WO2003051996A1

WO2003051996A1 - Catalytic palladium mixture

Info

Publication number: WO2003051996A1
Application number: PCT/EP2001/015422
Authority: WO
Inventors: Eric D. Carlson; Thomas Crevier; Anne-Marie La Pointe; Yves Giraud; Sébastien STERIN
Original assignee: Rhodia Chimie; Symyx Technologies, Inc
Priority date: 2001-12-19
Filing date: 2001-12-19
Publication date: 2003-06-26
Also published as: JP2005513185A; EP1456301A1; AU2002226403A1

Abstract

This invention relates to the use of an effective amount of a composition based on a palladium catalyst for preparing a polyaddition heat type curable polyorganosiloxane elastomer. It is also directed to a polyaddition heat type curable polyorganosiloxane elastomer.

Description

Catalytic Palladium mixture

The present invention relates to a catalytic composition based on a palladium catalyst. The Catalyst may optionally be modified by additives such as a nitrogen heterocycle derivative convenient for the preparation of polyaddition- curable polyorganosiloxane compositions.

More specifically, the present invention is directed to the employment of a new catalytic composition in a polyaddition heat type curable polyorganosiloxane elastomer.

Polyaddition curable polyorganosiloxane compositions are well known in the art. A typical addition curable polyorganosiloxane composition involves an addition reaction in the presence of an effective amount of a PGM catalyst, such as platinum or rhodium catalyst, between a "vinylpolysiloxane" and a multi- hydrogen functional silicon-hydride material, such as a "silicon hydride siloxane". The "vinylpolysiloxane" can be an polyorganosiloxane having alkenyl radicals, for example vinyl radicals attached to silicon by carbon-silicon bonds. Usually, the PGM catalyst is employed as a mixture with the vinyl polysiloxane prior to contact with the multi-hydrogen functional silicon-hydride material. Upon mixing the various ingredients, crosslinking or cure, often occurs within seconds at ambient temperatures.

Various procedures have been developed in the art to achieve effective results with one part mixtures. While two part mixtures have the advantage of an indefinite shelf-life over a wide temperature range, in order to achieve the desired advantages in the one part mixture, the catalyst, generally based on platinum, must be rendered inactive, or "masked" at ambient temperatures. It is reactivated at the command of the end user at an appropriate higher temperature. Accordingly, the platinum catalysts have generally been used in combination with separately added inhibitors. Furthermore, in order to inhibit room temperature curing, systems often require high molar inhibitor to platinum ratios, such as 35:1. The high levels of inhibitor required to inhibit curing at room temperature often result in a system that requires an excessively high temperature to cause curing within a reasonable time. This invention solves the problem by applying a new catalyst to the system. Unexpectedly, it has been discovered that catalysts based on palladium could be efficiently used with polyorganosiloxane having at least one unsaturated group and multi-hydrogen functional silicon-hydride material for obtaining elastomer silicone composition. Upon mixing the various ingredients, crosslinking or cure, does not occur at ambient temperatures.

The present invention relates mainly to the use of an effective amount of a composition based on a combination of an effective amount of a palladium catalyst to yield a polyaddition heat type curable polyorganosiloxane elastomer. The catalyst may be modified by addition of an optional nitrogen heterocycle derivative for preparing a polyaddition type heat curable polyorganosiloxane elastomer.

As specified herein, polyaddition heat type curable polyorganosiloxane compositions are well known in the art. A typical addition curable polyorganosiloxane composition involves an addition reaction in the presence of an effective amount of a PGM catalyst, such as platinum or rhodium catalyst, between a polyorganosiloxane (A) containing at least one unsaturated group and a polyorganohydrogenosiloxane (B). The polyorganosiloxane (A) can be an polyorganosiloxane having alkenyl radicals, for example vinyl radicals attached to silicon by carbon-silicon bonds. The hydrosilylation reactions concerned by the present invention can be represented as follows :

— Si— H +^,c = c ^ » Si-C — c —

The claimed composition is particularly advantageous in regard to the usual catalytic compositions based on platinum because the presence of a catalyst inhibitor is optional.

