JPH09188767A - Fluororesin-based sheet, sheet laminate, production and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluororesin based sheet having both of excellent mechanical characteristics and sliding characteristics and consisting essentially of an aromatic polyamide pulp and a fluororesin, a sheet laminate and a sliding material by a simple producing step comprising a sheet-making step. SOLUTION: Aromatic polyamide pulp and fluororesin powder are dispersed in water and a flocculating agent for making disperse of the fluororesin powder unstable is added to the dispersion to fix fluororesin powder on the aromatic polyamide pulp and the dispersion is made into a solid and dried to afford a sheet-like material, which is then pressurized by a roll and baked to produce the objective fluororesin-based sheet having >=250kgf/cm<2> tensile strength and hardly having anisotropy of tensile strength. Plural sheets of the sheet-like material are laminated and pressurized and baked to provide the objective sheet laminate. The sliding material is produced from the fluororesin-based sheet or the laminate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to various packings,
TECHNICAL FIELD The present invention relates to a sheet useful for bearings, thrust washers, gears, sealing materials, etc., a sheet laminate, a method for producing the same, and applications thereof. More specifically, an aromatic polyamide pulp having excellent mechanical properties, friction and abrasion properties, heat resistance and chemical resistance, and a fluorine resin-based sheet containing a fluororesin as a main component, a sheet laminated composite, a method for producing the same, and the fluorine resin. The present invention relates to a sliding material made of a resin sheet or a sheet laminated composite.

[0002]

2. Description of the Related Art Fluororesin is widely used as a sliding material for various packings, bearings, thrust washers, etc. because of its excellent friction and wear characteristics, heat resistance and chemical resistance. However, since the fluororesin alone is easily deformed by an external force and has a large amount of abrasion, various reinforcing fillers have been blended in order to improve these defects.

On the other hand, a thin sheet-shaped sliding material is required for applications such as packing and thrust washers, but since fluororesins are generally difficult to melt or dissolve in a solvent, nylon, polyethylene, etc. The sheet molding methods such as casting and blow molding which are generally used for the thermoplastic resin of 1 cannot be applied.

Therefore, a method called a skiving method is generally used in which a cylindrical block is compression molded, fired, and then cut into a thin wall. However, since this method is low in productivity, there has been a demand for a method for producing a sheet-like material which has higher productivity and is economical.

Further, by adding a fibrous filler such as glass fiber or a particulate filler such as graphite or bronze powder to the fluororesin, properties such as hardness and abrasion performance can be improved. Mechanical properties such as tensile strength cannot be improved due to poor adhesion to the material.

In order to improve this point, the present inventors have proposed a resin composition for a sliding material, which is a combination of highly fibrillated aromatic polyamide pulp and fluororesin powder (Japanese Patent Laid-Open No. 5-117476). In this composition, since highly fibrillated aromatic polyamide pulp is used as a reinforcing material, the fluororesin is reinforced by the physical entanglement of the aromatic polyamide pulps, and a large reinforcing effect is obtained. However, although the composition is suitable for producing a block-shaped product having an excellent reinforcing effect, it is not necessarily satisfactory for directly producing a sheet-like product having an excellent reinforcing effect.

That is, the sheet manufactured by the skiving method from this block-shaped product has strong anisotropy, and it is difficult to obtain sufficient tensile strength in all directions of the sheet surface, and tensile strength in all directions of the sheet surface is Is 250 Kgf /
Those having a size of cm ² or more have not been obtained. It is considered that this is because the fibers are oriented mainly in the direction perpendicular to the pressing direction during the pressure molding of the block, and are difficult to be oriented in the pressing direction.

Japanese Patent Publication No. 36181/1992 discloses a method in which a tetrafluoroethylene resin (PTFE) polymer is fixed to a fiber sheet to give the sheet. However, in this method, chopped fibers obtained by cutting long fibers instead of pulp are used as reinforcing fibers, so uniform dispersion is not always easy, and since the dispersant uses a mixture of water and isopropanol, drainage A general papermaking method that requires a treatment step and uses only water as a dispersant cannot be directly applied.

Japanese Patent Publication No. 6-511029 discloses a method in which a mat obtained from a fibrous material and an aqueous dispersant for a fluoropolymer are brought into contact with each other to precipitate the fluoropolymer on the mat to obtain a composite. Has been done. However, in such a method, fibrous materials, mats, etc. are manufactured in advance,
Next, two steps of impregnating these with an aqueous dispersion of a fluororesin are required, and a more efficient method has been desired.

On the other hand, if the cut fibers are used as they are without using a fibrous material or mat, there is a problem that the ratio of the fluororesin deposited on the cut fibers (fixing rate) is small (Comparative Example described later). 5).

As described above, in the prior art, there is known a method having excellent productivity of a sheet having sufficient tensile strength with almost no anisotropy, which uses aromatic polyamide pulp as a reinforcing material and fluororesin as a matrix. There was a strong demand for such a method.

[0012]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a sheet containing aromatic polyamide pulp and fluororesin as main components, which has little anisotropy in two-dimensional directions and has excellent mechanical properties and friction and abrasion properties. To provide a sheet laminated composite, a method for producing the same, and a sliding member made of the sheet.

