WO2021261489A1 - Rubber particles and method for producing same - Google Patents

Rubber particles and method for producing same Download PDF

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Publication number
WO2021261489A1
WO2021261489A1 PCT/JP2021/023610 JP2021023610W WO2021261489A1 WO 2021261489 A1 WO2021261489 A1 WO 2021261489A1 JP 2021023610 W JP2021023610 W JP 2021023610W WO 2021261489 A1 WO2021261489 A1 WO 2021261489A1
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Prior art keywords
rubber
cyclized
particles
natural rubber
solution
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PCT/JP2021/023610
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French (fr)
Japanese (ja)
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恵子 西田
幸大 小川
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根上工業株式会社
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Priority to JP2022532498A priority Critical patent/JP7153412B2/en
Publication of WO2021261489A1 publication Critical patent/WO2021261489A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C19/00—Chemical modification of rubber
    • C08C19/10—Isomerisation; Cyclisation
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
    • C08C2/00—Treatment of rubber solutions
    • C08C2/06—Wining of rubber from solutions
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • C08J3/16—Powdering or granulating by coagulating dispersions

Definitions

  • the present invention relates to rubber particles and a method for producing the same.
  • This application claims priority based on Japanese Patent Application No. 2020-108942 filed in Japan on June 24, 2020, the contents of which are incorporated herein by reference.
  • particles such as acrylic beads, polystyrene beads, and polyurethane beads have been used in various products such as paints, plastics, adhesives, and cosmetics.
  • the issue of microplastics in the marine environment has been widely addressed, and the need for micrometer-scale particles made from natural products is increasing.
  • Patent Document 1 discloses cellulose spherical particles produced by the following methods (1) and (2) using cellulose ester.
  • An object of the present invention is to provide a method for easily producing flexible particles using a natural product as a raw material and particles having flexibility using a natural product as a raw material.
  • the present invention has the following aspects.
  • the rubber particles of the above [1] having an average particle diameter of 1 to 300 ⁇ m.
  • a method for producing rubber particles comprising a step of suspending the cyclized rubber solution in the presence of a turbidity stabilizer.
  • a radical polymerization initiator is added to the cyclized rubber solution.
  • the radical polymerization initiator preferably contains one or more organic peroxides or one or more azo compounds.
  • the organic peroxide preferably contains one or more selected arbitrarily from t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, and t-hexylperoxypivalate. .. [8] The method for producing rubber particles according to any one of [5] to [7], wherein the solvent contains aromatic hydrocarbons. Here, it is preferable that the aromatic hydrocarbon contains at least one arbitrarily selected from toluene, xylene and ethylbenzene. [9] The method for producing rubber particles according to any one of [5] to [8], wherein sulfuric acid, an organic sulfonic acid or a metal halogen compound is added to the solvent as a cyclization catalyst.
  • the cyclization catalyst preferably contains organic sulfonic acid, and is arbitrarily selected from p-toluene sulfonic acid, monofluoromethane sulfonic acid, difluoromethane sulfonic acid, xylene sulfonic acid, and alkylbenzene sulfonic acid. It is more preferable to include the above.
  • the neutralization is preferably carried out by adding an aqueous solution of an alkali metal carbonate or an alkali metal hydrogen carbonate to the cyclized rubber solution.
  • the suspension stabilizer contains at least one selected arbitrarily from a cellulosic water-soluble resin, polyvinyl alcohol, polyacrylate, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and a tertiary phosphate.
  • the suspension stabilizer preferably contains a cellulosic water-soluble resin, and more preferably contains one or more arbitrarily selected from methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.
  • the coagulant preferably contains one or more arbitrarily selected from aluminum sulfate, sodium chloride, and calcium chloride.
  • the surfactant preferably contains an anionic surfactant, and more preferably contains sodium lauryl sulfate.
  • the rubber particles of the first aspect of the present invention are formed from natural rubber.
  • Natural rubber is generally a rubber whose main component is a polymer having cis-1,4-polyisoprene as a main skeleton. Natural rubber is obtained from the sap of plants such as Hevea brasiliensis. In addition to the rubber component, the sap contains water and non-rubber components (for example, impurities such as proteins, fatty acids, and inorganic salts). The natural rubber may contain a non-rubber component as long as the effect of the present invention is not impaired.
  • the natural rubber a natural rubber latex obtained by purifying the sap by a known purification / solid-liquid separation method may be used, or a smoked sheet obtained by solidifying the sap may be used.
  • a natural rubber latex emulsion liquid of natural rubber
  • a dispersion medium such as water
  • the rubber component with respect to the total mass of the natural rubber latex Is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and even more preferably 30 to 60% by mass.
  • the yield of the target rubber particles increases, which is preferable.
  • the natural rubber forming the rubber particles of this embodiment is not limited to the one collected from a plant, and may be a so-called artificial natural rubber obtained by chemically polymerizing an isoprene molecule by a known method.
  • Examples of the weight average molecular weight of the natural rubber forming the rubber particles of this embodiment include 10,000 to 1,000,000.
  • the natural rubber contained in the rubber particles of this embodiment is preferably a cyclized rubber. If the natural rubber is cyclized rubber, the chemical resistance, heat resistance and weather resistance of the rubber particles are enhanced. In addition, the adhesiveness to non-polar polymers such as polyolefin, polar polymers such as polyester, polyurethane and alkyd resin, and metals such as iron is enhanced.
  • the cyclized rubber is obtained by cyclizing a natural rubber using a cyclization catalyst. The cyclization reaction will be described in detail later. In the present specification, the natural rubber that has been cyclized to become cyclized rubber may be referred to as "cyclized natural rubber".
  • the cyclization rate of the cyclized rubber is preferably 60 to 90%, more preferably 65 to 85%.
  • the cyclization rate of the cyclized rubber is at least the above lower limit value, it can be easily made into particles without being affected by the tack of the natural rubber. If the cyclization rate of the cyclized rubber is not more than the above upper limit value, the cross-linking rate can be expected to be improved by the remaining double bond.
  • the cyclization rate of the cyclized rubber can be adjusted by adjusting the amount of the cyclization catalyst used, and the cyclization rate tends to increase as the amount of the cyclization catalyst used increases.
  • the shape of the rubber particles in this embodiment may be spherical or not spherical, but is preferably spherical.
  • the rubber particles are spherical, the flexibility of the individual rubber particles can be increased, the slipperiness when the rubber particles come into contact with each other can be increased, and the flexibility of the aggregate (whole) of the rubber particles can be increased. be able to.
  • the "spherical shape” is not limited to a true spherical shape, but also includes a shape close to a sphere such as an ellipsoid, a sphere having an uneven surface, and the like.
  • shapes such as plate-shaped, flaky-shaped, and rod-shaped do not correspond to spherical shapes.
  • the shape of the rubber particles is determined by observing with an optical microscope or an electron microscope. Even when spherical rubber particles and non-spherical rubber particles are mixed, as long as the requirements of the present invention are satisfied as an aggregate (whole) of the rubber particles and the effect of the present invention is obtained, the present invention It is not excluded from the scope of the invention.
  • the amount of the non-spherical rubber particles is preferably 10% by volume or less, more preferably 5% by volume or less, still more preferably 1 with respect to the total volume of the aggregates of the rubber particles of this embodiment. It is less than% by volume.
  • the average particle size of the rubber particles of this embodiment is preferably 1 ⁇ m to 500 ⁇ m, more preferably 1 ⁇ m to 300 ⁇ m, further preferably 1 ⁇ m to 200 ⁇ m, and particularly preferably 1 ⁇ m to 180 ⁇ m.
  • the rubber particles can be suitably used for cosmetics.
  • the "average particle size" is a particle size (volume average particle size) corresponding to 50% of the cumulative distribution on a volume basis measured by a laser diffraction type particle size distribution meter.
  • the volume average particle diameter is the median diameter (d50).
  • the rubber particles of this embodiment substantially do not contain components other than natural rubber.
  • substantially free means that the component other than the component unavoidably mixed in the production is not contained.
  • the content of natural rubber with respect to the total mass of the rubber particles is preferably 99% by mass or more, more preferably 99.5% by mass or more, further preferably 99.9% by mass or more, and 100% by mass. Is most preferable.
  • the non-rubber component that can be contained in natural rubber derived from a plant does not fall under "components other than natural rubber”.
  • the content of cis-1,4-polyisoprene (including cyclized ones) with respect to the total mass of the rubber particles of this embodiment is preferably 95% by mass or more, more preferably 98% by mass or more, and 99% by mass or more. More preferably, 99.5% by mass or more is particularly preferable, and 99.9% by mass or more is most preferable.
  • the method for producing rubber particles of the present embodiment includes a step of dissolving natural rubber in a solvent and performing a cyclization reaction to obtain a cyclized rubber solution (cyclization step), and in the presence of water and a suspension stabilizer. It has a step of suspending the cyclized rubber solution (suspension step).
  • a step of removing the solvent from the suspension to obtain an aqueous dispersion in which the rubber particles are dispersed in water (solvent removal step) and a solvent removal step are performed. It may have a step of solid-liquid separating the aqueous dispersion obtained in the step and washing the recovered rubber particles with water (washing step) and a step of drying the washed rubber particles (drying step).
  • the cyclization step is carried out in the state of a rubber solution in which natural rubber is dissolved in a solvent. At this time, it is preferable that the water content in the rubber solution is small. Therefore, when natural rubber latex is used as the natural rubber, it is preferable to solidify the natural rubber latex by salting out before the cyclization step and recover the natural rubber in a solid state (salting out step).
  • the salting out step is a step of salting out the natural rubber latex and separating the natural rubber from a dispersion medium such as water.
  • a natural rubber latex is coagulated by salting out using a coagulant, and then the solid material is recovered by solid-liquid separation and dried to obtain a solid material of natural rubber.
  • the coagulant include aluminum sulfate, sodium chloride, calcium chloride and the like.
  • the amount of the coagulant added is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass with respect to 100 parts by mass of the natural rubber in the natural rubber latex. If the amount of the coagulant added is not less than the above lower limit, the natural rubber latex can be sufficiently salted out, but even if the amount exceeds the above upper limit, the effect of the coagulant reaches a plateau, and the cost is only increased.
  • Salting out may be performed in the presence of a detergent.
  • the surfactant is not particularly limited, and known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used.
  • As the surfactant one type may be used alone, or two or more types may be used in combination.
  • the amount of the surfactant added is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the natural rubber in the natural rubber latex. When the amount of the surfactant added is not less than the above lower limit, the natural rubber can be easily taken out as a slurry without remarkably agglutinating.
  • Preferred combinations of the coagulant and the surfactant include, for example, a combination of aluminum sulfate and an anionic surfactant such as sodium lauryl sulfate. In this preferred combination, the preferred addition amounts of each are as described above.
  • the drying temperature is preferably 50 to 120 ° C, more preferably 70 to 100 ° C.
  • the drying time is preferably 10 to 48 hours, more preferably 15 to 24 hours.
  • the cyclization step is a step of dissolving natural rubber in a solvent to carry out a cyclization reaction to obtain a cyclized rubber solution.
  • natural rubber is dissolved in a solvent to prepare a natural rubber solution.
  • the solvent is not particularly limited as long as it can dissolve natural rubber, but for example, aromatic hydrocarbons such as toluene, xylene and ethylbenzene; and aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane. Hydrocarbons; examples include alicyclic hydrocarbons such as cyclopentane and cyclohexane. Among these, toluene is preferable from the viewpoint of boiling point.
  • the solvent one type may be used alone, or two or more types may be used in combination.
  • the content of the natural rubber with respect to the total mass of the natural rubber solution is preferably 5 to 60% by mass, more preferably 10 to 40% by mass. Within this preferable range, the viscosity of the natural rubber solution becomes easy to handle.
  • the solvent may be heated from the viewpoint of making it easier to dissolve the natural rubber in the solvent.
  • the temperature at the time of heating is preferably 20 to 120 ° C, more preferably 40 to 100 ° C.
  • a cyclization catalyst is added to the natural rubber solution to carry out a cyclization reaction.
  • Natural rubber is cyclized by the cyclization reaction to become cyclized rubber.
  • the cyclized rubber is obtained in the form of a solution.
  • the cyclization catalyst include sulfuric acid; organic sulfonic acids such as p-toluene sulfonic acid, monofluoromethane sulfonic acid, difluoromethane sulfonic acid, xylene sulfonic acid, and alkylbenzene sulfonic acid; boron trifluoride, boron trichloride, and tetrachloride.
  • Examples thereof include metal halogen compounds such as tin, titanium tetrachloride, aluminum chloride, diethylaluminum monochloride, aluminum bromide, antimony pentachloride, tungsten hexachloride, and iron chloride.
  • metal halogen compounds such as tin, titanium tetrachloride, aluminum chloride, diethylaluminum monochloride, aluminum bromide, antimony pentachloride, tungsten hexachloride, and iron chloride.
  • organic sulfonic acid is preferable, and p-toluenesulfonic acid is more preferable, from the viewpoint of removing the acid catalyst residue.
  • One type of cyclization catalyst may be used alone, or two or more types may be used in combination.
  • the acidic cyclization catalyst is preferably neutralized after the cyclization reaction.
  • the acid catalyst residue produced after neutralization is preferably removed from the cyclized rubber solution.
