WO2006015440A1

WO2006015440A1 - Method of forming a composite material

Info

Publication number: WO2006015440A1
Application number: PCT/AU2005/001206
Authority: WO
Inventors: Eric Quevauvilliers
Original assignee: Pacific Strategies Consultants Pty Ltd
Priority date: 2004-08-12
Filing date: 2005-08-11
Publication date: 2006-02-16
Also published as: CN101128303A; TW200613412A

Abstract

A process for producing a composite material including the steps of inserting a pre-selected quantity of preformed foam particles into a mould and injecting a matrix composition into said mould, whereby said matrix composition flows around the particles to form a composite material having foam particles encased within the matrix composition.

Description

METHOD OF FORMING A COMPOSITE MATERIAL

TECHNICAL FIELD

The invention described herein relates to a method of forming a composite material and in particular, the invention is directed to, a method of forming a light weight composite material which includes foam particles, although the scope of the invention is not necessarily limited thereto.

BACKGROUND ART

Plastics materials find use in the manufacture of a large range of products. Various manufacturing methods have increased the usefulness of plastic materials, using them as an alternative material for products previously made from metals such as automobile or white good panels. In particular, plastics materials may possess high strength qualities combined with good toughness, lower production costs and lightweight characteristics.

In order to reduce the production costs and control the mechanical properties of the components produced from plastics materials fillers have been incorporated into plastics materials. Many filled plastic components incorporate light weight fillers. Lightweight, inexpensive fillers such as polystyrene foam have been used to form a composite material which has the improved properties of being lightweight, stronger than aggregated foamed products and having improved characteristics.

Various light weight fillers such as foamed particles can impart shock absorbing characteristics or noise attenuation characteristics on the products manufactured therefrom. For example, foamed balls of polystyrene have been foamed in a mould so as to form an aggregated component that has good shock absorbing characteristics. Such products have been encased within a skin subsequently applied to the aggregated foam balls to form bicycle helmets and the like. Other applications such as in shock resistant packaging, noise attenuation and the like have been found for components formed in this way. These materials, whilst providing good shock absorbing properties, generally do not provide the required toughness or strength in that they are readily broken as the foamed particles aggregated together do not provide a high strength product.

Other techniques for producing this type of product involve the foaming of polystyrene beads in a mould of an injection moulding machine. The formation of foamed particles of polystyrene in a mould prior to the injection of a matrix material has the potential to result in an inconsistent product in that the density of the expanded polystyrene particles may vary according to the conditions in the mould, the source and type of polystyrene beads and other factors. The range of expansion density may be from 10-lOOg/L.

Previous methods have tried to form such a product by introducing polystyrene beads

(precursors of the foamed particles) into moulds and then applying steam to expand the beads into foamed particles. These particles must be dried in situ before filling the mould with a plastics material to form the desired composite material. The expansion of the raw product tends to be unpredictable resulting in variable quality of such composite materials, the quality of parts being non-reproducible with different batches of raw product used. Additionally, once the raw product has been expanded, it must be dried before a substrate or a matrix can be introduced into the mould to form the finished product.

There are drawbacks associated with this process as the steam used to expand the raw product promotes the formation of bubbles, being air pockets, which produce cavities in the finished product. Additionally, as the plastic material needs to be introduced into the mould quickly, the turbulent flow further promotes the formation of bubbles, exacerbating the problem of the formation of cavities.

This process is complex, time consuming and consumes a large amount of energy including the steps of the method and applying pressure to form the material in the mould and results in a product of variable quality which is inclined to include holes.

We have now devised a new method to form a particulate composite material in a simple and consistent quality to possess desired characteristics. This method substantially ameliorates the above problems or at least provides a consumer with a useful commercial choice.

SUMMARY OF THE INVENTION

According to a first embodiment of the invention, there is provided a process for producing a composite material including the steps of inserting a pre-selected quantity of preformed foam particles into a mould and injecting a matrix composition into said mould, whereby said matrix composition flows around the particles to form a composite material having foam particles encased within the matrix composition. According to a second broad form of the invention, there is provided a composite foam formed from the above method.

The process of the present invention involves taking preformed particles, introducing them into the mould in a desired quantity, and filling the mould with the matrix composition such that the matrix composition fills the interstices between the particles to envelop them and fills the mould, preferably slowly at a substantially laminar flow rate, whereby the formation of air bubbles is limited and substantially fills the mould to reduce air gaps and shrinkage.

