WO2021254987A1

WO2021254987A1 - Expandable granular material on the basis of a renewable raw material, method for producing same and its use

Info

Publication number: WO2021254987A1
Application number: PCT/EP2021/066025
Authority: WO
Inventors: Tolga Sengül; Sebastian Drabben; Marco Vogel
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2020-06-15
Filing date: 2021-06-15
Publication date: 2021-12-23
Also published as: DE102020115765A1; EP4165113A1

Abstract

The present invention relates to the technical field of materials development. Specifically, the present invention relates to expandable granular material, more particularly for producing biodegradable expanded granular material and foam bodies, and to a method for producing expandable granular material and to the use of expandable granular material for producing biodegradable, more particularly home-compostable, expanded granular material and foam bodies.

Description

Expandable granulate based on a renewable raw material as well as a process for its production and its use

The present invention relates to the technical field of materials development. In particular, the present invention relates to an expandable granulate which is particularly suitable for the production of biodegradable expanded granulates and foam bodies.

In addition, the present invention relates to a method for producing expandable granules and the use of expandable granules for producing biodegradable, in particular home-compostable, expanded granules and foam bodies.

The present invention further relates to a biodegradable, in particular home-compostable, expanded granulate based on renewable raw materials and a method for its production.

In addition, the present invention relates to the use of an expanded granulate in the construction and packaging sectors.

The present invention also relates to a biodegradable, in particular home compostable, foam body based on renewable raw materials and a method for its production. Finally, the present invention relates to the use of a biodegradable foam body as a building material, in the packaging sector and in the DIY and handicraft sector.

Plastics, metals, non-metallic materials, such as, for example, glass, and natural substances, such as, for example, wood, are the essential materials that are used in the production of consumer goods, that is to say both consumer goods and consumer goods. In view of a world population and economy that has been growing steadily over decades in connection with an equally steadily increasing consumption, production quantities and raw material requirements continue to rise, which affects not only the production of consumer goods but also the amount of packaging required transmits. In Germany, for example, the amount of packaging material used has increased by a total of 23% since 2000, with an increase of 79% for plastic packaging alone. As a consequence of this development, the amount of waste generated, for example through packaging waste, is also increasing steadily. For example, the amount of packaging waste generated in Germany in 2017 was 18.7 million tonnes, which corresponds to a per capita amount of approx. 227 kg and an increase of 3% compared to the previous year's figure in 2016.

The main packaging materials used are paper, followed by plastics, glass and metal. In particular, the recycling of plastic waste is expensive, if not impossible in many cases, since the necessary separation of the different plastic materials is often hardly practicable.

In Germany, for example, 3.19 million tonnes of plastic packaging waste were generated in 2017, of which only 49.7% could be recycled. The remaining, non-recyclable part of the plastic packaging waste is predominantly used thermally, i.e. incinerated in waste incineration plants, or given to landfills for further recycling or disposal.

Both thermal recycling and landfill disposal, especially in the event of improper disposal, represent a burden for the environment. The main problem is the often long retention time or only very slow rotting of plastic packaging waste, so that residues, especially in the form of microplastics, For example, they can accumulate in soils, rivers and seas and thus enter the food cycle.

In addition, a large number of the plastics commonly used for packaging are produced on the basis of finite or non-renewable resources, for which petroleum in particular is used as the starting material. The vast majority of plastic-based packaging materials thus combine the disadvantages of a short lifespan or service life with a simultaneous consumption of finite resources in the context of production and costly recycling or disposal. One possibility of counteracting the excessive consumption of finite resources, the increasing disposal and waste problems and the resulting environmental pollution is the development and use of materials that are manufactured on the basis of renewable raw materials and, in particular, are biodegradable, whereby the aspect in particular biodegradability poses a challenge.

Biodegradable materials or plastics from renewable, in particular vegetable, raw materials can be obtained, in addition to cellulose and sugar, especially from starch, for example from maize, wheat or potatoes. Of the biodegradable plastics made from renewable raw materials that have been developed in recent years, starch plastics, polylactide and polyhydroxy fatty acid polyesters have prevailed. The main fields of application for biodegradable materials and plastics in Europe are currently in the packaging and catering sector, as well as in agriculture, horticulture, and in the pharmaceutical and medical sectors. For example, products such as rubbish bags, carrier bags, disposable tableware, packaging films, bottles, fruit and vegetable bowls, packaging aids (loose-fill chips), expandable foams, mulch films or flower pots made from renewable raw materials are available on a larger scale.

The development of bio-based and biodegradable foams, which can be used as packaging material or aids, cushioning or stabilizing material or as spacers, e.g. in the lightweight construction sector, is interesting and relevant to an environmentally friendly replacement for - For example, Styrofoam or polyurethane foams, which are largely made from fossil raw materials and can only be recycled at great expense.

For example, the use of polylactide for the production of bio-based polymer particle foams is known. The material is biodegradable insofar as it can be composted industrially, ie it rots at temperatures of approx. 60 ° C within a period of several weeks in appropriate industrial composting plants. However, under natural conditions, ie in the free environment, polylactide rots much more slowly, ie polylactide cannot be composted at home, for example. In addition, it is only slightly soluble in water, so that improper disposal can pollute both soil and water. Another suitable material for the production of polymer foams is starch. In general, starch belongs to the material group of polysaccharides and is composed of individual glucose building blocks which, depending on the type of glycosidic linkage, are subdivided into the two starch components amylose or amylopectin. Depending on the species and genus of the respective plant from which the starch is obtained, the various starches differ both in their composition, ie with regard to the amylose or amylopectin content, as well as with regard to their nature, ie for example the color, Grain sizes and shapes. The foam structure in the foamed material, for example, can be influenced by selecting a specific thickness.

In practice, a mixture or blend of starch and hydrophobic polymers and, if necessary, other additives have been used to date for the production of starch-based materials. Such a starch blend is described, for example, in European patent application EP 0 596 437 A2 and is suitable, for example, for the production of single-layer or multilayer films.

Through the choice of additives, the starch can be made thermoplastically processable, while the hydrophobic polymers essentially contribute to reducing the water solubility of the material. Due to the different chemical and physical properties of the polymers used, especially with regard to their hydrophilicity or hydrophobicity, the stability of the blend and, in general, the miscibility of the components can be reduced or require the use of specific phase mediators. The polymers and additives used in starch blends can, in particular, have a negative impact on the biodegradability of the starch blend, especially with regard to degradation of the blend under natural, i.e. non-industrial, conditions.

In addition to the production of foils, starch blends are suitable for the production of continuous foams, i.e. depending on the nozzle geometry of foam strands or sheets. This is described, for example, in the European patent applications EP 0 711 322 A1 and EP 1 127 914 A1.

In this regard, EP 0 711 322 A1 relates to a method for producing an essentially borrowed biodegradable polymer foam, within the framework of which thermoplastic or destructured starch or a starch blend using a fiber ser-like or capsule-like material, which has the ability to bind water in a capillary-active manner, is processed under control of pressure and temperature in such a way that the capillary-bound water in the material is released in order to cause the polymer to foam.

Furthermore, EP 1 127 914 A1 discloses a foamed sheet which comprises structured or complexed starch in a blend with, for example, polyvinyl alcohol and additives such as glycerine, the starch blend being foamed as a continuous phase. The foamed sheet is suitable for use in the food packaging sector, for example as a packaging tray or so-called tray for food such as meat, dairy products, vegetables, eggs or fruit.

Another interesting use for biodegradable foams can be found in the construction sector, especially in lightweight construction. Composite materials or, in particular, composite panels with a core made of synthetic polymer foams, such as polyurethane (PUR) or polystyrene (PS), are conventionally used here. The synthetic polymers mentioned are largely petroleum-based and are difficult to recycle. European patent application EP 0 781 199 A1 provides a proposal for a component that is to be assessed more positively from the environmental point of view. In detail, this relates to the production of a sandwich material with a biodegradable cover material made of paper or cardboard or foil and a core made of extruded starch foam. For this purpose, a continuous process is used in which a starch foam is produced in an extrusion process, inserted in situ between paper or cardboard webs or film and pressed and processed in a continuously operating roller press. The sandwich material obtained by the process can be endlessly cut into rolls or, after the pressing process, cut to size into defined sandwich panels.

The disadvantage of the aforementioned method for direct foaming of the starch-based starting materials, however, is that, in particular, subsequent shaping for the production of, for example, thick-walled molded parts or molded parts with defined or complex geometries is not possible. The previously known processes for the production of starch-based foams are correspondingly limited with regard to their applicability and design. In contrast, there are also approaches in the prior art to provide multistage processes for the production of polymer foam bodies. For example, European patent application EP 2 623288 describes a process for the production of molded foam parts, in which a polymer foam granulate provided is mixed with a glue composition and then converted to the molded foam part with the supply of heat and air. In particular, provision is made here for already foamed polymer foam granules to be used as the starting material, ie specifically such granules that do not contain any blowing agent. The production of the molded foam part is therefore essentially based on an adhesive process instead of foaming, since this already takes place in a preceding step. Furthermore, EP 2 623288 also describes the use of biogenic or recycled plastics, but these are primarily plastics that are hardly biodegradable or are only industrially compostable. Thus, the state of the art still lacks flexibly designed processes that make foam bodies available based on materials that are as free as possible of plastics that are obtained on the basis of non-renewable raw materials or are only poorly biodegradable. In contrast, it would be desirable to develop a possibility for more flexible production of polymer foams based on renewable raw materials, the possibility of producing foam bodies with more complex geometries or thick-walled structures being of particular interest. At the same time, it would also be desirable to provide a starting material for this purpose that, in particular, is degradable under natural environmental conditions and can be obtained on the basis of renewable raw materials.

It is accordingly an object of the present invention to eliminate the disadvantages associated with the described prior art, or at least to reduce them.

In particular, an object of the present invention is to provide a material that allows the production of environmentally friendly materials, in particular for use in the packaging and construction sectors, as well as decoration and handicrafts, which can be classified as unproblematic, especially with regard to their disposal are. The present invention according to a first aspect of the present invention is accordingly an expandable granulate according to claim 1; further advantageous refinements of this aspect of the invention are the subject of the relevant subclaims.

Another object of the present invention according to a second aspect of the present invention is a method for producing an expandable granulate according to claim 8; further advantageous refinements of this aspect of the invention are the subject of the relevant subclaims.

Another object of the present invention according to a third aspect of the present invention is the use of the expandable granules for the production of biodegradable expanded granules according to claim 12. Again another object of the present invention according to a fourth aspect of the present invention is a method for producing a biodegradable , in particular home compostable, based on renewable raw materials expanded granules according to claim 13. Furthermore, the present invention according to a fifth aspect of the present invention is a biodegradable, in particular home compostable, based on renewable raw materials expanded granules according to claim 14 The present invention according to a sixth aspect of the present invention is the use of the expanded granules in the construction sector and / or in the packaging sector according to claim 15.

