FR2910499A1 - Preparing fibrous support coated on one/both sides by reinforced elastomeric silicone layer, comprises forming silicone composition, applying composition on sides of support and crosslinking, by heating/electromagnetic radiation of deposit - Google Patents

Abstract

Preparing a woven, knitted or non-woven fibrous support coated on one or both sides by a reinforced elastomeric silicone layer comprises: preparing a silicone composition for crosslinkable coating (A) comprising organopolysiloxane for 100 parts by weight, a reinforcement constituted of polyamide microfibers; applying (A) on one or two sides of the woven, knitted or non-woven fibrous support; and crosslinking, preferably by heating or electromagnetic radiation of the deposit formed in applying step to form at least one reinforced elastomeric silicone layer. Preparing a woven, knitted or non-woven fibrous support coated on one or both sides by a reinforced elastomeric silicone layer comprises: preparing a silicone composition for crosslinkable coating (A) comprising organopolysiloxane of 0.5-15 parts by weight, preferably 2-6 parts by weight for 100 parts by weight, a reinforcement constituted of polyamide microfibers comprising a titre of 0.1-15 dtex, preferably 0.5-2.5 dtex, and length of 0.1-10 mm, preferably 0.2-5 mm; applying 20 g/m 2> of (A), preferably 100 g/m 2> on one or two sides of the woven, knitted or non-woven fibrous support; and crosslinking, preferably by heating or electromagnetic radiation of the deposit formed in applying step to form at least one reinforced elastomeric silicone layer, where the polyamide is nylon 6, polyamide 6.6, polyamide 4, polyamide 11, polyamide 12, polyamides 4-6, 6-10, 6-12, 6-36, 12-12 and their copolymers and mixtures. An independent claim is included for a woven, knitted or non-woven fibrous support coated on one or both sides, which is obtained by implementing the above process.

Description

Process for preparing woven, knitted or nonwoven fibrous support

  coated on one or both sides by at least one reinforced elastomeric silicone layer.

  The general field of the invention is that of the coating of silicone compositions that can be cold vulcanized (but whose vulcanization is generally accelerated by heat), in particular those of the two-component type (EVF 11), crosslinking by hydrosilylation or polyaddition. to produce an elastomeric coating. These coatings are suitable, for example for the protection or mechanical reinforcement of different substrates, in particular textile material such as fibrous, woven, knitted or non-woven supports. Silicone elastomer coatings on textile substrates provide some of the intrinsic characteristics of silicones to the resulting composites. According to the applications, for example, a search is made for: a thermal protection associated with a mechanical reinforcement in the case of airbag fabrics without weighing down the resulting part, a mechanical function coupled with an anti-fouling character for the complexes intended for textile architecture, and / or - a character of pronounced mechanical strength for the conveyor belts. Silicones do not always have all the characteristics in question and it is often a question of settling compromises. Thus in the case of textile architecture, the silicones do not make it possible to satisfy the antisoiling character and they must be covered by a hard varnish; this varnish deposited on a soft substrate tends to fragment during mechanical stresses and it does not reveal its full potential.

  In these circumstances, one of the essential objectives of the present invention is to provide a method for preparing a woven, knitted, or nonwoven fibrous support coated on one or both sides with at least one reinforced elastomeric silicone layer.

  The Applicant has found, quite fortuitously and surprisingly: a) that the mechanical properties of the silicone crosslinkings can be optimized on a woven, knitted or non-woven fibrous support, in particular to increase their stiffness without penalizing their elongation capacity by adding short microfibers in their formulation, b) this operation is not done to the detriment of the density of the resulting elastomer, and c) that such compositions are thin-film-enducible on the textile substrates concerned.

These objects, among others, are achieved by the invention which relates to a process for preparing a woven, knitted, or non-woven fibrous support coated on one or both sides with at least one reinforced elastomeric silicone layer comprising the following steps: ) the preparation of a crosslinkable silicone coating composition (A) characterized in that it comprises, per 100 parts by weight of organopolysiloxane: from 0.5 to 15 parts by weight, preferably from 0.5 to 15 parts by weight, 10 parts by weight and even more preferably 2 to 6 parts by weight, of a reinforcement consisting of polyamide microfibers which have: a title of between 0.1 and 15 dtex, preferably between 0.1 and 10 dtex and more preferably between 0.5 and 2.5 dtex, and - a length of between 0.1 and 10 mm, preferably between 0.1 and 6 mm and even more preferably between 0.2 and 5 mm, and said polyamide is chosen from the group consisting of: polyamide 6 , polyamide 6.6, polyamide 4, polyamide 11, polyamide 12, polyamides 4-6, 6-10, 6-12, 6-36, 12-12, their copolymers and mixtures, b) the application of at least 20 g / m 2, preferably at least 40 g / m 2 and even more preferably at least 100 g / m 2, on one or both sides of a woven, knitted or non-woven fibrous support of the silicone composition coating (A) prepared in step a), and c) the crosslinking, in particular by heating or by electromagnetic radiation, of the deposit formed in step b) to form at least one reinforced elastomeric silicone layer.

