JP2022144234A - Styrenic seed resin particle for seed polymerization and use of the same - Google Patents

Abstract

To provide foamable polystyrene-based resin particles which have a small particle size and narrow particle size distribution and are excellent in foamability, and styrenic seed resin particles which improve productivity of polystyrene-based foamed particles excellent in appearance.SOLUTION: Styrenic seed resin particles for seed polymerization contain a base material resin containing a styrene unit as a constitutional unit, contain specific amounts of a plasticizer and a nucleating agent, have an average particle diameter of 0.20-0.50 mm, and UT indicating variations in particle size distribution of 2.15 or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to styrenic seed resin particles for seed polymerization to obtain expandable polystyrene resin particles and uses thereof.

Uniform polystyrene foam particles are used for cushion beads, lightweight aggregates, and moldings that require beauty. Uniform styrenic seed resin particles are a useful material because uniform expandable polystyrene resin particles can be obtained by impregnating and polymerizing styrene and then impregnating the particles with a foaming agent.

Various styrene seed resin particles have been developed so far. For example, Patent Document 1 discloses a styrene seed resin obtained by sieving polystyrene resin particles containing a nucleating agent and a plasticizer prepared by suspension polymerization to have a particle size of 0.425 mm to 0.500 mm. Particles are disclosed.

Patent Document 2 discloses styrene-based seed resin particles having an average particle diameter of 0.55 mm and containing a nucleating agent produced by a droplet generator.

Japanese Patent Laid-Open No. 2015-203042 WO1998-029485

However, since the styrene seed resin particles described in Patent Document 1 are produced by a suspension polymerization method, the particle size distribution of the styrene seed resin particles is wide. Expandable polystyrene-based resin particles have a problem of uniformity of particle size. Since the styrene seed resin particles described in Patent Document 2 do not contain a plasticizer, the expandable polystyrene resin particles obtained by seed polymerization using the styrene seed resin particles have low expandability. Since the cells of the cell are coarse, the beauty is not sufficient, and there is room for further improvement.

One embodiment of the present invention has been made in view of the above problems, and its object is to provide expandable polystyrene resin particles having a small particle size, a narrow particle size distribution and excellent foamability, and polystyrene foam particles having excellent beauty. An object of the present invention is to provide styrenic seed resin particles having good particle productivity.

As a result of intensive studies to solve the above problems, the present inventors found that the amount of plasticizer and the amount of nucleating agent are within specific ranges, and the UT, which indicates variation in particle size distribution, is not more than a specified value. The present inventors have found that it is possible to obtain polystyrene seed resin particles that are uniform in diameter and excellent in design, and which can be produced with good productivity, thereby completing the present invention.

That is, one embodiment of the present invention includes the following configurations.
[1] A seed resin for seed polymerization composed of a base resin containing a styrene unit as a structural unit,
Containing 0.5 to 5.0 parts by weight of a plasticizer with respect to 100 parts by weight of the base resin,
Containing 0.03 to 0.30 parts by weight of a nucleating agent with respect to 100 parts by weight of the base resin,
Styrenic seed resin particles for seed polymerization, having an average particle size of 0.20 to 0.50 mm and a UT indicating variation in particle size distribution of 2.15 or less.

[2] The styrene seed resin particles for seed polymerization according to [1], wherein the base resin contains 90% or more of styrene units.
[3] The styrenic seed resin particles for seed polymerization according to [1] or [2], wherein the nucleating agent is an acrylic resin and the weight average molecular weight of the nucleating agent is 500,000 to 1,500,000. .
[4] Expandable polystyrene resin particles obtained by seed polymerization using the styrene seed resin particles according to any one of [1] to [3] [5] [4] 3. Expanded polystyrene particles obtained by expanding the expandable polystyrene resin particles according to 1.
[6] A polystyrene foam-molded product obtained by in-mold molding the polystyrene foam particles of [5].

