CA2038560A1

CA2038560A1 - Moulded product

Info

Publication number: CA2038560A1
Application number: CA002038560A
Authority: CA
Inventors: Llewellyn E. Depew
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-03-19
Filing date: 1991-03-19
Publication date: 1992-09-20
Also published as: AU1544792A; WO1992016370A1

Abstract

ABSTRACT OF THE DISCLOSURE

In the invention provides a unitary structure for use as a preform in manufacturing articles pressed 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, at least sufficient SEBS to create a synergistic of impact strength, and at least one other of the layers being of a reinforcing matting. A method of manufacture is also provided.

Description

This invention relates to products made by recycling plastics and to processes for manufacturlng the products.
Society produces three general types of plastics used in sufficient quantities to represent the major components of plastics waste materials. These are Polyethylene Terephthalate (PET), Yolyethylene, both high and low densities, (PE), and Polyvinyl Chloride (PVC). It has been founded on average recycleable waste plastics are made up of about 60 to 70 percent PET, 15 to 30 percent PE and 5 to 10 percent PVC. There are of course some minor amounts of other products but these do not represent major parts of the waste.
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 recycleable 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 used 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.

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There has been some research into the possibility of using 2ET 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'l of October 1989 shows that PET and high density PE can be blended with SEsS
(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 SEsS. 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 in the ratio 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, sorting is necessary 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 J' ' ~ ~'S '1 the melted plastic when put into a bulk Eorm 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 and 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 mixture as of PET, PE, and PVC as it is normally found.
In one of its aspects, the present invention provides a unitary structure for use as a preform in manufacturing articles press formed from the preform, the unitary structure including 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 at least sufficient SEBS to create a synergistic increase of impact strength, and at least one other of the layers being of a reinforcing matting.
In another of its aspects, the invention provides a railway tie comprising a plurality of layers extending in parallel from the center of the tie to the cutside, at least one of the layers including reclaimed PET, reclaimed PE and at least sufficient SEBS to create a synergistic increase in impact strength, and at least one other of the layers being of a reinforcing matting.
In yet another of its aspects~ the invention provides a method of making an elongate structure such as a railway tie and the like, the method comprising the steps of preparing a mixture f~ ~ 'J ..~ ~ r ~
of PET, PE and SEBS, the PET and PE being in the ratio no less than two to one and the amount of SEBS being sufficient to create a synergistic increase in impact strength. The mixture is extruded into a sheet and the sheet passes, while soft, between rolls together with a reinforcing layer and pressure is applied by the rolls to create a laminate of the sheet and layer. The laminate is cut into selected lengths and while maintained warm and deformable, is rolled into individual intermediate forms having essentially round cross sections with the sheet and layer defining parallel spirals. The resulting form is then placed in a mould defining the selected final shape of the elongate structure, and heat and pressure applied in the mould to shape the form into the desired shape needed to make the structure.
These and other aspects of the invention will be better understood with reference to the drawings, in which:
Fig. 1 is a isometric view of a preform made according to a process of the invention; and Fig. 2 is a diagrammatic representation of the process used to make the preform.
With reference to the drawings, a typical preform 20 is shown in Fig. 1. It will be seen that the preform is rectangular in general shape and there is an indication at 22 that it is made of layers wrapped continuously from the center to the outer surface.
The process is indicated very generally in Fig. 2.
PET, PE and PBC are contained in respective supply systems 24, 26, and 28. They are fed to a mixing structure 30 where SEBS iS

