Rubber composition containing biotechnologically modified rubber particles

Abstract

The present invention relates to a rubber composition comprising natural rubber, butadiene rubber, styrene-butadiene rubber, synthetic polyisoprene or ethylene-propylene-diene rubber, or a blend of two or more types of rubber, fillers, a crosslinking system, and recycled rubber particles. The recycled rubber particles are biotechnologically modified. The addition of the modified rubber particles improves the physical properties of the rubber composition and the service life of engine mounts or bushings. Through the biotechnological treatment of vulcanized rubber and the use of expensive modified rubber particles, the amount of waste and CO2 emitted is significantly reduced through the use of recycled materials, and the recycling rate within the product is also increased. Furthermore, the present invention relates to the use of the rubber composition according to the present invention for technical rubber articles, preferably for engine mounts and bushings.

Description

Technology Field

[0001] The present invention relates to a rubber composition according to the preamble of claim 1 and a method according to claim 11. Background Technology

[0002] Every year, the rubber processing industry produces large tonnes of defective vulcanized rubber due to the process; these defective products are either treated as waste or processed into low-quality products. Because rubber has a high thermal value (3.3 * 10⁻⁶ 4 (KJ / kg), the fundamental disposal possibility lies in controlled incineration, particularly in the case of tires, for energy recovery and as an alternative fuel for the production of steam, electric energy, pulp, paper, lime, and steel, alongside coal. In the cement industry, in particular, even entire tires are utilized, where cement kilns operate at temperatures exceeding 1,200°C, ensuring the complete incineration of all components. The incineration of waste causes a greater release of carbon dioxide (CO2) and removes large amounts of material from the recyclable-material cycle. Many tire manufacturers have already announced that they will utilize prescribed quotas of recycled or biologically produced materials in tires starting in 2030 and will steadily increase these quotas. In practice, these efforts are particularly relevant to plastics, yet other materials such as rubber are not excluded and can make a significant contribution to a similarly circular value creation chain in the future.

[0003] In recent years, the rubber industry has also accelerated its exploration of the potential for recycling materials. One approach involves the pyrolysis of waste rubber and the utilization of the resulting "recovered carbon black," pyrolysis oil, and recovered steel products. Another possibility for processing vulcanized rubber waste for reuse is desulfurization, the purpose of which is to extract sulfur from the material. In these processes, sulfur bridges must be severed without cleaving the bonds within the polymer chains. To achieve this, various methods are applied. In addition to thermal-mechanical processing within the extruder, additives, ultrasound, or supercritical CO2 are also used as aids to improve desulfurization and reduce polymer chain cleavage. However, using very high temperatures exceeding 150°C and up to 300°C causes not only sulfur bridges but also polymer chains to cleave, resulting in a degradation of properties. Accordingly, the standard desulfurization method is rather downcycling rather than recycling.

[0004] US2019 / 0382564A1 describes a rubber composition based on an elastomer, a filler, a cross-link system, and rubber granules. The rubber granules are obtained through the recycling of rubber materials by grinding them into particles having a defined particle size distribution.

[0005] Tire granules derived from waste tires or rubber waste and used in the above applications are not modified and frequently degrade the properties of new rubber compositions.

[0006] The main features of the present invention are specified in the feature portion of claim 1. Other embodiments are the subject of dependent claims or are described below.

[0007] The rubber composition according to the present invention

[0008] - Rubber selected from natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), synthetic polyisoprene (IR) or ethylene-propylene-diene rubber (EPDM) or a blend of two or more types of rubber,

[0009] - At least one filler,

[0010] - At least one bridging system and

[0011] - Contains recycled rubber particles.

[0012] The recycled rubber particles consist of biotechnologically modified polyisoprene selected from natural rubber, synthetic polyisoprene, or a mixture thereof, ground. The recycled rubber particles include a surface functionalized with functional groups.

[0013] Rubber refers to natural or synthetic rubber containing additional components in addition to rubber. The rubber composition according to the present invention includes natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), synthetic polyisoprene (IR), or ethylene-propylene-diene rubber (EPDM), or a mixture of two or more types of rubber. Preferably, the rubber composition comprises a mixture of natural rubber and synthetic polyisoprene as rubber.

