AU2764502A - Method of forming an article from plastic containers - Google Patents

Description

S&FRef: 589025

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

S

S

S

S

Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: P W Saddington and Sons Pty. Ltd.

75-77 Lambton Road Broadmeadow New South Wales 2292 Australia David Lees Saddington Spruson Ferguson St Martins Tower,Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Method of Forming an Article from Plastic Containers ASSOCIATED PROVISIONAL APPLICATION DETAILS [33] Country [31] Applic. No(s) AU PR5458 [32] Application Date 04 Jun 2001 The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5815c Method of Forming an Article from Plastic Containers Technical Field The present invention relates to the recycling of plastic containers, and in particular relates to a method of forming an article from reclaimed plastic containers.

Background of the Invention Used plastic containers are typically recycled by a process of chopping or chipping the containers into small pieces, then forming the chopped or chipped plastic pieces into desired shapes through various moulding processes such as plastic injection moulding, plastic rotary moulding or plastic extrusion moulding.

These currently available processes require general sorting of the various kinds of plastic prior to the chopping/chipping process. Current methods of sorting and .°..:chipping are both labour intensive and expensive.

Breaking down of recycled plastic into small pieces and melting the same during the moulding process provides a unitary mass of plastic, without taking advantage of the Is voids that are already formed in the original whole plastic containers.

S.i Object of the Invention It is the object of the present invention to provide a method of forming articles from plastic containers without the requirement of sorting or chipping and which enables utilisation of the voids in the plastic containers.

Summary of the Invention In a broad form the present invention provides a method of forming an article from plastic containers comprising the steps of: providing a plurality of whole plastic containers; placing said plastic containers in a mould; bonding and moulding said plastic containers under pressure in said mould into a desired article shape.

In a first embodiment, said plastic containers are bonded by a liquid adhesive poured over said containers in said mould.

In a second embodiment said plastic containers are bonded by a liquid adhesive sprayed onto said containers prior to placing said containers in said mould.

In the first and second embodiments, said adhesive may be a foam-type adhesive.

[R:\LIBLL]12758.doc:TCW:caa Preferably, the foam-type adhesive is methylene dioisocyonate monomer.

Alternatively, said adhesive is a contact-type adhesive.

The contact-type adhesive may contain methyl ethyl ketone, toluene and/or N-Lexane-type petroleum solvent.

s In the first and second embodiments, said pressure is typically maintained in said mould until said adhesive cures.

In a third embodiment, said plastic containers are bonded by heating said plastic containers until the external surfaces of said plastic containers are rendered sticky then allowing said containers to cool under said pressure in said mould.

Typically, said plastic containers are heated prior to placing in said mould.

Typically, said plastic containers are passed along a conveyor means through a S* •heat tunnel for said heating then passed along said conveyor into said mould.

In a fourth embodiment, said plastic containers are bonded by encapsulating said plastic containers with a filler material substantially filling gaps between said plastic 15 containers.

Preferably, said filler material is an expanding filler material.

Preferably, said expanding filler material is poured over said containers in said mould in a granular form and subsequently expanded.

Preferably said expanding filler material is styrene-based and is expanded with o. •20 injection of steam into said mould.

Alternatively, said filler material may be aerated concrete.

Preferably, said filler material adheres to the exterior surfaces of said plastic containers.

Brief Description of the Drawings Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic view of a first method of forming an article from plastic containers.

Fig. 2 is a schematic view of a second method of forming an article from plastic containers.

Fig. 3 is a schematic view of a third method of forming an article from plastic containers.

Fig. 4 is a schematic view of a fourth method of forming an article from plastic containers.

[R:\LIBLL]12758.doc:TCW:caa 3 Detailed Description of the Preferred Embodiments According to a first embodiment of the present invention as depicted in Figure 1, reclaimed empty plastic containers 1 are placed into a mould 2, typically by travelling along and off the end of a conveyor 3. Once the mould 2 has been filled with containers 1, the external surface of each of the plastic containers 1 within the mould 2 are rendered adhesive by pouring a liquid adhesive 4 over the containers 1 at ambient temperature.

