JP2019038949A - Method for producing composite particle and composite particle obtained by production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for producing a composite particle containing a coating layer composed of cellulose fibers and a polymer covered by the coating layer. A method for producing a composite particle containing a coating layer composed of cellulose fibers and a polymer covered by the coating layer, wherein the cellulose fibers are placed on the surface of an aggregate of polymerizable monomers in an aqueous solvent. A method for producing a composite particle, which comprises a first step of forming a coating layer composed of the above, and a second step of polymerizing a polymerizable monomer in the aggregate on which the coating layer is formed. [Selection diagram] FIG. 5

Description

  The present invention relates to a method for producing composite particles containing cellulose nanofibers and a polymer, and to composite particles that can be produced by the method.

  Microparticles are fine particles composed of a polymer (resin). It is possible to bind other materials than the polymer to the surface of the microparticle. For this reason, if the substance which exhibits a predetermined function is used as another substance, microparticles can be functionalized. The functionalized microparticles can be used in various applications such as ion exchange resins, liquid crystal display spacers, and antibody carriers.

  Cellulose fibers are fibers that are obtained by subjecting cellulose raw materials such as pulp to chemical treatment and mechanical treatment to fibrillate (miniaturize), and microfibrillated cellulose, cellulose nanofibers, and cellulose nanocrystals are known. Yes. Although these cellulose fibers are about 1/5 lighter than steel, they are more than five times stronger than steel. In patent document 1, the characteristic of such a cellulose fiber is utilized, the cellulose fiber is made to contain in resin, and the intensity | strength of a resin molding is improved.

JP 2010-59304 A

  An object of this invention is to provide the novel manufacturing method of the composite particle which has the coating layer comprised by a cellulose fiber, and the polymer covered with this coating layer. Moreover, an object of this invention is to provide the composite particle which can be manufactured by the said method.

The gist of the present invention is as follows.
(1) A method for producing composite particles comprising a coating layer composed of cellulose fibers and a polymer covered by the coating layer, wherein the cellulose fibers are formed on the surface of the aggregate of polymerizable monomers in an aqueous solvent. And a second step of polymerizing the polymerizable monomer in the aggregate on which the coating layer is formed. The method for producing composite particles, comprising: .
(2) The method for producing composite particles according to (1), wherein the polymerizable monomer has two or more vinyl groups.
(3) The method for producing composite particles according to (2), wherein the polymerizable monomer is divinylbenzene.
(4) The method for producing composite particles according to any one of (1) to (3), wherein the cellulose fiber has an anionic group different from a hydroxyl group on the surface.
(5) The method for producing composite particles according to (4), wherein the cellulose fiber is a cellulose nanofiber having a carboxyl group on the surface.
(6) A composite particle comprising a coating layer composed of cellulose fibers and a polymer covered with the coating layer.
(7) The composite particle according to (6), wherein the polymer is a polymer of a polymerizable monomer having two or more vinyl groups.
(8) The composite particle according to (7), wherein the polymerizable monomer is divinylbenzene.
(9) The composite particle according to any one of (6) to (8), wherein the cellulose fiber has an anionic group different from a hydroxyl group on a surface thereof.
(10) The composite particle according to (9), wherein the cellulose fiber is a cellulose nanofiber having a carboxyl group on the surface.

  ADVANTAGE OF THE INVENTION According to this invention, the novel manufacturing method of the composite particle containing the coating layer comprised by a cellulose fiber and the polymer covered with a coating layer can be provided. Moreover, according to this invention, the composite particle which can be manufactured by the said method can be provided.

Schematic showing the aqueous solvent after ultrasonic treatment and stirring treatment Schematic showing the aqueous solvent after polymerizing the polymerizable monomer Optical micrograph of divinylbenzene in the reaction solution Optical micrograph of polymer of divinylbenzene in reaction solution Scanning electron micrograph of the composite particles of Example 1 Scanning electron micrograph of the cross section of the composite particle of Example 1

  Hereinafter, embodiments of the present invention will be described in detail.

  The manufacturing method of this embodiment includes a first step and a second step.

  In the first step, a coating layer composed of cellulose fibers (hereinafter also simply referred to as “coating layer”) is formed on the surface of an aggregate of polymerizable monomers (hereinafter also simply referred to as “aggregate”) in an aqueous solvent. Form.

  Although the method of forming the coating layer on the surface of the aggregate is not particularly limited, for example, ultrasonic treatment or stirring treatment can be used. In addition, you may form a coating layer on the surface of an aggregate | assembly using ultrasonic treatment and stirring processing together.

  When using ultrasonic treatment, first, an aqueous solvent containing cellulose fibers and a polymerizable monomer is prepared. And a coating layer can be formed in the surface of an aggregate | assembly by irradiating an ultrasonic wave with respect to the aqueous solvent containing a cellulose fiber and a polymerizable monomer.

The conditions for irradiating the ultrasonic waves are not particularly limited. For example, the frequency of the ultrasonic waves can be 15 kHz or more and 40 kHz or less, and the output of the ultrasonic waves is 50 W / cm ² or more and 300 W / cm ^2. The irradiation time of ultrasonic waves can be 30 seconds or longer and 300 seconds or shorter.

  When using the stirring treatment, first, an aqueous solvent containing cellulose fibers and a polymerizable monomer is prepared. And a coating layer can be formed in the surface of an aggregate by stirring the aqueous solvent containing a cellulose fiber and a polymerizable monomer.

