WO2013147040A1 - Composite resin particles, expandable composite resin particles, pre-expanded particles, molded foam, and core material for bumper - Google Patents

Abstract

Composite resin particles which comprise, as resin components, 100 parts by mass of a polyolefin resin and 100-400 parts by mass of a polystyrene resin, wherein the polyolefin resin has a Vicat softening point of 110-125ºC and a dispersity ratio of 1.5-4.8.

Description

Composite resin particles, expandable composite resin particles, pre-expanded particles, foamed moldings, and bumper core materials

The present invention relates to composite resin particles, expandable composite resin particles, pre-expanded particles, foamed molded products, and bumper core materials. Specifically, the present invention relates to composite resin particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability, and expandable composite resin particles obtained from the composite resin particles, pre-expanded particles The present invention relates to a foam molded body and a bumper core material.

Conventionally, foamed molded products containing polystyrene resin as a resin component have excellent physical properties such as molding processability, heat insulation, impact resistance and buffering properties. Widely used as a member.

Especially in the application of automobile structural members, higher impact resistance is particularly required for foamed molded products. Moreover, as what satisfy | fills such a characteristic, the patent document 1, 2 and 3 describe the foaming molding which contains a polystyrene-type resin and a polyolefin-type resin as a resin component.

Japanese Unexamined Patent Publication No. 2010-024353 Japanese Unexamined Patent Publication No. 2011-208067 International Publication No. 2006/027944

Currently, from the viewpoint of protecting pedestrians in the event of an accident, an automotive foam molded body such as a bumper core material is required to have improved energy absorption characteristics, that is, higher impact resistance.

On the other hand, from the same point of view, a pedestrian detection function is also installed in automobiles. For this reason, in addition to the above-described characteristics, the foamed molded body is also required to have high dimensional stability under a high temperature environment, that is, excellent heating dimensional stability in order to prevent malfunction of the detection function.

However, the foamed molded products described in Patent Documents 1 to 3 have a certain effect, but are not always satisfactory from such a viewpoint. The present invention has been made in view of the above problems, and is obtained from composite resin particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability, and obtained from the composite resin particles. It is an object of the present invention to provide expandable composite resin particles, pre-expanded particles, a foam molded article, and a bumper core material.

As a result of intensive studies, the present inventors have determined that, as a resin component, from a composite resin particle containing a polyolefin resin having a specific range of Vicat softening point and dispersity and a polystyrene resin, impact resistance and heat dimensional stability. The present inventors have found that an excellent foam molded article can be provided, and have come to carry out the present invention.

Thus, according to the present invention, the resin component includes 100 parts by mass of polyolefin resin and 100 to 400 parts by mass of polystyrene resin, and the polyolefin resin has a Vicat softening point of 110 to 125 ° C. and 1.5 to 4.8. Composite resin particles having a degree of dispersion of 5 are provided.

Further, according to the present invention, there is provided foamable composite resin particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability.

Further, according to the present invention, pre-expanded particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability are provided.

Further, according to the present invention, a foamed molded article excellent in impact resistance and heat dimensional stability is provided.

Further, according to the present invention, a core material for a bumper excellent in impact resistance and heating dimensional stability is provided.

According to the present invention, it is possible to provide composite resin particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability. Specifically, it is possible to provide composite resin particles capable of obtaining a foamed molded article having excellent energy absorption characteristics and heat dimensional stability under a high temperature environment.

Further, according to the present invention, when the composite resin particles contain 100 parts by mass of a polyolefin resin and 100 to 300 parts by mass of a polystyrene resin as resin components, a foamed molded article having superior impact resistance and heat dimensional stability can be obtained. The composite resin particle which can be obtained can be provided.

Further, according to the present invention, when the composite resin particles have a dispersity of 2.0 to 4.5, the composite resin particles capable of obtaining a foamed molded article superior in impact resistance and heat dimensional stability are obtained. Can be provided.

Further, according to the present invention, when the polyolefin resin is a polyethylene resin or a polypropylene resin, it is possible to provide composite resin particles capable of obtaining a foamed molded article superior in impact resistance and heat dimensional stability.

Further, according to the present invention, when the composite resin particles have a Vicat softening point of 110 to 130 ° C., it is possible to provide composite resin particles that can obtain a foamed molded article that is superior in impact resistance and heat dimensional stability.

Further, according to the present invention, when the composite resin particles contain 0.5 to 3.0 parts by mass of carbon black with respect to 100 parts by mass of the resin component, the composite resin particles contain carbon black as a colorant in a suitable ratio. In addition, composite resin particles capable of obtaining a foamed molded article having excellent impact resistance and heat dimensional stability and also excellent design properties can be provided.

According to the present invention, it is possible to provide foamable composite resin particles capable of obtaining a foamed molded article having excellent impact resistance and heat dimensional stability from the composite resin particles as described above.

According to the present invention, it is possible to provide pre-expanded particles capable of obtaining a foamed molded article having excellent impact resistance and heat dimensional stability from the expandable composite resin particles as described above.

According to the present invention, it is possible to provide a foamed molded article excellent in impact resistance and heat dimensional stability from the above pre-expanded particles.

Further, according to the present invention, when the foamed molded product has a density of 0.020 to 0.10 g / cm ³ , it is possible to provide a foamed molded product that is superior in impact resistance and heat dimensional stability.

Further, according to the present invention, it is possible to provide a foamed molded article excellent in impact resistance and heat dimensional stability, which shows an absorbed energy of 1.2 to 3.0 J in the impact test of ASTM D3763-92.

Further, according to the present invention, it is possible to provide a foamed molded article excellent in impact resistance and heating dimensional stability, which exhibits a heating dimensional change rate of 1.0% or less in a heating dimensional change test of JIS K6767: 1999. .

According to the present invention, it is possible to provide a bumper core material excellent in impact resistance and heat dimensional stability from the foamed molded article as described above.

The present invention includes 100 parts by mass of a polyolefin resin and 100 to 400 parts by mass of a polystyrene resin as resin components, and the polyolefin resin has a Vicat softening point of 110 to 125 ° C. and a dispersity of 1.5 to 4.8. It relates to composite resin particles having

Specifically, the composite resin particles of the present invention contain a polyolefin resin and a polystyrene resin in suitable proportions. For this reason, the composite resin particle has characteristics such as rigidity, heat insulation, light weight, water resistance and foaming moldability possessed by polystyrene resin and chemical resistance, heat resistance and impact resistance possessed by polyolefin resin (impact Absorptivity) and the like.

