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Title:
POLYMERIC COMPOUND WITH ADJUSTABLE DEGRADATION, FLAME-RESISTANCE AND MANUFACTURING METHOD
Document Type and Number:
WIPO Patent Application WO/2020/148290
Kind Code:
A1
Abstract:
A dry polymeric compound that dissolves in aqueous environment and preferably is flame-resistant comprises a dry polymeric composition consisting of polyvinyl alcohol, polyvinyl acetate, stabilizing agent, thickening agent and glucose and is treated with tetraborate and carbonate. Such compound can be adjusted with regard to its disintegration time and formed into foils or three-dimensional objects.

Inventors:
GEORGIEV IVAN VASILEV (BG)
Application Number:
PCT/EP2020/050827
Publication Date:
July 23, 2020
Filing Date:
January 14, 2020
Export Citation:
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Assignee:
TAOSS AG (CH)
International Classes:
C08J3/24; C08L29/04; C08J7/14; C08K5/1545; C08L1/28; C08L31/04
Domestic Patent References:
WO2003051989A12003-06-26
WO2003051989A12003-06-26
Foreign References:
US20120142849A12012-06-07
DE2425558A11974-12-19
US20100304116A12010-12-02
Attorney, Agent or Firm:
E. BLUM & CO. AG (CH)
Download PDF:
Claims:
Claims

1. A dry polymeric compound comprising a dry polymeric composition consisting of the following components

50 to 90 % polyvinyl alcohol (PV-OH),

10 to 40 % polyvinyl acetate (PV-Ac),

0 to 10 % stabilizing agent, in particular methyl cellulose (MC)

0 to 10 % thickening agent, in particular carboxymethyl cellulose (CMC) and

0 to 5 % glucose (glu) ,

the sum of the percentages of the above indicated components amounting to 100 %,

said polymeric compound comprising borate and carbonate groups at least on the surface, said borate and carbonate groups being obtainable by a treatment of the polymeric composition with at least one tetraborate and at least one carbonate and

said polymeric compound degrades and/or dis solves and/or disintegrates in an aqueous medium and preferably is flame-resistant.

2. The dry polymeric compound of claim 1, wherein the polymeric composition is composed of

50 to 90 % polyvinyl alcohol,

10 to 40 % polyvinyl acetate,

4 to 8 % stabilizing agent, in particular methyl cellulose

2 to 8 % thickening agent, in particular carboxymethyl cellulose and

1 to 4 % glucose.

3. The dry polymeric compound of claim 1 or 2, wherein the tetraborate is an alkali metal tetra- borate, in particular sodium tetraborate and the carbonate is an alkali metal carbonate, in particular sodium carbonate .

4. The dry polymeric compound of any one of the preceding claims, additionally comprising additives or adjuvants, in particular glycerin, in amounts of up to 5 %, in particular 1 to 3 % such as 2 %, and fillers, in particular kaolin, wood flour, chalk, in amounts up to 200 %, in particular up to 150 %, referred to the poly meric composition as 100 %.

5. The dry polymeric compound of any one of the preceding claims, wherein the polyvinyl alcohol has a degree of polymerization of 1200 to 2000 and a degree of hydrolysis of at least 70 %, preferably a degree of polymerization of 1200 to 1600 and/or a degree of hydrol ysis of 80 to 99 %, and/or wherein the polyvinyl acetate has a molecular weight of 14,000 to 32,000 and an appar ent viscosity of 50 to 200 mNs/m2.

6. The dry polymeric compound of any one of the preceding claims comprising at least one and prefera bly all of the stabilizing agent, thickening agent and glucose, in particular methyl cellulose and/or carboxyme- thyl cellulose, especially methyl cellulose with a meth- oxy number of 23 to 57, more preferred 23 to 33.

7. The dry polymeric compound of any one of the preceding claims, that degrades and/or dissolves and/or disintegrates in an aqueous medium within about 2 hours up to about 6 months.

