Lignin-containing polyethylene composites

Abstract

There is provided a process for preparing pellets of a polyethylene (PE) composition in an extruder device, wherein the process comprises the steps of: a) supplying lignin to the extruder device; b) supplying oil to the extruder device; c) supplying an additive to the extruder device, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO); d) supplying a PE to the extruder device; e) mixing the lignin, the oil, the PE and the additive in the extruder device at a temperature of at least 170 °C to form a PE composition; f) pelletizing the PE composition, wherein the formed pellets comprises: - the lignin in a content of 15-75 wt% by dry weight of the composition; - the oil in a content of 0.5-15 wt% by dry weight of the composition; - the PE in a content of 15-70 wt% by dry weight of the composition; and - the additive in a content of 2-35 wt% by dry weight of the composition.

Description

LIGNIN-CONTAINING POLYETHYLENE COMPOSITESTECHNICAL FIELD

[0001] The present disclosure relates to the field of lignin-containing composites and in particular to lignin-containing polyethylene composites.BACKGROUND

[0002] The shift towards sustainable materials in the industry is particularly evident in the effort to replace traditional, fossil -based plastics with biobased alternatives. This transition is driven by the urgent need to address environmental concerns and reduce dependence on non-renewable resources.

[0003] A notable development in this area is the use of lignin as a substitute for part of the fossil-based components in plastics. Lignin, a complex organic polymer found in the cell walls of plants, is abundant as a by-product of the paper and pulp industry. Its incorporation into plastic production presents a sustainable approach.

[0004] The integration of lignin in plastic manufacturing brings several benefits including reduced environmental pollution and landfill waste. However, challenges exist in achieving uniformity and consistency in the properties of lignin-based plastics.

[0005] There has been work conducted in this sector focused on overcoming these challenges. Efforts include enhancing the processability of lignin and improving the compatibility of lignin with other bioplastic components to produce materials with desirable physical properties. But, there are still improvements to be made.SUMMARY

[0006] There is an objective of the present disclosure aims to provide a process for producing polyethylene (PE)-based plastics having an improved carbon footprint compared with neat PE-plastics and still provide desirable properties, in particular mechanical properties. Moreover, within the present disclosure there is also an objective to provide PE-films having a combination of appearance, mechanical properties and reduced environmental impact.

