JP2012188543A - Resin particle, foamable resin particle, method for producing the same, foamed particle and formed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polyestyrene resin particles which give a foamed molding having excellent foaming, foamed particle properties and thermal insulating properties.SOLUTION: The resin particles for impregnating a vinyl group-containing fluorine base volatile foaming agent includes a resin mixture of a styrenic resin of 70 to 90 mass% and a fluorine group-containing polyacrylic resin of 30 to 10 mass% as a base material resin.

Description

  The present invention relates to resin particles, expandable resin particles, a method for producing the same, foamed particles, and a method for producing a foamed molded product. More specifically, the present invention relates to polystyrene-based resin particles capable of providing a foamed molded article having excellent foamability, moldability and heat insulation properties, expandable resin particles obtained from the resin particles, production method thereof, foamed particles and foamed It relates to a molded body.

  Conventionally, expandable polystyrene particles have been widely used as expandable resin particles that are raw materials for producing expanded molded articles. A foaming molding is obtained as follows, for example. That is, expandable resin particles such as expandable polystyrene particles are heated and pre-expanded to obtain pre-expanded particles. The obtained pre-expanded particles are filled into the mold cavity. Next, a foam-molded article can be obtained by integrating the pre-expanded particles by heat fusion while secondary-expanding the filled pre-expanded particles.

Since the foamed molded product forms a closed cell structure containing air, it has low thermal conductivity (high thermal insulation), so it can be used in various applications such as thermal insulation for homes, thermal insulation containers, and thermal insulation panels for refrigeration equipment. Has been used. In recent years, foam molded articles have been improved with the aim of further improving performance (particularly heat insulation).
For example, in Japanese Translation of PCT International Publication No. 2010-527399 (Patent Document 1), an expanded molded article containing an alkenyl aromatic resin such as a styrene-acrylonitrile copolymer as a base resin and containing a chlorine-free fluorinated foaming agent has a heat insulating property. It is said that it is useful for improvement.

Special table 2010-527399 gazette

  However, even with the technology described in the above publication, the heat insulating property of the foamed molded product is not sufficient, and the molded product density is high. To provide a foamed molded product having a further improved heat insulating property and a low molded product density. Was desired.

  The inventor of the present invention reviewed the base resin and the foaming agent in order to improve the heat insulating property of the foam molded article. As a result, it has been found that the heat insulation can be improved by leaving the vinyl group-containing fluorine-based volatile foaming agent in the foamed molded article. However, if the foaming agent is simply replaced with the above agent, the amount of the vinyl group-containing fluorine-based volatile foaming agent impregnated in the resin particles is low, and high-magnification foaming is difficult. The remaining amount was also low. Therefore, it has been found that if a fluorine group-containing polyacrylic resin is used for the base resin, it is possible to simultaneously expect an improvement in the content of the foaming agent and an improvement in heat insulation by the fluorine group-containing polyacrylic resin itself. It came to.

  Thus, according to the present invention, a vinyl group-containing fluorine-based volatile foaming agent impregnated containing a resin mixture of 70-90% by mass of a styrene resin and 30-10% by mass of a fluorine-containing polyacrylic resin as a base resin. Resin particles are provided.

Further, according to the present invention, a base resin containing a resin mixture of 70 to 90% by mass of a styrene resin and 30 to 10% by mass of a fluorine-containing polyacrylic resin, and a vinyl group-containing fluorine-based volatile foaming agent. Expandable resin particles are provided.
Furthermore, according to the present invention, expanded particles obtained by expanding expanded resin particles are provided.
Moreover, according to this invention, the foaming molding obtained by foam-molding the said foaming particle is provided.

Furthermore, according to the present invention, the step of absorbing the fluorine group-containing acrylic monomer in the seed particles containing the styrene resin,
A step of obtaining resin particles by polymerizing the fluorine group-containing acrylic monomer at the time of absorption or after absorption;
Provided is a method for producing expandable resin particles, which comprises a step of impregnating the resin particles with a vinyl group-containing fluorine-based volatile foaming agent during or after polymerization.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the resin particle which can give the foaming molding excellent in heat insulation, an expandable resin particle, an expanded particle, and an expandable resin particle can be provided. The inventors believe that this effect is achieved by suppressing the removal of the vinyl group-containing fluorine-based volatile foaming agent and using a fluorine-group-containing polyacrylic resin as the base resin. The foamed molded product having high heat insulating properties of the present invention can be used for a wide range of applications such as heat insulating materials, automobile members, and building materials for housing.
Moreover, when a fluorine group containing polyacrylic-type resin has a C1-C10 fluorine substituted alkyl group, the resin particle which can give the foaming molding which was more excellent in heat insulation can be provided.

