JP6656647B1 - Composite resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite resin composition capable of forming a film in which cellulose nanofibers are uniformly dispersed in a resin, and a method for producing the same. A composite resin composition comprising an aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers dispersed in the aqueous dispersion medium, the resin particles comprising: Contains at least one selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles, and the nonvolatile content of the composite resin composition is 0.01 to 0. The cellulose nanofibers were dispersed when a sample obtained by dripping a liquid diluted with an amount of water in the range of 1% by mass onto a measurement substrate and observing it with an atomic force microscope, and And a composite resin composition in which a structure in which the resin particles are attached to the cellulose nanofibers is observed. [Selection diagram] None

Description

  The present invention relates to a composite resin composition and a method for producing the composite resin composition.

  Cellulose nanofiber (hereinafter, sometimes referred to as "CNF") is a fiber material obtained by finely disintegrating (defibrating) cellulose fibers mainly derived from the cell wall of a plant to a nanometer size. CNF has many advantages, such as light weight, high strength, high elastic modulus, and small deformation due to heat, and has a small environmental load because it can be extracted from various biomass derived from plants. Therefore, development of composite materials with other materials such as rubber and resin is also in progress.

  For example, Patent Literature 1 discloses a composite resin composition containing cellulose nanofibers having an average diameter of 3 to 400 nm in a resin and configured to enable production of a molded article having both transparency and strength. It has been disclosed. Patent Document 2 discloses a latex emulsion in which a predetermined amount of cellulose nanofiber is blended with a natural rubber-based latex or an acrylic emulsion in order to increase the holding power of the latex emulsion.

  Further, Patent Literature 3 discloses a composite resin composition obtained by polymerizing a polymerizable compound in a dispersion in which a polymerizable compound and cellulose nanofibers are dispersed in a solvent. Patent Document 4 discloses a composite containing a cellulose nanofiber and a copolymer composed of an ethylenically unsaturated monomer by copolymerizing an ethylenically unsaturated monomer in a cellulose nanofiber dispersion. A method of making a body is disclosed.

JP 2012-167202 A JP 2015-218228 A JP 2014-105217 A JP-A-2006-155897

  In a conventional composite resin composition containing CNF and a resin, when mixing the CNF and the resin, the dispersibility of the CNF may be low, such as aggregation or non-uniform dispersion of the CNF. In Patent Documents 3 and 4, the dispersibility of CNF in a resin is increased by polymerizing the polymerizable compound in a dispersion containing a predetermined polymerizable compound, CNF, an emulsifier, and water. Has been proposed.

  On the other hand, when a molded product such as a film is formed from a composite resin composition containing CNF and a resin, the effect (for example, improvement in tensile strength and the like) due to the inclusion of CNF is sufficiently exhibited. It is desirable to obtain a film in which cracks and aggregates of CNF are hardly observed. As a result of the study by the present inventors, in the above-described conventional technology, depending on the manufacturing conditions of the molded product such as the composite resin composition and the film, from the composite resin composition, CNF was uniformly dispersed at a high level in the resin. It was found that a film could not be formed.

  Accordingly, an object of the present invention is to provide a composite resin composition capable of forming a film in which cellulose nanofibers are sufficiently uniformly dispersed in a resin, and a method for producing the same.

  The present invention is a composite resin composition containing an aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers dispersed in the aqueous dispersion medium, wherein the resin particles Contains at least one member selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles, and has a non-volatile content of 0.01 to 0 for the composite resin composition. When a sample diluted with water in an amount falling within a range of 1% by mass was dropped on a measurement substrate and dried, the cellulose nanofibers were dispersed when observed by an atomic force microscope, and And a composite resin composition having a structure in which the resin particles are adhered to the cellulose nanofiber.

  Further, the present invention provides a resin emulsion in which at least one resin particle selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles is emulsified in an aqueous dispersion medium. And the cellulose nanofibers are brought into contact with each other under the condition that the temperature is 50 ° C. or more, and a mixing step of mixing them is performed. By the mixing step, the aqueous dispersion medium and the aqueous dispersion medium are emulsified. Provided is a method for producing a composite resin composition, which obtains a composite resin composition containing the resin particles and the cellulose nanofibers dispersed in the aqueous dispersion medium.

  According to the present invention, it is possible to provide a composite resin composition capable of forming a film in which cellulose nanofibers are sufficiently uniformly dispersed in a resin, and a method for producing the same.

4 is an image observed by an atomic force microscope (AFM) for each of the resin compositions obtained in Examples 1 and 5 and Comparative Example 4. It is the photograph which image | photographed the surface of each film | membrane obtained in Examples 1-3 and Comparative Examples 1, 3, and 4.

  Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

  As described above, in the conventional composite resin composition containing cellulose nanofiber (CNF) and a resin, the dispersibility of CNF may be low. In contrast, Patent Documents 3 and 4 disclose a composite resin composition obtained by emulsion-polymerizing a predetermined polymerizable compound in a dispersion containing a predetermined polymerizable compound forming a resin, CNF, an emulsifier, and water. It has been proposed to improve the dispersibility of CNF in a resin.

  However, as a result of the investigations by the present inventors, CNF is converted into a resin from the composite resin composition depending on the production conditions of the conventional composite resin composition and the conditions for producing a molded article such as a film from the composite resin composition. It was found that it was sometimes impossible to form a molded article uniformly dispersed at a high level.

  Specifically, the present inventors have developed a resin obtained by emulsifying at least one kind of resin particles of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles in an aqueous dispersion medium. A composite resin composition containing an emulsion and CNF was studied. More specifically, an aqueous dispersion containing CNF is also charged into the initially charged water at the time of obtaining the resin emulsion, and a method of polymerizing the monomer component forming the resin particles by dropping is experimentally performed. I went to. As a result, it was found that in this method, a large amount of aggregates containing CNF might be generated in the polymerization stage (see Comparative Example 10 described later). Further, in the case where a pre-emulsion containing the monomer component, water, and an emulsifier contains an aqueous dispersion containing CNF, and a method of polymerizing the monomer component is experimentally performed. It was also found that a large amount of aggregates containing CNF were sometimes generated in the polymerization stage (see Comparative Example 11 described later). Therefore, when an attempt is made to form a film from the composite resin composition obtained in these cases, a film having cracks or aggregates containing CNF is formed.

  Based on the above results, the present inventors aggregate CNF in the composite resin composition before film formation in order to obtain a homogeneous film from which cracks and aggregates are hardly observed from the composite resin composition. Therefore, the present inventors thought that it was necessary to uniformly disperse them at a higher level, and made intensive studies on a method for producing a composite resin composition. Among them, the multi-stage polymerization technique is applied, and the polymerization of the above monomer component is completed as the first stage, and then the aqueous dispersion containing CNF is added as the second and subsequent stages, whereby the aqueous dispersion is obtained. An attempt was made to obtain a composite resin composition containing resin particles emulsified in a medium and CNF dispersed in an aqueous dispersion medium. As a result, it was found that the composite resin composition obtained by the method can form a film in which CNF is uniformly dispersed in the resin.

  In the above method, a resin emulsion containing a polymer obtained by polymerizing the above monomer component is obtained, and then an aqueous dispersion containing CNF is added. Have tried a method of adding a CNF-containing aqueous dispersion at room temperature (about 23 ° C.) to a resin emulsion prepared in advance. However, it was found that in the film formed by the composite resin composition obtained by the method, the dispersibility of CNF in the resin was low. Based on this result, the present inventors further examined, the composite resin composition obtained by a method of heating a resin emulsion prepared in advance to a predetermined temperature, and adding CNF to the resin emulsion under the temperature conditions, It was found that it was possible to form a film in which CNF was uniformly dispersed in the resin. In a method such as the above-described multi-stage polymerization, the method of adding CNF as the second and subsequent stages also involves adding CNF immediately after polymerization, so that the temperature of the resin emulsion was not lower than room temperature when CNF was added. Based on this, the present inventors conducted further verification experiments. As a result, it is possible to form a film in which CNF is sufficiently uniformly dispersed in the resin by a method including a step of bringing the resin emulsion into contact with CNF at a temperature of 50 ° C. or higher and mixing them. It has been found possible.

  Further, since the composite resin composition obtained by the above production method was able to form a film in which CNF was sufficiently uniformly dispersed in the resin, the inventors of the present invention considered that in the composite resin composition before the film was formed, , CNF was considered to be uniformly dispersed at a higher level, and the composite resin composition was analyzed. In general, it is difficult to confirm the dispersibility of CNF in a liquid composite resin composition in detail. Therefore, in order to observe in a state close to the state of the composite resin composition, the composite resin composition is diluted with a large amount of water, and one to several drops of the liquid are dropped on the measurement base material and dried. A sample on which no film was formed (a non-film dried sample) was used, and the sample was observed with an atomic force microscope (AFM). As a result, with respect to the composite resin composition capable of forming a film in which CNF was sufficiently uniformly dispersed in the resin, a structure in which CNF was dispersed and resin particles were attached to the CNF was observed. Was not confirmed for the composite resin composition having formed a film having low dispersibility of CNF in the resin, and was found to be specific.

  The composite resin composition found as a result of the above examination and the method for producing the composite resin composition will be described in detail below.

<Composite resin composition>
The composite resin composition of one embodiment of the present invention contains an aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers (CNF) dispersed in the aqueous dispersion medium. The resin particles in the composite resin composition include at least one selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles. The composite resin composition is dried by dropping a liquid obtained by diluting the composite resin composition with water in such an amount that the non-volatile content thereof is in the range of 0.01 to 0.1% by mass on the measurement substrate. When the sample thus obtained is observed with an atomic force microscope, a structure in which CNF is dispersed and resin particles are clumped to the CNF is observed.

  With such a configuration, the composite resin composition can form a film in which CNF is sufficiently uniformly dispersed in the resin. In the composite resin composition in which the above structure is observed by an atomic force microscope, CNF is hardly agglomerated in the aqueous dispersion medium, and is uniformly dispersed at a higher level. It is thought that they are dispersed so as to cling together. Thereby, it is considered that the composite resin composition can uniformly disperse CNF at a high level in the resin and form a uniform film. In addition, since the composite resin composition can form a film in which CNF is sufficiently uniformly dispersed in the resin, by using the composite resin composition, a molded article in which CNF is sufficiently uniformly dispersed in the resin can be obtained. It is also possible to obtain.

