A method for producing a thermoplastic vulcanizate and a thermoplastic vulcanizate produced thereby

Abstract

The present application relates to the technical field of thermoplastic vulcanized rubber, and particularly relates to a preparation method of thermoplastic vulcanized rubber and the prepared thermoplastic vulcanized rubber. s The preparation method comprises the following steps: mixing raw materials at a temperature lower than T n , to obtain a premix; performing temperature-variable dynamic vulcanization on the premix; the raw materials comprise rubber, plastic and a vulcanization system; the temperature-variable dynamic vulcanization is a continuous process; the temperature-variable dynamic vulcanization is gradually increased from T 1 to T 2 in sequence. The premix is melted at a lower temperature while dynamic vulcanization occurs; at this time, the dynamic vulcanization is slow and the degree of dynamic vulcanization is low. Since the vulcanization system, rubber and plastic in the premix are uniformly dispersed, the position where vulcanization begins at T 1 is uniformly dispersed rather than concentrated; thus, the problem of poor tensile strength, elongation at break and hardness of the thermoplastic vulcanized rubber prepared by the existing preparation method is solved.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic vulcanized rubber preparation technology, and more specifically, to a method for preparing thermoplastic vulcanized rubber and the prepared thermoplastic vulcanized rubber. Background Technology

[0002] Thermoplastic vulcanized rubber is mainly made from rubber and plastic 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 thermoplastic plastic, thus forming thermoplastic vulcanized rubber that has both the excellent elasticity of traditional rubber and the good processing properties of plastic.

[0003] To ensure that the vulcanized rubber particles are dispersed within the plastic, the raw materials need to be in a molten state before dynamic vulcanization. However, the temperature required to melt the raw materials is usually higher than the vulcanization temperature of the rubber. Therefore, it is necessary to prevent the rubber from vulcanizing while melting the raw materials. Thus, existing preparation methods include the following four: First, melting and mixing rubber, plastic, antioxidant, and compatibilizer, and then adding it to the vulcanization system for dynamic vulcanization; Second, melting and mixing rubber, plastic, antioxidant, compatibilizer, and vulcanizing agent, and then adding a catalyst for dynamic vulcanization; Third, melting and mixing rubber, plastic, antioxidant, and compatibilizer, then dividing it into two parts, adding a vulcanizing agent to one part and a catalyst to the other, and then mixing the two parts for dynamic vulcanization; Fourth, melting and mixing rubber, plastic, antioxidant, and compatibilizer, cooling, and then mixing it with the vulcanization system at room temperature to obtain a rubber-plastic premix, and then dynamically vulcanizing the premix.

[0004] The first three preparation methods all suffer from the following problems: before dynamic vulcanization, all raw materials are not mixed uniformly; there are always instances where the vulcanization system, catalyst, or vulcanizing agent within it is not fully mixed with the other raw materials. Therefore, dynamic vulcanization always occurs locally, leading to increased local viscosity and poor dispersibility of the rubber-plastic system. A uniformly dispersed rubber-plastic premix is ​​ideal for dynamic co-vulcanization; only with a uniformly dispersed premix can dynamic vulcanization yield thermoplastic vulcanized rubber with excellent tensile strength, elongation at break, and hardness. The fourth preparation method involves a cumbersome process, making continuous industrial production difficult. Although it avoids the problems described in the first three methods, the tensile strength, elongation at break, and hardness of the resulting thermoplastic vulcanized rubber are still relatively poor. Therefore, all four preparation methods suffer from poor tensile strength, elongation at break, and hardness of the resulting thermoplastic vulcanized rubber. Summary of the Invention

[0005] To address the problem that thermoplastic vulcanizates prepared by existing methods have poor tensile strength, elongation at break, and hardness, this invention proposes a new method for preparing thermoplastic vulcanizates, as well as the thermoplastic vulcanizates prepared using this method.

[0006] One of the objectives of this invention is to provide a novel method for preparing thermoplastic vulcanized rubber.

[0007] The method for preparing the thermoplastic vulcanized rubber includes: the raw materials are heated at a temperature below T... s The materials are mixed under temperature conditions to obtain a premix; the premix is ​​then subjected to variable temperature dynamic vulcanization; the raw materials include rubber, plastics, and a vulcanization system.