One embodiment of the present invention has been made in view of the above problems, and its object is to improve the productivity of expandable polystyrene resin particles with narrow particle size distribution and excellent expandability, and polystyrene expanded particles with excellent beauty. An object of the present invention is to provide styrenic seed resin particles which are excellent in

An embodiment of the invention will be described below, but the invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope of the claims. Further, embodiments or examples obtained by appropriately combining technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. In addition, all the scientific literatures and patent documents described in this specification are used as references in this specification. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)".

[1. Styrene seed resin particles]
One embodiment of the present invention has been made in view of the above problems, and the object thereof is to produce expandable polystyrene resin particles with uniform particle size distribution and excellent expandability, and polystyrene expanded particles with excellent beauty. An object of the present invention is to provide styrenic seed resin particles having good properties.

The present inventors have completed the present invention in order to achieve the object of improving the productivity of expandable polystyrene resin particles with uniform particle size distribution and excellent expandability and polystyrene expandable particles with excellent beauty. Embodiments of the present invention are described below.

A styrenic seed resin particle for seed polymerization according to one embodiment of the present invention is a styrenic seed resin particle for seed polymerization comprising a base resin containing a styrene unit as a structural unit, wherein the base resin 0.5 to 5.0 parts by weight of a plasticizer is contained with respect to 100 parts by weight, and 0.03 to 0.30 parts by weight of a nucleating agent is contained with respect to 100 parts by weight of the base resin, and an average The particle diameter is 0.20 to 0.50 mm, and the UT, which indicates variation in particle size distribution, is 2.15 or less.

The styrene seed resin particles according to one embodiment of the present invention can be used to provide expandable polystyrene resin particles by a known method. In addition, such expandable polystyrene-based resin particles can be obtained by producing polystyrene-based expanded particles by a known method using the expandable polystyrene-based resin particles, and performing expansion molding using such polystyrene-based expanded particles by a known method. can provide a polystyrene foam molded product.

In this specification, "styrene seed resin particles according to one embodiment of the present invention" may be simply referred to as "styrene seed resin particles". That is, the term "styrene seed resin particles" intends one embodiment of the styrene seed resin particles in the present invention.

The base resin contained in the present styrenic seed resin particles mainly contains styrene units as structural units. As used herein, a "styrene unit" is a structural unit derived from a styrene monomer. Here, "mainly containing styrene units as structural units" means that the number of styrene units is 50% or more when the total number of structural units contained in the base resin is 100%. The base resin of the styrene-based resin seed particles in the present invention preferably contains 90% or more of styrene units as structural units. If the styrene unit content is 90% or more, the styrene monomer can be efficiently absorbed during seed polymerization.

The styrene-based resin seed particles in the present invention are generally known styrene-based resin particles, and examples of such particles include styrene, α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, and the like. or esters of acrylic and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, cetyl methacrylate, or acrylonitrile, dimethyl fumarate, ethyl fumarate and copolymer particles obtained by mixing such as. Bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate may also be used in combination.

Generally known styrenic resin seed particles are produced by (1) a conventional suspension polymerization method, and (2) a polymerizable monomer is passed through a nozzle under regular vibration to form a group of droplets in an aqueous medium. It is obtained by a method such as dispersion, coalescence and polymerization without causing additional dispersion. Uniform styrenic seed resin particles having a UT of 2.15 or less as in the present invention can be obtained by the method (2).

As the polymerization initiator for the above-mentioned monomer in the present invention, a radical-generating polymerization initiator generally used in the production of thermoplastic polymers can be used. Oxide, t-butyl perbenzoate, t-butyl perpivalate, t-butyl peroxy isopropyl carbonate, t-butyl peroxy acetate, 2,2-di-t-butyl peroxybutane, t-butyl peroxy-3 , 3,5-trimethylcyclohexanoate, di-t-butylperoxyhexahydroterephthalate, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane and other organic peroxides, and azo azo compounds such as bisisobutyronitrile and azobisdimethylvaleronitrile; These polymerization initiators can be used alone or in combination of two or more.

