Stable microdispersions and microgels based on acrylic polymers,

Details Stable microdispersions and microgels based on acrylic polymers, Stable microdispersions and microgels based on acrylic polymers,

1996-06-12

1998-01-27

Webman, Edward J.

Drug, bio-affecting and body treating compositions

Manicure or pedicure compositions

424487, 424501, 528402, 525 94, 525221, 525227, 525301, 525302, A61K 910, C08L 5300, C08L 3306

Patent

active

057119406

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to novel stable microdispersions of polymer particles, to the microgels obtained from these dispersions and to compositions, particularly cosmetic compositions, containing these microdispersions or microgels. It further relates to a method of preparing these dispersions and microgels.
In terms of the invention, microdispersion is understood as meaning a dispersion of particles whose size can range up to 120 nm and is preferably less than 100 nm. The polymer constituting these particles is in precipitated form in the reaction medium, the particles being stabilized by a copolymer.
In line with Antonietti et al. in "Makromol. Chem., Makromol. Symp." 30, 81-93 (1989), a microgel is defined according to the invention as being a micro-particle of crosslinked polymer, in swollen form, dispersed in an organic solvent; its size, which is governed by the swelling ratio, depends on the crosslinking density. The polymer of which the microgel is composed, in the non-crosslinked form, is soluble in this same solvent; only crosslinking prevents the particles from being dissolved.
The essential difference between a microdispersion and a microgel is the fact that the former exists in precipitated form in the reaction medium formed by a solvent which does not solubilize the polymer, whereas the microgel is in swollen form in solvents for the polymer.
By way of example, a PMMA microdispersion prepared in an alcoholic reaction medium exists in precipitated form because the alcohol is not a solvent for PMMA, the microdispersion in precipitated form being stabilized by the block copolymer. Being crosslinked, these same particles make it possible to obtain microgels in swollen form when they are transferred into a solvent for PMMA, such as butyl acetate.
Methods of preparing acrylic microgels in aliphatic hydrocarbons, either on their own or mixed with other hydrocarbons or with alcohols, have been described in a number of publications.
Thus patent U.S. Pat. No. 4 558 075 describes the preparation of acrylic microparticles in the presence of PGMA-PMMA-PMAA random copolymers in a reaction medium consisting of heptane, and their application in the field of automotive paint containing aluminum flakes. The polymer particles have dimensions of between 0.01 and 10.mu..
D. H. EVERETT and J. F. STAGEMAN (Discus. Faraday Soc. 65, 230, 1978) have described the preparation of polystyrene or PMMA dispersions in the presence of PDMS-b-PS-b-PDMS three-block copolymers using alkanes as the reaction medium. The polymer particles obtained according to said document have dimensions of the order of 0.1.mu..
J. V. DAWKINS, S. A. SHAKIR and T. G. CROUCHER, Europ. Polym. J. 23, 173-175, 1987, have described the synthesis of PMMA dispersions in cyclohexane in the presence of PS-PMMA copolymers as stabilizers.
German patent DE 3 439 128 describes the preparation of acrylic microgels, stabilized either by polyesters or by copolymers of the "polyhydroxystearic acid-PMMA-PAA" type, in a reaction medium consisting of water or aliphatic hydrocarbons, and their applications in the preparation of metallic lacquers based on aqueous microgels or white lacquers based on titanium oxide in the case of microgels in aliphatic hydrocarbons. The dimensions of the polymer particles described in said document are of the order of 0.01 to 10.mu..
Other publications cite the use of mixtures of hydrocarbons and alcohols as the reaction medium. This is the case of European patent EP 251 553, in which acrylic microgels are prepared in the presence of copolymerizable stabilizers, which are copolymerized with acrylic monomers to produce a core-shell. The dispersions obtained can be used for painting metals.
This is also the case of the publication by C. H. BAMFORD et al., J. Appl. Polym. Sci., 25, 2559-2566, 1980, which again describes microgels in a solvent medium consisting of a mixture of alcohol and hydrocarbon, except that the use of a surface-active stabilizer is dispensed with.
It therefore appears that, as far as acrylic microgels are conce

REFERENCES:
patent: 4558075 (1985-12-01), Suss et al.
European Polymer Journal, vol. 23, No. 2, 1987, Oxford, pp. 173-175, J.V. Dawkins, `Non-Aqueous Poly (Methyl Methacrylate Dispersions: Radical Dispersion Polymerization in the Presence of the Diblock Copolymer Poly(Styrene-B-Methyl Methacrylate)`.
Antonietti et al, Makromol. Chem., Makromol. Symp., 30, 81-93 (1989).
Everett and Stageman, Discus. Faraday Soc., 65, 230 (1978).
Bamford et al, J. Appl. Polym. Sci, 25, 2559-2566 (1980).

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