A method for preventing mildew of natural rubber

Abstract

The present invention provides a method for preventing mildew of natural rubber, belonging to the technical field of polymer materials. In the present invention, cellulose nanofibers are mixed with a volatile organic solvent to obtain a mildew-proof agent dispersion; the mildew-proof agent dispersion is coated on the surface of natural rubber. The present invention uses cellulose nanofibers as a mildew-proof agent, which can efficiently kill bacteria, effectively delay the mildew phenomenon of natural rubber during storage, has the characteristics of low toxicity, high efficiency, broad spectrum, long-term effectiveness, and environmental friendliness, can significantly improve the mildew-proof performance of natural rubber, and has no impact on the subsequent use of natural rubber. In the present invention, the mildew-proof agent dispersion is evenly coated on the surface of natural rubber, and after waiting for the solvent to volatilize, it can be packaged and stored.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly to a method for preventing mildew of natural rubber. Background Art

[0002] Natural rubber has the characteristics of high tear strength and good comprehensive performance. It is an indispensable material for national security and economic construction and has extensive applications in national defense, transportation, daily life, etc.

[0003] Natural rubber is formed by coagulating latex. The composition of natural latex is complex. As a naturally synthesized macromolecular compound, its rubber material is not pure polyisoprene. It contains 10% non-rubber substances by mass. The non-rubber substances largely determine the structure and properties of natural rubber, and protein is the most representative substance among the non-rubber substances. During the rubber-making process, a part of the latex protein flows away with the whey, and the remaining part remains in the product. The presence of protein can provide the stability of latex, accelerate the vulcanization process, and is beneficial to the improvement of the strength and aging performance of the material. Therefore, protein is essential and cannot be removed. On the other hand, protein is also a nutrient for the reproduction of molds, and protein has strong water absorption. Under suitable temperature and humidity conditions, it is easy for rubber and rubber products to breed various molds. The growth and spread of molds will cause irreversible changes in the internal molecular structure of natural rubber, resulting in the deterioration or even loss of the use performance of natural rubber. In addition, rubber products made from mildewed rubber have potential quality and safety hazards during storage and application. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preventing mildew of natural rubber. By using the method of the present invention, bacteria can be efficiently killed, the mildew phenomenon of natural rubber during storage can be effectively delayed, and it has no influence on the subsequent use of natural rubber.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preventing mildew of natural rubber, comprising the following steps:

[0007] Mix cellulose nanofibers with a volatile organic solvent to obtain a mildew-proof agent dispersion;

[0008] Coat the mildew-proof agent dispersion on the surface of natural rubber.

[0009] Preferably, the volatile organic solvent includes an alcohol solvent.

[0010] Preferably, the alcohol solvent includes ethanol.

[0011] Preferably, the mass content of cellulose nanofibers in the mildew-proof agent dispersion is 5-20%.

[0012] Preferably, the coating includes spraying.

[0013] Preferably, the coating amount of the mildew-proof agent dispersion is 9-12 mL / m 2 .

[0014] Preferably, the preparation method of the cellulose nanofibers includes the following steps:

[0015] Mix sodium hydroxide, pulp and water. After the sodium hydroxide is dissolved, add 2,3-epoxypropyltrimethylammonium chloride to the obtained mixed solution and carry out a water bath reaction to obtain a modified fiber liquor;

[0016] Adjust the pH value of the modified fiber liquor to neutral to obtain a neutral fiber slurry;

[0017] Wash the neutral fiber slurry, dry it to obtain solid cellulose;

[0018] Dilute the solid cellulose with water into a slurry with a solid content of 0.8-1.0 wt%, homogenize the slurry, and freeze-dry it to obtain cellulose nanofibers.

[0019] Preferably, the temperature of the water bath reaction is 40-70 °C and the time is 6-8 h.

[0020] Preferably, the number of times of homogenization treatment is multiple.

[0021] Preferably, the mass of the pulp is based on dry weight, the mass ratio of sodium hydroxide to pulp is 1:(1-2), and the mass ratio of pulp to 2,3-epoxypropyltrimethylammonium chloride is 1:(14-15).