  For the observation by the atomic force microscope (AFM), specifically, the composite resin composition is diluted with water to about several hundred times by mass (for example, 500 times by mass), and the non-volatile content of the composite resin composition is reduced to zero. A liquid (diluent) adjusted within the range of 0.01 to 0.1% by mass is used. Then, from the diluent, a dried sample on which no film is formed (non-film dried sample). Specifically, one to several drops (within a range of 0.01 to 0.1 mL) of the above-mentioned diluent as a measurement base material to a mica standard sample (manufactured by Hitachi High-Tech Science) used for AFM observation. A sample was dropped and dried for 24 hours in a glass desiccator in which dried silica gel was sealed. The temperature condition at the time of drying can be a temperature at which the resin particles in the diluting liquid can take a particle form according to the properties of the composite resin composition. Then, the sample is observed using an atomic force microscope (trade name “AFM5100N”, manufactured by Hitachi High-Technologies Corporation). In such an AFM observation, as shown in the examples below, a structure in which cellulose nanofiber (CNF) is used as a shaft and resin particles are gathered along the shaft around the shaft in a tuft of grapes. Is preferably observed.

(Cellulose nanofiber)
Cellulose nanofiber (CNF) is present in the composite resin composition in a state of being dispersed in an aqueous dispersion medium. The type of CNF is not particularly limited, and any type of CNF can be used. Examples of the type of CNF include, for example, CNF mainly obtained by physical / mechanical fibrillation (hereinafter, may be described as “mechanically fibrillated CNF”), and mainly chemical fibrillation. Examples thereof include CNF obtained by the treatment (hereinafter, may be referred to as “chemically defibrated CNF”), and CNF obtained by a treatment combining any of them as a main treatment. One of them may be used alone, two or more CNFs may be used in combination, or a mixture of two or more CNFs may be used. Further, for example, CNF manufactured from a raw material (raw material fiber) such as pulp may be used, or a commercially available CNF product may be used.

  Examples of the mechanical defibration type CNF include CNF obtained by an underwater collision method (ACC method), CNF obtained by a method of pulverization using a machine, and other physical and mechanical defibration treatments. And the like can be mentioned. CNF by the ACC method, for example, pressurizes a suspension water containing a raw material such as pulp, jets and collides from an opposing nozzle, cleaves bonds between fibers by energy generated at the time of collision, and makes the raw material nano-sized. Can be obtained. As the CNF according to the ACC method, for example, a trade name “nanoforest (registered trademark)” manufactured by Chuetsu Pulp and Paper Co., Ltd. can be used. Further, CNF by mechanical pulverization is, for example, a high-speed stirring using a wet stirring device (for example, a high-pressure homogenizer, an ultra-high-speed homogenizer, an ultrasonic homogenizer, a bead mill, etc.) Can be obtained by mechanically defibrating.

  As the chemical fibrillation type CNF, for example, CNF obtained by a method of removing (fibrillating) fibers in water by subjecting suspension water containing a raw material such as pulp to chemical treatment or enzymatic treatment, and other chemical fibrillation-type CNFs And CNF obtained by a suitable defibration method. Examples of CNF obtained by a method using a chemical treatment include CNF produced by a TEMPO catalytic oxidation method. Examples of such a TEMPO-oxidized CNF include “cellenia (registered trademark)” manufactured by Nippon Paper Industries, and “Leocrista (registered trademark)” manufactured by Daiichi Kogyo Seiyaku. Examples of CNF obtained by a method using enzyme treatment include CNF produced by treatment with cellulase (cellulose hydrolase).

  Various pulp can be mentioned as a main raw material of CNF. As the pulp, for example, wood pulp such as softwood pulp and hardwood pulp; rice pulp, kenaf pulp, hemp (linen) pulp, mulberry pulp, bagasse pulp, straw pulp, cotton pulp, bamboo pulp, fruit pulp, rug pulp, and linter Non-wood pulp such as pulp; waste paper pulp; and synthetic fiber pulp. As the pulp, for example, mechanical pulp such as groundwood pulp (GP), refiner ground pulp (RGP), thermomechanical pulp (TMP), and chemishermomechanical pulp (CTMP); Chemical pulp such as KP), sulfide pulp (SP), and alkali pulp (AP); and unbleached pulp and bleached pulp. Further, as a raw material of CNF, for example, cellulose derived from animal materials (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria), and microbial products can also be mentioned.

  The size of CNF is not particularly limited as long as the fiber width is approximately nano-size (1000 nm or less). The fiber width of CNF is, for example, preferably in the range of 1 to 1000 nm, more preferably in the range of 2 to 500 nm, and still more preferably in the range of 3 to 300 nm. The fiber length of CNF is, for example, preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.1 to 100 μm, and further preferably in the range of 0.1 to 50 μm. preferable.

  When CNF is used, when CNF is contained in the composite resin composition, a liquid, paste, or gel in which CNF is dispersed in an aqueous dispersion medium may be used, and CNF is dried. Solid materials may be used. From the viewpoint of easy production of the composite resin composition, it is preferable to use an aqueous dispersion in which the content of CNF is adjusted, for example, within a range of about 0.01 to 10% by mass.

  The content of the cellulose nanofiber (CNF) in the composite resin composition is 0.1 to 10 parts by mass per 100 parts by mass of the resin particles (the total amount of the monomer components constituting the resin particles) in the composite resin composition. Is preferably within the range. From the viewpoint of increasing the tensile strength of a molded product such as a film obtained from the composite resin composition, the content of the CNF is more preferably 0.2 parts by mass or more, and 0.3 parts by mass or more. Is more preferable, and it is still more preferable that the amount is 0.5 parts by mass or more. In addition, from the viewpoint of increasing the ductility (elongation) of a molded product such as a film obtained from the composite resin composition, the content of CNF is more preferably 8 parts by mass or less, and is 7 parts by mass or less. More preferably, it is even more preferably 5 parts by mass or less.

(Aqueous dispersion medium)
As the aqueous dispersion medium contained in the composite resin composition, water is suitable as in the case of the aqueous dispersion medium generally used in the resin emulsion, water alone may be used, or water and a water-soluble organic A mixture with a solvent may be used. Examples of the water-soluble organic solvent include, but are not limited to, methanol, ethanol, isopropanol, ethyl carbitol, ethylene glycol, propylene glycol, glycerin, and N-methylpyrrolidone. One or more organic solvents may be used.

(Resin particles)
The resin particles are present in the composite resin composition by being emulsified in an aqueous dispersion medium, and form a resin emulsion together with the aqueous dispersion medium. The resin particles include at least one selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles.

  In the present specification, the term “(meth) acryl” means that both terms “acryl” and “methacryl” are included. Similarly, the term “(meth) acrylate” means that both the terms “acrylate” and “methacrylate” are included.

  Furthermore, in the present specification, “(meth) acrylic resin” refers to a polymer obtained by polymerizing a (meth) acrylate or a monomer obtained by polymerizing a monomer component containing (meth) acrylate as a main component. Refers to a polymer. Similarly, “styrene-based resin” refers to a polymer in which a styrene-based monomer is polymerized or a copolymer in which a monomer component containing a styrene-based monomer as a main component is polymerized. The “(meth) acrylonitrile-based resin” refers to a polymer obtained by polymerizing (meth) acrylonitrile or a copolymer obtained by polymerizing a monomer component containing (meth) acrylonitrile as a main component. The “main component” in the monomer component forming the resin refers to the monomer (one monomer) having the highest content in the monomer component forming the resin. Two or more main components may be present in the monomer component forming the resin, and any one of them may correspond to the main component described above, and “(meth) acrylic resin”, “styrene-based resin” Resins ”and“ (meth) acrylonitrile-based resins ”may be used. Hereinafter, the homopolymerization and the copolymerization may be simply referred to as "polymerization" including both of them without distinction.

  The monomer component forming each of the above resins may be one or two types of monomers having a polymerizable unsaturated bond (polymerizable monomer) in addition to the monomer as a main component. The above may be included. Therefore, each of the above resin particles may contain a structural unit derived from one or more other polymerizable monomers in addition to a structural unit derived from a monomer as a main component. Good. In the present specification, “structural unit” means a unit of a polymerizable monomer that forms a resin (polymer). "Structural unit derived from (polymerizable monomer)" refers to, for example, a structure in which a polymerizable double bond (C = C) in a monomer is cleaved to form a single bond (-CC-). Unit and the like.

  The content of the main component monomer (one monomer having the highest content) in the monomer components forming the resin particles (of the structural unit derived from the main component monomer in the particles) Content) is preferably in the range of 20 to 90% by mass, more preferably in the range of 30 to 80% by mass, based on the total mass of the monomer components forming the resin particles. More preferably, it is in the range of 40 to 70% by mass.

  Examples of the (meth) acrylate used for the (meth) acrylic resin particles include, for example, alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, and (meth) acrylate. Examples thereof include aralkyl acrylate, aryl (meth) acrylate, and other (meth) acrylates. One or more of these (meth) acrylates can be used. Among these, the monomer component forming the (meth) acrylic resin particles preferably contains at least an alkyl (meth) acrylate, and more preferably contains it as a main component.

  Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, tert-butyl (meth) acrylate, sec-butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (me ) Linear chains such as acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and behenyl (meth) acrylate Or a (meth) acrylic acid alkyl ester having a branched alkyl group; and cyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, And alicyclic alkyl (meth) acrylates such as dicyclopentenyl (meth) acrylate. One or more of these alkyl (meth) acrylates can be used. Among these, a (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 18 (more preferably 1 to 12) carbon atoms is preferable.

  Examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, -Hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate. Can be mentioned. One or more of these can be used.

  Examples of the alkoxyalkyl (meth) acrylate include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, ethoxyethoxyethyl (meth) acrylate, and 2 -Phenoxyethyl (meth) acrylate and the like. One or more of these can be used.

  Examples of the aralkyl (meth) acrylate include benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, and naphthylmethyl (meth) acrylate. One or more of these can be used.

  Examples of the aryl (meth) acrylate include phenyl (meth) acrylate, 4-hydroxyphenyl (meth) acrylate, tolyl (meth) acrylate, and naphthyl (meth) acrylate. One or more of these can be used.

