GB2109390A

GB2109390A - Light-crosslinkable polysiloxanes

Info

Publication number: GB2109390A
Application number: GB08227636A
Authority: GB
Inventors: Gerd Greber; Dieter Lohmann
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1981-10-01
Filing date: 1982-09-28
Publication date: 1983-06-02
Also published as: FR2514013A1; CA1192204A; GB2109390B; CH649772A5; DE3235663A1; JPS5869229A

Abstract

Novel light-crosslinkable polysiloxanes having an average molecular weight of 750 to 1.500.000 and consisting of 10 to 100 mole % of recurring structural units of the formula I <IMAGE> and of 0 to 90 mole % of recurring structural units of the formula <IMAGE> such that each molecule contains on average at least three structural units of the formula I, and A, R1, R2, R3 and R4 are as defined in claim 1, are suitable e.g. for making moulded articles, photosensitive resists, electrical insulating materials, films, finishes and coatings, if desired in admixture with compounds of the formula X <IMAGE>

Description

SPECIFICATION Light-crosslinkable polysiloxanes The present invention relates to novel lightcrosslinkabie polysiloxanes, to the preparation thereof, and to the crosslinked polysiloxanes so obtained.

Polysiloxaneswhich contain phenylmaleimide groups and the use thereof for the production of photohardened films and coatings are described in German Auslegeschrift 25 57 940. Similar polysiloxanes which contain maleimide groups and are substituted in the 2- or 3-position by aromatic or heterocyclic groups, and the use thereof for the production of printing plates, are described in Japanese published patent specifications 77-106864 and 77-105002.

The present invention provides novel lightcrosslinkable polysiloxanes of high light sensitivity, which polysiloxanes have an average molecular weight of 750 to 1,500,000 and consist of 10 to 100 mole % of recurring structural units of the formula I

and of 0 to 90 mole % of recurring structural units of the formula II

such that each molecule contains on average at least three structural units of the formula 1, in which formulae A is a -CpH2p- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by -O-, -NH- or -NH-C,-C,al kyl, Rr is hydrogen, methyl, phenyl or vinyl, R2 is methyl or phenyl, and each of R3 and R4 independently of the other is C,-C4alkyl or together they are trimethylene or tetramethylene, each unsubstituted or substituted by a methyl group.

In the different structural units of the formulae I and Il, each of the symbols A, A1, R2, R3 and R4 may denote identical or different radicals as defined herein. Preferably they each denote identical radi cals.

A-CpH2p- radical represented by A may be straight chain or branched. The radical A may be e.g.: -(CH2)p-, in which p = 2-10,-CH2CH2OCH2CH2-, -CH2CH#NHCH2CH2-, -CH2CH2NHCH2CH2NHCH2CH2-, -CH2CH2NH(CH263, -CH2CH2N(CH3)CH2CHr, #H2CH(CH3)-, -CH2CH2CH(CH3)-, -CH2CH2CH (CH3)CH2CH2- and -CH2CH (CH3)CH (CH3)CH2-. Preferably A is #CK2)p#, in which p is 2 to 10 and, most preferably, -(CH2)2 or -(CH2)3.

R1 is preferably hydrogen or methyl. R2 is preferably methyl. Alkyl groups R3 and R4 may be straight chain or branched, but are preferably straight chain.

It is preferred that each of R3 and R4 is methyl.

The average molecular weights may be determined in a manner known per se., e.g. by light scattering or by vapour pressure osmometry (weight or number average).

The light-crosslinkable polysiloxanes of this invention may be prepared in a manner which is known per se, e.g. either by a) cohydrolysing a compound of the formula Ill

with 10 to 100 mole % of a compound of the formula IV

and subsequently equilibrating the reaction product, or b) reacting a poly - H siloxane of the formula V

with 10 to 100 mole % of a compound of the formula VI

Certain of the Chemical formula(e) appearing in the printed specification were submitted after the date of filing, the formula(e) originally submitted being incapable of being satisfactorily reproduced.

in which formulae above A, R2, R3 and R4 are as defined for formulae I and Il, At is a -CpH2p~,- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by -0,-NH-or -NH-C1-C4aIkyI, and R', is hydrogen, methyl or phenyl, but must be hydrogen in at least 10 mole % of the structural units of the formula V.

