CS273871B1 - Method of making semi-products or products from composites with thermoplastic matrix - Google Patents

Abstract

Products and semi-products of composite materials with thermoplastic polymer matrix and reinforcement based on long, or infinite fibres are currently produced by several procedures. The first one is for example the so-called wet method, which uses a dispersion of material of polymer matrix and reinforcing fibres in the form of long staple in water. Another method consists in pressing of semi-product prepared by layering of fleece of long infinite fibres and thermoplastic foils. Both these procedures, and eventually also other similar procedures comprise many material and technological limitations. These drawbacks are removed by a solution, whose principle consists in the fact that fibrous admixtures, consisting of reinforcing fibres, on which single or multi-layer coating of sintered powder material of polymer matrix is fixed by means of an anchoring intermediate layer of fusible agent, affine to polymer matrix is used for preparation of a preliminary confection semi-product by dry confection, or eventually with admixture of other material of polymer matrix in the form of powder. This semi-product is subsequently pressed into the form of the final product or semi-product.

Description

The present invention relates to a process for the manufacture of semi-finished products or composite products with a thermoplastic polymer matrix and long or continuous filament reinforcement.

The thermoplastic matrix composites, and the products and blanks thereof, are prepared in various ways. However, certain limitations apply to composites with long and / or continuous filaments, especially if they are brittle fibers that break during the preparation of the composite. By shortening the length of the fibers, the properties of the final products are deteriorated, therefore, in these cases, the surface treatment of the fibers or the matrix is necessary. Among the specific methods for preparing composite materials and articles thereof, for example, a wet composite preparation process is known in which the fibers in the form of long staple fibers, the respective polymer and optionally other components are dispersed in an aqueous medium. This will facilitate and greatly improve their intermixing, but at the same time there will be a problem associated with the removal of water, which causes both environmental problems and energy requirements.

Another method utilizes the placement of filaments or long fibers into webs which are reinforced by needling and deposited between thermoplastic films. The interconnection of the fibers with the thermoplastic then takes place under the influence of heat and pressure in the presses. However, this process does not allow the use of a higher fiber content and the distribution of the fibers in the matrix is highly dependent on the viscosity of the molten thermoplastic and the pressure used. In addition, the fibers can easily break during compression.

While it is possible to shorten the polymer flow length of the matrix by folding several layers of fibers and foils, this in turn limits the ratio of fiber content to matrix material.

The method for producing the semi-finished products or the composite products with the thermoplastic polymer matrix and the reinforcement based on the long or continuous filaments according to the invention contributes to the elimination of the aforementioned drawbacks in the preparation of the composite materials, respectively the manufacture of articles and semi-finished products thereof. It consists in that one or more layers of sintered powder of the polymer matrix material are fixed with a dry ready-made material, optionally with the addition of another polymer material, of fibrous masterbatches comprising reinforcing fibers on which an anchor layer of the fusible agent affinity to the polymer matrix is fixed a matrix in the form of a powder; by the action of heat and talc, it transforms into the final product or semi-finished product.

For example, it is possible to continuously press the belts on the rotary presses, discontinuously press the sheets of the fiber premix blanks, etc., as described above. Various techniques can be applied to form a powdered polymer coating on the fiber (in the preparation of fiber premixes). However, the coated fiber must be easy to handle so that the garment is not directly bound to the preparation of the fiber premix. The fibrous premix with good manageability can also be processed by precision winding into products which can be pressed directly as hollow products or after being split as plain products. The filament provided with the thermoplastic sheath may also be cut to different lengths and then processed in this form by conventional techniques such as extrusion, injection molding and compression molding.

The main benefit of the method according to the invention is the fact that the composite products or blanks are prepared on a not very demanding machine, practically without harmful effects on the working environment, since it is dry-working. This is a versatile method of production which produces blanks or products in which the fibers in the composite are uniformly distributed and reliably coated with the matrix. Their infinite or adequate length imparts excellent properties to the composites and reduces the need for possible surface treatment of the fibers or matrix.

The following practical example illustrates the preparation of a thin molded board of composite material to further illustrate the invention. The sintered glass fiber of polypropylene is deposited with the aid of a ready-made device on a belt or in a flat tool, for example in the form of spatial loops or in another desired shape with respect to future stresses on the final product. The layer thus deposited is further processed by pressing at temperature

CS 273871 Bl

180 to 220 ° C and a pressure of 2 to 20 MPa. Lower pressures relate to the pressing of the belts, higher pressures to the pressing of the final product of more complex shapes. The center of the interval belongs to the pressing of flat blank in the mold. The glass fiber content of the polypropylene matrix may range from 20 to 70% by weight. After cooling, the blank or article is capable of further processing or can be directly applied.

Claims (1)

Process for the manufacture of semi-finished products or products made of composites with thermoplastic matrix and reinforcement based on long or continuous filaments, characterized in that one or more fibrous masterbatches comprising reinforcing fibers on which the polymer matrix is affixed by means of an anchor layer a multilayer coating of the sintered powder of the polymeric matrix material, with a dry ready made fabric, optionally with the addition of additional polymeric matrix material in the form of a powder, prepares a prefabricated blank which is then compressed to form the final product or blank.