The use of biodegradable plastics in the manufacture of packaging and the like in place of non-biodegradable plastics is desirable for environmental reasons. However, certain disadvantages exist with the commercially available biodegradable plastics materials which restrict their uses. In particular, many commercially available biodegradable plastics or additives used in the plastics do not adequately decompose or degrade under standard environmental conditions and can be highly toxic when partially degraded. Accordingly, many such commercially available biodegradable plastics are not widely employed and are perceived as only being applicable for niche markets. As a result, biodegradable plastics materials are not employed for mass market consumer products such as gas-impermeable films for use on surfaces of articles such as containers, flushable toiletry articles, packaging for unit doses of detergent and the like and packaging devices for cans, bottles, jars etc.

Many materials currently available for sealing packages also suffer the disadvantage that they are too permeable to gases such as air and that the permeability varies with atmospheric conditions and in particular with relative humidity. For example, cartons of chocolates and other confectionery, cigarettes and tobacco, and many other products are currently sealed in materials formed from extruded acetate. However, such acetate films are highly gas permeable and accordingly, metal foil is also used in conjunction with the acetate film for sealing the package. However, the use of metal foil is clearly environmentally unfriendly and also increases the costs of the packaging material.

It is also known to use moulded/extruded resin containers such as polyethylene terephthalate (PET) bottles or polyolefin containers such as low destiny polyethylene bottles for packaging. Such materials are industrially convenient in that they are easy to manufacture and enjoy good consumer acceptance. However, such containers are gas permeable and therefore suffer from disadvantages when used for perishable products to be stored for prolonged periods. Examples of such products include wines and olive oil.

Many toiletry articles are currently made from rigid or non- biodegradable plastics and accordingly present problems for disposal in an environmentally friendly fashion. Examples of such toiletry articles include short rods used as carriers for cotton buds, tampon applicators and applicator nozzles for intimate personal use e.g. treatments for haemorrhoids and vaginal candidiasis.

Users of such toiletry articles frequently dispose of the products by flushing the products into the sewage system thereby giving rise to processing problems in sewage treatment plants and environmental/pollution hazards in environments where sewage is simply directed into the sea or other waterways. Similarly,

static sewage disposal systems such as septic tanks and the like can become clogged with such toiletry articles and must therefore be emptied prematurely.

To overcome the aforementioned problems associated with toiletry articles, attempts have been made to manufacture toiletry articles from biodegradable materials such as card, paperboard or other cellulose based products. However, card, paperboard and other cellulose based products tend to lack sufficient rigidity and can be expensive or indeed difficult to manufacture.

Accordingly, a need to exists for a biodegradable or compostable product having physical characteristics such as sufficient rigidity for the manufacture of toiletry articles such as cotton bud rods, tampon applicators and the like which can also be conveniently and economically manufactured.

The use of detergents and the like also presents a number of problems to end users due to the potentially caustic or skin damaging nature of the detergents e.g. dishwasher detergents. In addition, significant amounts of packaging are used with detergents due to the nature of the detergents and the need to prevent deterioration of the detergent over prolonged storage periods.

Accordingly, a need exists for detergent formulations which avoid skin contact and which can simplify the dispensing of suitable quantities of such cleansing agents at point of use. In an attempt to address such problems, dishwasher detergents have been provided in tablet form. However, a user must still come into contact with the tablet to open the sachet, wrapper or the like in which the tablet may be packed for later use.

Similarly, laundry detergent compositions have been packed in unit doses in sachet form to facilitate correct dosing of the detergent into a washing machine in use. However, generally, the

sachet must be opened and subsequently disposed of in order to correctly dose the washing machine.

Accordingly, a need exists for a unit dosing package for cleaning materials which obviates the need for an end user to contact the cleaning materials prior to or during use.

Plastics materials are also widely used in the packaging of beverage and foodstuffs in cans, bottles, jars and the like. More particularly, cans of beverages such as beer are conveniently sold in four or six packs in which the individual cans are linked together by having their ends placed in circular openings in a flat sheet or web formed from a non-biodegradable polyolefin plastics sheet material. Packaging devices of this type are used in large numbers and accordingly present a serious environmental hazard following use.

