JP2011068821A - Expandable composite resin particle, preliminary foamed particle, method for producing these, and foamed molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expandable composite resin particle that includes a polyolefine-based resin and a polystyrene-based resin, and gives a foamed molded article good in fusionability even after long elapse of days since preliminary foaming, and excellent in crack resistance, and to provide a preliminary foamed particle derived from an expandable composite resin including a polyolefine-based resin and a polystyrene-based resin. <P>SOLUTION: The expandable composite resin particle includes a composite resin particle, that includes 100 pts.wt. polyolefine-based resin and 120-560 pts.wt. polystyrene-based resin, 0.05-2.5 pts.wt. nonionic surfactant against 100 pts.wt. of the composite resin particle, and a foaming agent, and can form the preliminary foamed particle having the value A/B of 2-6 obtained by dividing the average cell diameter A of bubbles contacting with the epidermal layer of the preliminary foamed particle by the average cell diameter B of bubbles passing through the point at one half of radius of the preliminary foamed particle in the case observing a picture photographed by electron microscope scanning a cross section divided into two parts from the surface through center thereof of a prefoamed particle obtained by prefoaming the expandable composite resin particle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an expandable composite resin particle containing a polyolefin resin and a polystyrene resin, pre-expanded particles, a production method thereof, and an expanded molded article.
The pre-expanded particles of the present invention have a so-called double cell structure in which the average cell diameters of the bubbles in contact with the skin layer and the bubbles inside are greatly different. If the pre-expanded particles having such a structure are molded, it is possible to obtain a foamed molded article having excellent appearance and moldability and excellent crack resistance. In addition, since the production method of the present invention does not use a large amount of water, it can not only produce a foamed molded product at a low cost in a plant capable of mass production, but also has the above characteristics by adding a small amount of a specific surfactant. The pre-expanded particles can be produced efficiently.

  Expandable polystyrene resin particles imparted with foaming performance are obtained by impregnating polystyrene resin particles with a volatile foaming agent such as propane, butane, or pentane. Expandable polystyrene resin particles have good retention of the foaming agent and can be stored at room temperature or in a refrigerated state. Accordingly, it is possible to heat the expandable polystyrene resin particles at appropriate times to obtain pre-expanded particles, which are filled in a mold of a molding machine and heated to obtain a foam molded product. Since this foamed molded article is excellent in heat insulation, buffer and lightness, it is widely used as a food container such as a fish box, a shock absorber for home appliances, a heat insulator for building materials, and the like. However, this foamed molded product has a problem that it is easily broken by an impact or the like, and there has been a limit to expansion of applications.

  On the other hand, in addition to the features of foamed molded products made of polystyrene resin, foamed molded products made of polyolefin resins such as polyethylene resins and polypropylene resins are flexible and resistant to cracking (excellent crack resistance). It has been known. However, since polyolefin resin particles are inferior in retention of the foaming agent, there is a problem that they cannot be stored in the state of expandable resin particles. In addition, since it is necessary to precisely control the foam molding conditions, there is a problem that the manufacturing cost is high.

  In order to solve the above problems, various foamable composite particles have been proposed in which a polyethylene resin particle is impregnated and polymerized with a styrene monomer in an aqueous medium to modify the polystyrene resin with a polyethylene resin. .

For example, in JP-A-2006-7022 (Patent Document 1), 300 to 1000 parts by weight of a polystyrene resin component and volatile to 100 parts by weight of a polyethylene resin component having a melting point of 95 to 115 ° C. containing an inorganic nucleating agent. Expandable composite resin particles containing a foaming agent and having a surface layer portion of at least 5 μm from the particle surface in which polystyrene resin particles of 0.8 μm or less are dispersed have been proposed.
In addition, International Publication No. 2005/021624 pamphlet (Patent Document 2) proposes a pre-expanded polystyrene resin particle modified with a polyolefin resin and a method for producing the same.

  In addition, in Japanese Patent Publication No. 7-91405 (Patent Document 3), Japanese Patent No. 2760361 (Patent Document 4), and Japanese Patent Publication No. 7-91406 (Patent Document 5), the composite resin particles having a reduced moisture content are used. It has been proposed that when a specific organic compound is allowed to coexist in water when impregnated with a foaming agent, a foamed molded article having excellent appearance and fusion property can be obtained even when the water content is reduced.

JP 2006-70202 A International Publication No. 2005/021624 Pamphlet Japanese Examined Patent Publication No. 7-91405 Japanese Patent No. 2760361 Japanese Patent Publication No. 7-91406

  The expandable resin particles described in JP-A-2006-70202 are pre-expanded so that a foamed molded article having good fusion property and surface appearance can be obtained when the polystyrene resin component is excessively larger than the polyethylene resin component. Although the particle molding period (hereinafter referred to as foamed particle life) has been improved, the influence of outside air temperature and crack resistance have been insufficient, and improvement has been demanded.

  In the pre-expanded particles described in the pamphlet of International Publication No. 2005/021624, although the above-mentioned problems have been improved, it is hoped that both the retention of the foaming agent due to the influence of the outside air temperature and the high resistance to cracking can be achieved at a high level. It is rare.

  Further, in Japanese Patent Publication No. 7-91405, Japanese Patent No. 2760361 and Japanese Patent Publication No. 7-91406, it is necessary to add a small amount of water at the time of impregnation with the foaming agent. There was a need for further improvements in life.

  Accordingly, the present invention provides a foamable composite resin particle comprising a polyolefin resin and a polystyrene resin, which can provide a foamed molded article having good fusion properties and excellent crack resistance even after a long period of time after preliminary foaming, and An object is to provide pre-expanded particles.

  The present inventor obtains expandable composite resin particles by impregnating a composite resin particle containing a polyolefin resin and a polystyrene resin with a foaming agent in the presence of a nonionic surfactant, and further pre-expands it. In the pre-expanded particles obtained, it was found that the pre-expanded particles having a double-cell structure in which the size of the bubbles in contact with the skin layer and the size of the internal bubbles (average cell diameter) are different can extend the life of the expanded particles.

