Gelatin powder comprising kaolin

Abstract

The invention relates to a crumb composed of particles of ground tire innerliners, said crumb comprising kaolin. The crumb is capable of improving the tear resistance of rubber compositions containing the crumb.

Description

Technical Field

[0001] This invention relates to rubber powder obtained from tire rubber compositions. Background Technology

[0002] Specifically, it is currently advantageous for tire manufacturers to promote the recycling and reuse of end-of-life tires in new tires or other new rubber products in order to reduce the environmental impact of their activities.

[0003] It is also beneficial for manufacturers to find solutions to reduce the cost of rubber compositions without adversely affecting the performance of tires or other rubber products that use these compositions.

[0004] One possible approach to addressing these two points of interest is to introduce rubber powder obtained from grinding or micronizing vulcanized rubber compositions into rubber compositions used in tires or rubber articles. Tires produced by this type of process are described in the prior art, for example in document WO2020 / 128255.

[0005] Tire manufacturers sometimes also incorporate rubber powder obtained from the recycling of tires or cured capsules into compositions used for tire airtight layers, as described in documents KR100943526, EP1612242 and US6730732.

[0006] However, rubber products, especially tire airtight layers, must also possess good mechanical strength properties, including after aging. Surprisingly, the applicant has discovered that the use of specific rubber powders (particularly those containing kaolin) in rubber compositions can improve the post-aging tear strength properties of the resulting compositions. Summary of the Invention

[0007] Therefore, the first subject of the present invention is a rubber powder composed of particles containing kaolin from the ground tire airtight layer.

[0008] Another subject of the invention is a rubber composition comprising the rubber powder according to the invention.

[0009] Another subject of the invention is a tire comprising a rubber composition or powder according to the invention.

[0010] Another subject of the invention is a rubber article comprising a rubber composition or powder according to the invention. Detailed Implementation

[0011] Any range of values ​​expressed as “between a and b” represents a range of values ​​from greater than a to less than b (i.e., excluding the extreme values ​​a and b), while any range of values ​​expressed as “from a to b” means a range of values ​​from a to b (i.e., including the strict extreme values ​​a and b).

[0012] The abbreviation "phr" refers to parts by weight of 100 parts of elastomer present in the elastomer matrix. The elastomer matrix is ​​understood to refer to all elastomers present in the rubber composition.

[0013] The compounds mentioned in the specification (typically polymers, fillers, plasticizers, coupling agents, vulcanization systems, other additives, etc.) can be fossil-derived or bio-based. In the latter case, they can be partially or entirely derived from biomass, or obtained from renewable starting materials derived from biomass. Similarly, the mentioned compounds can also be derived from the recycling of previously used materials; that is, they can be partially or entirely derived from the recycling process, or obtained from starting materials that themselves originate from the recycling process.

[0014] The present invention, described in more detail below, relates to at least one subject matter as defined according to any of the embodiments listed below: 1- Rubber powder composed of ground tire airtight layer particles, said rubber powder including kaolin.

[0015] 2- The adhesive powder according to embodiment 1 has a median particle size between 50 and 500 μm, preferably between 100 and 400 μm.

[0016] 3- The rubber powder according to any one of the foregoing embodiments contains at least 40% by weight of halogenated butyl rubber.

[0017] 4- The adhesive powder according to any one of the foregoing embodiments comprises 0 to 20% by weight of polyisoprene elastomer, wherein the polyisoprene elastomer preferably contains more than 90 mol% of cis-1,4- bonds.

[0018] 5- The rubber powder according to any one of the foregoing embodiments, wherein the halogenated butyl rubber is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of both.

[0019] 6- The adhesive powder according to any one of the foregoing embodiments comprises reinforcing fillers.

[0020] 7- The adhesive powder according to embodiment 6, wherein the weight percentage of the reinforcing filler is 10% to 40%, preferably 20% to 30%.

[0021] 8- The adhesive powder according to any one of embodiments 6 and 7, wherein the reinforcing filler comprises carbon black, wherein the carbon black accounts for more than 50% by weight of the total weight of the reinforcing filler, preferably more than 80% by weight, and even more preferably 100% by weight.

