GB2066278A

GB2066278A - Radiation curable organopolysiloxanes

Info

Publication number: GB2066278A
Application number: GB8038899A
Authority: GB
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1979-12-26
Filing date: 1980-12-04
Publication date: 1981-07-08
Also published as: JPS6359423B2; DE3048636C2; FR2472592A1; ZA807425B; JPS56106958A; DE3048636A1; GB2066278B; FR2472592B1; AU6583880A

Abstract

Fluid mixtures of alkoxy silanes and silanol terminated organopolysiloxanes containing onium salts of Group Va, VIa and VIIa elements have been found to cure to the elastomeric state when exposed to radiant energy. In instances where a sensitizing dye is used in the fluid mixtures, visible light cure can also be achieved.

Description

SPECIFICATION Radiation curable organopolysiloxanes Prior to the present invention, room temperature vulcanizing organopolysiloxane compositions, such as shown by Bruner Patent 3,070,555, were based on the moisture cure of a mixture of a silanol terminated polydiorganosiloxane and an acyloxy silane. Although these moisture curable organopolysiloxanes have been found to be useful in a variety of applications, acetic acid is liberated during the cure resulting in undesirable odor and reaction of the acid with various substrates. Improved results were achieved when Viventi U.S. Patent 3,816,282, assigned to the same assignee as the present invention, discovered that organopolysiloxanes could be cured by radiation, based on the use of a mercapto polysiloxane and a free radical source. Fox et al, U.S.Patent 4,101,513 show that onium catalysts of Group Va, Vla and Vlla have been found to be useful for the condensation of hydrolyzable silanes under the influence of ultraviolet light.

The present invention is based on the discovery that radiation curable organopolysiloxane compositions which are free of acetic acid odors and curable under both UV radiation or visible light, can be obtained when utilizing a mixture of a silanol terminated polydiorganosiloxane and an alkoxy silane in combination with an onium salt of a Group Va, Vla or Vlla element. Unlike the compositions of Viventi, the radiation curable organopolysiloxane compositions of the present invention are based on silanol condensation. In instances where a visible light cure is desired, an appropriate sensitizing organic dye can be employed in combination with the aforementioned onium salts.

There is provided by the present invention radiation curable organopolysiloxane compositions comprising (A) 100 parts of a silanol terminated organopolysiloxane consisting essentially of chemically combined diorganosiloxy units of the formula, (1) R2SiO, (B) 2 to 200 parts of an alkoxy silane of the formula, (2) (RlO)a (R2)bSi, (C) 0.1 to 20 parts of an onium salt of a Group Va, Group Vla, or Group Vlla element and (D) O to 20 parts of an organic dye sensitizer, where R is a monovalent hydrocarbon radical or halogenated monovalent hydrocarbon radical, R' is a C(, ,2) alkyl radical, R2 is selected from R radicals and C(, 8) glycidyl alkyl radicals, a is an integer having a value of from 2 to 4 inclusive, b is a whole number having a value of from 0 to 2 inclusive and the sum of a and b is equal to 4.

Radicals included by R of formulas (1) and (2) are, for example, monovalent aryl radicals, halogenated monovalent aryl radicals, such as phenyl, xylyl, chlorophenyl, naphthyl; aralkyl radicals such as benzo, phenylethyl, aliphatic and cycloaliphatic, such as alkyl, alkenyl, cycloalkyl; chloralkyl such as methyl, ethyl, propyl, chloropropyl, vinyl, allyl, trifluoropropyl, cyclohexyl, etc. and cyanoethyl, cyanopropyl, cyanobutyl, etc. Radicals included by R' are, for example, methyl, ethyl, propyl, etc.

The onium salts used in the practice of the present invention, are included within the formula, (3) Y]+LJ]-, where J is a non-nucleophilic counterion defined more particularly below, and Y is a cation selected from the class consisting of an aromatic halonium cation, (4) [(R3)c (R4)d D], an aromatic Group Va cation, (5) [(R3),(R5)9 (R6)h E], and an aromatic Group Vla cation, 1(R3) (R7)k (RS)m G], where R3 is a monovalent aromatic organic radical, R4 is a divalent aromatic organic radical, R5 and R7 are monovalent organic aliphatic radicals selected from alkyl, cyclo alkyl and substituted alkyl, R6 and R8 are polyvalent organic radicals forming a heterocylic or fused ring structure selected from aliphatic radicals and aromatic radicals with E or G, D is a halogen radical such as I, E is a Group Va element selected from N, P, As, Sb and Bi, G is a Group Vla element selected from S, Se and Te, "c" is a whole number equal to O or 2, "d" is a whole number equal to O or 1 and when c is 0, d is 1 and when d is O c is 2, "f" is a whole number equal to O to 4 inclusive, "g" is a whole number equal to O to 2 inclusive, "h" is a whole number equal to O to 2 inclusive, and the sum of "f" + "g" + "h" has a value equal to 4 or the combining value of E, "j" is a whole number equal to O to 3 inclusive, "k" is a whole number equal to O to 2 inclusive, and "m" is a whole number equal to O or 1, where the sum of "j" + "k" + "m" has a value equal to 3 or the combining value of G.

