Rubber compound mixture

Abstract

The present invention relates to a matrix of unvulcanized rubber containing micronized rubber powder and a rubber compound mixture containing one or more auxiliaries. The present invention also relates to a method for preparing such a rubber compound mixture and to rubber molded articles. The object of the present invention is to develop a method for chemically activating / functionalizing the micronized rubber powder.

Description

Detailed Description of the Invention

[0001] (Description) The present invention relates to a rubber compound mixture comprising a matrix of unvulcanized rubber containing micronized rubber powder and one or more auxiliaries. The present invention also relates to a method for preparing such a rubber compound mixture and to rubber molded articles.

[0002] Micronized rubber (MRP) is a low-cost and sustainable raw material that replaces natural rubber-based materials derived from crude oil. MRP is a freely flowing black rubber powder that disperses in many systems and applications. Due to its micron size, MRP can be incorporated into multiple polymers and gives a smooth surface appearance to the final product. In some cases, MRP may be chemically treated to activate, i.e., "functionalize," the surface of the powder particles in order to improve compatibility and performance with the host material. This is called functionalized MRP or FMRP. Non-functionalized MRP is only used as an inexpensive filler. Micronized rubber powder (MRP) typically contains a significant proportion of rubber particles with a particle size of less than 100 microns. Powders with a particle size of 40 mesh (420 microns) or less are considered micronized rubber powder.

[0003] MRP has evolved beyond previous post-manufacture rubber technologies. The most basic rubber processing technology is to convert used tires and rubber materials after industrial waste treatment into rubber chips, usually with a size of 10 to 50 cm or more. These chips are used as fuel derived from tires and in civil engineering projects. MRP is a micron-sized material, and many sizes are produced, ranging from 80 mesh (177 microns) to 325 mesh (44 microns). Only FMRP is used in high-end applications such as high-performance tires, industrial rubber, consumer and industrial plastic products, asphalt, coating agents, and construction materials. MRP is used as a compound extender that offsets the use of natural rubber, synthetic polymers, and furnace carbon black, and also functions as a process aid in material manufacturing.

[0004] Rubber compounds containing micronized rubber powder are known in the art.

[0005] The international application WO2021 / 167457 in the name of the inventors relates to a method for producing micronized rubber powder, including the grinding of rubber granulated raw materials, the size classification and storage of the micronized rubber powder thus obtained, and a chemical agent is used during the grinding process to prevent the rubber powder particles from adhering to themselves.

[0006] US2016 / 297243 relates to a tire composed of a toroidal carcass having an outer tread, two beads arranged at intervals, at least one ply extending from bead to bead, and sidewalls extending radially from the above tread and connecting to the above beads, and the sidewalls contain micronized rubber powder.

[0007] US2016 / 152805 relates to a rubber composition composed of solution styrene-butadiene rubber; a functionalized recycled rubber composition composed of an elastomeric polymer and a stabilizer, and a reinforcing filler containing reinforcing silica.

[0008] EP 3 045 492 relates to a rubber compound useful for rubber products or components of rubber products subject to polishing force, and the rubber compound contains at least one natural rubber or synthetic rubber, and 1 to 30 weight percent of a micronized rubber composition having a particle size in the range of 40 mesh (420 microns) to 200 mesh (74 microns), and the micronized rubber composition contains at least 10 weight percent of solution styrene butadiene rubber.

[0009] US2014 / 128535 relates to a method for functionalizing recycled elastomeric materials, and this method includes subjecting the particles of the recycled elastomeric material to shear at a temperature below 100°C so that the intermolecular bonds of the recycled elastomeric material are broken.

