JP3132969B2 - Molded products for tape sliding members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded article for a tape sliding member having excellent sliding properties with a tape such as a magnetic tape, and particularly to a guide or post for running a magnetic tape.

[0002]

2. Description of the Related Art
Various fixed guides and posts for guiding tape, such as cassette tapes, audio tapes, and magnetic tapes that run in VTR equipment, are made of metal such as aluminum and stainless steel that have been cut and polished to ensure stable running of the tapes. Have been. However, there is a problem that a metal material requires grinding and polishing, which is complicated and costly. So in recent years,
Attempts have been made to reduce the cost, reduce the weight, simplify the manufacturing process, and the like by converting these into resin, and further integrating the base member (post base or the like) that supports these members into resin. . By the way, as the characteristics required for the tape sliding member, it is necessary to have excellent sliding characteristics such as lubricity and friction / wear characteristics, and also to have conductivity in order to remove static electricity generated by running the tape. Furthermore, dimensional stability, mechanical strength, heat resistance, and the like are also required, and it is often difficult to satisfy all of them. In particular, the guide or post for running the magnetic tape often changes the direction of the running tape to a steep angle, and the contact pressure with the tape is high. Means to improve the sliding characteristics of resin materials include compounding solid lubricants such as fluorocarbon resins, carbon fibers, graphite, graphite fluoride, and molybdenum disulfide, and synthesizing liquid fluorine oil and silicone oil at room temperature. Conventionally, a method of adding a liquid lubricant such as oil or mineral oil has been proposed.However, the liquid lubricant easily oozes to the surface of the molded article and adheres to the tape to cause trouble. However, it is difficult to say that the sliding properties such as damage to members and other physical properties are sufficient, and further improvement is desired. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in a molded product for a tape sliding member and to provide a synthetic resin tape sliding member that can be used as a substitute for metal.

[0003]

Means for Solving the Problems As a result of research to achieve the above object, the present inventor has found that a molded article comprising a composition obtained by blending a specific amount of carbon fiber and a specific amount of talc with a specific thermoplastic resin, In addition, they have found that it is particularly effective to have a specific surface roughness, and have completed the present invention.
That is, the present invention provides 10 to 40 % by weight (based on the composition) of carbon fiber and
A polyarylene sulfide resin or a liquid crystalline polyester resin composition containing 5 to 30% by weight of talc (based on the composition) , having a surface resistance of 10 ⁷ Ω or less and a center line average roughness (Ra) of A molded product for a tape sliding member, characterized in that the thickness is 0.5 to 10.0 μm.

The base resin component constituting the molded article for a tape sliding member of the present invention is preferably a polyarylene sulfide resin or a liquid crystalline polyester resin from the viewpoint of slidability, dimensional stability, mechanical strength, heat resistance and the like. preferable. Here, the polyarylene sulfide (PAS) resin is a resin mainly composed of a repeating unit-(Ar-S-)-(where Ar is an arylene group) as a molecular structure. Examples of the arylene group (—Ar—) include, for example, p-phenylene group, m-phenylene group, o-phenylene group, and substituted phenylene group (provided that the substituent is an alkyl group, preferably a C _{1 to} C ₅ alkyl group, or Phenyl group), p, p'-diphenylene sulfone group, p, p'-biphenylene group, p, p'-diphenylene ether group, p, p'-diphenylenecarbonyl group, naphthalene group and the like. In this case, in the arylene sulfide group composed of the above-mentioned arylene group, a polymer using the same repeating unit, that is, a homopolymer can be used, and from the viewpoint of processability of the composition, a heterogeneous repeating unit is used. In some cases are preferred. As the homopolymer, a substantially linear polymer having a p-phenylene sulfide group as a repeating unit in which an arylene group is a p-phenylene group is particularly preferably used. or,
As the copolymer, among the arylene sulfide groups composed of the above-mentioned arylene groups, two or more different combinations can be used, and among them, a combination mainly containing p-phenylene sulfide groups and including m-phenylene sulfide groups is particularly preferable. Used. Among them, a substantially linear one containing at least 60 mol%, more preferably at least 70 mol% of a p-phenylene sulfide group is suitable from the viewpoint of physical properties such as heat resistance, moldability and mechanical properties. The polyarylene sulfide resin as the resin component used in the present invention may be a polymer having a relatively low molecular weight linear polymer whose viscosities are increased by oxidative cross-linking or thermal cross-linking to improve the molding processability. It is also possible to use a high molecular weight polymer having a substantially linear structure obtained by polycondensation from a monomer mainly comprising a hydrophilic monomer. In many cases, the physical properties of the obtained molded product are more preferable for the latter substantially linear structure polymer. Further, as the PAS resin of the present invention, in addition to the above-mentioned polymer, a branched or cross-linked PAS resin polymerized by mixing and using a monomer having three or more functional groups as a part of the monomer, or the linear or cross-linked PAS resin A blended resin blended with a polymer can also be used, which is preferable.

