A nitrogen vulcanization method for tires

Abstract

The present invention relates to the technical field of tire vulcanization, and provides a nitrogen vulcanization method for tires. The present invention proposes a diversified vulcanization temperature for the vulcanization of the entire tire, and the internal temperature of the tire, the external temperature crown temperature, and the external temperature sidewall temperature are different, so as to realize and enable different parts of the tire blank to be vulcanized at a suitable temperature, so that the temperature rise rate of the entire tire during the vulcanization process is close, and the vulcanization uniformity of the tire is achieved; in particular, the setting of the external temperature is significantly lower than the temperature of the external temperature in the traditional vulcanization method, thereby saving a lot of energy. The nitrogen vulcanization method provided by the present invention is used to manufacture tires, which can greatly reduce the over-vulcanization degree of the sidewall of the agricultural radial tire, improve the vulcanization uniformity of the tire, improve the performance of the carcass cord of the sidewall of the agricultural radial tire, and increase the service life of the tire.

Description

Technical Field

[0001] The invention relates to the technical field of tire vulcanization, and in particular to a tire nitrogen vulcanization method. Background Art

[0002] The cord arrangement of agricultural radial tires is different from that of bias tires. The cords of agricultural radial tires are not arranged crosswise with each other, but are nearly parallel to the cross-section of the outer tire, like the meridian of the earth. The cord angle is small, generally 0°, and there is no intersection between the carcass cords. Due to its own structural advantages, compared with bias tires, under the conditions of the same pattern shape and pattern depth, agricultural radial tires provide higher traction, lower soil compaction, better puncture resistance, wear resistance, and cut resistance, and lower fuel consumption.

[0003] However, the sidewall thickness of agricultural radial tires is usually 10 to 20 mm, and the crown thickness is 60 to 150 mm. The difference in crown / side thickness is huge. If the traditional vulcanization method is used to vulcanize agricultural radial tires, when the thickest crown reaches the positive vulcanization, the sidewall and the tread will be severely over-vulcanized, and the degree of over-vulcanization will reach 8 to 10 times that of the crown. Therefore, the vulcanization uniformity of the tire is difficult to ensure, resulting in uneven vulcanization degree in different parts, which in turn affects the performance of the tire. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a nitrogen vulcanization method for tires, which can significantly improve the vulcanization uniformity of the entire tire and shorten the vulcanization time.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for nitrogen vulcanization of tires, wherein a green tire is heated and vulcanized in a mold, wherein the mold comprises a mold sleeve and upper and lower side plates, wherein the mold sleeve corresponds to a crown of the green tire, and the upper and lower side plates correspond to sidewalls of the green tire, and the method comprises the following steps:

[0007] (1) shaping a green tire in the mold to obtain a shaped green tire;

[0008] (2) performing internal temperature vulcanization and external temperature vulcanization on the shaped tire blank simultaneously;

[0009] The internal temperature vulcanization includes sequentially performing internal temperature steam vulcanization and nitrogen pressure maintenance; the internal temperature steam vulcanization includes internal temperature steam pressurization and internal temperature steam condensation removal;

[0010] The external temperature vulcanization includes synchronously heating the crown with steam circulation in the mold sleeve area and heating the sidewalls with steam circulation in the upper and lower side plate areas;

[0011] The temperature of the steam circulation heating in the mold sleeve area is 150-162°C, the temperature of the steam circulation heating in the upper and lower side plate areas is 120-140°C, and the temperature of the internal temperature steam used for internal temperature steam pressurization and internal temperature steam decondensation is 190-205°C.

[0012] Preferably, the pressure of the steam cycle in the mold sleeve area in step (2) is 0.4-0.5 MPa, and the cycle time is 60-95 min.

[0013] Preferably, the pressure of the steam cycle in the upper and lower side plate regions in step (2) is 0.16 to 0.3 MPa, and the cycle time is 60 to 95 min.

