JP2905005B2 - Deproteinized natural rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deproteinized natural rubber containing substantially no protein and a method for producing the same.

[0002]

2. Description of the Related Art Natural rubber has been widely used from industrial goods such as automobile tires, belts and adhesives to household goods such as gloves. Such a natural rubber is obtained as a latex containing water, protein, inorganic salts, and the like in addition to the rubber component. Raw rubber (crepe rubber or smoked sheet rubber) is obtained by coagulating rubber from natural rubber latex.
Is obtained from the raw rubber through mastication, blending of compounding agents, molding and vulcanization.

Recently, however, medical devices such as surgical gloves, various catheters, and anesthesia masks made of natural rubber products cause patients to have difficulty breathing and anaphylaxis-like symptoms (angioedema, urticaria, collapse, cyanosis, etc.). ) Was reported in the United States. In addition, there have been reports of cases in which women with a history of allergies used home rubber gloves made of natural rubber, showing pain in the hands, hives, and angioedema around the eyes.

[0004] The cause is presumed to be proteins in natural rubber, and the US Food and Drug Administration (FD)
A) says he is working with natural rubber product manufacturers to reduce protein content. Further, reducing the protein in natural rubber contributes to a reduction in the water absorption of the natural rubber and improves the electrical properties such as insulation properties of the natural rubber product. The almost complete removal of the non-rubber component provides an advantageous raw material for producing a rubber product having low energy loss and excellent mechanical properties. Provide advantageous raw materials for producing rubber products with improved creep properties and aging resistance. One of the major drawbacks of natural rubber is that the raw material properties are not stable due to differences in the place of production and the time of production peculiar to natural products. By removing the non-rubber component that causes it, the instability of the vulcanization characteristics is eliminated, and it becomes a raw rubber having a constant quality like synthetic rubber, improving the accuracy of the mechanical characteristics of natural rubber products. Useful.

[0005] As a method of reducing the protein content in natural rubber, a method of thoroughly washing the latex with water has conventionally been adopted. That is, (i) aggregate the rubber particles in the very diluted latex, (ii) centrifuge the very diluted latex to separate the concentrated latex,
(iii) A method of dialyzing latex is known.

Other methods include (a) decomposing proteins by bacteria or enzymes, (b) decomposing proteins by adding alkali to latex and heating, and (c) producing rubber particles by soaps. Methods such as releasing adsorbed proteins are known. When actually performed, these methods are appropriately combined to produce the following deproteinized natural rubber. (1) Crepe H A small amount of ammonia is added so that the pH of the latex becomes 7.1, and the mixture is stirred for 6 to 48 hours. During this time, the protein is decomposed by the action of bacteria and enzymes mixed into the latex after sampling. . In this case, after the completed pre-coagulated product is removed, the decomposition products are removed by centrifugation or creaming, and then the crepe is finished. (2) Crepe G Soap or other surfactant is added to the ammonia-stabilized latex to adsorb proteins, and centrifugation is repeated to remove salts and proteins from the latex. This is then very diluted and solidified to give a crepe. (3) Crepe CD In this method, fresh coagulated material before being rolled is immersed in running water to hydrolyze proteins, separated by dialysis, and finished in crepe.

On the other hand, as an improved deproteinized natural rubber,
After reducing the ammonia concentration of the concentrated latex stored in ammonia to 0.2% and adding 0.4 phr of ammonium naphthenate as a preservative, the protease
0.25 phr se is added, and the enzyme is decomposed for 20 hours.
Then, a latex is prepared by diluting and coagulating with phosphoric acid (natural rubber, vol.
6, No. 8, 274-281 (1974)).

[0008] The protein content of natural rubber is usually determined by the Kjeldahl method.
6.3 times as much as About 3 to 5% by weight (about 0.5 to 0.8 as N%) of fresh natural rubber latex (field latex) as a percentage by weight based on solid content;
Not less than about 2% by weight (about 0.3% as N%) in commercially available purified latex and raw rubber (smoked sheet rubber). Compared to these general commercially available natural rubbers, although the protein content of the deproteinized natural rubber is significantly reduced,
The N% was 0.11 in crepe CD and 0.06 in the latter improved method, and deproteinization was not complete and was an insufficient material for allergy control.

