MXPA99011096A - Procedures for the preparation of molded parts of fiber fabrics with superf refining - Google Patents

Abstract

The invention relates to a process for the manufacture of molded parts of fiber cloth with refined surface through the application of a film, wherein the application of film on the surface (the surfaces) to be refined of molded parts of cloth fiber is carried out with a duroplastic resin, or a mixture of resin-hardener in combination with a sheet, and the parts manufactured in this way are heated to temperatures above the melting point and above the starting temperature of the hardening reaction of the duroplastic resin used, and said parts are cooled after the hardening of the film.

Description

PROCEDURE FOR THE PREPARATION OF MOLDED PARTS OF FIBER FABRICS WITH SUPERFICIAL REFINEMENT The invention relates to the manufacture of molded parts made from fiber fabrics based on natural and / or synthetic fibers, in which at least one of the surfaces, in general terms the side that is in view, is refined through the application of a layer, especially the application of a sheet of high value. These molded parts are used mainly in the automotive industry. Molded parts of fiber fabrics are flat molded parts made from a duroplastic resin, especially fiber fabrics reinforced with phenolic resin or epoxy resin, especially from processed fiber articles. For its manufacture, the fiber article and the resin powder are mixed, formed into a cloth, and possibly subjected to a prior hardening. The hardening is carried out in the case of flat articles immediately after the formation of the fabric in the furnace or this pre-reinforced fabric is cut into frames and using pressure is hardened in pressure molds. Then the molded parts are perforated (see Kunststoff-Handbuch, volume 10"Duroplaste", Hanser Verlag, 2nd Edition (1988), page 763-775). The refinement of the surface can be carried out during the hardening of the fiber fabrics or in a separate second step. For the application of the sheet, the subsequently visible flat structure, the sheet metal material, is adhered with the aid of a thermoplastic adhesive (melting glue) or with special contact adhesives, on the molded part of fiber cloth which now serves as support base. In the film application process, an application of thermoplastic masses, pigmented, in the form of pastes or solutions is carried out. In an improved process, a thermoplastic mixture, in the form of a powder with a lower melt viscosity, which is melted by re-application of heat and then cooled, is dispersed on the surface of the sheet metal material. In this way, a unitary film is obtained on the surface of the sheet. The drawback of this method is that the recoil force of the sheet material in the hot state is often stronger than the adhesive strength of the melting glue. This entails, especially in the case of geometrically complicated parts, faults, in which the sheet material is detached from the substrate. The detachment effect is more noticeable in the case of molded parts subjected to frequent changes of temperature or to intense solar irradiation.

