Low density foams and process for their production

Claim 2

Silicone foams, according to the invention, were prepared on a laboratory scale from polymers RTF-761A and B, and and RTF-762A and B, described previously, with various amounts of reactive diluent PS-340 and appropriate catalysts. No additional inorganic filler was used, other than that contained in the polymers as commercially obtained. In these laboratory preparations, the resin compositions were mixed together in a cardboard, open-topped container of about 250 ml capacity, stirring with a wooden stirrer to form a homogeneous mixture. Then they were poured into paper molds and allowed to foam and cure, to produce foam samples of size about 20-35 cubic inches.

Claim 3

Further samples were prepared similarly, but on a semi-industrial scale, by mixing the ingredients in a vessel with a mechanical hand mixer and then pouring into a mold to cure and form foam samples of size 14-24 inches by 14-24 inches by 4-6 inches.

Claim 4

Further such samples were prepared similarly, but on an industrial scale, producing foam slabs of size 3 feet x 6 feet x 6 inches thick. In the industrial preparations, automatic air-excluding mixes were used to prepare the foamable compositions, to a high degree of homogeneity, with automatic ingredient proportioning and pouring into the the shallow slab molds.

Claim 5

The conditions and results are given below in TaoLe 1. The above figures are derived from several repeated samples. Some variation in composition and performance is noted between batches of the same commercially available resins. Example 5

Claim 6

Forms were prepared in accordance with the present invention from the commercially available RTF-761A and B, and RTF-762A and B, organosiloxane prepolymers, and reactive diluent P S-340 previously described. Manufacturers' recommended proprietary catalysts for the respective prepolymers were used. Small amounts of water were included in each foaming formulation - prepolymer RTF-762A contains a little water in its composition whereas RTF-761 does not. However, the curative 761-B, used with resin RTF-761A, includes a small amount of water. Accordingly, each of the formulations contained about 8 parts of water per 100 parts by weight of catalyst. Mixing, foaming and curing took place in an open-topped vessel, and the viscosity of the mixture was measured after homogeneous mixing, but before addition of the catalyst to cause foaming.

Claim 7

The formulations and results are given below in Table 2. It is to be noted that the reported properties of viscosity and density are averages of several formulations, since minor variations were encountered between specific prepolymer batches and reactive diluent batches.

Claim 8

(B3) the B-part comprising at least one second viscous liquid uncured organosiloxane polymer having stcuctucal units of general formula II above in which R, R 1 , R 2 and R 3 are independently selected from hydrogen, C 1 -C 4 alkyl groups and phenyl groups, said second polymer having a minor but significant amount of internal Si-H bonding; said composition also comprising: (4) water; (5) inorganic filler;

Claim 9

the viscosity of the mixture of components Al, A2 and.5 being from about 30,000 to about 65,000 cps, said composition being capable of reaction to foam and cure under the action of a complex platinum catalyst.

Claim 10

The composition of claim 1 wherein the groups R, R 1 , R 2 and R 3 in the first organosiloxane polymer (Al) are selected from methyl, ethyl and phenyl.

Claim 11

The composition of claim 2 wherein the groups R, R 1 , R 2 and R 3 in the second organosiloxane polymer (B3) are selected from hydrogen, methyl, ethyl and phenyl.

Claim 12

The composition of claim 3 wherein the first organosiloxane polymer is present in weight excess over the second organosiloxane polymer.

Claim 13

The composition of claim 4 wnerein the organosiloxane polymer mixture contains a molar excess of Si- H bonds over vinyl bonds.

Claim 14

The composition of claim 5 including 3.5-10 parts by weight of said reactive diluent (A2), per L00 parts by total weight of components Al and 5;

Claim 15

The composition of claim 1 wherein the reactive diluent has a hydroxyl functionality of 2.7-3.1 per cent.

Claim 16

The composition of claim 7 wherein the amount of reactive diluent is from about 4.5-7.5 parts by weight, per 100 parts by weight of components Al and 5.

Claim 17

The composition of claim 1 wherein the amount of water is from about 5-12 parts by weight per 100 parts of second organosiloxane polymer B3.

Claim 18

The composition of claim 1 wherein the relative amounts of water and reactive diluent are such that 85-95 mole percent of hydroxyl groups in the reactive composition are derived from water and 15-5 mole percent thereof from the reactive diluent.

