METHOD FOR COATING A FLEXIBLE SUPPORT WITH A SILICONE COMPOSITION

Abstract

The present invention concerns a method for coating a textile material with a silicone elastomer composition crosslinkable by condensation reactions, to produce a solid silicone elastomer, optionally in a thin layer, on a flexible support that can be made from a textile material, paper, polyvinyl chloride, polyester, polypropylene, polyamide, polyethylene, polyurethane, non-woven glass fibre fabric or polyethylene terephthalate.

Claims

1. A process for coating a liquid silicone composition that is crosslinkable via condensation reaction to form a solid silicone elastomer on a flexible support, comprising a), b) and c) below: a) a liquid silicone composition that is crosslinkable via condensation reactions is prepared, comprising: at least one organosilicon compound comprising at least two identical or different hydrolyzable and condensable groups, or at least two silanol functions SiOH, at least one crosslinking agent, optionally at least one filler, and a catalytically effective amount of at least one catalyst which is a magnesium complex comprising in a structure thereof, two identical or different carboxylate ligands, comprising from 10 to 32 carbon atoms, b) on a flexible support, which may optionally be pre-covered on one or two faces with one or more layers of a polymer material, said silicone composition is deposited continuously or discontinuously onto one face of said flexible support or optionally onto the two faces of said flexible support, and c) said silicone composition is left to crosslink in the presence of humidity provided by ambient air or by exposure to water vapor, or by prior addition of water to said silicone composition so as to form a crosslinked solid silicone elastomer.

2. The process as claimed in claim 1, in which, in b), a sufficient amount of said silicone composition is deposited so as to form either a bead or a continuous layer on said flexible support.

3. The process as claimed in claim 1, in which, in c), said silicone composition is left to crosslink in the presence of humidity provided by ambient air or by exposure to water vapor, or by prior addition of water to said silicone composition at a temperature of between 20 and 90 C., optionally between 40 and 90 C., and optionally between 50 and 90 C.

4. The process as claimed in claim 1, wherein catalyst is a complex of formula (1) below:
[Mg(C.sup.1).sub.x(C.sup.2).sub.y] (1) in which: the symbols C.sup.1 and C.sup.2 are identical or different ligands chosen from the group of carboxylates comprising from 10 to 32 carbon atoms, optionally from 10 to 20 carbon atoms and from 10 to 15 carbon atoms, the symbols x and y represent the number of carboxylate ligands and are integers equal to 0, 1 or 2 with the condition that the sum x+y=2.

5. The process as claimed in claim 1, wherein the catalyst is a complex of formula (2) below:
[Mg(C.sup.1).sub.2] (2) in which: the symbol C.sup.1 is a ligand chosen from the group of carboxylates comprising from 10 to 32 carbon atoms, optionally from 10 to 20 carbon atoms and optionally from 10 to 15 carbon atoms.

