JP2002295626A - Resinous nut - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resinous nut for a feed screw mechanism, capable of preventing obstruction due to electrifying and having superior friction and abrasion characteristics and is capable of eliminating the risk of damaging a spiral shaft. SOLUTION: This thermoplastic resin composition is composed of the resin A, composed mainly 40-90 wt.%, polybutylene terephthalate or polyphenylene sulfide 5-30 wt for carbon fiber B, and 5-30 wt.% spherical graphite carbon fine powder obtained by burning the spherical fine powder phenol resin in the non-oxidization gas atmosphere at 800-2,000 deg.C, and the total of these three components is 100 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin nut for a feed screw mechanism used for a feed mechanism or a positioning mechanism of office equipment, industrial equipment, and the like.

[0002]

2. Description of the Related Art With regard to feed mechanisms for office equipment, industrial equipment, etc., feed screw mechanisms are frequently used as devices for converting rotary motion into linear motion and as accurate positioning devices based on the motion. Among them, a feed screw mechanism using a resin nut is structurally simpler than a feed screw mechanism using a ball bearing, but its use range is expanding.

Conventionally, as a resin nut for a feed screw mechanism, a polyacetal resin in which polytetrafluoroethylene powder is dispersed (JP-A-51-34357) and an ultrahigh-molecular-weight polyethylene (JP-A-Heisei 1-43) are used.
JP-A 1-220127), a mixture of a thermoplastic polyimide resin and graphite and a phenolic resin (Japanese Patent Laid-Open No. 6-1).
No. 93701), a polyphenylene sulfide resin to which a tetrafluoroethylene resin, an aromatic polyamide fiber and artificial graphite are added (Japanese Patent Application Laid-Open No. 7-41780), and a product using a thermosetting polyimide resin (Japanese Patent Application Laid-Open No.
-203650) and the like.

However, when a thermosetting resin is used, the workability is poor, such as the necessity of cutting, and the thermoplastic resin is an extremely expensive material such as a polyimide resin. Hinders Furthermore, since each of them is made of resin, electrostatic charging attracts dust and the like, which lowers sliding characteristics and the like, and there is a risk that the charging may cause an abnormality in an electronic circuit near the feed screw mechanism. .

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art such as workability and mass productivity, there is no obstacle due to electrification, excellent friction and wear characteristics, and an attack on a helical shaft. An object of the present invention is to provide a resin nut for a feed screw mechanism having no resistance.

[0006]

SUMMARY OF THE INVENTION A resin for a feed screw mechanism which solves the above-mentioned problems, has excellent workability and mass productivity, has no obstacles due to charging, has excellent friction and wear characteristics, and has no aggression to the helical shaft. As a result of intensive studies to provide a nut, injection molding is possible and (A) a resin mainly composed of polybutylene terephthalate or a resin mainly composed of polyphenylene sulfide 40 to 90% by weight,
(B) 5 to 30% by weight of carbon fiber, (C) spherical fine powder phenol resin in a non-oxidizing gas atmosphere at 800 to 2000 ° C.
Consists of a thermoplastic resin composition comprising 5 to 30% by weight of the spherical graphitized carbon fine powder obtained by calcination in which the total of the three components is 100% by weight. The inventors succeeded in finding that a resin nut having a volume specific resistivity of 9 × 10 ⁴ Ω · m or less was used to form a resin nut to achieve the object.

That is, according to the present invention, in a nut of a feed screw mechanism which moves on the axis of a helical shaft in accordance with the rotation of the axis, (A) a resin mainly composed of polybutylene terephthalate or a resin mainly composed of polyphenylene sulfide 40 to 90% by weight %, (B) 5 to 30% by weight of carbon fiber, and (C) 5 to 30% by weight of spherical graphitized carbon fine powder obtained by sintering phenolic resin at 800 to 2000 ° C. in a non-oxidizing gas atmosphere. An injection molded resin nut, comprising a thermoplastic resin composition comprising three components, wherein the total of the three components is 100% by weight. Hereinafter, the present invention will be described in detail.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a polyester resin or a polyphenylene sulfide resin mainly composed of polybutylene terephthalate is used as a base resin. These resins are suitable for injection molding applications,
Moreover, it is excellent as a resin having no dimensional change due to water absorption.

