JPH06329702A - Modified natural rubber and its production - Google Patents

Abstract

PURPOSE:To provide a modified natural rubber which is obtd. at a high modification efficeiny, hence exhibits an excellent modification effect, and is useful as measures against allergy. CONSTITUTION:After the content of protein in a natural rubber is reduced to a nitrogen content of 0.10wt.%, the rubber is modified e.g. by graft copolymn., epoxidation, etc.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, natural rubber has been widely used from industrial products such as automobile tires, belts and adhesives to household products such as gloves. Natural rubber has excellent mechanical properties as a vulcanized rubber, and also has much better raw rubber strength (green strength) than synthetic rubber. Therefore, natural rubber is excellent in processability in kneading, sheeting and various molding processes. In addition, since latex has a high gel strength upon coagulation and can be easily formed into a film, it has been manufactured and supplied as various products such as condoms, surgical gloves and various catheters.

However, natural rubber cannot compete with synthetic rubber having special properties such as butyl rubber having excellent gas permeability and nitrile rubber having excellent oil resistance. for that reason,
Natural rubber has been modified in order to impart other rubber properties while maintaining the excellent properties such as mechanical properties and film-forming ability of natural rubber. Known examples of the modification include graft copolymerization of an organic compound having an unsaturated bond and epoxidation. Methyl methacrylate, styrene, acrylonitrile, etc. are used as monomers in the graft copolymerization of organic compounds having unsaturated bonds, and the natural rubber graft copolymerization of methyl methacrylate is commercially available as "MG latex". Has been done.

These modifications to natural rubber are generally carried out in a latex state stabilized with a surfactant in view of cost and easy handling, but in some cases, they are also carried out in solid rubber or a rubber solution. However, 5% of non-rubber components such as proteins are contained in ordinary natural rubber latex.
Exists to some extent. Also, about 3% for commercially available concentrated latex
There are non-rubber components. As a result, these non-rubber components, especially proteins, may hinder the modification of natural rubber. For example, in the case of graft copolymerization, the graft ratio and the graft efficiency decrease, and a high modification effect cannot be obtained. There is.

On the other hand, recently, patients have difficulty breathing due to medical devices such as surgical gloves using natural rubber products, various catheters, masks for anesthesia, anaphylactoid symptoms (angioedema, urticaria, collapse, cyanosis, etc.). ) Has been reported in the United States. It has also been reported that when a woman with a history of allergies uses household rubber gloves made of natural rubber, hand pain, urticaria, and angioedema around the eyes appear.

It is speculated that the cause may be a protein in natural rubber. Therefore, it is required to remove the protein content in natural rubber products. Such a problem can occur not only in a natural rubber product but also in a modified rubber obtained by modifying the natural rubber product. Further, natural rubber has a drawback that the raw material characteristics are not stable due to the difference in the production area, production time, etc. peculiar to natural products. Since the cause is the non-rubber component, removing the non-rubber component eliminates the instability of the vulcanization characteristics and makes it a raw material rubber with stable quality, similar to synthetic rubber, and uses modified natural rubber. It helps improve the precision of rubber mechanical properties.

As the deproteinized natural rubber, crepe H, crepe G, crepe CD and the like are actually commercially available. Generally, the protein content of natural rubber has been usually expressed as 6.3 times the nitrogen content determined by the Kjeldahl method. According to the research conducted by the present inventors, the nitrogen content of fresh natural rubber latex (field latex) is about 0.5-0.8% by weight, and that of commercially available purified latex and raw rubber (smoked sheet rubber) is about 0. It is at least 3% by weight. In addition, in the conventional deproteinized natural rubber, although the protein content is significantly reduced,
Even in crepe CD with the lowest protein content, the nitrogen content is about 0.11% by weight, deproteinization is not complete, and therefore the efficiency of modification cannot be increased, and it is also a material that is insufficient as a countermeasure against allergies. Met.

A main object of the present invention is to provide a modified natural rubber modified with high efficiency and a method for producing the same. Another object of the present invention is to provide a modified natural rubber that does not cause allergies and a method for producing the same.