The present invention in accordance with a seventh aspect of the present invention again further provides the use of the expandable granulate for the production of biodegradable foam bodies according to claim 16.

The present invention also provides, according to an eighth aspect of the present invention, a method for producing a biodegradable, in particular home compostable, foam body based on renewable raw materials according to claim 17; further advantageous refinements of this aspect of the invention are the subject of the relevant subclaims. In addition, the subject of the present invention according to a ninth aspect of the present invention is a biodegradable, in particular home compostable, foam body based on renewable raw materials according to claim 20; further advantageous refinements of this aspect of the invention are the subject of the related sub-claim.

Another object of the present invention according to a tenth, eleventh and twelfth aspect of the present invention is a use of the biodegradable foam body as a building material, in the packaging sector and in the DIY and handicraft sector according to claims 22, 23 and 24.

It goes without saying that the special configurations mentioned below, in particular special embodiments or the like, which are only described in connection with one aspect of the invention, also apply accordingly with regard to the other aspects of the invention, without this needing to be explicitly mentioned.

Furthermore, with all of the relative or percentage, in particular weight-related, quantitative data mentioned below, it should be noted that these are to be selected by the person skilled in the art within the scope of the present invention in such a way that in the sum of the ingredients, additives or auxiliaries or the like, always 100 percent or 100% by weight result. However, this goes without saying for the person skilled in the art. In addition, all parameter data or the like mentioned below can in principle be determined or determined using standardized or explicitly stated determination methods or with determination methods known per se to the person skilled in the art. Having said that, the subject matter of the present invention is explained in more detail below.

The present invention - according to a first aspect of the present invention - is an expandable granulate, in particular for the production of biodegradable foam bodies, the granulate containing a renewable raw material and a particulate physical blowing agent. The expandable granulate according to the invention, which is available on the basis of a renewable raw material and a particulate physical blowing agent, ie a particulate physical blowing agent, is a particularly environmentally friendly material that can be used and further processed as such in a variety of ways, especially with regard to its production as well as its use or recycling can be classified as resource-saving and sustainable.

In particular, an advantage of the expandable granules and of products that can be made from them is that they can be composted at home, i.e. both the granules and, for example, foam bodies obtained from them rot under natural environmental conditions and at normal outside temperatures. Thus, the granulate according to the invention and products made from it, in particular foam bodies, are especially superior to those biodegradable materials or plastics that are only industrially compostable, ie can only be degraded under artificial conditions in composting plants and at temperatures of at least 60 ° C . Likewise, industrial composting of the expandable granulate and its products, in particular within comparatively short times, is also possible.

Another particular advantage of the expandable granulate according to the invention and the products obtainable therefrom, such as, for example, foam bodies, is in particular that the materials have high water solubility, so that, for example, even if the granulate is improperly disposed of in the environment, degradation of the granulate or The foam body produced from this is ensured. In this way, pollution of the soil and water can be efficiently avoided.

The granulate according to the invention is also particularly well suited for the production of foam bodies or foamed structures. In particular, by using the granulate according to the invention, it is specifically possible to exert a wide range of influences on the final shape, foam structure, foam stability, resilience and durability of the corresponding product, in particular foam body. Thus, the present invention or the granules provided by the present invention allow, in particular, a wide range of foam bodies to be accessible and a wide range of options Design of this is granted. Here it is, for example, specifically possible to produce particularly thick-walled or complex foam bodies from the granulate according to the invention, which, depending on requirements, can have a high level of stability and strength or also a soft and flexible structure.

Regardless of the excellent biodegradability of the granulates according to the invention or the products obtainable from them, such as, for example, foam bodies, the granulates or, for example, foam bodies have a high durability. In particular, the expandable granulate can be stored for several months in a normal room climate, i.e. at room temperature and an average humidity of approx. 50%, without the granulate forming mold or losing its functionality, i.e. expandability. Extensive studies in this regard by the applicant have shown that the expandable granules still have their original expandability even after several weeks of storage and can therefore continue to be processed without problems, in particular into foam bodies.

Another essential advantage of the present invention is that the granulate according to the invention preferably has a particularly simple composition, ie a composition limited with regard to the number of ingredients used. The granulate according to the invention essentially consists only of the renewable raw material, which is preferably, in particular native, starch. In addition to the particulate physical blowing agent, the granulate can also contain water and possibly a small proportion of additives. In this way, on the basis of essentially only two to three ingredients, a highly functional granulate can be obtained which, in particular, allows it to be further processed in a simple and problem-free manner into a wide variety of products, in particular foams. Furthermore, on the basis of the, in particular simple, composition according to the invention of the granulate according to the invention, it becomes possible to produce it reliably and with high process stability. This also makes it possible to reproducibly obtain a uniformly composed granulate, so that finally the products obtained on the basis of the granulate according to the invention, such as, for example, foam bodies, have a very uniform and regular and, in particular, regulatable or controllable structure, with which, as it were, a targeted control of the properties of the products can be achieved. The use of a particulate blowing agent means that foaming and expansion of the granulate according to the invention to form foam bodies with a preferably fine and compact foam structure is possible. At the same time, the foaming or the expansion process of the granulate according to the invention to form a foam body can be controlled in such a way that, in particular, closed-cell foam bodies are obtained which have a uniform and closed outer surface. This has a particularly positive effect on the durability, structural integrity and resistance of the foam bodies, so that, starting from the granulate according to the invention, in particular stable and resilient products can be obtained.

These products, in particular foams or foam bodies, are particularly ideal as packaging materials or packaging aids, such as spacers or cushioning material, due to the aforementioned properties. Particularly advantageous here is the biodegradability of the granulate according to the invention and the products that can be made from it, since the granulate or the foam body can be easily disposed of and recycled via home compost after use or use.

In particular, a faster degradation and rotting process is given, so that an essential aspect in the disposal of, for example, packaging materials can be solved quickly, environmentally friendly, sustainable and user-friendly by the present invention.

Likewise, foams or foam bodies according to the invention made from the expandable granulate according to the present invention are particularly ideal for applications in the construction sector, in particular for lightweight construction applications. Here, the foams according to the invention can be used, for example, as a temporary filling material for hollow bodies. The particularly good water solubility of the materials according to the invention, ie both the expandable granulate and the foam body, allows foams according to the invention to be easily removed from corresponding hollow structures easily and within a short time, while the hollow body was previously stabilized by the foam body. One Another preferred application from the lightweight construction sector is that of sandwich panels, in which the foam core is laminated or laminated with top and bottom cover panels. The present invention thus provides, on the basis of the expandable granulate according to the invention and the foam bodies according to the present invention obtainable therefrom, in particular extremely flexible materials which can also be obtained and disposed of in an environmentally friendly manner. In the context of the present invention, a renewable raw material is understood to mean an organic raw material that originates from agricultural and forestry production and is used specifically for further applications outside of the food and feed sector. In the context of the present invention, it has proven particularly useful if the granulate contains the renewable raw material in amounts of 85 to 99.9% by weight, in particular 87.5 to 99% by weight, preferably 90 to 98.5% by weight, based on the total granulate composition. A decisive advantage of the present invention is thus to be seen in particular in the fact that the granulate according to the invention is formed essentially or for the most part from a renewable raw material, so that sustainable sources in particular are primarily used for its production. In this context, it is particularly advantageous that in particular almost no non-renewable raw material sources are used for the production of the granulate according to the invention, so that the granulate according to the invention can be classified as positive and sustainable from an environmental point of view.

Furthermore, the granulate according to the invention, which is preferably obtained from an extrusion process, can be produced inexpensively and in a resource-saving manner. In particular, it is possible to work with low energy inputs in the course of production, so that likewise only little energy is consumed for the production of the granulate according to the invention. The same also applies to the further processing of the granulate according to the invention into, for example, foam bodies, since, for example, an expansion of the expandable granulate is achieved within just a few seconds to minutes. According to the invention, the renewable raw material can generally be of animal or vegetable origin. In the context of the present invention, however, it has proven useful if the renewable raw material is a vegetable raw material.

In this context, it is further preferred if the renewable raw material is obtained from plants selected from the group of tuber-forming plants, legumes, cereal plants and mixtures thereof, in particular from maize, rice, barley, wheat, spelled, potatoes, cassava, peas and their mixtures, preferably corn, potatoes, peas and their mixtures.

In this regard, it is particularly advantageous that the sources from which the renewable raw material can be obtained or obtained are particularly inexpensive to produce or obtain, so that the granulate according to the invention is based on inexpensive starting materials and also overall inexpensive can be obtained. In particular, the renewable raw material that is used in the context of the present invention or for the granulate according to the invention can be obtained or obtained more cheaply than, for example, plastics that are bio-based, but still have a number of processing steps as part of their production or provision must be subjected to, as is the case, for example, for polylactide from renewable raw material sources.

Furthermore, it is preferably provided within the scope of the present invention that the renewable raw material contains a polysaccharide, in particular a polysaccharide of glucose or its derivatives, preferably consists of it.

In the context of the present invention, a derivative is understood to mean a substance or compound which is derived from a parent compound or basic substance and differs from this only in a few aspects, for example with regard to any functional groups that the parent compound has . A corresponding derivative of glucose would therefore be, for example, / V-acetylglucosamine, which forms the basic building block of chitin. It has also proven useful here if the polysaccharide is selected from the group of cellulose, chitin, starch, their derivatives and / or mixtures thereof, in particular starch and their derivatives. In the context of the invention, starch is assigned to organic compounds, in particular to polysaccharides. Starch is made up of the basic building block aD-glucose, which is linked via glycosidic bonds, with different linking patterns occurring. About 20 to 30% of the starch usually consists of polymeric chains with a helical structure, which are connected via α-1,4-glycosidic bonds. This structural unit is called amylose. In contrast, there are approx. 70 to 80% of the starch consists of highly branched glucose structures, within which a-1, 6- and a-1, 4-glycosidically linked building blocks are present. These structural units are called amylopectin. With regard to starch, derivatives of starch are understood to mean in particular so-called modified starches in the context of the present invention, it being possible to carry out not just one conversion step but several conversion steps or processes in succession in the context of the production of modified starches. The term modified starch includes, for example, acetylated and oxidized starches, acid-treated or alkaline-modified starches, bleached starches, enzymatically modified starches, phosphate esters of starch and starch acetates or else hydroxyalkyl starches.

In the context of the present invention, however, it is particularly preferred if the renewable raw material, in particular native starch, preferably contains potatoes, in particular consists thereof.

Here, potato starch is particularly characterized in that it has a degree of branching of approx. 2% and forms relatively large starch grains or particles, which can have a diameter of approx. 20 to 70 μm. In this sense, the present invention is particularly characterized in that it starts from a renewable raw material that is as natural as possible or uses this in the granulate according to the invention. As far as the particulate physical blowing agent is concerned, it has proven useful in the context of the present invention if the granules contain the particulate physical blowing agent in amounts of 0.1 to 10% by weight, in particular 0.2 to 7% by weight, preferably 0.5 to 5% by weight, based on the total granulate composition.

