Biodegradable polymer materials

Abstract

Various bio-based biodegradable materials, films, packaging materials, and methods of manufacture are provided herein. For example, such components may include polyvinyl alcohol (PVA) based materials that include lactic acid (LA) such as in the form of polylactic acid (PLA). In this regard, the synthesis of various PVA based copolymer on which PLA oligomers are grafted as a result of synthesis from LA. The result is a PVA-g-PLA copolymer, which is distinct from PVA and PLA blends.

Description

BIODEGRADABLE POLYMER MATERIALSFIELD

[0001] The present application is directed to bio-based biodegradable polymer materials such as biodegradable packaging for comestibles and methods of manufacture.BACKGROUND

[0002] Packaging materials are used to contain and protect a variety of items during storage and transport. A variety of materials such as cardboard, plastics, metal, and glass have historically been used for packaging. However, many packaging materials are deposited in a landfill after use. Non-renewable resources such as petroleum have been used to produce conventional non-biodegradable plastics. Though plastic-based packaging may be desirable due to their low cost, packaging materials containing such plastics can persist for a considerable period of time in the environment after disposal.

[0003] There has been increasing demand that renewable resources and / or materials that more readily degrade in the environment be used to produce packaging materials. For instance, polylactic acid (PLA) is a bio-based biodegradable polymer formed from lactic acid (LA) that can be used for packaging. However, PLA is oftentimes brittle with high glass transition temperatures and high melting points. In other words, PLA, while being bio-based and biodegradable, may not be suitable for some packaging as it may not provide the necessary physical properties, chemical properties, and the like.

[0004] For example, PLA may not be suitable for packaging for comestibles due to water content, pH, shelf life, or other attributes of the comestible or requirements of the packaging. However, because PLA is a renewable material that can be biodegradable, it may be desirable to incorporate the material with other components to form packaging for comestibles. In this regard, it may be desirable to provide for biobased biodegradable materials containing PLA that can be used as packaging for condiments, such as ketchup.

[0005] Poly (vinyl alcohol) (PVA) is a synthetic polymer material that has many uses, such as in medical and pharmaceutical applications due to its biocompatibility. However, PVA fdms may also have disadvantages such as brittleness, low fracture elongation, poor water resistance, and processability.

[0006] PVA and PLA blends have also been utilized to try to improve upon the performance of the materials. However, the blended form of these materials may still not provide suitable performance and function, such as for comestible packaging, depending on the usage.SUMMARY

[0007] Various bio-based biodegradable materials, fdms, packaging materials, and methods of manufacture are provided herein. For example, such components may include polyvinyl alcohol (PVA) based materials that include lactic acid (LA) such as in the form of polylactic acid (PLA). In this regard, the synthesis of various PVA-based copolymer on which PLA oligomers are grafted as a result of synthesis from LA. The result is a PVA-g-PLA copolymer, which is distinct from PVA and PLA blends.

[0008] The amounts of the components and reaction materials may be modified to provide desired performance in the resulting material and packaging. Similarly, the reaction and process parameters may also be modified to achieve desired performance and functionality.

[0009] For example, the ratio of polyvinyl alcohol to lactic acid (PVA:LA ratio), the amount of catalyst and the total amount of water used as a solvent, the synthesis time and temperature may be modified separately or in combination, as needed. For example, a ratio of the amount to PVA to PLA is in a range of about 1 : 1 to about 1 :4. The synthesis time may also be varied to achieve the desired function, such as having a time of about 5 hours to about 7 hours.

[0010] The copolymer may also be crosslinked. For example, crosslinking may be accomplishing using crosslinking agents such as citric acid, succinic acid, and the like. Additionally, higher temperatures, UV radiation, and the like may be used to help crosslink the copolymer as desired.

[0011] The material may also be combined with other materials to form the film. Similarly, the material may be formed into a polymer film and then joined with other films, coated, and the like to achieve desired properties.

[0012] The resulting material is a bio-based copolymer that has desirable transparent film properties along with high flexibility and high cohesive strength. The obtained material is easily sealable into a sachet by welding under simple laboratory conditions.

[0013] These and other aspects may be understood more readily from the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a Differential Scanning Calorimetry (DSC) plot for Copolymer 12 before drying.

[0015] FIG. 2 is a DSC plot for Copolymer 12 after drying at 80°C for 100 min.

[0016] FIG. 3 is a DSC plot for Copolymer 13 before drying.

[0017] FIG. 4 is a DSC plot for Copolymer 13 after drying at 80°C for 100 min.

[0018] FIG. 5 is a DSC plot for Copolymer 14 after drying at 80°C for 100 min.

[0019] FIG. 6 is a DSC plot for Copolymer 15 after drying at 80°C for 100 min.

[0020] FIG. 7 is a plot of molecular weight distribution for Copolymer 6.

[0021] FIG. 8 is a DSC plot for Copolymer 6.

[0022] FIG. 9 is a DSC plot for Copolymer 6.

[0023] FIG. 10 is a DSC plot for Copolymer 6.

[0024] FIG. 11 is a DSC plot for Copolymer 6.

[0025] FIG. 12 is an FTIR plot for Copolymer 6.

[0026] FIG. 13 is a TGA plot for Copolymer 6.

[0027] FIG. 14 is a DSC plot for further samples of Copolymer 6.

[0028] FIGS. 15A-C are plots and distribution for Sample A.

[0029] FIGS. 16A-C are plots and distribution for Sample B.

[0030] FIGS. 17A-C are plots and distribution for Sample C.

