EA039308B1 - Degradable polymer and method of production thereof - Google Patents

Abstract

The invention provides a degradable polymer composition comprising: (a) a polyolefin; (b) two or more transition metal compounds in a total amount of from 0.15 to 0.6 wt.%, wherein the transition metal compounds comprise a stearate moiety; (c) a mono- or poly-unsaturated C14-C24 carboxylic acid in an amount of from 0.04 to 0.08 wt.%; wherein transition metals in the two or more transition metal compounds comprise: (i) iron, manganese and copper; or (ii) manganese and copper; or (iii) iron and manganese. Furthermore, the invention relates to an additive formulation for forming the above mentioned degradable polymer composition on addition to a polyolefin and to a method of production of the degradable polymer composition.

Description

The present invention relates to a polymer composition, in particular to a degradable composition with a controlled degradation rate and improved material properties, as well as to a method for its preparation.

Polymeric materials have numerous advantages and can be durable, chemically and biologically inert materials at a relatively low cost. Unfortunately, many of these characteristics make it difficult to dispose of them without causing deep damage to the environment. The low cost and favorable mechanical properties often allow the use of polymeric materials for a very short service life. This leads to a rapid accumulation of wastes that are inert to most of the physical and chemical stresses they are exposed to during traditional disposal (eg landfills).

As humanity becomes more aware of its impact on climate, ecosystems and the planet as a whole, there is an increasing need to reduce the amount of non-degradable waste disposed of in landfills. Accordingly, there is a growing demand for degradable alternatives for traditional polymeric materials. In particular, there is a strong demand for degradable polymer compositions that can be formed into sheets and films for use in a variety of conventional articles such as packaging.

A number of degradable polymer compositions have been developed. However, there are significant drawbacks associated with these conventional degradable polymers. Traditional degradable polymers (such as aliphatic polyesters) tend to be more complex and difficult to process, resulting in decreased productivity. These materials have a significantly higher density and lower strength than traditional non-degradable commercial polymers.

US Pat. No. 4,016,117 discloses the use of biodegradable filler materials, such as starch, and auto-oxidizing agents, such as fat, which, when exposed to transition metals in soil, form peroxides that attack the bonds between carbon atoms in the resin.

US Pat. No. 4,931,488 discloses adding a biodegradable substance (starch), an iron compound (FeOH(stearate) ₂ ), and a fatty acid or fatty acid ester (eg, soybean oil, which is a mixture of fatty acid esters) to a thermoplastic polymer. The resulting plastic composition decomposes under the action of heat and/or ultraviolet radiation and/or solar radiation. These compositions have disadvantages in terms of abiotic degradation and biodegradation rates.

Accordingly, it is desirable to provide degradable polymer compositions and a process for their preparation that address at least some of the problems of the prior art, or at least to provide industrially applicable alternatives.

It is also a feature of the present invention that additive-containing polyolefin-based plastics can be recycled in existing polyolefin recycling schemes prior to degradation.

The essence of the invention

According to a first aspect of the present invention, there is provided a degradable polymer composition comprising (a) a polyolefin;

(b) two or more transition metal compounds in a total amount of from 0.15 to 0.6 wt.%, where the transition metal compounds contain a stearate moiety;

(c) mono - or polyunsaturated C14-C24-carboxylic acid in an amount of from 0.04 to 0.08 wt.%; and (d) synthetic rubber in an amount of 0.04 to 0.2% by weight;

where the transition metals in two or more transition metal compounds contain (i) iron, manganese and copper, or (ii) manganese and copper, or (iii) iron and manganese.

According to one variant of the first aspect, the degradable polymer composition further comprises (e) dry starch in an amount of up to 20 wt.%; and/or (f) calcium oxide in an amount up to 1% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of up to 0.2% by weight.

According to another embodiment of the first aspect, the polyolefin contains ethylene and/or propylene monomers and optionally additionally contains monomers selected from the list of acetate, vinyl acetate, methyl methacrylate, vinyl alcohol and acrylic acid.

According to another embodiment of the first aspect, the polyolefin is selected from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), very low density polyethylene (VLDPE), ethylene vinyl acetate (EVA) , ethylene vinyl alcohol (EVOH), ethylene-methyl methacrylate copolymer

- 1 039308 (EMMA) and a copolymer of ethylene and acrylic acid (EAA).

According to another variant of the first aspect, said composition decomposes within no more than 90 days in air.

