A tire co-extrusion-vulcanization collaborative control method, tire and device, and storage medium

Abstract

The present application relates to a tire production control method, in particular to a tire co-extrusion-vulcanization collaborative control method, a tire and equipment, and a storage medium. The method comprises: determining the complex viscosity, elastic recovery, flow front speed and vulcanization characteristic parameters of the conductive groove glue and the adjacent tread glue; generating a weak band risk coefficient of the conductive groove center according to the complex viscosity ratio, the elastic recovery difference, the flow front speed difference, the T30 difference and the local temperature rise rate difference; when the threshold value is exceeded, the glue formula and the co-extrusion and vulcanization process are collaboratively adjusted; the interface strain accumulation is controlled in the co-extrusion stage, and the crosslinking growth rate difference is controlled in the vulcanization stage, so as to inhibit the formation of the conductive groove center low density band, the micro gap or the continuous weak band. The tread structure obtained thereby has high center continuity, interface peeling strength and conductive stability, can reduce the conductive resistance fluctuation rate and the 0KM abnormal rate, and is suitable for new energy automobile tires and high-performance passenger car tires.

Description

Technical Field

[0001] This invention relates to tire production control methods, and more particularly to a tire co-extrusion-vulcanization synergistic control method, tires and equipment, and storage media. Background Technology

[0002] As passenger car tires and new energy vehicle tires develop towards lower rolling resistance, higher wet grip, and higher wear resistance, the proportion of silica and silane coupling systems used in tread compounds is gradually increasing. While silica systems are beneficial for reducing rolling resistance and improving wet grip, their conductivity is generally weaker than that of traditional high-carbon-black tread compounds, making it easy for static electricity accumulated during tire driving or braking to be unstable and not discharged. Therefore, incorporating conductive strips, conductive grooves, or conductive pathways into the tread to create an electrical connection between the tread's grounding surface and the conductive rubber portions in the tire carcass, belt layers, or tread base has become an important technical approach to address the insufficient conductivity of silica treads.

[0003] For example, prior art CN1291947A discloses a conductive tire and an apparatus for extruding conductive portions. The basic idea is to incorporate conductive portions formed from a conductive rubber mixture into the relatively low-conductivity tread rubber, allowing these conductive portions to extend from the tire's interior to the grounded surface of the tread, thus forming an electrostatic discharge path. As another example, prior art US7029544B2 discloses a tire tread structure with electrostatic discharge characteristics. This structure improves the tire's conductivity while maintaining the low rolling resistance of the tread body by forming small-volume conductive paths with a high carbon black concentration within the tread. These technologies primarily focus on the presence or absence of conductive paths, the placement of conductive rubber strips, and the overall tread resistance reduction effect, and can address the electrostatic discharge problem of low-conductivity tread rubber to a certain extent.

[0004] However, in actual tire production, the conductive rubber strip or conductive groove structure is not merely a geometric embedding relationship. It typically needs to flow and form together with adjacent tread rubber during the extrusion stage, and undergo processes such as heating, flow freezing, cross-linking growth, and localized shrinkage during subsequent molding and vulcanization. Conductive groove rubber often contains conductive carbon black, graphite, or other conductive fillers, and its filler structure, Mooney viscosity, elastic recovery, vulcanization initiation time, and cross-linking growth rate often differ from those of the adjacent silica tread rubber. When the complex viscosity, elastic recovery, and flow front velocity of the two rubber compounds differ significantly during the co-extrusion stage, the central region of the conductive groove is prone to flow trapping, localized stretching, interfacial strain accumulation, or insufficient density. When the T10, T30, T90, or localized heating rates of the two rubber compounds are mismatched during the subsequent vulcanization stage, the aforementioned flow inhomogeneity may be further amplified by differences in cross-linking shrinkage and densification, ultimately forming continuous weak bands, micro-voids, low-modulus bands, or preferential areas for peeling and cracking in the center of the conductive groove.

[0005] For example, the existing technology CN218084075U discloses an extrusion die for tire treads with conductive rubber strips. By setting guide grooves, crown openings, and related flow guiding structures on the upper and lower plates of the die, it reduces extrusion pressure, increases rubber flow, improves production speed, and ensures that the conductive rubber penetrates the entire tread. This technology improves the extrusion molding conditions of treads with conductive rubber strips from the perspective of die structure, which is of positive significance for the penetration of conductive rubber through the tread and improving production efficiency. However, this type of solution mainly focuses on mold structure and rubber flow channel design, and does not further establish a unified control relationship for the complex viscosity ratio, elastic recovery difference, flow front speed difference, T30 difference, crosslinking growth rate difference, and local heating rate difference between the conductive groove rubber and adjacent tread rubber. It also does not reveal that the weak band in the center of the conductive groove has a defect chain that is generated in the co-extrusion stage and amplified in the vulcanization stage.

[0006] Furthermore, traditional processes often address abnormalities in the conductive groove by increasing the amount of conductive filler, adding tackifying resin, adjusting the die temperature, changing the extrusion speed, or individually adjusting the accelerator system. While these measures may improve conductivity, adhesion, or extrusion stability in some aspects, they are prone to unintended consequences because they do not simultaneously consider co-extrusion flow matching and vulcanization process matching. For example, simply increasing the amount of conductive carbon black may improve conductivity, but it may also increase the viscosity and elastic recovery of the conductive groove rubber, exacerbating co-extrusion flow mismatch; simply accelerating the vulcanization speed of the conductive groove rubber may shorten the production cycle, but it may also cause the conductive groove rubber to densify and shrink before the adjacent tread rubber, thus amplifying the weak central band; simply increasing the tackifying system may improve initial adhesion, but it cannot eliminate the central continuity defects caused by differences in flow front and crosslinking growth.

[0007] Therefore, although existing technologies have disclosed conductive treads, conductive rubber strips, conductive pathways, and extrusion cuffs for conductive rubber strip treads, they still lack an engineering control method for the formation mechanism of the weak band at the center of the conductive groove. In particular, there is a lack of a method that synergistically constrains the rheological matching, interfacial strain accumulation, vulcanization phase matching, and local heating rate control of the conductive groove rubber and adjacent tread rubber as a single technical chain, in order to reduce the width of the weak band at the center of the conductive groove, improve interfacial peel strength, reduce conductivity resistance fluctuation, and improve the 0km stability of the finished tire without significantly sacrificing rolling resistance, wear resistance, and processing window. Summary of the Invention

[0008] The purpose of this invention is to provide a co-extrusion-vulcanization synergistic control method, tread structure, and tire to suppress the formation of a weak zone in the center of the conductive groove. By taking the complex viscosity, elastic recovery, flow front velocity, and interfacial strain accumulation of the conductive groove rubber and the adjacent tread rubber during the co-extrusion stage, as well as the differences in T10, T30, t90, local heating rate, and crosslinking growth rate during the vulcanization stage as synergistic control objects, this invention solves the problem of weak zones, micro-voids, or preferential peeling cracking zones formed in the center of existing conductive groove structures during co-extrusion and vulcanization due to flow mismatch, differences in interfacial strain history, and crosslinking shrinkage mismatch. This improves the continuity of the conductive groove center and the quality stability of the finished tire.

[0009] Firstly, in order to achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] A co-extrusion-vulcanization synergistic control method for suppressing the formation of weak bands in the center of tire conductive grooves, the method comprising the following steps:

[0011] S1. Select conductive groove rubber and adjacent tread rubber located on both sides of the conductive groove rubber. Under the same extrusion temperature and the same test frequency, measure the complex viscosity, elastic recovery rate, flow front velocity and vulcanization characteristic parameters of the conductive groove rubber and the adjacent tread rubber respectively. The vulcanization characteristic parameters include at least T10, T30 and t90.

[0012] S2. Based on the complex viscosity, elastic recovery rate, flow front velocity, T30, and the local heating rate of the conductive groove region and the adjacent tread region, generate the risk factor for the weak zone at the center of the conductive groove. And reduce the risk factor of the weak band at the center of the conductive groove. Not greater than the preset risk threshold The risk factor of the weak band at the center of the conductive groove is... Determine using the following formula:

[0013] In the formula: Risk factor for the weak band at the center of the conductive groove; The weighting coefficient for the complex viscosity mismatch term; This is the complex viscosity mismatch term; For the elastic recovery mismatch term weighting coefficient; For flexible recovery of mismatch; The weighting coefficient for the velocity mismatch term of the flowing front; For the speed mismatch of the forward; The weighting coefficient for the sulfidation phase mismatch term; This is a mismatch term for T30; This represents the weighting coefficient for the localized temperature rise mismatch term; This represents the local heating rate mismatch term; the sum of all weighting coefficients is 1. To preset risk thresholds;

[0014] S3, when the risk factor of the weak band at the center of the conductive groove Greater than the preset risk threshold At the same time, at least one of the following: polymer composition, plasticizing system, reinforcing filler structure, accelerator system, and sulfur system of the conductive groove rubber and / or adjacent tread rubber is adjusted to make the complex viscosity ratio of the conductive groove rubber to the adjacent tread rubber such that... The T30 value should be controlled between 0.90 and 1.10, and the difference between the conductive groove rubber and the adjacent tread rubber should be controlled between -0.2 and 1.2 min.

