NOVEL SILICONE COMPOSITION CROSSLINKING CATALYSTS

Abstract

The invention relates to a crosslinkable composition X, comprising: at least one organopolysiloxane compound A comprising, per molecule, at least two C2-C6 alkenyl radicals bonded to silicon atoms; at least one organohydrogenopolysiloxane compound B comprising, per molecule, at least two hydrogen atoms bonded to an identical or different silicon atom; at least one catalyst C which is a complex corresponding to the following formula: [Co(L1)2] in which: the symbol Co represents cobalt at degree of oxidation II; the symbols L1, which may be identical or different, represent a ligand which is a -dicarbonylato anion or the enolate anion of a -dicarbonylated compound; optionally at least one adhesion promoter D; and optionally at least one charge E. The invention also relates to the use of the previously described catalyst C as silicone composition crosslinking catalyst, to a silicone composition crosslinking method, characterized in that it consists in heating the composition X to a temperature of between 70 and 200 C., and to the resulting crosslinked silicone material Y.

Claims

1- A crosslinkable composition X comprising: at least one organopolysiloxane compound A comprising, per molecule, at least two C.sub.2-C.sub.6 alkenyl radicals bonded to silicon atoms, at least one organohydrogenopolysiloxane compound B comprising, per molecule, at least two hydrogen atoms bonded to an identical or different silicon atom, at least one catalyst C which is a complex corresponding to the following formula:
[Co(L.sup.1).sub.2] in which: the symbol Co represents cobalt in oxidation state II, the symbols L.sup.1, which may be identical or different, represent a ligand which is a -dicarbonylato anion or the enolate anion of a -dicarbonyl compound, optionally at least one adhesion promoter D and optionally at least one filler E.

2- The composition X as claimed in claim 1, wherein the catalyst C is present in a content ranging from 0.001 to 10 mol % of cobalt per number of moles of C.sub.2-C.sub.6 alkenyl radicals bonded to silicon atoms in the organopolysiloxane compound A, optionally from 0.01 to 7%, and more optionally from 0.1 to 5%.

3- The composition X as claimed in claim 1, wherein said composition is free of catalyst based on platinum, palladium, ruthenium or rhodium.

4- The composition X as claimed in claim 1, wherein the ligand L.sup.1 is an anion derived from a compound of formula (1):
R.sup.1COCHR.sup.2COR.sup.3 (1) in which: R.sup.1 and R.sup.3, which may be identical or different, represent a linear, cyclic or branched C.sub.1-C.sub.30 hydrocarbon-based radical, an aryl containing between 6 and 12 carbon atoms or a radical OR.sup.4 with R.sup.4 representing a linear, cyclic or branched C.sub.1-C.sub.30 hydrocarbon-based radical, R.sup.2 is a hydrogen atom or a hydrocarbon-based radical, optionally an alkyl radical comprising from 1 to 4 carbon atoms; with R.sup.1 and R.sup.2 may be joined together to form a C.sub.5-C.sub.6 ring, and R.sup.2 and R.sup.4 may be joined together to form a C.sub.5-C.sub.6 ring.

5- The composition X as claimed in claim 1, in which the compound of formula (1) is chosen from the group formed by the following -diketones: 2,4-pentanedione (acac); 2,4-hexanedione; 2,4-heptanedione; 3,5-heptanedione; 3-ethyl-2,4-pentanedione; 5-methyl-2,4-hexanedione; 2,4-octanedione; 3,5-octanedione; 5,5-dimethyl-2,4-hexanedione; 6-methyl-2,4-heptanedione; 2,2-dimethyl-3,5-nonanedione; 2,6-dimethyl-3,5-heptanedione; 2-acetylcyclohexanone (Cy-acac); 2,2,6,6-tetramethyl-3,5-heptanedione (TMHD); 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (F-acac); benzoylacetone; dibenzoylmethane; 3-methyl-2,4-pentadione; 3-acetyl-2-pentanone; 3-acetyl-2-hexanone; 3-acetyl-2-heptanone; 3-acetyl-5-methyl-2-hexanone; benzoylstearoylmethane; benzoylpalmitoylmethane; octanoylbenzoylmethane; 4-t-butyl-4-methoxydibenzoylmethane; 4,4-dimethoxydibenzoylmethane and 4,4-di-tert-butyldibenzoylmethane, and optionally from the -diketones 2,4-pentanedione (acac) and 2,2,6,6-tetramethyl-3,5-heptanedione (TMHD).

