JP2002138157A - Method of producing foamed plastics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed plastics having uniform foamed structure. SOLUTION: This method of producing a foamed plastics comprises the steps of mixing a vegetable fiber and/or vegetable powder with a thermoplastic resin in melt, adding water under high pressure to mix with the molten mixture uniformly, releasing pressure to start foaming, and cooling it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a foamed plastic.

[0002]

2. Description of the Related Art Conventionally, foamed plastics are produced by a chemical foaming method in which a resin is mixed with a chemical foaming agent or a low-boiling-point solvent which generates gas when decomposed, and heated and foamed. Air is blown into a resin melt. In other words, a mechanical foaming method has been provided in which bubbles are mixed by stirring. Furthermore, a capsule method has been provided in which a foamable capsule in which a low boiling point solvent is encapsulated in microcapsules is mixed with a resin and foamed by heating.

[0003]

The above-mentioned chemical foaming method and mechanical foaming method have a problem that it is difficult to form a uniform foamed structure, and a capsule method has a problem that microcapsules are expensive.

[0004]

According to the present invention, as a means for solving the above-mentioned conventional problems, water is added under high pressure to a molten mixture obtained by mixing vegetable fiber and / or vegetable powder with a thermoplastic resin. The present invention provides a method for producing a foamed plastic in which high pressure is released, foamed, and cooled after being uniformly mixed by mixing the thermoplastic resin and the vegetable fiber and / or vegetable powder with an extruder (1). ) Cylinder
The water is melt-kneaded in (2), the water is injected into the molten mixture at high pressure in the middle of the cylinder (2), and the water is injected into the cylinder (2).
It is desirable that the mixture is uniformly mixed with the molten mixture in the inside, and the water-containing mixture is discharged from a nozzle (7) or a die at the tip of the extruder (1) to release high pressure to foam and cool. To obtain foamed plastic molded articles of various shapes, the extruder (1) is an extruder (1) of an injection molding apparatus.
The nozzle (7) of the extruder is connected to a mold, and the water-containing mixture is injected into the mold (8) to release high pressure and cool down by an injection molding method. I do. The high pressure is desirably set to 50 kg / cm ² or more. The release of the water-containing mixture under high pressure is desirably performed at atmospheric pressure or lower. Further, the foamed plastic is preferably used as artificial wood, and furthermore, the foamed plastic is preferably used as a heat insulating and / or sound insulating material.

[0005]

According to the present invention, it is easy to uniformly mix vegetable fibers and / or vegetable powders in a molten thermoplastic resin. In particular, when kneading with a screw in a cylinder of an extruder, mixing is easily performed uniformly. Further, when water is poured into the mixture under high pressure and uniformly mixed, the water is introduced into the resin melt due to the hydrophilicity of the vegetable fibers and / or vegetable powder uniformly dispersed in the resin melt. Disperse evenly. When the high pressure is set to 50 kg / cm ² or more, the water is absorbed more smoothly. Such a water-containing mixture releases high pressure, and desirably at atmospheric pressure or lower, water absorbed in the vegetable fiber and / or vegetable powder rapidly evaporates and enters the resin. A foam structure is formed, and the foam structure is fixed by cooling.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below. [Thermoplastic resin] As the thermoplastic resin (hereinafter simply referred to as resin) used in the present invention, for example, polypropylene,
Polyethylene, polystyrene, polyester, polyvinyl chloride, acrylonitrile-butadiene-styrene resin and the like are common, but other styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butadiene-styrene Elastomers such as styrene-based thermoplastic elastomers such as copolymers, block copolymers such as butadiene-styrene block copolymers, styrene-rubber intermediate blocks-styrene copolymers, polyamides, polyacetals, polycarbonates, polyethylene terephthalates, and polybutylenes Terephthalate, polysulfone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyetheretherketone, polyamideimide, polyamide , Polyetherimide, polyaminobismaleimide, methylpentene copolymer, polyaminobismaleimide, engineering plastics such as bismaleimide-triazine-based thermosetting aromatic polyimides and the like are also objects of the present invention. Further, starch / modified polyvinyl alcohol mixtures, Biodegradable resins such as chitosan / cellulose mixtures, starch / polycaprolactam mixtures, starch / polyethylene mixtures, microbial-produced polyesters, aliphatic polyesters, etc. are also an object of the present invention.