[0010] US2017 / 114155 relates to a method for producing a chemically functionalized recycled rubber composition, including the steps of manufacturing a blend mixture by blending micronized rubber powder, i.e., styrene-butadiene rubber, with a processing aid and a functionalizing agent, manufacturing a reaction mixture by treating the blend mixture under conditions of high shear and low temperature, and adding a stabilizer, i.e., N-cyclohexyl (thio) phthalimide, to the reaction mixture to produce recycled rubber. The treatment under high shear conditions is carried out on a two-roll mill, where the functionalizing agent is a compound selected from the group consisting of alkyl thiuram sulfide, aryl thiuram sulfide, heterocyclic thiuram sulfide, thiuram disulfide, thiuram polysulfide, thiuram disulfide, thiuram multisulfide, tetrabenzyl thiuram disulfide, cyclohexylsulfonamide, t-butylsulfonamide, tetraalkyl thiuram disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, dipentamethyl thiuram monosulfide, and tetramethyl thiuram disulfide.

[0011] The inventors have the opinion that the greatest role that micronized rubber powders (MRPs) can play in the future towards CO2 reduction and the realization of cradle-to-cradle / circular economy principles is to reuse them in tires. Approximately 25 million tons of new tires are manufactured annually, and currently about half of them are recycled every year and enter the end-of-life (EOL) tire management waste stream. As a result, how to process used tires in an environmentally friendly way and maximize the value and quantity of circular materials derived from used tires has become an urgent global issue.

[0012] The object of the present invention is to develop a method for chemically activating / functionalizing MRP.

[0013] Another object of the present invention is to further enhance the rubber-internal performance characteristics of activated / functionalized micronized rubber powder (FMRP).

[0014] Another object of the present invention is to compound a high concentration of activated / functionalized fine rubber powder (FMRP) into a natural rubber compound.

[0015] Another object of the present invention is to develop a method for converting functionalized MRP into a solid strip or slab while maintaining performance and dispersibility.

[0016] Accordingly, the present invention relates to a rubber compound mixture comprising a matrix of unvulcanized rubber containing micronized rubber powder and one or more auxiliaries, wherein the surface of the micronized rubber powder is functionalized with a silica component, a silane component, and one or more functionalized components.

[0017] The inventors have found that one or more objects are achieved by functionalizing the surface of the micronized rubber powder through the combination of these three components. The inventors have found that by reactivating the vulcanization potential of MRP through a chemical treatment based on the combination of these three components, both the mechanical performance and the dynamic performance of MRP in the rubber compound can be significantly improved, thereby opening the door to large-scale reuse within the tire and TRG fields.

[0018] In one embodiment, the one or more functionalized components are selected from the group consisting of diphenylguanidine, hexylamine, decylamine, octadecylamine, cyclohexylamine, dicyclohexylamine, quinuclidine, di-o-tolylguanidine, dithiophosphate, phosphoryl polysulfide, and diazabicycloundecene, and diphenylguanidine is a preferred embodiment of such a functionalized component.

[0019] In one embodiment, the one or more functionalized components are selected from the group consisting of zinc dialkyldithiophosphate (ZDTP), polyethyleneimine (PEI), 1,6-bis((dibenzylthiocarbamoyl)disulfanyl)hexane, and dialkyl pentasulfide.

[0020] In one embodiment of the rubber compound, the amount of one or more functionalized components is at least 0.1% by weight and at most 1% by weight, based on the total weight of the rubber compound mixture.

[0021] In one embodiment of the rubber compound, the silica component is selected from the group of synthetic amorphous precipitated silica having a BET surface area of at least 165 m 2 / g. The BET surface area is relevant to specifying the grade of the precipitated silica. An example of a preferred silica is Ultrasil VN3, which has a nominal specific nitrogen surface area of 180 m 2 / g as measured in accordance with ISO9277 (multi-point). The inventors preferably use a fluffy type of precipitated silica, i.e., precipitated silica in a non-fine-grained form, to maximize dispersion and coating on the rubber particle surface.

[0022] In one embodiment of the rubber compound, the amount of the silica component is at least 7% by weight, preferably at least 15% by weight, and at most 36% by weight, preferably at most 25% by weight, based on the total weight of the rubber compound mixture.

[0023] In one embodiment of the rubber compound, the silane component is selected from the group of polysulfide organosilanes.

