A method for producing expandable thermoplastic resin particles.

Abstract

To provide a method for producing foamable thermoplastic resin particles which is suitable for obtaining a foam molding having low charging property while suppressing powder peeling such as an antistatic agent.SOLUTION: A method for producing foamable thermoplastic resin particles includes: a step of obtaining a foamable thermoplastic resin body containing a foaming agent; a first coating step of coating a liquid antistatic agent A containing 90% or more of a predetermined amount of alkylamine onto the surface of the foamable thermoplastic resin body; and a second coating step of coating at least one of a powdery antistatic agent B1 containing 90% or more of a predetermined amount of alkylamine and a powdery antistatic agent B2 containing 90% or more of fatty acid glyceride onto the surface of the foamable thermoplastic resin body after the first coating step.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing expandable thermoplastic resin particles. [Background technology]

[0002] Expandable thermoplastic resin particles are a socially useful material because they are relatively inexpensive, can be expanded using steam or other means without using special methods, and provide high cushioning and heat insulation effects. The resulting expanded molded products are used in a wide range of applications, such as for fish boxes, agricultural product boxes, food containers, cushioning materials for home appliances, and heat insulation materials for building materials. For example, there are expandable styrene resin particles produced by a method of impregnating styrene resin particles with a blowing agent (i.e., a readily volatile aliphatic hydrocarbon that only slightly swells the particles, such as butane, pentane, etc.). In recent years, when used as cushioning materials for home electric appliances and precision parts, there has been a demand for cushioning materials having low electrostatic properties, i.e., low surface resistance, from the viewpoint of preventing dust and the like from getting onto the precision parts. To address this problem, Patent Document 1 proposes a method in which expandable styrene particles are produced, dried, and then mixed with a hydroxyalkylamine compound having 13 to 20 carbon atoms (N-hydroxyethyl-N-(2-hydroxytetradecyl)amine).

[0003] Furthermore, Patent Document 2 proposes expandable styrene-based resin particles coated with hydroxyalkylamine (N-hydroxyethyl-N-(2-hydroxytetradecyl)amine) and fatty acid amide.

[0004] Patent Document 3 proposes expandable resin particles containing N-hydroxyethyl-N-2-hydroxyalkylamine, the compound being contained in an amount of 0.036 to 0.10% by weight relative to the expandable polystyrene-based resin particles. Patent Document 4 proposes a production method in which N-hydroxyethyl-N-2-hydroxyalkylamine is applied to expandable styrene-based resin particles after dehydration. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 07-278340 [Patent Document 2] JP 2005-015593 A [Patent Document 3] JP 2013-72039 A [Patent Document 4] JP 2017-114987 A Summary of the Invention [Problem to be solved by the invention]

[0006] The techniques of Patent Documents 1 to 4 have a problem in that the antistatic agent peels off from the resin particles during piping transportation of the resin particles, pre-foaming steps, and the like, and tend to make it difficult to efficiently achieve antistatic performance. An object of the present invention is to provide a method for producing expandable thermoplastic resin particles which is suitable for obtaining a foamed molded article having low electrostatic charge while suppressing peeling of powder. [Means for solving the problem]

[0007] After extensive research, the inventors have discovered that a method for solving this problem is to apply a specific liquid antistatic agent to the surface of the expandable thermoplastic resin particle body, and then apply a specific powdered antistatic agent to the particle body, thereby preventing the powdered antistatic agent and the like from peeling off from the resin particle body. That is, one embodiment of the present invention includes the following configuration.

[0008] [1] A step of obtaining an expandable thermoplastic resin particle body containing a foaming agent; a first coating step of coating a surface of the expandable thermoplastic resin particle body with 0.01 to 3 parts by weight of a liquid antistatic agent A containing 90% or more of alkylamine per 100 parts by weight of the expandable thermoplastic resin particle body; a second coating step of coating, after the first coating step, a surface of the expandable thermoplastic resin particle body with at least one of a powdered antistatic agent B1 containing 90% or more of an alkylamine or a powdered antistatic agent B2 containing 90% or more of a fatty acid glyceride; Equipped with In the second coating step, The amount of the antistatic agent B1 used is 0 parts by weight or more and 9 parts by weight or less, The amount of the antistatic agent B2 used is 0 parts by weight or more and 9 parts by weight or less, a weight ratio of the total of the antistatic agent B1 and the antistatic agent B2 to the antistatic agent A is 1-10.

[0009] [2] The expandable thermoplastic resin particle body is provided on the surface of the expandable thermoplastic resin particle body. The method for producing expandable thermoplastic resin particles according to [1], further comprising coating a fusion inhibitor in an amount of 0.5 parts by weight or less per 100 parts by weight.

[0010] [3] The method for producing expandable thermoplastic resin particles according to [1] or [2], wherein the antistatic agent A, the antistatic agent B1 and the antistatic agent B2 are poorly soluble in water.

[0011] [4] The method for producing expandable thermoplastic resin particles according to any one of [1] to [3], wherein the alkylamine of the antistatic agent A contains at least one of polyoxyethylene alkylamines or alkyl alkanolamides, each of which has an alkyl group with 10 to 20 carbon atoms.

[0012] [5] The method for producing expandable thermoplastic resin particles according to any one of [1] to [4], wherein the alkylamine of the antistatic agent B1 contains an N,N-bis(2-hydroxyethyl)alkylamine (the number of carbon atoms in the alkyl group, C=10 to 20) having one amino group and two hydroxyl groups in the molecule.