  Thus, according to the present invention, composite resin particles containing 100 parts by weight of polyolefin resin and 120 to 560 parts by weight of polystyrene resin, and 0.05 to 2.5 nonionic surfactant per 100 parts by weight of composite resin particles. A section of a cross-section of a foamed composite resin particle containing a weight part and a foaming agent, the pre-foamed particle obtained by pre-foaming the foamable composite resin particle being divided into two from the surface through the center. When photographed with a microscope, the value A / B obtained by dividing the average bubble diameter A of the bubbles in contact with the skin layer of the pre-expanded particles by the average bubble diameter B of the bubbles passing through the half of the radius of the pre-expanded particles. It is possible to provide expandable composite resin particles characterized in that pre-expanded particles having a ratio of 2 to 6 can be formed.

  Further, according to the present invention, composite resin particles containing 100 parts by weight of polyolefin resin and 120 to 560 parts by weight of polystyrene resin, and 0.05 to 2 parts of nonionic surfactant per 100 parts by weight of composite resin particles. The pre-expanded particles are derived from expandable composite resin particles containing 5 parts by weight and a foaming agent, and the pre-expanded particles are divided into two from the surface of the pre-expanded particles through the center by 5 to 60 times. When the cross section of the cut section was photographed with a scanning electron microscope, the average bubble diameter A of the bubbles in contact with the skin layer of the pre-expanded particles was determined as the average bubble diameter of the bubbles passing through the half of the radius of the pre-expanded particles. Pre-expanded particles are provided in which the value divided by B is 2-6.

  Further, according to the present invention, there is provided a method for producing the expandable composite resin particles, wherein 100 parts by weight of the composite resin particles are mixed with 0.05 to 2.5 parts by weight of a nonionic surfactant and 50 parts by weight or more. Provided is a method for producing expandable composite resin particles, wherein the composite resin particles are impregnated with the foaming agent in the presence of a foaming agent.

  Further, according to the present invention, there is provided a method for producing the foamable composite resin particles, wherein 100 parts by weight of the composite resin particles are present in the presence of 0.05 to 2.5 parts by weight of a nonionic surfactant and an aqueous medium. There is provided a method for producing expandable composite resin particles, wherein the composite resin particles are impregnated with the foaming agent in the absence of.

In addition, according to the present invention, there is provided a method of pre-foaming the foamable composite resin particles by pre-foaming the bulk multiple of 5 to 60 times.
Moreover, according to this invention, the foaming molding obtained by carrying out in-mold shaping | molding of the said pre-expanded particle is provided.

The foamable composite resin particles containing the polyolefin resin and the polystyrene resin of the present invention and the pre-expanded particles of the composite resin particles containing the polyolefin resin and the polystyrene resin obtained by heating are the conventional polyolefin resin and polystyrene. Expanded particle life, which was a problem of pre-expanded particles of composite resin particles containing a resin, can be improved.
That is, even in the in-mold foam molding conditions in which a molded article with a good nobi could not be obtained with the pre-foamed resin particles of the composite resin particles containing the conventional polyolefin-based resin and polystyrene-based resin after the days after the pre-foaming If pre-expanded resin particles are used, it is possible to obtain a foam-molded article having good nobi.

  Said effect was not acquired when the composite resin particle containing polyolefin resin and polystyrene resin was processed by surfactants other than a nonionic surfactant. The above effect is because the nonionic surfactant has a high affinity with the composite resin particles containing a polyolefin resin and a polystyrene resin, and therefore, when impregnated with the foaming agent, the nonionic surfactant converts the foaming agent into resin particles. It may be localized near the surface.

It is a figure explaining the measuring method of the average bubble diameter of a pre-expanded particle. 2 is an electron micrograph of a cut surface of pre-expanded particles of Example 1. FIG. 7 is an electron micrograph of a cut surface of pre-expanded particles of Example 6. FIG. 4 is an electron micrograph of a cut surface of pre-expanded particles of Comparative Example 1. 4 is an electron micrograph of a cut surface of pre-expanded particles of Comparative Example 3.

Expandable composite resin particles Expandable composite resin particles (also referred to as expandable composite resin particles) containing the polyolefin resin and polystyrene resin of the present invention are:
(1) Impregnation with 0.05 to 2.5 parts by weight of a nonionic surfactant and a foaming agent with respect to 100 parts by weight of composite resin particles including 100 parts by weight of polyolefin resin and 120 to 560 parts by weight of polystyrene resin And
(2) When the cross section of the pre-expanded particles obtained by pre-expanding the expandable composite resin particles through the center through the center is photographed with a scanning electron microscope, the pre-expanded particles are in contact with the skin layer of the pre-expanded particles. The value obtained by dividing the average bubble diameter A of the bubbles by the average bubble diameter B of the bubbles passing through the half of the radius of the pre-expanded particles (hereinafter referred to as A / B value) becomes 2-6. Particles that can form particles. The latter measurement method will be described in detail in the Examples section. The A / B value is a value that is hardly affected by the bulk multiple of the pre-expanded particles.

The foamable composite resin particles containing the polyolefin resin and the polystyrene resin are obtained by impregnating a foaming agent into the composite resin particles containing the polyolefin resin and the polystyrene resin in the presence of a nonionic surfactant. can get.
(Composite resin particles)
Composite resin particles (also referred to as composite resin particles) containing a polyolefin resin and a polystyrene resin are resin particles containing a polyolefin resin and a polystyrene resin.
It does not specifically limit as polyolefin-type resin, A well-known resin can be used. The polyolefin resin may be cross-linked. For example, polyethylene resins such as branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, and cross-linked products of these polymers And polypropylene resins such as propylene homopolymer, propylene-vinyl acetate copolymer, ethylene-propylene random copolymer, propylene-1-butene copolymer, and ethylene-propylene-butene random copolymer. In the above example, low density is preferably 0.91~0.94g / cm ^3, more preferably 0.91~0.93g / cm ^3. High density is preferably 0.95~0.97g / cm ^3, more preferably 0.95~0.96g / cm ^3. The medium density is an intermediate density between these low density and high density.

  The polystyrene resin is polystyrene or a copolymer of styrene as a main component and another monomer copolymerizable with styrene. The main component means that styrene accounts for 70% by weight or more of the total monomers. Other monomers include halogenated styrene such as chlorostyrene and bromostyrene, alkyl styrene such as vinyl toluene, α-methyl styrene and p-methyl styrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid and alkyl acrylate ester. Methacrylic acid alkyl ester, divinylbenzene, polyethylene glycol dimethacrylate and the like. In the examples, alkyl means alkyl having 1 to 8 carbon atoms.

  The polystyrene resin is contained in the composite resin particles in the range of 120 to 560 parts by weight of the polystyrene resin with respect to 100 parts by weight of the polyolefin resin.