It is particularly preferred in the context of the present invention if the particulate physical blowing agent is an endothermic blowing agent. A particular advantage when using particulate physical, in particular endothermic, blowing agents is that in the course of further processing of the granulate according to the invention, in particular foaming or expansion to form a foam body, no substances that are harmful to health or odor-causing substances, such as ammonia, which for example is partially released from chemical propellants.

In the context of the present invention, an endothermic propellant is understood to mean, in particular, such a propellant that, when energy is supplied, for example in the form of heat, expands, i.e. expands or expands.

Accordingly, within the scope of the present invention, it is preferably provided that the propellant contains gaseous constituents or constituents which can be converted into the gaseous state, in particular carbon dioxide, water vapor and / or lower alkanes, preferably lower alkanes.

In the context of the present invention, a gaseous component or a component which can be converted into the gaseous state is understood to mean a substance or a compound which is or is in gaseous form under standard conditions, ie room temperature and normal or atmospheric pressure, or in another Physical state is present, for example in the form of a liquid, this substance or this compound then changing into the gaseous state when the temperature is supplied, in particular where temperatures in a range of less than 200 ° C. are sufficient. In the context of the present invention, this means, in particular, a change in the physical state of the constituent contained in the propellant and not its evaporation, for example, through decomposition or a similar degradation reaction thereof.

In the context of the present invention, a lower alkane is understood to mean an organic compound of carbon which essentially contains carbon, hydrogen and optionally oxygen, nitrogen, sulfur and / or phosphorus, in particular consists of these. The aforementioned components or Atoms are essentially linked via single bonds; however, it can also be possible that to a small extent multiple bonds, ie double or triple bonds, are formed between the aforementioned atoms.

With regard to the number of carbon atoms contained in the lower alkanes claimed according to the invention, this is in particular in a range from 1 to 20 carbon atoms, in particular 1 to 15, preferably 1 to 12, carbon atoms. The molecular structure of the alkanes can be either linear or branched. It is also preferred according to the invention if the lower alkanes are present under standard conditions, i.e. room temperature and normal or atmospheric pressure, in gaseous or liquid, in particular liquid, form.

It has proven particularly useful if the gaseous constituents or constituents which can be converted into the gaseous state, in particular carbon dioxide, water vapor and / or lower alkanes, preferably lower alkanes, are encapsulated in the propellant.

In this sense, it is particularly preferred in the context of the present invention if the blowing agent is in the form of expandable polymer particles, in particular hollow micro-particles. It is furthermore preferably provided that the expandable polymer particles, in particular hollow micro-particles, contain, in particular encapsulate, the gaseous or gaseous constituents, preferably carbon dioxide, water vapor and / or lower alkanes, preferably lower alkanes.

According to the invention, it is further preferred if the propellant releases the gaseous or gaseous constituents, in particular carbon dioxide, water vapor and / or lower alkanes, preferably lower alkanes, in particular at elevated temperatures.

In the context of the present invention, particularly good results are obtained if the blowing agent, in particular the expandable polymer particles, preferably hollow micro-particles, the gaseous or convertible into the gaseous state components, preferably carbon dioxide, steam and / or lower alkanes, preferably lower alkanes Temperatures in the range of more than 115 ° C, in particular more than 120 ° C, preferably more than 125 ° C, releases.

In the context of the present invention, the expandable polymer particles or hollow micro particles preferably used according to the invention are understood to mean thermoplastic spheres or hollow microspheres which enclose or contain a gas or the aforementioned gaseous or gaseous constituents. When heat is supplied, the constituents or substances enclosed in the spherical expandable polymer particles expand and, if necessary, change gradually from the liquid to the gaseous state of aggregation with increasing temperature.

As a result of the pressure building up in this way and the supply of heat, the polymer particle shell softens and expands, so that as a result of the expansion of the encapsulated substance there is also an expansion, and in particular also partial dissolution or destruction of the polymer shell. This ultimately leads to a significant increase in the volume of the renewable raw material surrounding the polymer particles, which ultimately floats up through the release of the encapsulated constituents from the particles and forms foam structures.

The preferred use of expandable polymer particles in the context of the present invention allows, in particular, precise metering of the blowing agent and contributes significantly to the formation of, in particular, fine-celled and closed-cell foams.

According to the invention, it has proven particularly useful if the blowing agent, in particular the expandable polymer particles, preferably hollow micro-particles, are lower alkanes selected from the group of linear and / or branched propanes, butanes, pentanes, hexanes, as gaseous or convertible components into the gaseous state, Heptanes, octanes, nonanes and mixtures thereof, in particular branched pentanes, hexanes, heptanes, octanes and mixtures thereof, preferably 2,2,4-trimethylpentane, 2-methybutane and mixtures thereof. With regard to the further composition of the granules according to the invention, it has also proven to be advantageous in the context of the present invention if the granules contain water. In the event that water is contained in the expandable granules according to the invention, it has also proven useful if the granules are based on water in amounts of 5 to 20% by weight, in particular 6 to 15% by weight, preferably 8 to 12% by weight - gene on the total granulate composition contains.

If the granulate contains water, in particular in the aforementioned preferred amounts, it has proven particularly useful in accordance with the invention if the amount of the renewable raw material is adjusted, in particular slightly reduced. For this purpose, it has proven to be advantageous if the granulate contains the renewable raw material in amounts of 70 to 95% by weight, in particular 75 to 94% by weight, preferably 80 to 92% by weight, based on the total granulate composition. According to the invention, the water contained in the granulate is in particular in the form of moisture or as residual moisture in the starch or bound by it or stored in it. In this context, it is particularly surprising and an essential advantage of the present invention that the expandable granulate according to the invention has a long shelf life regardless of its water content, ie can be stored in a stable manner over several weeks under normal room climatic conditions, and at the same time its functionality, ie its expandability, not forfeit.

Furthermore, it was observed in particular within the scope of the present invention that, precisely with the addition of water, better and even more efficient foaming or expansion of the granulate according to the invention can be achieved. In this sense it can be assumed that - without wishing to be bound by this theory - the water added to the granulate acts as a kind of co-blowing agent.

Furthermore, it can be provided in the context of the present invention with regard to the composition of the expandable granules that the granules, in particular biogenic and / or biodegradable additives, in particular selected from the group of processing aids, plasticizers, hardeners, stabilizers, preservatives , Dyes or mixtures thereof. In the context of the present invention, it is preferably provided that all additives based on natural, biodegradable raw materials are obtainable or consist of them, so that the granules obtained can continue to be composted at home overall. According to the invention, the additives used can be selected from fatty acid esters, polyvinyl alcohols, in particular from renewable raw materials, sorbitol, malt flour, and mixtures thereof.

In this context, it has also proven useful if the granulate contains the additives in amounts of 0 to 5% by weight, based on the total granulate composition.

According to a preferred embodiment of the present invention, it can be provided, in particular with regard to the solid components, that the granulate

(i) a renewable raw material, in particular in amounts of 85 to 99.9% by weight, and

(ii) a particulate physical blowing agent, in particular in amounts of 0.1 to 10% by weight, and

(iii) if appropriate, contains additives, in particular in amounts of 0 to 5% by weight, based on the total granulate composition.

For these preferred embodiments of the present invention, all of the aforementioned advantages, special features and further explanations apply accordingly. With regard to its physical nature, the granulate according to the invention can be designed or can be varied. In the context of the present invention, however, it is particularly preferred if the granulate has a volume in the range from 40 to 65 mm ³ , in particular 45 to 60 mm ³ , preferably 45 to 55 mm ³ , based on the individual granulate particles. According to the invention it is preferred for the determination of the volume of the granulate if, according to the shape of the granulate, first an idealized body, such as a sphere or an ellipsoid, is taken as the basis and the granulate is then measured in such a way that based on the measured relevant values, i.e. e.g. diameter, side length genes, heights, widths or depths, the volume of the granulate can be calculated using generally known formulas for, for example, spheres or ellipsoids. In addition, particularly good results are achieved within the scope of the present invention if the granulate has an expansion capacity in a range from 2 to 7 times, in particular 2.5 to 6.5 times, preferably 2.75 to 6 times its original volume having. Accordingly, within the scope of the present invention it is preferably provided that the granulate in the expanded state has a volume in the range from 100 to 350 mm ³ , in particular 110 to 330 mm ³ , preferably 120 to 310 mm ³ , based on the individual granulate particles. In the context of a further preferred embodiment of the present invention, it has also proven particularly useful, in particular with regard to water-containing granulate compositions, if the granulate

(i) a renewable raw material, in particular in amounts of 70 to 95% by weight,

(ii) contains, in particular consists of, a particulate physical blowing agent, in particular in amounts of 0.1 to 10% by weight, (iii) water, in particular in amounts of 5 to 20% by weight, based on the total granulate composition. According to an even further preferred embodiment of the present invention, it has furthermore proven to be advantageous, in particular with regard to water-containing granulate compositions, if the granulate

(i) a renewable raw material, in particular in amounts of 70 to 95% by weight,

(ii) a particulate physical blowing agent, in particular in amounts of 0.1 to 10% by weight, (iii) water, in particular in amounts of 5 to 20% by weight

(iv) additives, in particular in amounts of 0 to 5% by weight, based on the total granular composition, contains, in particular consists of it. For these preferred embodiments of the present invention, all of the aforementioned advantages, special features and further explanations apply accordingly.

Furthermore, it is preferably provided within the scope of the present invention that the granulate is, in particular at least substantially, free of synthetic, in particular hydrophobic, polymers and / or plastics. In the context of the present invention, this is to be understood in particular that the granulate according to the invention, with the exception of the particulate blowing agent, which also makes up a comparatively small proportion of the granulate, preferably no synthetic polymers or plastics are added. In particular, the renewable raw material in the granulate is preferably completely free of additives based on plastic and preferably also has no hydrophobic modification based on corresponding polymers. According to the invention, it should thus be ensured that the granulate is reliably biodegradable, in particular can be composted at home.

According to the invention, a synthetic or hydrophobic polymer or plastic is understood to mean in particular a material that can be obtained from non-renewable or renewable raw materials, but is not entirely of natural origin, as is the case, for example, for polyethylene (PE) or polyethylene terephthalate (PET ), or with these related plastics.

Finally, in the context of the present invention, with regard to the granulate according to the invention, it has proven particularly useful if the granulate can be obtained by means of compounding, in particular by means of a preferably continuous extrusion process.