[0013] [6] The method for producing expandable thermoplastic resin particles according to any one of [1] to [5], wherein the aliphatic glyceride of the antistatic agent B2 contains at least one selected from the group consisting of fatty acid monoglycerides, fatty acid diglycerides, and fatty acid triglycerides. Effect of the Invention

[0014] According to the present invention, a liquid antistatic agent is applied to the main body of expandable thermoplastic resin particles containing a foaming agent, and then a powdered antistatic agent is attached, thereby suppressing contamination of equipment due to powder peeling of the antistatic agent, etc. during the pre-expansion step and molding step, and providing a method for producing a foamed molded product having low surface resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope of the claims. In addition, embodiments or examples obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic documents and patent documents described in this specification are incorporated herein by reference. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and smaller than B)".

[0016] In this specification, the expandable thermoplastic resin particle itself (itself) is referred to as the "expandable thermoplastic resin particle body", the expandable thermoplastic resin particle body to which an external additive (antistatic agent, fusion inhibitor) or the like has been applied is referred to as the "expandable thermoplastic resin particle", and the particles obtained by pre-expanding (primary expansion) the expandable thermoplastic resin particles are referred to as the "pre-expanded particles".

[0017] Expandable thermoplastic resin particles [Outline of one embodiment of the present invention] A method for producing a foamed molded article having low surface resistance by using expandable thermoplastic resin particles with an antistatic agent attached to the body of the expandable thermoplastic resin particles is known. The antistatic agent exerts its antistatic effect by adsorbing moisture in the air to the antistatic agent present on the surface of the resin particles themselves.

[0018] Patent Documents 1 to 4 propose a method of attaching an antistatic agent (N-hydroxyethyl-N-(2-hydroxyalkyl)amine) or the like to the expandable styrene-based resin particles themselves, but there is a tendency for the antistatic agent to peel off (powder peeling) while the expandable styrene-based resin particles are moving through piping in the pre-expanding process, molding process, etc., making it difficult to apply the agent uniformly and efficiently exhibit antistatic performance, and there is also the problem that the powder peeled off from the expandable styrene-based resin particles adheres to the inside of the piping, etc., and contaminates the equipment.

[0019] One embodiment of the present invention solves the above-mentioned technical problem. That is, it is possible to provide expandable thermoplastic resin particles suitable for obtaining a foamed molded article having low surface resistance and in which the antistatic agent attached to the expandable thermoplastic resin particle body is not easily peeled off. Furthermore, the expandable thermoplastic resin particles of the present invention can provide expandable resin particles suitable for obtaining a foamed molded article having good fusibility while maintaining the fluidity of the resin particles in a good state, as well as the above-mentioned technical problem. That is, the present invention can provide a method for producing expandable thermoplastic resin particles suitable for obtaining a foamed molded article having good fusibility and low electrostatic charge, while maintaining the fluidity of the resin particles in a good state and suppressing the peeling of powder. [Expandable Thermoplastic Resin Particle Body] The expandable thermoplastic resin particle body is a particle made of an expandable resin containing a base resin, a foaming agent, and, if necessary, additives.

[0020] (Base resin) In this specification, the base resin includes thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polytetrafluoroethylene, styrene-based resins, and acrylic-based resins. These thermoplastic resins are blended with appropriate additives and melt-kneaded in an extruder to obtain resin particles. Alternatively, resin particles may be obtained by polymerizing a monomer in which an additive is dissolved, using a pressure-resistant vessel, by an aqueous suspension polymerization method or a seed polymerization method. The styrene resin produced by polymerization of a monomer may be a homopolymer of styrene or a copolymer of a styrene monomer and a monomer other than a styrene monomer. Examples of the monomer other than a styrene monomer include ethylene, butadiene, acrylonitrile, a styrene derivative, and an acrylic acid ester. Examples of the styrene derivative include α-methylstyrene, paramethylstyrene, t-butylstyrene, and chlorostyrene. Examples of the acrylic acid ester include acrylic acid alkyl esters such as methyl acrylate and butyl acrylate. These monomers other than a styrene monomer may be used alone or in combination of two or more.

[0021] In addition, the expandable styrene-based resin particle body may be coated with a nonionic surfactant and then dried to form a crack structure on the resin particle surface. The formation of the crack structure tends to increase the adhesion of the liquid antistatic agent A applied in the first application step. Specific examples of the nonionic surfactant include polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, and polyoxyethylene oleate. These nonionic surfactants may be used alone or in combination of two or more.

[0022] (foaming agent) Methods for impregnating a foaming agent into resin particles include known methods such as a method of injecting a foaming agent into a resin melted and kneaded in an extruder (quench method) and a method of impregnating a foaming agent into resin particles obtained in an extruder in a pressure-resistant vessel at a temperature lower than the melting point of the resin (post-mini-pellet impregnation method).On the other hand, when producing by a polymerization method, known methods are known, such as impregnating a foaming agent into resin particles after polymerization in a pressure-resistant vessel. Examples of the blowing agent include aliphatic hydrocarbons such as propane, butane, and pentane; alicyclic hydrocarbons such as cyclobutane and cyclopentane; halogenated hydrocarbons such as methyl chloride, dichlorodifluoromethane, and dichlorotetrafluoroethane; and the like. Among these, butane is more preferred because of its good blowing power. These blowing agents may be used alone or in combination of two or more.

[0023] The content of the foaming agent in the expandable thermoplastic resin particle body is appropriately selected according to the desired expansion ratio of the final product, which is the foamed molded article, and is preferably 3.0 parts by weight or more, more preferably 3.5 parts by weight or more, and preferably 7.0 parts by weight or less, more preferably 5.0 parts by weight or less, relative to 100 parts by weight of the expandable thermoplastic resin particle body. If the content of the foaming agent is within the above range, it is possible to prevent the heating time in the pre-expansion step from becoming long, suppress blocking, and shorten the time required to produce the foamed molded article and the molding cycle in the molding step.