[0015] S4. Co-extrude the conductive groove rubber that meets the conditions of step S3 with the adjacent tread rubber. During the co-extrusion process, control the difference in flow front velocity, die dwell time, and cumulative interfacial strain between the conductive groove rubber and the adjacent tread rubber. This prevents a continuous, low-density interface band from forming in the central region of the conductive groove after extrusion.

[0016] S5. Preheat and vulcanize the co-extruded tread semi-finished product. During the vulcanization stage, control the difference in local heating rate and crosslinking growth rate between the conductive groove area and adjacent tread areas. This prevents the conductive groove rubber from undergoing densification relative to the adjacent tread rubber, which would otherwise lead to central shrinkage and amplification.

[0017] S6. Obtain a tread structure with improved continuity of the conductive groove center or a pneumatic tire containing the tread structure.

[0018] As a further improvement, in step S2, the complex viscosity ratio... Determine using the following formula:

[0019] ;

[0020] In the formula: The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; The complex viscosity of the conductive groove adhesive at the extrusion temperature; The complex viscosity refers to the viscosity of adjacent tread compounds at the same extrusion temperature; the extrusion temperature is 90–115°C, and the testing frequency is 1–20 Hz; preferably, the complex viscosity ratio is... The Mooney viscosity is 0.95 to 1.05, and the difference in Mooney viscosity between the conductive groove rubber and the adjacent tread rubber is no greater than 8 MU;

[0021] And / or, in step S2, the complex viscosity mismatch term Determine using the following formula:

[0022] ;

[0023] In the formula: This is the complex viscosity mismatch term; The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; It is the natural logarithm function;

[0024] And / or, in step S2, the T30 mismatch term Determine using the following formula:

[0025] ;

[0026] In the formula: This is a mismatch term for T30; The time required for the conductive groove adhesive to reach 30% curing degree; The time required for adjacent tread rubbers to reach 30% vulcanization; The target vulcanization phase difference is set to 0–0.6 min; and the T10 difference between the conductive groove rubber and the adjacent tread rubber is controlled within -0.5–1.5 min, and the T90 difference is controlled within -1.0–2.0 min.

[0027] As a further improvement, in step S4, the cumulative amount of interfacial strain Determine using the following formula:

[0028] ;

[0029] In the formula: This refers to the cumulative amount of interfacial strain. The effective flow length for the conductive groove rubber and the adjacent tread rubber to form a common interface within the die; The integral position along the effective flow length; For conductive groove adhesive at position The shear strain or equivalent shear strain at the point; For adjacent tread rubber in position The shear strain or equivalent shear strain at the point; To prevent the correction constant from having a denominator of zero; the cumulative interfacial strain The value should be controlled to be no greater than 0.18, preferably no greater than 0.12.

[0030] As a further improvement, in step S4, at least three process parameters are controlled during co-extrusion molding: die temperature is 85-115℃, traction speed is 8-35m / min, the die dwell time difference between the conductive groove rubber and the adjacent tread rubber is not greater than 15%, the flow front speed difference between the conductive groove rubber and the adjacent tread rubber is not greater than 8%, and the cooling rate after extrusion is 5-25℃ / min.

[0031] As a further improvement, in step S5, the sulfur conversion rate is used... The crosslinking process of the conductive groove rubber or adjacent tread rubber, the vulcanization conversion rate. Determine using the following formula:

[0032] ;

[0033] In the formula: For rubber vulcanization time Vulcanization conversion rate; Indicates conductive groove adhesive or adjacent tread rubber ; For rubber vulcanization time Torque under; For rubber The minimum torque; For rubber The highest torque.

[0034] Preferably, in step S5, the difference in crosslinking growth rate between the conductive groove adhesive and the adjacent tread adhesive is... Determine using the following formula:

[0035] ;

[0036] In the formula: The difference in crosslinking growth rate between the conductive groove rubber and the adjacent tread rubber; For the conductive groove adhesive during the curing time Vulcanization conversion rate; For adjacent tread rubbers at vulcanization time Vulcanization conversion rate; The rate of increase in vulcanization conversion of the conductive groove adhesive; The rate of increase in vulcanization conversion of adjacent tread rubbers; To prevent a correction constant with a denominator of zero; the difference in crosslinking growth rates The limit is no more than 25%;

[0037] And / or, in step S5, during the vulcanization stage, the local temperature difference between the corresponding area of ​​the conductive groove in the mold and the corresponding area of ​​the adjacent tread is controlled to not exceed ±3℃, the preheating time of the conductive groove area is 20-120s, and the difference in local heating rate between the conductive groove area and the adjacent tread area is not greater than 0.05℃ / s; when the width of the weak band at the center of the conductive groove is detected to be greater than 0.20mm or the conductivity resistance fluctuation rate is greater than 6%, the T30 difference between the conductive groove rubber and the adjacent tread rubber is reduced, the difference in local heating rate is reduced, and / or the cumulative amount of interfacial strain is reduced. .

[0038] As a further improvement, the conductive groove rubber is a diene rubber composition containing at least one of conductive carbon black, graphite, carbon nanotubes and conductive polymers; the adjacent tread rubber is a tread rubber composition containing silica and / or carbon black; by adjusting the conductive filler structure, processing oil amount, tackifying resin amount, accelerator type, sulfur amount in the conductive groove rubber, as well as the silane coupling agent, reinforcing filler and scorch safety system in the adjacent tread rubber, the conductive groove rubber and the adjacent tread rubber can simultaneously meet the rheological matching conditions and the vulcanization phase matching conditions.

[0039] Secondly, the present invention also provides a tread structure, the tread structure being obtained by the method described above, the tread structure comprising adjacent tread rubber regions and conductive groove rubber regions embedded between the adjacent tread rubber regions and extending from the tread ground contact surface into the tread interior; the central joint area of ​​the conductive groove rubber region satisfies at least three of the following conditions: the width of the central weak band is not greater than 0.20 mm; the length of continuous defects accounts for not more than 5% of the total length of the conductive groove; the microhardness difference between the two sides of the center line of the conductive groove is not greater than 8%; the interfacial peel strength between the conductive groove rubber and the adjacent tread rubber is not less than 26 N; and the conductivity resistance fluctuation rate is not greater than 6%.

[0040] Thirdly, the present invention also provides a pneumatic tire, wherein the tread portion of the pneumatic tire includes the aforementioned tread structure, and the conductive groove rubber region constitutes a continuous conductive path from the tread contact surface to the conductive component inside the tread; the abnormality rate of the conductive groove in the pneumatic tire during 0KM inspection is no greater than 2.0%, and compared to the risk factor of no weak band at the center of the conductive groove... Control, interfacial strain accumulation Poor control and crosslinking growth rate The controlled control tires showed reduced width of the weak band at the center of the conductive groove, increased interfacial peel strength, and reduced conductivity resistance fluctuation.

[0041] Fourthly, the present invention also provides an electronic device, including a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method described above.

[0042] Fifthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described thereon.

[0043] After adopting the technical solution of the present invention, the conductive groove rubber and the adjacent tread rubber are no longer locally optimized solely by the amount of conductive filler, the tackifying system, or a single extrusion parameter. Instead, the risk factor of the weak zone at the center of the conductive groove is considered. Interfacial strain accumulation and the difference in crosslinking growth rate This invention integrates constraints on the process of defects generated during co-extrusion and amplified during vulcanization, ensuring that the conductive groove rubber and adjacent tread rubber have similar flow fronts and strain histories within the die, and maintain a more convergent crosslinking process and shrinkage behavior during vulcanization heating. This effectively reduces the width of the weak band and the proportion of continuous defect length in the center of the conductive groove, decreases the generation of low-density bands, micro-voids, and preferential areas for interfacial cracking, and improves the interfacial peel strength and microhardness uniformity between the conductive groove rubber and adjacent tread rubber. Simultaneously, due to the improved continuity and interfacial integrity of the conductive groove center, the tire's conductive path is more stable, reducing the conductivity resistance fluctuation rate and the abnormality rate of the conductive groove in 0KM testing. Compared to solutions that simply increase conductive filler, adjust die temperature alone, or change vulcanization speed alone, this invention improves the manufacturing consistency, finished product reliability, and mass production adaptability of the conductive groove tread structure while maintaining or essentially maintaining stable rolling resistance, wear resistance, and processing window. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall process of a co-extrusion-vulcanization synergistic control method for suppressing the formation of a weak zone in the center of a tire conductive groove according to the present invention.

