JP6223097B2 - Expandable polystyrene resin particles and production method thereof, and polystyrene resin pre-expanded particles and expanded molded body - Google Patents

Description

  The present invention relates to an expandable polystyrene resin particle and a method for producing the same, and a polystyrene resin pre-expanded particle and an expanded molded article.

Foam molded products should be used for packaging cushioning materials such as home appliances, heat insulation and cold boxes such as fish boxes and vegetable boxes, and structural members of buildings because of their excellent lightness, heat insulation, shock absorption, etc. There is.
For example, expandable polystyrene resin particles containing a foaming agent are expanded by heating with a heating medium such as water vapor to form pre-expanded particles, and the pre-expanded particles are filled into the mold cavity. Then, a heating medium such as water vapor is press-fitted into the mold, and the pre-foamed particles are heated and foamed. The foamed molded body is manufactured through a cooling process for cooling in a mold.

As the expandable polystyrene resin particles, particles containing a styrene resin, an organic foaming agent having a boiling point of 5 ° C. or less at normal pressure, and a plasticizer are present as main components in natural animal and vegetable oils. The thing which made the triglyceride of the fatty acid to exist exist is proposed (refer patent document 1).
In addition, a medium chain saturated fatty acid triglyceride having 7 to 12 carbon atoms is added to the thermoplastic resin and particles containing a thermoplastic resin and a hydrocarbon having a boiling point lower than the softening point of the thermoplastic resin as a blowing agent. Expandable thermoplastic resin particles have been proposed in an amount of 0.3 to 2.5% by weight (see Patent Document 2).

By the way, in manufacture of a foaming molding, the ratio of the time which a cooling process occupies is large among the time which all the processes require. For this reason, in order to shorten the molding cycle (unit time from the start to the end of the molding process), it is an important problem to shorten the cooling time.
On the other hand, additives (high cycle agents) such as stearic acid triglyceride (powder) and methylphenyl silicone oil (liquid) are conventionally used.

JP 52-127968 A JP-A-60-202134

In recent years, there has been an increasing demand for energy saving, and in the production of foam molded articles, there is a further demand for shortening the molding cycle.
In general, in the case of producing a foam molded article having a large average cell diameter (average cell diameter of 150 to 300 μm), in the case of producing a foam molded article having a small average cell diameter (average cell diameter of 60 to 100 μm). In comparison, the molding cycle tends to be long.
In particular, the average cell diameter (about 150 to 300 μm) of a foamed molded product obtained by using foamable polystyrene resin particles obtained by extruding a molten resin containing a polystyrene resin and a foaming agent into a granular shape is suspended. It is larger than the average cell diameter (about 60 to 100 μm) of the foamed molded product obtained by using general-purpose expandable polystyrene resin particles prepared by a polymerization method or the like. For this reason, in the production of the former foamed molded article, the molding cycle tends to be long, and there is a strong demand for shortening the molding cycle.
However, when the expandable polystyrene resin particles described in Patent Document 1 are used, the desired effect of shortening the molding cycle cannot be obtained, and furthermore, there is a problem that triglycerides of fatty acids are easily peeled from the polystyrene resin particles. is there. In addition, when the expandable polystyrene resin particles described in Patent Document 2 are used, there is a problem that the mechanical strength of the obtained foamed molded product tends to be low.
Further, the conventional high cycle agent has a small effect of shortening the molding cycle, and in order to obtain a sufficient effect of shortening the molding cycle, it is necessary to increase the amount of the high cycle agent used than usual. However, with the increase in the amount of high cycle agent used, when using a powdery high cycle agent, there is a problem that the high cycle agent peels off from the resin particles. When using a liquid high cycle agent However, the surface of the resin particles was sticky from the time of preparation to the time of use, and the fluidity of the particles was poor, and there was a problem that poor transportation was likely to occur.

  The present invention has been made in view of the above circumstances, and a high-strength foam molded article is obtained. Further, the molding cycle is shortened, and the high cycle agent is hardly peeled off from the resin particles. It is an object to provide good expandable polystyrene resin particles.

  The expandable polystyrene resin particles of the present invention comprise a polystyrene resin (A), a foaming agent (B), a triglyceride (C) of a fatty acid mainly composed of a fatty acid having 6 to 11 carbon atoms and glycerin. And the content of the triglyceride (C) is 0.01 parts by mass or more and less than 0.3 parts by mass with respect to 100 parts by mass of the polystyrene resin (A).

The method for producing expandable polystyrene resin particles of the present invention is a method for producing the expandable polystyrene resin particles of the present invention, wherein the polystyrene resin (A) contains the foaming agent (B), Step (i) of obtaining foaming agent-containing polystyrene resin particles, and Step (ii) of applying the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles obtained in the step (i). It is characterized by providing.
In such a method for producing expandable polystyrene resin particles, it is preferable that the triglyceride (C) is applied on the surface of the foaming agent-containing polystyrene resin particles in the step (ii) and then left for an arbitrary time.

The polystyrene resin pre-expanded particles of the present invention are obtained by heating and foaming the expandable polystyrene resin particles of the present invention.
The foam-molded article of the present invention is characterized in that the polystyrene resin pre-expanded particles of the present invention are filled in a cavity of a mold and heated and subjected to in-mold foam molding.

  According to the expandable polystyrene-based resin particles of the present invention, a high-strength foam-molded product is obtained, the molding cycle is shortened, the high cycle agent is not easily peeled off from the resin particles, and the fluidity is good. It is.

It is a schematic diagram which shows an example of the manufacturing apparatus of a foaming agent containing polystyrene-type resin particle. It is sectional drawing which shows an example of the mixer used when apply | coating a triglyceride on the surface of a foaming agent containing polystyrene-type resin particle. It is a schematic diagram of the testing apparatus used when measuring the peeling amount of a coating agent in evaluation of the peeling property of the coating agent performed in the Example.

<Expandable polystyrene resin particles>
The expandable polystyrene resin particles of the present invention comprise a polystyrene resin (A), a foaming agent (B), a triglyceride (C) of a fatty acid mainly composed of a fatty acid having 6 to 11 carbon atoms and glycerin. contains.

(Polystyrene resin (A))
The polystyrene resin (A) (hereinafter also referred to as “component (A)”) is not particularly limited. For example, styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene. , Homopolymers of styrene monomers such as bromostyrene or copolymers thereof. Among the components (A), a resin containing 50% by mass or more of a styrene monomer unit is preferable. Of the styrene monomers, styrene is preferable.

Component (A) is a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer, the styrene monomer as a main component. May be.
Examples of such vinyl monomers include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and cetyl (meth) acrylate; (meth) acrylonitrile, dimethyl maleate In addition to monofunctional monomers such as ate, dimethyl fumarate, diethyl fumarate, and ethyl fumarate, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate are exemplified.
The above-mentioned “mainly comprising a styrene monomer” means that the styrene monomer is 50% by mass or more based on the total of the styrene monomer and the vinyl monomer. Means that.

The mass average molecular weight (Mw) of (A) component is not specifically limited, For example, it is preferable that it is 120,000 or more and 450,000 or less, More preferably, it is 150,000 or more and 400,000 or less.
When the Mw of the component (A) is not less than the preferred lower limit value, a foamed molded article having sufficient strength is easily obtained, and when it is not more than the preferred upper limit value, a foamed molded article having a beautiful appearance is easily obtained. .

