Method for producing aggregate of natural rubber, and apparatus for producing aggregate of natural rubber

Abstract

This method for producing an aggregate of natural rubber comprises: a step of dropping a first mixture comprising a natural rubber latex and an acid toward a mixture flow channel in which a serum component of natural rubber is flowing, so as to obtain a second mixture comprising the first mixture and the serum component; and an aggregation step of pouring the second mixture, that has flowed along the mixture flow channel, into a receiving container so as to obtain an aggregate in which the natural rubber latex and the acid are aggregated.

Description

Method for producing natural rubber agglomerates and apparatus for producing natural rubber agglomerates

[0001] The present disclosure relates to a method for producing a natural rubber agglomerate and an apparatus for producing a natural rubber agglomerate.

[0002] Natural rubber latex is generally produced in tropical countries such as Thailand, Malaysia, and Indonesia. Due to its excellent physical properties, natural rubber latex is widely used in large quantities in the rubber and tire industries. Natural rubber latex is produced in the following order: tapping, coagulation, washing (washing with water), dehydration, drying, and packing. It is classified by its type and grade, and is broadly classified into ribbed smoke sheet (RSS) and technically graded rubber (TSR) based on the grading criteria of the International Quality Packaging Standard for Various Grades of Natural Rubber Latex (commonly known as the Green Book).

[0003] In the rubber industry, when natural rubber obtained by the above-mentioned methods is used to produce rubber products for various uses, it is usually subjected to a mastication process before use, in order to improve mixing efficiency by reducing the molecular weight and gel content.

[0004] For example, Japanese Patent Application Laid-Open No. 2003-313366 discloses a natural rubber mixture obtained by treating natural rubber latex with at least one selected from the group consisting of surfactants and enzymes, and then adding a hydrazide compound and / or a serum component of natural rubber.

[0005] Conventionally, attempts have been made to obtain coagulated natural rubber by adding an acid to natural rubber latex. However, when an acid is added to natural rubber latex, coagulation proceeds rapidly, resulting in the formation of non-uniform coagulates, and large amounts of unreacted natural rubber latex and acid remain. Therefore, there is a need to prevent the remaining unreacted natural rubber latex and acid when adding an acid to natural rubber latex to obtain a natural rubber coagulate.

[0006] Therefore, an object of the present disclosure is to provide a method and an apparatus for producing natural rubber agglomerates that can suppress the remaining unreacted natural rubber latex and acid.

[0007] Means for solving the above problems include the following aspects: A method for producing a natural rubber agglomerate, comprising: a step of dropping a first mixture of natural rubber latex and an acid toward a mixture flow path through which a serum component of natural rubber flows, to obtain a second mixture of the first mixture and the serum component; and an agglomeration step of pouring the second mixture that has flowed through the mixture flow path into a receiving container, to obtain an agglomerate of the natural rubber latex and the acid.

[0008] According to the present disclosure, it is possible to provide a method for producing a natural rubber agglomerate and an apparatus for producing a natural rubber agglomerate that can suppress the remaining unreacted natural rubber latex and acid.

[0009] FIG. 1 is a schematic diagram illustrating an example of an apparatus for producing a natural rubber aggregate according to an embodiment of the present disclosure.

[0010] An embodiment that is an example of the present disclosure will be described. These descriptions are intended to exemplify the embodiment and do not limit the scope of the invention. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the embodiments of the present disclosure.

[0011] In this disclosure, a numerical range expressed using "to" means a range that includes these numerical values ​​as the lower and upper limits. In numerical ranges described in stages in this disclosure, the upper limit of a certain numerical range may be replaced with the upper limit of another numerical range described in stages. Furthermore, the lower limit of a certain numerical range may be replaced with the lower limit of another numerical range described in stages. In this disclosure, even when an element is expressed in the singular, the presence of a plurality is not excluded unless otherwise specified, unless technical contradiction arises. Furthermore, with regard to content, "%" means "mass %" unless otherwise specified.

