Additives for producing foam-containing compositions

Abstract

Provided is an additive for use in the production of an air bubble-containing composition, which can impart both of high air bubble stability and foaming properties. Carboxymethylated cellulose nanofibers in each of which the carboxymethyl substitution degree is 0.01 to 0.50 per a glucose unit and the crystallization degree of cellulose type-I is 40% or more are combined with a nonionic water-soluble polymer and / or a surfactant to produce an additive for use in the production of an air bubble-containing composition.

Description

[Technical Field]

[0001] The present invention relates to an additive for the production of a bubble-containing composition, which, when added during the production of the aerated composition or to the aerated composition, promotes foaming and improves the stability of the bubbles formed. [Background technology]

[0002] Cellulose-based materials such as carboxymethyl cellulose have been used as additives to form fine, creamy foam, maintain good foam dispersion, and improve foam stability in foods, cosmetics, cleaning agents (such as solid soaps, kitchen detergents, body washes, shampoos, and toothpastes), resins, agricultural chemicals, civil engineering products, and boring (such as foam shields) that contain bubbles or are intended to generate foam during use.

[0003] For example, Patent Document 1 discloses the use of carboxymethylcellulose sodium salt, which has an etherification degree of 0.8 to 2.0 and a viscosity of a 2% aqueous solution of 1 to 30 mPa·s, as a stabilizer for ice cream with a low air content. Patent Document 2 also discloses that the foam stability of egg-processed foods can be improved by blending crystalline fibrous cellulose and / or a dry cellulose composition containing 30 to 95% by mass of the fibrous cellulose and 5 to 70% by mass of a water-soluble polymer and / or a hydrophilic substance into liquid egg.

[0004] Furthermore, Patent Document 3 describes the use of chemically modified cellulose nanofibers as an additive for aerated compositions. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-143321 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-065836 [Patent Document 3] Japanese Patent Application Publication No. 2017-66283 Summary of the Invention [Problem to be solved by the invention]

[0006] The methods of Patent Document 1, which uses water-soluble carboxymethyl cellulose, and Patent Document 2, which uses chemically unmodified fibrous cellulose, do not provide sufficient bubble persistence (bubble stability). In contrast, the method of Patent Document 3, which uses chemically modified cellulose nanofibers, provides a bubble stabilization effect. However, it has now been discovered that when only chemically modified cellulose nanofibers are used as an additive, foamability (the ability to initially form bubbles) is somewhat inferior. The present invention aims to further improve the method described in Patent Document 3 and provide an additive for producing bubble-containing compositions that maintains bubble stability while also providing high foamability (the ability to form bubbles). [Means for solving the problem]

[0007] As a result of extensive research into the above-mentioned problems, the present inventors have found that by using carboxymethylated cellulose nanofibers having a specific degree of carboxymethyl substitution and cellulose type I crystallinity together with a nonionic water-soluble polymer and / or a surfactant as an additive for producing a bubble-containing composition, it is possible to improve the foaming ability of the composition while maintaining the bubble stability. The present invention includes, but is not limited to, the following. [1] An additive for producing a bubble-containing composition, comprising carboxymethylated cellulose nanofibers having a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50 and a cellulose type I crystallinity of 40% or more, and a nonionic water-soluble polymer and / or surfactant. [2] The additive for producing a bubble-containing composition according to [1], which contains at least a nonionic water-soluble polymer, and the nonionic water-soluble polymer is at least one selected from hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose. [3] The additive for producing a bubble-containing composition according to [1], which contains at least a nonionic water-soluble polymer, wherein the nonionic water-soluble polymer is at least one selected from polyethylene glycol, polyvinylpyrrolidone, a copolymer of vinylpyrrolidone and vinyl acetate, lactan, pullulan, mannan, sclerotium gum, and guar gum. [4] The additive for producing a bubble-containing composition according to any one of [1] to [3], which contains at least a surfactant, wherein the surfactant is at least one selected from sodium lauryl sulfate, lauramidopropyl hydroxysultaine, decyl dimethylamine oxide, lauramine oxide, sodium oleate, sodium laureth sulfate, sodium cocoyl methyl taurate, sodium cocoyl glutamate, potassium laurate, cocamidopropyl betaine, cocamidodiethanolamide, lauramidopropyl betaine, hydrogenated lecithin, and sodium cocoamphoacetate. [5] The additive for producing a bubble-containing composition according to any one of [1] to [4], wherein the amount of the nonionic water-soluble polymer and / or surfactant (when both the nonionic water-soluble polymer and the surfactant are contained, the total amount of both) is 1 to 5,000 parts by mass per 100 parts by mass of the carboxymethylated cellulose nanofibers. [6] A method for producing a bubble-containing composition, comprising mixing the additive for producing a bubble-containing composition according to any one of [1] to [5] with a material for a bubble-containing composition and stirring the material to foam the material. [7] A method for stabilizing bubbles in a bubble-containing composition, comprising adding the additive for producing a bubble-containing composition according to any one of [1] to [5] to the bubble-containing composition. [Effects of the Invention]