The foam particles may be preformed polystyrene beads which have been expanded in a separate process from crystals or beads. By using preformed foam particles variation of the density in the foam particles is catered for prior to the filling of the mould with the particles resulting in a more consistent product. We have found that whilst the materials handling of the pre-foamed particles is more complex than unfoamed beads, the improved properties of the component produced in accordance with the present invention render the process a substantial improvement over previously used processes. In order to change the desired characteristics of a formed object, the density of polystyrene within the composite can be altered by varying the quantity of particles introduced into the mould. Thus for example, a composite comprising 20% volume polystyrene particles will have higher impact strength but lower insulation properties than a composite comprising 80% volume polystyrene particles.

It will be understood by a person skilled in the art that other foamed particles may be used to form the foam particles such as polyurethane, polypropylene or another suitable foamed materials. Preferably, the foam particles are in the form of expanded foam balls.

The foam particles can be pigmented such that the particles and the matrix are of complimentary or contrasting colour, to create an aesthetic appeal such as when the material is cut, worn down or damaged in any fashion. In this way, the formed object can sustain impacts without detrimentally affecting the aesthetic appeal of the object.

The matrix composition preferably produces a integral skin around the perimeter of the mould such that the particles are contained, sandwiched between the skin forming the perimeter of the moulded product. Without wishing to be bound by theory, it is believed that the flow of the matrix around the periphery of the mould urges the foamed particles away from the mould and allows the matrix to for a peripheral skin. In one embodiment of the present invention, a skin polymer may be injection moulded about the matrix to form a skin. The matrix can be formed from any suitable plastic material such as polyethylene, polyurethane, polyurethane elastomer, phenolic polymer or a foamed PER. Preferably, the matrix has a high impact resistance characteristic to maintain the impact strength of the composite material.

The integrity of the strength of the plastic is complemented by the lightweight and good insulation characteristics of the filling particulate material.

The composite foam of the present invention may include a variety of additional components. The composite may include pigments, plasticizers, reinforcing agents, fillers and the like. The composite foam of the present invention may include recycled materials such as crumbed material. For example, in a polyurethane matrix, crumbed polyurethane or crumbed rubber such as from tyre waste, maybe incorporated into the polyurethane matrix so as to either improve the mechanical properties of the foamed composite or reduce the cost. Reinforcing materials such as chopped fibres may also be incorporated into the composite foam to provide the desired mechanical characteristics. Additives such as fillers and reinforcing agents compatible with the composite foam may be used.

The foamed particles may be introduced into the mould in a variety of convenient ways preferably by a venturi system. A venturi system creates a vacuum which draws the lightweight particles into the mould. For each mould, the timing of suction can be regulated to coincide with specific quantities or percentage volume of particles within the mould. Thus for each mould, the timing of the vacuum may be calibrated according to the desired quantity of particles as a percentage volume of the mould. For example, it may be desirous to calibrate five settings each corresponding to the timing to fill the mould with 20% particles.

The matrix may be either simultaneously or subsequently injected with the particles. The matrix, where it is a thermosetting polymer such as a polyurethane, may be injected in the form of monomer and catalyst introduced into the mould while a pressure is applied externally. The composite consistency provides the benefit of reducing the in mould pressure required to 250psi in comparison with the higher pressures required for manufacturing an object from the polyurethane alone. Additionally, the composite has the advantage of producing a product which can be one tenth or less of the weight of a similar product made out of solid polyurethane. The pre- formed foam particles may be injected into the mould separately or integrally with the matrix composition, hi one form of the present invention, the pre-formed foam particles may be injected into the mould along with the matrix composition, hi one embodiment, the pre-formed foam particles may be pre-mixed with the matrix composition prior to injecting into the mould. In this embodiment, the pre-formed foam particles are feed via a hopper into the flight of an extruder and the matrix composition also injected into the extruder downstream from the incorporation of the pre-formed foam particles. Where the matrix composition is a thermo-setting polymer and the monomer and the catalyst are separately injected into the extruder or combined prior to injection into the extruder. We have found that it is advantageous to pre-mix the pre-formed foam particles with the matrix composition, particularly where the matrix composition is a polyurethane as this permits the pre-mixed components to be quickly incorporated into the mould and the mould sealed prior to the reaction between the monomer and the catalyst. In this way we have found that we achieve better filling of the mould and provide a more consistent product of even density. Where the matrix composition is a polyurethane foam, the mould may be sealed prior to the foaming of the matrix.

