JP6262114B2 - Method for producing composite resin particles - Google Patents

Description

  The present invention relates to a method for producing composite resin particles. More specifically, the present invention relates to the deodorization of odors derived from the components contained in the resin particles, which is necessary when foam-molding styrene composite polyolefin resin particles using a foaming agent to produce a desired foam-molded article. The present invention relates to a method for producing composite resin particles that can reduce or omit the steps.

Foamed molded articles 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 polystyrene composite resin particles having the characteristics of the two different resins and foamed molded products using them have been proposed.
However, an odor derived from the components contained in the foamed molded product may be generated. Particularly when the foamed molded product is used for automobiles, its regulation is strict and some deodorizing process is required, and various technologies have been proposed. ing.

For example, in JP2013-123851A (Patent Document 1), composite resin particles for producing a foamed molded article containing a polyolefin-based resin and a polystyrene-based resin were blown from the bottom of the container in a container ( Disclosed is a method for reducing odor derived from the raw material and manufacturing method of composite resin particles by flowing with a gas at T-40) ° C. to (T-10) ° C. (T is the softening temperature of the composite resin particles). .
According to this technique, the odor in the composite resin particles can be reduced to an odor level value of 200 or less in a measurement atmosphere at 55 ° C.

  Further, in Japanese Patent No. 523297 (Patent Document 2), in a pressure vessel, modified polystyrene resin particles obtained by impregnating a polyolefin resin with a styrene monomer and polymerizing and modifying the particles are placed, Then, when the Vicat softening temperature of the modified polystyrene resin particles is T ° C, the temperature in the pressure vessel is set to (T-60) ° C to (T-30) ° C, and the pressure in the pressure vessel is 10 MPa or more. Carbon dioxide is injected into the pressure vessel so that the volume of the modified polystyrene resin particles / the volume of the pressure vessel is 1/3 or less, and the modified polystyrene resin is held for 1 hour or more. After the particles are impregnated with carbon dioxide, the pressure in the pressure vessel is released, and the modified polystyrene that performs the process of extracting and removing the volatile matter and odor remaining in the modified polystyrene resin particles at least twice Method for producing a down-based resin particles is disclosed.

Furthermore, in Japanese Patent No. 5528428 (Patent Document 3), composite resin particles containing a polyolefin resin and a polystyrene resin at a specific ratio were blown from the bottom of the container (T-40) ° C. Disclosed is a method of reducing odor derived from the raw material and production method of composite resin particles by flowing with a gas of ~ (T-10) ° C (T is the softening temperature of the composite resin particles).
According to this technique, the average value of the odor intensity of the foamed molded product obtained by impregnating the composite resin particles with reduced odor after impregnating the foaming agent and then pre-foaming and then in-mold molding is increased by 100,000 times. It is said that it can be reduced to 3 or less in an odor test in which the odor of isovaleric acid diluted to 3 is used as a standard odor of 3 in 0 to 5 odor intensity. As a result, it is said that it is possible to obtain a foamed molded product that can be used for automotive interior applications that require a lower level of odor content than conventional ones.

Patent No. 4282000 (Patent Document 4) includes expandable styrene resin particles having a total content of four types of organic volatile components of toluene, xylene, ethylbenzene, and styrene monomer of 0.2% by weight or less. The foamable styrene resin particles containing 0.1 to 3 parts by weight of a halogen-based flame retardant and 0.1 to 3 parts by weight of a phosphate ester compound with respect to 100 parts by weight of the base resin of the resin particles Is disclosed.
According to this technology, the foamability that can provide a foamed molded article having excellent mechanical properties, flame retardancy, and heat insulation properties despite the low content of volatile components that cause chemical sensitivity. It is said that styrene resin particles are obtained.

JP2013-123851A Japanese Patent No. 523297 Japanese Patent No. 5528428 Japanese Patent No. 4282000

However, in the prior arts such as Patent Documents 1 to 3, a deodorizing step for odor derived from the resin particle-containing component is essential.
In particular, when the foamed molded product is used for automobiles, the regulation is severe, and reduction or omission of the deodorizing process in the manufacturing process is required.
In addition, although patent document 4 is a technique which makes the subject reduction of an organic volatile component, it is a technique regarding the polystyrene-type resin which makes flame retardance a main subject.

  Then, this invention makes it a subject to solve the said subject and to provide the manufacturing method of the composite resin particle which makes it possible to reduce or abbreviate | omit the deodorizing process of the odor originating in the component contained in the resin particle.

  The inventor of the present invention, as a result of intensive studies to solve the above-mentioned problems, uses a polymerization initiator having a specific molecular structure in the polymerization of monomers in the production process of composite resin particles, and adjusts the temperature. By polymerizing the monomer under conditions, it was found that the deodorizing step of odor derived from the resin particle-containing component can be reduced or omitted, and the present invention has been completed.

Thus, according to the present invention, it is a method for producing composite resin particles containing 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of a polyolefin resin.
(A) A step of dispersing the polyolefin resin particles in an aqueous medium containing a dispersant to obtain a suspension;
(B) Next, a styrene monomer and a polymerization initiator are added to the obtained suspension, and the styrene monomer is heated to a temperature at which the styrene monomer is not substantially polymerized. (C) Next, when the melting point of the polyolefin resin is T ° C., the temperature is (T−10) ° C. to (T + 20) ° C. Or a step of polymerizing the styrenic monomer to obtain composite resin particles by heating the obtained reaction liquid, or (D) and then the step (C) ), A styrene monomer and a polymerization initiator are added, and when the melting point of the polyolefin resin is T ° C, the temperature is (T-25) to (T + 15) ° C. The obtained reaction solution is heated to polymerize the styrene monomer to form a composite tree. Further comprising the step of obtaining the particles,
The polymerization initiator has the following formula:

(In the formula, R _{1 to} R ₃ and R ^′ _{1 to} R ^′ ₃ are linear alkyl groups in which the total number of carbon atoms of each substituent is 6 to 20, and R ₁ , R ₃ , R ^′ ₁ And R ^′ ₃ are the same, and R ₂ and R ^′ ₂ are the same)
The manufacturing method of the composite resin particle characterized by being represented by these is provided.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite resin particle which makes it possible to reduce or abbreviate | omit the deodorizing process of the odor originating in the content component of the resin particle can be provided.
The above effect is considered to be due to the fact that the polymerization initiator used does not have a structure capable of causing odor such as a benzene ring in the molecule.
The inventor of the present invention tested using a polymerization initiator having a structure containing a benzene ring in the molecule, which has been widely used in the past, and confirmed the aromatic odor in the volatile components of the resin after polymerization. did.

Moreover, the method for producing the composite resin particles of the present invention comprises:
(1) the polymerization initiator is selected from di-t-butyl peroxide, di-t-amyl peroxide and di-t-hexyl peroxide; and (2) the polymerization initiator is a step (B) and (D In the case of satisfying at least one condition of 0.05 to 0.5% by mass with respect to each of the styrenic monomers added at the same time, the above-described excellent effects are further exhibited.