[0031] FIGS. 18A-C are plots of XPS analysis.

[0032] FIG. 19 is a graph of CO2 and O2 content changes for Copolymer 6.

[0033] FIG. 20 is a graph of CO2 and O2 content changes for a sample soil reference.

[0034] FIG. 21 is a table of properties for various copolymer materials.DETAILED DESCRIPTION

[0035] As an initial matter, all of the percentages and ratios herein are based on weight, unless otherwise noted. Further, it should be appreciated that the materials described herein relate to materials, such as copolymers, that are based on PVA where LA has been grafted onto the PVA material. This is distinct from PVA and LA or PLA blends. The methods of preparation as well as the properties and performance are different from blends, as discussed in more detail below.

[0036] Provided herein are various biodegradable films, materials, laminates, packaging, and the like as well as various methods for manufacture. These components may be considered bio-based and may be used to form polymers, copolymers, and the like, such as in the form of polymer films. Similarly, the materials may be used to form pellets that are then used to form polymer films, such as in industrial processing and packaging systems.

[0037] The materials described herein are generally obtained by the synthesis of a PVA-based copolymer on which PLA oligomers are grafted as a result of synthesis from lactic acid, thus forming PVA-g-PLA. In other words, PVA-g-PLA copolymers can be prepared whereby PLA chains are started by initiating polymerization of lactic acid on a PVA backbone. These polymerizations can be accomplished using various catalysts, as described below.

[0038] By forming PVA-g-PLA, it is possible to reduce the solubility of the resulting material and increase its mechanical properties and improve its barrier properties. By bio-combining the two materials, improvements in the poor properties of a traditional blend of PVA and PLA or LA can be achieved.

[0039] For example, the PVA-g-PLA materials show varying levels of water solubility depending on the conditions and components of the synthesis and production of polymer blends. The materials show high mechanical strength and a wide range of mechanical properties, from hard and brittle to similar to thermoplastic elastomers depending on the conditions and components of the synthesis and production of polymer blends. Further, varying degrees ofhydrophilicity of the copolymers can also be achieved, which may permit controlling the solubility depending on the synthesis conditions and the ratio of the ingredients used.

[0040] The PVA-g-PLA materials described herein may have many uses as the copolymers can be formed having varying properties and functional performance. The materials may also be bio-based and biodegradable, which may make them especially suitable to replace other non- biodegradable plastics and similar materials. For example, the materials described herein may be used as packaging for various comestibles having different moisture content, pH, oxygen susceptibility, and the like. In this regard, the PVA-g-PLA materials may be used with condiments such as ketchup. Other exemplary condiments include mayonnaise, mustard, relish, ponzu sauce, oil, vinegar, tartar sauce, fry sauce, and soy sauce.

[0041] Biodegradable ketchup packaging presents a challenge due to the moisture content and pH of the ketchup material which must be balanced with the solubility and biodegradability of the packaging material. The materials must be able to contain the ketchup while also being biodegradable and / or water soluble.

[0042] Similarly the packaging material should also provide suitable barrier performance. For example, the packaging material should provide a suitable water vapor transmission rate and a suitable oxygen transmission rate. The packaging material would also be capable of providing a suitable shelf life.

[0043] The components used to form the PVA-g-PLA materials are not especially limited. In general, the components include, but are not limited to, PVA, LA, optional fillers, crosslinkers, and the like.

[0044] The PVA material used may be provided in any form and used in various amounts to achieve the desired characteristics. For example, the PVA may be initially supplied as beads that are combined with a solvent or otherwise provided in solution form. The PVA can be prepared to have a concentration of about 10% to about 60% or otherwise provided directedly in solid form with a solvent during synthesis.

[0045] In some forms, the concentration of aqueous PVA solutions could include a water content to of from 0 to 10%, but other amounts can be used. Due to the processing conditions on a laboratory scale, mainly the high viscosity of the solutions and the ability to achieve suitablemixing and homogenization of the solutions, a concentration of PVA aqueous solutions in a range of 20-25% was easily achieve. The more water, the greater the ease of mixing due to the decrease in viscosity of the mixture, but the excess water also acted as a catalyst deactivator and reduced the degree of grafting and the length of the grafted chains. It is believed that with a suitable apparatus, the water content of the PVA racemate could be reduced to 50% or even to an anhydrous reaction.

[0046] The LA, which is used to form PLA in the grated copolymer, may also be provided in various forms and concentrations. For example, the LA may be initially supplied in a solid form that is combined with a solvent, such as water or otherwise provided in prediluted form. The LA may be provided in a concentration of about 25% to about 100% or otherwise provided directly in solid form with a solvent during synthesis.

[0047] The PVA and LA may be provided in various amounts relative to one another to achieve different performance and properties for the resulting PVA-g-PLA material. For example, the ratio of PVA to LA may be varied, such as from about L 1 to about 1 :4.Additionally, or in the alternative, the ratio may be about 1 :2 to about 1 :3.

[0048] The PVA-g-PLA material may also include other components, including but not limited to fillers, coatings, stabilizers, polyhydroxyalkanoates, polycaprolactone, other biopolymers, and the like. For example, fillers can be used to increase barrier properties, enhance water resistance, and the like. Such fillers include, but are not limited to, alkyl ketene dimer (AKD), tomato peel material, and the like.

