WO2001068763A2 - Coating biodegradable shaped bodies - Google Patents

Abstract

The invention relates to a biodegradable shaped body on the basis of a composite consisting of starch and a biodegradable fiber material. Said shaped body is at least partially coated, said coating comprising a film curable or cured by irradiation of energy in a wavelength range of approximately 10 nm to approximately 400 nm. The invention further relates to a method for producing such a shaped body.

Description

 Coating of biodegradable moldings

The invention relates to a biodegradable molded body based on a composite formed from starch and biodegradable fiber material, and to a method for producing the same.

Packaging materials are produced in large quantities in industry, trade and in the household. For example, fast food chains sell large quantities of food such as hamburgers, French fries, bratwurst etc. as well as hot and cold drinks in plastic packaging such as packaging based on polyethylene, polypropylene, polystyrene, etc. Plastic-based packaging is also widely used in retail. For example, fruit in plastic trays is offered for sale in advance. Furthermore, for example, apples or peaches are also transported and offered in carriers provided with hemispherical depressions. For example, an apple or a peach is placed in each hemispherical recess. These carriers are increasingly made of plastic.

The aforementioned plastic containers made in the form of cups, plates, cups, bowls, boxes and carriers of all types have the advantage that they are light in weight. A light weight of these containers is advantageous with regard to the transport costs incurred, both when transporting the unfilled containers themselves and when transporting goods stored in these containers, such as fruit.

The containers made of plastic are regularly disposed of after being used once. Due to the wide range of applications and the large number of pieces in which these containers are used regularly, these containers lead to a considerable amount of waste. It is extremely disadvantageous that these containers made of plastic have an extraordinary longevity. There are currently essentially two methods for disposing of these plastic containers.

In the first method, the plastic containers contained in the waste are burned in a waste incineration plant. This approach is disadvantageous. On the one hand, the manufacture of plastic containers is based on the consumption of petroleum, ie a non-renewable source of raw materials. Furthermore, this procedure requires the construction of further waste incineration plants or the greater use of existing waste incineration plants. In the course of the increased public However, environmental awareness means that the construction of new waste incineration plants can hardly be implemented today. In this respect, there are increasing disposal difficulties with regard to the steadily growing amount of waste.

In the second method, the plastic containers are reprocessed as the starting material for new plastic containers to be produced. This procedure, however, first requires the plastic containers to be produced in a single variety and, finally, after the plastic containers have been used, a complicated separation of the containers depending on the type of plastic used. Since the plastic containers are still used in particular for fast food chains, the containers must be cleaned of food waste, fat, ketchup, etc. after use. However, such a procedure is complex and costly, so that the used containers are regularly incinerated in a waste incineration plant in accordance with the above-mentioned method.

In view of the disadvantages associated with plastic containers, attempts have been made for some time to produce biodegradable containers which can be used as plates, cups, trays, carriers, etc. in the above-mentioned uses.

Shaped bodies based on starch are known in the prior art which are partially or fully biodegradable.

PCT / EP95 / 00285 (WO 96/23026) discloses a process for the production of moldings in which a viscous mass of biodegradable fiber material, water and starch is baked in a baking mold to form a fiber-starch composite. Waste paper, recycled material or biodegradable fiber material is used as fiber material, which is previously shredded while being crushed. The proportion of starch to water in the viscous mass is preferably 1: 3 to 1: 2.

US 5,607,983 discloses a method for producing a biodegradable molded body. Short vegetable fibers, vegetable fiber powder, gelling material, water, blowing agent and auxiliary agents are stirred into a dough and then heated at a temperature of 150 ° C to 200 ° C for 2 to 3 minutes and then dried for 20 minutes at a temperature of 120 ° C ,

From WO 95/04104 a method for producing an essentially biodegradable polymer foam is known, whereby thermoplastic or destructurized starches, a biodegradable hydrophobic polymer and a biodegradable fibrous or capsule-like material that has the ability to capillary-bind water.

From DE 40 09 408 AI it is known that a dough can be produced from cellulose-containing and protein-containing materials as well as water, which is then shaped and then baked to provide a decomposable, disposable article. The disposable article produced by this process consists of a protein structure in which cellulose is embedded.