[0013]

That is, the present invention is a fluororesin-based sheet characterized by comprising aromatic polyamide pulp and fluororesin as main components and having a tensile strength of 250 Kgf / cm ² or more.

The present invention also provides the following (a) to (d):
250 Kgf / cm ² containing aromatic polyamide pulp and fluororesin as main components, characterized in that
It is a method for producing a fluorine resin sheet having the above strength. (A) a step of preparing a dispersion liquid in which the aromatic polyamide pulp and the fluororesin powder are dispersed in water, (b) a step of adding a flocculant to the dispersion liquid to deposit the fluororesin powder on the aromatic polyamide pulp, ( (C) A step of forming an aromatic polyamide pulp having fluororesin powder deposited thereon and drying it to obtain a sheet-like material, and (d) a step of pressing and firing the sheet-like material.

Further, according to the present invention, the aromatic polyamide pulp and the fluororesin are the main components, and the tensile strength thereof is 250 Kg.
It is a sliding member made of a fluororesin-based sheet having a f / cm ² or more. Furthermore, the present invention is a laminated body of a composite sheet containing an aromatic polyamide pulp and a fluororesin as a main component and having a tensile strength of 250 Kgf / m ² or more.

The present invention also comprises a composite comprising an aromatic polyamide pulp and a fluororesin as main components and having a tensile strength of 250 Kgf / m ² or more, characterized by comprising the following steps (a) to (d): It is a method for manufacturing a molded body. (A) a step of preparing a dispersion liquid in which the aromatic polyamide pulp and the fluororesin powder are dispersed in water, (b) a step of adding a flocculant to the dispersion liquid to deposit the fluororesin powder on the aromatic polyamide pulp, ( (C) A step of forming an aromatic polyamide pulp on which fluororesin powder is deposited and drying it to obtain a sheet-like material, and (d) a step of laminating a plurality of the sheet-like materials and firing.

Further, the present invention is a sliding member comprising the above-mentioned composite molded body.

Hereinafter, the present invention will be described in detail.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide resin used as the raw material for the aromatic polyamide pulp used in the present invention has at least 85 mol% of amide bonds, and 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, and 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 a part of the benzene nucleus of an aromatic diamine is 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.

The aromatic polyamide pulp used in the present invention refers to a highly fibrillated fiber 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.

If the value of the BET specific surface area of the pulp is too small, the entanglement of the pulps cannot be sufficiently obtained, so that a sheet having high mechanical strength cannot be obtained, and it is difficult to deposit the fluororesin particles on the pulp. Become. On the other hand, if the value of the specific surface area is too large, the drainage is inevitably deteriorated, so that it takes a long time for papermaking and the economical efficiency is deteriorated.

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.
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.

The mixing ratio of the aromatic polyamide pulp and the fluororesin powder is appropriately selected depending on the intended final product, but the aromatic polyamide pulp / fluororesin ratio (weight ratio) is in the range of 10/90 to 70/30. Is preferred.

In the first step of the method for producing a sheet and a composite molded article of the present invention, a dispersion liquid in which the above aromatic polyamide pulp and fluororesin powder are dispersed in water is prepared.
The method for preparing the dispersion is not particularly limited. For example, a dispersion in which the fluororesin powder is dispersed in water is prepared in advance, and the dispersion in which the fluororesin powder is dispersed in water and the aromatic polyamide pulp are prepared in water. , A method in which a fluororesin powder is dispersed in water in advance, and the aromatic polyamide pulp is dispersed in the dispersion in which the fluororesin powder is dispersed in water, or the fluororesin powder and the aromatic polyamide pulp are dispersed. And the like. Hereinafter, a preferable method for preparing the dispersion will be specifically described.

A fluororesin powder is stably dispersed in water containing an anionic, cationic or nonionic surfactant to prepare a fluororesin dispersion (hereinafter sometimes referred to as fluororesin dispersion or emulsion). . It is also possible to prepare a similar dispersion liquid of the fluororesin powder by subjecting the monomers of the fluororesin raw material to aqueous polymerization in the presence of one or more kinds of the above-mentioned surfactants.

It is also possible to use a commercially available aqueous dispersion of fluororesin powder as it is. Examples of such an aqueous dispersion of fluororesin powder include fluororesin dispersions of fluororesin powder commercially available from Asahi Glass Co., Ltd., Daikin Industries, Ltd., and the like.

Next, the fluororesin powder dispersion and the aromatic polyamide pulp are dispersed in water. As the dispersion method at this time, a method that has been conventionally used for making wood pulp can be applied as it is. For example, the dispersion can be prepared by using various disintegrators (pulper), various beaters such as Niagara beater, and various refiners such as single disk refiner.

The concentrations of the aromatic polyamide pulp and the fluororesin powder in the dispersion liquid can be freely selected according to the purpose, but it is economically advantageous to select the highest concentration as long as the fluidity of the dispersion liquid is not impaired. Desirable in terms.

The blending ratio of aromatic polyamide pulp / fluororesin powder in the dispersion is determined from the composition ratio of aromatic polyamide pulp / fluororesin of the final product, but the weight ratio is 10/90 to 70/30. It is preferably in the range.