[0012] Each component may contain multiple corresponding substances. When referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, the total amount of those multiple substances present in the composition is meant unless otherwise specified. The term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0013] <Method and Apparatus for Producing Natural Rubber Agglomerate> A method for producing a natural rubber agglomerate according to an embodiment of the present disclosure includes a step of dropping a first mixture of natural rubber latex and an acid into a mixture flow path through which a serum component of natural rubber flows, to obtain a second mixture of the first mixture and the serum component, and an agglomeration step of pouring the second mixture that has flowed through the mixture flow path into a receiving container, to obtain an agglomerate of natural rubber latex and an acid.

[0014] A natural rubber agglomerate manufacturing apparatus according to an embodiment of the present disclosure includes a mixture flow path through which a serum component of natural rubber flows, a drop section through which a first mixture of natural rubber latex and an acid falls vertically downward toward the mixture flow path, and a receiving container into which a second mixture obtained by mixing the first mixture with the serum component in the mixture flow path flows, and is capable of producing an agglomerate formed by agglomerating the natural rubber latex and the acid.

[0015] Hereinafter, a method for producing a natural rubber agglomerate and an apparatus for producing a natural rubber agglomerate according to an embodiment of the present disclosure will be specifically described with reference to the drawings.

[0016] FIG. 1 is a schematic diagram illustrating an example of an apparatus for producing a natural rubber aggregate according to an embodiment of the present disclosure.

[0017] 1 includes a first gutter 41 forming a first flow path through which natural rubber latex 2 flows, a second gutter 42 forming a second flow path through which acid 4 flows, a contact section 40 where the natural rubber latex 2 flowing through the first flow path comes into contact with the acid 4 flowing through the second flow path, a drop section 50 through which the first mixture falls from the contact section 40, a slider 43 disposed vertically below the contact section 40 and forming a mixture flow path through which the natural rubber serum component 6 flows and through which the first mixture falls through the drop section 50, and a receiving container 74 into which a second mixture obtained by mixing the first mixture and the serum component 6 on the slider 43 flows. Formic acid, for example, is used as the acid 4.

[0018] The manufacturing apparatus 100 will be described in more detail below.

[0019] A first tank 21 serving as a first storage tank for storing natural rubber latex 2 and having a plurality of first holes 210 in the floor surface is provided upstream of the first gutter 41 .

[0020] A first storage container 11 that stores natural rubber latex 2 is provided upstream of the first tank 21. A pH meter 61 that monitors the pH of the natural rubber latex 2 is disposed in the first storage container 11. A pH adjustment nozzle 14 for adding an alkaline pH adjusting solution (e.g., ammonia) is disposed in the upper part of the first storage container 11. The pH adjustment nozzle 14 has an adjustment valve 14a. An agitator 18 for stirring the natural rubber latex 2 is disposed in the first storage container 11. The pH adjusting solution is added from the pH adjustment nozzle 14 to the natural rubber latex 2 in the first storage container 11 in accordance with the pH monitored by the pH meter 61, and the natural rubber latex 2 is stirred by the agitator 18, thereby controlling the pH of the natural rubber latex 2 within a certain range.

[0021] The natural rubber latex 2 is poured into the first tank 21 from the first storage container 11 through a first nozzle 31. The first nozzle 31 has an adjustment valve 31 a, and the amount of natural rubber latex 2 poured into the first tank 21 can be controlled by the adjustment valve 31 a.

[0022] The first tank 21 has a plurality of first holes 210 on its floor surface. The natural rubber latex 2 stored in the first tank 21 falls as droplets 2a from the first holes 210 toward the first gutter 41, which forms the first flow path. The state of the natural rubber latex 2 falling from the first tank 21 toward the first flow path formed by the first gutter 41 is not limited to droplets, and may be, for example, thin streaks (i.e., a state in which a small amount of liquid falls continuously). The amount of natural rubber latex 2 falling from the first holes 210 is controlled by the diameter of the first holes 210 and the distance between the first holes 210. By allowing the natural rubber latex 2 to fall from the first tank 21 through the first holes 210, the amount of natural rubber latex 2 supplied to the first gutter 41, which forms the first flow path, can be adjusted.

