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: [Fe(L1)2] in which: the symbol Fe represents iron 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, wherein it comprises 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:
[Fe(L.sup.1).sub.2] in which: the symbol Fe represents iron 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 iron 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 optionally from 0.1 to 5%.

3- The composition X 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 [Fe(acac).sub.2] and [Fe(TMHD).sub.2].

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 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 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 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 more preferentially 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 proportions of the organopolysiloxane A and of the organohydrogenopolysiloxane B are such that the mole ratio of 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 a catalyst C, which is a complex corresponding to the following formula:
[Fe(L.sup.1).sub.2] in which: the symbol Fe represents iron 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, wherein said process comprises 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., a composition X as claimed in claim 1.

Description

EXAMPLE: IRON-BASED CATALYSTS FOR THE CROSSLINKING OF M.SUP.vi .D.SUB.70 .M.SUP.vi .WITH MD.SUB.50.M

I) Constituents

[0176] 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) and (B)

[0177] ##STR00010##

The catalysts (A) and (B) are obtained via a synthesis that is well known to those skilled in the art:

##STR00011##

The acac or THMD compound (supplier: Strem) 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 an iron chloride (FeCl.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.

[0178] The complex [Fe(acac).sub.2] is in the form of an orangey brown solid.

[0179] The complex [Fe(THMD).sub.2] is in the form of an oily bright red solid.

II) Formulations and Results:

[0180] For each formulation tested, the catalyst is weighed and introduced at room temperature into a glass flask.
5 g of oil M.sup.viD.sub.70M.sup.vi are then introduced, followed by 0.6 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 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 (dvtms) being 4:1.
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 Start of Catalyst temperature catalyst.sup.(1) Ratio R Atmosphere crosslinking Formulation 1 [Fe(acac).sub.2] 200 C. 2% 4:1 Not inert Between (invention) 6 h and 20 h Formulation 2 [Fe(TMHD).sub.2] 200 C. 2% 4:1 Not inert 24 h (invention) .sup.(1)Expressed as mol % of iron per number of moles of vinyl radicals bonded to silicon (SiCHCH.sub.2) in dvtms

[0181] The results show that the formulations 1 and 2 according to the invention, in which the catalyst is a Fe(II) complex bearing two-dicarbonyl ligands, crosslink between 6 h and 24 h.