JPH0364553B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a thermoplastic resin composition, and more particularly to a thermoplastic resin composition that does not corrode kneading machines, molding machines, etc. BACKGROUND ART Conventionally, in order to obtain resin molded articles having the texture of natural wood, a resin composition prepared by blending wood flour with a thermoplastic resin has been used as a molding material. However, resin compositions containing this wood flour have disadvantages such as the wood vinegar gas in the wood flour corroding kneading machines, molding machines, molding molds, etc. and causing rust. For this reason, countermeasures have been taken, such as making these kneading machines etc. from special steel that does not easily corrode, and applying anti-corrosion plating to molding dies. However, manufacturing machines using special steel is very expensive and economically unfavorable. In addition, even when using a molding mold with anti-corrosion plating, split molds,
Protruding pins, gas vents, etc. cannot avoid rusting due to long-term molding, and it is difficult or impossible to plate them in molds for molded products with complex shapes or acute angles. Ta. Therefore, the present inventors conducted intensive research to develop a method for producing a resin composition that does not corrode kneading machines, molds, etc. and has the texture of natural wood. Based on this knowledge, we discovered that the objective could be achieved by kneading a blend of modified polyolefin at high speed, then adding quicklime and kneading at low speed, and then kneading and extruding using an extruder. The invention has been completed. In other words, the present invention uses a thermoplastic resin selected from the group consisting of polypropylene, polyethylene, acrylonitrile-butadiene-styrene resin, and polyamide, and wood flour, with the former being 20 to 90 parts by weight, when the total of both is 100 parts by weight, The latter is used in a proportion of 80 to 10 parts by weight, and the modified polyolefin is used for a total of 100 parts by weight of the thermoplastic resin and wood flour.
After kneading a mixture using a proportion of 0.5 to 6 parts by weight with a high-speed mixer, adding quicklime in a proportion of 2 to 8% by weight with respect to the wood flour to the obtained kneaded product, and kneading with a low-speed mixer. , provides a method for producing a thermoplastic resin composition characterized by kneading and extruding using a uniaxial extruder. In the method of the present invention, a thermoplastic resin selected from the group consisting of polypropylene, polyethylene, acrylonitrile-butadiene-styrene resin (ABS resin), and polyamide (such as nylon-6) is used. The blending amount of the thermoplastic resin is 20 to 90 parts by weight when the total of the thermoplastic resin and wood flour is 100 parts by weight.
Preferably it is 30 to 70 parts by weight. If it is less than 20 parts by weight, the original properties of the thermoplastic resin composition will be lost, which is not preferable. Wood flour is then added to give the thermoplastic a natural wood texture and also to improve mechanical strength. The wood powder is made from crushed wood such as pine, fir, hemlock, and poplar, and has a particle size of 80 to 325 mesh.
Preferably it is 100 to 150 meshes. The amount of wood flour blended is 10 to 80 parts by weight, preferably 30 to 70 parts by weight, when the total of the thermoplastic resin and wood flour is 100 parts by weight. If the amount of wood flour is less than 10 parts by weight, a sufficient natural wood texture cannot be obtained. The modified polyolefin is added to improve the mechanical strength of the resin composition by reacting with wood flour. As the modified polyolefin, polyolefins chemically modified with liquid rubber and/or unsaturated carboxylic acids (including anhydrides) or derivatives thereof are preferably used. Here, as the liquid rubber, unterminated hydroxylated polybutadiene is suitable. In producing this chemically modified polyolefin, polyolefins such as polypropylene, liquid rubber and/or unsaturated carboxylic acids or derivatives thereof are mixed with xylene, toluene,
The reaction may be carried out using a radical generator such as benzoyl peroxide in a solvent such as heptane or monochlorobenzene. Details of the method for producing this chemically modified polyolefin are disclosed in JP-A-54-124049. The blending amount of the modified polyolefin is 0.5 to 6 parts by weight per 100 parts by weight of the thermoplastic resin and wood flour.
Parts by weight, preferably 1 to 5 parts by weight. If it is less than 0.5 parts by weight, the improvement in mechanical strength will not be sufficient, and if it exceeds 6 parts by weight, the fluidity will deteriorate and the appearance of the molded product will be poor, making it impossible to put it into practical use. Furthermore, quicklime, that is, calcium oxide, absorbs wood vinegar gas and moisture in wood flour and carbon dioxide gas in the air to become calum hydroxide or calcium carbonate. It is added to prevent corrosion of molding dies, etc., and to improve the appearance of molded products due to migration and adhesion of rust, etc. Various types of quicklime can be used regardless of quality, but from the viewpoint of workability etc., the particle size is
0.5 to 10μ, preferably 2 to 5μ is suitable. The amount of quicklime blended is 2 to 8% by weight based on wood flour.