  • the acidic cyclization catalyst can be neutralized by adding an aqueous solution of an alkali metal carbonate (for example, sodium carbonate) or an alkali metal hydrogen carbonate (for example, sodium hydrogen carbonate) to the cyclized rubber solution and stirring the solution.
  • the neutralized cyclization catalyst is easily dissolved in an aqueous solution.
  • the stirring is stopped, the cyclized rubber solution, which is an organic phase, and the aqueous solution, which is an aqueous phase, are naturally separated from each other, so that the aqueous solution containing the neutralized cyclization catalyst can be easily removed.
  • the amount of the cyclization catalyst added is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the natural rubber in the natural rubber solution. When the amount of the cyclization catalyst added is within the above range, the cyclization rate of the cyclized rubber can be easily adjusted to a desired value.
  • the reaction temperature of the cyclization reaction is preferably 50 to 150 ° C, more preferably 80 to 110 ° C.
  • the reaction time of the cyclization reaction is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
  • Preferred combinations of the solvent constituting the natural rubber solution and the cyclization catalyst include, for example, a combination of an aromatic hydrocarbon such as toluene and an organic sulfonic acid such as p-toluenesulfonic acid.
  • an aromatic hydrocarbon such as toluene
  • an organic sulfonic acid such as p-toluenesulfonic acid.
  • the preferred content of natural rubber, the preferred amount of cyclization catalyst added, the preferred reaction temperature and reaction time of the cyclization reaction are as described above.
  • the suspension step is a step of suspending the cyclized rubber solution in the presence of water and a suspension stabilizer.
  • the suspension stabilizer include cellulosic water-soluble resins (eg, methyl cellulose, hydroxyethyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyacrylic acid salt, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. And so on.
  • the amount of the suspension stabilizer used is preferably 1 to 30 parts by mass, more preferably 10 to 30 parts by mass, based on 100 parts by mass of the cyclized rubber in the cyclized rubber solution. When the amount of the suspension stabilizer used is within the above range, the suspension state can be sufficiently stabilized.
  • a dispersion medium in which a suspension stabilizer is dissolved in water and a cyclized rubber solution are mixed to prepare a suspension, and the obtained suspension is heated and cyclized.
  • the rubbers may be subjected to a cross-linking reaction (suspension cross-linking reaction).
  • the cyclized rubber solution may be concentrated in advance or further diluted with a solvent so that the content of the cyclized rubber is 5 to 30% by mass with respect to the total mass of the cyclized rubber solution.
  • the solvent used for dilution include the solvents exemplified above in the description of the cyclization step.
  • the cyclization rate of the cyclized rubber does not change before and after the suspension cross-linking reaction because a site different from the cyclized site is crosslinked.
  • the reaction temperature of the suspension crosslinking reaction is preferably 40 to 150 ° C, more preferably 60 to 130 ° C.
  • the reaction time of the suspension cross-linking reaction is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
  • a surfactant may be used in combination for the purpose of further stabilizing the suspended state.
  • the surfactant is not particularly limited, and known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used.
  • As the surfactant one type may be used alone, or two or more types may be used in combination.
  • the amount of the surfactant added is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the cyclized rubber in the cyclized rubber solution.
  • the surfactant is preferably added to the dispersion medium.
  • the cyclized rubber contained in the cyclized rubber solution may be suspended while being crosslinked.
  • the solvent resistance of the obtained rubber particles is improved.
  • the cyclized rubber solution may be suspended in the presence of water, a suspension stabilizer and a radical polymerization initiator. Specifically, it was obtained by mixing a dispersion medium in which a suspension stabilizer was dissolved in water and a mixed solution in which a radical polymerization initiator was added to a cyclized rubber solution to prepare a suspension for cross-linking.
  • the cross-linking suspension may be heated and reacted.
  • the reaction temperature for crosslinking is preferably 40 to 150 ° C, more preferably 60 to 130 ° C.
  • the reaction time for crosslinking is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
  • the 10-hour half-life temperature of the radical polymerization initiator is preferably 35 to 150 ° C, more preferably 45 to 130 ° C.
  • the 10-hour half-life temperature of the radical polymerization initiator is at least the above lower limit value, it is possible to suppress the reaction from running out of control and the handling becomes easy.
  • the 10-hour half-life temperature of the radical polymerization initiator is not more than the above upper limit value, it is easy to inactivate the residue of the radical polymerization initiator by heating.
  • radical polymerization initiator examples include benzoyl peroxide (10-hour half-life temperature: 74 ° C.), dilauroyl peroxide (10-hour half-life temperature: 62 ° C.), and t-butylperoxybenzoate (10-hour half-life temperature:: 12 ° C.).
  • -Azobis (2,4-dimethylvaleronitrile) (10-hour half-life temperature: 51 ° C.), 1,1-azobis (cyclohexane-1-carbonitrile) (10-hour half-life temperature: 88 ° C.), and the like.
  • organic peroxides are preferable from the viewpoint of forming cross-linking points by hydrogen extraction, and t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, and t-hexylperoxypivalate are more preferable. ..
  • the radical polymerization initiator may be used alone or in combination of two or more.
  • One or more kinds arbitrarily selected from the above-exemplified group of organic peroxides are preferable, two or more kinds are more preferable, and three or more kinds are further preferable.
  • a polymerization initiator that generates radicals at an early low temperature a polymerization initiator having a low half-life temperature
  • a radical at a late high temperature a radical at a late high temperature.
  • the radical generation of the polymerization initiator (polymerization initiator having a high half-life temperature) that produces the above can be promoted, and the cross-linking reaction can proceed rapidly.
  • the total amount of the radical polymerization initiator added is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the cyclized rubber in the cyclized rubber solution. If the amount of the radical polymerization initiator added is at least the above lower limit value, the cyclized rubber can be sufficiently crosslinked, but even if the above upper limit value is exceeded, the effect of the radical polymerization initiator reaches a plateau, and the cost increases. Is.
  • the solvent removing step is a step of removing the solvent from the suspension after the suspension step to obtain an aqueous dispersion in which the rubber particles are dispersed in water.
  • the rubber particles are obtained in a state of being dispersed in water as an oil component together with a solvent. Therefore, by removing the solvent from the suspension in the solvent removing step, an aqueous dispersion in which the rubber particles are dispersed in water can be obtained.
  • the suspension may be heated.
  • the heating temperature is preferably 70 to 120 ° C, more preferably 80 to 100 ° C.
  • the heating time is preferably 1 to 10 hours, more preferably 2 to 5 hours. It should be noted that the heat treatment in the solvent removing step may cause a small amount of cross-linking between the cyclized rubbers, similar to the suspension cross-linking reaction described above.
  • the cleaning step is a step of solid-liquid separating the aqueous dispersion obtained in the solvent removing step and cleaning the recovered rubber particles with water.
  • the washing method with water is not particularly limited, and examples thereof include a method of suspending the rubber particles in water and then recovering the rubber particles by solid-liquid separation such as filtration or precipitation.
  • the drying step is a step of drying the rubber particles after washing.
  • a heat drying method for example, a heat drying method, an air flow drying method, a vacuum drying method, an infrared drying method, or the like is applied.
  • the drying temperature is preferably 40 to 120 ° C, more preferably 60 to 100 ° C.
  • the drying time is preferably 2 to 48 hours, more preferably 6 to 24 hours.
  • the method for producing rubber particles is not limited to the above-described embodiment.
  • natural rubber latex is used as the natural rubber, but natural rubber in a solid state such as a smoked sheet may be used.
  • natural rubber in a solid state it is preferable to knead the natural rubber before the cyclization step.
  • kneading means adjusting the elasticity and plasticity to a state in which it is easy to process by applying a mechanical shearing force.
  • rubber particles made of uncyclized natural rubber can be produced, for example, as follows. That is, submicron-sized rubber particles can be obtained by modifying the surface of the natural rubber particles contained in the natural rubber latex with a vinyl monomer or the like and then drying the natural rubber latex.
  • the rubber particles of the present invention described above are made of natural rubber, they are made of natural products and have flexibility. Further, according to the method for producing rubber particles of the present invention, particles can be easily formed by cyclizing natural rubber, so that flexible particles can be easily produced using a natural product as a raw material.
  • the rubber particles of the present invention can be used as naturally-derived microbeads used in fillers such as paints, plastics, adhesives, cosmetics, paper coating materials, textile processing materials, writing tools, and markers.
  • the cyclization rate of the cyclized rubber was determined by measuring 1 H-NMR using a nuclear magnetic resonance apparatus. Specifically, 1 H-NMR was measured for the natural rubber before and after the cyclization reaction under the following measurement conditions , and the peak area (S 0 ) of the proton derived from the double bond of the natural rubber before the cyclization reaction was obtained. The peak area (S 1 ) of the proton derived from the double bond of the natural rubber after the cyclization reaction was measured, and the cyclization rate of the cyclized rubber was determined from the following formula (i).
  • Cyclization rate (%) ⁇ 1- (S 1 / S 0 ) ⁇ ⁇ 100 ⁇ ⁇ ⁇ (i) (Measurement conditions) ⁇ Equipment: "JNM-ECP600” manufactured by JEOL Ltd. -Solvent: Chloroform-d 1 ⁇ Concentration: 0.01 g / mL ⁇ Resonance frequency: 600MHz ⁇ Number of integrations: 32 times ⁇ Amount of natural rubber used as measurement sample: 0.02 mg
  • volume average particle diameter of the particles was measured using a laser diffraction type particle size distribution meter (“SALD2100” manufactured by Shimadzu Corporation).
  • the solid matter was recovered by solid-liquid separation using a filter cloth and dried at 80 ° C. for 20 hours to obtain a solid matter of natural rubber (salting out step).
  • the amount of sodium lauryl sulfate added was 1 part by mass and the amount of aluminum sulfate added was 18.7 parts by mass with respect to 100 parts by mass of natural rubber.
  • 120 g of a solid natural rubber and 480 g of toluene were charged in a separable flask equipped with a 2 L stirrer, heated to 100 ° C., and the natural rubber was dissolved in toluene to prepare a natural rubber solution having a concentration of 20% by mass.
  • the content of the cyclized rubber (cyclized natural rubber) is 20% by mass with respect to the total mass of the obtained cyclized rubber solution (however, the added sodium hydrogencarbonate aqueous solution is not taken into consideration), and the content of toluene is. It was 80% by mass.
  • the cyclization rate of the cyclized rubber was 83.5%. When measuring the cyclization rate, a part of the cyclized rubber solution was sampled, the solvent was removed, and the obtained residue was dried and used for the measurement.
  • a cyclized rubber solution was obtained in the same manner as in Production Example 1 except that the amount of p-toluenesulfonic acid added was changed to 3 g.
  • the amount of p-toluenesulfonic acid added was 2.5 parts by mass with respect to 100 parts by mass of natural rubber.
  • the content of the cyclized rubber (circulated natural rubber) was 20% by mass and the content of toluene was 80% by mass with respect to the total mass of the obtained cyclized rubber solution.
  • the cyclization rate of the cyclized rubber was 67.8%.
  • Example 1 600 g of water was charged into a separable flask equipped with a 2 L stirrer, and 15 g of hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium. While stirring the dispersion medium at a rotation speed of 400 rpm of the stirrer, 300 g of the cyclized rubber solution obtained in Production Example 1 was added to prepare a suspension. The suspension was heated to 80 ° C. while continuing stirring, and a suspension crosslinking reaction was carried out at 80 ° C. for 2 hours (suspension step).
  • hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium. While stirring the dispersion medium at a rotation speed of 400 rpm of the stirrer, 300 g of the cycl
  • the amount of hydroxypropylmethylcellulose added was 25 parts by mass with respect to 100 parts by mass of the cyclized rubber.
  • the suspension after the suspension step was heated to 100 ° C. and held at 100 ° C. for 1 hour to remove toluene from the suspension to obtain an aqueous dispersion in which rubber particles were dispersed in water (solvent). Removal step). After cooling the aqueous dispersion to room temperature (20 ° C.), solid-liquid separation was performed, and the recovered rubber particles were washed with water (washing step). The washed rubber particles were dried at 70 ° C. for 20 hours to obtain spherical rubber particles. By electron microscopic observation, it was confirmed that almost all of the obtained rubber particles were spherical. The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
  • Example 2 Spherical as in Example 1 except that the amount of hydroxypropylmethylcellulose added was changed to 9 g (corresponding to 15 parts by mass with respect to 100 parts by mass of cyclized rubber) and the rotation speed of the stirrer was changed to 250 rpm. Rubber particles were obtained. The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
  • Example 3 600 g of water was charged into a separable flask equipped with a 2 L stirrer, and 15 g of hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium.
  • hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium.
  • 1.2 g of t-butylperoxypivalate, 1.2 g of t-butylperoxy-2-ethylhexanoate and t- as radical polymerization initiators were added.
  • a mixed solution was prepared by adding 1.2 g of hexylperoxypivalate.
  • Example 4 Spherical rubber particles were obtained in the same manner as in Example 3 except that 300 g of the cyclized rubber solution obtained in Production Example 2 was used instead of 300 g of the cyclized rubber solution obtained in Production Example 1. The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
  • the rubber particles obtained in each example were superior in flexibility to the cellulose particles obtained in Comparative Example 2.
