Flame-retardant low-shrinkage elastic nitrile rubber and preparation method thereof

Abstract

The present invention provides a flame retardant low shrinkage elastic nitrile rubber and a preparation method thereof, the preparation method comprising: preparing a low shrinkage flame retardant additive and a rubber system, uniformly mixing the low shrinkage flame retardant additive and the rubber system, extruding and vulcanizing to obtain a flame retardant low shrinkage elastic nitrile rubber, wherein the low shrinkage flame retardant additive comprises polyurethane, polyethylene glycol, polymer solution, antimony oxide, zinc borate and chlorinated paraffin, and the rubber system comprises nitrile rubber, an activator and a curing agent. The low shrinkage elastic rubber prepared by the present invention has a shrinkage rate of less than 2%, which greatly solves the problem of high elasticity and easy shrinkage and deformation of nitrile rubber in the prior art, and can achieve a good flame retardant effect. The rubber prepared by the present invention has both flame retardant performance and low shrinkage performance, and has a wider range of applications.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a flame-retardant low-shrinkage elastic nitrile rubber and a preparation method thereof. Background Art

[0002] Nitrile rubber (NBR) is a copolymer of butadiene and acrylonitrile. Among general-purpose rubbers, NBR has the best resistance to non-polar media. It also has good antistatic properties, wear resistance, heat aging resistance and air tightness. It is an elastomeric material widely used in the fields of petrochemicals, aerospace, etc. At present, intermittent high-temperature emulsion polymerization is used in industry to prepare high-strength nitrile rubber and high-acrylonitrile-containing nitrile rubber to meet the application needs in the fields of automobiles, aerospace, sealing gaskets, etc. However, there are some problems in the application of nitrile rubber at present. On the one hand, due to its strong elasticity, nitrile rubber is prone to serious shrinkage and deformation when the rubber is cured to form a product, and the size control is difficult, which in turn affects the mechanical properties of the rubber product. On the other hand, nitrile rubber is easily decomposed by high-temperature external heat. The combustible gas generated after decomposition reacts with oxygen in the air and burns. After combustion, a large amount of heat is generated, which aggravates this cycle, thereby limiting the application of nitrile rubber. Based on this, the present invention provides a low-shrinkage elastic nitrile rubber with flame retardant properties and a preparation method thereof to solve the above problems, which can achieve the effects of low cost, low shrinkage and strong flame retardancy. Summary of the invention

[0003] The purpose of the present invention is to provide a flame retardant, low-shrinkage elastic nitrile rubber and a preparation method thereof in view of the deficiencies in the prior art, so as to prepare a rubber material with a shrinkage rate of less than 2% and flame retardant properties, which greatly solves the difficulties of the nitrile rubber having a high shrinkage rate and easy high-temperature decomposition.

[0004] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0005] (I) The present invention provides a flame retardant, low shrinkage elastic nitrile rubber, the raw materials and weight proportions of which are: 150 parts of a rubber system and 60 parts of a low shrinkage flame retardant additive; the rubber system comprises nitrile rubber, an activator and a curing agent; the low shrinkage flame retardant additive comprises polyurethane, polyethylene glycol, a polymer solution, antimony oxide, zinc borate and chlorinated paraffin.

[0006] Furthermore, the weight proportions of the components in the rubber system are: 90 to 100 parts of nitrile rubber, 5 to 10 parts of activator, and 30 to 40 parts of curing agent.

[0007] Furthermore, the weight proportions of the components in the low shrinkage flame retardant additive are: 10 parts of polyurethane, 5-10 parts of polyethylene glycol, 10 parts of polymer solution, 3-10 parts of antimony oxide, 10-15 parts of zinc borate, and 15-30 parts of chlorinated paraffin.

[0008] Furthermore, the activator includes zinc oxide and stearic acid, and the weight ratio of zinc oxide to stearic acid is 3:1.

[0009] Furthermore, the curing agent includes carbon black, tert-butyl perbenzoate and 2-ethylcobalt acetate, and the weight ratio of the three is 5:1:1.

[0010] Furthermore, the polymer solution is a mixture of styrene and polymethyl methacrylate, and the volume ratio of styrene to polymethyl methacrylate is 15:4.1.