[0009]

Means and Actions for Solving the Problems The modified natural rubber of the present invention for achieving the above object is a natural rubber from which proteins in the natural rubber have been removed to a nitrogen content of 0.10% by weight or less. It is a modified product. The method for producing a modified natural rubber of the present invention is characterized in that the protein in the natural rubber latex is removed until the nitrogen content becomes 0.10 wt% or less, and then the natural rubber is modified. To do.

Thus, the nitrogen content is 0.10% by weight.
By using the natural rubber deproteinized up to the following, it becomes possible to efficiently modify the natural rubber,
A high modification effect can be obtained. The modified natural rubber of the present invention includes:
Examples thereof include those obtained by graft-copolymerizing an organic compound having an unsaturated bond with natural rubber deproteinized as described above, and those obtained by epoxidation.

The natural rubber to be modified preferably has a protein content of 0.05 wt% or less in terms of nitrogen content, and more preferably 0.02 wt% or less. Generally, natural rubber is known to be a mixture of a high molecular weight component having a molecular weight of 1,000,000 to 2,500,000 and a low molecular weight component having a molecular weight of 100,000 to 200,000. It is presumed that the high-molecular weight component is branched from the low-molecular weight component by being bonded to each other through the abnormal group (mainly peptide molecule) contained in the natural rubber. If the molecular weight of the low-molecular weight rubber considered to be produced by the original biosynthesis is 100,000, 1 molecule of this low-molecular weight rubber has 1 peptide molecule intervening in the intermolecular bond.
The nitrogen content when one atom of a molecule, that is, a nitrogen atom (atomic weight 14) is bonded is 0.014%. It is considered that nitrogen corresponding to this amount remains without being removed. Therefore, it is unavoidable that a nitrogen content of about 0.02% or less remains, so it is judged that the natural rubber from which the nitrogen content is removed to a level of 0.02% or less has almost completely removed proteins. To be done.

Further, in the present invention, the almost completely deproteinized natural rubber does not show the absorption at 3280 cm ^-1 peculiar to the polypeptide in the infrared absorption spectrum. Therefore, in order to confirm more accurately that the protein has been removed, it is desirable to adopt an analysis method using infrared absorption spectrum. As the deproteinized natural rubber in the present invention, the deproteinized natural rubber previously proposed by the present applicants (Japanese Patent Application Nos. 4-208754 and 4-2087).
55). Such deproteinized natural rubber is
It can be produced by a method of degrading protein by adding proteolytic enzyme or bacteria to latex, or a method of repeatedly washing with a surfactant such as soap. In particular, a method proposed by the present applicants, in which the protease and the surfactant are treated simultaneously or sequentially (Japanese Patent Application Nos. 4-208756 to 4-208758).
No. 1) is more preferably used.

As the latex used as a starting material for obtaining the deproteinized natural rubber, both commercially available ammonia-treated latex and field latex can be used. The proteolytic enzyme is not particularly limited, and any of bacterial origin, filamentous fungus origin, and yeast origin may be used.
It is preferable to use ze.

As the surface active agent, for example, an anionic surface active agent and / or a nonionic surface active agent can be used. Examples of the anionic surfactant include carboxylic acid-based surfactants, sulfonic acid-based surfactants, sulfate ester-based surfactants, and phosphoric acid ester-based surfactants. 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 preferably used.

In order to decompose the protein in natural rubber latex with a proteolytic enzyme, the proteolytic enzyme is added to a field latex or an ammonia-treated latex in an amount of about 10 to 0.
It is advisable to add it in a proportion of 001% by weight. The treatment time with the enzyme is not particularly limited, but it is preferable to perform the treatment for several minutes to about one week. The latex may be agitated or left standing. Moreover, the temperature may be adjusted if necessary, and an appropriate temperature is 5 ° C.
To 90 ° C, preferably 20 ° C to 60 ° C. If the treatment temperature is higher than 90 ° C, the enzyme is rapidly deactivated, and if it is lower than 5 ° C, the reaction of the enzyme is difficult to proceed.