  When there is more content of a polystyrene-type resin than 560 weight part, the crack resistance of a foaming molding may fall. On the other hand, if the amount is less than 120 parts by weight, the cracking resistance is greatly improved, but the dissipation of the foaming agent from the surface of the expandable composite resin particles tends to be accelerated. Therefore, the bead life of the foamable composite resin particles may be shortened due to a decrease in the retention of the foaming agent. A more preferable content of the polystyrene resin is 140 to 450 parts by weight, and a more preferable content is 150 to 400 parts by weight.

The composite resin particles can be obtained by impregnating and polymerizing a styrene monomer in a polyolefin resin particle to produce a polystyrene resin.
The polyolefin resin particles can be obtained by a known method. For example, polyolefin resin particles can be prepared by first melt-extruding a polyolefin resin using an extruder and then granulating it by underwater cutting, strand cutting, or the like. Usually, the shape of the polyolefin resin to be used is, for example, a true spherical shape, an elliptical spherical shape (egg shape), a cylindrical shape, a prismatic shape, a pellet shape, or a granular shape. Hereinafter, the polyolefin resin particles are also referred to as micropellets.

  The polyolefin resin may contain a radical scavenger. The radical scavenger may be added to the polyolefin resin in advance, or may be added simultaneously with melt extrusion. As the radical scavenger, a compound having an action of scavenging radicals such as a polymerization inhibitor (including a polymerization inhibitor), a chain transfer agent, an antioxidant, a hindered amine light stabilizer, and the like, which is difficult to dissolve in water, is preferable. .

  Examples of the polymerization inhibitor include phenol polymerization inhibitors, nitroso polymerization inhibitors, aromatic amine polymerization inhibitors, phosphite ester polymerization inhibitors, thioether polymerization inhibitors, and the like.

  Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, amine antioxidants, and the like.

The amount of the radical scavenger used is preferably 0.005 to 0.5 parts by weight with respect to 100 parts by weight of the polyolefin resin.
Polyolefin-based resins include talc, calcium silicate, calcium stearate, synthetic or naturally produced silicon dioxide, ethylene bis-stearic acid amide, methacrylic acid ester copolymer and the like, and triallyl isocyanurate 6 A flame retardant such as bromide and a colorant such as carbon black, iron oxide and graphite may be included.

Next, the micropellets are dispersed in an aqueous medium in a polymerization vessel and polymerized while impregnating the styrenic monomer into the micropellets.
Examples of the aqueous medium include water and a mixed medium of water and a water-soluble solvent (for example, alcohol).

  As the styrenic monomer, any of styrene and substituted styrene (substituent includes lower alkyl, halogen atom (especially chlorine atom) and the like) can be used. The styrene monomer is a mixture of styrene and substituted styrene, a small amount of other monomers copolymerizable with styrene (for example, acrylonitrile, alkyl methacrylate (about 1 to 8 carbon atoms in the alkyl portion), maleic acid Mixtures with mono- or dialkyls (about 1 to 4 carbon atoms in the alkyl moiety), divinylbenzene, ethylene glycol mono- or diacrylic acid or methacrylic acid ester, maleic anhydride, N-phenylmaleide, etc. can be used. In these mixtures, styrene preferably occupies a dominant amount (for example, 50% by weight or more).

A solvent (plasticizer) such as toluene, cyclohexane, ethyl acetate, or isobutyl adipate may be added to the styrene monomer.
The usage-amount of a styrene-type monomer is 120-560 weight part with respect to 100 weight part of polyolefin-type resin particles. More preferably, it is 140-450 weight part, More preferably, it is 150-400 weight part.

  If the amount of the styrene monomer used exceeds 560 parts by weight, the polystyrene resin particles may be generated without being impregnated into the polyolefin resin particles. In addition, not only the crack resistance of the foamed molded product is lowered, but also the chemical resistance may be lowered. On the other hand, if it is less than 120 parts by weight, the ability to hold the foaming agent of the foamable composite resin particles may be lowered. If it falls, it will become difficult to make it highly foamed. In addition, the rigidity of the foamed molded product may be reduced.

  The impregnation of the polyolefin resin particles with the styrene monomer may be performed while polymerizing, or may be performed before the polymerization is started. Of these, it is preferable to carry out the polymerization. When the polymerization is performed after impregnation, polymerization of the styrene monomer near the surface of the polyolefin resin particles tends to occur, and the styrene monomer not impregnated in the polyolefin resin particles is polymerized alone. In some cases, a large amount of fine particle polystyrene resin particles are produced.

When the impregnation is carried out while polymerizing, the polyolefin resin particles for calculating the content are particles composed of a polyolefin resin, an impregnated styrene monomer, and an impregnated polystyrene resin that has already been impregnated. Means.
In order to maintain the content at 0 to 35% by weight, the styrenic monomer can be continuously or intermittently added to the aqueous medium in the polymerization vessel. In particular, it is preferable to gradually add the styrenic monomer into the aqueous medium.

  An oil-soluble radical polymerization initiator can be used for the polymerization of the styrene monomer. As this polymerization initiator, a polymerization initiator generally used for the polymerization of styrene monomers can be used. For example, benzoyl peroxide, lauroyl peroxide, t-butyl peroxy octoate, t-hexyl peroxy octoate, t-butyl peroxy benzoate, t-amyl peroxy benzoate, t-butyl peroxybivalate, t- Butyl peroxyisopropyl carbonate, t-hexyl peroxyisopropyl carbonate, t-butyl peroxy-3,3,5-trimethylcyclohexanoate, di-t-butylperoxyhexahydroterephthalate, 2,2-di-t- Examples thereof include organic peroxides such as butyl peroxybutane, di-t-hexyl peroxide, and dicumyl peroxide. These oil-soluble radical polymerization initiators may be used alone or in combination.

Various methods can be used as a method of adding the polymerization initiator to the aqueous medium in the polymerization vessel. For example,
(1) A method in which a polymerization initiator is dissolved and contained in a styrene monomer in a container different from the polymerization container, and the styrene monomer is supplied into the polymerization container.
(2) A solution is prepared by dissolving a polymerization initiator in a part of a styrene monomer, a solvent such as isoparaffin or a plasticizer. A method of simultaneously supplying this solution and a predetermined amount of styrenic monomer into the polymerization vessel,
(3) A dispersion in which a polymerization initiator is dispersed in an aqueous medium is prepared. Examples thereof include a method of supplying the dispersion and the styrene monomer into a polymerization vessel.
The amount of the polymerization initiator used is usually preferably 0.02 to 2.0% by weight based on the total amount of styrene monomer used.

