JP6243186B2 - Method for producing antistatic composite resin expanded particles and molded antistatic composite resin expanded particles - Google Patents

Description

  The present invention relates to a method for producing antistatic composite resin foam particles, and a molded body obtained by in-mold molding of antistatic composite resin foam particles obtained by the method.

  The composite resin foamed particle molded body obtained by in-mold molding of composite resin foam particles composed of a polystyrene resin component and a polyolefin resin component is characterized by excellent molding processability of the polystyrene resin and the polyolefin resin. Since it is possible to achieve both the characteristics of excellent heat resistance and toughness, it is widely used as a packaging material for electronic equipment and precision equipment and as a buffer packaging material.

  In such applications, it is required to impart antistatic performance to the composite resin foamed particle molded body in order to prevent electrical damage due to the occurrence of overcurrent such as dust adhesion or discharge due to static electricity.

  As a method for obtaining the composite resin foamed particles, for example, polyolefin resin particles are used as core particles, vinyl aromatic monomers such as styrene are impregnated in the polyolefin resin particles, and vinyl aromatics are contained in the polyolefin resin particles. A method of obtaining composite resin foamed particles by polymerizing monomers to form composite resin particles, impregnating the composite resin particles with a foaming agent to form foamable composite resin particles, and then foaming the foamable composite resin particles It has been known.

In addition, in order to impart antistatic performance to such a foamed particle molded body, an antistatic agent such as a surfactant is added, and the specific method is as follows (1). The method of (3) is known.
(1) Method of kneading antistatic agent at the time of core particle preparation (2) Method of adding antistatic agent when impregnating monomer into core particle (3) Antistatic agent in dispersion medium in which composite resin particles are dispersed And adding the antistatic agent together with the foaming agent to impregnate the composite resin particles

  However, when a resin composed of a single component is used as a base resin, there is no problem even if an antistatic agent is added by the methods (1) and (2) above, whereas a composite resin is used. In the case of production, the above methods (1) and (2) have a problem in that good antifoaming composite resin particles cannot be obtained because the polymerization of the vinyl aromatic monomer is inhibited by the antistatic agent. In the method (3), when the antistatic agent is impregnated together with the foaming agent, the antistatic agent deeply impregnated in the resin excessively plasticizes the resin so that a large amount of the dispersant adheres to the foamed particles. Thus, there arises a problem that the fusibility between the particles is remarkably lowered, a problem that the heat resistance of the foamed particles is lowered at the time of molding, and the molded body is deformed.

  Further, in the method (3), if the amount of the antistatic agent is increased in order to exhibit sufficient antistatic performance, there arises a problem that the mold filling property of the expanded particles is deteriorated. As described above, according to the conventional methods, it has been difficult to obtain a composite resin foamed particle molded body having good antistatic performance.

  The present invention solves the above-mentioned problems of the prior art, has excellent fusion properties and mold filling properties, and further does not deteriorate the physical properties of the obtained foamed particle molded body, and has excellent antistatic performance. To provide a method for producing an antistatic composite resin foam particle capable of obtaining a particle molded body, and an antistatic composite resin foam particle molded body obtained by in-mold molding of the foam particles obtained by the production method. Objective.

According to this invention, the manufacturing method of the antistatic composite resin expanded particle shown below and the antistatic composite resin expanded particle molded object are provided.
[1] A composite resin containing 50 to 95% by mass of a polystyrene resin component and 5 to 50% by mass of a polyolefin resin component (however, the total amount of the polystyrene resin component and the polyolefin resin component is 100% by mass) (A) and / or (b) a cationic antistatic agent that does not contain chlorine in an amount of 0.4 to 100 parts by mass with respect to 100 parts by mass of the composite resin foam particles. A method for producing antistatic composite resin foamed particles, wherein 3.5 parts by mass is applied.
[ 2 ] The method for producing antistatic composite resin foamed particles according to [1] , wherein the cationic antistatic agent (a) is lauryldimethylethylammonium ethyl sulfate.
[ 3 ] The antistatic composite resin according to [1] , wherein the cationic antistatic agent (b) is a mixture of 1-ethyl-3-methylimidazolium ethyl sulfate and lauryldiethanolamine. A method for producing expanded particles.
[ 4 ] A surface resistivity of 1 × 10 ¹³ Ω or less, obtained by in-mold molding of the antistatic composite resin foamed particles obtained by the production method according to any one of [1] to [3] , An antistatic composite resin foamed particle molded body having a voltage decay time of 3 seconds or less and a density of 10 to 200 kg / m ³ .

According to the present invention, by applying a specific amount of a cationic antistatic agent to a composite resin foamed particle including a polystyrene resin component and a polyolefin resin component, the antistatic agent has a good antistatic performance and a mold. Antistatic composite foamed resin particles having excellent filling properties and fusion properties can be obtained. Further, the antistatic composite resin foamed particle molded body (hereinafter also simply referred to as a foamed particle molded body or a molded body) obtained by in-mold molding of the antistatic composite resin foamed particles obtained in the present invention is shrunk. It is difficult to form a foamed particle molded body.
In particular, by using the antistatic agent (a) and / or (b), it is possible to obtain a foamed particle molded body having excellent fusion property and less shrinkage deformation, and reducing the voltage decay time of the foamed particle molded body. In addition, a specific effect that the surface resistivity can be reduced is obtained.
According to the present invention, since the antistatic composite resin foam particles (hereinafter also simply referred to as foam particles) are produced by applying a cationic antistatic agent to the composite resin foam particles, the antistatic agent There is no risk of spilling into the waste water, and excellent environmental harmony is obtained.

