Patent Application
20050192382
The present invention relates to extrusion processes. In particular, the present invention relates to an extrusion method and apparatus for composite material.
The process of solid-state extrusion is known. Extrusion processes that are used include ram extrusion and hydrostatic extrusion. Ram extrusion utilises a chamber in which polymer billets are placed, one end of which contains a die and the other an axially mobile ram. The billet is placed within the chamber such that the sides of the billet are touching the sides of the chamber. The mobile ram pushes the billets and forces them through the die.
In hydrostatic extrusion processes, the billet is of a smaller size than the chamber and does not come into contact with the sides of the chamber. The chamber contains a pressure generating device at one end and a die at the other. The space between the billet and the chamber is filled with a hydraulic fluid, pumped into the chamber at the end containing the pressure generating device. During operation pressure is increased on the hydraulic fluid and this in turn transmits pressure to the surface of the billet. As the billet passes through the die some of the hydraulic fluid adheres to the surface of the billet, providing additional lubrication to the process.
Both processes produce a polymer that is oriented in a longitudinal direction, having increased mechanical properties, such as tensile strength and stiffness. However, the orientation in a longitudinal direction can also make the polymer weak and subject to transverse cracking or fibrillation under abrasion. The process of pushing the polymer through a die can also create surface imperfections caused by frictional forces.
U.S. Pat. No. 5,204,045 to Courval et al. discloses a process for extruding polymer shapes with smooth, unbroken surfaces. The process includes heating the polymer shape to below the melting point of the polymer and then extruding the polymer through a die that is heated to a temperature at least as high as the temperature of the polymer. The process also involves melting a thin surface layer of the polymer to form a thin, smooth surface layer. The process produces a material of a uniform appearance and subsequent commercial applications are limited as a result.
A composite material comprising an oriented polymer and a particulate filler dispersed throughout the oriented polymer. The composite material has a reduced density which is less than the combined masses of the oriented polymer and a particulate filler divided by their combined respective volumes.
The particulate filler may be non-adhering to the polymer.
The particulate filler and the polymer are selected to have respective mismatching polarities.
The oriented polymer may be of plastic and the particulate filler may be selected from the group consisting of wood, slate, talc, vermiculite and mica.
The plastic may be polypropylene, polyethylene and polyvinyl chloride and present in an amount of from 95% to 60% by weight as compared to the particulate filler.
According to one embodiment, the oriented polymer is polypropylene and the particulate filler is wood sawdust having a particle size of about 60 mesh and present in amount of from 20% to 30% by weight as compared to the weight of the oriented polymer.
A process for producing an oriented composite material, said process comprising the steps of combining:
The extrudable polymer may be of plastic, such as polypropylene, polyethylene or polyvinyl chloride.
The particulate filler may be wood, slate, talc, vermiculite or mica.
The extrudable polymer may be present in an amount of from 95% to 60% by weight in the starting material.
According to one embodiment, the extrudable polymer is polypropylene, the particulate filler is wood sawdust having a particle size of about 60 mesh, the wood sawdust being present in an amount from about 20% to 30% by weight in the starting material.
The rate of drawing through the drawing die may be sufficient to cause the composite material to have a density of from 0.5 to 0.9 of the density of the starting material.
A composite material is provided which includes a filler for enhancing the physical properties of the composite material and a binding agent mixed with the filler for permitting extrusion of the composite material in a plastic extrusion process to provide a predetermined dispersion pattern of the filler in the composite material; the filler being non-adhering to the binding agent.
The filler and the binding agent are selected to have respective mismatching polarities.
The filler may be natural or synthetic fiber and the binding agent may be a polymer.
A composite material is provided which comprises a particulate material dispersed in an oriented polymer, the particulate material being non-adhering to the polymer.
The particulate material and the polymer are selected to have respective mismatching polarities.
The particulate material may be wood sawdust having a particle size of about 60 mesh The oriented polymer may be polyethylene with the oriented polymer forming from 60% to 95% by weight of the composite material.
A strip of composite material is provided, suitable for strip flooring and having parallel upper and lower faces with first and second parallel edges extending between the upper and lower faces. The first edge has a tongue extending therefrom with parallel upper and lower curved surfaces. The second edge has a groove extending thereinto with curved parallel opposite sides. The tongue and the groove are of complimentary curvature for the tongue of a first strip to be rotatable into registration with the groove of an adjacent strip to resist lateral separation between the first strip, and the adjacent strips by interference between the upper and lower curved surfaces and the curved parallel opposite sides.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
Referring now to
Filler 12 can be a natural fibre, such as wood and agricultural fibres such as hemp, flax, straw or wheat; a synthetic fibre such as nylon, polyethylene terephthalate, glass or polypropylene fibre with a polyethylene matrix. Filler 12 can also be a mineral based filler such as slate, talc, vermiculite or mica. In a presently preferred embodiment, filler 12 is a wood fibre concentrate. Filler 12 has a mesh in the range of 10-300, more preferably in the range 10-150. In the presently preferred embodiment filler 12 has a 60 mesh.
Binding agent 14 is a polymer or other suitable extrudable plastic, such as polypropylene (PP), polyethylene (PE) or polyvinyl chloride (PVC). Binding agent 14 forms approximately 55-95% by weight of feedstock 20. Other ranges for the % weight of binding agent 14 in feedstock 20 may be appropriate depending on the filler chosen. More limited ranges of 60-95% or 70-90% may be required depending on the chosen filler 12.
Once filler 12 and binding agent 14 have been fed to feeder 16, they pass to melt extruder 18. A predetermined volume of filler 12, in accordance with the % weight of binding agent 14 that is used, and binding agent 14 are mixed in melt extruder 18 and extruded in a conventional manner to produce feedstock 20. The resultant feedstock 20 is fed by melt extruder 18 to extruder 22.
