JP2000281908A - Production of formed article from thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a formed article from a thermoplastic resin which prevents the generation of foaming due to an aluminum hydroxide in the step of mixing and forming and therefore gives a formed article having no foam mark and having improved appearance by mixing a thermoplastic resin, an aluminum hydroxide and a specific adsorbent and forming the mixture. SOLUTION: A thermoplastic resin, 1-80 wt.%, preferably 15-50 wt.%, aluminum hydroxide having an average particle size of 5-100 μm and 0.01-2 wt.%, preferably 0.1-1.5 wt.%, adsorbent having an adsorption speed of not less than 5 wt.%/hr, preferably 7-15 wt.%/hr and containing not more than 1 wt.% particles of a size of not less than 30 μm are fed to an extrusion machine provided with a ring die having a screen such as a woven metal wire of 10-200 mesh or the like and mixed at a temperature of 160-200 deg.C for 5-30 min and then extruded to produce a formed article. In the case when the thus-produced formed article is thermally disposed together with other wastes, an extraordinary temperature elevation in an incinerator can be prevented. Furthermore, the generation of a toxic gas such as a chlorine gas, a dioxin or the like can be inhibited and the generation of a carbon monoxide can also be inhibited by virtue of the effect of accelerating combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic resin molded article. More specifically, the present invention relates to a method for producing a thermoplastic resin molded article which prevents foaming caused by aluminum hydroxide during mixing and molding, has no foaming marks, and has a good appearance.

[0002]

2. Description of the Related Art Synthetic resins have become very familiar in our living space and are widely used in various applications. For example, polyethylene, polypropylene and vinyl chloride are various packaging materials, carpets for cars and homes,
Used for interior materials such as lining, and for covering electric wires. Polystyrene, AS resin, ABS resin, polyamide, polycarbonate, and epoxy resin are used for TVs, housings for personal computers and other electrical products, electronic component packages, or automobile-related components. ing.

[0003] The resin molded articles used for the above applications are partially recycled after use, but most of them are still incinerated or landfilled. When these resins are incinerated alone or together with other waste, hydrogen chloride gas, carbon monoxide gas, dioxin, etc. may be generated. It is known that a trace amount of heavy metal contained therein has a problem of dissolving and leaking in rainwater or the like at a landfill.

[0004] In order to solve such a problem, a thermoplastic resin bag using aluminum hydroxide (Japanese Patent Laid-Open No. 9-3237).
No. 35) has been proposed. When such a thermoplastic resin bag is incinerated with other garbage, it is possible to prevent abnormal temperature rise in the incinerator, to suppress harmful gases such as chlorine gas in exhaust gas, and to use chromium etc. It is known that leakage of heavy metal ions can be prevented.

[0005] However, aluminum hydroxide has a stable range of crystallization water up to about 200 ° C, and it is known that, depending on the use conditions, it decomposes and emits water even at a temperature lower than that. There was a problem of foaming when mixing and molding (for example, the practice of flame retardation of polymer materials and the development trend of new flame retardants, Industrial Technology Research Institute sponsored by AIST 5-1, September 1986) 2 to 3 days). To solve this problem, a method of mixing calcium oxide in addition to aluminum hydroxide has been proposed (for example, Japanese Patent Application Laid-Open No.
No. 44145).

However, the method of mixing aluminum hydroxide, thermoplastic resin and calcium oxide involves mixing,
Although it has the effect of suppressing foaming generated during molding to some extent, it is not possible to sufficiently prevent the occurrence of foaming, and it is not possible to obtain a thermoplastic resin molded article without foaming, or a thermoplastic resin molded article with a good appearance In some cases, it could not be obtained. In order to satisfy the diversifying demands of consumers, there has been a long-felt need for a method for producing a thermoplastic resin molded article which not only prevents the occurrence of foaming marks but also has a better appearance than ever before.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a thermoplastic resin molded article obtained by mixing and molding a hygroscopic agent such as aluminum hydroxide, a thermoplastic resin and calcium oxide. An object of the present invention is to provide a method for producing a thermoplastic resin molded article which prevents the occurrence of foaming due to aluminum hydroxide and has good appearance without foam marks.

As a result of intensive studies, the present inventors have found that a specific amount of a specific hygroscopic agent is mixed in a method for producing a thermoplastic resin molded article obtained by mixing and molding a thermoplastic resin, aluminum hydroxide and a hygroscopic agent. In such a case, they found that such a problem could be solved, and completed the present invention.