Hereinafter, the manufacturing method of the antistatic composite resin expanded particle of the present invention and the antistatic composite resin expanded particle molded body obtained by the method will be described in detail.
In the production method of the present invention, for example, first, composite resin particles are produced (composite resin particle production process), and the composite resin particles are impregnated with a foaming agent and further expanded to produce composite resin foam particles (composite resin foam particle production). Process). Next, the antistatic composite resin foamed particles are obtained by applying an antistatic agent to the foamed particles (antistatic agent coating step).

[Antistatic coating process]
As the antistatic agent used in the method of the present invention, a cationic antistatic agent is used. Since polyolefin polymers such as polyethylene are generally easily charged negatively, it is considered that excellent antistatic performance is exhibited when a cationic antistatic agent is used. Since chloride ions may corrode metals such as molding dies, it is preferable to use those that do not contain chloride ions as counter ions.

As the cationic antistatic agent, the following (a) and (b) are preferable.
(A) Aliphatic quaternary ammonium sulfate (b) Mixture of imidazolium sulfate and aliphatic amino alcohol

Examples of (a) include compounds represented by the following formula (1).

In the formula (1), R _{1 to} R ₄ groups each represent an alkyl group having 1 to 17 carbon atoms.
The R _{2 to} R ₄ groups in the formula (1) are each preferably a linear saturated alkyl group having 1 to 3 carbon atoms, and the R ₁ group is preferably a linear saturated alkyl group having 5 to 17 carbon atoms. . In particular, lauryldimethylethylammonium ethyl sulfate in which R ₁ group is a straight-chain saturated alkyl group having 12 carbon atoms, R ₂ group is an ethyl group, and R ₃ and R ₄ groups are methyl groups is preferable.
Specific examples of the antistatic agent (a) include lauryldimethylethylammonium ethyl sulfate “Katiogen ES-L” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

Examples of the aliphatic amino alcohol (b) include compounds represented by the following formula (2).

In the formula (2), R ₅ OH and R ₆ OH are each preferably a linear saturated alcohol chain having 1 to 3 carbon atoms, and the linear saturated alcohol chain is more preferably ethanol. The number of carbon atoms in the linear alkyl group R ₇ is preferably an integer of 5 to 17, and particularly preferably a carbon number of 12.

Examples of the imidazolium sulfate (b) include compounds represented by the formula (3).

The imidazolium compound of imidazolium sulfate represented by formula (3), R ₈ group is preferably a carbon number of R ₉ groups is from 1 to 3 alkyl groups each, R ₈ group, R ₉ groups are 1-ethyl-3-methylimidazolium ethyl sulfate, which is a methyl group and an ethyl group, respectively, is more preferable.

  Further, the mixing ratio of the aliphatic amino alcohol and the imidazolium sulfate of the antistatic agent (b) is preferably 10:90 to 50:50, more preferably 20:80 to 40:60 by weight. preferable. If it is this range, it can be set as the expanded particle which exhibits antistatic performance effectively.

Specific examples of the antistatic agent (b) include 1-ethyl-3-methylimidazolium ethyl sulfate “Elegan C607L” manufactured by NOF Corporation.

  By using a cationic antistatic agent typified by (a) and / or (b), the antistatic performance of the composite resin foamed particles is improved, and a molded product obtained by molding the composite resin particles in a mold Is excellent in fusibility and shrinkage deformation is small. As described above, since polyolefin polymers such as polyethylene are generally easily charged negatively, it is considered that excellent antistatic performance is exhibited when cationic antistatic agents such as (a) and (b) are used. In addition, since chloride ions may corrode metals such as molding dies, the antistatic agent used in the present invention is one containing no chloride ions as a counter ion.

In the method of the present invention, the antistatic agent is applied in an amount of 0.4 to 3.5 parts by mass with respect to 100 parts by mass of the composite resin foam particles. If the coating amount is too small, sufficient antistatic performance may not be exhibited. On the other hand, when the coating amount is too large, the foamed particles are agglomerated when the foamed particles are filled into the mold, and the filling property into the mold is lowered.
From the above viewpoint, the application amount of the antistatic agent is preferably 0.5 to 3 parts by mass, and more preferably 0.7 to 2.5 parts by mass with respect to 100 parts by mass of the composite resin foamed particles.

The amount of the antistatic agent attached to the actual foamed particles is slightly smaller than the coating amount, and is about 85 to 95% by weight.
The adhesion amount of the antistatic agent is determined by subtracting the weight of the composite resin foamed particles before coating from the weight of the composite resin foamed particles sufficiently dried after the antistatic agent is applied.

  It is important to apply the antistatic agent to the composite resin foam particles. In the method of kneading the antistatic agent when polymerizing the core particles and composite resin particles, there is a possibility that good foamable composite resin particles may not be obtained due to inhibition of polymerization, or even if expanded particles are obtained. There is a possibility that a sufficient antistatic performance cannot be obtained. In the method in which the antistatic agent is impregnated in the pressure vessel, when the molded body is formed, there is a possibility that the fusion rate is lowered or the molded body is contracted and deformed. In addition, the method of applying to the composite resin foam particle molded body is more uneven when applying the antistatic agent than the method of applying to the composite resin foam particle, and the antistatic performance becomes non-uniform and antistatic. There is a possibility that a part where the performance is insufficient may be formed.

