Gum powder containing kaolin

Abstract

The present invention relates to a rubber powder consisting of ground inner rubber particles from tires, which rubber powder comprises kaolin. The rubber powder improves the tear resistance of rubber compositions containing the powder.

Description

Title of the invention: Gum powder containing kaolin

[0001] The invention relates to rubber powders derived from rubber compositions for tires.

[0002] Indeed, it is now in the interest of tire manufacturers to promote the recycling of end-of-life tires into new tires or other new rubber articles in order to reduce the environmental impact of their activity.

[0003] It is also in the interest of manufacturers to find solutions to lower the costs of rubber compositions without penalizing the performance of tires or other rubber articles using these compositions.

[0004] One possible way to address these two points of interest is to incorporate rubber crumbs (or "rubber crumbs") obtained from the grinding or micronization of vulcanized rubber compositions into rubber compositions for tires or rubber articles. Tires produced using this type of process are described in the prior art, for example in document WO2020 / 128255.

[0005] Tire manufacturers have sometimes also incorporated rubber powders from tire recycling or curing membranes into tire inner rubber compositions, as described in documents KR100943526, EP1612242 and US6730732.

[0006] However, rubber articles, particularly inner tire rubbers, must also exhibit good mechanical resistance properties, including after aging. Surprisingly, the Applicant discovered that the use, in rubber compositions, of specific rubber powders containing kaolin improves the tear resistance properties after aging of the resulting compositions.

[0007] Thus, a first object of the invention is a rubber powder made up of ground inner tire rubber particles including kaolin. The invention also relates to a rubber composition comprising a rubber powder according to the invention. Another object of the invention is a tire comprising a rubber composition or a rubber powder according to the invention. The invention also relates to a rubber article comprising a rubber composition or a rubber powder according to the invention. Detailed description

[0008] Any interval of values ​​designated by the expression "between a and b" represents the domain of values ​​going from more than a to less than b (that is to say, bounds a and b excluded) while any interval of values ​​designated by the expression "from a to b" means the domain of values ​​going from a to b (that is to say, including the strict bounds a and b).

[0009] The abbreviation "pce" means parts by weight per hundred parts of elastomers present in the elastomer matrix. The elastomer matrix is ​​understood to mean all the elastomers present in a rubber composition.

[0010] The compounds mentioned in the description (typically polymers, fillers, plasticizers, coupling agents, the vulcanization system, other additives, etc.) may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. Similarly, the compounds mentioned may also come from the recycling of already used materials; that is, they may be partially or totally derived from a recycling process, or obtained from raw materials themselves derived from a recycling process.

[0011] The invention described in more detail below relates to at least one of the objects defined according to any one of the following embodiments: 1. Gum powder consisting of ground inner tire rubber particles, which gum powder includes kaolin. 2. Gum powder according to embodiment 1 having a median particle size by volume between 50 and 500 pm, preferably between 100 and 400 pm. 3. Gum powder according to any of the preceding embodiments comprising at least 40% by mass of a halogenated butyl rubber. 4. Gum powder according to any of the preceding embodiments comprising from 0 to 20% by mass of a polyisoprene elastomer, the polyisoprene elastomer preferably containing more than 90% by mole of 1,4-cis bonding. 5. Gum powder according to any one of the preceding embodiments in which the halogenated butyl rubber is a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two. 6. Gum powder according to any of the preceding embodiments comprising a reinforcing filler. 7. Gum powder according to embodiment 6, wherein the mass percentage of the reinforcing filler ranges from 10 to 40%, preferably approximately 20 to 30%. 8. Gum powder according to one of embodiments 6 or 7 in which the reinforcing filler comprises a carbon black representing more than 50% by mass, preferably more than 80% by mass, even more preferably 100% by mass of the total mass of the reinforcing filler. 9. Gum powder according to any of the preceding embodiments in which the mass percentage of kaolin in the gum powder ranges from 3 to 30%, preferably from 5 to 20%. 10. Gum powder according to any of the preceding embodiments comprising a vulcanization system. 11. Rubber composition comprising a rubber powder according to any of the preceding embodiments. 12. Tire comprising a rubber composition according to embodiment 11 or a rubber powder according to any one of embodiments 1 to 10. 13. Rubber article comprising a rubber composition according to embodiment 11 or a rubber powder according to any one of embodiments 1 to 10. Gum powder

[0012] The invention has as its first object a gum powder.