[0009]

That is, the present invention relates to a method for producing a thermoplastic resin molded article obtained by mixing and molding a thermoplastic resin, aluminum hydroxide and a moisture absorbent, wherein the moisture absorption rate of the moisture absorbent is 5% by weight. % / Hr or more, and the mixing amount is 0.01% by weight based on the thermoplastic resin molded article.
It is an object of the present invention to provide a method for producing a thermoplastic resin molded product, which is characterized in that the content is about 2% by weight.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention is an improved method for producing a thermoplastic resin molded article obtained by mixing and molding a thermoplastic resin, aluminum hydroxide, and a moisture absorbent.

The moisture absorbent used in the present invention has a moisture absorption rate of 5% by weight / hr or more, preferably 7% by weight / hr to 15% by weight.
And the mixing amount thereof is from 0.01% by weight to 2% by weight, preferably from 0.1% by weight to 2% by weight, based on the thermoplastic resin molded article.
It is characterized by being 1.5% by weight.

When the amount of the moisture absorbing agent is more than 2% by weight based on the thermoplastic resin molded article, it is possible to prevent the occurrence of foaming due to aluminum hydroxide during mixing and molding, but to obtain the obtained heat. The appearance of the plastic resin molded article becomes poor. In addition, clogging of the screen attached to the apparatus may occur. The mixing amount of the hygroscopic agent is 0.01
If the amount is less than 10% by weight, the occurrence of foaming due to aluminum hydroxide during mixing and molding cannot be prevented,
It is not possible to obtain a thermoplastic resin molded article without foam marks. In the present invention, the appearance was evaluated by visually observing irregularities of 50 μm or more on the surface of the thermoplastic resin molded article. The evaluation of the foaming marks was performed by measuring the presence or absence of bubbles existing in the thermoplastic resin molded article.

When the moisture absorbing rate of the moisture absorbent is less than 5% by weight / hr, foaming due to aluminum hydroxide cannot be sufficiently prevented during kneading. Further, even if the mixing amount of the hygroscopic agent having a moisture absorption rate of less than 5% by weight / hr is increased, it is not possible to obtain a thermoplastic resin molded article having no foaming marks and good appearance.

The moisture absorbent may have a moisture absorption rate of 5% by weight / hr or more. For example, phosphorus pentoxide, magnesium perchlorate, anhydrous calcium sulfate, magnesium oxide, and the like having a moisture absorption rate of 5% by weight / hr or more. At least one selected from the group consisting of calcium oxide and anhydrous calcium chloride
Species are mentioned, and among others, the application of calcium oxide having a moisture absorption rate of 5% by weight / hr or more is recommended.

It is desirable that the desiccant does not substantially contain particles having a size of 30 μm or more.
The content of particles having a size of 0 μm or more is 1% by weight or less. 30
Particles having a size of not less than μm may cause a reduction in the smoothness of the surface of the obtained thermoplastic resin molded article. In addition, 30
The presence of particles having a size of μm or more may be determined, for example, by a method of confirming by SEM observation, a method of using a particle size distribution measuring device, or the like.

The thermoplastic resin used in the present invention is, for example, a homopolymer which is at least one derivative selected from the group consisting of ethylene, propylene, styrene, vinyl chloride, vinyl acetate, acrylonitrile, butadiene, vinyl alcohol, acryl and acryl. Examples thereof include polymers, copolymers, and thermoplastic polyesters represented by polyamides and polyethylene terephthalates.

The aluminum hydroxide used in the present invention includes, for example, gibbsite, bayerite, boehmite, nordstrandite, etc. Among these, gibbsite is easily produced at low cost because it is produced in large quantities as a raw material for alumina by the Bayer method. It is preferred because it is available.
The aluminum hydroxide generally has an average particle size of about 0.3.
It is 5 μm to about 100 μm, and can be appropriately selected depending on the use. As a specific example, in a film application, the average particle diameter is about 0.5 μm to about 10 μm for the purpose of imparting high tensile strength.
In order to provide transparency, it is recommended to use those having a large primary particle diameter, while to provide concealment, it is recommended to use those having a small primary particle diameter.

