JPS6028088A - Slip sheet for cassette tape and its production - Google Patents

Abstract

PURPOSE:To obtain a sheet which has improved wear resistance, heat resistance, etc. by extruding a material molded by mixing carbon black and specific fluoropolymer with a polyolefin resin respectively at a specific ratio then subjecting the same to thermal embossing to form many projecting parts having arc-shaped tips. CONSTITUTION:A molding material prepd. by mixing 2-50wt% a PE resin such as PE, ethylene/vinyl acetate copolymer or the like, more particularly high-density PE and a polymer of CF2=CF2 and a copolymer of CF2=CF2 and CF3CF= CF2 respectively alone or a mixture composed thereof and 2-30wt% carbon black is extruded to form a sheet. Many projecting parts 2 having arc-shaped tips are formed by heat embossing and thereafter the sheet is cut to a required shape. A slip sheet 5 for a cassette tape having good workability and adequate rigidity and impact resistance is thus obtd. of a relatively inexpensive material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a grooved sheet for a cassette tape and a method for manufacturing the same.

Generally speaking, cassette tapes are designed to reduce frictional resistance between the case and reel tape, and to make the tape run smoothly.
Furthermore, a sliding sheet is provided that acts as a cushion between the case and the reel tape. Previously, the name sheet company
They were made from sheet materials such as conductive carbon-containing ultra-high molecular weight polyethylene sheets, conductive carbon-containing tetrafluoroethylene polymer sheets, and carbon-containing special paper sheets impregnated with silicone. There was a drawback.

In other words, since the conductive carbon-containing tetrafluoroethylene polymer sheet is flexible, the sheet edges may bend, fold, or tear when handled, and the sheet may curl into a cigar shape when heated, resulting in poor heat resistance. However, since it lacks shape stability and has a high melting point of 320'C or higher and lacks fluidity at high temperatures, it must be processed using special machines and methods compared to the commonly used film forming method. Therefore, it has the disadvantage of high processing cost in addition to raw material cost. In addition, conductive carbon-containing ultra-high molecular weight polyethylene is
7-fluorochemically modified tyrene polymers have been improved, especially the four-electrode force.
It was commercially available as a material that improves the flexibility and raw material cost of bonded tetrafluoroethylene polymer sheets, but it is not perfect due to poor heat resistance, and like tetrafluoroethylene polymers, it lacks fluidity at high temperatures. Therefore, a special processing method must be used.

That is, ultra-high molecular weight polyethylene powder and carbon powder must be molded under heat and pressure into a block shape and then cut into a film of desired thickness, resulting in low production efficiency and high processing costs.

In addition, since the rigidity is extremely high, the shear strength is extremely large, and there are disadvantages such as abrasion of the punching blade when punching into a predetermined shape and formation of cracks in the punched product. In addition, special paper sheets containing carbon impregnated with silicon have the advantage of low cost, but have poor performance, especially when they have protrusions for surface smoothness, abrasion resistance, or lubricity effects. The disadvantage is that it is inferior.

Furthermore, conventional lubricant sheets made of tetrafluoroethylene polymer sheets, ultra-high polymer l/polyethylene sheets, etc., require embossing as shown in Fig.
There is one with 8. In the figure, numeral 19 indicates a conventional sliding sheet for cassette tapes. However, as mentioned above, these require a special processing method during film formation, so it is possible to perform in-line embossing continuously after film formation. There was a drawback that production efficiency was low and processing costs were high even at the embossing stage.

Further, since the surface of the embossing is a flat convex portion 18, the contact with the tape is a surface contact, and therefore, the contact area with the tape is large, and there is a drawback that the frictional resistance cannot be sufficiently reduced.

The present invention overcomes all the drawbacks of the above-mentioned prior art.
An object of the present invention is to provide a smooth cassette tape sheet having excellent lubricity, surface abrasion resistance, heat resistance, and rigidity, and free from scratches, walnuts, curls, etc., and a method for producing the same.

That is, one of the aspects of the present invention is to add 2 to 30% by weight of carbon black to a polyolefin resin, a tetrafluoroethylene polymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene compound, ! = Mixture of 4-fluoroethylene-6-fluoropropylene copolymer 2 to 5
In the ib sheet for cassette tape, which is made of a sheet formed by molding a molding material mixed with 0 weight The gist of the present invention is a cassette tape smooth sheet characterized by providing a convex portion.