  • the rubber particles of Examples 3 and 4 using the cyclized rubber crosslinked with a radical polymerization initiator after cyclizing the natural rubber have a high gel content and excellent solvent resistance. rice field.

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Abstract

The rubber particles of the present invention are made of natural rubber and are spherical. The rubber particles preferably have an average particle size of 1-300 μm. A method for producing the rubber particles has a step for dissolving the natural rubber in a solvent to carry out a cyclization reaction and obtain a cyclized rubber solution and a step for suspending the cyclized rubber solution in the presence of water and a suspension stabilizer.

Description

ゴム粒子及びその製造方法Rubber particles and their manufacturing method
　本発明は、ゴム粒子及びその製造方法に関する。本願は、２０２０年６月２４日に、日本に出願された特願２０２０－１０８９４２号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to rubber particles and a method for producing the same. This application claims priority based on Japanese Patent Application No. 2020-108942 filed in Japan on June 24, 2020, the contents of which are incorporated herein by reference.
　従来、アクリルビーズ、ポリスチレンビーズ、ポリウレタンビーズ等の粒子が、塗料、プラスチック、粘着剤、化粧品等の種々の製品に使用されている。
　近年、海洋環境におけるマイクロプラスチックの問題が大きく取り上げられているため、天然物を原料とするマイクロメートルスケールの粒子のニーズが高まっている。 Conventionally, particles such as acrylic beads, polystyrene beads, and polyurethane beads have been used in various products such as paints, plastics, adhesives, and cosmetics.
In recent years, the issue of microplastics in the marine environment has been widely addressed, and the need for micrometer-scale particles made from natural products is increasing.
　天然物を原料とするマイクロメートルスケールの粒子として、例えば特許文献１にはセルロースエステルを用い、下記の（１）、（２）の方法で製造したセルロース球状粒子が開示されている。
（１）：セルロースエステルの有機溶媒中の溶液を原液として、乾式紡糸法により製造したセルロースエステルのフィラメントを切断してチップとなし、チップを媒体中で加熱溶融することによりセルロースエステルの球状粒子を形成し、次いでこれを鹸化する方法。
（２）：セルロースエステルの有機溶媒中の溶液を原液として、原液をその有機溶媒に溶解しないか又はわずかしか溶解しない媒体中に懸濁させ、懸濁粒子を含有する媒体を加熱して有機溶媒を蒸発させることにより、セルロースエステルの球状粒子を形成し、次いでこれを鹸化する方法。 As micrometer-scale particles made from natural products, for example, Patent Document 1 discloses cellulose spherical particles produced by the following methods (1) and (2) using cellulose ester.
(1): Using a solution of cellulose ester in an organic solvent as a stock solution, a filament of cellulose ester produced by a dry spinning method is cut to form a chip, and the chip is heated and melted in a medium to form spherical particles of cellulose ester. A method of forming and then saponifying it.
(2): Using a solution of cellulose ester in an organic solvent as a stock solution, suspend the stock solution in a medium that does not dissolve or hardly dissolve in the organic solvent, and heat the medium containing the suspended particles to heat the organic solvent. A method of forming spherical particles of a cellulose ester by evaporating the above, and then saponifying the spherical particles.
特公昭５５－４０６１８号公報Special Publication No. 55-40618
　しかし、セルロースは柔軟性に劣る傾向があり、セルロースを原料として製造したセルロース粒子も硬くなりやすい。硬い粒子を例えば化粧品に用いると、感触が悪くなる場合がある。
　本発明は、天然物を原料とし、柔軟性を有する粒子と、天然物を原料とし、柔軟性を有する粒子を簡便に製造する方法を提供することを目的とする。 However, cellulose tends to be inferior in flexibility, and cellulose particles produced from cellulose tend to become hard. When hard particles are used, for example, in cosmetics, the feel may be poor.
An object of the present invention is to provide a method for easily producing flexible particles using a natural product as a raw material and particles having flexibility using a natural product as a raw material.
　本発明者らは鋭意検討した結果、柔らかい特性を有する天然ゴムに着目したが、天然ゴムはタック（表面の粘着性）が強い傾向にあり、粒子化が困難となる場合があることが判明した。
　そこで、天然ゴムの粒子化についてさらに検討した結果、天然ゴムを環化させることで容易に粒子化できることを見出し、本発明を完成するに至った。 As a result of diligent studies, the present inventors focused on natural rubber having soft properties, but found that natural rubber tends to have a strong tack (adhesiveness on the surface), which may make it difficult to form particles. ..
Therefore, as a result of further study on the particle formation of natural rubber, it was found that the particle formation can be easily performed by cyclizing the natural rubber, and the present invention has been completed.
　すなわち、本発明は以下の態様を有する。
［１］　天然ゴムからなり、球状である、ゴム粒子。
［２］　平均粒子径が１～３００μｍである、前記［１］のゴム粒子。
［３］　前記天然ゴムが、環化された環化ゴムである、前記［１］又は［２］のゴム粒子。
［４］　前記環化ゴムの環化率が６０～９０％である、前記［３］のゴム粒子。
［５］　前記［１］～［４］のいずれかのゴム粒子の製造方法であって、天然ゴムを溶剤に溶解して環化反応を行い、環化ゴム溶液を得る工程と、水及び懸濁安定剤の存在下で、前記環化ゴム溶液を懸濁させる工程と、を有する、ゴム粒子の製造方法。
［６］　前記環化ゴム溶液を撹拌しながら４０～１５０℃に加熱する、［５］のゴム粒子の製造方法。
［７］　前記環化ゴム溶液にラジカル重合開始剤を添加する、［５］又は［６］のゴム粒子の製造方法。ここで、前記ラジカル重合開始剤は、有機過酸化物の１種以上又はアゾ化合物の１種以上を含むことが好ましい。前記有機過酸化物は、ｔ－ブチルパーオキシピバレート、ｔ－ブチルパーオキシ－２－エチルヘキサノエート、及びｔ－ヘキシルパーオキシピバレートから任意に選択される１種以上を含むことが好ましい。
［８］　前記溶剤が芳香族炭化水素を含む、［５］～［７］のいずれかのゴム粒子の製造方法。ここで、前記芳香族炭化水素はトルエン、キシレン及びエチルベンゼンから任意に選択される１種以上を含むことが好ましい。
［９］　前記溶剤に環化触媒として、硫酸、有機スルホン酸又は金属ハロゲン化合物を添加する、［５］～［８］のいずれかのゴム粒子の製造方法。ここで、前記環化触媒は有機スルホン酸を含むことが好ましく、ｐ－トルエンスルホン酸、モノフルオロメタンスルホン酸、ジフルオロメタンスルホン酸、キシレンスルホン酸、及びアルキルベンゼンスルホン酸から任意に選択される１種以上を含むことがより好ましい。
［１０］　前記環化反応の後、前記環化触媒を中和する、［９］のゴム粒子の製造方法。前記中和は、アルカリ金属炭酸塩又はアルカリ金属炭酸水素塩の水溶液を前記環化ゴム溶液に添加することにより行うことが好ましい。前記水溶液は中和後に前記環化ゴム溶液から分離することが好ましい。
［１１］　前記懸濁安定剤がセルロース系水溶性樹脂、ポリビニルアルコール、ポリアクリル酸塩、ポリエチレングリコール、ポリビニルピロリドン、ポリアクリルアミド、及び第３リン酸塩類から任意に選択される１種以上を含む、［５］～［１０］のいずれかのゴム粒子の製造方法。ここで、前記懸濁安定剤はセルロース系水溶性樹脂を含むことが好ましく、メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルメチルセルロース、及びカルボキシメチルセルロースから任意に選択される１種以上を含むことがより好ましい。
［１２］　前記環化ゴム溶液に含まれる環化ゴムの環化率が６０～９０％である、［５］～［１１］のいずれかのゴム粒子の製造方法。
［１３］　前記天然ゴムが、天然ゴムラテックスに凝固剤を添加し、前記天然ゴムラテックスに含まれる分散媒から分離して得られたものである、［５］～［１２］のいずれかのゴム粒子の製造方法。ここで、前記凝固剤は、硫酸アルミニウム、塩化ナトリウム、及び塩化カルシウムから任意に選択される１種以上を含むことが好ましい。
［１４］　前記天然ゴムラテックスにさらに界面活性剤を添加した後で、前記天然ゴムを前記分散媒から分離して得る、［１３］のゴム粒子の製造方法。ここで、界面活性剤はアニオン系界面活性剤を含むことが好ましく、ラウリル硫酸ナトリウムを含むことがより好ましい。 That is, the present invention has the following aspects.
[1] Rubber particles made of natural rubber and spherical.
[2] The rubber particles of the above [1] having an average particle diameter of 1 to 300 μm.
[3] The rubber particles of the above [1] or [2], wherein the natural rubber is a cyclized rubber.
[4] The rubber particles of the above [3], wherein the cyclization rate of the cyclized rubber is 60 to 90%.
[5] The method for producing rubber particles according to any one of [1] to [4], wherein a natural rubber is dissolved in a solvent to carry out a cyclization reaction to obtain a cyclized rubber solution, and water and a suspension. A method for producing rubber particles, comprising a step of suspending the cyclized rubber solution in the presence of a turbidity stabilizer.
[6] The method for producing rubber particles according to [5], wherein the cyclized rubber solution is heated to 40 to 150 ° C. while stirring.
[7] The method for producing rubber particles according to [5] or [6], wherein a radical polymerization initiator is added to the cyclized rubber solution. Here, the radical polymerization initiator preferably contains one or more organic peroxides or one or more azo compounds. The organic peroxide preferably contains one or more selected arbitrarily from t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, and t-hexylperoxypivalate. ..
[8] The method for producing rubber particles according to any one of [5] to [7], wherein the solvent contains aromatic hydrocarbons. Here, it is preferable that the aromatic hydrocarbon contains at least one arbitrarily selected from toluene, xylene and ethylbenzene.
[9] The method for producing rubber particles according to any one of [5] to [8], wherein sulfuric acid, an organic sulfonic acid or a metal halogen compound is added to the solvent as a cyclization catalyst. Here, the cyclization catalyst preferably contains organic sulfonic acid, and is arbitrarily selected from p-toluene sulfonic acid, monofluoromethane sulfonic acid, difluoromethane sulfonic acid, xylene sulfonic acid, and alkylbenzene sulfonic acid. It is more preferable to include the above.
[10] The method for producing rubber particles according to [9], which neutralizes the cyclization catalyst after the cyclization reaction. The neutralization is preferably carried out by adding an aqueous solution of an alkali metal carbonate or an alkali metal hydrogen carbonate to the cyclized rubber solution. It is preferable that the aqueous solution is separated from the cyclized rubber solution after neutralization.
[11] The suspension stabilizer contains at least one selected arbitrarily from a cellulosic water-soluble resin, polyvinyl alcohol, polyacrylate, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and a tertiary phosphate. A method for producing rubber particles according to any one of [5] to [10]. Here, the suspension stabilizer preferably contains a cellulosic water-soluble resin, and more preferably contains one or more arbitrarily selected from methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose.
[12] The method for producing rubber particles according to any one of [5] to [11], wherein the cyclization rate of the cyclized rubber contained in the cyclized rubber solution is 60 to 90%.
[13] The rubber according to any one of [5] to [12], which is obtained by adding a coagulant to the natural rubber latex and separating the natural rubber from the dispersion medium contained in the natural rubber latex. How to make particles. Here, the coagulant preferably contains one or more arbitrarily selected from aluminum sulfate, sodium chloride, and calcium chloride.
[14] The method for producing rubber particles according to [13], wherein the natural rubber is separated from the dispersion medium after a surfactant is further added to the natural rubber latex. Here, the surfactant preferably contains an anionic surfactant, and more preferably contains sodium lauryl sulfate.
　本発明によれば、天然物を原料とし、柔軟性を有する粒子と、天然物を原料とし、柔軟性を有する粒子を簡便に製造する方法を提供できる。 According to the present invention, it is possible to provide a method for easily producing a particle having flexibility using a natural product as a raw material and a particle having flexibility using a natural product as a raw material.
［ゴム粒子］
　本発明の第一態様のゴム粒子は、天然ゴムから形成されたものである。天然ゴムは、一般に、シス－１，４－ポリイソプレンを主骨格とする重合体が主成分のゴムである。天然ゴムは、例えばパラゴムノキ等の植物の樹液から得られる。樹液には、ゴム成分の他、水や非ゴム成分（例えばタンパク質、脂肪酸、無機塩類等の不純物）が含まれている。天然ゴムは本発明の効果を損なわない範囲内であれば非ゴム成分を含んでいてもよい。また、天然ゴムとして、樹液を公知の精製・固液分離の手法により精製した天然ゴムラテックスを用いてもよいし、樹液を固化したスモークドシート等を用いてもよい。
　本態様のゴム粒子の製造時に、水等の分散媒に天然ゴムが分散された天然ゴムラテックス（天然ゴムの乳濁液）を用いる場合、天然ゴムラテックスの総質量に対するゴム成分（すなわち、天然ゴム）の含有量は１０～８０質量％が好ましく、２０～７０質量％がより好ましく、３０～６０質量％がさらに好ましい。
　上記範囲の下限値以上であると、目的のゴム粒子の収量が多くなるので好ましい。上記範囲の上限値以下であると、乳濁液中の天然ゴムの分散性が高くなるので好ましい。
　なお、本態様のゴム粒子を形成する天然ゴムは、植物から採取されたものに限らず、イソプレン分子を公知方法で化学的に重合させて得た、いわゆる人工天然ゴムであってもよい。
　本態様のゴム粒子を形成する天然ゴムの重量平均分子量として、例えば１万～１００万が挙げられる。 [Rubber particles]
The rubber particles of the first aspect of the present invention are formed from natural rubber. Natural rubber is generally a rubber whose main component is a polymer having cis-1,4-polyisoprene as a main skeleton. Natural rubber is obtained from the sap of plants such as Hevea brasiliensis. In addition to the rubber component, the sap contains water and non-rubber components (for example, impurities such as proteins, fatty acids, and inorganic salts). The natural rubber may contain a non-rubber component as long as the effect of the present invention is not impaired. Further, as the natural rubber, a natural rubber latex obtained by purifying the sap by a known purification / solid-liquid separation method may be used, or a smoked sheet obtained by solidifying the sap may be used.