According to another variant of the first aspect, the mass ratio of iron stearate and manganese stearate to copper stearate is from 4:1 to 8:1.

According to another variant of the first aspect, the composition contains a phenolic antioxidant stabilizer.

According to another variant of the first aspect, the composition further comprises a color additive, preferably carbon black or titanium oxide.

According to another variant of the first aspect mono - or polyunsaturated C ₁ 4-C ₂ 4-carboxylic acid is a linear C ₁₆ -C ₂₀ -carboxylic acid, preferably oleic acid.

According to another variant of the first aspect, the synthetic rubber contains an unsaturated polymer, preferably a styrene-isoprene-styrene copolymer, more preferably a mixture of styrene-isoprene-styrene and styrene-isoprene copolymers.

According to another variant of the first aspect, the composition contains (b) two or more transition metal stearates in a total amount of from 0.2 to 0.3 wt.%; and/or (c) monounsaturated linear C ₁₆ -C ₂₀ -carboxylic acid in an amount of from 0.04 to 0.06 wt.%; and/or (d) synthetic rubber in an amount of 0.08 to 0.12% by weight; and/or (e) dry starch in an amount of 0.1 to 0.4% by weight; and/or (f) calcium oxide in an amount of 0.1 to 0.3% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of 0.02 to 0.15% by weight.

According to the second aspect of the present invention, an additive composition is provided for obtaining the above degradable polymer composition by adding to a polyolefin, wherein the additive composition contains two or more transition metal compounds, mono- or polyunsaturated C14-C ₂ 4-carboxylic acid, synthetic rubber, while the additive composition additionally contains a polymer carrier and is designed to dilute the polyolefin at a content of 1 to 20 wt.% of the additive composition in the degradable polymer composition.

According to one variant of the second aspect, the additive composition contains dry starch and/or calcium oxide and/or a phenolic antioxidant stabilizer.

According to another variant of the second aspect, the additive composition is designed to dilute the polyolefin at a content of from 1 to 4 wt.% of the additive composition in the degradable polymer composition.

According to a third aspect of the present invention, there is provided a method for producing the above degradable polymer composition, the method comprising (i) obtaining the above additive by hot extrusion under nitrogen atmosphere of a polymer carrier, two or more transition metal compounds, a mono- or polyunsaturated C14-C2 ₄ -carboxylic acid , synthetic rubber;

(iii) mixing the additive and the polyolefin to obtain a mixture containing from 1 to 20% by weight of the additive.

According to one variant of the third aspect, stage (i) includes obtaining an additive by hot extrusion in a nitrogen atmosphere of a polymer carrier, two or more transition metal compounds, a mono- or polyunsaturated C ₁₄ -C ₂₄ carboxylic acid, synthetic rubber and calcium oxide and/or phenolic antioxidant stabilizer.

According to another variant of the third aspect, the method comprises an additional step (ii) of adding starch, wherein step (ii) is carried out before step (iii) and after step (i).

According to another variant of the third aspect, stage (iii) includes mixing the additive and the polyolefin to obtain a mixture containing from 1 to 4 wt.% of the additive.

According to yet another embodiment of the third aspect, the method further comprises forming a degradable polymer composition to form a film having a thickness of 5 to 50 µm, preferably 10 to 25 µm.

According to another variant of the third aspect, the film is a composite product, additionally containing a cellulose substrate.

According to yet another embodiment of the third aspect, the method further comprises flat die extrusion molding of a degradable polymer composition to form a sheet having a thickness of up to 1000 microns.

According to yet another embodiment of the third aspect, the method further includes injection molding a degradable polymer composition to form a molded plastic article.

Detailed description

According to the first aspect of the present invention, a degradable polymer composition is provided.

- 2 039308 containing (a) a polyolefin;

(b) two or more transition metal compounds in a total amount of 0.15 to 0.6% by weight;

(c) mono - or polyunsaturated With ₁₄ -C ₂₄ -carboxylic acid or its ester, anhydride or amide in an amount of from 0.04 to 0.08 wt.%;

(d) synthetic rubber in an amount of 0.04 to 0.2% by weight; and optionally (e) dry starch in an amount of from 0 to 20 wt.%; and/or (f) calcium oxide in an amount of 0 to 1% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of 0 to 0.2% by weight;

moreover, two or more transition metal compounds are selected from compounds of iron, manganese, copper, cobalt and cerium, while the transition metals in the two or more transition metal compounds are different.

