Methods for obtaining natural rubber from plant materials

Abstract

The present invention relates to a method for obtaining natural rubber from plant material, the method comprising at least the step of grinding the plant material in at least one ball mill having grinding elements. The invention also relates to the natural rubber obtained by the method and to the use of at least one ball mill having grinding elements for grinding the plant material in the process of obtaining natural rubber from the plant material, in which the ball mill has a non-metallic lining and / or the grinding elements have at least one non-metallic surface.

Description

Technical Field

[0001] The present invention relates to a method for obtaining natural rubber from plant materials, comprising at least the step of grinding the plant materials in at least one ball mill containing a grinding medium. The present invention further relates to the natural rubber obtained by this method and the use of at least one ball mill containing a grinding medium for grinding plant materials when obtaining natural rubber from plant materials.

Background Art

[0002] Many consumer goods in modern daily life are made of rubber. Here, natural rubber is often superior to synthetically produced rubber with respect to possible stress and quality. For a long time, natural rubber has mainly been obtained from rubber trees of the genus Hevea, particularly the plant species Hevea brasiliensis, which is mainly cultivated in Asia.

[0003] In recent years, a search has been made for suitable alternatives for obtaining rubber, with particular interest in plants that grow even under the climatic conditions of central Europe. A known suitable alternative for obtaining natural rubber is the dandelion, particularly the Russian dandelion (Taraxacum kok-saghyz). The latter can supply rubber as a dry matter of more than 10% (w / w) per plant, and the natural rubber obtained is very similar to that obtained from Hevea brasiliensis.

[0004] Methods for obtaining natural rubber from dandelions and other plants and the use of natural rubber in rubber products such as tires are already known.

[0005] International Publication No. 2018036825A1 describes the first type of method, in which a portion of the dandelion plant is crushed and / or pressed to form pulp, which is then separated into a phase that is rich in inulin and low in rubber, and a phase that is rich in rubber and low inulin. The crushing and pressing can usually be done using a bead mill or a ball mill.

[0006] U.S. Patent No. 814,407 also already describes the use of a ball mill for processing rubber-containing plant parts.

[0007] Ball mills, which use cast iron balls or steel balls as the grinding medium in a steel milling chamber equipped with wear plates, are commonly used.

[0008] While natural rubber can be obtained using such ball mills, it does not necessarily possess the desired quality and high aging stability. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a method for obtaining natural rubber from plant material, comprising the step of grinding the plant material in at least one ball mill containing a grinding medium, which enables the acquisition of high-quality natural rubber with improved aging resistance. [Means for solving the problem]

[0010] This objective is achieved in accordance with the present invention by a ball mill having a grinding medium with a nonmetallic lining and / or at least a nonmetallic surface. [Modes for carrying out the invention]

[0011] Surprisingly, the absence of metal materials in the ball mill that can come into contact with the plant material being ground results in improved quality natural rubber, and therefore, an improved, more reproducible product. Natural rubber is also characterized by improved aging behavior (reduced polymer degradation). This is thought to be because, without metal materials, heavy metal ions that impair the stability and quality of the rubber cannot penetrate it.

[0012] Preferably, the nonmetallic lining and / or nonmetallic surface of the grinding medium is free of heavy metals and / or transition metals, preferably free of cobalt, iron, copper, manganese, and nickel, and particularly preferably free of iron. Iron has been shown to be particularly associated with impairing aging resistance and should not be present in nonmetallic linings and surfaces, for example, in the form of soluble salts.

[0013] According to a preferred development of the present invention, the nonmetallic surface of the nonmetallic lining and / or grinding medium is made of ceramic, glass, mineral, porcelain and / or polymer material.

[0014] When the nonmetallic surface of the nonmetallic lining and / or grinding medium is made of a ceramic material, particularly excellent results can be achieved in terms of reducing polymer degradation and therefore aging resistance. The ceramic material is based, for example, on silicate-based raw materials, oxide-based raw materials, or non-oxide-based raw materials. Preferably, the nonmetallic surface of the nonmetallic lining and / or grinding medium is made of aluminum oxide ceramic containing 90% to 96% aluminum oxide. For example, corundum (Al2O3) can be used.

[0015] When designing a ball mill, the lining and grinding media surfaces can be manufactured from a variety of materials that are as wear-resistant as possible. The grinding media must have at least a non-metallic surface; however, they can also consist entirely of non-metallic materials.

[0016] To minimize mutual wear, it has been found advantageous when the non-metallic lining and the non-metallic surface of the grinding medium are made of the same material, such as corundum.

[0017] The method according to the present invention uses at least one ball mill. Multiple ball mills may also be used, preferably in sequence having different dimensions, grinding media, and linings. According to a preferred development of the present invention, the ball mill may be a drum mill or a tube mill, or the multiple ball mills may be multiple drum mills and / or multiple tube mills. These types of mills enable a continuous process for grinding plant material.