[0049] Further, the PVA-g-PLA material may be modified with other materials, such as cross-linking agents. The barrier properties and other properties of the PVA-g-PLA material can be modified by using various degrees of cross-linking the PVA copolymer, such as using citric acid, succinic acid, high temperature, UV radiation, combinations thereof, and the like. Crosslinking is facilitated by unreacted PVA hydroxyl groups. The process itself reduces the solubility of the copolymer. In some forms, samples cross-linked with citric acid did not dissolve in water, but swelled very much to a hydrogel structure, while the copolymer cross-linked with succinic acid was highly cross-linked and it was neither dissolved in water nor strongly swollen.

[0050] Tn some forms, the crosslinking agents are bifunctional and multifunctional compounds containing a minimum of 2 carbonyl groups (-COOH) in their structure, e.g., organic carboxylic or amino dio acids (-NH2). Due to the fact that PVA is the main component of the copolymer, it is also possible to cross-link by using certain salts containing multivalent ions, e.g. sodium tetraborate. Typically, up to 2% of the crosslinking agent is used. The more crosslinking substances there are, the less flexible, but the stronger the material becomes. In general, as crosslinking increases, solubility and biodegradability decreases.

[0051] Coatings may also be used to modify the properties and function of the PVA-g-PLA material, especially when used as packaging for comestibles. Such coatings includes, but are not limited to, beeswax, acrylic, other bio-polymers, and the like. Similarly, the PVA-g-PLA material may be layered with other materials such that the PVA-g-PLA may be an inner layer, an outer layer, and / or an intermediate layer. Further, multiple layers of the PVA-g-PLA material may be used by itself or in combination with other layers. Examples of other layers include, but are not limited to, ethylcellulose, soy protein, other bio-polymers, and the like.

[0052] The PVA-g-PLA material may be prepared having varying thicknesses, as desired. The PVA-g-PLA material may also be provided in a solid form, such as in pellets or the like. The solid form may then be processed, such as through extrusion or other processes, to form films, packaging, and the like. Typically, the PVA-g-PLA material fill be formed into a film that can be further processed to for packaging, such as for comestibles. For example, the film can be formed into sachets that are used to store and distribute condiments such as ketchup.

[0053] The PVA-g-PLA material may be provided with varying properties and performance. For example, the PVA-g-PLA may have varying molecular weights, a glass transition temperatures, and the like.

[0054] In general, the PVA-g-PLA material is synthesized using the PVA-based copolymer on which PLA oligomers were grafted as a result of synthesis from lactic acid. The PVA is combined with the LA in the presence of a catalyst and / or under temperature and time conditions sufficient to graft LA onto the PLA backbone. After the reaction, the material can be dried such as in the form of solid pellets, a film, and the like.

[0055] Various catalysts can be used in various amounts. For example, Sn(Oct)2, Sn salts such as SnCh, Zn salts such as ZnCh, and combinations thereof can be used as catalysts. The amount of catalyst may also vary. For example, l-1.5wt.% of Sn(Oct)2 may be used. A minor amount of catalyst may be quickly deactivated by the water contained in the reaction mixture and formed as a reaction by-product. In order to reduce the amount of catalyst used, the reactions could be carried out in a smaller amount of solvent or H2O would have to be vacuum-stripped off during the reaction.

[0056] However, in addition to varying the composition and components of the PVA-g-PLA material, the synthesis and process for preparing the material may also be varied to achieve different properties and performance. In fact, the synthesis parameters can have a notable impact on developing a material with desired properties. Indeed, materials obtained under different conditions showed water solubility, but to varying degrees depending on both conditions and synthesis components. The materials also exhibited high mechanical strength and a wide range of mechanical properties: from hard and brittle to similar to thermoplastic elastomers, depending on the components as well as processing parameters. Similarly, the hydrophilicity of the copolymers can be controlled depending on the synthesis conditions and the proportion of components used.

[0057] As will be illustrated from the below examples, the ratio of poly (vinyl alcohol) to lactic acid (PVA:LA ratio) can have an impact on the properties of the PVA-g-PLA material. Similarly, the amount of catalyst and the total amount of water, used as a solvent can also have an impact on the properties and performance. The synthesis time and temperature also changes the properties and performance of the resulting PVA-g-PLA material.

[0058] The presence and amount of cross-linking agent, i.e., citric acid or other crosslinkers, may also impact the synthesis and resulting properties. Firstly, it changes the pH of the reaction medium, and secondly, it enhances the cross-linking process, which involves bonds forming as a result of the chemical reaction between polymer chains in order to link them together into network. In this way, the formed network density has an effect on the material properties obtained, such as solubility, mechanical strength and stiffness, hardness, and the like.

[0059] The reaction temperature may also be modified. The reaction temperature may vary.However, the minimum reaction temperature is 100 ° C. Below this temperature there is no effective grafting of the lactic acid on the PVA surface.

[0060] The amount of water used as a solvent during the synthesis in laboratory conditions can also be varied. For example, in some forms, the ratio of water to PVA is about 4: 1 by weight. The synthesis can be more effective with a lower water content, but in laboratory conditions, due to the high viscosity, a solvent is added to reduce its value.

[0061] The reaction time and conditions may also be varied. The reaction or synthesis time of about 4 to about 10 hours may be used and modified to achieve various performance and properties. One range of reaction time is 5-7 hours. Shorter time can be less effective and there is no high conversion of lactic acid to oligoPLA, wasting reagents and not achieving the desired properties. Time exceeding 12 hours may cause hydrothermal degradation of the obtained copolymer under the tested conditions, which causes a partial decomposition of the obtained copolymer and deterioration of its properties. In some cases, a more than three times longer synthesis time, i.e., 24 h instead of 7 h, did not entail a visible improvement in mechanical properties, transparency and degree of grafting of the lactic acid on the PVA.