Here, the polyester resin mainly composed of polybutylene terephthalate mainly includes a dicarboxylic acid mainly composed of terephthalic acid or an ester-forming derivative thereof and a diol mainly composed of 1,4-butanediol or an ester-forming derivative thereof. It is a polymer, a copolymer or a blend of a polymer and a copolymer obtained by a condensation reaction as a component.

Here, the dicarboxylic acid component further includes isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, bisbenzoic acid, bis (p-carboxyphenyl) methane, anthracenedicarboxylic acid Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenoxyethane dicarboxylic acid, adipic acid, sebacic acid, azelaic acid, dodecane diacid, 1,3-cyclohexane dicarboxylic acid, 1,
4-cyclohexanedicarboxylic acid or an ester-forming derivative thereof may be used as a mixture.

On the other hand, diol components include ethylene glycol, propylene glycol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, decamethylene glycol, cyclohexanedimethanol, cyclohexanediol, and a molecular weight of 400-6.
00 long-chain glycols or their ester-forming derivatives may be used in admixture.

The polyphenylene sulfide resin is described in US Pat. No. 3,354,129 (corresponding patent, Japanese Patent Publication No. 45-45).
No. -3368), obtained by reacting p-dichlorobenzene and sodium disulfide with each other in an N-methylpyrrolidone solvent under pressure at 160 to 250 ° C., and further obtaining the obtained resin by air. Crosslinking by medium heating or introduction of a functional group by an acid anhydride or isocyanate may be used. Idemitsu Petrochemical “Idemitsu PPS” and Dainippon Ink and Chemicals “DIC · P”
Unfilled resin such as “PS” and “Toprene” of Tonen Kagaku can be used.

As the carbon fiber used in the present invention, a PAN obtained by heating and firing a commercially available acrylic fiber such as polyacrylonitrile fiber in a non-oxidizing gas atmosphere is used.
Pitch fibers obtained by melting and spinning petroleum pitch by-produced during the refining of petroleum, etc., and then heating and firing the pitch fibers in a non-oxidizing gas atmosphere. Can be used without any problem. In addition, in the form of the raw material used, any form such as short fiber, long fiber, yarn, cloth, milled, and cotton can be used.
It is preferable to be a chopped strand in which 5000 single fibers are converged and cut into a length of 3 to 10 mm. In addition, the surface of these carbon fibers may be subjected to a coupling treatment of a silane type, an epoxy type, a titanium type or the like.

The amount of carbon fiber added is 5 to 30% by weight.
Must be within the range. When the content is less than 5% by weight, the volume resistivity is extremely high, and charging is recognized. When the content is more than 30% by weight, the surface of the resin screw obtained by injection molding is roughened to increase friction.

The spherical graphitized carbon fine powder obtained by calcining the spherical fine powder phenol resin used in the present invention at 800 to 2000 ° C. in a non-oxidizing gas atmosphere is a mixture of 15 to 22% by weight hydrochloric acid and 7% at room temperature. While stirring a mixed aqueous solution consisting of -15% by weight of formaldehyde, a mixture of phenol or a phenol and a nitrogen-containing compound such as urea, melamine, or aniline is added to the mixed aqueous solution at a ratio of 1/15 or less, Stirring was stopped before the turbidity was formed in the reaction system, and the mixture was allowed to stand to produce and precipitate a pink spherical fine-grained phenol resin in the reaction system. After completion of the reaction by heating and raising the temperature to the temperature described above, washing with water is carried out, followed by neutralization with a 0.1 to 1% by weight aqueous ammonia solution, followed by washing, dehydration and drying. The phenol resin in the form of fine spherical powder obtained by the method described in JP-A-17114 or the like is fired at 800 to 2000 ° C. in a non-oxidizing gas atmosphere consisting of a single or mixed gas composition of nitrogen, helium, argon, hydrogen and the like. It is obtained by this.