Examples of the aqueous dispersion medium used in the present invention include water.

Dispersants used in the present invention include water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyvinylpyrrolidone, and polyacrylamide, and water-soluble polymers such as tribasic calcium phosphate, hydroxyapatite, magnesium phosphate, and magnesium pyrophosphate. Examples include sparingly soluble inorganic substances. When using an inorganic substance that is sparingly soluble in water, the use of an anionic surfactant such as sodium dodecylbenzenesulfonate in combination increases the effect of stabilizing the dispersion. It is also effective to use a water-soluble polymer and a sparingly water-soluble inorganic substance together.

In the present invention, a nucleating agent that can be finely dispersed in a styrenic resin matrix is used. Nucleating agents include, for example, methacrylic acid ester polymers, methacrylic acid ester-acrylic acid ester copolymers, methacrylic acid ester polymers such as methyl methacrylate-butadiene-styrene copolymers, styrene-butadiene copolymers, High impact polystyrene, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrenic copolymer such as acrylonitrile-styrene copolymer, polyethylene wax, ethylene-vinyl acetate copolymer Olefinic waxes such as polymeric waxes, glycerin monostearate, glycerin monobehenate, glycerin mono-12-hydroxystearate, glycerin monolaurate, glycerin tri-12-hydroxystearate, glycerin tristearate, glycerin tripalmitate, Fatty acid esters such as glycerin trilaurate, glycerin tribehenate, pentaerythol tetrastearate, hydrogenated vegetable oils such as castor oil, soybean oil, rapeseed oil, fatty acid amides, fatty acid dicarboxylic acid diamides, aromatic bisamides, Amides such as aromatic dicarboxylic acid diamides, higher fatty acids such as stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid and lactic acid, fatty acid metal salts such as zinc stearate and calcium stearate, polyethylene glycol monostearate, poly One or a mixture of two or more selected from surfactants such as oxyethylene stearyl ether and polyoxyethylene lauryl ether can be used.
Nucleating agents that are insoluble in monomers such as styrene, such as polystyrene wax, do not disperse uniformly in the droplet generation process and cause nozzle clogging. It is preferable to use Nucleating agents soluble in monomers such as styrene include acrylic resins such as methacrylic acid ester-acrylic acid ester copolymers. When an acrylic resin is used as a nucleating agent, it preferably has a weight-average molecular weight of 500,000 to 1,500,000 in terms of its solubility in monomers and its nucleating effect. When the acrylic resin is used as a nucleating agent, if the weight average molecular weight of the acrylic resin is 500,000 or more, an effective nucleating effect is likely to be obtained, and if it is 1,500,000 or less, the weight average molecular weight of the styrene seed resin particles is tend to be evenly distributed in the

These nucleating agents are used in an amount of 0.03 to 0.30 parts by weight, preferably 0.05 to 0.15 parts by weight, per 100 parts by weight of the styrene resin. If the amount used is less than 0.03 parts by weight, the cells obtained by foaming will be non-uniform and coarse, resulting in poor foamability of the expandable polystyrene resin particles and beauty of the polystyrene foam particles. descend. If the amount exceeds 0.30 parts by weight, in the step of generating droplets by vibrating the styrenic seed resin particles, the droplets are not cut well, coalesced particles are formed, and the UT deteriorates.

Examples of plasticizers used in the present invention include (a) fatty acid glycerides such as stearic acid triglyceride, palmitic acid triglyceride, lauric acid triglyceride, stearic acid diglyceride, and stearic acid monoglyceride; (b) coconut oil, palm oil, and palm kernel oil. (c) aliphatic esters such as dioctyl adipate and dibutyl sebacate; and (d) organic hydrocarbons such as liquid paraffin and cyclohexane. These plasticizers may be used alone or in combination of two or more.
These plasticizers are used in an amount of 0.50 to 5.0 parts by weight, preferably 1.0 to 3.0 parts by weight, per 100 parts by weight of the styrene resin. If the amount used is less than 0.5 parts by weight, the cells of the expandable polystyrene resin particles obtained by seed polymerization become non-uniform and coarse, resulting in the expandability and expandability of the expandable polystyrene resin particles. The foamability of the polystyrene-based resin particles during foaming is lowered, and a high magnification cannot be obtained. If the amount used exceeds 5.0 parts by weight, shrinkage during foaming will increase and a high magnification cannot be obtained.