The variable ratios of density of particles to the density of matrix substance provides a range of characteristics with higher quantities of polystyrene as a percentage volume producing increased softness and insulation characteristics whilst lower quantities of polystyrene produce a harder and less dampening material.

The desired end product will affect the optimal ratio of particle to matrix to produce the desired characteristics for the specific application.

This composite material may be used for producing panels for applications such as marine craft, vehicle panels, caravan and camper wall panels, automobile parts, car panels, foams for seats, interiors and dashboards, safety helmets and safety barriers, white good panels, packaging materials, building panels, acoustic and sound-proofing panels, fire retardant panels and space craft panels.

This composite material may have application as a replacement for plastic materials in the formation of products such as white goods and black goods, especially where insulation is a desirable quality such as to encase electrical wiring in personal computers or mobile telephones. The composite foam of the present invention advantageously may be used in refrigeration. We have found that a composite foam formed from a foamed polyurethane matrix with pre-formed polystyrene particles may be of sufficient strength and have sufficient insulating properties to provide an improved insulating material for refrigeration.

Surprisingly, we have found that the composite material of the present invention may be used for forming pallets. Surprisingly, we have found that pallets formed from the composite material are of sufficient strength to support many loads that are traditionally supported on timber pallets. The pallets formed from the composite material of the present invention may weigh approximately half the weight of a timber pallet and yet be of sufficient strength to provide a useful alternative.

The strength to weight ration of the composite material of the present invention provides a variety of unique applications to which the composite material may be put. For example, in the mining industry, large trucks often need to be chocked, such as when a wheel is being changed, typically chocks are formed from timber or steel. The weight of such chocks, due to the size required to effectively chock a mining vehicle is such that they are difficult to lift and manipulate. We have found that the composite material of the present invention may be readily formed into chocks suitable for use with mining equipment and which are sufficiently light as to be readily manipulated and carried.

In order that the invention may be more readily understood and put into practice, one or more preferred embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a cross-section through a component for a high stress application produced according to the process of the present invention;

Figure 2 shows a cross-section through a bicycle helmet produced according to a second embodiment of the process of the present invention;

Figure 3 shows a cross-section through a tile produced according to a third embodiment of the process of the second invention;

Figure 4 is a perspective view of a pallet formed from the composite material of the present invention; and Figure 5 is a vehicle chock formed from the composite material of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows a component 1 that is designed for high stress applications. The component has an inside skin 2 and an outer skin 3. The component 1 is formed from a polyurethane matrix 5 which is a semirigid polyurethane with a free rise density of 180 grams per litre. The moulding density of the polyurethane matrix 5 is between 220 and 270 grams per litre.

The foamed particles 4 are formed from PPE/PPU with a particles size of from 3 to 4 mm in diameter and having a density of 50 to 55 grams per litre. The foamed particles 4 are pigmented with a black pigment to match the colour of the pigmented polyurethane matrix 5.

The foamed particles 4 were dried and fed into clean moulds prior to the injection of the polyurethane matrix 5.

Figure 2 shows a cross-section of a bicycle helmet 11. The bicycle helmet 11 is formed from a polyurethane matrix 15. The polyurethane matrix 15 years semirigid and has a free rise density of 80 grams per litre. The moulding density of the polyurethane matrix 15 is between 120 and 150 grams per litre.

The foamed particles 14 are formed from PPE/PPU with a particles size of from 3 to 4 mm in diameter and having a density of 30 to 35 grams per litre.

The inner skin 12 of the bicycle 11 shows the foamed particles 14 extending through the matrix 15 which is due to the high volume of foamed particles 14 relative to the polyurethane matrix 15. The outer skin 13 is applied over the pre-formed helmet to provide an attractive and protective layer such that the foamed particles are protected from the weather.

Figure 3 shows a cross-section of a tile 31. The tile 31 has an outer skin 32. The outer skin 32 is formed by the polyurethane matrix 15 displacing foamed particles 34 from against the moulds in which the tile 31 is formed.