  The conditions for stirring the aqueous solvent are not particularly limited. For example, the stirring speed can be 200 rpm or more and 1000 rpm or less, and the stirring time can be 1 minute or more and 30 minutes or less.

  FIG. 1 is a schematic view showing an aqueous solvent after being subjected to ultrasonic treatment or stirring treatment. As shown in FIG. 1, when ultrasonic treatment or stirring treatment is applied to an aqueous solvent 13 containing cellulose fibers and polymerizable monomers, the entire surface of the polymerizable monomer aggregate 11 is composed of cellulose fibers. The covering layer 12 is formed, and the aggregate 11 and the aqueous solvent 13 are separated by the covering layer 12. A plurality of aggregates 11 on which the coating layer 12 is formed are formed in the aqueous solvent 13 and dispersed in the aqueous solvent 13. That is, an emulsion (O / W) in which the aggregate 11 on which the coating layer 12 is formed is dispersed in the aqueous solvent 13 when the aqueous solvent 13 containing cellulose fibers and polymerizable monomers is subjected to ultrasonic treatment or stirring treatment. Type emulsion) is formed.

  The coating layer is formed on the surface of the aggregate by, for example, freezing the aggregate on which the coating layer is formed with an aqueous solvent and observing the cross section of the frozen aggregate using a scanning electron microscope. I can confirm. The surface of the aggregate means an interface between the aqueous solvent and the aggregate, and the coating layer does not necessarily have to be in contact with the aggregate.

  Although the thickness of a coating layer is not specifically limited, For example, it is 3 nm or more and 50 nm or less. The thickness of the coating layer can be obtained, for example, by freezing the aggregate on which the coating layer is formed together with an aqueous solvent, and measuring the thickness of the coating layer in the cross section of the frozen aggregate using a scanning electron microscope. it can.

  The aqueous solvent used in the first step is a solvent that dissolves in water, and is water, an organic solvent that dissolves in water, or a mixture thereof. Examples of the organic solvent that dissolves in water include alcohols such as methanol, ethanol, and isopropanol, and highly polar organic solvents such as acetone, N, N-dimethylformamide, and dimethyl sulfoxide. The aqueous solvent can be appropriately selected depending on the type of cellulose fiber, but water is preferable because a coating layer is easily formed on the surface of the aggregate.

  The polymerizable monomer used in the first step is a monomer (polymerizable monomer) that can form a polymer (polymer) by polymerization. The polymerizable monomer is not particularly limited as long as it is a substance that does not dissolve in an aqueous solvent. For example, a monofunctional or polyfunctional polymerizable monomer can be used. Specifically, monomers such as acrylic monomers, methacrylic monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl ether monomers, vinyl monomers, and halogen-containing vinyl monomers can be used.

  More specifically, monofunctional acrylic monomers include acrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethyl acrylate acrylate, cyclohexyl acrylate, mistyryl acrylate, palmityl acrylate. , Stearyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 3-aminopropyl acrylate, 3-N acrylic acid, N-diethylaminopropyl and the like. Examples of the methacrylic monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate. 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, glycidyl methacrylate, 3-aminopropyl methacrylate, 3-N, N-diethylaminopropyl methacrylate Etc.

  Monofunctional aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, sodium styrenesulfonate, vinylpyridine, 2 -Acryloyloxyethyl phthalic acid, itaconic acid, fumaric acid, etc. are mentioned.

  Examples of the monofunctional vinyl ester monomer include vinyl formate, vinyl acetate, and vinyl propionate.

  Examples of the monofunctional vinyl ether monomer include vinyl methyl ether, vinyl ethyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like.

  Examples of the monofunctional vinyl monomer include vinyl chloride, vinylidene chloride, ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene and the like.

  Polyfunctional polymerizable monomers include ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, ethylene oxide modified trimethylol. Propane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythrole hexaacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol Diacrylate, trimethylolpropane dimethacrylate , Trimethylolpropane trimethacrylate, ethylene oxide modified trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythrole hexamethacrylate, diallyl phthalate, diallyl malate, diallyl fumarate, diallyl succinate, Examples include triallyl isocyanurate, divinylbenzene, butadiene, divinylbiphenyl, divinylnaphthalene, diallyl phthalate and the like.

  The aggregate is formed by aggregating a plurality of the polymerizable monomers described above. The above-mentioned polymerizable monomers can be used alone or in combination of two or more. The polymerizable monomer is not limited to the above-described substances, and a ring-opening polymerizable monomer such as ε-caprolactam can also be used.

The polymerizable monomer used in the first step is preferably a monomer having two or more vinyl groups such as ethylene glycol dimethacrylate, trimethylolpropane triacrylate, divinylbenzene, and is preferably divinylbenzene. Particularly preferred. When the polymerizable monomer has two or more vinyl groups, the polymerizable monomer is easily polymerized in a state where a coating layer is formed on the surface of the aggregate in the second step described later. For this reason, composite particles (hereinafter also simply referred to as “composite particles”) having a coating layer composed of cellulose fibers and a polymer covered with the coating layer are easily manufactured. Therefore, the yield of composite particles can be improved. The yield of composite particles can be calculated based on the following formula (1).
Yield (%) of composite particles = A / B × 100 (1)
In the above formula (1), A represents the mass (g) of the produced composite particles, and B represents the total mass (g) of the raw materials excluding the aqueous solvent among the raw materials used for producing the composite particles.