[0013] It should be noted that rubber powders are generally in the form of granules (or granulates), possibly in the form of a rubber sheet. Most often, rubber powders are a recycled material product: they result from the grinding, particularly micronization, of cured rubber compositions already used for a first application, for example as tire curing membranes (as in document US6730732) or as end-of-life tires (as in document KR100943526). Any method or process that does not degrade the rubber during grinding is suitable as a method for grinding rubber compositions.For example, a grinding method using water, such as those described in documents US4374573, US4714201, US5238194, and US5411215, can be chosen. This method keeps the gum temperature sufficiently low to prevent reversion, i.e., the degradation of the gum's cross-linking network. A cryogenic grinding method can also be used. Depending on the resulting object size distribution, the gum powder obtained by the aforementioned processes can undergo an additional sieving step to control this distribution. Sieving can be performed using various technologies (vibration, centrifugation, aspiration) known to those skilled in the art. The gum powders obtained from... The grinding process generally produces microparticles. By "microparticles" we mean particles that have a size, namely their diameter in the case of spherical particles or their largest dimension in the case of anisotropic particles, of a few tens or hundreds of microns.

[0014] According to one embodiment of the invention, the gum powder according to the invention is in the form of microparticles preferably having a median volume size between 50 and 500 pm, preferably between 100 and 400 pm. These particle size ranges can be applied to any one of the embodiments of the invention. inner tire rubber

[0015] An essential characteristic of the rubber powder according to the invention is that it is made up of ground inner rubber particles from tires. In other words, the constituent elements of the rubber powder are inner rubber particles from tires. The rubber powder useful for the purposes of the invention can then be manufactured by a process that consists of recovering inner rubber from tires and then grinding or micronizing this inner rubber using a process as described above.

[0016] The composition of a rubber powder useful for the needs of the invention is typically a vulcanized rubber composition constituting an inner rubber.

[0017] As is well known, a tire inner rubber compound, hereinafter referred to as the inner rubber compound, comprises a halogenated butyl elastomer. The halogenated butyl elastomer typically represents 40% to 75% by mass, preferably 50% to 75% by mass, of the total mass of an inner rubber compound. An inner rubber compound may also contain natural rubber. In this case, the natural rubber represents less than 20% by mass of the total mass of elastomer in an inner rubber compound.

[0018] An inner rubber compound also contains a reinforcing filler which contains carbon black, the reinforcing filler then typically representing 10% to 50% by mass of the total mass of an inner rubber compound.

[0019] An inner rubber compound also contains a vulcanization system, i.e., a sulfur-based (or sulfur donor-based) system and a primary vulcanization accelerator. In an inner rubber compound, sulfur is used at a preferential rate of between 0.5 and 5 parts by weight per 100 parts by weight of the inner rubber compound. The primary vulcanization accelerator is used at a preferential rate between 0.5 and 5 parts per cubic inch (ppc). Various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (particularly diphenylguanidine), or known vulcanization retardants, can be added to this basic vulcanization system. Examples of vulcanization accelerators (primary or secondary) include any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, notably thiazole-type accelerators and their derivatives, sulfenamide, thiuram, dithiocarbamate, dithiophosphate, thiourea, and xanthate-type accelerators. The vulcanization system for an inner rubber compound does not include a curing resin, such as phenolic resins.

