JP2007284638A - Method for producing microorganism-treated natural rubber latex, natural rubber and its rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably producing a microorganism-treated natural rubber latex having excellent processability and physical properties at a low cost and provide a natural rubber and its rubber composition. <P>SOLUTION: The method for producing a microorganism-treated natural rubber latex comprises the decomposition of proteins, lipids and carbohydrates by the addition of microorganism to natural rubber. The pH in the decomposition of proteins, lipids and carbohydrates by the addition of microorganism is preferably 5-10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a microorganism-treated natural rubber latex that is stable and inexpensive and has excellent processability and physical properties, natural rubber, and a rubber composition thereof.

  In general, natural rubber contains about 6% by mass of non-rubber components such as protein. Major non-rubber components include lipids, carbohydrates and the like in addition to proteins. Among these non-rubber components, proteins and lipids have a bad influence on processability, and sugars have a bad influence on low loss and wear resistance.

  Therefore, the applicant of the present application has proposed a technique that can improve the processability and physical properties of the rubber composition by treating the latex with an enzyme effective for various non-rubber components (for example, Patent Documents 1 to 3). 3). In addition, natural rubber latex removes proteins from raw rubber and is a natural protein that contains deproteinized natural rubber substantially free of protein (see, for example, Patent Document 4), protease, and a specific surfactant as active ingredients. A deproteinizing agent for rubber (for example, see Patent Document 5) is known.

However, many of the commercially available enzymes described in the above-mentioned documents and currently used are concentrated concentrates of specific microorganisms released into the medium during growth. Theoretically, the microorganisms can be grown in latex. Natural rubber with excellent processability and physical properties can be produced. In fact, rubbers with excellent processability and physical properties are often found in rubber plantations, but they cannot be reproduced stably.
There are two reasons for this. The first is that the microbial species that grows in natural rubber latex depends on chance, and the second is that the desired performance is obtained before the enzymatic reaction proceeds sufficiently even if effective bacteria propagate. Is not possible.
International Publication No. WO2003 / 08925 (Claims, Examples, etc.) JP-A-2004-189773 (Claims, Examples, etc.) JP-A-2004-189774 (Claims, Examples, etc.) JP-A-6-56902 (Claims, Examples, etc.) JP-A-6-56906 (Claims, Examples, etc.)

  The present invention has been made in view of the above-mentioned problems and current state of the prior art, and is intended to solve this problem. A method for producing a microbially treated natural rubber latex excellent in processability and physical properties stably and inexpensively, natural rubber, and An object is to provide the rubber composition.

As a result of diligent research to solve the above-described conventional problems, the present inventor uses a specific microorganism that grows quickly and easily releases an enzyme in a culture solution, thereby achieving the above-described target microorganism-treated natural product. It is an object of the present invention to provide a method for producing rubber latex, a method for producing natural rubber and a rubber composition thereof, a natural rubber and a rubber composition thereof.
That is, the present invention resides in the following (1) to (7).
(1) A method for producing a microorganism-treated natural rubber latex, characterized in that microorganisms are added to natural rubber latex to decompose proteins, lipids and carbohydrates.
(2) The method for producing a microorganism-treated natural rubber latex as described in (1) above, wherein a surfactant is added.
(3) The method for producing a microorganism-treated natural rubber latex as described in (1) or (2) above, wherein a pH buffer is further added.
(4) The microorganism-treated natural as described in any one of (1) to (3) above, wherein the pH when adding microorganisms to degrade proteins, lipids and carbohydrates is 5 to 10 A method for producing rubber latex.
(5) The method for producing a microorganism-treated natural rubber latex as described in any one of (1) to (4) above, wherein the microorganism is a bacterium.
(6) A natural rubber obtained by coagulating and drying a microorganism-treated natural rubber latex obtained by the production method according to any one of (1) to (5) above.
(7) A rubber composition comprising the natural rubber according to (6) above.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of microbial treatment natural rubber latex excellent in processability and physical property stably and cheaply, natural rubber, and its rubber composition are provided.

