Preparation method of thermoplastic vulcanized rubber and prepared thermoplastic vulcanized rubber

Abstract

The invention relates to the technical field of preparation of thermoplastic vulcanized rubber, in particular to a preparation method of thermoplastic vulcanized rubber and the prepared thermoplastic vulcanized rubber. The preparation method provided by the invention comprises the following steps: mixing raw materials at a temperature lower than Ts to obtain a premix; performing variable-temperature dynamic vulcanization on the premix; the raw materials comprise rubber, plastic and a vulcanization system; the variable-temperature dynamic vulcanization is a continuous process; the temperature of variable-temperature dynamic vulcanization is gradually increased from T1 to Tn. The premix is melted at a relatively low temperature and is dynamically vulcanized at the same time; at the moment, dynamic vulcanization is slow, and the dynamic vulcanization degree is low. Due to the fact that the vulcanization system, the rubber and the plastic in the premix are evenly dispersed, the positions where vulcanization begins at the temperature T1 are evenly dispersed instead of being concentrated; therefore, the problems of poor tensile strength, elongation at break, hardness and the like of the thermoplastic vulcanized rubber prepared by the existing preparation method are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of thermoplastic vulcanized rubber, and more particularly to a method for preparing thermoplastic vulcanized rubber and the prepared thermoplastic vulcanized rubber. Background Art

[0002] Thermoplastic vulcanizates are mostly made of rubber and plastic as the main raw materials through dynamic vulcanization. Dynamic vulcanization refers to the vulcanization of rubber during the melt blending process of rubber and thermoplastic plastic. While the rubber is vulcanizing, it is also continuously mixed with the thermoplastic plastic. Therefore, the vulcanized rubber is distributed as a dispersed phase in the continuous phase of the thermoplastic plastic, thus forming a thermoplastic vulcanizate that has both the excellent elasticity of traditional rubber and the good processing performance of plastic.

[0003] In order to disperse the vulcanized rubber particles in the plastic, each raw material needs to be in a molten state before dynamic vulcanization. However, the temperature required to melt each raw material is usually higher than the vulcanization temperature of the rubber, so when the raw materials are melted, the rubber should be prevented from vulcanizing. Therefore, the existing preparation methods include the following four methods: First, melt-mixing rubber, plastic, antioxidant and compatibilizer, and then adding a vulcanization system for dynamic vulcanization; second, melt-mixing rubber, plastic, antioxidant, compatibilizer and vulcanizer, and then adding a catalyst for dynamic vulcanization; third, melt-mixing rubber, plastic, antioxidant and compatibilizer, and then dividing into two parts, adding a vulcanizer to one part and a catalyst to the other part, and then mixing the two parts for dynamic vulcanization; fourth, melt-mixing rubber, plastic, antioxidant and compatibilizer, cooling, and then mixing with a vulcanization system at room temperature to obtain a rubber-plastic premix, and then dynamically vulcanizing the rubber-plastic premix.

[0004] The first three preparation methods all have the following problems: before dynamic vulcanization, not all raw materials are mixed evenly, and there is always a situation where the vulcanization system, the catalyst in the vulcanization system, or the vulcanizing agent in the vulcanization system are not mixed evenly with other raw materials; therefore, dynamic vulcanization is always carried out locally first, which increases the local viscosity and causes the dispersion of the rubber-plastic system to deteriorate. A uniformly dispersed rubber-plastic premix is ​​the ideal state for the dynamic co-vulcanization process. Only when the uniformly dispersed rubber-plastic premix is ​​dynamically vulcanized can a thermoplastic vulcanized rubber with excellent properties such as tensile strength, elongation at break and hardness be obtained. The fourth preparation method has a cumbersome processing process and is difficult to carry out industrial continuous production; although there are no problems described in the first three methods, the tensile strength, elongation at break and hardness of the prepared thermoplastic vulcanized rubber are still poor. Therefore, the above four preparation methods all have the problem of poor tensile strength, elongation at break and hardness of the prepared thermoplastic vulcanized rubber. Summary of the invention

[0005] Aiming at the problem that the thermoplastic vulcanized rubber prepared by the existing preparation method of thermoplastic vulcanized rubber has poor properties such as tensile strength, elongation at break and hardness, the present invention provides a new preparation method of thermoplastic vulcanized rubber and thermoplastic vulcanized rubber prepared by the method.

