Powder composition, method for producing the same, and rheology control agent for aqueous coatings

Abstract

This invention provides a high-solids content cellulose nanofiber (CNF)-containing powder composition having excellent redispersibility and pseudoplasticity-imparting effects on aqueous resins, a method for producing the same, and a rheology control agent for aqueous coatings. [Solution] A CNF-containing powder composition comprising a composite nonionic CNF which is a nonionic CNF compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, wherein the substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 The composite nonionic CNF is selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, and when the total mass of the composite nonionic CNF and the substrate contained in the powder composition is 100% by mass, the content of the composite nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass.

Description

[Technical Field]

[0001] This invention relates to a powder composition, a method for producing the same, and a rheology control agent for aqueous coatings. [Background technology]

[0002] Cellulose nanofiber (hereinafter sometimes referred to as "CNF") is a biomass (plant-derived) raw material that can be expected to have effects such as imparting high pseudoplasticity, stabilizing pigment dispersion, and strengthening physical properties (such as coating film strength). Among CNFs, bacterial nanocellulose (hereinafter sometimes referred to as "BNC"), which is produced by bacterial fermentation of a compound with hydroxypropyl cellulose (hereinafter sometimes referred to as "HPC") or carboxymethyl cellulose (hereinafter sometimes referred to as "CMC"), has excellent dispersibility in water-based resins and has a higher pseudoplasticity-imparting effect and physical property strengthening performance than wood-derived CNF.

[0003] On the other hand, CNF containing BNC compounded with HPC or CMC is usually used in the form of an aqueous dispersion, and its solid content concentration is low, at 1-3%. Therefore, when such CNF is incorporated into an aqueous resin composition, the amount of water introduced into the aqueous resin exceeds the upper limit of the amount of water that can be incorporated into the aqueous resin composition, making it impossible to achieve the designed resin solid content, and in many cases, the incorporation of CNF itself had to be abandoned. In addition, low solid content concentrations of CNF not only increase transportation costs per unit of CNF solids, but also present storage challenges such as increased susceptibility to mold growth due to the presence of moisture.

[0004] One possible solution to these problems is to dry (evaporate the water from) an aqueous dispersion of CNF to achieve high solidity. However, if the aqueous dispersion of CNF is simply dried, the CNF will aggregate during the drying process, making it impossible to redisperse in water or other media. Furthermore, in an aggregated state, the properties of CNF, such as imparting high pseudoplasticity and strengthening physical properties, cannot be exhibited. Moreover, if a paint containing an aqueous dispersion of aggregated CNF is applied, the aggregated CNF itself becomes a source of defects in the CNF-containing paint film. To address these problems, various dried CNF products that can be redispersed in water have been proposed.

[0005] For example, Patent Document 1 discloses a bacterial nanocellulose composite powder obtained by adding hydroxyethylcellulose or hydroxypropylcellulose to bacterial nanocellulose composited with hydroxypropylcellulose, bacterial nanocellulose composited with hydroxyethylcellulose, or bacterial nanocellulose composited with carboxymethylcellulose, and then drying it in a constant temperature bath.

[0006] Patent Document 2 discloses a powder formulation containing bacterial cellulose and carboxymethylcellulose, hydroxyethylcellulose, etc., which can be redispersed in an aqueous medium at 20°C by low-shear mixing. This powder formulation is produced by adding a third component such as carboxymethylcellulose or hydroxyethylcellulose to an aqueous suspension of bacterial cellulose, then drying and grinding the bacterial cellulose.

[0007] Patent Document 3 discloses a method for producing a dried dispersible bacterial nanocellulose, which involves adding an organic solvent to an aqueous dispersion of bacterial nanocellulose, and then removing the water and organic solvent from the dispersion to dry the bacterial nanocellulose. Examples of drying methods include heat drying, forced-air drying, and freeze-drying.

[0008] Patent Document 4 discloses a resin composition comprising a thermoplastic resin, cellulose fibers, a water-soluble resin, and a modified olefin resin. The examples in this document describe spray-drying a mixture containing mechanically defibrated cellulose nanofibers, an aqueous resin, and water, and then melt-kneading the dried mixture with a thermoplastic resin or the like.

[0009] Patent Document 5 discloses a resin composition comprising a dried cellulose nanofiber, acid-modified polypropylene, and a polyolefin resin. The examples in this document describe mixing mechanically defibrated cellulose nanofibers with oleic acid, spray-drying the mixture, and then mixing it with a polyolefin resin. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2021-126054

[0011] [Patent Document 2] Special Publication No. 2022-517739

[0012] [Patent Document 3] International Publication No. 2018 / 038055 Brochure

[0013] [Patent Document 4] Special Publication No. 2012-236906

[0014] [Patent Document 5] Japanese Patent Publication No. 2019-131774 [Overview of the project] [Problems that the invention aims to solve]

[0015] However, none of Patent Documents 1 to 5 disclose a CNF dried product having redispersibility in water, an aqueous medium not containing an aqueous resin, or thermoplastic resins, or a method for producing the same. A CNF dried product that can be redispersed in an aqueous resin or a composition containing an aqueous resin has not been disclosed.

[0016] Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a high-solid-content cellulose nanofiber-containing powder composition having excellent redispersibility in an aqueous resin and a pseudoplasticity imparting effect, a method for producing the same, and a rheology control agent for aqueous coating using the cellulose nanofiber-containing powder composition.

Means for Solving the Problems

[0017] As a result of intensive studies to solve the above problems, the present inventors mixed nonionic CNF (complexed nonionic CNF) complexed with HPC or CMC and a specific substrate at a predetermined ratio, and spray-dried this mixture, and found that a high-solid-content CNF dried product having excellent redispersibility in an aqueous resin and a pseudoplasticity imparting effect can be obtained, and the present invention has been completed based on this finding.

[0018] That is, the present invention is a cellulose nanofiber-containing powder composition containing complexed nonionic CNF, which is a nonionic cellulose nanofiber complexed with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, wherein the substrate is a saccharide, a sucrose fatty acid ester having an HLB of 11 or more, and a nonionic water-soluble polymer having a 2% aqueous solution viscosity of 5 mPa·s or less at 25°C and 1000 s -1 and is at least one selected from the group consisting of, and when the total mass of the complexed nonionic CNF and the substrate contained in the powder composition is 100% by mass, the content of the complexed nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass.

[0019] In one embodiment of the present invention, the composite nonionic CNF of the present invention may be bacterial nanocellulose.

[0020] In another embodiment of the powder composition of the present invention, the nonionic water-soluble polymer may be a polymer having a total light transmittance of 80% or more in a 2% aqueous solution.

[0021] In another embodiment of the powder composition of the present invention, the sugars may be monosaccharides or disaccharides.

[0022] In another embodiment of the powder composition of the present invention, the powder composition may be a powder obtained by spray-drying and granulating a dispersion containing the composite nonionic CNF and the substrate.

[0023] In another embodiment of the powder composition of the present invention, the powder composition may be used as a rheology control agent for aqueous coatings.

[0024] Furthermore, the present invention relates to a method for producing a cellulose nanofiber-containing powder composition comprising composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, comprising a spray drying granulation step in which a dispersion containing the composite nonionic CNF and the substrate is dried into particles by spray drying, wherein the substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 The method for producing a powder composition is to use at least one nonionic water-soluble polymer selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, wherein in the dispersion, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the amount of the composite nonionic CNF is 5 to 80% by mass, and the amount of the substrate is 20 to 95% by mass.

[0025] In one embodiment of the method for producing the powder composition of the present invention, the composite nonionic CNF is bacterial nanocellulose, and in the spray-drying granulation step, the composite nonionic CNF and the substrate may be mixed with water to form the dispersion.

[0026] In another embodiment of the method for producing the powder composition of the present invention, the nonionic water-soluble polymer may be a polymer having a total light transmittance of 80% or more in a 2% aqueous solution.

[0027] In another embodiment of the method for producing the powder composition of the present invention, the sugars may be monosaccharides or disaccharides.

[0028] Furthermore, the present invention contains composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, wherein the substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 This is a rheology control agent for water-based coatings, comprising at least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, wherein, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the content of the composite nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass. [Effects of the Invention]

[0029] According to the present invention, it is possible to provide a high-solids-content CNF dried body that has excellent redispersibility and pseudoplasticity-imparting effect on aqueous resins. [Modes for carrying out the invention]

[0030] Preferred embodiments of the present invention will be described in detail below.

[0031] [Powder composition] The powder composition of the present invention is a CNF-containing powder composition containing nonionic cellulose nanofibers (hereinafter referred to as "composite nonionic CNF") compounded with hydroxypropyl cellulose (HPC) or carboxymethyl cellulose (CMC), and a substrate. The powder composition of the present invention is a high-solids content CNF dry product, has high dispersibility in aqueous resins (exhibits excellent redispersibility), and exhibits a high pseudoplasticity-imparting effect.

