JP2003226742A - Phenol resin composition for friction material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phenol resin composition for friction materials requiring no degassing in molding, producing no voids or cracks and having good flexibility and high abrasion resistance, and its production method. <P>SOLUTION: The composition contains a novolak type phenol resin, an epoxy resin and a hardening catalyst, and at least part of the phenol resin is modified with a thermoplastic resin. Preferably, the thermoplastic resin consists of one or more of NBR, phenoxy resins and ethylene-acrylic rubber. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a phenol resin composition for friction materials and a method for producing the same.

[0002]

2. Description of the Related Art Conventional phenolic resin compositions for friction materials are those in which hexamethylenetetramine is used as a curing agent based on a novolac type phenolic resin, or a resol type phenolic resin alone or in combination with a novolak type phenolic resin. Was common. When such a phenol resin composition is used, ammonia gas generated by decomposition of condensed water and hexamethylenetetramine is generated during molding, that is, in the resin curing reaction. Water vapor and ammonia gas resulting from these condensed water hinder the uniform curing of the resin and cause voids, cracks, etc. in the molded product to deteriorate the appearance of the molded product, lower the mechanical strength, etc. There was a problem. For this reason, there is a problem in that it is necessary to perform degassing work during molding, which complicates the process and takes a long time, resulting in poor efficiency and workability. In order to solve such a problem, a phenol resin composition in which a novolac-type phenol resin, an epoxy resin, and a curing catalyst are uniformly melt-mixed to generate substantially no gas resulting from a curing reaction during molding was invented. Some of them are put to practical use (Japanese Patent Laid-Open No. 2001-213941). However, such a phenol resin composition may lack flexibility in applications exposed to a high degree of impact, and when used as a friction material, there is a problem that squeaking and abnormal noise occur.

[0003]

DISCLOSURE OF THE INVENTION The present invention does not require degassing at the time of molding, does not cause voids or cracks in a molded product, has excellent flexibility, and has excellent wear resistance. A resin composition and a method for producing the same are provided.

[0004]

This object is achieved by the inventions (1) to (5) described below. (1) A phenol for a friction material, which contains a novolac type phenolic resin, an epoxy resin, and a curing catalyst as essential components, and at least a part of the novolac type phenolic resin is modified with a thermoplastic resin. Resin composition. (2) The thermoplastic resin is NBR, phenoxy resin,
And at least one selected from ethylene acrylic rubber
The phenol resin composition for friction materials according to (1) above, which is one or more kinds. (3) The phenol resin composition for a friction material according to claim 1 or 2, wherein the thermoplastic resin is 3 to 45% by weight based on the entire novolac type phenol resin. (4) The phenol resin composition for a friction material according to any one of (1) to (3) above, which is obtained by melt-mixing a novolac type phenol resin, an epoxy resin, and a raw material containing a curing catalyst as essential components. . (5) A method for producing the phenol resin composition for a friction material according to (4), wherein a raw material containing a novolac type phenol resin, an epoxy resin, and a curing catalyst as essential components is melted by a pressure-type kneading device. A method for producing a phenolic resin composition for a friction material, which comprises mixing.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The phenol resin composition for a friction material and the method for producing the same of the present invention will be described below. The friction resin phenol resin composition of the present invention (hereinafter, simply referred to as "composition") contains a novolac type phenol resin, an epoxy resin, and a curing catalyst as essential components, and at least a part of the novolac type phenol resin. It is characterized by being modified with a thermoplastic resin. In addition, the method for producing the phenol resin composition for friction materials of the present invention (hereinafter, simply referred to as “production method”) is a pressure-type kneading of raw materials containing the novolac type phenol resin, the epoxy resin, and the curing catalyst as essential components. It is characterized in that it is melted and mixed by an apparatus. First, the composition of the present invention will be described.

The novolac type phenolic resin used in the composition of the present invention is one in which at least a part thereof is modified with a thermoplastic resin (hereinafter referred to as "modified novolac type phenolic resin"). The thermoplastic resin used here is not particularly limited, but for example, elastomers such as NBR (nitrile butadiene rubber), isoprene rubber, polybutadiene rubber, acrylic rubber, ethylene acrylic rubber, polyamide resin, phenoxy resin, polyvinyl butyral resin, polyethylene terephthalate,
Examples thereof include polyurethane, methyl methacrylate-based copolymer, polyester resin, cellulose acetate polymer, polyvinyl alcohol and the like. These can be used alone or in combination. Since these thermoplastic resins have a long-chain structure excellent in elasticity and flexibility, introduction of this into a novolac type phenol resin can impart the above effect to the modified novolac type phenol resin. Among these, NBR, phenoxy resin, and ethylene acrylic rubber are preferably used. As a result, the compatibility with the novolac type phenol resin and the uniform mixing property can be improved, and the effect of imparting flexibility can be made particularly large. Further, since ethylene acrylic rubber has excellent heat resistance as an elastomer, it is possible to maintain heat resistance in addition to the above effects.