  It is preferable to dissolve a water-soluble radical polymerization inhibitor in the aqueous medium. The water-soluble radical polymerization inhibitor not only suppresses the polymerization of the styrene monomer on the surface of the polyolefin resin particles, but also prevents the styrene monomer floating in the aqueous medium from being polymerized alone. This is because the generation of fine particles can be reduced.

As the water-soluble radical polymerization inhibitor, a polymerization inhibitor that dissolves 1 g or more in 100 g of water can be used. For example, thiocyanate such as ammonium thiocyanate, zinc thiocyanate, sodium thiocyanate, potassium thiocyanate, aluminum thiocyanate Nitrate, mercapto Ethanol, monothiopropylene glycol, thioglycerol, thioglycolic acid, thiohydroacrylic acid, thiolactic acid, thiomalic acid, thioethanolamine, 1,2-dithioglycerol, 1,3-dithioglycerol, etc. Water-soluble sulfur-containing organic compounds, mention may be made more ascorbic acid, sodium ascorbate and the like. Of these, nitrite is particularly preferable.
As the usage-amount of the said water-soluble radical polymerization inhibitor, 0.001-0.04 weight part is preferable with respect to 100 weight part of water of an aqueous medium.

In addition, it is preferable to add a dispersant to the aqueous medium. Examples of such a dispersant include organic dispersants such as partially saponified polyvinyl alcohol, polyacrylate, polyvinyl pyrrolidone, carboxymethyl cellulose, and methyl cellulose, magnesium pyrophosphate, calcium pyrophosphate, calcium phosphate, calcium carbonate, and magnesium phosphate. And inorganic dispersants such as magnesium carbonate and magnesium oxide. Of these, inorganic dispersants are preferred.
When an inorganic dispersant is used, it is preferable to use a surfactant in combination. Examples of such surfactants include sodium dodecylbenzene sulfonate (sodium), sodium α-olefin sulfonate, and the like.

The shape and structure of the polymerization vessel are not particularly limited as long as they are conventionally used for suspension polymerization of styrene monomers. Usually, a polymerization vessel provided with a stirring blade is used.
Further, the shape of the stirring blade is not particularly limited, and specifically, a paddle blade such as a V-shaped paddle blade, a fiddler blade, an inclined paddle blade, a flat paddle blade, a pull margin blade, a turbine blade, a fan turbine blade, etc. Examples include a turbine blade and a propeller blade such as a marine propeller blade. Of these stirring blades, paddle blades are preferred. The stirring blade may be a single-stage blade or a multi-stage blade. A baffle may be provided in the polymerization container.

  The temperature of the aqueous medium when polymerizing the styrene monomer in the micropellet is not particularly limited, but is preferably in the range of −30 to + 20 ° C. of the melting point of the polyolefin resin to be used. More specifically, 70-140 degreeC is preferable and 80-130 degreeC is more preferable. Furthermore, the temperature of the aqueous medium may be a constant temperature from the start to the end of the polymerization of the styrenic monomer, or may be increased stepwise. When raising the temperature of an aqueous medium, it is preferable to make it raise at the temperature increase rate of 0.1-2 degree-C / min.

  Examples of the crosslinking agent used for crosslinking the polyolefin resin include 2,2-di-t-butylperoxybutane, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxy. An organic peroxide such as hexane may be mentioned. In addition, a crosslinking agent may be individual or may be used together 2 or more types. Moreover, the usage-amount of a crosslinking agent has preferable 0.05-1.0 weight part normally with respect to 100 weight part of polyolefin resin particles (micro pellet).

  As a method of adding a crosslinking agent, for example, a method of directly adding a crosslinking agent to a polyolefin resin, a method of adding a crosslinking agent after dissolving it in a solvent, a plasticizer or a styrene monomer, and dispersing the crosslinking agent in water For example, a method of adding after adding them. Among these, the method of adding after dissolving a crosslinking agent in a styrene-type monomer is preferable.

  The average particle size of the composite resin particles is preferably 800 to 2400 μm. Composite resin particles having an average particle diameter of less than 800 μm tend to have a reduced bead life due to a decrease in foam retention. When it exceeds 2400 μm, the filling property to the mold tends to be deteriorated when a foamed molded article having a complicated shape is molded. A preferable average particle diameter is 1200-2000 micrometers.

(Non-ionic surfactant treatment)
Next, before the composite resin particles are impregnated with the foaming agent, the composite resin particles are previously treated with a nonionic surfactant. The method of treating the composite resin particles with a nonionic surfactant can be performed by a method known per se. For example, it can be carried out by a method in which a composite resin particle is flowed and a nonionic surfactant is introduced in a rotary mixer having a hermetic pressure resistance such as V type, C type, or DC type.
With respect to the present invention, in order to efficiently impregnate the composite resin particles with the nonionic surfactant, it is carried out without using an aqueous medium in a hermetic pressure-resistant rotary mixer.

  The treatment with the nonionic surfactant is preferably performed in an atmosphere of 20 to 80 ° C. and a pressure of 0.01 to 0.12 MPa for 0.5 to 6 hours. If the temperature, pressure and time are out of the range, the resin may not be sufficiently contained.

  The nonionic surfactant is not particularly limited, and various known nonionic surfactants can be used. For example, polyoxyalkylene alkyl ethers such as polyoxyethylene alkyl ether, single chain length polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene polyoxypropylene alkyl ether (for example, polyoxyethylene propylene lauryl ether) Etc.), polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivatives, ether oxide derivatives of alkylphenol formalin condensates, polyoxyethylene polyoxypropylene block polymers, etc .; Esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene sorbitan fat Esters including esters and polyoxyethylene sorbitol fatty acid esters; including polyethylene glycol fatty acid esters, ethylene glycol fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, sucrose fatty acid esters Ester type; fatty acid alkanolamide, polyoxyethylene fatty acid amide, alkyldiethanolamine (for example, N, N-di (hydroxyethyl) laurylamine), alkylethanolamine (for example, N-hydroxyethyllaurylamine), polyoxyethylene Examples thereof include nitrogen-containing nonionic surfactants containing alkylamine (for example, polyoxyethylene laurylamine). Of these, polyoxyalkylene alkyl ether, alkyldiethanolamine, alkylethanolamine or polyoxyethylene alkylamine is preferred.