Accordingly, an object of the present invention is a method for the surface refinement of molded parts of fiber fabrics which can be carried out in such a technically simple and elegant manner as what is known as the melt application process, however in the which the disadvantage of the detachment effect is not observed. This object is achieved through a process according to claims 1 to 10, as well as through molded parts of fiber fabrics manufactured in accordance with one or more of these claims. It was found that a high-value surface refinement of molded parts of fiber cloth is also obtained when non-stick duroplastic resins at room temperature are used for the sheet or resin and hardener mixtures as adhesive for the sheet. A sheet material with such an adhesive is applied on the prepared fiber cloth or on a molded part of fiber cloth and the product obtained is heated to a temperature which is above the reaction start temperature of the fiber. hardening of the resin or of the resin-hardener mixture. The duroplastic resins are hardened in this way as a film which is bound by the hardening reaction with the surface of the fiber fabrics and a flat adhesive is obtained, irreversible of the sheet, which does not cause detachment neither when the object is subject to extreme temperature changes or to solar irradiation. This is surprising insofar as the melt viscosity of the duroplastic substances in general is higher than the melt viscosity of the thermoplastic substances and the curing temperature used is markedly higher than the melting temperature of the thermoplastic binders used up to the date and consequently in the case of a pressure in the pressure device the recoil forces are significantly greater than in the case of the use of thermoplastics. The duroplastic resins are generally fragile. Accordingly, it is a further surprising effect that, in accordance with the present invention, the sheets coated with duroplastic resins remain stable also in the case of rolling or molding and do not fall apart. A further advantage of the process according to the present invention is that the surface refinement of the molded parts of fiber fabrics is carried out when the hardened thermoset resin has not yet hardened or the hardened resin-hardener mixture can still be applied both on the molded parts of fiber fabrics prepared as on the sheet metal material. Furthermore, in accordance with this embodiment, it is possible that in the edge area, the duroplastic resin used for surface refining is crosslinked with the resins that are used as a binder of the textile fibers. This is especially the case when the same resins or resins reacting between them are used both for the agglomeration of the fibers and for the improvement of the surface of the molded parts. Through this crosslinking reaction in the edge region the stability of the molded parts increases, which represents an additional advantage. According to the present invention, a duroplastic resin or a mixture of resin and hardener and a sheet metal material are applied on the surface or the surfaces to be refined of the molded parts, and the units obtained in this way are heated to temperatures that they are above the melting point and above the start temperature of the hardening reaction of the duroplastic resins. After hardening of the duroplastic resins, the refined surface parts obtained are further processed in a known manner. A further simplification of the entire manufacturing process is carried out by applying a duroplastic resin, a resin-hardener mixture and a sheet metal material on the surface (the surfaces) to be refined prepared or on the fabrics of prepared fibers. The parts manufactured in this way are heated under pressure and molding to temperatures that are above the melting point and above the start temperature of the hardening reaction of the resins integrated in the film and above the temperature of reaction of the resins used as binder in the fabrics. In this way the binder in the fabric and the resin in the film are hardened at the same time and, to the extent that the binder in the fabric and the resin in the film are identical or can react with each other, it is obtained in the edge area a crosslinking of these duroplastic substances between them. After hardening the film and the binder in the fabric, the parts obtained are processed in a known manner. In the case of surface refinement in relation to a sheet metal material, the following processing variants can be used: • the thermoset resin or the resin-hardener mixture is applied to a pre-hardened or not yet heat treated fiber cloth and it is heated to a temperature that is above the melting temperature, but below the starting temperature of the hardening reaction of the resin. In this way the resin melts and extends in a thin layer. On this layer, either directly or after an intermediate cooling and reheating the sheet metal material and finally, possibly in a mold, the product produced in this way is brought to a temperature higher than the starting temperature of the reaction. Hardening of the resin and after hardening of the thermoset resin is cooled and further processed in a known manner. The duroplastic resin or the resin-hardener mixture is applied to the sheet metal material and heated to a temperature which is higher than the melting temperature but lower than the starting temperature of the hardening reaction of the resin. In this way, the resin melts and extends in a thin layer. The sheet material that this glue has is applied either directly or after an intermediate period and an overheating on the fiber cloth already hardened or not yet heat treated and finally, eventually in a mold, the product (object) manufactured in this way it is brought to a temperature higher than the starting temperature of the hardening reaction of the resin and after hardening of the thermoset resin, said product is cooled and further processed in a known manner.

The duroplastic resin or the resin-hardener mixture is applied to a preformed and hardened molded part and heated to a temperature above the melting temperature but below the starting temperature of the hardening reaction. of the resin. In this way the resin melts and extends in a thin layer. On this layer is applied either directly or after an intermediate cooling and reheating the sheet material and finally the product manufactured in this way is brought to a temperature higher than the start temperature of the resin hardening reaction and then from hardening the duroplastic resin the product is further cooled and processed in a known manner. The duroplastic resin or the resin-hardener mixture is applied to the sheet metal material and heated to a temperature above the melting temperature but below the starting temperature of the resin hardening reaction. . In this way the resin melts and extends in a thin layer. On this layer is applied either directly or after an intermediate cooling and reheating, a molded part of hardened and preformed fiber cloth and finally the product manufactured in this way is brought to a temperature higher than the starting temperature of the reaction of hardening the resin and after hardening the duroplastic resin the product is cooled and further processed in a known manner. In the first mode, as a thermoset resin for film application, it is preferable to use a formaldehyde-hardenable resin, especially a resin Novolak without hardener or a modified Novolak resin free from hardener, when the binder in the fiber fabric is a mixture of a formaldehyde hardenable resin and a product that releases formaldehyde when subjected to heat, for example a Novolak- hexamethylenetetramine. The formaldehyde released by hardening this binder is sufficient to also harden the melted Novolak in a thin layer.

