JP5713944B2 - Method for producing foamable styrene resin particles having antistatic properties - Google Patents

Description

The present invention relates to the production how the expandable styrene resin particles child having antistatic properties.

Expanded molded articles of styrene-based resin particles are widely used as cushioning packaging materials for returnable boxes for machine parts such as automobile parts and electrical products because of their excellent impact resistance, wear resistance and oil resistance.
However, since styrene resins have high electrical insulation properties, they are easily charged by friction, and not only the appearance of the foamed molded product is impaired by dust adhesion, but also the contents are contaminated by dust collection and electrostatic breakdown. There has been a problem in using it as a packaging material for electronic parts such as.
Therefore, various methods for preventing charging have been reported. For example, a method of impregnating resin particles with a foaming agent and then impregnating a surfactant (Japanese Patent No. 4105195: Patent Document 1) is known. .

Japanese Patent No. 4105195

  With the above method, it is possible to prevent charging to some extent. However, further prevention of electrification has been desired from the viewpoint of further improving the beauty of the appearance of the foamed molded product and further preventing contamination and electrostatic breakdown due to dust collection of the contents.

  The inventors of the present invention have made researches to solve these problems, and as a result, upon dry impregnation of a foaming agent into styrene resin particles, a cationic surfactant and a water-insoluble nonionic surfactant It was found that expandable styrene resin particles having excellent antistatic properties can be obtained by the presence of a specific ratio.

Thus, according to the present invention, when the styrenic resin particles are dry-impregnated with the foaming agent in the presence of the surfactant, the foamable resin particles are obtained.
The surfactant is used in an amount of 1 to 4 parts by weight with respect to 100 parts by weight of the styrenic resin particles, and the cationic surfactant and water-insoluble in a weight ratio of 1: 0.03 to 0.8. And a nonionic surfactant. A method for producing expandable styrenic resin particles having antistatic properties is provided.

According to the production method of the present invention, expandable styrene resin particles having excellent antistatic properties can be provided.
Further, when the nonionic surfactant is used in an amount of 0.03 to 1.6 parts by weight with respect to 100 parts by weight of the styrene resin particles, it is possible to provide expandable styrene resin particles having more excellent antistatic properties. .
Further, when the styrene resin particles are composite resin particles of a styrene resin and an ethylene resin, and the ethylene resin is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the styrene resin, it is more charged. It is possible to provide expandable styrenic resin particles having excellent prevention properties and high strength.

  Further, the cationic surfactant is represented by the following formula 1

(In the above formula, R ¹ represents a linear or branched alkyl group having 5 to 20 carbon atoms)
When selected from the agents represented by the formula, expandable styrene-based resin particles having more excellent antistatic properties can be provided.
Further, when the nonionic surfactant is selected from dialkanolamine, polyoxyethylene polyoxypropylene glycol (ie, polyoxyethylene polyoxypropylene block polymer), fatty acid monoglyceride and pentaerythritol fatty acid ester, it is more antistatic. It is possible to provide an expandable styrene-based resin particle that is excellent in quality.
The expandable styrenic resin particles, pre-expanded particles and foamed molded product of the present invention are excellent in antistatic properties.

It is a graph which shows the relationship between the attenuation rate of Examples 8-11 and Comparative Examples 5-6, and the weight ratio represented by nonionic surfactant / cationic surfactant.

  The inventors of the present invention examined the behavior of a surfactant as an antistatic agent from the production of expandable styrene resin particles (hereinafter also referred to as expandable resin particles) to the manufacture of a foamed molded product. As a result, during the foaming process of the pre-foamed particles and foamed molded product, the surfactant is washed away by being exposed to water vapor, and the pre-foamed particles and foam-molded in which the surfactant is not present or non-uniformly present. I found the phenomenon that the body was manufactured. It has also been found that this phenomenon becomes more prominent as the bulk expansion ratio of the pre-expanded particles and the expansion ratio of the expanded molded body are higher. This is presumed to be because the degree of exposure to water vapor of the surfactant is higher when the bulk expansion ratio and expansion ratio are high.

  Therefore, in view of the above phenomenon, the inventors of the present invention present the cationic surfactant and the water-insoluble nonionic surfactant in a specific ratio when the styrene resin particles are dry-impregnated with the foaming agent. Thus, the present inventors have surprisingly found that an excellent antistatic effect can be imparted to the expandable resin particles because the surfactant can be prevented from flowing out even when exposed to water vapor in the subsequent foaming step.

Hereinafter, the present invention will be described in more detail.
(Method for producing expandable styrene resin particles)
Expandable styrene resin particles can be produced by dry impregnation of a foaming agent into styrene resin particles in the presence of a surfactant. Unlike the wet impregnation, the dry impregnation does not use an aqueous medium for impregnation of the foaming agent, so that the cationic surfactant can be prevented from flowing into the aqueous medium, and as a result, the cationic surfactant of the expandable resin particles can be prevented. There is an advantage that the remaining amount of the agent can be increased.

(1) Surfactant The surfactant contains a cationic surfactant and a water-insoluble nonionic surfactant. The surfactant preferably contains only a cationic surfactant and a water-insoluble nonionic surfactant.
(A) It does not specifically limit as a cationic surfactant, Any well-known cationic surfactant can be used. Examples thereof include aliphatic alkyl quaternary ammonium salts and trialkylbenzyl ammonium salts. The alkyl group of these exemplified surfactants varies depending on the type of the surfactant, but an alkyl group having 5 to 20 carbon atoms (for example, n-pentyl, i-pentyl, n-hexyl, i-hexyl). , N-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, n-undecyl, i-undecyl, n-dodecyl, i-dodecyl, n -Tridecyl, i-tridecyl, n-tetradecyl, i-tetradecyl, n-pentadecyl, i-pentadecyl, n-hexadecyl, i-hexadecyl, n-heptadecyl, i-heptadecyl, n-octadecyl, i-octadecyl, n-nonadecyl , I-nonadecyl, n-icosyl, i-icosyl).