  Other (meth) acrylates include, for example, polyalkylene glycol (meth) acrylates such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and methoxypolyethylene glycol mono (meth) acrylate; 2 Alkyl (meth) acrylate having a halogen atom, such as -chloroethyl (meth) acrylate, trifluoroethyl (meth) acrylate, 2- (perfluorobutyl) ethyl (meth) acrylate, and perfluorooctylethyl (meth) acrylate An amino group such as 2- (dimethylamino) ethyl (meth) acrylate, 2- (diethylamino) ethyl (meth) acrylate, and 3- (dimethylamino) propyl (meth) acrylate; (Meth) acrylic acid ester having a carboxy group such as carboxyethyl (meth) acrylate and carboxypentyl (meth) acrylate; glycidyl (meth) acrylate, glycerin mono (meth) acrylate, (Meth) acrylic acid esters having an epoxy group such as methyl glycidyl (meth) acrylate and 3,4-epoxycyclohexylmethyl (meth) acrylate and derivatives thereof; 2-sulfoethyl (meth) acrylate, and 3-sulfopropyl (meth) ) (Meth) acrylates having a sulfonic acid group such as acrylate; (meth) acrylates having a phosphate group such as 2- (phosphonooxy) ethyl (meth) acrylate; isocyanates such as 2-isocyanatoethyl (meth) acrylate (Meth) acrylate having a nate group; (meth) acrylate having a heterocyclic ring such as tetrahydrofurfuryl (meth) acrylate; alkyl group or aryl such as methoxypolyethylene glycol (meth) acrylate and phenoxy polyethylene glycol (meth) acrylate Group-terminated polyalkylene glycol mono (meth) acrylate and the like can be mentioned. One or more of these can be used.

  The total content of the (meth) acrylate in the monomer component forming the (meth) acrylic resin particles (the total content of structural units derived from the (meth) acrylate in the resin particles) is: It is preferably from 50 to 100% by mass, more preferably from 60 to 99% by mass, further preferably from 65 to 98% by mass, based on the total mass of the monomer components forming the resin particles. preferable.

  The monomer components forming the styrene-based resin particles and the (meth) acrylonitrile-based resin particles also include, in addition to their main components (styrene-based monomer and (meth) acrylonitrile, respectively), (meth) acrylic acid It preferably contains an ester, and more preferably contains an alkyl (meth) acrylate. The total content of the (meth) acrylate in each monomer component forming the styrene-based resin particles and the (meth) acrylonitrile-based resin particles (of the structural unit derived from the (meth) acrylate in the resin particles) (Total content ratio) is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, based on the total mass of the monomer components forming the resin particles.

  Examples of the styrene monomer used for the styrene resin particles include, for example, styrene, α-methylstyrene, o-, m-, p-methylstyrene, o-, m-, p-ethylstyrene, and 4-tert-. Butylstyrene, o-, m-, p-hydroxystyrene, o-, m-, p-methoxystyrene, o-, m-, p-ethoxystyrene, o-, m-, p-chlorostyrene, o-, Examples thereof include m-, p-bromostyrene, o-, m-, p-fluorostyrene, and o-, m-, p-chloromethylstyrene. One or more of these can be used. Among these, the monomer component forming the styrene-based resin particles preferably contains at least styrene, and more preferably contains styrene as a main component.

  In addition, each of the monomer components forming the (meth) acrylic resin particles and the (meth) acrylonitrile resin particles also includes, in addition to their main components ((meth) acrylic acid ester and (meth) acrylonitrile, respectively), styrene It may contain a system monomer.

  The (meth) acrylonitrile used for the (meth) acrylonitrile-based resin particles is acrylonitrile and methacrylonitrile, and one or both of them can be used.

  In addition, each of the monomer components forming the (meth) acrylic resin particles and the styrenic resin particles also includes, in addition to their main components ((meth) acrylic acid ester and styrene monomer, respectively), It may contain acrylonitrile.

  As described above, the monomer components forming the (meth) acrylic resin particles, the styrene resin particles, and the (meth) acrylonitrile resin particles are (meth) acrylic acid ester, styrene monomer, and ( In addition to (meth) acrylonitrile, other polymerizable monomers may be contained. As the other polymerizable monomer, an unsaturated carboxylic acid-based monomer is preferable from the viewpoint of facilitating the preparation of the composite resin composition, and the resin particles are structural units derived from the unsaturated carboxylic acid-based monomer. It is preferable to include In the present specification, the unsaturated carboxylic acid monomers include unsaturated carboxylic acids, and anhydrides and monoesters thereof.

  Examples of the unsaturated carboxylic acid monomer include unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and citraconic acid; maleic anhydride, itaconic anhydride, and the like. And monoesters of unsaturated carboxylic acids such as monomethyl maleate, monobutyl maleate, monomethyl itaconate, and monobutyl itaconate. It is preferable to use one or more of these unsaturated carboxylic acid monomers, and among them, it is more preferable to use (meth) acrylic acid.

  The total content of unsaturated carboxylic acid monomers in the monomer component forming the resin particles (total content of structural units derived from unsaturated carboxylic acid monomers in the resin particles) Is preferably 30% by mass or less based on the total mass of the monomer components forming the polymer. The total content of the unsaturated carboxylic acid-based monomer is more preferably 20% by mass or less, and further preferably 15% by mass or less. When an unsaturated carboxylic acid monomer is used for the resin particles, the total content of the unsaturated carboxylic acid monomer is preferably 0.1% by mass or more. The content is more preferably 5% by mass or more, and further preferably 1% by mass or more.

  Examples of the polymerizable monomer other than the unsaturated carboxylic acid monomer include, for example, an unsaturated monomer having a nitrogen atom other than the above (meth) acrylonitrile; a vinyl monomer; an unsaturated alcohol; Monomer; vinyl ester monomer; unsaturated monomer having an epoxy group; and unsaturated monomer having a sulfonic acid group.

  Examples of the unsaturated monomer having a nitrogen atom include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (Meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N- [2-dimethylaminoethyl] (meth) acrylamide, N- [3-dimethyl (Aminopropyl) (meth) acrylamide monomers such as (meth) acrylamide, diacetone acrylamide, 4-acryloylmorpholine and 4-methacryloylmorpholine; vinyls such as N-vinylacetamide and N-vinyl-N-methylacetamide Acetamido with group Nitrogen-containing heterocycle having a vinyl group such as N-vinyl-2-pyrrolidone, 4-vinylpyridine, 1-vinylimidazole, 2-vinyl-2-oxazoline, and 2-isopropenyl-2-oxazoline. Formula compounds and the like can be mentioned. One or more of these can be used. Among the unsaturated monomers having a nitrogen atom, the above-mentioned (meth) acrylamide-based monomers are preferable, and (meth) acrylamide is more preferable, from the viewpoint of facilitating the preparation of the composite resin composition.

  The total content of the unsaturated monomer having a nitrogen atom other than (meth) acrylonitrile in the monomer component forming the resin particles (the structure derived from the unsaturated monomer having a nitrogen atom in the resin particles) (The total content of the units) is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total mass of the monomer components forming the resin particles. Further, when using the unsaturated monomer having a nitrogen atom in the resin particles, the total content of the unsaturated carboxylic acid-based monomer is preferably 0.1% by mass or more, More preferably, it is at least 0.2% by mass.

  Examples of the vinyl monomer include vinyl chloride and vinyl fluoride. Examples of the unsaturated alcohol include vinyl alcohol and allyl alcohol. Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, phenyl vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caprylate, vinyl laurate, vinyl stearate, and vinyl versatate. Examples of the unsaturated monomer having an epoxy group include allyl glycidyl ether. Examples of the unsaturated monomer having a sulfonic acid group include vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, and 2- (meth) acrylamido-2-methylpropane sulfonic acid. . One or more of these can be used.

  Further, a monomer (crosslinkable monomer) capable of functioning as a crosslinking agent can be used as a polymerizable monomer as a monomer component forming the resin particles. As the crosslinkable monomer, a monomer having two or more polymerizable unsaturated bonds can be used. Examples of the crosslinkable monomer include 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, and 1,4. -Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, tri Ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol Bifunctional (meth) acrylates such as recall di (meth) acrylate and glycerin di (meth) acrylate; pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate And polyfunctional (meth) acrylates; allyl (meth) acrylate; divinylbenzene; and diallyl phthalate. One or more of these can be used.

  Examples of the crosslinkable monomer include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylmethyldimethoxysilane. Silane coupling agents such as acryloxypropyltrimethoxysilane can also be mentioned, and one or more of them can be used.

  The resin particles in the composite resin composition can be obtained by polymerizing a monomer component containing one or more polymerizable monomers in the aqueous dispersion medium described above. Further, for example, the resin particles separately produced from the aqueous dispersion medium contained in the composite resin composition, the aqueous dispersion medium contained in the composite resin composition, post-emulsification by a method such as forced emulsification or self-emulsification. May be. The resin particles are preferably obtained by emulsion-polymerizing a monomer component forming the resin particles in an aqueous dispersion medium contained in the composite resin composition.

  The average particle size of the resin particles by the dynamic light scattering method is not particularly limited, but is preferably 25 to 1000 nm, more preferably 35 to 600 nm, and still more preferably 45 to 400 nm. In the present specification, the average particle size of the resin particles by the dynamic light scattering method is determined by a particle size distribution measuring apparatus using the dynamic light scattering method (for example, trade name “Dense particle size analyzer FPAR-1000”, Otsuka Electronics Co., Ltd.) The average particle diameter determined by the cumulant method analysis using the formula (1).