  Examples of the method of applying the antistatic agent to the composite resin foam particles include spray coating, airless coating, dip coating, blending, or other coating methods based on these methods and principles. In spray coating, the antistatic agent is allowed to flow when sprayed onto the composite resin foam particles, or the composite foam particles are agitated after spraying and the antistatic agent solution adheres to the entire surface of the composite resin foam particles. It is preferable to do so.

  In addition, the antistatic agent used for application | coating may be dilution liquids, such as a stock solution, powder, water, or alcohol, and there is no restriction | limiting in the density | concentration. Furthermore, the container for applying the antistatic agent to the foamed particles may be either a closed system or an open system, and the temperature only needs to be equal to or lower than the heat resistant temperature of the composite resin foamed particles. Specifically, for example, an antistatic agent is diluted with water to form an aqueous solution, and after the aqueous solution is applied to the composite resin foam particles, the composite resin particles are stirred and mixed to uniformly apply the antistatic agent to the composite resin foam particles. Is possible. In the method of the present invention, any of the above coating methods or a combination thereof can be used.

[Composite resin particle manufacturing process]
An example of a method for producing composite resin particles (hereinafter also simply referred to as resin particles) used in the present invention is an impregnation polymerization method. Specifically, polyolefin resin particles (core particles) made of polyethylene or the like are first produced by an extruder or the like, and the polyolefin resin particles are placed in a heat and pressure resistant reaction vessel with a dispersion medium, a dispersant, a styrene monomer, and polymerization starts. The olefin monomer is impregnated with the styrene monomer by heating and stirring together with the agent, and polymerized to produce composite resin particles. In addition to the impregnation polymerization method, an extrusion melt-kneading method, and other production methods based on these methods and principles can be employed.

  The polyolefin resin used in the present invention is low density polyethylene, linear low density polyethylene, high density polyethylene, ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer. Ethylene resins such as a polymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-acrylic acid alkyl ester copolymer, and an ethylene-methacrylic acid alkyl ester copolymer can be used. Also, propylene resins such as propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, propylene-4-methylpentene-1 copolymer Can be used. Furthermore, a mixture of two or more of these may be used.

  The melting point of the polyolefin resin is preferably 70 ° C to 160 ° C, and more preferably 85 ° C to 145 ° C. If the melting point is too low, it is necessary to take measures to prevent sticking in order to prevent the particles from sticking together when the composite resin foamed particles are produced. As a result, the manufacturing cost may increase. Further, in this case, the heat resistance performance of the composite resin foamed particle molded body is remarkably lowered, making it difficult to use in a high temperature environment, and the practicality may be deteriorated. On the other hand, if the melting point is too high, the temperature of the heating medium required for in-mold molding becomes too high when molding composite resin foam particles by in-mold molding, making molding with existing molding machines difficult. There is a risk. The melting point of the olefinic resin seed particles is 2 to 4 mg of the olefinic resin particles based on the heat flux DSC of JIS K7121 (1987) “when melting temperature is measured after performing a certain heat treatment”. It is the peak temperature of the endothermic peak in the DSC curve obtained by heating at a rate of temperature increase of 10 ° C./min.

  As other additives, the polyolefin-based resin particles may contain additives such as a bubble adjusting agent, a pigment, a slip agent, and a flame retardant, as long as the effects of the present invention are not impaired. Examples of the air conditioner for adjusting the average cell diameter of the composite resin expanded particles include conventionally known inorganic materials such as talc, silica, aluminum hydroxide, zinc borate, and polytetrafluoroethylene powder. The organic type can be used.

  Examples of the method for producing the polyolefin resin particles include a method of blending the above-mentioned additives and the like into the polyolefin resin, melt-kneading and then finely pulverizing. Melt kneading and atomization can be performed by an extrusion apparatus. At this time, the additive can be kneaded as it is into the base resin, but in order to perform more uniform kneading, a master batch in which the additive is dispersed in the polyolefin resin is usually prepared. It is preferable to use a method in which the polyolefin resin and the polyolefin resin are supplied to an extruder and kneaded.

  Fine granulation for obtaining the polyolefin resin particles can be obtained by pelletizing the melt-kneaded product obtained by the extruder by a strand cut method, a hot cut method, an underwater cut method or the like. In addition, as long as the desired polyolefin resin particle is obtained, it can also be performed by other methods.

  In order to produce the composite resin particles, styrene monomers impregnated in the core particles include styrene and α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinyl which are styrene derivatives. Toluene, p-ethylstyrene, 2,4-dimethylstyrene, p-methoxystyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, 2,4-dichlorostyrene, pn- Examples thereof include butyl styrene, pt-butyl styrene, pn-hexyl styrene, p-octyl styrene, styrene sulfonic acid, sodium styrene sulfonate, and the like.

  In the production of the foamed composite resin particles, the styrene monomer impregnated in the core particles is a composite resin containing 50 to 95% by mass of a polystyrene resin component and 5 to 50% by mass of a polyolefin resin component. To be added. The polystyrene resin component in the composite resin particles is preferably 60 to 90 mass%, more preferably 65 to 85 mass%, and the polyolefin resin component is preferably 10 to 40 mass%, more preferably 15 to 35 mass%.

