WO2025048695A1

WO2025048695A1 - Lignin-containing composites

Info

Publication number: WO2025048695A1
Application number: PCT/SE2024/050639
Authority: WO
Inventors: Matilda BORG; Johan VERENDEL
Original assignee: Lignin Industries Ab
Priority date: 2023-08-31
Filing date: 2024-06-26
Publication date: 2025-03-06
Also published as: SE2351013A1

Abstract

There is provided a composition comprising: - lignin in a content of 2-45 wt% by dry weight of the composition; - a polymer matrix in a content of 30-90 wt% by dry weight of the composition, and - an additive in a content of 2-35 wt% by dry weight of the composition, wherein o the additive is a thermoplastic elastomer and the polymer matrix is a polyolefin, or o the additive is an ester-containing thermoplastic and the polymer matrix is a copolymer comprising styrene and acrylonitrile or a biodegradable polyester, wherein the ester-containing thermoplastic and the biodegradable polyester are distinct.

Description

LIGNIN-CONTAINING COMPOSITES

TECHNICAL FIELD

[0001] The present disclosure relates to the field of lignin-containing composites, and in particular to composites made from lignin and a polymer matrix together with an additive.

BACKGROUND

[0002] There is a constant strive to provide more environmentally friendly plastics. One alternative to replace traditional plastic material with a component coming from a renewable source.

[0003] One such alternative of a renewable source is lignin. Lignin is the most available natural polymer next to cellulose. Lignin is found in the cell walls of fibrous plants and woods along with cellulose and hemicellulose. Lignin acts as a matrix material for polysaccharides, micro-fibrils and fibres and provides strength to plant stem. It is a phenolic macromolecule that is typically containing three different types of monolignol monomers p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. Most often, lignin that has been separated from wood fibres is used for energy recovery.

[0004] When replacing part of a traditional plastic with lignin, the mechanical properties is often impaired. Hence, there is a desire to improve the mechanical properties of composites based on lignin and plastic.

SUMMARY

[0005] There is an objective of the present disclosure to provide a composition which optimizes the mechanical properties, in particular the impact strength, of lignin-based composites where part of a traditional plastic material has been replaced by lignin.

[0006] Accordingly, the present disclosure provides a composition comprising:

- lignin in a content of 2-45 wt% by dry weight of the composition;

- a polymer matrix in a content of 30-90 wt% by dry weight of the composition, and - an additive in a content of 2-35 wt% by dry weight of the composition, wherein o the additive is a thermoplastic elastomer and the polymer matrix is a polyolefin, or o the additive is an ester-containing thermoplastic and the polymer matrix is a copolymer comprising styrene and acrylonitrile or a biodegradable polyester, wherein the ester-containing thermoplastic and the biodegradable polyester are distinct.

[0007] The inventors have realized that lignin-containing composites having high impact strength can be provided if certain combinations of lignin + polymer matrix + type of additive is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 shows the impact strength of acrylonitrile butadiene styrene (ABS) with different additives as well as ABS without any additive.

[0009] Figure 2 shows the impact strength of ABS + lignin with different additives as well as ABS without any additive.

[0010] Figure 3 shows the impact strength of polypropylene (PP) as well as PP + lignin with and without different additives.

[0011] Figure 4 shows the impact strength of polylactic acid (PLA) as well as PLA + lignin with and without different additives.

DETAILED DESCRIPTION

[0012] As a first aspect, the present disclosure provides a composition comprising:

- lignin in a content of 2-45 wt% by dry weight of the composition;

- a polymer matrix in a content of 30-90 wt% by dry weight of the composition, and

- an additive in a content of 2-35 wt% by dry weight of the composition, wherein o the additive is a thermoplastic elastomer and the polymer matrix is a polyolefin, or o the additive is an ester-containing thermoplastic and the polymer matrix is a copolymer comprising styrene and acrylonitrile or a biodegradable polyester, wherein the ester-containing thermoplastic and the biodegradable polyester are distinct.

[0013] The lignin can be different types of lignin and is typically obtained from pulping of wood pulp. When wood pulp 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 lignin directly 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. There is no limitation in the source of the lignin. The lignin can be hardwood lignin or softwood lignin. The lignin can also be retrieved plant fibres, such as from crops, grass, bagasse, bamboo, kenaf, flax, hemp, rice husks, cotton stalks, coconut coir and corn stover. The lignin content may be 10-45 wt% by dry weight of the composition, such as 5-30 wt% by dry weight of the composition, such as 10-25 wt% by dry weight of the composition. It is beneficial from an environmental perspective to replace the polymer matrix with as much lignin as possible, while providing satisfactory mechanical properties. Accordingly, the preferred range of the lignin content is 10-45 wt% by dry weight of the composition.

