JPH10168217A - Foamable styrene resin particle and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain foamable styrene resin particles improved in mechanical strengths, surface smoothness, and surface hardness just after molding in a good balance by making the concn. of the nucleating agent near at the surface of each foamable styrene resin particle contg. specified amts. of a highly volatile blowing agent and a nucleating agent lower than the concn. inside the particle. SOLUTION: In foamable styrene resin particles prepd. by compounding 100 pts.wt. styrene resin with 3-20 pts.wt. easily volatile blowing agent and 0.001-1.0 pt. wt. nucleating agent, the concn. of the nucleating agent near at the surface of the particle is made lower than the concn. inside the particle. Such particles can be obtd. by causing the nucleating agent in an amt. of 0.001-1 pt.wt. (based on 100 pts.wt. finally resulting styrene resin) to exist at least partly in seed particles before a styrenic monomer is added to the polymn. system in a seed polymn. process. Examples of the nucleating agent are a methacrylic ester polymer, a styrene copolymer, an olefin wax, and a fatty acid ester.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to expandable styrene resin particles and a method for producing the same. When the expandable styrene-based resin particles are heated by steam, hot air, or the like, a number of bubbles are generated in the particles, and the expanded styrene-based resin particles become pre-expanded resin particles. When the pre-expanded resin particles are filled in a mold having a desired shape and heated by steam, the pre-expanded resin particles are fused to each other to obtain a foam molded article.

[0002]

2. Description of the Related Art Styrene resin foam is relatively inexpensive.
Because of its light weight and good buffering and heat insulating properties, it is used for food containers, cushioning materials, heat insulating materials and the like. However, the required properties of the foam differ depending on the application in which it is used, and the balance of the properties varies. Taking a fish box in which fresh fish and the like are taken as an example, of course, sufficient mechanical strength is required so that the bottom of the box does not come off or the handle part does not break when the fish is put in and transported. Also,
The smaller the particle gap on the surface of the molded product and the higher the surface smoothness, the better the appearance and the better the printed surface, so the surface smoothness is also an important factor in determining the commercial value. Further, there is a case where printing is performed on the surface of the molded body immediately after molding. At this time, if the surface is soft, traces of rollers of a printing machine remain on the surface, which impairs the commercial value of the molded body. Therefore,
The surface hardness (surface hardness) of the molded body immediately after molding is also important.

However, mechanical strength, surface smoothness,
It is very difficult to balance all of the surface hardness immediately after molding at a high level, and at present, such a foam molded article has not yet been obtained.

[0004]

As a method for improving the surface smoothness of a foam molded article, Japanese Patent Application Laid-Open Nos. 63-69843, 63-69844 and 1-299 have been proposed.
No. 843 proposes a method for dissipating a blowing agent present in the vicinity of the surface of expandable styrene resin particles. However, according to this method, although the surface smoothness is improved, the mechanical strength is not always sufficient.

[0005]

In view of this situation, the present inventors have conducted intensive studies to balance, at a high level, three incompatible properties such as mechanical strength, surface smoothness, and surface hardness immediately after molding. Surprisingly, they have found that the object can be achieved by having a small amount of nucleating agent near the surface of the expandable particles and a large amount inside the particles, thereby completing the present invention.

That is, the present invention relates to a styrene resin 10
In a foamable styrene resin particle containing 3 to 20 parts by weight of a volatile foaming agent and 0.001 to 1 part by weight of a nucleating agent with respect to 0 part by weight, the concentration of the nucleating agent near the particle surface is reduced. An object of the present invention is to provide expandable styrene-based resin particles characterized by having a concentration lower than the concentration of an internal nucleating agent.

