JPH0741586A - Production of foam - Google Patents

Abstract

PURPOSE:To obtain easily a uniform foam by hermetically kneading a molding material consisting of a moist thermoplastic resin or a molding material consisting of a specified easily water-absorptive resin and water, and expansion- molding the kneaded material. CONSTITUTION:A foam is obtained by melt-kneading a molding material consisting of a thermoplastic resin (A) having a moisture absorption of 0.1wt.% or above (desirably 3% or below) in a hermetically sealed melt kneader, and expanding the kneaded material. Component A may be replaced by a mixture thereof with a thermoplastic resin having a moisture absorption of below 0.1% and other components. A foam is obtained more easily by melt-kneading a molding material essentially consisting of a powdery copolymer (A') which is a copolymer essentially consisting of a styrene monomer and a diene monomer and having a diene monomer content of 40-85wt.% and has a weight-mean particle diameter of 1000mum or below, a thermoplastic resin other than resin A' and water, and extrusion-molding the kneaded material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a thermoplastic resin foam, and more particularly, to produce a thermoplastic resin foam by using the moisture in a thermoplastic resin having absorbed moisture as a foaming agent. On how to do.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a thermoplastic resin foam, a thermal decomposition type foaming agent which decomposes by heating to generate nitrogen gas or carbon dioxide, or a low boiling point liquid or liquefied gas is used. In addition, a method is used in which after melt-kneading under pressure, foaming is performed while lowering the pressure.

However, in the case of a heat-decomposition type foaming agent, decomposition residues are generated, which causes coloring and a bad odor of the resin foam, and it is difficult to control foaming. On the other hand, when a low boiling point liquid or liquefied gas is used as a foaming agent, the foaming agent is ignited during the foaming process and during storage of the foam, there is a risk of explosion and food hygiene problems, and handling methods and There are restrictions on the manufacturing method.

As a method for improving these, Japanese Patent Publication No. 47-2
Japanese Patent Publication No. 8096 discloses a method for producing a thermoplastic resin foam using water-containing resin particles containing fine water droplets, and Japanese Patent Publication Nos. 63-28455 and 63-284.
No. 56 and Japanese Patent Laid-Open No. 19332/1999, a thermoplastic resin powder coated with a hydrophilic solid fine powder of talc, calcium carbonate or the like is used to heat an aqueous medium such as water. The respective methods for producing the plastic resin foam are described.

[0005]

However, the method using water-containing resin particles requires a special step of producing water-containing resin particles in the presence of an emulsifier or a dispersant using a special device such as a suspension device. Yes, and because it contains water as water droplets, the water is separated from the resin as vapor at the start of the extrusion process, and part of it flows backward, which hinders the fine dispersion of water and causes a decrease or fluctuation in the extrusion amount. As a result, there is a problem in that a uniform expansion cannot be obtained because the expansion ratio and the wall thickness fluctuate during foam molding. It is considered that this is because, since the water-containing resin particles contain water as water droplets, most of the water is separated from the resin as vapor at the start portion of the extrusion step, which hinders fine dispersion of water.

Further, the method of using the thermoplastic resin powder particles coated with the hydrophilic solid fine powder requires a special step for producing the thermoplastic resin powder particles whose surface is coated with the hydrophilic solid fine powder. In addition, since the surface covering portion contains a large amount of water, there is a problem that a uniform foam cannot be obtained due to the decrease or fluctuation of the extrusion amount and poor fine dispersion of water as in the above case. Further, there is also a problem that only a foam containing a large amount of hydrophilic solid fine powder can be obtained.

[0007]

In view of the above facts, the present inventors have earnestly studied, and as a result, use a molding material containing a thermoplastic resin that absorbs 0.1% by weight or more of water, or
When a resin that easily absorbs specific water is used as a molding material together with water, the foaming agent can be added by an easy means of moisture absorption, and the separation of water and resin at the start of the extrusion process can be achieved. The present invention is completed by finding that a uniform foam can be easily obtained by foam molding, because it is difficult to cause water to be finely dispersed, there is no decrease or fluctuation in extrusion rate, and there is no fluctuation in expansion ratio or wall thickness. Came to.

