Acrylic telomers with grafts which can be cross linked by light,

Details Acrylic telomers with grafts which can be cross linked by light, Acrylic telomers with grafts which can be cross linked by light,

1984-12-10

1987-01-20

Bleutge, John C.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Compositions to be polymerized by wave energy wherein said...

428462, 522149, 522173, 522183, 525922, 526312, 5263181, 5263182, C08F 250, C08F 2216, C08F 2038

Patent

active

046380183

DESCRIPTION:

BRIEF SUMMARY
The invention relates to acrylic telomers with grafts which can be cross linked by light, their synthesis and their applications in coating metals and particularly aluminium.
Telomers are organic synthesised products resulting from a reaction known as telomerisation, during which a non-saturated compound Xi described as the taxogen reacts, in the presence of catalysts or initiators, with another compound AZ described as the telogen, giving rise to the formation of a sequence of n divalent --Xi-- links and the division of the telogen into two parts, which are fixed onto the ends of the sequence to form a product of the general formula
These telomers can in turn act as a telogenic agent to another taxogen Yi and lead to the formation of dual-sequence cotelomers of the general formula: A'--(Yi).sub.n' --(A"--(Xi).sub.n --Z where A' and A" result from the division of A.
Applicants have been most interested in derivatives of these telomers obtained by fixing non-saturated organic grafts on a limited number of links, more particularly grafts with at least one double bond which can be cross linked by light, so as to form grafted telomers of the general formula: ##STR1## where x+y=n and where x gives the number of non-grafted links and y the number of links on which the graft R has been fixed. These derivatives combine in their properties those of the non-grafted molecules of taxogen, which may e.g. have free acid or alcohol functions, making them well suited to adhere to metals, and those of grafted molecules which, in the present case, have a capacity for cross linking by the action of radiation. Thus in their French Pat. No. 2 510 125 Applicants describe grafted telomers of the general formula: ##STR2## where the taxogen may be an acrylic acid.
In this case, however, the telogen is a halogen derivative such as carbon tetrachloride and the telomerising reaction necessitates the use of a catalyst of the redox type such as the ferric chloride/benzoin pair, with the disadvantage that telomerising speeds are relatively low and the products are coloured by the iron salts. The disadvantages due to the iron can indeed be avoided by carrying out telomerisation through radical initiation with a peroxide initiator such as benzoyl peroxide or azobisisobutyronitrile and by using bromotrichloromethane as the telogen. However, the coefficient of transfer C.sub.T of this compound, that is to say, the factor which determines what fraction of this element is liable to be fixed on the taxogen, although considerable, is still fairly small and leads to limited yields when reactions on an industrial scale are required.
In this patent, moreover, the telomers are synthesised discontinuously and the problem bound up with radical catalysts in this type of process is that of the polydispersion of the products obtained. As a matter of fact, since the degree of polymerisation varies with the concentration of the reagents, the compounds formed at the beginning of the reaction do not have the same degree of polymerisation as those obtained at the end of the operation. The polydispersion index, corresponding to the ratio of the mean number of molecules by weight to the mean number of molecules by number, is therefore 1.6 to 1.8, resulting in different products where the heterogeneity of their properties may be troublesome for certain applications. The various telomers can indeed be separated by solvent according to the value of n, but this operation has been found to be expensive and tedious.
With regard to the grafting, when a taxogen based on acrylic acid is used, for example, the graft employed may be allyl alcohol, cinnamic alcohol or ethylene glycol acrylate. In this case the bond between the compounds may be formed by esterification, a reaction which is relatively slow and incomplete and often ill-adapted to industrial application. The acid functions are therefore generally activated before grafting, by passing them through acid chloride, e.g. using thionyl chloride. This intermediate step makes it possible to achieve higher speeds and

REFERENCES:
patent: 4013824 (1977-03-01), Uranecr

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