[0062] The drying time and temperature may also impact performance. For example, the drying time and / or temperature may affect the stiffness of the synthesized material as well as its resistance to stretching and tearing during mechanical testing. The drying temperature can also vary. For example, in some forms, the drying temperature can be about 80°C. The drying time can also vary. However, typically the minimum time is 6h because at lower temperatures the water contained in the copolymer mass and unreacted lactic acid do not evaporate effectively. Higher temperature than 100°C and time over 16h can cause material degradation manifested by yellowing of the material and an increase in its brittleness.

[0063] Results have shown that the materials described herein could be used to help protect filled ketchup from moisture loss (lower than 3%) within one week (RH=50%~90%, sealed in the desiccator). The sachet exhibited suitable moisture barrier property (weight loss=16%, 1 month) in a storage test with lower RH (-20-40%, open). Overall, the bio-based solution may be suitable as a green packaging choice for ketchup.

[0064] Various examples were prepared and tested to compare the impact of starting materials, method of manufacture and other variables associated with the materials.

[0065] Example 1

[0066] The equipment used in a laboratory for PVA-g-PLA synthesis included a magnetic stirrer with heating function, an oil bath, a flask with a thermometer, a cooler and an excess solvent receiver. The reagents used to carry out the reaction included poly(vinyl alcohol) (PVA), lactic acid 80%, catalyst tin (II) octanoate, and distilled water. Gelatine was also used in some of the reactions.

[0067] For manufacturing the polymer blends, Solution A was prepared by dissolving a weighed amount of PVA in distilled water and heated on a magnetic stirrer in an oil bath with vigorous stirring. Solution B was prepared by dissolving a weighed amount of gelatine in distilled water in an oil bath with constant stirring. The resulting solutions were pooled and stirred while increasing the temperature gradually. After homogenization, the solution was poured into a large crystallizer lined with a PTFE sheet and placed in an oven to evaporate the water.

[0068] Example 2

[0069] A sample laboratory composition was prepared with the following amounts of components. In a 500 ml flask, weigh 40 g of PVA, 100 g of H2O and 87.5 g of an 80% lactic acid solution. Put the dipole in and stir with heating under a reflux condenser on a magnetic stirrer until the temperature of the reaction solution is a minimum of 85°C with a homogeneous consistency (time about Ih). Then Sn (Oct)2 catalyst is added. Then the mixture is heated up to 100 ± 5 °C with intensive stirring. After reaching temperature, the reaction continued for another 2 hours. After this, citric acid solution is added while allowing the reaction to continue for another 5 hours. The rotation of the magnetic dipole is adjusted throughout, paying attention to the high viscosity of the reaction mixture. After the process is finished, the reaction mixture is poured in the form of a thin film into a cuvette lined with a PTFE foil to prevent excessive adhesion. The poured films are left for 16 hours for the solvent to evaporate, and then dried in a lab dryer at 80°C for 12h.

[0070] Example 3

[0071] Summary of Reaction Parameters for Various Blends and Copolymers Syntheses

[0072] Various blends of PVA and gelatin were prepared to evaluate the resulting materials.The amounts of materials as well as processing and / or reaction time is summarized below in Table 1.Table 1 Summary table of the composition and conditions for the production of blends

[0073] Blend B l was prepared as outlined above in Table 1. The blend was poured into Petri dishes and left for 24 hours at 40°C in an oven in order to evaporate the solvent. Blend B l was PVA and gelatin. A transparent film with high mechanical strength was obtained that was highly soluble in water. With samples of greater thickness and thus longer evaporation time, precipitation of 2 phases and a decrease in transparency occurred. The processing conditions are outlined in Table 1.

[0074] Blend B_2 was prepared in a similar manner as Blend B l , then poured and mixed for another 30 minutes, gradually increasing the temperature from 55 to 70°C. After this time, 1 g of citric acid dissolved in 30 ml of water was diluted. The mixture was heated for 30 minutes at 50°C. After this time, it was poured into a crystallizer lined with PTFE foil and placed in a dryer for 24 hours at 40°C in order to evaporate the water. The next day, the product was sieved for 1 hour at 130°C. The product is stiff and hard, softened when it comes into contact with moisture. Blend B_2 was more difficult to dissolve than B l .

[0075] Blend B_3 was prepared as a copolymer blend PVA-g-PLA which was poured together and mixed for 30 minutes at 100°C. After this time, the solution was poured into a large vessel lined with PTFE foil and put in the dryer for 24 hours at 40°C in order to evaporate the water. The produced polymeric material was flexible and felt like tomato peel to the touch.

[0076] Example 4

[0077] Various PVA-g-PLA copolymers were prepared in accordance with a number of the teachings found above. The amounts of the components as well as the various processing and reaction times are outlined below in Table 2.Table 2. Summary of the composition and production conditions of copolymers in Example 4.

[0078] Copolymer 1 had some difficulty with homogenization of the mixture at low temperatures due to too high of viscosity. The synthesis was not desirable and the PLA was cut out in a separate phase. Resulted in a yellow product, possibly partially degraded.

[0079] Copolymer 2 included pre-homogenization before catalyst addition. The resulting product was more homogeneous due to a higher amount of solvent and was a transparent product.

[0080] Copolymer 3 had initial homogenization at 80°C for Ih before the catalyst was added. After synthesis, the hot solution was poured onto a PTFE film to form a copolymer film, and then the solvent was evaporated in an oven for 24 hours at 40°C.