[0008] The variable-temperature dynamic vulcanization is a continuous process; the temperature of the variable-temperature dynamic vulcanization gradually increases from T1 to T2. n ;

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

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

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

[0012] T k The optimal temperature for dynamic vulcanization;

[0013] T1 is greater than or equal to the lowest temperature at which the raw material can melt, 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 highest temperature at which dynamic vulcanization can be achieved;

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

[0016] The gradient ascent involves maintaining a certain temperature for a period of time, then rising to another temperature and maintaining that temperature for a period of time.

[0017] Optimal temperature for dynamic vulcanization T kThis refers to the optimal temperature at which dynamic vulcanization produces thermoplastic vulcanizates with the best overall properties (e.g., optimal tensile strength, elongation at break, hardness (Shore A), and apparent condition). The optimal dynamic vulcanization temperature is determined based on the raw materials used; different raw materials result in different optimal dynamic vulcanization temperatures. In practice, the optimal dynamic vulcanization temperature can be determined experimentally; that is, the temperature at which the best overall properties of the prepared thermoplastic vulcanizate are obtained by dynamically vulcanizing the raw materials using any available method at different temperatures is the optimal dynamic vulcanization temperature T. k .

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

[0019] After the raw materials were determined, T s T k T1, T n This can be determined; specifically, the highest temperature, lowest temperature, and T that enable dynamic vulcanization. k All of these can be determined through preliminary experiments and 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 hydrogen-containing 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 For 60℃, T k The maximum temperature at which dynamic vulcanization can be achieved is 190℃, the maximum temperature is 210℃, and the minimum temperature is 120℃; T1 can be selected from any temperature greater than or equal to 120℃. n It can be selected from any temperature between 190°C and 210°C.

[0020] The mixing process can be achieved using any existing mixing equipment. The premixed material after mixing has the following states: 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 ​​similar to a date cake; the premix can be added to a twin-screw extruder without extrusion granulation.

[0021] T1 is greater than or equal to the lowest temperature at which the raw material can melt and the lowest temperature at which dynamic vulcanization can be achieved. sTherefore, at temperature T1, the premix can both melt and undergo dynamic vulcanization; that is, the premix melts and undergoes dynamic vulcanization simultaneously at temperature T1. 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 uniformly dispersed, the initial location of vulcanization at temperature T1 is uniformly dispersed rather than concentrated.

[0022] Then, vulcanization is carried out sequentially at higher temperatures. At T k Previously, the temperature was consistently below the optimal temperature for dynamic vulcanization, resulting in a slow process. As the degree of dynamic vulcanization gradually increased, the rubber viscosity and the molten plastic viscosity gradually became more compatible. When the temperature reached T... k At this point, the viscosity of the rubber gradually matches the viscosity of the molten plastic. Therefore, at T... k Under certain temperature conditions, the material exhibits good dispersibility. The longer the high-temperature shearing time is maintained under these 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.

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

[0024] The total vulcanization time is related to the material system. The total vulcanization time and temperature can be determined through preliminary experiments and static vulcanization. Once the total vulcanization time is determined, it is then determined that the vulcanization time is within the specified time (T). k The vulcanization time under the given conditions is greater than that under conditions below T. k The sum of vulcanization times under the given conditions can be arbitrarily allocated between T1 and T2. 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 achieve viscosity matching; the rubber and plastic viscosity matching refers to a rubber to plastic viscosity ratio of 1:(0.5~1.5). The minimum value of n is 3, meaning that dynamic vulcanization must be performed under at least 3 temperature conditions; in this case, T2 = T k The second temperature condition is the optimal temperature condition for dynamic vulcanization. Under the same raw material conditions, there exists an optimal value of n that results in the best overall performance of the prepared thermoplastic vulcanized rubber (e.g., optimal tensile strength, elongation at break, hardness (Shore A), and apparent condition). Typically, 5 ≤ n ≤ 15, and preferably, 5 ≤ n ≤ 10. In some embodiments disclosed in this invention, n = 5, T4 = T k .

[0026] Different raw material systems require different temperature gradient differences. These can be isothermal or non-isothermal. The difference between two adjacent temperatures can be determined by considering the time and temperature at which the rubber and plastic phases reach viscosity matching, as well as the constant (n). An optimal temperature gradient difference exists. Typically, the difference between two adjacent temperatures is 1–20°C, preferably 5–15°C. In some embodiments disclosed in this invention, the temperature difference is 10°C or 20°C.

