JP2017066359A - Styrene modified polyolefin resin particle and manufacturing method therefor, expandable particle, foam particle and foam molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a styrene modified polyolefin resin particle capable of providing a foam molded body having good molding processability and excellent heat resistance and a manufacturing method therefor, an expandable particle, the foam particle and a foam molded body obtained therefrom.SOLUTION: The above described problem is solved by a styrene modified polyolefin resin particle containing polystyrene resin of 100 to 300 pts.mass based on 100 pts.mass of a polyolefin resin, where the polyolefin resin has the melting point of 124 to 145°C and the polystyrene resin contains a resin component derived from an α-methylstyrene of 10 to 35 mass%.SELECTED DRAWING: None

Description

  The present invention relates to styrene-modified polyolefin resin particles and a method for producing the same, and expandable particles, expanded particles, and expanded molded articles obtained thereby. More specifically, the present invention relates to a styrene-modified polyolefin resin particle capable of providing a foamed molded article having both good moldability and excellent heat resistance, and a method for producing the same, and expandable particles obtained thereby, foaming The present invention relates to particles and a foamed molded product.

Foamed molded bodies made of polystyrene resin are widely used as packaging materials and heat insulating materials because they have excellent buffering properties and heat insulating properties and are easy to mold. However, since the impact resistance and flexibility are insufficient, cracks and chips are likely to occur, and it is not suitable, for example, for packaging precision instrument products.
On the other hand, a foam-molded article made of polyolefin resin is excellent in impact resistance and flexibility, but requires a large facility for molding. Also, due to the nature of the resin, it must be transported from the raw material manufacturer to the molding processing manufacturer in the form of pre-expanded particles. Therefore, bulky pre-expanded particles are transported, and there is a problem that the manufacturing cost increases.
Therefore, various styrene-modified polyolefin resin particles (also referred to as “modified polyolefin resin particles” and “modified resin particles”) having the characteristics of the above two different resins and foam molded articles using them are disclosed. Proposed.

For example, Japanese Patent No. 5732299 (Patent Document 1) includes 100 parts by mass of a polyethylene resin and 200 to 900 parts by mass of a polystyrene resin as resin components, and 0.900 to 0.916 g of polyethylene resin. Modified resin particles having a density of / cm ³ , 190 ° C., a melt flow rate of 1.0 to 5.0 g / 10 min measured under a load of 2.16 kg and a Vicat softening temperature of 88 to 95 ° C. The modified resin particles are configured such that when the expandable particles obtained from the modified resin particles are allowed to stand for 300 seconds at 90 to 100 ° C., the modified resin particles have two foaming peaks. Has been.

  In addition, in Japanese Patent No. 4845862 (Patent Document 2), a styrene-based resin having a mass exceeding 300 parts by mass and not more than 1,000 parts by mass with respect to 100 parts by mass of a non-crosslinked linear low-density polyethylene resin component. A base resin containing components and a volatile foaming agent are contained, and 3.2 to 40% by mass of a gel component made of a graft polymer of a low density polyethylene resin component and a polystyrene resin component is contained in the base resin. A slurry containing styrene-modified linear low-density polyethylene-based expandable particles having a powder amount of 0.8% by mass or less, wherein the amount of powder includes styrene-modified linear low-density polyethylene-based expandable particles. Procedure for passing through a 35-mesh wire mesh, procedure for measuring the dry powder mass of polymer powder that has passed through the wire mesh, and the dry resin mass of resin particles that have not passed through the wire mesh, and the powder relative to the dry resin mass Styrene-modified linear low-density polyethylene-based expandable particles are disclosed is a value obtained by following the procedure of calculating the weight percent of 燥質 amount.

  Furthermore, Japanese Patent No. 4202716 (Patent Document 3) discloses a thermoplastic resin foam molded article in which polyolefin resin foam particles (B) are dispersed in a foam (A) made of polystyrene resin, and further polystyrene. The polystyrene resin constituting the foam (A) made of a resin is a copolymer having a monomer composition of 0 to 70% by mass of styrene, 10 to 80% by mass of α-methylstyrene, and 5 to 50% by mass of acrylonitrile. Certain thermoplastic resin foam moldings are disclosed.

Japanese Patent No. 5732299 Japanese Patent No. 4845862 Japanese Patent No. 4202716

However, even in the prior arts of the above Patent Documents 1 to 3, modified polyolefin resin particles and foamed molded products that can satisfy all the conditions have not been obtained.
For example, improvement of heat resistance of modified polyolefin resin particles and foamed molded articles has been a conventional problem. For example, high heat resistance of polyolefin resin, adjustment of air bubbles, adjustment of molding conditions, change of polyolefin / polystyrene ratio, etc. Measures have been tried.
Although these methods were certainly effective in improving the heat resistance, there were disadvantages such as a decrease in molding processability.

  Therefore, the present invention provides a styrene-modified polyolefin resin particle capable of providing a foamed molded article having both good moldability and excellent heat resistance, and a method for producing the same, and the foamable particles, foamed particles and It is an object to provide a foam molded article.

  The inventors of the present invention, as a result of intensive studies to solve the above-mentioned problems, pay attention to the modifying component among the modified polyolefin-based modified resin particles, and have a melting point of 124 ° C. to 145 ° C. By using a polystyrene resin and using a polystyrene resin containing a resin component derived from 10 to 35% by mass of α-methylstyrene, and including 100 to 300 parts by mass of the polystyrene resin with respect to 100 parts by mass of the polyolefin resin, The present inventors have found that a foamed molded article having excellent heat resistance can be obtained without greatly deteriorating moldability and capable of drastically improving moldability, thereby completing the present invention.

Thus, according to the present invention, including 100 to 300 parts by mass of polystyrene resin with respect to 100 parts by mass of polyolefin resin,
The polyolefin resin has a melting point of 124 to 145 ° C .;
Provided is a styrene-modified polyolefin resin particle, wherein the polystyrene resin contains 10 to 35% by mass of a resin component derived from α-methylstyrene.

Moreover, according to this invention, the expandable particle | grains containing said styrene modified polyolefin resin particle and a foaming agent are provided.
Furthermore, according to the present invention, there are provided expanded particles obtained by pre-expanding the expandable particles.
Furthermore, according to this invention, the foaming molding obtained by carrying out the foaming molding of said foaming particle is provided.
Moreover, according to this invention, the motor vehicle exterior material comprised by said foaming molding is provided.

Moreover, according to the present invention, there is provided a method for producing the above styrene-modified polyolefin resin particles,
(A) Dispersing seed particles composed of a polyolefin resin in an aqueous medium containing a dispersant, absorbing the styrene monomer in the seed particles, and then heating to polymerize the styrene monomer. 1 polymerization step;
(B) Then, a second polymerization step of polymerizing the styrene monomer while absorbing the styrene monomer is included, or the steps (A) and (B) are (C) then the step A process for producing styrene-modified polyolefin resin particles is further provided, which further comprises the step of repeating (B).

  According to the present invention, a styrene-modified polyolefin resin particle capable of providing a foamed molded article having both good moldability and excellent heat resistance, a method for producing the same, and the foamable particles, foamed particles and A foamed molded article can be provided.

Styrene modified polyolefin resin particles of the present invention,
(1) The styrene-modified polyolefin resin particles have a polystyrene-equivalent weight average molecular weight Mw of 50,000 to 250,000,
(2) The modified polyolefin resin particles contain 1.5 to 5.0% by mass of carbon black,
(3) The polyolefin-based resin contains 3.0 to 10.0% by mass of carbon black, and (4) Coexists with 0.01 to 0.1% by mass of styrene-based monomer with respect to the polystyrene-based resin. The above excellent effect is further exhibited when at least one condition of further including a resin component derived from a polymerizable aromatic polyfunctional vinyl monomer is satisfied.
The method for producing styrene-modified polyolefin-based resin particles of the present invention includes all the styrene-based monomers to be charged after adding a styrene-based monomer containing a monomer of a resin component derived from α-methylstyrene in the step (B). In the case where a styrene monomer occupying 5 to 80% by mass of the monomer is added, the above excellent effect is further exhibited.