As a method of washing the latex particles with a surfactant, for example, a method of adding a surfactant to the latex which has been subjected to the enzyme treatment and centrifuging can be suitably adopted. At that time, the surfactant is 0.00 relative to the latex.
It is suitable to add in the range of 1 to 10% by weight. Further, instead of centrifugation, a washing method in which latex particles are aggregated and separated can be adopted. Centrifuge 1
You can do it once or several times. Further, when cleaning the natural rubber, a synthetic rubber or a synthetic rubber latex may be used in combination.

Among the modified natural rubbers of the present invention, the graft copolymer obtained by graft-copolymerizing an organic compound having an unsaturated bond is suitable by adding the organic compound having an unsaturated bond to the latex of deproteinized natural rubber. It is obtained by adding a different polymerization initiator and reacting. As the organic compound having an unsaturated bond, for example, methacrylic acid, acrylic acid, methyl methacrylate, methyl acrylate, methacrylic acid such as 2-hydroxyethyl methacrylate or acrylic acid or a derivative thereof, acrylonitrol, vinyl acetate, styrene, acrylamide, Examples thereof include graft copolymerizable monomers such as vinylpyrrolidone. When adding an organic compound having an unsaturated bond to the latex, add an emulsifier in the latex in advance, or
Alternatively, after emulsifying an organic compound having an unsaturated bond,
Add to latex. The emulsifier is not particularly limited, but a nonionic surfactant is preferably used.

The amount of the organic compound having an unsaturated bond added is usually 5 to 1 with respect to 100 parts by weight of the deproteinized natural rubber.
The amount is 00 parts by weight, preferably 10 to 50 parts by weight. If the amount of vinyl monomer added exceeds this range, the production of homopolymer will increase and the grafting efficiency will decrease. Conversely, if it falls below this range, the amount of grafted organic compounds with unsaturated bonds will decrease and modification will occur. The effect becomes small and neither is preferable.

Examples of the polymerization initiator include benzoyl peroxide, hydrogen peroxide, cumene hydroperoxide, t
ert-butyl hydroperoxide, di-tert
-Butyl peroxide, 2,2-azobisisobutyrotitryl, peroxides such as potassium persulfate,
In particular, it is preferable to use a redox type polymerization initiator in order to reduce the polymerization temperature. In the redox type polymerization initiator, examples of the reducing agent combined with the peroxide include tetraethylenepentamine, mercaptans, sodium acid sulfite, reducing metal ions, and ascorbic acid. As a preferred combination example of the redox type polymerization initiator, tert-
Butyl hydroperoxide and tetraethylene pentamine, hydrogen peroxide and Fe ²⁺ salt, K ₂ SO ₂ O ₈ and NaH
SO ₃ and so on.

The amount of the polymerization initiator added is 0.3 to 10 mol% based on 100 mol of the organic compound having an unsaturated bond,
It is preferably 0.5 to 1 mol%. A graft copolymer is obtained by charging these components into a reaction vessel and carrying out a reaction at 30 to 80 ° C. for 2 to 10 hours. The deproteinized natural rubber used may be in a latex state, a rubber solution or a solid rubber.

The deproteinized natural rubber graft copolymer thus obtained has a high graft ratio (a ratio of the weight of the graft-polymerized monomer to the weight of the main chain polymer,
Since it has a grafting efficiency (usually about 15 to 25%) and a grafting efficiency (the ratio of the weight of the graft-polymerized monomer to the total polymerization weight of the monomer, usually about 40 to 60%), the adhesiveness and other properties can be maintained while maintaining the strength. It is excellent and therefore can be suitably used for applications such as adhesives.

The epoxidation of the deproteinized natural rubber in the present invention is carried out using an organic peracid. As an organic peracid,
Examples thereof include perbenzoic acid, peracetic acid, performic acid, perphthalic acid, perpropionic acid, trifluoroperacetic acid and perbutyric acid. These organic peracids may be added directly to the latex, but it is preferable to add two components which form the organic peracid to the latex so that the generated organic peracid reacts with the natural rubber in the latex. For example, when forming formic acid, formic acid and hydrogen peroxide may be sequentially added. In the case of peracetic acid, glacial acetic acid and hydrogen peroxide may be sequentially added and reacted.