In the present invention, “mass average molecular weight (Mw) of resin” indicates a value measured as follows.
Method for measuring mass average molecular weight (Mw) of resin:
About 50 mg of the sample resin is immersed in 10 mL of tetrahydrofuran (THF) and stored at room temperature for 24 hours. After filtering this with a non-aqueous 0.45 μm chromatodisc, measurement is performed using HPLC to determine the molecular weight in terms of polystyrene. In the measurement, chloroform can be used instead of THF.
Specifically, for example, HPLC (Detecter 484, Pump 510) manufactured by Waters is used as a measuring device. Two Shodex GPCK-806L (diameter 0.8 mm × length 300 mm) manufactured by Showa Denko KK are used as columns.
The measurement conditions are set such that the column temperature is 40 ° C., the mobile phase is THF, the mobile phase flow rate is 1.2 mL / min, the injection / pump temperature is room temperature, the detection is UV 254 nm, and the injection amount is 50 μL.
As standard polystyrenes for calibration curves, Shodex (molecular weight: 1.30,000) manufactured by Showa Denko KK and molecular weights manufactured by Tosoh Corporation: 5.48 million, 3.84 million, 345,000, 102,000, 37900, 9100, 2630 And 495 are used.

The component (A) includes, for example, a homopolymer of the styrenic monomer, a copolymer of the styrenic monomer, the styrenic monomer having the styrenic monomer as a main component, and the If a copolymer with a vinyl monomer is a main component, other resins may be included.
Other resins include diene rubber-like polymers such as polybutadiene, styrene-butadiene copolymer, and ethylene-propylene-nonconjugated diene three-dimensional copolymer as resins that improve the impact resistance of the foam molded article. A rubber-modified polystyrene resin (impact-resistant polystyrene resin such as so-called high impact polystyrene) is preferable.
Alternatively, other resins include polyethylene resins, polypropylene resins, acrylic resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, and the like.

Polystyrene resins that can be used as raw materials include non-recycled polystyrene resins (such as ordinary commercially available polystyrene resins, polystyrene resins newly produced by suspension polymerization, bulk polymerization methods, etc.) Virgin polystyrene) can be used, and a regenerated polystyrene resin obtained by regenerating a used polystyrene resin foam molded article can also be used.
As recycled polystyrene-based resin, used polystyrene-based resin foam molded products, such as packaging cushioning materials for household appliances, fish boxes, food packaging trays, etc., were collected and regenerated by the limonene dissolution method or heating volume reduction method. Polystyrene resin can be used.
In addition, the recycled polystyrene-based resin is not limited to those obtained by reprocessing used polystyrene-based resin foam moldings, but also home appliances (for example, televisions, refrigerators, washing machines, air conditioners, etc.) and office equipment (for example, A non-foamed polystyrene resin molded product separated and collected from a copying machine, a facsimile machine, a printer, etc.) can be crushed, melt-kneaded, and re-pelletized recycled polystyrene resin can be used.

(Foaming agent (B))
Examples of the blowing agent (B) (hereinafter also referred to as “component (B)”) include aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, and neopentane; 1,1-dichloro-1-fluoro Ethane (HCFC-141b), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123), chlorodifluoromethane (HCFC-22), 1-chloro-1,2,2,2-tetra Chlorofluorocarbons such as fluoroethane (HCFC-124); 1,1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane ( Fluorocarbons such as HFC-134a) and difluoromethane (HFC-32); various alcohols, carbon dioxide, water, nitrogen, etc. Physical blowing agents, and the like. Among these, as the component (B), an aliphatic hydrocarbon is preferable, and n-butane, isobutane, n-pentane, isopentane, and neopentane are more preferable. Among them, n-pentane, isopentane, and neopentane are more preferable, and n-pentane and isopentane are particularly preferable because they are suitable for producing foaming agent-containing polystyrene resin particles by a melt extrusion method.
(B) A component may be used individually by 1 type and may use 2 or more types together.
In the expandable polystyrene resin particles, the content of the component (B) is preferably 3 to 10 parts by mass and more preferably 4 to 8 parts by mass with respect to 100 parts by mass of the component (A).

(Triglyceride (C))
The triglyceride in the present invention (hereinafter also referred to as “component (C)”) is a triglyceride of a fatty acid mainly composed of a fatty acid having 6 to 11 carbon atoms and glycerin. By containing the component (C), the molding cycle can be shortened. In addition, the component (C) hardly peels from the resin particles, and the foamable polystyrene resin particles exhibit good fluidity by using the component (C).
“Fatty acid having 6 to 11 carbon atoms as a main component” means a fatty acid in which the ratio of fatty acids having 6 to 11 carbon atoms (C6 to 11 fatty acids) in the whole fatty acid is 50% by mass or more. . By using a triglyceride of a fatty acid having a C6-11 fatty acid ratio of 50% by mass or more and glycerin, the molding cycle is shortened, and the high cycle agent is hardly peeled off from the resin particles. Polystyrene resin particles exhibit good fluidity. The ratio of the C6-11 fatty acid is preferably 65% by mass or more, more preferably 80% by mass or more, and most preferably 100% by mass.
“The ratio (mass%) of C6-11 fatty acid in the total fatty acid” is calculated by the following equation.
Ratio (mass%) of C6-11 fatty acid to the whole fatty acid
= Mass of fatty acid component having 6 to 11 carbon atoms / mass of all fatty acid components × 100

Among the fatty acids mainly composed of fatty acids having 6 to 11 carbon atoms, fatty acids mainly composed of fatty acids having 8 to 10 carbon atoms are preferable.
Specifically, as the fatty acid having 6 to 11 carbon atoms, caproic acid having 6 carbon atoms (C ₅ H ₁₁ COOH: melting point −3 ° C. (freezing point)), caprylic acid having 8 carbon atoms (C ₇ H ₁₅ COOH: melting point 16). ° C (titer)) and capric acid having 10 carbon atoms (C ₉ H ₁₉ COOH: melting point 31 ° C (titer)) are preferred, and caprylic acid and capric acid are more preferred.

The component (C) is one in which all three acyl groups (fatty acid residues) in one molecule are the same, all three acyl groups are different, or two of the three acyl groups are the same and 1 One of them may be different from the two, or a mixture thereof.
However, among all the acyl groups in the component (C), the proportion of the acyl group having 6 to 11 carbon atoms is 50% by mass or more, preferably 65% by mass or more, more preferably 80% by mass or more. And most preferably 100% by weight.

Component (C) preferably has a melting point in the range of -20 to 40 ° C. under a pressure of 1 atm, and particularly preferably liquid at room temperature (25 ° C.).
Specific examples of the component (C) include a triglyceride of caproic acid and glycerin, a triglyceride of caprylic acid and glycerin, a triglyceride of capric acid and glycerin, or a mixture thereof.
In addition, as the component (C), a triglyceride of a fatty acid having 6 to 11 carbon atoms and glycerin as a main component and a triglyceride of a fatty acid other than 6 to 11 carbon atoms and glycerin are used in combination; It includes a triglyceride in which an acyl group having 6 to 11 carbon atoms and an acyl group other than 6 to 11 carbon atoms are mixed, and among all the acyl groups in the triglyceride mixture, the proportion of the acyl group having 6 to 11 carbon atoms is 50 What is mass% or more is also mentioned.

Fatty acids other than those having 6 to 11 carbon atoms include lauric acid having 12 carbon atoms, myristic acid having 14 carbon atoms, palmitic acid having 16 carbon atoms; stearic acid having 18 carbon atoms, oleic acid, and linol. Examples include acids, linolenic acid, ricinoleic acid, and the like, and examples of fatty acids having 5 or less carbon atoms include tangled acids having 4 carbon atoms.
Examples of triglycerides of fatty acids other than those having 6 to 11 carbon atoms and glycerin include lauric acid triglyceride, myristic acid triglyceride, palmitic acid triglyceride, stearic acid triglyceride, oleic acid triglyceride, linoleic acid triglyceride, linolenic acid triglyceride, and tangled acid triglyceride. It is done.

  Among these, as the component (C), a triglyceride of caprylic acid and glycerin (C8 triglycer), a triglyceride of capric acid and glycerin (C10 triglycer), or a mixture thereof is preferable, and a triglyceride of caprylic acid and glycerin. , A mixture of C8 triglycer and C10 triglycer is more preferable, and a triglyceride of caprylic acid and glycerin is particularly preferable.