The usage-amount of a nonionic surfactant is 0.05-2.5 weight part with respect to 100 weight part of composite resin particles, Preferably it is 0.1-2.0 weight part.
When the amount of the nonionic surfactant used is less than 0.05 parts by weight, it is not possible to obtain expandable composite resin particles and pre-expanded particles having desired performance. No further effect is exhibited, and the foamable composite resin particles may become sticky, resulting in high costs.

(Expandable composite resin particles)
In order to obtain the expandable composite resin particles of the present invention, the composite resin particles are impregnated with a foaming agent. The impregnation of the foaming agent can be performed, for example, in the presence of 0.05 to 2.5 parts by weight of the nonionic surfactant and 50 parts by weight or more of the above-mentioned nonionic surfactant on 100 parts by weight of the composite resin particles. Alternatively, 100 parts by weight of the composite resin particles can be carried out in the presence of 0.05 to 2.5 parts by weight of a nonionic surfactant and in the absence of an aqueous medium. Here, the former is referred to as the soaking method, and the latter is referred to as the dry impregnation method.
When impregnation of the foaming agent is performed in the absence of an aqueous medium, the addition ratio of the foaming agent is preferably 10 to 20 parts by weight with respect to 100 parts by weight of the composite resin particles.

  The impregnation with the foaming agent can be performed by a method known per se under pressure or normal pressure. For example, a rotary mixer such as a V type, C type, or DC type, in which a composite resin particle is flowed in a sealed pressure resistant container and a foaming agent is introduced and impregnated. Examples include a method of impregnating resin particles by immersing them in a foaming agent, and a method of pressing and impregnating a foaming agent into a closed container in which a styrene monomer is polymerized.

The impregnation with the foaming agent is preferably performed under an atmosphere of 30 to 80 ° C. and a pressure of 0.05 to 0.12 MPa for 0.5 to 6 hours. Outside these temperature, pressure and time ranges, the foaming agent and the nonionic surfactant may not be sufficiently contained in the resin, and the foaming cannot be performed to the desired bulk multiple, and the desired performance was obtained. Expandable composite resin particles may not be obtained.
Further, the impregnation with the foaming agent is preferably performed simultaneously with the treatment of the nonionic surfactant in order to increase the impregnation efficiency.

As the foaming agent, various known volatile foaming agents can be used. Examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, industrial pentane, petroleum ether, cyclohexane, cyclopentane and the like alone or as a mixture. Among these, propane, n-butane, isobutane, n-pentane, isopentane, and cyclopentane are preferable.
Further, a foaming aid may be used. Examples of the foaming aid include solvents such as xylene, ethylbenzene, cyclohexane, and d-limonene, and plasticizers (high boiling point solvents) such as diisobutyl adipate, diacetylated monolaurate, and coconut oil. In addition, as addition amount of a foaming adjuvant, 0.1-2.5 weight part is preferable with respect to 100 weight part of composite resin particles.

  After impregnating the foaming agent at a predetermined temperature for a predetermined time, the foaming agent may be removed, and the foamable composite resin particles may be filled again in a sealed container and aged for 12 hours or more in an environment of 70 ° C. or less. There are no particular restrictions on the aging conditions, but aging may not be sufficient if it is 12 hours or less. On the other hand, when the temperature is higher than 70 ° C., the foamable composite resin particles may be bonded in the closed container.

  The content of the foaming agent is preferably 6 to 12% by weight with respect to the foamable composite resin particles. If the content of the foaming agent is less than 6% by weight, the foamability of the foamable composite resin particles may be lowered. When foamability is lowered, it becomes difficult to obtain low-bulk density pre-expanded particles having a high bulk ratio, and the foam-molded product obtained by molding the pre-expanded particles in a mold has a lower fusion rate and is resistant to cracking. May decrease. On the other hand, when the content exceeds 12% by weight, the bubble size in the pre-expanded particles tends to be excessive, and the moldability may be deteriorated and the strength characteristics such as compression and bending of the obtained foamed molded article may be deteriorated. A more preferable content of the blowing agent is in the range of 7.5 to 11% by weight.

  The average particle diameter of the expandable composite resin particles is preferably 800 to 2400 μm. The foamable composite resin particles having an average particle size of less than 800 μm need to reduce the average particle size of the polyolefin resin particles as the raw material, and in that case, the yield of the polyolefin resin particles deteriorates and the cost increases. There is. In addition, the retention property of the foaming agent tends to be reduced and the bead life tends to be shortened. When it exceeds 2400 μm, the filling property to the mold tends to be deteriorated when the foamed molded product having a complicated shape is molded. A preferable average particle diameter is 1200-2000 micrometers.

Pre-foamed particles and foamed molded product Next, a method for obtaining pre-foamed particles and further foamed molded products from the foamable composite resin particles will be described.
Pre-expanded particles can be obtained by heating the expandable composite resin particles using a heating medium such as water vapor and pre-expanding them to a predetermined bulk density as necessary.
The pre-expanded particles preferably have a bulk multiple of 5 to 60 times (bulk density 0.016 to 0.2 g / cm ³ ). When the bulk multiple is larger than 60 times, the closed cell ratio of the expanded particles is lowered, and the strength of the foamed molded product obtained by foaming the pre-expanded particles may be decreased. On the other hand, if it is less than 5 times, the weight of the foamed molded product obtained by foaming the pre-foamed particles may increase.

  Further, the pre-expanded particles are usually stored and aged for about 24 hours. Thereafter, pre-expanded particles are filled in the mold, heated again, the pre-expanded particles are expanded in-mold, the particles are thermally fused, and cooled to obtain a foam-molded article. As the heating medium, water vapor with a gauge pressure of 0.05 to 0.15 MPa is preferably used. As the molding machine, there can be used an EPS molding machine or the like used when producing a foam molded body from pre-expanded particles of polystyrene resin.

  The obtained foamed molded product can be used for applications such as cushioning materials (cushion materials) for home appliances, electronic parts, various industrial materials, food containers and the like. Moreover, it can also be suitably used as an impact energy absorbing material such as a vehicle bumper core material and a door interior cushioning material.

