Method for setting extrusion shrinkage ratio of tread and opening ratio of die plate

Abstract

The invention provides a method for setting the extrusion shrinkage ratio of a tread and the opening ratio of a mouth-shaped plate. The method comprises the following steps: S1, obtaining the volume flow rate V of rubber materials with different rubber numbers in advance; s2, establishing a relation curve of the volume flow rate V of the tread rubber and the corresponding shrinkage ratio M; s3, establishing a relation curve between the shrinkage ratio M and the opening ratio N of the corresponding mouth-shaped plate through the shrinkage ratio M; and S4, determining the width opening size of the mouth-shaped plate according to the opening ratio N of the mouth-shaped plate. The method for setting the extrusion shrinkage ratio of the tread and the opening ratio of the die plate solves the technical problems of unstable tread size and poor product performance caused by lack of a standardized shrinkage ratio and opening ratio setting method in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of tire production lines, and in particular to a method for setting a tread extrusion shrinkage ratio and a die plate opening ratio. Background Art

[0002] During the tire tread production process, the rubber compound is extruded from the extruder and needs to go through multiple processes to form the final tire tread. After extrusion, the rubber compound is in a high-temperature and high-plastic state, so the molding size is prone to instability. Therefore, each extruded rubber compound needs to be equipped with a corresponding die plate during production, and usually needs to go through at least three extrusion tests. This repeated test not only increases production costs, but also affects production efficiency.

[0003] The extrusion dimensional accuracy of the rubber compound plays a key role in the quality of the tire, so the design accuracy of the die plate directly affects the dimensional stability of the extruded rubber compound and the reduction of the number of tests. However, the die plate design alone cannot completely control the dimensional stability after extrusion. In order to ensure that the tread after extrusion maintains dimensional stability on the linkage line, a three-stage forced shrinkage roller group is usually set near the rubber outlet of the extruder to mechanically force the highly plastic tread to shrink, ensuring the dimensional and weight stability of the tread during the subsequent transportation process.

[0004] However, the prior art lacks a specific method for setting the forced shrinkage ratio. For example, Chinese invention patent application CN112231843B discloses a method for establishing a standard for the opening of a tread extrusion die plate, which calculates the shrinkage rate of the tread rubber material by the initial length and the length after shrinkage of the film, and is used to calculate the opening rate of the die plate. However, the way to obtain the shrinkage rate of the tread rubber material is to cut the tread rubber material, measure it, and then calculate it. It is easy to produce errors during the cutting and measuring process, which will directly affect the opening rate of the die plate, thereby affecting the extrusion quality of the tread.

[0005] At present, there is a lack of specific standardized methods for setting the forced shrinkage ratio, which not only makes the performance of the tread rubber compound unguaranteed, but also makes the forced shrinkage device on the linkage line unable to function effectively. As a result, the tread size is prone to fluctuations during transportation and parking, which in turn leads to unstable performance of the finished tire, affecting its service life and safety.

[0006] Therefore, the prior art needs to be further developed. Summary of the invention

[0007] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide a method for setting the tread extrusion shrinkage ratio and the die plate opening ratio, so as to solve the technical problems of unstable tread size and poor product performance caused by the lack of standardized shrinkage ratio and opening ratio setting method in the related technology.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: a method for setting the tread extrusion shrinkage ratio and the die plate opening ratio is provided, comprising the following steps: S1, obtaining the volume flow rate V of rubber materials with different rubber numbers in advance; S2, establishing a relationship curve between the volume flow rate V of the tread rubber material and the corresponding shrinkage ratio M; S3, establishing a relationship curve between the shrinkage ratio M and the corresponding die plate opening ratio N through the shrinkage ratio M; S4, determining the width opening size of the die plate according to the opening ratio N of the die plate.

[0009] Furthermore, the width opening size of the die plate = opening ratio * standard size of the extruded tread.

[0010] Furthermore, the viscosity of different rubber materials is measured and the corresponding volume flow rate V is calculated based on the viscosity.

