Title of Invention: Biopolymer composite material based on polyactic acid.

Field of the Invention

[0001] The invention relates to a material composition of a biopolymer composite with a wear-resistant particulate filler of animal origin.

Background of the Invention

[0002] Biopolymer materials and their composites are among the most progressively de veloping materials, not only in terms of application possibilities but also in terms of environmental aspects. These materials represent an essential segment of production, for example, in the packaging industry, food processing, healthcare or the automotive industry, wherein their share is constantly growing. The biopolymer PLA material (polylactic acid polymer - polylactide) is the most important and widespread biopolymer. It is characterized by workability comparable to standard synthetic ther moplastics and affordable price. Due to the gradual expansion of PLA application pos sibilities, this type of polymer is often added in order to improve mechanical or physical properties. The most common additivation is to add one-dimensional fibrous fillers to the polymer matrix in order to increase the final properties. If it is necessary to obtain a part with increased hardness and abrasion resistance, metal fillers based on aluminium alloys, copper alloys, steel or glass fillers in the form of fibres or beads are added to the matrix for this purpose. Another possible filler is calcium silicate, which, however, significantly absorbs water or air humidity and thus negatively affects the PLA polymer matrix. However, these types of fillers place a significant burden on production equipment, such as injection moulding machines, extrusion machines, moulds, calibration units, etc., regarding their wear and lifetime. Another disadvantage is their problematic recycling and almost zero biodegradation.

[0003] The object of the invention is to provide a biopolymer composite material that would eliminate the prior art’s disadvantages.

Summary of the Invention

[0004] The above-mentioned drawbacks are largely eliminated by the biopolymer polyactic acid-based composite material according to the invention. Its essence is that it contains 50 to 80% by weight of polylactic acid polymer and 20 to 50% by weight of crushed dry egg shells.

[0005] The particles of the crushed dry matter of the eggshells preferably have a size from 50 qm to 350 mhi.

[0006] The invention provides a biopolymer composite material with a PLA matrix filled with a high proportion of particulate filler of animal origin - eggshell dry matter.

[0007] The biopolymer composite material comprises a biopolymer matrix and a natural filler in the form of a fine crushed eggshell dry matter, which contains 95 to 98% calcium carbonate and significantly increases hardness and resistance to abrasion and wear. At the same time, the particulate filler increases the modulus of elasticity in tension and bending. Injected and extruded parts and products are characterized by minimal deformation, reduced tendency to form sink marks, reduced shrinkage value and overall quasi-isotropic behaviour. It is possible to use standard machinery for the production of parts, which is also used for other types of fillers. The wear and abrasive load of machinery is lower compared to metal or glass fillers.

[0008] The composition of the biopolymer composite, i.e. the matrix and the filler, is of completely natural origin and all its components are subject to biodegradation. The material is extremely environmentally friendly and suitable for industrial composting, as the calcium carbonate contained acts as a natural fertilizer.

[0009] The research has shown that the best properties both in terms of wear resistance and final properties and in terms of preparation and processing of biopolymer composite are achieved by crushed eggshell dry matter in size from 50 pm to 350 pm. In the given particle size range, the filler has the highest effect on increasing the tensile modulus in tension and the flexural modulus up to 30 per cent, increasing hardness up to 40 per cent, wherein the biopolymer composite has excellent abrasion resistance.

[0010] In terms of material composition, the biopolymer composite material does not contain any chemical compatibilizers and additives, and the cohesion at the interfacial interface between the filler and the polymer matrix is given mainly by the geometric bond and adhesive forces. To ensure sufficient compatibility and interconnection at the interfacial interface, the eggshell dry matter needs to be soaked in warm soapy water at before grinding, thus removing cuticle residues containing substances such as galactose and mannose peptides and hexosamine, reducing cohesion of particles with a polymer matrix. After soaking, it is necessary to rinse eggshells with clean water and dry.

Examples of the Invention Embodiments

[0011] An exemplary biopolymer polyactic acid-based composite material contains 80% by weight of polylactic acid polymer and 20% by weight of crushed eggshell dry matter. The particles of the crushed eggshell dry matter preferably have a size in the range from 150 pm to 300 pm.

[0012] The biopolymer composite with increased abrasion resistance is further described by the following examples, including a suitable application, wherein component A consists of biopolymer matrices based on polylactic acid (PLA) and component B consists of particles of finely crushed or ground eggshells in size from 50 pm to 350 mih.

Examples of variants [0013] Variant no. 1

[0014] Component A: 70% by weight of PLA

[0015] Component B: 30% by weight of eggshell particles

[0016] Variant no. 2

[0017] Component A: 50% by weight of PLA

[0018] Component B: 50% by weight of eggshell particles

[0019] The biopolymer composite material with eggshell particles is suitable for a wide range of injection moulded and extruded parts, where the resistance of the surface to abrasion or increased hardness are essential. Parts made of this biopolymer composite are characterized by high hardness and stiffness, which is now achieved exclusively with the help of metal or glass fillers. The advantages of the biopolymer composite are the 100% natural origin of the matrix from renewable sources and particulate filler, biodegradability and environmental friendliness after the end of its life.

Industrial Applicability

[0020] The biopolymer composite material filled with eggshell particles according to the present invention is in the granulated form suitable for the production of injection moulded parts with a thickness of 0.8 to 5 mm or extruded parts.