Resin sheet for thrust bearing and method for manufacturing the same

Abstract

To provide an inexpensive resin sheet for a thrust bearing which can improve heat resistance and durability, can support the load of a rotation axis, and can omit heat treatment work after molding, and a method for manufacturing the same.SOLUTION: A resin film 7 for a thrust bearing can slidably support a lower end 3 of a rotation axis 2 of a motor 1 as an actuator as a receiver plate of a thrust bearing 6 is obtained by melting, extruding and molding a molding material 9 containing at least a crystalline thermoplastic polyimide resin, wherein a taper wear amount at 23°C is 1 mg or more and 50 mg or less when being measured according to JIS K 7204. The resin film 7 for the thrust bearing is formed of the crystalline thermoplastic polyimide resin instead of polyacetal resin or polyamide imide resin, which can obtain excellent wear resistant characteristics, toughness, heat resistance, solvent resistance, dimensional stability, low water absorption, flame retardance, electric insulation property, recyclability, and mechanical properties and the like.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin sheet for thrust bearings used in information devices such as personal computers and mobile phones, office equipment such as copiers and printers, multimedia devices such as audio and digital versatile (multi-purpose) disks, home appliances, air conditioning equipment such as cooling fans, and a method for manufacturing the same.

Background Art

[0002] In recent years, with the improvement in performance of information devices, office equipment, multimedia devices, etc., small motors used in these devices are required to have a high rotational speed exceeding 10,000 revolutions per minute. In response to this demand, various materials and structures of high-speed small motors capable of withstanding high-speed rotation have been developed. In this high-speed small motor exceeding 10,000 revolutions per minute, a rotating shaft is formed of a metal with high hardness, and a metal that contributes to sliding characteristics with little wear amount is used for the receiving plate of the thrust bearing on the surface that contacts the rotating shaft.

[0003] However, when a metal such as stainless steel or iron is used for the receiving plate of the thrust bearing, there are problems such as an increase in weight, time-consuming and costly for high-precision processing, and an increase in cost. Also, when both the rotating shaft and the receiving plate of the high-speed small motor are made of a metal with high hardness, wear occurs due to sliding contact, resulting in problems in terms of durability. From the above, the design of a high-speed small motor using a metal for the receiving plate of the thrust bearing has quite a few problems.

[0004] Therefore, a method has been proposed in which a resin with excellent sliding characteristics with little wear amount is used for the receiving plate of the thrust bearing that contacts the rotating shaft of the high-speed small motor. For example, (1) a thrust bearing formed of polyacetal resin having a surface smoothness in contact with the rotating shaft of the motor of 5 to 1000 μm in terms of center line average roughness (Ra) (see Patent Document 1), (2) a thrust bearing formed of polyamideimide resin having a surface smoothness in contact with the rotating shaft of the motor of 5 to 1000 μm in terms of center line average roughness (Ra) (see Patent Document 2) have been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when using polyacetal resin for the thrust bearing of (1), although excellent wear resistance characteristics can be obtained by the polyacetal resin, due to its inferior heat resistance, deformation, cracking, etc. may occur due to frictional heat during sliding, resulting in problems with durability. In addition, since it cannot support the load of the rotating shaft, a depression may occur in the thrust bearing portion.

[0007] Also, when using polyamide-imide resin for the thrust bearing of (2), although excellent wear resistance characteristics can be obtained by the polyamide-imide resin, heat treatment is required after molding for the purpose of improving heat resistance and removing residual stress. Since this heat treatment needs to be continued at a high temperature for a long time, the resulting thrust bearing becomes very expensive, causing problems in terms of cost.

[0008] The present invention has been made in view of the above, and an object thereof is to provide an inexpensive resin sheet for a thrust bearing that can improve heat resistance and durability, support the load of a rotating shaft, and omit the heat treatment operation after molding, and a manufacturing method thereof.

Means for Solving the Problems

[0009] As a result of intensive research, the inventors of the present invention focused on a crystalline thermoplastic polyimide resin that is excellent in wear resistance characteristics, toughness, heat resistance, solvent resistance, dimensional stability, low water absorption, flame retardancy, electrical insulation, recyclability, etc. among thermoplastic resins, and completed the present invention. That is, in the present invention, in order to solve the above problems, it is a device that slidably supports the end of the rotating shaft of the actuator, It is formed of a molding material containing at least a crystalline thermoplastic polyimide resin, and when the taper wear amount at 23 °C is measured in accordance with JIS K7204, it is 1 mg or more and 50 mg or less.

[0010] When the maximum tensile strength at 23 °C is measured in accordance with JIS K7127, it is preferably 50 MPa or more and 250 MPa or less, and when the elongation at break in tension at 23 °C is measured in accordance with JIS K7127, it is preferably 100% or more and 500% or less. Also, when the heat resistance is measured by the storage elastic modulus at 250 °C, it is 1×10 7 Pa or more and 1×10 10 Pa or less, and when the tensile elastic modulus at 23 °C is measured in accordance with JIS K7127, it is preferably 2000 MPa or more and 2700 MPa or less.

[0011] Also, when the static friction coefficient and the dynamic friction coefficient at 23 °C are measured in accordance with JIS K7125, the static friction coefficient is preferably 0.10 or more and 0.50 or less, and the dynamic friction coefficient is preferably 0.05 or more and 0.50 or less. Also, the actuator is composed of a motor, the rotating shaft of this motor is supported through a radial bearing, a groove is cut out in the circumferential direction on either the circumferential surface of the rotating shaft or the inner diameter surface of the radial bearing, and it is preferable that the end of the rotating shaft protruding from the radial bearing is slidably supported by a thrust bearing.

[0012] Also, in the present invention, in order to solve the above problems, it is a method for manufacturing a resin sheet for a thrust bearing according to claim 1 or 2, A molding material containing at least a crystalline thermoplastic polyimide resin is melt-kneaded, this molding material is extruded in a substantially strip shape from a die, and the extruded molding material is brought into contact with a cooling roll to form a resin sheet for a thrust bearing.

[0013] Here, the actuator in the claims includes at least motors used in information devices, office equipment, multimedia devices, home appliances, air-conditioning equipment, etc. Specifically, it includes various DC motors, various AC motors, fan motors, etc. When a groove is cut out on either the circumferential surface of the rotating shaft of this motor or the inner diameter surface of the radial bearing, the groove includes at least a herringbone groove.

[0014] The crystalline thermoplastic polyimide resin is a thermoplastic polyimide resin having a melting point. In contrast, the amorphous thermoplastic polyimide resin is a thermoplastic polyimide resin having no melting point. Here, the melting point of the crystalline thermoplastic polyimide resin (also referred to as the crystal melting or melting temperature) is the temperature corresponding to the maximum value of the melting peak measured by the differential scanning calorimetry (DSC) method. Also, the numerical values in the claims include, in addition to measurement errors, different numerical values when there are no differences in the effects of the present invention.

[0015] The resin sheet for thrust bearings is not particularly limited to being transparent, opaque, translucent, non-stretched sheet, uniaxially stretched sheet, or biaxially stretched sheet. The biaxial stretching may be carried out continuously or batchwise. This resin sheet for thrust bearings may be a single sheet or multiple sheets. Also, the resin sheet for thrust bearings includes both thick resin sheets and thin resin film sheets.

[0016] The up-down, front-back, left-right directions of the resin sheet for thrust bearings according to the present invention are directions based on the drawing and can be appropriately changed as needed. Furthermore, although the object of the present invention is the resin sheet for thrust bearings, configurations for other uses that are the same as the configuration of the present invention and can be diverted to the resin sheet for thrust bearings belong to the technical scope of the present invention when the effects of the present invention are achieved.

[0017] According to the present invention, since the resin sheet for thrust bearings is formed of a crystalline thermoplastic polyimide resin rather than a polyacetal resin, polyamide-imide resin, etc., excellent wear resistance, toughness, heat resistance, solvent resistance, dimensional stability, low water absorption, flame retardancy, electrical insulation, recyclability, mechanical properties, etc. can be obtained.

Advantages of the Invention

[0018] According to the present invention, there is an effect that the heat resistance and durability of the resin sheet for thrust bearings can be improved, and the load on the rotating shaft can be supported. Further, there is an effect that the resin sheet for thrust bearings can be provided at low cost by omitting the heat treatment operation after molding.

[0019] According to the invention described in claim 2, when the maximum tensile strength of the resin sheet for thrust bearings at 23°C is measured in accordance with JIS K7127, it is 50 MPa or more and 250 MPa or less, and when the elongation at break in tension at 23°C is measured in accordance with JIS K7127, it is 100% or more and 500% or less. Therefore, sufficient toughness can be imparted to the resin sheet for thrust bearings, and troubles such as breakage, cracking, and tearing can be prevented when it is used as the receiving plate of the thrust bearing. Further, when the resin sheet for thrust bearings is melt-extrusion molded, it is possible to prevent an excessive load from acting on the melt-extrusion molding machine, so good melt-extrusion molding over a long period can be expected.

[0020] According to the invention described in claim 3, when the heat resistance of the resin sheet for thrust bearings is measured by the storage elastic modulus at 250°C, it is 1×10 7 Pa or more and 1×10 10Since it is below Pa, sufficient heat resistance can be obtained, deformation such as dents and distortions can be prevented from occurring in the receiving plate of the thrust bearing, and practical convenience can also be achieved. Further, since the tensile elastic modulus at 23°C is 2000 MPa or more and 2700 MPa or less when measured in accordance with JIS K7127, it is possible to prevent dents and distortions from occurring in the resin sheet for thrust bearings due to the weight of the rotating shaft of the actuator. Moreover, it is possible to simplify and speed up the operation of processing the resin sheet for thrust bearings into the receiving plate of the thrust bearing, and reduce the processing cost.