[0011] Furthermore, the volume flow rate of rubber materials with different rubber numbers is measured using a capillary rheometer, the viscosity data of the rubber materials is input into the capillary rheometer, and the rubber materials are placed in the capillary rheometer to measure and calculate the rubber material extrusion volume flow rate; the calculation formula of the volume flow rate V is: , where R is the radius of the capillary, ΔP is the pressure difference, L is the length of the capillary, and η is the viscosity of the rubber. Furthermore, a relationship curve between the volume flow rate V and the corresponding contraction ratio M is: M=a1*V+b1, wherein a1 and b1 are constants, and a1 is a negative number.

[0012] Furthermore, a relationship curve between the contraction ratio M and the opening ratio N of the corresponding die plate is: N=a2*M+b2, wherein a2 and b2 are constants, and a2 is a positive number.

[0013] Furthermore, a method for generating a relationship curve between the volume flow rate V and the corresponding shrinkage ratio M includes: using a tread with a die plate opening ratio of 100% for extrusion, and adjusting the shrinkage ratio until the tread is close to a bulging state on a forced shrinkage roller to obtain an optimal shrinkage ratio, and thereby establishing a linear relationship between the volume flow rate V and the shrinkage ratio M of different rubber compounds.

[0014] Furthermore, the initial forced shrinkage ratio and die plate opening ratio are set first, and the relationship between the rubber extrusion volume flow rate V, the shrinkage ratio M and the die plate opening ratio N is in the range of: 1000mm 3 :0.9:1~4000mm 3 :0.7:1.

[0015] Furthermore, the capillary rheometer is a plunger rheometer, and its operating steps are: inputting the viscosity data of the rubber material, kneading the long strip rubber material sample into a cylindrical shape and then putting it into the plunger rheometer, and heating and extruding the rubber material at a constant pressure to determine its volume flow rate V.

[0016] Furthermore, the heating temperature is set to 100±0.5°C, the pressure setting range is 30~60Mpa, and the extrusion time is set to 40 seconds.

[0017] Beneficial effects: 1. The prior art calculates the shrinkage rate by measuring the initial length of the rubber and the length after shrinkage. This process is prone to measurement errors, which affects the opening rate of the die plate. The present invention uses a capillary rheometer to measure the volume flow rate of the rubber, and combines the linear relationship between the flow rate and the shrinkage ratio to determine the optimal shrinkage ratio and opening ratio. This method is more accurate and ensures the accuracy and consistency of the set shrinkage ratio and opening ratio in the production process, avoiding the dimensional inaccuracy problem caused by rubber cutting and measurement errors in the prior art.

[0018] 2. The present invention generates a standardized setting method by establishing relationship curves between volume flow rate and shrinkage ratio, and between shrinkage ratio and opening ratio, so that rubber materials of different batches and different formulations can maintain stable size and shape during the extrusion process, thereby significantly improving product performance.

[0019] 3. The present invention sets a reasonable shrinkage ratio and opening ratio through precise measurement and relationship curves, and no longer needs to conduct multiple repeated tests, and the optimal process parameters can be directly determined, thereby significantly reducing the number of production tests and improving production efficiency.