[Vegetable fiber] The vegetable fiber (hereinafter simply referred to as fiber) used in the present invention includes, for example, pulp,
There are cotton, hemp fiber, bamboo fiber, coconut fiber, kenaf fiber and waste paper disintegrated material.

[Vegetable Powder] Examples of the vegetable powder (hereinafter simply referred to as powder) used in the present invention include wood powder, bamboo powder, coconut powder, rice husk powder, charcoal powder, activated carbon powder and the like.

[Other components] In the present invention, in addition to the above components, for example, in addition to fibers, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium sulfite, calcium phosphate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide , Magnesium oxide, titanium oxide, iron oxide, zinc oxide, alumina, silica, diatomaceous earth, dolomite, gypsum, talc, clay, asbestos, mica, glass fiber, calcium silicate, bentonite, white carbon, iron powder, aluminum powder Inorganic fillers such as stone powder, blast furnace slag, fly ash, cement, zirconia powder, etc., organic synthetic fibers such as polyamide fiber, polyester fiber, acrylic fiber, viscose fiber, acetate fiber, vinyl chloride fiber, vinylidene chloride fiber, asbestos fiber Glass fibers, carbon fibers, ceramic fibers, metal fibers, inorganic fibers such as whiskers, dyes, pigments, antioxidants, plasticizers, UV absorbers, antioxidants and the like may be added.

[Production of foam] In the present invention, the above-mentioned fibers and / or powder are usually added to the above-mentioned resin in an amount of usually 20%
It is added in an amount of from 70% by weight to 70% by weight. If the content of the fibers and / or powder is less than 20% by weight, it is difficult to uniformly disperse water in the molten mixture, and a uniform foamed structure cannot be obtained. If the content exceeds 70% by weight, the moldability of the molten mixture is reduced. It deteriorates and the strength of the molded product also decreases. The resin and the fiber and / or powder are filled in, for example, a stirrer additional pressure vessel, a cylinder of a single screw or multi-screw extruder having two or more screws, and heated and melted at a temperature not lower than the melting point of the resin.

The fibers and / or powders are uniformly dispersed in the resin melt by the effect of stirring with a stirrer or screw.
Water is added to the molten mixture under a high pressure of not less than kg / cm ^{2 and not} more than 500 kg / cm ² and uniformly kneaded. The water is evenly dispersed in the molten mixture under high pressure due to the hydrophilicity of the fibers and / or powders dispersed in the molten mixture.

When the above-mentioned hydrated mixture is released from the high pressure, and desirably under atmospheric pressure or higher, water uniformly dispersed in the molten mixture is rapidly vaporized to form a foamed structure. By cooling, the foamed structure is fixed. When the water-containing mixture is filled in a pressurized container, the container is returned to normal pressure or reduced in pressure and cooled after water addition and mixing. In this case, the water-containing mixture is foamed, cooled and solidified to form a block-shaped foam, and if desired, the block-shaped foam is sliced into an appropriate thickness to form a plate. When the hydrated mixture is extruded from the nozzle of the extruder, the high pressure is released and cooled at the moment of the extrusion to form a string or rod-shaped foam, and the string or rod-shaped foam may be formed into a suitable foam if desired. Cut to length and make it granular. When the hydrated mixture is extruded from a die of an extruder, it becomes a pipe-like foam, a sheet-like foam, a plate-like foam, a rod-like foam, or the like depending on the shape of the die. Cut to length. In this case, the hydrated mixture may be extruded from a nozzle or a die of an extruder into a reduced-pressure cooling chamber. When the nozzle of the extruder is connected to a mold, the hydrated mixture foams in a mold cavity. Upon cooling and solidification, it becomes a foam molded article having a shape corresponding to the cavity shape.
A number of vent holes may be provided on the inner surface of the mold cavity, and a vacuum may be applied to the cavity from the vent holes.

