JPS60113385A - Friction liner for holding magnetic tape - Google Patents

Abstract

PURPOSE:To obtain a friction liner for holding a magnetic tape with almost the same sliding characteristics as that of ultra-high mol.wt. polyethlene by adding graphite powder, etc., to prescribed ethylene unsaturated silane compound copolymer and by executing cross-linking under the presence of water after forming a film. CONSTITUTION:An ethylene-unsaturated silane compound copolymer obtained by graft-polymerizing polyethlene having 0.1-1.0 million molecular weight with a silane radical is polyethlene of high or low density organic silane modified, and an activated silane radical of the entire polyethlene is normally below 10%. The activated silane is cross-linked under the presence of water, and a gel fraction after cross-linking is made 40-80%. After adding carbon black or graphite powder to the polymerized polyethlene, a film is formed. When the film is passed in a steam chamber, for instance, of 100-130 deg.C, the activated silane forms a network structure between moleculars. By using the polyethlene obtained in such a way, the tape holding friction liner having excellent uniformity of a surface, excellent antiwear property and excellent antifriction property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic tape holding friction device which has excellent anti-static properties, friction and wear resistance, flatness, etc., and which has a simple manufacturing process and low production cost. It concerns the liner.

In general, the film that holds the magnetic tape contained in compact cassettes, micro cassettes, video cassettes, etc. is made of materials such as tetrafluoroethylene resin, ultra-high molecular weight polyethylene, paper, and polyester resin. However, among these, ultra-high molecular weight polyethylene can be said to be the most excellent in terms of the balance between cost and sliding properties. Ultra-high molecular weight polyethylene has a high melt viscosity, making it difficult to apply ordinary extrusion molding methods, so it has been mainly molded by compression molding methods. When manufacturing thin plate products such as sheets (including films), the compression molded product is placed on a lathe and skived using a knife. resistance; therefore, flatness is lost by one point. As a result, post-processing to correct the 7-rant properties of the sheet is essential. Furthermore, when making skives, the blades are chipped due to the use of sharp-edged tools, which creates large unevenness on the sheet surface and causes trouble for each use of the product. had to be sorted out and the product yield was very poor. Furthermore, since raw polyethylene is generally granular and large, there are many restrictions on the type and amount of filler, making it difficult to formulate a composition that can meet various needs.

This invention was made in view of the current situation, and includes carbon black or graphite powder as an essential component of the ethylene-unsaturated silane compound copolymer, which is obtained by graft polymerizing silane groups to polyethylene with a molecular weight of 100,000 to 1,000,000. Alternatively, by adding a mixed powder of these, forming it into a film in a molten state, and then water-crosslinking it,
The present invention provides a friction liner for holding a magnetic tape, which has a gel fraction of 0 to 80% and has sliding properties close to those of ultra-high molecular weight polyethylene.

In this invention, the ethylene-unsaturated silane compound copolymer obtained by graft polymerizing a silane group to polyethylene with a molecular weight of 100,000 to 1 million is, for example, If) i Linkron or 141ALH8f manufactured by Mitsubishi Yuka Co., Ltd., Linkron-X. In organic silane-modified high-density (HD) or low-density (LD) polyethylene (PE), the active silane groups (-S i -0-R, where k is an alkyl group) in the entire polyethylene are usually 10%. These are as follows. These active silane groups crosslink in the presence of water,
Compared to conventional chemical crosslinking methods, radiation crosslinking methods, etc., it does not require special equipment or have any design constraints; instead, polyethylene is pre-formed into any shape using normal molding methods. It crosslinks very easily just by contacting with moisture, greatly improving its thermal, chemical and mechanical properties. Note that a masterbatch containing a catalyst (for example, containing about 1% dibutyltin dilaurate) for smoothly promoting the crosslinking reaction with water may be added as appropriate. In this invention, the reason why the gel fraction after water crosslinking is set to 40 to 80% is as shown in the figure.
This is because polyethylene with a content of less than 80% or more than 80% cannot provide wear resistance close to that of ultra-high molecular weight polyethylene.
This is because particularly excellent wear resistance can be obtained at a gel fraction of around 65%. Here, the wear coefficient in the figure is calculated using polyester (PUT) as the mating material and an NTN thrust-thrust type wear tester, P V = Q, 53 x 34 = 21 ((k
g/cm2)-(m/m1n)).

In this invention, carbon black or graphite powder alone or in a mixture is added to polyethylene graft-polymerized with silane groups, and the particle size range of carbon black is 0.01 to 0.5 μm, and the amount added is 3 to 16% by weight is desirable, and for graphite powder, the particle size range is 1 to 100 μm, and the amount added is 5 to 100 μm.
It is preferable to set it as 30% of market weight. The reason for setting this range is that if the particle size is smaller than the lower limit, the surface area of the added filler will become too large and the film strength will be weakened, whereas if the particle size is larger than the upper limit, the film will become weak. This is because the surface roughness of the carbon increases.Furthermore, if the amount added is less than the lower limit, it will generate static electricity and cause cracks during punching, and if the amount exceeds the upper limit, the carbon will damage the magnetic tape and the galafite will This is because it tends to fall off, which is undesirable. Oh, these carbon blacks,
Even if graphite or the like is added in the form of a masterbatch to prevent scattering, it will not cause any trouble in the present invention. In addition, a small amount of solid lubricant such as lutamene, fluororesin, molybdenum disulfide, etc. may be added to improve the sliding properties.