[0022] The present invention provides a method for preventing mildew of natural rubber, including the following steps: mixing cellulose nanofibers with a volatile organic solvent to obtain a mildew-proof agent dispersion; coating the mildew-proof agent dispersion on the surface of natural rubber. The present invention uses cellulose nanofibers as a mildew-proof agent, which can efficiently kill bacteria, effectively delay the mildew phenomenon of natural rubber during storage, has the characteristics of low toxicity, high efficiency, broad spectrum, long-term effectiveness, and environmental friendliness, can significantly improve the mildew-proof performance of natural rubber, and has no impact on the subsequent use of natural rubber. The present invention uniformly coats the mildew-proof agent dispersion on the surface of natural rubber, and after waiting for the solvent to volatilize, it can be packaged and stored. Detailed Embodiments

[0023] The present invention provides a method for preventing mildew of natural rubber, including the following steps:

[0024] Mix cellulose nanofibers with a volatile organic solvent to obtain a mildew-proof agent dispersion;

[0025] Coat the mildew-proof agent dispersion on the surface of natural rubber.

[0026] In the present invention, the cellulose nanofibers can be commercially available products well-known in the art or prepared by methods well-known in the art.

[0027] When prepared, the preparation method of the cellulose nanofibers preferably includes the following steps: Mix sodium hydroxide, pulp and water, and after the sodium hydroxide is dissolved, add 2,3-epoxypropyltrimethylammonium chloride to the obtained mixed solution, and carry out a water bath reaction to obtain a modified fiber liquor;

[0028] Adjust the pH value of the modified fiber liquor to neutral to obtain a neutral fiber slurry;

[0029] Wash the neutral fiber slurry, and dry it to obtain solid cellulose;

[0030] Dilute the solid cellulose with water into a slurry with a solid content of 0.8 - 1.0 wt%, homogenize the slurry, and freeze-dry it to obtain cellulose nanofibers.

[0031] In the present invention, sodium hydroxide, pulp and water are mixed, and after the sodium hydroxide is dissolved, 2,3-epoxypropyltrimethylammonium chloride (EPTAC) is added to the obtained mixed solution, and a water bath reaction is carried out to obtain a modified fiber liquor.

[0032] In the present invention, the mass of the pulp is based on dry weight, and the mass ratio of sodium hydroxide to pulp is preferably 1:(1 - 2), more preferably 1:1; there is no special requirement for the amount of water used in the present invention, as long as the sodium hydroxide can be completely dissolved. In the present invention, the role of sodium hydroxide is to remove excess lignin and hemicellulose in the pulp.

[0033] In the present invention, the mass of the pulp is based on dry weight, and the mass ratio of the pulp to 2,3-epoxypropyltrimethylammonium chloride is preferably 1:(14 - 15), more preferably 1:14.5.

[0034] In the present invention, the temperature of the water bath reaction is preferably 40 - 70 °C, more preferably 50 - 65 °C, the time of the water bath reaction is preferably 6 - 8 h, more preferably 7 - 8 h; the water bath reaction is preferably carried out under stirring conditions. In the present invention, during the water bath reaction, 2,3-epoxypropyltrimethylammonium chloride reacts with cellulose, introducing an ammonium salt onto the cellulose, increasing the polarity of the cellulose, and promoting the uniform dispersion of the cellulose in water.

[0035] After obtaining the modified fiber liquor, the present invention adjusts the pH value of the modified fiber liquor to neutral to obtain a neutral fiber slurry. By adjusting the pH value of the modified fiber liquor to neutral, the present invention can reduce the solubility of the modified cellulose in acid and alkali solutions and obtain more cellulose.

[0036] The present invention preferably uses a dilute hydrochloric acid solution to adjust the pH value of the modified fiber liquor; the concentration of the dilute hydrochloric acid solution is preferably 0.1 mol / L.