[0023] The first gutter 41 has an inclined surface 41a that slopes toward the contact portion 40. The inclined surface 41a forms a first flow path. Droplets 2a of the natural rubber latex 2 that fall from the first tank 21 through the first hole 210 reach the inclined surface 41a of the first gutter 41. Then, the natural rubber latex 2 that has reached the first gutter 41 flows on the inclined surface 41a in the inclined direction (i.e., the direction of arrow A) and reaches the contact portion 40.

[0024] Here, the method of supplying the natural rubber latex 2 to the inclined surface 41 a of the first gutter 41 is not limited to the method of dropping droplets 2 a of the natural rubber latex 2 from the first tank 21 through the first hole 210 as shown in FIG. 1 . For example, the natural rubber latex 2 may be directly supplied from the first storage container 11 to the inclined surface 41 a of the first gutter 41 through a nozzle. When supplying the natural rubber latex 2 from the first storage container 11 to the inclined surface 41 a through a nozzle, it is preferable to arrange a plurality of nozzles in a first orthogonal direction (i.e., the direction of arrow E) that is perpendicular to the inclination direction of the inclined surface 41 a (i.e., the direction of arrow A). By arranging a plurality of nozzles in the direction of arrow E, the amount of natural rubber latex 2 supplied to the first gutter 41 forming the first flow path can be adjusted.

[0025] A second tank 22 serving as a second storage tank for storing the acid 4 and having a plurality of second holes 220 in the floor surface is provided upstream of the second gutter 42 .

[0026] A second storage vessel 12 that stores acid 4 is provided upstream of the second tank 22. The acid 4 is poured into the second tank 22 from the second storage vessel 12 through a second nozzle 32. The second nozzle 32 has an adjustment valve 32a, and the amount of acid 4 injected into the second tank 22 can be controlled by the adjustment valve 32a.

[0027] The second tank 22 has a plurality of second holes 220 on its floor. The acid 4 stored in the second tank 22 falls as droplets 4a from the second holes 220 toward the second gutter 42, which forms the second flow path. The state of the acid 4 falling from the second tank 22 toward the second flow path formed by the second gutter 42 is not limited to droplets, but may be, for example, thin streaks (i.e., a state in which a small amount of liquid falls continuously). The amount of acid 4 falling from the second holes 220 is controlled by the diameter of the second holes 220 and the spacing between the second holes 220. By allowing the acid 4 to fall from the second tank 22 through the second holes 220, the amount of acid 4 supplied to the second gutter 42, which forms the second flow path, can be adjusted.

[0028] The second gutter 42 has an inclined surface 42a that slopes toward the contact portion 40. The inclined surface 42a forms a second flow path. Droplets 4a of acid 4 that fall from the second tank 22 through the second hole 220 reach the inclined surface 42a of the second gutter 42. The acid 4 that reaches the second gutter 42 then flows on the inclined surface 42a in the inclined direction (i.e., the direction of arrow B) and reaches the contact portion 40.

[0029] Here, the method of supplying the acid 4 to the inclined surface 42a of the second gutter 42 is not limited to the method of dropping droplets 4a of the acid 4 from the second tank 22 through the second hole 220 as shown in FIG. 1 . For example, the acid 4 may be supplied directly to the inclined surface 42a of the second gutter 42 from the second storage container 12 through a nozzle. When supplying the acid 4 to the inclined surface 42a from the second storage container 12 using a nozzle, it is preferable to arrange multiple nozzles in a second orthogonal direction (i.e., the direction of arrow E) that is perpendicular to the inclination direction of the inclined surface 42a (i.e., the direction of arrow B). By arranging multiple nozzles in the direction of arrow E, the amount of acid 4 supplied to the second gutter 42, which forms the second flow path, can be adjusted.

[0030] The natural rubber latex 2 flowing through the first flow path on the inclined surface 41 a of the first gutter 41 and the acid 4 flowing through the second flow path on the inclined surface 42 a of the second gutter 42 come into contact with each other at the contact portion 40 to form a first mixture (first mixing process).

[0031] The first mixture obtained by contacting the natural rubber latex 2 with the acid 4 in the contact section 40 falls down the falling section 50 in a vertical downward direction from the contact section 40 (i.e., in the direction of arrow C).

