METHOD FOR THE PREPARATION OF ORGANOPOLYSILOXANES HAVING (METH)ACRYLATE FUNCTIONS

Abstract

The invention relates to a method for preparing polyorganosiloxanes functionalized by (meth)acrylate groups, preferably acrylate groups.

Claims

1. A process for preparing a composition X comprising at least one organopolysiloxane A comprising at least one (meth)acrylate group, said process comprising: a) at least one organopolysiloxane B comprising at least one epoxy group is reacted, at a temperature of between 50 and 130 C., optionally between 70 and 130 C. and optionally between 90 and 125 C., with acrylic acid or methacrylic acid or a mixture of the two, in the absence of alcohol and in the presence: of a catalyst C which is a complex of chromium in the oxidation state (III), of at least 4.5% by weight, relative to the total weight of the reaction medium of this step a), of a solvent S and of an inhibitor of polymerization of acrylic acid or of methacrylic acid, b) the reaction medium obtained at the end of step a) is devolatilized and c) said composition X comprising at least one organopolysiloxane A is obtained.

2. The process as claimed in claim 1, wherein, the molar ratio between the acrylic acid and the epoxy group(s) borne by the organopolysiloxane B is greater than 1 and optionally between 1.05 and 1.50, and optionally between 1.02 and 1.20.

3. The process as claimed in claim 1, wherein the content of solvent S used is between 4.5% and 20% by weight, optionally between 4.5% and 15% by weight and optionally between 5% and 15% by weight, relative to the total weight of the reaction medium used in a) of the process.

4. The process as claimed in claim 1, wherein the catalyst C is a complex of chromium in the oxidation state (III), of formula (1) below
[Cr(L.sup.1).sub.3](1) wherein the symbols L.sup.1, which may be identical or different, represent a carboxylate anion.

5. The process as claimed in claim 4, wherein the catalyst C is a carboxylate of chromium in the oxidation state (III), chosen from the group consisting of chromium(III) acrylate, chromium(III) methacrylate, chromium(III) acetate, chromium(III) 2-ethylhexanoate, chromium(III) neodecanoate and mixtures thereof.

6. The process as claimed in claim 1, wherein the organopolysiloxane B comprises siloxyl units (I.1) and (I.2), of formulae below: $\begin{array}{cc}{Y}_a.Math.Z_b^1.Math.{\mathrm{SiO}}_{\frac{4-\left(a+b\right)}{2}}.Math..Math.\mathrm{and}& \left(I.Math.\mathrm{.1}\right)\\ Z_c^2.Math.{\mathrm{SiO}}_{\frac{4-c}{2}}& \left(I.Math.\mathrm{.2}\right)\end{array}$ wherein: a=1 or 2, b=0, 1 or 2 and a+b=1, 2 or 3, c=0, 1, 2 or 3, the symbols Y, which may be identical or different, represent a hydrocarbon-based group comprising an epoxy group and optionally also comprising one or more heteroatoms, such as an oxygen atom, said hydrocarbon-based group Y optionally having from 2 to 20 carbon atoms inclusive, and, optionally, Y is chosen from the group consisting of an alkyl glycidyl ether, a linear, branched or cyclic epoxyalkyl, a linear, branched or cyclic epoxyalkenyl and a carboxylic acid glycidyl ester; the symbols Z.sup.1 and Z.sup.2, which may be identical or different, represent a monovalent hydrocarbon-based group having from 1 to 30 carbon atoms, optionally chosen from the group consisting of alkyl groups having from 1 to 8 carbon atoms and aryl groups having from 6 to 12 carbon atoms, and optionally chosen from the group consisting of a methyl, ethyl, propyl, 3,3,3-trifluoropropyl, xylyl, tolyl and phenyl group; and said organopolysiloxane B comprising, per molecule, at least two silicon atoms and at least one siloxyl unit (I.1).

7. The process as claimed in claim 6, wherein, for the siloxyl unit (I.1), the symbol Y is chosen from the group consisting of the hydrocarbon-based groups (R-1) to (R-6) of formulae below: ##STR00008##

8. The process as claimed in claim 1, wherein the organopolysiloxane B contains from 1% to 60% by weight of hydrocarbon-based groups Y comprising an epoxy group, optionally from 1% to 30% by weight and optionally from 1% to 15% by weight.

9. The process as claimed in claim 1, wherein, in a), the solvent S is chosen from the group consisting of methyl isobutyl ketone, methyl ethyl ketone, toluene, xylene, chlorobenzene and mixtures thereof.

10. The process as claimed in claim 1, wherein, in a), the solvent S is methyl isobutyl ketone.

11. A composition X which can be obtained by means of the process described in claim 1.

12. A process for producing a coating on a substrate, comprising the following: a) a composition X is prepared according to the process of claim 1, b) a radically crosslinkable silicone composition W is prepared, comprising: i. said composition X, ii. a photoinitiator, and iii. optionally at least one additive, c) said composition W is applied to a substrate, and d) said composition W is crosslinked by exposure to radiation.

13. The process as claimed in claim 12, wherein the radiation is ultraviolet light.

14. The process as claimed in claim 12, wherein the crosslinking d) is carried out at a temperature of between 40 and 100 C.

15. The process as claimed in claim 12, wherein the substrate is made of textile, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyethylene terephthalate, polyurethane or nonwoven glass fibers.

