DE112013001815T5 - Composite resin particles, foamable composite resin particles, pre-expanded particles, molded foam parts and core material for bumpers - Google Patents

Abstract

Composite resin particles comprising as resin components 100 parts by weight of polyolefin resin and 100-400 parts by weight of polystyrene resin, said polyolefin resin having a Vicat softening point of 110-125 ° C and a degree of dispersion of 1.5-4.8.

Description

Technological area

The present invention relates to composite resin particles, foamable composite resin particles, pre-expanded particles, molded foam parts and core material for bumpers. More specifically, the present invention relates to composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained, as well as foamable composite resin particles, pre-expanded particles, molded foam pieces, and core material for bumpers obtainable from the aforementioned composite resin particles.

State of the art

To date, foamable composite resin particles containing polystyrene resin as a resin component are widely used as a cushioning material for packaging, automotive components, building materials, etc. because of their excellent material properties such as moldability, insulating properties, impact resistance and damping properties.

Especially when used for components of automobiles, a higher impact resistance is particularly required in the molded foam parts. Shaped foam parts that fulfill such properties are described in Patent Literatures 1, 2 and 3. These contain as resin components polystyrene resin and polyolefin resin.

Documents on the state of the art

patent literature

• Patent Literature 1: JP 2010-024353
• Patent Literature 2: JP 2011-208067
• Patent Literature 3: WO 2006/027944

Description of the invention

Problems to be solved by the invention

Nowadays, from the viewpoint of protecting pedestrians in accidents on automobile moldings such as bumper core materials, an improvement in energy absorption, that is, higher impact resistance, is required.

On the other hand, automobiles are equipped with a pedestrian recognition function from the same viewpoint. For this reason, in addition to the above-mentioned properties, in the molded foam pieces for preventing disturbance of the recognition function, etc., high dimensional stability at high temperatures, that is, excellent thermoforming stability, is required.

However, although the molded foam pieces described in Patent Literature 1 to 3 have some effect, it has not always been satisfactory from such viewpoints. The present invention has been accomplished in view of these problems, and its object is to provide composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained, and foamable composite resin particles, pre-expanded particles, molded foam pieces and core material for bumpers obtainable from the aforementioned composite resin particles ,

Means of solving the problems

The inventors of this application have found, as a result of their extensive investigations, that molded foam particles excellent in impact resistance and thermoforming stability can be obtained from composite resin particles containing as resin components polyolefin resin having a Vicat softening point and a degree of dispersion in a certain range, and polystyrene resin; to achieve the present invention.

Thus, according to the present invention, composite resin particles containing as resin components 100 parts by weight of polyolefin resin and 100-400 parts by weight of polystyrene resin, said polyolefin resin having a Vicat softening point of 110-125 ° C and a degree of dispersion of 1.5-4.8 Provided.

Further, according to the present invention, there are provided foamable composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained.

Further, according to the present invention, prefoamed particles are provided from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained.

Further, according to the present invention, molded foam pieces excellent in impact resistance and thermoforming stability are provided.

Further, according to the present invention, bumper core material having excellent impact resistance and thermoforming stability is provided.

Advantageous Effects of the Invention

According to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained are provided. More specifically, composite resin particles from which molded foam pieces having excellent energy absorption and thermoforming stability at high temperatures can be obtained can be provided.

Further, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be obtained when the composite resin particles contain, as resin components, 100 parts by weight of polyolefin resin and 100-300 parts by weight of polystyrene resin.

Further, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be obtained when the composite resin particles have a degree of dispersion of 2.0-4.5.

Further, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be obtained when the polyolefin resin is a polyethylene resin or a polypropylene resin.

Further, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be obtained when the composite resin particles have a Vicat softening point of 110-130 ° C.

Further, when the composite resin particles contain 0.5 to 3.0 parts by weight of carbon black per 100 parts by weight of the resinous component, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability and excellent in design properties can be obtained can be obtained Composite resin particles contain carbon black as a suitable amount of dye.

According to the present invention, from the composite resin particles described above, foamable composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be provided.

According to the present invention, prefoamed particles of the foamable composite resin particles described above can be provided, from which molded foam pieces having excellent impact resistance and thermoforming stability can be obtained.

According to the present invention, molded foam pieces excellent in impact resistance and thermoforming stability can be provided from the above-described pre-expanded particles.

Further, according to the present invention, molded foam pieces excellent in impact resistance and thermoforming stability can be provided when the molded foam pieces have a density of 0.020-0.10 g / cm ³ .

Further, according to the present invention, molded foam pieces excellent in impact resistance and thermoforming stability can be provided which exhibit an absorption energy of 1.2-3.0 J in the impact test according to ASTM D3763-92.

Further, according to the present invention, there can be provided molded foam pieces excellent in impact resistance and thermoforming stability, which exhibit a thermal strain rate of 1.0% or less in the thermal strain test of JIS K6767: 1999.

According to the present invention, core material for bumpers having excellent impact resistance and thermoforming stability can be provided from the molded foam members described above.

Embodiment of the invention

The present invention relates to composite resin particles containing as resin components 100 parts by weight of polyolefin resin and 100-400 parts by weight of polystyrene resin, said polyolefin resin having a Vicat softening point of 110-125 ° C and a degree of dispersion of 1.5-4.8.

More specifically, the composite resin particles of the present invention contain polyolefin resin and polystyrene resin in an appropriate ratio. Thereby, the composite resin particles can combine the properties of the polyolefin resin such as strength, heat insulating properties, light weight, water resistance and foamability, and the properties of the polystyrene resin such as chemical resistance, heat resistance and impact resistance (impact absorption).

Further, the polyolefin resin has a Vicat softening point of 110-125 ° C and a degree of dispersion of 1.5-4.8. For this reason, by appropriately adjusting the polymer chain and the structure, the impact resistance and thermoforming stability of molded foam pieces obtained from polyolefin resin and polystyrene resin-containing composite resin particles can be improved. As a result, molded foam pieces obtained from such composite resin particles can be widely used as packing material for spare parts, automobile components, cushioning material and core material for bumpers. They are particularly suitable as core material for bumpers. Here, the degree of dispersion (Mw / Mn) means the value showing the degree of single dispersion of the chain length distribution obtained by using the number average molecular weight (Mn) and the weight average molecular weight (Mw).