When a mixture of C8 trig and C10 trig is used as component (C), the mixing ratio (mass ratio) of C8 trig and C10 trig is C10 trig / C8 trig = 90/10/1/99. Preferably, it is 80 / 20-2 / 98.
If the mass ratio is at least the preferred lower limit, the flowability of the expandable polystyrene resin particles is further increased, while if the mass ratio is at most the preferred upper limit, peeling of triglycerides from the resin particles is further suppressed. The

As the component (C), more specifically, those exemplified below can be used.
Actor M-1, which is a triglyceride (medium chain fatty acid triglyceride) of fatty acid and glycerin manufactured by Riken Vitamin Co., Ltd. (fatty acid composition is 60% by mass of fatty acid having 8 carbon atoms, 40% by mass of fatty acid having 10 carbon atoms: melting point − 6.5 ° C. (cloud point)), Actor M-2 (fatty acid composition is fatty acid 100% by mass of carbon number 8: melting point −12 ° C. (cloud point)), Actor M-3 (fatty acid composition is carbon number 8) Fatty acid 75 mass%, carbon number 10 fatty acid 25 mass%: melting point −5 ° C. or lower (cloud point)), actor M-4 (fatty acid composition is carbon number 8 fatty acid 85 mass%, carbon number 10 fatty acid 15 Mass%: melting point −5 ° C. or less (cloud point)), Actor M-107FR (fatty acid composition is 40 mass% of 8 fatty acids, 30 mass% of 10 fatty acids, 30 mass% of other fatty acids: melting point− 5 ° C or less (cloud point) .

  Cocoonade RK, which is a triglyceride (medium chain fatty acid triglyceride) of fatty acid and glycerin manufactured by Kao Corporation. Fatty acid composition is 0.5% by mass of 6 fatty acids, 97.3% by mass of 8 fatty acids, carbon Tens of fatty acids 2.2% by mass: melting point 7 ° C. (freezing point)), cocoonade MT (fatty acid composition: carbon number 6 fatty acid 0.3% by mass, carbon number 8 fatty acid 81.6% by mass, carbon number 10 17.4% by mass of fatty acid, 0.4% by mass of fatty acid having 12 carbon atoms: melting point −15 ° C. (freezing point)), Coconut ML (fatty acid composition is 1.9% by mass of fatty acid having 6 carbon atoms, 8 carbon atoms) Fatty acid 37.6% by mass, carbon number 10 fatty acid 33.9% by mass, carbon number 12 fatty acid 20.2% by mass, carbon number 14 fatty acid 3.9% by mass, carbon number 16 fatty acid 1.5% by mass , Fatty acids with 18 carbon atoms Phosphoric acid) 0.4% by mass, C18 fatty acid (oleic acid) 0.6% by mass: melting point −3 ° C. (freezing point)), MT-N (fatty acid composition is C6 fatty acid 0.1 mass) %, Carbon number 8 fatty acid 74.7% by mass, carbon number 10 fatty acid 24.7% by mass, carbon number 12 fatty acid 0.2% by mass, carbon number 14 fatty acid 0.3% by mass: melting point −10 ° C. (Freezing point)).

  Wako Pure Chemical Industries, Ltd. Triglyceride of fatty acid and glycerin, coconut oil (fatty acid composition is 7.8% by weight of C8 fatty acid, 7.6% by weight of C10 fatty acid, 12 carbons) Fatty acid 44.8 mass%, C14 fatty acid 18.1 mass%, C16 fatty acid 9.5 mass%, C18 fatty acid (stearic acid) 2.4 mass%, C18 fatty acid ( Oleic acid) 8.2 mass%, carbon number 18 fatty acid (linoleic acid) 1.5 mass%: melting point 24 ° C. (freezing point)), palm oil (fatty acid composition is carbon number 12 fatty acid 0.2 mass%, C14 fatty acid 1.1 mass%, C16 fatty acid 44.0 mass%, C18 fatty acid (stearic acid) 4.5 mass%, C18 fatty acid (oleic acid) 39.2 mass %, C18 fatty acid (linoleic acid) 0.1 wt%, carbon number 18 of fatty acids (linolenic acid) 0.4 wt%: mp 39 ° C. (freezing point)).

As the component (C), one type may be used alone, or two or more types may be used in combination.
In the expandable polystyrene resin particles, the content of the component (C) is 0.01 parts by mass or more and less than 0.3 parts by mass with respect to 100 parts by mass of the component (A), and 0.02 to 0.28 masses. Part is preferable, and 0.03 to 0.25 part by mass is more preferable.
If content of (C) component is more than a preferable lower limit, in manufacture of a foaming molding, cooling time can be shortened more and shortening of a molding cycle can be aimed at. On the other hand, if the content of the component (C) is less than the preferable upper limit value, a foam molded article having high strength can be obtained.

The expandable polystyrene resin particles may contain components other than the above component (A), component (B) and component (C).
Examples of other components include foaming nucleating agents (inorganic fine powders such as talc, chemical foaming agents, etc.), antistatic agents (polyethylene glycol, stearic acid monoglyceride, etc.), blocking agents (such as zinc stearate), and the like.

  The expandable polystyrene resin particles of the present invention are preferably those in which at least a part of the surface is coated with the component (C), and a part or all of the surface is coated with the component (C) (C ) The component may be impregnated in the resin particles.

<Method for producing expandable polystyrene resin particles>
The expandable polystyrene resin particles of the present invention described above include the step (i) of obtaining the foaming agent-containing polystyrene resin particles by adding the foaming agent (B) to the polystyrene resin (A), and the step ( It can be suitably produced by a method comprising the step (ii) of applying the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles obtained in i).

(Process (i))
In the step (i), the foaming agent-containing polystyrene resin particles are obtained by adding the foaming agent (B) to the polystyrene resin (A).
This foaming agent-containing polystyrene resin particles can be produced by a known method, for example,
(1) A melt extrusion method in which a molten resin containing a polystyrene-based resin (A) and a foaming agent (B) is formed into granules,
(2) After supplying the aqueous medium and the polystyrene resin particles into the autoclave and dispersing the polystyrene resin particles in the aqueous medium, the monomer is continuously or intermittently heated and stirred in the autoclave. Then, the polystyrene resin particles are polymerized in the presence of a polymerization initiator while absorbing the monomer into the polystyrene resin particles (by seed polymerization method) to prepare polystyrene resin particles, and a foaming agent ( A method of containing B),
(3) Supply an aqueous medium, a monomer containing a styrenic monomer and a polymerization initiator into the autoclave, and suspension-polymerize the monomer while heating and stirring in the autoclave, and classify as necessary. A method of preparing polystyrene resin particles and adding the foaming agent (B) to the polystyrene resin particles.

Method (1) above:
Examples of the melt extrusion method (1) include the following methods.
First, a resin containing a polystyrene resin (A) is melted to obtain a molten resin, and a foaming agent (B) is press-fitted and kneaded into the molten resin to obtain a foaming agent-containing molten resin. While extruding the obtained foaming agent-containing molten resin directly into the cooling liquid from the small holes, the extrudate is cut in the cooling liquid, and the extrudate is cooled and solidified by contact with the cooling liquid. To do.
By using such a melt extrusion method, the foaming agent-containing polystyrene resin particles in which the foaming agent (B) is uniformly dispersed in the polystyrene resin (A) can be obtained.

FIG. 1 shows an embodiment of an apparatus for producing a foaming agent-containing polystyrene resin particle.
A manufacturing apparatus 10 shown in FIG. 1 includes an extruder 1, a die 2, a high-pressure pump 4, and a cutting chamber 7.
The extruder 1 is provided with a raw material supply hopper 3 for introducing a polystyrene resin (A) and the like, and a high-pressure pump 4 for press-fitting the foaming agent (B) into the extruder 1 through a supply port 5.
The die 2 is attached to the tip of the extruder 1 and has a large number of small holes.
In the cutting chamber 7, cooling water for cooling the resin discharged from the small holes of the die 2 is circulated and supplied, and a cutter 6 (high-speed rotary blade) that cuts the resin while cooling is provided rotatably.

