Coagulant for natural rubber latex and method for producing natural rubber

Abstract

To provide a coagulant for natural rubber latex capable of exhibiting superior odor suppression of natural rubber when used to coagulate natural rubber latex.SOLUTION: A coagulant for natural rubber latex comprises a salt and / or an acid and a saccharide, where the saccharide is a bound substance composed of fewer than sixteen monosaccharides.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coagulant for natural rubber latex and a method for producing natural rubber. [Background technology]

[0002] Generally, natural rubber is made by solidifying the sap (latex) extracted from the rubber tree, known as Hevea brasiliensis. It is produced by coagulating it with an acid such as formic acid, forming it into a sheet, and drying it; by allowing it to coagulate naturally in a cup used for extracting latex; or by adding acid to the cup to coagulate it. The resulting cup lump is then crushed, washed repeatedly, dried, and pressed to produce a solidified product.

[0003] For example, a method for producing natural rubber has been proposed (Patent Document 1), which comprises tapping natural rubber latex, aging it for 12 hours or more, mechanically separating it, and then coagulating and drying the resulting latex. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-241121 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, various studies have been conducted on the production method of natural rubber, but there is still room for improvement, particularly with regard to the coagulant used to coagulate natural rubber latex during the process.

[0006] The present invention has an object to solve the above problems and to provide a coagulant for natural rubber latex that is excellent in suppressing the odor of natural rubber when used to coagulate natural rubber latex. [Means for solving the problem]

[0007] The present invention relates to a coagulant for natural rubber latex, which comprises a salt and / or an acid and a saccharide, the saccharide being a combination of less than 16 monosaccharides. [Effects of the Invention]

[0008] According to the present invention, a coagulant for natural rubber latex contains a salt and / or an acid and a saccharide, wherein the saccharide is a bond of less than 16 monosaccharides. Therefore, when used to coagulate natural rubber latex, the coagulant for natural rubber latex has excellent properties for suppressing the odor of natural rubber. DETAILED DESCRIPTION OF THE INVENTION

[0009] This specification describes a coagulant for natural rubber latex and a method for producing natural rubber. First, the coagulant for natural rubber latex is described, followed by a method for producing natural rubber.

[0010] (Coagulant for natural rubber latex) The natural rubber latex coagulant contains a salt and / or an acid and a sugar, and the sugar is a bond of less than 16 monosaccharides. Therefore, when used to coagulate natural rubber latex, the coagulant is excellent at suppressing the odor of natural rubber.

[0011] The reason why the above-mentioned effects are obtained is not entirely clear, but it is presumed that the following mechanism is involved. As mentioned above, natural rubber is generally produced by solidifying the sap (latex) collected from rubber trees, forming it into sheets, and drying it; or by allowing the latex to coagulate naturally in a cup used for collecting latex, or by adding acid to the cup to coagulate the latex, and then crushing and washing the resulting cup lump, drying it, and pressing it. However, natural rubber produced by these methods contains non-rubber components such as proteins, lipids, and sugars. During storage of the raw material, these non-rubber components are decomposed and spoiled by bacteria and microorganisms, releasing odor-causing substances and resulting in a foul odor. For example, it is known that the decomposition of proteins in the non-rubber components by bacteria and microorganisms produces odor-causing substances such as short-chain fatty acids and skatole.

[0012] Therefore, by adding sugars composed of less than 16 monosaccharides to the coagulant used to coagulate natural rubber latex, bacteria and microorganisms are thought to decompose the sugars composed of less than 16 monosaccharides in the coagulant before they decompose the non-rubber components in natural rubber. As a result, the decomposition and decay of the non-rubber components in natural rubber is inhibited, and the generation of odor-causing substances is suppressed, making it possible to suppress the odor of natural rubber. Furthermore, the addition of sugars composed of less than 16 monosaccharides may reduce the activity of bacteria and microorganisms, thereby inhibiting the decomposition and decay of the non-rubber components in natural rubber.

[0013] The coagulant for natural rubber latex includes a salt and / or an acid and a saccharide that is a combination of less than 16 monosaccharides.

[0014] As the salt and / or acid, a salt may be used, an acid may be used, or a salt and an acid may be used in combination. Note that one kind of salt or acid may be used, or two or more kinds may be used in combination.

[0015] The salt is not particularly limited and may be an organic salt or an inorganic salt. In this specification, an organic salt refers to a salt formed from an organic acid and an inorganic base, a salt formed from an inorganic acid and an organic base, or a salt formed from an organic acid and an organic base, and an inorganic salt refers to a salt formed from an inorganic acid and an inorganic base.

[0016] In this specification, the term "organic acid" refers to an organic compound that exhibits acidity. Examples of the organic acid include carboxylic acid and sulfonic acid. Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, oxalic acid, and citric acid.

[0017] The organic acid is preferably a carboxylic acid from the viewpoint of obtaining a better effect. Among them, formic acid and acetic acid are preferred as the carboxylic acid, and formic acid is more preferred.