It shows the figure representations according to

1A shows a foam body according to the invention made from the expandable granulate according to the present invention in plan view; 1B shows a foam body according to the invention made from the expandable granulate according to the present invention with a view of its underside;

1C shows a foam body according to the invention made from the expandable granulate according to the present invention in a side view with a view of the upper side;

1 D shows a foam body according to the invention made from the expandable granulate according to the present invention in a side view with a view of the underside;

2A shows a foam body according to the invention based on potato starch as a renewable raw material and "Unicell MS 190 D" as a particulate blowing agent;

2B is a foamed body based on potato starch as a renewable raw material and "Fleco ^® Foam 900 C" as a blowing agent as a comparative example.

2C shows a foam body based on potato starch as a renewable raw material and "Urea 46% N" as a blowing agent as a comparative example;

FIG. 2D is a foam body on the basis of potato starch as a renewable raw material and a 1: 1 mixture of "Fleco ^® Foam 900 C" and "Urea 46% N" as a blowing agent as a comparative example;

FIG. 2E a foam body on the basis of potato starch as a renewable raw material and a 1: 6 mixture of "Fleco ^® Foam 900 C" and "Urea 46% N" as a blowing agent as a comparative example;

Fig 2F a foam body on the basis of potato starch as a renewable raw material and a. 6: 1 mixture of "Fleco ^® Foam 900 C" and "Urea 46% N" as a blowing agent as a comparative example;

3A shows a foam body according to the invention based on potato starch as a renewable raw material with "Poval LM-20" polyvinyl alcohol as an additive;

3B shows a foam body according to the invention based on potato starch as a renewable raw material with "Poval LM-30" polyvinyl alcohol as an additive;

3C shows a foam body according to the invention based on potato starch as a renewable raw material with sorbitol as an additive; 4A shows a comparative foam body based on potato starch as a renewable raw material, which was produced by means of an already expanded granulate;

4B shows a foam body according to the invention based on potato starch as a renewable raw material which was produced from a non-pre-expanded granulate according to the invention;

5 a comparison of exemplary and inventive expandable granules, both in the non-expanded and in the expanded state;

6 micrographs of the foam cell structure of foam bodies based on potato starch as a renewable raw material without propellant (A), with "Urea 46% N" as propellant (B) or according to the invention with "Unicell MS 190 D" as particulate physical propellant (C);

7 microscopic recordings of the foam cell structure in the edge area of foam bodies according to the invention based on potato starch as a renewable raw material and "Unicell MS 190 D" or "Tracel MB 121 FG" as a particulate physical blowing agent;

8 shows a schematic representation of a multi-part foam body which can be obtained by simply gluing two side surfaces to one another;

9 shows an overview of the method according to the invention for producing foam bodies from an expandable granulate according to the present invention; Another object of the present invention - according to a second aspect of the present invention - is a method for producing a, in particular inventive, expandable granulate, wherein the granulate by compounding a renewable raw material and a particulate physical blowing agent, in particular by means of a, preferably continuous, extrusion process renewable raw material and a particulate physical blowing agent.

According to the invention, it has proven particularly useful if the compounding, in particular the extrusion process, is carried out at temperatures of less than 140.degree. C., in particular less than 130.degree. C., preferably less than 120.degree. It is even more preferred in the context of the present invention if the compounding, in particular the extrusion process, is carried out at temperatures in a range from 40 to 140.degree. C., in particular 60 to 130.degree. C., preferably 70 to 120.degree.

In the context of the present invention, it is therefore provided in particular that the compounding, in particular the extrusion process, is carried out at comparatively moderate temperatures, which has the particular advantage that, in the context of the production method according to the invention, an expandable granulate can be produced in a particularly energy-efficient manner, so that the method according to the present invention can also be assessed as positive from an environmental point of view. In addition, when carrying out the method according to the invention at the preferred aforementioned temperatures, it can be ensured that premature expansion of the expandable granulate, in particular the particulate physical blowing agent, does not occur or does not occur, although this is also not desirable according to the invention in the context of the manufacturing process. Rather, within the scope of the present invention, it is particularly provided that the method according to the invention gives such a granulate that is still expandable and accordingly has a particularly compact and dense internal structure, which is also characterized by a preferably uniform and closed outer surface.

In contrast, the prior art usually provides that comparable, for example starch-containing, compositions are foamed directly in the course of the extrusion process or compounding. However, this considerably limits the flexibility of the foaming process or of the products accessible with the foaming process, since only thin foam sheets or strands can regularly be obtained.

The present invention overcomes this disadvantage on the basis of the method according to the invention in particular in that the expandable granulate according to the invention does not yet expand or foam in the course of the compounding or in particular the extrusion process, but merely extrudes and is granulated. In particular, this is not a matter of course, since the suppression of premature foaming places particular process engineering demands on the extrusion and granulation step, in particular with regard to the temperatures and pressures used here.

The present invention makes it particularly advantageous that instead of direct foaming as part of the compounding or extrusion process, it relies on a more flexible, multi-stage process in which an expandable granulate is first produced, which can then be used later as desired Time can be expanded, for example in particular to foam bodies, the shape, geometry, structure and properties of which can then be set and placed in a variable manner as required.

In the context of the present invention, it has proven particularly useful if the compounding, in particular the extrusion process, is carried out in an extruder. With regard to the choice of the extruder, it is possible according to the invention to use the extruders customarily known to the person skilled in the art, i.e. for example screw extruders, twin-screw extruders or planetary roller extruders. In the context of the process according to the invention, however, it is particularly preferred if the compounding, in particular the extrusion process, is carried out in a twin-screw extruder.

With regard to the process sequence, it can be provided according to the invention that the renewable raw material and the blowing agent are provided separately from one another and / or are introduced into the extruder separately from one another. Likewise, it is preferably also possible for a dry mixture of the raw material and the blowing agent to be provided and / or for the raw material and the blowing agent to be introduced into the extruder together. The use of a dry mix has the advantage that it can be prepared in advance, and in particular also in stock, so that a constant granulate composition and quality can be achieved in advance over several batches with little effort.

It has proven to be advantageous for the method according to the invention if the renewable raw material is provided in particulate form, in particular in the form of particles with an average particle size in a range from 10 to 100 μm, preferably 20 to 70 μm. It is also preferably provided within the scope of the present invention that the propellant is provided in the form of particles with an average particle size in a range from 15 to 45 μm, in particular 20 to 30 μm, preferably 25 to 35 μm.

In the context of the present invention, particularly good results are also obtained when the renewable raw material and the propellant are in a weight ratio of renewable raw material to propellant in a range from 10: 1 to 100: 0.1, in particular 20: 1 to 100: 0.5, preferably 25: 1 to 100: 1, provided or mixed with one another.

With regard to the process sequence, it has proven useful for the method according to the invention, in particular regardless of the way in which the raw material and blowing agent is provided and introduced, if the renewable raw material and the blowing agent are continuously mixed with one another in the extruder, in particular into a homogeneous one Mixture, preferably powder mixture, are transferred.

According to the invention, a homogeneous mixture, for example a powder mixture of renewable raw material and particulate propellant, is understood in particular as a mixture in which the mixture constituents are present in a highly uniformly distributed manner. In particular, such mixtures preferably do not have any different local concentrations of the individual constituents.

For the method according to the invention, it can now also be provided that the renewable raw material and the blowing agent, in particular their homogeneous powder mixture, are mixed with water in the extruder, in particular converted into a, in particular viscous or pasty, mixture.

The obtained, in particular viscous or pasty, mixture of renewable raw material, water and particulate propellant can - without wishing to be limited to this - also be understood as a dispersion, whereby the renewable raw material, such as starch, and water as a homogeneous mixture Form dispersion medium and the particulate propellant represents the disperse phase. It is accordingly under a dispersion in the context of the present invention in particular a heterogeneous mixture of at least two substances. Insoluble constituents or substances, such as the particulate blowing agent used and / or other additives, which may also be added, which can also be referred to as the disperse phase, are finely distributed in a further, in particular continuous substance or mixture of substances, which or which in the context of the present invention is, for example, a viscous or pasty raw material-water mixture. According to the invention, a viscous or pasty mixture or a viscous or pasty mixture is also understood to mean a particularly viscous or only slightly flowable composition.

According to the invention, the mixing process preferably proceeds in such a way that a, in particular homogeneous, mixture, preferably powder mixture, of renewable raw material and particulate blowing agent is mixed with water in the extruder, whereupon the water is distributed, in particular dissolved, in the renewable raw material. As a result, the renewable raw material, in particular, for example, the starch, can be plasticized, so that a continuous, in particular viscous or pasty, mixture of renewable raw material and water can be obtained. Likewise, continuous mixing in the extruder ensures that the blowing agent is evenly distributed, in particular dispersed, in the raw material-water mixture. In this way, an evenly or uniformly distributed, in particular viscous or pasty, mixture of renewable raw material, particulate propellant and water can be obtained overall.

In the context of the present invention, it is also preferably provided that the, in particular homogeneous, mixture, preferably powder mixture, of the renewable raw material and the propellant and / or the, in particular viscous or pasty, mixture of the renewable raw material, propellant and water to the expandable Extruded granules, in particular extruded and granulated, is.

In the context of the present invention, it can furthermore be advantageous if the renewable raw material and / or the propellant, in particular the, in particular homogeneous, mixture, preferably powder mixture, of the renewable raw material and the propellant and / or the, in particular viscous or pasty, Mixture of the renewable raw material, blowing agent and water, additives are added. In this case, it has proven particularly useful if the additives are added in amounts of 0 to 5% by weight, based on the composition.

With regard to the extrusion process, particularly good results are now obtained within the scope of the process according to the invention if the extrusion, in particular granulation, is carried out at a pressure in a range from 10 to 120 bar, in particular 20 to 80 bar, preferably 25 to 70 bar .

Furthermore, it has proven to be advantageous in the context of the present invention if the extrusion, in particular granulation, is carried out by means of hot die cutting, in particular at a speed in a range from 200 to 500 rpm, preferably 300 to 450 rpm.

In the context of the present invention, in particular using the aforementioned preferred process parameters, an ellipsoidal, lenticular or spherical, compact granulate is obtained, which is characterized by a uniform and closed surface structure. On the basis of this special nature of the expandable granules according to the invention, the advantageous longer shelf life of the granules, which can range from several weeks to months, can also be explained. In particular, regardless of any water content, in particular in the form of moisture or residual moisture, under standard room climatic conditions, for example, no mold formation occurs on the granulate according to the invention, which is obtainable by the method according to the invention.

In a preferred embodiment of the method according to the invention, it is preferably provided that in a first process step (A) of the compounding, in particular the extrusion process, the renewable raw material and the blowing agent are separated from one another or provided in the form of a dry mixture and / or that the Raw material and the propellant are introduced separately from one another or together in a first process zone of the extruder.