If the proportion of the aromatic polyamide pulp is too small, a sufficient reinforcing effect cannot be obtained, and conversely, if the proportion is too large, a sheet having sufficient mechanical strength and friction and abrasion characteristics cannot be obtained. Further, for the purpose of improving the performance of the sheet or imparting other characteristics, a filler such as graphite or bronze powder, an additive or other component is added to the dispersion within a range not impairing the homogeneity of the dispersion. You can also do it.

Then, a coagulant having a function of destabilizing the dispersion of the fluororesin particles is added to the dispersion liquid of the aromatic polyamide pulp / fluororesin powder to deposit the fluororesin particles on the aromatic polyamide pulp. Let The type of coagulant to be applied and the amount thereof added 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 powder is stabilized by an anionic surfactant, a strong acid or a strong electrolyte, or a polymer flocculant such as polyacrylamide or sodium polyacrylate, is used as the flocculating agent. Can be applied in combination with these polymeric flocculants and strong acids or strong electrolytes.

When the particles of the fluororesin are stabilized with a cationic surfactant, a base or a strong electrolyte, or a polymer aggregating agent such as polyacrylamide or polymethacrylic acid ester is used as an aggregating agent. Further, these polymer flocculants and a base or a strong electrolyte can be applied in combination.

When the particles of the fluororesin are stabilized with a nonionic surfactant, a strong electrolyte or a polymer aggregating agent such as polyacrylamide is used as the aggregating agent.
Furthermore, these polymer flocculants and a strong electrolyte can be applied in combination.

It is particularly effective to use a condensate of polyhydroxyaromatic carboxylic acid and glucose and a polyvalent metal salt together as the coagulant, regardless of the kind of the 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 particularly important to select the optimum combination of the aromatic polyamide pulp, the fluororesin dispersion liquid and the flocculant, keeping the following points in mind. (1) Deposit the fluororesin powder in the dispersion as much as possible on the aromatic polyamide pulp, preferably deposit substantially all of the fluororesin on the aromatic polyamide pulp. This is important from the viewpoint of effective use of expensive fluororesin raw materials, but if there is fluororesin that does not deposit and flows into the wastewater during papermaking, it will be necessary to treat the wastewater accordingly, which is economically feasible. Is damaged. From this point of view, that substantially all of the fluororesin is deposited here means that the amount of fluororesin flowing out into the wastewater at the time of papermaking is reduced to a level at which the wastewater treatment is not particularly required. (2) The fluororesin powder that has been destabilized in dispersion and deposited on the aromatic polyamide pulp is uniformly deposited on the aromatic polyamide pulp without forming large flocs. (3) The dispersion liquid after depositing the fluororesin powder on the aromatic polyamide pulp has an appropriate drainage property. This can be evaluated by measuring the freeness of the dispersion by the method described below.

From these points, as described above, the aromatic polyamide pulp has a BET specific surface area of preferably 3 to 25 m ² / g, more preferably 5 to 20.
m ² / g, more preferably appropriately in a range of 9~16m ² / g, as the fluorine resin powder, an average particle diameter of preferably 0.01 to 10 [mu] m, more preferably 0.1 1 μm is suitable.

Further, since the dispersion liquid of the fluororesin powder is more easily destabilized when stabilized with the anionic surfactant than when stabilized with the nonionic surfactant, deposition of the fluororesin powder There is a tendency that the amount of coagulant required for the process is small. However, large flock tends to be formed, and it tends to be difficult to obtain a uniform sheet.

On the other hand, those stabilized with a nonionic surfactant tend not to be easily destabilized, but fine fluororesin powder is uniformly deposited on the surface of the aromatic polyamide pulp, and a uniform sheet can be obtained. In the present invention, it is preferable to use a nonionic dispersion liquid as a raw material.

As a method for destabilizing the dispersion of the fluororesin powder, as described above, a condensate of polyhydroxyaromatic carboxylic acid and glucose and a polyvalent metal salt are used in combination, especially tannic acid and aluminum sulfate. The combined use method is particularly effective. This combination is preferable for the nonionic dispersion liquid, and is also preferable for the anionic liquid dispersion because it is effective with a smaller addition amount than that using other coagulants.

Then, the pulp (and the fluororesin) in which the dispersion of the fluororesin is destabilized by the coagulant in this way
The dispersion of (1) is made into paper according to a conventional method, dehydrated if necessary, and then dried to obtain a sheet-like material. Here, the papermaking broadly refers to a known process of making a paper (sheet) material from a liquid containing pulp dispersed therein. In the method of the present invention, papermaking can be carried out by directly applying a generally used Fourdrinier or round-netted papermaking machine.

In order to produce the fluororesin-based sheet according to the present invention, this sheet-like material is pressed to have a dense structure,
Sequentially or simultaneously, baking is performed at a temperature equal to or higher than the melting point or softening point of the fluororesin to obtain the target sheet. For example, when PTFE having a melting point of 320 ° C. is used as the fluororesin, 300
The desired sheet is obtained by firing at ~ 450 ° C, preferably 350-400 ° C. Pressing can be performed using a press machine or the like, but it is desirable to press with a roll because of high productivity. The firing is preferably performed in a nitrogen atmosphere. The pressure at the time of pressurization is preferably 300 to 1500 Kgf / m
m ² and it is desirable that the pressure be gradually increased from normal pressure within about 2 minutes.