The foamed plastic produced in this way has a uniform foamed structure and is reinforced by fibers and / or powders, and the fibers and / or powders give a plastic-like feel to a warmer feel. Improved, insulation material, soundproofing material, cushioning material,
It is useful for packaging materials, automobile interior materials, concrete panels, U-shaped grooves for cable piping and lids of the U-shaped grooves, cabinets for televisions and the like, household goods, gardening goods, and the like.

Embodiment 1 A melt kneader (1) of an injection molding apparatus shown in FIG. 1 comprises a cylinder (2), a screw (3) inserted in the cylinder (2), and a cylinder (2). 2) and a water tank (5) connected to the middle of the cylinder (2), and a ratio L between the length L and the diameter D of the cylinder (2). / D is set in the range of 20 to 40. The water tank (5) is in communication with the pressurized path (6),
The tip nozzle (7) of the cylinder (2) is connected to a mold (8). A number of vent holes are provided in the cavity of the mold (8), and a vacuum is applied to the inside of the cavity by the vacuum path (9) through the vent holes.

[0015] Polypropylene resin 50% by weight, wood flour 40
A mixture M of 10% by weight of waste paper and 10% by weight of waste paper is put into a cylinder (2) from a raw material hopper (4), and heated to 180 ° C. to melt the polypropylene resin. It progresses while being uniformly kneaded with the powder and the waste paper. Water W is added to the molten mixture by opening a valve (5A) from a water tank (5) in a cylinder (2), and a high pressure of 400 kg / cm ² is applied in the water tank (5). ing. The added amount of the water is 0.3% by weight.
The water is uniformly dispersed in the molten mixture by the stirring effect of the screw (3) and the hydrophilicity of the wood flour and the waste paper.

The aqueous mixture is passed through a nozzle (7) into a mold.
The inside of the cavity of the mold (8) is subjected to a vacuum of 450 mmHg by a vacuum path (9). The water-containing mixture foams in the cavity of the mold (8) due to rapid vaporization of the water in the molten mixture, and is cooled and solidified. The foaming ratio of the polypropylene foam molded article thus obtained is about 2 times, has a uniform foamed structure, is reinforced by wood flour and waste paper defibrated material, and the plastic-like feel is also improved. It is useful as a synthetic wood having the feel of warm natural wood.

[Embodiment 2] A water tank (13) and a vacuum path (14) are connected to the agitator (12) additional pressure vessel (11) shown in FIG. The pressurizing path (15) is connected to the water tank (13). The container (11) is filled with a mixture M ′ of 60% by weight of polystyrene pellets, 30% by weight of bamboo fiber, and 10% by weight of kenaf fiber, and the mixture is heated and kneaded at 150 ° C. with the lid (11A) closed. When the fibers are substantially uniformly mixed with the polystyrene melt, the valve (13A) is opened, and 1% by weight of water W is added. The water tank (13) has a pressure of 300 kg /
A high pressure of cm ² is applied.

At the time when the water is uniformly mixed and dispersed in the molten mixture, the high pressure is released and the water is removed from the vacuum path (14).
When a vacuum of 0 mmHg is applied and the container (11) is cooled,
The water in the molten mixture evaporates rapidly, forming a foamed structure and solidifying by cooling.

The fiber-reinforced polystyrene block obtained in this way is, as shown in FIG.
The panel is heat-softened at 130 ° C., and then formed by cold pressing to form an automobile ceiling substrate (17) as shown in FIG. The expansion ratio of the foamed molded product is about 5 times and has a uniform foamed structure. Therefore, it is excellent in heat retention, heat insulation and soundproofing, is reinforced by fiber, and can also expect the deodorizing and sterilizing effect of bamboo fiber.

Example 3 50 parts by weight of a polypropylene resin and 50 parts by weight of a bamboo powder were melt-mixed in an extruder, and 0.5% by weight of water was added to the molten mixture, followed by uniform mixing.
It is extruded into a rod shape from the die of the extruder, foamed and solidified by cooling. The foaming ratio of the rod-shaped foam molded article thus formed is 1.5 times, and is cut to a predetermined size, and is useful as a handrail bar for, for example, stairs, bathrooms, toilets, and the like. The foamed article is reinforced with bamboo powder, has a natural wood-like warm feeling, and has antibacterial properties.