..
~ . . ' ' added and mixed in prearranged proportions is added from a supply 32 and mixed in prearranged proportions be~ore being fed through a supply conduit 34 to an extruder 36. This extruder heats the mixture and provides a continuous sheet 38 of material.
The mixture of PET to PE is preferably no less than two to one and the PE is normally in the form of HDPE. PsC is provided only if it is available since it is a filler in the product. It should therefore only be in small proportions.
The resulting extruded sheet 38 passes through a nip between a pair of rolls 40 where matting 42 is brought from a supply roll 44. The resulting pressure creates a mechanical bond and a flying blade 46 cuts the resulting laminate into sections which are then matched with a cover layer from a supply 48 to provide a UV resistant wrapper. The resulting laminate is shown at 50 and this is then rolled into a preformed 52 before being placed in a mould opening 54 which is closed by first mould 56 and the second mould 58 is brought down to complete the required shape of the preform 20 (Fig. 1). All of this is 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, modifiers could be used on the various layers to ensure that they are compatible and will bound to one another. Such variations are within the scope of the invention.

Claims

1. A unitary structure for use as a preform in manufacturing articles press formed from the preform, the structure 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 at least sufficient SEBS to create a synergistic increase in impact strength, and at least one other of the layers being of a reinforcing matting.

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

3. A structure as claimed in claim 1 in which the ratio by weight of PET to HDPE is no less than two to one.

4. A structure as claimed in claim 1 in which the ratio by weight of PET to HDPE is no less than three to one.

5. A structure as claimed in claims 1 to 4 in which the structure is rolled so that each of the layers is in the form of a spiral.

6. A structure as claimed in claims 1 to 4 in which the structure is rolled so that each of the layers is in the form of a spiral and the structure is tubular.

7. A structure as claimed in claims 1 to 4 in which the layers are extruded in a first direction and in which the structure is 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.

8. A structure as claimed in claims 1 to 4 in which the reinforcing layer is of glass fibres.

9. A structure as claimed in claims 1 to 4 and further including an outer layer of UV resistant material, and in which the structure is rolled so that each of the layers is in the form of a spiral with said outer layer outermost to provide UV
protection to the structure.

10. A structure as claimed in claim 1 in which the PET is in the range 60 to 70 percent, the HDPE is in the range 15 to 30 percent, and the SEBS is at least 12 percent.

11. A structure as claimed in claim 10 in which said one of the layers further includes 5 to 10 percent PVC.

12. A railway tie comprising:

a plurality of layers extending in parallel from the centre of the tie to the outside, at least one of the layers including reclaimed PET, reclaimed PE and at least sufficient SEBS to create a synergistic increase in impact strength, and at least one other of the layers being of a reinforcing matting.

13. A railway tie as claimed in claim 12 in which the tie has a generally rectangular cross-section.

14. A railway tie as claimed in claims 12 or 13 in which the reinforcing matting is of glass fibres.

15. A railway tie as claimed in claim 12 in which said one of the layers further includes PVC.

16. A railway tie as claimed in claim 12 in which the PET
is in the range 60 to 70 percent, the HDPE is in the range 15 to 30 percent, and the SEBS is at least 12 percent.

17. A railway tie as claimed in claim 16 in which said one of the layers further includes 5 to 10 percent PVC.

18. A plurality of layers as claimed in claim 12 in which said one of the layers was extruded and the direction of extrusion is at right angles to the longest axis of the railway tie.

19. A railway tie as claimed in claims 12, 16, 17 or 18 and further comprising an outer layer, said outer layer being UV
resistant to minimize effects of UV radiation on the railway tie.

20. A method of making an elongate structure such as a railway tie and the like, the method comprising the steps:
prepare a mixture of PET, HDPE and SEBS, the PET and HDPE being in the ratio of no less than 2 to 1 and the amount of SEBS being sufficient to create a synergistic increase in impact strength;
extrude the mixture into a sheet;
pass the sheet while still soft between rolls with a reinforcing layer and apply pressure to create a laminate of the sheet and layer;
cut the laminate into selected lengths and maintain the laminate warm sufficient to make the sheet readily deformable;
roll each of the selected lengths into individual intermediate forms having essentially round cross-sections withthe sheet and layer defining parallel spirals in the form;
place the form in a mould defining the selected final shape of said elongate structure; and apply heat and pressure in the mould to shape the form into the desired shape.