Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1983-01-27
1984-12-11
Ball, Michael
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156283, 1563096, 1563099, 156311, 156322, 156324, B32B 3100
Patent
active
044876475
DESCRIPTION:
BRIEF SUMMARY
THE PRIOR ART
The production of glass fibers-reinforced sheets, either cut or continuous, suited to be successively thermomolded by heating and compression into finished articles of different shape has been already described in literature.
Typical methods and processes for preparing such sheets are described for example, in U.S. Pat. Nos. 3,664,909, 3,713,962, 3,850,723 and in German Pat. No. 2,312,816.
The glass fibers which are utilized in the above-cited patents are generally pretreated with sizing agents and are always in the form of a continuous or discontinuous, and sometimes needled mat.
According to the methods therein described, a thermoplastic polymer is introduced between two mat layers in the form of a melt, whereupon the aggregate is compressed in continuous and discontinuous flat presses.
Feeding is then stopped, the material is compressed between the plates of a flat press, which have been suitably cooled to permit the thermoplastic polymer to solidfy in order to form a finished sheet. The pressure exerted on the flat press plates is such as to assure a penetration of the molten polymer into the mat.
According to a continuous production method described in German Pat. No. P 2,948,235.7, two layers of glass fiber mat, obtained by needle-bonding the fibers, are conveyed into a continuous press by means of conveyor belts. A thermoplastic polymeric material is extruded inside, i.e. between, the two mat layers, while the upper and lower faces of the mat are preferably coated with a film of said extruded polymer. The film, molten polymer and mat aggregate is conveyed to a continuous press, in the first portion of which the material is subjected to a pressure of 0,1-20 bars, wherefore air is removed, and the polymer is best distributed among the glass fibers.
Successively the material is conveyed to the second portion of the press, operating at the same pressure as the first one, but at a lower temperature, such as to solodify the polymer into sheets.
A process of such type involves therefore the utilization of needle-bonded mats, with consequent sensible increase of the total costs and creation of problems of environmental hygiene due to the splitting of a part of the glass fibers owing to needling.
THE PRESENT INVENTION
One of the objects of the present invention consists therefore in a process for continuously preparing sheets from thermoplastic polymers reinforced with glass fibers, which is free from the above mentioned drawbacks and offers considerable advantages of economic and ecological, as well as technical nature, as it permits to obtain--at the same production speed as in the above-said process--sheets having a better distribution of the glass fibers and a higher homogeneity due to the extreme reduction of entrapped air content, as is proved by their high density which reaches values equal to 98% of the theoretical value. A further object of this invention consists in a device for carrying out said process.
The process according to the present invention comprises, in the order, the steps of: accomplished by deposition from above, onto the surface of a moving conveyor belt, of glass strands having a count ranging from 10 to 220 tex, the linear feed speed of the strands being higher than the sliding speed of the belt; of the thermoplastic polymer used for producing the sheets in the successive operation (c), or of the polymer having the lowest melting temperature among those used in the subsequent operation (c); polymer in powder; either of the same type as the one of operation (c) or of different type; temperature of the polymer present, or of the polymer having the highest softening temperature among those present in the mat; either of the same type as, or of different type from the one of operations (c) and (e); to a temperature higher by at least 50.degree. C. than the melting temperature of the thermoplastic polymer present, or to the melting temperature of the polymer having the highest melting temperature among the polymers present; plurality of glass monofilaments and have pre
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Ferrari Roberto
Omacini Alberto
Rizzotto Vittorino
Rossi Carlo
Semeghini Gian L.
Ball Michael
Montepolimeri S.p.A.
Vitrofil S.p.A.
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