Novel tread wear mark and preparation process thereof

Abstract

The invention relates to the technical field of vehicle design, and particularly discloses a novel tread wear mark and a preparation process thereof. The tread is provided with a first color layer, a second color layer and a third color layer along the depth direction of a pattern groove, the first color layer extends from the outer surface of the tread to 2 / 3 of the depth of the pattern groove, and the second color layer extends from 1 / 3 of the depth of the pattern groove to a normal wear identification position of the tread; the first color layer, the second color layer and the third color layer extend from the tread normal wear identification position to the bottom of the pattern groove, the colors of the first color layer, the second color layer and the third color layer are different from one another, and the tread normal wear identification position corresponds to the position with the pattern depth of 1.6-2.6 mm. The novel tread abrasion mark can be used for various motor vehicle tires and has the advantages of being clear and visual in abrasion indication, clear in early warning stage, high in color contrast ratio, firm in interlayer combination and good in durability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vehicle design, more particularly, it relates to a new tread wear mark and a preparation process thereof. BACKGROUND

[0002] The tread wear mark is a raised mark designed in the tire groove, which is mainly applied in the field of vehicle safety maintenance. When the tire pattern is worn to the same level as the mark, it can provide objective and intuitive replacement warning for the driver. Its advantage lies in significantly improving active safety, preventing the decrease of grip, the extension of braking distance and the risk of water sliding on wet road caused by excessive wear of the tread, helping the vehicle owner to reasonably plan the replacement cycle and save vehicle cost, and indirectly promoting the driving state of vehicles in line with safety specifications. It is an important safety design with low cost and outstanding performance.

[0003] The related tread wear mark provides wear warning by setting a raised mark of a single material or color in the tire groove. However, such a mark is often similar to the tread background color and lacks dynamic visual cues, and is easily covered with dirt and dust or affected by light conditions in daily use, resulting in low recognition and making it difficult for the driver to perceive wear progression, delaying replacement decisions, and thus increasing the safety risks caused by the decline in tire performance. SUMMARY

[0004] In order to solve the problem that the related tread wear mark provides wear warning by setting a raised mark of a single material or color in the tire groove, making it difficult for the driver to perceive wear progression, delaying replacement decisions, and thus increasing the safety risks caused by the decline in tire performance, the present application provides a new tread wear mark and a preparation process thereof.

[0005] In the first aspect, the present application provides a new tread wear mark, which adopts the following technical solution: A new tread wear mark, the tread is provided with a first color layer, a second color layer and a third color layer along the depth direction of the pattern groove, wherein the first color layer extends from the outer surface of the tread to 2 / 3 of the depth of the pattern groove, the second color layer extends from 1 / 3 of the depth of the pattern groove to the normal wear mark position of the tread, and the third color layer extends from the normal wear mark position of the tread to the bottom of the pattern groove, wherein the colors of the first color layer, the second color layer and the third color layer are different from each other, and the normal wear mark position of the tread corresponds to a position with a pattern depth of 1.6-2.6mm.

[0006] By adopting the above technical scheme, since three color layers of different colors are arranged in sequence along the depth direction of the pattern groove, and the starting and ending positions thereof are accurately divided, the wear state of the tire in use can be intuitively shown in stages. When the tire is in a brand-new or light wear state, only the black first color layer on the surface can be seen; as the wear intensifies, when the tire is worn to about 1 / 3 of the groove depth, the gray second color layer in the middle layer begins to show, providing an early wear warning for the driver; when worn to the wear limit specified by the regulations, i.e. 1.6-2.6mm in depth, the white third color layer at the bottom is completely exposed, forming a strong visual contrast, clearly indicating that the tire has reached the safety limit that must be replaced. The structure realizes continuous and clear indication of the wear state of the tire through the phased change of colors, thereby effectively improving the driving safety, helping the user to judge the tire replacement time in a timely manner, and meeting the relevant safety standards.

[0007] Preferably, the first color layer, the second color layer and the third color layer are all made of a rubber composition including the following ingredients by weight: natural rubber 40-60 parts, styrene-butadiene rubber 20-40 parts, operating oil 5-15 parts, zinc oxide 3-5 parts, stearic acid 1-2 parts, antioxidant 1-2 parts, accelerator 0.5-1.5 parts and sulfur 1.5-2.5 parts.

[0008] By adopting the above technical scheme, since the main material system of natural rubber and styrene-butadiene rubber is used, the natural rubber provides high strength and high elasticity, and the styrene-butadiene rubber improves wear resistance and reduces heat generation, and the two complement each other to make the rubber composition have good physical and mechanical properties and durability. The addition of operating oil can soften the rubber compound, improve the processing fluidity and help the dispersion of fillers. Zinc oxide and stearic acid as an activation system can effectively activate the accelerator, improve the vulcanization efficiency and the uniformity of the crosslinking network. The introduction of the antioxidant can delay the aging of the rubber due to heat and oxygen during use, ensuring the service life of the identification layer. The accelerator and sulfur form a vulcanization system to form a stable three-dimensional crosslinking network in the subsequent vulcanization process, giving the identification layer the final shape stability and mechanical properties. The formula system provides a reliable matrix material for the color layer, thereby obtaining the effects of meeting the performance requirements of the tread part and ensuring that the color layers are not easily peeled off or failed under complex use conditions.