  In the method of the present invention, a monomer copolymerizable with the styrenic monomer can be used in combination. Examples of the copolymerizable monomer include alkyl esters having 1 to 10 carbon atoms of acrylic acid such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. Also, methacrylic acid having 1 to 10 carbon atoms such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate, containing no nitrile groups such as acrylonitrile and methacrylonitrile. And saturated compounds. These monomer components copolymerizable with the styrenic monomer can be copolymerized with the styrenic monomer alone or in combination of two or more. The ratio of the copolymerization monomer component to the styrene monomer is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the styrene monomer.

In the composite resin particle production process, in order to uniformly polymerize the styrene monomer in the polyolefin resin particles, it is important to polymerize after impregnating the polyolefin resin particles with the styrene monomer. In this case, crosslinking may occur with the polymerization of the styrene monomer. Therefore, in the polymerization of the styrene monomer, a crosslinking reaction can be intentionally caused by using a crosslinking initiator together with a polymerization initiator as necessary. When using a polymerization initiator and a crosslinking agent, it is preferable to dissolve in a styrene monomer in advance.
In the polymerization process of the styrene-based monomer, the olefin contained in the polyolefin-based resin particles may be cross-linked. Therefore, in this specification, “polymerization” is used to include “cross-linking”.

  As said polymerization initiator, what is used for the suspension polymerization method of the styrene-type monomer at the time of obtaining a well-known polystyrene resin, for example, is soluble in a styrene-type monomer, and 10 hours half-life temperature is 50-120 degreeC Can be used. Specifically, for example, cumene hydroxy peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t- Organic peroxides such as amylperoxy-2-ethylhexyl carbonate, hexylperoxy-2-ethylhexyl carbonate, lauroyl peroxide, and azo compounds such as azobisisobutyronitrile can be used. These polymerization initiators can be used alone or in combination of two or more.

  As the crosslinking agent, one that does not decompose at the polymerization temperature but decomposes at the crosslinking temperature can be used. Specifically, for example, peroxides such as dicumyl peroxide, 2,5-t-butyl perbenzoate, and 1,1-bis-t-butyl peroxycyclohexane can be used. The said crosslinking agent can be used individually or in combination of 2 or more types. It is preferable that the compounding quantity of the said crosslinking agent is 0.1-5 mass parts with respect to 100 mass parts of styrene-type monomers. In addition, the same compound can also be employ | adopted as the said polymerization initiator and the said crosslinking agent.

  If necessary, other additives such as a plasticizer, an oil-soluble polymerization inhibitor, a flame retardant, a dye, and a bubble regulator can be added to the styrene monomer.

  In addition, a surface coating agent can be added to the composite resin particles dehydrated and dried after polymerization as long as the effects of the present invention are not hindered. Examples of the surface coating agent include zinc stearate, stearic acid triglyceride, stearic acid monoglyceride, castor hardened oil, and the like.

[Production process of foamed composite resin particles]
The composite resin foamed particles used in the present invention can be produced, for example, by a dispersion medium releasing foaming method. Specifically, the prepared resin particles are dispersed in an aqueous medium in a closed container and heated to impregnate a physical foaming agent to form expandable resin particles, and the expandable resin particles are aqueous from the closed container at an appropriate foaming temperature. It can be released with the medium to produce expanded particles. In this method, the foaming agent impregnation step and the foaming step can be carried out as separate steps, but usually the foaming agent impregnation step and the foaming step are carried out continuously as described above.

In the production of the composite resin foamed particles, as a dispersion medium for dispersing the composite resin particles, a medium that does not dissolve the composite resin particles can be used. As such a dispersion medium, for example, ethylene glycol, glycerin, methanol, ethanol and the like can be used, but water is preferably used.
In the dispersion medium, a poorly water-soluble inorganic substance such as aluminum oxide, tricalcium phosphate, magnesium pyrophosphate, zinc oxide, and kaolin so that the composite resin particles are uniformly dispersed in the dispersion medium as necessary. It is preferable to disperse a dispersing aid such as a dispersing agent such as anionic surfactants such as sodium dodecylbenzenesulfonate and sodium alkanesulfonate.

  The amount of the dispersant added to the dispersion medium when producing the composite resin foam particles can be determined based on the mass of the composite resin particles, and the mass of the composite resin particles and the mass of the dispersant The ratio (mass of the composite resin particles / mass of the dispersant) is preferably 20 to 2000, and more preferably 30 to 1000. The ratio of the mass of the dispersant to the mass of the dispersion aid (the mass of the dispersant / the mass of the dispersion aid) is preferably 0.1 to 500, and more preferably 1 to 50.

  Further, in the step of impregnating the resin particles with the physical foaming agent by press-fitting the physical foaming agent into the pressure vessel, a liquid phase impregnation method or a gas phase impregnation method can be appropriately selected. In the gas impregnation pre-foaming method, as the physical foaming agent, nitrogen, carbon dioxide, argon, air, helium, water and other inorganic gases, methane, ethane, propane, normal butane, isobutane, cyclobutane, normal pentane, isopentane, neopentane, cyclohexane Organic volatile gases such as pentane, normal hexane, cyclohexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane can be used.

  The blending amount of the physical foaming agent is determined in consideration of the apparent density of the target composite resin foamed particles, the composition of the base resin, the type of the physical foaming agent, and the like. So as to be impregnated in the range of 0.5 to 30 parts by mass with respect to parts.

