JP2017095532A - Gas barrier agent for foamable resin particle and foamable resin particle containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide foamable styrene modified thermoplastic resin particles capable of retaining high foamability even when stored at normal temperature for 20 or more days; preliminary foamed particles thereof; and a foam molding excellent in crack resistance obtained from them.SOLUTION: There are provided foamable styrene modified thermoplastic resin particles using a gas barrier agent for foamable resin particles made from an acrylic resin which contain 0.1-30 mol% of an acryloyl monomer (A) having a (meth)acrylate group and/or a (meth)acrylamide group, 20-60 mol% of a monomer (B) having a styrene skeleton, and 15-70 mol% of a vinyl monomer (C) (excluding A) having a nitrile group and/or a hydroxyl group as structural units, has a weight average molecular weight of 1,000-80,000, and a solubility to the styrene of 50 g (/100 g and 25°C) or more; preliminary foamed particles thereof; and a foam molding obtained from them.SELECTED DRAWING: None

Description

  The present invention relates to a gas barrier agent for expandable resin particles containing a thermoplastic acrylic resin, and expandable resin particles containing the same. More specifically, using a gas barrier agent containing a specific thermoplastic acrylic resin, there is no aggregation due to adhesion between particles during production and storage, and a foamable resin that can maintain high foamability even when stored at room temperature for 20 days or more The present invention relates to particles, pre-expanded particles comprising the same, and a foam molded article having excellent crack resistance.

By impregnating polystyrene resin particles with propane, butane, pentane, or the like as a volatile foaming agent, expandable polystyrene resin particles imparted with foaming performance can be obtained. Expandable polystyrene resin particles can hold volatile foaming agents relatively well, so they are usually stored at room temperature or in a refrigerated state, heated at an appropriate time according to use, and filled into a mold as pre-expanded particles. A foamed molded article can be obtained by heating. Such a foamable polystyrene resin molded article has a density of 0.01 to 0.7 g / cm ³ , is very lightweight, and has excellent heat insulation and buffering properties. Widely used as food containers such as timber and fish boxes. However, a foamed molded product of expandable polystyrene has a high rigidity, but is weak against impact and easily broken, so that it cannot be used for applications requiring impact resistance.

  On the other hand, foamed molded products made of polyolefin resin with ethylene, propylene, etc. as the main skeleton are very lightweight like foamed polystyrene resin molded products, and in addition to being excellent in heat insulation and buffering properties, they are flexible. It is known to be resistant to cracking. However, since the rigidity is low, the compressive strength is weak, and the polyolefin resin particles have poor retention of the volatile foaming agent. The expandable polyolefin resin particles obtained by impregnating propane, butane, pentane, etc. Since it cannot be stored or transported, a special storage facility is required until foam molding, and it has been very expensive to transport it in order to transport it. In addition, since the content of the foaming agent is likely to change, it is necessary to precisely control the foam molding conditions, and there is a problem that the manufacturing cost and capital investment increase.

  As a method for improving such a defect, several foamable styrene-modified polyolefin resin particles obtained by impregnating a polyethylene resin with styrene and polymerizing them have been proposed (Patent Documents 1 and 2).

  The foamable styrene-modified polyolefin resin particles described in Patent Document 1 have a surface layer made of a polyolefin resin and a core made of a polystyrene resin, and the resulting foamed molded body is hard to break, and has low temperature characteristics and rigidity. Has been improved. In Patent Document 2, it is described that rigidity, impact resistance, and chemical resistance are excellent by adding an inorganic nucleating agent such as silicon dioxide to expandable styrene-modified polyolefin resin particles. However, in these expandable styrene-modified polyolefin resin particles, even if a certain amount of volatile foaming agent can be retained in the polystyrene resin part, the surface layer made of polyethylene resin has a significant volatile foaming agent dissipation. In practical use, it cannot withstand long-term storage and transportation at room temperature.

  In Patent Document 3, 0.01 to 5% by mass of hydrated silicon dioxide is included as a surface cell regulator at the time of foam molding, and there is no influence on foam molding when foamed immediately after impregnation with a volatile foaming agent and after several hours. However, practically, it cannot withstand long-term storage and transportation at room temperature.

  In Patent Document 4, styrene or a mixed monomer of styrene and acrylate 140 to 600 parts by mass is impregnated with 100 parts by mass of polyolefin resin particles, and a volatile foaming agent is added to the resulting polyolefin and polystyrene composite particles. It is described that the foamed resin particles having good foaming agent retention and the foamed molded article having excellent crack resistance can be produced by containing. However, from the properties of the polyolefin resin content and excellent crack resistance in the composite particles, it can be estimated that there are many portions where the polyolefin resin exists as a continuous phase in the particles, that is, foaming It is unavoidable that the agent escapes out of the particles along the polyolefin continuous phase having poor retention, and the object of the present invention of long-term retention of the blowing agent cannot be achieved.

  In Patent Documents 5 to 7, in order to improve retention of butane and isobutane which are volatile foaming agents, an acrylonitrile-styrene copolymer called a dispersion diameter expanding agent or a dispersed phase expanding agent is used for polyolefin and polystyrene. It has been proposed to be used for expandable composite particles. According to the description of these patent documents, the dispersion diameter expanding agent is dispersed in a continuous polystyrene-based resin with a size of 0.3 μm or more. As a result, the adhesion area of both phases of the polyolefin-based resin and the polystyrene-based resin is reduced. The foaming agent that is reduced and held in the polystyrene resin phase can suppress the dissipation to the polyolefin resin phase. However, since the polyolefin system contains 20 to 55% by mass in these expandable composite particles, it cannot exist as a complete separated phase, and the foaming agent is quickly escaped from the continuously existing part, It is difficult to maintain the foaming agent which is the object of the present invention for a long period of time. Moreover, if there are few polyolefin resin parts which exist continuously, there exists a problem that the crack resistance of a foamable resin particle and a foaming molding formed from it falls remarkably.

JP 54-119563 A JP 2006-70202 A Japanese Patent Laid-Open No. 04-130143 JP 2008-133449 A JP2013-112765A JP 2011-256244 A Patent No. 2014-62171

  The present invention relates to expandable resin particles that can maintain high foamability even when stored at room temperature for 20 days or more without causing aggregation due to adhesion between particles during production and storage, and pre-expanded particles having uniform foam and high expansion ratio It is another object of the present invention to provide a foamed molded article having excellent rigidity and crack resistance.

