Advanced stabilizer for ammonia-free natural rubber production

Abstract

The invention discloses an advanced stabilizer for ammonia-free natural rubber production, which is made of the following ingredients: chitosan, sodium diacetate, methyl parahydroxybenzoate, alginate, citric acid, sodium sorbate, and a special active agent; compared with conventional commercially available ammonia-containing preservatives, the natural rubber latex preservative prepared by the invention does not contain ammonia, and not only has a longer shelf life, but also, because it does not contain ammonia, it can avoid the tedious deamination of downstream manufacturers, improve production efficiency, and save production costs. By adopting the natural rubber latex preservative prepared by the invention, the active ingredients contained can act on the cell wall and cell membrane of microorganisms, and by destroying or damaging the cell wall of the microorganism, the synthesis mechanism of the cell wall of the microorganism is interfered, resulting in the leakage of substances in the microorganism cell, thereby inhibiting the growth and reproduction of the microorganism and improving the stabilizing effect on natural rubber latex.

Description

Technical Field

[0001] The invention belongs to the technical field of latex production, in particular to an advanced stabilizer for the production of ammonia-free natural rubber. Background Art

[0002] Rubber is an important industrial raw material, and is one of the four major industrial raw materials along with steel, petroleum and coal. Rubber has a wide range of uses due to its unique high elasticity, good physical and mechanical properties and electrical insulation properties.

[0003] Commonly used rubbers include natural rubber and synthetic rubber. The current global demand is 20 million tons per year, of which 12 million tons are artificial synthetic rubber and 8 million tons are natural rubber. However, artificial synthetic rubber cannot replace natural rubber; natural rubber is rubber extracted from rubber plants. The latex collected from rubber trees is a milky white liquid that looks similar to milk. It is a product of the biosynthesis of rubber trees and has a very complex composition. In addition to rubber hydrocarbons and water, it also contains a wealth of non-rubber substances such as proteins, sugars, lipids, inorganic salts, enzymes, etc. Under the action of bacteria and enzymes, it is easy and quick to spoil, thus affecting product quality and economic benefits.

[0004] In the prior art, in order to improve the stabilizing effect of natural rubber latex, ammonia water is added to the natural rubber latex to improve the stabilizing effect of natural rubber latex. However, on the one hand, ammonia water has a strong pungent odor and is highly volatile, which can easily affect the working environment and endanger the health of operators. At the same time, after the addition of ammonia water, downstream manufacturers need to perform deammoniation treatment, which increases the processing steps and increases the production cost.

[0005] Therefore, the present invention solves the corresponding problems by providing an advanced stabilizer for ammonia-free natural rubber production. Summary of the invention

[0006] The object of the present invention is to provide an advanced stabilizer for ammonia-free natural rubber production to address the deficiencies in the prior art.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The advanced stabilizer for ammonia-free natural rubber production includes the following ingredients by weight: 3.6-4.8 parts of chitosan, 1-3 parts of sodium diacetate, 2-4 parts of methyl paraben, 1-2 parts of alginate, 3-4 parts of citric acid, 0.5-0.8 parts of sodium sorbate, and 1.2-1.6 parts of a special active agent;

[0009] The weight ratio of chitosan to the specially prepared active agent is 3:1;

[0010] Among them, the special active agent is made from camellia seed oil.

[0011] As a further technical solution: the method for preparing the specially prepared active agent complex is:

[0012] Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate;

[0013] Adding the camellia oil distillate to the solvent, stirring and mixing evenly to obtain a camellia oil distillate solution;

[0014] Place the camellia oil distillate solution in an ice bath and keep warm for 30 minutes;

[0015] Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution;

[0016] Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution;

[0017] The reaction solution is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction solution is adjusted to perform a neutralization reaction to obtain a neutralization product. The neutralization product is dissolved in anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the product is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

[0018] As a further technical solution: the distillation extraction parameters are:

[0019] The distillation extraction is carried out at a temperature of 225-250°C and a pressure of 5-6 mmHg.

[0020] As a further technical solution: the mixing ratio of the camellia oil distillate and the solvent is 20-24g:100mL;

[0021] The mixing ratio of chlorosulfonic acid and solvent is 8-10g:40mL;

[0022] The ice bath temperature was 2°C.

