Liquid natural rubber, ultra-high-hardness easily-processed apex rubber composition as well as preparation method and application of apex rubber composition

Abstract

The invention discloses liquid natural rubber, an ultrahigh-hardness easily-processed apex rubber composition as well as a preparation method and application of the liquid natural rubber and the ultrahigh-hardness easily-processed apex rubber composition. The liquid natural rubber is prepared by carrying out aerobic cracking on plasticated natural rubber in a screw shearing manner. The liquid natural rubber which can be cross-linked and has plasticizing capacity is developed, the molecular weight range of the liquid natural rubber is controlled, it is guaranteed that the liquid natural rubber can easily form a cross-linked network through sulfur and an accelerant, and the liquid natural rubber has an excellent plasticizing effect when not cross-linked. The liquid natural rubber is introduced into the apex rubber composition for plasticizing, so that the processability is improved, meanwhile, the influence on the hardness and modulus of vulcanized rubber can be reduced by virtue of the crosslinkable property of the liquid natural rubber, and meanwhile, the modulus and hardness are further optimized by virtue of phenolic resin, so that the composition has the characteristics of easiness in processing and ultrahigh hardness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tire production, in particular to a liquid natural rubber, super-high-hardness and easy-to-process bead rubber composition, and a preparation method and application thereof. BACKGROUND

[0002] The bead rubber (also known as the bead filler) of a tire is an important component in tire manufacturing, which is mainly installed near the tire bead (the part where the rim contacts the tire) and is usually located between the steel wire bead (or rim bead) and the air barrier layer. It mainly serves to preserve air, improve the structural stability of the tire bead area, provide additional rigidity, reduce the deformation of the bead during high-load or high-speed driving, and transmit drive.

[0003] Currently, the bead rubber compositions on the market mostly use natural rubber and synthetic rubber in combination, and achieve high hardness and high modulus by adding a large amount of carbon black and sulfur. However, this design has a negative effect of high heat generation and poor processing performance of the bead rubber.

[0004] Currently, there have been many studies to improve the heat generation performance of the bead rubber. For example, the published invention patent CN119751989A developed a high-hardness and low-heat-generation bead rubber compound, but the hardness of the bead rubber could only reach 83. The published invention patent CN117844071A developed a bead rubber composition for special off-road tires, but the hardness of the bead rubber was at most 88.

[0005] With the rapid development of new energy vehicles, high control requirements are also put forward for tires, so the traditional high and medium hardness bead rubber compositions cannot meet the needs of high-performance new energy tires. Therefore, it is an urgent need in the current industry to develop a super-high-hardness and easy-to-process bead rubber composition. SUMMARY

[0006] To solve the problems in the prior art, the present application provides a liquid natural rubber, super-high-hardness and easy-to-process bead rubber composition, and a preparation method and application thereof. The present application uses high molecular weight liquid natural rubber prepared by aerobic cleavage of natural rubber to invent a super-high-hardness and easy-to-process bead rubber composition, which can improve the control and response performance of high-performance tires for new energy vehicles, and at the same time solve the problem of difficult processing of high-hardness bead rubber.

[0007] One of the purposes of the present application is to provide a liquid natural rubber prepared by aerobic cleavage of plasticated natural rubber using screw shearing.

[0008] In a preferred embodiment of the present application,

[0009] The number average molecular weight of the liquid natural rubber is 35000-50000 g / mol, and the molecular weight distribution is 1-3; preferably, the number average molecular weight of the liquid natural rubber is 40000-50000 g / mol, and the molecular weight distribution is 1.8-2.6.

[0010] A second object of the present application is to provide a preparation method of the liquid natural rubber of one of the objects of the present application, comprising the step of performing aerobic cleavage on the plasticated natural rubber by screw shearing; preferably,

[0011] The preparation method of the liquid natural rubber comprises the following steps:

[0012] 1) plasticating the natural rubber;

[0013] 2) feeding the plasticated natural rubber into a first screw extruder for preheating and softening;

[0014] 3) feeding the preheated and softened natural rubber into a second screw extruder for thermal degradation in an aerobic environment;

[0015] 4) feeding the thermally degraded natural rubber into a third screw extruder for cooling and discharging to obtain the liquid natural rubber.