  On the other hand, a polymerizable monomer having only one vinyl group or a polymerizable monomer having no vinyl group can be formed in the second step even if a coating layer can be formed on the surface of the aggregate in the first step. By being polymerized, it is easily released from the inside of the coating layer to the outside. The polymerizable monomer (or an aggregate thereof) that is released to the outside of the coating layer and disperses the aqueous solvent is not covered with the coating layer, and thus cannot form a polymer covered with the coating layer. In addition, the polymerizable monomer (or aggregate thereof) released to the outside of the coating layer and held on the surface of the coating layer is polymerized together with the polymerizable monomer remaining inside the coating layer, and the coating layer is brought into the polymer. I will take it in. For this reason, it becomes difficult to produce | generate the polymer covered with the coating layer. Therefore, it becomes difficult to improve the yield of the composite particles.

  The content of the polymerizable monomer contained in the aqueous solvent is not particularly limited as long as a coating layer can be formed on the surface of the aggregate. For example, the content is 5 parts by mass or more and 20 parts by mass with respect to 100 parts by mass of the aqueous solvent. It can be as follows.

  Cellulose fibers used in the first step are composed of microfibrils. Microfibrils are the smallest structural units of fibers that cellulose constitutes in cellulose raw materials. Cellulosic fibers can be obtained by subjecting cellulose raw materials to chemical treatment or physical treatment and defibration (miniaturization). it can. Examples of cellulose raw materials used to obtain cellulose fibers include softwood or hardwood kraft pulp, sulfite pulp, thermomechanical pulp, wood pulp such as recycled pulp, cotton pulp such as cotton linter and cotton lint, Non-wood pulp derived from straw, bagasse, bamboo, hemp, jute, kenaf and the like can be mentioned. These may be used individually by 1 type and may use 2 or more types together. The cellulose fiber is a concept that does not include a polymer obtained by decomposing microfibrils (that is, a polymer not composed of microfibrils).

  The cellulose fiber may be any fiber that does not dissolve in an aqueous solvent. For example, microfibrillated cellulose, cellulose nanofiber, or cellulose nanocrystal can be used.

  Microfibrillated cellulose is a fiber that has been fibrillated by subjecting the cellulose raw material only to physical treatment (for example, beating treatment, homogenization treatment, pulverization treatment), and can be produced by a known method. For example, it can be produced by subjecting an aqueous suspension of cellulose raw material to a high-pressure homogenizer treatment and miniaturization. Since the microfibrillated cellulose is a fiber produced by performing only physical treatment, the surface thereof does not have a functional group other than a hydroxyl group derived from cellulose. Note that the microfibrillated cellulose can have a diameter of 10 nm to 100 nm and a length of 1 μm or more, for example.

  Cellulose nanofibers are chemically treated (for example, carboxylated (oxidized), carboxymethylated, and phosphoric esterified) on cellulose raw materials to introduce functional groups different from hydroxyl groups on the surface of microfibrils. A fibrillated fiber, a functional group different from a hydroxyl group is introduced on the surface of the cellulose nanofiber. The functional group introduced to the surface of the cellulose nanofiber is preferably an anionic group different from a hydroxyl group such as a carboxyl group, a carboxymethyl group, and a phosphate ester group. Cellulose nanofibers having an anionic group different from the hydroxyl group on the surface of the aggregate in which the coating layer is formed are compared with the microfibrillated cellulose having no anionic group other than the hydroxyl group on the surface. A large charge can be generated on the surface or the surface of the composite particle. The cellulose nanofibers can have a diameter of 3 nm to 10 nm and a length of 0.5 μm to 5 μm, for example. Although cellulose nanofiber can be manufactured by a well-known method, the following manufacturing methods can be mentioned, for example.

  Cellulose nanofibers having a carboxyl group on the surface can be produced, for example, by carboxylating (oxidizing) a cellulose raw material using a co-oxidant in the presence of an N-oxyl compound, and defibrating the carboxylated cellulose raw material. . The amount of the carboxyl group in the cellulose nanofiber can be, for example, 0.6 mmol / g or more and 2.0 mmol / g or less, and preferably 1.0 mmol / g or more and 2.0 mmol / g or less.

  Examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and derivatives thereof (for example, 4-hydroxy TEMPO). The amount of the N-oxyl compound used is not particularly limited as long as it is an amount capable of oxidizing the cellulose raw material. For example, 0.01 mmol to 10 mmol is preferable with respect to 1 g of the cellulose raw material, and 0.01 mmol to 1 mmol is preferable. More preferably, it is 0.05 mmol or more and 0.5 mmol or less.

  Examples of the co-oxidant include halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like. The appropriate amount of the co-oxidant is, for example, preferably from 0.5 mmol to 500 mmol, more preferably from 0.5 mmol to 50 mmol, further preferably from 1 mmol to 25 mmol, and more preferably from 3 mmol to 10 mmol, based on 1 g of the cellulose raw material. Is most preferred.

  Carboxylation (oxidation) of the cellulose raw material can be performed by mixing the cellulose raw material into an aqueous solution containing an N-oxyl compound, a co-oxidant, and a dispersion medium. As the dispersion medium, for example, water can be used. Although the temperature conditions of aqueous solution are not specifically limited, For example, they can be 4 to 40 degreeC, and can also be 15 to 30 degreeC. In addition, the time condition for carrying out carboxylation is not particularly limited, but can be, for example, 0.5 hours to 6 hours, or 0.5 hours to 4 hours. In addition, since the pH of the aqueous solution containing the N-oxyl compound and the co-oxidant may decrease with the reaction, an alkaline solution such as an aqueous sodium hydroxide solution is added to adjust the pH of the aqueous solution to 8 to 12, preferably It can be maintained at about 10 or more and 11 or less.

