JP3203186B2 - Manufacturing method of sliding material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a sliding material, for example, a bearing, a gear, a thrust washer, a seal material of various industrial equipment, and a sliding bearing used for a support portion of a pier, a pipe or the like.

[0002]

2. Description of the Related Art The present inventors have invented a sheet and a sheet laminate composite comprising an aromatic polyamide pulp and a fluororesin having excellent sliding properties (Japanese Patent Application No. 7-19835).
0), the use of sliding materials has been developed. However,
According to the manufacturing method of the technique, when a sheet having a large content of the fluororesin is produced, the papermaking time becomes long. When producing a laminate from a sheet, if the sheet is cut into a predetermined shape and laminated, the time required for cutting the sheet becomes longer when producing a thick laminate, and the thickness is 20 mm.
It has been found that there is a problem that a defect such as swelling or cracking occurs when the above-described laminate is produced.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a laminated composite of a sheet-like material comprising an aromatic polyamide pulp and a fluororesin without the above-mentioned problems.

[0004]

That is, the present invention is the following invention. (1) A method for producing a sliding material comprising a sheet of an aromatic polyamide pulp and a fluororesin, comprising the following steps (a) to (d): Adding a flocculant and a fluororesin powder dispersion in any order to the dispersion obtained by dispersing the fluororesin powder in the aromatic polyamide pulp; Group A polyamide pulp is formed and heated at a temperature of 200 ° C. or higher and lower than the melting point of the fluororesin to obtain a sheet-like material. (C) The sheet-like material is loaded into a mold in a laminated state, Pressurizing to produce a preform,
(D) a step of firing the preform to produce a sliding material. (2) The aromatic polyamide pulp used in the step (a) has a BET specific surface area of 3 to 25 m ² / g, and the fluororesin powder has an average particle size of 0.01 to 10 μm. Manufacturing method of sliding material. (3) In the step (a), the coagulant is first added to the dispersion of the aromatic polyamide pulp, and then the aqueous dispersion of the fluororesin powder is added to deposit the fluororesin powder on the aromatic polyamide pulp. The method for manufacturing a sliding material according to claim 1, wherein: (4) The method for manufacturing a sliding material according to claim 1, wherein in the step (c), the sheet-like material is laminated in a state of being wound into a cylindrical shape or in a folded state. (5) sheet used in step (c) The production method of claim 1 sliding material, wherein the is an average size of 1 cm ² 100 cm ^2. (6) The method for manufacturing a sliding material according to claim 1, wherein the firing in the step (d) is performed at a temperature equal to or higher than the melting point of the fluororesin.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide resin used as the raw material of the aromatic polyamide pulp used in the present invention has at least 85 mol% or more of the amide bond as an aromatic diamine.
It is obtained from an aromatic dicarboxylic acid component.

Specific examples thereof include polyparaphenylene terephthalamide, polymetaphenylene terephthalamide, polyparabenzamide, poly-4,4'-diaminobenzanilide, polyparaphenylene-2,6-naphthalic amide, copolypara Phenine / 4,4 '-(3
3'-dimethylbiphenylene) terephthalamide, copolyparaphenylene / 2,5-pyridylene terephthalamide, polyorthophenylene phthalamide, polymetaphenylene phthalamide, polyparaphenylene phthalamide, polyorthophenylene isophthalamide, polymetaphenylene isophthalate Amide, polyparaphenylene isophthalamide, polyorthophenylene terephthalamide, poly-1,5-naphthalenephthalamide, poly-
4,4'-diphenylene orthophthalamide, poly-
4,4'-diphenylene isophthalamide, poly-1,
4-naphthalenephthalamide, poly-1,4-naphthaleneisophthalamide, poly-1,5-naphthaleneisophthalamide and the like, and part of the benzene nucleus of these aromatic diamines can be formed by piperazine, 1,5-dimethylpiperazine, Polyamide containing an alicyclic amine typified by a compound substituted with 5,5-diethylpiperazine or an aromatic diamine is an ether such as 8,3′-oxydiphenylenediamine and 3,4-oxydiphenylenediamine forming _{stage, -S -, - SO 2 -} , - CO -, - NH- 2 pieces of copolymers of aromatic polyamide containing a phenyl group linked by groups such as, for example, poly-8,8'-oxydiphthalic Phenylene terephthalamide / polyparaphenylene terephthalamide copolymer, poly-3,4-oxydiphenylene terephthalate Bromide / poly-para Feret down terephthalamide copolymer and the like.