As the extruder 1, either an extruder using a screw or an extruder not using a screw can be used. Examples of the extruder using a screw include a single-screw extruder, a multi-screw extruder, a vent-type extruder, and a tandem extruder. Examples of the extruder that does not use a screw include a plunger type extruder and a gear pump type extruder. Moreover, any extruder can use a static mixer. Among these extruders, an extruder using a screw is preferable from the viewpoint of productivity.
Moreover, the conventionally well-known thing used in the granulation method by melt extrusion of resin can also be used for the cutting chamber 7 in which the cutter 6 was provided.

  In order to obtain foaming agent-containing polystyrene resin particles using the production apparatus 10 shown in FIG. 1, first, a raw material polystyrene resin (A) and, if necessary, an additive (foaming nucleating agent, etc.) are weighed. The raw material supply hopper 3 is then charged into the extruder 1. The raw material polystyrene resin (A) may be put into a pellet or granule and mixed in advance and then charged from one raw material supply hopper. For example, when using a plurality of lots, supply each lot. A plurality of raw material supply hoppers 3 whose amounts are adjusted may be charged and mixed in the extruder 1. Also, when using a combination of recycled materials from multiple lots, thoroughly mix the raw materials from multiple lots and remove foreign matter in advance by appropriate sorting means such as magnetic sorting, sieving, specific gravity sorting, and air sorting. It is preferable to keep it.

After supplying polystyrene-type resin (A) and an additive as needed in the extruder 1, polystyrene-type resin (A) is heat-melted. The heating temperature is preferably 150 to 250 ° C.
Next, while the heated and melted polystyrene-based resin (molten resin) is transferred to the die 2 side, the foaming agent (B) is injected from the supply port 5 by the high-pressure pump 4 to mix the molten resin and the foaming agent. The pressure in the extruder 1 when the foaming agent (B) is press-fitted is preferably about 5 to 25 MPa.
Next, the melted material in which the foaming agent (B) is press-fitted is transferred to the die 2 side while being further kneaded through a foreign matter removing screen provided in the extruder 1 as necessary. It extrudes from a small hole in the die 2 attached to the tip of the die.

  When the melted material in which the foaming agent (B) is press-fitted is extruded from the small hole of the die 2 into the cutting chamber 7, the extruded melt is cut into particles by the cutter 6 rotating in the cutting chamber 7. And is rapidly cooled to solidify with foaming being suppressed to form foaming agent-containing polystyrene resin particles.

  The formed foaming agent-containing polystyrene-based resin particles are transferred from the cutting chamber 7 together with the flow of cooling water and are transported to the dehydrating dryer 11 with a solid-liquid separation function, where they are separated from the cooling water and dehydrated and dried. . The dried foaming agent-containing polystyrene-based resin particles are sent to the storage container 12 and stored. The separated cooling water is sent to the water tank 8 and returned to the cutting chamber 7 by the high-pressure pump 9.

The average particle diameter of the foaming agent-containing polystyrene resin particles produced by the method (1) is preferably about 0.3 to 2.0 mm, more preferably about 0.5 to 1.7 mm.
In the present invention, “average particle diameter of resin particles” indicates a value measured by performing a classification operation using a low-tap type sieve shaker (manufactured by Iida Seisakusho).
The shape of the foaming agent-containing polystyrene resin particles is preferably spherical or substantially spherical.

Method (2), method (3):
Examples of the monomer used in the method (2) or (3) include a styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. Examples thereof include styrene monomers and vinyl monomers exemplified in the description of (resin).

  The polymerization initiator used in the method (2) or (3) is not particularly limited. For example, benzoyl peroxide, lauryl peroxide, t-butyl peroxybenzoate, di-t-butyl peroxide, t -Butyl peroxypivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyacetate, 2,2 Organic peroxides such as bis (t-butylperoxy) butane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate; azobisisobutyro Azo compounds such as nitrile and azobisdimethylvaleronitrile It is below. These polymerization initiators may be used individually by 1 type, and may use 2 or more types together.

The aqueous medium contains water as a main component and may contain a small amount of a water-soluble organic solvent such as alcohol, ketone, or ether.
In the suspension polymerization method or seed polymerization method, a suspension stabilizer may be added in advance to the aqueous medium in order to stabilize the dispersibility of the monomer droplets or the thermoplastic resin seed particles. . Examples of the suspension stabilizer include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone; and poorly water-soluble inorganic salts such as tricalcium phosphate and magnesium pyrophosphate. When using a poorly water-soluble inorganic salt, an anionic surfactant is usually used in combination.
Examples of the anionic surfactant include alkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher fatty acid salts such as sodium oleate, β-tetrahydroxynaphthalene sulfonate, and the like. Among them, alkylbenzene sulfonate is preferable.

In the method of (2) or (3), examples of the method of incorporating the foaming agent (B) into the polystyrene resin particles include a method of impregnating the polystyrene resin particles with the foaming agent (B).
In order to impregnate the polystyrene resin particles with the foaming agent (B), for example, a slurry in which polystyrene resin particles are dispersed in an aqueous medium is placed in a pressure-resistant container such as an autoclave, and then the foaming agent (B) is pressure-resistant. What is necessary is just to supply in a container and hold | maintain for a fixed time.

  The average particle diameter of the foaming agent-containing polystyrene resin particles produced by the method (2) or (3) is preferably about 0.3 to 2.0 mm, more preferably 0.5 to 1. It is about 4 mm.

  Among these, as the method for obtaining the foaming agent-containing polystyrene resin particles, the method (1) is preferable because it is easy to use a recycled polystyrene resin as a raw material.

(Step (ii))
In the step (ii), on the surface of the foaming agent-containing polystyrene resin particles obtained in the step (i), the triglyceride (C) (a fatty acid mainly containing a fatty acid having 6 to 11 carbon atoms, glycerin, Of triglyceride).
The method of applying the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles is not particularly limited, and examples thereof include a method of mixing the foaming agent-containing polystyrene resin particles and the triglyceride (C).

FIG. 2 shows an embodiment of a mixer used when mixing the foaming agent-containing polystyrene resin particles and the triglyceride (C).
The mixer 20 shown in FIG. 2 includes a cylindrical stirring tank 26, a shaft 23, and a motor 25 that drives the shaft 23 to rotate.
The stirring tank 26 has an inlet 21 through which raw materials (foaming agent-containing polystyrene-based resin particles and triglyceride (C), etc.) are put in the upper part thereof, and a foaming agent containing a preparation (triglyceride (C), etc.) applied in the lower part thereof. And a discharge port 22 through which polystyrene resin particles) are discharged.
The shaft 23 is inserted into the stirring tank 26 so as to be rotatable in a direction perpendicular to the vertical direction of the stirring tank 26. The shaft 23 is provided with a plurality of stirring blades 24 spaced apart from each other.

In order to apply the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles using the mixer 20 shown in FIG. 2, a predetermined amount of the foaming agent-containing polystyrene resin particles and the triglyceride (C) are respectively added. What is necessary is just to stir with the stirring blade 24 rotated integrally with the shaft 23 by throwing in the stirring tank 26 from the opening | mouth 21 and driving the motor 25 and throwing in these raw materials.
At this time, as for triglyceride (C), content of the triglyceride (C) in the expandable polystyrene resin particle finally prepared is 0.01 parts by mass or more and 0.3 parts by mass with respect to 100 parts by mass of the polystyrene resin. It mix | blends so that it may become less than a mass part.