Preferably it is 5 to 7% by weight. If the blending amount is less than 2% by weight based on the wood flour, the absorption of wood vinegar gas etc. will be insufficient, the corrosion prevention effect of molding molds etc. will not be sufficient, and furthermore, the appearance of the molded product will be poor. On the other hand, if it exceeds 8% by weight, the spiral flow length (SFL) becomes small and moldability becomes poor, and unreacted quicklime adsorbs water over time, causing silver formation on the molded product and the appearance. becomes defective, which is not desirable. In the method of the present invention, the above components are used as raw materials, but if necessary, lubricants, inorganic fillers, organic fillers other than wood flour, antistatic agents, colorants, flame retardants,
Auxiliary additives such as antioxidants, UV absorbers, plasticizers, etc. can be added. As lubricants, hydrocarbon-based liquid paraffin, natural paraffin, wax, etc., fatty acid-based higher fatty acids, oxyfatty acids, etc.
Ester-based fatty acid lower alcohol esters, etc.
Examples include alcoholic aliphatic alcohols and polyglycols, metal compounds such as calcium stearate and barium stearate, and examples of silicone such as silicone oil and modified silicone. Inorganic fillers include calcium carbonate, barium sulfate, talc, silica, mica, clay,
Examples of organic fillers other than wood flour include powdered shells of fruits such as walnuts and coconuts, and waste paper. Various surfactants are used as the antistatic agent. In addition, colorants include poorly soluble azo dyes, red colorants, cadmium yellow, chrome yellow, titanium white, etc. Flame retardants include inorganic antimony oxide, zirconium oxide, etc., and organic phosphate esters, trichloride, etc. Examples include cresyl phosphate. As the antioxidant, a phenol type is used, and as the ultraviolet absorber, a triazole type, salicylic acid type, or acrylonitrile type is used. Further, plasticizers include phthalic acid diesters, butanol diesters, phosphoric acid esters, etc., and crosslinking agents and vulcanizing agents include sulfur, organic sulfur compounds, organic peroxides, metal oxides, polyamines, polyisocyanates, etc. Can be mentioned. In the method of the present invention, the above-mentioned components are used as raw materials, and the following kneading and extrusion are performed. First, a predetermined amount of a mixture of thermoplastic resin, wood flour, and modified polyolefin is kneaded at a temperature of 100 to 250°C for 5 to 20 minutes using a high-speed mixer. The high-speed mixer used here preferably has blades in the shape shown in Figures 1 and 2, and the rotational speed of the high-speed mixer in this case is usually 200 to 1000 rpm,
Preferably it is 400-900 rpm. If the rotational speed is less than 200r.pm, gelation may be insufficient and kneading may not be possible, and if the rotational speed exceeds 1000r.pm, the material temperature may rise abnormally and cause material deterioration. There is. Next, a predetermined amount of quicklime is added to the obtained kneaded product, and the mixture is kneaded for 5 to 10 minutes using a low-speed mixer at a temperature of 80 to 100°C. In this kneading step, since the kneading proceeds at a relatively low temperature, the kneaded material is gradually cooled and becomes fine lumps. There is no particular limit to the rotation speed of the low-speed mixer, but it is usually 100~
It is 200rpm. The kneaded product obtained through the above-mentioned two-stage kneading process is kneaded and extruded using a single screw extruder, usually at 190 to 230°C. In this step, it is important not only to perform a simple extrusion operation but also to perform sufficient kneading together with extrusion. In addition, when adding auxiliary additives such as lubricants, they may be added at this stage. The method of the present invention is characterized in that kneading is thoroughly carried out in three stages. There are cases where the proportion of components other than thermoplastic resins in the blend to be kneaded is very large, and in such cases, a more powerful power source is required for kneading than in the case of ordinary resin blends. Therefore, the kneader or extruder used here may be one for plastics, but it is more preferable to use one used in the ceramic industry. By carrying out kneading in three stages under specific conditions as in the present invention, better results can be obtained than in the case of other methods. For example, if all the ingredients are added at the same time from the beginning or if quicklime is added after kneading with a low-speed mixer, corrosion of the kneading machine etc. cannot be sufficiently prevented and the appearance of the molded product will be poor. In the present invention, the above resin composition is usually cut into pellets in an appropriate size under heat to form a pellet-like resin composition. It is preferable to cut the extruded resin composition as soon as possible while the resin composition itself is still hot; good results will not be obtained if the cutting is carried out after cooling. In other words, when the resin composition is cut while it is hot, the molten or semi-molten thermoplastic resin flows at the cut surface.