[0020] Since the rubber composition of the constituent particles of the rubber powder useful for the purposes of the invention is a rubber composition of an internal rubber, it also does not contain a curing resin, such as phenolic resins. Consequently, it should not be confused with a rubber composition for an expandable curing membrane (in English, bladdef) which contains a curing resin, particularly a phenolic resin, as a crosslinking agent. Kaolin

[0021] The gum powder according to the invention has as its essential characteristic the presence of kaolin. Kaolin (Al₂O₃ 2SiO₂ 2H₂O) is a non-reinforcing, lamellar mineral filler belonging to the family of natural phyllosilicates.

[0022] According to one embodiment of the invention, kaolin represents from 3 to 30% by mass, preferably from 5 to 20% by mass, of the total mass of the gum powder according to the invention. These mass percentage ranges of kaolin in the gum powder according to the invention can be applied to any one of the embodiments of the invention. Elastomer

[0023] In the usual way, the terms "elastomer" and "rubber" are used interchangeably in the text.

[0024] According to one embodiment of the invention, the rubber powder according to the invention contains a halogenated butyl rubber. The halogenated butyl rubber can be used alone or in a mixture with one or more other diene elastomers.

[0025] Butyl rubber means a copolymer of isobutylene and a 1,3-diene, in particular a copolymer of isobutylene and isoprene, as well as halogenated derivatives, in particular generally brominated or chlorinated, of these copolymers.

[0026] Butyl rubbers are well known to those skilled in the art, particularly for their airtightness. Generally, isobutylene copolymers and 1,3-diene copolymers, particularly isoprene, contain 1 to 5% by mole of diene units, particularly isoprene units, and have a Mooney viscosity (ML 1+8 at 125°C) of 30 to 60. Halogenated copolymers of isobutylene and 1,3-diene, particularly isoprene, generally have a halogen content of 1 to 4% by mass of the copolymer mass.

[0027] Examples of halogenated butyl rubbers particularly suitable for the realization of the invention include bromo-butyl rubbers such as brominated isobutylene-isoprene copolymer (BIIR), chlorobutyl rubbers such as chlorinated isobutylene-isoprene copolymer (CIIR) and mixtures of these rubbers.

[0028] According to any one of the embodiments of the invention, the halogenated butyl rubber is preferably a brominated copolymer of isobutylene and isoprene, a chlorinated copolymer of isobutylene and isoprene, or a mixture of the two.

[0029] By "diene" elastomer, whether natural or synthetic, a known definition should be understood as an elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not). Suitable diene elastomers include, in particular, those commonly used in rubber compositions for the manufacture of tires, such as polyisoprenes, polybutadienes, isoprene copolymers, and butadiene copolymers such as butadiene-styrene copolymers.

[0030] According to one embodiment of the invention, the rubber powder according to the invention comprises from 0 to 20% by mass of a diene elastomer other than a halogenated butyl rubber and selected from the group consisting of polyisoprenes, polybutadienes, butadiene copolymers, isoprene copolymers and mixtures thereof, the mass percentage being calculated relative to the total mass 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% by mole of 1,4-cis bonding. These preferred ranges of mass percentage of elastomer in the gum powder according to the invention and of molar percentage of 1,4-cis bonding in the polyisoprene elastomer as well as these preferred choices of diene elastomer can be applied to any of the embodiments of the invention.

[0031] According to any one of the embodiments of the invention, the mass percentage of halogenated butyl rubber in the gum powder according to the invention is preferably greater than or equal to 40%, a mass percentage calculated relative to the total mass of the gum powder. Preferably, the only other rubber present in the gum powder relevant to the needs of the invention is natural rubber. Charge

[0032] According to one embodiment of the invention, the rubber powder according to the invention comprises at least one reinforcing filler. Any type of so-called reinforcing filler, known for its ability to strengthen a rubber composition usable in particular for the manufacture of tires, can be used, for example an organic reinforcing filler such as carbon black, an inorganic reinforcing filler such as silica, or a mixture of these two types of fillers.

[0033] According to one embodiment of the invention, the mass percentage of the reinforcing filler in the gum powder according to the invention ranges from 10 to 40%, preferably from 20 to 30%, mass percentage calculated in relation to the total mass of the gum powder.