By varying parameters of the ram extrusion process, such as temperature, pressure and die contours, properties of composite material 24 can be changed. The properties of composite material 24 can also be changed by varying amounts of filler 12, and by changing the composition of filler 12. This will affect the physical properties of composite material 24, such as colour, texture, electrical conductivity, glow in the dark and fire retardancy.
The oriented product 48 of composite material 24 can be manipulated in order to meet a manufacturer's specifications with regards to the final commercial application Oriented product 48 can be cut and shaped during the ram extruding process. In the presently preferred embodiment, composite material 24 is extruded as oriented product 48 of varying specifications, however it can also be extruded as a sheet for use in commercial applications such as indoor and outdoor furniture manufacturing.
The present invention provides a new composite material, and a method and apparatus for extruding the composite material. The invention includes the initial mixing of a binding agent and a filler to produce a feedstock which is subsequently extruded as a billet of a composite material. The composite material is stronger and more durable then the starting materials. The composite material also contains striations of the filler which allows the manufacturer to produce a composite material that can reflect the image of a natural product and can be used in commercial applications such as floor coverings. The properties of the composite material can also be changed, in order to met the requirements for the commercial application of the product, by the incorporation of different types of filler and by varying the amount of filler used.
Once the tongue 52 and the groove 62 are nested, removal in a lateral direction indicated by arrows 80 is prevented first by interference between an upper edge 58 of the tongue and a depending edge 68 of the groove. Lateral separation is further inhibited by an upwardly extending edge 69 of the groove 62 interfering with a lowermost portion 59 of the tongue 52.
Extrusion rates for the composite material 24 will vary depending on various factors such as the particular composite material 24 selected, the degree of reduction, and the cross-sectional area of the extruded strip or column. Extrusion rates are however rather slow and rates on the order of six inches per minute (6 in./min.) are not atypical.
It has been found that rather than extruding the composite material 24, by pressing it through the die 38, the composite material may be drawn through the die 38.
Drawing (i.e., die drawing or free drawing) the composite material results in a material having a relative density significantly less that that of its starting billet. It is believed that this reduced density is a result of the particulate filler and the polypropylene not adhering to each other (possibly due to a mismatch in the respective polarities of the particulate filler and the polypropylene), but rather remaining apart and thereby creating voids during the drawing process.
The constituent materials of the polymer matrix and the filler are selected so as to result in a mismatch of the respective matrix and filler polarities. For example, if polypropylene, which is a non-polar molecule, is selected as the constituent matrix material, a polar filler (such as wood fibre) is required in order to result in a polarity mismatch. If polyethylene terephthalate (PET), which is a polar molecule, is selected as the constituent matrix material, a non-polar filler is required in order to result in a polarity mismatch.
One manner of drawing the composite material through the die 38 is to initially commence by extrusion, as discussed above, Once an end 100 of the oriented product 48 begins to emerge from the die 38, the end may be gasped, such as by a clamp 102 and pulled. The pulling would typically be done with no further pressing force being applied and yields an oriented end product 104.
In tests, pulling rates of up to 14 ft./min. (fourteen feet per minute) have been achieved which was limited by machine capacity. It is expected that pulling rates of 20 ft./min. (twenty feet per minute) are entirely feasible.
The properties of the oriented end product 104 produced by drawing are significantly different than those produced by extrusion. By way of example, a starting billet 110 was first formed by combining a wood fiber plastic concentrate containing 60% wood particles of about 60 mesh size and 50% polypropylene with virgin polypropylene in a 1:1 ratio. This yielded a composition having about 30% wood fiber and 70% polypropylene. The resulting combination was heated and extruded to form the billet 110.
The billet 110 was of rectangular cross-section measuring about two inches by two inches (2″×2 ). The billet 110 was heated in an oven to about 150° C. (ie. close to but below the melting point of polypropylene which is about 160° C.) and transferred to the pressure chamber 30 and initially forced through the die 38. The extruded material was then grasped using the clamp 102 and drawn at a rate of about 4 ft./min. (Four feet per minute) and once it had been entirely drawn through the die 38, allowed to cool into the oriented end product 104. The draw ratio (i.e. the initial cross-sectional area divided by the final cross-sectional area) was 10:4.
The oriented end product 104 bore a remarkable similarity both in look and in feel to wood. The oriented end product 104 diminished in density by about half compared to the starting billet 110. The density of the oriented end product 104 was about 0.59 g/cc (grams per cubic centimeter) compared to a density of about 1 g/cc for the starting billet 110.
The oriented end product 104 could be shaped as if it were wood and in planing and sawing behaved very much like wood producing shavings remarkably like wood shavings and sawdust remarkably like wood sawdust. The oriented end product 104 received both nails and screws without splitting much like wood.
In testing, the oriented end product was found to have a density and flexural strength not unlike wood and a modulus of elasticity of about half that of wood. Typical properties were a density of 0.059 g/cc, flexural strength of 6,353 lb/in2 and a modulus of elasticity of 799,298 lb/in2. Unlike wood however the oriented product 104 was virtually non adsorptive to water.
Although testing was carried out using a starting billet 110, the process can no doubt be automated as schematically illustrated in
The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.
This application is a Continuation-in-Part of application Ser. No. 10/168,716 filed Jun. 19, 2002, a National Phase Entry application of PCT application no. PCT/CA00/01555, filed Dec. 19, 2000, which in turn claims priority from U.S. Provisional patent application Ser. No. 60/172,586, filed Dec. 20, 1999.
| Number | Date | Country | |
|---|---|---|---|
| 60172586 | Dec 1999 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10168716 | Oct 2002 | US |
| Child | 11046628 | Jan 2005 | US |