[0008] Adding the additive of the present invention to a bubble-containing composition during production can enhance the foaming properties of the composition and also increase the persistence of the formed bubbles (bubble stability). Furthermore, adding the additive to a bubble-containing composition can promote further foaming and also impart bubble stability. That is, the additive of the present invention can impart both foaming properties and bubble stability to a bubble-containing composition. The additive for producing a bubble-containing composition of the present invention contains a specific carboxymethylated cellulose nanofiber and a nonionic water-soluble polymer and / or surfactant. However, when an anionic water-soluble polymer is used instead of the nonionic water-soluble polymer, the above-mentioned effects cannot be obtained, as shown in Comparative Examples 1 to 3.

[0009] The additive for producing a bubble-containing composition of the present invention can be suitably used in, for example, foods and beverages that contain bubbles or are intended to be foamed upon use (e.g., ice cream, cake and pancake batter, bread, whipped cream), cosmetics (e.g., facial cleanser, shaving cream), cleaning agents (e.g., solid soap, kitchen detergent, body wash, shampoo, toothpaste), resins, agricultural chemicals, civil engineering works, boring (e.g., bubble shield), etc. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a photograph showing the results of Example 1. [Figure 2] 1 is a photograph showing the results of Example 2. [Figure 3] 1 is a photograph showing the results of Comparative Example 1. [Figure 4] 10 is a photograph showing the results of Comparative Example 2. [Figure 5] 10 is a photograph showing the results of Comparative Example 3. [Figure 6] 1 is a photograph showing the results of Example 3. [Figure 7] 1 is a photograph showing the results of Example 4. [Figure 8] 10 is a photograph showing the results of Example 5. [Figure 9] 1 is a photograph showing the results of Example 6. [Figure 10]1 is a photograph showing the results of Example 7. [Figure 11] 10 is a photograph showing the results of Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Carboxymethylated cellulose nanofiber> In the present invention, carboxymethylated cellulose nanofibers (hereinafter, "carboxymethylated" may be abbreviated as "CM" and cellulose nanofibers as "CNF") are obtained by micronizing carboxymethylated cellulose (CM-cellulose) to a fiber width on the nanometer level. These nanofibers typically have a fiber width of approximately 3 to several hundred nm, e.g., 4 to 500 nm. The aspect ratio is not limited, but is, for example, 50 or greater, and preferably 100 or greater. The average fiber diameter and average fiber length of CM-cellulose CNF can be determined by calculating the average fiber diameter and fiber length values ​​obtained from observations of 200 randomly selected fibers using an atomic force microscope (AFM), a transmission electron microscope (TEM), or a field-emission scanning electron microscope (FE-SEM). The aspect ratio can also be calculated by dividing the average fiber length by the average fiber diameter. CM-cellulose CNF can be obtained by applying a mechanical force to CM-cellulose to micronize (defibrate) it.