The firing can be carried out in a batch system in which a sheet obtained by pressurizing at room temperature is heated in an oven at a temperature higher than the melting point of the fluororesin, as in the case of a general fluororesin molding. . Further, the sheet obtained by pressurizing at a temperature not higher than the melting point of the fluororesin may be passed through a heating roll having a temperature not lower than the melting point of the fluororesin to be fired. It is also possible to pass the dried sheet-like material directly through a heating roll having a temperature equal to or higher than the melting point of the fluororesin, and to pressurize and fire at the same time. This method is particularly preferable because it has high productivity and economic efficiency.

In a preferred embodiment of the step (d) of the present invention, ie, the step of pressurizing and firing the sheet-shaped material, the sheet-shaped material is melted at the melting point of fluororesin (320 in the case of PTFE).
Rolling pressure at a temperature of less than (° C), then baking the sheet-like material at a temperature equal to or higher than the melting point of the fluororesin using an oven or a heating roll, and rolling the sheet-like material at a temperature below the melting point of the fluororesin, Then, a step of firing while pressing with a roll at a temperature equal to or higher than the melting point of the fluororesin, or a step of firing while pressing the sheet-shaped material with a roll at a temperature equal to or higher than the melting point of the fluororesin can be exemplified.

In order to make a composite molding according to the invention,
A plurality of sheet materials obtained in the above papermaking process, for example, 2 to
100 sheets are stacked, and thereafter, pressed and fired in the same manner as above. Preferably, if the sheet-like material is preliminarily cut into a predetermined shape and then laminated, pressed, and fired, waste of material due to cutting can be reduced. The pressurizing method is the same as that for the sheet, but in order to prevent air from remaining between the sheets and forming a void, pressing is performed under vacuum or pressure increase from normal pressure to a predetermined pressure is 2 to It is preferable to perform gradually over 30 minutes.

According to the method of the present invention, a fluorine-containing resin sheet having an aromatic polyamide pulp and a fluororesin as main components and having a tensile strength of 250 Kgf / cm ² or more in any direction can be obtained by conventional general papermaking. It can be manufactured by the method.

Further, since the method of the present invention can fix substantially all of the fluororesin powder to the aromatic polyamide pulp, it is an industrially excellent method from the viewpoint of wastewater treatment.

The fluororesin-based sheet and the composite molded article of the present invention are particularly useful as a sliding material because they have excellent mechanical properties and friction and abrasion properties.

[0051]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited thereto.

Various physical property values in the examples were measured according to the measuring methods described below. Sheet physical property evaluation method 1. Freeness 1.1. Freeness of Aromatic Polyamide Pulp The freeness of aromatic polyamide pulp is JIS P812.
1 Measured in accordance with the Canadian standard type method of "pulp freeness test method". 1.2. Freeness of Aromatic Polyamide Pulp / Fluorine Resin Dispersion The freeness of the aromatic polyamide pulp / fluorine resin dispersion after destabilizing the fluororesin particles was measured as follows. (1) An amount of the dispersion liquid containing 1.2 g of aromatic polyamide pulp is collected from the dispersion liquid. (2) Dilute this to 1 liter with a graduated cylinder. (3) The freeness is measured according to the Canadian standard type method of JIS P8121.

This freeness value is 200 to 600 ml,
More preferably, the papermaking can be suitably performed when the amount is 300 to 500 ml. 2. The COD COD of the papermaking filtrate is 10 in accordance with JIS K0102.17.
It was measured by the KMnO ₄ method at 0 ° C. 3. Fluorine Resin Fixing Rate The fixing rate of the fluororesin to the aromatic polyamide pulp was calculated by the following equation, assuming that all the charged amount of the aromatic polyamide pulp remains in the sheet.

Fluororesin fixing rate [%] = {(dry weight of sheet-amount of aromatic polyamide pulp) / (amount of fluororesin)} × 100 4. Tensile strength of sheet-shaped sliding material Using JIS No. 3 dumbbell-shaped test piece, gauge length 4
The tensile strength of the sheet-like sliding material was measured under the conditions of 0 mm and a pulling speed of 100 mm / min. 5. Friction and Wear Performance of Sheet-Shaped Sliding Material A frictional wear test of the sheet-shaped sliding material was conducted under the following test methods and conditions.

Tester: Ring-on-disk vertical friction wear tester (manufactured by Takachiho Seiki Co., Ltd.) Specimen: disk-shaped Mating material: S55C, ring-shaped Pressure: 6 Kgf / cm ² Speed: 40 m / min Test time: 4 hours 6 ． Limit PV value of sheet-shaped sliding material The limit PV value of the sheet-shaped sliding material was determined by the following test method and conditions.

Testing machine: Ring-on-disk vertical friction wear testing machine (manufactured by Takachiho Seiki Co., Ltd.) Test piece: disk-shaped, mating material: S55C, ring-shaped Speed: constant at 150 m / min.