Furthermore, the method for producing the composite resin particles of the present invention includes:
(3) When the polyolefin resin particles are carbon black-containing polyolefin resin particles containing 1.5 to 17.0% by mass of carbon black with respect to the polyolefin resin,
(4) After step (C) or (D), (E) 1.5-6.0 masses as a flame retardant with respect to 100 mass parts of said composite resin particles in the liquid mixture containing the said composite resin particles. Parts of tri (2,3-dibromopropyl) isocyanurate or bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, and 0.1 to 2.0 as flame retardant aid In the case of further comprising a step of adding a part by weight of 2,3-dimethyl-2,3-diphenylbutane to flame retardant the composite resin particles,
In addition to the above-described excellent effects, a method for producing composite resin particles capable of providing a foamed molded article that exhibits excellent blackness and excellent flame retardancy (slow flame retardancy) is provided.

[Production method of composite resin particles]
The method for producing composite resin particles of the present invention is a method for producing composite resin particles containing 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of a polyolefin resin.
(A) A step of dispersing the polyolefin resin particles in an aqueous medium containing a dispersant to obtain a suspension;
(B) Next, a styrene monomer and a polymerization initiator are added to the obtained suspension, and the styrene monomer is heated to a temperature at which the styrene monomer is not substantially polymerized. (C) Next, when the melting point of the polyolefin resin is T ° C., the temperature is (T−10) ° C. to (T + 20) ° C. Or a step of polymerizing the styrenic monomer to obtain composite resin particles by heating the obtained reaction liquid, or (D) and then the step (C) ), A styrene monomer and a polymerization initiator are added, and when the melting point of the polyolefin resin is T ° C, the temperature is (T-25) to (T + 15) ° C. The obtained reaction solution is heated to polymerize the styrene monomer to form a composite tree. Further comprising the step of obtaining the particles,
The polymerization initiator has the following formula:

(In the formula, R _{1 to} R ₃ and R ^′ _{1 to} R ^′ ₃ are linear alkyl groups in which the total number of carbon atoms of each substituent is 6 to 20, and R ₁ , R ₃ , R ^′ ₁ And R ^′ ₃ are the same, and R ₂ and R ^′ ₂ are the same)
It is the dialkyl peroxide represented by these.

The characteristic of the manufacturing method of the composite resin particle of this invention exists in the temperature control at the time of superposition | polymerization of the polymerization initiator used by process (B) and (D), and a styrene monomer.
First, the polymerization initiator will be described, and each step including temperature adjustment during polymerization will be described sequentially.

The polymerization initiator used in the present invention is a dialkyl peroxide represented by the above formula.
The substituents R _{1 to} R ₃ and R ^′ _{1 to} R ^′ ₃ in the formula are linear alkyl groups in which the total number of carbon atoms of each substituent is 6 to 20, and R ₁ , R ₃ , R ^′. ₁ and R ^′ ₃ are the same, and R ₂ and R ^′ ₂ are the same.
Examples of the substituent include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl and octyl.

Dialkyl peroxides include di-t-butyl peroxide (R _{1 to} R ₃ , R ^′ _{1 to} R ^′ ₃ = methyl) and di-t-hexyl peroxide (R ₁ , R ₃ , R ^′ ₁ and R). ^' ₃ = methyl, R ₂ and R ^' ₂ = propyl), which are marketed by NOF Corporation under the trade names “Perbutyl D” and “Perhexyl D”, respectively. Can do. Further, di-t-amyl peroxide (R ₁ , R ₃ , R ^′ ₁ and R ^′ ₃ = methyl, R ₂ and R ^′ ₂ = ethyl) can be mentioned. It is marketed as “Lupelox DTA” and can be suitably used.

  The polymerization initiator used in the present invention has a linear alkyl group in its side chain and generates a tertiary alkoxy radical. The polymerization initiator used in the present invention does not include other functional groups such as a benzene ring that is included in conventional polymerization initiators such as dicumyl peroxide and t-butyl hydroperoxide. It is considered that the odor in the polymerized composite resin particles can be greatly reduced. Therefore, the cost and time required for the deodorization process can be reduced.

It is preferable that a polymerization initiator is 0.05-0.5 mass% with respect to each of the styrene-type monomer added simultaneously in process (B) and (D).
When the addition amount of the polymerization initiator is less than 0.05% by mass with respect to the styrene monomer, the polymerization of the styrene monomer is not completed and remains in the composite resin particles as a volatile component, which may cause odor. May be. On the other hand, when the addition amount of the polymerization initiator exceeds 0.5% by mass with respect to the styrene monomer, the polymerization rate increases, so that the polymerization is performed before the styrene monomer is impregnated in the polyolefin resin. The reaction proceeds, and preferable physical properties such as generation of polymer powder, blackness, and chemical resistance may not be obtained. A preferable addition amount of the polymerization initiator is 0.1 to 0.45% by mass.

[Step (A)]
First, polyolefin resin particles (hereinafter also referred to as “polyolefin resin particles”) are dispersed in an aqueous medium containing a dispersant to obtain a suspension.
(Polyolefin resin particles)
The polyolefin resin (PO) constituting the polyolefin resin particles is not particularly limited as long as it is a polyolefin resin used in the technical field, and includes a resin obtained by a known polymerization method, which is crosslinked. May be. For example, polyethylene resins such as branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and cross-linked products of these polymers And polypropylene resins such as propylene, ethylene-propylene random copolymer, propylene-1-butene copolymer, and ethylene-propylene-butene random copolymer. These low-density polyethylene preferably has a density of 0.90~0.94g / cm ^3, more preferably having a density of 0.91~0.94g / cm ^3, 0.91~0. Most preferably, it has a density of 93 g / cm ³ . Specifically, commercially available products such as those used in the examples can be mentioned.

  The polyolefin resin particles become core resin particles (also referred to as “seed particles”), and can be obtained, for example, by melt-kneading the polyolefin resin with an extruder, extruding it into a strand shape, and cutting it to a desired particle diameter. . When carbon black is used as a colorant described later, it is preferably added and kneaded here.

In a die for obtaining core resin 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 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 at 2.0 to 6.0 mm. It is preferable.
Desired core resin particles can be obtained by combining an extruder and a die having the screw structure, extrusion conditions, and underwater cutting conditions.
Moreover, the said core resin particle can contain additives, such as compatibilizer of a polyolefin resin and a polystyrene resin, a bubble regulator, and an antistatic agent, unless the effect of this invention is impaired.

  The particle diameter of the core resin particles can be adjusted as appropriate according to the average particle diameter of the composite 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.

(Dispersant)
Further, in the above production method, a dispersant (suspension stabilizer) is used to stabilize the dispersibility of the styrene monomer droplets and the core resin particles. Such a suspension stabilizer is not particularly limited as long as it is conventionally used for suspension polymerization of a styrene monomer, and examples thereof include water-soluble substances such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone. And a poorly soluble inorganic compound such as tribasic calcium phosphate, hydroxyapatite, and magnesium pyrophosphate.
Moreover, when using a poorly soluble inorganic compound, an anionic surfactant is used together normally.