Of the above cationic surfactants, aliphatic alkyl quaternary ammonium salts are preferred. The aliphatic alkyl quaternary ammonium salt has the following formula [(R ¹ ) ₄ N] ⁺ C ₂ H ₅ OSO ₃ ^−.
Can be expressed as In the formula, R ¹ may be the same or different and may be branched alkyl groups having 1 to 20 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, n -Pentyl, i-pentyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, n-undecyl I-undecyl, n-dodecyl, i-dodecyl, n-tridecyl, i-tridecyl, n-tetradecyl, i-tetradecyl, n-pentadecyl, i-pentadecyl, n-hexadecyl, i-hexadecyl, n-heptadecyl, i -Heptadecyl, n-octadecyl, i-octadecyl, n-nonadecyl, i-nonadecyl, n-icosyl, i-icosyl). Further, out of the four R ^{1 s} , three are preferably alkyl groups having 1 to 3 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl). Particularly preferred aliphatic alkyl quaternary ammonium salts are cationic surfactants selected from agents represented by the following formula 1.

In the above formula, R ¹ is a linear or branched alkyl group having 5 to 20 carbon atoms (for example, n-pentyl, i-pentyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, n-undecyl, i-undecyl, n-dodecyl, i-dodecyl, n-tridecyl, i-tridecyl, n- Tetradecyl, i-tetradecyl, n-pentadecyl, i-pentadecyl, n-hexadecyl, i-hexadecyl, n-heptadecyl, i-heptadecyl, n-octadecyl, i-octadecyl, n-nonadecyl, i-nonadecyl, n-icosyl, i-icosyl) is preferred. R ¹ is more preferably a linear alkyl group having 6 to 14 carbon atoms. For example, Catiogen ES-O manufactured by Daiichi Kogyo Seiyaku is included when R ¹ is a linear alkyl group.
The cationic surfactant is usually marketed in the form of an aqueous solution. The foaming agent is dry impregnated into the styrenic resin particles. However, since the surfactant is small as described below, the impregnation of the foaming agent in the presence of water that constitutes an aqueous solution is also applicable to the present invention. Then, it is called dry type.

(B) The nonionic surfactant is not particularly limited as long as it is water-insoluble, and any known nonionic surfactant can be used. Here, water-insoluble means 10 or less when expressed in HLB. Here, HLB is a value calculated by the Griffin equation.
The inventors consider that the nonionic surfactant plays a role of preventing the surfactant from flowing out due to water vapor during the foaming process, in addition to the effect of preventing charging.

  Nonionic surfactants include polyoxyethylene alkylamine, polyethylene glycol fatty acid ester, fatty acid glyceride (for example, fatty acid monoglyceride), pentaerythritol fatty acid ester, alkyldiethanolamide, dialkanolamine (for example, alkyldiethanolamine), polyalkylene glycol Derivatives (for example, polyoxyethylene polyoxypropylene glycol (that is, polyoxyethylene polyoxypropylene block polymer)) and the like. These agents may be used alone or in combination. The alkyl group and alkylene group of these exemplified surfactants vary depending on the type of the surfactant, but an alkyl group having 5 to 20 carbon atoms (for example, n-pentyl, i-pentyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl, n-nonyl, i-nonyl, n-decyl, i-decyl, n-undecyl, i-undecyl, n-dodecyl, i- Dodecyl, n-tridecyl, i-tridecyl, n-tetradecyl, i-tetradecyl, n-pentadecyl, i-pentadecyl, n-hexadecyl, i-hexadecyl, n-heptadecyl, i-heptadecyl, n-octadecyl, i-octadecyl, n-nonadecyl, i-nonadecyl, n-icosyl, i-icosyl) and alkylene groups (eg, pentenyl, Seniru, heptenyl, octenyl, nonenyl, Deshireniru, undecylenyl, Dodeshireniru, Torideshireniru, Tetoradeshireniru, Pentadeshireniru, Le to Re Hekisadeshi, Heputadeshireniru, Okutadeshireniru, Nonadeshireniru, include a Ikoshireniru) preferred.

More preferable nonionic surfactants include dialkanolamine, polyoxyethylene polyoxypropylene glycol, fatty acid monoglyceride, pentaerythritol fatty acid ester and the like.
As the alkyldiethanolamine, one selected from agents represented by the following formula 2 can be used.

In the above formula 2, R ² is a linear or branched alkyl group having 10 to 18 carbon atoms (for example, n-decyl, i-decyl, n-undecyl, i-undecyl, n-dodecyl, i-dodecyl). , N-tridecyl, i-tridecyl, n-tetradecyl, i-tetradecyl, n-pentadecyl, i-pentadecyl, n-hexadecyl, i-hexadecyl, n-heptadecyl, i-heptadecyl, n-octadecyl, i-octadecyl) Preferably there is. R ² is more preferably a linear alkyl group having 12 to 18 carbon atoms. For example, Antista 80FS manufactured by Tanaka Chemical Laboratory is included in the above formula 2.
In polyoxyethylene polyoxypropylene glycol, the ethylene oxide content is preferably 40% or less, and the propylene oxide repeat number n is preferably 4-8. The repetition number n can be 5, 6 and 7.
Examples of the fatty acid monoglyceride include stearic acid monoglyceride.
Further, the fatty acid monoglyceride may be used in combination with a pentaerythritol fatty acid ester.

