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 mixing step in which a treated natural rubber latex flowing in a first flow path and an acid flowing in a second flow path are brought into contact with each other at a point of contact between the first flow path and the second flow path so as to obtain a mixture of the treated natural rubber latex and the acid; and an aggregation step in which the mixture is dropped toward a third flow path disposed vertically below the point of contact, and then the mixture that has flowed along the third flow path is poured into a receiving container so as to obtain an aggregate in which the treated 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 is widely used in large quantities in the rubber and tire industries. Natural rubber is produced in the following order: latex collection by tapping, coagulation, washing (washing with water), dehydration, drying, and packing. It is classified by its species and grade, and is broadly divided 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 (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 acid to natural rubber latex. Meanwhile, natural rubber has been developed in which proteins and lipids have been partially decomposed by pretreatment such as enzyme treatment, with the aim of modifying natural rubber. However, when acid is added to pretreated natural rubber latex, coagulation proceeds rapidly, resulting in the formation of non-uniform coagulated materials, and uncoagulated natural rubber latex and acid remain, resulting in a problem of reduced yield of coagulated natural rubber. Therefore, there is a need to prevent the uncoagulated natural rubber latex and acid from remaining when adding acid to natural rubber latex to obtain natural rubber coagulates.

[0006] Therefore, an object of the present disclosure is to provide a method for producing a natural rubber agglomerate and an apparatus for producing a natural rubber agglomerate that can suppress the remaining unaggregated 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 pretreatment step of decomposing at least one selected from the group consisting of proteins and lipids in natural rubber latex by pretreatment to obtain treated natural rubber latex, a mixing step of bringing the treated natural rubber latex flowing through a first flow path into contact with an acid flowing through a second flow path at a contact point between the first flow path and the second flow path to obtain a mixture of the treated natural rubber latex and the acid, and an agglomeration step of dropping the mixture toward a third flow path located vertically below the contact point and pouring the mixture that has flowed through the third flow path into a receiving container to obtain an agglomerate of the treated 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 unagglomerated 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 pretreatment step of decomposing at least one selected from the group consisting of proteins and lipids in natural rubber latex through pretreatment to obtain treated natural rubber latex; a mixing step of bringing the treated natural rubber latex flowing through a first flow path into contact with an acid flowing through a second flow path at a contact point between the first flow path and the second flow path to obtain a mixture of the treated natural rubber latex and the acid; and an aggregation step of dropping the mixture toward a third flow path located vertically below the contact point, and then pouring the mixture through the third flow path into a receiving container to obtain an agglomerate of the treated natural rubber latex and the acid.

[0014] A natural rubber agglomerate manufacturing apparatus according to an embodiment of the present disclosure includes a first flow path through which treated natural rubber latex flows, a second flow path through which acid flows, a contact section where the treated natural rubber latex flowing through the first flow path comes into contact with the acid flowing through the second flow path to obtain a mixture of the treated natural rubber latex and the acid, a drop section through which the mixture falls vertically downward from the contact section, a third flow path that is disposed vertically below the contact section and through which the mixture that has fallen through the drop section flows, and a receiving container into which the mixture that has flowed through the third flow path flows, and is capable of obtaining an agglomerate of the treated 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 tank 21 serving as a first storage tank for storing treated natural rubber latex 2 and having a plurality of first holes 210 in its floor surface, a second tank 22 serving as a second storage tank for storing acid 4 and having a plurality of second holes 220 in its floor surface, a first gutter 41 forming a first flow path through which the treated natural rubber latex 2 flows, a second gutter 42 forming a second flow path through which the acid 4 flows, a contact section 40 where the treated 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 mixture falls from the contact section 40, a slider 43 disposed vertically below the contact section 40 and forming a third flow path through which the mixture that has fallen through the drop section 50 flows, and a receiving container 74 into which the mixture that has flowed through the third flow path flows. Formic acid, for example, is used as the acid 4.

