Reinforcing agent for nitrile rubber as well as preparation method and application of reinforcing agent

Abstract

The invention provides a reinforcing agent for butadiene-acrylonitrile rubber and a preparation method and application thereof, the preparation method of the reinforcing agent for butadiene-acrylonitrile rubber takes an olefin glycidyl ether substance containing an epoxy group, tannic acid and a boron-containing compound as raw materials, and the raw materials react under the action of a catalyst to obtain the rubber reinforcing agent. According to the method disclosed by the invention, the olefin glycidyl ether substance containing the epoxy group, the tannic acid and the boron-containing compound are introduced for reaction, and the prepared reinforcing agent can effectively improve the physical and mechanical properties of the nitrile rubber material, especially wear resistance and tear resistance. The reinforcing agent not only enhances the strength of the rubber material, but also improves the processability of the rubber material, so that the final product has longer service life and better hand feeling.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high polymer material modification, more particularly to a reinforcing agent for nitrile rubber, a preparation method and application thereof. BACKGROUND

[0002] Nitrile rubber (NBR) gloves have gradually replaced latex gloves due to their excellent oil resistance, chemical resistance and biocompatibility. However, the mechanical properties (such as tensile strength and tear resistance) of traditional nitrile gloves usually rely on increasing the material gram weight or adding inorganic fillers (such as SiO2 and CaCO3), which results in insufficient strength of low gram weight gloves (≤3g / pair) and reduces flexibility due to conventional filler addition, affecting the wearing comfort. Agglomeration of fillers: nanoparticles are prone to aggregation, leading to stress concentration and reducing durability. Limited chemical stability: traditional crosslinking agents (such as sulfur vulcanization) may affect solvent resistance.

[0003] Currently, the main methods for enhancing nitrile gloves include: physical blending enhancement, such as carbon nanotubes and graphene, which are high in cost and difficult to disperse. Chemical crosslinking modification: using peroxide or polyamine crosslinking agents, but which may reduce elasticity. Natural polyphenol modification: tannic acid (TA) can interact with rubber due to its polyphenolic hydroxyl groups, but the crosslinking efficiency is low when used alone. Therefore, further improvement and development are needed. SUMMARY

[0004] In view of the deficiencies of the prior art, in order to solve the above problems, a reinforcing agent for nitrile rubber, a preparation method and application thereof are proposed, and the following technical solutions are provided: A preparation method of a reinforcing agent for nitrile rubber, which uses an olefin glycidyl ether containing an epoxy group, tannic acid and a boron-containing compound as raw materials to react under the action of a catalyst to obtain a rubber reinforcing agent.

[0005] Further, the mass ratio of the olefin glycidyl ether containing an epoxy group, tannic acid and the boron-containing compound is 100:150-200:5-20.

[0006] Further, the boron-containing compound is one or more of boric acid, borax, boron fiber or boric acid ester.

[0007] Further, the olefin glycidyl ether containing an epoxy group is one or more of allyl glycidyl ether, methylallyl glycidyl ether, butadiene monoglycidyl ether, vinylbenzyl glycidyl ether, 10-undecenyl glycidyl ether, oleic acid glycidyl ether, perfluoroallyl glycidyl ether and silanized allyl glycidyl ether.

[0008] Further, the catalyst is one or more of tetrabutylammonium bromide, triethylbenzylammonium chloride, cetyltrimethylammonium bromide, tetrabutylphosphonium bromide, triphenyl ethyl phosphonium bromide, and tetrabutylammonium hydroxide.

[0009] Further, the specific steps are as follows: the tannic acid is dissolved in a mixed solvent of ethanol and water, a boron-containing compound is added, an olefin glycidyl ether containing an epoxy group is added dropwise in the presence of a catalyst at 50-60 DEG C, the pH value of the reaction system is controlled to be 5-8, and the reaction is carried out for 6-9 hours to obtain the reinforcing agent for nitrile rubber.

[0010] Further, the pH value of the reaction system is controlled to be 6.5-7.5 by adding an alkaline adjusting agent; the alkaline adjusting agent is an aqueous solution of sodium hydroxide, potassium hydroxide, or tetrabutylammonium hydroxide.