[0045] Figure 2 Risk factor of weak band at the center of the conductive groove in this invention A schematic diagram of the generation and determination process.

[0046] Figure 3 This refers to the cumulative interfacial strain during the co-extrusion stage of this invention. Control diagram, in which Figure 3 (a) shows the flow front, common flow interface, and die residence time difference when the conductive groove rubber and the adjacent tread rubber flow together in the die. Figure 3 (b) shows the process for controlling the interfacial strain accumulation in the central bonding zone of the conductive groove after extrusion, which is used to reduce the risk of central low-density band formation.

[0047] Figure 4 This is a schematic diagram of crosslinking convergence control during the vulcanization stage of the present invention, wherein... Figure 4 Figure (a) shows the relationship between the preheating, local temperature difference, and local heating rate difference between the conductive groove region and the adjacent tread region in the mold. Figure 4 Figure (b) shows the vulcanization conversion curves of the conductive groove rubber and the adjacent tread rubber, achieved by controlling the difference in crosslinking growth rate. This reduces the risk that the weak zone in the center of the conductive groove will be further amplified during the vulcanization stage.

[0048] Figure 5 This is a schematic diagram of the detection result feedback and parameter correction process of the present invention.

[0049] Figure 6This is a schematic diagram comparing the cross-sectional morphology of the conductive groove center connector in the embodiment of the present invention and the comparative example.

[0050] Figure 7 This is a comparison diagram of the center weak band width and interface peel strength between the embodiments and comparative examples of the present invention. The upper diagram shows the difference in center weak band width between the embodiments and comparative examples, and the lower diagram shows the difference in interface peel strength between the embodiments and comparative examples.

[0051] Figure 8 This is a comparison chart of the conductivity resistance fluctuation rate and 0KM anomaly rate between the embodiments and the comparative examples of the present invention. The upper chart shows the difference in conductivity resistance fluctuation rate between the embodiments and the comparative examples, and the lower chart shows the difference in 0KM anomaly rate between the embodiments and the comparative examples.

[0052] Figure 9 This is a schematic diagram illustrating the correlation between the key control indicators of this invention and the width of the central weak band, wherein... Figure 9 (a) shows the risk factor of the weak band at the center of the conductive groove. A positive correlation between the width of the central weak band and the width of the central weak band. Figure 9 (b) shows the cumulative interfacial strain. A positive correlation between the width of the central weak band and the width of the central weak band. Figure 9 (c) in the diagram shows the difference in crosslinking growth rate. A positive correlation between the width of the central weak band and the width of the band. Detailed Implementation

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings. It should be understood that the following specific embodiments are used to explain the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Without departing from the technical solution of the present invention, those skilled in the art can make adaptive adjustments to the formula ratio, process window and detection threshold according to tire specifications, tread rubber system, type of conductive filler, co-extrusion equipment structure and vulcanizing machine model.

[0055] 1. Terminology Explanation

[0056] In this embodiment, the conductive groove rubber refers to a rubber composition disposed in the tread structure to form an electrostatic discharge path, which typically contains conductive carbon black, graphite, carbon nanotubes, conductive polymers, or combinations thereof. The conductive groove rubber area can be in the form of a narrow strip, a groove, a chimney, or other continuous conductive structure extending from the ground surface of the tread into the interior of the tread.

[0057] Adjacent tread compounds refer to rubber compositions located on both sides of the conductive groove rubber and forming the tread ground contact portion together with the conductive groove rubber. Adjacent tread compounds can be silica-reinforced tread compounds, carbon black-reinforced tread compounds, or silica / carbon black blended tread compounds, especially silica tread compounds commonly used in low rolling resistance passenger car tires or new energy vehicle tires.

[0058] The weak zone in the center of the conductive groove refers to the central bonding area of ​​the conductive groove rubber region or the adjacent central area between the conductive groove rubber and the adjacent tread rubber. It is characterized by a continuous low-density zone, low-modulus zone, micro-voids, preferential areas for localized peeling and cracking, or areas with abnormal conductivity stability formed after extrusion and vulcanization. This weak zone can be characterized indirectly or directly through microsectioning, microhardness testing, peel strength testing, or conductivity resistance fluctuation testing.

[0059] Complex viscosity This refers to the viscoelastic flow resistance exhibited by the rubber compound under oscillating shear test conditions, which can be measured near the extrusion temperature using a rubber processing analyzer or a dynamic rheometer. In this embodiment, the complex viscosity of the conductive groove rubber and the adjacent tread rubber is preferably measured under test conditions of 90–115°C and 1–20Hz.

[0060] Elastic recovery rate refers to the ability of a rubber compound to return to its original shape after being subjected to shear or tensile deformation. When the difference in elastic recovery between the conductive groove rubber and the adjacent tread rubber is too large, springback differences are likely to occur at the die exit, which in turn induces differences in strain history in the central region of the conductive groove.

[0061] Flow front speed refers to the speed at which the leading edge of the conductive groove rubber or adjacent tread rubber advances near the exit of the co-extrusion die. When the difference in flow front speed between the two rubber compounds is too large, the central area of ​​the conductive groove is prone to trapping, dragging, local stretching, or low-density interface bands.

[0062] T10, T30, and t90 represent the characteristic times when the rubber compound reaches the predetermined degree of vulcanization. T10 represents the initial stage of vulcanization, T30 represents the vulcanization phase where crosslinking growth enters a significant stage, and t90 represents the near-positive vulcanization state. This invention focuses on the T30 difference between the conductive groove rubber and the adjacent tread rubber, because the T30 stage corresponds to the critical interval in which the rubber compound transitions from a flowable state to a crosslinking-restricted state. If the difference between the conductive groove rubber and the adjacent tread rubber is too large at this stage, the small strain differences already formed during the co-extrusion stage can be further amplified during the vulcanization stage.

[0063] 2. System Structure and Process Implementation Basis

[0064] Combination Figure 1 and Figure 5 The method of this invention can be implemented through a detection-calculation-control system in a tire production line. This system may include a raw material parameter acquisition unit, a risk factor generation unit, a formula parameter adjustment unit, a co-extrusion molding control unit, a vulcanization control unit, and a finished product detection feedback unit.

[0065] The raw material parameter acquisition unit is used to determine the complex viscosity, Mooney viscosity, elastic recovery rate, flow front velocity, T10, T30, t90, vulcanization torque, and temperature rise curves of the conductive groove rubber and adjacent tread rubber. This unit can consist of a rubber processing analyzer, a rotorless vulcanizer, a Mooney viscometer, thermocouples, an infrared temperature measuring device, a die pressure sensor, and an online image detection device, or it can consist of both offline laboratory test data and online production line data.

[0066] The risk coefficient generation unit is used to generate complex viscosity ratios. Poor elastic recovery, poor flow front velocity, T30 sulfidation phase difference, and local heating rate difference are converted into a risk factor for a weak band in the center of the conductive trough. This risk factor does not simply evaluate whether a single rubber compound is qualified, but rather evaluates the compatibility between the conductive groove rubber and the adjacent tread rubber during the co-extrusion-vulcanization continuous process.

[0067] The formula parameter adjustment unit is used in Greater than During this process, adjustments are made to the conductive groove adhesive and / or adjacent tread adhesives. These adjustments target the polymer composition, plasticizing system, reinforcing filler structure, conductive filler structure, silane coupling system, accelerator system, sulfur system, and tackifying resin system. This adjustment does not simply involve increasing the conductive filler content, but rather aims to achieve convergence in the complex viscosity ratio, T30 difference, elastic recovery difference, and localized heating rate difference.

[0068] The co-extrusion molding control unit is used to control the flow state of the conductive groove compound and adjacent tread compound within the die, including die temperature, screw speed, gear pump speed, traction speed, die dwell time, flow front speed, and post-extrusion cooling rate. The goal of this unit is to prevent the formation of a continuous, low-density interface band in the central region of the conductive groove after extrusion.

[0069] The vulcanization control unit is used to control the local heating rate, preheating time, local temperature difference of the mold, vulcanization pressure and vulcanization time of the tread semi-finished product during the vulcanization process, so that the conductive groove rubber and the adjacent tread rubber maintain a relatively convergent cross-linking growth rate during the process from the flowable state to the cross-linking fixed state.

