A biodegradable composite, a method for manufacture thereof, and articles made of said composite

Abstract

The present invention relates to biodegradable composites and methods for manufacture thereof. The biodegradable composites can be used to produce packaging and various disposable and reusable articles, and disposable cutlery such as plates, cups, forks, and spoons. The composite biodegrades under compost conditions within a maximum of 90 days. The biodegradable composite comprises a polybutylene succinate of 60 to 90 % by weight; and a lignocellulose containing filler of 10 to 40 % by weight. The filler is at least a mix of grains, hemp and fruits.

Description

[0001] A BIODEGRADABLE COMPOSITE, A METHOD FOR MANUFACTURE THEREOF, AND ARTICLES MADE OF SAID COMPOSITE

[0002] DESCRIPTION

[0003] Field of the invention

[0004]

[0001] The present invention relates to biodegradable composites and methods for the manufacture thereof. The composites can be used for the production of packaging and various disposable and reusable articles, and disposable cutlery such as plates, cups, forks, and spoons.

[0005] Background of the invention

[0006]

[0002] Biodegradable biopolyesters, such as polylactide material, and lignocellulosebased composites based on these polymers are widely used for packaging and other articles (Murariu, M., Dubois, P. PLA composites: From production to properties (2016) Advanced Drug Delivery Reviews, 107, pp. 17-46). Known techniques include moulding polymeric materials in the molten state at elevated temperatures, which is above 150°C.

[0007]

[0003] The extrusion processing technique is used for PLA material. The extrusion is carried out, for example, in a single-worm extruder. The disadvantages of this technique are the degradation of the polymer material during extrusion, the low viscosity of the polymers and the limited possibility of viscosity adjustment. PLA polymer materials are characterized by limited biodegradability under normal room temperature conditions in compost. Efficient biodegradation of such PLA polymers and composites in compost takes place only under industrial conditions above 50 °C (Rosli, N.A., Karamanlioglu, M., Kargarzadeh, H., Ahmad, I. Comprehensive exploration of natural degradation of poly(lactic acid) blends in various degradation media: A review. (2021) International Journal of Biological Macromolecules, 187, pp. 732-741).

[0008]

[0004] There is a known technique for producing packaging using extruded lignocellulosic waste (Ahankari, S.S., Subhedar, A.R., Bhadauria, S.S., Dufresne, A. Nanocellulose in food packaging: A review. (2021) Carbohydrate Polymers, 255, art. no. 117479). The disadvantage of the known lignocellulosic compositions used for such food packaging and articles is that the natural biodegradable polymers (cellulose, hemicellulose) of the lignocellulosic materials used degrade very rapidly under composting conditions and such polymeric materials are unsustainable in the environment, especially when in contact with aqueous media and moisture.

[0009]

[0005] A composite of PLA, lignocellulose, wood chips and dust for biodegradable food packaging is also known (Pilla, S., Gong, S., O'Neill, E., Rowell, R.M. and Krzysik, A.M. (2008), Polylactide-pine wood flour composites. Polym Eng Sci, 48: 578-587), the production of which involves thermoplastic mixing of up to 40 % pine wood dust and PLA polymer in an extruder and subsequent injection moulding of the polymer composite. A silane-based additive is used as a modifier to increase the bonding between the lignocellulose and the polymer matrix and to improve the mechanical properties of the material. The implementation of this method involves a 2-step process, namely extrusion, and compression, while the use of the toxic silane additive limits food contact, and impairs processability by increasing viscosity, and biodegradation by increasing the degree of cross-linking.

[0010]

[0006] The object of the invention is to overcome abovementioned problems and to prepare a composite with performance characteristics that permit use in contact with food, to provide such mechanical and rheological properties that are sufficient for the manufacture of various articles such as plates, cups, forks, spoons, and to biodegrade under compost conditions within a maximum of 90 days.

[0011] Summary of the invention

[0012]

[0007] The aim is reached by design of a biodegradable composite, a method for manufacture thereof and articles made of said composite as stated in the claims.

[0013]

[0008] The biodegradable composite comprises biopolyester, which is a polybutylene succinate, and a lignocellulose containing filler. The polybutylene succinate is 60 to 90 % by weight of the composite, while the lignocellulose containing filler is 10 to 40 % by weight of the biodegradable composite.

