Method for vulcanizing all-steel bus and truck tires

Abstract

The present application relates to a kind of all-steel truck tire vulcanization method, belong to tire vulcanization field.The following steps are included: after tire blank shaping mold is closed, sulfurizing medium N1 is passed into vulcanization capsule, and heat preservation, pressure maintaining cycle is carried out, duration ta;Stop circulating sulfurizing medium N1, sulfurizing medium N2 is passed into vulcanization capsule, and pressure maintaining is carried out, duration tb;Stop passing in sulfurizing medium, duration tc, finally after nitrogen recovery, nitrogen discharge, after vacuumizing, mold is opened, and tire vulcanization process is completed.Compared with traditional steam / nitrogen vulcanization process, the vulcanization process of the present application can reduce the temperature difference between upper and lower mold during tire vulcanization, improve the uniformity of tire upper and lower mold vulcanization effect, improve tire durability;Single tire vulcanization energy consumption cost is reduced by more than 30%, production efficiency is improved by more than 4%, service life of vulcanization capsule is improved, nitrogen vulcanizing medium consumption is saved, tire defect rate is reduced, and economic benefit is remarkable.

Description

Technical Field

[0001] This invention relates to the field of tire vulcanization, and more specifically to a method for vulcanizing all-steel truck and bus tires. Background Technology

[0002] As is well known, vulcanization is a major energy-consuming step in tire production. Although the steam / nitrogen vulcanization process commonly used in the tire industry consumes less energy than steam / superheated water vulcanization processes, it still accounts for more than 50% of the total energy consumption in tire production. Furthermore, the steam / nitrogen vulcanization process generates a large amount of condensate, resulting in a large temperature difference between the upper and lower molds, reducing the uniformity of the vulcanization effect between the upper and lower molds, and consequently affecting the quality of tire vulcanization. To address the aforementioned technical problems, patent CN116728860A, a method and system for all-nitrogen vulcanization of tires, proposes a solution where the vulcanizing medium is changed from steam / nitrogen to all-nitrogen. Specifically, buffer nitrogen is introduced first, followed by high-pressure nitrogen for heating. This method results in delayed heating during the vulcanization process. For tire quality, this can lead to delayed cross-linking between the inner liner rubber and the airtight layer rubber, causing excessive rubber flow. This results in interlayer penetration between the inner liner and airtight layer rubbers, reducing tire airtightness and lifespan. In severe cases, penetration from the inner liner and airtight layer rubber into the tire carcass rubber reduces the adhesion between the tire skeleton material and the rubber, leading to premature tire damage such as blowouts. Furthermore, this method reduces vulcanization production efficiency. Additionally, the constant pressure maintenance during vulcanization is detrimental to the lifespan of the vulcanizing bladder and increases the amount of nitrogen vulcanizing medium used, raising energy costs. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a vulcanization method for all-steel truck and bus tires, which further saves energy and reduces emissions, lowers tire production costs, improves tire quality, and increases production efficiency.

[0004] The technical solution adopted by this invention to solve its technical problem is: a vulcanization method for all-steel truck and bus tires, comprising the following steps:

[0005] 1. After the embryo is shaped and molded, vulcanizing medium N1 is introduced into the vulcanizing capsule, and the capsule is kept warm and pressurized for a duration of ta.

[0006] 2. Stop circulating the vulcanizing medium N1, introduce the vulcanizing medium N2 into the vulcanizing capsule, and maintain the pressure for a duration of tb.

[0007] 3. Stop the flow of the vulcanizing medium, duration tc;

[0008] In step one, the vulcanizing medium N1 is nitrogen gas, the temperature is 190-220℃, the pressure is 1.30-2.00MPa, and the oxygen content is ≤50ppm. In step two, the vulcanizing medium N2 is nitrogen gas, the temperature is 22.0-45.0℃, the pressure is 2.65-2.95MPa, and the oxygen content is ≤50ppm.