The amount of the organic peracid added is usually 10 to 100 parts by weight, preferably 20 to 70 parts by weight, based on 100 parts by weight of the deproteinized natural rubber. Even when the two components that produce the organic peracid are added, the addition amount is adjusted so that the produced organic peracid is within this range. When the amount of the organic peracid added exceeds the above range, the physical properties are largely deteriorated due to side reactions and the like, and when the amount is less than the above range, the modifying effect becomes small, which is not preferable.

Prior to adding these organic peracids or their reaction components to the latex, an emulsifier such as a nonionic type is added to the latex and the pH of the latex is kept stable at about 5 to 7 which is near neutral. It is preferable to convert it into The epoxidation reaction is usually performed at a temperature of 30 to 60 ° C. for 3 to
It is carried out by reacting for 10 hours.

The deproteinized natural rubber used may be in the latex state as in the case of the above grafting, or may be a rubber solution or a solid rubber. The epoxidized product of the deproteinized natural rubber thus obtained has a high epoxidation rate (rate of conversion of unsaturated bond to epoxy group, and is usually 50 to 70).
%, It has excellent properties such as oil resistance and gas permeation resistance while maintaining strength, and therefore can be suitably used for applications such as hoses and inner liners of tires.

[0026]

EXAMPLES The modified natural rubber of the present invention will be described below with reference to Reference Examples and Examples. Reference Example 1 Alkalas 2.0M from Novo Nordisk Bioindustry Co., Ltd. as a proteolytic enzyme, and natural rubber latex is solid rubber 60.2 from Soctech (Malaysia).
% Was used.

200 ml of 15 ml of natural rubber latex
Diluted with distilled water and stabilized with 0.12% sodium naphthenate. The pH was adjusted to 9.2 by adding sodium dihydrogen phosphate. Alcalase 2.0M 0.78g
Was dispersed in 10 ml of distilled water and then added to the diluted natural rubber latex. Further, after the pH was readjusted to 9.2, it was maintained at 37 ° C. for 24 hours. The nonionic surfactant "Emulgen 810" (trade name, manufactured by Kao Corporation) was added to the latex after the enzyme treatment at a concentration of 1%, and the mixture was centrifuged at 11,000 rpm for 30 minutes. The resulting creamy fraction was redispersed in 200 ml of distilled water containing 1% "Emulgen 810" (supra) and centrifuged again. After repeating this operation three times, a predetermined amount of the cream dispersion was dispersed in distilled water to obtain a deproteinized rubber latex.

The deproteinized rubber latex was cast on a glass plate and dried at room temperature, and the obtained film was dried at room temperature under reduced pressure. The nitrogen content of the obtained film was measured by the RRIM test method (Rubber Research Institute of Malaysia (1973).
'SMR Bulletin No. 7'). For the infrared absorption spectrum, a film was formed on a KBr disk, and the absorbance was measured with a JASCO 5300 Fourier transform infrared spectroscope.

As a result, the solid rubber obtained had a nitrogen content of 0.008% or less, and absorption of a short chain peptide or amino acid of 3320 cm ^-1 was present, but 3280 cm.
The absorption of the high molecular weight polypeptide of ^-1 could not be detected. Reference Example 2 As the natural rubber latex, a high ammonia type commercially available latex of Guthrie (Malaysia) was used. The solid rubber content was 62.0%.

The natural rubber latex was diluted with a 0.12% sodium naphthenate aqueous solution so that the solid rubber content was 10% by weight. Sodium dihydrogen phosphate was added to adjust the pH to 9.2, and Alcalase 2.0M was added to the rubber component 1
0.87 g was added to 0 g. Furthermore, pH
Was reconstituted to 9.2 and then kept at 37 ° C. for 24 hours.

The non-ionic surfactant "Emulgen 810" (mentioned above) was added to the latex which had been treated with the enzyme.
% Aqueous solution to adjust the rubber concentration to 8%,
Centrifuged at 00 rpm for 30 minutes. The resulting creamy fraction was dispersed with a 1% aqueous solution of "Emulgen 810" (supra), adjusted to have a rubber concentration of about 8%, and then centrifuged again. After repeating the centrifugation operation once, the obtained cream was dispersed in distilled water to prepare a deproteinized rubber latex having a solid rubber content of 60%.

