Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1996-09-09
1998-08-11
Cain, Edward J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253276, C08F 2008
Patent
active
057928169
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a crosslinking agent on the basis of amines for polymers containing acid anhydride groups.
Crosslinkable polymers with acid anhydride groups are valuable reactive raw materials which can replace isocyanate prepolymers, polysulfides, epoxy or acrylic resins in many applications for liquid or solid plastics, for example in adhesives, sealants and coatings. Amines have been particularly proven as crosslinking agents. They are excellent when used for the manufacture of hydrolytically stable and thermally resistant crosslinking products.
Aliphatic and aromatic amines have the disadvantage that they react very rapidly with the polymers containing acid anhydride groups. At room temperature or at elevated temperatures, the blends of components show a pot life of a few seconds to a few minutes. Pot lives in the range of 5 to 300 minutes are obtained if sterically hindered aromatic amines are used as crosslinking agents. Such systems, as described in WO 94/04624, have the disadvantage that the sterically hindered amines are expensive and mostly available as solids, so that they can only be used as solutions in plasticizers or solvents.
Alternatively, amines can be converted into a less reactive form with known blocking agents, for example into the form of a ketimine, aldimine or oxazolane. By the action of water, the amines are deblocked and can react with the acid anhydride groups. The blocking agents that are also released have the disadvantage, however, that they impart a long-term unpleasant odor to the crosslinked product, and also increase the volatile portion of the blends.
Objects of the invention are crosslinking agents on the basis of amines with the characterizing features of claim 1, a method of manufacture of storage-stable polymer systems with polymers containing acid anhydride groups according to claim 17, and the polymer systems themselves, according to claim 22. The sub-claims describe advantageous embodiments of the invention.
The object of the invention is particularly fulfilled by the molecular sieve powders loaded with amines as a crosslinking agent which are suited to the controlled reaction with crosslinkable polymers in a particularly advantageous way, since the release of the adsorbed amines is attained specifically by means of moisture, or by desorption temperatures of above 80.degree. C.
Molecular sieves are synthetically manufactured crystalline metal aluminosilicates that belong to the class of minerals known as zeolites. The dehydrated crystals form a network of hollow spaces interconnected by defined capillaries that leads to a large internal surface. They are capable of adsorbing polar chemicals on their crystal structure, respectively their internal surface.
The zeolites used according to the invention are alkali metal aluminosilicates or alkaline earth metal aluminosilicates, and possess a very large number of pores with uniform dimensions. Molecules that are sufficiently small can penetrate into the pores of the anhydrous molecular sieve, and become adsorbed. The pores have regular diameters that, depending on the composition of the zeolite and the temperature, can be between 0.3 and 1.5 nm. For the crosslinking agent according to the invention, commercially available molecular sieve powders are preferred, mainly those with a pore diameter of 0.38 nm (standard commercial designation: type 4A), 0.44 nm (type 5A) and 0.8 nm or 0.84 nm (types 10.times. or 13.times.) and marketed by various manufacturers. Free-flowing powder with particle sizes of less than 50 .mu.m, and particularly less than 20 .mu.m, are preferred.
Depending on type, and in a state of equilibrium, the adsorption capacity of the molecular sieve powder for water at room temperature amounts from 20 to 34 percent by weight. The anhydrous molecular sieve powders can be loaded with 3 to 30, preferably with 5 to 25 percent by weight amine.
The loading of molecular sieve powders with polar chemicals is know in the art, and the most common methods are, for example, described by S. Borgmann et. al. in P
REFERENCES:
patent: 3036980 (1962-05-01), Dunham, Jr. et al.
patent: 3533987 (1970-10-01), Ciamdra et al.
patent: 3725360 (1973-04-01), Adams
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