[0037] After obtaining the neutral fiber slurry, the present invention washes and dries the neutral fiber slurry to obtain solid cellulose. The present invention has no special requirements for the water washing and drying processes, and the well-known water washing and drying processes in the art can be used.

[0038] After obtaining the solid cellulose, the present invention dilutes the solid cellulose with water into a slurry with a solid content of 0.8-1.0 wt%, homogenizes the slurry, and freeze-dries it to obtain cellulose nanofibers.

[0039] In the present invention, the homogenization treatment is preferably carried out in a high-pressure homogenizer; the number of homogenization treatments is preferably multiple times, more preferably 4 times, the pressure of the first homogenization treatment is preferably 300 bar, the pressure of the second homogenization treatment is preferably 600 bar, and the pressures of the third and fourth homogenization treatments are preferably 1000 bar. The time of each homogenization treatment is preferably 15 min.

[0040] The present invention uses homogenization treatment to obtain a uniform and transparent aqueous dispersion of cellulose nanofibers.

[0041] The present invention has no special requirements for the freeze-drying, and the well-known freeze-drying in the art can be used.

[0042] The present invention mixes cellulose nanofibers with a volatile organic solvent to obtain a mildew-proof agent dispersion.

[0043] In the present invention, the volatile organic solvent preferably includes an alcohol solvent, and the alcohol solvent preferably includes ethanol. In the present invention, the mass content of cellulose nanofibers in the mildew-proof agent dispersion is preferably 5-20%, more preferably 8-17%, and further preferably 10-15%.

[0044] After obtaining the mildew-proof agent dispersion, the present invention coats the mildew-proof agent dispersion on the surface of natural rubber.

[0045] The present invention has no special requirements for the natural rubber, which can be a natural rubber product or a natural rubber compound. In the present invention, the coating preferably includes spraying.

[0046] In the present invention, the coating amount of the mildew-proof agent dispersion is preferably 9-12 mL / m 2 , more preferably 10-11 mL / m 2 , and further preferably 10.5 mL / m 2 .

[0047] In the present invention, cellulose nanofibers are used as the mildew-proof agent, which can efficiently kill bacteria, effectively delay the mildew phenomenon of natural rubber during storage, and has the characteristics of low toxicity, high efficiency, broad spectrum, long-term effectiveness and environmental friendliness. It can significantly improve the mildew-proof performance of natural rubber and has no influence on the subsequent use of natural rubber.

[0048] In the present invention, the mildew-proof agent dispersion is uniformly coated on the surface of natural rubber, and after the solvent volatilizes, it can be packaged and stored.

[0049] The following examples are used to illustrate in detail the mildew-proof method of natural rubber provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0050] The preparation process of the cellulose nanofibers used in the following examples is as follows:

[0051] 2 g of NaOH and 2 g of pulp (dry weight) are successively added to a three-necked round-bottom flask containing 200 mL of deionized water. After the NaOH solid is completely dissolved, 29 g of 2,3-epoxypropyltrimethylammonium chloride (EPTAC) solid is quickly added. After stirring evenly, it is placed in a water bath at 65 °C and stirred for 8 h. After the reaction is completed, the pH value is adjusted to neutral with 0.1 mol / L dilute hydrochloric acid solution, and the pulp fibers are washed thoroughly with deionized water and dried. The dried pulp fibers are diluted with deionized water to a slurry with a solid content of 0.8-1.0 wt%, and then homogenized with a high-pressure homogenizer at 300 bar for 15 min, 600 bar for 15 min, and 1000 bar for 15 min (homogenized 2 times), a total of 4 times of homogenization, to obtain a uniform and transparent cellulose nanofiber aqueous dispersion. Finally, the homogenized sample is freeze-dried to obtain cellulose nanofibers.