Also, the polyolefin resin has a Vicat softening point of 110 to 125 ° C. and a dispersity of 1.5 to 4.8. For this reason, the impact resistance and heat dimensional stability of foamed moldings obtained from polyolefin resin and composite resin particles containing polyolefin resin are improved by suitably setting the polymer chain and structure in polyolefin resin. Can be made. As a result, the foam molded product obtained from such composite resin particles can be widely used as a component packing material, an automobile member, a cushioning material, or a bumper core material, particularly as a bumper core material. The degree of dispersion (Mw / Mn) means a value indicating the degree of monodispersity of the chain length distribution obtained using the number average molecular weight (Mn) and the weight average molecular weight (Mw).

Therefore, according to the present invention, it is possible to provide composite resin particles capable of obtaining a foamed molded article excellent in impact resistance and heat dimensional stability. Hereinafter, the composite resin particles of the present invention will be described more specifically.

<Composite resin particles>
In the present invention, the composite resin particle means a resin particle obtained by combining a plurality of resin components. Specific examples include resin particles obtained by modifying a polyolefin resin with a polystyrene resin derived from a styrene monomer. “Composite” means that a polyolefin resin and a polystyrene resin are present in the particle, and “modification” means impregnating and polymerizing a styrene monomer in the polyolefin resin. To do.

The composite resin particles of the present invention contain a polyolefin resin and a polystyrene resin in a suitable ratio. Specifically, the composite resin particles contain 100 to 400 parts by mass, preferably 100 to 300 parts by mass, and more preferably 150 to 230 parts by mass of a polystyrene resin with respect to 100 parts by mass of the polyolefin resin. When the composite resin particles contain 100 parts by mass of polyolefin resin, specific values of polystyrene resin content are 100, 130, 150, 180, 200, 230, 240, 250, 270, 300, 350, 400 parts by mass and the like can be mentioned.

When the amount of the polystyrene resin is less than 100 parts by mass, the ratio of the polystyrene resin in the composite resin particles becomes low, and the composite resin particles may not be able to obtain sufficient characteristics derived from the polystyrene resin. On the other hand, when the amount of the polystyrene resin is more than 400 parts by mass, the ratio of the polyolefin resin in the composite resin particles becomes low, and the characteristics derived from the polyolefin resin may not be sufficiently obtained.

The composite resin particles preferably have a Vicat softening point of 110 to 130 ° C., more preferably 110 to 125 ° C. The Vicat softening point is one of the indices representing the heat resistance of the resin, and the composite resin particles are measured according to the method described in JIS K7196: 1991 “Softening temperature test method by thermomechanical analysis of thermoplastic film and sheet”. What you did. Specific measurement methods are as in the following examples. The Vicat softening point of the composite resin particle means the Vicat softening point of the composite resin particle itself containing the composite resin particle when the composite resin particle contains other components other than the resin component such as carbon black. On the other hand, when the composite resin particle does not contain other components, the Vicat softening point of the composite resin particle means the Vicat softening point of the resin component itself of the composite resin particle. Specific numerical values of the Vicat softening point of the composite resin particles are 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130 ° C. and the like.

When the Vicat softening point of the composite resin particles is lower than 110 ° C., the composite resin particles may not have sufficient heat resistance. On the other hand, when the Vicat softening point of the composite resin particles is higher than 130 ° C., the foamable composite resin particles may not have sufficient foamability.

The composite resin particles preferably have an average particle diameter of 0.71 to 2.5 mm, more preferably 0.85 to 1.6 mm. The shape is preferably spherical to substantially spherical. Specific numerical values of the average particle diameter of the composite resin particles are 0.71, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5 mm, etc. It is done.

<Polyolefin resin>
The polyolefin resin is not particularly limited, and means an olefin homopolymer or a copolymer of an olefin monomer as a main component and another monomer copolymerizable with the olefin monomer. . Here, the main component of the olefin monomer means that the olefin monomer occupies 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more of the total monomers. . Specific values of the proportion of the olefinic monomer when the total monomer is 100% by mass are 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100% by mass. Etc.

Specifically, examples of the polyolefin resin include an α-olefin resin such as a polyethylene resin, a polypropylene resin, and a polybutylene resin. Moreover, since a desired physical property can be obtained more easily, a polyethylene resin, a polypropylene resin, and a combination thereof are preferable as the polyolefin resin.

The polyolefin resin of the present invention has a Vicat softening point of 110 to 125 ° C, preferably 112 to 125 ° C, more preferably 113 to 123 ° C. The Vicat softening point is one of the indices representing the heat resistance of the resin. For polyolefin resins, the Vicat softening point is measured according to the method described in JIS K7206: 1999 “Plastics—Thermoplastics—Vicat softening temperature test method”. . Specific values of the Vicat softening point of the polyolefin resin include 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125 ° C., and the like. .

When the Vicat softening point of the polyolefin resin is lower than 110 ° C., the composite resin particles may not have sufficient heat resistance. On the other hand, when the Vicat softening point of the polyolefin resin is higher than 125 ° C., the expandable composite resin particles may not have sufficient expandability.

The polyethylene resin preferably has a weight average molecular weight (Mw) of 60 × 10 ³ to 200 × 10 ³ , more preferably 70 × 10 ³ to 190 × 10 ³ . Specific numerical values of the weight average molecular weight of the polyethylene resin include 60 × 10 ³ , 70 × 10 ³ , 80 × 10 ³ , 90 × 10 ³ , 100 × 10 ³ , 150 × 10 ³ , 160 × 10 ³ , 170 * 10 < ³ >, 180 * 10 < ³ >, 190 * 10 < ³ >, 200 * 10 < ³ > etc. are mentioned.

When the weight average molecular weight is lower than 60 × 10 ³ , the composite resin particles may not have sufficient heat resistance. On the other hand, when the weight average molecular weight is higher than 200 × 10 ³ , the expandable composite resin particles may not have sufficient expandability.

The polyethylene resin preferably has a number average molecular weight (Mn) of 10 × 10 ³ to 80 × 10 ³ , more preferably 15 × 10 ³ to 80 × 10 ³ . Specific numerical values of the number average molecular weight of the polyethylene resin are 10 × 10 ³ , 15 × 10 ³ , 20 × 10 ³ , 30 × 10 ³ , 40 × 10 ³ , 50 × 10 ³ , 60 × 10 ³ , 70 * 10 < ³ >, 80 * 10 < ³ > etc. are mentioned.

Also in this case, when the number average molecular weight is lower than 10 × 10 ³ , the composite resin particles may not have sufficient heat resistance. On the other hand, when the number average molecular weight is higher than 80 × 10 ³ , the expandable composite resin particles may not have sufficient expandability.