6- The composition X as claimed in claim 1, in which the catalyst C is chosen from the complexes [Co(acac).sub.2], [Co(TMHD).sub.2], [Co(keto ester).sub.2] and [Co(Rhodiastab 50).sub.2], in which acac means the anion derived from the compound 2,4-pentanedione, TMHD means the anion derived from the compound 2,2,6,6-tetramethyl-3,5-heptanedione, keto ester means the anion derived from a methyl ester of acetylacetic acid and Rhodiastab 50 means a mixture of anions derived from the compound benzoylstearoylmethane, and anions derived from the compound benzoylpalmitoylmethane.

7- The composition X as claimed in claim 1, wherein the organopolysiloxane A comprises: (i) at least two siloxyl units (A.1), which may be identical or different, having the following formula: $\begin{array}{cc}{W}_a.Math.Z_b.Math.{\mathrm{SiO}}_{\frac{4-\left(a+b\right)}{2}}& \left(A.Math.\mathrm{.1}\right)\end{array}$ in which: a=1 or 2, b=0, 1 or 2 and a+b=1, 2 or 3; the symbols W, which may be identical or different, represent a linear or branched C.sub.2-C.sub.6 alkenyl group, and the symbols Z, which may be identical or different, represent a monovalent hydrocarbon-based group containing from 1 to 30 carbon atoms, optionally chosen from the group formed by alkyl groups containing from 1 to 8 carbon atoms and aryl groups containing between 6 and 12 carbon atoms, and even more optionally chosen from the group formed by methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl radicals, (ii) and optionally at least one siloxyl unit having the following formula: $\begin{array}{cc}{Z}_a^1.Math.{\mathrm{SiO}}_{\frac{4-a}{2}}& \left(A.Math.\mathrm{.2}\right)\end{array}$ in which: a=0, 1, 2 or 3, the symbols Z.sup.1, which may be identical or different, represent a monovalent hydrocarbon-based group containing from 1 to 30 carbon atoms, optionally chosen from the group formed by alkyl groups containing from 1 to 8 carbon atoms inclusive and aryl groups containing between 6 and 12 carbon atoms, and even optionally chosen from the group formed by methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl radicals.

8- The composition X as claimed in claim 1, in which the organohydrogenopolysiloxane compound B comprises at least three hydrogen atoms per molecule directly bonded to an identical or different silicon atom.

9- The composition X as claimed in claim 1, in which the organohydrogenopolysiloxane compound B is an organopolysiloxane comprising: (i) at least two siloxyl units and optionally at least three siloxyl units having the following formula: $\begin{array}{cc}{H}_d.Math.Z_e^3.Math.{\mathrm{SiO}}_{\frac{4-\left(d+e\right)}{2}}& \left(B.Math.\mathrm{.1}\right)\end{array}$ in which: d=1 or 2, e=0, 1 or 2 and d+e=1, 2 or 3, the symbols Z.sup.3, which may be identical or different, represent a monovalent hydrocarbon-based group containing from 1 to 30 carbon atoms, optionally chosen from the group formed by alkyl groups containing from 1 to 8 carbon atoms and aryl groups containing between 6 and 12 carbon atoms, and even optionally chosen from the group formed by methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl radicals, and (ii) optionally at least one siloxyl unit having the following formula: $\begin{array}{cc}{Z}_c^2.Math.{\mathrm{SiO}}_{\frac{4-c}{2}}& \left(B.Math.\mathrm{.2}\right)\end{array}$ in which: c=0, 1, 2 or 3, the symbols Z.sup.2, which may be identical or different, represent a monovalent hydrocarbon-based group containing from 1 to 30 carbon atoms, optionally chosen from the group formed by alkyl groups containing from 1 to 8 carbon atoms and aryl groups containing between 6 and 12 carbon atoms, and even optionally chosen from the group formed by methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl radicals.

10- The composition X as claimed in claim 1, wherein said composition comprises a second organopolysiloxane compound comprising, per molecule, at least two C.sub.2-C.sub.6 alkenyl radicals bonded to silicon atoms, different from the organopolysiloxane compound A, said second organopolysiloxane compound optionally being divinyltetramethyl siloxane.

11- The composition X as claimed in claim 1, wherein the proportions of the organopolysiloxane A and of the organohydrogenopolysiloxane B are such that the mole ratio of the hydrogen atoms bonded to silicon in the organohydrogenopolysiloxane B to the alkenyl radicals bonded to silicon in the organopolysiloxane A is between 0.2 and 20, optionally between 0.5 and 15, optionally between 0.5 and 10 and optionally between 0.5 and 5.