[0052] Examples 1-4

[0053] Cellulose nanofibers are mixed with ethanol to prepare mildew-proof agent dispersions with different concentrations. The mass contents of cellulose nanofibers in the mildew-proof agent dispersions are 5%, 10%, 15% and 20% respectively;

[0054] Take 4 production rubber blocks with a length of 670 mm, a width of 330 mm and a height of 250 mm (the formula is shown in Table 1) as test samples, and according to 10.5 mL / m 2The spraying amount is evenly sprayed with the cellulose nanofiber mildew preventive on all surfaces of the test samples. The test is carried out according to the rubber mildew resistance test method HG / T 4301-2012. The results are shown in Table 3, and the mildew resistance grade evaluation standard refers to Table 2.

[0055] Comparative Example 1

[0056] The difference from the example is that the mildew preventive dispersion liquid is not sprayed, serving as a blank sample.

[0057] Table 1 Raw rubber detection formula

[0058] Raw material name Ratio (parts by weight) Raw rubber 100.00 Stearic acid 0.50 Zinc oxide 6.00 Accelerator M 0.50 Sulfur 3.50

[0059] Table 2 Mildew grade evaluation

[0060]

[0061]

[0062] Table 3 Mildew resistance

[0063] Sample name Treatment method Mildew-proof grade Control Example 1 No mildew-proof agent sprayed 2 Example 1 Spray 5% mildew-proof agent 1 Example 2 Spray 10% mildew-proof agent 0 Example 3 Spray 15% mildew-proof agent 0 Example 4 Spray 20% mildew-proof agent 0

[0064] As can be seen from the results in Table 3, using cellulose nanofibers as the mildew preventive, after treating natural rubber, it can efficiently kill bacteria and has good mildew prevention effect.

[0065] The processed raw rubber materials of Examples 1-4 and Comparative Example 1 are placed in the warehouse for 4 months to conduct the mildew prevention test in the storage environment. The test results of the raw rubber performance are shown in Table 4.

[0066] Table 4 Test results of raw rubber performance

[0067]

[0068]

[0069] As can be seen from the results in Table 4, the mildew preventive adopted in the present invention has little influence on the various performances of rubber and does not damage the molecular structure and appearance of rubber. After long-term storage of natural rubber with mildew prevention treatment, the performance degradation rate does not exceed 10%, which has no impact on the subsequent use of natural rubber.

[0070] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preventing mildew of natural rubber, characterized in that, It includes the following steps: Mix cellulose nanofibers with a volatile organic solvent to obtain a mildew-proof agent dispersion; Coat the mildew-proof agent dispersion on the surface of natural rubber; The preparation method of the cellulose nanofibers includes the following steps: Mix sodium hydroxide, pulp and water. After the sodium hydroxide is dissolved, add 2,3-epoxypropyltrimethylammonium chloride to the obtained mixed solution and carry out a water bath reaction to obtain a modified fiber liquor; Adjust the pH value of the modified fiber liquor to neutral to obtain a neutral fiber slurry; Wash the neutral fiber slurry with water and dry it to obtain solid cellulose; Dilute the solid cellulose with water into a slurry with a solid content of 0.8-1.0 wt%, homogenize the slurry, and freeze-dry it to obtain cellulose nanofibers.

2. The mildew-proof method according to claim 1, characterized in that, The volatile organic solvent includes an alcohol solvent.

3. The mold-proof method according to claim 2, characterized in that, The alcohol solvent includes ethanol.

4. The mildew-proof method according to any one of claims 1 to 3, characterized in that, The mass content of cellulose nanofibers in the mildew-proof agent dispersion is 5-20%.

5. The mildew-proof method according to claim 1, wherein The coating includes spraying.

6. The mold-proof method according to claim 1 or 5, characterized in that, The coating amount of the mildew-proof agent dispersion liquid is 9-12 mL / m 2 .

7. The mold-proof method according to claim 1, wherein The temperature of the water bath reaction is 40-70 °C and the time is 6-8 h.

8. The mildew-proof method according to claim 1, wherein The number of times of the homogenization treatment is multiple times.

9. The mold-proof method according to claim 1, wherein The mass of the pulp is calculated on a dry weight basis. The mass ratio of sodium hydroxide to pulp is 1:(1-2), and the mass ratio of pulp to 2,3-epoxypropyltrimethylammonium chloride is 1:(14-15).

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