It is an object of the present invention to remove proteins and other impurities from natural rubber, to improve water absorption, to have high electrical insulation, to reduce energy loss, to have excellent mechanical properties, and to obtain colorless and transparent appearance characteristics. And to provide a deproteinized natural rubber which is excellent as a novel material and is useful as a new material.

[0010]

Deproteinized natural rubber of the means and the action to an aspect of the present invention, which contains substantially no protein, protein raw rubber obtained from the natural rubber latex, the nitrogen content 0. 02% or less of the level, or
In the infrared absorption spectrum of green rubber film, poly
No absorption at 3280 cm ^-1 specific to peptides
It has been removed to the level . Generally, natural rubber has a molecular weight of 1,000,000 to 2.5 million and 10,000,000, respectively.
It is known that it is a mixture of 10,000 to 200,000 high molecular weight components and low molecular weight components. It is presumed that the high molecular weight components are linked to each other via an abnormal group contained in the natural rubber and branched off. When one molecule of low molecular weight rubber having a molecular weight of 100,000, which is considered to be produced in the original biosynthesis, is linked with one molecule of peptide molecule intervening in intermolecular bonding, ie, one nitrogen atom (atomic weight 14), the nitrogen content is 0. 0.014%. It is believed that this amount of nitrogen remains without being removed. Therefore, since a nitrogen content of about 0.02% or less inevitably remains, natural rubber from which the nitrogen content has been removed to a level of 0.02% or less is judged to have completely removed protein. .

[0011] However, in the highly natural rubbers deproteinized, the protein content can not be said to be completely accurate in the method of estimating the nitrogen content was <br/> thus made the present inventors It was found by studying the infrared absorption spectrum of the deproteinized purified rubber. The reason is that there is a protein bonded to a rubber molecule, and even after the protein is hydrolyzed by a protease, an amino acid or a short-chain peptide molecule remains at the bonding portion with the rubber. On the other hand, the allergic effects of proteins are specific to high molecular polypeptides, and there is no concern about allergic effects of amino acid or short-chain peptide molecules.

Therefore, in order to more accurately confirm that the protein has been removed , in addition to the above measurement of the nitrogen content,
Te, it is desirable to employ an analytical technique based infrared absorption spectrum developed by the present inventors. That is,
The present inventors measured the infrared absorption spectrum of natural rubber purified to various levels using a Fourier transform infrared spectrometer. Naumann et al. (Biopolymers
26, by 795.) That is compared with the infrared absorption spectrum of peptides in, 3315～3320Cm ^-1 remains due to the> N-H in short-chain peptides or amino acids linked the protein is removed with the rubber molecules Revealed that the absorption at 3280 cm ^-1 due to the polypeptide disappeared. Therefore, the deproteinized natural rubber of the present invention has a nitrogen content
It is a natural rubber that has been purified to a level of 0.02% or less and to a level at which no absorption at 3280 cm ^-1 is detected in the infrared absorption spectrum of the raw rubber film.

[0013] As in the present invention, natural rubber from which proteins have been almost completely removed has never been obtained. Since this deproteinized natural rubber is substantially free of protein, it is not only useful as a countermeasure against allergy to natural rubber, but also has properties (low water absorption, low water absorption, It is expected to exhibit electrical properties, low hysteresis loss, colorless and transparent, etc., and to eliminate the difference between lots peculiar to natural products, and to be a high quality raw material for high precision products.

In addition, natural rubber has a phenomenon of storage hardening, in which curing progresses during storage, and there has been an inconvenience that mastication is indispensable for plasticization during use. Rubber was found not to exhibit this phenomenon. Furthermore, natural rubber has a drawback that it is colored or colored over time because it contains carotenoids, which are polyenes having structural units of isoprene and having a large number of conjugated double bonds, as impurities. In the process of reducing protein, carotenoid-based impurities are also removed, and a colorless and transparent natural rubber comparable to synthetic rubber can be obtained.