[0021] According to the invention described in claim 4, when the rotating shaft of the motor rotates, the lubricant in the radial bearing is collected in the groove, so that dynamic pressure is generated and the rotating shaft of the motor can be supported with high precision. According to the invention described in claim 5, since the melt extrusion molding method is adopted as the manufacturing method of the resin sheet for thrust bearings, it is possible to continuously manufacture the resin sheet for thrust bearings in a substantially strip shape. In addition, the thickness accuracy, productivity, and handleability of the resin sheet for thrust bearings can be improved, and simplification of the equipment can also be expected.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0023] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. The resin sheet for thrust bearings in this embodiment is a resin film 7 for thrust bearings that slidably supports the lower end 3 of the rotating shaft 2 of the motor 1, which is an actuator, as a receiving plate of the thrust bearing 6, as shown in FIGS. 1 and 2. It is formed of a molding material 9 containing at least a crystalline thermoplastic polyimide resin, and the taper wear amount at 23°C is 1 mg or more and 50 mg or less when measured in accordance with JIS K7204, contributing to the achievement of Goal 9 of the SDGs adopted at the United Nations Summit.

[0024] As shown in FIG. 1, the motor 1 is composed of, for example, a high-speed and small spindle motor or a DC motor, etc. The lower end 3 of the high-hardness rotating shaft 2 extending downward is formed as a flat surface or is curved in a substantially hemispherical shape. In the axial direction of the rotating shaft 2 of this motor 1, a plurality of helical grooves 4 extending in the circumferential direction are arranged at predetermined intervals, and the lower part of the rotating shaft 2 is supported through the radial bearing 5 with the plurality of helical grooves 4 facing the inner peripheral surface of the radial bearing 5. The lower end 3 of the rotating shaft 2 protruding from the radial bearing 5 is slidably supported from below by the resin film 7 for thrust bearings, which is the receiving plate of the thrust bearing 6.

[0025] Between the rotatable rotating shaft 2 of the motor 1 and the inner diameter surface of the radial bearing 5, and between the lower end 3 of the rotating shaft 2 and the resin film 7 for thrust bearings, which is the receiving plate of the thrust bearing 6, lubricants 8 such as oil or grease that exhibit a wear suppression function are filled or applied as required. As the radial bearing 5, for example, a ball bearing or a deep groove ball bearing, etc. are used. When the rotating shaft 2 of such a motor 1 rotates, the lubricant 8 is collected in the plurality of helical grooves 4 and functions to generate hydrodynamic pressure and support the high-speed rotating rotating shaft 2 with high precision.

[0026] The molding material 9 for the thrust shaft receiving resin film 7 is prepared mainly from a crystalline thermoplastic polyimide resin excellent in abrasion resistance, toughness, heat resistance, solvent resistance, dimensional stability, low water absorption, flame retardancy, electrical insulation, recyclability, mechanical properties, etc. This crystalline thermoplastic polyimide resin is contained in an amount of 51% by mass or more and 100% by mass or less, preferably 75% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and still more preferably 95% by mass or more and 100% by mass or less.

[0027] A crystalline thermoplastic polyimide resin is used for the molding material 9. This is because if an amorphous thermoplastic polyimide resin is used, the abrasion resistance will be lowered, causing problems in extending the service life of the thrust shaft receiving resin film 7. In addition, since the heat resistance is lowered, the thrust shaft receiving resin film 7 will be deformed or melted in a temperature environment exceeding 250°C.

[0028] From the viewpoint of obtaining excellent heat resistance, the crystalline thermoplastic polyimide resin is preferably a thermoplastic polyimide resin having a melting point (hereinafter referred to as Tm) of 300°C or higher. As this crystalline thermoplastic polyimide resin, a thermoplastic polyimide resin composed of a diamine component and a terephthalic acid component is suitable. Such a crystalline thermoplastic polyimide resin is formed into any of powder, granule, flake, and pellet forms, and is used alone or in a blend of two or more kinds.

[0029] Examples of the crystalline thermoplastic polyimide resin include a thermoplastic polyimide resin obtained by dehydrating and cyclizing a polyamic acid obtained by reacting a diamine component and a tetracarboxylic dianhydride, and a crystalline thermoplastic polyimide resin composed of a diamine component mainly composed of an aliphatic diamine component and a tetracarboxylic acid component.

[0030] As the diamine component used in the thermoplastic polyimide resin obtained by dehydrating and cyclizing a polyamic acid obtained by reacting a diamine component and a tetracarboxylic dianhydride, a monocyclic aromatic group having one benzene ring, a condensed polycyclic aromatic group having a naphthalene group or the like, or a non-condensed polycyclic aromatic group in which a plurality of aromatic groups are directly bonded and interconnected by a crosslinking member such as a carbonyl group, a sulfone group, a sulfide group, a sulfoxide group, an ether group, or a sulfide group can be used. Examples of this diamine component include diamines described in JP-A-2004-27137 and Japanese Patent No. 4629894.

[0031] Specific examples of the diamine include the following diamines. That is, 4,4'-bis(3-aminophenoxy)biphenyl, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis(3-aminophenyl)sulfide, bis(4-aminophenyl)sulfide, (3-aminophenyl)(4-aminophenyl)sulfide, bis(3-aminophenyl)sulfoxide, bis(4-aminophenyl)sulfoxide, (3-aminophenyl)(4-aminophenyl)sulfoxide, bis(3-aminophenyl)sulfone, bis(4-aminophenyl)sulfone, (3-aminophenyl)(4-aminophenyl)sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]butane, 2,2-bis[3-(3-aminophenoxy)phenyl]1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]1,1,1,3,3,3-hexafluoropropane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-Bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]dibenzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzene]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-Dibiphenoxybenzophenone, 4,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 4,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(3-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 6,6'-bis(2-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spiroindane, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spiroindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spiroindane, etc. can be mentioned.,

[0032] These diamines can be used alone or in a mixture of two or more. Among these, 1,3-bis(4-aminophenoxy)benzene and 4,4'-bis(4-aminophenoxy)biphenyl are optimal.,

[0033] As the tetracarboxylic dianhydride component used in the thermoplastic polyimide resin obtained by dehydrating and cyclizing the polyamic acid obtained by reacting a diamine component with a tetracarboxylic dianhydride, a monocyclic aromatic group having one benzene ring, a condensed polycyclic aromatic group having a naphthalene ring, etc., or a tetracarboxylic dianhydride having a crosslinking member of a plurality of aromatic groups directly bonded, a carbonyl group, a sulfone group, a sulfoxide group, an ether group, or a sulfide group can be used. As this tetracarboxylic dianhydride component, for example, the tetracarboxylic dianhydrides described in JP-A-2004-27137 and Japanese Patent No. 4629894 can be used.

[0034] Specific examples of the tetracarboxylic dianhydride component include the following tetracarboxylic dianhydrides. That is, ethylene tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 2,3,3’,4’-benzophenone tetracarboxylic dianhydride, 2,2’,3,3’-benzophenone tetracarboxylic dianhydride, 3,3’,4,4’-biphenyl tetracarboxylic dianhydride, 2,2’,3,3’-biphenyl tetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2’-bis(3,4-dicarboxyphenyl)-1,1,3,3,3-hexafluoropropane dianhydride, pyromellitic dianhydride, 1,4-difluoropyromellitic acid, 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluorobenzene dianhydride, 2,2’-bis[4-(3,4-carboxyphenoxy)benzene]-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, etc.

[0035] These tetracarboxylic dianhydrides can be used alone or in admixture of two or more thereof. Further, compounds obtained by hydrolyzing all or part of the above tetracarboxylic dianhydrides can also be used. Among these, pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride are preferred. These tetracarboxylic dianhydrides are used alone or in admixture of two or more thereof.

[0036] When the diamine component is 4,4'-bis(3-aminophenoxy)biphenyl, the combination of the tetracarboxylic dianhydride component with pyromellitic dianhydride is preferred. When the diamine component is 1,3-bis(4-aminophenoxy)benzene, the tetracarboxylic dianhydride component is preferably 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0037] The thermoplastic polyimide resin having repeating structural units of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride is excellent in the moldability, heat resistance, mechanical properties, electrical insulating properties, creep resistance, chemical resistance, low water absorption properties, etc. of the resin film 7 for thrust shaft use, and is suitable. Specific examples of the thermoplastic polyimide having repeating structural units of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride include the Aurum series of U.S. Patent No. 5,043,419 [Product name: manufactured by Mitsui Chemicals, Inc.].

[0038] The Tm of the thermoplastic polyimide resin having repeating structural units of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride is 350°C or higher and 450°C or lower, preferably 370°C or higher and 420°C or lower, more preferably 380°C or higher and 400°C or lower, and still more preferably 385°C or higher and 395°C or lower. This is because when Tm exceeds 450°C, the load on the melt extrusion machine 10 becomes large when melt-extrusion molding the resin film 7 for thrust shaft use with the die 14, making it difficult to mold the resin film 7 for thrust shaft use.

[0039] 4. The Tm (unit: °C) of the crystalline thermoplastic polyimide resin composed of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride can be determined by thermal analysis using a differential scanning calorimeter.

[0040] The apparent melt viscosity of the thermoplastic polyimide resin having a repeating structural unit of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride, measured with a constant load extrusion capillary rheometer using a die with a diameter of 1.0 mm × length of 10 mm under the conditions of a temperature of 390 °C and a load of 50 kgf, is 5.0×10 1 Pa·s or more and 5.0×10 4 Pa·s or less, preferably 1.0×10 2 Pa·s or more and 1.0×10 4 Pa·s or less, more preferably 2.5×10 2 Pa·s or more and 7.5×10 3 Pa·s or less, still more preferably 2.5×10 2 Pa·s or more and 5.0×10 3 Pa·s or less.