[0007] Accordingly, there is provided the following list of itemized embodiments:1. A process for preparing pellets of a polyethylene (PE) composition in an extruder device, wherein the process comprises the steps of: a) supplying lignin to the extruder device; b) supplying oil to the extruder device; c) supplying an additive to the extruder device, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO); d) supplying a PE to the extruder device; e) mixing the lignin, the oil, the PE and the additive in the extruder device at a temperature of at least 160 °C to form a PE composition; f) pelletizing the PE composition, wherein the formed pellets comprises:- the lignin in a content of 15-75 wt% by dry weight of the composition;- the oil in a content of 0.5-15 wt% by dry weight of the composition;- the PE in a content of 15-70 wt% by dry weight of the composition; and- the additive in a content of 2-35 wt% by dry weight of the composition.2. The process of item 1, wherein the oil is a vegetable oil or a glycidyl ether oil or a modified fatty acid ester.3. The process of item 2, wherein the vegetable oil is rapeseed oil, olive oil, soybean oil, sunflower oil, palm oil, coconut oil, canola oil, corn oil, sesame oil, peanut oil, epoxidized vegetable oil, such as epoxidized soybean oil or epoxidized cashew nut oil, or mixtures thereof.4. The process of item 2 or 3, wherein the modified fatty acid ester is an epoxidized fatty acid ester.5. The process according to any one of the preceding items wherein PE is low- density polyethylene (LDPE) and / or linear low-density polyethylene (LLDPE).6. The process according to any one of the preceding items, wherein the process further comprises the step of: mixing the lignin and the oil prior to supplying the additive as well as the PE to the extruder device.7. The process according to item 6, wherein the mixing of the lignin and the oil is at least partially conducted at a temperature in the range 110-250 °C, such as 120- 190 °C.8. The process according to any one of the preceding items, wherein a step of evacuation of atmospheric gas and / or moisture is conducted after step a) and prior to step f) in the extruder device.9. The process according to any one of the preceding items, wherein the saccharide content in the lignin according to NREL / TP-51O-42618:2OO8 is below 7 wt% by dry weight, such as below 5 wt% by dry weight, such as below 4 wt% by dry weight.10. The process according to any one of the preceding items, wherein the dry content of the lignin when supplied in step a) is above 90 wt% by dry weight, such as above 93 wt% by dry weight, such as above 95 wt% by dry weight.11. The process according to any one of the preceding items, wherein the content of the lignin in the formed pellets is 25-65 wt% by dry weight.12. The process according to any one of the preceding items, wherein the content of the oil in the formed pellets is 0.5-13 wt% by dry weight, such as 2-13 wt% by dry weight.13. The process according to any one of the preceding items, wherein the PE content in the formed pellets is 20-65 wt% by dry weight.14. The process according to any one of the preceding items, wherein the additive content in the formed pellets is 3-35 wt% by dry weight, such as 5-35 wt% by dry weight, such as 3-20 wt% by dry weight, such as 5-20 wt% by dry weight, such as 3-17 wt% by dry weight, such as 5-15 wt% by dry weight.15. The process according to any one of the preceding items, wherein step e) is conducted in the extruder device at a temperature of at least 170 °C to form the PE composition.16. A process for film blowing a PE film having a lignin content of 2-45 wt% by dry weight from a film blowing composition comprising the pellets of the PE composition produced according to any one of the preceding items and a second PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-85 wt% by dry weight and the second PE in a content of 15-93 wt% by dry weight in an extruder device while heating to form a molten mixture;- blow a film from the molten mixture in a film blowing device.17. The process according to item 16, wherein the PE in the pellets is low-density polyethylene (LDPE) and / or linear low-density polyethylene (LLDPE).18. The process according to item 17, wherein the PE in the pellets is a mixture of LDPE and LLDPE and the dry weight ratio of LDPE to LLDPE is 1:0.3 to 1:2.5, such as 1:1 to 1:2.19. The process according to any one of the items 16-18, wherein the temperature of the molten mixture is 180-210 °C, such as 180-200 °C, such as 180-190 °C.20. The process according to any one of the items 16-19, wherein the film blowing composition further comprises a lubricant in a content of 0.5-5 wt% by dry weight of the composition.21. The process according to any one of the items 16-20, wherein the film blowing composition has a calcium oxide content of <2 wt% by dry weight of the composition.22. The process according to any one of the items 16-21, wherein the second PE is LDPE.23. The process according to any one of the items 16-22, wherein the lignin content in the produced film is 5-45 wt% by dry weight, such as 5-40 wt% by dry weight, such as 10-30 % by dry weight.24. A film produced according to any one of the items 16-23 having a lignin content of 2-45 wt%.25. The film according to item 24, wherein the film has a puncture resistance according to ASTM D5748-95 of at least 30 N.26. The film according to item 24 or 25, wherein the film has a tear strength according to ISO 6383-2:1983 in cross direction (CD) at least 5000 mN and in machine direction (MD) of at least 1000 mN, such as at least 2000 mN.27. The film according to any one of the items 24-26, wherein the film comprises calcium oxide in a content of <2 wt% by dry weight.28. A process for injection moulding a PE article having a lignin content of 2-60 wt% by dry weight from an injection moulding composition comprising pellets of the PE composition produced according to any one of the items 1-15 and a third PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-95 wt% by dry weight, and the third PE in a content of 5-93 wt% in an extruder device while heating to form a molten mixture;- injection mould the molten mixture in an injection moulding device.29. The process according to item 28, wherein the third PE is high density polyethylene (HDPE).30. A PE composition comprising:- lignin in a content of 15-75 wt% by dry weight of the composition;- oil in a content of 0.5-15 % by dry weight of the composition;- PE in a content of 15-70 % by dry weight of the composition; and- an additive in a content of 2-35 % by dry weight of the composition, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO).31. The composition according to item 30, wherein the at least 95% by dry weight of the composition is constituted by the lignin, the oil, the polyethylene and the additive.32. Use of a film according to any one of the items 24-27 in plastic bags, in e- commerce, in packaging, in wrapping, in agriculture, in transport or protective films.

[0008] The inventors have realized that the process for preparing pellets of the polyethylene (PE) composition provides a good starting material in downstream processing, such as film blowing of PE-fihns. In such films the properties are dependent on how the pellets were made, and it has been realized that desirable films are provided in the process of the present disclosure.DETAILED DESCRIPTION

[0009] According to a first aspect of the present disclosure there is provided a process for preparing pellets of a polyethylene (PE) composition in an extruder device, wherein the process comprises the steps of:a) supplying lignin to the extruder device; b) supplying oil to the extruder device; c) supplying an additive to the extruder device, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO); d) supplying a PE to the extruder device; e) mixing the lignin, the oil, the PE and the additive in the extruder device at a temperature of at least 160 °C to form a PE composition; f) pelletizing the PE composition, wherein the formed pellets comprises:- the lignin in a content of 15-75 wt% by dry weight of the composition;- the oil in a content of 0.5-15 wt% by dry weight of the composition;- the PE in a content of 15-70 wt% by dry weight of the composition; and- the additive in a content of 2-35 wt% by dry weight of the composition

[0010] Within the meaning of the present disclosure an extruder device is a device that melt blends components followed by the ejection of the melt -blended components. Examples of an extruder device includes an extruder, a brabender, a melt compounder, a banbury mixer and a melt kneader.

[0011] The steps a), b), c) and d) can be conducted in any order. They can be conducted as individual steps, at the same time or partly at the same time. The latter is for example if steps a) and b) are conducted simultaneously followed by step c) and step d) conducted one after the other.

