JP2020084077A - Foaming polystyrene-based resin particle and utilization thereof - Google Patents

Abstract

To provide a new foaming polystyrene-based resin particle and a manufacturing method thereof having good productivity of the polystyrene-based foaming particle, and utilization of the foaming polystyrene-based resin particle.SOLUTION: Foaming polystyrene-based resin particle contains a base material resin and a foaming agent. Mean diameter and weight-average molecular weight (Mw) is within the specify. The foaming polystyrene-based resin particle further contains specific amount of magnesium stearate further.SELECTED DRAWING: None

Description

The present invention relates to expandable polystyrene resin particles and use thereof.

The expandable polystyrene-based resin particles are relatively inexpensive, can be foam-molded with steam without using a special method, and can obtain a high cushioning effect and a heat insulating effect, and thus are socially useful materials.

Various types of expandable polystyrene resin particles have been developed so far. For example, Patent Document 1 discloses expandable styrene-based polymer particles having a large particle size (also referred to as particle size) (700 to 1100 μm).

On the other hand, depending on the application of the expandable polystyrene resin particles, expandable polystyrene resin particles having a small particle size are preferred. Examples of expandable polystyrene-based resin particles having a small particle size include the techniques disclosed in Patent Documents 2 to 4 below.

Patent Document 2 discloses expandable styrene resin particles having a particle diameter of 200 to 600 μm and containing a specific amount of butane as a foaming agent.

Patent Document 3 discloses expandable polystyrene resin particles having an average particle diameter of 200 to 450 μm and containing zinc stearate on the surface in the presence of an antistatic agent.

Patent Document 4 discloses expandable styrene-based resin particles in which the total amount of organic compounds and the particle size distribution are each within a specific range, and the average particles are 0.3 to 0.6 mm.

JP-A-6-116435 JP 2004-155870 A JP2011-74239A Japanese Patent Laid-Open No. 2010-100860

However, the conventional technology as described above is not sufficient from the viewpoint of the productivity of the polystyrene-based foamed particles obtained by foaming the expandable polystyrene-based resin particles, particularly from the viewpoint of suppressing blocking during the production of the polystyrene-based foamed particles, There was room for further improvement in terms of productivity.

One embodiment of the present invention has been made in view of the above problems, and an object thereof is to suppress blocking, and to improve the productivity of polystyrene-based expanded particles, a novel expandable polystyrene-based resin particle and the same. It is to provide utilization technology.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the average particle diameter and the weight average molecular weight (Mw) are within specific ranges, and contain a specific amount of magnesium stearate, thereby suppressing blocking. The inventors have found that it is possible to obtain expandable polystyrene-based resin particles that have good polystyrene-based expanded particle productivity, and have completed the present invention.

That is, one embodiment of the present invention includes the following configurations.
[1] Expandable polystyrene-based resin particles containing a base resin and a foaming agent, wherein (a) the average particle size is 0.25 mm or more and 0.5 mm or less, and (b) the weight average molecular weight (Mw) is It is 180,000 or more and less than 270,000, and (c) further contains 0.5 parts by weight or more and 1.9 parts by weight or less of magnesium stearate with respect to 100 parts by weight of the expandable polystyrene resin particles. Expandable polystyrene-based resin particles.
[2] The foaming agent is (a) 1.5 parts by weight or more and 3.0 parts by weight or less of cyclohexane, and (b) 7.0 parts by weight or more and 9.0 parts by weight with respect to 100 parts by weight of the base resin. The expandable polystyrene-based resin particles according to [1], characterized in that the content of butane is not more than 1 part by weight.
[3] The expandable polystyrene resin particle according to [1] or [2], which has a particle size distribution (UT) of 2.10 or less.
[4] Further containing 0.05 to 0.60 parts by weight of N-hydroxyethyl-N-(2-hydroxyalkyl)amine with respect to 100 parts by weight of the expandable polystyrene resin particles. The expandable polystyrene resin particle according to any one of [1] to [3], which is characterized.
[5] Expanded polystyrene-based particles, which are obtained by expanding the expandable polystyrene-based resin particles according to any one of [1] to [4].
[6] The expanded polystyrene particles according to [5], which has a bulk density of 0.0140 g/cm ³ or more and 0.0240 g/cm ³ or less.
[7] A polystyrene foam molded article, which is obtained by molding the polystyrene foam particles according to [5] or [6] in a mold.
[8] A composition for lightweight concrete, comprising the expanded polystyrene particles according to [5] or [6].

According to one embodiment of the present invention, it is possible to obtain the effect that it is possible to obtain the expandable polystyrene-based resin particles that can suppress blocking and improve the productivity of the expanded polystyrene-based particles.

One embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications can be made within the scope of the claims. Further, embodiments or examples obtained by appropriately combining the technical means disclosed in the 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 of the embodiments. In addition, all the academic documents and patent documents described in this specification are incorporated as a reference in this specification. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more (including A and larger than A) and B or less (including B and smaller than B)”.

[1. Expandable polystyrene resin particles]
(1-1. Technical idea)
An object of one embodiment of the present invention is to provide a novel expandable polystyrene-based resin particle having good productivity of expanded polystyrene-based particles. More specifically, it is to provide expandable polystyrene resin particles having a small particle size and capable of suppressing blocking during the production of expanded polystyrene particles.

The above-mentioned Patent Document 1 discloses a technique for preventing blocking during the production of expanded polystyrene particles for expandable styrene polymer particles having a large particle size. On the other hand, Patent Documents 2 and 4 do not specifically disclose measures for preventing blocking during the production of expanded polystyrene particles. Further, Patent Document 3 discloses expandable polystyrene resin particles containing zinc stearate on the surface in order to improve the fluidity.

Here, in the production of expanded polystyrene-based particles, the inventors have found that the smaller the molecular weight of the expandable polystyrene-based resin particles used and/or the larger the expansion ratio of the expanded polystyrene-based particles to be produced, blocking occurs. We have uniquely found the technical problem of being easy.

Further, when the particle size is large as in Patent Document 1, zinc stearate is often used as the antiblocking agent. However, as a result of studies by the present inventors, it was found that the expandable polystyrene resin particles having a small particle size and a small weight average molecular weight (for example, less than 270,000) have a surface containing zinc stearate. Also, it was found for the first time that blocking during the production of expanded polystyrene particles was not improved.

The present inventors have completed the present invention to achieve the purpose of suppressing blocking and improving productivity. Embodiments of the present invention will be described below.