Hereinafter, embodiments of the present invention will be described in detail for each invention.
The method for producing a microorganism-treated natural rubber latex of the present invention is characterized in that microorganisms are added to natural rubber latex to decompose proteins, lipids and carbohydrates.
As the method of the present invention, for example, microorganisms that grow faster than the collected natural rubber latex and easily release enzymes that degrade proteins, lipids, and carbohydrates of the natural rubber latex into the culture solution are used. By culturing and inoculating a part of this pre-cultured solution in a natural rubber latex-based medium, it degrades proteins, lipids and carbohydrates, which are adverse components in natural rubber latex, and excels in processability and physical properties. Natural rubber latex can be produced.

  The natural rubber latex used as a raw material for the present invention means a field latex obtained from a natural rubber tree, and it is preferable to use a fresh field latex.

The microorganism used in the present invention is not particularly limited as long as it is a microorganism capable of degrading proteins, lipids, and carbohydrates of natural rubber latex. For example, an enzyme (protease, lipase, amylase) that degrades proteins, lipids, and carbohydrates. Bacteria that are the production bacteria.
Specific examples of the bacterium that can be used include at least one bacterium belonging to the genus Bacillus and Pseudomonas, which are producers of enzymes (proteases, lipases, amylases) that degrade proteins, lipids, and carbohydrates. Seeds (each alone or a mixture of two or more). For example, a commercially available subtilis ATCC 6633 strain can be used for the Becillus genus, and a commercially available putida ATCC 49218 strain can be used for the Pseudomonas genus.

In the method of the present invention, as a method of treating natural rubber latex using the microorganism, for example, the microorganism can be directly added to natural rubber latex, but a fungus group having an effective effect on processability and physical properties can be used. From the viewpoint of stable growth, it is preferable to use a preculture solution in which microorganisms are precultured.
As a preparation method (cultivation conditions) of the preculture solution, the medium for culturing the microorganism is sterilized, then the microorganism used in the present invention is inoculated into the medium, and the preculture solution is prepared by aerobic preculture. can do.
The pre-cultured solution obtained above is inoculated into a medium containing natural rubber latex, stirred under aerobic conditions, and maintained at a pH of preferably 7.0 or higher, thereby adversely affecting processability. Thus, a natural rubber latex can be obtained in which lipids are decomposed and carbohydrates that adversely affect low loss and wear resistance are decomposed.

The medium used for the pre-culture is not particularly limited as long as microorganisms such as each bacterium to be used grow favorably and can produce enzymes (proteases, lipases, amylases) that decompose proteins, lipids, and carbohydrates to the maximum extent. Not.
The amount of the microorganism used is desirably 0.01 to 2.0 parts by mass with respect to 100 parts by mass of the rubber component in the natural rubber latex.

In the present invention, it is preferable to add a surfactant from the viewpoint of further promoting the release of the target enzyme from microorganisms such as bacteria and obtaining a more effective microorganism-treated latex.
Examples of the surfactant that can be used include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Is preferred.
In particular, the polyoxyethylene ether type is desirable from the viewpoint of damaging the cell wall to the extent that it is not fatal to bacteria and the like, and maximally inducing the enzyme into the medium, and specifically, Triton X-100 and the like can be mentioned.

The amount of the surfactant added is preferably 0.005 to 10 parts by mass, more preferably 0.01 to 1.0 parts by mass with respect to 100 parts by mass of the solid component in the natural rubber latex. It is desirable to be.
When the amount of the surfactant added is less than 0.005 parts by mass, the cell wall damaging action becomes insufficient and the effect of further treatment becomes low. On the other hand, when the amount exceeds 10 parts by mass, bacteria and the like are excessively removed. There is a risk of damage or inactivation.