[0011] Further, the volume ratio of ethanol to water is 6-8:2-4.

[0012] In addition, the application further provides a reinforcing agent for nitrile rubber, which is prepared by the above method.

[0013] The application further provides the application of the reinforcing agent for nitrile rubber, which is applied to the preparation of nitrile gloves; in a nitrile latex compound, 1-3 phr of the reinforcing agent for nitrile rubber according to claim 9 is added to 100 phr of nitrile latex, and then the nitrile gloves are prepared through dipping, leaching, and vulcanization processes. 1. The method of the application introduces an olefin glycidyl ether containing an epoxy group, tannic acid, and a boron-containing compound to prepare the reinforcing agent, which can effectively improve the physical and mechanical properties of nitrile rubber materials, especially the wear resistance and tear resistance. The reinforcing agent not only enhances the strength of the rubber material, but also improves the processing performance, so that the final product has a longer service life and a better hand feeling. 2. On the one hand, the epoxy group in the olefin glycidyl ether reacts with the phenolic hydroxyl group in the tannic acid to introduce a double bond, which improves the crosslinking density of the nitrile gloves during the vulcanization process, further improves the strength of the low-grain nitrile gloves, and on the other hand, the boron compound is introduced in situ, which forms a dynamic borate ester bond with the unreacted catechol unit and the secondary hydroxyl group generated by the reaction of the tannic acid, and on the other hand, can coordinate with the nitrile group (-CN) of the nitrile rubber after the gloves are vulcanized, which can produce a stronger synergistic enhancement effect during the vulcanization of the rubber. 3. The pH value is controlled to be 5-8, which not only ensures the activity of boron, but also makes the epoxy ring-opening reaction mild and controllable, realizes the “partial functionalization” of the tannic acid, retains sufficient phenolic hydroxyl groups for physical interaction, and avoids the violent reaction and degradation of raw materials under strong alkaline conditions. DETAILED DESCRIPTION

[0014] In order to make the technical solutions of the present application better understood by the people in the art, the technical solutions of the present application are described clearly and completely below in combination with the embodiments of the present application, and other similar embodiments obtained by the people in the art without making creative efforts on the basis of the embodiments in the present application shall all belong to the scope of protection of the present application.

[0015] The application discloses a preparation method of a reinforcing agent for nitrile rubber. The reinforcing agent is prepared by reacting an olefin glycidyl ether containing an epoxy group, tannic acid and a boron-containing compound under the action of a catalyst. The reinforcing agent can effectively improve the physical and mechanical properties of the nitrile rubber material, especially the wear resistance and tear resistance. The reinforcing agent not only enhances the strength of the rubber material, but also improves the processing performance of the rubber material, so that the final product has a longer service life and a better hand feeling. On one hand, the epoxy group in the olefin glycidyl ether reacts with the phenolic hydroxyl group in the tannic acid to introduce a double bond, so as to improve the crosslinking density of the nitrile glove in the vulcanization process and further improve the strength of the low-grain nitrile glove. On the other hand, the boron-containing compound is introduced in situ, which forms a dynamic borate ester bond with the unreacted catechol unit in the tannic acid and the secondary hydroxyl group generated in the reaction, and can also coordinate with the nitrile group (-CN) of the nitrile rubber after the glove is vulcanized. The boron-containing compound can produce a stronger synergistic reinforcing effect in the rubber vulcanization.

[0016] The mass ratio of the olefin glycidyl ether containing an epoxy group, the tannic acid and the boron-containing compound is 100:150-200:5-20. The feeding amount of the olefin glycidyl ether containing an epoxy group, the tannic acid and the boron-containing compound is strictly controlled, so that part of the catechol unit in the tannic acid reacts with the olefin glycidyl ether containing an epoxy group, and the other part combines with the boron-containing compound, so that the prepared reinforcing agent can enhance the strength of the nitrile rubber.