[0018] A first storage vessel 11 that stores treated natural rubber latex 2 is provided upstream of the first tank 21. A pH meter 61 that monitors the pH of the treated natural rubber latex 2 is disposed in the first storage vessel 11. A pH adjustment nozzle 14 for adding an alkaline pH adjusting solution (e.g., ammonia) is disposed at the top of the first storage vessel 11. The pH adjustment nozzle 14 has an adjustment valve 14a. A stirrer 18 for stirring the treated natural rubber latex 2 is disposed in the first storage vessel 11. The pH adjusting solution is added from the pH adjustment nozzle 14 to the treated natural rubber latex 2 in the first storage vessel 11 in accordance with the pH monitored by the pH meter 61, and the treated natural rubber latex 2 is stirred by the stirrer 18, thereby controlling the pH of the treated natural rubber latex 2 within a certain range.

[0019] The treated 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 treated natural rubber latex 2 poured into the first tank 21 can be controlled by the adjustment valve 31 a.

[0020] The first tank 21 has a plurality of first holes 210 on its floor. The treated 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 (first falling step). The state of the treated 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 treated 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 treated natural rubber latex 2 to fall from the first tank 21 through the first holes 210, the amount of treated natural rubber latex 2 supplied to the first gutter 41, which forms the first flow path, can be adjusted.

[0021] The first gutter 41 has an inclined surface 41a that slopes toward the contact section 40. The inclined surface 41a forms a first flow path. Droplets 2a of the treated 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. The treated natural rubber latex 2 that reaches the first gutter 41 then flows on the inclined surface 41a in the inclined direction (i.e., the direction of arrow A) to reach the contact section 40. Because the amount of treated natural rubber latex 2 supplied from the first tank 21 to the first gutter 41 can be adjusted, the supply amount of treated natural rubber latex 2 that flows on the inclined surface 41a of the first gutter 41 to reach the contact section 40 can also be adjusted.

[0022] 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.

[0023] 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 (second falling process). 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.

[0024] The second gutter 42 has an inclined surface 42a that slopes toward the contact section 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) to reach the contact section 40. Because the amount of acid 4 supplied from the second tank 22 to the second gutter 42 can be adjusted, the amount of acid 4 that flows on the inclined surface 42a of the second gutter 42 and reaches the contact section 40 can also be adjusted.

[0025] The treated 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 section 40 to form a mixture (mixing step). In an embodiment of the present disclosure, the amount of treated natural rubber latex 2 flowing on the inclined surface 41 a of the first gutter 41 to reach the contact section 40 and the amount of acid 4 flowing on the inclined surface 42 a of the second gutter 42 to reach the contact section 40 can both be appropriately adjusted. In other words, the treated natural rubber latex 2 and the acid 4 can be contacted in appropriate amounts at the contact section 40.

[0026] The mixture obtained by contacting the treated natural rubber latex 2 with the acid 4 in the contact section 40 falls down the falling section 50 in a vertical downward direction (i.e., in the direction of arrow C) from the contact section 40 .

[0027] The slider 43 has an inclined surface 43a that slopes toward the receiving container 74. The inclined surface 43a forms a third flow path. The mixture that falls 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 mixture that reaches the slider 43 then flows on the inclined surface 43a in the inclined direction (i.e., the direction of arrow D) and into the receiving container 74. A pH meter 62 that monitors the pH of the mixture flowing in the direction of arrow D is disposed on the inclined surface 43a.

[0028] In the mixture obtained by contacting the treated natural rubber latex 2 with the acid 4 in the contact section 40, aggregation of the treated natural rubber latex 2 and the acid 4 progresses. That is, while the mixture is falling down the falling section 50 in the direction of arrow C from the contact section 40, while flowing along the inclined surface 43a of the slider 43 toward the receiving container 74 and before flowing into the receiving container 74, and after flowing into the receiving container 74, aggregates 72 of the treated natural rubber latex 2 and the acid 4 are formed in the mixture (aggregation step), and the aggregates 72 are stored in the pool 70 of the receiving container 74. The pool 70 contains a liquid other than the treated natural rubber latex 2 and the acid 4 (e.g., serum). A pH meter 63 for monitoring the pH is disposed in the pool 70 in the receiving container 74.

[0029] 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 treated natural rubber latex to obtain a natural rubber agglomerate, it is possible to suppress the remaining un-aggregated treated natural rubber latex and acid. The reason why this effect is achieved is described below.

