JPH11322998A - Thermoplastic resin powder mixture, its preparation and production of foam using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mixture which gives a foam excellent in expansion magnification and expansion uniformity and having a complicated shaped by mixing a thermoplastic resin powder having a specific average particle diameter with a minute hollow sphere comprising a thermoplastic resin containing a gas or a volatile liquid in a specific ratio. SOLUTION: A thermoplastic resin powder (85-99 wt.%) having an average particle diameter of 75-500 μm and 1-15 wt.% of a minute hollow sphere comprising a thermoplastic resin containing a gas or a volatile liquid are mixed. The minute hollow sphere preferably has an average particle diameter of 5-100 μm. A mixture is obtained by dry blending, i.e., by mixing the thermoplastic resin powder and the minute hollow sphere with a gas such as air as a medium without plasticization. As a suitable method to heat-treat the mixture to foam the same and to impart a complicated shape to the foam, powder molding, especially powder slash molding is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin powdery mixture for foaming which gives a thermoplastic resin foam having an excellent expansion ratio and uniformity of foam and having a complicated shape, a method for producing the same, and a process for producing the same. And a method for producing a foam.

[0002]

2. Description of the Related Art In general, a thermoplastic resin foam can be obtained by gasifying and expanding a foaming agent added to a resin. For example, an extrusion foaming method in which a foaming agent and a resin are melt-kneaded in a kneading machine such as an extruder and the foaming agent is gasified, and then extruded under atmospheric pressure to form a sheet-like or tube-like foam molding. An injection foaming method for injecting a molten resin containing a foaming agent gasified in a kneader in a kneader in the same manner as the extrusion foaming method into a mold to obtain a foamed molded product, a mixture of a resin and a foaming agent. Filling in a heated mold, decomposing and gasifying the foaming agent in the mixture under pressure sealing conditions, then opening the mold and expanding the gas to obtain a foam molded product After uniformly dispersing the resin powder and the foaming agent in a medium such as water or a plasticizer, a method of foaming by gasifying the foaming agent by heat treatment, filling the pre-expanded particles in a mold, By steam or the like that passes the pre-expanded particles into the mold Such as heating to mold molding method of pre-expanded particles to obtain a foamed molded article of the mold product by fusing are widely known.

[0003] The foaming agent used in these foam moldings is generally a decomposable chemical foaming agent which decomposes upon heating to generate a gas, or a volatile substance represented by a hydrocarbon-based low-boiling compound. Widely used.

[0004]

However, with these conventional foam molding methods, it is difficult to obtain a thermoplastic resin foam having an excellent expansion ratio and foam uniformity and a complicated shape. In the extrusion foaming method, the shape of the foam is determined by the shape of the discharge port of the extruder. However, even if the shape of the discharge port is complicated, the detailed shape disappears due to expansion of the resin. Also, a method of forming a sheet-like foam by an extrusion foaming method and then shaping it by a method such as vacuum pressure forming method is known, but it is difficult to give a complicated shape by these methods, and Is also inferior. Further, in the case of the mold foaming method, similarly to the extrusion foaming method, the shape of the details is lost due to the resin expansion when the mold is opened. Regarding the injection foaming method, it is possible to give a certain shape by using a material having excellent fluidity, but a foam having a very complicated shape such as a foam layer constituting an instrument panel as an automobile interior material can be provided. If it is to be obtained, since further high fluidity is required, the viscoelasticity of the resin necessary for obtaining good foaming properties is lost, and as a result, a product with poor foaming properties and appearance is obtained. Only. Regarding the in-mold molding method of the pre-expanded particles, the particle size of the pre-expanded particles is large,
In addition, since the specific gravity is low, there is a problem in the filling property in the mold.
In addition, since the thermal conductivity of the pre-expanded particles is low, a method of feeding steam or the like into the mold to fuse the pre-expanded particles, and then draining the drain is generally known. Alternatively, a technique is required, and the method is less versatile. In a method using a medium such as water or a plasticizer, since the resin mixture containing a foaming agent has excellent fluidity, it is possible to transfer a complex mold shape and foam the same, but it takes a drying step of the medium. It is not an industrially superior method in terms of time, cost, and the like. In addition, when a foam containing a large amount of a medium is used, problems such as adhesion and thermal stability occur.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above problems, and as a result, have found that a thermoplastic resin powder having a specific average particle size and a fine hollow sphere containing a gas or a volatile liquid are used. It has been found that the resulting thermoplastic resin mixture for foaming is excellent in foaming ratio and foam uniformity and can give a foam having a complicated shape, thereby completing the present invention.