  The nonionic surfactant is preferably selected from dialkanolamine, polyoxyethylene polyoxypropylene glycol, fatty acid monoglyceride, and pentaerythritol fatty acid ester when the cationic surfactant is selected from Formula 1 above. A preferable reason is that many of the nonionic surfactants have ethylene oxide or an alkyl hydroxyl group as a hydrophilic portion. For this reason, it has a very weak anion polarity, and it is considered that the interaction between the hydrophilic portion of the cationic surfactant and the ions works. Therefore, it is considered that the non-water-soluble property of the nonionic surfactant is effective and makes it difficult for the cationic surfactant due to water vapor or the like to flow out.

(C) Use Ratio of Surfactant The surfactant containing the cationic surfactant and the nonionic surfactant is used in an amount of 1 to 4 parts by weight with respect to 100 parts by weight of the styrene resin particles. When the amount used is less than 1 part by weight, the antistatic property of the expandable resin particles may not be sufficient. On the other hand, when the amount is more than 4 parts by weight, the foamable resin particles are extremely sticky and difficult to handle, and the antistatic property does not change even when added more, so the cost may increase. . The amount used is, for example, 1.3 parts by weight, 1.6 parts by weight, 1.9 parts by weight, 2.2 parts by weight, 2.5 parts by weight, 2.8 parts by weight, 3.1 parts by weight, 3 parts by weight, 3.6 parts by weight and 3.9 parts by weight. A more preferable use amount is 1 to 3.5 parts by weight.

Moreover, the use ratio of a cationic surfactant and a nonionic surfactant is the range of 1: 0.03-0.8 (weight ratio). When the use ratio of the nonionic surfactant is less than 0.03, the effect of adding the nonionic surfactant is insufficient, and good antistatic properties may not be obtained. On the other hand, when it is more than 0.8, the effect of adding the cationic surfactant is weakened, and good antistatic properties may not be obtained. The use ratio is, for example, 1: 0.05, 1: 0.1, 1: 0.15, 1: 0.2, 1: 0.25, 1: 0.3, 1: 0.35, 1 : 0.4, 1: 0.45, 1: 0.5, 1: 0.55, 1: 0.6, 1: 0.65, 1: 0.7 and 1: 0.75. A more preferable use ratio is 1: 0.03 to 0.75.
It is preferable that the usage-amount of a nonionic surfactant is 0.03-1.6 weight part with respect to 100 weight part of styrene resin particles. When the amount is less than 0.03 parts by weight, the effect of adding the nonionic surfactant may be insufficient, and good antistatic properties may not be obtained. On the other hand, when the amount is more than 1.6 parts by weight, the effect of addition may be reduced by reducing the amount of the cationic surfactant used, and good antistatic properties may not be obtained. The amount used is, for example, 0.23 parts by weight, 0.43 parts by weight, 0.63 parts by weight, 0.83 parts by weight, 1.03 parts by weight, 1.23 parts by weight and 1.43 parts by weight. . A more preferable usage amount is 0.03 to 1.0 part by weight.
Note that the amounts of the cationic surfactant and the nonionic surfactant remaining in the expandable resin particles are substantially the same as the amounts of both the surfactants used.

(2) Styrenic resin particles The styrene resin constituting the styrene resin particles is, for example, a resin derived from a styrene monomer such as styrene or substituted styrene (substituent is lower alkyl, halogen atom (especially chlorine atom)). Is mentioned. Examples of the substituted styrene include α-methylstyrene, p-methylstyrene, t-butylstyrene, vinyltoluene and the like. Furthermore, the styrene resin may be a copolymer of a styrene monomer and another monomer copolymerizable with the styrene monomer. Other monomers include, for example, acrylonitrile, alkyl (meth) acrylate (about 1 to 8 carbon atoms of the alkyl moiety, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, n-pentyl, i-pentyl, n-hexyl, i-hexyl, n-heptyl, i-heptyl, n-octyl, i-octyl), divinylbenzene, mono- or di (meth) acrylate of ethylene glycol, anhydrous Maleic acid, N-phenylmaleimide and the like can be mentioned.

When using another monomer, it is preferable to use it in 30 weight part or less with respect to 100 weight part of styrene-type monomers.
The polystyrene resin is more preferably a resin derived from styrene only.
Further, when the styrene resin particles are composite resin particles of a styrene resin and an ethylene resin, the effects of the present invention are more remarkably obtained. The reason for this is that since the foaming power of ethylene-based resins is inferior to that of styrene-based resins, the amount of water vapor necessary for foaming is increased, and the water vapor application time is increased. As a result, the possibility that the surfactant flows out increases. In the present invention, since a specific amount of a specific surfactant is used, the possibility of outflow can be suppressed.

Examples of the ethylene resin include low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and other ethylene resins. It is done. In the above example, low density is preferably 0.91~0.94g / cm ^3, more preferably 0.91~0.93g / cm ^3. High density is preferably 0.95~0.97g / cm ^3, more preferably 0.95~0.96g / cm ^3. The medium density is an intermediate density between these low density and high density.