[0032] The slider 43 has an inclined surface 43a that slopes toward the receiving container 74. The inclined surface 43a forms a mixture flow path. A natural rubber serum component 6 is supplied to the inclined surface 43a of the slider 43 from the third nozzle 33. The third nozzle 33 has an adjustment valve 33a, which can control the amount of serum component 6 supplied to the inclined surface 43a. The serum component 6 supplied to the inclined surface 43a of the slider 43 flows on the inclined surface 43a in the inclined direction (i.e., in the direction of arrow D).

[0033] The first mixture, which has fallen from the contact section 40 through the falling section 50 in the direction of arrow C, reaches the inclined surface 43a of the slider 43. The first mixture that has fallen onto the inclined surface 43a comes into contact with and is mixed with the serum component 6 that has flowed on the inclined surface 43a in the direction of arrow D, thereby obtaining a second mixture of the first mixture and the serum component 6 (second mixing step).

[0034] The second mixture then flows on the inclined surface 43a in the inclined direction (i.e., the direction of arrow E) and into the receiving container 74. A pH meter 62 is disposed on the inclined surface 43a to monitor the pH of the second mixture flowing in the direction of arrow E.

[0035] In the first mixture obtained by contacting the natural rubber latex 2 with the acid 4 in the contact section 40, and in the second mixture obtained by contacting the first mixture with the serum component 6 on the inclined surface 43 a of the slider 43, aggregation of the natural rubber latex 2 and the acid 4 progresses. That is, while the mixture falls down the falling section 50 in the direction of arrow C from the contact section 40, flows along the inclined surface 43 a of the slider 43 toward the receiving container 74 and flows into the receiving container 74, and after flowing into the receiving container 74, aggregates 72 of the natural rubber latex 2 and the acid 4 are formed in the first mixture and the second mixture (aggregation process), and the aggregates 72 are stored in the pool 70 of the receiving container 74. The second mixture flowing into the pool 70 contains at least the natural rubber latex 2, the acid 4, and the serum component 6. A pH meter 63 for monitoring the pH is provided in the pool 70 in the receiving container 74.

[0036] According to the method and apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure, when an acid is added to natural rubber latex to obtain a natural rubber agglomerate, it is possible to suppress the remaining unreacted natural rubber latex and acid. The reason why this effect is achieved is described below.

[0037] A conventional method involves adding acid to natural rubber latex to obtain coagulated natural rubber. However, when acid is added to natural rubber latex, coagulation proceeds rapidly, resulting in non-uniform coagulation, meaning that large amounts of unreacted natural rubber latex and acid may remain in the first mixture. This is thought to be because coagulation proceeds rapidly at the points where the natural rubber latex and acid come into contact in the first mixture, and the unreacted acid is incorporated into the coagulated areas, leaving unreacted acid and natural rubber latex. Therefore, there is a need to prevent the remaining unreacted natural rubber latex and acid when adding acid to natural rubber latex to obtain natural rubber coagulation.

[0038] In contrast, in the method and apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure, a serum component is further mixed into a first mixture of natural rubber latex and acid. The addition of the serum component stabilizes the aggregation of natural rubber latex and acid, and reduces the amount of unreacted natural rubber latex and acid remaining. Furthermore, by allowing the first mixture of natural rubber latex and acid to fall toward a mixture flow path through which the natural rubber serum component flows, the natural rubber latex, acid, and serum component are more uniformly mixed. This more uniform mixing of the components promotes the reaction between the natural rubber latex and acid. From this perspective, the amount of unreacted natural rubber latex and acid remaining is also reduced.

[0039] As described above, the method and apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure can reduce the amount of unreacted natural rubber latex and acid remaining when adding acid to natural rubber latex to obtain a natural rubber agglomerate, thereby reducing variation in the quality of the obtained natural rubber agglomerate and increasing the yield.