[0009] The lignocellulose containing filler is a mix of grains, hemp and fruits, such as apples. In addition, coffee grounds can be added. The fruits and berries are selected from the group of apples, pears, guavas, quince, plums, gooseberries, oranges, and combination thereof. Those fruits are selected because they contain high amounts of pectin and organic acids. Hemp is important component as it provides to the biodegradable composite such properties as increased thermos-insulation and strength. Hence, the articles, where a thermal-insulation is necessary, such a coffee cups, can be produced without any additional technical features to added to such articles.

[0014]

[0010] In one embodiment of the invention the lignocellulose containing filler comprises a combination of grains, fruits, and hemp, and wherein the grains are 30 to 50 % by weight of the filler; the fruits are 30 to 50 % by weight of the filler, and the hemp is 10 to 30 % by weight of the filler.

[0015]

[0011] By using aforementioned mix and concentrations of the fillers, upgraded mechanical properties can be obtained compared to known biodegradables such as biopolyester, especially polybutylene succinate, while maintaining desired biodegradability. Various articles can be made from the biodegradable composite such as but not limited to food containers, plates, spoons, forks, cups, films, or laminates.

[0016]

[0012] Another embodiment of the invention involves a biodegradable composite that comprises polybutylene succinate that is 60 to 90 % by weight of the composite, while the lignocellulose containing filler that is 10 to 40 % by weight of the composite. The lignocellulose containing filler comprises grains in amount of 30 to 50 % by weight of the filler, hemp in amount of 30 to 50 % by weight of the filler, and fruits in amount of 10 to 30 % by weight of the filler.

[0017]

[0013] Hemp provides mechanical tensile strength by acting as a binding agent for the internal structural elements, grains provide mechanical resistance to compression and deformation, and apples provide elasticity, internal deformability, and plasticity. Concentrations of less than 10 % by weight of the filler do not improve the biodegradability of the composite. The filler concentrations above 40 % by weight are not desirable as the mechanical properties of the composite deteriorate. It becomes too hard and difficult to process and mould. The optimum limit of the filler concentration up to which positive technical effects can be achieved is between 10 and 60 % by weight, preferably 10 and 40 % by weight. The pectin and other organic substances (mainly acids) in the apples, as well as the acids in the coffee grounds, improve the bond between the filler particles and the polymer matrix. The physicochemical properties of the filler components are complementary and have a synergistic effect, providing viscosity, mechanical and rheological properties of the composite, allowing production of different packaging and food containers and allowing biodegradation of the used products, solving the problem of waste disposal. Coffee grounds have similar properties to the blend of grains, hemp, and apples. The use of the developed fillers in the composite allows the use of the toxic modifier silane to be avoided and, by ensuring the sorption of harmful by-products of the polymerization process, increases the possibility of the products being used in contact with food products.

[0018]

[0014] The object of the invention is also a method for manufacture of said biodegradable composite. The method comprises the steps of: a) drying the lignocellulose containing filler; b) grinding of the dried filler; and c) mixing the ground filler with the polybutylene succinate so that the polybutylene succinate is 60 to 90 % by weight of the mix and the ground filler is 10 to 60 % by weight of the mix. The step of mixing is performed by extrusion mixing and in a temperature that is above a melting temperature of the polybutylene succinate, in result of which the biodegradable composite is obtained.

[0019]

[0015] The step of extrusion may be performed by use of a twin-screw extruder. The extrusion itself facilitates bonding of polybutylene succinate with lignocellulose containing filler. One embodiment of extrusion may involve the following parameters: temperature of 150°C, extrusion time of 7 min, a rotation speed of the twin-screw extruder of 70 rpm, a torque of extrusion of 200 Nm.

[0020]

[0016] Other aspect of the present method of manufacture includes drying of the filler. Drying is necessary to remove excess moisture in the filler. The permissible moisture content of the filler shall be limited to 10 % by the weight of water. Convection dryer with a temperature above 60°C is optimal for drying. The particle size of filler components may range from 10 nm to 1 mm, but for most applications it is advisable to use filler components with the particle size smaller than 0.25 mm. The particle size should be adapted to the formation of thin polymer films and other articles. The size should be optimized for an energy-efficient solution based on the desired mechanical properties of the composite for a specific product type, including the requirements for fast and efficient grinding of the filler components.