[0006] One of the objects of the present invention is to provide a new method for preparing a thermoplastic vulcanizate.

[0007] The preparation method of the thermoplastic vulcanized rubber comprises: s The raw materials include rubber, plastic and vulcanization system;

[0008] The variable temperature dynamic vulcanization is a continuous process; the temperature of the variable temperature dynamic vulcanization increases gradually from T1 to T n ;

[0009] T2 to T n At least one of T k Preferably, T2 to T n-1 At least one of T k More preferably, T n-1 =T k ;

[0010] In T k The curing time under the condition is greater than that under the condition below T k The sum of the vulcanization time under the conditions;

[0011] T s The lowest temperature at which dynamic vulcanization can be achieved;

[0012] T k It is the optimal temperature for dynamic vulcanization;

[0013] T1 is greater than or equal to the lowest temperature that can melt the raw material or T s , less than or equal to T k ;

[0014] T n Greater than or equal to T k , less than or equal to the maximum temperature at which dynamic vulcanization can be achieved;

[0015] The n is selected from a natural number greater than or equal to 3.

[0016] The gradient rise is to maintain a certain temperature for a period of time, then rise to another temperature and maintain it for a period of time.

[0017] Dynamic vulcanization optimum temperature T kIt means that the thermoplastic vulcanized rubber obtained by dynamic vulcanization at this temperature has the best comprehensive performance (for example, tensile strength, elongation at break, hardness (Shore A) and apparent state are optimal). The optimal temperature of dynamic vulcanization is determined according to the selected raw materials; different raw materials have different optimal temperatures of dynamic vulcanization. In practice, the optimal temperature of dynamic vulcanization can be determined by experiments; that is, the raw materials are dynamically vulcanized at different temperatures using any existing method, and the temperature at which the thermoplastic vulcanized rubber has the best comprehensive performance is the optimal temperature of dynamic vulcanization T. k .

[0018] T1 is greater than or equal to the lowest temperature that can melt the raw materials and T s , means that T1 is greater than or equal to the lowest temperature that can melt the raw material and is greater than or equal to T s That is, T1 is greater than or equal to the lowest temperature that can melt the raw material and T s The higher temperature of the two. If the lowest temperature that can make the raw material melt is greater than T s , then T1 is greater than or equal to the lowest temperature that can melt the raw material; if the lowest temperature that can melt the raw material is less than T s , then T1 is greater than or equal to T s .

[0019] After the raw materials are determined, T s , T k , T1, T n Specifically, the highest temperature, lowest temperature and T k All can be determined by preliminary experiments-static vulcanization. For example, the raw materials are: 60 parts by weight of liquid silicone rubber, 40 parts by weight of polycaprolactone, 10 parts by weight of silane-modified polyurethane, 7 parts by weight of hydrogenated silicone oil, 0.4 parts by weight of platinum catalyst, 1.2 parts by weight of inhibitor, and 0.1 parts by weight of antioxidant; its T s 60℃, T k is 190°C, the highest temperature that can achieve dynamic vulcanization is 210°C, and the lowest temperature that can achieve dynamic vulcanization is 120°C; T1 can be selected from any temperature greater than or equal to 120°C, T n The temperature may be selected from any temperature between 190°C and 210°C.

[0020] The mixing can be achieved by using any available mixing equipment. The premix after mixing is in the following state: when the rubber in the raw material is liquid rubber, the premix is ​​in a semi-solid state; when the rubber in the raw material is solid rubber, the premix is ​​in a shape similar to a date cake; the premix can be added to the twin-screw extruder without extrusion granulation.

