CA2092047A1 - Polysiloxanes - Google Patents

Abstract

ABSTRACT

Polysiloxane compounds with the structure:

, where the following applies:
E = epoxyfunctional remainder, Z = photopolymerizable remainder, R1 = alkyl with 1 to 4 C atoms or phenyl, R2 = R1, E or Z.

Description

POLYSILOXANES
FIELD OF THE INVENTION
The invention relates to epoxyfunctional polysiloxanes which can be cured with radicals, as well as to methods for their production.
BACKGROUND OF THE INVENTION
Because of their chemical structure, polyorgano- ;
siloxanes possess a number of specific properties, such as ~ UV stability, flexibility~elasticitY,/
chemical and ther-mal stablrlty,ylow water absorption, good dielectric qualities and non-toxic behavior. Because of these properties and possible combinations of properties, polyorgano-siloxanes find use in many areas of technology. It is particularly noteworthy that linear-polymer polysiloxanes are liquid up to molecular masses of approximately 150,000, and are therefore particularly suitable for use in impregnation and release coating systems, adhesives, ~e~ tionlagents, resists, covering masses, reflection and protective layers as well as for other special purposes of use, particularly also in medicine and medical technology.
For the purposes stated, highly viscous siloxane types a~ter shaping are used;~dcpcn~ing on thcir struct-u~, they are cross-linked or cured by means of different processes, with reactions of a radical or ionic nature taking place. For thin layers, in particular, photo-cross-linking has proven itself to be extremely advantageous (see in this regard: "Adhasion"
["Adhesion"], Vol. 29 (1985), No. 10, pages 28 to 35: "Kautschuk + Gummi, Kunststoffe" ["Natural Rubber ~ Rubber, Plastics"], Vol. 41 (1988), pages 1131 to 1138).
By variation of the organic remainders in chain positions, or by introduction of suitable functional groups, the property spec~rum of the polyorganosiloxanes can be modified in a tar~eted manner, l.e., adapted to various technical requirements. Thus, it i5 known to produce liquid-crystalline polysiloxanes by introduction o~ mesogènlc groups ("Mol. Cryst~
Liq. Cryst. Inc. Nonlin. Opt.", Vol. 157 (1988), pages 193 to 202; "Polymer", Vol. 29 (1988), pages 1318 to 1322; "Makromol.
Chem.", Vol. 188 (1987), pages 2759 to 2767).
By the introduction of a remainder that can be photo-cross-linked, such as acrylate, methacrylate and malelnimide remainders, polysiloxanes can be adjusted so they can be cross-linked or structured with light. By cross-linking such modified polyorganosiloxanes, selectively transporting layers are produced ("Makromol. Chem., Rapid Commun.", Vol. 9 (1988), pages 35 to 38; "J. Polym. Sci., Part A: Polym. Chem.", Vol. 27 (1989), pages 1439 to 1443), as are biocompatible layers - I abhesive (U.5. patent 4,822,741) and layers with pdhe~ behavior (DE-OS
33 16 166, EP-OS 0 28~ 681, and U.S. patent 4,576,999).
For the in~roduction of remainders or functions into polyorganosiloxanes, hydrosilylation, e~., the addition of compounds with olefin double bonds in end position to SiH groups of the siloxane chain, has proven to be advantageous (E.R.
Corey, J.Y. Corey and P.P. Gaspar, "Silicon Chemistry", John Wiley & Sons, New York 1988, pages 123 to 132). However, groups I that can be polymerized with radicals, with acrylate or J methacrylate remainders, cannot be directly introduced with this method, since the reaction does not progress selectively and the addition of allyl acrylate, for example, takes place both at the allyl group and the acryl group (R.P. Eckberg in conference i report "Radcure '84", pages 1 to 17). The introduction of these ¦ groups therefore has to take place in two steps. In-the first ¦ step, an a-olefin with a reactive remainder which does not interfere with hydrosilylation, for example a halogen or epoxy remainder, is added. This remainder then serves or the introduction of the photopolymerizable yroup in the second step.