Example 4 50 parts by weight of ABS resin, 30 parts by weight of coconut powder, and 20 parts by weight of wood powder were melt-mixed in an extruder, and 0.3% by weight of water was added to the molten mixture to obtain a uniform mixture. The mixture is extruded into a plate shape from a die of the extruder, foamed, and cooled and solidified. The expansion ratio of the plate-like foam molded article thus formed is 1.3 times, and has a natural wood-like feel.
It is used as a face plate for furniture and the like, an automobile interior base material, and the like.

Example 5 50 parts by weight of a polystyrene foam scrap pulverized material and 50 parts by weight of a waste paper defibrated material were melt-mixed with a melt kneader (1) of an injection molding apparatus in the same manner as in Example 1, and water 5 % By weight and uniformly dispersed in the molten mixture, and then injected into a mold (8) as in Example 1 to carry out foam molding. The expansion ratio of the obtained foamed molded product is 50 times, and the foamed molded product is useful as a heat insulating material, a soundproofing material, a packaging material and the like.

[0023]

According to the present invention, as the water carrier, vegetable fibers and / or vegetable powders which are easily dispersed uniformly in the resin melt are used.
Alternatively, it can be uniformly and integrally dispersed in a molten mixture with the powder, so that a plastic molded article having a uniform foam structure can be obtained. The plastic foam molded article obtained by the present invention is reinforced by the fibers and / or powders, and the plastic-like feel is improved to a warm feel, resulting in a molded article of high commercial value.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a melt kneader of an injection molding apparatus used in Example 1.

FIG. 2 is an explanatory view of a pressurized container used in Example 2.

FIG. 3 is a perspective view of a panel obtained in Example 2.

FIG. 4 is a perspective view of an automobile ceiling base material obtained from the panel.

[Explanation of symbols]

 1 Melting and kneading machine for injection molding equipment 2 Cylinder 3 Screw 4 Hopper 5,13 Water tank 6,15 Pressurized path 7 Nozzle 8 Mold 9,14 Vacuum path 11 Pressurized vessel 12 Stirrer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 31:10 B29L 31:10 F-term (Reference) 4F074 AA20 AA74 BA34 CA22 CA26 CC22X DA32 DA50 4F206 AA11 AA13 AB02 AB19 AD16 AE02 AE06 AG20 AH46 JA04 JF04 JF12 JL02 JM01 4F207 AA11 AA13 AB02 AB19 AD16 AE02 AE06 AG20 AH46 KA01 KA11 KF03 KF04 KF12 KK04 KK52

Claims (7)

[Claims] 1. A method of adding water under high pressure to a molten mixture obtained by mixing vegetable fiber and / or vegetable powder with a thermoplastic resin, uniformly mixing the mixture, releasing the high pressure, foaming the mixture, and cooling the mixture. Characteristic method for producing foamed plastic 2. The thermoplastic resin and the vegetable fiber and / or vegetable powder are melt-kneaded in a cylinder of an extruder, and the water is injected into the molten mixture at an intermediate portion of the cylinder under high pressure. The foaming method according to claim 1, wherein water is uniformly mixed with the molten mixture in the cylinder, and the water-containing mixture is discharged from a nozzle or a die at the tip of the extruder to release high pressure to foam and cool. Plastic manufacturing method 3. The extruder is an extruder of an injection molding apparatus, wherein a nozzle of the extruder is connected to a mold, and the high pressure is released by injecting the water-containing mixture into the mold. The method for producing a foamed plastic according to claim 2, wherein the foamed plastic is cooled together with. 4. The method according to claim 1, wherein the high pressure is set to 50 kg / cm ² or more. 5. The process for producing a foamed plastic according to claim 1, wherein the high-pressure release of the water-containing mixture is carried out under atmospheric pressure or lower. 6. The method for producing a foamed plastic according to claim 1, wherein said foamed plastic is used as artificial wood. 7. The method for producing a foamed plastic according to claim 1, wherein said foamed plastic is used as a heat insulating and / or sound insulating material.