(1) Styrene-modified polyolefin-based resin particles The styrene-modified polyolefin-based resin particles of the present invention (hereinafter also referred to as “modified resin particles”) are 100-300 parts by weight of polystyrene-based resin with respect to 100 parts by weight of polyolefin-based resin. The polyolefin resin has a melting point of 124 to 145 ° C., and the polystyrene resin contains 10 to 35% by mass of a resin component derived from α-methylstyrene.

In Comparative Example 2 of Patent Document 1, linear low-density polyethylene resin (LLDPE, manufactured by Nihon Unicar Company, product name: FMRN-063, melting point 124 ° C., melt flow rate 1.3 g / 10 min, density Composite resin particles using 0.914 g / cm ³ (Vicat softening temperature 97 ° C.) are described. In addition, in paragraphs 0043 and 0044 of the specification, the styrene monomer occupies 90 parts by mass or more with respect to 100 parts by mass of all monomers, and α-methylstyrene may be included as another monomer. Is described.
On the other hand, the present invention is different from Patent Document 1 in that it contains 10 to 35% by mass of a resin component derived from α-methylstyrene among polystyrene resins.
In Example 15 of Patent Document 2, styrene monomer (358 parts by mass with respect to 100 parts by mass of polyethylene) and α-methylstyrene (100 parts by mass of polyethylene) were obtained using seed particles of polyethylene resin having a melting point of 126 ° C. It is described that a foamed molded article was obtained through a process of adding 2 parts by mass) to the part.
On the other hand, the amount of α-methylstyrene added in the present invention is different as described above.

Patent Documents 1 and 2 describe that α-methylstyrene is used as a vinyl monomer (a monomer of a polystyrene resin) for a styrene-modified polyolefin resin.
However, even if the inventors of the present invention add 10-35% by mass of α-methylstyrene of the monomer of the polystyrene resin by the methods described in Patent Documents 1 and 2, the low molecular weight component increases. It has been confirmed by tests that sufficient heat resistance cannot be improved due to increase in residual monomers.
In the present invention, foam molding is possible and excellent heat resistance by a production method as described later (a combination of two kinds of initiators or multistage polymerization in which a monomer of a styrene resin is divided and added). A foamed molded article of modified resin particles is obtained.

Further, Patent Document 3 described above describes a foamed molded body obtained by integrally molding foamed particles of a copolymer of styrene and α-methylstyrene and polyolefin resin foamed particles during molding.
On the other hand, the present invention is different in that a polyolefin resin, a styrene resin and a resin component derived from α-methylstyrene are combined at the time of polymerization, and there are structural differences as follows.
In the foamed molded article of the present invention, a copolymer of styrene and α-methylstyrene is finely dispersed in a polyolefin resin component with a particle diameter of about 50 to 1000 nm, and the resin particle surface layer has a large amount of polyolefin. In contrast, the foamed molded product described in Patent Document 3 has a structure in which foamed particles of styrene and α-methylstyrene and foamed polyolefin particles are combined at the time of molding. The top is very different.

[Polyolefin resin]
The polyolefin resin used in the present invention has a melting point of 124 to 145 ° C.
The melting point is measured by analysis with a differential scanning calorimeter (DSC), and the details thereof will be described in Examples.
When the melting point of the polyolefin resin is within the above range, styrene-modified polyolefin resin particles capable of providing a foamed molded article having both good moldability and excellent heat resistance can be obtained.
When the melting point of the polyolefin resin is lower than 124 ° C., the heat resistance of the foamed molded product may be insufficient. On the other hand, when the melting point of the polyolefin-based resin exceeds 145 ° C., the foaming power of the foamable particles becomes low, and a low-density foam molded article cannot be produced, and the weight reduction effect may not be sufficiently exhibited.
The melting point of the polyolefin resin is, for example, 124 ° C, 125 ° C, 126 ° C, 127 ° C, 128 ° C, 129 ° C, 130 ° C, 131 ° C, 132 ° C, 133 ° C, 134 ° C, 135 ° C, 135 ° C, 136 ° C, 137 ° C. 138 ° C, 139 ° C, 140 ° C, 141 ° C, 142 ° C, 143 ° C, 144 ° C, and 145 ° C.
The melting point of the preferred polyolefin resin is 130 to 145 ° C.

The polyolefin-based resin is not particularly limited as long as it has the above melting point, and includes a resin obtained by a known polymerization method, which may be cross-linked. For example, branched low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, these polymers And polypropylene resins such as propylene, ethylene-propylene random copolymer, propylene-1-butene copolymer, and ethylene-propylene-butene random copolymer. Specifically, commercially available products such as those used in the examples can be mentioned.
In the present invention, one of the above polyolefin-based resins can be used alone or in combination of two or more.
The polyolefin resin preferably contains a component selected from polypropylene resin and polyethylene resin from the viewpoint of chemical resistance and molding processability.

[Polystyrene resin]
In the present invention, the polystyrene-based resin is included as a modified resin component of the polyolefin-based resin, and includes 10 to 35% by mass of a resin component derived from α-methylstyrene.
The polystyrene resin is not particularly limited as long as it is a resin mainly composed of a styrene monomer used in the technical field, and examples thereof include a styrene or a styrene derivative alone or a copolymer.
Examples of the styrene derivative include vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like. These may be used alone or in combination.
As the polystyrene resin, a polystyrene resin is preferable from the viewpoint of molding processability such as foamability and mechanical properties such as strength of a molded product.

If the resin component derived from α-methylstyrene is less than 10% by mass, the effect of improving the heat resistance of the obtained foamed molded product may not be expected. On the other hand, if the resin component derived from α-methylstyrene exceeds 35% by mass, the polymerization efficiency may be extremely deteriorated in the production process, the low molecular weight component may be increased, and the foamability may be greatly reduced. A large amount of styrene-derived monomers remain, which may cause odor and may reduce heat resistance due to the plasticizing effect of the remaining monomers.
The content (mass%) of the resin component derived from α-methylstyrene is, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25. 26, 27, 28, 29, 30, 31, 32, 33, 34, 35.
The content of the resin component derived from α-methylstyrene is preferably 10 to 25%.

The polystyrene resin contains 100 to 300 parts by mass with respect to 100 parts by mass of the polyolefin resin.
If the polystyrene resin is less than 100 parts by mass with respect to 100 parts by mass of the polyolefin resin, the modification effect by the polystyrene resin may not be obtained. On the other hand, when the polystyrene-based resin exceeds 300 parts by mass with respect to 100 parts by mass of the polyolefin-based resin, the amount of residual monomer in the modified resin particles increases, resulting in a decrease in heat resistance due to the plastic effect and generation of odor. It may cause.
Content (mass part) with respect to 100 mass parts of polyolefin resin of a polystyrene-type resin is 100,110,120,130,140,150,160,170,180,190,200,210,220,230,240, for example. 250, 260, 270, 280, 290, 300.
The preferable content of polystyrene resin with respect to 100 parts by mass of polyolefin resin is 120 to 220 parts by mass.

[Resin component derived from aromatic polyfunctional vinyl monomer]
The modified resin particle of the present invention comprises a resin component derived from an aromatic polyfunctional vinyl monomer copolymerizable with 0.01 to 0.1% by mass of a styrene monomer relative to a polystyrene resin. Further inclusion is preferred.
Examples of the resin component derived from the aromatic polyfunctional vinyl monomer include divinylbenzene such as o-divinylbenzene, m-divinylbenzene, and p-divinylbenzene, and these may be used alone. , May be used in combination.
Among these, divinylbenzene is particularly preferable from the viewpoint of reactivity with the styrene resin.