A method for dispersing cellulose-containing fibers in water is known from EP 0 683 831 B1. This method allows the use of interconnected cellulosic fibers, such as e.g. exist in paper material. With a solids content of up to 80%, an aqueous dispersion of cellulose-containing fibers hydrocolloids, such as Starch, vegetable or animal protein, added under strong mechanical action to provide a highly viscous mass in which the cellulose-containing fibers are torn apart and distributed in the viscous mass.

A disadvantage of shaped bodies based on starch is their sensitivity to moisture or liquids. Thus, these starch-based molded articles can be used as containers for moist or wet goods, i.e. not be used for drinks or food or only to a very limited extent.

The object of the present invention is to provide a biodegradable molded body which has improved resistance to moisture or liquids. There is also a need for a method for producing such a shaped body.

The object of the present invention is achieved by a biodegradable molded body based on a composite formed from starch and biodegradable fiber material, the molded body being at least partially provided with a coating, the coating providing a radiation of energy in a wavelength range from approximately 10 nm to about 400 nm curable or cured film.

For the purposes of the invention, the term “starch” is understood to mean natural starch, chemically and / or physically modified starch, technically produced or genetically modified starch and mixtures thereof. As a starch, corn starch are used, for example from corn, waxy maize, wheat, barley, rye. Oats, millet, rice, etc or manioc or sorghum is of course also the starch contained in legumes such as beans or peas or starch contained in fruits such as chestnuts, acorns or bananas. The starch contained in roots or tubers can also be used

Particularly suitable is potato starch, the potato starch contains advantageously _j e 200 to 400 anhydroglucose units, a phosphorus Esther group The negatively charged phosphate groups are the anhydroglucose Emheit connected to the C6-Posιtιon In preparing a bakeable mass of the dry mixture, the negatively charged phosphate groups cause over the mutual repulsion a detangling of the individual potato-amylopectm molecules. The branches of the amylopectin molecules are largely unfolded or stretched out due to the mutual repulsion of the negatively charged phosphate groups. The presence of esterified phosphate groups causes a high viscosity of potato-strong water mixtures

The term "biodegradable fiber material" is understood to mean, in particular, vegetable and animal fibers. In the context of the invention, vegetable fibers are preferably cellulose-containing fibers. Cellulose-containing fibers and fibers of any kind which contain cellulose or consist of cellulose. Animal fibers include so-called protein fibers such as for example wool, hair or silk understood

Vegetable fibers which can be of different lengths and widths are particularly preferably used. In particular, plant fibers are used which have a length in the range from approximately 50 μm to approximately 3000 μm, preferably from approximately 100 μm to approximately 2000 μm, further preferably from approximately 150 μm to about 1500 microns, more preferably from about 200 microns to about 900 microns, most preferably from 300 microns to about 600 microns, the width of the plant fibers can range from about 5 microns to about 100 microns, preferably from about 10 microns to about 60 μm, particularly preferably from approximately 15 μm to approximately 45 μm, are mainly the fibers made from wood, hemp or cotton. Such fibers can be produced in a manner known to the person skilled in the art

Furthermore, the biodegradable shaped bodies can also contain further additives on the basis of a composite formed from strong and biodegradable fiber material. For example, the shaped body can contain protein The following explanations relate to biodegradable moldings produced using protein. Of course, moldings which do not contain any additive in the form of protein can also be used in the present invention. In this respect, the following explanations also apply to moldings which are produced without the addition of protein

A dry mixture containing strong, biodegradable fiber material and protein can be used in the manufacture of the biodegradable molded body

The term "protein" is understood to mean biopolymers based on amino acids. All so-called proteinogenic amino acids, that is to say the amino acids which are usually involved in protein synthesis, come into question as well as the so-called non-proteinogenic amino acids which are usually not involved in the synthesis of proteins

The term "protein" is also understood to mean peptides or polypeptides. The term "protein" in the context of the invention also includes naturally occurring protein, chemically modified protein, enzymatically modified protein, recombinant protein, protein hydrolyzates or mixtures thereof. The protein can be of vegetable or animal origin sem

