WO2012004347A1

WO2012004347A1 - Filled moulding compounds

Info

Publication number: WO2012004347A1
Application number: PCT/EP2011/061517
Authority: WO
Inventors: Rainer Schmidt
Original assignee: Landshuter Werkzeugbau Alfred Steinl Gmbh & Co. Kg
Priority date: 2010-07-08
Filing date: 2011-07-07
Publication date: 2012-01-12
Also published as: DE102010026532A1

Abstract

The invention relates to a moulding compound for producing a moulded article by injection moulding, containing a biodegradable thermoplastic binder and a fibre material of plant origin as a filling material, and to a method for producing the moulding compound. The moulding compound is characterised by a high fibre material content, which is no less than 50 wt. % based on the total weight of the moulding compound.

Description

Filled molding compounds

The present invention relates to a biodegradable molding composition containing a fiber material of vegetable origin as a filler and is suitable for processing by injection molding, and the Hersteilung this molding composition.

Biodegradable molding compounds are increasingly in demand in various industries, such as in the packaging industry as well as in the automotive industry. However, suitable polymer materials based on renewable raw materials are relatively expensive compared to conventional polymer materials, which are largely fossil origin. The use of low-cost fillers can be compensated here. However, it is not always guaranteed that the filled molding compounds process efficiently and thereby give moldings with the required properties.

Filled molding compositions in which fibrous materials of plant origin are used as filler are known. Such fillers may be beneficial to the biodegradability of the molding composition. Predominantly, however, relatively complex molding processes, such as compression molding, are used for processing such compositions.

The object of the present invention was to provide a biodegradable molding composition which can be inexpensively processed and processed into shaped articles with the aid of efficient processes.

This object is achieved by means of the molding composition defined in the claims below, which combines a biodegradable thermoplastic binder with a fiber material of vegetable origin as a filler, wherein the content of the Fiber material, based on the total amount of the molding composition, not less than 50 wt .-% is. Surprisingly, such molding compositions can be processed using an injection molding to high-quality molded articles.

Accordingly, another object of the invention is a process for producing a molded article comprising the step of injection molding the molding composition of the present invention, and a molded article obtainable by injection molding of this molding material.

A biodegradable thermoplastic binder in the context of the present invention can also be compostable at the same time, ie can be decomposed to natural components such as CO ₂ , water, humus and / or biomass by the ingress of moisture, soil microorganisms and / or fungi. Compostability can be assessed, for example, in accordance with the EN 13432 standard.

The binder content of the molding composition should preferably be obtainable from at least 90% by weight, more preferably at least 95% by weight and in particular at 100% by weight, based on the total amount of the binder, of renewable raw materials. Accordingly, it is also preferred that the molding composition according to the invention contain no binders based on fossil raw materials.

From renewable raw materials available or obtained components of the inventive molding compositions are usually those derived from raw materials of plant or animal, preferably vegetable origin. These may be substances which can be obtained directly from plant or animal material, or else. Substances obtained by processing a plant or animal material, which should not contain added synthetic and / or fossil derived ingredients during processing. Examples of such processing steps are the reaction with other plant or animal materials, the processing by microorganisms (eg fermentation) and / or the polymerization or polycondensation of substances obtained from vegetable or animal material. Binders which are obtainable from renewable raw materials may also be present as such in vegetable or animal materials (eg starch), or may be obtained by processing substances present in vegetable or animal material (eg cellulose acetate). In addition, they can also be obtained by polymerization of monomers which are present in vegetable or animal materials or which are obtained by processing, eg fermentation, of such materials (eg polylactic acid).

Preferred biodegradable thermoplastic binders for use in the present invention are selected from polysaccharides, polyesters, lignins, gelatin, and mixtures of at least two of these binders.

Polysaccharides can be used in their natural form, or in the form of derivatives, for example, substances in which hydroxyl groups of the natural polyester saccharide have been subjected to ether or ester formation. A preferred polysaccharide useful as the biodegradable thermoplastic binder in the present invention is starch, especially thermoplastic starch. The latter is described inter alia in WO 90/05161. Starch is preferably used in its natural form, as it is obtained for example from corn, wheat or potatoes. If required, it can be mixed with a plasticizer and / or plasticizer, in particular natural materials such as glycerol. Another polysaccharide useful in this invention is a celluiose ester, e.g. Cellulose acetate, cellulose acetopropionate or cellulose acetobutyrate. Cellulose acetate is preferred among these substances.