The resin component derived from the aromatic polyfunctional vinyl monomer has an effect of improving the mass average molecular weight of the modified resin particles, and when the content is less than 0.01% by mass with respect to the polystyrene resin, There are cases where the effect cannot be expected. On the other hand, when the content exceeds 0.1% by mass with respect to the polystyrene resin, the molecular weight and the degree of crosslinking become too high, and foamability may be lowered.
The content (% by mass) of the resin component derived from the aromatic polyfunctional vinyl monomer with respect to the polystyrene resin is, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1.
The content of the resin component derived from the aromatic polyfunctional vinyl monomer more preferably with respect to the polystyrene resin is 0.02 to 0.05% by mass.

[Mass average molecular weight Mw of modified resin particles]
The modified resin particles of the present invention preferably have a polystyrene-equivalent weight average molecular weight Mw of 50,000 to 250,000.
When the weight average molecular weight Mw in terms of polystyrene of the modified resin particles is in the above range, in addition to improving the heat resistance of the obtained foamed molded article, excellent foamability can be expected.
When the weight average molecular weight Mw in terms of polystyrene of the modified resin particles is less than 80,000, the foamable particles obtained do not have melt tension suitable for foaming, and in addition to the decrease in heat resistance of the foamed molded product obtained, foamability May also decrease. On the other hand, when the weight average molecular weight Mw in terms of polystyrene of the modified resin particles exceeds 200,000, the foamability of the foamable particles obtained may be lowered.
The polystyrene-reduced weight average molecular weight Mw (× 10 ³ ) of the modified resin particles is, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190. , 200, 210, 220, 230, 240, 250.
More preferable modified resin particles have a polystyrene-equivalent mass average molecular weight Mw of 100,000 to 200,000.

(2) Method for Producing Styrene-Modified Polyolefin Resin Particles The method for producing the modified resin particles of the present invention includes:
(A) Dispersing seed particles composed of a polyolefin resin in an aqueous medium containing a dispersant, absorbing the styrene monomer in the seed particles, and then heating to polymerize the styrene monomer. 1 polymerization step;
(B) Then, a second polymerization step of polymerizing the styrene monomer while absorbing the styrene monomer is included, or the steps (A) and (B) are (C) then the step The method further includes the step of repeating (B).

The above method is a seed polymerization method. In general, the modified resin particles can be obtained by allowing the seed particles to absorb the monomer and polymerizing the monomer after or while absorbing the monomer. In addition, the foamed particles can be obtained by impregnating the modified resin particles with a foaming agent after polymerization or while polymerizing.
In the method for producing the modified resin particles of the present invention, the polymerization step of impregnating and polymerizing the styrene resin monomer into the seed particles made of polyolefin resin is repeated at least twice.
By repeating the polymerization process twice or more, the shape of the modified resin particles can be made spherical, and the polymerization of the monomer of the styrene resin impregnated in the seed particles made of polyolefin resin proceeds. easy.

[Step (A): First polymerization step]
Disperse seed particles comprising a polyolefin resin in an aqueous medium containing a dispersant, and absorb the styrene resin monomer in the seed particles, and then raise the temperature to polymerize the styrene resin monomer. .
In the first polymerization step, a monomer of a styrene resin that does not contain a monomer of the resin component derived from α-methylstyrene is used, and in the first polymerization step, a single amount of the resin component derived from α-methylstyrene is used. It is preferable to use a monomer of a styrene resin containing a body.

(Seed particles)
The seed particles can be obtained, for example, by melt-kneading the polyolefin-based resin with an extruder, extruding it into a strand shape, and cutting it with a desired particle diameter.
As for the die for obtaining seed particles of a predetermined size, the diameter of the resin discharge hole is preferably 0.2 to 1.0 mm, and the land length of the resin flow path is to maintain the high dispersibility of the polystyrene resin. The resin temperature at the die inlet of the resin extruded from the extruder is adjusted to 200 to 270 ° C. so that the pressure at the die resin flow path inlet can be maintained at 10 to 20 MPa. Is preferred.
Desired seed particles can be obtained by combining an extruder and a die having the screw structure, extrusion conditions, and underwater cutting conditions.
The seed particles may contain additives such as a polyolefin resin compatibilizing agent, a bubble adjusting agent, and an antistatic agent as long as the effects of the present invention are not impaired.

  The particle diameter of the seed particles can be adjusted as appropriate according to the average particle diameter of the modified resin particles, and the preferable particle diameter is in the range of 0.4 to 1.5 mm, more preferably 0.4 to 1.0 mm. The average mass is 30 to 90 mg / 100 grains. In addition, examples of the shape include a true spherical shape, an elliptical spherical shape (egg shape), a cylindrical shape, and a prismatic shape.

(Aqueous medium)
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, a lower alcohol such as methyl alcohol or ethyl alcohol).

(Dispersant)
In the aqueous medium, a dispersant may be used to stabilize the dispersibility of the styrene monomer droplets and seed particles. Examples of such a dispersant include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinyl pyrrolidone, carboxymethyl cellulose, and methyl cellulose; magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, magnesium phosphate, Examples thereof include inorganic dispersants such as magnesium carbonate and magnesium oxide. Among these, an inorganic dispersant is preferable because a more stable dispersion state may be maintained.
When an inorganic dispersant is used, it is preferable to use a surfactant in combination. Examples of such surfactants include sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate.

(Polymerization initiator)
Styrene monomers are usually polymerized in the presence of a polymerization initiator. The polymerization initiator is usually impregnated into the seed particles simultaneously with the styrene monomer.
The polymerization initiator is not particularly limited as long as it is conventionally used for the polymerization of styrene monomers. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxyisopropyl carbonate, t-butyl peroxyacetate, 2, 2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate, 2,5-dimethyl-2,5-bis (benzoyl) Organic peroxides such as peroxy) hexane and dicumyl peroxide. These polymerization initiators may be used alone or in combination of two or more. The usage-amount of a polymerization initiator is the range of 0.1-5 mass parts with respect to 100 mass parts of styrene-type monomers, for example.

  In order to uniformly absorb the polymerization initiator from the seed particles or the seed particles to the growing particles, the polymerization initiator is suspended or emulsified and dispersed in advance in the aqueous medium when the polymerization initiator is added to the aqueous medium. It is preferable to add to the dispersion liquid above, or to add the polymerization initiator to the aqueous medium after previously dissolving it in the styrene monomer.

The addition amount of a polymerization initiator is 0.1-0.9 mass part per 100 mass parts of styrene-type monomers.
When the addition amount of the polymerization initiator is less than 0.1 part by mass, the molecular weight becomes too high and foamability may be lowered. On the other hand, when the addition amount of the polymerization initiator exceeds 0.9 parts by mass, the polymerization rate may become too fast, and the dispersion state of the polystyrene resin particles in the polyolefin resin may not be controlled. A preferable addition amount of the polymerization initiator is 0.2 to 0.5 parts by mass.

The polymerization of the monomer of the styrene resin can be performed, for example, by heating at 60 to 150 ° C. for 2 to 40 hours.
In the polymerization step, it is preferable to hold at a polymerization temperature or higher than the polymerization temperature for a long time, that is, to anneal.
In the previous steps up to the annealing step, the styrene monomer and polymerization initiator absorbed in the seed particles have not completely completed the reaction, and there are not a few unreacted substances inside the modified resin particles. Existing. Therefore, when a foamed molded product is obtained using modified resin particles obtained without annealing, the mechanical properties and heat resistance of the foamed molded product are affected by the influence of low-molecular weight unreacted materials such as styrene monomers. Odor due to reduction or volatile unreacted matter becomes a problem. Therefore, by introducing an annealing step, it is possible to secure a time for the unreacted material to undergo a polymerization reaction, and to remove the remaining unreacted material so as not to affect the physical properties of the foam molded article.