  The fibrillation of the carboxylated cellulose raw material can be performed using a disperser. Examples of the disperser include a disaggregator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-axis extruder, a twin-screw extruder, an ultrasonic stirrer, and a home juicer mixer. It is done. The fibrillation of the carboxylated cellulose raw material can be performed in a state where the carboxylated cellulose raw material is contained in the dispersion medium. As the dispersion medium, for example, an aqueous solvent used in the first step can be used.

  The carboxylated cellulose raw material may be subjected to a purification treatment to remove impurities such as unreacted co-oxidant before being fibrillated. Examples of the purification treatment include a method of washing a carboxylated cellulose raw material with water.

  Cellulose nanofibers having a carboxymethyl group on the surface can be produced by a known method. For example, a cellulose raw material is carboxymethylated using halogenated acetic acid in water and / or an alcohol solvent, and carboxymethylated. It can be manufactured by defibrating the cellulose raw material. The amount of the carboxymethyl group in the cellulose nanofiber can be, for example, 0.6 mmol / g or more and 2.0 mmol / g or less, and preferably 1.0 mmol / g or more and 2.0 mmol / g or less.

  Examples of the halogenated acetic acid include monochloroacetic acid, monobromoacetic acid, monofluoroacetic acid and the like. The amount of halogenated acetic acid used is not particularly limited as long as it is an amount capable of carboxymethylating the cellulose raw material.

  The alcohol used for the solvent is preferably a lower alcohol having 5 or less carbon atoms, and examples of the lower alcohol include methanol, ethanol, isopropyl alcohol, and n-butanol. These may be used alone or in admixture of two or more. The temperature condition of the reaction solvent is not particularly limited, but is preferably 10 ° C or higher and 80 ° C or lower, and more preferably 20 ° C or higher and 70 ° C or lower. Moreover, the time conditions for performing carboxymethylation can be 0.5 hours or more and 8 hours or less, and can also be 1 hour or more and 5 hours or less.

  The carboxymethylated cellulose raw material can be defibrated using a method similar to the defibrated method of the carboxylated cellulose raw material, and the carboxymethylated cellulose raw material is contained in the dispersion medium. It can be carried out. As the dispersion medium, for example, an aqueous solvent used in the first step can be used.

  In addition, the cellulose nanofiber obtained by carboxymethylating a cellulose raw material is a substance different from carboxymethylated cellulose obtained by decomposing microfibrils (that is, not composed of microfibrils).

  Cellulose nanofibers having a phosphoric acid group on the surface can be produced by a known method. For example, a cellulose raw material obtained by phosphorylating a cellulose raw material in the presence of a compound having a phosphoric acid group to form a phosphoric acid ester Can be produced by defibration.

  The amount of phosphate groups in the cellulose nanofiber can be, for example, 0.6 mmol / g or more and 2.0 mmol / g or less, and preferably 1.0 mmol / g or more and 2.0 mmol / g or less. Examples of the compound having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, and the like. The usage-amount of the compound which has a phosphoric acid group should just be the quantity which can phosphorylate a cellulose raw material, and is not restrict | limited especially.

  Phosphate esterification of the cellulose raw material can be performed by mixing the cellulose raw material in an aqueous solution containing a compound having a phosphate group and a dispersion medium. As the dispersion medium, for example, water can be used. The cellulose ester material that has been phosphorylated can be defibrated using a method similar to the method for defibrating the carboxylated cellulose material, and the phosphoric esterified cellulose material is contained in the dispersion medium. Can be done in the state. As the dispersion medium, for example, an aqueous solvent used in the first step can be used.

  Cellulose nanocrystals are fibers defibrated by acid hydrolysis of a cellulose raw material and can be produced by a known method. For example, the cellulose nanocrystal can have a diameter of 5 nm to 10 nm and a length of 0.1 μm to 0.2 μm.

  Cellulose nanocrystals can be produced, for example, by treating a cellulose raw material with sulfuric acid or hydrochloric acid. The amount of sulfuric acid and hydrochloric acid used is not particularly limited as long as it is an amount capable of acid-hydrolyzing the cellulose raw material, and can be, for example, 100 mmol or more and 150 mmol or less with respect to 1 g of the cellulose raw material.

  The acid hydrolysis of the cellulose raw material can be performed by suspending the cellulose raw material in sulfuric acid or hydrochloric acid. Although the temperature conditions of sulfuric acid and hydrochloric acid are not particularly limited, for example, the temperature can be 25 ° C. or higher and 90 ° C. or lower. The treatment time with sulfuric acid or hydrochloric acid is not particularly limited, but can be, for example, 30 minutes or more and 240 minutes or less. Note that the cellulose raw material subjected to the acid hydrolysis treatment may be neutralized using an alkali such as sodium hydroxide.

  Cellulose nanocrystals obtained by acid hydrolysis of cellulose raw material with sulfuric acid have a small amount of sulfo groups (anionic groups) introduced on the surface, so microfibrils that do not have anionic groups other than hydroxyl groups on the surface Compared with the fluorinated cellulose, a large charge can be generated on the surface of the aggregate on which the coating layer is formed or on the surface of the composite particles. On the other hand, an anionic group is not introduced into the surface of cellulose nanocrystals obtained by treating a cellulose raw material with hydrochloric acid. That is, like microfibrillated cellulose, it does not have functional groups other than the hydroxyl group derived from cellulose. For this reason, it is difficult to generate a large charge on the surface of the aggregate on which the coating layer is formed or the surface of the composite particles.