  As a result of intensive studies to solve these problems, the inventors of the present invention have 1-30 mol% of acryloyl monomer (A) having a (meth) acrylate group and / or (meth) acrylamide group, and a styrene structure. Monomer (B) 20 to 60 mol%, vinyl monomer (C) having nitrile group and / or hydroxyl group (C) (excluding A) 15 to 70 mol% as a constitutional unit, weight average molecular weight 1,000 to 80,000 In addition, after synthesizing a gas barrier agent composed of an acrylic resin having a solubility in styrene of 50 g (/ 100 g, 25 ° C.) or more, it is dissolved in styrene and foamed styrene that can be stored for a long time by impregnation polymerization in thermoplastic particles. It has been found that modified plastic resin particles can be easily obtained. In addition, since the gas barrier agent covers the surface of the expandable resin particles as the outermost layer component, the escape of the foaming agent to the outside of the particles is essentially suppressed, and it is difficult to close and uniformly disperse within the particles. , To obtain pre-expanded particles having a uniform and high expansion ratio by heat foaming, and to obtain a foamed molded article having excellent rigidity and crack resistance by using these expandable resin particles and pre-expanded particles. The present invention has been reached.

That is, the present invention is (1) 0.1-30 mol% of acryloyl monomer (A) having (meth) acrylate group and / or (meth) acrylamide group, 20-60 mol% of monomer (B) having styrene structure, A vinyl monomer (C) having a nitrile group and / or a hydroxyl group (C) (excluding A) containing 15 to 70 mol% as a constituent unit, having a weight average molecular weight of 1,000 to 80,000 and a solubility in styrene of 50 g ( / 100 g, 25 ° C.) gas barrier agent for expandable resin particles made of an acrylic resin,
(2) The acryloyl monomer (A) is a linear, branched or cyclic alkyl group and / or alkyl ether group having 1 to 30 carbon atoms, an aliphatic ring and / or cyclic ether group having 5 to 30 carbon atoms. Or at least one monomer selected from the group consisting of (meth) acrylates having an aromatic ring having 6 to 35 carbon atoms and N-substituted (meth) acrylamide, as described in (1) above Gas barrier agent for foamable resin particles,
(3) In the above (1) or (2), the acryloyl monomer (A) is a (meth) acrylate having an alkyl group having 4 to 30 carbon atoms and / or an N-substituted (meth) acrylamide. The gas barrier agent for expandable resin particles according to (4), further comprising an ionic vinyl monomer (D) as a structural unit of an acrylic resin, according to any one of (1) to (3), Gas barrier agent for foamable resin particles,
(5) The gas barrier agent for expandable resin particles according to any one of (1) to (4), wherein the acrylic resin has a glass transition temperature (Tg) in the range of 40 to 95 ° C.
(6) The gas barrier agent according to any one of (1) to (5) is 5 to 30% by mass, the polystyrene resin is 10 to 70% by mass, and the thermoplastic particles are 20 to 85% by mass. Expandable resin particles characterized by containing,
(7) The foamable resin particles according to (6), wherein the thermoplastic particles are at least one kind of particles selected from polyolefin resin particles, polycarbonate resin particles, and ABS resin particles. It is to provide.

  The gas barrier agent of the present invention includes an acryloyl monomer (A) having a (meth) acrylate group and / or a (meth) acrylamide group, a monomer (B) having a styrene structure, and a vinyl monomer (C) having a nitrile group and / or a hydroxyl group. In the process of dissolving in styrene, impregnating the styrene with thermoplastic particles, and polymerizing it, it is made of an acrylic resin obtained by copolymerization of styrene and has good solubility in styrene and a specific molecular weight range. Is impregnated inside the particle, and the gas barrier agent made of acrylic resin forms a layer having a thickness of 5 to 200 μm on the particle surface, and is fixed in a state of covering the particle as the outermost layer of the particle along with the polymerization of styrene. The retention property of the resulting foamable resin particles with respect to the volatile foaming agent is very good.

  In addition, when the glass transition temperature of the acrylic resin is in the range of 40 to 95 ° C., it is easy to press the volatile foaming agent into the particles by adjusting the temperature and pressure, and the surface layer is not sticky during storage. The adhesion and aggregation between particles due to blocking caused by the property can be reduced. Further, by adding the ionic vinyl monomer (D) to the acrylic resin, the generation of static electricity between the foamable resin particles is suppressed, the workability is good, and the investment in static elimination equipment and the transportation cost can be greatly reduced.

  The foaming agent press-fitted into the expandable resin particles of the present invention does not pass through the outermost gas barrier layer, dispersibility within the particles increases with time, and the pre-expanded particles obtained therefrom have a uniform and high expansion rate. It is characterized by having. In addition, a foamed molded article having excellent rigidity and crack resistance (impact resistance) can be obtained from these expandable resin particles and pre-expanded particles.

The present invention is described in detail below.
The gas barrier agent of the present invention comprises 1-30 mol% of acryloyl monomer (A) having a (meth) acrylate group and / or (meth) acrylamide group, 20-60 mol% of a monomer (B) having a styrene structure, and a nitrile group. And / or an acrylic resin obtained by copolymerization of 15 to 70 mol% of a vinyl monomer (C) having a hydroxyl group.

  The acryloyl monomer (A) is a monomer having a (meth) acrylate group and / or a (meth) acrylamide group, and specifically, acrylic acid, methacrylic acid, and acrylic acid esters, methacrylic acid derivatives thereof. Examples include acid esters, acrylamides, methacrylamides, N-substituted acrylamides and N-substituted methacrylamides.