The adhesive 4 is allowed to flow over the containers 1 and down between the individual containers such that at least a significant portion of the external surface of each of the containers 1 is covered in the adhesive. Rather than waiting until all of the containers 1 1o have been deposited into the mould 2, it is envisaged that the flow of liquid adhesive 4 might commence whilst containers 1 are still being deposited into the mould 2. This will S• assist in ensuring that those containers 1 placed toward the base of the mould 2, particularly where there are several layers of containers, will be sufficiently coated with S. adhesive.

15 After the mould 2 has been filled and the adhesive 4 has been deposited, the lid 2a of the mould 2 is placed over the mould and pressed down on to the containers with sufficient pressure to force the containers to take the shape of the mould 2. The pressure ""is maintained with the lid 2a of the mould 2 closed until the adhesive 4 is cured, bonding the plastic containers. Once cured, the lid 2a of the mould 2 is removed and the article 20 which has been formed by the interior shape of the mould 2 is ejected, leaving the mould ready for the receipt of further containers for the forming of a second article.

The adhesive 4 will typically be a foam-type adhesive, such as methylene dioisocyonate monomer. As the foam-type adhesive starts to cure it will foam and expand to act as a filler filling gaps between adjacent containers. Alternatively, the adhesive can be a contact-type adhesive. Such a contact-type adhesive might contain methyl ethyl ketone, toluene and/or N-Lexane-type petroleum solvent. The typical curing time for the above preferred adhesives will be of the order of three minutes, enabling reasonable processing rates of articles through the mould. Other suitable adhesives will be apparent to the person skilled in the art. If the adhesive has sufficiently low viscosity to flow through the gaps between the containers rapidly, adhesive with shorter cure times might be suitable to increase production rates.

The article produced will be largely made up of voids defined by the interior of the original plastic containers 1, providing for lightweight articles for various purposes.

The exterior form of the article will be defined by the interior cavity of the mould 2.

Depending on the pressure applied during curing, the exterior of the article will be [R:\LIBLL]12758.doc:TCW:caa relatively rough, as a result of the crushed surfaces of the container and gaps therebetween at the external faces of the article. The surface quality can be improved with increased pressure and the use of excess foam-type adhesive to act as a filler in more completely filling gaps between containers.

Various articles might be formed utilising this method. Particularly suitable articles are lightweight articles where exterior surface quality is not of prime concern.

Suitable articles include concrete formwork and load bearing structural members such as building blocks. The exterior surfaces of a structure formed of such building blocks can be rendered so as to provide a desired surface texture. Articles formed using the methods of the present invention are ideal, low cost alternatives to equivalent structural articles formed entirely of styrene.

In accordance with a second embodiment of the present invention as depicted in Figure 2, the plastic containers 1 are sprayed with an adhesive 4 as they pass along the conveyor 3 immediately prior to being placed into the mould 2 as they fall off the end of i* Is the conveyor 3. Once sufficient containers 1 have been sprayed and placed into the •i mould 2, the mould lid 2a is closed and pressure applied as per the first embodiment to force the containers to take-up the shape of the mould and to assist in curing of the ""adhesive which has been sprayed on to the container external surfaces to bond the containers together. Again in this embodiment the adhesive will preferably be a foam- 20 type adhesive such as methylene dioisocyonate monomer as discussed above, however contact-type adhesives might also be suitable.

In accordance with a third embodiment of the present invention as depicted in Figure 3, the containers 1 are bonded by heating the plastic containers 1, typically prior to placing the containers 1 into the mould 2, and then cooled in the mould 2. Here the containers 1 pass through a heat tunnel 5 as they move along the conveyor 3, with the heat tunnel heating the plastic containers to a sufficient degree such that they begin to melt and the external surfaces become sticky. A suitable temperature will vary according to the type of plastic being heated, and it is preferred that some basic form of classification of plastic container material types is carried out prior to utilising this method. After passing through the heat tunnel 5, the containers 1 fall from the end of the conveyor 3 into the mould. Once the mould 2 has been filled the mould lid 2a is again closed and pressure applied to mould the containers into the desired shape and to cause the sticky containers to bond together to form a single article. As the containers 1 cool in the mould, the containers solidify as a single mass. To speed the process, cooling water [R:\LIBLL] 12758.doc:TCW:caa can be injected into the mould to accelerate the cooling of the containers, solidifying the plastic material more rapidly.