[0007] The aromatic polyamide pulp used in the present invention is obtained by highly fibrillating fibers of the above aromatic polyamide resin. BET specific surface area is often used as an indicator of fibrillation, but BET of aromatic polyamide pulp suitable for the method of the present invention is preferred.
The value of the specific surface area is 3 to 25 m ² / g, more preferably 5 to 25 m ² / g.
20 m ² / g, more preferably from 9~16m ² / g. When the value of the BET specific surface area of the pulp is too small, entanglement between fibers cannot be sufficiently obtained, so that a sheet having high mechanical strength cannot be obtained, and it becomes difficult to deposit fluororesin particles on the pulp. Therefore, a sliding material having excellent mechanical strength cannot be obtained. On the other hand, if the specific surface area is too large, the drainage inevitably deteriorates, so that a long time is required for the papermaking, resulting in poor economic efficiency.

The fluororesin used in the present invention includes:
For example, tetrafluoroethylene resin (hereinafter, sometimes referred to as PTFE), perfluoro-alkoxy resin (hereinafter, referred to as PTFE)
PFA), ethylene tetrafluoride-propylene hexafluoride copolymer resin (hereinafter, sometimes referred to as FEP), ethylene tetrafluoride-ethylene copolymer resin (hereinafter, referred to as FEP)
ETFE), vinylidene fluoride resin (hereinafter sometimes referred to as PVDF), ethylene trifluorochloride resin (hereinafter sometimes referred to as PCTFE), and the like. PTFE is particularly preferred in terms of characteristics and the like.

The preferred average particle size of the fluororesin powder is 0.1.
It is from 0.1 to 10 μm, more preferably from 0.1 to 1 μm. If the particle size is too small, it is difficult to deposit the particles on the fiber surface, and if it is too large, it is difficult to obtain a stable dispersion, and it is difficult to uniformly disperse the resin in the sheet.

In the step (a) of the present invention, an aromatic polyamide pulp is dispersed in water to prepare a dispersion, and a flocculant and a fluororesin powder dispersion are added to the dispersion in an arbitrary order. The resin powder is deposited on the aromatic polyamide pulp.

Although the concentration of the aromatic polyamide pulp in the dispersion can be freely selected, it is desirable from the viewpoint of economy to select a concentration as high as possible without impairing the fluidity of the dispersion. As a method of dispersing the aromatic polyamide pulp, a method conventionally used in papermaking of wood pulp can be applied as it is. For example, various disintegrators (pulver), various beaters such as Niagara beater,
Alternatively, the dispersion liquid can be adjusted using various refiners such as a single disk refiner.

The mixing ratio of the aromatic polyamide pulp and the fluororesin powder in the dispersion depends on the intended sliding material, but is generally 10/90 as the aromatic polyamide pulp / fluororesin powder ratio (weight ratio). To 70/30. If the proportion of the aromatic polyamide pulp is too small, a sufficient reinforcing effect cannot be obtained, and if it is too large, a sheet having sufficient mechanical strength and friction and wear characteristics cannot be obtained. Further improve the performance of the seat,
For the purpose of imparting other properties, fillers, additives or other components such as graphite, bronze powder, molybdenum disulfide and the like can be added as long as the homogeneity of the dispersion is not impaired.

A fluororesin dispersion (sometimes called a dispersion or an emulsion) is prepared by stably dispersing a fluororesin powder in water containing an anionic, cationic or nonionic surfactant. In general, a similar dispersion liquid of a fluororesin powder can be prepared by subjecting a monomer as a raw material of the fluororesin to aqueous polymerization in the presence of one or more surfactants.

Further, a commercially available dispersion of a fluororesin powder can be used as it is.
As an aqueous dispersion of such a fluororesin powder, for example,
Fluororesin dispersions of fluororesin powders commercially available from Asahi Glass Co., Ltd., Daikin Industries, Ltd., and the like.

