Unsaturated polysiloxanes and polymers thereof

• US 4,605,712 A
• Filed: 09/24/1984
• Issued: 08/12/1986
• Est. Priority Date: 09/24/1984
• Status: Expired due to Term

• Current Assignee: CIBA Vision Corporation (Bayer AG)
• Original Assignee: Ciba-Geigy Corporation (Novartis Ag)
• Inventors: Mueller, Karl F., Falk, Robert A., Lohmann, Dieter
• Primary Examiner(s): Marquis, Melvyn I.
• Application Number:
  US06/653,416
• Time in Patent Office: 687 Days
• Field of Search: 528/32, 528/24, 528/26, 528/28, 528/29, 526/279, 351/160 R, 351/160 H, 525/100, 525/101, 525/479, 525/474
• US Class Current: 525/474
• CPC Class Codes: C08F 290/148 Polysiloxanes
• CPC Class Codes: C08F 299/08 from polysiloxanes
• CPC Class Codes: C08G 18/61 Polysiloxanes
• CPC Class Codes: C08G 18/8108 having only one isocyanate or isothiocyanate group
• CPC Class Codes: C08G 18/8158 with unsaturated compounds having only one group containing active hydrogen
• CPC Class Codes: C08G 77/388 containing nitrogen
• CPC Class Codes: C08G 77/54 Nitrogen-containing linkages C08G77/485 takes precedence
• CPC Class Codes: C08L 51/085 on to polysiloxanes
• CPC Class Codes: C08L 83/00 Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
• CPC Class Codes: G02B 1/043 Contact lenses

Abstract

Polysiloxanes of uniform molecular weight (MW) distribution with 500-10,000 MW segments of polysiloxane and containing at least one vinyl group connected to said polysiloxane segments through intervening alkylene-urea or -urethane linkages are prepared from polysiloxane-polyols, -polyamines or -polythiols by reaction with an unsaturated compound containing an isocyanato moiety, for example 2-isocyanatoethyl methacrylate. The polysiloxanes containing the vinyl groups are useful as radiation- or thermally curable coatings for glass, textiles, plastics, wood, ceramics, metals, as films or bandages for medicinal purposes, or molded shapes, in form of contact lenses, catheters or implants, either by themselves or in combination with other vinyl monomers; and are particularly useful in preparing hard or soft contact lenses, including hydrogel contact lenses.

Claims

1. A linear or branched polysiloxane macromer having a molecular weight from about 400 to 100,000, as measured by end group analysis or gel permeation chromatography, said macromer containing at least one terminal or pendant, polymerizable olefinic group per each 5000 molecular weight unit of polysiloxane, said group being attached to the polysiloxane through one urethane, thiourethane or urea linkage, said macromer having the structure A₁, A₂, A₃ or A₄ ##STR22## wherein:

R₁ is a linear or branched alkylene group with 2-6 carbon atoms or a polyoxyalkylene group of structure G or G₁ ##STR23## wherein R₃ is hydrogen or methyl and p is an integer from 1-50, R₂, R_a, R_b, R_c, R_d, R_e, R_f, R_g, R_h, R_i, R_j and R_k are independently methyl or phenyl, x₁, x₂ are integers from 1 to 500 with the proviso that the sum of x₁ +x₂ is 7 to 1300, y₁ is 0 to 14 and y₂ is 1 to 13 with the proviso that the ratio of ##EQU3## is not greater than 70, X is --Z₁ --CO--NH--

Z₁ is oxygen, sulfur or NR₅, wherein R₅ is hydrogen or lower (C₁ -C₄) alkyl, Z₁ is connected to R₁ ;

Y₁ is ##STR24## wherein;

R₆ is;

hydrogen, methyl, --COOR₅ or --COOR₇ OH,

Z₂ =oxygen or --NR₅ --

Y is the same as Y₁, or Y may also be H, alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, o-tolyl, m-tolyl or p-tolyl, with the proviso that at least one of Y must have the same meaning as Y₁,

R₇ is a linear or branched alkylene of 2 to 10 carbon atoms, phenylene or phenylalkylene with 2 to 10 carbon atoms in the alkylene, or polyoxyalkylene of structure G or G₁ ;

R₈ is an alkylene group of from 2 to 6 carbon atoms,

R₄ is a diradical obtained by removing the NCO-groups from an aliphatic, cycloaliphatic, araliphatic or aromatic diisocyanate;

T is the group ##STR25## T₁ is the group ##STR26## n is 0 to 10.