16. A substrate comprising at least one coating which can be obtained according to the process as described in claim 12.

Description

EXAMPLES

[0131] 1-Preparation of the Compositions Comprising Organopolysiloxanes Comprising Acrylate Groups

[0132] The following are charged, with stirring, to a 250 ml reactor equipped with magnetic-bar stirring, a reflux condenser, an air inlet and a thermometric sheath: [0133] 130 g of a polydimethylsiloxane oil H functionalized with epoxy groups with a dynamic viscosity at 25 C. of approximately 60 mPa.Math.s. This oil contains hydrocarbon-based groups Y comprising an epoxy group of formula (R-4) below:

##STR00007## [0134] The molar content of epoxy in the oil H is 232 mmol per 100 g, which corresponds to an amount of epoxy groups per molecule of between 2 and 15; [0135] 25 g of acrylic acid, [0136] 0.086 g of chromium(III) acetate, [0137] 0.039 g of methyl ether of hydroquinone (MEHQ), and [0138] variable amounts of solvent (see table 1).

[0139] The stirring is adjusted to 700 rpm, then the reactor is heated at 115 C. with an aluminum hotplate while an air flow of approximately 130 ml/h is maintained. Samples are taken over time in order to measure the degree of conversion (or of transformation) of the epoxy groups by potentiometry. After 3 h 30 of reaction, the mixture is devolatilized under vacuum (gradually up to 1 mbar) while at the same time maintaining bubbling of air in order to evaporate off the acrylic acid which has not been consumed and the reaction solvents. After cooling, the composition obtained is filtered under pressure on a cellulose filter. The acrylate functions are quantitatively determined by .sup.1H NMR.

[0140] The acrylation yield is calculated as the ratio between the number of moles of acrylate quantitatively determined in the composition and the number of moles of epoxy initially introduced, multiplied by 100.

[0141] The acrylation selectivity is equal to the acrylation yield over the degree of conversion of the epoxy groups. The desired objective is to obtain the highest possible selectivity.

[0142] The results are presented in table 1 below.

TABLE-US-00001 MIBK n-Butanol Degree of solvent solvent epoxy Acrylation (% by (% by Reaction conversion Acrylation selectivity Tests weight) weight) medium (%) yield (%) (mol %) Comparative 4.6 5.7 Homogeneous 98.5 93 94.4 1 & clear Comparative 0 0 Heterogeneous 99 96.5 97.5 2 and cloudy Comparative 2 0 Heterogeneous nd nd nd 3 and cloudy Comparative 4 0 Slightly 99.1 97.6 98.5 4 heterogeneous and cloudy Invention 2 7 0 Homogeneous 98.8 98.4 99.6 & clear Invention 3 10 0 Homogeneous 98.5 97.2 98.7 & clear

[0143] These tests shows that the process according to the invention makes it possible to obtain a good yield and a good acrylation selectivity with a homogeneous and clear reaction medium in step a) of the process. The composition obtained after devolatilization is also homogeneous and does not have any unpleasant odor.

[0144] For comparative test 1 in the presence of two solvents (MIBK and n-butanol), the reaction medium is homogeneous and clear, but the acrylation selectivity is less than 95% and the acrylation yield is only 93%. Furthermore, the composition obtained has an unpleasant odor.

[0145] For comparative tests 2, 3 and 4, the reaction medium is cloudy and heterogeneous, which is not desirable for an industrial implementation.

TABLE-US-00002 TABLE 2 MIBK n-Butanol solvent solvent (% by (% by Viscosity Mw Tests weight) weight) mPa .Math. s.sup.1 g/mol Comparative 1 4.6 5.7 570 3790 Comparative 2 0 0 673 4500 Comparative 3 2 0 nd nd Comparative 4 4 0 675 4500 Invention 2 7 0 656 4350 Invention 3 10 0 648 4170

[0146] In order to characterize the compositions obtained during each test, weight-average molecular weight (Mw) was measured by a GPC analysis. It is noted that the compositions obtained during comparative tests 2 and 4 have the highest viscosity and average molecular weight, which may be an indicator of a greater presence of traces of coupling products resulting from the side reaction between an epoxy group and the hydroxyl function of the hydroxyacrylate.

[0147] The tests according to the invention make it possible to obtain the desired compromise, that is to say a process in which the reaction medium is homogeneous and clear, which makes it possible to obtain very good acrylation yields and selectivities while at the same time controlling the coupling side reactions.

[0148] 2-Tests for Preparation of a Non-Stick Coating on a Flexible Support

[0149] 30 g of the compositions comprising acrylate-f unction-comprising polyorganosiloxanes obtained according to the tests above (see tables 1 and 2) and 2 g of a radical photoinitiator which is ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate are added to 70 g of a polydimethylsiloxane oil with acrylate units, sold under the trade name Silcolease UV Poly 110 (viscosity 880 mPA.Math.s and 5.7% by weight of acrylate group).

[0150] Each of these formulations is coated onto an LDPE GLD2 film from the company Granger, with an amount of deposit of between 0.9 and 1.1 g/m.sup.2. The samples of coated film are crosslinked with a UV lamp which has a power of 100 W/cm. The traveling speed of the coated samples under the UV lamp is 200 m/min.

[0151] The quality of the polymerization and the attachment of the coating were evaluated by means of various trade tests.

[0152] The Rub-Off measurement used to verify the adhesion to the support and the abrasion resistance of the silicone layer consists in rubbing the index finger on the siliconized support in order to apply mechanical stresses to the layer. The number of back and forward movements with the finger until the appearance of the rub-off (or scrubbing) phenomenon, corresponding to the silicone coating being torn into shreds, is scored. The score of 1 indicates poor abrasion resistance of the silicone layer and the score of 10 indicates excellent abrasion resistance of the silicone layer. This application test is scored from 1, the poorest, to 10, the best result.

[0153] The samples according to the invention have excellent attachment performances which are much better than comparative 1.