[0021] Brief description of drawing

[0022]

[0017] The drawings illustrate through examples embodiments of the invention falling within the scope of the invention as defined by the claims.

[0023]

[0018] Fig. 1 illustrates one of rheological curves of some embodiments of the biodegradable composites. The rheological curves are complex viscosity curves. It illustrates viscosity of a composite comprising only a polybutylene succinate (PBS - FD92), and a biodegradable composite comprising polybutylene succinate and 10 %, 20 %, 30 % and 40 % by weight of the lignocellulose containing filler, wherein the filler is a mix of grains in amount of 40 % by weight, hemp in amount of 40 % by weight and fruits, such as apples, in amount of 20 % by weight (marked as 10% to 40% in Fig. 1).

[0024]

[0019] Fig. 2 illustrates a strength deformation property (stress-strain graph) of polybutylene succinate (PBS) and biodegradable composites of various amounts of fillers, from 10 % to 40 % by weight (marked as 10% to 40% in Fig. 2).

[0025]

[0020] Fig. 3 illustrates a strength deformation property (modulus) of polybutylene succinate and biodegradable composites comprising polybutylene succinate and various amounts of filler, from 10 % to 40 % by weight (marked as 10% to 40% in Fig. 3).

[0026] Detailed description of the embodiments

[0027]

[0021] The embodiments of the invention are described with reference to figures to illustrate the objectives, the advantages and efficiency of the present invention.

[0028]

[0022] In one embodiment of the invention the biodegradable composite comprises a polybutylene succinate PBS FZ71 (MCCP) of 60 to 90 % by weight; and a lignocellulose containing filler of 10 to 40 % by weight, wherein the filler comprises grains in amount of 40 % by weight, hemp in amount of 40 % by weight, and apples in amount of 20 % by weight. The processing of the filler components includes drying for 24 hours in a freezedrier and subsequent mechanical grinding. The grinding is performed in 3 stages in a Retsch planetary crusher at 1500 rpm using 4 mm, 2 mm and 0.25 mm sieves. Ground apples and grains were found to form spherical particles, while hemp formed a fibrous reinforcement. A thermoplastic mixer - Brabender extruder - was used for mixing. The mixing conditions were 150°C, 7 min, 70 rpm, and 200 Nm. A Carver press (135°C, 1.5 min heating, 3 min under 3 tons pressure, 4 min cooling, 0.5 mm thickness) was used for extrusion. The biodegradable composite obtained has good processability, as shown by the rheological curves in Fig. 1. The increase in complex viscosity and the change in rheological properties are relatively small, even at the maximum filler level of 40 % weight.

[0023] The biodegradable composites exhibit adequate mechanical properties suitable for the manufacture of packaging, household food containers, and other articles. The compressive strength was the highest at an amount of the filler of 30 % by weight, and at 40 % by weight obtained 11 MPa, which is sufficient for packaging applications. The mechanical and rheological properties of the filler 10 % by weight allows the manufacture of films and laminates. Biodegradable composites with 20 % and 40 % of weight provide sufficient mechanical stiffness and are suitable for the manufacture of a variety of containers, cups, cutlery, and rigid containers.

[0029]

[0024] Fig. 2 illustrates a strength deformation property (stress-strain graph) of polybutylene succinate (PBS) and biodegradable composites of various amounts of fillers, from 10 % to 40 % by weight (10% to 40%). The tests were performed in order to identify the physical properties of the biodegradable composite. Multiple samples were prepared. A reference sample was a sample comprising 100% by weight the polybutylene succinate (PBS). Other four samples were prepared as follows. The filler was made comprising mix of grains, hemp and fruits. The grains were 40 % weight, hemp 40 % weight and fruits, mainly apples, 20 % weight. One biodegradable composite sample comprised a mix of polybutylene succinate and filler of 10 % by weight (10%). Second biodegradable composite sample comprised a mix of polybutylene succinate and filler of 20 % by weight (20%). Third biodegradable composite sample comprised a mix of polybutylene succinate and filler of 30 % by weight (30%), and fourth biodegradable composite sample comprised a mix of polybutylene succinate and filler of 40 % by weight (40%). In stress-strain graph as seen in Fig. 2 it is evident that the biodegradable composites have higher stress values than pure polybutylene succinate (PBS). Hence, the new biodegradable composites (10% to 40%) are stronger than the material comprising polybutylene succinate of 100 % by weight (PBS).