The polypropylene resin preferably has a weight average molecular weight of 200 × 10 ³ to 400 × 10 ³ , more preferably 250 × 10 ³ to 390 × 10 ³ . Specific numerical values of the weight average molecular weight of the polypropylene resin include 200 × 10 ³ , 230 × 10 ³ , 250 × 10 ³ , 300 × 10 ³ , 310 × 10 ³ , 320 × 10 ³ , 330 × 10 ³ , 340 * 10 < ³ >, 350 * 10 < ³ >, 360 * 10 < ³ >, 370 * 10 < ³ >, 380 * 10 < ³ >, 390 * 10 < ³ >, 400 * 10 < ³ > etc. are mentioned.

When the weight average molecular weight is lower than 200 × 10 ³ , the composite resin particles may not have sufficient heat resistance. On the other hand, when the weight average molecular weight is higher than 400 × 10 ³ , the expandable composite resin particles may not have sufficient expandability.

The polypropylene resin preferably has a number average molecular weight (Mn) of 70 × 10 ³ to 160 × 10 ³ , more preferably 80 × 10 ³ to 150 × 10 ³ . Specific numerical values of the number average molecular weight of the polypropylene resin include 70 × 10 ³ , 75 × 10 ³ , 80 × 10 ³ , 90 × 10 ³ , 100 × 10 ³ , 110 × 10 ³ , 120 × 10 ³ , ^{130 × 10 3, 140 × 10} 3, 150 × 10 3, 155 × 10 3, 160 × 10 3 , and the like.

Also in this case, when the number average molecular weight is lower than 70 × 10 ³ , the composite resin particles may not have sufficient heat resistance. On the other hand, when the number average molecular weight is higher than 160 × 10 ³ , the expandable composite resin particles may not have sufficient expandability.

The polyolefin resin of the present invention has a dispersity (Mw / Mn) of 1.5 to 4.8, preferably 2.0 to 4.5. Specific numerical values of the dispersibility of the polyolefin resin include 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 3.0, 3.5, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4. 8 etc. are mentioned.

If the dispersity is lower than 1.5, the manufacturing cost may be a problem. On the other hand, when the degree of dispersion is higher than 4.8, the impact resistance of the foamed molded product may be lowered.

When a polyethylene resin is used as the polyolefin resin, the polyethylene resin is preferably 0.927 to 0.950 kg / m ³ , more preferably 0.927 to 0.945 kg / m ³ , and still more preferably 0.930. It has a density of ˜0.945 kg / m ³ . In this case, specific numerical values of the density of the polyethylene resin are 0.927, 0.928, 0.929, 0.930, 0.931, 0.932, 0.933, 0.934, 0.935. 0.936, 0.937, 0.938, 0.939, 0.940, 0.941, 0.942, 0.943, 0.944, 0.945, 0.946, 0.947, 0 948, 0.949, 0.950 kg / m ^{3 and the} like.

When the density of the polyethylene resin is lower than 0.927 kg / m ³ , the composite resin particles may not have sufficient heating dimensional stability. On the other hand, when the density of the polyethylene resin is higher than 0.950 kg / m ³ , the resin component may not be sufficiently softened during the polymerization process, and the expandable composite resin particles may not have sufficient expandability.

When the polyethylene resin of the present invention is measured at 190 ° C. under a load of 2.16 kg, the polyolefin resin is preferably 1.0-10.0 g / 10 min, more preferably 1.0-7.0 g / min. It has a melt flow rate of 10 minutes. In this case, specific numerical values of the melt flow rate of the polyolefin resin are 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 6.5, 6.8, 7.0, 7.2, 7.4, 7.6, 7.8, 8. 0, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, 9.8, 10.0 g / 10 min.

When the polypropylene resin of the present invention is measured at 230 ° C. under a load of 2.16 kg, the polyolefin resin is preferably 1.0 to 10.0 g / 10 min, more preferably 2.0 to 9. It has a melt flow rate of 0 g / 10 min. In this case, specific numerical values of the melt flow rate of the polyolefin resin are 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 3.0, 4.0, 5.0, 6.0, 7. 0, 7.5, 8.0, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0 g / 10 min, etc. are mentioned.

If the melt flow rate of these polyolefin resins is lower than 1.0 g / 10 min, it may be impossible to obtain a foam having a predetermined multiple. On the other hand, when the melt flow rate of the polyolefin-based resin is higher than 10.0 g / 10 minutes, it may be impossible to obtain a predetermined multiple of foam.

When the polyolefin resin in the composite resin particles has such Vicat softening point, weight average molecular weight, number average molecular weight, dispersity, density and melt flow rate, expandable composite resin particles obtained from the composite resin particles, pre-expanded The polyolefin resin in the particles, the molded foam and the bumper core material also has substantially the same Vicat softening point, weight average molecular weight, number average molecular weight, dispersity, density and melt flow rate, respectively.

<Production method of polyolefin resin>
Polyolefin resins such as polyethylene resins and polypropylene resins can be produced according to known methods. Furthermore, in the case of producing a polyethylene resin and a polypropylene resin having the above characteristics, a polymerization method using a metallocene compound as a catalyst is preferable because they can be produced more easily.

Examples of the metallocene compound include known metallocene compounds. For example, a metallocene compound containing a tetravalent transition metal element can be preferably used.

<Polystyrene resin>
The composite resin particle contains a polystyrene resin as a resin component. For this reason, the composite resin particles can have excellent properties such as rigidity, heat insulation, light weight, water resistance, and foam moldability of the polystyrene resin.

The polystyrene resin means a styrene homopolymer or a copolymer of a styrene monomer as a main component and another monomer component copolymerizable with the styrene monomer. Furthermore, the styrene monomer as a main component means that the styrene monomer occupies 50 parts by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more in 100 parts by mass of all monomer components. Means. Specific values of the proportion of the styrenic monomer when the total monomer is 100% by mass are 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100% by mass. Etc.

As the copolymer component contained in the polystyrene resin, a known monomer can be used as long as it does not affect the desired physical properties. Specifically, cyclic olefin monomers, diene monomers, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, Mention may be made of vinylic monomers such as maleic anhydride and methylstyrene. Moreover, these can also be used by 1 type (s) or 2 or more types.

<Other ingredients>
Since the composite resin particle of the present invention can obtain a foamed molded article having a black color and excellent design, carbon black is preferably used in an amount of 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the resin component. More preferably, the content is 0.5 to 2.0 parts by mass. Specific numerical values of the carbon black content in the composite resin particles are 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1 with respect to 100 parts by mass of the resin component. 0.5, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0 parts by mass and the like.

When the amount of carbon black is less than 0.5 parts by mass, the composite resin particles may not have sufficient colorability. On the other hand, when carbon black is contained more than 3.0 parts by mass, the composite resin particles may not have impact resistance.