[0022] 9- The adhesive powder according to any one of the foregoing embodiments, wherein the weight percentage of kaolin in the adhesive powder is 3% to 30%, preferably 5% to 20%.

[0023] 10- The rubber powder according to any one of the foregoing embodiments comprises a vulcanization system.

[0024] 11- A rubber composition comprising rubber powder according to any one of the foregoing embodiments.

[0025] 12- Tires comprising the rubber composition according to embodiment 11 or the rubber powder according to any one of embodiments 1 to 10.

[0026] 13- A rubber article comprising the rubber composition according to embodiment 11 or the rubber powder according to any one of embodiments 1 to 10.

[0027] glue powder The first subject of this invention is a kind of adhesive powder.

[0028] It should be recalled that rubber powder is typically in the form of granules (or microspheres) and optionally formed into rubber sheets. Often, rubber powder is a product of material recycling: it is obtained from the milling (particularly micronization) of cured rubber compositions that have already been used for initial applications, such as as tire curing capsules (e.g., in US6730732) or as tires that have reached the end of their lifespan (e.g., in KR100943526). Suitable methods for milling rubber compositions can include any method or process that does not degrade the rubber during the milling process. For example, methods of milling in the presence of water can be selected, such as those described in US4374573, US4714201, US5238194, and US5411215: these methods are able to maintain the temperature of the rubber at a sufficiently low level to avoid reversion, i.e., degradation of the rubber's cross-linked network. Cryogenic milling can also be used. Depending on the obtained object size distribution, the rubber powder obtained by these methods can undergo an additional sieving step to control this distribution. Sieving can be performed using various techniques known to those skilled in the art (vibration, centrifugation, suction). The powder obtained from the grinding process is usually in the form of microparticles. The term "microparticle" is understood to mean particles with a size (the diameter for spherical particles, and the maximum size for anisotropic particles) of tens or hundreds of micrometers.

[0029] According to one embodiment of the invention, the adhesive powder according to the invention is in the form of microparticles, the median volume size of which is preferably between 50 μm and 500 μm, and more preferably between 100 μm and 400 μm. These particle size ranges are applicable to any embodiment of the invention.

[0030] Tire airtight layer A key feature of the rubber powder according to the invention is that it consists of particles of ground tire airtight layer. In other words, the constituent elements of the rubber powder are particles of tire airtight layer. The rubber powder suitable for the purposes of this invention can then be prepared by a method comprising recovering the tire airtight layer and then grinding or micronizing it using the method described above.

[0031] The compositions of rubber powders that can be used for the purposes of this invention are typically vulcanized rubber compositions that form an airtight layer.

[0032] As is well known, rubber compositions used in tire airtight layers (hereinafter referred to as airtight layer rubber compositions) contain halogenated butyl elastomers. The halogenated butyl elastomers typically comprise 40% to 75% by weight, preferably 50% to 75% by weight, of the total weight of the airtight layer rubber composition. The airtight layer rubber composition may also contain natural rubber. Natural rubber comprises less than 20% by weight of the total weight of the elastomers in the airtight layer rubber composition.

[0033] The airtight rubber composition also includes a reinforcing filler containing carbon black, which typically accounts for 10% to 50% by weight of the total weight of the airtight rubber composition.

[0034] The airtight rubber composition also comprises a vulcanization system, i.e., a system based on sulfur (or sulfur donor) and a primary vulcanization accelerator. In the airtight rubber composition, sulfur is used at a preferred content of 0.5 to 5 parts by weight per 100 parts by weight of the airtight rubber composition. The primary vulcanization accelerator is used at a preferred content of 0.5 to 5 phr. In addition to this basic vulcanization system, various known secondary vulcanization accelerators or vulcanization activators exist, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders. As a (primary or secondary) vulcanization accelerator, any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur can be mentioned, particularly thiazole-type accelerators and their derivatives, as well as accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. The vulcanization system of the airtight rubber composition does not contain any curing resin, such as phenolic resin.