[0027] The premix can be dynamically vulcanized at varying temperatures using a twin-screw extruder. The twin-screw extruder can be any existing twin-screw extruder capable of dynamic vulcanization. When the raw materials are mixed using an internal mixer, the mixer can also be connected in series with the twin-screw extruder; this further reduces processing steps and increases productivity.

[0028] Compared to two-stage twin-screw extruders, single-stage twin-screw extruders have only one set of screw drives, resulting in a simpler structure that is easier to operate, maintain, and clean, thus reducing operating costs. Due to its simpler structure, the manufacturing and maintenance costs of single-stage twin-screw extruders are also lower, leading to lower initial purchase and subsequent maintenance costs. Therefore, the preferred twin-screw extruder is a single-stage twin-screw extruder.

[0029] In practical operation, the twin-screw extruder can be divided into N zones, from front to back: Zone 1, ..., Zone N; correspondingly, the temperature of Zone 1 is T1, the temperature of Zone N is T... n The length ratio of each zone can be determined based on T. n The ratio of vulcanization time under specific temperature conditions is determined. Specifically, T... n The longer the vulcanization time under the given temperature conditions, the higher the temperature T. n The longer the corresponding zone, the better. Once the length ratio of each zone is determined, the vulcanization time of the material in each zone and at each temperature is further adjusted by adjusting the rotation speed of the twin-screw extruder. The length of the twin-screw extruder is fixed. With the length of each zone fixed, the higher the rotation speed, the shorter the vulcanization time in each zone (the effect of temperature on material flowability can be ignored).

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

[0031] The rotational speed of the single-stage twin-screw extruder is 100–1000 rpm, preferably 200–800 rpm, more preferably 200–600 rpm, and even more preferably 300–500 rpm. For example, 400 rpm.

[0032] According to some embodiments disclosed in this 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, preferably selected from at least one of liquid silicone rubber, liquid styrene-butadiene rubber, and liquid cis-butadiene rubber.

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

[0036] 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 isopropanol complexes of chloroplatinic acid, platinum catalysts coordinated with tetrahydrofuran, and platinum catalysts coordinated with methylvinylsiloxane; and the inhibitor is selected from at least one of alkynyl alcohol inhibitors, azo inhibitors, and heavy metal ion compounds.

[0037] The raw materials also include compatibilizers and antioxidants;

[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 phenolic antioxidants, phosphite antioxidants, and thiopropionic acid ester antioxidants.

[0040] The second objective of this invention is to provide a thermoplastic vulcanized rubber.

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

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] This provides a new preparation process for the preparation of thermoplastic vulcanizates.

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

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

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

[0047] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

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

[0049] The liquid silicone rubber is from Anbia Specialty Silicones Co., Ltd., and its model number is VS165000.

[0050] Polycaprolactone (Mn = 50000) is from Tianjin Xins Biochemical Technology Co., Ltd.

[0051] The silane-modified polyurethane is from Meirui New Materials Co., Ltd., model number V-175;

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

[0053] The platinum catalyst is a methyl vinylsiloxane-coordinated platinum catalyst from Zijun Chemical Co., Ltd., with a Pt content of 100-10000 ppm.

[0054] The inhibitor is alkynol M622 from Guangzhou Silicon Friends New Materials Technology Co., Ltd.

[0055] The antioxidant is Antioxidant 1010 from BASF.

[0056] Example 1

[0057] The selected raw materials and their weight proportions 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] Inhibitor 1.2 parts by weight;

[0064] Antioxidant 0.1 parts by weight.

[0065] The minimum temperature at which all raw materials can melt is 60°C.