Various palladium catalysts can be used in accordance with the present invention and include preferably complexes of Pd° and Pd" . For instance the following complexes can be used : Pd(OAc)₂, Pd₂(di - benzylidene- acetone)₃, bis (tri-tert-butylphosphine) palladium(O), palladium (II) acetylacetonate, bis (tricyclohexylphosphine) palladium(O), transdichlorobis (tricyclohexylphosphine) palladium(ll), dichloro (1 ,5- cyclooctadiene) palladium (II), trans- dichlorobis (triphenylphosphine) palladium(ll),. dichlorobis(benzonitrile) palladium (II), Pd(0₂CCF3)₂., chloro(methyl)(1 ,5-cyclooctadiene) palladium(ll), and di(acetato)bis(3,5dimethylpyrazole) palladium(ll).

Regarding the optional additive compounds for the present invention, they are heterocycle derivatives with a ring size of 5-10 atoms and at least 2 nitrogen atoms. They are particularly useful as ligands for the palladium catalyst.

Representatives thereof are imidazole, triazole, tetrazole, pyrazole and their derivatives or analogs. In particular, they may be substituted by one or several organic substituents like, for example, alkyl, aryl, alkylaryl radicals and/or halogen atoms. Preferred representative thereof are pyrazoles bearing substituents at the 3- and/or 5- positions, such as 3,5dimethylpyrazole

The molar ratio of the optional nitrogen derivative to the paladium catalyst ranges from 1 to 10, preferably 2 to 5.

Yet another object of the invention is to provide a polyaddition heat type curable polyorganosiloxane elastomer, comprising :

- at least one polyorganosiloxane (A) containing at least two unsaturated groups bonded to silicon ;

- at least one polyorganohydrogenosiloxane (B) containing at least two hydrogen atoms bonded to silicon ;

- a catalytically effective amount of a palladium catalyst (C) and ;

- an optional nitrogen heterocycle derivative (D).

The unsaturated groups of the polyorganosiloxane A are for example C₂-C₈ alkenyl groups, e.g.: vinyl, allyl, 1-butenyl, 1-hexenyl, etc. The unsaturated groups may be bonded to the silicon atoms within the chain and/or right at the end. The organic substituents, different from unsaturated groups and hydrogen atom, are for example alkyl, cycloalkyl, aryl, aryalkyl and/or alkylaryl radicals and can be substituted.

The hydrogen and unsaturated radicals are present on siloxyl moieties M = [R₃SiO-] , D = [-(R)₂SiO-] and/or T = [-(R)SiO-], with R being partially as defined for Z hereafter.

Generally, the polyorganosiloxanes (A) and (B) used in the reaction have a molecular mass weight comprised between 10² and 10¹⁰ (g/mol).

The polyorganosiloxanes may comprise from 0.01% to 10% (preferably 0,.1 % to 2%) of unsaturated radicals by weight for the polyorganosiloxane (A) and from 0.001% to 5% (more preferably from 0.005% to 2%) of hydrogen by weight for the polyorganosiloxane (B). The vinyl groups in (A) and the hydrogen atoms in (B) are typically bonded to different silicon atoms.

According to a preferred embodiment, the weight of the palladium catalytic system (C) calculated as the weight of palladium metal, typically ranges from 1 to 10 000 ppm, and preferably from 10 to 1000 ppm, based on the total weight of the polyorganosiloxanes (A) and (B).

The various bases, i. e. : the mixture based on (A), (B), (C) and optionally filler(s) and processing aids, for the subject polyaddition silicone compositions, are well known to those of skill in the art. Most of them are available commercially.

