Polymer dispersion in a reactive organic medium, preparation method and uses

1. A polymer dispersion comprising a polymer in an organic medium, which comprises the product from the polymerization of at least one vinyl monomer in the presence of a radical initiator in a reactive organic dispersing medium, wherein the vinyl monomer is selected from the group consisting of the monomers of formula

in which

(1) X is a C 1 -C 18 alkyl radical, an aryl radical which can comprise one or more C 1 -C 4 alkyl substituents, or a C 7 -C 10 arylalkyl radical, and Y represents a hydrogen atom or a C 1 -C 4 alkyl radical, or

(2) X is an OR group in which R represents a C 1 -C 18 alkyl radical or a C 5 -C 8 cycloalkyl radical,

or a radical of formula

in which

R 1 and R 2 represent a hydrogen atom, a methyl radical or an ethyl radical, R 1 and R 2 being different,

m and n, which are identical or different, are equal to 1, 2, 3 or 4,

z and t, which are identical or different, are greater than 4,

z +t is less than or equal to 80,

and Y represents a hydrogen atom or a C 1 -C 4 alkyl radical, or

(3) X is an OCOR 1 group in which R 1 represents a C 1 -C 12 alkyl radical, a C 5 -C 8 cycloalkyl radical, or an aryl radical, and Y represents a hydrogen atom, or

(4) X is a COOR 2 group in which R 2 represents a C 4 -C 20 alkyl radical, a C 6 -C 20 cycloalkyl radical, an aryl radical, or a C 6 -C 20 arylalkyl radical, and Y represents a hydrogen atom or a methyl radical, or

(5) X is a group of formula

and Y represents a hydrogen atom;

and wherein the reactive organic dispersing medium comprises a silicone comprising at least one epoxy group in terminal position(s).

2. The dispersion as claimed in claim 1 , which exhibits a difference between the solubility parameter of the polymer (δt p ) and the solubility parameter of the dispersing medium (δt m ) which satisfies the relationship:

|δ t p −δt m |≧4.

3. The dispersion as claimed in claim 1 , wherein the vinyl monomer is selected from the group consisting of vinyl acetate, vinyl propionate, butyl acrylate, octyl acrylate, lauryl acrylate and N-vinylpyrrolidone.

4. The dispersion as claimed in claim 1 , wherein the dispersing medium is a silicone of formula

in which

n varies from 3 to 45

m varies from 1 to 20.

5. The dispersion as claimed in claim 1 , wherein the silicone has a molecular weight of between 450 and 4000.

6. The dispersion as claimed in claim 1 , wherein the polymer is in the form of fine substantially spherical particles with a size of less than 40 μm.

7. The dispersion as claimed in claim 6 , wherein the particles exhibit a narrow size distribution centered on a mean diameter of between 0.05 and 3 μm.

8. The dispersion as claimed in claim 1 , which comprises 20 to 70% by weight of polymer.

9. The dispersion as claimed in claim 1 , which exhibits a viscosity of less than 500 000 mPa·s.

10. The dispersion as claimed in claim 1 , which additionally comprises a stabilizing agent selected from the group consisting of

alkylene oxide copolymers,

polymers of alkylene oxide and of at least one other polymerizable monomer,

vinyl alcohol polymers, and

silicone polymers.

11. A process for the preparation of the dispersion as claimed in claim 1 , comprising the following stages

a) mixing the at least one vinyl monomer, the one radical initiator and the one reactive organic dispersing medium, and

b) reacting the mixture at a temperature of at least 20° C. and lower than the boiling point of the compound in the mixture having the lowest boiling point.

12. The process for the preparation of the dispersion as claimed in claim 11 , wherein the initiator can be activated thermally at the reaction temperature.

13. The process for the preparation of the dispersion as claimed in claim 12 , wherein the radical initiator is selected from the group consisting of peroxides, hydroperoxides and azo compounds.

14. The process for the preparation of the dispersion as claimed in claim 11 , wherein the amount of radical initiator represents 0.5 to 6% by weight of vinyl monomer.

15. The process for the preparation of the dispersion as claimed in claim 11 , wherein the vinyl monomer and the dispersing medium are employed in a ratio by volume not exceeding 70:30.

16. The process for the preparation of the dispersion as claimed in claim 11 , wherein the reaction temperature is greater than or equal to 40° C.

17. The process for the preparation of the dispersion as claimed in claim 11 , wherein a redox initiator is used and in that the reaction temperature does not exceed 40° C.

18. The process for the preparation of the dispersion as claimed in claim 11 , wherein a stabilizing agent is added to the mixture of stage a) in a proportion which can range up to 35% by weight of vinyl monomer.

19. A sizing composition capable of coating glass filaments, which comprises a dispersion as claimed in claim 1 .

20. A glass strand comprising glass filaments which are coated with the sizing composition as claimed in claim 19 .

21. A coating composition capable of coating glass strands or an assemblage of glass strands, which comprises a dispersion as claimed in claim 1 .

22. A glass strand or an assemblage of glass strands coated with a coating composition as claimed in claim 21 .

23. A glass strand comprising glass filaments which are coated with a sizing composition comprising a polymer dispersion comprising a polymer in an organic medium, which comprises the product from the polymerization of at least one vinyl monomer in the presence of a radical initiator in a reactive organic dispersing medium, wherein the vinyl monomer is selected from the group consisting of the monomers of formula

in which

(1) X is a C 1 -C 18 alkyl radical, an aryl radical which can comprise one or more C 1 -C 4 alkyl substituents, or a C 7 -C 10 arylalkyl radical, and Y represents a hydrogen atom or a C 1 -C 4 alkyl radical, or

(2) X is an OR group in which R represents a C 1 -C 18 alkyl radical or a C 5 -C 8 cycloalkyl radical,

or a radical of formula

in which

R 1 and R 2 represent a hydrogen atom, a methyl radical or an ethyl radical, R 1 and R 2 being different,

m and n, which are identical or different, are equal to 1, 2, 3 or 4,

z and t, which are identical or different, are greater than 4,

z +t is less than or equal to 80,

and Y represents a hydrogen atom or a C 1 -C 4 alkyl radical, or

(3) X is an OCOR 1 group in which R 1 represents a C 1 -C 12 alkyl radical, a C 5 -C 8 cycloalkyl radical, or an aryl radical, and Y represents a hydrogen atom, or

(4) X is a COOR 2 group in which R 2 represents a C 4 -C 20 alkyl radical, a C 6 -C 20 cycloalkyl radical, an aryl radical, or a C 6 -C 20 arylalkyl radical, and Y represents a hydrogen atom or a methyl radical, or

(5) X is a group of formula

and Y represents a hydrogen atom;

and wherein the reactive organic dispersing medium comprises a silicone comprising at least one epoxy group in terminal position(s).

24. The glass strand according to claim 23 , wherein the reactive organic dispersing medium is at least one selected from the group consisting of (1) silicones comprising at least one epoxy group in terminal position(s) and (2) polyols derived from saturated or unsaturated and linear, branched or cyclic hydrocarbons.