  Examples of such anionic surfactants include fatty acid soaps, N-acyl amino acids or salts thereof, carboxylates such as alkyl ether carboxylates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, and dialkyl sulfosuccinate esters. Sulfates such as alkyl sulfoacetates, α-olefin sulfonates, higher alcohol sulfates, secondary higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, etc. And phosphoric acid ester salts such as alkyl ether phosphoric acid ester salts and alkyl phosphoric acid ester salts.

(Other ingredients)
The composite 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 a range that does not impair the physical properties. Additives such as antistatic agents and spreading agents may be added.

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 composite resin particles of the present invention preferably contain 0.5 to 5.0% by mass of carbon black.
When the content of carbon black is less than 0.5% by mass, sufficient blackness may not be imparted to the foamed molded product. On the other hand, if the carbon black content exceeds 5.0% by mass, it may be difficult to ensure the flame retardancy of the foamed molded product. The carbon black content of the preferred composite resin particles is 1.5 to 3.0% by mass.
When using carbon black-containing polyolefin resin particles as in the examples described later, the polyolefin resin particles preferably contain 1.5 to 17.0% by mass of carbon black based on the polyolefin resin. . If the content of carbon black is within this range, the content of carbon black in the composite resin particles is within the above range, although it depends on the amount of styrene monomer used.

Examples of the flame retardant include tri (2,3-dibromopropyl) isocyanurate , bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, tetrabromocyclooctane, hexabromocyclododecane, tris Examples include dibromopropyl 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.

In particular, the composite resin particle of the present invention, and thus the expanded particle impregnated with a foaming agent, is used as a flame retardant with respect to 100 parts by mass of the expanded particle as 1.5 to 6.0 parts by mass of tri ( 2,3-dibromopropyl) isocyanurate or bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, and 0.1 to 2.0 parts by weight of 2 as a flame retardant aid. , 3-dimethyl-2,3-diphenylbutane is preferably further contained.
As a method of adding the flame retardant and the flame retardant aid, for example, as described in the step (E) and examples described later, the flame retardant and the flame retardant aid are added to the suspension of the composite resin particles, and heating is performed. The method of stirring and mixing under is mentioned.

If the addition amount of the flame retardant is less than 1.5 parts by mass, the flame retardancy may not be sufficiently imparted. On the other hand, when the addition amount of the flame retardant exceeds 6.0 parts by mass, the heat resistance of the foamed molded product may be lowered.
A preferable addition amount of the flame retardant is 2.0 to 5.0 parts by mass with respect to 100 parts by mass of the foamed particles.
If the addition amount of the flame retardant aid is less than 0.1 parts by mass, the flame retardancy may not be sufficiently imparted. On the other hand, when the addition amount of the flame retardant aid exceeds 2.0 parts by mass, the heat resistance of the foamed molded product may be lowered.
The addition amount of a preferable flame retardant aid is 1.0 to 2.0 parts by mass with respect to 100 parts by mass of the expanded particles.

The composite resin particles can contain a plasticizer having a boiling point exceeding 200 ° C. under 1 atm in order to maintain good foam moldability even when the pressure of water vapor used at the time of heat foaming is low.
Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid esters, 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 composite 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 silicon dioxide produced synthetically or naturally.

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.

(Stirring)
The power required for stirring (Pv) required to stir the aqueous medium 1 m ³ including the core resin particles, the styrenic monomer, and other dispersions and dissolved substances as required is 0.06 to 0.8 kW / Stirring conditions adjusted to m ³ are preferred. The power required for stirring was 0. It is preferable that it is 1-0.5 kw / m < ³ >. This required power for stirring corresponds to the net energy per unit volume received by the contents in the reaction vessel.

Here, the power required for stirring refers to that measured in the following manner.
That is, an aqueous medium containing core resin particles, styrene-based monomers, and other dispersions and dissolved substances as necessary is supplied into a polymerization vessel of a polymerization apparatus, and a stirring blade is rotated at a predetermined rotational speed. Stir the aqueous medium. At this time, the rotational driving load necessary to rotate the stirring blade is measured as a current value A ₁ (ampere). A value obtained by multiplying the current value A ₁ by an effective voltage (volts) is defined as P ₁ (watts).

Then, the stirring blade of the polymerization apparatus is rotated at the same rotation speed as described above in an empty state of the polymerization vessel, and the rotational driving load required to rotate the stirring blade is measured as a current value A ₂ (ampere). A value obtained by multiplying the current value A ₂ by an effective voltage (volt) is P ₂ (watts), and the required power for stirring can be calculated by the following formula. V (m ³ ) is the volume of the entire aqueous medium including the core resin particles, the styrene monomer, and other dispersions and dissolved substances as required.
Power required for stirring (Pv) = (P ₁ −P ₂ ) / V

The shape and structure of the polymerization vessel are not particularly limited as long as they are conventionally used for the polymerization of styrene monomers.
The stirring blade is not particularly limited as long as the power required for stirring can be set within a predetermined range.
Specifically, paddle blades such as V-type paddle blades, inclined paddle blades, flat paddle blades, fiddler blades, pull margin blades, turbine blades such as turbine blades and fan turbine blades, propeller blades such as marine propeller blades, etc. Can be mentioned. Of these stirring blades, paddle blades are preferable, and V-type paddle blades, inclined paddle blades, flat paddle blades, Ferdler blades, and pull margin blades are more preferable. The stirring blade may be a single-stage blade or a multi-stage blade.
Further, the size of the stirring blade is not particularly limited as long as the required power for stirring can be set within a predetermined range.
Furthermore, you may provide a baffle plate (baffle) in the superposition | polymerization container.

[Step (B)]
Next, a styrene monomer and a polymerization initiator are added to the obtained suspension, and the styrenic monomer is heated to a temperature at which the styrene monomer is not substantially polymerized. A reaction liquid is obtained by impregnating polyolefin resin particles.
(Styrene monomer)
The styrenic monomer is polymerized in the following steps (C) and (D) to become 100 to 400 parts by mass of a polystyrene resin (PS) with respect to 100 parts by mass of the polyolefin resin.
The amount of styrene monomer and the amount of polystyrene resin obtained after polymerization are almost the same.
If the polystyrene-based resin is less than 100 parts by mass, the ability to hold the foaming agent of the foamed particles may be lowered, and high foaming may not be possible, and the rigidity of the foamed molded product may be lowered. On the other hand, when the polystyrene resin exceeds 400 parts by mass, the polyolefin resin particles are not sufficiently impregnated into the polyolefin resin particles, and the polystyrene resin is present in a large amount on the surface of the composite resin particles, thereby generating white particles. This is not preferable. In addition, it is not preferable because not only the crack resistance of the foamed molded product is lowered but also the chemical resistance may be lowered. The polystyrene resin (parts by mass) with respect to 100 parts by mass of the preferred polyolefin resin is 120 to 300 parts by mass.

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 α-methyl styrene, vinyl toluene, chlorostyrene, ethyl styrene, isopropyl styrene, dimethyl styrene, bromostyrene, and the like. These styrenic monomers may be used alone or in combination.

