FR2707676A1 - Process for coating planar textile bodies with elastomers - Google Patents

Abstract

The invention relates to a process for producing silicone coated textile flat bodies by applying a liquid silicone rubber and curing the rubber. The flat textile body is exposed to a crown effect treatment before the application of the silicone rubber. The flat textile bodies coated in accordance with the invention are intended, for example, for the manufacture of airbags, otherwise called “airbags”.

Description

It is known that industrial fabrics as well as natural and

Textile plan bodies are

  often provided with coatings of polymeric materials in order to obtain better technical properties of use-5 tion.

  The number of these polymeric materials is large, and the goals of improving the technical properties can

to be of varied nature.

  Thus, it may be desirable, for example, for the fabric used to have a better water repellency or to have better seamability. It may be desirable to impart to the fabric as a whole reduced gas permeability or better

  ability to resist combustion.

  The polymeric materials used to obtain the different properties of the fabrics are multiple and can

  cover the full range of known polymeric materials.

  Among these materials, silicones have a dominant importance in many respects: they give the surfaces of textile fabrics and planar bodies treated with them a very good water-repellent property; one can vary with them the so-called touching behavior in the sense of flexibility and elasticity and

  give them the "silicone touch" well known to specialists

  your. Special products also provide textile materials thus primed with a certain capacity for resistance

to the flame.

  Of the silicone-based products that can be used, silicone rubbers offer particular advantages. They can be easily applied to the fabric or textile body by the various industrial processes and crosslinked in place to the corresponding silicone elastomers under appropriate conditions. In addition, they form for the fabric primed excellent mechanical and thermal protection, since it is known that the silicone elastomers are characterized by a very high stability to heat. Textile materials which are primed with polydimethylsiloxanes also have good cold flexibility as well as are very

nice to wear.

  Priming of fabrics and industrial body planes

  Silicone rubber is a known method in which the application of the non-cross-linked rubber material can be carried out by immersion, where appropriate from rubber solutions, by application to the pad (padding), application by spray or by

application to the doctor blade.

  By relying on chemical and physical modifications, it is possible to produce silicones for scarf application and exhaustion processes as well as for applications in the presence of solvents. It is thus possible to use these products on almost all textile materials and fibers by most of the application methods.

  From the point of view of compatibility with the environ-

  Recently, there has been a growing trend towards the use of solvent-free application systems, because these systems are normally less energy-intensive in their process of implementation compared to systems in which solvents are required. be eliminated, but also because the total recovery for example of organic solvents is linked to an expense

considerable technique.

  Silicone rubber-based materials which, on the one hand without the addition of solvents, have a viscosity sufficiently low that they can be used with a blade doctor for coating at an application weight of approximately 20 to 100 g / m 2, and which have on the other hand, in the fully crosslinked state, a relatively high mechanical strength to give coatings able to withstand mechanical loads, have been known for some years under the name of rubber of

liquid silicone.

  These are products based on polydimethylsiloxane

  loxanes bearing in the polymer chain vinyl terminal groups of pyrogenically produced silicas having a BET specific surface area of at least m2 / g and special auxiliary substances

  for the incorporation of silicic acid

in the polymer.

  The crosslinking of these products is carried out by reaction with oligomeric polymethylhydrogenosiloxanes or

  polymers in the simultaneous presence of platinum compounds.

  The technical disadvantage of coatings formed with such products is that they have

  low adhesion to organic substrates.

  A number of proposals have been made in the technical literature to overcome this drawback. For example, organopolysiloxane rubbers may be supplemented with organic silicon compounds which have the effect of improving the adhesion of the silicone rubber coating. It is further known that by treating, for example, a textile material with dilute solutions of the organosilicon compounds mentioned before application of the coating material, there are sometimes marked improvements in the adhesion of the coating. For textile materials with a high mechanical load, as used in particular for the manufacture of industrial textiles for airbags otherwise known as "airbags" in the automotive industry, the improvement that can be achieved concerning the adhesion of the coating however, is still not sufficient for the purpose of use. The object of the invention lies therefore in a method for producing flat planar bodies or woven fabrics, in particular for the manufacture of airbag fabrics with superior adhesion to a layer of silicone elastomer which is applied, characterized in that the textile or textile flat body is exposed to a silent electric discharge (corona discharge) prior to coating with the silicone rubber. Surprisingly, the use of adhesive agents in an organopolysiloxane rubber-based material only led in combination with a corona discharge treatment to a particularly durable connection between the silicone elastomer layer. and the supporting fabric used for production

  air bags.