More particularly, due to price constraints and ease of manufacture requirements, the can holding sheets are usually formed from a comparatively soft plastics such as low destiny polyethylene material. The polyethylene material must be sufficiently elastic to be forceable over the collars of a group of cans or jars to grip the necks of the jars or the sides of the cans. In such cases, the grip is achieved by assembling the cans into a pack with the web-like packaging device and applying heat to shrink the material so as to grip the can or jar tightly.

However, low destiny polyethylene and other similar materials used for such applications suffer poor elasticity and in particular a very limited "shape memory" therefore easily giving rise to permanent deformation. Deformation results in excessive stretching of the plastics material so that the pack sometimes disintegrates under the weight of the containers held by the sheet therefore necessitating repackaging of the cans. However, more importantly, the polyalkylene or polyvinyl material used to manufacture such sheets is essentially non-biodegradable and therefore cannot be easily re-cycled.

Polyvinyl alcohol (PVA) is a known biodegradable material.

However, its use in the manufacture of plastics articles has up to now been limited as it is technically difficult to work with PVA to produce an acceptable product. Accordingly, materials and products formed from PVA materials are regarded as costly, difficult to manufacture and hence commercially unsuccessful.

The use of polyvinyl acetate/polyvinyl alcohol (PVA) copolymers for the manufacture of biodegradable plastics materials is described in PCT Patent Specification No. W092/01556. The water soluble PVA dissolves readily in water and is broken down under environmental conditions within a relatively short time to carbon dioxide and water.

German Patent Specification No. 1127085 discloses that the incorporation of a plasticiser into PVA prevents undesirable thermal decomposition of the plastics material at temperatures above 1500C. The plasticised PVA can then be injection moulded and extruded by heating the material to a temperature in the range of 145"C to 1900C and at an injection pressure of 100 to 130 bar.

PCT Patent Specification No. W097/09379 discloses that by mixing a water soluble PVA copolymer with a plasticiser and a stabiliser, the resultant material can be worked by blow moulding, injection moulding and extrusion etc.

However, despite the disclosures of the prior art, PVA has not been put into use in plastics materials and products on a large scale particularly using extrusion techniques of the type used for polyalkylenes.

An object of the present invention is to overcome the problems of the prior art.

In particular, an object of the invention is to provide improved

biodegradable materials and products and improved methods for the manufacture of the biodegradable materials and products.

According to the invention there is provided a polyvinyl alcohol film comprising a non water soluble portion and a cold water soluble portion, the non-water soluble portion being gas impermeable.

Preferably the non water soluble portion comprises an impermeable layer disposed over the cold water soluble portion and the impermeable layer comprises cured polyvinyl alcohol.

Suitably the cured polyvinylalcohol comprises photocured polyvinylalcohol.

Preferably, the photocured polyvinylalcohol comprises ultra- violet photocured polyvinylalcohol.

Suitably, the polyvinyl alcohol film comprises a photocure activator, the photocure activator prefably comprising a dichromate activator.

Preferably, the film comprises from 0.5% to 2% by weight dichromate activator and'more preferably 1% by weight dichromate activator.

Advantageously, where the film is to be in the form of an aqueous solution, the film comprises from 30 to 75 grammes polyvinylalcohol per litre of water.

Suitably, the film comprises a colouring compound.

Advantageously, the film further comprises an ultra-violet reflective material and preferably the ultra-violet reflective material comprise titanium dioxide.

The invention also extends to a container comprising a polyvinyl alcohol film having a non water soluble portion and a cold water soluble portion, the non water soluble portion being gas impermeable.

Suitably, the container comprises paperboard or plastics.

The invention also extends to a toiletry article formed from polyvinylalcohol. Suitably the polyvinylalcohol comprises cold water soluble polyvinylalcohol and the cold water soluble polyvinylalcohol comprises partially hydrolysed polyvinylalcohol.

The toiletry article can comprise tampons, diapers, tampon applicators, incontinence pads and cotton bud rods. Preferably, the toiletry article comprises a cotton bud rod.

The invention also extends to a detergent pack comprising polyvinylalcohol. Advantageously, the polyvinylalcohol comprises cold water soluble polyvinylalcohol. Alternatively, the polyvinylalcohol comprises hot water soluble polyvinylalcohol.

The polyvinyl alcohol can also comprise hot and cold water soluble polyvinylalcohol to control the solubility of the detergent pack.

In a preferred embodiment of the invention, the detergent pack comprises a sachet. Alternatively, the detergent pack comprises a film. Suitably, the detergent comprises a detergent tablet.

