Environmentally friendly rubber material for knee pads and preparation method thereof

Abstract

The present invention discloses an environment-friendly rubber material for knee pads and a preparation method thereof, and relates to the technical field of rubber. In order to improve the elastic reset performance of the knee pads, the present invention prepares the environment-friendly rubber material for the knee pads, and through a foaming process, the rubber material has a smaller density, thereby reducing the burden during exercise. In consideration of environmental protection factors, the present invention also uses natural rubber as a raw material, thereby reducing the pollution caused by synthetic rubber to the environment. On this basis, in order to enable the rubber material to maintain the elastic reset ability for a long time, the present invention also modifies the filler and antioxidant in the rubber, effectively introducing antioxidant functional groups on the surface of kaolin, thereby avoiding the migration and dissolution of small molecule antioxidants in the rubber, thereby maintaining the flexibility of the rubber for a long time and avoiding the elastic reset failure of the rubber.

Description

Technical Field

[0001] The invention relates to the technical field of rubber materials, in particular to an environmentally friendly rubber material for knee pads and a preparation method thereof. Background Art

[0002] Knee pads are a type of protective device used to protect the knee joints during exercise and work. They have the function of keeping warm and cold. Compared with ordinary knee pads, sports knee pads also have the function of maintaining joints and reducing the burden on joints during exercise.

[0003] Sports knee pads are often fixed to the joint position using sleeves and fixing straps, and protect the joints in the process. However, since sports knee pads are mostly used in sports scenes, the knee joints often need to bend multiple times, which puts higher requirements on the elastic reset of the knee pads and also requires the knee pads to have higher antibacterial properties to prevent the growth of bacteria after the human body sweats. Summary of the Invention

[0004] The object of the present invention is to provide an environmentally friendly rubber material for knee pads and a preparation method thereof, so as to solve the problems raised in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0006] S1. Preparation of anti-aging modified kaolin;

[0007] S11. Heating kaolin to 800-900°C, calcining for 2-4 hours, stopping heating, cooling to room temperature, grinding the obtained kaolin through an 80-mesh sieve, mixing the ground product with hydrochloric acid, ultrasonically dispersing it evenly, heating to 70-85°C, stirring for 4-24 hours, centrifuging the precipitate and washing it 3-5 times with hydrogen peroxide, drying it to constant weight, and redispersing the kaolin mineral in toluene. Adding aminopropyltrimethoxysilane and deionized water, heating to 80-90°C, stirring for 8-12 hours in the dark, centrifuging the precipitate, washing it 3-5 times with anhydrous ethanol, and vacuum drying it to constant weight to obtain amino-modified calcined kaolin;

[0008] S12. Disperse p-aminodiphenylamine in hydrochloric acid, stir and mix thoroughly, and then add cyanamide under nitrogen atmosphere. Heat to 85-95°C and reflux with stirring for 4-8 hours. After removing excess solvent by rotary evaporation, wash with deionized water 1-2 times, and evaporate in vacuo to constant weight to obtain guanylated diphenylamine.

[0009] S13. The guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Maleic anhydride was added thereto under nitrogen atmosphere. The reaction was stirred at room temperature for 4-8 hours. The excess solvent was removed by rotary evaporation, washed with deionized water, and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0010] S14. The amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. Carboxylated diphenylamine was then added thereto. The temperature was raised to 55-56°C and the mixture was stirred under reflux for 4-24 hours. The excess solvent was removed by rotary evaporation. The dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0011] S2. Add anti-aging modified kaolin, foaming agent, stearic acid, accelerator, vulcanizing agent and softener to natural rubber, raise the temperature to 110-125 ° C, knead for 13-18 minutes, discharge, cool to 30-40 ° C, continue to masticate for 2-5 minutes, cut the sheet, cool to room temperature to obtain a film;

[0012] S3. After the film is allowed to stand for 12-24 hours, it is heated again to 35-45°C, a vulcanizing agent is added thereto, and plasticization is continued for 2-5 minutes. After vacuum continuous extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0013] Furthermore, in step S11, the mass ratio of the kaolin mineral to aminopropyltrimethoxysilane is 1:(5-20) in parts by weight;

[0014] The mass ratio of the aminopropyltrimethoxysilane to deionized water is 5:(1-3).