That is, the present invention provides an average particle size of 75 to 500.
a thermoplastic resin powder for foaming, comprising 85 to 99% by weight of a thermoplastic resin powder having a thickness of 1 μm and 1 to 15% by weight of fine hollow spheres made of a plastic resin containing a hot gas or a volatile liquid. The present invention relates to a mixture, a method for producing the mixture, and a method for producing a foam using the mixture.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

"Thermoplastic resin powder" The thermoplastic resin powder according to the present invention is a thermoplastic resin having an average particle diameter of 75 to 500 μm and capable of being molded by heating. Then, it is made of a thermoplastic resin having a property of being reversibly cured.

The thermoplastic resin used as the thermoplastic resin powder in the present invention will be exemplified below.

Polyolefin resins, for example, ethylene, propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene And olefins such as 1-hexadecene, 1-octadecene and 1-eicosene, or polymers obtained by homopolymerization or copolymerization of diolefins such as butadiene and isoprene, and vinyl acetate, acrylic acid and acrylic acid. Examples include copolymers with monomers such as esters, methacrylic acid, methacrylic esters, vinyl alcohol, and maleic acid.

[0011] Polyvinyl chloride resins include, for example, polyvinyl chloride, chlorinated polyvinyl chloride, polyvinylidene chloride and the like.

Polystyrene resin, for example, polystyrene, styrene / maleic acid derivative copolymer, styrene / acrylonitrile copolymer, acrylonitrile / butadiene / styrene copolymer, acrylonitrile / acrylic ester / styrene copolymer, methyl methacrylate / butadiene / Styrene copolymer.

Acrylic resin such as polymethyl methacrylate.

Polyamide is a crystalline resin constituting a main chain by repeating an acid amide bond (-CONH-). Specific examples thereof include polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11, polyamide 12, and polyamide 46. , Polyamide MXD6, modified polyamide 6T and the like.

Specific examples of the thermoplastic polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polycyclohexylene dimethylene terephthalate.

Thermoplastic elastomers Urethane-based, PVC-based, olefin-based, styrene-based, fluorine-based, polyamide-based, and polyester-based thermoplastic elastomers.

Others Specific examples include polyoxymethylene, polycarbonate, modified polyphenylene ether and the like.

The above-mentioned thermoplastic resins can be used alone or as a mixture of two or more kinds as a thermoplastic resin powder. Further, the thermoplastic resin used in the thermoplastic resin powder may contain various additives and low molecular weight polymers, rubbers, etc., and further, when adjusting the bulk specific gravity of the thermoplastic resin powder, or when foaming Various fillers may be contained for the purpose of, for example, uniformly miniaturizing bubbles, and as an additive, for example, a mineral oil-based softener such as a paraffin-based process oil, a silicone-based oil, a phenol-based, a phosphorus-based, Examples include amine-based and sulfur-based antioxidants, weather stabilizers, internally added release agents, coloring pigments, and the like.Examples of low-molecular-weight polymers include low-molecular-weight polyethylene, low-molecular-weight polypropylene, low-molecular-weight polystyrene, and oligoester acrylate. , Liquid rubber,
Examples include dicyclopentadiene resin, petroleum resin, polyhydroxy polyolefin, polybutene-1 and the like. Examples of rubbers include acrylic rubber, acrylonitrile / butadiene rubber, isoprene rubber, urethane rubber, liquid rubber, ethylene / propylene rubber, chlorosulfonated polyethylene, chloroprene rubber, silicone rubber, polysulfide rubber, butadiene rubber, butyl rubber, Synthetic rubber such as fluoro rubber, styrene / butadiene rubber, and the like, and natural rubber are exemplified. Examples of the filler include silica, alumina, zinc oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, oxides such as ferrites, calcium hydroxide, aluminum hydroxide, and basic magnesium carbonate. Hydroxide, calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dawsonite, carbonates such as hydrotalcite, calcium sulfate, barium sulfate, sulfates such as gypsum fiber, calcium silicate, talc, clay, mica, montmorillonite Activated clay, sepiolite, imogolite, sericite, glass fiber, glass beads, silicates such as silica-based balloons, nitrides such as aluminum nitride, boron nitride, silicon nitride, carbon black, graphite, carbon fibers, carbonized balloons, Carbons such as charcoal powder, Ron powder,
Organic substances such as wood powder, leather powder, pulp, rubber powder, various metal powders,
Potassium titanate, lead zirconate titanate, aluminum borate, molybdenum sulfide, silicon carbide, stainless steel fiber,
Zinc borate, various magnetic powders, slag fiber, aramid fiber,
Zeolite and the like can be mentioned.