That is, in the present invention, the moisture absorption rate is 0.1% by weight.
A method for producing a foam, which comprises melt-kneading the molding material containing the above thermoplastic resin (A) in a closed melt-kneading machine and then foam-molding the composition, and a styrene-based monomer and a diene-based monomer are essential. It is a copolymer as a component, and the diene monomer is 40 to 85% by weight of the whole.
And a powdery copolymer (A ′) having a weight average particle diameter of 1000 μm or less, a thermoplastic resin (B ′) other than (A ′), and water as essential components The present invention relates to a method for producing a foam, which comprises melt-kneading and then foam-molding.

The molding material used in the present invention is as follows.
When the thermoplastic resin (A) is used, the moisture absorption rate is 0.
Any material containing 1% by weight or more of the thermoplastic resin (A) may be used. For example, the thermoplastic resin (A) may be used alone as a molding material, or the thermoplastic resin (A) may be used.
In addition, other components such as a thermoplastic resin (B) having a moisture absorption rate of less than 0.1% by weight, a stabilizer and a nucleating agent may be mixed and used.

When the thermoplastic resin (B) and other components are used in combination, the amount of water used is not limited as long as the content of water in the obtained molding material is sufficient for foam molding. It can also be used in a large excess compared to A). Further, the thermoplastic resin (A) and the thermoplastic resin (B) can be used even if they are not compatible, but it is preferable that they are the same or compatible. The thermoplastic resin (A) used here has a moisture absorption rate of 0.2 to 3% by weight.
The above resin is particularly preferable, and further the thermoplastic resin (B)
As the resin, a resin having a moisture absorption rate of 0.07% by weight or less is particularly preferable.

The thermoplastic resin (A) used here may be any thermoplastic resin capable of absorbing 0.1% by weight or more of water, for example, rubber-modified polystyrene (HIP).
S), styrene-methacrylic acid copolymer (SMAA),
Styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer (AS resin), styrene-acrylonitrile-butadiene copolymer (ABS resin), polymethylmethacrylate, styrene-methylmethacrylate copolymer, Hygroscopic styrene-based resin such as rubber-styrene-methyl methacrylate copolymer (MBS resin), styrene-methacrylic acid-methyl methacrylate copolymer, styrene-methacrylic acid-n-butyl methacrylate copolymer, 6
-Nylon, 6,6-nylon polyamide resin, cellulose acetate, polyvinyl alcohol, polyvinyl acetate, polycarbonate, polyethylene terephthalate, etc., each of which may be used alone or as a thermoplastic resin. It can be used as a molding material by mixing with the resin (B). Among them, the hygroscopic styrene resin is used alone or as a molding material by mixing with a styrene resin having a moisture absorption rate of less than 0.1% by weight. It is preferable that the other resin is appropriately mixed with the following thermoplastic resin (B) and used as a molding material.

The shape of the thermoplastic resin (A) when used is not particularly limited, but it is usually used in the form of pellets, beads or the like. Examples of the rubber material used for the rubber-modified resin include polybutadiene and styrene-butadiene block copolymer.

The thermoplastic resin (B) is not particularly limited and is conventionally used in various plastic moldings, and any resin having a moisture absorption rate of less than 0.1% by weight is possible. For example, polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer (EV
A), ethylene-propylene copolymer, olefin resin such as petroleum resin; polyvinyl chloride, polyvinyl acetate,
Vinyl-based resins such as polyvinylidene chloride and polyvinyl alcohol; acrylic-based resins such as polymethacrylic acid (PMAA); polystyrene (GPPS), rubber-modified polystyrene (HIPS), styrene-methacrylic acid copolymer (SMAA), Styrene-acrylic acid copolymer (SA
A), styrene-acrylonitrile copolymer (AS resin), styrene-acrylonitrile-butadiene copolymer (ABS resin), styrene-methyl methacrylate copolymer, rubber-styrene-methyl methacrylate copolymer Examples thereof include styrene resins such as polymer (MBS resin), styrene-methacrylic acid-methyl methacrylate copolymer, and styrene-methacrylic acid-n-butyl methacrylate copolymer, which may be used alone or in combination of two or more. Can be used. The shape at the time of use is not particularly limited, but it is usually used in the form of granules such as pellets and beads.

As the above-mentioned molding material, among others, a molding material containing a styrene resin or an olefin resin as a main component, particularly a thermoplastic resin (A) having a moisture absorption rate of 0.1% by weight or more and a moisture absorption rate of 0.1%. A molding material containing less than wt% of a styrene resin or an olefin resin is preferable because it has excellent foam moldability and a uniform foam can be easily obtained.