[0041] This is because when the apparent melt viscosity is less than 1.0×10 2 Pa·s, the melt tension of the crystalline thermoplastic polyimide resin having a repeating structural unit of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride is small, and there are problems with the formability of the resin film 7 for the thrust shaft when melt extrusion molding is performed. In contrast, when it exceeds 5.0×10 4 Pa·s, it is based on the reason that the load on the melt extrusion molding machine 10 is too large and it becomes difficult to form a good resin film 7 for the thrust shaft by melt extrusion molding.

[0042] Examples of the crystalline thermoplastic polyimide resin include, in addition to the above-described crystalline thermoplastic polyimide resin, a crystalline thermoplastic polyimide resin composed of a diamine component mainly composed of an aliphatic diamine component and a tetracarboxylic acid component. It is important that the diamine component of such a crystalline thermoplastic polyimide resin is mainly composed of an aliphatic diamine component (including an alicyclic diamine).

[0043] As the crystalline thermoplastic polyimide resin, a random copolymer, an alternating copolymer, a block copolymer, a graft copolymer, or a modified product with other copolymerizable monomers can also be used as long as the effects of the present invention are not impaired. The shape of the crystalline thermoplastic polyimide resin may be any shape such as powder, flake, pellet, lump, etc.

[0044] That is, among the diamine components, it is important that the component exceeding 50 mol% is an aliphatic diamine, preferably 60 mol% or more, more preferably 80 mol% or more, and particularly preferably 90 mol% or more. In particular, it is optimal that all (100 mol%) of the diamine components are aliphatic diamines. By having this main component as an aliphatic diamine, excellent heat resistance, low water absorption, moldability, and secondary processability can be imparted to the resin film 7 for the thrust shaft bearing.

[0045] The aliphatic diamine contained in the diamine component is not particularly limited as long as it is a diamine component having amine groups at both ends of a hydrocarbon. However, when heat resistance is emphasized, it is preferable to include an alicyclic diamine having amine groups at both ends of a cyclic hydrocarbon.

[0046] The number of carbon atoms of this alicyclic diamine is preferably 6 or more and 22 or less. Specific examples include 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, 4,4'-methylenebis(2-methylcyclohexylamine), carbonyldiamine, isophoronediamine, norbornanediamine, bis(aminomethyl)tricyclodecane[5.2.1.02.6]decane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylpropane, and the like. Among these, 1,3-bis(aminomethyl)cyclohexane is optimal from the viewpoint of achieving both heat resistance, moldability, and secondary processability.

[0047] When emphasizing the moldability and secondary processability of the resin film 7 for the thrust shaft, it is preferable to include a linear aliphatic diamine having amine groups at both ends of a linear hydrocarbon as the aliphatic diamine contained in the diamine component. There is no particular limitation on this linear aliphatic diamine as long as it is a diamine component having amino groups at both ends of an alkyl group. Specific examples include ethylenediamine (carbon number 2), propylenediamine (carbon number 3), butanediamine (carbon number 4), pentanediamine (carbon number 5), hexanediamine (carbon number 6), heptanediamine (carbon number 7), octanediamine (carbon number 8), nonanediamine (carbon number 9), decanediamine (carbon number 10), undecanediamine (carbon number 11), dodecanediamine (carbon number 12), tridecanediamine (carbon number 13), tetradecanediamine (carbon number 14), pentadecanediamine (carbon number 15), hexadecanediamine (carbon number 16), heptadecanediamine (carbon number 17), octadecanediamine (carbon number 18), nonadecanediamine (carbon number 19), eicosane (carbon number 20), triacontane (carbon number 30), tetracosane (carbon number 40), pentacontane (carbon number 50), and the like.

[0048] Among these, from the viewpoint of excellent moldability, secondary processability, and low water absorption, linear aliphatic diamines having 4 to 12 carbon atoms are optimal. These linear aliphatic diamines may also be diamines having a branched structure with 1 to 10 carbon atoms.

[0049] As components other than the aliphatic diamine contained in the diamine component, other diamine components may be included. Specifically, 1,4-phenylenediamine, 1,3-phenylenediamine, 2,4-phenylenediamine, 2,4-toluenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, α,α'-bis(4-aminophenyl)1,4'-diisopropylbenzene, α,α'-bis(3-aminophenyl)-1,4-diisopropylbenzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,6-diaminonaphthalene, 1,5-diaminonaphthalene, p-xylylenediamine, m-xylylenediamine and other aromatic diamine components, polyethylene glycol bis(3-aminopropyl) ether, polypropylene glycol bis(3-aminopropyl) ether and other ether diamine components, siloxane diamines, etc. are applicable.

[0050] The diamine component may contain at least one of an alicyclic diamine and a linear aliphatic diamine. However, since it has an excellent balance between heat resistance and moldability, it is preferable to contain both an alicyclic diamine and a linear aliphatic diamine. When both an alicyclic diamine and a linear aliphatic diamine are contained, the respective contents are preferably in the range of alicyclic diamine:linear aliphatic diamine = 99:1 to 1:99 mol%, more preferably 80:20 to 20:80 mol%, and most optimally 60:40 to 40:60 mol%. This is because, as long as the ratio of the alicyclic diamine and the linear aliphatic diamine contained in the diamine component is within the relevant range, the balance between the heat resistance and moldability of the resin film 7 for the thrust shaft can be improved.

[0051] Examples of the tetracarboxylic acid component of the crystalline thermoplastic polyimide resin include cyclobutane-1,2,3,4-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, cyclohexane-1,2,3,5-tetracarboxylic acid, 3,3’,4,4’-benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-1,4-tetracarboxylic acid, pyromellitic acid, etc. Also, alkyl ester forms of these can be used.

[0052] Among these, it is preferable that more than 50 mol% of the components in the tetracarboxylic acid component is pyromellitic acid. This is because if the tetracarboxylic acid component is mainly composed of pyromellitic acid, the heat resistance, secondary processability, and low water absorption are improved. From this perspective, among the tetracarboxylic acid components, pyromellitic acid is preferably 60 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. In particular, it is optimal that all (100 mol%) of the tetracarboxylic acid component is pyromellitic acid.

[0053] The Tm of the crystalline thermoplastic polyimide resin is 300°C or higher and 400°C or lower, preferably 310°C or higher and 370°C or lower, more preferably 320°C or higher and 350°C or lower, and even more preferably 310°C or higher and 330°C or lower. This is because when the Tm is less than 300°C, the heat-resistant resin film 7 for the thrust shaft cannot be obtained.

[0054] On the other hand, when the Tm of the crystalline thermoplastic polyimide resin exceeds 400°C, it is because there is a risk that the thermoplastic polyimide resin will decompose violently. Also, problems such as limitations on the usable melt extrusion molding machine 10 will occur. The Tm of the crystalline thermoplastic polyimide resin can be determined by thermal analysis using a differential scanning calorimeter as described above.

[0055] The apparent melt viscosity of the crystalline thermoplastic polyimide resin composed of a diamine component mainly composed of an aliphatic diamine component and a tetracarboxylic acid component, when measured with a constant load extrusion capillary rheometer using a die with a diameter of 1.0 mm and a length of 10 mm under the conditions of a temperature of 350°C and a load of 50 kgf, is such that the apparent melt viscosity at a temperature of 350°C is 5.0×10 1 Pa·s or more and 5.0×10 4 Pa·s or less, preferably 1.0×10 2 Pa·s or more and 1.0×10 4 Pa·s or less, more preferably 2.5×10 2 Pa·s or more and 7.5×10 3 Pa·s or less, and even more preferably 2.5×10 2 Pa·s or more and 5.0×10 3 Pa·s or less.

[0056] This is based on the reason that when the apparent melt viscosity is less than 1×10 2 Pa·s, the melt tension of the molten crystalline thermoplastic polyimide resin is small, and problems occur in the moldability of the resin film 7 for the thrust shaft by melt extrusion molding. On the other hand, 5.0×10 4If it exceeds Pa·s, too much load is placed on the melt extruder 10, making it difficult to form a good resin film 7 for a thrust bearing by melt extrusion.

[0057] As the crystalline thermoplastic polyimide resin, a random copolymer, an alternating copolymer, a block copolymer, a graft copolymer, or a modified product with other copolymerizable monomers can be used as long as the effect of the present invention is not impaired. The shape of the crystalline thermoplastic polyimide resin may be any shape such as powder, flake, pellet, block, or the like.

[0058] The crystalline thermoplastic polyimide resin is not particularly limited, but is preferably the crystalline thermoplastic polyimide resin described in Japanese Patent No. 5365762, Japanese Patent No. 6024859, Japanese Patent No. 6037088, or Japanese Patent No. 6394662, and more preferably the crystalline thermoplastic polyimide resin described in Japanese Patent No. 6024859, Japanese Patent No. 6037088, or Japanese Patent No. 6394662. Specific examples of such crystalline thermoplastic polyimide resins include the Surprim (registered trademark) series (manufactured by Mitsubishi Gas Chemical Co., Ltd.: product name), which has high strength, high heat resistance, high solvent resistance, crystallinity, and excellent film moldability.