According to a preferred embodiment, the polyorganosiloxane (A) is an polyorganosiloxane comprising : • siloxy units of the formula (1) :

T_a Z_b Si 0[4_(_a+b)] / 2 (1) in which : - the radicals T, equal or different, are unsaturated groups and preferably vinyl type groups,

- the radicals Z, equal or different, are monovalent hydrocarbon groups which do not adversely affect the activity of the catalyst; Z being preferably selected from (i) alkyl groups containing from 1 to 8 carbon atoms, optionally substituted by at least an atom of halogen, (ii) cycloalkyl groups containing from 3 to 8 carbon atoms, optionally substituted by at least an atom of halogen, (ii) aryl groups from 6 to 32 carbon atoms such as xylyl and tolyl and phenyl, optionally substituted by at least an atom of halogen, (iv) alkylaryl groups with alkyl group(s) from 1 to 8 carbon atoms and aryl groups from 6 to 30 carbon atoms, optionally substituted by at least an atom of halogen,

- and a is 1 or 2, b is 0, 1 or 2, with a + b ranges from 1 to 3.

• with the proviso that the polyorganosiloxane (A) comprises at least two radicals T.

• and, if desired, other units are units of the average formula: (2)

Zc Si O₍₄_ _C) / 2 (2)

in which Z is as defined above and c has a value from 0 to 3.

The polyorganosiloxane (A) may have a linear, branched, ring or lattice structure.

Specific examples of siloxy units of formula (1) are the vinyldimethylsiloxy unit, the vinylphenylmethylsiloxy unit, the vinylsiloxy unit and the vinylmethylsiloxy unit.

Specific examples of siloxy units of formula (2) are the SiO _/2, dimethylsiloxy, methylphenylsiloxy, diphenylsiloxy, methylsiloxy and phenylsiloxy units.

The polyorganosiloxane (A) may be constituted solely by units of formula (1) or may additionally contain units of formula (2).

Regarding the polyorganohydrogenosiloxane (B), this latter is preferably an polyorganohydrogenosiloxane comprising : • siloxy units of the formula (3):

Hd W_e Si O[4-(d+e)]/ 2 (3) in which :

- W, equal or different, are monovalent hydrocarbon groups which do not adversely affect the activity of the catalyst and which has the same definition as Z,

- and d is 1 or 2, e is 0, 1 or 2, with d+e having a value from 1 to 3,

• with the proviso that the polyorganohydrogenosiloxane (B) comprises at least two hydrogen atoms. • and, if desired, all the other units are units of the average formula (4):

W_g Si O_(4-g) /2 (4)

in which W is as defined above, and g has a value from 0 to 3. All of the limiting values of a, b, c, d, e and g are included.

The polyorganosiloxane (B) may be constituted solely by units of formula (3) or may additionally contain units of formula (4).

The polyorganosiloxane (B) may have a linear, branched, ring or lattice structure. The degree of polymerization is 2 or more and is generally less than 5,000.

Examples of units of formula (3) are: H(CH₃)₂ Si0_1/2, HCH₃ SiO_2/2, H(C₆ H₅)SiO_2/2.

The examples of units of formula (4) are the same as those given above in the case of the units of formula (2).

The most preferred polyorganosiloxane (A) for the polyaddition heat curable polyorganosiloxane elastomer according to the present invention are those comprising : • siloxyl moieties having the general formula (5) :

(Z')_x SiO_(4-x)/2 (5)

• and / or siloxyl moieties of formula (6) : (T')_y (Z')_zSiO_(4-y-z)/2 (6) in which :

- the radicals Z', equal or different, represent hydrocarbonated preferably selected in the group consisting of : * alkyl radical, halogenoalkyl having from 1 to 5 carbon atoms and having from 1 to 6 chloride and/or fluorine atoms, * cycloalkyl and halogenocycloalkyl radicals having from 3 to 8 carbon atoms and containing from 1 to 4 chloride and/or fluorine atoms, * aryl, alkylaryl and halogenoaryl radicals having from 6 to 8 carbon atoms and containing from 1 to 4 chloride and/or fluorine atoms,

- the radicals T', equal or different, are unsaturated radicals C₂-C₆. - x is 0,1 , 2 or 3 ;

- y is 1 , 2 or 3 ; - z is 0,1 , 2 or 3 ;