[0018] In this specification, the term "inorganic acid" refers to a compound that exhibits acidity and does not fall under the category of organic acid. Examples of the inorganic acid include nitric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and carbonic acid. Among these, from the viewpoint of obtaining a better effect, hydrochloric acid, nitric acid, and sulfuric acid are preferred as the inorganic acid, nitric acid and sulfuric acid are more preferred, and sulfuric acid is particularly preferred.

[0019] In this specification, the organic base refers to an organic compound that exhibits basicity. Examples of the organic base include triethylamine, N-methylmorpholine, triethanolamine, and diisopropylethylamine. Among them, triethanolamine is preferred as the organic base from the viewpoint of obtaining a better effect.

[0020] In this specification, the term "inorganic base" refers to a compound that exhibits basicity and does not fall under the category of an organic base. Examples of the inorganic base include ammonia, potassium hydroxide, and sodium hydride. Among these, potassium hydroxide is preferred as the inorganic base from the viewpoint of obtaining a better effect.

[0021] Among the above salts, from the viewpoint of obtaining a better effect, salts containing at least one metal atom selected from the group consisting of sodium, potassium, calcium, and magnesium are preferred, and inorganic salts are more preferred, such as magnesium nitrate, calcium nitrate, magnesium sulfate, and calcium sulfate, with magnesium nitrate and calcium nitrate being even more preferred.

[0022] The acid is not particularly limited and may be an organic acid or an inorganic acid. As the organic acid and inorganic acid, the same acids as those described above can be used. Among them, from the viewpoint of obtaining a better effect, carboxylic acid and sulfuric acid are preferred, formic acid, acetic acid and sulfuric acid are more preferred, and formic acid and sulfuric acid are even more preferred.

[0023] The concentration of the salt in the coagulant for natural rubber latex (when two or more salts are contained, the total concentration of these salts) is preferably more than 5% by mass, more preferably more than 10% by mass. Also, it is preferably less than 50% by mass, more preferably less than 30% by mass, and even more preferably less than 20% by mass. Within the above range, better effects tend to be obtained.

[0024] The concentration of the acid in the coagulant for natural rubber latex (when two or more acids are contained, the total concentration of the acids) is preferably more than 2% by mass, more preferably more than 3% by mass, and even more preferably more than 5% by mass. Also, it is preferably less than 30% by mass, more preferably less than 20% by mass, and even more preferably less than 15% by mass. Within the above range, better effects tend to be obtained.

[0025] The saccharides are not particularly limited as long as they are a bond of less than 16 monosaccharides, and may be any of monosaccharides, disaccharides, trisaccharides, and polysaccharides. Note that the saccharides may be used alone or in combination of two or more.

[0026] From the viewpoint of suppressing the viscosity of the coagulant, the number of monosaccharide bonds in the saccharide is preferably less than 14, more preferably less than 12, and even more preferably less than 10. On the other hand, from the viewpoint of odor reduction effect, the number of monosaccharide bonds is preferably more than 1, more preferably more than 2, and even more preferably more than 3. Within the above range, the effect tends to be better obtained.

[0027] Examples of the monosaccharides include trioses (ketotriose, aldotriose, etc.); tetroses (aldotetroses such as ketotetrose, erythrose, threose, etc.); pentoses (ketopentoses such as ribulose, xylulose, etc.; aldopentoses such as ribose, arabinose, xylose, lyxose, etc.; deoxyribose, etc.); hexoses (ketohexoses such as psicose, fructose, sorbose, tagatose, etc.; aldohexoses such as allose, altrose, glucose, mannose, gulose, idose, galactose, talose, etc.; deoxysugars such as fucose, fuculose, rhamnose, etc.); heptoses (sedoheptulose, etc.); and derivatives thereof. Among these, fructose, galactose, and glucose are preferred, fructose and galactose are more preferred, and fructose is even more preferred.

[0028] When the saccharide is a saccharide formed by the bonding of two or more monosaccharides, it may be formed of one type of monosaccharide or two or more types of monosaccharides, and the bonding order is not particularly limited.

[0029] The concentration of the sugars in the coagulant for natural rubber latex (when two or more sugars are contained, the total concentration of these sugars) is preferably less than 5% by mass, more preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.5% by mass. Also, the concentration is preferably greater than 0.01% by mass, more preferably greater than 0.05% by mass, and even more preferably greater than 0.1% by mass. Within the above range, better effects tend to be obtained.

[0030] The method for preparing the natural rubber latex coagulant is not particularly limited, and the coagulant can be prepared by any known preparation method. For example, the coagulant can be prepared by adding the salt and / or acid and the sugars to an appropriate solvent such as water that can dissolve the salt and / or acid and the sugars, followed by stirring, mixing, etc.