[0070] The finished product inspection feedback unit is used to detect the width of the weak band at the center of the conductive groove, the proportion of continuous defect length, the interface peel strength, the difference in microhardness, the conductivity resistance fluctuation rate and the 0KM anomaly rate, and feeds the test results back to the risk coefficient generation unit and the formula parameter adjustment unit for correction in subsequent batches.

[0071] 3. Specific technical route for implementing the method of the present invention

[0072] 3.1S1: Parameter determination of conductive groove rubber and adjacent tread rubber

[0073] Combination Figure 1 In this embodiment, a conductive groove rubber and adjacent tread rubbers located on both sides of the conductive groove rubber are first selected. The conductive groove rubber can use natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, or a blend thereof as the matrix, and conductive carbon black, graphite, or carbon nanotubes are added to form a conductive network. The adjacent tread rubbers can use a solution-polymerized styrene-butadiene rubber and cis-butadiene rubber blend system, and add silica, silane coupling agent, carbon black, processing oil, antioxidant, sulfur, and accelerator.

[0074] During the parameter determination stage, test conditions that correspond as closely as possible to the actual extrusion and vulcanization processes should be used. For example, if the tread extrusion temperature is controlled between 95 and 105°C, the complex viscosity should preferably be measured around 100°C; if the actual vulcanization temperature is 160°C, T10, T30, and t90 should preferably be measured using a rotorless vulcanizer at 160°C. This method yields data that more closely approximates actual production conditions, avoiding judgment biases caused by evaluating the rubber compound only under normal temperature or non-process conditions.

[0075] Complex viscosity ratio Determine using the following formula:

[0076] ;

[0077] In the formula: The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; The complex viscosity of the conductive groove adhesive at the extrusion temperature; It represents the complex viscosity of adjacent tread compounds at the same extrusion temperature.

[0078] when When the value is significantly greater than 1, it indicates that the conductive groove rubber is relatively viscous compared to the adjacent tread rubber. During co-extrusion, this can easily lead to flow lag, insufficient central compaction, or the tread rubber on both sides dragging and pulling the conductive groove rubber along with the conductive groove rubber. When the value is significantly less than 1, it indicates that the conductive groove rubber is relatively thinner than the adjacent tread rubber. This makes the conductive groove rubber prone to premature flow within the die, localized displacement, or morphological instability in the central region. Therefore, this embodiment preferably uses... The concentration should be controlled between 0.90 and 1.10, more preferably between 0.95 and 1.05.

[0079] In addition to complex viscosity, the elastic recovery rate of the conductive groove compound and the adjacent tread compound should also be measured. Due to the presence of conductive fillers with higher structure, the conductive groove compound often exhibits higher elastic recovery and more pronounced exit swell behavior. If the difference in elastic recovery is too large, even if the complex viscosities of the two compounds are similar, a difference in rebound may occur at the die exit, causing micro-tears or low-density bands in the central joint area of ​​the conductive groove. Therefore, simultaneously measuring the elastic recovery rate in S1 can compensate for the viscoelastic differences that complex viscosity cannot fully characterize.

[0080] The flow front velocity can be obtained through transparent simulation of the die, extrusion process slicing, online image acquisition, or numerical simulation. For mass production processes, it can also be indirectly calculated using die pressure, gear pump flow rate, screw speed, and traction speed. The smaller the flow front velocity difference, the more consistent the propulsion state of the conductive groove rubber and the adjacent tread rubber at the die exit, and the lower the risk of weak band formation in the center of the conductive groove.

[0081] 3.2S2: Risk factor of weak band at the center of the conductive groove The generation

[0082] Combination Figure 2 This embodiment unifies the key differences between the conductive groove rubber and the adjacent tread rubber during the co-extrusion and vulcanization stages into a risk factor for the weak zone in the center of the conductive groove. The purpose of this setup is to integrate the rheological parameters, vulcanization parameters, and local temperature rise parameters, which are traditionally treated separately, into a single judgment object, enabling process engineers to determine whether the current rubber compound composition poses a comprehensive risk of forming a central weak zone.

[0083] Risk factor of weak band at the center of conductive groove Determine using the following formula:

[0084] ;

[0085] In the formula: Risk factor for the weak band at the center of the conductive groove; The weighting coefficient for the complex viscosity mismatch term; This is the complex viscosity mismatch term; For the elastic recovery mismatch term weighting coefficient; For flexible recovery of mismatch; The weighting coefficient for the velocity mismatch term of the flowing front; For the speed mismatch of the forward; The weighting coefficient for the sulfidation phase mismatch term; This is a mismatch term for T30; This represents the weighting coefficient for the localized temperature rise mismatch term; This is the local heating rate mismatch term; the sum of all weighting coefficients is 1.

[0086] Among them, the complex viscosity mismatch term It can be determined by the following formula:

[0087] ;

[0088] In the formula: This is the complex viscosity mismatch term; The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; It is the natural logarithm function.

[0089] use The advantage is that both excessively viscous and excessively thin conductive groove adhesives increase the risk value, and when... As the value approaches 1, the complex viscosity mismatch term tends to be at a lower level. This avoids the problem of imbalance in the assessment of the two types of risks, namely, viscous and thinner viscosity, when only linear difference is used.

[0090] T30 mismatch item It can be determined by the following formula:

[0091] ;

[0092] In the formula: This is a mismatch term for T30; The time required for the conductive groove adhesive to reach the vulcanization degree corresponding to T30; The time required for adjacent tread rubber compounds to reach the vulcanization level corresponding to T30; The target sulfidation phase difference.

[0093] In this embodiment, The timeframe can be 0–0.6 min. This means that a slight difference in vulcanization phase is allowed between the conductive groove rubber and the adjacent tread rubber, but the conductive groove rubber is not allowed to enter the rapid crosslinking growth stage significantly earlier or later than the adjacent tread rubber. If the conductive groove rubber enters the obvious crosslinking stage too early, its flow and stress relaxation capabilities decrease, while the adjacent tread rubber remains in a relatively flowable state. In this case, the central area of ​​the conductive groove rubber is easily tightened by vulcanization shrinkage and forms a low-density band. If the conductive groove rubber enters the obvious crosslinking stage too late, the adjacent tread rubber will fix its shape first, and the conductive groove rubber may also experience center shift or interface stress concentration during subsequent shrinkage or densification.

[0094] Local heating rate mismatch term The temperature rise can be determined based on the measured temperature rise curves of the conductive groove region and adjacent tread regions. Because the filler systems of the conductive groove rubber and the adjacent tread rubber are different, their thermal conductivity, specific heat capacity, and local heating states may differ, especially in thick treads, wide conductive grooves, or high-wear-resistant tread structures for new energy tires. The temperature rise curve of the conductive groove region may differ from that of the adjacent tread region. If the difference in local heating rate is too large, even if the T30 of the two rubber compounds is close in the standard vulcanizer, an effective vulcanization phase misalignment may still occur in the actual tire vulcanization mold. Therefore, this invention introduces the difference in local heating rate... This allows risk assessments to more closely reflect the actual vulcanization process.

[0095] In practice, several batches of tests can be conducted first to determine the results. For example, rubber compound combinations with a central weak band width of no more than 0.20 mm, a conductivity resistance fluctuation rate of no more than 6%, and a 0KM anomaly rate of no more than 2.0% in historical batches are classified as low-risk combinations, and the corresponding... The upper limit or statistical quantile value is set as In subsequent production, when the new rubber compound is combined... Not greater than When, it can enter co-extrusion molding; when Greater than When that happens, you should enter the parameter adjustment in S3.

[0096] 3.3S3: Rheology-Vulcanization Synergistic Adjustment

[0097] S3 is a crucial implementation step that distinguishes this invention from single-formula optimization. When Greater than At that time, it's not simply a matter of increasing the conductive filler, adding tackifying resin, or increasing the vulcanization rate, but rather adjusting the treatment based on each mismatch. The sources of contribution will be adjusted accordingly.

[0098] when Too large and A viscosity greater than 1 indicates that the conductive bath adhesive is too viscous. In this case, the proportion of high-structure conductive carbon black in the conductive bath adhesive can be appropriately reduced, and some low-structure conductive carbon black, graphite, or composite conductive fillers can be used as substitutes. Alternatively, the amount of processing oil or low-volatility plasticizer can be appropriately increased, or the polymer blending ratio can be adjusted to reduce the flow resistance of the conductive bath adhesive at the extrusion temperature. However, it should be noted that reducing viscosity should not damage the conductive network. Therefore, a combination of filler structure adjustment, plasticizer system fine-tuning, and polymer compatibility adjustment is preferred, rather than simply reducing the total amount of conductive filler.