[0016] In a preferred embodiment of the present application,

[0017] In step 1),

[0018] The plastication is performed in an internal mixer, preferably, the rotor speed of the internal mixer is 35-60 rpm, the filling coefficient is 0.5-0.8, and the plastication time is 120-300 s; rpm is r / min; and / or,

[0019] The Mooney viscosity [ML(1+4)100℃] of the plasticated natural rubber is 90-130; and / or,

[0020] In step 2),

[0021] The first screw extruder is at least one of a single screw extruder; preferably, the control temperature of the single screw extruder is 150-200℃, the length-diameter ratio of the screw is 30-60, and the screw speed is 28-40 rpm to realize temperature-controlled conveying; and / or,

[0022] In step 3),

[0023] The second screw extruder is at least one of a twin-screw extruder, and the twin-screw extruder is provided with an air inlet for introducing oxygen to form an aerobic environment and an air outlet for discharging excess gas, the air inlet and the air outlet are formed on the side of the barrel of the twin-screw extruder, and the forming means is any conventional means in the art, which is not specially limited in the present application as long as the air inlet can smoothly introduce oxygen and the air outlet can smoothly discharge excess gas; preferably,

[0024] The length-diameter ratio of the screw of the twin-screw extruder is 30-90, the screw rotation speed is 50-100 rpm, the control temperature is 220-400℃, and the screw is divided into a temperature rising section, a shearing section and a temperature reducing section to control the temperature, the temperature rising section control temperature is 220-300℃, the shearing section control temperature is 300-400℃, and the temperature reducing section control temperature is 220-280℃; more preferably,

[0025] The air inlet is located on the side of the barrel at the junction of the temperature rising section and the shearing section, and the air outlet is located on the side of the barrel at the junction of the temperature reducing section and the shearing section; and / or,

[0026] The introduction speed of oxygen through the air inlet is 0.5-3 L / min; the introduction speed of oxygen can only ensure that the shearing section is filled with oxygen; and / or,

[0027] The length ratio of the temperature rising section, the shearing section and the temperature reducing section is 1:(1-3):(0.5-2); and / or,

[0028] In step 4),

[0029] The third screw extruder is at least one of a twin-screw extruder; preferably, the screw rotation speed of the twin-screw extruder is 35-55 rpm, and the length-diameter ratio of the screw is 30-60; and / or,

[0030] The heat-degraded natural rubber is sent into the third screw extruder to cool to 60-100℃ to discharge the rubber.

[0031] The preparation of the liquid natural rubber in the present application can adopt the following specific technical solutions:

[0032] Firstly, the natural rubber is plasticized, and the Mooney viscosity [ML(1+4)100℃] is controlled to be 90-130;

[0033] Secondly, the plasticized natural rubber is preheated and softened by a single screw extruder, the single screw control temperature is 150-200℃, and the screw rotation speed is 28-40 rpm;

[0034] In the third step, the softened natural rubber is preheated and enters a double screw extruder with an air inlet and an air outlet, so that the natural rubber is subjected to thermal degradation in an oxygen environment, the temperature of the double screw is controlled at 220-400 DEG C, and the rotation speed is 50-100 rpm.

[0035] In the fourth step, the thermally degraded natural rubber enters a double screw extruder for cooling, the rotation speed of the screw is 35-55 rpm, and the rubber is discharged after being cooled to 60-100 DEG C.

[0036] The third object of the present application is to provide a super-high-hardness and easy-to-process triangular rubber composition, which comprises a base rubber component, a reinforcing component, a plasticizing component, and a phenolic resin.

[0037] In a preferred embodiment of the present application,

[0038] The base rubber component is selected from at least one of natural rubber, isoprene rubber, styrene-butadiene rubber, and butadiene rubber, preferably the base rubber component is natural rubber; and / or,

[0039] The reinforcing component is selected from at least one of carbon black, silicon dioxide, kaolin, pottery clay, calcium carbonate, and diatomite, preferably the reinforcing component is carbon black; and / or,

[0040] The phenolic resin is selected from one or more of modified or unmodified phenolic resins, preferably the modified phenolic resin is selected from one or more of tall oil modified phenolic resin, cashew oil modified phenolic resin, and cardanol modified phenolic resin, preferably one or more of cardanol modified phenolic resin.

