JP3448860B2 - Wet friction material and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet friction material used in a vehicle, and more specifically, it is used for a friction portion such as a clutch plate, and has an adhesive property between wholly aromatic polyamide fibers and a compression characteristic thereof. The present invention relates to an improved wet friction material and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a wet clutch has been used as one of media for transmitting an output from a prime mover such as an automobile, a two-wheeled vehicle and an agricultural machine, and a wet friction material is used for the wet clutch. . Such a wet friction material is disposed in a friction portion of a clutch, for example, a contact portion between a flywheel and a clutch plate, and has a porous structure, so that a smooth driving force is transmitted and a friction surface is generated. In addition to diffusing the heat that is generated, it also allows the lubricating oil to come in and out.

As such a wet friction material, a fibrous base material composed of fibers (organic fibers, inorganic fibers), inorganic powder fillers (diatomaceous earth, viscous minerals such as calcium carbonate and silica) and friction modifiers is used. It is known that a thermosetting resin (phenolic resin, melamine resin and silicone resin) is impregnated and cured.
No. 0-23774 and the like. It should be noted that various pulps, cellulose fibers, aramid fibers and phenol fibers are used as the above-mentioned organic fibers, and glass fibers, asbestos fibers, metal fibers and the like are used as the inorganic fibers. As described above, in the conventional wet friction material, as the organic fiber material, cellulose fiber, aramid fiber, acrylic fiber, etc. are mainly used in order to maintain the stability of the friction coefficient and its structure. The conditions have been met.

[0004]

However, in recent years,
In particular, in the field of automobiles, the development of automatic transmissions is progressing, and it is required to increase the transmission torque capacity and the heat resistance required level, and the standards required for each component are becoming high. In particular, clutches tend to be required to transmit high torque at high temperatures year by year, and in the conventional wet friction material as described above, breakage of the bonding portion between the fiber materials and breakage of the fiber itself. It is speculated that the wet friction material may peel off from the clutch plate in some cases.

Therefore, in order to properly meet the recent demands as described above, the friction material has a high heat resistance, and has a porous characteristic (porosity) and a compression characteristic (particularly good slidability). In order to maintain high mechanical properties), it is necessary to use heat resistant fibers while improving the adhesion between the fibers. On the other hand, the heat-resistant resin fiber has a problem that it is very difficult to impart strong adhesion between the fibers because of its stable chemical structure. The present invention has been made by paying attention to such problems of the conventional technique, and an object of the present invention is to provide a wet friction material having high heat resistance and excellent porous characteristics and compression characteristics. And to provide a manufacturing method thereof.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that by using an aliphatic nylon or a resole resin containing an aliphatic nylon, a wholly aromatic polyamide fiber is obtained. Fine crystals of aliphatic nylon are grown on the surface to serve as an adhesive anchor, and the tie molecular chain extending from this crystal is the resol resin 3
It has been found that the incorporation of a three-dimensionally cross-linked structure enables to strongly bond between wholly aromatic polyamide fibers and achieve the above object, thereby completing the present invention. That is, the wet friction material of the present invention is characterized by containing aliphatic nylon or a resole resin containing aliphatic nylon and wholly aromatic polyamide fiber. Further, the method for producing a wet friction material of the present invention, in producing the above-mentioned wet friction material, prepare an impregnating solution containing an aliphatic nylon or a resole resin containing an aliphatic nylon, and aromatize the impregnating solution. Impregnated into a group polyamide fiber, then
It is characterized in that it is heat-cured at a temperature in the range of the melting point to the decomposition temperature of the aliphatic nylon.

[0007]

As described above, in a wet friction material using wholly aromatic polyamide fiber (aramid fiber), it is difficult to improve the adhesiveness between the fibers because of the chemical stability of the material itself. The high mechanical properties could not be fully utilized. Therefore, in the prior art, as is well known, the wholly aromatic polyamide fiber has been subjected to a surface treatment such as primer etching to improve the adhesive strength between the fiber and the resin. However, such a surface treatment causes defects on the fiber surface, resulting in impairing the original high mechanical properties of the wholly aromatic polyamide fiber.