The flocculant has a function of destabilizing the dispersion of the fluororesin particles in water, and plays a role of depositing the fluororesin particles on the surface of the aromatic polyamide pulp.
The type and amount of coagulant to be applied are determined by the type of surfactant used to disperse the fluororesin powder and the specific surface area of the aromatic polyamide pulp.

When the fluororesin particles are stabilized by an anionic surfactant, a strong acid or a strong electrolyte, or a polymer flocculant such as polyacrylamide or sodium polyacrylate may be used as a flocculant. Can be applied in combination with these polymer flocculants and strong acids or strong electrolytes.

When the fluororesin particles are stabilized with a cationic surfactant, the coagulant may be a base or a strong electrolyte, or a polymer coagulant such as a polyacrylamide or polymethacrylate ester; Further, these polymer flocculants can be used in combination with a base or a strong electrolyte.

When the fluororesin particles are stabilized with a nonionic surfactant, a strong electrolyte or a polymer coagulant such as polyacrylamide may be used as the coagulant.
Alternatively, these polymer flocculants and strong electrolytes can be used in combination.

It is particularly effective to use a condensate of polyhydroxyaromatic carboxylic acid and glucose and a polyvalent metal salt as a coagulant irrespective of the type of surfactant used. Examples of the condensate include tannic acid, gallic acid and the like. Examples of the metal salt include aluminum sulfate, calcium chloride and the like. At this time, adjusting the pH of the system to a range of 3.5 to 6.0 by adding an alkali component such as calcium hydroxide or ammonia to the system is effective because substantially all of the fluororesin powder is deposited on the pulp. It is.

In the present invention, it is important that an aromatic polyamide pulp, a fluororesin dispersion and a flocculant are optimally combined to produce an aromatic polyamide pulp sheet on which the fluororesin powder is densely and uniformly adhered. From this point, as the aromatic polyamide pulp, the value of the BET specific surface area is 3 to 25 m ² / g, more preferably 5 to 20 m ² / g.
² / g, more preferably in the range of 9 to 16 m ² / g is suitable.

As a method of depositing the fluororesin powder on the surface of the aromatic polyamide pulp, a dispersion in which the aromatic polyamide pulp and the fluororesin powder are dispersed in water is prepared,
A flocculant can be added to the dispersion. However, it is preferable to add a flocculant to a dispersion in which aromatic polyamide pulp is dispersed in water in advance, and then add a dispersion of a fluororesin powder dispersed in water. In the latter method, the present invention provides that the destabilization of the fluororesin is performed in a short time, and the agglomerates of the fluororesin powder are larger than those in the former method, so that the subsequent papermaking can be performed in a short time. Found them.

In the step (b), an aromatic polyamide pulp on which a fluororesin powder is deposited is formed by a conventional method,
Dewater as needed and then dry to obtain a sheet. In the method of the present invention, the papermaking can be carried out by directly applying a generally used long-mesh or round-mesh papermaking machine. The sheet thus formed contains several percent of the surfactant used for dispersing the fluororesin powder in water and the drug used for coagulation. The present inventors have discovered that, when the laminate is thick, these components are gasified during firing of the preform in the step (d) and cause defects such as cracks and swelling of the sliding material. Therefore, it is necessary to remove these components from the sheet before firing. The removal method varies depending on the type of surfactant or flocculant,
It is preferable to heat at a temperature from 200 ° C. to less than the melting point of the fluororesin. More preferably, the temperature ranges from 220 ° C. to 20 ° C. below the melting point of the fluororesin. This is because the drying for drying the sheet containing water and the heating for removing the surfactant and the like can be performed in the same step or at the same time, and the equipment and man-hour for the removal can be reduced. is there.

In the step (c), a preform is produced by loading a sheet made of an aromatic polyamide pulp and a fluororesin into a mold in a laminated state, and then pressurizing the sheet. The form of the sheet before pressurizing is preferably a form in which the sheet is rolled up into a cylindrical shape or folded in order to load the sheet into the mold in a short time. When manufacturing a hollow sliding material,
It is also possible to wind the sheet material around a cylindrical or polygonal core material and then remove the core material to form a hollow cylindrical laminate. Alternatively, molding can be performed in a short time by cutting and reducing the size of the sheet-like material, and then loading and laminating it in a mold. When the size of the sheet is less than 1 cm ² , the bulk density of the sheet is reduced, so that the handling property is deteriorated and it takes time to load the sheet. As described above, the lamination described in the present invention broadly refers to a state in which sheets are stacked, and the present invention is not limited by a method of laminating sheet-like objects.