Known carbon black can be used. Specific examples include carbon-based materials such as furnace black, channel black, thermal black, acetylene black, graphite, and carbon fiber.

In the present invention, a composition containing carbon black, a so-called master batch may be added. The master batch contains carbon black in a proportion of preferably 30 to 50 parts by mass, more preferably 35 to 45 parts by mass with respect to 100 parts by mass of the master batch. In this case, the specific value of the carbon black content in the master batch is 30, 31, 32, 33, 34, 35, 37, 40, 43, 45, 46, 47 with respect to 100 parts by mass of the master batch. 48, 49, 50 parts by mass, and the like. The base resin contained in the master batch is preferably an olefin resin.

As long as desired composite resin particles and the following expandable composite resin particles, pre-expanded particles, and foamed molded article can be obtained, these may contain other additives as appropriate. Specific examples include a bubble regulator, a coating agent, a light stabilizer, an ultraviolet absorber, a pigment, a dye, an antifoaming agent, a heat stabilizer, a lubricant, and an antistatic agent.

The mass and mass ratio of the raw material monomer, raw material resin, and other components, and the mass and mass of the composite resin particles, expandable composite resin particles, pre-expanded particles, resin components in the foamed molded product, and other components The ratio is substantially the same.

In addition, the qualitative and quantitative determination of the raw materials contained in the composite resin particles, expandable composite resin particles, pre-expanded particles and foamed molded products can be performed by nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), gel permeation. It can carry out according to a well-known method using chromatography (GPC) etc.

<Expandable composite resin particles>
Since the foamable composite resin particles of the present invention also use the composite resin particles as described above as a raw material, a foamed molded article excellent in impact resistance and heat dimensional stability can be obtained therefrom. The expandable composite resin particle means a composite resin particle exhibiting heat foamability, which is obtained by impregnating a composite resin particle with a foaming agent.

Specifically, the foaming agent content in the expandable composite resin particles is preferably 5 to 15 parts by mass, more preferably 8 to 10 parts by mass with respect to 100 parts by mass of the composite resin particles as the resin component. . Specific numerical values of the foaming agent content in the expandable composite resin particles are 5, 6, 7, 8, 9, 10, 11, 12, 13, with respect to 100 parts by mass of the composite resin particles as the resin component. 14, 15 parts by mass and the like.

When the foaming agent is lower than 5 parts by mass, the amount of the foaming agent is insufficient, and the foamable composite resin particles may not have sufficient foamability. On the other hand, when the amount of the foaming agent is more than 15 parts by mass, the amount of the foaming agent is excessive, and in this case as well, the foamable composite resin particles may not have sufficient foamability.

As the foaming agent, a known foaming agent having volatility can be used. For example, propane, n-butane (normal butane), i-butane (isobutane), n-pentane (normal pentane), i-isopentane (isopentane), n-hexane (normal hexane) and i-hexane (isohexane) alone Or a mixture thereof. Among these, any of n-butane, i-butane, n-pentane and i-pentane, which can introduce greater foaming performance into the foamable composite resin particles, is preferable. A foaming agent may be used independently and may use 2 or more types.

The expandable composite resin particles preferably have an average particle diameter of 0.71 to 2.5 mm, more preferably 0.85 to 1.6 mm. Specific numerical values of the average particle diameter of the expandable composite resin particles are 0.71, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.1, 1. 2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5mm etc. are mentioned. The shape is preferably spherical to substantially spherical.

<Pre-expanded particles>
Since the pre-expanded particles of the present invention also use the composite resin particles as a raw material, a foamed molded article excellent in impact resistance and heat dimensional stability can be obtained therefrom. The pre-expanded particles mean resin particles obtained by heating and foaming the expandable composite resin particles as described above to a predetermined bulk density.

The pre-expanded particles preferably have a bulk density of 0.020 to 0.10 g / cm ³ , more preferably 0.025 to 0.10 g / cm ³ . As specific numerical values of the bulk density of the pre-expanded particles, 0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.028, 0.030, 0 0.040, 0.050, 0.060, 0.070, 0.080, 0.090, 0.095, 0.098, 0.099, 0.10 g / cm ^{3 and the} like.

When the bulk density is lower than 0.020 g / cm ³ , the strength and heat resistance of the obtained foamed molded product may be lowered. On the other hand, when it is higher than 0.10 g / cm ³ , the weight of the obtained foamed molded product may increase.

The pre-expanded particles preferably have an average particle diameter of 1.0 to 9.0 mm, more preferably 2.0 to 6.4 mm. Specific numerical values of the average particle diameter of the pre-expanded particles are 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.2, 6.4, 6.6, 6.8, 7. 0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, 9.0 mm and the like. Similarly, the shape is preferably spherical to approximately spherical.

<Foamed molded product>
Since the foamed molded article of the present invention also uses the composite resin particles as described above, it is excellent in impact resistance and heat dimensional stability. The foamed molded product means a resin molded product obtained by thermally fusing the pre-expanded particles as described above.

Since the foamed molded article can have more excellent heat resistance and impact resistance, it preferably has a density of 0.020 to 0.10 g / cm ³ , more preferably 0.025 to 0.10 g / cm ³ . Have. Specific numerical values of the density of the foam molded article are 0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.028, 0.030, 0.0. 040, 0.050, 0.060, 0.070, 0.080, 0.090, 0.095, 0.096, 0.097, 0.098, 0.099, 0.10 g / cm ³ etc. Can be mentioned.

On the other hand, when the density is lower than 0.020 g / cm ³ , the strength and heat resistance of the obtained foamed molded product may be lowered. On the other hand, when it is higher than 0.10 g / cm ³ , the weight of the obtained foamed molded product may increase.

The foamed molded product of the present invention preferably exhibits an absorbed energy of 1.2 to 3.0 J, more preferably 1.3 to 3.0 J, in the impact test of ASTM D3763-92. Specific numerical values of the absorbed energy exhibited by the foam molded article are 1.2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.3, 2.5, 2.6, 2.7, 2.8, 2.9, and 3.0J.

Further, the foamed molded article exhibits a heating dimensional change rate of preferably 1.0% or less, more preferably 0.8% or less, in a heating dimensional change test of JIS K6767: 1999. As specific numerical values of the heating dimensional change rate exhibited by the foam molded article, 0.00%, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60% 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0.74% 0.75% 0.76% 0.77% 0.78% 0.79% 0.80% 0.81% 0.82% 0.83% 0.84% 0.85%, 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.94% 0.95%, 0.96%, 0.97%, 0.98%, 0.99%, 1.00%, and the like. Here, when the heating dimensional change rate is 1.0% or less, it means that the heating dimensional change rate is in the range of -1.0% to + 1.0%.