  The length of the cellulose fiber used in the first step can be measured using, for example, a transmission electron microscope. Moreover, the diameter of a cellulose fiber can be measured using an atomic force microscope. The amount of anionic groups other than hydroxyl groups on the cellulose fiber surface can be measured using electric conductivity titration.

  The content of the cellulose fiber contained in the aqueous solvent is not particularly limited as long as a coating layer can be formed on the entire surface of the aggregate. For example, it is 0.5 mass part or more and 5 mass parts or less with respect to 100 mass parts of aqueous solvents.

  The aqueous solvent may contain other substances in addition to the above-described cellulose fiber and polymerizable monomer. Examples of other substances include polymerization initiators and plasticizers. When other substances such as a polymerization initiator and a plasticizer are contained in the aqueous solvent, ultrasonic treatment and stirring treatment can be applied to the aqueous solvent containing the polymerizable monomer, cellulose fiber, and other substances.

  Examples of the polymerization initiator include radical polymerization initiators such as organic peroxides and azo initiators, and anionic polymerization initiators such as organic alkali metals.

  Examples of the organic peroxide include cumene hydroperoxide (CHP), ditertiary butyl peroxide, dicumyl peroxide, benzoyl peroxide (BPO), lauroyl peroxide (LPO), and dimethylbis (tertiary butyl peroxide). ) Hexane, dimethyl bis (tertiary butyl peroxy) hexyne-3, bis (tertiary butyl peroxy isopropyl) benzene, bis (tertiary butyl peroxy) trimethyl cyclohexane, butyl bis (tertiary butyl peroxy) valerate, Examples include 2-butylhexane peroxyacid tertiary butyl, dibenzoyl peroxide, paramentane hydroperoxide, and tertiary butyl peroxybenzoate.

  Examples of the azo initiator include 2,2-azobisisobutyronitrile, 2,2-azobis-2-methylbutyronitrile, 2,2-azobis-2,4-dimethylvaleronitrile, 2,2 -Azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2-azobis (methyl 2-methylpropanoate), 2,2-azobis (2-methylpropaneamidine) dihydrochloride .

  Examples of the organic alkali metal include ethyl lithium, n-butyl lithium, tertiary butyl lithium, ethyl sodium, lithium biphenyl, lithium naphthalene, lithium triphenyl, sodium naphthalene, potassium naphthalene, and α-methylstyrene sodium dianion. it can.

  When a polymerization initiator that does not dissolve in an aqueous solvent is contained in the aqueous solvent and subjected to ultrasonic treatment or stirring treatment, the polymerization initiator is covered with a coating layer together with an aggregate of polymerizable monomers. That is, an assembly of polymerizable monomers and a polymerization initiator coexist in the coating layer. For this reason, a polymerizable monomer becomes easy to superpose | polymerize in a 2nd process. Therefore, in the first step, it is preferable to subject the aqueous solvent containing the polymerization initiator, the polymerizable monomer, and the cellulose fiber not dissolved in the aqueous solvent to ultrasonic treatment or stirring treatment.

  Examples of the plasticizer include phthalic acid esters, adipine sun esters, polyesters, polyethers, phosphoric acid esters, epoxidized vegetable oils, maleic acid esters, and benzoic acid esters.

  The aqueous solvent preferably contains no emulsifier. When an emulsifier is included, the surface of the aggregate is easily covered with the emulsifier, and the coating layer may not be formed. In addition, the aggregates covered with the emulsifier tend to bond and fuse with each other when polymerizing the polymerizable monomer in the second step, so that it is difficult to produce fine composite particles, or the coating layer is inside the polymer. May be taken in. Therefore, in the first step, it is particularly preferable to subject the aqueous solvent containing only the polymerization initiator, the polymerizable monomer, and the cellulose fiber that are not dissolved in the aqueous solvent to ultrasonic treatment or stirring treatment.

  Examples of such emulsifiers include anionic emulsifiers such as alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkylphenyl sulfonates, dialkylsulfosuccinate salts, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and the like. Nonionic emulsifiers such as polyoxyethylene-polyoxypropylene block copolymers, vinyl sulfonates, polyoxyethylene sulfates of acrylic acid, polyoxyethylene sulfonates of methacrylic acid, polyoxyethylene alkenyl phenyl sulfonates, polyoxy Anionic reactive emulsifiers such as ethylene alkenyl phenyl sulfates, sodium allyl alkyl sulfosuccinate, polyoxypropylene sulfonate methacrylates, It can be exemplified polyoxyethylene alkenyl ether, a nonionic reactive emulsifier such as polyoxyethylene methacryloyl ether.

  In the second step, the polymerizable monomer is polymerized in the aggregate in which the coating layer is formed.

  The method for polymerizing the polymerizable monomer can be appropriately selected according to the type of the polymerizable monomer, and for example, an emulsion polymerization method or a suspension polymerization method can be used.

  The conditions for the emulsion polymerization method are not particularly limited, and known conditions can be used. For example, the polymerization initiator mentioned above may be added to an aqueous solvent containing the aggregate on which the coating layer is formed, and polymerization may be performed at 50 ° C. to 95 ° C. for 4 hours to 12 hours. In the first step, when the polymerization initiator is contained in the aqueous solvent, the polymerization initiator may not be contained in the second step.

  The conditions for the suspension polymerization method are not particularly limited, and known conditions can be used. For example, the above-mentioned polymerization initiator is added to an aqueous solvent containing an aggregate on which a coating layer is formed, and the conditions of stirring at 50 to 95 ° C. for 4 to 12 hours and 50 to 300 rpm are given. Can do. In the first step, when the polymerization initiator is contained in the aqueous solvent, the polymerization initiator may not be contained in the second step.