The addition of an epoxy compound,~s par-tic~ ly ~y to carr~

~71 for example the addition o~ a~ yl glycidyl ether, vinyl is Darticularlv easv to carrv out cyclohexene oxide, vinyl~norbornéne oxlde or limonene oxide~ in the first step, and the addition of acrylic or methacrylic acid ~or de~ivatives thereof~ ~o the oxirane rin~/
n tne second step (see ln this regard: DE-OS 30 44 317, DE-OS
EP-OS O 269 114~J
33 16 ~ EP-OS 0 281 681, U.S. patent 4,293,678, U.S. patent 4,331,704 and U.S. patent 4,576,999). In most cases, complete or almost complete conversion of the epoxy groups is the goal here. Only in some cases, for example in accordance with DE-OS
33 16 166 and U.S. patent 4,576,999, ~ partial conversion is described, i.e. products are produced which still contain epoxy groups, along with acrylate ester groups. During photo-cross-linking, these epoxy groups are then activated and included in cross-linking by the addition of onium sal-t photoinitiators.
Our own studies have now shown that products obtained by addition of (meth)acrylic acid and (meth)acrylates to proportion epoxyfunctional polysiloxanes, with a residual epoxy;potentiall of > 50~, are very unstable and already gel during processing, when the solvent is removed, or when they are stored with the exclusion of light. Products with a very low proportion of photopolymerizable groups, i.e. < 20%, and a correspondingly high epoxy proportion, prove to be particularly unstable. With a decreasing epoxy concentration, the products become increasingly more stable; residual epoxy contents of less than 20% hardly impair the stability of the products any more.
However, with regard to further functionalization of epoxyfunctional polysiloxanes that can be photo-cross-linked, products with a high epoxy content are of particular interest.
SUMMARY OF THE INVENTION
It is an object of the invention to provide easily accessible polysiloxanes which are storage stable and can be processed without problems, by p~o~ -linking with radicals, and have the highest possible epoxy content.
In accordance with the invention, this object is accomplished with polysiloxanes which can be photo-cross-linked, having the following structure:

.
Rl ~ R ~ R ~ 5i~ 5i_R2 where the following applies:
E = epoxyfunctional remainder with 4 to 20 C atoms, Z = photopolymerizable remainder with 8 to 40 C atoms, which can be obtained by addition of a photopolymerizable compound to a remainder E located at the siloxane chain, and subsequent addition of an aliphatic, cycloaliphatic or aromatic monoisocyanate or monoisothiocyanate with 2 to 10 C atoms to the secondary OH group formed upon opening of epoxide thelepoxil ring, Rl = alkyl with 1 to 4 C atoms or phenyl, R2 = Rl, E or Z, where the remainders R1 and R2 can be the same or different in ; each instance, : 50 x = ~ to 1000, y = 10 to 300, z = 3 to 8;
x is preferably about 3 to 10 times y. In the formula, the structural qrouPs, individua ~ o the polysiloxanes~are indicated in summary - form; in fact, these groups are statistically distributed over the polymer chain.

The epoxyfunctional remainder E is preferably one `of ¦ the following remainders:

\ (CH )3_0-CH2-CH /CH2 ~ -(CH2)2 \ / 2 2092~7 -CH2-CH(CH3 )-CH2-0-CH2-C~ ~CH2 -CH2-CH(CH3 )-COO-CH2_C~--CH2 , -(CH2)2-(~

2)2 ~ or C~2-CH(CH3)_(~CH3 DETAILED DESCRIPTION OF THE INVENTION
The epoxyfunctional polysiloxanes according to the invention are produced by reacting polysiloxanes having epoxy groups with an oleîinic-unsaturated compound containing hydroxyl mol ar or carboxyl groups in al~e~ ratio of < 1, with reference to the addinQ
epoxy groups, andld~po~lti~ a monoisocyanate or mono-isothiocyanate on the hydroxyl groups formed in this way.
The polysiloxanes with ~epoxy groups can be obtained by positioned addition of epoxy compounds with an ~positio~ C=C double bond to SiH-functional polysiloxanes. Suitable epoxy compounds are particularly allyl glycidyl ether, 2-methyl-allyl glycidyl ether, epoxy butene, methacrylic acid glycidyl ester, vinyl cyclohexene oxide, vinyl norbornene oxide and limonene oxide.
he same or very similar polysiloxanes are also accessible by positioned epoxidation of polysiloxanes with chain-poEitio~ ~-alkenyl, ~-alkenyl ether and ~-alkenyl ester groups.
Olefinic-unsaturated compounds which;are particularly the reaction suitable for ~on~crs~o~ with the epoxy groups of the polysiloxanes produced in the manner stated are acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl maleinim1de, cinnamic acid, I glycerol 2 0 9 ? ~ 4 7 diacrylate and ~ rcer-lnldimethacry~a~e~ or mixtures of these compounds. Acrylic acid and methacrylic acid, in particular, can also find use in a mixture with the corresponding anhydrides. The compounds according to the invention are reaction the addition , obtained by icon-~æslon~of the products formed bylconvcrsionlof the olefinic-unsaturated compounds to, `, ~ne poIyslloxaneS whlch have epoxy groups,~hcn th~
olcfinic-unG~ co~
reaction with monoisocyanate or monoisothiocyanate. In this con~e~s~
the iso(thio)cyanates react with the vicinal hydroxyl group, ¦ oxirane which is formed by opening of the ~ ring during the previous addition reaction. Preferably, propyl isocyanate is used as the monoisocyanate. Other possible compounds are, for example butyl isocyanate and phenyl isocyanate as well as propyl isothiocyanate and phenyl isothiocyanate.
The invention will now be explained in more detail, using embodiments.
Examples l to 5 Synthesis of polysiloxanes containing epoxy groups (polyepoxysiloxanes) as the starting compounds for the production of the epoxyfunctional polysiloxanes according to the inventi~ which can be photo-cross-linked _ _ (H3c)3si-o~si-o~[si-ol,--Si(CH ) ~ epoxy compound L 3 ~X LH ~ 3 3 (olefinic-unsaturated) I
( H 3 C ) 3 5 ~ O i 0~51 ( C H ) ' parts ~092~47 The masst~Eo~ortion~ o~ octamethyl cyclotetrasiloxane (OMCTS), Sil~-functional polymethyl siloxane with a chain length of n = 60 (PMS) and hexamethyl disiloxane (HMDS) as indicated in Table 1 are mixed with 0.2 g trifluoromethane sulfonic acid and 13 drops of distilled water, and stirred at 70C for 40 h.
After cooling, the reaction mixture is mixed with approximately 1 g Na2CO3, stirred for 2 h and filtered through a membrane filter with a pore diameter of 1.2 ~m, under pressure. Volatile constituents comp4~4~slare first removed at 100C/O.1 mbar, and then in a thin-layer evaporator at 120C/O.1 mbar.
The colorless liquid obtained is dripped into a solution of the amount of freshly distiiled ~*~ indicated in Table 1, i.e., allyl glycidyl ether (AGE), vinyl cyclohexene oxide (VCHO) or limonene oxide (LO), 0.13 g H2PtCl6.6 H20 and 0.5 ml tert.-butanol in 250 ml toluene, at 70C, within 6 to 7 h. The reaction mixture is then stirred at 70C until a minimum (verification by volumetric determination of SiH)/
converslon of Y5~ has been reached~ To remove the catalyst, 0.2 g cross-linked poly-4-vinyl pyrid:ine is added, then the mixture is stirred at room temperature for 2 h, and filtered under pressure through a membrane filter with a pore diameter of 1.2 ~ olvent as well as volatiletcom~ent~are removed in a vacuum at 70C/O.l mbar. Colorless liquids are obtained in almost quantitative yield. Table 1 contains the epoxy values and viscosities determined for characterization of the products.

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parts ~the productsJ
The mass propo-rtio~s of~roduct~ 1 and 2 given in Table 2 ) are dissolved in 500 ml water-free toluene under yellow light, parts with the mass proportion~ of acry:Lic acid (AS) or methacrylic acid (MAS) also indicated in Table 2, together with 2.5 g diethyl phosphite as the stabilizer and 2.5g N,N,N',N'-tetramethyl-4,4'-diamino diphenyl methane as the ~ catalyst, then stirred at 50C for 10 to 11 h. After cooling, I the reaction mixture is mixed with acid Al2O3 to remove the catalyst, stirred for 2 h and pressure-filtered through a ~ membrane filter with a pore diameter of 1.2 ~m. The solvent and ¦ constituents volatile ~ompone~t~ are removed at room temperature, in a ¦ vacuum (0.1 mbar). The products obtained are unstable and I already gel during further processing or when stored in the refrigerator.