[0012] CM-cellulose has a structure in which some of the hydroxyl groups in the glucose residues that make up cellulose are ether-bonded to carboxymethyl groups. CM-cellulose may take the form of a salt, and the term "CM-cellulose" as used herein also includes salts of CM-cellulose. Examples of CM-cellulose salts include metal salts such as sodium salt of CM-cellulose.

[0013] <Cellulose raw material> Examples of cellulose raw materials for producing carboxylated cellulose, which is the raw material for carboxylated CNF, include those derived from plant materials (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (e.g., softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.)), animal materials (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), and microbial products, and any of these can be used. Cellulose fibers derived from plants or microorganisms are preferred, and plant-derived cellulose fibers are more preferred.

[0014] <Commercialization of cellulose raw materials> The carboxymethylated cellulose used as the raw material for carboxylated CNF may be obtained by carboxymethylating the above-mentioned cellulose raw material using a known method, or a commercially available product may be used. In either case, the degree of carboxymethyl group substitution per anhydroglucose unit of the cellulose is preferably 0.01 to 0.50. The following method can be given as an example of a method for producing such carboxymethylated cellulose.

[0015] A cellulose raw material, 3 to 20 times the mass of water and / or a lower alcohol as a solvent, specifically, water, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, etc., alone or a mixed medium of two or more is used. As the mercerizing agent, an alkali metal hydroxide of 0.5 to 20 times the molar amount per anhydrous glucose residue of the cellulose raw material, specifically, sodium hydroxide and potassium hydroxide are used. The cellulose raw material, the solvent, and the mercerizing agent are mixed, and a mercerization treatment is performed at a reaction temperature of 0 to 70°C, preferably 10 to 60°C, and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a CM agent is added at 0.05 to 10.0 times the molar amount per glucose residue, and an etherification reaction is performed at a reaction temperature of 30 to 90°C, preferably 40 to 80°C, and a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours.

[0016] The carboxymethylated cellulose that is the raw material of CM-CNF maintains at least a part of its fibrous shape even when dispersed in water, and is distinguished from carboxymethyl cellulose, which is a kind of water-soluble polymer described later. When an aqueous dispersion of "carboxymethylated cellulose (carboxymethyl cellulose)" is observed with an electron microscope, fibrous substances can be observed. On the other hand, even when an aqueous dispersion of carboxymethyl cellulose, which is a kind of water-soluble polymer, is observed, no fibrous substances are observed. Also, "carboxymethylated cellulose" can observe the peak of cellulose type I crystal when measured by X-ray diffraction, but cellulose type I crystal is not seen in carboxymethyl cellulose, which is a water-soluble polymer.

[0017] <Defibration of carboxymethylated cellulose> CNF can be produced by defibrating carboxymethylated cellulose. The device used for defibration is not particularly limited, and devices such as high-speed rotary, colloid mill, high-pressure, roll mill, and ultrasonic devices can be used. During defibration, it is preferable to apply a strong shear force to the carboxymethylated cellulose dispersion. For particularly efficient defibration, it is preferable to apply a pressure of 50 MPa or more to the dispersion and to use a wet high-pressure or ultra-high-pressure homogenizer capable of applying a strong shear force. The pressure is more preferably 100 MPa or more, and even more preferably 140 MPa or more. Furthermore, prior to defibration and dispersion treatment using a high-pressure homogenizer, the dispersion may be pretreated, if necessary, using a known mixing, stirring, emulsifying, or dispersing device such as a high-speed shear mixer.

[0018] From the viewpoint of processing efficiency, the solids concentration of the carboxymethyl cellulose dispersion to be subjected to defibration is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and particularly preferably 0.3% by mass or more. From the viewpoint of fluidity, the solids concentration is preferably 10% by mass or less, and more preferably 6% by mass or less.