[0009] Preferably, the first color layer further adds black pigment, the black pigment is carbon black, and the amount of carbon black is 25-35% of the weight of the rubber composition; the second color layer further adds gray pigment, the gray pigment is composed of titanium dioxide and carbon black in a weight ratio of 2:1-1:1, the amount of titanium dioxide is 15-25% of the weight of the rubber composition, and the amount of carbon black is 8-15% of the weight of the rubber composition; the third color layer further adds white pigment, the white pigment is titanium dioxide, and the amount of titanium dioxide is 30-40% of the weight of the rubber composition.

[0010] By adopting the technical scheme, the first color layer as the main driving surface needs to have excellent wear resistance and tear resistance, and a high amount of carbon black can enhance the strength, hardness and wear resistance of the rubber compound while imparting black color. The second color layer as a warning transition layer uses titanium dioxide and carbon black to mix and match to obtain gray color, titanium dioxide provides hiding power and basic whiteness, and a small amount of carbon black is used for coloring. The ratio ensures that the gray color is clear and distinguishable, and forms an effective color contrast with the upper and lower layers. The third color layer as the final safety warning layer uses a high amount of titanium dioxide to ensure that it presents a bright and eye-catching pure white color when worn to the limit, having a strong visual warning effect. The amount of each layer of pigment is accurately set based on its hiding power, coloring power and influence on the physical properties of the rubber compound, thereby obtaining the effect of stable color phase, clear contrast and coordinated physical properties of the color layer and the main body of the tread.

[0011] Preferably, a plasticizer can be further added to the rubber composition, the plasticizer being phthalate, and the addition amount being 2-5% by weight of the rubber composition.

[0012] By adopting the technical scheme, since an appropriate amount of phthalate plasticizer is added to the rubber composition, the plasticizer molecules can penetrate between the rubber polymer chains, weaken the intermolecular forces and increase the chain segment activity. This effect can reduce the viscosity and modulus of the rubber compound during processing, improve the softness and plasticity of the rubber compound, make the subsequent mixing, extrusion and other processes easier to perform, and promote the uniform dispersion of pigments and fillers. In the final product, an appropriate amount of plasticizer helps to maintain the flexibility and elasticity of the rubber compound, reducing the risk of cracking caused by hardness and brittleness. Therefore, the effect of improving the processing performance of rubber, improving the uniformity of pigment dispersion and optimizing the flexibility of the final identification layer is achieved.

[0013] In a second aspect, the application provides a preparation process of a new type of tread wear identification, which adopts the following technical scheme: A preparation process of a new type of tread wear identification, comprising the following steps: S1: plasticizing natural rubber and synthetic rubber to obtain plasticized rubber; S2: adding operating oil, zinc oxide, stearic acid and anti-aging agent to the plasticized rubber obtained in S1, and mixing to obtain a masterbatch; S3: adding an accelerator and sulfur to the masterbatch obtained in S2, and performing final mixing to obtain a basic rubber composition; S4: dividing the basic rubber composition obtained in S3 into three parts, adding black pigment, gray pigment and white pigment respectively, and mixing uniformly to obtain a first color rubber composition, a second color rubber composition and a third color rubber composition; S5: extruding the first color rubber composition, the second color rubber composition and the third color rubber composition obtained in S4 to form a multi-layered tread blank, wherein the first color rubber composition forms a first color layer, the second color rubber composition forms a second color layer, and the third color rubber composition forms a third color layer; S6: winding the multi-layered tread blank onto a tire building drum to assemble a green tire with other tire components; S7: curing the green tire in a mold to obtain a final tire.

[0014] By adopting the above technical scheme, since the process route of step-by-step mixing and separate coloring is adopted, the rubber main body and the compounding agents except the vulcanization system are first mixed in the masterbatch mixing step, which makes the fillers and the operating oil fully dispersed. Then, the vulcanization system is added in the final mixing stage, which avoids the premature mixing of the accelerators and the like, so that the rubber compound does not occur scorching during subsequent storage or processing. The base rubber after the final mixing is divided and separately colored, which ensures that each color pigment can reach the optimal dispersion state in the respective rubber compound, and avoids color contamination. The three color rubbers are compounded into a tread blank with a specific layered structure through the extrusion process. During the subsequent molding and curing process, the color layers can be firmly combined and the relative positions are fixed. Finally, the rubber is crosslinked through vulcanization, and the multi-layer structure is permanently shaped. Therefore, the process flow is clear and controllable, and the multi-layer tread wear mark with clear color, firm layer combination and stable performance can be accurately prepared.

[0015] Preferably, before the step S1, a pretreatment step of drying the natural rubber and the synthetic rubber is further included, the drying temperature is 40-60℃, and the time is 2-4h; and, after drying, a crushing treatment is further carried out, and the particle size is 5-10mm.