[0014] Preferably, the pressure of the internal temperature steam used for the internal temperature steam pressurization and internal temperature steam decondensation is 1.4-1.9 MPa.

[0015] Preferably, the nitrogen pressure maintaining pressure is 2.6-3.2 MPa, and the pressure maintaining time is 36 min-88 min 40 s.

[0016] Preferably, the number of internal temperature steam pressurization is 3 to 5 times, and the number of internal temperature steam condensation is 3 to 5 times. The first internal temperature steam pressurization and the first internal temperature steam condensation are carried out simultaneously, and then they are cycled in the order of internal temperature steam pressurization first and internal temperature steam condensation second.

[0017] Preferably, nitrogen pressure maintenance is performed after the internal temperature steam vulcanization is completed; the time for a single internal temperature steam pressurization is 2 to 4 minutes, and the time for each internal temperature steam decondensation other than the first time is 10 to 60 seconds.

[0018] The present invention provides a method for nitrogen vulcanization of a tire, wherein a tire blank is heated and vulcanized in a mold, wherein the mold comprises a mold sleeve and upper and lower side plates, wherein the mold sleeve corresponds to the tire crown of the tire blank, and the upper and lower side plates correspond to the tire side of the tire blank, and the method comprises the following steps: (1) shaping the tire blank in the mold to obtain a shaped tire blank; (2) synchronously performing internal temperature vulcanization and external temperature vulcanization on the shaped tire blank; the internal temperature vulcanization comprises sequentially performing internal temperature steam vulcanization and nitrogen pressure holding; the internal temperature steam vulcanization comprises internal temperature steam pressurization and internal temperature steam condensation removal; the external temperature vulcanization comprises synchronously performing steam circulation heating of the tire crown in the mold sleeve area and steam circulation heating of the tire side in the upper and lower side plate areas; the steam circulation heating temperature in the mold sleeve area is 150-162°C, the steam circulation heating temperature in the upper and lower side plate areas is 120-140°C, and the temperature of the internal temperature steam used for the internal temperature steam pressurization and internal temperature steam condensation removal is 190-205°C. The present invention adopts steam as a heat source and strictly controls the vulcanization temperature of different parts of the tire blank, thereby realizing and enabling different parts of the tire blank to be vulcanized at a suitable temperature, making the temperature rise rate of the entire tire close during the vulcanization process, achieving uniform vulcanization of the tire, and controlling the outer temperature, inner temperature and start and end time of nitrogen pressure maintenance of the tire blank, which cooperates with the above-mentioned technical means to ultimately shorten the vulcanization time.

[0019] The present invention proposes a diversified vulcanization temperature for the vulcanization of the entire tire. The internal temperature of the tire, the external temperature crown temperature, and the external temperature sidewall temperature are different, so that different parts of the tire blank are vulcanized at appropriate temperatures, so that the temperature rise rate of the entire tire during the vulcanization process is close, and the vulcanization uniformity of the tire is achieved; in particular, the setting of the external temperature sidewall temperature is significantly lower than the external temperature in the traditional vulcanization method, thereby saving a lot of energy. The diversified vulcanization temperature proposed by the present invention provides more solutions for the optimization of the vulcanization process, and provides a practical reference value for the optimization of the vulcanization process of different types of tire products.

[0020] By using the nitrogen vulcanization method provided by the present invention to vulcanize the tire blank of the agricultural radial tire, the over-vulcanization degree of the sidewall of the agricultural radial tire can be greatly reduced, the tire vulcanization uniformity can be improved, and the performance of the carcass cord fabric on the sidewall of the agricultural radial tire can be improved. The adhesion strength between the cord layers reaches 16.1 KN / m, which is increased by about 5%, and the tensile strength of the sidewall rubber reaches more than 17.5 MPa, which is increased by about 15%, thereby increasing the service life of the tire. DETAILED DESCRIPTION