[0014] Preferably, the modified rubber particles are rubber particles treated with enzymes based on vulcanized isoprene rubber containing carbon black.

[0015] The rubber composition preferably comprises 15 to 75 phr, preferably at least 50 phr of recycled rubber particles. The rubber composition very preferably comprises 50 to 75 phr of recycled rubber particles.

[0016] The unit "phr" stands for Parts Per Hundred Rubber. In other words, X parts by weight of rubber particles or other components are additionally included per 100 parts by weight of raw rubber. The proportion of rubber within the rubber particles is not considered as raw rubber. The phr value always relates to the composition prior to vulcanization.

[0017] The modified rubber particles preferably have an average particle diameter of less than 700 µm, preferably less than 500 µm, additionally preferably less than 400 µm, and even more preferably less than 250 µm.

[0018] The modified rubber particles comprise a surface functionalized with functional groups. Preferably, the modified rubber particles comprise carbonyl groups, preferably terminal aldehyde groups and / or terminal ketone groups, as functional groups on the particle surface. Aldehyde and ketone groups are generated during the enzymatic degradation of polyisoprene, and consequently, carbonyl groups are generated on the partially degraded polyisoprene.

[0019] In addition to rubber particles functionalized with functional groups, functionalized oligomers are also generated during the enzymatic treatment of rubber powder. The number of these oligomers is strongly determined by the particle size of the starting material and increases as the size decreases. Figure 3 illustrates the ratio of oligo-isoprenoids after enzymatic treatment according to the average particle diameter of the ground rubber. When the particles are smaller and consequently have larger surfaces, stronger functionalization occurs, thereby generating a greater number of oligo-isoprenoids. These functionalized oligomers can fulfill various functions when incorporated into rubber compositions due to their specific properties. Furthermore, due to their small molecular weight, functionalized oligomers act as processing aids and plasticizers, and because of their functionality, they cannot be easily extracted like oil.

[0020] For example, liquid butadiene rubber exhibits advantages over TDAE (treated distillate aromatic extract) oil because it moves less and causes better dispersion of fillers due to its functional properties.

[0021] In addition, the functionalized oligomer can act as a mediator between the rubber chain and the modified particles through a combination of carbonyl functionality and an isoprene structure.

[0022] The above rubber composition includes, in addition to rubber, fillers, crosslinking agents, and other vulcanization aids. Suitable fillers are reinforcing fillers such as carbon black, silica, or mixtures thereof. In particular, when dark coloration of the rubber product is to be achieved, the filler is carbon black. The filler is included in an amount of 5 to 200 phr, preferably 10 to 150 phr. Suitable carbon black is ASTM grade carbon black such as N115, N220, N330, N550, N660, N772, and N990, but other carbon blacks for rubber articles are also possible.

[0023] The above rubber composition may include silica, or a mixture of various silicas.

[0024] The crosslinking system is preferably based on sulfur or a sulfur donor and a primary vulcanization accelerator. Additionally, secondary accelerators and activators, such as zinc oxide and stearic acid, may also be used. Preferably, sulfur is included in an amount of 0.1 phr to 5 phr, and particularly preferably in an amount of 0.5 to 3 phr.

[0025] In one embodiment, the rubber composition further comprises one or more additives selected from plasticizers, resins, antioxidants, and ozone-protecting waxes.

[0026] In a preferred embodiment, the rubber composition according to the present invention is

[0027] 100 phr of natural rubber and / or synthetic polyisoprene,

[0028] Modified rubber particles of 15 phr to 75 phr, preferably modified rubber particles of 50 to 75 phr,

[0029] 0.1 phr to 5 phr of sulfur,

[0030] Carbon black of 5 phr to 200 phr, preferably carbon black of 10 phr to 150 phr,

[0031] It includes 1 phr to 50 phr of additives, preferably 1 phr to 20 phr of additives, such as plasticizers, antioxidants, ozone-protecting waxes, resins, and accelerators.