[0017] The boron-containing compound is one or more of boric acid, borax, boron fiber or boric acid ester. In the synthesis process of the reinforcing agent, the boron-containing compound reacts with the tannic acid on one hand, and forms a more complex crosslinking network with the nitrile rubber on the other hand. The use of the boron-containing compound enhances the interaction between the rubber molecules. The boron-containing compound cooperates with the olefin glycidyl ether containing an epoxy group and the tannic acid in the basic scheme to form a more solid and stable interpenetrating network structure. By controlling the type and adding amount of the boron-containing compound, the performance of the reinforcing agent can be further optimized.

[0018] The olefin glycidyl ether raw material containing an epoxy group is one or more of allyl glycidyl ether, methylallyl glycidyl ether, butadiene monoglycidyl ether, vinylbenzyl glycidyl ether, 10-undecenyl glycidyl ether, glycidyl oleate, perfluoroallyl glycidyl ether, and silanized allyl glycidyl ether. The olefin glycidyl ether raw material containing an epoxy group, such as allyl glycidyl ether, methylallyl glycidyl ether, etc., is reacted with tannic acid under specific conditions, and a double bond is introduced through an epoxy ring-opening reaction of the epoxy group with the phenolic hydroxyl group, so as to form a tighter crosslinking network in the vulcanization process of the butadiene nitrile rubber. This reaction improves the crosslinking density of the butadiene nitrile glove, and thus significantly enhances the mechanical strength of the butadiene nitrile glove.

[0019] The pH is controlled at 5-8, which not only ensures the activity of boron, but also makes the epoxy ring-opening reaction mild and controllable, realizes the “partial functionalization” of tannic acid, retains sufficient phenolic hydroxyl groups for physical interaction, and avoids violent reaction and degradation of raw materials under strong alkaline conditions.

[0020] Example 1 Preparation of the reinforcing agent: 1. Dissolve 150 g of tannic acid in 500 ml of a mixed solvent of ethanol and water (volume ratio of ethanol to water 6:4), and heat to 50°C for stirring and dissolution; 2. Add 5 g of boric acid and stir for 10 minutes to disperse; 3. Add 2 g of the catalyst tetrabutylammonium bromide (TBAB), and the initial pH is 6.5; 4. Slowly add 100 g of allyl glycidyl ether (AGE), and the dropping time is 1 hour, and the reaction temperature is maintained at 50°C; 5. React for 6 hours, and maintain the pH at 6.5-7.0 with a NaOH solution during the reaction.

[0021] 6. After the reaction is completed, a light yellow viscous liquid, i.e., the reinforcing agent, is obtained.

[0022] Example 2 Preparation of the reinforcing agent: 1. Dissolve 200 g of tannic acid in 500 ml of a mixed solvent of ethanol and water (volume ratio of ethanol to water 8:2), and heat to 60°C for stirring and dissolution; 2. Add 20 g of borax and stir for 10 minutes to disperse; 3. Add 3 g of the catalyst cetyltrimethylammonium bromide (CTAB), and the initial pH is 7.5; 4. Slowly add 100 g of methylallyl glycidyl ether (MAGE), and the dropping time is 1.5 hours, and the reaction temperature is maintained at 60°C; 5. React for 9 hours, and maintain the pH at 7.0-7.5 with a NaOH solution during the reaction.

[0023] 6. After the reaction, a yellow viscous liquid, i.e. the reinforcing agent, was obtained.

[0024] Example 3 Preparation of the reinforcing agent: 1. 175 g of tannic acid was dissolved in a 500 ml mixed solvent of ethanol and water (volume ratio of ethanol to water 7:3), heated to 55°C and stirred to dissolve; 2. 12.5 g of trimethyl borate was added and stirred for 10 minutes to disperse; 3. Catalyst tetrabutylphosphonium bromide (TBPB) 2.5 g was added, and the initial pH was 7.0; 4. Butadiene monoglycidyl ether (BDMGE) 100 g was slowly added dropwise, the dropwise time was 1.2 hours, and the reaction temperature was maintained at 55°C; 5. The reaction was carried out for 7.5 hours, and during the reaction, the pH was maintained at 6.5-7 by using a tetrabutylammonium hydroxide (TBAOH) solution.