[0024] In one embodiment of the rubber compound, the amount of the silane component is at least 0.5% by weight, preferably at least 1% by weight, and at most 4% by weight, preferably at most 3% by weight, based on the total weight of the rubber compound mixture.

[0025] In one embodiment of the rubber compound, the unvulcanized rubber is natural rubber.

[0026] In one embodiment of the rubber compound, the amount of the micronized rubber powder is at least 1% by weight and at most 50% by weight, based on the total weight of the rubber compound mixture.

[0027] The particle size distribution (PSD) of the micronized rubber powder (MRP) is preferably D95 < 200 μm and D50 < 120 μm, more preferably D95 < 180 μm and D50 < 100 μm. These values refer to the micronized rubber powder (MRP) before adding chemicals. For example, SI69 silane swells and enlarges the particles.

[0028] The micronized rubber powder (MRP) can be derived from the following tire groups, namely, 100% all - truck / bus tires, 100% all - passenger car tires, 100% off - the - road (OTR) tires, 100% agricultural tires, 100% mining tires, 100% forklift and other solid tires, 100% motorcycle tires, 100% grand prix racing tires, and 100% bicycle tires, or blends thereof.

[0029] Furthermore, other examples of the micronized rubber powder (MRP) include types of used rubber products having a chemical composition similar to that of tires mainly composed of a mixture of natural rubber (NR), styrene - butadiene rubber (SBR), and polybutadiene rubber (BR), such as rubber tracks, conveyor belts, cables, molded products, and extruded products, various vulcanized internal waste streams from the tire manufacturing industry, and blends thereof optionally including any tire waste stream, but are not limited thereto.

[0030] Furthermore, other examples of the micronized rubber powder (MRP) include other types of heterogeneous rubber products not mainly composed of natural rubber (NR), styrene - butadiene rubber (SBR), polybutadiene rubber (BR), and blends thereof, such as waste products mainly composed of EPDM (ethylene - propylene - diene monomer rubber), polychloroprene (CR), chlorosulfonated polyethylene (CSM), polyacrylic acid and acrylate copolymer (ACM), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), chlorinated polyethylene (CPE), silicone rubber (VMQ), etc.

[0031] The present invention also relates to a method for preparing a rubber compound mixture comprising a matrix of unvulcanized rubber containing micronized rubber powder and one or more auxiliaries, the method comprising the following: a) providing micronized rubber powder; b) providing unvulcanized rubber; c) high-speed mixing the micronized rubber powder of step a) and one or more functionalized components in a mixing unit; d) adding a silica component and a silane component to the mixture of step c) at high speed; e) removing the functionalized micronized rubber powder from the mixing unit; f) mixing the functionalized micronized rubber powder of step e) with the unvulcanized rubber of step b) and one or more auxiliaries to obtain a rubber compound mixture.

[0032] In one embodiment of the method, the addition of the silane component in step d) is carried out after the addition of both the silica component and one or more functionalized components.

[0033] In one embodiment of the method, the one or more auxiliaries are selected from the group consisting of peptizers, carbon black, recycled carbon black, silica, stearic acid, scorch retardants, antioxidants, plasticizers, sulfur, accelerators, organic peroxides, peroxide curing aids and processing aids.

[0034] In one embodiment of step f) of the method, the unvulcanized rubber of step b) and one or more auxiliaries are premixed, and the resulting premix is mixed with the functionalized micronized rubber powder of step e) to obtain a rubber compound mixture.

[0035] In one embodiment of the present method, silica is first used as a deflocculant and therefore needs to be added upstream of the process of adding silane. The inventors have found that when silica is added after silane, not enough silane is adsorbed to be a sufficient enhancer of the functionalization chemistry. According to the preferred order of adding various chemical components, silica is added first, then any non-silane chemical is added, and silane is added third. In another embodiment, it is also possible to premix certain functionalized soluble / miscible components with silane (e.g., dialkyl pentasulfide) in a certain mixing ratio and add such a mixture.

