Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Layered – stratified traversely of length – or multiphase...
Patent
1996-11-04
1998-08-25
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Layered, stratified traversely of length, or multiphase...
156166, 156180, 264136, 425114, B29C 4124
Patent
active
057980683
DESCRIPTION:
BRIEF SUMMARY
1. FIELD OF THE INVENTION
The present invention relates to a process of melt impregnation, in particular for preparing fibre-reinforced resin materials.
2. BACKGROUND OF THE INVENTION
Fibre-reinforced resin materials are high in strength but light in weight, and are therefore highly desirable building materials in a number of industries.
A process of making such materials is described in EP-B-0167303, in which a fibre bundle is slid over a heated extruder head having an arcuate surface, and molten thermoplastic polymer is injected into the fibre bundle, from a slot in the arcuate surface, in a direction transverse to the array of filaments making up the fibre bundle.
When this process is used with relatively viscous materials, a significant operational problem is experienced, in that the extruded polymer tends to push the fibre bundles away from the surface of the extruder head rather than penetrating the bundle and thereby coating the individual fibres thereof. Fibres that are not encircled with polymer (wetted) do not contribute to the mechanical properties of the composite material. In further processing steps the fibre wetting can be improved but this often leads to a degradation in fibre length and consequently reduces the reinforced efficiency of the fibres. Attempting to overcome this problem by increasing fibre pressure onto the extruder head leads to unacceptably high friction over the extruder head.
EP-A-397506 discloses a process which differs from that of EP-B-167303 in the presence of two slit-like feed openings to the opposite sides of the arcuate surface, or more than 2 such openings. EP-A-397506 does not disclose any technical effect of having more than one slit-like opening.
The present invention provides a process of making a fibre-reinforced polymeric material comprising the steps of sliding a fibre bundle over an arcuate support surface in the line of the arc, and injecting into the bundle a molten or liquid polymer, characterized in that the polymer is injected through at least eight slots in the surface, each slot being substantially transverse to the bundle.
The process of the invention allows surprisingly effective impregnation of materials; for instance, it ensures that the individual fibres in the fibre bundle are encircled by polymer. It is therefore capable of producing more uniform materials than the prior art.
In addition, the process can be used to make fibre-reinforced polymeric resin materials at relatively high production speed and low capital costs.
4. BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a prospective view of part of the apparatus suitable for use in the process of the invention; and
FIG. 2 is a part cross section of the apparatus of FIG. 1 in use, with a fibre bundle passing over its surface.
5. DETAILED DESCRIPTION OF THE INVENTION
Describing the process of the invention in more detail; a fibre bundle is slid over an arcuate surface. Use of an arcuate surface enables axial tension in the fibre to be converted into a radial force of the fibre towards the support surface. This radial force can be influenced by the axial pretension in the fibre, the contact angle of the fibre on the surface and the radius of the surface. Within these parameters, the surface geometry can be optimised for a certain pultrusion speed, fibre permeability and polymer viscosity.
The arcuate support can be provided by the surface of a support, for example, when the support is cylindrical. Alternatively, it can be provided by cutting an arcuate section, or trench, through a support. The remainder of the support can be any suitable shape to allow co-operation with other equipment with which it is to be used. For example, it may be mounted on an extruder. It is preferred that side walls extend upwardly from the surface, to facilitate handling of the fibre bundle passing over it and to prevent polymer from escaping sideways from under the fibre bundle.
Molten or liquid polymer, typically a thermoplastic polymer (though thermoset resins can be used), is pressed through a plurality of
REFERENCES:
patent: 4537801 (1985-08-01), Takeda
Carmen Dennis V.
Eashoo Mark
Shell Research Limited
Silbaugh Jan H.
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