  Although content of the polymerization initiator contained in an aqueous solvent is not specifically limited, For example, it is 0.01 mass part or more and 1 mass part or less with respect to 100 mass parts of aqueous solvents.

  When a photocurable monomer such as 1,6-hexanediol diacrylate or a ring-opening polymerizable monomer such as ε-caprolactam is used as the polymerizable monomer, an aqueous solvent is used in the first step or the second step. It is not necessary to add a polymerization initiator. When a photocurable monomer is used, the photocurable monomer constituting the aggregate can be polymerized only by irradiating light (radiation, electron beam, or ultraviolet ray) to the aggregate on which the coating layer is formed. Can do. When a ring-opening polymerizable monomer is used, the ring-opening polymerizable monomer can be polymerized only by adding an acid or a base catalyst to the aggregate in which the coating layer is formed.

  FIG. 2 is a schematic view showing an aqueous solvent after polymerizing a polymerizable monomer in an assembly in which a coating layer is formed. As shown in FIG. 2, a polymer 14 is formed inside the coating layer 12 by polymerizing a polymerizable monomer in the assembly 11 in which the coating layer 12 is formed. The polymer 14 is dispersed in the aqueous solvent 13 with the entire surface covered with the coating layer 12.

  In addition, it can confirm that a polymer is covered with the coating layer using a scanning electron microscope, and you may confirm by observing the cross section of the polymer covered with the coating layer.

  The shape and particle diameter (diameter) of the polymer (composite particles) covered with the coating layer are not particularly limited, and can be, for example, spherical with a particle diameter of 1 μm to 100 μm. The particle diameter of the polymer (composite particles) covered with the coating layer can be measured using a dynamic light scattering method or an optical microscope. Moreover, the thickness of the coating layer is not particularly limited, but can be, for example, 3 nm or more and 50 nm or less. The thickness of the coating layer can be obtained by measuring the thickness of the coating layer in the cross section of the polymer using a scanning electron microscope.

  Although content of the cellulose fiber in the polymer (composite particle) covered with the coating layer is not particularly limited, for example, it can be 0.1% by mass or more and 10% by mass or less. Cellulose fiber content is calculated by measuring the mass reduction rate at 100 to 300 ° C. of the polymer (composite particles) covered with the coating layer using a differential thermal and thermogravimetric simultaneous measurement (TG-DTA) device. can do.

  In the process of polymerizing the polymerizable monomer constituting the aggregate, the cellulose fiber in which the aqueous solvent is dispersed may be taken into the coating layer, or a part of the cellulose fiber may be released from the coating layer. For this reason, the coating layer covering the polymer and the coating layer covering the aggregate of polymerizable monomers may have the same thickness or different thicknesses.

  Although the manufacturing method of this embodiment may be comprised only by the 1st process and 2nd process which were mentioned above, in addition to a 1st process and a 2nd process, the 3rd process which isolate | separates composite particles from an aqueous solvent, A fourth step of washing the composite particles separated from the aqueous solvent may be included.

  In the third step, the composite particles are separated from the aqueous solvent. The method for separating the composite particles from the aqueous solvent is not particularly limited, and examples thereof include a method of centrifuging the aqueous solvent containing the composite particles. The conditions for centrifugation are not particularly limited, and examples include conditions for centrifugation at 1000 rpm to 10,000 rpm for 5 minutes to 30 minutes.

  In the fourth step, the composite particles separated from the aqueous solvent are washed. The method for washing the composite particles is not particularly limited, and examples thereof include a method of immersing the composite particles in water.

  According to the production method of the present embodiment including the first step and the second step, a novel method for producing composite particles having a coating layer composed of cellulose fibers and a polymer covered with the coating layer is provided. Can do.

  Further, when cellulose fibers having an anionic group different from hydroxyl groups on the surface are used as cellulose fibers, the coating layer is compared with the case where cellulose fibers having no anionic group other than hydroxyl groups are used on the surface. A large charge can be given to the surface of the aggregate in which is formed. For this reason, in an aqueous solvent, aggregates repel each other and aggregates become difficult to fuse. Accordingly, fine composite particles can be produced, and the particle size distribution (particle diameter distribution range) of the produced composite particles can be narrowed. Moreover, since the produced composite particles have a large charge on the surface, like the aggregate on which the coating layer is formed, they can exhibit excellent dispersibility.

  The composite particles produced by the production method of the present embodiment can be used in various applications such as ion exchange resins, liquid crystal display spacers and antibody carriers.

  Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1
5 g (absolutely dried) bleached unbeaten kraft pulp derived from coniferous trees (absolutely dried) is added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 514 mg (5 mmol) of sodium bromide are dissolved. Stir until evenly dispersed. After adding 50 ml of an aqueous sodium hypochlorite solution (effective chlorine 5%) to the reaction system, the pH was adjusted to 10 with an aqueous 0.5N hydrochloric acid solution to initiate an oxidation reaction. During the reaction, the pH in the system was lowered, but a 0.5N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and sufficiently washed with water to obtain oxidized (carboxylated) pulp. A slurry in which oxidized pulp is suspended in water is treated with a double cylinder type homogenizer (7500 rpm) for 2 minutes, then treated with an ultrasonic homogenizer (20 kHz) for 3 minutes, and cellulose nanofibers having a carboxyl group on the surface (hereinafter referred to as “TEMPO”). Also referred to as “oxidized CNF”. In addition, when measured using an atomic force microscope, the TEMPO oxidized CNF had a diameter of 3 nm and a length of 0.5 μm or more and 1.5 μm or less.