8. A method for manufacturing a dry polymeric compound of any one of the preceding claims, said method comprising (i) adding water into a mixer and option ally and preferably heating said water to up to 60°C, preferably about 40 to 50°C,

(ii) adding the other ingredients of the polymeric composition (the PVAc preferably as an aqueous dispersion) and mixing at desired temperature, such as up to 60°C, preferably about 40 to 50°C, until a homogeneous wet polymeric composition is obtained and until a desired amount of water is removed or desired viscosity for fur- ther processing obtained, respectively,

(iii) optionally treating the wet polymeric composition of step (ii) with an aqueous solution of at least one tetraborate and an aqueous solution of at least one carbonate,

(iv) further processing the wet polymeric composition of step (ii) or (iii) by thermally treating and forming it at elevated temperature of at least 70°C (and in general not more than 150°C),

(v) optionally treating the polymeric composition of step (iv) with an aqueous solution of at least one tetraborate and an aqueous solution of at least one carbonate, and

(vi) drying the polymeric composition at temperatures of 30 to 90 °C, preferably 30 to 80°C, more preferred 30 to 70 °C to obtain the dry polymeric compound,

wherein at least one of the treatments (iii) and/or (v) is performed. 9. The method of manufacturing of claim 8, wherein the components of the polymeric composition in step (ii) are not added simultaneously but with the following sequence:

a) adding polyvinylalcohol and mixing for up to 1 hour,

b) adding polyvinylacetate, preferably in form of a dispersion, such as a 50 % dispersion, with continued mixing for up to 20 minutes, in general 10 to 15 minutes,

c) optionally and preferably adding the me thyl cellulose and/or the carboxymethyl cellulose and/or the glucose and mixing for another up to 20 minutes, in general 10 to 15 minutes.

10. The method of claim 8 or 9, wherein dur ing mixing 10 to 60 % of the originally present water are removed.

11. The method of any one of claims 8 to 10, wherein the wet polymeric compound is further processed with rolling and calendering if the remaining amount of water after mixing is 80 to 150 %, preferably 100 to 130 %, and by extrusion if the remaining amount of water is at most 50 %, in particular 10 to 40 % water, referred to the dry polymeric composition as 100 %.

12. The method of any one of claims 8 to 11, wherein the polyvinylacetate is added as a dispersion, in particular as a dispersion comprising 40 to 70 % polyvinyl acetate, more preferred 45 to 60 %, in particular 48 to 56 % .

Description:
POLYMERIC COMPOUND WITH ADJUSTABLE

DEGRADATION , FLAME -RES I STANCE AND MANUFACTURING METHOD

Technical Field The invention relates to a polymeric material with adjustable degradation time and low to no inflamma bility that is suitable for producing plastic articles, e.g. packaging materials, for use in the chemical, food and other industries, and a method for producing such ma- terial.

Background Art

Modern polymeric packaging materials contain mainly thermoplastic polymers and copolymers based on polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyamide and others. It is known that modified polyvinyl alcohol, polyvinyl alcohol/polyvinyl acetate, carboxymethyl cellulose, methyl cellulose, dex- trins, wheat starch, potato starch are used for the prep aration of packaging materials. Over the last years there has been a tendency to apply the so called biopolymers, bio-based polymers, as well as oxo- and photodegradable polymers. Their application, however, is still limited. Polylactic acid (PLA) is derived from biomass, but this does not make it biodegradable according to the global standards. The degradation period may exceed 100 years. What is more, the processing of PLA requires technology made of specific steel alloys, which are rather expen sive .

WO 03/051989 discloses a polymer composition with adjustable decomposition time in aqueous media.

Packiging material obtained from the polymer composition can be used for packing products of the chemical, food and other industries and has good recyclability. The pol ymer composition contains polyvinylalcohol , polyvinylacetate dispersion, methylcellulose , carboxymethyl- cellulose, glucose and water in given proportions of the components and can be produced from a dry or viscous mass of the polymer composition by moulding. Before or after the moulding the material is treated successively with aqueous sodium tetraborate solution and aqueous formalde hyde solution for influencing the degradation time.

