Thermoplastic material

Abstract

The invention relates to a thermoplastic material, wherein the material contains starch and further components, wherein the further components comprise cellulose and talcum as fillers, wherein the further components comprise sorbitol as plasticiser in a concentration of at least wt.% and at most 9.5 wt.% sorbitol in relation to the total weight of the material in the dried state.

Description

[0001] Thermoplastic material

[0002] Description

[0003] The invention relates to a thermoplastic material and a method for producing a shaped body from a thermoplastic material and a shaped body.

[0004] Thermoplastic materials containing starch and other components are known from the prior art, for example, EP 0 397 819 A1. Such thermoplastic materials can be used as biodegradable materials produced from renewable resources. Due to the increased environmental awareness among consumers in recent years, such materials are enjoying increasing popularity.

[0005] A disadvantage of such materials, however, is that they lack sufficient resistance for many applications, for example, to moisture. This makes materials of the type in question currently unsuitable for many uses. For example, utensils typically used in bathrooms cannot generally be made from materials of the type in question due to the high humidity prevailing there. They would absorb moisture and thus soften so quickly that they would hardly be suitable for manufacturing products with a reasonable service life under such conditions.

[0006] Materials containing a starch component are also known from US 2012 / 0022188 A1. However, these materials contain significant amounts of petroleum-based plastics. These, in turn, have a negative impact on biodegradability. Overall, therefore, there is a conflict of objectives between the properties of the known materials. The properties that are important for materials of the type in question include, in particular, their resistance to moisture, but also their other, particularly mechanical, properties, their processability, which includes, in particular, flowability during injection molding, and their biodegradability.

[0007] The invention is therefore based on the object of providing a thermoplastic material and a method for producing a shaped body from a thermoplastic material, as well as a shaped body, which has an overall advantageous combination of the above-mentioned properties and which has at least satisfactory properties with regard to stability, mechanical properties, processability and degradability.

[0008] The problem is solved by a material and a method, as well as a molded body having the features of the independent claims. The features of the dependent claims relate to advantageous embodiments.

[0009] This problem is solved by a thermoplastic material containing starch and other components. The other components include cellulose and talc as fillers. Furthermore, the other components include sorbitol as a plasticizer in a concentration of at least 5 wt.% and at most 9.5 wt.% sorbitol, based on the total weight of the material in the dried state. It has been shown that the combination of these fillers with sorbitol as a plasticizer in the specified concentration range allows particularly good mechanical properties to be achieved. In particular, a good compromise between tensile strength and ductility can be achieved.

[0010] In practice, drying the components to a residual moisture content of 0 wt.% is often difficult. Therefore, the concentrations in the dried state with regard to the material and / or its components are to be understood in particular as the theoretical anhydrous concentrations after calculating out any residual moisture in the material and / or its components. The residual moisture can be determined by a suitable measurement.

[0011] The starch concentration can be, in particular, at least 45% by weight, in particular at least 47.5% by weight, and / or at most 55% by weight, in particular at most 52% by weight, based on the total weight of the material in the dried state. The starch can, in particular, be corn starch.

[0012] The additional components may also include other fillers. These fillers may, in particular, be chalk, bentonite, mustard seed hulls, organic fibers, and / or waste materials. It has proven advantageous if the total concentration of the fillers is at least 22.5 wt.%, in particular at least 26 wt.%, and / or at most 37 wt.%, in particular at most 33 wt.%, based on the total weight of the material in the dried state.

[0013] In particular, the additional components may comprise talc as a filler in a concentration of at least 21 wt.%, in particular at least 23.6 wt.%, and / or at most 29 wt.%, in particular at most 27 wt.%, talc based on the total weight of the material in the dried state. It has been shown that at this concentration of talc as a filler, very good mechanical properties can be achieved while still maintaining sufficient processability of the material.

[0014] In particular, the additional components may comprise cellulose as a filler in a concentration of at least 1.5 wt.%, in particular 2.4 wt.%, and / or at most 8 wt.%, in particular at most 6 wt.%, cellulose based on the total weight of the material in the dried state. It has been shown that at this cellulose concentration, particularly good surface qualities of the material can be achieved.