After the addition of carbon black or graphite powder alone or as a mixture to the polyethylene graft-polymerized with silane groups as described above, it is molded using a commonly used molding method such as the T-die method or inflation, for example. , 07-0, 12. Form a film with a thickness of about mm. Then, the obtained film is wound into a roll and immersed in hot water at a temperature of about 60 to 80°C for about a day and night, or when it is continuously passed through a steam chamber at a temperature of about 100 to 130°C. The active silane groups form a network structure by forming 18i-0-8i- bridges between molecules, so that it can be converted into a film with excellent mechanical properties as well as molecular weight. Therefore, it is possible to form a thin film of polyethylene with sliding properties similar to those of ultra-high molecular weight polyethylene, which has been difficult in the past, by forming a film of polyethylene with an appropriate amount of active silane groups as described above, and then subjecting it to a crosslinking reaction with water. This can be achieved extremely easily. As described above, when a film is extruded in a state where the molecular weight is relatively low before the molecular weight is increased by water crosslinking, the surface of the film becomes extremely homogeneous. Therefore, the friction liner for holding a magnetic tape of the present invention is a sheet that has excellent surface homogeneity, as well as abrasion resistance and abrasion resistance comparable to that of ultra-high molecular weight polyethylene.

Compared to the conventional method 1, the friction liner for holding magnetic tapes of the present invention as described above has improved productivity in that direct film forming is performed, the number of processes is significantly reduced, and there is no E line defect in terms of product yield. Therefore, the cost increases significantly, and as a result, the manufacturing cost becomes extremely cheap. In addition, in order to maintain running stability of the magnetic tape and prevent uneven winding, the holding friction liner is required to have a certain level of curling and flatness, but by forming a pattern during water cross-linking, it is possible to achieve any stable curling. It is possible to obtain smooth and flat products, and rough embossing can be done at the same time.
Post-processes can be simplified.

Moreover, since the 7-reaction liner of this invention has a crosslinked structure, it has good thermal stability at high temperatures like a thermosetting resin, and when it is made of ordinary ultra-high molecular weight polyethylene, it has a 100° After leaving it for 1 hour, 1
00mm, a dimensional change of 1 mm or more occurs over time, but the friction liner of this invention changes by 0.3 mm or more.
mm[, and there is almost no change in curling or flatness.Furthermore, because the melt viscosity of the raw material resin is low, it melts evenly during molding, making it easier to bond between the base resin particles. The significance of this invention is that it was possible to increase the allowable range of the amount of graphite, etc., to about 40% by weight, and that it enabled a wide range of modification and improvement to meet demand. It can be said that it is extremely large.

Examples are shown below. Note that all molecular weights are based on viscosity measurements.

[Example 1] 5 parts by weight of a crosslinking accelerator masterbatch (containing dibutyltin dilaurate) was added to 100 parts of an organic silane-modified polymer (Mitsubishi Yuka Co., Ltd. Nilinclon By adding % market weight and 17% by weight of graphite, L/D22, CR3,
3. Has a full-flight screw with a rotation speed of 3 Orpm or more, cylinder diameter 50 mm, and T-die width 300 m.
m extruder, resin temperature 200℃, extrusion amount approximately 20
A film with a thickness of 0.1 mm was molded under the condition of kg/h. - This film was immersed in a water tank at about 70°C for one day and night, resulting in a gel fraction of 65%.

The friction coefficient, abrasion coefficient, and electrical properties of the obtained product film are summarized in Table 1 in comparison with other resins. In addition,
The friction coefficient is the value when the load is 11 g, the sliding speed is 3 m/min, and the mating material is polyester (PET), and the wear coefficient is the value according to Table 1 of rough wear (taper wear test and sand ablation test). Also, the dimensional stability is 1 at 100'C.
It is shown as a change over time in the dimensions per 100 mm after being left for a period of time. Furthermore, the gel fraction was determined using a Soxhlet extractor.
It is expressed as a percentage of the weight 1w of the resin insoluble matter when extracted under the boiling point of xylene to the total weight WO of the resin before extraction.

[Examples 2 to 4] Various physical properties were measured for product films obtained in the same manner as in Example 1, except that the type or composition of the filler and the gel fraction after water crosslinking were changed to 55% and 70%. The results are also listed in Table 1.

If the above results are taken together, the superiority of the magnetic tape holding friction liner of the present invention is clear.

[Brief explanation of the drawing]

The figure is a diagram showing the relationship between the type of resin and the wear coefficient. A, Is, C, D, , gel fraction is 30, 5, respectively.
Organosilane-modified polyethylene after water crosslinking with a concentration of 0°65.80%, E...Ultra high molecular weight polyethylene, F...
HDPE,,G,...LI)PE0

Claims (1)

[Claims] This is an ethylene-unsaturated silane compound co-merchandised product obtained by graft polymerizing silane groups to polyethylene with a molecular weight of 100,000 to 1,000,000. Carbon black or graphite powder or a mixed powder thereof is added as an essential component, and this is mixed in a molten state. A friction liner for holding a magnetic tape, characterized in that a film is molded and then cross-linked with water to have a gel fraction of 40 to 80%, giving it sliding properties close to those of ultra-high molecular weight polyethylene.