On the other hand, in the present invention, the aliphatic nylon is soluble in the uncured resol resin of phenols and the formic acid, and the aliphatic nylon is adsorbed on the oriented crystal layer of wholly aromatic polyamide. Then, by utilizing the ability to form a microcrystalline layer (lamella layer) connected by tie molecular chains, it was decided to firmly bond the wholly aromatic polyamide / resin. Therefore, according to the present invention, it is possible to manufacture a wet friction material having excellent compression characteristics and porous characteristics as compared with conventional products. In addition, as described above, in order to generate the fine crystals of the aliphatic nylon on the surface of the wholly aromatic polyamide fiber, it is necessary to apply a temperature above the melting point of the aliphatic nylon and below the decomposition point, and this temperature is It is also preferably compatible with the curing temperature of the resole resin.

Further, in the wet friction material of the present invention, the tie molecular chain extending from the aliphatic nylon microcrystals is incorporated into the crosslink structure of the resole resin, whereby the brittle properties inherent in the resole resin are improved, and the wholly aromatic polyamide is used. It has also become possible to impart toughness to a wet friction material containing fibers.
In the past, there has been no example in which wholly aromatic polyamide is adhesively reinforced with an aliphatic nylon or a combination of a thermosetting resin and an aliphatic nylon.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The wet friction material of the present invention will be described in detail below. As described above, the wet friction material of the present invention contains aliphatic nylon or a resole resin containing aliphatic nylon, and wholly aromatic polyamide fiber. Here, as the wholly aromatic polyamide fiber, Kevlar (Dupont) made of para-type aramid homopolymer is used.
Manufactured by Teikoku Co., Ltd.) and Technora (manufactured by Teijin Limited) consisting of the copolymer, and Nomex (Dupo) which is a meta-aramid.
(manufactured by nt Co.) and the like, but wholly aromatic polyamides other than these may be used.

Next, the aliphatic nylon and resole resin which function as an adhesive resin will be described. First, as the aliphatic nylon, nylon 6 (manufactured by Ube Industries, Ltd .; molecular weight 30,000), nylon 66 (manufactured by Asahi Kasei; molecular weight 1)
5,000) and nylon 46 (manufactured by Teijin Ltd .; molecular weight 1)
5,000) and the like, but the invention is not limited thereto. That is, any aliphatic polyamide can be used as long as it can be dissolved and mixed in the resol resin solution before thermosetting and has the ability to form fine crystals on the surface of the wholly aromatic polyamide fiber. Further, the resole resin is not particularly limited, and a liquid novolac resin, melamine resin, epoxy resin, silicone resin, polyimide resin or the like can be used before thermosetting, and for example, commercially available products (DIC Corporation) (A methanol solution containing 40% by weight of a resole resin) can be preferably used. It is considered that the heat resistance of the fiber / resin bonded portion can be improved by using the thermosetting resin.

The wet friction material of the present invention having the above material constitution is excellent in compressive elastic modulus and porosity, and is preferably 5
It has a compressive modulus of ˜55 MPa and a porosity of 15 to 50%. If the compression elastic modulus is less than 5 Pa, the settling (permanent strain) occurs during compression, and if it exceeds 55 Pa, the porosity decreases due to excessive resin impregnation, which is not preferable. On the other hand, if the porosity is less than 15%, the number of continuous pores for oil permeation decreases, and if it exceeds 50%, the compressive elastic modulus remarkably decreases, which is not preferable.

The contents of the aliphatic nylon and the resole resin in the wet friction material of the present invention can be appropriately changed depending on the intended performance and the place of use, and are not unambiguously determined, but are typical. When applied to the friction part of an automobile clutch, the content (adhesion amount) of aliphatic nylon or a mixture of aliphatic nylon and resole resin is
15-6 by dry weight, based on wholly aromatic polyamide fibers
It is preferably 0%. If it is less than 15%, the compressive elastic modulus of the friction material is lowered to cause fatigue, and if it exceeds 60%, the porosity associated with the continuous pores in the friction material for oil permeation is lowered, which is not preferable.