[0040] Natural Rubber Serum Component The natural rubber serum component (also referred to as "serum") used in embodiments of the present disclosure contains useful components that exhibit heat aging prevention effects on the rubber component, such as inositol, carbohydrates, proteins such as α-globulin, sugars, an ammonia source, minerals, glutathione, enzymes, and nucleic acids. The addition of the serum component stabilizes the aggregation of natural rubber latex and acid, and suppresses the remaining unreacted natural rubber latex and acid. Furthermore, the use of the serum component enables effective utilization of natural rubber resources.

[0041] As the serum component of natural rubber, for example, serum obtained from natural rubber latex by centrifugation or its coagulated product can be used.

[0042] The amount of the natural rubber serum component added is preferably 2 parts by mass or more, and more preferably 5 to 30 parts by mass, per 100 parts by mass of the dry content of the natural rubber latex, calculated as solids. By adding the serum component in an amount of 2 parts by mass or more, the aggregation of the natural rubber latex and the acid is further stabilized, and the remaining unreacted natural rubber latex and acid are further suppressed.

[0043] Natural Rubber Latex: The natural rubber latex used in the embodiments of the present disclosure is not particularly limited, and general natural rubber latex that forms coagulates upon reaction with acid can be used. From the perspectives of reducing odor and improving processability, it is preferable to use natural rubber latex that has been treated to reduce the amount of non-rubber components, such as proteins, in the natural rubber (specifically, by decomposing at least one selected from the group consisting of proteins and lipids (preferably both proteins and lipids)). Examples of methods for obtaining natural rubber latex from which at least one selected from the group consisting of proteins and lipids has been decomposed include treating natural rubber latex with at least one selected from the group consisting of surfactants and enzymes, and saponifying natural rubber latex (e.g., adding aqueous sodium hydroxide solution to natural rubber latex to decompose at least one selected from the group consisting of proteins and lipids). Of these, natural rubber latex treated with at least one selected from the group consisting of surfactants and enzymes (hereinafter also referred to as "treated natural rubber latex") is preferable.

[0044] However, natural rubber latex (particularly treated natural rubber latex) in which at least one selected from the group consisting of proteins and lipids has been decomposed tends to coagulate more rapidly when acid is added, and as a result, unreacted natural rubber latex and acid are likely to remain in the first mixture. However, according to the method for producing a natural rubber agglomerate and the apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure, it is possible to suppress the remaining unreacted natural rubber latex and acid, as described above.

[0045] Examples of natural rubber latex include tapped natural rubber latex itself, natural rubber latex stabilized by adding an acid such as sulfuric acid or an alkali such as ammonia, and concentrated natural rubber latex obtained by centrifuging with a centrifuge, and the rubber concentration (Dry rubber content; DRC) of these natural rubber latexes is 5% by mass or more in terms of solid content.

[0046] The surfactants that can be used when obtaining natural rubber latex that has been treated to reduce the amount of non-rubber components in the natural rubber (specifically, by decomposing at least one selected from the group consisting of proteins and lipids) are not particularly limited as long as they reduce the amount of non-rubber components in the natural rubber, and examples include anionic surfactants, nonionic surfactants, etc. Examples of anionic surfactants include carboxylates such as fatty acid soaps, N-acylamino acids and their salts, polyoxyethylene or POE alkyl ether carboxylates, and acylated peptides; sulfonates such as alkyl sulfonates, alkylbenzene and alkylnaphthalene sulfonates, naphthalene sulfonate-formalin polycondensates, sulfosuccinates, α-olefin sulfonates, and N-acylsulfonates; sulfate ester salts such as sulfated oils, alkyl sulfates, alkyl ether sulfates, polyoxyethylene or POE alkyl allyl ether sulfates, and alkylamide sulfates; and phosphate ester salts such as alkyl phosphates, polyoxyethylene or POE alkyl ether phosphates, and polyoxyethylene or POE alkyl allyl ether phosphates. Examples of nonionic surfactants include ether-type surfactants such as polyoxyethylene alkyl and alkylphenyl ethers, alkylallyl formaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block copolymers, and polyoxyethylene polyoxypropyl alkyl ethers; ether-ester-type surfactants such as polyoxyethylene ethers of glycerin esters, polyoxyethylene ethers of sorbitan esters, and polyoxyethylene ethers of sorbitol esters; ester-type surfactants such as polyoxyethylene glycol fatty acid esters, glycerin esters, polyglycerin esters, sorbitan esters, propylene glycol esters, and sucrose esters; and nitrogen-containing surfactants such as fatty acid alkanolamides, polyoxyethylene fatty acid amides, and polyoxyethylene alkylamines.Enzymes that can be used to obtain natural rubber latex that has been treated to reduce the amount of non-rubber components in the natural rubber (specifically, by decomposing at least one selected from the group consisting of proteins and lipids) are not particularly limited as long as they reduce the amount of non-rubber components in the natural rubber, and examples include protease enzymes such as papain and Alcalase, and cellulase enzymes such as Cellzyme. These can be used alone or in combination of two or more. Preferably, protease enzymes or cellulase enzymes are used in order to reduce the amount of non-rubber components in the natural rubber.