[0024] (Additives) Examples of additives that may be added to the base resin include solvents, plasticizers, nucleating agents, flame retardants, and flame retardant assistants. Specific examples of solvents and plasticizers include aliphatic hydrocarbons having 6 or more carbon atoms, such as hexane and heptane; alicyclic hydrocarbons having 6 or more carbon atoms, such as cyclohexane and cyclooctane, diisobutyl adipate, dioctyl adipate, dibutyl sebacate, glycerin tristearate, glycerin tricaprylate, coconut oil, palm oil, rapeseed oil, and the like. Specific examples of the nucleating agent include methyl methacrylate copolymers, polyethylene wax, talc, fatty acid bisamides, ethylene-vinyl acetate copolymers, etc. Specific examples of the fatty acid bisamides include methylene bisstearyl amide, ethylene bisstearyl amide, hexamethylene bispalmitic acid amide, ethylene bisoleic acid amide, etc.

[0025] As the flame retardant, a known flame retardant can be used. Specific examples include halogenated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromobutane, and hexabromocyclohexane; brominated phenols such as tetrabromobisphenol A, tetrabromobisphenol F, and 2,4,6-tribromophenol; tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), and tetrabromobisphenol A-diglycidyl ether. brominated phenol derivatives such as 2,2-bis[4'-(2",3"-dibromoalkoxy)-3',5'-dibromophenyl]-propane; brominated styrene-butadiene block copolymers, brominated random styrene-butadiene copolymers, brominated styrene-butadiene graft copolymers and other brominated butadiene-vinyl aromatic hydrocarbon copolymers (for example, EMERALD3000 manufactured by Chemtura Corporation or the copolymers described in JP-A-2009-516019); and the like.

[0026] As the flame retardant auxiliary, known flame retardant auxiliary can be used, specific examples of which include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, etc.

[0027] These additives may be used alone or in combination of two or more.

[0028] [Volume average particle diameter of expandable thermoplastic resin particle body] The volume average particle diameter of the expandable thermoplastic resin particle body of the present invention can be said to be the average particle diameter of the expandable thermoplastic resin particle body. The volume average particle diameter of the expandable thermoplastic resin particle of the present invention can be appropriately set according to the use of the foamed molded product, etc., but from the viewpoint of moldability, it is preferably 0.5 mm or more, more preferably 0.6 mm or more, preferably 2.0 mm or less, and more preferably 1.2 mm or less. In this specification, the volume average particle diameter of the expandable thermoplastic resin particle body is a value measured using an image processing method Microtrack JPA.

[0029] [Expandable thermoplastic resin particles] The expandable thermoplastic resin particles of the present invention are obtained by the manufacturing method of the expandable thermoplastic resin particles of the present invention. More specifically, the expandable thermoplastic resin particles of the present invention are obtained by applying a predetermined amount of liquid antistatic agent A containing 90% or more of alkylamine to the surface of the expandable thermoplastic resin particle body obtained by the above-mentioned various methods, and then applying a predetermined amount of powdered antistatic agent B1 containing 90% or more of alkylamine or powdered antistatic agent B2 containing 90% or more of fatty acid glyceride.

[0030] [Method for producing expandable thermoplastic resin particles] The method for producing expandable thermoplastic resin particles of the present invention includes a step of obtaining an expandable thermoplastic resin particle body containing a foaming agent, and a first coating step of coating the surface of the expandable thermoplastic resin particle body with 0.01 to 3 parts by weight of a liquid antistatic agent A containing 90% or more of alkylamine per 100 parts by weight of the expandable thermoplastic resin particle body, a second coating step of coating, after the first coating step, a surface of the expandable thermoplastic resin particle body with at least one of a powdered antistatic agent B1 containing 90% or more of an alkylamine or a powdered antistatic agent B2 containing 90% or more of a fatty acid glyceride, relative to 100 parts by weight of the expandable thermoplastic resin particle body; In the second coating step, The amount of the antistatic agent B1 used is 0 parts by weight or more (including 0 parts by weight) and 9 parts by weight or less, The amount of the antistatic agent B2 used is 0 parts by weight or more (including 0 parts by weight) and 9 parts by weight or less, In the production method, the weight ratio of the total of the antistatic agent B1 and the antistatic agent B2 to the antistatic agent A is 1-10.

[0031] (Step of Obtaining Expandable Thermoplastic Resin Particle Body) The process for obtaining the expandable thermoplastic resin particle body is a process for obtaining the expandable thermoplastic resin particle body containing a foaming agent. As described in the above [Expandable thermoplastic resin particle body], the process for obtaining the expandable thermoplastic resin particle body is not particularly limited, and includes known processes such as the process adopted in the quenching method, the process adopted in the mini-pellet post-impregnation method, and the process adopted in the polymerization method.

[0032] (1st coating process) The first application step is a step of applying a predetermined amount of antistatic agent A containing 90% or more of alkylamine onto the surface of the expandable thermoplastic resin particle body.

[0033] The antistatic agent A is a liquid antistatic agent at room temperature (25° C.). The antistatic agent A is preferably poorly soluble in water. The alkylamine of the antistatic agent A more preferably contains at least one of polyoxyethylene alkylamines or alkyl alkanol amides, the alkyl group of which has 10 to 20 carbon atoms, more preferably 10 to 16 carbon atoms.