Thus, the polyamide microfibers according to the invention are obtained by cutting yarns, filaments or cables using a cutting technique known to those skilled in the art, for example by means of a guillotine or a knife wheel. Cable means a large set of continuous filaments made without torsion, assembled in a form similar to a loose rope and held together. A cable is generally obtained by melt spinning filaments, gathering and stretching these filaments.

The microfibres according to the invention are manufactured according to the conventional methods known to those skilled in the art and for example by extrusion of the molten polyacid material through a die and then optionally stretching the son, ribbons, cables or plies, and then cutting of these microfiber products.

Furthermore, any step, conventional in the field of the manufacture of textile microfibers, intended for example to dimensionally stabilize the fibers (heat setting) or to give them volume through a compression box (crimping), can be applied. Any other microfiber manufacturing process is also suitable. The microfibers usable in the present invention may have sections of any shape, be they round, serrated or fluted, or bean-shaped, but also multilobed, especially trilobed or pentalobed, X-shaped, ribbon-like. , hollow, square, triangular, elliptical and others. The shape of the microfiber section, however, is not an essential feature of the invention. All forms of fiber section resulting from the process of manufacturing said microfibers are acceptable. Similarly, the microfibers used in the present invention may be of diameter and / or constant section or have variations.

According to the present invention, the polyamide microfibers used are characterized: by a titer of between 0.1 and 15 dtex, preferably between 0.1 and 10 dtex and even more preferentially between 0.5 and 2.5 dtex; a length of between 0.1 and 10 mm, preferably between 0.1 and 6 mm and even more preferably between 0.3 and 5 mm, and the nature of the polyamide which is chosen from the group consisting of: polyamide 6, polyamide 6.6, polyamide 4, polyamide 11, polyamide 12, polyamides 4-6, 6-10, 6-12, 6-36, 12-12, their copolymers and mixtures.

According to a preferred embodiment, the polyamide microfibers come from the section of cables formed from a plurality of continuous filaments of polyamide 6 or polyamide 6.6. All the cut fibers thus obtained are called Flock because they are commonly used in flocking processes for producing, for example, coatings for applications in the automobile or building.

According to another preferred embodiment, the polyamide microfibers have the following characteristics: a uniform and calibrated length of between 0.1 and 10 mm, preferably between 0.1 and 6 mm and even more preferentially between 0 and 10 mm; , 3 and 5 mm, and - a titre between 0.1 and 15 dtex, preferably between 0.1 and 10 dtex and even more preferably between 0.5 and 2.5 dtex. According to an advantageous embodiment of the invention, the polyamide microfibers are in the form of flocks before incorporation into said composition.

The raw polyamide microfiber may be treated, before being mixed with the slurry containing the hydraulic binder, with one or more of the additives known in the field of manufacturing textile fibers or microfibers according to various known methods. Among these, mention may be made, by way of examples and in a non-limiting manner, of the technique for treating the raw fiber with a roller, by spray or vaporization, by dipping, the technique of padding, as well as any method used. in the textile industry processing synthetic fibers. This treatment can be carried out at different stages of the manufacture of the microfiber. These include, among other things, all the steps in which sizing is conventionally added. It is thus possible to apply the additive at the bottom of the spinning machine before winding. It is also possible, in the case of "fiber" processes, to apply the additive before, during or after the drawing, crimping or drying steps, for example. Examples of additives are delustrants, mattifying agents, for example titanium dioxide and / or zinc sulphide particles, colored pigments, stabilizers, property modifiers such as antistaticity, hydrophilicity, anti-stain or anti-fouling effect and flame retardancy. Silicone coating is defined as the action of coating a support with a crosslinkable liquid silicone composition and then curing the coated film on the support to produce a coating. Silicone Compositions The curable polyorganosiloxane compositions contemplated in the context of the present invention, presented in one or more packages (single or multicomponent), contain, in addition to the microfibres according to the invention, a main constituent formed of a or more polyorganosiloxane component (s), a suitable catalyst and optionally one or more compound (s) such as, for example, reinforcing fillers, crosslinking agents, anti-structuring agents, adhesion promoters, The polyorganosiloxane compositions are intended to obtain a silicone elastomer crosslinking in the presence of a metal catalyst at room temperature or to heat by means of polyaddition reactions ( LSR or RTV polyaddition) or by polycondensation reactions (polycondensation RTV).