[0032] In this invention, "solid content (CNF concentration)" refers to the mass ratio of CNF in the powder composition when the total mass of the powder composition is taken as 100% by mass. Furthermore, in this invention, "high solid content" means that the above solid content is 5% by mass or more. Preferably, the solid content of the powder composition of this invention is 10% by mass or more. As mentioned above, the solid content of conventional aqueous dispersions of CNF is 1 to 3% by mass.

[0033] In the present invention, "high dispersibility" means that the particle size measured with a grind gauge having a maximum groove depth of 100 μm and a scale interval of 10 μm is 90 μm or less, and that no poorly dispersed particles are observed by visual inspection of the dispersion obtained by dispersing a CNF dry material (the powder composition of the present invention is also a type of CNF dry material) in an aqueous resin. On the other hand, "low dispersibility (insufficient dispersibility for the powder composition of the present invention)" means that the particle size measured with the above grind gauge is 100 μm or more, or that poorly dispersed particles are observed by visual inspection of the above dispersion. A particle size of 30 μm or less is particularly suitable for high dispersibility. Poorly dispersed particles refer to undispersed particles or clumps of a size visible to the naked eye in a composition containing an aqueous resin.

[0034] Furthermore, in this invention, "particle size" refers to the particle size measured using a grind gauge with a maximum groove depth of 100 μm, a scale interval of 10 μm, a groove width of 12 mm, and a groove length of 140 mm. In this particle size measurement, the point at which prominent spots begin to appear in the above-mentioned dispersion sample is observed in accordance with JIS K5600-2-5:1999. Specifically, points containing 5 or more particles in one scale division (a band with a width of 13 mm) along the groove are observed. Sparse spots that appear before the point at which prominent spots begin to appear are ignored. The uppermost scale division closest to the upper limit of the point containing 5 or more particles was defined as the particle size.

[0035] Next, in this invention, "pseudoplasticity" refers to the property of a paint or dispersion or other object that has high viscosity before force is applied, and whose viscosity decreases when force is applied. In this invention, "high pseudoplasticity imparting effect" means that the TI value (100s) -1 viscosity η 100 1s for -1 The ratio of viscosity η1 in: η1 / η 100 This means that the ) is 2.0 or higher. The TI value is preferably 4.0 or higher, and more preferably 9.0 or higher. In these cases, the pseudoplasticity imparting effect is particularly high.

[0036] (Complex nonionic CNF) Cellulose nanofibers (CNF) are cellulose fibers with a fiber diameter of several nanometers to approximately 100 nanometers. CNF can be obtained by mechanically defibrating wood-derived materials, by chemically modifying (such as anionic modification) wood-derived materials before mechanical defibration, or by synthesizing them with bacteria. CNF has functions such as imparting pseudoplasticity, stabilizing pigment dispersion, and enhancing physical properties (such as coating film strength and water resistance).

[0037] In the powder composition of the present invention, nonionic CNF is used. For example, anionically modified CNF maintains a thin fiber diameter due to interionic repulsion in an aqueous dispersion, but when water is removed, the interionic repulsion is lost, causing strong aggregation. Therefore, in the present invention, nonionic CNF is used to prevent strong aggregation of CNF.

[0038] Fibrous cellulose synthesized by bacteria is called bacterial cellulose (hereinafter sometimes referred to as "BC"). BC is obtained by culturing bacteria such as acetic acid bacteria, and fibrous cellulose with a fiber diameter of 100 nm or less is called bacterial nanocellulose (BNC) and is considered a type of CNF. The fiber diameter of CNF can be measured, for example, by diluting a CNF dispersion with water so that the solid content (CNF concentration) is 0.05% by mass, freeze-drying the resulting fibers, and observing them with a scanning electron microscope (SEM). The average fiber length of BNC is not particularly limited, but is generally around 10-20 μm.

[0039] BNC has a larger fiber diameter and fiber aspect ratio than wood-derived CNF, resulting in a higher effect of strengthening the physical properties of the coating film and imparting pseudoplasticity.

[0040] The CNF used as the composite nonionic CNF in the present invention is CNF composited with HPC or CMC (composite CNF). Here, "composite" CNF with HPC or CMC means that the hydroxyl groups of HPC or CMC and the hydroxyl groups in the cellulose backbone of CNF are bonded by hydrogen bonds or van der Waals forces, resulting in a structure in which HPC or CMC is intricately intertwined with CNF. In this way, the CNF is composited with HPC or CMC, which improves its dispersibility in aqueous resins. Therefore, the CNF-containing powder composition of the present invention can suppress the re-aggregation of CNF after dispersion in an aqueous resin. Examples of CNF composited with HPC or CMC include bacterial nanocellulose composited with HPC (HP-BNC) and bacterial nanocellulose composited with CMC (CM-BNC).

[0041] One method for obtaining HP-BNC or CM-BNC is to synthesize CNF using bacteria while HPC or CMC is present in the culture medium (biological synthesis). Alternatively, another method involves introducing HPC or CMC together with the cellulose material when defibrating materials derived from wood or other materials, or chemically processed raw materials thereof, using equipment such as a high-pressure homogenizer (mechanical defibration process). Of these methods, the biological synthesis method involves bacteria synthesizing a single nano-sized fiber and moving while expelling the synthesized fiber from the bacterial cell. At this time, by placing HPC or CMC on the culture medium, HPC or CMC can be directly and efficiently bound to each CNF fiber. As a result, the amount of HPC or CMC compounded with CNF increases, and HPC or CMC becomes less likely to detach from CNF. On the other hand, in the case of compounding by mechanical defibration, the defibrated CNF is compounded by physically binding with HPC or CMC that are simultaneously charged. However, since the CNFs are also in close proximity during this process, re-aggregation of the CNFs can occur probabilistically. Therefore, compared to the biological synthesis method, the amount of HPC or CMC compounded with the CNF is reduced, and the HPC or CMC is more likely to detach from the CNF.

[0042] For the reasons stated above, biological synthesis provides a higher re-aggregation prevention effect after dispersion in the aqueous resin than mechanical defibration treatment. From this viewpoint, the CNF used in the present invention is preferably HP-BNC or CM-BNC produced by biological synthesis.

[0043] <Content of complex nonionic CNF> The content of composite nonionic CNF in the powder composition of the present invention is 5% to 80% by mass, when the total mass of composite nonionic CNF and substrate contained in the powder composition is taken as 100% by mass. A composite nonionic CNF content within the range of 5% to 80% by mass allows the CNF to disperse in the aqueous resin and exhibit a high pseudoplasticity-imparting effect when the powder composition of the present invention is added to an aqueous resin. If the composite nonionic CNF content is less than 5% by mass, the amount of substrate added to the composition containing the aqueous resin becomes too large, potentially reducing the physical properties of the coating film, such as water resistance. On the other hand, if the composite nonionic CNF content exceeds 80% by mass, the pseudoplasticity-imparting effect of CNF cannot be achieved. To further enhance the pseudoplasticity-imparting effect, the composite nonionic CNF content is preferably 5% to 50% by mass, and more preferably 10% to 50% by mass.

[0044] (HPC, CMC) The powder composition of the present invention contains either HPC, CMC, or both HPC and CMC in a compounded state with CNF. HPC and CMC interact with CNF through hydrogen bonding or van der Waals forces between their hydroxyl groups and the hydroxyl groups in the cellulose backbone of CNF, resulting in adsorption to CNF in a complexly intertwined state. This suppresses the aggregation of CNF, allows for high dispersibility in aqueous resins, and exhibits higher dispersibility in aqueous resins than CNF that is not compounded with HPC or CMC.

[0045] <Content of HPC and CMC in composite CNF> The content of HPC and CMC in the composite CNF used in the powder composition of the present invention is not particularly limited and can be set as appropriate. For example, when BNC is used as nonionic CNF, if the content of HPC and CMC is 10 to 35 parts by mass when the total mass of HP-BNC and CM-BNC is 100 parts by mass, high dispersibility in aqueous resins can be obtained. If the content of HPC and CMC is less than 10 parts by mass, the re-aggregation of CNF cannot be prevented, and aggregates will be formed when added to aqueous resins. On the other hand, if the content of HPC and CMC exceeds 35 parts by mass, the thickening effect of HPC and CMC relatively reduces the pseudoplastic effect derived from CNF, and the handling of the dispersion containing them decreases, resulting in a decrease in manufacturing efficiency. The content of HPC and CMC in the composite CNF can be determined as follows: The composite CNF is freeze-dried, tetrabutylphosphonium hydride is added and dissolved, and then water is added to precipitate only the cellulose. The precipitate is filtered and dried, and the mass of the dried product (corresponding to cellulose in the composite CNF) is subtracted from the dry mass of the composite CNF to determine the HPC and CMC content in the composite CNF.