  C1-C30 linear or branched alkyl group, alkyl ether group, aliphatic ring or (meth) acrylate monomer having an aromatic ring having 6-35 carbon atoms and N-substituted (meth) acrylamide system Specifically, (meth) acrylate monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) Acrylate, isononyl (meth) acrylate , Undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (Meth) acrylate, isodecyl (meth) acrylate, isomistyryl (meth) acrylate, isostearyl (meth) acrylate, propylheptyl (meth) acrylate, isoundecyl (meth) acrylate, isododecyl (meth) acrylate, isotridecyl (meth) acrylate, iso Pentadecyl (meth) acrylate, isohexadecyl (meth) acrylate, isoheptadecyl (meth) acrylate, isoborni (Meth) acrylate, terpene-based (meth) acrylate, dicyclopentanyl (meth) acrylate, phenoxyethyl acrylate, phenol EO-modified (n = 2, 4, 9, 13) acrylate, and the like. ) As the acrylate-based monomer, it has a linear or branched alkyl ether group having 1 to 30 carbon atoms such as methoxymethyl (meth) acrylate, ethoxybutyl (meth) acrylate, butoxyhexyl (meth) acrylate ( And (meth) acrylate monomers. Examples of N-substituted (meth) acrylamide monomers include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N- n-butyl (meth) acrylamide, N-isobutyl (meth) acrylamide, Nt-butyl (meth) acrylamide, Nn-hexyl (meth) acrylamide, cyclohexyl (meth) acrylamide, Nn-octyl (meth) Acrylamide, N-isooctyl (meth) acrylamide, N-2-ethylhexyl (meth) acrylamide, N-isononyl (meth) acrylamide, N-undecyl (meth) acrylamide, N-lauryl (meth) acrylamide, N-tridecyl (meth) Acrylic N-tetradecyl (meth) acrylamide, N-pentadecyl (meth) acrylamide, N-hexadecyl (meth) acrylamide, N-heptadecyl (meth) acrylamide, N-stearyl (meth) acrylamide, N-behenyl (meth) acrylamide, N-isodecyl (meth) acrylamide, N-isomistyryl (meth) acrylamide, N-isostearyl (meth) acrylamide, N-propylheptyl (meth) acrylamide, N-isoundecyl (meth) acrylamide, N-isododecyl (meth) acrylamide, N-isotridecyl (meth) acrylamide, N-isopentadecyl (meth) acrylamide, N-isohexadecyl (meth) acrylamide, N-isoheptadecyl (methacrylamide, N-i Examples include bornyl (meth) acrylamide, terpene (meth) acrylamide, N-dicyclopentanyl (meth) acrylamide, diacetone acrylamide, and the like. Similarly, alkoxy (meth) acrylate monomers include methoxymethyl (meth) acrylate. , (Meth) acrylate monomers having a linear or branched alkyl ether group having 1 to 30 carbon atoms such as ethoxybutyl (meth) acrylate and butoxyhexyl (meth) acrylate, and N, Examples of N-disubstituted (meth) acrylamide monomers include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-di-n-propyl (meth) acrylamide, N, N- Diisopropyl (meth) acrylamide, N, N-me Substituents such as linear or branched alkyl groups, alkyl ether groups, aliphatic rings or aromatic rings having 1 to 30 carbon atoms such as ruethyl (meth) acrylamide and N, N-ethylhexyl (meth) acrylamide As a di-substitution having a rational structure obtained by arbitrarily combining as (meth) acrylamide, acryloylmorpholine, N-vinylpyrrolidone, diacetone acrylamide, N-vinylcaprolactone, N, N-dimethylaminoethylacrylamide, N, N -Diethylaminoethylacrylamide, N, N-diisopropylaminoethylacrylamide, N, N-diallylaminoethylacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide, N, N-diisopropylamino B pills acrylamide, N, N-diallyl-amino propyl acrylamide. These monomers are not limited to one type, and a plurality of types may be used in combination.

  The acryloyl monomer (A) is a linear, branched or cyclic alkyl group and / or alkyl ether group having 4 to 30 carbon atoms, an aliphatic ring and / or cyclic ether group having 5 to 30 carbon atoms, or In the case of (meth) acrylate and N-substituted (meth) acrylamide having an aromatic ring having 6 to 35 carbon atoms, the obtained gas barrier agent can be densely arranged on the surface of the expandable resin particles, and the expandability This is particularly preferred because it has the effect of imparting slipperiness between resin particles and suppressing the adhesion of the particle surface. Further, (meth) acrylates and N-substituted (meth) acrylamides having a linear or branched alkyl group having 8 to 30 carbon atoms are most preferred because Tg is easy to control and the solubility in styrene is excellent.

  Specific examples of the monomer (B) having the styrene structure include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, t-butylstyrene, o-ethylstyrene, o-chlorostyrene, o, p. -Dichlorostyrene etc. are mentioned. These styrene derivatives can be used singly or in combination of two or more, and styrene and α-methylstyrene are particularly preferable because inexpensive industrial products are easily available.

  Specific examples of the vinyl monomer having a nitrile group and / or a hydroxyl group include (meth) acrylonitrile, hydroxymethyl (meth) acrylamide, hydroxyethyl (meth) acrylamide, hydroxypropyl (meth) acrylamide, hydroxyisopropyl ( (Meth) acrylamide, hydroxyisobutyl (meth) acrylamide, N-methyl-hydroxyethyl (meth) acrylamide, dihydroxyethyl (meth) acrylamide, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxyisopropyl (meth) acrylate, Hydroxybutyl (meth) acrylate, hydroxyisobutyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3 Such as Fano hydroxypropyl (meth) acrylate. In addition, since the gas barrier property is high and the thermal characteristics are easy to adjust, acrylonitrile, methacrylonitrile, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 1,4-cyclohexanedimethanol mono Particularly preferred are acrylate, 2-hydroxy-3-phanoxypropyl acrylate, 1,4-cyclohexanedimethanol monomethacrylate, and 2-hydroxy-3-phanoxypropyl methacrylate.

  In the acrylic resin used for the gas barrier agent of the present invention, the acryloyl monomer (A) is preferably blended in a proportion of 1 to 30 mol%. When the component A is more than 30 mol%, the content of the component C is relatively decreased, and the retention of the volatile foaming agent is extremely lowered. On the other hand, when the component A is less than 1 mol, the particle surface of the gas barrier agent is reduced. In some cases, the wettability of the gas becomes poor and it is difficult to form a uniform gas barrier layer. From the balance between the retention of the volatile foaming agent and the wetness to the particle surface, it is more preferably 1 to 20 mol, and most preferably 3 to 15 mol.

  In the acrylic resin, the monomer (B) having a styrene structure is preferably blended in a proportion of 20 to 60 mol%. If it exceeds 60 mol%, the content of component A is relatively reduced, the wettability of the gas barrier agent to the particle surface is deteriorated, and it may be difficult to form a uniform gas barrier layer. On the other hand, when the amount is less than 20 mol%, the solubility in styrene deteriorates. Further, it is more preferably 20 to 60 mol%, most preferably 30 to 60 mol%.

  In the acrylic resin, the vinyl monomer (C) having a nitrile group and / or a hydroxyl group is preferably blended in a proportion of 15 to 70 mol%. When it is more than 70 mol%, the solubility in styrene deteriorates, while when it is less than 15 mol%, the retention of the volatile foaming agent is extremely lowered. In order to satisfy both the solubility in styrene and the retention of the volatile foaming agent, the more preferable blending ratio is 20 to 60 mol%, most preferably 40 to 60 mol%. The mixing ratio of the vinyl monomer having a nitrile group and the vinyl monomer having a hydroxyl group constituting the vinyl monomer (C) is as follows: vinyl monomer having a nitrile group / vinyl monomer having a hydroxyl group = 100/0 to 0/100 (mol) / Mol). From the ease of control of the glass transition temperature of a polymer, it is 100 / 0-50 / 50, More preferably, it is 100 / 0-70 / 30.