[0018] The plant material is ground in a ball mill in the presence of a liquid, preferably water. In this way, natural rubber can be easily obtained / extracted from the plant material.

[0019] To facilitate the processing of plant materials and obtain natural rubber of the highest possible purity, it has been found advantageous if the plant materials are purified, preferably with water, before being ground in the ball mill. This removes surface deposits such as sand, loam, and clay. Purification can be carried out using conventional equipment, processes, and purifying agents commonly used to purify plant materials.

[0020] It has been found that pre-grinding of plant material before grinding in the ball mill is useful in reducing the residence time of plant material in the ball mill. Pre-grinding can be carried out by conventional cutting or crushing processes, such as using a cutting machine or hammer mill.

[0021] The method according to the present invention can be applied to all plants suitable for obtaining natural rubber. Particularly preferably, the plant material is derived from plants of the genus Taraxacum. Plant material of this genus can be crushed particularly well by this method.

[0022] In order to obtain a particularly high proportion of natural rubber from plant material, the plant material is derived from plants of the Russian dandelion species (Taraxacum kok - saghyz) or its descendants (hybrids).

[0023] When plants of the Taraxacum genus are used, the whole plant can be ground in this method. However, since the roots and hypocotyls of the dandelion contain the highest proportion of natural rubber, preferably, the plant material essentially comprises these plant parts.

[0024] The present invention also includes the natural rubber obtained by this method. Due to the low content of heavy metal ions, this natural rubber is characterized by excellent quality and improved aging resistance. This natural rubber can be used in the manufacture of various rubber products, preferably tires. Products manufactured from this natural rubber, such as vehicle tires, are characterized by excellent mechanical and dynamic properties and aging stability. For this purpose, the natural rubber obtained by this method can be processed by mixing and vulcanization together with conventional mixture components such as fillers, anti - aging stabilizers, plasticizers, sulfur, and vulcanization accelerators, in the same manner as natural rubber obtained from conventional Para rubber (Hevea brasiliensis), to form vulcanizates.

[0025] The present invention further relates to the use of at least one ball mill containing a grinding medium for grinding plant material when obtaining natural rubber from plant material, wherein the ball mill has a non - metallic lining and / or the grinding medium has at least a non - metallic surface.

[0026] Here, the present invention will be described in more detail by comparative examples and examples. Table 1 shows the linings and grinding media used and the analysis results obtained.

Examples

[0027] 1 - 4 kg of fresh roots of Russian dandelion purified with water were boiled in 5 - 10 times the amount of water for 20 - 60 minutes, separated from the boiling water, and transferred to a ball mill (KM30, nominal volume 30 L, 30 kg of milling balls (ball diameter 1.5 - 6 cm)) together with 3 - 10 times the amount of pure water. Then, the ball / root / water mixture was pulverized at a speed of 0.5 - 0.75*n (critical) for 1 - 4 hours. The exact pulverization parameters depend on the quality (size, etc.) of the roots, and the optimal pulverization result is characterized by the formation of rubber flakes with a diameter of about 0.5 - 5 cm and in a homogeneous plant pulp. At the same time, the lining of the mill and the pulverization medium were changed according to Table 1. The obtained suspension was filtered using, for example, a plate with holes of 5 mm diameter (other filter screens, or devices, or grids are also possible and suitable, and flotation separation can also be used for separation). The filter cake contains the rubber flakes formed during the pulverization process. The rubber flakes were washed several times with water and then dried at room temperature. The milling balls could be separated by a ball trap when emptying the mill.

[0028] The natural rubber thus obtained was analyzed for the following parameters: - The iron content (Fe content) of the rubber by ash content (100 - 150 mg) at 550 °C by XRF (X-ray fluorescence spectrometry) is direct by a SPECTRO XEPOS device in an XRF SpectroMicro sample cup (inner diameter 6.1 mm) with a PROLENE film from Spectro. - The number-average molar mass M of the natural rubber relative to a polystyrene standard by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the eluent in accordance with DIN 55672-1 n and the weight-average molar mass M w .

[0029]