It has proven particularly useful if the renewable raw material and the blowing agent are heated in the first process zone of the extruder, in particular to temperatures in the range from 20 to 90 ° C., in particular 45 to 85 ° C., preferably with continuous mixing. According to the invention, the first process zone can also be understood or referred to as the feed zone of an extruder. Furthermore, within the scope of the present invention, good results are obtained if in a second process step (B) of compounding, in particular the extrusion process, following the first process step, the renewable raw material and the blowing agent, in particular their homogeneous mixture, preferably powder mixture, in a second process zone of the extruder.

In this context, it is preferably provided that the renewable raw material and the blowing agent, in particular their homogeneous mixture, preferably a powder mixture, are mixed with water in the second process zone of the extruder. The second process zone can therefore also be understood or referred to as a mixing zone in the context of the present invention.

For this purpose, it has proven to be advantageous if the water is added at temperatures in the range from 95 to 110.degree. C., in particular 95 to 105.degree. C., in the second process zone of the extruder.

In addition, it is preferred according to the invention if the water is used in a ratio of water to renewable raw material of 1: 2 to 1: 6, in particular 1: 2.5 to 1: 5, preferably 1: 2 to 1: 4, is set to.

Furthermore, within the scope of the present invention it has been found to be advantageous if, in a third process step (C) of compounding, especially the extrusion process, following the second process step, the renewable raw material and the blowing agent, especially their homogeneous mixture, preferably powder mixture , are reacted with the water to form an, in particular viscous or pasty, mixture.

For this purpose, it is preferably provided that the conversion to the, in particular viscous or pasty, mixture is carried out at temperatures in a range from 105 to 120.degree. C., in particular 105 to 115.degree. Furthermore, in the context of this preferred embodiment of the method according to the invention, it has proven particularly useful if, in a fourth process step (D) of the compounding, in particular the extrusion process, following the third process step, the, in particular viscous or pasty, mixture of renewable raw material, Propellant and water is conveyed into a third process zone of the extruder.

In this context, particularly good results are obtained if the, in particular viscous or pasty, mixture of renewable raw material, blowing agent and water is compressed and cooled in the third process zone of the extruder, in particular to temperatures in a range from 95 to 110 ° C, preferably 95 to 105 ° C. The third process zone can thus also be understood or referred to as a compression or discharge zone in the context of the present invention.

Furthermore, in the context of this preferred embodiment of the method according to the invention, it is preferably provided that in a fifth process step (E) of the compounding, in particular the extrusion process, following the fourth process step, the particularly viscous or pasty mixture of renewable raw material, blowing agent and water is extruded and is granulated to form the expandable granules.

It has been found to be particularly suitable for this purpose if the extrusion is carried out at a pressure in a range from 10 to 120 bar, in particular 20 to 80 bar, preferably 25 to 70 bar.

In addition, particularly good results are obtained within the scope of the present invention if the granulation is carried out by means of hot die cutting, in particular at a speed in a range from 200 to 500 rpm, preferably 300 to 450 rpm.

In the context of the present invention, in particular in connection with the preferred embodiment of the present invention described above, it has proven to be a central or decisive aspect that the temperature profile described above is adhered to as best as possible, in particular to avoid premature expansion of the granules produced . According to a further, particularly preferred embodiment of the method according to the invention, it has also proven useful if the expandable granulate is obtained by means of compounding, in particular by means of a, preferably continuous, extrusion process, wherein

(I) in a first process step (A) the renewable raw material and the propellant are separated from one another or provided in the form of a dry mixture and / or the raw material and the propellant are introduced and heated separately from one another or together in a first process zone of the extruder, in particular to temperatures in a range from 20 to 90 ° C., in particular 45 to 85 ° C., and

(II) in a second process step (B) the renewable raw material and the blowing agent, in particular their homogeneous mixture, preferably powder mixture, are conveyed into a second process zone of the extruder and mixed with water, and

(III) in a third process step (C) the renewable raw material and the propellant, in particular their homogeneous mixture, preferably powder mixture, are reacted with the water to form an, in particular viscous or pasty, mixture, and

(IV) in a fourth process step (D) the, in particular viscous or pasty, mixture of renewable raw material, blowing agent and water is conveyed into a third process zone of the extruder and compressed and cooled, in particular to temperatures in a range from 95 to 110 ° C, preferably 95 to 105 ° C, and

(V) in a fifth process step (E) the, in particular viscous or pasty, mixture of renewable raw material, propellant and water is extruded and granulated to form the expandable granulate.

For further details on the method according to the invention for producing an expandable granulate, reference can be made to the above statements on the expandable granulate according to the invention, which apply accordingly in relation to the method according to the invention.

Another object of the present invention - according to a third aspect of the present invention - is the use of an expandable one, in particular one according to the invention or obtainable by the process according to the invention Granules for the production of biodegradable, in particular home-compostable, expanded granules.

For further details on the use according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the use according to the invention.

A further object of the present invention - according to a fourth aspect of the present invention - is a process for the production of a biodegradable, in particular home compostable, expanded granulate based on renewable raw materials, wherein an expandable granulate, in particular according to the invention or obtainable by the process according to the invention, is a renewable one Raw material and a particulate physical blowing agent containing granules is provided and expanded.

In the context of the method according to the invention, it is preferably provided that the expansion of the expandable granulate is carried out in the presence of elevated temperatures, in particular by means of hot air, preferably by means of circulating hot air. In this way, a uniform and, in particular, simultaneous expansion of the granulate or, in particular, of the particulate propellant contained in the granulate can be achieved in a targeted manner, so that advantageously a fine and uniform pore pattern can be obtained in the expanded granulate. In this context, it has also proven useful if the expansion is carried out at temperatures in a range of more than 150.degree. C., in particular more than 160.degree. C., preferably more than 170.degree. C., preferably more than 175.degree.

In the context of the present invention, it is also preferred if the expanded granulate is designed in particular spherical or ellipsoidal or also lens-shaped. Accordingly, it is preferably provided that the expansion is carried out without pressure, i.e. at atmospheric pressure. In this way, a particularly uniform expansion of the granulate in all spatial directions can be ensured in the best possible way.

As far as the duration within which the expansion of the granulate is achieved is concerned, this can vary. Particularly good results will be in the frame of the present invention is achieved when the expansion is carried out over a period of 20 to 200 seconds, in particular 30 to 180 seconds, preferably 45 to 150 seconds. Accordingly, in the context of the present invention or on the basis of the expandable granules according to the invention, the expanded granules can be obtained within a very short time.

For further details on the method according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the method according to the invention.

Another object of the present invention - according to a fifth aspect of the present invention - is a biodegradable expanded granulate based on renewable raw materials, in particular obtainable by the process according to the invention or from the expandable granulate according to the invention.

The expanded granules according to the invention are distinguished from known granules from the prior art by a particularly homogeneous and fine-pored foam structure. The formation of this fine-pored and uniform foam structure can be largely attributed to the composition of the expandable granulate according to the invention, which in particular enables uniform and uniform expansion.

On the basis of this advantageous quality, the expanded granulate according to the invention is furthermore characterized by a particularly comparatively high integral stability, so that it can, for example, withstand pressure loads well. The expanded granulate according to the invention is therefore ideally suited as a loose filler material or packaging material which, due to its composition, can also be disposed of easily and in an environmentally friendly manner after use.

Another advantageous use of the expanded granulate according to the invention is in the construction sector, where it is suitable as an insulating material due to its low density and composition. The granulate according to the invention can be designed in many ways, in particular with regard to its physical properties. As part of the In this context, it is preferred in the present invention if the granulate has a volume in the range from 100 to 500 mm ³ , in particular 110 to 400 mm ³ , preferably 120 to 350 mm ³ , based on the individual granulate particles.

Furthermore, it is preferably provided within the scope of the present invention that the expanded granules are spherical, lenticular or ellipsoidal, in particular spherical or ellipsoidal. With regard to the composition of the expanded granules, this essentially corresponds to the composition of the expandable granules. In particular, there are only differences between expandable and expanded granules with regard to the water content, since the water contained in the expandable granules escapes in the course of the expansion process, together with the gaseous components contained in the particulate propellant or components that can be converted into the gaseous state. In the context of the present invention, it has ultimately proven to be particularly advantageous if the expanded granulate consists of more than 90%, in particular more than 93%, preferably more than 95% of the renewable raw material.

For further details on the expanded granules according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the expanded granules according to the invention.

Another object of the present invention - according to a sixth aspect of the present invention - is the use of an expanded granulate, in particular according to the invention or obtainable by the method according to the invention, in the construction sector, in particular as insulating material or insulating filler material, and / or in the packaging sector, in particular as Packaging material, filling material and / or cushioning material.

For further details on the use according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the use according to the invention. Another object of the present invention - according to a seventh aspect of the present invention - is the use of an expandable granulate, in particular according to the invention or obtainable by the process according to the invention, for the production of biodegradable, in particular home compostable, foam bodies.

Yet another subject matter of the present invention - according to an eighth aspect of the present invention - is a method for producing a biodegradable, in particular home compostable, foam body based on renewable raw materials, wherein an expandable, in particular according to the invention or obtainable by the method according to the invention, a renewable raw material and a particulate physical blowing agent containing granules are provided and converted into a foam body.

According to the invention, it has proven particularly useful if the conversion to the foam body is carried out under the action of pressure and / or temperature, in particular pressure and temperature.

In the context of the present invention, particularly good results are obtained when the conversion to the foam body is carried out at a temperature in a range of more than 120.degree. C., in particular more than 150.degree. C., preferably more than 170.degree.

It has also proven particularly advantageous if the conversion to the foam body is carried out at a pressure in a range from 20 to 40 bar, in particular 22 to 35 bar, preferably 23 to 30 bar.

It is particularly advantageous according to the invention if the conversion to the foam body, in particular the action of pressure and / or temperature, preferably pressure and temperature, over a period of 70 to 250 s, in particular 90 to 220 s, preferably 100 to 200 s, is carried out. In the context of the present invention, it has proven to be particularly advantageous if the conversion to the foam body is carried out in a device for generating pressure and / or temperature, in particular pressure and temperature.

In this context, it is particularly preferred in the context of the present invention if the conversion to the foam body is carried out by means of a pressing process, in particular in a pressing tool, preferably in a plate press.

According to a preferred embodiment of the method according to the invention, it has proven particularly useful if, in a first method step (a), in particular the pressing process, the granulate is fed into the device for generating pressure and / or temperature, in particular pressure and temperature, preferably a pressing tool , is introduced.

Furthermore, it is preferred within the scope of the present invention according to this preferred embodiment of the method according to the invention if in a second method step (b) following the first step, in particular the pressing process, the granules in the device for generating pressure and / or temperature , in particular pressure and temperature, preferably the pressing tool, under increased pressure and / or increased temperature, in particular increased pressure and temperature, is converted to a foam body. In the context of this preferred embodiment of the method according to the invention, it has also proven useful if, in a third method step (c) following the second step, in particular the pressing process, the pressure and / or the temperature, in particular the pressure and the temperature, are reduced. It is preferably provided here that the granulate is expanded as a result of the reduction in pressure and / or temperature, in particular pressure and temperature.