[0023] As a further technical solution: the solvent is chloroform.

[0024] As a further technical solution: the pH is adjusted as follows:

[0025] The pH value of the solution was adjusted to 8.5 at 20° C. using a sodium hydroxide solution with a mass fraction of 10 wt %.

[0026] As a further technical solution: the alginate is sodium alginate.

[0027] A method for preparing an advanced stabilizer for ammonia-free natural rubber production comprises the following steps:

[0028] (1) Preparation:

[0029] Weigh out the following parts by weight:

[0030] Chitosan, sodium diacetate, methyl paraben, alginate, citric acid, sodium sorbate, special active agent;

[0031] (2) Raw material mixing:

[0032] Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain;

[0033] Among them, the stirring speed is 800r / min and the time is 40min.

[0034] As a further technical solution: the method for using the advanced stabilizer for ammonia-free natural rubber production prepared by the method is:

[0035] Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

[0036] As a further technical solution: the advanced stabilizer for the production of ammonia-free natural rubber is added in a proportion of 1-1.5% based on the total amount of fresh natural rubber latex.

[0037] Beneficial effects:

[0038] Compared with conventional commercially available ammonia-containing preservatives, the preservative for natural rubber latex prepared by the present invention does not contain ammonia, and not only has a longer shelf life, but also, because it does not contain ammonia, it can avoid the tedious deammoniation of downstream manufacturers, thereby improving production efficiency and saving production costs.

[0039] The natural rubber latex preservative prepared by the present invention can act on the cell wall and cell membrane of microorganisms, disrupt or injure the cell wall of microorganisms, interfere with the synthesis mechanism of the cell wall of microorganisms, and cause the leakage of substances in microbial cells, thereby inhibiting the growth and reproduction of microorganisms and improving the stabilizing effect on natural rubber latex.

[0040] The coordinated action of the various components in the natural rubber latex prepared by the present invention can act on the enzyme system in the microorganism, inhibit the activity of the enzyme in the microorganism, and interfere with the normal metabolic pathway of the microorganism, thereby further weakening the survival ability of the microorganism.

[0041] Since the activities of microorganisms in natural rubber latex will produce acidic metabolites, these products will reduce the stability of the latex, and the components in the natural rubber latex prepared by the present invention can neutralize these acidic metabolites, prevent the natural rubber latex from coagulating due to excessive acidity, and avoid a significant decrease in the stabilization effect.

[0042] After the natural rubber latex prepared by the present invention is introduced, it can play a certain pH adjustment function, and by being able to keep the natural rubber latex in a relatively stable acid-base environment, it is beneficial to prolong the storage time of the natural rubber latex and ensure the stabilization effect of the natural rubber latex.

[0043] The rubber particles in the latex are surrounded by a mixed film formed by a layer of protein and other substances. This protective film is crucial to maintaining the stability of the latex. The natural rubber latex preservative prepared by the present invention can enhance the strength of this protective film to prevent it from being destroyed and causing the latex to coagulate. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Mechanical stability statistics of advanced stabilizers produced for ammonia-free natural rubber. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] The following are specific embodiments

[0047] Example 1

[0048] A method for preparing an advanced stabilizer for ammonia-free natural rubber production comprises the following steps:

[0049] (1) Preparation:

[0050] Weigh out the following parts by weight:

[0051] 3.6 parts of chitosan, 1 part of sodium diacetate, 2 parts of methyl parahydroxybenzoate, 1 part of sodium alginate, 3 parts of citric acid, 0.5 parts of sodium sorbate, 1.2 parts of special active agent;

[0052] The weight ratio of chitosan to the specially prepared active agent is 3:1;

[0053] Among them, the special active agent is made from camellia seed oil.

[0054] The method for preparing the special active agent complex is as follows:

[0055] Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate;

[0056] The camellia oil distillate is added into a solvent, and the mixture is stirred and evenly mixed to obtain a camellia oil distillate solution; the solvent is chloroform.

[0057] The camellia oil distillate solution was placed in an ice bath and kept warm for 30 minutes; the ice bath temperature was 2°C.

