Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-12-04
2002-09-24
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C428S413000, C428S414000, C525S523000, C525S533000
Reexamination Certificate
active
06455662
ABSTRACT:
The use of unsubstituted or substituted imidazole as a curing catalyst in the curing of epoxy resins is known. For example, H. Lee and K. Neville in “Handbook of Epoxy Resins”, pages 10-17 (1967), report the property of epoxy resins cured with 2-ethyl-4-methyl-imidazole.
It has, surprisingly, been found that certain substituted imidazoles in admixture with epoxy resins have an even better latency at room temperature than mixtures of epoxy resins with imidazole or with 2-ethyl-4-imidazole, and at elevated temperature are distinguished by a high reactivity.
The present invention accordingly relates to novel curable mixtures comprising:
a) an epoxy resin having more than one 1,2-epoxy group per molecule and
b) as curing catalyst, an imidazole compound of formula I
wherein R
1
, R
2
and R
3
are each independently of the others a hydrogen atom, a halogen atom, alkyl having from 1 to 20 carbon atoms, alkoxy having from 1 to 20 carbon atoms, unsubstituted or halo-, nitro-, C
1-4
alkyl- or C
1-4
alkoxy-substituted aralkyl having from 7 to 20 carbon atoms, or unsubstituted or halo-, nitro-, C
1-4
alkyl- or C
1-4
alkoxy-substituted aryl having from 6 to 20 carbon atoms, and
R
4
is alkyl having from 1 to 20 carbon atoms, alkenyl having from 2 to 20 carbon atoms, alkynyl having from 2 to 20 carbon atoms, unsubstituted or halo-, nitro-, C
1-4
alkyl- or C
1-4
alkoxy-substituted aralkyl having from 7 to 20 carbon atoms or unsubstituted or halo-, nitro, C
1-4
alkyl- or C
1-4
alkoxy-substituted aryl having from 6 to 20 carbon atoms. Suitable epoxy resins (a) for the preparation of the curable mixtures according to the invention are the epoxy resins customarily employed in epoxy resin technology. Examples of epoxy resins are:
I) Polyglycidyl and poly(&bgr;-methylglycidyl) esters, obtainable by reaction of a compound having at least two carboxy groups per molecule with epichlorohydrin or &bgr;-methyl-epichlorohydrin, respectively. The reaction is advantageously carded out in the presence of bases. An aliphatic polycarboxylic acid may be used as compound having at least two carboxy groups per molecule. Examples of such polycarboxylic acids are oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and dimerised or trimerised linoleic acid. It is also possible, however, to use cycloaliphatic polycarboxylic acids, for example tetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, hexahydrophthalic acid or 4-methylhexahydrophthalic acid. Aromatic polycarboxylic acids may also be used, for example phthalic acid, isophthalic acid or terephthalic acid.
II) Polyglycidyl or poly(&bgr;-methylglycidyl) ethers, obtainable by reaction of a compound having at least two free alcoholic hydroxy groups and/or phenolic hydroxy groups with epichlorohydrin or &bgr;-methylepichlorohydrin, respectively, under alkaline conditions, or in the presence of an acid catalyst with subsequent alkali treatment.
Such glycidyl ethers are derived, for example, from acyclic alcohols, such as from ethylene glycol, diethylene glycol and higher poly(oxyethylene) glycols, propane-1,2-diol or poly-(oxypropylene) glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene) glycols, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, pentaerythritol, sorbitol, and also polyepichlorohydrins. They may also, however, be derived, for example, from cycloaliphatic alcohols, for example 1,4-cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane or 2,2-bis(4-hydroxycyclohexyl)propane, or they have aromatic nuclei, such as N,N-bis(2-hydroxy-ethyl)aniline or p,p′-bis(2-hydroxyethylamino)diphenylmethane.
The glycidyl ethers may also be derived from mononuclear phenols, for example from resorcinol or hydroquinone, or are based on polynuclear phenols, for example bis(4-hydroxyphenyl)methane, 4,4′-dihydroxybiphenyl, bis(4-hydroxyphenyl)sulfone, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, or from novolaks, obtainable by condensation of aldehydes, for example formaldehyde, acetaldehyde, chloral or furfuraldehyde, with phenols, such as phenol, or with phenols that are substituted in the nucleus by chlorine atoms or by C
1
-C
9
alkyl groups, for example 4-chlorophenol, 2-methylphenol or 4-tert-butylphenol, or by condensation with bisphenols, for example those of the type mentioned above.