When the triglyceride (C) is blended, only a triglyceride of a fatty acid mainly composed of a fatty acid having 6 to 11 carbon atoms and glycerin may be used, and an ester of a triglyceride (C) and a fatty acid and glycerin (monoester or And a fatty acid glycerin ester mixture containing a diester).
In the latter case, the fatty acid glycerin ester mixture is preferably liquid at room temperature (25 ° C.) because the molding cycle can be shortened and it is difficult to peel from the resin particles.
Moreover, it is preferable that this fatty-acid glycerol ester mixture contains 50 mass% or more of triglycerides (C), and it is more preferable that the triglyceride (C) contains 65 mass% or more. If the ratio of triglyceride (C) is more than this preferable lower limit, the molding cycle can be shortened and the flowability of the expandable polystyrene resin particles is further increased. The fatty acid glycerin ester mixture particularly preferably contains 65% by mass or more of a triglyceride of a fatty acid having 8 to 10 carbon atoms and glycerin.
Further, when mixing the foaming agent-containing polystyrene resin particles and the triglyceride (C), in addition to the triglyceride (C), an antistatic agent (polyethylene glycol, stearic acid monoglyceride, etc.), a blocking agent (such as zinc stearate), etc. May be mixed together.

  After mixing the foaming agent-containing polystyrene resin particles and the triglyceride (C) with the mixer 20, the foaming agent-containing polystyrene resin particles coated with the triglyceride (C) are taken out from the discharge port 22, Expandable polystyrene resin particles are obtained.

  The method of applying the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles may be a method other than the method of mixing both as shown in FIG. A method of spraying (C) may be used. Thus, triglyceride (C) can be apply | coated to the surface of this resin particle by a simple method, and according to the manufacturing method mentioned above, productivity is high.

In such a method for producing expandable polystyrene resin particles, it is preferable that in step (ii), triglyceride (C) is applied to the surface of the foaming agent-containing polystyrene resin particles and then left for an arbitrary time.
As time to leave after apply | coating a triglyceride (C) to the foaming agent containing polystyrene-type resin particle surface, 3 hours or more are preferable, 8-120 hours are more preferable, 10-100 hours are further more preferable. By setting the time allowed to stand after the coating to be equal to or longer than the preferable time, the stickiness of the surface of the expandable polystyrene resin particles is sufficiently reduced, the fluidity of the particles is increased, and poor transportation or the like is less likely to occur.

  According to the expandable polystyrene resin particles of the present invention manufactured by the above-described manufacturing method, even if the amount of triglyceride (C) applied to the surface of the foaming agent-containing polystyrene resin particles is increased, it is sticky immediately after application. However, the stickiness is reduced with time and good fluidity is exhibited.

The average particle diameter of the finally obtained expandable polystyrene resin particles is preferably 0.3 to 2.0 mm, and more preferably 0.5 to 1.7 mm.
The shape of the expandable polystyrene resin particles is preferably spherical or substantially spherical.

<Polystyrene resin pre-expanded particles>
The polystyrene resin pre-expanded particles of the present invention (hereinafter also simply referred to as “pre-expanded particles”) are foamed by heating the expandable polystyrene resin particles of the present invention by steam heating or the like using a known apparatus and method. It is something to be made.
The average particle diameter of the pre-expanded particles is preferably 0.3 to 8.0 mm, and more preferably 0.5 to 7.0 mm, because a high-strength foamable shape can be easily obtained.

Moreover, it is preferable that the pre-expanded particles have a bulk density comparable to the density of the foam molded article to be produced. The bulk density of the pre-expanded particles is not particularly limited, but is preferably in the range of 0.010~0.60g / cm ^3, more preferably in the range of 0.015~0.20g / cm ^3, 0.015~ More preferably within the range of 0.10 g / cm ³ .
The bulk expansion ratio of the pre-expanded particles is determined in consideration of the intended use of the foamed molded product to be produced, and is preferably 10 times or more (bulk density of 0.10 g / cm ³ or less), preferably 30 times or more (bulk) density 0.033 g / cm ³ or less), more preferably, 40 times or more (bulk density 0.025 g / cm ³ or less) are more preferred. If the bulk expansion ratio of the pre-expanded particles is equal to or more than the preferred lower limit value, it can be applied to foam molded articles for various uses.

In the present invention, the bulk density of the pre-expanded particles refers to those measured in accordance with JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. For example, it can be measured as follows.
Method for measuring bulk density of pre-expanded particles:
Weigh the mass (W) g of the pre-expanded particles to the second decimal place. Next, the pre-expanded particles weighed in the graduated cylinder are filled by natural dropping, and the volume (V) cm ³ of the pre-expanded particles dropped in the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. taking measurement. Then, the bulk density of the pre-expanded particles is obtained based on the following formula.
Bulk density (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

The bulk expansion ratio of the pre-expanded particles is a numerical value calculated by the following formula.
Bulk foaming factor = 1 / bulk density (g / cm ³ )

<Foamed molded product>
The foamed molded product of the present invention is obtained by filling the above-mentioned polystyrene resin pre-expanded particles of the present invention into a cavity of a molding die and heating and molding it in-mold.
The density of the foamed molded article of the present invention is not particularly limited, but preferably in the range of 0.010~0.60g / cm ^3, more preferably in the range of 0.015~0.20g / cm ^3, More preferably within the range of 0.015-0.10 g / cm ³ .
The expansion ratio of the foamed molded product is determined in consideration of the use of the foamed molded product intended for production, and is preferably 10 times or more (density 0.10 g / cm ³ or less), preferably 30 times or more (density 0. 033 g / cm ³ or less), more preferably 40 times or more (density 0.025 g / cm ³ or less). If the expansion ratio is not less than the above lower limit value, it can be applied to foam molded articles for various uses.

In the present invention, the density of the foamed molded product refers to that measured by the method described in JIS K7122: 1999 “Measurement of foamed plastic and rubber-apparent density”.
Method for measuring density of foamed molded product:
A test piece (foamed molded body) of 50 cm ³ or more is cut so as not to change the original cell structure of the material, its mass is measured, and the following equation is calculated.
Density (g / cm ³ ) = Test piece mass (g) / Test piece volume (cm ³ )
As a test piece, it was cut out from a foamed molded article that had passed 72 hours or more after molding, and a temperature of 23 ° C. ± 2 ° C. and a relative humidity of 50% ± 5% or a temperature of 27 ° C. ± 2 ° C. and a relative humidity of 65% ± 5% Use those that have been left under atmospheric conditions for at least 16 hours.

The expansion ratio of the foamed molded product is a numerical value calculated by the following equation.
Foaming factor = 1 / density (g / cm ³ )

(Function and effect)
In the expandable polystyrene resin particles of the present invention, as a high cycle agent, a fatty acid having 6 to 11 carbon atoms of 0.01 to less than 0.3 parts by mass with respect to 100 parts by mass of the polystyrene resin (A). By using the triglyceride (C) of glycerin, the cooling time at the time of molding can be shortened, and the molding cycle is shortened. In addition, the use of the triglyceride (C) as a high cycle agent makes it difficult for the high cycle agent to peel off from the resin particles during the transportation or transfer of the expandable polystyrene resin particles. The flowability of the conductive polystyrene resin particles is good.
In addition, as described above, when the foaming agent-containing polystyrene resin particles are produced by the melt extrusion method of (1), the obtained foamed molded article has a large average cell diameter, and the molding cycle tends to be long. The expandable polystyrene resin particles and the production method thereof of the present invention are particularly effective in such a case.

Furthermore, since the foamed molded article of the present invention is obtained by using the polystyrene resin pre-expanded particles obtained by heating and foaming the above expandable polystyrene resin particles, a machine such as bending strength is obtained. It has high strength and, in addition, has a beautiful appearance.
Such foamed molded products can be suitably used for, for example, packing cushioning materials for home appliances, heat insulation and cold boxes such as fish boxes and vegetable boxes, building structural members, food containers, and heat insulating materials.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. In the following examples, “%” means “% by mass”, and “part” means “part by mass”.
The high cycle agent (triglyceride) used in this example is shown below.

C-1: Actor M-2 (trade name, manufactured by Riken Vitamin Co., Ltd.) Triglyceride of fatty acid and glycerin. The composition of the fatty acid is 100% by mass of C8 fatty acid (caprylic acid).