As the molding material containing the styrene resin as the main component, for example, a styrene resin having a moisture absorption rate of 0.1% by weight or more alone or a styrene resin having a moisture absorption rate of 0.1% by weight or more and a moisture content can be used. Examples thereof include those containing, as a main component, a styrene resin having a moisture absorption rate of less than 0.1% by weight. Among them, rubber modified polystyrene (HIPS) having a moisture absorption rate of 0.1 to 3% by weight or styrene-methacrylic acid copolymer (SMAA) alone, or rubber modified polystyrene having a moisture absorption rate of 0.2 to 3% by weight ( HIP
S), styrene-methacrylic acid copolymer (SMAA) or rubbery-styrene-methyl methacrylate copolymer (M
(BS resin) and polystyrene (GPPS) having a moisture absorption rate of 0.07% by weight or less as main components, particularly rubber-styrene-methyl methacrylate having a moisture absorption rate of 0.2 to 3% by weight. Copolymer (MBS resin) and polystyrene (GPPS) with a moisture absorption rate of 0.07% by weight or less
A molding material containing as a main component is preferable because it has excellent foaming moldability and can be easily recycled as a styrene resin.

As the molding material containing an olefin resin as a main component, for example, polymethylmethacrylate having a moisture absorption rate of 0.1% by weight or more, preferably 0.2 to 3% by weight,
6-nylon, 6,6-nylon, cellulose acetate, polyvinyl alcohol, polyvinyl acetate, polycarbonate
Moisture absorption rate of less than 0.1% by weight, preferably less than 0.1%.
The resin containing, as a main component, an olefin resin in an amount of 07% by weight or less is included. As the olefin resin used here, any of various olefin resins can be used, and among them, polyethylene and polypropylene are preferable.

The method for obtaining the thermoplastic resin (A) having a moisture absorption rate of 0.1% by weight or more is not particularly limited. For example, the thermoplastic resin (A) and water are put in a polyethylene bag and mixed, A method in which the mouth of the bag is bound with a rubber band and the like, and the mixture is left in a dryer at 40 to 80 ° C. to absorb moisture, and then the moisture on the surface of the thermoplastic resin (A) is removed by blowing air or the like, a thermoplastic resin ( A), humidity 70-100%, temperature 40-80
After leaving it in the constant temperature and humidity device at ℃ to absorb moisture,
Method of removing water on the surface of the thermoplastic resin (A) by blowing air, etc., after immersing in a water tank of 40 to 80 ° C to absorb moisture, and then removing water on the surface of the thermoplastic resin (A) by blowing And a method of leaving the thermoplastic resin (A) to stand in a high humidity place, and any method may be used.

To the water used here, a surfactant, a water-soluble resin, alcohols, a hydratable organic solvent and the like may be appropriately added and used for the purpose of improving the dispersibility of water. The addition amount of these is usually 0.5 to 10 parts by weight, preferably 2 to 5 parts by weight, relative to 100 parts by weight of water used.

If water droplets are attached to the surface of the thermoplastic resin (A) obtained by absorbing moisture by these methods, a decrease in the amount of extrusion or a fine dispersion of water is likely to occur. It is preferable to dry by a method of drying with a low temperature drier or blowing, a method of leaving it in a bag having no moisture resistance, etc. and leaving it.

The moisture absorption rate of the thermoplastic resin (A) obtained by absorbing moisture varies depending on the moisture absorption conditions, the type of resin, the comonomer content in the copolymer, the drying conditions after moisture absorption and the like. For example, the moisture absorption when left in an atmosphere of relatively high humidity at room temperature is about 0.07% by weight for polystyrene (GPPS) and rubber modified polystyrene (HIP).
S) about 0.3 wt%, styrene-methacrylic acid copolymer (SMAA) 0.1-0.6 wt%, rubber-styrene-methyl methacrylate copolymer (MBS resin)
It is about 0.1 to 0.8% by weight. It should be noted that, after absorbing moisture under heating, when returning to normal temperature, it becomes supersaturated, and since it is possible to obtain a thermoplastic resin having a higher moisture absorption rate than when left at room temperature and normal pressure, higher moisture absorption It is preferable to use it when the thermoplastic resin (A) of high ratio is required.

Here, as the moisture absorption rate, the temperature is 23
A value obtained by measuring the water content with a water content meter (manufactured by Hiranuma Sangyo Co., Ltd.) after being left for 60 minutes in a thermostatic chamber at a temperature of 50 ° C., a relative humidity of 50% and a pressure of 1 atm is mentioned.