Further, according to the present invention, a styrene-based resin seed particle is suspended in an aqueous dispersion medium, and then a styrene-based monomer is continuously or intermittently added to the dispersion medium. In a method of obtaining an expandable styrene-based resin particle by polymerizing while impregnating and adding an easily volatile blowing agent during the polymerization or after the polymerization is completed (also referred to as a seed polymerization method), the styrene-based monomer is used. Foaming characterized in that at least one part of the nucleating agent is present in the seed particles in an amount of 0.001 to 1 part by weight, based on 100 parts by weight of the styrene resin finally obtained, before the addition of It is intended to provide a method for producing functional styrene resin particles.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The styrene-based resin seed particles in the present invention are generally known styrene-based resin granules. Examples of such particles include styrene, α-methylstyrene, paramethylstyrene, and t-methylstyrene. -Butyl styrene,
Styrene derivatives such as chlorostyrene, methyl acrylate, butyl acrylate, methyl methacrylate,
Examples include acrylic acid and methacrylic acid esters such as ethyl methacrylate and cetyl methacrylate, and homopolymer particles of various monomers such as acrylonitrile, dimethyl fumarate, and ethyl fumarate, or copolymer particles obtained by mixing. Further, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate may be used in combination.

Such resin seed particles are dispersed in an aqueous medium as droplets by (1) a normal suspension polymerization method and (2) a polymerizable monomer passing through a nozzle under regular vibration. And polymerizing without causing coalescence and additional dispersion. When a particle having a uniform particle size is required, the method (2) is preferably used, but the resin particles obtained by the suspension polymerization method (1) may be classified.

The use amount of these particles is preferably 1 to 80% by weight, particularly preferably 5 to 50% by weight based on the total amount of the resin after the polymerization. If the amount used is less than 1% by weight, the ratio of the added monomer to be a single polymer in a powder form without being impregnated into the particles increases, which is not preferable. The ratio of the particle diameter of the particles becomes small, which is economically disadvantageous.

The styrene monomer used in the present invention includes styrene derivatives such as styrene, α-methylstyrene, paramethylstyrene, t-butylstyrene, chlorostyrene, methyl acrylate, butyl acrylate, methyl methacrylate, ethyl Methacrylate, esters of acrylic acid and methacrylic acid such as cetyl methacrylate, or various monomers such as acrylonitrile, dimethyl fumarate, and ethyl fumarate, and these monomers may be used alone or in combination of two or more. be able to. Also, divinylbenzene,
A bifunctional monomer such as alkylene glycol dimethacrylate may be used in combination.

As the polymerization initiator of the above-mentioned monomer in the present invention, a radical-generating polymerization initiator generally used for producing a thermoplastic polymer can be used. A typical example is benzoyl peroxide. , Lauroyl peroxide, t-butyl perbenzoate, t
-Butyl perpivalate, t-butyl peroxyisopropyl carbonate, t-butyl peroxy acetate, 2,2-di-t-butyl peroxybutane, t-butyl peroxy-3,3,5-trimethylcyclohexanoate , Di-t-butylperoxyhexahydroterephthalate, 1,1-di-t-butylperoxy-
Organic peroxides such as 3,3,5-trimethylcyclohexane, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile are exemplified. These polymerization initiators can be used alone or in combination of two or more.

The aqueous dispersion medium used in the present invention includes, for example, water.

The dispersing agents used in the present invention include well-known water-soluble polymers such as polyvinyl alcohol, methylcellulose, polyvinylpyrrolidone and polyacrylamide, calcium tertiary phosphate, hydroxyapatite, magnesium phosphate, magnesium pyrophosphate and the like. Inorganic substances that are hardly soluble in water. When an inorganic substance that is hardly soluble in water is used, the dispersion stabilizing effect increases when an anionic surfactant such as sodium dodecylbenzenesulfonate is used in combination. It is also effective to use a water-soluble polymer and a water-insoluble inorganic substance in combination.

The volatile volatile blowing agent used in the present invention includes aliphatic hydrocarbons such as propane, butane, pentane and hexane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; difluoroethane and tetrafluoroethane. Fluorocarbons and carbon dioxide having an ozone depletion potential of zero are mentioned. These may be used alone or in combination of two or more, and may be added during the polymerization step, or may be added after the polymerization step.