[0014] The polymer matrix is either a biodegradable polyester, a copolymer comprising styrene and acrylonitrile or a polyolefin. The IUPAC gold book, i.e. the Compendium of Chemical Terminology, is a book published by the International Union of Pure and Applied Chemistry (IUPAC) containing internationally accepted definitions for terms in chemistry. In accordance with the gold book a copolymer is a polymer derived from more than one species of monomer. Examples of copolymers are copolymers that are obtained by copolymerization of two monomer species sometimes termed bipolymers, copolymers obtained from three monomers sometimes termed terpolymers, and copolymers obtained from four monomers sometimes termed quaterpolymers. Hence, a copolymer comprising styrene and acrylonitrile is a copolymer at least comprising styrene and acrylonitrile as monomeric units. Typically, the copolymer comprising styrene and acrylonitrile is acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA) or styrene acrylonitrile (SAN). The biodegradable polyester is typically polylactic acid (PLA) or polycaprolactone (PCL) or polybutylene adipate terephthalate (PBAT) or polybutylene succinate (PBS) or polyhydroxyalkanoate (PHA) or mixtures therof. The polyolefin is typically polypropylene (PP) or polyethylene (PE). The content of the polymer matrix may be 5O-9Owt% by dry weight of the composition, such as 55-85 wt% by dry weight of the composition, such as 60-80 wt% by dry weight of the composition. The content of the polymer matrix may also be lower, such as 30-75 wt% by dry weight of the composition, such as 30-70 wt% by dry weight of the composition. It is beneficial from an environmental perspective to replace the polymer matrix with as much lignin as possible, while providing satisfactory mechanical properties. Accordingly, a lower polymer matrix content is preferred.

[0015] The content of the additive may be 5-20 wt%, by dry weight of the composition, such as the content of the additive may be 5-35 wt% by dry weight, such as 5-30 wt% by dry weight of the composition, such as 2-20 wt% by dry weight, such as 5-20 wt% by dry weight, such as 3-17 wt% by dry weight of the composition, such as 5-15 wt% by dry weight of the composition, such as 11-15 wt% by dry weight of the composition. If the additive content is too low or too high, unsatisfactory mechanical properties are obtained.

[0016] In a particularly preferred embodiment, by dry weight of the composition the composition comprises 10-45 wt % lignin, 30-75 wt% polymer matrix and 5- 30 wt% additive. Such embodiment is beneficial as it combines a high lignin content being advantageous for environmental impact together with favourable mechanical properties.

[0017] The additive is a thermoplastic elastomer and the polymer matrix is a polyolefin or the additive is an ester-containing thermoplastic and the polymer matrix is a copolymer comprising styrene and acrylonitrile or a biodegradable polyester, wherein the ester-containing thermoplastic and the biodegradable polyester are distinct. The inventors have realized that such combination of additive and polymer matrix together with lignin is beneficial for mechanical properties of the composition. For the avoidance of doubt, by that the ester-containing thermoplastic and the biodegradable polyester are distinct means that they are not the same. Thereby, there are at least three different components in the composition: lignin, a polymer matrix and an additive.

[0018] Without being bound to any theory it is believed that the thermoplastic elastomer and lignin interacts in the polyolefin matrix which is beneficial for the impact strength as well as strain at yield.

[0019] The thermoplastic elastomer is typically a styrenic thermoplastic elastomer (S-TPE) or a thermoplastic polyolefin elastomer (TPO). S-TPE is a thermoplastic elastomer containing rubbery and crystalline segments. S-TPE does not contain any ester groups. Accordingly, S-TPE is not an ester-containing thermoplastic or a thermoplastic polyester elastomer. Typically, the S-TPE is selected from the group consisting of SEBS, SEPS, SBS and SIS or mixtures thereof. For example, SEBS being Styrene-Ethylene-Butylene-Styrene, may be poly[styrene-b-(ethylene-co-butylene)-b- styrene], SEPS being Styrene-Ethylene-Propylene-Styrene, maybe poly[styrene-b- (ethylene-co- propylene)-b-styrene], SBS being Styrene-Butadiene-Styrene, maybe poly[styrene-b-(butadiene)-b-styrene] and SIS being Styrene-Isoprene-Styrene, may be poly[styrene-b-(isoprene)-b-styrene]. For example, the S-TPE maybe a mixture of at least any two of SEBS, SEPS, SBS and SIS.