The pressurizing pressure at the time of preform molding is preferably 300 to 1500 kgf / cm ² , and it is preferable to gradually increase the pressure from the normal pressure to the pressure over 5 minutes or more.

In the step (d), the preform is fired to produce a sliding material. The sintering needs to be performed at a temperature equal to or higher than the melting point of the fluororesin. For example, in the case of PTFE, since the melting point is about 320 ° C., it is preferable to fire at a temperature of 350 to 400 ° C.

The method of the present invention for producing a sliding material comprising a sheet of an aromatic polyamide pulp and a fluororesin is one in which molding is carried out efficiently in a short time.

[0027]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited to these examples. The measurement of the physical property values in the examples was performed according to the measurement methods described below. 1. Friction and wear test Tester: Ring-on-ring vertical friction and wear tester (manufactured by Takachiho Seiki Co., Ltd.) Test piece: outer diameter 25.6 mm, inner diameter 20.0 mm, height 1
5.0 mm Counterpart material: S55C, ring pressure: 6 kgf / cm ² , speed: 40 m / min, PV = 24
0 Test time: 48 hours

[0028]

Example 1 Rose-based aromatic polyamide pulp [Twaron 1094 (Nippon Aramid Co., Ltd.) having an absolute dry weight of 12.5 g
BET specific surface area: 12.9 m ² / g, weight average fiber length: 1.5 mm, freeness: 100 ml] were dispersed in 1652.5 g of water. 15 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate and 1 part of ammonia
7.5 g of a weight% aqueous solution was added.

While stirring the dispersion, 62.5 g of Fluon Disversion AD1 (produced by Asahi Glass Co., Ltd., P
A dispersion of a fluororesin powder obtained by diluting TFE average particle size: 0.25 μm, solid content concentration 60% by weight) in 312.5 g of water was added over 3 minutes, and stirring was further continued for 10 minutes. By this operation, the fluororesin powder was deposited on the surface of the aromatic polyamide pulp. Using a square sheet machine (manufactured by Kumagai Riki Co., Ltd.), the paper was made on a 250 mm square wire mesh, and then dehydrated and dried to obtain a sheet. In this way, a predetermined number of sheets were formed. The sheet was heated at 260 ° C. for 8 hours in the air to remove the surfactant and tannic acid contained in the sheet. Next, the obtained sheet was cut into a width of 80 mm and a length of 250 mm to produce four sheets of the same shape. Next, the four sheets are wound in the longitudinal direction to have a diameter of about 40 mm and a length of 80 mm.
mm and a height of 280 mm. And surface pressure 1
Pressing was performed at 000 kgf / cm ² to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. Thus, the weight ratio of the aromatic polyamide pulp / fluororesin is 25/75, the outer diameter is 40 mm, and the height is 3
A 3 mm sliding material was obtained.

The sheet making time was 2 minutes. No defects such as cracks and swelling were observed in the obtained sliding material. The wear coefficient of the sliding material is 7.0 × 10 ⁻⁵ mm / (km · Kgf / cm ² )
And the coefficient of friction was 0.20.

[0031]

Example 2 Rose-based aromatic polyamide pulp (Trowan 1094) having an absolute dry weight of 12.5 g was dispersed in 1652.5 g of water. Thereto were added 15 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate, and 7.5 g of an aqueous solution of 1% by weight of ammonia. While stirring this dispersion, a dispersion of fluororesin powder obtained by diluting 62.5 g of Fluon Dispersion AD1 in 312.5 g of water was added over 3 minutes, and stirring was further continued for 10 minutes. By this operation, the fluororesin powder was deposited on the surface of the aromatic polyamide pulp. Using a square sheet machine (manufactured by Kumagai Riki Co., Ltd.), the paper was made on a 250 mm square wire mesh, and then dehydrated and dried to obtain a sheet. In this way, a predetermined number of sheets were formed. Place the sheet in air at 260 ° C
For 8 hours to remove the surfactant and tannic acid contained in the sheet. Next, the obtained sheet is
The sheet was cut into mx120 mm to produce 45 sheets of the same shape. Next, forty-five sheets were laminated, and a surface pressure of 10
Pressing was performed at 00 kgf / cm ² to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. As a result, the weight ratio of the aromatic polyamide pulp / fluororesin was 25/75, 120 mm long and 120 mm wide.
mm and a sliding material having a thickness of 20 mm were obtained.