[0009] The specific steps for obtaining the heat preservation and pressure holding cycle time ta in step one include:

[0010] a) Take the rubber corresponding to the temperature measurement point of the embedded wire in the tire carcass, and test the vulcanization curves at four temperatures of 140℃, 145℃, 150℃ and 155℃ on the rheometer. Record the t10 and t90 data. Calculate the rubber vulcanization activation energy Ea using the Arenius equation for the t90 data. Input the Ea data into the vulcanization thermometer so that the equivalent vulcanization time can be calculated in real time during subsequent temperature measurements.

[0011] b) Select a tire blank of a certain specification and embed temperature measuring wires at the weakest point of the tire vulcanization effect, the tread position, and the upper and lower tire sidewall positions.

[0012] c) Set the temperature of the external temperature mold sleeve and the upper and lower hot plates, preset the temperature and pressure holding cycle time of the vulcanizing medium N1 in step one as ta, the pressure holding time of the vulcanizing medium N2 as tb, and the duration of stopping the vulcanizing medium flow as tc.

[0013] d) The above-mentioned tire blank is loaded into the vulcanizing machine for vulcanization. At the same time, a vulcanization temperature measuring instrument is used to measure the temperature and record the vulcanization temperature and vulcanization time data in real time. The software in the vulcanization temperature measuring instrument can automatically calculate the equivalent vulcanization time using the Arenius equation based on the recorded temperature and time. When the equivalent vulcanization time at the weakest point of the tire vulcanization effect at 145℃ reaches the rubber scorch time t10, the vulcanization time of the tire at this time is recorded as td.

[0014] f) The tire vulcanization cycle te is obtained by multiplying td by the vulcanization safety factor k, where k ranges from 1.10 to 1.30.

[0015] g) Compare the temperature at the weakest point of vulcanization effect of the tire of this specification at the te time point with the tread and upper and lower hot plate temperatures. The temperature at the weakest point of vulcanization effect should be ≥ the lowest temperature among the tread and upper and lower hot plate temperatures.

[0016] h) If the preset vulcanization conditions in c) do not meet the requirements in g), ta can be readjusted based on the temperature measurement results. The adjustment range is ta ± (1-5 min) until the requirements in g) are met. At this time, ta is the final heat preservation and pressure preservation cycle time ta in step one.

[0017] The weakest point of the tire vulcanization effect is the end point of the tire shoulder belt layer, or it can be obtained through the foaming point test method.

[0018] The pressure holding time tb is set for the first time, and a relatively long time is appropriately set to allow sufficient time for subsequent calculation and adjustment of relevant vulcanization parameters.

[0019] The temperature at the weakest point of the vulcanization effect should be ≤ the lowest of the three temperatures: the tread temperature, the upper and lower hot plates temperature, and +5℃.

[0020] The specific steps for obtaining the holding time tb in step two include:

[0021] tb = td - ta + (0 - 5min),

[0022] Where td is the tire vulcanization time at 145℃ when the equivalent vulcanization time of the rubber at the weakest point of the tire vulcanization effect reaches the rubber scorch time t10. t10 is obtained by taking the rubber at the weakest point of the tire vulcanization effect and testing it with a rheometer.

[0023] The specific steps for obtaining the duration tc in step three are as follows:

[0024] tc = te - ta - tb,

[0025] Where te = td * vulcanization safety factor k, and k takes a value ranging from 1.10 to 1.30.

[0026] The beneficial effects of this invention are that it can quickly, easily and accurately formulate a vulcanization process using a full nitrogen vulcanization medium, shorten the vulcanization process development time, and reduce development costs; using this vulcanization process can reduce the temperature difference between the upper and lower molds of the tire vulcanization process, improve the uniformity of the vulcanization effect between the upper and lower molds of the tire, and enhance the tire durability; the energy consumption cost of single tire vulcanization is reduced by more than 30%, and the production efficiency is increased by more than 4%, and vulcanization capsules are used. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 A schematic diagram of the embedded temperature measuring wire for a 12R22.5 tire in this embodiment of the invention.