Here, NBR is a kind of synthetic rubber obtained by copolymerizing butadiene and acrylonitrile, and has various properties depending on the content rate of acrylonitrile (usually 15 to 50% by weight). is there. When used in the present invention, it is not particularly limited, but medium-high nitrile and high-nitrile having a relatively high acrylonitrile content are often used. As a result, the compatibility with the novolac type phenol resin can be made particularly good. The phenoxy resin is a linear copolyether obtained by reacting an aromatic diol with epihalohydrin or an aromatic diglycidyl ether, and can be used as a thermosetting resin by adding a curing agent. When used in the present invention, although not particularly limited, the solution viscosity at 25 ° C. in a 20% cyclohexanone solution is 50%.
A medium molecular weight type of 0 to 750 cps is preferable. Thereby, the melt viscosity of the modified novolac type phenol resin can be made appropriate and the molding stability can be improved. Further, ethylene acrylic rubber is a kind of alkyl acrylate polymer, and examples thereof include those containing methyl acrylate or ethyl acrylate as a main component, or those obtained by copolymerizing this with other monomers. When used in the present invention, it is not particularly limited, but it is preferable to use ethylene acrylic rubber obtained by copolymerizing ethylene and methyl acrylate. This makes it possible to obtain an excellent balance of flexibility and heat resistance.

In the present invention, the modified novolac type phenol resin is obtained by dispersing or melting and mixing a thermoplastic resin and a novolac type phenol resin. Here, the thermoplastic resin may be mixed in the initial stage of producing the novolac type phenol resin, or may be mixed in the middle or after the completion of the reaction. The modified novolac type phenol resin thus obtained may be one in which a thermoplastic resin reacts with a phenol resin component, one dispersed in a phenol resin system, or a mixture of both. . Regardless of the form, it is possible to disperse the modified component in the composition containing the thermoplastic resin component with high accuracy by providing the thermoplastic resin component with excellent uniform dispersibility. As a result, flexibility can be imparted to the cured product, and mechanical properties and wear resistance when used as a friction material can be improved.

The method for producing a modified novolac type phenol resin using the above thermoplastic resin is not particularly limited, but a method for obtaining an ordinary novolac type phenol resin, that is, phenol (P) and formaldehyde (F).
In the process of reacting and with an acidic catalyst at a molar ratio (F / P) of 0.50 to 0.95, a method of reacting with formaldehyde in a state in which a thermoplastic resin is melted in phenol at the initial stage of the reaction, the latter stage of the reaction There is a method of adding and mixing the modifying substance and then dehydrating, or a method of melting and kneading with the modifying substance after completion of the dehydration. Further, instead of phenol or formaldehyde, it can also be obtained by using, as a raw material, phenols or aldehydes capable of imparting such a modified structure when made into a phenol resin. Moreover, you may use the commercial item adjusted to the target property.

In addition to the modified novolac type phenolic resin as described above, it is also possible to jointly use a normal non-modified novolac type phenolic resin. The properties of these novolac type phenolic resins or modified novolac type phenolic resins are not particularly limited, and any of liquid, solid, solid powder and the like can be used.

In the composition of the present invention, the amount of the thermoplastic resin used for modifying the novolac type phenolic resin is not particularly limited, but is 3 to 45% by weight based on the whole novolac type phenolic resin including the thermoplastic resin. Is preferable, and more preferably 5 to 25% by weight. As a result, in addition to the effect of imparting flexibility, it is possible to improve moldability when used as a friction material.
If the amount of the thermoplastic resin exceeds the above upper limit value, the composition tends to be hardened, and the moldability may decrease. If it is less than the lower limit, the effect of improving flexibility may not be sufficient. In the composition of the present invention, as the novolac type phenolic resin component, for example, only a modified novolac type phenolic resin modified with a thermoplastic resin may be used, or an unmodified novolac type phenolic resin may be used. You may mix and use it. Also, two or more of these may be used in combination. In any case, it is preferable that the ratio of the thermoplastic resin to the total amount of the novolac phenolic resin containing the thermoplastic resin as the modifying component is within the above range.