Claim 19

The composition ot cLaim 1, wherein the inorganic filler is present, in amounts from 35-100 parts by weight, per 100 parts by weight of first organosiloxane polymer Al.

Claim 20

A cured, flexible, fire resistant silicone foam composition of low density, said composition comprising: a polyorganosiloxane having a backbone polymeric structure containing a major proportion of the silicone structural unit general formula wherein each R, R 1 , R 2 and R 3 may be the same or different, and is independently selected from C 1 -C 4 alkyl groups and aryl groups, "n" is an integer of at least 2, and having a minor proportion of the ethylenic structural unit -CH 2 -CH 2 linking the above silicone structural units; said cured foam composition having a density of from about 5 to about 14 pcf.

Claim 21

The composition of claim 12 wherein the polyorganosiloxane is a copolymer of a major proportion of a first polyorganosiloxane polymer having a basic polymer backbone of structure: and vinyl terminal groups, where R 1 , R 2 , R 3 and R have the meanings given in claim 12; a minor proportion of a second organosiloxane polymer having structural units of the general formula: where R, R 1 , R 2 and R 3 are indepenaently selected from hydrogen, C 1 -C 4 .alkyl groups and phenyl groups, said second polymer having a minor but significant amount of internal Si-H bonding; and a minor proportion of a reactive polydimethyl siloxane diluent of viscosity less than that of the polyorganosiloxane polymers, and having a molecular weight in the range 1100-2000, having hydroxyl functionality of at least 2.5%, being essentially free from carbon-carbon unsaturation, and corresponding to the general formula: in which "m" is an integer suitaoly chosen for the appropriate molecular weight of the compound.

Claim 22

The composition of claim 13 also including an inorganic filler substantially homogeneously dispersed therein.

Claim 23

The composition of claim 14 wherein the inorganic filler is present in an amount of from about 35-100 parts by weight per 100 parts by weight of first organosiloxane polymers.

Claim 24

The composition of claim 15 having a density of 5-11 pcf.

Claim 25

A process for preparing low density flexible silicone foams of density in the range 5-14 pcf, which comprises preparing, by mixing at temperatures not exceeding 35 0 C, a viscous liquid composition comprising: (1) at least one first viscous liquid uncured organosiloxane polymer having structural units of the general formula: where R, R 1 , R 2 , and R 3 are independently selected from the group consisting of C 1 -C 4 alkyl groups and phenyl groups, "n" is an integer of from 2 to about 50, and having vinyl terminal groups: (2) at Least one second viscous liquid uncured organosiloxane polymer having structural units of general formula II above, in which R, R 1 , R2 and R 3 are independently selected from hydrogen, C 1 -C 4 alkyl groups and phenyl groups, said second polymer having a minor but significant amount of internal Si-H bonding; (3) from 2 to 12 parts by weight, per 100 parts by total weight of said organosiloxane poLymers, of at least one reactive polydimethyl siloxane diluent of viscosity less than that of the polymers, and having a molecular weight in the range 1500-2000, having hydroxyl functionality of at least 2.5, essentially free from carbon-carbon unsaturation and corresponding to the general formula: (4) inorganic filler, and, (5) water; the mixture of components 1, 3 ana 4 composition having a viscosity of from about 30,000 to about 65,000 cps; and reacting said composition with a platinum based catalyst to cause gelling, foaming and curing thereof, and to prepare a low density flexible silicone foam.

Claim 26

18 . The process of claim 16 wherein the groups R, R 1 , R 2 and R 3 in the first organosiloxane polymer are selected from methyl, ethyl and phenyl.

Claim 27

The composition of claim 17 wherein the groups R, R 1 , R 2 and R 3 in the second organosiloxane polymer are selected from hydrogen, methyl, ethyl and phenyl.

Claim 28

The process of claim 18 wherein the first organosiloxane polymer is present in the composition in weight excess over the second organosiloxane polymer.

Claim 29

2L The process of claim 19 wherein the organosiloxane polymer mixture contains a molar excess of Si-H bond over vinyl bonds.

Claim 30

22 The process of claim 20 wherein the composition includes 3.5-10 parts by weight of said reactive diluent (3) per 100 parts by total weight of said organosiloxane polymers.

Claim 31

The process of claim 1 wherein the reactive diluent (3) has a hydroxyl functionality of 2.7-3.1%.