6. The process as claimed in claim 1, wherein the carboxylate ligands are chosen from the group formed by: the anions: decanoate [CH.sub.3(CH.sub.2).sub.8COO].sup., undecanoate [CH.sub.3(CH.sub.2).sub.9COO].sup., dodecanoate or laurate [CH.sub.3(CH.sub.2).sub.10COO].sup., tridecanoate [CH.sub.3(CH.sub.2).sub.11COO].sup., tetradecanoate or myristate [CH.sub.3(CH.sub.2).sub.12COO].sup., pentadecanoate [CH.sub.3(CH.sub.2).sub.13COO].sup., hexadecanoate or palmitate [CH.sub.3(CH.sub.2).sub.14COO].sup., heptadecanoate [CH.sub.3(CH.sub.2).sub.15COO].sup., octadecanoate or stearate [CH.sub.3(CH.sub.2).sub.16COO].sup., nonadecanoate [CH.sub.3(CH.sub.2).sub.17COO].sup., eicosanoate [CH.sub.3(CH.sub.2).sub.18COO].sup., heneicosanoate [CH.sub.3(CH.sub.2).sub.19COO].sup., docosanoate or behenate [CH.sub.3(CH.sub.2).sub.20COO].sup., tricosanoate [CH.sub.3(CH.sub.2).sub.21COO].sup., tetracosanoate or lignocerate [CH.sub.3(CH.sub.2).sub.22COO].sup., pentacosanoate [CH.sub.3(CH.sub.2).sub.23COO].sup., hexacosanoate [CH.sub.3(CH.sub.2).sub.24COO].sup., heptacosanoate acid [CH.sub.3(CH.sub.2).sub.25COO].sup., octacosanoate [CH.sub.3(CH.sub.2).sub.26COO].sup., nonacosanoate [CH.sub.3(CH.sub.2).sub.27COO].sup., triacontanoate [CH.sub.3(CH.sub.2).sub.28COO].sup., hentriacontanoate [CH.sub.3(CH.sub.2).sub.29COO].sup., dotriacontanoate [CH.sub.3(CH.sub.2).sub.30COO].sup., palmitoleate [CH.sub.3(CH.sub.2).sub.5CHCH(CH.sub.2).sub.7COO].sup., oleate [CH.sub.3(CH.sub.2).sub.7CHCH(CH.sub.2).sub.7COO].sup., linoleate [CH.sub.3(CH.sub.2).sub.4(CHCHCH.sub.2).sub.2(CH.sub.2).sub.6COO].sup., linolenate [CH.sub.3CH.sub.2(CHCHCH.sub.2).sub.3(CH.sub.2).sub.6COO].sup. and arachidonate [CH.sub.3(CH.sub.2).sub.4(CHCHCH.sub.2).sub.4(CH.sub.2).sub.2COO].sup., the anions: 7,7-dimethyloctanoate [(CH.sub.3).sub.3C(CH.sub.2).sub.5COO].sup., 2,2-dimethyloctanoate [CH.sub.3(CH.sub.2).sub.5C(CH.sub.3).sub.2COO].sup., 2,2,3,5-tetramethylhexanoate [(CH.sub.3).sub.2CHCH.sub.2CH(CH.sub.3)C(CH.sub.3).sub.2COO].sup., 2,5-dimethyl-2-ethylhexanoate [(CH.sub.3).sub.2CH(CH.sub.2).sub.2C(CH.sub.3)(C.sub.2H.sub.5)COO].sup., 2,2-diethylhexanoate [CH.sub.3(CH.sub.2).sub.3C(C.sub.2H.sub.5).sub.2COO].sup., 2,4-dimethyl-2-isopropylpentanoate [(CH.sub.3).sub.2CHCH.sub.2C(CH.sub.3)(i-propyl)-COO].sup., and C.sub.10 to C.sub.20 and optionally C.sub.10 to C.sub.15 naphthenate anions.

7. The process as claimed in claim 1, wherein the carboxylate ligands are chosen from the group formed by carboxylates of empirical formula [C.sub.10H.sub.19O.sub.2].sup. and C.sub.10 to C.sub.20 and optionally C.sub.10 to C.sub.15 naphthenates.

8. The process as claimed in claim 1, wherein the catalyst (M) is the [Mg(neodecanoate).sub.2] complex or the [Mg(naphthenate).sub.2] complex with the naphthenate anion having a C.sub.10 to C.sub.20 and optionally C.sub.10 to C.sub.15 chemical structure.

9. The process as claimed in claim 1, in which the organosilicon compound is a polyorganosiloxane comprising: (i) at least two siloxyl units of formula (3) below: $\begin{array}{cc}{R}_a^1.Math.Z_b.Math.{\mathrm{SiO}}_{\left(\frac{4-\left(a+b\right)}{2}\right)}& \left(3\right)\end{array}$ in which: the symbols R.sup.1, which may be identical or different, represent C.sub.1 to C.sub.30 monovalent hydrocarbon-based radicals, the symbols Z, which may be identical or different, each represent a hydrolyzable and condensable group or a hydroxyl group and are optionally chosen from the group formed by groups optionally: hydroxyl, alkoxy, alkoxy-alkylene-oxy, amino, amido, acylamino, aminoxy, iminoxy, ketimonoxy, acyloxy, iminoxi, ketiminoxy and enoxy, a is equal to 0, 1 or 2, b is equal to 1, 2 or 3, the sum a+b is equal to 1, 2 or 3, and optionally (ii) one or more siloxyl units of formula (4) below: $\begin{array}{cc}{R}_c.Math.{\mathrm{SiO}}_{\left(\frac{4-c}{2}\right)}& \left(4\right)\end{array}$ in which: the symbols R, which may be identical or different, represent C.sub.1 to C.sub.30 monovalent hydrocarbon-based radicals optionally substituted with one or more halogen atoms or with groups from among: amino, ether, ester, epoxy, mercapto or cyano, and the symbol c is equal to 0, 1, 2 or 3.

