Ultraheat-resistant low-hardness nitrile rubber and preparation method thereof

Abstract

The raw material formula of the ultra-heat-resistant low-hardness nitrile rubber comprises the following raw materials in parts by weight: 100 parts of nitrile rubber formed by emulsion polymerization of butadiene and acrylonitrile; 15 to 25 parts of white carbon black; 0.1 to 1 part of sulfur; 1.5 to 2 parts of a vulcanization accelerator TMTD (tetramethylthiuram disulfide); 1.5 to 2.5 parts of 2, 5 dimethyl 2, 5 di (tert-butyl peroxide) hexane; 15-25 parts of a heat-resistant filler; 30-40 parts of a plasticizer; 5-10 parts of an active agent; and 1-2 parts of physical protection wax. The temperature-resistant components mainly comprise the raw nitrile rubber with the acrylonitrile content of 33%, the white carbon black, the calcium silicate and the zinc oxide, compared with an existing nitrile rubber composition, the nitrile rubber composition has good heat resistance due to the adoption of the white carbon black, the calcium silicate and the zinc oxide, in addition, the cost is reduced, and the nitrile rubber composition has higher application value.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber and relates to a super heat-resistant low-hardness nitrile rubber and a preparation method thereof. Background Art

[0002] At present, there is a wide demand for heat-resistant rubber in the market, and there are many types of heat-resistant rubber on the market, such as EPDM rubber and silicone rubber, but these rubber types have poor oil resistance, such as ASTM3# oil. Nitrile rubber has excellent oil resistance and excellent anti-swelling and anti-extraction properties for mineral oil and synthetic motor oil, but the conventional hardness of nitrile rubber will cause the hardness to increase after high-temperature aging, and the low hardness of nitrile rubber will cause the hardness to increase more significantly under high-temperature aging.

[0003] At present, in order to improve the heat resistance of nitrile rubber, heat-resistant fillers, heat-resistant plasticizers or other polar polymers are usually added to the rubber, and then blended to improve the heat resistance of nitrile materials, such as graphite, polytetrafluoroethylene, or hydrogenated nitrile rubber, acrylic rubber, but because heat-resistant fillers are usually more expensive, it is not easy to achieve uniform dispersion of the two phases through the blending method, and stratification is easy to occur, which will affect the stability of the physical properties of the nitrile rubber material. In addition, there are also hydrogenated nitrile and fluororubber with higher temperature and oil resistance on the market, but these two materials are expensive, have limited application value, and are suitable for special fields.

[0004] At present, it is more difficult to overcome the heat stability of low-hardness nitrile rubber. A large amount of plasticizers are needed to adjust the hardness of nitrile rubber with a Shore A hardness of 30 degrees. The solubility of plasticizers or heat-resistant plasticizers on the market in nitrile rubber is limited, and they will migrate out after cross-linking. After high-temperature aging, the hardness shows a significant upward trend. There is also a method of using peroxide as a vulcanization system to increase the heat resistance temperature. However, since the vulcanization bond of the peroxide vulcanization system is mainly CC single bond, the bond energy is large, and the cross-linking density is high, the hardness of the nitrile rubber composition is relatively high, and the lowest hardness can usually only reach 45 Shore A. It is impossible to make a low-hardness series of nitrile rubber compositions, and the cost of using this vulcanization system is relatively high. Summary of the invention

[0005] The object of the present invention is to provide a super heat-resistant low-hardness nitrile rubber and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose and other related purposes, the technical solution provided by the present invention is: a super heat-resistant low-hardness nitrile rubber, the raw material formula includes the following raw materials in parts by weight:

[0007] 100 parts of nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile;

[0008] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile has a mass content of 33% acrylonitrile and a Mooney viscosity ML (1+4) of 30±3 at 100°C;

[0009]

[0010]

[0011] The preferred technical solution is: the heat-resistant filler is calcium silicate with a particle size of 500-1000 mesh.