[0015] Furthermore, in step S12, the mass ratio of p-aminodiphenylamine to monocyanamide is 1:(0.23-1.38) in parts by weight.

[0016] Furthermore, in step S13, the mass ratio of the guanidinated diphenylamine to maleic anhydride is 1:(0.35-0.48) in parts by weight.

[0017] Furthermore, in step S14, the mass ratio of the amino-modified calcined kaolin to the carboxylated diphenylamine is 1:(0.1-0.45) in parts by weight.

[0018] Furthermore, in step S2, the environmentally friendly rubber material for knee pads is composed of 85-100 parts of natural rubber, 6-10 parts of anti-aging modified kaolin, 18-25 parts of foaming agent, 1.5-4 parts of stearic acid, 2-4 parts of accelerator and 20-25 parts of softener, by weight.

[0019] Furthermore, in step S2, the foaming agent is any one of foaming agent OBSH, foaming agent AC, and foaming agent ADCD10; and the accelerator is zinc oxide.

[0020] Furthermore, in step S2, the softener is cyclopentane oil.

[0021] Furthermore, an environmentally friendly rubber material for knee pads is prepared by the above method.

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

[0023] In order to improve the elastic reset performance of the knee pad, the present invention prepares an environmentally friendly rubber material for the knee pad. Through a foaming process, the rubber material has a lower density, thereby reducing the burden during exercise. In addition, for environmental protection reasons, the present invention also uses natural rubber as a raw material, reducing the pollution caused by synthetic rubber to the environment. On this basis, in order to enable the rubber material to maintain its elastic reset ability for a long time, the present invention also modifies the filler and antioxidant in the rubber. The present invention first uses kaolin as a raw material, calcines it at high temperature to remove organic matter, and then uses hydrochloric acid to soak it to remove soluble elements. The calcined kaolin has a higher porosity and a larger pore size, and amino groups are grafted on its surface.

[0024] On this basis, the present invention further uses p-aminodiphenylamine containing primary and secondary amine groups as a raw material and reacts it with monocyanamide containing a cyano group, thereby preparing guanylated diphenylamine having an antibacterial guanyl group and a secondary amine group with anti-aging function;

[0025]

[0026] Then, the obtained guanidinated diphenylamine is reacted with maleic anhydride to prepare carboxylated diphenylamine containing a carboxyl group;

[0027]

[0028] By mixing carboxylated diphenylamine containing free carboxyl groups with amino-modified calcined kaolin, the antioxidant functional groups can be effectively grafted onto the surface of the kaolin, thereby avoiding the migration and dissolution of small molecule antioxidants in the rubber, thereby maintaining the flexibility of the rubber for a long time and avoiding the elastic reset failure of the rubber. DETAILED DESCRIPTION

[0029] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0030] The kaolin used in this application is commercially available YDHT-04 kaolin with a particle size of 1250 mesh; the softener used is KN4006 cyclopentane oil;

[0031] Example 1. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0032] S1. Preparation of anti-aging modified kaolin;

[0033] S11. Heat kaolin to 900°C, calcinate for 3 hours, stop heating, cool to room temperature, grind the kaolin through an 80-mesh sieve, mix the ground product with hydrochloric acid, disperse it evenly with ultrasound, heat to 70-85°C, stir and react for 12 hours, centrifuge and separate the precipitate, wash it five times with hydrogen peroxide, and dry it to constant weight. Redisperse 1 part of kaolin mineral in toluene, add 5 parts of aminopropyltrimethoxysilane and 1 part of deionized water, heat to 0°C, stir and react for 12 hours in the dark, centrifuge and separate the precipitate, wash it four times with anhydrous ethanol, and dry it in vacuum to constant weight to obtain amino-modified calcined kaolin.