Next, the method for producing the wet friction material of the present invention will be described in detail. In the production method of the present invention, as described above, the wholly aromatic polyamide fiber is impregnated with the aliphatic nylon and the resole resin, and is cured by heating at a temperature in the range of the melting point to the decomposition temperature of the aliphatic nylon. Here, the wholly aromatic polyamide fiber used may be obtained by any method. For example, a wholly aromatic polyamide short fiber (diameter 13 μm, average fiber length 3 mm) and a friction modifier are used. And can be formed by a papermaking method. The friction modifier used may be H102 manufactured by Cashew.

The method of impregnating the wholly aromatic polyamide fiber with the aliphatic nylon or the resole resin containing the aliphatic nylon is not particularly limited, but the aliphatic nylon or the aliphatic nylon and the resole resin may be used. It is preferable to prepare an impregnating solution by the mixed system of and to impregnate the wholly aromatic polyamide fiber with the impregnating solution. Specifically, the above-mentioned aliphatic nylon is uniformly dissolved in a resol resin solution, formic acid or meta-cresol or a mixed solution thereof to prepare an impregnating solution, and the obtained impregnating solution is prepared from the above wholly aromatic polyamide. It is sufficient to impregnate the original papermaking paper.

In the impregnating solution, the content of the aliphatic nylon is preferably 0.1 to 60% by weight, and when the content is less than 0.1% by weight, the aliphatic nylon is contained in the wholly aromatic polyamide fiber surface. If it exceeds 60% by weight, the resin solution is saturated, the aliphatic nylon becomes insoluble, the viscosity of the solution becomes high, and impregnation into the papermaking becomes difficult, which is not preferable. The impregnating solution may contain other solvent in addition to the aliphatic nylon and the resole resin, and formic acid or metacresol can be used as such a solvent. In this case, the content of formic acid or meta-cresol is 4% of the impregnating solution.
It is preferably from 0 to 99.9% by weight, and when it is less than 40% by weight, the resin solution is saturated, the aliphatic nylon is insolubilized, the viscosity of the solution is increased, and impregnation into papermaking becomes difficult. If it exceeds 9% by weight, the amount of resin in the solution decreases, the resin adhesion rate to the papermaking decreases, the compression elastic modulus of the friction material also decreases, and it is not preferable because fatigue tends to occur.

In the production method of the present invention, after the impregnation treatment as described above, the paper roll of wholly aromatic polyamide is lightly passed through a roll, pre-dried at room temperature, and heat-cured to obtain a conventional product. It is possible to produce the wet friction material of the present invention that has higher compression characteristics than the wet friction material. Here, as the heat curing temperature, as described above, a temperature in the range of the melting point to the decomposition temperature of the aliphatic nylon is adopted, but the reason is that at a temperature lower than the melting point of the aliphatic nylon, the aromatic polyamide fiber is used. It is not preferable because the compression modulus of the friction material is not sufficiently improved because the crystals of the aliphatic nylon cannot be sufficiently grown on the surface, and when the decomposition temperature is exceeded, the aliphatic nylon deteriorates. . In addition, it is preferable that the heat curing temperature is substantially the same as the curing temperature of the resol resin.

[0018]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. For the friction material obtained in each example,
The compressibility test and the porosity measurement were performed under the following conditions. The obtained results are shown in Table 1 together with the material constitution of the friction material, the composition (% by weight) of the aliphatic nylon-containing resole resin solution, the heat curing temperature, and the friction material adhesion rate of the aliphatic nylon-containing resole resin in each example. Indicated. Sample size: length 30 mm × width 30 mm × thickness 1 mm (sample cut from friction material) Jig contact surface: diameter 10 mm (flat surface) temperature: 23 ° C, compression speed: 0.2 mm / min Also important as a friction material The porosity, which is a characteristic, was measured by the mercury penetration method.