The following is a further description of the present invention. In the following sections, various aspects of the present invention are presented in more detail. Each aspect so represented may be combined with any other aspect or aspects unless otherwise expressly stated. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

The present invention relates to a degradable polymer composition. In the following description, the term degradable polymer is used, which means synthetic polymer compositions that degrade to form CO ₂ , H2O, biomass and inorganic salts under normal composting conditions and other environments.

The degradable polymer composition contains a polyolefin. It represents the bulk of the composition, for example, preferably at least 50% by weight. In the following description, the term polyolefin is used, which means a class of polymers containing repeating units of the general formula -[CH2CRR']-, where the individual R and R' are preferably selected from the list that is hydrogen, methyl, ethyl, acetate, vinyl acetate, methyl methacrylate, vinyl alcohol and acrylic acid. Preferably, the polyolefin constitutes the remainder of the degradable polymer composition in addition to the listed components. Preferably, the degradable polymer composition contains less than 5% and more preferably less than 1% of other ingredients; most preferably, the degradable polymer composition is substantially free of additional ingredients or impurities.

Preferably, the polyolefin contains ethylene and/or propylene monomers and optionally contains additional monomers selected from the list of acetate, vinyl acetate, methyl methacrylate, vinyl alcohol and acrylic acid. Preferably the polyolefin is selected from LDPE, LLDPE, HDPE, MDPE, VLDPE, EVA, EVOH, EMMA and EAA.

The degradable polymer composition contains two or more transition metal compounds in a total amount of 0.15 to 0.6% by weight, preferably 0.2 to 0.3% by weight. In the following description, the term transition metal is used, which means any of the metal elements of groups IVB-VIII, IB and IIB or 4-12 of the Periodic Table of the Elements. Preferred transition metals are iron, manganese, copper, cobalt and cerium; preferably, when iron is used, it is present in the +3 oxidation state, and when copper is used, it is present in the +2 oxidation state. These compounds catalyze decomposition. The content of large amounts of transition metal increases the cost of the degradable composition and can lead to the accumulation of transition metal in waste disposal sites. In addition, since the transition metal plays the role of a catalyst in the decomposition process, increasing the transition metal content above the specified level leads to a decrease in the effect on the decomposition rate.

The two or more transition metal compounds are selected from iron, manganese, copper, cobalt, and cerium compounds, and the transition metals in the two or more transition metal compounds are different. Preferably, the two or more transition metal compounds are selected from iron(III), copper manganese, cobalt, and cerium compounds, and the transition metals in the two or more transition metal compounds are different.

Preferably the transition metal in the two or more transition metal compounds is (i) iron, manganese and copper, or (ii) manganese and copper, or (iii) iron and manganese.

The temperature of the polymer composition and its exposure to light can also affect its rate of degradation. The present inventors have surprisingly found that the choice of transition metal can be used to further control this effect. In particular, the present inventors have found that iron is a more efficient photocatalyst, while manganese is a more efficient process catalyst.

- 3 039308 thermal decomposition. Thus, the transition metal component can be used to control the rate of decomposition depending on the intended exposure to heat and light on a particular product.

Specific transition metals can affect the properties of the polymer composition. For example, iron compounds can color the polymer composition.

In addition, other metals, such as copper, advantageously increase the rate of degradation, but due to their toxicity, may render the polymer composition unsuitable for certain applications, such as food wrap applications. Accordingly, the use of iron in color-sensitive compositions can be avoided, while the use of copper can be avoided if the product is intended for use in the food industry.

The ligands in the metal compounds are preferably inorganic ligands and/or saturated organic ligands. The ligands in the metal compounds preferably do not contain a mono- or polyunsaturated Cl ₄ -C ₂₄ carboxylic acid or its ester, anhydride or amide.

Preferably, the transition metal compounds contain moieties selected from stearate, carboxylate, acetylacetonate, triazacyclononane, or a combination of two or more moieties. Preferably, the transition metal compounds may be present in a weight ratio of iron stearate and manganese stearate to copper stearate of 4:1 to 8:1. Preferably, the transition metal compounds may be present in a ratio of iron(III) stearate and manganese stearate to copper stearate of 4:1 to 8:1.

Alternatively, certain non-ionic ligands may also be present as an addition which play an active role in degradation. When non-ionic ligands are present, amines, imines, amides, phosphites, phosphines and carbenes are preferably chosen as such. The inventors of the present invention have found that such non-ionic ligands can have an advantageous effect on the degradation rate of the composition while maintaining the essential properties of the material. Non-ionic ligands preferably comprise at least 5% of the ligands and preferably up to 50% of the ligands, preferably 10 to 40% of the ligands.

