Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-09-15
2001-09-25
Weisberger, Richard (Department: 1775)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S166000, C156S176000, C156S180000, C442S327000, C442S341000, C442S344000, C425S112000, C264S165000, C264S172110, C264S175000
Reexamination Certificate
active
06294036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and an apparatus for implementing the said process for manufacturing composite sheets. It also relates to the composite products obtained.
2. Discussion of the Background
It is already known to manufacture composite sheets, in the form of panels or curved components, from fabrics formed both from reinforcing yarns and from thermoplastic yarns, by stacking the fabrics and then hot-pressing the stack thus formed, as described in Certificate of Utility FR 2,500,360. Such a process has, in particular, the disadvantage of being a batch process.
Moreover, the patent application filed in France under the filing number 96/00578 describes the manufacture of composite sheets from glass/organic material fabrics which are deposited continuously on a conveyor and then preheated in a hot-air oven before being introduced into a “belt press” (of the type described in Patent U.S. Pat. No. 4,277,539) where they are successively heated and cooled, while at the same time being compressed. Such a process is quick and can be used to obtain sheets suitable for moulding and having good mechanical properties.
However, on some of these sheets, defects are observed in the alignment of the glass filaments (presence of corrugations) in the longitudinal direction (direction of advance of the conveyor) or in the transverse direction, these defects being due to poor reorganization of the yarns after the preheating step and to the transverse shrinkage of the fabrics after this same step. These defects, which in many applications are not of great significance, may nevertheless not be desirable in certain very specific applications (especially in the manufacture of large flat thermoformed articles such as materials-handling boards, food trays, etc., where the filament alignment defects may be the cause of deformations within the articles).
SUMMARY OF THE INVENTION
The object of the present invention is to provide an improved process and an improved apparatus for the manufacture of composite sheets, this process and this apparatus not having the drawbacks of the aforementioned existing processes and apparatuses and making it possible to obtain sheets suitable, in particular, for the manufacture of flat articles with improved characteristics by thermoforming.
This object is achieved by virtue of the process according to the invention, which comprises at least the following steps:
at least one ply of yarns, this ply comprising at least two materials having different melting points, is introduced continuously into a zone where it is heated to a temperature lying between the said melting points and below the degradation temperature of the material having the lower melting point,
the ply is passed over at least one rotating bar heated to a temperature lying between the said melting points and below the degradation temperature of the material having the lower melting point,
the ply is compressed on leaving the bar or bars and is cooled so as to form a composite web,
the web is collected in the form of one or more composite sheets.
The term “sheet” is understood to mean, according to the present invention, an element which is not very thick compared with its area and is generally flat (but which could possibly be curved) and rigid but has, if need be, sufficient flexibility to be able to be collected and stored in reeled form. In general, it is a solid element but, in some cases, it may be apertured (thus, according to the invention, the term “sheet” also covers, by extension, structures of the mesh type).
The ply of yarns is formed from yarns of at least two materials having different melting points. These two materials may, for example, be thermoplastic organic materials but, preferably, they are a thermoplastic organic material and a material for reinforcing this thermoplastic organic material (for example, glass, carbon, aramid, etc.). In general and preferably, the ply consists of a reinforcing material (advantageously glass) and of one or optionally several thermoplastic organic material(s). The ply generally comprises between 20 and 90% by weight of reinforcing material, (preferably glass), preferably between 30 and 85% by weight of reinforcing material and particularly preferably between 40 and 80% by weight of reinforcing material. It may partly comprise yarns consisting of one of the materials and partly yarns consisting of the other material, these yarns being arranged alternately in the ply and being preferably intimately mixed. It may also comprise compound yarns obtained by combining and simultaneously winding yarns of one of the materials with yarns of the other material, it also being possible for these compound yarns to be mixed with yarns of one of the materials and/or with yarns of the other material.
Preferably, the ply of yarns comprises at least 50% (advantageously at least 80% and particularly preferably 100%) by weight of comingled yarns, i.e. yarns composed of filaments of one of the materials and of filaments of the other material, the filaments being mixed within the yarns (advantageously in an approximately homogeneous manner), these yarns generally being obtained by assembling the filaments directly during manufacture of the said filaments (according to the processes described, for example, in Patent Applications EP-A-0,590,695 and EP-A-0,616,055). The use of plies having at least 50% and preferably at least 80% by weight of comingled yarns makes it possible, in particular, to obtain more homogeneous composites having good mechanical properties, the composite sheets being furthermore produced in a short time and advantageously at a lower pressure.
Preferably, these comingled yarns consist of glass filaments and filaments of thermoplastic organic material, these filaments being intimately mixed.
In many cases, the ply of yarns is in the form of a network or number of networks of interlaced yarns and is preferably in the form of fabrics (generally a web of fabric(s)). The same yarns or combinations of yarns may be used to form the warp and weft of the fabric or network, or the weft and the warp may consist of different yarns or of different combinations of yarns. Thus, the ply of yarns may, for example, be in the form of fabric(s) whose warp consists of organic material/reinforcing material comingled yarns and whose weft consists of 80 to 100% of yarns of organic material of the same kind as that of the comingled yarns. The sheet obtained may then have a preferred direction of orientation of the reinforcing yarns unidirectional sheet). In particular embodiments of unidirectional sheets, the ply of yarns may also advantageously be in the form of bundles of parallel yarns which are touching or slightly placed apart (the spacing between the yarns preferably being less than 2 mm), these yarns preferably being, in this embodiment, comingled yarns.
According to a preferred embodiment of the present invention, the ply comprises a combination of approximately parallel continuous yarns which are oriented in the direction of movement of the ply during the process (longitudinal direction) and, particularly preferably, also comprises a second combination of approximately parallel yarns oriented transversely to this direction and interlaced (preferably woven) with the yarns of the first combination.
In the process according to the invention, the ply of yarns is usually unwound from a support or from several supports (as appropriate, when parallel yarns are involved) on which the ply is wound.
The ply of yarns (moving at a speed of, for example, between 0.5 and 5 m/min) passes through at least one zone where it is heated to a temperature lying between the melting points of the materials making up the ply, this temperature also being below the degradation temperature of the material having the lower melting point. By extension, in the present invention, “degradation temperature” denotes the minimum temperature at which decomposition of the molecules making up the material is observed (as conventionally defined
Debalme Jean-Paul
Loubinoux Dominique
Saint-John Charles
Voiron Jacques
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vetrotex France
Weisberger Richard
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