On the other hand, the liquid crystalline polyester resin used in the present invention is a thermoplastic melt-processable polyester exhibiting optical anisotropy (liquid crystallinity) when melted, and is generally classified as a thermotropic liquid crystal polymer. It is. In the polyester forming such an anisotropic molten phase, the polymer molecular chains are regularly arranged in a molten state (liquid crystal state).
It has the property of taking The properties of the anisotropic molten phase can be confirmed by a conventional polarization inspection method using an orthogonal polarizer. Specifically, the anisotropic molten phase can be confirmed by observing the molten sample placed on the hot stage under a nitrogen atmosphere at about 40 times magnification using a polarizing microscope. That is, when inspected between orthogonal polarizers, if the sample is optically anisotropic, polarized light will be transmitted even if it is in a molten stationary state. The liquid crystalline polyester used in the present invention is an aromatic polyester or an aromatic polyesteramide having the above liquid crystallinity, and is a polyester partially containing the aromatic polyester and the aromatic polyesteramide in the same molecular chain. You may. In terms of molecular structure, it is characterized by containing aromatic hydroxycarboxylic acid (eg, hydroxybenzoic acid) residue and aromatic-substituted derivative residue thereof as main constituent units,
Preferably, the hydroxy group and the carboxylic acid group are directly substituted with an aromatic ring, and the hydroxy group and the carboxylic acid group may be on the same aromatic ring or on different rings. It must be in the same molecule of the aromatic ring compound. Such a liquid crystalline polyester is disclosed in
These are described in detail in, for example, JP-A-69866 and JP-A-63-101448, and are commercially available, for example, under the trade name "VECTRA" (Polyplastics Co., Ltd.).

The molded article of the present invention contains the above-mentioned polyarylene sulfide resin or liquid crystalline polyester resin as a main resin component as a resin component, but a small amount of other thermoplastic resins such as a polyolefin resin as an auxiliary.
A polyamide resin, another polyester resin, a styrene resin, or the like may be used in combination.

The carbon fiber constituting the molded article of the tape sliding member in the present invention is not particularly limited as long as it is a carbon fiber prepared from a PAN-based, pitch-based, or cellulose-based material by a conventional method. Although not required, PAN-based and pitch-based carbon fibers are preferably used. The fiber diameter is preferably 3 to 15 μm, particularly preferably 5 to 15 μm.
12 μm. The carbon fibers used are desirably subjected to an appropriate surface treatment for the purpose of improving the adhesion to the resin. As the surface treating agent used for such purpose, a known surface treating agent such as an epoxy compound, an isocyanate compound (polyurethane), a silane compound, a titanate compound, and a polyamide compound is used. The lower limit of the compounding amount of the carbon fiber is at least 10% by weight, preferably 15% by weight, based on the molded product composition from the viewpoints of slidability, antistatic property, strength and the like, and the upper limit is the moldability (fluidity). ),
It is 40 % by weight in terms of mechanical properties.