Accordingly, according to the present invention, composite resin particles from which molded foam pieces excellent in impact resistance and thermoforming stability can be obtained can be provided. Hereinafter, the composite resin particles of the present invention will be described in detail.

<Composite resin particles>

Composite resin particles in the present invention mean resin particles composed of plural resin components. More specifically, they include resin particles in which polyolefin resin has been modified with polystyrene resin derived from styrene monomer. "Composite" means that polyolefin resin and polystyrene resin are present in the particles, "modified" means that polyolefin resin is impregnated with styrene monomer and polymerized.

The composite resin particles of the present invention contain polyolefin resin and polystyrene resin in an appropriate ratio. Specifically, the composite resin particles contain 100-400 parts by weight, preferably 100-300 parts by weight, more preferably 150-230 parts by weight of polystyrene resin per 100 parts by weight of the polyolefin resin. When the composite resin particles contain 100 parts by weight of polyolefin resin, the concrete numerical values of the content of polystyrene resin include 100, 130, 150, 180, 200, 230, 240, 250, 270, 300, 350, 400 parts by weight.

When less than 100 parts by weight of polystyrene resin is contained, the proportion of polystyrene resin in the composite resin particles becomes low, and the composite resin particles sometimes do not sufficiently obtain the properties resulting from the polystyrene resin. On the other hand, with more than 400 parts by weight of polystyrene resin, the proportion of polyolefin resin in the composite resin particles becomes low and it can occur that the composite resin particles are not sufficiently obtained from the polyolefin resin derived properties.

The Vicat softening point of the composite resin particles is preferably 110-130 ° C, more preferably 110-125 ° C. The Vicat softening point is one of parameters indicating the heat resistance of the resin. It is determined for composite resin particles according to JIS K7196: 1991 "Test method for determining the softening temperature of thermoplastic films and films by thermomechanical analysis". The concrete test method will be described below in the embodiments. On the other hand, when the composite resin particles do not contain other components, the Vicat softening point of the composite resin particles means the Vicat Concrete numerical values of the Vicat softening point of the composite resin particles are, for example, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126 , 127, 128, 129, 130 ° C.

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

The composite resin particles have an average particle size of preferably 0.71-2.5 mm, more preferably 0.85-1.6 mm. They are also preferably spherical or approximately spherical. Concrete numerical values of the average particle size are, for example, 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.

<Polyolefin>

Polyolefin resin means, without any particular limitation, a copolymer of monomeric olefin and another copolymerizable monomer, wherein the olefin homopolymer or the monomeric olefin is the main component. Here, monomeric olefin as a main component means that the monomeric olefin constitutes 50% by weight or more of the total amount of the monomer, preferably 60% by weight or more, more preferably 70% by weight or more. If the total monomer amount is taken as 100% by weight, concrete numerical values are the percentage occupied by the monomeric olefin, for example 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 100% by weight.

Concrete examples of polyolefin resins are α-olefin resins such as polyethylene resin, polypropylene resin and polybutylene resin. So that the desired properties can be achieved even more easily, it is preferable to use polyethylene resin, polypropylene resin and combinations thereof as the polyolefin resin.

The polyolefin resin of the present invention has a Vicat softening point of 110-125 ° C, preferably 112-125 ° C, more preferably 113-123 ° C. The Vicat softening point is one of parameters indicating the heat resistance of the resin. It is determined for polyolefin resin according to JIS K7206: 1999 "Plastics - Thermoplastic materials - Test method for determination of Vicat softening temperature". Concrete numerical values of the Vicat softening point of polyolefin resin are, for example, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125 ° C.

When the Vicat softening point of the polyolefin resin is lower than 110 ° C, the composite resin particles sometimes do not have sufficient heat resistance. On the other hand, when the Vicat softening point of the polyolefin resin is over 125 ° C, the foamable composite resin particles may not have sufficient foamability.

The weight-average molecular weight (Mw) of polyethylene resin is preferably 60 × 10 ³ -200 × 10 ³ , more preferably 70 × 10 ³ -190 × 10 ³ . Concrete numerical values of the weight average molecular weight of polyethylene resin are, for example, 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 .

When the weight average molecular weight is less than 60 × 10 ³ , the composite resin particles sometimes do not have sufficient heat resistance. On the other hand, it can happen that the foamable Composite resin particles do not have sufficient foamability, when the weight average molecular weight is above 200 × 10 ³ .

The number average molecular weight (Mn) of polyethylene resin is preferably 10 × 10 ³ -80 × 10 ³ , more preferably 15 × 10 ³ -80 × 10 ³ . Specific numerical values of the number-average molecular weight of polyethylene resin are, for example, 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 .

Also in this case, the composite resin particles sometimes do not have sufficient heat resistance when the number average molecular weight is below 10 × 10 ³ . On the other hand, it may happen that the foamable composite resin particles do not have sufficient foamability when the number average molecular weight is over 80 × 10 ³ .

The weight average molecular weight of polypropylene resin is preferably 200 × 10 ³ -400 × 10 ³ , more preferably 250 × 10 ³ -390 × 10 ³ . Concrete numerical values of the weight-average molecular weight of polypropylene resin are, for example, 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 × 103, 400 × 10 ³ .

When the weight average molecular weight is less than 200 × 10 ³ , the composite resin particles sometimes do not have sufficient heat resistance. On the other hand, when the weight average molecular weight is more than 400 × 10 ³ , the foamable composite resin particles may not have sufficient foamability.

The number average molecular weight (Mn) of polypropylene resin is preferably 70 × 10 ³ -160 × 10 ³ , more preferably 80 × 10 ³ -150 × 10 ³ . Specific numerical values of the number-average molecular weight of polypropylene resin are, for example, 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 × 103 ³ , 150 × 10 ³ , 155 × 10 ³ , 160 × 10 ³ .

Also in this case, the composite resin particles sometimes have insufficient heat resistance when the number average molecular weight is below 70 × 10 ³ . On the other hand, it may happen that the foamable composite resin particles do not have sufficient foamability when the number average molecular weight exceeds 160 × 10 ³ .

The polyolefin resin of the present invention has a degree of dispersion (Mw / Mn) of 1.5-4.8, preferably 2.0-4.5. Concrete numerical values of the degree of dispersion of polyolefin resin are, for example, 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.

If the degree of dispersion is below 1.5, the production cost may become a problem. On the other hand, the impact resistance of the molded foam pieces may decrease if the degree of dispersion is greater than 4.8.

