JPH06256404A - Method for removing allergen from natural rubber latex and production of molded natural rubber article - Google Patents

Abstract

PURPOSE:To decrease the content of impurities, such as protein or an excess cure accelerator, in a molded natural rubber article and thus prevent immediate or delayed allergy. CONSTITUTION:A molded rubber article is obtd. by subjecting a natural rubber latex to the prevulcanization step before or after the protein hydrolysis step using water and a protease, the centrifugal separation step using water, the molding step to mold into a desired shape, and the vulcaization step.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a natural rubber latex which does not cause an allergic reaction, in which free chemical substances including proteins and excess vulcanization accelerator contained in a raw natural rubber latex are removed. The present invention relates to a method for removing an allergy-inducing substance and a method for producing a natural rubber molded body.

[0002]

2. Description of the Related Art In recent years, many cases of allergies due to rubber products made from natural rubber latex have been reported. There are two cases, one based on immediate allergic reaction and one based on delayed allergic reaction.
The immediate allergic reaction is induced by the protein contained in the natural rubber latex as a raw material, and may cause shock such as anaphylaxis in the case of atopic patients. On the other hand, the delayed allergic reaction is caused by a free chemical substance containing an organic vulcanization accelerator used in the vulcanization process, and symptoms such as rash appear. Further, in the conventional manufacturing method, there is a problem that the obtained rubber molding has low waterproofness, electric insulation, transparency and the like.

Conventionally, in order to remove these allergens, a method of washing the molded body with water, a method of denaturing the protein by chlorine treatment, and the like have been applied. However, it was difficult to remove allergens to the extent that the onset of allergies could be prevented by either method.

[0004]

SUMMARY OF THE INVENTION As mentioned above,
It was difficult to prevent allergies by removing allergens contained in rubber products made from natural rubber latex. Therefore, the present invention removes the causative agent of immediate type and delayed type allergy to the extent that the onset of allergy can be prevented, is highly safe, and is also waterproof.
It is intended to provide a method for removing an allergen-inducing substance of natural rubber latex and a method for producing a natural rubber molded article, which can produce a natural rubber molded article excellent in electric insulation and transparency.

[0005]

The method for removing allergens from natural rubber latex according to the present invention comprises a step of prevulcanizing natural rubber latex and a step of decomposing proteins by adding a proteolytic enzyme and water in this order. Or in reverse order, and further comprising the step of adding water and centrifuging. Further, the method for producing a natural rubber molded article of the present invention comprises a step of prevulcanizing natural rubber latex and a step of degrading a protein by adding a proteolytic enzyme and water in this order or in the reverse order. The method is characterized by including a step of adding water and centrifuging and a step of molding into a desired shape and then vulcanizing.

The present invention will be described below step by step. In the present invention, a method or protein in which a step of prevulcanizing a natural rubber latex (prevulcanization step) is preceded by a step of proteolytic enzyme and water to decompose a protein (proteolytic step) is provided. First, the disassembly process
Next, any method of providing a pre-vulcanization step can be applied.

The prevulcanization step is a step of partially vulcanizing natural rubber latex which is untreated or in which the contained protein is decomposed. By the treatment in this step, workability such as centrifugation and molding in the subsequent step can be improved. As the vulcanization in this step, any method of sulfur vulcanization system, sulfur-free vulcanization system, peroxide vulcanization system or vulcanization by radiation can be applied.

Examples of the vulcanizing agent used here include sulfur, sulfur chloride, precipitated sulfur, insoluble sulfur, selenium and tellurium,
Examples thereof include sulfur-containing organic compounds such as tetramethylthiuram disulfide and tetraethylthiuram disulfide, organic peroxides such as benzoyl peroxide and dicumyl peroxide, and metal oxides such as zinc oxide, magnesium oxide and zinc peroxide. Examples of the vulcanization accelerator include known aldehyde ammonias, aldehyde amines, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. Furthermore, if necessary, known vulcanization accelerating aids, plasticizers, curing agents, antioxidants, surfactants as dispersants and stabilizers, etc. can be added, and these are not limited to this step. Also, it can be appropriately added in the subsequent steps.