Polysiloxanes of this invention may also be obtained by equilibrating a cyclotetrasiloxane of the formula Vlla

wherein at least one X is a group

and the others are a group

or R, if desired together with suitable amounts of a cyclotetrasiloxane of the formula Vllb

in which formulae above A, R" R2 R3 and R4 have the meanings previously assigned to them. In a further process, polysiloxanes of the present invention may also be obtained by reacting a polysiloxane consisting of 10 to 100 mole % of recurring structural units of the formula VIlla

and 0 to 90 mole % of recurring structural units of the formula Vlilb

with 10 to 100 mole % of an anhydride of the formula

in which formulae (Vlla), (Vllb), (Villa) and (Vlllb) above A, Rt, R2, R3 and R4 have the meanings previously assigned to them.

Oligomeric or polymeric linear or cyclic polysiloxanes are formed in the cohydrolysis of the compounds of the formula III with the compounds of the formula IV in accordance with process variant a). The cohydrolysis is conveniently carried out in aqueous medium or preferably in aqueous-organic medium.

Examples of suitable solvents are aliphatic ethers, preferably dialkyl ethers such as diethyl ether, methyl ethyl ether and diisopropyl ether, as well as 1,2-dimethoxyethane. In the subsequent equilibration, the mixtures of linear and cyclic siloxanes of different molecular weight are converted by redistribution of the Si# bonds into mixtures of linear siloxanes of higher and more uniform average molecular weights. These equilibration reactions may be catalysed by heat or by acids or bases. It is preferred to carry out the equilibration in the pres ence of an acid catalyst, preferably concentrated sul furicacid or an acid earth, and, if desired, in the presence of an inert organic solvent.

The addition of the maleimide of the formula Vitro the poly-H-siloxane of the formula V is conveniently carried out in the presence of an inert organic sol vent and of a catalyst. Examples of suitable solvents are: aromatic hydrocarbons such as benzene, toluene and xylenes, 1,2-dimethoxyethane and diethylene glycol dimethyl and diethyl ether.

The catalysts employed are normally noble metal catalysts, preferably platinum, palladium and rhodium catalysts, e.g. platinum on carbon, H2PtCl6, palladium acetate and rhodium phosphine com plexes. The preferred catalyst is H2PtCl6. The reaction is advantageously carried out at elevated temperature.

The reaction of the polysiloxanes which contain amino groups with the anhydrides of the formula IX is conveniently carried out in the presence of an inert organic solvent such as toluene, a xylene, N,Ndimethyl-formamide or N,N-dimethylacetamide, at elevated temperature and /or with the addition of a dehydrating agent, e.g. acetic anhydride.

The invention also relates to novel crosslinked polysiloxanes which may be obtained by crosslinking a light-crosslinkable polysiloxane as defined herein in the presence of O to 30 mole %, preferably 0 to 15 mole %, of a compound of the formula X

wherein A, Rt, R, R3 and R4 are as defined for formulae II and Ill and z is an integer from 1 to 20,000, by the action of light.

The compounds of the formula X are novel and likewise constitute an object of the invention. The symbols R1 and R2 in the recurring units may denote identical or different radicals. Preferably R1 and R2 in each structural unit have the same meaning. The preferred meanings of A, R1, Rg, R3 and R4 are the same as those given above. Preferred compounds of the formula X are those in which A is-(CH2)p- (p = 2-10) and z is an integer from 1 to 20.Particularly preferred compounds of the formula X are those in which A is -(CH2)T Or or-(CH2)3-, R1 is hydrogen or methyl, each of R, R3 and R4 is methyl and z is an integerfrom 1 to 20.

The compounds of the formula X may be obtained in a manner which is known per se, e.g. by A) equilibrating a compound of the formula X, in which x is at least 1, with a cyclotetrasiloxane of the formula Vllb

B) reacting a compound of the formula Xl

with a compound of the formula VI

in the molar ratio of 1:2, C) hydrolysing a compound of the formula XII

to the corresponding disiloxane and, if appropriate, equilibrating the reaction product with a suitable cyclosiloxane, or reacting said compound of the formula (XII) with a compound of the formula XIII

in the molar ratio of 2:1, or D) reacting a compound of the formula XIV

with an anhydride of the formula IX, in the molar ratio of 1:2.In the formulae (Vllb), (XI), (VI), (Xll), (Xlil) and (XIV) above, z, A, R1, R2, R3 and R4 have the meanings previously assigned to them, A1 is a -CpH2p~,- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by -O-, -NH- or-NH-C1-C4-aIkyI, and R'1 is methyl or phenyl.

The equilibration of the compounds of the formula (Vllb) is carried out under the same conditions as previously described above. The addition of the compounds of the formula Vl to the compounds of the formula Xl may be carried out under reaction conditions similar to those described above for the addition to the poly-Hsiloxanes of the formula V.

