JPH0229101B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a molded article made of petroleum resin by injection molding.
2000, petroleum resin with heating loss of 10% by weight or less, 100 parts by weight and inorganic powder filler 100 to 900 parts by weight, high molecular weight thermoplastic resin with an average molecular weight of 5000 to 250,000 0 to
The present invention relates to a method for producing a molded article, which comprises injection molding a mixture containing 50 parts by weight. In particular, the present invention relates to a manufacturing method characterized by excellent injection moldability using a composition in which the loss on heating of the petroleum resin as a base resin is limited to 10% by weight or less among the above compositions. Generally, petroleum resin compositions containing a large amount of inorganic powder filler have glass-like hard and brittle properties at around room temperature. If a high molecular weight thermoplastic resin is blended into this composition, the strength and impact resistance of the molded product can be improved, but if the amount is less than 50 parts by weight, it will not be possible to impart flexibility to the molded product. ,
It is hard. When injection molding such a hard and relatively brittle molded product, if the molded product sticks to the mold surface during the process of removing the product from the mold, it is likely to cause mold release failure, continuous automatic molding failure, and mold release failure. This causes various economically disadvantageous problems such as product cracking, decreased productivity, and the need to apply a mold release agent to the mold after each molding cycle. The causes of this sticking to the cooled mold surface and cracking during mold release are that because the composition is a highly filled system, the shrinkage of the molded product during cooling and solidification in the mold is small, and that the material is It is thought that deformation during mold release is not allowed due to hardness and brittleness, and that it is difficult to improve mold releasability by adding or increasing the amount of a lubricant or mold release aid. The present inventors believed that these causes were primarily caused by petroleum resin, which is essentially the base resin. That is, petroleum resins were not originally developed as resins for injection molding, but have been evaluated as effective as tackifiers in the fields of rubber and adhesives.
The present inventors have already filed a patent application for a clay target using petroleum resin as a base resin.
52-40800), even in production using these injection molding methods, there is a problem that the molded product sometimes cracks when it is difficult to mold. As a result of intensive research that included this problem, we found that petroleum resins with large heat loss causes such problems, so by reducing the heat loss of the base resin, petroleum resin, to 10% by weight or less. It was discovered that it is possible to completely eliminate mold stickiness when releasing a molded product. That is, ring and ball softening point 60-200℃, average molecular weight 300
-2000, injection molding of a mixture consisting of 100 parts by weight of a petroleum resin with a heating loss of 10% by weight or less, 100 to 900 parts by weight of an inorganic powder filler, and 0 to 50 parts by weight of a polymeric thermoplastic resin with an average molecular weight of 5000 to 200,000. By doing so, it was possible to obtain a molded article of a petroleum resin composition of excellent quality. The petroleum resin in the present invention refers to thermal decomposition of petroleum,
A cracked oil fraction that is liquid at room temperature and is a by-product of steam cracking or catalytic cracking, preferably a fraction whose main component is a _C9 aromatic hydrocarbon fraction with a boiling point of 120 to 280°C, more preferably a fraction of 140 to 280°C. Aromatic hydrocarbon fractions with a boiling point of 280°C are polymerized by thermal polymerization or a normal Friedel-Crafts type catalyst, or petroleum resins are added with unsaturated dibasic acid anhydrides such as maleic anhydride. JIS
Ring and ball softening point according to K2531 60~200℃ Preferably
It is a resin with a softening point of 90-180℃. softening point
When a petroleum resin with a temperature lower than 60°C is blended for the purpose of the present invention, the softening temperature of the composition becomes low, so
Not only does the cooling process during molding take longer, reducing productivity, but it also causes problems with the heat resistance of the molded product, causing it to deform when left in a hot place outdoors, or when transported or stored in stacks. Furthermore, if the softening point is set to 200° C. or higher, the melt viscosity becomes high and processability deteriorates, which is not preferable. The heating loss referred to in the present invention refers to a diameter of 75 mm and a depth of 20 mm.
5 g of petroleum resin was collected on a mm glass shear plate,
It is installed in the middle of an air constant temperature chamber with internal dimensions of 45 cm wide, 45 cm deep, and 50 cm high, and the temperature at the center of the tank is controlled.
Maintain temperature at 200±1℃ and supply air at 15/min.
It refers to the percent weight loss of petroleum resin after 3 hours when discharged. That is, if the weight before heating is M ₁ and the weight after heating is M ₂ , then the loss on heating (% by weight) is expressed by the following formula. Heating loss (weight %) = (M ₁ - M ₂ /M ₁ ) x 100 To reduce the heating loss of petroleum resin to 10% by weight or less, for example, put the petroleum resin in a metal container and heat it to 230°C while purging with nitrogen. Raise the temperature to , stop the nitrogen supply, and perform vacuum degassing. If this loss on heating is 10% by weight or more, the molded product tends to stick to the mold surface during the process of taking out the product from the mold during injection molding of a hard and relatively brittle molded product, resulting in poor mold release. Continuous automatic molding failures, product cracks during mold release, reduced productivity, the need to apply mold release agent to the mold after each molding cycle, etc.