The vulcanization conditions are appropriately determined depending on the compounding composition of the natural rubber latex and the molding method, but usually about 70
At ~ 120 ° C, about 0.1-24 hours is preferred.

When the radiation vulcanization method is applied, it can be carried out by a known method by adding a sensitizer such as an acrylic ester. The pre-vulcanization condition is appropriately determined according to the compounding composition of the natural rubber latex and the molding method.
About 1.0-5 Mrad is preferred.

The proteolysis step is a step in which a proteolytic enzyme and water are added to and retained in an unvulcanized or prevulcanized natural rubber latex to decompose the protein. The treatment in this step decomposes the protein in the natural rubber latex.

[0012] As the proteolytic enzyme used here, 0.01 to 1.0 weight percent of Esperase or Alcalase may be added. The amount of water used here is not particularly limited, but if it is diluted too much, the progress of the enzymatic reaction may be delayed, so that the solid content concentration in the natural rubber latex should be about 10 to 60% by weight. Is preferably added to.

The treatment conditions are not particularly limited, but it is usually preferable to carry out the treatment at about 20 to 60 ° C. for 10 to 120 minutes.
Prior to the reaction, it is preferable to adjust the pH of the enzyme to be used to the optimum pH with a pH adjuster.

Next, the natural rubber latex treated in the previous step is added with water and centrifuged. By the treatment in this step, free chemical substances such as protein degradation products and excess organic vulcanization accelerators are transferred to the aqueous phase and separated and removed.

This centrifugation can be carried out a plurality of times if necessary. The conditions of centrifugation are not particularly limited, and usually about 3000 to 13000 rpm and about 10 to 60 minutes are preferable.

Next, the natural rubber latex treated in the previous step is molded into a desired shape and post-vulcanized. Before the treatment of this step, if necessary, aqueous ammonia can be added to stabilize the latex.

The molding method is not particularly limited, and a known method,
For example, a dipping method, a casting method, or an extrusion method can be applied. The post-vulcanization conditions are not particularly limited and are usually about 70-12.
At 0 ° C, about 0.1-24 hours is preferred.

In the production method of the present invention, in addition to the above-mentioned steps, treatments of known rubber product production steps can be appropriately combined if necessary.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to examples. “Parts” in the examples and comparative examples represent “parts by weight”, and the measuring methods and the like are as follows. Protein content: Measurement of infrared absorption spectrum and Kjeldahl nitrogen analysis (YASUYUKI TANAKA etc., J.nat.
Rubb. Res., 7 (2), 152-155, 1992). In addition,
When measuring the protein content (total nitrogen content) by the Kjeldahl Nitrogen analysis method, the value was measured for the film produced without using chemicals containing nitrogen (vulcanization accelerator, antioxidant, etc.). . The content of impurities such as vulcanization accelerators is indicated by the elution rate with physiological saline and acetone measured according to JIS-K6350. The elution rate is calculated by the following equation: elution rate of free chemical substance (%) = (E / S) × 100 (where S is the initial film weight, E is the initial film weight and the film after the elution treatment) It represents the difference from the weight). Elution test: Measured according to the disposable blood transfusion set and liquid transfusion set standards defined by the Pharmaceutical Affairs Law. Water absorption rate: Measured according to JIS-K7209. The size of the test film is 0.2 ± 0.01 mm (similar in other tests). Insulation resistivity: Measured according to JIS-K6911. Physical Properties (1) and (2): For (1), the tensile strength and the elongation rate when the film was immersed in physiological saline at 37 ° C. for 24 hours were measured. In (2), the initial tensile strength and elongation of the film and those when the film was held at 70 ° C. for 166 hours were measured, and the average value for 10 sheets was displayed. Note that the tensile strength and elongation are ASTM-D3577.
It was measured according to -78a. Transparency: When a 2 mm thick film is placed on newspaper,
The case where the newspaper characters could be read through the film was rated as ◯, and the case where the newspaper characters were not readable was rated as x.