In the present invention, the thermoplastic resin used for the thermoplastic resin powder and the rubbers contained therein are partially cross-linked by a known method of dynamically heat-treating in the presence of an organic peroxide or the like. It may be something. And, as the organic peroxide used when performing partial crosslinking,
For example, benzoyl peroxide, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,
2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, t-butylhydroxy peroxide and the like can be used. Further, in this case, as a crosslinking aid for accelerating crosslinking, for example, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, 1,2-polybutadiene, divinylbenzene and the like may be used in combination.

The thermoplastic resin powder used in the present invention is a powder comprising the above-mentioned thermoplastic resin having an average particle diameter of 75 to 500 μm. Here, when the average particle size of the thermoplastic resin powder is less than 75 μm, the powder is easily scattered, which causes inconvenience in handling. On the other hand, when the average particle size of the thermoplastic resin powder exceeds 500 μm, the fusion property of the powder at the time of foam molding is reduced, so that the appearance is deteriorated or the physical properties of the foam are reduced.

As a method for producing such a thermoplastic resin powder, any method may be used as long as a powder made of a thermoplastic resin having an average particle size of 75 to 500 μm can be obtained. A method for obtaining a powder product from a manufacturing plant, a method for obtaining a powder by pulverizing a pelletized product, melting and kneading several kinds of thermoplastic resins and the like with a kneader to form a pellet, and then pulverizing these to form a powder. And the like. As a method of pulverizing the pellets, for example, a thermoplastic resin pellet is frozen at -50 to -100 ° C. with liquid nitrogen, dry ice, or the like, and a freeze-pulverization method of mechanically pulverizing with a pulverizer, a thermoplastic resin pellet is used. A room temperature pulverization method of mechanically pulverizing with a pulverizer while removing frictional heat with a large amount of air flow or without cooling means, dissolving a thermoplastic resin in a solvent at a high temperature, cooling and precipitating, A precipitation method utilizing the difference or a chemical pulverization method in which a non-solvent is added to the solution to precipitate the solution can be used.

"Micro hollow sphere" The micro hollow sphere containing a gas or a volatile liquid used in the present invention is composed of an outer shell made of a gas or a volatile liquid and a thermoplastic resin surrounding the same. When the thermoplastic resin mixture for foaming of the present invention is subjected to foam molding, it acts as a foaming agent.

Here, the thermoplastic resin forming the outer shell is:
Any thermoplastic resin may be used as long as it is softened by heating at the time of molding the foam. For example, the above-described thermoplastic resin can be used. Further, the gas or volatile liquid contained therein may be of any type as long as it expands by heating at the time of foaming and gives a foam, for example, propane, butane, isobutane, isopentane, hexane, etc. Alicyclic hydrocarbons such as aromatic hydrocarbons, cyclobutane, and cyclopentane; and inorganic gases such as hydrogen halide, carbon dioxide, and nitrogen.

When mixing the hollow microspheres with a thermoplastic resin powder, the mixing ratio is 1 to 15% by weight.
Range. Here, the mixing ratio of the micro hollow sphere is 1
If it is less than% by weight, the resulting foam will have poor foamability. On the other hand, the mixing ratio of the minute hollow spheres is 15% by weight.
When it exceeds, the obtained foam is in an over-foamed state, a coarse pinhole is generated in the foam, and the foam becomes brittle.