In the acrylic resin, it is preferable to further blend an ionic vinyl monomer (D) as a structural unit. The ionic vinyl monomer is an onium salt obtained by combining a cation and an anion. Specifically, the cation is a (meth) acrylate-based or (meth) acrylamide-based ammonium ion or imidazolium ion, and the anion is Cl ⁻ , Hal ion such as Br ⁻ and I ⁻ or OH ⁻ , CH ₃ COO ⁻ , NO ₃ ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ , BF ₄ ⁻ , HSO ₄ ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , Examples thereof include inorganic acid anions or organic acid anions such as CH ₃ C ₆ H ₆ SO ₃ ⁻ , C ₄ F ₉ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ and SCN ⁻ .

  As a method for synthesizing the ionic vinyl monomer (D) used in the present invention, a tertiary amine having a polymerizable group is generally selected from 4 groups such as alkyl halides, dialkyl sulfates, and methyl p-toluenesulfonate. A method of quaternizing with a quaternizing agent, a method of further performing anion exchange with a quaternary ammonium salt obtained by quaternization using a salt having a target anion, or a quaternary ammonium using an anion exchange resin There is a method in which a salt is converted into a hydroxide and then neutralized with an acid having a target anion. Details are disclosed in Japanese Patent Application Laid-Open No. 2011-012240, Japanese Patent Application Laid-Open No. 2011-074216, Japanese Patent Application Laid-Open No. 2011-140448, Japanese Patent Application Laid-Open No. 2011-140455, and Japanese Patent Application Laid-Open No. 2011-153109. Refer to.

  Since the ionic vinyl monomer (D) can be dissolved from water to a nonpolar organic solvent by a combination of a cation and an anion, the type of the cation and anion is not particularly limited, and the main constitution of the acrylic resin (E) According to the structure and blending ratio of the monomers A, B and C, those that can be dissolved in the monomer polymerization solution may be appropriately selected and combined. Since D exists as a side chain of the acrylic resin (E), it can be distributed on the surface of the expandable resin particles, and can provide the effect of permanently imparting antistatic properties without bleeding out. Moreover, it is preferable that the compounding quantity of D is 0.1-30 mol% in 100 mol% of acrylic resins (E). If it is added in an amount of 0.1 mol%, the antistatic effect can be confirmed, and if it exceeds 30 mol%, the foamable resin particles tend to aggregate and are not preferred.

  The molecular weight of the acrylic resin is in the range of 1,000 to 80,000 on a weight average basis. When the weight average molecular weight is larger than 80,000, the solubility in styrene is deteriorated, the viscosity of the solution is extremely increased, and handling becomes difficult. On the other hand, if the molecular weight is less than 1,000, it will penetrate into the center of the thermoplastic particles during the impregnation polymerization, so that surface layer defects are likely to occur, and the retention of the volatile foaming agent will deteriorate. Preferably, the weight average molecular weight is in the range of 2,000 to 50,000, more preferably 5,000 to 45,000.

  The glass transition temperature (Tg) of the acrylic resin is preferably in the range of 40 to 95 ° C. When Tg is higher than 95 ° C., the operating temperature and pressure when the volatile foaming agent is press-fitted into the expandable resin particles must be increased, and safety and workability are lowered. Further, since it is difficult to soften at the time of foaming, the fusion of the particles is hindered, the foaming ratio is low, and the mechanical properties are also lowered. On the other hand, if the Tg is lower than 40 ° C., the foamable resin particles tend to aggregate during production and storage, and the retention of the foaming agent is extremely lowered. Further, in order to prevent cracking of the foamed molded product and aggregation of particles during storage, the temperature is preferably in the range of 50 to 90 ° C, particularly preferably 55 to 85 ° C.

  The acrylic resin has a solubility in styrene at 25 ° C. of 50 (g / 100 g) or more, that is, E is soluble in 50 g or more with respect to 100 g of styrene. When the solubility is 50 (g / 100 g) or more, a high-concentration acrylic resin styrene solution can be prepared, and the acrylic resin can completely cover the particle surface when producing expandable resin particles by impregnation polymerization. . The solubility is more preferably 60 (g / 100 g) or more.

  The expandable resin particles of the present invention are composed of thermoplastic particles, a polystyrene resin and a gas barrier agent, and can be easily produced using a general impregnation polymerization technique. For example, after suspending thermoplastic particles in an aqueous medium, a mixed liquid composed of styrene, a gas barrier agent and an oil-soluble radical polymerization initiator is added with stirring, and suspension polymerization is performed by heating, simultaneously with the polymerization reaction or By impregnating with a volatile foaming agent after completion of the polymerization reaction, the expandable styrene-modified thermoplastic resin particles of the present invention (hereinafter also referred to as “expandable resin particles” in the present invention) can be obtained.

  The thermoplastic particles can be produced by a general granulation method such as melt extrusion using a known thermoplastic resin. As a raw material resin for the thermoplastic particles used in the present invention, polyolefin resins, polycarbonate resins, and ABS resins can be used alone or in combination. Examples of polyolefin resins include ultra-low density polyethylene, low density polyethylene, linear low density polyethylene (L-LDPE), medium density polyethylene, high density polyethylene, branched low density polyethylene, ethylene-vinyl acetate copolymer, Polyethylene resins such as ethylene-methyl methacrylate copolymer, polypropylene, ethylene-propylene random copolymer, propylene-1-butene copolymer, ethylene-propylene-butene random copolymer, polypropylene-polybutylene terephthalate-nylon- Examples include alloys of polyphenylene ether, and preferably ultra-low density polyethylene, low density polyethylene, linear low density polyethylene (L-LDPE), and medium density polyethylene, more preferably low density polyethylene. It includes linear low density polyethylene.

  The polycarbonate resin is composed of bisphenol derivatives such as 2,2-bis (4-oxyphenyl) butane, 1,1-bis (4-oxyphenyl) isobutane, and 1,1-bis (4-oxyphenyl) cyclohexane. A polycarbonate resin containing a polycarbonate component made of polycarbonate resin or poly (ester carbonate) can be mentioned.

  ABS resins include styrene, α-methylstyrene, t in the presence of a rubbery polymer such as polybutadiene, a random or block copolymer of vinyl monomer copolymerizable with butadiene, and a copolymer of vinyl monomer. -What was obtained by superposing | polymerizing 1 or more types of aromatic vinyl monomers, such as butyl styrene and chlorostyrene, and vinyl monomers which have 1 or more types of cyan groups, such as acrylonitrile, methacrylonitrile, chloroacrylonitrile, is mentioned.

  From the viewpoint of improving the crack resistance of the foamed molded article, the raw material resin for the thermoplastic particles is preferably a polyolefin resin alone or a mixture of polyolefin and other resins, more preferably ultra-low density polyethylene, low density polyethylene. , Linear low density polyethylene and medium density polyethylene.