[0034] Specific examples of polyoxyethylene alkylamines include polyoxyethylene-dodecylamine, polyoxyethylene-tetradecylamine, polyoxyethylene-hexadecylamine, polyoxyethylene-octadecylamine, polyoxyethylene-laurylamine, polyoxyethylene-alkyl(coconut)amines, polyoxyethylene-tallow alkylamines, polyoxyethylene-stearylamine, polyoxyethylene-oleylamine, and polyoxyethylene-alkylpropylenedimine. Specific examples of alkyl alkanolamides include capric acid diethanolamide, lauric acid diethanolamide, myristic acid diethanolamide, pentadecylic acid diethanolamide, palmitic acid diethanolamide, stearic acid diethanolamide, oleic acid diethanolamide, coconut fatty acid diethanolamide, coconut fatty acid diethanolamide, beef tallow fatty acid diethanolamide, coconut fatty acid monoethanolamide, lauric acid monoethanolamide, lauric acid isopropanolamide, polyoxyethylene-fatty acid monoethanolamide, and the like.

[0035] The coating amount of the antistatic agent A is 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, and 3 parts by weight or less, more preferably 2 parts by weight or less, based on 100 parts by weight of the expandable thermoplastic resin particle body. If the coating amount of the antistatic agent A is within the above range, it is possible to obtain expandable thermoplastic resin particles having low electrostatic properties. If the coating amount of the antistatic agent A is less than 0.01 parts by weight based on 100 parts by weight of the expandable thermoplastic resin particle body, low electrostatic properties cannot be obtained, and if it exceeds 3 parts by weight, the antistatic agent A cannot be uniformly mixed with the resin particles.

[0036] The antistatic agent A, which is liquid at room temperature (25°C), is applied to the surface of the resin particle body, and the antistatic agents B1 and B2 applied in the second application step are attached to the resin particle body, preventing peeling. If the antistatic agent A is poorly soluble in water, dissolution of the antistatic agent A by the heated steam used in the pre-expansion step and molding step is unlikely to occur, and therefore peeling of the antistatic agent B1 or B2 from the resin particle body can be prevented. On the other hand, when the antistatic agent is a liquid fatty acid ester, it corrodes the surface of the polystyrene resin particle body, causing microscopic holes on the surface of the obtained expanded beads, which tends to make it difficult to obtain the desired expansion ratio.

[0037] (2nd coating process) The second coating process is a process carried out after the first coating process, and is a process of coating the surface of the expandable thermoplastic resin particle body with at least one of a powdered antistatic agent B1 containing 90% or more of an alkylamine or a powdered antistatic agent B2 containing 90% or more of a fatty acid glyceride.

[0038] The alkylamine of the antistatic agent B1 preferably contains an N,N-bis(2-hydroxyethyl)alkylamine (the number of carbon atoms in the alkyl group, C=10 to 20) having one amino group and two hydroxyl groups in the molecule. Specific examples of the antistatic agent B1 include N-hydroxyethyl-N-(2-hydroxyalkyl)amine, 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-hydroxypropyl-N-(2-hydroxytetradecyl)amine, N-hydroxypropyl-N-(2-hydroxypropyl ... Examples of the 1-amino-2-hydroxy compounds include 1-amino-2-hydroxy compounds such as 1-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, N,N-bis(2-hydroxyethyl)hexadecylamine, and N,N-bis(2-hydroxyethyl)octadecylamine. These may be used alone or in combination of two or more.

[0039] The aliphatic glyceride of the antistatic agent B2 preferably contains at least one selected from the group consisting of fatty acid monoglycerides, fatty acid diglycerides, and fatty acid triglycerides, and is particularly preferably a fatty acid monoglyceride such as stearic acid monoglyceride, lauric acid monoglyceride, linoleic acid monoglyceride, etc. Fatty acid diglycerides and fatty acid triglycerides have a large effect of promoting fusion between pre-expanded particles, and tend to easily cause blocking.

[0040] The coating amount of the antistatic agent B1 and the antistatic agent B2 is 0 parts by weight or more (including 0 parts by weight) 9 parts by weight or less, preferably 1 part by weight or more, and more preferably 5 parts by weight or less, relative to 100 parts by weight of the expandable thermoplastic resin particle body. In the present invention, either the antistatic agent B1 or B2 must be coated, and when neither the antistatic agent B1 nor the antistatic agent B2 is added, the fluidity of the resin tends to deteriorate and the blocking amount during pre-expansion tends to increase. When the coating amount of the antistatic agent B1 and the antistatic agent B2 exceeds 9 parts by weight, the powder antistatic agent B1 and the antistatic agent B2 tend to peel off from the resin particle body.

[0041] The total weight ratio of the antistatic agent B1 and the antistatic agent B2 to the antistatic agent A is 1 to 10. If the weight ratio is less than 1, the fluidity of the resin particles is poor, and if the weight ratio exceeds 10, the antistatic agent peels off from the expandable thermoplastic resin particle body, contaminating the device. The total weight ratio of the antistatic agent B1 and the antistatic agent B2 to the antistatic agent A is preferably 2 to 9, and more preferably 3 to 8.

[0042] The antistatic agent B1 and the antistatic agent B2 are in the form of powder at room temperature (25°C). The antistatic agent B1 and the antistatic agent B2 are preferably poorly soluble in water. When the antistatic agent B1 and the antistatic agent B2 are in the form of powder at room temperature, they can be attached to the resin particle body via the liquid antistatic agent A applied in the first application step. In addition, when the antistatic agent B1 and the antistatic agent B2 are poorly soluble in water, they can be prevented from being dissolved or peeled off by the heated steam used in the pre-expansion step and the molding step.