[0041] In a preferred embodiment of the present application,

[0042] The reinforcing component is 60-80 parts by weight, the plasticizing component is 5-20 parts by weight, and the phenolic resin is 10-20 parts by weight, based on 100 parts by weight of the base rubber component; preferably, the reinforcing component is 70-80 parts by weight, the plasticizing component is 5-15 parts by weight, and the phenolic resin is 12-18 parts by weight, based on 100 parts by weight of the base rubber component.

[0043] In a preferred embodiment of the present application,

[0044] The triangular rubber composition further comprises an accelerator and a vulcanizing agent; preferably,

[0045] The accelerator is 1-6 parts by weight, and the vulcanizing agent is 1-10 parts by weight, based on 100 parts by weight of the base rubber component.

[0046] The accelerator and vulcanizing agent can be any conventional accelerator and vulcanizing agent in the art, and are not particularly limited in the present application.

[0047] The rubber composition of the triangular rubber also comprises conventional components in the art, such as anti-aging agents, zinc oxide, stearic acid, etc., and the amount of the components is also conventional, and the skilled person in the art can add them according to the actual situation.

[0048] The fourth object of the present application is to provide a preparation method of the ultra-high hardness and easy-to-process rubber composition of the triangular rubber of the third object of the present application, which comprises the steps of mixing the components comprising the base rubber component, the reinforcing component, the plasticizing component and the phenolic resin, and then adding the vulcanizing agent and the accelerator for final mixing. The mixing and final mixing are both conventional mixing and final mixing processes in the art, and are not particularly limited in the present application.

[0049] The fifth object of the present application is to provide the application of the ultra-high hardness and easy-to-process rubber composition of the triangular rubber of the third object of the present application or the ultra-high hardness and easy-to-process rubber composition of the triangular rubber prepared by the preparation method of the fourth object of the present application in the field of tires.

[0050] The beneficial effects of the technical solution are: compared with the prior art, the present application develops a liquid natural rubber which can be crosslinked and has plasticizing ability. By controlling the molecular weight range, it is ensured that it is easy to form a crosslinked network through sulfur and accelerator, and it has excellent plasticizing effect when not crosslinked. In the design of the rubber composition of the triangular rubber, the liquid natural rubber is introduced for plasticizing, which improves the processing performance. At the same time, the crosslinkability of the liquid natural rubber can reduce the influence on the hardness and modulus of the vulcanized rubber, and the specific phenolic resin is used to further optimize the modulus and hardness, so that the composition has the characteristics of easy processing and ultra-high hardness. DETAILED DESCRIPTION

[0051] The following specific embodiments are used to specifically describe the present application, and it is necessary to point out that the following embodiments are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments of the present application made by the skilled person in the art according to the content of the present application still belong to the protection scope of the present application.

[0052] The equipment used in the embodiments of the present application, such as the internal mixer, the single-screw extruder and the double-screw extruder, are all conventional equipment in the art. The gas inlet and the gas outlet of the double-screw extruder with the gas inlet and the gas outlet are opened on the side of the barrel of the conventional double-screw extruder. The gas inlet is located on the side of the barrel at the junction of the screw heating section and the shearing section, and the gas outlet is located on the side of the barrel at the junction of the screw cooling section and the shearing section. The opening means is any conventional means in the art, and is not particularly limited in the present application.