The glass transition temperature (Tg) of the resin particles is not particularly limited, but is preferably −50 to 100 ° C. In the present specification, the Tg of a resin particle is a value measured by DSC when the resin particle is a homopolymer. When the resin particles are a copolymer, the Tg of the resin particles is a theoretical value obtained from the following FOX formula using the Tg of the homopolymer.
_{1 / Tg = W 1 / Tg} 1 + W 2 / Tg 2 + ··· W n / Tg n
In the above formula, Tg represents a glass transition temperature (unit: K) of a polymer (copolymer) of n kinds of monomer components (monomers 1 to n). _{W 1, W 2, ··· W} n , each monomer to the total amount of n kinds of monomer components (1, 2, · · · n) represents the mass fraction _of, Tg 1, _Tg 2, · · · Tg _n are each monomer (1, 2, · · · n) a glass transition temperature of a homopolymer (unit: K) representing the. For example, taking the monomers and the like used in the examples described below as examples, the glass transition temperatures of the homopolymers of the monomers are as follows, and those values are the resins produced in the examples described below. It was used to calculate the Tg of the particles.
n-butyl acrylate (BA): -55 ° C
Methyl methacrylate (MMA): 105 ° C
Styrene (ST): 100 ° C
Acrylonitrile: 105 ° C
Acrylic acid (AAc): 105 ° C
Acrylamide (AM): 165 ° C

  The resin particles may be particles having a core portion and a shell portion (so-called core-shell type resin particles). When the resin particles have a core portion and a shell portion, the core portion and the shell portion may be completely compatible with each other and may have a homogeneous structure in which they cannot be distinguished. A core-shell composite structure or a micro-domain structure formed homogeneously may be used. In the above-described core-shell composite structure, it is preferable that the surface of the core portion is covered by the shell portion. In this case, the surface of the core portion is preferably completely covered with the shell portion, but may not be completely covered.For example, the core portion may be covered in a mesh form or in some places. The part may be exposed.

(Other components)
If necessary, the composite resin composition may contain other resin particles other than the aforementioned (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles, and various additives other than the aforementioned CNF. An agent may be contained. Examples of additives include colorants such as pigments and dyes, metal compounds, solvents, plasticizers, dispersants, surfactants (emulsifiers), foaming agents, lubricants, gelling agents, film-forming auxiliaries, and antifreezing agents. , Crosslinker, pH adjuster, viscosity adjuster, preservative, fungicide, bactericide, rust preventive, flame retardant, wetting agent, defoamer, antioxidant, antioxidant, ultraviolet absorber, stabilizer , An antistatic agent, an antiblocking agent and the like. One or more of these additives may be used.

  From the viewpoint of further increasing the dispersibility of CNF in the composite resin composition, the composite resin composition may contain a surfactant (emulsifier), and similarly, for example, a cellulose-based resin that can function as a dispersant or the like. A polymer compound may be contained. Examples of the emulsifier include emulsifiers that can be used in the case of emulsion polymerization described below, and may be the emulsifier used in the synthesis of the resin particles in the resin emulsion, or may be compounded separately from the synthesis of the resin particles. Emulsifiers may be used. Examples of the cellulosic polymer compound include carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, and hydroxypropylmethylcellulose, and one or more of these can be used.

  The nonvolatile content (solid content) of the composite resin composition is preferably in the range of 1 to 70% by mass, and more preferably in the range of 5 to 60% by mass, based on the total mass of the composite resin composition. More preferably, it is more preferably in the range of 10 to 50% by mass. In the present specification, the nonvolatile content (solid content) of the composite resin composition can take a value measured in accordance with the provisions of JIS K6833-1: 2008.

  The viscosity at 25 ° C. of the composite resin composition is preferably in the range of 1 to 10,000 mPa · s, more preferably in the range of 1 to 5000 mPa · s, and in the range of 5 to 1,000 mPa · s. It is more preferred that there be. In the present specification, the viscosity of the composite resin composition at 25 ° C. can be a value measured in accordance with JIS K6833-1: 2008.

<Production method of composite resin composition>
Next, the method for producing a composite resin composition as outlined above will be described in detail. In the method for producing a composite resin composition according to one embodiment of the present invention, at least one kind of resin particles selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles is used. The method includes a mixing step of bringing a resin emulsion emulsified in an aqueous dispersion medium into contact with cellulose nanofibers at a temperature of 50 ° C. or higher and mixing them. By this mixing step, a composite resin composition containing an aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers dispersed in the aqueous dispersion medium is obtained. The resin particles, aqueous dispersion medium, cellulose nanofiber (CNF), and the like used in the description of the method for producing the composite resin composition are the same as those described in the description of the composite resin composition according to the above-described embodiment. It is what is explained.

  According to the production method having the above configuration, it is possible to produce a composite resin composition capable of forming a film in which CNF is sufficiently uniformly dispersed in the resin. Further, according to the method for producing a composite resin composition, the composite resin composition according to the above-described embodiment can also be produced. From the viewpoint that these effects are more easily exerted, the temperature at which the resin emulsion is brought into contact with CNF in the mixing step is preferably 55 ° C. or higher, more preferably 60 ° C. or higher, and 100 ° C. or lower. Is preferred.

  When the resin emulsion is brought into contact with CNF, an aqueous dispersion containing CNF is preferably used from the viewpoint of easy production of the composite resin composition. The content of CNF in this aqueous dispersion is preferably in the range of 0.01 to 10% by mass, more preferably in the range of 0.1 to 10% by mass, and more preferably 0.2 to 5% by mass. More preferably, it is in the range of mass%. The time required for mixing the resin emulsion and CNF is, for example, preferably in the range of 10 to 120 minutes, more preferably in the range of 20 to 90 minutes, and in the range of 30 to 90 minutes. More preferably, it is within. After the mixing step, it is preferable to cool the obtained composite resin composition to normal temperature (within a range of 5 to 35 ° C.).

  In the mixing step, as long as the resin emulsion and CNF can be brought into contact with each other under the above temperature conditions, CNF may be added to the resin emulsion, the resin emulsion may be added to CNF, or both may be placed in separate containers. May be brought into contact with each other. From the viewpoint of easy production of the composite resin composition, the mixing step includes, in one of the aqueous dispersion containing the cellulose nanofiber and the resin emulsion (the one to be added), the other one (the one to be added), It is preferable to include a step of adding under the condition that one of the temperatures (to be added) is 50 ° C. or more. At this time, from the viewpoint of further increasing the dispersibility of CNF in the composite resin composition, it is further preferable that the temperature of the other one (the one to be added) is also 50 ° C. or more.

  For example, when one of the above (to be added) is an aqueous dispersion containing CNF and the other above (to be added) is a resin emulsion, in other words, the aqueous dispersion containing CNF is added. When a resin emulsion is added to the liquid, the following method can be adopted. That is, the method for producing a composite resin composition in that case further includes, before the mixing step, a heating step of heating the CNF-containing aqueous dispersion to 50 ° C. or higher, and the mixing step is performed at 50 ° C. or higher by the heating step. And adding a resin emulsion to an aqueous dispersion containing CNF heated to a temperature.

  Further, for example, when one of the above (to be added) is a resin emulsion and the other of the above (to be added) is an aqueous dispersion containing CNF, in other words, CNF is added to the resin emulsion. When adding an aqueous dispersion containing the following, the following method can be adopted. That is, the method for producing the composite resin composition in that case further includes, before the mixing step, a heating step of heating the resin emulsion to 50 ° C. or higher, and the mixing step includes heating the resin emulsion to 50 ° C. or higher by the heating step. The method may include a step of adding an aqueous dispersion containing CNF to the emulsion.

  For the resin emulsion used in the method for producing a composite resin composition, a resin emulsion produced as part of the method for producing a composite resin composition may be used, or a resin emulsion that has been produced in advance or purchased from the market, or the like. May be prepared and used. The resin emulsion produced in advance can be produced, for example, as in the polymerization step described later in the method for producing a composite resin composition.

  In the method for producing a composite resin composition, when one of the above (to be added) is a resin emulsion and the other (to be added) is an aqueous dispersion containing CNF, Before the process, a resin emulsion to which CNF is added can be manufactured. That is, in this case, the method of producing the composite resin composition includes, prior to the mixing step, a polymerization step in which a monomer component forming resin particles is emulsion-polymerized at a temperature of 50 ° C. or higher to obtain a resin emulsion. May be further included. Then, in this case, the mixing step preferably includes a step of adding the above-mentioned CNF-containing aqueous dispersion to the resin emulsion obtained in the polymerization step and having a temperature of 50 ° C. or higher, following the polymerization step. . As described above, when the temperature of the resin emulsion is set to 50 ° C. or higher, the production efficiency can be expected to be improved by utilizing the heat of polymerization of the monomer component forming the resin particles.

  In the aqueous dispersion containing CNF used in the mixing step performed after the polymerization step, a monomer component that forms resin particles together with the monomer component used in the polymerization step (remaining monomer component), and An emulsifier may be contained. In the mixing step, the resin emulsion obtained in the polymerization step is mixed with an aqueous dispersion containing CNF, a pre-emulsion containing the above-mentioned monomer component (remaining monomer component), an emulsifier, and water. May be added separately. As in these methods, a monomer component may be used in the mixing step, and the monomer component may be further polymerized in the resin emulsion obtained in the polymerization step. Further, the above-mentioned cellulose-based polymer compound may be contained in the aqueous dispersion containing CNF.

  In the polymerization step, a resin emulsion is obtained by emulsion-polymerizing one or more polymerizable monomers (monomer components) forming resin particles in an aqueous medium such as water serving as an aqueous dispersion medium. Is preferred. Specifically, it is preferable to carry out emulsion polymerization of a monomer component forming resin particles in an aqueous medium (preferably water) in the presence of a polymerization initiator and a surfactant (emulsifier). Emulsion polymerization methods include a method in which an aqueous medium, a monomer component, and a polymerization initiator are mixed at once and emulsion polymerization is performed, and an emulsion polymerization is performed using a pre-emulsion containing an aqueous medium and a monomer component. Methods and the like can be mentioned. More specifically, a pre-emulsion prepared by previously mixing an aqueous medium and a monomer component, and a polymerization initiator are respectively dropped into an separately prepared aqueous medium, and the monomer component is added to the aqueous medium. Is more preferably subjected to emulsion polymerization.

  The polymerization temperature at the time of the emulsion polymerization is, as described above, 50 ° C. or higher, preferably 55 ° C. or higher, more preferably 60 ° C. or higher, even more preferably 70 ° C. or higher, and 100 ° C. or lower. It is preferable to satisfy the following conditions. The polymerization time during the emulsion polymerization, and the types and amounts of the polymerization initiator and the emulsifier to be used can be appropriately determined within the same ranges as those of conventionally known emulsion polymerization. For example, the polymerization time is preferably in the range of about 1 to 15 hours. The method of adding (dropping) the pre-emulsion and the polymerization initiator described above is not particularly limited, and for example, a batch addition method, a continuous addition method, a multi-stage addition method, and the like can be employed. May be appropriately combined.

