impregnation methods, Tg of the base resin, the ratio of the area of the expanded particles, the ratio of the number of bubbles, the interface aspect ratio, and the bulk ratio of the expanded particles of the above Examples and Comparative Examples. In addition, Table 2 summarizes the cell area ratio, the cell number ratio, the interface aspect ratio, and the multiple of the foam molded body of the foam molded bodies of Examples 1-2 and Comparative Examples 1-2. Furthermore, the cross-sectional photograph of the expanded particle of an Example and a comparative example is shown in FIGS. 1-8, and the cross-sectional photograph of the foaming molding of Examples 1-2 and Comparative Examples 1-2 is shown in FIGS. In these figures, (a) is a photograph of the inside, and (b) is a photograph of the surface layer.

(Fiber-reinforced composite manufacturing process)
The foam particles produced in Examples 1 and 2 and Comparative Example 1 as the core material are filled in a molding die of 12 mm × 300 mm × 400 mm, heated with steam, and then the maximum surface pressure of the foamed molded product is 0 The foamed molded product was manufactured by cooling until the pressure decreased to 0.01 MPa, and cut into a square shape with a side of 150 mm to obtain a foamed molded product for core material.
On the other hand, as a fiber reinforced resin material (fiber reinforced plastic), a face material in which a twill weave made of carbon fiber is impregnated with resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name “Pyrofil Prepreg TR3523-395GMP”, basis weight: 200 g / m ² , thickness: 0.23 mm) were prepared. The face material had a planar square shape with a side of 150 mm, and the face material contained 40% by mass of an uncured epoxy resin as a thermosetting resin.

Two face materials were overlapped so that the warp yarns were 90 ° in length direction to form a multilayer face material. It was arrange | positioned on the front and back of the foaming molding for core materials, respectively, and the laminated body was obtained.
Subsequently, the laminated body is disposed between the flat plate molds, and the flat plate mold having a spacer having a thickness of 11 mm is clamped to press-mold, and the fiber reinforced plastic is thermally bonded to the foam, and the core material. The fiber reinforced composite provided with the surface layer part which consists of a part and a multilayer surface material was produced.
At the time of press molding, the laminate is made to be 120 ° C. and held for 8 minutes so that the resin contained in the fiber reinforced plastic is cured and the fibers of the fiber reinforced plastic are cured with an epoxy resin. The fiber reinforced composite was manufactured by laminating and fixing the fiber reinforced plastic on both sides of the foamed body.
Thereafter, the fiber reinforced composite was cooled to 30 ° C. or lower, and then the flat plate mold was opened to take out the fiber reinforced composite to obtain a fiber reinforced composite.

  From Tables 1 and 2, a foamed molded product obtained from expanded particles having a specific range of cell area ratio and a foamed molded product having a specific range of cell area ratio have excellent mechanical properties. I understand.

(Example 7)
(Resin particle manufacturing process)
Styrene-methyl methacrylate-maleic anhydride copolymer (trade name “DENKA RESISFY KX-435”, manufactured by Denki Kagaku Kogyo Co., Ltd., styrene: 61 parts by weight, methyl methacrylate: 12 parts by weight, maleic anhydride: 27 parts by weight , Density 1.15 g / cm ³ ) 100 parts by weight and 80 parts by weight, and the remaining 20 parts by weight of styrene-maleic anhydride-N-phenylmaleimide copolymer (trade name “DENKA IP MS-NIP”, electrochemistry Resin containing 100 parts by weight of styrene: 67 parts by weight, styrene: 67 parts by weight, maleic anhydride: 5 parts by weight, N-phenylmaleimide: 27 parts by weight, density 1.18 g / cm ³ , glass transition temperature Tg 186 ° C. 1 part by weight of the composition was supplied to a twin screw extruder having a diameter of 30 mm and melt kneaded at 265 ° C. Subsequently, the resin composition was extruded from each nozzle of a multi-nozzle mold (20 nozzles having a diameter of 1.0 mm arranged in a circle) attached to the front end of the twin-screw extruder. The extruded resin was immediately cooled in a cooling water bath. The cooled strand-shaped resin was sufficiently drained and then cut into small particles using a pelletizer to produce resin particles. The obtained resin particles had a particle length L of 1.3 to 1.8 mm and a particle diameter D of 1.0 to 1.2 mm.

(Impregnation process)
After 100 parts by weight of the resin particles were sealed in a pressure vessel and the inside of the pressure vessel was replaced with carbon dioxide, carbon dioxide was injected to an impregnation pressure of 0.5 MPa. After leaving still at 20 degreeC environment and 24 hours of impregnation time passed, the pressure vessel was pressure-removed slowly over 5 minutes. In this way, resin particles were impregnated with carbon dioxide gas to obtain expandable particles.
(Foaming process)
Immediately after the pressure removal in the impregnation step, the foamable particles were taken out from the pressure vessel, and 0.08 part by weight of calcium carbonate was added and mixed. Thereafter, the impregnated product was foamed with water vapor in a high-pressure foaming tank while being stirred with water vapor at a foaming temperature of 146 ° C. for 150 seconds. After foaming, the particles were taken out from the high-pressure foaming tank, and after removing calcium carbonate with an aqueous hydrogen chloride solution, drying was performed with an air dryer to obtain foamed particles. When the bulk density of the obtained foamed particles was measured by the method described above, it was 0.12 g / cm ³ .

(Molding process)
The obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day and then sealed in a pressure vessel. After the inside of the pressure vessel was replaced with carbon dioxide, the carbon dioxide was added to an impregnation pressure (gauge pressure) of 0.4 MPa. Press-fitted. It left still in a 20 degreeC environment, and pressure curing was implemented for 8 hours. After taking out, it is filled in a mold of 30 mm × 300 mm × 400 mm, heated with 0.45 MPa water vapor for 60 seconds, and then cooled until the maximum surface pressure of the foamed molded product is reduced to 0.01 MPa. Thus, a foamed molded product was obtained.