[0053] Preparation of liquid natural rubber:

[0054] Preparation Example 1

[0055] 100 parts by weight of natural rubber (Yunbiao No. 1 SCRWF) was added into an internal mixer for plasticizing, the rotor speed was 45 r / min, the filling coefficient was 0.6, and the plasticizing time was 300 s, to obtain a material with a temperature of 105°C and a Mooney viscosity value of 110; then the material was introduced into a single screw extruder (the length-diameter ratio of the screw was 30) through a continuous closed feeding device for preheating and softening, the temperature was controlled at 180°C, and the screw speed was 35 r / min; then the material was introduced into a double screw extruder with an air inlet and an air outlet through a continuous closed feeding device for thermal degradation in an aerobic environment (the oxygen inlet speed of the air inlet was 1 L / min), the length-diameter ratio of the screw was 60, the screw speed was 60 r / min, the screw was divided into a temperature control section (the length ratio of the heating section, the shearing section and the cooling section was 1:1:1), the conveying section temperature of the screw extruder was controlled at 220°C, the shearing section temperature was controlled at 350°C, and the cooling section temperature was controlled at 220°C; then the material was introduced into a double screw extruder through a conveying device, the length-diameter ratio of the screw was 50, the screw speed was 35 r / min, the barrel and core temperature of the double screw extruder was controlled at 60°C, the gas was removed, and the liquid natural rubber with a temperature below 100°C, a number average molecular weight Mn of 48000 g / mol and a molecular weight distribution of 1.9 was obtained.

[0056] Preparation Example 2

[0057] 100 parts by weight of natural rubber (Yunbiao No. 1 SCRWF) was added into an internal mixer for plasticizing, the rotor speed was 55 r / min, the filling coefficient was 0.6, and the plasticizing time was 240 s, to obtain a material with a temperature of 115°C and a Mooney viscosity value of 100; then the material was introduced into a single screw extruder (the length-diameter ratio of the screw was 30) through a continuous closed feeding device for preheating and softening, the temperature was controlled at 180°C, and the screw speed was 35 r / min; then the material was introduced into a double screw extruder with an air inlet and an air outlet through a continuous closed feeding device for thermal degradation in an aerobic environment (the oxygen inlet speed of the air inlet was 1 L / min), the length-diameter ratio of the screw was 60, the screw speed was 80 r / min, the screw was divided into a temperature control section (the length ratio of the heating section, the shearing section and the cooling section was 1:1:1), the conveying section temperature of the screw extruder was controlled at 220°C, the shearing section temperature was controlled at 360°C, and the cooling section temperature was controlled at 220°C; then the material was introduced into a double screw extruder through a conveying device, the length-diameter ratio of the screw was 50, the screw speed was 35 r / min, the barrel and core temperature of the double screw extruder was controlled at 45°C, the gas was removed, and the liquid natural rubber with a temperature below 100°C, a number average molecular weight Mn of 44000 g / mol and a molecular weight distribution of 2.3 was obtained.

[0058] Preparation Example 3

[0059] 100 parts by weight of natural rubber (Yunbiao No. 1 SCRWF) was added into an internal mixer for plasticizing, the rotor speed was 60 r / min, the filling coefficient was 0.6, and the mixing time was 210 s, so that a material with a temperature of 122°C and a Mooney viscosity value of 95 was obtained; then the material was introduced into a single-screw extruder (the length-diameter ratio of the screw was 30) through a continuous closed feeding device for preheating and softening, the temperature was controlled at 200°C, and the screw speed was 35 r / min; then the material was introduced into a double-screw extruder with an air inlet and an air outlet through a continuous closed feeding device for thermal degradation in an aerobic environment (the oxygen inlet speed of the air inlet was 1 L / min), the length-diameter ratio of the screw was 60, the screw speed was 90 r / min, the screw was divided into a temperature-raising section, a shearing section and a temperature-lowering section for section control of the temperature (the length ratio of the temperature-raising section, the shearing section and the temperature-lowering section was 1:1:1), the conveying section temperature of the screw extruder was controlled at 220°C, the shearing section temperature was controlled at 360°C, and the cooling section temperature was controlled at 220°C; then the material was introduced into a double-screw extruder through a conveying device, the length-diameter ratio of the screw was 50, the screw speed was 35 r / min, the barrel and the core shaft of the screw extruder were controlled at a temperature of 40°C, the gas was removed, and a liquid natural rubber with a temperature below 100°C, a number average molecular weight Mn of 40000 g / mol and a molecular weight distribution of 2.1 was obtained by extrusion.