10. The process as claimed in claim 1, in which the crosslinking agent B is optionally a silicon compound in which each molecule comprises at least three hydrolyzable and condensable groups and said crosslinking agent having formula (5) below:
R.sub.(4-a)SiY.sub.a (5) in which: the symbol R is a monovalent hydrocarbon-based radical comprising from 1 to 30 carbon atoms, the symbol Y is an alkoxy, alkoxy-alkylene-oxy, amino, amido, acylamino, aminoxy, iminoxy, ketiminoxy, acyloxy and enoxy group and optionally Y is an alkoxy, acyloxy, enoxy, ketiminoxy or oxime group, and the symbol a=3 or 4.

11. The process as claimed in claim 1, wherein the crosslinkable liquid silicone composition does not contain any catalyst having in a structure thereof, at least one tin atom.

12. The process as claimed in claim 1, wherein, in b), said silicone composition is deposited onto a flexible support which is a textile by transfer, by dip roll or by spraying using a nozzle, a doctor blade, a rotating frame or a reverse roll.

13. The process as claimed in claim 1, wherein the flexible support is a textile and optionally a lace or an elastic band.

14. A flexible support coated on one or two faces continuously or discontinuously with a solid silicone elastomer that may be obtained via the process as defined according claim 1.

15. A composite material comprising: a flexible support which may optionally be covered on one or two faces with one or more layers of a polymer material, and a coat on said flexible support or on said polymer material, formed by a solid silicone elastomer obtained according to the process as defined according to claim 1.

16. A liquid silicone composition that is crosslinkable via a condensation reaction of a process as defined according to claim 1, for coating a flexible support.

17. A catalyst, for obtaining transparent or translucent solid silicone elastomers comprising a magnesium complex comprising in a structure thereof, two identical or different carboxylate ligands, comprising from 10 to 32 carbon atoms.

18. A liquid silicone composition that is crosslinkable via condensation reaction, of a process as defined according to claim 1.

19. A solid silicone elastomer obtained by crosslinking in the presence of humidity provided by ambient air of a composition as described according to claim 18.

20. A one-pack RTV-1 composition which is in a single airtight pack and comprising a composition comprising a) a liquid silicone composition that is crosslinkable via condensation reactions is prepared, comprising: at least one organosilicon compound comprising at least two identical or different hydrolyzable and condensable groups, or at least two silanol functions SiOH, at least one crosslinking agent, optionally at least one filler, and a catalytically effective amount of at least one catalyst which is a magnesium complex comprising in a structure thereof, two identical or different carboxylate ligands, comprising from 10 to 32 carbon atoms.

21. A two-pack RTV-2 composition, which is a precursor of composition comprising a) a liquid silicone composition that is crosslinkable via condensation reactions is prepared, comprising: at least one organosilicon compound comprising at least two identical or different hydrolyzable and condensable groups, or at least two silanol functions SiOH, at least one crosslinking agent, optionally at least one filler, and a catalytically effective amount of at least one catalyst which is a magnesium complex comprising in a structure thereof, two identical or different carboxylate ligands, comprising from 10 to 32 carbon atoms said two-pack RTV-2 composition being in two distinct packs P1 and P2, wherein: a) pack P1 is airtight and comprises: a catalytically effective amount of at least one catalyst (M) which is a magnesium complex comprising in its structure two identical or different carboxylate ligands, comprising from 10 to 32 carbon atoms, and at least one crosslinking agent (B), and b) pack P2 does not contain either said catalyst (M) or said crosslinking agent (B) and comprises: per 100 parts by weight of at least one organosilicon compound (A) comprising at least two identical or different hydrolyzable and condensable groups, or at least two silanol functions SiOH, and from 0 to 10 parts by weight of water.