The dry mix, which comprises strong, biodegradable fiber material and protein, surprisingly enables the baking time to be reduced by up to 35%, preferably up to 50%. Furthermore, the use of protein in the dry mix enables the material requirement in the production of moldings to be reduced by up to 10 wt% to 20 wt%

In order to produce biodegradable moldings, the dry mixture containing the protein is first mixed with the addition of water to form a baking mass or a dough. The baking mass produced from the dry mixture is creamy, foamy and voluminous and thus has a lower density to produce a certain volume when using a dry mixture containing protein, less baked material is required compared to a dry mixture which does not contain any protein

To produce a biodegradable molded body, a certain volume of bakeable mass (baking mass, dough) is placed in a baking pan.These baking tins are known from the waffle baking technique Increased volume of the bakable mass based on the protein-containing dry mixture thus reduces the material requirement. Since the shaped bodies produced using the dry mixture are produced in very large numbers, a reduction in the material requirement by up to 10% by weight to 20% by weight means an enormous reduction in costs.

Furthermore, the molded body produced using the protein-containing dry mixture has a more closed surface. A more closed surface is particularly advantageous with regard to the thermal insulation ability of the molded body.

The protein can be selected from the group consisting of naturally occurring protein, chemically modified protein, enzymatically modified protein, recombinant protein, protein hydrolyzates and mixtures thereof.

The dry mix preferably contains about 0.5 to about 12% by weight, more preferably about 2 to about 10% by weight and most preferably about 4 to about 8% by weight of protein.

For example, proteins of animal origin such as actin, myoglobin, myosin, hemoglobin, collagen, elastin, immunoglobulins, keratins, fibroin, conchagens, ossein, albumins, caseins, FPC (fish protein concentrate) can be used as proteins.

Prolamines such as e.g. Gliadin, Secalin, Hordein, Zein and corn and soy protein can be used. Soy protein in particular has proven to be extremely suitable. Soy protein is also extremely advantageously available commercially in large quantities at low cost.

Hydrophobic proteins are preferably used as proteins. Hydrophobic proteins are characterized by a high proportion of uncharged amino acids in the amino acid sequence. In particular, these proteins contain high proportions of glycine, alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, proline and methionine, all of which give the protein a hydrophobic character.

It is clear to the person skilled in the art that the proteins listed above are only an exemplary selection to illustrate the invention. Of course, other proteins or protein mixtures can also be used. Essential criterion is that the price of the protein to be used or the protein mixture is low in view of the very large numbers of moldings to be produced.

Casein, alkali caseinate, alkaline earth caseinate, casein hydrolyzate and mixtures thereof can also be used as protein.

The casein is used regularly in the form isolated from milk. It is of course also possible to use the α, β and γ subunits of casein separately or in certain combinations thereof. Usable casein is commercially available as acid casein from the company BMI-Landshut. The casein can be used as such or as an alkali caseinate or alkaline earth caseinate. Calcium caseinate has proven to be particularly useful. Calcium caseinate that can be used is commercially available as Caseinato Di Calcio from the company BMI-Landshut.

Furthermore, the protein-containing dry mixture can comprise further additives. These additives make it possible to influence the properties of the biodegradable molded article produced from the dry mixture. For example, hydrophobicizing agents, whitening agents, food colors, flavorings etc. can be contained in the dry mixture as additives.

The dry mixture preferably contains up to 10% by weight, preferably 0.3 to 5% by weight, particularly preferably 0.9 to 1.8% by weight of additive.

The term "additive" includes any compounds that are suitable for influencing the product properties of the molded body. These additives are preferably completely or essentially completely biodegradable. Preferred examples of these additives are hydrophobizing agents, whitening agents, colorants, food colors, flavorings, etc.