When a natural rubber latex (emulsion liquid of natural rubber) in which natural rubber is dispersed in a dispersion medium such as water is used in the production of the rubber particles of this embodiment, the rubber component with respect to the total mass of the natural rubber latex (that is, natural rubber). ) Is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and even more preferably 30 to 60% by mass.
When it is at least the lower limit of the above range, the yield of the target rubber particles increases, which is preferable. When it is not more than the upper limit of the above range, the dispersibility of the natural rubber in the emulsion is high, which is preferable.
The natural rubber forming the rubber particles of this embodiment is not limited to the one collected from a plant, and may be a so-called artificial natural rubber obtained by chemically polymerizing an isoprene molecule by a known method.
Examples of the weight average molecular weight of the natural rubber forming the rubber particles of this embodiment include 10,000 to 1,000,000.
　本態様のゴム粒子が含む天然ゴムは、環化された環化ゴムであることが好ましい。天然ゴムが環化ゴムであれば、ゴム粒子の耐薬品性、耐熱性及び耐候性が高まる。加えて、ポリオレフィンなどの非極性ポリマーや、ポリエステル、ポリウレタン、アルキッド樹脂などの極性ポリマー、鉄などの金属等との接着性も高まる。
　環化ゴムは、環化触媒を用いて天然ゴムを環化反応することで得られる。環化反応については、詳しくは後述する。
　なお、本明細書において、環化されて環化ゴムとなった天然ゴムを「環化天然ゴム」ということがある。 The natural rubber contained in the rubber particles of this embodiment is preferably a cyclized rubber. If the natural rubber is cyclized rubber, the chemical resistance, heat resistance and weather resistance of the rubber particles are enhanced. In addition, the adhesiveness to non-polar polymers such as polyolefin, polar polymers such as polyester, polyurethane and alkyd resin, and metals such as iron is enhanced.
The cyclized rubber is obtained by cyclizing a natural rubber using a cyclization catalyst. The cyclization reaction will be described in detail later.
In the present specification, the natural rubber that has been cyclized to become cyclized rubber may be referred to as "cyclized natural rubber".
　環化ゴムの環化率は６０～９０％が好ましく、６５～８５％がより好ましい。環化ゴムの環化率が上記下限値以上であれば、天然ゴムが有するタックの影響を受けることなく、容易に粒子化できる。環化ゴムの環化率が上記上限値以下であれば、残存する二重結合により、架橋率の向上が見込める。
　環化ゴムの環化率は、環化触媒の使用量を調節することにより調整でき、環化触媒の使用量が多くなるほど、環化率は高くなる傾向にある。
　本発明において、「環化率」とは、環化ゴム中における環化部の割合を意味し、１Ｈ－ＮＭＲにより求められる。具体的には、環化反応前の天然ゴムの二重結合由来のプロトンのピーク面積（Ｓ０）と、環化反応後の天然ゴム（環化ゴム）の二重結合由来のプロトンのピーク面積（Ｓ１）をそれぞれ測定し、下記式（ｉ）より環化ゴムの環化率を求める。
　環化率（％）＝｛１－（Ｓ１／Ｓ０）｝×１００　　・・・（ｉ） The cyclization rate of the cyclized rubber is preferably 60 to 90%, more preferably 65 to 85%. When the cyclization rate of the cyclized rubber is at least the above lower limit value, it can be easily made into particles without being affected by the tack of the natural rubber. If the cyclization rate of the cyclized rubber is not more than the above upper limit value, the cross-linking rate can be expected to be improved by the remaining double bond.
The cyclization rate of the cyclized rubber can be adjusted by adjusting the amount of the cyclization catalyst used, and the cyclization rate tends to increase as the amount of the cyclization catalyst used increases.
In the present invention, the "cyclization rate" means the ratio of the cyclized portion in the cyclized rubber, and is determined by 1 H-NMR. Specifically, the peak area of protons derived from the double bond of natural rubber before the cyclization reaction (S 0 ) and the peak area of protons derived from the double bond of natural rubber (cyclized rubber) after the cyclization reaction. (S 1 ) is measured respectively, and the cyclization rate of the cyclized rubber is obtained from the following formula (i).
Cyclization rate (%) = {1- (S 1 / S 0 )} × 100 ... (i)
　本態様のゴム粒子の形状は球状であってもよいし、球状でなくてもよいが、球状であることが好ましい。ゴム粒子が球状であると、個々のゴム粒子の柔軟性を高めることができ、ゴム粒子同士が接触した際の滑り性を高めことができ、ゴム粒子の集合体（全体）の柔軟性を高めることができる。本発明において、「球状」とは真球状に限られず、楕円体のような球体に近い形状や、表面に凹凸がある球体等も含まれる。一方、板状、薄片状、棒状等の形状は球状には該当しない。ゴム粒子の形状は光学顕微鏡又は電子顕微鏡で観察することにより判定される。
　なお、球状のゴム粒子と、非球状のゴム粒子とが混在しているような場合も、ゴム粒子の集合体（全体）として本発明の要件を満たし、本発明の効果が得られる限り、本発明の範囲から排除されるものではない。この場合、非球状のゴム粒子の量は、本態様のゴム粒子の集合体の総体積に対して、好ましくは１０体積％以下であり、より好ましくは５体積％以下であり、さらに好ましくは１体積％以下である。 The shape of the rubber particles in this embodiment may be spherical or not spherical, but is preferably spherical. When the rubber particles are spherical, the flexibility of the individual rubber particles can be increased, the slipperiness when the rubber particles come into contact with each other can be increased, and the flexibility of the aggregate (whole) of the rubber particles can be increased. be able to. In the present invention, the "spherical shape" is not limited to a true spherical shape, but also includes a shape close to a sphere such as an ellipsoid, a sphere having an uneven surface, and the like. On the other hand, shapes such as plate-shaped, flaky-shaped, and rod-shaped do not correspond to spherical shapes. The shape of the rubber particles is determined by observing with an optical microscope or an electron microscope.
Even when spherical rubber particles and non-spherical rubber particles are mixed, as long as the requirements of the present invention are satisfied as an aggregate (whole) of the rubber particles and the effect of the present invention is obtained, the present invention It is not excluded from the scope of the invention. In this case, the amount of the non-spherical rubber particles is preferably 10% by volume or less, more preferably 5% by volume or less, still more preferably 1 with respect to the total volume of the aggregates of the rubber particles of this embodiment. It is less than% by volume.
　本態様のゴム粒子の平均粒子径は１μｍ～５００μｍが好ましく、１μｍ～３００μｍがより好ましく、１μｍ～２００μｍがさらに好ましく、１μｍ～１８０μｍが特に好ましい。特に、ゴム粒子の平均粒子径が１μｍ～３００μｍであれば、ゴム粒子を化粧品に好適に使用できる。
　本発明において、「平均粒子径」は、レーザ回折式粒度分布計で測定した体積基準での累積分布の５０％に相当する粒子径（体積平均粒子径）である。ここで、体積平均粒子径はメジアン径（ｄ５０）である。 The average particle size of the rubber particles of this embodiment is preferably 1 μm to 500 μm, more preferably 1 μm to 300 μm, further preferably 1 μm to 200 μm, and particularly preferably 1 μm to 180 μm. In particular, when the average particle size of the rubber particles is 1 μm to 300 μm, the rubber particles can be suitably used for cosmetics.
In the present invention, the "average particle size" is a particle size (volume average particle size) corresponding to 50% of the cumulative distribution on a volume basis measured by a laser diffraction type particle size distribution meter. Here, the volume average particle diameter is the median diameter (d50).
　本態様のゴム粒子は、天然ゴム以外の成分を実質的に含まないことが好ましい。ここで、「実質的に含まない」とは、製造上、不可避的に混入した成分以外の成分を含まないことを意味する。具体的には、ゴム粒子の総質量に対する天然ゴムの含有量は、９９質量％以上が好ましく、９９．５質量％以上がより好ましく、９９．９質量％以上がさらに好ましく、１００質量％であることが最も好ましい。ここで、植物に由来する天然ゴムが含み得る非ゴム成分は、「天然ゴム以外の成分」に該当しない。
　本態様のゴム粒子の総質量に対するシス－１，４－ポリイソプレン（環化したものを含む）の含有量は、９５質量％以上が好ましく、９８質量％以上がより好ましく、９９質量％以上がさらに好ましく、９９．５質量％以上が特に好ましく、９９．９質量％以上が最も好ましい。 It is preferable that the rubber particles of this embodiment substantially do not contain components other than natural rubber. Here, "substantially free" means that the component other than the component unavoidably mixed in the production is not contained. Specifically, the content of natural rubber with respect to the total mass of the rubber particles is preferably 99% by mass or more, more preferably 99.5% by mass or more, further preferably 99.9% by mass or more, and 100% by mass. Is most preferable. Here, the non-rubber component that can be contained in natural rubber derived from a plant does not fall under "components other than natural rubber".
The content of cis-1,4-polyisoprene (including cyclized ones) with respect to the total mass of the rubber particles of this embodiment is preferably 95% by mass or more, more preferably 98% by mass or more, and 99% by mass or more. More preferably, 99.5% by mass or more is particularly preferable, and 99.9% by mass or more is most preferable.
＜ゴム粒子の製造方法＞
　以下、本発明の第二態様の「ゴム粒子の製造方法」の実施形態の一例について説明する。
　本実施形態のゴム粒子の製造方法では、天然ゴムを溶剤に溶解し、環化反応を行って得られた環化ゴム溶液を水及び懸濁安定剤の存在下で懸濁させて、ゴム粒子を得る。
　すなわち、本実施形態のゴム粒子の製造方法は、天然ゴムを溶剤に溶解して環化反応を行い、環化ゴム溶液を得る工程（環化工程）と、水及び懸濁安定剤の存在下で、環化ゴム溶液を懸濁させる工程（懸濁工程）とを有する。
　また、本実施形態のゴム粒子の製造方法は、懸濁工程の後、懸濁液から溶剤を除去してゴム粒子が水に分散した水性分散液を得る工程（溶剤除去工程）と、溶剤除去工程で得られた水性分散液を固液分離し、回収したゴム粒子を水で洗浄する工程（洗浄工程）と、洗浄後のゴム粒子を乾燥する工程（乾燥工程）を有してもよい。
　なお、環化工程は、天然ゴムが溶剤に溶解したゴム溶液の状態で行われるが、このとき、ゴム溶液中の水分は少ないほど好ましい。よって、天然ゴムとして天然ゴムラテックスを用いる場合は、環化工程の前に天然ゴムラテックスを塩析により凝固させ、天然ゴムを固形物の状態で回収しておくことが好ましい（塩析工程）。 <Manufacturing method of rubber particles>
Hereinafter, an example of an embodiment of the "method for producing rubber particles" according to the second aspect of the present invention will be described.
In the method for producing rubber particles of the present embodiment, natural rubber is dissolved in a solvent, and the cyclized rubber solution obtained by performing a cyclization reaction is suspended in the presence of water and a suspension stabilizer to form the rubber particles. To get.
That is, the method for producing rubber particles of the present embodiment includes a step of dissolving natural rubber in a solvent and performing a cyclization reaction to obtain a cyclized rubber solution (cyclization step), and in the presence of water and a suspension stabilizer. It has a step of suspending the cyclized rubber solution (suspension step).
Further, in the method for producing rubber particles of the present embodiment, after the suspension step, a step of removing the solvent from the suspension to obtain an aqueous dispersion in which the rubber particles are dispersed in water (solvent removal step) and a solvent removal step are performed. It may have a step of solid-liquid separating the aqueous dispersion obtained in the step and washing the recovered rubber particles with water (washing step) and a step of drying the washed rubber particles (drying step).
The cyclization step is carried out in the state of a rubber solution in which natural rubber is dissolved in a solvent. At this time, it is preferable that the water content in the rubber solution is small. Therefore, when natural rubber latex is used as the natural rubber, it is preferable to solidify the natural rubber latex by salting out before the cyclization step and recover the natural rubber in a solid state (salting out step).