[0025] 6. After the reaction, a yellow viscous liquid, i.e. the reinforcing agent, was obtained.

[0026] Example 4 1. 160 g of tannic acid was dissolved in a 500 ml mixed solvent of ethanol and water (volume ratio of ethanol to water 7:3), heated to 55°C and stirred to dissolve; 2. 18 g of trimethyl borate was added and stirred for 10 minutes to disperse; 3. Catalyst tetrabutylphosphonium bromide (TBPB) 2.5 g was added, and the initial pH was 7.2; 4. Butadiene monoglycidyl ether (BDMGE) 100 g was slowly added dropwise, the dropwise time was 1.2 hours, and the reaction temperature was maintained at 55°C; 5. The reaction was carried out for 7.5 hours, and during the reaction, the pH was maintained at 6.5-7 by using a tetrabutylammonium hydroxide (TBAOH) solution.

[0027] 6. After the reaction, a yellow viscous liquid, i.e. the reinforcing agent, was obtained.

[0028] Example 5 Preparation of the reinforcing agent: 1. 175 g of tannic acid was dissolved in a 500 ml mixed solvent of ethanol and water (volume ratio of ethanol to water 7:3), heated to 55°C and stirred to dissolve; 2. 12.5 g of trimethyl borate was added and stirred for 10 minutes to disperse; 3. Catalyst tetrabutylphosphonium bromide (TBPB) 2.5 g was added, and the initial pH was 7.0; 4. Slowly add butadiene monoglycidyl ether (BDMGE) 100 g over 1.2 hours, maintaining the reaction temperature at 55 °C; 5. React for 7.5 hours, maintaining the pH at 7.5-8 using a solution of tetrabutylammonium hydroxide (TBAOH) during the reaction.

[0029] 6. After the reaction is complete, a yellow viscous liquid is obtained, which is the reinforcing agent.

[0030] Comparative Example 1 Preparation of the reinforcing agent: 1. Dissolve 175 g of tannic acid in a 500 ml mixture of ethanol and water (volume ratio of ethanol to water 7:3), heat to 55 °C and stir to dissolve; 3. Add the catalyst tetrabutylphosphonium bromide (TBPB) 2.5 g; 4. Slowly add butadiene monoglycidyl ether (BDMGE) 100 g over 1.2 hours, maintaining the reaction temperature at 55 °C; 5. React for 7.5 hours, maintaining the pH at 6.5-7 using a solution of tetrabutylammonium hydroxide (TBAOH) during the reaction.

[0031] 6. After the reaction is complete, a viscous liquid is obtained, which is the reinforcing agent.

[0032] Comparative Example 2 Preparation of the reinforcing agent: 1. Dissolve 100 g of tannic acid in a 500 ml mixture of ethanol and water (volume ratio of ethanol to water 7:3), heat to 55 °C and stir to dissolve; 2. Add 12.5 g of trimethyl borate, stirring for 10 minutes to disperse it; 3. Add the catalyst tetrabutylphosphonium bromide (TBPB) 2.5 g; 4. Slowly add butadiene monoglycidyl ether (BDMGE) 100 g over 1.2 hours, maintaining the reaction temperature at 55 °C; 5. React for 7.5 hours, maintaining the pH at 6.5-7 using a solution of tetrabutylammonium hydroxide (TBAOH) during the reaction.

[0033] 6. After the reaction is complete, a yellow viscous liquid is obtained, which is the reinforcing agent.

[0034] Comparative Example 3 Preparation of the reinforcing agent: 1. Dissolve 175 g of tannic acid in a 500 ml mixture of ethanol and water (volume ratio of ethanol to water 7:3), heat to 55 °C and stir to dissolve; 2. Add 12.5 g of trimethyl borate, stirring for 10 minutes to disperse it; 3. Add catalyst tetra-butyl-phosphonium bromide (TBPB) 2.5 g, initial pH 7.0; 4. Slowly add butadiene monoglycidyl ether (BDMGE) 100 g, drop time 1.2 hours, maintain reaction temperature 55°C; 5. React for 7.5 hours, maintain pH 4-5 with dilute hydrochloric acid solution during reaction.