Pressure is 5, 10, 15, 20, 25 Kgf
/ Cm ² and 5 Kgf / cm ² while sequentially increasing the pressure, the test was carried out for 10 minutes each, and the PV value at the limit where the friction coefficient suddenly changed or the sheet broke was determined. 7. Compression Creep of Sheet-Shaped Sliding Material The compression creep of the sheet-shaped sliding material was determined under the following test method and conditions.

Testing machine: Creep testing machine PSS-6 type
(Manufactured by Shimadzu Corporation) Test piece: 4 to 5 disks each having a diameter of 5 mm were stacked,
The thickness is 2-3 mm.

Temperature: Room temperature Pressure: 140 Kgf / cm ² hours: 24 hours Example 1, Comparative Example 1 Para aromatic polyamide pulp, Twaron 1094 (manufactured by Nippon Aramid Co., Ltd., BET specific surface area: 13.5 m ² /
g, freeness: 100 ml) 1.0 g (dry weight, hereinafter also referred to as absolute dry weight), nonionic dispersion of PTFE, Fluon Dispersion AD1 (Asahi Glass Co., Ltd.)
Made, PTFE average particle size: 0.25 μm, solid content: 60
6.67 g (solid content: 4.0 g) of (% by weight) was weighed,
It was dispersed in ion-exchanged water to obtain 400 g of a dispersion liquid.
The flocculant described in Table 1 was added to this dispersion liquid to a predetermined concentration, and the mixture was stirred for 10 minutes. At that time, Example 1
In, the pH of the dispersion was adjusted to 3.5 to 4.5 by adding aqueous ammonia. After that, No. It was filtered with the filter paper No. 1 and the filtered product was dried to obtain a sheet-like product. Then, it was weighed to determine the fixing rate of the fluororesin powder on the aromatic polyamide pulp. The results are shown in Table 1.

[0060]

[Table 1] ─────────────────────────────────── Flocculant Aluminum sulfate Fluorine resin Product name Concentration (ppm) Concentration (ppm) Fixation rate (%) ──────────────────────────────────── Example 1 Tannic acid 600 400 100 Comparative Example 1 None − 2000 5 ─────────────────────────────────── Example 2 to Example 5 para aromatic polyamide pulp, Twaron 1094 (manufactured by Nippon Aramid Co., Ltd., BET specific surface area: 13.5 m ² /
g, freeness: 100 ml) and 1.0 g (dry weight),
Anion dispersion liquid of PTFE, Fluon Dispersion AD2 (manufactured by Asahi Glass Co., Ltd., average particle diameter of PTFE: 0.
7.27 g (solid content: 17 μm, solid content: 55%)
4.0 g) is weighed and dispersed in ion-exchanged water.
A dispersion of 00 g was prepared. The flocculants listed in Table 2 were added to the dispersion so that the required concentrations were obtained, and then 1
Stirred for 0 minutes. After that, No. It was filtered with the filter paper No. 1 and the filtered product was dried to obtain a sheet-shaped product. Then, it was weighed to determine the fixing rate of the fluororesin powder on the aromatic polyamide pulp. The results are shown in Table 2. Sumifloc is a polymer flocculant manufactured by Sumitomo Chemical Co., Ltd.

[0061]

[Table 2] ─────────────────────────────────── Flocculant Aluminum sulfate Fluorine resin Product name Concentration (ppm) Concentration (ppm) Fixation rate (%) ─────────────────────────────────── Example 2 Tannic acid 60 40 100 Example 3 Sumifloc FN-10H 250 40 89 Example 4 Sumifloc FC-145 250-89 Example 5 Sumifloc FC-145 250 40 89 ──────────────────── ───────────────── Example 6 Twaron 1094 having an absolute dry weight of 15.9 g and 83.3 g of Fluon Dispersion AD1 (solid content: 50 g) were added to 2 l of ion-exchanged water. 20 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate after being dispersed in
Was added to adjust the concentration of tannic acid in the system to 600 ppm and the concentration of aluminum sulfate to 400 ppm. 200 mg of calcium hydroxide powder was added to this to adjust the pH, and the mixture was stirred for 10 minutes as it was to fix the fluororesin powder to the aromatic polyamide pulp.

Next, a square sheet machine (Kumagaya Riki Co., Ltd.)
Was manufactured on a metal mesh of 250 mm square and then dehydrated and dried to obtain a sheet-like material. CO of the filtrate during this papermaking
The value of D was 14 ppm. The fixing rate of the fluororesin powder was 100%.

Then, the sheet-like material was heated at room temperature to 100 Kgf /
After roll-pressing with a linear pressure of cm, the product was baked for 1 hour in a nitrogen atmosphere oven at 380 ° C. A sheet (sheet-shaped sliding material) having a composition ratio of aromatic polyamide pulp / fluororesin of 24/76 (weight ratio) and a thickness of 0.55 mm was obtained.