Hydrophobizing agents are constituents which impart hydrophobic properties to the shaped body produced from the dry mixture. Whiteners are compounds that are used to lighten the color of the moldings. For example, blue dyes are used as dyes, which are used, for example, for coloring fruit bowls or fruit carriers. The following blue dyes can be used, for example: natural colors or lacquered colors. Green dyes are also used, for example, which are used for coloring shells to hold plants. Following green Dyes can be used, for example, natural colors or lacquered colors

Food colors are dyes used for the color design of the packaging of food. The flavoring can be used in the sense of the invention, in particular any biodegradable flavoring which, for example, imparts a certain smell and / or taste to the molded body made from the dry mixture

A particularly preferred example of hydrophobizing agents are fluoroalkyl polymers, the term "fluoroalkyl polymers" indicating that they are polymers which are composed of, in particular, recurring alkyl units, it being possible for example for one or more, possibly even all, hydrogen atoms to be replaced by fluorine atoms A hydrophobizing agent based on a perfluoroalkyl acrylate copolymer can be used

The whitening agent can be a compound having at least one disulfone group. Such compounds are well known to the person skilled in the art in this technical field. An example of such a disulfonic acid compound is 4,4'-bis (1,3,5-tπaziny lammo) stιlben- 2,2 'disulfonic acid

A baked mass is produced from the dry mixture by adding water and / or gelatinized starch

The term "bakable mass" is understood to mean a baking mass or a dough which can be baked in baking devices known from waffle baking technology, such as, for example, baking tongs to form a shaped body. The bakable mass is, for example, placed in a heated baking mold of such a known baking device, whereupon distributes the bakeable mass in the baking mold and fills it completely. The baking capable mass present in the baking mold releases water or water vapor when heated, which escapes from the baking mold through the provided outlet channels. During this process, the bakeable mass is solidified, providing the desired shaped body

The baked mass can be prepared by adding water and optionally additives, if these are not already contained in the dry mixture, with mixing, such as stirring or kneading, from the dry mixture The baked mass preferably contains about 3% to about 15% by weight. preferably about 5% by weight to about 10% by weight, most preferably 7.8% by weight to about 9.8% by weight of biodegradable fiber material, preferably cellulose-containing fibers

Furthermore, the bakeable mass preferably contains about 6% by weight to about 30% by weight, preferably about 10% by weight to about 20% by weight, most preferably about 16.1% by weight to about 20.05% by weight of native starch

Furthermore, the bakeable mass preferably contains about 2% by weight to about 10% by weight, preferably about 4% by weight to about 8% by weight, most preferably about 5.4% by weight to 6.8% by weight of pregelatinized starch

Furthermore, the baked mass preferably contains about 45% to about 90%, preferably about 60% to about 80%, more preferably about 60% to about 75%, most preferably about 63% % to about 71% by weight of water

Protein in the baked mass is preferably in an amount of up to 10% by weight, preferably up to about 5% by weight. more preferably contain up to about 3% by weight protein, most preferably up to about 2% by weight

The above data in percent by weight are based in each case on the total weight of the baked mass

Pre-gelatinized starch can be produced from about 90 to about 99.9% by weight and about 0.1 to about 10% by weight of native starch, more preferably from about 95% by weight of water and about 5% by weight of native starch A starch suspension is first produced from these two components. This starch suspension can then be heated and then cooled to give pre-gelatinized starch

The heating is preferably carried out to a temperature at which the water suspension of starch granules changes into a paste-like form. This temperature is also known as the Kofler gelatinization temperature. The Kofler gelatinization temperature is between 56 and 66 ° C for potato starch and between 62 and 72 ° C for corn starch The suspension is kept in this temperature range, for example, for a period of about 10 minutes. The pre-gelatinized starch is then cooled. The temperature to which cooling is preferably about 50 ° C. or less The above description for the production of pre-gelatinized starch is only to be understood as an exemplary production process. Of course, those skilled in the art are aware of other methods of making pregelatinized starch that can be used in the present invention. For example, the starch suspension or slurry can also be gelatinized with steam in a so-called jet cooker.

The bakable mass can of course also be produced without using the dry mixture described above. The respective individual components, i.e. Starch, biodegradable fiber material, protein and optionally additives can be mixed with water in any order to prepare the bakable mass. For example, a dough can first be made from starch, biodegradable fiber material and water, to which protein and optionally additives are then added.