In accordance with a fourth embodiment of the present invention as depicted in Figure 4, the containers are bonded by encapsulating them with a filler material 6. The filler material 6 substantially fills the gaps between the plastic containers 1, encapsulating the plastic containers and effectively bonding them into place. The filler material 6 is here an expanding styrene material which is poured over the containers 1, whilst they are in the mould 2, in a granular bead form. The mould 2 is then closed and steam is injected into the mould 2 to expand the filler material beads, providing an expanded foam material which encapsulates the plastic containers 1.

It is preferred that the filler material selected also acts to adhere to the exterior surface of the plastic containers 1, so as to more effectively bind those plastic containers located at the boundaries of the article defined by the shape of the mould 2. If the filler material does not adhere to the plastic containers 1, then plastic containers at the i 15 boundaries of the article so-formed may not be sufficiently encapsulated in filler material to be retained integral with the remaining containers and filler. This will not, however, be of particular concern for applications such as concrete formwork where the outer surface •.o of the article is not of any prime concern.

*go• ooo As an alternative to an expanding filler material such as a styrene-based material, S. 20 other filler materials such as aerated concrete might be used to fill the gaps between the plastic containers and encapsulate the same. An article formed in such a manner will, :however, clearly have a much greater mass than that formed utilising a low density filler such as expanding styrene.

The person skilled in the art will appreciate other possible modifications of the above embodiments.

[R:\LIBLL]12758.doc:TCW:caa

Claims (13)

1. A method of forming an article from plastic containers comprising the steps of: providing a plurality of whole plastic containers; placing said plastic containers in a mould; bonding and moulding said plastic containers under pressure in said mould into a desired article shape.

2. The method of claim 1, wherein said plastic containers are bonded by a liquid adhesive poured over said containers in said mould.

3. The method of claim 1, wherein said plastic containers are bonded by a liquid adhesive sprayed onto said containers prior to placing said containers in said mould. The method of either of claims 2 and 3, wherein said adhesive is a foam-type adhesive. 15 5. The method of claim 4, wherein said foam-type adhesive is methylene dioisocyonate monomer.

6. The method of either of claims 2 and 3, wherein said adhesive is a contact-type adhesive.

7. The method of claim 6, wherein said contact-type adhesive contains methyl ethyl ketone, toluene and/or N-Lexane-type petroleum solvent.

8. The method of any one of claims 2 to 7, wherein said pressure is maintained in said mould until said adhesive cures. The method of claim 1, wherein said plastic containers are bonded by heating said plastic containers until the external surfaces of said plastic containers are rendered sticky then allowing said containers to cool under said pressure in said mould. The method of claim 9, wherein said plastic containers are heated prior to placing in said mould.

11. The method of claim 10, wherein said plastic containers are passed along a conveyor means through a heat tunnel for said heating then passed along said conveyor into said mould.

12. The method of claim 1, wherein said plastic containers are bonded by encapsulating said plastic containers with a filler material substantially filling gaps between said plastic containers.

13. The method of claim 12, wherein said filler material is an expanding filler material. [R:\LIBLL]12758.doc:TCW:caa 4 1 7

14. The method of claim 13, wherein said expanding filler material is poured over said containers in said mould in a granular form and subsequently expanded. The method of either of claims 13 and 14, wherein said expanding filler material is styrene-based and is expanded with injection of steam into said mould.

16. The method of claim 12, wherein said filler material is aerated concrete.

17. The method of any one of claims 12 to 15, wherein said filler material adheres to the exterior surfaces of said plastic containers.

18. A method of forming an article from plastic containers substantially as hereinbefore described with reference to any one of the accompanying drawings. DATED this Twenty-Second Day of March, 2002 P W Saddington and Sons Pty Ltd Patent Attorneys for the Applicant SPRUSON FERGUSON *00* 0 [R:\LIBLL]12758.doc:TCW:caa