[0021] T1 is greater than or equal to the lowest temperature at which the raw material can be melted and the lowest temperature at which dynamic vulcanization can be achieved. sTherefore, at T1 temperature, the premix can both melt and undergo dynamic vulcanization; that is, the premix melts at T1 temperature and undergoes dynamic vulcanization at the same time; at this time, due to the low dynamic vulcanization temperature, the dynamic vulcanization is slow and the degree of dynamic vulcanization is low. Since the vulcanization system, rubber, and plastic in the premix are already evenly dispersed, the location where vulcanization occurs at T1 temperature is evenly dispersed rather than concentrated.

[0022] Then, vulcanization is carried out at higher temperatures. k Previously, the temperature was always lower than the optimal temperature for dynamic vulcanization, and dynamic vulcanization was always slow. As the degree of dynamic vulcanization gradually increased, the viscosity of the rubber gradually matched the viscosity of the molten plastic. When the temperature rose to T k When T k Under the temperature conditions, the dispersion of the material is good; the longer the high temperature shearing time is maintained under the temperature conditions, the higher the fine dispersion of the rubber-plastic premix is ​​obtained, and the better the performance of the product prepared by dynamic vulcanization is.

[0023] Therefore, in T k The curing time under the condition is greater than that under the condition below T k The sum of the curing times under the conditions; that is, the curing time under the optimal temperature of dynamic vulcanization should be greater than that under the conditions below T k The sum of the vulcanization times under the optimal temperature conditions for dynamic vulcanization should be greater than the sum of the vulcanization times at other temperatures.

[0024] The total vulcanization time is related to the material system. The total vulcanization time and vulcanization temperature can be determined through preliminary experiments - static vulcanization. After the total vulcanization time is determined, the vulcanization temperature is 400 °C. k The curing time under the condition is greater than that under the condition below T k The sum of the curing time under the conditions of "the sum of the curing time under the conditions of" can be arbitrarily allocated between T1 and T n Vulcanization time under temperature conditions.

[0025] n can be determined based on the time and temperature required for the rubber and plastic phases to reach viscosity matching; the rubber and plastic viscosity matching refers to the rubber to plastic viscosity ratio of 1: (0.5-1.5). n is at least 3, that is, dynamic vulcanization is carried out under at least 3 temperature conditions; at this time, T2 = T k , the second temperature condition is the optimal temperature condition for dynamic vulcanization. Under the same raw materials, there is an optimal n value that makes the prepared thermoplastic vulcanizate have the best comprehensive performance (for example, tensile strength, elongation at break, hardness (Shore A) and surface state). Usually, 5≤n≤15, preferably, 5≤n≤10. In some embodiments disclosed in the present invention, n=5, T4=T k .

[0026] Different raw material systems are suitable for different temperature gradient differences. It can be an isothermal difference or a non-isothermal difference. The difference between two adjacent temperatures can be determined by combining the time and temperature and n at which the rubber and plastic phases reach viscosity matching; there is an optimal temperature gradient difference. Normally, the difference between two adjacent temperatures is 1 to 20°C, preferably 5-15°C. In some embodiments disclosed in the present invention, the temperature difference is 10°C or 20°C.

[0027] The premix can be subjected to variable temperature dynamic vulcanization by using a twin-screw extruder. The twin-screw extruder can be any existing twin-screw extruder that can be used for dynamic vulcanization. When the raw materials are mixed by using a mixing device, the mixing device can also be connected to the twin-screw extruder in series; this can further reduce the processing steps and improve productivity.

[0028] Compared with the double-stage twin-screw extruder, the single-stage twin-screw extruder has only one set of screw transmission, which is simpler in structure, easier to operate, maintain and clean, and reduces the cost of use. Due to the simple structure, the manufacturing and maintenance costs of the single-stage twin-screw extruder are also lower, which makes its equipment purchase cost and subsequent maintenance cost lower. Therefore, the twin-screw extruder is preferably a single-stage twin-screw extruder.