The water content in the molding material used in the present invention varies depending on the target expansion ratio, but is usually 0.1 to 3% by weight, preferably 0.2 to 1% by weight. Is. Therefore, the moisture absorptivity of the thermoplastic resin (A) and the amount of the thermoplastic resin (B) and other components used in combination as necessary are controlled so that the moisture content in the molding material falls within this range. It needs to be adjusted. For example, when the mixing ratio of the thermoplastic resins (A) and (B) is not specified, the water content suitable for foaming is set to the (A) ratio.
And (B) may be mixed, and when the mixing ratio of (A) and (B) is specified, a thermoplastic resin (A) that absorbs an appropriate amount of water should be selected. It may be mixed with a prescribed amount of the thermoplastic resin (B).

Further, in the present invention, among the resins used for the thermoplastic resin (A), it is a copolymer having a styrene-based monomer and a diene-based monomer as essential components, and the diene-based monomer is used. When a powdery copolymer (A ′) having a weight average particle diameter of 1000 μm or less, which is used in a proportion of 40 to 85% by weight of the whole, is used, the hygroscopicity of the copolymer (A ′) is Since it is extremely excellent, it is not necessary to absorb moisture in advance before adjusting the molding material,
It can be used as a molding material containing a copolymer (A '), another thermoplastic resin (B') and water as essential components. That is, by adopting such a usage pattern, the foamed molded article can be manufactured more easily.

As described above, when the weight average particle diameter of the copolymer (A ') is 1000 μm or less, excellent hygroscopicity can be imparted to the copolymer (A'). Usually, it is preferably from 1000 to 10 μm, and above all, from the viewpoint that a more uniform foam can be obtained and the hygroscopicity of the copolymer (A ′) is also extremely excellent, it is from 300 to 1
The range of 00 μm is preferable.

The copolymer (A ') is not particularly limited, and the diene-based monomer in the total amount of 40 to 85 can be used.
The average particle size of the copolymerized styrene-based monomer and the diene-based monomer as essential components used in the range of 10% by weight may be 1,000 μm or less. For example, styrene-butadiene block copolymer, styrene- Examples thereof include hydrogenated butadiene block copolymers, acrylonitrile-butadiene copolymers, rubber-styrene-methyl methacrylate copolymers (MBS resins), and the like. Among them, the rubber-styrene-methyl methacrylate copolymer (MBS resin) is preferable because it is excellent in hygroscopicity and finely disperses water in the molding material to obtain a uniform foam.

Other thermoplastic resins (B ') include
The thermoplastic resin is not particularly limited and may be a moldable thermoplastic resin. For example, of the resins constituting the resin (A) and the resin (B) described above, one having a rubber content of less than 40% by weight or one not modified with rubber can be used.

The mixing ratio of water in the molding material in this manufacturing method is the same as in the case of using the resin (A) described above.
The amount is usually 0.1 to 3% by weight, preferably 0.2 to 1.5% by weight, although it depends on the target expansion ratio. The mixing ratio of the copolymer (A '), the thermoplastic resin (B'), and water is not particularly limited, but is (A ') / (B') / water on a weight basis. = (1-
10) / (98.9 to 87) / (0.1 to 3) is preferable.

Water used in the production method using the copolymer (A ') and the thermoplastic resin (B') includes
As described above, for the purpose of improving the dispersibility of water, a surfactant,
It goes without saying that water-soluble resins, alcohols, hydratable organic solvents and the like can be appropriately added and used. The amount added of these is usually 0.5 with respect to 100 parts by weight of water used.
10 to 10 parts by weight, preferably 2 to 5 parts by weight.

As a method for mixing the three essential components of the copolymer (A '), the thermoplastic resin (B') and water as mentioned above, a known and conventional blending method, for example, a drum tumbler or a Henschel is used. The blending method using a mixer or the like may be applied as it is.

The molding material used in any of the above-mentioned production methods of the present invention is, together with the thermoplastic resin component, a nucleating agent, a filler, a lubricant, a foaming aid, a plasticizer, an antioxidant and a flame retardant, if necessary. , Other components such as an ultraviolet absorber, an antistatic agent, and a coloring agent may be contained. These other components may be added individually or may be added in a masterbatch form.