[0047] These surfactants and enzymes can be used alone or in combination of two or more. From the viewpoint of the stability of natural rubber latex, it is preferable to use long-chain fatty acid salts (soaps) such as sodium laurate, alkyl sulfates (AS) such as sodium dodecyl sulfate, alkyl polyoxyethylene sulfates (AES), α-olefin sulfonates (AOS), alkylbenzene sulfonates (ABS, LAS), and potassium dehydrated castor oil. Commercially available detergents containing the surfactants and enzymes, such as Kao Corporation's "Attack," "New Attack," and "Attack New Compound," which contain cellulase enzymes, Miyoshi Oil & Fats' "High Density Compact Soap," which contains a surfactant but no enzymes, Shabondama Snowl, which is manufactured by Shabondama Soap Co., Ltd., and Okamoto Corporation's "Gentle Soap," can also be used.

[0048] As a means for treating natural rubber latex by adding at least one selected from the group consisting of a surfactant and an enzyme, for example, at least one selected from the group consisting of a surfactant and an enzyme may be added before coagulation of the collected natural rubber latex, or may be applied by immersion or spraying before drying, or may be added using a dry pre-breaker after drying, and the mixture may be kneaded using a mixer, kneader, or the like, to obtain the desired natural rubber mixture.

[0049] The amount of at least one selected from the group consisting of surfactants and enzymes is desirably 0.02 parts by mass or more, preferably 0.05 to 4 parts by mass, per 100 parts by mass of the dry content of natural rubber latex. By adding 0.02 parts by mass or more of at least one selected from the group consisting of surfactants and enzymes, the amount of non-rubber components in the natural rubber can be reduced without causing adverse effects such as a decrease in the physical properties of the rubber.

[0050] The acid added to the natural rubber latex to obtain the acid coagulate may be, for example, formic acid, acetic acid, propionic acid, sulfuric acid, etc. Formic acid is particularly preferred.

[0051] From the viewpoint of suppressing the remaining unreacted natural rubber latex and acid, it is preferable to adjust the amount of acid added to the mixture so that the pH of the mixture immediately after the natural rubber latex and the acid come into contact with each other at the contact portion (the pH measured by pH meter 62 arranged on inclined surface 43 a in FIG. 1 ) falls within the range described below.

[0052] pH of the First Mixture The pH of the first mixture immediately after contact between the natural rubber latex and the acid at the contact section (as measured by pH meter 62 arranged on inclined surface 43 a in FIG. 1 ) is preferably 4.2 or more and 5.2 or less. By controlling the pH of the first mixture within the above range, coagulation of the natural rubber latex and the acid proceeds smoothly, and the amount of remaining unreacted natural rubber latex and acid is further reduced. The pH of the first mixture immediately after contact between the natural rubber latex and the acid is more preferably 4.4 or more and 5.0 or less.