  In 100% by mass of the expandable resin particles of the present invention, the blending amount of the thermoplastic particles is 20 to 85% by mass, preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. When the blending amount of the thermoplastic particles is more than 85% by mass, the foaming agent retention of the expandable resin particles is remarkably reduced. When the blending amount is less than 20% by mass, the foaming resistance of the foamed molded product obtained therefrom is low. There was a problem of lowering.

  In 100% by mass of the expandable resin particles of the present invention, the blending amount of the polystyrene resin is 10 to 70% by mass, preferably 30 to 60% by mass. When the blending amount of the polystyrene resin is more than 70% by mass, the cracking resistance of the expandable resin particles, the pre-expanded particles and the foamed molded product obtained therefrom is lowered, and when the blending amount is less than 10% by mass, the expandable resin particles are obtained. This is not preferable because the foaming agent retention property and the mechanical properties of the foamable molded article may be extremely deteriorated.

  The compounding amount of the gas barrier agent is 5 to 30% by mass in 100% by mass of the expandable resin particles of the present invention. Within this range, the surface layer having a gas barrier agent content of 50% by mass or more and having a thickness of 5 to 200 μm is formed as the outermost layer of the expandable resin particles, although it varies somewhat depending on the size of the expandable resin particles. The

  Examples of the volatile foaming agent used in the foamed resin particles of the present invention include propane, butane, isobutane, pentane, dimethyl ether and the like. These volatile blowing agents may be used alone or in combination. The content of these volatile foaming agents is 5.5 to 13.0 mass% with respect to the foamable resin particles. When the volatile foaming agent is less than 5.5% by mass, the foaming property is lowered, and pre-foamed particles having a low bulk density and a high foaming ratio cannot be obtained, and foam molding obtained by molding the pre-foamed particles in the mold. Since the body has low fusing properties, crack resistance is reduced. On the other hand, if it exceeds 13.0% by mass, pre-expanded particles having a high expansion ratio can be obtained, but the cell diameter becomes too large, and mechanical properties such as compression and bending of the foamed molded product deteriorate. The preferred volatile blowing agent content is in the range of 6.0 to 12.0% by weight.

  The average particle diameter of the expandable resin particles produced by the production method of the present invention is 1 to 3 mm. When the average particle diameter is larger than 3 mm, the filling property to the mold tends to be deteriorated. If it is smaller than 1 mm, the cost increases due to a decrease in the yield during granulation after melt extrusion of the polyolefin-based resin, and the retention of the foaming agent is lowered, and the retention time of the volatile foaming agent is shortened. . A preferable average particle diameter is 1-2 mm.

Further, the expandable resin particles of the present invention are characterized in that a surface layer mainly composed of a gas barrier agent is formed on the outermost layer. In the cross-section of the expandable resin particle cut from the particle surface through the center, analysis is performed with a microscopic Raman spectrophotometer, and the Raman spectrum relating only to the gas barrier agent, for example, the gas barrier agent is constituted from the region near the particle surface. acryloyl-functional group (1730 cm ^-1 around the ester bond, an amide bond in the vicinity of 1645 cm ^-1) of the acrylic resin and / or (nitrile bonds in the vicinity of 2230 cm ^-1) nitrile functionality specific peak derived is observed strongly expandable resin The presence of a gas barrier layer mainly composed of a gas barrier agent was confirmed on the surface of the particles. The thickness of the gas barrier layer can be adjusted mainly by the blending ratio of the gas barrier agent and the thermoplastic particles, but if it is in the range of 5 to 200 μm, it can provide a sufficiently satisfactory level of gas barrier properties, and expandable resin particles and This is preferable because it does not affect the foaming properties of the pre-foamed particles and the properties of the molded product such as crack resistance and solvent resistance.

By using the foamable resin particles of the present invention, the foamed resin particles can be prefoamed to a predetermined bulk density by heating with a heating medium such as water vapor to obtain prefoamed particles. The pre-expanded particles of the present invention are composed of a main part composed of a thermoplastic resin and a polystyrene resin, and a surface layer mainly composed of a gas barrier agent, and a bulk density of 0.015 to 0.40 g / cm ³ . A range is preferable. Such pre-expanded particles are filled in a mold of a molding machine, the thickness after secondary foaming at the time of thermoforming is stabilized, and no aging period is required until the normal secondary foam thickness is stabilized. In addition, since the glass transition temperature (Tg) of the acrylic resin of the gas barrier layer on the surface of the pre-expanded particles can be adjusted within a range of 40 to 95 ° C. depending on the blending ratio of the constituent components, The particles can be easily fused with each other without breaking the shape, and a molded product having excellent dimensional stability can be produced.

   Further, using the expandable resin particles of the present invention, a foamed molded article can be produced by filling and foaming directly into a mold after impregnation with a foaming agent without prefoaming. Such a single-stage foaming method is characterized by a short molding cycle, easy operation, and high productivity.

  The foamed molded product used in the present invention can be produced by any one of the above-described one-stage foaming method or pre-foaming method. Further, the obtained foamed molded article has a gas barrier layer mainly composed of a gas barrier agent formed on the surface in the same manner as the expandable resin particles and pre-expandable particles of the present invention, and the gap between the particles is extremely small, and the molding accuracy is high. High and good surface gloss. Furthermore, since the particles constituting the foamed molded product contain both a thermoplastic resin and a polystyrene resin, the foamed molded product has high strength and rigidity and good crack resistance.

  Although it does not specifically limit as a use of the foaming molding concerning this invention, It is a buffer material (cushioning agent), the heat insulating material for building materials, the container for foodstuffs and an electrical product, a precision instrument, the member of an electrical appliance, and the member of an automobile Various applications such as impact energy absorbing materials such as bumper core materials, raising materials, cushioning materials for door interiors, and disappearance model materials can be mentioned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In the following, “part” and “%” are all based on mass unless otherwise specified.

