Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-12
2003-12-16
Moore, Margaret (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06664343
ABSTRACT:
TECHNICAL FIELD
The present invention relates to phenolic resin compositions. More particularly, the present invention pertains to a phenolic resin composition which is stable against an environmental moisture change and is excellent in fast curing, flexibility and heat resistance.
BACKGROUND OF THE INVENTION
A phenolic resin is relatively favorable in curing property, molding property and the like and a cured product thereof is excellent in electrical and mechanical characteristics so that the cured product thereof has widely been utilized for a molding material, a laminated material, a friction material for a disc brake pad and the like, a shell molding material, a casting material, a foamed material and the like as a well-balanced material thereby allowing the cured product thereof to be of an industrially valuable material.
However, the phenolic resin is liable to absorb moisture when an environmental moisture is changed and, once the phenolic resin absorbs the moisture, a curing behavior thereof is changed such that a curing rate is accelerated whereupon, for example, a yield of molded products at the time of molding was deteriorated, qualities of the molded products were varied from one another and the like. However, no effective measure to solve these problems has actually been proposed.
Further, though the phenolic resin can be a binder which has excellent mechanical characteristics, electrical characteristics, heat resistance, adhesivity and the like, the molded product thereof has a drawback that it is inferior in flexibility and vibration absorption. In order to improve these performances, studies on modified phenolic resins have actively been conducted. For example, among others, studies on oil-modified phenol resins, cashew-modified phenol resins, silicone-modified phenolresins, epoxy-modified phenolresins, melamine-modified phenol resins and the like have been conducted whereby some of the above-described modified phenol resins are put in an actual use.
To give one example of such usage, a first Japanese Patent laid-open, namely, Japanese Patent Laid-Open No. 323080/1999, discloses a method of producing a phenol resin composition in which a silicone gel based on an addition reaction type silicone having from 10 to 500 of a penetration number is kneaded into a phenol resin by using a pressure mixer. However, though a modified phenol resin composition obtained by this method has been improved in flexibility, vibration absorption and the like to some extent, stability against the environmental moisture change was insufficient.
Further, a second Japanese Patent laid-open, namely, Japanese Patent Laid-Open No. 071497/1999, discloses a rubber-modified phenol resin composition which is a phenolic resin composition containing a phenol resin which is a polycondensate of a phenol and an aldehyde and has a ratio (o/p ratio) of an ortho-bonding to a para-bonding at a methylene bonding in the resin being from 1.0 to less than 4.5 and a rubber component as essential components, in which acrylonitrile-butadiene rubber (NBR) and an elastomer containing an acrylic acid ester are used as the above-described rubber component.
However, though such a rubber-modified phenolic resin composition as described above has been improved in flexibility, vibration absorption and the like to some extent, heat resistance and stability against the environmental moisture change were insufficient. On this occasion, the o/p ratio described in the above-described Japanese Patent laid-open, namely, the second Japanese Patent laid-open, is determined by a ratio of absorbance of the ortho-bonding appearing in a range of from 730 cm
−1
to 770 cm
−1
to that of the para-bonding appearing in a range of from 800 cm
−1
to 840 cm
−1
in an infrared absorption spectrum. A value of the o/p ratio obtained by this measuring method comes out lower than that obtained by a measuring method described in embodiments according to the present invention. Specifically, a range of from 1.0 to less than 4.5 of the o/p ratio obtained by this measuring method approximately corresponds to that of from 0.4 to less than 2 of the o/p ratio obtained by the measuring method described in the embodiments according to the present invention.
Furthermore, a third Japanese Patent laid-open, namely, Japanese Patent Laid-Open No. 144106/2000, describes a rubber-modified high-ortho phenolic resin for use as a binder for a non-asbestos-based friction material in which NBR is used as such a rubber component as described above and the ratio (o/p ratio) of the ortho-bonding to the para-bonding at a methylene bonding in a resin portion of the high-ortho phenol resin is 1.0 or more, and, preferably, from 1.0 to 4.5. However, though such a rubber-modified phenolic resin as described above has been improved in flexibility, vibration absorption and the like to some extent, heat resistance and stability against the environmental moisture change were insufficient. On this occasion, the o/p ratio described in this Japanese Patent laid-open, namely, the third Japanese Patent laid-open, is determined by a same measuring method as in Japanese Patent Laid-Open No. 071497/1999, namely, the above-described second Japanese Patent laid-open; therefore, in a same manner as in the second Japanese Patent laid-open, a range of the o/p ratio described in this Japanese Patent laid-open comes out lower than that of the o/p ratio according to the present invention.
DISCLOSURE OF INVENTION
In view of the above-described problems, an object of the present invention is to provide a phenolic resin composition which is stable against an environmental moisture change and excellent in fast curing property, flexibility and heat resistance.
Inventors of the present invention have found as a result of an intensive study that, when a resin composition comprising a phenolic resin and a rubber component as essential components is produced, the above-described problems can be solved by using a resin in which a ratio (o/p ratio) of an ortho-bonding to a para-bonding at a methylene bonding in the phenolic resin is controlled to be in a specified range and, further, incorporating a specified quantity of a specified rubber component thereto to achieve the present invention.
In other words, the present invention is a phenolic resin composition, comprising from 70% by weight to 97% by weight of a phenolic resin and from 3% by weight to 30% by weight of a silicone-based rubber component, which is characterized in that a ratio (o/p ratio) of an ortho-bonding to a para-bonding at a methylene bonding in a phenolic resin is from 2 to 9.
As for a preferred aspect of the phenolic resin composition according to the present invention, mentioned is such a resin composition as described above in which a viscosity of a silicone-based rubber is from 5000 mm
2
/s to 200000 mm
2
/s at 50° C. Further, mentioned is such a phenolic resin composition as described above which is characterized by being a compound of from 85% by weight to 99% by weight of an organopolysiloxane having a silanol group at each terminal of a molecule thereof and from 1% by weight to 15% by weight of a crosslinking agent for silanol condensation as the silicone-based rubber.
As for the organopolysiloxane having a silanol group in each terminal of a molecule thereof, mentioned is a compound which is expressed by the following general formula (1):
wherein
R
1
and R
2
are same or different from each other and each individually represents any one of a monovalent hydrocarbon group, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group or the like, an aryl group such as a phenyl group, a xylyl group or the like, and a halogenated monovalent hydrocarbon such as a &ggr;-chloropropyl group, a 3,3,3-trifluoropropyl group or the like; and
n represents an integer of from 4 to 675.
Further, as for the crosslinking agent for silanol condensation, mentioned is a multifunctional silane compound in which three or more functional groups of at least one type selected from the group consist
Hattori Minoru
Kaneko Masahiro
Maeda Masanobu
Narisawa Hiroaki
Mitsui Chemicals Inc.
Moore Margaret
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