It is an additional advantage of this modality that the formaldehyde emissions are significantly reduced in this manufacturing process. From this, the following preferred embodiments emerge: • with a sheet metal material equipped with a formaldehyde-hardenable thermoset resin, or a resin mixture of this type as an adhesive, is applied in a continuous strip manufacturing process endless a formaldehyde hardenable resin and a hardener that releases formaldehyde through application of heat is applied onto a pre-hardened fiber cloth, and the obtained object is hardened under pressure at a temperature that is above the starting temperature of the hardening reaction of the binder used in the fiber fabric and above the start temperature of the hardening reaction of the glue, whereby the formaldehyde released from the hardening reaction of the binder serves as a hardener for the glue. In this way a completely hardened product is obtained which can be perforated or cut according to the size and shape desired from the plates. With a sheet material equipped with a thermoset resin, hardenable with formaldehyde or a resin mixture as a glue, it is applied in a continuous endless band manufacturing process on a pre-hardened fiber cloth or only prepared a formaldehyde hardenable resin and a hardener that releases formaldehyde by application of heat, and the object obtained is then heated to a temperature above the melting temperature of the glue and to the extent that a fiber cloth not yet hardened is used, above the temperature of the resin used as binder, tempered, and then cooled and finally perforated or cut. The perforated or cut product (the semi-finished product) is finally hardened under pressure and molding application at a temperature that is above the starting temperature of the binder hardening reaction used in the fiber cloth and above the starting temperature of the hardening reaction of the glue, whereby the formaldehyde released from the hardening reaction of the binder serves as a hardener for the glue. Alternatively, a sheet metal material having a formaldehyde hardenable thermoset resin as a glue is applied, in a discontinuous manufacturing process in cut form onto a pre-hardened or prepared and cut fiber cloth, a resin hardened with formaldehyde and a hardener which frees formaldehyde when heat is applied, and the object obtained is then brought to a temperature which is above the starting temperature of the hardening reaction of the binder used in the fiber cloth and which is above the starting temperature of the fiber. the hardening reaction of the glue, whereby the formaldehyde released from the binder during the hardening reaction serves as a hardener for the glue.