The condensation of the siloxane diol of the formula (XIII) with the chlorosilyl compound of the formula (XII) is advantageously carried out in the presence of a a base, e.g. triethylamine or pyridine. The reaction of the diamine of the formula (XIV) with the anhydride of the formula (IX) is carried out as described above for the reaction of the polysiloxanes which contain amino groups with the anhydrides of the formula (IX).

The starting compounds of the formulae (III) to (IX) and (Xl) to (XIV) are known or they may be prepared by methods which are known per se. As regards the preparation of the silanes and siloxanes to be used, attention is drawn e.g. to Noll, Chemie und Technologie der Silicone, Verlag Chemie GmbH, Weinheim, 1968.

In principle, any light sources may be used for crosslinking the polysiloxanes of the invention, if desired in admixture with a crosslinking agent of the formula X. Examples of such light sources are: sunlight, carbon arc lamps, xenon lamps, metal halide vapour lamps and, in particular, mercury high pressure lamps. If desired, exposure may be made with the addition of a photosensitiser, e.g. benzophenone or a thioxanthone derivative.

The crosslinked products obtainable with the polysiloxanes of this invention have a high corona resistance and good permeability to oxygen. The light-crosslinkable polysiloxanes of the present invention are suitable e.g. for the preparation of photosensitive resists or high temperature resistant insulating materials and, in particular, for making moulded articles such as contact lenses, sealings, films, coatings and finishes on different materials such as glass, ceramics, plastics, e.g. polyesters and polyimides, cellulosics, and especially metals such as aluminium and copper. Depending on the degree of crosslinking, they give soft, elastic to tough firm layers which have in particular good adhesion to metals such as aluminium and copper.

The invention is illustrated by the following nonlimitative Examples.

Example 1:

With efficient stirring, a mixture of 11.2 g (0.04 mole) of N - (3 - methyl - dichlorosilylpropyl) - 2,3 dimethylmaleimide, 16.5 g (0.128 mole) of dimethyl dichlorosilane and 100 ml of diethyl ether is added dropwise to 250 ml of ice-water. When the hydrolysis is complete, the ethereal phase is separated and washed with distilled water until neutral, dried over sodium sulfate, and concentrated to a volume of about 20 ml. To this solution are added 3.5 ml of conc. H2SO4 and the mixture is shaken for 24 hours at room temperature. After dilution with 30 ml of diethyl etherthe organic phase is washed until neutral, dried over sodium sulfate and then freed from solvent in a high vacuum. Yield: 14.5 g (77% of theory). Viscosity [ a ] :4,6 ml g-I (measured in toluene at 25 C). Nitrogen content: 3.25%.

The starting N - (3 - methyl - dichlorosilylpropyl) 2,3 - dimethylmaleimide may be obtained as described in German Offenlegungsschrift 29 34 550.

Equilibration of 1 part of 1,2,3,4 - tetramethylcyc lotetrasiloxanewith 3 parts of 1,1,2,2,3,3,4,4 octamethylcyclotetrasiloxane using hexamethyl disiloxane as chain terminator gives a poly - H - siloxane having the following properties: intrinsic viscosity: 0.887 Pa s/250C [ rl ] = 16.7 ml/g, content of H-Si groups = 3.4 m-equiv./g.

A mixture of 11.6 g (0.07 mole) of N - allyl - 2,3 dimethylmaleimide, 0.3 ml of a solution of H2PtC16 (0.05 m in 2-propanol) and 50 ml of toluene is added dropwise at 90 C, under nitrogen, to a solution of 20 g (corresponding to 0.068 equiv. Si-H) of the above prepared polysiloxane in 100 ml of toluene. When the addition is complete, the reaction mixture is heated for 60 minutes to reflux and then filtered with the aid of 1 g of activated carbon and 2 g of fuller's earth. All volatile constituents are removed (finally in a high vacuum) to give 28.6 g (91 % of theory) of a viscous oil; [ 77 ] = 26.3 ml/g in toluene at 250C; nitrogen content = 2.76%; average molecular weight (determined by light scattering) = 70,000.

Example 3:

In accordance with the procedure of Example 2, 6.66 g (corresponding to 0.0225 equiv. Si-H) are reacted with 2 g (0.014 mole) of N - vinyl - 2,3 dimethylmaleimide. Working up is as described in Example 2. Yield: 7.7 g (89% of theory). Nitrogen content: 1-95%; average molecular weight: 70,000 (determined by lightscattering); H-Si content: 1.6 m-equiv./g.