The invention also extends to a packaging device for holding receptacles comprising polyvinylalcohol. Suitably the polyvinyl alcohol of the receptacles is formed into a web for receiving receptacles. Advantageously, the receptacles are receivable in holes defined in the web. Suitably, the polyvinylalcohol comprises cold water soluble polyvinylalcohol.

Alternatively, the polyvinyl alcohol of the web comprises hot water soluble polyvinylalcohol. The polyvinylalcohol of the web can also comprise hot and cold water soluble polyvinylalcohol.

The invention also extends to a method of forming an impermeable polyvinylalcohol film comprising doping a polyvinylalcohol solution with a photocure additive, applying the solution to a surface, drying the solution to form a barrier and exposing the solution to ultra-violet light to activate the photocure additive to cure the barrier surface. Suitably the photocure additive comprises a dichromate.

The invention also extends to a method of manufacturing a biodegradable plastics material comprising mixing water soluble polyvinyl alcohol with a plasticiser at a temperature above 80"C and rapidly cooling the mixture to below 60"C. Suitably the mixture is heated to a temperature above 95"C. Alternatively, the mixture is heated to a temperature between 80 and 85"C.

Preferably, the mixture is cooled rapidly to 500C.

In a preferred method of the invention, the water soluble polyvinylalcohol is mixed with a photocure additive.

Advantageously, the photocure additive comprises an ultra-violet curable dichromate. Suitably, the cooled mixture is exposed to ultra-violet radiation to cure the surface of the mixture.

Advantageously, the polyvinyl alcohol comprises a cold water soluble polyvinylalcohol. Alternatively, the polyvinylalcohol comprises a hot water soluble polyvinylalcohol.

Suitably, the polyvinylalcohol comprises a mixture of cold water soluble polyvinylalcohol and hot water soluble polyvinylalcohol.

The invention also extends to a method of manufacturing a biodegradable plastics material comprising mixing water soluble polyvinyl alcohol with a plasticiser at a temperature in the range of between 106 to 140"C and extruding the mixed material.

Suitably, the polyvinyl alcohol is mixed with a photocure additive. Advantageously, the photocure additive comprises a dichromate. Suitably the extruded material is photocured.

As previously described, the polyvinyl alcohol can comprise a cold water soluble polyvinylalcohol, a hot water soluble polyvinyl alcohol or a mixture of cold water soluble polyvinylalcohol and hot water soluble polyvinylalcohol.

In a preferred embodiment of the invention, the biodegradable plastics material is formed into an article. The article can selected from a group comprising a polyvinylalcohol film, a toiletry article, a detergent pack and a packaging device.

Suitably, the toiletry article is selected from the group comprising tampons, diapers, tampon applicators, incontinence pads and cotton bud rods.

The invention also extends to the use of polyvinylalcohol in the preparation of a polyvinyl alcohol film having a non water soluble portion and a cold water soluble portion, to use of polyvinyl alcohol in the manufacture of a toiletry article and in particular in the manufacture of a toiletry article selected from the group comprising tampons, diapers, tampon applicators, incontinence pans and cotton bud rods.

The invention also extends to the use of polyvinylalcohol in the manufacture of a detergent pack and a packaging device for holding receptacles.

The invention will now be described more particularly with reference to the following non-restricting examples and Figs. 1 to 11 of the accompanying drawings, in which: Fig. 1 is a perspective view of a cotton bud rod in accordance with the invention; Fig. 2 is a cross-sectional view through a unit dose detergent package in accordance with the invention in a polyvinyl alcohol film;

Fig. 3 is a plan-view from above of a four-can packaging device in accordance with the invention; Fig. 4 is a side elevation of a screw used for extrusion of the materials and products in accordance with the present invention; Fig. 5 is a top elevation of the extrusion barrel in which the screw of Fig. 4 is inserted showing Zones A, B, C and D; Fig. 6 is a side elevation of a die for use in the extrusion of the materials and products in accordance with the invention; Fig. 7 is a top plan view of the die of Fig. 6; Fig. 8 is a front elevation of the mandrel of the die of Figs. 6 and 7; Fig. 9 is a side elevation of the mandrel of the die of Figs. 6 and 7; Fig. 10 is an enlarged side elevation of a die adapted to extrude a sheet from the die, and Fig. 11 is an enlarged front elevation of a portion of the die of Fig. 10 from the direction indicated by the arrow in Fig. 10 showing the sheet thickness adjusting means of the die.