[0036] The present invention also relates to a method for manufacturing a rubber molded article through vulcanization, where the rubber compound mixture described above or the rubber compound mixture obtained by the method described above is vulcanized under increased pressure and increased temperature.

[0037] The present invention also relates to a rubber molded article including a vulcanized rubber matrix containing functionalized micronized rubber powder.

[0038] The method for manufacturing micronized rubber powder is disclosed in the international application WO2021 / 167457 in the name of the inventors, and the relevant information of the method is incorporated herein by reference.

[0039] The principle of "surface activation" is to form a chemical crosslink between the vulcanized MRP and the unvulcanized rubber compound during the vulcanization of a new rubber product. The powder no longer exists as "discontinuous and disruptive" particles in the new compound matrix, but instead becomes an integrated (bonded) part of a more homogeneous matrix. Surface activation can be achieved, for example, by coating the surface of the powder with a crosslinkable (unsaturated) polymer together with certain vulcanizing agent chemicals such as zinc oxide, stearic acid, sulfur, and organic accelerators.

[0040] The surface treatment can be carried out, for example, by a continuous extrusion or continuous powder mixing process. The conversion to a solid strip is another process that takes place after the MRP has already been converted to FMRP. The extrusion or grinding process converts the powder into a solid strip or slab. Such a process has the advantage of converting a low bulk density powder into an extruded solid (e.g., strip, sheet) in which the powder particles are bound by a new polymer and additives of other processes. Furthermore, by converting the low bulk density powder into a solid material, the bulk density of the powder becomes approximately three times (~400 kg / m 3 from ~1150 kg / m 3 ), which facilitates efficient transportation and avoids the costly bagging cost of the powder.

[0041] For the purpose of facilitating the understanding of the principles of the present invention, reference is made to the embodiments illustrated in the table. However, it will be understood that the scope of the present disclosure is not intended to be limited thereby; any changes and further modifications to the described or illustrated embodiments, as well as any further applications of the principles of the present disclosure illustrated therein, are contemplated as would normally occur to those skilled in the art to which the present invention pertains.

[0042] The terms "functionalized" or "activated" refer to a functionalized or "surface-desulfurized" material made from micronized rubber powder, as described above herein. The terms "functionalization" and "activation" have the same meaning in context. Such meaning is the ability to generate interfacial crosslinking during vulcanization.

[0043] The term "subjected to shear" refers to the process of feeding a rubber compound into the nip between a first and a second opposing rotating roll, where the first roll rotates at a different speed than the second roll.

[0044] The implementation of the present invention can be further understood by referring to the following examples. These examples are provided for illustrative purposes only and are not intended to be limiting.

[0045] (Example) To examine the performance of the rubber composition, several test examples (see Tables 1 and 2) were prepared.

[0046] The test examples were compared with so-called test recipes. The compositions of the test recipes are shown in Tables 1 and 2. Table 1 is a natural rubber compounding recipe (ASTM D3192), and Table 2 is a reference SBR rubber compounding recipe (ASTM D3191). Neither recipe contains functionalized micronized rubber powder.

[0047] Tests were conducted with natural rubber (conforming to ASTM D3192) and SBR rubber (conforming to ASTM D3191).

[0048] The weight concentrations of the evaluated functionalized micronized rubber powder (FMRP) were 0%, 15%, 25%, and 50% for natural rubber and 0% and 15% for SBR rubber.

[0049] The reference compounds were premixed at the Banbury Research Institute without adding functionalized micronized rubber powder (FMRP).

[0050] The mixing of the functionalized micronized rubber powder (FMRP) samples was carried out using a laboratory two-roll mill with a roll temperature of 60 °C. The batch size was 55 grams.

[0051] The vulcanization of the natural rubber test slabs was carried out at 160 °C for 10 minutes using a laboratory compression molding machine. The vulcanization of the SBR test slabs was carried out at 160 °C for 16 minutes using a laboratory compression molding machine.