The mixing amount of the aluminum hydroxide is usually about 1% by weight to the obtained thermoplastic resin molded article.
It may be appropriately selected so as to be in the range of about 80% by weight, preferably 15% by weight to about 50% by weight. When the amount is less than about 1% by weight, the effect of preventing an abnormal temperature rise in the incinerator when the obtained thermoplastic resin molded article is incinerated may not be obtained. If it is more than about 80% by weight, the appearance of the obtained molded article may be poor. Especially when incinerated with other garbage, the effect of preventing abnormal temperature rise in the incinerator, the effect of suppressing the generation of harmful gases such as chlorine gas and dioxin in exhaust gas, and the generation of carbon monoxide by the effect of promoting combustion The amount of aluminum hydroxide should be about 15% by weight or more in order to positively impart the effect of suppressing the pollution or the effect of preventing the leakage of heavy metal ions such as chromium, lead, and copper when reclaiming incineration ash. It is recommended that there be.

The mixing and molding of the present invention may be usually carried out by one kind selected from the group consisting of an injection molding machine, an extrusion molding machine, a blow molding machine, etc., having a screen. As the extruder, T die, ring die, strand die,
Extrusion molding machines to which a pipe die and other dies for irregularly formed shapes are attached are exemplified. The screen serves to prevent the mixing of coarse particles and to homogenize the thermoplastic resin molded article, and is made of a wire mesh of about 10 mesh to about 200 mesh. Further, in the present invention, mixing,
The molded body obtained by molding may be processed using a vacuum molding machine, a compression molding machine, or the like.

In mixing and molding according to the present invention, for example, an extruder (an inflation molding machine equipped with a screen) equipped with a ring die equipped with a screen containing a thermoplastic resin, aluminum hydroxide and a moisture absorbent is used. After mixing at about 160 ° C. to about 200 ° C. for about 5 minutes to about 30 minutes, a film or the like may be formed.

Alternatively, aluminum hydroxide may be previously kneaded with a thermoplastic resin to prepare an aluminum hydroxide-containing masterbatch, and then subjected to the mixing of the present invention. When performing the kneading, for example, about 1 hour of aluminum hydroxide is used.
From about 130 parts by weight to about 500 parts by weight and 100 parts by weight of polyethylene, using one kind selected from the group consisting of a pressure kneader, a Banbury mixer, a single screw extruder, a twin screw extruder, and the like. Kneading may be performed at 200 ° C. for about 5 minutes to about 30 minutes. Furthermore, when the aluminum hydroxide-containing masterbatch obtained by kneading is pelletized, for example, a hot cut method, a melt pulverization method, a strand cut method, an underwater cut method, or the like may be used.

Further, a moisture-absorbing agent may be kneaded with a thermoplastic resin in advance to prepare a thermoplastic resin composition containing a moisture-absorbing agent (hereinafter, referred to as a mixture) and then subjected to the mixing of the present invention. When mixing and molding using an injection molding machine or the like equipped with a screen, by kneading in advance, clogging of the screen attached to the apparatus during mixing and molding can be prevented. The kneading is, for example, a pressure kneader,
One selected from the group consisting of a Banbury mixer, a single screw extruder, a twin screw extruder, and the like. After kneading, if the mixture is to be pelletized, the mixture is cut without contact with water and cooled, for example, a hot cut method,
It is recommended to use a melt-pulverization method. In preparing a mixture by previously kneading the above-mentioned moisture absorbent with a thermoplastic resin, usually, about 100 parts by weight to about 300 parts by weight of calcium oxide having a moisture absorption rate of 5% by weight or more and 100 parts by weight of polyethylene are used. The kneading may be performed using a pressure kneader under the conditions of a kneading temperature of about 130 ° C. to about 200 ° C. and a kneading time of about 5 minutes to about 30 minutes. Further, when the obtained mixture is left in the air for a long period of time, when the left standing mixture is used for the mixing and molding of the present invention, the effect of pre-kneading is not obtained, and clogging of the screen accompanying the apparatus occurs. There are cases.