The deproteinized natural rubber of the present invention can be obtained by adding a proteolytic enzyme to latex to degrade the protein, and then repeatedly washing with a surfactant. Washing may be performed by centrifugation or the like. The latex as a starting material for obtaining the deproteinized natural rubber of the present invention means a field latex obtained from a natural rubber tree, and the latex may be a commercially available ammonia-treated latex or a fresh field latex. Either can be used.

The proteolytic enzyme is not particularly limited, and may be of bacterial origin, of filamentous fungi or of yeast origin. Among them, the use of bacterial protease is preferred. preferable. As the surfactant, for example, an anionic surfactant and / or a nonionic surfactant can be used. Examples of the anionic surfactant include carboxylic acid-based, sulfonic acid-based, sulfate-based, and phosphate-based surfactants.
Examples of the carboxylic acid-based surfactant include fatty acid salts having 6 to 30 carbon atoms, polyvalent carboxylate, rosinate, dimer acid salt, polymer acid salt, and trol oil fatty acid salt. And a carboxylate having 10 to 20 carbon atoms. When the number of carbon atoms is 6 or less, dispersion and emulsification of proteins and impurities are insufficient, and when the number of carbon atoms is 30 or more, it is difficult to disperse in water.

Examples of the sulfonic acid surfactant include alkyl benzene sulfonate, alkyl sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate, diphenyl ether sulfonate and the like. Examples of the sulfate-based surfactant include alkyl sulfates, polyoxyalkylene alkyl sulfates, polyoxyalkylenealkylphenyl ether sulfates, tristyrenated phenol sulfates, and polyoxyalkylene distyrenes. Phenol sulfate and the like. Examples of the phosphate-based surfactant include an alkyl phosphate salt and a polyoxyalkylene phosphate salt. As salts of these compounds, metal salts (Na, k, Ca, Mg,
Zn), ammonia salts, amine salts (such as triethanolamine salts) and the like.

As the nonionic surfactant, for example, polyoxyalkylene ether type, polyoxyalkylene ester type, polyhydric alcohol fatty acid ester type, sugar fatty acid ester type, alkyl polyglycoside type and the like are preferable. used. Examples of the polyoxyalkylene ether-based nonionic surfactant include polyoxyalkylene alkyl ether, polyoxyalkylene alkylphenyl ether, polyoxyalkylene polyol alkyl ether, and polyoxyalkylene styrenated phenol. Examples include luether, polyoxyalkylene distyrenated phenol ether, and polyoxyalkylene tristyrenated phenol ether. Examples of the polyol include polyhydric alcohols having 2 to 12 carbon atoms, such as propylene glycol, glycerin, sorbitol, sucrose, pentaerythritol, and sorbitan.

Examples of the polyoxyalkylene ester-based nonionic surfactant include polyoxyalkylene fatty acid esters. Examples of the polyvalent alcohol fatty acid ester-based nonionic surfactant include those having 2 to 2 carbon atoms.
Twelve polyhydric alcohol fatty acid esters or polyoxyalkylene polyhydric alcohol fatty acid esters. More specifically, for example, sorbitol fatty acid ester, sorbitan fatty acid ester, fatty acid monoglyceride, fatty acid diglyceride, polyglycerin fatty acid ester and the like can be mentioned. Further, these polyalkylene oxide adducts (for example, polyoxyalkylene sorbitan fatty acid ester, polyoxyalkylene glycerin fatty acid ester, etc.) can also be used.

Examples of nonionic surfactants of sugar fatty acid esters include sucrose, glucose, maltose, fructose, and fatty acid esters of polysaccharides, and polyalkylene oxide adducts thereof can also be used. Examples of the alkyl polyglycoside nonionic surfactant include alkyl glucoside, alkyl polyglucoside, polyoxyalkylene alkyl glucoside, polyoxyalkylene alkyl polyglucoside, and the like, and fatty acid esters thereof. Also,
These polyalkylene oxide adducts can also be used.