[0016] By adopting the above technical scheme, since the rubber raw material is preheated and dried before plasticating, the water adsorbed in the rubber and part of the low-volatility impurities can be effectively removed. On the one hand, this can prevent the water vaporization during subsequent high-temperature mixing, which causes the rubber compound to produce bubbles and affects the density of the final product; on the other hand, the hardness of the dried rubber increases, which is more easily sheared and broken in the open mill or internal mixer, thereby improving the plasticating efficiency. The subsequent crushing treatment changes the large rubber into small particles with uniform size, which increases the specific surface area of the rubber, so that it can be more quickly and uniformly contacted and mixed with other compounding agents during mixing. This pretreatment step lays a foundation for the smooth progress of the subsequent mixing process, thereby achieving the effects of improving mixing uniformity, reducing product defects and improving overall process stability.

[0017] Preferably, in the step S2, the mixing temperature is 80-100℃, the time is 10-20min, and the pressure is 0.5-1.0MPa.

[0018] By adopting the above technical scheme, since the temperature is controlled in the range of 80-100℃ in the mixing step, this temperature range can not only ensure that the softening agent such as operating oil has sufficient fluidity to infiltrate the rubber and filler, but also prevent excessive degradation of the rubber molecular chain or premature consumption of the antioxidant and other auxiliary agents caused by excessively high temperature. The mixing time of 10-20 min combined with the pressure of 0.5-1.0 MPa provides sufficient mechanical shear force and action time for the dispersion of the filler particles in the rubber matrix, ensuring that the small materials such as zinc oxide and stearic acid are uniformly distributed. Sufficient dispersion is a prerequisite for obtaining a performance-uniform masterbatch, and also creates good conditions for the uniform mixing of vulcanizing agents in the subsequent finishing stage. The parameter setting is based on the kinetics and thermodynamics requirements of rubber and filler mixing, thereby obtaining the effect of a uniformly mixed, stable performance, and masterbatch that is beneficial to subsequent processing.

[0019] Preferably, in the S4 step, a dispersing agent is also added when the pigment is added, the dispersing agent is a fatty acid salt, the amount is 1-3% of the total weight of the pigment, and the addition timing is simultaneous with the addition of the pigment; and a lubricant is also added, the lubricant is zinc stearate, the amount is 0.5-1 part, and the addition timing is 5-10 min after the addition of the pigment.

[0020] By adopting the above technical scheme, since the dispersing agent of the fatty acid salt is introduced in the pigment mixing stage, the dispersing agent can be adsorbed on the surface of the pigment particles, reducing the surface energy and effectively preventing the re-agglomeration of the pigment particles due to van der Waals force, promoting the micro-uniform dispersion of the pigment in the rubber. Simultaneous addition with the pigment can ensure that the dispersing agent plays a role in the early stage of contact between the pigment and the rubber. In the late dispersion stage, zinc stearate is added as a lubricant, which can form a lubricating film between the rubber molecular chains and between the rubber and the metal surface of the processing equipment, reducing internal friction and adhesion. This not only further assists the dispersion of the pigment, but also improves the processing fluidity and demolding performance of the rubber compound, providing a guarantee for the state of the rubber compound in the next multi-layer co-extrusion process. This combination of measures solves the dispersion problem under high pigment dosage, thereby obtaining the effect of a colored rubber composition with high pigment dispersion, bright and uniform color, and good processing performance of the rubber compound.

[0021] Preferably, in the S5 step, the multi-layer tread blank is extruded by multi-layer co-extrusion, the extrusion temperature is 85-95℃, and the extrusion pressure is 8-15 MPa.

[0022] By adopting the above technical scheme, since the multi-layer co-extrusion technology is adopted, three rubber compositions of different colors are simultaneously extruded through an extruder head with a composite flow channel, are combined and bonded in the die to form an integrated multi-layer tread blank. The extrusion temperature is controlled at 85-95 DEG C, at which temperature the rubber has suitable viscous flow, which can ensure that the rubber passes through the flow channel smoothly, and can also make the rubber layers produce appropriate adhesion at the interface, which is beneficial to the bonding between the layers. The extrusion pressure of 8-15 MPa ensures that the rubber is fully compacted, the existing bubbles are discharged, and the blank has a dense internal structure and precise cross-sectional shape. Precise temperature and pressure control is the key to ensuring that the boundaries of each color layer are clear, there is no mutual color bleeding, and the layers are tightly bonded, thereby obtaining the effect of a multi-layer tread blank with stable size, clear layer structure and good integrity.

[0023] Preferably, in the S7 step, the vulcanization temperature is 150-160 DEG C, the pressure is 15-20 MPa, and the time is 15-25 min.

[0024] By adopting the above technical scheme, since the vulcanization process is a decisive link for the linear macromolecules of rubber to form a three-dimensional network structure under the action of heat, pressure and vulcanization system. The vulcanization temperature is controlled at 150-160 DEG C, which can effectively activate the accelerator, make the sulfur crosslinking reaction proceed at a moderate speed, ensure sufficient crosslinking and avoid rubber aging or performance degradation due to too high temperature. The high pressure of 15-20 MPa, on the one hand, forces the green tire rubber to fill the mold cavity, replicating the precise pattern, and on the other hand, promotes the further fusion between the rubber layers and inhibits the generation of bubbles due to the generation of low molecular volatile substances during the vulcanization process. The vulcanization time of 15-25 min is set according to the thickness, thermal conductivity and formula characteristics of the rubber, to ensure uniform heat transfer from the outside to the inside, so that the entire tread, especially the thicker parts, can reach the state of positive vulcanization. The vulcanization system is set based on the kinetics of rubber vulcanization reaction, thereby obtaining the effect of a final tire product with clear tread pattern, firm bonding between color layers, optimal and stable physical and mechanical properties.