DE OS 2 425 558 discloses insoluble fibers of phenolic resin and PV-OH. An aqueous mixture comprising the phenolic resin and the PV-OH is processed into an acidic coagulation solution comprising a boron compound able to form boron esters with the hydroxyl groups provid ing flame retardancy but also insolubility.

US 2010/0304116 A1 concerns the surface treat ment of an absorbent substrate like paper and textiles. The surface treatment comprises treating the substrate with tetraborate as cross-linking agent and with PV-OH and op ¬ tionally additional hydroxyl groups containing polymers. The PV-OH cross-linked with borate results in reduced sol ubility and in flame resistance and self-extinguishing properties .

While the decomposition in water of the mate ¬ rial of WO 03/051989 can be adjusted, it has the disad ¬ vantage that it is treated with formaldehyde, a substance known to have safety and health risks the use of which in processing of polymer films is even forbidden in many countries such as in the European Union. In addition, the products of WO 03/051989 are inflammable. Disclosure of the Invention

Hence, it is a general object of the inven tion to provide a decomposable material, later on termed a dry polymeric compound, suitable for environmentally friendly packaging that can be produced without the use of harmful chemicals and that preferably is hardly inflammable or flame-resistant and a method for producing such polymeric compounds and products with different times of decomposition/dissolution.

Now, in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the decom posable dry polymeric compound is manifested by the fea tures that it comprises a dry polymeric composition con sisting of the following components

50 to 90 % polyvinyl alcohol (PV-OH),

10 to 40 % polyvinyl acetate (PV-Ac) ,

0 to 10 % stabilizing agent, in particular methyl cellulose (MC)

0 to 10 % thickening agent, in particular carboxymethyl cellulose (CMC) and

0 to 5 % glucose (glu),

the sum of the percentages of the above indi cated components amounting to 100 %,

said polymeric compound comprising borate and carbonate groups at least on the surface, said borate and carbonate groups being obtainable by a treatment of the polymeric composition with at least one tetraborate and at least one carbonate and

said polymeric compound preferably being flame-resistant .

The term flame-resistant as it is used herein encompasses flame-resistant and hardly inflammable prod- ucts, i.e. products that are classified as A, B or C ac cording to DIN EN 1351-1:2010-01, as well as self-extin guishing products.

In a preferred embodiment, the polymeric composition is composed of

50 to 90 % polyvinyl alcohol, 10 to 40 % polyvinyl acetate, 4 to 8 % stabilizing agent, in particular methyl cellulose

2 to 8 % thickening agent, in particular carboxymethyl cellulose and

1 to 4 % glucose.

In another preferred embodiment, the tetra borate is an alkali metal tetraborate, in particular so dium tetraborate and the carbonate is an alkali metal carbonate, in particular sodium carbonate.

The dry polymeric compound may additionally comprise additives or fillers in amounts of up to 5 % for additives, in particular 1 to 3 % such as 2 % and up to 200 % for fillers, in particular up to 150 %, referred to the polymeric composition as 100 %, i.e. the polymeric composition may be "diluted " with filler in a ratio up to 2 to 1 (filler to polymeric composition, preferably 3 to 2 ) .

Additives or adjuvants are e.g. glycerin that might be added for facilitating extrusion, of fillers like kaolin, wood flour, chalk etc. for improving the final characteristics of the polymeric compound for spe ¬ cific applications.

Any percentages herein are % by weight unless otherwise indicated or referring to clear features as e.g. the degree of hydrolysis that indicates the percent ¬ ages of hydrolyzed groups.

During the manufacturing of the dry polymeric compound water is added, in general part of it as "pure" water (in general deminerlized water without any ingredi- ents) and part of it in form of a dispersion of polyvi nylacetate. This water is in particular needed for facil itating homogeneous mixing of the ingredients, but at least part of it may also be useful in the subsequent forming process, such as extrusion or rolling and calen dering .