[0035] Since the rubber composition forming the particles suitable for the purposes of this invention is an airtight rubber composition and does not contain any curing resin, such as phenolic resin, it should not be confused with rubber compositions used in expandable curable capsules, which contain curing resin, particularly phenolic curing resin, as a crosslinking agent.

[0036] Kaolin The basic characteristic of the adhesive powder according to the present invention is that it contains kaolin. Kaolin (Al2O3·2SiO2·2H2O) is a non-reinforced plate-shaped mineral filler, which belongs to the natural layered silicate class.

[0037] According to one embodiment of the invention, kaolin accounts for 3% to 30% by weight of the total weight of the adhesive powder according to the invention, preferably 5% to 20% by weight. These ranges of the weight percentage of kaolin in the adhesive powder according to the invention can be applied to any embodiment of the invention.

[0038] elastomer Generally, the interchangeable terms "elastomer" and "rubber" are used interchangeably in the text.

[0039] According to one embodiment of the present invention, the rubber powder according to the invention comprises halogenated butyl rubber. The halogenated butyl rubber can be used alone or blended with one or more other diene elastomers.

[0040] Butyl rubber should be understood to mean copolymers of isobutylene and 1,3-diene, especially copolymers of isobutylene and isoprene, as well as halogenated derivatives of these copolymers, particularly brominated or chlorinated derivatives.

[0041] Butyl rubber is well known to those skilled in the art, especially for its impermeability. Typically, copolymers of isobutylene and 1,3-diene (particularly isoprene) contain 1 to 5 mol% diene units (particularly isoprene units) and have a Mooney viscosity of 30 to 60 (ML 1+8 at 125°C). Halogenated copolymers of isobutylene and 1,3-diene (particularly isoprene) typically have a halogen content of 1% to 4% by weight of the copolymer.

[0042] As examples particularly suitable for implementing the present invention, reference will be made to brominated butyl rubbers such as brominated copolymers of isobutylene and isoprene (BIIR), chlorinated butyl rubbers such as chlorinated copolymers of isobutylene and isoprene (CIIR), and mixtures of these rubbers.

[0043] According to any of the foregoing embodiments, the halogenated butyl rubber is preferably a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of both.

[0044] "Diene elastomer," whether natural or synthetic, should be understood in the known manner to mean an elastomer at least partially (i.e., a homopolymer or copolymer) composed of diene monomer units (monomers with two conjugated or non-conjugated carbon-carbon double bonds). As potentially suitable diene elastomers, particular reference will be made to diene elastomers commonly used in the manufacture of tires, such as polyisoprene, polybutadiene, isoprene copolymers, and butadiene copolymers, such as copolymers of butadiene and styrene.

[0045] According to one embodiment of the invention, the rubber powder of the invention comprises 0% to 20% by weight of a diene elastomer other than halogenated butyl rubber, said diene elastomer being selected from polyisoprene, polybutadiene, butadiene copolymers, isoprene copolymers, and mixtures thereof, wherein the weight percentage is calculated relative to the total weight of the rubber powder. Preferably, the diene elastomer is a polyisoprene elastomer, and even more preferably, the diene elastomer is a polyisoprene elastomer containing more than 90 mol% of cis-1,4-bonds. These preferred ranges of the weight percentage of the elastomer in the rubber powder of the invention and the molar percentage of cis-1,4-bonds in the polyisoprene elastomer, as well as these preferred selections of the diene elastomer, can be applied to any embodiment of the invention.

[0046] According to any embodiment of the invention, the weight percentage of halogenated butyl rubber in the rubber powder according to the invention is preferably greater than or equal to 40%, which is calculated relative to the total weight of the rubber powder. Preferably, the only other rubber present in the rubber powder suitable for the purposes of the invention is natural rubber.