[0025] In summary, the present application has the following beneficial effects: 1. Since the present application adopts a structure in which three color layers of different colors are arranged in sequence along the depth direction of the pattern groove, and the starting and ending positions of each color layer are divided, the tire wear process presents a clear phased color change from the initial black first color layer to the intermediate gray warning layer to the final white safety warning layer, achieving continuous and intuitive indication of the wear condition, thereby solving the problem of difficult identification of related markings, assisting users in observing the tire wear degree, and timely replacing the tire to improve driving safety.

[0026] 2, The application preferably adopts different pigment systems and cooperates with specific rubber composition formula, wherein high dosage of carbon black enhances the wear resistance of the surface layer, titanium dioxide is compounded with carbon black to realize the pre-warning gray of the middle layer, high dosage of titanium dioxide ensures the warning white of the bottom layer, and the rubber matrix is improved through the use of natural rubber and styrene-butadiene rubber and the vulcanization system, so as to obtain clear color difference of each color layer, long-term stability, and coordination with the mechanical properties of the tread, avoiding the effect of misleading users due to premature failure or peeling of the identification layer.

[0027] 3, The method of the application, through the preparation process of step-by-step mixing, separate coloring and multi-layer co-extrusion, wherein the temperature and pressure are controlled in the mixing stage to promote the dispersion of fillers, and dispersants and lubricants are added in the coloring stage to ensure uniform mixing of pigments, and then the parameters are adjusted during extrusion and vulcanization to ensure the interlayer bonding and shape setting, so that a multi-layer identification structure with stable interlayer adhesion, clear color boundary and strong overall durability is efficiently prepared, which supports the reliability and long-term effectiveness of the wear identification, further avoiding the effect of use misunderstanding caused by blurred or fallen identification. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A structural schematic diagram of a new tread wear identification proposed by the application; Figure 2 A flowchart of the preparation process of a new tread wear identification proposed by the application. DETAILED DESCRIPTION

[0029] The application will be further described in detail below in combination with the drawings and examples.

[0030] Example 1 This example provides a new tread wear identification, wherein the first color layer 1, the second color layer 2 and the third color layer 3 are all made of a rubber composition, and the rubber composition comprises the following ingredients by weight: natural rubber 40 parts, styrene-butadiene rubber 20 parts, operating oil 5 parts, zinc oxide 3 parts, stearic acid 1 part, antioxidant 1 part, accelerator 0.5 part and sulfur 1.5 parts.

[0031] The first color layer 1 extends from the outer surface of the tread to 2 / 3 of the depth of the groove, the second color layer 2 extends from 1 / 3 of the depth of the groove to the normal wear mark position of the tread, and the third color layer 3 extends from the normal wear mark position of the tread to the bottom of the groove, wherein the normal wear mark position corresponds to a groove depth of 1.6mm; the first color layer 1 further adds carbon black, and the amount is 25% of the weight of the rubber composition; the second color layer 2 further adds a gray pigment composed of titanium dioxide and carbon black in a weight ratio of 2:1, wherein the amount of titanium dioxide is 15% of the weight of the rubber composition, and the amount of carbon black is 8% of the weight of the rubber composition; the third color layer 3 further adds titanium dioxide, and the amount is 30% of the weight of the rubber composition. The rubber composition can further add plasticizer phthalate, and the amount is 2% of the weight of the rubber composition.

[0032] The preparation process of the above-mentioned new tread wear mark includes the following steps: S1: plasticize natural rubber and synthetic rubber to obtain plasticized rubber.

[0033] Before S1, the natural rubber and synthetic rubber are dried and pretreated, the drying temperature is 40℃, and the time is 2 hours; after drying, the crushing treatment is carried out, and the particle size is 5mm.

[0034] S2: add operating oil, zinc oxide, stearic acid and antioxidant to the plasticized rubber obtained in S1, and mix to obtain a masterbatch.

[0035] In S2, the mixing temperature is 80℃, the time is 10 minutes, and the pressure is 0.5MPa.

[0036] S3: add accelerator and sulfur to the masterbatch obtained in S2 to finish mixing to obtain a basic rubber composition.

[0037] S4: divide the basic rubber composition obtained in S3 into three parts, add black pigment, gray pigment and white pigment respectively, and mix uniformly to obtain first color rubber composition, second color rubber composition and third color rubber composition.

[0038] In S4, when adding the pigment, a dispersing agent fatty acid salt is also added, and the amount is 1% of the total weight of the pigment, which is added at the same time as the pigment; and a lubricant zinc stearate is added, and the amount is 0.5 parts, which is mixed for 5 minutes after the pigment is added.

[0039] S5: extrude the first color rubber composition, the second color rubber composition and the third color rubber composition obtained in S4 to form a multilayer tread blank, wherein the first color rubber composition forms the first color layer 1, the second color rubber composition forms the second color layer 2, and the third color rubber composition forms the third color layer 3.