The manufacturing method in general comprises

(i) adding water into a mixer and option ally and preferably heating said water to up to 60°C, preferably about 40 to 50°C,

(ii) adding the other ingredients of the polymeric composition (the PVAc preferably as an aqueous dispersion) and mixing at desired temperature, such as up to 60°C, preferably about 40 to 50°C, until a homogeneous wet polymeric composition is obtained and until a desired amount of water is removed or desired viscosity for fur ther processing obtained, respectively,

(iii) optionally treating the wet polymeric composition of step (ii) with an aqueous solution of at least one tetraborate and an aqueous solution of at least one carbonate,

(iv) further processing the wet polymeric composition of step (ii) or (iii) by thermally treating and forming it at elevated temperature of at least 70°C (and in general not more than 150°C),

(v) optionally treating the polymeric composition of step (iv) with an aqueous solution of at least one tetraborate and an aqueous solution of at least one carbonate, and

(vi) drying the polymeric composition at temperatures of 30 to 90 °C, preferably 30 to 80°C, more preferred 30 to 70 °C to obtain the dry polymeric com ¬ pound,

wherein at least one of the treatments (iii) and/or (v) is performed. The functional treatment can be broadly var ied. For example sodium tetraborate solutions with a con centrations in water of 5 % to 30 % can be applied for 5 to 600 seconds, solutions of sodium carbonate in water with a concentration of 5 to 40 %, also for 5 to 600 seconds. However, these concentrations and times need not be limiting and other concentrations and times can be better for certain final features.

In a preferred manufacturing method the in- gredients of the polymeric composition, step (ii), are added in different steps separated from each other by a mixing period. A preferred sequence of addition is:

a) adding polyvinylalcohol and mixing for up to 1 hour,

b) adding polyvinylacetate, preferably in form of a disperision, such as a 50 % dispersion, with continued mixing for up to 20 minutes, in general 10 to 15 minutes,

c) optionally and preferably adding the me- thyl cellulose and/or the carboxymethyl cellulose and/or the glucose and mixing for another up to 20 minutes, in general 10 to 15 minutes.

The total mixing time is mainly dependent from the mixing time of step a) or the therein used poly- vinyl alcohol, respectively. Highly hydrolysed PV-OH may take longer for full homogenization or dissolution and may also exhibit a higher or less pronounced ability to bind water. Therefore it may take longer to remove the desired amount of water or obtain the desired viscosity, respectively.

The amount of water that has been removed during mixing can be measured with a humidity meter or a pin moisture meter, making at least one measurement at at least two different times and calculating the water loss. Suitably a first measurement is e.g. performed after add ing polyvinylalcohol and polyvinylacetate dispersion to primary water and a second measurement after completing the mixing process of all ingredients.

During mixing, in general 10 to 60 % of the originally present water are removed.

If the water content after mixing still ex ceeds an about 4 to 5 ratio (water to polymeric composi tion) , i.e. if the amount of water is 80 to 150 %, preferably 100 to 130 %, such viscous mixture can e.g. be further processed via rolling followed by calendering. If the viater to polymeric compound ratio is at most 1 to 2, i.e. at most 50 % water to 100 % polymeric compound, in particular 10 to 40 % water, further processing, i.e. thermal treatment and forming, by means of extrusion is preferred .

As indicated above, the treatment with func tional solutions, i.e. tetraborate and carbonate can be performed prior to the further processing and/or after such processing, i.e. with the wet or dry polymeric com position .

Treatment prior to the temperature processing is advantageous for thicker final products, i.e. foils or objects, since the borate and/or carbonate is incorporated not only on the surface and a layer extending from the surface, but within the whole material.

Treatment after the temperature processing is advantageous for thin foils.