[0015] In particular, the additional components may comprise plasticizers in a total concentration of at least 16.5 wt.%, in particular at least 19 wt.%, and / or at most 25.3 wt.%, in particular at most 23.3 wt.% plasticizer, based on the total weight of the material in the dried state. It has been shown that this plasticizer content, in a material of the type in question, results in a particularly good compromise between hardness, strength, ductility, and flow behavior during processing.

[0016] In particular, the further components may comprise glycerol as a plasticizer in a concentration of at least 11.5% by weight, in particular at least 12.5% ​​by weight and / or at most 15.8% by weight, in particular at most 14.8% by weight of glycerol based on the total weight of the material in the dried state.

[0017] In particular, the further components may comprise sorbitol as a plasticizer in a concentration of at least 5% by weight, in particular at least 6.5% by weight and / or at most 9.5% by weight, in particular at most 8.5% by weight of sorbitol based on the total weight of the material in the dried state.

[0018] It has been shown that the use of glycerin and sorbitol as plasticizers or plasticizers in precisely these concentrations results in significantly increased moisture resistance of the thermoplastic material or of articles made from the thermoplastic material. Surprisingly, the ratio of the amounts of sorbitol and glycerin to each other also plays a role. In addition to the aforementioned components, the material may also contain other components. These additional components are, in particular, components that are biodegradable and / or consist of renewable raw materials and / or are bioinert inorganic components.

[0019] In particular, the material is free of petroleum-based components, and furthermore, in particular, free of petroleum-based plastics as components. Petroleum-based components, especially petroleum-based plastics, have a negative impact on the biodegradability of the material or molded articles made from it. Alternatively and / or additionally, the proportion of biogenic carbon in the total carbon content of the material can be at least 99%. In this context, the proportion of biogenic carbon in the total carbon content of the material is understood in particular to mean the proportion of biogenic carbon in the total carbon content of the material determined according to ASTM D 6866.

[0020] In particular, the components are selected such that the thermoplastic material is industrially compostable and / or home compostable. In this context, a home compostable material is understood to mean, in particular, a material that is considered home compostable according to the NF T51 - 800:2015-11-14 standard. An industrially compostable material is understood to mean, in particular, a material that is considered industrially compostable according to the DIN EN 13432:2000-12 standard.

[0021] The method for producing the material can provide for the components of the thermoplastic material described above to be filled into an extruder and extruded. The extruder, in particular, forces the material through the nozzles. The extruder can, in particular, be a twin-screw extruder. When carrying out the method, the extruder, in addition to extrusion, also melts and / or homogenizes the material. In particular, the components are thoroughly mixed prior to extrusion, i.e., in particular, prior to the introduction of the mixed components of the material into the extruder, in particular the twin-screw extruder.

[0022] Preferably, the mixing and / or extrusion is carried out such that the residual moisture content of the material and / or its components immediately before and / or immediately at the start of extrusion is below 3 wt.%. Particularly preferably, the mixing and / or extrusion is carried out such that the residual moisture content of the material and / or its components immediately before and / or immediately at the start of extrusion is below 2 wt.%. In particular, the material and / or its components can be dried during mixing. It has been shown that, in conjunction with the compositions described above, the production of a starch-based thermoplastic material can be successful even with such low residual moisture contents of the components or of the resulting thermoplastic material.

[0023] The thermoplastic material described above can serve as a starting material in a process for producing a molded article. For this purpose, the material can be in the form of granules, for example. For this purpose, it can be formed into strands through dies and then cut, particularly into sections a few millimeters long. The extruder, in particular, forces the material through the dies.

[0024] The method for producing a molded body provides that a thermoplastic material described above and / or a thermoplastic material produced as described above is processed into a molded body. It has been shown that such a thermoplastic material can be used to produce molded bodies. The method for producing a molded body from the thermoplastic material can, in particular, be an injection molding process. Injection molding processes are particularly suitable for the cost-effective production of molded bodies in large quantities. It has been shown that the material described above or produced as described above is well suited to processing by injection molding.