[0040] In the step S5, the multi-layered tread blank is prepared by multi-layer co-extrusion, the extrusion temperature is 85℃, and the extrusion pressure is 8MPa.

[0041] S6: winding the multi-layered tread blank on a tire forming drum to assemble a green tire with other tire components.

[0042] S7: curing the green tire in a mold to obtain a final tire.

[0043] In the step S7, the curing temperature is 150℃, the pressure is 15MPa, and the time is 15 minutes.

[0044] Example 2 The present embodiment provides a new tread wear indicator, wherein the first color layer 1, the second color layer 2 and the third color layer 3 are all made of a rubber composition comprising the following ingredients by weight: natural rubber 50 parts, styrene-butadiene rubber 30 parts, operating oil 10 parts, zinc oxide 4 parts, stearic acid 1.5 parts, antioxidant 1.5 parts, accelerator 1 part and sulfur 2 parts.

[0045] In the present embodiment, the first color layer 1 extends from the outer surface of the tread to 2 / 3 of the depth of the groove, the second color layer 2 extends from 1 / 3 of the depth of the groove to the normal wear indicator position of the tread, and the third color layer 3 extends from the normal wear indicator position of the tread to the bottom of the groove, the normal wear indicator position of the tread corresponds to a groove depth of 2.1mm. In the first color layer 1, carbon black is further added in an amount of 30% by weight of the rubber composition; in the second color layer 2, a gray pigment composed of titanium dioxide and carbon black in a weight ratio of 1.5:1 is further added, wherein the amount of titanium dioxide is 20% by weight of the rubber composition, and the amount of carbon black is 11.5% by weight of the rubber composition; in the third color layer 3, titanium dioxide is further added in an amount of 35% by weight of the rubber composition. A plasticizer, phthalate, can be further added to the rubber composition in an amount of 3.5% by weight of the rubber composition.

[0046] The preparation process of the above-mentioned new tread wear indicator comprises the following steps: S1: plasticizing natural rubber and synthetic rubber to obtain plasticized rubber.

[0047] Before the step S1, the natural rubber and synthetic rubber are dried and pretreated, the drying temperature is 50℃, and the time is 3 hours; after drying, the pretreated rubber is crushed to a particle size of 7.5mm.

[0048] S2: adding operating oil, zinc oxide, stearic acid and antioxidant to the plasticized rubber obtained in S1 to mix and obtain a masterbatch.

[0049] In the S2 step, the mixing temperature is 90°C, the time is 15 minutes, and the pressure is 0.75 MPa.

[0050] S3: Addition of accelerators and sulfur to the masterbatch obtained in S2, and final mixing to obtain a base rubber composition.

[0051] S4: The base rubber composition obtained in S3 is divided into three parts, and black pigment, gray pigment and white pigment are added respectively, and mixed uniformly to obtain a first color rubber composition, a second color rubber composition and a third color rubber composition.

[0052] In the S4 step, a dispersant fatty acid salt is also added when the pigment is added, and the amount is 2% of the total weight of the pigment, which is added at the same time as the pigment; and a lubricant zinc stearate is added, and the amount is 0.75 parts, which is mixed for 7.5 minutes after the pigment is added.

[0053] S5: Extrusion of the first color rubber composition, the second color rubber composition and the third color rubber composition obtained in S4 to form a multi-layer tread blank, wherein the first color rubber composition forms a first color layer 1, the second color rubber composition forms a second color layer 2, and the third color rubber composition forms a third color layer 3.

[0054] In the S5 step, the multi-layer tread blank is extruded by multi-layer co-extrusion, and the extrusion temperature is 90°C, and the extrusion pressure is 11.5 MPa.

[0055] S6: The multi-layer tread blank is wound onto a tire forming drum to assemble a green tire with other tire components.

[0056] S7: The green tire is placed in a mold for vulcanization to obtain a final tire.

[0057] In the S7 step, the vulcanization temperature is 155°C, the pressure is 17.5 MPa, and the time is 20 minutes.

[0058] Example 3 This example provides a new type of tread wear mark, wherein the first color layer 1, the second color layer 2 and the third color layer 3 are all made of a rubber composition, and the rubber composition includes the following ingredients by weight: natural rubber 60 parts, styrene-butadiene rubber 40 parts, operating oil 15 parts, zinc oxide 5 parts, stearic acid 2 parts, antioxidant 2 parts, accelerator 1.5 parts and sulfur 2.5 parts.

[0059] The first color layer 1 extends from the outer surface of the tread to 2 / 3 of the depth of the groove, the second color layer 2 extends from 1 / 3 of the depth of the groove to the normal wear mark position of the tread, and the third color layer 3 extends from the normal wear mark position of the tread to the bottom of the groove, and the normal wear mark position corresponds to a groove depth of 2.6mm. The first color layer 1 further adds carbon black, and the amount is 35% of the weight of the rubber composition; the second color layer 2 further adds a gray pigment composed of titanium dioxide and carbon black in a weight ratio of 1:1, wherein the amount of titanium dioxide is 25% of the weight of the rubber composition, and the amount of carbon black is 15% of the weight of the rubber composition; the third color layer 3 further adds titanium dioxide, and the amount is 40% of the weight of the rubber composition. The rubber composition can further add plasticizer phthalate, and the amount is 5% of the weight of the rubber composition.

