Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1990-12-19
1994-06-21
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253288, 525379, 526 79, 52631842, 52631845, C08F 832
Patent
active
053228979
DESCRIPTION:
BRIEF SUMMARY
The invention relates to copolymers soluble in organic solvents and containing hydroxyl groups, which can be prepared by free-radical solution polymerization of vinyl ester monomers, vinylaromatic monomers, hydroxyalkyl ester monomers and, if desired, other copolymerizable monomers, to a process for the preparation thereof and to the use thereof in coating compositions.
Acrylate polymers containing hydroxyl groups are well known, as are coating compositions which contain these polymers as the major binder component (cf. for example EP-A-103,199, EP-A-52,223, EP-B-39,797, EP-A-136,667 and EP-B-64,338).
It is further known that problems occur in the preparation of acrylate copolymers if monomers are used which, compared with acrylate monomers, possess widely differing reactivities, for example vinyl esters of aliphatic monocarboxylic acids of 5 to 15 carbon atoms branched in the .alpha.-position. In these cases it is difficult to obtain uniform, i.e. randomly and homogeneously distributed copolymers.
One possibility of solving this problem lies in the process, described in U.S. Pat. No. 4,039,734, for copolymerization of monomers of different reactivities, in which process at least a part of the reactive monomers is continuously added to the reaction mixture in such an amount that the relative ratio of the monomers remains constant. The amount of monomers required in each case for this purpose is determined from the liberated heat of reaction.
The process described in DE-PS 2,032,647 furnishes homogeneous vinyl ester, vinylaromatic and hydroxyacrylate copolymers corresponding to stepwise addition of the individual monomers. This process initially uses the total amount of vinyl esters together with 5 to 15% by weight of the total amount of the vinylaromatic hydrocarbons and the total amount of the other hydroxyl monomers and unsaturated carboxylic acids. The remaining amount of the monomers is then either added gradually in toto or at such a rate that the addition of the OH-- and COOH-containing monomers takes longer than that of the vinylaromatic hydrocarbons. A disadvantage of this process are the very high residual monomeric content (i.e. the amount of unreacted starting monomer, expressed in % by weight, based on the total amount of this monomer used originally) of up to 40% by weight of vinyl esters when a high proportion of vinylaromatic hydrocarbons of up to 50% by weight is used, as well as the associated toxicity problems. Because of the contamination of the environment by solvents when paint films are drying, a further disadvantage is the high solvent content of the coating composition due to the high viscosity of the binder solutions. There is the additional risk of cloudiness occurring in polymeric solutions with a high solids content which can only be eliminated by the addition of further solvents.
The English language technical report by Shell "VeoVa polymers LR-40 and LR-2041 for water-thinnable paints" describes copolymers containing vinyl esters, vinylaromatic hydrocarbons and hydroxyalkyl esters which, however, also suffer from precisely the shortcomings described above.
Finally, a few mass polymerization processes for the preparation of copolymers containing vinyl esters in which the total amount of the vinyl ester is heated, if desired with a part of the total amount of the other monomers and, if desired, an initiator, and the remaining amount of monomers and initiator or is then added gradually (cf. for example DE-PS 2,422,043 and DE-OS 2,615,101), are also known. It is true that these processes succeed in completely incorporating the vinyl ester (residual monomer content<10% by weight), but the copolymer solutions obtained in this manner are cloudy after the polymer mass has dissolved, and are unsuitable for paint formulations.
The object of the invention has thus been to make available copolymers containing hydroxyl groups, based on vinyl ester monomers, vinylaromatic monomers and hydroxyalkyl ester monomers as well as, if desired, other copolymerizable monomers, which can be prepare
REFERENCES:
patent: 3669942 (1972-06-01), Van Westrenen et al.
patent: 3956245 (1976-05-01), Van Steenis et al.
patent: 4062908 (1977-12-01), van Acker et al.
Jung Werner A.
Vorbeck Udo
BASF Lacke
Farben Aktiengesellschaft
Lipman Bernard
Sabourin Anne Gerry
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