The present invention includes a polyolefin resin containing 2 to 30% by weight of carbon black, a tetrafluoroethylene polymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a tetrafluoroethylene polymer and a tetrafluoroethylene polymer. ethylene-6
A resin composition consisting of 2 to 50% by weight of a mixture of fluorinated propylene copolymer is extruded from an extruder, and a sheet for producing a lubricant sheet for cassette tape is applied thereto, followed by heat embossing to form a large number of group 1 arc-shaped tips. The gist of the present invention is a method for manufacturing a cassette tape smooth sheet, which is characterized in that the convex portions are yx, -H and cut into a desired shape.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

2 and 3 show a sliding sheet 1 for a cassette tape according to an embodiment of the present invention, and 2 is a convex portion.

The polyolefin resin is polyethylene for extrusion molding and has a melt index of 0.01 to 1o, op/
It is preferably about 0.05 to 5.0 minutes. +1/10 minutes,
Density is 0.9401! /c++! The above high-density polyethylene is preferred.This material has appropriate stiffness and impact resistance, and has excellent processability compared to conventional ultra-high molecular weight polyethylene and tetrafluoroethylene polymer, and is used as a general-purpose polyethylene film. The film can be formed using a T-die extruder or an inflation extruder that is used when forming a film. In addition, polyethylene-vinyl acetate copolymer, polyethylene-ethyl acrylate copolymer, polypropylene, polyethylene and various additives such as antioxidants, lubricants, anti-prolag agents, antistatic agents, etc. can be used instead of polyethylene as polyolefin resins. Extrusion moldable resins such as resins containing fillers, ionomer resins, polyamide resins, and polyester resins can also be used.

The carbon black to be mixed with the polyolefin resin is conductive carbon black powder, which has a particle size of 10 to 60 nm and an oil absorption of 100 to 400 cc.
/1001, produced by the thermal decomposition method of acetylene or the incomplete combustion method of heavy oil and sold commercially under the names of Ketjen black, acetylene black, furnace black, etc., and tetrafluoroethylene polymerization material (hereinafter referred to as PTF)
(referred to as E) is 10μ or less.

In the present invention, the composition ratio of carbon black and PTFE is preferably 2 to 3% by weight in the carton, and the surface resistance value when formed into a sheet is preferably in the range of 102 to 1012 Ω, and is 2% or less. If so, it must be 101Ω or more.
The anti-static performance is poor, and if it exceeds 30%, the fluidity of polyethylene at high temperatures decreases, making film formation difficult. Also PT
The amount of FE and/or 6-fluorinated propylene (hereinafter referred to as FEP) is preferably 2 to 50 M, and when formed into a sheet, the coefficient of friction is preferably 0.15 or less.

As an example of the method of inserting the sheet 1 of the present invention, for example, polyethylene, carbon black, or PT having a predetermined composition may be used.
FE and/or FEP are mixed, melt-kneaded using a Banbury mixer, three-roll mixer, etc., pelletized using a pelletizer, and then formed into a film using a T-die extruder or inflation extruder.

After forming the sheet, the sheet is heated, embossed, and cut into a desired shape to obtain a cassette tape 9 sheet 1. FIG. 4 shows a schematic diagram of an apparatus for embossing sheets extruded from a T-die extruder. In the figure, 3 is an extruder, 4 is a T-die, 5 is a sheet, 6 and 7 are cooling rolls, 8 is a tension roll, and 9 is a heat treatment/boss roll. The sheet 5 extruded from the T-die 1 is cooled to a required temperature by a cooling roll 6, and passed between hot embossing rolls 9 via a tension roll 8. After the embossing □ is applied here, it is further cooled by a cooling roll 7.

In this case, since the film forming process and the embossing process are performed in-line, the embossing process can be performed using residual heat of the sheet extruded from the T-die number. Heating methods include induction heating rolls, heater casting rolls,
Examples include blowing hot air from a hair dryer and flames.

The heating temperature of the sheet is 30 to 150°C when polyethylene, polyethylene-vinyl acetate copolymer, polyethylene-ethyl acrylate copolymer, polypropylene, or ionomer is used as the polyolefin resin, and 30 to 200°C for polyamide and polyester. If the temperature is below the above lower limit temperature, the embossing tends to disappear and the wrinkles, sagging, and curls of the sheet cannot be sufficiently removed. Moreover, if the temperature is above the above upper limit, the sheet melts and wrinkles, walnuts, and curls are likely to occur, which is not suitable.