[0034] S12. By weight, 1 part of p-aminodiphenylamine was dispersed in hydrochloric acid, stirred and mixed, and then 0.23 parts of monocyanamide was added under nitrogen atmosphere. The temperature was raised to 93 ° C. After stirring under reflux for 8 h, the excess solvent was removed by rotary evaporation, and the mixture was washed twice with deionized water and evaporated in vacuo to constant weight to obtain guanidinated diphenylamine;

[0035] S13. In parts by weight, 1 part of guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Then, 0.35 parts of maleic anhydride was added thereto. The mixture was stirred under nitrogen atmosphere at room temperature for 8 hours. After the reaction was removed by rotary evaporation, the excess solvent was washed with deionized water and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0036] S14. In parts by weight, 1 part of amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. 0.1 part of carboxylated diphenylamine was added thereto, and the temperature was raised to 56 ° C. The reaction was stirred under reflux for 8 h. After the excess solvent was removed by rotary evaporation, the dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0037] S2. In parts by weight, 9 parts of anti-aging modified kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15min, discharged, cooled to 30-40 ° C, continued to masticate for 4min, cut out the sheet, cooled to room temperature to obtain a film;

[0038] S3. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0039] Example 2. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0040] Compared with Example 1, this embodiment increases the amount of aminopropyltrimethoxysilane added in step S11;

[0041] S1. Preparation of anti-aging modified kaolin;

[0042] S11. Heat kaolin to 900°C, calcinate for 3 hours, stop heating, cool to room temperature, grind the kaolin through an 80-mesh sieve, mix the ground product with hydrochloric acid, disperse it evenly with ultrasound, heat to 70-85°C, stir and react for 12 hours, centrifuge and separate the precipitate, wash it five times with hydrogen peroxide, and dry it to constant weight. Redisperse 1 part of kaolin mineral in toluene, add 20 parts of aminopropyltrimethoxysilane and 4 parts of deionized water, heat to 0°C, stir and react for 12 hours in the dark, centrifuge and separate the precipitate, wash it four times with anhydrous ethanol, and dry it in vacuum to constant weight to obtain amino-modified calcined kaolin.

[0043] S12. By weight, 1 part of p-aminodiphenylamine was dispersed in hydrochloric acid, stirred and mixed, and then 0.23 parts of monocyanamide was added under nitrogen atmosphere. The temperature was raised to 93 ° C. After stirring under reflux for 8 h, the excess solvent was removed by rotary evaporation, and the mixture was washed twice with deionized water and evaporated in vacuo to constant weight to obtain guanidinated diphenylamine;

[0044] S13. In parts by weight, 1 part of guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Then, 0.35 parts of maleic anhydride was added thereto. The mixture was stirred under nitrogen atmosphere at room temperature for 8 hours. After the reaction was removed by rotary evaporation, the excess solvent was washed with deionized water and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0045] S14. In parts by weight, 1 part of amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. 0.1 part of carboxylated diphenylamine was added thereto, and the temperature was raised to 56 ° C. The reaction was stirred under reflux for 8 h. After the excess solvent was removed by rotary evaporation, the dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0046] S2. In parts by weight, 9 parts of anti-aging modified kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15min, discharged, cooled to 30-40 ° C, continued to masticate for 4min, cut out the sheet, cooled to room temperature to obtain a film;

[0047] S3. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0048] Example 3. A method for preparing an environmentally friendly rubber material for a kneepad, comprising the following steps:

[0049] Compared with Example 2, this embodiment increases the amount of cyanamide added in step S12;

[0050] S1. Preparation of anti-aging modified kaolin;

[0051] S11. Heat kaolin to 900°C, calcinate for 3 hours, stop heating, cool to room temperature, grind the kaolin through an 80-mesh sieve, mix the ground product with hydrochloric acid, disperse it evenly with ultrasound, heat to 70-85°C, stir and react for 12 hours, centrifuge and separate the precipitate, wash it five times with hydrogen peroxide, and dry it to constant weight. Redisperse 1 part of kaolin mineral in toluene, add 20 parts of aminopropyltrimethoxysilane and 4 parts of deionized water, heat to 0°C, stir and react for 12 hours in the dark, centrifuge and separate the precipitate, wash it four times with anhydrous ethanol, and dry it in vacuum to constant weight to obtain amino-modified calcined kaolin.