Polyesters which can be used in the context of the invention are, for example, polymyric acid, a polyhydroxy fatty acid, polyglycolic acid and mixtures of at least two of these polyesters or copolymers which consist of monomers of at least two of the stated polyesters. In particular, a copolymer of lactic acid and gycolic acid monomers may be mentioned as the copolymer. Polyhydroxyfatty acid is in particular polyhydroxybutyrate (also referred to as PHB or polyhydroxybutyric acid), polyhydroxyvaierate or a copolymer of hydroxybutyrate and hydroxyvalerate units. Particularly preferred as thermoplastic binders are starch, in particular thermoplastic starch, polylactic acid and polyhydroxybutyric acid.

If necessary, additives may be added to the biodegradable thermoplastic binder, e.g. Plasticizers or other processing aids. Again, it is preferred to use additives that are available from renewable resources.

The melting point of the thermoplastic binder is generally less than 240 ° C, preferably less than 220 ° C. It is preferably in the range of 100 to 200 ° C.

The amount of the binder in the molding composition according to the invention is generally at least 10 wt .-%, preferably at least 20 wt .-%, based on the total weight of the molding composition. In terms of the content of the filler, it is below 50 wt .-%.

Another main constituent of the molding composition of the invention, which is present in an amount of not less than 50% by weight, based on the total weight of the molding composition, is a fiber material of plant origin. Such fiber materials are generally compostable. It should therefore be understood that biodegradability, as explained in more detail above with respect to the thermoplastic binder, is ensured for the entire molding composition. Suitable fiber material of plant origin are plants or plant parts which, for example after a corresponding comminution, can be used directly, but also fiber materials which are obtained from plants or parts of plants by extraction.

Examples of suitable fiber materials are wood (eg wood shavings or wood flour), cereal waste (eg grain husks, also referred to as husks, especially spelled or rice husks), palm fibers, coconut fibers, reeds, hemp, jute, bast, cotton, hay, straw from grain or other grasses or combinations of at least two of these materials. Preferably, husks, in particular spelled or rice husks, are used. The length of the fibers in the fiber material of plant origin is preferably below 30 mm, more preferably below 20 mm. The fibers are preferably longer than 1 mm.

The content of the fiber material in the molding composition according to the invention is, based on the total weight of the molding composition, not less than 50% by weight, preferably not less than 55% by weight and more preferably not less than 60% by weight. The content of the fiber material is usually below 90 wt .-%, and preferably below 80 wt .-%.

Particularly preferred within the scope of the invention are combinations of starch, polylactic acid or polyhydroxybutyric acid as thermoplastic binder and spelled or rice husks as filler.

In principle, conventional additives such as impact modifiers, flame retardants, heat and UV stabilizers, antioxidants, dyes and / or mold release agents can be added to the molding compositions according to the invention. However, in order to ensure good environmental compatibility and biodegradability, the amounts of such additives used should be as low as possible, their content in the molding composition according to the invention should not exceed 5% by weight, preferably 2% by weight, based on the total weight of the molding composition It should be completely abandoned. It also applies to the additives used in the context of the present invention that they should as a rule be obtainable from renewable raw materials. In addition, the molding composition according to the invention is preferably free from additives such as resin acids or modified, e.g. esterified with polyols, resin acids or natural hard resins, soft resins and / or Schleimharzen containing such resin acids as main components.

In the context of the invention, molding compositions are preferred whose organic constituents (in particular the fiber material and the binder) consist to 100% of constituents of biological origin or whose organic components are completely obtainable from renewable raw materials. Particularly preferred within the scope of the invention are molding compositions which consist to 100% of constituents of biological origin or whose components are completely available from renewable raw materials.

To produce the molding composition according to the invention, the constituents mentioned are mixed, preferably at a temperature which is above the melting point of the thermoplastic binder. This mixing process preferably takes place in an extruder, preferably in a twin-screw extruder. According to an example preferred method, the raw material is melted in a twin-screw extruder in several stages, mixed and degassed.

After mixing, the material can be used directly for injection molding, but preference is first given to producing a granulate of the molding composition according to the invention by extrusion. For the granules are all known in the art granular forms with spherical or cylindrical shape into consideration. The granule size, which can be determined, for example, by sieve analysis, is at least 70% by weight, preferably 80% by weight, particularly preferably at least 90% by weight, of the granule particles in the range from 0.1 to 5 cm, preferably in the range from 0.1 to 2 cm. Particularly preferred are granules having a substantially cylindrical shape of the granules, wherein the preferred diameter is in the range of 3 to 10 mm, and the length in the range of 5 to 20 mm.

The injection molding of the molding composition according to the invention is usually carried out at temperatures in the range of 130 to 250 ° C, preferably 150 to 230 ° C. The injection pressure Hegt usually in the range of 1300 to 2000 bar, preferably in the range of 1500 to 1800 bar.