[0052] The micronized rubber powder from which the functionalized micronized rubber powder (FMRP) test samples were produced was derived from 100% all-truck tire raw materials and cryogenically ground to a particle size distribution with D95 < 180 μm. As methods for measuring the particle size distribution, there are two possibilities: the use of a sieve tower (ISO 3310-1:2016) and the use of laser diffraction and light scattering techniques (ISO 13320:2019).

[0053] The preparation of functionalized micronized rubber powder (FMRP) by adding silica component, silane component and functionalized component was carried out in a high-speed powder mixer for laboratory use with a workable batch size of 250 grams. As the functionalized component, diphenylguanidine in powder form was used. As the silica component, Hi-Sil 255 (synthetic amorphous precipitated silica, PPG) in powder form was used. As the silane component, Nansil 4 (bis-(3-[triethoxysilyl]-propyl)-tetrasulfane) or silane coupling agent Si 69 (Evonik) was used. Si 69 is bis(triethoxysilylpropyl)tetrasulfide (TESPT) or (in IUPAC name) tetrasulfanediyldi(propane-3,1-diyl)]bis(triethoxysilane).

[0054] The addition order was as follows: 0 seconds: Add diphenylguanidine over about 10 seconds 30 seconds: Add silica over about 5 seconds 60 seconds: Use a thin spray bottle to add silane over about 40 - 50 seconds 120 seconds: Remove from the mixer

[0055] The temperature at the end of the mixing cycle did not exceed 50 °C.

[0056] Tensile properties were carried out according to ISO 37 Type 2.

[0057] Tear strength was measured according to ISO 34-1 Method C.

[0058]

Table 1

[0059]

Table 2

[0060] To examine the performance of the rubber composition, several additional test examples (see Tables 3 and 4) were prepared, namely, Table 3 (natural rubber) and Table 4 (SBR).

[0061]

Table 3

[0062] From the results in Table 3, it is clear that Recipe #1 is the reference recipe, i.e., the composition without the addition of functionalized micronized rubber powder (FMRP). Recipes #2 - 4 are compositions with different concentrations of functionalized micronized rubber powder (FMRP), namely 15 wt%, 25 wt%, and 50 wt% respectively. The properties of the test slabs decrease significantly. For example, the tensile strength decreased from 21.0 MPa to 11.2 MPa when loaded with 50 wt% FMRP.

[0063] The addition of silica component, silane component, and functionalized component results in an improvement in properties. It can be seen that the tear strength (kN / m) of Recipe #7 (31.2 kN / m) is much higher compared to Recipe #6 (only the addition of silica component and silane component, 24.0 kN / m). The same is true for Recipe #9 compared to Recipe #10.

[0064]

Table 4

[0065] From the results in Table 4, it is clear that the beneficial results demonstrated for natural rubber in Table 3 were not observed in SBR. In fact, when silica component, silane component, and functionalized component are added to SBR, the tear strength deteriorates. Refer to Recipe #4 compared to the reference Recipe #1 in this context.

[0066] From both Tables 3 and 4, it was concluded that the properties deteriorated when non-functionalized MRP was added. The higher the addition concentration, the more severe the deterioration. Furthermore, when 5% of silane was added alone, a significant beneficial effect was obtained, and in the combination of 0.5% of silica and 5% of silane, the performance was improved compared to the case where only 5% of silane was added.

[0067] The inventors surprisingly found that a combination of 0.5 wt% of silica, 5 wt% of silane, and 0.1 to 2 wt% of diphenylguanidine, preferably 0.1 to 1 wt% of diphenylguanidine, resulted in satisfactory results. Furthermore, the properties of SBR were improved by the addition of 0.5 wt% of silica and 5 wt% of silane, but were not further improved by the addition of diphenylguanidine.

Claims

1. A rubber compound mixture comprising a matrix of unvulcanized rubber containing micronized rubber powder and one or more auxiliaries, wherein the surface of the micronized rubber powder is functionalized with a silica component, a silane component and one or more functionalized components.