[0059] In addition to the crystalline thermoplastic polyimide resin, the molding material 9 can selectively add thermoplastic resins such as polyethylene (PE) resin, polypropylene (PP) resin, polyolefin resins such as polymethylpentene (PMP) resin and polystyrene (PS) resin, acid-modified olefin resins such as maleic anhydride-modified polyethylene resin and maleic anhydride-modified polypropylene resin, polyester resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin and polyethylene naphthalate (PEN) resin, polyamide-imide (PAI) resin, polyamide 4T (PA4T) resin, polyamide 6T (PA6T) resin, modified polyamide 6T (modified PA6T) resin, polyamide 9T (PA9T) resin, polyamide 10T (PA10T) resin, polyamide 11T (PA11T) resin, polyamide resins such as polyamide 6 (PA6) resin, polyamide 66 (PA66) resin and polyamide 46 (PA46) resin, polysulfone (PSU) resin, polysulfone resins such as polyether sulfone (PES) resin and polyphenylene sulfone (PPSU) resin, polyphenylene sulfide (PPS) resin, polyphenylene sulfide ketone resin, polyarylene sulfide resins such as polyphenylene sulfide sulfone resin and polyphenylene sulfide ketone sulfone resin, polyarylene ether ketone (PAEK) resins such as polyether ketone (PEK) resin, polyether ketone ketone (PEKK) resin, polyether ether ketone ketone (PEEKK) resin, polyether ketone ether ketone ketone (PEKEKK) resin, fluororesins such as polytetrafluoroethylene (PTFE) resin, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropyl copolymer (FEP) resin, tetrafluoroethylene-ethylene copolymer (ETFE) resin, polychlorotrifluoroethylene (PCTFE) resin, polyvinylidene fluoride (PVDF) resin, fluororesin copolymers such as vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer resin and acid-modified fluororesin, polycarbonate (PC) resin, polyarylate (PAR) resin, polyacetal (POM) resin, liquid crystal polymer (LCP), aliphatic polyketone resin, etc.

[0060] In addition to the crystalline thermoplastic polyimide resin, various additives such as crystal nucleating agents, antioxidants, heat stabilizers, lubricants, plasticizers, antistatic agents, antiblocking agents, fillers, viscosity modifiers, anti-coloring agents, lubricants, etc. can be added to the molding material 9 as long as the object of the present invention is not impaired. Further, particles can be contained in the crystalline thermoplastic polyimide resin of the molding material 9. In this case, inorganic particles or organic particles are preferably used.

[0061] Examples of the inorganic particles include metal oxides such as silica, alumina, titanium dioxide, and zirconia, and barium sulfate, calcium carbonate, aluminum silicate, calcium phosphate, mica, talc, kaolin, clay, zeolite, etc. Among these, metal oxides such as silica, alumina, titanium dioxide, and zirconia, and calcium carbonate are preferable.

[0062] On the other hand, as the organic particles, cross-linked particles of dimethylpolysiloxane, cross-linked particles of polymethoxysilane-based compounds, fine powder of cured products of polyorganosilsesquioxane, cross-linked particles of polystyrene-based compounds, cross-linked particles of acrylic-based compounds, cross-linked particles of polyurethane-based compounds, cross-linked particles of polyester-based compounds, cross-linked particles of fluorine-based compounds, carbon nanotubes, graphene, and fullerene can be used alone or in combination of two or more.

[0063] The average particle size of the inorganic particles and the organic particles is preferably in the range of 0.01 μm or more and 5.0 μm or less. This average particle size is preferably in the range of 0.05 μm or more and 3.0 μm or less, more preferably in the range of 0.07 μm or more and 2.0 μm or less, and still more preferably in the range of 0.1 μm or more and 1.0 μm or less. This is because when the average particle size is less than 0.01 μm, aggregation occurs and the dispersibility in the crystalline thermoplastic polyimide resin decreases, resulting in a decrease in the mechanical properties of the resin film 7 for the thrust shaft, making it more likely to crack or break during bending processing, and also causing a decrease in handleability.

[0064] On the other hand, when it exceeds 5.0 μm, it is due to the fact that the mechanical properties of the resin film 7 for the thrust shaft are deteriorated, making it easy to crack or break during bending processing, or causing deterioration of electrical insulation properties and water absorption. As a method for measuring the average particle diameter of inorganic particles and organic particles, there is a method of using the equivalent circle diameter obtained by image processing from a transmission electron micrograph of the particles and calculating and measuring the weight average diameter.

[0065] By adding such inorganic particles and organic particles, the surface of the resin film 7 for the thrust shaft can be roughened, and it becomes possible to improve the slidability of the resin film 7 for the thrust shaft.

[0066] As the addition amount of the inorganic particles and the organic particles, when the crystalline thermoplastic polyimide resin is 100 parts by mass, it is in the range of 0.01 part by mass or more and 10 parts by mass or less, preferably 0.1 part by mass or more and 8.0 parts by mass or less, more preferably 0.5 part by mass or more and 5.0 parts by mass or less, and still more preferably 1.0 part by mass or more and 3.0 parts by mass or less. This is because when the addition amount is less than 0.01 part by mass, the handleability is insufficient. On the other hand, when it exceeds 10 parts by mass, the mechanical properties of the resin film 7 for the thrust shaft are deteriorated, so there is a risk that the crystalline resin film 7 for the thrust shaft may be broken or cracked during the bending process of the resin film 7 for the thrust shaft.

[0067] Also, if the addition amount of the inorganic particles and the organic particles is within the range of 0.01 part by mass or more and 10 parts by mass or less, it is possible to prevent the quality deterioration of the resin film 7 for the thrust shaft accompanying the generation of eye varnish. Regarding this point, when the resin film 7 for the thrust shaft is formed into a film using the die 14, a large amount of deposits called eye varnish may adhere and accumulate at the outlet of the die 14 (also called the die lip). When this eye varnish accumulates, die lines may occur on the resin film 7 for the thrust shaft, or the eye varnish may separate from the outlet of the die 14 and mix into the resin film 7 for the thrust shaft, resulting in quality deterioration of the resin film 7 for the thrust shaft.

[0068] According to this embodiment, since the addition amount of inorganic particles or organic particles is in the range of 0.01 parts by mass or more and 10 parts by mass or less, it is possible to effectively prevent the occurrence of die lines in the resin film 7 for thrust shaft use or the inclusion of eye varnish in the resin film 7 for thrust shaft use, which may lead to a deterioration in quality.

[0069] When it is desired to prevent aggregation of inorganic particles or organic particles or to improve the affinity with a crystalline thermoplastic polyimide resin, various coupling agents such as silane coupling agents [vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-trimethoxysilylpropylsuccinic anhydride, imidazole silane, etc.], titanate coupling agents [isopropyltriisostearoyl titanate, isopropyl (dioctyl pyrophosphate) titanate, isopropyl tris(N-aminoethyl-aminoethyl) titanate, tetraoctyl bis(di-tridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl) bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, isopropyltrioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyltridecylbenzenesulfonyl titanate, isopropylisostearoyldiacryl titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyltricumylphenyl titanate, tetraisopropyl (dioctyl phosphite) titanate, etc.], aluminate coupling agents [acetoxy aluminum diisopropylate, etc.] can be used to treat the inorganic particles or organic particles within a range that does not impair the properties of the resin film 7 for the thrust shaft.

[0070] When the treatment amount of the coupling agent is based on 100 parts by mass of inorganic particles or organic particles, it is preferably in the range of 0.01 part by mass or more and 5.0 parts by mass or less, more preferably 0.1 part by mass or more and 3.0 parts by mass or less, still more preferably 0.5 part by mass or more and 2.0 parts by mass or less, and even more preferably 0.5 part by mass or more and 1.5 parts by mass or less. This is because when the addition amount is less than 0.01 part by mass, it may not be possible to prevent aggregation of the particles, and there is a possibility that the affinity for the crystalline thermoplastic polyimide resin cannot be improved, resulting in a decrease in dispersibility in the crystalline thermoplastic polyimide resin and a possible decrease in mechanical properties.

[0071] On the other hand, when it exceeds 5.0 parts by mass, due to the excessive addition of the coupling agent, the inorganic particles or organic particles become sticky, and the particles aggregate. When added to the crystalline thermoplastic polyimide resin, the mechanical properties of the resin film 7 for the thrust shaft will deteriorate. Also, it is due to the reason that the coupling agent oozes out from the resin film 7 for the thrust shaft and causes contamination.

[0072] The resin film 7 for the thrust shaft is formed into a thin resin film, and examples of this forming method include a melt extrusion molding method, a calender molding method, or a casting method. Among these forming methods, from the viewpoints of the thickness accuracy of the resin film 7 for the thrust shaft, the productivity of the thin film, the improvement of handling properties, and the simplification of equipment, the melt extrusion molding method capable of continuously extruding the resin film 7 for the thrust shaft into a strip shape is the most suitable.

[0073] As shown in FIG. 2, the melt extrusion molding method uses a melt extrusion molding machine 10 to melt-knead a molding material 9 containing a crystalline thermoplastic polyimide resin, and continuously extrudes the molten crystalline thermoplastic polyimide resin in a strip shape from a die 14 such as a T-die or a round die connected to the tip of the melt extrusion molding machine 10. The resin film 7 for the thrust shaft is manufactured by sandwiching and cooling this crystalline thermoplastic polyimide resin between a pair of pressure rolls 17 and a plurality of cooling rolls 18.

[0074] The melt extrusion molding machine 10 is composed of, for example, a single-screw extrusion molding machine, a twin-screw extrusion molding machine, etc. A raw material inlet 11 for the molding material 9 is installed above the rear part. An inert gas supply pipe 12 for supplying an inert gas such as helium gas, neon gas, argon gas, krypton gas, nitrogen gas, etc. as required is connected to this raw material inlet 11. By supplying the inert gas through this inert gas supply pipe 12, oxidative degradation, oxygen crosslinking, and thermal crosslinking of the molding material 9 are effectively prevented.

[0075] The melting temperature during the melt kneading of the melt extrusion molding machine 10 is not particularly limited as long as melt kneading and dispersion are possible and the crystalline thermoplastic polyimide resin does not decompose. However, a range of not less than the Tm of the crystalline thermoplastic polyimide resin and less than the thermal decomposition temperature of the crystalline thermoplastic polyimide resin is preferable. This is because when it is less than the Tm of the crystalline thermoplastic polyimide resin, the melt fluidity cannot be obtained for the crystalline thermoplastic polyimide resin, so the resin film 7 for the thrust shaft cannot be molded by the melt extrusion molding method. On the other hand, when it is not less than the thermal decomposition temperature of the crystalline thermoplastic polyimide resin, the decomposition of the crystalline thermoplastic polyimide resin is caused.