[0020] 4. The shrinkage ratio and opening ratio set by the present invention can effectively control the dimensional fluctuation of the tread during the extrusion and transportation process, and provide a scientific shrinkage ratio setting method. The forced shrinkage device on the linkage line can accurately adjust the shrinkage amount according to the flow characteristics of different rubber materials, so that it can play a more efficient role in the production process and avoid poor tire performance caused by dimensional instability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of a method for setting a tread extrusion shrinkage ratio and a die plate opening ratio in an embodiment of the present invention; Figure 2 is a curve diagram showing the relationship between the volume flow rate and the corresponding shrinkage ratio of each rubber material in the embodiment of the present invention; Figure 3 It is a curve diagram showing the relationship between the shrinkage ratio of each rubber material and the opening ratio of the corresponding die plate in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0023] According to an embodiment of the present invention, a method for setting the tread extrusion shrinkage ratio and the die plate opening ratio is provided. Figures 1 to 3 , including the following steps: S1. Pre-obtain the volume flow rate V of different rubber materials First, measure the viscosity of rubber compounds with different rubber numbers, then use a capillary rheometer to measure the volume flow rate of rubber compounds with different rubber numbers, input the measured rubber viscosity data into the capillary rheometer, and put rubber compounds with different rubber numbers into the capillary rheometer one by one to measure and calculate the rubber compound extrusion volume flow rate. The measurement method and steps are as follows: weigh about 35g of sample of each rubber number, use scissors to make the sample into a long strip sample of about 50mm (length) × 5mm (width) × 4mm (thickness), pinch about 4~5 long strip samples into cylindrical strips with a diameter of about 10mm, and add one cylindrical strip at a time when adding materials to the barrel; then add a rubber sample of the rubber number into the circular barrel of the plunger capillary rheometer (Gottfort RCR-II capillary rheometer, barrel inner diameter 30mm, length 40mm), extrude the rubber under the conditions of heating temperature set to 100±0.5℃, pressure setting range of 30~60Mpa, and extrusion time set to 40 seconds, and force the rubber to pass through the capillary die at the bottom of the barrel to measure its flow properties. By analyzing the flow field of the sample in the capillary die, the rubber extrusion volume flow rate is calculated; according to the above operation, other rubbers are placed in the capillary rheometer to measure and calculate the rubber extrusion volume flow rate. The calculation formula of the rubber volume flow rate V is: , where R is the radius of the capillary, ΔP is the pressure difference, L is the length of the capillary, and η is the viscosity of the rubber.

[0024] S2. Establish the relationship curve between the volume flow rate V of the tread rubber material and the corresponding shrinkage ratio M The extrusion volume flow rate V measured for rubber compounds with different rubber numbers is correlated with the forced shrinkage ratio to form a linear relationship, and the relationship curve between the volume flow rate V and the corresponding shrinkage ratio M is obtained: M=a1*V+b1, where a1 and b1 are constants, and a1 is a negative number.

[0025] The steps to determine the optimal forced shrinkage ratio of different rubber grades through experiments are as follows: (1) First, set the range of the rubber volume flow rate, forced shrinkage ratio and die plate opening ratio. Set the range of the rubber extrusion volume flow rate value: forced shrinkage ratio: die plate opening ratio to 1000mm. 3 :0.9:1~4000mm 3 :0.7:1. By setting a reasonable initial range as the experimental basis, the parameter selection for each test can be concentrated within the range that may meet the conditions, avoiding blind adjustments. (2) Select a standard tread with a die plate opening ratio of 100% (the opening ratio and the standard tread size are 1:1) for extrusion, and observe the extrusion state of the tread, such as the traction speed, whether it is stretched or piled, etc. Test the molding effect of the tread under standard conditions to ensure that the tread size, traction speed and molding quality meet the conditions; through this step, the behavior of the tread after extrusion can be observed, thereby providing a reference for subsequent parameter adjustments. (3) After the extruded tread is conveyed to the forced contraction roller, visually confirm that the tread is in the forced contraction section state. When the tread is conveyed on the forced contraction section roller without bulging, the forced contraction ratio of the last section can be reduced; if it bulges, increase the forced contraction ratio until the tread is in a state close to bulging on the roller. By adjusting the forced shrinkage ratio, an optimal point is found that can compress the rubber compound without causing bulging. This state means that the forced shrinkage ratio of the rubber compound of this rubber number has reached the optimal setting value, ensuring the dimensional stability of the tread in the subsequent process. (4) Test different extrusion volume flow rates and record the forced shrinkage ratio of each rubber number under the optimal bulging state. These data are used to establish a linear relationship between volume flow rate and forced shrinkage ratio and form a formula. Generate a standard formula so that the shrinkage ratio setting of the same rubber compound can be directly calculated using the formula in the future. After the above steps, the optimal forced shrinkage ratio of different rubber compounds was experimentally verified and standardized, thereby establishing a formula relationship between volume flow rate and shrinkage ratio, and finally achieving the purpose of reducing the number of tests in the production process, improving production efficiency and product dimensional stability.