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Examples 9 to 16Production of the epoxyfunctional polysiloxanes according to the invention, which can be photo-cross-linked (H3C)~5i-0 ~ Si-0 ~ S~-0 ~ Si-0 ~ Si(CH3)3 IV
, parts The mass ~r~ r~ion~ of the products 1 to 5 indicated in reacted Table 3 arelc~nvcrtcd~ in toluene, as described in Examples 6 to 8, with acrylic acid or methacrylic acid, 2.5 g diethyl phosphite and 2.5 g N,N,N',N'-tetramethyl-4,4'-diamino diphenyl methane. However, the solution is not concentrated after the ¦ catalyst has been removed, but rather mixed with 14.2 g propyl tin isocyanate and 20 drops of dibutyllstannou~ dilaurate, and I stirred at room temperature for 120 h. Then, excess isocyanate j is inactivated by adding a few drops of methanol, and then the I constituents I solvent as well as volatile ~ cnt~lare removed at room temperature, in a vacuum (0.1 mbar). Colorless clear liquids are obtained in yields between 90 and 100%. Further information relating to the products obtained (epoxy value, acrylate content, viscosity~ is summarized in Table 4.
The products must be stored in the refrigerator. An evaluation of the storage stability by weekly determinations of viscosity, which is allowed to increase by a maximum of 5%, yields values of > 3 months.

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2~92~7 No. Polysiloxane IV which can be photo-cross-linked ~ de Acrylate Viscosity [mol/lOOq]~mol/100~]lmPa.s 9 0.16 0.04 2200 0.17 0.03 2400 11 0.17 0.03 2380 12 0.18 0.03 3000 13 0.19 0.02 2850 14 0.20 0.01 2800 0.16 0.03 2400 16 0.14 0~04 2500

Claims (16)

1. An epoxyfunctional polysiloxane having the structure:

, where the following applies:

E = an epoxyfunctional residue with 4 to 20 C atoms, Z = a photopolymerizable residue with 8 to 40 C atoms, R1 = alkyl with 1 to 4 C atoms or phenyl, R2 = R1, E or Z, x = 50 to 1000, y = 10 to 300, z = 3 to 8.

2. The epoxyfunctional polysiloxane according to claim 1 wherein Z is obtained by addition of a photo-polymerizable compound to a residue; E located at the siloxane chain, and subsequent addition of an aliphatic, cycloaliphatic or aromatic monoisocyanate or monoisothiocyanate with 2 to 10 C
atoms to the secondary OH group formed upon opening of the epoxide ring.

3. The epoxyfunctional polysiloxane according to claim 1 wherein E is: , , , , , or .

4. A method for the production of an epoxyfunctional polysiloxane according to claim 1 comprising the steps of reacting a polysiloxane having epoxy groups with an olefinic-unsaturated compound containing hydroxyl or carboxyl groups in a molar ratio of < 1 with reference to the epoxy groups, and adding a monoisocyanate or monoisothiocyanate on the hydroxyl groups formed in this way.

5. A method for the production of an epoxyfunctional polysiloxane according to claim 2 comprising the steps of reacting a polysiloxane having epoxy groups with an olefinic-unsaturated compound containing hydroxyl or carboxyl groups in a molar ratio of < 1 with reference to the epoxy groups, and adding a monoisocyanate or monoisothiocyanate on the hydroxyl groups formed in this way.

6. A method for the production of an epoxyfunctional polysiloxane according to claim 3 comprising the steps of reacting a polysiloxane having epoxy groups with an olefinic-unsaturated compound containing hydroxyl or carboxyl groups in a molar ratio of < 1 with reference to the epoxy groups, and adding a monoisocyanate or monoisothiocyanate on the hydroxyl groups formed in this way.

7. The method according to claim 4 wherein the olefinic-unsaturated compound is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl maleinimide, cinnamic acid, glycerol diacrylate and glycerol dimethacrylate, and mixtures thereof.

8. The method according to claim 5 wherein the olefinic-unsaturated compound is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl maleinimide, cinnamic acid, glycerol diacrylate and glycerol dimethacrylate, and mixtures thereof.

9. The method according to claim 6 wherein the olefinic-unsaturated compound is selected from the group consisting of acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxyethyl maleinimide, cinnamic acid, glycerol diacrylate and glycerol dimethacrylate, and mixtures thereof.

10. The method according to claim 4 wherein the monoisocyanate is propyl isocyanate.

11. The method according to claim 5 wherein the monoisocyanate is propyl isocyanate.

12. The method according to claim 6 wherein the monoisocyanate is propyl isocyanate.

13. The method according to claim 7 wherein the monoisocyanate is propyl isocyanate.

14. The method according to claim 8 wherein the monoisocyanate is propyl isocyanate.

15. The method according to claim 9 wherein the monoisocyanate is propyl isocyanate.

16