[0076] The melting temperature of the crystalline thermoplastic polyimide resin is preferably not less than [Tm of the crystalline thermoplastic polyimide resin + 10°C] and not more than [Tm of the crystalline thermoplastic polyimide resin + 100°C], more preferably not less than [Tm of the crystalline thermoplastic polyimide resin + 20°C] and not more than [Tm of the crystalline thermoplastic polyimide resin + 70°C], and even more preferably not less than [Tm of the crystalline thermoplastic polyimide resin + 30°C] and not more than [Tm of the crystalline thermoplastic polyimide resin + 60°C]. The Tm (unit: °C) of the crystalline thermoplastic polyimide resin can be determined by thermal analysis using a differential scanning calorimeter as described above.

[0077] The die 14 is connected to the tip of the melt extrusion molding machine 10 via a connecting pipe 13, and functions to continuously extrude the molten crystalline thermoplastic polyimide resin downward in a strip shape. There are various types of this die 14, but a T-die capable of obtaining the resin film 7 for thrust shafts with excellent thickness accuracy is optimal. It is preferable that a gear pump 15 and a polymer filter 16 are respectively attached to the connecting pipe 13 upstream of the die 14.

[0078] The gear pump 15 functions to transfer the molding material 9 melt-kneaded by the melt extrusion molding machine 10 to the downstream die 14 through the polymer filter 16 at a constant flow rate and with high precision. Further, the polymer filter 16 functions to separate unmelted crystalline thermoplastic polyimide resin, foreign substances, etc. from the molten crystalline thermoplastic polyimide resin, and transfer the molten crystalline thermoplastic polyimide resin to the die 14.

[0079] The polymer filter 16 is made of, for example, a circle having a large number of holes concentrically, a sintered metal having a large number of holes, or a metallic mesh, and has a plurality of small openings that are 0.5 times or more and 6 times or less, preferably 0.5 times or more and 4 times or less, more preferably 0.5 times or more and 3.8 times or less the average thickness of the resin film 7 for thrust shafts. The reason for being 0.5 times or more the average thickness of the resin film 7 for thrust shafts is that if it is less than 0.5 times, the extrusion pressure amount of the molding material 9 becomes high, which may cause damage to the polymer filter 16, and moreover, the productivity is significantly reduced.

[0080] The temperature during extrusion of the die 14 is preferably in the range of not less than the Tm of the crystalline thermoplastic polyimide resin and less than the thermal decomposition temperature of the crystalline thermoplastic polyimide resin. This is because if it is less than the Tm of the crystalline thermoplastic polyimide resin, the molten fluidity cannot be obtained in the crystalline thermoplastic polyimide resin, so the resin film 7 for thrust shafts cannot be molded by the melt extrusion molding method. Also, if it is at or above the thermal decomposition temperature of the crystalline thermoplastic polyimide resin, decomposition of the crystalline thermoplastic polyimide resin is caused, which is not preferable.

[0081] On the other hand, the extrusion temperature of the die 14 of the crystalline thermoplastic polyimide resin is preferably [Tm of the crystalline thermoplastic polyimide resin + 10°C] or higher and [Tm of the crystalline thermoplastic polyimide resin + 100°C] or lower, more preferably [Tm of the crystalline thermoplastic polyimide resin + 20°C] or higher and [Tm of the crystalline thermoplastic polyimide resin + 70°C] or lower, and still more preferably [Tm of the crystalline thermoplastic polyimide resin + 30°C] or higher and [Tm of the crystalline thermoplastic polyimide resin + 60°C] or lower.

[0082] Below the die 14, a pair of pressure-bonding rolls 17 facing each other with a space therebetween are rotatably supported. Between this pair of pressure-bonding rolls 17, a plurality of cooling rolls 18 arranged in a row and in sliding contact with each other are rotatably supported. Among these plurality of cooling rolls 18, the upstream cooling roll 18 and the downstream cooling roll 18 are in sliding contact with the circumferential surface of the pressure-bonding roll 17, respectively. Each pressure-bonding roll 17 is configured to have a reduced diameter, and each cooling roll 18 is configured to have a larger diameter than the pressure-bonding roll 17.

[0083] Further downstream of the downstream pressure-bonding roll 17 among the pair of pressure-bonding rolls 17, a winding machine 20 for winding the resin film 7 for thrust bearings around a rotatable winding tube 19 is installed. Between this winding machine 20 and the downstream pressure-bonding roll 17, a slit blade 21 for forming a slit in the longitudinal direction of the side portion of the resin film 7 for thrust bearings is disposed so as to be movable up and down. Between this slit blade 21 and the winding machine 20, the necessary number of tension rolls 22 for applying tension to the resin film 7 for thrust bearings and smoothly winding it are rotatably supported.

[0084] Each pressure roller 17 is adjusted to a temperature range of [Tg of the crystalline thermoplastic polyimide resin - 100°C] or higher and lower than the Tm of the crystalline thermoplastic polyimide resin, preferably [Tg of the crystalline thermoplastic polyimide resin - 50°C] or higher and [Tm of the crystalline thermoplastic polyimide resin - 50°C] or lower, more preferably [Tg of the crystalline thermoplastic polyimide resin] or higher and [Tm of the crystalline thermoplastic polyimide resin - 100°C] or lower, and even more preferably [Tg of the crystalline thermoplastic polyimide resin] or higher and [Tm of the thermoplastic polyimide resin - 120°C], and slidably contacts the resin film 7 for the thrust shaft and presses it against the cooling roll 18.

[0085] The reason why the temperature of the pressure roller 17 is in such a range is that when it is lower than [Tg of the crystalline thermoplastic polyimide resin - 100°C], the molten-extruded strip-shaped crystalline thermoplastic polyimide resin cannot be brought into close contact with the cooling roll 18, so a smooth resin film 7 for the thrust shaft cannot be obtained. On the other hand, when it exceeds the Tm of the crystalline thermoplastic polyimide resin, it is based on the reason that there is a risk of sticking to and breaking on the pressure roller 17. Examples of the temperature adjustment method of the pressure roller 17 include a method using a heat medium such as air, water, or oil, a method using an electric heater, a method using induction heating, and the like.

[0086] On the circumferential surface of each pressure roller 17, from the viewpoint of improving the adhesion between the crystalline thermoplastic polyimide resin and the cooling roll 18, at least a rubber layer made of natural rubber, isoprene rubber, butadiene rubber, norbornene rubber, acrylonitrile-butadiene rubber, nitrile rubber, urethane rubber, silicone rubber, fluororubber, etc. is formed by coating as required, and an inorganic compound such as silica or alumina is selectively added to this rubber layer. Among these rubbers, the selection of silicone rubber or fluororubber with excellent heat resistance is optimal.

[0087] The plurality of cooling rolls 18 are made of, for example, a metal roll having a larger diameter than the pressure roll 17, and are rotatably supported below the die 14 to sandwich the extruded crystalline thermoplastic polyimide resin between the circumferential surface of the pressure roll 17. While cooling the crystalline thermoplastic polyimide resin together with the pressure roll 17, a resin film 7 for a thrust bearing is formed, and functions to control the thickness of the resin film 7 for a thrust bearing within a predetermined range.

[0088] Each cooling roll 18, similar to the pressure roll 17, is adjusted to a temperature range of not less than [Tg of the crystalline thermoplastic polyimide resin - 100°C] and less than the Tm of the crystalline thermoplastic polyimide resin, preferably not less than [Tg of the crystalline thermoplastic polyimide resin - 50°C] and not more than [Tm of the crystalline thermoplastic polyimide resin - 50°C], more preferably not less than [Tg of the crystalline thermoplastic polyimide resin] and not more than [Tm of the crystalline thermoplastic polyimide resin - 100°C], and still more preferably not less than [Tg of the crystalline thermoplastic polyimide resin] and not more than [Tm of the crystalline thermoplastic polyimide resin - 120°C]. It is in sliding contact with the resin film 7 for a thrust bearing and presses it against another adjacent cooling roll 18.

[0089] As a method for adjusting the temperature of the cooling roll 18, similar to the pressure roll 17, for example, methods using a heat medium such as air, water, or oil, methods using an electric heater, methods utilizing induction heating, etc. can be mentioned.

[0090] After the molding material 9 is extruded into a strip-shaped crystalline thermoplastic polyimide resin, this crystalline thermoplastic polyimide resin is wound around a pair of pressure rolls 17, a plurality of cooling rolls 18, a tension roll 22, and the winding tube 19 of the winder 20 to form a resin film 7 for a thrust bearing. After both side portions of the resin film 7 for a thrust bearing are cut in the longitudinal direction by the slit blade 21 respectively, and then sequentially wound around the winding tube 19 of the winder 20, a long resin film 7 for a thrust bearing can be manufactured.

[0091] The thickness of the resin film 7 for the thrust bearing, which is cooled by the cooling roll 18, is 25 μm or more and 1000 μm or less, preferably 50 μm or more and 800 μm or less, more preferably 75 μm or more and 600 μm or less, and still more preferably 100 μm or more and 500 μm or less. This is because when the thickness of the resin film 7 for the thrust bearing is less than 25 μm, there is a problem with the life as the receiving plate of the thrust bearing 6, and conversely, when it exceeds 1000 μm, it becomes difficult to make the motor 1 thin.