（塩析工程）
　塩析工程は、天然ゴムラテックスを塩析し、水等の分散媒から天然ゴムを分離させる工程である。
　塩析工程では、凝固剤を用いて天然ゴムラテックスを塩析により凝固させた後、固液分離により固形物を回収し、乾燥させて天然ゴムの固形物を得る。
　凝固剤としては、例えば硫酸アルミニウム、塩化ナトリウム、塩化カルシウムなどが挙げられる。
　凝固剤は、１種を単独で用いてもよく、２種以上を併用してもよい。
　凝固剤の添加量は、天然ゴムラテックス中の天然ゴム１００質量部に対して、５～２００質量部が好ましく、１０～１５０質量部がより好ましい。凝固剤の添加量が、上記下限値以上であれば天然ゴムラテックスを充分に塩析できるが、上記上限値を超えても凝固剤の効果は頭打ちになるため、コストが高くなるばかりである。 (Salting out process)
The salting out step is a step of salting out the natural rubber latex and separating the natural rubber from a dispersion medium such as water.
In the salting out step, a natural rubber latex is coagulated by salting out using a coagulant, and then the solid material is recovered by solid-liquid separation and dried to obtain a solid material of natural rubber.
Examples of the coagulant include aluminum sulfate, sodium chloride, calcium chloride and the like.
As the coagulant, one type may be used alone, or two or more types may be used in combination.
The amount of the coagulant added is preferably 5 to 200 parts by mass, more preferably 10 to 150 parts by mass with respect to 100 parts by mass of the natural rubber in the natural rubber latex. If the amount of the coagulant added is not less than the above lower limit, the natural rubber latex can be sufficiently salted out, but even if the amount exceeds the above upper limit, the effect of the coagulant reaches a plateau, and the cost is only increased.
　塩析は、界面活性剤の存在下で行ってもよい。
　界面活性剤としては特に制限されず、公知のアニオン系界面活性剤、カチオン系界面活性剤、ノニオン系界面活性剤、両性界面活性剤などを用いることができる。
　界面活性剤は、１種を単独で用いてもよく、２種以上を併用してもよい。
　界面活性剤の添加量は、天然ゴムラテックス中の天然ゴム１００質量部に対して、０.５～１０質量部が好ましく、１～５質量部がより好ましい。界面活性剤の添加量が、上記下限値以上であれば天然ゴムが著しく凝集することなくスラリーとして容易に取り出すことができる。界面活性剤の添加量が、上記上限値以下であればコストを抑えることができる。
　凝固剤と界面活性剤の好ましい組み合わせとしては、例えば、硫酸アルミニウムとラウリル硫酸ナトリウム等のアニオン系界面活性剤との組み合わせが挙げられる。この好ましい組み合わせにおいて、それぞれの好ましい添加量は、上述の通りである。 Salting out may be performed in the presence of a detergent.
The surfactant is not particularly limited, and known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used.
As the surfactant, one type may be used alone, or two or more types may be used in combination.
The amount of the surfactant added is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, based on 100 parts by mass of the natural rubber in the natural rubber latex. When the amount of the surfactant added is not less than the above lower limit, the natural rubber can be easily taken out as a slurry without remarkably agglutinating. If the amount of the surfactant added is not more than the above upper limit, the cost can be suppressed.
Preferred combinations of the coagulant and the surfactant include, for example, a combination of aluminum sulfate and an anionic surfactant such as sodium lauryl sulfate. In this preferred combination, the preferred addition amounts of each are as described above.
　乾燥温度は５０～１２０℃が好ましく、７０～１００℃がより好ましい。
　乾燥時間は１０～４８時間が好ましく、１５～２４時間がより好ましい。 The drying temperature is preferably 50 to 120 ° C, more preferably 70 to 100 ° C.
The drying time is preferably 10 to 48 hours, more preferably 15 to 24 hours.
（環化工程）
　環化工程は、天然ゴムを溶剤に溶解して環化反応を行い、環化ゴム溶液を得る工程である。
　環化工程では、まず、天然ゴムを溶剤に溶解させて天然ゴム溶液を調製する。
　溶剤としては、天然ゴムを溶解できるものであれば特に限定されないが、例えばトルエン、キシレン、エチルベンゼン等の芳香族炭化水素；ｎ－ペンタン、ｎ－ヘキサン、ｎ－ヘプタン、ｎ－オクタン等の脂肪族炭化水素；シクロペンタン、シクロヘキサン等の脂環族炭化水素などが挙げられる。これらの中でも、沸点の観点からトルエンが好ましい。
　溶剤は、１種を単独で用いてもよく、２種以上を併用してもよい。 (Cyclation process)
The cyclization step is a step of dissolving natural rubber in a solvent to carry out a cyclization reaction to obtain a cyclized rubber solution.
In the cyclization step, first, natural rubber is dissolved in a solvent to prepare a natural rubber solution.
The solvent is not particularly limited as long as it can dissolve natural rubber, but for example, aromatic hydrocarbons such as toluene, xylene and ethylbenzene; and aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane. Hydrocarbons; examples include alicyclic hydrocarbons such as cyclopentane and cyclohexane. Among these, toluene is preferable from the viewpoint of boiling point.
As the solvent, one type may be used alone, or two or more types may be used in combination.
　天然ゴム溶液の総質量に対する天然ゴムの含有量は、５～６０質量％が好ましく、１０～４０質量％がより好ましい。この好ましい範囲であると天然ゴム溶液の粘度が扱いやすい程度になる。
　天然ゴム溶液を調製する際は、天然ゴムを溶剤に溶解させやすくする観点から、溶剤を加温してもよい。加温する際の温度は、２０～１２０℃が好ましく、４０～１００℃がより好ましい。 The content of the natural rubber with respect to the total mass of the natural rubber solution is preferably 5 to 60% by mass, more preferably 10 to 40% by mass. Within this preferable range, the viscosity of the natural rubber solution becomes easy to handle.
When preparing the natural rubber solution, the solvent may be heated from the viewpoint of making it easier to dissolve the natural rubber in the solvent. The temperature at the time of heating is preferably 20 to 120 ° C, more preferably 40 to 100 ° C.
　次いで、天然ゴム溶液に環化触媒を添加し、環化反応を行う。環化反応により天然ゴムが環化されて環化ゴムとなる。環化ゴムは溶液の状態で得られる。
　環化触媒としては、例えば硫酸；ｐ－トルエンスルホン酸、モノフルオロメタンスルホン酸、ジフルオロメタンスルホン酸、キシレンスルホン酸、アルキルベンゼンスルホン酸等の有機スルホン酸；三フッ化ホウ素、三塩化ホウ素、四塩化スズ、四塩化チタン、塩化アルミニウム、ジエチルアルミニウムモノクロリド、臭化アルミニウム、五塩化アンチモン、六塩化タングステン、塩化鉄等の金属ハロゲン化合物などが挙げられる。これらの中でも、酸触媒残渣の除去の観点から有機スルホン酸が好ましく、ｐ－トルエンスルホン酸がより好ましい。
　環化触媒は、１種を単独で用いてもよく、２種以上を併用してもよい。
　酸性の環化触媒は環化反応の後で中和されることが好ましい。中和後に生成した酸触媒残渣は環化ゴム溶液から除去されることが好ましい。アルカリ金属炭酸塩（例えば炭酸ナトリウム）又はアルカリ金属炭酸水素塩（例えば炭酸水素ナトリウム）の水溶液を環化ゴム溶液に添加し、攪拌することにより、酸性の環化触媒を中和することができる。中和された環化触媒は水溶液に溶解し易い。上記の攪拌を停止すると、有機相である環化ゴム溶液と、水相である前記水溶液とは自然に分離するので、中和された環化触媒を含む水溶液を容易に除去することができる。 Next, a cyclization catalyst is added to the natural rubber solution to carry out a cyclization reaction. Natural rubber is cyclized by the cyclization reaction to become cyclized rubber. The cyclized rubber is obtained in the form of a solution.
Examples of the cyclization catalyst include sulfuric acid; organic sulfonic acids such as p-toluene sulfonic acid, monofluoromethane sulfonic acid, difluoromethane sulfonic acid, xylene sulfonic acid, and alkylbenzene sulfonic acid; boron trifluoride, boron trichloride, and tetrachloride. Examples thereof include metal halogen compounds such as tin, titanium tetrachloride, aluminum chloride, diethylaluminum monochloride, aluminum bromide, antimony pentachloride, tungsten hexachloride, and iron chloride. Among these, organic sulfonic acid is preferable, and p-toluenesulfonic acid is more preferable, from the viewpoint of removing the acid catalyst residue.
One type of cyclization catalyst may be used alone, or two or more types may be used in combination.
The acidic cyclization catalyst is preferably neutralized after the cyclization reaction. The acid catalyst residue produced after neutralization is preferably removed from the cyclized rubber solution. The acidic cyclization catalyst can be neutralized by adding an aqueous solution of an alkali metal carbonate (for example, sodium carbonate) or an alkali metal hydrogen carbonate (for example, sodium hydrogen carbonate) to the cyclized rubber solution and stirring the solution. The neutralized cyclization catalyst is easily dissolved in an aqueous solution. When the stirring is stopped, the cyclized rubber solution, which is an organic phase, and the aqueous solution, which is an aqueous phase, are naturally separated from each other, so that the aqueous solution containing the neutralized cyclization catalyst can be easily removed.
　環化触媒の添加量は、天然ゴム溶液中の天然ゴム１００質量部に対して、０．５～３０質量部が好ましく、１～２０質量部がより好ましい。環化触媒の添加量が上記範囲内であれば、環化ゴムの環化率を所望の値に調節しやすい。
　環化反応の反応温度は、５０～１５０℃が好ましく、８０～１１０℃がより好ましい。環化反応の反応時間は、０．５～１０時間が好ましく、２～５時間がより好ましい。
　天然ゴム溶液を構成する溶剤と環化触媒の好ましい組み合わせとしては、例えば、トルエン等の芳香族炭化水素とｐ－トルエンスルホン酸等の有機スルホン酸との組み合わせが挙げられる。この好ましい組み合わせにおいて、天然ゴムの好ましい含有量、環化触媒の好ましい添加量、環化反応の好ましい反応温度及び反応時間は、上述の通りである。 The amount of the cyclization catalyst added is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the natural rubber in the natural rubber solution. When the amount of the cyclization catalyst added is within the above range, the cyclization rate of the cyclized rubber can be easily adjusted to a desired value.
The reaction temperature of the cyclization reaction is preferably 50 to 150 ° C, more preferably 80 to 110 ° C. The reaction time of the cyclization reaction is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
Preferred combinations of the solvent constituting the natural rubber solution and the cyclization catalyst include, for example, a combination of an aromatic hydrocarbon such as toluene and an organic sulfonic acid such as p-toluenesulfonic acid. In this preferred combination, the preferred content of natural rubber, the preferred amount of cyclization catalyst added, the preferred reaction temperature and reaction time of the cyclization reaction are as described above.
（懸濁工程）
　懸濁工程は、水及び懸濁安定剤の存在下で、環化ゴム溶液を懸濁させる工程である。環化ゴム溶液を懸濁させることで、ゴム粒子が溶剤と共に油分として水中に分散した状態で得られる。
　懸濁安定剤としては、セルロース系水溶性樹脂（例えばメチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルメチルセルロース、カルボキシメチルセルロース等）、ポリビニルアルコール、ポリアクリル酸塩、ポリエチレングリコール、ポリビニルピロリドン、ポリアクリルアミド、第３リン酸塩類などが挙げられる。
　懸濁安定剤は、１種を単独で用いてもよく、２種以上を併用してもよい。
　懸濁安定剤の使用量は、環化ゴム溶液中の環化ゴム１００質量部に対して、１～３０質量部が好ましく、１０～３０質量部がより好ましい。懸濁安定剤の使用量が上記範囲内であれば、懸濁状態を充分に安定化させることができる。 (Suspension process)
The suspension step is a step of suspending the cyclized rubber solution in the presence of water and a suspension stabilizer. By suspending the cyclized rubber solution, the rubber particles can be obtained in a state of being dispersed in water as an oil component together with the solvent.
Examples of the suspension stabilizer include cellulosic water-soluble resins (eg, methyl cellulose, hydroxyethyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyacrylic acid salt, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and tertiary phosphates. And so on.
As the suspension stabilizer, one type may be used alone, or two or more types may be used in combination.
The amount of the suspension stabilizer used is preferably 1 to 30 parts by mass, more preferably 10 to 30 parts by mass, based on 100 parts by mass of the cyclized rubber in the cyclized rubber solution. When the amount of the suspension stabilizer used is within the above range, the suspension state can be sufficiently stabilized.
　懸濁工程では、例えば、水に懸濁安定剤を溶解させた分散媒と、環化ゴム溶液とを混合して懸濁液を調製し、得られた懸濁液を加温して環化ゴム同士を架橋反応（懸濁架橋反応）させてもよい。このとき、環化ゴム溶液の総質量に対する環化ゴムの含有量が５～３０質量％となるように、予め環化ゴム溶液を濃縮したり、溶剤でさらに希釈したりしてもよい。希釈に用いる溶剤としては、環化工程の説明において先に例示した溶剤が挙げられる。なお、環化ゴム同士が架橋する場合、環化した部位とは異なる部位が架橋するので、懸濁架橋反応の前後において、環化ゴムの環化率は変化しない。
　懸濁架橋反応の反応温度は、４０～１５０℃が好ましく、６０～１３０℃がより好ましい。懸濁架橋反応の反応時間は、０．５～１０時間が好ましく、２～５時間がより好ましい。 In the suspension step, for example, a dispersion medium in which a suspension stabilizer is dissolved in water and a cyclized rubber solution are mixed to prepare a suspension, and the obtained suspension is heated and cyclized. The rubbers may be subjected to a cross-linking reaction (suspension cross-linking reaction). At this time, the cyclized rubber solution may be concentrated in advance or further diluted with a solvent so that the content of the cyclized rubber is 5 to 30% by mass with respect to the total mass of the cyclized rubber solution. Examples of the solvent used for dilution include the solvents exemplified above in the description of the cyclization step. When the cyclized rubbers are crosslinked with each other, the cyclization rate of the cyclized rubber does not change before and after the suspension cross-linking reaction because a site different from the cyclized site is crosslinked.