(1-2. Expandable polystyrene resin particles)
The expandable polystyrene-based resin particles according to an embodiment of the present invention are expandable polystyrene-based resin particles containing a base resin and a foaming agent, and (a) have an average particle size of 0.25 or more and 0.5 mm or less. And (b) the weight average molecular weight (Mw) is 18 or more and less than 270,000, and (c) 0.5 parts by weight or more and 1.9 parts by weight or less with respect to 100 parts by weight of the expandable polystyrene resin particles. And magnesium stearate of.

The expandable polystyrene-based resin particles according to an embodiment of the present invention have the above-mentioned configuration, and thus have the advantage of improving the productivity of the polystyrene-based expanded particles, specifically, blocking during the production of the polystyrene-based expanded particles. It has the advantage that it can be suppressed. In addition, the expandable polystyrene resin particles according to one embodiment of the present invention have the above-mentioned configuration, and thus can provide polystyrene expanded particles capable of satisfying the following (A) to (C): (A) Average particle size Small; (B) Small bulk density (for example, 0.0240 g/cm ³ or less); (C) A polystyrene foam molded article having excellent surface beauty can be provided.

Expandable polystyrene resin particles according to an embodiment of the present invention, the polystyrene foam particles are produced by a known method using the expandable polystyrene resin particles, by a known method using such polystyrene foam particles. By performing foam molding, a polystyrene foam molded article can be provided.

In the present specification, the "expandable polystyrene resin particles according to one embodiment of the present invention" may be simply referred to as "the expandable polystyrene resin particles". That is, the term “the expandable polystyrene-based resin particles” means one embodiment of the expandable polystyrene-based resin particles in the present invention.

In the present specification, “blocking” means that the polystyrene-based expanded particles are fused (also referred to as a bond) with each other during the production of the polystyrene-based expanded particles, resulting in a lump. When blocking occurs, the productivity of expanded polystyrene particles decreases. In addition, the polystyrene-based foamed particles produced in a state where blocking has occurred include lumps derived from blocking.

(1-3. Base resin)
The base resin contained in the expandable polystyrene-based resin particles mainly contains a styrene unit as a constitutional unit. In the present specification, the “styrene unit” is a structural unit derived from a styrene monomer. Here, “mainly containing styrene units as constitutional units” means that the number of styrene units is 50% or more when the number of all constitutional units contained in the base resin is 100%.

The base resin may be a homopolymer of styrene. The base resin is a copolymer of (a) styrene monomer and (b) various monomers such as styrene derivative, ester of acrylic acid and methacrylic acid, acrylonitrile, dimethyl fumarate, or ethyl fumarate. It may be a polymer. Examples of the styrene derivative include α-methylstyrene, paramethylstyrene, t-butylstyrene and chlorostyrene. Examples of the ester of acrylic acid and methacrylic acid include methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and cetyl methacrylate. The copolymer may further contain a constitutional unit derived from a bifunctional monomer such as divinylbenzene and alkylene glycol dimethacrylate.

(1-4. Foaming agent)
In the present specification, the foaming agent is intended to mean a volatile compound capable of slightly swelling polystyrene-based resin particles. Examples of the foaming agent contained in the expandable polystyrene-based resin particles include (a) aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, normal pentane, and hydrocarbons such as neopentane cyclohexane, and (b) ) Difluoroethane and fluorinated hydrocarbons having a zero ozone depletion potential such as tetrafluoroethane and the like, and volatile blowing agents such as, but not limited to. The above-mentioned foaming agents may be used alone or in combination of two or more kinds.

The foaming agent contained in the expandable polystyrene-based resin particles preferably contains butane and cyclohexane. The foaming agent contained in the expandable polystyrene-based resin particles is (a) 1.5 parts by weight or more and 3.0 parts by weight or less of cyclohexane, and (b) 7.0 parts by weight with respect to 100 parts by weight of the base resin. More preferably, the content of butane is not less than 9.0 parts by weight and not more than 9.0 parts by weight. According to the above configuration, the expandable polystyrene-based resin particles have a expansion ratio of 40 times or more and 70 times or less and/or a polystyrene density of 0.0140 g/cm ³ or more and 0.0240 g/cm ³ or less. Foamed particles can be provided. Moreover, according to the said structure, the expandable polystyrene type resin particle can provide a polystyrene type expanded particle which can provide a polystyrene type expanded molded article excellent in fusion property.

Examples of butane that can be suitably contained in the expandable polystyrene-based resin particles include isobutane, normal butane, and a mixture of isobutane and normal butane. Of the mixture of isobutane and normal butane, the mixture containing 50% by weight or more of normal butane with respect to 100% by weight of the mixture is also referred to as normal rich butane. The expandable polystyrene-based resin particles more preferably contain, as butane, normal butane and/or normal rich butane.

The content of cyclohexane in the foaming agent is more preferably 1.6 parts by weight or more and 2.8 parts by weight or less, based on 100 parts by weight of the base resin, and 1.7 parts by weight or more and 2.5 parts by weight or less. Is more preferable, and 1.8 parts by weight or more and 2.3 parts by weight or less is particularly preferable. The content of butane in the foaming agent is more preferably 7.2 parts by weight or more and 8.8 parts by weight or less, and 7.5 parts by weight or more and 8.5 parts by weight or less with respect to 100 parts by weight of the base resin. Is more preferable, and it is particularly preferable that the amount is 7.7 parts by weight or more and 8.3 parts by weight or less.

The total content of the foaming agent in the expandable polystyrene-based resin particles is preferably 8.5 parts by weight or more and 12.0 parts by weight or less, and 9.0 parts by weight or more 11 with respect to 100 parts by weight of the base resin. The amount is more preferably 0.5 parts by weight or less, further preferably 9.5 parts by weight or more and 10.5 parts by weight or less. When the total content of the foaming agent in the expandable polystyrene-based resin particles is (a) 8.5 parts by weight or more, the expandable polystyrene-based resin particles obtain a sufficient expansion power during the production of the expanded polystyrene-based resin particles. When (b) is 12.0 parts by weight or less, when the expandable polystyrene-based resin particles are foamed, shrinkage of the polystyrene-based expanded particles due to plasticization of the base resin does not become too large. That is, according to the above-mentioned composition, it is possible to obtain expanded polystyrene particles having high magnification (for example, 40 times or more) and/or low bulk density (for example, 0.0240 g/cm ³ or less).