These measurement results indicate that the foamed molded product of the present invention has superior impact resistance and heat dimensional stability compared to conventional ones.

<Production method of composite resin particles, expandable resin particles, pre-expanded particles, and foamed molded article>
First, the composite resin particles can be produced, for example, as follows. That is, 100 parts by mass of polyolefin resin particles, 100 to 400 parts by mass of a styrene monomer, and a polymerization initiator are dispersed in an aqueous suspension. In addition, you may mix and use a styrene-type monomer and a polymerization initiator previously.

The polyolefin resin particles can be obtained by a known method. For example, a polyolefin resin is melt-kneaded in an extruder together with an inorganic nucleating agent and additives as necessary to obtain a strand, and the obtained strand is cut in air, cut in water, The method of granulating by cutting while heating is mentioned.

Examples of the inorganic nucleating agent include talc, silicon dioxide, mica, clay, zeolite, calcium carbonate and the like. The amount of the inorganic nucleating agent used is preferably 2 parts by mass or less, more preferably 0.2 to 1.5 parts by mass with respect to 100 parts by mass of the polyethylene resin. Specific values for the amount of the inorganic nucleating agent used are 0.2, 0.5, 1.0, 1.3, 1.5, 1.7, 1.8 with respect to 100 parts by mass of the polyethylene resin. 1.9, 2 mass parts, etc. are mentioned. Examples of the aqueous medium constituting the aqueous suspension include water and a mixed medium of water and a water-soluble solvent (for example, lower alcohol).

As the polymerization initiator, those generally used as an initiator for suspension polymerization of a styrene monomer can be used. For example, benzoyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxy- Organic peroxides such as 3,5,5-trimethylhexanoate and t-butyl-peroxy-2-ethylhexyl carbonate. These polymerization initiators may be used alone or in combination of two or more.

The amount of the polymerization initiator used is preferably 0.1 to 0.9 parts by mass and more preferably 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the styrene monomer. Specific values of the amount of the polymerization initiator used are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0 with respect to 100 parts by mass of the styrene monomer. 0.7, 0.8, 0.9 parts by mass and the like. If it is less than 0.1 part by mass, it may take too much time to polymerize the styrene monomer. If the polymerization initiator exceeds 0.9 parts by mass, the molecular weight of the styrene resin may be lowered.

A dispersant may be added to the aqueous suspension as necessary. The dispersant is not particularly limited, and any known dispersant can be used. Specific examples include hardly soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, magnesium oxide. Further, a surfactant such as sodium dodecylbenzenesulfonate may be used.

Next, the obtained dispersion is heated to a temperature at which the styrene monomer is not substantially polymerized to impregnate the polyolefin resin particles with the styrene monomer. A suitable time for impregnating the polyolefin resin particles with the styrene monomer is 30 minutes to 2 hours. Specific values for the impregnation time of the styrene monomer include 30 minutes, 45 minutes, 1 hour, 1 hour 15 minutes, 1 hour 30 minutes, 1 hour 45 minutes, 2 hours, and the like. If the polymerization proceeds before being sufficiently impregnated, a polymer powder of a styrene resin may be produced. The temperature at which the monomer is not substantially polymerized is advantageous in that the higher the temperature, the higher the impregnation rate. However, it is necessary to determine the temperature considering the decomposition temperature of the polymerization initiator.

Next, styrene monomer is polymerized. The polymerization is not particularly limited, but is preferably performed at 115 to 140 ° C. for 1.5 to 5 hours. Specific values of the polymerization temperature include 115, 120, 125, 130, 135, 140 ° C., and the like. Specific values for the polymerization time include 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 hours, and the like. The polymerization is usually carried out in an airtight container that can be pressurized. The impregnation and polymerization of the styrene monomer may be performed in a plurality of times. By dividing into multiple times, the generation of polystyrene polymer powder can be minimized. In consideration of the decomposition temperature of the polymerization initiator, the polymerization may be carried out while impregnating the styrene monomer with the polyolefin resin particles instead of impregnating the styrene monomer. Composite resin particles can be obtained by the above process.

Next, the expandable resin particles can be obtained by impregnating the composite resin particles during or after the polymerization with a foaming agent. This impregnation can be performed by a method known per se. For example, the impregnation during the polymerization can be performed by performing the polymerization reaction in a sealed container and press-fitting a foaming agent into the container. The impregnation after the completion of the polymerization is performed by press-fitting a foaming agent in a sealed container.

Furthermore, the pre-expanded particles can be obtained by pre-expanding the expandable resin particles to a predetermined bulk density by a known method.

Since the expandable composite resin particles of the present invention are excellent in heat resistance, the pre-expanded particle manufacturing method preferably uses heated steam of 0.05 to 0.15 MPa, more preferably 0.06 to 0.10 MPa. A step of pre-foaming the expandable composite resin particles. Specific numerical values of the pressure of the heating steam at the time of preliminary foaming are 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13. 0.14, 0.15 MPa, and the like. In this case, it is possible to reduce manufacturing cost and manufacturing time by using higher-pressure heating steam.

Further, the foamed molded product can be obtained by filling the pre-foamed particles in a mold of a foam molding machine and heat-sealing the foamed particles while foaming the pre-foamed particles by heating again. Water vapor can be suitably used as the heating medium.

Other manufacturing conditions such as process temperature, process pressure, and process time in each manufacturing process are appropriately set according to manufacturing equipment, raw materials, and the like to be used.

The foamed molded product of the present invention has excellent impact resistance and heat dimensional stability. For this reason, the foam molded article is suitably used in applications that require excellent impact resistance and heat dimensional stability, such as parts packaging materials, automobile members, cushioning materials, or bumper core materials, particularly bumper core materials. be able to.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Number average molecular weight (Mn), weight average molecular weight (Mw) and dispersity (Mw / Mn))
The gel permeation chromatography (GPC) apparatus used for the measurement is HLC-8121GPC / HT manufactured by Tosoh Corporation, TSKgel GMHhr-H (20) HT manufactured by Tosoh Corporation is used as the column, and the column temperature is set to 140 ° C. Set and use 1,2,4-trichlorobenzene as eluent. The measurement sample is adjusted to a concentration of 1.0 mg / mL, and the amount injected into the GPC device is 0.3 mL. The calibration curve for each molecular weight is calibrated using a polyethylene sample or polypropylene sample with a known molecular weight. Mn and Mw are determined as polystyrene equivalent values. Moreover, dispersity (Mw / Mn) is measured using the obtained Mn and Mw.

(Resin density)
The density of the resin is measured by a density gradient tube method in accordance with JIS K6922-1: 1998.