A bakable mass is preferably characterized by a homogeneous distribution of all components and a viscosity required for the respective purpose. The viscosity of the bakable mass can be adjusted via the proportion of water added to the dry mixture consisting of starch, biodegradable fiber material and protein and optionally additives. The viscosity of the bakable mass which is preferably to be set for the particular molded article to be produced can be determined by a few experiments. Depending on the shape, the size and the respective wall thickness of the molded body to be produced or the size of the baking mold used in each case for baking the molded body, it may be advantageous to adjust the viscosity of the baking mixture accordingly.

The baked mass produced is then baked. For this purpose, the bakeable mass is placed in a baking dish and heated at a temperature of preferably about 100 ^C to about 200 ° C C., particularly preferably at about 150 ° C in a closed baking mold.

The baking pan is designed depending on the shape of the desired end product, for example in the form of a bowl or a cup. The baking mold can be formed by at least two baking plates, ie an upper and a lower baking plate, which are accommodated in a baking tongs, the inner surface of the baking plates being kept spaced apart in a closed, locked state of the baking mold to form a mold cavity. The mold cavity will then filled in by the bakeable mass. The baking mold has specially shaped evaporation openings for discharging the water vapor. A plurality of baking tongs can also be used for the simultaneous production of a plurality of shaped bodies. Such baking devices are based on the waffle baking technology known per se.

The duration of the baking process is essentially determined by the size of the shaped body to be baked and by the wall thickness of the shaped body set in each case. The baking time is usually between 10 s and approximately 100 s, preferably approximately 30 s to approximately 80 s, more preferably 60 s to 70 s.

A fat-containing release agent can be added to the bakeable mass itself or during the preparation of the bakeable mass from the protein-containing dry mixture. Of course, it is also possible to put the fat-containing release agent directly into the baking mold immediately before the baking process.

The production of a bakable mass for the production of biodegradable molded articles based on a composite formed from starch and biodegradable fiber material is explained in more detail below.

To produce a bakable mass, native starch and cellulose fibers were placed in a fluidized bed system on a Conidur floor with an area of 1862 cm ² (26.6 cm x 70.0 cm). The total dumping height was approximately 225 mm. Potato starch (powdered goods) with a moisture content of about 16% by weight was used as the native starch. Cellulose fibers with a length of approximately 600 μm and a width of approximately 30 μm were used as the biodegradable fiber material.

The native potato starch and the cellulose fibers were mixed dry in a fluidized bed. Warm air at a temperature of about 70 ° C. and a volume flow of 480 m ³ / h was passed through the starch-cellulose fiber mixture from below the floor to produce a fluidized bed.

Pre-gelatinized starch was sprayed from above the fluidized bed at a spray rate of 65 g / min for 5 minutes through two nozzles, each with a nozzle diameter of 0.8 mm and a spray pressure of 1.2 bar. The temperature of the sprayed solution of pre-gelatinized starch was below 50 ° C. The product obtained was a granulate in which starch and cellulose fibers are evenly connected to one another. (The product temperature was 42 ° C and the product moisture was 8.6% by weight.)

The granules thus produced were mixed with water so that the concentration ranges given below were set:

The bakeable mass indicated above was portioned and, as indicated below, 0.5% by weight to 10% by weight, preferably 0.5% by weight to 2% by weight, protein, i.e. for example, soy, casein or calcium caseinate. The protein was homogeneously distributed in the proportions given below in the bakable mass by mixing. The amount of protein wt .-% refers to 100 wt .-% of the above baked mass.

The biodegradable moldings produced by this process have a residual moisture content of about 6% by weight after the baking process, which increases to about 10% by weight residual moisture after storage of the moldings at ambient humidity. Setting a residual moisture content of about 10% by weight has proven to be advantageous with regard to the flexibility of the molded articles produced. It has been shown that a residual moisture content of about 10% by weight makes the moldings more flexible.

The more closed surface of the moldings enables a moisture and grease-repellent coating to be reliably applied in the form of a varnish.

