A natural rubber applicable to an aviation tire tread rubber and a preparation method thereof

Abstract

The present invention provides a natural rubber applicable to an aircraft tire tread rubber and a preparation method thereof, belonging to the technical field of natural rubber processing. The preparation method of the natural rubber applicable to the aircraft tire tread rubber according to the present invention comprises the following steps: dissolving protease, active bacteria and sugar in water to obtain a coagulant solution; adding the coagulant solution into natural latex and aging to obtain the natural rubber applicable to the aircraft tire tread rubber. The present invention uses natural latex as a raw material, protease, active bacteria and sugar as a coagulation system, and adopts the processing technology of domestic standard rubber to prepare a high-performance domestic natural rubber. The domestic natural rubber has the advantages of high strength, wear resistance, heat resistance, etc., is green and environmentally friendly, and can meet the use requirements of the aircraft tire tread rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of natural rubber processing, and particularly relates to a natural rubber applicable to an aviation tire tread rubber and a preparation method thereof. Background Art

[0002] The service conditions of aviation tire tread rubber are very harsh. When the tire touches the ground under load conditions and accelerates to a higher speed, the tread needs to withstand the impact force generated during the instant of aircraft landing, and also withstand the frictional force generated during aircraft takeoff. It is required that the tread rubber has good wear resistance, impact resistance, tear resistance, puncture resistance and fatigue resistance, and low heat generation and rolling resistance. With the development of aviation technology, the takeoff and landing speeds of aircraft are getting higher and higher, and traditional bias tires can no longer meet the usage requirements of high speed and high load. Natural rubber is the main component of tread rubber, and the dosage of raw rubber accounts for 80-100%, which plays a key role in the performance of tread rubber. Through investigation, it is found that domestic aviation tire manufacturers all import a large amount of foreign natural rubber, and the performance of domestic natural rubber cannot meet the requirements of aviation tire tread rubber. The reason is that traditional acid-coagulated domestic natural rubber has defects such as low strength, high heat generation and unstable quality compared with imported rubber, resulting in problems such as non-wear-resistant tread rubber, chunking and short service life. Summary of the Invention

[0003] The purpose of the present invention is to provide a natural rubber applicable to an aviation tire tread rubber and a preparation method thereof. The domestic natural rubber prepared by the method of the present invention has performance reaching that of imported Indonesian No. 1 smoked sheet rubber, and has advantages such as high strength, wear resistance and heat resistance, and can meet the usage requirements of aviation tire tread rubber.

[0004] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a preparation method of a natural rubber applicable to an aviation tire tread rubber, including the following steps: dissolving protease, active bacteria and sugar in water to obtain a coagulant solution;

[0006] Adding the coagulant solution to natural latex, and aging to obtain a natural rubber applicable to an aviation tire tread rubber.

[0007] Preferably, the protease includes lysozyme or chymosin.

[0008] Preferably, the mass of the protease is 0.1-0.2% of the dry weight of natural latex.

[0009] Preferably, the active bacteria include Bifidobacterium or Lactobacillus.

[0010] Preferably, the mass of the active bacteria is 0.1-0.2% of the dry weight of natural latex.

[0011] Preferably, the sugar includes white granulated sugar.

[0012] Preferably, the mass of the sugar is 0.2-0.4% of the dry weight of the natural latex.

[0013] Preferably, the solid content of the natural latex is 20-25%.

[0014] Preferably, after ripening, the obtained raw rubber clot is successively dehydrated, granulated and dried.

[0015] The present invention provides natural rubber applicable to an aircraft tire tread rubber prepared by the preparation method described in the above solution.

[0016] The present invention provides a preparation method of natural rubber applicable to an aircraft tire tread rubber, comprising the following steps: dissolving protease, active bacteria and sugar in water to obtain a coagulant solution; adding the coagulant solution into natural latex and ripening to obtain natural rubber applicable to an aircraft tire tread rubber.