  In the dispersion medium release foaming method, the softened composite resin particles impregnated with the physical foaming agent in the pressure resistant container are discharged together with the dispersion medium from the pressure resistant container to a lower pressure region (usually under atmospheric pressure) than in the container. Thus, the foamable composite resin particles are foamed to obtain composite resin foam particles. When releasing expandable composite resin particles from the pressure vessel, the temperature and pressure in the pressure vessel must be kept constant in order to reduce the variation in apparent density and bubble diameter of the obtained expanded particles. Or gradually increasing. In this case, the pressure in the pressure vessel is adjusted so that the pressure in the pressure vessel is not lowered rapidly by applying a back pressure in the pressure vessel with a gas similar to the foaming agent, or an inorganic gas such as nitrogen or air, This is done by releasing the contents.

  The foaming method of the composite resin particles that can be used in the method of the present invention is not limited to the above-described method, and any method may be used as long as a molded body can be obtained by filling the mold and heating. .

The foamed particles obtained as described above preferably have an apparent density of 10 to 300 kg / m ³ , more preferably 20 to 200 kg / m ³ .

[Antistatic composite resin foam particles]
The antistatic composite resin expanded particle molded body of the present invention (hereinafter also simply referred to as expanded particle molded body) is filled with antistatic agent-based composite resin particles obtained by the above-described method in a mold, and saturated water vapor. It can be obtained by in-mold molding that is heated by a heating medium such as The composite resin foam particle molded body obtained from the composite resin foam particles has excellent antistatic performance, and is excellent in the fusion property between the foam particles and the dimensional stability.

  The fusion rate as an index of the mutual fusion state of the composite resin foam particles constituting the foamed particle molded body is preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more. In the present invention, since the cationic antistatic agent is used, the mutual fusion state of the expanded particles becomes good.

The density of the composite resin expanded particle molded body is preferably 10 to 200 kg / m ³ , particularly preferably 15 to 100 kg / m ³ . If the density of the molded body is within this range, thermal shrinkage will not occur during molding heating, and mechanical properties may be insufficient due to a significant increase in molding vapor pressure or density variation of the foamed particle molded body. Absent.

The surface resistivity of the composite resin foamed particle molded body based on JIS K 6271 is preferably 1 × 10 ¹³ Ω / □ or less, more preferably 5 × 10 ¹² Ω / □ or less, and 2 × 10 ^12. More preferably, it is Ω / □ or less.
Further, the charged voltage decay time of the composite resin foamed particle molded body is preferably within 10 seconds, more preferably 5 seconds or less, and particularly preferably 3 seconds or less.

  The charged voltage decay time is measured using a CPM (charged plate monitor). Specifically, the test piece is cut out from the molded body so that the skin surface remains, and the test piece left to stand for 24 hours or more in an atmosphere of 23 ° C. and 50% humidity is applied to the detection plate using a CPM (charged plate monitor). Place the electrodes in contact with each other, charge the detection plate to 1.25 kV, contact the ground with the skin surface on the upper surface of the sample, and reduce the voltage from the time until the voltage of the detection plate drops from 1.0 kV to 0.1 kV Measure time.

  In addition, it is preferable that the composite resin foamed particle molded body in the present invention satisfies the above range in both the surface resistivity and the charged voltage decay time.

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to the examples.

[Example 1]
[Composite resin particle manufacturing process]
(1) Production of core particles 14.36 kg of linear low-density polyethylene resin (trade name: Nipolon 9P51A, manufactured by Tosoh Corporation) and an ethylene-vinyl acetate copolymer (Tosoh) having a vinyl acetate component content of 15% by mass Co., Ltd., trade name: Ultrasen 625) 4.98 kg, linear low density polyethylene resin (manufactured by Tosoh Corporation, trade name: Nipolon 9P51A) and zinc borate (Tonda Pharmaceutical Co., Ltd., boric acid) 0.66 kg of 10% zinc borate masterbatch containing 10% by weight of zinc 2335, average particle size: 6 μm) was manufactured by an extruder (Ecage Co., Ltd., model: MS50-28; 50 mmφ single screw extruder, Maddock type Screw) kneading at 230-250 ° C, extruding, and 0.4-0.6mg / piece (average 0.5mg / piece) polyethylene resin by underwater cutting method Give the child (nuclear particles).

(2) Production of Composite Resin Particles After adding 1000 g of deionized water to an autoclave with an internal volume of 3 L equipped with a stirrer and adding 6 g of sodium pyrophosphate, powdered magnesium nitrate hexahydrate 12. 9 g was added and stirred at room temperature for 30 minutes. This produced the magnesium pyrophosphate slurry as a suspending agent.
Next, 1.5 g of sodium lauryl sulfonate (10 wt% aqueous solution) as a surfactant, 5.0 g of sodium nitrite (1 wt% aqueous solution) as a water-soluble polymerization inhibitor, and core particles 150 g was charged.
Subsequently, 1.715 g of benzoyl peroxide (“NIPER BW” manufactured by NOF Corporation, water-diluted powder product) as a polymerization initiator and 0.258 g of t-butylperoxy-2-ethylhexyl monocarbonate (NOF ( "Perbutyl E"), and 1,1-di (tertiarybutylperoxy) cyclohexane ("Lupelox 331M70" manufactured by Arkema Yoshitomi Co., Ltd.) as a cross-linking agent, 335 g of styrene as a monomer and The resultant was dissolved in 15 g of butyl acrylate, and the dissolved product was charged into the suspension in the autoclave while stirring at a stirring speed of 500 rpm.