As the embossing method, it is preferable to use an embossing roll, and an embossing roll 9 is shown in FIGS. 5 to 8. FIG. 5 shows a combination of an embossing roll 9 having a large number of convex portions lO having an arcuate tip and a flat roll 11 whose roll surface is made of metal, paper, rubber, etc., and FIG. and an embossing roll 13 having a large number of arcuate concave portions 12 corresponding to the convex portions 10 of the roll. FIGS. , a flat plate 11 made of a surface of metal, paper, rubber, etc., or a flat plate 15 having a concave portion 12 corresponding to the convex portion 10, respectively. Embossing is performed by passing a heated sheet between rolls, rolls, and flat plates as described above. At this time, the printing pressure between rolls or between rolls and flat plate is 0.5~
20 Ky/crl, preferably 2 Ky/cr1
~10 Ky/crl is good. If it is less than 0.5 y/cr&, the embossing will not be used sufficiently, and if it is more than 20 Ky/cri, there is no difference in the effect from less than that, and accidents such as sheet destruction and roll wear will be severe, which is not preferable.

FIG. 9 is a schematic side view of an apparatus for film forming and embossing processes using an inflation extruder, in which 16 indicates an inflation die and 17 indicates a nip roll. The hot embossing process can be performed in-line with film formation using a KT die extruder, an inflation extruder, etc. as shown in FIGS. 4 and 9, but it may be performed in a separate process if necessary.

The sliding sheet for cassette tapes and the method for manufacturing the same according to the present invention described above have the following effects.

Compared to conventional tetrafluoroethylene polymer and ultra-high molecular weight polyethylene sheets, processability and productivity are improved and costs can be reduced. In other words, the processing method for tetrafluoroethylene polymers, etc. is to heat and pressure mold (compression mold) the powder into a block, plate, or round bar, and then cut it into a sheet. It is either made into a sheet by mixing an auxiliary agent with the raw material, making it into a paste, extrusion molding, rolling processing, and extraction of the auxiliary agent, and then it is made into a sheet by extrusion molding, rolling, and extraction of the auxiliary agent.Moreover, since it cannot be embossed in-line continuously with sheet forming, it is embossed in the other two in-lines. However, with the present invention, mass production is possible using a normal method that is exactly the same as the method used to form a film for general-purpose resins, and it can be done in-line with the film formation, and even at the time of film formation. Embossing can be done using the residual heat of the embossing, making it highly efficient and economical. Furthermore, in the conventional case, expensive tetrafluoroethylene polymers and ultra-high molecular weight polyethylene had to be used as raw materials, but according to the present invention, raw material costs can be reduced because inexpensive polyethylene is used as the main component. In addition, the embossed slide sheet of the present invention has a large number of convex portions with arcuate tips on its surface so that the contact with the cassette tape is a point contact, unlike the conventional slide sheet shown in FIG. Compared to sliding notebooks that have convexities due to surface contact embossing, the contact area with the tape is significantly reduced, and therefore the frictional resistance is significantly smaller, and the lubricity and surface abrasion resistance are improved accordingly.
Moreover, it has excellent elasticity, heat resistance, and rigidity, and is made of walnut.
It has a uniform effect without curling.

Next, specific examples will be described in more detail.

Example 1 High-density polyethylene Shorex N5008 (melt index 0.9, manufactured by Showa Denko), 15% conductive carbon black (Denka Black, manufactured by Denki Kagaku ■) and PT
After 5g6 of FE resin (Phos I 70 TFLP 9202, manufactured by Hex) was melted and mixed into pellets, a film was formed using a T-die extruder. After that, the sheet was heated to 110℃ using a paper embossing roll as shown in Figure 5.
The sheet was die-embossed with a printing pressure of /era and punched into a predetermined shape to obtain a slip sheet. After loading the sheet into a tape cassette and playing and rewinding the tape 400 times, the wow and flutter of the tape was examined and found to be 0.
041, which was a huge difference from before the tape run. - When similar measurements were made on a sheet made of ultra-high molecular weight polyethylene having a flat convex portion on the blade surface, it was found that wow and flutter increased by 0.05→o, o s % before and after running. In addition, when each of the sheets made as a prototype sheet made of FTFB, FTFW, and ultra-high molecular weight polyethylene was left open at 100°C for 1 hour, there was almost no change in the prototype sheet, but the sheets made of FTFB and ultra-high molecular weight polyethylene were left open for 1 hour. The sheet curled into a cigar shape, and the embossment #1 of the sheet made of ultra-high molecular weight polyethylene almost disappeared.