The present expandable styrene-based seed resin particles may further contain a flame retardant, a flame retardant aid, etc. within a range that does not impair the physical properties.

Flame retardants include (a) brominated polystyrene, copolymers of brominated butadiene and vinyl aromatics, brominated novolak resin allyl ethers, brominated poly(1,3-cycloalkadiene) and brominated poly (4-vinylphenol allyl ether), and (b) polyglycerol dibromopropyl ether, tetrabromobisphenol A and tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether), etc. and low-molecular-weight compounds.

Flame retardant aids include, for example, cumene peroxide, dicumyl peroxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane. type of organic matter.

The present styrene seed resin particles have an average particle size of 0.20 mm or more and 0.50 mm or less. If the average particle diameter is less than 0.20 mm, a large amount of fine particles are generated in the step of generating droplets by vibrating the styrene seed resin particles, making it difficult to provide styrene seed expanded particles with a UT of 2.15 or less. Tend. If the average particle diameter is larger than 0.5 mm, the interior of the resin is not well impregnated with the monomer when the expandable polystyrene resin particles are produced by seed polymerization, resulting in resin particles with different physical properties between the interior of the resin and the vicinity of the outer layer. When the resin particles are formed into the resin particles, the cells are not uniform and the appearance is inferior. In the present specification, the average particle size is calculated from a distribution table showing the cumulative distribution of particle sizes measured on a volume basis. The particle size (also referred to as the median size) at which the cumulative volume percentage is 50% was taken as the average particle size.

The styrene seed resin particles preferably have a particle size distribution (also referred to as UT) of 2.15 or less, more preferably 2.10 or less. When the particle size distribution is 2.5 or less, the particle size of the expanded polystyrene particles obtained by expanding the expandable polystyrene resin particles obtained by seed polymerization is uniform, so that the polystyrene particles are excellent in design. It becomes foamed particles.

In the present specification, the particle size distribution (UT) is calculated from a distribution table in which particle diameters measured on a volume basis are expressed as a cumulative distribution. Specifically, when the particle diameters at which the cumulative volume percentages are 90%, 60%, 40%, and 10% are D90, D60, D40, and D10, respectively, the numerical values obtained by the following formula are distribution (UT).
Particle size distribution (UT) = D90/D40 + D60/D10
If all the particles have exactly the same particle size, the particle size distribution (UT) will be 2.00. Therefore, the lower limit of the particle size distribution (UT) of the expandable polystyrene resin particles is 2.00 or more.

[2. Expandable polystyrene resin particles]
[1. Styrene-based seed resin particles] can be obtained by a seed polymerization method using the present styrene-based seed resin particles described in the section. A known seed polymerization method can be employed as a method for producing the present expandable polystyrene-based resin particles.

The seed polymerization method is, for example, a method comprising the following (1) to (4): (1) water, styrenic seed resin particles, dispersant, polymerization initiator, and optionally other additives (plasticizer , foam modifiers, flame retardants, flame retardant aids, etc.) are mixed to prepare an aqueous suspension; (2) Next, the aqueous suspension is heated to a predetermined temperature; (3) At a predetermined temperature, a monomer containing a styrene monomer is added to the aqueous suspension over a predetermined period of time, and at the same time, the aqueous suspension is reacted to carry out a polymerization reaction, thereby removing the additive. (4) During or after (3) above, the base resin composition is impregnated with a foaming agent.