The epoxy resin used in the composition of the present invention is not particularly limited, but may be one having at least two epoxy groups in one molecule and solid or liquid at room temperature, for example, bisphenol A.
Type, bisphenol S type, phenol novolac type, cresol novolac type, biphenyl type, naphthalene type,
Examples thereof include aromatic amine type. Moreover, these can be used individually or in combination of multiple. The compounding amount of the epoxy resin in the composition of the present invention is not particularly limited, but the epoxy group contained in the epoxy resin is 0.1 to 2.5 equivalents relative to 1.0 equivalent of the phenolic hydroxyl group contained in the novolac type phenol resin. Is preferable, and more preferably 0.4 to 1.4 equivalents. If the equivalent number of the epoxy group to the phenolic hydroxyl group is less than the lower limit value or exceeds the upper limit value, curing of the resin component may be insufficient, whereby the cured product has sufficient mechanical strength. It may not be obtained.

The curing catalyst used in the composition of the present invention is not particularly limited. For example, tertiary amine compounds such as triethylamine, benzyldimethylamine and α-methylbenzyldimethylamine, organic phosphines such as triphenylphosphine and tributylphosphine. Examples thereof include compounds, imidazole compounds such as 2-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methylimidazole. Moreover, these can be used individually or in combination of multiple. The addition amount of the curing catalyst is not particularly limited, but is preferably 0.1 to 5.0 parts by weight, more preferably 0.3, based on 100 parts by weight of the total amount of the novolac type phenol resin and the epoxy resin. ~ 2.5 parts by weight. If the addition amount of the curing catalyst is less than the lower limit value, curing of the resin may be insufficient, while if it exceeds the upper limit value, the curing of the resin will be accelerated and the fluidity will be lowered, so that mechanical It may cause reduction in strength.

Since the curing of the resin in the composition of the present invention proceeds by the addition reaction between the phenol resin and the epoxy resin, the polycondensation reaction which is the usual curing reaction of the phenol resin does not occur, and the gas caused by this does not occur. Occurrence can be virtually eliminated. Therefore, degassing work at the time of molding is not required, and it is also preferable in terms of environmental hygiene.

Next, a method for producing the composition of the present invention will be described. The production method of the present invention is not particularly limited, and examples thereof include a method of melting and mixing the raw materials, a method of dry pulverizing and mixing, and a method of dry pulverizing and mixing the melt-mixed raw materials. The method for melt-mixing the raw materials is not particularly limited, and for example, a method of charging a raw material containing a predetermined amount of a novolac-type phenol resin, an epoxy resin, and a curing catalyst into a pressure-type kneading device and performing melt-mixing under pressure can be mentioned. To be The temperature at the time of mixing is suitable in the range where the phenol resin and the epoxy resin melt but the curing reaction does not start. This method is preferable because a composition in which the raw material components are uniformly dispersed can be obtained. Here, the pressure-type kneading device is not particularly limited, but a roll-type kneader, a pressure kneader, a twin-screw extruder, a single-screw extruder or the like is suitable. When the raw materials used in the composition of the present invention are melt-mixed using an ordinary reaction vessel, it is difficult to carry out due to the reason that the resin viscosity increases, or the gelation reaction starts, etc. By using a kneader,
It is possible to obtain a composition in which a novolac type phenol resin, an epoxy resin, a curing catalyst and the like are uniformly dispersed without curing the resin component.

The method of dry pulverizing and mixing the raw materials is not particularly limited. For example, each raw material component is continuously supplied to the pulverizing device in a predetermined amount according to its compounding ratio, and pulverization and mixing are performed simultaneously to form a composition. The method of obtaining the thing is mentioned. Further, the method for dry pulverizing and mixing the raw materials that have been melt-mixed is not particularly limited, but for example, a novolac-type phenol resin and / or a part of the epoxy resin and a curing catalyst that are melt-mixed and solidified, The novolac-type phenol resin and / or the epoxy resin other than those used in the above are solidified by melting and mixing, and are continuously supplied to the crushing device in predetermined amounts according to the mixing ratio thereof,
Examples thereof include a method of obtaining a composition by simultaneously performing pulverization and mixing. This method is preferable because the resin component and the curing catalyst can be accurately dispersed and mixed even when the amount of the curing catalyst contained in the composition is small.

[0017]

EXAMPLES The present invention will be described below with reference to examples. However, the present invention is not limited to these examples. In addition, "part" described in Examples and Comparative Examples
And "%" all indicate "parts by weight" and "% by weight".