[0034] According to one embodiment of the invention, the reinforcing filler comprises carbon black. Any type of carbon black may be suitable, including those conventionally used in tires. This carbon black may be used in its isolated form, as commercially available, or in any other form, for example, as a carrier for certain rubber additives used.

[0035] According to an embodiment of the invention in which the reinforcing filler comprises carbon black, the carbon black represents more than 50% by mass, preferably more than 80% by mass, and even more preferably 100% by mass of the reinforcing filler of the gum powder according to the invention. In this even more preferred embodiment, the reinforcing filler consists solely of carbon black, which is the only reinforcing filler present in the gum powder. Vulcanization system

[0036] According to one embodiment of the invention, the gum powder according to the invention comprises a vulcanization system, that is to say, a crosslinking system based on sulfur (or a sulfur-donating agent) and a primary vulcanization accelerator. Various known secondary accelerators or vulcanization activators, such as zinc oxide, stearic acid or equivalent compounds, guanidine derivatives (in particular diphenylguanidine), or known vulcanization retardants, can be added to this basic vulcanization system. Examples of vulcanization accelerators (primary or secondary) include any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, in particular thiazole-type accelerators and their derivatives, sulfenamide, thiuram, dithiocarbamate, and dithio-type accelerators. Phosphates, thioureas, and xanthates. Sulfur is used in the gum powder at a preferential rate of between 0.5 and 12% by mass of the total elastomer mass of the gum powder, particularly between 0.5 and 5% by mass of the total elastomer mass of the gum powder. The primary vulcanization accelerator is used in the gum powder at a preferential rate of between 0.5 and 10% by mass, more preferably between 0.5 and 5.0% by mass of the total elastomer mass of the gum powder. These preferred ranges for sulfur and accelerator levels can be applied to any of the embodiments. Other additives

[0037] The rubber powder according to the invention may also include all or part of the usual additives commonly used in rubber compositions for the manufacture of tires, such as plasticizers, lubricants, pigments, protective agents such as anti-ozone waxes, chemical anti-ozonants, antioxidants, anti-fatigue agents and mixtures of such compounds. Other objects of the invention

[0038] The rubber composition according to the invention is characterized in that it comprises the rubber powder according to the invention, for example, in quantities of 5 to less than 40 parts per unit area. It can be manufactured in suitable mixers, generally using two successive preparation phases well known to those skilled in the art: a first phase of thermomechanical working or mixing at high temperature, up to a maximum temperature between 90°C and 150°C, preferably between 100°C and 130°C, followed by a second phase of mechanical working to a lower temperature, typically below 110°C, for example, between 40°C and 100°C, a finishing and homogenization phase of the rubber composition. The rubber composition according to the invention can be in either the raw state (before crosslinking or vulcanization) or the cured state (after crosslinking or vulcanization).

[0039] The invention also relates to a tire or any other rubber article comprising a rubber composition or a rubber powder according to the invention, which tire or rubber article is in both the raw and cured states. In the present invention, the term "tire" means a pneumatic or non-pneumatic tire. A pneumatic tire usually comprises two beads for contacting 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 both Beading. A non-pneumatic tire, on the other hand, usually comprises a base, designed for example for mounting on a rigid rim, a crown reinforcement ensuring the connection with a tread, and a deformable structure, such as spokes, ribs, or dimples, this structure being arranged between the base and the crown. Such non-pneumatic tires do not necessarily include a sidewall. Non-pneumatic tires are described, for example, in documents WO 03 / 018332 and FR2898077. According to any one of the embodiments of the invention, the tire according to the invention is preferably a pneumatic tire.