[0099] when Too large and A value less than 1 indicates that the conductive groove adhesive is too thin. In this case, the reinforcing filler structure of the conductive groove adhesive can be appropriately increased, an appropriate amount of tackifying resin can be added, or the proportion of high molecular weight rubber components can be increased to make it closer to the co-extrusion flow front of the adjacent tread rubber. If the conductive groove adhesive is only made thinner, although the extrusion pressure will be lower in the short term, the conductive groove adhesive is prone to center morphology drift and local enrichment in the die, which will increase the risk of weak central bands or fluctuations in conductivity resistance.

[0100] when If the T30 phase difference is too large, it indicates that the T30 phase difference between the conductive groove rubber and the adjacent tread rubber deviates from the target range. If the T30 of the conductive groove rubber is significantly earlier than that of the adjacent tread rubber, the crosslinking growth of the conductive groove rubber can be delayed by reducing the activity of the accelerator, adjusting the ratio of accelerators, reducing some sulfur, or adding an appropriate amount of scorch safety agent. If the T30 of the conductive groove rubber is significantly later than that of the adjacent tread rubber, the activity of the accelerator system can be appropriately increased or the sulfur / accelerator ratio can be adjusted so that it enters the crosslinking growth stage synchronously with the adjacent tread rubber during the vulcanization process.

[0101] when or If the viscosity is too high, it indicates that even if the complex viscosity is close to T30, there will still be problems with exit springback or inconsistent flow fronts. In this case, process corrections can be made by adjusting the die temperature, gear pump speed, traction speed, die runner cross-section, and post-extrusion cooling rate. For example, without causing scorching risk, the die temperature on the viscous side can be appropriately increased to make its flow front catch up; or the traction speed can be reduced to allow both compounds more time to stabilize at the die exit.

[0102] Through the above adjustments, the complex viscosity ratio of the conductive groove rubber to the adjacent tread rubber is adjusted. The viscosity should be controlled within the range of 0.90 to 1.10, preferably within the range of 0.95 to 1.05; the T30 difference between the conductive groove rubber and the adjacent tread rubber should be controlled within the range of -0.2 to 1.2 min; the Mooney viscosity difference between the conductive groove rubber and the adjacent tread rubber should not exceed 8 MU. The above range can balance the consistency of co-extrusion flow, the stability of the center shape of the conductive groove, and the vulcanization convergence.

[0103] 3.4S4: Interfacial strain accumulation control during co-extrusion stage

[0104] Combination Figure 3 The co-extrusion stage is the initial stage for the formation of the weak zone in the center of the conductive groove. The conductive groove rubber and the adjacent tread rubber flow together in the die. If there are significant differences in the flow velocity, shear strain, and exit springback of the two rubbers, an uneven strain history will be generated in the central region of the conductive groove. Even if no visible defects are formed in this stage, a central bonding area with low density, insufficient stress relaxation, or abnormal local orientation may be formed, providing the initial conditions for subsequent vulcanization shrinkage amplification.

[0105] Interfacial strain accumulation It can be determined by the following formula:

[0106] ;

[0107] In the formula: This refers to the cumulative amount of interfacial strain. The effective flow length for the conductive groove rubber and the adjacent tread rubber to form a common interface within the die; This refers to the starting position of the effective flow length; This refers to the termination position of the effective flow length; The integral position along the effective flow length; For conductive groove adhesive at position The shear strain or equivalent shear strain at the point; For adjacent tread rubber in position The shear strain or equivalent shear strain at the point; To prevent correction constants where the denominator is zero.

[0108] In actual production, and The results can be obtained through rheological testing combined with a die flow channel model, or through finite element flow simulation. For production lines without simulation capabilities, equivalent indicators can be used instead, such as estimating the results through the die pressure difference, flow rate difference, outlet velocity difference, and cross-sectional shape change after extrusion between the conductive groove rubber and adjacent tread rubber. When the estimate is obtained If the temperature is too high, it should be corrected by reducing the shear change in the die flow channel, adjusting the die temperature, reducing the traction speed, or changing the gear pump ratio.

[0109] During co-extrusion molding, the preferred die temperature is 85–115℃, the traction speed is 8–35 m / min, the die dwell time difference between the conductive groove rubber and the adjacent tread rubber is no more than 15%, the flow front velocity difference between the conductive groove rubber and the adjacent tread rubber is no more than 8%, and the cooling rate after extrusion is 5–25℃ / min. These parameter ranges are not isolated but work together to affect the morphological stability of the central region of the conductive groove. If the die temperature is too low, insufficient flow on the viscous side can easily lead to insufficient central compaction; if the die temperature is too high, it may increase exit springback and dimensional instability, and increase the risk of scorching. If the traction speed is too fast, the central region of the conductive groove is stretched before stabilization at the exit, easily forming a low-density band; if the cooling is too fast, it may freeze interfacial stress, making it difficult to eliminate in the subsequent vulcanization stage.

[0110] In this embodiment, the co-extruded tread semi-finished product should be inspected by cross-sectional slices. If a continuous low-density band exists in the central area of ​​the conductive groove, or if the conductive groove rubber area is offset relative to the adjacent tread rubber area, it should be adjusted back to the original position. The speed difference between the forwards and the flow of forwards If only localized, discontinuous, minor morphological fluctuations exist, but the proportion of continuous defect length can be controlled to below 5%, then the vulcanization stage can begin.

[0111] 3.5S5: Control of crosslinking growth rate difference during vulcanization stage

[0112] Combination Figure 4 The vulcanization stage is a critical stage where the weak zone in the center of the conductive groove is amplified. Even if there is only a slight difference in density in the central region of the conductive groove after co-extrusion, if the crosslinking growth rate difference between the conductive groove rubber and the adjacent tread rubber is large during the vulcanization heating process, the aforementioned difference may be amplified due to local shrinkage, crosslinking fixation, and insufficient stress release. Therefore, this invention introduces a vulcanization conversion rate during the vulcanization stage. and the difference in crosslinking growth rate .

[0113] Sulfurization conversion rate Determine using the following formula:

[0114] ;

[0115] In the formula: For rubber vulcanization time Vulcanization conversion rate; Indicates conductive groove adhesive or adjacent tread rubber ; For rubber vulcanization time Torque under; For rubber The minimum torque; For rubber The highest torque.

[0116] poor crosslinking growth rate Determine using the following formula:

[0117] ;

[0118] In the formula: The difference in crosslinking growth rate between the conductive groove rubber and the adjacent tread rubber; For the conductive groove adhesive during the curing time Vulcanization conversion rate; For adjacent tread rubbers at vulcanization time Vulcanization conversion rate; The rate of increase in vulcanization conversion of the conductive groove adhesive; The rate of increase in vulcanization conversion of adjacent tread rubbers; To prevent correction constants where the denominator is zero.

[0119] When expressed as a percentage, the above ratio can be multiplied by 100%. In this embodiment, it is preferable to... The content should be controlled to no more than 25%, more preferably no more than 20%. When the crosslinking growth of the conductive groove rubber and the adjacent tread rubber differs significantly within the same time period, it can easily lead to one side fixing first while the other side continues to flow or shrink, which in turn causes stress concentration and micro-defect amplification in the central joint area.

[0120] During the vulcanization stage, the difference in local heating rates should also be controlled. Because the conductive groove rubber contains conductive fillers, its thermal conductivity may differ from that of adjacent silica tread rubbers. If the conductive groove area heats up faster, its actual T30 may be earlier than the laboratory isothermal test results; if the conductive groove area heats up slower, it may cause adjacent tread rubbers to crosslink and fix first. To avoid this difference, this embodiment preferably controls the local temperature difference between the corresponding area of ​​the conductive groove in the mold and the corresponding area of ​​the adjacent tread to not exceed ±3℃, the preheating time of the conductive groove area is 20–120 s, and the difference in local heating rates between the conductive groove area and the adjacent tread area is not greater than 0.05℃ / s.

[0121] In the specific vulcanization process, the above control can be achieved by adjusting the local heating channels of the mold, steam pressure, hot plate temperature, tire preheating time, and vulcanizing medium temperature. For specifications with a higher risk of weak bands in the center of the conductive groove, the preheating time can be appropriately increased to ensure that the conductive groove rubber and the adjacent tread rubber have a closer temperature field before entering the rapid crosslinking growth stage. For combinations where the T30 of the conductive groove rubber is significantly earlier, the initial heating rate of the corresponding area of ​​the conductive groove can be appropriately reduced to prevent premature densification of the conductive groove rubber.