(Example 1) Kevlar 49 (Dupont)
95% by weight of a product (diameter 13 μm, length 3 mm) and 5% by weight of a friction modifier (H102, manufactured by Cashew Co., Ltd.) are dispersed in water, and a paper is made into paper to prepare a fiber original fabric (length 30 cm × width 30 cm × thickness). 1.5 mm) was obtained, and this raw fabric was vacuum dried at 60 ° C. for 24 hours. Next, 0.2 g of nylon 6 (manufactured by Ube Industries, Ltd .; molecular weight 30,000) was uniformly dissolved in 100 g of a dissolved commercial resole resin solution (manufactured by DIC; 40% by weight of resole resin, 60% by weight of methanol) to obtain a solution. The above solution is impregnated with the obtained impregnating solution, and 5 to 100 kgf / cm
^The roll loaded with the load of ² was passed through. Furthermore, after leaving this original fabric for 24 hours at room temperature, it is placed in a heating oven for 23 hours.
The friction agent of this example was prepared by heat curing at 0 ° C. for 2 minutes. A sample of 30 × 30 × 1 mm was cut out from the obtained friction agent and subjected to a compression test, and about 2 g was cut out and the porosity was measured by the mercury porosimetry method.

Example 2 5 g of nylon 6 was added to formic acid 57
The same procedure as in Example 1 was repeated, except that 38 g of the solution was mixed with 38 g of the commercially available resol solution to obtain an impregnating solution.

Example 3 Nylon 6 was added in an amount of 10
g, 54 g of formic acid, and 36 g of the resol resin solution, except that the same operation as in Example 2 was repeated.

(Example 4) The amount of nylon 6 added was 3.9.
g, formic acid 66.5 g, resole resin solution 29.6 g
The same operation as in Example 2 was repeated except that

Example 5 The same operation as in Example 2 was repeated except that nylon 46 (manufactured by Teijin Ltd .; molecular weight: 15,000) was used as the aliphatic nylon and the heat curing temperature was 310 ° C.

(Example 6) Nylon 66 (made by Asahi Kasei; molecular weight 15,000) was used as the aliphatic nylon,
The same operation as in Example 2 was repeated except that the heat curing temperature was 280 ° C.

Example 7 As a wholly aromatic polyamide fiber, Technora fiber (manufactured by Teijin Ltd .; diameter 13 μm, length 3 m)
The same operation as in Example 2 was repeated except that m) was used and metacresol was used instead of formic acid.

(Example 8) Nomex fiber (manufactured by Dupont; diameter 13 μm, as wholly aromatic polyamide fiber)
The same operation as in Example 2 was repeated, except that a length of 3 mm) was used and metacresol was used instead of formic acid.

Example 9 50 g of nylon 6 was added to formic acid 5
Example 1 except that the solution dissolved in 0 g was used as it was.
The same operation was repeated.

(Example 10) The addition amount of nylon 6 was adjusted to 0.
The same operation as in Example 2 was repeated except that the amount was 01 g.

Example 11 Nylon 6 was added in an amount of 1
The same operation as in Example 1 was repeated except that the amount was 8.2 g. The added nylon 6 was not completely dissolved.

Example 12 3.2 g of nylon 6 was dissolved in 72.6 g of formic acid, and this was dissolved in the commercially available resol solution 2 described above.
Example 2 except that it was mixed with 4.2 g to obtain a solution for impregnation.
The same operation was repeated.

(Example 13) Nylon 6 was used as the heat curing temperature.
The same operation as in Example 2 was repeated except that the temperature was 180 ° C, which is lower than the melting point (225 ° C) of

(Example 14) Nylon 6 was used as the heat curing temperature.
The same operation as in Example 2 was repeated except that the decomposition start temperature (350 ° C.) or higher was 360 ° C. After heat curing, discoloration was confirmed on a part of the friction material.

(Example 15) As a thermosetting resin solution,
Example 2 except that a melamine resin solution (manufactured by DIC; 40% by weight melamine resin, 60% by weight methanol) was used.
The same operation was repeated.

