PROCESS FOR MOULDING POLYMERIC PRODUCTS WITH STRENGTHENING OF FIBRES OR FILAMENTS

Abstract: The process consists essentially of a way to mould polymeric products, with total or partial strengthening, by making pressure by means of an elastic membrane on the walls of the mould, giving at the same time, form to the polymeric product and subjecting the strengthening to a defined and permanent residual lengthening.

Description: ' Descriptive Report of the Invention Patent for a "PROCESS FOR MOULDING POLYMERIC PRODUCTS WITH STRENGTHENING OF FIBRES OR FILAMENTS". The present invention is relative to a process for obtaining polymeric products, strengthened, wholly or partly, with fibres or filaments, either natural, artificial or syn¬ thetic, in conventional moulds, utilizing as a moulding ele¬ ment, a vacuum and/or a fluid under pressure. It is already public knowledge that vullcanization chambers are used in the moulding or mending of tyres. The vulcanizing chamber, used with water, steam or air pressure, moulds the body of the tyre or of the mend on the mould. The vulcanizing is processed for a given time, the pressure is then relaxed and the moulded or mended tyre is withdrawn from the vulcanizing chamber. Subsequently, other processes were developped, using expanding chambers for the moulding of cylindrical parts, pre¬ pared with strengthened thermoplastic, as is the case with A e rican patent 3:937.781, in which the plastic cylinder, streng- thened with fibres is pressed against the walls of the mould by a rubber bag and is later cooled, taking on the form defined by the mould. In this case, the pressure serves merely to squeeze the part mounted on a chuck, while the thermoplastic cools and takes on the desired form. Another process, described in Brazilian request .... PI-8008367 a "PROCESS FOR MOULDING REINFORCED RESIN PRODUCTS 2 . AND THE APPARATUS FOR CARRYING OUT THE PROCESS", where the textile reinforcement is impregnated with a liquid resin which is injected under pressure and an elastic bag presses it against the walls of the mould. All the processes mentioned, merely press the pro¬ duct on to the walls of the mould. There are presently in the industry, two methods for the manufacture of polymeric products which are rein¬ forced wholly or partly with fibres or filaments. One of the methods most used, is that in which the deformation is made beforehand, namely, the reinforce¬ ment is moulded, with or without lengthening, and is sub¬ sequently covered with the polymeric product, and is then placed in the mould to take on the desired form. Normally, the mould is constituted of two principal parts, male and female, made of the same material, which is generally metal. Another method is to place the reinforced polymeric product directly in the mould, without prior modelling or deformation. Both methods, in addition to not allowing the per¬ manence of a constant residual lengtheningς*, run the risk of spoiling th final product, in the case of very thin products, owing to the contact of the male and female parts of the mould, cutting the strengthening material. It some times happens tha the loss of the material in addition to spoiling the strengthened polymeric material, emI by spoiling the mould. The present invention, consists of • a system, in which a flat plastic membrane is used and on this is placed 05 the polymeric product, wholly or partly strengthened with fibres or filaments. The mould is hermetically sealed a and pressure is made on the elastic membrane, with a fluid which compresses the strengthened polymeric product, which then takes on the form of the .mould. 10 As is known, any strengthening must maintain a re¬ sidual lengthening, related directly to the work it has to do.This residual lengthening is what maintains the pro¬ duct always at the same size, within the pressures it has to bear. 15 As described, if the strengthened polymeric product is free of tensions and is pressured by the elastic mem¬ b ane into taking the form of the mould, its lengthening is spread equally along the whole body, proportionately to the form of the mould. It is thus easy to calculate 20 the residual lengthening at which the strengthening should be maintained, without creating a tension for the poly¬ meric product. The process consists of a mould (Fig.A), composed of a base 1, a lid 2, the strengthened polymeric product 3, 25 the elastic membrane 4, and two apertures, the one on the base 6, and the one on the lid 5. Placing the strengthened polymer 3, on the elastic membrane 4, and this in turn on base 1, the lid 2, closes the mould hermetically. Maintaining the base 1 and the lid 2, pressed against each other, for example, between the faces of a press, either by screws or by excentrics, or by weights etc., a fluid is injected under pressure through tube 6, and at the same time, air is expelled through tube 5, putting pressure on the elastic membrane 4, which in turn puts pressure on the strengthened polymeric product 3, against the walls of the lid 2, thus pressing into the form of the mould, either by heat or by cooling. The strengthening which had a residual lengthening , when flat, of X%, now with the lengthening caused by the pressure of the fluid against the walls of the mould, has been reduced to X/Y%. Thus, as the relationship of de¬ formation, between the plane area and the deformed area part of the residual lengthening in the processing is with- drawn, which was previously done in the strengthening. Example 1. It is desired to maintain a residual lengthening of 5% in a strengthening, the original lengthening of which was 12%. The relation between the plane area and the de¬ formed area is 5%. Thus, a pre-treatment lengthening of 2% is made, and the strengthening changes from 12% to 10%. Example 2. It is desired to maintain a residual lengthening of 3% in a strengthening, the initial lengthening of which is 15%. The relation between the plane area and the deformed area is 2%. Thus, a pre-treatment lengthening of 10% is made, and the strengthening changes from 15% to 5%.

Claims: C L A I M S 1 - A process to mould polymeric products, with fib. e or filament strengthening, where the strengthened polymeric product is pressured by an elastic membrane on to the walls of the mould, by the pressure exerted by a fluid injected under pressure, or by a vacuum, characterized by the fact that at the same time during which the polymeric product takes on the form of the mould, it it subjects the strengthening to a defined and permanent residual leng¬ thening . 2 - a process in accordance with claim 1, character¬ ized by the fact that the polymeric product, may be a plastic, a resin, an elastomere or a mixture of these among themselves or with other raw materials. 3 - A process in accordance with claim 1, character- ized by the fact that the strengthening may be of natural, .irtificial or synthetic fibres or filaments, either woven or not. 4 - A process in accordance with claim 1, character¬ ized by the fact that the moulding may be made either with cooling or heating. 5 - A process in accordance with claim 1, character¬ ized by the fact that the elastic membrane may be smooth, have a design on it or be grooved. 6 - A process in accordance with claim 1, character- ized by the fact that the moulding may be exercised by a cold or hot fluid. 7 - A process in accordance with claim 1, character¬ ized by the fact that the moulding may be exercised by a vacuum. 8 - A process in accordance with claim 1, character¬ ized by the fact that the moulding of the polymeric pro- duct can be made by the pressure of the elastic membrane or directly, without the help of the same.

Inventors: OLIVEIRA DE CUNHA LIMA LUIZ CA, OLIVEIRA DE CUNHA LIMA, LUIZ, CARLOS
Applicants: OLIVEIRA DE CUNHA LIMA LUIZ CA, OLIVEIRA DE CUNHA LIMA, LUIZ, CARLOS
Application year: 1986
Main classification: B29C51
IPC codes: B29C43, B29C51