The polystyrene resin may be a combination of a vinyl monomer copolymerizable with a styrene monomer.
Examples of the vinyl monomer include divinylbenzene such as o-divinylbenzene, m-divinylbenzene and p-divinylbenzene, alkylene glycol di (meth) acrylate such as ethylene glycol di (meth) acrylate and polyethylene glycol di (meth) acrylate. And polyfunctional monomers such as (meth) acrylate; (meth) acrylonitrile, methyl (meth) acrylate, butyl (meth) acrylate and the like. Among these, polyfunctional monomers are preferable, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate having 4 to 16 ethylene units, and divinylbenzene are more preferable, and divinylbenzene, ethylene glycol di ( Particularly preferred is (meth) acrylate. In addition, a monomer may be used independently or may be used together.
Moreover, when using a monomer together, it is preferable that the content is set so that it may become the quantity (for example, 50 mass% or more) which a styrene-type monomer becomes a main component.
In the present invention, “(meth) acryl” means “acryl” or “methacryl”.

(heating)
The temperature at which the styrene monomer is not substantially polymerized may be appropriately set according to the type and blending ratio of the raw material resin, the physical properties of the foamed particles to be produced, etc., but is usually 45 to 80 ° C.
The time for impregnating the styrene monomer inside the polyolefin resin particles is suitably 30 minutes to 2 hours. This is because if the polymerization proceeds before sufficient impregnation, polystyrene polymer powder is produced.

[Step (C)]
Next, when the melting point of the polyolefin resin is T ° C., the obtained reaction solution is heated to a temperature of (T−10) ° C. to (T + 20) ° C. to polymerize the styrene monomer.
When the polymerization temperature is less than (T-10) ° C., there are few polystyrene-based resins in the center of the obtained resin particles, and resin particles and foamed molded articles showing good blackness and mechanical properties may not be obtained. is there. On the other hand, if the polymerization temperature exceeds (T + 20) ° C., the polymerization starts before the styrene monomer is sufficiently impregnated with the polypropylene resin particles, so that the resin particles exhibit good blackness and mechanical properties. In some cases, foam molded articles cannot be obtained.
For example, when the melting point of the polyolefin resin is 140 ° C, the polymerization temperature is 130 to 160 ° C.

The polymerization time is usually about 1 to 6 hours, and preferably 1.5 to 3 hours, considering the quality and productivity of the resulting composite resin particles.
Moreover, the pressure in the system at the time of polymerization is usually about 0.05 to 0.5 MPa, and preferably 0.1 to 0.3 MPa in consideration of safety in terms of workability of polymerization stability.
In addition, the temperature rise or fall time to the set temperature of each process varies depending on the outside air temperature, but when converted in the entire section from the start temperature to the target temperature, 0.3 ° C./min to 3.0 ° C. / min is appropriate.
In particular, if the rate of temperature rise is too fast, polymerization will start before the styrene monomer is sufficiently impregnated with the polyolefin resin particles, so resin particles and foam molding exhibiting good blackness and mechanical properties. The body may not be obtained. On the other hand, if the rate of temperature increase is too slow, the process becomes longer and the manufacturing cost is increased. More preferably, it is 0.4 degreeC / min-2.5 degreeC / min.
Other polymerization conditions may be appropriately set depending on the composition of the composite resin particles to be produced.
The manufacturing method of the composite resin particle of this invention includes said process (A)-(C), or includes the following process (D) in said process (A)-(C).

[Step (D)]
Next, when a styrene monomer and a polymerization initiator are added to the reaction solution obtained in the step (C) and the melting point of the polyolefin resin is T ° C, (T-25) to (T + 15) ) The obtained reaction solution is heated to a temperature of ° C. to polymerize the styrene monomer.
This step is different in that the monomer is polymerized while being absorbed by the core resin particles, but is a modification of the above steps (B) and (C), and corresponds to a repetition thereof, that is, a two-stage polymerization step.
Moreover, you may repeat the process (B)-(C), ie, the impregnation of the styrene-type monomer to the polyolefin-type resin particle, and superposition | polymerization as needed.
Including the steps (B) and (C), the amount of the styrene monomer used for one polymerization may be appropriately divided so that the mass ratio of the polyolefin resin and the polystyrene resin is as described above. .

In the last steps (C) and (D), after the polymerization, it is preferable to hold at a temperature of (T−10) ° C. to (T + 20) ° C. for a longer time than the previous steps, that is, to anneal.
Here, the necessity of annealing will be described.
In the process up to the annealing process, the styrene monomer and polymerization initiator absorbed in the core resin particles have not completely completed the reaction, and there are not a few unreacted substances inside the composite resin particles. Existing. Therefore, when a foamed molded product is obtained using composite resin particles obtained without annealing, the mechanical properties and heat resistance of the foamed molded product are degraded due to the influence of low molecular weight unreacted materials such as styrene monomers. And odor caused by volatile unreacted materials 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.

[Step (E)]
In the method for producing composite resin particles of the present invention, after step (C) or (D),
(E) In a mixed solution containing composite resin particles, 1.5 to 6.0 parts by mass of tri (2,3-dibromopropyl) isocyanurate or bis [ 3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, and 0.1 to 2.0 parts by weight of 2,3-dimethyl-2,3-diphenylbutane as a flame retardant aid. It is preferable to further include a step of adding a flame retardant treatment to the composite resin particles.
The flame retardant and the flame retardant aid may be kneaded with the resin raw material in the same manner as the other additives described in the step (A). It is preferable that a flame retardant and a flame retardant aid are present on the surface of the composite resin, and it is preferable that the surface of the composite resin particles be flame retardant as described above.

[Composite resin particles]
The composite resin particles obtained by the method for producing composite resin particles of the present invention preferably have an average particle diameter of 0.5 to 3.0 mm.
When the average particle diameter of the composite resin particles is less than 0.5 mm, high foamability may not be obtained. On the other hand, when the average particle diameter of the composite resin particles exceeds 3.0 mm, the pre-expanded particles may not be sufficiently filled during the molding process. More preferably, the average particle size of the composite resin particles is 0.5 to 2.0 mm.

[Expandable particles]
Expandable particles can be obtained by impregnating the above composite resin particles with a foaming agent by a known method.
When the temperature at which the composite resin particles are impregnated with the foaming agent is low, it takes time for the impregnation, and the production efficiency of the expandable particles may be reduced. On the other hand, when the temperature is high, the coalescence between the expandable particles is large. Since it may generate | occur | produce, 50-130 degreeC is preferable and 60-100 degreeC 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 volatile foaming agent in the foamable particles is usually in the range of 2 to 10% by weight, preferably in the range of 3 to 10% by weight, and particularly preferably in the range of 3 to 8% by weight.
If the content of the volatile 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 Cannot be obtained, the appearance of the foamed molded product may deteriorate. On the other hand, when the content of the volatile 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.

[Foamed particles]
The foamable particles can be obtained by heating the foamable particles with steam (steam) having a gauge pressure of 0.004 to 0.09 MPa introduced in a sealed container and 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 preferably have a bulk density of 0.015 to 0.25 g / cm ³ . When the bulk density of the foamed particles is less than 0.015 g / cm ³ , the foamed 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 expanded particles exceeds 0.25 g / cm ³ , the merit of weight reduction as a foamed molded product may be impaired. A preferred bulk density of the expanded particles is 0.025 to 0.033 g / cm ³ .
The method for measuring the bulk density will be described in detail in Examples.