(1-5. Antiblocking agent)
The expandable polystyrene resin particles contain magnesium stearate. During the production of expanded polystyrene particles using expandable polystyrene resin particles, since blocking can be suppressed, the expandable polystyrene resin particles contain magnesium stearate on the surface of the expandable polystyrene resin particles. Is preferred. When magnesium stearate is included on the surface of the expandable polystyrene resin particles, the magnesium stearate can be said to be an antiblocking agent. The expandable polystyrene resin particles containing magnesium stearate on the surface can be obtained by adding (applying) magnesium stearate to the surface of the expandable polystyrene resin particles.

Regarding the expandable polystyrene-based resin particles, a fatty acid metal salt such as zinc stearate is generally used as an antiblocking agent. The present inventors have found that with the present expandable polystyrene resin particles having a small average particle size and a small weight average molecular weight (Mw), blocking is not suppressed when zinc stearate is contained, but blocking when magnesium stearate is contained on the surface. It was found for the first time that is suppressed.

The content of magnesium stearate in the expandable polystyrene-based resin particles is preferably 0.5 parts by weight or more and 1.9 parts by weight or less, based on 100 parts by weight of the expandable polystyrene-based resin particles, and 0.6 parts by weight. It is more preferably from 1.5 parts by weight or more to 1.5 parts by weight or less, further preferably from 0.7 parts by weight to 1.2 parts by weight, more preferably from 0.6 parts by weight to 1.2 parts by weight. Particularly preferred.

When the content of magnesium stearate in the expandable polystyrene-based resin particles is (a) 0.5 part by weight or more based on 100 parts by weight of the expandable polystyrene-based resin particles, a sufficient blocking prevention effect can be obtained. When (b) is 1.9 parts by weight or less, the polystyrene-based foam molded article that can be provided by the expandable polystyrene-based resin particles has excellent fusion bondability.

(1-6. Antistatic agent)
The expandable polystyrene-based resin particles and the expanded polystyrene-based particles that can be provided by the expandable polystyrene-based resin particles are likely to be charged, and thus static electricity is likely to occur. The static electricity generated in the expandable polystyrene resin particles and the polystyrene expanded particles is accompanied by a risk of sparking due to discharge. Further, consider a case where the expandable polystyrene resin particles and the polystyrene foam particles have static electricity. In this case, when the expandable polystyrene-based resin particles and the polystyrene-based expanded particles are handled, the expandable polystyrene-based resin particles and the polystyrene-based expanded particles may cling to surrounding devices or equipment (instruments). Therefore, in the case described above, there is a drawback that the handling property (productivity) is deteriorated. Therefore, the expandable polystyrene-based resin particles and the polystyrene-based expanded particles preferably further contain an antistatic agent, and more preferably the surface of the expandable polystyrene-based resin particles and polystyrene-based expanded particles contains an antistatic agent. The expanded polystyrene particles containing an antistatic agent on the surface can be obtained by (a) foaming expandable polystyrene resin particles containing an antistatic agent on the surface, and (b) polystyrene excellent in antistatic performance. A foamed molded article can be provided. The expandable polystyrene resin particles containing an antistatic agent on the surface can be obtained by adding (applying) an antistatic agent to the surface of the expandable polystyrene resin particles.

The method of applying the antistatic agent is not particularly limited, but a method of applying by stirring the expandable polystyrene resin particles together with the antistatic agent in a stirrer is preferable. As the agitator, a Nauta mixer, a super mixer, a universal mixer, a tumbler mixer, a Loedige mixer or the like is used.

Examples of the antistatic agent include 1-amino-2-hydroxy compound, glycerin, fatty acid monoglyceride (also referred to as fatty acid monoglyceride), polyoxyethylene alkyl ether, and polyoxyethylene fatty acid ester. The 1-amino-2-hydroxy compound is a compound having one amino group and two hydroxyl groups in one molecule, and examples thereof include N-hydroxyethyl-N-(2-hydroxyalkyl)amine and N,N-bis. (Hydroxyethyl)dodecylamine, N,N-bis(hydroxyethyl)tetradecylamine, N,N-bis(hydroxyethyl)hexadecylamine, N,N-bis(hydroxyethyl)octadecylamine, N-hydroxyethyl- N-(2-hydroxytetradecyl)amine, N-hydroxyethyl-N-(2-hydroxyhexadecyl)amine, N-hydroxyethyl-N-(2-hydroxyoctadecyl)amine, N-hydroxypropyl-N-( 2-hydroxytetradecyl)amine, N-hydroxybutyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2- Hydroxyhexadecyl)amine, N-hydroxypentyl-N-(2-hydroxyoctadecyl)amine, N,N-bis(2-hydroxyethyl)dodecylamine, N,N-bis(2-hydroxyethyl)tetradecylamine, Examples thereof include N,N-bis(2-hydroxyethyl)hexadecylamine and N,N-bis(2-hydroxyethyl)octadecylamine. Examples of the fatty acid glyceride include stearic acid triglyceride, palmitic acid triglyceride, lauric acid triglyceride, stearic acid diglyceride, stearic acid monoglyceride and the like. These antistatic agents may be used alone or in combination of two or more kinds.

The expandable polystyrene-based resin particles preferably contain N-hydroxyethyl-N-(2-hydroxyalkyl)amine, which is excellent in antistatic performance, as an antistatic agent. The expandable polystyrene-based resin particles more preferably contain N-hydroxyethyl-N-(2-hydroxyalkyl)amine on the surface of the expandable polystyrene-based resin particles. According to the above-mentioned composition, it is possible to obtain the expandable polystyrene-based resin particles excellent in antistatic performance.

In N-hydroxyethyl-N-(2-hydroxyalkyl)amine, the larger the number of carbons in (a) hydroxyalkyl, the more the expandable polystyrene resin particles of N-hydroxyethyl-N-(2-hydroxyalkyl)amine. The adhesive force tends to be stronger, and the smaller the number of carbon atoms in the hydroxyalkyl (b), the more the solubility of N-hydroxyethyl-N-(2-hydroxyalkyl)amine in water tends to increase.

In one embodiment of the present invention, the hydroxyalkyl in N-hydroxyethyl-N-(2-hydroxyalkyl)amine preferably has 8 to 16 carbon atoms. In other words, the N-hydroxyethyl-N-(2-hydroxyalkyl)amine contained in the expandable polystyrene-based resin particles is N-hydroxyethyl-N-(2-hydroxy) having hydroxyalkyl having 8 to 16 carbon atoms. It is preferable that the main component is an alkyl)amine. According to the above configuration, the adhesive force of N-hydroxyethyl-N-(2-hydroxyalkyl)amine to the expandable polystyrene resin particles becomes sufficient. Therefore, there is no possibility that N-hydroxyethyl-N-(2-hydroxyalkyl)amine will be removed from the expandable polystyrene-based resin particles or the polystyrene-based expanded particles during foaming and foam molding. As a result, the expanded polystyrene particles and expanded polystyrene molded article that can be provided by the expandable polystyrene resin particles have excellent antistatic performance.