2. A polysiloxane macromer according to claim 1 wherein R₁ is alkylene of 3 or 4 carbon atoms, R₂, R_a, R_b, R_c, R_d, R_e, R_f, R_g, R_h, R_i, R_j and R_k are each methyl, x₁ +x₂ is 10 to 100, y₁ is 0 to 2, y₂ is 1 to 3, Z₁ is --O-- or --NH-- and R₄ is a diradical of an aliphatic or cycloaliphatic diisocyanate with 6 to 10 carbon atoms, and Y is the same as Y₁ R₆ is hydrogen, R₈ is ethylene, and Z₂ is --O-- or --NC(CH₃)₃ --.

3. A polysiloxane macromer according to claim 2 where the polysiloxane is of structure A₂, Z₁ and Z₂ are each --O--, and y₂ is 1 or 2.

4. A polysiloxane macromer according to claim 1 wherein the polysiloxane is of structure A₃ or A₄, where R₄ is the diradical derived from isophorone diisocyanate.

41. A polysiloxane macromer according to claim 2 where the polysiloxane is of structure A₁, Z₁, and Z₂ are each --O-- and y₁ is 0.

5. A polymer, suitable for use in contact lenses, comprising the crosslinked copolymerization product of

(A) from 5 to 75% by weight of said polymer of a linear or branched polysiloxane macromer having a molecular weight from about 400 to about 100,000, as measured by end group analysis or gel permeation chromatography, said macromer containing at least two terminal or pendant, polymerizable olefinic groups per each 5000 molecular weight unit of polysiloxane, said groups being attached to the polysiloxane, said groups being attached to the polysiloxane through one urethane, thiourethane or urea linkage, said macromer having the structure A₁ A₂, A₃ or A₄, ##STR27## wherein:

R₁ is a linear or branched alkylene group with 2-6 carbon atoms or a polyoxyalkylene group of structure G or G₁ ##STR28## wherein R₃ is hydrogen or methyl and p is an integer from 1-50, R₂, R_a, R_b, R_c, R_d, R_e, R_f, R_g, R_h, R_i, R_j and R_k are independently methyl or phenyl, x₁, x₂ are integers from 1 to 500 with the proviso that the sum of x₁ +x₂ is 7 to 1300, y¹ is 0 to 14 and y² is 1 to 13 with the proviso that the ratio of ##EQU4## is not greater than 70, X is --Z₁ --CO--NH--

Z₁ is oxygen, sulfur or NR₅, wherein R₅ is hydrogen or lower (C₁ -C₄) alkyl, Z₁ is connected to R₁ ;

Y₁ is ##STR29## wherein R₆ is;

hydrogen, methyl, --COOR₅ or --COOR₇ OH,

Z₂ =oxygen or --NR₅ --

Y is the same as Y₁, or Y may also be H, alkyl of 1 to 8 carbon atoms, cyclohexyl, phenyl, o-tolyl, m-tolyl or p-tolyl, with the proviso that at least one of Y must have the same meaning as Y₁,

R₇ is a linear or branched alkylene of 2 to 10 carbon atoms, phenylene or phenylalkylene with 2 to 10 carbon atoms in the alkylene, or polyoxyalkylene of structure G or G₁ ;

R₈ is an alkylene group of from 2 to 6 carbon atoms,

R₄ is a diradical obtained by removing the NCO-groups from an aliphatic, cycloaliphatic, araliphatic or aromatic diisocyanate;

T is the group ##STR30## T₁ is the group ##STR31## n is 0 to 10, and (B) 95 to 25% by weight of said polymer of one or more mono-, di- or trifunctional vinyl monomer polymerizable by free radical polymerization.

6. A polymer according to claim 5, comprising the crosslinked copolymerization product of

(A) from 15 to 60% by weight of said polymer of a linear or branched polysiloxane macromer defined in claim 5, and

(B) 85 to 40% by weight of said polymer of a mixture of water-soluble and water-insoluble monomers or water-insoluble monomers, said monomers being monoolefinic, diolefinic or a mixture of monoolefinic and diolefinic monomers, with from 80 to 100% by weight of the total monomers being water-insoluble (B₁), with 100 to 0% by weight of total monomers being water-soluble (B₂), and 30 to 0% of the total monomers being diolefinic (B_x).