[0030] A conventional method for obtaining natural rubber coagulates involves adding acid to treated natural rubber latex, which has been prepared by pretreating at least one selected from the group consisting of proteins and lipids in natural rubber latex. However, when acid is added to the treated natural rubber latex, coagulation proceeds rapidly, resulting in non-uniform coagulates. This means that uncoagulated natural rubber latex and acid remain in the mixture, resulting in a decrease in the yield of coagulated natural rubber. This is thought to be because coagulation proceeds rapidly at the point where the treated natural rubber latex and acid come into contact in the mixture, and uncoagulated acid is incorporated into the coagulated portion, leaving uncoagulated acid and treated natural rubber latex remaining. Therefore, there is a need to prevent the remaining uncoagulated treated natural rubber latex and acid when adding acid to treated natural rubber latex to obtain natural rubber coagulates.

[0031] In contrast, in the method and apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure, the amounts of treated natural rubber latex and acid supplied to the contact section can be adjusted. That is, appropriate amounts of treated natural rubber latex and acid can be brought into contact with each other in the contact section. By bringing appropriate amounts of treated natural rubber latex and acid into contact with each other, even if coagulation progresses rapidly, the amount of uncoagulated acid incorporated into the resulting agglomerates can be reduced. This allows the coagulation reaction between the treated natural rubber latex and the acid to be promoted continuously and efficiently. Furthermore, the mixture of treated natural rubber latex and acid mixed in the contact section falls from the contact section onto the third flow path, thereby more uniformly mixing the mixture. This more uniform mixing of the two promotes the reaction between the treated natural rubber latex and the acid. From this perspective, the amount of uncoagulated acid incorporated into the agglomerates can also be reduced.

[0032] As described above, the method and apparatus for producing a natural rubber agglomerate according to the embodiments of the present disclosure can suppress the remaining unagglomerated natural rubber latex and acid when adding acid to treated natural rubber latex to obtain a natural rubber agglomerate, thereby suppressing variation in the quality of the obtained natural rubber agglomerate and increasing the yield.

[0033] pH The pH of the mixture immediately after contact of the treated natural rubber latex with 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 within the above range, the coagulation of the treated natural rubber latex and the acid proceeds smoothly, and the amount of uncoagulated treated natural rubber latex and the remaining acid is further reduced. It is even more preferable that the pH of the mixture immediately after contact of the treated natural rubber latex with the acid is 4.4 or more and 5.0 or less.

[0034] The pH of the mixture immediately after contact between the treated natural rubber latex and the acid can be adjusted by the pH of the treated natural rubber latex (for example, the pH of treated 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 amount of treated natural rubber latex and acid supplied to the contact section (for example, referring to the amounts of treated natural rubber latex 2 and acid 4 supplied to contact section 40 in FIG. 1 . Specifically, the amount of treated natural rubber latex 2 dropping from first holes 210 can be adjusted by adjusting the diameter of first holes 210 and the spacing between first holes 210, and the amount of acid 4 dropping from second holes 220 can be adjusted by adjusting the diameter of second holes 220 and the spacing between second holes 220). Note that there are no particular restrictions on the pH of the treated natural rubber latex, but a pH of 9.0 or higher is preferred from the standpoint of maintaining a stable state without coagulation. There are also no particular restrictions on the pH of the acid, but from the viewpoint of ensuring appropriate dispersion of the acid and mixing a sufficient amount of liquid in order to adjust the pH of the mixture at the time of coagulation to 4.7±0.5, the pH is preferably 1.0 or higher, and more preferably 2.0 or higher.

[0035] First Holes and Second Holes The first storage tank preferably has a plurality of first holes on its floor surface, and the first holes are preferably arranged in a first orthogonal direction perpendicular to the direction in which the treated natural rubber latex flows through the first flow path. That is, as shown in FIG. 1 , the first tank 21 preferably has a plurality of first holes 210 on its floor surface, and the first holes 210 are preferably arranged in a first orthogonal direction (i.e., the direction of arrow E) perpendicular to the direction in which the treated natural rubber latex 2 flows through the first flow path on the inclined surface 41 a of the first gutter 41 (i.e., the direction of arrow A). From the viewpoint of appropriately adjusting the amount of treated natural rubber latex supplied to the contact section to suppress the remaining unaggregated treated natural rubber latex and acid, the average hole diameter of the first holes and the average spacing of the first holes in the first orthogonal direction are preferably within the following ranges: Average hole diameter of the first holes: 1 mm or more and 10 mm or less (more preferably 1 mm or more and 5 mm or less) Average spacing of the first holes in the first orthogonal direction: 10 mm or more and 50 mm or less (more preferably 15 mm or more and 30 mm or less).