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.
<Pre-foaming conditions>
10-15 kg of foamable composite resin particles are charged into a normal pressure pre-foaming machine (SKK-70 manufactured by Sekisui Koki Co., Ltd.) preheated with steam, and air is introduced while introducing steam at a setting of about 0.02 MPa while stirring. Is also supplied and foamed to a predetermined bulk density (bulk multiple) in about 2 to 3 minutes.

<Bulk density and bulk multiple of pre-expanded particles>
The weight (a) of about 5 g of pre-expanded particles is weighed to the second decimal place. Next, weighed pre-expanded particles in a 500 cm ³ graduated cylinder with a minimum memory unit of 5 cm ³ , and a round resin plate slightly smaller than the caliber of the graduated cylinder, about 1.5 cm wide at the center, The volume (b) of the pre-expanded particles is read by applying a pressing tool in which a rod-shaped resin plate having a length of about 30 cm is fixed upright, and the bulk density (g) of the pre-expanded particles is calculated according to the formula (a) / (b). / Cm ³ ). The bulk multiple is the reciprocal of the bulk density, that is, the formula (b) / (a).

<Calculation of average cell diameter of pre-expanded particles and ratio of inner and outer cell diameter>
Measured as follows according to the test method of ASTM D2842-69.
First, pre-expanded particles that have been pre-expanded to a bulk ratio of 5 to 60 times are prepared, and 10 pre-expanded particles are arbitrarily collected and divided into two from the surface of the razor through the center. The cross section of the divided section is magnified 15 to 30 times with a scanning electron microscope (S-3000N manufactured by Hitachi, Ltd.) and photographed. Next, the photographed screen is printed one by one on A4 paper. From the printed image, as shown in FIG. 1, the length of the epidermis and the number of bubbles in contact with the epidermis layer, the length of the curve passing through the half point of the radius, and the number of bubbles on the curve are measured. Measure the bubbles in contact).

From the measurement result, the average chord length (t) of the bubbles is calculated by the following formula. However, in any straight line, bubbles are prevented from touching only at the contact points as much as possible (in the case of contact, they are included in the number of bubbles).
Average chord length (t) = line length / (number of bubbles x multiple of photo)
And the bubble diameter of each particle | grain is calculated by following Formula using average chord length (t).
Bubble diameter D = t / 0.616
Furthermore, let the arithmetic mean of those be an average bubble diameter.
Divide the average bubble diameter (B) calculated from the average bubble diameter (A) in contact with the skin layer from the curve passing through the half point of the radius to calculate the internal and external bubble diameter ratio (A / B). To do.

<In-mold foam molding conditions>
The pre-expanded particles are filled into a molding machine mold, and after being heated and cooled with steam under the following conditions, the foam molded article is taken out from the mold. The set steam pressure is set to a value at which a good molded article can be obtained with nobi-fusion on the 7th day after the preliminary foaming, and the same set pressure is used from the 14th to 35th day after that.
Molding machine: ACE-3SP manufactured by Sekisui Koki Seisakusho
Mold dimension: 300mm (width) x 400mm (length) x 30mm (thickness)
Molding conditions Mold heating: 5 seconds
Meanwhile heating: 5 seconds
Reverse one-side heating: 5 seconds
Double-sided heating: 15 seconds
Water cooling: 15 seconds
Vacuum cooling: Until the foam pressure of the molded body is 0.05 kgf / cm ² or less. Set steam pressure: 0.6 kgf / cm ^{2 to} 1.0 kgf / cm ²

  Pre-foamed particles to be used are pre-foamed, put in a cloth bag with good air permeability, and stored in an environment at a temperature of 23 ° C. and a humidity of 50%. A foam-molded article is obtained under the above-described foam-molding conditions on the 7th, 14th, 21st, 28th, and 35th days after the preliminary foaming.

<Evaluation of surface smoothness (novi)>
A test piece with a skin of 25 mm × 25 mm is cut out from a foamed product having a predetermined bulk multiple, and the number of particles on the surface of the test piece (skin surface) is measured. Between particles to be measured refers to a contact point where three or more pre-expanded particles are in contact. Next, the number of pinholes (indentations) between particles is measured.
From the above results, the nobility (smoothness) of the surface of the foamed molded product is evaluated by the following formula.
Novi of foamed molded article = (1−number of pinholes between particles / number of all particles) × 5
The criterion is that the foam molded article has a Nobi of 4 or more and a circle of less than 4 is x.

<Evaluation of internal fusion>
A cut line having a depth of about 1 cm is made with a cutter knife along a straight line connecting the centers of a pair of long sides on the surface of the obtained foam molded body, and then the foam molded body is manually moved along the cut line. For foamed particles on the fracture surface, the number of broken particles (a) and the number of broken particles (b) at the interface between the particles are counted, and the formula [(a) / ((A) + (b))] × 100, and the value obtained by substituting it into the fusion rate (%).
In the present invention, a fusion rate of 80% or more is acceptable and less than 80% is unacceptable.

<Falling ball impact strength of foam molding>
In accordance with JIS K 7211, a test piece of 215 mm (length) × 40 mm (width) × 20 mm (thickness) cut out from a predetermined multiple of the foamed molded product was placed on a space of 150 mm between fulcrums, A 321 g hard ball is dropped, and the falling ball impact strength, that is, the 50% breaking height is calculated by the following formula. In addition, the test piece shall have no epidermis on all six sides.
H50 = Hi + d [Σ (i · ni) /N±0.5]
H50: 50% fracture height (cm)
Hi: Test height (cm) when the height level (i) is 0 and the height at which the test piece is expected to break d: Height interval (cm) when the test height is raised or lowered
i: Height level when Hi is 0, and a level that increases or decreases 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) (N = Σni) (whichever is greater is used) Either can be used for the same number)
± 0.5: Negative when using destroyed data, positive when using non-destructed data.
The test piece used was molded on the 35th day after foaming.