Description

EXAMPLES

Example 1

Preparation or Origin of the Catalysts

[0205] a) Catalyst (I-1): Magnesium Bis-Neodecanoate [(Mg(ND) 2)]

[0206] CAS No.: 57453-97-1; ND=neodecanoate anion.

[0207] Mg(OEt).sub.2+2 mol of neodecanoic acid+toluene.fwdarw.[Mg(ND).sub.2]+2 EtOH

[0208] 31.41 g of magnesium ethoxide (0.274 mol) and 150 ml of toluene are placed in a 500 ml round-bottomed flask.

[0209] Two equivalents of neodecanoic acid (94.92 g) are added. The heterogeneous mixture is stirred at a temperature of 20 C. until the grains of magnesium ethoxide have disappeared. The solution is then heated to 125 C. to distill off the toluene-ethanol azeotrope, i.e. for 2 hours. The solution obtained after cooling is filtered through a No. 3 sinter, concentrated again to obtain 200 g of solution containing 50% by weight of magnesium neodecanoate, which is clear and pale yellow to orange (quantitative yield).

[0210] b) Catalyst (I-2): Magnesium Bis-Naphthenate [Mg (Naphthenate).sub.2]

[0211] Mg(OEt).sub.2+2 mol of naphthenic acid (C.sub.14-C.sub.15)+toluene.fwdarw.[Mg(naphthenate).sub.2]+2 EtOH

[0212] 6.96 g of magnesium ethoxide (60.5 mmol) and 30 ml of toluene are placed in a 100 ml round-bottomed flask. Two equivalents of aliphatic naphthenic acid (mixture of C.sub.14-C.sub.15 alkylcyclopentane) with a mean molecular mass of 236.8 g/mol (28.65 g) are added in a single portion. The heterogeneous mixture is stirred at a temperature of 20 C. until the last grains of magnesium ethoxide have disappeared. The solution is then heated to 125 C. to distill off the toluene-ethanol azeotrope, i.e. for 2 hours. The solution obtained after cooling is filtered through a No. 3 sinter and concentrated again to obtain 60 g of a solution containing 50% by weight of magnesium naphthenate of red color (quantitative yield).

[0213] c) Catalyst (C-1) Magnesium Bis-2-ethylhexanoate [Mg(2-ethylhexanoate).sub.2]

[0214] CAS No.: 15602-15-0

[0215] Mg(OEt).sub.2+2 2-ethylhexanoic acid+toluene.fwdarw.[Mg(2-ethylhexanoate).sub.2]+2 EtOH

[0216] 11.114 g of magnesium ethoxide (96.5 mmol) and 30 ml of toluene are placed in a 100 ml round-bottomed flask. Two equivalents of 2-ethylhexanoic acid (28.13 g) are added in a single portion. The heterogeneous mixture is stirred at a temperature of 20 C. until the last grains of magnesium ethoxide have disappeared. The solution is then heated to 125 C. to distill off the toluene-ethanol azeotrope, i.e. for 2 hours. The solution obtained after cooling is filtered through a No. 3 sinter and concentrated again to obtain 60 g of a solution containing 50% by weight of magnesium 2-ethylhexanoate and is rediluted to 40% (total 75 g) to give a clear orange oil.

[0217] d) Catalyst (C-2) Calcium Bis-Neodecanoate [Ca(ND).sub.2]

[0218] CAS No.: 27253-33-4-ND=neodecanoate anion Ca(OMe).sub.2+2 neodecanoic acid+toluene.fwdarw.[Ca(ND).sub.2]+2 MeOH

[0219] 4.8 g of 97% calcium methoxide (47 mmol) and 25 ml of toluene are placed in a 100 ml round-bottomed flask. Two equivalents of neodecanoic acid (16.28 g) are added over 20 minutes. The heterogeneous mixture is stirred at a temperature of 20 C. until the last grains of calcium methoxide have disappeared. The solution is then heated to 100 C. to distill off the toluene-methanol azeotrope, i.e. for 2 hours. The solution obtained after cooling is filtered through a No. 3 sinter and then diluted with toluene to obtain a solution containing 30% by weight of calcium neodecanoate (60 g) that is virtually colorless and clear.