[0058] Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution;

[0059] Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution;

[0060] The reaction liquid is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction liquid is adjusted to 8.5 using a sodium hydroxide solution with a mass fraction of 10wt% at a temperature of 20°C; a neutralization reaction is carried out to obtain a neutralization product, the neutralization product is dissolved with anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the solution is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

[0061] The distillation extraction parameters are:

[0062] The distillation extraction was carried out at a temperature of 225°C and a pressure of 5 mmHg.

[0063] The mixing ratio of camellia oil distillate and solvent is 20g:100mL;

[0064] The mixing ratio of chlorosulfonic acid and solvent is 8g:40mL;

[0065] (2) Raw material mixing:

[0066] Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain;

[0067] Among them, the stirring speed is 800r / min and the time is 40min.

[0068] The advanced stabilizer for ammonia-free natural rubber production prepared by the method is used as follows:

[0069] Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

[0070] The amount of advanced stabilizer added in the production of ammonia-free natural rubber is calculated based on the total amount of fresh natural rubber latex and is added at a ratio of 1%.

[0071] Example 2

[0072] A method for preparing an advanced stabilizer for ammonia-free natural rubber production comprises the following steps:

[0073] (1) Preparation:

[0074] Weigh out the following parts by weight:

[0075] 3.9 parts of chitosan, 2 parts of sodium diacetate, 3 parts of methyl parahydroxybenzoate, 1.2 parts of sodium alginate, 3.6 parts of citric acid, 0.7 parts of sodium sorbate, 1.3 parts of special active agent;

[0076] The weight ratio of chitosan to the specially prepared active agent is 3:1;

[0077] Among them, the special active agent is made from camellia seed oil.

[0078] The method for preparing the special active agent complex is as follows:

[0079] Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate;

[0080] The camellia oil distillate is added into a solvent, and the mixture is stirred and evenly mixed to obtain a camellia oil distillate solution; the solvent is chloroform.

[0081] The camellia oil distillate solution was placed in an ice bath and kept warm for 30 minutes; the ice bath temperature was 2°C.

[0082] Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution;

[0083] Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution;

[0084] The reaction liquid is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction liquid is adjusted to 8.5 using a sodium hydroxide solution with a mass fraction of 10wt% at a temperature of 20°C; a neutralization reaction is carried out to obtain a neutralization product, the neutralization product is dissolved with anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the solution is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

[0085] The distillation extraction parameters are:

[0086] The distillation extraction was carried out at a temperature of 230°C and a pressure of 5.5 mmHg.

[0087] The mixing ratio of camellia oil distillate and solvent is 21g:100mL;

[0088] The mixing ratio of chlorosulfonic acid and solvent is 8g:40mL;

[0089] (2) Raw material mixing:

[0090] Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain;

[0091] Among them, the stirring speed is 800r / min and the time is 40min.

[0092] The advanced stabilizer for ammonia-free natural rubber production prepared by the method is used as follows:

[0093] Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

[0094] The amount of advanced stabilizer added in the production of ammonia-free natural rubber is calculated based on the total amount of fresh natural rubber latex and is added at a ratio of 1.3%.

[0095] Example 3

[0096] A method for preparing an advanced stabilizer for ammonia-free natural rubber production comprises the following steps:

[0097] (1) Preparation:

[0098] Weigh out the following parts by weight:

[0099] 4.2 parts of chitosan, 2 parts of sodium diacetate, 2.5 parts of methyl parahydroxybenzoate, 1.8 parts of sodium alginate, 3.5 parts of citric acid, 0.7 parts of sodium sorbate, 1.4 parts of special active agent;

[0100] The weight ratio of chitosan to the specially prepared active agent is 3:1;

[0101] Among them, the special active agent is made from camellia seed oil.

[0102] The method for preparing the special active agent complex is as follows:

[0103] Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate;

[0104] The camellia oil distillate is added into a solvent, and the mixture is stirred and evenly mixed to obtain a camellia oil distillate solution; the solvent is chloroform.

[0105] The camellia oil distillate solution was placed in an ice bath and kept warm for 30 minutes; the ice bath temperature was 2°C.