The fine hollow spheres used in the present invention are excellent in dispersibility when mixed with a thermoplastic resin powder, and in particular, a foam having excellent foam uniformity is obtained. , 5 to 100 μm.

"Powdered thermoplastic resin mixture and method for producing the same" The thermoplastic resin powdered mixture of the present invention is a powdery mixture of the above-mentioned thermoplastic resin powder and fine hollow spheres. As a method for producing the same, dry blending, that is, a method in which a thermoplastic resin powder and micro hollow spheres are mixed without plasticizing using a gas such as air as a medium is used.For example, a thermoplastic resin powder and micro hollow spheres are tumbled. Mixer, Henschel mixer, a method of dry blending by a known and publicly used method such as a V-type blender, in the process of producing the above-mentioned thermoplastic resin powder, supplying fine hollow spheres together with thermoplastic resin pellets to a crusher, and crushing the pellets. At the same time, a method of performing dry blending with the minute hollow spheres can be used.

The thermoplastic resin powder mixture for foaming of the present invention thus obtained can be regarded as a kind of fluid using an air layer as a medium, and has a much higher fluidity than a viscoelastic molten resin. Because it is excellent, it can be formed into a very complicated shape.

By the way, as a method of mixing a thermoplastic resin and a foaming agent, which is generally used conventionally, a method of melting and kneading in a kneading machine such as an extruder, a Banbury mixer, a roll forming machine, and a pressure kneader to mix. Is widely known. However, when such a method is used in the present invention,
A part of the foaming agent expands during the melt-kneading, or the foaming agent breaks by receiving a shearing force in the kneader after the expansion, which causes a problem that the foaming agent lacks expandability during foam molding. In addition, since the powder mixture contains the expanded hollow body, the thermal conductivity of the powder mixture decreases, and problems such as a decrease in the fusion property between the powders during foam molding and the transferability of the mold shape also occur. .

"Method for Producing Foam" The foam in the present invention is obtained by heating a powdery thermoplastic resin mixture for foaming. That is, by this heating operation, the thermoplastic resin powders are fused together, and the micro hollow spheres expand to form a foam. The heating temperature should be appropriately selected according to the thermoplastic resin powder to be used, or the minute hollow sphere, but is usually 50 to 350 in consideration of the heating speed and the durability of the heating device from an industrial viewpoint. It is preferably in the range of ° C. Further, such a heat treatment can be performed once, but it is more preferable to perform the heat treatment in two stages. That is, in the first heating, the fusion of the thermoplastic resin powder mainly proceeds, and in the second heating, the fused resin powder is melted and the micro hollow spheres are expanded. By this two-stage heating operation, it is possible to suppress generation of a coarse pinhole due to expansion of the foaming agent in a state where the powder is not fused.

As described above, as a method suitable for subjecting the thermoplastic resin powder mixture for foaming to heat treatment so as to cause foaming and imparting a complicated shape to the foam, specifically, thermoplastic thermoplastic powder is used. A resin powder molding method, among which a powder slush molding method is particularly preferred. With the powder slush molding method, a thermoplastic resin powder is first adhered to a coating or a mold heated in advance in a first step to a uniform thickness, and the powders are fused together, and then the powder is removed in a second step. This is a molding method in which the adhered mold is heated in a heating furnace or the like by hot air, infrared rays, radiant heat, or the like, thereby melting the resin powder to form a uniform film, and finally cooling and solidifying the same to obtain a product. The advantages of this powder slush molding method include that the mold and equipment costs are low, and the powder slush molding method is suitable for production of small lots and many types, and suitable for molding products having complicated shapes.