[0021] The present invention provides a method for nitrogen vulcanization of tires, wherein a green tire is heated and vulcanized in a mold, wherein the mold comprises a mold sleeve and upper and lower side plates, wherein the mold sleeve corresponds to a crown of the green tire, and the upper and lower side plates correspond to sidewalls of the green tire, and the method comprises the following steps:

[0022] (1) shaping a green tire in the mold to obtain a shaped green tire;

[0023] (2) performing internal temperature vulcanization and external temperature vulcanization on the shaped tire blank simultaneously;

[0024] The internal temperature vulcanization includes sequentially performing internal temperature steam vulcanization and nitrogen pressure maintenance; the internal temperature steam vulcanization includes internal temperature steam pressurization and internal temperature steam condensation removal;

[0025] The external temperature vulcanization includes synchronously heating the crown with steam circulation in the mold sleeve area and heating the sidewalls with steam circulation in the upper and lower side plate areas;

[0026] The temperature of the steam circulation heating in the mold sleeve area is 150-162°C, the temperature of the steam circulation heating in the upper and lower side plate areas is 120-140°C, and the temperature of the internal temperature steam used for internal temperature steam pressurization and internal temperature steam decondensation is 190-205°C.

[0027] The present invention shapes the tire blank in the mold to obtain a shaped tire blank. In the present invention, the sidewall thickness of the tire blank is preferably 10 to 25 mm, and the crown thickness of the tire blank is preferably 30 to 150 mm; the present invention has no special requirements for the vulcanization bladder used for shaping the tire blank, and the butyl bladder commonly used by those skilled in the art can be selected; the present invention has no special requirements for the operation process of shaping the tire blank, and the conventional operation familiar to those skilled in the art can be selected. The present invention limits the thickness of the sidewall and crown, which is more conducive to the temperature rise rate of the entire tire being close during the vulcanization process, thereby improving the vulcanization uniformity of the tire.

[0028] After obtaining the shaped tire blank, the present invention simultaneously performs internal temperature vulcanization and external temperature vulcanization on the shaped tire blank; the internal temperature vulcanization includes sequentially performing internal temperature steam vulcanization and nitrogen pressure maintenance; the internal temperature steam vulcanization includes internal temperature steam pressurization and internal temperature steam condensation removal; the external temperature vulcanization includes synchronously steam circulation heating of the tire crown in the mold sleeve area and steam circulation heating of the tire sidewalls in the upper and lower side plate areas; the steam circulation heating temperature of the mold sleeve area is 150-162°C, preferably 153-162°C, the steam circulation heating temperature of the upper and lower side plate areas is 120-140°C, preferably 126-140°C, and the temperature of the internal temperature steam used for the internal temperature steam pressurization and internal temperature steam condensation removal is 190-205°C, preferably 197-203°C. In the present invention, the specific manner of synchronously performing internal temperature vulcanization and external temperature vulcanization on the shaped tire blank is: the internal temperature vulcanization and external temperature vulcanization are performed and ended simultaneously; the specific manner of the external temperature vulcanization including synchronously steam-circulating heating of the crown in the mold sleeve area and steam-circulating heating of the sidewalls in the upper and lower side plate areas is: steam-circulating heating of the crown in the mold sleeve area and steam-circulating heating of the sidewalls in the upper and lower side plate areas are performed and ended simultaneously. In the present invention, the steam circulation pressure in the mold sleeve area is preferably 0.4-0.5MPa, more preferably 0.41-0.45MPa, and the cycle time is preferably 60-95min, more preferably 65-95min; the steam circulation pressure in the upper and lower side plate areas is preferably 0.16-0.3MPa, more preferably 0.16-0.28MPa, and the cycle time is preferably 60-95min, more preferably 65-95min. The present invention uses steam as a heat source, strictly controls the vulcanization temperature of the tire blank, and vulcanizes different parts of the tire blank, so that the temperature rise rate of the entire tire during the vulcanization process is close, which is beneficial to the vulcanization uniformity of the tire.