Example 1
(Manufacture of composite resin particles)
To 100 parts by weight of ethylene-vinyl acetate copolymer resin particles (LV-211, manufactured by Nippon Polyethylene Co., Ltd., melt flow rate 0.3 g / 10 min, vinyl acetate content 6.2% by weight), calcium silicate 0 as a foam regulator .3 parts by weight and 0.1 part by weight of calcium stearate were added and kneaded uniformly with an extruder to obtain granulated pellets by an underwater cutting method (ethylene-vinyl acetate copolymer resin particles per 100 grains). Adjusted to 80 mg).
Add 40 parts by weight of the above pellets, 120 parts by weight of pure water, 0.45 parts by weight of magnesium pyrophosphate, and 0.02 parts by weight of sodium dodecylbenzenesulfonate to a pressure-resistant container with a stirrer having an internal volume of 100 liters, and stir pure water. Suspended in.
Next, a mixed solution obtained by dissolving 0.03 part by weight of dicumyl peroxide as a radical polymerization initiator in 20 parts by weight of styrene monomer was dropped into this suspension over 30 minutes. After maintaining for 30 minutes after dropping, the temperature of the reaction system was increased to 143 ° C., maintained for 2 hours, and then cooled to room temperature.

  Further, 0.16 part by weight of sodium dodecylbenzenesulfonate was added to this suspension, and then the temperature of the reaction system was raised to 90 ° C., and 0.3 parts by weight of benzoyl peroxide and radical polymerization initiator were used. A mixture of 0.02 parts by weight of t-butyl peroxybenzoate and 0.8 parts by weight of dicumyl peroxide dissolved in 40 parts by weight of styrene monomer is dropped over 2 hours, and polymerization is performed while absorbing the styrene monomer. went. Then, after maintaining at 90 ° C. for 3 hours, the temperature was raised to 135 ° C. and maintained at that temperature for 3 hours to complete the polymerization. After completing the above series of polymerizations, it was cooled to room temperature to obtain composite resin particles.

(Impregnation with foaming agent and nonionic surfactant and pre-foaming)
N-hydroxyethyl laurylamine (Nymeen (registered trademark) L-201 manufactured by NOF Corporation) 0 as a nonionic surfactant in a V-type blender having an internal volume of 50 liters and capable of being sealed with a pressure resistance and 100 parts by weight of composite resin particles .25 parts by weight and 0.5 parts by weight of diisobutyl adipate were added, and 14 parts by weight of butane were press-fitted while sealing and stirring. And after hold | maintaining the inside of a container at 50 degreeC for 2 hours, it cooled and took out the expandable composite resin particle.
The taken-out expandable composite resin particles were immediately pre-expanded to a bulk multiple of 30 times with a batch-type pre-expander, and then stored in a temperature-controlled room at a temperature of 23. The average cell diameters A and B and the ratio A / B of the obtained pre-expanded particles are shown in Table 1.

(Foam molding)
The obtained pre-expanded particles were subjected to in-mold foam molding 7 days, 14 days, 21 days, 28 days, and 35 days after the preliminary foaming. Pre-expanded particles were introduced into a 300 mm (width) × 400 mm (length) × 30 mm (thickness) mold, and 0.6 kgf / cm ² of water vapor was introduced for 30 seconds and heated. After the heating, cooling was performed until the foaming pressure of the foamed molded product decreased to 0.05 kgf / cm ² or less, and a foamed molded product with a bulk multiple of 30 times was taken out.
After foam molding, it was allowed to stand for 6 hours or more in an atmosphere of 35 ° C., and evaluation of nobi and internal fusion was performed. The falling ball impact strength of the molded product on the 35th day after foaming was determined. The results are shown in Table 1.

Example 2
Pre-expanded particles and a foamed molded product are obtained in the same manner as in Example 1 except that the amount of N-hydroxyethyllaurylamine added during impregnation with the foaming agent and the nonionic surfactant is 1.00 parts by weight. It was. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 3
Pre-expanded particles and a foamed molded product are obtained in the same manner as in Example 1 except that the amount of N-hydroxyethyllaurylamine added during impregnation with the foaming agent and nonionic surfactant is 2.00 parts by weight. It was. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 4
N-hydroxyethyl laurylamine added at the time of impregnation with the foaming agent and the nonionic surfactant was polyoxyalkylene alkyl ether (DKSNL-Dash400 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and the addition amount was 1.00 parts by weight Except for the above, pre-foamed particles and a foam-molded article were obtained in the same manner as in Example 1. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 5
N-hydroxyethyl laurylamine to be added at the time of impregnation with the foaming agent and the nonionic surfactant is N, N-di (hydroxyethyl) laurylamine (Nymeen (registered trademark) L-202, manufactured by NOF Corporation) Pre-expanded particles and a foam-molded article were obtained in the same manner as in Example 1 except that the amount was 1.00 parts by weight. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 6
N-hydroxyethyl laurylamine added at the time of impregnation with the foaming agent and the nonionic surfactant is polyoxyethylene laurylamine (Elegan (registered trademark) S-100 manufactured by NOF Corporation), and the addition amount is 1.0 part by weight. Except that, pre-expanded particles and a foam-molded article were obtained in the same manner as in Example 1. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 7
30 parts by weight of the pellets obtained in Example 1, 120 parts by weight of pure water, 0.45 parts by weight of magnesium pyrophosphate and 0.03 parts by weight of sodium dodecylbenzenesulfonate were added and suspended by stirring. Next, a mixed solution prepared by dissolving 0.03 part by weight of dicumyl peroxide in 15 parts by weight of styrene monomer was dropped into this suspension over 30 minutes. After holding for 30 minutes after dropping, the temperature of the reaction system was raised to 135 ° C., held for 2 hours, and then cooled to room temperature.
After adding 0.17 parts by weight of sodium dodecylbenzenesulfonate to the cooled suspension, the temperature of the reaction system was raised to 90 ° C., and 0.3 parts by weight of benzoyl peroxide and t-butyl pers. A mixture prepared by dissolving 0.02 parts by weight of oxybenzoate and 0.8 parts by weight of dicumyl peroxide in 15.4 parts by weight of styrene monomer was dropped over 2 hours, and 39.5 parts by weight of styrene monomer was added over 2 hours. And dripped. Then, it hold | maintained at 90 degreeC for 1 hour, raised to 143 degreeC, and after hold | maintaining for 2 hours, it cooled to normal temperature and obtained the composite resin particle which consists of 30 weight part of polyolefin resin and 70 weight part of polystyrene resin.
Otherwise, in the same manner as in Example 1, impregnation with a foaming agent, preliminary foaming, and foam molding were performed. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Example 8
Linear low density polyethylene resin particles (NF-464A manufactured by Nippon Polyethylene Co., Ltd.) were heated and mixed with an extruder, and granulated into pellets by an underwater cutting method (adjusted to 80 mg per 100 grains). 20 parts by weight of this linear low density polyethylene, 100 parts by weight of pure water, 0.9 part by weight of magnesium pyrophosphate, and 0.01 part by weight of sodium dodecylbenzenesulfonate were added. These were stirred and suspended. Next, 10 parts by weight of a styrene monomer in which 0.03 parts by weight of dicumyl peroxide was dissolved as a polymerization initiator was dropped into this suspension over 30 minutes. After dripping, after maintaining at 60 ° C. for 30 minutes, the temperature was raised to 135 ° C. and maintained for 2 hours.
Then, it cooled to 115 degreeC and 0.04 weight part of sodium dodecylbenzenesulfonate was added to the suspension. Thereafter, 70 parts by weight of a styrene monomer in which 0.28 parts by weight of t-butyl peroxybenzoate as a polymerization initiator was dissolved was dropped over 6 hours, held at 115 ° C. for 1 hour, then heated to 143 ° C., After holding for 3 hours, it was cooled to room temperature.
Otherwise, in the same manner as in Example 1, impregnation with a foaming agent, preliminary foaming, and foam molding were performed. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Comparative Example 1
Pre-expanded particles and a foamed molded article were obtained in the same manner as in Example 1 except that the nonionic surfactant was not added at the time of impregnation with the foaming agent and the nonionic surfactant. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Comparative Example 2
Pre-expanded particles and a foamed molded article are obtained in the same manner as in Example 1 except that the amount of N-hydroxyethyllaurylamine added during impregnation with the foaming agent and the nonionic surfactant is 0.01 parts by weight. It was. Table 1 shows the average cell diameters A and B and the ratio A / B of the obtained pre-expanded particles, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