[0031] The coagulant for natural rubber latex may further contain a polymer flocculant. Examples of the polymer flocculant include cationic polymer flocculants such as polymers of methyl chloride quaternary salts of dimethylaminoethyl (meth)acrylate, anionic polymer flocculants such as polymers of acrylates, nonionic polymer flocculants such as acrylamide polymers, and amphoteric polymer flocculants such as copolymers of methyl chloride quaternary salts of dimethylaminoethyl (meth)acrylate-acrylate. The amount of polymer flocculant added can be adjusted as appropriate.

[0032] The coagulant for natural rubber latex preferably further contains an antiseptic and disinfectant. Here, a preservative disinfectant is a chemical agent having a bactericidal effect to kill bacteria and microorganisms, or a preservative added to suppress the physiological activity of bacteria and microorganisms and inhibit their growth for the purpose of preserving a product. By further adding a preservative and disinfectant to the natural rubber latex coagulant, even if bacteria or microorganisms adhere to the raw materials during storage, the bacteria or microorganisms are killed, or their physiological activity is suppressed, inhibiting their growth and reducing their activity, thereby suppressing the decomposition of non-rubber components, and thereby further suppressing odors.

[0033] The antiseptic disinfectant is not particularly limited as long as it has a bactericidal or antiseptic effect against bacteria and microorganisms, but is preferably at least one selected from the group consisting of triazines, parabens (parahydroxybenzoic acid esters), boric acids, glycol ethers, and organic acids and metal salts thereof with a pKa of 4 or higher. Among these, from the viewpoint of odor suppression, boric acids, glycol ethers, organic acids and metal salts thereof with a pKa (acid dissociation constant) of 4 or higher are more preferred. The antiseptic and disinfectant may be used alone or in combination of two or more.

[0034] As the triazines, those having bactericidal or antiseptic effects against bacteria and microorganisms can be used, and examples thereof include 1,3,5-triazine, ametryn, atrazine, cyanazine, desmetryn, dimethyntryn, prometon, prometryn, propazine, simazine, simetryn, terbumeton, terbuthylazine, terbutryn, trietazine, and anilazine.

[0035] As parabens (parahydroxybenzoic acid esters), those having bactericidal and antiseptic effects against bacteria and microorganisms can be used, and examples thereof include methylparaben, ethylparaben, propylparaben, butylparaben, isopropylparaben, and isobutylparaben.

[0036] As the boric acid, those having a bactericidal action or an antiseptic action against bacteria and microorganisms can be used, and examples thereof include orthoboric acid, metaboric acid, and tetraboric acid.

[0037] As glycol ethers, those having a bactericidal action or an antiseptic action against bacteria and microorganisms can be used, and examples thereof include phenoxyethanol, phenoxypropanol, and phenoxyisopropanol.

[0038] As the organic acids and metal salts thereof, those having bactericidal or antiseptic properties against bacteria and microorganisms can be used. Examples of organic acids having a pKa of 4 or higher include benzoic acid, sorbic acid, dehydroacetic acid, gluconic acid, ascorbic acid, succinic acid, tartaric acid, citric acid, and oxalic acid. Examples of metal salts of organic acids having a pKa of 4 or higher include metal salts of these organic acids (alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as calcium salts), such as sodium benzoate, potassium sorbate, sodium dehydroacetate, sodium citrate, sodium acetate, sodium formate, and sodium oxalate.

[0039] The concentration of the preservative and disinfectant in the coagulant for natural rubber latex (when two or more preservative and disinfectant types are contained, the total concentration of these) is preferably less than 5% by mass, more preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.5% by mass. Also, it is preferably more than 0.01% by mass, more preferably more than 0.05% by mass, and even more preferably more than 0.1% by mass. Within the above range, better effects tend to be obtained.

[0040] The coagulant for natural rubber latex is added in a coagulation step when natural rubber latex is coagulated to produce natural rubber. The natural rubber produced in this manner can be used when producing tire components, and therefore the coagulant can also be referred to as a coagulant for tire components.

[0041] (Natural rubber manufacturing method) The above-mentioned method for producing natural rubber includes a step of coagulating natural rubber latex using a coagulant, and the coagulant contains a salt and / or an acid and a sugar. Therefore, the method is excellent at suppressing the odor of the resulting natural rubber.

[0042] The reason why the above-mentioned effects are obtained is not entirely clear, but it is presumed that the following mechanism is involved. When coagulating natural rubber latex, using a coagulant containing sugars is thought to inhibit the decomposition and decay of non-rubber components in natural rubber because the sugars in the coagulant are broken down before bacteria and microorganisms can decompose the non-rubber components. This is thought to inhibit the generation of odor-causing substances and reduce the odor of the resulting natural rubber. Furthermore, the inclusion of sugars in the coagulant may reduce the activity of bacteria and microorganisms, thereby inhibiting the decomposition and decay of non-rubber components in natural rubber.

[0043] The method for producing natural rubber includes a step of coagulating natural rubber latex using a coagulant containing a salt and / or an acid and a sugar. In addition, the above-mentioned method for producing natural rubber may include other steps such as a washing step described below, so long as it includes the above-mentioned coagulation step, and each step may be carried out once or multiple times.