[0066] The highest temperature at which dynamic vulcanization can be achieved is 210℃;

[0067] The lowest temperature at which dynamic vulcanization can be achieved is 120℃

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

[0069] According to the above formula, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in an internal mixer at room temperature (30℃, the same below) to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which consisted of 12 zones (each zone of equal length, the same below). The temperatures were set to Zone I (150℃), Zone II (170℃), Zone III (180℃), Zones IV-X (190℃), Zone XI, and Zone XII (210℃), with a rotation speed of 200 rpm, for dynamic vulcanization to obtain silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0070] Example 2

[0071] According to the formulation of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in a Banbury mixer at room temperature to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which had 12 zones with temperatures set at Zone I (150°C), Zone II (170°C), Zone III (180°C), Zones IV-X (190°C), Zone XI, and Zone XII (210°C), and a rotation speed of 400 rpm for dynamic vulcanization to obtain a silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0072] Example 3

[0073] According to the formulation of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in a Banbury mixer at room temperature to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which had 12 zones with temperatures set at Zone I (150°C), Zone II (170°C), Zone III (180°C), Zones IV-X (190°C), Zone XI, and Zone XII (210°C), and a rotation speed of 600 rpm for dynamic vulcanization to obtain a silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0074] Example 4

[0075] According to the formulation of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in a Banbury mixer at room temperature to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which had 12 zones set to temperatures of zones I-III (170°C), IV-X (190°C), XI, and XII (210°C), and a rotation speed of 400 rpm for dynamic vulcanization to obtain a silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0076] Example 5

[0077] According to the formulation of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in a Banbury mixer at room temperature to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which had 12 zones set to temperatures of zones I-III (150°C), IV-X (190°C), XI, and XII (210°C), and a rotation speed of 400 rpm for dynamic vulcanization to obtain a silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0078] Example 6

[0079] According to the formulation of Example 1, silicone rubber, polycaprolactone, antioxidant, silane-modified polyurethane, and the vulcanization system were thoroughly mixed in a Banbury mixer at room temperature to obtain a rubber-plastic premix. The premix was then transferred to a twin-screw extruder, which had 12 zones set to temperatures of Zone I (160°C), Zone II (170°C), Zones III-X (180°C), Zone XI, and Zone XII (210°C), and a rotation speed of 400 rpm for dynamic vulcanization to obtain a silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance is shown in Table 1.

[0080] Comparative Example 1

[0081] According to the formulation of Example 1, liquid silicone rubber, polycaprolactone, antioxidant, and silane-modified polyurethane were thoroughly mixed at 170°C and 160 rpm, then discharged and cooled to room temperature. At room temperature, the mixture was then uniformly mixed with hydrogen-containing silicone oil, platinum catalyst, and inhibitor to obtain a rubber-plastic premix. The premix was placed in an internal mixer, and vulcanization was performed at 170°C and 160 rpm to obtain a liquid silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance test results are shown in Table 1.

[0082] Comparative Example 2

[0083] According to the formulation in Example 1, silicone rubber, polycaprolactone, hydrogen-containing silicone oil, antioxidants, and compatibilizers were fed into the pellet feed inlet of a twin-screw extruder at 210°C and 700 rpm for melt blending. Then, a platinum catalyst was added via a metering pump, and dynamic vulcanization was performed to obtain liquid silicone rubber / polycaprolactone thermoplastic vulcanizate (TPV). The TPV was pressed into 2 mm thick sheets according to standards, and its performance was tested. The performance test results are shown in Table 1.

[0084] Table 1

[0085]

[0086]

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

[0088] The only difference between Examples 1-3 is the rotational speed of the single-stage twin-screw extruder. The rotational 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 to Example 2, the residence time of the material in the extruder and the vulcanization time are both shortened in Example 1. Compared to Example 2, the residence time of the material in the extruder and the vulcanization time are both extended in Example 3.

[0089] The data in Table 1 show that, among Examples 1-3, Example 2 exhibits the highest tensile strength, elongation at break, and hardness. Compared to Example 2, the tensile strength, elongation at break, and hardness of Examples 1 and 3 decrease. This indicates that both excessively short and excessively long residence times of the material in the extruder are detrimental to dynamic vulcanization, leading to a reduction in the overall performance of the prepared thermoplastic vulcanizate. The rotational speed used in Example 2 represents the optimal speed for this material system.

[0090] Example 2 divided the twin-screw extruder into five zones with a length ratio of 1:1:1:7:2; Examples 4 and 5 divided the twin-screw extruder into three zones with a length ratio of 3:7:2. Compared to Example 2, Examples 4 and 5 had fewer zones; compared to Example 2, Example 6 had the same number of zones, but different length ratios and temperatures in each zone. Table 1 shows that the tensile strength, elongation at break, and hardness of the thermoplastic vulcanized rubber prepared in Examples 4 and 5 decreased compared to Example 2. This indicates that, under the same material system, dividing the twin-screw extruder into five zones is more effective than dividing it into three zones.