[0220] e) Catalyst (C-3) Lithium Neodecanoate [Li(ND)]

[0221] CAS No.: 27253-30-1 ND=neodecanoate anion

[0222] LiOH.H.sub.2O+MeOH/EtOH=neodecanoic acid.fwdarw.LiND 6.09 g of lithium hydroxide hydrate (145.1 mmol) and 90 ml of methanol are placed in a 250 ml round-bottomed flask, and 25 g of neodecanoic acid (145.1 mmol) diluted in 80 ml of ethanol are then added to the suspension obtained. After stirring for 1 hour, the milky solution is filtered and then evaporated to dryness to give a white solid as a foam. This is dissolved with the same mass of ethanol (25.8 g) to give a clear solution at 50% by weight of lithium neodecanoate.

[0223] f) Catalyst (C-4): Strontium bis(2-ethylhexanoate)-[Sr(Oct).sub.2]

[0224] CAS No.: 2457-02-5, Oct=bis(2-ethylhexanoate) anion; Sold by the company ABCR GmbH 7 Co. KG.

[0225] g) Catalyst (C-5): Zinc Neodecanoate [Zn(Nd).sub.2]

[0226] ND=neodecanoate anion; sold by the company Shepherd Chemical Company.

[0227] h) Catalyst (C-6): tetra-n-butyl titanate [Ti(O-butyl).sub.4]

[0228] CAS No.: 5593-70-4; Tyzor TnBT sold by the company Dorf Ketal Specialty Catalyst LLC.

[0229] i) Catalyst (C-7): dioctyltin dilaurate (DOctSnDL) Metatin 812 sold by the company ACIMA.

Example 2

Preparation of the Liquid Silicone Compositions that are Crosslinkable Via Condensation Reactions

[0230] 40 g of a slurry constituted by: [0231] 74% by weight of an ,(dimethyl)hydroxysilyl polydimethylsiloxane oil with a dynamic viscosity at 25 C. of 50 000 mPa.Math.s, [0232] 6.2% by weight of an ,dimethyl)hydroxysilyl polydimethylsiloxane oil with a dynamic viscosity at 25 C. of 14 000 mPa.Math.s, [0233] 6.4% by weight of a silica Aerosil200 (BET specific surface area=200 m.sup.2/g) which has been surface-treated with hexamethyldisilazane, [0234] 3.9% by weight of a silica Aerosil200 (BET specific surface area=200 m.sup.2/g), and [0235] 9.5% by weight of a polydimethylsiloxane oil with a dynamic viscosity at 25 C. of 500 mPa.Math.s,

[0236] are placed in a 185 ml plastic jar.

[0237] 1.62 g of a crosslinking agent XL1 sold by the company Nitrochemie (mixture of methyltriacetoxysilane and ethyltriacetoxysilane) are then added. The mixture is stirred with a Speed Mixer (DAC 150 FV from the company Hauschild) for 25 seconds and at a spin speed of 1800 rpm. An amount, expressed as a weight percentage relative to the total weight of the composition, of test catalyst (pure or in an organic solvent) is then added, followed by mixing using a speed mixer for 25 seconds at 1800 rpm, before conditioning the final mixture in a leaktight cartridge.

[0238] For the transparency measurements, the compositions are also debubbled in the following manner: the jar containing the silicone composition is placed under a bell jar, the lid is removed and a negative pressure of about 0.09 MPa is then gradually applied for about 5 min; the system is then returned to ambient pressure. This operation is repeated once or twice so as to remove all the bubbles in the compositions to be evaluated after coating and crosslinking on a flexible support.