As the nucleating agent used here, any of various nucleating agents can be used, and examples thereof include wollastonite, mica,
Examples thereof include talc, clay, calcium carbonate, titanium, titanium calcium, and barium sulfate. These nucleating agents can be used alone or in combination of two or more, and usually 1 to 100 parts by weight of the thermoplastic resin component.
Used in a proportion of 150 parts by weight.

Examples of the filler include glass beads, glass powder, glass flakes, asbestos, welllastonite, mica, talc, clay, calcium carbonate,
Examples thereof include calcium titanate and barium sulfate, which can be used alone or in admixture of two or more.

As the lubricant, for example, JP-A-58-966 is used.
No. 41, saturated fatty acid and / or ester thereof,
Mineral oil described in JP-A-61-19648,
Hydroxyl compounds and the like described in JP-A-59-230043 are examples of foaming aids such as JP-A-60-18115.
The organic polysiloxanes and the like described in JP-A No. 7 are difficult to use as plasticizers, for example, the polyester-based plasticizers and the like described in JP-A-61-21147, and the antioxidants include hindered amine-based compounds and the like. Examples of the flame retardant include triphenyl phosphate, tri (nonylphenyl) phosphate, and their oligomers, polymer type phosphorus flame retardants, and others issued by Taisei Co., Ltd. (February 1987) "Polymer". The flame retardants described in "Flame retardation", tetrabromobisphenol A / epichlorohydrin co-condensation polymer, and the like, respectively.

Further, the molding material may be mixed with a flow modifier and used. The flow modifier is not particularly limited, and conventionally used flow modifiers can be used, and terpene-based resins can be used. Examples of the terpene-based resin include a terpene homopolymer and a terpene copolymer with a monomer copolymerizable with the terpene.

The above-mentioned two kinds of molding materials thus obtained can be melt-kneaded in a closed melt-kneading machine and then made into a foam by a known and conventional method. For example, it can be easily obtained by a method in which the molding material is charged into an extruder, heated, melted and kneaded, cooled to a foaming suitable temperature, extruded from a circular die or a T die, and foamed.

Further, in the production method of the present invention, it is possible to use water in the thermoplastic resin (A) or water used together with the copolymer (A ') as a foaming agent together with other foaming agents. For example, the molding material is put into an extruder, heated, melted and kneaded, and then a low-boiling halogen hydrocarbon such as dichlorodifluoromethane; a low-boiling hydrocarbon such as propane and butane; a carbon dioxide gas; soda carbonate, nitrogen, and the like. , A method of decomposing at a high temperature and then injecting a foaming agent such as a compound capable of generating a gas, cooling to a foaming suitable temperature, extruding from a circular die or a T-die, and foaming. They can be used alone or in combination of two or more. Butane is preferably used as the foaming agent other than water.

[0037]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the examples, parts and% are based on weight unless otherwise specified.

Example 1 A styrene-methacrylic acid copolymer (methacrylic acid content: 10%) was allowed to stand in a thermo-hygrostat at a humidity of 100% and a temperature of 70 ° C. for 24 hours, and then in a blow dryer at 30 ° C. After standing for a minute, a resin (A-1) having a moisture absorption rate of 0.8% was obtained.

Next, a resin (A
-1) 50 parts, Dick styrene CR-4500 [polystyrene manufactured by Dainippon Ink and Chemicals, Inc.] and 2 parts of talc were mixed with a drum tumbler, and then tandem of 50 mmφ and 65 mmφ connected by a single pipe. The first stage of the die extruder is put into a 50 mmφ extruder, and the temperature is 20
While melt-kneading at 0 to 260 ° C., then transferred to the second stage 65 mmφ extruder and cooled to 150 to 200 ° C., while being extruded in a cylindrical shape from a circular die attached to the extruder. It was made to foam. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1 mm and a foaming ratio of 5 times.

This foamed sheet is excellent in heat resistance and oil resistance,
It was useful as a food container. Example 2 Extrusion foaming was performed in the same manner as in Example 1 except that 1 part of n-butane was press-fitted in the middle of the 50 mmφ extruder. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The foamed sheet obtained had a thickness of 2 mm and a foaming ratio of 10
It was double.

Example 3 Styrene was used instead of Dick Styrene CR-4500.
Methacrylic acid copolymer (methacrylic acid content: 10%)
Extrusion foaming was performed in the same manner as in Example 1 except that was used.
There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1 mm and a foaming ratio of 5 times.