The alkyl group in these surfactants is, for example, an alkyl group having 4 to 30 carbon atoms. Further, the polyoxyalkylene group may have 2 carbon atoms.
Examples thereof include those having from 4 to 4 alkylene groups, for example, those having an addition mole number of ethylene oxide of about 1 to 50 mol. In addition, as the fatty acid, for example, carbon number 4
-30 straight or branched saturated or unsaturated fatty acids.

In order to degrade the protein in the natural rubber latex with the protease, the protease is added to the field latex or the ammonia-treated latex in about 10 to 0.1%.
001% by weight. If the amount is less than 0.001% by weight, the effect is not sufficiently obtained because the amount is too small. If the amount is more than 10% by weight, the amount is too large, leading to an increase in cost and a reduction in enzyme activity.

In addition, when the enzyme is added, other additives, for example, phosphates such as potassium phosphate, potassium phosphate and sodium phosphate, and acetates such as potassium acetate and sodium acetate as pH adjusters. Further, acids such as sulfuric acid, acetic acid, hydrochloric acid, nitric acid, citric acid and succinic acid or salts thereof, or ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like may be used in combination. Further, the enzyme can be used in combination with an enzyme such as lipase, esterase, amylase, laccase, and cellulase.

Further, if necessary, styrene sulfonic acid copolymer, naphthalene sulfonic acid formalin condensate, lignin sulfonic acid, polycyclic aromatic sulfonic acid copolymer,
Dispersants such as acrylic acid and maleic anhydride homopolymers and copolymers, isobutylene-acrylic acid, and isobutylene-maleic anhydride copolymers can be used in combination.

Although the treatment time with the enzyme is not particularly limited, it is preferable to carry out the treatment for several minutes to about one week. In addition, the latex may be stirred or may be allowed to stand. The temperature may be adjusted if necessary. An appropriate temperature is 5 ° C to 90 ° C, preferably 2 ° C to 90 ° C.
0 ° C to 60 ° C. When the treatment temperature exceeds 90 ° C., the enzyme is quickly deactivated, and when the treatment temperature is less than 5 ° C., the reaction of the enzyme becomes difficult to proceed.

As a method for washing latex particles with a surfactant, for example, a method in which a surfactant is added to latex that has been subjected to enzyme treatment and centrifugation is performed can be suitably employed. At that time, the surfactant is 0.00
It is appropriate to add in the range of 1 to 10% by weight. Further, instead of the centrifugal separation, a washing method of aggregating and separating latex particles can be employed. Centrifuge 1
It may be done once or several times. When washing natural rubber, synthetic rubber or synthetic rubber latex can be used in combination.

In the above description, after the enzymatic decomposition, a surfactant is added to wash the latex, but the enzyme and the surfactant may be added and treated at the same time. The method for obtaining the deproteinized natural rubber of the present invention is not particularly limited.

[0028]

EXAMPLES The deproteinized natural rubber of the present invention will be described below with reference to examples. Example 1 Alcalase 2.0M from Novo Nordisk Bioindustry Co., Ltd. as a proteolytic enzyme, and a natural rubber latex of 60.2% solid rubber content of Soctech (Malaysia) Ltd.
%.

15 ml of natural rubber latex to 200 ml
And stabilized with 0.12% sodium naphthenate. 8. Add sodium dihydrogen phosphate to adjust pH to 9.
2 was prepared. 0.78 g of Alcalase 2.0M
After dispersing in 0 ml of distilled water, it was added to the diluted natural rubber latex. After the pH was readjusted to 9.2, it was maintained at 37 ° C. for 24 hours. Nonionic surfactant Triton X-1 is added to the latex after enzyme treatment.
00 (manufactured by Toho Chemical Industry Co., Ltd.) at a concentration of 1%.
Centrifuged at 1,000 rpm for 30 minutes. The resulting creamy fraction was subjected to 1% Triton X-100 (supra).
Was re-dispersed in 200 ml of distilled water containing, and centrifuged again. After repeating this operation three times, calcium rubber was added to the cream dispersion to isolate a solid rubber.