The terms RTV and LSR are well known to those skilled in the art: RTV is an abbreviation for "Room Temperature Vulcanizing"; LSR is an abbreviation for "Liquid Silicone Rubber" and HCR stands for "Heat Cured Rubber". The invention is particularly applicable to a silicone coating composition (A) which comprises: (a) at least one polyorganosiloxane (I) having, per molecule, at least two silicon-bonded C2-C6 alkenyl groups, (B) at least one polyorganosiloxane (II) having, per molecule, at least two silicon-bonded hydrogen atoms, (c) a catalytically effective amount of at least one catalyst (III), composed of at least one metal belonging to the platinum group, (d) at least one adhesion promoter (IV), (e) optionally at least one polyorganosiloxane resin (V) (f) optionally at least one crosslinking inhibitor (VI). h) optionally at least one staining additive (VII), (i) optionally at least one additive (VIII) to improve the fire resistance, and (j) from 0.5 to 15 parts by weight, preferably from 0, 5 to 10 parts by weight and even more preferably 2 to 10 parts by weight, per 100 parts by weight of the composition of a reinforcement consisting of polyamide microfibers according to the invention and as defined above. The silicone coating compositions (A) are two-component or one-component polyorganosiloxane compositions which cross-link at room temperature or with heat by polyaddition reactions, essentially by reaction of hydrogenosilyl groups with alkenylsilyl groups, in the presence of a metal catalyst, generally based on platinum, are described for example in US-A-3,220,972, 3,284,406, 3,436,366, 3,697,473 and 4,340,709.

A particularly preferred silicone coating composition (A) is described in FR-2861753.

If it is necessary to retard the crosslinking, an inhibitor (f ') of the platinum catalyst may be added to the polyorganosiloxane crosslinking composition by polyaddition reactions. These inhibitors are known. It is possible in particular to use organic amines, silazanes, organic oximes, diesters of dicarboxylic acids, acetylenic ketones and especially, and these are the preferred inhibitors, acetylenic alcohols (see, for example, FR-A- 1,528,874 and 2,704,553) and cyclic polydiorganosiloxanes consisting essentially of units (II) where Z = vinyl and where x = y = 1, optionally associated with units (I) where n = 2. Inhibitor, when one is used, is employed in a proportion of 0.005 to 5 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts of the gum (a ').

These acetylenic alcohols, which form part of the preferred hydrosilylation reaction heat blockers, have the formula: ## STR5 ## wherein R 'is a linear or branched alkyl radical, or a phenyl radical; -R 2 is H or a linear or branched alkyl radical, or a phenyl radical; - The radicals R ', R2 and the carbon atom located at a of the triple bond may optionally form a ring; and the total number of carbon atoms contained in R 'and R2 being at least 5, preferably 9 to 20.

Said alcohols are preferably chosen from those having a boiling point greater than 250.degree. C. By way of examples, mention may be made of: ethynyl-1-cyclohexanol 1; 30 . 3-methyl-1-dodecyn-3-ol; . 3,7,3-trimethyl-1-dodecyn-3-ol; . 1,1-diphenyl propyne-2 of-1; . 3-ethyl-6-ethyl-1-nonyne-3-ol; . 3-methylpentadecyn-1-ol-3.

These α-acetylenic alcohols are commercial products.

Examples of two-component or one-component organopolysiloxane compositions which crosslink at room temperature by moisture-based polycondensation reactions, in the generally presence of a metal catalyst, for example a tin or titanium compound, are described for example for the single-component compositions in US-A-3,065,194, 3,542,901, 3,779,986, 4,417,042, and FR-A-2,638,752, and for the two-component compositions in US Pat. U.S. Patent Nos. 3,678,002, 3,888,815, 3,993,729 and 4,064,096. The polycondensation composition may also include a silane bearing two hydrolyzable and silane-extending groups. These difunctional silanes are well known to those skilled in the art. The last subject of the invention relates to a woven, knitted or non-woven fibrous support, coated on one or both faces that can be obtained by the process according to the invention and as described above. The invention will now be described in more detail using embodiments taken as non-limiting examples. EXAMPLES EXAMPLE 1 Reinforced Silicone Formulation for Textile Coating Textile Support: The support sample is a glass fabric (indifferent nature) with a surface weight of approximately 250 g / m 2.

The coating of the support is carried out with a laboratory squeegee allowing a deposit of the order of 200 m; its crosslinking on the support is carried out for 2 minutes in a ventilated oven maintained at 160 ° C.

Fibrous reinforcement: This is polyamide 6-6 microfibers initially in the form of flocks (microfibers of 0.9 dtex title with a calibrated length cut to 0.4 mm, washing desensitization and simple drying). These suitably dried fibers are incorporated into the composition. elastomer composition using a centrifugal type laboratory stirrer.

A varnish is applied to the silicone support by means of a Mayer bar suitable for a deposit of the order of 5 g / m 2; the crosslinking is carried out by residence in a ventilated oven at 180 ° C. for 2 minutes.