7. A polymer according to claim 5 wherein R₁ is alkylene of 3 or 4 carbon atoms, R₂, R_a, R_b, R_c, R_d, R_e, R_f, R_g, R_h, R_i, R_j and R_k are each methyl, x₁ +x₂ is 10 to 100, y₁ is 0 to 2, y₂ is 1 to 3, Z₁ is --O-- or --NH-- and R₄ is a diradical of an aliphatic or cycloaliphatic diisocyanate with 6 to 10 carbon atoms, and Y is the same as Y₁, R₆ is hydrogen, R₈ is ethylene, and Z₂ is --O-- or --NC(CH₃)₃ --.

8. A polymer according to claim 7 where the polysiloxane is of structure A₂, Z₁ and Z₂ are each --O--, and y₂ is 1 or 2.

9. A polymer according to claim 5 wherein the polysiloxane is of structure A₃, or A₄, where R₄ is the diradical derived from isophorone diisocyanate.

10. A polymer according to claim 6 wherein monomer B is a water insoluble monomer B₁ which is an acrylate or methacrylate of formula CH₂ ═

CR₃ COOR₁₂, an acrylamide or methacrylamide of formula CH₂ ═

CH₃ CONHR₁₂, a maleate or fumarate of formula R₁₂ OCOCH═

CHCOOR₁₂, an itaconate of formula R₁₂ OCOC(═

CH₂)CH₂ COOR₁₂, a vinyl ester of formula R₁₂ COOCH═

CH₂, a vinyl ether of formula CH₂ ═

CHOR₁₂, or a mixture of said monomers, wherein R₃ is hydrogen or methyl, and R₁₂ is a linear or branched aliphatic, cycloaliphatic or aromatic alkyl group with from 1 to 21 carbon atoms and which may contain ether or thioether linkages or a --CO-- group;

or is a heterocyclic alkyl group containing oxygen, sulfur or nitrogen atoms, or a polypropylene oxide or poly-n-butylene oxide group with from 2 to 50 repeating alkoxy units;

or is perfluorinated alkyl groups with from 1-12 carbon atoms;

or is alkyl containing siloxane groups with from one to six Si atoms;

or --SO-- and --SO₂ -- groups.

11. A polymer according to claim 10 wherein the water insoluble monomer B₁ is selected from the group consisting of methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, hexafluoroisopropyl methacrylate and mixtures thereof.

12. A polymer according to claim 11 wherein the water insoluble monomer B₁ is selected from the group consisting of methyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof.

13. A polymer according to claim 6 wherein component (B) contains 1 to 30%, based on the total weight of monomer, of a diolefinic monomer (B_x).

14. A polymer according to claim 6 wherein diolefinic monomer (B_x) of component B is the acrylate or methacrylate of allyl alcohol, of a straight or branched chain alkylene glycol of 2 to 6 carbon atoms, of poly(ethylene oxide)glycol, of poly(propylene oxide)glycol, of poly(n-butylene oxide)glycol, of thiodiethylene glycol, of neopentylene glycol, of trimeth ylolpropane, or of pentaerthyritol;

or the reaction product obtained by reacting one mol of a di- or tri-isocyanate of structure OCN--R₄ --(NCO)_v, where R₄ is the radical derived by removing NCO groups from said isocyanate and v is 1 or 2, with 2 or 3 moles of a hydroxyalkyl acrylate or methacrylate.

15. A polymer according to claim 6 wherein component B is a mixture of methyl methacrylate and 1 to 25% by weight of the total monomer of neopentylene glycol diacrylate, ethylene glycol dimethacrylate or the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

16. A polymer according to claim 10 wherein the water insoluble monomer B₁ is a mixture of vinyl acetate and dimethyl maleate in a 2/1 to 5/1 mol ratio plus methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate or hexafluoroisopropyl methacrylate or mixtures thereof.

17. A polymer according to claim 10 wherein the water insoluble monomer B₁ is selected from the group consisting of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-butyl acrylate, n-butyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n-decyl acrylate, n-decyl methacrylate, perfluoroalkyl (C₆ -C₁₀) substituted alkyl acrylate or methacrylate;

and mixtures thereof.