[0122] 3.6S6: Tread structure and tire acquisition and testing feedback

[0123] After processing S1 to S5, the tread structure is obtained. The tread structure includes a conductive groove rubber area and adjacent tread rubber areas. The conductive groove rubber area extends from the ground surface of the tread into the interior of the tread and forms a continuous conductive path with the internal conductive components. The central joint area of ​​the conductive groove rubber area does not form a continuous, low-density interface band, or the length of the continuous defect accounts for no more than 5% of the total length of the conductive groove.

[0124] After the tread structure is vulcanized, its technical effect can be evaluated in the following ways: First, select multiple cross-sections along the length of the conductive groove for microscopic slicing and measure the width of the central weak band; Second, conduct microhardness tests on both sides of the center line of the conductive groove to evaluate the uniformity of hardness; Third, measure the interfacial peel strength between the conductive groove rubber and the adjacent tread rubber by the slice peeling method or the small sample peeling method; Fourth, conduct multi-point resistance tests between the tread ground surface and the internal conductive components of the tire and calculate the conductivity resistance fluctuation rate; Fifth, statistically analyze the abnormality rate of the conductive groove in the 0KM inspection of the finished tire.

[0125] Conductivity fluctuation It can be determined by the following formula:

[0126] ;

[0127] In the formula: The conductivity resistance fluctuation rate; The standard deviation of the conductivity resistance at multiple test points; This represents the average conductivity resistance at multiple test points.

[0128] When the test results show that the width of the central weak band is greater than 0.20 mm, the proportion of continuous defect length is greater than 5%, the interface peel strength is less than 26 N, or the conductivity resistance fluctuation rate is greater than 6%, it can be handled according to... Figure 6 The feedback process shown should be adjusted. If the main symptoms are an excessively wide central weak band and low peel strength, priority should be given to checking... , and If the main manifestation is a large fluctuation in conductivity resistance but an insignificant weak band width, priority should be given to checking the dispersion of conductive filler, the continuity of conductive path, and the geometric stability of the conductive groove adhesive area; if the main manifestation is a high 0KM anomaly rate, then a comprehensive check should be made of the flow front velocity difference in the co-extrusion stage, the local heating rate difference in the vulcanization stage, and the defect distribution of the finished product slices.

[0129] Through the above-mentioned testing and feedback, this invention can form a closed-loop technical route of parameter measurement—risk assessment—formula / process adjustment—co-extrusion control—vulcanization control—finished product feedback. This closed-loop route is suitable for the development of new tire specifications, and also for the analysis of the causes of conductive groove anomalies and batch stability control during mass production.

[0130] 4. Specific application examples and experimental data

[0131] 4.1 Experimental Objectives of the Application Examples

[0132] This application example is used to verify the effect of the co-extrusion-vulcanization synergistic control method described in this invention on suppressing the weak zone in the center of the tire conductive groove.

[0133] 4.2 Experimental Materials and Equipment

[0134] This application example uses a 225 / 55R18 passenger car tire tread as the verification object. The conductive groove rubber adopts a diene rubber system, with the matrix rubber including styrene-butadiene rubber and cis-butadiene rubber, and the conductive filler including conductive carbon black and flake graphite; the adjacent tread rubber adopts a solution-polymerized styrene-butadiene rubber / cis-butadiene rubber blend system reinforced with silica, containing silane coupling agent, processing oil, antioxidant, sulfur and accelerator.

[0135] The rubber compound was mixed and finalized using an internal mixer, and the rubber sheets were left to stand for at least 8 hours after final mixing. The rheological properties, vulcanization properties, and extrusion properties of the conductive groove rubber and adjacent tread rubber were tested separately. Complex viscosity was measured using a rubber processing analyzer at 100℃ and 10Hz; T10, T30, and T90 were measured using a rotorless vulcanizer at 160℃; Mooney viscosity was measured using a Mooney viscometer; the width of the weak band at the center of the conductive groove was determined using microscopic section image analysis; interfacial peel strength was determined using the section peel method; conductivity resistance fluctuation rate was calculated using multi-point resistance test data of the tread; and the 0KM anomaly rate was statistically analyzed based on the combined inspection results of the finished tire's appearance and electrical properties.

[0136] Conductivity fluctuation Determine using the following formula:

[0137] ;

[0138] In the formula: The conductivity resistance fluctuation rate; The standard deviation of the conductivity resistance at multiple test points; This is the average value of the conductivity resistance at multiple test points. When expressed as a percentage, multiply the result by 100%.

[0139] 4.3 Examples and Comparative Designs

[0140] To verify the necessity of the rheology-sulfurization synergistic control in this invention, Examples 1 to 8 and Comparative Examples 1 to 8 were set up. All examples followed... Figure 1 The method described involves first measuring the parameters of the conductive groove rubber and adjacent tread rubber, and then calculating the risk factor of the weak zone at the center of the conductive groove. Based on the source of risk, the conductive groove rubber formulation, adjacent tread rubber formulations, co-extrusion process, and vulcanization process are synergistically adjusted. In contrast, conventional conductive groove rubber solutions are used, or only the conductive filler, rubber flowability, vulcanization speed, or tackifier system is adjusted individually, without further adjustments. , and Coordinated control.

[0141] Risk factor of weak band at the center of conductive groove Determine using the following formula:

[0142] ;

[0143] In the formula: Risk factor for the weak band at the center of the conductive groove; The weighting coefficient for the complex viscosity mismatch term; This is the complex viscosity mismatch term; For the elastic recovery mismatch term weighting coefficient; For flexible recovery of mismatch; The weighting coefficient for the velocity mismatch term of the flowing front; For the speed mismatch of the forward; The weighting coefficient for the sulfidation phase mismatch term; This is a mismatch term for T30; This represents the weighting coefficient for the localized temperature rise mismatch term; This is the local heating rate mismatch term; the sum of all weighting coefficients is 1.

[0144] In this application example, the embodiment aims to reduce... , and Adjustments are made to achieve the target. The above three control conditions are met even when the proportions differ.

[0145] 4.4 Formulation and Process Control Data

[0146] Table 1 shows the main formulation adjustments and key control parameters for the examples and comparative examples.

[0147]

[0148] As shown in Table 1, the embodiments do not simply increase the conductive filler content of the conductive groove rubber, but rather focus on the complex viscosity ratio between the conductive groove rubber and the adjacent tread rubber. The differences in T30, elastic recovery, flow front velocity, and local heating rate are adjusted in combination. Examples 4 to 8 are preferred embodiments. The T30 difference is closer to 1, which is closer to the target vulcanization phase difference. This allows the conductive groove rubber and the adjacent tread rubber to have a more consistent deformation history and cross-linking process during the co-extrusion and vulcanization stages.

[0149] 4.5 Risk Coefficient and Process Control Results

[0150] Table 2 shows the risk factors of weak bands at the center of the conductive trench in the embodiments and comparative examples. Interfacial strain accumulation and the difference in crosslinking growth rate .

[0151]

[0152] From Table 2 and in combination Figure 2 , Figure 3 and Figure 4 It can be seen that Examples 4 to 8 , and Both were at low levels, indicating that the flow mismatch and interfacial strain accumulation were small during the co-extrusion stage, and the difference in crosslinking growth rate was also small during the vulcanization stage. Although Comparative Examples 1 and 2 could form conductive paths, The deviation from 1 is significant, and the T30 difference is large, leading to... Significantly higher; although the ratio 3 was reduced by adjusting liquidity. However, the T30 difference was not controlled synchronously. Therefore, there is still a risk of defects being amplified during the vulcanization stage; although the vulcanization system was adjusted in Comparative Example 4, the conductive groove adhesive was still significantly sticky, and the cumulative interfacial strain was excessive. The temperature is too high, so the co-extrusion stage is still prone to initiating defects in the central weak zone.

[0153] The above results demonstrate that the core of this invention does not lie in improving a single parameter, but rather in... , and As three control points in a continuous defect chain, the weak band at the center of the conductive groove is suppressed in both the extrusion and sulfurization amplification stages.

[0154] 4.6 Test Results of Weak Zone and Interface Performance at the Center of Conductive Groove

[0155] Table 3 shows the width of the central weak zone, the percentage of continuous defect length, the interfacial peel strength, and the difference in microhardness of the tread structure after vulcanization in the examples and comparative examples.