Using the protein-containing dry mixture or the protein-containing bakable mass, inexpensive, high-quality, biodegradable moldings can be produced. For example, the moldings can have wall thicknesses of approximately 1.6 to 1.8 mm. Of course, moldings with thinner wall thicknesses such as, for example, from approximately 0.8 to approximately 1.4 mm or thicker wall thicknesses such as, for example, from approximately 2.0 to approximately 3.2 mm can also be produced. The biodegradable moldings are extremely advantageously made from renewable raw materials and can be completely or essentially completely biodegradable. In this respect, the dry mix or bakeable mass is not subject to the "Green Dot" system created in Germany for the disposal of packaging. In other words, a manufacturer of the above-mentioned shaped bodies in the form of packaging material does not have to make the mandatory contributions to the "Green Dot" disposal system in the case of conventional packaging.

The shaped bodies produced in accordance with the above explanations have a fiber material-starch composite or, if protein is used, a fiber material-starch-protein composite.

For the purposes of the invention, a film is understood to mean a coherent layer which is arranged on the surface of the biodegradable moldings. The substances that make up the film, i.e. the film-forming material are preferably applied to the shaped body in the form of solutions, dispersions or suspensions and can of course also partially penetrate into the pore structure of the shaped body. For example, lacquers which cure under the influence of UV light can be used as the film-forming material.

In the context of the invention, hardening is understood to mean that the applied film-forming material hardens to form a stable surface layer (so-called lacquer hardening). When the film-forming material, for example a lacquer, hardens, the applied film-forming material crosslinks.

The coating applied in the form of a film has sufficient resistance to moisture and liquids for normal use of the moldings. This means that the biodegradable moldings according to the invention can be used, for example, as cups or plates for drinks and dishes. Furthermore, the biodegradable molded articles according to the invention can also be used as storage containers for fresh meat or raw fish, for example.

It is preferred that the radiated energy is in a wavelength range from approximately 200 nm to approximately 350 nm. The radiated energy is more preferably in a wavelength range from approximately 240 nm to approximately 320 nm. The use of radiation with a wavelength of 10 nm to 400 nm, ie of ultraviolet radiation, extremely advantageously enables the applied coating to harden within a few seconds.

A short curing time of the applied coating is very advantageous in a manufacturing process that is geared towards high throughput quantities. The moldings according to the invention are articles which are produced in very large numbers. Shortening the manufacturing time enables an increase in productivity and thus a reduction in manufacturing costs.

For example, a mercury vapor lamp, such as an Hg low-pressure lamp, can be used as the light source.

According to a preferred development, the film is produced from film-forming material which is selected from the group consisting of acrylic resin, polyester resin, polyurethane resin, alkyd resin, silicon lacquers, natural lacquers and mixtures thereof. For the purposes of the invention, any lacquer which can be hardened by irradiation with ultraviolet light (UV light) can be used. Furthermore, within the meaning of the invention, the resins listed above are understood to be paints which can be cured by exposure to UV light or UV radiation (so-called UV paints).

Acrylate resin or acrylic resin are resins which are obtained by homo- or copolymerization of (meth) acrylic acid esters. For example, methyl methacrylate can be used.

As the polyester resin, for example, polycondensation products of di- and polyvalent carboxylic acids, e.g. Phthalic acid, adipic acid, trimelitic anhydride, and alcohols, e.g. Glycerin, trimethylolpropane, neopentyl glycol, butanediols, etc. can be used. However, unsaturated polyesters can also be produced from unsaturated dicarboxylic acids. These resins are also known as unsaturated polyester resins (UP resins).

Resins based on polyisocyanate and polyhydroxy compounds are used as the polyurethane resin.

Alkyd resins are polyester resins modified with natural fats and oils and / or synthetic fatty acids. For example, alkyd resins can be used for the esterification of di- and polyfunctional alcohols such as ethylene glycol, 1,2-propylene glycol, glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol. Etc. with dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, dimer fatty acid, etc. or their anhydrides and saturated and unsaturated fatty acids.

Silicon paints are paints that form an SiO ₂ matrix when exposed to UV light.

Natural lacquers are more preferably used. Linseed oil is particularly preferably used. Dried substances (siccatives) can also be added to the linseed oil (varnish).