The pressure used in this process is in an order of importance similar to the pressure applied in corresponding procedures according to the current state of the art. For the application of sheet metal on molded parts of fiber cloth it is preferred to use a sheet material having as adhesive a resin-hardener mixture in cut form on formed and hardened molded portions of fiber cloth, and the obtained object is heated by above the start temperature of the hardening reaction of the resin-hardener mixture. The application of sheet metal on molded parts of prepared and hardened fiber cloth has the advantage that to harden the thin layer of thermoplastic resin requires a less heat treatment compared to the hardening of a textile fabric. In this way, it is possible to use products having a lower thermal resistance as sheet material. For the process according to the present invention, the same fiber articles can be used as for the manufacture of molded parts of fiber fabrics manufactured according to the prior art. These are mainly processed fiber products made from textile processing and consist essentially of cotton or polyester fibers, however they contain, in general terms, other fibers such as wool, jute, linen, henequen, polyamide fibers or well acrylic. These fibers may contain known additives such as, for example, fungistatic or hydrophobic agents. Fiber material can also be inorganic fibers. The manufacture of the pre-hardened fiber fabrics or of the molded parts of fiber fabrics is carried out in a known manner, for example in accordance with that indicated in Kunststoffhandbuch, volume 10"Duroplaste", pages 766 to 768. As a material It is also possible to use flat structures, such as, for example, high-value fabrics or fabrics, as has been used to date to place sheets on molded parts of fiber fabrics, insofar as they are sufficiently thermally stable in such a way that they do not damage in the hardening temperatures of the duroplastic resins. For the glue of the sheet, in principle, all duroplastic resins or resin-hardener mixtures can be used without tack at room temperature, as well as resins and possibly mixtures containing hardeners with resins modified in a known manner. Examples of these hardenable resins are epoxy resins, unsaturated polyesters, urea-formaldehyde resin, melanin-formaldehyde resin, melanin-phenol-formaldehyde resin or phenol-aldehyde resin as well as combinations of these resins with each other as well as other resins modified, especially with resins of 5-50% flexibilization, such as for example polyvinyl butyral, polyvinyl alcohols or phenoxy resins. Preferably, phenol-formaldehyde resins are used. The direct application of film on the molded parts of fiber cloth of non-hardened or unprepared fiber cloth or of sheet metal materials is carried out according to known procedures, by means of spray, pour, dispersion, tamping, application with spatula, immersion in corresponding pastes, aqueous dispersions, or solutions in organic solvents. The preferred application is carried out in accordance with a powder process. In this process, the duroplastic resins or resin-hardener mixtures in the form of a fine powder are applied to the surface. For this purpose, fibers or fiber-hardener mixtures are particularly suitable whose melt viscosity during subsequent heating is so low that the substrate is sufficiently cross-linked. The preferred viscosity, measured at a temperature of 175 ° C, is less than 1000 mPas. In this short period heating above the melting point of the thermosetting resin, preferably by means of IR radiation, a thin, continuous film of resin or mixture is formed in the textile fabric or in the sheet material. resin-hardener, which cools quickly and therefore remains solid and free of glue. In the following process fiber fabrics and sheet metal material are integrated among them in accordance with one of the described procedures and under application of pressure and temperature are joined between them. Then the molded part obtained in this way is cooled and further processed in a known manner. EXAMPLE 1 The duroplastic resin used as the surface refining agent in this example is a phenolic Novolak resin modified with 10% phenoxy resin with a melting point of 70 ° C and a melt viscosity, measured at a temperature of 175 ° C, 420 mPas. By means of the aerodynamic fabric formation, a non-hardened textile fabric having a content of 25% phenolnovolak-hexamethylenetetramine as a binder (base fabric) is produced. This fiber fabric receives a thin layer (20 g / m2) of modified Novolak phenol, with the addition of high optical value fabric (40 g / m2) (covering fabric) and is fixed on the base fabric by applying heat (75 ° C) in an oven.

Then, the fabric coated in this way is subjected to a process of molding and hardening in a hot tool at a temperature of 180 to 220 ° C. In this way, a large amount of formaldehyde is released from the hexamethylenetetramine present in the base material as a curing agent, so that the phenol-Novolak layer on the side can harden. internal coating fabric applied. A molded part of textile fabric is obtained with a pasted duroplastic agent representing the surface refinement layer. As an additional advantage of this embodiment a remarkable reduction of the resulting formaldehyde emission is obtained from the base fabric. EXAMPLE 2 The duroplastic resin used for the surface refinement in Example 2 is a phenol-novolak resin modified with 10% by weight of phenoxy resin with a melting point of 70 ° C and a content by weight of hexamethylenetetramine of 6%. This finely ground resin-hardener mixture is applied on one side of a molded portion of hardened fiber cloth and formed into a thin layer and heated above the melting temperature. A knitted fabric of high optical value is applied to this molded part of layered fiber cloth. Through rapid cooling the high-value fabric is fixed with high flexibility on the molded part of fiber cloth through a thin film that can melt again. In a second processing step, through application of temperature and pressure, said temperature being above the start temperature of the resin hardening reaction (90s to 150 ° C), the thin film hardens. This method allows a surface refinement with a sheet material, which has a lower thermal stability than in example 1. It is a further advantage of this embodiment, that the duroplastic binder in the fabric, and the duroplastic resin used for the surface refinement can have different chemical structures and different chemical crosslinking reactions. EXAMPLE 3 The duroplastic resin used in Example 3 for surface refining is a phenol-Novolak resin modified with 10% by weight of phenoxy resin with a melting point of 70 ° C and 6% by weight of hexamethylenetetramine. This finely ground resin-hardener mixture is applied on one side in a thin layer onto a knitted fabric of high optical value and heated above the melting temperature of the resin. On this layered fabric a molded part of hardened fiber cloth, prepared, is applied. Through rapid cooling this high value fabric is flexibly fixed on the molded part of fiber cloth through a thin film, which can melt again. In a second process step, the thin film is hardened by application of temperature and pressure, at a temperature above the starting temperature of the resin hardening reaction (90s at 150 ° C).