In the present invention, a nucleating agent finely dispersible in a styrene resin matrix is used. For example, methacrylate polymer, methacrylate-acrylate copolymer, methacrylate polymer such as methyl methacrylate-butadiene-styrene copolymer, styrene-butadiene copolymer, high impact polystyrene, styrene- Butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene copolymer such as acrylonitrile-styrene copolymer, olefin such as polyethylene wax, ethylene-vinyl acetate copolymer wax Wax, glycerin monostearate, glycerin monobehenate, glycerin mono 12-hydroxystearate, glycerin monolaurate, glycerin tri 12-hydroxystearate, glycerin triste , Glycerin tripalmitate, glycerin trilaurate, glycerin tribehenate, fatty acid esters such as pentaerythritol tall tetrastearate,
Hardened vegetable oils such as castor hardened oil, soybean hardened oil, rapeseed hardened oil, fatty acid amides, fatty acid dicarboxylic diamides, aromatic bisamides, amides such as aromatic dicarboxylic diamides, stearic acid, behenic acid, oleic acid, linoleic acid, Higher fatty acids such as linolenic acid and lactic acid, fatty acid metal salts such as zinc stearate and calcium stearate,
One type or a mixture of two or more types selected from surfactants such as polyethylene glycol monostearate, polyoxyethylene stearyl ether and polyoxyethylene lauryl ether.

These nucleating agents include styrene resin 100
0.001 to 1.0 parts by weight based on parts by weight.
If the amount is 0.001 part by weight or less, the cells obtained by foaming are non-uniform and coarse, and as a result, the surface hardness of the molded body immediately after molding decreases,
If the content is 1.0% by weight or more, the cells obtained by foaming become too fine, which not only impairs the smoothness of the surface of the molded product but also is disadvantageous economically.

In the present invention, the concentration of the nucleating agent near the particle surface is lower than the concentration of the nucleating agent inside the particle, and preferably, the concentration of the nucleating agent near the surface is the concentration of the nucleating agent inside the particle. It is important that it is 90% or less, more preferably 80% or less. The nucleating agent may not be provided near the surface. The term "in the vicinity of the particle surface" as used herein refers to a portion having a depth from the particle surface to 10% of the particle radius, and the remaining portion is referred to as the inside. The concentration of the nucleating agent near the particle surface is
When the concentration of the nucleating agent inside the particle is the same or higher,
The mechanical strength and the smoothness of the surface of the formed body are deteriorated.

The type of nucleating agent used may be different between near and inside the particle surface.

The nucleating agent concentration is measured as follows. Prepare two sheets of No. 300-600 sandpaper stuck on a plate with a thickness of about 5 mm, place one of them on a table with the sandpaper surface facing up, and place a particle radius on it in advance. About 1 gram of resin particles having a known size of x μm and a nucleating agent concentration A (% by weight) are placed thereon. Another plate is placed on the resin particles so that the surface of the sandpaper is facing down, lightly weighted by hand and moved in a circular motion on the resin particles, the surface of the particles is scraped. When about 10% of the particle radius is shaved, the resin particles are taken out, and the nucleating agent concentration B (% by weight) inside the particle is determined by measuring the nucleating agent concentration, and the nucleating agent existing near the particle surface is obtained. Can be derived by the following equation. The concentration of the nucleating agent is measured, for example, by using an infrared spectrophotometer when the methacrylic acid ester polymer is used.
The concentration in the polymer was measured from the absorbance of the zero absorption band (1750 to 1735 cm ^-1 ).

[0021]

(Equation 1)

In the present invention, all or a part of the nucleating agent, preferably at least 50% by weight of the nucleating agent, more preferably substantially the entire amount of the nucleating agent is present in the styrene resin seed particles. As the method, (1) a method of dissolving or dispersing all or a part of a nucleating agent in a monomer used in advance when producing seed particles, (2) including a nucleating agent, or After dispersing the seed particles not contained in the aqueous dispersion medium, before adding the styrene-based monomer, dissolve or disperse the nucleating agent alone or in a small amount of a solvent or a styrene-based monomer. A method of adding to the aqueous dispersion medium in an impregnated form and impregnating the seed particles is included. The remainder of the nucleating agent may be used by dissolving or dispersing it in the styrene monomer to be added.

In the present invention, in addition to the above-mentioned raw materials, substances generally used in the production of expandable thermoplastic resin particles, such as plasticizers, solvents and flame retardants, impair the effects of the present invention. It can be used together in a range that does not exist.