100 parts by mass of water (aqueous solvent), 1 part by mass of TEMPO-oxidized CNF, 10 parts by mass of divinylbenzene (polymerizable monomer), 2,2-azobis-2,4-dimethylvaleronitrile (polymerization initiator) 5 parts by mass was added to obtain a reaction solution. The obtained reaction solution was irradiated with ultrasonic waves having a frequency of 20 kHz and an output of 100 W / cm ² for 1 minute to form a coating layer composed of TEMPO-oxidized CNF on the surface of divinylbenzene (aggregate).

  The reaction solution irradiated with ultrasonic waves was heated to 70 ° C. and maintained for 8 hours to polymerize divinylbenzene covered with the coating layer. After 8 hours, the reaction solution was cooled and centrifuged at 10,000 rpm to recover a polymer (composite particles) of divinylbenzene covered with a coating layer.

(Example 2)
As the microfibrillated cellulose (hereinafter also referred to as “MFC”), MFC (trade name: Celish PC110S) manufactured by Daicel Chemical Industries, Ltd. was used. In addition, when measured using an atomic force microscope, the MFC had a diameter of 10 nm to 100 nm and a length of 1 μm or more.

100 parts by weight of water (aqueous solvent), 1 part by weight of MFC, 10 parts by weight of divinylbenzene (polymerizable monomer), and 0.5 parts by weight of 2,2-azobis-2,4-dimethylvaleronitrile (polymerization initiator) Part was added to obtain a reaction solution. The obtained reaction solution was irradiated with ultrasonic waves having a frequency of 20 kHz and an output of 100 W / cm ² for 1 minute to form a coating layer composed of MFC on the surface of divinylbenzene (aggregate).

  The reaction solution irradiated with ultrasonic waves was heated to 70 ° C. and maintained for 8 hours to polymerize divinylbenzene covered with the coating layer. After the elapse of 8 hours, the reaction solution was cooled and centrifuged at 10,000 rpm, and the polymer (composite particles) of divinylbenzene covered with the coating layer was recovered.

(Example 3)
As the cellulose nanocrystal (hereinafter also referred to as “MCC”), MCC (trade name: Avicel PH101) manufactured by Fuluka Corporation was used. This MCC was a cellulose nanocrystal obtained by treating a cellulose raw material with hydrochloric acid. When measured using an atomic force microscope, the MCC had a diameter of 5 nm to 10 nm and a length of 0.1 μm to 0.3 μm.

100 parts by weight of water (aqueous solvent), 1 part by weight of MCC, 10 parts by weight of divinylbenzene (polymerizable monomer), and 0.5 parts by weight of 2,2-azobis-2,4-dimethylvaleronitrile (polymerization initiator) Part was added to obtain a reaction solution. The obtained reaction solution was irradiated with ultrasonic waves having a frequency of 20 kHz and an output of 100 W / cm ² for 1 minute to form a coating layer composed of MCC on the surface of divinylbenzene (aggregate).

  The reaction solution irradiated with ultrasonic waves was heated to 70 ° C. and maintained for 8 hours to polymerize divinylbenzene covered with the coating layer. After 8 hours, the reaction solution was cooled and centrifuged at 10,000 rpm to recover a polymer (composite particles) of divinylbenzene covered with a coating layer.

(Comparative Example 1)
As the carboxymethylated cellulose (hereinafter also referred to as “CMC”), CMC manufactured by Wako Pure Chemical Industries, Ltd. was used. The amount of carboxyl groups in CMC was 2.54 mmol / g. In addition,

100 parts by weight of water (aqueous solvent), 1 part by weight of CMC, 10 parts by weight of divinylbenzene (polymerizable monomer), 0.5 parts by weight of 2,2-azobis-2,4-dimethylvaleronitrile (polymerization initiator) Part was added to obtain a reaction solution. The obtained reaction solution was irradiated with ultrasonic waves having a frequency of 20 kHz and an output of 100 W / cm ² for 1 minute.

  The reaction solution irradiated with ultrasonic waves was heated to 70 ° C. and maintained for 8 hours to polymerize divinylbenzene. After 8 hours, the reaction solution was cooled and centrifuged at 10,000 rpm to recover a divinylbenzene polymer.

(Comparative Example 2)
A divinylbenzene polymer was recovered under the same conditions as in Example 1 except that TEMPO-oxidized CNF was not used.

[Confirmation of divinylbenzene in the reaction solution after ultrasonic irradiation]
About Examples 1-3 and Comparative Examples 1-2, the divinylbenzene (aggregate) in the reaction liquid after ultrasonic irradiation was confirmed using the optical microscope. The optical micrographs of divinylbenzene of Examples 1 to 3 and Comparative Example 1 are shown in FIG. In the reaction solution of Comparative Example 2, it was confirmed visually that divinylbenzene was separated from water and a divinylbenzene layer was formed.

  As can be understood from FIG. 3, in Examples 1 to 3 and Comparative Example 1, a plurality of divinylbenzenes were dispersed in water in a spherical state. In particular, in Example 1 and Comparative Example 1, the dispersibility of divinylbenzene was higher than in Examples 2-3.