[0036] The second storage tank preferably has a plurality of second holes 220 on its floor surface, and the second holes 220 are preferably arranged in a second orthogonal direction perpendicular to the direction in which the acid flows through the second flow path. That is, as shown in FIG. 1 , the second tank 22 preferably has a plurality of second holes 220 on its floor surface, and the second holes 220 are preferably arranged in a second orthogonal direction (i.e., the direction of arrow E) perpendicular to the direction in which the acid 4 flows through the second flow path on the inclined surface 42 a of the second gutter 42 (i.e., the direction of arrow B). From the viewpoint of suppressing the remaining unaggregated treated natural rubber latex and acid by appropriately adjusting the amount of acid supplied to the contact section, the average hole diameter of the second holes and the average spacing of the second holes in the second orthogonal direction are preferably within the following ranges: Average hole diameter of the second holes: 1 mm or more and 10 mm or less (more preferably 1 mm or more and 5 mm or less) Average spacing of the second holes in the second orthogonal direction: 10 mm or more and 50 mm or less (more preferably 15 mm or more and 30 mm or less).

[0037] The average hole diameter of the first holes is calculated by measuring the maximum diameter of each of all first holes arranged on the floor surface of the first storage tank and taking the arithmetic mean value of the measured diameters. The average hole diameter of the second holes is calculated in a similar manner. The average spacing of the first holes in the first orthogonal direction is calculated by measuring the spacing between adjacent first holes in the first orthogonal direction (specifically, the distance from the center point of one first hole to the center point of the adjacent first hole) on the floor surface of the first storage tank in the first orthogonal direction (the direction of arrow E in FIG. 1) for all pairs of adjacent first holes and taking the arithmetic mean value of the measured spacing. The average spacing of the second holes in the second orthogonal direction is calculated in a similar manner.

[0038] From the viewpoint of efficiently promoting the coagulation reaction between the treated natural rubber latex and the acid, the first storage tank preferably has one to five rows of first holes (rows of first holes) arranged in the first orthogonal direction on its floor surface in a direction intersecting the first orthogonal direction (the direction of arrow F in FIG. 1 ). The first tank 21 shown in FIG. 1 has three rows of first holes 210 in the direction of arrow F. From the viewpoint of efficiently promoting the coagulation reaction between the treated natural rubber latex and the acid, the second storage tank preferably has one to five rows of second holes (rows of second holes) arranged in the second orthogonal direction on its floor surface in a direction intersecting the second orthogonal direction (the direction of arrow F in FIG. 1 ). The second tank 22 shown in FIG. 1 has three rows of second holes 220 in the direction of arrow F.

[0039] 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. In the method for producing a natural rubber coagulate according to the embodiments of the present disclosure, from the viewpoints of reducing odor in the latex and improving processability, the natural rubber latex is subjected to a pretreatment step in which at least one component selected from the group consisting of proteins and lipids (preferably both proteins and lipids) is decomposed by pretreatment to obtain treated natural rubber latex. Furthermore, the apparatus for producing a natural rubber coagulate according to the embodiments of the present disclosure uses treated natural rubber latex in which at least one component selected from the group consisting of proteins and lipids has been decomposed by pretreatment. Methods for obtaining treated natural rubber latex in which at least one selected from the group consisting of proteins and lipids has been degraded include, for example, a method of treating natural rubber latex before treatment with at least one selected from the group consisting of surfactants and enzymes, a method of saponifying natural rubber latex before treatment (for example, a method of adding an aqueous sodium hydroxide solution to natural rubber latex to degrade at least one selected from the group consisting of proteins and lipids), etc. Among these, treated natural rubber latex treated with at least one selected from the group consisting of surfactants and enzymes is preferred.

[0040] Examples of natural rubber latex (natural rubber latex before treatment) include tapped natural rubber latex itself, natural rubber latex stabilized by adding an alkali such as ammonia, and concentrated natural rubber latex obtained by centrifugal separation, and examples of these latexes have a rubber concentration (Dry rubber content; DRC) of 5% by mass or more in terms of solid content.