12- The composition X as claimed in claim 1, wherein said composition comprises one or more functional additives chosen from: silicone resins, adhesion modifiers, consistency-enhancing additives, pigments, and heat-resistance, oil-resistance or fire-resistance additives, optionally metal oxides.

13- A product comprising catalyst C, which is a complex corresponding to the following formula:
[Co(L.sup.1).sub.2] in which: the symbol Co represents cobalt in oxidation state II, the symbols L.sup.1, which may be identical or different, represent a ligand which is a -dicarbonylato anion or the enolate anion of a -dicarbonyl compound as a catalyst for crosslinking of one or more silicone compositions.

14- A process for crosslinking one or more silicone compositions, comprising heating a composition X as claimed in claim 1 to a temperature ranging from 70 to 200 C., optionally from 80 to 150 C. and optionally from 80 to 130 C.

15- A crosslinked silicone material Y obtained by heating to a temperature ranging from 70 to 200 C., optionally from 80 to 150 C. and optionally from 80 to 130 C., of a composition X as claimed in claim 1.

Description

[0172] The present invention is illustrated in greater detail in the following nonlimiting implementation examples.

Example 1: Cobalt-Based Catalysts for the Crosslinking of dvtms with MD.SUB.50.M

I) Constituents

[0173] 1) Organopolysiloxane A: divinyltetramethylsiloxane (dvtms) (1.073 mol of vinyl radicals bonded to silicon per 100 g of oil)
2) Organohydrogenopolysiloxane B: of formula: MD.sub.50M (1.58 mol of hydrogen atoms bonded to silicon per 100 g of oil), with: M: (CH.sub.3).sub.3SiO.sub.1/2; and D: (CH.sub.3)HSiO.sub.2/2

3) Catalysts (A), (B), (C), (D), (E) and (F):

[0174] ##STR00010##

The catalysts (A), (B), (C) and (D) are commercially available, for example under the references Sigma-Aldrich 99% purity for the compound [Co(acac).sub.2], Strem purity >98% for the compound [Co(TMHD).sub.2].
The catalyst (E) is obtained via a synthesis that is well known to those skilled in the art:

##STR00011##

The keto ester compound with R.sub.1=Methyl and R.sub.2=Methoxy (supplier: Sigma-Aldrich) is, in a first stage, deprotonated using one equivalent of Bu-Li (supplier: Sigma-Aldrich) at low temperature (78 C.). The salt obtained is recrystallized from diethyl ether. The deprotonated ligand obtained (lithium salt) is added to a cobalt chloride (CoCl.sub.2) dissolved in THF at room temperature (12 hours). After separation of the phases by settling, filtration and concentration, the complex is recrystallized from THF.
The complex [Co(keto ester).sub.2] is in the form of a dark violet solid.
The catalyst (F) is also obtained via a synthesis that is well known to those skilled in the art:

##STR00012##

The diketone compound with R.sub.1=Phenyl and R.sub.2=C.sub.17H.sub.35 or C.sub.15H.sub.31 (supplier: Solvay) is, in a first stage, deprotonated using one equivalent of Bu-Li (supplier: Sigma-Aldrich) at low temperature (78 C.). The salt obtained is recrystallized from diethyl ether. The deprotonated ligand obtained (lithium salt) is added to a cobalt chloride (CoCl.sub.2) dissolved in THF at room temperature (12 hours). The complex obtained is dark blue and viscous. A recrystallization step makes it possible to obtain a solid.

II) Formulations and Results:

[0175] For each formulation tested, the catalyst is weighed and introduced at room temperature into a glass flask.
1.87 g of divinyltetramethylsiloxane (dvtms) are then introduced, followed by 1.27 g of oil MD.sub.50M.
The flask is stirred in an oil bath which will be heated to the desired reaction temperature.
The ratio R corresponds to the mole ratio of hydrogen atoms bonded to silicon (SiH) in the organohydrogenopolysiloxane (MD.sub.50M) to the alkenyl radicals (in this instance vinyl) bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (dvtms).
The start of crosslinking is measured. The start of crosslinking is defined as being the stopping of stirring due to an increase in the viscosity of the medium.

