Organosiloxane compositions

1. A moisture curable composition capable of cure to an elastomeric body comprising

(a) a diluted polymer comprising

(i) a silicon containing polymer of the formula

X-A-X 1

where X and X 1 are independently selected from silyl groups which contain one or more condensable substituents per group and A is a polymeric chain having a number average molecular weight (M n ) of at least 132,000, and

(ii) an organic extender and/or plasticiser

which diluted polymer is obtained by polymerisation in the presence of the organic extender and/or plasticiser

(b) a suitable cross-linking agent which comprises at least two groups which are reactable with the condensable groups in the diluted polymer,

(c) a suitable condensation catalyst, and optionally

(e) one or more fillers.

2. A composition in accordance with claim 1 wherein A is a siloxane polymeric chain, an organic polymeric chain, a siloxane copolymeric chain or a siloxane/organic block copolymeric chain.

3. A composition in accordance with claim 1 wherein X 1 or X are silyl groups comprising hydroxyl-terminating or hydrolysable substituents selected from —Si(OH) 3 , —(R a )Si(OH) 2 , —(R a ) 2 SiOH, —R a Si(OR b ) 2 , —Si(OR b ) 3 , —R a 2 SiOR b or —R a 2 Si—R c —SiR d p (OR b ) 3−p where each R a independently represents an alkyl group; each R b and R d group is independently an alkyl or alkoxy group in which the alkyl groups suitably have up to 6 carbon atoms; R c is a divalent hydrocarbon group which may be interrupted by one or more siloxane spacers having up to 6 silicon atoms; and p has the value 0, 1 or 2.

4. A composition in accordance with claim 1 wherein the extender and/or plasticiser is selected from one or more of the group of:

trialkylsilyl terminated polydimethyl siloxane,

polyisobutylenes (PIB),

phosphate esters,

polyalkylbenzenes, and

linear and/or branched alkylbenzenes esters of aliphatic monocarboxylic acids.

5. A composition in accordance with claim 1 wherein the extender is selected from one or more of the group comprising:

linear or branched mono unsaturated hydrocarbons; and

mineral oil fractions comprising linear (n-paraffinic) mineral oils, branched (iso-paraffinic) mineral oils, cyclic (naphthenic) mineral oils, and mixtures thereof.

6. A composition in accordance with claim 1 wherein the cross-linking agent is one or more silane or siloxane which contain acyloxy groups and/or ketoximino groups and the catalyst is a tin catalyst.

7. A composition in accordance with claim 1 wherein the cross-linking agent is one or more silane or siloxane which contain alkoxy groups and alkenyloxy groups and the catalyst is a titanate or zirconate or a chelated titanate or chelated zirconate.

8. A composition in accordance with claim 1 wherein the filler is present and comprises one or more finely divided, reinforcing fillers selected from the group of high surface area fumed silica, precipitated silica, and calcium carbonate, and/or one or more extending fillers selected from the group of crushed quartz, diatomaceous earth, barium sulphate, iron oxide, titanium dioxide, carbon black, talc, and wollastonite.

9. A composition in accordance with claim 1 wherein the diluted polymer is obtained by polymerisation in the extender and/or plasticiser via one of the following pathways:

(i) condensation;

(ii) ring opening/equilibrium;

(iii) polyaddition; and

(iv) chain extension

wherein where required polymers resulting from the above polymerisation routes may be end-capped to provide the required hydrolysable end-groups.

10. Joint sealants, adhesives, moulded bodies, coatings and formed-in-place gaskets comprising the composition in accordance with claim 1 .

11. A sealant composition comprising the composition of claim 1 .

12. A method of sealing a space between two units, said method comprising applying a composition in accordance with claim 1 and causing or allowing the composition to cure.

13. A composition in accordance with claim 2 wherein the (i) silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C.

14. A composition in accordance with claim 3 wherein the (i) silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C.

15. A composition in accordance with claim 6 wherein the (i) silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C.

16. A composition in accordance with claim 7 wherein the (i) silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C.

17. A composition in accordance with claim 9 wherein the (i) silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C.

18. A moisture curable composition capable of cure to an elastomeric body comprising:

(a) a diluted polymer comprising;

(i) a silicon containing polymer of the formula

X-A-X 1

where X and X1 are independently selected from silyl groups which contain one or more condensable substituents per group and A is a siloxane polymeric chain, an organic polymeric chain, a siloxane copolymeric chain or a siloxane/organic block copolymeric chain having a number average molecular weight (Mn) of at least 132,000, and wherein said silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C., and

(ii) an organic extender and/or plasticizer,

which diluted polymer is obtained by polymerisation in the presence of the organic extender and/or plasticizer,

(b) a suitable cross-linking agent which comprises one or more silanes or siloxanes which contain acyloxy groups, ketoximino groups, alkoxy groups and/or alkenyloxy groups which are reactable with the condensable groups in the diluted polymer,

(c) a condensation catalyst selected from the group consisting of tin, a titanate, a zirconate, a chelated titanate, and a chelated zirconate, and optionally

(e) one or more fillers.

19. A composition in accordance with claim 18 wherein X 1 or X are silyl groups comprising hydroxyl-terminating or hydrolysable substituents selected from —Si(OH) 3 , —(R a )Si(OH) 2 , —(R a ) 2 SiOH, —R a Si(OR b ) 2 , —Si(OR b ) 3 , —R a 2 SiOR b or —R a 2 Si—R c —SiR d p (OR b ) 3−p where each R a independently represents an alkyl group; each R b and R d group is independently an alkyl or alkoxy group in which the alkyl groups suitably have up to 6 carbon atoms; R c is a divalent hydrocarbon group which may be interrupted by one or more siloxane spacers having up to 6 silicon atoms; and p has the value 0, 1 or 2.

20. A moisture curable composition capable of cure to an elastomeric body comprising:

(a) a diluted polymer comprising;

(i) a silicon containing polymer of the formula

X-A-X 1

where X and X 1 are independently selected from silyl groups which contain one or more condensable substituents per group and A is a polymeric chain having a number average molecular weight (M n ) of at least 132,000, and wherein said silicon containing polymer has a viscosity of greater than 1,000,000 mPa·s at 25° C., and

(ii) an organic extender and/or plasticizer,

which diluted polymer is obtained by polymerisation in the presence of the organic extender and/or plasticizer,

(b) a suitable cross-linking agent which comprises at least two groups which are reactable with the condensable groups in the diluted polymer,

(c) a suitable condensation catalyst, and optionally

(e) one or more fillers.

21. A composition in accordance with claim 1 wherein A includes siloxane units of the formula: —(R 5 s SiO (4−s)/2 ) wherein each R 5 is independently an organic group having from 1 to 18 carbon atoms, a substituted hydrocarbon group having from 1 to 18 carbon atoms or a hydrocarbonoxy group having up to 18 carbon atoms and s has a value of from 1 to 3.