The content of the antistatic agent in the expandable polystyrene-based resin particles is preferably 0.05 parts by weight or more and 0.60 parts by weight or less, based on 100 parts by weight of the expandable polystyrene-based resin particles, and is 0.08. The amount is more preferably not less than 0.50 parts by weight, more preferably not less than 0.10 parts by weight and not more than 0.30 parts by weight, and not less than 0.13 parts by weight and not more than 0.20 parts by weight. Is particularly preferable.

According to the above configuration, the expandable polystyrene-based resin particles can stably provide the polystyrene-based expanded particles having a reduced charge amount. When the content of the antistatic agent in the expandable polystyrene-based resin particles is (a) 0.05 parts by weight or more with respect to 100 parts by weight of the expandable polystyrene-based resin particles, the expandable polystyrene-based resin particles are It is possible to provide expanded polystyrene particles having excellent antistatic performance, and when (b) is 0.60 parts by weight or less, there is no risk of blocking during the production of expanded polystyrene particles.

(1-7. Other additives)
The expandable polystyrene-based resin particles may further contain a plasticizer, a foam control agent, a flame retardant, a flame retardant aid, etc. within a range that does not impair the physical properties.

Examples of the plasticizer include (a) stearic acid triglyceride, palmitic acid triglyceride, lauric acid triglyceride, stearic acid diglyceride, stearic acid monoglyceride and other fatty acid glycerides, (b) coconut oil, palm oil, palm kernel oil and other vegetable oils, Examples thereof include (c) dioctyl adipate, dibutyl sebacate and other aliphatic esters, and (d) liquid paraffin, cyclohexane and other organic hydrocarbons. These plasticizers may be used alone or in combination of two or more.

Examples of the air bubble modifier include (a) methylenebisstearic acid amide, aliphatic bisamide such as ethylenebisstearic acid amide, and (b) polyethylene wax.

As the flame retardant, (a) brominated polystyrene, a copolymer of brominated butadiene and vinyl aromatic, brominated novolac resin allyl ether, brominated poly(1,3-cycloalkadiene) and brominated poly Brominated polymers such as (4-vinylphenol allyl ether), and (b) polyglycerin dibromopropyl ether, tetrabromobisphenol A and tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl ether), etc. Low molecular weight compounds.

Examples of the flame retardant aid include high-temperature decomposition such as cumene peroxide, dicumyl peroxide, t-butyl hydroperoxide, and 2,3-dimethyl-2,3-diphenylbutane, which have a high 10-hour half-life temperature. Type organic matter.

(1-8. Physical properties)
The expandable polystyrene resin particles have an average particle diameter of 0.25 mm or more and 0.5 mm or less, and preferably 0.35 mm or more and 0.42 mm or less. When the average particle diameter is less than 0.25 mm, (a) blocking may occur during the production of expanded polystyrene-based particles, and/or (b) the expandable polystyrene-based resin particles are inferior in expandability and expanded. It tends to be difficult to provide polystyrene-based expanded particles having a magnification of 40 times or more and/or a bulk density of 0.0240 g/cm ³ or less. When the average particle diameter is larger than 0.5 mm, the polystyrene foam molded article produced by using the polystyrene foam particles that can be provided by the expandable polystyrene resin particles has poor surface beauty. In the present specification, the average particle size of the expandable polystyrene resin particles is calculated from a distribution table in which particle sizes measured on a volume basis are displayed as cumulative distributions. The particle size at which the cumulative volume percentage is 50% (also referred to as median size) was defined as the average particle size.

The present expandable polystyrene-based resin particles preferably have a weight average molecular weight (also referred to as Mw) of 180,000 or more and less than 270,000, and more preferably 190,000 or more and less than 220,000. When the weight-average molecular weight is (a) less than 180,000, when the expandable polystyrene-based resin particles are expanded, the polystyrene-based expanded particles shrink largely, and (b) when it is 270,000 or more, the expandable polystyrene. The resin particles become difficult to foam. Therefore, when the weight average molecular weight is outside the above range, polystyrene-based expanded particles having a sufficient expansion ratio (for example, 40 times or more) and/or a desired bulk density (for example, 0.0240 g/cm ³ or less) are obtained. I can't. The method for measuring the weight average molecular weight of the expandable polystyrene resin particles will be described in detail in the examples below. In addition, polystyrene-based expanded particles that do not have a sufficient expansion ratio and/or a desired bulk density are polystyrene-based expanded particles required for producing a polystyrene-based foamed molded product or lightweight concrete having a desired lightness. However, the cost performance is lacking.

The expandable polystyrene-based resin particles preferably have a particle size distribution (also referred to as UT) of 2.10 or less, and more preferably 2.03 or less. According to the above configuration, when a polystyrene-based foamed article is produced using the polystyrene-based foamed particles that can be provided by the resulting expandable polystyrene-based resin particles, a polystyrene-based foamed article having excellent surface beauty can be obtained.

In the present specification, the particle size distribution (UT) is calculated from a distribution table in which particle sizes measured on a volume basis are displayed as a cumulative distribution. Specifically, when the particle diameters where the cumulative volume percentages are 90%, 60%, 40%, and 10% are D90, D60, D40, and D10, the numerical values obtained by the following formula are Distribution (UT).
Particle size distribution (UT)=D90/D40+D60/D10
When all the particles have the same particle size, the particle size distribution (UT) is 2. Therefore, the lower limit of the particle size distribution (UT) of the expandable polystyrene resin particles is 2 or more.

Further, in the present specification, as the average particle size and particle size distribution (UT) of the expandable polystyrene resin particles, the value of the expandable polystyrene resin particles containing no magnesium stearate and the antistatic agent may be adopted. .. This is because the influence of the average particle size and the particle size distribution (UT) by the magnesium stearate and the antistatic agent contained in the expandable polystyrene resin particles can be ignored.

It is preferable that the expandable polystyrene resin particles have a smaller charge amount. More specifically, the charge amount of the expandable polystyrene resin particles is preferably 0.35 kV or less in absolute value, more preferably 0.30 kV or less. The charge amount of the expandable polystyrene-based resin particles can be measured using a static electricity measuring device.