[0081] Copolymer 4 had initial homogenization at 80°C for Ih before the catalyst was added. After synthesis, the hot solution was poured onto a PTFE film to form a copolymer film, and then the solvent was evaporated in an oven for 24 hours at 40°C.

[0082] Copolymer 5 had initial homogenization at 80°C for Ih before the catalyst was added. After 2.5 hours of the process, a solution of 0.3 g of ground tomato skins dispersed in 15 ml of water was added. Then the reaction was carried out for 2.5 hours at 100°C. After synthesis, the hot solution was poured onto a PTFE film to form a copolymer film, and then the solvent was evaporated in an oven for 24 hours at 40°C.

[0083] Copolymer 6 was transparent and creates a homogeneous foil. Immediately after drying, the material is stiffer as it absorbs some of the moisture from the environment until it reaches an equilibrium state. After this time, it becomes more flexible and has satisfactory mechanical properties. The product is soluble in water. It is characterized by good barrier properties, high flexibility, and acceptable strength. Its surface is slightly sticky. The copolymers showed a degradation in terms of biodegradability within a month. Copolymer 6 was less viscous than copolymer 7 such that it was easier to mix and had a smoother consistency. After addition of catalyst to copolymer 6, when grafting occurred, the viscosity increased.

[0084] Initial mechanical properties of Copolymer 6 conditioned for 24h at 23 °C and 50% humidity: average strength for 100% elongation 0.746 ± 0.107 [MPa]; average strength for 200% elongation 1.29 ± 0.19 [MPa]; average tension at maximum commanded force 1.54 ± 0.08 [MPa]; average elongation at maximum commanded force 215.2 ± 37.7 [%].

[0085] Initial mechanical properties of Copolymer 6 conditioned for 24h at 30°C and 80% humidity: average strength for 100% elongation 0.628 ± 0.067 [MPa]; average strength for 200% elongation 0.984 ± 0.107 [MPa]; average tension at maximum commanded force 1.28 ± 0.14 [MPa]; average elongation at maximum commanded force 286.2 ± 0.6 [%].

[0086] Example 5

[0087] Additional copolymers were prepared similar to those described above in Example 4. The composition and processing conditions are summarized below in Table 3.Table 3. Summary table of the composition and production conditions of the second batch of copolymers with the designations from 7 to 11.

[0088] Copolymer 7 included mechanically powdered tomato peelings, which were added to Copolymer 6 described above. For Copolymer 7, 4 g of ground tomato skins (4 wt.% With respect to PVA + LA) were added. The tomato skins were added to the reaction after 2.5 hours and in the form of a dispersion in 25 ml of water. The obtained product is characterized by good mechanical strength, orange colour, and a characteristic smell of processed tomatoes. The film is not completely transparent because the scattered ground tomato peels are dispersed throughout the mass. The dispersion of this additive is satisfactory and even in places with a flat surface.

[0089] Copolymer 8 was prepared with a change in PVA:LA ratio as well as synthesis time. A ratio of poly (vinyl alcohol) to lactic acid in the structure of the copolymer was tested at 2:3. Additionally, the drying time and temperature were changed. Under these drying conditions, the product becomes stiffer. It is more resistant to stretching and tearing mechanically. The results are still homogeneous and transparent films are still soluble in water. It is hypothesized that drying at a higher temperature causes more moisture and unreacted lactic acid to evaporate from the product. It is also hypothesized that during drying, a further copolymerization reaction and an increase in the length of the oligomeric chains of the lactic acid may also take place. Under these conditions, there is no significant thermo-oxidative degradation of the material, slight thermo-crosslinking processes may take place.

[0090] Copolymer 9 was prepared with a change in PVA:LA ratio as well as synthesis time. The PVA:LA ratio was 3:7 with a 24 hour synthesis time. The catalyst content was 1.5 wt.%. Similar observations were made as in the case of Copolymer 8. However, the product after drying is mechanically less durable, faster and to a greater extent absorbs water from the environment, becoming more sticky on the surface.

[0091] In some forms, for the copolymerisation process, the process temperature can be approximately 100°C in the flask, but the solution needs to be partitioned to a temperature of 140-160 C for the polycondensation of PLA to PVA to take place. In some forms, PVA to LA ratios of 3 / 7 with an excess of lactic acid and extending the synthesis to 24 h were used to produce the highest possible degree of grafting and to produce the longest possible PLA chains in the copolymer structure. In some forms, the more lactic acid there was in the reaction mixture, the viscosity of the solution decreased. However, the degree of lactic acid reactivity in the PLAand the residue of this unreacted monomer may reduce the yield and make it difficult to remove unreacted material from the product.

[0092] Copolymer 10 was prepared with the same ratio of PVA and LA as Copolymer 9. However, the amount of catalyst was reduced to 1 wt.% and the synthesis time was time was changed. The synthesis took 7 hours, but did not translate into a visible improvement in mechanical properties, transparency and the degree of lactic acid grafting on the PVA surface. The lower amount of the catalyst resulted in a lower amount of PLA in the copolymer structure.

[0093] Copolymer 11 was prepared with a change in PVA:LA ratio to 4:7 but the same synthesis time as Copolymer 10. The catalyst was Sn(Oct)2 in an amount of 1.5 wt.%. The amount of water added as a solvent was 4 times the weight of PVA. The results included better properties than Copolymer 10, however worse than examples with 5-7 hour syntheses. It is hypothesized that this may be due to partial hydrothermal degradation of the ester bonds present in the structure after chain growth no longer occurs due to completion of the reaction after deactivation of the active molecules in the reaction.