If treatment is performed prior to temperature processing, the first functional solution is added to the composition in the mixer after mixing and then left there for a predetermined time, prior to being di luted with demineralized water and removed by centrifuga tion. Since more than one functional treatment is performed, the above described procedure is performed with each of the subsequent functional solutions, with drying after the last washing step. If the treatment is performed after the tem perature treatment, i.e. if a foil is treated, the func tional treatment can be performed by spraying. In this case it was found that no washing between the application of the different functional solutions is necessary. As an alternative, an endless foil or a foil on an endless band or a three-dimensional object can be immersed into the functional bathes, optionally separated by washing bathes .

Each functional treatment with two or more functional solutions is terminated by a final drying step resulting in the dried polymeric composite of the present invention .

Although already the treatment with one func- tional solution results in good flame-resistance, treat ment with tetraborate and carbonate or even tetraborate, carbonate and again tetraborate is preferred.

Dependent on the functional treatment, the polymeric composition must be adjusted for disintegra- tion. In general the following influences have been found :

Higher amounts of polyvinylacetate dispersion result in slower dissolution.

The higher the temperature during temperature treatment/processing and the longer the treatment time the slower the dissolution.

The longer the time of treatment with func tional solutions and the higher their concentrations, the longer the time of dissolution, with the carbonate exhib- iting a modulating function.

Contrary thereto, the higher the level of polyvinyl alcohol hydrolysis the faster the dissolution.

Although the mechanism is unknown, it is assumed that the carbonate prevents full cross-linking by the tetraborate or boric acid, respectively, treatment.

The more or less water comprising polymeric composition cannot only be formed into foils by rolling and calendering or extrusion, but also directly molded into three-dimensional objects or by subsequent blast forming, vacuum molding etc.

A suitable polyvinyl alcohol has a degree of polymerization of 1200 to 2000 and a degree of hydrolysis of at least 70 %, preferably a degree of polymerization of 1200 to 1600 and/or a degree of hydrolysis of 80 to 99 %. A higher degree of polymerization results in higher resistance against decay and a higher level of polyvinyl alcohol hydrolysis to a faster dissolution.

Polyvinyl alcohol has the advantage that it does not decompose into monomers under hydrolysis and does not break down under the influence of bacteria. It is physiologically harmless, which allows the use of the packaging in the food industry and for medical purposes.

The polyvinyl acetate is preferably used in form of an aqueous dispersion, the water content of which forms part of the amount of the water as specified for the wet polymeric composition. A suitable polyvinyl ace- tate dispersion has the following characteristics:

- A dry residue of 40 to 70 %, in particular 45 to 60 % such as 48 to 56%;

- A molecular weight of 14,000 to 32,000;

- An apparent viscosity of 50 to 200 mNs/m 2 . Polyvinyl acetate is harmless to the human body, even when water is removed from the composition. In the forced orientation of the material, the tensile strength increases to 9-10 MPa.

A much preferred stabilizing agent is methyl- cellulose since it does not only provide the polymeric compound with a higher resistance against decaying and microorganisms, but also has some thickening effect. This component influences the regulation of the decomposition of the packaging material in aquatic environment depend- ing on the degree of esterification (methoxy number 23 to 57). The use of a moderately methylated methylcellulose with a methoxy number from 23 to 33 is presently pre ferred. Lower degree of esterification results in faster dissolution of the polymeric compound, higher degree in slower dissolution.

A much preferred thickening agent is carbox- ymethyl cellulose that can be added as viscosity adjust ing agent.

Finally, glucose can be added for improving the dissolution characteristics.

The functionally treated compound material obtainable by the method of the present invention can be adjusted such that its degradation/dissolution/disinte gration/decay time in an aqueous medium is from about 2 hours up to - in particular if additionally fillers are added - 6 months.

With regard to the behavior of the polymeric compound of the invention in aqueous environment, the terms decay, dissolution and disintegration are used in terchangeably.

The dry polymeric compound of the present in ¬ vention can be a foil or a shaped body obtainable by a forming process like molding including blow molding.

The decay products of the polymer compound can be recycled after use by extraction from aqueous solutions at elevated temperatures such as up to 60°C by coagulation with complex salts until agglomerated state is reached.