The transition metal ligands are preferably chosen to make the transition metals physically and chemically compatible with the polymer. Advantageously, the choice of ligands can influence the catalytic activity of the transition metals. The ligands can be chosen to make the metal compatible with the particular polyolefin used and to control the degradation rate of the polymer composition.

The degradable polymer composition contains mono- or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid in an amount of 0.04 to 0.08 wt.%, preferably from 0.04 to 0.06 wt.%. In the following description, the term carboxylic acid is used, which means a number of compounds whose molecules contain a carboxyl fragment -COOH. The carboxylic acid according to the present invention is mono- or polyunsaturated and has a carbon skeleton containing from 14 to 24 carbon atoms, and it contains at least one double bond in its carbon skeleton. The carbon skeleton of a carboxylic acid can be linear, branched, or aromatic. Preferably the mono- or polyunsaturated carboxylic acid is a C ₁₆ -C ₂₀ carboxylic acid. Preferred carboxylic acids are oleic, linoleic and cinnamic acids, the most preferred carboxylic acid is oleic acid.

Alternatively, the degradable polymer composition contains an ester, anhydride or amide of a mono- or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid in an amount of from 0.04 to 0.08 wt.%, preferably from 0.04 to 0.06 wt. .%.

The carboxylic acid or its ester, anhydride or amide components are preferably free or uncoordinated in the sense that they do not form part of the transition metal compound.

When the degradable polymer composition contains an ester of a mono- or polyunsaturated C ₁₄ -C ₂₄ carboxylic acid, the alcohol component is preferably a C ₁ -C ₃₀ alcohol, more preferably a saturated straight chain C ₁ -C ₃₀ alcohol.

When the degradable polymer composition contains an anhydride mono - or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid, this anhydride may be symmetrical or unsymmetrical. The second carboxylic acid component is preferably a C ₁ -C ₃₀ carboxylic acid, more preferably a saturated straight chain C ₁ -C ₃₀ carboxylic acid.

When the degradable polymer composition contains a mono- or polyunsaturated C ₁ 4-C ₂ 4-carboxylic acid amide, this amide may be a primary, secondary or tertiary amide. When a secondary or tertiary amide is present, each of the carbon chains preferably contains from 1 to 30 carbon atoms, more preferably each carbon chain is a C ₁ -C ₃₀ alkyl group.

Unless otherwise stated, when features of a carboxylic acid are discussed herein, it is contemplated that they also apply to its ester, anhydride, or amide.

- 4 039308

While not wishing to be bound by theory, we believe that the mono- or polyunsaturated C14-C24 carboxylic acid in the polymer composition undergoes auto-oxidation to form peroxides that can attack the bonds between carbon atoms in the polymer chain, making the polymer susceptible to normal degradation processes. The transition metals present catalyze autoxidation, increasing the rate of degradation of the polymer composition.

The content of more than 0.08 wt.% mono - or polyunsaturated With ₁₄ -C ₂₄ -carboxylic acid can make the polymer excessively sensitive to air. Excessive auto-oxidation of the carboxylic acid can produce relatively high concentrations of peroxides and cause rapid degradation of the polymer structure. This can create life-shortening problems. On the other hand, the content of less than 0.04 wt.% mono - or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid can lead to an excessively low decomposition rate. The authors of the present invention have found that the content of from 0.04 to 0.08 wt.% mono - or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid allows you to control the rate of decomposition at desired levels for numerous applications.

The present inventors have surprisingly found that linear monounsaturated acids, in particular oleic acid, have the greatest effect on the rate of degradation. This could not be predicted on the basis of the chemical stability of these compounds in pure form, since, as a rule, the more double bonds a carboxylic acid contains, the more susceptible it is to oxidation.

The degradable polymer composition contains synthetic rubber in an amount of from 0.04 to 0.2 wt.%, preferably from 0.08 to 0.12 wt.%, most preferably about 0.1 wt.%. In the following description, the term rubber is used, which means viscous elastic polymers. Rubbers are amorphous polymers that exist at temperatures above their glass transition temperature. Preferably the rubber of the present invention is an unsaturated rubber, more preferably the rubber of the present invention is polyisoprene, styrene-isoprene (SI), styrene-isoprene-styrene (SIS), or a mixture of two or more of these polymers.