<Example 1> 1000 parts of phenol and 10 parts of oxalic acid were placed in a reactor equipped with a stirrer, a reflux condenser and a thermometer.
After the parts were charged, the temperature was gradually raised, and after the temperature reached 100 ° C., 630 parts of 37% formalin was added portionwise over 60 minutes,
Then, a reflux reaction was performed for 120 minutes. Normal-pressure dehydration was performed until the internal temperature reached 110 ° C, and then vacuum dehydration was performed. When the temperature in the system was raised to 160 ° C, ethylene acrylic rubber (Baymac G manufactured by Showa Denko / Dupont Co., Ltd.) was heated to 300 ° C. When 1 part was charged and uniformly dissolved, the content was taken out from the reactor to obtain 1370 parts of a novolac type phenol resin modified with ethylene acrylic rubber which was solid at room temperature. 500 parts of this ethylene acrylic rubber modified novolac type phenolic resin, 500 parts of novolac type phenolic resin (PR-50731 manufactured by Sumitomo Bakelite Co., Ltd.), epoxy resin (Araldite AER26 manufactured by Asahi Ciba Co., Ltd.)
64) 2200 parts (equivalent ratio (epoxy group / hydroxyl group) =
1.0), 15 parts of triethylamine was charged into a pressure kneader, heated to 90 ° C., melted, and mixed for 30 minutes,
Composition 305 which is solid at room temperature when taken out from the pressure kneader
I got 0 copies. 1000 parts of the obtained solid composition was pulverized to obtain 990 parts of a powder composition.

<Example 2> NB solid at room temperature was prepared in the same manner as in Example 1 except that NBR (Nipol 1041 manufactured by Nippon Zeon Co., Ltd.) was used instead of ethylene acrylic rubber.
1370 parts of R-modified novolac type phenol resin was obtained.
500 parts of this NBR modified novolac type phenolic resin,
Novolac-type phenol resin (Sumitomo Bakelite Co., Ltd.)
PR-50731) 500 parts, epoxy resin (Asaru Chiba Co., Ltd. Araldite ECN1299) 2200 parts (equivalent ratio (epoxy group / hydroxyl group) = 1.0), triphenylphosphine 20 parts, inlet temperature 90 ° C, outlet Temperature 1
The composition was supplied to a twin-screw extruder controlled at 00 ° C. so that the supply amount per unit time was equal, and 3100 parts of a solid composition at room temperature was obtained from the outlet. The obtained solid composition 1000
Parts were crushed to obtain 990 parts of a powder composition.

<Example 3> Example 1 except that 150 parts of phenoxy resin (Phenototo YP-50S manufactured by Tohto Kasei Co., Ltd.) was used instead of 300 parts of ethylene acrylic rubber.
In the same manner as above, 1220 parts of a phenoxy resin-modified novolac type phenol resin which was solid at room temperature was obtained. 500 parts of this phenoxy resin modified novolac type phenol resin, novolac type phenol resin (manufactured by Sumitomo Bakelite Co., Ltd.)
PR-50731) 500 parts, epoxy resin (Aradite AER6021 manufactured by Asahi Ciba Co., Ltd.) 2200 parts (equivalent ratio (epoxy group / hydroxyl group) = 1.0), 15 parts of 2-methylimidazole, surface temperature to 70 ° C. Kneading was performed for 20 minutes with the above roll type kneader to obtain 3180 parts of a solid composition at room temperature. 1000 parts of the obtained solid composition was pulverized to obtain 990 parts of a powder composition.

<Comparative Example 1> Novolak type phenolic resin (PR-50731 manufactured by Sumitomo Bakelite Co., Ltd.) 10
00 parts and 100 parts of hexamethylenetetramine were charged into a crusher and crushed and mixed to obtain 1090 parts of a powder composition.

<Comparative Example 2> Novolak type phenolic resin (PR-50731 manufactured by Sumitomo Bakelite Co., Ltd.) 10
00 parts, 2200 parts of epoxy resin (Araldite ECN1299 manufactured by Asahi Ciba Co., Ltd.), and 20 parts of triphenylphosphine are supplied to a twin-screw extruder controlled at an inlet temperature of 90 ° C and an outlet temperature of 100 ° C per unit time. Were supplied so as to be equal to each other, and 3100 parts of a solid composition was obtained from the outlet at room temperature. 1000 parts of the obtained solid composition was pulverized to obtain 990 parts of a powder composition.