The aforementioned film-forming materials can also contain additives. For example, the film-forming material can comprise photosensitizers or photoinitiators, such as, for example, acetophenone, benzophenone, thioxanone or their derivatives.

Furthermore, dyes can also be used as additives for coloring the moldings. The dyes can also act as photosensitizers at the same time.

The cured film preferably has a layer thickness of approximately 10 μm to approximately 100 μm, preferably approximately 20 μm to approximately 60 μm.

The moldings according to the invention have a very thin coating, which is extremely advantageous. This leads to a very low material requirement and further reduces the manufacturing costs. Furthermore, the moldings can thus be made extremely lightweight. In view of the large numbers in which the moldings are manufactured and delivered, they decrease due to the

Weight reduction the transportation costs.

Furthermore, the object underlying the invention is achieved by providing a

Process for producing a biodegradable molded body solved, wherein

(a) film-forming material is applied to the shaped body in a solvent, (b) the film-forming material by irradiating energy in one

Wavelength range from about 10 nm to about 400 nm, preferably from about 200 nm to about 350 nm, is cured. The film-forming material, which is specified in more detail above, is applied to the shaped body in a solvent. The film-forming material can be applied by dipping, pouring, rolling, spraying or electrostatic coating.

The film-forming material is preferably sprayed on. By applying the film-forming material in the form of small droplets, the shaped body can be coated evenly. In particular, spraying enables the molded body to be coated even in areas with difficult-to-access shapes, such as in corners or edges.

If a certain layer thickness is desired, in the case of spraying, the layer thickness can simply be set via the control or regulation of the spraying time or the set droplet size. Furthermore, the spraying process can be repeated, i.e. one or more further layers are applied in a second or further spray pass.

In the case of electrostatic coating or electrostatic painting, the paint particles are charged electrostatically and applied to the molded body. The film formers can be used in aqueous or solvent dispersions, e.g. EPC (electrophoretic powder coating), APS (aqueous powder suspension), PLW (powder coating in water), NAD (non-aqueous dispersion) or ESTA.

The film-forming material (film former) can be dissolved in the solvent or can also form a dispersion, suspension or emulsion with the solvent.

The solvent is preferably water and / or organic solvents.

Ether alcohols, aliphatics, alcohols, aromatics, halogenated hydrocarbons, esters, hydroaromatics, ketones, terpene hydrocarbons or mixtures thereof can be used as organic solvents.

Preferred organic solvents are alcohols, such as e.g. Ethanol.

With regard to occupational safety and from an ecological point of view, water is preferred as the solvent. According to a further preferred embodiment, a drying step (c) is provided between step (a) and step (b), in which the solvent is largely removed.

In particular when using water as a solvent, a drying step is provided before the film-forming material is cured.

Drying can be done by irradiation with infrared radiation (so-called infrared drying). The shaped bodies provided with the film-forming material can be transported through a drying tunnel in which infrared radiators are arranged. The infrared light can be, for example, in the wavelength range from 1 μm to 3 μm. Heating elements such as e.g. Heating coils can be arranged.

Of course, a drying chamber can also be used, for example with heating elements, e.g. Heating coils, and / or infrared radiators is equipped.

Drying in the form of convection drying can also be carried out. For example, heated gases such as air or inert gases, e.g. e.g. Noble gases (argon) or nitrogen are passed over the moldings (so-called nozzle drying). These heated gases absorb the solvent, e.g. water, and thus cause the shaped body to dry, i.e. Removal of the solvent used. The film-forming material remains on the surface of the molding.

When the molded body is dried in a drying chamber at 50 ° C., the drying process takes about 20 minutes. When using nozzle drying at 70 ° C, it takes about 5 minutes to dry a comparable molded article. When using infrared radiation, the drying time is reduced to about 1 to 3 seconds. If the shaped body is arranged in an inert gas atmosphere, preferably a nitrogen atmosphere, and irradiation with infrared radiation, the drying period is reduced to less than one second. High-frequency radiators that emit microwaves can also be used for drying. Even when using high frequency emitters, drying times of less than one second are obtained.