The amount of nitrogen in the raw rubber obtained from this latex was 0.05%, and the infrared absorption spectrum thereof had an absorption at 3320 cm ^-1 but no absorption at 3280 cm ^-1 . Reference Example 3 In the same manner as in Reference Example 2, the non-ionic surfactant "Emulgen 810" was added to the latex after the enzyme treatment.
The rubber concentration was adjusted to 8% by adding the 1% aqueous solution (described above), and the mixture was centrifuged at 11000 rpm for 30 minutes. The obtained cream was dispersed in distilled water to prepare a deproteinized rubber latex having a solid rubber content of 60%.

The raw rubber obtained from this latex has a nitrogen content of 0.1% and its infrared absorption spectrum shows 3%.
Absorption at 320 cm ^-1 was present, but absorption at 3280 cm ^-1 was not observed. Example 1 (Production of Graft Copolymerized Natural Rubber) A latex of the deproteinized natural rubber obtained in Reference Example 1 (solid content 60%) was placed in a four-necked flask equipped with a stir bar, a dropping funnel, a nitrogen introducing tube and a condenser. 300 g was added, and 0.92 g of a nonionic emulsifier (“Emulgen 930” manufactured by Kao Corporation) dissolved in 250 ml of distilled water was added at once while stirring slowly under a nitrogen atmosphere. Next, 91.6 g of methyl methacrylate was added and vigorously stirred for several seconds to mix each chemical well. Then, distilled water 50
Polymerization initiator tert-butyl hydroperoxide 1.43 g and tetraethylenepentamine 15.0
and g were added and reacted at 30 ° C. for 3 hours. Since the latex after the reaction was coagulated, the unreacted natural rubber, homopolymer and graft copolymer were separated by extraction with petroleum ether and then extraction with a 2: 1 mixed solvent of acetone and methanol. . These are FT-IR, N
It was confirmed by MR that they were independent of each other. Examples 2 to 3 (Production of modified natural rubber graft-copolymerized) Deproteinized rubber latex obtained in Reference Example 2 (solid content 60%)
And the deproteinized rubber latex obtained in Reference Example 3 (solid content 6
A graft copolymer was obtained in the same manner as in Example 1 except that each of 0%) was used. Comparative Example 1 (Production of Graft-Copolymerized Natural Rubber) HA type latex obtained from Guthrie (Malaysia) was diluted to 30% concentration and then centrifuged to 60%.
Concentrated to. The nitrogen content obtained by this is 0.1
A graft copolymer was obtained in the same manner as in Example 1 except that 6% of natural rubber latex (61% solid content) was used. Comparative Example 2 (Production of Graft-Copolymerized Natural Rubber) A latex of natural rubber having a nitrogen content of 0.34% (solid content 61) obtained from Guthrie Co. (Malaysia).
%) Was used to obtain a graft copolymer in the same manner as in Example 1.

With respect to the graft copolymers obtained in the respective examples and comparative examples, the graft ratio and the graft efficiency for evaluating the degree of polymerization were determined by the following formulas.

[0035]

[Equation 1]

The obtained graft ratio and graft efficiency are shown in Table 1 together with the nitrogen content of each natural rubber used.

[0037]

[Table 1]