(Other ingredients)
The modified resin particles have a colorant, a flame retardant, a flame retardant aid, a plasticizer, a binding inhibitor, a cell regulator, a cross-linking agent, a filler, a lubricant, and a fusion promoter within the range that does not impair the physical properties. You may add additives, such as an agent, an antistatic agent, and a spreading agent.

Examples of the colorant include furnace black, ketjen black, channel black, thermal black, acetylene black, graphite, carbon fiber, and other carbon black, and may be a masterbatch blended in a resin.
The carbon black content of the modified resin particles is preferably 1.5 to 5.0% by mass.
Moreover, content of carbon black of a preferable polyolefin-type resin is 3.0-10.0 mass%.
If the content of the carbon black in the modified resin particles and the polyolefin resin is in the above range, a coloring effect can be obtained without inhibiting the effects of the present invention.

Examples of the flame retardant include tri (2,3-dibromopropyl) isocyanate, bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, tetrabromocyclooctane, hexabromocyclododecane, and trisdibromo. Examples thereof include propyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-bis (2,3-dibromopropyl ether), and the like.
Examples of the flame retardant aid include organic peroxides such as 2,3-dimethyl-2,3-diphenylbutane, 3,4-dimethyl-3,4-diphenylhexane, dicumyl peroxide, and cumene hydroperoxide. It is done.
The content of the flame retardant and the flame retardant auxiliary in the modified resin particles is preferably 1.0 to 5.0% by mass and 0.1 to 2.0% by mass, respectively.

Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and glycerin diacetomonostearate, adipic acid esters such as diisobutyl adipate, and plasticizers such as coconut oil. .
The content of the plasticizer in the modified resin particles is preferably 0.1 to 3.0% by mass.

Examples of the binding inhibitor include calcium carbonate, silica, zinc stearate, aluminum hydroxide, ethylene bis stearamide, tricalcium phosphate, dimethyl silicon and the like.
Examples of the air conditioner include ethylene bis stearamide, polyethylene wax and the like.
As a crosslinking agent, 2,2-di-t-butylperoxybutane, 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t -Organic peroxides such as butylperoxyhexane.
Examples of the filler include synthetically or naturally produced silicon dioxide.

Examples of the lubricant include paraffin wax and zinc stearate.
Examples of the fusion accelerator include stearic acid, stearic acid triglyceride, hydroxystearic acid triglyceride, stearic acid sorbitan ester, and polyethylene wax.
Examples of the antistatic agent include polyoxyethylene alkylphenol ether, stearic acid monoglyceride, polyethylene glycol and the like.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.

[Step (B): Second polymerization step]
Next, the styrene monomer is polymerized while absorbing the styrene resin monomer.
In the second polymerization step, it is preferable to use together polymerization initiators having different 10-hour half-lives.
When the melting point of the polyolefin resin to be used is T ° C, the 10-hour half-life temperature (R1 ° C) of the first polymerization initiator is in the range of (T-40) to (T-20), and the second polymerization The 10 hour half-life temperature of the initiator is preferably in the range of (R1 + 5) to (R1 + 20).
In the second polymerization step, styrene occupying 5 to 80% by mass of the total monomer to be charged after the mixture of the monomer of the styrene resin and the monomer of the resin component derived from α-methylstyrene is added. It is preferable to add a monomer of a resin based on 40 to 80% by mass.

[Step (C): Repeated polymerization step]
Then, step (B) is optionally repeated.
The conditions are the same as in step (B).

(Average particle size)
The modified resin particles preferably have an average particle diameter of 0.8 to 2.5 mm.
If the average particle diameter of the modified resin particles is less than 0.8 mm, high foamability may not be obtained. On the other hand, when the average particle diameter of the modified resin particles exceeds 2.5 mm, the filling property of the pre-expanded particles during the molding process may be insufficient. A more preferable average particle diameter of the modified resin particles is 1.0 to 1.8 mm.

(3) Expandable particles The expandable particles of the present invention are obtained by impregnating the modified resin particles of the present invention with a foaming agent by a known method.
When the temperature at which the modified resin particles are impregnated with the foaming agent is low, it takes time to impregnate, and the production efficiency of the expandable particles may decrease. 50 to 130 ° C is preferable, and 60 to 100 ° C is more preferable.

(Foaming agent)
The foaming agent is preferably a volatile foaming agent and is not particularly limited as long as it is conventionally used for foaming polystyrene resins. For example, carbon such as isobutane, n-butane, isopentane, n-pentane, neopentane, etc. Examples include volatile foaming agents such as aliphatic hydrocarbons having a number of 5 or less, and butane-based foaming agents and pentane-based foaming agents are particularly preferable. In addition, pentane can be expected to act as a plasticizer.

The content of the foaming agent in the expandable particles is usually in the range of 2 to 10 mass%, preferably in the range of 3 to 10 mass%, particularly preferably in the range of 3 to 8 mass%.
When the content of the foaming agent is small, for example, less than 2% by mass, it may not be possible to obtain a low-density foam molded product from the foamable particles, and the effect of increasing the secondary foaming power during in-mold foam molding is obtained. Therefore, the appearance of the foamed molded product may deteriorate. On the other hand, when the content of the foaming agent is large, for example, it exceeds 10% by mass, the time required for the cooling step in the production process of the foamed molded article using the foamable particles becomes long and the productivity may be lowered.

(Foaming aid)
The foamable particles can contain a foaming aid together with the foaming agent.
The foaming aid is not particularly limited as long as it is conventionally used for foaming polystyrene resins. For example, aromatic organic compounds such as styrene, toluene, ethylbenzene, xylene, cyclohexane, methylcyclohexane, etc. Examples thereof include solvents having a boiling point of 200 ° C. or less under 1 atm, such as cycloaliphatic hydrocarbons, ethyl acetate, and butyl acetate.

The content of the foaming aid in the expandable particles is usually in the range of 0.3 to 2.5% by mass, and preferably in the range of 0.5 to 2% by mass.
When the content of the foaming aid is small, for example, less than 0.3% by mass, the plasticizing effect of the polystyrene resin may not be exhibited. On the other hand, if the content of the foaming aid is large and exceeds 2.5% by mass, the foamed molded product obtained by foaming the foamable particles may be shrunk or melted to deteriorate the appearance, or foamable. The time required for the cooling step in the production process of the foamed molded article using the particles may be long.

(Foaming)
The foamable particles of the present invention preferably have a foaming ratio of 30 times or more, more preferably 35 times or more after 1-minute foaming with a gauge pressure of 0.07 MPa steam.
The evaluation method will be described in Examples.

(4) Foamed particles The foamed particles of the present invention are obtained by pre-foaming the foamable particles of the present invention and, for example, heating them with steam (steam) with an introduced gauge pressure of 0.004 to 0.09 MPa in a sealed container. It is obtained by pre-foaming to a predetermined bulk density.
Examples of the method include batch-type foaming in which steam is introduced, continuous foaming, and release foaming under pressure, and when necessary, air may be introduced simultaneously with water vapor.

(The bulk density)
The expanded particles of the present invention preferably have a bulk density of 20 to 500 kg / m ³ .
When the bulk density of the expanded particles is less than 20 kg / m ³ , the expanded molded product tends to shrink and the appearance may be impaired, and the mechanical strength may not be sufficient. On the other hand, when the bulk density of the foamed particles exceeds 500 kg / m ³ , the merit of weight reduction as a foamed molded product may be impaired. A preferred bulk density of the expanded particles is 25 to 100 kg / m ³ .
The measuring method will be described in Examples.