[0012] The preferred technical solution is: the active agent is zinc oxide.

[0013] The preferred technical solution is: the plasticizer is at least one of dioctyl terephthalate and trioctyl trimellitate.

[0014] To achieve the above-mentioned purpose and other related purposes, the technical solution provided by the present invention is: a method for preparing the super heat-resistant low-hardness nitrile rubber, comprising the following steps:

[0015] Step 1: Plasticize

[0016] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile is plasticized in an internal mixer for 60-80 seconds. The current value on the internal mixer is recorded as current A1.

[0017] Step 2: Mixing

[0018] First, add the active agent and physical protective wax to the product of step 1, add white carbon black, heat-resistant filler and plasticizer after mixing for 40-60 seconds, and the current on the internal mixer is greater than A1; after 60-80 seconds, add sulfur, vulcanization accelerator TMTD, and 2,5-dimethyl 2,5-di(tert-butyl peroxide)hexane, and when the mixing temperature reaches 105-110°C, discharge the rubber to the open mixer;

[0019] Step 3: Start Refining

[0020] The mixing process was continued on an open mixing mill for 2 m and 30 s, with a mixing mill speed ratio of 1.3. After the time was reached, the sheets were removed and the super heat-resistant low-hardness nitrile rubber was obtained after cooling.

[0021] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0022] 1. The heat-resistant components of the present invention are mainly nitrile rubber raw rubber with an acrylonitrile content of 33%, white carbon black, calcium silicate and zinc oxide. Compared with the existing nitrile rubber composition, it uses white carbon black, calcium silicate and zinc oxide to achieve good heat resistance. In addition, it reduces the cost and has more application value.

[0023] 2. The present invention uses a sulfur and peroxide composite vulcanization system. After vulcanization, a cross-linking structure mainly composed of CC single bonds, monosulfide bonds and disulfide bonds will be generated. The CC single bond energy is as high as 154KJ / mol to overcome the attack of high temperature and effectively resist the breakage of cross-linking bonds. The monosulfide bonds and polysulfide bonds of 60KJ / mol can ensure a good cross-linking structure and ensure that the hardness can be made lower, reaching a low hardness of 30A. DETAILED DESCRIPTION

[0024] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in the embodiments.

[0025] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0026] Unless otherwise specified, the reagents or materials described in the following examples are commercially available.

[0027] Example 1: A super heat-resistant low-hardness nitrile rubber and its preparation method

[0028] The ultra-heat-resistant low-hardness nitrile rubber material is composed of the following raw materials in parts by weight: 100 parts of nitrile rubber, 20 parts of white carbon black, 1 part of sulfur, 2 parts of vulcanization accelerator, 2 parts of 2,5-dimethyl-2,5-di(tert-butyl peroxide)hexane, 25 parts of calcium silicate, 40 parts of plasticizer, 10 parts of activator, and 1 part of physical protective wax. The mass content of nitrile rubber is 33%, and the Mooney viscosity ML (1+4) at 100°C is 30±3; the brand is ARLANXEO KRYNAC 3330C.

[0029] This embodiment is only for nitrile rubber with 33% acrylonitrile and Mooney viscosity of 33, and the brand is ARLANXEO KRYNAC3330C. The reasons are as follows: 1. The higher the acrylonitrile content of nitrile rubber, the greater the polarity and the worse the compatibility with plasticizer.

[0030] Compared with the nitrile rubber with a Mooney viscosity of 40-60, the nitrile rubber with a Mooney viscosity of 33 has a smaller molecular weight and higher plasticity. During mixing and preparation, it has higher processability. The inorganic filler and plasticizer are more evenly dispersed in the rubber microstructure, presenting a more ideal sea island structure.

[0031] Synthetic preparation method

[0032] S1 Plastication: Plasticize the nitrile rubber in an internal mixer for 60-80 seconds and record the current A1.