Furthermore, when the fluorine group-containing polyacrylic resin is dispersed in a granular form in the styrene resin, it is possible to provide resin particles that can give a foamed molded article with better heat insulation.
Furthermore, when the styrene-based resin is a styrene resin or a copolymer resin of styrene and acrylonitrile, resin particles that can give a foamed molded article with better heat insulation can be provided.
When the vinyl group-containing fluorine-based volatile foaming agent is a foaming agent having a trifluoromethyl group, it is possible to provide resin particles that can give a foamed molded article with better heat insulation.

2 is an electron micrograph of Example 1. 4 is an electron micrograph of Example 3. 4 is an electron micrograph of Comparative Example 2.

(Resin particles)
The resin particles of the present invention contain a resin mixture of 70 to 90% by mass of a styrene resin and 30 to 10% by mass of a fluorine group-containing polyacrylic resin as a base resin. The resin particles of the present invention are used for impregnation with a vinyl group-containing fluorine-based volatile foaming agent. Since the resin particles of the present invention contain a fluorine group-containing polyacrylic resin, they are familiar with the vinyl group-containing fluorine-based volatile foaming agent and can improve the content of the foaming agent. .
(1) Styrenic resin The styrenic resin is not particularly limited, and examples thereof include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, and bromostyrene. Homopolymers of these or copolymers thereof.

The polystyrene resin may be a copolymer of the styrene monomer and a vinyl monomer copolymerizable with the styrene monomer. 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, and dimethyl maleate. And monofunctional monomers such as ate, dimethyl fumarate, diethyl fumarate and ethyl fumarate, and bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate.
Of the styrene resins, styrene resins or copolymer resins of styrene and acrylonitrile are more preferable.

(2) Fluorine group-containing polyacrylic resin The fluorine group-containing polyacrylic resin is a polyacrylic resin having a fluorine-substituted alkyl group having 1 to 10 carbon atoms, from the viewpoint of easy compatibility with a styrene resin. preferable.
Examples of the fluorine-substituted alkyl group having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-pentyl, i-pentyl, n Examples include groups in which one or more hydrogen atoms constituting -hexyl, i-hexyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl and the like are substituted with one or more fluorine atoms.

Specifically, one or more hydrogen atoms in an alkyl group in a monomer such as methyl (meth) acrylate, ethyl (meth) acrylate, propylene (meth) acrylate, and butyl (meth) acrylate are substituted with fluorine atoms. Examples thereof include polymers of fluorinated monomers. The number of substitution with fluorine atoms is 1 or more and less than or equal to the number of hydrogen atoms in the alkyl group.
A particularly preferred fluorine group-containing polyacrylic resin is trifluoromethyl (meth) acrylate.

(3) Content Ratio of Styrenic Resin and Fluorine Group-Containing Polyacrylic Resin The resin particles include a resin mixture of a styrene resin and a fluorine group-containing polyacrylic resin as a base resin.
In the resin mixture, the content ratios of the styrene resin and the fluorine group-containing polyacrylic resin are 70 to 90% by mass and 30 to 10% by mass. When the content ratio of the styrene resin is less than 70% by mass, it is difficult to obtain a high-magnification foamed molded article, and thus a foamed molded article having sufficient heat insulation may not be obtained. When the content is more than 90% by mass, the contribution to the heat insulation of the fluorine-containing polyacrylic resin is reduced, and the remaining amount of the vinyl group-containing fluorine-based volatile foaming agent is reduced. A molded body may not be obtained. The content rate of a preferable styrene-type resin and fluorine group containing polyacrylic-type resin is 85-75 mass% and 15-25 mass%.