Claims (1)

1. CLAIMS A process for the manufacture of molded parts of fiber fabrics with surface refinement through the application on the surface (surfaces) to be refined of a sheet material or a mass of duroplastic film, characterized in that, as a glue, it is used a non-tacky duroplastic resin at room temperature or a resin-hardener mixture. A process according to claim 1, characterized in that, this sheet material having as a glue a formaldehyde curable, duroplastic resin, is applied in a continuous manufacturing process as an endless band on a pre-hardened or prepared fiber cloth, which It contains a formaldehyde hardenable resin and a hardener that releases formaldehyde when heat is applied, and the product obtained afterwards under pressure and hardens at a temperature that is above the starting temperature of the hardening reaction of the binder used in the fabric. of fiber and of the glue, whereby the formaldehyde released from the hardening reaction of the binder serves as a hardener for the glue. A method according to claim 1, characterized in that the sheet metal material having a formaldehyde hardenable resin, as a glue, is applied in a continuous manufacturing process as an endless band on the pre-hardened or only prepared fiber fabric containing a formaldehyde hardenable resin and a hardener that releases formaldehyde when heat is applied, and the object obtained is then hardened at a temperature above the melting temperature of the glue and eventually above the melting temperature of the binder used in the former. the fiber cloth, and then cooled and finally perforated or cut, the perforated or cut product is finally hardened under pressure and molding at a temperature that is above the starting temperature of the hardening reaction of the binder contained in the fiber cloth and above the start temperature of hardening reaction of the glue, whereby the formaldehyde released by the hardening reaction of the binder serves as a hardener for the glue. A method according to claim 1, characterized in that the sheet material having a duroplastic resin as an adhesive in discontinuous production in cut form is applied on a prepared or pre-hardened and cut fiber cloth containing a phenolic resin and a hardener, and the product obtained is then hardened at a temperature that is above the starting temperature of the hardening reaction of the binder used in the fiber cloth and above the starting temperature of the hardening reaction of the glue, by what the formaldehyde released from the hardening reaction of the binder serves as a hardener for the glue. A method according to claim 1, characterized in that a sheet material having a resin-hardener mixture as an adhesive is applied in cut form to elaborate shaped and hardened shaped parts > of fiber fabrics, and the product obtained is heated above the starting temperature of the hardening reaction of the resin-hardener mixture. A process according to any of claims 1 to 5, characterized in that the resin used as glue is a Novolak resin free of hexamethylenetetramine. A process according to any of claims 1 to 6, characterized in that the resin used as glue is a modified phenolic resin. A process according to claim 7, characterized in that the resin used as an adhesive is a phenolic resin modified with phenoxy resin. A method according to any of claims 1 to 8, characterized in that the resin or mixture of resin-hardener in the form of powder is applied to the sheet metal material. . A process according to claim 9, characterized in that the melt viscosity of the resin or resin-hardener mixture, measured at a temperature of 175 ° C, is less than 1000 mPas. A molded part of fiber cloth, manufactured in accordance with one or more of claims 1 to 10.