[0030]

[0025] Fig. 3 illustrates a strength deformation property (modulus) of polybutylene succinate and biodegradable composites comprising polybutylene succinate and various amounts of filler, from 10 % to 40 % by weight (10% to 40%). Testing the same samples, it was proved that the biodegradable composites (10% to 40%) have higher modulus rather than the material comprising polybutylene succinate of 100 % by weight (PBS).

[0031]

[0026] In summary, it can be concluded that 10 % by weight filler retains very similar properties to biopolymer and it will be possible to make films and laminates from it. On the other hand, materials with a degree of filling from 20 to 40 % by weight are significantly stronger and are suitable for the production of various dishes, glasses, food utensils and hard containers. Optimum properties were observed at a filling level of 30 % by weight of the filler.

[0032]

[0027] The biodegradable composites show good thermal stability and start to disintegrate at temperatures above 250 °C, well above the processing temperature of 135 - 150 °C. No thermal degradation of the material occurs during processing and subsequent use. Depending on amount of the filler, the resulting composite varies in color from light yellow to dark brown. The biodegradability of the composite was tested under composting conditions for 70 days at 58 °C and a soil moisture content above 50%. Lignocellulose significantly improves the degradability of the resulting biodegradable composites under composting conditions. Biodegradable composites with the filler of 10 % and 20 % by weight decompose after 50 days, while Biodegradable composites with the filler of 30 % and 40 % by weight decompose after 30 days.

[0033]

[0028] While the invention may be susceptible to various modifications and alternative forms, specific embodiments of which have been described in detail herein, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the following claims.

Claims

CLAIMS1. A biodegradable composite, wherein the composite comprises: a polybutylene succinate of 60 to 90 % by weight; and a lignocellulose containing filler of 10 to 40 % by weight, wherein the filler is a mix of grains, hemp and fruits.

2. The biodegradable composite according to Claim 1, wherein the filler comprises a combination of grains, fruits and hemp, and wherein the grains are 30 to 50 % by weight of the filler; the fruits are 30 to 50 % by weight of the filler, and the hemp is 10 to 30 % by weight of the filler.

3. The biodegradable composite according to Claim 1 or 2, wherein the fruits are selected from the group of apples, pears, guavas, quince, plums, gooseberries, oranges, and combination thereof.

4. The biodegradable composite according to any of Claims 1 to 3, wherein the filler further comprises coffee grounds.

5. An article made of composite according to any of Claims 1 to 4, wherein the article is a food container, a plate, a spoon, a fork, a cup, a film, or a laminate.

6. A method for manufacture of a biodegradable composite, wherein the method comprises the steps of: a) drying a lignocellulose containing filler, wherein the filler is a mix of grains, hemp and fruits; b) grinding of the dried filler; c) mixing the ground filler with the polybutylene succinate so that the polybutylene succinate is 60 to 90 % by weight of a mix and the filler is 10 to 40 % by weight of the mix, wherein the mixing is performed by extrusion mixing and in a temperature that is above a melting temperature of thepolybutylene succinate, in result of which the biodegradable composite is obtained.

7. The method according to Claim 6, wherein the filler comprises a combination of grains, fruits and hemp, and wherein the grains are 30 to 50 % by weight of the filler; the fruits are 30 to 50 % by weight of the filler, and the hemp is 10 to 30 % by weight of the filler.

8. The method according to Claim 6 or 7, wherein the fruits are selected from the group of apples, pears, guavas, quince, plums, gooseberries, oranges, and combination thereof.

9. The method according to any of Claims 6 or 8, wherein coffee grounds are added to the filler in the step a).

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