In the present invention, a foam can be obtained by utilizing such a powder slush molding method. That is, a foaming agent is added to the resin powder to be supplied to the molding in advance, and the powder is adhered to the coating or the mold in the first step, and the resin is melted and the foaming agent is expanded in the second step. It foams. By the way, in the powder slush molding method, the resin powder must be melted only by a heat treatment without applying an external force such as compression or kneading, so that the resin material used is required to have high fluidity at a low shear rate. However, such high fluidity is a property that is opposite to resin properties suitable for foaming, that is, properties such as maintaining viscoelasticity enough to form bubbles even when large deformation is applied by the expansion pressure of the foaming agent. For this reason, foam molding using the powder slush molding method often results in breakage, coarsening, or non-uniformity of air bubbles. Therefore, in the present invention, this problem has been solved by using minute hollow spheres containing gas or volatile liquid as a foaming agent. That is, when the gas or volatile liquid expands in the minute hollow sphere, the gas breaks the resin film in the growth process and escapes to the outside of the resin, thereby reducing the foaming property and the uniformity of the bubbles. Can be avoided. In addition, it can be said that controlling the expansion pressure and expansion rate of the gas by the viscoelasticity of the outer wall of the micro hollow sphere favorably improves the uniformity of foaming and the expansion ratio. Furthermore, since the degree of expansion of the gas, that is, the degree of expansion of the minute hollow spheres, does not differ greatly between the respective minute hollow spheres, as long as the minute hollow spheres are evenly dispersed in the thermoplastic resin powder,
The uniformity of foaming during foaming is maintained.

The thermoplastic resin powder mixture for foaming in the present invention is used not only to obtain a foam by directly adhering it to a mold or the like, but also to form a thermoplastic resin powder as described above in advance by powder slush molding. Forming a non-foamed molded body by subjecting the foamed thermoplastic resin mixture of the present invention to powder slush molding to foam, thereby backing the foam to the non-foamed molded body. It can also be used, whereby a laminated foam having a non-foamed layer and a foamed layer can be obtained. Specifically, after the thermoplastic resin powder is attached to the mold in the first step, it is heated and melted in a heating furnace or the like to form a non-foamed layer. Next, in the second step, the thermoplastic resin powder mixture for foaming is adhered to the non-foamed layer maintained in a molten state,
Further, the foaming agent is expanded in a heating furnace or the like to form a laminated foam.

The foam molded article of the present invention can be used, for example, in interior materials such as instrument panels, doors, ceilings, steering wheel covers, fender covers, pillars, and sun visors in the field of automobiles, and in packaging and packaging fields. Backing materials in the construction field, such as materials, cushioning materials for transportation, precision equipment cases, parts passing, etc., joint materials in the civil engineering field, packing materials, oil fences, panels, fenders, floats, vibration-proof mats, curing sheets, etc. Roofing materials, ceiling materials, flooring materials, jointing materials, roof tarpaulins,
Heat storage layers, anti-vibration panels, pipe fixing materials, etc., refrigerated containers in the heat insulation field, various dew proof materials, tank heat insulating materials, pipe heat insulating materials, etc., agricultural heat insulating sheets in the agriculture, forestry and fisheries fields, fish nets, cultivation shelves, hydroponics Golf back cushions, gymnastics mats, surfboards, jumping box cores, underwater sports equipment, various protector cores, putter courses, etc., toys, health equipment, educational equipment, bedding, various mats, joints, etc. Carpet, pad material for clothing, desk mat, cut letter, food shelf sheet,
Suitable for footwear, bags, etc.

[0034]

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

* Method for producing thermoplastic resin powder Thermoplastic resin powder was obtained by pulverizing thermoplastic resin pellets at room temperature with a pulverizer (Turbo Kogyo Co., Ltd., device name "Turbomill T-400").

* Measurement of average particle size of thermoplastic resin powder The average particle size of the thermoplastic resin powder obtained as described above was evaluated according to the following method. That is, five nominal dimensions (X1 to X5) of 100 g of the resin powder are shown below.
JIS Z8801 standard sieve (frame diameter 200m
m, depth 45 mm), and the mixture was shaken with a sieve shaker with hammer (manufactured by Iida Seisakusho) for 15 minutes, and then the weight (Y1 to Y5) of the powder remaining on each sieve was measured.

Tyler standard 32 mesh 250 μm (X2); Tyler standard 60 mesh 180 μm (X3); Tyler standard 80 mesh 106 μm (X4); Tyler standard 150 mesh 75 μm (X5); Tyler standard 200 mesh The average particle size of the thermoplastic resin powder was determined according to the following equation.