Radicals included by R3 can be the same or different, aromatic carbocylic or heterocyclic radicals having from 6 to 20 carbon atoms, which can be substituted with from 1 to 4 monovalent radicals selected from C(1 ,2) alkoxy, C(1 12) alkyl, nitro, chloro, etc., R3 is more particularly phenyl, chlorophenyl, nitrophenyl, methoxyphenyl, pyridyl etc.Radicals included by R4 are divalent radicals, such as

R5 and R7 radicals include C(1 12) alkyl, such as methyl, ethyl, etc., substituted alkyl, such as -C2H40CH3, -CH2COOC2H5, -CH2COCH3, Q' is defined below, etc., R6 and R8 radicals include such structures as

where Q' is selected from -0-, (-CH2-)n, = N-R' and -S-, n is an integer equal to 1-4 inclusive; Z is selected from -0-, -S- and

and R' is selected from hydrogen, C(1 8) alkyl, C(6 13) aryl, etc.

Non-nucleophilic counterions included by J of formula (3) are MQd anions, where M is a metal or metalloid, Q is a halogen radical, and d is an integer such as 4-6 inclusive. In addition, J of formula (3), also can include non-nucleophilic counterions such as perchlorate, CF3SO3- and C6H4SO3-, etc.; J of formula (3) also can be a halide counterion such as Cl-, Br-, F-, etc., as well as nitrate, phosphate, etc.

Metal or metalloids included by M of the non-nucleophilic counterion, MQd previously defined and included within J of formula (3) are transition metals such as Sb, Fe, Sn, Bi, Al, Ga, In, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth elements such as the lanthanides, for example, Cd, Pr, Nd, etc., actinides, such as Th, Pa, U, Np, etc., and metalloids such as B, P, As, etc. Complex anions included by MQd are, for example, BF4-, PF6-, AsF6-, SbF6-, FeCI4-, SnCl6-, SbCI6-, BiCI5=, etc.

Halonium salts included by formula (3) and having formula (4) cations are for, example,

Group Va onium salts included by formula (3) and having formula (5) cations are, for example,

BF4-, SbF6-, BF4-, BF4-, PF4-,

AsF6-, PF6-, BF4-, BF4-, BF4-, BF4-, BF4-, etc.

Group Vla onium salts included by formula (3) and having formula (6) cations are, for example,

BF4-, PF6-, AsF6-,

SbF6-, FeCl4-, SnCl6-, SbCl6-, BiCl5=, BF4-,

PF6-, etc.

included by the silanol terminated organopolysiloxanes consisting essentially of chemically combined units of formula (1) are linear diorganopolysiloxanes of the formula,

where R is as defined above and q is an integer having an average value equal to about 5 to 3000 inclusive. This fluid preferably has a viscosity in the range of from about 2,000 to 50,000 centipoises when measured at 25"C. These silanol-terminated fluids can be made by treating a higher molecular weight organopolysiloxane, such as dimethylpolysiloxane with water in the presence of a mineral acid, or base catalyst, to tailor the viscosity of the polymer to the desired range. Methods for making such higher molecular weight organopolysiloxane utilized in the production of silanol-terminated diorganopolysiloxane of formula (7) are well known.For example, hydrolysis of diorganohalosilane such as dimethyldichlorosilane, diphenyldichlorosilane, methylvinyldichlorosilane, etc., or mixtures thereof can provide for the production of low molecular weight hydrolyzate. Equilibration thereafter can provide for higher molecular weight organopolysiloxane. Equilibration of cyclopolysiloxane such as octamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, or mixtures thereof, will also provide for higher molecular weight polymers. Preferably, such polymers are decatalyzed of equilibration catalyst by standard procedures prior to use, such as shown by Boot Patent 3,1 53,007, assigned to the same assignee as the present invention.

Silanol-terminated organopolysiloxanes having viscosities below 1 200 centipoises can be made by treating organopolysiloxanes consisting essentially of chemically combined units of formula (1) with steam under pressure. Other methods that can be employed to make silanolterminated organopolysiloxanes are more particularly described in Patent 2,607,792, Warrick and U.K. Patent 835,790.

