FR2720466A1 - Process for the production of an impregnated flat lining. - Google Patents

Abstract

The process for manufacturing a flat lining impregnated from at least one non-woven prepreg takes place by impregnating a non-woven which has been previously reinforced with a binder, with a mixture of polymers capable of prior crosslinking in the form of a solution, a dispersion or a suspension. The final crosslinking takes place optionally after the laminating of several layers under pressure and at elevated temperature, in a drying oven with a corresponding thermal effect.

Description

94PA0046

94PA0046 272046e-F132 - / FR

  PROCESS FOR THE MANUFACTURE OF A FLAT IMPREGNATED TRIM

  The invention relates to a method for the manufacture of an impregnated flat lining, consisting of at least one non-woven prepreg, in which a flat product consisting of fibers or asbestos-free fiber mixtures is coated. organic or inorganic origin using a binder, it is impregnated with solutions, dispersions or suspensions of a reactive polymer mixture, suitable for prior crosslinking, then their prior crosslinking is started by drying at high temperature and finally subjecting the polymers to a crosslinking end in the strip (s) of prepreg packing obtained, under pressure and at elevated temperature, possibly together with a reinforcement

metallic.

  A process of this type is described in DE-GM 84 25 480.7. It is in this case a flat lining impregnated in a soft material, in particular a lining of a cylinder head for internal combustion machines, constituted by a nonwoven possibly with metal reinforcement, constituted by fibers and / or mixtures of fibers of organic and / or inorganic origin possibly free of asbestos, by a binder and optionally by a filler whose form goes from a pulverulent form to a fine-grained form, the nonwoven being impregnated with a liquid, in which the liquid impregnating agent is crosslinked in the filling ready for incorporation to obtain a plastic to elastic final state. In known garnishes, criticism

  on the low flow limit manifested by non

  woven fabrics impregnated when subjected to very high pressure stress. To solve this problem, it is proposed to incorporate, before impregnating with a liquid, in addition 3 to 15% by weight reported

  impregnated nonwovens, synthetic duromer resins.

  Preferred are melamine resins, resins

epoxides and / or phenolics.

  For the manufacture of impregnated nonwovens, it is emphasized as essential that the resins

  synthetic duromers must be present in the non

  woven in a still reactive form before proceeding

  the impregnation proper using a liquid.

  As a possible operating variant, it is proposed to impregnate the nonwovens before the actual impregnation using a liquid, with solutions, dispersions or suspensions of the pre-crosslinked reactive synthetic resins. The final crosslinking of the synthetic resins can then also take place after the impregnation during the crosslinking of the impregnating agent. The characteristic state of the art resides in the fact of starting from nonwovens, that is to say from fibrous flat products which are still relatively unconsolidated. The disadvantage linked in this case, in particular, in a continuous operating mode, resides in the fact that, in order to maintain fluctuations in density and properties as minimal as possible, it is necessary to guarantee a uniform distribution of all the components in the nonwoven. To this end, very costly operating and control steps are required during the treatment of the fibers and during the mixing of the components used in the process. Among other things, care must be taken to exclude the appearance or absorption of fibrous dust that poses a threat to health. In addition, handling and transporting unconsolidated fibrous flat products becomes extremely complicated when

  during the process, due to the lack of mechanical stability.

  The object of the invention is, based on the state of the art mentioned above, to indicate a process of the type mentioned, which can be carried out continuously, which guarantees constant material quality and, while avoiding fibrous dust, which allows to get away with starting materials and intermediates manifesting

  superior mechanical resistance.

  The implementation of the invention lies in a process characterized in that the impregnation is carried out with the mixture of polymers capable of prior crosslinking on strips of fibrous nonwoven already reinforced with a binder, then left run the strips of impregnated fibrous nonwoven between two wringing rollers, then remove, in a drying oven, the dissolution, dispersing or suspending agent until drying and until prior crosslinking of the polymer blend, so that a desired number of pre-impregnated non-woven webs are laminated and mutually bonded, under pressure and with heat sufficient to effect the final crosslinking of the polymers, in the goal of getting the impregnated packing ready for use. Advantageous embodiments

  are indicated in the dependent claims.

  It is essential for the invention, the fact that one uses,

  already as fibrous flat products, nonwovens, that is

  say fibrous nonwovens reinforced with a binder, in which, using one or more subsequent processing methods, the cohesion of the fibers is high and which are available in the form of flat products and materials in rolls. Thanks to the types of fibers, to the mixture of different fibers, to the type of reinforcement processes, to the distribution of the fibers and to the subsequent mechanical treatment, nonwovens with defined physical and chemical properties adapted to the object can be produced. respective use. The manufacture of corresponding variants of nonwoven properties of this type is practically unlimited and only determined by the use of the flat lining which is obtained from there. The provision of corresponding nonwovens is the subject of a multiple state of the art, it can be easily implemented by a person skilled in the art and it does not

is not the subject of the invention.

  Consequently, in accordance with the invention, the impregnation using the mixture of polymers having undergone prior crosslinking takes place on strips of fibrous nonwoven already reinforced with the aid of a binder. The polymer blend can

  understand load materials or not.

  Before its introduction into the drying oven, the impregnated strip is made to pass between two drying rollers. By adjusting the viscosity of the polymer blend, as well as the distance between the wringing rollers, one can control the fraction of the polymers and the thickness of the polymer layer. Corresponding preliminary tests can be easily carried out, since the result appears

  immediately after treatment with the rollers.