When polyethylene resin is used as the polyolefin resin, the polyethylene resin preferably has a density of 0.927-0.950 kg / m ³ , more preferably 0.927-0.945 kg / m ³ , still more preferably 0.930-0.945 kg / m ³ . In this case, concrete numerical values for the density of the polyethylene resin are, for example, 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 .

When the density of the polyethylene resin is less than 0.927 kg / m ³ , the composite resin particles sometimes do not have sufficient thermoforming stability. On the other hand, it may happen that the resin components do not sufficiently soften in the polymerization process and that the foamable composite resin particles do not have sufficient foamability when the density of the polyethylene resin is over 0.950 kg / m ³ .

When the polyethylene resin of the present invention was measured at 190 ° C under a load of 2.16 kg, the polyolefin resin exhibits a melt flow rate of preferably 1.0-10.0 g / 10 min, more preferably 1.0-7.0 g / 10 min. In this case, concrete numerical values for the melt flow rate that the polyolefin resin may have 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.

Further, the polyolefin resin has a melt flow rate of preferably 1.0-10.0 g / 10 min, more preferably 2.0-9.0 g / 10 min, when the polypropylene resin of the present invention is heated at 230 ° C under a load of 2, 16 kg was measured. In this case, concrete numerical values for the melt flow rate, the the polyolefin resin may have, for example, 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 ..

When the melt flow rate of this polyolefin resin is less than 1.0 g / 10 min, sometimes the predetermined multiple of the foam is not obtained. On the other hand, even if the melt flow rate of these polyolefin resins is over 10.0 g / 10 min, it may happen that the predetermined multiple of the foam is not obtained.

Also, when the polyolefin resins in the composite resin particles have a Vicat softening point, a weight average molecular weight, number average molecular weight, a degree of dispersion, a density and a melt flow rate in this size, the Vicat softening point, the weight average molecular weight, number average molecular weight, the degree of dispersion , the density and melt flow rate of the polyolefin resins in the foamable composite resin particles, pre-expanded particles, molded foam pieces, and core material for bumpers obtained from the composite resin particles, respectively, are approximately equal.

<Production Method for the Polyolefin Resins>

Polyolefin resins such as polyethylene resin and polypropylene resin can be prepared by known methods. For an even easier production of polyethylene resin and polypropylene resin having the aforementioned properties, it is preferable to use polymerization methods using metallocene compounds as catalysts.

The metallocene compounds include known metallocene compounds. For example, metallocene compounds containing tetravalent transition metals are suitable.

<Polystyrene resin>

Composite resin particles contain polystyrene resin as a resin component. For this reason, composite resins can have the excellent properties of polystyrene resin such as strength, heat insulating properties, light weight, water resistance and foamability.

Polystyrene resin means a copolymer of monomeric styrene and another copolymerizable monomer, wherein the styrene homopolymer or the monomeric styrene is the main component. Monomeric styrene as the main component means that in 100 parts by weight of the total monomer components, 50 parts by weight or more of the monomeric styrene is contained, preferably 60% by weight or more, more preferably 70% by weight or more. If the total monomer amount is taken as 100% by weight, concrete numerical values are the percentage occupied by the monomeric styrene, for example 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100% by weight.

As the copolymer components contained in polystyrene resin, known monomers can be used unless they affect the desired properties. Concrete examples thereof include vinyl monomers such as cyclic olefin monomers, diene monomers, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, maleic anhydride and methyl styrene. Of these, 1 or 2 and more species can be used.

<Other components>

In order to obtain molded foam pieces distinguished by an even darker color design, the composite resin particles of the present invention preferably contain 0.5-3.0 parts by weight, more preferably 0.5-2.0 parts by weight, of carbon black per 100 parts by weight of the resin component. Concrete numerical values for the content of carbon black in the composite resin particles are, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 1.8, 2.0, 2, 2, 2.4, 2.6, 2.8 3.0.

When the contained amount by weight of carbon black is less than 0.5, the composite resin particles sometimes do not obtain sufficient color. On the other hand, it may happen that the composite resin particles have no impact resistance when the contained amount by weight of carbon black is above 3.0.

As the carbon black, known products can be used. Specifically, carbon-based materials such as furnace black, channel black, thermal black, acetylene black, graphite, and carbon fibers can be cited.

In the present invention, a mixture containing carbon black, the so-called masterbatch, may also be added. Per 100 parts by weight, the masterbatch contains the carbon black in a proportion of preferably 30-50 parts by weight, more preferably 35-45 parts by weight. In this case, concrete numerical values for the content of carbon black in the masterbatch per 100 parts by weight of masterbatch 30, 31, 32, 33, 34, 35, 37, 40, 43, 45, 46, 47, 48, 49 are 50. As the base resin the masterbatch preferably an olefinic resin.

If it is possible to obtain the desired composite resin particles and the below-mentioned foamable composite resin particles, pre-expanded particles and molded foam parts, they may contain other additives, etc. in a suitable manner. These include in particular foam control agents, coating agents, light stabilizers, UV absorbers, pigments, dyes, defoamers, heat stabilizers, lubricants and antistatic agents.

The amounts and proportions of the starting monomers, the raw resins and the other components and the amounts and proportions of the resin components in the composite resin particles, foamable composite resin particles, pre-expanded particles and molded foam parts and the other components are almost the same.

The determination of quality and quantity of the raw materials contained in the composite resin particles, foamable composite resin particles, pre-expanded particles and molded foam parts can be carried out using known methods such as nuclear magnetic resonance (NMR), infrared spectroscopy (IR), gel permeation chromatography (GPC) and so on.

<Foamable Composite Resin Particles>

Also, because the above-mentioned composite resin particles are used as the raw material for the foamable composite resin particles of the present invention, molded foam parts excellent in impact resistance and thermoforming stability can be obtained therefrom. Further, foamable composite resin particles means that the composite resin particles are saturated with blowing agents and that they are composite resin particles which exhibit foamability on heating.

More specifically, the content of the blowing agent in the foamable composite resin particles is preferably 5-15 parts by weight, more preferably 8-10 parts by weight per 100 parts by weight of the composite resin particles functioning as the resin component. Specific numerical values for the content of blowing agent in the foamable composite resin particles are, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts by weight per 100 parts by weight of the composite resin particles functioning as a resin component.