[0060] Preparation of the triangular rubber composition:

[0061] The formulations of the triangular rubber compositions of Comparative Examples 1-3, the Reference Example (the formulation of the Reference Example is a commonly used formulation of the triangular rubber composition in the prior art) and Examples 1-5 are shown in Table 1:

[0062] Table 1

[0063]

[0064] The Reference Example, the Comparative Examples and the Examples were all prepared according to the same mixing and finishing processes, and the specific process was as follows:

[0065] Mixing process:

[0066] 1. Add natural rubber, SBR1500 rubber (if any), and press the ram to mix for 25 s at a speed of 50 rpm;

[0067] 2. Raise the ram, add carbon black, environmentally friendly oil (if any), liquid natural rubber, zinc oxide, stearic acid, antioxidant, plasticizer A (if any), and SL-2201Y resin, press the ram to mix to 125°C at a speed of 50 rpm;

[0068] 3. Raise the ram to the position and keep for 5 s at a speed of 50 rpm;

[0069] 4. Press the top bolt to 150℃, the speed of 50 rpm;

[0070] 5. The extruder tabletting skin to get the mixing rubber.

[0071] Final refining process:

[0072] 1. Add the mixing rubber, sulfur, accelerator, resorcinol-80 (if any), RA-65 (if any), press the top bolt to 75℃, the speed of 28 rpm;

[0073] 2. Press the top bolt to 97℃, the speed of 28 rpm;

[0074] 3. The extruder tabletting skin to get the final refining rubber.

[0075] The final refining rubber is vulcanized at 160℃ for 15 min by a flat vulcanizing machine to prepare test pieces for hardness test. The hardness test refers to GB / T 531.1-2008 / ISO 7619-1:2004. The higher the hardness, the better the control and response. The processing performance is characterized by the Mooney viscosity of the mixing rubber. The Mooney viscosity test refers to GB / T 1232.1-2016 / ISO 289-1:2014. The lower the Mooney viscosity, the easier the processing. The test results are shown in Table 2.

[0076] Table 2

[0077]

[0078] From the examples and comparative examples, it can be seen that:

[0079] Comparative example 1 and comparative example 2 use the plasticizing component environmental oil commonly used in the prior art. Although the Mooney viscosity can be reduced by increasing the environmental oil, the hardness is reduced. However, example 2 of the present application uses liquid natural rubber as a plasticizing component, which can not only reduce the Mooney viscosity, but also improve the hardness.

[0080] Although comparative example 3 also uses liquid natural rubber as a plasticizer, the number average molecular weight is low, so the hardness is not as good as example 2.

[0081] Examples 1-5 of the present application control the molecular weight range of liquid natural rubber to ensure that it can easily form a crosslinked network with sulfur and accelerators, and has excellent plasticizing effect when not crosslinked. In the design of the triangular rubber composition, the liquid natural rubber is introduced for plasticizing, which improves the processing performance. At the same time, the crosslinkability of the liquid natural rubber can reduce the influence on the hardness and modulus of the vulcanized rubber, so that the composition has the characteristics of easy processing and ultra-high hardness.

[0082] The foregoing is a description of the embodiments of the present application. The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A liquid natural rubber prepared by aerobic cracking of masticated natural rubber using a screw shearing method.

2. The liquid natural rubber according to claim 1, wherein: The number average molecular weight of the liquid natural rubber is 35,000-50,000 g / mol, and the molecular weight distribution is 1-3; preferably, the number average molecular weight of the liquid natural rubber is 40,000-50,000 g / mol, and the molecular weight distribution is 1.8-2.

6.

3. A method for preparing the liquid natural rubber according to any one of claims 1 to 2, comprising the step of aerobic cracking of the masticated natural rubber by screw shearing; preferably, The preparation method of the liquid natural rubber comprises the following steps: 1) Plasticizing natural rubber; 2) feeding the plasticized natural rubber into a first screw extruder for preheating and softening; 3) feeding the preheated and softened natural rubber into a second screw extruder for thermal degradation in an aerobic environment; 4) sending the thermally degraded natural rubber into a third screw extruder for cooling and debonding to obtain the liquid natural rubber.