The tile 31 is formed from a polyurethane matrix 35 which is a semirigid polyurethane with a free rise density of 180 grams per litre. The moulding density of the polyurethane matrix 35 is between 220 and 270 grams per litre. The foamed particles 34 are formed from PPE/PPU with a particles size of from 3 to 4 mm in diameter and having a density of 50 to 55 grams per litre.

Figure 4 shows a pallet 40 formed from a composite material of the present invention. The pallet 40 has legs 41 moulded from the composite material of the present invention. The deck 42 of the pallet 40 is also formed from the composite material of the present invention.

Figure 5 shows a vehicle wheel chock 50 formed from a composite material having a polyurethane matrix with polystyrene particles embedded therein according to the present invention. The vehicle wheel chock 50 has a chocking surface 51, a pair of opposed side walls 52 and a base 53. The chock 50 is solid at its narrow portion and hollow at the thickened portion. The narrow portion generally abuts and restrains the wheel of the vehicle whilst the thickened portion is subjected to lateral rather than compressive loading and accordingly being of hollow construction does not significantly reduce its performance while reducing the weight of the chock 50 to render it more manoeuvreable. Aperture 55 permits the chock to be formed of reduced weight whilst still providing adequate resistance to movement of the vehicle.

The foregoing embodiments are illustrative only of the principles of the invention, and various modifications and changes will readily occur to those skilled in the art. The invention is capable of being practiced and carried out in various ways and in other embodiments. It is also to be understood that the terminology employed herein is for the purpose of description and should not be regarded as limiting.

Claims

THE CLAIMS:

1. A process for producing a composite material including the steps of inserting a pre¬ selected quantity of preformed foam particles into a mould and injecting a matrix composition into said mould, whereby said matrix composition flows around the particles to form a composite material having foam particles encased within the matrix composition.

2. A process according to claim 1 wherein the preformed particles are selected from the group consisting of foamed polystyrene, foamed polyurethane and foamed polypropylene.

3. A process according to either claim 1 or claim 2 wherein the pre- formed foam particles are polystyrene foam balls.

4. A process according to any one of claims 1 to 3 wherein the matrix composition forms a skin around the composite material.

5. A process according to any one of claims 1 to 4 wherein the matrix composition is selected from the group consisting of polyethylene, polyurethane, polyurethane elastomer, phenolic polymer or a foamed PIR.

6. A process according to claim 5 wherein the matrix composition is a polyurethane.

7. A process according to claim 6 wherein the polyurethane is a polyurethane foam.

8. A process according to any one of claims 1 to 7 wherein the composition further includes pigments, plasticizers, reinforcing agents or fillers.

9. A process according to any one of claims 1 to 8 wherein the composition comprises pre-formed polystyrene foamed particles and a polyurethane matrix composition.

10. A process according to claim 9 wherein the matrix composition further includes crumbed polyurethane or crumbed rubber.

11. A process according to any one of claims 1 to 10 wherein the pre-formed foam particles are inserted into the mould by a venturi system.

12. A process according to any one of claims 1 to 11 wherein the matrix is a thermosetting polymer and said matrix is injected in the form of monomer and catalyst introduced into the mould while a pressure is applied externally.

13. A process according to any one of claims 1 to 12 wherein the pre-formed foam particles are injected integrally with matrix composition.

14. A process according to claim 14 wherein the pre-formed foam particles are feed via a hopper into the flight of an extruder and the matrix composition also injected into the extruder downstream from the incorporation of the pre-formed foam particles.

15. A process according to claim 14 wherein the matrix composition is a thermo-setting polymer and the monomer and the catalyst are separately injected into the extruder or are combined prior to injection into the extruder.

16. A composite material formed by a process according to any one of claims 1 to 15.

17. A composite material according to claim 16 whe4rein said composite material is used in applications selected from the group consisting of marine craft, vehicle panels, caravan and camper wall panels, automobile parts, car panels, foams for seats, interiors and dashboards, safety helmets and safety barriers, white good panels, packaging materials, building panels, acoustic and sound-proofing panels, fire retardant panels and space craft panels.

18. an insulating panel formed from a composite material according to claim 16.

19. A pallet formed from a composite material according to claim 16.

20. A vehicle chock formed from a composite material according to claim 16.