[0053] The pH of the first mixture immediately after the natural rubber latex and the acid have come into contact can be adjusted by the pH of the natural rubber latex (for example, the pH of natural rubber latex 2 stored in first storage container 11 in FIG. 1 ), the pH of the acid (for example, the pH of acid 4 stored in second storage container 12 in FIG. 1 ), and the amounts of natural rubber latex and acid supplied to the contact section (for example, the amounts of natural rubber latex 2 and acid 4 supplied to contact section 40 in FIG. 1 ). The pH of the natural rubber latex (for example, the pH of natural rubber latex 2 stored in first storage container 11 in FIG. 1 ) is preferably controlled to, for example, pH 10±0.5. Furthermore, the pH of the acid (for example, the pH of acid 4 stored in second storage container 12 in FIG. 1 ) is adjusted to 4.4 or more and 5.0 or less for the purpose of adjusting the pH of the first mixture during aggregation (i.e., the pH of the first mixture immediately after contact between the natural rubber latex and the acid) to 4.4 or more and 5.0 or less, from the viewpoint of properly ensuring dispersion of the acid and mixing a sufficient amount of liquid. Therefore, the pH of the acid (for example, the pH of acid 4 stored in second storage container 12 in FIG. 1 ) is preferably 1.0 or more, and more preferably 2.0 or more, from the viewpoint of properly ensuring dispersion of the acid and mixing a sufficient amount of liquid.

[0054] pH of the Second Mixture The pH of the second mixture (i.e., pool 70) that has flowed into receiving vessel 74 (as measured by pH meter 63 disposed in receiving vessel 74 in FIG. 1 ) is preferably 4.2 or higher and 5.2 or lower. By controlling the pH of the second mixture within the above range, the coagulation of the natural rubber latex and the acid proceeds smoothly, and the remaining amounts of unreacted natural rubber latex and acid are further suppressed. The pH of the second mixture that has flowed into receiving vessel 74 is more preferably 4.4 or higher and 5.0 or lower.

[0055] The pH of the second mixture that has flowed into the receiving vessel 74 can be adjusted by the pH of the natural rubber latex, the pH of the acid, the amounts of natural rubber latex and acid supplied to the contact portion, the pH of the serum component (e.g., the pH of serum component 6 supplied to the inclined surface 43a of the slider 43 in FIG. 1 ), and the amount of serum component 6 supplied to the first mixture (e.g., the amount of serum component 6 that flows down the inclined surface 43a of the slider 43 and is mixed with the first mixture in FIG. 1 ). The pH of the serum component 6 (e.g., the pH of serum component 6 supplied to the inclined surface 43a of the slider 43 in FIG. 1 ) is preferably controlled to, for example, pH 4.7±0.5.

[0056] The natural rubber agglomerate obtained by the method for producing a natural rubber agglomerate according to an embodiment of the present disclosure and the natural rubber agglomerate obtained using the apparatus for producing a natural rubber agglomerate according to an embodiment of the present disclosure (hereinafter, both will be collectively referred to as the "natural rubber agglomerate according to an embodiment of the present disclosure") may be used as a natural rubber alone, or may be used by mixing with various other synthetic rubbers. As the other synthetic rubber, a diene-based synthetic rubber is preferably used from the viewpoint of polymer compatibility (uniform dispersion). Examples of diene-based synthetic rubbers that can be used include at least one selected from isoprene rubber, styrene-butadiene copolymer rubber, butadiene rubber, and styrene-isoprene copolymer rubber. In particular, from the viewpoint of heat resistance, at least one selected from isoprene rubber, styrene-butadiene copolymer rubber, and butadiene rubber is desirable. When mixed with other synthetic rubbers, the content of the natural rubber agglomerate according to an embodiment of the present disclosure is preferably 2 to 100% by mass, more preferably 5 to 80% by mass, and even more preferably 10 to 70% by mass, based on the total amount of all rubber components.

[0057] The natural rubber agglomerate according to the embodiment of the present disclosure may contain optional components such as fillers, reinforcing agents, softeners, vulcanizing agents, vulcanization accelerators, vulcanization accelerator aids, antioxidants, and resins, as needed. The natural rubber agglomerate according to the embodiment of the present disclosure can be suitably used for various rubber products, including rubber for tires, for example.