When the content of the blowing agent is less than 5 parts by weight, the amount of the blowing agent is insufficient, so that the foamable composite resin particles may not obtain sufficient foamability. On the other hand, if the content of the blowing agent is more than 15 parts by weight, the amount of blowing agent becomes too large, and also in this case, the foamable composite resin particles may not have sufficient foamability.

As blowing agents known volatile leavening agents can be used. They include propane, n-butane (normal butane), i-butane (isobutane), n-pentane (normal pentane), i-isopentane (isopentane), n-hexane (normal hexane) and i-hexane (isohexane) as a single compound or mixtures thereof. Of these, n-butane, i-butane, n-pentane, i-pentane are preferably used because they can be introduced into the foamable composite resin particles for greater foaming efficiency. These leavening agents may be used singly or 2 or more mixed.

The foamable composite resin particles have an average particle size of preferably 0.71-2.5 mm, more preferably 0.85-1.6 mm. Concrete numerical values for the average particle size of the foamable composite resin particles are, for example, 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, 2.5 mm ,

<Pre-expanded particles>

Also, because the aforementioned composite resin particles are used as the raw material for the pre-expanded particles of the present invention, there can be obtained therefrom molded foam pieces excellent in impact resistance and thermoforming stability. Pre-expanded particles mean resin particles in which the aforementioned foamable composite resin particles are heat-foamed to a certain bulk density.

The prefoamed particles have a bulk density of preferably 0.020-0.10 g / cm ³ , more preferably 0.025-0.10 g / cm ³ . Concrete numerical values for the bulk density of the pre-expanded particles are, for example, 0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.028, 0.030, 0.040, 0.050, 0.060, 0.070, 0.080, 0.090, 0.095, 0.098, 0.099, 0.10 g / cm ³ .

If the bulk density is less than 0.020 g / cm ³ , the strength and heat stability of the molded foam pieces obtained may decrease. On the other hand, the weight of the molded foam pieces obtained may increase when it is over 0.10 g / cm ³ .

The pre-expanded particles have an average particle size of preferably 1.0-9.0 mm, more preferably 2.0-6.4 mm. Concrete numerical values for the average particle size of the prefoamed particles are, for example, 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. Likewise, they are also preferably spherical to approximately spherical

<Molded foam parts>

Also, because the aforementioned composite resin particles are used as a raw material for the molded foam pieces of the present invention, they have excellent impact resistance and thermoforming stability. Molded foam parts mean resin moldings obtained from the aforementioned prefoamed particles by thermal fusion bonding.

In order for the molded foam pieces to have even better heat resistance and impact resistance, they preferably have a density of 0.020-0.10 g / cm ³ , more preferably 0.025-0.10 g / cm ³ . Specific numerical values for the density of the molded foam parts are, for example, 0.020, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.028, 0.030, 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 .

If the density is less than 0.020 g / cm ³ , the strength and heat stability of the molded foam pieces obtained may decrease. On the other hand, the weight of the molded foam pieces obtained may increase when it is over 0.10 g / cm ³ .

The molded foam pieces of the present invention show an absorption energy of preferably 1.2-3.0 J, more preferably 1.3-3.0 J, in the impact test according to ASTM D3763-92. Concrete numerical values for the absorption energy of the molded foam pieces are, for example, 1, 2, 1.3, 1.4, 1.5, 1.7, 2.0, 2.3, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 J ,

The molded foam pieces exhibit a thermal strain rate of JIS K6767: 1999 of preferably 1.0% or less, more preferably 0.8% or less. Concrete numerical values for the thermal strain rate shown by the molded foam pieces are, for example, 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%. A thermal strain rate of 1.0% or less here means that it can range from -1.0% to + 1.0%.

These measurement results show that the molded foam pieces of the present invention have excellent impact resistance and thermoforming stability as compared with the prior art.

<Production Method of Composite Resin Particles, Foamable Composite Resin Particles, Pre-expanded Particles and Molded Foam Parts>

First, the composite resin particles can be produced, for example, by the following methods. In aqueous suspension, 100 parts by weight of polyolefin resin particles, 100-400 parts by weight of styrene Monomer and a polymerization initiator dispersed. The styrenic monomer and the polymerization initiator may also be mixed before use.

The polyolefin resin particles can be prepared by known methods. For example, one method is to obtain a strand of polyolefin resin, if necessary together with an inorganic nucleating agent and additives, in an extruder by melt-kneading and extruding, which is granulated by air-cutting, water-cutting or heating.

The inorganic nucleating agents include, for example, talc, silica, mica, clay, zeolite, calcium carbonate, etc. The amount of inorganic nucleating agent used per 100 parts by weight of the polyolefin resin is preferably 2 parts by weight or less, more preferably 0.2-1.5 parts by weight. Concrete numerical values for the amount of inorganic nucleating agent used per 100 parts by weight of polyolefin resin are, for example, 0.2, 0.5, 1.0, 1.3, 1.5, 1.7, 1.8, 1.9, 2 parts by weight , As the aqueous medium for the aqueous suspension may be mentioned water and mixtures of water and water-soluble solvents (for example, lower alcohols).

As the polymerization initiators, there may be used compounds normally used for the initiation of the suspension polymerization of styrene monomer. They include, for example, organic peroxides such as benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, tert-butyl peroxy-3,5,5-trimethylhexanoate tert-butyl peroxy-2-ethylhexyl carbonate, etc. These polymerization initiators may be used alone, but 2 or more of them may be used simultaneously.

The amount of the polymerization initiator used per 100 parts by weight of styrene monomer is preferably 0.1-0.9 parts by weight, more preferably 0.2-0.5 parts by weight. Concrete numerical values for the amount of the polymerization initiator used per 100 parts by weight of the styrene monomer are, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0 , 9, etc. parts by weight. Below 0.1 parts by weight, the polymerization of the styrene monomer may take too long. When using more than 0.9 parts by weight of the polymerization initiator, the molecular weight of the styrenic resin may be low.

If necessary, dispersants may be added to the aqueous suspension. As dispersants, all known substances can be used without any particular restriction. In particular, they include sparingly soluble inorganic materials such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, magnesium oxide, etc. In addition, surfactants such as sodium dodecylbenzenesulfonate may be used.