[0094] Example 6

[0095] Additional copolymers were prepared with further variations. The composition and processing conditions are summarized below in Table 4.Table 4. Summary table of the composition and production conditions of the third batch of copolymers with the designations from 12 to 15.

[0096] Copolymer 12 was prepared and based on Copolymer 10. However, the effect of cross-linking substance citric acid (CA) on the properties of the copolymer and the acidification of the environment on the equilibrium shift of the grafting reaction was checked. After 2 hours of reaction, 13.3 g (10% by weight of PVA + LA) citric acid solution dissolved in 25 ml of water was added in order to change the pH of the reaction medium with an equilibrium shift and to partially cross-link the copolymer. The obtained material turned out to have the highest level of ester and carbonyl groups content in the structure so far, which indicates the highest LA bonds in the copolymer structure. This was determined through FTIR spectroscopic analysis. However, the resulting product, after drying, had a significant surface tack.

[0097] Copolymer 13 was prepared and based on the composition tested for Copolymer 11. However, as with Copolymer 12, citric acid was used to cross-link the hydroxyl groups present in PVA that were not reacted during the grafting reaction. After reaction for 2 hours, 11 (10% by weight of PVA + LA) of citric acid solution dissolved in 25 ml of water were added. Similar results as in Copolymer 12 were found. The greater addition of the catalyst, however, appeared to make the obtained film no longer sticky after drying.

[0098] Copolymer 14 was prepared with a similar composition as Copolymer 10. However, succinic acid, having an even lower pH than the citric acid (used in Copolymer 12), was used as the crosslinker. After the initial homogenization and after 2 hours of the copolymerization reaction with the addition of the catalyst, succinic acid solution dissolved in 25 ml and 60°C was added. The obtained product is a transparent film with high flexibility and high cohesive strength. The surface is slightly sticky.

[0099] Copolymer 15 was prepared with a similar composition as Copolymers 11 and 13. In this case, succinic acid was used as crosslinker. The higher PVA to LA ratio and the greater amount of catalyst eliminated surface stickiness with a slight difference in grafting of lactic acid to poly (vinyl alcohol). The product is less flexible than Copolymer 14 and is more resistant to stretching and breaking as determined through a tensile test. The addition of succinic acid made the product a little less transparent (slightly milky).

[0100] Example 7

[0101] Creation of a bonded fdm from PVA-g-PLA copolymer and a fdm comprising ethylcellulose. Copolymer 6 was hot joined to ethylcellulose by physically joining the two films using heat. In this example, the synthesis of the PVA-g-PLA copolymer was carried out and then poured the hot film onto Teflon foil. After being poured, the modified ethylcellulose was placed on its surface and smoothed. The combined films were transported to a laboratory dryer for 12 h at 80°C to be dried. The connection turned out to be permanent, however, significant amounts of bubbles were formed at the connection points. It is hypothesized this may have been the result of difficult evaporation of moisture.

[0102] Example 8

[0103] Another combined material was attempted using a copolymer of hydroxypropyl methylcellulose grafted with PLA (HPMC-g-PLA) in a ratio of 1 :9. The HPMC was used as a bioadhesive to bond with other polymers. It is a viscous liquid resembling honey in consistency and colour. It exhibits certain adhesive properties, and due to its similar chemical nature (presence of hydroxyl groups and similar viscosity), it should have a high affinity for both materials to be joined. Then the combined material was placed at the temperature of 80°C in a laboratory drier for 4 hours. The connection turned out to be durable, it contained fewer bubbles, in the places where the excess HPMC-g-PLA copolymer was left as an adhesive, the materials partially dissolved.

[0104] Elongation testing was conducted on various samples described above. The results of the testing is shown below in Table 5.Table 5. Elongation testing. SE100; SE200; SE3300 - stress at 100, 200 and 300% elongation, respectively; TS - tensile stress; Eb - elongation at break

[0105] A brief discussion of the materials is provided comparing behavior. ForCopolymer 8, the material was slightly heterogeneous in behavior. For Copolymer 9, it was more heterogeneous. With Copolymer 10, the sample was sticky such that the strain gauge (i.e., extensometer) jaws slide over the sample giving the most uncertain measurement. Copolymer 10 behaved most differently from the others and most heterogeneously when tested. Copolymer 11 was the most stable specimen during measurement and the most homogeneous in terms of its behavior during the tensile test. Copolymer 13 was slightly heterogeneous in behavior.

[0106] Thermal analysis of various copolymer samples was also conducted using differential scanning calorimetry DSC Methodology. The temperature ranges for phase changes for Copolymers 12-15 were obtained utilizing Differential Scanning Calorimetry (DSC) (Mettler Toledo DSC analyser, TA 2920, TA Instruments). 5 to 6 mg of samples were placed in 40 pL aluminium pans and heated from -20 to 200°C at a rate of 10°C / min. Before the measurement, the films were dried at 80°C for 100 min. Comparative thermograms of Copolymers 12 and 13 before drying are also shown. The results are presented in FIGS. 1-6.

[0107] The glass transition temperatures (Tg) of Copolymers 12-15 after drying at 80°C for 100 min are presented below in Table 6.Table 6. Tg Glass Transition [°C],

[0108] All copolymers had a glass transition temperature. The glass transition temperature of Copolymers 12 and 13 was about 17-18°C (onset) and Copolymers 14 and 15 was around 29-31 °C (onset). Despite the drying of the copolymers before the DSC measurement, the desorption of water present in the fdms was visible in the thermograms (wide peak in the 60-190°C range). Due to the desorption of water, the measurement of the glass transition temperature may be affected by some error.