(Y1 × X1 + Y2 × X2 + Y3 × X3 +
Y4 × X4 + Y5 × X5) / (Y1 + Y2 + Y3 + Y4
+ Y5) * Method for evaluating foam The evaluation of the foam molded articles obtained in Examples and Comparative Examples was based on the following criteria. 1) Foaming ratio A test piece of 5 cm square was collected from the obtained foamed molded article, and
According to IS K6767-1976, apparent density (S
1) was measured. The density (S2) of a test piece obtained by compressing and melting the same thermoplastic resin pellets as those supplied to the pulverizer by a compression molding machine and then cooling the same is determined by JIS K
7112-1980 Calculated according to the method A, and S2 is calculated as S1
The value obtained by dividing by the above was defined as the expansion ratio.

2) Thickness The thickness of the obtained foam molded article was measured with a dial gauge.

3) Foaming uniformity The foaming uniformity was evaluated according to the following criteria. ：: Uniform foaming, good thickness balance. Δ: Either uniformity of foaming or thickness balance is poor. X: Uneven foaming and poor thickness balance.

4) Bubble state The bubble state was evaluated according to the following criteria. ：: There are no coarse bubbles of 5 mm or more in the foam molded article. Δ: Some coarse bubbles of 5 mm or more are observed in the foamed molded article. ×: Many large bubbles of 5 mm or more are observed in the foamed molded article.

Example 1 Ethylene-vinyl acetate copolymer resin (trade name "Ultracene 530" manufactured by Tosoh Corporation, MFR 75 g / 1)
0 minutes (190 ° C., 2.16 kgf)) was pulverized at room temperature to obtain a powder having an average particle size of 198 μm.
Particle size of 10 containing isopentane gas per 0 parts by weight
3 parts by weight of a fine hollow sphere having a size of １６16 μm (manufactured by Expancel, trade name “EXPANCEL 091DU”) was added, and dry blending was performed with a Henschel mixer to obtain a thermoplastic resin powder mixture for foaming. Next, a stainless steel rectangular container having a size of 300 mm × 300 mm and a depth of 250 mm (hereinafter referred to as a powder supply box <a plan view in FIG. 1, a three-dimensional view in FIG. 2, and a three-dimensional view in FIG. 2 kg) was input to <>). 300 mm × 300 mm, heated to 250 ° C., depth 10
A nickel electroforming mold of 0 mm (a plan view is shown in FIG. 4 and a side view is shown in FIG. 5) was attached by a clamp, and the powder supply box and the electroforming mold were simultaneously rotated left and right by 5 rotations each.
Then, after tapping the electroformed mold two or three times to remove excess powder, the electroformed mold was removed from the supply box,
The adhered resin was heated in a heating furnace at 50 ° C. for 3 minutes. Then, the electroformed mold taken out of the heating furnace was cooled with water, and the molded product was removed from the mold. The resulting foam had good foaming properties and excellent uniformity of cells. Table 1 shows the results.

Example 2 Polyethylene resin (manufactured by Nippon Unicar Co., Ltd., trade name "NUC polyethylene-LL MG365", MFR1
10 g / 10 min (190 ° C., 2.16 kgf)) was pulverized at room temperature to obtain a powder having an average particle size of 185 μm, and then, based on 100 parts by weight of the powder, micro hollow spheres having a particle size of 9 to 15 μm and containing isopentane gas. (Expancel
(Product name “EXPANCEL 092DU”)
The mixture was added in parts by weight and dry-blended using a Henschel mixer to obtain a thermoplastic resin powder mixture for foaming. Next, the powdery mixture was subjected to foam molding according to the same method as in Example 1. As a result, a foam having good foamability and excellent cell uniformity was obtained. Table 1 shows the results.