[0011] (ii) The present invention also provides a method for preparing the flame retardant low shrinkage elastic nitrile rubber described above, comprising the following steps:

[0012] S1. preparing a low shrinkage flame retardant additive;

[0013] S2, preparing a rubber system: weighing nitrile rubber, an activator and a curing agent and mixing them to prepare a rubber system;

[0014] S3, preparing flame retardant low shrinkage elastic nitrile rubber: uniformly mixing the low shrinkage flame retardant additive of step S1 with the rubber system of step S2, and then extruding and vulcanizing to obtain flame retardant low shrinkage elastic nitrile rubber.

[0015] Furthermore, S1 specifically comprises: mixing polyurethane, polyethylene glycol, polymer solution, antimony oxide, zinc borate and chlorinated paraffin in a small mixer for 60 minutes until a smooth and uniform texture is obtained to obtain a low shrinkage flame retardant additive.

[0016] Furthermore, the S2 is specifically:

[0017] S2.1, the nitrile rubber is mixed in an internal mixer at 120°C and then plasticized in an open mixer, and placed at room temperature for 24 hours as the main rubber after plasticization;

[0018] S2.2, add the plasticized main rubber into the internal mixer for mixing at a temperature of 60-80°C for 3-5 minutes;

[0019] S2.3, add activator into internal mixer and mix at 90-110℃ for 3-5 minutes;

[0020] S2.4. Add curing agent into internal mixer and mix at 90-120°C. Discharge after 2-5 minutes. Cool at room temperature for 24 hours and use as mixing base rubber to obtain rubber system.

[0021] Furthermore, in S3, the vulcanization molding temperature is 150°C to 160°C.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) In the preparation of the flame-retardant, low-shrinkage elastic nitrile rubber of the present invention, a certain amount of zinc borate, antimony oxide and chlorinated paraffin are added, which can be used as inorganic flame retardants and organic flame retardants respectively. Zinc borate can release a large amount of crystal water at high temperature, which plays a role in absorbing heat and cooling. When it is used in combination with halogen flame retardants and antimony oxide, it has a more ideal flame retardant synergistic effect; when zinc borate and halogen flame retardants are used in combination and contacted with flames, in addition to releasing crystal water, gaseous boron halides and zinc halides can also be generated. At high temperatures, zinc halides and zinc borate form a glass-like covering layer on the rubber surface, and gaseous zinc halides and boron halides shroud the rubber. These three covering layers can both insulate heat and isolate air, achieve good flame retardant effects, and have good strength; and chlorinated paraffin is easy to obtain in industry and has low cost;

[0024] (2) In the present invention, the low shrinkage additive can be attached to the main chain of the polymer to hinder the shrinkage of the rubber when the conditions change. In addition, zinc borate will release a large amount of crystal water at high temperature, and generate a large amount of internal stress after vaporization, which offsets the residual stress causing shrinkage and achieves the result of low shrinkage. The present application obtains a low shrinkage elastic rubber with a shrinkage rate of less than 2% by adding a low shrinkage additive to the rubber system and mixing it evenly, and then extruding and vulcanizing it to form it. This greatly solves the problem of high elasticity and easy shrinkage and deformation of nitrile rubber in the prior art; in addition, the preparation method of the present invention is simple and easy to operate. The prepared rubber has both flame retardant properties and low shrinkage properties, and has a wider range of applications. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Example 1

[0027] The embodiment of the present invention provides a method for preparing a flame-retardant low-shrinkage elastic nitrile rubber, comprising the following steps: (1) preparing a low-shrinkage flame-retardant additive;

[0028] Weigh 10 parts of polyurethane, 5 parts of polyethylene glycol, 10 parts of polymer solution, 6 parts of antimony oxide, 10 parts of zinc borate and 20 parts of chlorinated paraffin according to their mass ratios. First, mix the polyurethane, polyethylene glycol, polymer solution, antimony oxide and chlorinated paraffin. During the stirring process, add zinc borate in several times and stir evenly.

[0029] The mixture was stirred for 60 minutes until a smooth and uniform texture was obtained to obtain a low shrinkage flame retardant additive, wherein the polymer solution was a mixture of styrene and polymethyl methacrylate, and the volume ratio of styrene to polymethyl methacrylate was 15:4.1.