  It is preferable that 20-100 weight part of ethylene-type resin is contained with respect to 100 weight part of styrene resin. If the amount is less than 20 parts by weight, the elasticity of the ethylene-based resin is high, and it may be difficult to develop the characteristics that the oil resistance and the impact resistance are good. Furthermore, styrene is not sufficiently absorbed inside the ethylene-based resin, and a large amount of polymer powder may be generated due to polymerization of styrene alone. Moreover, when it exceeds 100 weight part, the characteristic that the rigidity of a styrene-type resin is favorable may become difficult to express. Moreover, since the retainability of the foaming agent is deteriorated, it may be difficult to reduce the density, and the foam moldability may be poor. Content of ethylene resin is 30 weight part, 40 weight part, 50 weight part, 60 weight part, 70 weight part, 80 weight part, and 90 weight part, for example.

  Here, the composite resin is sufficient if a styrene resin and an ethylene resin are present in the resin, and the presence form is not limited. For example, a method of kneading both resins in an extruder and cutting the kneaded product, a method of impregnating seed particles made of an ethylene-based resin with a styrene monomer in an aqueous medium, and then polymerizing the monomer, etc. It is done. Of these, composite resin particles obtained by the latter method are preferred. These particles are referred to as modified resin particles from the viewpoint that they are particles obtained by modifying a styrene resin with an ethylene resin. The modification means that the ethylene resin particles are simply impregnated with a styrene monomer for polymerization, the ethylene resin particles are impregnated with a styrene monomer for graft polymerization, and both. To do.

Below, the manufacturing method of a modified resin particle is demonstrated. The modified resin particles are, for example, 120 to 500 parts by weight of a styrenic monomer (for example, 200 parts by weight, 300 parts by weight, etc.) in a dispersion obtained by dispersing 100 parts by weight of the following (i) seed particles in an aqueous solvent. A monomer impregnation step of impregnating seed particles into 400 parts by weight),
(Ii) It can be manufactured by passing through a step including a polymerization step of polymerizing a styrene monomer simultaneously with or after impregnation.
The impregnation amount of the styrene monomer is, for example, 200 parts by weight, 250 parts by weight, 300 parts by weight, 350 parts by weight, 400 parts by weight, and 450 parts by weight.

(A) Monomer impregnation step (a-1) The seed particles can be obtained by a known method. For example, firstly, after extruding an ethylene-based resin using an extruder, the seed particles can be produced by granulation by underwater cutting, strand cutting, hot cutting, or the like. Usually, the shape of the seed particles to be used can be, for example, a true sphere, an oval sphere (egg), a cylinder, a prism, a pellet, or a granular.

  There is no particular limitation on the average particle size of individual seed particles. However, considering that the average particle diameter of the modified resin particles is defined by this average particle diameter, the average particle diameter can be 0.2 to 1.5 mm. When the average particle diameter is less than 0.2 mm, the retention of the foaming agent of the expandable resin particles becomes low, and it may be difficult to reduce the density. If it exceeds 1.5 mm, the filling property of the foamed resin particles into the mold may be lowered, and it may be difficult to reduce the thickness of the foamed molded product. The average particle diameter is, for example, 0.5 mm, 0.8 mm, and 1.1 mm.

(A-2) As an aqueous medium, the mixed medium of water and water and a water-soluble solvent (for example, alcohol) is mentioned. The aqueous medium may contain a dispersant in order to stabilize the dispersibility of the styrene monomer droplets and seed particles.
Examples of the dispersant include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic compounds such as tricalcium phosphate, magnesium pyrophosphate, and calcium carbonate. Here, when a hardly soluble inorganic compound is used, it is preferable to use a surfactant. It is preferable that the usage-amount of a dispersing agent is 0.1 to 4 weight% in the aqueous medium containing a dispersing agent. The amount used is, for example, 1% by weight, 2% by weight and 3% by weight.

      (A-3) The impregnation of the styrene monomer into the seed particles is usually performed at a temperature at which the polymerization of the styrene monomer does not substantially occur. Moreover, you may superpose | polymerize a styrene-type monomer, making a seed particle impregnate a styrene-type monomer. The impregnation temperature is usually in the range of 50 to 100 ° C. The impregnation temperature is, for example, 60 ° C., 70 ° C., 80 ° C., and 90 ° C.

(B) Polymerization process The polymerization process is performed simultaneously with or after the impregnation.
(B-1) The polymerization of the styrene monomer can be carried out in the presence of a polymerization initiator.
As the polymerization initiator, any polymerization initiator used in ordinary styrene polymerization can be used. Examples thereof include initiators that generate tertiary alkoxy radicals, initiators such as benzoyl peroxide and lauryl peroxide, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile. These polymerization initiators may be used alone or in combination of two or more. In order to adjust the molecular weight and reduce the residual monomer, it is preferable to use a plurality of polymerization initiators having a decomposition temperature in the range of 80 to 120 ° C. in order to obtain a half-life of 10 hours. The decomposition temperatures are, for example, 90 ° C, 100 ° C, and 110 ° C.

(B-2) The styrenic monomer contains a plasticizer, a chain transfer agent, a nucleating agent, a flame retardant, a flame retardant aid, an oil-soluble polymerization inhibitor, a water-soluble polymerization inhibitor, a bubble regulator, and the like. Also good.
Examples of the plasticizer include toluene, xylene, cyclohexane, ethyl acetate, dioctyl phthalate, and the like.
Examples of chain transfer agents include mercaptans and α-methylstyrene.
Examples of the nucleating agent include zinc stearate, aluminum stearate, ethylene bis stearic acid amide and the like.
Examples of the colorant include carbon black, iron oxide, and graphite.
Examples of the flame retardant include known brominated flame retardants, chlorinated flame retardants, chlorinated bromine-containing flame retardants, phosphorus-based flame retardants, and inorganic flame retardants.