Next, after the inside of the autoclave was purged with nitrogen, the temperature was raised and the temperature was raised to 88 ° C. over 1 hour and a half. After the temperature increase, the temperature was maintained at 88 ° C. for 30 minutes, and then the stirring speed was lowered to 450 rpm and the temperature was cooled to 82 ° C. over 15 minutes. After cooling, the temperature was maintained at 82 ° C. for 5 hours. Next, the temperature was raised to 120 ° C. over 2 hours and held at 120 ° C. for 5 hours.
Then, it cooled to the temperature of 90 degreeC over 1 hour, the stirring speed was reduced to 400 rpm, and it hold | maintained at the temperature of 90 degreeC for 3 hours. Further, the temperature was raised to 105 ° C. over 2 hours, held at 105 ° C. for 5 hours, and then cooled to 30 ° C. over about 6 hours.
After cooling, the contents were taken out, and nitric acid was added to dissolve the magnesium pyrophosphate adhering to the surface of the composite resin particles. Thereafter, it is dehydrated and washed with a centrifugal separator, and water adhering to the surface is removed with an air flow dryer. Composite resin particles having an average particle diameter (d63) of about 1.5 mm (69% by weight of polystyrene component, 31% by weight of polyethylene component) %).

[Production process of foamed composite resin particles]
Using 500 g of the composite resin particles obtained in the composite resin particle production process as a dispersion medium, 3.5 L of water is charged into a 5 L pressure vessel equipped with a stirrer, and further 3 g of kaolin as a dispersant and a surface activity in the pressure vessel. 0.04 g of sodium alkylbenzene sulfonate as an agent was added. Next, after the temperature was raised to 160 ° C. while stirring at 300 rpm, carbon dioxide as an inorganic physical foaming agent was pressed into the pressure resistant container to 4.0 MPa and held for 15 minutes with stirring to obtain expandable resin particles. Thereafter, the valve is opened and foamed while maintaining the pressure in the pressure vessel at 4.0 MPa with the back pressure of carbon dioxide, and the composite resin foam particles are sent to the receiving net tank through the pipe, and then in an oven at 60 ° C. for 3 hours. By drying, composite resin expanded particles having an apparent density of 49 kg / m ³ were obtained.

[Antistatic agent application process]
As an antistatic agent, 100 parts by mass of the composite resin foam particles, 0.5 parts by mass of lauryldimethylethylammonium ethyl sulfate (Daiichi Kogyo Seiyaku Co., Ltd. “Catiogen ES-L” (active ingredient 50%) 1 mass) Part) diluted with 4 parts by mass of water was put into a 50 L plastic bag and the mouth was closed. After thoroughly shaking this, the bag was placed in a tumbler and mixed for 30 minutes, and an antistatic agent was applied to the foamed particles. The coated composite resin foamed particles were dried in an oven at 40 ° C. for 12 hours.

[In-mold]
The antistatic composite resin foamed particles were filled into a flat plate mold having a length of 200 mm, a width of 700 mm, and a thickness of 50 mm using an in-mold molding machine, and molded. The molding conditions were as follows: the molded article after molding was heated for 15 seconds at a steam pressure of 0.1 MPa (gauge pressure) at which the surface smoothness was visually good. When the pressure reached 02 MPa (gauge pressure), the mold was opened to release the molded body.
The obtained foamed molded article had excellent antistatic performance with a CPM band voltage decay time of 1.3 seconds and a surface resistivity of 7.7 × 10 ¹² Ω.

[Example 2]
In the antistatic agent coating step of Example 1, foamed particles were produced in the same manner except that 3 parts by mass of lauryldimethylethylammonium ethyl sulfate was applied to 100 parts by mass of the composite resin foamed particles. Compared with Example 1, since the coating amount was as large as 3 parts by mass, a molded article having more excellent antistatic performance was obtained.

Example 3
In the antistatic agent coating step described in Example 1, a mixture of 1-ethyl 3-methylimidazolium ethyl sulfate (33 wt%) and lauryl diethanolamine (67 wt%) with respect to 100 parts by mass of the composite resin expanded particles Expanded particles were prepared by the same method except that 1 part by mass (“Elegan C607L” manufactured by NOF Corporation) was applied.
Even when the antistatic agent was used, a foamed particle molded article excellent in antistatic performance was obtained.

[Comparative Example 1]
In the antistatic agent coating process described in Example 1, the coating amount is an amount smaller than the range of the present invention. It was produced in the same manner as in Example 1 except that lauryldimethylethylammonium ethyl sulfate was applied as 0.25 part by mass with respect to 100 parts by mass of the composite resin foamed particles. Since the amount of the antistatic agent was too small, the value of the charged voltage decay time and the surface resistivity was large, and sufficient antistatic performance could not be obtained.

[Comparative Example 2]
In the antistatic agent coating step described in Example 1, the coating amount is an amount larger than the range of the present invention. Since there were too many lauryl dimethyl ethyl ammonium ethyl sulfate with 4 mass parts with respect to 100 mass parts of composite resin expanded particles, mold filling property worsened and the favorable composite resin expanded particle molded object was not obtained.

[Comparative Example 3]
In the composite resin particle manufacturing process of Example 1, 1 part by mass of lauryldimethylethylammonium ethyl sulfate (“Katiogen ES-L” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (effective) An attempt was made to produce composite resin particles by the same method as in Example 1 except that 50%) and 2 parts by mass) were added during the preparation of the core particles. As a result, polymerization was inhibited and good foamable composite resin particles could not be obtained.