The rubber content can advantageously improve the mechanical properties of the resin composition. In addition, rubbers generally have less chemical resistance than bulk polymerized polyolefins. Accordingly, the rubber content can improve the degradation rate without adversely affecting the physical properties of the polymer. Thus, it appears to act as a co-catalyst.

Advantageously, the presence of synthetic rubber in the polymeric composition improves elasticity. This makes it possible to counteract the embrittlement of the polymer composition caused by other additives. A content of less than 0.04% synthetic rubber can render the polymer excessively brittle and unusable. A content of more than 0.12% synthetic rubber can lead to a high degradation rate and can adversely affect the properties of the polymeric material. In addition, the authors believe that the content of synthetic rubber increases the rate of decomposition without the need to increase the content of the transition metal, starch or carboxylic acid.

The degradable polymer composition optionally contains dry starch in an amount of 0 to 20 wt.%, preferably 0 to 10 wt.%, more preferably 0.1 to 1 wt.% and most preferably 0.1 to 0.4 wt. .%. In the following description, the term starch is used, which means a polysaccharide containing a large number (typically from 500 to 2,000,000) glucose monomer units connected by glycosidic bonds. The starch according to the present invention is dry starch, that is, starch containing less than 5 wt.% water and preferably less than 1 wt.% water; most preferably the starch is substantially free of water.

The content of large amounts of starch can increase the density and reduce the tensile strength of the polymer. In addition, a high starch content can cause short shelf life problems due to rapid degradation. The high starch content makes the polymer composition susceptible to cosmetic and physical damage due to water and micro-organisms. If the starch content is insufficient, the additive may have little effect on the rate of biodegradation.

The degradable polymer composition optionally contains calcium oxide in an amount of 0 to 1% by weight, preferably 0 to 0.4% by weight, more preferably 0.1 to 0.3% by weight. In the following description, the term calcium oxide is used, which means a crystalline solid having the chemical formula CaO. Advantageously, the calcium oxide during the reaction immobilizes water in the composition. This stabilizes the composition during processing and can reduce the likelihood of surface defects and discoloration of the final product. Surprisingly and unpredictably, the present inventors have also found that increasing the calcium oxide content of the polymer composition can increase the rate of degradation. Advantageously, the CaO content can be used to improve degradability without the need to increase the transition metal content of the starch. The content of more than 0.4 wt.% CaO leads to embrittlement of the polymer.

- 5 039308

The degradable polymer composition optionally contains an oxygen generating additive. The oxygen producing additives may be organic or inorganic. Preferably, nitrates, peroxides, sulfates and phosphates or combinations of two or more of these substances are chosen as the oxygen-producing additive. The oxygen producing additive is preferably calcium nitrate. Preferably, the oxygen generating additive is present in an amount of 0.1 to 1.0% by weight. The oxygen producing additive has been found to further increase the rate of oxidation of the polymer.

The degradable polymer composition optionally contains a phenolic antioxidant stabilizer in an amount of 0 to 0.2% by weight, preferably 0.02 to 0.15% by weight. Phenolic antioxidant stabilizers are well known in the art and are, for example, Irganox 1076 and Irganox 1010. The phenolic antioxidant stabilizer has been found to provide improved control of the rate of polymer degradation. In particular, the content of the phenolic antioxidant stabilizer can delay the onset of degradation, increasing the shelf life of the product and the period during which the product can be recycled in existing polyolefin processing lines.

Preferably, the polymer decomposes within no more than 90 days in air. For certain applications, the embrittlement of the polymer should occur within no more than 90 days in a natural environment, such as in the field. This result can be achieved by the present invention.

Preferably, the composition further comprises a color additive, such as, but not exclusively, carbon black or titanium oxide.

Accordingly, the present invention provides a composition based on a specific combination of ingredients that allows an ideal degradable composition to be obtained. In particular, decomposition can be adjusted according to the application chosen for the mixture of said ingredients used.

According to a preferred embodiment of the present invention, there is provided a degradable polymer composition which comprises a polyolefin together with one or more of the following:

(b) two or more transition metal compounds, preferably transition metal stearates, in a total amount of 0.2 to 0.3% by weight; and/or (c) monounsaturated linear C ₁₆ -C ₂₀ -carboxylic acid or its ester, anhydride or amide in an amount of from 0.04 to 0.06 wt.%; and/or (d) synthetic rubber in an amount of 0.08 to 0.12% by weight; and/or (e) dry starch in an amount of 0.1 to 0.4% by weight; and/or (f) calcium oxide in an amount of 0.1 to 1% by weight, preferably 0.1 to 0.3% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of 0.02% to 0.15% by weight;

wherein the two or more transition metal compounds are selected from iron(III), manganese, copper, cobalt and cerium compounds, wherein the transition metals in the two or more transition metal compounds are different.