[0109] Water desorption dominated on thermograms of Copolymers 12 and 13 before drying the samples. Therefore, these results may be subject to a significant error and have not been included in Table 6.

[0110] Additional testing was conducted on a number of the copolymers. Such testing included the water vapor transmission rate (WVTR), oxygen transmission rate (OTR), the tensile strength and the puncture strength. The results are shown in Tables 7 and 8 where Copolymer 6 in Table 7 corresponds to Lodz-1 in Table 8.Table 7. Water vapor transmission, oxygen transmission, tensile, and puncture testing.Table 8. Results for Copolymer 6 (Lodz-1).

[0111] As shown above, at least some of the copolymers had cold water solubility and also showed desirable disintegration in home composting conditions.

[0112] Example 9

[0113] As found in FIG. 7, the molecular weight distribution is shown for Copolymer 6, described above. The sample was tested using a Viscotek GPC Max, 2*30cm Agilent OH60 GPC columns, with the eluent water plus 0.2m sodium nitrate with a 1.0 ml / min flow rate at 40°C. As shown in the figure, the Mw was 30,000, the Mn was 1,200, with the Mw / Mn at 25.0 and 25 Mz. The compositions can be modified to achieved desired molecular weight and distribution.

[0114] Example 10

[0115] DSC analysis was also run for sample materials based on Copolymer 6. Plots for the runs can be found in FIGS. 8-11. Samples were subjected to a heat / cool / reheat to 270°C (tx2395) and a fresh sample to 150°C (tx2401). The first run appears stable to around 155°C. The glass transition onset in the as-received sample was measured at -51.5°C. The variation in melting points in each as received run which may indicate variations in the polymer composition across the film. The glass transition onset on a reheat after a cool from 270°C is 72.8°C and it is - 39.0°C after a cool from 150°C.

[0116] Example 11

[0117] Additional tests were conducted on samples of Copolymer 6. Fourier transform infrared spectroscopy (FTIR) was conducted with the results shown in FIG. 12. Samples of polymer composites were tested for the content of functional groups using a Thermo Scientific Nicolet 6700 FT-IR spectrophotometer that performs Fourier transform absorption measurements in the spectrum with a wave number of 4000-400 cm-1 with the Smart Orbit ATR diamond attachment in the absorption mode and 64 scans.

[0118] Thermogravimetric analysis was also conducted on Copolymer 6. A Mettler Toledo TGA / DSC 1 STARe System equipped with a Gas Controller GC10(Greifensee, Switzerland) was employed during this investigation. The measurement was conducted by combustion in synthetic air (temperature range: 25-600°C, heating rate: 15°C / min; air flow of 50 cm3 / min). The examined samples were placed in alumina cubicles and the results are shown in FIG. 13.

[0119] Additional DSC analysis was performed on further samples of Copolymer 6. The temperature ranges of PVA-g-PLA phase changes for Copolymer 6 were obtained utilizing Differential Scanning Calorimetry (DSC) (Mettler Toledo DSC analyser, TA 2920, TA Instruments). Samples of 5 to 6 mg of material was placed ini 00 pL aluminium pans and heated from -20 to 300 °C at a rate of 10 °C / min. The results are shown in FIG. 14.

[0120] Gel permeation chromatography was conducted on three samples of Copolymer 6. Copolymer solutions were prepared with concentrations of 7 and 4 g / 1, respectively. The polymers were dissolved in 0. IM NaNCh by autoclaving and 24-hour storage at 50°C. A GPC system with a triple detection was used in the study. A multi-angle scattered light intensitydetector - MALLS (Brookhaven Instruments Corporation, Brookhaven, NY, USA) and a dual refractometric-viscometric detector - RI / DP (Testa Analytical Solutions, Berlin, Germany) were used. Two Suprema Lux Linear XL analytical columns (suitable for neutral and anionic polymers) with Suprema Lux SDV analytical pre-column (PSS Polymer Standards Service GmbH, Mainz, Germany) were used in all measurements. Chromatographic measurements were carried out using 0.1M NaNCh as eluent. The flow rate was Iml / min and the temperature was 50°C. Each sample was measured three times. The results for Sample A are shown in FIGS. 15A-C, the results for Sample B are shown in FIGS. 16A-C, and the results for Sample C are shown in FIGS. 17A-C. The molecular weights are shown below in Table 9.Table 9. Molecular weights of Samples A-C.

[0121] X-ray photoelectron spectroscopy was also conducted on Copolymer 6. The chemical analysis was carried out by XPS method using an X-ray photoelectron spectrometer (Omicron NanoTechnology) with 128-channel collector. XPS measurements were performed in ultra-high vacuum conditions, at a pressure below 1.1 xlO-8 mBar. The photoelectrons were excited by a Mg-Ka X-Ray source. The X-ray anode was operated at 15 keV and 300 W. Omicron Argus hemispherical electron analyzer with round aperture of 4 mm was used for analyzing of emitted photoelectrons. XPS spectra were analyzed with Casa-XPS software using a Shirley background subtraction and Gaussian-Lorentzian curve as a fitting algorithm. Collected spectra were deconvoluted by several curves corresponding to various chemical states. The results are shown in FIGS. 18 A-C.

[0122] Respirometric tests were also performed on Copolymer 6. A Micro-Oxymax Respirometer was used for automatic testing of biodegradation progress under conditions simulating intensive aerobic composting process. The device allowed simultaneous testing in four chambers, with one chamber containing soil alone as a reference sample. The chambers were placed in an oil bath with a controlled temperature of 40°C. During the conducted test, theamount of CO2 released over time was measured for 30 days. The results are shown in FIG. 19 while the sample soil reference is shown in FIG. 20.

[0123] Example 12

[0124] Properties for various copolymers described above were analyzed. These properties include oxygen transmission, water vapor transmission, gauge, average gauge, tensile strength, puncture strength, shelf life, dispersibility, and disintegration. These features were tested as outlined above and / or in accordance with standard testing methodology. Some of the features of Copolymer 6 are separately outlined in the examples above.

[0125] Various observations have been made on the copolymers discussed above. The addition of more lactic acid above the PVA: LA ratio of 30:70 increases the stickiness of the copolymer surface. It is hypothesized that this may be due to either all the lactic acid not reacting during the synthesis reaction or due to the increased barrier nature of the product, which does not adequately transmit water from its structure during the drying process. Moreover, an increased amount of LA in the structure appears to reduce the mechanical strength of the obtained copolymers while increasing flexibility. The addition of citric acid to the reaction to cross-link the copolymer and change the reaction medium causes a large increase in the viscosity of the reaction mixture, however, the mechanical strength did not increase, but the flexibility increased.

[0126] Comparisons between the various copolymers regarding the influence of drying and thermosetting on the properties of the starting copolymer was also performed. Samples of the Copolymers 8-13 were dried at 40°C, 60°C, 80°C and 100°C. The influence of drying time was also investigated in the time intervals of 2h, 6h and 12h. After the tests and observations of the samples, one preferred drying and thermo-crosslinking time is 12h at 80°C. The product prepared in this way shows an increase in stiffness, greater mechanical strength, lower surface stickiness, still high transparency and low thermo-oxidative degradation.

[0127] It should be appreciated that the synthesis of copolymers based on PVA and LA can result in a transparent, thermoplastic material for packaging. The obtained material is compostable and water-soluble in a controlled manner. Controlling the solubility process of the obtained copolymer can be modified by changing the proportion of the substrates and the synthesis parameters.

[0128] By bio-crosslinking the copolymer, the material can result in excellent physicochemical, mechanical and optical properties. The degree of crosslinking allows the material stiffness and strength to be modified, and the solubility of the material can be modified by appropriate cross-linking.

[0129] The material and process for manufacturing can be modified to achieve desirable properties for packaging for different products. For example, the materials and process can be modified to provide for properties of the PVA-LA copolymer so that it does not exhibit high solubility in ketchup. Similarly, the material may be designed so that it can withstand the transport of ketchup specified by the manufacturer.

[0130] The copolymers described herein may be bio-based, resulting in a transparent film with high flexibility and high cohesive strength. The obtained material can be easily sealable into a sachet by welding. In some forms, the surface may be slightly sticky, however it can be controlled by the amount of catalyst, as a higher catalyst addition caused the obtained film to stop being sticky after drying.

[0131] The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of Applicant’s contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.

Claims

CLAIMSWhat is claimed is:

1. A composition comprising: poly (vinyl alcohol) (PVA) backbone; and lactic acid (LA) grafted onto the PVA backbone.

2. The composition of claim 1 wherein the PVA is provided in a ratio to the LA (PVA:LA) in a range of about 1 : 1 to about 1 :

43. The composition of claim 1 further comprising a filler.

4. The composition of claim 3 wherein the filler is selected from the group consisting of alkyl ketene dimers, tomato skin material, and combinations thereof.

5. The composition of claim 1 wherein the material is crosslinked.

6. The composition of claim 1 wherein the material is biodegradable.

7. The composition of claim 1 wherein the material is in the form of pellets used to form a polymeric film.

8. The composition of claim 1 wherein the material is in the form of a polymeric film.

9. A method for preparing a biodegradable packaging material, the method comprising the steps of: providing a poly (vinyl alcohol) (PVA) material; providing a lactic acid (LA) containing material;reacting the PVA material with the LA containing material in the presence of a catalyst to synthesize a PVA backbone with poly lactic acid (PLA) grafted onto the PVA backbone to form PVA-g-PLA.

10. The method of claim 9 wherein a ratio of the PVA material to the LA containing material is about 1 : 1 to 1 :4.

11. The method of claim 9 wherein the catalyst is provided in an amount of about 1 to about 1.5 wt.%12. The method of claim 9 wherein the catalyst includes at least one of Sn(Oct)2, SnCk, ZnCk, and combinations thereof.

13. The method of claim 9 wherein the reaction is carried out over a time period of about 5 to about 7 hours.

14. The method of claim 9 wherein the reaction is carried out at a temperature of about 80°C to about 100°C.

15. The method of claim 9 further comprising the step of adding at least one of alkyl ketene dimers, fillers, coatings, stabilizers, polyhydroxyalkanoates, polycaprolactone, other biopolymers and combinations thereof.

16. The method of claim 9 further comprising the step of adding a cross-linking agent.

17. The method of claim 16 wherein the cross-linking agent includes at least one of citric acid, succinic acid, and combinations thereof.

18. The method of claim 9 further comprising the step of cross-linking the PVA-g-PLA using at least one of citric acid, succinic acid, UV radiation, and combinations thereof.

19. The method of claim 9 further comprising the step of forming the PVA-g-PLA into a film.

20. The method of claim 19 further comprising the step of combining the film with a second film.

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