The thermoplastic resin molded product obtained by the production method of the present invention is generally used for home appliances and electric parts, containers, packing supplies, transportation machine parts such as automobiles, office supplies, toys, building materials, sports goods, agricultural goods, It is used for various purposes ranging from daily necessities to industrial materials, medical equipment, general machinery and precision equipment parts. Examples of home appliances and electrical components include housing and covers for various products, structural components such as casters and frames, precision components such as gears and connectors, and small components such as switches.
Examples include an electric insulator such as a wire covering material, and a clear cover for lighting equipment. Containers include beverage pottle, fixtures, lunch boxes, food trays, stretch films, food packaging containers, tappers,
Storage containers for precision instruments and valuables, pharmaceuticals, cosmetics, containers for various chemicals, cool containers, tool boxes, clothing cases, accessory cases,
Packing supplies such as plastic bags and packing include containers, boxes, wooden boxes, boxes for seafood and marine products, straps or tapes for packing, packing sheets, covers, shock absorbing materials,
Examples include a net, a container for packing a beverage container, and an assembly cap. Transportation equipment parts such as automobiles include soundproofing materials,
Examples include heat insulating materials, interior materials such as carpets and ceiling materials, cushion materials, dashboards, engine covers, ducts, exterior materials such as bumpers and wheel caps, curve mirrors, electric components, hull components, and buoys. Office supplies include writing implements, binders, organizing trays, clips, name tags, pen cases, writing implement stands, frames, three-dimensional maps, underlays, rulers, erasers, bulletin boards, and organizing files. Examples of toys and leisure goods include outdoor goods such as tents and portable chairs, parts of fishing gear, parts of dolls and toys, life-saving equipment such as floats, and parts of models or models. Building materials include flooring materials, carpets, heat insulation materials, wall materials and wallpapers, interior materials such as ceiling materials, exterior wall materials, signboards, wall materials for concrete casting, wall materials for simple buildings, alternative plates to veneer and plywood, Construction site enclosures, shoji boards, partitions,
Examples include a tatami mat core, an underfloor insulation material holding plate, and furniture such as a chair and a table. Sports goods include various rackets, balls, shuttles, shoes, helmets, protectors, agricultural goods such as films for tunnel houses, containers, heat absorbing films, watering hoses, and plastic bags for packing fertilizers and pesticides. Daily necessities include tableware such as chopsticks, spoons and forks, tableware, cooking utensils, imitation ornaments, artificial flowers, combs, trash boxes, garbage bags, plastic bags, fashion bags, shopping bags, product outer bags, cards, and various tools. Pattern, laundry scissors, futon slap, fly slap, fan bone, garden pots such as flowerpots, core of chair / desk,
Furniture backplates, pet supplies such as catching collars, reels, eyeglass parts, bag parts, shoes, sanitary goods, non-slip rubber, hit rubber, hooks, handles, aquariums, gloves, baskets, picks, and the like. Industrial materials include sheets or films of various sizes, pipes, pipes, hoses, valves, sweat faces,
Display shelves, side plates of pallets, trays, warehouse storage boxes, curing boards, floor boards for belt conveyors, partition boards, slip sheets, transport caul plates, assembled partition boards, cushioning materials, tapes, product outer bags, screws or nail chains And the like. Examples of medical instruments include syringe cylinders, blood bags, hoses and pipes, and general equipment and precision equipment parts such as various industrial equipment parts, clock parts, and precision parts such as gears.

Further, when the thermoplastic resin molded article obtained by the production method of the present invention is incinerated with other refuse, abnormal temperature rise in the incinerator can be prevented, and harmful gases such as chlorine gas and dioxin in the exhaust gas can be prevented. This has the effect of suppressing the generation of carbon monoxide due to the effect of promoting combustion, and preventing the leakage of heavy metal ions such as chromium, lead, and copper when landfilling incineration ash.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. The average particle diameter, moisture absorption rate, BET specific surface area, evaluation of foaming marks, evaluation of appearance, and tensile strength were measured by the following methods.

Average particle size (μm): Laser scattering particle size distribution analyzer [Lead & North Slap (LEED &
NORTHRUP) Microtrack]
The 0% by weight diameter was measured. Moisture absorption rate (wt% / hr): temperature 23 ° C, humidity 50%
The specimen was stored in a thermo-hygrostat kept in the state described above, and the time-dependent change in weight was measured. The amount of increase in weight from the start of the measurement to the lapse of one hour was expressed in percentage. BET specific surface area (m ² / g): measured by a nitrogen adsorption method. Evaluation of foaming marks (-): The presence or absence of bubbles present in the thermoplastic resin molded article was measured. Evaluation of appearance (pieces / cm ² ): The number of irregularities of 50 μm or more on the surface of the thermoplastic resin molded article was measured. The result is 1
It was expressed in number per cm ² . Tensile strength (kg / cm ² ): Performed by a method based on JIS Z1702. Ten dumbbell-shaped samples were measured using a tensile strength tester Autograph AGS-500 (manufactured by Shimadzu Corporation) and a load cell (maximum measurement load: 5 kg), and the average value was obtained.