Comparative Example 1 Commercially available resole resin solution 1
The same operation as in Example 1 was repeated except that 00 g was used as it was.

[0035]

[Table 1]

In Table 1, Examples 1 to 3 show the results of the friction materials prepared by changing the amount of the aliphatic nylon added. As the weight% of nylon 6 dissolved in the resole solution increases, the amount of resin adhering to the stock made of Kevlar fibers and the compression elastic modulus increase, but the porosity tends to decrease. Here, Comparative Example 1 which is a conventional friction material
Comparing (a friction material using a resol resin containing no aliphatic nylon) with Examples 1 to 3, although the difference in the resin adhesion ratio of the friction material is not so great, the latter has porous characteristics and compression elasticity. It can be seen that the rate has improved significantly. This means that the nylon 6 used in Examples 1 to 3 grows fine crystals on the surface of the Kevlar fiber, the crystals contribute to the adhesion of the fiber / resin, and the tie molecular chain of nylon 6 extending from the fine crystals is a resol. Since it is firmly incorporated in the crosslinked structure of the resin, it is considered that the fiber / resin bond is further strengthened. In addition, when observing the fracture surface of the friction material, the peeling of the wholly aromatic polyamide fiber / resole resin and the cracking or chipping of the resole resin observed in Comparative Example 1 were observed in Example 1.
It is relatively low in ~ 3.

Regarding the content of nylon 6 in the impregnating solution, Examples 1 to 3 and Examples 10 and 11
As can be seen from the above, the compressive elastic modulus decreases when the content is 0.01% by weight or less, while the porosity, which is an important characteristic in the friction material, may decrease when the content is 18.2% by weight or more. When the content of nylon 6 is 18.2% by weight or more, it is difficult to completely dissolve nylon 6 in the resol solution. Therefore, the content of the aliphatic nylon in the impregnating resol solution is preferably 0.1 to 15% by weight.

Examples 3 and 4 and Examples 11 and 12 show the effect of formic acid content in the nylon 6 / resole solution impregnation solution. A commercially available resole resin solution has a weight ratio of resole resin and methanol of 40%.
/ 60. When the formic acid content is in the range of 40 to 66.5% by weight (Examples 1 to 8), it is possible to prepare a friction material having good porous characteristics and compression characteristics, but the formic acid content is 49.1% by weight. % Or less (Example 11) or 72.6% by weight or more (Example 12), the porous properties or the compression properties may be significantly reduced.

That is, when the formic acid content is 49.1% by weight or less, the compression property is improved as the resin adhesion amount is increased, but the porous property may be decreased. On the other hand, when the formic acid content is 72.6% by weight or more, the resin adhesion rate and the porous property decrease, but the compression property decreases. For this reason,
The compounding amount of formic acid or metacresol in the aliphatic nylon / resole resin solution is preferably 50 to 70% by weight.

Next, the heat curing temperature range of the wholly aromatic polyamide raw material impregnated with the aliphatic nylon / resole resin solution will be examined. In Examples 1 to 3, as already shown, the fully aromatic polyamide raw fabric impregnated with the above-mentioned resole resin was used as
It was heat-cured at 0 ° C. for 2 minutes. On the other hand, Example 13
14 and 14, the heat curing temperature is set to the melting point of nylon 6 (22
The temperature was lower than 5 ° C. or higher than the decomposition starting temperature (350 ° C.), and the above nylon 6 / resole resin-impregnated Kevlar fiber fabric was heat-treated for 2 minutes.

In the former case (Example 13), since the crystallite growth of nylon 6 does not proceed on the surface of the Kevlar fiber,
The adhesion between Kevlar fibers is weak and the compression modulus remains low. In the latter case (Example 14), the elongation of the friction material was lost and weakened due to thermal oxidation deterioration of nylon 6, the compression elastic modulus was lowered, and discoloration was observed in a part of the friction material. Therefore, it can be said that it is desirable to use the temperature from the melting point to the decomposition temperature of the aliphatic nylon as the heat curing temperature range of the wholly aromatic polyamide raw material impregnated with the aliphatic nylon / resole resin solution.