The composition of the varnish is described in patent application FR-2849445. Pre-impregnated glass fabric is coated and varnished on one side Cross-linking of the coating is done in 2 minutes at 160 ° C. Crosslinking of the varnish is done in 1 minute at 120 ° C. Table 1 Formulations Tested (in grams): Constituents Comparative 1 Comparative Invention 2 Empast = mixture. Resin 180.18 192.8 180.33 MMV'DDV'Q 56% by weight + CaCO3 = 16.1% by weight Flock PA 6.6, 0.9 dtex; 0.4 mm 12.5 Crushed quartz 25 Polyorganosiloxane (1): oil 38.85 9.56 12.11 polydimethylsiloxane blocked at each of the chain ends by a (CH 3) 2 ViSiO 5 motif, crosslinker: poly (dimethyl) oil 19.95 27.56 25.01 (hydrogenomethyl) siloxane blocked at each chain ends with a (CH3) 2HSiOo55, VTMO = vinyltrimethoxysilane 5.09 5.02 5.03 GLYMO = 2.49 2.5 2.5 glycidoxypropyltrimethoxysilane ECH = ethynyl-1-cyclohexanol-1 0.1141 0.077 0.081 Total 250 250 250 Conclusions: It can be seen that the addition of Polyamide short microfibers make it possible to measure the hardness: + 20 Shore A points. The inclusion of polyamide 6.6 microfibers, in particular in the form of flocks, in the composition of a silicone elastomer gives the latter an increased reinforcement without increasing its density. The mechanical properties are globally improved with a significant effect on Shore A hardness.

Claims (2)

  A process for preparing a woven, knitted, or non-woven fibrous support coated on one or both sides with at least one reinforced elastomeric silicone layer comprising the following steps: a) the preparation of a crosslinkable silicone coating composition (A) characterized in that it comprises, per 100 parts by weight of organopolysiloxane: from 0.5 to 15 parts by weight, preferably from 0.5 to 10 parts by weight and even more preferably from 2 to 6 parts by weight, a reinforcement consisting of polyamide microfibers which have: a titre of between 0.1 and 15 dtex, preferably between 0.1 and 10 dtex and even more preferentially between 0.5 and 2.5 dtex, and length between 0.1 and 10 mm, preferably between 0.1 and 6 mm and even more preferably between 0.2 and 5 mm, and said polyamide is chosen from the group consisting of: polyamide 6, polyamide 6.6, polyamide 4, polyamide 11, polyamide 12, polyamides mides 4-6, 6-10, 6-12, 6-36, 12-12, their copolymers and mixtures, b) the application of at least 20 g / m 2, preferably at least 40 g / m 2 and still more preferably at least 100 g / m 2, on one or both sides of a woven, knitted, or non-woven fibrous support of the silicone coating composition (A) prepared in step a), and c) the crosslinking , in particular by heating or by electromagnetic radiation, the deposit formed in step b) to form at least one reinforced elastomeric silicone layer. 2 - Process according to claim 1 characterized in that the polyamide microfibers come from the section of cables formed of a plurality of continuous filaments of polyamide 6 or polyamide 6.6. 3 -Procédé according to one of the preceding claims characterized in that the polyamide microfibers have the following characteristics: - a uniform and calibrated length of between 0.1 and 10 mm, preferably between 0.1 and 6 mm and 30 mm; more preferably between 0.3 and 5 mm, and - a titre between 0.1 and 15 dtex, preferably between 0.1 and 10 dtex and even more preferably between 0.5 and 2.5 dtex. 4 -Procédé according to one of the preceding claims characterized in that the polyamide microfibers are in the form of flocks before incorporation into said composition. Process according to one of the preceding claims, in which the silicone coating composition (A) comprises: (a) at least one polyorganosiloxane (I) having, per molecule, at least two C 2 -C 6 alkenyl groups; related to silicon, (b) at least one polyorganosiloxane (II) having, per molecule, at least two silicon-bonded hydrogen atoms, (c) a catalytically effective amount of at least one catalyst (III), composed of at least one metal belonging to the platinum group, (d) at least one adhesion promoter (IV), (e) optionally at least one polyorganosiloxane resin (V) (f) optionally at least one crosslinking inhibitor (VI ), (h) optionally at least one coloring additive (VII), (i) optionally at least one additive (VIII) to improve the fire resistance, and (j) from 0.5 to 15 parts by weight, preferably from 0.5 to 10 parts by weight and still more preferably from 2 to 10 parts by weight, per 100 parts by weight of the composition of a reinforcement consisting of polyamide microfibers as defined in any one of claims 1 to 4. 7 - woven fibrous support, knitted or nonwoven, coated on one or both faces susceptible to be obtained by the process of any preceding claim.