Suitable complex salts for recycling are e.g. boric acid, optionally in combination with iron salts.

The polymeric compound is a mixture of proven ecologically pure non-toxic substances which, in natural or forced decay in an aquatic environment, maintain their pH at 6.8 to 7.2, which is virtually neutral. This is as ¬ sumed to be due to the fact that the polymeric compound, when it gets into nature and comes into contact with wa ¬ ter or wet soils, disintegrates without decomposing into monomers. In contrast to other so-called 'polymers' it does neither emit carbon dioxide nor any harmful solid and/or liquid substances and/or other gases. There is no need to build special landfills for composting and degradation. The polymeric compound does also not react with oils, acids and bases.

The polymeric compound preferably is flame- resistant and/or self-extinguishing . It can be provided with different mechanical properties by adapting the polymeric composition, additives and treatments. Its time of degradation in aqueous environment can be adjusted within a range from about 2 hours up to about 6 months.

Some possible applications are:

1. Flexible polymer packaging (pouches, bags, packets and all kinds of foil material) .

2. Vacuum moulded products (cups, boxes, trays and other products) .

3. Blast-shaped items (bottles, vials, etc.).

The packages are physiologically harmless and their application is unlimited in terms of the type of packed products. Packages made of the polymeric compound can e.g. be used to pack products of the chemical, food and other industries.

The benefits of the inventive materials are that by substituting some of the commonly used packaging materials or plastics articles, their environmentally harmful influences can be settled. The most important influences of such commonly used packaging materials with an unusually long life before decomposition is the indis criminate pollution of large areas in populated and uninhabited places and the death of animals erroneously eating plastics instead of their usual food.

Besides of the above indicated ecological benefits, there is also an economic one:

In the production of the polymeric compound and manufacturing of products, low temperatures can be used which are 30 to 50% lower than those usually used for the production of conventional plastics products. The products made of the inventive material can be recycled. This results in cheap materials for technical articles due to the low recycling costs, namely extraction of the secondary material from the aqueous environment without the need to use energy for milling and high temperatures for the granulation of the material. This makes the sec ondary material cost-effective.

Modes for Carrying Out the Invention

In the Examples, the following ingredients were used:

The dissolution/disintegration properties were determined at ambient temperatures of about 22 °C. In natural environment, in general 10 to 35°C are found.

The water loss during mixing was determined by measuring remaining moisture content with a humidity meter or a pin moisture meter, at least twice during the drying procedure.

The final drying step was performed until no easily removable water was present anymore. Flame-resistance was tested by horizontally holding a piece of finally dried compound material of 2 mm diameter into the flame of a lighter until the com pound material lost shape, i.e. bent into vertical posi- tion (see the Figure). All products of the following examples proved to be inflammable in this test.

Example 1 .

A viscous wet polymeric composition with the following composition in parts by weight has been pre pared :

polyvinyl alcohol - 30, polyvinyl acetate dispersion - 12, methylcellulose - 3, carboxymethylcellu- lose - 3, glucose - 1, and demineralised water - 60.

The degree of polymerization of polyvinyl al cohol was 1400 and the degree of hydrolysis was 99%.

60 g of water were placed in a blade mixer and heated to a temperature of 40-50°C. Then 30 g of polyvinyl alcohol were added. After mixing for 40-50 minutes, 12 g of polyvinyl acetate dispersion (50% in water) were added and mixing continued for 10-15 minutes. Then 3 g methylcellulose, 3 g carboxymethylcellulose and 1 g glucose were added followed by additional mixing. Mixing was continued until 9 g of the water had evapo- rated.

The viscous polymeric composition (dynamic viscosity measured with viscosimeter was 350 mPa-s) was then subjected to rolling followed by calendering at a processing temperature of 70 to 100°C in steps of 10°C. The texture of the formed film was monitored. The film was ready when it became smooth. The resulting polymer film was subjected to treatment with functional solutions by spraying as follows:

Treatment with sodium tetraborate solution (5% in water) for 5-10 seconds, directly followed by treatment with sodium carbonate solution (10% in water) for 5-10 seconds and finally treatment with sodium tetraborate solution (10% in water) for 10-15 seconds followed by washing with demineralized water. All functional treatment steps were performed at a temperature of 20- 30°C. The spraying was performed with at least 20 ml/m 2 .