(Average particle size)
The expanded particles of the present invention preferably have an average particle size of 1.5 to 7.5 mm.
When the average particle diameter of the expanded particles is less than 1.5 mm, the foamability at the time of foam molding is low, and the elongation of the surface of the molded article may be deteriorated. On the other hand, when the average particle diameter of the expanded particles exceeds 7.5 mm, the filling properties of the expanded particles at the time of molding may be insufficient. A more preferable average particle diameter of the expanded particles is 2.5 to 5.0 mm.

(5) Foam molded body The foam molded body of the present invention is obtained by foam-molding the foam particles of the present invention, for example, filling the foam particles into a mold (cavity) of a foam molding machine, and heating again to expand the foam particles. It is obtained by thermally fusing the foamed particles while foaming.

(Pressure adjustment during molding)
The pressure regulation during molding of the foamed molded article of the present invention, that is, the lowest vapor pressure at which a 90% fusion rate is obtained, is preferably 0.05 to 0.27 MPa in terms of gauge pressure.
If the pressure during molding is less than 0.05 MPa in gauge pressure, the steam control during molding may vary and the quality of the molded product may not be stable. On the other hand, if the pressure adjustment at the time of molding exceeds 0.27 MPa in gauge pressure, the amount of steam used at the time of molding increases and productivity may deteriorate, or equipment that can withstand high pressure use may be required. A preferable pressure during molding is 0.15 to 0.25 MPa in terms of gauge pressure.
The measuring method will be described in Examples.

(density)
The foamed molded product of the present invention preferably has a density of 20 to 500 kg / m ³ . If the density of the foamed molded product is less than 20 kg / m ³ , the impact resistance may not be sufficient. On the other hand, when the density of the foamed molded product exceeds 500 kg / m ³ , the effect of reducing the weight of the foamed molded product is limited. The bulk density of a preferable foamed molded product is 20 to 100 kg / m ³ .
The measuring method will be described in Examples.

(Dimensional change rate)
The foamed molded article of the present invention preferably has a dimensional change rate of less than 3.5%. A more preferable dimensional change rate is less than 2.0%.
The measuring method will be described in Examples.

(chemical resistance)
The foamed molded article of the present invention has chemical resistance such that the appearance does not change even after 24 hours exposure to oils such as engine oil and brake oil, and chemicals such as grease, washer fluid, gasoline, and light oil. The evaluation method will be described in Examples.

(Use)
The foamed molded product of the present invention can be used for various applications. Examples of the use include bumper core materials, automobile interior members, automobile exterior members, electronic parts, various industrial materials including glass, food cushioning materials and transport containers. In particular, since the foamed molded article of the present invention has high heat resistance, it is a part that is attached to a position close to the engine or the radiator, and is easily affected by the outside air temperature or the heat of the internal combustion engine, among the above applications. It can be suitably used for an automobile exterior member (bumper core material).
Here, “automobile” means a vehicle that includes a prime mover, a steering device, and the like, and can travel on the ground by using them. Also includes vehicles connected to overhead lines such as trolley buses.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, the following examples are only illustrations of this invention and this invention is not limited only to the following examples.
In Examples and Comparative Examples, raw material resins, obtained modified resin particles, expandable particles, expanded particles, and expanded molded articles were evaluated as follows.

<Melting point of polyolefin resin>
The melting point (° C.) is measured by the method described in JIS K7121: 1987 “Method for measuring the transition heat of plastic”.
That is, using a differential scanning calorimeter device (Seiko Denshi Kogyo Co., Ltd., model: DSC 6220), 7 mg of the sample was filled in the measurement container, and the nitrogen gas flow rate was 30 mL / min. The temperature is raised, lowered, and raised repeatedly at a temperature raising / lowering rate of ° C./min, and the melting peak temperature of the DSC curve at the second temperature rise is defined as the melting point (° C.).

<Mass average molecular weight (Mw) of the modified resin particles>
For the measurement, a gel permeation chromatography (GPC) apparatus (manufactured by Tosoh Corporation, model: HLC-8121GPC / HT) and a column (manufactured by Tosoh Corporation, model: TSKgel GMHhr-H (20) HT) are used. .
As measurement conditions, the column temperature is set to 140 ° C., and 1,2,4-trichlorobenzene is used as the 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 with a known molecular weight, and the mass average molecular weight (Mw) is determined as a polystyrene equivalent value.

<Foaming properties of expandable particles>
The mass a (g) of about 2 g of expandable particles is weighed with two significant figures after the decimal point. The weighed expandable particles are put in a container, and it is confirmed that the temperature in the foaming tank is 90 ° C. or less. The container in which the expandable particles are put in the foaming tank is put, and water vapor with a gauge pressure of 0.07 MPa (vapor temperature: 117 C)), the inside of the foaming tank is pressurized to raise the temperature in the foaming tank to 110 to 117 [deg.] C and heat foam. At this time, the heating time is set to 1 minute, and the expansion ratio of the expanded particles immediately after taking out from the expansion tank is measured. The heating time is from the time when the temperature in the foaming tank becomes 110 ° C. or higher. The expansion ratio (times) is obtained by putting expanded particles in a graduated cylinder, measuring the volume b (cm ³ ), and dividing the volume b by the mass a.
From the obtained expansion ratio, the expandability of the expandable particles is evaluated based on the following criteria.
○ (Good): Foaming factor of 35 times or more Δ (Slightly bad): Foaming factor of 30 times or more and less than 35 times × (Poor): Foaming factor of less than 30 times

<Bulk density of expanded particles>
The bulk density (kg / m ³ ) of the expanded particles is measured as follows.
First, the expanded particles are filled in a graduated cylinder to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one expanded particle reaches the scale of 500 cm ³ , the filling is finished. Next, the mass of the expanded particles filled in the measuring cylinder is weighed with two significant figures after the decimal point, and the bulk density of the expanded particles is calculated from the mass W (g) by the following formula.
Bulk density of expanded particles (kg / m ³ ) = W / 500 × 1,000

<Expansion multiple of expanded particles>
Based on the bulk density (kg / m ³ ) of the expanded particles, the expansion factor is calculated by the following formula.
Expansion multiple (times) = bulk particle bulk density × 1,000

<Pressure control during molding of foamed molded product>
The foamed particles are filled in a 400 mm × 300 mm × 30 mm mold of a foam molding machine, and the foamed particles are heat-fused while being heated with water vapor, and the foamed particles are heat-sealed to have a top surface of 400 mm long × 300 mm wide. Thus, a rectangular parallelepiped foam molded body having a thickness of 30 mm is obtained.
When heating with water vapor, the vapor pressure of the water vapor is changed from 0.08 MPa to 0.25 MPa in increments of 0.01 MPa, and water vapor is introduced for 40 seconds to perform a molding test.
As a result of the above molding, the obtained foamed molded product is evaluated according to the following criteria based on the lowest vapor pressure with a fusion rate of 90% or more. The lowest vapor pressure at which a 90% fusion rate is obtained is referred to as molding pressure adjustment.
The fusion rate is measured by the following procedure.