[0029] Figure 2 This is a graph showing the pressure over time during the tire vulcanization process of this invention.

[0030] Figure 3 This is a graph showing the temperature change over time during the tire vulcanization process of this invention.

[0031] In the diagram, 1-end point of the second belt layer of the lower mold; 2-end point of the second belt layer of the upper mold; 3-center of the rubber core of the lower mold; 4-center of the rubber core of the upper mold; 5-inner liner surface of the lower mold; 6-inner liner surface of the upper mold; 7-tread surface; 8-sidewall surface of the lower mold; 9-sidewall surface of the upper mold. Detailed Implementation

[0032] This invention utilizes the internal temperature and pressure provided by the vulcanizing medium within the vulcanizing capsule. Vulcanizing medium N1 is heated by an electromagnetic heating sleeve installed on the internal temperature vulcanizing pipeline, and pressurized by a booster pump. This pipeline is connected to the inlet and outlet of the vulcanizing capsule, forming a self-circulating pipeline. Vulcanizing medium N2 is another pipeline connected to the vulcanizing capsule, with its vulcanizing medium pressurized by a booster pump from the factory power station. The tire vulcanizing mold, including the mold sleeve and upper and lower side plates, provides an external temperature, which is achieved by heating with resistance wires embedded within the mold sleeve and side plates.

[0033] This embodiment describes the vulcanization process for a 12R22.5 tire, and the steps are as follows:

[0034] 1) Take rubber samples corresponding to the temperature measurement points embedded in the tire carcass and test the vulcanization curves at four temperatures: 140℃, 145℃, 150℃, and 155℃ on a rheometer. Record the t10 and t90 data. Calculate the rubber vulcanization activation energy Ea using the Arenius equation based on the t90 data. Input the Ea data into the vulcanization thermometer for real-time calculation of the equivalent vulcanization time during subsequent temperature measurements.

[0035] 2) Set the external temperature mold sleeve temperature to 145℃ and the external temperature upper and lower hot plates temperature to 148℃. Preheat the vulcanizing machine for 4 hours to allow the tire vulcanizing mold to reach a stable thermal equilibrium state.

[0036] 3) Temperature sensing wires are pre-embedded at the weakest points of the tire's vulcanization effect (shoulder), tread, upper and lower sidewalls, inner liner, and rubber core. Specific locations are detailed in [link to relevant documentation]. Figure 1 In the aforementioned Figure 1 Includes:

[0037] 1-End point of the second belt layer of the lower mold (weakest point of vulcanization effect); 2-End point of the second belt layer of the upper mold; 3-Center of the rubber core of the lower mold; 4-Center of the rubber core of the upper mold; 5-Surface of the inner liner of the lower mold; 6-Surface of the inner liner of the upper mold; 7-Surface of the tread; 8-Surface of the sidewall of the lower mold; 9-Surface of the sidewall of the upper mold.

[0038] 4) The preset vulcanization steps of the vulcanizing machine are as follows: Nitrogen gas (N1) is introduced into the vulcanizing bladder at a pressure of 1.65-1.85 MPa and a temperature of 200-208℃. The circulation of N1 into the vulcanizing bladder is controlled by a PLC program to maintain the internal temperature and pressure within the above range. The circulation time is 15 minutes. The introduction of nitrogen gas (N1) is stopped, and nitrogen gas (N2) is introduced at a pressure of 2.75-2.90 MPa and a temperature of 22-35℃. The introduction of N2 into the vulcanizing bladder is controlled by a PLC program to maintain the internal pressure within the above range. The pressure holding time is 35 minutes. The introduction of the vulcanizing medium is stopped for 20 minutes. Nitrogen gas is recovered for 40 seconds, nitrogen gas is discharged for 10 seconds, and a vacuum is drawn for 10 seconds. Vulcanization is completed, the mold is opened, and the tire is removed.

