WO1992016370A1

WO1992016370A1 - Products made from waste plastics materials

Info

Publication number: WO1992016370A1
Application number: PCT/CA1992/000118
Authority: WO
Inventors: Llewellyn E. Depew
Original assignee: Depew Llewellyn E
Priority date: 1991-03-19
Filing date: 1992-03-19
Publication date: 1992-10-01
Also published as: CA2038560A1; AU1544792A

Abstract

The invention provides a unitary structure which is either in the form of a complete article or is a preform used in manufacturing articles formed from the preform. The unitary structure includes a plurality of layers attached to one another by application of heat and pressure, at least one of the layers including reclaimed PET, reclaimed PE, and compatibilisers, and at least one other of the layers being of a reinforcing matting. A method of manufacture is also provided.

Description

PRODUCTS MADE PROM WASTE PLASTICS MATERIALS DESCRIPTION

TECHNICAL FIELD This invention relates to products made by recycling waste plastics materials and to processes used in manufacturing the products.

Consumers and industries in advanced countries are discarding large volumes of plastics materials. Attempts made to reuse these materials have met with great difficulties due to the complex mixtures of plastics and also due to the fact that much of the waste is contaminated by contact with non-plastic materials. This invention provides products made from such materials and a method for making the products.

BACKGROUND APT

Three general types of plastics are used currently in industrialized nations in sufficient quantities to represent the major components of plastics waste materials. These are Polyethylene Terephthalate (PET), Polyethylene, both high and low densities, (PE), and Polyvinylchloride (PVC) . It has been found that these materials commonly occur in waste plastics in the ranges of about 60 to 70 percent PET, 15 to 30 percent PE and 5 to 10 percent PVC. There are of course other waste plastics but these do not represent major parts of the waste. The difficulty of analysing the waste is compounded by the fact that the materials are usually mixed, laminated, or otherwise comingled with one another.

There is great political pressure to increase the amount of plastics being recycled and turned into useful products. It is now common for households to separate garbage into various types, including plastics. The garbage is collected and sorted into the three main types, and it has been found that PVC and PE can be used to manufacture such things as imitation wood, outdoor furniture, and other products where the quality and strength of secondary importance because bulk can be used to get the strength.

By contrast with the use of PE and PVC, PET, which represents the largest single part of waste, is not used in large quantities because it is difficult to recycle. It has found limited use in such things as carpet backing, but is not in use to produce bulk objects. Before it would be possible to use PET along with PE and PVC, compatibility and bonding must be achieved and the problems of bulk manufacture must also be addressed.

To date, plastics separated in household and commercial waste provide a very small percentage of useful material due to the problems of contamination with other non-plastics materials, to the comingling, and also due to the lack of a process that can use such waste efficiently and produce useful materials and products economically.

There has been some research into the possibility of using PET with the other waste plastics, particularly PE in the high density form, and this has shown significant test results. An article appearing in "Plastics Engineering" of October 1989 shows that PET and high density PE can be blended with a compatibiliser SEBS (Styrene-Ethylene/Butene Styrene) . The experimental results showed that while the addition of SEBS showed a linear decrease in yield strength with increasing elastomer content, there was a synergistic result when the effects of SEBS were studied in relation to the impact strength of the finished test products. It was found that with a mix of 3.5 to 1 PET to high density PE (HDPE), the impact strength jumped dramatically above 10 percent SEBS. There was an increase in the order of 10 fold between 10 and 13 percent SEBS. By contrast with this, the use of EPDM (Ethylene/Propylene/Diene) elastomers showed no synergistic results.

While these test results have been available for some time, they do not solve the problem of making use of PET with PE and other plastics found in waste. This is primarily because of the difficulty of simply treating and using the plastics to produce an end product. Clearly it would be beneficial if the waste materials could be used as found without sorting. Working against this is the fact that PET is hygroscopic and must be ground and dried at elevated temperatures above those at which PVC and PE would melt. Consequently, it is conventional to require sorting to conduct the drying.

Bulk products have been tried, and they of course use a lot of material. Also they suffer from the disadvantage that the melted plastic when put into a bulk form takes a long time to cool and tends to suffer from skin fractures due to premature cooling of the surface and long term cooling of the core. Also, if the product is not supported for an extensive time, it will sag. The results have been less than desirable, and certainly not useful for products where significant stress is to be expected, such as for instance in railway ties or fence posts.

It is to a background of these problems that the present invention addresses the question of using the available mixtures of PET, PE, and PVC and other materials as they are normally found to produce useful products.

DISCLOSURE OF THE INVENTION

In one of its aspects, the present invention provides a product comprising: a plurality of layers attached to one another by the application of heat and pressure, at least one of the layers including reclaimed PET, reclaimed PE and a compatibiliser, and at least one other of the layers being of a reinforcing matting. In another of its aspects, the invention provides a method of making a preform for a product from waste plastics materials, the method comprising the steps: preparing a mixture of the waste plastics materials including significant proportions of PET and PE; extruding the mixture into a sheet; passing the sheet while still soft between rolls with a reinforcing layer and appling pressure to create a laminate of the sheet and layer to bond the sheet and layer.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an isometric view of a typical product made according to a process of the invention; and

Fig. 2 is a diagrammatic representation of the process used to make the product. BEST MODE FOR CARRYING OUT THE INVENTION

With reference to the drawings, a typical product 20 is shown in Fig. 1. It will be seen that the product is rectangular in general shape and there is an indication at 22 that it is made of parallel layers wrapped continuously from the center to the outer surface.