Alkoxy silanes of formula (2) include, for example, methyl trimethoxysilane, dimethyldimethoxysilane, methyl orthosilicate, ethyl orthosilicate, n-butyl trimethoxysilane, trimethyl methoxysilane, methyl triethoxysilane, phenyl trimethoxysilane, diphenyldiethoxysilane, and higher condensates such as dimethyl tetramethoxydisiloxane, 2-glycidyl trimethoxysilane.

Organic dyes which can be employed in the practice of the invention are, for example; acridine orange, acridine yellow, phosphine R, benzoflavin haematoporphrin, 9,10-diethylanthracene, Mitchler's ketone, Setflavin T, perylene, coronene, etc.

In the practice of the invention the various ingredients of the mixture, such as the silanol fluid, the alkoxy silane, and onium salt can be mixed together. In the event that the onium salt and the silanol terminated polydiorganosiloxane or "silanol fluid" does not form a solution, the onium salt can first be dissolved in a liquid diluent which is inert to the components of the mixture. Suitable inert diluents include alcohols, such as ethanol, ethyl acetate, ethers, acetonitrile, etc. The alkoxy silane can be added prior to, or along with the onium salt to the silanol fluid.

In instances where a visible light cure is desired, the organic dye can be added to the ingredients under total or limited darkness to minimize the premature activation of the onium salt.

Various fillers and pigments can be incorporated into the radiation curable composition such as, for example, silica, talc, mica, titanium dioxide, gypsum, iron oxide, alumina, wood flour, glass fibers, graphite, carbon black, fly ash, etc. The amount of filler which can be used can be varied within wide limits. However, the choice of filler and amount can influence the effectiveness of the cure of the mixture and therefore the amount can vary widely depending upon the requirements of the application and the length of cure which can be tolerated. A typical mixture, for example, can be from 1 to 30 parts of filler per 100 parts of silanol fluid.

Compositions of the present invention can be employed as construction sealants, caulking compounds, etc. The compositions of the present invention can be stored for an indefinite period of time. In the event a sensitizing organic dye is utilized in the mixture, however, the curable organopolysiloxane compositions must be protected from daylight to minimize activation of the onium salt.

In order that those skilled in the art will be better able to practice of the invention, the following examples are given by way of illustration and not be way of limitation. All parts are by weight.

Example 1 A mixture of 10 parts of a silanol terminated polydimethylsiloxane fluid having a viscosity of 35,000 centipoises and an OH content of 0.09%, 1 part of ethylorthosilicate, and 0.3 part of di(4-n-butylphenyl)iodonium hexafluoroarsenate was spread as a 3 mil film onto a glass plate and irradiated using a GE H3T7 medium pressure mercury arc lamp at a distance of 7 inches.

After an irradiation time of 20 seconds, there was obtained a rubbery film.

A copper wire is immersed into the above UV curable organopolysiloxane and the coated wire is exposed to ultra-violet light as previously described. There is obtained an adherent elastomeric silicone rubber coating on the wire after 10 seconds of exposure which is useful as an insulating coating.

Example 2 The procedure of Example 1 was repeated, except that methyltriethoxy silane was substituted for ethylorthosilicate. The curable silicone formulation was spread as a one mil film onto a glass plate and irradiated at a distance of 7 inches following the same procedure of Example 1. There was obtained a rubbery crosslinked film after 10 seconds of irradiation. When the same curable silicone formulation was spread onto craft paper as a 0.1 mil film and cured as described above.

Papers coated with pressure resistant adhesives could not be made to permanently bond to the craft paper. The coating was nonsmearing and could not be rubbed off.

Example 3 A solution comprising 0.2g di(4-n-heptylphenyl) iodonium hexafluoroarsenate, 10g difunctional hydroxyl terminated polydimethylsiloxane fluid having a viscosity of 35,000 cp, and 1 g methylorthosilicate. The above mixture was coated as a 1 ml film onto an aluminum plate and exposed at a distance of 3 inches from a GE H3T7 lamp. Fifteen seconds irradiation was sufficient to give a tack-free rubbery coating.

Example 4 A polymerizable mixture was prepared using 1 part of a 47,000 cp hydroxyl terminated polydimethylsiloxane fluid, 5 parts 2-glycidyltrimethoxysilane and 0.1 part of a phenyl sulfide triphenylsulfonium salt of the formula,

AsP6 When the above mixture was irradiated for 1.0 minute, as a 1 mil film on a glass plate, a transparent hard film was obtained. Irradiation was carried out using a GE H3T7 medium pressure mercury arc lamp.