[0032] For the production of modified rubber particles, that is, enzyme-treated rubber particles, rubber waste consisting of a mixture of natural rubber or synthetic polyisoprene, or other rubber, preferably BR or SBR, carbon black, silica, or other fillers and a blend of natural rubber or polyisoprene; preferably rubber waste derived from waste tires; or rubber waste derived from other rubber products is ground into particles. The rubber particles obtained through grinding have an average particle diameter of less than 700 µm, preferably less than 500 µm, preferably less than 400 µm, and preferably less than 250 µm. The rubber particles are first pretreated after grinding. For pretreatment, the rubber particles are extracted with an organic solvent, preferably ethyl acetate, acetone, chloroform, n-pentane, cyclohexane, hexane, dichloromethane, toluol, or a mixture thereof, and very preferably acetone, cyclohexane, chloroform, or a mixture of cyclohexane and acetone. For the degradation of the rubber composition into oligo-isoprene and for surface modification of the pretreated rubber particles, an enzyme selected from Lcp (latex clearing protein), RoxA (rubber oxygenase), RoxB (rubber oxygenase), and mixtures thereof, preferably Lcp1 VH2 It is mixed with.

[0033] LCP (latex removal protein), RoxA, and RoxB are rubber oxygenases that promote the addition of molecular oxygen to cis double bonds, thereby causing oxidative cleavage that results in the formation of aldehyde and ketone groups on the rubber chains. Through the use of rubber particles, oxidative cleavage occurs on the surface, generating functional groups therefrom. Preferably, LCP K30 , Lcp1 VH2 , RoxA XSp , RoxBXSp is used, and very preferably Lcp1 VH2 is used.

[0034] Enzymes are, for example, E.coli It is manufactured in C41 through a fed-batch fermentation process.

[0035] The treatment of rubber particles may take place in a test tube within an incubation shaker containing a buffer, such as TRIS / HCl buffer at pH 7. Enzyme addition may be performed through individual additions or in multiple stages, for example, over a period of several days, preferably daily over five days.

[0036] Accordingly, modified rubber particles are preferably manufactured by the following steps.

[0037] - A step of providing rubber waste that is a mixture of natural rubber and synthetic polyisoprene, or based on natural rubber or synthetic polyisoprene, each of which includes carbon black, silica, or other fillers;

[0038] - A step of crushing the rubber waste into particles having an average particle diameter of less than 700 μm, preferably less than 500 μm, additionally preferably less than 400 μm, and even more preferably less than 250 μm;

[0039] - A step of pre-treating the rubber particles with an organic solvent in the extraction step; and

[0040] - A step of treating the rubber particles with an enzyme selected from Lcp, RoxA, RoxB, and mixtures thereof.

[0041] Through this manufacturing method for modified rubber particles, the cleavage of sulfur bridges is prevented, and selective cleavage of rubber chains and functionalization of the rubber particle surface using carbonyl groups are achieved. Fig. 1 illustrates, as an example, modified rubber particles containing carbonyl groups and polyisoprene residues on the surface. Through increased chain flexibility and polar functionalization after cleavage, the resulting material can be incorporated into a new rubber composition as an active filler; however, while the properties of the resulting material are very similar to the original material, the desulfurized material causes a clear deterioration of properties. In particular, the high temperature required for successful desulfurization irreversibly damages the material.

[0042] Accordingly, rubber particles are modified under conditions where enzymes are used, while the sulfur network of the recycled rubber is maintained. As a result, the rubber particles are functionalized on the surface, thereby exhibiting improved bonding to the rubber matrix. Thus, more than 15 phr of functionalized rubber particles can be added to a new rubber mixture with unchanged or improved properties, whereas less than 10 phr of unmodified particles can be added.

[0043] Through the addition of modified rubber particles, the physical properties of the rubber composition and the service life of engine mounts or bushings are improved. Through the use of enzyme-treated rubber granules, including functionalized surfaces, superior bonding to the rubber matrix is ​​achieved. In particular, expensive rubber waste generated directly during rubber production can be introduced into recycling management and no longer needs to be incinerated.