[0024]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Examples 1-4 and Comparative Examples 1-2 In a 5 liter reactor equipped with a flat stirring blade having a lower inlet, 3000 ppm of tribasic calcium phosphate fine powder was added.
3 L of an aqueous dispersion medium prepared so that polyvinyl alcohol (Gohsenol PH-20: manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) became 50 ppm and sodium dodecylbenzenesulfonate became 50 ppm, and stirring was started.

Next, 2.1 g of benzoyl peroxide and 700 g of a methyl methacrylate-butyl acrylate copolymer (Kaneace PA manufactured by Kanebuchi Chemical Industry Co., Ltd.) as a nucleating agent in 700 g of a styrene monomer. −
20) was dissolved, and the resulting solution was 0.2 mmφ as shown in FIG.
0.8 liter / droplet in a droplet generator with 5 nozzles
The liquid is supplied at a rate of hr and a mechanical vibration of 500 Hz is applied to generate a liquid enemy group 8 in the aqueous dispersion medium 7, which is introduced into the above 5 liter reactor through the droplet introduction pipe 5 by using buoyancy. did. When 500 g of droplets were introduced, the formation of droplets was stopped, and the dispersion in the reactor was heated to 90 ° C. and polymerized for 3 hours. Further, the temperature of the dispersion was raised to 110 ° C. and maintained for 1 hour to complete the polymerization. The slurry in the reactor was cooled, dehydrated and dried to obtain polymer particles. The obtained particles are referred to as seed particles.

Subsequently, 1.8 liters of pure water and 7.2 tricalcium phosphate were placed in a 5 liter reactor equipped with a stirrer.
g, 21 cc of a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate, 1.8 g of sodium chloride, 180 g of seed particles
And the dispersion in the reactor was heated to 90 ° C. with stirring. Then, 18 g of dioctyl phthalate, 4.9 g of benzoyl peroxide, 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane.
A solution in which 8 g was dissolved in 1620 g of a styrene monomer was charged into a reactor over 7 hours while performing polymerization. Immediately after the charging of the monomer solution is completed, butane 14 is used as a blowing agent.
4 g and 1.8 g of cyclohexane were added, the temperature was raised to 120 ° C., and post-polymerization and impregnation of a blowing agent were performed for 3 hours. After cooling, the obtained expandable resin particles were taken out and dehydrated and dried. The nucleating agent concentration in the particles was as shown in Tables 1 and 2.

Further, the obtained expandable resin particles were heated by steam in a batch type pre-expansion machine to obtain pre-expanded particles having an apparent volume of about 60 times. After the pre-expanded particles are cured and dried in the air for 24 hours, the external dimensions are 30 × 4 by using a Fu-300 automatic molding machine (manufactured by Toyo Machine Metal Co., Ltd.).
A box-shaped compact having a height of 0 × 20 cm (thickness: 25 mm) was obtained. The bending strength (kgf / cm ² ), surface smoothness, and surface hardness (kgf / cm ² ) of the obtained molded body were evaluated by the following methods. The results are shown in Tables 1 and 2.

Evaluation method Bending strength The bottom surface of the molded body was taken out, and the bending strength was measured by a method according to JIS A9511.

2. Surface smoothness The amount of the particle gap on the surface of the molded product was visually evaluated. The sample having no particle gap was designated as A, the sample having only a few particles as B, the sample having many particles as C, and the sample having no particle gap filled at all.

3. Surface hardness immediately after molding A hardness tester (Asker
TYPECS (Polymer Meter) was pressed, and the highest value at that time was read. This was performed at four locations, and the average value was defined as the surface hardness.

Examples 5 to 8 and Comparative Examples 3 to 4 Methyl methacrylate-butadiene-styrene copolymer (Kaneace B-5, manufactured by Kanekachi Chemical Industry Co., Ltd.) was used as a nucleating agent.
The same operation as in Example 1 was performed except that 6) was used in the amounts shown in Tables 1 and 2. Tables 1 and 2 show the nucleating agent concentration in the obtained particles and the bending strength, surface smoothness, and surface hardness of the obtained molded body.