4. The preparation method according to claim 3, wherein: In step 1), The mastication is carried out in an internal mixer, preferably, the rotor speed of the internal mixer is 35-60 rpm, the filling factor is 0.5-0.8, and the mastication time is 120-300 s; and / or, The natural rubber has a Mooney viscosity of 90-130 after mastication; and / or In step 2), The first screw extruder is at least one of a single screw extruder; preferably, the control temperature of the single screw extruder is 150-200° C., the aspect ratio of the screw is 30-60, and the screw speed is 28-40 rpm; and / or, In step 3), The second screw extruder is at least one of a twin-screw extruder, and the twin-screw extruder has an air inlet and an optional exhaust port; preferably, The twin-screw extruder has a screw length-diameter ratio of 30-90, a screw speed of 50-100 rpm, a controlled temperature of 220-400°C, and the screw is divided into a heating section, a shearing section, and a cooling section for segmented temperature control. The heating section is controlled at 220-300°C, the shearing section is controlled at 300-400°C, and the cooling section is controlled at 220-280°C. More preferably, The air inlet is located on the side of the barrel at the junction of the temperature rising section and the shearing section, and the exhaust port is located on the side of the barrel at the junction of the temperature falling section and the shearing section; and / or, The oxygen introduction rate of the air inlet is 0.5-3 L / min; and / or, The length ratio of the heating section, the shearing section and the cooling section is 1:(1-3):(0.5-2); and / or, In step 4), The third screw extruder is at least one of a twin-screw extruder; preferably, the screw speed of the twin-screw extruder is 35-55 rpm, and the aspect ratio of the screw is 30-60; and / or, The thermally degraded natural rubber is fed into the third screw extruder and cooled to 60-100°C for rubber discharge.

5. An ultra-high hardness and easy-to-process apex rubber composition, comprising a base rubber component, a reinforcing component, a plasticizing component and a phenolic resin, wherein: The plasticizing component is the liquid natural rubber described in any one of claims 1-2 or the liquid natural rubber prepared by the preparation method described in any one of claims 3-4.

6. The apex rubber composition according to claim 5, wherein: The base rubber component is selected from at least one of natural rubber, isoprene rubber, styrene-butadiene rubber, and butadiene rubber. Preferably, the base rubber component is natural rubber; and / or, The reinforcing component is selected from at least one of carbon black, silicon dioxide, kaolin, clay, calcium carbonate, and diatomaceous earth. Preferably, the reinforcing component is carbon black; and / or, The phenolic resin is selected from one or more modified or unmodified phenolic resins. Preferably, the modified phenolic resin is selected from one or more of tall oil modified phenolic resin, cashew oil modified phenolic resin, and cardanol modified phenolic resin, preferably one or more of cardanol modified phenolic resin.

7. The apex rubber composition according to claim 5, wherein: Based on 100 parts by weight of the base rubber component, the reinforcing component is 60-80 parts by weight, the plasticizing component is 5-20 parts by weight, and the phenolic resin is 10-20 parts by weight; preferably, based on 100 parts by weight of the base rubber component, the reinforcing component is 70-80 parts by weight, the plasticizing component is 5-15 parts by weight, and the phenolic resin is 12-18 parts by weight.

8. The apex rubber composition according to any one of claims 5 to 7, wherein: The apex rubber composition further comprises an accelerator and a vulcanizing agent; preferably, Based on 100 parts by weight of the base rubber component, the accelerator is 1-6 parts by weight, and the vulcanizer is 1-10 parts by weight.

9. A method for preparing an apex rubber composition as claimed in any one of claims 5 to 8, comprising the steps of mixing components including a base rubber component, a reinforcing component, a plasticizing component and a phenolic resin and then adding a vulcanizing agent and an accelerator for final mixing.

10. Use of the apex rubber composition according to any one of claims 5 to 8 or the apex rubber composition prepared by the preparation method according to claim 9 in the field of tires.

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