Covers the filler material that is exposed on the surface, so that
A pellet-like resin composition is obtained whose surface is substantially completely coated with a layer of thermoplastic resin. A molded product is obtained by molding this using a mold or the like. Since the resin composition obtained by the method of the present invention causes almost no corrosion in the kneading machine, molding die, etc., it is not necessary to make them of special steel or to apply anti-corrosion plating. In addition, there is no migration or adhesion of rust to the surface of the molded product, and the moldability, appearance, etc. of the molded product are extremely good, and a product having the texture of natural wood can be obtained. Therefore, the thermoplastic resin composition obtained by the method of the present invention can be used very effectively as a material for lacquerware products, acoustic products, various housings, and the like. Next, the present invention will be explained in detail using examples and the like. The results were measured or evaluated using the following method. (1) Number of rust shots Using a molding machine (manufactured by Toshiba Machine, 10 oz.),
The resin composition was molded at a molding temperature of 200° C. and a molding time of 60 seconds into a box-shaped product having a wall thickness of 4 mm, a length of 90 mm, a width of 80 mm, a height of 150 mm, and a hole with a diameter of 70 mm in the center of the bottom. The number of shots where rust occurred on the mold surface and ejector pins was visually determined. Note that the molding temperature was 230°C in Production Example 19 and 250°C in Production Example 20. (2) Formability Expressed by spiral flow length (cm). Using Archimedes type, temperature 240℃, pressure 1000
The flow length when molded at Kg/cm ² was measured. Note that the molding temperature was 250°C only in Production Example 20. (3) Appearance (1) For the measurement of the number of rust occurrence shots, mold a maximum of 300 shots using a molded box-shaped object. If no rust occurs, the appearance after molding 300 shots. If rust occurs, The appearance of each shot immediately after rusting was visually observed and evaluated as follows.

[Table] (4) Tensile test Based on ASTM D-638. (5) Performance after one month Compliant with ASTM D-638. After the tensile test piece was left immersed in water at room temperature for one month, the tensile strength and elongation rate were measured. In addition, the appearance of the above box-shaped object was evaluated in the same manner as in (3). Production example of modified polyolefin Polypropylene (melt index 8 g/10 minutes, density 0.91 g/cm ² , product name:
J700G, manufactured by Idemitsu Petrochemical Co., Ltd.) per 100 parts by weight of terminal hydroxylated 1,4-polybutadiene (number average molecular weight 3000, trade name: Poly bd R45HT,
(manufactured by ARCO chem.Div.) 5 parts by weight, maleic anhydride 20 parts by weight, dicle peroxide 1.72 parts by weight,
600 parts by weight of xylene was charged, heated in an oil bath using an immersion heater, and reacted with stirring at 120°C for 1 hour, and then continued at 140°C for 3 hours. After the reaction was completed, the mixture was cooled, precipitated in a large excess of acetone, filtered with suction, and dried (at 70°C for 50 hours) to obtain a white powder. This powder was then placed in a Soxhlet extractor and extracted with acetone for 16 hours.
Unreacted polybutadiene and maleic anhydride were removed by time extraction to obtain a chemically modified polyolefin. Production Example 1 A predetermined amount of the thermoplastic resin shown in Table 1, wood flour, and the chemically modified polyolefin obtained above were blended, and this mixture was supplied to a high-speed mixer heated to 200°C, and the mixture was mixed at a rotation speed of 500 r.pm. After stirring for 15 minutes, the mixture was heated to 230°C by heat transfer and stirring heat.
gelatinized. Next, the above mixture was cooled in a low-speed mixer cooled to 20°C until the temperature reached 60°C, and the first
Add the specified amount of quicklime shown in the table and increase the rotation speed to 150 r.p.