(1-9. Method for producing expandable polystyrene resin particles)
As a method for producing the expandable polystyrene-based resin particles, known methods such as suspension polymerization method and seed polymerization method can be used and are not particularly limited.

The suspension polymerization method is, for example, a method including the following (1) to (5): (1) water, a monomer containing a styrene monomer, a dispersant, a polymerization initiator, and optionally other Additives (plasticizer, foam control agent, flame retardant, flame retardant aid, etc.) are mixed to prepare an aqueous suspension; (2) Next, the aqueous suspension is heated to a predetermined temperature; (3) Next, an aqueous suspension is reacted at a predetermined temperature for a predetermined time to carry out a polymerization reaction to obtain a base resin containing an additive (also referred to as a base resin composition); (4) The base resin composition is impregnated with a foaming agent in the middle of (3) or after (3); (5) Next, a base resin composition containing a foaming agent (pre-foaming property). Magnesium stearate and optionally an antistatic agent are added (applied) to the surface of the polystyrene resin particles).

The seed polymerization method is a method including, for example, the following (1) to (5): (1) water, polystyrene resin particles, a dispersant, a polymerization initiator, and optionally other additives (plasticizer, (Bubble conditioner, flame retardant, flame retardant aid, etc.) are mixed to prepare an aqueous suspension; (2) Next, the aqueous suspension is heated to a predetermined temperature; (3) Next, At a given temperature, the monomer containing the styrene monomer is added to the aqueous suspension over a given period of time, and at the same time, the aqueous suspension is reacted to carry out a polymerization reaction to contain the additive. A base resin (also referred to as a base resin composition) is obtained; (4) Same as the suspension polymerization method; (5) Same as the suspension polymerization method.

The seed polymerization method is a method in which polystyrene-based resin particles dispersed in an aqueous suspension are polymerized while impregnating a monomer, as described above. The polystyrene resin particles used in the seed polymerization method can be said to be polystyrene resin seed particles.

The polystyrene-based resin seed particles are (a) an ordinary suspension polymerization method, or (b) a styrene monomer containing a polymerization initiator is passed through a nozzle under regular vibration to form a droplet group in an aqueous medium. It can be obtained by a method of dispersing and polymerizing without causing coalescence and additional dispersion. In the seed polymerization method in the present method for producing expandable polystyrene-based resin particles, since expandable polystyrene-based resin particles having a narrow particle size distribution can be easily obtained, the polystyrene-based resin species obtained by the method (b) above is used. It is preferable to use particles.

The amount of polystyrene-based resin seed particles in the seed polymerization method is preferably 5 to 60% by weight when the amount of expandable polystyrene-based resin particles finally obtained 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 alone but is polymerized in the polystyrene resin seed particles alone. When the proportion of the body tends to increase and (b) is 60% by weight or less, more monomers can be polymerized in one production, which is economically advantageous.

As a method for producing the expandable polystyrene-based resin particles, the seed polymerization method is preferable because it is easy to obtain expandable polystyrene-based resin particles having a narrow particle size distribution.

Examples of the dispersant include (a) tricalcium phosphate, magnesium pyrophosphate, hydroxyapatite, kaolin and other poorly water-soluble inorganic salts, and (b) polyvinyl alcohol, methylcellulose, polyacrylamide, polyvinylpyrrolidone, and other highly water-soluble dispersants. Examples include molecules.

Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxide include benzoyl peroxide, lauroyl peroxide, t-butylperoxybenzoate, isopropyl-t-butylperoxycarbonate, butyl perbenzoate, t-butylperoxy-2-ethylhexanoate, t-butyl perpivalate, t-butyl peroxyisopropyl carbonate, di-t-butyl peroxyhexahydroterephthalate, 1,1-di(t-butyl peroxy) 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 compound include azobisisobutyronitrile and azobisdimethylvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. t-Butylperoxy-2-ethylhexyl carbonate is also called t-butylperoxy-2-ethylhexyl monocarbonate.

In the method for producing expandable polystyrene-based resin particles, a chain transfer agent and a polymerization modifier may be further used. Examples of the chain transfer agent include mercaptan compounds such as n-octyl mercaptan, n-dodecyl mercaptan and t-dodecyl mercaptan. Examples of the polymerization modifier include α-methylstyrene dimer and the like which are generally used for polymerization of acrylonitrile-styrene resin.

Regarding the amount of magnesium stearate used in the method for producing the expandable polystyrene-based resin particles, the content of magnesium stearate in the expandable polystyrene-based resin particles described in the above section (1-5. Antiblocking agent) It is preferably the same mode as In addition, in the present specification, the “use amount” can also be referred to as an “addition amount”.

Regarding the amount of the antistatic agent used in the method for producing the expandable polystyrene-based resin particles, the content of the antistatic agent in the expandable polystyrene-based resin particles described in the above section (1-6. Antistatic agent) It is preferably the same mode as

[2. Polystyrene foam particles]
The expanded polystyrene particles according to one embodiment of the present invention include [1. Expandable polystyrene-based resin particles], and the expandable polystyrene-based resin particles are expanded. The expanded polystyrene particles according to one embodiment of the present invention have the above-mentioned configuration and therefore can satisfy the above-mentioned (A) to (E). In addition, the polystyrene-based expanded particles according to the embodiment of the present invention contain almost no lumps derived from blocking.

In the present specification, "polystyrene-based expanded particles according to one embodiment of the present invention" may be simply referred to as "main expanded particles". That is, the term “the expanded beads” intends one embodiment of the polystyrene-based expanded particles in the present invention.

This foamed particles is preferably the bulk density is less than 0.0140g / cm ³ or more 0.0240g / cm ^3, more preferably 0.0140g / cm ³ or more 0.0200 g / cm ³ or less, 0 It is more preferably 0.0140 g/cm ³ or more and 0.0167 g/cm ³ or less. When the bulk density is 0.0140 g/cm ³ or more, the particle size of the polystyrene-based expanded particles is small, and thus the gap between the expanded particles is small on the surface of the polystyrene-based expanded molded article produced using the polystyrene-based expanded particles. Become. As a result, the polystyrene foam molding has excellent surface beauty. When the bulk density is 0.0240 g/cm ³ or less, the amount of the polystyrene-based foamed particles required for producing the polystyrene-based foamed molded product or the lightweight concrete having desired lightness does not become too large, and the cost is reduced. Excellent performance.

It is preferable that the polystyrene-based expanded particles have a smaller charge amount. More specifically, the charge amount of the polystyrene foam particles is preferably 0.35 kV or less in absolute value, more preferably 0.30 kV or less. The charge amount of the polystyrene foam particles can be measured using a static electricity measuring device. The method for measuring the charge amount of the polystyrene foam particles will be described in detail in the following examples.