[0008] As further moldings compositions used in the present invention, in addition to the upper Symbol carbon fiber, you combination formulation talc. The effect of talc itself is not only excellent in sliding properties without damaging the running tape because it has low Mohs hardness of 1 and has cleavage, and it is easy to use together with carbon fiber. Another point is that the surface roughness (center line average roughness Ra) of the molded article aimed at by the present invention can be obtained. The surface roughness can be adjusted and provided by various methods as described later, for example, when obtaining a target molded product by injection molding,
When talc is used together with carbon fiber as a component of the molded product, the surface is obviously moderately moderate compared to the case where it is not used together , and it remains injection molded without surface cutting.
The present inventor has found that the desired surface roughness of the molded article is obtained and the carbon fibers are easily exposed to the surface, which is effective. The amount of talc to be used, depending on the amount of the carbon fibers, a pair for 5 to 30 wt% in the molded product composition from the viewpoint of such as surface roughness and moldability of interest. The average particle size is 20 μm or less, preferably 0.1 to 10 μm.

Further, in the present invention, for the purpose of supplementing the lubricity, friction and wear characteristics, a fluororesin such as tetrafluoroethylene, graphite, fluorinated graphite, potassium titanate fiber, molybdenum disulfide, boron nitride, etc. are supplemented. It can be used in combination. A particularly preferable filler for such a purpose is a fluororesin, and its compounding amount is preferably 5 to 30% by weight from the viewpoint of moldability.

When the desired surface resistivity cannot be obtained only by blending carbon fibers, a conductive filler may be further added. Examples of the conductive filler include carbon black and carbon beads. Further, in the present invention, in order to obtain a molded article having excellent performances such as mechanical strength, heat resistance, and dimensional stability (deformation resistance and warpage), the sliding property with the tape, which is the object of the present invention, is not impaired. One or more inorganic fillers such as glass fibers, glass flakes, calcium carbonate, kaolin, clay, mica and the like may be supplementarily used in combination within the range.

Further, the molded article composition used in the present invention comprises:
Known substances that are generally added to thermoplastic resins, namely stabilizers such as antioxidants, flame retardants, coloring agents such as dyes and pigments,
A lubricant, a crystallization accelerator, a crystal nucleating agent, and the like can be appropriately added according to required performance.

One of the characteristics of the molded article for a tape sliding member of the present invention is that the surface roughness (center line average roughness Ra) of at least the sliding surface of the molded article is 0.5 to 10.0 μm. ,
By doing so, the sliding characteristics as members such as guides and posts that slide with tapes such as magnetic tapes are further improved, and the present invention is synergistically combined with the effects of the component requirements of the molded article composition. Has the effect of further improving the desired properties of the above. The center line average roughness (Ra) in the present invention is a value measured according to JIS-B0601. The present invention is characterized in that the center line average roughness Ra is 0.5 to 10 μm, preferably 0.8 to 5 μm. Such surface roughness can be adjusted and provided by various methods. For example, the molding can be performed by appropriately adjusting the molding conditions for injection molding of the target molded article. For example, as a general tendency, the surface roughness tends to increase by lowering the mold temperature, and a desired surface roughness can be obtained by selecting the mold temperature. Also, by molding a target object using a die having a desired roughness in a necessary portion of the mold itself (corresponding to a tape sliding portion), the desired surface roughness can be obtained. It is also possible to transfer and apply it to the surface. Also, after molding under general standard molding conditions in advance, adjust the surface to the desired roughness by mechanical post-treatment such as appropriate sand blasting or chemical post-treatment such as etching with a suitable chemical. Can also. Adjusting the surface roughness to 0.5 to 10 μm can be achieved by combining the carbon fiber with a specific amount of talc as described above.
Sufficient surface roughness can be obtained as it is
This is extremely advantageous in terms of manufacturing efficiency in that no chemical processing is required. On a smooth surface with a surface roughness of 0.5 μm or less, the slidability is unexpectedly poor. On the other hand, if the surface roughness is as large as 10 μm or more, the sliding characteristics deteriorate, which is not preferable.

