Gels
The present invention relates to silicon-containing biostable gels and processes for their preparation. The gels possess properties which make them useful in the manufacture and repair of biomaterials and medical devices, articles or implants, in particular the manufacture of soft tissue implants such as breast implants and the repair of orthopaedic joints such as spinal discs.
1. A chemical gel comprising at least one silicon-containing biostable polymer having monomers with an average functionality in the range of from 2.05 to 3.5 in which the biostable polymer is a polyurethane or polyurethane urea which is a reaction product of:
(a) at least one silicon-containing polyol or polyamine having 2 or more functional groups in which the silicon-containing polyol or polyamine is a compound of formula (II)
in which R 1 is selected from C 1-6 alkylene optionally substituted with OH or NR′R″ in which R′ and R″ are independently selected from H, CO 2 H and C 1-6 alkyl;
R 9 is C 1-4 alkyl;
R 10 is optionally substituted C 1-4 alkyl or
in which R 1 and R 9 are as defined above;
x is 5 to 30;
y is 1 to 10; and
n is 1 to 10;
(b) a polyisocyanate; and
(c) at least one non-silicon containing compound selected from a polycarbonate or a C 1-6 alkane having 1 or more functional groups selected from OH, NR′R″ in which R′ and R″ are the same or different and selected from H, CO 2 H and C 1-6 alkyl; wherein the gel has an NCO/OH or NH 2 ratio less than 1.
2. A gel according to claim 1 in which the average functionality is from 2.1 to 3.25.
3. A gel according to claim 1 in which the compound of formula (II) is as follows:
in which n is as defined in claim 1 , wherein the molecular weight of the compound of formula (IIa) or (IIb) is from 1000-5000.
4. A gel according to claim 1 in which the polyisocyanate (b) is polymeric 4,4′-diphenylmethane diisocyanate (MDI), methylene biscyclohexyl diisocyanate (H 12 MDI), p-phenylene diisocyanate (p-PDI), trans-cyclohexane-1,4-diisocyanate (CHDI), 1,6-diisocyanatohexane (DICH), 1,5-diisocyanatonaphthalene (NDI), para-tetramethylxylenediisocyanate (p-TMXDI), meta-tetramethylxylene diisocyanate (m-TMXDI), 2,4-toluene diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone diisocyanate (IPDI).
5. A gel according to claim 1 in which the polycarbonate is a poly(alkylene carbonate); a polycarbonate prepared by reacting alkylene carbonate with alkanediol or a silicon based polycarbonate prepared by reacting alkylene carbonate with 1,3-bis(4-hydroxybutyl)-1,1,3,3-tetramethyldisiloxane (BHTD) and/or alkanediol.
6. A gel according to claim 1 in which the C 1-6 alkane having 1 or more functional groups is methane diol, butane diol or hexane diol.
7. A gel according to claim 1 in which the NCO/OH or NH 2 ratio is from 0.4 to 0.7.
8. A gel according to claim 1 having less than 35% extractables.