[0029] In specific operation, the twin-screw extruder equipment can be divided into N zones, which are the first zone, ..., and the Nth zone from front to back; correspondingly, the temperature of the first zone is T1, the temperature of the Nth zone is T2, and the temperature of the Nth zone is T3. n The length ratio of each zone can be calculated based on the T n The vulcanization time ratio under temperature conditions is determined. Specifically, T n The longer the curing time under temperature conditions, the n The longer the length of the corresponding zone is. After the length ratio of each zone is determined, the vulcanization time of the material in each zone and temperature condition can be further adjusted by adjusting the speed of the twin-screw extruder. The length of the twin-screw extruder is fixed. When the length of each zone is determined, the higher the speed, the shorter the vulcanization time in each zone (the effect of temperature on material fluidity can be ignored).

[0030] According to some embodiments disclosed in the present invention: the twin-screw extruder can be divided into 5 zones, namely the first zone, ..., and the fifth zone from front to back; the length ratio of the first zone, ..., and the fifth zone is 1:1:1:7:2; wherein T1 is 145-155°C, T2 is 165-175°C, T3 is 175-185°C, T4 is 185-195°C, and T5 is 205-215°C;

[0031] The rotation speed of the single-stage twin-screw extruder is 100 to 1000 rpm, preferably 200 to 800 rpm, more preferably 200 to 600 rpm, and further preferably 300 to 500 rpm, for example, 400 rpm.

[0032] According to some embodiments disclosed in the present invention:

[0033] The weight ratio of the rubber to the plastic is 40-90:60-10, preferably 50-70:50-30.

[0034] The rubber is a liquid rubber, and is preferably selected from at least one of liquid silicone rubber, liquid styrene-butadiene rubber and liquid butadiene rubber.

[0035] The plastic is selected from at least one of thermoplastic polyurethane, polycaprolactone, polylactic acid and polybutylene succinate.

[0036] The vulcanization system comprises hydrogen-containing silicone oil, a platinum catalyst and an inhibitor, wherein the platinum catalyst is selected from at least one of an isopropanol complex of chloroplatinic acid, a platinum catalyst coordinated with tetrahydrofuran and a platinum catalyst coordinated with methylvinylsiloxane; and the inhibitor is selected from at least one of an acetylenic alcohol inhibitor, an azo inhibitor and a heavy metal ion compound.

[0037] The raw materials also include a compatibilizer and an antioxidant;

[0038] The compatibilizer is selected from at least one of silane-modified polyurethane and ethylene-methyl acrylate copolymer;

[0039] The antioxidant is selected from at least one of hindered phenol antioxidants, phosphite antioxidants and thiopropionate antioxidants.

[0040] A second object of the present invention is to provide a thermoplastic vulcanizate.

[0041] The thermoplastic vulcanized rubber is prepared by the preparation method described in one of the purposes of the invention.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] A new preparation process is provided for the preparation of thermoplastic vulcanized rubber.

[0044] Compared with the existing preparation method, the thermoplastic vulcanized rubber prepared by the method of the present invention has greatly improved tensile strength, elongation at break and hardness, and has a smooth extruded surface.

[0045] The preparation method of the invention has few steps and is simple to operate, and only one mixing step is required before dynamic vulcanization.

[0046] In the preparation method of the present invention, the premix can be directly transferred to a twin-screw extruder for dynamic vulcanization, thereby achieving continuous and large-scale production, and can be applied in actual production. The preparation method of the present invention can reduce processing costs, simplify processing technology, and improve production efficiency. DETAILED DESCRIPTION

[0047] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0048] The raw materials used in the following examples and comparative examples are all commercially available products.

[0049] Liquid silicone rubber was from Ambiya Special Silicone Co., Ltd., model VS165000;

[0050] Polycaprolactone (Mn = 50000) was from Tianjin Xiensi Biochemical Technology Co., Ltd.;

[0051] Silane-modified polyurethane was from Meirui New Materials Co., Ltd., model number V-175;

[0052] The hydrogen-containing silicone oil was from Zijun Chemical Co., Ltd., with an active hydrogen content of 0.8 wt%;

[0053] The platinum catalyst is a methylvinylsiloxane coordinated platinum catalyst from Zijun Chemical Co., Ltd., with a Pt content of 100 to 10,000 ppm;

[0054] The inhibitor was alkynol M622 from Guangzhou Siyou New Materials Technology Co., Ltd.;

[0055] The antioxidant was antioxidant 1010 from BASF.