Polvvinvl alcohol (PVA) The term PVA as used herein and refers to a polyvinyl acetate polymer which has been partially hydrolysed to convert (a proportion of) the acetate groups to the corresponding alcohol.

Therefore, the term refers to a polyvinyl alcohol polymer or a

polyvinyl alcohol copolymer. Solubility of PVA copolymers is dependant, amongst other things, on the degree to which the PVA is hydrolysed.

"Cold soluble" PVA denotes a copolymer which is generally referred to as "partially hydrolysed" polyvinyl acetate where typically, the partially hydrolysed copolymer comprises about 72 to about 92.4 weight percent of the alcohol, with the remainder comprising a residual acetate. Such a "cold soluble" material in soluble in cold water i.e. water at about 20"C.

"Hot soluble" PVA denotes a "fully hydrolysed" polyvinyl alcohol.

Typically, the fully hydrolysed copolymer comprises about 92.5 to about 100.0% and preferably at least 96% or greater of the alcohol which results in a marked decrease in solubility at ambient temperatures. The fully hydrolysed polymer is usually thought of as being insoluble. However, the fully hydrolysed polymer is in fact soluble in water at a temperature of about 50"C or greater.

Both hot and cold soluble PVA's, once dissolved, are fully biodegradable in nature to carbon dioxide and water. Moreover, the undegraded materials and their partially degraded derivatives are non-toxic.

Generally, mean average weights having regard to their molecular weights in the range of about 14,000 to 200,000 are usable.

Products formed from PVA's falling into the lower part of this range will be softer and more pliable. A selection of PVA's from the upper end of the range will allow much harder plastics to be made for example for making products such as toiletry articles and the like.

The preferred molecular weight range is from 30,000 to 150,000.

PVA's in this range, when processed in accordance with the methods of the invention herein described may readily be extruded

to give good quality product.

Polyvinyl alcohol compositions are well known and can be obtained in a range of water solubilities, depending, as indicated above, on the percentage of free-hydroxyl groups in the polyvinyl alcohol as compared witch extra groups. Typical products are Mowiol (Trade Mark) available from Hoechst A.G. and Elvanol (Trade Mark) available from Du Pont Industries.

Gas Impermeable Films In accordance with the present invention, gas impermeable films can be formed from biodegradable materials for use on the surfaces of articles such as containers for foodstuffs, drinks, pharmaceuticals and other products requiring air tight storage and in particular containers made of paperboard or moulded synthetic resins. The films are formed from cold-water soluble PVA.

In accordance with the present invention the PVA film is applied directly to the surface or formed directly on the surface to be rendered gas impermeable. The film forms a barrier on the surface to be rendered gas impermeable and is provided with an outer surface which is substantially inert to changes in relative humidity but is nevertheless degraded under normal composting conditions due to the biodegradation of the cold water soluble portion.

In contradistinction, the PVA films and coatings of the prior art are generally regarded as being of little use in producing water- resistant reliable gas-impermeable barrier systems.

The PVA film in accordance with the invention is applied to a surface as an aqueous solution containing a minimum effective amount of a doping photocure additive.

The aqueous solution is dried and the surface is irradiated

sufficiently to photocure a surface portion only of the film coating to render the surface water and gas impermeable.

Alternatively, the PVA film can be a preformed blown film and applied to the surface as a formed film. Examples of blown film formulations are to be found below.

The aqueous solution to be applied to a surface typically contains from about 30 to about 75 grammes of PVA per litre of water, preferably from about 40 to about 65 grammes of PVA per litre of water and more preferably from about 44 to about 60 grammes of PVA per litre of water.

The aqueous solution can also contain a colouring compound to impart a suitable colour to the gas impermeable film so that the film may be adapted or matched where desired to the colour of a container or the like. Examples of suitable colouring compounds include water soluble colouring compounds such as Brilliant Blue F.C.F., Tartrazine (yellow) and Ponso-4R (red).

The photocure additive is conveniently a dichromate salt of an alkaline metal or ammonium, or a suitable diazo compound. It is known to add such materials in the production of photoresist screens in order to render it water insoluble on exposure to irradiation e.g. with ultra violet light. The unexposed areas of the material are washed away with water leaving the exposed areas to block the etching process. In another use, exposed insoluble areas can provide a surface relief image to be used as a printing plate. However, in such uses, it is necessary to add sufficient photocure material and to irradiate the film sufficiently that the exposed areas become completely water-insoluble.