- and y+z ranges from 1 to 3 ;

The most preferred polyorganohydrogenosiloxane (B) for the polyaddition heat curable organopolysiloxane elastomer according to the present invention are those comprising :

• siloxyl moieties having the general formula :

(Z')x Si0_4-x/2 (5')

• and/or siloxyl moieties of formula :

(H)y (Z'JzSiO-t-y-zfc (6') in which : - the radicals Z', equal or different, represent a hydrocarbonated preferably selected in the group consisting of : * alkyl radical, halogenoalkyl having from 1 to 5 carbon atoms and having from 1 to 6 chloride and/or fluorine atoms, ^* cycloalkyl and halogenocycloalkyl radicals having from 3 to 8 carbon atoms and containing from 1 to 4 chloride and/or fluorine atoms,

*aryl, alkylaryl and halogenoaryl radicals having from 6 to 8 carbon atoms and containing from 1 to 4 chloride and/or fluorine atoms,

- x is 0,1 , 2 or 3 ; - y is 1 , 2 or 3 ;

- z is 0,1 , 2 or 3 ;

- and y+z ranges from 1 to 3 ; • with the proviso that the polyorganohydrogenosiloxane (B) comprises at least two hydrogen atoms.

More preferably, Z' is selected in the group consisting of methyl ; ethyl propyl ; isopropyl ; butyl ; isobutyl ; n-pentyl ; t-butyl ; chloromethyl dichloromethyl ; α-chloroethyl ; fluoromethyl ; trifluoro cyclopropyl ; phenyl (mono)(di)(tri)(tetra)chlorophenyl ; tolyl ; α,α, -trifluorotolyl; xylyl and more preferably is methyl or phenyl, these radicals being optionally halogenated.

Specific examples of polyorganosiloxanes (A) are dimethylpolysiloxanes with dimethylvinylsiloxy end groups, the methylvinyldimethylpolysiloxane copolymers with trimethylsiloxy end groups, methylvinyldimethylpolysiloxane copolymers with dimethylvinylsiloxy end groups and cyclic methylvinylpolysiloxanes.

Specific examples of polyorganohydrogenosiloxanes (B) are dimethylpolysiloxanes with hydrodimethylsilyl end groups, dimethylhydromethylpolysiloxane copolymers with trimethylsiloxy end groups, dimethylhydromethylpolysiloxane copolymers with hydrodimethylsiloxy end groups, hydromethylpolysiloxanes with trimethylsiloxy end groups, cyclic hydromethylpolysiloxanes and copolymers methylhydrogenomethyloctylsiloxane copolymers. For the polyorganosiloxane (A), it includes in particular with regard to dynamical viscosity at 25°C the following polyorganosiloxanes :

A1 - polyorganosiloxane vulcanisable by heating (EVC) by polyaddition, having a viscosity at least equal to 10⁴ mPa.s, preferably comprised between 10⁶ and 10⁷ mPa.s ; and

A2 - polyorganosiloxane vulcanisable by heating, by polyaddition of liquid elastomer silicones (LSR), having a viscosity preferably comprised between 10¹ and 10⁴ mPa.s.

According to a preferred embodiment of the invention, the claimed polyorganosiloxane compositions are vulcanisable by heating (EVC) by polyaddition and include polyorganosiloxane A1 and a polyorganohydrogenosiloxane B having a viscosity of 10² to 10⁷ mPa.s at 25°C.

The viscosity is evaluated with a Brookfield viscometer according to

AFNOR NFT 76 106 of May 1982. All viscosities referred in the instant specification correspond to a dynamical viscosity at 25^CC said "Newtonian".

The polyaddition silicone compositions according to the invention may additionally comprise reinforcing or semireinforcing or extending fillers (E), which are preferably siliceous fillers.

The reinforcing fillers are selected from the pyrogenic silicas and precipitated silicas. They have a specific surface area, measured according to the BET method, of at least 50 m² /g, preferably greater than 70 m2 /g, a mean primary particle size of less than 0.1 micrometer and an apparent density of less than 200 g/liter.