The tensile strength of this sheet-shaped sliding material is 420K
It was gf / cm ² , and there was almost no anisotropy in tensile strength. When the frictional wear performance of this sheet-shaped sliding material was measured, the dynamic friction coefficient was 0.18, and the wear coefficient was 2 × 10 5.
^{It was −5} mm / (km · Kgf / cm ² ). The sheet-like sliding material has a PV limit of 3500 kg / cm ²
-It was m / min, and the value of compression creep was 1.0%, which was excellent. As is clear from these data,
The obtained sheet-like sliding material had excellent mechanical strength and sliding characteristics. Comparative Example 3 The PTFE sheet not reinforced with the aromatic polyamide pulp had a dynamic friction coefficient of 0.26 and an abrasion coefficient of 4000 × 10 ⁻⁵ mm / measured in the same manner as in Example 6.
It was (km · Kgf / cm ² ). Also the limit PV
The value was 1000 Kg / cm ² · m / min, and the value of compression creep was 10%. Example 7 Twaron 1094 having an absolute dry weight of 13.7 g and 58.1 g of Fluon Dispersion AD2 (solid content: 32 g) were dispersed in ion-exchanged water in 2 l, and then tannic acid 6 was added.
20% by weight and an aqueous solution containing 4% by weight of aluminum sulfate
g was added to adjust the concentration of tannic acid in the system to 60 ppm and the concentration of aluminum sulfate to 40 ppm. This was stirred as it was for 10 minutes to fix the fluororesin powder to the aromatic polyamide pulp. Of this dispersion, an amount containing 1.2 g of pulp was weighed and collected, diluted to 1 l, and then the freeness thereof was measured to be 350 ml. The remaining dispersion liquid (containing 12.5 g of pulp)
250 using a square sheet machine (made by Kumagai Riki Co., Ltd.)
Paper was formed on a square metal mesh and then dehydrated and dried to obtain a sheet. At this time, the COD value of the filtrate was 15 ppm. The fixing rate of the fluororesin powder was 100%.

This sheet-like product was heated to 100 kgf / c at room temperature.
After roll-pressing with a linear pressure of m, the composition was baked in a nitrogen atmosphere oven at 380 ° C. for 1 hour to have an aromatic polyamide pulp / fluororesin composition ratio of 32/68 (weight ratio) and a thickness of 0.3.
A 9 mm sheet (sheet-like sliding material) was obtained. The tensile strength of this sheet-shaped sliding material was 270 Kgf / cm ² , and there was almost no anisotropy in tensile strength. Comparative Example 4 After dispersing 12.5 g of milled glass fiber MFB (Asahi Glass Co., Ltd., average fiber length: 200 μm) and 83.3 g of Fluon Dispersion AD1 (solid content 50 g) in 2 l of ion-exchanged water. , Tannic acid 6% by weight
And 20 g of an aqueous solution containing 4% by weight of aluminum sulfate were added to adjust the concentration of tannic acid in the system to 600 ppm and the concentration of aluminum sulfate to 400 ppm. 200m to this
g of calcium hydroxide powder was added to adjust the pH, and the mixture was stirred as it was for 10 minutes to fix the fluororesin powder. 2 using a square sheet machine (Kumagaya Riki Co., Ltd.)
The sheet was formed on a wire mesh of 50 mm square and dried to obtain a sheet. The weight was 17.1 g, and the fluororesin powder remained in the sheet only 9% of the charged amount.

Further, the mechanical strength of the obtained sheet was so weak that it could not be handled. Comparative Example 5 13.7 g of p-aramid fiber having a fiber length of 3 mm and 53.
3g of Fluon Dispersion AD1 (solid content 32
g) is dispersed in ion-exchanged water in 21 and then 15 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate is added to the system so that the concentration of tannic acid in the system and the concentration of alnium sulfate are each 450 ppm. And 300 ppm. 7.5 g of 1% aqueous ammonia solution was added to this to adjust the pH, and the mixture was stirred for 10 minutes as it was to precipitate the fluororesin. This is a square sheet machine (Kumagaya Riki Co. Ltd.)
Was manufactured on a metal mesh of 250 mm square to obtain a sheet-like product, but the weight was 135 g, and only 3.5% of the charged amount of PTFE remained in the sheet. The sheet obtained by pressurizing and firing this in the same manner as in Example 6 had a tensile strength of 27 Kgf / cm ² . Comparative Example 6 Twaron 1094 having an absolute dry weight of 12.5 g and PTFE particles of 37.5 g (trade name: Freon G163, manufactured by Asahi Glass,
(Average particle size: 25 μm) was dispersed in 2 l of a 0.8% aqueous solution of lauryltrimethylammonium chloride,
The concentration of tannic acid in the system was adjusted to 4 by adding 15 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate.
The concentration of 50 ppm and aluminum sulfate was adjusted to 300 ppm. To this was added 3.75 g of a 1% aqueous ammonia solution, the pH was adjusted, and the mixture was stirred as it was for 10 minutes to fix the fluororesin to the aromatic polyamide pulp. 250m using a square sheet machine (Kumagaya Riki Co., Ltd.)
Paper was formed on a square metal mesh and then dehydrated and dried to obtain a sheet. The sheet-like material was roll-pressed at a linear pressure of 189 Kgf / cm at room temperature and then fired for 1 hour in a nitrogen atmosphere oven at 380 ° C., so that the composition ratio of aromatic polyamide pulp / fluorine resin was 26/74 (weight). Ratio) 0.50
mm sheet-like sliding material was obtained. The tensile strength of this product is 6
It was 6 Kgf / cm ² . Comparative Example 7 For comparison with the sheet of Example 6, commercially available PTFE sheet containing bronze powder, Nitoflon 900B containing bronze powder.
(Nitto Denko Co., Ltd.) Various physical properties were evaluated, and the following results were obtained.