[0026] Taking 10 rubber numbers MT13, MT28, MT02, MT11, MT03, MT01, MT04, MT05, MT19, and MT15 as examples, when setting the forced shrinkage ratio of the tread production of rubber materials with different rubber numbers, the rubber extrusion volume flow rate value is substituted into the formula to obtain the forced shrinkage ratio corresponding to the above rubber number rubber materials. The above rubber number rubber extrusion volume flow rate values ​​and forced shrinkage ratios are shown in Tables 1 and Figure 2 .

[0027] Table 1 Data table of volume flow rate and corresponding shrinkage ratio of different rubber grades Combining the data in Table 1 and Figure 2 From the linear equation shown: M=-0.00004V+0.92911, it can be seen that there is a negative correlation between the rubber extrusion volume flow rate V and the corresponding forced shrinkage ratio M, where a1=-0.00004 and b1=0.92911.

[0028] S3, by establishing the relationship curve between the shrinkage ratio M and the opening ratio N of the corresponding die plate The process of adjusting the die opening ratio to ensure that the tread width reaches the standard size is: (1) Substitute the volume flow rate of different rubber grades into the formula established in the early stage to obtain the optimal forced shrinkage ratio of the corresponding rubber. (2) Based on the set forced shrinkage ratio, use a standard die plate with an opening ratio of 100% (that is, the opening ratio and the standard tread size are 1:1) for extrusion to ensure that the traction speed of the tread is normal after extrusion, without stretching, pile-up and other abnormalities. This step uses a die plate with a standard opening ratio to test the performance of the tread under stable conditions to ensure that the tread reaches the ideal initial width at the optimal traction speed. (3) When the tread enters the forced shrinkage section, measure the width dimension L of the tread on the forced shrinkage roller. 实测值 If the tread width L 实测值 =L 标准值 When the die plate opening ratio is set to the optimal value; if the tread width dimension L 实测值 >L 标准值 If the tread width L is too large, the opening ratio needs to be reduced to reduce the tread width so that the measured value reaches the standard value. 实测值 <L 标准值 When the opening ratio is too small, it means that the opening ratio needs to be increased to increase the tread width so that the measured value meets the standard value. The overall effect of these steps is to ensure the precise control of the width of each rubber compound during extrusion and forced shrinkage, and to achieve the standard size of the finished tread by gradually measuring and adjusting the opening ratio.

[0029] According to the above adjustment results, a linear relationship between the forced shrinkage ratio M and the die plate opening ratio N is set, and the die plate opening ratio N=a2*M+b2, where a2 and b2 are constants and a2 is a positive number. The data of the forced shrinkage ratio and die plate opening ratio corresponding to each rubber number are recorded in Table 2 and Figure 3 middle.

[0030] Table 2 Data table of shrinkage ratio of different rubber grades and corresponding die opening ratio From the data in Table 2 and Figure 3 From the linear equation shown: N=1.1429M-0.0711, it can be seen that there is a positive correlation between the rubber shrinkage ratio M and the corresponding die opening ratio N, where a2=1.1429, b2=-0.0711.

[0031] Based on the correlation between the volume flow rate value of the rubber compound measured by the capillary rheometer and the forced contraction section and the die plate opening ratio to form a linear relationship, the standardization of the forced contraction ratio and the die plate opening ratio is achieved, see Table 3.

[0032] Table 3 Data table of volume flow rate values ​​of different rubber grades and corresponding shrinkage ratios and opening ratios S4. Determine the width opening size of the die plate according to the die opening ratio N of the die plate According to the industry construction standards, the standard size of the tread rubber and the die plate opening ratio N obtained in the above steps are substituted into the formula: Die plate width opening size = opening ratio * standard size of the extruded tread, and the die plate width opening size is obtained, so that the determination of the die plate width opening size is fast and standardized.