These silicas may be incorporated as such or preferably after they have been treated with organosilicon compounds usually employed for this purpose.

These compounds include methylpolysiloxanes such as hexamethyldisiloxane and octamethylcyclotetrasiloxane, methylpolysilazanes such as hexamethyl- disilazane and hexamethylcyclotrisilazane, chlorosilanes such as dimethylchlorosilane, trimethylchlorosilane, methylvinyldichlorosilane and dimethylvinylchlorosilane, and alkoxysilanes such as dimethyldimethoxysilane, dimethylvinylethoxysilane and trimethylmethoxysilane. In the course of this treatment, the silicas may increase in their initial weight up to a proportion of 20%, preferably approximately 18%.

The semireinforcing or extending fillers have a particle diameter greater than 0.1 micrometer and are preferably selected from among ground quartz, calcined clays and diatomaceous earths.

From 5 to 100 parts, preferably from 5 to 50 parts of filler (E) may generally be employed per 100 parts of the total amount of the polyorganosiloxanes (A)+(B).

The compositions according to the invention may be kneaded could as such and may be extruded or molded in the form of unit modules (elements); the composition may, for example, be molded into the shape of a cylinder with a diameter of from 0.5 to 9 cm. After curing, the silicone composition cylinders which are obtained may be cut to the desired length, in the case of their being employed in boreholes, such that the cylinder contains a sufficient quantity of iodine equivalent for a release over preferably at least one year. At the end of this period, the cylinders are replaced.

The present invention concerns also said silicone composition in crosslinked elastomeric state.

The present invention is also directed to shaped article comprising the claimed silicone composition curable, or cured by hydrosilylation in crosslinked elastomeric state or not. In order to further illustrate the present invention and the advantages thereof, the following specific examples are given, it being understood that same are intended only as illustrative and in nowise limitative.

Examples: preparation of the silicone composition according to the invention.

In each of the following examples, the reaction mixture is prepared as follows: In a small container the following components are added and mixed: 85μL of a silicon hydride oil (Gelest HMS-301 , MW 1900-2000, mole% MeHSiO = 25- 30); 15μL of silicon vinyl oil (divinyltetramethylsiloxane; Aldrich ref: 37,190-4); and 6.7μL of a solution of palladium acetate (Strem ref: 46-1780) in toluene (10mg/mL). A reference vessel that contains 85μL of the silicon hydride oil and 15 μL of the silicon vinyl oil is also prepared.

Example 1.

Said reaction mixture is a low viscosity oil. Said reaction mixture is covered and stored at room temperature. Said reaction mixture remains a low viscosity oil when stored at room temperature for 8 weeks.

Example 2.

10μL of said reaction mixture is placed in a DSC pan. DSC is run at 5°C/min from 25°C to 200°C. Said reaction mixture shows an exotherm onset at 175°C and an exothem peak at 180°C.

Example 3.

Said reaction mixture and said reference vessel are place in an insulated block and the samples and block are placed in a convection oven. The oven is heated at 0.5°C/min. An infrared camera is used to monitor the samples through a port in the top of the oven (see WO 98/15813). By subtracting the IR emission signal of said reference vessel from the emission signal of said reaction mixture, the exothermic behavior of said reaction mixture is revealed. Using this method we find that the palladium sample has an exotherm onset temperature of 135°C with a peak at 140°C.

Samples are allowed to cool to room temperature and are removed from the oven. Said reference vessel remains a low viscosity oil while said reaction mixture is a cured sample that will not flow.

Example 4.

Silicon hydride oil, silicon vinyl oil, and a solution of palladium acetate in toluene (10mg/mL) are purged with argon and are introduced into a dry box that excludes water and oxygen. Components are added to form a reaction mixture as described above. Said reaction remains an uncured, low viscosity oil at room temperature. Said reaction mixture is placed on a heating block and is heated to 180°C. When held at high temperature in said dry box for 1 hour, said reaction remains an uncured, low viscosity oil.

Example 5.