A cutting line having a length of 300 mm and a depth of about 5 mm is put along the horizontal direction with a cutter on the upper surface of a 30 mm-thick rectangular foam-shaped body having an upper surface of length 400 mm × width 300 mm. The foamed molded product is divided into two. And about the expanded particle of the fracture surface of the foamed molded product divided into two, the number of expanded particles broken in the expanded particle (a) and the number of expanded particles broken at the interface between the expanded particles (b) Measure and calculate the fusion rate (%) based on the following formula.
Fusing rate (%) = 100 × (a) / [(a) + (b)]

<Density of foam molding>
After molding, a test piece having a length of 75 × width of 300 × thickness of 35 mm was cut out from a foamed molded body dried at a temperature of 50 ° C. for 4 hours or more, and its mass a (kg) and volume b (m ³ ) were significant figures It measures so that it may become 3 digits or more, and calculates the density of a foaming molding based on a following formula.
Density of foamed molded product (kg / m ³ ) = a / b

<Heat dimensional change rate of foamed molded product>
The change in the heating dimension of the foamed molded product is measured according to the method B described in JIS K 6767: 1999 “Foamed Plastics-Polyethylene Test Method”, and the foamed molded product is evaluated from the obtained results.
Specifically, a test piece having a length of 150 mm, a width of 150 mm, and a height of 20 mm is cut out from the foamed molded body. Then, on the surface of the test piece, three straight lines with a length of 50 mm directed in the vertical direction are written in parallel with each other at intervals of 50 mm, and three straight lines with a length of 50 mm directed in the horizontal direction are parallel with each other. Fill in every 50mm interval. After that, the test piece was left in a hot air circulating dryer having a temperature of 95 ° C. for 168 hours and then taken out, and the test piece was taken under standard conditions (temperature 20 ± 2 ° C., humidity 65 ± 5%) for 1 hour. Leave it over.
Next, the lengths of the six straight lines entered on the surface of the test piece are measured, and the arithmetic average value L1 of the lengths of the six straight lines is calculated. Then, the degree of change S is calculated based on the following formula, and the absolute value of the degree of change S is defined as the heating dimensional change rate (%).
S = 100 × (L1-50) / 50
Moreover, based on the obtained heating dimensional change rate, the heating dimensional change (mm) of a structure having a length of 2,000 mm was assumed.

From the heating dimensional change rate of the obtained foamed molded product, the foamed molded product is evaluated based on the following criteria.
◎ (excellent): small dimensional change rate (0 ≦ S <2.0), excellent dimensional stability ○ (good): small dimensional change rate (2.0 ≦ S <3.5), dimensional stability △ (possible): Dimensional change rate is seen (3.5 ≦ S <4.0), but practical use is possible × (impossible): dimensional change rate is noticeable (4.0 <S) , Practical use is impossible

<Chemical resistance of foamed molded products>
A flat rectangular plate-shaped test piece having a length of 100 mm, a width of 100 mm, and a thickness of 20 mm is cut out from the foamed molded article, and left for 24 hours under conditions of a temperature of 23 ° C. and a humidity of 50%. In addition, a test piece is cut out from a foaming molding so that the upper surface whole surface of a test piece may be formed from the skin of a foaming molding. Next, 1 g of gasoline is uniformly applied to the upper surface of the test piece and left for 60 minutes under the conditions of a temperature of 23 ° C. and a humidity of 50%. Then, the chemical | medical agent is wiped off from the upper surface of a test piece, the upper surface of a test piece is visually observed, and it judges based on the following reference | standard.
About chemical resistance, the chemical resistance of a foaming molding is determined based on the following reference | standard.
○ (good): No change △ (possible): surface softening × (impossible): surface depression (shrinkage)

<Measurement method of residual monomer amount>
After precisely weighing 1 g of the modified resin particles in an Erlenmeyer flask, 25 ml of carbon disulfide and 1 ml of toluene as an internal standard solution are added and extracted at room temperature for 12 hours or more to obtain a sample solution. Using a gas chromatograph (manufactured by Shimadzu Corporation, model: GC-14A), the chromatogram of the obtained sample solution is measured under the conditions shown below, and the amount of residual monomer is quantified by an internal standard method.
(Measurement condition)
Apparatus: Gas chromatograph (manufactured by Shimadzu Corporation, model: GC-14A)
Column: Column (manufactured by GL Sciences Inc., inner diameter 3.2 mm × length 2.6 m)
Liquid phase (PEG-20M PT 25%)
Carrier (Chromosorb W)
Carrier particle size: lower limit 60 mesh / upper limit 80 mesh Column temperature: 105 ° C
Inlet temperature: 230 ° C
Detector temperature: 230 ° C
Detector: FID (hydrogen flame ion detector)
Carrier gas: nitrogen Carrier gas flow rate: 30 ml / min
Injection volume: 1.8 μL
Quantitative method: Internal standard method = Toluene

[Example 1]
(Preparation of seed particles)
Polypropylene resin PP (melting point 140 ° C .; manufactured by Prime Polymer Co., Ltd., brand: Prime Polypro F-744NP) is supplied to an extruder (Toshiba Machine Co., Ltd., model: SE-65) and melt-kneaded at 230 to 250 ° C. Then, it was granulated by an underwater cutting method and cut into an oval shape (egg) to obtain seed particles. The average mass of the seed particles was 0.6 mg.

(First polymerization)
Next, in a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 g of pure water. Thus, a dispersion medium was obtained. In the resulting dispersion medium, 800 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, 260 g of styrene and α-methyl prepared by dissolving 0.6 g of dicumyl peroxide (10 hour half-life temperature 116.4 ° C.) as a polymerization initiator in advance in the obtained suspension were prepared. A mixture of 85 g of styrene was added dropwise over 30 minutes. After completion of dropping, the seed particles were impregnated (absorbed) by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
Next, the temperature of the first polymerization reaction liquid is lowered (cooled) to 125 ° C., and 10 dispersions prepared in advance by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water are prepared. It was added dropwise over a period of time. Thereafter, 2.7 g of dicumyl peroxide (10-hour half-life temperature 116.4 ° C.) as a polymerization initiator and 3.7 g of di-tert-butyl peroxide (10-hour half-life temperature 123.7 ° C.) were dissolved in advance. A mixture of 520 g of styrene, 215 g of α-methylstyrene and 0.24 g of divinylbenzene prepared previously was added dropwise over 7 hours. After completion of the dropping, 120 g of styrene was dropped over 1 hour while maintaining the temperature at 125 ° C. Thereafter, the seed particles were impregnated and polymerized by holding for 1 hour. After the polymerization, the temperature was raised to 140 ° C. and kept at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles and polystyrene: 40/60).

(Production of expandable particles)
Subsequently, it cooled to 30 degrees C or less, and took out the modified resin particle from the autoclave.
The resulting modified resin particles (2,000 g), water (2,000 g), and sodium dodecylbenzenesulfonate (2.0 g) as a surfactant were again placed in a 5-liter autoclave equipped with a stirrer. Furthermore, 300 g of butane (n-butane: i-butane = 7: 3) (520 mL, 15 parts by mass with respect to 100 parts by mass of the modified resin particles) was injected into the autoclave as a foaming agent. After the injection, the temperature was raised to 70 ° C., and stirring was continued at this temperature for 4 hours to obtain 2200 g of expandable particles.
Then, it cooled to 30 degrees C or less, taken out the foamable particle from the autoclave, and made it dehydrated and dried.

(Production of expanded particles)
Next, while confirming the foamability of the resulting foamable particles, 1,000 g of the foamable particles was put into a 40-liter canister pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., model: PSX40) and placed in the can. Water vapor with a gauge pressure of 0.07 MPa was introduced and heated, and pre-foamed to a bulk density of 25 kg / m ³ to obtain expanded particles.