[Comparative Example 4]
After preparing composite resin particles by the same method as in Example 1, 100 parts by weight of composite resin particles and 1 part by weight of lauryldimethylethylammonium ethyl sulfate as an antistatic agent (“Kachiogen ES-L” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (effective 2% by weight of component 50%) was placed in a 10 L plastic bag and the mouth was closed. After thoroughly shaking this, it was dried in an oven at 40 ° C. for 12 hours. After drying, 500 g of the composite resin particles were mixed with 3 g of kaolin and 0.04 g of sodium dodecylbenzenesulfonate (“Neogen S20-F” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersion aid in a sealed container having an internal volume of 5 liters. Disperse in 3500 g of water, raise the temperature to 165 ° C. while stirring at 300 rpm, introduce carbon dioxide as a foaming agent into the container until the pressure in the container reaches 4.0 MPa, hold for 15 minutes, and then carbon dioxide. Is introduced into the container, a back pressure equal to the equilibrium vapor pressure of the blowing agent is applied, and the contents in the pressure-resistant container are released under atmospheric pressure so as to keep the container internal pressure constant, and an apparent density of 49 g / L. Composite resin foam particles were obtained. In-mold molding was performed in the same manner as in Example 1 except that the antistatic agent was not applied using the obtained composite resin foamed particles. When the antistatic agent is applied at the stage of the composite resin particles before foaming, in addition to the surface resistivity being too high to be measured, the charged voltage decay time is longer than 10 seconds, and sufficient antistatic performance is obtained. It was not obtained.

[Comparative Example 5]
After preparing composite resin particles in the same manner as in Example 1, 500 g of composite resin particles were placed in a sealed container having an internal volume of 5 L, 3 g of kaolin, and sodium dodecylbenzenesulfonate as a dispersion aid (Neogen S20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). -F ") is dispersed in 3500 g of water containing 0.04 g, heated to 165 ° C while stirring at 300 rpm, and carbon dioxide as a blowing agent is introduced into the container until the pressure in the container reaches 4.0 MPa. After holding for 15 minutes, carbon dioxide is introduced into the container and a back pressure equal to the equilibrium vapor pressure of the blowing agent is applied to keep the container internal pressure constant. The composite resin foamed particles having an apparent density of 49 g / L were obtained. In-mold molding was performed in the same manner as in Example 1 except that the antistatic agent was not applied using the obtained composite resin foamed particles.
When an antistatic agent was added in the foaming step, in addition to the surface resistivity being 10 ¹⁵ Ω or more, the charged voltage decay time was longer than 10 seconds, and sufficient antistatic performance was not obtained. In addition, dents due to shrinkage deformation were observed in the obtained molded product, and a good molded product could not be obtained.

[Comparative Example 6]
A molded body was prepared in the same manner as in Example 1 except that the antistatic agent was not applied to the expanded particles, and 1 mass of lauryldimethylethylammonium ethyl sulfate with respect to 100 parts by mass of the composite resin expanded particles on the entire surface of the obtained molded body. 2 parts by weight of a part (2 parts by weight of “Kachiogen ES-L” (active ingredient 50%) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied with a brush and then dried in an oven at 40 ° C. for 12 hours or more. I let you.
When an antistatic agent was applied to the molded body, the charged voltage decay time was longer than 10 seconds, and sufficient antistatic performance could not be obtained. Further, in the method of applying the antistatic agent to the molded body with a brush, the antistatic agent is not uniformly applied, and the antistatic performance is uneven.

[Comparative Example 7]
The composite was made in the same manner as in Example 1 except that 1 part by mass of polyoxyethylene alkylamine ether phosphate ester (“Plysurf A208F” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to 100 parts by mass of the composite resin expanded particles. Resin foam particles were prepared. The surface resistivity was 1.3 × 10 ¹⁴ Ω, and sufficient surface resistivity was not obtained.

[Comparative Example 8]
This is an example in which the antistatic agent is changed in the antistatic agent application step. In the same manner as in Example 1, except that 1 part by mass of polyoxyethylene alkylamine ether (“Amiradin C1802” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to 100 parts by mass of the composite resin foamed particles. Then, a molded body was produced in the same manner as in Example 1. The obtained molded body had a charged voltage decay time longer than 10 seconds, and sufficient antistatic performance could not be obtained.

[Comparative Example 9]
This is an example in which the antistatic agent is changed from that of Example 1. Example 1 was applied except that 1 part by mass of sodium alkyl sulfate (2 parts by mass of “Electro Stripper ME2” (active ingredient 50%) manufactured by Kao Corporation) was applied to 100 parts by mass of the composite resin foamed particles. Composite resin foam particles were prepared, and a molded body was prepared in the same manner as in Example 1. In addition to the surface resistivity of the obtained molded body being 10 ¹³ Ω or more, the charged voltage decay time was longer than 10 seconds, and sufficient antistatic performance was not obtained.

[Comparative Example 10]
This is an example in which the antistatic agent is changed from that of Example 1. Implementation was performed except that 1 part by mass of lauryldimethylaminoacetic acid betaine (2.6 parts by mass of “Amorgen S” (active ingredient 38%) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was applied to 100 parts by mass of the composite resin expanded particles. Composite resin foam particles were produced in the same manner as in Example 1, and further, a molded article was produced in the same manner as in Example 1. The obtained molded article had a surface resistivity of 10 ¹⁵ Ω or more, sufficient antistatic performance could not be obtained, and the charged voltage decay time was longer than 10 seconds, and sufficient charged voltage decay performance could not be obtained.