[0019] <Carboxymethyl substitution degree> The carboxymethyl-substituted CNF has a degree of carboxymethyl substitution per anhydroglucose unit of cellulose of 0.01 to 0.50. If the degree of carboxymethyl substitution is less than 0.01, sufficient foam stability and foamability cannot be obtained. If the degree of carboxymethyl substitution exceeds 0.50, the cellulose tends to dissolve in aqueous media, making it impossible to maintain the fiber form and resulting in reduced foam stability. The lower limit of the carboxymethyl-substituted degree is more preferably 0.10 or more, and even more preferably 0.20 or more. The upper limit of the carboxymethyl-substituted degree is more preferably 0.40 or less. The carboxymethyl-substituted degree of the carboxymethyl-substituted CNF can be adjusted by controlling the amount of carboxymethylating agent added to be reacted during the production of the carboxymethyl-substituted cellulose, the raw material, the amount of mercerizing agent, the composition ratio of water to organic solvent, and the like. The carboxymethyl-substituted degree of the carboxymethyl-substituted cellulose is usually the same as the carboxymethyl-substituted degree of the carboxymethyl-substituted CNF obtained by defibrating it.

[0020] In this specification, anhydroglucose unit refers to each anhydroglucose (glucose residue) that constitutes cellulose. The degree of carboxymethyl substitution (also called the degree of etherification) refers to the proportion of hydroxyl groups in the glucose residues that constitute cellulose that have been substituted with carboxymethyl ether groups (the number of carboxymethyl ether groups per glucose residue). The degree of carboxymethyl substitution is sometimes abbreviated as DS.

[0021] The degree of carboxymethyl substitution is measured as follows: Weigh out approximately 2.0 g of sample and place it in a 300 mL Erlenmeyer flask with a stopper. Add 100 mL of nitric acid methanol (a solution of 1000 mL of methanol and 100 mL of special-grade concentrated nitric acid) and shake for 3 hours to convert carboxymethyl cellulose salt (CMC) to H-CMC (hydrogenated carboxymethyl cellulose). Weigh out 1.5 to 2.0 g of the bone-dry H-CMC and place it in a 300 mL Erlenmeyer flask with a stopper. Wet the H-CMC with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake for 3 hours at room temperature. Using phenolphthalein as an indicator, back-titrate the excess NaOH with 0.1 N H2SO4, and calculate the degree of carboxymethyl substitution (DS value) using the following formula: A = [(100 × F' - 0.1N-H2SO4 (mL) × F) × 0.1] / (bone-dry mass of H-CMC (g)) Carboxymethyl substitution degree = 0.162 x A / (1 - 0.058 x A) F': Factor of 0.1N-H2SO4 F: Factor of 0.1N NaOH.

[0022] <Crystallization of cellulose type I> The crystallinity of cellulose type I in carboxylated CNF is 40% or more, preferably 50% or more, and more preferably 60% or more, from the viewpoint of improving foamability and foam stability. The crystallinity of cellulose type I in carboxylated CNF can be controlled by the concentration of the mercerizing agent during the production of the raw material carboxylated cellulose, the temperature during treatment, and the degree of carboxylation. Because high concentrations of alkali are used in mercerization and carboxylation, cellulose type I crystals are likely to be converted to type II. However, the desired crystallinity can be maintained by, for example, adjusting the amount of alkali (mercerizing agent) used to control the degree of modification. The upper limit of the crystallinity of cellulose type I is not particularly limited. In reality, the upper limit is thought to be around 90%. The crystallinity of cellulose type I in carboxylated cellulose and the crystallinity of cellulose type I in carboxylated CNF obtained by defibrating it are usually the same.

[0023] The method for measuring the crystallinity of cellulose type I is as follows: The sample is placed in a glass cell and measured using an X-ray diffraction measurement device (LabX XRD-6000, manufactured by Shimadzu Corporation). The degree of crystallinity is calculated using the method of Segal et al., where the diffraction intensity at 2θ = 10° to 30° in the X-ray diffraction pattern is used as the baseline, and the degree of crystallinity is calculated using the diffraction intensity of the 002 plane at 2θ = 22.6° and the diffraction intensity of the amorphous part at 2θ = 18.5° using the following formula: Xc = (I002c - Ia) / I002c × 100 Xc = Crystallinity of cellulose type I (%) I002c: 2θ=22.6°, diffraction intensity of the 002 plane Ia: 2θ=18.5°, diffraction intensity of the amorphous part.