[0091] Example 6 divided the twin-screw extruder into five zones with a length ratio of 1:1:8:1:1. Compared to Example 2, Example 6 had the same number of zones, but the length ratios and temperatures of each zone differed. Table 1 shows that the tensile strength, elongation at break, and hardness of the thermoplastic vulcanizate prepared in Example 6 decreased compared to Example 2. This indicates that, with the same number of zones, changes in the length ratios and temperatures of each zone affect the properties of the prepared thermoplastic vulcanizate.

[0092] Comparative Examples 1 and 2 both used existing preparation methods and the same raw material formulations as Examples 1-6. The only difference between Comparative Examples 1 and 2 and Examples 1-6 is the preparation method used. Table 1 shows that, compared to Examples 1-6, the tensile strength, elongation at break, and hardness of Comparative Examples 1 and 2 are significantly reduced. This indicates 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 thermoplastic vulcanized rubber, characterized in that, The preparation method includes: the raw materials are heated at a temperature below T... s The materials are mixed under temperature conditions to obtain a premix; the premix is ​​then subjected to variable temperature dynamic vulcanization; the raw materials include rubber, plastics, and a vulcanization system. The variable-temperature dynamic vulcanization is a continuous process; the temperature of the variable-temperature dynamic vulcanization gradually increases from T1 to T2. n ; T2 to T n At least one of them is selected from T k ; In T k The vulcanization time under the given conditions is greater than that under conditions below T. k The sum of vulcanization times under the given conditions; T s The minimum temperature at which dynamic vulcanization can be achieved; T k The optimal temperature for dynamic vulcanization refers to the temperature at which thermoplastic vulcanized rubber exhibits the best overall performance. T1 is greater than or equal to the lowest temperature at which the raw material can melt 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 highest temperature at which dynamic vulcanization can be achieved; 5≤n≤15； The difference between two adjacent temperatures is 1 to 20°C; The rubber is a liquid rubber; The premix is ​​vulcanized using a twin-screw extruder to achieve variable temperature dynamic vulcanization. The twin-screw extruder is divided into N zones, numbered from front to back as zone 1, ..., zone N. Correspondingly, the temperature of zone 1 is T1, and the temperature of zone N is T. n ; N=5； T1 is 145–155℃; T2 is 165–175℃; T3 is 175–185℃; T4 is 185–195℃; T5 is 205~215℃.

2. The preparation method according to claim 1, characterized in that, T2 to T n-1 At least one of them is selected from T k ; or / and, The vulcanization time at the optimal dynamic vulcanization temperature should be greater than the sum of the vulcanization times at other temperatures; or / and, 5 ≤ n ≤ 10; or / and, The difference between two adjacent temperatures is 5 to 15°C.

3. The preparation method according to claim 1, 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.

4. The preparation method according to claim 3, characterized in that, The rotational speed of the single-stage twin-screw extruder is 100–1000 rpm.

5. The preparation method according to claim 3, characterized in that, The rotational speed of the single-stage twin-screw extruder is 200–800 rpm.

6. The preparation method according to claim 3, characterized in that, The rotational speed of the single-stage twin-screw extruder is 300–500 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.

8. The preparation method according to claim 1, characterized in that, The weight ratio of the rubber to the plastic is 50-70:50-30.

9. The preparation method according to claim 1, characterized in that, The liquid rubber is selected from at least one of liquid silicone rubber, liquid styrene-butadiene rubber, and liquid cis-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 isopropanol complexes of chloroplatinic acid, platinum catalysts coordinated with tetrahydrofuran, and platinum catalysts coordinated with methylvinylsiloxane; and the inhibitor is selected from at least one of alkynyl alcohol inhibitors, azo inhibitors, and heavy metal ion compounds.

10. The preparation method according to claim 1, characterized in that, The raw materials also include compatibilizers and antioxidants; 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 phenolic antioxidants, phosphite antioxidants, and thiopropionic acid ester antioxidants.

11. A thermoplastic vulcanized rubber, characterized in that, It is prepared by the preparation method described in any one of claims 1-10.

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