[0025] The fact that the thermoplastic material has good flow properties even at low residual moisture levels has a particularly positive effect. In practice, starch-based thermoplastic materials are often mixed with water and processed in specialized injection molding machines in which the material is dried. This leads to longer cycle times and thus high unit costs. The described material can be processed in an injection molding machine, especially with a residual moisture content of less than 1 wt.%. The material can be heated to a temperature of at least 180°C, in particular at least 190°C, and / or at most 210°C, in particular at most 230°C, to liquefy it. This enables the use of standard plastic injection molding machines for thermoplastics and also short cycle times.

[0026] In particular, the injection molding process can be carried out in a hot runner injection molding system. Hot runner injection molding systems can, in particular, feature needle valves for the injection molding nozzles. Such injection molding systems offer the advantage that the material remains liquid right up to the nozzle outlet. This avoids the formation of a sprue. This avoids the generation of waste material and the need for corresponding post-processing, and the quality of the molded articles produced is increased by the absence of a sprue. Further practical embodiments and advantages of the invention are described below in conjunction with the drawings. They show:

[0027] Fig. 1 to 4: Measurements of mechanical properties of exemplary

[0028] Material compositions with a varied concentration of talc as a filler.

[0029] Fig. 5 to 8: Measurements of mechanical properties of exemplary

[0030] Material compositions with a varied concentration of cellulose as filler.

[0031] Fig. 9 to 18 Measurements of mechanical properties of a particularly advantageous material composition in comparison to comparison compositions with different proportions of the plasticizers sorbitol and glycerin.

[0032] All concentrations given below refer to the material in its dried state.

[0033] In practice, it has been shown that the concentrations of the different components, in particular the total concentration of fillers and plasticizers, as well as the concentrations of sorbitol, glycerol, talc and cellulose, influence each other with regard to the properties of the resulting materials.

[0034] Therefore, only exemplary measurements for different properties of various material compositions are given below.

[0035] Figures 1 to 4 show the results of mechanical tests on thermoplastic materials containing different proportions of talc as a filler. The concentrations of the components of the individual materials can be found in Table 1 below:

[0036] Table 1

[0037] It can be seen that with increasing talc concentration in the concentration range under consideration, an improvement can be achieved, particularly in the tensile modulus and tensile strength. Impact strength and elongation (up to the point of fracture of the specimen) initially increase from low talc concentrations, then decrease slightly and remain constant thereafter.

[0038] However, it has also been shown that excessive talc concentrations increase the abrasiveness of the material, which affects its processability. Therefore, increasing the talc content beyond certain limits, which also depend on the other components of the material, does not seem sensible.

[0039] Figures 5 to 8 show the results of mechanical tests on thermoplastic materials containing different proportions of cellulose as a filler. The concentrations of the components of the individual materials can be found in Table 2 below: Table 2

[0040] It turns out that the dependence of properties on concentration is less clear for cellulose than for talc. In particular, a significant continuous reduction in elongation (until the specimen breaks) is observed at high cellulose concentrations. However, even relatively low concentrations of cellulose can significantly increase tensile strength. Based on the measurements conducted, an exemplary thermoplastic material has proven particularly advantageous in terms of overall properties. Its composition is shown below in Table 3:

[0041] Table 3

[0042] In the following Figures 9 to 18, the results of the measurements of the properties of this material are marked with an X. In addition to the properties of this material, Figures 9 to 18 show the properties of comparison materials. The compositions of the comparison materials were deliberately varied with regard to the ratio between stronger plasticizers and the ratio between glycerin and sorbitol. The compositions of the comparison materials can be seen in Tables 4 to 6:

[0043] Table 4 Table 5 Table 6

[0044] It is shown that, in particular, the strength values—i.e., hardness, tensile modulus, flexural modulus, flexural strength, and tensile strength—of the exemplary material exhibit good values ​​compared to the reference materials. As expected, the mechanical properties show a strong dependence on the total concentration of the plasticizers present. The exemplary material represents an optimization within this fundamental context, which not only leads to a good profile of mechanical properties but also enables good processability of the material. In particular, the exemplary material can be processed in injection molding machines in the dry state, i.e., particularly with residual moisture contents of less than one percent.This allows the use of unmodified plastic injection moulding machines, which would not be practical for use with starch-based thermoplastic materials that require a significant water content to achieve satisfactory flowability.