After vacuum-drying the isolated solid rubber, 16
Acetone extraction was performed for an hour. Then, it was dissolved in toluene at a concentration of 1% and centrifuged at 11,000 rpm for 30 minutes. The resulting clear rubber solution was separated and precipitated in excess methanol. The obtained solid rubber was dried at room temperature under vacuum. Comparative Example 1 Natural rubber latex was diluted 15-fold with distilled water and stabilized with 1% Triton X-100 (supra). The diluted latex was centrifuged at 11,000 rpm for 30 minutes. The resulting creamy fraction is 1% Triton
Redispersed in the same volume of distilled water containing X-100 (supra) and centrifuged again. After repeating this work three times,
Solid rubber was isolated by adding calcium chloride to the cream dispersion. The isolated solid rubber was treated as in Example 1. Comparative Example 2 After diluting natural rubber latex 5 times with distilled water, 1%
Formic acid was added and the solid rubber was isolated. The isolated solid rubber was treated as in Example 1.

The nitrogen content of these solid rubbers was determined by RRIM
Test method (Rubber Research Institute of Malaysia (197
3). Analyzed by 'SMR Bulletin No. 7'). Also,
The infrared absorption spectrum was obtained by forming a film on a KBr disk and measuring the absorbance using a JASCO 5300 Fourier transform infrared spectrometer. Table 1 shows the analysis results.
Example Sample not more than 0.01% nitrogen content, the absorption of short-absorbing chain peptides or amino acids are present but the 3280 cm ^-1 polymeric polypeptide of 3320 cm ^-1 as apparent from FIG. 1 Cannot be detected.

Although the sample of Comparative Example 1 was purified to a considerable level, it had a nitrogen content of 0.04%, and at this level, in addition to the absorption of short-chain peptides or amino acids, 3
A polypeptide absorption of 280 cm ^-1 remains. Comparative Example 2
In the sample, the protein level was lower than that of the commercially available rubber in this treatment, but the nitrogen content was 0.16% and the absorption of the polypeptide was very strong.

[0033]

[Table 1]

Example 2 As the natural rubber latex, a commercially available latex of the high ammonia type manufactured by Guthrie (Malaysia) was used. The solid rubber content was 62.0%. The above natural rubber latex was solidified with a 0.12% aqueous sodium naphthenate solution having a solid rubber content of 10%.
Diluted to weight%. The pH was adjusted to 9.2 by adding sodium dihydrogen phosphate, and Alcalase 2.0 was added.
M was added at a ratio of 0.87 g to 10 g of the rubber component.
After the pH was readjusted to 9.2, it was maintained at 37 ° C. for 24 hours.

1% of the nonionic surfactant Triton X-100 (described above) is added to the latex after the enzyme treatment.
The rubber content was adjusted to 8% by adding an aqueous solution, and
Centrifuged at 0 rpm for 30 minutes. The resulting creamy fraction was dispersed in a 1% aqueous solution of Triton X-100 (described above), adjusted to a rubber concentration of about 8%, and centrifuged again. After the centrifugation operation was repeated once, the obtained cream was dispersed in distilled water to prepare a deproteinized rubber latex having a solid rubber content of 60%.

The nitrogen content of the raw rubber obtained from this latex was 0.009%, and its infrared absorption spectrum is present absorption of 3320 cm ^-1 was not observed in the absorption of 3280 cm ^-1. For the preparation of a raw rubber test film, 36 g of latex was cast on a glass plate of 18 cm × 12 cm, dried at room temperature, peeled off the glass plate, and the surface in contact with the glass surface was dried for one day. Then, it was dried under vacuum to obtain a test sample.