It has proved to be advantageous to control the water content in the mixture of the fiber material and the binder in the production of the fiber-filled molding composition. This is especially true when using a polyester, such as polylactic acid, as a thermoplastic binder. Thus, fiber materials may typically contain up to about 10% by weight of water. When extruding and mixing the fiber material with a hydrolyzable binder, the water can cause dissolution of the molecular chains in the binder. This can lead to embrittlement of the material and a reduction in the impact strength in the end product. To prevent this it may be helpful to use a fiber material with a low water content or to reduce the water content of the fiber material before it is mixed with the binder. For example, a fiber material can be used which has a low water content of 0-5% by weight, preferably 0-3% by weight, in particular 0-2% by weight, based on the total weight of the fiber material. The water content of the fiber material can be adjusted to appropriate values, for example by predrying the fiber material before mixing with the binder.

Advantageously, e.g. in the extrusion process, the fiber material by a upstream extruder, or even a side feed, at temperatures of typically 90 - 140 ° C, pre-dried. This enables production of the molding composition according to the invention in one process step without additional intermediate steps (such as drying and intermediate storage of the dried material). The predried fiber material with reduced water content can then be conveyed after drying in an upstream extruder together with the binder, which is usually present in the form of granules, in the same feed opening of the actual mixing extruder. Alternatively, the pre-dried fiber material with reduced water content can also be fed by side feed to the already melted binder in the extruder.

Another advantageous possibility for controlling the water content, which is an alternative to the use of a fibrous material with a low water content or additionally available, is the addition of a desiccant to the molding composition. Here typically pulverulent desiccants are used, such as hygroscopic salts. By way of example, halides or nitrates of alkaline earth metals, such as magnesium chloride, calcium chloride or calcium nitrate may be mentioned here, calcium chloride is preferably used. The desiccant can bind water molecules, so that it can not come to a reaction of the water with the binder molecules. The desiccant, such as calcium chloride, is effective even in small amounts and may be added to the molding material in amounts of 0.01 to 5 wt.% Relative to the weight of the fibrous material, preferably 0.025 to 1 wt.%, Especially 0.025 to 0.5 % By weight. The novel molding compositions can be used in many fields. They are suitable, for example, for the production of packaging materials for which, in particular, a largely CO ₂ -neutral production and problem-free disposal are advantageous. Another field of application is in the field of gardening supplies, since the molded articles disintegrate after introduction into the soil without the presence of harmful residues or are decomposed by soil organisms. Here are, for example, planters to call. However, the molding compositions are also suitable for the production of more durable components, such as components of motor vehicles that combine environmental compatibility with good physical properties.

Claims

1. A molding composition for producing a molded article by injection molding, comprising a biodegradable thermoplastic binder and a fiber material of vegetable origin as a filler, characterized in that the content of the fiber material, based on the total weight of the molding composition, not less than 50 wt.% Amounts.

2. A molding composition according to claim 1, wherein the biodegradable thermoplastic binder is selected from polysaccharides, polyesters, gelatin, lignins and mixtures of at least two of these binders.

3. A molding composition according to claim 2, wherein the polysaccharide is selected from starch, cellulose or derivatives thereof in which hydroxyl groups of the natural polysaccharide have been subjected to ether or ester formation.

4. molding compound after. Claim 2, wherein the polyester is selected from polylactic acid, a polyhydroxy fatty acid, polyglycolic acid and mixtures of at least two of these polyesters and copolymers which consist of monomers at least two of said polyesters.

5. Molding composition according to one of claims 1 to 4, wherein the entire binder contained in the molding composition is available from renewable raw materials.

6. Molding composition according to one of claims 1 to 5, wherein the fiber material of plant origin is selected from wood, cereal waste, palm fibers, coconut fibers, reeds, hemp, jute, bast, cotton, hay, straw or a combination of at least two of these materials.

7. Molding composition according to one of claims 1 to 6, wherein the molding composition consists of 100% of components of biological origin.

8. Molding composition according to one of claims 1 to 6, wherein the molding composition additionally comprises a Trockenmittei,

A molding composition according to claim 8, wherein the desiccant is calcium chloride.

10. Molding composition according to one of claims 1 to 9, wherein the molding composition is in the form of granules.

1 1. A process for preparing a molding composition according to any one of claims 1 to 10, comprising the step of mixing the binder with a fiber material! with a water content of 0 - 5 wt.%.

12. The method of claim 1 1, wherein the water content of the fiber material is adjusted by pre-drying before the step of mixing with the binder.

13. A process for producing a molded article, comprising the step of injection molding a molding composition according to any one of claims 1 to 10.

14. A molded article obtainable by injection molding a molding compound according to any one of claims 1 to 10.

15. A molded article according to claim 14, wherein the article is a packaging material, a component of a motor vehicle or a planter.