(4) Dispersion form in resin particles of fluorine group-containing polyacrylic resin and styrene resin The fluorine group-containing polyacrylic resin can take a form dispersed in a styrene resin. When the fluorine group-containing polyacrylic resin is dispersed in a granular form, the retention of the vinyl group-containing fluorine-based volatile foaming agent can be further improved. In addition, it can confirm by observing with a transmission electron microscope (TEM) that the fluorine-group containing polyacrylic-type resin is disperse | distributing granularly.
A dispersion form can be prescribed | regulated by the average number and average particle diameter of a granular material, for example. Each defining method is described in the examples, but the method is outlined below.

(I) Average number First, a cross section of the inner part of 50 μm from the surface layer of the resin particles is photographed with a TEM at 10,000 times. In the obtained TEM photograph, it can be visually observed that the fluorine group-containing polyacrylic resin is present in a granular form. Count the number of granular areas in the TEM picture. The average value of the number obtained by performing this operation with five resin particles is the average number. The average number is preferably in the range of 100 to 600. When the average number is less than 100, the contribution of the fluorine group-containing polyacrylic resin to the heat insulation is reduced, and the residual amount of the vinyl group-containing fluorine-based volatile foaming agent is reduced. A foamed molded product having the same may not be obtained. If the number is more than 600, it is difficult to obtain a high-magnification foamed molded article, and thus a foamed molded article having sufficient heat insulation may not be obtained. A more preferable average number is in the range of 200 to 500.

(Ii) Average particle diameter The particle diameter of the granular material in the TME photograph obtained similarly to the case of the average number is measured, and the average value is taken. By performing this operation with five resin particles, an average value of five is obtained. A value obtained by dividing the total of the five average values by 5 is the average particle diameter. The average particle size is preferably in the range of 10 to 100 nm. When the average particle size is less than 10 nm, the contribution to the heat insulation of the fluorine group-containing polyacrylic resin is reduced, and the residual amount of the vinyl group-containing fluorine-based volatile foaming agent is reduced. A foamed molded product having the same may not be obtained. When it is larger than 100 nm, it is difficult to obtain a high-magnification foamed molded article, and thus a foamed molded article having sufficient heat insulation may not be obtained. A more preferable average particle diameter is in the range of 30 to 80 nm.

(5) Other resins The base resin may contain other resins as necessary.
Examples of other resins include polyolefin resins such as polyethylene and polypropylene, polycarbonate resins, and polyester resins.
The resin mixture of the styrene resin and the fluorine-containing polyacrylic resin is preferably contained in the base resin at 80% by mass or more, more preferably 90% by mass or more. More preferably, all are resin mixtures.

(6) Additives The resin particles have a flame retardant, a flame retardant aid, a plasticizer, a lubricant, a binding inhibitor, a fusion accelerator, an antistatic agent, a spreader, and a bubble adjuster as long as the physical properties are not impaired. Additives such as an agent, a crosslinking agent, a filler, and a colorant may be contained.
As flame retardants, tetrabromocyclooctane, hexabromocyclododecane, trisdibromopropyl phosphate, tetrabromobisphenol A, tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples of the flame retardant include bis (2,3-dibromopropyl ether).
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. .

Examples of the plasticizer include glycerin fatty acid esters such as phthalic acid ester, glycerin diacetomonolaurate, glycerin tristearate and diacetylated glycerin monostearate, and adipic acid esters such as diisobutyl adipate.
Examples of the lubricant include paraffin wax and zinc stearate.
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 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 and stearic acid monoglyceride.
Examples of the spreading agent include polybutene, polyethylene glycol, and silicone oil.
Examples of the bubble regulator include methacrylic acid ester copolymer, ethylene bis stearamide, polyethylene wax, ethylene-vinyl acetate copolymer, and the like.

(7) Shape of resin particles The shape of the resin particles is not particularly limited. For example, spherical shape, cylindrical shape, etc. are mentioned. Of these, a spherical shape is preferable. The average particle diameter of the resin particles can be appropriately selected depending on the application, and for example, those having an average particle diameter of 0.2 to 5 mm can be used. In consideration of the filling properties into the mold, the average particle diameter is more preferably 0.3 to 2 mm, and still more preferably 0.3 to 1.4 mm.