[0060] The preparation process of the above-mentioned new tread wear mark includes the following steps: S1: plasticize natural rubber and synthetic rubber to obtain plasticized rubber.

[0061] Before S1 step, the natural rubber and synthetic rubber are dried and pretreated, the drying temperature is 60℃, and the time is 4 hours; after drying, the crushing treatment is carried out, and the particle size is 10mm.

[0062] S2: Add operating oil, zinc oxide, stearic acid and antioxidant to the plasticized rubber obtained in S1, and mix to obtain a masterbatch.

[0063] In S2 step, the mixing temperature is 100℃, the time is 20 minutes, and the pressure is 1.0MPa.

[0064] S3: Add accelerator and sulfur to the masterbatch obtained in S2 to perform final mixing to obtain a basic rubber composition.

[0065] S4: Divide the basic rubber composition obtained in S3 into three parts, add black pigment, gray pigment and white pigment respectively, and mix uniformly to obtain first color rubber composition, second color rubber composition and third color rubber composition.

[0066] In S4 step, when adding the pigment, a dispersing agent fatty acid salt is also added, and the amount is 3% of the total weight of the pigment, which is added at the same time as the pigment; and a lubricant zinc stearate is added, and the amount is 1 part, which is mixed for 10 minutes after the pigment is added.

[0067] S5: Extrude the first color rubber composition, the second color rubber composition and the third color rubber composition obtained in S4 to form a multilayer tread blank, wherein the first color rubber composition forms the first color layer 1, the second color rubber composition forms the second color layer 2, and the third color rubber composition forms the third color layer 3.

[0068] In step S5, the multi-layered tread blank is prepared by multi-layer co-extrusion, with an extrusion temperature of 95 °C and an extrusion pressure of 15 MPa.

[0069] S6: The multi-layered tread blank is wound onto a tire building drum and assembled with other tire components to form a green tire.

[0070] S7: The green tire is placed in a mold for vulcanization to obtain the final tire.

[0071] In step S7, the vulcanization temperature is 160 °C, the pressure is 20 MPa, and the time is 25 minutes.

[0072] Comparative Example 1 This comparative example refers to the content of Example 1, except that the amount of carbon black added in the first color layer 1 is 12.5% by weight of the rubber composition, and the rest of the content is the same as Example 1.

[0073] Comparative Example 2 This comparative example refers to the content of Example 1, except that the total amount of gray pigment added in the second color layer 2 is reduced to 11.5% by weight of the rubber composition, and the weight ratio of titanium dioxide to carbon black remains unchanged at 2:1, and the rest of the content is the same as Example 1.

[0074] Comparative Example 3 This comparative example refers to the content of Example 1, except that the tread wear indicator only contains two color layers: the first color layer extends from the outer surface of the tread to 1 / 2 of the groove depth, and the second color layer extends from 1 / 2 of the groove depth to the bottom of the groove. The intermediate gray warning layer is removed, and there is no specific wear indicator position corresponding to a depth of 1.6 mm. The rubber composition base formula used in the two layers is the same as Example 1, and the coloring scheme is the same as the first color layer and the third color layer of Example 1, respectively, and the rest of the content is the same as Example 1.

[0075] Comparative Example 4 This comparative example refers to the content of Example 1, except that all of the natural rubber in the rubber composition is replaced with an equal amount of styrene-butadiene rubber, i.e., the formula is changed to: styrene-butadiene rubber 60 parts, operating oil 5 parts, zinc oxide 3 parts, stearic acid 1 part, antioxidant 1 part, accelerator 0.5 parts, and sulfur 1.5 parts. The pigment addition ratio and distribution of each color layer are the same as Example 1, and the rest of the content is the same as Example 1.

[0076] Comparative Example 5 This comparative example refers to the content of Example 1, except that in step S7, the vulcanization temperature is reduced to 105 °C, the vulcanization pressure is reduced to 7.5 MPa, and the vulcanization time is reduced to 7.5 minutes, and the rest of the content is the same as Example 1.

[0077] Performance test Sample preparation: All test samples were prepared according to the formulations and processes of Examples 1-3 and Comparative Examples 1-5, and tire tread test pieces and complete tire samples with multi-layer color structure were prepared for subsequent performance testing.

[0078] Color contrast and color difference detection: First, the Lab color space values of the black first color layer, gray second color layer, and white third color layer regions were measured under standard light source conditions using a color difference meter, and at least five different positions were measured for each sample to obtain the average value; then the color difference ΔE value between adjacent color layers was obtained to evaluate the visual distinction; at the same time, the wear process was simulated, and the tire surface was gradually polished to different depths, and the color exposure order and clarity were observed and recorded to verify the identification effect of the mark at different wear stages. This detection was carried out in accordance with the standards ISO 7724-3 "Determination of color of paint and varnish - Part 3: Calculation of color difference" and ASTM D2244 "Standard practice for designation of colors by using the Munsell system".