[0044] In the coagulation step, a coagulant containing a salt and / or an acid and a sugar is added to the natural rubber latex to coagulate the natural rubber latex. The method for solidifying the mixture is not particularly limited, and known methods such as stirring and mixing can be used.

[0045] Usable natural rubber latex includes raw latex (field latex) obtained by tapping rubber trees, and concentrated latex concentrated by centrifugation or creaming (refined latex, high ammonia latex to which ammonia has been added in the usual way, LATZ latex stabilized with zinc oxide, TMTD, and ammonia, etc.).

[0046] The coagulant includes a salt and / or an acid, and a sugar. The salts and / or acids may be the same as those mentioned above and used in the same amounts.

[0047] The saccharides are not particularly limited as long as they are monosaccharides or monosaccharides linked together, and may be any of monosaccharides, disaccharides, trisaccharides, and polysaccharides, and the number of monosaccharide bonds is not particularly limited. However, from the viewpoint of odor reduction effect, the number of monosaccharide bonds in the saccharides is preferably more than 1, more preferably more than 2, and even more preferably more than 3. Furthermore, from the viewpoint of suppressing the viscosity of the coagulant, the number is preferably less than 20, more preferably less than 16, even more preferably less than 14, even more preferably less than 12, and even more preferably less than 10. Note that the saccharides may be used alone or in combination of two or more.

[0048] As the monosaccharide, the same monosaccharides as those mentioned above can be used.

[0049] When the saccharide is a saccharide formed by the bonding of two or more monosaccharides, it may be formed of one type of monosaccharide or two or more types of monosaccharides, and the bonding order is not particularly limited.

[0050] The concentration of the sugars in the coagulant for natural rubber latex (when two or more sugars are contained, the total concentration of these sugars) is preferably less than 5% by mass, more preferably less than 3% by mass, even more preferably less than 1% by mass, and even more preferably less than 0.5% by mass. Also, the concentration is preferably greater than 0.01% by mass, more preferably greater than 0.05% by mass, and even more preferably greater than 0.1% by mass. Within the above range, better effects tend to be obtained.

[0051] The coagulant can be prepared by the same method as described above. The coagulant may further contain a polymer flocculant and an antiseptic and disinfectant. The polymer flocculant and the antiseptic and disinfectant may be the same as those mentioned above and used in the same amounts.

[0052] A coagulated material (raw material) is obtained by the coagulation step, and natural rubber can be produced by washing and drying the coagulated material as needed.

[0053] The washing step is not particularly limited, and known washing methods can be applied. For example, there are methods such as diluting the raw materials with water and then centrifuging them, leaving the raw materials to float in a water bath and discharging only the aqueous phase, washing the raw materials while stirring them in a water bath and discharging only the aqueous phase, etc. The raw materials to be subjected to the washing step may be used as a coagulated product as is, or may be cut and crushed to an appropriate size and used as crushed products.

[0054] The drying step is not particularly limited, and known drying methods can be used. The drying temperature is preferably 140°C or lower. This can suppress the generation of lower fatty acids due to the decomposition of non-rubber components, thereby reducing odor. The drying temperature is more preferably 135°C or lower, even more preferably 130°C or lower, even more preferably 125°C or lower, and particularly preferably 120°C or lower. There is no particular lower limit, but from the viewpoint of productivity, it is preferably 75°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher. The drying time can be set appropriately depending on the drying temperature and drying conditions.

[0055] Before the washing step, the coagulum may be subjected to a dehydration step to reduce its moisture content. This step removes odor-causing substances along with the moisture, thereby reducing the odor.

[0056] In the dehydration step, the method for reducing the moisture content of the coagulum is not particularly limited as long as it can reduce the moisture content of the coagulum, but a method of squeezing the coagulum (such as a method of squeezing the coagulum) is preferred from the viewpoint of also removing the moisture contained inside the coagulum. Examples of methods for squeezing the coagulum include a method of passing the coagulum through rolls such as milling rolls to squeeze the coagulum. A creeper may be used as a device for passing the coagulum through rolls to squeeze it.

[0057] When the coagulum is passed through rolls and compressed, the compressed coagulum has a relatively flat shape. From the viewpoint of productivity, the thickness of the compressed coagulum is preferably 3 mm or more, more preferably 5 mm or more, and even more preferably 8 mm or more. On the other hand, from the viewpoint of the effect of the dehydration step, the upper limit is preferably 3 cm or less, more preferably 2 cm or less.

[0058] The moisture content of the coagulum after the dehydration step is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, and even more preferably 15% or less, from the viewpoint of suppressing the progression of spoilage during storage. There is no particular lower limit, and the lower the better, but from the viewpoint of the efficiency of moisture content adjustment, it is preferably 3% or more, more preferably 5% or more, and even more preferably 10% or more. The moisture content can be measured from the difference in weight of the coagulum after the dehydration step before and after drying.