According to another aspect of the present invention, an additive composition is provided for obtaining a degradable polymer composition when added to a polyolefin, wherein the additive composition contains two or more transition metal compounds, a mono- or polyunsaturated C ₁₄ -C ₂₄ carboxylic acid or its ester, anhydride or amide synthetic rubber and optionally dry starch and/or phenolic antioxidant stabilizer and/or calcium oxide, wherein the additive composition additionally contains a polymeric carrier and is designed to dilute the polyolefin at a content of from 1 to 20 wt.% and preferably from 1 to 4 wt.% additive composition in a degradable polymer composition.

The additive composition is suitable for obtaining a polymer composition according to the present invention.

According to another aspect, the present invention provides a method for preparing a degradable polymer composition, the method comprising (i) obtaining an additive composition by hot extrusion under nitrogen atmosphere of a polymer carrier, two or more transition metal compounds, a C ₁₄ -C ₂₄ mono- or polyunsaturated carboxylic acid, synthetic rubber and optionally calcium oxide and/or phenolic antioxidant stabilizer;

(ii) optional addition of starch;

(iii) mixing the additive and the polyolefin to form a mixture containing 1 to 20% by weight of the additive, preferably 1 to 4% by weight of the additive.

Preferably, the additive may be prepared by a process comprising mixing the following, based on the combined weight of additive and polymer:

(a) two or more transition metal compounds in a total amount of 0.15 to 0.6% by weight;

(b) mono - or polyunsaturated C ₁ 4-C ₂ 4-carboxylic acid or its ester, anhydride or amide in an amount of from 0.04 to 0.08 wt.%;

- 6 039308 (c) synthetic rubber in an amount of from 0.04 to 0.2 wt.%; and optionally (d) dry starch in an amount of 0 to 20% by weight; and/or (e) calcium oxide in an amount of 0 to 1% by weight; and/or (f) a phenolic antioxidant stabilizer in an amount of 0 to 0.2% by weight;

moreover, two or more transition metal compounds are selected from compounds of iron, manganese, copper, zinc, titanium, cobalt and cerium, while the transition metals in the two or more transition metal compounds are different.

This method is suitable for obtaining a polymer composition according to the present invention. The additive composition according to the present invention is suitable for use in this method.

The addition of starch after the hot extrusion step prevents the starch from being exposed to elevated temperatures. When heat is applied to starch, it decomposes to form dextrins. Thus, the addition of starch after the hot extrusion step preserves its structure and prevents brown discoloration and premature weakening of the polymer structure.

The method according to the present invention may further include molding the resin composition into a film having a thickness of 5 to 50 µm, preferably 10 to 25 µm.

The film may be applied to a cellulose substrate such as paper or cardboard.

The method of the present invention may include molding the resin composition into a sheet having a thickness of up to 1000 µm, preferably 100 to 750 µm.

The process of the present invention may include flat die extrusion molding of a degradable polymer composition to form a sheet having a thickness of up to 1000 microns. Such a sheet can then be thermoformed into multiple articles using known techniques. Alternatively, the method may include injection molding a degradable polymer composition into a molded plastic article such as a container or bottle.

The degradable polymer according to the present invention may have a controlled degradation rate. That is, the rate of polymer degradation can be controlled by selecting certain additional components and their amounts. For certain applications, in particular for some agricultural applications, film embrittlement must occur within 90 days. Subsequent biodegradation must be fast enough to prevent long-term accumulation of polymer fragments. On the other hand, in order to achieve a sufficient shelf life and service life, decomposition should only start after a certain period of time. For most items that pass through the regular food retail chain, this period can be as long as two years.

Unlike conventional degradable polymer compositions, the polymer compositions of the present invention are advantageously compatible with many common polymer color additives such as carbon black and titanium dioxide.

All percentages used herein are by weight unless otherwise noted.

Examples

Hereinafter, the present invention will be described in more detail. Additional advantages of the present invention become apparent by reference to the detailed description when considered in conjunction with the examples.