[0046] (substrate) The substrate according to the present invention is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 The substrate is selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution. The substrate is present between the fibers of the composite CNF (when referred to as "composite CNF," it is not limited to nonionic CNF), thereby suppressing aggregation of the composite CNF during the manufacturing process of the CNF-containing powder composition of the present invention. Furthermore, when the CNF-containing powder composition is added to an aqueous resin, the substrate rapidly disperses or dissolves, allowing the composite CNF to be dispersed in the aqueous resin without aggregation. This enables the composite CNF to exhibit excellent dispersibility in the aqueous resin while also exhibiting the pseudoplastic effect and coating film property strengthening characteristics of the composite CNF.

[0047] Suitable characteristics required for the above-mentioned substrate are: (I) being solid at 40°C, (II) being nonionic, (III) having high affinity with the composite CNF, (IV) having a relatively low molecular weight, and (V) having high water solubility.

[0048] The fact that the above-mentioned substrate is solid at 40°C is necessary for the CNF-containing powder composition of the present invention to be in a solid form. When using a liquid substrate at 40°C, aggregation of CNF during the drying process may not be sufficiently suppressed. Therefore, the substrate of the present invention is preferably solid at 40°C.

[0049] The reason for using a nonionic substance as the substrate is that when using an anionic substrate, even if the above-mentioned composite nonionic CNF and the substrate are mixed to prepare a CNF dispersion and this dispersion is dried, a powdery composition cannot be obtained. Also, when using an amphoteric substrate, it is not suitable because it reduces the dispersibility of CNF in the aqueous resin. Therefore, in the present invention, a nonionic substrate is used. Furthermore, a characteristic of having high affinity with the composite CNF is also required. When the affinity with the composite CNF is low, aggregation of the composite CNFs cannot be suppressed. To increase the affinity with the composite CNF, those capable of forming a hydrogen bond with cellulose or having a structure similar to cellulose are suitable.

[0050] The compound selected as the substrate preferably has a low molecular weight and high water solubility in consideration of the diffusibility of the substrate in the aqueous resin. When the molecular weight of the substrate is high or the water solubility is low, the dispersibility of the CNF-containing powder composition in the aqueous resin decreases. The characteristic of the "low molecular weight" of the substrate of the present invention means that in the present invention, saccharides and sucrose fatty acid esters with an HLB of 11 or more are non-polymer compounds, and for nonionic water-soluble polymers, at 25°C, 1000s -1This corresponds to the viscosity of a 2% aqueous solution being 5 mPa·s or less. Generally, it is known that viscosity and weight-average molecular weight correlate regardless of the type of compound. The fact that the preferred range of viscosity for a 2% aqueous solution of the water-soluble polymers of the present invention is in the low viscosity region corresponds to the fact that these polymers have relatively low molecular weights.

[0051] Substrates having the above characteristics include sugars, sucrose fatty acid esters with an HLB of 11 or higher, and 25°C, 1000s -1 It is at least one selected from the group consisting of nonionic water-soluble polymers whose viscosity in a 2% aqueous solution is 5 mPa·s or less.

[0052] <Sugars> Suitable sugars for use as substrates in the present invention include monosaccharides and disaccharides. Examples of monosaccharides include glucose, galactose, and fructose. Examples of disaccharides include sucrose, lactulose, lactose, maltose, cellobiose, and trehalose.

[0053] <Sucrose fatty acid ester> The sucrose fatty acid ester usable as a substrate in this invention has an HLB of 11 or higher. If the HLB is less than 11, the sucrose fatty acid ester cannot be dissolved or dispersed in water, and therefore cannot be adsorbed around the CNF, resulting in no effect of substrate inclusion, i.e., no effect of preventing aggregation of the complexed CNFs. On the other hand, a high HLB does not pose any particular problem, and the maximum HLB of a sucrose fatty acid ester usable as a substrate is 19. Commercially available sucrose fatty acid esters generally have a maximum HLB of around 16.

[0054] In this invention, HLB is a value experimentally determined using standard samples. Specifically, first, multiple emulsions are prepared by changing the mixing ratio of two emulsifiers with different HLB values ​​(the HLB values ​​of the two emulsifiers are known). As a result, multiple standard samples are obtained in which the average HLB calculated from the mixing ratio changes in stages. Next, an aqueous solution of sucrose fatty acid ester is prepared, and by visual inspection, the HLB of the one that looks closest to the multiple standard samples can be estimated to be the HLB of the sucrose fatty acid ester. In this invention, this estimated HLB value is used as the HLB value of the sucrose fatty acid ester.

[0055] Examples of fatty acids used in the synthesis of such sucrose fatty acid esters include those with 12 to 18 carbon atoms. Specifically, examples of sucrose fatty acid esters that can be used as substrates include sucrose laurate, sucrose myrilic acid, sucrose parimitic acid, and sucrose stearate.

[0056] <Water-soluble polymer> In the present invention, "water-soluble" means that the total light transmittance of a 2% aqueous solution of the polymer is 80% or higher. The total light transmittance can be measured by placing a 2% aqueous solution of the water-soluble polymer in a cell with a path length of 1 cm and using an NDH7000 (manufactured by Nippon Denshoku Industries Ltd.) in accordance with JIS K7361-1:1997.

[0057] Furthermore, the water-soluble polymers of the present invention include not only those generally referred to as polymers, but also those referred to as oligomers. Specifically, the water-soluble polymers of the present invention include polymers or copolymers having three or more repeating units.

[0058] Examples of such water-soluble polymers include vinyl polymers containing vinylpyrrolidone or vinyl alcohol as constituent units (e.g., polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), copolymers containing vinylpyrrolidone and vinyl alcohol as constituent units), polyacrylamide, starch, dextrin, HPC, HEC, methylhydroxypropylcellulose, methylhydroxyethylcellulose, methylcellulose, polyethylene glycol (PEG), polyoxyethylene alkyl ethers, and polymers having a PEG backbone or hydroxyl groups (e.g., nonionic polymers consisting of combinations of unsaturated polymerizable monomers having a PEG backbone or hydroxyl groups, including (meth)acrylic polymers and vinyl ester polymers). Examples of nonionic polymers consisting of combinations of unsaturated polymerizable monomers having a PEG backbone or hydroxyl groups include copolymers of monomers such as PEG (meth)acrylate, alkyl PEG (meth)acrylate, and hydroxyalkyl (meth)acrylate with other nonionic polymerizable monomers (alkyl (meth)acrylate, alkyl vinyl ester, etc.). Among these water-soluble polymers, PVP, dextrin, HPC, and PEG are particularly preferred due to their good stability in aqueous resins.

[0059] The viscosity of the 2% aqueous solution of the water-soluble polymer of the present invention is set to 5 mPa·s or less because if the viscosity at high shear rates is high, the handling properties of compositions such as water-based paints containing this water-soluble polymer as a substrate deteriorate, the cohesive force of the substrate becomes strong, making it impossible to disperse the powder composition of the present invention in aqueous resin, and the pseudoplastic effect and physical property strengthening performance of CNF are lost. In order to further improve the anti-coagulation effect of CNF during the drying process and the dispersibility of the CNF-containing powder composition in aqueous resin, the viscosity of the 2% aqueous solution of the water-soluble polymer is preferably 2 mPa·s or less. On the other hand, there is no particular lower limit to the viscosity of the 2% aqueous solution of the water-soluble polymer, but from the viewpoint of dispersion stability, it is preferably 0.1 mPa·s or more.

[0060] The viscosity of a 2% aqueous solution of a water-soluble polymer is determined using a rheometer with a shear rate of 1000 s⁻¹. -1 The values ​​were measured at 25°C using a geometry (cone plate) with a diameter of 60 mm and an angle of 1° between the generatrix and the circular surface of the cone.

[0061] <Substrate content> The substrate content in the powder composition of the present invention is 20% to 95% by mass, when the total mass of the composite nonionic CNF and substrate contained in the powder composition is taken as 100% by mass. A substrate content within the range of 20% to 95% by mass allows the CNF to disperse in the aqueous resin and exhibit a high pseudoplasticity-imparting effect when the powder composition of the present invention is added to an aqueous resin. If the substrate content is less than 20% by mass, the pseudoplasticity-imparting effect of CNF cannot be achieved. On the other hand, if the substrate content exceeds 95% by mass, the amount of substrate added to the composition containing the aqueous resin becomes too large, potentially reducing the physical properties of the coating film, such as water resistance. To further enhance the pseudoplasticity-imparting effect, the substrate content is preferably 50% to 95% by mass, and more preferably 50% to 90% by mass. The substrate content can also be calculated by dispersing the CNF-containing powder composition in water, dissolving the substrate, centrifuging the dispersion, and then calculating the heat residue of the supernatant liquid.