(Average particle size)
The expanded particles obtained by expanding the composite resin particles preferably have an average particle diameter of 0.8 to 12.0 mm.
When the average particle diameter of the foamed particles is less than 0.8 mm, the foamability at the time of foam molding is low, and the elongation of the surface of the molded body may be deteriorated. On the other hand, if the average particle diameter of the expanded particles exceeds 12.0 mm, the pre-expanded particles may not be sufficiently filled during the molding process. More preferably, the average particle diameter of the composite resin particles is 0.8 to 6.0 mm.

(Amount of surface polystyrene resin)
The expanded particles preferably have a surface polystyrene resin amount of 5 to 50% by mass.
When the surface polystyrene-based resin amount of the expanded particles is less than 5% by mass, the polystyrene-based resin component is locally ejected from the pre-expanded particles at the time of preliminary foaming, and appearance defects such as unevenness of blackness may occur at the time of foam molding. On the other hand, when the surface polystyrene-based resin content of the expanded particles exceeds 50% by mass, sufficient blackness may not be imparted to the foamed molded product, and at the same time, chemical resistance and impact resistance may be reduced.
The surface polystyrene-based resin amount (% by mass) is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50.
The amount of surface polystyrene-based resin of the preferred expanded particles is 5 to 30% by mass.
The method for measuring the amount of surface polystyrene resin will be described in detail in Examples.

[Foamed molded product]
The pre-expanded particles can be foam-molded in a mold to obtain a foam-molded product.
Specifically, the foam-molded product is obtained by a known method, for example, filling pre-expanded particles in a mold (cavity) of a foam-molding machine, and heating again to foam the pre-expanded particles. It can be obtained by heat sealing.

(density)
The foamed molded product preferably has a density in the range of 0.015 to 0.25 g / cm ³ . If the density of the foamed molded product is less than 0.015 g / m ³ , the impact resistance may not be sufficient. On the other hand, if the density of the foamed molded product exceeds 0.25 g / cm ³ , the effect of reducing the weight of the foamed molded product is limited. The bulk density of a preferable foamed molded product is 0.025 to 0.033 g / cm ³ .

(Blackness)
The foamed molded article containing carbon black has the following formula in color difference measurement based on JIS Z8729-2004 “Color Display Method—L ^* a ^* b ^* Color System”:
ΔE ′ = L ^* + | a ^* | + | b ^* | <31
(Where ΔE ′ is blackness, L ^* is lightness, a ^* and b ^* are color coordinates)
And the standard deviation σ of ΔE ′ preferably satisfies the relationship of σ <1.0.
The method for measuring the blackness will be described in detail in Examples.

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, the obtained pre-expanded particles and foamed molded products were evaluated as follows.

“Bulk density of pre-expanded particles (g / cm ³ )”
The bulk density of the pre-expanded particles is measured as follows.
The mass (a) of about 5 g of pre-expanded particles is weighed at the second decimal place, and the weighed pre-expanded particles are put into a 500 cm ³ graduated cylinder having a minimum memory unit of 5 cm ³ . Next, a pressing tool, which is a round resin plate slightly smaller than the diameter of the graduated cylinder, and a rod-shaped resin plate having a width of about 1.5 cm and a length of about 30 cm is fixed upright at the center. The volume (b) of the pre-expanded particles is read.
From the mass (a) of the obtained pre-expanded particles and the volume (b) of the pre-expanded particles, the bulk density (g / cm ³ ) = (a) / (b) of the pre-expanded particles is obtained by the following formula.

“Surface polystyrene resin (PS) content (%) of pre-expanded particles”
The absorbance ratio (D698 / D1376) is measured as follows.
In addition, each light absorbency obtained from an infrared absorption spectrum says the height of the peak originating in the vibration of each resin component contained in a composite resin particle.
Ten particles selected at random are subjected to surface layer analysis by infrared spectroscopic analysis ATR measurement method to obtain infrared absorption spectra. In this analysis, an infrared absorption spectrum in the depth range from the particle surface to several μm (about 2 μm) is obtained.
The individual absorbance ratio (D698 / D1376) is calculated from each infrared absorption spectrum, and the arithmetic average of the individual absorbance ratios calculated for the surface layer is defined as the absorbance ratio.
The polystyrene resin ratio (% by mass) is calculated from the absorbance ratio (D698 / D1376) based on a calibration curve described later.
The absorbances D698 and D1376 are measured under the following conditions using a measuring device manufactured by Nicolet; trade name “Fourier transform infrared spectrometer MAGNA 560” and “Thunder Dome” manufactured by Spectra-Tech as an ATR accessory.

(Measurement condition)
High refractive index crystal seed: Ge (germanium)
Incident angle: 45 ° ± 1 °
Measurement area: 4,000 cm ^{-1 to} 675 cm ^-1
Fractional dependence of measurement depth: No correction Number of reflections: 1 Detector: DTGS KBr
Resolution: 4cm ^-1
Number of integrations: 32 times Others: An infrared absorption spectrum is measured under the above conditions without contacting the sample, and the measured infrared absorption spectrum is used as the background. When measuring the sample, the measurement data is processed so that the background does not contribute to the measurement spectrum. In the ATR method, the intensity of the infrared absorption spectrum changes depending on the degree of adhesion between the sample and the high refractive index crystal. Therefore, the maximum load that can be applied by the “Thunder Dome” of the ATR accessory is applied to perform the measurement with a substantially uniform contact degree.

The infrared absorption spectrum obtained under the above conditions is subjected to peak processing as follows to determine the respective absorbances.
The absorbance D698 at 698 cm ⁻¹ obtained from the infrared absorption spectrum is an absorbance corresponding to the absorption spectrum derived from the out-of-plane vibration of the benzene ring contained in the polystyrene resin. In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 698 cm ⁻¹ . Absorbance D698 is a straight line connecting the 1,280Cm ^-1 and 860 cm ^-1 as a baseline, means the maximum absorbance between 710 cm ^-1 and 685cm ^-1.
Further, the absorbance D1376 at 1,376 cm ⁻¹ obtained from the infrared absorption spectrum is the absorbance corresponding to the absorption spectrum derived from the symmetrical bending vibration of CH ₃ of —C—CH ₃ hydrocarbon contained in the polypropylene resin. It is. In this absorbance measurement, peak separation is not performed even when other absorption spectra overlap at 1376 cm ⁻¹ . Absorbance D1376 is a straight line connecting the 1,414Cm ^-1 and 1,340Cm ^-1 as a baseline, means the maximum absorbance between 1,400Cm ^-1 and 1,350cm ^-1.