Comparative Example 3
In the step of impregnating the foaming agent, 2 kg of composite resin particles and 2 L of isopentane were put into a 5 L autoclave equipped with a pressure stirrer, held at 35 ° C. for 285 minutes, then cooled to 25 ° C. or lower, and the expandable composite resin particles were taken out Obtained the pre-expanded particles and the expanded molded body in the same manner as in Example 1. Table 1 shows the average cell diameters A and B and the ratio A / B of the pre-expanded particles obtained, and the evaluation results of the foam molded article's Novi, internal fusion, and falling ball impact strength.

2 and 3, in the pre-expanded particles of Examples 1 and 6, the average bubble diameter of the bubbles in contact with the skin layer is larger than the average bubble diameter of the bubbles passing through the half point of the radius. I understand.
From FIG. 4, it can be seen that the pre-expanded particles of Comparative Example 1 have no change in the average bubble diameter of the bubbles in contact with the skin layer and the average bubble diameter of the bubbles passing through half the radius.
From FIG. 5, it can be seen that the pre-expanded particles of Comparative Example 3 have a very large average bubble diameter of bubbles in contact with the skin layer with respect to the average bubble diameter of the bubbles passing through the half of the radius. I understand.
From Table 1, it can be seen that, according to the examples, even if the pre-expanded particles are long after the pre-expansion, the appearance is beautiful and a foam molded article having a high falling ball impact strength can be obtained.
From the examples and comparative examples, if the ratio A / B is in the range of 2 to 6, even if the pre-foamed particles are long after pre-foaming, the appearance is beautiful and has a high falling ball impact strength. It turns out that a foaming molding is obtained.
From Examples and Comparative Example 2, before impregnating the foaming agent, the amount of the nonionic surfactant to be pretreated is 0.05 to 2.5 parts by weight with respect to 100 parts by weight of the composite resin particles. Thus, it can be seen that even if the pre-foamed particles have a long time after pre-foaming, the appearance is beautiful and a foam-molded article having a high falling ball impact strength can be obtained.

Claims (8)

  Composite resin particles containing 100 parts by weight of a polyolefin resin and 120 to 560 parts by weight of a polystyrene resin, 0.05 to 2.5 parts by weight of a nonionic surfactant per 100 parts by weight of the composite resin particle, and a foaming agent When the cross-section of a section obtained by pre-foaming the foamable composite resin particles obtained by pre-foaming the foamable composite resin particles and dividing the section into two parts through the center from the surface is taken with a scanning electron microscope, Preliminary value A / B obtained by dividing the average bubble diameter A of the bubbles in contact with the skin layer of the pre-expanded particles by the average bubble diameter B of the bubbles passing through half the radius of the pre-expanded particles is 2-6. Expandable composite resin particles characterized by being capable of forming expanded particles.   The expandable composite resin particle according to claim 1, wherein the nonionic surfactant is polyoxyalkylene alkyl ether, alkyldiethanolamine, alkylmonoethanolamine or polyoxyethylene alkylamine.   Composite resin particles containing 100 parts by weight of a polyolefin resin and 120 to 560 parts by weight of a polystyrene resin, 0.05 to 2.5 parts by weight of a nonionic surfactant per 100 parts by weight of the composite resin particle, and a foaming agent It is a pre-expanded particle derived from the expandable composite resin particle, and the pre-expanded particle has a bulk magnification of 5 to 60 times, and a cross section of the section divided into two from the surface of the pre-expanded particle through the center is a scanning electron. When photographed with a microscope, the value obtained by dividing the average bubble diameter A of the bubbles in contact with the skin layer of the pre-expanded particles by the average bubble diameter B of the bubbles passing through half the radius of the pre-expanded particles is 2 to 2. Pre-expanded particles, characterized in that   It is a manufacturing method of the foamable composite resin particle of Claim 1 or 2, Comprising: 100-weight part of the said composite resin particle is 0.05-2.5 weight part of nonionic surfactant, and foaming of 50 weight part or more. A method for producing expandable composite resin particles, comprising impregnating the composite resin particles with the foaming agent in the presence of an agent.   It is a manufacturing method of the expandable composite resin particle of Claim 1 or 2, Comprising: 100 weight part of the said composite resin particle is presence of 0.05-2.5 weight part of nonionic surfactant, and an aqueous medium. A method for producing expandable composite resin particles, wherein the composite resin particles are impregnated with the foaming agent in the absence.   The production method according to claim 5, wherein the impregnation of the foaming agent is performed in the presence of 10 to 20 parts by weight of the foaming agent with respect to 100 parts by weight of the composite resin particles.   A method for pre-expanding particles by pre-expanding the expandable composite resin particles according to claim 1 or 2 to 5 to 60 times in bulk.   A foam molded article obtained by molding the pre-expanded particles of claim 3 in-mold.