[0062] (Uses of powder compositions) The CNF-containing powder composition according to the present invention is particularly suitable as a rheology control agent for aqueous coatings. That is, as described above, the CNF-containing powder composition of the present invention has high dispersibility in aqueous resins and a high pseudoplasticity-imparting effect, making it especially suitable as a rheology control agent for aqueous coatings.

[0063] [Method for producing powder composition] The powder composition according to the present invention is a powder obtained by spray-drying and granulating a dispersion containing the above-mentioned composite nonionic CNF and a substrate. The method for producing the CNF-containing powder composition of the present invention will be described in detail below.

[0064] The method for producing the powder composition according to the present invention includes a spray drying granulation step in which a dispersion containing the above-mentioned composite nonionic CNF and a substrate is dried into dry particles by spray drying.

[0065] (Method for producing and obtaining complex nonionic CNF) Complex nonionic CNF can be manufactured as exemplified below, or it can be obtained commercially.

[0066] The method for producing the composite nonionic CNF of the present invention is not particularly limited, but as an example, the method for producing nonionic CNF in the case of BNC is described below. For example, bacterial cellulose (hereinafter sometimes referred to as "BC")-producing bacteria can be cultured with aeration and stirring in a medium supplemented with HPC or CMC, and the bacterial components can be removed from the resulting culture solution to purify the BNC, thereby obtaining bacterial-derived composite nonionic CNF. CNF obtained by bacteria in this way is preferable because, compared to CNF obtained by mechanical defibration of woody materials, the fiber diameter and fiber aspect ratio are larger, resulting in higher performance in strengthening the physical properties of the coating film and a higher pseudoplastic effect. The amount of HPC or CMC added to the medium can be appropriately set according to the desired amount of HPC or CMC binding to the composite nonionic CNF. For example, in order to achieve the above-mentioned preferred range for HPC or CMC content, the final concentration of the first substrate in the medium should be set to 0.5 to 5.0% (w / v).

[0067] As BC-producing bacteria, known bacteria capable of producing BC can be used, such as Gluconacetobacter xylinus strain ATCC53582, Gluconacetobacter hansenii strain ATCC23769, Gluconacetobacter xylinus strain ATCC700178 (BPR2001), Gluconacetobacter swingsii strain BPR3001E, Acetobacter xylinum strain JCM10150, Enterobacter sp. CJF-002 strain, and Gluconacetobacter intermedius strain SIID9587 (accession number NITE BP-01495).

[0068] The culture conditions for BC-producing bacteria can be those known to be used for culturing the aforementioned bacteria. Examples of culture conditions include an aeration rate of 1-10 L / min, a rotation speed of 100-800 rpm, a temperature of 20-40°C, and a culture period of 1-7 days. In addition, known culture media used for culturing the aforementioned bacteria, such as Hestrin-Schramm standard medium (HS medium), can be used as the culture medium.

[0069] To purify BNC from the culture medium, first, an aqueous sodium hydroxide (NaOH) solution is added to the culture medium and the mixture is heated to approximately 60°C and stirred for several hours to lyse the bacterial cells. This is then subjected to centrifugation, and the supernatant is removed to remove the bacterial components and collect the precipitate. Next, water is added to the precipitate and centrifugation is performed, followed by removal of the supernatant. This process is repeated until the pH of the precipitate is 7 or lower. This yields a liquid in which CNF (BNC) complexed with HPC or CMC, i.e., HP-BNC or CM-BNC, is dispersed in water (BNC dispersion).

[0070] Note that commercially available HP-BNC or CM-BNC connectors may be used. Examples of commercially available HP-BNC or CM-BNC connectors include Fibnano® HP-NFBC and Fibnano® CM-NFBC (both manufactured by Kusano Sakko Co., Ltd.).

[0071] (Spray drying granulation process) This process involves drying a dispersion containing the composite nonionic CNF and substrate obtained as described above into dry particles by spray drying.

[0072] <Method for preparing dispersion> The method for preparing the dispersion is not particularly limited; the substrate can be directly dispersed in the composite nonionic CNF, or water can be added to the composite nonionic CNF and substrate and dispersed. In particular, when the nonionic CNF is BNC, in the spray-drying granulation process, the dispersion is prepared by mixing the BNC composited with HPC or CMC with the substrate, or by adding water to the mixture. For example, the above dispersion can be prepared by adding the substrate in the following proportion range to water, stirring with a disperser or the like to dissolve it, then adding the BNC composited with HPC or CMC (HP-BNC or CM-BNC in this invention), and stirring with a disperser or the like. Note that the stirring method during the preparation of the dispersion is not limited to a disperser; any method is acceptable as long as the composite nonionic CNF and substrate are sufficiently dispersed in water.

[0073] In the above dispersion, when the total mass of composite nonionic CNF and substrate is 100% by mass, the amount of composite nonionic CNF is between 5% by mass and 80% by mass. By keeping the amount of composite nonionic CNF within the range of 5% by mass to 80% by mass, when the composition obtained by the method for producing the powder composition of the present invention is added to an aqueous resin, the CNF can be dispersed in the aqueous resin and exhibit a high pseudoplasticity-imparting effect. If the amount of composite nonionic CNF is less than 5% by mass, the amount of substrate added to the composition containing the aqueous resin becomes too large, which may reduce the physical properties of the coating film, such as water resistance. On the other hand, if the amount of composite nonionic CNF exceeds 80% by mass, the pseudoplasticity-imparting effect of CNF cannot be exhibited. To further enhance the pseudoplasticity-imparting effect, the amount of composite nonionic CNF blended is preferably 5% to 50% by mass, and more preferably 10% to 50% by mass, when the total mass of composite nonionic CNF and substrate is 100% by mass.

[0074] The amount of composite nonionic CNF blended with the total mass of the above dispersion is not particularly limited, but considering the manufacturing efficiency in the spray drying process and the atomization properties of the dispersion, 0.3% to 3.0% by mass is preferred, and 0.3% to 1.0% by mass is more preferred. If the amount of composite nonionic CNF blended with the total mass of the above dispersion is less than 0.3% by mass, it is undesirable because the manufacturing efficiency decreases, such as the drying time required per unit weight of the obtained CNF powder becoming longer or the yield decreasing. If the amount of composite nonionic CNF blended with the total mass of the above dispersion exceeds 3.0% by mass, it is undesirable because the fluidity of the dispersion becomes low and the atomization properties decrease, making it impossible to obtain a homogeneous powder.

[0075] Furthermore, the amounts of HPC and CMC in the dispersion are determined by the final concentrations of HPC and CMC added to the culture medium, as described above.

[0076] Furthermore, in the above dispersion, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the amount of substrate is 20% to 95% by mass. By having a substrate amount within the range of 20% to 95% by mass, when the composition obtained by the method for producing the powder composition of the present invention is added to an aqueous resin, the CNF can be dispersed in the aqueous resin and exhibit a high pseudoplasticity-imparting effect. If the substrate amount is less than 20% by mass, the pseudoplasticity-imparting effect of the CNF cannot be exhibited. On the other hand, if the substrate amount exceeds 95% by mass, the amount of substrate added to the composition containing the aqueous resin becomes too large, which may reduce the physical properties of the coating film, such as water resistance. To further enhance the pseudoplasticity-imparting effect, the substrate amount, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, is preferably 50% to 95% by mass, and more preferably 50% to 90% by mass.

[0077] <Spray drying method> The spray drying method is not particularly limited, and known methods can be used. One example is a method in which a spray dryer is used to spray and dry the dispersion containing the nonionic CNF at a spray pressure of 0.2 to 0.6 MPa, a hot air temperature of 100 to 250°C, and a delivery rate of 0.1 to 30 kg / h. This yields a CNF-containing powder composition containing nonionic CNF compounded with HPC or CMC and a substrate. The particle size of the CNF-containing powder composition obtained in this way has a median diameter (D50) of approximately 5 μm to 20 μm. Furthermore, it is preferable that the CNF-containing powder composition produced by spray drying has a circularity of 0.9 or higher. Circularity is the value obtained by dividing the equivalent circumference of a circle calculated from the average particle size of the primary particles of the obtained powder by the average value of the particle circumferences estimated by image analysis or the like. Commercially available spray dryers can be used.

[0078] The CNF-containing powder composition of the present invention obtained by the manufacturing method described above is a high-solids content CNF dry body that has excellent redispersibility and pseudoplasticity-imparting effect on aqueous resins.

[0079] [Aqueous resin composition] The CNF-containing powder composition of the present invention described above exhibits excellent redispersibility in aqueous resins. Therefore, the aqueous resin composition obtained by dispersing the CNF-containing powder composition of the present invention in an aqueous resin has a high TI value due to the high pseudoplasticity-imparting effect of CNF.

[0080] The aqueous resin composition of the present invention contains the above-mentioned CNF-containing powder composition and an aqueous resin as essential components, and contains other components as optional components.