In contrast, in the present invention, the smallest possible amount of photocure material is used and the briefest irradiation is given such that only the surface of the film becomes water- insoluble while the interior of the film renains cold-water

soluble.

Accordingly, the present invention ensures that the compostability of the product is maintained while sensitivity to relative humidity is removed.

Typically, the coating solution according to the invention contains about 0.5% to about 2% by weight of the composition, preferably about 1% by weight of the composition of photocure additive. For packaging uses, the film is preferably clear, colourless and transparent and is impermeable only at the surface after irradiation. Desirably, such an effect can be best achieved by using a two-layer film in which the outer layer only contains the photocure materials.

The blown films in accordance with the invention can range in thickness from about 10 Fm to about 150 Fm in thickness. The thickness of films applied as an aqueous solution to a surface will depend on the amount of solution applied to the surface.

Where transparency is not a problem or is even undesirable, for example in intimate hygiene products, in particular pantyliners and external sanitary protection and nappies and the like, surface-only photocure can be achieved by inclusion of a ultra- violet reflectant material such as titanium dioxide. The titanium dioxide is dispersed throughout the interior of the film so that, under irradiation, only the surface-layer where the PVA is exposed, becomes cured. A two-layer film can also be used if desired, in which the inner layer is pigmented and opaque and the outer layer is transparent and contains a photocure material.

The two-layer film can be a co-extruded surface film or a laminate. Using a 30 watt U.V. light source an irradiation time of about 5 minutes to about 100 minutes is satisfactory for photocuring films having the abovementioned range of thicknesses.

For example, modern hygiene products of the type which are to absorb body fluids are typically constructed with an impervious backing sheet, a highly porous outer cover and an internal absorbent material which is sandwiched between the backing sheet and the outer cover. The same basic construction is used for various absorption products including pantyliners, female sanitary protection, diapers as well as incontinence pads for adult patients. In all cases, the backing sheet is conventionally formed of a water insoluble resin film material, typically polyethylene. Accordingly, disposal of such products presents serious environmental hazards due to the lack of biodegradability of the backing film. Accordingly, the construction of the films in accordance with the present invention ensures that a major, exposed part of the backing sheet is formed of a cold water soluble film thereby enabling the product to be flushed and to biodegrade in water in the sewage- system. However, at the same time, the water insoluble surface adjacent the absorptive materials ensures that the backing sheet is an effective barrier in use, thereby preventing leakage.

The pre-formed surface treated cold water PVA film according to the invention can be simply attached to the remaining layers of the product using conventional means in the art such as adhesives which can also be PVA based, welding techniques and the like.

Tests were carried out on a film with a thickness of 30 tim and irradiated using a 30 watt ultraviolet light source at 6 inches distant for a period of 20 minutes. It was subsequently found that when ruptured the insoluble cross-linked portion of the film was 2 Fm thick. The body or bulk of the film dissolved readily in cold water. The remaining insoluble layer, being unable to support its own weight, broke up.

Toiletry Articles The invention also embraces the provision of standard, commercially available water-soluble polyvinyl alcohol materials

which are sufficiently rigid for the manufacture of toiletry articles yet which are still compostible to facilitate flushing where required without damage to sewage systems and the like.

More particularly, disposable solid toiletry articles are contemplated in particular carriers or rods for cotton buds, tampon applicators and applicator nozzles, which are formed from hot extruded hot or cold-water soluble, preferably cold-water soluble polyvinyl alcohol.

In contradistinction, cotton bud rods of the prior art are generally formed from polypropylene or high impact polystyrene which are clearly environmentally unfriendly products which cannot be biodegraded but which are nevertheless frequently disposed of by consumers into sewage systems and the like.

Examples of suitable PVA compositions for use in the manufacture of toiletry articles are given below while Fig. 1 of the accompanying drawings shows a cotton bud rod 30 in accordance with the invention having an elongate rod portion proper 31 and cotton buds (shown in broken lines) 32 located at each end of the rod 31.

Unit Dosina Packaaina The present invention also provides a unit dose of a cleansing material in a sealed container formed from a hot or cold water- soluble polyvinyl alcohol.