Example 3

Coating on a Flexible Support of Lace Type

[0239] 3.1) Coating Process

[0240] A polyamide and elastane lace is attached to a wooden support allowing it to be pulled slightly taut, and a metal plate is placed under the lace. The test silicone composition prepared according to Example 2 is spread on a support (lace made of polyamide and elastane) in the form of two uniform strips, which are formed by passing over them a doctor blade or a metal film drawer in the form of two strips 1 cm wide. After having removed the metal plate, crosslinking is performed in a climatic chamber (Weiss type), optionally after preliminary treatment (for 15 seconds) in a pressure cooker that generates water vapor. After crosslinking the thickness of the solid silicone elastomer coat is between 0.25 and 0.60 mm (checked by means of a micrometer or Palmer). The blocking results for the various test catalysts are given in tables 1 to 10 below.

[0241] 3.2) Results

[0242] 3.2.1) Measurement of the Blocking:

[0243] On exiting the oven or the climatic chamber, the coated fabric is folded on itself so as to produce silicone-against-silicone bonding over a length of at least 13 cm (the width is controlled by the width of the doctor blade and the thickness of the coating is controlled with a comparator or Palmer). Unless otherwise mentioned, this measurement is performed by peeling with a tensile testing machine on a lace (made of polyamide and elastane) coated with two silicone strips 1 cm wide and folded on itself immediately on exiting the oven, and after application of a 600 g weight for 24 hours or 300 g for 48 hours. The coating thickness is generally between 0.25 and 0.60 mm. The blocking force is then measured by peeling with a Zwick tensile testing machine, which gives the value of the peel force (expressed in the tables in N for a 2 cm peel front). The peeling speed is 100 mm/min. The maximum value of the force required for detachment (Fmax, unit N) and the mean of the five highest values are measured (referred to as blocking, unit N). The lower the values, the less the blocking phenomenon is present.

TABLE-US-00001 TABLE 1 Measurement of the blocking obtained - catalyst (I-1) added in a diluted form (content of 40% by weight) in neodecanoic acid - coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (I-1) Thickness of [Mg(ND).sub.2] Number of the solid Weight % mmol of silicone coat relative to catalyst after the total (I-1) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Inv-1 0.36 0.98 mmol 0.39-0.53 2.0 2.2 Inv-2 0.29 0.79 mmol 0.23-0.47 1.6 1.8 Inv-3 0.26 0.71 mmol 0.30-0.63 1.3 1.4 Inv-4 0.24 0.65 mmol 0.42-0.63 1.0 1.3

[0244] The results regarding the blocking are suitable for the application.

TABLE-US-00002 TABLE 2 Study of the accelerated aging of composition Inv-2, stored beforehand in a leaktight cartridge (RTV-1) at 40 C. for 30 or 60 days. Followed by coating according to paragraph 3.1) and crosslinking for 10 min in a climatic chamber regulated at 80 C. and 20% RH. Thickness of the solid Aging time at 40 C. silicone coat after leaktight cartridge crosslinking Blocking Fmax (days) min-max (mm) (N) (N) 0 0.32-0.43 1.6 1.8 30 0.30-0.50 1.7 1.8 60 0.41-0.54 1.9 2.4

[0245] The composition Inv-2 according to the invention, containing the catalyst (I-1) ([Mg(ND).sub.2]), has good aging properties since no increase in blocking is observed for a composition stored in a leaktight cartridge.

[0246] The compositions according to the invention may be conditioned in RTV-1 form (airtight pack) and stored without degrading the properties of the elastomer obtained after coating (absence of blocking).

TABLE-US-00003 TABLE 3 Measurement of the blocking obtained with a composition comprising catalyst (I-2) [Mg(naphthenate).sub.2] added in a diluted form (content 50% by weight) in toluene - coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (I-1) Thickness of [Mg(naphthenate).sub.2] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (I-2) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Inv-5 0.50 1 mmol 0.41-0.56 1.36 2.88

[0247] The results regarding the blocking are appropriate for the application.

TABLE-US-00004 TABLE 4 Measurement of the blocking obtained with the catalyst (C-1) magnesium bis-2-ethylhexanoate [Mg(2-ethylhexanoate).sub.2] added in a diluted form (content 40% by weight) in toluene - coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-1) [Mg(2-ethyl- Thickness of hexanoate).sub.2] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (C-1) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Comp-1 0.40 1.25 mmol 0.30-0.47 7.4 8.3 Comp-2 0.35 1.12 mmol 0.26-0.42 8.1 9.4 Comp-3 0.30 0.97 mmol 0.36-0.67 25.3 29.1 Comp-4 0.26 0.83 mmol 0.29-0.39 20.5 29.1

[0248] The blocking values observed for catalyst (C-1) (magnesium bis-2-ethylhexanoate, [Mg(2-ethylhexanoate).sub.2]) are not satisfactory for the application (excessively high blocking).