Example 1 Melt flow rate: 2.0 g / 10 min, density: 0.9
100 parts by weight of a linear low-density polyethylene of 2 g / cm ³ and aluminum hydroxide 23 having an average particle diameter of 3 μm
3 parts by weight were kneaded using a pressure kneader at 160 ° C. for 15 minutes to obtain a master batch containing 70% aluminum hydroxide. Next, a melt flow rate of 25 g / 10
min, 100 parts by weight of linear low-density polyethylene having a density of 0.91 g / cm ³ , a moisture absorption rate of 10% by weight / hr, a BET specific surface area of 4.5 m ² / g, and 30 μm
Calcium oxide 186 substantially free of the above particles
The mixture was kneaded with a weight part at 160 ° C. for 15 minutes using a pressure kneader to obtain a mixture.

Subsequently, a melt flow rate of 0.04
g / 10 min, 100 parts by weight of high-density polyethylene having a density of 0.95 g / cm ³ ,
% Masterbatch 75 parts by weight (the aluminum hydroxide content is 30% by weight based on the thermoplastic resin molded product) and 3.5 parts by weight of the mixture (the calcium oxide content is based on the thermoplastic resin molded product). 1.3% by weight.) Using an inflation molding machine (manufactured by Modane) equipped with a screen set at a cylinder temperature of 170 to 180 ° C. and a die temperature of 170 ° C., and molded to a thickness of 30 μm. A thermoplastic resin film having a folding width of 650 mm was produced. The screen is 8 at the cylinder outlet.
A total of three sheets were installed in such a manner that a 0-mesh wire mesh was sandwiched by a 50-mesh wire mesh. As a result, clogging of the screen did not occur, there was no foaming mark in the obtained film, and the evaluation of the external appearance was 4.0 cells / cm ² , which was good. Also,
The tensile strength of the film is 429 kg in MD (molding direction).
/ Cm ² , TD (perpendicular to molding direction) 313 kg / c
m ² .

Comparative Example 1 Melt flow rate: 2.0 g / 10 min, density: 0.9
100 parts by weight of a linear low-density polyethylene of 2 g / cm ³ and aluminum hydroxide 2 having an average particle diameter of 3 μm.
33 parts by weight were kneaded using a pressure kneader at 160 ° C. for 15 minutes to obtain a master batch containing 70% aluminum hydroxide. In the above, the aluminum hydroxide was subjected to a moisture absorption rate of 4% by weight / hr and a BET specific surface area of 3.0 m ² / g.
Was obtained in the same manner except that the amount was changed to 100 parts by weight of calcium oxide.

Subsequently, a melt flow rate of 0.04
g / 10 min, 100 parts by weight of high-density polyethylene having a density of 0.95 g / cm ³ ,
% Masterbatch 75 parts by weight (the aluminum hydroxide content is 30% by weight based on the thermoplastic resin molded product) and 3.5 parts by weight of the mixture (the calcium oxide content is based on the thermoplastic resin molded product). 1.0% by weight.) Was mixed and molded using an inflation molding machine (manufactured by Placo Co., Ltd.) equipped with a screen set at a cylinder temperature of 170 ° C. to 180 ° C. and a die temperature of 170 ° C. A thermoplastic resin film having a folding width of 650 mm was produced. The screen is 8 at the cylinder outlet.
A total of three sheets were installed in such a manner that a 0-mesh wire mesh was sandwiched by a 50-mesh wire mesh. As a result, the evaluation of the appearance of the obtained film was 256 pieces / cm ² , which was poor.

[0031]

As described in detail above, according to the method for producing a thermoplastic resin molded article of the present invention, the occurrence of foaming due to aluminum hydroxide during mixing and molding is prevented, and the appearance is good without foam marks. The present invention provides an excellent thermoplastic resin molded article, and its industrial value is great.

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Claims (3)

[Claims] 1. A method for producing a thermoplastic resin molded article obtained by mixing and molding a thermoplastic resin, aluminum hydroxide and a moisture absorbent, wherein the moisture absorbent has a moisture absorption rate of 5% by weight / hr or more, and A method for producing a thermoplastic resin article, wherein the amount is 0.01% to 2% by weight based on the thermoplastic resin article. 2. The method for producing a thermoplastic resin article according to claim 1, wherein said moisture absorbent is calcium oxide. 3. The method for producing a thermoplastic resin molded article according to claim 1, wherein the mixing amount of the aluminum hydroxide is 15% by weight to 50% by weight based on the thermoplastic resin molded article. .