  Examples of the polymerization initiator include peroxides such as persulfates, organic peroxides, and hydrogen peroxide, and azo compounds. One or more polymerization initiators may be used. Can be. Further, one or more reducing agents may be used as a redox polymerization initiator used in combination with a peroxide or as a polymerization accelerator.

  Specific examples of the persulfate include potassium persulfate, sodium persulfate, and ammonium persulfate. Specific examples of the organic peroxide include diacyl peroxides such as benzoyl peroxide and dilauroyl peroxide, dialkyl peroxides such as t-butylcumyl peroxide and dicumyl peroxide, and t-butylperoxylaurate. And peroxyesters such as t-butylperoxybenzoate, and hydroperoxides such as cumene hydroperoxide and t-butyl hydroperoxide. Specific examples of the azo compound include 2,2'-azobis (2-amidinopropane) dihydrochloride and 4,4'-azobis (4-cyanopentanoic acid). Specific examples of the reducing agent include ascorbic acid and its salts, tartaric acid and its salts, sulfurous acid and its salts, bisulfite and its salts, thiosulfuric acid and its salts, and iron (II) salts.

  When synthesizing the resin particles, a known chain transfer agent may be used to adjust the molecular weight of the resin particles. Examples of the chain transfer agent include hexyl mercaptan, lauryl mercaptan, octyl mercaptan, and alkyl mercaptans such as n- or t-dodecyl mercaptan.

  Examples of the emulsifier (surfactant) that can be used when synthesizing the resin particles include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. One or more emulsifiers can be used. As the emulsifier, an anionic surfactant and a nonionic surfactant are preferable, and an anionic surfactant is more preferable.

  Examples of the anionic surfactant include fatty acid salts such as sodium stearate; alkyl sulfate salts such as sodium lauryl sulfate; polyoxyalkylene alkyl ether sulfate salts such as sodium polyoxyethylene alkyl ether sulfate; dodecylbenzene sulfonic acid Alkyl benzene sulfonates such as sodium; sodium dialkyl sulfosuccinate; sodium alkyl diphenyl ether disulfonate; and reactive anionic surfactants such as ammonium polyoxyalkylene alkenyl ether sulfate and ammonium polyoxyethylene styrenated propenyl phenyl ether sulfate. Can be. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyalkylene derivatives such as polyoxyalkylene alkyl ether; Reactive nonionic surfactants such as oxyalkylene alkenyl ether and polyoxyethylene styrenated propenyl phenyl ether can be exemplified.

  After obtaining the resin particles by the polymerization step, more preferably after the mixing step, it is preferable to neutralize the obtained composite resin composition with a neutralizing agent. When the resin particles have a carboxy group, the carboxy group is preferably neutralized with a basic neutralizing agent. By the neutralization, the composite resin composition is stabilized. The neutralizing agent is not particularly limited and includes, for example, alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; monomethylamine, dimethylamine, trimethylamine, Examples thereof include organic amines such as monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. One or more kinds of organic amines can be used.

  As described in detail above, the composite resin composition according to one embodiment of the present invention contains the above-described resin particles, CNF, and an aqueous dispersion medium, and is obtained by AFM using a sample (non-film dried sample) obtained under the above-described conditions. When observed by the above, an aggregate containing CNF is hardly observed, and a structure in which CNF is dispersed and resin particles are clumped to the CNF is observed. In addition, the composite resin composition obtained by the production method of one embodiment of the present invention is obtained by adding CNF to a resin emulsion in which the above resin particles are emulsified in an aqueous dispersion medium at a temperature of 50 ° C. or higher. Is obtained by adding

  Therefore, it is possible to form a molded product such as a film in which CNF is sufficiently uniformly dispersed in the resin and wrinkles and cracks are not easily generated by the composite resin composition. As a result, by using these composite resin compositions, it is possible to obtain a molded article such as a film having enhanced tensile strength as compared with a molded article such as a film obtained from an equivalent resin composition except that CNF is not contained. Can be expected. In addition, CNF has a high water retention capacity, is slowly dried, and has a characteristic of a small linear thermal expansion coefficient. It can be expected that shrinkage is suppressed.

  Furthermore, the composite resin composition according to one embodiment of the present invention and the composite resin composition obtained by the production method according to one embodiment of the present invention can also form a molded product such as a film having a high gel fraction. . Therefore, by using these composite resin compositions, it is possible to obtain a molded product such as a film having improved solvent resistance as compared with a molded product such as a film obtained from an equivalent resin composition except that CNF is not contained. Can be expected.

The composite resin composition according to one embodiment of the present invention can have the following configuration.
[1] A composite resin composition containing an aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers dispersed in the aqueous dispersion medium, wherein the resin particles are , (Meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles. The composite resin composition has a nonvolatile content of 0.01 to 0.1. When observed by an atomic force microscope, a sample obtained by dropping a liquid diluted with water in an amount falling within the range of 1% by mass onto a measurement base material and dispersing the cellulose nanofibers, and A composite resin composition in which a structure in which the resin particles are adhered to the cellulose nanofiber is observed.
[2] In the observation with the atomic force microscope, a structure in which the cellulose nanofibers are used as a shaft portion and the resin particles are gathered in a bunch of grapes around the shaft portion along the shaft portion is observed. The composite resin composition according to the above [1].
[3] The above-mentioned [1], wherein the content of the cellulose nanofibers in the composite resin composition is in the range of 0.1 to 10 parts by mass per 100 parts by mass of the resin particles in the composite resin composition. Or the composite resin composition according to [2].
[4] The resin particles further include a structural unit derived from at least one polymerizable monomer selected from the group consisting of unsaturated carboxylic acid monomers and (meth) acrylamide monomers. The composite resin composition according to any one of [1] to [3].

Further, the method for producing a composite resin composition according to one embodiment of the present invention can have the following configuration.
[5] A resin emulsion in which at least one resin particle selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles is emulsified in an aqueous dispersion medium; A mixing step of bringing nanofibers into contact with each other at a temperature of 50 ° C. or higher and mixing them, and by the mixing step, the aqueous dispersion medium and the resin particles emulsified in the aqueous dispersion medium A method for producing a composite resin composition, comprising: obtaining a composite resin composition containing: and a cellulose nanofiber dispersed in the aqueous dispersion medium.
[6] In the mixing step, either one of the aqueous dispersion containing the cellulose nanofiber and the resin emulsion is added under the condition that the temperature of either one is 50 ° C. or higher. The method for producing a composite resin composition according to the above [5], comprising a step.
[7] The composite resin composition according to the above [6], wherein the mixing step includes a step of adding the other one to the one under the condition that the temperature of the other is also 50 ° C. or more. Production method.
[8] One of the above is an aqueous dispersion containing the cellulose nanofiber, and the other is the above resin emulsion, and the aqueous dispersion containing the cellulose nanofiber before the mixing step. The method further includes a heating step of heating the liquid to 50 ° C. or higher, and the mixing step includes a step of adding the resin emulsion to an aqueous dispersion containing the cellulose nanofibers heated to 50 ° C. or higher by the heating step. The method for producing a composite resin composition according to the above [6] or [7].
[9] One of the two is the resin emulsion, and the other is an aqueous dispersion containing the cellulose nanofibers, and the resin emulsion is heated to 50 ° C. or more before the mixing step. The above-mentioned [6] or [6], further comprising a heating step of adding the aqueous dispersion containing the cellulose nanofiber to the resin emulsion heated to 50 ° C. or higher by the heating step. The method for producing the composite resin composition according to [7].
[10] One of the above is the resin emulsion, and the other is an aqueous dispersion containing the cellulose nanofiber, and a monomer that forms the resin particles before the mixing step. The component further comprises a polymerization step of subjecting the component to emulsion polymerization under a condition of a temperature of 50 ° C. or higher to obtain the resin emulsion, wherein the mixing step is performed after the polymerization step and the temperature obtained in the polymerization step is 50 ° C. The method for producing a composite resin composition according to the above [6] or [7], comprising a step of adding an aqueous dispersion containing the cellulose nanofiber to the resin emulsion at a temperature of not less than ° C.

  Hereinafter, further specific examples of the above-described embodiment will be described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Production Example A of Resin Composition>
In the following Examples 1 to 11, using a resin emulsion prepared in advance, bringing the resin emulsion into contact with cellulose nanofibers (CNF) under a specific temperature condition, and mixing them. Thus, a composite resin composition was produced. Specifically, in Examples 1 to 8, after heating the resin emulsion to a specific temperature, an aqueous dispersion (about 20 ° C.) containing CNF is added thereto, and in Example 9, the resin emulsion is added to the resin emulsion. The aqueous dispersion containing CNF was also heated to a specific temperature. In Example 10, after heating the aqueous dispersion containing CNF to a specific temperature, a resin emulsion (about 20 ° C.) was added thereto, and in Example 11, the aqueous dispersion containing CNF was added to the aqueous dispersion. The resin emulsion was also heated to a specific temperature. In addition, in order to facilitate relative evaluation, in each example, the composition of the monomer component forming the resin was adjusted so that the glass transition temperature (Tg; theoretical value) of the resin (polymer) became equivalent. did.

(Preparation Example 1)
53.5 parts by mass of deionized water was charged into a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and the internal temperature was raised to 80 ° C. while stirring.
On the other hand, separately from the separable flask, 42.9 parts by mass of n-butyl acrylate (hereinafter sometimes referred to as “BA”) and methyl methacrylate (hereinafter sometimes referred to as “MMA”). From 54.6 parts by mass, 2.0 parts by mass of acrylic acid (hereinafter sometimes referred to as “AAc”), and 0.5 parts by mass of acrylamide (hereinafter sometimes referred to as “AM”) A monomer component (total amount of 100 parts by mass), and 2.0 parts by mass of polyoxyethylene styrylphenyl ether ammonium sulfate as an anionic emulsifier (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid content: 30% by mass)) 6 0.7 parts by mass) and 38.0 parts by mass of deionized water were emulsified with a homodisper to prepare a pre-emulsion.
Next, while the internal temperature in the separable flask was maintained at 80 ° C., the prepared pre-emulsion was uniformly dropped from the dropping funnel into the deionized water in the separable flask over 3 hours. 6.0 parts by mass of a 5% by mass aqueous solution of ammonium persulfate were uniformly added dropwise over 3 hours. After completion of the dropwise addition, the mixture was aged at 80 ° C. for 3 hours to terminate the reaction (polymerization). Next, after cooling to room temperature (23 ± 2 ° C.), neutralization is performed by adding 1.0 part by mass of 25% by mass aqueous ammonia, the pH is adjusted, and the resin emulsion containing (meth) acrylic resin particles ( Nonvolatile content: about 50% by mass). The Tg (theoretical value) of the (meth) acrylic resin particles in the resin emulsion is 15 ° C.

