Curable resin composition and adhesive

Details Curable resin composition and adhesive Curable resin composition and adhesive

1999-07-29

2001-03-06

Dawson, Robert (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...

C556S413000, C556S482000, C528S038000, C528S421000, C528S044000, C525S452000, C525S523000

Reexamination Certificate

active

06197882

ABSTRACT:

This invention relates to a curable resin composition comprising a curable resin such as an epoxy or urethane resin and a ketimine structure-bearing organosilicon compound. It also relates to an adhesive comprising the same.
BACKGROUND OF THE INVENTION
Organoalkoxysilanes having a ketimine structure are known in the art (see U.S. Pat. No. 2,942,019). The ketimine structure is inactive as such with its amino group remaining non-reactive. Upon contact with moisture or water, the ketimine structure readily degrades to regenerate a primary amino group so that the reactivity of amino group is resumed. By virtue of this characteristic, the ketimine structure can serve as an adhesion modifier when added to mixtures of an epoxy resin and a polyamide resin. It is also known from JP-B 57-11582 to use the ketimine structure as a curing agent. JP-B 2-19866 discloses that a ketimine structure-bearing organosilicon compound obtained by reacting an aminosilane with a dicarbonyl compound is used as an additive to polyurethane resins. JP-A 3-263421 discloses that the ketimine structure-bearing organosilicon compound serves as an adhesion modifier and curing agent in mixtures of an epoxy resin and a modified silicone resin.
Analyzing the ketimine structure-bearing organosilicon compounds used in these known resin compositions and adhesives, the inventor found that these compounds have not completed reaction and some of the amino group-containing organosilicon compound used as the reactant is left in the system. Since water resulting from the synthesis has not been fully removed from the system, the end compound contains a substantial proportion of oligomers and is not fully shelf stable.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved curable resin composition comprising a ketimine structure-bearing organosilicon compound which is shelf stable and highly adhesive. Another object is to provide an adhesive comprising the composition.
The invention provides a curable resin composition comprising (A) a curable resin and (B) a ketimine structure-bearing organosilicon compound obtained by reacting an amino group-containing organosilicon compound of the following general formula (1) with a monocarbonyl compound of the following general formula (2).
R
1
is a monovalent hydrocarbon group of 1 to 4 carbon atoms, R
2
is a divalent hydrocarbon group of 1 to 10 carbon atoms, and n is equal to 1, 2 or 3.
R
3
and R
4
each are hydrogen or a monovalent hydrocarbon group of 1 to 10 carbon atoms, with the proviso that both R
3
and R
4
are not hydrogen at the same time, and R
3
and R
4
may form a cyclic structure with the carbon atom of the carbonyl group. The ketimine structure-bearing organosilicon compound should have a monomer purity of 50 to 95% and an amino group blockage of at least 90%. This resin composition is shelf stable and remains highly adhesive.
Also contemplated herein is an adhesive comprising the curable resin composition defined above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The curable resin composition of the invention contains (A) a curable resin and (B) a ketimine structure-bearing organosilicon compound as essential components.
The curable resin (A) may be selected from among epoxy resins, phenolic resins, urethane resins, melamine resins, polyimide resins, and furan resins, and mixtures of two or more of these resins. Of these, epoxy and urethane resins are desirable.
Any of prior art well-known epoxy resins may be used. Examples include bisphenol A and bisphenol F type epoxy resins obtained by reacting bisphenol A or bisphenol F with epichlorohydrin, hydrogenated ones of these epoxy resins, glycidyl ester type epoxy resins, novolac type epoxy resins, urethane-modified epoxy resins, nitrogenous epoxy resins, and rubber-modified epoxy resins.
Any of prior art well-known urethane resins may be used. Exemplary urethane resins are those based on urethane prepolymers obtained by reacting polyols such as polyoxyalkylene polyols, polyester polyols, hydroxyl group-containing polybutadiene polyols, acrylic polyols, castor oil derivatives, and tall oil derivatives, with an excess of polyisocyanate compounds.
Component (B) is a ketimine structure-bearing organosilicon compound which is obtained by reacting an amino group-containing organosilicon compound of the following general formula (1) with a monocarbonyl compound of the following general formula (2).
Formula (1):
In formula (1), R
1
is a monovalent hydrocarbon group of 1 to 4 carbon atoms, R
2
is a divalent hydrocarbon group of 1 to 10 carbon atoms, and n is equal to 1, 2 or 3.
Illustrative groups represented by R
1
are alkyl groups such as methyl, ethyl, propyl and butyl, and alkenyl groups such as vinyl, allyl, propenyl and butenyl, with the alkyl groups being preferred. Illustrative groups represented by R
2
are alkylene groups such as methylene, ethylene, propylene and butylene, arylene groups such as phenylene, and alkylene arylene groups, with the alkylene groups being preferred. The letter n is preferably equal to 2 or 3.
Illustrative examples of the amino group-containing organosilicon compound of formula (1) are given below.
Of these, the following compounds are preferred on practical use.
Formula (2):
In formula (2), R
3
and R
4
each are hydrogen or a monovalent hydrocarbon group of 1 to 10 carbon atoms, with the proviso that both R
3
and R
4
are not hydrogen at the same time, and R
3
and R
4
may form a cyclic structure with the carbon atom of the carbonyl group.
Exemplary groups represented by R
3
and R
4
include hydrogen, alkyl groups such as methyl, ethyl, propyl, butyl, cyclohexyl and octyl, aryl groups such as phenyl and tolyl, aralkyl groups such as benzyl and phenylethyl, and substituted ones of these groups in which some or all of the hydrogen atoms are replaced by halogen atoms. Both R
3
and R
4
are not hydrogen at the same time. R
3
and R
4
may bond together to form a divalent saturated hydrocarbon group (such as an alkylene group of 5 to 10 carbon atoms) which forms a cyclic structure with the carbon atom of the carbonyl group.
Illustrative examples of the monocarbonyl compound of formula (2) are given below. In the following formulae, Ph is phenyl.
Of these, the following compounds are preferable because they are more hydrophobic.
The ketimine structure-bearing organosilicon compound used herein may be prepared by any desired method although the following method is preferred in order to prepare the end compound having a monomer purity of 50 to 95% and an amino group blockage (or percentage of blocked amino groups) of at least 90%. An amino group-containing organosilicon compound or amino-functional alkoxysilane is reacted with a monocarbonyl compound by introducing the amino-functional alkoxysilane to the monocarbonyl compound under heating. During this introduction, reaction takes place to form water which is azeotroped off with the monocarbonyl compound. The molar ratio of the monocarbonyl compound to the amino-functional alkoxysilane is preferably 2/1 to 10/1, and more preferably from 3/1 to 5/1. If the monocarbonyl compound is less than 2 mol per mol of the amino-functional alkoxysilane, active amino groups would be left after reaction, failing to achieve an amino group blockage of at least 90%. Thus the molar ratio should preferably be at least 2. If the molar ratio exceeds 10, the pot yield would become too low, leading to an increased cost.
The temperature at which the amino-functional alkoxysilane is introduced, that is, reaction temperature is preferably from approximately the azeotropic temperature of a mixture of the monocarbonyl compound and water to approximately the reflux temperature of the monocarbonyl compound. In one typical example, the monocarbonyl compound is methyl isobutyl ketone which is reacted with an amino-functional alkoxysilane. A mixture of methyl isobutyl ketone and water has an azeotropic temperature of about 80° C. and methyl isobutyl ketone has a reflux temperature of 130° C. Then the introduction temperature of the

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