[0079] Wear resistance detection: The tire tread sample was fixed on the test machine platform, and the sample surface was rubbed at a certain speed under a specified load and sand wheel. After a certain period of rubbing, the test was stopped, the wear volume of the sample was measured, and whether the surface color was blurred or peeled off due to excessive wear was observed. The test continued until the first color layer was worn out and the second color layer was exposed, and the rubbing period and wear amount at this time were recorded. Further rubbing to expose the third color layer, the data was recorded again, to evaluate the color retention ability and stage display effect of each layer under actual wear conditions. This detection was carried out in accordance with the standards ISO 4649 "Determination of abrasion resistance of vulcanized or thermoplastic rubber - Rotating drum abrasion machine method" or GB / T 9867 "Determination of abrasion resistance of vulcanized or thermoplastic rubber".

[0080] Interlayer adhesion strength detection: Standard size test pieces were cut from the vulcanized tire tread sample, and a tensile testing machine was used to perform a T-type peeling test at a specified speed, with the peeling direction perpendicular to the interlayer interface. Then the maximum force and average force during the peeling process were recorded, and the peeling strength per unit width was obtained, and the peeling surface morphology was observed to determine whether the failure occurred at the interlayer interface or the rubber inside, to represent the adhesion quality and overall structural integrity between the color layers. This detection was carried out in accordance with the standards ASTM D1876 "Standard test methods for adhesive strength by T-peel test" or GB / T 2791 "Adhesives - T-peel strength test method".

[0081] Mechanical property coordination detection: according to the standard method, the vulcanized rubber test piece was prepared, the Shore A hardness of each color layer rubber was measured by using the hardness tester; the tensile strength, elongation at break and stress at specific elongation were tested by using the tensile testing machine, and the stress-strain curve was obtained; at the same time, the resilience and compression permanent deformation test were carried out. By comparing the performance data between each layer and the base rubber of the tread, it is evaluated whether it can provide clear color difference while maintaining the mechanical behavior suitable for tire use requirements. This detection is carried out according to standards ISO 37 "Determination of the tensile stress-strain properties of vulcanized or thermoplastic rubber", ISO 7619-1 "Determination of indentation hardness of rubber - Part 1: Shore hardness tester method" and ISO 4662 "Determination of resilience of vulcanized rubber".

[0082] Aging resistance and color stability detection: in order to investigate the color stability and anti-aging ability of the multi-layer wear mark in long-term use environment, the accelerated aging test was carried out; the tread sample was placed in a hot air aging oven, and the aging treatment was carried out under the set temperature and time conditions to simulate the state after long-term use; after the aging was completed, the sample was taken out and cooled to room temperature, and the color parameters of each color layer were measured again, and the color difference ΔE value before and after aging was calculated; at the same time, the mechanical property change rate of the sample after aging was tested, and whether the surface appeared crack, discoloration or interlayer separation and other phenomena were observed, so as to comprehensively evaluate the durability and reliable warning function of the mark in complex environment; this detection is carried out according to standards ISO 188 "Accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber" and ASTM D1149 "Standard test method for rubber aging surface cracking".

[0083] Table 1: Color contrast and wear resistance performance parameters

[0084] Table 2: Adhesion strength, mechanical properties and aging resistance performance parameters

[0085] Example conclusion: It can be seen from examples 1-3 and comparative example 1 and tables 1 and 2 that when the amount of carbon black is insufficient, the color saturation and hiding power of the first color layer decrease, resulting in the weakening of the visual contrast with the intermediate gray warning layer; at the same time, as a reinforcing filler, the insufficient amount of carbon black will also weaken the mechanical strength and wear resistance of the rubber; by using sufficient amount of carbon black, not only the first color layer presents bright and stable dark color, but also the layer has high mechanical properties, so that the clear color difference is formed with the intermediate layer, and the structural integrity and wear resistance are maintained.

[0086] In combination with Examples 1-3 and Comparative Example 2 and in combination with Tables 1 and 2, it can be seen that reducing the total amount of gray pigments will result in the color of the intermediate warning layer becoming lighter and less bright, weakening its warning effect in the early stage of wear and making it difficult to be clearly distinguished from the black layer; by optimizing the ratio and total amount of titanium dioxide and carbon black, the gray layer has moderate lightness and high hiding power, forming an effective visual buffer and warning stage between the black and white layers, improving the progressive warning effect of the marking and the color gradation of the overall structure.

[0087] In combination with Examples 1-3 and Comparative Example 3 and in combination with Tables 1 and 2, it can be seen that canceling the intermediate gray warning layer and directly transitioning from black to white will make the color change too abrupt and lack intermediate indication of the wear progress; the black, gray, and white three-layer progressive structure used in the examples can more smoothly and accurately indicate the depth change of the tread wear, providing more intuitive and phased warning information for the driver, thereby improving the safety of tire use.

[0088] In combination with Examples 1-3 and Comparative Example 4 and in combination with Tables 1 and 2, it can be seen that simply using styrene-butadiene rubber has a lower cost, but it is inferior to natural rubber in strength, elasticity, and process adhesion; by using a formulation system that combines natural rubber and styrene-butadiene rubber, the complementary advantages between the high strength and high adhesion of natural rubber and the wear resistance and aging resistance of styrene-butadiene rubber are utilized, so that each color layer is not only bright in color, but also balanced in mechanical properties, interlayer adhesion, and durability.