Example 4:

In accordance with the procedure described in Example 2, 9 (corresponding to 0.156 equivalent Si-H) of a commercial polymethyl hydrogensiloxane (Silgel W# available from Wacker-Chemie, Burghausen West Germany) are reacted with 25.7 g (0.156 mole) of N - allyl - 2,3 - dimethylmaleimide.

After the exothermic reaction has subsided, the reaction mixture is heated for a further 5 hours to reflux.

Example 5: The catalyst is removed and the resultant polysiloxane is isolated by precipitating the reaction solution in 1 litre of hexane. The viscous product is dried for 24 hours at 800C10.0133 Pa. Yield: 32 g (92% of theory). Molecular weight (determined by vapour pressure osmometry in CHCl2): 10,300; nitrogen content 6% l calculated degree of silicon content 13.8% I substitution 96%.

20.15 g (0.15 mole) of tetramethyl disiloxane are added dropwise at 60 C, under nitrogen, to a mixture of 50 g (0.3 mole) of N - allyl - 2,3 - dimethylmaleimide and 0.8 ml of a 0.05 m solution of H2PtCl6 in 2-propanol. The temperature of the reaction mixture rises for a time to 1400C and is then kept for 1 hour at 1 100C. The resultant oil crystallises after dis Example 6: tillation in a high vacuum, affording 53.2 g (0.11 mole = 76% of theory) of 1,3 - bis - [3 - (2,3 dimethylmaleimidyl)prnpyl ] - 1,1,3,3 -tetramethyl disiloxane with a boiling point of 2200-2220C/0.2 mbar and melting point 55 -57 C; nitrogen content: 6.03%.

A mixture of 4.65 g (0.01 mole) of 1,3 - bis - [ 3 - (2,3 - dimethylmaleimidyl)propyl ] -1,1,3,3- tetramethyl disiloxane, 14.83 g (0.05 mole) of octamethylcyclotetrasiloxane, 30 ml of dimethoxyethane and 3 ml of conc. H2SO4 is shaken for 24 hours at room temperature. The resultant oil is diluted with 100 ml of diethyl ether and the organic phase is washed with water until neutral, dried over sodium sulfate and freed from solvent. After filtration through a G3 glass frit, the product is dried to constant weight at 100 C/0.2 mbar. Yield: 17.7 g. Intrinsic viscosity: 0.0363 Pa s. [ TI ] = 2.2 ml/g~' (at 250C in toluene).M (average molecular weight, determined by vapour pressure osmometry in CHCI3): 1874-2096; z = 19-21; nitrogen content: 1.5%.

Example 7: Photochemical crosslinking of a polydimethylsiloxane containing 3 - (2,3 - dimethylmaleimidyl)propyl groups. A 20% solution of the polysiloxane obtained in Example 2 in toluene is applied to roughened aluminium sheeting from a centrifugal applicator on a rotating disc. The coated sheet is subsequently dried for 15 minutes at 90 C.

Curing of the liquid layer is effected by exposure with a mercury high pressure lamp (700 W) for 5 minutes. A clear, firm coating is obtained. At nonexposed areas the still fluid polysiloxane may be removed with an organic solvent such as trichloroethylene, acetone, tetrahydrofuran or cyclohexane, and the metal etched with CHI/H20JH20 without destroying the coating.

Examples 8-10: In accordance with the procedure described in Example 7, the polysiloxanes obtained in Examples 2 and 3 are photochemically crosslinked with and without the concurrent use of benzophenone as sensitiser. Irradiation is effected with a metal halide vauour lamp (5000 W). The results are reported in the table.

Polysiloxane Benzophenone Exposure time Coating Example 2 5% by weight 2 minutes firm, good adhesion Example 3 0 3.5 minutes firm, good adhesion Example 3 5% by weight 2 minutes firm, good adhesion Example ii: In accordance with the procedure described in Example 7, a mixture of 10 g of the polysiloxane obtained in Example 4 and 0.2 g of n-octyl 3chlorothioxanthone - 1 - carboxylate is applied to copper sheeting and exposed. A hard, mechanically resistant coating is obtained.

Example 12: In accordance with the procedure described in Example 7, a mixture of 10 g of the polysiloxane obtained in Example 2 and 2 g of the polysiloxane obtained in Example 6 is applied to copper sheeting and exposed. A firm, very elastic coating is obtained.

The copper can be etched at the non-exposed areas with FeCI3 solution after development with trichloroethylene.