C-2: Actor M-1 (trade name, manufactured by Riken Vitamin Co., Ltd.) Triglyceride of fatty acid and glycerin. The composition of the fatty acid is 60% by mass of C8 fatty acid (caprylic acid) and 40% by mass of C10 fatty acid (capric acid).

C-3: Coconut ML (trade name, manufactured by Kao Corporation). Triglyceride of fatty acid and glycerin. The composition of the fatty acid is 1.9% by mass of a fatty acid having 6 carbon atoms (caproic acid), 37.6% by mass of fatty acid having 8 carbon atoms (caprylic acid), and 33.9% by mass of fatty acid having 10 carbon atoms (capric acid). , 20.2% by mass of fatty acids having 12 carbon atoms (lauric acid), 3.9% by mass of fatty acids having 14 carbon atoms (myristic acid), 1.5% by mass of fatty acids having 16 carbon atoms (palmitic acid), 18 carbon atoms Fatty acid (stearic acid) 0.4 mass%, C18 fatty acid (oleic acid) 0.6 mass%.

C-4: Coconut oil (manufactured by Wako Pure Chemical Industries, Ltd.). Triglyceride of fatty acid and glycerin. The fatty acid composition is 7.8% by mass of C8 fatty acid (caprylic acid), 7.6% by mass of C10 fatty acid (capric acid), and 44.8% by mass of C12 fatty acid (lauric acid). , C14 fatty acid (myristic acid) 18.1% by mass, C16 fatty acid (palmitic acid) 9.5% by mass, C18 fatty acid (stearic acid) 2.4% by mass, C18 Fatty acid (oleic acid) 8.2 mass%, C18 fatty acid (linoleic acid) 1.5 mass%.

C-5: Palm oil (manufactured by Wako Pure Chemical Industries, Ltd.). Triglyceride of fatty acid and glycerin. The composition of the fatty acid is 0.2% by mass of C12 fatty acid (lauric acid), 1.1% by mass of C14 fatty acid (myristic acid), and 44.0% by mass of C16 fatty acid (palmitic acid). , C18 fatty acid (stearic acid) 4.5 mass%, C18 fatty acid (oleic acid) 39.2 mass%, C18 fatty acid (linoleic acid) 10.1 mass%, C18 Fatty acid (linolenic acid) 0.4 mass%.

C-6: stearic acid triglyceride (manufactured by Riken Vitamin Co., Ltd.) Triglyceride of fatty acid and glycerin. The composition of the fatty acid is 100% by mass of a fatty acid having 18 carbon atoms (stearic acid).

Example 1
<Manufacture of expandable polystyrene resin particles>
Step (i):
A foaming agent-containing polystyrene-based resin particle) was obtained in the following manner using the same apparatus as the manufacturing apparatus shown in FIG.
0.3 parts by mass of fine powder talc is added to 100 parts by mass of polystyrene resin raw material (recycled polystyrene, mass average molecular weight 280,000), and these are continuously supplied to a single-screw extruder with a diameter of 90 mm at 130 kg per hour. did. After setting the temperature in the extruder to the maximum temperature of 210 ° C. and melting the polystyrene resin raw material and fine powder talc, pentane (isopentane: normal pentane = 20: 80 (100 parts by mass) with respect to 100 parts by mass of the polystyrene resin. (Mass ratio)) 6 parts by mass were press-fitted from the middle of the extruder (pressure in the extruder: 15 MPa). The polystyrene resin and the foaming agent are kneaded and cooled in the extruder, and the land length is 0.6 mm in diameter while maintaining the resin temperature at the top of the extruder at 170 ° C. and the pressure at the resin introduction part of the die at 13 MPa. The foaming agent-containing molten resin is extruded into a cutting chamber connected to the discharge side of this die and having a water circulation of 30 ° C. from a die having 200 small holes of 3.0 mm in length, and at the same time in the circumferential direction. The extrudate was cut with a high-speed rotary cutter having 10 blades. The particles formed by cutting were conveyed to a particle separator while being cooled with circulating water, and the particles were separated from the circulating water. Furthermore, the collected particles were dehydrated and dried to obtain polystyrene resin particles (foaming agent-containing polystyrene resin particles) containing a foaming agent.
The obtained foaming agent-containing polystyrene-based resin particles were almost perfect spheres without deformation or beard, and the average particle diameter was about 1.1 mm.

Step (ii):
0.03 parts by mass of polyethylene glycol (molecular weight 300), 0.15 parts by mass of zinc stearate, and 0.05 parts by mass of monoglyceride stearate with respect to 100 parts by mass of the obtained foaming agent-containing polystyrene resin particles And 0.10 parts by mass of C-1 (100% by mass of C6-11 fatty acids in the total fatty acids in triglycerides) as triglycerides, and using the same form as the mixer shown in FIG. In this way, the foaming agent-containing polystyrene resin particles were uniformly coated on the entire surface.
The polyethylene glycol, zinc stearate, stearic acid monoglyceride and triglyceride are collectively referred to as a coating agent hereinafter.

Using the mixer 20 having the same form as the mixer shown in FIG. 2, first, a predetermined amount of each of the foaming agent-containing polystyrene resin particles and polyethylene glycol are charged into the stirring tank 26 from the charging port 21. The starting material was driven and the charged raw material was stirred by the stirring blade 24 for a predetermined time. Next, while stirring, a predetermined amount of zinc stearate and monostearate monoglyceride were added and stirred for a predetermined time. Further, while stirring, a predetermined amount of C-1 was added and stirred for a predetermined time. As a result, the coating agent was uniformly applied to the entire surface of the foaming agent-containing polystyrene resin particles.
Thereafter, the stirring is stopped, and the foaming agent-containing polystyrene resin particles coated with the coating agent are taken out from the discharge port 22, placed in a 15 ° C. cool box, and left for 72 hours to obtain the desired foaming property. Polystyrene resin particles were obtained. The obtained expandable polystyrene resin particles were almost perfect spheres, and the average particle diameter was about 1.1 mm.

<Production of pre-expanded particles>
The obtained expandable polystyrene resin particles were supplied to a cylindrical batch type pre-foaming machine, and heated and foamed with steam having a blowing pressure of 0.05 MPa to obtain polystyrene resin pre-expanded particles.
The obtained polystyrene resin pre-expanded particles had a bulk density of 0.020 g / cm ³ (bulk expansion ratio: 50 times).

<Manufacture of foam molding>
Subsequently, after the polystyrene resin pre-expanded particles obtained were allowed to stand for 24 hours in a room temperature atmosphere, they were filled into a mold having a rectangular cavity of length 400 mm × width 300 mm × height 50 mm. Thereafter, the inside of the cavity of the mold was heated with steam at a gauge pressure of 0.08 MPa for 10 seconds to perform in-mold foam molding. Then, it cooled until the pressure in the cavity of a shaping | molding mold became 0.01 Mpa, Then, the shaping | molding die was opened and the rectangular foam molded object of length 400mm * width 300mm * height 50mm was taken out.
The obtained foamed molded article had a density of 0.020 g / cm ³ (foaming factor: 50 times).

(Example 2)
The coating amount of C-1 used as a triglyceride (100% by mass of C6-11 fatty acid in the total fatty acids in triglyceride) is 0.02 parts by mass with respect to 100 parts by mass of the foaming agent-containing polystyrene resin particles. Except for the change, in the same manner as in Example 1, expandable polystyrene resin particles, polystyrene resin pre-expanded particles, and foamed molded articles were obtained.

(Example 3)
The coating amount of C-1 used as a triglyceride (100% by mass of the C6-11 fatty acid in the total fatty acids in the triglyceride) is 0.29 parts by mass with respect to 100 parts by mass of the foaming agent-containing polystyrene resin particles. Except for the change, in the same manner as in Example 1, expandable polystyrene resin particles, polystyrene resin pre-expanded particles, and foamed molded articles were obtained.