(Polyethylene resin melt flow rate (MFR))
MFR is measured according to JIS K7210-1: 1999 under a load of 190 ° C. and 2.16 kg.
(Melt flow rate (MFR) of polypropylene resin)
The MFR is measured under a load of 2.16 kg at 230 ° C. in accordance with JIS K7210-1: 1999.

(Vicat softening point of polyolefin resin (Vicat softening temperature))
Measured by the method described in JIS K7206: 1999 "Plastics-Thermoplastics-Vicat softening temperature test method".

(Vicat softening point of composite resin particles)
Measured by the method described in JIS K7196: 1991 "Method for testing softening temperature by thermomechanical analysis of thermoplastic film and sheet". That is, after the resin particles are hot-pressed and crushed to a thickness of 2 mm, a flat rectangular film-shaped test piece having a length of 10 mm × width of 20 mm × thickness of 2 mm is produced, and a heat / stress / strain measuring device (manufactured by Seiko Instruments Inc.) , Product name “TMA / SS6200”), needle test mode (needle tip area 1 mm ² ), load 50 g, the needle is applied to the film-like test piece, and the temperature is increased at a rate of temperature increase of 5 ° C./min. Then, the temperature at which the distortion of the film-like test piece occurs is defined as the Vicat softening point of the resin particles.

(Bulk density of pre-expanded particles)
The bulk density of the pre-expanded particles is measured as follows. First, pre-expanded particles are filled in a measuring cylinder to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one pre-foamed particle reaches the scale of 500 cm ³ , the filling is finished. Next, the weight of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the weight is defined as W (g). The bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (g / cm ³ ) = W / 500

(Density of foam molding)
The weight (a) and volume (b) of a test piece (example 150 × 150 × 30 mm) cut out from a foamed molded product (after being molded and dried at 50 ° C. for 4 hours or more) each have three or more significant figures. Then, the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b).

(Heat dimensional stability of foamed molded products)
Measured by the method B described in JIS K6767: 1999 “Foamed Plastics—Polyethylene—Test Method”. The test piece is 150 mm × 150 mm × 30 mm (thickness), and three straight lines are written in the center in parallel to each other in the vertical and horizontal directions at intervals of 50 mm, and a hot air circulating dryer at 90 ° C. After 24 hours, the sample is taken out and left in a standard state for 1 hour, and then the vertical and horizontal line dimensions are measured by the following formula.
S = (L1-L0) / L0 × 100
In the formula, S represents a heating dimensional change rate (%), L1 represents an average dimension (mm) after heating, and L0 represents an initial average dimension (mm).

About heating dimensional stability
(1) When the heating dimensional change rate is 1% or less: ○
(2) When heating dimensional change rate is greater than 1%: ×
Is determined.

(Impact resistance of foamed molded product (Dyna tap impact test (ASTM D3763-92)))
The impact resistance of the foamed molded product is measured according to ASTM D3763-92.
Test device: Dynatap impact test device GRC 8250 (manufactured by General Research Corp)
Test piece: 100 × 100 × 20 T (mm)
Span: round hole inner diameter 76mm
Test speed: 4.05 m / min Test temperature: 23 ° C.
Drop height: 59cm
Drop weight distance: 16cm
Test load 3.17kg
Number of tests: 5

About impact resistance
(1) When absorbed energy is 1.2 to 3.0 J: ○
(2) When absorbed energy is less than 1.2 J: ×
Is determined.

Example 1
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 (mass ratio) Polyethylene resin (manufactured by Prime Polymer, product name “SP4020”, density: 0.937 / cm ³ , Vicat softening point: 117 ° C., melt flow rate: 1.8 g / 10 minutes) 100 parts by mass is supplied to an extruder, melted and kneaded, granulated by an underwater cutting method, and an oval (egg-like) polyethylene system Resin particles were obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 12 kg of the polyethylene resin particles in a dispersion medium. Further, 11.4 g of t-butyl peroxybenzoate as a polymerization initiator was dissolved in 6 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Subsequently, the temperature of the reaction system was lowered to 115 ° C., and a second styrene monomer in which 41.8 g of t-butyl peroxybenzoate was dissolved in 22 kg of styrene monomer as a polymerization initiator was added 4 per hour. By continuously dropping at a rate of 0.6 kg, polymerization (second polymerization) was performed while impregnating the polyethylene resin particles with the second styrene monomer. After completion of the dropping, the mixture was held at 115 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (product name “PSX40” manufactured by Kasahara Kogyo Co., Ltd.) and pre-foamed using steam at a pressure of 0.05 MPa to obtain a bulk density of 0.033 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam having a pressure of 0.18 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape of 400 mm long × 300 mm wide × 30 mm high and having a density of 0.033 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Example 2)
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 Polyethylene resin (manufactured by Prime Polymer, product name “SP4020”, density: 0.937 g / cm ³ , Vicat softening point 117 ° C., melt flow rate: 1.8 g / 10 min) 100 parts by mass, 40% by mass carbon black masterbatch (28E-40 manufactured by DOW, base resin LDPE (low density polyethylene resin)) 7.7 Mass parts were supplied to an extruder, melted and kneaded, and granulated by an underwater cutting method to obtain elliptical (egg-like) polyethylene resin particles. The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 12 kg of the carbon-containing polyethylene resin particles in a dispersion medium. Further, 12.0 g of dicumyl peroxide as a polymerization initiator was dissolved in 6 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Next, the temperature of the reaction system was lowered to 125 ° C., and a second styrene monomer obtained by dissolving 100.8 g of dicumyl peroxide as a polymerization initiator in 22 kg of styrene monomer was 4.6 kg per hour. The second styrene monomer was impregnated into the polyethylene resin particles to cause polymerization (second polymerization). After the completion of the dropping, the mixture was held at 125 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization to obtain composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., product name “PSX40”) and pre-foamed using steam at a pressure of 0.05 MPa to obtain a bulk density of 0.033 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam having a pressure of 0.18 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape of 400 mm long × 300 mm wide × 30 mm high and having a density of 0.033 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Example 3)
Polyethylene resin (Ube) instead of polyethylene resin (manufactured by Prime Polymer, product name “SP4020”, density: 0.937 g / cm ³ , Vicat softening point: 117 ° C., melt flow rate: 1.8 g / 10 min) Manufactured by Maruzen Polyethylene Co., Ltd., product name “3540FC”, density: 0.931 g / cm ³ , Vicat softening point: 114 ° C., melt flow rate: 3.6 g / 10 min) The others were the same as in Example 1.

(Example 4)
Polyethylene resin (Ube) instead of polyethylene resin (manufactured by Prime Polymer, product name “SP4020”, density: 0.937 g / cm ³ , Vicat softening point: 117 ° C., melt flow rate: 1.8 g / 10 min) (Made by Maruzen Polyethylene Co., Ltd., product name “4040FC”, density: 0.938 g / cm ³ , Vicat softening point: 120 ° C., melt flow rate: 3.5 g / 10 min) The others were the same as in Example 1.