TABLE-US-00005 TABLE 5 Measurement of the blocking observed with catalyst (C-2) calcium bis-neodecanoate [Ca(ND).sub.2] - Coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-2) Thickness of [Ca(ND).sub.2] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (C-2) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Comp-5 2.50 6.60 mmol 0.31-0.40 17.3 18.6 Comp-6 1.75 4.57 mmol 0.35-0.54 28.5 30.0 Comp-7 1.44 3.77 mmol 0.25-0.36 27.0 28.3

[0249] It was necessary to add amounts >2% by weight of [Ca(ND).sub.2] relative to the total weight of the composition in order to obtain crosslinking. The blocking values observed for catalyst (C-2) (calcium bis-neodecanoate [Ca(ND).sub.2]) are not satisfactory for the application (excessively high blocking).

TABLE-US-00006 TABLE 6 Measurement of the blocking obtained with catalyst (C-3) lithium neodecanoate [Li(ND)] - Coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-3) Thickness of [Li(ND)] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (C-3) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Comp-8 1.40 3.92 mmol 0.34-0.42 23.2 26.3 Comp-9 0.70 1.96 mmol 0.28-0.36 10.0 11.6

[0250] The blocking values observed for catalyst (C-3) lithium neodecanoate [Li(ND)] are not satisfactory for the application (excessively high blocking).

TABLE-US-00007 TABLE 7 Measurement of the blocking obtained with catalyst (C-4): strontium bis(2-ethylhexanoate)-[Sr(Oct).sub.2] - Coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-4) Thickness of [Sr(Oct).sub.2] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (C-4) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Comp-10 0.48 1.28 mmol 0.36-0.47 29.5 32.7 Comp-11 0.28 0.75 mmol 0.39-0.46 28.7 29.7

[0251] The blocking values observed for catalyst (C-4): strontium bis(2-ethylhexanoate)-[Sr(Oct).sub.2] are not satisfactory for the application (excessively high blocking).

TABLE-US-00008 TABLE 8 Measurement of the blocking obtained with catalyst (C-5): Zinc neodecanoate [Zn(ND).sub.2] - Coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-5) Thickness of [Zn(ND).sub.2] Number of the solid Weight % mmol of silicone relative to catalyst coat after the total (C-5) per crosslinking weight of the 100 g of min-max Blocking Compositions composition composition (mm) (N) Fmax (N) Comp-12 1.25 3.06 mmol 0.44-0.57 4.1 5 Comp-13 0.62 1.52 mmol 0.35-0.49 8.5 9.3

[0252] The blocking values observed for catalyst (C-5) (zinc neodecanoate [Zn(ND).sub.2]) are not satisfactory for the application (excessively high blocking).

TABLE-US-00009 TABLE 9 Measurement of the blocking obtained with catalyst (C-6): tetra-n-butyl titanate [Ti(O-butyl).sub.4]. Catalyst (C-6) Thickness of the [Ti(O-butyl).sub.4] solid silicone Weight % relative to coat after the total weight of crosslinking min-max Blocking Compositions the composition (mm) (N) Fmax (N) Comp-14 0.019 0.35-0.53 17.3 18.6 Comp-15 0.029 0.32-0.43 16.5 20.16 Comp-16 0.015 0.34-0.43 21.6 23.0 Comp-17 0.010 0.40-0.49 21.5 24.05

[0253] For composition Comp-14: coating crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). However, at this level of humidity, the coating becomes too opaque.

[0254] For compositions Comp-15, Comp-16 and Comp-17: coating crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 10% relative humidity (RH).