[0033] S2 mixing: first add the active agent and physical protective wax, mix for 40-60s, then add white carbon black, heat-resistant filler and plasticizer. The current is greater than A1.

[0034] After 60-80 seconds, sulfur, vulcanization accelerator TMTD and 2,5-dimethyl-2,5-di(tert-butyl peroxide)hexane are added, and when the mixing temperature reaches 105-110°C, the rubber is discharged to the mixing mill.

[0035] S3 refining: refining on the open mill for 2m30s, the speed ratio of the open mill is 1.3, after the time is reached, the sheets are unloaded, cooled and packaged. S4 vulcanization: the semi-finished products in S3 are vulcanized to obtain finished products (O-rings, sheaths, etc.). The finished products of the patent of this invention are particularly suitable for use in oil-resistant and heat-resistant working environments, especially suitable for use in motor product seals.

[0036] The physical protective wax is mainly processed from paraffin wax, microcrystalline paraffin wax, etc., and is a commercially available product.

[0037] Comparative Example 1: Nitrile rubber material is composed of the following raw materials in parts by mass: 100 parts of nitrile rubber, 20 parts of carbon black, 1 part of sulfur, 2 parts of vulcanization accelerator, 40 parts of plasticizer, 5 parts of activator, and 1 part of physical protective wax.

[0038] Comparative Example 2: Nitrile rubber material, composed of the following raw materials in parts by mass: 100 parts of nitrile rubber, 30 parts of carbon black, 1 part of sulfur, 2 parts of vulcanization accelerator, 40 parts of plasticizer, 5 parts of activator, and 1 part of physical protective wax.

[0039] Comparative Example 3: Nitrile rubber material, composed of the following raw materials in parts by mass: 100 parts of nitrile rubber, 20 parts of carbon black, 4 parts of 2,5-dimethyl-2,5-di(tert-butyl peroxide)hexane, 1 part of triallyl isocyanurate, 40 parts of plasticizer, 5 parts of activator, and 1 part of physical protective wax.

[0040] According to the test method (wherein the Shore A hardness test refers to GB / T 531-2008; the tensile test refers to GB / T 528-2009); the properties of the nitrile rubber obtained in Example 1 and the comparative example were tested, and the results are as follows:

[0041]

[0042]

[0043] As shown in the table above, the heat-resistant filled composite nitrile rubber material has excellent basic physical and mechanical properties in the hardness range of 30-35. After hot air aging at 100℃*96h, the physical and mechanical properties change slightly, and the hardness does not change. Compared with the nitrile material without heat-resistant filler and peroxide / sulfur / accelerator composite, it has excellent heat aging resistance.

[0044] Example 2: A super heat-resistant low-hardness nitrile rubber and its preparation method

[0045] A super heat-resistant low-hardness nitrile rubber, the raw material formula includes the following raw materials in parts by weight:

[0046] 100 parts of nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile;

[0047] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile has a mass content of 33% acrylonitrile and a Mooney viscosity ML (1+4) of 30±3 at 100°C;

[0048]

[0049] The preferred technical solution is: the heat-resistant filler is calcium silicate with a particle size of 500-1000 mesh.

[0050] The preferred technical solution is: the active agent is zinc oxide.

[0051] The preferred technical solution is: the plasticizer is trioctyl trimellitate.

[0052] The preparation method comprises the following steps:

[0053] Step 1: Plasticize

[0054] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile is plasticized in an internal mixer for 80 seconds: the current value on the internal mixer is recorded as current A1;

[0055] Step 2: Mixing

[0056] First, add the active agent and physical protective wax to the product of step 1, add white carbon black, heat-resistant filler and plasticizer after mixing for 60 seconds, and the current on the internal mixer is greater than A1; after 80 seconds, add sulfur, vulcanization accelerator TMTD, and 2,5-dimethyl 2,5-di(tert-butyl peroxide)hexane, and when the mixing temperature reaches 110°C, discharge the rubber to the open mixer;

[0057] Step 3: Start Refining

[0058] The mixing process was continued on an open mixing mill for 2 m and 30 s, with a mixing mill speed ratio of 1.3. After the time was reached, the sheets were removed and the super heat-resistant low-hardness nitrile rubber was obtained after cooling.