(Comparative Example 1)
In Comparative Example 1, the resin emulsion obtained in Preparation Example 1 was used as it was as a resin composition of Comparative Example 1. In the following Examples 1 to 7, 9 to 11, and Comparative Examples 2 to 7, the resin emulsion obtained in Preparation Example 1 was used for producing a composite resin composition.

(Example 1)
The resin emulsion obtained in Preparation Example 1 was placed in a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and heated to 80 ° C. While maintaining the resin emulsion in the separable flask at 80 ° C., the resin emulsion was added to a water dispersion containing mechanically defibrated CNF (CNF by ACC method) (trade name “nanoforest” manufactured by Chuetsu Pulp Industry Co., Ltd.). 133 parts by mass (liquid obtained by diluting -S (BB-C)) (1.2% by mass of solid content) with deionized water so that the solid content becomes 0.75% by mass (1.0 part by mass as CNF) Was uniformly dropped from the dropping funnel over 1 hour. After completion of the dropping, the mixture was cooled to room temperature (23 ± 2 ° C.), and the obtained liquid was filtered using a 120-mesh filter cloth to obtain a CNF-containing composite resin composition.
Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 2)
A composite resin composition containing CNF was produced in the same manner as in Example 1, except that the temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 60 ° C. .

(Example 3)
A composite resin composition containing CNF was produced in the same manner as in Example 1, except that the temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 50 ° C. .

(Example 4)
A composite resin composition containing CNF was obtained in the same manner as in Example 1, except that the amount of the aqueous dispersion containing CNF was changed to 400 parts by mass (3.0 parts by mass as CNF). Was. In this way, water, (meth) acrylic resin particles, and 3 parts by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 5)
A composite resin composition containing CNF was obtained in the same manner as in Example 1, except that the amount of the aqueous dispersion containing CNF was changed to 667 parts by mass (5.0 parts by mass as CNF). Was. In this way, water, (meth) acrylic resin particles, and 5 parts by mass of mechanically defibrated CNF with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 6)
133 parts by mass of the aqueous dispersion containing the mechanical fibrillation type CNF used in Example 1 was mixed with the aqueous dispersion containing the chemical fibrillation type CNF (trade name “cellenia” (manufactured by Nippon Paper Co., Ltd. (TEMPO oxidized CNF standard product)). Solid content of 1.0% by mass) was changed to 133 parts by mass (1.0 part by mass as CNF) diluted with deionized water so that the solid content became 0.75% by mass. A composite resin composition containing CNF was obtained in the same manner as in Example 1. In this way, water, (meth) acrylic resin particles, and 1 part by mass of the chemically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 7)
133 parts by mass of the mechanically defibrated CNF-containing aqueous dispersion used in Example 1 was mixed with the chemically defibrated CNF-containing aqueous dispersion (trade name “cellenia” (manufactured by Nippon Paper Co., Ltd. (TEMPO-oxidized CNF short fiber)). Product (solid content: 5.0 mass%) was changed to 133 mass parts (1.0 mass part as CNF) diluted with deionized water so that the solid content became 0.75 mass%. A composite resin composition containing CNF was obtained in the same manner as in Example 1. In this way, water, (meth) acrylic resin particles, and 1 part by mass of the chemically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 8)
First, the amount of the anionic emulsifier used in Preparation Example 1 was changed to 1.9 parts by mass of ammonium polyoxyethylene styrylphenyl ether sulfate (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid content: 30% by mass)). Resin emulsion containing (meth) acrylic resin particles (Tg (theoretical value): 15 ° C.) (nonvolatile content: about 50% by mass) in the same manner as in Preparation Example 1 except that the amount was changed to 3 parts by mass. ) Got. Further, an aqueous dispersion containing a mechanical defibration type CNF (CNF by the ACC method) (trade name “nanoforest-S (BB-C)” manufactured by Chuetsu Pulp Industry Co., Ltd.) (solid content: 1.2% by mass) was mixed with a solid content. Is 133 parts by mass (1.0 part by mass as CNF), and 0.1 parts by mass of polyoxyethylene styryl phenyl ether ammonium sulfate (Kao) as an anionic emulsifier. Brand name "Latemul E-1000A" (solid content 30% by mass) 0.3 parts by mass) and carboxymethyl cellulose (CMC) 1.0 part by mass (Daiichi Kogyo Seiyaku Co., Ltd. product name "Selogen 6A") (Solid content: 100% by mass)) to obtain an aqueous dispersion containing CNF.
Next, the resin emulsion obtained above was placed in a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and heated to 80 ° C. While maintaining the resin emulsion in the separable flask at 80 ° C., the aqueous dispersion containing CNF obtained above was dropped uniformly onto the resin emulsion from the dropping funnel over 1 hour. After completion of the dropping, the mixture was cooled to room temperature (23 ± 2 ° C.), and the obtained liquid was filtered using a 120-mesh filter cloth to obtain a CNF-containing composite resin composition.
In this manner, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles); And a composite resin composition containing the CMC of the present invention.

(Example 9)
Before adding the aqueous dispersion containing CNF to the resin emulsion, the aqueous dispersion containing CNF is also heated to 80 ° C., and the 80 ° C. aqueous dispersion containing CNF is added to the resin emulsion at 80 ° C. Except for the addition, a composite resin composition containing CNF was obtained in the same manner as in Example 1.

(Example 10)
In a four-necked separable flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, an aqueous dispersion containing mechanically defibrated CNF (CNF by the ACC method) (trade name of Chuetsu Pulp & Paper Co., Ltd.) 133 parts by mass of "nanoforest-S (BB-C)" (1.2 mass% solid content) diluted with deionized water so that the solid content becomes 0.75 mass% (1.0 mass as CNF) Part), and the temperature was raised to 80 ° C. With the inside of the separable flask maintained at 80 ° C., the resin emulsion obtained in Preparation Example 1 was uniformly dropped into the aqueous dispersion containing CNF from the dropping funnel over 1 hour. After completion of the dropping, the mixture was cooled to room temperature (23 ± 2 ° C.), and the obtained liquid was filtered using a 120-mesh filter cloth to obtain a CNF-containing composite resin composition.
Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 11)
Before adding the resin emulsion to the aqueous dispersion containing CNF, the resin emulsion was also heated to 80 ° C, except that the 80 ° C resin emulsion was added to the 80 ° C aqueous dispersion containing CNF. A composite resin composition containing CNF was obtained in the same manner as in Example 10.

(Comparative Example 2)
A composite resin composition containing CNF was obtained in the same manner as in Example 1, except that the temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 45 ° C. .

(Comparative Example 3)
A composite resin composition containing CNF was obtained in the same manner as in Example 1, except that the temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 40 ° C. .

(Comparative Example 4)
A composite resin composition containing CNF was obtained in the same manner as in Example 1, except that the temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 20 ° C. .

(Comparative Example 5)
The temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 20 ° C., and the amount of the aqueous dispersion containing CNF was changed to 400 parts by mass (3.0 parts by mass as CNF). Part), a composite resin composition containing CNF was obtained in the same manner as in Example 1.

(Comparative Example 6)
The temperature condition of the resin emulsion when the aqueous dispersion containing CNF was added to the resin emulsion was changed to 20 ° C., and the amount of the aqueous dispersion containing CNF was changed to 667 parts by mass (5.0 parts by mass as CNF). Part), a composite resin composition containing CNF was obtained in the same manner as in Example 1.

(Comparative Example 7)
Example 10 was repeated except that, when the resin emulsion was added to the aqueous dispersion containing CNF, the temperature of the aqueous dispersion containing CNF was maintained at about 20 ° C. without increasing the temperature. By the same method as described above, a composite resin composition containing CNF was obtained.

<Production Example B of Resin Composition>
In the following Examples 12 to 24, following the step of emulsion-polymerizing a monomer component forming resin particles under a specific temperature condition to obtain a resin emulsion (without cooling the resin emulsion), The contained aqueous dispersion (about 20 ° C.) was added to produce a composite resin composition in which CNF was composited with a resin emulsion. In addition, in order to facilitate relative evaluation, in each example, the composition of the monomer component forming the resin was adjusted so that the glass transition temperature (Tg; theoretical value) of the resin (polymer) became equivalent. did.

(Example 12)
53.5 parts by mass of deionized water was charged into a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and the internal temperature was raised to 80 ° C. while stirring.
On the other hand, separately from the separable flask, 42.9 parts by mass of n-butyl acrylate (BA), 54.6 parts by mass of methyl methacrylate (MMA), 2.0 parts by mass of acrylic acid (AAc), and acrylamide (AM) 0.5 parts by mass of a monomer component (100 parts by mass in total) and 2.0 parts by mass of polyoxyethylene styrylphenyl ether ammonium sulfate as an anionic emulsifier (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid 6.7 parts by mass) and 38.0 parts by mass of deionized water were emulsified with a homodisper to prepare a pre-emulsion.
Next, while maintaining the internal temperature of the separable flask at 80 ° C., the prepared pre-emulsion was uniformly dropped from the dropping funnel into the deionized water in the separable flask over a period of 3 hours. 6.0 parts by mass of a 5% by mass aqueous solution of ammonium persulfate were uniformly added dropwise over 3 hours. Immediately after the completion of the dropping, an aqueous dispersion containing mechanical fibrillation type CNF (CNF by the ACC method) (trade name “nanoforest-S (BB-C)” manufactured by Chuetsu Pulp Industry Co., Ltd.) (solid content: 1.2%) (Mass%) was diluted with deionized water so that the solid content was 0.75 mass%) 133 parts by mass (1.0 part by mass as CNF) was dropped into the separable flask from the dropping funnel for 1 hour. And the mixture was aged at 80 ° C. for 3 hours. Thereafter, the mixture was cooled to room temperature (23 ± 2 ° C.), neutralized by adding 1.0 part by mass of 25% by mass aqueous ammonia, and the solution obtained by adjusting the pH was filtered using a 120-mesh filter cloth. The mixture was filtered to obtain a composite resin composition.
Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured. The Tg (theoretical value) of the (meth) acrylic resin particles in this resin composition is 15 ° C.