[0029] In the present invention, the number of times of internal temperature steam pressing is preferably 3 to 5 times, the number of times of internal temperature steam decondensation is preferably 3 to 5 times, the first internal temperature steam pressing and the first internal temperature steam decondensation are preferably carried out simultaneously, and then the cycle is carried out in the order of internal temperature steam pressing first and then internal temperature steam decondensation; nitrogen pressure is preferably carried out after the internal temperature steam vulcanization is completed; the time of a single internal temperature steam pressing is preferably 2 to 4 minutes, and the time of each non-first internal temperature steam decondensation is preferably 10 to 60 seconds; the specific manner in which the first internal temperature steam pressing and the first internal temperature steam decondensation are preferably carried out simultaneously is: the first internal temperature steam pressing and the first internal temperature steam decondensation are carried out and ended at the same time; the pressure of the internal temperature steam used for the internal temperature steam pressing and the internal temperature steam decondensation is preferably 1.4 to 1.9 MPa, and more preferably 1.45 to 1.85 MPa. By limiting the operation mode of internal temperature steam pressing and internal temperature steam decondensation of the tire blank, the present invention can provide sufficient heat for tire vulcanization heating on the one hand, and on the other hand, reduce the accumulation of condensed water in the bladder to affect the temperature of the internal temperature. In the present invention, the nitrogen pressure holding pressure is preferably 2.6-3.2 MPa, more preferably 2.65-3.05 MPa, and the pressure holding time is preferably 36 min-88 min 40 s, more preferably 55-80 min; the nitrogen vulcanization equipment is preferably a 65.5-inch tire shaping vulcanizer.

[0030] In order to further illustrate the present invention, the nitrogen vulcanization method of the tire provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0031] The vulcanization equipment used in the embodiment of the present invention is a shaping vulcanizer, model 65.5-inch tire shaping vulcanizer, the mold of the shaping vulcanizer includes a mold sleeve and upper and lower side plates, the mold sleeve corresponds to the crown of the tire blank, and the upper and lower side plates correspond to the sidewalls of the tire blank.

[0032] Example 1

[0033] (1) shaping a green tire in a mold to obtain a shaped green tire, wherein the bladder is a common butyl bladder, the shaping pressure is 0.06 MPa, and the sidewall thickness of the tire is 15 mm and the crown thickness is 70 mm;

[0034] (2) After obtaining the shaped tire blank, the crown is heated by steam circulation in the mold sleeve area, and the sidewalls are heated by steam circulation in the upper and lower side plate areas. The heating of the crown and the sidewalls is carried out and ended simultaneously, wherein the temperature of the steam circulation in the mold sleeve area is 155±2° C., the pressure is 0.42±0.02 MPa, and the time is 83 min. The temperature of the steam circulation in the upper and lower side plate areas is 138±2° C., the pressure is 0.26±0.02 MPa, and the time is 83 min.

[0035] When heating the tire sidewalls and tire crowns begins, the tire blank is subjected to internal temperature steam pressure and internal temperature steam condensation of the tire blank, specifically:

[0036] The tire blank is subjected to internal temperature steam pressing and internal temperature steam condensation at the same time, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0037] The tire blank is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0038] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 30 seconds;

[0039] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0040] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 18S;

[0041] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0042] Maintain the green tire pressure at 1.65±0.2MPa and the temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 12S;

[0043] After the internal temperature steam pressurization and internal temperature steam decondensation are completed, the tire blank is pressurized with nitrogen until the heating of the tire sidewalls and tire crown is completed at the same time. The nitrogen pressure is 2.8MPa and the nitrogen pressure holding time is 70min.