(Production of foamed molded product)
Next, the obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day, and then filled into a cavity of a mold having an internal cavity of 400 mm × 300 mm × 30 mm.
Subsequently, 0.24 MPa of water vapor is introduced into the mold for 40 seconds and heated, and then cooled until the maximum surface pressure of the foamed molded article is reduced to 0.01 MPa, and a density of 25 kg / min with a fusion rate of 90% or more is obtained. An m ³ foamed molded article was obtained, and various physical properties were evaluated.
The appearance of the obtained foamed molded product was good.
Molding processability (dimensional change rate) and chemical resistance of the obtained foamed molded product were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

[Comparative Example 1]
(Preparation of seed particles)
In the same manner as in Example 1, seed particles having an average mass of 0.6 mg were obtained.
(First polymerization)
Next, in a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 g of pure water. Thus, a dispersion medium was obtained. In the resulting dispersion medium, 800 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, 340 g of styrene prepared by dissolving 0.6 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise to the obtained suspension over 30 minutes. After completion of dropping, the seed particles were impregnated (absorbed) by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
Next, the temperature of the first polymerization reaction liquid is lowered (cooled) to 125 ° C., and 10 dispersions prepared in advance by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water are prepared. It was added dropwise over a period of time. Thereafter, 860 g of styrene prepared by dissolving 4.0 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise over 4 hours. After completion of the dropping, the seed particles were impregnated and polymerized by maintaining at 125 ° C. for 1 hour. After the polymerization, the temperature was raised to 140 ° C., and polymerization was carried out by maintaining at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles to polystyrene: 40/60).

(Production of expandable particles)
Next, in the same manner as in Example 1, 2,200 g of defoamed and dried expandable particles were obtained.
(Production of expanded particles)
Next, in the same manner as in Example 1, the foamability of the foamable particles obtained was confirmed, and foamed particles were obtained.

(Production of foamed molded product)
Next, the obtained expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day, and then filled into a cavity of a mold having an internal cavity of 400 mm × 300 mm × 30 mm.
Next, 0.19 MPa of water vapor was introduced into the mold for 20 seconds and heated, and then cooled until the maximum surface pressure of the foamed molded product was reduced to 0.01 MPa. A density of 25 kg / An m ³ foamed molded article was obtained, and various physical properties were evaluated.
The appearance of the obtained foamed molded product was good.
Molding processability (dimensional change rate) and chemical resistance of the obtained foamed molded product were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

[Example 2]
The blending amount of the mixture of styrene and α-methylstyrene in (first polymerization) is 287.5 g and 57.5 g, respectively, and the blending amount of the mixture of styrene and α-methylstyrene used in (second polymerization) The foamed molded products were obtained in the same manner as in Example 1 except that the weight was 612.5 g and 122.5 g, respectively, and their physical properties including intermediate products were evaluated.

[Example 3]
Except for changing (first polymerization) and (second polymerization) as follows, foamed molded articles were obtained in the same manner as in Example 1, and their physical properties including intermediate products were evaluated.
(First polymerization)
In a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 g of pure water and dispersed. A medium was obtained. In the resulting dispersion medium, 900 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, a mixture of 278 g of styrene and 107 g of α-methylstyrene prepared by dissolving 0.7 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise to the obtained suspension over 30 minutes. . After completion of dropping, the seed particles were impregnated with styrene by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
The temperature of the first polymerization reaction liquid was lowered to 125 ° C. (cooled), and a dispersion prepared by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water in advance was taken for 10 minutes. And dripped. Thereafter, 2.3 g of dicumyl peroxide as a polymerization initiator and 3.4 g of di-tert-butyl peroxide were prepared and dissolved in 437 g of styrene, 168 g of α-methylstyrene and 0.22 g of divinylbenzene. The mixture was added dropwise over 7 hours. After completion of dropping, 110 g of styrene was added dropwise over 1 hour while maintaining at 125 ° C. Thereafter, the seed particles were impregnated and polymerized by holding for 1 hour. After the polymerization, the temperature was raised to 140 ° C. and held at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles to polystyrene: 45/55).

[Example 4]
(Second polymerization) In the same manner as in Example 3 except that divinylbenzene was not used, foamed molded articles were obtained, and their physical properties including intermediate products were evaluated.

[Example 5]
Except for changing (first polymerization) and (second polymerization) as follows, foamed molded articles were obtained in the same manner as in Example 1, and their physical properties including intermediate products were evaluated.
(First polymerization)
In a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 g of pure water and dispersed. A medium was obtained. In the resulting dispersion medium, 600 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, a mixture of 186 g of styrene and 72 g of α-methylstyrene prepared by dissolving 0.5 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise to the obtained suspension over 30 minutes. . After completion of dropping, the seed particles were impregnated with styrene by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
The temperature of the first polymerization reaction liquid was lowered to 125 ° C. (cooled), and a dispersion prepared by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water in advance was taken for 10 minutes. And dripped. Thereafter, 3.0 g of dicumyl peroxide as a polymerization initiator and 4.0 g of di-tert-butyl peroxide were prepared and dissolved in 724 g of styrene, 278 g of α-methylstyrene and 0.28 g of divinylbenzene. The mixture was added dropwise over 9 hours. After the completion of dropping, 140 g of styrene was dropped over 1.5 hours while maintaining at 125 ° C. Thereafter, the seed particles were impregnated and polymerized by holding for 1 hour. After the polymerization, the temperature was raised to 140 ° C. and kept at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles to polystyrene: 30/70).

[Example 6]
In (preparation of seed particles), using polyolefin-based resin PE1 (melting point: 126 ° C .; manufactured by Ube Maruzen Polyethylene Co., Ltd., brand: Umerit 140HK), dropping of a mixture of styrene and α-methylstyrene in (second polymerization) Carried out at 115 ° C. and in the (second polymerization) 2.7 g of dicumyl peroxide and 3.7 g of di-tert-butyl peroxide as t-butyl peroxybenzoate (10-hour half-life temperature) (104.3 ° C.) Except for changing to 3.0 g and dicumyl peroxide 2.0 g, a foamed molded product was obtained in the same manner as in Example 1, and the physical properties including intermediate products were evaluated.

[Comparative Example 2]
The blending amount of styrene and α-methylstyrene in (first polymerization) is 326 g and 19 g, respectively, and the blending amount of styrene and α-methylstyrene in (second polymerization) is 694 g and 41 g, respectively. In the same manner as in Example 1 except that the foamed molded article was obtained, and the physical properties including intermediate products were evaluated.

[Comparative Example 3]
The blending amount of styrene and α-methylstyrene in (first polymerization) is 171 g and 214 g, respectively, and the blending amount of styrene and α-methylstyrene in (second polymerization) is 269 g and 336 g, respectively. In the same manner as in Example 3 except that, foamed molded articles were obtained, and their physical properties including intermediate products were evaluated.

[Comparative Example 4]
In the same manner as in Example 1 except that polyolefin resin PE2 (melting point: 121 ° C .; brand name: Harmolex NF444A) is used in (preparation of seed particles), a foam molded article is obtained, and an intermediate product is obtained. Their physical properties were evaluated.
In Examples 1 to 3, the residual monomer amount of the modified resin particles was measured.

From the results in Tables 1 and 2, the following can be understood.
It turns out that the foaming molded object of Examples 1-6 has favorable moldability and the outstanding heat resistance compared with the foaming molded object of Comparative Examples 1-4.
Since Comparative Example 1 does not use α-methylstyrene, the moldability is excellent but the heat resistance is poor. Moreover, when there is little usage-amount of (alpha) -methylstyrene like the comparative example 2, the heat-resistant improvement effect is not enough. On the other hand, when α-methylstyrene is excessively added as in Comparative Example 3, the foamability is remarkably lowered, and the effect of reducing the weight, which is an advantage of the foam, cannot be obtained.
Furthermore, when polyolefin having a low melting point is used, even when the present invention is used as in Comparative Example 4, it can be seen that the heat resistance is insufficient.