This causes various disadvantageous economic problems. In addition, the inorganic powder filler referred to in the present invention is usually an inorganic powder with a particle size of 0.01μ to 500μ, such as calcium carbonate, talc, clay, alumina white, mica powder, aluminum sulfate, barium sulfate,
These include gypsum, calcium sulfite, lithopone, pumice powder, glass powder, zinc white, magnesium carbonate, metal powder, asbestos powder, titanium oxide, or a mixture thereof. Furthermore, the high molecular weight thermoplastic resin as used in the present invention refers to polyethylene with an average molecular weight of about 5,000 to 200,000,
Polypropylene, polybutene-1, crystallinity 1,2
High molecular weight thermoplastic resins such as polybutadiene, polystyrene, poly-α-methylstyrene, polyvinyl chloride, polymethyl methacrylate, polyamide, polyester, thermoplastic polyurethane,
Furthermore, ethylene-propylene block copolymer,
Copolymer type thermoplastic resins such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, styrene-butadiene block copolymer, styrene, isoprene block copolymer, etc. Among these, Powdered polyethylene, polypropylene, polystyrene, etc., which are inexpensive and highly effective in improving physical properties, are preferably used. The quantitative relationship between the petroleum resin component, the inorganic powder filler component, and the high molecular weight thermoplastic resin component is as follows:
Per 100 parts by weight of a petroleum resin with an average molecular weight of 300 to 2000 and a ring and ball softening point of 60 to 200°C, 100 to 900 parts by weight of an inorganic powder filler, preferably 200 to 900 parts by weight, and 0 to 900 parts by weight of a high molecular weight thermoplastic resin. 50 parts by weight, preferably 0 to 40 parts by weight. If the amount of inorganic powder filler is less than 100 parts by weight, the heat resistance of the molded product will be poor;
When stored in the summer or left unattended, the surface becomes sticky, causing problems such as fusion and merging of molded products. Also, it is expensive,
It doesn't suit the purpose. If the amount of inorganic powder filler is more than 900 parts by weight, the price of the material as a whole will be low and it is advantageous, but the melt viscosity during molding will increase extremely, causing loss of fluidity and making molding difficult. This results in a significant drop in productivity. Furthermore, in the present invention, the amount of high molecular weight thermoplastic resin blended with 100 parts by weight of petroleum resin is 0 to 50 parts by weight, and the resin itself is selected from among the high molecular weight thermoplastic resins as described above. The optimum amount of addition differs depending on the purpose of the molded product. That is, when adding a high molecular weight thermoplastic resin with excellent strength and impact resistance when the molded product is a clay vision, the preferable amount to be added is 0 to 20
The preferable addition amount of the high molecular weight thermoplastic resin which is good in parts by weight and has low impact strength is 0 to 40 parts by weight. If 50 parts by weight or more is added, the strength of the molded product will be excessive. In addition, in the present invention, the mixture of the present invention consisting of a petroleum resin, an inorganic powder filler, and a high molecular weight thermoplastic resin may optionally contain a small amount of a processing aid, for example, 15 parts by weight or less per 100 parts by weight of petroleum resin. ,
Pigment antioxidants and the like can be added. When blending and preparing the mixture of the present invention, which is based on a petroleum resin with a heating loss of 10% by weight or less, it is heated and kneaded using a kneader, Banbury mixer, roll mill, or other general-purpose plastic kneader or mixer. , the mixture may be granulated and fed to an injection molding machine. More preferably, all of the weighed raw materials are put into a high-speed rotating mixer such as a Benciel mixer or a super mixer, pulverized and mixed without heating, and the powdered dry blend composition is transferred to an injection molding machine. It can also be supplied directly. The injection molding machine for molding these mixtures is
Ram-type and pot-type injection molding machines used for molding general polymeric materials can be applied as is, but molding machines equipped with a pre-plasticizing device, such as an injection molding machine with a blend feeder (Nissei Plastics Co., Ltd. By using a powder dry blend mixture that omits the heating step during mixing, it is possible to directly supply and injection mold the powdered dry blend mixture. Products that can be injection molded with the composition of the invention include:
For example, containers, pipes, flowerpots, clay target targets, seedling boxes, ornaments (statues and other figurines), tiles,
We can provide a wide range of products at low prices, from civil engineering, construction, and leisure supplies such as wallboards to household items. It is particularly suitable as a flower pot and clay target. The present invention will be explained in more detail below with reference to Examples. Examples 1 to 3 and Comparative Examples 1 to 4 As shown in the table, petroleum resins, heavy calcium carbonate, high molecular weight thermoplastic resins, processing aids, and pigments were each weighed in predetermined parts by weight, and 250 A powdery mixture was prepared by dry blending using a Henschel mixer at room temperature and 1600 rpm for 3 minutes. These raw materials were supplied to the hopper of an injection molding machine with a blend feeder (manufactured by Nissei Jushi Kogyo Co., Ltd.), and a flowerpot was molded with the heating cylinder temperature set at 170°C. Examples 1 to 3 all contain petroleum fats with a heating loss of 10% by weight or less, but good moldability was achieved regardless of the type and amount of high molecular weight thermoplastic resin and the presence or absence of processing aids. Fully automatic continuous operation was also easy. Furthermore, the plated surface of the mold cavity was mirror-like throughout, confirming that the molded product was hardly stuck to the cavity surface. Comparative Example 1 was formulated with a petroleum resin with a heating loss of 11.9% by weight, but although it was able to be continuously molded, several out of 100 pieces cracked and were released from the mold.