(Example 5)
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 4/6 Polyethylene resin (manufactured by Prime Polymer, product name “SP4020”, density: 0.937 g / cm ³ , Vicat softening point : 117 ° C., melt flow rate: 1.8 g / 10 min) 100 parts by mass is supplied to an extruder, melted and kneaded, and granulated by an underwater cutting method to obtain oval (egg-like) polyethylene resin particles. It was. The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 16 kg of the polyethylene resin particles in a dispersion medium. Further, 15.2 g of t-butyl peroxybenzoate as a polymerization initiator was dissolved in 8 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Next, the temperature of the reaction system was lowered to 115 ° C., and a second styrene monomer obtained by dissolving 33.6 g of t-butyl peroxybenzoate as a polymerization initiator in 16 kg of styrene monomer was 4 per hour. By continuously dropping at a rate of 0.6 kg, polymerization (second polymerization) was performed while impregnating the polyethylene resin particles with the second styrene monomer. After completion of the dropping, the mixture was held at 115 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (product name “PSX40” manufactured by Kasahara Kogyo Co., Ltd.) and pre-foamed using steam at a pressure of 0.05 MPa to obtain a bulk density of 0.033 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam with a pressure of 0.18 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape with a length of 400 mm × width of 300 mm × height of 30 mm and a density of 0.033 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Example 6)
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 Polyethylene resin (manufactured by Ube Maruzen Polyethylene Co., Ltd., product name “4540F”, density: 0.944 g / cm ³ , Vicat softening (Point: 123 ° C., Melt flow rate: 4.0 g / 10 min) 100 parts by mass are supplied to an extruder, melt-kneaded, granulated by an underwater cutting method to obtain oval (egg-like) polyethylene resin particles. Obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 12 kg of the polyethylene resin particles in a dispersion medium. Further, 11.4 g of t-butyl peroxybenzoate as a polymerization initiator was dissolved in 6 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Subsequently, the temperature of the reaction system was lowered to 115 ° C., and a second styrene monomer in which 41.8 g of t-butyl peroxybenzoate was dissolved in 22 kg of styrene monomer as a polymerization initiator was added 4 per hour. By continuously dropping at a rate of 0.6 kg, polymerization (second polymerization) was performed while impregnating the polyethylene resin particles with the second styrene monomer. After completion of the dropping, the mixture was held at 115 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (product name “PSX40” manufactured by Kasahara Kogyo Co., Ltd.) and pre-foamed using steam at a pressure of 0.10 MPa to obtain a bulk density of 0.025 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam having a pressure of 0.23 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape of length 400 mm × width 300 mm × height 30 mm and a density of 0.025 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Example 7)
Production of Composite Resin Particles of Polypropylene Resin (PP) / Polystyrene Resin (PS) = 4/6 As a polypropylene resin, product name “RFG4VA” manufactured by Nippon Polypro Co., Ltd. (melting point: 135 ° C., density: 0.900 g / cm ³ , melt flow rate: 6.0 g / 10 min, Vicat softening point: 115 ° C.) 100 parts by mass is supplied to an extruder, melted and kneaded, and granulated by an underwater cut method to form an oval (egg-like) shape. Polypropylene resin particles (polyolefin resin particles) were obtained. The average weight of the polypropylene resin particles at this time was 0.8 mg.

Next, 400 g of magnesium pyrophosphate and 10 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water in a 100 L autoclave equipped with a stirrer to obtain a dispersion medium. A suspension was obtained by dispersing 16 kg of the polypropylene resin particles in a dispersion medium. Further, 16 g of dicumyl peroxide as a polymerization initiator was dissolved in 8.0 kg of a styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polypropylene system is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour, so that the first styrene monomer is contained in the polypropylene resin particles. The body was impregnated. Next, the temperature of the reaction system was raised to 140 ° C., the same as the melting point of the polypropylene resin, and maintained for 2 hours, and the styrene monomer was polymerized (first polymerization) in the polypropylene resin particles.

Next, the temperature of the reaction system was lowered to 125 ° C., and a second styrene monomer in which 72 g of dicumyl peroxide was dissolved in 16 kg of styrene monomer as a polymerization initiator was continuously added at a rate of 4 kg per hour. Then, the second resin was polymerized (second polymerization) while impregnating the polypropylene resin particles with the second styrene monomer. After completion of the dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 143 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., product name “PSX40”) and pre-foamed using steam at a pressure of 0.05 MPa to obtain a bulk density of 0.025 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam with a pressure of 0.18 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape of length 400 mm × width 300 mm × height 30 mm and a density of 0.025 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Comparative Example 1)
Manufacture of Composite Resin Particles of Polypropylene Resin (PP) / Polystyrene Resin (PS) = 4/6 As a polypropylene resin, product name “F-744NP” (melting point: 140 ° C., density: 0. 900 g / cm ³ , melt flow rate: 7.0 g / 10 min, Vicat softening point: 117 ° C. 100 parts by mass are supplied to an extruder, melt-kneaded, granulated by an underwater cut method, and oval (egg-like) ) Polypropylene resin particles (polyolefin resin particles). The average weight of the polypropylene resin particles at this time was 0.8 mg.

Next, 400 g of magnesium pyrophosphate and 10 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water in a 100 L autoclave equipped with a stirrer to obtain a dispersion medium. A suspension was obtained by dispersing 16 kg of the polypropylene resin particles in a dispersion medium. Further, 16 g of dicumyl peroxide as a polymerization initiator was dissolved in 8.0 kg of a styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polypropylene system is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour, so that the first styrene monomer is contained in the polypropylene resin particles. The body was impregnated. Next, the temperature of the reaction system was raised to 140 ° C., the same as the melting point of the polypropylene resin, and maintained for 2 hours, and the styrene monomer was polymerized (first polymerization) in the polypropylene resin particles.

