Curable Organosiloxane Resins Containing Boron

Abstract

The invention relates to a curable composition showing antimicrobial activity in cured state, the composition comprising (A) at least one boron containing siloxane resin consisting of constitutional units of formula (I)

(YZ).sub.nSiR.sup.1.sub.mX.sub.pO.sub.q(I) wherein: R.sup.1 groups may be the same or different and each is independently selected from a hydrogen atom or a linear, branched, or cyclic hydrocarbon residue having 1 to 20 carbon atoms which may contain at least one heteroatom; X is a hydrolysable group, including, but not limited to OH (hydroxy), Cl, Br, I, or OR.sup.2 (alkoxy or aryloxy), wherein R.sup.2 is a linear, branched or cyclic hydrocarbon residue having 1 to 20 carbon atoms which may contain at least one heteroatom; Z is selected from a linear, branched or cyclic hydrocarbon residue having 2 to 60 carbon atoms which may contain at least one heteroatom; Y is a boron containing group; n, and q are integers from 1 to 3, and m and p are integers from 0 to 2 wherein n+m+p+q=4; (B) optionally, at least one curing catalyst.

The invention also relates to an adhesive, sealant, or coating material comprising the curable composition and to use of the curable composition as an adhesive, sealant, or coating material.

Claims

1. A curable composition comprising: (A) at least one boron containing siloxane resin consisting of constitutional units of formula (I)
(YZ).sub.nSiR.sup.1.sub.mX.sub.pO.sub.q(I) wherein: each R.sup.1 group may be the same or different and each is independently selected from a hydrogen atom or a linear, branched, or cyclic hydrocarbon residue having 1 to 20 carbon atoms which may contain at least one heteroatom; X is a hydrolysable group, including, but not limited to OH (hydroxy), Cl, Br, I, or OR.sup.2 (alkoxy or aryloxy), wherein R.sup.2 is a linear, branched or cyclic hydrocarbon residue having 1 to 20 carbon atoms which may contain at least one heteroatom; Z is selected from a linear, branched or cyclic hydrocarbon residue having 2 to 60 carbon atoms which may contain at least one heteroatom; Y is a boron containing group; n, and q are integers from 1 to 3, and m and p are integers from 0 to 2 wherein n+m+p+q=4; (B) optionally, at least one curing catalyst.

2. The curable composition according to claim 1, wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of a C.sub.1-C.sub.12 alkyl group, a C.sub.2-C.sub.8 alkenyl group, a C.sub.2-C.sub.8 alkynyl group, a C.sub.5-C.sub.10 cycloalkyl group, a C.sub.6-C.sub.18 aryl group and a C.sub.6-C.sub.18 aralkyl group, which groups may contain at least one heteroatom.

3. The curable composition according to claim 2, wherein R.sup.1 and R.sup.2 are independently selected from the group consisting of a C.sub.1-C.sub.8 alkyl group which may contain at least one heteroatom or a C.sub.6-C.sub.18 aryl group which may contain at least one heteroatom.

4. The curable composition according to claim 2, wherein said heteroatom selected from O, N, S, Si, P, Cl, Br or F.

5. The curable composition according to claim 3, wherein said C.sub.1-C.sub.8 alkyl group is selected from methyl, ethyl, n-propyl, fluoropropyl, n-butyl, sec-butyl, or tert-butyl.

6. The curable composition according to claim 3, wherein said C.sub.6-C.sub.18 aryl group is selected from phenyl, tolyl or benzoyl.

7. The curable composition according to claim 3, wherein R.sup.1 and R.sup.2 are the same or different and independently selected from methyl or phenyl.

8. The curable composition according to claim 1, showing antimicrobial activity in cured state.

9. The curable composition according to claim 1, wherein the curing catalyst (B) is selected from tin catalysts, titanium catalysts, aluminum catalysts, or zirconium catalysts, or mixtures thereof.

10. The curable composition according to claim 1, wherein the curable composition does not comprise a curing catalyst (B).

11. The curable composition according to claim 1, wherein n=1-2; m=0-1; p=0-1 and q=2-3.

12. The curable composition according to claim 1, comprising dimers, obtained by partial condensation of two boron containing siloxane molecules, with constitutional units of the general formula (I) with n=1 or 2; m=0, 1 or 2; p=0, 1 or 2; q=1; and/or trimers, obtained by partial condensation of three boron containing siloxane molecules, with constitutional units of the general formula (I), wherein the central organosilicone unit is according to the general formula (I) with n=1 or 2; m=0 or 1; p=0 or 1; and q=2; and the two terminal organosilicone units are according to the general formula (I) with n=1 or 2; m=0, 1 or 2; p=0, 1 or 2; q=1.

13. The curable composition according to claim 1, wherein (i) the amount of the boron containing siloxane resin (A) is from about 15 to about 100% by weight, based on the total weight of the composition; and/or (ii) the amount of the curing catalyst (B) is 0 to about 2% by weight, based on the total weight of the composition.