[0092] The surface of the resin film 7 for the thrust bearing can form fine irregularities and reduce the friction coefficient of the surface. As methods for forming these fine irregularities, (1) a crystalline thermoplastic polyimide resin is melt-kneaded by a melt extrusion molding machine 10, and the melt-kneaded crystalline thermoplastic polyimide resin is discharged from a die 14 onto a cooling roll 18 having fine irregularities on its circumferential surface and adhered thereto, and the resin film 7 for the thrust bearing is sandwiched between a pressure roll 17 to form fine irregularities; (2) an inorganic compound such as fine zirconia, glass, or stainless steel, a polycarbonate resin, a polyamide resin, or an organic compound such as a plant seed is sprayed onto the resin film 7 for the thrust bearing to form fine irregularities; and (3) the resin film 7 for the thrust bearing is press-molded with a mold having fine irregularities to form fine irregularities.

[0093] The wear amount of the resin film 7 for the thrust bearing can be evaluated by the taper wear amount in an environment of 23°C ± 2°C and 50% RH ± 5% RH, and this taper wear amount can be measured in accordance with JIS K7204. The taper wear amount of the resin film 7 for the thrust bearing is 1 mg or more and 50 mg or less, preferably 3 mg or more and 45 mg or less, more preferably 5 mg or more and 40 mg or less, still more preferably 7 mg or more and 35 mg or less, and most preferably 10 mg or more and 33 mg or less.

[0094] This is because when the taper wear amount is less than 1 mg, there is a risk that the receiving plate will be deformed due to heat generation caused by friction between the rotating shaft 2 of the motor 1 and the receiving plate of the thrust bearing 6. Conversely, when the taper wear amount exceeds 50 mg, the wear amount is large, which becomes a problem in terms of extending the service life.

[0095] The toughness of the resin film 7 for the thrust bearing can be evaluated by the maximum tensile strength and the elongation at break under the environment of 23°C ± 2°C and 50% RH ± 5% RH. These maximum tensile strength and elongation at break can be measured with respect to MD (extrusion direction) and TD (width direction perpendicular to the extrusion direction) in accordance with JIS K7127.

[0096] The maximum tensile strength of the resin film 7 for the thrust bearing is preferably 50 MPa or more and 250 MPa or less, more preferably 55 MPa or more and 200 MPa or less, still more preferably 60 MPa or more and 150 MPa, and even more preferably 65 MPa or more and 120 MPa or less. Also, the elongation at break of the resin film 7 for the thrust bearing is preferably 100% or more and 500% or less, more preferably 105% or more and 450% or less, still more preferably 110% or more and 400% or less, and even more preferably 115% or more and 350% or less, and most preferably 115% or more and 310% or less.

[0097] This is because when the maximum tensile strength is less than 50 MPa and the elongation at break is less than 100%, the resin film 7 for the thrust bearing does not have sufficient toughness, so troubles such as breakage, cracking, and tearing will occur when used as the receiving plate of the thrust bearing 6. On the other hand, when the maximum tensile strength of the resin film 7 for the thrust bearing exceeds 250 MPa and the elongation at break exceeds 500%, the melt viscosity of the molding material 9 is high, the load on the melt extrusion molding machine 10 is too large, and it becomes difficult to perform good molding by melt extrusion molding.

[0098] The heat resistance of the resin film 7 for thrust bearings can be represented by the storage modulus at 250°C. From the perspective of obtaining excellent heat resistance, the heat resistance of this resin film 7 for thrust bearings is such that when the storage modulus at 250°C is measured under the conditions of a frequency of 1 Hz and a heating rate of 3°C / min, both in the MD and TD directions, it is 1.0×10 7 Pa or more, preferably 7.5×10 7 Pa or more, more preferably 1.0×10 8 Pa or more, still more preferably 1.3×10 8 Pa or more is optimal.

[0099] This is because when the storage modulus at 200°C is less than 1.0×10 7 Pa, sufficient heat resistance cannot be obtained due to frictional heat caused by friction, and thus deformation such as dents and distortions will occur on the receiving plate of the thrust bearing 6. The upper limit value of the storage modulus of the resin film 7 for thrust bearings at 250°C is not particularly limited, but in practical applications, it is preferably 1.0×10 10 Pa or less.

[0100] The rigidity of the resin film 7 for thrust bearings can be evaluated by the tensile modulus in an environment of 23°C ± 2°C and 50% RH ± 5% RH. This tensile modulus can be measured with respect to the MD and TD in accordance with JIS K7127. The tensile modulus of the resin film 7 for thrust bearings is 2000 MPa or more and 2700 MPa or less, preferably 2050 MPa or more and 2650 MPa or less, more preferably 2100 MPa or more and 2600 MPa or less, still more preferably 2150 MPa or more and 2550 MPa or less, and most preferably 2200 MPa or more and 2500 MPa or less.

[0101] This is because when the tensile modulus is less than 2000 MPa, problems will occur in the rigidity of the receiving plate of the thrust bearing 6, leading to the occurrence of dents and distortions due to the weight of the rotating shaft 2 of the motor 1. On the other hand, when the tensile modulus exceeds 2700 MPa, it will be time-consuming to process the receiving plate of the thrust bearing 6 using the resin film 7 for thrust bearings, resulting in a very high processing cost.

[0102] The slidability of the resin film 7 for thrust bearings can be evaluated by the static friction coefficient and the dynamic friction coefficient in an environment of 23°C ± 2°C and 50% RH ± 5% RH. The static friction coefficient and the dynamic friction coefficient of this resin film 7 for thrust bearings can be measured with respect to MD and TD in accordance with JIS K7125.

[0103] The static friction coefficient (MD, TD) of the resin film 7 for thrust bearings is optimally 0.10 or more and 0.50 or less, preferably 0.15 or more and 0.45 or less, more preferably 0.20 or more and 0.40 or less, and still more preferably 0.25 or more and 0.35 or less. This is because when the static friction coefficient exceeds 0.50, the slidability is low, so the friction is large and deformation such as dents and distortions occurs in the receiving plate of the thrust bearing 6 due to frictional heat. In addition, problems occur in terms of achieving a long service life with wear.

[0104] Also, the dynamic friction coefficient (MD, TD) of the resin film 7 for thrust bearings is optimally 0.05 or more and 0.50 or less, preferably 0.07 or more and 0.40 or less, more preferably 0.10 or more and 0.30 or less, and still more preferably 0.12 or more and 0.25 or less. This is based on the reason that when the dynamic friction coefficient exceeds 0.50, when used as the receiving plate of the thrust bearing 6, due to the low slidability, the friction is large and deformation such as dents and distortions occurs in the receiving plate due to frictional heat. In addition, it is based on the reason that problems occur in terms of achieving a long service life with wear.

[0105] According to the above, since the resin film 7 for thrust bearings is formed of a crystalline thermoplastic polyimide resin instead of a polyacetal resin or a polyamide-imide resin, excellent wear resistance, toughness, heat resistance, solvent resistance, dimensional stability, low water absorption, flame retardancy, electrical insulation, recyclability, mechanical properties, etc. can be obtained. Therefore, it is possible to effectively prevent deformation, cracking, etc. from occurring in the resin film 7 for thrust bearings due to frictional heat during sliding, and moreover, it is possible to appropriately support the load of the rotating shaft 2 of the motor 1.

[0106] In addition, since it is not necessary to improve the heat resistance of the resin film 7 for the thrust bearing by heat treatment after molding, the thrust bearing can be provided at low cost. Further, since the taper wear amount of the resin film 7 for the thrust bearing is in the range of 1 mg or more and 50 mg or less, it is possible to effectively wipe out the possibility that the receiving plate is deformed due to heat generation caused by friction between the rotary shaft 2 of the motor 1 and the receiving plate of the thrust bearing 6. In addition, since the wear amount is small, a long service life can be highly expected.

[0107] In the above embodiment, a plurality of herringbone grooves 4 are arranged and formed on the peripheral surface of the rotary shaft 2. However, a plurality of herringbone grooves 4 may be arranged and formed on the inner diameter surface of the radial bearing 5, and a lubricant 8 may be collected in the plurality of herringbone grooves 4 to generate hydrodynamic pressure to support the rotary shaft 2 with high precision. Further, screw-shaped grooves other than the herringbone grooves 4 may be arranged and formed, or the herringbone grooves 4 may be omitted when not particularly necessary.

[0108] In the above embodiment, the molten crystalline thermoplastic polyimide resin is pressed against the cooling roll 18 by the pressure roll 17 to be adhered, but it is not limited thereto. For example, an electrostatic printing method (or a pinning method) or an air knife may be adopted to adhere the molten strip-shaped crystalline thermoplastic polyimide resin to the cooling roll 18. Further, when cooling the molten crystalline thermoplastic polyimide resin, a method of adhering the molten strip-shaped crystalline thermoplastic polyimide resin to a metal belt or the like, spraying water on the molten strip-shaped crystalline thermoplastic polyimide resin, or putting the molten strip-shaped crystalline thermoplastic polyimide resin into water may be adopted.

[0109] In addition, at least one of the front and back surfaces of the resin film 7 for the thrust bearing can be subjected to plasma treatment such as corona treatment, vacuum plasma treatment or atmospheric pressure plasma treatment, surface activation treatment such as ultraviolet treatment or itro treatment. Further, by performing printing, various functional coatings, lamination, etc., various properties can be added to the resin film 7 for the thrust bearing to further improve its value.

[0110] It is also possible to divide the melt extrusion molding machine 10 into first, second, and third melt extrusion molding machines to produce the resin film 7 for a thrust bearing having a three-layer structure. Further, the receiving plate of the thrust bearing 6 may be the resin film 7 for a thrust bearing alone, or may have a multilayer structure of the resin film 7 for a thrust bearing, or may have a multilayer structure with other resin films or resin sheets other than the resin film 7 for a thrust bearing. Furthermore, all the technologies described in this specification are subject to obtaining rights by amendment, divisional application, etc.