Example 1 100 parts of high ammonia natural rubber latex (made in Malaysia, solid content 60%, total nitrogen content 0.200%), 2 parts potassium laurate, 2 parts sulfur, 1 part zinc oxide
Parts, 0.5 parts of zinc di-N-butyldithiocarbamate (total nitrogen content 0.06%) as a vulcanization accelerator were added, and heated at 50 ° C. for 15 hours while stirring (prevulcanization step).

After cooling, 0.5 parts of a phenolic anti-aging agent (total nitrogen content 0%) and 3 parts of potassium laurate were added as an anti-aging agent, and then 2 parts of sodium dihydrogen phosphate were added to the system. PH was adjusted to 9. Next, after adding 0.5 part of Alcalase, pure water was added so that the solid content concentration was about 30%, and the system was uniformly dispersed.
Hold at 5 ° C for 5 hours (proteolysis step).

Subsequently, the object to be treated after being left to cool is set at 13,000.
Centrifugation at 0 rpm for 30 minutes gave a creamy latex (solid content concentration about 80%). Then, 1 part of potassium laurate was added to this creamy latex, diluted with pure water to a solid content concentration of 30%, and centrifuged again under the same conditions (centrifugation step). In the treatment of this step, since the latex was pre-vulcanized, it was not sticky, and the workability such as washing and removal of the latex film attached to the rotor was good.

1% ammonia was added to the thus obtained creamy latex (solid content concentration about 80%) to dilute it to a solid content concentration of 60%. Next, this latex was cast on a glass plate and left at room temperature for 24 hours. Then, the film peeled from the glass plate was immersed in a 1% sodium hydroxide solution and leached at 80 ° C. for 15 hours. Next, it is washed with pure water, dried at 90 ° C. for 30 minutes, further immersed in a 1% sodium hypochlorite solution and a 0.5% hydrochloric acid solution, and then immersed in 1% ammonia for neutralization, A film was obtained by drying (film molding and post-vulcanization step).

The nitrogen content in this film is 0.018
%, And the result of infrared absorption spectrum measurement was 3280.
The N—H stretching vibration of cm ⁻¹ had disappeared. The elution rate of free chemical substances containing excess vulcanization accelerator is 0.227% for physiological saline solution and 1.5% for acetone.
It was 36%. As is clear from these results, most of the protein in the raw material latex was removed, the amount of free chemical substances eluted was also small, and the amount eluted with physiological saline, which was close to the practical state, was very small.
In addition, the film was subjected to an eluate test, and the waterproof property (water absorption rate), electrical insulation resistivity, physical properties and transparency were measured. The results are shown in Table 1.

Comparative Example 1 0.5 part of a phenolic antioxidant as an antioxidant was added to the latex after the pre-vulcanization step in Example 1,
Dispersed evenly. Using this latex, a film was obtained according to the film forming and post-vulcanization steps of Example 1.

The nitrogen content of this film is 0.192%
Met. In addition, as a result of infrared absorption spectrum measurement, 3
N-H stretching vibration of 280 cm ^-1 appeared. In addition, the elution rate of free chemical substances including vulcanization accelerators is 0.425% for physiological saline and 2.096% for acetone.
And all the values were very large as compared with Example 1. From these results, it was found that most of the free chemical substances including the protein and the vulcanization accelerator in the raw rubber latex were not removed. The same test as in Example 1 was performed on this film. The results are shown in Table 1.

[0027]

[Table 1]

The fact that the consumption of KMnO ₄ in the eluate test in Table 1 was 0 also proved that the content of free chemical substances in the film of Example 1 was small. In addition, the film of Example 1 was superior to the film of Comparative Example 1 in all of the waterproof property, the electrical property, the physical property and the transparency. Even when the order of the pre-vulcanization step and the proteolysis step was reversed, there was no inconvenience in the work, and the various properties of the obtained film were almost the same as in Example 1.