The unit dose can be a solid tablet form, for example a tablet of dishwasher or laundry detergent or a lavatory cleansing block.

The container can be a simple sachet or bag formed from a water soluble polyvinyl alcohol film, for example, a film produced by a melt-extrusion process as shall be explained more fully below.

As will be appreciated by those skilled in the art, by appropriately selecting cold water and hot water soluble PVA's

having the required degrees of hydrolysis, a dissolvable packaged unit dose product is provided which can be dissolved in use, either rapidly in hot water e.g. when used in a dishwasher, or slowly in cold water when used in a lavatory cistern or the like.

In an alternative embodiment of the invention, the PVA packaging can be formed as a film directly on the surface of a solid tablet of detergent, either using melt-extrusion or coating with a water-based solution similar to the gas impermeable films previously described.

Examples of suitable formulations and manufacturing methods are given below while Fig. 2 of the accompanying drawings shows a cross-sectional view through a detergent tablet 33 provided with a polyvinyl alcohol outer film 34 which defines a sealed container 35 on the tablet 33.

Packaging Device for use with cans. bottles.

iars and the like The present invention also provides a biodegradable packaging device or container holder in the form of a film web having openings to receive the containers. The film is formed from a hot or cold-water soluble polyvinyl alcohol. The hot-water soluble packaging device is suitable for use outdoors where the packaging device may be exposed to the elements.

As indicated above, the solubility of the film is determined by the percentage of free-hydroxyl groups in the polyvinyl alcohol as compared with ester groups and the PVA in the film is selected to produce a film having the desired degree of solubility.

As indicated above, the polyvinyl alcohol film can be produced by melt-extrusion and is usually selected to be of an appropriate thickness for the load to be carried.

Known devices are formed from polyethylene which as also

indicated previously is subject to stretching and has a poor elastic memory so that cans and the like cannot be replaced in the device.

In contradistinction, the packaging devices of the present invention have a good elastic memory to facilitate replacement of removed cans.

Typically, a PVA film of from about 40 to about 70 Fm in thickness is appropriate for supporting cans depending on the weight and number of containers to be packed. In contradistinction, polyethylene devices of the prior art have a thickness of approximately 1.5 mm and can only support a maximum of about four cans. Accordingly, the amount of packaging is approximately double that of the present invention for equal numbers of cans and is also non-biodegradable. With a film having a thickness in the above range, it is possible to achieve a close-packed array of containers where the neck diameter is generally less than the maximum diameter e.g. in a container holder for four 330ml cans of beer or soft drink where the cans have a container top diameter of approximately 65 mm, the film of the invention in this instance has an opening for the can of about 145 mm and gap between holes in the film of approximately 20 mm.

A food can, e.g. for baked beans typically has a can top diameter of about 100 mm. Accordingly, the device of the invention will have a gap between holes of approximately 7 mm.

The relative dimensions of the holes and the gaps therebetween will be determined by the dimensions and weight of the container.

Fig. 3 is a plan view from above of a four-can web-like packaging device 36 formed from polyvinyl alcohol in accordance with the invention. As shown in the drawing, the packaging device 36 is made up of a four-sided flat web 37 shaped to define four

openings 38 for cans. Use of material is minimised by the provision of a central opening 39 between the four can openings 38.

Method of manufacture for biodegradable materials and products Generally, the biodegradable materials and products in accordance with the invention may be sub-divided into two groups namely cold water-soluble products and hot water-soluble products. The cold water-soluble products and hot water-soluble products are determined by the PVA blends used for the plastics material prior to extrusion. The PVA's are therefore blended to arrive at a cold water-soluble product mix or a hot water-soluble product mix as required. The method of manufacture of the present invention has a particular advantage in that following mixing of the polyvinyl alcohols to arrive at a cold water-soluble product mix or a hot water-soluble product mix, a broadly similar extrusion process may be used for both products to provide ease of manufacture and thereby facilitate large scale manufacture of the materials and products in accordance with the invention.

Example A. Mix for extrusion of a cold water-soluble product Materials used A partially hydrolysed PVA was used having a mean molecular weight of 103,000, and an 88 mol% degree of hydrolysis and whose viscosity, measured as a 4% aqueous solution was 26 mPa.S2.

This raw material was Mowiol (Trade Mark) 26-88 available from Hoechst AG. The plasticised composition mix had the following composition (parts or proportions are by weight per 100 parts of Mowiol 26-88).

