Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1991-11-29
1993-11-30
Teskin, Fred
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
526175, 526178, 526181, 526185, 526183, 5263291, 5263292, 5263295, 5263297, 502152, 502154, 502155, 502157, 502202, C08F 2010, C08F 454
Patent
active
052666670
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the polymerisation of acrylic monomers and optionally of nonacrylic comonomers with the aid of initiating agents or polymerisation initiators of formula: R denotes a straight- or branched-chain alkyl radical containing 2 to 6 carbon atoms or an aryl radical.
Processes for the polymerisation of acrylic or methacrylic monomers such as alkyl acrylates and methacrylates are known, as well as processes for the copolymerisation of such acrylic or methacrylic monomers as well as of nonacrylic comonomers, in the presence of various initiating agents or polymerisation initiators, especially those of formula (I) given above, such as sec-butyllithium and other initiating agents, such as lithium tertiary alcoholates.
From patent application Ser. No. EP-A-185,641 it is also known to employ, in polymerisation reactions of acrylic and methacrylic monomers as well as in copolymerisation reactions of such monomers and of nonacrylic comonomers, cocatalysts or additives consisting of alkali or alkaline-earth metal salts, preferably halides of such a metal. These cocatalysts make it possible to avoid secondary reactions and make it possible to obtain polymers with a polydispersity index (M.sub.w /M.sub.n ratio) which is very low.
However, two problems remain to be solved in these processes: on the one hand, that of the reaction kinetics and, on the other hand, that of the control of the molecular mass of the polymers. In fact, the use of an alkali or alkaline-earth metal salt decreases the reactivity of the initiating agent, and this can be detrimental to the output efficiency of the process through a lengthening of the period needed for a complete conversion of the monomer. Furthermore, in the case where the acrylic monomer is methyl methacrylate, these known processes make it easily possible to obtain polymers of high molecular mass. On the other hand, they appear to be poorly adapted to yielding polymers or copolymers comprising a polymethyl methacrylate block whose number-average molecular mass is, for example, lower than 35,000.
The present invention is based on the surprising finding that, in order to solve at least one of the problems outlined above, it is advantageous to carry out the polymerisation of acrylic or methacrylic monomers, if appropriate with nonacrylic comonomers, with the aid of a catalyst of formula (I) which is given above, by employing a cocatalyst or additive consisting of an organic derivative of an alkali metal, on condition that this organic derivative is neither an alcoholate nor an ester of a carboxylic acid substituted by the said metal in the .alpha. position.
Thus, a first subject of the present invention consists of an initiating system for the anionic polymerisation of (meth)acrylates, comprising at least one initiator of formula R--M (I) in which M denotes a metal chosen from alkali and alkaline-earth metals and R denotes a straight- or branched-chain alkyl radical containing from 2 to 6 carbon atoms or an aryl radical or an arylalkyl radical, characterised in that it additionally comprises at least one organic derivative of an alkali metal, on condition that this organic derivative is neither an alcoholate nor an ester of a carboxylic acid substituted by the said metal in the .alpha. position.
Among the organic alkali metal derivatives which can be employed within the scope of the present invention there may be mentioned especially the derivatives in which the alkali metal is associated with a group chosen from:
(A) the groups, of formula: ##STR1## in which R.sub.1 is a linear or branched alkyl radical containing from 1 to 20 carbon atoms or else a cycloalkyl radical containing from 3 to 20 carbon atoms or, again, an aryl radical containing from 6 to 14 carbon atoms,
(B) the groups of formula: ##STR2##
in which:
Y and Z, which are identical or differ from each other, are chosen from the hydrogen atom and halogen atoms;
n is an integer ranging from 0 to 4,
X is a halogen atom, and
m is an integer ranging from 0 to 2,
(C) the groups of formula:
REFERENCES:
patent: 3294768 (1968-12-01), Wofford
patent: 3526604 (1970-09-01), Wadsworth
patent: 4647634 (1987-03-01), Jalics
patent: 4767824 (1988-08-01), Ouhadi et al.
Fayt Roger
Teyssie Philippe
Varshney Sunil K.
Elf Atochem S.A.
Teskin Fred
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