The method for expanding the expandable polystyrene-based resin particles, that is, the method for producing the expanded particles is not particularly limited, and a known method can be used. Examples of the foaming method include a method of sequentially performing the following (1) to (3): (1) Putting expandable polystyrene resin particles in a container equipped with a stirrer, and (2) by a heat source such as steam. By heating the expandable polystyrene-based resin particles, (3) foaming is performed until the desired expansion ratio is reached to obtain polystyrene-based expanded particles. The expanded polystyrene particles may be referred to as pre-expanded polystyrene resin particles, and therefore, the foaming method for obtaining the pre-expanded polystyrene resin particles may be referred to as the pre-expansion method.

[3. Polystyrene foam molding)
A polystyrene-based foam molded article according to an embodiment of the present invention is described in [2. The expanded polystyrene particles described in the section [Polystyrene-based expanded particles] are molded in a mold. The polystyrene-based foam molded article according to one embodiment of the present invention has the above-mentioned configuration and therefore has an advantage of being excellent in surface beauty and fusion bondability.

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

The in-mold molding method of polystyrene-based foamed particles, that is, the manufacturing method of the foamed molded article is not particularly limited, and a known method can be used. Examples of the in-mold molding method include a method in which a foamed particle is filled in a mold which can be closed but not sealed, and the foamed particle is heated and fused with steam to form a foamed molded body. Further, as the 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 formed in the wall surface, and steam is discharged from the small mold holes. After heating it to a temperature above the softening point of the expanded particles by ejecting a heating medium such as, and making them fuse with each other, after undergoing a cooling step, it is taken out from the mold and a polystyrene type peak shaped product of a desired shape is manufactured. There is a way to do it.

[4. Lightweight concrete composition)
Expandable polystyrene-based resin particles according to an embodiment of the present invention, and polystyrene-based expanded particles according to an embodiment of the present invention obtained by foaming the expandable polystyrene-based resin particles are used as a polystyrene-based foam molded article. There are other uses as well for compositions for making lightweight concrete. The composition for lightweight concrete according to one embodiment of the present invention is [2. Polystyrene-based expanded particles] may be used as long as they include the expanded foamed particles described in the section [1] Since the composition for lightweight concrete according to one embodiment of the present invention has the above-mentioned configuration, it is possible to provide lightweight concrete having excellent cost performance. The composition for lightweight concrete according to one embodiment of the present invention can be produced by a known method, for example, by mixing a material for lightweight concrete and the expanded beads.

By using the composition for lightweight concrete containing the present expanded granule particles, lightweight concrete, that is, lightweight concrete can be produced. The method for producing lightweight concrete is not particularly limited, and a known method can be used.

The polystyrene-based expanded particles contained in the composition for lightweight concrete according to one embodiment of the present invention are produced from expandable polystyrene-based resin particles having an average particle size of 0.5 mm or less. Therefore, the buoyancy of the polystyrene foam particles in the lightweight concrete composition is small and uniform. As a result, the dispersibility of the expanded polystyrene particles in the composition for lightweight concrete becomes good. The expanded polystyrene particles contained in the composition for lightweight concrete according to one embodiment of the present invention are preferably produced from expandable polystyrene resin particles having a particle size distribution (UT) of 2.10 or less. According to the above configuration, the polystyrene-based foamed particles have a uniform buoyancy in the lightweight concrete composition. As a result, the dispersibility of the expanded polystyrene particles in the composition for lightweight concrete becomes good. The expanded polystyrene particles contained in the composition for lightweight concrete according to one embodiment of the present invention preferably have a bulk density of 0.0140 g/cm ³ or more. According to the above configuration, the expanded polystyrene particles can be uniformly dispersed in the lightweight concrete composition. The expanded polystyrene particles contained in the composition for lightweight concrete according to one embodiment of the present invention preferably have a bulk density of 0.0240 g/cm ³ or less. According to the said structure, the composition for lightweight concrete can provide the lightweight concrete which has desired lightweightness.

Examples and comparative examples will be given below, but the present invention is not limited thereto.

Various measuring methods and evaluation methods of the expandable polystyrene resin particles, the polystyrene foam particles, and the polystyrene foam moldings in Examples and Comparative Examples are as follows. Further, "part" and "%" are based on weight unless otherwise specified.

(Measurement method of weight average molecular weight (Mw))
The expandable polystyrene resin particles were dissolved in tetrahydrofuran and measured by GPC (Tosoh Corp. HLC-8020, column: TSKgel Super HZM-H, column temperature: 40° C., flow rate: 0.35 ml/1 min). .. The weight average molecular weight was calculated as a standard polystyrene conversion value.

(Average particle size and particle size distribution (UT) distribution evaluation)
Using an image processing system Millitrack JPA particle size analyzer, the particle size of expandable polystyrene resin particles containing no magnesium stearate and an antistatic agent (also referred to as pre-expandable polystyrene resin particles) on a volume basis. It was measured. The results were displayed as a cumulative distribution, and a particle size distribution table was prepared. Using the obtained distribution table, the average particle size and the particle size distribution (UT) of the expandable polystyrene resin particles were calculated according to the above definition.

(Measuring Method and Evaluation Method of Blocking Amount during Production of Expanded Polystyrene Particles)
The entire amount of the polystyrene-based foamed particles obtained by foaming the expandable polystyrene-based resin particles was passed through a wire net having a 1 cm stitch interval. The weight (g) of the polystyrene-based expanded particles remaining on the wire mesh was measured, and the blocking amount (%) was calculated by the following formula:
Blocking amount (%)=weight of polystyrene-based expanded particles remaining on the wire mesh (g)/weight of total amount of polystyrene-based expanded particles (g)×100
Regarding the blocking amount at the time of producing polystyrene-based expanded particles, when the obtained blocking amount (%) is 0.05% or less, it is ○, and when it is more than 0.05% and 0.1% or less, Δ, 0.1%. When it was larger than that, it was determined to be x.

(Expandable polystyrene resin particles, a method for measuring the bulk density and an evaluation method for expandability)
The expandable polystyrene-based resin particles were placed in a steamer at 100° C. and heated for 4 minutes to obtain polystyrene-based expanded particles. 10 g of the obtained polystyrene-based expanded particles were put in a graduated cylinder of 1000 cm ³ , and the volume (cm ³ ) of the polystyrene-based expanded particles was measured. The bulk density (g/cm ³ ) was calculated with the following formula:
Bulk density (g/cm ³ )=10 g/volume of polystyrene-based expanded particles (cm ³ ).
Using the obtained bulk density, the expandability of the expandable polystyrene resin particles was evaluated based on the following index: When the bulk density is 0.0167 g/cm ³ or less ○: When it is 0.0240 g/cm Δ: × when it exceeds 0.0240 g/cm ³ .