[Confirmation of polymer of divinylbenzene in reaction solution]
About Examples 1-3 and Comparative Examples 1-2, the polymer of the divinylbenzene in the reaction liquid after divinylbenzene polymerization was confirmed using the optical microscope. Optical micrographs of the divinylbenzene polymers of Examples 1 to 3 and Comparative Example 1 are shown in FIG. In the reaction solution of Comparative Example 2, it was confirmed visually that the polymer lump of divinylbenzene was separated from water.

  As can be understood from FIG. 4, in Examples 1 to 3, a plurality of polymers of divinylbenzene were dispersed in water in a spherical shape in the same manner as divinylbenzene before polymerization. Particularly, in Example 1, the dispersibility of the polymer of divinylbenzene was higher than those in Examples 2-3. On the other hand, in Comparative Example 1, a plurality of divinylbenzene polymers were fused to form a fused body.

[Confirmation of coating layer]
A scanning electron micrograph was obtained for the polymer (composite particles) of divinylbenzene collected in Example 1. FIG. 5 shows a scanning electron micrograph showing the appearance of the polymer (composite particles) of divinylbenzene, and FIG. 6 shows a scanning electron micrograph of a cross section of the polymer (composite particles) of divinylbenzene.

  As can be understood from FIGS. 5 and 6, in the composite particles of Example 1, a coating layer having a uniform thickness was formed on the entire surface of the polymer. Moreover, the cellulose fiber was not contained in the inside of a polymer. When the thickness of the coating layer was measured from the scanning electron micrograph shown in FIG. 6, the thickness of the coating layer was uniformly 8 nm.

[Measurement of surface potential of composite particles]
The zeta potential on the surface of the composite particles of Examples 1 to 3 was measured using a surface potential measuring device (Delsa Max manufactured by Beckman Coulter). The results are shown in Table 1 described later.

[Measurement of yield of composite particles]
The yield of the composite particles of Examples 1 to 3 was calculated based on the following formula (1). The results are shown in Table 1 described later.
Yield (%) = A / B × 100 (1)
In the above formula (1), A is the mass (g) of the recovered composite particles, and B is the total mass (g) of the raw materials excluding the aqueous solvent among the raw materials used for manufacturing the composite particles.

[Measurement of particle diameter range and average particle diameter of composite particles]
Using the dynamic light scattering method (Delsa Max manufactured by Beckman Coulter), the particle size distribution of the composite particles of Examples 1 to 3 was obtained, and the average particle size of the composite particles was obtained. The particle diameter distribution range and average particle diameter of the composite particles of Examples 1 to 3 are shown in Table 1 described later.

[Measurement of cellulose fiber content in composite particles]
The mass reduction rate at 100 ° C. to 300 ° C. of the composite particles of Example 1 was measured using a differential thermal / thermogravimetric simultaneous measurement apparatus (TG-DTA2000SE, manufactured by Netzsch). Based on the measured mass reduction rate, the content of cellulose fibers relative to 100% by mass of the composite particles was calculated. The results are shown in Table 1 described later.

  In addition, as is clear from the confirmation result of the polymer of divinylbenzene in the reaction solution, the production methods of Comparative Examples 1 and 2 have a coating layer composed of cellulose fibers and a polymer covered with the coating layer. Composite particles could not be produced. For this reason, about Comparative Examples 1-2, the measurement (The surface potential, the yield, the range of particle diameter, the average particle diameter, and the content of cellulose fibers) related to the composite particles was not performed.

[Table 1]

  From the above results, it was understood that according to the production method of the present embodiment, composite particles having a coating layer composed of cellulose fibers and a polymer covered with the coating layer can be produced.

In particular, as can be understood from Table 1, the composite particles of Example 1 in which TEMPO-oxidized CNF was used had a lower surface potential than the composite particles of Examples 2-3. For this reason, the composite particle of Example 1 had high dispersibility compared with the composite particle of Examples 2-3, as can be understood from FIG. Further, as can be understood from Table 1, the composite particle of Example 1 had a narrow particle size distribution range as compared with the composite particles of Examples 2-3. This is considered to be caused by the fact that the TEMPO oxidized CNF constituting the coating layer suppressed the fusion of the aggregates of divinylbenzene during the polymerization process of divinylbenzene.

Claims (10)

A method for producing composite particles comprising a coating layer composed of cellulose fibers and a polymer covered by the coating layer,
A first step of forming a coating layer composed of cellulose fibers on the surface of an aggregate of polymerizable monomers in an aqueous solvent;
A method for producing composite particles, comprising: a second step of polymerizing the polymerizable monomer in the aggregate on which the coating layer is formed.   The method for producing composite particles according to claim 1, wherein the polymerizable monomer has two or more vinyl groups.   The method for producing composite particles according to claim 2, wherein the polymerizable monomer is divinylbenzene.   The said cellulose fiber has an anionic group different from a hydroxyl group on the surface, The manufacturing method of the composite particle as described in any one of Claim 1 to 3 characterized by the above-mentioned.   The said cellulose fiber is a cellulose nanofiber which has a carboxyl group on the surface, The manufacturing method of the composite particle of Claim 4 characterized by the above-mentioned. A coating layer composed of cellulose fibers;
And a polymer covered with the coating layer.   The composite particle according to claim 6, wherein the polymer is a polymer of a polymerizable monomer having two or more vinyl groups.   The composite particle according to claim 7, wherein the polymerizable monomer is divinylbenzene.   The composite particle according to any one of claims 6 to 8, wherein the cellulose fiber has an anionic group different from a hydroxyl group on a surface thereof. The composite particle according to claim 9, wherein the cellulose fiber is a cellulose nanofiber having a carboxyl group on a surface thereof.