18. A polymer according to claim 6 where in monomer B the water soluble monomer B₂ is an acrylate or methacrylate of formula CH₂ ═

CR₃ COOR₁₃, an acrylamide or methacrylamide of formula CH₂ ═

CR₃ CONHR₁₄ or CH₂ ═

CH₃ CON(R₅)₂, a maleate or fumarate of formula R₁₃ OCOCH═

CHCOOR₁₃, a vinyl ether of formula CH₂ ═

CHOR₁₃, an N-vinyl lactam;

or a mixture of said monomers,

wherein R₃ is hydrogen or methyl, R₅ is hydrogen or lower (C₁ -C₄) alkyl, R₁₃ is a hydrocarbon residue of 1 to 10 carbon atoms substituted by one or more water solubilizing groups such as carboxy, hydroxy or tert.-amino, or a polyethylene oxide group with from 2-100 repeating units, or a group which contains sulfate, phosphate, sulfonate or phosphonate groups, and R₁₄ is defined as R₁₃ or as R₅.

19. A polymer according to claim 18 wherein the water soluble monomer B₂ is selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid and N-vinyl-2-pyrrolidone.

20. A polymer according to claim 6 where component A is a polysiloxane structure wherein R₁ is alkylene of 3 or 4 carbon atoms, R₂, R_a, R_b, R_c, R_d, R_e, R_f, R_g, R_h, R_i, R_j and R_k are each methyl, x₁ +x₂ is 10 to 100, y₁ is 0 to 2, y₂ is 1 to 3, Z₁ is --O-- or --NH-- and R₄ is a diradical of an aliphatic or cycloaliphatic diisocyanate with 6 to 10 carbon atoms, and Y is the same as Y₁, R₆ is hydrogen, R₈ is ethylene, and Z₂ is --O-- or --NC(CH₃)₃ --, and component B contains from 0 to 30% based on total monomer of a diolefinic monomer (B_x) which is the acrylate or methacrylate of allyl alcohol, of a straight or branched chain alkylene glycol of 2 to 6 carbon atoms, of poly(ethylene oxide)glycol, of poly(propylene oxide)glycol, of poly(n-butylene oxide) glycol, of thiodiethylene glycol, of neopentylene glycol, of trimethylolpropane, or of pentaerthyritol;

or the reaction product obtained by reacting one mol of a di- or tri-isocyanate of structure OCN--R₄ --(NCO)_v, where R₄ is the radical derived by removing NCO groups from said isocyanate and v is 1 or 2, with 2 or 3 moles of a hydroxyalkyl acrylate or methacrylate.

21. A polymer according to claim 20 wherein B_x is neopentylene glycol diacrylate, ethylene glycol dimethacrylate or the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

22. A polymer according to claim 20 wherein component B contains the water insoluble monomer B₁ selected from the group consisting of methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, hexafluoroisopropyl methacrylate and mixtures thereof.

23. A polymer according to claim 22 wherein component B contains the water insoluble monomer B₁ selected from the group consisting of methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof.

24. A polymer according to claim 21 wherein component B contains as the water insoluble monomer B₁ methyl methacrylate, isobornyl methacrylate or mixtures thereof.

25. A polymer according to claim 20 wherein component B contains the water insoluble monomer B₁ which is a mixture of vinyl acetate and dimethyl maleate in a 2/1 to 5/1 mol ratio plus methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate or hexafluoroisopropyl methacrylate and mixtures thereof.

26. A polymer according to claim 20 wherein component B contains the water insoluble monomer B₁ selected from the group consisting of 2-ethylhexyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n-decyl arylate, n-decyl methacrylate, perfluoroalkyl (C₆ -C₁₀) substituted alkyl acrylate or methacrylate;

and mixtures thereof.

27. A polymer according to claim 20 wherein component B contains the water soluble monomer B₂ selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid and N-vinyl-2-pyrrolidone.

28. A polymer according to claim 20 which comprises

(A) from 15 to 40% by weight of a polysiloxane of structure A₂, Z₁ and Z₂ are each --O--, and y₂ is 1 or 2, and

(B) from 85 to 60% by weight of a mixture of a water-insoluble monomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

B₁ is from 60 to 95% of a water-insoluble monomer selected from the group consisting of methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof,

B₂ is from 20 to 0% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid, N-vinyl-2-pyrrolidone and mixtures thereof, and

B_x is from 30 to 5% of a diolefinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

29. A polymer according to claim 20 which comprises

(A) from 40 to 60% by weight of a polysiloxane of structure A₂, Z₁ and Z₂ are each --O--, and y₂ is 1 or 2, and

(B) from 60 to 40% by weight of a mixture of a water-insoluble monomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