[0052] S12. By weight, 1 part of p-aminodiphenylamine was dispersed in hydrochloric acid, stirred and mixed, and then 1.38 parts of monocyanamide was added under nitrogen atmosphere. The temperature was raised to 93 ° C, and the reaction was stirred under reflux for 8 h. After removing the excess solvent by rotary evaporation, the mixture was washed twice with deionized water and evaporated in vacuo to constant weight to obtain guanidinated diphenylamine.

[0053] S13. In parts by weight, 1 part of guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Then, 0.35 parts of maleic anhydride was added thereto. The mixture was stirred under nitrogen atmosphere at room temperature for 8 hours. After the reaction was removed by rotary evaporation, the excess solvent was washed with deionized water and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0054] S14. In parts by weight, 1 part of amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. 0.1 part of carboxylated diphenylamine was added thereto, and the temperature was raised to 56 ° C. The reaction was stirred under reflux for 8 h. After the excess solvent was removed by rotary evaporation, the dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0055] S2. In parts by weight, 9 parts of anti-aging modified kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15min, discharged, cooled to 30-40 ° C, continued to masticate for 4min, cut out the sheet, cooled to room temperature to obtain a film;

[0056] S3. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0057] Example 4. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0058] Compared with Example 3, this embodiment increases the amount of maleic anhydride added in step S13;

[0059] S1. Preparation of anti-aging modified kaolin;

[0060] S11. Heat kaolin to 900°C, calcinate for 3 hours, stop heating, cool to room temperature, grind the kaolin through an 80-mesh sieve, mix the ground product with hydrochloric acid, disperse it evenly with ultrasound, heat to 70-85°C, stir and react for 12 hours, centrifuge and separate the precipitate, wash it five times with hydrogen peroxide, and dry it to constant weight. Redisperse 1 part of kaolin mineral in toluene, add 20 parts of aminopropyltrimethoxysilane and 4 parts of deionized water, heat to 0°C, stir and react for 12 hours in the dark, centrifuge and separate the precipitate, wash it four times with anhydrous ethanol, and dry it in vacuum to constant weight to obtain amino-modified calcined kaolin.

[0061] S12. By weight, 1 part of p-aminodiphenylamine was dispersed in hydrochloric acid, stirred and mixed, and then 1.38 parts of monocyanamide was added under nitrogen atmosphere. The temperature was raised to 93 ° C, and the reaction was stirred under reflux for 8 h. After removing the excess solvent by rotary evaporation, the mixture was washed twice with deionized water and evaporated in vacuo to constant weight to obtain guanidinated diphenylamine.

[0062] S13. In parts by weight, 1 part of guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Then, 0.48 parts of maleic anhydride was added thereto under nitrogen atmosphere. After stirring at room temperature for 8 hours, the excess solvent was removed by rotary evaporation, washed with deionized water, and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0063] S14. In parts by weight, 1 part of amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. 0.1 part of carboxylated diphenylamine was added thereto, and the temperature was raised to 56 ° C. The reaction was stirred under reflux for 8 h. After the excess solvent was removed by rotary evaporation, the dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0064] S2. In parts by weight, 9 parts of anti-aging modified kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15min, discharged, cooled to 30-40 ° C, continued to masticate for 4min, cut out the sheet, cooled to room temperature to obtain a film;

[0065] S3. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0066] Example 5. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0067] Compared with Example 4, this embodiment increases the amount of carboxylated diphenylamine added in step S14;

[0068] S1. Preparation of anti-aging modified kaolin;

[0069] S11. Heat kaolin to 900°C, calcinate for 3 hours, stop heating, cool to room temperature, grind the kaolin through an 80-mesh sieve, mix the ground product with hydrochloric acid, disperse it evenly with ultrasound, heat to 70-85°C, stir and react for 12 hours, centrifuge and separate the precipitate, wash it five times with hydrogen peroxide, and dry it to constant weight. Redisperse 1 part of kaolin mineral in toluene, add 20 parts of aminopropyltrimethoxysilane and 4 parts of deionized water, heat to 0°C, stir and react for 12 hours in the dark, centrifuge and separate the precipitate, wash it four times with anhydrous ethanol, and dry it in vacuum to constant weight to obtain amino-modified calcined kaolin.