  This is followed by the treatment of the flat nonwoven product impregnated in the drying oven where the solution-dissolving, dispersing or suspending agent is removed so that after leaving the oven, the polymer fraction is, in fact, dry, but not yet completely cured. At the level of this crosslinking

  beforehand, a strip of prepreg is thus obtained in non-

  woven, which has bonding and sealing properties. These strips of prepreg can be superimposed in the desired quantity corresponding to the desired final thickness of a flat lining and connect them to each other under the influence of pressure and heat. The composite which is obtained must in any case be subjected first to a heat treatment which is sufficient to trigger the final crosslinking of the polymer fraction in the prepreg. Another preferred embodiment of the method resides in the fact that pre-impregnated strips of nonwoven are deposited from above and from below on a sheet of synthetic or metallic material, these layers are laminated and connects the laminate between pairs of heated rollers or, if longer lamination times are required, in a double belt press to obtain a filling material. The final crosslinking takes place again in a drying oven. Packings made to this extent, having a consolidation core, are no longer flaccid at flexion and essentially facilitate assembly, in particular when the latter is to take place completely automatically. An advantageous improvement of this operating variant lies in the fact that the non-woven prepreg is shaped, for example by stamping or by laser cutting, and the support layer, for example by stamping, by laser cutting. or by injection, each separately. On the support profiled beforehand in this measurement, the molded elements of the prepreg made of non-woven fabric also subjected to a preliminary profiling are applied with precision on both sides.

  rolling corresponding to the process indicated above

  above, with subsequent final crosslinking of the polymers.

  The advantage linked to this process lies in the fact that the waste is essentially reduced during the manufacture of the lining and that it is easy to recycle,

  respectively eliminate, these.

  All the operating variants mentioned can be carried out continuously; the nonwoven provided with a prior reinforcement withstands, in all phases, the mechanical and thermal stresses of the processing machines. The mentioned flat linings, the central part of which has been reinforced, may, in particular for use as cylinder head cylinder linings, be provided with moldings. In this case, it turns out that, when using the method according to the invention, it is indeed possible

  deform the layers of the lining reinforced by non-

  woven onto the reinforcement sheet during molding; in this case, no formation of cracks or any essential reduction in the thickness of the layer is observed on

the garnish.

  The example below is intended to explain the invention.

  We build, with a non-woven prepreg, a

  flat gasket reinforced with sheet steel.

  Formulation of the impregnation bath (parts = parts by weight): parts of a commercially available 50% aqueous dispersion of a copolymer based on n-butyl acrylate, methyl acrylate, styrene and acrylonitrile parts of a commercially available 40% aqueous dispersion of a copolymer of acrylonitrile and butyl acrylate 6 parts of red phosphorus (filler) parts of 2,4,6-triamino -1.3.5-triazine (filler) i part of a preparation capable of being dispersed in water, commercially available, of copper phthalocyanine 5.9 parts of a 60% aqueous solution, commercially available aminoplast precondensate containing methylol groups

parts of water.

  The components are mixed by stirring with a bar mixer. To obtain an optimal distribution and size of the fillers, the mixture is flattened to

  using rollers in a roller mill.

  A coating device is filled by immersion using the mixture and a nonwoven having a weight of flat product of 50 g / m2, mainly consisting of aramid fibers, is impregnated in this installation with binder fibers. polyester, and dried for 2 minutes in a continuous drying oven at 150 C. The prepreg made of nonwoven thus obtained is applied, on both sides, to a degreased and brushed steel sheet (1 mm thick) using a laminating device with heated rollers, then it is compressed with a processing pressure of 7 kp / cm 2 and a temperature of 190 C. The speed of travel through the laminating device with rollers amounts to

1.4 m / min.

  Then the metal-reinforced packing material is completely cured in an oven at 130 ° C for 14 hours. From this material, we then cut the

  flat packing with a mass cutting tool.

94PA0046 272046-F132 - / FR

Claims (4)

  1. Process for the manufacture of a flat packing   impregnated, consisting of at least one prepreg in non   woven, in which a flat product consisting of fibers or mixtures of asbestos-free fibers of organic or inorganic origin is coated with a binder, it is impregnated with solutions, dispersions or suspensions of a reactive polymer mixture, capable of prior crosslinking, then their prior crosslinking is triggered by drying at high temperature and finally the polymers are subjected to a terminal crosslinking in the strip or strips of prepreg linings obtained, under pressure and at temperature high, possibly together with a metallic reinforcement, characterized in that the impregnation is carried out with the mixture of polymers capable of prior crosslinking on strips of fibrous nonwoven already reinforced with a binder, the strips are then allowed to pass of fibrous nonwoven impregnated between two wringing rollers, then the agen is removed in a drying oven t dissolving, dispersing or suspending until drying and prior to crosslinking of the polymer mixture, so that a desired number of prepreg strips are laminated and glued to each other nonwoven obtained, under pressure and with a heat which is sufficient to carry out the final crosslinking of the polymers, in order to obtain the   impregnated packing ready for use.   2. Method according to claim 1, characterized in that the pre-impregnated strips of nonwoven are laminated one on the other in a heated roller laminator or in a heated double strip press and then, we proceed to the final crosslinking and hardening in a drying oven.   3. Method according to claim 2, characterized in that a sheet of plastic or metal is laminated between   two non-woven prepreg strips.   4. Method according to claim 3, characterized in that before rolling, the prepregs made of nonwoven and the sheet of synthetic material or metal are subjected to prior and separate profiling to give them their shape.   final ordered by their destination.