Table 1

[0030] Table 1 shows that using non-metallic materials as lining and / or grinding media can significantly reduce polymer degradation and, consequently, natural rubber aging. This is particularly advantageous when the lining and grinding media consist of corundum. While this application relates to the invention described in the claims, it may also encompass the following other embodiments. 1. A method for obtaining natural rubber from plant material, comprising at least the step of grinding the plant material in at least one ball mill containing a grinding medium, wherein the ball mill has a non-metallic lining and / or the grinding medium has at least a non-metallic surface. 2. A method for obtaining natural rubber from plant materials as described in 1 above, characterized in that the nonmetallic lining and / or the nonmetallic surface of the grinding medium does not contain heavy metals and / or transition metals. 3. A method for obtaining natural rubber from plant materials as described in 2 above, characterized in that the nonmetallic lining and / or the nonmetallic surface of the pulverized medium does not contain iron. 4. A method for obtaining natural rubber from plant materials according to any one of items 1 to 3 above, characterized in that the nonmetallic lining and / or the nonmetallic surface of the grinding medium is made of ceramic, glass, mineral, porcelain and / or polymer material. 5. A method for obtaining natural rubber from plant materials according to any one of items 1 to 4 above, characterized in that the nonmetallic lining and / or the nonmetallic surface of the grinding medium is made of a ceramic material, preferably aluminum oxide ceramic. 6. A method for obtaining natural rubber from plant materials according to any one of items 1 to 5 above, characterized in that the nonmetallic lining and the nonmetallic surface of the grinding medium are made of the same material. 7. A method for obtaining natural rubber from plant material according to any one of items 1 to 6 above, characterized in that the ball mill is a drum mill or a tube mill, or the plurality of ball mills are a plurality of drum mills and / or a plurality of tube mills. 8. A method for obtaining natural rubber from a plant material according to any one of items 1 to 7 above, characterized in that the plant material is pulverized in the ball mill in the presence of a liquid, preferably water. 9. A method for obtaining natural rubber from a plant material according to any one of items 1 to 8 above, characterized in that the plant material is purified, preferably washed with water, before being ground in the ball mill. 10. A method for obtaining natural rubber from a plant material according to any one of items 1 to 9 above, characterized in that the plant material is pre-ground before being ground in the ball mill. 11. A method for obtaining natural rubber from a plant material according to any one of items 1 to 10 above, characterized in that the plant material is derived from a plant of the genus Taraxacum. 12. A method for obtaining natural rubber from the plant material described in 11 above, characterized in that the plant material is derived from the Russian dandelion species (Taraxacum kok-saghyz) or its offspring (hybrid). 13. A method for obtaining natural rubber from the plant material described in 11 or 12 above, characterized in that the plant material essentially contains roots and hypocotyls. 14. Natural rubber obtained by the method described in any one of items 1 to 13 above. 15. Use of at least one ball mill comprising a grinding medium for grinding plant material when obtaining natural rubber from plant material, wherein the ball mill has a non-metallic lining and / or the grinding medium has at least a non-metallic surface.

Claims

1. A method for obtaining natural rubber from plant material, comprising at least the step of grinding the plant material in at least one ball mill containing a grinding medium, - The grinding medium has at least a non-metallic surface, or - The ball mill has a non-metallic lining, and the grinding medium has at least a non-metallic surface, and The non-metallic surface of the grinding medium is made of ceramic, glass, mineral, and / or porcelain. A method characterized by the following.

2. The method for obtaining natural rubber from plant materials according to claim 1, characterized in that the nonmetallic lining does not contain heavy metals and / or transition metals.

3. The method for obtaining natural rubber from plant materials according to claim 2, wherein the non-metallic lining does not contain iron.

4. A method for obtaining natural rubber from plant materials according to any one of claims 1 to 3, characterized in that the non-metallic lining consists of ceramic, glass, mineral, porcelain and / or polymer material.

5. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 4, characterized in that the nonmetallic lining and / or the nonmetallic surface of the grinding medium is made of a ceramic material.

6. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 5, characterized in that the nonmetallic lining and the nonmetallic surface of the grinding medium are made of the same material.

7. A method for obtaining natural rubber from plant material according to any one of claims 1 to 6, characterized in that the ball mill is a drum mill or a tube mill, or the plurality of ball mills are a plurality of drum mills and / or a plurality of tube mills.

8. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 7, characterized in that the plant material is pulverized in the ball mill in the presence of a liquid.

9. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 8, characterized in that the plant material is purified before being ground in the ball mill.

10. A method for obtaining natural rubber from a plant material according to claim 9, characterized in that the plant material is washed with water before being ground in the ball mill.

11. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 10, characterized in that the plant material is pre-ground before being ground in the ball mill.

12. A method for obtaining natural rubber from a plant material according to any one of claims 1 to 11, characterized in that the plant material is derived from a plant of the genus Taraxacum.

13. A method for obtaining natural rubber from a plant material according to claim 12, characterized in that the plant material is derived from a Russian dandelion (Taraxacum kok-saghyz) plant or its offspring (hybrid).

14. A method for obtaining natural rubber from a plant material according to claim 12 or 13, characterized in that the plant material essentially includes roots and hypocotyls.

15. In the use of at least one ball mill containing a grinding medium for grinding plant material when obtaining natural rubber from plant material, - The grinding medium has at least a non-metallic surface, or - The ball mill has a non-metallic lining, and the grinding medium has at least a non-metallic surface, The use is characterized in that the non-metallic surface of the grinding medium is made of ceramic, glass, mineral and / or porcelain.

16. The use according to claim 15, characterized in that the non-metallic lining consists of ceramic, glass, mineral, porcelain and / or polymer material.

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