[0081] (Water-based resin) The aqueous resins usable in the aqueous resin composition of the present invention are those in which resin components are dispersed in a water-based medium. Examples of resin components include acrylic resins, acrylic silicone resins, alkyd resins, polyester resins, urethane resins, epoxy resins, silicone resins, and fluororesins. Aqueous resins can be classified into water-soluble, colloidal dispersion, and emulsion forms depending on their dispersion form, but any form is applicable. These resins may be heat-curable, UV-curable, electron-beam-curable, oxidative-curable, photocationic-curable, peroxide-curable, or curable through a chemical reaction in or without a catalyst. They may also be resins with a high glass transition temperature that do not involve a chemical reaction and form a film simply by the volatilization of the diluent. Examples of curing agents include amino resins, melamine resins, isocyanate compounds, blocked isocyanate compounds, and epoxy compounds.

[0082] (Other ingredients) The aqueous resin composition of the present invention may contain other additives, such as pigments, dehydrating agents (e.g., silane coupling agents), adhesion enhancers, surfactants, curing catalysts, film-forming aids, dryers, anti-fouling agents, sensitizers, antioxidants, light stabilizers, UV absorbers, water-resistant agents, anti-corrosion and antifungal agents, defoamers, leveling agents, dispersants, flame retardants, antistatic agents, release agents, deodorizers, pH adjusters, and fragrances, to the extent that its properties and the objectives of the present invention are not impaired.

[0083] (Uses of water-based resin compositions) The aqueous resin composition of the present invention can be suitably used as a water-based paint containing general coloring pigments and extender pigments, or as an aqueous coating material such as an aqueous ink.

[0084] (Method for manufacturing aqueous resin compositions) The aqueous resin composition of the present invention can be manufactured in accordance with known methods for manufacturing aqueous paints, aqueous coating materials, etc. For example, the components other than the CNF-containing powder composition (rheology control agent for aqueous coatings) and pigments described above can be mixed while stirring in a water-based medium such as deionized water, and then the pH can be adjusted as necessary to produce a clear coating. The aqueous resin composition can be manufactured by adding the CNF-containing powder composition (rheology control agent for aqueous coatings) and pigments to this clear coating and dispersing them in the clear coating.

[0085] [Mechanism of action] As described above, HPC or CMC are compounded with CNF by hydrogen bonds or van der Waals forces. CNF compounded with HPC or CMC (compounded CNF such as HP-BNC or CM-BNC) has high dispersibility in aqueous resins and is less likely to cause CNF aggregation when added to aqueous resins. Therefore, it is possible to prevent the cellulose fibers from re-aggregating after the CNF-containing powder composition has dispersed in an aqueous resin. This effect is particularly high when BNC is used as the compounded nonionic CNF. As described above, this is because, in BNC, HPC or CMC is compounded with each individual CNF fiber.

[0086] Furthermore, in order to powderize CNF, a solid medium component is considered necessary between the cellulose fibers to prevent aggregation during the drying process. Considering the dispersibility of the CNF-containing powder composition in aqueous resins, a material with high affinity for water should be selected as this medium component. If a medium with poor diffusivity to aqueous resins, such as a high molecular weight substrate, is selected as the medium, adding a large amount will result in the formation of poorly dispersed materials and the loss of the viscous characteristics (high pseudoplasticity imparting effect) of CNF. Such loss of viscous characteristics can include, for example, the unnecessary thickening of high shear viscosity (viscosity at high shear rates) due to the thickening properties of polysaccharides. Therefore, a low molecular weight substrate is suitable as a medium to prevent aggregation during the drying process.

[0087] In this invention, by using a nonionic, low-molecular-weight substrate as a base in addition to the composite nonionic CNF, it is possible to form a powder in which the substrate is adsorbed onto cellulose fibers to which HPC or CMC is adsorbed. As a result, when the CNF-containing powder composition is added to an aqueous resin, the substrate portion is immediately dissolved or dispersed, providing a state in which the CNF composited with HPC or CMC is dispersed. Therefore, even when using a powder composition with a high CNF content, excellent dispersibility in aqueous resins and a high pseudoplasticity imparting effect can be obtained.

[0088] According to the mechanism described above, the following effects can be obtained in a preferred embodiment of the present invention.

[0089] When BNC is used as the composite nonionic CNF of the present invention, BNC has a larger fiber diameter and aspect ratio than CNF obtained by mechanical defibration of woody materials (mechanically defibrated CNF), and therefore can exhibit a higher pseudoplasticity imparting effect than mechanically defibrated CNF. Furthermore, in the case of BNC composited with HPC or CMC, such as HP-BNC and CM-BNC, the HPC or CMC is adsorbed on the surface of the CNF, which prevents re-aggregation in water-soluble resins. Therefore, the CNF-containing powder composition of the present invention exhibits excellent effects derived from CNF (pseudoplasticity imparting effect, coating property strengthening effect) in aqueous resins.

[0090] Furthermore, by atomizing a dispersion containing composite nonionic CNF and a substrate into a powder composition by spray drying, higher dispersibility in aqueous resins can be achieved compared to drying by other methods. For example, if the dispersion is dried in a constant temperature bath, drying takes a long time and the CNF is exposed to high temperatures for a long period, which may cause aggregation during drying. Also, if the dispersion is freeze-dried, freeze-drying is a drying method in which volume shrinkage of the dispersion is less likely to occur during drying, and the substrate may dry without being able to adsorb around the CNF. Therefore, when high-solids CNF without adsorbed substrate is added to aqueous resins, it may cause aggregation of CNF. In contrast to these drying methods, atomization drying occurs immediately after shearing, accompanied by volume shrinkage of the dispersion, so the substrate is effectively adsorbed to the composite CNF. Therefore, even in a high-solids differentiated state, the presence of the substrate on the surface of the CNF composited with HPC or CMC prevents aggregation of CNF, resulting in high dispersibility in aqueous resins and a high pseudoplasticity-granting effect.

[0091] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. That is, other embodiments or various modifications that a person skilled in the art could conceive of within the scope of the invention as described in the claims are also understood to fall within the technical scope of the present invention.