TABLE-US-00001 TABLE 1 Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation 1 [Co(acac).sub.3] 110 C. 0.25% 1:1 Not inert No (comparative) crosslinking Formulation 2 [Co(TMHD).sub.3] 110 C. 0.25% 1:1 Not inert No (comparative) crosslinking Formulation 3 [Co(acac).sub.2] 110 C. 0.25% 1:1 Not inert 15 min (invention) Formulation 4 [Co(TMHD).sub.2] 110 C. 0.25% 1:1 Not inert 15 min (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in dvtms

[0176] The results show that the comparative formulations 1 and 2, in which the catalyst is a Co(III) complex, do not crosslink, whereas formulations 3 and 4 according to the invention, in which the catalyst is a Co(II) complex bearing two -dicarbonyl ligands, crosslink in 15 minutes.

[0177] The cobalt catalysts according to the invention were moreover tested under the following various operating conditions:

TABLE-US-00002 TABLE 2 Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation 5 [Co(acac).sub.2] 90 C. 0.25% 1:1 Not inert Less than (invention) 25 minutes Formulation 6 [Co(TMHD).sub.2] 110 C. 0.125% 1:1 Not inert 25 minutes (invention) Formulation 7 [Co(acac).sub.2] 130 C. 0.125% 1:1 Not inert Instantaneous (invention) crosslinking Formulation 8 [Co(keto ester).sub.2] 90 C. 0.25% 1:1 Not inert 20 minutes (invention) Formulation 9 [Co(keto ester).sub.2] 90 C. 0.125% 1:1 Not inert 50 minutes (invention) Formulation 10 [Co(Rhodiastab50).sub.2] 90 C. 0.125% 1:1 Not inert 25 minutes (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in dvtms

[0178] Formulation 5 according to the invention shows that crosslinking is obtained from 90 C., even if this crosslinking is slower than that observed for formulation 3 performed at 110 C.

[0179] Formulations 6, 7, 8 and 10 according to the invention show that crosslinking is obtained from 0.125 mol % of catalyst, which makes it possible to avoid or limit the coloring of the crosslinked material.

[0180] It is moreover noted that the temperature increase makes it possible to significantly reduce the crosslinking time (formulations 6 and 7).

Example 2: Cobalt-Based Catalysts for the Crosslinking of M.SUP.vi .D.SUB.70 .M.SUP.vi .with MD.SUB.50.M

I) Constituents

[0181] 1) Organopolysiloxane A of formula M.sup.viD.sub.70M.sup.vi (0.038 mol of vinyl radicals bonded to silicon per 100 g of oil), with: Vi=Vinyl; M.sup.vi: (CH.sub.3).sub.2ViSiO.sub.1/2 and D: (CH.sub.3).sub.2SiO.sub.2/2
2) Organohydrogenopolysiloxane B of formula: MD.sub.50M (1.58 mol of hydrogen atoms bonded to silicon per 100 g of oil), with: M: (CH.sub.3).sub.3SiO.sub.1/2; and D: (CH.sub.3)HSiO.sub.2/2
3) Catalysts (A), (B), (C), (D), (E) and (F) as described in example 1.

II) Formulations and Results:

[0182] For each formulation tested, the catalyst is weighed and introduced at room temperature into a glass flask.
The oil M.sup.viD.sub.70M.sup.vi was then introduced, followed by the oil MD.sub.50M.
For a ratio R corresponding to the mole ratio of hydrogen atoms bonded to silicon (SiH) in the organohydrogenopolysiloxane (MD.sub.50M) to the alkenyl radicals (in this instance vinyl) bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi) of 1:1, 4.39 g of oil M.sup.viD.sub.70M.sup.vi are introduced, followed by 0.105 g of oil MD.sub.50M.
The contents of oil M.sup.viD.sub.70M.sup.vi and of oil MD.sub.50M are adjusted according to the desired ratio R.
The flask is stirred in an oil bath which will be heated to the desired reaction temperature.
The start of crosslinking is measured.

[0183] The cobalt catalysts according to the invention were tested under the following various operating conditions:

[0184] Study of the Crosslinking Time According to the Catalyst Used

TABLE-US-00003 TABLE 3 Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation 11 [Co(acac).sub.2] 110 C. 1.6% 1:1 Not inert 30 (invention) minutes Formulation 12 [Co(TMHD).sub.2] 110 C. 1.6% 1:1 Not inert 1 h (invention) Formulation 13 [Co(keto ester).sub.2] 110 C. 1.6% 1:1 Not inert <20 h (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi)

[0185] Study of the Effect of the Catalyst Concentration

TABLE-US-00004 TABLE 4 Effect of increasing the catalyst (1) concentration Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation 14 [Co(TMHD).sub.2] 110 C. 2% 1:1 Not inert 2 h 15 (invention) Formulation 15 [Co(TMHD).sub.2] 110 C. 4% 1:1 Not inert Less than (invention) 1 h 15 (2) Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi)

[0186] Formulations 14 and 15 according to the invention show that increasing the catalyst concentration makes it possible to significantly reduce the crosslinking time.

