JPH0422176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultra-high molecular weight polyethylene composition that maintains the abrasion resistance of ultra-high molecular weight polyethylene while imparting flowability and facilitating molding. [Prior art] Ultra-high molecular weight polyethylene has an average molecular weight of
It is more than 1 million, and resins with an average molecular weight of 6 million are currently being manufactured. Such ultra-high molecular weight polyethylene has high hardness and excellent wear resistance. However, due to strong intermolecular cohesive forces, flowability is poor and molding is extremely difficult.Generally, molding is performed under pressure and high temperature, but when a special shape of resin is required, Since processing is performed by cutting, products cannot be supplied at low prices. In addition to the above-mentioned pressure press method, ram extrusion, single screw, double screw
Extrusion molding using special equipment for the shaft has been attempted, but the productivity is poor and the cost is comparable to the press cutting method, making it impractical. JP-A-51-90360 discloses a screw in the kneading and molding process. However, even with this disclosure technology,
There is no substantial improvement in the flowability of the resin.
Because the fluidity of the molten resin in the molding machine is still poor, it is only possible to mold it slowly in small quantities, resulting in poor productivity and high costs. Furthermore, molding of this resin requires a high temperature of 240 to 250° C., similar to the above-mentioned pressure pressing method or extrusion method, which causes thermal decomposition of the resin, resulting in a decrease in molecular weight and a decrease in wear resistance. Further, JP-A-58-59243 discloses a method in which approximately 30% of an aliphatic cyclic hydrocarbon polymer is added to facilitate molding. Although the additive dilutes the resin and improves the flowability slightly, it is still not sufficient, so molding using this method can only be applied to specific molding equipment such as extrusion molding machines, and the concentration of the ultra-high molecular weight polyethylene itself As it becomes thinner, chemical resistance and abrasion resistance decrease. [Object of the Invention] An object of the present invention is to provide an ultra-high molecular weight polyethylene composition that has flowability and is easily molded without reducing the abrasion resistance and chemical resistance of the ultra-high molecular weight polyethylene. . [Structure of the Invention] The gist of the present invention is to prepare ultra-high molecular weight polyethylene consisting of 100 parts by weight of ultra-high molecular weight polyethylene having an average molecular weight of 1 million or more and 3 to 30 parts by weight of α-methylstyrene monomer or a mixed monomer of α-methylstyrene and styrene. molecular weight polyethylene composition. In the present invention, α-methylstyrene monomer alone or a mixed monomer of α-methylstyrene and styrene is added to ultra-high molecular weight polyethylene with an average molecular weight of 1 million or more.
The mixed monomer preferably has a ratio of α-methylstyrene to styrene of 1:9 to 9:1. Also α-
If the addition amount of methylstyrene monomer or a mixed monomer of α-methylstyrene and styrene is small, it will not be effective, and if it is too large, it will affect the wear resistance of the resin.
It is added in an amount of 3 to 30 parts by weight since solvent resistance etc. decrease. The α-methylstyrene monomer and styrene monomer act as a solvent for the ultra-high molecular weight polyethylene and provide flowability. Furthermore, the added heat causes a polymerization reaction. At high temperatures, styrene monomer or its modified polymer acts as a solvent for ultra-high molecular weight polyethylene, and after molding, it is completely transformed into a polymer by residual heat. The polymer that solidifies after being cooled to room temperature has a network structure and has moderate strength, so it has the wear resistance and wear resistance inherent to ultra-high molecular weight polyethylene.
It does not impair chemical resistance etc. It is also preferable to add an aliphatic metal soap to the above composition as a lubricant, and examples of the aliphatic metal soap include organic carboxylic acids such as stearic acid and montanic acid such as magnesium, calcium, strontium, barium, zinc, cadmium, and lead. The amount of the metal salt added is preferably 0.1 to 3 parts by weight per 100 parts by weight of the above composition. [Effects of the Invention] The composition of the ultra-high molecular weight polyethylene composition of the present invention is as described above, and it contains an α-methylstyrene monomer or a mixed monomer of α-methylstyrene and styrene that can be turned into a polymer by heating. , flowability can be improved without impairing the excellent properties of ultra-high molecular weight polyethylene, such as abrasion resistance, and as a result, molding can be performed easily. Therefore, the productivity of molded products is improved, and molded products can be supplied at low prices. [Example] Next, an example of the present invention will be described. Examples 1 and 2, Comparative Examples 1 to 3 A blend of ultra-high molecular weight polyethylene with an average molecular weight of 2 million and 6 million, α-methylstyrene monomer, and styrene monomer and having the composition shown in Table 1 was supplied to a spar mixer. and mixed for 10 minutes at room temperature to obtain a mixed solution. The resulting mixture was supplied to a Koka type flow tester, and the shear rate and apparent viscosity (fluidity) were measured and are shown in Table 1. Also, the obtained mixture was made into 2 pieces with a diameter of 30 cm.
The mixture was fed to a axial extruder to obtain a sheet with a width of 15 cm and a thickness of 2.5 mm. Set temperature of extruder screw tip,
Table 1 shows the load during extrusion, the extrusion conditions, and the appearance of the obtained sheet. The abrasion resistance of the obtained sheet was also measured and the results are shown in Table 1. Wear resistance was measured by applying 100 meshes of foundry sand sprayed from a nozzle vertically to a sample sheet 2.5 mm thick, 5 cm wide, and 7 cm long for 3 minutes, and measuring the amount of wear per 100 g of the sheet. Example 3 Ultra-high molecular weight polyethylene 100 with an average molecular weight of 6 million
parts by weight, 5 parts by weight of α-methylstyrene monomer,
A mixture of 5 parts by weight of styrene monomer and 0.5 parts by weight of calcium montanate was supplied to a spar mixer and mixed at a temperature ranging from room temperature to 80°C for 15 minutes, but at the same time as in Example 1.
The results are shown in Table 1. Comparative Example 4 When we measured the fluidity of ultra-high molecular weight polyethylene alone with an average molecular weight of 1 million in the same manner as in Example 1, it was impossible to measure it, and it was also impossible to extrude and mold it with an extruder, so 220 A sheet with a thickness of 2.5 mm was obtained by pressing at 100 atm at 100° C. for 7 minutes, and its abrasion resistance was measured. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. An ultra-high molecular weight polyethylene composition comprising 100 parts by weight of ultra-high molecular weight polyethylene having an average molecular weight of 1 million or more and 3 to 30 parts by weight of an α-methylstyrene monomer or a mixed monomer of α-methylstyrene and styrene.