Example 4
Expandable polystyrene resin particles and polystyrene resin in the same manner as in Example 1 except that the type of triglyceride was changed to C-2 (100% by mass of the C6-11 fatty acid occupying the whole fatty acid in the triglyceride). Pre-foamed particles and foamed molded products were obtained.

(Example 5)
Expandable polystyrene resin particles and polystyrene in the same manner as in Example 1 except that the type of triglyceride was changed to C-3 (the ratio of C6-11 fatty acid in the total fatty acid in triglyceride was 73.4% by mass). -Based resin pre-expanded particles and expanded molded articles were obtained.

(Example 6)
The kind of triglyceride is a mixture of 0.05 part by mass of C-1 and 0.05 part by mass of C-4 (the proportion of C6-11 fatty acids in the total fatty acids in triglycerides is 57.7% by mass). Except that it was changed to, expandable polystyrene resin particles, polystyrene resin pre-expanded particles, and foamed molded articles were obtained in the same manner as in Example 1.

(Example 7)
<Manufacture of expandable polystyrene resin particles>
Step (i):
In a 100 liter autoclave with a stirrer, 64 g of magnesium pyrophosphate obtained by the metathesis method, 2.4 g of sodium dodecylbenzenesulfonate, 107 g of benzoyl peroxide (purity 75% by mass), t-butylperoxy-2-ethylhexyl 28 g of monocarbonate, 40 kg of ion-exchanged water and 40 kg of styrene monomer (styrene) were supplied, and the stirring blade was rotated at a rotational speed of 150 rpm and stirred to prepare a suspension.
Next, while the stirring blade is rotated at the same rotational speed of 150 rpm and the suspension is stirred, the temperature in the autoclave is raised to 90 ° C. and maintained at 90 ° C. for 6 hours. Was raised to 125 ° C., and the styrene monomer was subjected to suspension polymerization by maintaining 125 ° C. for 2 hours.
Thereafter, the temperature in the autoclave is cooled to 25 ° C., the polystyrene resin particles are taken out from the autoclave, washed and dehydrated repeatedly, and after a drying process, classification is performed and an average particle diameter of 0.6 mm is obtained. Further, polystyrene resin particles (seed particles) having a mass average molecular weight of 300,000 were obtained.

Next, 30 kg of ion-exchanged water, 4 g of sodium dodecylbenzenesulfonate, and 100 g of magnesium pyrophosphate were supplied into another 100 liter autoclave equipped with a stirrer. Thereafter, 11 kg of the polystyrene-based resin particles were supplied as seed particles in the autoclave, and were uniformly dispersed in water by stirring.
In addition, a dispersion in which 2 g of sodium dodecylbenzenesulfonate and 20 g of magnesium pyrophosphate were dispersed in 6 kg of ion-exchanged water, 88 g of benzoyl peroxide (purity 75% by mass) as a polymerization initiator and t-butyl in 5 kg of a styrene monomer. A styrene monomer solution in which 50 g of peroxy-2-ethylhexyl monocarbonate is dissolved is prepared, and the styrene monomer solution is added to the above dispersion and stirred to homogenize using a homomixer. To obtain an emulsion.
Then, the inside of the autoclave is heated to 75 ° C. and maintained at 75 ° C., and then the emulsion is added in the autoclave, so that the styrene monomer and benzoyl peroxide are smoothly contained in the polystyrene resin particles (seed particles). For 30 minutes to be absorbed. Thereafter, 28 kg of styrene monomer was continuously added dropwise over 160 minutes in the autoclave while increasing the temperature in the autoclave from 75 ° C. to 108 ° C. at a rate of 0.2 ° C./min. 20 minutes after dropping of the styrene monomer is completed, the temperature is raised to 120 ° C. at a rate of 1 ° C./min, and 120 ° C. is maintained for 90 minutes. A reaction solution containing was obtained. At this time, all styrene monomers were used for the polymerization.

Next, to 2 kg of ion-exchanged water, 0.8 g of sodium dodecylbenzenesulfonate as a surfactant and 20 g of magnesium pyrophosphate obtained by metathesis as a hardly water-soluble inorganic salt were added and stirred. 308 g of diisobutyl adipate (trade name “DI4A”, manufactured by Taoka Chemical Co., Ltd.) was added as an agent, and the mixture was stirred at a rotational speed of 7000 rpm for 30 minutes to prepare a dispersion.
Next, after the inside of the autoclave was cooled to 90 ° C. at a temperature lowering rate of 1 ° C./min, the dispersion was added to the reaction solution containing the polystyrene resin particles obtained by the seed polymerization.
Then, after 30 minutes have passed since the dispersion was supplied in the autoclave, the autoclave was sealed, and then 3520 g of butane (isobutane / normal butane (mass ratio) = 30/70) as a foaming agent (100 parts by mass of polystyrene resin particles). 8 parts by mass) was press-fitted into the autoclave by nitrogen pressurization for 30 minutes and held in that state for 3 hours.
Thereafter, the inside of the autoclave is cooled to 25 ° C., the polystyrene resin particles containing the foaming agent (foaming agent-containing polystyrene resin particles) are taken out from the autoclave, washed, dehydrated repeatedly, and dried. Then, classification was performed to obtain a foaming agent-containing polystyrene resin particle having an average particle diameter of 0.9 mm and a mass average molecular weight of 300,000.

Step (ii):
In the same manner as in Example 1, with respect to 100 parts by mass of the obtained foaming agent-containing polystyrene resin particles, 0.03 part by mass of polyethylene glycol 300, 0.15 part by mass of zinc stearate, and monoglyceride stearate 0.05 parts by mass and 0.10 parts by mass of C-1 as a triglyceride (100% by mass of C6-11 fatty acids in the total fatty acids in triglycerides), and having the same form as the mixer shown in FIG. Was applied uniformly over the entire surface of the foaming agent-containing polystyrene resin particles.
Thereafter, the foaming agent-containing polystyrene resin particles coated with fatty acid triglyceride and the like were placed in a 15 ° C. cool box and allowed to stand for 72 hours to obtain the desired expandable polystyrene resin particles.

<Preparation of pre-expanded particles and foamed molded article>
Using the expandable polystyrene resin particles obtained above, polystyrene resin pre-expanded particles and expanded molded articles were obtained in the same manner as in Example 1.

(Comparative Example 1)
Except that no fatty acid triglyceride was added, expandable polystyrene resin particles, polystyrene resin pre-expanded particles, and foamed molded articles were obtained in the same manner as in Example 1.

(Comparative Example 2)
Expandable polystyrene resin particles and polystyrene in the same manner as in Example 1 except that the type of triglyceride was changed to C-4 (the ratio of C6-11 fatty acid to 15.4% by mass of the total fatty acids in triglyceride). -Based resin pre-expanded particles and expanded molded articles were obtained.

(Comparative Example 3)
Expandable polystyrene resin particles and polystyrene resin in the same manner as in Example 1 except that the type of triglyceride was changed to C-5 (the proportion of C6-11 fatty acid in the total fatty acid in triglyceride is 0% by mass). Pre-foamed particles and foamed molded products were obtained.

(Comparative Example 4)
Expandable polystyrene resin particles and polystyrene resin in the same manner as in Example 1 except that the type of triglyceride was changed to C-6 (the proportion of C6-11 fatty acids in the total fatty acids in triglycerides was 0% by mass). Pre-foamed particles and foamed molded products were obtained.

(Comparative Example 5)
The coating amount of C-1 used as a triglyceride (the proportion of C6-11 fatty acids in the total of fatty acids in triglycerides is 100% by mass) is 0.35 parts by mass with respect to 100 parts by mass of the foaming agent-containing polystyrene resin particles. Except for the change, in the same manner as in Example 1, expandable polystyrene resin particles, polystyrene resin pre-expanded particles, and foamed molded articles were obtained.