[0041] The surfactant that can be used when obtaining treated natural rubber latex in which at least one selected from the group consisting of proteins and lipids has been degraded is not particularly limited as long as it reduces the amount of non-rubber components such as proteins in the natural rubber, and examples thereof 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.The enzymes that can be used to obtain treated natural rubber latex in which at least one selected from the group consisting of proteins and lipids has been degraded are not particularly limited, as long as they reduce the amount of non-rubber components, such as proteins, in the natural rubber, and examples thereof include protease enzymes such as papain and alcalase, and lipase enzymes. These may be used alone or in combination of two or more. Preferably, protease enzymes or lipase enzymes are used in order to reduce branching in the natural rubber.

[0042] These surfactants and enzymes can be used alone or in combination of two or more. From the viewpoint of the stability of the treated 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 "Attack," "New Attack," and "Attack New Compound" manufactured by Kao Corporation, which contain cellulase enzymes, "High Density Compact Soap" manufactured by Miyoshi Oil & Fats Co., Ltd., which contains a surfactant but no enzymes, "Shabondama Snow" manufactured by Shabondama Soap Co., Ltd., and "Gentle Soap" manufactured by Okamoto Corporation, can also be used.

[0043] As a means for treating natural rubber latex (natural rubber latex before treatment) by adding at least one selected from the group consisting of a surfactant and an enzyme, for example, the target natural rubber mixture can be obtained by adding at least one selected from the group consisting of a surfactant and an enzyme before coagulation of the collected natural rubber latex.

[0044] 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 the at least one selected from the group consisting of surfactants and enzymes, branching can be reduced without causing adverse effects such as a decrease in the physical properties of the rubber.

[0045] The mixture of treated natural rubber latex and acid may further contain a natural rubber serum component. The natural rubber serum component contains useful components, such as inositol, carbohydrates, proteins such as α-globulin, sugars, ammonia sources, minerals, glutathione, enzymes, and nucleic acids, that also have heat-resistant anti-aging effects on rubber components. The inclusion of this natural rubber serum component can enhance heat-resistant anti-aging effects and enable effective utilization of natural rubber resources. For example, serum obtained from centrifuged natural rubber latex or its coagulate can be used as this natural rubber serum component. The amount of natural rubber serum component added is preferably 2 parts by mass or more, more preferably 5 to 30 parts by mass, per 100 parts by mass of the dry content of the treated natural rubber latex, calculated as solids.

[0046] The acid added to the treated 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.

[0047] From the viewpoint of suppressing the remaining unaggregated treated 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 treated natural rubber latex comes into contact with the acid at the contact portion (the pH as measured by pH meter 62 arranged on inclined surface 43 a in FIG. 1 ) falls within the aforementioned range.

[0048] 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 after drying, 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.

[0049] The natural rubber obtained by drying the natural rubber agglomerate according to an 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 obtained by drying the natural rubber agglomerate according to an embodiment of the present disclosure can be suitably used for various rubber products, including, for example, rubber for tires.

