JPS58157830A - Preparation of sliding sheet - Google Patents

Abstract

PURPOSE:To obtain a sliding sheet having improved wear resistance, by heat- treating a sheet obtained by molding powder of an ultrahigh molecular weight polyethylene in such a way that its dimension is not changed, crosslinking it to provide a specific gel fraction. CONSTITUTION:Powder of an ultra-high-molecular-weight polyethylene (>= 1,000,000 molecular weight by viscosity method) is fed to a mold, compression molded previously at normal temperature at about 150-300kg/cm<2>, the pressure is lowered to about 50-100kg/cm<2>, the temperature is raised to >= the melting point so that it is melted and molded. The pressure is then raised to about 150- 300kg/cm<2>, the polyethylene is annealed to room temperature in this state to give a block, which is processed into a sheet with about 0.05-0.5mm. thickness by a lathe, etc., the sheet is heat-treated usually at 90 deg.C- the melting point (preferably 110-125 deg.C) in such a way that its dimension is not changed by fixing it into a frame, etc., and crosslinked by ionizing radiation, etc. to provide 60-90% (preferably 70-80%) gel fraction, so that a sliding sheet is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sliding sheet! No. 14, the sliding sheet, is arranged on the surface of the member that performs relative movement, and is used to reduce the reinforcement force generated between the members when they move.

Conventionally, ultra-high molecular weight polyethylene (hereinafter referred to as UHPE) was formed into a block shape under pressure as a sliding sheet.
Sheets made by cutting this to a predetermined thickness are known.

This UHPE sliding sheet not only has a low coefficient of friction, but also has good abrasion resistance and has the advantage of being thick.
There is a steel wire that tends to deform into a curved shape when exposed to high temperatures.

For example, between the inner wall of the case and the magnetic tape wound on the reel [UHPE sliding sheet? When the resulting audio cassette is used in a car stereo in the summer, the sliding sheet is exposed to high temperatures and gradually deforms into a curved shape.''7 This causes excessive pressure on the magnetic tape, making tape running unstable. Please note that this may adversely affect the sound quality.

As a result of various studies aimed at solving the above-mentioned problems of the prior art, the present inventors formed UHPE powder into a block shape under pressure, cut it to a predetermined thickness to form a sheet, and then The sheet is subjected to Pk treatment so that its dimensions do not change, and then this sheet is cross-linked and the gel fraction is set within a predetermined range, so that even when exposed to high temperatures, it will not deform into a curved shape and will not be easily ploughed. The present inventors have discovered that a sliding sheet with a low coefficient of friction and excellent wear resistance can be obtained without any friction, and has thus completed the present invention.

That is, the method for manufacturing a sliding sheet according to the present invention involves cutting a block-like object obtained by molding UHPE powder under pressure to form a sheet, and then cutting the sheet into a sheet so that its dimensions do not change. Heat treatment 17, then gel fraction 60-90
It is characterized by cross-linking in a manner that results in vomiting.

In accordance with the present invention, the UHPE powder is first formed into a block shape [1i] under pressurized conditions. Due to the characteristics of UHPH, this molding is performed by filling a mold with UHPE powder and applying a pressure of 15°C at room temperature.
After compression preforming under the conditions of 0~30G#/d, the pressure is lowered to about 50~100#/d and the temperature is 'tUHP.
The UHPE powder is melted and fired at a temperature higher than the melting point of E.
Next, the pressure can be increased to about 150 to 30 G#/df, and this pressurized state is maintained and the temperature is slowly cooled to room temperature.
0,000,000 or more, which is thicker than that of general polyethylene, which is about 2,800,000, and products such as Jlplg, Hi-Zex Million (manufactured by Mitsui Petrochemicals), and Hostalene GUR (manufactured by Hoechst). It is marketed under the name

In addition, in order to impart conductivity to the sliding sheet and prevent it from being charged due to sliding with a mating member during use, UHPE is used.
It can be molded by adding about 20% by weight of tetraelectric powder such as carbon, graphite, metal powder, etc. to the powder.

The block-shaped product thus obtained is then cut using a lathe or the like to form a sheet having a thickness of about 0.05 to 0.5 parts. This sheet is made up of residual l-
Since the surface has minute irregularities due to machining, heat treatment is performed in the present invention to remove residual stress and smooth the surface.

In the heat treatment in the present invention, the sheet is fixed in a frame and heated.
This is done in such a way that the dimensions of the sheet do not change, such as by heating the sheet and passing it along a roll or drum with smooth surfaces. The heat treatment temperature is determined depending on the pressure applied during molding into a block-like product and the heat treatment time, but is usually 90°C to UHPH melting point, preferably 110°C.
~125C.