Tensile strength: 200 Kgf / cm ² Limit PV value: 2000 Kg / cm ² · m / min Compression creep: 5.3% Evaluation method for physical properties of composite molded body 1. Bending test Specimen shape: 60 × 13 × 2.5 mm Span: 40 mm Crosshead speed: 1 mm / min. Three-point bending 2. Friction and wear test of molded body A friction and wear test of the molded body was performed under the following conditions.

Tester: Ring-on-disk vertical friction wear tester (manufactured by Takachiho Seiki Co., Ltd.) Specimen: disk-shaped Mating material: S55C, ring-shaped Pressure: 6 Kgf / cm ² Speed: 40 m / min, PV = 240 Test time : 24 hours 3. Tensile strength Same as for sheet. Example 8 Para-aromatic polyamide pulp having an absolute dry weight of 15.0 g (Twaron 1094: manufactured by Nippon Aramid Co., Ltd., BET specific surface area: 13.5 m ² / g, freeness: 100 ml) and 7
4.8 g of Fluon Dispersion AD1 (manufactured by Asahi Glass Co., Ltd., PTFE average particle size: 0.25 μm, solid content 6)
0%) was dispersed in 2 l (liter) of ion-exchanged water, and then 15 g of an aqueous solution containing 6% by weight of tannic acid and 4% by weight of aluminum sulfate was added to adjust the concentrations of tannic acid and aluminum sulfate in the system, respectively. 145mmp and 300
Adjusted to ppm. 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. Using a square sheet machine (manufactured by Kumagai Riki Co., Ltd.), this was made into a sheet on a 250 mm square wire mesh, and then dehydrated and dried to obtain a sheet.

Next, the sheet-like material obtained was 85 × 75 m
It cut | disconnected to m and laminated 6 sheets. The height of the six laminated sheets was about 6 mm. Next, the laminated sheets are
Set in a mold with an inner diameter of × 75 mm and press at room temperature (contact pressure: 1000 kgf / cm ² , press time: 10
Min) to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. As a result, the composition ratio (weight basis) of aromatic polyamide pulp / fluororesin is 25/75, and the dimension of length × width × thickness is
A 85 × 75 × 2.5 mm composite molded body in which the aromatic polyamide pulp and the fluororesin were uniformly dispersed was obtained.

The obtained composite molded article was evaluated for use as a sliding material. The composite molded body (sliding material) has a tensile strength of 420 Kgf / cm ² and a bending strength of 6.26 kgf.
/ Mm ² , the flexural modulus was 261 kgf / mm ² . No peeling between the laminated sheets was observed in the test piece after the bending test. The wear coefficient is 1 × 10 ^-5 mm
/ (Km · kgf / cm ² ), the coefficient of friction was 0.14, and it was found that the sliding material had good friction and wear performance. Example 9 A sheet-shaped material produced in the same manner as in Example 8 was prepared to have a size of 85 × 75 m.
It cut | disconnected to m and laminated 6 sheets. The height of the six laminated sheets was about 6 mm. Next, the laminated sheets are
Set in a mold with an inner diameter of × 75 mm and press at room temperature (contact pressure: 500 kgf / cm ² , pressing time: 10
Min) to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. As a result, the composition ratio (weight basis) of aromatic polyamide pulp / fluororesin is 25/75, and the dimension of length × width × thickness is
A composite molded body of 85 × 75 × 2.5 mm was obtained.

The bending strength of the obtained composite molded body (sliding material) was 5.29 kgf / mm ² , and the bending elastic modulus was 218 kg.
f / mm ² . No peeling between the laminated sheets was observed in the test piece after the bending test. Further, the wear coefficient was 1 × 10 ⁻⁵ mm / (km · kgf / cm ² ) and the friction coefficient was 0.18, and it was found that the sliding material has good friction and wear performance. Comparative Example 8 A molded body made of aromatic polyamide pulp and PTFE was produced as follows. (A) 15 g of dried pulp of Twaron 1094, P
TFE (Fluon G163 (trade name, manufactured by Asahi Glass Co., Ltd.,
60g of composition consisting of 45g of average particle size 25μm)
A vertical high speed super mixer (manufactured by Kawata) was used to stir (stir speed 2000 rpm, stir time 2 minutes) to prepare a uniform mixture. (B) After filling 30 g of the mixture into a mold having an inner diameter of 85 × 75 mm, press (contact pressure: 1000 kgf / cm ² ,
(Pressing time: 10 minutes), and a preform was prepared at room temperature. The height of the mixture when it was filled in the mold was about 20 mm. (C) Under normal pressure, the preform was kept at 380 ° C. for 1 hour to prepare a molded body.