(B-3) The polymerization temperature is preferably in the range of 70 to 140 ° C, more preferably in the range of 90 to 130 ° C. Polymerization temperature is 80 degreeC, 90 degreeC, 100 degreeC, 110 degreeC, and 120 degreeC, for example. The polymerization temperature may be raised for some time in a constant or stepwise manner. The heating rate is preferably 0.1 to 2 ° C./min. The heating rate is, for example, 0.5 ° C./min, 1 ° C./min, and 1.5 ° C./min.
(B-4) You may bridge | crosslink an ethylene-type resin as needed. Examples of the crosslinking agent include organic peroxides such as 2,2-bis (t-butylperoxy) butane, dicumyl peroxide, and 2,5-dimethyl-2,5-di-t-butylperoxyhexane. Is mentioned. These crosslinking agents can be used alone or in admixture of two or more. It is preferable that the usage-amount of a crosslinking agent is 0.05-1 weight part with respect to 100 weight part of polyolefin resin. The amount of the crosslinking agent used is, for example, 0.1 parts by weight, 0.2 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 0.6 parts by weight, or 0.7 parts by weight. 0.8 parts by weight and 0.9 parts by weight.

  Examples of the timing of crosslinking include before and after polymerization of the styrene monomer. The cross-linking agent may be added alone to the polymerization system. The crosslinking agent is preferably added in the form of a solution dissolved in a solvent, a plasticizer or a styrene monomer, or a dispersion dispersed in water, from the viewpoint of work safety.

(3) Foaming agent As the blowing agent, for example, hydrocarbons such as propane, butane, isobutane, pentane, isopentane, cyclopentane, hexane and the like can be used alone or in admixture of two or more. Although the usage-amount of a foaming agent is determined by the foaming multiple of the target molded object, it is preferable that it is 10-20 weight part with respect to 100 weight part of styrene resin particles. The amount of the foaming agent used is, for example, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight or 19 parts by weight.

(4) Dry impregnation Dry impregnation of the foaming agent is not particularly limited and can be performed under known conditions. For example, the impregnation temperature can be 40 to 140 ° C. The impregnation temperature is, for example, 60 ° C., 80 ° C., 100 ° C., and 120 ° C. A treatment with two kinds of surfactants is also performed during the dry impregnation.
The impregnation with the foaming agent may be performed in the presence of a foaming aid. Examples of the foaming aid include solvents such as toluene, xylene, ethylbenzene, and cyclohexane, and plasticizers (high boiling point solvents) such as diisobutyl adipate, diacetylated monolaurate, and coconut oil. The amount of the foaming auxiliary added is preferably 0.2 to 2.5 parts by weight with respect to 100 parts by weight of the styrene resin particles. The amount of foaming aid added is, for example, 0.7 parts by weight, 1.2 parts by weight, 1.7 parts by weight and 2.2 parts by weight.
If necessary, a surface treatment agent (for example, a binding inhibitor, a fusion accelerator, a spreading agent, etc.) may be added to the system during impregnation with the foaming agent.
The addition amount (total value) of these surface treatment agents is preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the styrene resin particles. The addition amount of a surface treating agent is 0.5 weight part, 1 weight part, 1.5 weight part, and 1.8 weight part, for example.

(Pre-expanded particles)
The foamable resin particles obtained as described above are prefoamed to a predetermined density by a known method (for example, heated with water vapor with a gauge pressure of 0.01 to 0.10 MPa), for example, 10 to 50 times. And pre-expanded particles having a bulk expansion ratio of In particular, in the present invention, sufficient antistatic properties can be imparted even with pre-expanded particles having a magnification of 30 times or more. The gauge pressure is, for example, 0.03 MPa, 0.05 MPa, 0.07 MPa, and 0.09 MPa.

(Foamed molded product)
The foamed molded article is composed of a fusion product of pre-expanded particles containing a styrene resin. Further, the foamed molded article made of the fused body contains a cationic surfactant and a water-insoluble nonionic surfactant. The foamed molded article preferably exhibits a charge amount attenuation factor of 90% or more. The attenuation rate of the charge amount can be used as an index as to whether or not the foamed molded product has sufficient antistatic properties.
The foamed molded article of the present invention can be used for various applications, and in particular, can be suitably used for a return box for machine parts such as automobile parts, a buffer packaging material for electrical products, and the like.
The foamed molded article of the present invention can be obtained, for example, as a foaming factor of 10 to 50 times by filling the prefoamed particles in a mold and heating again to heat-seal the prefoamed particles. As the heating medium, water vapor with a gauge pressure of 0.05 to 0.15 MPa is preferably used. In particular, in the present invention, a sufficient antistatic property can be imparted even with a foamed molded article of 30 times or more. The gauge pressure is, for example, 0.08 MPa, 0.1 MPa, and 0.12 MPa.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples. Various measurement methods in the examples are described below.
<Bulk foam multiple>
The bulk expansion ratio of the pre-expanded particles is measured according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, first, Wg is collected using pre-expanded particles as a measurement sample, and this measurement sample is naturally dropped into a measuring cylinder. The volume Vcm ³ of the measurement sample dropped into the graduated cylinder is measured using an apparent density measuring instrument based on JIS K6911. By substituting Wg and Vcm ³ into the following formula, the bulk density of the pre-expanded particles is calculated.
Bulk density of pre-expanded particles (g / cm ³ ) = weight of measurement sample (W) / volume of measurement sample (V)
The bulk foaming factor is the reciprocal of the bulk density.