The reaction temperature of the suspension crosslinking reaction is preferably 40 to 150 ° C, more preferably 60 to 130 ° C. The reaction time of the suspension cross-linking reaction is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
　また、懸濁状態をより安定化させる目的で、界面活性剤を併用してもよい。
　界面活性剤としては特に制限されず、公知のアニオン系界面活性剤、カチオン系界面活性剤、ノニオン系界面活性剤、両性界面活性剤などを用いることができる。
　界面活性剤は、１種を単独で用いてもよく、２種以上を併用してもよい。
　界面活性剤の添加量は、環化ゴム溶液中の環化ゴム１００質量部に対して、０．１～３０質量部が好ましく、０．５～１５質量部がより好ましい。界面活性剤の添加量が、上記下限値以上であれば懸濁状態を充分に安定化できるが、上記上限値を超えても界面活性剤の効果は頭打ちになるため、コストが高くなるばかりである。
　界面活性剤は、分散媒に添加するのが好ましい。 In addition, a surfactant may be used in combination for the purpose of further stabilizing the suspended state.
The surfactant is not particularly limited, and known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used.
As the surfactant, one type may be used alone, or two or more types may be used in combination.
The amount of the surfactant added is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the cyclized rubber in the cyclized rubber solution. If the amount of the surfactant added is at least the above lower limit, the suspended state can be sufficiently stabilized, but even if the above upper limit is exceeded, the effect of the surfactant will reach a plateau, and the cost will only increase. be.
The surfactant is preferably added to the dispersion medium.
　懸濁工程においては、環化ゴム溶液に含まれる環化ゴムを架橋しながら懸濁させてもよい。環化ゴム同士を架橋することで、得られるゴム粒子の耐溶剤性が向上する。
　環化ゴム溶液に含まれる環化ゴムを積極的に架橋させる場合は、水、懸濁安定剤及びラジカル重合開始剤の存在下で、環化ゴム溶液を懸濁させればよい。具体的には、水に懸濁安定剤を溶解させた分散媒と、環化ゴム溶液にラジカル重合開始剤を添加した混合液とを混合して架橋用懸濁液を調製し、得られた架橋用懸濁液を加温して反応させればよい。
　架橋の反応温度は、４０～１５０℃が好ましく、６０～１３０℃がより好ましい。架橋の反応時間は、０．５～１０時間が好ましく、２～５時間がより好ましい。 In the suspension step, the cyclized rubber contained in the cyclized rubber solution may be suspended while being crosslinked. By cross-linking the cyclized rubbers with each other, the solvent resistance of the obtained rubber particles is improved.
When the cyclized rubber contained in the cyclized rubber solution is positively crosslinked, the cyclized rubber solution may be suspended in the presence of water, a suspension stabilizer and a radical polymerization initiator. Specifically, it was obtained by mixing a dispersion medium in which a suspension stabilizer was dissolved in water and a mixed solution in which a radical polymerization initiator was added to a cyclized rubber solution to prepare a suspension for cross-linking. The cross-linking suspension may be heated and reacted.
The reaction temperature for crosslinking is preferably 40 to 150 ° C, more preferably 60 to 130 ° C. The reaction time for crosslinking is preferably 0.5 to 10 hours, more preferably 2 to 5 hours.
　ラジカル重合開始剤の１０時間半減期温度は３５～１５０℃が好ましく、４５～１３０℃がより好ましい。ラジカル重合開始剤の１０時間半減期温度が上記下限値以上であれば、反応が暴走することを抑制でき、取り扱いが容易となる。ラジカル重合開始剤の１０時間半減期温度が上記上限値以下であれば、加熱によるラジカル重合開始剤の残渣の不活性化が容易である。 The 10-hour half-life temperature of the radical polymerization initiator is preferably 35 to 150 ° C, more preferably 45 to 130 ° C. When the 10-hour half-life temperature of the radical polymerization initiator is at least the above lower limit value, it is possible to suppress the reaction from running out of control and the handling becomes easy. When the 10-hour half-life temperature of the radical polymerization initiator is not more than the above upper limit value, it is easy to inactivate the residue of the radical polymerization initiator by heating.
　ラジカル重合開始剤としては、例えばベンゾイルパーオキサイド（１０時間半減期温度：７４℃）、ジラウロイルパーオキサイド（１０時間半減期温度：６２℃）、ｔ－ブチルパーオキシベンゾエート（１０時間半減期温度：１０４℃）、ｍ－トルイルパーオキサイド、ジイソプロピルパーオキシジカーボネート（１０時間半減期温度：４１℃）、ｔ－ブチルパーオキシピバレート（１０時間半減期温度：５８℃）、クミルパーオキシネオデカノエート（１０時間半減期温度：３８℃）、ｔ－ブチルパーオキシ－２－エチルヘキサノエート（１０時間半減期温度：７７℃）、オクタノイルパーオキサイド（１０時間半減期温度：６２℃）、デカノイルパーオキサイド、ｔ－ブチルパーオキシ－２－エチルヘキサノエート（１０時間半減期温度：７２℃）、ｔ－ブチルパーオキシイソプロピルカーボネート（１０時間半減期温度：９９℃）、クミルパーオキシオクタエート、ｔ－ヘキシルパーオキシピバレート（１０時間半減期温度：５３℃）等の有機過酸化物；２，２－アゾビスイソブチロニトリル（１０時間半減期温度：６５℃）、２，２－アゾビス（２，４－ジメチルバレロニトリル）（１０時間半減期温度：５１℃）、１，１－アゾビス（シクロヘキサン－１－カルボニトリル）（１０時間半減期温度：８８℃）等のアゾ化合物などが挙げられる。これらの中でも水素引き抜きによる架橋点形成の観点から有機過酸化物が好ましく、ｔ－ブチルパーオキシピバレート、ｔ－ブチルパーオキシ－２－エチルヘキサノエート、ｔ－ヘキシルパーオキシピバレートがより好ましい。
　ラジカル重合開始剤は、１種を単独で用いてもよく、２種以上を併用してもよい。前記有機過酸化物の例示した群から任意に選択される１種以上が好ましく、２種以上がより好ましく、３種以上がさらに好ましい。特に、１０時間半減期温度が互いに異なる複数のラジカル重合開始剤を併用すると、低温の早い時期にラジカルを生成する重合開始剤（半減期温度が低い重合開始剤）が、高温の遅い時期にラジカルを生成する重合開始剤（半減期温度が高い重合開始剤）のラジカル生成を促進して、架橋反応を速やかに進行させることができる。
　ラジカル重合開始剤の合計の添加量は、環化ゴム溶液中の環化ゴム１００質量部に対して、０．５～３０質量部が好ましく、１～２０質量部がより好ましい。ラジカル重合開始剤の添加量が、上記下限値以上であれば環化ゴムを充分に架橋できるが、上記上限値を超えてもラジカル重合開始剤の効果は頭打ちになるため、コストが高くなるばかりである。 Examples of the radical polymerization initiator include benzoyl peroxide (10-hour half-life temperature: 74 ° C.), dilauroyl peroxide (10-hour half-life temperature: 62 ° C.), and t-butylperoxybenzoate (10-hour half-life temperature:: 12 ° C.). 104 ° C.), m-toluyl peroxide, diisopropylperoxydicarbonate (10-hour half-life temperature: 41 ° C.), t-butylperoxypivalate (10-hour half-life temperature: 58 ° C.), Kumilperoxyneodecano Ate (10-hour half-life temperature: 38 ° C.), t-butylperoxy-2-ethylhexanoate (10-hour half-life temperature: 77 ° C.), octanoyl peroxide (10-hour half-life temperature: 62 ° C.), Decanoyl peroxide, t-butylperoxy-2-ethylhexanoate (10-hour half-life temperature: 72 ° C.), t-butylperoxyisopropyl carbonate (10-hour half-life temperature: 99 ° C.), Kumilperoxyocta Organic peroxides such as ate, t-hexyl peroxypivalate (10-hour half-life temperature: 53 ° C.); 2,2-azobisisobutyronitrile (10-hour half-life temperature: 65 ° C.), 2,2. -Azobis (2,4-dimethylvaleronitrile) (10-hour half-life temperature: 51 ° C.), 1,1-azobis (cyclohexane-1-carbonitrile) (10-hour half-life temperature: 88 ° C.), and the like. Can be mentioned. Among these, organic peroxides are preferable from the viewpoint of forming cross-linking points by hydrogen extraction, and t-butylperoxypivalate, t-butylperoxy-2-ethylhexanoate, and t-hexylperoxypivalate are more preferable. ..
The radical polymerization initiator may be used alone or in combination of two or more. One or more kinds arbitrarily selected from the above-exemplified group of organic peroxides are preferable, two or more kinds are more preferable, and three or more kinds are further preferable. In particular, when a plurality of radical polymerization initiators having different 10-hour half-life temperatures are used in combination, a polymerization initiator that generates radicals at an early low temperature (a polymerization initiator having a low half-life temperature) becomes a radical at a late high temperature. The radical generation of the polymerization initiator (polymerization initiator having a high half-life temperature) that produces the above can be promoted, and the cross-linking reaction can proceed rapidly.
The total amount of the radical polymerization initiator added is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the cyclized rubber in the cyclized rubber solution. If the amount of the radical polymerization initiator added is at least the above lower limit value, the cyclized rubber can be sufficiently crosslinked, but even if the above upper limit value is exceeded, the effect of the radical polymerization initiator reaches a plateau, and the cost increases. Is.
（溶剤除去工程）
　溶剤除去工程は、懸濁工程の後、懸濁液から溶剤を除去してゴム粒子が水に分散した水性分散液を得る工程である。
　上述したように、ゴム粒子は溶剤と共に油分として水中に分散した状態で得られる。そこで、溶剤除去工程で溶剤を懸濁液から除去することで、ゴム粒子が水に分散した水性分散液が得られる。
　懸濁工程の後の懸濁液から溶剤を除去するには、懸濁液を加熱すればよい。加熱温度は、７０～１２０℃が好ましく、８０～１００℃がより好ましい。加熱時間は、１～１０時間が好ましく、２～５時間がより好ましい。
　なお、溶剤除去工程における加熱処理によって、上述した懸濁架橋反応と同様に、環化ゴム同士の架橋が少し起きることがある。 (Solvent removal process)
The solvent removing step is a step of removing the solvent from the suspension after the suspension step to obtain an aqueous dispersion in which the rubber particles are dispersed in water.
As described above, the rubber particles are obtained in a state of being dispersed in water as an oil component together with a solvent. Therefore, by removing the solvent from the suspension in the solvent removing step, an aqueous dispersion in which the rubber particles are dispersed in water can be obtained.
To remove the solvent from the suspension after the suspension step, the suspension may be heated. The heating temperature is preferably 70 to 120 ° C, more preferably 80 to 100 ° C. The heating time is preferably 1 to 10 hours, more preferably 2 to 5 hours.
It should be noted that the heat treatment in the solvent removing step may cause a small amount of cross-linking between the cyclized rubbers, similar to the suspension cross-linking reaction described above.
（洗浄工程）
　洗浄工程は、溶剤除去工程で得られた水性分散液を固液分離し、回収したゴム粒子を水で洗浄する工程である。水による洗浄方法は特に制限されず、例えば、ゴム粒子を水に懸濁した後、濾過や沈殿等の固液分離によってゴム粒子を回収する方法が挙げられる。 (Washing process)
The cleaning step is a step of solid-liquid separating the aqueous dispersion obtained in the solvent removing step and cleaning the recovered rubber particles with water. The washing method with water is not particularly limited, and examples thereof include a method of suspending the rubber particles in water and then recovering the rubber particles by solid-liquid separation such as filtration or precipitation.
（乾燥工程）
　乾燥工程は、洗浄後のゴム粒子を乾燥する工程である。
　乾燥方法としては、例えば加熱乾燥法、気流乾燥法、真空乾燥法、赤外線乾燥法などが適用される。
　例えば、加熱乾燥法を適用した場合、乾燥温度は４０～１２０℃とすることが好ましく、６０～１００℃がより好ましい。乾燥時間は２～４８時間とすることが好ましく、６～２４時間がより好ましい。 (Drying process)
The drying step is a step of drying the rubber particles after washing.
As the drying method, for example, a heat drying method, an air flow drying method, a vacuum drying method, an infrared drying method, or the like is applied.
For example, when the heat drying method is applied, the drying temperature is preferably 40 to 120 ° C, more preferably 60 to 100 ° C. The drying time is preferably 2 to 48 hours, more preferably 6 to 24 hours.