Example 3 Polyethylene resin (manufactured by Dow Chemical Company, trade name "Affinity SM1350", MFR 30 g / 10 min <190
° C, 2.16 kgf>) at room temperature and pulverized at room temperature.
After the powder having a thickness of μm, 3 kg was put into a powder supply box of a single-shaft rotary powder molding machine used for foam molding.
Then, 250 ° C. was previously placed on top of the powder supply box.
A nickel electroformed mold having a size of 300 mm x 300 mm and a depth of 100 mm heated was mounted on a powder supply box with a clamp, and the powder supply box and the electroformed mold were simultaneously rotated left and right by 5 rotations each. Next, the electroforming mold is
After tapping three times to remove excess powder, remove the electroforming mold from the supply box and heat the adhered resin in a 250 ° C. heating furnace for 3 minutes to form a non-foamed layer in a molten state on the mold surface. Formed. Next, 2 kg of the thermoplastic resin powdery mixture for foaming described in Example 1 was charged into a powder supply box, and the nickel electroformed mold having a non-foamed layer formed on the surface of the former mold was again placed in the powder supply box. The powder supply box and the electroforming mold were simultaneously rotated left and right by 5 rotations each. Next, after tapping the electroformed mold two or three times to remove excess powder, the electroformed mold was removed from the powder supply box,
The adhered resin was heated in a heating furnace at a temperature of 3 ° C for 3 minutes. Then, the electroformed mold removed from the heating furnace was cooled with water, and the molded product was removed from the mold. The obtained composite foamed molded article was composed of a non-foamed layer having excellent surface properties and thickness uniformity, and a foamed layer having good foamability and excellent cell uniformity. Table 1 shows the results.

Comparative Example 1 In Example 1, foam molding was carried out in the same manner as in Example 1 except that 0.5 parts by weight of the fine hollow spheres was mixed with 100 parts by weight of the thermoplastic resin powder. Was excellent in uniformity, but a foam having insufficient foamability was obtained. Table 1 shows the results.

Comparative Example 2 In Example 1, foam molding was carried out in the same manner as in Example 1 except that 20 parts by weight of the fine hollow spheres were mixed with 100 parts by weight of the thermoplastic resin powder. Many coarse cavities were observed in the foam. Table 1 shows the results. Comparative Example 3 Polyethylene resin (manufactured by Dow Chemical Company, trade name “Affinity SM1350”, MFR 30 g / 10 min <190
° C, 2.16 kgf>) To the weight part, polypropylene resin (manufactured by Chisso Corporation, trade name “K7750”,
MFR 50g / 10min <230 ° C, 2.16kgf>)
After dry blending 30 parts by weight, a pressure kneader (manufactured by Moriyama Seisakusho Co., Ltd., device name "DS3-7.5-MHH")
-E ”), melted and kneaded, taken out and formed into a sheet by a roll forming machine, and then pelletized with a sheet pelletizer (trade name: SGG-360, manufactured by Torai Iron Works Co., Ltd.). The pellets were pulverized to obtain a thermoplastic resin powder having an average particle size of 530 μm. Next, a micro hollow sphere (Ex) containing 10% to 16 μm in particle diameter containing isopentane gas was added to 100 parts by weight of the powder.
Pancel Corporation, trade name "EXPANCEL 091"
DU ") was added thereto and dry-blended using a Henschel mixer to obtain a thermoplastic resin powder mixture for foaming. Then, the powdery mixture was subjected to foam molding according to the same method as in Example 1. As a result, a foam having poor appearance and containing many coarse cells was obtained. Table 1 shows the results.

Comparative Example 4 In Example 2, the thermal decomposition type chemical blowing agent 4,4-
Dry blending of 4 parts by weight of oxybis (benzenesulfonylhydrazide) (manufactured by Sankyo Chemical Co., Ltd., CellMike S) with 100 parts by weight of a polyethylene resin using a Henschel mixer to obtain a thermoplastic resin powder mixture for foaming. Was. Then, the adhered resin was heated in a heating furnace at 250 ° C. for 3 minutes in the same manner as in Example 2, and then the mold was cooled with water and the molded product was removed from the mold. The obtained foam had poor foaming properties, and the results are shown in Table 1. Comparative Example 5 In Example 2, the thermal decomposition type chemical foaming agent 4,4-
A powder mixture was obtained by dry blending 4 parts by weight of oxybis (benzenesulfonyl hydrazide) (trade name: CellMike S, manufactured by Sankyo Chemical Co., Ltd.) together with 100 parts by weight of a polyethylene resin. Then, in the same manner as in Example 2, the adhered resin was heated in a heating furnace at 250 ° C. for 5 minutes, and then the mold was cooled with water and the molded product was removed from the mold. The resulting foam contained coarse cells and was poor in cell uniformity. Table 1 shows the results.