The powder compositions obtained in Examples and Comparative Examples were evaluated as follows. 1. Thermoplastic resin ratio The ratio of the thermoplastic resin to the total amount of the novolac type phenolic resin containing the thermoplastic resin was calculated in% by weight. 2. The glass test tube was immersed in an oil bath set at a gas generation amount of 180 ° C. and allowed to stand until the temperature became stable. afterwards,
About 3 g of the precisely weighed composition was put into a cylindrical aluminum foil and inserted into a tube. The volume of the generated gas was measured for 10 minutes while keeping the pressure constant while lowering the liquid level by the volume deducted by the simple gas volume meter. 3. Evaluation of Friction Material The materials and formulations shown in Table 1 were mixed. This formulation at a temperature of 1
Molded at 60 ° C., pressure 19.6 MPa for 10 minutes,
A molded product of × 150 × 20 mm was obtained. The obtained molded product was fired at 200 ° C. for 5 hours to prepare an evaluation sample corresponding to a friction material, and the following evaluation was performed using the sample. (1) Materials used Aramid fiber: Dry pulp Fiber length 2 mm Calcium carbonate: Average particle size 20 μm Barium sulfate: Average particle size 20 μm (2) Evaluation method Rockwell hardness: Measured according to JIS K7202. Normal bending strength: Measured according to JIS K7203. Bending strength after heat history: J after processing at 350 ° C for 4 hours
It was measured according to IS K 7203. Abrasion amount: Measured by JASO C 406. Table 2 shows the above measurement results.

[0024]

[Table 1]

[0025]

[Table 2]

Each of Examples 1 to 3 contains a novolac type phenol resin, an epoxy resin, and a curing catalyst as essential components, and at least a part of the novolac type phenol resin is modified with a thermoplastic resin. No gas was generated during curing. In the evaluation of a molded article corresponding to a friction material using this composition, the flexibility represented by Rockwell hardness was improved and the amount of wear could be reduced without affecting the normal bending strength. Usually, when a novolac-type phenol resin modified with a thermoplastic resin is used, the bending strength after heat history tends to be slightly decreased within a range where there is no practical problem, but in Example 1, heat resistance Since the modified novolac type phenolic resin modified with ethylene acrylic rubber which is an elastomer was used, it was possible to maintain the flexural strength after heat history. On the other hand, Comparative Example 1 was a composition in which hexamethylenetetramine was blended with a novolac type phenol resin, and gas generation during curing was observed. When a molded article corresponding to a friction material was prepared using this composition, degassing was carried out four times during molding. For reference, molding was attempted without degassing operation, but swelling due to gas occurred, and a good molded product could not be obtained. Further, in Comparative Example 2, a novolac type phenol resin, an epoxy resin, and a curing catalyst were blended. In the evaluation of the molded product, in both Comparative Examples 1 and 2, the modified novolac type phenol resin modified with the thermoplastic resin was not used, so that the flexibility was decreased and the wear amount was increased as compared with the Examples. .

[0027]

Industrial Applicability The present invention is a composition containing a novolac type phenol resin, an epoxy resin, and a curing catalyst as essential components, wherein at least a part of the novolac type phenol resin is modified with a thermoplastic resin. Since the gas caused by the reaction is not substantially generated, it is not necessary to perform the degassing work during molding, and the workability is excellent. Further, by using this composition, it is possible to obtain a friction material having excellent flexibility and good wear resistance.

Claims (5)

[Claims] 1. A friction material comprising a novolac-type phenol resin, an epoxy resin, and a curing catalyst as essential components, and at least a part of the novolac-type phenol resin modified with a thermoplastic resin. Phenolic resin composition for use. 2. The phenol resin composition for a friction material according to claim 1, wherein the thermoplastic resin is at least one selected from NBR, phenoxy resin, and ethylene acrylic rubber. 3. The phenol resin composition for a friction material according to claim 1, wherein the thermoplastic resin is 3 to 45% by weight with respect to the entire novolac type phenol resin. 4. The phenol resin composition for a friction material according to claim 1, wherein the novolac type phenol resin, the epoxy resin, and a raw material containing a curing catalyst as essential components are melt-mixed. 5. A method for producing the phenol resin composition for a friction material according to claim 4, wherein a raw material containing a novolac type phenol resin, an epoxy resin, and a curing catalyst as essential components is prepared by a pressure-type kneading device. A method for producing a phenol resin composition for a friction material, which comprises melt-mixing.