Example

[0111] Hereinafter, examples of the resin sheet for a thrust bearing and a method for manufacturing the same according to the present invention will be described together with comparative examples. 〔Example 1〕 First, as a crystalline thermoplastic polyimide resin for a molding material, a crystalline thermoplastic polyimide resin composed of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride [manufactured by Mitsui Chemicals, Inc., product name: Aurum PL450C (hereinafter referred to as "PL450C")] was prepared, and this PL450C was put into a dehumidifying hot air dryer heated to 200°C and dried for 12 hours or more. This crystalline thermoplastic polyimide resin composed of 4,4'-bis(3-aminophenoxy)biphenyl and pyromellitic dianhydride will hereinafter be abbreviated as TPI resin (A).

[0112] The apparent melt viscosity of PL450C, which is a crystalline thermoplastic polyimide resin, was measured using a constant load extrusion capillary rheometer [manufactured by Shimadzu Corporation: product name Shimadzu Flow Tester CFT-500D]. Specifically, 1.5 cm of PL450C dried at 200°C for 12 hours or more 3 was filled into a cylinder equipped with a die (diameter: 1 mm, length: 10 mm), and a plunger with an area of 1 cm 2 was attached to the upper part of this cylinder. When the temperature of the cylinder reached 390°C, it was preheated for 5 minutes, and immediately after the preheating, a load of 50 kgf was applied to melt and flow out the PL450C to measure its apparent melt viscosity. The method for measuring the apparent melt viscosity of PL450C was the same for the following examples.

[0113] The Tm of PL450C was measured using a differential scanning calorimeter [manufactured by SII NanoTechnology Inc., product name: high-sensitivity differential scanning calorimeter X-DSC7000], in accordance with JIS K7121, under the condition of a heating rate of 10 °C / min. As a result of the measurement, the Tm of the PL450C resin was 385 °C.

[0114] After drying PL450C, it was confirmed that the moisture content of the dried PL450C was 300 ppm or less. This PL450C was put into a single-screw melt extrusion molding machine equipped with a T-die shown in Fig. 2 and melt-kneaded. The melt-kneaded PL450C was continuously extruded from the T-die of the single-screw melt extrusion molding machine and cooled with a cooling roll, thereby forming a belt-shaped TPI resin (A) film, which is a resin sheet for a thrust shaft. The moisture content of PL450C was confirmed by the Karl Fischer titration method using a trace moisture measuring device [manufactured by Nitto Seiko Analytic Co., Ltd., product name: CA-310 type]. The moisture content was measured by the same method for the following examples.

[0115] When charging PL450C into the single-screw melt extrusion molding machine, nitrogen gas was supplied at 8 L / min through an inert gas supply pipe. Also, the cylinder temperature of the single-screw melt extrusion molding machine was 350 to 420 °C, the temperature of the T-die was 420 °C, the temperature of the connecting pipe connecting the single-screw melt extrusion molding machine and the T-die was 420 °C, and the gear pump and the polymer filter were each adjusted to 420 °C. When measuring the temperature of the molten molding material from the resin temperature at the inlet of the T-die, it was 423 °C.

[0116] Next, after melt-extruding the TPI resin (A) film, both side portions of the continuous TPI resin (A) film were cut with a slit blade and sequentially wound around the winding tube of a winder to produce the TPI resin (A) film. At this time, the TPI resin (A) film was sequentially wound around a pair of pressure-bonding rolls made of silicone rubber, a plurality of metal cooling rolls having unevenness on the peripheral surface and heated to 240 °C, and a 6-inch winding tube located downstream thereof, and was sandwiched between the pair of pressure-bonding rolls and the plurality of cooling rolls.

[0117] Once the TPI resin (A) film, which is a resin sheet for thrust shafts, was obtained, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of the obtained TPI resin (A) film were evaluated and listed in Table 1. The wear characteristics of the TPI resin (A) film were evaluated by the taper wear amount, the toughness by the maximum tensile strength and the elongation at break, the heat resistance by the storage modulus at 250 °C, the rigidity by the tensile modulus, and the slidability by the static and dynamic friction coefficients.

[0118] · Thickness of the resin sheet (film) for thrust shafts The thickness of the resin sheet for thrust shafts was measured using a micrometer [Product name: Coolant-proof micrometer, Mitutoyo Corporation, code MDC-25PJ] in an environment of temperature 23 °C ± 2 °C and relative humidity 50% RH ± 5% RH. For this measurement, 10 arbitrary locations in the width direction of the resin sheet for thrust shafts (the direction perpendicular to the extrusion direction (hereinafter abbreviated as "TD")) were measured, and the average value was taken as the sheet thickness.

[0119] · Wear characteristics of the resin sheet for thrust shafts The wear characteristics of the resin sheet for thrust shafts were evaluated by the taper wear amount. This taper wear amount was measured under the conditions of temperature 23 °C ± 2 °C, relative humidity 50% RH ± 5% RH, in accordance with JIS K7204, with a wear wheel of H22, a load of 1 kg, a rotation number of 1000 rotations, and a rotation speed of 60 rpm.

[0120] · Toughness of the resin sheet for thrust shafts The toughness of the resin sheet for thrust shafts was evaluated by the maximum tensile strength and the elongation at break at 23 °C. These maximum tensile strength and elongation at break were measured for the extrusion direction (hereinafter abbreviated as "MD") and TD. The measurement was carried out in accordance with JIS K7127, under the conditions of a tensile speed of 50 mm / min, temperature 23 °C ± 2 °C, and relative humidity 50% RH ± 5% RH.

[0121] · Heat resistance of the resin sheet for thrust shafts The heat resistance of the resin sheet for thrust shaft bearings was evaluated by the storage elastic modulus (E’) of the resin sheet for thrust shaft bearings at 250°C. This storage elastic modulus was measured for the MD and TD of the resin sheet for thrust shaft bearings.

[0122] Specifically, when measuring the storage elastic modulus of the MD of the resin sheet for thrust shaft bearings, it was cut into a size of MD: 60 mm × TD: 6 mm, and when measuring the storage elastic modulus of TD, it was cut into a size of MD: 6 mm × TD: 60 mm for measurement. During the measurement, using a tensile mode with a viscoelastic spectrometer [manufactured by TA Instruments Japan, product name: RSA-G2], it was measured under the conditions of a frequency of 1 Hz, a strain of 0.1%, a heating rate of 3°C / min, a measurement temperature range of -60 to 360°C, and a check interval of 21 mm, and the storage elastic modulus at 250°C was obtained.

[0123] · Rigidity of the resin sheet for thrust shaft bearings The rigidity of the resin sheet for thrust plate bearings was evaluated by the tensile elastic modulus at 23°C. This tensile elastic modulus was measured for the MD and TD. The measurement was carried out in accordance with JIS K7127 under the conditions of a tensile speed of 50 mm / min, a temperature of 23°C ± 2°C, and a relative humidity of 50% RH ± 5% RH.

[0124] · Sliding property of the resin sheet for thrust shaft bearings The sliding property of the resin sheet for thrust shaft bearings was evaluated by measuring the static friction coefficient and the dynamic friction coefficient. These static and dynamic friction coefficients were measured in accordance with JIS K7125.

[0125] Specifically, using a surface property measuring machine [manufactured by Shin-Tech Co., Ltd., product name: HEDON-14], it was measured under the conditions of a test speed of 100 mm / min, a load of 200 g, and a contact area of 63.5 mm × 63.5 mm in an environment of 23°C ± 2°C and 50% RH ± 5% RH. Then, the resin sheet for thrust shaft bearings was fixed on the moving table side, a φ10 mm ball indenter was fixed on the fixed table side, and a load of 200 g was applied to measure the static friction coefficient and the dynamic friction coefficient respectively at a speed of 100 mm / min.

[0126] 〔Example 2〕 Basically, it is the same as Example 1, but a TPI resin (A) film with a different thickness from that of Example 1 was molded. Both sides of this TPI resin (A) film were cut with a slit and sequentially wound around the winding tube of a winder to produce a TPI resin (A) film. After producing the TPI resin (A) film in this way, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this TPI resin (A) film were evaluated by the same method as in Example 1 and are shown in Table 1.

[0127] 〔Example 3〕 Basically, it is the same as Example 1, but a TPI resin (A) film with a different thickness from those of Examples 1 and 2 was molded. Both sides of this TPI resin (A) film were cut with a slit and sequentially wound around the winding tube of a winder to produce a TPI resin (A) film. After producing the TPI resin (A) film in this way, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this TPI resin (A) film were evaluated by the same method as in Example 1 and are shown in Table 1.

[0128] 〔Example 4〕 As a commercially available crystalline thermoplastic polyimide resin, a crystalline thermoplastic polyimide resin composed of an aliphatic diamine and pyromellitic acid [manufactured by Mitsubishi Gas Chemical Company, product name: Surplime TO-65 (hereinafter referred to as "TO-65")] was prepared. This crystalline thermoplastic polyimide resin composed of an aliphatic diamine and pyromellitic acid was put into a dehumidifying dryer heated to 160°C and dried for 12 hours or more. This crystalline thermoplastic polyimide resin composed of an aliphatic diamine and pyromellitic acid will hereinafter be referred to as TPI resin (S).

[0129] The apparent melt viscosity of TO-65 at 350°C was measured at 390°C in Example 1, but in Example 4, it was changed to 350°C for measurement. As a result of the measurement, the apparent melt viscosity of TO-65 was 1530 Pa·s.

[0130] The Tm of TO-65 was measured using a differential scanning calorimeter [manufactured by SII NanoTechnology Inc., product name: high-sensitivity differential scanning calorimeter X-DSC7000], in accordance with JIS K7121, under the condition of a heating rate of 10 °C / min. As a result of the measurement, the Tm of TO-65 was 324 °C.