（他の実施形態）
　ゴム粒子の製造方法は、上述した実施形態に限定されない。
　上述した実施形態では、天然ゴムとして天然ゴムラテックスを用いているが、スモークドシート等の固形物の状態の天然ゴムを用いてもよい。固形物の状態の天然ゴムを用いる場合は、環化工程の前に天然ゴムを素練りしておくことが好ましい。ここで、素練りとは、機械的せん断力を加えることによって、弾性や可塑性を加工し易い状態に調整することをいう。 (Other embodiments)
The method for producing rubber particles is not limited to the above-described embodiment.
In the above-described embodiment, natural rubber latex is used as the natural rubber, but natural rubber in a solid state such as a smoked sheet may be used. When using natural rubber in a solid state, it is preferable to knead the natural rubber before the cyclization step. Here, kneading means adjusting the elasticity and plasticity to a state in which it is easy to process by applying a mechanical shearing force.
　また、環化されていない天然ゴムからなるゴム粒子は、例えば以下のようにして製造できる。すなわち、天然ゴムラテックスに含まれる天然ゴムの粒子表面をビニルモノマーなどにより改質させた後、天然ゴムラテックスを乾燥することにより、サブミクロンサイズのゴム粒子が得られる。 Further, rubber particles made of uncyclized natural rubber can be produced, for example, as follows. That is, submicron-sized rubber particles can be obtained by modifying the surface of the natural rubber particles contained in the natural rubber latex with a vinyl monomer or the like and then drying the natural rubber latex.
＜作用効果＞
　以上説明した本発明のゴム粒子は、天然ゴムからなるので、天然物を原料とし、柔軟性を有する粒子である。また、本発明のゴム粒子の製造方法によれば、天然ゴムを環化させることで容易に粒子化できるので、天然物を原料とし、柔軟性を有する粒子を簡便に製造できる。 <Action effect>
Since the rubber particles of the present invention described above are made of natural rubber, they are made of natural products and have flexibility. Further, according to the method for producing rubber particles of the present invention, particles can be easily formed by cyclizing natural rubber, so that flexible particles can be easily produced using a natural product as a raw material.
＜用途＞
　本発明のゴム粒子は、塗料、プラスチック、粘着剤、化粧品、紙塗工材、繊維加工材、筆記具、マーカー等のフィラー等に使用される天然由来のマイクロビーズとして利用できる。 <Use>
The rubber particles of the present invention can be used as naturally-derived microbeads used in fillers such as paints, plastics, adhesives, cosmetics, paper coating materials, textile processing materials, writing tools, and markers.
　以下、本発明を実施例により具体的に説明するが、本発明は以下の記載によっては限定されない。 Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.
［測定方法］
＜環化率の測定＞
　環化ゴムの環化率は、核磁気共鳴装置を用いて１Ｈ－ＮＭＲを測定することで求めた。具体的には、環化反応前後の天然ゴムについて、以下の測定条件にて１Ｈ－ＮＭＲを測定し、環化反応前の天然ゴムの二重結合由来のプロトンのピーク面積（Ｓ０）と、環化反応後の天然ゴムの二重結合由来のプロトンのピーク面積（Ｓ１）をそれぞれ測定し、下記式（ｉ）より環化ゴムの環化率を求めた。
　環化率（％）＝｛１－（Ｓ１／Ｓ０）｝×１００　　・・・（ｉ）（測定条件）
・装置：日本電子株式会社製、「ＪＮＭ－ＥＣＰ６００」
・溶媒：クロロホルム－ｄ１
・濃度：０．０１ｇ／ｍＬ
・共鳴周波数：６００ＭＨｚ
・積算回数：３２回
・測定試料とした天然ゴムの量：０．０２ｍｇ [Measuring method]
<Measurement of cyclization rate>
The cyclization rate of the cyclized rubber was determined by measuring 1 H-NMR using a nuclear magnetic resonance apparatus. Specifically, 1 H-NMR was measured for the natural rubber before and after the cyclization reaction under the following measurement conditions , and the peak area (S 0 ) of the proton derived from the double bond of the natural rubber before the cyclization reaction was obtained. The peak area (S 1 ) of the proton derived from the double bond of the natural rubber after the cyclization reaction was measured, and the cyclization rate of the cyclized rubber was determined from the following formula (i).
Cyclization rate (%) = {1- (S 1 / S 0 )} × 100 ・ ・ ・ (i) (Measurement conditions)
・ Equipment: "JNM-ECP600" manufactured by JEOL Ltd.
-Solvent: Chloroform-d 1
・ Concentration: 0.01 g / mL
・ Resonance frequency: 600MHz
・ Number of integrations: 32 times ・ Amount of natural rubber used as measurement sample: 0.02 mg
＜体積平均粒子径の測定＞
　粒子（ゴム粒子又はセルロース粒子）の体積平均粒子径は、レーザ回折式粒度分布計（株式会社島津製作所製、「ＳＡＬＤ２１００」）を用いて測定した。 <Measurement of volume average particle size>
The volume average particle diameter of the particles (rubber particles or cellulose particles) was measured using a laser diffraction type particle size distribution meter (“SALD2100” manufactured by Shimadzu Corporation).
＜柔軟性の評価＞
　下記評価基準に基づき、粒子（ゴム粒子又はセルロース粒子）を肌に塗布した際の触感を評価した。
　〇：粒子の硬さが原因で発生するきしみ感がない。
　×：粒子の硬さが原因で発生するきしみ感がある。 <Evaluation of flexibility>
Based on the following evaluation criteria, the tactile sensation when the particles (rubber particles or cellulose particles) were applied to the skin was evaluated.
〇: There is no squeaky feeling caused by the hardness of the particles.
X: There is a squeaky feeling caused by the hardness of the particles.
＜耐溶剤性の評価＞
　耐溶剤性の評価として、ゴム粒子をトルエンに溶解させた時のゲル分率を以下のようにして求めた。
　ゴム粒子を容器に精秤（Ｗ１）し、そこにトルエンをゴム粒子の濃度が０．６２５質量％になるように投入した。２４時間経過した後、容器内の液を濾紙（保持粒子径：８μｍ）で濾過し、得られた濾紙上の残渣（トルエン不溶分）を１１０℃で２時間乾燥し、トルエン不溶分の質量（Ｗ２）を測定し、下記式（ii）よりゲル分率を求めた。ゲル分率が高いほど耐溶剤性に優れることを意味する。なお、得られた粒子を保持できればどのような濾紙を用いてもよい。
　ゲル分率（％）＝（Ｗ２／Ｗ１）×１００　　・・・（ii） <Evaluation of solvent resistance>
As an evaluation of solvent resistance, the gel fraction when the rubber particles were dissolved in toluene was determined as follows.
The rubber particles were precisely weighed in a container (W 1 ), and toluene was added thereto so that the concentration of the rubber particles was 0.625% by mass. After 24 hours have passed, the liquid in the container is filtered through a filter paper (holding particle size: 8 μm), and the obtained residue (toluene insoluble matter) on the filter paper is dried at 110 ° C. for 2 hours, and the mass of the toluene insoluble matter (retaining particle size: 8 μm). W 2 ) was measured, and the gel fraction was calculated from the following formula (ii). The higher the gel fraction, the better the solvent resistance. Any filter paper may be used as long as the obtained particles can be retained.
Gel fraction (%) = (W 2 / W 1 ) x 100 ... (ii)
［製造例１］
　５Ｌ撹拌機付きセパラブルフラスコにイオン交換水３８００ｇを仕込み、この中に天然ゴムラテックス（住友ゴム工業株式会社製、「ＳｅＬａｔｅｘ１１００」、天然ゴムの含有量：６０質量％、水等の分散媒の含有量：４０質量％）８００ｇと、ラウリル硫酸ナトリウム４．８ｇを投入してラテックス液を調製した。そこへ濃度３３．６質量％の硫酸アルミニウム水溶液２６７．２ｇを投入し、天然ゴムラテックスの塩析を行った。次いで、ろ布を用いて固液分離により固形物を回収し、８０℃で２０時間乾燥して、天然ゴムの固形物を得た（塩析工程）。天然ゴム１００質量部に対して、ラウリル硫酸ナトリウムの添加量は１質量部であり、硫酸アルミニウムの添加量は１８．７質量部であった。
　２Ｌ撹拌機付きセパラブルフラスコに天然ゴムの固形物１２０ｇとトルエン４８０ｇを仕込み、１００℃に加温して、天然ゴムをトルエンに溶解させて濃度２０質量％の天然ゴム溶液を調製した。次いで、ｐ－トルエンスルホン酸１２ｇ投入し、１００℃で環化反応を開始した。ｐ－トルエンスルホン酸の投入から２時間半後、濃度２５質量％の炭酸ナトリウム水溶液１９．２ｇを投入して反応を停止し、環化ゴム溶液を得た（環化工程）。天然ゴム１００質量部に対して、ｐ－トルエンスルホン酸の添加量は１０質量部であった。なお、ｐ－トルエンスルホン酸は炭酸ナトリウムと反応して炭酸ナトリウム水溶液に溶解した。
　得られた環化ゴム溶液（ただし、投入した炭酸水素ナトリウム水溶液を考慮しない。）の総質量に対する、環化ゴム（環化天然ゴム）の含有量は２０質量％であり、トルエンの含有量は８０質量％であった。
　また、環化ゴムの環化率は８３．５％であった。なお、環化率を測定するに際しては、環化ゴム溶液の一部を採取し、溶剤を除去して得られた残渣を乾燥したものを測定に用いた。 [Manufacturing Example 1]
3800 g of ion-exchanged water was placed in a separable flask equipped with a 5 L stirrer, and natural rubber latex (“SeLatex1100” manufactured by Sumitomo Rubber Industries, Ltd., natural rubber content: 60% by mass, containing a dispersion medium such as water) was charged therein. (Amount: 40% by mass) 800 g and 4.8 g of sodium lauryl sulfate were added to prepare a latex solution. 267.2 g of an aqueous aluminum sulfate solution having a concentration of 33.6% by mass was added thereto, and salting out of natural rubber latex was performed. Then, the solid matter was recovered by solid-liquid separation using a filter cloth and dried at 80 ° C. for 20 hours to obtain a solid matter of natural rubber (salting out step). The amount of sodium lauryl sulfate added was 1 part by mass and the amount of aluminum sulfate added was 18.7 parts by mass with respect to 100 parts by mass of natural rubber.
120 g of a solid natural rubber and 480 g of toluene were charged in a separable flask equipped with a 2 L stirrer, heated to 100 ° C., and the natural rubber was dissolved in toluene to prepare a natural rubber solution having a concentration of 20% by mass. Then, 12 g of p-toluenesulfonic acid was added, and the cyclization reaction was started at 100 ° C. Two and a half hours after the addition of p-toluenesulfonic acid, 19.2 g of a sodium carbonate aqueous solution having a concentration of 25% by mass was added to stop the reaction, and a cyclized rubber solution was obtained (cyclization step). The amount of p-toluenesulfonic acid added was 10 parts by mass with respect to 100 parts by mass of natural rubber. The p-toluenesulfonic acid reacted with sodium carbonate and dissolved in an aqueous sodium carbonate solution.
The content of the cyclized rubber (cyclized natural rubber) is 20% by mass with respect to the total mass of the obtained cyclized rubber solution (however, the added sodium hydrogencarbonate aqueous solution is not taken into consideration), and the content of toluene is. It was 80% by mass.
The cyclization rate of the cyclized rubber was 83.5%. When measuring the cyclization rate, a part of the cyclized rubber solution was sampled, the solvent was removed, and the obtained residue was dried and used for the measurement.
［製造例２］
　ｐ－トルエンスルホン酸の添加量を３ｇに変更した以外は、製造例１と同様にして環化ゴム溶液を得た。天然ゴム１００質量部に対して、ｐ－トルエンスルホン酸の添加量は２．５質量部であった。
　得られた環化ゴム溶液の総質量に対する、環化ゴム（環化天然ゴム）の含有量は２０質量％であり、トルエンの含有量は８０質量％であった。
　また、環化ゴムの環化率は６７．８％であった。 [Manufacturing Example 2]
A cyclized rubber solution was obtained in the same manner as in Production Example 1 except that the amount of p-toluenesulfonic acid added was changed to 3 g. The amount of p-toluenesulfonic acid added was 2.5 parts by mass with respect to 100 parts by mass of natural rubber.
The content of the cyclized rubber (circulated natural rubber) was 20% by mass and the content of toluene was 80% by mass with respect to the total mass of the obtained cyclized rubber solution.
The cyclization rate of the cyclized rubber was 67.8%.
［製造例３］
　製造例１と同様にして塩析工程を行い、天然ゴムの固形物を得た。
　２Ｌ撹拌機付きセパラブルフラスコに天然ゴムの固形物１２０ｇとトルエン４８０ｇを仕込み、１００℃に加温して、天然ゴム溶液を得た。
　得られた天然ゴム溶液の総質量に対する、天然ゴムの含有量は２０質量％であり、トルエンの含有量は８０質量％であった。 [Manufacturing Example 3]
The salting out step was carried out in the same manner as in Production Example 1 to obtain a solid natural rubber.