The method of manufacture is indicated diagrammatically in Fig. 2. Bulk waste plastics materials are contained in a storage container 24. These materials have been shredded and ground, and metallic materials removed. The materials have then been washed and dried before storage. The waste will vary in make up but will usually include PET, PE and PVC. They are fed to a mixing structure 30 where a compatibiliser is added and mixed in prearranged proportions from a supply 32 before being fed through a supply conduit 34 to an extruder 36. This extruder heats the mixture and provides a continuous sheet 38 of hot, soft material.

For best results, the mixture of PET to PE is preferably no less than two to one and the PE is normally in the form of HDPE. PVC is provided only if it is available since it is a filler in the product and should therefore only be in small proportions. The preferred compatibiliser is styrene methylene/butene styrene (SEBS) . In general the compatibiliser is preferably a thermoplastic rubber (TPR) such as styrene-ethylene/butene styrene (SEBS), ethylenepropylenediene rubber (EPOR), or ethylenepropylene rubber (EPR) . Of course other compatibilisers can be advantageous if they cause any form of bonding between the disparate materials. This is because the end product does not depend entirely for its strength on the layers made of waste plastics. (This will become apparent from the following description) . For instance, it has been found that ethyl vinyl acetate will combine with compounds to cause some binding in the waste material.

The resulting extruded sheet 38 passes through a nip between a pair of rolls 40 where reinforcing matting 42 is brought from a supply roll 44. The matting is preferably fibreglass which can be made from waste glass products. This is another advantage of the process. Glass bottles, etc. are used in a variety of colours and to be recycled for use as bottles, they must be separated. In the present process, these coloured glasses can be mixed and melted to make the fibreglass reinforcing.

The resulting pressure in roll 40 creates a mechanical bond between the reinforcing and the soft sheet 38. A flying blade 46 is used to cut the resulting laminate into sections which are then matched with a cover layer from a supply 48 to provide a UV resistant wrapper. This step will of course depend on the final use since it may not always be needed. Also other final sheets can be used if preferred. For instance to give a particular colour to the final product. The resulting laminate is shown at 50 and this is then rolled into a preform 52 before being placed in a mould opening 54 in a first mould half 56. The second mould half 58 is brought down to press and heat the preform and deform it under load into the required shape of the product 20 (Fig. 1). All of this is of course done with the material warm enough to be deformed under pressure.

This simple exemplary use of the process may be refined within the scope of the invention. For instance, coatings or modifiers could be used on the various layers to ensure that they are compatible and will bind to one another. Such variations are within the scope of the invention.

Although the product includes only one layer of plastics materials and one layer of reinforcing in parallel with the plastics materials, the effect in cross-section is to create a product which is made up of alternating layers of plastics materials and reinforcing materials. Also product can be made by adding layers to one another if preferred.

The products have significant rigidity and resistance to deformation. This is caused by a number of factors including the reinforcing layers being separated by the plastics sheets, the mechanical bonding between all of the layers, and the use of compatibilisers. It has been found that the mix of the plastics and the proportions of compatibilisers will have effects on final products. However the basic process will accept a wide variety of mixes and plastics, even those contaminated with paper, metals and other impurities. Consequently, there is a very wide and varied range of uses for the products and processes and the foregoing description is purely exemplary of such products or processes.

It should also be appreciated that the reinforcing can be varied as required to facilitate changing the shape of the preform in the mould.

INDUSTRIAL ACCEPTABILITY

Products made by the process have uses as substitutes for wood fence posts, railway ties and other structures susceptible to manufacture by laminating and rolling to create a preform, and then applying heat and pressure to create the final required shape.

INDEX OF REFERENCE SIGNS

Claims

1. A product comprising a plurality of layers (22) attached to one another by the application of heat and pressure, at least one of the layers including reclaimed PET, reclaimed PE and a compatibiliser, and at least one other of the layers being of a reinforcing matting (42).

2. A product as claimed in claim 1 in which said one of the layers further includes PVC.

3. A product as claimed in claim 1 in which there are two layers in parallel with one another.

4. A product as claimed in claim 3 in which the layers extend generally in a spiral arrangement.

5. A product as claimed in claim 1 in which the layers are extruded in a first direction and rolled in a second direction so that each of the layers is in the form of a spiral about an axis in said first direction.

6. A product as claimed in claims 1 or 5 in which the reinforcing layer is of glass fibres.

7. A product as claimed in claims 1 or 5 and further including an outer layer of UV resistant material (48).

8. A method of making a preform for a product from waste plastics materials, the method comprising the steps: preparing a mixture of the waste plastics materials including significant proportions of PET and PE; extruding the mixture into a sheet; passing the sheet while still soft between rolls with a reinforcing layer and appling pressure to create a laminate of the sheet and layer to bond the sheet and layer.

9. The method of claim 8 and further comprising the steps: cutting the laminate into selected lengths while maintaining the laminate warm sufficient to make the sheet readily deformable; rolling each of the selected lengths into individual intermediate preforms having essentially round cross-sections with the sheet and layer defining parallel spirals in the preform; placing the preform in a mould defining the selected final shape of said elongate product; and appling heat and pressure to the mould to shape the form into the desired shape.