[0056] Example 1

[0057] The selected raw materials and weight parts are as follows:

[0058] 60 parts by weight of liquid silicone rubber;

[0059] 40 parts by weight of polycaprolactone;

[0060] 10 parts by weight of silane-modified polyurethane;

[0061] 7 parts by weight of hydrogen-containing silicone oil;

[0062] 0.4 parts by weight of platinum catalyst;

[0063] 1.2 parts by weight of inhibitor;

[0064] Antioxidant 0.1 parts by weight.

[0065] The lowest temperature that can melt all raw materials is 60℃.

[0066] The maximum temperature that can achieve dynamic vulcanization is 210°C;

[0067] The lowest temperature for dynamic vulcanization is 120°C

[0068] The optimal temperature for dynamic vulcanization is 190°C.

[0069] According to the above formula, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system are fully mixed and uniformly discharged at room temperature (30°C, the same below) using an internal mixer to obtain a rubber-plastic premix; then the rubber-plastic premix is ​​transferred to a twin-screw extruder, which is divided into 12 zones (each zone has an equal length, the same below), and the temperature is set to zone I (150°C), zone II (170°C), zone III (180°C), zone IV-X (190°C), zone XI and zone XII (210°C), the speed is 200rpm, and the silicone rubber / polycaprolactone thermoplastic vulcanizate TPV is obtained by dynamic vulcanization. TPV is pressed into a 2mm thick sheet according to the standard and the performance is tested. The performance is shown in Table 1.

[0070] Example 2

[0071] According to the formula of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system were fully mixed and uniformly discharged at room temperature using an internal mixer to obtain a rubber-plastic premix; the rubber-plastic premix was then transferred to a twin-screw extruder, which was divided into 12 zones, and the temperatures were set to zone I (150°C), zone II (170°C), zone III (180°C), zone IV to zone X (190°C), zone XI and zone XII (210°C), the speed was 400rpm, and the silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2mm thick sheet according to the standard and the performance was tested. The performance is shown in Table 1.

[0072] Example 3

[0073] According to the formula of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system were fully mixed and uniformly discharged at room temperature using an internal mixer to obtain a rubber-plastic premix; the rubber-plastic premix was then transferred to a twin-screw extruder, which was divided into 12 zones, and the temperatures were set to zone I (150°C), zone II (170°C), zone III (180°C), zone IV to zone X (190°C), zone XI and zone XII (210°C), and the speed was 600rpm. The silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2 mm thick sheet according to the standard and the performance was tested. The performance is shown in Table 1.

[0074] Example 4

[0075] According to the formula of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system were fully mixed and uniformly discharged at room temperature using an internal mixer to obtain a rubber-plastic premix; the rubber-plastic premix was then transferred to a twin-screw extruder, which was divided into 12 zones, with the temperatures set to zones I to III (170°C), zones IV to X (190°C), zones XI and zones XII (210°C), and the speed was 400 rpm, and the silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2 mm thick sheet according to the standard and the performance was tested, and the performance is shown in Table 1.

[0076] Example 5

[0077] According to the formula of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system were fully mixed and uniformly discharged at room temperature using an internal mixer to obtain a rubber-plastic premix; the rubber-plastic premix was then transferred to a twin-screw extruder, which was divided into 12 zones, with the temperatures set to zones I to III (150°C), zones IV to X (190°C), zones XI and zones XII (210°C), and the speed was 400 rpm, and the silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2 mm thick sheet according to the standard and the performance was tested, and the performance is shown in Table 1.