It is a particular advantage of the method according to the invention that the expanded granulate, which is converted into the foam body, cures simultaneously in the course of the production process according to the invention, ie in the course of expansion, so that in particular post-expansion of the foam body obtained or the expanded granulate is avoided can. Equally educates The simultaneous or instantaneous hardening of the expanded granulate in the foam body obtained results in a uniform and closed surface with an in particular closed-cell structure, which is additionally characterized by a particularly uniform outer skin.

On this basis, in particular the durability of the foam body obtained can be positively influenced since, for example, the access of water and in particular also molds or bacteria is made more difficult by the closed surface. Accordingly, in the context of the present invention, in particular in the context of the method according to the invention for producing the biodegradable foam body according to the invention, a particularly durable foam body is obtained, regardless of the aspect that it is in particular largely or at least essentially based on a renewable raw material, preferably Strength that is based.

The particularly fine-pored and closed-cell foam structure produced on the basis of the process according to the invention in the foam body according to the invention furthermore makes it possible to obtain a very stable and resilient product. In comparison to conventional foams of the prior art, thick-walled foam parts in particular can also be produced within the scope of the present invention, which is not possible especially with single-stage extrusion and foaming processes, as are used in the majority in the prior art. The present invention thus opens up a new and, in particular, extensive field of application of foam bodies according to the invention which, based on the expandable granules according to the invention, can be designed and adapted in a diverse and needs-based manner within the scope of the method according to the invention.

According to the invention, within the scope of an even more preferred embodiment of the method according to the invention, it is now provided in particular that the conversion of the expandable granules to the foam body is carried out under the action of pressure and / or temperature, in particular pressure and temperature, preferably by means of a pressing process, with in a first method step (a) the granules are introduced into the device for generating pressure and / or temperature, in particular pressure and temperature, preferably the pressing tool, and in a second step (b) the granules are converted to the foam body under increased pressure and / or temperature, in particular increased pressure and temperature, and in a third step (c) the pressure and / or the temperature, in particular the pressure and the temperature, are lowered, in particular wherein the granules are expanded as a result of the lowering of pressure and / or temperature, in particular pressure and temperature. For further details on the method according to the invention for producing a biodegradable foam body, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the method according to the invention. Another object of the present invention - according to a ninth aspect of the present invention - is a biodegradable foam body based on renewable raw materials, in particular obtainable by the process according to the invention or from the expandable granulate according to the invention.

According to the invention, it is particularly preferred if the foam body consists of more than 90%, in particular more than 93%, preferably more than 95% of the renewable raw material. In addition, the foam body according to the present invention is preferably characterized in that the foam body has a compressive strength of more than 120 kPa, in particular more than 130 kPa, preferably more than 135 kPa. Furthermore, within the scope of the present invention it is preferably provided that the foam body has a molded part density in a range from 50 to 200 kg / m ³ , in particular 55 to 175 kg / m ³ , preferably 60 to 150 kg / m ³ . In the context of the present invention, the density is preferably determined by determining the weight and calculating the volume of the foam bodies. For this purpose, idealized bodies in accordance with the shape of the foam body, such as, for example, cuboids, cubes, spheres or ellipsoids, can be assumed or the foam bodies can be brought into one of the aforementioned shapes. Subsequently the foam bodies are measured so that the volume can be calculated on the basis of the relevant values measured, ie for example side lengths, heights, widths or depths using generally known formulas. For further details on the foam body according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the foam body according to the invention.

Again another subject of the present invention - according to a tenth aspect of the present invention - is the use of a, in particular according to the invention or by the method according to the invention or obtainable from the expandable granules according to the invention, biodegradable foam body as a building material, in particular as, preferably temporary, spacer , preferably temporary, support structure, preferably soluble core, preferably for hollow composite parts, sandwich composite parts, lightweight components, lightweight constructions.

Another object of the present invention - according to one aspect of the present invention - is the use of a biodegradable granulate, in particular according to the invention or obtainable by the method according to the invention or from the expandable granulate according to the invention

Foam body in the packaging sector, in particular as packaging material, filling material and / or cushioning material. In this context, use of the foam body according to the invention with foils, in particular with or without additional lamination or lamination, can also be provided.

For further details on the use according to the invention, reference can be made to the above statements on the other aspects of the invention, which apply accordingly in relation to the use according to the invention. Finally, a further subject matter of the present invention - according to a twelfth aspect of the present invention - is the use of a biodegradable foam body, in particular according to the invention or obtainable by the method according to the invention or from the expandable granulate according to the invention, in the DIY and handicraft sector, especially as decoration and handicraft material.

The subject matter of the present invention is explained below in a non-limiting manner with reference to the illustration of the figures through preferred embodiments.

1A shows a foam body according to the invention which can be obtained from the expandable granulate according to the present invention or according to the method according to the invention for producing a foam body based on renewable raw materials. The preferred renewable raw material used for the foam body according to FIGS. 1A to 1D is, in particular, native starch, preferably from potatoes. Expandable polymer particles such as "Unicell MS 190 D" or "Tracel MB 121 FG" are used as preferred particulate blowing agents. These preferred propellants contain lower alkanes, in particular branched pentanes or octanes, preferably 2,2,4-trimethylpentane or 2-methybutane or a mixture thereof. Specifically, polymer particles of the "Unicell MS 190 D" type contain a combination of 2,2,4-trimethylpentane (> 15 - <20%) and 2-methylbutane (> 5 - <10%) and polymer particles of the "Tracel MB 121 FG" type "2-methylbutane (> 15-20%). The polymer particle shell of the particles contains or consists, for example, of an acrylonitrile / methacrylonitrile / methyl methacrylate copolymer (> 70 - <80%).

In FIG. 1A and the associated FIGS. 1B to 1D it can be seen in particular that especially thick-walled and also compact foam bodies can be obtained within the scope of the present invention. This advantage of the present invention is based in particular on the fact that, within the scope of the present invention, an expandable granulate is first produced or provided and this is then carried out in a subsequent, in particular temporally separated, Is foamed and expanded step to the foam body according to the invention. In this way, in the context of the present invention, the shape, nature, geometry, structure and stability of the foam body obtained can be influenced.

It is particularly preferred in the context of the present invention if the expandable granules according to the invention, which can subsequently be expanded to form the foam body according to the invention, only contain the renewable raw material, e.g. , the particulate blowing agent, such as expandable polymer particles, and optionally water. The addition of water to the expandable granulate can in particular have the advantage that the water acts as a supporting blowing agent in the course of the expansion process for the foam body according to the invention.

For the resulting foam body according to the invention, it is again preferably provided within the scope of the present invention that it contains the renewable raw material, for example, in particular native starch, preferably from potatoes, in amounts of more than 95% by weight, based on the total composition of the foam body.

2A to 2F give an overview of how the addition of different blowing agents can affect the foaming and expansion properties of the expandable granulate. 2A shows a foam body according to the invention which is formed on the basis of potato starch as a renewable raw material and the particulate physical blowing agent "Unicell MS 190 D" which is preferred according to the invention. As in FIGS. 1 A to 1 D, it can also be seen in FIG. 2A that on the basis of this composition of the expandable granulate according to the invention, compact and uniform foam bodies with a foam structure with fine and closed cells are obtained.

In FIGS. 2B to 2F comparative examples are shown of foam bodies obtained from granules based on potato starch as a renewable raw material, as well as chemical blowing agents "Heco ^® Foam 900 C" and "Urea 46% N". For these variants it can be seen that the foaming of the granulate runs less consistently, so that inconsistent foam bodies with an inhomogeneous foam cell profile are obtained. In some cases, a collapse of the foam structure can be observed (cf. FIG. 2D) or excessive expansion and inflation of the granulate, so that cavities and tears result (cf. FIGS. 2C and 2F).

Overall, it is not possible to achieve such a uniform and uniform degree of foaming with chemical blowing agents as is the case for granulates according to the invention. For example, it can also be seen from FIGS. 2B and 2E that the expansion of granules with chemical blowing agents is sometimes sluggish, so that non-uniformly formed and structurally poorly intact foam bodies are obtained. In contrast, expandable granules according to the present invention have superior properties. 3A to 3C show the influence of additives, which can preferably be added to the expandable granulate, on the foam body formed from the expandable granulate. Polyvinyl alcohol and sorbitol are particularly suitable as additives. For all the cases shown in FIGS. 3A to 3C, it could be observed that a more flexible, more ductile foam body is obtained, which is also or unchanged characterized by good foaming capacity and a high degree of expansion. In this way, within the scope of the present invention, not only are particularly hard and stable foams accessible, but, in contrast, softer, malleable foams can also be produced.

Furthermore, FIGS. 4A and 4B show the influence, in particular, of the pressure parameter on the expansion behavior of the expandable granulate according to the invention. It can be seen in FIG. 4A that, in particular, a pre-expansion of the expandable granulate in advance of the foam body production should be avoided. The foam body produced from pre-expanded granules has a comparatively small thickness and foaming. If, on the other hand, an expandable granulate according to the present invention is used, which in particular - as provided according to the invention in particular for the method for producing the expandable granulate - is not pre-expanded, a thick-walled, compact and structurally integral foam body can be obtained. In FIGS. 5A to 5C, expandable - ie not yet expanded - granulate particles are shown in the upper row. The granules in FIG. 5A serve as a reference and have no propellant. The granulate according to the invention according to FIG. 5B contains “Unicell MS 190D” as the particulate physical blowing agent and according to FIG. 5C “Tracel MB 121 FG”. These two granules have been produced by the method according to the invention.

The granules according to the invention are distinguished in particular by the fact that they have a lenticular to spherical shape, a closed, uniformly designed surface and an overall compact structure. In particular, it can be clearly seen that the expandable granules according to the invention in FIGS. 5B and 5C, which were produced with the relevant production process according to the present invention, have not yet expanded, but are merely extruded and then granulated within the scope of the production process.

In contrast, the lower part of FIG. 5 shows how the expandable granulate particles according to the invention look in the expanded state. The fine-line structure that the expanded granules have according to FIGS. 5B and 5C can be seen in particular. Due to the pronounced cell wall thicknesses, the expanded granulate particles or foam particles can withstand pressure loads longer than, for example, the expanded starch granulate shown as a reference in Figure 5A without an additional propellant. Without the addition of propellant, an easily fragile and porous foam cell structure is formed in the course of foaming or expansion to form the foam body, so that corresponding granulates or foam bodies produced therefrom are not very resilient and hardly stable in practice.

In this context, the microscopic images of the foam structures produced in the expanded granules shown in FIG. 6 also show that different foam cell structures are obtained depending on the addition of blowing agent. 6A shows the structure of expanded starch granules which do not contain any propellant. In contrast, FIGS. 6B and 6C show the foam cell structure for expanded granulate particles which contain a chemical or, according to the invention, a particulate physical blowing agent.