  Table 1 shows the types of antistatic agents and active ingredients in Examples and Comparative Examples, Table 2 shows the manufacturing conditions, physical properties and evaluation of the foamed particles and the molded foamed products, and Table 3 shows the comparative examples. 4 shows.

Measurement and evaluation of physical properties in Examples and Comparative Examples were performed by the following methods.
[Measurement of antistatic agent adhesion]
In the antistatic agent application step, first, the weight of the expanded particles before application of the antistatic agent was precisely weighed. Thereafter, the composite resin foam particles were coated with an arbitrary antistatic agent coating amount (effective component amount) by a required method, and then dried at 40 ° C. for 24 hours, and then the weight of the foamed particles was measured. The value obtained by subtracting the weight before coating from the weight after coating is divided by the weight of the composite resin foam particles before application of the antistatic agent, and the value is multiplied by 100 to prevent the charge to 100 parts by mass of the composite resin foam particles. The adhesion amount of the agent was determined.

[Apparent density of expanded particles]
The foamed particles were dried in an oven at 40 ° C. for 12 hours, and then allowed to stand in an environment at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. The foamed particles were submerged in a graduated cylinder containing water to determine the volume. The apparent density (kg / m ³ ) of the composite resin foamed particles was determined by dividing the weight by the volume and converting the unit.

[Foamed particle density]
The volume was determined from the external dimensions of the foamed particle molded body that was allowed to stand for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%. Subsequently, the weight of the foamed particle molded body was divided by the volume, and the unit density was calculated to obtain the molded body density (kg / m ³ ) of the composite resin foamed particle molded body.

[Evaluation of voltage attenuation]
The charged voltage attenuation performance of the compact was evaluated. A molded sample coated with an antistatic agent of skin surface (150 × 150) × thickness (50 mm), which was allowed to stand for 24 hours or more in an atmosphere of 23 ° C. and 50% humidity, was a handheld charged plate monitor manufactured by Trek Japan Co., Ltd. 159HH) was placed so that the skin surface was in contact with it, and the detection plate was charged to 1.25 kV. The decay time until the voltage of the detection plate was lowered from 1.0 kV to 0.1 kV by contacting the ground with the skin surface on the upper surface of the sample was measured.
In addition, when the voltage did not attenuate to 0.1 kV even after 30 seconds, “not attenuated” was set.
In the evaluation of the voltage decay, when the decay time was within 10 seconds, the test was evaluated as ◯.

[Surface resistivity]
The antistatic performance of the molded body was evaluated by measuring the surface resistivity. The surface resistivity was measured after curing the molded body for 1 day under the conditions of 23 ° C. and 50% humidity by a method based on JIS K 6271 (2008). The surface resistivity in the table is a geometric mean value of values obtained by cutting a foam molded body into a length of 200 mm, a width of 200 mm, and a thickness of 50 mm to prepare a measurement test piece, and measuring the skin surface at four points using the measurement test piece. is there. Incidentally, those portions of the surface resistivity is not less than 10 ¹⁵ Omega had also at one point was denoted as "10 15 ^<". Those having a resistance of 10 ¹³ Ω or less were regarded as non-defective products. “HIRESTA MCP-HT450” manufactured by Mitsubishi Chemical Corporation was used as a measuring device.

[Evaluation of mold filling properties]
When the expanded particles were sent to a molding machine and subjected to in-mold molding, it was evaluated whether or not normal filling was possible. The case where it was omissible if it could be normally filled and a lump of expanded particles was seen and the mold could not be filled smoothly was evaluated as x.

[Fusability evaluation]
The foamed particle molded body is bent approximately equally, and the number of foam particles broken by observing the fracture surface is divided by the number of all foam particles present on the fracture surface to give 100. The fusion rate (percentage) was obtained by multiplying, and those having a fusion rate of 60% or more were evaluated as “○” and those less than 60% as “×”.

[Evaluation of molding shrinkage]
After molding the expanded particles and curing the molded body for 1 day under the conditions of 23 ° C. and 50% humidity, it is visually determined whether or not the formed molded body is contracted and deformed. What was seen was set as x.

Claims (4)

A composite resin containing 50 to 95% by mass of a polystyrene resin component and 5 to 50% by mass of a polyolefin resin component (however, the total amount of the polystyrene resin component and the polyolefin resin component is 100% by mass). ) To the composite resin foamed particles composed of the following (a) and / or (b) a chlorine-free cationic antistatic agent in an amount of 0.4 to 3.5 with respect to 100 parts by mass of the composite resin foamed particles. A method for producing an antistatic composite resin foamed particle, characterized by applying a mass part.
(A) Aliphatic quaternary ammonium sulfate
(B) Mixture of imidazolium sulfate and aliphatic amino alcohol
The method for producing antistatic composite resin foamed particles according to claim 1 , wherein the cationic antistatic agent (a) is lauryldimethylethylammonium ethyl sulfate.
The antistatic composite resin foamed particles according to claim 1 , wherein the cationic antistatic agent (b) is a mixture of 1-ethyl-3-methylimidazolium ethyl sulfate and lauryl diethanolamine. Method.
An antistatic composite resin foamed particle obtained by the production method according to any one of claims 1 to 3 , wherein the surface resistivity is 1 × 10 ¹³ Ω or less and the voltage decay time is 3 seconds. Hereinafter, an antistatic composite resin foam particle molded body having a density of 10 to 200 kg / m ³