JPS6115814B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing transparent non-static sliding sheets. In order to reduce friction between members that move relative to each other,
A low-friction sliding sheet is used. For example, in a magnetic tape cassette, a sliding sheet is placed between the cassette body and the magnetic tape wound up into a roll inside the body to reduce the friction between the wall of the cassette body and the edge of the tape when the tape runs. By reducing this, tape running is stabilized. Further, in such a sliding sheet, a non-electrostatic treatment is applied to the sheet in order to prevent hiss noise and the like caused by static electricity generated by friction. By the way, recently there has been a demand for transparent magnetic tape cassettes to improve the product image, but there are many cases where magnetic tape cassettes are made transparent by mixing carbon into the sheet or by applying a carbon-containing coating onto the surface of the sheet. All sheets are black and opaque,
The use of such an opaque sliding sheet cannot meet the above requirements. Therefore, sliding sheets have been proposed in which a metal vapor deposited layer is provided on the surface of polyethylene terephthalate film, or a transparent resin is mixed with a surfactant-based antistatic agent, but the former not only has a high coefficient of friction but also has a metal vapor deposited The performance deteriorates quickly due to early wear of the layer, and the latter has problems such as the antistatic agent leaching onto the sheet surface and contaminating the tape, so it is still not suitable for practical use. The present invention provides a sliding sheet that is low-friction and non-static, has excellent transparency, and can maintain its initial performance for a long period of time. 2 or less metal powder or metal compound powder is uniformly mixed and formed into a sheet shape, and then this sheet material is made transparent by rolling it under heating conditions so that the thickness becomes 50% or less. It is characterized by this. In the present invention, first, a synthetic resin and metal powder or metal compound powder are mixed uniformly and formed into a sheet with a thickness of usually 50 to 300 microns. The synthetic resin used in this case is a low-friction thermoplastic resin, such as polytetrafluoroethylene (hereinafter referred to as PTFE), tetrafluoroethylene-
Fluorine-based polymers such as hexafluoropropylene copolymer, perfluoroalkoxy resin, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, HiZex Million (manufactured by Mitsui Petrochemicals)
Alternatively, ultra-high molecular weight polyethylene with a molecular weight of 500,000 or more (measured by viscosity method), which is commercially available under the trade name Hostalen GUR (manufactured by Hoechst), etc.
(referred to as UHPE), polyacetal, or polybutylene terephthalate, but PTFE, UHPE, or polybutylene terephthalate is preferable from the viewpoint of wear resistance and low friction. Incidentally, these low friction synthetic resins are usually used in the form of powder or pellets. On the other hand, the powder mixed with this synthetic resin is tin,
Powders of conductive metals such as copper, zinc, silver, and aluminum, or powders of compounds of these metals (metal oxides, metal chlorides, etc.), and the amount of the mixture depends on the type of metal powder and metal compound powder and their It is determined depending on the particle size and the degree of conductive performance required of the sliding sheet, but it is usually 5 to 15% by weight. For forming a sheet of the mixture of the synthetic resin, metal powder, and metal compound powder (hereinafter both are collectively referred to as metal conductive powder), a method depending on the synthetic resin used can be adopted. For example, when using synthetic resins other than PTFE and UHPE, extrusion molding, which is a molding method for general thermoplastic resins, can be replaced by calendering, etc.
A sheet-like product can be obtained. In addition, when using PTFE or UHPE,
A sheet molding method specific to these resins can be adopted.
For example, a suitable amount of liquid lubricant such as naphtha or liquid paraffin is added to PTFE powder and metal conductive powder, and the mixture is uniformly mixed. After compression preforming of this mixture, extrusion and rolling are sequentially performed. An example of a method is to obtain a sheet-like material, then remove the liquid lubricant by heating or extraction, and then heat the material to a temperature higher than the melting point of PTFE and sinter it. Furthermore, PTFE or UHPE powder and metal conductive powder are uniformly mixed, filled into a mold, compressed and preformed, and then the resin is once melted and fired under pressure to form a block, and then slowly cooled. It is also possible to adopt a method in which the block-like material is removed from the mold and cut to a predetermined thickness to obtain a sheet-like material. The sheet material thus obtained has a small coefficient of friction and is non-static, but its total light transmittance is usually less than 50% when the thickness is about 100 microns, and it is not transparent. It is something. In the present invention, the opaque sheet material is then rolled under heated conditions. When the sheet-like material is a short product, rolling of the sheet-like material is preferably performed by a press machine, and when the sheet-like material is a long product, it is suitable to perform rolling by roll rolling. . The heating temperature during this rolling is mainly determined by the softening temperature of the sheet material and the degree of rolling.