"Blackness ΔE '"
The blackness ΔE ′ of the foamed molded product is evaluated by color difference measurement based on JIS Z8729-2004 “Color Display Method—L ^* a ^* b ^* Color System”.
For the measurement, a color difference meter (manufactured by Konica Minolta, model: CR-400) and a standard white plate calibration plate (Y: 94.3, x: 0.3144, y: 0.3208) are used in accordance with the standard.
Specifically, from any 10 points on the vertical and horizontal surfaces of the foamed molded product, the measurement area was measured as φ8 mm, and the average value was calculated from the lightness L ^* value, color coordinate a ^* value, and b ^* value. ΔE ′ is calculated as the degree.
ΔE ′ = L ^* + | a ^* | + | b ^* |

"Flame retardance"
The flame retardancy of the foamed molded product is evaluated by measuring the burning rate based on the US automobile safety standard FMVSS 302.
The burning rate of a 350 mm × 100 mm × 12 mm (thickness) test piece cut out from the foam molded article is measured, and flame retardancy is evaluated according to the following criteria.
Combustion rate 80 mm / min or less: Good (◯)
Exceeds burning speed of 80 mm / min: defective (x)

"Compressive strength"
Measured according to ASTM D 3575.
A test piece obtained by cutting a foamed molded product into a length of 50 mm, a width of 50 mm, and a thickness of 25 mm is compressed under a compression speed of 12.5 mm / min, and the strength (MPa) at 50% compression is measured.

"Odor determination"
The molded body is placed in a constant temperature bath at 55 ° C. for 1 hour and then taken out and left at 23 ° C. for 24 hours.
Thereafter, a flat rectangular plate-shaped test piece having a length of 100 mm, a width of 100 mm, and a thickness of 30 mm was cut out from the foamed molded article, and the test piece was placed in a stainless steel container with a lid having a diameter of 160 mm and a depth of 200 mm. It is taken out after being placed in a constant temperature bath at 60 ° C. for 1 hour and left at 23 ° C. for 30 minutes.
Next, the odor of valeric acid diluted by a factor of 10,000 (made by Daiichi Yakuhin Sangyo Co., Ltd.) (3 out of 0 to 5 odor intensity) is sniffed and used as a reference odor.
Next, the lid of the stainless steel container is opened a little, the smell inside the container is sniffed, the odor intensity is set to 4 or 5 when the odor is stronger than the reference odor, and the odor intensity is brought close to 5 when the odor is stronger. On the other hand, when the odor is weaker than the reference odor, the odor intensity is set to 0, 1 or 2, and when the odor is weaker, the odor intensity is brought close to 0.
This test is conducted by five people in the same manner, and the average value of the five people is defined as the odor intensity, and is evaluated according to the following criteria.
Odor intensity 4-5; x
Odor intensity 3 △
Odor intensity 0-2;

"Organic volatile content"
As organic volatile components contained in the foamed molded product, the content (%) of styrene, toluene, xylene and ethylbenzene is measured as follows.
In a 20 mL vial, 0.2 g of the foamed molded product is added, 1 mL of dimethylformamide (DMF) containing diethylbenzene (DEB) is added as a solvent, and the sample is dissolved in the solvent to prepare a sample solution. Next, after the vial containing this sample solution was heated at 90 ° C. for 1 hour, the vapor of this sample solution was collected, and this vapor was gas chromatograph (manufactured by Shimadzu Corporation, trade name “GC-18A”). Is quantified by the internal standard method under the following measurement conditions.

(Measurement condition)
Column: Column of diameter 0.25 mm × length 30 m, film thickness 0.25 μm (manufactured by J & W, trade name “DB-WAX”)
Detector: Flame ionization type detector (Flame Ionization Detector, FID)
Column temperature condition: after holding at 50 ° C. for 2 minutes, temperature was raised to 100 ° C. at 10 ° C./min, held at 100 ° C. for 5 minutes, then heated to 220 ° C. at 40 ° C./min, and heated at 220 ° C. for 2 minutes. Holding Column inlet temperature: 150 ° C
Detector temperature: 250 ° C
Measurement sample solution injection amount: 2 mL
Split ratio: 70: 1
Column flow rate: 1.6 mL / min (He)
Gas pressure: 122 kPa

"Melting point (℃)"
It is measured by the method described in JIS K7121-1987 “Method for Measuring Transition Temperature of Plastic”. However, the sampling method and temperature conditions are as follows.
Using a differential scanning calorimeter DSC6220 (made by SII NanoTechnology Co., Ltd.), about 6 mg of sample is filled in the bottom of the aluminum measuring container so that there is no gap, and from 30 ° C. under a nitrogen gas flow rate of 20 mL / min. The temperature was lowered to −40 ° C., held for 10 minutes, heated from −40 ° C. to 220 ° C. (1st Heating), held for 10 minutes, cooled from 220 ° C. to −40 ° C. (Cooling), held for 10 minutes, − A DSC curve is obtained when the temperature is raised from 40 ° C. to 220 ° C. (2nd Heating). All the temperature increases / decreases are performed at a rate of 10 ° C./min, and alumina is used as a reference material. In the present invention, the melting point is a value obtained by reading the temperature at the top of the melting peak observed in the 2nd Heating process.

Example 1
(Preparation of core resin particles)
Polypropylene resin (manufactured by Prime Polymer Co., Ltd., trade name “Prime Polypro (film)”, brand name “F-744NP”, melting point 140 ° C.) 1,900 g, and furnace black (manufactured by Mitsubishi Chemical Corporation, 100 g of trade name “Mitsubishi Carbon Black” and brand “Intermediate Color (MCF) # 900”) were put into a tumbler mixer and mixed for 7 minutes.
Next, the obtained mixture is supplied to an extruder (Toshiba Machine Co., Ltd., model: SE-65), heated and melted, extruded, and granulated into pellets by an underwater cut method, so that furnace black is added to polypropylene resin. 5% by mass of spherical carbon black-containing polypropylene resin particles (5.0% by mass of carbon black based on polyolefin resin) was obtained. Resin particles at this time were adjusted to 74 mg per 100 particles and an average particle diameter of about 1 mm.
In the following examples / comparative examples, the temperature increase / decrease rate was 1 ° C./min for polymerization, flame retardancy, and preparation of expandable particles.

(Preparation of carbon black-containing composite resin particles)
(Preparation of suspension: Step (A))
Next, 760 g of the obtained carbon black-containing polypropylene resin particles were placed in a 5 liter autoclave with a stirrer (manufactured by Nitto Koatsu Co., Ltd.), and further 2,000 g of pure water as an aqueous medium and pyrroline as a dispersant. 20 g of magnesium acid, 0.2 g of sodium dodecylbenzenesulfonate as a surfactant, and 150 mg of sodium nitrite as a polymerization inhibitor were added. The resulting mixture was stirred and suspended in an aqueous medium, held at 25 ° C. for 10 minutes, and then heated to 70 ° C. to obtain a suspension.

(First polymerization: Steps (B) and (C))
Subsequently, 0.3 g of di-t-butyl peroxide (manufactured by NOF Corporation, trade name “Perbutyl D”) as a polymerization initiator was previously dissolved in the obtained suspension. 320 g of styrene monomer was added dropwise over 30 minutes to allow the carbon black-containing polypropylene resin particles to absorb the styrene monomer. Next, the temperature of the reaction solution was raised to 140 ° C. and held at the same temperature for 2 hours to polymerize the styrene monomer in the carbon black-containing polypropylene resin particles.