[0092] For example, the present invention may also be the inventions listed below. (1) A cellulose nanofiber-containing powder composition comprising composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, A powder composition in which, when the total mass of the composite nonionic CNF and the substrate contained in the powder composition is taken as 100% by mass, the content of the composite nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass. (2) The powder composition according to (1), wherein the composite nonionic CNF is bacterial nanocellulose. (3) The powder composition according to (1) or (2), wherein the content of the composite nonionic CNF is 5 to 50% by mass. (4) The powder composition according to any one of (1) to (3), wherein the content of the composite nonionic CNF is 10 to 50% by mass. (5) The powder composition according to any one of (1) to (4), wherein the content of the substrate is 50 to 95% by mass. (6) The powder composition according to any one of (1) to (5), wherein the content of the substrate is 50 to 90% by mass. (7) The powder composition according to any one of (1) to (6), wherein the nonionic water-soluble polymer is a polymer with a total light transmittance of 80% or more in a 2% aqueous solution. (8) The powder composition according to (7), wherein the nonionic water-soluble polymer is a vinyl polymer containing vinylpyrrolidone or vinyl alcohol as a constituent unit, polyacrylamide, starch, dextrin, hydroxypropyl cellulose (in this case, hydroxypropyl cellulose compounded with the nonionic cellulose nanofiber does not fall under the category of the substrate), hydroxyethyl cellulose, methylhydroxypropyl cellulose, methylhydroxyethyl cellulose, methylcellulose, polyethylene glycol (PEG), polyoxyethylene alkyl ether, or a polymer having a PEG backbone or hydroxyl groups. (9) The powder composition according to (8), wherein the polymer having a PEG skeleton or hydroxyl group is a copolymer of at least one monomer selected from the group consisting of PEG (meth)acrylate, alkylPEG (meth)acrylate and hydroxyalkyl (meth)acrylate and at least one monomer selected from the group consisting of alkyl (meth)acrylate and alkyl vinyl ester, a (meth)acrylic polymer, or a vinyl ester polymer. (10) The powder composition according to any one of (1) to (9), wherein the sugars are monosaccharides or disaccharides. (11) The powder composition according to (10), wherein the monosaccharide is glucose, galactose, or fructose. (12) The powder composition according to (10) or (11), wherein the disaccharide is sucrose, lactulose, lactose, maltose, cellobiose, or trehalose. (13) The powder composition according to any one of (1) to (12), wherein the sucrose fatty acid ester with an HLB of 11 or more is sucrose laurate, sucrose myrilic acid, sucrose parimitic acid, or sucrose stearate. (14) 25℃, 1000s -1 The powder composition according to any one of (1) to (13), wherein the viscosity of a 2% aqueous solution of the water-soluble polymer in is 2 mPa·s or less. (15) The powder composition according to any one of (1) to (14), which is a powder obtained by spray-drying and granulating a dispersion containing the composite nonionic CNF and the substrate. (16) A powder composition according to any one of (1) to (15) used as a rheology control agent for aqueous coatings. (17) A method for producing a cellulose nanofiber-containing powder composition comprising composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, The process includes a spray drying granulation step in which a dispersion containing the composite nonionic CNF and the substrate is dried into particles by spray drying. The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, A method for producing a powder composition, wherein, in the dispersion, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the amount of composite nonionic CNF is 5 to 80% by mass, and the amount of the substrate is 20 to 95% by mass. (18) The composite nonionic CNF is bacterial nanocellulose, A method for producing the powder composition according to (17), wherein in the spray drying granulation step, water is added to the composite nonionic CNF and the substrate to obtain the dispersion. (19) A method for producing the powder composition according to (17) or (18), wherein the amount of the composite nonionic CNF is 5 to 50% by mass. (20) A method for producing the powder composition according to any one of (17) to (19), wherein the amount of the composite nonionic CNF is 10 to 50% by mass. (21) A method for producing the powder composition according to any one of (17) to (20), wherein the amount of the substrate is 50 to 95% by mass. (22) A method for producing the powder composition according to any one of (17) to (21), wherein the amount of the substrate is 50 to 90% by mass. (23) A method for producing the powder composition according to any one of (17) to (22), wherein the nonionic water-soluble polymer is a polymer with a total light transmittance of 80% or more in a 2% aqueous solution. (24) A method for producing the powder composition according to (23), wherein the nonionic water-soluble polymer is a vinyl polymer containing vinylpyrrolidone or vinyl alcohol as a constituent unit, polyacrylamide, starch, dextrin, hydroxypropyl cellulose (in this case, hydroxypropyl cellulose compounded with the nonionic cellulose nanofiber does not fall under the category of the substrate), hydroxyethyl cellulose, methylhydroxypropyl cellulose, methylhydroxyethyl cellulose, methylcellulose, polyethylene glycol (PEG), polyoxyethylene alkyl ether, or a polymer having a PEG backbone or hydroxyl groups. (25) A method for producing the powder composition according to (24), wherein the polymer having a PEG skeleton or hydroxyl group is a copolymer of at least one monomer selected from the group consisting of PEG (meth)acrylate, alkylPEG (meth)acrylate and hydroxyalkyl (meth)acrylate and at least one monomer selected from the group consisting of alkyl (meth)acrylate and alkyl vinyl ester, a (meth)acrylic polymer, or a vinyl ester polymer. (26) A method for producing the powder composition according to any one of (17) to (25), wherein the sugars are monosaccharides or disaccharides. (27) A method for producing the powder composition according to (26), wherein the monosaccharide is glucose, galactose, or fructose. (28) A method for producing the powder composition according to (26) or (27), wherein the disaccharide is sucrose, lactulose, lactose, maltose, cellobiose, or trehalose. (29) A method for producing the powder composition according to any one of (17) to (28), wherein the sucrose fatty acid ester with an HLB of 11 or more is sucrose laurate, sucrose myrilutate, sucrose parimitate, or sucrose stearate. (30) 25℃, 1000s -1 A method for producing a powder composition according to any one of (17) to (29), wherein the viscosity of a 2% aqueous solution of the water-soluble polymer in is 2 mPa·s or less. (31) A composite nonionic CNF which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000s -1 At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution, A rheology control agent for aqueous coatings, wherein, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the content of the composite nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass. (32) The rheology control agent for aqueous coatings according to (31), wherein the composite nonionic CNF is bacterial nanocellulose. (33) The rheology control agent for aqueous coatings according to (31) or (32), wherein the content of the composite nonionic CNF is 5 to 50% by mass. (34) The rheology control agent for aqueous coatings according to any one of (31) to (33), wherein the content of the composite nonionic CNF is 10 to 50% by mass. (35) The aqueous rheology control agent for coating according to any one of (31) to (34), wherein the content of the substrate is 50 to 95% by mass. (36) The aqueous rheology control agent for coating according to any one of (31) to (35), wherein the content of the substrate is 50 to 90% by mass. (37) The rheology control agent for water-based coatings according to any one of (31) to (36), wherein the nonionic water-soluble polymer is a polymer with a total light transmittance of 80% or more in a 2% aqueous solution. (38) The rheology control agent for water-based coatings according to (37), wherein the nonionic water-soluble polymer is a vinyl polymer containing vinylpyrrolidone or vinyl alcohol as a constituent unit, polyacrylamide, starch, dextrin, hydroxypropyl cellulose (in this case, hydroxypropyl cellulose compounded with the nonionic cellulose nanofiber does not fall under the category of the substrate), hydroxyethyl cellulose, methylhydroxypropyl cellulose, methylhydroxyethyl cellulose, methylcellulose, polyethylene glycol (PEG), polyoxyethylene alkyl ether, or a polymer having a PEG backbone or hydroxyl groups. (39) The rheology control agent for aqueous coatings according to (38), wherein the polymer having a PEG skeleton or hydroxyl group is a copolymer of at least one monomer selected from the group consisting of PEG (meth)acrylate, alkylPEG (meth)acrylate and hydroxyalkyl (meth)acrylate and at least one monomer selected from the group consisting of alkyl (meth)acrylate and alkyl vinyl ester, a (meth)acrylic polymer, or a vinyl ester polymer. (40) The aqueous rheology control agent for coatings according to any one of (31) to (39), wherein the sugars are monosaccharides or disaccharides. (41) The rheology control agent for aqueous coatings according to (40), wherein the monosaccharide is glucose, galactose, or fructose. (42) The rheology control agent for aqueous coatings according to (40) or (41), wherein the disaccharide is sucrose, lactulose, lactose, maltose, cellobiose, or trehalose. (43) The rheology control agent for aqueous coatings according to any one of (31) to (42), wherein the sucrose fatty acid ester with an HLB of 11 or more is sucrose laurate, sucrose myrilic acid, sucrose parimitic acid, or sucrose stearate. (44) 25℃, 1000s -1A rheology control agent for water-based coatings according to any one of (31) to (43), wherein the viscosity of a 2% aqueous solution of the water-soluble polymer in is 2 mPa·s or less. (45) A rheology control agent for aqueous coatings according to any one of (31) to (44), which is a powder obtained by spray-drying and granulating a dispersion containing the composite nonionic CNF and the substrate. [Examples]

[0093] The present invention will be described in detail below with reference to examples. However, the present invention is not limited in any way to these examples. Furthermore, unless otherwise specified, "%" and "parts" in the examples refer to "mass%" and "parts by mass," respectively.

[0094] [Preparation of dispersion for dry granulation] A dispersion of CNF for the drying and granulation process (hereinafter referred to as "drying and granulation dispersion") was prepared as follows.

[0095] (Samples No. E-1 to E-22 and C-2, C-5 to C-15) A predetermined amount of the substrate listed in Table 1 was added to water, and the mixture was stirred with a disperser to prepare an aqueous solution in which the substrate was dissolved in water. Then, using bacterial nanocellulose (BNC) dispersions (dispersions in which HP-BNC or CM-BNC are dispersed in water), either Fibnano® HP-NFBC or Fibnano® CM-NFBC (both manufactured by Kusano Sakko Co., Ltd.) was added to the aqueous solution of the substrate, and the mixture was stirred with a disperser to prepare a dry granulation dispersion containing nonionic CNF (complexed nonionic CNF) compounded with HPC or CMC and the substrate. Fibnano® HP-NFBC has an HP-BNC content of 1%, and Fibnano® CM-NFBC has a CM-BNC content of 1%. Here, the amount of BNC dispersion added was adjusted so that the HP-BNC or CM-BNC content in the dry granulation dispersion was 0.3%. The amount of substrate added was adjusted to match the mixing ratio shown in Table 2 relative to the amount of HP-BNC or CM-BNC added as described above.

[0096] (Sample No. C-3) Fibnano® HP-NFBC was used as the HP-BNC dispersion. The dispersion for dry granulation was prepared by adding HP-NFBC to water and stirring with a disperser so that the HP-BNC content in the dry granulation dispersion was 0.3%.

[0097] (Sample No. C-4) As the CNF dispersion, bacterial cellulose (hereinafter referred to as "BC") that is not complexed with HPC or CMC was prepared as follows. Gluconacetobacter intermedius SIID9587 strain, a BC-producing bacterium, was inoculated into Helitrin-Schram standard medium (HS medium) (composition: bacto pepton 0.5% (w / v), yeast extract 0.5% (w / v), Na2HPO4 0.27% (w / v), citric acid 0.115% (w / v), glucose 2% (w / v)). BC was produced by aerated stirring culture for 3 days under conditions of aeration rate of 7-10 L / min, rotation speed of 200-500 rpm, and temperature of 30°C. Subsequently, an equal volume of 4% (w / v) NaOH aqueous solution was added to the culture medium, and the bacterial cells were lysed by swirling at 70°C and 150 rpm for 2 hours. Furthermore, 6NH2SO4 was added to neutralize the solution, and after centrifugation, the supernatant was removed and the precipitate was recovered to remove water-soluble bacterial components. Ultrapure water was added to the obtained precipitate and centrifugation was performed, and the supernatant was removed. This process was repeated in a wet state until the pH of the precipitate reached approximately 7, thereby purifying the BC. The resulting aqueous dispersion of BC was used as the BC dispersion. The BC content in the BC dispersion was 6.3%. Next, using the BC dispersion prepared as described above, a dispersion for dry granulation was prepared by adding BC to water and stirring with a disperser so that the BC content in the dry granulation dispersion was 0.3%.