TABLE-US-00005 TABLE 5 effect of increasing the catayst (2) concentration Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation 16 [Co(acac).sub.2] 110 C. 0.08% 3.1:1 Not inert 12 h (invention) Formulation 17 [Co(acac).sub.2] 110 C. 0.16% 3.1:1 Not inert 4 h (invention) Formulation 18 [Co(acac).sub.2] 110 C. 0.4% 3.1:1 Not inert 1 h 45 (invention) Formulation 19 [Co(acac).sub.2] 110 C. 0.8% 3.1:1 Not inert 1 h (invention) Formulation 20 [Co(acac).sub.2] 110 C. 1.6% 3.1:1 Not inert 25 minutes (invention) Formulation 21 [Co(acac).sub.2] 110 C. 3.1% 3.1:1 Not inert 30 minutes (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi)

[0187] Formulations 16 to 21 according to the invention show that increasing the catalyst concentration makes it possible to significantly reduce the crosslinking time. Formulation 16 moreover shows that crosslinking may be observed even with very low contents of catalyst, which makes it possible to avoid or limit the coloring of the crosslinked material.

[0188] Study of the Effect of the Ratio R

TABLE-US-00006 TABLE 6 Effect of the ratio R (1) Start of Reaction mol % of Ratio cross- Catalyst temperature catalyst.sup.(1) R linking Formulation 22 [Co(acac).sub.2] 110 C. 2% 2:1 Less (invention) than 17 h Formulation 23 [Co(acac).sub.2] 110 C. 2% 4:1 1 h 20 (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi)

TABLE-US-00007 TABLE 7 Effect of the ratio R (2) mol % Start of Reaction of Ratio cross- Catalyst temperature catalyst.sup.(1) R linking Formulation 24 [Co(acac).sub.2] 110 C. 1.6% 1.6:1 40 (invention) minutes Formulation 25 [Co(acac).sub.2] 110 C. 1.6% 3.1:1 20 (invention) minutes .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi)

[0189] The crosslinkings are performed under a non-inert atmosphere. Formulations 22 to 25 show that increasing the ratio R makes it possible to significantly reduce the crosslinking time.

[0190] Study of the Effect of the Temperature

TABLE-US-00008 TABLE 8 Effect of increasing the temperature Reaction mol % of Ratio Start of Catalyst temperature catalyst.sup.(1) R Atmosphere crosslinking Formulation [Co(acac).sub.2] 90 C. 1.6% 3.1:1 Not inert 1 h 45 26 (invention) Formulation [Co(acac).sub.2] 110 C. 1.6% 3.1:1 Not inert 20 minutes 27 (invention) Formulation [Co(acac).sub.2] 130 C. 1.6% 3.1:1 Not inert 15 minutes 28 (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (MviD70Mvi)

[0191] Formulations 26 to 28 according to the invention show that increasing the temperature makes it possible to significantly reduce the crosslinking time.

[0192] Study of the Effect of Adding dvtms

[0193] The tests presented in table 9 show the impact of adding a few molar equivalents of dvtms to the reaction medium. In these tests, the dvtms was added after the catalyst, and before the oils M.sup.viD.sub.70M.sup.vi and MD.sub.50M.

TABLE-US-00009 TABLE 9 Effect of adding dvtms Reaction mol % of Start of Catalyst temperature catalyst.sup.(1) Ratio R dvtms.sup.(2) crosslinking Formulation [Co(acac).sub.2] 110 C. 2% 2:1 Less than 29 (invention) 17 h Formulation [Co(acac).sub.2] 110 C. 2% 2:1 10 eq/Co 45 minutes 30 (invention) Formulation [Co(acac).sub.2] 110 C. 2% 4:1 1 h 20 31 (invention) Formulation [Co(acac).sub.2] 110 C. 2% 4:1 10 eq/Co 30 minutes 32 (invention) .sup.(1)Expressed as mol % of cobalt per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in the organopolysiloxane (M.sup.viD.sub.70M.sup.vi) .sup.(2)Expressed as molar equivalent relative to the cobalt

[0194] The crosslinkings are performed under a non-inert atmosphere.

[0195] The results of table 9 show that adding dvtms makes it possible to significantly reduce the crosslinking time.