Example 1

An additive composition was obtained, which consists, wt.%: i) dry starch - 10.00, ii) manganese stearate - 4.00, iii) iron(III) stearate - 8.00, iv) copper stearate - 1.30, v) oleic acid - 2.00, vi) SIS/SI copolymer - 4.00, vii) calcium oxide - 10, viii) LLDPE - 60.70% by weight.

Example 2

An additive composition was obtained, which consists, wt.%: i) dry starch - 10.00, ii) manganese stearate - 2.00, iii) iron(III) stearate - 10.00, iv) Irganox 1076 - 13.0, v) oleic acid 1.00, vi) SIS/SI copolymer 2.00, vii) calcium oxide 10.00, viii) LLDPE 52.0.

Example 3

An additive composition was obtained, which consists, wt.%: i) dry starch - 10.00, ii) manganese stearate - 4.00, iii) copper stearate - 8.00, iv) oleic acid - 6.00, v) copolymer SIS/SI - 2.00, vi) LLDPE - 70.00.

In examples 1, 2 and 3, components ii) to viii) were hot extruded and then starch was added separately. By adding separately after the heating steps, damage to the structure can be prevented.

The additive composition was then blended with additional polyolefin and molded into sheets of 15 µm thick film which were used in the manufacture of bags for

- 7 039308 garbage.

Example 4

An additive composition was obtained, which consists, wt.%: i) manganese stearate - 4.00, ii) iron(III) stearate - 8.00, iii) copper stearate - 1.30, iv) oleic acid - 6.00, v) SIS/SI copolymer 1.00, vi) calcium oxide 10.00, vii) LLDPE 69.70.

Example 5

An additive composition was obtained, which consists, wt.%: i) manganese stearate - 4.00, ii) iron(III) stearate - 8.00, iii) copper stearate - 1.30, iv) oleic acid - 2.00, v) SIS/SI copolymer 1.00, vi) calcium oxide 10.00, vii) Irganox 1076 10.00, viii) LLDPE 63.70.

In examples 4 and 5, the components were hot extruded.

The compositions are briefly described in the table below. ______________________________

one 2 3 4 5 i) Dry starch 10.0 10.0 10.0 j) Manganese stearate 4.0 2.0 4.0 4.0 4.0 iii) Iron(III) stearate 8.0 10.0 8.0 8.0 iv) Copper stearate 1.3 8.0 1.3 1.3 v) Oleic acid 2.0 1.0 6.0 6.0 2.0 vi) SIS/SI copolymer 4.0 2.0 2.0 ι, ο ι, ο vii) Calcium oxide 10.0 10.0 10.0 10.0 viii) LLDPE 60.7 52.0 70.0 69.7 63.7 ix) Irganox 1076 13.0 10.0

The additive composition was then blended with additional polyolefin and molded into 15 micron film sheets which were used in the manufacture of trash bags. The additional polyolefin was LLDPE and was present in sufficient quantity to make up 98% by weight of the final polymer.

Under accelerated weather test conditions, Compositions 1-5 described above exhibited a degradation rate increased by at least 50% compared to pure polyethylene. In addition, the compositions exhibited a degradation rate increased by at least 10% compared to a control composition containing only polyethylene and 0.25% stearate (similar to the transition metal content). However, the properties of the polyolefin film, such as strength and elasticity, remained unchanged.

While the present document describes in detail the preferred embodiments of the present invention, those skilled in the art will appreciate that appropriate modifications may be made without departing from the scope of the present invention or the appended claims.

CLAIM

Claims (22)

