Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2002-02-05
2003-10-28
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S271000, C528S274000, C528S303000, C528S306000, C528S376000, C528S390000, C528S419000, C528S422000, C428S500000
Reexamination Certificate
active
06639046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition comprising:
a compound comprising two or more olefinically unsaturated groups comprising at least one electron-withdrawing functionality linked to a carbon atom of the unsaturated bond;
a compound comprising at least two mercapto-functional groups; and
a catalyst.
BACKGROUND OF THE INVENTION
Unsaturated groups, such as acryloyl groups, can react with active hydrogen-containing compounds. Such a reaction is believed to involve an addition of an anion derived from the nucleophilic, active hydrogen-containing compound, acting as a donor, to the activated unsaturated group, which serves as an acceptor. When these active hydrogen-containing compounds are C—H compounds such as malonic ester or acetoacetate, the reaction is known as the Michael addition reaction. It is also known that SH-compounds may function as active hydrogen-containing compounds in a reaction mechanism which is similar to the Michael addition reaction. Hereinafter, such a reaction mechanism with SH-compounds is called a thio-Michael reaction.
A composition such as described in the opening paragraph, which is curable by such a thio-Michael reaction, is known from European patent application EP-A 0 160 824. Catalysts mentioned in this disclosure are quaternary ammonium compounds, tetramethyl guanidine, diaza-bicyclo-undecene, and diaza-bicyclo-nonene. Thio-Michael reactions catalysed by these strong bases are hard to control. Such reactions take place either much too fast or not at all, depending on the concentration of the used catalyst. Tertiary amines may be present but, according to this publication, are not reactive at ambient temperatures. Furthermore, the base-catalysed reaction may suffer from acid inhibition.
Carbon dioxide present in the air or an acidic substrate may severely retard or even stop cross-linking.
U.S. Pat. No. 2,759,913 discloses a copolymerisation process of unsaturated monomers with mercapto-functional compounds with a basic catalyst such as trimethyl benzyl ammonium hydroxide. As mentioned above, reactions with such a catalyst are hard to control.
British patent application GB-A 2,166,749 discloses a room temperature curable coating composition comprising an unsaturated polyester and a compound comprising at least three thiol groups and a catalyst which is a tertiary amine, such as triethyl amine. However, as can be seen from the Examples in GB-A 2,166,749, this reaction takes about 16 hours to cure at ambient temperatures. Faster reaction will only take place at high temperatures.
SUMMARY OF THE INVENTION
European patent application EP-A-0 284 374 discloses a polymerizable vinyl compound having a polythioether skeleton prepared from a compound comprising two or more olefinically unsaturated groups comprising at least one electron withdrawing functionality linked to a carbon atom of the unsaturated bond, a compound comprising at least two mercapto-functional groups, and a catalyst such as diethylamine. It is not disclosed that these reactant as such may be used in a coating or adhesive composition.
United States patent U.S. Pat. No. 5,840,823 discloses an adhesive composition comprising a compound comprising two or more olefinically unsaturated groups comprising at least one electron-withdrawing functionality linked to a carbon of the unsaturated bond, and a compound comprising a plurality of groups selected from thiol groups, primary amino groups or secondary amino groups. However, in U.S. Pat. No. 5,840,823 it is not taught nor suggested to use a compound with primary or secondary amino groups in combination with a compound comprising thiol groups.
The object of the invention is to provide a composition which overcomes the above-mentioned drawbacks.
DETAILED DESCRIPTION OF THE INVENTION
The object of the invention is achieved with a composition of the type described in the opening paragraph comprising a catalyst comprising at least one, optionally blocked, NH-group.
Surprisingly, it has been found that although the prior art teaches that strong basic catalysts are needed, thio-Michael curable compositions comprising a catalyst according to the invention show rapid curing at ambient temperatures. This has the evident advantage that short production times are possible. Energy costs can be saved since curing takes place at ambient temperatures. Furthermore, in comparison with Michael and thio-Michael reactions catalysed by strong bases, the reaction time is much less dependent on the amount of catalyst This is advantageous for ease of formulation. It has also been found that the process can be carried out with low viscous oligomers. This has the advantage that compositions can be prepared which contain few if any solvents, but are still sprayable. The reactive groups involved in the curing reaction are much less toxic than most cross-linkable reactive groups in other adhesives or coating compositions, such as isocyanates. After curing, the applied layer is resistant to hydrolysis and degradation. Also, the thermal stability of the sulphide bond is high.
In the compound comprising two or more olefinically unsaturated groups, the olefinically unsaturated groups comprise at least one electron-withdrawing functionality linked to a carbon atom of the unsaturated bond. The olefinically unsaturated bond may be a double or a triple bond. Preferably, the olefinically unsaturated groups of the compound comprising two or more olefinically unsaturated groups have a structure according to the following formula I:
wherein at least one of R1, R2, R3, and R4 comprises an electron-withdrawing functionality linked to a carbon atom of the unsaturated bond and at least one of R1, R2, R3, and R4 is linked to a polyvalent group comprising at least two valencies.
Examples of the electron-withdrawing functionality include carbonyl, carboxyl, ester, thiocarbonyl, thiocarboxyl, thioesters, sulfoxide, sulfonyl, sulfo, phosphate, phosphite, phosphonite, phosphinite, nitro, nitrile, and amide.
In the case of R1, R2, R3, and/or R4 being monovalent, the electron-withdrawing functionality may be attached to a hydrogen atom, linear or branched alkyl, cycloalkyl, alkenyl, cyclo-alkenyl, alkynyl, cyclo-alkynyl, and aryl which may optionally be substituted with various other functionalities, such as carboxylic acid or hydroxide. If they do not comprise an electron-withdrawing functionality, R1, R2, R3, and/or R4 may be independently selected from a hydrogen atom, linear or branched alkyl, cycloalkyl, alkenyl, cyclo-alkenyl, alkynyl, cyclo-alkynyl, and aryl which may optionally be substituted with various functionalities, such as carboxylic acid or hydroxide. When at least one of R1, R2, R3, and R4 is linked to a polyvalent group and it is not an electron-withdrawing functionality, it may be a simple bond. The polyvalent group links at least two groups according to formula I. The polyvalent group may be selected from a simple bond, substituted or unsubstituted alkylene, cycloalkylene, alkenylene, cycloalkenylene, alkynylene, cycloalkynylene, arylene, or combinations thereof. The polyvalent group may optionally comprise hetero atoms such as —O—, —S—, —Si—, and —P—, and groups such as amide, urea, and ester groups.
Preferably, the group according to formula I is derived from an unsaturated carboxylic acid comprising 2 to 10, preferably 3 to 6, carbon atoms. The carboxylic acid may be mono- or polyunsaturated and may be a monocarboxylic or polycarboxylic acid. Examples of suitable monocarboxylic acids are acrylic acid, methacrylic acid, cinnamic acid, propargylic acid, and dehydrolevulinic acid. Examples of suitable polycarboxylic acids are citraconic acid, maleic acid, itaconic acid, or the anhydrides thereof, and mesaconic acid and fumaric acid. Also monoesters of mono- and polycarboxylic acids and diesters of polycarboxylic acids may be used such as acrylic acid esters, maleic acid mononitrile-monoesters, diethyl maleate, cyanoacrylic acid esters, and alkylidene malonic acid esters as disclosed in WO 98/41561. Acrylic acid or its ester, maleic acid, its
Acquah Samuel A.
Akzo Nobel N.V.
McGillycuddy Joan M.
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