In addition, in order to prevent the pH from decreasing due to respiration of bacteria and coagulation for a certain period of time, a pH buffering agent is added to natural rubber lux, or microorganisms are added to natural rubber latex proteins, lipids, and carbohydrates with a base. It is desirable to adjust the pH at the time of decomposing preferably 5 to 10, particularly preferably 6 to 9. As a result, it is possible to further earn time for the enzyme released from bacteria or the like to sufficiently react.
Examples of the pH buffer that can be used include phosphates such as monopotassium phosphate, dipotassium phosphate, and sodium phosphate, acetates such as potassium acetate and sodium acetate, and sulfuric acid, acetic acid, hydrochloric acid, and nitric acid. Acids such as citric acid and succinic acid or salts thereof, or at least one of ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like can be used in an amount within the above-mentioned preferable pH range.

In the method of the present invention configured as described above, the collected natural rubber latex grows fast among microorganisms and easily releases enzymes that degrade proteins, lipids, and carbohydrates of the natural rubber latex into the culture solution. By pre-incubating microorganisms and inoculating a part of this pre-cultured liquid in a natural rubber latex-based medium, it degrades proteins, lipids, and carbohydrates, which are harmful components in natural rubber latex, A natural rubber latex having excellent physical properties can be produced.
In the method of the present invention, it is possible to obtain a natural rubber latex obtained by a plurality of enzyme treatments having excellent processability and physical properties stably and inexpensively without using individual concentrated enzymes. In addition, since the residual sugar content in the wastewater is almost consumed due to the growth of microorganisms, the wastewater treatment facility can be simplified.

The natural rubber of the present invention is obtained by coagulating and drying a microorganism-treated natural rubber latex having the above characteristics obtained by the above production method.
Specifically, the latex of natural rubber that has been subjected to microbial treatment is acid-coagulated with an acid such as formic acid, and then clarified through a creper or a shredder. After washing, the latex is usually used in vacuum dryers, air dryers, drum dryers, etc. The natural rubber in the present invention can be obtained by drying using a dryer.

The rubber composition of the present invention is characterized by containing a natural rubber having the above characteristics as a rubber component.
The rubber composition of the present invention preferably contains at least 5% by mass, preferably 5 to 100% by mass, as a rubber component. If this amount is less than 5% by weight, a rubber composition having desired physical properties may not be obtained.
Examples of the rubber component used in combination with the natural rubber include ordinary natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include styrene-butadiene copolymer (SBR), polybutadiene (BR), and polyisoprene. (IR), butyl rubber (IIR), ethylene-propylene copolymer, and mixtures thereof.

Further, the filler compounded in the rubber composition of the present invention is not particularly limited, but those usually used in the rubber industry such as carbon black, silica, alumina, aluminum hydroxide, clay, calcium carbonate are used. it can. As carbon black, carbon black of various grades, such as SAF, HAF, ISAF, HAF, FEF, GPF, can be used, for example. Silica is not particularly limited, but wet silica, dry silica, and colloidal silica are preferable. Such fillers can be used alone or in admixture of two or more.
The total amount of the filler is preferably in the range of 30 to 120 parts by mass and more preferably 40 to 80 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition of the present invention, various chemicals usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, a process oil, an antioxidant, as long as the object of the present invention is not impaired. A scorch inhibitor, zinc white, stearic acid and the like can be contained.

  The rubber composition of the present invention can be used for applications such as anti-vibration rubber, belts, hoses and other industrial products as well as tire applications. In particular, it is suitably used as tire rubber, and can be applied to all tire members such as tread rubber (including cap rubber and base rubber), side rubber, ply rubber, and bead filler rubber.

  Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited to the following Example.

[Examples 1-2 and Comparative Examples 1-4]
Example 1
(1) Pre-culture of microorganisms:
Place 50 ml of the medium A shown below in a 300 ml Erlenmeyer flask and sterilize at 121 ° C. for 20 minutes. Then inoculate 1 platinum ear of Becillus subtilis ATCC6633 and perform aerobic shaking culture at 30 ° C. for 24 hours. A preculture solution (I) was obtained.
Medium A
Glucose 2.0% (W / V)
Polypeptone S 1.0% (W / V)
Yeast extract 0.05% (W / V)
Monopotassium phosphate 0.1% (W / V)
Magnesium sulfate heptahydrate 0.02% (W / V)
Sodium carbonate (separate sterilization) 1.0% (W / V) (no pH adjustment)