(Second polymerization: Step (D))
Next, the reaction solution was cooled (cooled) to 125 ° C. which was 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant was added to the reaction solution. . Thereafter, 920 g of a styrene monomer prepared by dissolving 2.0 g of di-t-butyl peroxide (trade name “Perbutyl D”, manufactured by NOF CORPORATION) as a polymerization initiator in advance over 4 hours. The styrene monomer was polymerized while being absorbed by the carbon black-containing polypropylene resin particles. After completion of the dropping, the temperature was maintained at the same temperature for 1 hour and 30 minutes, and then the reaction solution was heated to 140 ° C. and maintained at the same temperature for 3 hours to complete the polymerization to obtain carbon black-containing polypropylene resin particles.

(Flame retardant: Process (E))
Subsequently, the temperature of the reaction solution is lowered (cooled) to 60 ° C., and 60 g of tri (2,3-dibromopropyl) isocyanurate (manufactured by Nippon Kasei Co., Ltd.) as a flame retardant is added to the reaction solution. 2,3-dimethyl-2,3-diphenylbutane (manufactured by Kayaku Akzo Co., Ltd.) 10 g was added. After the addition, the temperature of the reaction solution was raised to 140 ° C., and kept at the same temperature and stirring for 4 hours to flame-treat the carbon black-containing composite resin particles.
Next, after the reaction solution was cooled to 25 ° C., the dispersant was removed by acid washing using a 20% hydrochloric acid aqueous solution, and 2,000 g of carbon black-containing composite resin particles were taken out from the autoclave.

(Production of expandable particles)
Next, 2,000 g of the carbon black-containing composite resin particles and 2,000 g of water taken out were again put into an autoclave with a capacity of 5 liters equipped with a stirrer, and butane as a blowing agent (normal butane: isobutane = 7: 3). ) 300 g was injected. After the injection, the mixture was heated to 70 ° C. and kept at the same temperature and stirring for 4 hours.
Thereafter, the mixture was cooled to 25 ° C., the carbon black-containing composite resin particles were taken out from the autoclave, dehydrated and dried, and 2,100 g of expandable carbon black-containing composite resin particles were obtained.

(Production of expanded particles)
Next, 1,000 g of the obtained expandable carbon black-containing composite resin particles was put into a pre-foaming machine (manufactured by Kasahara Kogyo Co., Ltd., model: PSX40) having a can capacity of 40 liters, and a gauge pressure of 0.04 MPa was put in the can. Steam was introduced and heated, and pre-foamed to a bulk foaming ratio of 42 times to obtain foamed particles.

(Production of composite resin foam molding)
Next, the pre-expanded particles obtained were left at 25 ° C. for 1 day, and then filled into a cavity of a mold having an internal dimension of 400 mm long × 300 mm wide × 30 mm thick. Of water vapor was introduced for 50 seconds and heated, and then cooled until the maximum surface pressure of the foamed molded product was reduced to 0.001 MPa, to obtain a composite resin foamed molded product.
Various physical properties of the obtained foamed molded article were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

(Example 2)
(First polymerization: Steps (B) and (C))
In a suspension obtained in the same manner as in Example 1, 0.4 g of di-t-amyl peroxide (manufactured by Arkema Yoshitomi Co., Ltd., trade name “Lupelox DTA”) as a polymerization initiator was dissolved in advance. 320 g of the prepared styrene monomer was dropped over 30 minutes, and the styrene monomer was absorbed into the carbon black-containing polypropylene resin particles. Next, the temperature of the reaction solution was raised to 140 ° C. and held at the same temperature for 2 hours to polymerize the styrene monomer in the carbon black-containing polypropylene resin particles.

(Second polymerization: Step (D))
Next, the reaction solution was cooled (cooled) to 125 ° C. which was 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant was added to the reaction solution. . Thereafter, 920 g of a styrene monomer prepared by dissolving 2.6 g of di-t-amyl peroxide (manufactured by Arkema Yoshitomi Co., Ltd., trade name “Lupelox DTA”) as a polymerization initiator in advance for 4 hours. The styrene monomer was polymerized while being absorbed by the carbon black-containing polypropylene resin particles. After completion of dropping, the reaction solution was held at the same temperature for 1 hour and 30 minutes, and then the reaction solution was heated to 140 ° C. and held at the same temperature for 3 hours to complete the polymerization to obtain carbon black-containing polypropylene resin particles. Except for the above, a composite resin foam molded article was obtained in the same manner as in Example 1, and its physical properties were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

(Example 3)
(First polymerization: Steps (B) and (C))
In a suspension obtained in the same manner as in Example 1, 0.6 g of di-t-hexyl peroxide (trade name “Perhexyl D”, manufactured by NOF Corporation) as a polymerization initiator was dissolved in advance. 320 g of the prepared styrene monomer was dropped over 30 minutes, and the styrene monomer was absorbed into the carbon black-containing polypropylene resin particles. Next, the temperature of the reaction solution was raised to 140 ° C. and held at the same temperature for 2 hours to polymerize the styrene monomer in the carbon black-containing polypropylene resin particles.

(Second polymerization: Step (D))
Next, the reaction solution was cooled (cooled) to 125 ° C. which was 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant was added to the reaction solution. . Thereafter, 920 g of a styrene monomer prepared by dissolving 3.7 g of di-t-hexyl peroxide (trade name “Perhexyl D”, manufactured by NOF CORPORATION) as a polymerization initiator in advance over 4 hours. The styrene monomer was polymerized while being absorbed by the carbon black-containing polypropylene resin particles. After completion of dropping, the reaction solution was held at the same temperature for 1 hour and 30 minutes, and then the reaction solution was heated to 140 ° C. and held at the same temperature for 3 hours to complete the polymerization to obtain carbon black-containing polypropylene resin particles. Except for the above, a composite resin foam molded article was obtained in the same manner as in Example 1, and its physical properties were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

(Comparative Example 1)
(Preparation of core resin particles)
In the same manner as in Example 1, spherical carbon black-containing polypropylene resin particles were obtained.
(Preparation of carbon black-containing composite resin particles)
(Preparation of suspension)
Next, 760 g of the obtained carbon black-containing polypropylene resin particles were placed in a 5 liter autoclave with a stirrer (manufactured by Nitto Koatsu Co., Ltd.), and further 2,000 g of pure water as an aqueous medium and pyrroline as a dispersant. 20 g of magnesium acid, 0.2 g of sodium dodecylbenzenesulfonate as a surfactant, and 150 mg of sodium nitrite as a polymerization inhibitor were added. The resulting mixture was stirred and suspended in an aqueous medium, held at 25 ° C. for 10 minutes, and then heated to 70 ° C. to obtain a suspension.

(First polymerization)
Next, in the obtained suspension, a styrene unit amount prepared by dissolving 0.6 g of dicumyl peroxide (manufactured by NOF Corporation, trade name “Park Mill D”) as a polymerization initiator in advance. The body 320g was dripped over 30 minutes, and the styrene monomer was absorbed in the carbon black containing polypropylene resin particle. Next, the temperature of the reaction solution was raised to 140 ° C. and held at the same temperature for 2 hours to polymerize the styrene monomer in the carbon black-containing polypropylene resin particles.