2. The rubber compound according to claim 1, wherein the one or more functionalized components are selected from the group consisting of diphenylguanidine, hexylamine, decylamine, octadecylamine, cyclohexylamine, dicyclohexylamine, quinuclidine, di-o-tolylguanidine, dithiophosphate, phosphoryl polysulfide, and diazabicycloundecene.

3. The rubber compound according to claim 1, wherein the functionalized component is diphenylguanidine.

4. The rubber compound according to any one of claims 1 to 3, wherein the amount of the one or more functionalized components is at least 0.1% by weight and at most 1% by weight based on the total weight of the rubber compound mixture.

5. The silica component is selected from the group of synthetic amorphous precipitated silica having a BET surface area of at least 165 m ２ / g, and the rubber compound according to any one or more of claims 1 to 4.

6. The rubber compound according to any one of claims 1 to 5, wherein the amount of the silica component is at least 7% by weight, preferably at least 15% by weight and at most 36% by weight, preferably at most 25% by weight based on the total weight of the rubber compound mixture.

7. The rubber compound according to any one of claims 1 to 6, wherein the silane component is selected from the group of polysulfide organic silanes.

8. The rubber compound according to any one of claims 1 to 7, wherein the amount of the silane component is at least 0.5% by weight, preferably at least 1% by weight and at most 4% by weight, preferably at most 3% by weight based on the total weight of the rubber compound mixture.

9. The rubber compound according to any one of claims 1 to 8, wherein the unvulcanized rubber is natural rubber.

10. The rubber compound according to any one of claims 1 to 9, wherein the amount of the micronized rubber powder is at least 1% by weight and at most 50% by weight based on the total weight of the rubber compound mixture.

11. The rubber compound according to any one or more of claims 1 to 10, wherein the one or more functionalized components are selected from the group consisting of zinc dialkyldithiophosphate (ZDTP), polyethyleneimine (PEI), dialkyl pentasulfide, and 1,6-bis((dibenzylthiocarbamoyl)disulfanyl)hexane.

12. The rubber compound according to any one or more of claims 1 to 11, wherein the particle size distribution (PSD) of the micronized rubber powder (MRP) is D95 < 200 μm and D50 < 120 μm, preferably D95 < 180 μm and D50 < 100 μm.

13. A method for preparing a rubber compound mixture comprising a matrix of unvulcanized rubber containing micronized rubber powder and one or more auxiliaries, the method comprising: a) providing the micronized rubber powder; b) providing the unvulcanized rubber; c) rapidly mixing the micronized rubber powder of step a) and one or more functionalized components in a mixing unit; d) rapidly adding a silica component and a silane component to the mixture of step c); e) removing the functionalized micronized rubber powder from the mixing unit; f) mixing the functionalized micronized rubber powder of step e) with the unvulcanized rubber of step b) and one or more auxiliaries to obtain a rubber compound mixture.

14. The method according to claim 13, wherein in step d), the silane component is added after the silica component and the one or more functionalized components.

15. The method according to any one of claims 13 to 14, wherein the one or more auxiliaries are selected from the group consisting of peptizer, carbon black, recycled carbon black, silica, stearic acid, scorch retarder, antioxidant, plasticizer, sulfur, accelerator, organic peroxide, peroxide curing aid, and processing aid.

16. The method according to any one of claims 13 to 15, wherein in step f), the unvulcanized rubber of step b) and the one or more auxiliaries are premixed, and the resulting premix is mixed with the functionalized micronized rubber powder of step e) to obtain a rubber compound mixture.

17. A method for manufacturing a rubber molded article through vulcanization, comprising vulcanizing the rubber compound mixture according to any one or more of claims 1 to 12, or the rubber compound mixture obtained by the method according to claims 13 to 16, under high pressure and high temperature.

18. A rubber molded article comprising a vulcanized rubber matrix containing a functionalized micronized rubber powder, obtained by the method for producing a vulcanized rubber molded article according to claim 17.

Images