GB2576141A

GB2576141A - Porous plastic drainage profiles from recycled thermoplastic

Info

Publication number: GB2576141A
Application number: GB1812028.7A
Authority: GB
Inventors: Andrew Nattrass Mark; Michael Berville Graham
Original assignee: Mg Ip Ltd
Current assignee: Mg Ip Ltd
Priority date: 2018-07-24
Filing date: 2018-07-24
Publication date: 2020-02-12
Also published as: GB201812028D0

Abstract

A method of manufacturing connectable or non-connectable porous plastic profiles, utilises an extruder 2 producing substantially endless random strands 5 of thermoplastic, welded together and compressed by pulling them through a forming tool 6, 7. The strand mass contained by the tool can be reduced in volume by means of adjustment to one or more of the tool walls 7, allowing fine tuning to the compression of the contents and control of the void ratio within the strand mass. A haul-off 9 may transfer the profiles 20 to a travelling saw 10 and is cross cut to the required length by a circular saw blade 11 creating finished profiles 12. Pressurised coolant may be added to the contact surfaces or internal voids within the tool, further cooling may be provided by a water bath 8. A further embodiment provides a number of rollers, these can be idle or driven, belted or un-belted, still allowing for compressive force to be transferred to the strand mass. Performance enhancing or colour inducing additives may be added before or during extrusion. A temperature-controlled extrusion barrel extension containing may be provided. Inserts (16, 3) may be added to the inside surfaces of the tool to create either uniform recesses, protuberances or both to the finished profile. Vertically orientated plate-like inserts (15, fig 3) may also be added to the tool, to cause the random strand mass to split longitudinally, in the machine direction 4, causing a plurality of narrower profiles to be produced simultaneously.

Description

Description Porous Plastic Drainage Profiles from Recycled Thermoplastic

This invention relates to a method of making porous plastic profiles from recycled plastics which can be connectable (Figure 4).

Porous plastic profiles, sometimes referred to as planks and bats, are used for the control of liquids and gases.

However, the method of production of these items outlined under reference W02004082912 immediately below cause inherent difficulties.

These difficulties are summarised further below and addressed by this invention.

W02004082912 describes a method of manufacturing porous plastic drainage bats from recycled plastics. It describes a method of densifying chopped plastic particles into many hot soft noodles measuring between 5mm to 50mm using a Friction Plate Agglomerator which generates heat through friction. The resulting hot noodles fall from the Friction Plate Agglomerator into a chilled compactor funnel in which the noodles meld together. The melded noodle mass exits the compactor turning approximately 90 degrees onto a moving conveyor belt upon which water is sprayed to cool down both the conveyor and the noodle mass into a continuous sheet containing voids which is cut to length into bats/planks. The bats/planks are about 250mm in width, 50mm in depth and of convenient length.

The above described method produces only bats/planks of limited fixed dimensions and cannot produce multiple bats/planks simultaneously. It also does not provide for creating integral joining characteristics in the material flow direction.

As the heat generated is by means of friction there is resultant wear upon the friction plates which is exacerbated by non-plastic impurities in the feedstock. In order for the machine to perform optimally these plates require frequent repair or replacement. This is time consuming and causes unnecessary expense.

The production of boards which connect together by integral means in the web flow direction retaining similar overall depth is not feasible. Downstream pulling is required in order to achieve this successfully; however, it is not in the scope of this embodiment. The passage of the melded noodle mass exiting the compactor funnel through 90 degrees adds additional friction. This, coupled with the weakened meld strength of the noodle mass, renders the use of a pulling device downstream impractical as the noodle mass is not strong enough to withstand a sufficient pulling force without breaking. The introduction of any attachments to the side walls of the conveyor creating indentations or protuberances to provide a joining mechanism in the material flow direction would create additional friction and further exaggerate this issue.

A Friction Plate Agglomerator is designed to densify flexible plastic waste thus minimising potential feedstock supply as much of the available waste feedstock is in hard plastic form. This method is also restricted to producing softened, not fully melted, short noodles into bats/planks.

The noodles contained therein have reduced linear strength directly related to their short length and have also not experienced enough heat as a Friction Plate Agglomerator has little adjustable control over the temperature of the resultant noodles providing for poor plastic homogenisation, incomplete melt, and reduced weld strength.

The bats I boards produced by this method are therefore weak, friable and unable to sustain integral jointing attributes.

This invention relates to a method of making porous plastic profiles from endless strands of recycled plastics. These profiles can be connectable as demonstrated in Figure 4.

Embodiments of the invention are hereinafter further described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of the extrusion line for producing porous plastic profiles.

Figure 2 is a schematic representation showing both front and side elevations of the heated die plate producing uniform molten substantially endless spaghetti like strands accumulating in a random fashion into the substantially horizontally mounted tool.

Figure 3 is a schematic representation showing both front and side elevations of the substantially horizontally mounted tool showing the inserts that allow the strand mass to be split longitudinally and allow recesses to be created within the profile.

Figure 4 is a schematic representation showing examples of the cross sections of porous plastic profiles.

Figure 5 is a schematic representation showing porous plastic profiles abutted longitudinally end to end forming a ribbon like drainage element.

Figure 6 is a schematic representation showing porous plastic profiles joined horizontally to one another.

Figure 7 is a schematic representation showing porous plastic profiles joined vertically to one another.

Figure 8 is a schematic representation showing a cross section of partially rolled porous plastic profiles complete with hinges.

Porous bats/planks are commonly used to conduct fluids or gases. This embodiment describes a process for manufacturing porous plastic profiles. These profiles can be used horizontally abutted to one another as in Figure 6 forming a mat on roofs, floors or sub floors; or vertically, singly or placed one on top of another to form walls as in Figure 7. Whether used horizontally or vertically, the jointing of the boards together with (17) or without separate fixings, as in Figure 4, is a key feature of this embodiment. When forming a floor or substrate from a number of individual pieces it is beneficial to be both uniform in thickness and for the pieces to be firmly attached to each other, as this reduces the risk of tripping. This embodiment therefore is preferable to existing alternatives and offers distinct advantages in the market.

Another embodiment is the provision for the attachment of substantially flexible elements (18) to recesses in the boards in the machine direction post production achieving a hinge effect. This allows for the joining of numerous profiles together. The hinge effect allows the resulting chain of profiles to be rolled up for ease of deployment as in Figure 8. This addition offers numerous advantages in the market providing the production of temporary or semi-permanent roll out surfaces.

When used underground abutted longitudinally end to end forming a ribbon like drainage element, as in Figure 5, the necessity for jointing is not required and as such the production of non-joinable profiles is also a feature of our embodiment.

As opposed to the process used in patent W02004082912 -melding- this embodiment describes a method of melting of either soft, hard or mixed waste thermoplastics to produce porous plastic profiles. This embodiment utilises an extruder (2) equipped with at least one feed opening (1) and one Archimedes screw (not shown) within a temperature-controlled barrel (19) which pumps melted thermoplastics through a fixed heated die plate (3) containing a plurality of holes. This barrel may be equipped with a filtration device (not shown) to allow the removal of unwanted contaminants often found in thermoplastic waste.

The uniform, molten, substantially endless spaghetti-like strands (5) exit the heated die plate (3). Having exited the heated die plate (3), the strands (5) fall and accumulate (13) into the first part of the substantially-horizontally mounted tool (6 and 7). This accumulation disturbs the uniformity of the strands created by the heated die plate and causes a build-up of a random mass of strands which, upon contact with each other, weld together (13) without adhering to the tool (6 and 7).

The strand mass contained by this tool (6 and 7) can be reduced in volume by means of adjustment to one or more of the tool walls (7), allowing fine tuning to the compression of the contents and hence control of the void ratio (plastic: void) within the strand mass (13). The internal surfaces of the tool may be treated to minimise friction between the strand mass (13) and the contact surfaces of the tool. This may also be achieved by adding pressurised coolant to the contact surfaces or internal voids within the substantially horizontally mounted tool (6 and 7). This mass is drawn by means of a haul-off (9) which is controllable in both line speed and degree of nip force exerted onto the profile causing a pulling force which pulls the randomised strand mass (13) into the substantially-horizontally mounted tool (6 and 7) from the extruder end. This tool further compresses the still hot strand mass (13) into the desired shape. This compression increases the contact weld between strands improving overall strength. The resultant cooled strand mass (14) still retains voids between the strands with a void ratio of between 20% and 80% dependent upon the specific application. Should additional cooling of the strand mass be required this embodiment allows for further cooling by the addition of a water bath (8).

Without necessitating a complete substantially-horizontal tool (6 and 7) changeover, inserts (16) may be added to the inside surfaces of the tool (6 and 7) to create either uniform recesses, protuberances or both to the finished profile. Vertically orientated plate-like inserts (15) may also be added to the substantially-horizontal tool (6 and 7) which will cause the random strand mass (13) to split longitudinally, in the machine direction (4), causing a plurality of narrower profiles to be produced simultaneously.

The now completely formed profile (20) exits the haul-off (9) and transfers to a travelling saw (10) and is cross cut to the required length by a circular saw blade (11) creating finished profiles (12).

The overall width of profiles achievable is from 100mm wide upwards and depth up to 500mm.

A further embodiment provides for the substitution of the substantially-horizontal tool (6) and (7) with a number of rollers, these can be idle or driven, belted or un-belted, still allowing for compressive force to be transferred to the strand mass (13).

This embodiment allows for repeat impression printing onto the surface of the profile whilst still hot enough.

As anyone skilled in the art would appreciate the addition of colourants, performance enhancers, UV stabilisers, blowing agents and other additives may also be introduced into to the extruder as common practice as and when required.

Non-melting additives unable to be processed in the extruder may be added to the strand mass (13) whilst hot or adhered to the profile (12) when cooled.

Another embodiment provides for the addition of a temperature-controlled extrusion barrel extension with a minimum wall thickness of 5mm to be fitted between the extruder and die plate in order to raise the die plate height relative to the substantiallyhohzontal tool providing a greater strand fall without raising the whole extruder. This barrel extension must contain more than one bend.

To increase the randomisation of the substantially continuous strand there is provision to apply a horizontally oscillating action to the substantially-horizontal tool (6 and 7).

Claims

1. A method of forming porous thermoplastic profiles with more than one substantially parallel plane, which can be connectable, formed from substantially endless uniform strands of extruded recycled thermoplastic which are randomised, contact welded together and shaped by compression.

2. The method of claim 1 and further comprising the cooling of the porous plastic profile.

3. The method of any of the preceding claims, and further comprising the pulling of the porous plastic profile by a variable speed device(s).

4. The method of any of the preceding claims further comprising the cross cutting of the resultant continuous profile into required lengths once sufficiently cooled.

5. The method of any of the preceding claims further comprising a method of applying adjustable compressive force to the random strand mass pre-completion of cooling.

6. The method of any of the preceding claims further comprising the addition of substantially vertically orientated plate(s) causing numerous profiles to be produced simultaneously.

7. The method of any of the preceding claims further comprising the addition of substantially horizontally mounted inserts within the strand mass creating longitudinal recesses allowing the connection together of numerous profiles.

8. The method of any of the preceding claims further comprising the addition of perforations to the substantially horizontally mounted tool in order for the cooling agent to penetrate through the tool walls.

9. The method of any of the preceding claims further comprising the addition of an internal cooling method within the walls of the substantially horizontally mounted tool.

10. The method of any of the preceding claims further comprising the addition of additives to the molten strand mass after extrusion and before or during compression.

11. The method of any of the preceding claims further comprising the addition of performance enhancing or colour inducing additives before or during extrusion.

12. The method of any of the preceding claims further comprising the alteration or adjustment of the extrusion line geometry in such a way so as to allow the introduction of woven or non-woven linear items into the molten strand mass after extrusion and before or during compression thus altering the performance characteristics of the profiles.

13. The method of any of the preceding claims further comprising the addition of a temperature-controlled extrusion barrel extension containing more than one bend with a minimum wall thickness of 5mm fitted between the extruder and die plate in order to alter the height of the die plate relative to the landing level of the molten uniform strand.

14. The method of any of the preceding claims further comprising the addition of pre-cooling to the molten uniform spaghetti like strands prior to accumulation and randomisation.

15. The method of any of the preceding claims further comprising the reduction in temperature of the die plate causing the surface of the molten uniform spaghetti like strand to develop a roughened surface caused by the increase in friction between the molten plastic and the die plate as it exits the die plate holes.

16. The method of any of the preceding claims further comprising the repeat indentation into the surface of the profiles using roller(s) with machined surfaces horizontally oriented substantially at 90 degrees to the machine direction.

17. The method of any of the preceding claims further comprising the addition post production of any mechanism or fixing of numerous profiles to be indirectly joined together allowing a plurality of profiles to be connected which can be formed into a substantially continuous temporary roll.

18. The method of any of the preceding claims further comprising the addition post production of any mechanism or fixing allowing a plurality of profiles to be directly joined together creating a substantially even surface with reduced inter profile movement and flexibility.