[0045] The features of the invention disclosed in the present description, the drawings, and the claims may be essential, both individually and in any combination, for the realization of the invention in its various embodiments. The invention is not limited to the described embodiments. It may be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art.

Claims

Patent claims 1. Thermoplastic material, wherein the material contains starch and other components, wherein the other components comprise cellulose and talc as fillers, wherein the other components comprise sorbitol as plasticizer in a concentration of at least 5% by weight and at most 9.5% by weight of sorbitol based on the total weight of the material in the dried state.

2. Material according to claim 1, characterized in that the concentration of the starch is at least 45% by weight, in particular at least 47.5% by weight and / or at most 55% by weight, in particular at most 52% by weight of starch, based on the total weight of the material in the dried state.

3. Material according to one of the preceding claims, characterized in that the total concentration of the fillers is at least 22.5% by weight, in particular at least 26% by weight, and / or at most 37% by weight, in particular at most 33% by weight, based on the total weight of the material in the dried state.

4. Material according to one of the preceding claims, characterized in that the further components comprise talc as filler in a concentration of at least 21% by weight, in particular at least 23.6% by weight, and / or at most 29% by weight, in particular at most 27% by weight, of talc based on the total weight of the material in the dried state.

5. Material according to one of the preceding claims, characterized in that the further components comprise cellulose as filler in a concentration of at least 1.5% by weight, in particular 2.4% by weight, and / or at most 8% by weight, in particular at most 6% by weight, of cellulose based on the total weight of the material in the dried state. Material according to one of the preceding claims, characterized in that the further components comprise plasticizers in a total concentration of at least 16.5 wt.%, in particular at least 19 wt.%, and / or at most 25.3 wt.%, in particular at most 23.3 wt.%, plasticizers based on the total weight of the material in the dried state. Material according to one of the preceding claims, characterized in that the further components comprise glycerol as plasticizer in a concentration of at least 11.5 wt.%, in particular at least 12.5 wt.%, and / or at most 15.8 wt.%, in particular at most 14.8 wt.%, glycerol based on the total weight of the material in the dried state. Material according to one of the preceding claims, characterized in that the further components comprise sorbitol as plasticizer in a concentration of at least 5 wt.%, in particular at least 6.5 wt.%, and / or at most 9.5 wt.%, in particular at most 8.5 wt.% sorbitol based on the total weight of the material in the dried state. Material according to one of the preceding claims, characterized in that the material is free from petroleum-based components, in particular free from petroleum-based plastics as a component, and / or the proportion of biogenic carbon in the total carbon of the material is at least 99%. Material according to one of the preceding claims, characterized in that the components are selected such that the thermoplastic material is industrially compostable and / or home compostable. Process for producing a thermoplastic material according to one of the preceding claims, characterized in that the components of the thermoplastic material are mixed and extruded to obtain the thermoplastic material, wherein the Mixing and / or extrusion is carried out in such a way that the residual moisture content of the material and / or of its constituents immediately before and / or immediately at the start of extrusion is below 3% by weight, in particular below 2% by weight. A method for producing a shaped body, characterized in that the shaped body is produced from a thermoplastic material according to one of claims 1 to 10 and / or from a thermoplastic material produced by a method according to claim 11. A method according to claim 12, characterized in that the thermoplastic material is processed into the shaped body in an injection molding process, in particular in a hot runner system, the thermoplastic material being heated to a temperature of at least 180°C, in particular at least 190°C, and / or at most 210°C, in particular at most 230°C, in order to liquefy it.Shaped body produced from a material according to claim 1 to 11 and / or from a thermoplastic material produced by a process according to claim 11 and / or produced by a process according to claim 12 or 13. * * * * * * *

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