[0017] The inventor has found through research that the protein content of non-rubber hydrocarbon substances in fresh latex accounts for 2-3%. Protein is positively charged under neutral or alkaline pH conditions and has an important impact on the colloidal stability of fresh latex. Adding protease can decompose part of the protein. On the one hand, it destroys the stability of the latex and achieves the effect of coagulating the latex; on the other hand, the amino acids after protein decomposition can promote the vulcanization of rubber and play a role in improving the strength and elongation properties of the tread rubber. At the same time, the inventor further found that the combined use of active bacteria and sugar can accelerate the coagulation of latex. The action of microorganisms can change the non-rubber substances in the latex. Proteins, sugars, phosphates, etc. in the latex are nutrients required for the reproduction of bacteria. Sugars are absorbed and utilized by bacteria and converted into acids. Proteins are also decomposed into amino acids by enzymes secreted by bacteria and absorbed and utilized or denatured, resulting in the destruction of the stability of rubber particles and the continuous decrease of the pH value until it reaches or approaches the isoelectric point of the latex. Adding active bacteria and providing them with nutrient sugar can accelerate the coagulation speed of the latex.

[0018] By reducing the protein content in natural rubber, the present invention greatly reduces the heat generation of raw rubber, extends the shelf life of the raw rubber and the service life of the tire. The protein content of the raw rubber is reduced by 40-50% compared with traditional acid coagulation, and the compression heat generation is reduced by 3-5°C. At the same time, protein has strong water absorption, which can increase the water absorption and conductivity of raw rubber and rubber products. Reducing the protein content can greatly improve the problem of mildew of raw rubber and rubber products and extend the shelf life of the product.

[0019] In addition, the present invention also improves the strength and aging resistance of natural rubber. The coagulation system maintains the molecular structure of rubber hydrocarbon without being damaged, greatly improving the strength of raw rubber. On the other hand, the decomposition products of protein can promote the vulcanization of rubber, improve the modulus at a specified elongation and tensile strength of rubber, delay the aging of rubber, improve the wear resistance and aging resistance of the tread rubber of aircraft tires, and extend the service life of the tires.

[0020] The present invention uses a biological method to coagulate natural latex, which is non-toxic, safe, does not add acid, does not damage the molecular structure of rubber hydrocarbon, has high coagulation efficiency and is environmentally friendly.

[0021] The present invention adopts the production and processing technology of domestic standard natural rubber, and is prepared by coagulation (ripening), thinning and dehydrating, creping and dehydrating, and drying. The raw materials of the coagulation system used are all safe and non-toxic, and have no damage to equipment and production personnel, which is a green and environment-friendly preparation method. Specific embodiments

[0022] The present invention provides a preparation method of natural rubber applicable to the tread rubber of aircraft tires, comprising the following steps: dissolving protease, active bacteria and sugar in water to obtain a coagulant solution;

[0023] Adding the coagulant solution to natural latex, and ripening to obtain natural rubber applicable to the tread rubber of aircraft tires.

[0024] In the present invention, without special instructions, the raw materials used are all well-known commercially available products in the art.

[0025] The present invention dissolves protease, active bacteria and sugar in water to obtain a coagulant solution.

[0026] In the present invention, the protease preferably includes lysozyme or chymosin; the active bacteria preferably include Bifidobacterium or Lactobacillus; the sugar preferably includes granulated sugar. The present invention uses lysozyme or chymosin, which can play a good enzymatic hydrolysis role within different pH value ranges; using Lactobacillus or Bifidobacterium as active bacteria has the advantage of high activity. The present invention has no special requirements for the dosage of the water, and it is only necessary to completely dissolve the protease, active bacteria and sugar.

[0027] After obtaining the coagulant solution, the present invention adds the coagulant solution to natural latex, and ripening to obtain natural rubber applicable to the tread rubber of aircraft tires.

[0028] In the present invention, the natural latex preferably has no gel and the ammonia content is lower than 0.05 wt%. In the present invention, the solid content of the natural latex is preferably 20-25%, more preferably 21-24%. In the present invention, the natural latex is preferably obtained by diluting fresh latex with water.

[0029] In the present invention, the mass of protease in the coagulant solution is preferably 0.1-0.2%, more preferably 0.1-0.15% of the dry weight of natural latex; the mass of active bacteria in the coagulant solution is preferably 0.1-0.2%, more preferably 0.1-0.15% of the dry weight of natural latex; the mass of sugar in the coagulant solution is preferably 0.2-0.4%, more preferably 0.2-0.3% of the dry weight of natural latex. The present invention preferably adds the coagulant solution to natural latex under stirring conditions.