[0033] According to the correlation and regression equation between the rubber extrusion volume flow rate V and the linkage line forced shrinkage ratio M and the die plate opening ratio M, the optimal forced shrinkage ratio and die plate opening ratio can be set for the extrusion of rubber treads with different rubber numbers, respectively. A standard setting method for "forced shrinkage ratio and die plate opening ratio" can be established with a scientific method to improve the tread size, weight stability and finished tire quality, and reduce the size, weight unqualified return rate and production cost. Compared with the prior art, the shrinkage rate is calculated by measuring the initial length of the rubber and the length after shrinkage, resulting in measurement errors that affect the opening ratio of the die plate. The present invention uses a capillary rheometer to measure the volume flow rate of the rubber, and combines the linear relationship between the flow rate and the shrinkage ratio to determine the optimal shrinkage ratio and opening ratio. This method is more accurate and ensures the accuracy of the set shrinkage ratio and opening ratio during the production process.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0036] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0037] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0038] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for setting the tread extrusion shrinkage ratio and the die plate opening ratio, characterized in that: The steps include: S1. Pre-obtain the volume flow rate V of rubber materials with different rubber numbers; S2, establishing a relationship curve between the volume flow rate V of the tread rubber material and the corresponding shrinkage ratio M; S3, establishing a relationship curve between the shrinkage ratio M and the opening ratio N of the corresponding die plate through the shrinkage ratio M; S4. Determine the width opening size of the die plate according to the opening ratio N of the die plate.

2. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 1, characterized in that: The width opening size of the die plate = opening ratio * standard size of the extruded tread.

3. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 1, characterized in that: The viscosity of different rubber compounds is measured and the corresponding volume flow rate V is calculated based on the viscosity.

4. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 3, characterized in that: The volume flow rate of rubber with different rubber numbers was measured using a capillary rheometer, the viscosity data of the rubber was input into the capillary rheometer, and the rubber was placed in the capillary rheometer to measure and calculate the volume flow rate of the rubber extrusion; the calculation formula of the volume flow rate V is: , Where R is the radius of the capillary, ΔP is the pressure difference, L is the length of the capillary, and η is the viscosity of the rubber.

5. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 4, characterized in that: The relationship curve between the volume flow rate V and the corresponding contraction ratio M is: M=a1*V+b1, Where a1 and b1 are constants, and a1 is a negative number.

6. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 5, characterized in that: The relationship curve between the shrinkage ratio M and the opening ratio N of the corresponding die plate is: N=a2*M+b2, Wherein, a2 and b2 are constants, and a2 is a positive number.

7. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 6, characterized in that: The method for generating a relationship curve between the volume flow rate V and the corresponding shrinkage ratio M includes: using a tread with a die plate opening ratio of 100% for extrusion, and adjusting the shrinkage ratio until the tread is close to a bulging state on a forced shrinkage roller to obtain an optimal shrinkage ratio, and thereby establishing a linear relationship between the volume flow rate V and the shrinkage ratio M of different rubber compounds.

8. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 4, characterized in that: First set the initial forced shrinkage ratio and die plate opening ratio. The relationship between the rubber extrusion volume flow rate V, shrinkage ratio M and die plate opening ratio N is as follows: 1000mm 3 :0.9:1~4000mm 3 :0.7:

1.

9. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 4, characterized in that: The capillary rheometer is a plunger rheometer, and its operating steps are: inputting the viscosity data of the rubber material, kneading the long strip rubber material sample into a cylindrical shape and then putting it into the plunger rheometer, and heating and extruding the rubber material at a constant pressure to measure its volume flow rate V.

10. The method for setting the tread extrusion shrinkage ratio and the die plate opening ratio according to claim 9, characterized in that: The heating temperature was set to 100±0.5°C, the pressure setting range was 30~60Mpa, and the extrusion time was set to 40 seconds.

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