[0043] In the first coating step and / or the second coating step of the method for producing expandable thermoplastic resin particles of the present invention, a further adhesive may be applied to the surface of the expandable thermoplastic resin particle body depending on the required performance. Furthermore, the method for producing expandable thermoplastic resin particles of the present invention may include a further coating step in addition to the first coating step and the second coating step depending on the required performance. If the adhesive is powdery at room temperature, it is preferably applied after the first coating step, and may be applied in the second coating step together with the antistatic agent B1 and the antistatic agent B2. Examples of the adhesive include adhesion inhibitors and adhesion promoters.

[0044] Examples of fusion inhibitors include higher fatty acid metal salts such as zinc stearate and magnesium stearate that are powdery at room temperature (25° C.), polymers such as polyethylene having a higher melting point than the base resin, and inorganic substances such as magnesium hydroxide, calcium hydroxide, talc, mica, magnesium silicate, silica (silicon dioxide) such as kaolin, silicates, alumina, diatomaceous earth, calcium carbonate, magnesium carbonate, calcium phosphate, feldspar apatite, barium sulfate, etc. These fusion inhibitors may be used alone or in combination of two or more. The fusion inhibitor does not have to be applied to the expandable thermoplastic resin particle body, but the amount of the fusion inhibitor applied is preferably 0 weight or more, more preferably 0.1 weight or more, preferably 0.5 weight or less, and more preferably 0.4 weight or less, relative to 100 weight parts of the expandable thermoplastic resin particle body. If the amount of the fusion inhibitor added is within the above range, blocking during pre-expansion is suppressed, and a foamed molded product that does not easily break and has practical strength can be obtained.

[0045] Examples of the fusion promoter include fatty acid triglycerides such as lauric triglyceride, stearic triglyceride, linoleic triglyceride, and hydroxystearic triglyceride; fatty acid diglycerides such as lauric diglyceride, stearic diglyceride, and linoleic diglyceride; fatty acid monoglycerides such as lauric monoglyceride, stearic monoglyceride, and linoleic monoglyceride; and vegetable oils such as castor hardened oil (hydroxystearic triglyceride). These fatty acid glycerides may be used alone or in combination of two or more. The amount of the fusion promoter applied is preferably 0 weight or more, more preferably 0.1 weight or more, more preferably 0.5 weight or less, and more preferably 0.4 weight or less, relative to 100 weight parts of the expandable thermoplastic resin particle body. If the amount of the fusion promoter added is within the above range, blocking is suppressed during pre-expansion, and the surface film of the pre-expanded particle is prevented from breaking.

[0046] In the method for producing expandable thermoplastic resin particles of the present invention, various known methods can be used to apply antistatic agent A, and antistatic agent B1 or antistatic agent B2, and if necessary, other additives, to the surface of the expandable thermoplastic resin particle body, such as a method using a mixing device.

[0047] When a mixer is used in the first coating step and the second coating step, it is preferable to use a mixer capable of uniformly mixing the expandable thermoplastic resin particle body, the antistatic agent A, the antistatic agent B1 and / or the antistatic agent B2. Examples of such mixers include mixers such as Super Mixer, Nauta Mixer, Universal Mixer, Proshare Mixer, Apex Mixer, Henschel Mixer, and Loedige Mixer; and blenders such as ribbon blender and tumbler type blender. The mixer can be appropriately selected taking into consideration the coating amount of the additive, etc.

[0048] The mixing time in each of the above steps is not particularly limited, and can be appropriately adjusted depending on the mixing capacity of the mixer.

[0049] [2. Pre-expanded particles] The pre-expanded particles according to one embodiment of the present invention are obtained by pre-expanding (primary expansion) the above-mentioned expandable thermoplastic resin particles.

[0050] As a method for pre-expanding, a conventional method can be used, for example, using a cylindrical pre-expanding device and heating and expanding the expandable thermoplastic resin particles with a heating medium such as steam.

[0051] The pre-expansion device and the conditions of the pre-expansion step may be appropriately set depending on the type of base resin of the expandable thermoplastic resin particle body, the desired pre-expansion ratio, etc., and are not particularly limited.

[0052] 3. Foam Molded Articles The foamed molded article according to one embodiment of the present invention is obtained by heating and foaming (secondary foaming) the above-mentioned pre-foamed particles, and molding the same.

[0053] The method of heating and expanding the pre-expanded particles to form them can be, for example, a conventional method such as an in-mold expansion molding method in which the pre-expanded particles are filled into a mold and heated by blowing in a heating medium such as steam.

[0054] A specific example of an in-mold foam molding method is a method in which pre-expanded particles are filled into a mold that can be closed but cannot be sealed, and the pre-expanded particles are heated and fused with a heating medium to form an in-mold foam molded article.

[0055] The apparatus used for heat expansion and the conditions for heat expansion may be appropriately set depending on the composition of the expandable thermoplastic resin particle body, the desired expansion ratio, etc., and are not particularly limited.

[0056] The foamed molded products, particularly in-mold foamed molded products, have the advantage of being easy to produce molded products of desired shapes, and are therefore suitable for use as, for example, packaging materials (trays) for food containers and the like, transport packaging materials for fish boxes and the like, and particularly as cushioning materials for home appliances and precision parts that require low electrostatic properties. EXAMPLES

[0057] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that "parts" and "%" are by weight unless otherwise specified.

[0058] The various measuring and evaluation methods for the expandable thermoplastic resin particles and the foamed molded articles in the examples and comparative examples are as follows.

[0059] <Evaluation of the fluidity of expandable thermoplastic resin particles> The fluidity of the expandable thermoplastic resin particles was evaluated using an evaluation device of an angle of repose measuring machine on the following 5-point scale. The higher the value, the better the fluidity, and a value of "3" or more was judged as passing.