[0131] After drying TO-65, it was confirmed that the moisture content of the dried TO-65 was 300 ppm or less. This TO-65 was then charged as a molding material into a single-screw melt extrusion molding machine equipped with a T-die and melt-kneaded. The melt-kneaded TO-65 was continuously extruded from the T-die of the single-screw melt extrusion molding machine and cooled to form a strip-shaped TPI resin (S) film, which is a resin sheet for thrust shafts.

[0132] The moisture content of TO-65 was measured in the same manner as in Example 1. Also, when charging TO-65 into the single-screw melt extrusion molding machine, nitrogen gas was supplied at 20 L / min through an inert gas supply pipe. The cylinder temperature of the single-screw melt extrusion molding machine was 210 to 360 °C, the temperature of the T-die was 360 °C, the temperature of the connecting pipe connecting the single-screw melt extrusion molding machine and the T-die was 365 °C, and the gear pump was adjusted to 365 °C. In addition, when measuring the temperature of the molten molding material from the resin temperature at the inlet of the T-die, it was 363 °C.

[0133] Next, after melt-extruding the TPI resin (S) film of TO-65, both side portions of the continuous TPI resin (S) film were cut with a slit blade and sequentially wound around the winding tube of a winder to produce a TPI resin (S) film. At this time, the TPI resin (S) film was sequentially wound around a pair of pressure rollers made of silicone rubber, a plurality of metal cooling rollers having unevenness on the peripheral surface and heated to 140 °C, and a 6-inch winding tube located downstream thereof, and sandwiched between the pair of pressure rollers and the plurality of cooling rollers.

[0134] After thus producing the TPI resin (S) film of TO-65, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this TPI resin (S) film were evaluated in the same manner as in Example 1 and are shown in Table 1.

[0135] Example 5 Basically, it is the same as Example 4, but a TPI resin (S) film with a different thickness from that of Example 4 was molded. Both side portions of this TPI resin (S) film were cut with a slit and sequentially wound around a winding tube of a winder to produce a TPI resin (S) film. After the TPI resin (S) film was produced, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this TPI resin (S) film were evaluated by the same method as in Example 1 and summarized in Table 2.

[0136] Comparative Example 1 First, as an amorphous thermoplastic polyimide resin for a molding material, a commercially available polyetherimide resin [product name: ULTEM1010 - 1000 - NB (hereinafter abbreviated as "1010") manufactured by SABIC] was prepared. This polyetherimide resin was put into a dehumidifying hot air dryer heated to 160 °C and dried for 12 hours or more. This polyetherimide resin is hereinafter abbreviated as PEI resin. Also, 1010 is a condensation polymer of 4,4'-[isopropylidene bis(p - phenyloxy)] diphthalic dianhydride and m - phenylenediamine. When the apparent melt viscosity of this 1010 at 370 °C was measured, it was 455 Pa·s.

[0137] When the apparent melt viscosity of 1010, which is an amorphous thermoplastic polyimide resin, was measured by the same method as in Example 1, it was 471 Pa·s. Also, when the Tm of 1010 was measured by the same method as in Example 1, no absorption related to the Tm of 1010 was observed. The water content of the dried 1010 was measured by the same method as in Example 1, and it was confirmed that the water content of the dried 1010 was 300 ppm or less.

[0138] After drying 1010 in this way, this 1010 was put into a single - screw melt extrusion molding machine equipped with a T - die as a molding material and melt - kneaded. The melt - kneaded 1010 was continuously extruded from the T - die of the single - screw melt extruder and cooled to form a strip - shaped PEI resin film, which is a resin sheet for a thrust shaft.

[0139] The cylinder temperature of the single-screw melt extrusion machine was 310 - 370 °C, the temperature of the T-die was 370 °C, the temperature of the connecting pipe connecting the single-screw melt extrusion machine and the T-die was 375 °C, and the gear pump and the polymer filter were each adjusted to 375 °C. Also, when charging 1010 into the single-screw melt extrusion machine, nitrogen gas was supplied at 13 L / min through the inert gas supply pipe. When measuring the temperature of the molten molding material from the resin temperature at the T-die inlet, it was 375 °C.

[0140] Next, after melt-extruding the 1010 PEI resin film, both side portions of this PEI resin film were cut with a slit blade and sequentially wound around the winding pipe of the winder to produce a PEI resin film. At this time, the PEI resin film was successively wound around a pair of pressure-bonding rolls made of silicone rubber, a plurality of cooling rolls made of metal heated to 160 °C with unevenness on the peripheral surface, and a 6-inch winding pipe located downstream thereof, and was sandwiched between the pair of pressure-bonding rolls and the plurality of cooling rolls. When a 1010 PEI resin film was obtained, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this PEI resin film were evaluated in the same manner as in Example 1 and summarized in Table 2.

[0141] 〔Comparative Example 2〕 First, as a commercially available amorphous thermoplastic polyimide resin, the PEI resin of Comparative Example 1 [Product name: 1010] was changed to ULTEM CRS5001-1000-NB [manufactured by SABIC; hereinafter abbreviated as "CRS5001"], and a PEI resin film having a different thickness from that of Comparative Example 1 was formed into a strip shape in the same manner as in Comparative Example 1. CRS5001 is a polycondensate of 4,4'-[isopropylidene bis(p-phenyleneoxy)diphthalic dianhydride] and p-phenylenediamine.

[0142] At this time, CRS5001 was put into a dehumidifying hot air dryer heated to 160°C and dried for 12 hours. When the apparent melt viscosity of this CRS5001 at 370°C was measured by the same method as in Example 1, the melt viscosity was 977 Pa·s. Also, as a result of measuring the Tm of CRS5001 by the same method as in Example 1, no absorption regarding the Tm of CRS5001 was observed. The moisture content of the molding material dried by the same method as in Example 1 was measured, and it was confirmed that the water content of the dried CRS5001 was 300 ppm or less.

[0143] After confirmation, a PEI resin film of CRS5001 was produced by the same method as in Example 1. Both side portions of this PEI resin film were cut with a slit blade and sequentially wound around the winding tube of a winder to produce a PEI resin film. When the PEI resin film of CRS5001 was obtained, the thickness, wear characteristics, toughness, heat resistance, rigidity, and slidability of this PEI resin film were evaluated by the same method as in Example 1 and summarized in Table 2.

[0144]

Table 1

[0145]

Table 2

[0146] 〔Results〕 In the case of each example, the taper wear amount of the resin sheet for the thrust shaft at 23°C was 35 mg or less, and excellent wear resistance characteristics could be ensured. Also, the maximum tensile strength was 50 MPa or more and the elongation at tensile break was 120% or more, having sufficient toughness. Furthermore, the storage elastic modulus of the resin sheet for the thrust shaft at 250°C was 1.56×10 8 Pa or more in both the MD and TD directions, and no decrease in heat resistance was observed at all.

[0147] In contrast, in the case of Comparative Examples 1 and 2, since the resin sheet for the thrust shaft was manufactured from a polyetherimide resin, which is an amorphous thermoplastic polyimide resin, the taper wear amount was very large, 88.9 mg or more, and the wear characteristics were extremely poor. Also, since the elongation at break in tension was 90% or less, a problem occurred in toughness. Furthermore, since the storage elastic modulus at 250°C was less than 1.0×10 7 Pa both in the MD and TD directions, only insufficient heat resistance was obtained. From the above results, it was found that in the case of Comparative Examples 1 and 2, it is inappropriate as a resin sheet for the thrust shaft.

Industrial Applicability

[0148] The resin sheet for the thrust shaft and the manufacturing method thereof according to the present invention are used in fields such as information devices, office equipment, multimedia devices, home appliances, and air-conditioning equipment.

Explanation of Symbols

[0149] 1 Motor (Actuator) 2 Rotating shaft 3 Lower end (End) 4 Herringbone groove (Groove) 5 Radial bearing 6 Thrust bearing 7 Resin film for thrust shaft (Resin sheet for thrust shaft) 8 Lubricant 9 Molding material 10 Melt extrusion molding machine 14 Die 17 Pressure-bonding roll 18 Cooling roll 20 Take-up machine

Claims

1. A resin sheet for a thrust bearing that slidably supports an end portion of a rotating shaft of an actuator, which is formed from a molding material containing at least a crystalline thermoplastic polyimide resin, and has a taper wear amount at 23°C of 1 mg or more and 50 mg or less when measured in accordance with JIS K7204. The resin sheet for a thrust bearing is characterized by this.

2. The resin sheet for a thrust bearing according to Claim 1, wherein the maximum tensile strength at 23°C is 50 MPa or more and 250 MPa or less when measured in accordance with JIS K7127, and the elongation at break in tension at 23°C is 100% or more and 500% or less when measured in accordance with JIS K7127.

3. When the heat resistance is measured by the storage elastic modulus at 250°C, it is 1×10 ７ Pa or more and 1×10 １０ Pa or less, and when the tensile elastic modulus at 23°C is measured in accordance with JIS K7127, it is 2000 MPa or more and 2700 MPa or less. The resin sheet for a thrust shaft according to claim 1 or 2.

4. The actuator consists of a motor. The rotating shaft of this motor is supported through a radial bearing, and a groove is cut out in the circumferential direction in either the circumferential surface of the rotating shaft or the inner diameter surface of the radial bearing. The end portion of the rotating shaft protruding from the radial bearing is slidably supported by a thrust bearing. The resin sheet for a thrust bearing according to Claim 1 or 2.

5. A method for manufacturing a resin sheet for a thrust bearing according to Claim 1 or 2, characterized by melt-kneading a molding material containing at least a crystalline thermoplastic polyimide resin, extruding this molding material in a substantially strip shape from a die, and bringing the extruded molding material into contact with a cooling roll to form a resin sheet for a thrust bearing.

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