  For the expandable polystyrene resin particles obtained in each Example and each Comparative Example, evaluation of peelability using the amount of coating agent peeled as an index and evaluation of fluidity using the angle of repose as an index were performed. In addition, when manufacturing the foam molded article, the molding cycle was evaluated using the cooling time as an index. Moreover, the mechanical strength was measured about the foaming molding obtained by each Example and each comparative example. Furthermore, comprehensive evaluation was performed. These results are shown in Table 1.

[Evaluation of releasability of coating agent in expandable polystyrene resin particles]
About the expandable polystyrene resin particle (measurement sample) obtained in each Example and each comparative example, the peeling amount of the coating agent containing a high cycle agent (triglyceride) was measured using the test apparatus shown in FIG.

  The test apparatus 30 shown in FIG. 3 includes a transparent polyvinyl chloride funnel 31, an acrylic plate 32 that is slightly spaced and inclined below a tube 31 t of the funnel 31, and a fixing that holds the acrylic plate 32. And a table 33. The dimensions a to d of each part of the test apparatus 30 were a funnel diameter a = 250 mm, a funnel 31 height b = 120 mm, a tube 31t length c = 1040 mm, and a distance d between the tube 31t and the acrylic plate 32 = 30 mm. The diameter of the tube 31t was 20 mm, the dimensions of the acrylic plate 32 were 50 mm in length, 50 mm in width, and 2 mm in thickness. The inclination of the acrylic plate 32 was 30 °.

After measuring the mass (initial) of the acrylic plate 32, the acrylic plate 32 was fixed to the fixing base 33. The operation of putting 2000 g of the measurement sample from the upper opening of the funnel 31 and dropping it was repeated 5 times, and then the acrylic plate 32 was removed and the mass was measured.
The difference in mass of the acrylic plate 32 before and after the measurement sample is dropped is defined as the amount of peeling of the coating agent. Based on the following evaluation criteria, the amount of peeling of the coating agent in the expandable polystyrene resin particles Evaluated.
Evaluation criteria Very good (◎): The amount of coating agent peeled is less than 5 mg.
Good (◯): The amount of peeling of the coating agent is 5 mg or more and less than 15 mg.
Poor (x): The amount of coating agent peeled off is 15 mg or more.

[Evaluation of fluidity of expandable polystyrene resin particles]
300 cm ³ (bulk volume) of the expandable polystyrene resin particles (measurement sample) obtained in each example and each comparative example is placed in a cylindrical frame body having a diameter of 80 mm and a height of 70 mm on a horizontal surface. It was. Next, the frame was lifted and removed. Measure the angle between each of the two ridges of the mountain with respect to the horizontal plane when the mountain is viewed from one side, using a protractor. Was the average angle.
This operation was repeated 5 times each immediately after the production of the expandable polystyrene resin particles and 72 hours later, and the arithmetic average value of the obtained average angles was taken as the repose angle, based on the following evaluation criteria: The fluidity of the expandable polystyrene resin particles was evaluated.
Evaluation criteria Very good (◎): angle of repose is less than 25 °.
Good (◯): The angle of repose is 25 ° or more and less than 30 °.
Poor (x): Repose angle is 30 ° or more.

[Evaluation of molding cycle]
The polystyrene resin pre-expanded particles obtained in each example and each comparative example were filled into a mold having a rectangular cavity of length 400 mm × width 300 mm × height 50 mm, and then into the mold cavity This was heated with steam at a gauge pressure of 0.08 MPa for 10 seconds to perform in-mold foam molding. Thereafter, the cooling time until the pressure in the cavity of the mold became 0.01 MPa was measured, and the molding cycle was evaluated based on the following evaluation criteria.
Evaluation criteria Very good (◎): Cooling time is less than 180 seconds.
Good (O): Cooling time is 180 seconds or more and less than 240 seconds.
Defect (x): Cooling time is 240 seconds or more.

[Evaluation of mechanical strength of foamed molded product]
About the foaming molding obtained by each Example and each comparative example, bending strength was measured according to the method as described in JIS A9511: 2006 "foaming plastic heat insulating material."
Specifically, a Tensilon universal testing machine UCT-10T (manufactured by Orientec Co., Ltd.) is used, the size of the foamed molded body (test piece) is 75 mm × 300 mm × 50 mm, the compression speed is 10 mm / min, and the tip jig is Measurement was performed with a pressure wedge 10R and a support 10R as a distance between fulcrums of 200 mm, and the bending strength was calculated by the following equation. The number of test pieces was three, and the average value was obtained.
Bending strength (MPa) = 3FL / 2uh ²
In the formula, F represents the maximum bending load (N), L represents the distance between supporting points (mm), u represents the width (mm) of the test piece, and h represents the thickness (mm) of the test piece.
Thus, the average value of bending strength was calculated | required and the mechanical strength of the foaming molding was evaluated based on the following evaluation criteria.
Evaluation criteria Very good (◎): Bending strength is 0.26 MPa or more.
Good (O): Bending strength is 0.23 MPa or more and less than 0.26 MPa.
Defect (x): Bending strength is less than 0.23 MPa.

[Comprehensive evaluation]
[Evaluation of peelability of coating agent in expandable polystyrene resin particles], [Evaluation of fluidity of expandable polystyrene resin particles (72 hours after coating of coating agent)], [Evaluation of molding cycle] Based on the evaluation results in [Evaluation of mechanical strength of foamed molded product] and [Evaluation of mechanical strength of foamed molded product], comprehensive evaluation was performed according to the following evaluation criteria.
Evaluation criteria Very good (◎): All evaluations were very good (◎).
Good (◯): In all evaluations, there is no defect (×), and it is good (◯) or very good (◎).
Defect (x): There was one or more defects (x).

  From the results shown in Table 1, according to the expandable polystyrene-based resin particles of Examples 1 to 7 to which the present invention is applied, a foamed molded body having high strength is obtained, and the molding cycle is shortened. It can be confirmed that the high cycle agent does not easily peel from the resin and the fluidity is good.

  DESCRIPTION OF SYMBOLS 1 ... Extruder, 2 ... Die, 3 ... Raw material supply hopper, 4 ... High pressure pump, 5 ... Supply port, 6 ... Cutter, 7 ... Cutting chamber, 8 ... Water tank, 9 ... High pressure pump, 10 ... Manufacturing apparatus, 11 ... Dehydrating and drying machine, 12 ... storage container, 20 ... mixer, 21 ... inlet, 22 ... outlet, 23 ... shaft, 24 ... stirring blade, 25 ... motor, 26 ... stirring tank, 30 ... test device, 31 ... funnel, 32 ... acrylic plate, 33 ... fixed base.

Claims (5)

At least a part of the surface is coated with a triglyceride (C) of a fatty acid and a glycerin containing a polystyrene resin (A) and a foaming agent (B), the main component of which is a fatty acid having 6 to 11 carbon atoms,
Expandable polystyrene resin particles in which the content of the triglyceride (C) is 0.01 parts by mass or more and less than 0.3 parts by mass with respect to 100 parts by mass of the polystyrene resin (A). A method for producing the expandable polystyrene resin particles according to claim 1,
A step (i) in which the foaming agent (B) is contained in the polystyrene resin (A) to obtain foaming agent-containing polystyrene resin particles;
Applying the triglyceride (C) to the surface of the foaming agent-containing polystyrene resin particles obtained in the step (i) (ii);
A process for producing expandable polystyrene resin particles.   The method for producing expandable polystyrene resin particles according to claim 2, wherein the triglyceride (C) is applied to the surface of the foaming agent-containing polystyrene resin particles in the step (ii) and then allowed to stand for an arbitrary time.   Polystyrene resin pre-expanded particles obtained by heating and expanding the expandable polystyrene resin particles according to claim 1.   A foam molded article obtained by filling the polystyrene resin pre-expanded particles according to claim 4 into a cavity of a molding die and heating to form in-mold foam molding.

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