[0020] The TPO is typically an ethylene/ alpha-olefin 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.

[0021] Ester-containing thermoplastics are polymers that include ester groups (- COO-) in their backbone or side chains. Preferably, the ester-containing additive is a thermoplastic polyester elastomer or methyl methacrylate butadiene styrene (MBS).

[0022] Accordingly, in one embodiment the composition comprises lignin in a content of 2-45 wt% by dry weight of the composition, a biodegradable polyester in a content of 30-90 wt% by dry weight and an ester-containing thermoplastic, preferably a thermoplastic polyester elastomer or methyl methacrylate butadiene styrene (MBS), in a content of 2-35 wt%. A preferred ester-containing thermoplastic when the polymer matrix is a biodegradable polyester is a thermoplastic polyester elastomer. Accordingly, in one preferred embodiment the composition comprises lignin in a content of 2-45 wt% by dry weight of the composition, a biodegradable polyester in a content of 30-90 wt% by dry weight and a thermoplastic polyester elastomer in a content of 2-35 wt%.

[0023] In another preferred embodiment, the composition comprises lignin in a content of 2-45 wt% by dry weight of the composition a copolymer comprising styrene and acrylonitrile in a content of 30-90 wt% by dry weight and an ester- containing thermoplastic, preferably a thermoplastic polyester elastomer or methyl methacrylate butadiene styrene (MBS), in a content of 2-35 wt%.

[0024] Thermoplastic polyester elastomers (TPEEs) are also known as copolyester elastomer (COPE), thermoplastic polyether ester elastomer (also abbreviated TPEE) or thermoplastic copolyester elastomer (TPC). Thermoplastic polyester elastomers contains both rubbery and crystalline segments. For example is MBS a core shell additive having a rubbery core with compatibilizing groups surrounding it.

[0025] The lignin can be either used as received, i.e. unmodified, or chemically modified. Chemically modified lignin is typically carrying one or several of O- substituents of Formulae I-S to VIII-S:

wherein R is comprising at least 4 carbon atoms. For the avoidance of doubt, R’ and R” in Formulae VII-S and VIII-S are not necessarily 4 carbon atoms. Moreover, at least one of R’ and R” contains an ester group. By O-substituents is meant that where the dashed bond line ends there is an oxygen atom. Accordingly, when the substituent is bound to lignin, the following is provided.

[0026] Formula I and II are groups R linked to the lignin via an alkylene glycol linkage, i.e. a -0CH2CH(0H)CH20- group as depicted in Formula I or a - 0CH2CH(CH20H)0- group as depicted in Formula II. Formula I and/or II is obtainable for example by the reaction of lignin with glycidyl ether oil. Typically a mixture of lignin modified with Formula I and lignin modified with formula II is obtained in such reaction. In Formula III the lignin has been modified with groups R linked to the lignin via a carbamate moiety, i.e. a -NHC(=0)0- group obtainable by for example through the reaction of lignin with an isocyanate. Formula IV are groups R linked to the lignin via an ether-linkage. Such linkage is obtainable by for example the reaction of the lignin and a fatty acid methyl ester (FAME). In Formula V the lignin is modified with groups R linked to the lignin via an ester moiety, i.e. a - C(=0)0- group. Formula V is obtainable for example by reacting the lignin with an acyl halide, an anhydride or a carboxylic acid as further described in US2016355535 A. In Formula VI the lignin is modified with groups R linked to the lignin via a dimethylsilyloxy moiety, i.e. a -Si(Me)20- group. Formula VI is obtainable for example by reacting the lignin tert-butyldimethylsilyl chloride. In Formula VII R groups (R’, R”) are linked to the lignin via an opened internal epoxide, i.e. - CH(OH)CH-. R’ and R” maybe of the same type or different type. Formula VII and VIII are obtainable for example by the reaction of lignin with epoxidised fatty acid esters or epoxidized triglycerides.