CLAIM 1. Degradable polymer composition containing (a) polyolefin; (b) two or more transition metal compounds in a total amount of from 0.15 to 0.6 wt.%, where the transition metal compounds contain a stearate moiety; (c) mono - or polyunsaturated With ₁₄ -C ₂₄ -carboxylic acid in an amount of from 0.04 to 0.08 wt.%; and (d) synthetic rubber in an amount of 0.04 to 0.2% by weight; where the transition metals in two or more transition metal compounds contain (i) iron, manganese and copper, or (ii) manganese and copper, or (iii) iron and manganese. 2. The degradable polymer composition according to claim 1, where the degradable polymer composition further comprises (e) dry starch in an amount of up to 20 wt.%; and/or (f) calcium oxide in an amount up to 1% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of up to 0.2% by weight. 3. The degradable polymer composition according to any one of claims 1 or 2, wherein the polyolefin contains ethylene and/or propylene monomers and optionally additionally contains monomers selected from the list of acetate, vinyl acetate, methyl methacrylate, vinyl alcohol and acrylic acid. 4. The degradable polymer composition according to any one of the preceding claims, wherein - 8 039308 lyolefin selected from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), medium density polyethylene (MDPE), very low density polyethylene (VLDPE), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), ethylene-methyl methacrylate copolymer (EMMA) and ethylene-acrylic acid copolymer (EAA). 5. A degradable polymer composition according to any one of the preceding claims, which decomposes within no more than 90 days in air. 6. The degradable polymer composition of claim 1, wherein the weight ratio of iron stearate and manganese stearate to copper stearate is between 4:1 and 8:1. 7. The degradable polymer composition according to any one of the preceding claims, wherein the composition contains a phenolic antioxidant stabilizer. 8. A degradable polymer composition according to any one of the preceding claims, wherein the composition further comprises a color additive, preferably carbon black or titanium oxide. 9. The degradable polymer composition according to any one of the preceding claims, wherein the mono- or polyunsaturated C14-C24 carboxylic acid is a linear _C16 - _C20 carboxylic acid, preferably oleic acid. 10. A degradable polymer composition according to any one of the preceding claims, wherein the synthetic rubber comprises an unsaturated polymer, preferably a styrene-isoprene-styrene copolymer, more preferably a mixture of styrene-isoprene-styrene and styrene-isoprene copolymers. 11. Degradable polymer composition according to any one of the preceding paragraphs, where the composition contains (b) two or more transition metal stearates in a total amount of from 0.2 to 0.3 wt.%; and/or (c) monounsaturated linear C ₁₆ -C ₂₀ -carboxylic acid in an amount of from 0.04 to 0.06 wt.%; and/or (d) synthetic rubber in an amount of 0.08 to 0.12% by weight; and/or (e) dry starch in an amount of 0.1 to 0.4% by weight; and/or (f) calcium oxide in an amount of 0.1 to 0.3% by weight; and/or (g) a phenolic antioxidant stabilizer in an amount of 0.02 to 0.15% by weight. 12. An additive composition for obtaining a degradable polymer composition according to any one of claims 1 to 11 by adding to a polyolefin, and the additive composition contains two or more transition metal compounds, mono- or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid, synthetic rubber, with this additive composition additionally contains a polymeric carrier and is designed to dilute the polyolefin at a content of from 1 to 20 wt.% additive composition in the degradable polymer composition. 13. An additive composition according to claim 12, wherein the additive composition contains dry starch and/or calcium oxide and/or a phenolic antioxidant stabilizer. 14. Additive composition according to claim 12 or 13, where the additive composition is intended to dilute the polyolefin at a content of from 1 to 4 wt.% of the additive composition in the degradable polymer composition. 15. A method for producing a degradable polymer composition according to any one of claims 1 to 11, wherein the method includes (i) obtaining an additive according to any one of claims 12 to 14 by hot extrusion in a nitrogen atmosphere of a polymer carrier, two or more transition metal compounds, mono- or polyunsaturated C ₁₄ -C ₂₄ -carboxylic acid, synthetic rubber; (iii) mixing the additive and the polyolefin to obtain a mixture containing from 1 to 20% by weight of the additive. 16. The method according to claim 15, where stage (i) includes obtaining an additive according to any one of claims 12-14 by hot extrusion in a nitrogen atmosphere of a polymer carrier, two or more transition metal compounds, mono- or polyunsaturated C ₁₄ -C ₂₄ - carboxylic acid, synthetic rubber and calcium oxide and/or phenolic antioxidant stabilizer. 17. The method according to claim 15 or 16, wherein the method comprises the additional step (ii) of adding starch, step (ii) being carried out before step (iii) and after step (i). 18. The method according to any one of claims 15 to 17, wherein step (iii) comprises mixing the additive and the polyolefin to form a mixture containing 1 to 4% by weight of the additive. 19. The method according to any one of claims 15 to 18, further comprising forming a degradable polymer composition to obtain a film having a thickness of 5 to 50 µm, preferably 10 to 25 µm. 20. The method of claim 19, wherein the film is a composite product further comprising a cellulose substrate. 21. The method according to any one of claims 15 to 18, further comprising flat die extrusion molding of the degradable polymer composition to form a sheet having a thickness of up to 1000 microns. - 9 039308 22. The method of any one of claims 15-18, further comprising injection molding a degradable polymer composition to form a molded plastic article.