(Example 13)
Except that the addition amount of the aqueous dispersion containing CNF was changed to 66.7 parts by mass (0.5 parts by mass as CNF), a composite resin composition containing CNF was produced in the same manner as in Example 12. I got In this manner, water, (meth) acrylic resin particles, and 0.5 part by mass of mechanical fibrillation type CNF with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles). A composite resin composition was produced.

(Example 14)
A composite resin composition containing CNF was obtained in the same manner as in Example 12, except that the amount of the aqueous dispersion containing CNF was changed to 100 parts by mass (0.75 parts by mass as CNF). Was. Thus, water, (meth) acrylic resin particles, and 0.75 parts by mass of mechanical fibrillation type CNF with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles). A composite resin composition was produced.

(Example 15)
A composite resin composition containing CNF was obtained in the same manner as in Example 12, except that the amount of the aqueous dispersion containing CNF was changed to 400 parts by mass (3.0 parts by mass as CNF). Was. In this way, water, (meth) acrylic resin particles, and 3 parts by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 16)
A composite resin composition containing CNF was obtained in the same manner as in Example 12, except that the amount of the aqueous dispersion containing CNF was changed to 667 parts by mass (5.0 parts by mass as CNF). Was. In this way, water, (meth) acrylic resin particles, and 5 parts by mass of mechanically defibrated CNF with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 17)
133 parts by mass of the aqueous dispersion containing the mechanical fibrillation type CNF used in Example 12 was combined with the aqueous dispersion containing the chemical fibrillation type CNF (trade name “cellenia” (manufactured by Nippon Paper Co., Ltd. (TEMPO oxidized CNF standard product)). Solid content of 1.0% by mass) was changed to 133 parts by mass (1.0 part by mass as CNF) diluted with deionized water so that the solid content became 0.75% by mass. In the same manner as in Example 12, a composite resin composition containing CNF was obtained. In this way, water, (meth) acrylic resin particles, and 1 part by mass of the chemically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 18)
133 parts by mass of the aqueous dispersion containing the mechanical fibrillation type CNF used in Example 12 was mixed with the aqueous dispersion containing the chemical fibrillation type CNF (trade name “cellenia” (manufactured by Nippon Paper Co., Ltd. (TEMPO oxidized CNF short fiber)). Product (solid content: 5.0 mass%) was changed to 133 mass parts (1.0 mass part as CNF) diluted with deionized water so that the solid content became 0.75 mass%. In the same manner as in Example 12, a composite resin composition containing CNF was obtained. In this way, water, (meth) acrylic resin particles, and 1 part by mass of the chemically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 19)
53.5 parts by mass of deionized water was charged into a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and the internal temperature was raised to 60 ° C. while stirring.
On the other hand, separately from the separable flask, 42.9 parts by mass of n-butyl acrylate (BA), 54.6 parts by mass of methyl methacrylate (MMA), 2.0 parts by mass of acrylic acid (AAc), and acrylamide (AM) 0.5 parts by mass of a monomer component (100 parts by mass in total) and 2.0 parts by mass of polyoxyethylene styrylphenyl ether ammonium sulfate as an anionic emulsifier (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid 6.7 parts by mass) and 38.0 parts by mass of deionized water were emulsified with a homodisper to prepare a pre-emulsion.
Next, while maintaining the internal temperature in the separable flask at 60 ° C., the prepared pre-emulsion was uniformly dropped from the dropping funnel into the deionized water in the separable flask over 3 hours. 6.0 parts by mass of a 5% by mass aqueous solution of ammonium persulfate and 2.5 parts by mass of a 10% by mass aqueous solution of sodium bisulfite were uniformly dropped over 3 hours. Immediately after the completion of the dropping, an aqueous dispersion containing a mechanical fibrillation type CNF (CNF by the ACC method) (trade name “nanoforest-S (BB-C)” manufactured by Chuetsu Pulp Industry Co., Ltd.) (solid content 1.2 (Mass%) was diluted with deionized water so that the solid content became 0.75 mass%) 133 parts by mass (1.0 part by mass as CNF) was dropped into the separable flask from the dropping funnel for 1 hour. And the mixture was aged at 60 ° C. for 3 hours. Thereafter, the mixture was cooled to room temperature (23 ± 2 ° C.), neutralized by adding 1.0 parts by mass of 25% by mass aqueous ammonia, and adjusted by adjusting the pH. The obtained solution was filtered using a 120-mesh filter cloth. The mixture was filtered to obtain a composite resin composition.
In this way, a resin emulsion containing (meth) acrylic resin particles in which 1 part by mass of cellulose nanofiber was combined with 100 parts by mass of the monomer component was produced. That is, a composite resin composition containing water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles). Was manufactured. The Tg (theoretical value) of the (meth) acrylic resin particles in this resin emulsion is 15 ° C.

(Example 20)
The monomer component (100 parts by mass in total) used in Example 12 was obtained by adding 42.3 parts by mass of n-butyl acrylate (BA), 27.6 parts by mass of methyl methacrylate (MMA), and styrene (hereinafter referred to as “ST”). It may be described.) 27.6 parts by mass, 2.0 parts by mass of acrylic acid (AAc), and 0.5 parts by mass of acrylamide (AM) were changed to a monomer component (100 parts by mass in total). Except for the above, a composite resin composition containing CNF was obtained in the same manner as in Example 12. Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 21)
The monomer components (100 parts by mass in total) used in Example 12 were obtained by adding 42.2 parts by mass of n-butyl acrylate (BA), 45.5 parts by mass of methyl methacrylate (MMA), and acrylonitrile (hereinafter referred to as “AN”). It may be described.) It has been changed to a monomer component (100 parts by mass in total) consisting of 9.8 parts by mass, 2.0 parts by mass of acrylic acid (AAc) and 0.5 parts by mass of acrylamide (AM). Except for the above, a composite resin composition containing CNF was obtained in the same manner as in Example 12. Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Example 22)
The monomer component (100 parts by mass in total) used in Example 12 was obtained by adding 41.9 parts by mass of n-butyl acrylate (BA), 6.8 parts by mass of methyl methacrylate (MMA), and 48.8 parts by mass of styrene (ST). Parts, a monomer component consisting of 2.0 parts by mass of acrylic acid (AAc) and 0.5 parts by mass of acrylamide (AM) (total amount: 100 parts by mass), except that the composition was changed to the same method as in Example 12. And a composite resin composition containing CNF. Thus, a composite resin composition containing water, styrene-based resin particles, and 1 part by mass of mechanically defibrated CNF based on 100 parts by mass of the resin particles (the monomer component forming the resin particles) Was manufactured.

(Example 23)
The monomer component (100 parts by mass in total) used in Example 12 was 42.7 parts by mass of n-butyl acrylate (BA), 6.8 parts by mass of methyl methacrylate (MMA), and 48.0 parts by mass of acrylonitrile (AN). Parts, a monomer component consisting of 2.0 parts by mass of acrylic acid (AAc) and 0.5 parts by mass of acrylamide (AM) (total amount: 100 parts by mass), except that the composition was changed to the same method as in Example 12. And a composite resin composition containing CNF. In this way, water, (meth) acrylonitrile-based resin particles, and 1 part by mass of mechanically defibrated CNF are contained with respect to 100 parts by mass of the resin particles (the monomer component forming the resin particles). A composite resin composition was manufactured.

(Example 24)
The monomer component (total amount of 100 parts by mass) used in Example 12 was mixed with 42.5 parts by mass of n-butyl acrylate (BA) and 57.5 parts by mass of methyl methacrylate (MMA) (total amount). A composite resin composition containing CNF was obtained in the same manner as in Example 12 except that the composition was changed to 100 parts by mass. Thus, water, (meth) acrylic resin particles, and 1 part by mass of mechanically defibrated CNF per 100 parts by mass of the resin particles (the monomer component forming the resin particles) are contained. A composite resin composition was manufactured.

(Comparative Example 8)
In the same manner as in Example 12, except that the amount of deionized water equivalent to that in Example 12 was dropped over 1 hour from the dropping funnel in place of the aqueous dispersion containing CNF, and no CNF was contained. , Water and a (meth) acrylic resin particle were produced.

(Comparative Example 9)
In the same manner as in Example 19, except that the same amount of deionized water was dropped from the dropping funnel over 1 hour in place of the CNF-containing aqueous dispersion in Example 19, and no CNF was contained. , Water and a (meth) acrylic resin particle were produced.

(Comparative Example 10)
An aqueous dispersion containing 53.5 parts by mass of deionized water and mechanically defibrated CNF (CNF by ACC method) in a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel. (A liquid obtained by diluting “nanoforest-S (BB-C)” (trade name, manufactured by Chuetsu Pulp and Paper Co., Ltd.) (solid content: 1.2% by mass) with deionized water so that the solid content becomes 0.75% by mass) (1.0 parts by mass as CNF), and the internal temperature was raised to 80 ° C. while stirring.
On the other hand, separately from the separable flask, 42.9 parts by mass of n-butyl acrylate (BA), 54.6 parts by mass of methyl methacrylate (MMA), 2.0 parts by mass of acrylic acid (AAc), and acrylamide (AM) 0.5 parts by mass of a monomer component (100 parts by mass in total) and 2.0 parts by mass of polyoxyethylene styrylphenyl ether ammonium sulfate as an anionic emulsifier (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid 6.7 parts by mass) and 38.0 parts by mass of deionized water were emulsified with a homodisper to prepare a pre-emulsion.
Next, while maintaining the internal temperature of the separable flask at 80 ° C., the prepared pre-emulsion was added from a dropping funnel to a mixture of deionized water and an aqueous dispersion containing CNF in the separable flask. The mixture was dropped uniformly over a period of time, and at the same time, 6.0 parts by mass of a 5% by mass aqueous solution of ammonium persulfate was dropped uniformly over a period of 3 hours. However, a large amount of aggregate containing CNF was generated, and a composite resin composition could not be obtained.

