Polyphenol resin, process for its production, epoxy resin...

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

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Details

C525S492000, C528S143000, C528S153000, C528S165000, C568S719000, C568S720000, C568S732000

Reexamination Certificate

active

06723801

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a polyphenol resin which can provide an excellently noninflammable cured product and has flexibility enough to form a film; an epoxy resin; and the cured product, though it does not contain a halogenide flame-retardant or an antimony compound.
BACKGROUND ART
An epoxy resin can be cured by various curing agents to provide a cured product and it is generally excellent in mechanical properties, water proofing, chemicals resistance, heat resistance and electric properties. Therefore it has been widely utilized in the fields of adhesive, paint, laminate, molding material and casting material for example. The most popular epoxy resin which has been used includes a bisphenol A type epoxy resin. Other, tetrabromobisphenol A and the epoxylated product thereof, or the compound produced by reacting a bisphenol A type epoxy resin with tetrabromobisphenol A are generally known as a flame-retardant. As a curing agent for an epoxy resin, an acid anhydride or an amine compound is known, but a phenol novolac has been more often used in the field of electric and electronic parts because of the high reliability.
However, the above bromine-containing compound, if burned to waste, is liable to generate a substance to cause environmental pollution, though it is excellent in non-inflammability. An antimony compound used for the non-inflammable auxiliary agent also is concerned to have the toxicity.
Under this circumstance, recent increasing of consideration to environmental conservation demands to develop a halogen-free and antimony-free epoxy resin composition. On the other hand, an epoxy resin cured by a phenol novolac gives a cured product which is too tough and lacking in flexibility though it has excellent creditability. The recently developed electric/electronic parts do not take the conventional shape of a large package or a substrate made of glass fiber as the base material, but takes a molded shape of sheet obtained by coating a rasin in the form of varnish on a polyimide or PET(polyethylene glycol terephthalate) film or on a metallic foil and then removing the solvent. Therefore, it needs to use the resin having sufficient flexibility.
DISCLOSURE OF THE INVENTION
In view of these circumstances, the present inventors have studied diligently to find out an epoxy resin composition that can provide an excellently non-inflammable cured product and can be molded to a shape of sheet without losing the flexibility. As the result, the present invention has been completed.
Namely the present invention is as follows:
(1) A polyphenol resin represented by formula (1):
wherein, n is an average degree of polymerization as specified by the average molecular weight,
and having a weight-average molecular weight of 3,000 or more as determined by gel permeation chromatography (GPC, hereinafter same).
(2) A method for producing a polyphenol resin having a weight-average molecular weight of 3,000 or more as determined by GPC, comprising reacting to condense a polyphenol compound represented by formula (1′)
wherein, n′ is an average degree of polymerization as specified by the average molecular weight,
and having a weight-average molecular weight of 1,500 or less as determined by GPC
with a biphenyl compound represented by formula (2):
wherein, X is a halogen, a C1-3 alkoxy group or hydroxyl group, in an amount of 0.01 mol or more and less than 0.5 mol relative to 1 equivalent of the phenolic hydroxyl group of the polyphenol compound.
(3.) An epoxy resin composition comprising (a) an epoxy resin having at least two epoxy groups in the molecule and (b) the polyphenol resin according to (1) mentioned above.
(4) The epoxy resin composition according to the above term (3) mentioned above, wherein the epoxy resin is represented by formula (a):
wherein, m is an average degree of polymerization and a positive number.
(5) The epoxy resin composition according to the above term (3) or (4) further comprising a curing accelerator.
(6) A varnish comprising the polyphenol resin according to the above term (1) and a solvent.
(7) The varnish comprising the epoxy resin composition according to any one of the above terms (3)-(5) containing a solvent.
(8) A sheet comprising a layer formed by drying the varnish according to the above term (6) or (7) on the surface of a flat supporting substrate.
(9) The sheet according to the above term (8), wherein the flat supporting substrate is a polyimide film.
(10) The sheet according to the above term (8), wherein the flat supporting substrate is a metallic foil.
(11) The sheet according to the above term (8), wherein the flat supporting substrate is a release film.
(12) A cured product obtained by curing the epoxy resin composition according to any one of the above terms (3)-(5).
(13) A curing agent for an epoxy resin comprising the polyphenol resin according to the above term (1).
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will be described in details below.
In the below description, “part(s)” and “%” are “part(s) by mass” and “% by mass” respectively, unless otherwise stated.
In the present invention, a halogen includes chlorine, bromine and iodine; and a C1-3 alkoxy group includes methoxy group, ethoxy group, n-propoxy group and i-propoxy group. In the formula (2), the substituent XCH
2
— on each phenyl group substitutes at any position of the positions 2, 3, and 4 or the positions 2′, 3′ and 4′. In the formula (1), the bridging group (—CH
2
—) corresponding to this substituent is also same as mentioned above.
The polyphenol resin of the present invention having a structure represented by the formula (1) and having a weight-average molecular weight of 3,000 or more as determined by GPC can be obtained for example by reacting to condense a polyphenol compound represented by the above formula (1′) with a biphenyl compound represented by the formula (2) in the absence or presence of a solvent generally in amount of 0.01 mol or more and less than 0.5 mol, preferably 0.01-0.45 mol, and more preferably 0.05-0.4 mol relative to 1 equivalent of phenolic hydroxyl group of the polyphenol compound.
In the condensation reaction, an acid catalyst may be used if necessary. An acid catalyst, if the X is a halogen in the biphenyl compound of the formula (2), is not necessary, but if the X is an alkoxy group or hydroxyl group, it is necessary.
The polyphenol resin of the present invention may be obtained by synthesizing a polyphenol compound represented by the formula (1′) by a method as described later (the first condensation reaction) and then without isolation of the polyphenol compound reacting to condense the polyphenol compound with a biphenyl compound of the formula (2) (the second condensation reaction).
The biphenyl compound of the formula (2) includes 2,2′-, 3,3′- or 4,4′-bismethoxymethyl biphenyl, 2,2′-, 3,3′- or 4,4′-bisethoxymethyl biphenyl, 2,2′-, 3,3′- or 4,4′-bispropoxymethyl biphenyl, 2,2′-, 3,3′- or 4,4′-bischloromethyl biphenyl, 2,2′-, 3,3′- or 4,4′-bisbromomethyl biphenyl, and 2,2′-, 3,3′- or 4,4′-bihydroxymethyl biphenyl.
The preferable compound of the formula (2) includes a compound where X is a halogen, preferably chlorine or an alkoxy group, preferably methoxy group. For a compound of the formula (2), a mixture of 2,2′product, 3,3′product, 4,4′ product and the others is available on the market. A mixture containing 4,4′product as the main component is preferable.
The preferable biphenyl compound represented by the formula (2) to use in the condensation reaction of the present invention includes a compound where X is a halogen, preferably chlorine.
The biphenyl compound of the above formula (2) in the condensation reaction of the present invention is used generally in an amount of 0.01 mol or more and less than 0.5 mol, preferably 0.01-0.45 mol, and more preferably 0.05-0.4 mol relative to 1 equivalent of phenolic hydroxyl group of the

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