Thereafter, the resulting dispersion is heated to a temperature at which the styrene monomer does not substantially polymerize, and impregnated the polyolefin resin particles with the styrene monomer. The appropriate period for soaking the polyolefin resin particles with the styrenic monomer is 30 minutes-2 hours. Specific values for the duration of impregnation with styrene monomer are, for example, 30 minutes, 45 minutes, 1 hour, 1 hour 15 minutes, 1 hour 30 minutes, 1 hour 45 minutes, 2 hours. If the polymerization takes place before sufficient saturation has occurred, it can also happen that a polymer powder of the styrene resin is formed. If the above-mentioned temperature at which the monomer does not polymerize in substance is high, it is advantageous to accelerate the rate of penetration, but it must be set in consideration of the decomposition temperature of the polymerization initiator.

Subsequently, the styrene monomer is polymerized. The polymerization is carried out at 115-140 ° C for 1.5-5 hours without any particular limitation. Concrete numerical values for the polymerization temperature include 115, 120, 125, 130, 135, 140 ° C, etc. Concrete numerical values for the polymerization time are, for example, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 , 5 hours. The polymerization is usually carried out in closed pressure-resistant containers. The impregnation and the polymerization of the styrene monomer can be divided into several steps. The division into several steps minimizes the formation of polymer powder from polystyrene. Further, considering the decomposition temperature of the polymerization initiator, the polymerization can be carried out not only when the polyolefin resin particles are impregnated with styrene monomer but also during styrene monomer saturation. With the aid of the process described above, the composite resin particles can be obtained.

Next, during the aforementioned polymerization or by soaking the composite resin particles with blowing agent after the completion of the polymerization, the foamable resin particles can be obtained. This impregnation can be carried out by methods known per se. For example, soaking may be performed during the polymerization by injecting the blowing agent into the closed vessel in which the polymerization reaction takes place. The impregnation after the end of the polymerization can be carried out in the closed vessel by injecting the propellant.

Further, the prefoamed particles can be obtained by prefoaming the above-mentioned foamable resin particles by known methods to a certain bulk density.

Since the foamable composite resin particles of the present invention have excellent heat resistance, the production method of the prefoamed resin particles involves a process of heating the above, preferably 0.05-0.15 MPa, more preferably 0.06-0.10 MPa Composite resin particles are prefoamed. Concrete prefilm pressure values include 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0, 15 MPa, etc. In this case, by using higher pressure heating steam, the production cost and production time can be reduced.

Furthermore, the molded foam pieces can be obtained by packing the prefoamed particles into the metal mold of a foam molding machine, reheating them, and thermofusing the foam particles with each other while allowing the prefoamed particles to foam. Water vapor is particularly suitable as a heat transfer medium.

The other manufacturing conditions in each production step such as the process temperature, the working pressure and the processing time are appropriately determined according to the production equipment used and the starting materials.

The molded foam pieces of the present invention have excellent impact resistance and thermoforming stability. For this reason, the molded foam pieces are suitable for applications requiring excellent impact resistance and thermoforming stability, such as packaging material, automobile components, cushioning material or core material for bumpers, being particularly suitable as a core material for bumpers.

embodiments

In the following, the present invention will be described in detail by embodiments and comparative examples, but it is not limited to these embodiments.

(Number average molecular weight (Mn), weight average molecular weight (Mw) and degree of dispersion (Mw / Mn))

For measurements by gel permeation chromatography (GPC), the HLC-8121GPC / HT apparatus from Tosoh Corp. is used. TSKgel GMHhr-H (20) HT from Tosoh Corp. is used as the column, the column temperature is set to 40 ° C. and 1,2,4-trichlorobenzene is used as the eluent. The test sample is adjusted to a concentration of 1.0 mg / ml, of which 0.3 ml is used as the injection rate for the GPC device. Calibration curves for all molecular weights are calibrated using samples of polyethylene and polypropylene of known molecular weight. Mn and Mw are determined as polystyrene equivalent. Using the obtained values of Mn and Mw, the degree of dispersion (Mw / Mn) is determined.

(Density of the resin)

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

(Melt flow rate (MFR) of polyethylene resin)

The melt flow rate is determined in accordance with JIS K7210-1: 1999 at 190 ° C under a load of 2.16 kg.

(Melt Flow Rate (MFR) of Polypropylene Resin)

The melt flow rate is determined in accordance with JIS K7210-1: 1999 at 230 ° C under a load of 2.16 kg.

(Vicat softening point (Vicat softening temperature) of polyolefin resin)

The determination is made according to the method described in JIS K7206: 1999 "Plastics - Thermoplastic materials - Test method for determining the Vicat softening temperature".

(Vicat softening point of composite resin particles)

The determination is made according to the method described in JIS K7196: 1991 "Test method for determining the softening temperature of thermoplastic films and films by thermomechanical analysis". That is, the resin particles are hot-pressed and after being compressed to a thickness of 2 mm, they are processed into a flat rectangular film test pattern of 10 mm height x 20 mm width x 2 mm thickness. A device is used to measure heat, stress and twist (Model "TMA / SS6200", manufactured by Seiko Instruments). In the needle penetration test mode, a needle (area of the needle tip 1 mm ² ) with a load of 50 g is applied to the film test pattern and the temperature is heated at a rate of 5 ° C / min. elevated. The temperature at the time of twisting the film test pattern gives the Vicat softening point of the resin particles.

(Bulk density of pre-expanded resin particles)

The bulk density of the prefoamed resin particles is measured as described below. First, the prefoamed resin particles are filled in a graduated cylinder to the 500 cm ³ mark. However, as soon as viewed in the measuring cylinder from the horizontal direction, a grain of the prefoamed resin particles reaches the 500 cm ³ mark, the filling is completed. Then, the weight of the prefoamed particles filled in the measuring cylinder is exactly determined up to 2 significant digits after the decimal point and this weight is designated as W (g). The bulk density of the prefoamed resin particles is calculated by the following equation. Bulk density (g / cm ³ ) = W / 500

(Density of molded foam body)

The weight (a) and the volume (b) of test samples (for example, 150 × 150 × 30 mm) cut out of the molded foam bodies (after being molded for 4 hours or more at 50 ° C) are each reduced to 3 or more significant points determined and determined from the equation (a) / (b), the density of the molded foam body.