[0030] In the present invention, adding protease can decompose part of the protein. On the one hand, it destroys the stability of the latex and achieves the effect of coagulating the latex; on the other hand, the amino acids after protein decomposition can promote the vulcanization of rubber and improve the strength and elongation properties of the tread rubber. The combination of active bacteria and sugar can accelerate the coagulation of latex.

[0031] In the present invention, the ripening is preferably carried out under room temperature conditions, and the ripening time is preferably within 12 h. During the ripening process of the present invention, natural latex coagulates under the action of the coagulant to form raw rubber coagulum. When the ripening time is too long, the coagulum will become hard, which is not conducive to subsequent dehydration and drying.

[0032] After completing the ripening, the present invention preferably further includes dehydrating, granulating and drying the obtained raw rubber coagulum to obtain natural rubber suitable for the tread rubber of aircraft tires.

[0033] In the present invention, the dehydration preferably includes thinning dehydration and creping dehydration; the present invention has no special requirements for the granulating and drying processes, and the well-known granulating and drying processes in the art can be adopted.

[0034] The present invention uses natural latex as the raw material, protease, active bacteria and sugar as the coagulation system, and adopts the processing technology of domestic standard rubber to prepare high-performance domestic natural rubber.

[0035] The present invention provides natural rubber suitable for the tread rubber of aircraft tires prepared by the preparation method described in the above solution.

[0036] By reducing the protein content in natural rubber, the present invention greatly reduces the heat generation of raw rubber, extends the shelf life of raw rubber and the service life of tires. The protein content of raw rubber is reduced by 40-50% compared with traditional acid coagulation, and the compression heat generation is reduced by 3-5 °C. At the same time, protein has strong water absorption, which can increase the water absorption and conductivity of raw rubber and rubber products. Reducing the protein content can greatly improve the problem of mildew of raw rubber and rubber products and extend the shelf life of products.

[0037] In addition, the present invention also improves the strength and aging resistance of natural rubber. The coagulation system maintains the molecular structure of rubber hydrocarbon without being damaged, greatly improving the strength of raw rubber. On the other hand, the decomposition products of proteins can promote the vulcanization of rubber, improve the modulus at a specified elongation and tensile strength of rubber, delay the aging of rubber, improve the wear resistance and aging resistance of the tread rubber of aircraft tires, and extend the service life of tires.

[0038] The following examples are used to illustrate in detail the natural rubber applicable to the tread rubber of aircraft tires and its preparation method provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] Take 5 kg of latex in a bucket, with a dry content of 30%, and the dry rubber is 1.5 kg. Add water to dilute it to a dry content of 21%. Accurately weigh 1.5 g of lysozyme with a dry rubber content of 0.1%, 1.5 g of Lactobacillus with a dry rubber content of 0.1%, and 3.0 g of granulated sugar with a dry rubber content of 0.1%. After dissolving lysozyme, Lactobacillus and sugar in water, add them to the latex, stir evenly, let it stand for 10 h, press and dehydrate the coagulated mass after sufficient coagulation, granulate it, and then obtain the finished natural rubber on the drying line.

[0041] Example 2

[0042] Take 5 kg of latex in a bucket, with a dry content of 30%, and the dry rubber is 1.5 kg. Add water to dilute it to a dry content of 21%. Accurately weigh 1.5 g of rennet with a dry rubber content of 0.1%, 1.5 g of Bifidobacterium with a dry rubber content of 0.1%, and 3.0 g of granulated sugar with a dry rubber content of 0.1%. After dissolving rennet, Bifidobacterium and sugar in water, add them to the latex, stir evenly, let it stand for 10 h, press and dehydrate the coagulated mass after sufficient coagulation, granulate it, and then obtain the finished natural rubber on the drying line.

[0043] Example 3

[0044] The inventor carried out industrial trial production on the production line. 1000 kg of latex, with a dry content of 30%, and the dry rubber is 300 kg. Add water to dilute it to a dry content of 21%. Accurately weigh 3.0 kg of lysozyme, 3.0 kg of Lactobacillus, and 6.0 kg of granulated sugar. The subsequent process is in accordance with Example 1.

[0045] Example 4

[0046] The inventor carried out industrial trial production on the production line. 1000 kg of latex, with a dry content of 30%, and the dry rubber is 300 kg. Add water to dilute it to a dry content of 21%. Accurately weigh 3.0 kg of rennet, 3.0 kg of Bifidobacterium, and 6.0 kg of granulated sugar. The subsequent process is in accordance with Example 2.