[0030] (II) Preparation of rubber system:

[0031] (1) Weigh 100 parts of nitrile rubber, 10 parts of an activator and 40 parts of a curing agent according to their weight ratios, wherein the activator comprises zinc oxide and stearic acid, and the weight ratio of zinc oxide to stearic acid is 3:1; the curing agent comprises carbon black, tert-butyl perbenzoate and 2-ethylcobalt acetate, and the weight ratio of the three is 5:1:1;

[0032] (2) The nitrile rubber is mixed in an internal mixer at 120° C. and then plasticized in an open mixer, and placed at room temperature for 24 hours to serve as the plasticized main rubber for standby use;

[0033] (3) Add the plasticized main rubber into the internal mixer for mixing at a temperature of 80°C for 5 minutes;

[0034] (4) adding the activator into the internal mixer and mixing at a mixing temperature of 110° C. for 5 minutes;

[0035] (5) Add curing agent into internal mixer and mix at 120°C for 4 minutes. Discharge the material and cool at room temperature for 24 hours. Use the mixed base rubber as standby to obtain the rubber system.

[0036] (III) Preparation of flame retardant low shrinkage elastic nitrile rubber:

[0037] 60 parts of low shrinkage flame retardant additives were added into 150 parts of rubber system and mixed evenly, and then extruded and vulcanized at 150° C. to obtain a low shrinkage elastic nitrile rubber product with flame retardant properties.

[0038] Density test:

[0039] The flame retardant, low shrinkage elastic nitrile rubber (before vulcanization molding) prepared in Example 1 and the fully cured rubber sample were cut into small cubes with a side length of 1 cm and placed in an ST-100 fully automatic electronic density meter to obtain the solid density; the density test data are shown in Table 1.

[0040] Table 1 Density data of low shrinkage elastic rubber obtained in Example 1

[0041]

[0042] Flame retardant performance test:

[0043] After two 10-second combustion tests on the sample, the residual flame and residual combustion are extinguished within 30 seconds. The dripping particles cannot ignite the cotton. The sample reaches the V-0 level.

[0044] Example 2

[0045] The embodiment of the present invention provides a method for preparing a flame-retardant low-shrinkage elastic nitrile rubber, comprising the following steps: (1) preparing a low-shrinkage flame-retardant additive;

[0046] Weigh 10 parts of polyurethane, 8 parts of polyethylene glycol, 10 parts of polymer solution, 3 parts of antimony oxide, 12 parts of zinc borate and 30 parts of chlorinated paraffin according to their mass ratios. First, mix the polyurethane, polyethylene glycol, polymer solution, antimony oxide and chlorinated paraffin together. During the stirring process, add zinc borate in several times and stir evenly.

[0047] The mixture was stirred for 60 minutes until a smooth and uniform texture was obtained to obtain a low shrinkage flame retardant additive, wherein the polymer solution was a mixture of styrene and polymethyl methacrylate, and the volume ratio of styrene to polymethyl methacrylate was 15:4.1.

[0048] (II) Preparation of rubber system:

[0049] (1) Weigh 100 parts of nitrile rubber, 5 parts of an activator and 35 parts of a curing agent according to their weight ratios, wherein the activator comprises zinc oxide and stearic acid, and the weight ratio of zinc oxide to stearic acid is 3:1; the curing agent comprises carbon black, tert-butyl perbenzoate and 2-ethylcobalt acetate, and the weight ratio of the three is 5:1:1;

[0050] (2) The nitrile rubber is mixed in an internal mixer at 120° C. and then plasticized in an open mixer, and placed at room temperature for 24 hours to serve as the plasticized main rubber for standby use;

[0051] (3) Add the plasticized main rubber into the internal mixer for mixing at a temperature of 70°C for 5 minutes;

[0052] (4) adding an activator into an internal mixer and mixing at a mixing temperature of 100° C. for 5 minutes;

[0053] (5) Add curing agent into internal mixer and mix at 110°C. Discharge after 5 minutes and cool at room temperature for 24 hours. Use as mixing base rubber for standby use to obtain rubber system.

[0054] (III) Preparation of flame retardant low shrinkage elastic nitrile rubber:

[0055] 60 parts of low shrinkage flame retardant additives were added into 150 parts of rubber system and mixed evenly, and then extruded and vulcanized at 150° C. to obtain a low shrinkage elastic nitrile rubber product with flame retardant properties.