During product inspection after molding, more than half of the products were found to have cracks, and including cracks during molding, 76% of the products were defective. Comparative Examples 2 and 3 were formulated with petroleum resin with a heating loss of 12.8% by weight, but in Comparative Example 2, all cracked and were released from the mold during manual operation before switching to automatic operation.
The surface of the mold cavity became heavily soiled with each shot, confirming that the mold was stuck with considerable force. In Comparative Example 3, the amount of stearic acid blended was twice that of Comparative Example 2, but the mold release effect was not improved and the result was the same as Comparative Example 2. Comparative Example 4 contains a petroleum resin with a heating loss of 11.3% by weight, and the amount of polystyrene was also increased to 20 parts by weight to improve product strength. As a result, fully automatic operation became possible, but 15% of the molded products had cracks. In addition, the plating surface of the mold cavity was also compared to Comparative Example 2.
Although it was not as bad as 3, it was observed that it gradually became dirty each time molding was repeated.

[Table] Number of moldings
Example 4 10 kg of petroleum resin with a heating loss of 12.8% by weight and a softening point of 97°C, which is the same as that blended in Comparative Examples 2 and 3, was
Pour into a stainless steel pot and replace with nitrogen.
The temperature was raised to 230°C, nitrogen supply was stopped, and vacuum degassing was performed to obtain a petroleum resin with a heating loss of 8% by weight and a ring and ball softening point of 110°C. When this petroleum resin was again prepared to have the same composition as in Comparative Example 2 and molded into a flowerpot again, there was no mold release cracking at all, and the mold plating surface also had a mirror finish, as in Examples 1 to 3. It was possible to mold the product fully automatically while maintaining the same conditions, and there were no cracks during product inspection. Example 5 Aromatic petroleum resin (Nisseki Neopolymer) with a heating loss of 7.8% by weight and a ring and ball softening point of 104°C (Nisseki Neopolymer) 30Kg, heavy calcium carbonate (Whiten P50) 160Kg, powdered polystyrene (Toporex #525 powder) 4Kg,
After putting 4 kg of titanium oxide and 2 kg of stearic acid into a 300 Henschel mixer and pulverizing and mixing at room temperature 600 rpm for 5 minutes, the dry blend powder mixture was placed in an injection molding machine with a blend feeder (manufactured by Nissei Jushi Kogyo Co., Ltd.). When the material was supplied to a hopper and molded into clay shooting targets, there was no mold sticking phenomenon, and white shooting targets that did not require painting could be formed with zero defects in the molding process.

Claims (1)

[Claims] 1 (1) Among the hydrocarbon fractions by-produced when producing lower olefins by thermal cracking, steam cracking, or catalytic cracking of petroleum, a fraction at 140 to 280°C is polymerized. Ring and ball method consisting of aromatic hydrocarbons obtained
60~200℃, number average molecular weight 300~2000, heat loss
A mixture consisting of 100 parts by weight of a petroleum resin of 10% by weight or less, (2) 100 to 900 parts by weight of an inorganic powder filler, and (3) 0 to 50 parts by weight of a high molecular weight thermoplastic resin with a number average molecular weight of 5,000 to 200,000. A method for producing a molded article, characterized by injection molding. 2. The method for producing a molded article according to claim 1, wherein the mixture is supplied to an injection molding machine in the form of a powder dry blend. 3. The method for producing a molded article according to claim 1 or 2, wherein the molded article is a flower pot. 4. The method for producing a molded article according to claim 1 or 2, wherein the molded article is a clay target.