Example 2 10% conductive carbon black (Kette Embratori EC, manufactured by Lion Akzo) and a tetrafluoroethylene-hexafluoropropylene copolymer (Neoflon NP-) were added to high-density polyethylene (Hisexfu 0O0F≠I Petrochemical Co., Ltd.). 2
0. After mixing 10% (manufactured by Daikin), a T-die film is formed as shown in Figure 4, and immediately the residual heat from film formation is used to apply a printing pressure of about 10mm to an induction heating roll for embossing. On the sheet surface, surface protrusions generated during film formation were no longer noticeable, and scratches, scratches, wrinkles, walnuts, curls, etc. could be removed.

Then, the sheet is punched into a predetermined shape, and the resulting sheet is played back 500 times in a 46-minute cassette tape. After performing a rewinding test, the winding torque value of the tape is 5 to 711.
- α showed the same value as before running the tape. On the other hand, when similar measurements were performed on a sheet made of ultra-high molecular weight polyethylene, it was found that the resistance increased from 6 to 10 F-cm.

In addition, the prototype sheet was tested using PTF in the same heat resistance test as in Example 1.
E. It was found that it was significantly superior to each sheet made of ultra-high molecular weight polyethylene.

Example 3 20% conductive carbon (Condatex 975, manufactured by Columbia Carbon) and FTFB powder (Lupp) were added to polypropylene (Noprene FL-200, manufactured by Mitsui Toatsu Chemical Co., Ltd.)
L-2. Daikin (manufactured by Daikin)) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP resin 5) manufactured by Mitsui Fluorochemicals (manufactured by Mitsui Fluorochemicals) (2 parts) were kneaded and mixed, and then an inflation film was formed as shown in Figure 9, approximately 15 Kg/cl. Embossing is performed using an induction heated roll with a printing pressure of . The sliding sheet completed by punching was run with the tape in Example 2,
In the torque test, the winding torque was 7 to 9 I-, which was no different from before the tape was run. Further, in the heat resistance test of Example 1, no abnormalities such as curling or disappearance of embossing were observed.

More wear resistant than t-to made of ultra-high molecular weight polyethylene.
Heat resistance and rigidity were improved, and surface protrusions, scratches, wrinkles, walnuts, and curls that occurred during film formation were removed.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of a main part of a conventional embossed grooved υ sheet for cassette tapes, Fig. 2 is a schematic plan view showing an embodiment of the sliding sheet of the present invention, and Fig. 3 is a diagram of Fig. 2. TII
A vertical cross-sectional view taken along line -III, Figures 4 and 9 are schematic side views showing equipment for film formation and embossing processes, and Figures 5 to 8 are schematic perspective views showing the state in which a sheet is embossed. It is. l... Groove sheet for cassette tape, 2... Convex portion 3
... Extruder patent applicant Dai Nippon Printing Co., Ltd.

Claims (2)

[Claims] (1) Carbon black 2 to polyolefin resin
30% by weight, tetrafluoroethylene polymer or tetrafluoroethylene-hexafluoropropylene copolymer or mixture of tetrafluoroethylene polymer and tetrafluoroethylene-hexafluoropropylene copolymer 2- In a sliding sheet for a cassette tape, which is made of a sheet formed by molding a molding material mixed with 50% by weight, the surface of the sheet is heat-embossed with a large number of arc-shaped tips so that the contact with the cassette tape is point contact. A sliding sheet for cassette tapes, characterized by having a convex portion. (2) Carbon black 2 to polyolefin resin
30% by weight, 2 to 50% by weight of a tetrafluorinated ethylene polymer or a tetrafluorinated ethylene-hexafluorinated propylene copolymer or a mixture of a tetrafluorinated ethylene polymer and a tetrafluorinated ethylene-hexafluorinated propylene copolymer A resin composition consisting of the above is extruded through an extruder, a sheet for producing a grooved sheet for a cassette tape is formed into an eaves section, and then hot embossing is performed to form a large number of convex portions with arcuate tips (6+2) and cut into a desired shape. A method for manufacturing a grooved sheet for cassette tapes, characterized by: