EP0500600A1

EP0500600A1 - Cleaning of container

Info

Publication number: EP0500600A1
Application number: EP90916084A
Authority: EP
Inventors: Anthony Harold Gregory
Original assignee: Zeneca Ltd; Imperial Chemical Industries Ltd
Current assignee: Syngenta Ltd
Priority date: 1989-11-10
Filing date: 1990-10-29
Publication date: 1992-09-02
Also published as: GB2237790B; CA2069862A1; AU6630490A; AU643470B2; WO1991007240A1; GB9023338D0; PT95828A; IE903850A1; ZA908753B; GB8925472D0; GB2237790A; JPH05503485A; KR920703222A; BR9007820A

Abstract

Récipient comportant une coquille externe à une ou plusieurs couches caractérisé en ce que la coquille externe (2) est dotée d'une paroi ou d'un revêtement interne (3) constitué d'un matériau qui est insoluble lorsque le récipient est utilisé, mais qui est soluble ou solubilisable dans un liquide de lavage. Des résidus des matériaux contenus dans le récipient peuvent être enlevés entièrement et en sécurité par une dissolution de la paroi ou du revêtement interne (3) dans le liquide de lavage.Container comprising an outer shell with one or more layers characterized in that the outer shell (2) has an inner wall or coating (3) made of a material which is insoluble when the container is used, but which is soluble or soluble in a washing liquid. Residues of the materials contained in the container can be removed completely and safely by dissolving the wall or the internal coating (3) in the washing liquid.

Description

CONTAINER

The present invention relates to a container adapted for safe disposal of hazardous residues, and to a method of producing a container.

Thermoplastic containers are known in the art. Conventional containers may have removable inner linings. EP-A-182094 discloses a package and a method for producing a package with a flexible inner liner. The contents of the inner liner can be evacuated under positive or negative pressure exerted between the outer support and the inner liner. The inner liner can then be removed manually.

Soluble films are also known in the art in many different fields. In recent years such films have been used, for example in the laundry industry, to provide dosage units where the whole sachet or envelope is added to the fluid and the film dissolves completely. In this way the user does not come into contact with the contained chemical. Examples are disclosed in US 4,765,916 and EP 011502. The disadvantage of the sachet where more toxic chemicals are concerned is that the film is liable to rupture. One idea to overcome this problem is to suspend the sachet within a rigid container so that the sachet is protected from damage, and in use is tipped whole from the container into the fluid. Such an arrangement is described in EP-A-347219. However, this arrangement also has disadvantages. It does not completely remove the risk of spillage within the container in transit and any weaknesses in the film would increase this risk.

Furthermore, the user may be tempted to remove the sachet from the container and may rupture it in the process, particularly if it is suspended by a tear strip.

There is an increasing awareness of the need for safe disposal of the residues of chemicals used in numerous fields of activity. However, this invention is concerned with the safe disposal of residues from containers, packages, drums, and the like which are used for transport and distribution of chemicals. It is known that stored chemicals absorb to the walls of the containers and that mere rinsing does not necessarily remove such residues. It has been shown that the residues may be desorbed from the wall over a period of time. This poses a potential risk during disposal of the containers. Furthermore, in countries or districts where containers are in short supply and with no formal facilities for disposal of containers they may, despite advice to the contrary, subsequently be used as containers for consumables, particularly water.

Conventional techniques for disposal of containers involve thorough rinsing with water, for example, triple rinsing is recommended for pesticides, before the container is disposed of, for example, by incineration or recycling. This is expensive and time consuming for the user. The present invention seeks to overcome the disadvantages associated with the safe disposal of hazardous residues in conventional containers and packages, thus enabling them to be safely destroyed, or re-used, for example, for the storage of non-toxic substances. Accordingly there is provided a container comprising a single or multi-layer outer shell characterised in that the outer shell is provided with an inner-most wall or coating of a material which is insoluble while the container is in use but is soluble or so ulisable in a wash liquid.

The present invention is suitable for many different types of conventional rigid or semi-rigid containers, for example, bottles, cartons, drums, tanks. The outer shell of the container is rigid or semi-rigid and may suitably made of a thermoplastic material such as polyethylene, ethylvinyl alcohol (EVOH), nylon, polypropylene or polyethylene terephthalate (polyester) or mixtures of these plastics. The outer shell may be single layered or multi-layered with almost any combination of thermoplastic materials. Alternatively the container may be in the form of a drum or pail made with an outer shell of metal such as steel or tin plate.

Containers with an outer shell made of plastics may have been produced by a moulding process, where the outer shell is built up in layers of the same or different plastics with or, in some cases, without an adhesive bonding layer (tie-bond) between the plastics layers. A layer may also consist of a blend of different plastics as, for example, with Selar (Trademark of Dupont) plastic which is a blend of polyethylene with platelets of nylon. The neck of the container can be made of a. different plastics material than the body of the container. The adhesive layer is a plastics material which has the property of binding to the given materials on either side of it. Commonly used examples are polyethylene and polyamide. The layers of plastics are generally hundreds of microns thick and the adhesive layer is generally only a few microns thick. The final laminate is generally l-2mm thick in.total. The container may also be of the 'bag in the box' type, where the inner flexible bag itself could be provided with a soluble or solulisable inner wall or coating or indeed the inner flexible bag could be completely soluble according to the present invention. It is known to produce plastics containers by blow moulding. One or more concentric tubes of plastics material are extruded and passed into a blow mould. The blow moulding operation forms the outer shell of the container and incorporates in the structure of the shell such inner or outer barriers or other layers as are required. The method comprising extrusion and blow-moulding operations when used to form a multi-layer container is generally known as a co-extrusion or multi-extrusion technique.

A further method is co-injection stretch blow-moulding, for example, with polyethylene terephthalate containers the outer shell may be in the form of an envelope of polyethylene with a different plastics material sandwiched between.

A yet further alternative method of forming the inner wall or coating is by spraying onto the inside of the outer shell of the container as a secondary operation after the outer shell has been formed by conventional methods, for example, extrusion blow moulding or injection stretch blow-moulding. Conventional or electrostatic spray techniques could be used. Alternatively again, the outer shell of the container could be dip coated on the inside and, if wished, on the outside. If the container is a drum the inner soluble wall or coating could be powder coated onto the inside. in the case of containers which are co-extrusion moulded or co-injection moulded it is envisaged that the inner wall is co-extruded or co-injected in the same process as the formation of the outer shell of the container provided the material of the inner wall is -suitable for use in this process.

Conventionally the base of a blow moulded container is pinched at the base between the two halves of the mould to form a weld. Occasionally the weld in the outer shell is insufficient to be air or fluid tight and in order to make the weld air or fluid tight a secondary welding operation is carried out. The inner wall or coating can be pushed back into the container while the base weld is formed along the pinch.

An alterative method is to provide a plug which fits tightly or is welded within the opening left in the base. Such a plug and opening arrangement may be used as an access port for the application of an external pressure for evacuating the contents of the container. External pressure applied in this way has a similar effect as dispensation of the contents under vacuum from the neck of the container.

In a further alternative the base can be left open to the atmosphere, so that when the inner wall or coating is removed, the outer shell is open to the atmosphere and the container is no longer suitable for its purpose. Thus according to a further aspect of the invention there is provided a process for manufacture of a container as described herein by co-extrusion or co-injection moulding techniques wherein the outer shell and the inner-most wall or coating are moulded in a single operation. In a further alternative aspect of the invention there is also provided a process for manufacture of a container as described herein wherein the container is manufactured by any conventional technique and the inner-most wall or coating is applied in a separate operation.

The thickness of the inner wall or coating can be anything from a few angstroms (ie. one or two molecules thick) to a film which is sufficiently thick to stand alone, for example, to support the weight of the contents for the container and sufficiently thick to resist mechanical abrasion from a powder or granules. Thus the films may range from 1 angstrom to 200 microns depending on the size of container. A small container such as a plastics bottle containing typically between 1 and 15 litres of a formulated chemical may have a inner wall or coating of from 1 angstrom to 60 microns or more preferably from 1 micron to 40 microns. Typically the inner wall or coating is from 20 to 30 microns thick. For larger containers such as a drum containing from 20 to 200 litres of formulated chemical or an intermediate bulk container holding up to 400 US gallons, the inner wall or coating may be between 1 micron and 200 microns, and is typically from 50 to 150 microns thick.

The contents of the container may be, for example, aqueous based or non-aqueous based liquids or fluids, (for example, emulsifiable concentrates), gels, powders, granules and the like.

The nature of the inner wall or coating must be appropriate for the material or substance contained such that the material is insoluble while the container is in use but is soluble or solulisable in a wash liquid. Thus a non-aqueous based substance can be contained in :

(a) a water soluble inner wall or coating, such that when empty the container is rinsed with water to remove the inner wall or coating containing residues; (b) a solvent soluble inner wall or coating, such that when empty the container is rinsed with a suitable solvent to remove the inner wall or coating containing residues.

An aqueous based substance can be contained in : (a) a water soluble inner wall or coating, such that when empty the container is rinsed with water containing a trigger or catalyst which reacts with the inner wall or coating to remove it and the residues;

(b) a non-aqueous solvent soluble inner wall or coating, such that when empty the container is rinsed with a suitable solvent to remove the inner wall or coating containing residues.

The terms insoluble, soluble and solulisable are intended to have their usual meanings. That is to say insoluble is substantially non-soluble in the given material or substance, soluble means soluble to the extent of dissolving the inner wall or coating into the wash liquid and the term solulisable is interchangeable with solublisable meaning that there is the potential for the inner wall or coating to dissolve into the wash liquid under the correct conditions.. A particularly suitable wash liquid is water.

The inner wall or coating of the container may be formed of a water-soluble substance such as polyvinyl alcohol (PVOH), polyvinyl pyrollidone (PVP), polyethylene oxide, polyethylenimine, acrylic based films, for example polyacrylic acid and polyacrylamide, high amylose cornstarch, or hydroxylated methyl, ethyl and propyl celluloses; or a suitable blend of such materials. Specific examples of suitable PVOH coating materials are Mowiol (Registered Trademark of Hoechst), Polyox (Registered Trademark of Union Carbide Corporation) and Vinex (Trademark of Air Products and Chemicals, Inc.) resins. For example, Mowiol can be thermoplastically processed with the addition of known plasticizers and a little water. Typical plasticizers are water and polyhydric alcohols such as glycerol, trimethylol propane, triethanolamine and ethoxylated phosphoric esters, diglycol, triglycol and neopentyl glvcol. Typically between 5 and 50% by weight of plasticizer is added. This mixture can be processed on conventional thermoplastics processing machines such as extrusion blow moulding, injection moulding and compression moulding machines. The water solubility of the film produced by this method can be varied depending on the degree of hydrolysis of the Mowiol grade used. Such films are biodegradable in aqueous solution, resistant to most organic solvents, resistant to mechanical stress, non-toxi^ and have good weldability and bondability. There are few solvents apart from water for Mowiol. The grade of Mowiol, plasticizer concentration, extrusion temperature and residence time in the extrusion cylinder determine the solubility of an extruded Mowiol film in cold water.

Another method of making PVOH suitable for thermoplastic uses is to use an internal plasticizer by polymerisation reaction in the presence of comonomers, grafting reactions or post reaction. Vinex is an internally plasticized, water soluble, thermoplastic resin which is a copolymer of PVOH with poly(alkyleneoxy)- acrylate. A typical Vinex 4025 Resin film (1-1.5mm thickness) in distilled water with slight agitation breaks up in 14 seconds and takes 25 seconds to dissolve totally.

Alternately, if the container is coated by other means there will be no need for addition of a plasticizer. Table 1 gives some general examples of solubilities of polyvinyl alcohol films of different thickness at 20°C :

TABLE 1.

EF-210 Cold Water Soluble Polyvinyl Alcohol Film

Note : the solubility was determined by soaking a sample specimen in water and measuring the time to dissolve and disperse without agitation. Any of the films known in the art which have a dissolvability in an aqueous or non-aqueous wash liquid of 10 minutes or less with agitation of the rinse solution are particularly suitable for use in the present invention. Ideally the film is designed to dissolve in 3 minutes or less. However, on standing with a wash liquid the film could take up to 24 hours to dissolve without agitation. Thus any of the films known in the art which have these properties and can be coated onto the inside of a container by any of the means described herein, are useful in the present invention. For example, US

3,892,905 discloses films which comprise a mixture of polyvinyl alcohol and polyvinyl pyrollidone. Some examples of the solubility in water of such films are given in Table 2 :

Table 2.

Polyvinyl alcohol and polyvinyl pyrollidone films

A preferred method of triggering or catalysing the solulisation is to make the inner wall or coating εo3uble in a pH which is different to the pH of the contents of the container and to provide a trigger or catalyst with the container so that the pH of the rinse water or solvent can be manipulated at the spray site. The inner wall or coating may require additives to manipulate its solubility and render it sensitive, for example, to pH changes. Materials which are sensitive to pH in this manner are known, for example, US 4,469,728 discloses films which are insoluble in water and soluble in a basic medium. Homopolymeric or copolymeric acids are suitable for such a film, particularly an acid which itself is produced using an acrylic acid, methacrylic acid, crotonic acid or maleic acid and their anhydrides, for example, vinyl ether, acrylate or methacrylate.

Suitable solutions for dissolving such films are borates, amines, for example triethanolamine, water -soluble carbonate, silicates, and secondary and tertiary phosphates, for example, triammonium phosphate. The use of borates to dissolve the inner wall or coating would be particularly convenient since such solutions can be found in most households in the form of domestic laundry materials.

Table 3 gives examples of solubility of such films in water, sodium hydroxide and triammonium phosphate.

Table 3.

MAA = maleic acid anhydride 1 insoluble

EVE = ethyl vinyl ether 2 swells

MAC = methyl acrylate 3 slowly soluble

BAC = n-butyl acrylate 4 quickly soluble TAP - triammonium phosphate

Alternately the inner-most wall or coating may be formed of a water-insoluble material which is soluble in common organic solvents. For example, polyvinyl acetate is a thermoplastic high polymer which is soluble in readily available low molecular weight axcohols such as methanol or ethanol, and polyvinyl ether which is soluble in for example, cyclohexanone or methylethylketone. in a further alternative chemicals can be provided which when mixed with water can be used in a spray which will dissolve a particular waterproof plastic, or such chemicals can be incorporated into the inner wall or coating of the container so that as soon as water or solvent touches it the plastic starts to degrade. Such materials are known, for example, Belland materials. Consideration must also be given to the resources available to the user and the conditions under which the container will be used. Thus the container may be provided with an amount of solvent or catalyst, for example in the cap which enables the user to provide the correct conditions for solulising the inner wall or coating. A further method of enabling an aqueous based substance to be contained in a water soluble inner wall or coating is to use surfactants in the contained substance to stabilise the wall or coating while the container is in use. The rinses may be disposed of by putting into the spray tank or using a portable detoxifier, or in the normal way.

A container according to the present invention could be used for storage and distribution of a wide range of substances, for example, agrochemicals, including public health and household chemicals, fertilizers, organic chemicals, pharmaceuticals, coatings and finishings in the paints industry, and hazardous materials in general. According to a further aspect of the invention there is provided a method of providing solvent resistance to a conventional thermoplastic container comprising applying an inner-most wall or coating to said container which is soluble only in aqueous wash liquid. The invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional view of a container in a mould;

Figure 2 is a cross-sectional view of the wall of a container; Figure 3 is an additional cross-sectional view of the wall of a container; Figure 4 is a cross-sectional view of the base of a container;

Figure 5 is an additional cross-sectional view of the base of a container; Figure 6 is a cross-sectional view of a vacuum dispensing container;

Figure 7 is a cross-sectional view of a container containing a formulated chemical;

Thus, referring to Figure 1, the container 1 is illustrated while inside the mould 4 in which the co-extrusion or co-injection blow moulding operation takes place. The mould 4 is formed in two halves 4a, 4b, and the layers of molten plastics materials are extruded or injected from tubes 5 placed one inside the other inside the mould 4. During extrusion or injection air is blown into the inner space 6 pushing out the layers to the shape of the mould 4. The container is formed with an outer shell 2 which is rigid or semi-rigid according to the users' requirements and to achieve this may be made up of layers of different plastics materials. The outer shell 2 has an inner wall or coating 3.

Figures 2 and 3 demonstrate single and multi-layer outer shells respectively, with an inner wall or coating 3. Multi-layer outer shells may require an adhesive tie layer 7 between two layers of thermally incompatible materials. The inner wall 3 is a single layer of a solulisable material. When the extrusion or injection process is complete, the two halves of the mould 4, 4a are separated to reveal the container 1.

Figure 4 shows the base of the container 1 in greater detail. Where the two halves of the outer shell 2 meet at the pinch 8 these are unable to weld because of the inner wall or coating 3. Thus when ejected from the mould 4, the container 1 is open at the base 9 of the outer shell 2. Figure 5 demonstrates a method of overcoming the inability to weld the base 9. In this case the inner wall or coating 3 is 'pushed' back into the outer shell 2 and the opening is welded as a separate operation, for example, by the application of heat or ultrasonic welding. Figure 6 illustrates a vacuum dispensing container 1 which has an inner collapsible bag 11. The outer shell 2 has several layers the innermost of which 10 is thermally incompatible to and not adhesive tie bonded to the rest. The inner wall or coating 3 is found on the inside of the inner collapsible bag. A suitable pump 12 for vacuum dispensing is provided on the neck 13 of the container 1. In use, as the contents are dispensed the inner collapsible bag 11 is drawn away from the outer shell 2 to ensure full evacuation of the container 1. In practice the bag 11 itself could be formed from the inner wall or coating 3.

Figure 7 illustrates a finished container 1 containing a formulation of a chemical 13. The container 1 is provided with a cap (not shown) and optionally with a seal 14 which is made of a suitable material such as plastics or metal foil.

It will be appreciated that the following examples do not limit the broad applicability of the present invention.

EXAMPLE 1

A 1 litre polyethylene terephthalat<ϊ bottle (formed by injection stretch blow moulding technique) was coated on the inner wall with 2 grams of Mowiol (Grade 383) PVOH. The coating was applied by putting a solution of Mowiol 383 in water in the bottle and swirling the solution around until a film covered the entire inner surface of the bottle. The bottle was dried in a air oven. The thickness of the resultant film was 20 microns thick. The bottle was filled with an 2.5% emulsion concentrate formulation of lambda-cyhalothrin (insecticide) and left in storage for 1 week at 40°C and 90% relative humidity and 1 week at 23°C and 50% relative humidity. After storage the contents were decanted. The solvent from the formulation was allowed to evaporate off the inner PVOH film surface and then the bottle was cut in half horizontally. The inner lining of PVOH film was separated from the polyethylene outer shell. The film had retained its flexibility.

The detached PVOH film was immersed in a 1 litre glass beaker of tap water at approximately 20°C. Rapid dissolution of 75% of the film occurred within 30 seconds. The remainder of the film dissolved within a further 90 seconds with gentle agitation of the water.

In the following examples the containers are provided with an inner wall or coating of a suitable poly- vinyl alcohol. However, the examples serve to illustrate the invention and the containers described may suitably be provided with any of the coating materials mentioned herein.

EXAMPLE 2

This example demonstrates a number of different plastics for containers made of a single material and provided with an inner wall or coating of polyvinyl alcohol.

(a) polyamide (nylon) (b) ethylene vinyl alcohol (EVOH)

(c) polyacetal

(d) polyacrylonitrile

(e) polyethylene terephthalate

(f) glycol modified polyethylene terephthalate (g) high density polyethylene

(h) high molecular high density polyethylene (i) polypropylene (j) polyvinyl chloride (k) polycarbonate (m) polyvinylidene chloride

EXAMPLE 3

This example demonstrates materials for co-extruded multilayer plastic containers provided with an inner wall or coating of polyvinyl alcohol. The 1st layer is the outermost layer.

(a) 1st layer = high molecular high density polyethylene 2nd layer = regrind layer 3rd layer = adhesive layer

4th layer = polyamide layer (barrier)

5th layer = adhesive layer

6th layer = high density polythene inner coating = polyvinyl alcohol

(b) 1st layer = high molecular high density polyethylene 2nd layer = regrind layer

3rd layer = adhesive layer

4th layer = polyacrylonitrile layer (barrier) 5th layer = adhesive layer

6th layer = high density polythene inner coating = polyvinyl alcohol

(c) 1st layer = high molecular high density polyethylene 2nd layer = regrind layer

3rd layer = adhesive layer

4th layer = ethylene vinyl alcohol layer (barrier) 5th layer = adhesive layer 6th layer = high density polythene inner coating = polyvinyl alcohol EXAMPLE 4

This example demonstrates the diversity of materials which can be used for containers and in each example the container is provided with a coating of polyvinyl alcohol.

(a) polyethylene (high, medium or low density), surface treated with fluorine gas to produce a fluoro-carbon layer;

(b) laminar technology concentrates, such as nylon, together with a coupling agent are blended with polyolefins, such as high density polyethylene to produce containers with a layered structure. For example:

(i) high density polyethylene with polyamide platelets;

(ϋ) polypropylene with polyamide platelets;

(c) solid or corrugated fibreboard (single layer);

_2

(d) double wall corrugated casing of 200gm mottled

_2 kraft paper, 125 gm middle straw or chip and 300

2 gm- test paper as the inner facing;

(e) 1 litre carton made from 5 micron folding boxboard

_2 coated with 95 gm low density polyethylene. This could also be a wax coated carton;

EXAMPLE 5

This example demonstrates bag-in-box designs. There are two designs (i) the container is provided with a liner which is detached from the wall of the container and the liner is provided with the inner wall or coating or (ii) the inner wall or coating is detachable from the container and serves as the liner. Each of the following examples is provided with an inner coating of polyvinyl alcohol.

(a) solid or corrugated fibreboard (single layer)

_2

(b) double wall corrugated casing of 200gm mottled

_2 kraft paper, 125 gm middle straw or chip and 300

₂ gm- test paper as the inner facing

(c) (i) polyamide (nylon)

(ii) ethylene vinyl alcohol (EVOH) (iii) polyethylene terephthalate

(iv) high density polyethylene

(v) polypropylene

(d) 1st layer = high molecular high density polyethylene 2nd layer = regrind layer

3rd layer = adhesive layer

4th layer = polyacrylonitrile layer (barrier) 5th layer = adhesive layer 6th layer = high density polythene inner coating = polyvinyl alcohol

EXAMPLE 6

This example demonstrates materials which can be used for drums provided with an inner wall or coating of polyvinyl alcohol.

(a) 210 litre fixed end metal drum (mild steel) with welded side seams and triple seamed ends internally lacquered with internal treatment of 2 coats of epoxy phenolic lacquer; (b) as (a) with a separate blow moulded inner liner (3.3kg/lmm thick) replacing the lacquer. (This is known as a "composite drum"). The liner is attached to 2h inch (63.5mm) bung holes;

(c) 200 litre blow moulded high molecular high density polyethylene (9kg/8mm minimum wall thickness) with 2 bungs.

Claims

1. A container comprising a single or multi-layer outer shell characterised in that the outer shell (2) is provided with an inner-most wall or coating (3) of a material which is insoluble while the container is in use but is soluble or solulisable in a wash liquid.

2. A container according to claim 1 wherein the inner- most wall or coating (3) is soluble or solulisable in an aqueous wash liquid.

3. A container according to claim 1 wherein the inner¬ most wall or coating (3) is soluble or solulisable in a non-aqueous solvent or an aqueous wash liquid containing a catalyst or trigger.

4. A container according to claim 1 wherein the inner¬ most wall or coating (3) is impregnated with chemicals which degrade the inner-most wall or coating (3) on contact with the wash liquid.

5. A container according to any of the preceding claims wherein the inner-most wall or coating (3) is a plastics material or a blend of plastic materials.

6. A container according to claim 5 wherein the inner¬ most wall or coating (3) is a plastic material selected from one of the following : polyvinyl alcohol, polyvinyl pyrollidone, polyethylene oxide, polyethylenimine, polyacrylic acid, polyacrylamide, polyvinylacetate and polyvinyl ether; or is a blend of two or more plastics selected from this group.

7. A container according to claim 6 wherein the inner¬ most wall or coating (3) comprises polyvinyl alcohol.

8. A container according to any of claims 1 to 4 wherein the inner-most wall or coating (3) is formed from high amylose cornstarch or hydroxylated methyl, ethyl and propyl celluloses.

9. A container according to any of the preceding claims wherein the inner wall or coating (3) is from 1 angstrom to 200 microns thick.

10. Process for manufacture of a container described in any of claims 1 to 9 by co-extrusion or co-injection moulding techniques wherein the outer shell and the inner-most wall or coating are moulded in a single operation.

11. Process for manufacture of a container described in any of claims 1 to 9 wherein the container is manufactured by any conventional technique and the inner-most wall or coating is applied in a separate operation.

12. Process according to claim 11 wherein the separate operation to apply the inner-most wall or coating is by conventional or electrostatic spraying or dip or powder coating.

13. Use of a container as described in any of claims 1 to 9 for storing or distributing toxic or hazardous materials.

14. Use of a container as described in any of claims 1 to 9 for storing or distributing agroche icals, organic chemicals, fertilizers, pharmaceuticals, or coatings and finishings in the paints industry.

15. Method of removing chemical residues from a conventional container by providing the container with an inner-most wall or coating (3) of a material which is insoluble while the container is in use but is soluble or solulisable in a wash liquid.

16. Method of providing solvent resistance to a conventional thermoplastic container comprising applying an inner-most wall or coating to said container which is soluble only in aqueous wash liquid.