[0027] In case the lignin is chemically modified, the lignin typically is carrying one or several O-substituents of Formula I-S and/or II-S;

^LS II-S wherein R is being independently selected from C₄-C₂5-alkyl, phenyl, ortho-methyl phenyl, para-methyl phenyl, cyclohexyl, 4-tertbutyl phenyl, 2-ethyl hexyl, cardanyl and nonylphenyl.

[0028] Alternatively, the lignin is chemically modified with an epoxidized fatty acid ester. One example of such ester is Lankroflex™ ED6, and the lignin will in such case be carrying an O-substiuent of Formula VII-S and/or Formula VIII-S. Below is illustrated a typical structure when the lignin is substituted with an epoxidized fatty ester or epoxidized unsaturated triglyceride. In the figures below, R is an alkyl group or a glyceride and both n and m are integers of 0-18. In the left figure is the direct addition product and in the right figure the product obtained by addition and subsequent elimination of water. For the avoidance of doubt, n and m can both be the same integer number but can also be different.

vn-s VIII-S

[0029] The degree of modification of the hydroxyl groups of the lignin can be expressed as number of equivalents to lignin repeating units (eq/ru). The eq/ru may be 0.01 or higher, 0.05 or higher, 0.1 or higher, 0.2 or higher, or 0.4 or higher, or 0.6 or higher, or 0.8 or higher. The eq/ru maybe 0.01-0.8, such as 0.01-0.6, such as 0.01-0.4, such as 0.01-0.2, such as 0.01-0.1.

[0030] Typically, the lignin, the polymer matrix and the additive constitute at least 96.0% by dry weight of the composition, such as at least 98.0% by dry weight of the composition, such as at least 99.0% by dry weight of the composition, such as at least 99.5% by dry weight of the composition.

[0031] Typically, the composition does not contain any metal powder. It is beneficial from an environmental and recycling perspective to not include metal powders.

[0032] As a second aspect, the present disclosure provides a method of extruding an extruded material comprising the composition according to the first aspect of the present disclosure, comprising the steps of: a. mixing a composition according to the first aspect of the present disclosure; b. melt extruding the composition to form an extruded material; c. optionally, turning the extruded material into pellets or powder; and d. optionally, drying the extruded material.

[0033] Mixing the composition according to the first aspect of the present disclosure is typically done by melt compounding. The compounding can be conducted in a pre-step prior to extruding the mixture so that step a. and step b. are conducted in two separate equipment. In such case either a twin screw extruder or a single screw extruder can be used. Alternatively, the mixing is conducted inside an extruder by melt compounding so that step a. and step b. is conducted in the same equipment. In such case it is preferred to use a twin screw extruder to obtain good mixing. The extruded material obtained in step b. may be turned into pellets or powder which may then be dried. Turning the extruded material into pellets in step c. is typically conducted by cutting and turning the extruded material into powder in step c. is typically conducted by cutting and/or grinding.

[0034] Melt extrusion may be conducted at a temperature of at least 65°C, such as at least 70 °C, such as 70-250 °C.

[0035] The examples and embodiments discussed above in connection to the first aspect apply to the second aspect mutatis mutandis.

[0036] As a third aspect, the present disclosure provides a method of injection moulding a product comprising the composition according to the first aspect of the present disclosure, comprising the steps of: i. providing pellets or powder of the composition according to the first aspect of the present disclosure; ii. optionally, mixing the pellets or powder with an additional polymer matrix to provide a mixture; hi. melting the pellets or powder or mixture into a melt; and iv. injection moulding the melt into a desired shape.

[0037] Melting the composition maybe done at a temperatures of at least 75°C, such as at least 8o°C, such as 80-240 °C. The pellets or powder of the composition according to the first aspect of the present disclosure may be the pellets or powder obtainable from the extrusion according to the second aspect of the present disclosure. Injection moulding facilitates provision of complex shapes and structures to be prepared.

[0038] Preferably, in case of mixing the pellets or powder with an additional polymer matrix to provide a mixture, the additional polymer matrix is the same type of polymer matrix as the polymer matrix present in the pellets or powder. In the case of mixing the pellets or powder with an additional polymer matrix, the pellets or powder are a masterbatch mixed with additional polymer matrix to provide a final composition of a desired end product. The preparation of the masterbatch and the desired end product can be conducted at two different locations. Alternatively, they are conducted at the same location, i.e. within the same facility.

[0039] Typically, mixing of the pellets or powder with an additional polymer matrix to provide a mixture is made in the following contents. Pellets or powder in a content of 1-65 wt% by dry weight, and the additional polymer matrix in a content of 35-99 wt%. The pellets or powder may be added in a content of 15-65 wt% by dry weight and the additional polymer matrix maybe added in a content of 35-85 wt% by dry weight.

[0040] The examples and embodiments discussed above in connection to the first and second aspects apply to the third aspect mutatis mutandis.

EXAMPLES

Preparation of compositions

[0041] Composites were prepared consisting of lignin (16 wt%) additive (11 wt%) and polymer matrix (73 wt%) by melt blending the components at a temperature of 70-200 °C.

[0042] The lignin was provided as a dried powder and was used either as received, i.e. unmodified, or modified by introduction of an alkylene glycol linkage by reacting the lignin with glycidyl ether oil to provide the lignin with a O-substituents of Formula I-S and/or II-S, R being a Ci2-Ci4-alkyl or an ortho methyl phenyl. Lignin was also provided as lignosulfonates.

^LS II-S

[0043] The additives used were: thermoplastic polyester elastomer also known as thermoplastic copolyester elastomer (TPC) (Skypel G130D, SK Chemicals), methyl methacrylate butadiene styrene (MBS) (Paraloid EXL-2650J, Dow), styrenic thermoplastic elastomer (S-TPE) (C2000, Kraton), thermoplastic polyurethane elastomer (TPU), acrylonitrile butadiene rubber (NBR), polybutylene adipate terephthalate (PBAT), as well as two thermoplastic polyolefin elastomers (TPO) being ethylene octene copolymer functionalized with maleic anhydride (TPO-1) (SCONA TSPOE 1002GBLL) and polypropylene elastomer functionalized with maleic acid anhydride (TPO-2) (SCONA TSPPR 30113 GB).

[0044] The polymer matrix was either acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) or polypropylene (PP).

[0045] Composites were also prepared with the same process as above blending modified lignin (30 wt%), TPC (20 or 30 wt%; Arnitel) and ABS (50 or 60 wt%).

Impact strength test - Charpy impact test

[0046] The impact strength was evaluated using Charpy impact test. This test determines how much energy a material absorbs during fracture and can thus be used to determine the impact strength of a material. The measurements were conducted according to ISO 179-1:2000.

[0047] The sample size was 80 x 10 x 4 mm (length x width x thickness) with a 45⁰ V-notch machined in the middle of the sample having a radius of the notch tip of 0.25 mm (Type A according to ISO 179-1:2000). The measurement is done by releasing a pendulum with a determined weight from a determined angle. The energy needed to break the sample is measured by finding to what angle the pendulum is raised after the break and is measured in joule. The energy absorbed was divided by the cross- sectional area of the sample at the V-notch to calculate the impact strength.

[0048] In table 1 below, the impact strengths of the different composites are presented and compared with the polymer matrices without any lignin added. As a reference, also the impact strength of the neat polymer matrices without any additive “none” is presented. The comparison is expressed in percentage, a positive percentage means an improvement in impact strength and a negative percentage means that the additive reduced the impact strength.

[0049] The data of the impact strength measurements is also presented in figures 1-4.

Table 1. Results from measurements of impact strength.

*Unmodified lignin; **Lignosulfonates; ***20 wt% TPC; **** 30 wt% TPC

[0050] In Figure i as well as Table i, the impact strength of ABS as well as ABS + lignin with four different additives is presented. In Figure i a dashed line has been inserted for visual guidance of the impact strength of neat ABS without any additive added, the sample denoted “none”. As can be seen, TPU was the best additive providing an improvement in impact strength of nearly 50 %.

[0051] In Figure 2 as well as Table 1, the impact strength of ABS as well as ABS + lignin with six different additives is presented. In Figure 2 a dashed line has been inserted for visual guidance of the impact strength of ABS + lignin without any additive added, the sample denoted “none”. The inventors have realized that for a mixture of ABS + lignin, the additives TPC and MBS, both being ester-containing thermoplastics, were the best additives giving an increase in impact resistance of about 90 %. Hence, it was not the expected additive TPU that was the best for neat ABS that gave the best results. In fact, TPU being the best for neat ABS, gave only a minor improvement to the ABS+lignin composite of about 5 %.

[0052] Moreover, according to the manufacturer of the TPC, this compound is not even sold or advertised as being an additive, but a resin to be used by itself for injection moulding and/or extrusion. The inventors have thereby realized, in contrary to the information by the manufacturer, that TPC is suitable as an additive for improving impact strength and that, in contrary to neat ABS, the impact strength is significantly improved in the mixture of ABS + lignin.

[0053] Regarding MBS, according to the manufacturer, it is designed to improve impact resistance of polycarbonate (PC) or polybutylene adipate terephthalate (PBAT). ABS is not mentioned as a polymer matrix by the manufacturer. This was confirmed, as shown in Fig. 1, wherein MBS does not improve the impact resistance of ABS. Hence, the inventors have unexpectedly realized that MBS is improving the impact strength of ABS when the ABS is mixed with lignin.

[0054] Both modified and unmodified lignin was added to the ABS and TPC additive and as seen in Figure 2 and Table 1 there is substantial improvement of about 40 % in impact strength. The composite consisting of ABS + unmodified lignin + TPC outperformed the composites of ABS + modified lignin + additive being TPU or S-TPE or NBR or PBAT. Moreover, the composite with ABS + lignosulfonates + TPC also outperformed the composites of ABS + modified lignin + additive being TPU or S-TPE or NBR or PBAT. Furthermore, also for addition levels of the additive of 20wt% and 30 wt% the effect has been shown.

[0055] In Figure 3 as well as Table 1, the impact strength of PP with and without an additive as well as PP + lignin with and without four different additives is presented. In Figure 3 a dashed line has been inserted for visual guidance of the impact strength of PP + lignin without any additive added, the sample denoted “none”. Turning to Figure 3, neat PP without any lignin or additive has about twice as high impact strength as when lignin replaced part of the PP but no additive was added (2.7 kJ/m² of PP+lignin compared with 5.5 kJ/m² for neat PP).

[0056] Addition of TPC as an additive to PP without any lignin added slightly decreased the impact strength of the PP (4.9 kJ/m² of PP + TPC compared with 5.5 kJ/m² for neat PP). On the other hand, using TPC as additive improved the impact strength for the mix of lignin and PP compared with lignin and PP without any additive by 22.2 %. However, the impact strength was still well below the one of neat PP as well as the one for PP+TPC (3.3 kJ/m² of PP+lignin+TPC compared with 5.5 kJ/m² for neat PP and 4.9 kJ/m² for PP + TPC). There was a decrease of about 40% in impact strength when comparing neat PP with PP+lignin+TPC.

[0057] The inventors then realized that if adding the additive S-TPE to PP+lignin, the impact strength was improved almost 300 % compared with PP + lignin without any additive added (10.5 kJ/m² of PP+lignin+S-TPE compared with 2.7 kJ/m² for PP+lignin).

[0058] Thereby, two insights were made, the impact strength is improved over PP + lignin when S-TPE is added to an even higher extent than for neat PP + S-TPE (PP+lignin+S-TPE improved 288.9% while lignin+S-TPE improved 96.4%), and the impact strength is also of substantially the same value as neat PP + additive (10.5 kJ/m² of PP+lignin+S-TPE compared with 10.8 kJ/m² for PP+S-TPE). That is, PP can surprisingly be partially replaced by lignin and yet a composite that does not compromise with the impact strength is provided when adding S-TPE as an additive. Such composite also outperforms neat PP in terms of impact strength. Without being bound to any theory it is believed that the S-TPE and lignin interacts in the PP matrix yielding such high impact strength as if it would be no lignin in the mix.

[0059] S-TPE added to PP without any lignin provided an increased impact strength of 96.4%. Therefore, it was expected that the maximum increase in impact strength for a mixture of PP+lignin upon inclusion of S-TPE would also be 96.4%, i.e. from 2.7kJ/m² to 5.3 kJ/m². Surprisingly, the impact strength of PP+lignin+S-TPE was about twice as high as the maximum expectation. The inventors surprisingly realized that addition of S-TPE provided a composite containing PP and lignin with about the same impact strength as the maximum obtained impact strength for neat PP without any lignin.

[0060] Further, addition of TPO-1 to PP without any lignin provided about the same impact strength as the one of neat PP (-4%). When lignin was added to PP, the impact strength decreased about 50%, while when TPO-i was included in a mixture of PP+lignin the impact strength was improved with 74% over PP+lignin. In fact, it was almost the same as for neat PP (4.7 kJ/m² for PP+lignin+TPO-1 compared with 5.5 kJ/m² for PP). The inventors thereby realized that even though TPO-i added to PP does not provide any significant difference in impact strength, part of the PP can be replaced with lignin and still have about the same impact strength as neat PP if the lignin is added together with TPO-i. Similarly, when TPO-2 was added with the lignin, the impact strength was even slightly improved of the mixture of PP+lignin+TPO-2 compared with the neat PP.

[0061] In Figure 4 as well as Table 1, the impact strength of PLA as well as PLA + lignin without an additive as well as PLA + lignin with 2 different additives is presented. Turning to Figure 4, neat PLA without any lignin or additive has about the same impact strength as PLA + lignin without any additive. The inventors have then realized that for PLA + lignin, the best additive is TPC providing an improvement in impact strength of about 100 %, which outperforms S-TPE as an additive.

[0062] Moreover, as laid out above regarding ABS, according to the manufacturer of the TPC, this compound is not even sold or advertised as being an additive, but a resin to be used by itself for injection moulding and/or extrusion. The inventors have thereby also realized regarding PLA that, in contrary to the information by the manufacturer, TPC is suitable as an additive for significantly improving the impact strength in the mixture of PLA + lignin.

Strain at yield

[0063] In addition to the impact strength, the strain at yield was evaluated for the composites containing PP, S-TPE and lignin. Strain at yield specifically refers to the amount of strain (elongation) the composite has undergone when it reaches its yield point during the tensile test. It is a critical measure because it indicates the composites’ ability to undergo non-plastic deformation when exposed to mechanical strain. The strain at yield was determined according to ASTM D638 - 14. In Table 3 below, the strain at yield of the different composites is presented and compared with the neat PP without any lignin or additive added.

[0064] The lignin was added either in a content of 20 wt% by dry weight compared with a reference of 25 wt% by dry weight or in a content of 40 wt% by dry weight compared with a reference of 50 wt% by dry weight. It is believed that a reference having 40 wt% lignin without any S-TPE added would give similar results as the reference having 50 wt% lignin without any S-TPE added as both contain a high amount of poorly compatibilized lignin in the PP.

Table 3. Strain at yield for composites having PP as polymer matrix.

[0065] Thereby, the inventors realized that also the strain at yield was maintained or even improved upon addition of S-TPE to PP and lignin. For example, by addition of 10% S-TPE, 40% of the PP could be replaced with lignin and still provide the same strain at yield as the neat PP. By addition of 10% of S-TPE together with a 20% replacement of PP for lignin, the strain at yield was even improved by about 20% compared with neat PP.

ITEMIZED LIST OF EMBODIMENTS

1. A composition comprising: - lignin in a content of 2-45 wt% by dry weight of the composition;

- a polymer matrix in a content of 50-90 wt% by dry weight of the composition, and

- an additive in a content of 2-20 wt% by dry weight of the composition, wherein o the additive is a thermoplastic polyester elastomer and the polymer matrix is a biodegradable polyester or a copolymer comprising styrene and acrylonitrile, or o the additive is methyl methacrylate butadiene styrene (MBS) and the polymer matrix is a copolymer comprising styrene and acrylonitrile, or o the additive is a styrenic thermoplastic elastomer (S-TPE) and the polymer matrix is a polyolefin.

2. The composition according to claim 1, wherein the biodegradable polyester is polylactic acid (PLA) or polycaprolactone (PCL).

3. The composition according to claim 1 or 2, wherein the copolymer comprising styrene and acrylonitrile is acrylonitrile butadiene styrene (ABS) or acrylonitrile styrene acrylate (ASA) or styrene acrylonitrile (SAN).

4. The composition according to any one of the preceding claims, wherein the polyolefin is polypropylene (PP) or polyethylene (PE).

5. The composition according to any one of the preceding claims, wherein the lignin content is 5-30 wt% by dry weight of the composition, such as 10-25 wt% by dry weight of the composition.

6. The composition according to any one of the preceding claims, wherein the content of the polymer matrix is 55-85 wt% by dry weight of the composition, such as 60-80 wt% by dry weight of the composition.

7. The composition according to any one of the preceding claims, wherein the thermoplastic polyester elastomer is a copolyester elastomer (COPE), thermoplastic polyether ester elastomer (TPEE) or thermoplastic copolyester elastomer (TPC). 8. The composition according to any one of the preceding claims, wherein the content of the additive is 3-17 wt% by dry weight of the composition, such as 5-15 wt% by dry weight of the composition, such as 11-15 wt% by dry weight of the composition.

9. The composition according to any one of the preceding claims, wherein the lignin is a chemically modified carrying one or several of the O-substituents of Formula I-S to VI-S

wherein R is comprising at least 4 carbon atoms.

10. The composition according to claim 9, wherein the chemically lignin is carrying one or several O-substituents of Formula I-S and/or II-S;

^LS II-S wherein R is independently selected from C₄-C₂5-alkyl, phenyl, ortho-methyl phenyl, para-methyl phenyl, cyclohexyl, 4-tertbutyl phenyl, 2-ethyl hexyl, cardanyl and nonylphenyl. 11. A method of extruding an extruded material comprising the composition according to any one of the preceding claims, comprising the steps of: a. mixing a composition according to any one of the preceding claims; b. melt extruding the composition to form an extruded material; c. optionally, turning the extruded material into pellets or powder; and d. optionally, drying the extruded material.

12. A method of injection moulding a product comprising the composition according to any one of the claims 1-10, comprising the steps of: i. providing pellets or powder of the composition according to any one of the claims 1-10; and ii. melting the pellets or powder into a melt; and in. injection moulding the melt into a desired shape

Claims

1. A composition comprising:

- lignin in a content of 2-45 wt% by dry weight of the composition;

2. The composition according to claim 1, wherein the biodegradable polyester is polylactic acid (PLA) or polycaprolactone (PCL) or polybutylene adipate terephthalate (PBAT) or polybutylene succinate (PBS) or polyhydroxyalkanoate (PHA) or mixtures therof.

5. The composition according to any one of the preceding claims, wherein the lignin content is 10-45 wt% by dry weight of the composition, such as 5-30 wt% by dry weight of the composition, such as 10-25 wt% by dry weight of the composition.

6. The composition according to any one of the preceding claims, wherein the content of the polymer matrix is 30-75 wt% by dry weight of the composition, such as 50-90 wt% by dry weight of the composition, such as 55-85 wt% by dry weight of the composition, such as 60-80 wt% by dry weight of the composition.

7. The composition according to any one of the preceding claims wherein the ester-containing thermoplastic is a thermoplastic polyester elastomer or methyl methacrylate butadiene styrene (MBS).

8. The composition according to any one of the preceding claims, wherein the thermoplastic elastomer is a styrenic thermoplastic elastomer (S-TPE) or a thermoplastic polyolefin elastomer (TPO).

9. The composition according to claim 8, wherein the S-TPE is selected from the group consisting of SEBS, SEPS, SBS and SIS or mixtures thereof.

10. The composition according to claim 8, wherein the TPO is an ethylene/ alphaolefin copolymer, such as ethylene/C3-C8 alpha-olefin copolymer.

11. The composition according to any one of the preceding claims, wherein the content of the additive is 5-35 wt% by dry weight, such as 5-30 wt% by dry weight, such as 2-20 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, such as 11-15 wt% by dry weight of the composition.

12. The composition according to any one of the preceding claims, wherein the lignin is a chemically modified carrying one or several of the O-substituents of Formula I-S to VIII-S

wherein R is comprising at least 4 carbon atoms.

13. The composition according to claim 12, wherein the chemically lignin is carrying one or several O-substituents of Formula I-S and/or II-S;

^LS II-S wherein R is independently selected from C₄-C₂5-alkyl, phenyl, ortho-methyl phenyl, para-methyl phenyl, cyclohexyl, 4-tertbutyl phenyl, 2-ethyl hexyl, cardanyl and nonylphenyl or wherein the chemically modified lignin is carrying one or several O-substituents of Formula VII-S and/or VIII-S, wherein the chemically modified lignin is having a formula according to:

VII-S VIII-S wherein both n and m are integers of 0-18 and R is an alkyl group or a glyceride.

14. A method of extruding an extruded material comprising the composition according to any one of the preceding claims, comprising the steps of: a. mixing a composition according to any one of the preceding claims; b. melt extruding the composition to form an extruded material; c. optionally, turning the extruded material into pellets or powder; and d. optionally, drying the extruded material.

15. A method of injection moulding a product comprising the composition according to any one of the claims 1-13, comprising the steps of: i. providing pellets or powder of the composition according to any one of the claims 1-13; ii. optionally, mixing the pellets or powder with an additional polymer matrix to provide a mixture; hi. melting the pellets or powder or mixture into a melt; and iv. injection moulding the melt into a desired shape.