Subsequently, the temperature of the reaction system was lowered to 120 ° C., and a second styrene monomer in which 72 g of dicumyl peroxide was dissolved in 16 kg of styrene monomer as a polymerization initiator was continuously added at a rate of 4 kg per hour. Then, the second resin was polymerized (second polymerization) while impregnating the polypropylene resin particles with the second styrene monomer. After completion of the dropping, the mixture was held at 120 ° C. for 1 hour, then heated to 143 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were charged into a 5 L autoclave with a stirrer, and 16 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (product name “PSX40” manufactured by Kasahara Kogyo Co., Ltd.) and pre-foamed using steam at a pressure of 0.1 MPa to obtain a bulk density of 0.033 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, steam with a pressure of 0.25 MPa was supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape with a length of 400 mm × width of 300 mm × height of 30 mm and a density of 0.033 g / cm ³ A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Comparative Example 2)
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 Polyethylene resin (manufactured by Nippon Polyethylene Co., Ltd., product name “NF464A”, density: 0.918 g / cm ³ , Vicat softening point : 98 ° C., melt flow rate: 2.0 g / 10 min) 100 parts by mass is supplied to an extruder, melted and kneaded, and granulated by an underwater cutting method to obtain oval (egg-like) polyethylene resin particles. It was. The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 12 kg of the polyethylene resin particles in a dispersion medium. Further, 11.4 g of t-butyl peroxybenzoate as a polymerization initiator was dissolved in 6 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Subsequently, the temperature of the reaction system was lowered to 115 ° C., and a second styrene monomer in which 41.8 g of t-butyl peroxybenzoate was dissolved in 22 kg of styrene monomer as a polymerization initiator was added 4 per hour. By continuously dropping at a rate of 0.6 kg, polymerization (second polymerization) was performed while impregnating the polyethylene resin particles with the second styrene monomer.
After completion of the dropping, the mixture was held at 115 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., product name “PSX40”), pre-foamed using water vapor at a pressure of 0.03 MPa, and a bulk density of 0.025 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, water vapor at a pressure of 0.10 MPa was supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and a bumper having a rectangular parallelepiped shape of length 400 mm × width 300 mm × height 30 mm and a density of 0.025 g / cm ³ . A core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

(Comparative Example 3)
Production of composite resin particles of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 Polyethylene resin (manufactured by Tosoh Corporation, product name “09S53B”, density: 0.936 g / cm ³ , Vicat softening point: 117 ° C., melt flow rate: 2.0 g / 10 min) 100 parts by mass were supplied to an extruder, melted and kneaded, and granulated by an underwater cutting method to obtain oval (egg-like) polyethylene resin particles. . The average weight of the polyethylene resin particles was 0.6 mg.

Next, in a 100 L autoclave with a stirrer, 128 g of magnesium pyrophosphate and 32 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. A suspension was obtained by dispersing 12 kg of the polyethylene resin particles in a dispersion medium. Further, 11.4 g of t-butyl peroxybenzoate as a polymerization initiator was dissolved in 6 kg of styrene monomer to prepare a first styrene monomer. The temperature of the suspension containing the polyethylene resin particles is adjusted to 60 ° C., and the styrene monomer is added in a fixed amount over 30 minutes, and then stirred for 1 hour so that the first styrene is contained in the polyethylene resin particles. The monomer was impregnated. Next, the temperature of the reaction system was raised to 135 ° C. and held for 3 hours, and the styrene monomer was polymerized (first polymerization) in the polyethylene resin particles.

Subsequently, the temperature of the reaction system was lowered to 115 ° C., and a second styrene monomer in which 41.8 g of t-butyl peroxybenzoate was dissolved in 22 kg of styrene monomer as a polymerization initiator was added 4 per hour. By continuously dropping at a rate of 0.6 kg, polymerization (second polymerization) was performed while impregnating the polyethylene resin particles with the second styrene monomer.
After completion of the dropping, the mixture was held at 115 ° C. for 1 hour, then heated to 140 ° C. and held for 3 hours to complete the polymerization, thereby obtaining composite resin particles.

Subsequently, 2 kg of composite resin particles and 2 L of water were put into a 5 L autoclave with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (mass ratio)) was injected as a blowing agent at room temperature. After the injection, the temperature was raised to 70 ° C. and stirring was continued for 2 hours. Thereafter, the mixture was cooled to room temperature, taken out from the 5 L autoclave, dehydrated and dried to obtain expandable composite resin particles.

The obtained expandable composite resin particles were immediately supplied to a pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., product name “PSX40”), pre-foamed using water vapor at a pressure of 0.03 MPa, and a bulk density of 0.025 g / cm. ^Three pre-expanded particles were obtained.

Next, the pre-expanded particles were allowed to stand at room temperature for 1 day and then filled into a mold of a molding machine. Then, water vapor with a pressure of 0.10 MPa is supplied into the mold for 30 seconds to foam-mold the pre-expanded particles, and the density of the rectangular parallelepiped shape having a length of 400 mm × width of 300 mm × height of 30 mm is 0.025 g / cm ^3.
Bumper core material was manufactured. Both the fusion rate and appearance of the obtained bumper core material were good.

In Table 1, the raw material seed | species and evaluation result of an Example and a comparative example are explained in full detail.
In Table 1, PE represents a polyethylene resin, PS represents a polystyrene resin, and PP represents a polypropylene resin.

Table 1 shows that the foamed molded product of the present invention is excellent in impact resistance and heat dimensional stability. Therefore, the foamed molded article of the present invention can be suitably used as a component packing material, an automobile member, a cushioning material, or a bumper core material, particularly as a bumper core material.

Claims (13)

1. As a resin component, 100 parts by mass of a polyolefin resin and 100 to 400 parts by mass of a polystyrene resin, and the polyolefin resin has a Vicat softening point of 110 to 125 ° C. and a dispersity of 1.5 to 4.8 particle.
2. The composite resin particles according to claim 1, wherein the composite resin particles include 100 parts by mass of a polyolefin resin and 100 to 300 parts by mass of a polystyrene resin as resin components.
3. The composite resin particles according to claim 1, wherein the composite resin particles have a dispersity of 2.0 to 4.5.
4. The composite resin particle according to claim 1, wherein the polyolefin resin is a polyethylene resin or a polypropylene resin.
5. The composite resin particle according to claim 1, wherein the composite resin particle has a Vicat softening point of 110 to 130 ° C.
6. The composite resin particle according to claim 1, wherein the composite resin particle contains 0.5 to 3.0 parts by mass of carbon black with respect to 100 parts by mass of the resin component.
7. Expandable composite resin particles obtained from the composite resin particles according to claim 1.
8. Pre-expanded particles obtained from the expandable composite resin particles according to claim 7.
9. A foam-molded article obtained from the pre-expanded particles according to claim 8.
10. The foam molded article according to claim 9, wherein the foam molded article has a density of 0.020 to 0.10 g / cm ³ .
11. The foamed molded product according to claim 9, wherein the foamed molded product exhibits an absorbed energy of 1.2 to 3.0 J in an impact test of ASTM D3763-92.
12. The foamed molded product according to claim 9, wherein the foamed molded product exhibits a heating dimensional change rate of 1.0% or less in a heating dimensional change test of JIS K6767: 1999.
13. A bumper core material obtained from the foamed molded article according to claim 9.