(Method of measuring charge amount (kV))
The expanded polystyrene particles were placed in a polyethylene bag (OK bag No. 15, Okura Industry Co., Ltd.) (hereinafter referred to as a polyethylene bag). The polyethylene bag containing the polystyrene-based foamed particles was stored overnight in a thermostatic chamber at 23° C. and a humidity of 50% with the entrance of the polyethylene bag open (that is, without sealing). After the storage, 300 g of expanded polystyrene particles were put in a new polyethylene bag, and shaken 100 times with the entrance of the polyethylene bag tied. Then, the polyethylene bag was opened, and the charge amount (absolute value) on the surface of the polystyrene foam particles was measured three times or more by a static electricity measurement device (Stachilon DX manufactured by Shishido Electrostatics). The average value was used as the charge amount of the expanded polystyrene particles. The charge amount was measured in an atmosphere of a temperature of 23° C., a measurement distance of 30 mm, and a relative humidity of 50%.

(Measuring method of magnesium stearate contained on the surface of expandable polystyrene resin particles)
In Examples 1 to 9 and Comparative Examples 1, 2, 4 and 5, magnesium stearate is contained in the expandable polystyrene resin particles on the surface of the expandable polystyrene resin particles. The amount of magnesium stearate contained in the expandable polystyrene resin particles was measured by the following method.

100 g of expandable polystyrene resin particles were weighed and put into a 500 ml beaker, and then 200 ml of ethanol was put into the beaker. Then, after washing with an ultrasonic cleaner for 5 minutes, magnesium stearate contained in the supernatant was collected by filtration. After drying, the weight of magnesium stearate recovered was measured.

(Evaluation method of surface beauty of polystyrene foam molding)
The surface condition of the polystyrene foam molded article was visually observed, and the surface beauty of the polystyrene foam molded article was evaluated according to the following criteria.
◯: Beautiful with little melting and/or intergranular surface.
X: A large amount of surface melting and/or intergranular particles and poor appearance.

(Evaluation method of fusion-bonding property of polystyrene foam molding)
In the evaluation of the fusion-bonding property, the polystyrene-based foamed particles are foam-molded in the mold at a steam pressure of 0.03 MPa to 0.08 MPa to form a plate-shaped polystyrene resin foam having a length of 450 mm, a width of 300 mm, and a thickness of 25 mm. The body was molded. The foamed molded product immediately after molding (immediately after being dispensed from the mold) was broken along the thickness direction, and the fracture surface was evaluated according to the following criteria to evaluate the fusion property.
◯: When the broken surface was rubbed with a finger, the foamed particles were hardly removed.
Δ: When the broken surface is rubbed with a finger, some of the foam particles are peeled off.
X: When the broken surface is rubbed with a finger, the foamed particles are peeled off.

(Example 1)
<Production of expandable polystyrene resin particles>
In a 6 L autoclave equipped with a stirrer, 85 parts by weight of pure water, 0.57 parts by weight of tribasic calcium phosphate, 0.00476 parts by weight of α-olefin sodium sulfonate, 0.1 part by weight of sodium chloride, average particle size of 0.25 mm After charging 32 parts by weight of the polystyrene-based resin seed particles of No. 3, stirring was started. Then, 0.225 parts by weight of dibenzoyl peroxide was charged as a polymerization initiator. Then, the temperature inside the autoclave was raised to 92° C., and then (a) t-butylperoxy-2-ethylhexyl carbonate (0.08 part by weight) was used as a polymerization initiator for 4 hours and 50 minutes, and (b) styrene alone. Polymerization was carried out while adding 68 parts by weight of the monomer to the autoclave over 5 hours and 30 minutes. After that, the inside of the autoclave was kept at 92° C. for 30 minutes, then immediately raised to 120° C. and kept for 1 hour to prepare a base resin composition. After cooling the inside of the autoclave to 95° C., 8.0 parts by weight of butane (normal rich butane (normal butane/isobutane=70/30)) and 2.0 parts by weight of cyclohexane were charged as a foaming agent into the autoclave. The base resin composition was impregnated with the foaming agent by holding at 120° C. for 3 hours. Then, the inside of the autoclave was cooled to room temperature, and the pre-expandable polystyrene resin particles were taken out from the autoclave. The taken out pre-expandable polystyrene resin particles were washed, dehydrated and dried. Here, the average particle size and particle size distribution (UT) of the pre-expandable polystyrene resin particles were measured and used as the average particle size and particle size distribution (UT) of the expandable polystyrene resin particles. The results are shown in Table 1.

The obtained pre-expandable polystyrene-based resin particles, magnesium stearate and antistatic agent were put into a super mixer [SMV-20 manufactured by Kawada Co., Ltd.] and blended at 1000 rpm for 120 seconds. As a result, expandable polystyrene resin particles containing magnesium stearate and an antistatic agent on the surface were obtained. Here, with respect to 100 parts by weight of the pre-expandable polystyrene resin particles, (a) 1.0 part by weight of magnesium stearate [manufactured by NOF Corporation] as magnesium stearate, and (b) as an antistatic agent 0.15 part by weight of N-hydroxyethyl-N-(2-hydroxyalkyl)amine [carbon number of alkyl group C=14: manufactured by Tanaka Chemical Laboratory Co., Ltd., Antista 80FS] was used. The weight average molecular weight (Mw) of the obtained expandable polystyrene resin particles was measured. The results are shown in Table 1.

<Production of expanded polystyrene particles>
The expandable polystyrene-based resin particles obtained were placed in a rotary stirring foaming device. Then, the expandable polystyrene-based resin particles were expanded in water vapor at about 100° C. until the bulk density was expanded to 60 times to obtain polystyrene-based expanded particles. The amount of blocking was measured during the production of expanded polystyrene particles. With respect to the obtained polystyrene-based expanded particles, the bulk density was measured, and the expandability and the charge amount were evaluated. The results are shown in Table 2. The expanded polystyrene particles are used after being stored under constant temperature and humidity conditions for half a year.

<Production of polystyrene foam molding>
The obtained polystyrene-based foamed particles were subjected to in-mold foaming and molding at a steam pressure of 0.03 MPa to 0.08 MPa to obtain a 40- to 70-fold polystyrene-based foamed molded product. With respect to the obtained polystyrene-based foamed molded product, the surface beauty and the fusion property were evaluated. The results are shown in Table 2.