[0040] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of several examples of embodiments of the invention, given by way of illustration and not limitation. Examples Measurements and tests used

[0041] Determination of the tear resistance properties of rubber compositions

[0042] The tensile strength per unit thickness (hereinafter denoted F^z and expressed in N / mm of thickness) and the elongation at break (hereinafter denoted Ardz and expressed as a percentage) are measured on a specimen stretched at 500 mm / min to cause the specimen to break on a tensile testing machine equipped with a system for measuring and acquiring the force and displacement of the moving crosshead. The tensile specimen consists of a parallelepiped-shaped rubber plate, 2.5 mm thick, 145 mm long, and 10 mm wide. Before the start of the test, three very fine cuts perpendicular to the length of the specimen are made using a razor blade to a depth of 3 mm, on one edge of the specimen, one in the middle and the other two on either side of the first and 6 mm away from it.FRDz is defined as the force (expressed in N per mm of specimen thickness) required to achieve fracture, and Ardz is measured as the elongation (expressed as a percentage) required to achieve fracture. The test was conducted in air at a temperature of 100°C. The tear coefficient (expressed in N / mm) is calculated as the product of FRDz and ARI. High values ​​indicate good cohesion of the rubber composition, even though crack initiation may be present. In the examples below, measurements were performed both on "new" tensile test specimens, i.e., those that had not undergone any prior aging, and on specimens that had been subjected to thermo-oxidative aging. for 21 days in air at 77°C before traction. The results are given on a base of 100: an arbitrary value of 100 is given for the tear resistance coefficient of the control, a result greater than 100 indicates improved tear resistance properties compared to the control.

[0043] Determination of the size of gum powder particles

[0044] The volume size distribution of gum powder particles can be measured by laser granulometry using a Malvern Mastersizer 3000 instrument. A 1-minute ultrasonic treatment is performed prior to measurement to ensure proper dispersion. The measurement is carried out in a liquid state: the gum powder particles are dispersed in alcohol. The measurement is performed in accordance with ISO 13320-1 and, based on the determination of the laser diffraction angles by the gum powder particles, allows for the determination of, in particular, the D10 and D50, i.e., the diameters below which 10% and 50% of the total particle population, respectively, are present. Preparation of rubber compositions

[0045] Four rubber compositions Cl, C2, C3 and C4 are prepared. The formulations (in pieces) of these compositions are described in Table 1.

[0046] Rubber compositions C3 and C4 conform to the invention; rubber compositions Cl and C2 do not conform to the invention. Rubber compositions C1, C2, C3, and C4 all contain a rubber powder made from ground inner rubber from a tire. Rubber compositions C1 and C2, which do not conform to the invention, comprise 10 and 30 parts, respectively, of a rubber powder of composition A (given in Table 2) which does not contain kaolin and is therefore not in accordance with the invention; rubber compositions C3 and C4, which do conform to the invention, comprise 10 and 30 parts, respectively, of a rubber powder of composition B (given in Table 2) which contains kaolin and is in accordance with the invention.

[0047] The results are considered by comparing the properties of Cl (not in accordance with the invention) and C3 (in accordance with the invention) on the one hand, and those of C2 (not in accordance with the invention) and C4 (in accordance with the invention) on the other hand.

[0048] The tests are carried out as follows: the halogenated butyl rubber is introduced first into an internal mixer, filled to 70% by volume and with an initial tank temperature of approximately 40°C. This is followed by the reinforcing filler, the rubber powder, the vulcanizing system, and the other additives of the rubber composition. A single-stage thermomechanical process is then carried out, lasting approximately 3 to 4 minutes in total, until a maximum "drop" temperature of 115°C is reached.

[0049] The mixture thus obtained is collected, cooled on an external mixer (roller tool) at 30°C, kneading everything to homogenize the mixture for an appropriate time (for example between 5 and 12 min). The resulting compositions are then calendered into sheets (2 to 3 mm thick) or thin sheets of rubber to measure their physical and mechanical properties after vulcanization for 20 minutes at 150 °C. Properties of rubber compositions

[0050] The properties of the Cl, C2, C3 and C4 rubber compositions are given as a basis of 100 relative to Cl in Table 3.