[0106] Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution;

[0107] Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution;

[0108] The reaction liquid is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction liquid is adjusted to 8.5 using a sodium hydroxide solution with a mass fraction of 10wt% at a temperature of 20°C; a neutralization reaction is carried out to obtain a neutralization product, the neutralization product is dissolved with anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the solution is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

[0109] The distillation extraction parameters are:

[0110] The distillation extraction was carried out at a temperature of 240°C and a pressure of 5.2 mmHg.

[0111] The mixing ratio of camellia oil distillate and solvent is 21g:100mL;

[0112] The mixing ratio of chlorosulfonic acid and solvent is 9g:40mL;

[0113] (2) Raw material mixing:

[0114] Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain;

[0115] Among them, the stirring speed is 800r / min and the time is 40min.

[0116] The advanced stabilizer for ammonia-free natural rubber production prepared by the method is used as follows:

[0117] Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

[0118] The amount of advanced stabilizer added in the production of ammonia-free natural rubber is calculated based on the total amount of fresh natural rubber latex and is added at a ratio of 1.4%.

[0119] Example 4

[0120] A method for preparing an advanced stabilizer for ammonia-free natural rubber production comprises the following steps:

[0121] (1) Preparation:

[0122] Weigh out the following parts by weight:

[0123] 4.8 parts of chitosan, 3 parts of sodium diacetate, 4 parts of methyl parahydroxybenzoate, 2 parts of sodium alginate, 4 parts of citric acid, 0.8 parts of sodium sorbate, 1.6 parts of special active agent;

[0124] The weight ratio of chitosan to the specially prepared active agent is 3:1;

[0125] Among them, the special active agent is made from camellia seed oil.

[0126] The method for preparing the special active agent complex is as follows:

[0127] Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate;

[0128] The camellia oil distillate is added into a solvent, and the mixture is stirred and evenly mixed to obtain a camellia oil distillate solution; the solvent is chloroform.

[0129] The camellia oil distillate solution was placed in an ice bath and kept warm for 30 minutes; the ice bath temperature was 2°C.

[0130] Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution;

[0131] Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution;

[0132] The reaction liquid is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction liquid is adjusted to 8.5 using a sodium hydroxide solution with a mass fraction of 10wt% at a temperature of 20°C; a neutralization reaction is carried out to obtain a neutralization product, the neutralization product is dissolved with anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the solution is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

[0133] The distillation extraction parameters are:

[0134] The distillation extraction was carried out at a temperature of 250°C and a pressure of 6 mmHg.

[0135] The mixing ratio of camellia oil distillate and solvent is 24g:100mL;

[0136] The mixing ratio of chlorosulfonic acid and solvent is 10g:40mL;

[0137] (2) Raw material mixing:

[0138] Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain;

[0139] Among them, the stirring speed is 800r / min and the time is 40min.

[0140] The advanced stabilizer for ammonia-free natural rubber production prepared by the method is used as follows:

[0141] Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

[0142] The amount of advanced stabilizer added in the production of ammonia-free natural rubber is calculated based on the total amount of fresh natural rubber latex and is added at a ratio of 1.5%.

[0143] Comparative Example 1:

[0144] Based on the technical solution of Example 1, no special active agent is added, and the rest of the technical solutions remain unchanged.

[0145] Comparative Example 2:

[0146] Based on the technical solution of Example 1, chitosan is not added, and the rest of the technical solutions remain unchanged.

[0147] test:

[0148] The storage time of natural rubber latex in the embodiment and ammonia water was tested at a storage temperature of 25°C:

[0149] Table 1

[0150] Storage time / h Example 1 ≥810 Example 2 ≥818 Example 3 ≥830 Example 4 ≥825 Comparative Example 1 ≥550 Comparative Example 2 ≥680 5% ammonia water ≤10

[0151] It can be seen from Table 1 that, compared with ammonia water, the preservative of the present invention has a longer storage time.

[0152] The mechanical stability of the samples in the examples was tested according to GB / T8301□2008 Determination of Mechanical Stability of Concentrated Natural Rubber Latex. The average values ​​are shown in Table 2:

[0153] Storage time: 30 days;

[0154] Table 2

[0155] Mechanical stability Example 1 638 Example 2 627 Example 3 615 Example 4 622 Comparative Example 1 813 Comparative Example 2 765

[0156] It can be seen from Table 2 that 30 days after the preservative of the present invention is used, the natural rubber latex has a more suitable mechanical stability.