For example, the temperature is preferably 150 to 170°C in the case of a sheet material whose main component is PTFE, and the temperature is 95 to 120°C in the case of a sheet material whose main component is UHPE. Also,
In the case of sheet materials made of resins other than PTFE or UHPE, the temperature is usually 10 to 50°C above the melting point of the resin.
Rolling is performed at a low temperature to make it transparent. As described above, the present invention involves rolling an opaque sheet under heated conditions, and the degree of rolling is such that the thickness of the sheet is 50% or less of the thickness before rolling, preferably 45 to 20%. It must be rolled so that The thickness of the sheet material is 50% of the thickness before rolling.
Insufficient rolling conditions, such as below, are not preferred because the desired transparent sliding sheet cannot be obtained. By this rolling, the synthetic resin itself in the sheet-like material becomes transparent, the sheet surface is smoothed, and the scattering of visible light is suppressed, and furthermore, due to the action of shear stress caused by rolling, the metal conductive powder in the state of secondary particles is Because it becomes a primary particle and loses most of its scattering and absorption ability for visible light (reduction in the intensity), it is a transparent non-woven material with a total light transmittance of more than 60% when the thickness is approximately 100 microns. A chargeable sliding sheet is obtained. In the present invention, if the particle size of the metal conductive powder is 1/2 or more of the shortest wavelength of visible light (approximately 0.4 microns), the sheet-like material will not be made transparent even by rolling, and the desired transparent non-woven material will not be made transparent. This is not preferred because a chargeable sliding sheet cannot be obtained. For the above reasons, the particle size of the metal conductive powder should be 1/2 or less of the wavelength of visible light. However, as the particle size of the metal conductive powder to be added becomes smaller, the coverage rate for visible light decreases and the transparency decreases. It is preferable to set it to 0.1 micron or less, as this further improves the surface area. The sliding sheet obtained by the method of the present invention is
Normally, it can be used alone, but in cases where thick products or stiffness are required, it is used as a multi-layered product laminated on one or both sides of a transparent thermoplastic synthetic resin sheet such as polyethylene, polypropylene, or polycarbonate. You can also do that. Further, in the present invention, the sheet-like material is laminated on one or both sides of a transparent thermoplastic synthetic resin sheet by fusion, etc., and then this laminated sheet is rolled, and the thickness of the sheet-like material is adjusted to the thickness before rolling. Even if the method of making the sheet transparent,
Thick products or strong multi-layer sliding sheets can be obtained. Since the transparent synthetic resin sheet does not function as a sliding layer in a sliding sheet, it is made of a synthetic resin with a relatively large coefficient of friction such as polyethylene, polyethylene terephthalate, polycarbonate, polystyrene, polymethyl methacrylate, etc. It's okay. The present invention is configured as described above, and includes mixing,
It has the characteristic that the desired purpose can be achieved by an easy-to-implement method called rolling. In addition, the sliding sheet obtained by the method of the present invention is not only transparent, but also has low friction and is non-static, and has all the characteristics required for a sliding sheet for magnetic tape cassettes, etc. There is. Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that all "parts" in the examples indicate "parts by weight." Example 1 10 parts of UHPE powder (manufactured by Mitsui Petrochemical Co., Ltd., trade name Hi-Zex Million 240M) and tin oxide powder with an average particle size of 0.1 micron (manufactured by Mitsubishi Metals Co., Ltd., trade name
40 parts of ECP T-1) in a Henschel mixer.
After mixing for a minute, fill it into a mold and heat it for 100 minutes at a temperature of 25℃.
After compression preforming by applying a pressure of Kg/ ^cm2 for 10 minutes, the pressure was reduced to 30Kg/ ^cm2 and the temperature was reduced to 210°C.
℃ and kept this condition for 120 minutes to melt the UHPE powder, then the pressure was increased to 100Kg/cm ² .
While maintaining this pressure, cool to room temperature for 120 minutes and remove from the mold.Outer diameter 80 mm, inner diameter 40 mm, length.
A cylindrical molding, which is a fired block of 100 mm, is obtained. Thereafter, this molded product was cut to obtain a long UHPE sheet with a thickness of 250 microns.
A UHPE sheet is rolled between rolling rolls made of metal kept at 110°C to a thickness of 100μ (40μ of the thickness before rolling).
%) in the longitudinal direction to obtain a transparent non-conductive sliding sheet (Sample No. 1). Furthermore, apart from this, the thickness of the above sheet-like material is 60 mm.