[0044] In addition, the present invention relates to the use of the rubber composition according to the present invention for technical rubber articles, preferably for engine mounts and bushings.

[0045] The rubber composition according to the present invention, comprising biotechnologically modified rubber particles, can be used for parts in the automotive sector. The newly developed material is used in engine mounts or bushings. However, other typical applications for natural rubber mixtures can also be considered.

[0046] Through the biotechnological processing of vulcanized rubber and the use of expensive modified rubber particles in new compositions, the amount of waste and CO2 emitted is clearly reduced through the use of recycled materials, and the recycling rate within the product is also increased. In the example of tires, which have been the most frequently investigated due to their volume, it was confirmed that material recycling achieved a CO2 saving of 2.5 tons per ton of tire compared to incineration in the cement industry. Therefore, a similar scale is expected in the case of vulcanized rubber compositions.

[0047] Modified rubber particles can be mixed as recycled materials at a high ratio of 50 phr (parts by weight per 100 parts by weight of rubber). Brief explanation of the drawing

[0048] In FIG. 1, modified rubber particles containing carbonyl groups and polyisoprene residues on the surface are shown as an example. FIG. 2 illustrates an example of an elastomer bushing having an outer sleeve (1), an elastomer body (2), and an inner sleeve (3). Figure 3 shows the ratio of oligo-isoprenoids after enzyme treatment according to the average particle diameter of the crushed rubber. Specific details for implementing the invention

[0049] Examples

[0050] Example I: Preparation of Modified Particles

[0051] For the manufacture of modified particles, Lcp1 VH2Rubber granules were placed in a glass container with a buffer [TRIS / HCl buffer (0.2M, pH 7)] and treated for 5 days in a culture shaker at 30°C. For this purpose, 500 mg of enzyme was used per gram of rubber granules, and the container was shaken at 90 rpm.

[0052] Example II: Preparation of a rubber composition

[0053] Rubber compositions having the composition specified in Table 1 were prepared.

[0054] Rubber composition M1 Comparative composition V1 Natural rubber (NR) 100 100 Modified rubber particles of Example I 50 -- Carbon Black (ASTM N550) 80 80 zinc oxide 5 5 stearic acid 2 2 Antioxidant*(6PPD) 2 2 Accelerator* (CBS) 2 2 sulfur 2 2

[0055] Formulation of rubber compositions prior to vulcanization.

[0056] 6PPD = N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine,

[0057] CBS = N-cyclohexyl-2-benzothiazyl-sulfenamide-based promoter;

[0058] CBS and Hwang form a bridge system together.

[0059] The aforementioned components were mixed in two stages in an internal mixer. In the first stage, all components except the crosslinking system were mixed until a maximum temperature of 110°C to 190°C was reached. In the second stage, the crosslinking system was added and mixed for up to 5 minutes at a temperature below 110°C.

[0060] The obtained compositions were vulcanized at 150°C for 15 minutes to obtain a 2 mm plate and an elastomer bushing according to Fig. 2.

[0061] FIG. 2 illustrates an example of an elastomer bushing having an outer sleeve (1), an elastomer body (2), and an inner sleeve (3), which is placed in a test device (6, 7). Fx,y represents the force applied to the test device (6). The test device (6) connects the moving part of the test device to the outer sleeve (1). Additionally, the elastomer bushing is fixed to the fixed part (7) of the test device using a bolt (5), and in particular, the core (4) of the bushing is fixed to the fixed part (7) of the test device with the help of the bolt (5).

[0062] Measurement of material properties

[0063] The rubber compositions prepared in Example II were analyzed for mechanical properties according to DIN 53504. In addition, mount bushings were manufactured as sample parts using the obtained compositions and periodically radially loaded in a fatigue test at a temperature of 23°C and two amplitude conditions according to Fig. 2. The measured properties and service life test results of the reference composition and the composition containing rubber particles modified to 50 phr are presented in Table 2.

[0064] In this case, compared to the standard composition V1 that does not contain elastomer particles, the properties of the rubber composition according to Example M1 could be clearly improved to the same extent as the service life of the elastomer bushing manufactured with said composition.