[0098] (Sample No. C-16, C-17) Using a BC dispersion (aqueous dispersion of BC) prepared in the same manner as Sample No. C-4, a predetermined amount of substrate listed in Table 1 was added to water and stirred with a disperser to prepare an aqueous solution in which the substrate was dissolved. Subsequently, the BC dispersion was added to the aqueous solution of the substrate and stirred with a disperser to prepare a dry granulation dispersion containing nonionic CNF (BC) and substrate. Here, the amount of BC dispersion added was adjusted so that the BC content in the dry granulation dispersion was 0.3%. The amount of substrate added was adjusted to match the mixing ratio (BC amount: substrate amount = 50:50) with respect to the amount of BC added as adjusted above.

[0099] (Sample No. C-18, C-19) Fibnano® HP-NFBC was used as the HP-NFBC dispersion. A predetermined amount of substrate was added to this HP-NFBC dispersion, and a dispersion for dry granulation was prepared by stirring with a disperser. The amount of substrate added was adjusted to match the mixing ratio shown in Table 2 relative to the HP-BNC content adjusted as described above.

[0100] (Sample No. C-20) Fibnano® HP-NFBC was used as the HP-BNC dispersion. An equal amount of tert-butanol (t-BuOH) was added to the HP-BNC dispersion, stirred, and then centrifuged. After discarding the supernatant, the same amount of t-BuOH was added, and this process was repeated five times to replace the water with t-BuOH, thereby preparing a dry granulation dispersion.

[0101] (Sample No. C-21) Dissolved pulp (manufactured by Marubeni Corporation) was mixed with water to a concentration of 2% and stirred with a disperser. The resulting aqueous dispersion was subjected to micronization treatment using a high-pressure homogenizer to prepare a mechanically defibrated CNF dispersion containing 2% mechanically defibrated CNF. Subsequently, PVP K90 was added to water and dissolved by stirring with a disperser. The resulting mechanically defibrated CNF dispersion was added to the aqueous solution containing dissolved PVP K90 and stirred with a disperser to prepare a dispersion for dry granulation. Here, the amount of mechanically defibrated CNF dispersion added was adjusted so that the mechanically defibrated CNF content in the dry granulation dispersion was 0.3%. The amount of substrate added was adjusted to the mixing ratio shown in Table 2 relative to the amount of mechanically defibrated CNF added as described above.

[0102] (Sample No. C-1) For sample No. C-1, without preparing a dispersion for dry granulation and performing the subsequent dry granulation process, PVP K15 (reagent powder) was added directly to the aqueous resin in the test example described later.

[0103] [Table 1]

[0104] [Table 2]

[0105] [Drying and granulation] In Table 2, for the CNF-containing powder composition samples dried by spray drying, a spray dryer manufactured by Priss, Inc. (product name: Sprayboy) was used, with a spray pressure of 0.4 MPa and a hot air temperature (inlet temperature of the spray dryer) of 150°C. The dry granulation dispersion obtained as described above was sprayed at a liquid delivery rate of 1 kg / h, and dry granulation was performed.

[0106] Furthermore, in Table 2, for the samples dried in a constant temperature bath, the dry granulation dispersion was dried in a constant temperature bath at 80°C for 8 hours, and then ground using a Lechs ZM200 ultracentrifuge (manufactured by Verder Scientific Co., Ltd.) under conditions of a screen pore size of 0.5 mm and a rotor rotation speed of 18,000 rpm, and the powder that passed through 300 mesh was collected.

[0107] Furthermore, in Table 2, for the freeze-dried samples, the obtained t-BuOH-substituted HP-BNC dispersion was frozen at -40°C and dried at 20°C under vacuum conditions. The resulting dried material was pulverized in a mortar.

[0108] The compositions of samples E-1 to 22 and C-1 to 21 of the CNF-containing powder compositions obtained as described above are shown in Table 2.

[0109] [Test Example 1: Effect of CNF Content on Effects] In Test Example 1, the effect of the solid content of the CNF-containing powder composition (i.e., the CNF content in the CNF-containing powder composition) on the dispersibility and pseudoplasticity-imparting effect in aqueous resins was evaluated.

[0110] (Preparation of aqueous resin composition) In this test, three types of aqueous resins were used: Barnock® WD-551 (an isocyanate-curable acrylic dispersion manufactured by DIC Corporation), Barnock WE-304 (an isocyanate-curable acrylic emulsion manufactured by DIC Corporation), and Polysol® AP-3900 (an acrylic-silicone emulsion manufactured by Resonac Co., Ltd.). To each of these three types of aqueous resins, the CNF-containing powder compositions of Samples No. E-1 to E-10 and C-1 to C-4 were added according to the formulations shown in Tables 3 to 5. Next, the mixture of the CNF-containing powder composition and the aqueous resin was mixed using a disperser at 1000 rpm for 10 minutes while stirring to disperse the CNF in the aqueous resin, thereby preparing the aqueous resin compositions of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-4. After degassing these aqueous resin compositions using a rotation-orbit mixer, the presence or absence of poorly dispersed material was visually confirmed.

[0111] In Tables 3-5, the amount (parts) x of the CNF-containing powder composition represents the amount of CNF-containing powder composition added to the aqueous resin composition (resin liquid containing the CNF-containing powder composition and aqueous resin) so that the amount of HP-BNC or CM-BNC in the composition reaches 0.3%. Furthermore, when the powder composition contained only the substrate (when using sample No. C-1), the powder composition was added so that the amount of the substrate in the aqueous resin composition reached 3%. In addition, when the CNF-containing powder composition contained only composite CNF (BNC), the CNF-containing powder composition was added so that the amount of composite CNF in the aqueous resin composition reached 0.3%.

[0112] [Table 3]

[0113] [Table 4]

[0114] [Table 5]

[0115] (Evaluation method) The aqueous resin compositions of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-4 obtained as described above were evaluated for their dispersibility with aqueous resins (hereinafter sometimes simply referred to as "resin dispersibility") and their pseudoplasticity-imparting effect.

[0116] <Evaluation of resin dispersibility> The particle size of the aqueous resin composition obtained as described above was measured using a grind gauge with a maximum groove depth of 100 μm, a division interval of 10 μm, a groove width of 12 mm, and a groove length of 140 mm. In this particle size measurement, the point at which prominent spots begin to appear in the dispersion sample was observed in accordance with JIS K5600-2-5:1999. Specifically, points containing 5 or more particles in one division (a band with a width of 13 mm) along the groove were observed. Sparse spots appearing before the point at which prominent spots begin to appear were ignored. The uppermost division closest to the upper limit of the point containing 5 or more particles was taken as the particle size.

[0117] Based on the particle size measured as described above, the resin dispersibility was evaluated according to the following criteria. It was determined that the effects of the present invention were not achieved if at least one of the three aqueous resins received a rating of C. A: Particle size 30 μm or less B: Particle size 40μm~90μm C: Particle size of 100 μm or larger, or poorly dispersed particles can be visually confirmed.

[0118] <Evaluation of pseudoplasticity-granting effect> Using a rotary rheometer DHR2 (manufactured by TA Instruments), the shear rate (shear rate) was measured at 1 s. -1 and 100s -1 Using a geometry (cone plate) with a diameter of 60 mm and an angle of 1° between the generatrix and the circular surface of the cone, the viscosity η1(1s) at 25°C was measured. -1 viscosity in and η 100 (100s-1 The viscosity (in which) was measured. From these measurement results, the TI value (η1 / η) was calculated. 100 The following criteria were used to calculate the pseudo-composition imparting effect. It was determined that the effects of the present invention were not achieved if at least one of the three aqueous resins received a rating of D. A: TI is 9.0 or higher B: TI is between 4.0 and 9.0 C:TI is between 2.0 and 4.0 D:TI is less than 2.0

[0119] (Evaluation results) Table 6 shows the results of the evaluation of resin dispersibility and pseudoplasticity imparting effect as described above. As shown in Table 6, all aqueous resin compositions exhibited high dispersibility (rated A) in terms of resin dispersibility. Regarding the pseudoplasticity imparting effect, the aqueous resin compositions of Examples 1-1 to 1-10 all exhibited high TI values ​​(rated A to C). Furthermore, particularly high pseudoplasticity imparting effects were observed when the CNF content was 10-50% and the substrate content was 50-90%. Comparative Example 1-1, which contained only substrate, Comparative Examples 1-2 and 1-3, which contained less than 20% substrate, and Comparative Example 1-4, which did not contain substrate, all received low ratings for pseudoplasticity imparting effect.