(Thermoforming stability of molded foam body)

The determination is made in accordance with the method B described in JIS K6767: 1999 "Foamed Plastic - Polyethylene Test Method". The test pattern of 150 mm × 150 mm × 30 mm (thickness) draws straight in the middle in the vertical and horizontal directions parallel to each other 3 Lines spaced 50 mm apart, store the sample for 24 hours at 90 ° C in a circulating hot air dryer, remove it, leave it in place for 1 hour under normal conditions, and determine the amount of vertical and horizontal lines as follows Formula. S = (L1-L0) / L0 × 100

In this formula, S represents the thermal rate of change (%), L1 is the average length (mm) after heating, and L0 is the initial average length (mm).

• (1) Im Fall einer thermischen Maßänderungsrate von 1% oder weniger: O
• (2) Im Fall einer thermischen Maßänderungsrate größer als 1%: x

The thermoforming stability is evaluated as follows

• (1) In the case of a thermal rate of change of 1% or less: O
• (2) In the case of a thermal rate of change rate greater than 1%: x

(Impact Resistance of Molded Foam Body (Dynatup Impact Test (ASTM D3763-92)))

The impact strength of molded foam bodies is determined according to ASTM D3763-92
Meter: Dynatup Impact Tester GRC 8250 (manufactured by General Research Corp.)
Test sample 100 × 100 × 20 T (mm)
Span: Inner diameter of the round opening 76 mm
Test speed: 4.05 m / min.
Test temperature: 23 ° C
Fall height: 59 cm
Distance of the drop weight: 16 cm
Test load: 3.17 kg
Number of experiments: 5

• (1) Im Fall einer Absorptionsenergie von 1,2–3,0 J: O
• (2) Im Fall einer Absorptionsenergie von weniger als 1,2 J: x

The impact resistance is evaluated as follows

• (1) In the case of absorption energy of 1.2-3.0 J: O
• (2) In the case of an absorption energy of less than 1.2 J: x

(Embodiment 1)

Production of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 3/7 (weight ratio)

100 parts by weight of polyethylene resin (product name "SP4020", manufactured by Prime Polymer Co., density: 0.937 / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 1.8 g / 10 min) were charged into an extruder, melt-kneaded and passed through Granulating the underwater cutting process. In this way, elliptical-spherical (egg-shaped) polyethylene resin particles were obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped 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. In the dispersion medium, 12 kg of the aforementioned polyethylene resin particles were dispersed to a suspension. Then, by dissolving 11.4 g of the polymerization initiator tert-butyl peroxybenzoate in 6 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were soaked by stirring with the 1st styrene monomer for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 115 ° C, which was added dropwise by dissolving 41.8 g of the polymerization initiator tert-butyl peroxybenzoate in 22 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4.6 kg per 1 hour continuously and, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 115 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

 Then, 2 kg of composite resin particles and 21 of water were placed in a 5-liter autoclave equipped with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged into a pre-foaming apparatus (Model "PSX40" manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.05 MPa. In this way, prefoamed particles having a bulk density of 0.033 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The interior of the metal mold was charged with water vapor at a pressure of 0.18 MPa for 30 seconds, the foam-prefoamed particles were formed, and thus a cuboid core material for bumpers having dimensions of 400 mm × width 300 mm × height 30 mm and a density of 0.033 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Embodiment 2)

Production of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 3/7

100 parts by weight of polyethylene resin (product name "SP4020", manufactured by Prime Polymer Co., density: 0.937 g / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 1.8 g / 10 min) and 7.7 parts by weight of 40 wt The carbon black-containing raw material base compound (28E-40, manufactured by Dow Chemical Co. (base resin LDPE (low-density polyethylene resin)) was charged into an extruder, melt-kneaded and granulated by the underwater cutting method, thus becoming elliptical The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped with a stirrer, 128 g of magnesium pyrophosphate and 32 g of dodecylbenzenesulfonic acid sodium salt were dispersed in 40 kg of water to a dispersion medium. In the dispersion medium, 12 kg of the foregoing carbon black-containing polyethylene resin particles were dispersed into a suspension. Then, by dissolving 12.0 g of the polymerization initiator dicumyl peroxide in 6 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were impregnated with the 1st styrene monomer by stirring for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 125 ° C, the dropwise by dissolving 100.8 g of the polymerization initiator dicumyl peroxide in 22 kg of styrene monomer obtained second styrene monomer in an amount of 4.6 kg per 1 hour and dropwise, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 125 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Then, 2 kg of composite resin particles and 21 of water were placed in a 5-liter autoclave equipped with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged into a pre-foaming apparatus (Model "PSX40" manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.05 MPa. In this way, prefoamed particles having a bulk density of 0.033 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The interior of the metal mold was charged with water vapor at a pressure of 0.18 MPa for 30 seconds, the foam-prefoamed particles were formed, and thus a cuboid core material for bumpers having dimensions of 400 mm × width 300 mm × height 30 mm and a density of 0.033 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Embodiment 3)

Polyethylene resin ("3540FC", product name "SP4020", manufactured by Prime Polymer Co., density: 0.937 g / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 1.8 g / 10 min.) Was used instead of polyethylene resin. manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.931 / cm ³ , Vicat softening point: 114 ° C, melt flow rate: 3.6 g / 10 min), and otherwise in the same manner as in Embodiment 1.

(Embodiment 4)

Polyethylene resin (product name "SP4020", manufactured by Prime Polymer Co., density: 0.937 / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 1.8 g / 10 min) became polyethylene resin ("4040FC", manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.938 / cm ³ , Vicat softening point: 120 ° C, melt flow rate: 3.5 g / 10 min), and otherwise in the same manner as in the embodiment 1 proceed.

(Embodiment 5)

Preparation of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 4/6 (weight ratio)

100 parts by weight of polyethylene resin (product name "SP4020" manufactured by Prime Polymer Co., density: 0.937 g / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 1.8 g / 10 min) were charged into an extruder, melt-kneaded and granulated by the underwater cutting process. In this way, elliptical-spherical (egg-shaped) polyethylene resin particles were obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped 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. In the dispersion medium, 16 kg of the aforementioned polyethylene resin particles were dispersed to a suspension. Then, by dissolving 15.2 g of the polymerization initiator tert-butyl peroxybenzoate in 8 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were soaked by stirring with the 1st styrene monomer for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 115 ° C, which was added dropwise by dissolving 33.6 g of the polymerization initiator tert-butyl peroxybenzoate in 16 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4.6 kg per 1 hour continuously and, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 115 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Subsequently, 2 kg of composite resin particles and 2 l of water were placed in a stirrer-equipped 5 liter autoclave, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged in a pre-foaming machine (Model "PSX40" manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.05 MPa. In this way, prefoamed particles having a bulk density of 0.033 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The interior of the metal mold was charged with water vapor at a pressure of 0.18 MPa for 30 seconds, the foam-prefoamed particles were formed, and thus a cuboid core material for bumpers having dimensions of 400 mm × width 300 mm × height 30 mm and a density of 0.033 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Embodiment 6)