[0070] S12. By weight, 1 part of p-aminodiphenylamine was dispersed in hydrochloric acid, stirred and mixed, and then 1.38 parts of monocyanamide was added under nitrogen atmosphere. The temperature was raised to 93 ° C, and the reaction was stirred under reflux for 8 h. After removing the excess solvent by rotary evaporation, the mixture was washed twice with deionized water and evaporated in vacuo to constant weight to obtain guanidinated diphenylamine.

[0071] S13. In parts by weight, 1 part of guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Then, 0.48 parts of maleic anhydride was added thereto under nitrogen atmosphere. After stirring at room temperature for 8 hours, the excess solvent was removed by rotary evaporation, washed with deionized water, and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine.

[0072] S14. In parts by weight, 1 part of amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. 0.45 parts of carboxylated diphenylamine was added thereto, and the temperature was raised to 56 ° C. The reaction was stirred under reflux for 8 h. After removing the excess solvent by rotary evaporation, the dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin.

[0073] S2. In parts by weight, 9 parts of anti-aging modified kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15min, discharged, cooled to 30-40 ° C, continued to masticate for 4min, cut out the sheet, cooled to room temperature to obtain a film;

[0074] S3. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0075] Comparative Example 1. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0076] Compared with Example 1, this comparative example did not prepare anti-aging modified kaolin, but only used an equal amount of kaolin as a substitute;

[0077] S1. To 100 parts of natural rubber, 9 parts of kaolin, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added by weight, heated to 125 ° C, kneaded for 15 minutes, discharged, cooled to 30-40 ° C, continued to masticate for 4 minutes, cut out the sheet, and cooled to room temperature to obtain a film;

[0078] S2. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0079] Comparative Example 2. A method for preparing an environmentally friendly rubber material for knee pads, comprising the following steps:

[0080] Compared with Example 1, this comparative example uses a mixture of kaolin and antioxidant instead of the antioxidant modified kaolin;

[0081] S1. In parts by weight, 9 parts of kaolin, 3 parts of antioxidant TMQ, 18 parts of foaming agent ADCD10, 2 parts of stearic acid, 2 parts of zinc oxide accelerator and 20 parts of naphthenic oil softener were added to 100 parts of natural rubber, heated to 125 ° C, kneaded for 15 minutes, discharged, cooled to 30-40 ° C, continued to masticate for 4 minutes, cut out the sheet, cooled to room temperature to obtain a film;

[0082] S2. After the film is allowed to stand for 24 hours, it is heated again to 35-40°C, 2 parts of sulfur is added thereto, and plasticization is continued for 5 minutes. Then, it is continuously extruded in a vacuum at a pressure of 3.5 MPa. After extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

[0083] The environmentally friendly rubber materials for knee pads prepared in Examples 1-5 and Comparative Examples 1-2 were prepared as test specimens. The tensile strength and elongation at break of the test specimens prepared in Examples 1-5 and Comparative Examples 1-3 were tested in accordance with GB / T 528-1998.

[0084] The test specimens prepared in Examples 1-5 and Comparative Examples 1-3 were placed in a 35°C environment for 30 days, and then placed in a 150°C environment for hot air aging for 7 days. The tensile strength and elongation at break were then tested.

[0085] According to QB / T 4341-2012, the test samples prepared in Examples 1-5 and Comparative Examples 1-3 were tested for their anti-Staphylococcus aureus performance;

[0086] The test results are shown in Table 1 below;

[0087] Table 1.