[0059] Example 3: A super heat-resistant low-hardness nitrile rubber and its preparation method

[0060] A super heat-resistant low-hardness nitrile rubber, the raw material formula includes the following raw materials in parts by weight:

[0061] 100 parts of nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile;

[0062] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile has a mass content of 33% acrylonitrile and a Mooney viscosity ML (1+4) of 30±3 at 100°C;

[0063]

[0064] The preferred technical solution is: the heat-resistant filler is calcium silicate with a particle size of 500-1000 mesh.

[0065] The preferred technical solution is: the active agent is zinc oxide.

[0066] The preferred technical solution is: the plasticizer is dioctyl terephthalate.

[0067] The preparation method comprises the following steps:

[0068] Step 1: Plasticize

[0069] The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile is plasticized in an internal mixer for 60-80 seconds. The current value on the internal mixer is recorded as current A1.

[0070] Step 2: Mixing

[0071] First, add the active agent and physical protective wax to the product of step 1, add white carbon black, heat-resistant filler and plasticizer after mixing for 40 seconds, and the current on the internal mixer is greater than A1; after 60 seconds, add sulfur, vulcanization accelerator TMTD, and 2,5-dimethyl 2,5-di(tert-butyl peroxide)hexane, and when the mixing temperature reaches 105°C, discharge the rubber to the open mixer;

[0072] Step 3: Start Refining

[0073] The mixing process was continued on an open mixing mill for 2 m and 30 s, with a mixing mill speed ratio of 1.3. After the time was reached, the sheets were removed and the super heat-resistant low-hardness nitrile rubber was obtained after cooling.

[0074] The above description is only used to explain the preferred embodiments of the present invention, and is not intended to limit the present invention in any form. Therefore, any modifications or changes made to the present invention under the same inventive spirit should still be included in the scope of protection intended by the present invention.

Claims

1. A super heat-resistant low-hardness nitrile rubber, characterized in that: The raw material formula includes the following raw materials in parts by weight: 100 parts of nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile; The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile has a mass content of 33% acrylonitrile and a Mooney viscosity ML (1+4) of 30±3 at 100°C; 2. The super heat-resistant low-hardness nitrile rubber according to claim 1, characterized in that: The heat-resistant filler is calcium silicate with a particle size of 500-1000 meshes.

3. The super heat-resistant low-hardness nitrile rubber according to claim 1, characterized in that: The active agent is zinc oxide.

4. The super heat-resistant low-hardness nitrile rubber according to claim 1, characterized in that: The plasticizer is at least one of dioctyl terephthalate and trioctyl trimellitate.

5. A method for preparing the ultra-heat-resistant low-hardness nitrile rubber according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Plasticize The nitrile rubber prepared by emulsion polymerization of butadiene and acrylonitrile is plasticized in an internal mixer for 60-80 seconds. The current value on the internal mixer is recorded as current A1. Step 2: Mixing First, add the active agent and physical protective wax to the product of step 1, add white carbon black, heat-resistant filler and plasticizer after mixing for 40-60 seconds, and the current on the internal mixer is greater than A1; after 60-80 seconds, add sulfur, vulcanization accelerator TMTD, and 2,5-dimethyl 2,5-di(tert-butyl peroxide)hexane, and when the mixing temperature reaches 105-110°C, discharge the rubber to the open mixer; Step 3: Start Refining The mixing process was continued on an open mixing mill for 2 m and 30 s, with a mixing mill speed ratio of 1.

3. After the time was reached, the sheets were removed and the super heat-resistant low-hardness nitrile rubber was obtained after cooling.

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