Stir for 10 minutes at m. The thus obtained kneaded product was extruded using a single screw extruder (diameter 125 mm, vent type, manufactured by Nakatani Kikai Co., Ltd.) at a resin temperature of 200° C. to obtain a rod-shaped resin composition. Next, it was made into pellets (3φ x 5mm) by a conventional method. Production Example 2 In Production Example 1, the temperature of the high-speed mixer was set to 150
A resin composition was obtained under the same conditions as Production Example 1, except that the heating temperature after stirring was 200°C, and the temperature of the low-speed mixer was 150°C. It was then pelletized. Production Examples 3 to 16 In Production Example 1, the temperature of the high-speed mixer was set to 150
A resin composition was obtained using the components and predetermined amounts shown in Table 1 under the same conditions as in Production Example 1 except that the heating temperature after stirring was 200°C. Then,
Turned into pellets. Production Example 17 In Production Example 1, the temperature of the high-speed mixer was set to 150
A resin composition was obtained under the same conditions as in Production Example 1, except that the heating temperature after stirring was 250°C, and the stirring temperature in the low-speed mixer was 100°C, and then pelletized. Cutting example 18 In production example 1, the temperature of the high speed mixer was set to 150
A resin composition was obtained under the same conditions as in Production Example 1, except that the heating temperature after stirring was 270°C, and the stirring temperature in the low-speed mixer was 120°C, and then pelletized. Production Examples 19 and 20 In Production Example 1, the temperature of the high speed mixer was set to 150
A resin composition was obtained using the components and predetermined amounts shown in Table 1 under the same conditions as in Production Example 1, except that the heating temperature after stirring was 200°C, and then pelletized. Comparative Examples 1 to 7 In Production Example 1, the temperature of the high-speed mixer was set to 150
A resin composition was obtained using the components and predetermined amounts shown in Table 1 under the same conditions as in Production Example 1, except that the heating temperature after stirring was 200°C, and then pelletized. Comparative Example 8 In Production Example 1, the temperature of the high speed mixer was set to 150
A resin composition was obtained under the same conditions as in Production Example 1, except that the heating temperature after stirring was 200°C, and the predetermined amount of quicklime shown in Table 1 was kneaded together with other ingredients from the beginning. Then, it was pelletized. Comparative Example 9 A resin composition was obtained under the same conditions as in Production Example 1, except that a predetermined amount of quicklime shown in Table 1 was kneaded together with other ingredients from the beginning, and then pelletized. Comparative Example 10 A resin composition was obtained under the same conditions as in Production Example 2, except that a predetermined amount of quicklime shown in Table 1 was kneaded together with other ingredients from the beginning, and then pelletized. Comparative Example 11 In Production Example 1, the temperature of the high speed mixer was set to 150
A resin composition was prepared under the same conditions as in Production Example 1, except that the heating temperature after stirring was 200°C, and the predetermined amount of quicklime shown in Table 1 was added after kneading in the high-speed mixer and the low-speed mixer. was obtained and then pelletized. Comparative Example 12 A resin composition was obtained under the same conditions as in Production Example 1, except that a predetermined amount of quicklime shown in Table 1 was added after kneading in the high-speed mixer and the low-speed mixer, and then pelletized. Examples Molded products and test pieces were formed using the pellets obtained in Production Examples 1 to 20 and Comparative Examples 1 to 12, and various tests were conducted. The results are shown in Table 1.

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【table】 [Brief explanation of drawings]

FIG. 1 shows an example of a blade attached to the upper part of a high-speed mixer used in the method of the present invention, and FIG. 2 shows an example of a blade attached to the lower part of the high-speed mixer.

Claims (1)

[Claims] 1 A thermoplastic resin selected from the group consisting of polypropylene, polyethylene, acrylonitrile-butadiene-styrene resin, and polyamide, and wood powder, when the total of both is 100 parts by weight, the former
Used at a ratio of 20 to 90 parts by weight, the latter 80 to 10 parts by weight,
A mixture in which modified polyolefin is used in a ratio of 0.5 to 6 parts by weight based on 100 parts by weight of the thermoplastic resin and wood flour in total is kneaded using a high-speed mixer, and the resulting kneaded product is mixed with 1. A method for producing a thermoplastic resin composition, which comprises adding quicklime in an amount of 2 to 8% by weight, kneading with a low-speed mixer, and then kneading and extruding using a single-screw extruder.