Drying was carried out with purified hot air at temperatures from 30 to 70°C in steps of 10°C in a tunnel dryer as obtainable from Kerone.

From the polymer films with thicknesses of 0.015 mm, 0.025 mm and 0.040 mm, single packs suitable for storage in a dry environment were manufactured. After use, the packages were completely dissolved in cold water within 2-3 hours, with dissolution times within this range dependent on the foil thickness.

Example 2 .

A wet polymeric compound was prepared having the following composition in parts by weight:

polyvinyl alcohol - 65; polyvinyl acetate dispersion - 24; methylcellulose - 4; carboxymethyl cel lulose - 3; glucose - 1.4 and demineralized water - 18.

The degree of polymerization of the polyvinyl alcohol was 1200 and the degree of hydrolysis was 86%

18 g of water were placed in a blade mixer and heated to a temperature of 40-50°C. Then 65 g of polyvinyl alcohol were added. After mixing for 20 minutes,

24 g of polyvinyl acetate dispersion (50% in water) were added and mixing continued for 10-15 minutes. Then 4 g methylcellulose, 3g carboxymethyl cellulose and 1.4 g glucose were added and the mixing continued for 10-15 mins. During the mixing in the blender, 15.4 g of the water evaporated and the rest of it remained bound in the composition .

The wet polymeric composition was extruded with the addition of glycerin (0.5% to 1% of the total composition) in order to aid processing by extrusion. The processing temperatures in the different zones of a non- conical twin-screw extruder without compression were 100, 110, 120, 130, and 140°C. The resulting polymer film was treated with the functional solutions by spraying as fol lows: first treatment with 15% sodium tetraborate solu tion for 15-20 seconds; followed by treatment with 20% sodium carbonate solution for 30-35 seconds. The treat ment was performed at a temperature of 20-30 °C without drying between treatments and in amounts of at least 20 ml/m 2 per functional solution. At the end of the treat ment, a washing step was performed with demineralized wa ter, followed by drying with purified warm air in a tun nel dryer (obtainable e.g. from Kerone) at temperatures from 30 to 70°C in steps of 10°C.

Cups, plates, trays, etc. were made from such polymer films (0.015 mm, 0.025 mm and 0.040 mm) by vacuum molding .

They had a 24 hour durability versus liquid compositions containing water. After use, the packages were gradually dissolved in water. Complete dissolution was fulfilled within up to 62-80 hours.

Example 3

A wet polymeric composition was prepared with the following composition in parts by weight: polyvinyl alcohol - 63; polyvinyl acetate dispersion - 24; methyl- cellulose - 4.6; carboxymethyl cellulose - 4.0; glucose - 2.3 and demineralized water - 14.1.

The degree of polyvinyl alcohol polymerization was 1600 and the degree of hydrolysis was 86%.

The wet polymeric composition was prepared according to Example 2. During mixing 12 g water evapo rated. Before extrusion, the wet polymeric composition was then pre-treated with the functional solutions as follows: treatment with 15% sodium tetraborate solution for 120-130 seconds; treatment with 30% sodium carbonate solution for 190-200 seconds. Each treatment was per- formed with 10 ml functional solution per lOOg wet poly meric composition . Between each treatment with func tional solution and after the last treatment with func tional solutions, the wet polymeric composition was washed by adding demineralized water that was then re moved by centrifugation together with the functional solution. After the last washing/centrifugation step, a drying step was carried out with purified hot air at temperatures from 30 to 70 °C in steps of 10°C in a tunnel drying machine as e.g. obtainable from Kerone.

