Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1987-03-17
1989-03-28
Anderson, Philip
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
264 453, 264 465, 264257, 428282, 428286, 4283099, 4283175, B32B 326, B32B 520, B29C 6722, B29C 3912
Patent
active
048163295
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the technical field of materials with a basis of thermoplastic resins, and more particularly materials of the type generally called laminates, usable directly as they are, or as elements in the manufacture of laminated articles.
PRIOR ART
Generally thermoplastic resins are known to be unusable in the production of laminated materials reinforced with very long fibrous elements such as in the case of thermosetting resins.
One way of reinforcing thermoplastic resins, normally molded under a high pressure of between 100 and 600 bars, is for example, to incorporate short glass fibers. The fibers are incorporated to the resin prior to the molding, their length varying between five and ten millimeters and the resulting mixture is presented in granule form. Molding is then performed from said granules by high pressure injection. During the different production phases, the average length of the fibers decreases considerably. It has also been found that, on the inside of the molded article, the longest fibers were all oriented in the flowing direction of the material, which presents certain disadvantages.
Also, the installation necessary for producing such laminates based on thermoplastic resins (injection press and mold) is very expensive, and furthermore it can become rapidly damaged, due to the very abrasive nature of certain fibers. And in all these techniques, the problem arises of evacuating the air when producing a fiber-reinforced laminated structure: defects can occur in the finished article, if such evacuation is not total.
Finally, when producing a part molded in thermoplastic resins reinforced with fibers (glass-fibers for example), the viscosity of the resin is increased, so that only articles of limited surfaces and of relatively large thickness can be obtained. Such articles, although they may react better to mechanical stresses than articles produced from pure resin, nevertheless have a fatigue strength to repeated bending stresses which is limited by the fact that a rise of temperature occurs between the fibers and the resin, or between the fibers themselves.
As a result, and despite all the advantages presented heretofore by thermoplastic resins, their use in the field of laminated articles remains reduced to a minimum compared with the thermosetting resins.
Said raw materials and production process are not really suitable for producing either a base material, or a laminated material with good structural cohesion which gives it suitable mechanical properties and the ability of being coupled in layers or strata form with other materials, in order to obtain laminated articles free from any risks of delamination.
Yet, there is a latent need for such a material usable as is, or as base material in the production of cohering laminated composites, such as walls, partition walls or articles required to have a good coefficient of sound and heat insulation with the added ability to be coupled with other materials.
A solution to this problem could have been that proposed in French Pat. No. A-70-33 052 (2 061 313). Said patent indeed describes a method for producing a material and/or a laminated article containing thermoplastic resins. According to said patent, a material is produced by placing in a mold a layer of thermoplastic fibers, which are pressed and heated up to the melting temperature. The mold may be heated, simultaneously on both its faces in order to obtain a plate or the like with two smooth surfaces, or on only one face, to obtain a plate with one smooth surface and one fibrous surface.
Such a new material is obtained from a closed mold, heated up to the melting temperature of the material, and in which the thermoplastic material undergoes a pressure.
This production method is unsatisfactory for the reasons given below.
The main disadvantage in using a closed mold is that air or other gaseous phases remain trapped in the material, with all the problems attached to this.
First of all, these air or other gaseous trappings confer to the material
REFERENCES:
patent: 3394043 (1968-07-01), Parlin et al.
patent: 3660555 (1972-05-01), Rains et al.
patent: 4130614 (1978-12-01), Saidla
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