[0044] The vulcanization time is 83 minutes. Compared with the traditional vulcanization method, the total time for vulcanizing the same type of tire is 100 minutes. The nitrogen vulcanization process saves 14 minutes and improves efficiency by 14%. At the same time, there is no abnormality in the overall performance of the tire, the crown properties are normal, and the sidewall properties are within the normal range. The tensile strength of the tire sidewall after nitrogen vulcanization is 14.8MPa, which is the same as the sidewall strength of the tire vulcanized by the traditional vulcanization process; the bonding strength between the carcass cord layers reaches 15.6KN / m, which is about 2% higher than the bonding strength between the vulcanized wheel layers by the traditional vulcanization process.

[0045] Example 2

[0046] (1) shaping a green tire in a mold to obtain a shaped green tire, wherein the bladder is a common butyl bladder, the shaping pressure is 0.06 MPa, and the sidewall thickness of the tire is 15 mm and the crown thickness is 80 mm;

[0047] (2) After obtaining the shaped tire blank, the crown is heated by steam circulation in the mold sleeve area, and the sidewalls are heated by steam circulation in the upper and lower side plate areas. The heating of the crown and the sidewalls is carried out and ended simultaneously, wherein the temperature of the steam circulation in the mold sleeve area is 155±2°C, the pressure is 0.42±0.02MPa, and the time is 77min10s, and the temperature of the steam circulation in the upper and lower side plate areas is 140°C, the pressure is 0.28MPa, and the time is 77min10s;

[0048] When heating the tire sidewalls and tire crowns begins, the tire blank is subjected to internal temperature steam pressure and internal temperature steam condensation of the tire blank, specifically:

[0049] The tire blank is subjected to internal temperature steam pressing and internal temperature steam condensation at the same time, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0050] The tire blank is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0051] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 30 seconds;

[0052] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0053] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 18S;

[0054] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0055] Maintain the green tire pressure at 1.65±0.2MPa and the temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 12S;

[0056] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0057] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 10S;

[0058] After the internal temperature steam pressurization and internal temperature steam decondensation are completed, the tire blank is pressurized with nitrogen until the heating of the tire sidewalls and tire crown is completed at the same time. The nitrogen pressure is 2.8MPa and the nitrogen pressure holding time is 60min.

[0059] The vulcanization time is 77min10S. There is no abnormality in the overall performance of the tire, the crown properties are normal, the sidewall properties are normal, and the tensile strength of the tire sidewall after nitrogen vulcanization is 15.0MPa, which is about 1.3% higher than the tensile strength of the tire sidewall vulcanized by traditional vulcanization process; the interlayer bonding strength of the carcass reaches 15.7KN / m, and the interlayer bonding strength of the tire vulcanized by traditional vulcanization process is increased by about 3%.

[0060] Example 3

[0061] (1) shaping a green tire in a mold to obtain a shaped green tire, wherein the bladder is a common butyl bladder, the shaping pressure is 0.06 MPa, and the sidewall thickness of the tire is 18 mm and the crown thickness is 90 mm;

[0062] (2) After obtaining the shaped tire blank, the crown is heated by steam circulation in the mold sleeve area, and the sidewalls are heated by steam circulation in the upper and lower side plate areas. The heating of the crown and the sidewalls is carried out and ended simultaneously, wherein the temperature of the steam circulation in the mold sleeve area is 155±2°C, the pressure is 0.42±0.02MPa, and the time is 68min, and the temperature of the steam circulation in the upper and lower side plate areas is 135±2°C, the pressure is 0.2±0.02MPa, and the time is 68min;

[0063] When heating the tire sidewalls and tire crowns begins, the tire blank is subjected to internal temperature steam pressure and internal temperature steam condensation of the tire blank, specifically:

[0064] The tire blank is subjected to internal temperature steam pressing and internal temperature steam condensation at the same time, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0065] The tire blank is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0066] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 30 seconds;

[0067] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0068] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 18S;

[0069] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0070] Maintain the green tire pressure at 1.65±0.2MPa and the temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 12S;

[0071] After the internal temperature steam pressurization and internal temperature steam decondensation are completed, the tire blank is pressurized with nitrogen until the heating of the tire sidewalls and tire crown is completed at the same time, wherein the nitrogen pressure is 2.85±0.2MPa and the nitrogen pressure holding time is 55min.