(2) Microbial treatment of natural rubber latex Next, the obtained preculture solution (I) is inoculated into the following medium B at 2% (v / v), stirred under aerobic conditions, and adjusted to pH 7. While maintaining at 0 or more, it was kept at 30 ° C. for 48 hours to obtain a natural rubber latex (A).
Medium B:
Natural rubber latex (solid content 20%) 1.0L
Monopotassium phosphate 0.70g
Magnesium sulfate heptahydrate 0.14g
Sodium carbonate 7.0 g (pH 9.0)
Triton X-100 0.70g

(3) Coagulation / Drying Step The rubber obtained by acid coagulation of the natural rubber latex (A) was dried for 180 minutes with a hot air dryer set at 120 ° C. to produce a natural rubber (a).

(Example 2)
(1) Pre-culture of microorganisms:
50 ml of medium C (L-broth) shown below was put into a 300 ml Erlenmeyer flask and sterilized at 121 ° C. for 20 minutes, and then Pseudomonas putida ATCC 49218 strain was inoculated and pre-cultured overnight at 250 ° C. Thus, a preculture liquid (II) was obtained.
Medium C
Bactotripton 1.0% (W / V)
Yeast extract 0.5% (W / V)
Sodium chloride 0.5% (W / V)
Glucose 0.1% (W / V)
Sodium carbonate (separate sterilization) 1.0% (W / V) (no pH adjustment)

(2) Microbial treatment of natural rubber latex Next, 2% (v / v) of the obtained preculture liquid (II) is inoculated into the following medium D, and stirred under aerobic conditions to adjust the pH to 7 While maintaining at 0.0 or more, it was kept at 30 ° C. for 48 hours to obtain a natural rubber latex (B).
Medium B:
Natural rubber latex (solid content 20%) 1.0L
Dipotassium phosphate 3.0g
Ammonium sulfate 0.5g
Magnesium sulfate 2.0g
Zinc sulfate 0.1g (pH 9.0)
Triton X-100 0.7g

(3) Coagulation / drying step Natural rubber (b) was produced in the same manner as in Example 1 except that the natural rubber latex (B) was used.

(Comparative Example 1)
(1) Collection and preparation of natural rubber latex To 600 g of natural rubber latex (stock solution, no NH ₃ added) (solid content of 120 g), a surfactant (“SS-40N” 10.0 g, manufactured by Kao Corporation) was added. Natural rubber latex (III) adjusted to pH 9.0 was obtained.
(2) Enzyme treatment step of natural rubber latex 0.10 g of protease (enzyme, manufactured by Novozymes, “Alcalase 2.5 L, type DX”) as an enzyme was added to 400 g of water and mixed to prepare solution (IV). .
Next, 600 g of natural rubber latex (III) was kept at a constant temperature of 30 ° C. in a water bath, and while stirring, the solution (IV) was added dropwise, stirring was continued for 3 hours at the same temperature, and allowed to stand for 45 hours. A treated natural rubber latex (C) was obtained.
(3) Coagulation / drying step Natural rubber (c) was produced in the same manner as in Example 1 except that enzyme-treated natural rubber latex (C) was used.

(Comparative Examples 2 and 3)
In Comparative Example 1 (2), instead of the enzyme: protease, Comparative Example 2 is lipase (manufactured by Meito Sangyo Co., Ltd., “Lipase OF”, 0.10 g), and Comparative Example 3 is cellulase (manufactured by Amano Enzyme, “Cellulase A”, 0.10 g) was used to obtain each enzyme-treated natural rubber latex (D), (E), and then coagulated and dried in the same manner as in Example 1 to obtain each natural rubber (d), (E) was produced.

(Comparative Example 4)
In Comparative Example 1, natural rubber (f) was produced by directly coagulating and drying without adding the enzyme and without undergoing the enzyme treatment step.

In the said Examples 1-2 and Comparative Examples 1-4, pH measurement (normal method) at the time of preparation of natural rubber latex, nitrogen amount, molecular weight (Mw), and gel content (%) were measured by the following method.
These results are shown in Table 1 below.