III) Poly(N-glycidyl) compounds, obtainable by dehydrochlorination of the reaction products of epichlorohydrin with amines that contain at least two amine hydrogen atoms. The amines are, for example, aniline, n-butylamine, bis(4-aminophenyl)methane, m-xylylenediamine or bis(4-methylaminophenyl)methane.
The poly(N-glycidyl) compounds, however, also include triglycidyl isocyanurate, N,N′-di-glycidyl derivatives of cycloalkyleneureas, such as ethyleneurea or 1,3-propyleneurea, and diglycidyl derivatives of hydantoins, such as 5,5-dimethythydantoin.
IV) Poly(S-glycidyl) compounds, for example di-S-glycidyl derivatives that are derived from dithiols, for example ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.
V) Cycloaliphatic epoxy resins, for example bis(2,3-epoxycyclopentyl) ethers, 2,3-epoxycyclopentylglycidyl ether, 1,2-bis(2,3-epoxycyclopentyloxy)ethane or 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate.
It is also possible, however, to use epoxy resins in which the 1,2-epoxy groups are bonded to different hetero atoms or functional groups; those compounds include, for example, the N,N,O-triglycidyl derivative of 4-aminophenol, glycidyl ethers/glycidyl esters of salicylic acid, N-glycidyl-N′-(2-glycidyloxypropyl)-5,5-dimethylhydantoin and 2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane.
For the preparation of the epoxy resin compositions according to the invention it is preferred to use a liquid or solid polyglycidyl ether or ester, especially a liquid or solid diglycidyl ether of bisphenol or a solid or liquid diglycidyl ester of a cycloaliphatic or aromatic dicarboxylic acid, or a cycloaliphatic epoxy resin. It is also possible to use mixtures of epoxy resins.
Suitable solid polyglycidyl ethers and esters are compounds having melting points from above room temperature up to approximately 250° C. Preferably, the melting points of the solid compounds are in the range from 50 to 150° C. Such solid compounds are known and some of them are available commercially. As solid polyglycidyl ethers and esters it is also possible to use the advancement products obtained by pre-extension of liquid polyglycidyl ethers and esters.
The epoxy resin compositions according to the invention especially comprise a liquid polyglycidyl ether or ester.
The curable mixtures according to the invention comprise as component (b) preferably imidazole compounds of formula I wherein
R
1
and R
2
are each independently of the other a hydrogen atom, a halogen atom, alkyl having from 1 to 6 carbon atoms, alkoxy having from 1 to 6 carbon atoms or phenyl,
R
3
is a hydrogen atom or phenyl, and
R
4
is alkyl having from 1 to 10 carbon atoms, alkenyl having from 2 to 10 carbon atoms, unsubstituted or substituted phenyl or unsubstituted or substituted benzyl.
Suitable single or multiple substituents of phenyl or of benzyl are halogen atoms and nitro, C
1
-C
4
alkyl- and C
1
-C
4
alkoxy groups.
The mixtures according to the invention especially comprise as component (b) an imidazole compound of formula I wherein
each of R
1
and R
3
is a hydrogen atom.
R
2
is phenyl, and
R
4
is alkenyl having from 2 to 10 carbon atoms, or unsubstituted or substituted phenyl or unsubstituted or substituted benzyl, or wherein
R
1
is branched alkyl having from 3 to 6 carbon atoms, each of R
2
and R
3
is a hydrogen atom, and
R
4
is unsubstituted or substituted phenyl, unsubstituted or substituted benzyl or branched alkyl having from 3 to 6 carbon atoms.
In an especially preferred embodiment, the mixtures according to the invention comprise an imidazole compound of the formula
In th
Lyon & Lyon LLP
Neuman, Esq. Kristin H.
Sellers Robert E. L.
Shalek, Esq. James H.
Vantico Inc.
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