Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-03-27
1997-10-28
Reddick, Judy M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523204, 523205, 524 31, 524315, 524413, 524425, 524430, 524431, 524432, 524492, 524493, 524497, 524505, 524533, C08L 108
Patent
active
056818777
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a novel use of acrylic block copolymers as wetting and/or dispersing agents for solid particles, and to dispersions of solid particles containing these block copolymers.
The use of macromolecular surfactants for treating surfaces in non-aqueous media has formed the subject of numerous studies, particularly laboratory studies aimed at specifying the mechanism and kinetics of the fixing of polymers to the surface of particular powders.
The following may be mentioned as examples of such studies: A and B representing the two blocks and b indicating that block copolymers are involved; the aid of block copolymers based on butyl methacrylate and dimethylaminoethyl methacrylate (Wu, Yokoyama, Setterquist, Polym. J. (91) vol. 23, page 409); polystyrene-b-polybutadiene copolymers (Adv. Chem. Ser. (71), vol. 99, page 379); polystyrene-b-polyvinylpyridine copolymers in toluene, for example: J. F. Tassin, R. L. Siemens, Wing T. Tang, G. Hadziioannou, J. D. Swales, B. A. Smith, J. Phys. Chem. 1989, 93, 2106-2111; page 108, on the dispersion of carbon black by polystyrene-b-polystearyl methacrylate copolymers; and being the study of the adsorption onto TiO.sub.2 of random amphiphilic copolymers having a skeleton consisting of methyl methacrylate and acrylonitrile and carrying heptameric grafts of hydroxystearic acid, said study being published in J. of Colloid and Interface Sci., 26, 214-221 (1968).
Block copolymers are known between acrylic or methacrylic acid (symbolized by the block A) and alkyl acrylate or methacrylate (symbolized by the block B), the alkyl chain being between C1 and C10. These copolymers can be of the two-block type (A-b-B) or three-block type (A-b-B-b-A or B-b-A-b-B). They are symbolized hereafter by AB irrespective of whether they are two-block or three-block. Their synthesis is described in particular by: P. Teyssie, Macromolecules, vol. 24, p. 4997-5000 (1991), for two-block and three-block acrylic acid/methyl methacrylate copolymers; McGrath, Polym. Prep., vol. 28(2), p. 214-216 (1987), for two-block methacrylic acid/2-ethylhexyl methacrylate copolymers; McGrath, Polym. Prep., vol. 29(1), p. 343-345 (1988), for three-block methacrylic acid/2-ethylhexyl methacrylate copolymers; McGrath, Polym. Prep., vol. 30(1), p. 210-203 (1989), for two-block and three-block methacrylic acid
-hexyl methacrylate copolymers.
The process described makes it possible to vary the nature and length of each of the polymer blocks by adjusting the concentration of initiator and monomers.
The Applicant has now discovered that this family of acrylic copolymers, symbolized hereafter by AB, and particularly PAA-b-PMMA, can advantageously be used to modify the surface energy of solid particles relative to organic liquids, resulting in their use as wetting and/or dispersing agents for these particles in organic media in order to obtain stable dispersions. Thus the use of these block copolymers provides an advantageous solution to the problem of the formation of aggregates of particles when attempting to form stable dispersions of these particles in a solvent.
Thus, according to one of its essential characteristics, the invention relates to the use of block copolymers, symbolized by AB, of acrylic or methacrylic acid, the corresponding block(s) being symbolized by A, and of alkyl acrylate or methacrylate with the alkyl chain being between C.sub.1 and C.sub.10, the corresponding block(s) being symbolized by B, as wetting and/or dispersing agents for solid particles in an essentially organic medium consisting of a solvent or solvent mixture solubilizing the block B.
In the present description, essentially organic medium is understood as meaning a medium containing less than 5% of water and preferably less than 1% of water.
For the different copolymers of the family, depending on the nature of the medium in which it is desired to disperse the powder, and on the nature of the powder, the Applicant's studies have led it: defined as the ratio of the amount of "fixed" copolymer to the initial amount.
REFERENCES:
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Macromolecules, vo. 24, 1991, US, pp. 4997-5000, Varshney et al `Anionic Polymerization of Acrylic Monomers`.
Hosotte-Filbert Claude
Meybeck Alain
Riess Henri-Gerard
Tondeur Carole
Tranchant Jean-Fran.cedilla.ois
LVMH Recherche
Reddick Judy M.
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