Examples 9 to 11 The same operation as in Example 1 was performed except that high-impact polystyrene (EXG-11 manufactured by Asahi Kasei Corporation) was used in the amounts shown in Tables 1 and 2 as nucleating agents. Tables 1 and 2 show the nucleating agent concentration in the obtained particles and the bending strength, surface smoothness, and surface hardness of the obtained molded body.

Examples 12 to 15 The same operation as in Example 1 was performed except that pentaerythol tetrastearate (EW-400, manufactured by Riken Vitamin Co., Ltd.) was used in the amount shown in Table 1 as a nucleating agent. . Table 1 shows the nucleating agent concentration in the obtained particles and the bending strength, surface smoothness, and surface hardness of the obtained molded body.

Example 16 Seed particles were obtained in the same manner as in Example 1 except that no nucleating agent was used. Subsequently, 1.8 liters of pure water and 7.2 tribasic calcium phosphate were placed in a 5 liter reactor equipped with a stirrer.
g, 21 cc of a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate, 1.8 g of sodium chloride, 180 g of seed particles
And the dispersion in the reactor was heated to 90 ° C. with stirring. Next, 0.09 g of a methyl methacrylate-butyl acrylate copolymer (Kaneace PA-20, manufactured by Kaneka Chemical Industry Co., Ltd.) was dissolved as a nucleating agent in 10 g of a styrene monomer. The solution was added dropwise over 10 minutes, and left as it was for 30 minutes to impregnate the seed particles. Then
18 g of dioctyl phthalate, 4.9 g of benzoylperoxide, 1,1 bis-t-butylperoxy 3,
A solution prepared by dissolving 1.8 g of 3,5-trimethylcyclohexane in 1610 g of a styrene monomer was charged into the reactor over 7 hours while polymerizing. Immediately after the charging of the monomer solution was completed, 144 g of butane and 1.8 g of cyclohexane were added as blowing agents, and the temperature was raised to 120 ° C. for 3 hours.
Post-polymerization and impregnation with a blowing agent were performed. After cooling, the obtained expandable resin particles were taken out and dehydrated and dried. The nucleating agent concentration in the particles was as shown in Table 1.

Further, the obtained expandable resin particles were heated by steam in a batch type pre-expansion machine to obtain pre-expanded particles having an apparent volume of about 60 times. After the pre-expanded particles are cured and dried in the air for 24 hours, the external dimensions are 30 × 4 by using a Fu-300 automatic molding machine (manufactured by Toyo Machine Metal Co., Ltd.).
A box-shaped compact having a height of 0 × 20 cm (thickness: 25 mm) was obtained. Table 1 shows the bending strength, surface smoothness, and surface hardness of the obtained molded body.

Example 17 After seed particles were obtained in the same manner as in Example 1, 1.8 liters of pure water, 7.2 g of tribasic calcium phosphate, sodium dodecylbenzenesulfonate 1 were placed in a 5-liter reactor equipped with a stirrer. 21% by weight aqueous solution, sodium chloride 1.8
g and 180 g of seed particles, and the dispersion in the reactor was heated to 90 ° C. with stirring. Then, dioctyl phthalate 1
8 g, benzoyl peroxide 4.9 g, 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane 1.8 g, methyl methacrylate-butyl acrylate copolymer as nucleating agent (Kanebuchi Chemical Industry Co., Ltd.) A solution prepared by dissolving 0.09 g of Kaneace PA-20 (trade name, manufactured by Co., Ltd.) in 1620 g of a styrene monomer was charged into the reactor over 7 hours while polymerizing. Immediately after the charging of the monomer solution was completed, 144 g of butane and 1.8 g of cyclohexane were added as blowing agents, and the temperature was raised to 120 ° C. for 3 hours.
Post-polymerization and impregnation with a blowing agent were performed. After cooling, the obtained expandable resin particles were taken out and dehydrated and dried. The nucleating agent concentration in the particles was as shown in Table 1.