Example 2 High Ammonia Latex (Malaysia, solid content 6
0%, total nitrogen content 0.200%) 5 parts of n-butyl acrylate as a sensitizer was added to 100 parts of γ of 2.5 Mrad.
It was pre-vulcanized by irradiating a wire. Next, 0.5 part of a phenolic anti-aging agent was added as an anti-aging agent and dispersed uniformly. Thereafter, the same treatment as in Example 1 was carried out to obtain a film.

The nitrogen content in this film was 0.018.
%, And the result of infrared absorption spectrum measurement was 3280.
The N—H stretching vibration of cm ⁻¹ had disappeared. The elution rate of free chemical substances including vulcanization accelerators is 0.213% for physiological saline and 1.527% for acetone.
Met. As is clear from these results, most of the protein in the raw material latex was removed, the amount of free chemical substances eluted was also small, and the amount eluted with physiological saline, which was close to the practical state, was very small. Also,
The film was subjected to an eluate test, and further, waterproofness,
Insulation resistivity, physical properties and transparency were measured. The results are shown in Table 2.

Comparative Example 2 0.5 part of a phenolic anti-aging agent as an anti-aging agent was added to a latex radiation-vulcanized in the same manner as in Example 2 and uniformly dispersed. Using this latex, Example 1
A film was obtained according to the film forming and post-vulcanization steps of.

The nitrogen content of this film is 0.145%
And the result of infrared absorption spectrum measurement is 3280c.
The NH stretching vibration of m ⁻¹ appeared. Further, the elution rate of the free chemical substance containing the vulcanization accelerator and the like is 0.444% in the case of physiological saline and 2.090% in the case of acetone, and both values are compared with Example 1. And was very big. From these results, it was found that most of the free chemical substances including the protein and the vulcanization accelerator in the raw rubber latex were not removed. The same test as in Example 1 was performed on this film. The results are shown in Table 2.

[0033]

[Table 2]

The content of free chemical substances in the film of Example 2 was also small because the consumption of KMnO ₄ in the eluate test in Table 2 was 0. In addition, the film of Example 2 was superior to the film of Comparative Example 2 in all of waterproofness, electrical properties, physical properties and transparency.

[0035]

EFFECTS OF THE INVENTION According to the method for removing allergen-inducing substances of natural rubber latex and the method for producing a natural rubber molded article of the present invention, the protein in natural rubber latex that causes immediate type allergy and the cause of delayed type allergy. It is possible to remove a free chemical substance containing an excessive vulcanization accelerator and the like added at the time of vulcanization to the extent that the above allergy is not induced. Therefore, the rubber molded product obtained by the manufacturing method of the present invention is highly safe for human body and is also excellent in waterproof property, electrical insulating property, physical property and transparency. Further, in the present invention, since pre-vulcanization is performed, there is no inconvenience such as stickiness of latex, and workability such as centrifugation and molding in the subsequent step is good. The rubber molded product obtained by the manufacturing method of the present invention is a condom, a surgical glove, various catheters and tubes, an enema device, a surgical balloon, an immersion molded product such as gloves for electrical work, and a cast molding of toys. It can also be applied to products, extruded products such as thread rubber and tubes.

Claims (2)

[Claims] 1. A step of prevulcanizing natural rubber latex and a step of degrading a protein by adding a proteolytic enzyme and water in this order or in the reverse order, and further comprising a step of adding water and centrifuging. A method for removing an allergen-inducing substance from natural rubber latex, comprising: 2. A step of prevulcanizing a natural rubber latex and a step of decomposing a protein by adding a proteolytic enzyme and water in this order or in the reverse order, and further adding water and centrifugation. A method for producing a natural rubber molded article, which comprises a step of molding into the shape described above and then vulcanizing.