[0060] The angle of repose was measured by the following method. First, a box with a dam on one side was prepared, and the expandable thermoplastic resin particles were poured into the box until it was completely leveled. After pouring, the dam was removed, and the expandable thermoplastic resin particles were allowed to spill naturally. Then, the angle of the expandable thermoplastic resin particles remaining in the box was measured, and this angle was taken as the angle of repose (degrees).

[0061] 4: The angle of repose is 40 degrees or less, the fluidity is very good, and the resin particles roll easily. 3: The angle of repose is greater than 40 degrees and less than 50 degrees, the fluidity is good, and the resin particles roll, but some remain on the evaluation device. 2: The angle of repose is between 50 degrees and 60 degrees. Although the fluidity is good, a vibrator is required to roll the resin particles. 1: The angle of repose exceeds 60 degrees, the fluidity is very poor, and the resin particles do not roll.

[0062] <Evaluation of powder peeling of expandable thermoplastic resin particles> 1 kg of expandable thermoplastic resin particles was weighed and sieved for 2 minutes using a mesh (mesh size: 355 μm, 42 mesh, φ750 mm) attached to an electric sieve (DY-50). The powder that passed through the mesh was then collected (however, if resin was mixed in, the resin was removed), and its weight was measured to determine the amount of peeling. The peeling rate of the external additives was calculated based on the following formula: (peeling rate [wt %]) = (peeling amount [g]) / (total amount of external additives added to expandable thermoplastic resin particles [g]) x 100, and expandable thermoplastic resin particles with a peeling rate of 5.00 wt % or less were evaluated as passing.

[0063] <Blocking rate measurement> Expandable thermoplastic resin particles were put into a pressurized pre-expanding machine (manufactured by Daikai Kogyo Co., Ltd., CH-100) equipped with an agitator, and pre-expanded (primary expansion) was performed by heating with steam as a heating medium and a blowing steam pressure of 0.1 MPa, to obtain pre-expanded particles with a bulk ratio (apparent expansion ratio) of 35 times. When the pre-expanded particles were taken out of the pre-expanding machine, the pre-expanded particles were passed through a net with a mesh size of 1 cm, and the pre-expanded particles that did not pass through the net were collected and weighed to obtain the blocking amount. The blocking rate was calculated based on the following calculation formula, and pre-expanded particles with a blocking rate of 2.0% by weight or less were evaluated as passing.

[0064] Blocking rate [wt%] = blocking amount [g] / total amount of pre-expanded particles [g] × 100

[0065] <Evaluation of foamed molded products> (1) Evaluation of fusion rate The obtained foamed molded article was broken and the broken surface was observed to determine the percentage of the foamed beads that had broken rather than the foamed bead interface (fusion rate). A fusion rate of 60% or more was evaluated as acceptable.

[0066] (2) Surface resistivity The foamed molded body was cut into a sample having a size of 100 mm x 100 mm x 10 mm (t), and the surface resistivity was measured on the uncut surface with the surface skin layer. First, the sample was placed in a temperature and humidity chamber (temperature 23 ° C, relative humidity 50%) for 24 hours. Next, the surface resistivity of the surface skin layer of the sample was measured using a digital ultra-resistance meter (8340A ULTRA HIGH RESISTANCE METER (ADC Corporation)) in a sample chamber 1270A RESISTANCE CHAMBER (ADC Corporation) installed in the temperature and humidity chamber (measurement conditions: after 30 seconds of static elimination, charging at 1000 V for 30 seconds, and measurement was performed).

[0067] The external additives used in the examples are listed below. <Antistatic agent that is liquid at room temperature> (Antistatic agent A containing 90% or more alkylamine) A(1); Polyoxyethylene alkylamine: alkyl group carbon number C=12, Tanaka Chemical Laboratory Co., Ltd., KN2009A A(2); Alkyl alkanolamide: alkyl group carbon number C=12, Tanaka Chemical Laboratory Co., Ltd. KN2009B (Antistatic agent that does not contain more than 90% alkylamines; fatty acid glyceride) C(1); Polyoxypropylene sorbitol: HS-1600D, manufactured by Nippon Oil & Fats Co., Ltd. C(2); Diglycerol laurate: L-51-D, manufactured by Riken Vitamin Co., Ltd.

[0068] <Antistatic agent in powder form at room temperature> (Antistatic agent B1 containing 90% or more alkylamine) B1: NN-bis(2-hydroxyethyl)alkylamine: alkyl group carbon number C=14, Tanaka Chemical Laboratory Co., Ltd., Antista 80FS (Antistatic agent B2 containing more than 90% fatty acid glyceride) B2: Stearic acid monoglyceride: S-100, manufactured by Riken Vitamin Co., Ltd.

[0069] <Fusion inhibitor in powder form at room temperature> Magnesium stearate: manufactured by Nippon Oil & Fats Co., Ltd. Zinc stearate: manufactured by Nippon Oil & Fats Co., Ltd. Magnesium hydroxide: Hirose Chemical Co., Ltd. Talc: PK-S manufactured by Hayashi Kasei Co., Ltd.

[0070] <Fusion accelerator in powder form at room temperature> Castor wax: Castor wax, manufactured by Nippon Oil & Fats Co., Ltd.