[0059] For example, when using a creeper to reduce the moisture content of the coagulated material, it is preferable to pass it through the creeper four times or less, more preferably three times or less, and a single pass can be sufficient to achieve a sufficient odor improvement effect. If it is passed through the creeper five times or more, the moisture removal efficiency decreases, and the odor improvement effect relative to the labor hours becomes small. Generally, if the coagulated material is passed through the creeper once, the moisture content of the coagulated material after passing through the creeper will be 30% or less, and if it is passed through the creeper three times, the moisture content of the coagulated material after passing through the creeper will be 20% or less. On the other hand, if it is passed through the creeper five times, the moisture content of the coagulated material after passing through the creeper will be reduced to 10% or less.

[0060] Before the washing step, in addition to the dehydration step, the coagulated material may be subjected to a base treatment step in which the coagulated material is contacted with a basic solution. That is, after the dehydration step, it is preferable to carry out a base treatment step in which the coagulated material obtained by the dehydration step is contacted with a basic solution. Even if the coagulated material (raw material) is stored after the dehydration step, the generation of lower fatty acids, which are odor-causing substances, can be suppressed, but the generation cannot be completely suppressed. On the other hand, if the raw material (coagulated material) after storage is contacted with a basic solution, the small amount of lower fatty acids generated is neutralized and removed, thereby reducing the odor. In the base treatment step, when the raw material (coagulated material) is contacted with the basic solution, the coagulated material may be used as is, or may be cut and crushed to an appropriate size and then crushed.

[0061] In the base treatment step, the coagulate can be brought into contact with a basic solution by, for example, applying the basic solution to the coagulate, spraying it with a spray or shower, or immersing the coagulate in the basic solution. From the viewpoint of deodorizing effect and efficiency, the method of immersing the coagulate in the basic solution is preferred. When the method of immersing the coagulate in the basic solution is adopted, the coagulate can be left standing in the basic solution. However, the deodorizing effect can be further promoted by further stirring and / or irradiating with microwaves during immersion.

[0062] The contact time (treatment time) between the coagulum and the basic solution is not particularly limited, but from the viewpoint of odor reduction effect, it is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 30 minutes or more, and particularly preferably 3 hours or more. The upper limit is not particularly specified because it depends on the pH and concentration of the basic solution, but from the viewpoint of productivity, it is preferably 48 hours or less, more preferably 24 hours or less, even more preferably 16 hours or less, and particularly preferably 6 hours or less.

[0063] The temperature at which the coagulum is contacted with the basic solution (treatment temperature) is not particularly limited, but is preferably 10 to 50°C, more preferably 15 to 35°C, and particularly preferably room temperature (20 to 30°C).

[0064] The basic solution is not particularly limited as long as it is a basic solution, but a solution containing at least one basic substance (basic inorganic substance) selected from the group consisting of metal carbonates, metal bicarbonates, metal phosphates, and ammonia is preferably used. This effectively neutralizes and removes odorous components, reducing odor and preventing deterioration of physical properties such as heat aging resistance. Examples of the basic solution include an aqueous solution containing the basic substance and an alcoholic solution containing the basic substance, with the aqueous solution containing the basic substance being preferred. The basic solution can be prepared by diluting and dissolving the basic substance in a solvent such as water or alcohol.

[0065] Examples of metal carbonates include alkali metal carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate; and alkaline earth metal carbonates such as magnesium carbonate, calcium carbonate, and barium carbonate. Examples of metal bicarbonates include alkali metal bicarbonates such as lithium bicarbonate, sodium bicarbonate, and potassium bicarbonate. Examples of metal phosphates include alkali metal phosphates such as sodium phosphate and sodium biphosphate. These may be used alone or in combination of two or more. Among these, metal carbonates, metal bicarbonates, and ammonia are preferred, with alkali metal carbonates, alkali metal bicarbonates, and ammonia being more preferred, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate being even more preferred, and sodium carbonate and sodium bicarbonate being particularly preferred.

[0066] The concentration of the basic substance in the basic solution is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 1.0% by mass or more, based on 100% by mass of the basic solution, from the viewpoint of neutralizing and removing odorous components. The upper limit of the concentration is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5.0% by mass or less, and particularly preferably 3.0% by mass or less, from the viewpoint of economic efficiency and maintaining the physical properties of the rubber after treatment (heat aging resistance, etc.).

[0067] From the viewpoint of neutralizing and removing odorous components, the basic solution preferably contains a surfactant in addition to the basic substance. The surfactant can be at least one selected from the group consisting of anionic surfactants, nonionic surfactants, and amphoteric surfactants. Examples of anionic surfactants include anionic surfactants such as carboxylic acid surfactants, sulfonic acid surfactants, sulfate ester surfactants, and phosphate ester surfactants. Examples of nonionic surfactants include nonionic surfactants such as polyoxyalkylene ester surfactants, polyhydric alcohol fatty acid ester surfactants, glycolipid ester surfactants, and alkyl polyglycoside surfactants. Examples of amphoteric surfactants include amino acid surfactants, betaine surfactants, and amine oxide surfactants. Among these, anionic surfactants are preferred. These surfactants may be used alone or in combination of two or more.