[0012] There is no limitation in the source of the lignin. The lignin may be hardwood lignin or softwood lignin. The lignin can also be retrieved from crops, grass, bagasse, bamboo, kenaf, flax, hemp, rice husks, cotton stalks, coconut coir and corn stover. In the case of hardwood lignin or softwood lignin, the lignin is typically obtained from pulping of wood. When wood is pulped, the lignin is separated from the pulp into liquor. The exact composition of the liquor varies and depends on the cooking conditions in the production process and the feedstock. There are various techniques to separate the lignin from the black liquor including Lignoboost® lignin, LignoForce™ lignin, precipitated lignin, and filtrated lignin. Other types of lignindirectly extracted from wood are also possible to use and those includes acetosolv lignin, lignin from soda pulping, organosolv lignin and lignin from biorefinery processes. For the avoidance of doubt, lignosulfonates are also lignin in the meaning of the present disclosure. It is preferred that the lignin has not been grafted with any functional groups, i.e. that the lignin is unmodified, as such grafting step adds complexity, time and cost. The inventors have also realized that there is no need for modification as desired results were obtained when adding unmodified lignin. Nonlimiting examples of such modifications that preferably are omitted are methylolation, hydroxymethylation, acetylation, alkylation, sulfonation, carboxylation, phenolation and oxidation. Accordingly, it is preferred to supply unmodified lignin in step a). The lignin content of the pellets maybe 15-70 wt% by dry weight of the composition, such as 15-65 wt% by dry weight of the composition, such as 20-65 wt% by dry weight of the composition, such as 25-65 wt% by dry weight. It is beneficial from an environmental perspective to incorporate as much lignin as possible, while providing pellets which can be transformed into materials with satisfactory processing and mechanical properties. The dry content of the lignin when supplied in step a) is typically above 90 wt% by dry weight, such as above 93 wt% by dry weight, such as above 95 wt%. Such dry content is beneficial for provision of a stable material flow in the extruder.

[0013] The oil is beneficial for smoother processing and in addition it reduces the smell in the pellets. The inclusion of oil in the composition is also beneficial for downstream products, such as a film blowing process as the one according to the second aspect of the present disclosure. In such process, a smooth film can be formed with reduced or even eliminated bubbles. In addition, certain mechanical properties of such film, e.g. tear strength, have been realized is substantially improved by addition of oil to the pellets. The beneficial effects on reduced bubble formation and improved tear strength was not provided by addition of glycerol as explained below in the EXAMPLE’S section. Bubbles are formed in film-blowing when water or other volatiles are present, or when excessive heating, shearing and / or residence time causes material decomposition. The oil is typically a vegetable oil or a glycidyl ether oil or a modified fatty acid ester. In case the oil is a vegetable oil, it is typically nonmodified vegetable oil, such as rapeseed oil, olive oil, soybean oil, sunflower oil, palm oil, coconut oil, canola oil, corn oil, sesame oil, peanut oil, or epoxidized vegetable oil, such as epoxidized soybean oil or epoxidized cashew nut oil, or mixtures thereof. Incase the oil is glycidyl ether oil, there is typically formed a link to the lignin via an alkylene glycol linkage, i.e. a -0CH2CH(0H)CH20- group and / or a - 0CH2CH(CH20H)0- group. In case the oil is a modified fatty acid ester it is typically an epoxidized fatty acid ester. The oil may also be pre-heated fat from food waste and / or waste from the meat- and fish-producing industries. The content of the oil in the formed pellets may be 0.5-13 wt% by dry weight, such as 2-13 wt% by dry weight.

[0014] The additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO). In the case of the additive bearing maleic anhydride grafts, the content of maleic anhydride grafts in the additive is typically above 0.5 wt% by dry weight, such as above 1 wt% by dry weight. Moreover, such additive typically contains ethylenic units. S-TPE is an unpolar thermoplastic elastomer containing rubbery and crystalline segments. Being nonpolar, also known as unpolar, S-TPE does not contain any polar groups, such as ester groups. TPO is typically an ethylene / alpha-olefm copolymer, such as ethylene / C3-C8 alpha-olefin copolymer. Just as S-TPE is TPO a thermoplastic elastomer void of ester groups. TPO is also known as polyolefin elastomer (POE). The TPO may contain anhydride moieties. Alternatively, the TPO is free of anhydride moieties. The additive content in the formed pellets may be 3-35 wt% by dry weight, such as 5-35 wt% by dry weight, such as 3-20 wt% by dry weight, such as 5-20 wt% by dry weight, such as 3-17 wt% by dry weight, such as 5-15 wt% by dry weight.

[0015] Polyethylene (PE), is a plastic used in several applications, from packaging and containers to toys and furniture. There are different grades of PE including high- density polyethylene (HDPE), low-density polyethylene (LDPE) and low-density polyethylene (LLDPE). The PE is typically low-density polyethylene (LDPE) and / or linear low-density polyethylene (LLDPE). The meaning of the terms HDPE, LDPE and LLDPE are well-known to the skilled person. LDPE has a highly branched structure, resulting in a less compact molecular arrangement and lower density. A typical density of LDPE is 0.905-0.940 g / cm3. LLDPE has a linear structure with short, uniform branches. A typical density is 0.910-0.950 g / cm3. HDPE has a mostly linear structure with minimal branching, leading to high crystallinity and density. A typical density is 0.940-0.980 g / cm3. The density maybe determined according to ISO 1183-1:2019. The PE maybe virgin PE, i.e. made form non-recycled material, thePE may also be recycled PE that has been reprocessed from post-consumer or postindustrial PE waste, turning it back into a usable material. Recycled PE is beneficial as it reduces plastic waste, conserves resources, reduces energy consumption, and minimizes environmental impact. Often the lower degree of purity of recycled PE is negative for the mechanical properties of material from it. However, the inventors have realized that with the process and compositions of the present disclosure this negative effect is reduced or even omitted. Thereby, products containing a high level of recycled PE in combination with lignin can be provided. Such material is also extra beneficial from an environmental perspective as a low amount, or even no amount, of virgin plastics is used. The PE content in the formed pellets maybe 20-65 wt% by dry weight.