  Devices for the production of electric discharges according to the invention for the modification of polymer surfaces are known under the concept of corona electrode and their use has been widely used for the surface treatment of

  synthetic materials, paper and metals in order to improve

  adhesion of colors, paints, glues and coatings. Advantageously, a corona discharge with a frequency of 1 to 500 kHz is used, in particular

from 5 to 30 kHz.

  The voltage can be between 3 and 30 kV,

preferably between 20 and 31 kV.

  Irradiation doses of 10 to 1000 gAh / m2 are generally sufficient, depending on the tissue. More doses

  strong do not result in further improvement of adhesion.

  The corona discharge may be conducted at ambient temperature in an atmosphere of air or an inert gas, with some humidity of the air, for example above 50%, being relatively advantageous. Coating with liquid silicone rubber should preferably be performed in a continuous installation immediately following the corona treatment. If corona treatment and coating are carried out at different times in separate installations in space, it may be necessary to use higher doses of irradiation in order to obtain the full effect in accordance with the invention, since the active centers promoting adhesion, created on the fabric

  by treatment with corona effect, are resorbed

beyond a certain time.

  The invention is illustrated in detail with the help of

examples below.

Examples

  The following materials were used: Fabrics: polyamide fabrics having a titer of 470 dtex Liquid silicone rubber, component A: mixture of: 100 parts by weight of a vinyl-terminated polydimethylsiloxane and having a viscosity of 10 Pa.s , parts by weight of pyrogenic silica (BET 300 m 2 / g), previously treated with 4.33 parts by weight of hexamethyldisilazane, 0.007 parts by weight of platinum catalyst

  in the form of a platinum-vinylsiloxane complex.

  Liquid silicone rubber, component B: Mixture as component A, with however 3 parts by weight of a methylhydrogensiloxane carrying 4

  mmol / g SiH groups in place of the platinum catalyst.

  Adhesive Preparations: 100 parts by weight of a solution of a vinyl-bearing silicone resin was mixed in

  ethanol (containing 60% of resin), with: a) 7.5 parts by weight of γ-aminopropyltriethoxysilane b) 15 parts by weight of γ-aminopropyltriethoxy-

silane

  c) 15 parts by weight of γ-methacryloxypropyltri

methoxysilane

  d) 15 parts by weight of γ-metharylpropyltrimidine

trimethoxysilane

  e) 15 parts by weight of γ-glycidoxypropyltrimidine

  trimethoxysilane. Blue colored paste: pigment dispersed in a linear polydimethylsiloxane with a trimethylsiloxy group

  chain termination, viscosity 25 Pa.s.

Examples 1 to 8

  Liquid silicone rubber, an adhesive preparation and a colored paste were mixed together in the quantitative proportions indicated in Table 1. The

  Viscosities of the mixtures were about 100 Pa.s.

  The blends were applied by roll squeegee to polyamide fabrics with a 50 gram slit opening. The applied mass was

in each case at 90 g / m2.

  The subsequent vulcanization was carried out by

  heating at 175 C for 2 minutes with hot air.

  The polyamide fabric according to Examples 6 to 8 was subjected to corona irradiation (25 kV voltage) prior to coating. The irradiation dose is indicated

in Table 1.

  Evaluation of the adhesion of the silicone rubber coatings to the substrate was performed according to the Scrubb test method which is described in

SNV 198 498 test standard.

  The resulting fabric coatings are bonded with relative strength to the base fabric. Therefore, they can not be totally detached from the base fabric, therefore their adhesion can not be directly determined by the layer separation test. The detachment

  coating is therefore produced by a diagonal tensile test

  alternation and the quality of adhesion is indicated by the number, reproduced in Table 1, of the races

must deploy for this purpose.

Table 1

  Example 1 2 3 4 5 6 7 8 Dose of effect - - - - - 225 225 225 crown W. min / m2 Coating composition, parts by weight: Component LSR A 50 50 50 50 50 50 50 5020 Component LSR B 50 50 50 50 50 50 50 50 Preparation of adhesive a) 5 Preparation 5 of adhesive b) 525 Preparation of adhesive c) 5 Preparation of adhesive d) 5 Preparation30 of adhesive e) 5 Colored paste 6 6 6 6 6 6 6 6 Adherence, race 100 350 150 150 50 400 800 1000

Claims (1)

CLAIM   Process for the production of silicone-coated textile planes by application of a liquid silicone rubber and curing of this rubber, characterized in that the textile planar body is exposed to   crown before the application of the silicone rubber.