[0047] filler According to one embodiment of the invention, the rubber powder according to the invention comprises at least one reinforcing filler. Any type of "reinforcing" filler known to be capable of reinforcing rubber compositions that can be particularly used in the manufacture of tires can be used, such as reinforcing organic fillers like carbon black, reinforcing inorganic fillers like silica, or mixtures of both types of fillers.

[0048] According to one embodiment of the invention, the reinforcing filler accounts for 10% to 40% by weight in the adhesive powder according to the invention, preferably 20% to 30%, and this weight percentage is calculated relative to the total weight of the adhesive powder.

[0049] According to one embodiment of the invention, the reinforcing filler comprises carbon black. Suitable carbon black may include all types of carbon black, particularly those commonly used in tires. These carbon blacks may be used alone, as commercially available, or in any other form, such as as a carrier for some of the rubber additives used.

[0050] According to one embodiment of the invention, the reinforcing filler comprises carbon black, which accounts for more than 50% by weight, preferably more than 80% by weight, and even more preferably 100% by weight of the reinforcing filler in the rubber powder according to the invention. In this even more preferred embodiment, the reinforcing filler consists only of carbon black, which is the only reinforcing filler present in the rubber powder.

[0051] vulcanization system According to one embodiment of the invention, the rubber powder according to the invention comprises a vulcanization system, namely a crosslinking system based on sulfur (or sulfur donor) and a primary vulcanization accelerator. In addition to this basic vulcanization system, there are various known secondary vulcanization accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, or guanidine derivatives (especially diphenylguanidine), or known vulcanization retarders. As a (primary or secondary) vulcanization accelerator, any compound capable of acting as a diene elastomer vulcanization accelerator in the presence of sulfur can be mentioned, particularly thiazole-type accelerators and their derivatives, as well as accelerators of the sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate types. Sulfur is used in the rubber powder at a preferred content between 0.5% by weight and 12% by weight of the total elastomer weight of the rubber powder, particularly at a preferred content between 0.5% by weight and 5% by weight of the total elastomer weight of the rubber powder. The primary vulcanization accelerator is used in the rubber powder at a preferred content between 0.5% and 10% by weight of the total elastomer weight of the rubber powder, more preferably between 0.5% and 5.0% by weight of the total elastomer weight of the rubber powder. These preferred ranges regarding sulfur and accelerator content are applicable to any embodiment.

[0052] Other additives The rubber powder according to the invention may also contain all or some of the commonly used additives typically used in rubber compositions intended for the manufacture of tires, such as plasticizers, lubricants, pigments, protective agents such as anti-ozone waxes, chemical anti-ozone agents, antioxidants, anti-fatigue agents, and mixtures of these compounds.

[0053] Other topics of the present invention The essential characteristic of the rubber composition according to the invention is that it contains rubber powder according to the invention, for example, in an amount of 5 to less than 40 phr. The rubber composition can be prepared in a suitable mixing mill, typically employing two consecutive preparation stages well known to those skilled in the art: a first stage is high-temperature thermomechanical processing or kneading, with a maximum temperature between 90°C and 150°C, preferably between 100°C and 130°C; followed by a second stage of mechanical processing at a lower temperature, typically below 110°C, for example between 40°C and 100°C, which is used for refining and homogenizing the rubber composition. The rubber composition according to the invention can be in an uncured state (before crosslinking or vulcanization) or in a cured state (after crosslinking or vulcanization).

[0054] This invention also relates to a tire or any other rubber article comprising a rubber composition or powder according to the invention, said tire or rubber article being in an uncured state or a cured state. In this invention, "tire" should be understood to mean either a pneumatic or non-pneumatic tire. A pneumatic tire typically comprises two beads intended to contact a rim, a crown consisting of at least one crown reinforcement and a tread, and two sidewalls, the tire being reinforced by a carcass reinforcement anchored in the two beads. On the other hand, a non-pneumatic tire typically comprises a base (e.g., designed for mounting on a rigid rim), a crown reinforcement (which ensures connection to the tread), and deformable structures such as spokes, ribs, or cells (this structure is placed between the base and the crown). Such a non-pneumatic tire does not necessarily include sidewalls. For example, non-pneumatic tires are described in WO 03 / 018332 and FR 2898077. According to any embodiment of the invention, the tire according to the invention is preferably a pneumatic tire.

