Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1985-09-09
1987-10-06
Schain, Howard E.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525504, 525509, 525510, 525523, 525524, 528118, 528142, 528143, 528144, 528149, 528150, 528151, 528153, 528154, 528163, C08G 1406, C08G 5914, C08L 6100
Patent
active
046984011
DESCRIPTION:
BRIEF SUMMARY
The invention relates to polyfunctional phenolic reaction products which are obtainable by reacting a phenol and an alkylated amine-aldehyde condensation product and which are soluble in organic solvents, to a process for preparing these reaction products, and to the use of these reaction products.
The reaction product from reacting a polyhydric alcohol or polyhydric phenol with an amine-aldehyde condensation product which preferably contains functional methylol groups is known. Thus, for example, U.S. Pat. No. 3,293,212 shows a heat-curable reaction product of a bisphenol and of a polyalkyl ether of a polymethylolmelamine which has been prepared by reacting 0.5 to 2 moles of bisphenol per mole of the polyalkyl ether of a polymethylolmelamine in the presence of an acid catalyst and of a solvent. The indicated molecular ratio of bisphenol and alkylated polymethylolmelamine corresponds to an equivalent ratio of phenolic hydroxyl groups to alkoxy groups of 4:6 to 2:12, so that, if the maximum amount of phenol is used, the reaction product formed contains at least two functional methylol ether groups. During the reaction it is necessary to monitor the degree of conversion, so that the reaction can be discontinued before the gelling, so as to prevent the formation of a non-utilisable product.
U.S. Pat. No. 3,449,228 describes similar heat-curable reaction products which are prepared by reacting a polyhydric alcohol or a polyhydric phenol such as bisphenol A, and an amine-aldehyde condensation product, such as a melamine-aldehyde condensation product. These reaction products can be used for electropainting either alone or in combination with other materials. Although it is stated in said patent specification that the ratio of the amine-aldehyde condensation product and of the polyhydric alcohol or phenol can vary within wide limits, the products which are specifically described contain as functional groups primarily methylol ether groups which make the resin curable by heating. In the case of this resin it is also necessary to monitor the reaction in order to devoid undesirable gelling.
U.S. Pat. No. 4,217,377 describes a low-molecular solid addition product which is used as a crosslinking agent for various polymeric pulverulent coating compositions. The curing agent contains the reaction product of a monohydroxyl-mononuclear aromatic compound and of a hexakis-(alkoxymethyl)-aminotriazine. In the preparation of this compound, the aromatic monohydroxyl compound and the hexakisalkyl ether are used in such an amount that two of the six theoretically possible methoxymethyl ether groups of the triazine remain in the reaction product. These methoxy groups confer on the reaction product the required functionality for the crosslinking.
Another crosslinking agent for epoxy resins having reactive phenolic OH groups, as opposed to functional methylol ether groups, is described in U.S. Pat. No. 4,393,181. This crosslinking agent is obtained by reacting a polyhydric phenol with a hexakisalkyl ether of hexamethylolmelamine in such amounts that the ratio of phenolic OH groups to alkoxy groups is at least 2:1, preferably 3:1. The reaction is carried out in the absence of a solvent and preferably in the presence of an alkaline catalyst until the development of methanol is complete, i.e. until all alkoxy groups have reacted. The resulting polyfunctional phenolic addition product is a solid friable material which is particularly suitable for use as a crosslinking agent for pulverulent epoxy resins.
However, it is a disadvantage that the curing agents described and the indicated ratio of phenolic hydroxyl groups to alkoxy groups leads to cured epoxy resins of relatively low glass transition temperature. However, on preparing, using the known methods, a curing agent having a lower ratio of phenolic OH groups to alkoxy groups of the amine-aldehyde condensation products, these reaction products are generally insoluble in customary organic solvents and are of only very limited use.
It is therefore the object of the invention to provide
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patent: 4393181 (1983-07-01), Allen
Klein Dieter H.
Koenig Raymond
Schain Howard E.
The Dow Chemical Company
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