(8) Manufacturing method of resin particle The manufacturing method of resin particle is not specifically limited. For example, it can be obtained by melting and kneading a styrene-based resin and a fluorine-containing polyacrylic resin and optionally other resins and additives with an extruder, extruding them into strands, and cutting the strands. Furthermore, resin particles can be obtained by absorbing and polymerizing fluorine group-containing polyacrylic monomers in seed particles made of a styrene resin.
Of the above methods, the latter method is preferred from the viewpoint that the styrene resin and the fluorine group-containing polyacrylic resin can be mixed more uniformly. The latter method will be described in detail below.

(I) Seed particles The seed particles can be produced by a known method. For example, (1) by melting and kneading a styrene resin with an extruder, extruding it into a strand, and cutting the strand (2) An aqueous medium, a styrene monomer and a polymerization initiator are fed into an autoclave, and the styrene monomer is subjected to suspension polymerization while being heated and stirred in the autoclave, thereby seed particles. (3) After supplying the aqueous medium and polystyrene resin particles into the autoclave and dispersing the polystyrene resin particles in the aqueous medium, the autoclave is heated and agitated while stirring. The polymer is supplied continuously or intermittently and polymerized in the presence of a polymerization initiator while the styrene monomer is absorbed by the polystyrene resin particles. The seed polymerization method etc. which manufacture particle | grains are mentioned.
In addition, the resin particles can be used for part or all of the seed particles. In the case of using a recovered product, production of seed particles by an extrusion method is suitable.

  The average particle size of the seed particles can be adjusted as appropriate according to the average particle size of the resin particles. For example, when obtaining resin particles having an average particle diameter of 1 mm, it is preferable to use seed particles having an average particle diameter of about 0.7 to 0.9 mm. Furthermore, the weight average molecular weight of the seed particles is not particularly limited, but is preferably 100,000 to 700,000, and more preferably 150,000 to 500,000.

(Ii) Impregnation step By supplying 10 to 30 parts by mass of a fluorine-containing polyacrylic monomer to 70 to 90 parts by mass of seed particles in a dispersion obtained by dispersing seed particles in an aqueous medium. The monomer is absorbed by the seed particles. The amount of the fluorine group-containing polyacrylic monomer substantially corresponds to the amount of the fluorine group-containing polyacrylic resin in the resin particles.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

  The fluorine group-containing polyacrylic monomer may contain a polymerization initiator. The polymerization initiator is not particularly limited as long as it is conventionally used for the polymerization of fluorine group-containing polyacrylic monomers. For example, benzoyl peroxide, t-butyl peroxybenzoate, t-butyl peroxy-2-ethylhexanoate, lauryl peroxide, t-butyl peroxide, t-butyl peroxypivalate, t-butyl peroxyisopropyl Organics such as carbonate, t-butyl peroxyacetate, 2,2-t-butylperoxybutane, t-butylperoxy-3,3,5-trimethylhexanoate, di-t-butylperoxyhexahydroterephthalate Examples thereof include peroxides, azo compounds such as azobisisobutyronitrile, azobisdimethylvaleronitrile, and the like. In order to reduce the residual monomer by adjusting the Z average molecular weight Mz and the mass average molecular weight Mw of the obtained fluorine-containing polyacrylic resin, the decomposition temperature for obtaining a half-life of 10 hours is 80 to 120 ° C. It is preferable to use two or more different polymerization initiators in combination. In addition, a polymerization initiator may be used independently or 2 or more types may be used together.

  The aqueous medium may contain a suspension stabilizer in order to stabilize the dispersion of the fluorine group-containing polyacrylic monomer droplets and seed particles. The suspension stabilizer is not particularly limited as long as it is conventionally used for suspension polymerization of a fluorine group-containing polyacrylic monomer. Examples thereof include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate, magnesium pyrophosphate, and magnesium oxide. And when using a sparingly soluble inorganic compound as said suspension stabilizer, it is preferable to use an anionic surfactant together, and as such anionic surfactant, for example, fatty acid soap, N-acylamino acid or its Salts, carboxylates such as alkyl ether carboxylates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl sulfoacetates, sulfonates such as α-olefin sulfonates; higher alcohol sulfuric acid Ester salts, secondary higher alcohol sulfates, sulfates such as alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, etc .; phosphates such as alkyl ether phosphates, alkyl phosphates, etc. Is mentioned.