Mowiol 26-88 (100) Glycerin (plasticiser) 25 Distilled water 10

The ingredients were all placed into a Baker Perkins high speed mixer (manufactured by Baker Perkins Ltd), which was preheated to llO"C. The mixer was then run at approximately 600 rpm for about 6 minutes, whereupon the material began to lift on the side of the mixer. The composition was then dumped into a cooler for approximately 15 minutes or until it's temperature fell below 40"C.

In the mixing process the glycerin plasticiser and the distilled water was absorbed into the Mowiol granules and the process was accompanied by a rise in temperature.

The amount of glycerin (plasticiser) and water used can be varied according to the product to be produced. For example, glycerin can be used at about 30 parts by weight per 100 parts PVA and preferably about 22 to about 27 parts by weight per 100 parts PVA. Water can be used at from about 5 to about 15 parts per 100 parts PVA, preferably 8 to 12 parts per 100 parts PVA. Toiletry articles including cotton bud rods, gas impermeable films and web-like packaging devices can be formed as required from such compositions.

B. Mix for extrusion of a hot water soluble product materials used The hot water soluble material was made using a 50:50 blend of Mowiol (Trade Mark) 56/98 and Mowiol (Trade Mark) 28/99 which are fully hydrolysed grades having viscosities and hydrolysis values substantially as indicated by their respective specification numbers, as before.

The plasticised 50:50 Mowiol 56-98: Mowiol 28-99 composition had the following composition mix (proportions are parts by weight per 100 parts of Mowiol mixture)

Mowiol 56-98 (50) Mowiol 28-99 (50) Glycerin (plasticiser) 35 Distilled Water 30 Powdered polyvinyl acetate (processing aid) 15 The ingredients other than the polyvinyl acetate were placed initially into a Baker Perkins high speed mixer which was preheated to llO"C. The mixer was run at approximately 600 rpm for 30 seconds and then at 1000-1200 rpm for approximately 15-17 minutes, whereupon the material began to lift on the side of the mixer. The composition was then dumped into a cooler for approximately 15 minutes or until its temperature fell below 40"C.

While the mixture was in the cooler the polyvinyl acetate was added and left for about 2 to 3 minutes.

The glycerin plasticiser suitably comprises from about 30 to about 40 parts per 100 parts polyvinylalcohol and preferably from about 32 to 38 parts per 100 parts polyvinyl alcohol while the water comprises from about 25 to about 35 parts per 100 parts polyvinyl alcohol and preferably from about 27 parts to about 33 parts per 100 parts polyvinylalcohol. The polyvinylacetate processing aid which functions as a slip agent advantageously comprises from about 10 to about 20 parts per 100 parts polyvinyl alcohol and preferably between about 12 and about 17 parts per 100 parts polyvinylalcohol.

Extrusion Process (the same irrespective of hot or cold water soluble finished product) The extrusion process will now be described having regard to Figs. 4 to 11 of the accompanying drawings.

Apparatus: Betol (Trade Mark) BC60 60 mm single screw extruder Betol short screw: 3:1 compression ratio with a length diameter

ratio of 25:1. Fig. 4 shows Betol short screw 1 having a compression ratio of 3:1 and a length to diameter ratio of 25:1.

The screw has two compression zones B, D separated by a zone C in which no compression of the polymer composition takes place. The screw 1 is mounted in a barrel 18 in which a vent 6 is defined in a barrel wall 7 which aliows the escape of steam. The screw 1 was operated at a speed of 24 rpm.

The plasticised composition of a hot or cold water soluble polyvinyl alcohol previously described is trickle fed into a feed throat 5 in the screw 1 so that the feed throat 5 is maintained 50% full. The composition is taken up by a first screw portion 20 in the screw 1 and passes into the barrel 18 of the extruder.

A short distance down the extruder barrel 18 the root diameter of the screw begins to taper outward towards the barrel wall 7 and then remains parallel with the barrel wall 7 for a distance about equal to the distance of taper. In a region 8 of the screw 1 the composition is compressed. Here the barrel 18 temperature at a compression zone B is maintained at about 225"C t 10°C.

