Polydiorganosiloxane preparation
A process for end capping and chain extending silanol terminated polydiorganosiloxanes with a mixture of one or more alkylacetoxydialkoxysilanes and one or more alkyldiacetoxyalkoxysilanes. The resulting capped polymeric material may be utilised as a polymer in e.g. a one-part alkoxy sealant composition such as, for example, an alkoxy low modulus clean (non-staining) or clear sealant composition.
1. A process for preparing a chain-extended alkoxy polydiorganosiloxane from a silanol terminated polydiorganosiloxane starting material, the process:
(i) reacting the silanol terminated polydiorganosiloxane starting material with a mixture of one or more alkylacetoxydialkoxysilanes and one or more alkyldiacetoxyalkoxysilanes wherein each alkyl group may be the same or different and contains from 1 to 6 carbons and each alkoxy group may be the same or different and contains from 1 to 6 carbons; and
(ii) neutralising the resulting mixture from step (i).
2. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein each alkylacetoxydialkoxysilane comprises an alkyl group having from 1 to 6 carbons and two alkoxy groups each of which contain from 1 to 6 carbons.
3. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein each alkyldiacetoxyalkoxysilane comprises an alkyl group having from 1 to 6 carbons and an alkoxy group containing from 1 to 6 carbons.
4. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein in step (i) the silanol terminated polydiorganosiloxane starting material is reacted with a mixture of methylacetoxydimethoxysilane and methyldiacetoxymethoxysilane.
5. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein a neutralising agent is utilised in step (ii) and is selected from the group consisting of hexylamine, dodecylamine, di-n-hexylamine, 2-ethylhexylamine, tert-butylamine, 2-ethylhexylamine, 1,6-hexanediamine, bis(2-ethylhexyl)amine, morpholine, dicyclohexylamine, 1,8-Diazabicyclo(5.4.0)undec-7-ene (DBU), (3-aminopropyl)-triethoxysilane, (3-aminopropyl)-trimethoxysilane, aminoethylaminopropyltrimethoxysilane bis(trimethoxysilylpropyl)amine, (dimethoxymethylsilyl)isobutyl)-ethylenediamine, dialkyldiacetamidosilanes, and combinations thereof.
6. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein a neutralising agent is utilised in step (ii) and is a dialkyldiacetamidosilane selected from N,N′-(dimethylsilylene)bis[N-ethylacetamide] and/or N,N′-(dimethylsilylene)bis[N-methylacetamide].
7. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein components of the reaction process are present in the following amounts:
(ai) silanol terminated polydiorganosiloxane starting material in an amount of from 95 to 99.5% by weight of the ingredients;
(aii) mixture of one or more alkylacetoxydialkoxysilanes and one or more alkyldiacetoxyalkoxysilanes in an amount of from about 0.25 to 2.55 by weight of the ingredients; and
(aiii) neutralising agent in an amount of from about 0.25 to 2.5 % by weight of the ingredients.
8. The process for preparing a chain-extended alkoxy polydiorganosiloxane in accordance with claim 1 , wherein once step (ii) has completed, the resulting polymeric product is collected and stored for future use or utilised in a process for preparing a one-part low modulus sealant composition, the sealant composition comprising:
(a) the chain-extended alkoxy terminated polydiorganosiloxane;
(b) reinforcing filler;
(c) cross-linker; and
(d) cure catalyst; and optionally
(e) adhesion promoter.
9. An alkoxy end-capped, chain extended polydiorganosiloxane polymer obtained from the process of claim 1 .
10. A one-part low modulus sealant composition comprising:
(a) a chain-extended alkoxy terminated polydiorganosiloxane;
(b) reinforcing filler;
(c) cross-linker; and
(d) cure catalyst; and optionally
(e) adhesion promoter;
wherein component (a) obtained from the process of claim 1 .
11. The one-part low modulus sealant composition in accordance with claim 10 , wherein cure catalyst (d) is selected from the group consisting of:
(i) a chelated titanate catalyst;
(ii) a chelated zirconate catalyst;
(iii) an optionally chelated titanate in combination with a metal carboxylate salt; and/or
(iv) an optionally chelated zirconate in combination with a metal carboxylate salt; and
combinations thereof;
optionally, wherein cure catalyst (d) additionally includes (v) a tin catalyst.
12. The one-part low modulus sealant composition in accordance with claim 10 , which is gunnable and/or self-levelling.
13. The one-part low modulus sealant composition in accordance with claim 10 , capable of being applied as a paste to a joint between two adjacent substrate surfaces where it can be worked, prior to curing, to provide a smooth surfaced mass which will remain in its allotted position until it has cured into an elastomeric body adherent to the adjacent substrate surfaces.
14. A silicone elastomer which is the reaction product of the one-part low modulus sealant composition in accordance with claim 10 .
15. A sealant suitable for use in the facade, insulated glass, window construction, automotive, solar and construction fields, wherein the sealant comprises or is formed from the one-part low modulus sealant composition in accordance with claim 10 .
16. A method for filling a space between two substrates so as to create a seal therebetween, the method comprising:
a) providing the one-part low modulus sealant composition in accordance with claim 10 ; and either b) or c);
b) applying the sealant composition to a first substrate, and bringing a second substrate in contact with the sealant composition that has been applied to the first substrate, or
c) filling a space formed by the arrangement of a first substrate and a second substrate with the sealant composition and curing the sealant composition.
17. The method for filling a space between two substrates in accordance with claim 16 , wherein the space is filled by introducing the sealant composition by way of extrusion or through a sealant gun.