[0078] Example 6

[0079] According to the formula of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane and vulcanization system were fully mixed and uniformly discharged at room temperature using an internal mixer to obtain a rubber-plastic premix; the rubber-plastic premix was then transferred to a twin-screw extruder, which was divided into 12 zones, and the temperatures were set to zone I (160°C), zone II (170°C), zone III to zone X (180°C), zone XI and zone XII (210°C), and the speed was 400rpm. The silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2mm thick sheet according to the standard and the performance was tested. The performance is shown in Table 1.

[0080] Comparative Example 1

[0081] According to the formula of Example 1, liquid silicone rubber, polycaprolactone, antioxidant and silane-modified polyurethane were fully mixed at 170°C and 160rpm, then discharged and cooled to room temperature; then uniformly mixed with hydrogenated silicone oil, platinum catalyst and inhibitor at room temperature to obtain a rubber-plastic premix; the rubber-plastic premix was placed in an internal mixer, the vulcanization temperature was set to 170°C, the speed was 160rpm, and the liquid silicone rubber / polycaprolactone thermoplastic vulcanizate TPV was obtained by dynamic vulcanization. TPV was pressed into a 2mm thick sheet according to the standard and the performance was tested. The performance test results are shown in Table 1.

[0082] Comparative Example 2

[0083] According to the formulation of Example 1, silicone rubber, polycaprolactone, hydrogenated silicone oil, antioxidant and compatibilizer were added to the pellet feed port of the twin-screw extruder at 210°C and 700rpm for melt blending, and then a platinum catalyst was added to the metering pump for dynamic vulcanization to obtain liquid silicone rubber / polycaprolactone thermoplastic vulcanizate TPV. TPV was pressed into a 2 mm thick sheet according to the standard and the performance was tested. The performance test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

[0087] In Table 1, the tensile strength is measured according to GB / T528-2009, the elongation at break is measured according to GB / T528-2009, and the hardness (Shore A) is measured according to GB / T 531.1-2008.

[0088] The difference between Examples 1-3 is that the speed of the single-stage twin-screw extruder is set differently. The speed of the single-stage twin-screw extruder determines the residence time of the material in the equipment; the faster the speed, the faster the extrusion speed and the shorter the vulcanization time. Compared with Example 2, the residence time of the material in Example 1 in the extruder is shortened and the vulcanization time is shortened. Compared with Example 2, the residence time of the material in Example 3 in the extruder is prolonged and the vulcanization time is prolonged.

[0089] The data in Table 1 show that among Examples 1-3, Example 2 has the largest tensile strength, elongation at break and hardness. Compared with Example 2, the tensile strength, elongation at break and hardness of Examples 1 and 3 are reduced. This indicates that too short or too long residence time of the material in the extruder is not conducive to dynamic vulcanization, resulting in reduced comprehensive performance of the prepared thermoplastic vulcanizate. The rotation speed used in Example 2 is the optimal rotation speed under this material system.

[0090] In Example 2, the twin-screw extruder is divided into five zones, and the length ratio of each zone is 1:1:1:7:2; in Examples 4 and 5, the twin-screw extruder is divided into three zones, and the length ratio of each zone is 3:7:2. Compared with Example 2, Examples 4 and 5 have fewer zones; compared with Example 2, Example 6 has the same number of zones, but different length ratios of each zone, and different temperatures of each zone. The data in Table 1 show that the tensile strength, elongation at break and hardness of the thermoplastic vulcanizate prepared in Examples 4 and 5 are reduced relative to Example 2. This shows that under the same material system as in the examples, the effect of dividing the twin-screw extruder into five zones is better than the effect of dividing the twin-screw extruder into three zones.

[0091] In Example 6, the twin-screw extruder is divided into five zones, and the length ratio of each zone is 1:1:8:1:1; compared with Example 2, the number of zones in Example 6 is the same, but the length ratio of each zone is different, and the temperature of each zone is different. The data in Table 1 show that the tensile strength, elongation at break and hardness of the thermoplastic vulcanizate prepared in Example 6 are reduced compared with Example 2. It shows that when the number of zones is the same, the change of the length ratio of each zone and the change of the temperature of each zone will affect the various properties of the prepared thermoplastic vulcanizate.