Immediately thereafter the root diameter reduces markedly and the pressure is thereby released in the region indicated by the reference numeral 9. Steam vents through an aperture 6 in the barrel wall 7. The compression is then repeated in the region indicated by the reference numeral 10 of the extruder. In this region 10, zone D, the barrel temperature is maintained at about 195"C i 10°C.

A Zone A in the barrel 18, located adjacent the feed throat 5, has a temperature of about 210°C i 10°C, the Zone B, preceding the vent 6 as stated earlier has a temperature of about 225"C s 100C, a Zone C located after the vent 6 a temperature of about 220"C s 10°C and the Zone D as stated earlier about 195"C i 10°C.

Temperature regulation is performed by means of conventional electric jackets.

A die 11, shown in Figs. 6 and 7, of the extruder is heated to

about 210°C and the heated PVA composition is then fed to the die 11 by the screw 1. At the same time warm air is blown through a hole 24 in the centre of the die 11. A blown film bubble can then be formed above the die 11 where, after cooling, air is blown in a conventional manner over the outside of the bubble over the die 11. The blown air dries the bubble rapidly to a non-tacky state such that it can be flattened by nip rollers of a conventional blown film tower, collected and folded flat to be cut into single sheet form subsequently.

Figs. 6 and 7 show a general purpose blown film die 11 having an adaptor 21 which has a controlled temperature of about 210°C provided by a heater band 25 which is clamped onto an exit part 26 of the extruder barrel 18 (see Fig. 5). The resulting melt is driven by the screw 1 through the barrel 18 and into a mandrel 22 shown in enlarged scale in Figs. 8 and 9. The melt enters the mandrel 22 at a point 12 and travels up and around a channel 13 as well as a reduced diameter portion 14 to ensure even distribution of the material by a point 15 around the outside of the mandrel 22. The material is then compressed by a pin and bush assembly 28, 29 shown in Figs. 6 and 7 through die lips 16 which form a tube of film. When compressed air is fed into a channel 23 in the die 11 it expands the hot bubble to the size required prior to cooling. Adjusting screws 17 serve to equalise the wall thickness around the bubble. Thickness of finished film can be made to vary typically from about 8 pin to 75 pin. The resulting film can then be converted to sachets for detergents, feminine hygiene products, carrier bags, refuse sacks and any other end product where plastic film is currently employed.

In the case of production of cotton bud rods, a standard pin and bush assembly is used in place of the blown film die described above whereby the resulting tube so formed is cooled by compressed air rather than with conventional materials by water prior to cutting to the required size. The process of manufacture cotton buds rods is more fully described below.

For a packaging device designed for the packaging of a number of cans (beverage food cans etc.) whereby a sheet of plastics has been press cut with a number of apertures or holes as previously to fit snugly around the neck of the cans and with increased strength requirements, it is preferable to manufacture continuous cast film utilising a die 11 as shown in Figs. 10 and 11 to produce a sheet due to the increased thickness requirements. The die 11 is provided with sheet thickness adjusting means 40 made up of adjusting screws 41 for adjusting the distance between die lips 42 where a web-like sheet 43 exits the die 11. This die 11 will produce a continuous cast sheet whereby the sheet typically has a thickness of 1.2 mm and is processed utilising the same temperature and screw speed parameters as the previously described blown film process. As the film is produced in a continuous sheet process rather than a bubble it can subsequently be press formed or cut into the required shape (e.g. beverage can holder, "blister" type packaging forms or any device where plastics sheet is currently employed).

Formation of cotton bud rod A cotton bud rod in accordance with the invention may be extruded on a 50-60 millimetre single screw extruded with an approximate temperature range of about 1900C to about 220"C through a conventional pin assembly which forms the extrudate into a tube.

The tube is then passed through a cold water bath and drawn to an outside diameter of approximately 2.5 mm before being conveyed via a haul-off to a cutter which subsequently cuts the now hardened off and cool material into approximately 73 mm lengths.

The 73 mm lengths are then packaged into boxes containing approximately 45,000 pieces before being taken to the next and separate stage of budding where cotton wool is spooled onto each of the rod. In this stage, the rod is then passed through a machine which forms small notches into the ends of the rod which provide a "key" for cotton wool.

The ends of the rod of PVA material may be moistened in order to slightly dissolve the ends of the rod to further enhance adherence of the cotton wool to the rod.

The invention is not limited to the specific details herein described which are given by way of example only and it will be appreciated that various modifications and alterations may be made within the scope of the appended claims.