Example 4 55 parts of a resin (A-1) which absorbed moisture, 45 parts of a styrene-acrylonitrile-butadiene copolymer [JSR ABS 10 manufactured by Japan Synthetic Rubber Co., Ltd.] and 2 parts of talc were used. Was subjected to extrusion foaming in the same manner as in Example 1. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1.2 mm and a foaming ratio of 5 times.

Example 5 Rubber-modified polystyrene (polybutadiene content: 7%)
Was placed in a polyethylene bag, 1 part of water was added and mixed, and the mixture was left at room temperature of 50 ° C. for 24 hours and then left in a blow dryer at 30 ° C. for 30 minutes to obtain a moisture absorption rate of 0.5. %
Resin (A-2) of was obtained.

Next, a resin (A
-2) After mixing 100 parts and 2 parts of calcium carbonate with a drum tumbler, 50 mm at the first stage of a tandem extruder of 50 mmφ and 65 mmφ connected by a single pipe.
It is charged into an extruder of φ, melt-kneaded at a temperature of 200 to 260 ° C., then transferred to a second stage 65 mm φ extruder, cooled to 150 to 200 ° C., and then attached to an extruder. -It was foamed while being extruded into a cylindrical shape from a die. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The foamed sheet obtained has a thickness of 1
The expansion ratio was 4 times in mm.

Example 6 Styrene-methyl methacrylate copolymer modified with styrene-butadiene block copolymer rubber (rubber content:
(7%, methyl methacrylate content: 55%) was placed in a metal container, 3 parts of water was added and mixed, and the mixture was allowed to stand at room temperature of 60 ° C for 24 hours, and then in a blow dryer at 30 ° C for 30 minutes. Upon standing, a resin (A-3) having a moisture absorption rate of 0.9% was obtained.

Next, a resin (A
-3) Foam extrusion was performed in the same manner as in Example 1 except that 40 parts, Dick styrene CR-5600 [polystyrene manufactured by Dainippon Ink and Chemicals, Inc.] 60 parts and 2 parts talc were used. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1 mm and a foaming ratio of 4 times.

Example 7 Foam extrusion was performed in the same manner as in Example 1 except that 100 parts of the resin (A-3) having a moisture absorption rate of 0.9% and 2 parts of talc were used. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The resulting foamed sheet had a thickness of 1.8 mm and a foaming ratio of 8 times.

Example 8 50 parts of a resin (A-3) having a moisture absorption rate of 0.9%, 50 parts of a styrene-acrylonitrile-butadiene copolymer [JSRABS10 manufactured by Japan Synthetic Rubber Co., Ltd.] and 2 parts of talc. Was used, and foam extrusion was performed in the same manner as in Example 1 except that 1.2 parts of n-butane was press-fitted in the middle of the 50 mmφ extruder. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1.6 mm and a foaming ratio of 8 times.

Example 9 50 parts of a resin (A-3) which absorbs moisture, low density polyethylene [Novatec LF101A manufactured by Mitsubishi Kasei Co., Ltd.] 5
Foam extrusion was performed in the same manner as in Example 1 except that 0 part and 2 parts of talc were used. During this extrusion, the amount of extrusion did not change, and a uniform foamed sheet without foaming unevenness was obtained. The obtained foamed sheet had a thickness of 1.8 mm and a foaming ratio of 6 times.

This foamed sheet was useful as a packaging material excellent for cushioning. Example 10 Kaneace M-511 [Butadiene content: 80%, weight average particle diameter: 230 μm, MBS manufactured by Kanegafuchi Chemical Industry Co., Ltd.]
Resin] 3 parts, 94.5 parts of styrene-methacrylic acid copolymer (methacrylic acid content: 10%), 0.7 parts of water, and 2 parts of talc were mixed with a drum tumbler and then connected with a single pipe. The 50 mmφ and 65 mmφ tandem type extruders were put into the first stage 50 mmφ extruder, and the temperature was adjusted to 2
While being melted and kneaded at 00 to 260 ° C., then transferred to a second stage 65 mmφ extruder and cooled to 150 to 200 ° C., and then from a circular die attached to the extruder,
It was foamed while extruding into a cylindrical shape. There was no change in the extrusion amount during this extrusion, and a uniform foamed sheet was obtained. The obtained foamed sheet had a thickness of 1 mm and a foaming ratio of 7 times.