[0039] 5) Load the above-mentioned tire blank into the vulcanizing machine for vulcanization. At the same time, use a thermometer to record the temperature data of the wires. Recording begins when the tire blank is loaded into the vulcanizing machine and the mold is closed for vulcanization. Recording stops and the data is saved after the vulcanization process ends and the mold is opened.

[0040] 6) During tire vulcanization and temperature measurement, the Arenius equation was used to calculate the equivalent vulcanization time at 145℃, where the vulcanization effect was weakest. When the equivalent vulcanization time reached the rubber scorch time t10, the tire vulcanization time was recorded as 43 min. The nitrogen (N2) pressure holding time for the vulcanizing medium was calculated as: 43 - 15 + 1 = 29 min. The tire vulcanization cycle was: 43 * 1.20 = 51.6 min, rounded down to 52 min. The duration of stopping the vulcanizing medium flow was: 52 - 15 - 29 = 8 min.

[0041] 7) Based on the above calculation results, immediately adjust the preset nitrogen (N2) holding time for the vulcanizing medium of the tire from 35 min to 29 min, and adjust the duration of stopping the vulcanizing medium supply from the preset 20 min to 8 min. Continue the tire vulcanization and temperature measurement until the reset vulcanization program is completed. Then, after 40 seconds of nitrogen recovery, 10 seconds of nitrogen emission, and 10 seconds of vacuuming, the mold opening and vulcanization are completed.

[0042] 8) According to the temperature measurement results, the weakest point of the vulcanization effect at 52 min of vulcanization cycle is about 141℃, which is lower than the actual measured tread temperature of 147℃ (the lowest measured temperature position of the tread and upper and lower sidewalls is the tread).

[0043] 9) Change the nitrogen N1 circulation of the sulfidation medium to 20 and 25 min respectively, and repeat steps 3) to 9) above.

[0044] See the graph showing the temperature and pressure changes over time during vulcanization. Figure 2 , Figure 3 .

[0045] The results of the embodiments are shown in Tables 1 and 2.

[0046] Table 1

[0047]

[0048] Table 2

[0049]

[0050] Table 2 shows that in Test 1, the temperature at the weakest point of the vulcanization effect does not meet the requirements, and the vulcanization effect at the weakest point is too low, failing to meet the tire vulcanization technology requirements. In Tests 2 and 3, the temperature at the weakest point of the vulcanization effect meets the requirements, and the vulcanization effect at the weakest point meets the tire vulcanization technology requirements. However, in Test 3, the overall vulcanization effect at the tire temperature measurement point is too high, indicating over-sulfurization, and the long circulation time of the high-temperature vulcanizing medium results in wasted energy. Comparing the three, Test 2 represents the optimal vulcanization process.

[0051] This invention provides a vulcanization method that allows for rapid, simple, and accurate development of a full-nitrogen vulcanization process, shortening the development time and reducing costs for vulcanization processes of different tire specifications. Compared to traditional steam / nitrogen vulcanization processes, this invention significantly reduces the temperature difference between the upper and lower molds and improves the uniformity of vulcanization effects. For 12R22.5 tires, the energy consumption cost per tire vulcanization using this invention is reduced by more than 30%, and production efficiency is increased by more than 4%. Compared to existing full-nitrogen vulcanization processes using internal temperatures, this invention rapidly introduces high-temperature, low-pressure nitrogen vulcanization medium into the vulcanizing bladder at the beginning of vulcanization, shortening the heat transfer time and further improving tire production efficiency and reducing tire defect rates. The addition of a high-temperature, low-pressure nitrogen medium circulation step further reduces the temperature difference between the upper and lower molds during vulcanization. The use of cooling and depressurization steps in the later stages of vulcanization increases the vulcanizing bladder's lifespan by more than 10% and saves more than 5% on nitrogen vulcanization medium usage.

Claims

1. A method for vulcanizing all-steel truck and bus tires, characterized in that, Includes the following steps:

1. After the embryo is shaped and molded, vulcanizing medium N1 is introduced into the vulcanizing capsule, and the capsule is kept warm and pressurized for a duration of ta.