[0047] Performance testing of the raw rubber products. The testing formula is shown in Table 1. The rubber mixing process is as follows: Use an open mill for rubber mixing. The roll gap of the roller is 3 mm. After adding materials according to Table 1, make three passes of the triangular package, extrude a sample of about 3 mm and let it stand for more than 12 h. After standing, the roll gap is 3 mm, it is passed thinly once, wrapped around the roll, cut three times on each side, extrude a sample of about 3 mm, and vulcanize at 140 °C for 30 min to obtain the test sample. The comparison samples are domestic standard rubber SCR5 and Indonesian No. 1 smoked sheet rubber. The specific test results are shown in Table 2.

[0048] Main components of the formula in Table 1

[0049]

[0050]

[0051] Testing results of the raw rubber performance in Table 2

[0052]

[0053] It can be seen from the results in Table 2 that the tensile strength and tear strength of the products in Examples 1 - 4 are higher than those of domestic standard rubber and reach the level of imported Indonesian No. 1 smoked sheet rubber. The protein content is low, which greatly reduces the heat generation.

[0054] Performance testing of the tread rubber formula: The comparison samples are domestic standard rubber SCR5 and Indonesian No. 1 smoked sheet rubber. The specific tread rubber formula is shown in Table 3, and the test results are shown in Table 4.

[0055] Main components of the tread rubber formula in Table 3

[0056] Raw material name Ratio (parts by weight) Raw rubber 100.0 Carbon black N110 30.0 Carbon black N234 25.0 Zinc oxide 3.5 Accelerator 1.5 Antioxidant 3.0 Vulcanizing agent 3.5 Aromatic oil 3.0 Total 169.5

[0057] Testing results of the tread rubber formula in Table 4

[0058] Test items Example 1 Example 2 Example 3 Example 4 SCR5 Indonesian No. 1 smoked sheet Tensile strength MPa 28.3 27.6 28.2 27.9 23.2 28.9 Elongation at break % 488 500 496 502 452 506 Tear strength KN / m 113 118 116 112 104 118 300% modulus MPa 15.1 16.4 16.3 16.5 14.1 16.5 Shore A hardness degree 70 72 73 72 65 73 <![CDATA[Ackermann abrasion cm 3 > 0.112 0.106 0.105 0.110 0.167 0.105 Compression fatigue temperature rise ℃ 36 34 33 35 43 35

[0059] Remarks: Vulcanization conditions: 143 °C × 40 min

[0060] It can be seen from the results in Table 4 that the performance of the domestic natural rubber tread rubber in Examples 1 - 4 of the present invention is far higher than that of domestic SCR5. The tensile strength, elongation at break, tear strength, 300% modulus at 100% elongation, hardness, Akron abrasion and compression fatigue temperature rise are close to those of imported Indonesian No. 1 smoked sheet rubber. Compared with domestic standard rubber, the natural rubber of the present invention can greatly improve the wear resistance, heat resistance and other properties of the tread rubber, is green and environmentally friendly, can meet the use requirements of the tread rubber of aircraft tires, and can replace imported smoked sheet rubber.

[0061] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing natural rubber suitable for aircraft tire tread rubber, characterized in that: The following steps are involved: Dissolving protease, active bacteria and sugar in water to obtain a coagulant solution; The coagulant solution is added to natural rubber latex and matured to obtain natural rubber suitable for aircraft tire tread rubber; the protease is chymosin; and the active bacteria is bifidobacterium; The mass of the protease is 0.1-0.2% of the dry weight of the natural rubber latex; the mass of the active bacteria is 0.1-0.2% of the dry weight of the natural rubber latex; the mass of the sugar is 0.2-0.4% of the dry weight of the natural rubber latex; The natural rubber latex is gel-free and has an ammonia content of less than 0.05 wt %.

2. The preparation method according to claim 1, characterized in that The sugar includes white sugar.

3. The preparation method according to claim 1, characterized in that The solid content of the natural rubber latex is 20-25%.

4. The preparation method according to claim 1, characterized in that After the aging, the obtained raw rubber agglomerate is sequentially dehydrated, granulated and dried.

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