The vulcanized rubber test film has a solid rubber content of 50.
%, The following formulation was performed, and after standing for 48 hours, a film was prepared in the same manner as above. Further, it was heated in an oven at 100 ° C. for 30 minutes to be vulcanized to obtain a test sample.
As a comparative sample, a similar sample was prepared from latex before purification.

[0038]

[Table 2]

The mechanical strength of each of the unvulcanized sheet and the vulcanized sheet was measured by using a JIS No. 4 dumbbell at a test speed of 500 mm / min to examine tensile strength, elongation at break, and modulus. The results are shown below. The numerical values in parentheses are the measured values of the comparative sample. (1) Unvulcanized sheet Tensile strength: 7.18 MPa (7.85) Elongation at break: 1180% (1160) 500% modulus: 0.45 MPa (0.52) (2) Vulcanized sheet Tensile strength: 23.7 MPa (24.3) Elongation at break: 840% (850) 500% Modulus: 2.66 MPa (2.68) Tear strength: 101.6 kN / M (90.9) , And excellent in colorless transparency. Further, the water absorption was improved to 0.87% (6.74), and the electric resistance was 6.6 × 10 ¹² (2.7 × 1).
0 ¹⁰ ), the volume resistance is 6.9 × 10 ¹⁵ (2.0 × 10 ¹⁴ )
And excellent electrical insulation.

FIG. 2 shows a viscoelastic spectrum of the vulcanized sample of this example. Although there is not much difference in the peak position and the magnitude of tan δ, in the temperature range of −20 ° C. or more, the ta
The n δ value is clearly lower, indicating that the material has less energy loss in the practical range. Table 3 shows the results of the accelerated test for storage hardening of raw rubber.

Two raw rubber sample films are superimposed,
A Wallace plastometer measurement sample was prepared with a special punch. The plasticity of Wallace was measured according to a conventional method, and the measured value was defined as the initial plasticity. Then, the plasticity of the sample which was placed in a container containing a 4A molecular sieve and left at 60 ° C. for 24 hours was measured. The difference between them is a measure of storage hardening.

[0042]

[Table 3]

From Table 3, it can be seen that hardening of the sample of the example hardly progressed.

[0044]

The deproteinized natural rubber of the present invention is characterized in that the protein in the raw rubber obtained from the natural rubber latex has a nitrogen content of 0.02 or less , and is unique to the polypeptide in the infrared absorption spectrum of the raw rubber film. Since it has been removed to such a level that no absorption at 3280 cm ^-1 is observed, it contains substantially no protein and is therefore useful as a countermeasure against allergy caused by natural rubber. Furthermore, the deproteinized natural rubber of the present invention, as compared to conventional natural rubber, is improved water resistance, electrical insulation is rather high, has excellent mechanical properties energy loss is small, the natural product-specific quality Since there is no variation, raw materials of high precision and high quality can be obtained. Furthermore, there is an effect that storage hardening is eliminated by substantially removing the protein, and a colorless and transparent natural rubber is obtained, which is not inferior to synthetic rubber.

[Brief description of the drawings]

FIG. 1 is a graph showing infrared absorption spectra of deproteinized natural rubber obtained in Examples and Comparative Examples.

FIG. 2 is a graph showing a viscoelastic spectrum of a vulcanized sample of Example 2.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoya Ichikawa 41-1, Uozumi-cho, Akashi-shi, Hyogo Sumitomo Rubber Industries, Ltd. Uozumi Dormitory (56) References UK Patent Application Publication 2098222 (GB, A) Rubber Board Bull . (India), Vol. 15, No. 3-4, p. 45-49 (1980) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08C 1/04 CA (STN)

Claims (1)

(57) [Claims] (1) A protein in a raw rubber obtained from a natural rubber latex has a nitrogen content of not more than 0.02% and an infrared absorption spectrum of a raw rubber film.
And absorption at 3280 cm ^-1 specific to the polypeptide
A deproteinized natural rubber substantially free of protein, which has been removed to an unacceptable level .