The above phenyl sulfide triphenylsulfonium salt was prepared as follows: A mixture of 1 9.6 parts of 86% potassium hydroxide, 33 parts of thiophenol and about 1 20 parts of dimethylacetamide was heated at a temperature of 120"C with stirring to effect the removal of water. After about 6.5 parts of water was collected, there was added to the resulting mixture 26.3 parts of para-dibromobenzene and the mixture was heated to reflux. After 6 hours at reflux the reaction mixture was allowed to cool and 300 parts of water was added. There was obtained a tan colored solid which was filtered and washed with water several times. The product was then dried. There was obtained 34.7 parts of 1 ,4-dithiphenoxybenzene based on method of preparation.

A mixture of 7.35 parts of the above disulfide, 11.75 parts of diphenyliodonium hexafluoroarsenate and 0.2 part of copper benzoate was heated for 3 hours at 120"C. The resulting reaction mixture was washed several times with about 50 part portions of diethylether and the remaining solid was recrystalized from 95% ethanol. There was obtained a 45% yield of a very light tan crystalline product having a melting point of 69-75" and the following elemental analysis: Calculated %C, 51.3; %H, 3.50; %S, 11.43. Found %C, 51.21; %H 3.59; %S, 11.37. Based on method of preparation there was obtained a triarylsulfonium salt having the formula,

AsF6- .

Example 5 To the reaction mixture of Example 4, there was added 0.02 part of perylene as a sensitizer.

The mixture was then coated onto a glass plate and another glass plate placed over the first to make a glass-to-glass joint. After irradiating the mixture through the glass using a GE EBR 375W photoflood visible light lamp for 1.5 minutes, a permanent joint was produced.

Example 6 To 4 parts ethyltrimethoxy silane there was added 1 part of a 47,000 centipoises hydroxyl terminated polydimethylsiloxane and 0.1 part didodecylphenyliodonium hexafluoroantimonate.

The solution was coated as a 2 mil film on an aluminum panel and irradiated at a distance of 6 inches from a GE H3T7 medium pressure mercury arc lamp. The film was cured to a hard transparent film after 1 minute of continuous irradiation.

Example 7 To the solution of Example 6, there was added 0.01 part of perylene and the film coated as before on an aluminum panel. The panel was irradiated with visible light using a GE EBR 374W photoflood lamp. A transparent, hard film was produced after 1 minute irradiation employing the above lamp mounted at a distance of 4 inches.

Example 8 Example 6 was repeated, except the photoinitiator was replaced with

SbF6 A cure time of 1.5 minutes was required to obtain a hard tack-free coating.

Although the above examples are directed to only a few of. the very many radiation curable silicone formulations included within the scope of the present invention, it should be understood that the present invention is directed to a much broader variety of silicone formulations based on the use of silanol-terminated polydiorgansiloxanes having formula (1) units, alkoxy silanes of formula (2), aromatic onium salts as set forth in the previous description and optionally a sensitizing organic dye.

Claims

1. A radiation curable organopolysiloxane composition comprising (A) 100 parts of a silanol-terminated organopolysiloxane consisting essentially of diorganosiloxy units of the formula, R2SiO, (B) 2 to 200 parts of an alkoxy silane of the formula, (RlO)a(R2)bSi, (C) 0.1 to 20 parts of an onium salt selected from a Group Va, Vla, or Groups Vlla element and (D) O to 20 parts of ano organic sensitizing dye, where R is selected from monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals, R' is selected from C(t ,2) alkyl radicals, R2 is selected from R radicals and C(, 8) glycidyl alkyl radicals, a is an integer equal to X to 4 inclusive, b is a whole number equal to O to 2 inclusive, and the sum of a + b is equal to 4.

2. A composition as claimed in claim 1, where the silanol terminated polydiorganosiloxane is a silanol terminated polydimethylsiloxane.

3. A composition as claimed in claim 1 or claim 2, where the alkoxy silane is ethylorthosilicate.

4. A composition as claimed in any one of the preceding claims, wherein the onium salt is di(4-n-butylphenyl)iodoniumhexafluoroarsenate.

5. A compositioon as claimed in any one of claims 1 to 3, where the onium salt is

PF66. A composition as claimed in any one of claims 1 to 3, where the onium salt is

SbF67. A composition as claimed in any one of claims 1 to 3, where the onium slat is

SbF6

8. A composition as claimed in any one of the preceding claims, where the dye is perylene.

9. A composition as claimed in any one of claims 1 to 7, where the dye is Micheis ketone.

10. A composition as claimed in claim 1, substantially as hereinbefore described with reference to any one of the examples.