Examples in which aliphatic nylon other than nylon 6 was used are shown in Examples 5 and 6. In Example 5,
Nylon 46 was used, and the thermosetting temperature of the friction material impregnated with the resole resin was 310 ° C., which was slightly higher than the melting point (300 ° C.) of nylon 46. Further, in Example 6, nylon 66 (melting point 270 ° C.) was used, and the heat curing temperature was 28.
It was set to 0 ° C. In each of Examples 5 and 6, a friction material having good porous characteristics and compression characteristics was obtained.

Examples using wholly aromatic polyamide fibers other than Kevlar are described in Examples 7 and 8. In Example 7,
Technora fiber made of para-aramid copolymer was used, and in Example 8, Nomex fiber made of meta-aramid was used. In both cases, a friction material having good porous characteristics and compression characteristics was obtained.

In Example 9, a friction material was trial-produced using only the formic acid solution of nylon 6. This friction material also shows good characteristics, but it is considered that the heat resistance is slightly inferior to that of the other examples because no thermosetting resin is used.

Further, an example using a melamine resin solution as the thermosetting resin solution is described in Example 15. A friction material having a porosity and compression characteristics almost equivalent to those obtained by using the resole resin was obtained.

[0046]

As described above, according to the present invention, since the aliphatic nylon or the resole resin containing the aliphatic nylon is used, it has high heat resistance and excellent porous characteristics. A wet friction material having compressive properties and a method for manufacturing the same can be provided. That is,
By heat-curing at a temperature above the melting point of the aliphatic nylon and below its decomposition temperature, the aromatic aromatic polyamide fibers are firmly bonded by the aliphatic nylon microcrystals, the aliphatic nylon tie molecular chain and the crosslinked resole resin. The wet friction material can be obtained. In addition, the reinforcing effect of the tie molecular chains connecting the aliphatic nylon microcrystals grown from the wholly aromatic polyamide fiber improves the shearing property, which is an essential disadvantage of the wholly aromatic polyamide fiber, and at the same time, the aliphatic nylon has Excellent friction characteristics can be imparted to the wet friction material.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Maeda 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (56) References JP-A-50-133361 (JP, A) JP-A-57- 70634 (JP, A) JP 7-207121 (JP, A) JP 4-339888 (JP, A) JP 9-59599 (JP, A) JP 58-77939 (JP, A) JP-A-7-19270 (JP, A) JP-A-8-61385 (JP, A) JP-A-62-266238 (JP, A) JP-A-7-151774 (JP, A) JP-A-7-97566 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09K 3/14 F16D 69/02 C08J 5/14

Claims (7)

(57) [Claims] 1. A wet friction material comprising aliphatic nylon or a resole resin containing aliphatic nylon and wholly aromatic polyamide fibers. 2. The wet friction material according to claim 1, which has a porosity of 15 to 50%. 3. The wet friction material according to claim 1, which has a compression elastic modulus of 5 to 55 MPa. 4. The adhesion ratio of the aliphatic nylon or the mixture of the aliphatic nylon and the resole resin to the wholly aromatic polyamide fiber is 15 to 60% by dry weight. The wet friction material according to any one of the items. 5. In producing the wet friction material according to any one of claims 1 to 4, an impregnating solution containing an aliphatic nylon or a resole resin solution containing an aliphatic nylon is prepared, and A method for producing a wet friction material, comprising impregnating an aromatic polyamide fiber with an impregnating solution, and then heat-curing the aliphatic nylon fiber at a temperature in the range of the melting point to the decomposition temperature of the aliphatic nylon. 6. The method for producing a wet friction material according to claim 5, wherein the amount of the aliphatic nylon added is 0.1 to 60% by weight of the impregnating solution. 7. The component other than the aliphatic nylon in the impregnating solution comprises a resol resin methanol solution, formic acid or metacresol, or a mixed solution thereof, and the content of formic acid or metacresol is 40 to 99.9% by weight. 7. The method for manufacturing a wet friction material according to claim 6, wherein: