Compounds that can be crosslinked by way of hydrosilylation reaction

Abstract

A platinum-catalyzed composition along with a process for producing the same and a shaped body or products made from the same. The platinum-catalyzed composition is crosslinkable by a hydrosilylation reaction. The composition includes strong acids (S) having a pKa of <2.5 is less than 0.3 ppm by weight The platinum catalysts are those having the formula R.sup.1.sub.3Pt{CpR.sup.2.sub.5} wherein Cp is the cyclopentadienyl radical and R.sup.1 may be identical or different and is a monovalent, optionally substituted, aliphatically saturated hydrocarbon radical. R.sup.2 may be identical or different and is a hydrogen atom, SiC-bonded silyl radical or a monovalent, optionally substituted hydrocarbon radical.

Claims

1-10. (canceled)

11. A platinum-catalyzed composition, comprising: wherein the platinum-catalyzed composition is crosslinkable by hydrosilylation reaction; wherein the content of strong acids (S) has a pKa of <2.5 is less than 0.3 ppm by weight and that the platinum catalysts are those of the formula
R.sup.1.sub.3Pt{CpR.sup.2.sub.5}  wherein Cp is the cyclopentadienyl radical; wherein R.sup.1 may be identical or different and is a monovalent, optionally substituted, aliphatically saturated hydrocarbon radical; and wherein R.sup.2 may be identical or different and is a hydrogen atom, SiC-bonded silyl radical or a monovalent, optionally substituted hydrocarbon radical.

12. The composition of claim 11, wherein the content of strong acids (S) are selected from hydrogen chloride, methanesulfonic acid, trifluoromethanesulfonic acid, sulfuric acid, and acid-activated bleaching earths and are less than 0.3 ppm by weight.

13. The composition of claim 11, wherein the content of strong acids (S) is less than 0.2 ppm by weight.

14. The composition of claim 11, wherein the composition further comprises: (i) at least one compound selected from the group comprising the compounds (A), (B), and (C); wherein compound (A) is an organic compound and/or an organosilicon compound containing at least one radical having an aliphatic carbon-carbon multiple bond; wherein compound (B) is an organosilicon compound containing at least one Si-bonded hydrogen atom; and wherein compound (C) is an organosilicon compound containing SiC-bonded radicals having aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms; wherein the compositions comprise at least one compound having aliphatic carbon-carbon multiple bonds and at least one compound having Si-bonded hydrogen atoms, and (ii) at least one platinum catalyst; and wherein the content of strong acids (S) has a pKa of <2.5 is less than 0.3 ppm by weight.

15. The composition of claim 11, further comprising a constituent (A), wherein the constituent (A) comprises at least one aliphatically unsaturated organosilicon compound.

16. The composition of claim 11, further comprising acid scavengers (H).

17. The composition of claim 16, wherein the acid scavengers (H) are metal carbonates, metal carboxylates or basic phosphonates.

18. A process for producing the composition as claimed in claim 11, wherein the process comprises mixing the individual components in any desired order.

19. The process of claim 18, wherein the process produces a shaped body by crosslinking.

20. A shaped body produced by crosslinking the composition as claimed claim 11.

Description

EXAMPLE 1

[0139] A model composition is subjected to accelerated storage, i.e. stored at high temperature. Rapid reaction of the siloxanes by hydrosilylation, as can be demonstrated by a decrease in the Si—H content, is undesirable.

[0140] A flask is charged under argon as inert gas with a mixture of 1,1,1,2,3,3,3-heptamethyltrisiloxane (multiply distilled) and 1,1,1,2,3,3,3-heptamethyl-2-vinyltrisiloxane (multiply distilled) in a ratio of 1.5 mol/1.0 mol and this is heated to 100° C. The HCl content is 0.0 ppm. To this is added 250 ppm of CpMePtMe.sub.3. The relative Si—H content is monitored by the ReactIR until no decrease in intensity is detectable. The point in time at which 50% of the total decrease in intensity (t.sub.50%) has occurred is 15 hours.

[0141] The composition shows good stability.

EXAMPLE 2

[0142] The procedure is as in example 1, except that 500 ppm of catalyst is used; t.sub.50% is 9.5 h. The composition shows good stability.

EXAMPLE 3

[0143] The procedure is as in example 1, except that 1000 ppm by weight of ammonium chloride (pK.sub.a=9.24) is additionally added as an example of a typical impurity in polydimethylsiloxanes; t.sub.50% is 13 h. The composition shows good stability.

COMPARATIVE EXAMPLE 1

[0144] The procedure is as in example 1, except that 1000 ppm by weight of p-toluenesulfonic acid (pK.sub.a=0.7) is additionally added; t.sub.50% is 3.25 h. The composition does not show good stability.

COMPARATIVE EXAMPLE 2

[0145] The procedure is as in example 1, except that 1000 ppm by weight of pyruvic acid (pK.sub.a=2.4) is additionally added; t.sub.50% is 3.5 h. The composition does not show good stability.

EXAMPLE 4

[0146] The procedure is as in example 1, except that 20 000 ppm by weight of potassium dihydrogen phosphate (pK.sub.a=6.82) is additionally added as an example of a typical impurity in polydimethylsiloxanes; t.sub.50% is 13 h. The composition shows good stability.

COMPARATIVE EXAMPLE 3

[0147] The procedure is as in example 1, except that 40 mg of hydrophilic fumed silica (BET=200 m.sup.2/g)/4 mL of siloxane mixture is additionally added (commercially available under the name HDK® V15 from Wacker Chemie AG), which contains traces of hydrogen chloride (pK.sub.a<1) in amounts of 10.sup.−3 mmol/g (pH determined in accordance with DIN EN ISO 787-9: 4.04); t.sub.50% is 4.5 h. The composition does not show good stability.

COMPARATIVE EXAMPLE 4

[0148] A mixture of 54.0 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 100 000 mPas), 7.5 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 20 000 mPas), 70 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 7000 mPas), 170 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 1000 mPas), and 44 parts by weight of (Me.sub.3SiO.sub.1/2).sub.x(ViMe.sub.2SiO.sub.1/2).sub.y(SiO.sub.4/2).sub.z where x+y/z=0.7 and x/y=7 (Mw 5300 g/ml, Mn 2400 g/mol) is mixed homogeneously. Additionally added to this are 3 parts by weight of Me.sub.3Si—O—[(Me.sub.2SiO).sub.x(MeHSiO).sub.y]—SiMe.sub.3 (x+y=50, x/y=0.3/1, 1.1% Si—H) and 15 parts by weight of HMe.sub.2Si—O—(Me.sub.2SiO).sub.x—SiHMe.sub.2 (x=60, 0.045% Si—H). The HCl content was determined to be 1.7 ppm by weight.

[0149] 21.5 parts by weight of a solution of a catalyst trimethyl[(3-bis(polydimethylsiloxy)methylsilyl)propylcyclopentadienyl]platinum(IV) in ViMe.sub.2Si—O—[(Me.sub.2SiO).sub.n]—SiMe.sub.2Vi (viscosity 1000 mPas) having a Pt content of 300 ppm by weight were mixed in. The overall mixture had an initial viscosity of 3761 mPas, a viscosity after 4 days at 25° C. of 7360 mPas, and was undesirably vulcanized after 7 days at 25° C.

EXAMPLE 5

[0150] 100 parts by weight of a composition according to comparative example 4 were, before addition of the platinum catalyst, diluted with 100 parts by weight of ethyl acetate and stirred with 1.5 parts by weight of NaHCO.sub.3 as acid scavenger for 1 h at 25° C., filtered, and the volatile solvent removed. The HCl content was determined to be 0.0 ppm. 21.5 parts by weight of a solution of a catalyst trimethyl[(3-bis(polydimethylsiloxy)methylsilyl)propylcyclopentadienyl]platinum(IV) in ViMe.sub.2Si—O—[(Me.sub.2SiO).sub.n]—SiMe.sub.2Vi (viscosity 1000 mPas) having a Pt content of 300 ppm by weight were mixed in. The overall mixture had an initial viscosity of 3176 mPas and a viscosity after 6 weeks at 25° C. of 3396 mPas.

[0151] Crosslinking by means of UV radiation was successful after 7 days of storage at 25° C. An elastomeric shaped body was obtained.

COMPARATIVE EXAMPLE 5

[0152] A mixture of 230 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 20 000 mPas), 40 parts by weight of ViMe.sub.2Si—O—(Me.sub.2SiO).sub.n—SiMe.sub.2Vi (viscosity 100 mPas), and 50 parts by weight of a hydrophobic fumed silica (BET=300 m.sup.2/g, commercially available under the name HDK® H30 from Wacker Chemie AG) is mixed homogeneously. Additionally mixed in to this are 9 parts by weight of Me.sub.3Si—O—[(Me.sub.2SiO).sub.x(MeHSiO).sub.y]—SiMe.sub.3 (x+y=50, 1.1% Si—H), 2.5 parts by weight of glycidoxypropyltrimethoxysilane, and 5.0 parts by weight of methacryloyloxytrimethoxysilane. To this are added and mixed in 17.7 parts by weight of a solution of MeCpPtMe.sub.3 in ViMe.sub.2Si—O—[(Me.sub.2SiO).sub.n]—SiMe.sub.2Vi (viscosity 1000 mPas) having a platinum content of 300 ppm by weight (catalyst content of the overall mixture is 15 ppm by weight). The acid content is 13.5 ppm by weight of H.sup.+.

[0153] The viscosity is determined to be 24 200 mPas. After storage for 1/7 days at 25° C., the viscosity is 29 440/30 041 mPas. After storage for 7 days at 25° C., complete crosslinking by means of UV radiation was not achieved and a sticky skin had formed. After a further 24 h of storage at 25° C., uncrosslinked material can be detected under the skin.

EXAMPLE 6

[0154] The procedure is as in comparative example 5, except that 0.05 parts by weight of zinc undecenylate are mixed in before adding the catalyst.

[0155] The viscosity is determined to be 24 000 mPas. After storage for 7/14/21 days at 25° C., the viscosity is 23 813/24 580/25 901 mPas.

[0156] Crosslinking by means of UV radiation was successful after 8 weeks of storage at 25° C. An elastomeric shaped body was obtained.

EXAMPLE 7

[0157] The procedure is as in comparative example 5, except that 0.1 parts by weight of lithium palmitate are mixed in before adding the catalyst. The viscosity is determined to be 24 700 mPas. After storage for 7/14/21 days at 25° C., the viscosity is 23 839/24 762/26 477 mPas.

[0158] Crosslinking by means of UV radiation was successful after 8 weeks of storage at 25° C. An elastomeric shaped body was obtained.