<Folding multiple of foamed molded product>
The weight (a) and volume (b) of a test piece (example 75 × 300 × 35 mm) cut out from a foamed molded product (after being molded and dried at 40 ° C. for 20 hours or more) each have three or more significant figures. Then, the density (g / cm ³ ) of the foamed molded product is obtained by the formula (a) / (b).
The expansion factor is the reciprocal of the density.

<Surface resistivity>
The surface resistivity is measured by the method described in JIS K 6911: 1995 “General Test Method for Thermosetting Plastics”. That is, using a test device (advantest digital long high resistance / microammeter R8340 and resiliency chamber R12702A), an electrode is pressure-bonded to a sample sample with a load of about 30 N, and the resistance value after charging for 500 V for 1 minute is obtained. taking measurement. The surface specific resistance value is calculated from the measured value by the following formula.
ρs = π (D + d) / (D−d) × Rs
ρs: surface resistivity (MΩ)
D: Inner diameter of surface annular electrode (cm)
d: outer diameter of inner circle of surface electrode (cm)
Rs: Surface resistance (MΩ)
The sample sample has a size of 100 mm × 100 mm × thickness 10 mm or less, and 10 pieces are cut out from the same foamed molded article. Ten cut sample samples are stored in an environment of 20 ° C. and 65% humidity for about 24 hours, and then the resistance values of the ten sample samples are measured.

<Attenuation rate>
The attenuation rate is obtained in accordance with the JIS L1094 fabric and knitted fabric charging test method. Specifically, a test piece cut to 40 × 40 × 3 (mm) (with skin) is left in an environment of 20 ± 2 ° C. RH 60% for 24 hours or more. Thereafter, while the test piece is set on the turntable and rotated, the amount of charge (initial charge amount) when applying 10 kV for 30 seconds is measured. Next, the application is stopped while the turntable is rotated, and the charge amount 30 seconds after the stop (charge amount after 30 seconds) is measured. The attenuation rate after 30 seconds is calculated by substituting the initial charge amount and the charge amount after 30 seconds into the formula for calculating the attenuation rate below.
The measurement conditions are as follows.
Measuring device: Static Honest Meter
Test piece: 40 × 40 × 3 (mm)
Applied voltage: 10 kV
Number of tests: 5
Test piece condition adjustment / test environment: 20 ± 2 ° C. RH 60% (in the above JIS, RH 40 ± 2%)
Decay rate (%) = (initial charge amount−charge amount after 30 seconds) × 100 / initial charge amount

<Comprehensive evaluation>
○ when the attenuation rate is 90% or more and the surface resistivity is 10 ¹⁰ Ω · cm or less, and Δ when the attenuation rate is less than 90%, 80% or more and the surface resistivity is more than 10 ¹⁰ Ω · cm, and the attenuation rate. X is less than 80% and the surface resistivity is more than 10 ¹⁰ Ω · cm.

Example 1
[Production of modified resin particles]
Linear low-density polyethylene resin particles (NF-444A manufactured by Nippon Polyethylene Co., Ltd.) were heated with an extruder and granulated into pellets by an underwater cutting method (resin particles were adjusted to 40 mg per 100 particles). 8 kg of the obtained polyethylene-based resin particles made of linear low-density polyethylene were placed in a 100 L autoclave with a stirrer. Furthermore, 40 kg of pure water as an aqueous medium, 360 g of magnesium pyrophosphate, and 0.85 g of sodium dodecylbenzenesulfonate were added. The obtained mixture was stirred to obtain a suspension of an aqueous medium, kept at room temperature for 10 minutes, and then heated to 60 ° C.

Next, 4 kg of styrene in which 10 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained at 60 ° C. for 30 minutes, and styrene was absorbed by the polyethylene resin particles. After absorption, the temperature was raised to 135 ° C., and stirring was continued at this temperature for 2 hours.
Thereafter, the temperature was lowered to 115 ° C., and 15 g of sodium dodecylbenzenesulfonate was added to the suspension. Thereafter, 28 kg of styrene in which 112 g of t-butyl peroxybenzoate and 400 g of ethylenebisstearic acid amide were dissolved as a polymerization initiator was added dropwise over 6 hours.

After completion of the dropping, the temperature was maintained at 115 ° C. for 1 hour, and then the temperature was raised to 140 ° C. and maintained at that temperature for 3 hours to complete the polymerization. Then, it cooled to normal temperature and took out particle | grains.
The composite resin particle which used 400 weight part of styrene-type monomers with respect to 100 weight part of linear low density polyethylene-type resin particles by the above process was obtained.

[Impregnation of foaming agent]
Cathogen ES-O (pure 50%) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. with 100 parts by weight of the obtained composite resin particles as a cationic surfactant in a V-type blender having an internal volume of 50 liters that can be sealed with pressure resistance Tanaka Chemical Research using 1.5 parts by weight of an aliphatic alkyl quaternary ammonium salt in which R ^{1 in} Formula 1 is a linear alkyl group having 6 to 14 carbon atoms as a water-insoluble nonionic surfactant Tokorosha made Anchisuta 80FS (HLB9.2) (dialkanolamines: is a linear alkyl group of R ² is from 12 to 18 carbon atoms of formula 2, n is 4-8 alkyl diethanolamine) 0.2 weight Part, 0.5 parts by weight of diisobutyl adipate were charged, sealed and stirred. While stirring, 16 parts by weight of butane was injected. After the butane was press-fitted, the inside of the vessel was kept at 60 ° C. for about 2 hours to take out the expandable resin particles.