Measurement or evaluation of various physical properties in Synthesis Examples and Examples was performed by the following methods.
(1) Molecular weight analysis: The molecular weight was measured using gel permeation chromatography (GPC) under the conditions shown below. LC-20AD, DGU-20A, CTO-20A and RID-10A (Shimadzu Corporation) set as analyzer, chloroform as eluent, KF-806L (shodex) as column, flow rate 0.5 mL / min, column Measurement was performed under the conditions of a temperature of 40 ° C., an injection amount of 20 μL, and a sample concentration of 0.5 wt%, the standard polystyrene molecular weight was converted as a standard, and the weight average molecular weight of the synthesized acrylic resin was calculated.
(2) Glass phase transition temperature (Tg) measurement: Using a differential scanning calorimeter (DSC 6220 manufactured by SII Nano Technology), 10 mg of a sample was filled into a measuring container, and the nitrogen gas flow rate was 40 ml / min. The temperature was raised to 200 ° C. at a temperature rising rate of ° C./min, held for 10 minutes, then cooled to −20 ° C. at a temperature lowering rate of 10 ° C./min, and held for 10 minutes. Thereafter, the temperature was raised again to 200 ° C. at a rate of 10 ° C./min, the change in calorie was measured, and the midpoint of the endothermic peak was taken as the glass phase transition temperature.
(3) Solubility in styrene: 5 g of the synthesized acrylic resin was added to 10 g of styrene and stirred at 25 ° C. for 5 hours to evaluate the solubility.
○: Uniform and transparent solution, solubility is 50 g (/ 100 g, 25 ° C.) or more.
(Triangle | delta): Although it is uniform, but it is a little white and it is not completely transparent, a liquid and solubility are less than 50g (/ 100g25 degreeC).
×: Many non-uniform white insolubles remained (does not dissolve)
(4) Raman spectrum measurement: Using synthesized foamed resin particles, cut from the particle surface through the center, and the surface analysis of the cross section is performed with a laser Raman spectrometer (manufactured by JASCO Corporation, model NRS-5100). It was.
(5) Measurement of initial foaming agent content: 1 g of expandable resin particles immediately after production was weighed and heated at 190 ° C. with a vented dryer, and the content of the foaming agent was determined from the amount of change in weight before and after heating. Calculated based on the formula.
Content of initial foaming agent = (weight immediately after production−weight after heating) / weight immediately after production × 100%
(6) Evaluation of foaming agent retention: foaming resin) After the particles were allowed to stand in a thermostatic chamber adjusted to 25 ° C. for 20 days after production, the foaming agent content after storage was measured in the same manner as described above.
Content of foaming agent after storage = (weight after storage−weight after heating) / weight after storage × 100%
A: The difference between the content of the initial foaming agent and the content of the foaming agent after storage is less than 1.0%.
○: The difference between the content of the initial foaming agent and the content of the foaming agent after storage is 1.0 to less than 2.0%.
Δ: The difference between the content of the initial foaming agent and the content of the foaming agent after storage is 2.0 to less than 3.0%.
X: The difference between the content of the initial foaming agent and the content of the foaming agent after storage is 3.0 or more.
(7) Adhesive evaluation between expandable resin particles: The produced expandable resin particles are allowed to stand in a thermostatic chamber adjusted to 25 ° C. for 1 day, and the presence or absence of adhesion between the particles is evaluated according to the following evaluation criteria. The adhesion between the expandable modified resin particles was evaluated.
○: (Good) No adhesion between particles ×: (Bad) Adhesion between particles (8) Foamability evaluation of expandable resin particles: Supply expandable resin particles to a cylindrical batch type pre-foaming machine The pre-expanded particles were obtained by heating with steam having a blowing pressure of 0.02 MPa. The resulting pre-expanded particles were filled into graduated cylinder capacity 500 cm ³ to the scale of 500 cm ^3, as measured to a precision weight W (g) of the filled pre-expanded particles, the following equation 1 the bulk density of pre-expanded particles Calculated. Further, the expansion ratio of the pre-expanded particles was calculated by the following formula 2 by utilizing the fact that the expansion ratio and the bulk density are inversely related.
Formula 1 Bulk density (g / cm ³ ) = W (g) / 500 cm ³
Formula 2 Foaming ratio = 1 / bulk density (g / cm ³ )
The foamability of the foamable resin particles was evaluated in light of the following criteria.
◎: (Good) Foaming ratio 50 times or more ○: (Slightly good) Foaming ratio 40 times or more to less than 50 times △: (Normal) Foaming ratio 30 times or more to less than 40 times X: (Poor) Foaming ratio less than 30 times ( 9) Evaluation of crack resistance: A falling ball impact test indicating the strength of crack resistance of the foamed molded article was measured according to JIS K 7211. Test pieces having a width, length, and thickness of 200 mm, 40 mm, and 20 mm are cut out from the foamed molded body to prepare a total of 20 pieces. A 321 g steel ball was dropped, and the 50% fracture height was calculated by the following formula. Higher values indicate higher impact resistance.
H50: 50% fracture height (cm)
Hi: Test height (cm) when the height level (i) is 0, and indicates the height at which the test piece is expected to break.
d: Height interval when moving the test height up and down (cm)
i: Height level when Hi is 0, and the height level is increased or decreased by 1 (i =... -3, -2, -1, 0, 1, 2, 3,...)
ni: number of test pieces destroyed (or not destroyed) at each level N: total number of test pieces destroyed (or not destroyed)
Use whichever data is greater. In the case of the same number, either may be used.
± 0.5: A negative sign is used when destroyed data is used, and a positive sign is used when data that is not destroyed is used.
A: (Good) 40 cm or more B: (Slightly good) 30 cm or more to less than 40 cm Δ: (Slightly bad) 20 or more to less than 30 cm X: (Bad) Less than 20 cm (10) Antistatic evaluation: Obtained foam molded article Cut out test pieces with widths, lengths and thicknesses of 110 mm, 110 mm and 25 mm, put them in a thermostatic chamber adjusted to a temperature of 23 ° C. and a relative humidity of 50%, and left for 3 hours to measure the surface resistivity. A sample was obtained. Based on JISK 6911, measurement was performed using a digital electrometer (R8252 type: manufactured by ADC Corporation). The lower the surface resistivity, the higher the antistatic property of the foamed molded product.
○: (with antistatic performance) less than 1 × 10 ¹² Ω / □
Δ: 1 × 10 ¹² Ω / □ or more (having a little antistatic performance) and less than 1 × 10 ¹³ Ω / □ ×: (not having antistatic performance) 1 × 10 ¹³ Ω / □ or more

Synthesis Example 1 Synthesis of Acrylic Resin 1 12.7 g (50 mmol) of dodecyl methacrylate as component (A) and styrene as component (B) in a 500 mL reaction vessel equipped with a stirrer, thermometer, cooler and dry nitrogen introduction tube 26.0 g (250 mmol), 26.5 g (500 mmol) of acrylonitrile as component (C) and 39.6 g (200 mmol) of 1,4-cyclohexanedimethanol monoacrylate, and azobisisobutyronitrile (AIBN) as a polymerization initiator 3.3 g (20 mmol) and dimethylformamide (DMF) 200 g were charged as a solvent. The reaction solution was purged with nitrogen while stirring at 30 ° C. for 1 hour under a dry nitrogen stream, then heated at 100 ° C. for 10 hours, and various residual monomers in the reaction system were less than 1% by gas chromatography. It was confirmed that various raw material monomers were polymerized at a predetermined mixing ratio to obtain a copolymer having a predetermined composition. Thereafter, the residual monomer and about half of the DMF were distilled off under reduced pressure, and methanol was further added to precipitate and dry the polymer to obtain 94 g of a white powdery solid. Moreover, the weight average molecular weight of the acrylic resin 1 was 1 million, Tg was 58 degreeC, and it confirmed that 50% or more melt | dissolved in styrene.