The film-forming material is preferably cured by irradiation with energy in a wavelength range from approximately 240 nm to approximately 320 nm. When using film-forming materials in organic solvents and irradiation of energy in a wavelength range from approximately 240 nm to approximately 320 nm, the coating applied to the biodegradable shaped bodies is cured within 2 to 5 seconds without drying.

According to a preferred embodiment, the shaped body is arranged in an atmosphere enriched with inert gas during the hardening in step (b). Nitrogen gas is preferably used as the inert gas.

If the molded body is arranged in step (b) in an atmosphere enriched with an inert gas, for example an atmosphere enriched with nitrogen, the time required for curing when irradiating energy in a wavelength range from about 240 nm to about 320 nm is reduced by up to fivefold. The greater the proportion of inert gas, preferably nitrogen, in the atmosphere, the shorter the time required for the hardening of the film-forming material, preferably the UV varnish.

In this respect, the shaped bodies coated with film-forming material can be guided on high-speed conveying devices through an atmosphere enriched with nitrogen or preferably a nitrogen atmosphere with simultaneous irradiation of UV light, preferably in the wavelength range from 240 nm to 320 nm, the coating or the UV varnish is cured.

With the method according to the invention, it is thus extremely advantageous to provide biodegradable moldings based on a fiber-starch composite with a liquid-resistant coating, very effectively.

The coating can of course only be applied to selected sides or surfaces of the molded body. For example, a molded body in the form of a bowl or a tray can only be coated on the inside. Of course, the molded body can also be coated on all sides. For example, a molded body designed as a cup can be coated both on the inside and on the outside.

Furthermore, the present invention relates to the use of a film curable or irradiated by irradiation of energy in a wavelength range from approximately 10 nm to approximately 400 nm for coating biodegradable molded articles based on a composite formed from starch and biodegradable fiber material. The UV lacquers listed above make it extremely advantageous to process biodegradable moldings in a simple and very efficient manner.

Claims

claims 1. Biodegradable molded article based on a composite formed from starch and biodegradable fiber material, characterized in that the molded article is at least partially provided with a coating, the coating being a by irradiation of energy in a wavelength range from about 10 nm to about 400 nm curable or cured film. 2. Biodegradable molded article according to claim 1, characterized in that the radiated energy is from about 200 nm to about 350 nm. 3. Biodegradable molded article according to claim 2, characterized in that the radiated energy is in a wavelength range from about 240 nm to about 320 nm. 4. Biodegradable molded article according to one of claims 1 to 3, characterized in that the film is produced from film-forming material which is selected from the group consisting of acrylic resin, polyester resin, polyurethane, alkyd resin, silicon lacquer, natural lacquer and mixtures thereof , 5. Biodegradable molded article according to claim 4, characterized in that the film-forming material is linseed oil. 6. Biodegradable molded article according to one of claims 1 to 5, characterized in that the hardened film has a layer thickness of about 10 microns to about 100 microns, preferably from about 20 microns to about 60 microns. 7. A method for producing a biodegradable molded article according to one of claims 1 to 6, wherein (a) film-forming material is applied to the molded body in a solvent, (b) the film-forming material is cured by irradiation with energy in a wavelength range from approximately 10 nm to approximately 400 nm, preferably from approximately 200 nm to approximately 350 nm. 8. The method of claim 7, wherein the film-forming material in step (a) is applied by dipping, pouring, rolling, spraying or electrostatic coating. 9. The method according to claim 7 or 8, wherein the solvent is water and / or alcohol. 10. The method according to any one of claims 7 to 9, wherein a drying step (c) is provided between step (a) and step (b), in which the solvent is largely removed. 11. The method according to any one of claims 7 to 10, wherein the film-forming material is cured by irradiation of energy in a wavelength range from about 240 nm to about 320 nm. 12. The method according to any one of claims 7 to 11, wherein the molded body is arranged during the hardening in step (b) in an atmosphere enriched with inert gas. 13. Use of a film curable or irradiated by irradiation of energy in a wavelength range from approximately 10 nm to approximately 400 nm for coating biodegradable molded articles based on a composite formed from starch and biodegradable fiber material.