No defects such as cracks and swelling were observed in the obtained sliding material. The wear coefficient of the sliding material is 6.0X
10 ^-5 (km · kgf / cm ² ), and the wear coefficient was 0.18.

[0033]

COMPARATIVE EXAMPLE 1 12.5 g of absolutely dry rose-based aromatic polyamide pulp (Trowan 1094) and 62.5 g of Fluon Dispersion AD1 were dispersed in ion-exchanged water in 1902 g, followed by tannic acid 6 wt%. 15 g of an aqueous solution containing 4% by weight of aluminum sulfate was added to bring the tannic acid and aluminum concentrations in the system to 450 ppm and 300 ppm, respectively. 7.5 g of a 1% aqueous ammonia solution was added thereto to adjust the pH, and the mixture was stirred for 10 minutes to deposit a fluororesin on the surface of the aromatic polyamide pulp. This was made into paper on a 250 mm square wire mesh using a square sheet machine, and then dehydrated and dried to obtain a sheet. In this way, a predetermined number of sheets were produced. Without heating the obtained sheet, 120 mm x 120 mm
Into 45 sheets of the same shape. next,
Forty-five sheets were laminated and pressed at a surface pressure of 1000 kgf / cm ² to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. As a result, the weight ratio of the aromatic polyamide pulp / fluororesin was 25/75, 120 mm long, 120 mm wide, and 23 mm thick.
mm of a sliding material was obtained. The sheet making time was 5 minutes and 40 seconds. The resulting sliding material swelled at the center.

[0034]

According to the method of the present invention, a sliding material in which a sheet-like material comprising an aromatic polyamide pulp and a fluororesin powder is laminated can be obtained economically and without any product defects.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-9-188767 (JP, A) JP-A-8-267478 (JP, A) JP-A-5-117476 (JP, A) JP-A 9-188 78455 (JP, A) JP-A-3-90693 (JP, A) JP-A-8-13348 (JP, A) JP-A-57-205473 (JP, A) JP-A-57-205472 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 5/16 C08L 27/12 C08L 77/10 F16C 33/24

Claims (6)

(57) [Claims] 1. A method for producing a sliding material comprising an aromatic polyamide pulp and a sheet of a fluororesin, comprising the following steps (a) to (d): (a) Aromatic polyamide pulp Adding a flocculant and a fluororesin powder dispersion in an arbitrary order to a dispersion obtained by dispersing the fluororesin in water, and depositing the fluororesin powder on the aromatic polyamide pulp; (ii) the fluororesin powder is deposited A step of producing the aromatic polyamide pulp and heating it at a temperature of 200 ° C. or higher and lower than the melting point of the fluororesin to obtain a sheet-like material; (c) loading the sheet-like material in a laminated state in a mold; Next, a step of producing a preform by pressing,
(D) a step of firing the preform to produce a sliding material. 2. The aromatic polyamide pulp used in the step (a) has a BET specific surface area of 3 to 25 m ² / g, and the fluororesin powder has an average particle size of 0.01 to 10 μm. 2. The method for producing a sliding material according to 1. 3. In step (a), a flocculant is first added to the dispersion of the aromatic polyamide pulp, and then an aqueous dispersion of the fluororesin powder is added to deposit the fluororesin powder on the aromatic polyamide pulp. The method for manufacturing a sliding member according to claim 1, wherein: 4. The method according to claim 1, wherein, in the step (c), the sheet-like material is laminated in a state of being rolled or folded in a cylindrical shape. 5. A sheet-like material used in step (c) The production method of claim 1 sliding material, wherein the is an average size of 1 cm ² 100 cm ^2. 6. The method according to claim 1, wherein the firing in the step (d) is performed at a temperature higher than the melting point of the fluororesin.