[0068] Specific examples of suitable anionic surfactants include alkyl sulfates, polyoxyethylene alkyl ether sulfates, alkylbenzene sulfonates, alkylnaphthalene sulfonates, and fatty acid salts. Examples of these salts include alkali metal salts (such as sodium salts), ammonium salts, and amine salts (alkanolamine salts such as monoethanolamine, diethanolamine, and triethanolamine salts). Among these, polyoxyethylene alkyl ether sulfates are particularly preferred.

[0069] As the alkyl sulfate, a higher alkyl sulfate (a higher alcohol sulfate) is preferred, and an alkali metal salt such as a sodium salt is preferred. The alkyl group in the alkyl sulfate preferably has 10 to 20 carbon atoms, more preferably 10 to 16 carbon atoms. Specific examples of the alkyl sulfate include sodium lauryl sulfate (sodium dodecyl sulfate), potassium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, sodium myristyl sulfate, potassium myristyl sulfate, sodium cetyl sulfate, and potassium cetyl sulfate. Among these, sodium lauryl sulfate is preferred because of its excellent effect in reducing protein content, etc.

[0070] The polyoxyethylene alkyl ether sulfate salt is preferably a polyoxyethylene alkyl ether sulfate salt having an alkyl group having 10 to 18 carbon atoms, more preferably an amine salt or a sodium salt, and even more preferably a sodium salt. The number of carbon atoms is preferably 10 to 14, more preferably 10 to 12. The average degree of polymerization of the oxyethylene group is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 2. Specific examples include sodium polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene myristyl ether sulfate, and sodium polyoxyethylene oleyl ether sulfate, and triethanolamine polyoxyethylene alkyl ether sulfate. Of these, sodium polyoxyethylene lauryl ether sulfate is preferred because of its excellent effect in reducing protein content, etc.

[0071] Examples of alkylbenzenesulfonates include alkylbenzenesulfonates having an alkyl group having 3 to 20 carbon atoms, and alkali metal salts are preferred. Specific examples include sodium salts, potassium salts, ammonium salts, triethanolamine salts, and calcium salts of dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, decylbenzenesulfonic acid, and cetylbenzenesulfonic acid. Of these, sodium dodecylbenzenesulfonate is preferred because of its excellent effect in reducing protein content, etc.

[0072] Examples of alkylnaphthalenesulfonates include alkali metal alkylnaphthalenesulfonates such as sodium mono-, di-, or triisopropylnaphthalenesulfonate, potassium mono-, di-, or triisopropylnaphthalenesulfonate, sodium octylnaphthalenesulfonate, potassium octylnaphthalenesulfonate, sodium dodecylnaphthalenesulfonate, and potassium dodecylnaphthalenesulfonate. Of these, sodium alkylnaphthalenesulfonate is preferred because of its excellent effect in reducing the amount of protein, etc.

[0073] The fatty acid salt is preferably a salt of a higher fatty acid having 10 to 20 carbon atoms, such as sodium salts or potassium salts. Specific examples include sodium salts or potassium salts of oleic acid, stearic acid, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, docosanoic acid, linoleic acid, 2-ethylhexanoic acid, 2-octylundecanoic acid, etc.; and sodium salts or potassium salts of mixed fatty acids derived from coconut oil, palm oil, castor oil, palm kernel oil, beef tallow, etc. (such as potassium castor oil soap). Of these, potassium oleate soap is preferred because of its excellent effect in reducing the amount of protein, etc.

[0074] The concentration of the surfactant in the basic solution is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and even more preferably 0.05% by mass or more, based on 100% by mass of the basic solution, from the viewpoint of neutralizing and removing odorous components. From the viewpoint of economic efficiency, the upper limit of the concentration is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less.

[0075] The base-treated coagulum obtained by the base treatment step may be subjected to a pH adjustment step in which the pH is adjusted to 2 to 7. That is, after the treatment with the basic solution, the washing step may be carried out as necessary, and the pH of the resulting treated coagulum may be further adjusted to 2 to 7. The adjusted pH range is preferably 3 to 6, more preferably 4 to 6. This pH adjustment maintains the deodorizing effect for a long period of time and prevents a decrease in heat aging resistance.

[0076] The pH was measured using a pH meter after cutting the base-treated coagulum (5 g) into pieces no larger than 2 mm square, immersing them in distilled water, and extracting them for 15 minutes at 90°C while irradiating them with microwaves. Since the water-soluble components cannot be completely extracted from inside the rubber even if the extraction is performed for 1 hour using an ultrasonic cleaner or the like, the internal pH cannot be accurately determined. However, by using the microwave extraction method, the actual pH of the coagulum after treatment can be determined.