[0088]

[0089] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing an environmentally friendly rubber material for knee pads, characterized in that: The following steps are involved: S1. Preparation of anti-aging modified kaolin; S11. Heating kaolin to 800-900°C, calcining at this temperature for 2-4 hours, stopping heating, cooling to room temperature, grinding the obtained kaolin through an 80-mesh sieve, mixing the ground product with hydrochloric acid, ultrasonically dispersing it evenly, heating to 70-85°C, stirring and reacting for 4-24 hours, centrifuging and precipitating it, washing it 3-5 times with hydrogen peroxide, and drying it to constant weight to obtain a kaolin mineral; re-dispersing the kaolin mineral in toluene, adding aminopropyltrimethoxysilane and deionized water thereto, heating to 80-90°C, stirring and reacting for 8-12 hours in the dark, centrifuging and precipitating it, washing it 3-5 times with anhydrous ethanol, and vacuum drying it to constant weight to obtain an amino-modified calcined kaolin; S12. Disperse p-aminodiphenylamine in hydrochloric acid, stir and mix thoroughly, and then add cyanamide under nitrogen atmosphere. Heat to 85-95°C and reflux with stirring for 4-8 hours. After removing excess solvent by rotary evaporation, wash with deionized water 1-2 times, and evaporate in vacuo to constant weight to obtain guanylated diphenylamine. S13. The guanidinated diphenylamine was dispersed in acetone and stirred to mix uniformly. Maleic anhydride was added thereto under nitrogen atmosphere. The reaction was stirred at room temperature for 4-8 hours. The excess solvent was removed by rotary evaporation, washed with deionized water, and evaporated in vacuo to constant weight to obtain carboxylated diphenylamine. S14. The amino-modified calcined kaolin was dispersed in acetone and uniformly dispersed by ultrasonication. Carboxylated diphenylamine was then added thereto. The temperature was raised to 55-56°C and the mixture was stirred under reflux for 4-24 hours. The excess solvent was removed by rotary evaporation. The dried product was collected and ground through a 1250 mesh sieve to obtain an anti-aging modified kaolin. S2. Add anti-aging modified kaolin, foaming agent, stearic acid, accelerator and softener to natural rubber, heat to 110-125 ℃, knead for 13-18min, discharge, cool to 30-40 ℃, continue to masticate for 2-5min, cut out the sheet, cool to room temperature to obtain a film; S3. After the film is allowed to stand for 12-24 hours, it is heated again to 35-45°C, a vulcanizing agent is added thereto, and plasticization is continued for 2-5 minutes. After vacuum continuous extrusion molding, it is vulcanized and foamed to obtain an environmentally friendly rubber material for knee pads.

2. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S11, the mass ratio of the kaolin mineral to aminopropyltrimethoxysilane is 1:(5-20) in parts by weight; The mass ratio of the aminopropyltrimethoxysilane to deionized water is 5:(1-3).

3. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S12, the mass ratio of p-aminodiphenylamine to monocyanamide is 1:(0.23-1.38) in parts by weight.

4. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S13, the mass ratio of the guanidinated diphenylamine to maleic anhydride is 1:(0.35-0.48) in parts by weight.

5. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S14, the mass ratio of the amino-modified calcined kaolin to the carboxylated diphenylamine is 1:(0.1-0.45) in parts by weight.

6. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: The environmentally friendly rubber material for knee pads comprises the following components by weight: 85-100 parts of natural rubber, 6-10 parts of anti-aging modified kaolin, 18-25 parts of foaming agent, 1.5-4 parts of stearic acid, 2-4 parts of accelerator and 20-25 parts of softener.

7. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S2, the foaming agent is any one of foaming agent OBSH, foaming agent AC, and foaming agent ADCD10; and the accelerator is zinc oxide.

8. The method for preparing an environmentally friendly rubber material for knee pads according to claim 1, characterized in that: In step S2, the softener is cyclopentane oil.

9. An environmentally friendly rubber material for knee pads prepared by the preparation method according to any one of claims 1 to 8.

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