As the phenol resin in the form of spherical fine powder before firing, there is no problem if a commercially available Bellpearl R800 manufactured by Kanebo Co., Ltd. can be used. You may get it. Further, the surface of the obtained spherical graphitized carbon fine powder may be subjected to a silane-based, epoxy-based, or titanium-based coupling treatment.

The addition amount of the spherical graphitized carbon fine powder is as follows.
It needs to be 5 to 30% by weight. If it is less than 5% by weight, the effect of reducing friction is lacking. Since the present spherical graphitized carbon fine powder is a very bulky substance, it is difficult to knead an amount exceeding 30% by weight. Further, even if the amount exceeds 30% by weight, evenly dispersed components cannot be obtained and cannot be put to practical use.

When carbon fiber is singly compounded, relatively good characteristics are exhibited, but the helical shaft, which is the mating material of the resin nut, is greatly worn. Further, when the spherical graphitized carbon fine powder is compounded alone, it is not preferable because the amount of abrasion of the resin is large and the resin is easily charged. Therefore, in the present invention, it is important that carbon fiber and carbon fine powder coexist in the resin.

As a means for compounding the carbon fiber and the spherical graphitized carbon powder to the base resin described above, a melt extruder such as a screw type extruder or a Banbury mixer can be used. Machine is most suitable. Further, the raw materials may be individually supplied to the melt mixer, or may be mixed in advance with a tumbler type blender, a rocking mixer, a shell mixer or the like and then supplied to the melt mixer. The temperature at the time of melt mixing is preferably from 250 to 290 ° C. for a polyester resin mainly composed of polybutylene terephthalate, and preferably from 300 to 350 ° C. for a polyphenylene sulfide resin.

In the present invention, known modifiers such as an antioxidant, a heat stabilizer, an ultraviolet stabilizer, an ultraviolet absorber, a pigment, a dye, a release agent, and a nucleating agent are used as long as the object of the present invention is not impaired.
It may be added to the thermoplastic resin composition.

Injection molding is used to obtain a resin nut from the resin composition obtained as described above. In the case of a polyester resin mainly composed of polybutylene terephthalate, the temperature condition at the time of injection molding is as follows.
It is preferable to mold at 90 ° C and a mold temperature of 60 to 100 ° C. In the case of polyphenylene sulfide resin, the resin temperature is 300 to 350 ° C and the mold temperature is 120 to 160 ° C.
It is preferable to carry out in. In any case, when the resin temperature and the mold temperature are low, the surface of the obtained resin nut tends to be rough and the friction is undesirably increased. Also,
Excessively increasing the resin temperature is not preferable because it leads to decomposition of the resin, and excessively increasing the mold temperature is not preferable from the viewpoint of industrial production because only the cooling time becomes longer.

[0022]

The present invention will be described below in detail with reference to examples. Examples 1 to 10, Comparative Examples 1 to 6 Polyester resin mainly composed of polybutylene terephthalate [PBT720 manufactured by Kanebo Gosen Co., Ltd.], carbon fiber [Vesfight HTA-C manufactured by Toho Rayon Co., Ltd.]
6-NRS] and spherical fine powder phenol resin (Bellepearl R-800 manufactured by Kanebo Co., Ltd.) under nitrogen atmosphere.
Spheroidal graphitized carbon powder obtained by firing at 000 ° C. was mixed in a tumbler blender at the ratio shown in Table 1, and then a twin screw kneader [TEX-30α manufactured by Nippon Steel Works Ltd.]
Cylinder temperature 270 ° C, screw rotation speed 200
The mixture was melt-kneaded at a rpm of 30 kg / hr and the strands coming out of the dies were cooled in water and then pelletized with a pelletizer to obtain a molding resin. The kneading conditions are shown according to the remarks in Table 1.