[0077] In the pH adjustment step, the pH of the base-treated coagulum can be adjusted to 2 to 7 by, for example, exposing the base-treated coagulum to an acidic atmosphere, applying an acidic compound and / or acidic solution to the base-treated coagulum, spraying the base-treated coagulum with an acidic compound and / or acidic solution by spraying or showering, or immersing the base-treated coagulum in an acidic solution. Among these, adjusting the pH to 2 to 7 by contacting the base-treated coagulum with an acidic solution is preferred.

[0078] The acidic solution is preferably adjusted to a pH of 6 or less. This provides a long-lasting deodorizing effect and excellent heat aging resistance. The upper limit of the pH of the acidic solution is more preferably 5 or less, and even more preferably 4.5 or less. The lower limit is not particularly limited, and although it depends on the contact time, if the acidity is too strong, the rubber may deteriorate or wastewater treatment may become more time-consuming. Therefore, the lower limit is preferably 1 or more, more preferably 2 or more.

[0079] The treatment time (contact time) and treatment temperature (contact temperature) of the base-treated coagulum with the acidic solution may be appropriately set, for example, within the range of 3 seconds to 30 minutes for the treatment time and 10 to 50°C for the treatment temperature.

[0080] The acidic solution is preferably an acidic compound solution. Examples of the acidic compound solution include an aqueous solution of an acidic compound and an alcohol solution of an acidic compound, with an aqueous solution of an acidic compound being preferred. The acidic solution can be prepared by diluting and dissolving an acidic compound with a solvent such as water or alcohol.

[0081] The acidic compound is not particularly limited, and examples thereof include inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, metaphosphoric acid, boric acid, boronic acid, sulfanilic acid, and sulfamic acid; formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, salicylic acid, methanesulfonic acid, itaconic acid, benzenesulfonic acid, toluenesulfonic acid, and sodium hydroxide. Examples of suitable organic acids include phthalenedisulfonic acid, trifluoromethanesulfonic acid, styrenesulfonic acid, trifluoroacetic acid, barbituric acid, acrylic acid, methacrylic acid, cinnamic acid, 4-hydroxybenzoic acid, aminobenzoic acid, naphthalenedisulfonic acid, hydroxybenzenesulfonic acid, toluenesulfinic acid, benzenesulfinic acid, α-resorcylic acid, β-resorcylic acid, γ-resorcylic acid, gallic acid, phloroglycine, sulfosalicylic acid, ascorbic acid, erythorbic acid, and bisphenolic acid. These acidic compounds may be used alone or in combination of two or more. Among these, sulfuric acid, formic acid, and acetic acid are preferred.

[0082] The concentration of the acidic compound in the acidic solution may be set as appropriate, but from the viewpoint of heat aging resistance, it is preferably 0.1 to 20 mass %, more preferably 0.3 to 10 mass %, and even more preferably 0.5 to 5.0 mass %, relative to 100 mass % of the acidic solution.

[0083] After the pH adjustment step of adjusting the pH of the base-treated coagulum to 2 to 7, a step of washing off the acidic solution remaining on the surface of the obtained product may be carried out. The washing step can be carried out by the method described above. [Example]

[0084] Below, examples (embodiments) that are considered preferable for implementation will be shown, but the scope of the present invention is not limited to the examples.

[0085] The various chemicals used in the production of natural rubber are summarized below. If necessary, the chemicals may be purified according to standard methods. Field latex: Field latex obtained from Muhibaratex Formic acid: Formic acid manufactured by Kanto Chemical Co., Ltd. Calcium nitrate: Calcium nitrate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Phenoxyethanol: Phenoxyethanol manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Fructooligosaccharide: Fructooligosaccharide (number of fructose bonds: 3-5) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0086] Examples and Comparative Examples After adjusting the solids concentration (DRC) of the field latex to 30% (w / v), approximately 15 g of the coagulant shown in Table 1 is added to 100 g of the solids of the latex, and the mixture is mixed to coagulate (flocculate) the latex to obtain a coagulated product (raw material). The coagulated product is stored for approximately one month. After storing the coagulum for about one month as described above, it is crushed, washed five times with water, and dried at 120°C to obtain each natural rubber.

[0087] Each natural rubber was evaluated as follows, and the results are shown in Table 1. [Analysis method for natural rubber] (Odor component index of natural rubber <1> ) The main substances that cause the odor of natural rubber include lower fatty acids such as acetic acid, valeric acid, isovaleric acid, isovaleric aldehyde, and butyric acid, and their aldehydes. Therefore, the peak area ratios of the above components detected using a head-space GCMS (Shimadzu Corporation, product name "GCMS-QP2010 Ultra," using a head-space sampler "HS-20" manufactured by Shimadzu Corporation) were corrected by the olfactory threshold of each component, and the sum of all the components was calculated as the odor component index. <1> Let's say.