[0092] Comparative Examples 1 and 2 both adopt the existing preparation method and the raw material formula adopted is the same as that of Examples 1-6. Compared with Examples 1-6, the difference between Comparative Examples 1 and 2 is only that the preparation method adopted is different. The data in Table 1 show that the tensile strength, elongation at break and hardness of Comparative Examples 1 and 2 are significantly reduced relative to Examples 1-6. It is shown that the method of the present invention significantly improves the tensile strength, elongation at break and hardness of the prepared thermoplastic vulcanizate.

Claims

1. A method for preparing a thermoplastic vulcanized rubber, characterized in that: The preparation method comprises: the raw materials are heated to below T s The raw materials include rubber, plastic and vulcanization system; The variable temperature dynamic vulcanization is a continuous process; the temperature of the variable temperature dynamic vulcanization increases gradually from T1 to T n ; T2 to T n At least one of T k Preferably, T2 to T n-1 At least one of T k ; In T k The curing time under the condition is greater than that under the condition below T k The sum of the vulcanization time under the conditions; T s The lowest temperature at which dynamic vulcanization can be achieved; T k It is the optimal temperature for dynamic vulcanization; T1 is greater than or equal to the lowest temperature that can melt the raw materials and T s , less than or equal to T k ; T n Greater than or equal to T k , less than or equal to the maximum temperature at which dynamic vulcanization can be achieved; The n is selected from a natural number greater than or equal to 3.

2. The preparation method according to claim 1, characterized in that 5≤n≤15; preferably, 5≤n≤10.

3. The preparation method according to claim 1, characterized in that: The difference between two adjacent temperatures is 1 to 20°C, preferably 5 to 15°C.

4. The preparation method according to claim 1, characterized in that: The premix is ​​subjected to variable temperature dynamic vulcanization by a twin-screw extruder. The twin-screw extruder is divided into N zones, which are the first zone, ..., and the Nth zone from front to back. Correspondingly, the temperature of the first zone is T1, the temperature of the Nth zone is T2, and the temperature of the Nth zone is T3. n .

5. The preparation method according to claim 4, characterized in that: The twin-screw extruder is a single-stage twin-screw extruder; or / and, The twin-screw extruder is a twin-screw extruder that rotates in opposite directions.

6. The preparation method according to claim 4, characterized in that: N＝5； T1 is 145~155℃; T2 is 165-175°C; T3 is 175-185°C; T4 is 185-195°C; T5 is 205-215℃; The rotation speed of the single-stage twin-screw extruder is 100 to 1000 rpm, preferably 200 to 800 rpm, and more preferably 300 to 500 rpm.

7. The preparation method according to claim 1, characterized in that: The weight ratio of the rubber to the plastic is 40-90:60-10, preferably 50-70:50-30.

8. The preparation method according to claim 1, characterized in that: The rubber is a liquid rubber, preferably at least one selected from liquid silicone rubber, liquid styrene-butadiene rubber and liquid butadiene rubber; or / and, The plastic is selected from at least one of thermoplastic polyurethane, polycaprolactone, polylactic acid and polybutylene succinate; or / and, The vulcanization system includes hydrogen-containing silicone oil, a platinum catalyst and an inhibitor; wherein the platinum catalyst is selected from at least one of an isopropanol complex of chloroplatinic acid, a platinum catalyst coordinated with tetrahydrofuran and a platinum catalyst coordinated with methylvinylsiloxane; and the inhibitor is selected from at least one of an acetylenic alcohol inhibitor, an azo inhibitor and a heavy metal ion compound.

9. The preparation method according to claim 1, characterized in that: The raw materials also include a compatibilizer and an antioxidant; The compatibilizer is selected from at least one of silane-modified polyurethane and ethylene-methyl acrylate copolymer; The antioxidant is selected from at least one of hindered phenol antioxidants, phosphite antioxidants and thiopropionate antioxidants.

10. A thermoplastic vulcanizate, characterized in that: The method is described in any one of claims 1 to 9.

Images