Comparative Example 6 In Example 2, 100 parts by weight of the polyethylene resin and 4 parts by weight of the fine hollow spheres were placed in a pressure kneader (“DS3-7.5-MHH-E” manufactured by Moriyama Seisakusho Co., Ltd.). The mixture was melted and kneaded, taken out, formed into a sheet by a roll forming machine, and then pelletized with a sheet pelletizer (trade name: SGG-360, manufactured by Torai Iron Works Co., Ltd.). Then, the pellet was pulverized to obtain a thermoplastic resin powder mixture for foaming having an average particle diameter of 450 μm.
When the powder mixture was observed at a magnification of 20 times with an optical microscope (manufactured by Nikon Corporation, trade name: SMZ-2T), a large number of hollow bodies expanded to 40 to 60 µm were observed. Next, the powder was subjected to foam molding in the same manner as in Example 2. As a result, the obtained foam had incomplete fusion of the powders and poor foamability.

COMPARATIVE EXAMPLE 7 In Example 2, 100 parts by weight of polyethylene and azodicarbonamide, a pyrolysis type foaming agent (trade name: Vinyl Hole AC # 1C, manufactured by Eiwa Chemical Co., Ltd.) were used instead of the hollow microspheres as a foaming agent. ) 4 parts by weight and a pressure kneader (Moriyama Seisakusho Co., Ltd., device name "DS3-7.5-M")
HH-E ”), melt-kneaded and taken out, formed into a sheet by a roll forming machine, and then pelletized with a sheet pelletizer (trade name: SGG-360, manufactured by Torai Iron Works Co., Ltd.). . The pellets were pulverized to obtain a thermoplastic resin powder mixture for foaming having an average particle diameter of 180 μm. Next, when the powder was subjected to foam molding in the same manner as in Example 2, a foam having poor cell uniformity including coarse cells was obtained. Table 1 shows the results.

[0050]

[Table 1]

[0051]

Industrial Applicability The thermoplastic resin powder mixture for foaming of the present invention is suitable as a raw material for a foam product having a complicated shape excellent in foamability and foam uniformity.

According to the method for producing the thermoplastic resin powder mixture for foaming of the present invention, since a part of the foaming agent does not expand or break, the foaming agent having excellent expandability during foam molding can be obtained. A thermoplastic resin powdery mixture can be produced.

The method for producing a thermoplastic resin foam of the present invention makes use of the moldability of a product having a complicated shape, which is a characteristic of powder molding, and provides excellent foamability and uniform foaming by using micro hollow spheres as a foaming agent. To achieve the nature.

[Brief description of the drawings]

FIG. 1 is a plan view of a powder supply box for powder molding used in Examples and Comparative Examples.

FIG. 2 is an elevation view of a powder supply box for powder molding used in Examples and Comparative Examples.

FIG. 3 is a side view of a powder supply box for powder molding used in Examples and Comparative Examples.

FIG. 4 is a plan view of a nickel electroforming mold for powder molding used in Examples and Comparative Examples.

FIG. 5 is a side view of a nickel electroforming mold for powder molding used in Examples and Comparative Examples.

[Explanation of symbols]

 1: Single axis rotating handle

Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29K 101: 00 105: 04

Claims (5)

[Claims] 1. Micro hollow spheres 1 to 85 made of a thermoplastic resin having an average particle diameter of 75 to 500 μm and a thermoplastic resin containing a gas or a volatile liquid and a gas or a volatile liquid.
15% by weight of a thermoplastic resin powder mixture for foaming. 2. Drying of 85 to 99% by weight of a thermoplastic resin powder having an average particle diameter of 75 to 500 μm and 1 to 15% by weight of fine hollow spheres containing a gas or a volatile liquid in an outer shell made of a thermoplastic resin. The method for producing a thermoplastic resin powder mixture for foaming according to claim 1, wherein the mixture is blended. 3. A method for producing a foam, comprising heating and expanding the thermoplastic resin powder mixture for foaming according to claim 1. 4. A method for producing a foam, comprising subjecting the thermoplastic resin powder mixture for foaming according to claim 1 to powder slush molding. 5. A first step of subjecting the thermoplastic resin powder to powder slush molding to form a non-foamed molded article, wherein the thermoplastic resin powder mixture for foaming according to claim 1 is subjected to powder slush molding. A method for producing a foam, comprising a second step of backing the foam with the non-foamed molded article obtained in one step.