B₁ is from 75 to 100% of a water-insoluble monomer selected from the group consisting of ethyl acrylate or methacrylate, n-butyl acrylate or methacrylate, n-hexyl acrylate or methacrylate, 2-ethylhexyl acrylate or methacrylate, n-octyl acrylate or methacrylate, n-decyl acrylate or methacrylate and mixtures thereof and with mixtures thereof with methyl or isobornyl methacrylate,

B₂ is from 25 to 0% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid, N-vinyl-2-pyrrolidone and mixtures thereof, and

B_x is from 5 to 0% of a diolefinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

30. A polymer according to claim 20 which comprises

(A) from 20 to 60% by weight of a polysiloxane of structure A₂, Z₁ and Z₂ are each --O--, and y₂ is 1 or 2, and

(B) from 80 to 40% by weight of a mixture of a water-insoluble monomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

B₁ is from 0 to 80% of a water-insoluble monomer selected from the group consisting of methyl methacrylate, 2-ethylhexyl acrylate, hexafluoroisopropyl methacrylate, perfluoroalkyl (C₆ -C₁₀) acrylate or methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof,

B₂ is from 100 to 20% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, N-vinyl-2-pyrrolidone acrylamide and mixtures thereof, and

B_x is from 0 to 5% of a diolefinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

31. A hard contact lens prepared from the polymer according to claim 5.

32. A hard contact lens prepared from the polymer according to claim 28.

33. A soft contact lens prepared from the polymer according to claim 5.

34. A soft contact lens prepared from the polymer according to claim 29.

35. A soft hydrogel contact lens prepared from the polymer according to claim 5.

36. A soft hydrogel contact lens prepared from the polymer according to claim 30.

37. A polymer according to claim 20 which comprises

(A) from 15 to 40% by weight of a polysiloxane of structure A₁, Z₁ and Z₂ are each --O--, and y₁ is 0 and

(B) from 85 to 60% by weight of a mixture of a water-insoluble momomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

39. A polymer according to claim 20 which comrpises

(A) from 40 to 60% by weight of a polysiloxane of structure A₃, Z₁ and Z₂ are each --O--, and y₁ is 0 and

(B) from 60 to 40% by weight of a mixture of a water-insoluble monomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

B₁ is from 75 to 100% of a water-insoluble monomer selected from the group consisting of ethyl acrylate or methacrylate, n-butyl acrylate or methacrylate, n-hexyl acrylate or methacrylate, 2-ethylhexyl acylate or methacrylate, n-octyl acrylate or methacrylate, n-decyl acrylate or methacrylate and mixtures thereof and with mixtures thereof with methyl or isoborynyl methacrylate,

B₂ is from 25 to 0% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid, N-vinyl-2-pyrrolidone and mixtures thereof, and

B_x is from 5 to 0% of a diolefinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

40. A polymer according to claim 20 which comprises

(A) from 20 to 60% by weight of a polysiloxane of structure A₃, Z₁ and Z₂ are each --O--, and y₁ is 0, and

(B) from 80 to 40% by weight of a mixture of a water-insoluble monomer (B₁), of a water-soluble monomer (B₂), and of a diolefinic monomer (B_x), wherein, based on percent by weight of the total weight of monomers,

B₁ is from 0 to 80% of a water-insoluble monomer selected from the group consisting of methyl methacrylate, 2-ethylhexyl acrylate, hexafluoroisopropyl methacrylate, perfluoroalkyl (C₆ -C₁₀) acrylate or methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof,

B₂ is from 100 to 20% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, N-vinyl-2-pyrrolidone, acrylamide and mixtures thereof, and

B_x is from 0 to 5% of a diolefinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocyanate and two moles of 2-hydroxyethyl methacrylate.

38. B₁ is from 60 to 95% of a water-insoluble monomer selected from the group consisting of methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate and mixtures thereof,

B₂ is from 20 to 0% of a water-soluble monomer selected from the group consisting of 2-hydroxyethyl methacrylate, N,N-dimethylacrylamide, acrylic acid, methacrylic acid, N-vinyl-2-pyrrolidone and mixtures thereof, and

B_x is from 30 to 5% of a dioelfinic monomer selected from the group consisting of neopentylene glycol diacrylate, ethylene glycol dimethacrylate and the reaction product of one mol of isophorone diisocynate and two moles of 2-hydroxyethyl methacrylate.