Production of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 3/7

100 parts by weight of polyethylene resin ("4540F", manufactured by Ube-Maruzen Polyethylene Co., Ltd., density: 0.944 g / cm ³ , Vicat softening point: 123 ° C, melt flow rate: 4.0 g / 10 min) were charged to an extruder filled, melt-kneaded and granulated by the underwater cutting process. In this way were obtained elliptical-spherical (egg-shaped) polyethylene resin particles. The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped 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. In the dispersion medium, 12 kg of the aforementioned polyethylene resin particles were dispersed to a suspension. Then, by dissolving 11.4 g of the polymerization initiator tert-butyl peroxybenzoate in 6 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were soaked by stirring with the 1st styrene monomer for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 115 ° C, which was added dropwise by dissolving 41.8 g of the polymerization initiator tert-butyl peroxybenzoate in 22 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4.6 kg per 1 hour continuously and, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 115 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Then, 2 kg of composite resin particles and 21 of water were placed in a 5-liter autoclave equipped with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged in a pre-foaming apparatus (Model "PSX40" manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.10 MPa. In this way, prefoamed particles having a bulk density of 0.025 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The inside of the metal mold was charged with water vapor at a pressure of 0.23 MPa for 30 seconds, the foam-prefoamed particles were formed, and thus a cuboid core material for bumpers having dimensions of 400 mm × width 300 mm × height 30 mm and a density of 0.025 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Embodiment 7)

Production of composite resin particles consisting of polypropylene resin (PP) / polystyrene resin (PS) = 4/6

As the polypropylene resin, 100 parts by weight of a product manufactured by Japan Polypropylene Corporation called "RFG4VA" (melting point 135 ° C, density: 0.900 g / cm ³ , melt flow rate: 6.0 g / 10 min, Vicat softening point: 115 ° C) filled into an extruder, melt-kneaded and granulated by the underwater cutting process. In this way, elliptical-spherical (egg-shaped) polypropylene resin particles (polyolefin resin particles) were obtained. The average weight of the polypropylene resin particles was 0.8 mg.

Subsequently, in a 100-liter autoclave equipped with a stirrer, 400 g of magnesium pyrophosphate and 10 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. In the dispersion medium, 16 kg of the aforementioned polypropylene resin particles were dispersed to a suspension. Then, by dissolving 16 g of the polymerization initiator dicumyl peroxide in 8.0 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polypropylene was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polypropylene resin particles were impregnated with the 1st styrene monomer by stirring for 1 hour. Then the temperature of the reaction system became increased to 140 ° C, the melting temperature of the polypropylene resin, and maintained at this temperature for 2 hours, and thus polymerized the styrene monomer in the polypropylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 125 ° C, which was added dropwise by dissolving 72 g of the polymerization initiator dicumyl peroxide in 16 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4 kg per 1 hour continuously and while the polypropylene resin particles with the second styrene monomer were saturated, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 120 ° C for 1 hour, then raised to 143 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Then, 2 kg of composite resin particles and 21 of water were placed in a 5-liter autoclave equipped with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged in a pre-foaming machine (Model "PSX40" manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.05 MPa. In this way, prefoamed particles having a bulk density of 0.025 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The inside of the metal mold was charged with water vapor at a pressure of 0.18 MPa for 30 seconds, the foam-prefoamed particles were molded, and thus a rectangular core material for bumps having lengths of 400 mm × width 300 mm × height 30 mm and a density of 0.025 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Comparative Example 1)

Production of composite resin particles consisting of polypropylene resin (PP) / polystyrene resin (PS) = 4/6

As the polypropylene resin, 100 parts by weight of a product manufactured by Prime Polymer Co. named "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) into an extruder, melt-kneaded and granulated by the underwater cutting process. In this way, elliptical-spherical (egg-shaped) polypropylene resin particles (polyolefin resin particles) were obtained. The average weight of the polypropylene resin particles was 0.8 mg.

Then, in a 100-liter autoclave equipped with a stirrer, 400 g of magnesium pyrophosphate and 10 g of sodium dodecylbenzenesulfonate were dispersed in 40 kg of water to obtain a dispersion medium. In the dispersion medium, 16 kg of the aforementioned polypropylene resin particles were dispersed to a suspension. Then, by dissolving 16 g of the polymerization initiator dicumyl peroxide in 8 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polypropylene was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polypropylene resin particles were impregnated with the 1st styrene monomer by stirring for 1 hour. Then, the temperature of the reaction system was raised to 140 ° C, the melting temperature of the polypropylene resin, and maintained at that temperature for 2 hours to thereby polymerize the styrene monomer in the polypropylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 120 ° C, which was added dropwise by dissolving 72 g of the polymerization initiator dicumyl peroxide in 16 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4 kg per 1 hour continuously and while the polypropylene resin particles with the second styrene monomer were saturated, polymerized (2nd polymerization). After the end of the dropping, the temperature was maintained at 120 ° C for 1 hour, then raised to 143 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Subsequently, 2 kg of composite resin particles and 2 l of water were placed in a 5 l autoclave equipped with a stirrer and 16 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and the Stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged into a pre-foaming machine (Model "PSX40", manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.1 MPa. In this way, prefoamed particles having a bulk density of 0.033 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The inside of the metal mold was charged with water vapor at a pressure of 0.25 MPa for 30 seconds, the foam-prefoamed particles were formed, and thus a rectangular core material for bumpers having dimensions of 400 mm × width 300 mm × height 30 mm and a density of 0.033 g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Comparative Example 2)

Production of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 3/7

100 parts by weight of polyethylene resin (product name "NF464A", manufactured by Japan Polyethylene Co., density: 0.918 g / cm ³ , Vicat softening point: 98 ° C, melt flow rate: 2.0 g / 10 min) were charged into an extruder, melt-kneaded and granulated by the underwater cutting process. In this way, elliptical-spherical (egg-shaped) polyethylene resin particles were obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped 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. In the dispersion medium, 12 kg of the aforementioned polyethylene resin particles were dispersed to a suspension. Then, by dissolving 11.4 g of the polymerization initiator tert-butyl peroxybenzoate in 6 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were soaked by stirring with the 1st styrene monomer for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 115 ° C, which was added dropwise by dissolving 41.8 g of the polymerization initiator tert-butyl peroxybenzoate in 22 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4.6 kg per 1 hour continuously and, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization).