[0035] 6. After reaction is complete, the system is turbid and the product precipitates.

[0036] The products obtained from the above Examples 1-5 and Comparative Examples 1-3 are applied to the preparation process of nitrile gloves, and the following raw material formula is designed: nitrile latex 100 phr (calculated based on dry rubber), reinforcing agent 2 phr, sulfur 1.5 phr, zinc oxide 3 phr, accelerator ZDEC 1 phr. Other process conditions are consistent. The reinforcing agent is mixed and dispersed with the nitrile latex and other additives, and the glove sample is prepared by impregnation, leaching, and vulcanization (120°C x 30 minutes).

[0037] The nitrile glove samples prepared from the products obtained from Examples 1-5 and Comparative Examples 1-3 are tested for performance: Tensile strength: tested according to GB / T 528-2009, sample size dumbbell, speed 500 mm / min.

[0038] Elongation at break: tested according to GB / T 528-2009.

[0039] Tear resistance: tested according to GB / T 529-2008.

[0040] Wear resistance: tested according to GB / T 9867-2008, expressed in wear amount.

[0041] Hardness: tested according to GB / T 531.1-2008.

[0042] Each sample is tested 5 times and the average value is taken.

[0043] The specific test results are shown in Table 1.

[0044] Table 1 Performance test results of nitrile glove samples prepared from the products obtained from Examples 1-5 and Comparative Examples 1-3 As can be seen from Table 1 above, the tensile strength, tear resistance and abrasion resistance of all the examples are significantly better than the comparative examples, indicating that the reinforcing agent of the present application can effectively enhance the performance of nitrile rubber. Example 3 performs best, with a tensile strength of 28.1 MPa, thanks to the synergistic effect between tannic acid, olefin glycidyl ether containing epoxy group and borax, and the optimal dosage ratio between the three, which has been explored by the present application. When no boron-containing compound is added, the performance decreases, indicating that the boron-containing compound is a key ingredient that enhances the crosslinking network by forming dynamic borate ester bonds and coordinating with nitrile groups. When the amount of tannic acid is too low, the performance of the product is poor, indicating that insufficient tannic acid leads to insufficient epoxy ring-opening reaction and low crosslinking density with the boron-containing compound. In addition, if the pH value of the reaction system is too low, the reaction will become violent, leading to degradation of raw materials, and the boron activity is low, resulting in loss of reinforcing effect.

[0045] The elongation at break of all the examples is maintained at more than 550%, and the hardness is moderate, indicating that the reinforcing agent enhances while maintaining flexibility, and is suitable for low-gauge gloves.

[0046] The reinforcing agent prepared by Example 3 was used as a reinforcing agent to explore the effect of the amount of reinforcing agent on the performance of nitrile gloves.

[0047] Test Example 1 The following formulation was designed: nitrile latex 100 phr (based on dry rubber), reinforcing agent 1 phr, sulfur 1.5 phr, zinc oxide 3 phr, accelerator ZDEC 1 phr. Other process conditions were consistent. The reinforcing agent was mixed with nitrile latex and other additives, stirred and dispersed, and then dipped, drained, and vulcanized (120°C x 30 minutes) to produce a glove sample.

[0048] Test Example 2 The following formulation was designed: nitrile latex 100 phr (based on dry rubber), reinforcing agent 3 phr, sulfur 1.5 phr, zinc oxide 3 phr, accelerator ZDEC 1 phr. Other process conditions were consistent. The reinforcing agent was mixed with nitrile latex and other additives, stirred and dispersed, and then dipped, drained, and vulcanized (120°C x 30 minutes) to produce a glove sample.

[0049] Test Example 3 The following formulation was designed: nitrile latex 100 phr (based on dry rubber), reinforcing agent 0.5 phr, sulfur 1.5 phr, zinc oxide 3 phr, accelerator ZDEC 1 phr. Other process conditions were consistent. The reinforcing agent was mixed with nitrile latex and other additives, stirred and dispersed, and then dipped, drained, and vulcanized (120°C x 30 minutes) to produce a glove sample.