[0065] Examples M1 V1 Destruction elongation rate [%] 331 330 tensile strength [N / ㎟] 18.9 16.9 Number of alternating loads (2mm amplitude) 842,500 272,500 Number of alternating loads (1.75mm amplitude) 2,200,000 1,610,000

[0066] Table 2: Results of mechanical properties and service life tests of vulcanized compositions

[0067] Accordingly, it was confirmed that the addition of functionalized elastomer waste not only achieves compositions having the same characteristics but can even clearly improve the said characteristics.

[0068] The present invention is not limited to the embodiments described above but can be modified in various ways.

[0069] All features and advantages that can be inferred from the claims, specification, and drawings, including structural details, spatial arrangement, and method steps, may be essential to the present invention not only individually but also in various combinations.

Claims

Claim 1 A rubber composition comprising: a rubber selected from natural rubber, butadiene rubber, styrene-butadiene rubber, synthetic polyisoprene or ethylene-propylene-diene rubber, or a blend of two or more types of rubber; at least one filler; at least one crosslinking system; and recycled rubber particles, wherein the recycled rubber particles are enzyme-treated rubber particles and have a surface functionalized with functional groups, wherein the enzyme is selected from latex clearing protein (Lcp), rubber oxygenase A (RoxA), rubber oxygenase B (RoxB), and mixtures thereof, and wherein the enzyme-treated rubber particles comprise carbonyl groups as functional groups on the particle surface. Claim 2 A rubber composition according to claim 1, characterized in that the enzyme-treated rubber particles are enzyme-treated rubber particles based on vulcanized isoprene rubber. Claim 3 A rubber composition according to claim 1, characterized in that the rubber composition comprises 15 to 75 phr of the enzyme-treated rubber particles. Claim 4 A rubber composition according to claim 1, characterized in that the rubber particles treated with the enzyme have an average particle diameter of less than 700 μm. Claim 5 A rubber composition according to claim 1, characterized in that the rubber composition comprises a mixture of natural rubber and synthetic polyisoprene as rubber. Claim 6 A rubber composition according to claim 1, wherein the filler is carbon black or silica. Claim 7 A rubber composition according to claim 1, characterized in that the crosslinking system is yellow. Claim 8 A rubber composition according to claim 1, characterized in that the rubber composition further comprises one or more of the components including a plasticizer, a resin, an antioxidant, and an accelerator. Claim 9 A rubber composition according to claim 1, characterized in that the rubber composition comprises 100 phr of natural rubber and / or synthetic polyisoprene, 15 phr to 75 phr of enzyme-treated rubber particles, 0.1 phr to 5 phr of sulfur, 5 phr to 200 phr of carbon black, and 1 phr to 50 phr of additional additives. Claim 10 A rubber composition according to claim 1, characterized in that the rubber particles treated with the enzyme are manufactured by a process comprising the following steps: a) providing rubber waste based on a mixture of natural rubber and synthetic polyisoprene, or natural rubber or synthetic polyisoprene, each comprising carbon black, silica, or other fillers; b) crushing the rubber waste into particles having an average particle diameter of less than 700 μm; c) pre-treating the rubber particles with an organic solvent in an extraction step; and d) treating the rubber particles with an enzyme selected from latex removal protein (Lcp), rubber oxygenation enzyme A (RoxA), rubber oxygenation enzyme B (RoxB), and mixtures thereof. Claim 11 A method for producing enzyme-treated rubber particles according to any one of claims 1 to 10, comprising: a) providing rubber waste based on a mixture of natural rubber and synthetic polyisoprene, or natural rubber or synthetic polyisoprene, each of which comprises carbon black, silica, or other fillers; b) crushing the rubber waste into particles having an average particle diameter of less than 700 μm; c) pre-treating the rubber particles with an organic solvent in an extraction step; and d) treating the rubber particles with an enzyme selected from latex removal protein (Lcp), rubber oxygenase A (RoxA), rubber oxygenase B (RoxB), and mixtures thereof. Claim 12 A rubber composition according to any one of claims 1 to 10, wherein the rubber composition is used for engine mounts and bushings. Claim 13 delete

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