[0255] The blocking values observed for catalyst (C-6): tetra-n-butyl titanate [Ti(O-butyl).sub.4] are not satisfactory for the application (excessively high blocking)

TABLE-US-00010 TABLE 10 Measurement of the blocking obtained with catalyst (C-7): Dioctyltin dilaurate (DOTDL) - Coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Catalyst (C-7) Thickness of the (DOTDL) solid silicone Weight % relative to coat after the total weight of crosslinking min-max Blocking Compositions the composition (mm) (N) Fmax (N) Comp-18 0.063 0.42-0.47 2.1 2.7

[0256] 3.2.2) Transparency Measurement:

[0257] The silicone composition to be tested is coated, according to the procedure described in Example 3 paragraph 3.1, on a Terphane transparent film (flexible support made of polyethylene glycol terephthalate) and crosslinked under controlled thickness, time, temperature and relative humidity conditions (crosslinking 10 min in humid chamber, temperature=80 C. and 20% relative humidity). The level of optical transmission is then characterized by means of a UV/visible spectrophotometer (Evolution 201 from the company ThermoScientific), at a wavelength of 500 nm. Unless otherwise mentioned, the thickness of the silicone coating for the transparency measurements is adjusted to 0.3 mm. It should be noted that at this wavelength, the Terphane film alone (without any solid silicone coat) has a transparency of 76%. The results are collated in Table 11 below.

TABLE-US-00011 TABLE 11 Transparency measurement - On Terphane film, coatings crosslinked in a climatic chamber for 10 min at 80 C. and regulated at 20% relative humidity (RH). Concentration Transparency Compositions Test catalyst (%) (%) Inv-6 (I-1) [Mg(ND).sub.2] 0.42 68 Comp-19 (C-5) [Zn(ND).sub.2] 1.20 54 Comp-20 (C-6) [Ti(O- 0.02 49 butyl).sub.4] Comp-21 (C-7) DOTDL 0.06 70

[0258] When catalyst (I-1), which is magnesium neodecanoate [Mg(ND).sub.2], is used according to the invention, films whose transparency is very similar to that obtained with a tin-based catalyst are obtained (composition Comp-21).

Example 4

Measurement of the Physical Properties after Crosslinking at Room Temperature (23 C.)

[0259] 4.1) Preparation of the Compositions

[0260] The following are placed in a blender: [0261] 100 g of an , dihydroxylated polydimethylsiloxane oil of viscosity 50 000 mPa.Math.s, [0262] dispersion of 6.2 g (i.e. 5.6%) of a fumed silica of Aerosil type, surface-treated with octamethyltetrasiloxane (D4) (specific surface area via the BET process of 300 m.sup.2/g), and [0263] 4.5 g (i.e. 4.1%) of crosslinking agent XL1, sold by the company Nitrochemie and constituted by a mixture of methyltriacetoxysilane and ethyltriacetoxysilane.

[0264] Next, intimate mixing is performed by blending for about 1 minute with a Speedmixer (from the company Hauschild). The amount of catalyst to be tested (expressed as a weight percentage relative to the total weight of the composition) is then added, dispersed with a spatula and stirred for about 1 minute with a Speedmixer. This operation is followed by debubbling of the composition by placing under vacuum for about 5 minutes, followed by conditioning in an airtight cartridge (one-pack RTV-1).

[0265] 4.2) Crosslinking at Room Temperature (23 C.)

[0266] Films 2 mm thick are spread with a doctor blade allowing the thickness to be controlled, and the silicone composition is left to crosslink in a conditioned room at 23 C. and 50% relative humidity.

[0267] The following are measured:

[0268] a) the skin formation time (SFT): time after which surface crosslinking is observed, and

[0269] b) the hardness (Shore A): this reflects formation of the three-dimensional network.

TABLE-US-00012 TABLE 12 Properties of solid silicone elastomer It is observed that magnesium neodecanoate (I-1) is more reactive (+30%) than C.sub.8 strontium carboxylate (C- 4) and makes it possible to obtain improved properties of hardness at 24 hours. Hardness after 24 hours of crosslinking Catalyst Catalyst dose (%) SFT (minutes) (Shore A) (I-1) 0.84 10.5 17 [Mg(ND).sub.2] (C-4) 0.86 13 15.6 [Sr(Oct).sub.2] (C-7) 0.06 6.5 20.7 DOTDL