[0072] The vulcanization time is 68 minutes. There is no abnormality in the overall performance of the tire, the crown properties are normal, and the sidewall properties are significantly higher than those of tires vulcanized by traditional vulcanization process. The tensile strength of the sidewall of the tire after nitrogen vulcanization is 17MPa, which is about 13% higher than the tensile strength of the sidewall of the tire vulcanized by traditional vulcanization process; the interlayer bonding strength of the carcass reaches 16.1KN / m, and the interlayer bonding strength of the tire vulcanized by traditional vulcanization process is increased by about 5%.

[0073] Example 4

[0074] (1) shaping a green tire in a mold to obtain a shaped green tire, wherein the bladder is a common butyl bladder, the shaping pressure is 0.08 MPa, and the sidewall thickness of the tire is 20 mm and the crown thickness is 120 mm;

[0075] (2) After obtaining the shaped tire blank, the crown is heated by steam circulation in the mold sleeve area, and the sidewalls are heated by steam circulation in the upper and lower side plate areas. The heating of the crown and the sidewalls is carried out and ended simultaneously, wherein the temperature of the steam circulation in the mold sleeve area is 160±2° C., the pressure is 0.42±0.02 MPa, and the time is 95 min. The temperature of the steam circulation in the upper and lower side plate areas is 128±2° C., the pressure is 0.2±0.02 MPa, and the time is 95 min.

[0076] When heating the tire sidewalls and tire crowns begins, the tire blank is subjected to internal temperature steam pressure and internal temperature steam condensation of the tire blank, specifically:

[0077] The tire blank is subjected to internal temperature steam pressing and internal temperature steam condensation at the same time, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 2min;

[0078] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0079] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 30 seconds;

[0080] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0081] Maintain the green tire pressure at 1.65±0.2MPa and temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 18S;

[0082] The tire green body is subjected to internal temperature steam pressing, wherein the pressing pressure is 1.65±0.2MPa, the temperature is 200±3℃, and the time is 4min;

[0083] Maintain the green tire pressure at 1.65±0.2MPa and the temperature at 200±3℃, and perform internal temperature steam condensation on the green tire for 12S;

[0084] After the internal temperature steam pressurization and internal temperature steam decondensation are completed, the tire blank is pressurized with nitrogen until the heating of the tire sidewalls and tire crown is completed at the same time, wherein the nitrogen pressure is 2.85±0.2MPa and the nitrogen pressure holding time is 80min.

[0085] The vulcanization time is 95 minutes. There is no abnormality in the overall performance of the tire, the crown properties are normal, and the sidewall properties are significantly higher than those of tires vulcanized by traditional vulcanization process. The tensile strength of the sidewall of the tire after nitrogen vulcanization is 17.5MPa, which is about 15% higher than the tensile strength of the sidewall of the tire vulcanized by traditional vulcanization process; the interlayer bonding strength of the carcass reaches 16.1KN / m, and the interlayer bonding strength of the tire vulcanized by traditional vulcanization process is increased by about 5%.

[0086] Comparative Example 1

[0087] The tire used in Example 1 was subjected to a conventional vulcanization process, with the internal temperature being heated by circulating superheated water at 173°C, the external temperature being heated by steam at 155°C and 0.45MPa provided by a steam chamber, the vulcanization time being 100min, and the tensile strength of the sidewall of the tire after conventional vulcanization being 14.8MPa, and the bonding strength value between the carcass cord layers being 15.24KN / m.