From Table 1, the protein has a nitrogen content of 0.10.
It can be seen that the examples in which the content is reduced to less than 10% are superior in the graft ratio and the graft efficiency as compared with the comparative example having a high nitrogen content. Example 4 (Production of Epoxidized Natural Rubber) 300 g of the deproteinized natural rubber latex (solid content 60%) obtained in Reference Example 1 was placed in a three-necked flask equipped with a stir bar, a dropping funnel and a condenser. . Then, 5.4 g of a nonionic emulsifier (“Emulgen 106” manufactured by Kao Corporation) dissolved in 300 ml of distilled water was slowly added with stirring. Next, acetic acid was added to adjust the pH to neutral, heated to 40 ° C., and 30.6 g of formic acid was added with stirring. Furthermore, it heats to 50 degreeC and 166.8 in 20 minutes.
Hydrogen peroxide (39% aqueous solution) (g) was added, and then the mixture was reacted at room temperature for 5 hours to obtain an epoxidized rubber. Examples 5 to 6 (Production of Epoxidized Natural Rubber) Deproteinized rubber latex obtained in Reference Example 2 (solid content 60%)
And the deproteinized rubber latex obtained in Reference Example 3 (solid content 6
An epoxidized rubber was obtained in the same manner as in Example 4 except that 0%) was used. Comparative Example 3 (Production of Epoxidized Natural Rubber) A latex of natural rubber having a nitrogen content of 0.16% (solid content 61), obtained from Guthrie (Malaysia).
%) Was used to obtain an epoxidized rubber in the same manner as in Example 1. Comparative Example 4 (Production of Epoxidized Rubber) A latex of natural rubber (solid content 61) having a nitrogen content of 0.34%, obtained from Guthrie (Malaysia).
%) Was used to obtain an epoxidized rubber in the same manner as in Example 1.

The epoxidation ratios of the epoxidized rubbers obtained in the respective examples and comparative examples were measured by using FT-IR and ¹³ C-NMR. Measurement is Chemical Demonstration of th
e Randomness of Epoxidized Natural Rubber, Br.Poly
According to mJ 1984, 16, 134 (Davey et al.), and in order to compare the reaction rates, the epoxidation rate of double bonds after 3 hours was measured. The results are shown in Table 2.

[0040]

[Table 2]

From Table 2, the protein has a nitrogen content of 0.10.
It can be seen that the epoxidation rate is higher in the examples in which the content is reduced to not more than%, as compared with the comparative example in which the nitrogen content is high.

[0042]

INDUSTRIAL APPLICABILITY According to the modified natural rubber and the method for producing the same of the present invention, a natural rubber having a nitrogen content of 0.10% by weight or less is used for modification such as graft copolymerization and epoxidation. Therefore, there is an effect that it has a high reforming efficiency and therefore an excellent reforming effect is obtained. Further, since the modified natural rubber of the present invention is substantially free of proteins, it is useful as a countermeasure against allergies.

Front Page Continuation (72) Inventor Toshiaki Sakaki 1314 Yoda, Onoe Town, Kakogawa City, Hyogo Prefecture (72) Inventor Yuichi Hioki 1293-7 Mutsuya, Wakayama City, Wakayama Prefecture (72) Masaharu Hayashi Wakayama City, Wakayama Prefecture Enohara 133-5

Claims (9)

[Claims] 1. A modified natural rubber, which is a modified natural rubber, wherein a protein in the natural rubber has a nitrogen content of 0.10% by weight or less. 2. A modified natural rubber, wherein the modified natural rubber contains 0.05% by weight or less of a protein in the natural rubber in terms of nitrogen content. 3. A modified natural rubber, which is a modified natural rubber, wherein a protein in the natural rubber has a nitrogen content of 0.02% by weight or less. 4. A modified natural rubber, wherein the protein in the natural rubber is 328 in the infrared absorption spectrum.
A modified natural rubber characterized by being removed to the extent that absorption at 0 cm ^-1 is not observed. 5. A natural rubber obtained by graft-copolymerizing an organic compound having an unsaturated bond, wherein the protein in the natural rubber has a nitrogen content of 0.10% by weight or less. Natural rubber. 6. A graft copolymerized natural rubber, which is an epoxidized natural rubber, wherein the protein in the natural rubber has a nitrogen content of 0.10% by weight or less. 7. A method for producing a modified natural rubber, which comprises modifying the natural rubber after removing the protein in the natural rubber latex until the nitrogen content becomes 0.10% by weight or less. 8. A natural rubber latex, wherein proteins in the natural rubber latex are removed to a nitrogen content of 0.10% by weight or less, and then an organic compound having an unsaturated bond is graft-copolymerized with the natural rubber. A method for producing a graft copolymerized natural rubber. 9. A method for producing an epoxidized natural rubber, which comprises removing proteins in a natural rubber latex until the nitrogen content is 0.10% by weight or less, and then epoxidizing the natural rubber.