According to FIG. 6C, an expandable granulate has been used which has the expandable polymer particles "Unicell MS 190D" as a blowing agent. It can be seen that on the basis of these expandable polymer particles, which are preferably used, a uniform and defined foam cell structure can be formed which is honeycomb-shaped or almost spherical. In this way, a high level of internal stability can be achieved in the foam body.

In contrast, the foam structure of the expanded granulate according to FIG. 6A appears brittle, thin-walled and overall poorly defined. The expanded granulate according to FIG. 6B contains granular urea 46% N fl arn substance as blowing agent. A thin-walled and irregular foam cell pattern can be recognized in the expanded granulate particles, which results in a lower load-bearing capacity and a non-uniform profile of properties under stress, ie when used, for example, as a spacer In contrast, excellent foaming results are obtained if - as is preferably provided in the context of the present invention - expandable polymer particles such as "Unicell MS 190 D" are used in the expandable granulate.

In addition, FIG. 7 shows microscopic recordings of the foam cell structure of foam bodies according to the invention in their edge region. According to Figure 7A, a foam body is shown, which was obtained on the basis of an expandable granulate with potato starch as a renewable raw material and "Unicell MS 190 D" as a particulate blowing agent. As in FIG. 5C, it can also be seen for FIG. 7A that the foam structure of the foam body according to the invention is particularly uniform and, in particular, honeycomb or almost spherical. The outer skin or the outer foam structure is closed off, so that a closed, continuous outer skin or outer structure is obtained on the surface of the foam body according to the invention. 7B shows a foam body made of a comparable expandable granulate which, compared to the foam body from FIG. 7A, has a lower molded part height or foam body height. The foam structure appears correspondingly compressed on the outside of the foam body according to the invention. By means of lower expansion heights it can accordingly be achieved within the scope of the present invention that foam bodies are formed which have a particularly dense and compact outer layer and in this way are particularly resistant to external loads or the penetration of external ones Factors such as moisture, mold or bacteria. On this basis it can also be explained in particular that the expandable granules according to the invention or the foam bodies obtainable therewith have an unexpectedly high storage stability, regardless of the aspect that in the context of the present invention in particular exclusively biodegradable and biogenic raw materials are used.

Similar good results as in FIGS. 7A and 7B are also obtained in the context of the present invention if the expandable granulate according to the invention contains so-called "Tracel MB 121 FG" spheres as the particulate blowing agent, in particular expandable polymer particles. The foam structures achieved in the related foam bodies according to the invention in turn have a particularly regular, compact and closed-cell structure based on the formation of honeycomb or almost spherical foam cells.

Even when using "Tracel MB 121 FG", a continuous outer surface closed to the outside is formed on the foam body, so that good storage stability and resistance to external influences result (cf. FIGS. 7C and 7D).

According to FIG. 8, a shaped body 1, which is composed of two foam bodies according to the invention, is shown by way of example or schematically. The corresponding shaped body 1 can in particular be obtained in that the foam bodies according to the invention are glued to one another by merely moistening their side surfaces. This bonding is stable and durable, so that it is in particular also possible to load the molded body 1 in one part with a weight 2 without the bond between the two foam bodies yielding. In this way, the high load-bearing capacity or stability of the foam bodies according to the invention and, in particular, of the molded parts made therefrom can be underlined once again.

Finally, the method according to the invention for producing a foam body is shown schematically in FIG. 9. According to the production process according to the invention, the expandable granules according to the invention are converted into a foam body, in particular under the action of pressure or temperature, preferably pressure and temperature. It has proven particularly useful in the context of the present invention if this conversion or conversion of the expandable granules according to the invention into the foam body at a temperature in a range of more than 120 ° C., in particular more than 150 ° C., preferably more than 170 ° C, and / or at a pressure in a range from 20 to 40 bar, in particular 22 to 35 bar, preferably 23 to 30 bar, preferably over a period of 70 to 250 seconds, in particular 90 to 200 seconds, preferably 100 to 200 seconds , is carried out.

For this purpose, the granulate according to the invention is converted into a foam body in a corresponding device for generating pressure and / or temperature, in particular pressure and temperature, this device preferably being a pressing tool, preferably a plate press. In process step A, the granulate according to the invention is introduced into the corresponding device in a molding tool located in the platen press. The press is then closed in step B and the granulate is heated under pressure at the aforementioned temperatures or pressures for the aforementioned period of time (cf. step C). The upper plate of the device is then moved back, in particular by the amount of the desired foam body thickness, whereupon the expandable granulate foams or expands to form the foam body according to the invention and cures simultaneously (cf. step D). After a short cooling phase, the foam body according to the invention obtained can then be removed from the device (cf. step E).

Embodiments:

1. Production of an expandable granulate according to the invention For the production of expandable granules according to the invention, the following starting materials are used in particular:

Renewable raw material:

Native starch from various vegetable sources is used as a renewable raw material:

• Potato starch (for example from Emsland GmbH, type "Superior G")

• Corn starch (for example from Cargill Deutschland GmbH, type "C * Size 03453)

• Pea starch (for example from Emsland GmbH, type "pea starch")

Blowing agents: In particular, the following expandable polymer particles are used as particulate physical blowing agents:

• Unicell MS190 D (Tramaco GmbH)

• Tracel MB 121 FG (from Tramaco GmbH) and, in the context of comparative examples, granular "Urea 46% N" urea (from Yara GmbH & Co. KG) and "Heco®Foam 900 C" (from HECOPLAST) as chemical blowing agents ® GmbH).

Additives:

Depending on requirements, one or more of the following additives are added to the granulate composition:

• Hardening agents, such as malt flour (for example from Teltomalz GmbH, type "Aroma malt flour barley EBC 10")

• Plasticizers, such as PVA (for example from Kuraray Europe GmbH, type “Poval LM-20” or “Poval L-30” or sorbitol (for example from Sigma Aldrich Chemie GmbH, type “D-sorbitol ") The granulate is produced on conventional twin-screw extruder systems, for example of the EMP 26-40 type, TSA Industriale Srl eight temperature zones. Accordingly, some of the process steps can also be carried out over several temperature zones if, for example, several of these are arranged in one process zone.

As part of the production of the granulate according to the invention, in a first process step (A) the renewable raw material and the blowing agent are provided in the form of a dry mixture and thus introduced together into the first process zone of the extruder and preferably heated to 80 ° C. In a second process step (B), the starting materials are continuously converted into an, in particular homogeneous, powder mixture and conveyed into the second process zone of the extruder, in which the mixture is mixed with water. In particular, the water is additionally fed into the extrusion process in order to preferably serve to break down the starch and also as an additional blowing agent. The addition of water takes place in particular at temperatures of approx. 100 ° C. Subsequently, in a third process step (C), the obtained, in particular viscous or pasty, mixture is continuously mixed further at temperatures of 110 ° C. and conveyed further into a third process zone of the extruder. Here the mixture is successively compressed and degassed and cooled, in particular initially to 105 ° C and finally to 100 ° C. In the fifth process step (E), the extrusion and granulation to give the expandable granulate according to the invention then takes place. For this purpose, a hot cut is flanged to the extruder, which works with a variable speed of the blades in a range from 100 to 500 rpm.

It is an essential aspect of the invention, in particular, that in the course of the extrusion described above, there is only a propellant loading, but not a pre-expansion of the granulate according to the invention. In this way, the foaming of the granulate to form a foam body, for example, can take place separately in time and can be adapted as required with regard to the shape, shape, structure and structure of the foam body. Expandable polymer particles or, in particular, spherical micro-hollow particles or spheres such as "Unicell MS190D" or "Tracel MB 121 FG" from Tramaco are preferably used as blowing agents. These include a combination from 2,2,4-trimethylpentane (> 15 - <20%) and 2-methylbutane (> 5 - <10%) or primarily 2-methylbutane (> 15-20%), the aforementioned lower alkanes, for example in Acrylonitrile / methacrylonitrile / methyl methacrylate copolymer (> 70 - <80%) are encapsulated. These preferred propellants are physical endothermic propellants, it being particularly advantageous in accordance with the invention that the propellant component of the propellant is encapsulated in a polymer shell. Thus, on the one hand, precise metering of the propellant is possible and, on the other hand, in particular with regard to the expansion or foaming of the granulate according to the invention, the formation of a fine- and closed-cell foam structure. In addition, the granulate according to the invention has a particularly long shelf life without losing its functionality.

In the course of the production of the granulate according to the invention, the method according to the invention is carried out with exemplary throughputs of:

• 2.5 to 2.8 kg / h solids content,

• 0.5 to 1.0 kg / h (or l / h) liquid metering (water) carried out at an extruder screw speed of 100 rpm.

Adjustments in terms of temperature control, throughput, speeds and water supply are possible or adapted to the respective process conditions (systems used, screw geometries and strength).

According to the invention, good results are obtained in particular when the moisture content of the extrudate (the moisture content of the extruded granules) is between 6 and 14% and preferably between 8 and 11%. In this case there is a sufficient foaming effect due to the water acting as a blowing agent, but there is still no mold formation during storage of the granules.

The following table gives an overview of the formulations and process parameters used for the production of the expandable granules according to the invention. In FIG. 5, three different granules are shown by way of example, ie a comparison granules and two expandable granules according to the invention and their expandates. Table 1: Overview of the exemplary embodiments 1 to 5

Legend:

KST: Potato starch quantities: in [parts per hundred rubber]

MST: corn starch throughput: in [kg / h]

EST: pea starch speed: in [mim ¹ ]

TM1-4: Propellant 1-4, where T: temperature, in [° C]

TM1 = "Unicell MS190 D" p: pressure, in [bar] TM2 = "Heco®Foam 900 C" TM3 = "Urea 46% N" E: according to the invention

TM4 = "Tracel MB 121 FG" V: comparative example Table 2: Overview of the exemplary embodiments 6 to 10

Legend:

KST: Potato starch quantities: in [parts per hundred rubber]

MST: corn starch throughput: in [kg / h]

EST: pea starch speed: in [mim ¹ ]

TM1-4: Propellant 1-4, where T: temperature, in [° C]

TM4 = "Tracel MB 121 FG" V: comparative example 2. Determination of expansion indices for expandable granules according to the invention.

To determine expansion indices for the expandable granulate according to the present invention, the volume of individual granulate particles was determined before and after the expansion of the granulate particle and these were then compared with one another. In the recipes, the amount of propellant is based on 100 parts of renewable raw material. In detail, a PC 3751 popcorn machine from Severin Elektrogeräte GmbH was used to carry out the experiments. In the test series, the heating temperature is kept constant at around 180 ° C, whereas the holding time varies between 1 and 2 minutes, depending on the foaming behavior. The sample of the expandable granulate is placed in the heating insert, the lid opening is closed with a filling cup and the heating process is initiated.