[Pre-foaming]
The taken-out expandable resin particles were immediately put into a batch type pre-foaming machine and pre-expanded to a bulk expansion ratio of 35 times to obtain pre-expanded particles.
[Foam molding]
The resulting pre-expanded particles were foamed in the mold. A foamed molded article is obtained by introducing pre-expanded particles into a 300 mm (width) × 400 mm (length) × 30 mm (thickness) mold, introducing 0.08 MPa water vapor for 30 seconds, and heating the pre-expanded particles. Got. After the heating, cooling was performed until the foaming pressure of the foamed molded product decreased to 0.005 MPa or less, and a foamed molded product having a desired expansion ratio was taken out. The removed foamed molded article was left in an atmosphere of 35 ° C. for 6 hours or more.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 2
Example except that Epan 710 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (polyoxyethylene polyoxypropylene glycol, oxyethylene content is about 10%, oxypropylene repeat number is about 7) is used instead of Antista 80FS. In the same manner as in Example 1, a foamed molded product was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 3
A foamed molded article was obtained in the same manner as in Example 1 except that PRE-7070 (stearic acid monoglyceride) manufactured by Onion Enterprise Co., Ltd. was used instead of Antistar 80FS.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 4
A foamed molded article was obtained in the same manner as in Example 1 except that instead of Antista 80FS, Resist PE132 (mixture of fatty acid monoglyceride and pentaerythritol fatty acid ester) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was used.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 5
A foamed molded product was obtained in the same manner as in Example 1 except that the amount of Antistar 80FS used was 0.3 parts by weight and the expansion ratio of the foamed molded product was 40 times.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 6
A foamed molded product was obtained in the same manner as in Example 1, except that the amount of Antista 80FS used was 0.4 parts by weight and the foaming ratio of the foamed molded product was 45 times.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 7
A foamed molded product was obtained in the same manner as in Example 1 except that the amount of Antista 80FS used was 0.5 parts by weight and the foaming ratio of the foamed molded product was 50 times.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 8
A foamed molded product was obtained in the same manner as in Example 2 except that the amount of Kathiogen ES-O added was 1.8 parts by weight and the expansion ratio of the foamed molded product was 40 times.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 9
Foaming was carried out in the same manner as in Example 2 except that the amount of addition of cationogen ES-O was 1.6 parts by weight, the amount of Epane 710 was 0.4 parts by weight, and the expansion ratio of the foamed molded product was 40 times. A molded body was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 10
Foaming is performed in the same manner as in Example 2 except that the amount of addition of cationogen ES-O is 1.4 parts by weight, the amount of Epane 710 is 0.6 parts by weight, and the expansion ratio of the foamed molded product is 40 times. A molded body was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 11
Foaming was carried out in the same manner as in Example 2 except that the amount of addition of cationogen ES-O was 1.2 parts by weight, the amount of Epan 710 was 0.8 parts by weight, and the expansion ratio of the foamed molded product was 40 times. A molded body was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 12
The same procedure as in Example 3 was conducted except that the addition amount of cationogen ES-O was 2.2 parts by weight, the use amount of PRE-7070 was 0.1 part by weight, and the expansion ratio of the foamed molded product was 40 times. A foamed molded product was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Example 13
Example 3 except that particles obtained by the following production method were used as the modified resin particles, the addition amount of cationogen ES-O was 3.0 parts by weight, and the expansion ratio of the foamed molded product was 40 times. Similarly, a foamed molded product was obtained.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.
[Production of modified resin particles]
Ethylene-vinyl acetate copolymer (EVA) (Nihon Unicar LV-115) as a polyethylene resin was heated in an extruder and granulated into pellets by an underwater cutting method (resin particles were adjusted to 80 mg per 100 grains). . 12.25 kg of the polyethylene resin particles made of the obtained ethylene-vinyl acetate copolymer were put into a 100 L autoclave with a stirrer. Furthermore, 40 kg of pure water as an aqueous medium, 360 g of magnesium pyrophosphate, and 0.85 g of sodium dodecylbenzenesulfonate were added. The obtained mixture was stirred to obtain a suspension of an aqueous medium, kept at room temperature for 10 minutes, and then heated to 60 ° C.

Next, 5 kg of styrene in which 7 g of dicumyl peroxide was dissolved in this suspension was dropped over 30 minutes. After dropping, the temperature was maintained at 60 ° C. for 30 minutes, and styrene was absorbed by the polyethylene resin particles. After absorption, the temperature was raised to 130 ° C., and stirring was continued at this temperature for 2 hours.
Thereafter, the temperature was lowered to 90 ° C., and 15 g of sodium dodecylbenzenesulfonate was added to the suspension. Thereafter, 85 g of dicumyl peroxide, 40 g of benzoyl peroxide and 4 g of t-butyl peroxide as polymerization initiators were gradually added in 23 kg of styrene, and polymerization was carried out at 90 ° C. for 4 hours.
After completion of the dropping, the temperature was maintained at 90 ° C. for 1 hour, then heated to 140 ° C. and maintained at that temperature for 3 hours to complete the polymerization. Then, it cooled to normal temperature and took out particle | grains.
The composite resin particle which used 400 weight part of styrene-type monomers with respect to 100 weight part of linear low density polyethylene-type resin particles by the above process was obtained.