[0071] Example 1 (Production of Expandable Thermoplastic Resin Particle Body (1)) In a 1500L pressure vessel equipped with a stirrer, 100 parts by weight of pure water, 0.2 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium dodecylbenzenesulfonate, and 0.25 parts by weight of benzoyl peroxide (manufactured by NOF Corp.) as an initiator, 0.29 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate (manufactured by NOF Corp.), and 0.2 parts by weight of polyethylene wax (850-80M, manufactured by Toyo Adle Co., Ltd.) as a nucleating agent were added. Next, 95 parts by weight of styrene monomer and 5 parts by weight of butyl acrylate were added while stirring at 250 rpm, and the temperature was raised to 98°C and polymerization reaction was carried out for 4 hours. The polymerization conversion rate of the resin particles after the polymerization reaction for 4 hours was 92%. Next, 6.0 parts by weight of butane (normal / iso = 50 / 50) as a foaming agent was pressed into the pressure vessel and the temperature was raised to 120°C. The polymerization slurry was then held at 120°C for 3 hours, cooled to room temperature, and taken out of the pressure vessel. The polymerized slurry was washed, dehydrated, and dried using an airflow dryer to obtain expandable thermoplastic resin particle bodies (1).

[0072] The polymerization conversion was measured by the following method. (Measurement of polymerization conversion rate) The styrene resin particles were collected from the polymerization vessel, and the moisture on the resin particle surface was wiped off with filter paper. The styrene resin particles were dissolved in methylene chloride (internal standard cyclopentanol), and the amount of residual styrene (ppm) contained in the styrene resin particles was quantified using a gas chromatography GC-2014 (capillary column: GL Science Rtx-1, column temperature conditions: 50 → 80 ° C (3 ° C / min), then 80 → 180 ° C (10 ° C / min), carrier gas: helium) manufactured by Shimadzu Corporation. The polymerization conversion rate was calculated from the amount of residual styrene.

[0073] (Production of Expandable Thermoplastic Resin Particles) 100 parts by weight of the expandable thermoplastic resin particle body (1) obtained above was put into a super mixer (Kawata Co., Ltd., SMV-20), 1.5 parts by weight of antistatic agent A (1) was added over 60 seconds, and the mixture was stirred for 60 seconds to complete the first coating step. Next, 5 parts by weight of antistatic agent B1 was added, and the mixture was stirred for another 60 seconds to complete the second coating step, thereby obtaining expandable thermoplastic resin particles.

[0074] (Production of pre-expanded particles) The expandable thermoplastic resin particles obtained above were put into a pressurized pre-expanding machine equipped with a stirrer (manufactured by Daikai Kogyo Co., Ltd., CH-100). The expandable thermoplastic resin particles in the pre-expanding machine were heated using steam (blowing steam pressure 60 kPa) as a heating medium to cause pre-expanding (primary expansion), and pre-expanded particles with a bulk expansion ratio (apparent expansion ratio) of 35 times were obtained. The obtained pre-expanded particles were then left at room temperature for 24 hours to be cured and dried.

[0075] (Production of foamed molded products) The pre-expanded particles after curing and drying were filled into a mold measuring 450 mm long x 300 mm wide x 20 mm thick. Next, using a molding machine (KR-57, manufactured by Daisen Co., Ltd.), the pre-expanded particles in the mold were heated for 10 seconds using steam (blowing steam pressure 80 kPa) as a heating medium. Next, the pre-expanded particles were cooled with water for 2 seconds and allowed to cool in a vacuum. When the surface pressure gauge (pressure of the foamed molded product) installed in the mold reached 40 kPa, the mold was opened and the foamed molded product was taken out.

[0076] The resin flowability and powder peeling of the expandable thermoplastic resin particles obtained above were evaluated, and the fusion rate and surface resistance of the foamed molded article were evaluated. The evaluation results are shown in Table 1.

[0077] [Examples 2 to 11, Comparative Examples 1 to 7] Using the expandable thermoplastic resin particle body (1) produced in Example 1, expandable thermoplastic resin particles, pre-expanded particles, and foamed molded products were obtained in the same manner as in Example 1, except that the types and amounts of antistatic agent A, antistatic agent B1, antistatic agent B2, antistatic agent C, and fusion inhibitor were changed. The evaluation results are shown in Table 1 or Table 2 (Examples) and Table 3 (Comparative Example).

[0078] Example 12 Expandable thermoplastic resin particles, pre-expanded particles, and foamed molded products were obtained in the same manner as in Example 1, except that the antistatic agent A, antistatic agent B1, antistatic agent B2, fusion inhibitor, and fusion promoter were changed in the expandable thermoplastic resin particle body (1) produced in Example 1. The evaluation results are shown in Table 2 (Examples).

[0079] Example 13 0.02 parts by weight of a nonionic surfactant polyoxyethylene monooleate (O-3, manufactured by Nippon Oil & Fats Co., Ltd.) was applied to 100 parts by weight of the expandable thermoplastic resin particle body (1) produced in Example 1, and dried to obtain an expandable thermoplastic resin particle body having cracks formed on the surface of the resin particle body. Hereinafter, the expandable thermoplastic resin particle body having cracks formed thereon is referred to as an expandable thermoplastic resin particle body (2). Except for using the expandable thermoplastic resin particle body (2) and changing the antistatic agent A, the antistatic agent B1, the antistatic agent B2, the fusion inhibitor, and the fusion promoter, the expandable thermoplastic resin particles, pre-expanded particles, and foamed molded products were obtained using the same method as in Example 1. The evaluation results are shown in Table 2 (Examples).