Synthesis Examples 2 to 4 and Comparative Synthesis Examples 9 to 11 Synthesis of Acrylic Resins 2 to 4 and 9 to 11 In Synthesis Examples 2 to 4, the components shown in Table 1 were synthesized in the compounding amounts shown in the same table. Polymerization and purification were performed in the same manner as in Example 1 to obtain acrylic resins 2 to 4 as white powdery solids. In Comparative Synthesis Examples 9 to 11, each component shown in Table 2 was polymerized and purified in the same manner as in Synthesis Example 1 at the blending amounts shown in the same table, and acrylic resin 9 to 11 was obtained. The molecular weight and Tg of the obtained acrylic resins 2 to 4 and 9 to 11 were measured, the solubility in styrene was examined, and the results are summarized in Tables 1 and 2.

Synthesis Example 5, Comparative Synthesis 15 Synthesis of Acrylic Resins 5 and 15 In Synthesis Example 5, each component shown in Table 1 was polymerized and purified in the same manner as in Synthesis Example 1 with the blending amounts shown in the same table. Acrylic resin 5 was obtained as a waxy solid. Moreover, as the comparative synthesis 15, the supernatant obtained in the polymer purification step of Synthesis Example 5 was used, and the solvent and residual monomers were completely removed while heating under reduced pressure, and the acrylic resin 15 was obtained as a pale yellow high-viscosity liquid. Acquired. The molecular weight and Tg of the resulting acrylic resins 5 and 15 were measured, the solubility in styrene was examined, and the results are summarized in Tables 1 and 2.

Synthetic Examples 6-8, Comparative Synthetic Examples 12-14 Synthesis of Acrylic Resins 6-8 and 12-14 In Synthetic Examples 6-8, each component shown in Table 1 was synthesized in the compounding amounts shown in the same table. In the same manner as in Example 1, the mixture was heated at 70 ° C. for 20 hours for polymerization and purification to obtain acrylic resins 6 to 8 as white powder solids. Further, in Comparative Synthesis Examples 12 to 14, the components shown in Table 2 were heated at 70 ° C. for 20 hours in the blending amounts shown in the same table at 70 ° C. for polymerization and purification to obtain a white powder. Acrylic resins 12 to 14 were obtained as solids. The molecular weight and Tg of the obtained acrylic resins 6 to 8 and 12 to 14 were measured, the solubility in styrene was examined, and the results are summarized in Tables 1 and 2.

Table 1

Table 2

Production Example 1 of Expandable Resin Particles (Expandable Styrene Modified Thermoplastic Particles)
100 parts by mass of low density polyethylene (Tosoh Corp., Nipolon Z 9P51A) and 0.5 parts by mass of talc as a nucleating agent are dry blended, supplied from the hopper of a twin screw extruder, melt kneaded at 220 ° C., and an extruder. Were extruded into strands and cut with a pelletizer to produce thermoplastic (resin) particle pellets.
Next, in a pressure-resistant polymerization vessel equipped with a stirrer, 100 parts by mass of water, 25 parts by mass of pellets of thermoplastic particles, 0.0175 parts by mass of magnesium pyrophosphate as a suspending agent, 0.0175 parts by mass of calcium dodecylbenzenesulfonate surfactant The temperature was raised to 90 ° C. with stirring. Thereafter, a solution comprising 0.1 part by mass of benzoyl peroxide and 0.05 part by mass of t-butylperoxybenzoate as a polymerization initiator, and 15 parts by mass of acrylic resin and 70 parts by mass of styrene as a gas barrier agent was taken over 4 hours. Added and polymerized. Furthermore, after performing polymerization at 130 ° C. for 3 hours, the mixture was cooled to 90 ° C. to obtain styrene-modified thermoplastic particles. Subsequently, 7.5 parts by mass of isobutane as a foaming agent was injected into the pressure-resistant polymerization vessel and held at 90 ° C. for 3 hours. Thereafter, it was cooled, dehydrated and dried to obtain expandable styrene-modified thermoplastic particles (abbreviated expandable resin particles). The initial foaming agent content of the obtained foamable resin particles, the foaming agent retention of the foamable resin particles, and the adhesion between the foamable resin particles were evaluated. The results are shown in Table 3.

Examples 2-10
Except that the thermoplastic particles, gas barrier agent and styrene were the varieties and masses shown in Table 3, Examples 2 to 10 were carried out in the same manner as in Example 1, and the initial foaming agent content of the obtained foamable resin particles, The foaming resin particle foaming agent retention and the adhesiveness between the foaming resin particles were evaluated, and the results are shown in Table 3.

Table 3

Comparative Examples 1-4
Except that the thermoplastic particles, acrylic resin and styrene are the varieties and masses shown in Table 4, as in Example 1, Comparative Examples 1 to 4 were carried out, and the initial foaming agent content of the obtained foamable resin particles, The foaming resin particle foaming agent retention property and the adhesiveness between the foaming resin particles were evaluated, and the results are shown in Table 4.

Table 4

Comparative Example 5
100 parts by mass of ethylene vinyl acetate copolymer (NUC-3221 (made by Nippon Unicar Co., Ltd., 5.0% by weight of vinyl acetate)) and 0.5 parts by mass of talc as a nucleating agent are dry blended, and a hopper of a twin screw extruder Then, the mixture was melt-kneaded at 220 ° C., extruded into a strand from an extruder, and cut by a pelletizer to produce thermoplastic particle pellets.
Next, in a pressure-resistant polymerization vessel equipped with a stirrer, 100 parts by mass of water, 35 parts by mass of pellets of thermoplastic particles, 0.0175 parts by mass of magnesium pyrophosphate as a suspending agent, 0.0175 parts of calcium dodecylbenzenesulfonate as a surfactant. A mass part was added and the temperature was raised to 90 ° C. while stirring. Thereafter, 0.1 parts by mass of benzoyl peroxide, 0.05 parts by mass of t-butylperoxybenzoate, 15 parts by mass of acrylonitrile and 50 parts by mass of styrene were added as polymerization initiators over 4 hours for polymerization. Furthermore, after superposing | polymerizing at 130 degreeC for 3 hours and cooling to 90 degreeC, 7.5 mass parts of isobutane was injected as a foaming agent in a pressure-resistant polymerization container, and it hold | maintained at 90 degreeC for 3 hours. Thereafter, it was cooled, dehydrated and dried to obtain expandable resin particles. The initial foaming agent content of the obtained foamable resin particles, the foaming agent retention of the foamable resin particles, and the adhesion between the foamable resin particles were evaluated. The results are shown in Table 4.