Next, the resin was dried at 140 ° C. for 4 hours, and then, with an injection molding machine set at a cylinder temperature of 270 ° C., a mold controlled at a temperature of 80 ° C. and having a diameter of 50 mm and a thickness of 3 mm.
mm disk-shaped test pieces were obtained. The test piece obtained was used as a substitute test for the feed screw mechanism, assuming that the test piece was a resin nut and the mating material was a helical shaft, and a Suzuki type friction and wear tester (Model EFM-III-F manufactured by Orientec Co., Ltd.) was used. , Using SC50 steel as the mating material, load 14.7N
/ Cm ² , sliding speed 500mm / sec, sliding distance 10
The coefficient of kinetic friction, the amount of resin wear, and the amount of steel wear when the test was performed under km conditions were measured, and the results are summarized in Table 2.

Table 2 also shows ASTM D25
The results of the evaluation of the charging property based on the volume specific resistance value by the method 7 and the evaluation of the chargeability based on whether or not the charcoal ash was attracted when the charcoal ash was approached immediately after rubbing the disc-shaped test piece 100 times with a polyester cloth were shown.

Examples 11 to 20, Comparative Examples 7 to 12 Polyphenylene sulfide resin resin [Tonen Chemical Co., Ltd.
TORPEN T-4], carbon fiber (Vesfight HTA-C6-NRS, manufactured by Toho Rayon Co., Ltd.) and spherical fine powder phenol resin (Bellpearl R-800, manufactured by Kanebo Co., Ltd.) are fired at 2000 ° C. in a nitrogen atmosphere. The spheroidal graphitized carbon powder obtained as described above was mixed in a tumbler blender at the ratio shown in Table 1, and then the cylinder temperature was 320 ° C. and the screw rotation number was increased with a twin screw kneader [TEX-30α manufactured by Nippon Steel Works, Ltd.]. 200 rpm, discharge amount 30
The mixture was melt-kneaded at a rate of kg / hr, and the strand coming out of the die was cooled in water and then pelletized with a pelletizer to obtain a molding resin. The kneading conditions are shown according to the remarks in Table 1.

Next, after drying the resin at 140 ° C. for 4 hours, a disc-shaped test piece having a diameter of 50 mm and a thickness of 3 mm was molded with an injection molding machine set at a cylinder temperature of 320 ° C. in a mold controlled at a temperature of 140 ° C. Obtained. The obtained test pieces were evaluated for dynamic friction coefficient, resin wear, steel wear, volume specific resistance, and chargeability in the same manner as in Examples 1 to 10, and the results were summarized in Table 2. .

[0027]

[Table 1]

[0028]

[Table 2]

Examples 21 to 24, Comparative Examples 13 to 16 Using the resin compositions of Examples 2, 3, 12, 13 and 5, and Comparative Examples 3, 4, 11, and 12, respectively, resin nuts were formed by injection molding. Create a spiral axis (effective spiral length 20
cm) with a resin nut, then rotate the helical shaft,
Table 3 shows the situation after the resin nut was reciprocated 10,000 times.

[0030]

[Table 3]

[0031]

The resin nut of the present invention has excellent friction and wear properties and is free from the possibility of causing various troubles due to electrification, so that it is very useful for a feed screw mechanism.

Continuation of the front page F term (reference) 3J062 AA35 AB22 AC07 BA05 BA17 BA32 CD02 CD22 CD27 CD54 4J002 CF071 CF081 CM01 CN011 DA016 DA027 FA046 FA087 FB096 FB097 FB166 FB167

Claims (2)

[Claims] 1. A nut in a feed screw mechanism which moves on the axis of a helical shaft in accordance with the rotation of the axis, (A) a resin mainly composed of polybutylene terephthalate or a resin mainly composed of polyphenylene sulfide 40 to 9
0% by weight, (B) 5 to 30% by weight of carbon fiber, (C) spherical fine powder phenol resin in a non-oxidizing gas atmosphere at 800 to
Spheroidal graphitized carbon fine powder 5 to 3 obtained by firing at 2000 ° C.
Consists of 0% by weight of the three components and the total of the three components is 100
What is claimed is: 1. A resin nut comprising a thermoplastic resin composition in a weight%. 2. The resin nut according to claim 1, wherein the volume specific resistivity is 9 × 10 ⁴ Ω · m or less.