The amount of the polystyrene-based resin seed particles in the seed polymerization method is preferably 5 to 60% by weight when the amount of the finally obtained expandable polystyrene-based resin particles is 100% by weight. When the amount of the polystyrene resin seed particles is (a) 5% by weight or more, the monomer added to the aqueous suspension does not polymerize by itself but polymerizes within the polystyrene resin seed particles. (b) 60% by weight or less, it is possible to polymerize a larger amount of monomers in a single production, which is economically advantageous.

Examples of the dispersant include (a) sparingly water-soluble inorganic salts such as tribasic calcium phosphate, magnesium pyrophosphate, hydroxyapatite, and kaolin; molecules and the like.

Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, isopropyl-t-butyl peroxycarbonate, butyl perbenzoate, t-butyl peroxy-2-ethylhexanoate, t-butyl perpivalate, t-butylperoxyisopropyl carbonate, di-t-butylperoxyhexahydroterephthalate, 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1 -bis(t-amylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)cyclohexane, t-butylperoxy-2-ethylhexyl carbonate, and the like. Examples of the azo compounds include azobisisobutyronitrile and azobisdimethylvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. t-Butyl peroxy-2-ethylhexyl carbonate is also called t-butyl peroxy-2-ethylhexyl monocarbonate.

In the present method for producing expandable polystyrene-based resin particles, a chain transfer agent and a polymerization modifier may also be used. Chain transfer agents include mercaptan compounds such as n-octylmercaptan, n-dodecylmercaptan and t-dodecylmercaptan. Examples of polymerization modifiers include α-methylstyrene dimer and the like, which are generally used for polymerization of acrylonitrile-styrene resins.

As used herein, the term "foaming agent" refers to a readily volatile compound that causes polystyrene resin particles to swell only slightly. The foaming agent contained in the present expandable polystyrene resin particles includes (a) aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, normal pentane, and neopentanecyclohexane, and (b ) volatile blowing agents such as, but not limited to, difluoroethane and fluorohydrocarbons with zero ozone depletion potential such as tetrafluoroethane. The foaming agents described above may be used alone or in combination of two or more.

The present expandable polystyrene-based resin particles, within a range that does not impair physical properties, are produced in the process of production, specifically in the step (1) of the above seed polymerization method, in which a plasticizer, a cell regulator, a flame retardant, It may be configured to further contain a plasticizer, a cell control agent, a flame retardant, a flame retardant aid, and the like by mixing a flame retardant aid and the like.

[3. Polystyrene foam particles]
The polystyrene-based foamed particles according to one embodiment of the present invention are described in [2. Expandable Polystyrene Resin Particles]. Since the polystyrene-based foamed particles according to one embodiment of the present invention have the above structure, they have a uniform particle size and are excellent in appearance.

The method for expanding the expandable polystyrene-based resin particles, that is, the method for producing the present expanded particles is not particularly limited, and known methods can be used. Examples of the foaming method include a method in which the following (1) to (3) are sequentially performed: (1) put expandable polystyrene resin particles in a container equipped with a stirrer; By heating the expandable polystyrene-based resin particles, (3) expansion is performed until a desired expansion ratio is reached to obtain polystyrene-based expanded particles. Polystyrene-based expanded particles are sometimes referred to as polystyrene-based resin pre-expanded particles, and therefore a foaming method for obtaining polystyrene-based resin pre-expanded particles is also referred to as a pre-expanded method.

[4. Polystyrene foam molded product]
[3. polystyrene-based foamed particles] is molded in a mold. Since the polystyrene-based foam molded article according to one embodiment of the present invention has the above structure, it has an advantage of excellent surface beauty.

In this specification, the "polystyrene foam molded article according to one embodiment of the present invention" may be simply referred to as "this foam molded article". That is, the term "present foam molded article" intends one embodiment of the polystyrene-based foam molded article in the present invention.

The method for in-mold molding of polystyrene-based foamed particles, ie, the method for producing the foam molded article, is not particularly limited, and known methods can be used. The in-mold molding method includes, for example, a method in which foamed particles are filled in a mold that can be closed but cannot be sealed, and the foamed particles are heated and fused with water vapor to form a foamed molded product. In addition, as an in-mold molding method, for example, the foamed particles are filled in a closed mold having a desired shape and having a large number of small holes on the wall surface, and steam is discharged from the small holes of the mold. After heating to a temperature above the softening point of the foamed particles by blowing out a heating medium such as . There is a way.

(Average particle diameter and particle size distribution (UT) of styrene seed resin particles, and evaluation of design (uniformity) of polystyrene foam particles)
The particle size of the styrenic seed resin particles was measured on a volume basis using an image processing type Millitrac JPA particle size analyzer. The results were expressed as a cumulative distribution to prepare a particle size distribution table. Using the resulting distribution table, the average particle size and particle size distribution (UT) of the styrene seed resin particles were calculated according to the above definition.
Using the obtained UT, the design (uniformity) of the polystyrene foam particles was evaluated based on the following indices: When the UT of the styrene seed resin particles was 2.10 or less, ◎; when the UT was 2.15 or less. Δ if there is; x if more than 2.15.

(Method for evaluating expandability of expandable polystyrene resin particles)
The expandable polystyrene resin particles were placed in a steamer at 100° C. and heated for 7 minutes to obtain expanded polystyrene particles. 10 g of the obtained polystyrene foam particles were placed in a measuring cylinder of 1000 cm ³ and the volume (cm ³ ) of the polystyrene foam particles was measured. Bulk density (g/cm ³ ) was calculated by the following formula:
Bulk density (g/cm ³ ) = 10 g/volume of polystyrene foam particles (cm ³ )

Using the obtained bulk density, the expandability of the expandable polystyrene resin particles was evaluated based on the following indices: when the bulk density is 0.0220 g/cm ³ or less ◎; when it is 0.0250 g/or less ◯: x when exceeding 0.0250 g/cm ³ .

(Method for evaluating design (beauty) of polystyrene foamed particles)
According to ASTM-D-2842-97, the average chord length of the cells of the polystyrene foam particles was measured from the number of cells on a straight line from the cut surface of the polystyrene foam particles projected on the photograph. .
The resulting average chord length was evaluated for the design (beauty) of the styrene seed resin particles based on the following indices: when the average chord length is 85 μm or less, ⊚; when it is 115 μm, ◯; when it exceeds 115 μm, × .

(Example 1)
<Production of styrene seed resin particles>
1.5 liters of an aqueous dispersion medium containing 11,000 ppm of tribasic calcium phosphate and 110 ppm of sodium dodecylbenzenesulfonate was placed in a 6-liter flat plate reactor having an inlet from a droplet generator at the bottom and equipped with stirring blades. was added and stirring was started.

Next, 9.7 g of 1,1-di(tert-butylperoxy)cyclohexane, 85 g of tert-butylperoxy-2-ethylhexanoate were added to 5000 g of styrene monomer in a vessel having a supply line to the droplet generator. , 50 g of liquid paraffin as a plasticizer, and 3.5 g of methyl methacrylate-butyl acrylate copolymer (Kane Ace PA-20 manufactured by Kanegafuchi Chemical Industry Co., Ltd.) as a nucleating agent in the amount shown in Table 1. Then, it was fed at a rate of 90 cc/min to a droplet generating device having one plate having 45 holes of 0.17 mmφ, and a mechanical vibration of 800 Hz was applied to form monomer droplets in the aqueous dispersion medium. and transferred into the 6 liter reactor. In addition, an aqueous dispersant prepared by dissolving 530 g of 3% polyvinyl alcohol and 20 g of sodium nitrite in 5000 g of pure water was added to a container having a supply line to a droplet generating device separate from the monomer mixed solution, The aqueous dispersion was transferred to the droplet generator at a rate of 80 cc/min.
After 1,500 g of the monomer solution was introduced into the 6-liter reactor, the generation of droplets was stopped, and the dispersion in the reactor was heated to 90° C. and polymerized for 3 hours. Further, the dispersion was heated to 120° C. and held for 1 hour to complete the polymerization. The slurry in the reactor was cooled, dehydrated and dried to obtain polymer particles. The resulting particle group is referred to as styrene-based seed particles.
Here, the average particle size and particle size distribution (UT) of the styrene seed resin particles were measured to evaluate design (uniformity). The results are shown in Table 1.

<Production of expandable polystyrene resin particles>
92 parts by weight of pure water, 0.38 parts by weight of tribasic calcium phosphate, 0.0104 parts by weight of sodium α-olefin sulfonate, 0.1 parts by weight of sodium chloride, and an average particle size of 0.43 mm were placed in a 6 L autoclave equipped with a stirrer. After charging 20 parts by weight of polystyrene resin seed particles, stirring was started. Subsequently, after heating the inside of the autoclave to 90° C., (a) 0.064 parts by weight of dibenzoyl peroxide for 4 hours and 50 minutes and (b) 80 parts by weight of styrene monomer were added as polymerization initiators. Polymerization was carried out while adding into the autoclave over 5 hours and 30 minutes. 0.064 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane was added at 4 hours and 45 minutes after the start of polymerization, and 0.012 parts by weight of divinylbenzene was added at 5 hours and 23 minutes after the start of polymerization. After that, the inside of the autoclave was held at 90° C. for 30 minutes, and then 6.5 parts by weight of butane (normal-rich butane (normal-butane/isobutane=70/30)) and 1.0 part by weight of cyclohexane were charged. The base resin composition was impregnated with the foaming agent by holding at 120° C. for a period of time. Thereafter, the inside of the autoclave was cooled to room temperature, and the expandable polystyrene resin particles were taken out from the autoclave. The expandable polystyrene resin particles taken out were washed, dehydrated and dried.
Here, the expandability of the expandable styrene-based resin particles was evaluated. The results are shown in Table 1.

<Production of polystyrene foam particles>
The obtained expandable polystyrene-based resin particles were put into a rotary stirring type expansion device. After that, the expandable polystyrene resin particles were expanded in steam at about 100° C. until the bulk density reached an expansion ratio of 50 times to obtain expanded polystyrene particles.
Here, the design properties (beauty) of the polystyrene-based foamed particles were evaluated. The results are shown in Table 1.

(Example 2)
As shown in Table 1, the same operation as in Example 1 was performed except that the liquid paraffin was changed to 0.7 parts by weight in the production process of the styrene seed resin particles, and the expandable polystyrene resin particles and the expanded polystyrene resin particles were prepared. The particles were evaluated similarly. The evaluation results are shown in Table 1.

(Example 3)
As shown in Table 1, the same operation as in Example 1 was performed except that the liquid paraffin was changed to 4.5 parts by weight in the production process of the styrene seed resin particles, and the expandable polystyrene resin particles and the expanded polystyrene resin particles were prepared. The particles were evaluated similarly. The evaluation results are shown in Table 1.

(Example 4)
As shown in Table 1, the same operation as in Example 1 was performed except that the nucleating agent PA-20 was changed to 0.03 parts by weight in the production process of the styrene seed resin particles. , were evaluated in the same manner as the polystyrene-based foamed particles. The evaluation results are shown in Table 1.

(Example 5)
As shown in Table 1, the same operation as in Example 1 was performed except that the nucleating agent PA-20 was changed to 0.25 parts by weight in the production process of the styrene seed resin particles. , were evaluated in the same manner as the polystyrene-based foamed particles. The evaluation results are shown in Table 1.

(Example 6)
As shown in Table 1, in the production process of styrene seed resin particles, a droplet generator having one plate having 148 holes of 0.10 mmφ was supplied with a monomer mixture at a rate of 90 cc/min, and The same operation as in Example 1 was carried out, except that the vibration was changed to mechanical vibration, and the expandable polystyrene resin particles and polystyrene expanded particles were evaluated in the same manner. The evaluation results are shown in Table 1.