Further, the obtained expandable resin particles were heated by steam using a batch type pre-expansion machine to obtain pre-expanded particles having an apparent volume of about 60 times. After the pre-expanded particles are cured and dried in the air for 24 hours, the external dimensions are 30 × 4 by using a Fu-300 automatic molding machine (manufactured by Toyo Machine Metal Co., Ltd.).
A box-shaped compact having a height of 0 × 20 cm (thickness: 25 mm) was obtained. Table 1 shows the bending strength, surface smoothness, and surface hardness of the obtained molded body.

Comparative Examples 5 to 8 1800 g of water was placed in a 5 L autoclave equipped with a stirrer.
Next, 10.8 g of tribasic calcium phosphate and 0.054 g of sodium dodecylbenzenesulfonate were added as a dispersant, and the mixture was uniformly dispersed by stirring, and 5.4 g of benzoyl peroxide and tert-butyl peroxybenzoate were added as a polymerization initiator. 3.6 g of a nucleating agent shown in Table 2 was dissolved in 1800 g of a styrene monomer, and this monomer solution was introduced into an autoclave. After purging with nitrogen, the mixture was kept at 90 ° C for 7 hours, and then butane 1
35 g was injected, the temperature was raised to 105 ° C., and the temperature was maintained for 3 hours.
After cooling, the obtained expandable resin particles were taken out and dehydrated and dried. Table 2 shows the nucleating agent concentrations in the particles.

Further, the obtained expandable resin particles were prefoamed and molded in the same manner as in Example 1. Table 2 shows the bending strength, surface smoothness, and surface hardness of the obtained molded body.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

According to the present invention, expandable styrene resin particles capable of providing a foam molded article having a well-balanced improvement in mechanical strength, surface smoothness, and surface hardness immediately after molding can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a droplet generation apparatus used in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle box 2 Nozzle plate 3 Vibrator vibrator 4 Styrene monomer introduction part 5 Droplet introduction tube 6 Diaphragm 7 Aqueous dispersion medium 8 Styrene monomer droplet group 9 Shaker support frame

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 25/00 C08L 25/00 // (C08L 25/00 33:10) (C08L 25/00 25:08) (C08L 25 / 00 23:04) (72) Inventor Masahide Ebisui 5-218-201 Nozoe Harima-cho Kako-gun Hyogo Prefecture

Claims (6)

[Claims] 1. A styrene-based resin is used in an amount of 3 to 20 parts by weight based on 100 parts by weight of a styrene-based resin.
The expandable styrene resin particles, wherein the concentration of the nucleating agent in the vicinity of the particle surface is lower than the concentration of the nucleating agent inside the particles in the expandable styrene resin particles containing 0 parts by weight. 2. The nucleating agent is a methacrylate polymer, a styrene copolymer, an olefin wax, a fatty acid ester, a hydrogenated vegetable oil, a fatty acid amide, a fatty acid dicarboxylic diamide, an aromatic bisamide, an aromatic dicarboxylic diamide, The resin particles according to claim 1, wherein the resin particles are selected from a higher fatty acid, a fatty acid metal salt, and a nonionic surfactant. 3. After the styrene resin seed particles are suspended in an aqueous dispersion medium, a styrene monomer is continuously or intermittently added to the dispersion medium and polymerization is performed while impregnating the seed particles. In a method for obtaining expandable styrene resin particles by adding an easily volatile blowing agent during or after polymerization, the styrene resin finally obtained at a stage before the addition of the styrene monomer A method for producing expandable styrene resin particles, characterized in that 0.001 to 1 part by weight of a nucleating agent in 100 parts by weight of particles is entirely or partially present in the seed particles. 4. The production method according to claim 3, wherein 50% by weight or more of the nucleating agent is present in the seed particles. 5. The method according to claim 3, wherein substantially all of the nucleating agent is present in the seed particles. 6. A nucleating agent comprising a methacrylate polymer, a styrene copolymer, an olefin wax, a fatty acid ester, a hydrogenated vegetable oil, a fatty acid amide, a fatty acid dicarboxylic diamide, an aromatic bisamide, an aromatic dicarboxylic acid diamide, The method according to claim 3, wherein the method is selected from higher fatty acids, metal salts of fatty acids, and nonionic surfactants.