[Example 7]
A foamed molded article was obtained in the same manner as in Example 1 except that (preparation of seed particles) was performed as follows, and their physical properties including intermediate products were evaluated.
Polypropylene resin PP (melting point 140 ° C .; manufactured by Prime Polymer Co., Ltd., Brand: Prime Polypro F-744NP) 100 parts by mass and 45% by mass-containing carbon black masterbatch (PP-RM10H381 manufactured by Dainichi Seika Kogyo Co., Ltd.) 12.5 mass The part is supplied to an extruder (made by Toshiba Machine Co., Ltd., model: SE-65), melt-kneaded at 230 to 250 ° C., granulated by an underwater cutting method, and cut into an oval (egg-like) seed particle. Obtained. The average mass of the seed particles was 0.6 mg.

[Example 8]
A foamed molded article was obtained in the same manner as in Example 3 except that (preparation of seed particles) was made in the same manner as in Example 7, and their physical properties including intermediate products were evaluated.

[Example 9]
Except for changing (preparation of seed particles), (first polymerization) and (second polymerization) as follows, in the same manner as in Example 1, foamed molded articles were obtained, including intermediate products. The physical properties of were evaluated.
(Preparation of seed particles)
Polypropylene resin PP (melting point 140 ° C .; manufactured by Prime Polymer Co., Ltd., Brand: Prime Polypro F-744NP) 100 parts by mass and 45% by mass-containing carbon black masterbatch (PP-RM10H381 manufactured by Dainichi Seika Kogyo Co., Ltd.) 12.5 mass The part is supplied to an extruder (made by Toshiba Machine Co., Ltd., model: SE-65), melt-kneaded at 230 to 250 ° C., granulated by an underwater cutting method, and cut into an oval (egg-like) seed particle. Obtained. The average mass of the seed particles was 0.6 mg.

(First polymerization)
Next, in a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 g of pure water. Thus, a dispersion medium was obtained. In the resulting dispersion medium, 800 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, 260 g of styrene and α-methyl prepared by dissolving 0.6 g of dicumyl peroxide (10 hour half-life temperature 116.4 ° C.) as a polymerization initiator in advance in the obtained suspension were prepared. A mixture of 85 g of styrene was added dropwise over 30 minutes. After completion of dropping, the seed particles were impregnated (absorbed) by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
Next, the temperature of the first polymerization reaction liquid is lowered (cooled) to 125 ° C., and 10 dispersions prepared in advance by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water are prepared. It was added dropwise over a period of time. Thereafter, 1.7 g of dicumyl peroxide (10-hour half-life temperature 116.4 ° C.) as a polymerization initiator and 3.7 g of di-tert-butyl peroxide (10-hour half-life temperature 123.7 ° C.) are dissolved in advance. A mixture of 160 g of styrene, 215 g of α-methylstyrene and 0.24 g of divinylbenzene prepared previously was added dropwise over 4 hours. After completion of dropping, 480 g of styrene prepared by dissolving 1.0 g of dicumyl peroxide (10-hour half-life temperature 116.4 ° C.) was added dropwise over 3 hours while maintaining the temperature at 125 ° C. Thereafter, the seed particles were impregnated and polymerized by holding for 1 hour. After the polymerization, the temperature was raised to 140 ° C. and kept at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles and polystyrene: 40/60).

[Example 10]
Except that the (first polymerization) and (second polymerization) were changed as follows, foamed molded articles were obtained in the same manner as in Example 9, and their physical properties including intermediate products were evaluated.
(First polymerization)
In a 5 liter autoclave with a stirrer (manufactured by Nitto High Pressure Co., Ltd.), 40 g of magnesium pyrophosphate as a dispersant and 0.6 g of sodium dodecylbenzenesulfonate as a surfactant are dispersed in 2,000 kg of pure water and dispersed. A medium was obtained. In the resulting dispersion medium, 900 g of seed particles were dispersed at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Next, a mixture of 165 g of styrene and 220 g of α-methylstyrene prepared by dissolving 0.7 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise to the obtained suspension over 30 minutes. . After completion of dropping, the seed particles were impregnated with styrene by holding for 30 minutes. After impregnation, the temperature was raised to 140 ° C. and maintained at this temperature for 2 hours to polymerize styrene in the seed particles (first polymerization).

(Second polymerization)
The temperature of the first polymerization reaction liquid was lowered to 125 ° C. (cooled), and a dispersion prepared by dispersing 3.0 g of sodium dodecylbenzenesulfonate as a surfactant in 20 g of pure water in advance was taken for 10 minutes. And dripped. Thereafter, 2 g of a mixture of 55 g of α-methylstyrene and 0.22 g of divinylbenzene prepared by dissolving 0.7 g of dicumyl peroxide and 1.2 g of di-tert-butyl peroxide as a polymerization initiator in advance were prepared. It was dripped over time. After the completion of dropping, 660 g of styrene prepared by dissolving 3.0 g of dicumyl peroxide as a polymerization initiator in advance was added dropwise over 4 hours while maintaining the temperature at 125 ° C. Thereafter, the seed particles were impregnated and polymerized by holding for 1 hour. After the polymerization, the temperature was raised to 140 ° C. and held at this temperature for 3 hours to obtain 2,000 g of modified resin particles (mass ratio of seed particles to polystyrene: 45/55).
In Examples 9 and 10, the residual monomer amount of the modified resin particles was measured.

From the results of Tables 3 and 4, the following can be understood.
It can be seen that even the carbon-containing foamed molded articles of Examples 7 and 8 can obtain good heat resistance by the α-methylstyrene modification.
As in Examples 9 and 10, it can be seen that the residual monomer in the obtained foamed molded article can be reduced by adjusting the addition amount of the styrene resin monomer in the second polymerization step.

Claims (11)

Including 100 to 300 parts by mass of polystyrene resin with respect to 100 parts by mass of polyolefin resin,
The polyolefin resin has a melting point of 124 to 145 ° C .;
The styrene-modified polyolefin resin particles, wherein the polystyrene resin contains 10 to 35% by mass of a resin component derived from α-methylstyrene.   The styrene-modified polyolefin resin particles according to claim 1, wherein the styrene-modified polyolefin resin particles have a polystyrene-equivalent weight average molecular weight Mw of 50,000 to 250,000.   The styrene-modified polyolefin resin particles according to claim 1 or 2, wherein the modified polyolefin resin particles contain 1.5 to 5.0% by mass of carbon black.   The styrene-modified polyolefin resin particles according to claim 3, wherein the polyolefin resin contains 3.0 to 10.0% by mass of carbon black.   The resin component derived from an aromatic polyfunctional vinyl monomer copolymerizable with 0.01 to 0.1% by mass of a styrene monomer with respect to the polystyrene resin. The styrene-modified polyolefin resin particles according to any one of the above.   Expandable particles comprising the styrene-modified polyolefin resin particles according to any one of claims 1 to 5 and a foaming agent.   Expanded particles obtained by pre-expanding the expandable particles according to claim 6.   A foam-molded product obtained by foam-molding the foamed particles according to claim 7.   The automobile exterior material comprised with the foaming molding of Claim 8. A method for producing a styrene-modified polyolefin resin particle according to any one of claims 1 to 5,
(A) Dispersing seed particles composed of a polyolefin resin in an aqueous medium containing a dispersant, absorbing the styrene monomer in the seed particles, and then heating to polymerize the styrene monomer. 1 polymerization step;
(B) Then, a second polymerization step of polymerizing the styrene monomer while absorbing the styrene monomer is included, or the steps (A) and (B) are (C) then the step The manufacturing method of the styrene modified polyolefin resin particle characterized by further including the process of repeating (B).   In the step (B), after adding a styrene monomer containing a monomer of a resin component derived from α-methylstyrene, a styrene monomer that accounts for 5 to 80% by mass of the total monomers to be charged The manufacturing method of the styrene modified polyolefin resin particle of Claim 10 which adds a body.