14. An adhesive, sealant, or coating material comprising the curable composition according to claim 1.

Description

EXAMPLE 1: PREPARATION OF OLIGOMER OR RESIN FROM ALLYLTRIMETHOXYSILANE AND PINACOL BORANE

[0114] ##STR00001##

[0115] A 100 mL round bottomed Schlenk flask (flame dried) containing LiAlH.sub.4 (0.1 mol % related to silane) and a magnetic stirrer bar was degassed under high vacuum (110.sup.3 mbar) and flushed with argon. Then, allyltrimethoxysilane was added, and vigorous stirring started. Pinacolborane was added dropwise, avoiding violent bubbling. The flask was closed, and the mixture heated to 110 C. for 3 h. The mixture was left to cool down to room temp. (23 C.). The solids were removed by filtration. The mixture was set under high vacuum (110.sup.3 mbar) and heated to 110 C. to remove all volatiles, after which the temperature was increased to 140 C. to ensure a complete removal of volatiles. The obtained product (yield 70 wt. %) was a colorless, transparent viscous liquid. On contact with the atmosphere the liquid cures.

Composition

[0116] The resin composition was assessed by LC-MS (LC Column: BEH-C18, 2.1100 mm, 1.7 m; Mobile phase: acetonitrile/Ammonium acetate reverse phase, 15 min run time, 0.3 L/min; Ionization: ESI and APCI in positive and negative ion modes; Solvent: dichloromethane), oligomeric molecules due to loss of Me-O-Me and MeOH units were detected. The resin contains mainly low degree of oligomers through SiOSi bond formation such as dimer, trimer, tetramer, pentamer, etc.

Gel Permeation Chromatography

[0117] The resin composition was assessed by Gel permeation chromatography (column set: 3 Polypore columns+guard; detector: RI; column temperature: 35 C.; flow rate 1 ml/min; injection volume: 100 l; run time 45 minutes; number of injections: 2/sample; mobile-phase: THF; standards for calibration: polystyrene (1.1 M-162 Da); instrument: Waters 2695; sample concentration: 5.3 to 6.5 mg/1.5 ml) and the results are summarized in Table 1.

TABLE-US-00001 TABLE 1 Retention Mn Mw Mp Mz Time (min) (Da) (Da) (Da) (Da) Polydispersity Area Silane 28.30 761 881 588 1086 1.2 50.7% oligomer 28.90 426 430 433 434 1.0 25.2% 29.59 257 270 308 281 1.0 47.1% 31.71 119 120 127 121 1.0 5.6% 32.88 83 84 87 85 1.0 6.8% *average molecular weights and distributions relative to polystyrene standards

Viscosity

[0118] Viscosity of the resin was measured in a ThermoScientific Rheostress 1 with ring/plate geometry under inert conditions, and it can be in the range from 24 mPas to 34 mPas.

UV Stability

[0119] Cured material was set in a heated UV radiation chamber (light source: 10 UV-A light tubes (18 W) with an irradiance of 3.15 mW/cm.sup.2 and 10 UV-B light tubes (20 W) with and irradiance of 2.21 mW/cm.sup.2) after 2 months under UV light and at 60 C. no visual changes detectable.

Thermal Stability

[0120] Cured material was subjected to TGA tests (Waters Discovery (2013 series)), degradation of the material was observed at 285-305 C. (roughly 300 C.) in air atmosphere. Thermal desorption tests (column: 30 m RTX-5 ms fused silica capillary, 0.25 mm ID, 0.25 mm film thickness; oven temperature: 50 C. for 2 min, to 300 C. at 10 C./min, hold for 8 min; flow rate: 1 ml/min; injector port temperature: 225 C.; injection: split 1:50; detector: 5973 MSD, electron impact (EI) ionization, 33-800 amu) of the cured material reveal that at 300 C. no volatiles were detected. In pyrolysis studies heating to 800 C. boron-containing volatiles could be detected, but no silicon containing volatiles.

EXAMPLE 2: REDUCTION OF RESPECTIVE MICROORGANISMS IN FILM CONTACT METHOD (DIN-EN-ISO 22196)

[0121] Antibacterial properties of films of the material were tested against Staphylococcus aureus (gram pos. bactericum), Pseudomonas aeruginosa (gram neg. bacterium), Exophilia dermatitidis (black yeast) using the Film-contact method (ISO 22196). This method measures the inactivation/killing of microorganisms (microbiocidal activity) after a certain incubation period. Reduction checked after 24 h and 48 h of contact. For investigations glass substrates coated with cured borolanosilane resin have been used.

TABLE-US-00002 TABLE 2 Antimicrobial activity test S. aureus P. aeruginosa E. dermatitis 24 h 48 h 24 h 48 h 24 h 48 h Siloxane resin 99.99% 99.90% 99.99% 99.99% consisting of constitutional units of formula I Mixture of siloxane 99.99% 99% 99.99% resin consisting of constitutional units of formula I and monomeric boron containing siloxane of formula (YZ).sub.1SiR.sup.1.sub.0X.sub.3O.sub.0