Silicon hydride oil, silicon vinyl oil, water, and a solution of palladium acetate in toluene (10mg/mL) are purged with argon and are introduced into a glove box that excludes oxygen. Water is added to the palladium toluene solution to make give 5 molar equivalents of water to palladium. Components are added to form a reaction mixture as described above. Said reaction remains an uncured, low viscosity oil at room temperature. Said reaction mixture is placed on a heating block and is heated to 180°C. Said reaction mixture changes from a low viscosity oil to a non-flowable, cured system within 5 minutes at elevated temperature.

Claims

CLAIMS.

1. Use of an effective amount of a composition based on a palladium catalyst as a polyaddition heat type curable polyorganosiloxane elastomer.

2. Use according to claim 1 , wherein the palladium catalyst is selected from the group consisting of complex of Pd° and /or Pd".

3. Use according to claim 1 or 2 wherein the catalyst is modified by addition of a nitrogenheterocycle.

4. Use according to claim 3 in which the heterocycle consists of a five or six membered ring containing at least two nitrogen atoms.

5. Use according to claims 1 to 4, wherein the nitrogen derivative includes imidazole, triazole, tetrazole, pyrazole and their derivatives.

6. Use according to claims 1 to 5 wherein the nitrogen derivative is 3,5- dimethylpyrazole.

7. Use according to claims 1 to 6, wherein the molar ratio of the nitrogen derivative to the palladium catalyst ranges from 1 to 10, preferably 2 to 5.

8. Polyaddition heat type curable polyorganosiloxane elastomer, comprising: - at least one polyorganosiloxane (A) containing at least two unsaturated groups bonded to silicon;

- at least one polyorganohydrogenosiloxane (B) containing at least two hydrogen atoms bonded to silicon and;

- a catalytically effective amount of a palladium catalyst (C) and, - an effective amount of a nitrogen heterocycle derivative (D).

9. Polyaddition heat type curable polyorganosiloxane elastomer according to claim 8 wherein the palladium catalyst is a complex of Pd° and/or Pd".

10. Polyaddition heat type curable polyorganosiloxane elastomer according to claim 8 or 9 wherein (C) and (D) are included under the form of a composition as defined in claims 1 to 7.

11. Polyaddition heat type curable polyorganosiloxane elastomer according to claims 8 to 10 wherein the polyorganosiloxane (A) is an polyorganosiloxane comprising :

• siloxy units of the formula (1) :

Ta Zb Si O_[4-(a₊b)] / 2 (1) in which :

- the radicals T, equal or different, are unsaturated groups and preferably vinyl type groups,

- and a is 1 or 2, b is 0, 1 or 2, with a + b ranges from 1 to 3. • with the proviso that the polyorganosiloxane (A) comprises at least two radicals T.

• and, if desired, other units are units of the average formula: (2)

Zc Si O_{4- c) / 2 (2) in which Z is as defined above and c has a value from 0 to 3.

12. Polyaddition heat type curable polyorganosiloxane elastomer according to claims 8 to 11 wherein the polyorganohydrogenosiloxane (B) is a polyorganohydrogenosiloxane comprising :

• siloxy units of the formula (3): Hd We Si O_[4-(d+e)]/ 2 (3) in which : - W, equal or different, are monovalent hydrocarbon groups which do not adversely affect the activity of the catalyst and which has the same definition as Z, - and d is 1 or 2, e is 0, 1 or 2, with d+e having a value from 1 to 3,

• with the proviso that the polyorganohydrogenosiloxane (B) comprises at least two hydrogen atoms.

• and, if desired, all the other units are units of the average formula (4):

Wg Si O₍₄-g) / 2 (4)

13. Polyaddition heat type curable polyorganosiloxane elastomer according to claims 8 to 12 wherein the palladium catalyst is a complex of Pd° and/or Pd", and the nitrogen derivative is 1 ,3-dimethylpyrazole.

14. Shaped article comprising the polyaddition heat type curable polyorganosiloxane elastomer according to claims 8 to 12.