[0088] Compared with Comparative Example 1, the internal temperature of the nitrogen vulcanization method of the present application is significantly higher than that of the traditional vulcanization process, and the higher the internal temperature, the lower the rubber performance, especially the oversulfurization degree of the sidewall with less material will increase by more than 100%, and the bonding strength between the carcass cord layers and the sidewall rubber performance will be seriously reduced. For this reason, the present invention reduces the oversulfurization degree of the side part by controlling the temperature of the sidewall side plate at 120-140°C, and finally the vulcanized tire provided by the present invention not only does not show performance degradation due to the increase of the internal temperature, but the performance is improved.

[0089] In terms of external temperature, since the traditional steam chamber heating method is overall heating, the steam consumption is large. In the same vulcanization time, the nitrogen vulcanization method provided by the present invention reduces the steam consumption by 30% to 40% compared with the traditional vulcanization method, which greatly saves energy.

[0090] In summary, the nitrogen vulcanization method provided by the present invention has a short vulcanization time, saves energy, has high tensile strength of the tire sidewall, high bonding strength between tire body layers, and has a vulcanization effect that is higher than that of the traditional vulcanization process.

[0091] Performance Testing

[0092] The sidewall tensile test of the nitrogen vulcanized tire is carried out in accordance with the national standard GB / T528-2009. The interlayer adhesion strength test of the carcass cord of the nitrogen vulcanized tire is carried out in accordance with the national standard GB / T 519-2017.

[0093] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for nitrogen vulcanization of tires, wherein a green tire is heated and vulcanized in a mold, wherein the mold comprises a mold sleeve and upper and lower side plates, wherein the mold sleeve corresponds to a crown of the green tire, and the upper and lower side plates correspond to sidewalls of the green tire, wherein: The following steps are involved: (1) shaping a green tire in the mold to obtain a shaped green tire; (2) performing internal temperature vulcanization and external temperature vulcanization on the shaped tire blank simultaneously; The internal temperature vulcanization includes sequentially performing internal temperature steam vulcanization and nitrogen pressure maintenance; the internal temperature steam vulcanization includes internal temperature steam pressurization and internal temperature steam condensation removal; The external temperature vulcanization includes synchronously heating the crown with steam circulation in the mold sleeve area and heating the sidewalls with steam circulation in the upper and lower side plate areas; The temperature of the steam circulation heating in the mold sleeve area is 150-162°C, the temperature of the steam circulation heating in the upper and lower side plate areas is 120-140°C, and the temperature of the internal temperature steam used for internal temperature steam pressurization and internal temperature steam decondensation is 190-205°C.

2. The nitrogen vulcanization method according to claim 1, characterized in that: The steam circulation pressure in the mold sleeve area of ​​the step (2) is 0.4-0.5 MPa, and the cycle time is 60-95 min.

3. The nitrogen vulcanization method according to claim 1 or 2, characterized in that: The pressure of the steam circulation in the upper and lower side plate regions of the step (2) is 0.16 to 0.3 MPa, and the circulation time is 60 to 95 min.

4. The nitrogen vulcanization method according to claim 1, characterized in that: The pressure of the internal temperature steam used in the internal temperature steam pressurization and internal temperature steam condensation is 1.4-1.9 MPa.

5. The nitrogen vulcanization method according to claim 1, characterized in that: The nitrogen pressure maintaining pressure is 2.6-3.2 MPa, and the pressure maintaining time is 36 min-88 min 40 s.

6. The nitrogen vulcanization method according to claim 1 or 4, characterized in that: The number of internal temperature steam pressure release is 3 to 5 times, and the number of internal temperature steam decondensation is 3 to 5 times. The first internal temperature steam pressure release and the first internal temperature steam decondensation are carried out simultaneously, and then the cycle is carried out in the order of internal temperature steam pressure release and internal temperature steam decondensation.

7. The nitrogen vulcanization method according to claim 6, characterized in that: After the internal temperature steam vulcanization is completed, nitrogen pressure is maintained; the time for a single internal temperature steam pressurization is 2 to 4 minutes, and the time for each internal temperature steam decondensation other than the first time is 10 to 60 seconds.