Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1990-09-27
1993-04-13
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524265, 524269, 524506, C08J 326, C08K 524
Patent
active
052023680
DESCRIPTION:
BRIEF SUMMARY
This invention relates to aqueous coating compositions and more particularly to aqueous coating compositions based on silicone compounds.
Coating compositions based on silicone compounds, that is, compounds which comprise at least one Si--O--Si linkage, have been widely used in industrial finishing, especially for coating coil, because they offer an outstanding combination of cost, flexibility (capability of withstanding forming operations subsequent to coating) and performance on exterior exposure. The resin used is often silicone-modified polyester, that is a polyester which has been reacted with a silicone compound, and often known in the trade as "SMP".
The silicone coating compositions which have hitherto been widely used and accepted by the industry have been solvent-borne. The desire to reduce pollution and minimise the loss of expensive solvent has led to various attempts to produce a water-borne silicone coating composition.
For example, Harder in GDR Patent 13461 describes a storage-stable aqueous paint which comprises a mixture of an acrylic film-forming dispersion, a polysiloxane resin in the form of an aqueous dispersion in the presence of organic solvent and a minor quantity of an aqueous anionic dispersion based on an acrylic acid ester copolymer. The resulting compositions are stated to have good adhesion and weathering properties. Japanese Patent Publications 59-161417 and 60-243167 (to Daicel Chemical Industry KK and Toa Gosei Chemical Industry KK respectively) describe similar mixed systems.
A system which has proved useful in practice is the siliconised latex, that is a dispersion of film-forming (generally acrylic) polymer which has been modified with silicone. The resulting resin system is water-borne and has good properties. A description of such systems may be found in, for example, "Resin Review", Volume XXXVII (1987), No. 1, p. 12-18 (published by the Rohm and Haas Co., Philadelphia, PA, USA). Systems such as those described in the prior art referred to hereinabove suffer from either or both of two problems, namely poor performance in comparison with solvent-borne systems in important areas such as exterior durability, or an inability to accept a suitably wide range of silicone compounds, thus limiting the range of coating compositions which can be made. The properties of silicone compounds, and therefore the properties of any coating composition in which they are incorporated, vary widely with the composition of the silicone compound itself. A silicone compound which is suitable for one end use may not be suitable for another, yet because of the different compatibilities of different silicone compounds with water, it is often not possible simply to substitute one silicone compound for another, and the entire coating composition may need to be reformulated.
It has now been found that is possible to provide a coating composition which allows the use of any kind of silicone compound currently available. Moreover, many of these coating compositions outperform the known equivalent water-borne systems and often the high-performance solvent-based systems. There is therefore provided, according to the present invention, an aqueous silicone compound coating composition comprising an addition polymer dispersion and at least one silicone compound, the silicone compound forming part of the disperse phase of a dispersion of multi-polymer particles.
By "multi-polymer particles" is meant particles which comprise a blend of at least two different polymers. They are prepared by dissolving or dispersing at least one polymer (known at the "pre-formed polymer") in unsaturated monomer, dispersing the resulting solution or emulsion in water and then polymerising the acrylic monomer to form multi-polymer particles. The technique is described in, for example, U.S. Pat. Nos. 4,373,054 and 4,413,073, which, while covering a wide range of pre-formed polymers, do not mention or exemplify the use of silicones. It has been found, as mentioned hereinabove, that the combination of multi-polymer particle technol
REFERENCES:
patent: 4444946 (1984-04-01), Alberts et al.
patent: 4446259 (1984-05-01), Vasta
patent: 4791029 (1988-12-01), Fau et al.
patent: 4803233 (1989-02-01), Narula et al.
Anderson Geoffrey B.
Babicka Alois
Davies Stephen P.
ICI Australia Operations Proprietary Limited
Michl Paul R.
Rajguru U. K.
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