[0080] Example 14 Into a 1500 L pressure vessel equipped with a stirrer, 100 parts by weight of pure water, 0.2 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium dodecylbenzenesulfonate, 0.15 parts by weight of benzoyl peroxide as an initiator, 0.25 parts by weight of t-butylperoxy-2-ethylhexyl monocarbonate, 2.0 parts by weight of tetrabromobisphenol-A-bis(2,3-dibromo-2-methylpropyl)ether (SR-130, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a flame retardant, 1.2 parts of dicumyl peroxide (Percumyl D, manufactured by Nippon Oil & Fats Co., Ltd.) as a flame retardant assistant, and 0.8 parts of α-methylstyrene dimer (MSD, manufactured by Nippon Oil & Fats Co., Ltd.) as a chain transfer agent were charged. Next, 71 parts by weight of styrene monomer, 24 parts by weight of acrylonitrile, and 5 parts by weight of α-methylstyrene were added while stirring at 250 rpm, and the temperature was raised to 90°C, and polymerization reaction was carried out for 5 hours. After the polymerization reaction was carried out for 5 hours, the polymerization conversion rate of the resin particles was 91%. Next, 5.0 parts by weight of normal butane as a blowing agent was pressed into the pressure vessel, and the temperature was raised to 115°C. Next, after holding at 115°C for 3 hours, it was cooled to room temperature, and the polymerization slurry was taken out from the pressure vessel. The polymerized slurry taken out was washed, dehydrated, and dried using an airflow dryer to obtain expandable thermoplastic resin particle main body (3). Except for using the expandable thermoplastic resin particle body (3) and changing the antistatic agent A, the antistatic agent B1, the antistatic agent B2, the fusion inhibitor, and the fusion promoter, the same method as in Example 1 was used to obtain expandable thermoplastic resin particles, pre-expanded particles, and foamed molded products. The evaluation results are shown in Table 2 (Examples).

[0081] [Comparative Examples 8 and 9] 100 parts by weight of the expandable thermoplastic resin particle body (1) produced in Example 1 was put into a super mixer (Kawata Co., Ltd., SMV-20), and predetermined amounts of antistatic agent B1, antistatic agent B2, fusion inhibitor, and fusion promoter (castor oil: NOF Corporation) were added, and the mixture was stirred for 120 seconds to obtain expandable thermoplastic resin particles. Pre-expanded particles and foamed molded products were obtained using the same method as in Example 1. The evaluation results are shown in Table 2.

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] As shown in Tables 1 and 2, the expandable thermoplastic resin particles of Examples 1 to 14 were excellent in that they exhibited good fluidity and suppressed powder peeling. In addition, the foamed molded articles obtained from the expandable thermoplastic resin particles had good fusion properties and surface resistance values.

[0086] In contrast, Comparative Examples 1 to 3, in which only a liquid antistatic agent was applied, had poor resin fluidity, and Comparative Examples 4 to 7, in which fatty acid glyceride was used as a liquid antistatic agent, had poor resin fluidity and high surface resistance. Also, Comparative Examples 8 and 9, in which all external additives were powder, had excellent resin fluidity, but there was a lot of powder peeling and the surface resistance value was high.

[0087] From these results, it can be seen that by applying a liquid antistatic agent containing 90% or more of alkylamine to the surface of the expandable thermoplastic resin particle body in the first application step, and then applying at least one of a powder antistatic agent containing 90% or more of alkylamine or a powder antistatic agent containing 90% or more of fatty acid glyceride in the second application step, expandable thermoplastic resin particles can be obtained that maintain good fluidity and suppress powder peeling, and that by using the expandable thermoplastic resin particles, a foamed molded product with appropriate fusion properties and low surface resistance can be obtained. In addition, by further applying a fusion inhibitor to the surface of the expandable thermoplastic resin particle body in the second application step, it is possible to obtain expandable thermoplastic resin particles that have better fluidity and suppress powder peeling.

Claims

1. A step of obtaining an expandable thermoplastic resin particle body containing a blowing agent; a first coating step of coating a surface of the expandable thermoplastic resin particle body with 0.01 to 3 parts by weight of a liquid antistatic agent A containing 90% or more of alkylamine per 100 parts by weight of the expandable thermoplastic resin particle body; a second coating step of coating, after the first coating step, a surface of the expandable thermoplastic resin particle body with at least one of a powdered antistatic agent B1 containing 90% or more of an alkylamine or a powdered antistatic agent B2 containing 90% or more of a fatty acid glyceride; Equipped with In the second coating step, The amount of the antistatic agent B1 used is 0 parts by weight or more and 9 parts by weight or less, The amount of the antistatic agent B2 used is 0 parts by weight or more and 9 parts by weight or less, a weight ratio of the total of the antistatic agent B1 and the antistatic agent B2 to the antistatic agent A is 1 to 10.

2. 2. The method for producing expandable thermoplastic resin particles according to claim 1, further comprising applying a fusion inhibitor to the surface of the expandable thermoplastic resin particle body in an amount of 0.5 parts by weight or less per 100 parts by weight of the expandable thermoplastic resin particle body.

3. The method for producing expandable thermoplastic resin particles according to claim 1 or 2, wherein the antistatic agent A, the antistatic agent B1, and the antistatic agent B2 are poorly soluble in water.

4. The method for producing expandable thermoplastic resin particles according to any one of claims 1 to 3, wherein the alkylamine of the antistatic agent A contains at least one of polyoxyethylene alkylamines or alkyl alkanol amides, each of which has an alkyl group having 10 to 20 carbon atoms.

5. The method for producing expandable thermoplastic resin particles according to any one of claims 1 to 4, wherein the alkylamine of the antistatic agent B1 contains N,N-bis(2-hydroxyethyl)alkylamine (the number of carbon atoms in the alkyl group, C=10 to 20) having one amino group and two hydroxyl groups in the molecule.

6. The method for producing expandable thermoplastic resin particles according to any one of claims 1 to 5, wherein the aliphatic glyceride of the antistatic agent B2 contains at least one selected from the group consisting of fatty acid monoglycerides, fatty acid diglycerides, and fatty acid triglycerides.

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