(Comparative example 1)
100 parts by weight of pure water, 0.4 parts by weight of tribasic calcium phosphate, 0.01 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of sodium chloride, and 0 parts by weight of coconut oil as a plasticizer were placed in a reactor equipped with a stirrer. 0.07 parts by weight of polyethylene wax as a nucleating agent was added and stirred to form an aqueous suspension, and then 0.2 parts by weight of benzoyl peroxide as a polymerization initiator was added to 100 parts by weight of styrene monomer. and 0.2 parts by weight of 1,1-bis(t-butylperoxy)cyclohexane were dissolved, added to the reactor, heated to 98° C., and polymerized over 4.5 hours. Next, the temperature was raised to 110° C., held for 1 hour, and then cooled. Except for this, the same operation as in Example 1 was carried out, and the expandable polystyrene resin particles and polystyrene expanded particles were evaluated in the same manner. The evaluation results are shown in Table 1.

(Comparative example 2)
As shown in Table 1, the same operation as in Example 1 was carried out, except that the amount of liquid paraffin was changed to 0 parts by weight in the production process of the styrene seed resin particles. evaluated to The evaluation results are shown in Table 1.

(Comparative Example 3)
As shown in Table 1, the same operation as in Example 1 was performed except that the liquid paraffin was changed to 6.0 parts by weight in the production process of the styrene seed resin particles, and the expandable polystyrene resin particles and the expanded polystyrene resin particles were prepared. The particles were evaluated similarly. The evaluation results are shown in Table 1.

(Comparative Example 4)
As shown in Table 1, the same operation as in Example 1 was performed except that the nucleating agent PA-20 was changed to 0.35 parts by weight in the production process of the styrene seed resin particles, and the expandable polystyrene resin particles were prepared. , were evaluated in the same manner as the polystyrene-based foamed particles. The evaluation results are shown in Table 1.

(Comparative Example 5)
As shown in Table 1, the same operation as in Example 1 was performed except that the nucleating agent PA-20 was changed to 0 parts by weight in the production process of the styrene seed resin particles, and the expandable polystyrene resin particles and polystyrene It was evaluated in the same manner as the system expanded particles. The evaluation results are shown in Table 1.

In Table 1, the parts by weight of the plasticizer and the nucleating agent are the contents per 100 parts by weight of the styrene monomer used in the production process of the styrene seed resin particles.

It is possible to provide styrene-based seed resin particles that have a uniform particle size distribution and that have good productivity for the expandable polystyrene-based resin particles that have excellent expandability and the polystyrene-based expanded particles that have excellent beauty. Therefore, one embodiment of the present invention can be suitably used for manufacturing cushion beads, foam moldings for building materials, and lightweight concrete.

Claims (6)

Styrenic seed resin particles for seed polymerization containing a base resin containing a styrene unit as a structural unit,
Containing 0.5 to 5.0 parts by weight of a plasticizer with respect to 100 parts by weight of the base resin,
Containing 0.03 to 0.30 parts by weight of a nucleating agent with respect to 100 parts by weight of the base resin,
Styrenic seed resin particles for seed polymerization, having an average particle size of 0.20 to 0.50 mm and a UT indicating variation in particle size distribution of 2.15 or less. 2. The styrene seed resin particles for seed polymerization according to claim 1, wherein the base resin contains 90% or more of styrene units as structural units. The nucleating agent is an acrylic resin,
3. The styrene seed resin particles for seed polymerization according to claim 1, wherein the nucleating agent has a weight average molecular weight of 500,000 to 1,500,000. Expandable polystyrene resin particles obtained by seed polymerization using the styrene seed resin particles according to any one of claims 1 to 3. Expanded polystyrene particles obtained by expanding the expandable polystyrene resin particles according to claim 4 . A polystyrene foam molded product obtained by molding the polystyrene foam particles according to claim 5 in a mold.