(Comparative Example 11)
91.5 parts by mass of deionized water was charged into a four-neck separable flask equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and the internal temperature was raised to 80 ° C. while stirring.
On the other hand, separately from the separable flask, 42.9 parts by mass of n-butyl acrylate (BA), 54.6 parts by mass of methyl methacrylate (MMA), 2.0 parts by mass of acrylic acid (AAc), and acrylamide (AM) 0.5 parts by mass of a monomer component (100 parts by mass in total) and 2.0 parts by mass of polyoxyethylene styrylphenyl ether ammonium sulfate as an anionic emulsifier (trade name “Latemul E-1000A” manufactured by Kao Corporation (solid 6.7 parts by mass), and an aqueous dispersion containing mechanical fibrillation-type CNF (CNF by ACC method) (trade name “nanoforest-S (BB-C)” manufactured by Chuetsu Pulp Industry Co., Ltd.) ( 133 parts by mass (solids 1.2% by mass) diluted with deionized water so as to have a solids content of 0.75% by mass (1.0 mass as CNF) ) Was emulsified in a homodisper to prepare a pre-emulsion.
Next, while maintaining the internal temperature in the separable flask at 80 ° C., the prepared pre-emulsion containing CNF was uniformly dropped from the dropping funnel into the deionized water in the separable flask over 3 hours. At the same time, 6.0 parts by mass of a 5% by mass aqueous solution of ammonium persulfate was dropped uniformly over 3 hours. However, a large amount of aggregate containing CNF was generated, and a composite resin composition could not be obtained.

<Evaluation method>
For the resin compositions obtained in each of the examples and comparative examples, the nonvolatile components, viscosity, dispersion state, film appearance, tensile strength, elongation, and gel fraction were measured or evaluated according to the methods described below.

(Non-volatile content)
The non-volatile content (solid content) (mass%) of each resin composition was measured under the conditions of a drying temperature of 140 ° C. and a drying time of 0.5 hour according to JIS K6828-1: 2003.

(viscosity)
According to the provisions of JIS K6833-1: 2008, the viscosity of each resin composition was measured using a BH type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., BHII type viscometer) at a rotational speed of 10 rpm and a temperature of 25 ° C. (MPa · s) was measured.

(Dispersibility of CNF and resin particles)
The produced resin composition was diluted 500 times by mass with water, and the nonvolatile content was adjusted within a range of 0.01 to 0.1% by mass to obtain a diluted solution. One drop (0.04 mL) of this diluent was dropped on a mica standard sample (manufactured by Hitachi High-Tech Science Corporation) as a measurement base material, and a temperature of 23 at which it was confirmed that the resin particles in the diluent could take a particle form. The sample was dried for 24 hours in a glass desiccator enclosing dry silica gel in an environment of ± 2 ° C. to prepare a sample. This sample was observed using an atomic force microscope (AFM; trade name “AFM5100N” manufactured by Hitachi High-Technologies Corporation), and the dispersibility of CNF and resin particles was evaluated according to the following evaluation criteria. It should be noted that Comparative Examples 1, 8 and 9 were excluded from the subject of this evaluation because CNF was not used. Further, as examples of the observation results by the AFM, each observation image (observation image in a 50 μm square region and observation image in a 10 μm square region) obtained in Examples 1 and 5 and Comparative Example 4 is shown in FIG.
A: CNF is uniformly dispersed, aggregates containing CNF are hardly observed, and almost all CNFs have CNF as a shaft part, and resin particles gather around the shaft part in a bunch of grapes. A clinging structure was observed.
B: CNF is uniformly dispersed, aggregates containing CNF are hardly observed, and a part to most of CNF has CNF as a shaft part, and resin particles are surrounded by a bunch of grapes along the shaft part. Structures gathered together and clinged together were observed.
C: An aggregate containing CNF was observed, and a structure in which the resin particles were also aggregated was observed.

(Film appearance)
A mixed solution obtained by mixing 10 parts by mass of Texanol as a film-forming aid with 100 parts by mass of the produced resin composition was applied on a release substrate, and dried at 23 ° C. and 50% RH for one week to obtain a long-lasting resin. A film having a thickness of about 210 mm, a width of about 90 mm, and a thickness of about 0.6 mm was produced. The prepared film was visually observed, and the appearance of the film was evaluated according to the following evaluation criteria. FIG. 2 shows photographs of the films obtained in Examples 1 to 3 and Comparative Examples 1, 3 and 4 as examples of the observation results of the film appearance.
A: Cracks were hardly observed in the film, CNF was uniformly dispersed, and aggregates were hardly observed.
B: Small cracks (cracks having a total length of cracks of 100% or less with respect to one long side of the film) were confirmed in the film, but CNF was uniformly dispersed, and almost no aggregates were observed.
C: Almost no cracks were found in the coating, but aggregates containing CNF were found.
D: Large cracks were observed in the coating (the total length of the cracks with respect to one long side of the coating exceeded 100%).

(Tensile strength and elongation)
A mixed solution obtained by mixing 10 parts by mass of Texanol as a film-forming aid with 100 parts by mass of the produced resin composition was dried for one week in an environment of 23 ° C. and 50% RH, and then a strip (measurement part length: approx. A film sample having a thickness of about 40 mm, a width of about 10 mm, and a thickness of about 0.6 mm) was prepared. The film sample was subjected to a tensile test using a tensile tester (trade name “Tensilon Universal Tester RTG-1210” manufactured by A & D Corporation) at 23 ° C. and a tensile speed of 300 mm / min. The tensile strength (MPa) and elongation (%) were measured.

(Gel fraction)
The produced resin composition was dried in an environment at 60 ° C. for 20 hours to prepare a coating sample having a thickness of about 1 mm and a square of about 20 mm, and the mass W ₁ (g) of the coating sample was measured. This film sample was immersed in ethyl acetate and allowed to stand in an environment of 23 ° C. and 50% RH for 20 hours. Thereafter, the film sample immersed in ethyl acetate was filtered using a 200-mesh wire net whose mass W ₂ (g) was measured in advance, and an insoluble matter was obtained on the wire net. The insoluble matter on the wire mesh was dried at 80 ° C. for 6 hours to obtain a dry insoluble matter on the wire mesh. The total mass W ₃ (g) of this wire mesh and the dry insoluble matter attached to and integrated with the wire mesh was measured. Then, the gel fraction was determined by the following equation.
Gel fraction (% by mass) = ((W ₃ −W ₂ ) / W ₁ ) × 100

  The above evaluation results are shown in Tables 1 to 6 together with the amounts of the monomer and CNF used in each Example and Comparative Example. The “resin / CNF ratio” in the table represents the content of CNF in the resin composition per 100 parts by mass of the resin particles (the total amount of the monomer components constituting the resin particles) in the resin composition. In the table, the “combination to (X ° C.)” in the “composite method” column means that a CNF-free resin emulsion was first prepared as a base material and then cooled (stopped reaction). 7 shows the methods performed in Examples 1 to 11 and Comparative Examples 2 to 7. Specifically, “Formulation 1 (X ° C.)” (refer to Examples 1 to 8 and Comparative Examples 2 to 6) is that an aqueous dispersion of about 20 ° C. containing CNF was added to a resin emulsion of X ° C. “Formulation 2 (X ° C.)” (see Example 9) represents a method in which an 80 ° C. aqueous dispersion containing CNF was added to an X ° C. resin emulsion. Similarly, “Formulation 3 (X ° C.)” (see Example 10 and Comparative Example 7) represents a method in which a resin emulsion at about 20 ° C. was added to an aqueous dispersion of X ° C. containing CNF, “Formulation 4 (X ° C.)” (see Example 11) represents a method in which a resin emulsion at 80 ° C. was added to an aqueous dispersion at X ° C. containing CNF. The “reaction (X ° C.)” (see Examples 12 to 24) was carried out by polymerizing the monomer components at X ° C. to produce a resin emulsion as a base, and cooling the resin emulsion without cooling the resin emulsion. Represents a method of adding and compounding.

  As shown in Tables 1 to 6, in each of the composite resin compositions manufactured in Examples 1 to 24, the evaluation result of dispersibility of CNF and resin particles was A or B. That is, in each of the composite resin compositions manufactured in Examples 1 to 24, when a sample prepared from the composite resin composition was observed by AFM, CNF was dispersed, and the CNF was used as a shaft portion. A structure in which the resin particles gathered in a bunch of grapes around the axis along the axis was confirmed (for example, see Examples 1 and 5 in FIG. 1). As a result, it was confirmed that each of the composite resin compositions manufactured in Examples 1 to 24 was capable of forming a film in which CNF was sufficiently uniformly dispersed in the resin (for example, Example in FIG. 2). 1-3).

  On the other hand, as shown in Tables 1 to 6, in each of the composite resin compositions produced in Comparative Examples 2 to 7, the evaluation result of the dispersibility of CNF and the resin particles was C. That is, in each of the composite resin compositions manufactured in Comparative Examples 2 to 7, when the sample prepared from the composite resin composition was observed by AFM, an aggregate containing CNF was observed, and the resin particles were also aggregated accordingly. This structure was observed (for example, see Comparative Example 4 in FIG. 1). As a result, a film having an aggregate containing CNF was formed from each of the composite resin compositions manufactured in Comparative Examples 2 to 7 (for example, see Comparative Examples 3 and 4 in FIG. 2).

Claims (4)

An aqueous dispersion medium, resin particles emulsified in the aqueous dispersion medium, and cellulose nanofibers dispersed in the aqueous dispersion medium, a composite resin composition containing:
The resin particles include at least one selected from the group consisting of (meth) acrylic resin particles, styrene resin particles, and (meth) acrylonitrile resin particles,
A sample obtained by dropping a liquid obtained by diluting the composite resin composition with water in such an amount that the non-volatile content thereof is in the range of 0.01 to 0.1% by mass on a measurement base material and drying the sample is subjected to an atomic force microscope. A composite resin composition in which the cellulose nanofibers are dispersed, and a structure in which the resin particles are attached to the cellulose nanofibers in the form of particles is observed.   2. The observation with the atomic force microscope, wherein the cellulose nanofiber is used as a shaft, and a structure in which the resin particles are gathered in a bunch of grapes around the shaft along the shaft is observed. 3. The composite resin composition according to item 1.   The content of the cellulose nanofiber in the composite resin composition is in a range of 0.1 to 10 parts by mass per 100 parts by mass of the resin particles in the composite resin composition. Composite resin composition.   The resin particles further include a structural unit derived from at least one polymerizable monomer selected from the group consisting of an unsaturated carboxylic acid-based monomer and a (meth) acrylamide-based monomer. 4. The composite resin composition according to any one of 3.