[0156]

[0157] From Table 3 and in combination Figure 6 and Figure 7 It can be seen that in Comparative Example 1, there is a wide, continuous low-density band in the central joint area of ​​the conductive groove, with a central weak band width of 0.43 mm, a continuous defect length ratio of 14.8%, and an interfacial peel strength of only 18.5 N. Although Comparative Example 2 increased the conductive filler content, the flow front difference and interfacial strain accumulation during the co-extrusion stage were not improved due to the further increase in the viscosity of the conductive groove. The central weak band width still reached 0.40 mm, indicating that simply increasing the conductive filler cannot solve the problem of the central weak band.

[0158] Comparative Example 3 only adjusted the flowability of the conductive groove adhesive to make Approaching 1, the width of the central weak band decreased from 0.43 mm in Comparative Example 1 to 0.31 mm, but its T30 difference and The T30 value remains high, and shrinkage mismatch still exists during the vulcanization stage, thus limiting the improvement. Comparative Example 4 only adjusted the vulcanization system of the conductive groove adhesive, resulting in a slight decrease in the T30 difference and a reduction in the width of the central weak band to 0.24 mm. However, due to… Still deviating from 1, The density is relatively high, and an initial low-density interface band is still formed during the co-extrusion stage, and the interface peel strength has not yet reached the optimal level.

[0159] In contrast, Examples 4 through 8 control simultaneously , and The width of the central weak zone decreased to 0.08–0.12 mm, the proportion of continuous defect length decreased to 1.6%–2.6%, the interfacial peel strength increased to 30.8–32.1 N, and the microhardness difference between the two sides of the center line decreased to 4.5%–5.8%. This indicates that the compactness, continuity, and interfacial bonding strength of the central bonding area of ​​the conductive groove have been significantly improved.

[0160] Among them, the width of the central weak band in Example 8 is the lowest, at 0.08 mm. This is because Example 8 simultaneously... The difference between T1 and T30 is close to the target vulcanization phase difference, and the crosslinking growth during the vulcanization stage is further converged by controlling the preheating for 80 seconds and the local heating rate difference. This result is consistent with... Figure 9 As shown , , When both decrease together, the width of the central weak band decreases synchronously, which is consistent with the trend.

[0161] 4.7 Conductivity stability and finished product 0KM test results

[0162] Table 4 shows the conductivity resistance fluctuation rate, 0KM anomaly rate, rolling resistance variation, and wear variation of the examples and comparative examples.

[0163]

[0164] From Table 4 and in combination Figure 8 It can be seen that the conductivity resistance fluctuation rate in the examples is significantly lower than that in the comparative examples. The conductivity resistance fluctuation rate of Comparative Example 1 is 12.5%, and the 0KM anomaly rate is 6.8%; although the conductive filler content of Comparative Example 2 is increased, the conductivity resistance fluctuation rate is still 11.4%, and the 0KM anomaly rate is still 6.2%, indicating that increasing the conductive filler content cannot guarantee that the conductive path remains stable and continuous in the tread length direction and the central area of ​​the conductive groove.

[0165] The conductivity resistance fluctuation rate of Examples 4 to 8 was 3.6% to 4.1%, and the 0KM anomaly rate was 1.2% to 1.6%, significantly better than the comparative examples. This indicates that when the width of the weak band in the center of the conductive groove is reduced, the proportion of continuous defect length is reduced, and the interface peel strength is improved, the conductivity path from the tread ground surface to the internal conductive components in the conductive groove rubber area is more stable, and the fluctuation of the finished tire in multi-point resistance testing and 0KM inspection is reduced.

[0166] Meanwhile, the relative values ​​of rolling resistance variation in the embodiments remained between 98 and 100, and the relative values ​​of wear variation remained between 101 and 103. This indicates that the present invention did not achieve conductive stability by significantly increasing the conductive filler or significantly sacrificing the performance of the tread body. Instead, it improved the manufacturing consistency of the conductive groove structure while maintaining the basic stability of rolling resistance and wear resistance. This effect is particularly beneficial for tires of new energy vehicles and low rolling resistance passenger car tires.

[0167] Combination Figure 6 It can be seen that the central joint area of ​​the conductive groove in Examples 6 and 8 is basically continuous and dense, with no through-type low-density solid bands; while the central joint areas of Comparative Examples 1 and 2 show dark weak bands extending along the length of the conductive groove, with localized tiny voids. This difference in microstructure indicates that the weak band in the center of the conductive groove is not only caused by poor dispersion of the conductive filler, but is closely related to co-extrusion flow mismatch and vulcanization shrinkage mismatch.

[0168] Combination Figure 7 It can be seen that the interfacial peel strength increases overall as the width of the central weak band decreases. In Examples 4 to 8, the width of the central weak band is no greater than 0.12 mm, and the interfacial peel strength is no less than 30.8 N. In contrast, the widths of the central weak bands in Comparative Examples 1 and 2 are 0.43 mm and 0.40 mm, respectively, and the interfacial peel strengths are 18.5 N and 19.6 N, respectively. This result indicates that the central weak band is not only a microscopic morphology issue but also reduces the interfacial load-bearing capacity between the conductive groove rubber and adjacent tread rubber.

[0169] Combination Figure 8 It can be seen that the conductivity resistance fluctuation rate and the 0KM anomaly rate increase with the increase of the width of the central weak band. In the comparative example, even if a conductive adhesive path is formed, the conductive path is locally unstable due to the continuous defects in the central bonding area; the embodiment improves the central continuity, thereby reducing the conductivity resistance fluctuation rate and the 0KM anomaly rate simultaneously.

[0170] Combination Figure 9 It can be seen that, , and The central weak band width shows a consistent trend. When all three are at low levels, the central weak band width decreases significantly; when only one indicator decreases while the others remain high, the improvement effect is limited. For example, in Comparative Example 3... It has been reduced to 0.128, but It remains at 33.8%, therefore the width of the central weak band remains at 0.31 mm; Comparative Example 4 It dropped to 21.5%, but The value remains 0.218, therefore the width of the central weak zone remains 0.24 mm. This result further demonstrates the necessity of the co-extrusion-vulcanization synergistic control employed in this invention.

[0171] Based on the above application examples and experimental data, it can be confirmed that the present invention achieves at least the following technical effects:

[0172] First, the present invention can reduce the width of the weak band at the center of the conductive groove. Compared with 0.43 mm in Comparative Example 1, the width in Examples 6 and 8 is reduced to 0.09 mm and 0.08 mm, respectively, demonstrating that... , and The coordinated control of these technologies can effectively suppress the formation of low-density solid bands or continuous weak bands in the center of the conductive groove.

[0173] Second, the present invention can reduce the proportion of continuous defect length. The proportion of continuous defect length in Examples 4 to 8 is 1.6% to 2.6%, which is significantly lower than the 7.9% to 14.8% in the comparative examples, indicating that the continuity of the central bonding area of ​​the conductive groove is improved.

[0174] Third, the present invention can improve the interfacial peel strength between the conductive groove rubber and the adjacent tread rubber. The interfacial peel strength of Examples 4 to 8 is 30.8 to 32.1 N, which is higher than 18.5 N of Comparative Example 1 and 19.6 N of Comparative Example 2, indicating that after the central weak band is suppressed, the bonding stability between the conductive groove rubber and the adjacent tread rubber is improved.

[0175] Fourth, this invention can reduce the conductivity resistance fluctuation rate and the 0KM anomaly rate. In Examples 4 to 8, the conductivity resistance fluctuation rate was reduced to 3.6%–4.1%, and the 0KM anomaly rate was reduced to 1.2%–1.6%; while in Comparative Examples 1 and 2, the conductivity resistance fluctuation rates were 12.5% ​​and 11.4%, respectively, and the 0KM anomaly rates were 6.8% and 6.2%, respectively. These results demonstrate that the improvement in the continuity of the conductive groove center structure by this invention can translate into improved electrical performance and initial quality stability of the finished tire.

[0176] Fifth, while improving the stability of the conductive groove, this invention does not significantly sacrifice rolling resistance and wear performance. The relative values ​​of rolling resistance change in the embodiment are maintained at 98-100, and the relative values ​​of wear change are maintained at 101-103. This indicates that this invention does not rely on significantly increasing the content of conductive filler to exchange for conductive stability, but rather achieves improved structural stability through rheology-vulcanization matching, making it suitable for engineering mass production applications.

[0177] The foregoing description of embodiments of the present invention, through which those skilled in the art are able to implement or use the present invention, will be readily apparent to those skilled in the art. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novelty disclosed herein.