[0050] The present disclosure includes the following aspects: A first aspect is a method for producing a natural rubber agglomerate, comprising: a pretreatment step of decomposing at least one selected from the group consisting of proteins and lipids in natural rubber latex by pretreatment to obtain treated natural rubber latex, a mixing step of bringing the treated natural rubber latex flowing through a first flow path into contact with an acid flowing through a second flow path at a contact point between the first flow path and the second flow path to obtain a mixture of the treated natural rubber latex and the acid, and an agglomeration step of dropping the mixture toward a third flow path located vertically below the contact point and pouring the mixture that has flowed through the third flow path into a receiving container to obtain an agglomerate of the treated natural rubber latex and the acid. A second aspect is the method for producing a natural rubber agglomerate according to the first aspect, comprising: a first dropping step of dropping the treated natural rubber latex from a first storage tank, the first storage tank having a first hole in its floor surface, toward the first flow path through the first hole; and a second dropping step of dropping the acid from a second storage tank, the second storage tank having a second hole in its floor surface, toward the second flow path through the second hole. A third aspect is the method for producing a natural rubber agglomerate according to the second aspect, wherein the first storage tank has a plurality of the first holes on the floor surface, the first holes are arranged in a first orthogonal direction that is orthogonal to the direction in which the treated natural rubber latex flows through the first flow path, the first holes have an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the first holes in the first orthogonal direction is 10 mm or more and 50 mm or less; and the second storage tank has a plurality of the second holes on the floor surface, the second holes are arranged in a second orthogonal direction that is orthogonal to the direction in which the acid flows through the second flow path, the second holes have an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the second holes in the second orthogonal direction is 10 mm or more and 50 mm or less. A fourth aspect is the method for producing a natural rubber agglomerate according to the third aspect, wherein the first storage tank has, on its floor surface, one to five rows of the first holes arranged in the first orthogonal direction in a direction intersecting the first orthogonal direction, and the second storage tank has, on its floor surface, one to five rows of the second holes arranged in the second orthogonal direction in a direction intersecting the second orthogonal direction.A fifth aspect is the method for producing a natural rubber coagulate according to any one of the first to fourth aspects, wherein the mixture has a pH of 4.2 or more and 5.2 or less immediately after the treated natural rubber latex and the acid have come into contact at the contact area. A sixth aspect is the method for producing a natural rubber coagulate according to any one of the first to fifth aspects, wherein the pretreatment step is a step of pretreating the natural rubber latex with at least one selected from the group consisting of a surfactant and an enzyme to decompose at least one selected from the group consisting of proteins and lipids, thereby obtaining the treated natural rubber latex.

[0051] A seventh aspect is an apparatus for producing a natural rubber agglomerate, comprising: a first flow path through which treated natural rubber latex flows; a second flow path through which acid flows; a contact section where the treated natural rubber latex flowing through the first flow path comes into contact with the acid flowing through the second flow path to produce a mixture of the treated natural rubber latex and the acid; a drop section through which the mixture falls vertically downward from the contact section; a third flow path disposed vertically below the contact section and through which the mixture that has fallen through the drop section flows; and a receiving container into which the mixture that has flowed through the third flow path flows, wherein the apparatus is capable of producing an agglomerate of the treated natural rubber latex and the acid. An eighth aspect is the apparatus for producing a natural rubber agglomerate according to the seventh aspect, comprising: a first storage tank that stores the treated natural rubber latex, has a plurality of first holes in its floor surface, and allows the treated natural rubber latex to fall from the first holes toward the first flow path; and a second storage tank that stores the acid, has a plurality of second holes in its floor surface, and allows the acid to fall from the second holes toward the second flow path. A ninth aspect is the apparatus for producing a natural rubber agglomerate according to the eighth aspect, wherein the first storage tank has a plurality of the first holes on the floor surface, the first holes are arranged in a first orthogonal direction that is orthogonal to the direction in which the treated natural rubber latex flows through the first flow path, the first holes have an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the first holes in the first orthogonal direction is 10 mm or more and 50 mm or less; and the second storage tank has a plurality of the second holes on the floor surface, the second holes are arranged in a second orthogonal direction that is orthogonal to the direction in which the acid flows through the second flow path, the second holes have an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the second holes in the second orthogonal direction is 10 mm or more and 50 mm or less. A tenth aspect is the apparatus for producing a natural rubber aggregate according to the ninth aspect, wherein the first storage tank has, on its floor surface, one to five rows of the first holes arranged in the first orthogonal direction in a direction intersecting the first orthogonal direction, and the second storage tank has, on its floor surface, one to five rows of the second holes arranged in the second orthogonal direction in a direction intersecting the second orthogonal direction.

[0052] The disclosure of Japanese Patent Application No. 2024-121383, 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.

[0053] 2 Treated natural rubber latex 4 Acid 2a, 4a Droplets 11 First storage container 12 Second storage container 14 pH adjustment nozzle 18 Agitator 21 First tank 22 Second tank 31 First nozzle 32 Second nozzle 31a, 32a Adjusting valve 40 Contact portion 41 First gutter 42 Second gutter 43 Slider 41a, 42a, 43a Inclined surface 50 Drop portion 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 pretreatment step of decomposing at least one selected from the group consisting of proteins and lipids in natural rubber latex through pretreatment to obtain treated natural rubber latex; a mixing step of bringing the treated natural rubber latex flowing through a first flow path into contact with an acid flowing through a second flow path at a contact point between the first and second flow paths to obtain a mixture of the treated natural rubber latex and the acid; and an agglomeration step of dropping the mixture toward a third flow path located vertically below the contact point and pouring the mixture that has flowed through the third flow path into a receiving container to obtain an agglomerate of the treated natural rubber latex and the acid.

