NZ518385A - Composition and methods for the control of plant growth - Google Patents

Abstract

A composition for use in a process for manufacturing a product for controlling plant growth, the composition including a water insoluble metallic salt, such as cuprous chloride, of between 20% and 40% by weight suitably compounded with a base polymer to form a plastic material such that when contacted with a suitable plant growing medium the ions of the metal salt are released to control the growth of plant roots.

Description

Our ref: SHA004 Patents Form No. 5 No. 518385 35 Dated: 17 April 2002 40 PATENTS ACT 1953 COMPLETE SPECIFICATION Intellectual Property Office of NZ 2 8 APR 2003 RfcCfclV ED METHODS AND COMPOSITIONS FOR CONTROLLING PLANT GROWTH I, Derek Richard Shaw, a New Zealand citizen of PO Box 66 165, Beach Haven, Auckland, 45 New Zealand, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 METHODS AND COMPOSITIONS FOR CONTROLLING PLANT GROWTH TECHNICAL FIELD This invention relates to methods and compositions for controlling plant growth. More particularly, but not exclusively, the present invention relates to a composition for manufacturing plastics products used for controlling plant root growth.

BACKGROUND ART Ideally, a plant should have a fine, dense root structure to ensure the efficient absorption of nutriments from the growing medium and also to provide a healthy root system for transplantation. However, plants grown in containers may, over a period of time, develop a coarse root system of long tendrils that may tend to grow around the perimeter of the 1 5 container as the plant seeks to gain nutriments from the enclosed growing medium. This growth pattern is considered undesirable.

It is an object of the invention to provide a method of, and composition for, controlling plant growth that can overcome at least some of the abovementioned problems, or at least provides 20 the public with a useful choice.

It is a further object of the invention to provide a material in the form of a container, bag or sheet or the like for use in controlling plant growth, that can overcome at least some of the abovementioned problems, or at least provides the public with a useful choice.

SUMMARY OF THE INVENTION According to a broad aspect of the invention there is provided a composition for use in a process for manufacturing a product for controlling plant growth, the composition including a water 30 insoluble metallic salt of an effective percentage by weight suitable compounded with a base polymer to form a plastics material such as, in use, to enable the release of ions of the metallic salt from the plastics material in contact with a suitable plant growing medium. 2 a y P\ r l © 0 s Preferably the water insoluble metallic salt comprises between substantially 20% and 40% by weight, and wherein the polymer comprises between substantially 60% and 80% by weight.

Desirably the metallic salt for use in controlling root growth is cuprous chloride. 5 Advantageously, the cuprous chloride comprises between substantially 20% and 40% by weight. Preferably, the cuprous chloride comprises between substantially 30% and 40% by weight.

According to a second aspect of the invention there is provided a method of manufacturing a product that will facilitate the controlled release of ions of the metallic salt into a growing 10 medium for use in influencing plant growth, the method comprising the steps of: blending a product or composition according to the first aspect of the invention with a base polymer to form a masterbatch compound; and blending the masterbatch compound with a plastics resin to be fed into at least one of the extruders of a co-extrusion process to form a surface layer of a multilayer structure used to form a plastics container, film or sheeting.

Preferably in step b. the masterbatch compound and the plastics resin are both blended in 20 equal parts.

Desirably the surface layer forms part of, or is substantially one layer of, a plastics material having a plurality of other layers. Preferably the one layer, in use, will be in contact with a growing medium for a plant.

Preferably the surface layer comprises a thickness that is less than the thickness of the other layer or the other layers.

Advantageously the plastics material being formed is a film structure, and wherein the surface 30 layer comprises a thickness of substantially 25 microns and the thickness of the other layer or the other layers are between substantially 50 to 100 microns.

Alternatively the plastics material being processed is a formed container either by thermoforming, blow moulding or injection moulding processes, and wherein the surface layer 3 1 ® ^ S 3 comprises a thickness of substantially 20 microns and the thickness of the other layer or the other layers are between substantially 500 to 1000 microns.

Desirably the plastics material formed comprises three layers in a sandwich construction 5 having two outer layers and a middle layer, and wherein the outer layers are the surface layers impregnated with the masterbatch compound, and wherein the middle layer is made of a plastics material that is not impregnated with the the masterbatch compound.

A preferred embodiment of the invention will now be illustrated, by way of example only, with reference to the accompanying drawings in which: Referring to figure 1, a cross sectional view of a plastics material, generally referred to as 1, in 20 accordance with a preferred embodiment of the invention, is illustrated.

The plastics material 1 preferably includes a first layer 2 dosed with an additive during the production process for manufacturing the plastics material 1. The plastics material 1 may be in the form of a container, film or sheeting. The additive is advantageously a water insoluble 25 metallic salt preferably in the form of a cuprous chloride or any other suitable substance for use in functioning to release ions into a growing medium 3. The growing medium 3 is desirably in the form of a suitable soil for allowing plants to grow within the growing medium.

The first layer 2 may be one layer of a multi-layered and structured plastics material having 30 advantageously at least a second layer 4. The second layer 4 is preferably composed of a composition absent of the additive forming part of the first layer 2. The second layer 4 may alternatively be a composite structure in the form of a plastics material including more than one layer.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: Shows a cross sectional view of a plastics material in accordance with a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS 4 The plastics material 1 may be any desirable and suitable material such as, for example only and not exclusively, a co-extruded planter bag made of a low density polyethylene ("LDPE"); a thermofoimed planter pot and trays formed from co-extruded sheeting, typically made of high impact polystyrene ("HIPS); a blow moulded container produced using the co-extrusion blow 5 moulding technique with either the plastics resins polypropylene ("PP") or polyethylene ("PE"); co-extruded injection moulded planter pots made from PP, polystyrene ("PS") or polyethylene ("PE"); film or sheets made from PE, or PP for use as a lining in standard mono-layered injection moulded pots; weed matting made from PP; and film sheeting made from PE. Other applications and structures made in accordance with aspects of the invention are envisaged, for 10 the non-limiting purposes of controlling the growth of plants, particularly root growth, controlling fungus growth in plants, and possibly slow release fertilisers.

In one aspect of the invention there is provided a composition including an additive such as a metallic salt or a pigment blended with a suitable or compatible base polymer during the 1 5 production process for manufacturing a suitable plastics material. This action is referred to as compounding, and the result is a "masterbatch" compound. The "masterbatch" can preferably be formed into pellets, and may desirably be formed to a size similar to the base polymer. Using any smtable and desirable metering device, the masterbatch compound will be mixed with the base polymer and then fed into an extruder to be melted and mixed further prior to being fed 20 into a suitable mould or die depending on the application and process required. Some applications have been detailed above.

It is envisaged that the structure of the plastics material 1 would be at least two layers, and the number of layers may depend on the equipment available to produce the product, whether 25 sheeting or a container or otherwise, and the desired application.

It is envisaged that the layer carrying the masterbatch is designed to be significandy thinner than the other layer or layers, thus allowing for a higher concentration of the metallic salt in the layer adjacent to the growing medium. Further, having a thin layer carrying the masterbatch can 30 reduce the amount of additive required compared with an embodiment whereby the additive were dispersed throughout the total wall thickness of the structure of the container. It is considered that the thinness of the layer can facilitate moisture permeability and hence the ready release of the ions of the metallic salt.

In one non-limiting embodiment of the plastics material being a film structure for use as a bag or sheet for lining a container, preferably the layer having the masterbatch can have a thickness of substantially 25 microns, and the other layer or layers combined have a thickness of between about 50 to 100 microns.

In the non-limiting embodiment of the plastics material being a formed container either by the thermoforming, blowmoulding or injection moulding processes, the container desirably has an inner layer with a thickness of substantially 20 microns, and an outer layer having a thickness of between about 500 to 1000 microns.

Alternatively the plastics material formed by the method of the invention can comprise more than two layers, and it is envisaged that it may be commercially viable to form a plastics material having the additive mixed to one outer layer and having at least two layers made of a plastics material not including the masterbatch of the invention.

It is considered an advantage to manufacture a plastics material with at least two layers, and with at least one layer being dosed with the additive. In the embodiment comprising a two layered structure, desirably the dosed first layer 2 is thinner than the second layer 4 and therefore the amount of metallic salt required in the masterbatch can be significandy reduced.

It has been established according to the invention that dosing or compounding the first layer 2 can result in a concentration of the metallic salt adjacent the outer surface 5 of the first layer 2 caused by migration of metallic salt to the outer surface 5 during crystallisation of the polymer.

It is seen that non-polymeric additives such as pigments, slip additives and the like will tend to migrate to the surface of a polymer product. This is due to the crystallisation of the polymer occurring subsequent to the extrusion or moulding stage of the process when the polymer is heated to a sufficient temperature to carry out the extrusion or moulding or otherwise. It may be seen that inclusions that do not form part of the polymer tend to be squeezed out from between 30 the interstices of the molecular chains of the polymer as the molecular chains settle into a desired arrangement ("crystallise") by normal inter-molecular forces. 6 £ F) "/7 i ' " Further, the rate of release of the metallic salt in the first layer 2 can be influenced by the level of concentration of metallic salt in the first layer 2, and by the thickness and type of polymer used for the first layer 2.

Advantageously the polymers used in the method of manufacturing the product are standard polymers normally used to manufacture plastic containers, bags, sheeting or matting such as, for example only, polyethylene or polypropylene.

It is seen therefore that one broad method of producing a plastics material for use in influencing 10 plant growth using the composition and masterbatch compound as aforesaid can include the steps of compounding a water insoluble metallic salt with a suitable base polymer to form a masterbatch, and then blending the masterbatch with a suitable plastics resin to be fed into one of the extruders in the co-extruding process and forming one of the surface layers of a multilayer structure used to form a plastics container, film or sheeting.

Some non-limiting Examples of the methods of construction are as follows: Example A To produce a film structure for use as a bag or sheet for lining a container, preferably the method comprises the steps of the steps of compounding a water insoluble metallic salt of 20 to 40% masterbatch, and then blending the masterbatch with a suitable plastics resin, and in this example is a low density polyethylene, to be fed into one of the extruders in the co-extruding process and forming one of the surface layers of a multilayer structure, and wherein two layers are formed by the extrusion process with one layer having the masterbatch can have a thickness of substantially 25 microns, and the other layer or layers combined have a thickness of between about 50 to 100 microns.

Example B To produce a plant container, preferably the method includes the steps of compounding a water insoluble metallic salt of 20 to 40% by weight with a suitable base polymer, and in this example is a low density polypropylene, to form a masterbatch, and then blending the by weight with a base polymer, and in this example is a low density polyethylene, to form a 7 masterbatch with a suitable plastics resin, and in this example is a low density polypropylene, to be fed into one of the extruders in the co-extruding process and forming one of the surface layers of a multilayer structure, and wherein a two layered container is formed by a thermoformed or injection moulding process, the container desirably has an inner layer with a 5 thickness of substantially 20 microns, and an outer layer having a thickness of between about 500 to 1000 microns.

Example C To produce a film structure for use as a bag or sheet for lining a container, preferably the method comprises the steps of the steps of compounding a water insoluble metallic salt of substantially 40% by weight with a suitable base polymer, and in this example is a low density polyethylene, of substantially 60% by weight to form a masterbatch, and then blending the masterbatch with a suitable plastics resin, and in this non-limiting example is a low density polyethylene, to be 1 5 fed into one of the extruders in the co-extruding process and forming one of the surface layers of a multilayer structure, and wherein two layers are formed by the extrusion process with one layer having the masterbatch can have a thickness of substantially 25 microns, and the other layer or layers combined have a thickness of between about 50 to 100 microns.

Example D To produce a plant container, preferably the method includes the steps of compounding a water insoluble metallic salt of substantially 40% by weight with a suitable base polymer to form a masterbatch, and then blending the masterbatch with a suitable plastics resin to be fed into one of the extruders in the co-extruding process and forming one of the surface layers of a multilayer structure, and wherein a two layered container is formed by a thermoformed or injection moulding process, the container desirably has an inner layer with a thickness of substantially 20 microns, and an outer layer having a thickness of between about 500 to 1000 microns.

It is envisaged that a first layer dosed with the masterbatch may be formed as a very thin layer that does not necessarily support the overall structure of the container, sheeting or film. It is envisaged that the first layer may possibly be as thin as about 8 to 10 microns. The other layers 8 18 of the plastics material not being dosed with the masterbatch can be sufficiently thick to support the structure of the plastics material, as required.

It will be understood that suitable plastics materials used in various products in the invention can 5 include a variety of commonly available plastics materials such as for a co-extruded planter bag made of a low density polyethylene ("LDPE"); a thermoformed planter pot and trays formed from co-extruded sheeting, typically made of high impact polystyrene ("HIPS); a blow moulded container produced using the co-extrusion blow moulding technique with either the plastics resins polypropylene ("PP") or polyethylene ("PE"); co-extruded injection moulded planter pots 10 made from PP, polystyrene ("PS") or polyethylene ("PE"); film or sheets made from PE, or PP for use as a lining in standard mono-layered injection moulded pots; weed matting made from PP; and film sheeting made from PE.

It will be appreciated that materials used for components of the invention include any suitable 1 5 and durable materials, for example only but not limited to, timber, metal, plastics materials, fabrics, rubber, glass or any combination thereof.

Wherein the aforegoing reference has been made to integers or components having known equivalents, then such equivalents are herein incorporated as if individually set forth. 20 Accordingly, it will be appreciated that changes may be made to the above described embodiments of the invention without departing from the principles taught herein.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Additional advantages of the present invention will become apparent for those skilled 25 in the art after considering the principles in particular form as discussed and illustrated. Thus, it will be understood that the invention is not limited to the particular embodiments described or illustrated, but is intended to cover all alterations or modifications which are within the scope of the appended claims. 9

Claims (16)

What I Claim is:

1. A composition for use in a process for manufacturing a product for controlling plant growth, the composition including a water insoluble metallic salt of between substantially 5 20% and 40% by weight suitably compounded with a base polymer to form a plastics material such as, in use, to enable the release of ions of the metallic salt from the plastics material in contact with a suitable plant growing medium.

2. A composition according to claim 1 wherein the metallic salt for use in controlling root 10 growth is cuprous chloride.

3. A composition according to claim 2 wherein the cuprous chloride comprises between substantially 30% and 40% by weight. 15

4. A method of manufacturing a product that will facilitate the controlled release of ions of the metallic salt into a growing medium for use in influencing plant growth, the method comprising the steps of: a.) blending a product or composition with a base polymer to form a 20 masterbatch compound, the composition including a water insoluble metallic salt of an effective percentage by weight suitably compounded with a base polymer to form a plastics material such as, in use, to enable the release of ions of the metallic salt from the plastics material in contact with a suitable plant growing medium; and 25 b.) blending the masterbatch compound with a plastics resin to be fed into at least one of the extruders of a co-extrusion process to form a surface layer of a multilayer structure used to form a plastics film or sheeting.

5. A method according to claim 4 wherein in step a. the composition being blended with 30 the base polymer comprises the composition according to any one of claims 1 to 3.

6. A method according to claim 4 wherein in step b. the masterbatch compound and the plastics resin are both blended in equal parts. Intellectual Property Office of NZ 10 ? 0 NOV 2003 ?

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16. A method according to either claim 5 or claim 6 wherein the surface layer forms part of, or is substantially one layer of, a plastics material having a plurality of other layers. A method according to either claim 5 or claim 6 wherein the one layer, in use, will be in contact with a growing medium for a plant. A method according to any one of claims 4 to 8 wherein the surface layer comprises a thickness that is less than the thickness of the other layer or the other layers. A method according to any one of claims 4 to 9 the plastics material being formed is a film structure, and wherein the surface layer comprises a thickness of substantially 25 microns and the thickness of the other layer or the other layers are between substantially 50 to 100 microns. A method according to any one of claims 4 to 10 wherein the plastics material being processed is a formed container either by thermoforming, blow moulding or injection moulding processes, and wherein the surface layer comprises a thickness of substantially 20 microns and the thickness of the other layer or the other layers are between substantially 500 to 1000 microns. A method according to claim 4 wherein the plastics material formed comprises three layers in a sandwich construction having two outer layers and a middle layer, and wherein the outer layers are the surface layers impregnated with the masterbatch compound, and wherein the middle layer is made of a plastics material that is not impregnated with the the masterbatch compound. A product produced by the composition according to any one of claims 1 to 3. A product according to claim 13 produced in pellet form. A composition substantially as herein described with reference to any one of the Examples. 11