Claims

1. A light-crosslinkable polysiloxane having an average molecular weight of 750 to 1,500,000 and consisting of 10 to 100 mole % of recurring structural units of the formula I

and of 0 to 90 mole % of recurring structural units of the formula II

such that each molecule contains on average at least three structural units of the formula I, in which for mulae A is a -CpH2p- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by -0,-NH- or-NH-C1-C4aIkyl, R1 is hydrogen, methyl, phenyl or vinyl, R2 is methyl or phenyl, and each of R3 and R4 independently of the other is C1-C4 alkyl or together they are trimethylene or tetramethylene, each unsubstituted or substituted by a methyl group.

2. A polysiloxane according to claim 1 having an average molecular weight of 750 to 120,000 and con sisting of 15 to 100 mole % of recurring structural units of the formula I and 0 to 85 mole % of recurring structural units of the formula II, and wherein A is -(CH2)p--

3. A polysiloxane according to claim 1 having an average molecular weight of 750 to 100,000 and con sisting of 25 to 96 mole % of recurring structural units of the formula I and 4 to 75 mole % of recurring structural units of the formula II, wherein A is -(CH2)2-or-(CH2)2-, R1 is hydrogen or methyl and each of R2, R3 and R4 is methyl.

4. A polysiloxane according to claim 1 substantially as described with reference to any of Examples 1 to 4.

5. A process for the preparation of a lightcrosslinkable polysiloxane according to claim 1, which process comprises a) cohydrolysing a compound of the formula III

with 10 to 100 mole % of a compound of the formula IV

and subsequently equilibrating the reaction product, or b) reacting a poly-H-siloxane of the formula V

with 10 to 100 mole % of a compound of the formula Vl

in which formulae above A, R2, R3 and R4 are as defined in claim 1,A1 is a -CpH2p~1- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by -0,-NH-or -NHC1C4 alkyl, and R', is hydrogen, methyl or phenyl, but must be hydrogen in at least 10 mole % of the structural units of the formula V.

6. A process according to claim 5 substantially as described with reference to any of Examples 1 to 4.

7. A crosslinkable polysiloxane which is obtainable by crosslinking a light-crosslinkable polysilox ane as claimed in claim 1, in the presence of O to 30 mole % of a compound of the formula X

wherein A, Fl1, Fl2, R3 and R4 are as defined in claim 1 and n is an integerfrom 1 to 20,000, by the action of light

8.A compound of the formula X

wherein A is a -CpH2p- radical, in which p is 2 to 10, the main chain of which radical may be interrupted by +, -NH- or -NH-C1-C4-alkyl, R1 is hydrogen, methyl, phenyl or vinyl, R2 is methyl or phenyl, each of R3 and R4 independently of the other is C1-C4 alkyl or together are trimethylene or tetramethylene, each of which is substituted by a methyl group, and z is an integer from 1 to 20,000.

9. A compound of the formula X according to claim 8, wherein A is -(CH2)p-, in which p is 2 to 10, and z is an integer from 1 to 20.

10. A compound of the formula X according to claim 8, wherein A is -(CH2)r or-(CH2)2-, R1 is hydrogen or methyl, each of R, R3 and R4 is methyl and z is an integer from 1 to 20.

11. A compound of formula X according to claim 8 substantially as described with reference to Example 5 or 6.

12. A process for the preparation of a compound of the formula X as claimed in claim 6, which process comprises A) equilibrating a compound oftheformula X, in which x is at least 1, with a cyclotetrasiloxane of the formula Vllb

B) reacting a compound of the formula Xl

with a compound of the formula Vl

in the molar ratio of 1:2; C) hydrolysing a compound of the formula XII

to the corresponding disiloxane and, if desired, equilibrating the reaction product with a suitable cyclosiloxane, or reacting said compound of the formula (XII) with a compound of the formula XIII

in the molar ratio of 2:1, or D) reacting a compound of the formula XIV

with an anhydride ofthe formula IX, in the molar ratio of 1: :2, in which formulae (Vllb), (Xl), (VI), (XII), (XIII) and (XIV) above, z, A, R1, R2, R3 and R4 are as defined in claim 6, A1 is a UpH2p~1- radical, in which p p is is 2 to 10, the main chain of which radical may be interrupted by -0,-NH- or -NH-C1-C4- alkyl, and R1 is hydrogen, methyl or phenyl.

13. A process according to claim 12 substantially as described with reference to Example 5 or 6.

14. A compound of formula X when prepared by a process claimed in claim 12 or 13.

15. A method of making moulded articles, films, finishes and coatings, which comprises the use of a crosslinkable polysiloxane as claimed in either of claims 1 to 7.