(Second polymerization)
Next, the reaction solution is cooled (cooled) to 125 ° C., which is 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant is added to the reaction solution. It was. Thereafter, 920 g of a styrene monomer prepared by dissolving 3.7 g of dicumyl peroxide (trade name “Park Mill D”, manufactured by NOF Corporation) as a polymerization initiator in advance is dropped over 4 hours. The styrene monomer was polymerized while being absorbed by the carbon black-containing polypropylene resin particles. After completion of the dropping, the temperature was maintained at the same temperature for 1 hour and 30 minutes, and then the reaction solution was heated to 140 ° C. and maintained at the same temperature for 3 hours to complete the polymerization to obtain carbon black-containing composite resin particles.
(Flame retardant)
In the same manner as in Example 1, flame-retardant treated carbon black-containing composite resin particles were obtained.

In the same manner as in Example 1, (Production of expandable particles), (Production of foamed particles) and (Production of composite resin foam molded product) were carried out to obtain a composite resin foam molded product.
Various physical properties of the obtained foamed molded article were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

(Comparative Example 2)
(First polymerization)
In the suspension obtained in the same manner as in Example 1, benzoyl peroxide (manufactured by NOF Corporation, trade name “NIPER BW” 0.5 g as a polymerization initiator was previously dissolved and prepared. 320 g of styrene monomer was added dropwise over 30 minutes to allow the carbon black-containing polypropylene resin particles to absorb the styrene monomer, and then the reaction solution was heated to 140 ° C. for 2 hours at the same temperature. The styrene monomer was polymerized in the carbon black-containing polypropylene resin particles.

(Second polymerization)
Next, the reaction solution was cooled (cooled) to 125 ° C. which was 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant was added to the reaction solution. . Thereafter, 920 g of styrene monomer prepared by dissolving 3.3 g of benzoyl peroxide (manufactured by NOF Corporation, trade name “NIPER BW”) in advance as a polymerization initiator was added dropwise over 4 hours. The monomer was polymerized while being absorbed into the carbon black-containing polypropylene-based resin particles, and was maintained at the same temperature for 1 hour and 30 minutes after the completion of the dropping, and then the temperature of the reaction solution was raised to 140 ° C. for 3 hours at the same temperature. A composite resin foamed molded article was obtained and evaluated for physical properties in the same manner as in Example 1 except that the polymerization was completed by maintaining the polymer, and carbon black-containing polypropylene resin particles were obtained.
The results are shown in Table 1 together with the raw materials and production conditions.

Example 4
(First polymerization)
In a suspension obtained in the same manner as in Example 1, 1.6 g of di-t-butyl peroxide (trade name “Perbutyl D”, manufactured by NOF Corporation) as a polymerization initiator was dissolved in advance. 320 g of the prepared styrene monomer was dropped over 30 minutes, and the styrene monomer was absorbed into the carbon black-containing polypropylene resin particles. Next, the temperature of the reaction solution was raised to 140 ° C. and held at the same temperature for 2 hours to polymerize the styrene monomer in the carbon black-containing polypropylene resin particles.

(Second polymerization)
Next, the reaction solution was cooled (cooled) to 125 ° C. which was 15 ° C. lower than the melting point of the polypropylene resin in the carbon black-containing polypropylene resin particles, and 0.7 g of sodium dodecylbenzenesulfonate as a surfactant was added to the reaction solution. . Thereafter, 920 g of a styrene monomer prepared by dissolving 7.7 g of di-t-butyl peroxide (trade name “Perbutyl D”, manufactured by NOF Corporation) as a polymerization initiator in advance is taken over 4 hours. The styrene monomer was polymerized while being absorbed by the carbon black-containing polypropylene resin particles. After completion of dropping, the reaction solution was held at the same temperature for 1 hour and 30 minutes, and then the reaction solution was heated to 140 ° C. and held at the same temperature for 3 hours to complete the polymerization to obtain carbon black-containing polypropylene resin particles. Except for the above, a composite resin foam molded article was obtained in the same manner as in Example 1, and its physical properties were evaluated.
The results are shown in Table 1 together with the raw materials and production conditions.

From the results of Table 1, the foamed molded products of Examples 1 to 4 produced using the composite resin particles of the present invention obtained by polymerization using a specific polymerization initiator have been generally used conventionally. Compared with the foamed molded articles of Comparative Examples 1 and 2 produced using composite resin particles obtained by polymerization using a polymerization initiator, a good odor determination can be obtained without going through a deodorization step. I understand that. Moreover, it turns out that sufficient blackness and a flame retardance are acquired even if it mix | blends carbon black and a flame retardant as a coloring agent.
From the above, it can be seen that the present invention is a method for producing odor-reducing composite resin particles that makes it possible to reduce or omit the deodorizing step of odors derived from the components contained in the foamed molded product.

Claims (5)

It is a method for producing composite resin particles containing 100 to 400 parts by mass of a polystyrene resin with respect to 100 parts by mass of a polyolefin resin.
(A) A step of dispersing the polyolefin resin particles in an aqueous medium containing a dispersant to obtain a suspension;
(B) Next, a styrene monomer and a polymerization initiator are added to the obtained suspension, and the styrene monomer is heated to a temperature at which the styrene monomer is not substantially polymerized. (C) Next, when the melting point of the polyolefin resin is T ° C., the temperature is (T−10) ° C. to (T + 20) ° C. Or a step of polymerizing the styrenic monomer to obtain composite resin particles by heating the obtained reaction liquid, or (D) and then the step (C) ), A styrene monomer and a polymerization initiator are added, and when the melting point of the polyolefin resin is T ° C, the temperature is (T-25) to (T + 15) ° C. The obtained reaction solution is heated to polymerize the styrene monomer to form a composite tree. Further comprising the step of obtaining the particles,
The polymerization initiator has the following formula:
(In the formula, R _{1 to} R ₃ and R ^′ _{1 to} R ^′ ₃ are linear alkyl groups in which the total number of carbon atoms of each substituent is 6 to 20, and R ₁ , R ₃ , R ^′ ₁ And R ^′ ₃ are the same, and R ₂ and R ^′ ₂ are the same)
The manufacturing method of the composite resin particle characterized by the above-mentioned.   The method for producing composite resin particles according to claim 1, wherein the polymerization initiator is selected from di-t-butyl peroxide, di-t-amyl peroxide, and di-t-hexyl peroxide.   The composite according to claim 1 or 2, wherein the polymerization initiator is 0.05 to 0.5 mass% with respect to each of the styrenic monomers added simultaneously in the steps (B) and (D). A method for producing resin particles.   The particle of the polyolefin resin is a particle of a carbon black-containing polyolefin resin containing 1.5 to 17.0% by mass of carbon black with respect to the polyolefin resin. The manufacturing method of the composite resin particle as described in one. After the step (C) or (D),
(E) In a mixed liquid containing the composite resin particles, 1.5 to 6.0 parts by mass of tri (2,3-dibromopropyl) isocyanurate or 100% by mass of the composite resin particles as a flame retardant Bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone and 0.1 to 2.0 parts by weight of 2,3-dimethyl-2,3-diphenyl as flame retardant aid The manufacturing method of the composite resin particle as described in any one of Claims 1-4 which further includes the process of adding a butane and carrying out the flame-retardant process of the said composite resin particle.