120 g of a solid natural rubber and 480 g of toluene were placed in a separable flask equipped with a 2 L stirrer and heated to 100 ° C. to obtain a natural rubber solution.
The content of natural rubber was 20% by mass and the content of toluene was 80% by mass with respect to the total mass of the obtained natural rubber solution.
［実施例１］
　２Ｌ撹拌機付きセパラブルフラスコに水６００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（信越化学工業株式会社製、「メトローズ９０ＳＨ－１００」）１５ｇを投入して水に溶解させ、分散媒を調製した。分散媒を撹拌機の回転数４００ｒｐｍで撹拌しながら、製造例１で得られた環化ゴム溶液３００ｇを添加して、懸濁液を調製した。撹拌を継続しながら懸濁液を８０℃に昇温し、８０℃で２時間、懸濁架橋反応を行った（懸濁工程）。環化ゴム１００質量部に対して、ヒドロキシプロピルメチルセルロースの添加量は２５質量部であった。
　懸濁工程の後の懸濁液を１００℃に昇温し、１００℃で１時間保持して懸濁液からトルエンを除去して、ゴム粒子が水に分散した水性分散液を得た（溶剤除去工程）。
　水性分散液を室温（２０℃）まで冷却した後、固液分離し、回収したゴム粒子を水で洗浄した（洗浄工程）。
　洗浄後のゴム粒子を７０℃で２０時間乾燥して、球状のゴム粒子を得た。電子顕微鏡観察によって、得られたゴム粒子の殆ど全てが球状であることを確認した。
　得られたゴム粒子について、体積平均粒子径を測定し、柔軟性及び耐溶剤性を評価した。結果を表１に示す。 [Example 1]
600 g of water was charged into a separable flask equipped with a 2 L stirrer, and 15 g of hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium. While stirring the dispersion medium at a rotation speed of 400 rpm of the stirrer, 300 g of the cyclized rubber solution obtained in Production Example 1 was added to prepare a suspension. The suspension was heated to 80 ° C. while continuing stirring, and a suspension crosslinking reaction was carried out at 80 ° C. for 2 hours (suspension step). The amount of hydroxypropylmethylcellulose added was 25 parts by mass with respect to 100 parts by mass of the cyclized rubber.
The suspension after the suspension step was heated to 100 ° C. and held at 100 ° C. for 1 hour to remove toluene from the suspension to obtain an aqueous dispersion in which rubber particles were dispersed in water (solvent). Removal step).
After cooling the aqueous dispersion to room temperature (20 ° C.), solid-liquid separation was performed, and the recovered rubber particles were washed with water (washing step).
The washed rubber particles were dried at 70 ° C. for 20 hours to obtain spherical rubber particles. By electron microscopic observation, it was confirmed that almost all of the obtained rubber particles were spherical.
The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
［実施例２］
　ヒドロキシプロピルメチルセルロースの添加量を９ｇ（環化ゴム１００質量部に対して、１５質量部に相当）に変更し、撹拌機の回転数を２５０ｒｐｍに変更した以外は、実施例１と同様にして球状のゴム粒子を得た。
　得られたゴム粒子について、体積平均粒子径を測定し、柔軟性及び耐溶剤性を評価した。結果を表１に示す。 [Example 2]
Spherical as in Example 1 except that the amount of hydroxypropylmethylcellulose added was changed to 9 g (corresponding to 15 parts by mass with respect to 100 parts by mass of cyclized rubber) and the rotation speed of the stirrer was changed to 250 rpm. Rubber particles were obtained.
The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
［実施例３］
　２Ｌ撹拌機付きセパラブルフラスコに水６００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（信越化学工業株式会社製、「メトローズ９０ＳＨ－１００」）１５ｇを投入して水に溶解させ、分散媒を調製した。別途、製造例１で得られた環化ゴム溶液３００ｇに、ラジカル重合開始剤としてｔ－ブチルパーオキシピバレート１．２ｇ、ｔ－ブチルパーオキシ－２－エチルヘキサノエート１．２ｇ及びｔ－ヘキシルパーオキシピバレート１．２ｇを添加して混合液を調製した。分散媒を撹拌機の回転数４００ｒｐｍで撹拌しながら、混合液３０３．６ｇを添加して、架橋用懸濁液を調製した。撹拌を継続しながら架橋用懸濁液を８０℃に昇温し、８０℃で２時間、架橋しながら懸濁架橋反応を行った（懸濁工程）。環化ゴム１００質量部に対して、ヒドロキシプロピルメチルセルロースの添加量は２５質量部であり、ラジカル重合開始剤の合計の添加量は６質量部であった。
　懸濁工程の後の架橋用懸濁液を１００℃に昇温し、１００℃で１時間保持して架橋用懸濁液からトルエンを除去して、ゴム粒子が水に分散した水性分散液を得た（溶剤除去工程）。
　水性分散液を室温（２０℃）まで冷却した後、固液分離し、回収したゴム粒子を水で洗浄した（洗浄工程）。
　洗浄後のゴム粒子を７０℃で２０時間乾燥して、球状のゴム粒子を得た。
　得られたゴム粒子について、体積平均粒子径を測定し、柔軟性及び耐溶剤性を評価した。結果を表１に示す。 [Example 3]
600 g of water was charged into a separable flask equipped with a 2 L stirrer, and 15 g of hydroxypropylmethyl cellulose (“Metro's 90SH-100” manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and dissolved in water to prepare a dispersion medium. Separately, in 300 g of the cyclized rubber solution obtained in Production Example 1, 1.2 g of t-butylperoxypivalate, 1.2 g of t-butylperoxy-2-ethylhexanoate and t- as radical polymerization initiators were added. A mixed solution was prepared by adding 1.2 g of hexylperoxypivalate. While stirring the dispersion medium at a stirring speed of 400 rpm, 303.6 g of the mixture was added to prepare a suspension for crosslinking. The suspension for crosslinking was heated to 80 ° C. while continuing stirring, and a suspension crosslinking reaction was carried out while crosslinking at 80 ° C. for 2 hours (suspension step). The amount of hydroxypropylmethylcellulose added was 25 parts by mass with respect to 100 parts by mass of the cyclized rubber, and the total amount of the radical polymerization initiator added was 6 parts by mass.
The cross-linking suspension after the suspension step was heated to 100 ° C. and held at 100 ° C. for 1 hour to remove toluene from the cross-linking suspension to obtain an aqueous dispersion in which rubber particles were dispersed in water. Obtained (solvent removal step).
After cooling the aqueous dispersion to room temperature (20 ° C.), solid-liquid separation was performed, and the recovered rubber particles were washed with water (washing step).
The washed rubber particles were dried at 70 ° C. for 20 hours to obtain spherical rubber particles.
The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
［実施例４］
　製造例１で得られた環化ゴム溶液３００ｇの代わりに、製造例２で得られた環化ゴム溶液３００ｇを用いた以外は、実施例３と同様にして球状のゴム粒子を得た。得られたゴム粒子について、体積平均粒子径を測定し、柔軟性及び耐溶剤性を評価した。結果を表１に示す。 [Example 4]
Spherical rubber particles were obtained in the same manner as in Example 3 except that 300 g of the cyclized rubber solution obtained in Production Example 2 was used instead of 300 g of the cyclized rubber solution obtained in Production Example 1. The volume average particle diameter of the obtained rubber particles was measured, and the flexibility and solvent resistance were evaluated. The results are shown in Table 1.
［比較例１］
　製造例１で得られた環化ゴム溶液３００ｇの代わりに、製造例３で得られた天然ゴム溶液３００ｇを用いた以外は、実施例３と同様にしてゴム粒子を製造しようとしたが、天然ゴムが粒子化せず、ゴム粒子を製造することができなかった。 [Comparative Example 1]
An attempt was made to produce rubber particles in the same manner as in Example 3 except that 300 g of the natural rubber solution obtained in Production Example 3 was used instead of 300 g of the cyclized rubber solution obtained in Production Example 1. The rubber did not become particles, and rubber particles could not be produced.
［比較例２］
　２Ｌ撹拌機付きセパラブルフラスコに酢酸エチル７２０ｇを仕込み、この中に酢酸セルロース（酢化度５５％）１８０ｇを溶解して酢酸セルロース溶液を調製した。この溶液の２５℃粘度は１４６０００ｍＰａ・ｓであった。
　これとは別に、２Ｌ撹拌機付きセパラブルフラスコに水３００ｇを仕込み、この中にヒドロキシプロピルメチルセルロース（信越化学工業株式会社製、「メトローズ９０ＳＨ－１００」）５ｇとラウリル硫酸ナトリウム１ｇを溶解して分散媒水溶液を調製した。
　酢酸セルロース溶液に分散媒水溶液を添加して、懸濁液を調製した。次いで、撹拌機の回転数３００ｒｐｍで撹拌しながら懸濁液を９０℃に昇温し、２時間懸濁液から酢酸エチルを揮発させた。次いで、９５℃に昇温し、水酸化ナトリウムを７０ｇ添加して、１．５時間保持し、酢酸セルロース粒子からアセチル基を脱離させ、セルロース粒子を得た。これにより、水中にセルロース粒子が分散したスラリーを得た。
　次いで、得られたスラリーを室温まで冷却した後、ろ過により固液分離し、回収した固形物を水で充分洗浄した後、７０℃で２０時間乾燥して、球状のセルロース粒子を得た。
　得られたセルロース粒子について、体積平均粒子径を測定し、柔軟性を評価した。結果を表１に示す。 [Comparative Example 2]
720 g of ethyl acetate was placed in a separable flask equipped with a 2 L stirrer, and 180 g of cellulose acetate (glycemicization degree 55%) was dissolved therein to prepare a cellulose acetate solution. The viscosity of this solution at 25 ° C. was 146000 mPa · s.
Separately, 300 g of water was placed in a separable flask equipped with a 2 L stirrer, and 5 g of hydroxypropylmethyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., "Metro's 90SH-100") and 1 g of sodium lauryl sulfate were dissolved and dispersed in the flask. A medium aqueous solution was prepared.
A suspension was prepared by adding a dispersion medium aqueous solution to the cellulose acetate solution. Then, the suspension was heated to 90 ° C. while stirring at a stirring speed of 300 rpm, and ethyl acetate was volatilized from the suspension for 2 hours. Then, the temperature was raised to 95 ° C., 70 g of sodium hydroxide was added, and the mixture was kept for 1.5 hours to remove the acetyl group from the cellulose acetate particles to obtain cellulose particles. As a result, a slurry in which cellulose particles were dispersed was obtained.
Then, the obtained slurry was cooled to room temperature, solid-liquid separated by filtration, and the recovered solid was sufficiently washed with water and then dried at 70 ° C. for 20 hours to obtain spherical cellulose particles.
The volume average particle diameter of the obtained cellulose particles was measured and the flexibility was evaluated. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１から明らかなように、各実施例で得られたゴム粒子は、比較例２で得られたセルロース粒子に比べて柔軟性に優れていた。
　特に、天然ゴムを環化させた後、さらにラジカル重合開始剤を用いて架橋した環化ゴムを用いた実施例３、４のゴム粒子は、ゲル分率が高く、耐溶剤性にも優れていた。 As is clear from Table 1, the rubber particles obtained in each example were superior in flexibility to the cellulose particles obtained in Comparative Example 2.
In particular, the rubber particles of Examples 3 and 4 using the cyclized rubber crosslinked with a radical polymerization initiator after cyclizing the natural rubber have a high gel content and excellent solvent resistance. rice field.

Claims (7)

  1. 　天然ゴムからなり、球状である、ゴム粒子。 Rubber particles made of natural rubber and spherical.
  2. 　平均粒子径が１～３００μｍである、請求項１に記載のゴム粒子。 The rubber particle according to claim 1, wherein the average particle size is 1 to 300 μm.
  3. 　前記天然ゴムが、環化された環化ゴムである、請求項１又は２に記載のゴム粒子。 The rubber particles according to claim 1 or 2, wherein the natural rubber is a cyclized rubber.
  4. 　前記環化ゴムの環化率が６０～９０％である、請求項３に記載のゴム粒子。 The rubber particles according to claim 3, wherein the cyclization rate of the cyclized rubber is 60 to 90%.
  5. 　請求項１～４のいずれか一項に記載のゴム粒子の製造方法であって、
    　天然ゴムを溶剤に溶解して環化反応を行い、環化ゴム溶液を得る工程と、
    　水及び懸濁安定剤の存在下で、前記環化ゴム溶液を懸濁させる工程と、
    　を有する、ゴム粒子の製造方法。     The method for producing rubber particles according to any one of claims 1 to 4.
    The process of dissolving natural rubber in a solvent and performing a cyclization reaction to obtain a cyclized rubber solution.
    The step of suspending the cyclized rubber solution in the presence of water and a suspension stabilizer, and
    A method for producing rubber particles.
  6. 　前記環化ゴム溶液を撹拌しながら４０～１５０℃に加熱する、請求項５に記載のゴム粒子の製造方法。 The method for producing rubber particles according to claim 5, wherein the cyclized rubber solution is heated to 40 to 150 ° C. while stirring.
  7. 　前記環化ゴム溶液にラジカル重合開始剤を添加する、請求項５又は６に記載のゴム粒子の製造方法。 The method for producing rubber particles according to claim 5 or 6, wherein a radical polymerization initiator is added to the cyclized rubber solution.
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