The molded article for a tape sliding member of the present invention has a surface resistivity (according to JIS-K6911) of 10 ⁷ Ω or less, preferably 10 ⁵ Ω or less. This is a necessary condition to eliminate the trouble of static electricity due to sliding (the problem of adhesion of foreign matter and sticking of the tape to the molded product), and can be adjusted by the amount of carbon fiber or other conductive auxiliary agent. Further, the surface roughness specification of the present invention effectively works on this point as well.

[0014]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5 and Comparative Examples 1 to 15 The components shown in Tables 1 and 2 were mixed and melt-kneaded by an extruder to obtain molding composition pellets. Next, a cylindrical (diameter 6 mm) test piece was prepared using an injection molding machine, the surface roughness was formed under the conditions described, and the following evaluation was performed. (1) Center line average roughness (Ra) Length direction of cylindrical test piece (perpendicular to tape running)
Center line average roughness of the surface is measured using a surface roughness meter (probe method) manufactured by Tokyo Seimitsu Co., Ltd.
Was measured under the following conditions. Magnification: 5000 times Stylus movement speed: 0.3 mm / sec Cut-off value: 0.8 mm Measurement length (L): 4 mm (2) Surface resistivity A 120 mm x 120 mm x 2 mm thick flat plate is formed and conforms to JIS-K6911. Was measured with a digital electrometer manufactured by Advantest Corporation. (3) Sliding test Using the apparatus shown in FIG. 1, one end of the magnetic tape 3 is attached to the load cell 4, and a constant weight 2 is attached to the other end. By changing the direction of the tape 3 at right angles through the cylindrical test piece 1 and suspending the weight 2 and moving the load cell 4 left and right, the test piece surface is reciprocally slid under the following conditions to detect a change in load. The coefficient of friction between the tape and the cylindrical test piece was calculated. The dynamic friction coefficient (μ) was shown by the following equation (Euler's equation). μ = (2 / π) ln (W / W ₀ ) where W ₀ : Weight (10 gr) W: Load when lifting weight Load cell: UT-100GR Minebea Co. Tape: 8 mm tape Diamagnetic side Cylindrical test piece : Outer diameter (r) 6mmΦ, length (m) 16mm Travel distance: 100mm Number of movements: 1000 reciprocations The dynamic friction coefficient was calculated and calculated for the initial (10 reciprocations) and the long term (1000 reciprocations). Further, after the sliding test, the degree of damage was examined by microscopic observation of the surface of the sliding portion of each of the tape and the cylindrical test piece, and the relative evaluation was performed as follows. ○: no flaw, △: slight flaw, ×: flaw

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

Industrial Applicability The molded article for a tape sliding member according to the present invention has a small coefficient of friction and stability over a long period of use from the initial stage of sliding, and the tape and the member are less damaged by sliding. There is no trouble due to static electricity, and it has excellent characteristics as posts and guides for guiding the tape running, and is very suitable.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a tape slidability test apparatus.

[Explanation of symbols]

 1 Cylindrical test piece 2 Weight 3 Tape 4 Load cell 5 Moving distance

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 15/60 C08L 81/02

Claims (4)

(57) [Claims] 1. Carbon fiber 10 to 40 % by weight (based on composition) and
A polyarylene sulfide resin or a liquid crystalline polyester resin composition containing 5 to 30% by weight of talc (based on the composition) , having a surface resistance of 10 ⁷ Ω or less and a center line average roughness (Ra) of A molded product for a tape sliding member having a thickness of 0.5 to 10.0 μm. 2. The molded article for a tape sliding member according to claim 1 , wherein the average particle size of the talc is 0.1 to 10 μm . 3. The molded article for a tape sliding member according to claim 1, wherein the resin composition further contains 5 to 30% by weight of a fluororesin. 4. The molded article for a tape sliding member according to claim 1, wherein the molded article for a tape sliding member is a guide or post for running a magnetic tape.