(Iii) Polymerization process Although a polymerization process changes with monomer types to be used, a polymerization initiator seed | species, a polymerization atmosphere seed | species, etc., it is normally performed by maintaining 60-120 degreeC heating for 2 to 12 hours. The polymerization step may be performed while impregnating the monomer.
In the polymerization step, the entire amount of the monomer to be used may be polymerized in one stage, or may be polymerized in two or more stages. When polymerizing in two or more stages, the impregnation process is usually performed in two stages. The polymerization temperature and time of the polymerization process divided into two or more steps may be the same or different.

(Expandable resin particles)
Expandable resin particles contain the base resin and a vinyl group-containing fluorine-based volatile foaming agent.
(1) Vinyl group-containing fluorine-based volatile foaming agent The vinyl group-containing fluorine-based volatile foaming agent preferably has a trifluoromethyl group. Among these, 1,3,3,3-tetrafluoropropene is particularly preferable. This 1,3,3,3-tetrafluoropropene may be a cis isomer, a trans isomer, or a mixture of both. In particular, the trans form is preferred.
A vinyl group-containing fluorine-based volatile foaming agent and other foaming agents may be used in combination. Examples of other foaming agents include foaming agents conventionally used for foaming polystyrene resins. Examples thereof include volatile foaming agents (physical foaming agents) such as aliphatic hydrocarbons having 5 or less carbon atoms such as propane, isobutane, n-butane, isopentane, neopentane, and the like.

  Furthermore, it is preferable that content of a foaming agent is the range of 5-20 mass%. If it is less than 5% by mass, a foamed molded article having a desired density may not be obtained from the expandable resin particles. In addition, since the effect of increasing the secondary foaming power at the time of in-mold foam molding is reduced, the appearance of the foam molded article may not be good. When the amount is more than 20% by mass, the time required for the cooling step in the production process of the foam molded article becomes long, and the productivity may be lowered. A more preferable content of the blowing agent is 7 to 16% by mass.

(2) Method for Producing Expandable Resin Particles Expandable resin particles can be obtained by impregnating the base resin with a vinyl group-containing fluorine-based volatile foaming agent. The impregnation may be performed wet simultaneously with the polymerization, or may be performed wet or dry after the polymerization. When it is carried out in a wet manner, it may be carried out in the presence of a suspension stabilizer and a surfactant exemplified in the polymerization step.
The impregnation temperature of the foaming agent is preferably 60 to 120 ° C. When the temperature is lower than 60 ° C., the time required for impregnating the resin particles with the foaming agent becomes long, and the production efficiency may decrease. On the other hand, when the temperature is higher than 120 ° C., the resin particles may be fused to generate bonded particles. A more preferable impregnation temperature is 70 to 110 ° C.
A foaming aid may be used in combination with a foaming agent. Examples of the foaming aid include isobutyl adipate, toluene, cyclohexane, and ethylbenzene.

(Foamed particles)
The foamed particles can be obtained by foaming to a desired bulk density using water vapor or the like. The foamed particles can be used as they are for applications such as cushioning fillers, and can be used as a raw material for foam molded articles for foaming in the mold. In the case of the raw material of the foam molded article, the expanded particles are generally referred to as pre-expanded particles, and the expansion to obtain the expanded particles is generally referred to as pre-expanded.
The bulk density of the expanded particles is preferably in the range of 0.01 to 0.03 g / cm ³ . When the pre-expanded particles have a bulk density of less than 0.01 g / cm ³ , shrinkage may occur in the foamed molded product to be obtained next and appearance may be deteriorated. In addition, the heat insulation performance and mechanical strength of the foamed molded product may deteriorate. On the other hand, when the bulk density is larger than 0.03 g / cm ³ , the lightweight property of the foamed molded product may be lowered.
In addition, it is preferable to apply powdered metal soaps such as zinc stearate to the surface of the expandable resin particles before foaming. By applying, the bonding between the foamed particles can be reduced in the foaming process of the foamable resin particles.

(Foamed molded product)
By filling the foamed particles in a closed mold with a large number of small holes, and again heating and foaming with pressurized steam, etc., filling the voids between the foamed particles and fusing the foamed particles together to integrate them A foamed molded product can be produced. At that time, the density of the foamed molded product can be adjusted, for example, by adjusting the filling amount of the foamed particles in the mold.
The foamed particles may be aged, for example, at normal pressure before molding the foamed molded product. The aging temperature of the expanded particles is preferably 20 to 60 ° C. When the aging temperature is low, the aging time of the expanded particles may be long. On the other hand, if it is high, the foaming agent in the foamed particles may dissipate and the moldability may deteriorate.

  The content of the vinyl group-containing fluorine-based volatile foaming agent in the foamed molded product is preferably in the range of 4 to 20% by mass. If it is less than 4% by mass, the heat insulating property of the foamed molded product may not be good. When the amount is more than 20% by mass, the time required for the cooling step in the production process of the foam molded article becomes long, and the productivity may be lowered. A more preferable content of the blowing agent is 7 to 16% by mass. In addition, content of the vinyl group containing fluorine-type volatile foaming agent in a foaming molding is suppressed to about 60% or less reduction | decrease than that of an expandable resin particle.

Hereinafter, specific examples of the present invention will be described by way of examples. However, the following examples are merely illustrative of the present invention, and the present invention is not limited to the following examples. In the following, “part” and “%” are based on mass unless otherwise specified.
<Content of foaming agent>
Content of a foaming agent is performed using the gas chromatograph Clarus500 by Perkin-Elmer, and HS autosampler TurboMatrix HS40. The expandable resin particles, the pre-expanded particles and the expanded molded product are put in a 20 ml dedicated vial in an amount of up to 20 mg, and sealed after precise weighing. Place vial in sampler and heat at 160 ° C. for 20 minutes. The amount of hydrocarbon generated by heating is measured with a chromatograph. The measurement conditions are listed below.
Column: DB-1 (1.0 μm × 0.25 mmφ × 60 m)
Detector: FID
Measurement conditions: Column temperature (50 ° C. (6 min) → 40 ° C./min→270° C. (1 min))
Inlet temperature (200 ° C), detector temperature (250 ° C), range = 20, Att = 1
Vent-additional gas = 30-5 mL / min (He), gas pressure = 18 (10) → 0.5 → 24 psi, quantitative method (MHE method)
Sampler conditions: heating temperature-time (160 ° C.-20 min), pressurized gas pressure-time (25 psi-1 min)
Needle temperature (160 ° C), transfer line temperature (180 ° C), sample introduction time (0.08min)

<Bulk density>
The bulk magnification of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = mass of measurement sample (W) / volume of measurement sample (V)

<Density of foam molding>
The mass (a) and the volume (b) of the test piece (example 75 × 300 × 35 mm) cut out from the foamed molded product (after being molded and dried at 40 ° C. for 20 hours or more) each have three or more significant figures. And the density (kg / m ³ ) of the foamed molded product is obtained from the formula (a) / (b).

<Average number of granular fluorine group-containing polyacrylic resin in resin particles, average particle diameter of granular fluorine group-containing polyacrylic resin>
The resin particles are cut so that the cross-sectional area becomes as large as possible. A cross-sectional portion 50 μm inside from the surface layer is photographed at a magnification of 10,000 using a transmission electron microscope (TEM). In order to distinguish between the styrene resin part and the fluorine group-containing polyacrylic resin part in the obtained photograph, binarization is performed using image processing software (Nano Hunter NS2K-Pro / Lt manufactured by Nanosystem). The number of grains made of a fluorine group-containing polyacrylic resin present in the binarized diagram is measured. The same measurement is performed with five resin particles, and the average value of the obtained areas is defined as the average area.
The particle diameter of the particles made of the fluorine group-containing polyacrylic resin present in the binarized figure is measured by measuring the distance between two points using the image processing software. Ten points are measured for each particle size, and the average value is taken as the average particle size.