[0055] The above and other features of the invention will become clearer by reading the following description of several exemplary embodiments of the invention, given as a non-limiting description.

[0056] Example The measurements and tests used Determination of tear strength property of rubber composition Using a force-measuring tensile testing machine equipped with a system for measuring and acquiring the force and displacement of the movable crossbeam, the tear tensile strength per unit thickness (hereinafter referred to as F) was measured on a specimen stretched at 500 mm / min to cause the specimen to break. RDz (expressed in N / mm thickness) and elongation at break at tear (hereinafter referred to as A) RDz(Indicated and expressed as a percentage). The tensile specimen consists of a parallelepiped-shaped rubber sheet 2.5 mm thick, 145 mm long, and 10 mm wide. Before starting the test, three very fine cuts, perpendicular to the length of the specimen and 3 mm deep, are made along one edge of the specimen using a razor blade; one cut is in the middle, and the other two are on either side of it, 6 mm apart from the middle cut. F is determined. RDz That is, the force applied to achieve fracture (expressed in N / mm specimen thickness), and the measurement of A. RDz Elongation (in %) is the elongation of the specimen used to determine fracture. The test was conducted in air at 100°C. The tear coefficient (in N / mm) is calculated as F. RDz and A RDz The product of and . A high value reflects good cohesion in the rubber composition, despite the presence of crack initiation.

[0057] In the following embodiments, measurements were performed on “new” tensile specimens (i.e., specimens that had not undergone any aging before) and specimens that had undergone 21 days of thermal oxidative aging in air at 77°C prior to the tensile test.

[0058] Results are expressed with 100 as the base: for the tear coefficient of the control, an arbitrary value of 100 is given, and results greater than 100 indicate improved tear strength properties relative to the control.

[0059] Determination of particle size of adhesive powder The volumetric size distribution of the adhesive powder particles can be measured using laser particle size analysis on a Malvern Mastersizer 3000 device. A one-minute sonication treatment is performed before measurement to ensure good dispersion. Measurement is performed using a liquid method: the adhesive powder particles are dispersed in alcohol. Measurements are performed according to standard ISO-13320-1, and the diffraction angles of the adhesive powder particles to the laser are measured, specifically D10 and D50, which represent the particle sizes smaller than 10% and 50% of the total particle group, respectively.

[0060] Preparation of rubber composition Four rubber compositions, C1, C2, C3 and C4, were prepared. The formulations of these compositions (in phr) are described in Table 1.

[0061] Rubber compositions C3 and C4 conform to the present invention; rubber compositions C1 and C2 do not conform to the present invention.

[0062] All four rubber compositions C1, C2, C3, and C4 contain rubber powder composed of ground tire airtight layers. Rubber compositions C1 and C2, which are not in accordance with the invention, contain 10 phr and 30 phr of composition A (given in Table 2, which does not contain kaolin and is therefore not in accordance with the invention) rubber powder, respectively; rubber compositions C3 and C4, according to the invention, contain 10 phr and 30 phr of composition B (given in Table 2) rubber powder, respectively, which does indeed contain kaolin and is in accordance with the invention.

[0063] The results are considered by comparing the properties of C1 (not in accordance with the present invention) and C3 (in accordance with the present invention) on the one hand, and comparing the properties of C2 (not in accordance with the present invention) and C4 (in accordance with the present invention) on the other hand.

[0064] The experiment was conducted as follows: First, halogenated butyl rubber was introduced into a mixer, followed by reinforcing fillers, rubber powder, vulcanization system, and other additives of the rubber composition, filling to 70% by volume, with an initial tank temperature of approximately 40°C. Then, thermomechanical processing was performed in a single step, lasting a total of approximately 3 to 4 minutes, until the maximum "discharge" temperature of 115°C was reached.

[0065] The resulting mixture is recovered and cooled on an external mixer (open mill) at 30°C. To homogenize the mixture, all substances are mixed for an appropriate time (e.g., between 5 and 12 minutes).