[0056] The data obtained from the density test are shown in Table 2.

[0057] Table 2 Density data of low shrinkage elastic rubber obtained in Example 2

[0058]

[0059] After two 10-second combustion tests on the sample, the residual flame and residual combustion are extinguished within 30 seconds. The dripping particles cannot ignite the cotton. The sample reaches the V-0 level.

[0060] Example 3

[0061] The embodiment of the present invention provides a method for preparing a flame-retardant low-shrinkage elastic nitrile rubber, comprising the following steps: (1) preparing a low-shrinkage flame-retardant additive;

[0062] Weigh 10 parts of polyurethane, 10 parts of polyethylene glycol, 10 parts of polymer solution, 10 parts of antimony oxide, 15 parts of zinc borate and 15 parts of chlorinated paraffin according to their mass ratios. First, mix the polyurethane, polyethylene glycol, polymer solution, antimony oxide and chlorinated paraffin together. During the stirring process, add zinc borate in several times and stir evenly.

[0063] The mixture was stirred for 60 minutes until a smooth and uniform texture was obtained to obtain a low shrinkage flame retardant additive, wherein the polymer solution was a mixture of styrene and polymethyl methacrylate, and the volume ratio of styrene to polymethyl methacrylate was 15:4.1.

[0064] (II) Preparation of rubber system:

[0065] (1) Weigh 90 parts of nitrile rubber, 8 parts of an activator and 30 parts of a curing agent according to their weight ratios, wherein the activator comprises zinc oxide and stearic acid, and the weight ratio of zinc oxide to stearic acid is 3:1; the curing agent comprises carbon black, tert-butyl perbenzoate and 2-ethylcobalt acetate, and the weight ratio of the three is 5:1:1;

[0066] (2) The nitrile rubber is mixed in an internal mixer at 120° C. and then plasticized in an open mixer, and placed at room temperature for 24 hours to serve as the plasticized main rubber for standby use;

[0067] (3) Add the plasticized main rubber into the internal mixer for mixing at a temperature of 80°C for 3 minutes;

[0068] (4) adding an activator into an internal mixer and mixing at a mixing temperature of 100° C. for 3 minutes;

[0069] (5) Add curing agent into internal mixer and mix at 90°C for 5 minutes. Discharge the material and cool at room temperature for 24 hours. Use the mixed base rubber as standby to obtain the rubber system.

[0070] (III) Preparation of flame retardant low shrinkage elastic nitrile rubber:

[0071] 60 parts of low shrinkage flame retardant additives were added into 150 parts of rubber system and mixed evenly, and then extruded and vulcanized at 160° C. to obtain a low shrinkage elastic nitrile rubber product with flame retardant properties.

[0072] The data obtained from the density test are shown in Table 2.

[0073] Table 3 Density data of low shrinkage elastic rubber obtained in Example 3

[0074]

[0075] After two 10-second combustion tests on the sample, the residual flame and residual combustion are extinguished within 30 seconds. The dripping particles cannot ignite the cotton. The sample reaches the V-0 level.

[0076] Comparative Example 1

[0077] The difference between Comparative Example 1 and Example 1 is that the low shrinkage flame retardant additive is configured in a different manner.

[0078] In Comparative Example 1, the preparation method of the low shrinkage flame retardant additive is as follows: 10 parts of polyurethane, 5 to 10 parts of polyethylene glycol and 10 parts of polymer solution (styrene and polymethyl methacrylate in a weight ratio of 15:4.1) are weighed, and mixed in a small mixer for 60 minutes until a smooth and uniform texture is obtained to obtain a low shrinkage additive.

[0079] The data obtained from the density test are shown in Table 4.

[0080] Table 4 Density data of the rubber system of Comparative Example 4

[0081]

[0082] After two 10-second combustion tests on the sample, the afterflame and afterburning are extinguished within 60 seconds. The dripping particles can ignite cotton. The flame retardant grade is V-2.

[0083] It can be seen from the density data of Comparative Tables 1 to 4 that the present invention reduces the shrinkage of the rubber prepared by adding the new special composite low shrinkage additive from 3.81% to 1.80% by adding zinc borate, chlorinated paraffin and antimony oxide, thereby solving the problem of large volume shrinkage of nitrile rubber during curing and reducing it to less than 2%. The process is simple, the process efficiency is high, and the rubber has excellent flame retardant properties.