2. Stop circulating vulcanizing medium N1, introduce vulcanizing medium N2 into the vulcanizing capsule, and maintain pressure for a duration of tb.

3. Stop the flow of the vulcanizing medium, duration tc; In step one, the vulcanizing medium N1 is nitrogen gas, the temperature is 190-220℃, the pressure is 1.30-2.00MPa, and the oxygen content is ≤50ppm. In step two, the vulcanizing medium N2 is nitrogen gas, the temperature is 22.0-45.0℃, the pressure is 2.65-2.95MPa, and the oxygen content is ≤50ppm. The specific steps for obtaining the heat preservation and pressure holding cycle time ta in step one include: a) Take the rubber corresponding to the temperature measurement point of the embedded wire in the tire carcass, and test the vulcanization curves at four temperatures of 140℃, 145℃, 150℃ and 155℃ on the rheometer. Record the t10 and t90 data. Calculate the rubber vulcanization activation energy Ea using the Arenius equation for the t90 data. Input the Ea data into the vulcanization thermometer so that the equivalent vulcanization time can be calculated in real time during subsequent temperature measurements. b) Select a tire blank of a certain specification and embed temperature measuring wires at the weakest point of the tire vulcanization effect, the tread position, and the upper and lower tire sidewall positions. c) Set the temperature of the external temperature mold sleeve and the upper and lower hot plates, preset the heat preservation and pressure preservation cycle time of the vulcanizing medium N1 in step one as ta, the pressure preservation time of the vulcanizing medium N2 as tb, and the duration of stopping the vulcanizing medium flow as tc. d) The above-mentioned tire blank is loaded into the vulcanizing machine for vulcanization. At the same time, a vulcanization temperature measuring instrument is used to measure the temperature and record the vulcanization temperature and vulcanization time data in real time. The software in the vulcanization temperature measuring instrument automatically calculates the equivalent vulcanization time using the Arenius equation based on the recorded temperature and time. When the equivalent vulcanization time at the weakest point of the tire vulcanization effect at 145℃ reaches the rubber scorch time t10, the vulcanization time of the tire at this time is recorded as td. e) The tire vulcanization cycle te is obtained by multiplying td by the vulcanization safety factor k, where k ranges from 1.10 to 1.

30. f) Compare the temperature at the weakest point of vulcanization effect of the tire of this specification at time point te with the tread and upper and lower hot plate temperatures. The temperature at the weakest point of vulcanization effect should be ≥ the lowest temperature among the tread and upper and lower hot plate temperatures. g) If the preset vulcanization conditions in c) do not meet the requirements in f), readjust ta according to the temperature measurement results. The adjustment range is ta ± (1-5 min) until the requirements in f) are met. At this time, ta is the final heat preservation and pressure preservation cycle time ta in step one.

2. The vulcanization method for all-steel truck and bus tires according to claim 1, characterized in that... The weakest point of the tire vulcanization effect is the end point of the tire shoulder belt layer, or it can be obtained through the foaming point test method.

3. The vulcanization method for all-steel truck and bus tires according to claim 1, characterized in that... The pressure holding time tb is set for the first time, and a relatively long time is appropriately set to allow sufficient time for subsequent calculation and adjustment of relevant vulcanization parameters.

4. The vulcanization method for all-steel truck and bus tires according to claim 1, characterized in that... The temperature at the weakest point of the vulcanization effect should be ≤ the lowest of the three temperatures: the tread temperature, the upper and lower hot plates temperature, and +5℃.

5. The vulcanization method for all-steel truck and bus tires according to claim 1, characterized in that... The specific steps for obtaining the holding time tb in step two include: tb = td - ta + (0 - 5min) Where td is the tire vulcanization time at 145℃ when the equivalent vulcanization time of the rubber at the weakest point of the tire vulcanization effect reaches the rubber scorch time t10. t10 is obtained by taking the rubber at the weakest point of the tire vulcanization effect and testing it with a rheometer.

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