[0050] The glove samples prepared in Test Example 1-3 were subjected to relevant performance tests, and the test results are shown in Table 2.

[0051] Table 2 Performance test results of glove samples prepared in Test Example 1-3 As can be seen from Table 2, when the addition amount is 2 phr, the tensile strength reaches a maximum of 28.5 MPa at 2 phr, and when the amount is increased to 3 phr, the strength is slightly decreased to 28.1 MPa. The elongation at break reaches a peak of 585% at 2 phr, and is significantly reduced to 550% at 3 phr. This is particularly critical, indicating that the use of 2 phr imparts the highest strength to the glove, while also providing the best toughness and suppleness, the tear resistance and wear resistance are excellent and close at 2 phr and 3 phr, but slightly better at 2 phr, indicating that it has the highest reinforcing efficiency. When the addition amount exceeds 2 phr to 3 phr, although the hardness continues to increase, the tensile strength no longer increases, and the elongation at break significantly decreases. This indicates that an excessive amount of reinforcing agent can begin to cause local agglomeration, limiting the mobility of the rubber molecular chain, making the material brittle, and thus compromising the toughness.

[0052] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing a reinforcing agent for nitrile rubber, characterized in that, Rubber reinforcing agents are obtained by reacting olefin glycidyl ethers containing epoxy groups, tannic acid, and boron-containing compounds under the action of a catalyst.

2. The method for preparing a reinforcing agent for nitrile rubber according to claim 1, characterized in that, The mass ratio of olefinic glycidyl ethers containing epoxy groups, tannic acid, and boron-containing compounds is 100:150-200:5-20.

3. The method for preparing a reinforcing agent for nitrile rubber according to claim 1, characterized in that, The boron-containing compound is one or more of boric acid, borax, boron fiber, or boron ester.

4. The method for preparing a reinforcing agent for nitrile rubber according to claim 1, characterized in that, Olefin glycidyl ether raw materials containing epoxy groups are one or more of allyl glycidyl ether, methyl allyl glycidyl ether, butadiene monoglycidyl ether, vinyl benzyl glycidyl ether, 10-undecenyl glycidyl ether, oleic acid glycidyl ether, perfluoroallyl glycidyl ether, and silanized allyl glycidyl ether.

5. The method for preparing a reinforcing agent for nitrile rubber according to claim 1, characterized in that, The catalyst is one or more of tetrabutylammonium bromide, triethylbenzylammonium chloride, hexadecyltrimethylammonium bromide, tetrabutylphosphonium bromide, triphenylethylphosphonium bromide, and tetrabutylammonium hydroxide.

6. The method for preparing a reinforcing agent for nitrile rubber according to claim 1, characterized in that, The specific steps are as follows: Tannic acid is dissolved in a mixed solvent of ethanol and water, a boron-containing compound is added, and in the presence of a catalyst, an olefinic glycidyl ether containing an epoxy group is added dropwise at 50-60℃. The pH of the reaction system is controlled to be 5-8, and the reaction is carried out for 6-9 hours to obtain a reinforcing agent for nitrile rubber.

7. The method for preparing a reinforcing agent for nitrile rubber according to claim 6, characterized in that, The pH of the reaction system is controlled at 6.5-7.5 by adding an alkaline regulator; the alkaline regulator is an aqueous solution of sodium hydroxide, potassium hydroxide or tetrabutylammonium hydroxide.

8. The method for preparing a reinforcing agent for nitrile rubber according to claim 6, characterized in that, The volume ratio of ethanol to water is 6-8:2-4.

9. A reinforcing agent for nitrile rubber prepared by the method according to any one of claims 1-8.

10. The application of the reinforcing agent for nitrile rubber according to claim 9, characterized in that, The method is applied to the preparation of nitrile gloves. In the compound of nitrile latex, 1-3 phr of the reinforcing agent for nitrile rubber as described in claim 9 is added to 100 phr of nitrile latex, and nitrile gloves are made by impregnation, leaching and vulcanization processes.

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