The treated polymeric composition was sub jected to extrusion treatment in a non-conical twin-screw extruder without compression with the addition of glycerin 0.5- 1.0% and processing temperatures of 100, 110, 120, 130, and 140°C to produce vacuum foils of a thick ness of 0.20 to 0.40 mm. The products had a durability of 1 month towards liquid compositions containing water. Af ter use, they were gradually dissolved in water, giving complete dissolution within 75 days.

Example 4. A wet polymeric composition was prepared with the following composition in parts by weight :

polyvinyl alcohol - 40; polyvinyl acetate dispersion - 42; methylcellulose - 5.4; carboxymethyl cellulose - 4.6; glucose - 2.0 and demineralized water - 27.

The degree of polymerization of polyvinyl al cohol was 1900 and the degree of hydrolysis was 80 %.

27 g of water were placed in a blade mixer and heated to a temperature of 40-50°C. Then 40 g of pol yvinyl alcohol were added. After mixing for 20 minutes,

42 g of polyvinyl acetate dispersion (50% in water) were added and mixing continued for 10-15 minutes. Then 5.4 g methylcellulose, 4.6 g carboxymethyl cellulose and 2 g glucose were added. The mixing was continued for 10-15 mins. During the mixing in the blender, 21 g of the water evaporated and the rest of it remained bound in the com position .

The wet polymeric composition was pre-treated with the functional solutions in a blender as follows: treatment with 15% sodium tetraborate solution for 60-120 seconds; treatment with 30% sodium carbonate solution for 190-200 seconds. Each functional solution was used in an amount of 10 ml per 100g of wet polymeric composition . The temperature of the treatment was 20-30°C. Between each treatment with functional solution and after the last treatment with functional solutions, the wet poly meric composition was washed by adding demineralized wa ter that was then removed by centrifugation together with the functional solution. After the last washing/centrifu gation step, a drying step was carried out with purified hot air in a tunnel dryer (obtainable e.g. from Kerone) at temperatures from 30 to 70 °C in steps of 10°C.

The treated polymeric mixture was then sub jected to extrusion treatment in a non-conical twin-screw extruder without compression with the addition of glyc erin 0,5-1% (added for facilitating the movement of the material in the extrusion process) at temperatures from 100, 110, 120, 130, 140°C and subsequent moulding to pro duce hollow products like bottles, vials, etc.

The products had a wall thickness of 0.20 to 0.40 mm and a durability of 3 months versus liquid compo sitions containing water. After use, they were gradually dissolved in water, with complete dissolution within up to 120 days.

Example 5 .

From the wet polymeric composition produced as in Example 1, a plastic mass was prepared with the ad ¬ dition of fillers such as kaolin, wood flour, chalk etc in an amount up to 70 percent of the wet polymeric composition obtained after mixing. Formed parts were made by compression of the so obtained mass in forms preheated to a temperature of 80-90°C. The duration of the pressing was dependent on the volume and the thickness of the walls of the desired resulted forms.

Forms of a wall thickness of 2 mm were sub jected to functional treatment by immersing them into functional bathes of 20 % tetraborate, 30 % carbonate and 15 % tetraborate, in each bath for 600 seconds with im- mersion into a bath of deminerlized water between each treatment and after the last treatment. The functionally treated forms were then dried with purified hot air in a tunnel dryer (obtainable e.g. from Kerone) at tempera tures from 30 to 70°C in steps of 10°C.

The resulting forms had resistance to aqueous compositions for up to 6 months. After this period, they gradually broke down in moisture-containing environments.

Example 6. A wet polymeric composition , was prepared as described in Example 2. Such wet polymeric composition was coextruded with an electrical cable at processing temperatures of 100, 110, 120, 130, and 140°C and then either functionally treated with a 20% aqueous solution of sodium tetraborate for 600 seconds at a tem- perature of 20 to 30°C before washing in demineralized water and drying at 70 °C or with treated first with 20 % tetraborate for 600 sec. followed by 30 % carbonate for 180 sec. and again 20 % for 600 sec. at 20°C with washing in demineralized water between and after treatments and a final drying at 70 °C.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.