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
2000-02-25
2003-02-18
Short, Patricia A. (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...
C525S420000, C525S425000, C525S437000, C525S447000, C528S289000, C528S293000, C528S303000, C528S306000, C528S345000
Reexamination Certificate
active
06521716
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to coating, adhesive and sealant compositions curable by Michael reaction, that is by addition of an anion derived from a nucleophilic group, for example a carbanion, to an activated carbon-carbon double bond. This involves reaction between (A) a Michael acceptor which is a compound or polymer generally containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least one and generally containing at least two nucleophilic groups.
BACKGROUND ART
Coating compositions curable by Michael reaction are disclosed in U.S. Pat. No. 4,408,018, GB-A-2048913, U.S. Pat. Nos. 4,602,061, 5,084,536, 5,169,979, EP-A-697444 and U.S. Pat. No. 4,730,013. In general, the Michael donor in these compositions is a compound having at least two activated methylene groups, for example acetoacetate groups, or a polyamine or polythiol.
U.S. Pat. No. 4,588,807 describes a benzylidenemalonic acid polyester and its use for the UV stabilisation of thermoplastics.
EP-A-599478 describes a coating or impregnating composition comprising an aqueous dispersion of a vinyl addition polymer and a reactive coalescent of the formula:
(CH
3
COCH
2
COO)
x
R or
where R is an organic radical of valency x=1-6 and R
1
is H or alkyl.
U.S. Pat. No. 5,451,653 describes improved crosslinking systems for coatings and adhesives comprising a crosslinkable polymer having activated ketomethylene (e.g. acetoacetate) groups and an aldimine curing agent.
U.S. Pat. No. 5,426,156 describes a two-component binder system comprising a CH-acid component that is a polymer with at least two enamine functions in the molecule and a compound containing at least two alpha, beta-unsaturated ester or amide groups.
Coating and Sealant compositions curing by Michael reaction have several advantages. Liquid polymers and oligomers can be crosslinked to form tough hard coatings, so that the coating composition need have little or no volatile organic solvent to achieve a viscosity suitable for spray application. The reactive groups involved in curing are less of a health and/or safety risk than most crosslinkable reactive groups. The cured materials are generally resistant to hydrolysis and degradation, particularly in the case where the Michael donor is an activated methylene group since the new bonds formed on crosslinking are C—C bonds. Ester linkages, such as acetoacetates, acquire greater steric hindrance and hence hydrolysis resistance as a result of the Michael crosslinking reaction. The Michael reaction is beneficial for water-borne systems because it involves the transfer of hydrogen (as a proton) from a more electronegative element (with potential for hydrogen bonding) to a less electronegative element, carbon, which is not capable of hydrogen bonding. The reaction mixture therefore becomes less polar during curing, and in a coating the affinity for water should consequently decrease as curing progresses. In some cases, a water-soluble polymer/crosslinker system can be transformed into a water-resistant cured coating upon crosslinking. There is, however, a need for Michael curing coatings which cure more rapidly, particularly at ambient temperature, and/or are capable of curing without the need for powerful alkaline catalysts.
DISCLOSURE OF INVENTION
According to one aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a polymer having repeating units of the formula:
where R is hydrogen or an alkyl or aryl group which is optionally substituted and R
1
is hydrogen or an alkyl group which is optionally substituted;
X and X
1
are each selected from an oxygen atom and a group of the formula
where R
1
is hydrogen or an alkyl or aryl group which is optionally substituted; and
A is a divalent organic group.
The alkyl groups mentioned above and throughout the remainder of the text may for example have up to 12 carbon atoms, preferably up to 4 or 6 carbon atoms, for example methyl or ethyl. The aryl groups mentioned above and throughout the remainder of the text may for example have 6 to 12 carbon atoms and are preferably phenyl. The alkylene and arylene groups referred to below and throughout the remainder of the text may be similarly defined except for being divalent instead of monovalent. Substituents for all such groups which may be mentioned are halogen, hydroxyl and other non-reactive groups. The divalent organic group A is linked to X
1
through a carbon atom. It may for example be an alkylene or arylene group which is optionally substituted.
According to another aspect of the invention a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two groups of the formula:
where A
1
is a divalent organic group or a linking bond whereby the group (II) is linked to the compound or polymer (A);
R
3
is hydrogen or an alkyl group; and
E and E
1
are each electron-withdrawing groups independently selected from groups of the formula:
where R
4
and R
5
each represent an optionally substituted alkyl or aryl group and each group R
6
represents a hydrogen atom or an optionally substituted alkyl or aryl group.
According to another aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated olefinic double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two groups of the formula:
where R and R
1
are defined as in formula (I) above and R
46
is an alkyl or aryl group which is optionally substituted.
We have found that the polymers of formula (I), (II) or (XLV), in which the olefinic C═C bond is doubly activated by having two electron-withdrawing groups on one of the carbon atoms at the C═C bond, are substantially more reactive in Michael curing systems than are polymers containing acrylate or methacrylate ester groups.
According to another aspect of the invention, a coating, adhesive or sealant composition curable by Michael reaction comprises (A) a Michael acceptor which is a compound or polymer containing at least two activated double bonds and (B) a Michael donor which is a compound or polymer containing at least two nucleophilic groups and is characterised in that the Michael acceptor (A) is a compound or polymer containing at least two doubly activated olefinic groups of the formula:
where R
7
is an electron-withdrawing group, R
8
and R
9
are each independently selected from hydrogen, alkyl, which is optionally substituted, and aryl, which is optionally substituted; X
2
is an —O— or
where R
10
is hydrogen or an alkyl group, and A
2
is an optionally substituted alkylene group linking the doubly activated olefinic group to the compound or polymer (A); and in that the nucleophilic groups of the Michael donor (B) are beta-ketoamide groups of the formula:
where at least one of the groups R
11
, R
12
and R
13
is an optionally substituted alkylene or arylene radical whereby the ketoamide group is linked to the compound or polymer (B) and the remaining groups R
11
, R
12
and R
13
are in the case of R
11
an optionally substituted alkyl or aryl group and in the case of R
12
and R
13
a hydrogen atom or an optionally substituted alkyl or aryl group, provided that at least one of R
12
an
Akzo Nobel N.V.
McGillycuddy Joan M.
Short Patricia A.
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