[0051] Rubber composition C3 contains the same proportion of rubber powder as rubber composition Cl, but the rubber powder in C3 includes kaolin (rubber powder composition B), unlike that in rubber composition Cl, which does not (rubber powder composition A). C3 therefore conforms to the invention and exhibits a tear resistance 17% higher than that of rubber composition Cl, which does not conform to the invention. Similarly, rubber compound C4 contains the same proportion of rubber powder as rubber compound C2, but the rubber powder in C4 includes kaolin (rubber powder of compound B), unlike that in rubber compound C2, which does not (rubber powder of compound A). Therefore, C4 conforms to the invention and exhibits higher tear resistance than rubber compound C2, which does not conform to the invention.

[0052] The results obtained therefore show that the rubber powder according to the invention does indeed solve the technical problem, in that it makes it possible to obtain rubber compositions with significantly better tear resistance properties after aging than those of rubber compositions comprising a powder not according to the invention. This result is all the more surprising since, before aging, the rubber compositions comprising powders according to the invention do not exhibit better tear resistance properties than those of the rubber compositions comprising powders not according to the invention. [Tables 1] Cl C2 C3 C4 Elastomer (1) 100 100 100 100 Carbon black (2) 40 40 40 40 Kaolin (3) 20 20 20 20 Stearic acid (4) 1.5 1.5 1.5 1.5 Zinc oxide (5) 1.5 1.5 1.5 1.5 Lubricant (6) 2 2 2 2 Accelerator (7) 1.2 1.2 1.2 1.2 Sulfur 1.5 1.5 1.5 1.5 Gum powder 1 (8) 10 30 0 0 Gum powder 2 (9) 0 0 10 30 1. Brominated Butyl X-ButylTM BB2030 from ARLANXEO 2. N770 ASTM grade from ORION 3. Natural kaolin grade Argirec B24 from the company IMERYS 4. Stearic acid from the company UMICORE 5. Zinc oxide from the company UMICORE 6. Struktol 40MS from the company STRUKTOL 7. 2-Mercaptobenzothiazole Disulfide Accelerator (“MBTS”) from Solutia 8. Vulcanized inner gum microparticles of composition A with a median size of 280 pm 9. Vulcanized inner gum microparticles of composition B with a median size of 280 pm [Tables 2] AB Elastomer (1) 100 100 Carbon black (2) 50 40 Kaolin (3) 0 20 Stearic acid (4) 1.5 1.5 Zinc oxide (5) 1.5 1.5 Lubricant (6) 2 2 Accelerator (7) 1.2 1.2 Sulfur 1.5 1.5 [Tables 3] C2 C3 C4 Tear strength coefficient when new [N / mm] 100 92 100 89 Tear strength coefficient after aging [N / mm] 100 117 119 130

Claims

Demands

1. Gum powder consisting of ground inner tire rubber particles, which gum powder comprises kaolin.

2. Gum powder according to claim 1 having a median volume particle size of between 50 and 500 pm, preferably between 100 and 400 pm.

3. Gum powder according to any one of the preceding claims comprising at least 40% by mass of a halogenated butyl rubber.

4. Gum powder according to any one of the preceding claims comprising from 0 to 20% by mass of a polyisoprene elastomer, the polyisoprene elastomer preferably containing more than 90% by mole of 1,4-cis bonding.

5. Gum 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 of both.

6. Gum powder according to any one of the preceding claims comprising a reinforcing filler.

7. Gum powder according to claim 6 wherein the mass percentage of the reinforcing filler is from 10 to 40%, preferably from 20 to 30%.

8. Gum powder according to any one of claims 6 or 7 wherein the reinforcing filler comprises a carbon black representing more than 50% by mass, preferably more than 80% by mass, even more preferably 100% by mass of the total mass of the reinforcing filler.

9. Gum powder according to any one of the preceding claims wherein the mass percentage of kaolin in the gum powder ranges from 3 to 30%, preferably from 5 to 20%.

10. Gum powder according to any one of the preceding claims comprising a vulcanization system.

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

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

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