Transparent non-static sliding sheet (sample number 2) rolled to a thickness of microns (24% of the thickness before rolling)
I got it. In order to know the characteristics of these sliding sheets, the total light transmittance and parallel light transmittance were measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., model ND-H67) according to the method of ASTM-D-1003. D
The surface resistivity and volume resistivity were measured by the method of -257, and the friction coefficient was measured using a Pauden-Leben type friction tester manufactured by Toyo Sokki Co., Ltd. The results are shown in Table 1. In addition, when measuring the friction coefficient, the temperature
The temperature was set at 25°C and the sliding speed was 10 mm/Sec, and a steel ball with a diameter of 10 mm was used as the sliding material. For comparison, the above sheet-like material (sample number 3),
Except for using a sliding sheet (sample number 4) obtained by rolling the sheet material to a thickness of 150 microns (60% of the thickness before rolling) and tin oxide powder with an average particle size of 0.5 microns. The data for the sliding sheet (sample number 5) obtained by performing the same operations as for sample number 1 are shown at the same time. Example 2 A long UHPE sheet with a thickness of 50 microns is obtained by cutting the cylindrical molded product in Example 1. On the other hand, using high-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name Yucalon EY-40),
A transparent long polyethylene sheet with a thickness of 300 microns is obtained by the T-die extraction method. Next, one UHPE sheet and one polyethylene sheet were laminated by heating and pressing at a temperature of 150° C. and a pressure of 10 kg/cm ² to obtain a laminated sheet with a thickness of 300 microns. Next, this laminated sheet was rolled in a press machine kept at 110℃ (pressure 150Kg/cm ² ), so that the total thickness was 100μm and the thickness of the UHPE sheet was 17μm (34μm of the thickness of the sheet). %) transparent multilayer non-static sliding sheet (Sample No. 6) was obtained. The properties of this sliding sheet are shown in Table 1. Example 3 A UHPE sheet with a thickness of 100 microns was obtained by cutting the cylindrical molded product in Example 1, and one sheet each of this sheet and a transparent polycarbonate sheet with a thickness of 200 microns were heated at a temperature of 180.
℃ and a pressure of 10 kg/cm ² by heating and pressing to obtain a 250 micron thick laminated sheet. Next, this laminated sheet is rolled with metal rolling rolls kept at 150°C to form a transparent multi-layer film in which the UHPE sheet has a thickness of 30 microns (30% of the thickness of the sheet) and the polycarbonate sheet has a thickness of 60 microns. A non-electrostatic sliding sheet (sample number 7) was obtained. The properties of this sliding sheet are shown in Table 1. As a comparative example, the data of a sliding sheet (sample number 8) obtained by rolling the above laminated sheet and using a UHPE sheet and a polycarbonate sheet with thicknesses of 60 microns (60% of the sheet) and 120 microns are also shown. Example 4 100 parts of unfired PTFE powder (manufactured by Mitsui Fluorochemical Co., Ltd., trade name Tyflon 6J), 10 parts of the same tin oxide powder used in Example 1, and 20 parts of liquid lubricant Naphtha No. 1 were uniformly mixed. Pressure 20Kg/
cm ² compression preforming, followed by extrusion and rolling to obtain a long PTFE sheet in a green state. Next, this sheet-like material is immersed in trichlorethylene to remove the liquid lubricant, and then taken out from the trichlorethylene, and then heated to 380° C. to sinter the sheet-like material. Then this sheet material (200 microns thick)
was rolled in the longitudinal direction between metal rolling rolls kept at 170°C to a thickness of 80 microns (40% of the thickness before rolling), and a transparent non-static sliding sheet (sample number 9) was obtained. ) was obtained. Separately, the fired sheet was rolled to a thickness of 50 microns (25% of the thickness before rolling) to obtain a transparent non-static sliding sheet (sample number 10). The properties of these sliding sheets are shown in Table 1. For comparison, the fired PTFE sheet material (sample number 11) and the sheet material with a thickness of 120 microns (thickness before rolling) were used for comparison. At the same time, data for a sliding sheet (sample no. 12) obtained by rolling the sheet to a thickness of 60%) is also shown.

[Table] As is clear from the above examples and comparative examples,
It can be seen that according to the method of the present invention, a sliding sheet with high light transmittance, excellent transparency, non-electrostatic properties, and low friction can be obtained.

Claims (1)

[Claims] 1. A low-friction synthetic resin and a metal powder or metal compound powder whose particle size is 1/2 or less of the wavelength of visible light are uniformly mixed and formed into a sheet, and then this sheet is formed into a sheet. A method for producing a transparent non-electrostatic sliding sheet, which is characterized by making the material transparent by rolling it under heating conditions so that the thickness becomes 50% or less. 2. A method for producing a transparent non-electrostatic sliding sheet according to claim 1, which comprises laminating a sheet-like material on one or both sides of a transparent synthetic resin sheet and rolling it.