(Example 8)
In the resin particle manufacturing process, except that 100 parts by weight of styrene-methyl methacrylate-maleic anhydride copolymer is 85 parts by weight and the remaining 15 parts by weight is styrene-maleic anhydride-N-phenylmaleimide copolymer. Were the same as in Example 7 to obtain expanded particles and expanded molded articles.

Example 9
In the resin particle production step, 100 parts by weight of styrene-methyl methacrylate-maleic anhydride copolymer is 90 parts by weight, and the remaining 10 parts by weight is styrene-maleic anhydride-N-phenylmaleimide copolymer, Expanded particles were obtained in the same manner as in Example 7 except that the temperature was 143 ° C.

(Molding process)
The obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day and then sealed in a pressure vessel. After the inside of the pressure vessel was replaced with carbon dioxide, the carbon dioxide was added to an impregnation pressure (gauge pressure) of 0.4 MPa. Press-fitted. It left still in a 20 degreeC environment, and pressure curing was implemented for 8 hours. After taking out, it is filled in a mold of 30 mm × 300 mm × 400 mm, heated with 0.43 MPa water vapor for 60 seconds, and then cooled until the maximum surface pressure of the foamed molded product is reduced to 0.01 MPa. Thus, a foamed molded product was obtained.

  Table 3 summarizes the types of the blowing agent impregnation method, Tg of the base resin, the bubble area ratio of the expanded particles, the ratio of the number of bubbles, the interface aspect ratio, and the bulk multiple of the expanded particles in the above examples. In addition, Table 4 shows the bubble area ratio, the bubble number ratio, the interface aspect ratio, and the multiple of the foam molded body of the foam molded bodies of Examples 7 to 9 described above. Furthermore, cross-sectional photographs of the expanded particles of Examples 7 to 9 are shown in FIGS. 13 to 15, and cross-sectional photographs of the expanded molded articles of Examples 7 to 9 are shown in FIGS. In these figures, (a) is a photograph of the inside, and (b) is a photograph of the surface layer.

  From Tables 3 and 4, the foamed molded article composed of a copolymer further containing a maleimide monomer as a base resin has excellent mechanical properties and also excellent heat resistance. I understand.

Claims (11)

Expanded particles composed of a base resin containing a copolymer of aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid, and the expanded particles have an area of 0.13 mm ² at 300 times In which a small bubble having a bubble diameter of 5 μm or more and less than 30 μm and a large bubble having a bubble diameter of 30 to 100 μm are provided, and the small bubble has a total area of 1 to 50 times the total area of the large bubble Expanded particles characterized by showing. ^2. The expanded particle according to claim 1, wherein the small bubbles are present in a number of 1 to 300 times the number of the large bubbles in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. The foamed particle according to claim 1, wherein the foamed particle comprises bubbles in the vicinity of the surface showing an interface aspect ratio of 0.2 to 0.8 in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. .   The aromatic vinyl is a styrene monomer, the (meth) acrylic acid ester is a (meth) acrylic acid alkyl ester (the alkyl group has 1 to 5 carbon atoms), and the unsaturated dicarboxylic acid has 2 to 6 carbon atoms. Each selected from an aliphatic unsaturated dicarboxylic acid, and the copolymer is 100 parts by weight of the total of units derived from the aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid, 30 to 80 parts by weight of units derived from the aromatic vinyl, 8 to 35 parts by weight of units derived from the (meth) acrylic acid ester, and 10 to 50 parts by weight of units derived from the unsaturated dicarboxylic acid The expanded particle according to any one of claims 1 to 3. A foamed molded article composed of a base resin containing a copolymer of an aromatic vinyl, a (meth) acrylic acid ester and an unsaturated dicarboxylic acid, and the foamed particles are 300 times 0.13 mm ² In a cross-sectional photograph taken of the area, it has small bubbles with a bubble diameter of 5 μm or more and less than 30 μm and large bubbles with a bubble diameter of 30 to 100 μm, and the small bubbles are 0.5 to 50 times the total area of the large bubbles A foamed molded article characterized by showing the total area of The foamed molded product according to claim 5, wherein the small bubbles are present in a number of 1 to 300 times the number of the large bubbles in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. 7. The foam according to claim 5, wherein the foamed molded article includes bubbles in the vicinity of the surface showing an interface aspect ratio of 0.37 to 0.8 in a cross-sectional photograph obtained by photographing an area of 0.13 mm ² at 300 times. Molded body.   The aromatic vinyl is a styrene monomer, the (meth) acrylic acid ester is a (meth) acrylic acid alkyl ester (the alkyl group has 1 to 5 carbon atoms), and the unsaturated dicarboxylic acid has 2 to 6 carbon atoms. Each selected from an aliphatic unsaturated dicarboxylic acid, and the copolymer is 100 parts by weight of the total of units derived from the aromatic vinyl, (meth) acrylic acid ester and unsaturated dicarboxylic acid, 30 to 80 parts by weight of units derived from the aromatic vinyl, 8 to 35 parts by weight of units derived from the (meth) acrylic acid ester, and 10 to 50 parts by weight of units derived from the unsaturated dicarboxylic acid The foaming molding as described in any one of Claims 5-7.   A fiber reinforced composite comprising the foam molded article according to any one of claims 5 to 8 and a fiber reinforced plastic layer laminated and integrated on a surface of the foam molded article.   The fiber-reinforced composite according to claim 9, which is used for a wind turbine blade, a robot arm, and an automobile part.   The automotive part comprised from the foaming molding of any one of Claims 5-8, or the fiber reinforced composite_body | complex of Claim 9.