JPS6036175B2 - Ultra-high molecular weight polyethylene composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high molecular weight polyethylene composition, and more particularly to an ultra-high molecular weight polyethylene composition that can be continuously molded by extrusion molding or the like.

Conventionally, so-called ultra-high molecular weight polyethylene, which has a molecular weight of 1 million or 1.5 million or more, has significantly improved impact resistance, stress cracking resistance, and various performances at low temperatures compared to ordinary low-pressure polyethylene. It has many features such as self-lubricating properties and excellent wear resistance, as well as excellent water absorption properties of the polyjethylene polymer, low specific gravity, sound damping properties, and excellent acid and alkali resistance. On the other hand, when molding, there is no suitable molding method other than an extrusion molding machine equipped with special mechanisms and equipment, or compression molding, which requires an extremely long time, and it is said to be inferior in mass production. There was a problem. Moreover, this ultra-high molecular weight polyethylene has a melting point (136
There is a problem in that when exposed for a certain period of time to a temperature exceeding q○), for example, a temperature of 20,000 or more, thermal decomposition occurs and the molecular weight decreases to less than 1 pm.

This thermal decomposition is not so severe as with polyacetal and polyamide resins that it causes significant decomposition gas generation and foaming, making it impossible to mold, but can be molded to some extent, so the decrease in molecular weight is often overlooked. be.

This decrease in molecular weight results in the loss of the various properties that ultra-high molecular weight polyethylene has described above.

The fact that there is no suitable molding method other than compression molding means that there is no other suitable method to mold ultra-high molecular weight poly-IJ ethylene without causing thermal deterioration or thermal decomposition during molding. However, if the reduction in molecular weight is ignored, it is possible to use an ordinary extrusion molding machine.

For example, according to experiments conducted by the present inventors, when the temperature of the heating cylinder of the extrusion molding machine is set at 320 to 3700°C,
Although it was possible to extrude ultra-high molecular weight polyethylene, the resulting molded product initially had an average molecular weight of over 1 million, but measurements showed that the average molecular weight had decreased to around 120,000. It was.

This product had a large melt index of 1 or more (the original melt index was 0.01 or less), and had changed to have the same properties as ordinary high-density polyethylene. In this case, it is true that ultra-high molecular weight polyethylene is extruded, but the result is no different from extrusion molding of ordinary high-density polyethylene from the beginning.

Therefore, it is strongly desired to enable continuous molding such as extrusion molding with excellent mass productivity without causing a decrease in molecular weight.

As a result of a series of experiments on blends of thermoplastic synthetic resins, the present inventors found that by using a homogeneous mixture of ultra-high molecular weight polyethylene and thermosetting polyimide resin, for example, Using an extrusion molding machine, the desired shape can be extruded very efficiently without increasing the temperature of the heating cylinder of the molding machine more than necessary, and therefore without causing thermal decomposition or significantly changing the physical properties. We have discovered that it is possible to continuously mold products. The ultra-high molecular weight polyethylene used in this invention has an average molecular weight of 100 as determined by the viscosity method.
10,000 or more (molecular weight by light scattering method is 3 million or more), melt index is 0.01 or less, and density is 0.930.
For example, HIZEX MILLION 240M, manufactured by Mitsui Petrochemical Industries, Ltd., which has a melting point of 136° C., or HOSTELAY OUR, manufactured by Hoechst, which has almost similar properties, are available.

The thermosetting polyimide resin is a polymerization product obtained by addition-polymerizing Bismaleimide A with an addition reaction product B of isocyanuric acid and butyl glycidyl ether, such as Imidalloy (trade name manufactured by Toshiba Chemical Co., Ltd.) or Bismaleimide. -A and alkylene diamine-8, which is a product of addition polymerization, such as Quinel, a trade name of Rhone-Poulenc.

These polyimide resins generally have good heat resistance;
Excellent adhesion and little loss of strength even at high temperatures.
It has features such as excellent dimensional stability, and good friction and wear properties. This polyimide resin has a cure time of 40 on a hot plate of 20,000.
Powder that passes through 200 mesh for ~60 seconds, 0.4 to 10% by weight based on ultra-high molecular weight polyethylene, and 0.5
~3% by weight is added.

That is, the average particle size is 200 microns, and the apparent density is 0.44.
The composition of the present invention can be obtained by a simple operation of uniformly mixing a predetermined amount of the polyimide resin powder with the ultra-high molecular weight polyethylene using, for example, a Henschel mixer. The blending amount of polyimide resin is 0.4
If the amount is less than 1% by weight, continuous molding such as extrusion molding cannot be performed, and if the amount exceeds 3% by weight, it becomes increasingly difficult to set the molding conditions, and if the amount is more than 1% by weight, satisfactory molding cannot be performed. The substance may not be obtained, or the physical properties may be significantly changed (in some cases, markedly reduced).

Depending on the intended use of the composition, coloring agents, solid lubricants such as graphite and molybdenum disulfide, and other organic and inorganic fillers may also be blended.

Hereinafter, a composition in which 0.5% by weight of polyimide resin (trade name Imidalloy) was blended with ultra-high molecular weight polyethylene (trade name HIZEX MILLION 240M) was molded into a round bar with a diameter of 60 mm using an ordinary single-screw extrusion molding machine. The conditions for molding and the physical properties of the obtained molded product are illustrated below. {1) Molding conditions ■ Heating cylinder and die temperature Rear temperature 10,000 Intermediate temperature 150oo Front temperature 16,000 Die temperature 19,000 Die temperature 20,000 ■ Screw and rotation speed constant pitch, semi-compression type, 8 to 30 revolutions per minute ■ Compression ratio 3 :1 ■ Heating cylinder length to heating cylinder diameter 20:1 (
2) Physical Properties However, the test conditions for the specific wear amount and the limit PV value are shown for the results of using carbon steel for mechanical structure as the mating material, applying a thin layer of Richiyu soap-based grease, and performing the test at a sliding speed of 20 m/side.

As can be understood from the table, there is a difference in physical properties between the product of the present invention obtained by extrusion molding of ultra-high molecular weight polyethylene and polyimide resin and the comparative product obtained by conventional compression molding of only ultra-high molecular weight polyethylene. No significant differences were observed.

Claims (1)

[Claims] 1 Ultra-high molecular weight polyethylene with an average molecular weight of 1 million or more determined by the viscosity method and thermosetting polyimide resin 0.4 to 10
% by weight of an ultra-high molecular weight polyethylene composition.