(Method for measuring nitrogen content)
The total nitrogen content was measured by the Kjeldahl method and calculated as a ratio (mass%) to the total amount.

(Measurement method of molecular weight Mw)
Each natural rubber based on Tosoh standard polystyrene using gel permeation chromatography [GPC]: Tosoh HLC-8020, column: Tosoh GMH-XL, detector: differential refractive index (RI) The weight average molecular weight in terms of polystyrene was determined.

(Method for measuring gel content)
Add 0.2 g of natural rubber sample to 50 ml of toluene and leave it for 24 hours, and use toluene centrifuge CP70G manufactured by Hitachi Koki Co., Ltd. under conditions of rotor temperature 10 ° C., rotating machine 35,000 rpm, 90 minutes. Separated. Thereafter, the separated gel was dried and weighed, and the ratio was calculated by determining the ratio to the total mass of the natural rubber used.

Using each of the above natural rubbers, a rubber composition was prepared with the composition shown in Table 2 below, and a trial rubber vulcanized under the conditions of a temperature of 145 ° C. for 33 minutes was obtained from the rubber composition.
Moreover, kneaded rubber viscosity (Mooney viscosity) and abrasion resistance of each prototype rubber were evaluated by the following methods, and the results are shown in Tables 1 to 3 below.
(1) Mooney Viscosity of Conbound (Rubber Composition) The Mooney viscosity [ML1 + 4/130 ° C.] was measured at 130 ° C. according to JIS K6300-1994. The smaller this value, the better the workability.
(2) Abrasion resistance (index)
Using a Lambourn type wear tester, the amount of wear at a slip rate of 60% at room temperature was measured, and indexed with Comparative Example 6 as a control (100). The higher the value, the better the wear resistance.
Moreover, the relationship between this abrasion resistance and the Mooney viscosity of a conbound (rubber composition) is shown in FIG.

老化防止剤６Ｃ：Ｎ−フェニル−Ｎ−１，３―ジメチルブチル−ｐ−フェニレンジアミン
加硫促進剤ＣＺ：Ｎ−シクロヘキシル−２−ベンゾチアゾリルスルフェンアミド

Anti-aging agent 6C: N-phenyl-N-1,3-dimethylbutyl-p-phenylenediamine Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazolylsulfenamide

  As is apparent from the results of Tables 1 and 2 and FIG. 1, Examples 1 and 2 treated with microorganisms within the scope of the present invention are Comparative Examples 1 to 4 subjected to conventional enzyme treatment and the like outside the scope of the present invention. Compared to the above, it has been found that the rubber composition can be obtained stably with natural rubber latex and natural rubber excellent in processability (nitrogen content, molecular weight, gel content) and physical properties (viscosity, wear resistance).

  In the present invention, a method for producing a microorganism-treated natural rubber latex having excellent processability and physical properties at a stable and low cost, its natural rubber and its rubber composition can be obtained, including tire applications, anti-vibration rubber, belts, It can be suitably used for applications such as hoses and other industrial products.

It is the characteristic surface which showed the characteristic of the compound viscosity and abrasion resistance of the rubber composition using the natural rubber obtained by the method of this invention.

Claims (7)

  A method for producing a microorganism-treated natural rubber latex, characterized in that microorganisms are added to natural rubber latex to decompose proteins, lipids, and carbohydrates.   A method for producing a microorganism-treated natural rubber latex according to claim 1, wherein a surfactant is added.   Furthermore, the pH buffer is added, The manufacturing method of the microorganisms processing natural rubber latex of Claim 1 or 2 characterized by the above-mentioned.   The method for producing a microorganism-treated natural rubber latex according to any one of claims 1 to 3, wherein the pH when adding microorganisms to decompose proteins, lipids and carbohydrates is 5 to 10.   The method for producing a microorganism-treated natural rubber latex according to any one of claims 1 to 4, wherein the microorganism is a bacterium.   A natural rubber obtained by coagulating and drying a microorganism-treated natural rubber latex obtained by the production method according to any one of claims 1 to 5.   A rubber composition comprising the natural rubber according to claim 6.

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