After the end of the dropping, the temperature was maintained at 115 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Subsequently, 2 kg of composite resin particles and 2 l of water were placed in a 5 l autoclave equipped with a stirrer and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged into a pre-foaming apparatus (Model "PSX40", manufactured by Kasahara Industry Co., Ltd.) and were charged by means of Prefilled steam at a pressure of 0.03 MPa. In this way, prefoamed particles having a bulk density of 0.025 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The inside of the metal mold was charged with water vapor at a pressure of 0.10 MPa for 30 seconds, the foam-prefoamed particles were molded, and thus a rectangular core material for bumps having dimensions of 400 mm × width 300 mm × 30 mm in height and 0.025 in density g / cm ³ made.

The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

(Comparative Example 3)

Production of composite resin particles consisting of polyethylene resin (PE) / polystyrene resin (PS) = 3/7

100 parts by weight of polyethylene resin (product name "09S53B", manufactured by Tosoh Corp., density: 0.936 / cm ³ , Vicat softening point: 117 ° C, melt flow rate: 2.0 g / 10 min) were charged into an extruder, melt-kneaded and passed through the extruder Underwater cutting process granulated. In this way, elliptical-spherical (egg-shaped) polyethylene resin particles were obtained. The average weight of the polyethylene resin particles was 0.6 mg.

Subsequently, in a 100-liter autoclave equipped 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. In the dispersion medium, 12 kg of the aforementioned polyethylene resin particles were dispersed to a suspension. Then, by dissolving 11.4 g of the polymerization initiator tert-butyl peroxybenzoate in 6 kg of styrene monomer, the 1st styrene monomer was prepared. The temperature of the suspension containing the polyethylene resin particles was adjusted to 60 ° C, and after the above-mentioned styrene monomer was added in the predetermined amount within 30 minutes, the polyethylene resin particles were soaked by stirring with the 1st styrene monomer for 1 hour. Then, the temperature of the reaction system was raised to 135 ° C and maintained at that temperature for 3 hours to thereby polymerize the styrene monomer in the polyethylene resin particles (1st polymerization).

Subsequently, the temperature of the reaction system was lowered to 115 ° C, which was added dropwise by dissolving 41.8 g of the polymerization initiator tert-butyl peroxybenzoate in 22 kg of styrene monomer obtained 2nd styrene monomer in an amount of 4.6 kg per 1 hour continuously and, while the polyethylene resin particles were impregnated with the 2nd styrene monomer, polymerized (2nd polymerization).

After the end of the dropping, the temperature was maintained at 115 ° C for 1 hour, then raised to 140 ° C, held for 3 hours, and the polymerization was completed. In this way, the composite resin particles were obtained.

Then, 2 kg of composite resin particles and 21 of water were placed in a 5-liter autoclave equipped with a stirrer, and 17 parts by weight of butane (n-butane: i-butane = 7: 3 (weight ratio)) was charged at normal temperature. After filling, the temperature was raised to 70 ° C and stirring continued for 2 hours. It was then cooled to normal temperature and the product was removed from the 5 l autoclave, dewatered and dried. In this way, the foamable composite resin particles were obtained.

The obtained foamable composite resin particles were immediately charged in a pre-foaming machine (Model "PSX40", manufactured by Kasahara Industry Co., Ltd.) and prefoamed by means of steam at a pressure of 0.03 MPa. In this way, prefoamed particles having a bulk density of 0.025 g / cm ^{3 were} obtained.

Thereafter, the prefoamed particles were allowed to stand at room temperature for one day and then filled in the metal mold of a molding machine. The inside of the metal mold was charged with water vapor at a pressure of 0.10 MPa for 30 seconds, the foam-prefoamed particles were molded, and thus a rectangular core material for bumps having dimensions of 400 mm × width 300 mm × 30 mm in height and 0.025 in density g / cm ³ made. The fusion bonding rate and appearance of the obtained core material for bumpers was excellent.

In Table 1, the kinds of the starting materials and the evaluation results of the embodiments and the comparative examples are explained in detail.

In Table 1, PE means polyethylene resin, PS polystyrene resin and PP polypropylene resin.

[Table 1]

It is clear from Table 1 that the molded foam pieces of the present invention have excellent impact resistance and thermoforming stability. Therefore, the molded foam pieces of the present invention are suitable for use as packaging material, automobile components, cushioning material or core material for bumpers, being particularly suitable as core material for bumpers.

Claims (13)

Composite resin particles comprising as resin components 100 parts by weight of polyolefin resin and 100-400 parts by weight of polystyrene resin, said polyolefin resin having a Vicat softening point of 110-125 ° C and a degree of dispersion of 1.5-4.8. The composite resin particle according to claim 1, wherein the composite resin particles comprise, as resin components, 100 parts by weight of polyolefin resin and 100-300 parts by weight of polystyrene resin. Composite resin particles according to claim 1, wherein the composite resin particles have a degree of dispersion of 2.0-4.5. The composite resin particle according to claim 1, wherein the polyolefin resin is a polyethylene resin or a polypropylene resin. The composite resin particle according to claim 1, wherein the composite resin particles have a Vicat softening point of 110-130 ° C. The composite resin particle according to claim 1, wherein the composite resin particles comprise from 0.5 to 3.0 parts by weight of carbon black per 100 parts by weight of the resin components. Foamable composite resin particles obtained from the composite resin particles according to claim 1. Pre-expanded particles obtained from the foamable composite resin particles according to claim 7. Shaped foam parts obtained from the prefoamed particles according to claim 8. Molded foam parts according to claim 9, wherein the molded foam parts have a density of 0.020-0.10 g / cm ³ . Molded foam parts according to claim 9, wherein the molded foam parts in the impact test according to ASTM D3763-92 have an absorption energy of 1.2-3.0 J. Molded foam pieces according to claim 9, wherein the molded foam pieces in the thermal strain test of JIS K6767: 1999 have a thermal strain rate of 1.0% or less. Core material for bumpers, which is obtained from the molded foam parts according to claim 9.