Comparative Example 6
50 parts by mass of low density polyethylene (Tosoh Corporation, Nipolon Z 9P51A), 50 parts by mass of acrylonitrile-styrene resin (manufactured by Denki Kagaku Kogyo Co., Ltd., AS-XGS, acrylonitrile 28%, weight average molecular weight 109000), nucleating agent As a dry blend of 0.5 parts by mass of talc, supplied from a hopper of a twin screw extruder, melt-kneaded at 220 ° C., extruded into a strand from the extruder, and cut by a pelletizer to produce thermoplastic particle pellets .
Next, in a pressure-resistant polymerization vessel equipped with a stirrer, 100 parts by mass of water, 60 parts by mass of pellets of thermoplastic particles, 0.0175 parts by mass of magnesium pyrophosphate as a suspending agent, 0.0175 parts of calcium dodecylbenzenesulfonate as a surfactant. A mass part was added and the temperature was raised to 90 ° C. while stirring. Thereafter, 0.1 parts by mass of benzoyl peroxide, 0.05 parts by mass of t-butylperoxybenzoate, and 40 parts by mass of styrene were added as polymerization initiators over 4 hours for polymerization. Furthermore, after performing polymerization at 130 ° C. for 3 hours, the mixture was cooled to 90 ° C. to obtain expandable resin particles. Subsequently, 7.5 parts by mass of isobutane as a foaming agent was injected into the pressure-resistant polymerization vessel, heated to 90 ° C. and held for 3 hours. Thereafter, it was cooled, dehydrated and dried to obtain expandable resin particles. The initial foaming agent content, foaming resin particle foaming agent retention, and adhesiveness between the foaming resin particles of the obtained foaming resin particles were evaluated, and the results are shown in Table 4.

Comparative Examples 7-14
Except that the thermoplastic particles, acrylic resin and styrene were the varieties and masses shown in Table 5, as in Example 1, Comparative Examples 7 to 14 were carried out, and the initial foaming agent content of the obtained foamable resin particles, The foamable resin particles were evaluated for foaming agent retention and adhesiveness between the foamable resin particles, and the results are shown in Table 5.

  The foamable resin particles produced in Examples 1 to 10 and Comparative Examples 1 to 14 were filled in a mold of a molding machine, and supplied to a cylindrical batch type foaming machine with water vapor at 100 ° C., and the blowing vapor pressure was 0.02 MPa. Heated with water vapor for 10 minutes to obtain pre-expanded particles. After pre-expanded particles were aged at room temperature for 24 hours, the expansion ratio was measured, and the results are shown in Table 5. Moreover, the pre-expanded particles aged at room temperature for 24 hours were filled in a closed mold of a molding machine and heated with water vapor to produce a foam molded article. The resulting foamed molded article was evaluated for crack resistance and antistatic properties, and the results are summarized in Tables 3-5.

Table 5

From the results of Examples and Comparative Examples, the gas barrier agent of the present invention polymerizes the acryloyl monomer (A), the monomer (B) having a styrene structure, and the vinyl monomer (C) having a nitrile group or a hydroxyl group at a specific mixing ratio. As a result, it was possible to form a gas barrier layer on the surface of the resin particles together with styrene impregnation polymerization. Due to the formation of the gas barrier layer, the foamable resin particles of the present invention did not aggregate due to adhesion between the particles during production and storage, and could maintain high foamability even when stored for 20 days or more at room temperature. On the other hand, in Comparative Example 5, even when acrylonitrile, which is a part of the constituent monomer of the acrylic resin, is impregnated and copolymerized simultaneously with styrene, the surface of the resin particle is infiltrated into the plastic particle and dissolved in water. In addition, the gas barrier layer could not be formed, and the retention of the foaming agent was poor. Further, in Comparative Example 6, it was recognized that the foaming agent was retained somewhat by mixing the acrylonitrile-styrene copolymer in advance with the thermoplastic particles, but because the gas barrier layer was not formed on the particle surface, Dissipation of the foaming agent from the surface could not be suppressed, and it could not be stored practically for a long time, and the object of the present invention could not be achieved.

  As described above, the expandable resin particles of the present invention have the gas barrier layer formed from the gas barrier agent of the present invention in the outermost layer, and the expandable resin particles that can maintain high foamability even when stored for 20 days or more at room temperature. Can be provided. In addition, pre-expanded particles having uniform foam and high expansion ratio can be obtained by heating and foaming the expandable resin. Furthermore, a foamed molded article having excellent rigidity and crack resistance can be produced from these expandable resin particles and pre-expanded particles. The expandable resin particles, pre-expanded particles and foamed molded product of the present invention can be suitably used for foods, electronic parts, containers and packaging materials for various industrial materials, automotive cushioning materials, heat insulating materials for buildings, and the like. it can.

Claims (7)

Acrylyl monomer having (meth) acrylate group and / or (meth) acrylamide group (A) 0.1-30 mol%, monomer having styrene skeleton (B) 20-60 mol%, having nitrile group and / or hydroxyl group A vinyl monomer (C) (excluding A) containing 15 to 70 mol% as a constituent unit, having a weight average molecular weight of 1,000 to 80,000 and a solubility in styrene of 50 g (/ 100 g, 25 ° C.) or more. A gas barrier agent for foamable resin particles comprising an acrylic resin. The acryloyl monomer (A) is a linear, branched or cyclic alkyl group and / or alkyl ether group having 1 to 30 carbon atoms, an aliphatic ring and / or cyclic ether group having 5 to 30 carbon atoms, or carbon 2. The expandable resin particle according to claim 1, which is at least one monomer selected from the group consisting of (meth) acrylate having an aromatic ring of several 6 to 35 and N-substituted (meth) acrylamide. Gas barrier agent. The foaming property according to claim 1 or 2, wherein the acryloyl monomer (A) is (meth) acrylate and / or N-substituted (meth) acrylamide having an alkyl group having 4 to 30 carbon atoms. Gas barrier agent for resin particles. The gas barrier agent for expandable resin particles according to any one of claims 1 to 3, further comprising an ionic vinyl monomer (D) as a structural unit of an acrylic resin. The gas barrier agent for expandable resin particles according to any one of claims 1 to 4, wherein the acrylic resin has a glass transition temperature (Tg) in the range of 40 to 95 ° C. The gas barrier agent according to any one of claims 1 to 5 contains 5 to 30% by mass, polystyrene resin 10 to 70% by mass, and thermoplastic particles 20 to 85% by mass as constituent components. Expandable resin particles. The foamable resin particles according to claim 6, wherein the thermoplastic particles are at least one kind of particles selected from polyolefin resin particles, polycarbonate resin particles, and ABS resin particles.