[0157] Taking Example 1 as the basic sample, the mechanical stability changes of natural rubber latex were compared under different storage times:

[0158] Table 3

[0159]

[0160]

[0161] It can be seen from Table 3 that with the increase of storage time, the mechanical stability of natural rubber latex first increases rapidly, and then the increase rate decreases continuously.

[0162] The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the specification, should be within the protection scope of the present invention.

Claims

1. Advanced stabilizer for ammonia-free natural rubber production, characterized in that, The composition includes the following ingredients by weight: 3.6-4.8 parts of chitosan, 1-3 parts of sodium diacetate, 2-4 parts of methyl parahydroxybenzoate, 1-2 parts of alginate, 3-4 parts of citric acid, 0.5-0.8 parts of sodium sorbate, and 1.2-1.6 parts of a special active agent; Among them, the weight ratio of chitosan to the specially prepared active agent is 3:1; Among them, the special active agent is made from camellia seed oil.

2. The advanced stabilizer for ammonia-free natural rubber production according to claim 1, characterized in that: The method for preparing the special active agent complex is as follows: Carrying out distillation extraction on camellia seed oil to obtain camellia seed oil distillate; Adding the camellia oil distillate to the solvent, stirring and mixing evenly to obtain a camellia oil distillate solution; Place the camellia oil distillate solution in an ice bath and keep warm for 30 minutes; Adding chlorosulfonic acid to the solvent, stirring and mixing evenly to obtain a chlorosulfonic acid solution; Add chlorosulfonic acid solution dropwise to the camellia oil distillate solution, stirring while adding dropwise for 1 hour. After the addition is completed, adjust the temperature of the reaction system to 25° C., continue to keep warm and stir for 2 hours to obtain a reaction solution; The reaction solution is subjected to rotary evaporation to remove the solvent, and the pH of the remaining reaction solution is adjusted to perform a neutralization reaction to obtain a neutralization product. The neutralization product is dissolved in anhydrous ethanol, and unreacted inorganic salts are separated and removed, and then the product is subjected to rotary evaporation and drying to obtain a specially prepared active agent complex.

3. The advanced stabilizer for ammonia-free natural rubber production according to claim 2, characterized in that: The distillation extraction parameters are: The distillation extraction is carried out at a temperature of 225-250°C and a pressure of 5-6 mmHg.

4. The advanced stabilizer for ammonia-free natural rubber production according to claim 2, characterized in that: The mixing ratio of the camellia oil distillate and the solvent is 20-24 g: 100 mL; The mixing ratio of chlorosulfonic acid and solvent is 8-10g:40mL; The ice bath temperature was 2°C.

5. The advanced stabilizer for ammonia-free natural rubber production according to claim 3, characterized in that: The solvent is chloroform; The pH is adjusted by using a sodium hydroxide solution with a mass fraction of 10 wt % at a temperature of 20° C. to adjust the pH to 8.5; The alginate is sodium alginate.

6. The method for preparing an advanced stabilizer for ammonia-free natural rubber production according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) Preparation of materials: Weigh out the following parts by weight: Chitosan, sodium diacetate, methyl paraben, alginate, citric acid, sodium sorbate, special active agent; (2) Raw material mixing: Add the weighed raw materials of each component into a mixer in turn and stir and mix them evenly to obtain; Among them, the stirring speed is 800r / min and the time is 40min.

7. The method for preparing an advanced stabilizer for ammonia-free natural rubber production according to claim 6, characterized in that: The advanced stabilizer for ammonia-free natural rubber production prepared by the method is used as follows: Add advanced stabilizer produced from ammonia-free natural rubber to the collected fresh natural rubber latex, mix well, and then seal and store away from light.

8. The method for preparing an advanced stabilizer for ammonia-free natural rubber production according to claim 7, characterized in that: The advanced stabilizer for the production of ammonia-free natural rubber is added in a proportion of 1-1.5% based on the total amount of fresh natural rubber latex.

Images