Example 14
A foam molded article was obtained in the same manner as in Example 13 except that the amount of PRE-7070 used was 0.1 parts by weight.
Table 1 shows the measurement results and overall evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 1
A foamed molded product was obtained in the same manner as in Example 1 except that Antistar 80FS was not used.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 2
A foamed molded article was obtained in the same manner as in Example 1 except that the amount of use of cationogen ES-O was 2.1 parts by weight and that Antista 80FS was not used.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 3
A foamed molded product was obtained in the same manner as in Example 1 except that Antista 80FS was not used and the foaming factor of the foamed molded product was 40 times.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 4
A foamed molded product was obtained in the same manner as in Example 1 except that Antista 80FS was not used and the foaming factor of the foamed molded product was 50 times.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 5
Foaming is carried out in the same manner as in Example 2 except that the addition amount of cationogen ES-O is 1.0 part by weight, the amount of Epan 710 is 1.0 part by weight, and the expansion ratio of the foamed molded product is 40 times. A molded body was obtained.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 6
Foaming was carried out in the same manner as in Example 2 except that the amount of Kathiogen ES-O added was 1.95 parts by weight, the amount of Epan 710 used was 0.05 parts by weight, and the foaming ratio of the foamed molded product was 40 times. A molded body was obtained.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 7
A foamed molded product was obtained in the same manner as in Example 2 except that 2.0 parts by weight of Epan 710 was added without adding the cationogen ES-O, and the expansion ratio of the foamed molded product was 40 times.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

Comparative Example 8
In the foaming agent impregnation step, 100 parts by weight of the modified resin particles obtained in Example 1 and 0.5 part by weight of diisobutyl adipate were placed in a V-type blender having an internal volume of 50 liters that can be sealed with pressure resistance, and sealed. Allowed to stir. While stirring, 16 parts by weight of butane was injected. After injecting butane, the inside of the vessel was kept at 60 ° C. for about 2 hours and cooled to 25 ° C. Thereafter, 1.5 parts by weight of Catiogen ES-O (pure 50%) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. as a cationic surfactant, and Antista manufactured by Tanaka Chemical Laboratory Co., Ltd. as a water-insoluble nonionic surfactant. 80 FS (HLB 9.2) was added at 0.2 parts by weight. The temperature in the V-type blender was maintained at 25 ° C. and the internal pressure was maintained at 0.20 MPa, and stirred for 30 minutes. Then, after cooling to 20 degreeC, the expandable resin particle was taken out.
Prefoaming and foaming were carried out in the same manner as in Example 1, and the foaming molding was obtained by increasing the expansion ratio of the foaming molding to 40 times.
Table 2 shows the measurement results and comprehensive evaluation of the surface resistivity and attenuation rate of the foamed molded product.

From Examples and Comparative Examples, by using a cationic surfactant and a water-insoluble nonionic surfactant in combination, a foam molded article having a low surface resistivity and a high charge decay rate can be obtained. I understand.
From Examples 1 to 14, it can be seen that, with various nonionic surfactants, foam molded articles having a low surface resistivity and a high charge attenuation rate can be obtained.

From Examples 1 and 5 to 7, it can be seen that even if the amount of the nonionic surfactant used is changed, a foamed molded article having a low surface resistivity and a high charge attenuation rate can be obtained. In particular, it can be seen that by increasing the amount used, a low surface resistivity and a high charge amount decay rate can be maintained even in a high-magnification foamed molded product.
From Examples 3 and 12, it can be seen that even if the amount of the cationic surfactant used is changed, a foamed molded article having a low surface resistivity and a high charge decay rate can be obtained.
From Examples 13 and 14, it can be seen that even if the resin type constituting the composite resin particles is changed, a foamed molded article having a low surface resistivity and a high charge attenuation rate can be obtained.

  FIG. 1 shows the relationship between the decay rates of Examples 8 to 11 and Comparative Examples 5 to 6 and the nonionic surfactant amount ratio when the amount of the cationic surfactant is 1. In all of these Examples and Comparative Examples, the total amount of the surfactant is 2.0 parts by weight, and the same cationic surfactant and nonionic surfactant are used. As can be seen from FIG. 1, when the nonionic surfactant amount ratio is in the range of 0.03 to 0.8, a high attenuation rate can be obtained.

Claims (5)

In obtaining foamable resin particles by dry impregnation of a foaming agent in the presence of a surfactant in styrene-based resin particles,
The surfactant is used in an amount of 1 to 4 parts by weight with respect to 100 parts by weight of the styrenic resin particles, and the cationic surfactant and water-insoluble in a weight ratio of 1: 0.03 to 0.8. And a nonionic surfactant. A method for producing expandable styrene resin particles having antistatic properties.   The nonionic surfactant is used in an amount of 0.03 to 1.6 parts by weight based on 100 parts by weight of the styrene resin particles. Production method.   The styrene resin particles are composite resin particles of a styrene resin and an ethylene resin, and the ethylene resin is contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the styrene resin. Or the manufacturing method of the expandable styrene-type resin particle which has antistatic property of 2. The cationic surfactant is represented by the following formula 1
(In the above formula, R ¹ represents a linear or branched alkyl group having 5 to 20 carbon atoms)
The method for producing expandable styrene-based resin particles having antistatic properties according to any one of claims 1 to 3, which is selected from the agents represented by:   The foam having an antistatic property according to any one of claims 1 to 4, wherein the nonionic surfactant is selected from dialkanolamine, polyoxyethylene polyoxypropylene glycol, fatty acid monoglyceride, and pentaerythritol fatty acid ester. For producing conductive styrene resin particles.