The obtained molded product has a tensile strength of 190 Kgf.
/ Cm ² , flexural strength was 3.49 kgf / mm ² , and flexural modulus was 134 kgf / mm ² . The wear coefficient of the molded product is 6.0 × 10 ^-5 mm / (km · kgf / cm
^{In 2} ), the coefficient of friction was 0.14. Comparative Example 9 Para-aromatic polyamide pulp having an absolute dry weight of 12.5 g,
Twaron 1094 and 37.5 g PTFE (Fluon G
163 (trade name, manufactured by Asahi Glass Co., Ltd., average particle size 25μ
m)) was dispersed in 2 l of ion-exchanged water and then stirred for 10 minutes as it was to prepare a dispersion liquid of PTFE and aromatic polyamide pulp. Using a square sheet machine (manufactured by Kumagai Riki Co., Ltd.), this was made into a sheet on a 250 mm square wire mesh, and then dehydrated and dried to obtain a sheet. further,
This operation was repeated twice to obtain two sheets. Next, the obtained sheets were cut into 85 × 75 mm and laminated seven sheets.
The height of the seven laminated sheets was about 9 mm. Next, the laminated sheets are set in a mold having an inner diameter of 85 × 75 mm and pressed at room temperature (contact pressure: 1000 kgf
/ Cm ² , pressing time: 10 minutes) to obtain a preform. The preform was held at 380 ° C. for 1 hour in nitrogen for firing. However, since the aromatic polyamide pulp was poorly dispersed in PTFE, a homogeneous and good molded product could not be obtained.

[0073]

According to the method of the present invention, the aromatic polyamide pulp is uniformly dispersed in the fluororesin, the two-dimensional anisotropy is small, and the fluororesin-based sheet excellent in mechanical properties and friction and abrasion performance, and A sheet laminated composite can be obtained. Since the method of the present invention can be applied to a conventional general papermaking method, it is possible to easily disperse the aromatic polyamide pulp uniformly in the fluororesin by a simple device and operation, and industrially. It is useful.

Further, the fluororesin sheet and the laminated composite of the present invention have excellent mechanical properties and sliding properties when used as a sliding material.

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Claims (11)

[Claims] 1. A fluororesin-based sheet comprising an aromatic polyamide pulp and a fluororesin as main components and having a tensile strength of 250 Kgf / cm ² or more. 2. The fluororesin-based sheet according to claim 1, which is obtained by simultaneously forming an aromatic polyamide pulp component and a fluororesin component from an aqueous dispersion. 3. A fluororesin-based sheet comprising an aromatic polyamide pulp and a fluororesin as main components and having a strength of 250 Kgf / cm ² or more, characterized by comprising the following steps (a) to (d): Production method (a) a step of preparing a dispersion liquid in which an aromatic polyamide pulp and a fluororesin powder are dispersed in water, (b) a step of adding a flocculant to the dispersion liquid and depositing the fluororesin powder on the aromatic polyamide pulp , (C) a step of forming an aromatic polyamide pulp having fluororesin powder deposited thereon, and drying it to obtain a sheet, and (d) a step of pressurizing and firing the sheet. 4. The aromatic polyamide pulp used in the step (a) is an aromatic polyamide pulp having a BET specific surface area of 3 to 25 m ² / g, and the fluororesin powder has an average particle diameter of 0.01 to 10 μm. The method for producing a fluororesin-based sheet according to claim 3, wherein the fluororesin powder is 5. The method according to claim 3, wherein the step (d) is a step of pressurizing the sheet-like material with a roll at a temperature lower than the melting point of the fluororesin and then baking the sheet at a temperature higher than the melting point of the fluororesin. A method for producing the fluororesin sheet described. 6. A sliding member comprising the fluororesin sheet according to claim 1. 7. A laminate of an aromatic polyamide pulp and a composite sheet containing a fluororesin as a main component, which is 250K.
A composite molded article having a tensile strength of gf / m ² or more. 8. A composite molded article comprising an aromatic polyamide pulp and a fluororesin as main components and having a tensile strength of 250 Kgf / m ² or more, characterized by comprising the following steps (a) to (d): Production method (a) a step of preparing a dispersion liquid in which an aromatic polyamide pulp and a fluororesin powder are dispersed in water, (b) a step of adding a flocculant to the dispersion liquid and depositing the fluororesin powder on the aromatic polyamide pulp (C) A step of forming an aromatic polyamide pulp on which fluororesin powder is deposited, and drying it to obtain a sheet, and (d) a step of laminating a plurality of the sheets and baking the sheets. 9. The aromatic polyamide pulp used in the step (a) is an aromatic polyamide pulp having a BET specific surface area of 3 to 25 m ² / g, and the fluororesin powder has an average particle diameter of 0.01 to. The method for producing a composite molded body according to claim 8, which is a fluororesin powder having a diameter of 10 μm. 10. The composite according to claim 8, wherein in the step (d), a plurality of the sheet-like materials are cut into a predetermined shape, laminated, pressed to produce a preform, and then the preform is fired. Method for manufacturing molded body. 11. A sliding member comprising the composite molded body according to claim 7.