[0088] (Odor component ratio of natural rubber <1> (%) Odor component index obtained above <1> The odor component rate is calculated using the following formula: <1> The higher the odor component ratio, the less odor there is. Odor component ratio of natural rubber <1> (%) = (Odor component index in natural rubber of Comparative Example 1) <1> / Odor component index for each natural rubber example <1> ) x 100

[0089] (Odor component index of natural rubber <2> ) In addition to the compounds mentioned above, skatole is also known to be a cause of the odor of natural rubber. Therefore, the peak area of ​​skatole detected using a head-space GCMS (Shimadzu Corporation, product name "GCMS-QP2010 Ultra" and Shimadzu Corporation "HS-20" used as a headspace sampler) was corrected by the olfactory threshold of skatole to give the odor component index. <2> Let's say.

[0090] (Odor component ratio of natural rubber <2> (%) Odor component index obtained above <2> The odor component rate is calculated using the following formula: <2> The higher the odor component ratio, the less odor there is. Odor component ratio of natural rubber <2> (%) = (Odor component index in natural rubber of Comparative Example 1) <2> / Odor component index for each natural rubber example <2> ) x 100

[0091] [Table 1]

[0092] The present invention (1) is a coagulant for natural rubber latex, which comprises a salt and / or an acid and a saccharide, and the saccharide is a bond of less than 16 monosaccharides.

[0093] The present invention (2) relates to the coagulant for natural rubber latex according to the present invention (1), wherein the salt is a salt containing at least one metal atom selected from the group consisting of sodium, potassium, calcium, and magnesium.

[0094] The present invention (3) is the coagulant for natural rubber latex according to the present invention (1) or (2), wherein the salt is an inorganic salt.

[0095] The present invention (4) is a coagulant for natural rubber latex in any combination with any of the present inventions (1) to (3), in which the acid is a carboxylic acid.

[0096] The present invention (5) is a coagulant for natural rubber latex, which is any combination with any of the present inventions (1) to (4), in which the concentration of the sugars in 100% by mass of the coagulant is less than 5% by mass.

[0097] The present invention (6) is a coagulant for natural rubber latex in any combination with any of the present inventions (1) to (5), further containing an antiseptic and bactericide.

[0098] The present invention (7) is a method for producing natural rubber, which includes a step of coagulating natural rubber latex using a coagulant, and the coagulant contains a salt and / or an acid and a sugar.

[0099] The present invention (8) is a method for producing natural rubber according to the present invention (7), wherein the saccharide is a bond of less than 20 monosaccharides.

[0100] The present invention (9) is the method for producing natural rubber according to the present invention (7) or (8), wherein the salt is a salt containing at least one metal atom selected from the group consisting of sodium, potassium, calcium, and magnesium.

[0101] The present invention (10) is a method for producing natural rubber in any combination with any of the present inventions (7) to (9), in which the salt is an inorganic salt.

[0102] The present invention (11) is a method for producing natural rubber in any combination with any of the present inventions (7) to (10), in which the acid is a carboxylic acid.

[0103] The present invention (12) is a method for producing natural rubber in any combination with any of the present inventions (7) to (11), in which the concentration of the sugars in the coagulant is less than 5% by mass.

[0104] The present invention (13) is a method for producing natural rubber in any combination with any of the present inventions (7) to (12), wherein the coagulant further contains an antiseptic and bactericide.

Claims

1. containing a salt and / or an acid and a sugar, A coagulant for natural rubber latex, wherein the saccharide is a bond of less than 16 monosaccharides.

2. 2. The coagulant for natural rubber latex according to claim 1, wherein the salt is a salt containing at least one metal atom selected from the group consisting of sodium, potassium, calcium, and magnesium.

3. 3. The coagulant for natural rubber latex according to claim 1, wherein the salt is an inorganic salt.

4. 3. The coagulant for natural rubber latex according to claim 1, wherein the acid is a carboxylic acid.

5. 3. The coagulant for natural rubber latex according to claim 1, wherein a concentration of the sugars in 100% by mass of the coagulant is less than 5% by mass.

6. 3. The coagulant for natural rubber latex according to claim 1, further comprising an antiseptic and disinfectant.

7. coagulating natural rubber latex with a coagulant; The method for producing natural rubber, wherein the coagulant contains a salt and / or an acid and a sugar.

8. 8. The method for producing natural rubber according to claim 7, wherein the saccharide is a bond of less than 20 monosaccharides.

9. 9. The method for producing natural rubber according to claim 7, wherein the salt is a salt containing at least one metal atom selected from the group consisting of sodium, potassium, calcium, and magnesium.

10. 9. The method for producing natural rubber according to claim 7 or 8, wherein the salt is an inorganic salt.

11. 9. The method for producing natural rubber according to claim 7 or 8, wherein the acid is a carboxylic acid.

12. 9. The method for producing natural rubber according to claim 7 or 8, wherein the concentration of the sugar in the coagulant is less than 5% by mass.

13. 9. The method for producing natural rubber according to claim 7, wherein the coagulant further contains an antiseptic and disinfectant.

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