[0089] In combination with Examples 1-3 and Comparative Example 5 and in combination with Tables 1 and 2, it can be seen that insufficient vulcanization will result in insufficient cross-linking density of the rubber molecules, thereby affecting the physical and mechanical properties of each color layer and the adhesion strength between the layers; by using a sufficient vulcanization process, the rubber composition is completely vulcanized, so that the pigments are fixed in the rubber network, thereby ensuring the color durability, high mechanical properties, and stable interlayer bonding of each color layer.

[0090] The specific embodiments are merely illustrative of the present application, and are not intended to limit the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, as long as the modifications are within the scope of the claims of the present application.

Claims

1. A novel tire wear indicator, characterized in that, The tread is provided with a first color layer (1), a second color layer (2) and a third color layer (3) along the depth of the tread groove. The first color layer (1) extends from the outer surface of the tread to 2 / 3 of the depth of the tread groove, the second color layer (2) extends from 1 / 3 of the depth of the tread groove to the normal wear indicator position, and the third color layer (3) extends from the normal wear indicator position to the bottom of the tread groove. The colors of the first color layer (1), the second color layer (2) and the third color layer (3) are different from each other, and the normal wear indicator position corresponds to a position with a tread depth of 1.6-2.6 mm.

2. The novel tire wear indicator according to claim 1, characterized in that, The first color layer (1), the second color layer (2) and the third color layer (3) are all made of a rubber composition, which includes the following components by weight: 40-60 parts of natural rubber, 20-40 parts of styrene-butadiene rubber, 5-15 parts of processing oil, 3-5 parts of zinc oxide, 1-2 parts of stearic acid, 1-2 parts of antioxidant, 0.5-1.5 parts of accelerator and 1.5-2.5 parts of sulfur.

3. The novel tire wear indicator according to claim 1, characterized in that, The first color layer (1) also contains a black pigment, which is carbon black, and its amount is 25-35% of the weight of the rubber composition; the second color layer (2) also contains a gray pigment, which is composed of titanium dioxide and carbon black in a weight ratio of 2:1-1:1, with the amount of titanium dioxide being 15-25% of the weight of the rubber composition and the amount of carbon black being 8-15% of the weight of the rubber composition; the third color layer (3) also contains a white pigment, which is titanium dioxide, and its amount is 30-40% of the weight of the rubber composition.

4. The novel tire wear indicator according to claim 1, characterized in that, The rubber composition may further contain a plasticizer, which is a phthalate ester, at 2-5% of the weight of the rubber composition.

5. A novel manufacturing process for tire tread wear indicators, characterized in that, A novel tire wear indicator according to any one of claims 1-4 includes the following steps: S1: Plasticize natural rubber and synthetic rubber to obtain plasticized rubber; S2: Add processing oil, zinc oxide, stearic acid and antioxidant to the plasticized rubber obtained in S1, and mix to obtain masterbatch; S3: Add accelerator and sulfur to the masterbatch obtained in S2, and perform final mixing to obtain the basic rubber composition; S4: Divide the basic rubber composition obtained in S3 into three parts, add black pigment, gray pigment and white pigment respectively, mix evenly to obtain the first color rubber composition, the second color rubber composition and the third color rubber composition; S5: The first color rubber composition, the second color rubber composition and the third color rubber composition obtained by extruding S4 are used to form a multi-layer tread blank, wherein the first color rubber composition forms a first color layer (1), the second color rubber composition forms a second color layer (2), and the third color rubber composition forms a third color layer (3). S6: The multi-layer tread blank is wound onto the tire forming drum and assembled with other tire components to form a green tire; S7: The green tire is placed in a mold for vulcanization to obtain the final tire.

6. The manufacturing process of a novel tire wear indicator according to claim 5, characterized in that, Before step S1, there is a pretreatment step of drying natural and synthetic rubber at a temperature of 40-60°C for 2-4 hours; and after drying, the rubber is crushed to a particle size of 5-10 mm.

7. The manufacturing process of a novel tire wear indicator according to claim 5, characterized in that, In step S2, the mixing temperature is 80-100℃, the time is 10-20 minutes, and the pressure is 0.5-1.0MPa.

8. The preparation process of a novel tire wear indicator according to claim 5, characterized in that, In step S4, a dispersant, which is a fatty acid salt, is added when adding pigment. The amount of the dispersant is 1-3% of the total weight of the pigment, and it is added at the same time as the pigment. In addition, a lubricant, which is zinc stearate, is added. The amount of the lubricant is 0.5-1 part, and it is added 5-10 minutes after the pigment is added and mixed.

9. The manufacturing process of a novel tire wear indicator according to claim 5, characterized in that, In step S5, the multi-layer tread blank is extruded by multi-layer co-extrusion at an extrusion temperature of 85-95℃ and an extrusion pressure of 8-15MPa.

10. The preparation process of a novel tire wear indicator according to claim 5, characterized in that, In step S7, the vulcanization temperature is 150-160℃, the pressure is 15-20MPa, and the time is 15-25 minutes.

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