<Heat sealability>
After molding, the plate-like foamed molded product of 300 mm × 400 mm × 30 mm is dried for 24 hours and then broken in half at the center in the length direction. With respect to the expanded particles on the fracture surface, the number (a) of particles broken in the particles and the number (b) of particles broken at the interface between the particles in an arbitrary range of 100 to 150 are counted. A value obtained by substituting the numbers (a) and (b) into the following equation is defined as a fusion rate (%).
Fusing rate (%) = formula [(a) / ((a) + (b))] × 100
The evaluation standard is that a fusion rate of 70% or more is good (◯) and less than 70% is bad (x).

<Thermal conductivity>
The thermal conductivity is measured in accordance with JIS A1412-2, measuring method of thermal resistance and thermal conductivity of thermal insulation material-part 2: heat flow meter method (HFM method). Specifically, a sample cut into 200 × 200 × 30 mm is set in AUTO-Λ HC-074 / 200 manufactured by Eihiro Seiki Co., Ltd., and one temperature measurement is performed at a measurement temperature of 23 ° C. and a temperature difference of 30 ° C.

Example 1
(Manufacture of seed particles)
Into a polymerization vessel equipped with a stirrer having a capacity of 100 liters, 40000 g of water, 100 g of calcium triphosphate as a suspension stabilizer and 2.0 g of calcium dodecylbenzenesulfonate as an anionic surfactant were stirred and stirred for 40000 g of styrene and a polymerization initiator. After adding 96.0 g of benzoyl peroxide and 28.0 g of t-butylperoxybenzoate, the temperature was raised to 90 ° C. for polymerization. And it hold | maintained at this temperature for 6 hours, and also, after heating up to 125 degreeC, it cooled after 2 hours and obtained the polystyrene (PS) resin particle (a).
The polystyrene resin particles (a) were sieved to obtain polystyrene resin particles (b) having a particle diameter of 0.71 to 1.0 mm and an average particle diameter of 0.85 mm as seed particles.
Next, 2500 g of water, 1600 g of polystyrene resin particles (b) and 10 g of polyvinyl alcohol as a suspension stabilizer were supplied into a polymerization vessel equipped with a stirrer having an internal volume of 5 liters and heated to 70 ° C. while stirring.

(Monomer impregnation and polymerization process)
Next, 1.44 g of benzoyl peroxide as a polymerization initiator with respect to 100 g of monomer and 0.2 g of t-butylperoxybenzoate were dissolved in 400 g of trifluoroethyl methacrylate to obtain a solution. The obtained solution was supplied to the 5 liter polymerization vessel and held at 70 ° C. for 60 minutes.
Next, after 60 minutes, the reaction solution was heated to 90 ° C. in 20 minutes, held at 90 ° C. for 2 hours and 30 minutes, then heated to 120 ° C. and cooled after 2 hours to obtain resin particles. Got. A transmission electron micrograph of the obtained resin particles is shown in FIG. FIG. 1 shows that the fluorine group-containing polyacrylic resin is present in a granular form in the styrene resin.

(Foaming agent impregnation process)
Subsequently, 2200 g of water, 2000 g of the resin particles, 10.0 g of magnesium oxide and 1.2 g of sodium dodecylbenzenesulfonate as a suspension stabilizer were supplied and stirred in another polymerization vessel equipped with a stirrer having a capacity of 5 liters.
Next, 24.0 g of diisobutyl adipate was placed in the polymerization vessel as a foaming aid and sealed. Next, 480 g of trans-1,3,3,3-tetrafluoropropene and 90 g of butane as a foaming agent were press-fitted into a polymerization vessel containing resin particles, and then heated to 110 ° C. Hold at 110 ° C. for 6 hours. Subsequently, it cooled to 30 degrees C or less, taken out the foamable resin particle from the inside of a polymerization container, and was made to dry.