[0084] Comparative Example 2

[0085] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 is a rubber system and does not include a low shrinkage flame retardant additive.

[0086] The rubber system of Comparative Example 2 comprises the following raw material components in parts by weight: 100 parts of nitrile rubber, 10 parts of activator and 40 parts of curing agent.

[0087] The data obtained from the density test are shown in Table 5.

[0088] Table 5 Density data of the rubber system of Comparative Example 2

[0089]

[0090] After two 10-second combustion tests on the sample, the afterflame and afterburning are extinguished within 60 seconds. The dripping particles can ignite cotton. The flame retardant grade is V-2.

[0091] By comparing the density data in Tables 1 to 3 and Table 5, it can be seen that the shrinkage of the rubber prepared by adding a special composite low shrinkage additive can be reduced from 8.55% to 1.80%, which effectively solves the problems of large volume shrinkage and poor flame retardant properties of nitrile rubber during curing. The process is simple and efficient.

[0092] The above are only preferred implementations of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A flame retardant low shrinkage elastic nitrile rubber, characterized in that: The raw materials and weight proportions thereof are: 150 parts of rubber system, 60 parts of low shrinkage flame retardant additive; The rubber system comprises nitrile rubber, an activator and a curing agent; The low shrinkage flame retardant additives include polyurethane, polyethylene glycol, polymer solution, antimony oxide, zinc borate and chlorinated paraffin; The weight proportions of the components in the rubber system are: 90-100 parts of nitrile rubber, 5-10 parts of activator, and 30-40 parts of curing agent; the weight proportions of the components in the low shrinkage flame retardant additive are: 10 parts of polyurethane, 5-10 parts of polyethylene glycol, 10 parts of polymer solution, 3-10 parts of antimony oxide, 10-15 parts of zinc borate, and 15-30 parts of chlorinated paraffin; the curing agent includes carbon black, tert-butyl perbenzoate and 2-ethylcobalt acetate, and the weight ratio of the three is 5:1:1; the polymer solution is a mixture of styrene and polymethyl methacrylate, and the volume ratio of styrene to polymethyl methacrylate is 15:4.

1.

2. The flame retardant low shrinkage elastic nitrile rubber according to claim 1, characterized in that: The activator comprises zinc oxide and stearic acid, and the weight ratio of zinc oxide to stearic acid is 3:

1.

3. The method for preparing the flame retardant low shrinkage elastic nitrile rubber according to claim 1 or 2, characterized in that: The steps include: S1. preparing a low shrinkage flame retardant additive; S2, preparing a rubber system: weighing nitrile rubber, an activator and a curing agent and mixing them to prepare a rubber system; S3, preparing flame retardant low shrinkage elastic nitrile rubber: uniformly mixing the low shrinkage flame retardant additive of step S1 with the rubber system of step S2, and then extruding and vulcanizing to obtain flame retardant low shrinkage elastic nitrile rubber.

4. The method for preparing the flame retardant low shrinkage elastic nitrile rubber according to claim 3, characterized in that: The S1 is specifically: The polyurethane, polyethylene glycol, polymer solution, antimony oxide, zinc borate and chlorinated paraffin are mixed until a smooth uniform texture is achieved to obtain a low shrinkage flame retardant additive.

5. The method for preparing the flame retardant low shrinkage elastic nitrile rubber according to claim 3, characterized in that: The S2 is specifically: S2.1, the nitrile rubber is mixed in an internal mixer at 120°C and then plasticized in an open mixer, and placed at room temperature for 24 hours as the main rubber after plasticization; S2.2, add the plasticized main rubber into the internal mixer for mixing at a temperature of 60-80°C for 3-5 minutes; S2.3, add activator into internal mixer and mix at 90-110℃ for 3-5 minutes; S2.

4. Add curing agent into internal mixer and mix at 90-120°C. Discharge after 2-5 minutes. Cool at room temperature for 24 hours and use as mixing base rubber to obtain rubber system.

6. The method for preparing the flame retardant low shrinkage elastic nitrile rubber according to claim 3, characterized in that: In the above S3, the vulcanization molding temperature is 150°C to 160°C.

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