[0120] [Table 6]

[0121] [Test Example 2: Effect of Substrate Type on the Effect] In Test Example 2, the influence of substrate type on dispersibility and pseudoplasticity-imparting effect in aqueous resins was evaluated.

[0122] (Preparation of aqueous resin composition) In this test example, the same aqueous resin as in Test Example 1 was used, and the CNF-containing powder compositions of Samples No. E-11 to E-22 and C-5 to C-15 were added to each of the three types of aqueous resins according to the formulations shown in Tables 7 to 9. The CNF content in each of these CNF-containing powder compositions was 20%. Next, the mixture of this CNF-containing powder composition and the aqueous resin was mixed using a disperser at 1000 rpm for 10 minutes while stirring to disperse the CNF in the aqueous resin, thereby preparing the aqueous resin compositions of Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-11. After degassing these aqueous resin compositions using a rotation-orbit mixer, the presence or absence of poorly dispersed material was visually confirmed. In this test example, the amount (parts) of the CNF-containing powder composition was adjusted so that the amount of HP-BNC in the aqueous resin composition (resin liquid containing the CNF-containing powder composition and aqueous resin) was 0.2%.

[0123] [Table 7]

[0124] [Table 8]

[0125] [Table 9]

[0126] (Evaluation method) The aqueous resin compositions of Examples 2-1 to 2-12 and Comparative Examples 2-1 to 2-11 obtained as described above were evaluated for their dispersibility in aqueous resins (hereinafter sometimes simply referred to as "resin dispersibility") and pseudoplasticity-imparting effect using the same method as in Test Example 1. If the presence of poorly dispersed particles was confirmed when the CNF-containing powder composition was dispersed in the aqueous resin, the resin dispersibility was judged to be extremely low, and viscosity measurements were not performed. Therefore, in this case, the TI value could not be calculated, and the pseudoplasticity-imparting effect was not evaluated.

[0127] (Evaluation results) The results of the evaluation of resin dispersibility and pseudoplasticity imparting effect, as described above, are shown in Table 10. As shown in Table 10, regarding resin dispersibility, the aqueous resin compositions of Examples 2-1 to 2-12, which used nonionic substrates, showed high dispersibility (rated A or B). Furthermore, regarding the pseudoplasticity imparting effect, the aqueous resin compositions of Examples 2-1 to 2-12 showed a very high pseudoplasticity imparting effect (rated A or B).

[0128] On the other hand, Comparative Examples 2-7 and 2-10, in which the substrate was anionic, and Comparative Examples 2-1 to 2-6 and 2-10, in which the viscosity of the 2% aqueous solution of the substrate exceeded 5.0 mPa·s, showed poor resin dispersibility (rating C). Furthermore, in Comparative Examples 2-1 to 2-6, 2-9, and 2-10, the presence of poorly dispersed materials was confirmed when the CNF-containing composition was dispersed in aqueous resin, so the resin dispersibility was judged to be extremely low, and viscosity measurement was discontinued. Therefore, the pseudoplasticity-imparting effect was not evaluated.

[0129] In Comparative Example 2-7, CNF-containing powder composition C-11 did not become a powder during spray drying. However, a film-like dried material was obtained, and when dispersed in an aqueous resin, the presence of poorly dispersed material was confirmed, so viscosity measurement was discontinued. In addition, CNF-containing powder compositions C-12 and C-15, used in Comparative Examples 2-8 and 2-11, did not become a powder during spray drying, nor did a film-like dried material be obtained, so all evaluation tests were discontinued.

[0130] [Table 10]

[0131] [Test Example 3: Regarding Other Comparative Examples] In Test Example 3, we examined comparative examples not listed in Test Examples 1 and 2.

[0132] (Preparation of aqueous resin composition) In this test example, the same aqueous resin as in Test Example 1 was used, and the CNF-containing powder compositions of Samples No. C-16 to C-21 were added to each of the three types of aqueous resins according to the formulations shown in Tables 11 to 13. Next, the mixture of this CNF-containing powder composition and the aqueous resin was mixed using a disperser at 1000 rpm for 10 minutes while stirring, and the CNF was dispersed in the aqueous resin to prepare the aqueous resin compositions of Comparative Examples 3-1 to 3-6. After degassing these aqueous resin compositions using a rotation-orbit mixer, the presence or absence of poorly dispersed material was visually confirmed. Note that the amount (parts) y of the CNF-containing powder composition listed in Tables 11 to 13 is the amount of CNF-containing powder composition added when the amount of HP-BNC or BC in the aqueous resin composition (resin liquid containing the CNF-containing powder composition and aqueous resin) is 0.3%.

[0133] [Table 11]

[0134] [Table 12]

[0135] [Table 13]

[0136] (Evaluation method) The aqueous resin compositions of Comparative Examples 3-1 to 3-6 obtained as described above were evaluated for resin dispersibility and pseudoplasticity-imparting effect using the same method as in Test Examples 1 and 2. If the presence of poorly dispersed particles was observed when the CNF-containing powder composition was dispersed in the aqueous resin, the resin dispersibility was judged to be extremely low, and viscosity measurement was not performed. Therefore, in this case, the TI value could not be calculated, and the pseudoplasticity-imparting effect was not evaluated.

[0137] (Evaluation results) Table 14 shows the results of the evaluation of resin dispersibility and pseudoplasticity imparting effect as described above. As shown in Table 14, regarding resin dispersibility, the aqueous resin compositions of Comparative Examples 3-1 to 3-5 showed low dispersibility (rating C), while Comparative Example 3-6 showed high dispersibility (rating A). Here, viscosity measurement was stopped for the aqueous resin compositions of Comparative Examples 3-1 to 3-5 because poorly dispersed material was confirmed. Therefore, the pseudoplasticity imparting effect was not evaluated for Comparative Examples 3-1 to 3-5. In addition, the aqueous resin composition of Comparative Example 3-6 showed poor pseudoplasticity imparting effect (rating D). This is thought to be because mechanically defibrated CNF (CNF not compounded with HPC or CMC) was used as the CNF.

[0138] [Table 14]

Claims

1. A cellulose nanofiber-containing powder composition comprising composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000 s －１ At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution. When the total mass of the composite nonionic CNF and the substrate contained in the powder composition is set to 100% by mass, the content of the composite nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass. A powder composition, wherein the powder is obtained by spray-drying and granulating a dispersion containing the composite nonionic CNF and the substrate.

2. The powder composition according to claim 1, wherein the composite nonionic CNF is bacterial nanocellulose.

3. The powder composition according to claim 1 or 2, wherein the nonionic water-soluble polymer is a polymer with a total light transmittance of 80% or more in a 2% aqueous solution.

4. The powder composition according to claim 1 or 2, wherein the sugars are monosaccharides or disaccharides.

5. The powder composition according to claim 1 or 2, used as a rheology control agent for aqueous coatings.

6. A method for producing a cellulose nanofiber-containing powder composition comprising composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate, The process includes a spray-drying granulation step in which a dispersion containing the composite nonionic CNF and the substrate is dried into particles by spray drying. The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000 s －１ At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution. A method for producing a powder composition, wherein, in the dispersion, when the total mass of the composite nonionic CNF and the substrate is 100% by mass, the amount of composite nonionic CNF is 5 to 80% by mass, and the amount of the substrate is 20 to 95% by mass.

7. The aforementioned composite nonionic CNF is bacterial nanocellulose, A method for producing the powder composition according to claim 6, wherein in the spray drying granulation step, water is added to the composite nonionic CNF and the substrate to obtain the dispersion.

8. A method for producing a powder composition according to claim 6 or 7, wherein the nonionic water-soluble polymer is a polymer with a total light transmittance of 80% or more in a 2% aqueous solution.

9. It contains composite nonionic CNF, which is a nonionic cellulose nanofiber compounded with hydroxypropyl cellulose or carboxymethyl cellulose, and a substrate. The substrate is a sugar, a sucrose fatty acid ester with an HLB of 11 or higher, and 25°C, 1000 s －１ At least one selected from the group consisting of nonionic water-soluble polymers having a viscosity of 5 mPa·s or less in a 2% aqueous solution. When the total mass of the complexed nonionic CNF and the substrate is 100% by mass, the content of the complexed nonionic CNF is 5 to 80% by mass, and the content of the substrate is 20 to 95% by mass. A rheology control agent for aqueous coatings, which is a powder obtained by spray-drying and granulating a dispersion containing the composite nonionic CNF and the substrate.

Images