[0066] The resulting composition is then calendered into rubber sheets (2 to 3 mm thick) or thin rubber sheets to measure their physical or mechanical properties after vulcanization at 150°C for 20 minutes.

[0067] Properties of rubber compositions Table 3 shows the properties of rubber compositions C1, C2, C3 and C4 relative to C1 (based on a base of 100).

[0068] Rubber composition C3 contains the same amount of rubber powder as rubber composition C1, but the rubber powder in C3 includes kaolin (the rubber powder of composition B), unlike rubber composition C1 which does not contain kaolin (the rubber powder of composition A). Therefore, C3 conforms to the present invention and has a tear strength 17% higher than that of rubber composition C1, which does not conform to the present invention.

[0069] Similarly, rubber composition C4 contains the same amount of rubber powder as rubber composition C2, but the rubber powder in C4 includes kaolin (the rubber powder of composition B), unlike rubber composition C2 which does not contain kaolin (the rubber powder of composition A). Therefore, C4 conforms to the present invention and has a higher tear strength than rubber composition C2, which does not conform to the present invention.

[0070] Therefore, the results obtained show that, in this case, the rubber powder according to the invention can indeed solve the technical problem, because the resulting composition exhibits significantly better tear strength properties after aging than rubber compositions containing rubber powder that does not conform to the invention. This result is even more surprising, because before aging, the tear strength properties of rubber compositions containing powder according to the invention are not better than those of rubber compositions containing powder that does not conform to the invention.

[0071] Table 1 (1) Bromobutyl X-Butyl™ BB2030 from ARLANXEO (2) ASTM grade N770, from ORION (3) Natural kaolin, Argirec B24 grade, from IMERYS (4) Stearic acid, from UMICORE (5) Zinc oxide, from UMICORE (6) Struktol 40MS, from STRUKTOL (7) 2-Mercaptobenzothiazole disulfide (“MBTS”) accelerator, from Solutia (8) Microparticles of the sulfide gas-tight layer of composition A with a median size of 280 μm (9) Microparticles of the sulfide gas-tight layer of composition B with a median size of 280 μm Table 2 Table 3

Claims

1. Rubber powder composed of ground tire airtight layer particles, said rubber powder containing kaolin.

2. The adhesive powder according to claim 1, wherein the median particle size of the adhesive powder is between 50 μm and 500 μm, preferably between 100 μm and 400 μm.

3. The rubber powder according to any one of the preceding claims, wherein the rubber powder comprises at least 40% by weight of halogenated butyl rubber.

4. The adhesive powder according to any one of the preceding claims, wherein the adhesive powder comprises 0 to 20% by weight of polyisoprene elastomer, wherein the polyisoprene elastomer preferably comprises more than 90 mol% of cis-1,4- bonds.

5. The rubber powder according to any one of the preceding claims, wherein the halogenated butyl rubber is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture thereof.

6. The adhesive powder according to any one of the preceding claims, wherein the adhesive powder comprises reinforcing filler.

7. The adhesive powder according to claim 6, wherein the reinforcing filler has a weight percentage of 10% to 40%, preferably 20% to 30%.

8. The adhesive powder according to any one of claims 6 and 7, wherein the reinforcing filler comprises carbon black, and the carbon black accounts for more than 50% by weight, preferably more than 80% by weight, and even more preferably 100% by weight of the total weight of the reinforcing filler.

9. The adhesive powder according to any one of the preceding claims, wherein the weight percentage of kaolin in the adhesive powder is 3% to 30%, preferably 5% to 20%.

10. The rubber powder according to any one of the preceding claims, wherein the rubber powder comprises a vulcanization system.

11. A rubber composition comprising rubber powder according to any one of the preceding claims.

12. A tire comprising the rubber composition according to claim 11 or the rubber powder according to any one of claims 1 to 10.

13. A rubber article comprising the rubber composition according to claim 11 or the rubber powder according to any one of claims 1 to 10.

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