(Pre-foaming)
Subsequently, pre-expanded particles were obtained by pre-expanding the expandable resin particles to a bulk density of 0.020 g / cm ³ using a pre-expanding device. The resulting pre-expanded particles were aged at 20 ° C. for 24 hours.
(Foam molding)
Then, the pre-expanded particles are placed in the cavity of an automatic foam bead molding machine (trade name “ACE 3 type” manufactured by Sekisui Koki Co., Ltd.) having a mold having a rectangular parallelepiped cavity with an inner dimension of 300 mm × 400 mm × 30 mm. Filled. Next, a foamed molded product having a density of 0.020 g / cm ³ was obtained by heat molding with water vapor having a gauge pressure of 0.07 Mpa for 15 seconds. Next, the foamed molded product in the cavity of the mold was cooled with water for 5 seconds, and then allowed to cool under reduced pressure (cooling step) to take out the foamed molded product.
The obtained foamed molded article did not shrink and had good heat-fusibility.

(Example 2)
A foamed molded article was obtained in the same manner as in Example 1 except that the amounts of the polystyrene resin particles (b) and trifluoroethyl methacrylate used were 1500 g and 500 g. The obtained foamed molded article did not shrink and had good heat-fusibility.
(Example 3)
A foamed molded article was obtained in the same manner as in Example 1 except that the amounts of the polystyrene resin particles (b) and trifluoroethyl methacrylate used were 1800 g and 200 g. The obtained foamed molded article did not shrink and had good heat-fusibility. A transmission electron micrograph of the resin particles obtained is shown in FIG. FIG. 2 shows that the fluorine group-containing polyacrylic resin is present in a granular form in the styrene resin.

Example 4
A foam molded article was obtained in the same manner as in Example 3 except that the polystyrene resin particles (b) were replaced with copolymer resin (AS) particles of styrene and acrylonitrile. The obtained foamed molded article did not shrink and had good heat-fusibility.
As the copolymer resin particles of styrene and acrylonitrile, AS727 manufactured by Asahi Kasei Chemical was used.

(Comparative Example 1)
A foamed molded article was obtained in the same manner as in Example 1 except that the amounts of the polystyrene resin particles (b) and trifluoroethyl methacrylate used were 1900 g and 100 g. The obtained foamed molded article was excellent in heat-fusibility, but the thermal conductivity was a high numerical value.
(Comparative Example 2)
A foamed molded article was obtained in the same manner as in Example 1 except that the amounts of the polystyrene resin particles (b) and trifluoroethyl methacrylate used were 1300 g and 700 g. The obtained foamed molded article had low foaming property, and only a molded product having a density of 0.05 g / cm ³ was obtained, and the heat fusion property was also low. Therefore, the thermal conductivity was not measured.
A transmission electron micrograph of the obtained resin particles is shown in FIG. FIG. 3 shows that many fluorine-group-containing polyacrylic resins are dispersed.
The results of Examples 1-4 and Comparative Examples 1-2 are summarized in Table 1.

Claims (9)

  Resin particles for impregnation with a vinyl group-containing fluorine-based volatile foaming agent, comprising a resin mixture of 70 to 90% by mass of a styrene resin and 30 to 10% by mass of a fluorine-containing polyacrylic resin as a base resin.   The resin particle according to claim 1, wherein the fluorine group-containing polyacrylic resin is a polyacrylic resin having a fluorine-substituted alkyl group having 1 to 10 carbon atoms.   The resin particle according to claim 1 or 2, wherein the fluorine group-containing polyacrylic resin is dispersed in a granular form in the styrene resin.   The resin particle according to any one of claims 1 to 3, wherein the styrene resin is a styrene resin or a copolymer resin of styrene and acrylonitrile.   The resin particle according to any one of claims 1 to 4, wherein the vinyl group-containing fluorine-based volatile foaming agent is a foaming agent having a trifluoromethyl group.   Expandable resin particles comprising a base resin containing a resin mixture of 70 to 90% by mass of a styrene resin and 30 to 10% by mass of a fluorine-containing polyacrylic resin, and a vinyl group-containing fluorine-based volatile foaming agent.   Expanded resin particles obtained by foaming the expandable resin particles according to claim 6.   A foam-molded product obtained by foam-molding the foamed particles according to claim 7. A step of absorbing a fluorine group-containing acrylic monomer into seed particles containing a styrene resin;
A step of obtaining resin particles by polymerizing the fluorine group-containing acrylic monomer at the time of absorption or after absorption;
A method for producing expandable resin particles, comprising a step of impregnating the resin particles with a vinyl group-containing fluorine-based volatile foaming agent during or after polymerization.