Each granulate sample is idealized for the most precise volume determination possible by assuming an elliptical shape for the non-expanded particles and a spherical shape for the foamed particles. To determine the volume of the spherical shape, the longest chord as well as the width and height of the granulate are measured. The mean value is then determined from the three measured values, this mean value then being used as the diameter for calculating the volume of a sphere. To calculate the volume of the elliptical shape, the longest chord as well as the width and height of the particles are also measured, with the longest chord as the first semiaxis, the width as the second semiaxis and the height as the third semiaxis.

The volumes are then calculated using the following formulas:

Volume of the ellipsoid:

Volume of the sphere:

Ten measurements are made on each sample. The dried particles are first measured with a vernier caliper. The volume is calculated from the measured values and the mean value is taken. The expandable granulate samples are then foamed while hot air is applied. After the foaming process, the granules are measured again and the volume is calculated based on the measured values and the mean value is calculated. The expansion index can then be calculated using the following formula from the volume ratio of the particles before and after their expansion.

Expansion index:

The related results and values are summarized in Table 3 below.

Table 3: Expansion indices for granules from the examples

Legend:

TM1 = "Unicell MS190 D"

TM2 = "Tracel MB 121 FG"

The result shows that particularly high expansion rates are achieved when using the preferred particulate blowing agent "Unicell MS190 D", but good expansion indices are achieved for the expandable granulate according to the invention even when using the particulate blowing agent "Tracel MB 121 FG", which is also preferably used especially in comparison to the reference, in which only water is used as a propellant. The granulate according to the invention accordingly has, in particular, a significantly increased expansion capacity and thus also stands out from comparable granulates of the prior art.

As already stated in the figure representations described above, the use of the preferred expandable polymer particles also gives a uniform foam cell pattern, so that overall structurally integral and externally resilient foam bodies based on the granulate according to the invention can be obtained. 3. Production of a biodegradable foam body according to the invention

Foam bodies can be produced from the expandable granules according to the invention which were obtained according to 1. using the foaming or expansion process described above.

The sequence of the method according to the invention is also shown in FIG. 9 by way of example.

The granules according to Examples 1 to 10 have been used for the production of foam bodies. For this purpose, 25 g of the granulate are weighed out and poured into a molding tool located in a platen press, for example of the LP-S-20 type, Labtech (cf. step A of FIG. 9). The press is closed (step B of FIG. 9) and the granulate is heated under pressure at a temperature of 200 ° C., based on both the lower and the upper plate, and a pressure of 25 bar for 150 seconds (step C of Fig. 9). The top plate is then moved back to the desired foam body thickness, whereupon the expandable granulate foams up to form the foam body and simultaneously hardens (step D of FIG. 9). The foam body obtained can then be removed (step E of FIG. 9). As a result, a particularly thick-walled foam body with freely configurable geometry can be obtained in this way, the geometry of the foam body in particular being able to be predetermined by the molding tool used. An exemplary illustration of a foam body according to the invention can be found in FIGS. 1A to 1D.

4. Compression hardening and durability of foam bodies according to the invention

Based on the specifications of DIN EN ISO 844: 2014, the compressive strength or compressive strength of foam bodies according to the invention were determined after different storage times. Deviations from the norm were the specimen heights of approx. 25 mm, 30 mm and 35 mm (instead of the required 50 mm) and areas of approx. 16 cm ² (instead of the required minimum area of 25 cm ² ).

The results are shown in Table 4 below.

Table 4: Compressive strengths of foam bodies, foamed 1 week after granulate production, tested after different storage times in a standard climate, granulates based on potato starch as a renewable raw material and 1.5 parts of "Unicell MS 190 D" as a particulate blowing agent, the amount of blowing agent being per 100 parts based on renewable raw materials.

As can be seen from the values, the compressive strength of the molded foam parts according to the invention tends to decrease slightly 1 week after their production, but then increases again and is in the range of the original hardness.

The experiment illustrates in particular the resilience and durability of the foam bodies according to the invention, which is also given in particular over several weeks. In particular, this effect is not self-evident because the foam bodies according to the invention and also the granules according to the invention have particularly good solubility in water, which contributes fundamentally to the excellent biodegradability of the products according to the invention. The fact that the foam bodies according to the invention nevertheless have the high compressive strengths according to Table 4 even after storage for several weeks in a relatively moist environment is to be assessed as all the more surprising and advantageous compared to known granulates.

Furthermore, the compressive strengths of foam bodies according to the invention, ie foam bodies made from expandable granules made from a natural raw material and a particulate physical blowing agent, were measured in comparison to foam bodies made from granules containing a chemical blowing agent. The relevant measurements are carried out as described above. The results obtained are summarized in the table below.

Table 5: Comparison of the compressive strengths of the outer skin and the foam cores of foam bodies according to the invention and comparison foam bodies, granules based on potato starch as a renewable raw material and with or without 1.5 parts of different particulate physical or non-inventive chemical blowing agents according to the invention, the amount of blowing agent is based on 100 parts of renewable raw material.

TM1-4: Propellant 1-4, where TM1 = "Unicell MS190 D"

TM2 = "Heco®Foam 900 C"

TM3 = "Urea 46% N"

TM4 = "Tracel MB 121 FG"

E: according to the invention C: comparative example

It can be seen from the measurement results obtained that foam bodies according to the invention have a higher compressive strength than comparable foam bodies which are foamed by means of a chemical blowing agent. These results Nisse emphasize once again that particularly resilient foam bodies can be produced within the scope of the present invention. This property is due in particular to the uniform and uniform fine-cell or closed-cell structure of the foam bodies, which can be obtained in particular on the basis of the granulate according to the invention and specifically using a particulate physical blowing agent.

List of reference symbols:

1 foam body 2 weight

Claims

Patent claims:

1. Expandable granules, in particular for the production of biodegradable foam bodies, characterized in that the granules contain a renewable raw material and a particulate physical blowing agent.

2. Granules according to claim 1, characterized in that the granules are based on the renewable raw material in amounts of 85 to 99.9% by weight, in particular 87.5 to 99% by weight, preferably 90 to 98.5% by weight the total granulate composition.

3. Granules according to claim 1 or 2, characterized in that the renewable raw material is a vegetable raw material.

4. Granules according to one of claims 1 to 3, characterized in that the granules contain the particulate physical blowing agent in amounts of 0.1 to 10% by weight, in particular 0.2 to 7% by weight, preferably 0.5 to 5% by weight .%, based on the total granulate composition.

5. Granules according to one of claims 1 to 4, characterized in that the granules contain water.

6. Granulate according to claim 5, characterized in that the granulate contains water in amounts of 5 to 20% by weight, in particular 6 to 15% by weight, preferably 8 to 12% by weight, based on the total granulate composition.

7. Granulate according to one of the preceding claims, characterized in that the granulate has a volume in the range from 40 to 65 mm ³ , in particular 45 to 60 mm ³ , preferably 45 to 55 mm ³ , based on the individual granulate particles.

8. A method for producing an expandable granulate, in particular according to one of claims 1 to 7, characterized in that the granulate is produced by compounding a renewable raw material and a particulate physical blowing agent, in particular by means of a preferably continuous extrusion process, a renewable raw material and a particulate physical blowing agent.

9. The method according to claim 8, characterized in that the compounding, in particular the extrusion process, is carried out at temperatures of less than 140 ° C, in particular less than 130 ° C, preferably less than 120 ° C.

10. The method according to any one of claims 8 or 9, characterized in that the renewable raw material and the propellant, in particular their, in particular homogeneous, mixture, preferably powder mixture, mixed with water, in particular reacted with it to form an, in particular viscous, mixture, will.

11. The method according to any one of claims 8 to 10, characterized in that the, in particular homogeneous, mixture, preferably powder mixture, of the renewable raw material and the propellant and / or the, in particular viscous, mixture of the renewable raw material, propellant and water to the expandable granules extruded, in particular extruded and granulated, is.

12. Use of an expandable granulate, in particular according to one of claims 1 to 7 and / or obtainable by a method according to one of claims 8 to 11, for the production of biodegradable, in particular home-compostable, expanded granules.

13. A method for producing a biodegradable, in particular home compostable, based on renewable raw materials expanded granules, characterized in that an expandable, a renewable raw material and a particulate physical blowing agent containing granules, in particular according to a of claims 1 to 7 and / or obtainable by a method according to one of claims 8 to 11, is provided and expanded.

14. Biodegradable, in particular home-compostable, expanded granules based on renewable raw materials, in particular obtainable by a method according to claim 13 and / or from an expandable granules according to one of claims 1 to 7.

15. Use of an expanded granulate, in particular according to claim 14 and / or obtainable by a method according to claim 13, in the construction sector, in particular as insulating material and / or insulating filler material, and / or in the packaging sector, in particular as packaging material, filler material and / or cushioning material.

16. Use of an expandable granulate, in particular according to one of the

Claims 1 to 7 and / or obtainable by a method according to one of Claims 8 to 11, for the production of biodegradable, in particular home-compostable, foam bodies.

17. A method for producing a biodegradable, in particular home compostable, foam body based on renewable raw materials, characterized in that an expandable, a renewable raw material and a particulate physical blowing agent containing granules, in particular according to one of claims 1 to 7 and / or obtainable according to a method according to any one of claims 8 to 11, provided and converted to a foam body.

18. The method according to claim 17, characterized in that the conversion to the foam body is carried out under the action of pressure and / or temperature, in particular pressure and temperature.

19. The method according to any one of claims 17 or 18, characterized in that the conversion to the foam body is carried out over a period of 70 to 250 s, in particular 90 to 220 s, preferably 100 to 200 s.

20. Biodegradable foam body based on renewable raw materials, in particular obtainable by a method according to one of claims 17 to 19 and / or from an expandable granulate according to one of claims 1 to 7.

21. Foam body according to claim 20, characterized in that the foam body consists of more than 90%, in particular more than 93%, preferably more than 95% of the renewable raw material.

22. Use of a biodegradable foam body, in particular according to one of claims 20 or 21 and / or obtainable by a method according to one of claims 17 to 19 and / or from an expandable granulate according to one of claims 1 to 7, as a building material, in particular as , preferably temporary, spacer, preferably temporary, support structure, preferably soluble core, preferably for hollow composite parts, sandwich composite parts, lightweight components, lightweight constructions.

23. Use of a biodegradable foam body in particular according to one of claims 20 or 21 and / or obtainable by a method according to one of claims 17 to 19 and / or from an expandable granulate according to one of claims 1 to 7, in the packaging sector, in particular as packaging material, filling material and / or cushioning material.

24. Use of a biodegradable foam body, in particular according to one of claims 20 or 21 and / or obtainable by a method according to one of claims 17 to 19 and / or from an expandable granulate according to one of claims 1 to 7, in the DIY and handicraft sector , especially as decorative and craft material.