Example 11 5 parts by weight of Kaneace B-22 [butadiene content: 50%, weight average particle diameter: 140 μm, MBS resin manufactured by Kanegafuchi Chemical Industry Co., Ltd.], modified with styrene-butadiene block copolymer rubber Styrene-methyl methacrylate copolymer (rubber content: 7%, methyl methacrylate content: 55%) 9
Extrusion foaming was carried out as in Example 10 except that 4.5 parts, 1 part water and 2 parts talc were used. There was no change in the discharge amount during this extrusion, and a uniform foam sheet was obtained. The obtained foamed sheet had a thickness of 1.5 mm and a foaming ratio of 8 times.

Example 12 7 parts of TR2000 (butadiene content: 60%, weight average particle size: 250 μm, styrene-butadiene block copolymer manufactured by Japan Synthetic Rubber Co., Ltd.), rubber-modified polystyrene (polybutadiene content: 7%) ) 94 parts, 0.5 part water,
Example 1 except that and 2 parts calcium carbonate were used
Extrusion foaming was carried out in the same manner as 0 There was no change in the discharge amount during this extrusion, and a uniform foam sheet was obtained. The obtained foamed sheet had a thickness of 1 mm and a foaming ratio of 4 times.

[0053]

In the method of the present invention, since a molding material containing a thermoplastic resin which has absorbed moisture or a resin which easily absorbs moisture is used together with water as a molding material, the addition of a foaming agent is referred to as moisture absorption. It can be carried out by easy means, and moreover, fine dispersion of water is easy, there is no decrease or fluctuation of the extrusion rate, and uniform foam without fluctuation of expansion ratio and wall thickness is extrusion foam molded,
There is an advantage that it can be easily obtained by various foam molding methods such as foam blow molding, profile extrusion foam molding, and injection foam molding.

Claims (16)

[Claims] 1. A method for producing a foam, wherein a molding material containing a thermoplastic resin (A) having a moisture absorption rate of 0.1% by weight or more is melt-kneaded in a closed melt-kneader and then foam-molded. Method. 2. The content of water in the molding material is 0.1-0.1%.
The manufacturing method according to claim 1, which is 3% by weight. 3. A thermoplastic resin (B) having a moisture absorption rate of less than 0.1% by weight, together with the thermoplastic resin (A).
The method according to claim 1 or 2, further comprising: 4. The moisture absorption rate of the thermoplastic resin (A) is 0.2.
~ 3 wt% thermoplastic resin, the thermoplastic resin (B)
The method according to claim 3, wherein is a thermoplastic resin having a moisture absorption rate of 0.07% by weight or less. 5. The method according to claim 4, wherein the thermoplastic resin (A) and the thermoplastic resin (B) are the same resin. 6. The method according to claim 4, wherein the thermoplastic resin (A) and the thermoplastic resin (B) are different resins. 7. The manufacturing method according to claim 1, wherein the thermoplastic resin (A) is a styrene resin. 8. The method according to claim 7, wherein the styrene resin is a rubber-modified polystyrene, a styrene-methacrylic acid copolymer or a rubbery-styrene-methyl methacrylate copolymer. 9. The thermoplastic resin (A) is rubber-modified polystyrene, styrene-methacrylic acid copolymer or rubber-
The production method according to claim 6, which is a styrene-methyl methacrylate copolymer and the thermoplastic resin (B) is polystyrene. 10. A foaming agent other than water is used in combination.
9. The manufacturing method according to any one of 9. 11. The production method according to claim 1, wherein a nucleating agent is used in combination. 12. A copolymer comprising a styrene-based monomer and a diene-based monomer as essential components, wherein the diene-based monomer is used in an amount of 40 to 85% by weight based on the total weight average particle diameter of 1000 μm. The following powdery copolymer (A '), a thermoplastic resin (B') other than (A '),
A method for producing a foam, comprising melt-kneading a molding material containing water as an essential component, and then foam-molding. 13. The production method according to claim 10, wherein the copolymer (A ′) is a rubber-styrene-methyl methacrylate copolymer. 14. The molding material comprises a copolymer (A ′), a thermoplastic resin (B ′) and water in a blending ratio of (A ′) / (B ′) / water = (weight basis). 1-10) / (98.9-
87) / (0.1-3), The manufacturing method of Claim 12 or 13. 15. A foaming agent other than water is used in combination.
15. The manufacturing method according to any one of to 14. 16. The production method according to claim 12, wherein a nucleating agent is used in combination.