(Example 2)
As shown in Table 1, the same operation as in Example 1 was carried out except that magnesium stearate was changed to 1.4 parts by weight, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded molded articles were obtained. Was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 3)
As shown in Table 1, the same operation as in Example 1 was carried out except that the amount of magnesium stearate was changed to 0.7 part by weight, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded molded articles were obtained. Was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 4)
In a 6 L autoclave equipped with a stirrer, water 100 parts by weight, tricalcium phosphate 0.16 parts by weight, sodium alkyldiphenyl ether sulfonate 0.00957 parts by weight, dibenzoyl peroxide 0.245 parts by weight, 1,1-bis(t-butylperoxide) 0.175 parts by weight of (oxy)cyclohexane, 95 parts by weight of styrene, and 5 parts by weight of butyl acrylate were charged, and polymerization was carried out at 98° C. for 4 hours. Subsequently, 8.0 parts by weight of butane (normal rich butane (normal butane/isobutane=70/30)) and 2.0 parts by weight of cyclohexane were charged into the autoclave, and the temperature inside the autoclave was raised to 120° C. And polymerized for 2 hours. Then, the inside of the autoclave was cooled to room temperature, and the pre-expandable polystyrene resin particles were taken out from the autoclave. The taken out pre-expandable polystyrene resin particles were washed, dehydrated and dried.

The obtained pre-expandable polystyrene resin particles were sieved so that the average particle diameter was 0.49 mm. Then, the same operation as in Example 1 was performed using the pre-expandable polystyrene resin particles to obtain the expandable polystyrene resin particles, the polystyrene foam particles, and the polystyrene foam molded article, and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 5)
As shown in Table 1, the same operations as in Example 1 were carried out except that cyclohexane was changed to 0.5 part by weight, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded molded articles were obtained. Was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 6)
As shown in Table 1, the same operation as in Example 1 was repeated except that N-hydroxyethyl-N-(2-hydroxyalkyl)amine was changed to 0.5 part by weight, and expandable polystyrene resin particles, The expanded polystyrene particles and the expanded polystyrene molded article were obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 7)
The same operation as in Example 1 was performed except that N-hydroxyethyl-N-(2-hydroxyalkyl)amine was not used, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene foam molding. The body was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 8)
As shown in Table 1, the same operation as in Example 1 was carried out except that N-hydroxyethyl-N-(2-hydroxyalkyl)amine was changed to polyethylene glycol (PEG), and expandable polystyrene resin particles, The expanded polystyrene particles and the expanded polystyrene molded article were obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Example 9)
As shown in Table 1, the same procedure as in Example 1 was repeated except that N-hydroxyethyl-N-(2-hydroxyalkyl)amine was changed to stearic acid monoglyceride (Likemar S-100), and expandable polystyrene was used. -Based resin particles, polystyrene-based expanded particles, and polystyrene-based expanded molded articles were obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 1)
As shown in Table 1, the same operations as in Example 4 were carried out except that sieving was performed so that the average particle size was 1.25 mm, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded foam. A molded body was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Comparative example 2)
As shown in Table 1, the same operations as in Example 4 were carried out except that sieving was performed so that the average particle size was 0.20 mm, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded foam. A molded body was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 3)
As shown in Table 1, the same operations as in Example 1 were carried out except that magnesium stearate was changed to zinc stearate to obtain expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded molded articles. , And evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Comparative Example 4)
Except for changing 0.225 parts by weight of dibenzoyl peroxide to 0.140 parts by weight of a 30% solution of benzoyl peroxide, the same operation as in Example 1 was performed, and expandable polystyrene resin particles, polystyrene expanded particles, and A polystyrene foam molding was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

(Comparative example 5)
As shown in Table 1, the same operations as in Example 1 were carried out except that magnesium stearate was changed to 2.0 parts by weight, and expandable polystyrene resin particles, polystyrene expanded particles, and polystyrene expanded molded articles were obtained. Was obtained and evaluated in the same manner. The evaluation results are shown in Tables 1 and 2.

In Table 1, the content of the foaming agent is the content with respect to the total 100 parts by weight of the polystyrene-based resin seed particles and the styrene monomer used. Since the polystyrene resin seed particles and the styrene monomer can form the base resin, the content of the foaming agent can be said to be the content with respect to 100 parts by weight of the base resin. Further, in Table 1, the content of components other than the foaming agent is the content with respect to 100 parts by weight of the pre-expandable polystyrene resin particles.

According to one embodiment of the present invention, it is possible to provide expandable polystyrene-based resin particles that can suppress blocking and have good polystyrene-based expanded particle productivity. Therefore, one embodiment of the present invention can be preferably used in the field of building materials, for example, for producing foamed molded articles for building materials and lightweight concrete.

Claims (8)

An expandable polystyrene resin particle containing a base resin and a foaming agent,
(A) The average particle size is 0.25 mm or more and 0.5 mm or less,
(B) the weight average molecular weight (Mw) is 180,000 or more and less than 270,000,
(C) 0.5 to 1.9 parts by weight of magnesium stearate is further contained with respect to 100 parts by weight of the expandable polystyrene resin particles, and the expandable polystyrene resin particles are characterized. The foaming agent is (a) 1.5 parts by weight or more and 3.0 parts by weight or less of cyclohexane, and (b) 7.0 parts by weight or more and 9.0 parts by weight or less with respect to 100 parts by weight of the base resin. The expandable polystyrene-based resin particle according to claim 1, which comprises a butane of The expandable polystyrene resin particles according to claim 1 or 2, wherein the particle size distribution (UT) is 2.10 or less. It is characterized by further containing 0.05 parts by weight or more and 0.60 parts by weight or less of N-hydroxyethyl-N-(2-hydroxyalkyl)amine with respect to 100 parts by weight of the expandable polystyrene resin particles. The expandable polystyrene resin particle according to any one of claims 1 to 3. Expanded polystyrene-based resin particles according to any one of claims 1 to 4, and expanded polystyrene-based particles. The expanded polystyrene particles according to claim 5, having a bulk density of 0.0140 g/cm ³ or more and 0.0240 g/cm ³ or less. A polystyrene-based foam molded article, which is obtained by molding the polystyrene-based expanded particles according to claim 5 or 6 in a mold. A lightweight concrete composition comprising the expanded polystyrene particles according to claim 5 or 6.