[0016] The process typically further comprises the step of: mixing the lignin and the oil prior to supplying the additive as well as the PE to the extruder device. In such case, steps a) and b) are conducted prior to steps c) and d). Typically, the lignin and the oil are mixed in the extruder device, which is preferred since it has been found that it is beneficial to fill the extruder device with lignin before heating to get a stable flow of lignin in the extruder device. Alternatively, the oil and the lignin may be supplied together or one after the other to the extruder device. In yet another alternative, the oil and the lignin are pre-mixed prior to supplying them to the extruder device. In such case, steps a) and b) are conducted simultaneously. Typically, the mixing of the lignin and the oil is at least partially conducted at a temperature in the range 110-250 °C, such as 120-190 °C. Such processing temperature during the mixing is beneficial for good mixing of the lignin and oil, and excess heating gives an uneven product with black particles, while lower temperatures gives an unstable process. In yet another alternative, the additive and the PE are supplied to the extruder device prior to the lignin and the oil. In such case, steps c) and d) are conducted prior to steps a) and b). In such case, typically steps c) and d) are conducted simultaneously followed by steps a) and b) conducted simultaneously.

[0017] Typically, the process comprises a step of evacuation of atmospheric gas and / or moisture conducted after step a) and prior to step f) in the extruder device. Air is sucked out of the lignin to increase density and force the material forward, which is beneficial for material flow and homogeneity of the pellets.

[0018] Step e) may be conducted in the extruder device at a temperature of at least 170 °C to form the PE composition.

[0019] The saccharide content in the lignin according to NREL / TP-510- 42618:2008 is typically below 7 wt% by dry weight, such as below 5 wt% by dry weight, such as below 4 wt% by dry weight. For the avoidance of doubt, the saccharide content refers to the total saccharide content including monosaccharides as well as polysaccharides. NREL / TP-51O-42618:2OO8 is substantially similar to ASTM E1758-01 “Standard method for the Determination of Carbohydrates by HPLC”. Such sugar content of the lignin is beneficial for obtaining good mixing when preparing the PE composition. Moreover, such saccharide content is also advantageous for downstream products made with the composition. For example by minimizing bubble formation as well as formation of a smooth surface of a film produced in a film blowing process as the one according to the second aspect of the present disclosure. These effects are even more favourable if the polysaccharide content is below 2wt% by dry weight.

[0020] By pelletizing the composition, pellets are obtained. Pellets are the same as granules.

[0021] The composition can be used for production of products as is and it can also be used as a masterbatch where the final products is produced via a mixing step of the composition with further components. A masterbatch is thereby an intermediate product.

[0022] As a second aspect of the present disclosure there is provided a process for film blowing a PE film having a lignin content of 2-45 wt% by dry weight from a composition comprising the pellets of the PE composition produced according the first aspect of the present disclosure and a second PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-85 wt% by dry weight and the second PE in a content of 15-93 wt% by dry weight in an extruder device while heating to form a molten mixture;- blow a film from the molten mixture in a film blowing device.

[0023] Preferably, the PE in the pellets is low-density polyethylene (LDPE) and / or linear low-density polyethylene (LLDPE). Typically, the PE in the pellets is a mixtureof LDPE and LLDPE and the dry weight ratio of LDPE to LLDPE is 1:0.3 to 1:2.5, such as 1:1 to 1:2. Such Ratio of LDPE / LLDPE is beneficial for obtaining an even film. The second PE is typically LDPE. To obtain a smooth film with desirable mechanical properties it is desirable to include LLDPE in the film, and from a processing perspective it is advantageous to include the LLDPE in the pellets. Typically, the second PE is LDPE.

[0024] Typically, the pellets are added in a content of 15-65 wt% by dry weight, such as 20-60 wt% by dry weight. Typically, the second PE is added in a content of 35-85 wt% by dry weight, such as 40-80 wt% by dry weight.

[0025] Typically, the temperature of the molten mixture is 180-210 °C, such as 180-200 °C, such as 180-190 °C. It has been found being beneficial to use such temperature to minimize bubble formations in the formed film. In particular 180- 200 °C balances minimized bubble formation with processability.

[0026] The composition typically further comprises a lubricant in a content of 0.5-5 wt% by dry weight of the composition. Examples of lubricants are polymer processing aides such as silicon- and fluoro-based lubricants. Addition of lubricants facilitates a smooth film formation by keeping the extrusion pressure low and preventing dirt to build up.

[0027] Typically, the film blowing composition has a calcium oxide content of <2 wt% by dry weight of the composition. It is beneficial for recyclability to have a low content of calcium oxide in the film because the automatic recycling systems in a recycling plant are interfered by calcium oxide. Regularly, a content of a few percent is needed for processability. However, the inventors have realized that by the inclusion of the pellets with a PE-composition according to the first aspect of the present disclosure, the calcium oxide content in the produced film can be kept low.

[0028] Typically, the lignin content in the produced film is 5-45 wt% by dry weight, such as 5-40 wt% by dry weight, such as 10-30 % by dry weight.

[0029] The examples and embodiments discussed above in connection to the first aspect apply to the second aspect mutatis mutandis.

[0030] As a third aspect of the present disclosure there is provided a film produced according to the second aspect of the present disclosure having a lignin content of 2-45 wt%.

[0031] The film typically has a puncture resistance according to ASTM D5748-95 of at least 30 N. In case the film is used in E-commerce, such puncture resistance is particularly advantageous due to handling and shipping operations.

[0032] The film typically has a tear strength according to ISO 6383-2:1983 in cross direction (CD) of at least 5000 mN and in machine direction (MD) of at least 1000 mN, such as at least 2000 mN.

[0033] The film typically comprises calcium oxide in a content of <2 wt% by dry weight.

[0034] The film typically has a content of oil being 0.1-8 wt%, such as 0.1-5% by dry weight of the film.

[0035] The film typically as a PE content of at least 50 wt%, such as at least 6owt% by dry weight of the film. A typical upper limit is 90 wt% by dry weight of the film.

[0036] Typically, the lignin content in the film is 5-45 wt% by dry weight, such as 5-40 wt% by dry weight, such as 10-30 % by dry weight.

[0037] The examples and embodiments discussed above in connection to the first and second aspects apply to the third aspect mutatis mutandis.

[0038] As a fourth aspect of the present disclosure there is provided a process for injection moulding a PE article having a lignin content of 2-60 wt% by dry weight from an injection moulding composition comprising pellets of the PE composition produced according to the first aspect of the present disclosure and a third PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-95 wt% by dry weight, and the third PE in a content of 5-93 wt% in an extruder device while heating to form a molten mixture;- injection mould the molten mixture in an injection moulding device.

[0039] Typically, the pellets are added in a content of 15-85 wt% by dry weight, such as 20-80 wt% by dry weight. Typically, the third PE is added in a content of 15- 85 wt% by dry weight, such as 20-80 wt% by dry weight.

[0040] The third PE is typically high density polyethylene (HDPE).

[0041] The injection moulding composition typically further comprises a lubricant in a content of 0.5-5 wt% by dry weight of the composition. Examples of lubricants are polymer processing aides such as silicon- and fluoro-based lubricants.

[0042] Typically, the injection moulding composition has a calcium oxide content of <2 wt% by dry weight of the composition. It is beneficial for recyclability to have a low content of calcium oxide in the article because the automatic recycling systems in a recycling plant are interfered by calcium oxide. Regularly, a content of a few percent is needed for processability. However, the inventors have realized that by the inclusion of the pellets with a PE-composition according to the first aspect of the present disclosure, the calcium oxide content in the produced article can be kept low.

[0043] Typically, the lignin content in the produced article is 5-60 wt% by dry weight, such as 10-50 % by dry weight.

[0044] The article typically has a content of oil being 0.1-8 wt%, such as 0.1-5% by dry weight of the article.

[0045] The article typically has a PE content of at least 35 wt%, such as at least 45wt% by dry weight of the article. A typical upper limit is 90 wt% by dry weight of the article.

[0046] The examples and embodiments discussed above in connection to the first aspect apply to the fourth aspect mutatis mutandis.

[0047] As a fifth aspect of the present disclosure, there is provided a PE composition comprising:- lignin in a content of 15-75 wt% by dry weight of the composition;- oil in a content of 0.5-15 % by dry weight of the composition;- PE in a content of 15-70 % by dry weight of the composition; and- an additive in a content of 2-35 % by dry weight of the composition, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO).

[0048] Typically, at least 95% by dry weight of the composition is constituted by the lignin, the oil, the polyethylene and the additive.

[0049] The examples and embodiments discussed above in connection to the first, second, third and fourth aspects apply to the fifth aspect mutatis mutandis.

[0050] As a sixth aspect of the present disclosure there is provided use of a film according to the third aspect of the present disclosure in plastic bags, in e-commerce, in packaging, in agriculture, in transport or protective films.

[0051] Plastic bags are a common type of packaging being lightweight and flexible. They are widely used due to their durability and moisture resistance.

[0052] E-commerce plastic bags are specifically designed for the shipping and handling requirements of online retail.

[0053] Packaging is typically for packaging goods, including food items, to protect them from moisture and dust. This includes shrink wraps, pallet wraps, and food wraps.

[0054] Agriculture is typically as mulch films, greenhouse covers, and silage covers to enhance crop growth and protect from environmental factors.

[0055] Transport is typically surface protection against scratches, dust, and damage during transport or for seat covers, parts wrapping, and other protective applications during manufacturing or repair of vehicles.

[0056] Protective films are typically surface protection against scratches, dust, and damage during manufacturing, transport, or storage.

[0057] The examples and embodiments discussed above in connection to the first, second, third, fourth and fifth aspects apply to the sixth aspect mutatis mutandis.

[0058] Any standard or qualifications mentioned in the present application are to be based on instructions valid on the date of priority of the present application unless stated otherwise.EXAMPLESPreparation of master batches (MBs)Masterbatch 1 (MB1)

[0059] Lignin used as received having a total saccharide content according to NREL / TP-51O-42618:2OO8 of 2.6 wt%, 3.4 wt% or 5.7 wt% and a dry content of above 95% was supplied to a production-scale extruder equipped with a twin-screw ata temperature of 30 °C. Evacuation of atmospheric gas was conducted followed by introduction of oil being either rapeseed oil or glycidyl ether oil into the extruder to mix with the lignin at a temperature of 30 °C. The lignin and oil were forwarded in the extruder and during the forwarding the heat was gradually increased up to a temperature of 170 °C. A second step of evacuation of atmospheric gas including released moisture was conducted. Low-density polyethylene (LDPE) and linear low- density polyethylene (LLDPE) were added together with a compatibilizing additive being an maleic anhydride grafted compound (Retain 3000, Dow Packaging and Speciality Plastics) as well as calcium oxide masterbatch (calcium oxide MB). The lignin, oil, LDPE, LLDPE and additives were subsequently homogenized in the extruder at a temperature of 200 °C, which was followed by cooling as well as a third step of evacuation of atmospheric gas including released moisture conducted at 100- 180 mbar. The mixture was cooled to obtain strands from the extruder which was followed by pelletizing the strands.Masterbatch 2 (MB2)

[0060] MB2 was produced in the same way as MBi but with a different composition and the lignin and oil were forwarded in the extruder and during the forwarding the heat was gradually increased up to a temperature of 130 °C instead of up to 170 °C.Masterbatch 3 (MB3)

[0061] MB3 was produced in a mini extruder according to the procedure of MBi and with epoxidized vegetable oil as the oil. The lignin used had a total saccharide content of 3.4 wt%.Masterbatch 4 (MB4)

[0062] MB4 was produced in the same way as MBi but with the difference that no calcium oxide MB was added. The lignin used had a total saccharide content of 3.4 wt%.Masterbatch 5 (MB5)

[0063] MB5 was produced in the same way as MBi but with the difference that no oil was added. The lignin used had a total saccharide content of 3.4 wt%.Masterbatch 6 (MB6)

[0064] MB6 was produced in the same way as MB2 but with the difference that no oil was added. The lignin used had a total saccharide content of 3.4 wt%.Masterbatch 7

[0065] MB7 was produced in the same way as MBi but with the difference that the compatibilizing additive was instead of the maleic anhydride grafted compound an ethylene vinyl acetate copolymer resin (EVA) having a vinyl acetate content of 9.4 wt% and no anhydride grafts (Escorene Ultra FL 00909, Exxon Mobile). The lignin used had a total saccharide content of 3.4 wt%.Masterbatch (MB8)

[0066] To an extruder equipped with a twin-screw, low-density polyethylene (LDPE). The LDPE was subsequently homogenized in the extruder at a temperature of 200 °C, which was followed by cooling as well as a step of evacuation of atmospheric gas including released moisture conducted at 100-180 mbar. The mixture was cooled to obtain strands from the extruder which was followed by pelletizing the strands.

[0067] In a further comparison, masterbatches were produced using either oil or glycerol. These masterbatches, described below, were prepared in a lab extruder, which is smaller than the extruder used for MB1-MB8. As a consequence, the mixing ability is not as good as in the larger extruder used for MB1-MB8.Masterbatch 9 (MB9)

[0068] MB9 was produced in a similar manner as MBi but with a lab extruder instead of a larger extruder. The lignin used had a total saccharide content of 3.4 wt%.Masterbatch 10 (MB10)

[0069] MB10 was produced in the same way as MB9 but with addition of glycerol instead of oil. The lignin used had a total saccharide content of 3.4 wt%.

[0070] The final compositions of the masterbatches (MB1-10) are presented in Table 1 below.MBi produced with addition of lignin and oil after addition of polymer (MBirev)

[0071] MB1 was also produced in the reverse order, MBirev, wherein the lignin and oil were added after addition of LDPE and LLDE to the extruder.

[0072] LDPE and LLDPE were added together with a compatibilizing additive being an maleic anhydride grafted compound (Retain 3000, Dow Packaging and Speciality Plastics) to the extruder heated to a temperature of 170 °C.

[0073] The lignin having a sugar content of below 6% and a dry content of above95% was separately mixed with oil being either rapeseed oil or glycidyl ether oil at room temperature and thereafter supplied to the extruder to mix with the LDPE and LLDPE at a temperature of 170 °C. A step of evacuation of atmospheric gas including released moisture was conducted.

[0074] The lignin, oil, LDPE, LLDPE and additive was subsequently homogenized in the extruder at a temperature of 200 °C, which was followed by cooling as well as a third step of evacuation of atmospheric gas including released moisture conducted at 100-180 mbar. The mixture was cooled to obtain strands from the extruder which was followed by pelletizing the strands.

[0075] The composition of the pellets were the same as for MBi.Table 1. Final compositions of the prepared masterbatches.aMaleic anhydride grafted compound;bEVA (MB7);cProduced in lab extruder

[0076] MB1, MB2 MB3, MB4, MB8, MB9 and MB10 were easy to process and produced the desired pellets. Likewise, MBirev was easy to process and produced the desired pellets.

[0077] MB5, MB6 and MB7, on the other hand gave unsatisfactory results. For MB5 the components did not mix well and there was a lot of die-drool (due to badly mixed lignin & polymer) which causes the threads to fall apart before pelletizing. It was not possible to produce a sample for film blowing at a reasonable throughput. In the case of MB6 it was possible to produce pellets, but the lignin was not kneaded properly and was still seen as powder reaching the polymer melt. MB7 was difficult to pelletize even if the strings had been allowed to cool down prior to pelletizing. MB7 also gave problems with die-drool.Film blowing

[0078] The masterbatch pellets were mixed with LDPE as well as polymer processing aid (PPA)fluor based and other process additives being colour and antislip. The mixture was heated and processed in an extruder at a temperature of 180- 200 °C at a pressure of 150-350 bar for 15-25 minutes to produce a homogenous melt. Thereafter, the melt was forwarded to a die head of a film blowing device to produce a film.

[0079] The final content of lignin in the films was about 15-25 wt% by dry weight of the films except for in the comparative PE-film produced from MB8 without any lignin.

[0080] The inventors realized that the added oil to the masterbatch gave smoother processing, less bubbles in film-blowing and less smell in the product. Moreover, a temperature below 200 °C was also realized having a positive effect on reduced bubble formation.

[0081] As laid out above, for MB5 it was not possible to produce a sample for film blowing at a reasonable throughput.

[0082] MB6 resulted in unsatisfactory results also in film forming. For MB6, the corresponding film produced had a burnt appearance and was full of large bubbles at the processing temperature and was therefore not measured further.

[0083] MBirev as well as MB3 could also be used to produce smooth films, while MB4 yielded an increased level of bubbles in the produced film.

[0084] The PE-film produced from MB10 containing glycerol gave substantial bubble formation, in particular at a temperature of 200 °C, which e.g. the PE-film from MB9 did not, which successfully produced a film with minimum bubble formation also at 200 °C.Effect of saccharide content of the lignin on film formation

[0085] Regarding the compositions MBi and MB2 as well as the films produced from these MBs an evaluation of lignin having a total saccharide content according to NREL / TP-51O-42618:2OO8 of 2.6 wt%, 3.4 wt% or 5.7 wt% was made. The results are summarized in Table 2 below.Table 2. Summary of the effect of MBs and films produced therefrom on the saccharide content of the lignin used.

[0086] With MBi the lignin with a saccharide content of 5.7% lead to issues producing masterbatch due to mixing very poor mixing so no films were produced. For MB2 the pellets could be produced, although with mixing issues.

[0087] On the other hand, when the saccharide content was 2.6 wt% or 3.4% there was an excellent processability and films were produced. In the case of a saccharide content of 3.4 % the lower polysaccharide content was shown to be beneficial in film formation. It is believed that the calcium oxide forms salts with polysaccharides which are unfavourable to mixing of the melt.

[0088] Overall, it was realized that for the lower saccharide contents films without bubbles could be produced at a broader temperature range in the processing and produced smoother films with reduced or even omitted bubbles. Bubbles are the same as voids.

[0089] For MBirev the bubble formation dependence on the temperature has not been quantified, but from visual inspections it has been observed that at above 190 °C MBi yields fewer bubbles than MBirev.

[0090] For MB7 there was a clear bubble formation at 180 °C and difficult to blow a film as a string of residue was produced in one side of the film and there were many aggregated particles leading to formation of bubbles and the film breakage. Films prepared from MB7 also contained more particles and had poor surface structure and smoothness.

[0091] The inventors thereby realized that the maleic anhydride-grafted additive was exceptionally good compared to other compatibilizers in terms of obtaining a well-dispersed lignin in the LDPE / LLDPE mixture.Properties of the produced films

[0092] The produced films were evaluated with respect to mechanical properties. The following measurements and standards presented in Table 3 were used.Table 3. Measurements and standards used.

[0093] The mechanical properties of the films produced from MB1 as basis for the pellets are presented in Table 4 below. As references, the film produced from MB7 and the PE film produced from MB8 are shown in the table.Table 4. Mechanical properties of films containing MB1, MB7 and MB8.N.M.: Not Measured

[0094] The film produced from MB1 displays an improved tear strength over the pure PE-film. Moreover, the tensile properties are comparable to those of the PE- fihn. On the other hand, the film produced from MB7 displayed tensile properties being impaired compared with the film produced from MB1.

[0095] In addition to the tensile and tear measurements, puncture resistance was measured on the film produced from MBi as well as a commercial fossil-based PE bag used in E-commerce. In E-commerce, the puncture resistance is of particular importance due to such exposure in handling and shipping operations, and such comparison was therefore made. The maximum force of puncture resistance of the film from MBi was 35 N, and in the commercial E-commerce bag it was 37 N. Hence, even though the MBi-film contained 15 wt% lignin, the puncture resistance was substantially the same as in a commercial bag solely based on PE.

[0096] In addition, films were produced using MB9 & MB10 to compare oil with glycerol in the film. Both films were produced on smaller scale with lab equipment. Nevertheless, the comparison between them can be made as both these films were produced in the same way. The results are shown in Table 5 below.Table 5. Mechanical properties of films containing MB9 and MB10.

[0097] As seen, the tear strength in both MD and CD was superior in the films produced with usage of oil instead of glycerol. In MD it was even more than twice as high when using oil instead of glycerol. Moreover, strain at yield in both MD and CD, as well as strain at break in MD were also improved. At the same time, stress at yield was also improved in both MD and CD, while stress at break remained substantially the same. Accordingly, the usage of oil instead of glycerol provides visually more appealing films having reduced bubble formation which also facilitates processing. Moreover, the films have superior mechanical properties, in particular regarding tear strength.

Claims

CLAIMS1. A process for preparing pellets of a polyethylene (PE) composition in an extruder device, wherein the process comprises the steps of: a) supplying lignin to the extruder device; b) supplying oil to the extruder device; c) supplying an additive to the extruder device, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO); d) supplying a PE to the extruder device; e) mixing the lignin, the oil, the PE and the additive in the extruder device at a temperature of at least 160 °C to form a PE composition; f) pelletizing the PE composition, wherein the formed pellets comprises:- the lignin in a content of 15-75 wt% by dry weight of the composition;- the oil in a content of 0.5-15 wt% by dry weight of the composition;- the PE in a content of 15-70 wt% by dry weight of the composition; and- the additive in a content of 2-35 wt% by dry weight of the composition.

2. The process of claim 1, wherein the oil is a vegetable oil or a glycidyl ether oil or a modified fatty acid ester.

3. The process of claim 2, wherein the vegetable oil is rapeseed oil, olive oil, soybean oil, sunflower oil, palm oil, coconut oil, canola oil, corn oil, sesame oil, peanut oil, epoxidized vegetable oil, such as epoxidized soybean oil or epoxidized cashew nut oil, or mixtures thereof.

4. The process according to any one of the preceding claims, wherein the saccharide content in the lignin according to NREL / TP-51O-42618:2OO8 is below 7 wt% by dry weight, such as below 5 wt% by dry weight, such as below 4 wt% by dry weight.

5. A process for film blowing a PE film having a lignin content of 2-45 wt% by dry weight from a film blowing composition comprising the pellets of the PE compositionproduced according to any one of the preceding claims and a second PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-85 wt% by dry weight and the second PE in a content of 15-93 wt% by dry weight in an extruder device while heating to form a molten mixture;- blow a film from the molten mixture in a film blowing device.

6. The process according to claim 5, wherein the PE in the pellets is low-density polyethylene (LDPE) and / or linear low-density polyethylene (LLDPE).

7. The process according to claim 6, wherein the PE in the pellets is a mixture of LDPE and LLDPE and the dry weight ratio of LDPE to LLDPE is 1:0.3 to 1:2.5, such as 1:1 to 1:2.

8. The process according to any one of the claims 5-7, wherein the film blowing composition has a calcium oxide content of <2 wt% by dry weight of the composition.

9. The process according to any one of the claims 5-8, wherein the second PE is LDPE.

10. A film produced according to any one of the claims 5-9 having a lignin content of 2-45 wt%.

11. The film according to claim 10, wherein the film has a puncture resistance according to ASTM D5748-95 of at least 30 N.

12. The film according to claim 10 or 11, wherein the film has a tear strength according to ISO 6383-2:1983 in cross direction (CD) of at least 5000 mN and in machine direction (MD) of at least 1000 mN, such as at least 2000 mN.

13. A process for injection moulding a PE article having a lignin content of 2-60 wt% by dry weight from an injection moulding composition comprising pellets of the PE composition produced according to any one of the claims 1-4 and a third PE, wherein the process comprises the steps:- mixing the pellets in a content of 7-95 wt% by dry weight, and the third PE in a content of 5-93 wt% in an extruder device while heating to form a molten mixture;- injection mould the molten mixture in an injection moulding device.14- A PE composition comprising:- lignin in a content of 15-75 wt% by dry weight of the composition;- oil in a content of 0.5-15 wt% by dry weight of the composition;- PE in a content of 15-70 wt% by dry weight of the composition; and- an additive in a content of 2-35 wt% by dry weight of the composition, wherein the additive is bearing maleic anhydride grafts or is a styrenic thermoplastic elastomer (S-TPE) or is a thermoplastic polyolefin elastomer (TPO).

15. Use of a film according to any one of the claims 10-12 in plastic bags, in e- commerce, in packaging, in wrapping, in agriculture, in transport or protective films.

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