2. The method for producing a natural rubber agglomerate according to claim 1, comprising: a first dropping step of dropping the treated natural rubber latex from a first storage tank that stores the treated natural rubber latex and has a first hole in its floor surface toward the first flow path through the first hole; and a second dropping step of dropping the acid from a second storage tank that stores the acid and has a second hole in its floor surface toward the second flow path through the second hole.

3. The method for producing a natural rubber agglomerate according to claim 2, wherein the first storage tank has a plurality of the first holes on its floor surface, the first holes being arranged in a first orthogonal direction perpendicular to the direction in which the treated natural rubber latex flows through the first flow path, the first holes having an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the first holes in the first orthogonal direction being 10 mm or more and 50 mm or less; and the second storage tank has a plurality of the second holes on its floor surface, the second holes being arranged in a second orthogonal direction perpendicular to the direction in which the acid flows through the second flow path, the second holes having an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the second holes in the second orthogonal direction being 10 mm or more and 50 mm or less.

4. The method for producing a natural rubber agglomerate according to claim 3, wherein the first storage tank has, on its floor surface, one to five rows of the first holes arranged in the first orthogonal direction in a direction intersecting the first orthogonal direction, and the second storage tank has, on its floor surface, one to five rows of the second holes arranged in the second orthogonal direction in a direction intersecting the second orthogonal direction.

5. The method for producing a natural rubber agglomerate according to claim 1, wherein the mixture has a pH of 4.2 or more and 5.2 or less immediately after the treated natural rubber latex and the acid come into contact at the contact area.

6. The method for producing a natural rubber agglomerate according to claim 1, wherein the pretreatment step is a step of pretreating the natural rubber latex with at least one selected from the group consisting of a surfactant and an enzyme to decompose at least one selected from the group consisting of proteins and lipids, thereby obtaining the treated natural rubber latex.

7. An apparatus for producing a natural rubber agglomerate, comprising: a first flow path through which treated natural rubber latex flows; a second flow path through which acid flows; a contact section where the treated natural rubber latex flowing through the first flow path comes into contact with the acid flowing through the second flow path to produce a mixture of the treated natural rubber latex and the acid; a drop section through which the mixture falls vertically downward from the contact section; a third flow path arranged vertically below the contact section and through which the mixture that has fallen through the drop section flows; and a receiving container into which the mixture that has flowed through the third flow path flows, wherein the apparatus is capable of producing an agglomerate of the treated natural rubber latex and the acid.

8. The apparatus for producing a natural rubber agglomerate according to claim 7, comprising: a first storage tank that stores the treated natural rubber latex, has a plurality of first holes in its floor surface, and allows the treated natural rubber latex to fall from the first holes toward the first flow path; and a second storage tank that stores the acid, has a plurality of second holes in its floor surface, and allows the acid to fall from the second holes toward the second flow path.

9. The apparatus for producing a natural rubber agglomerate according to claim 8, wherein the first storage tank has a plurality of the first holes on its floor surface, the first holes being arranged in a first orthogonal direction perpendicular to the direction in which the treated natural rubber latex flows through the first flow path, the first holes having an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the first holes in the first orthogonal direction being 10 mm or more and 50 mm or less; and the second storage tank has a plurality of the second holes on its floor surface, the second holes being arranged in a second orthogonal direction perpendicular to the direction in which the acid flows through the second flow path, the second holes having an average hole diameter of 1 mm or more and 10 mm or less, and the average spacing between the second holes in the second orthogonal direction being 10 mm or more and 50 mm or less.

10. The apparatus for producing a natural rubber agglomerate according to claim 9, wherein the first storage tank has, on its floor surface, one to five rows of the first holes arranged in the first orthogonal direction in a direction intersecting the first orthogonal direction, and the second storage tank has, on its floor surface, one to five rows of the second holes arranged in the second orthogonal direction in a direction intersecting the second orthogonal direction.

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