[0178] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0179] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0180] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0181] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0182] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0183] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0184] Computer-readable media include both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

Claims

1. A co-extrusion-vulcanization synergistic control method for suppressing the formation of a weak band in the center of the conductive groove of a tire, characterized in that, The method includes the following steps: S1. Select conductive groove rubber and adjacent tread rubber located on both sides of the conductive groove rubber. Under the same extrusion temperature and the same test frequency, measure the complex viscosity, elastic recovery rate, flow front velocity and vulcanization characteristic parameters of the conductive groove rubber and the adjacent tread rubber respectively. The vulcanization characteristic parameters include at least T10, T30 and t90. S2. Based on the complex viscosity, elastic recovery rate, flow front velocity, T30, and the local heating rate of the conductive groove region and the adjacent tread region, generate the risk factor for the weak zone at the center of the conductive groove. And reduce the risk factor of the weak band at the center of the conductive groove. Not greater than the preset risk threshold The risk factor of the weak band at the center of the conductive groove is... Determine using the following formula: In the formula: Risk factor for the weak band at the center of the conductive groove; The weighting coefficient for the complex viscosity mismatch term; This is the complex viscosity mismatch term; For the elastic recovery mismatch term weighting coefficient; For flexible recovery of mismatch; The weighting coefficient for the velocity mismatch term of the flowing front; For the speed mismatch of the forward; The weighting coefficient for the sulfidation phase mismatch term; This is a mismatch term for T30; This represents the weighting coefficient for the localized temperature rise mismatch term; This represents the local heating rate mismatch term; the sum of all weighting coefficients is 1. To preset risk thresholds; S3, when the risk factor of the weak band at the center of the conductive groove Greater than the preset risk threshold At the same time, at least one of the following: polymer composition, plasticizing system, reinforcing filler structure, accelerator system, and sulfur system of the conductive groove rubber and / or adjacent tread rubber is adjusted to make the complex viscosity ratio of the conductive groove rubber to the adjacent tread rubber such that... The T30 value should be controlled between 0.90 and 1.10, and the difference between the conductive groove rubber and the adjacent tread rubber should be controlled between -0.2 and 1.2 min. S4. Co-extrude the conductive groove rubber that meets the conditions of step S3 with the adjacent tread rubber. During the co-extrusion process, control the difference in flow front velocity, die dwell time, and cumulative interfacial strain between the conductive groove rubber and the adjacent tread rubber. This prevents a continuous, low-density interface band from forming in the central region of the conductive groove after extrusion. S5. Preheat and vulcanize the co-extruded tread semi-finished product. During the vulcanization stage, control the difference in local heating rate and crosslinking growth rate between the conductive groove area and adjacent tread areas. This prevents the conductive groove rubber from undergoing densification relative to the adjacent tread rubber, which would otherwise lead to central shrinkage and amplification. S6. Obtain a tread structure with improved continuity of the conductive groove center or a pneumatic tire containing the tread structure.

2. The method according to claim 1, characterized in that, In step S2, the complex viscosity ratio Determine using the following formula: ； In the formula: The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; The complex viscosity of the conductive groove adhesive at the extrusion temperature; The complex viscosity refers to the viscosity of adjacent tread compounds at the same extrusion temperature; the extrusion temperature is 90–115°C, and the testing frequency is 1–20 Hz; preferably, the complex viscosity ratio is... The Mooney viscosity is 0.95 to 1.05, and the difference in Mooney viscosity between the conductive groove rubber and the adjacent tread rubber is no greater than 8 MU; And / or, in step S2, the complex viscosity mismatch term Determine using the following formula: In the formula: This is the complex viscosity mismatch term; The ratio of the complex viscosity of the conductive groove rubber to that of the adjacent tread rubber; It is the natural logarithm function; and / or, in step S2, the T30 mismatch term Determine using the following formula: ； In the formula: This is a mismatch term for T30; The time required for the conductive groove adhesive to reach 30% curing. The time required for adjacent tread rubbers to reach 30% vulcanization; The target vulcanization phase difference is set to 0–0.6 min; and the T10 difference between the conductive groove rubber and the adjacent tread rubber is controlled within -0.5–1.5 min, and the T90 difference is controlled within -1.0–2.0 min.

3. The method according to claim 1, characterized in that, In step S4, the cumulative amount of interfacial strain Determine using the following formula: ； In the formula: This refers to the cumulative amount of interfacial strain. The effective flow length for the conductive groove rubber and the adjacent tread rubber to form a common interface within the die; The integral position along the effective flow length; For conductive groove adhesive at position The shear strain or equivalent shear strain at the point; For adjacent tread rubber in position The shear strain or equivalent shear strain at the point; To prevent the correction constant from having a denominator of zero; the cumulative interfacial strain The value should be controlled to be no greater than 0.18, preferably no greater than 0.

12.

4. The method according to claim 1, characterized in that, In step S4, at least three process parameters are controlled during co-extrusion molding: die temperature is 85-115℃, traction speed is 8-35m / min, the die dwell time difference between the conductive groove rubber and the adjacent tread rubber is not greater than 15%, the flow front velocity difference between the conductive groove rubber and the adjacent tread rubber is not greater than 8%, and the cooling rate after extrusion is 5-25℃ / min.

5. The method according to claim 1, characterized in that, In step S5, the sulfur conversion rate is used. The crosslinking process of the conductive groove rubber or adjacent tread rubber, the vulcanization conversion rate. Determine using the following formula: ； In the formula: For rubber vulcanization time Vulcanization conversion rate; Indicates conductive groove adhesive or adjacent tread rubber ; For rubber vulcanization time Torque under; For rubber The minimum torque; For rubber The highest torque; Preferably, in step S5, the difference in crosslinking growth rate between the conductive groove adhesive and the adjacent tread adhesive is... Determine using the following formula: ； In the formula: The difference in crosslinking growth rate between the conductive groove rubber and the adjacent tread rubber; For the conductive groove adhesive during the curing time Vulcanization conversion rate; For adjacent tread rubbers at vulcanization time Vulcanization conversion rate; The rate of increase in vulcanization conversion of the conductive groove adhesive; The rate of increase in vulcanization conversion of adjacent tread rubbers; To prevent a correction constant with a denominator of zero; the difference in crosslinking growth rates The limit is no more than 25%; And / or, in step S5, during the vulcanization stage, the local temperature difference between the corresponding area of ​​the conductive groove in the mold and the corresponding area of ​​the adjacent tread is controlled to not exceed ±3℃, the preheating time of the conductive groove area is 20-120s, and the difference in local heating rate between the conductive groove area and the adjacent tread area is not greater than 0.05℃ / s; when the width of the weak band at the center of the conductive groove is detected to be greater than 0.20mm or the conductivity resistance fluctuation rate is greater than 6%, the T30 difference between the conductive groove rubber and the adjacent tread rubber is reduced, the difference in local heating rate is reduced, and / or the cumulative amount of interfacial strain is reduced. .

6. The method according to claim 1, characterized in that, The conductive groove rubber is a diene rubber composition containing at least one of conductive carbon black, graphite, carbon nanotubes and conductive polymers; the adjacent tread rubber is a tread rubber composition containing silica and / or carbon black; by adjusting the conductive filler structure, processing oil amount, tackifying resin amount, accelerator type, sulfur amount in the conductive groove rubber, as well as the silane coupling agent, reinforcing filler and scorch safety system in the adjacent tread rubber, the conductive groove rubber and the adjacent tread rubber can simultaneously meet the rheological matching conditions and the vulcanization phase matching conditions.

7. A tread structure, characterized in that, The tread structure is obtained by the method according to any one of claims 1 to 6, the tread structure includes adjacent tread rubber regions and conductive groove rubber regions embedded between the adjacent tread rubber regions and extending from the tread ground surface into the tread interior; the central joint area of ​​the conductive groove rubber region satisfies at least three of the following conditions: the width of the central weak band is not greater than 0.20 mm; the length of continuous defects accounts for not more than 5% of the total length of the conductive groove; the difference in microhardness between the two sides of the center line of the conductive groove is not greater than 8%; the interfacial peel strength between the conductive groove rubber and the adjacent tread rubber is not less than 26 N; and the conductivity resistance fluctuation rate is not greater than 6%.

8. A pneumatic tire, characterized in that, The tread of the pneumatic tire includes the tread structure as described in claim 7, wherein the conductive groove rubber area forms a continuous conductive path from the tread contact surface to the conductive component inside the tread; the abnormality rate of the conductive groove in the pneumatic tire during 0KM inspection is no greater than 2.0%, and the risk factor for the weak band at the center of the conductive groove is lower than that of the tire without conductive groove center inspection. Control, interfacial strain accumulation Poor control and crosslinking growth rate The controlled control tires showed reduced width of the weak band at the center of the conductive groove, increased interfacial peel strength, and reduced conductivity resistance fluctuation.

9. An electronic device, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the method according to any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1 to 6.

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