The nine UHPE sheets heat treated as described above are then crosslinked to a gel fraction of 60-90%, preferably 70-80 ml. Crosslinking of the sheet can be carried out, for example, by irradiation with ionizing radiation such as electron beams and gamma rays. By this radiation irradiation method, the number of irradiation elements required to set the UHPE sheet to the above-mentioned predetermined gel fraction is determined according to the molecular weight of the UHPE, the sheet thickness, and the irradiation conditions. Usually, it is about 10 to 100 megarads.

In the present invention, if the gel fraction of the UHPE sheet after crosslinking is 60 parts or less, a sliding sheet with excellent shape stability during high temperature use cannot be obtained, and if the gel fraction is 9 parts or more, If this happens, the sheet becomes brittle [2], which not only reduces the mechanical strength but also increases the friction coefficient, which is not preferable.

The present invention is configured as described above, and involves cutting a block-like product obtained by molding UHPE powder under pressure conditions into a sheet shape, and sequentially subjecting the solid sheet to I-heat treatment and crosslinking. As a result, a sliding sheet with excellent tortoise shape stability can be obtained when used at high temperatures.

Hereinafter, the present invention will be further explained with reference to Examples. Note that parts in the examples are parts by weight.

Example UHPE powder (manufactured by Mitsui Petrochemicals Co., Ltd., trade name Hi-Zex Million 240M) 9711 was uniformly mixed with 3 parts of carbon powder, filled in gold rM, and heated at 200°C at a temperature of 25°C.
The UHPR powder was melted and fired by applying a pressure of 14 kg/14 minutes for tlo minutes (after compression preforming, the pressure was lowered by 50 #/cd weight, the temperature was raised to 210'c3, and this state was maintained for 120 minutes) to melt and sinter the UHPR powder. , then increase the pressure to 2
00 kg/dK, cooled to room temperature for 120 minutes while maintaining this pressure, and removed from the mold to obtain a cylindrical molded product with an outer diameter of 80 m and an inner diameter of 4 osww.

Thereafter, this stomach-shaped molded product was cut to obtain a sheet with a thickness of 100μ, and the four sides of this sheet were then fixed with a steel frame.
The embedding was carried out at a temperature of 120° C. for 3 minutes while making sure that the dimensions did not change.

Next, using an electron beam accelerator, this sheet was irradiated with an electron beam of 18 megafahrenheit in air. Te1J@Hashi Seshime,
A sliding sheet (sample number 1) with a glue fraction of 66 was obtained.

The gel fraction of the sliding sheet is determined by immersing the sheet in xylene at 130°C for 24 hours to dissolve the uncrosslinked portion, and then removing the crosslinked insoluble portion with a 50-mesh filter.
The value was calculated using the formula below. 6 Separately, using the above heat-treated sheet,
Sample number l, s4, except for the electron beam irradiation dose t-24 megarads and 45 megarads 2! ), two sliding sheets (sample numbers 2 and 3) with gel fractions of 73 and 80 g were obtained.

The friction coefficient, curl height and tensile strength of these sliding sheets were measured by the following test methods and the results are shown in Table 1. Note that the curl height data after heating in Table 1111 shows the data after heating the sliding sheet at a temperature of tlOθ°C for 48 hours and leaving it in a room at 11.25°C for 1 hour.

Coefficient of friction: Using a Pakuden-Leben type friction tester (manufactured by Toyo Bold Twin Co., Ltd., model EFM-4), using polyester film as the mating material, f11ml, speed 175 m/m, load 200
f. Measured at a temperature of 25°C.

(To) Curl height Place the sliding sheet on a surface plate and measure the maximum height of the curved part using a hide gauge.

(0 tensile strength JIS-6888 [maximum tensile strength was measured according to the method).

For comparison, the heat-treated sheet used to obtain the sliding sheet (sample number 4) was the same as that of sample number 1, except that the heat-treated sheet was subjected to an electron beam of t-5 megarads and 150 megarads. Work in the same way, and the gel fraction is 52
Sliding sheets obtained by crosslinking to 95 ml and 95 ml (
Data for sample numbers 5 and 6) are shown simultaneously.

Table 1 The product of the present invention obtained by successively heat-treating and crosslinking a sheet cut from a block-like material not only shows little change in the curvature state when exposed to high temperatures, but also has a small coefficient of friction and high tensile strength. It is proven to be very practical! 16

Claims (1)

[Claims] The block-like material obtained by molding ultra-high molecular weight glass powder under pressure is cut into a sheet, and then the sheet is heat-treated so that its dimensions do not change. A method for producing a sliding sheet characterized by crosslinking so that the fraction is 60 to 9.