[0058] The present disclosure includes the following aspects. A first aspect is a method for producing a natural rubber agglomerate, comprising: a step of dropping a first mixture of natural rubber latex and an acid toward a mixture flow path through which a serum component of natural rubber flows, to obtain a second mixture of the first mixture and the serum component; and an agglomeration step of pouring the second mixture that has flowed through the mixture flow path into a receiving container to obtain an agglomerate of the natural rubber latex and the acid. A second aspect is the method for producing a natural rubber agglomerate according to the first aspect, wherein the first mixture is obtained by bringing the natural rubber latex flowing through a first flow path into contact with the acid flowing through a second flow path at a contact point between the first and second flow paths, and wherein the first mixture is dropped toward the mixture flow path, which is disposed vertically below the contact point. A third aspect is the method for producing a natural rubber agglomerate according to the first or second aspect, wherein the natural rubber latex is treated with at least one selected from the group consisting of a surfactant and an enzyme.

[0059] A fourth aspect is an apparatus for producing a natural rubber agglomerate, comprising: a mixture flow path through which a serum component of natural rubber flows; a drop section through which a first mixture of natural rubber latex and an acid falls vertically downward toward the mixture flow path; and a receiving container into which a second mixture obtained by mixing the first mixture and the serum component in the mixture flow path flows, wherein the apparatus is capable of producing an agglomerate in which the natural rubber latex and the acid are agglomerated.A fifth aspect is the apparatus for producing a natural rubber agglomerate according to the fourth aspect, further comprising: a first flow path through which the natural rubber latex flows; a second flow path through which the acid flows; and a contact section where the natural rubber latex flowing through the first flow path comes into contact with the acid flowing through the second flow path to produce the first mixture of the natural rubber latex and the acid, wherein the first mixture falls vertically downward from the contact section in the drop section.

[0060] The disclosure of Japanese Patent Application No. 2024-121384, filed on July 26, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0061] 2 Natural rubber latex 4 Acid 2a, 4a Droplets 6 Serum component 11 First storage container 12 Second storage container 14 pH adjustment nozzle 18 Stirrer 21 First tank 22 Second tank 31 First nozzle 32 Second nozzle 33 Third nozzle 31a, 32a, 33a Adjusting valve 40 Contact part 41 First gutter 42 Second gutter 43 Slider 41a, 42a, 43a Inclined surface 50 Falling part 61, 62, 63 pH meter 70 Pool 72 Aggregate 74 Receiving container 100 Manufacturing device 210 First hole 220 Second hole

Claims

1. A method for producing a natural rubber agglomerate, comprising: a step of dropping a first mixture of natural rubber latex and acid into a mixture flow path through which a serum component of natural rubber flows, to obtain a second mixture of the first mixture and the serum component; and an agglomeration step of pouring the second mixture that has flowed through the mixture flow path into a receiving container, to obtain an agglomerate of the natural rubber latex and the acid.

2. The method for producing a natural rubber agglomerate according to claim 1, wherein the first mixture is obtained by bringing the natural rubber latex flowing through a first flow path into contact with the acid flowing through a second flow path at a contact point between the first flow path and the second flow path, and the first mixture is allowed to fall toward the mixture flow path, which is positioned vertically below the contact point.

3. The method for producing a natural rubber agglomerate according to claim 1, wherein the natural rubber latex is treated with at least one selected from the group consisting of surfactants and enzymes.

4. An apparatus for producing a natural rubber agglomerate, comprising: a mixture flow path through which a serum component of natural rubber flows; a drop section through which a first mixture of natural rubber latex and an acid falls vertically downward toward the mixture flow path; and a receiving container into which a second mixture obtained by mixing the first mixture with the serum component in the mixture flow path flows, wherein the apparatus is capable of producing an agglomerate formed by agglomerating the natural rubber latex and the acid.

5. The apparatus for producing a natural rubber agglomerate according to claim 4, further comprising: a first flow path through which the natural rubber latex flows; a second flow path through which the acid flows; and a contact section where the natural rubber latex flowing through the first flow path comes into contact with the acid flowing through the second flow path to produce the first mixture of the natural rubber latex and the acid, wherein the first mixture falls vertically downward from the contact section in the falling section.

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