[0024] <Nonionic water-soluble polymer and / or surfactant> The additive for producing bubble-containing compositions of the present invention is produced by mixing the above-mentioned carboxymethylated CNF with a nonionic water-soluble polymer and / or a surfactant. The additive of the present invention may contain both a nonionic water-soluble polymer and a surfactant, or only one of them. Examples of nonionic water-soluble polymers include, but are not limited to, cellulose-derived nonionic water-soluble polymers such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose. Other nonionic water-soluble polymers that may be used include polyethylene glycol, polyvinylpyrrolidone, copolymers of vinylpyrrolidone and vinyl acetate, galactan, pullulan, mannan, sclerotium gum, and guar gum. The nonionic water-soluble polymer may be a mixture of multiple types, or may be used alone. Among these, hydroxyethyl cellulose, methyl cellulose, and polyethylene glycol are preferred. Examples of surfactants include, but are not limited to, sodium lauryl sulfate, lauramidopropyl hydroxysultaine, decyl dimethylamine oxide, lauramine oxide, sodium oleate, sodium laureth sulfate, sodium cocoyl methyl taurate, sodium cocoyl glutamate, potassium laurate, cocamidopropyl betaine, cocamidodiethanolamide, lauramidopropyl betaine, hydrogenated lecithin, and sodium cocoamphoacetate. Among these, sodium lauryl sulfate, lauramidopropyl hydroxysultaine, decyl dimethylamine oxide, lauramine oxide, and sodium oleate are preferred, and sodium lauryl sulfate, lauramidopropyl hydroxysultaine, and decyl dimethylamine oxide are more preferred. The surfactants may be used by mixing multiple types of the above surfactants, or may be used alone. The specific types of nonionic water-soluble polymer and surfactant may be appropriately selected depending on the bubble-containing composition to be produced.

[0025] The mixing ratio of carboxymethylated CNF and nonionic water-soluble polymer and / or surfactant is preferably 1 to 5,000 parts by mass per 100 parts by mass of carboxymethylated CNF. It is more preferably 5 to 5,000 parts by mass, even more preferably 5 to 2,000 parts by mass, even more preferably 5 to 1,000 parts by mass, even more preferably 10 to 1,000 parts by mass, even more preferably 20 to 1,000 parts by mass, even more preferably 20 to 500 parts by mass. The "amount of nonionic water-soluble polymer and / or surfactant" refers to the amount of either the nonionic water-soluble polymer or the surfactant used when either one is used, or the total amount when both the nonionic water-soluble polymer and the surfactant are used. The amounts of carboxymethylated CNF, nonionic water-soluble polymer, and surfactant are all solids.

[0026] The method for mixing carboxylated CNF with a nonionic water-soluble polymer and / or surfactant is not particularly limited; dispersions of each of the two may be mixed together in a dispersion medium such as water, or one dispersion may be added to the other in powder or solid form and mixed.

[0027] <Additives for producing foam-containing compositions> As described above, additives for producing aerated compositions are prepared by mixing carboxymethylated CNF with a specific degree of carboxymethyl substitution and cellulose type I crystallinity with a nonionic water-soluble polymer and / or surfactant. Aerated compositions are typically formed by stirring a liquid with a mixer or whisk. Examples of aerated compositions include, but are not limited to, foods and beverages that contain bubbles or are intended to foam upon use (e.g., ice cream, cake and pancake batter, bread, whipped cream, etc.), cosmetics (e.g., facial cleanser, shaving cream), cleaning agents (e.g., bar soap, kitchen detergent, body wash, shampoo, toothpaste), resins, pesticides, civil engineering products, and boring (e.g., bubble shield).

[0028] "Additives for producing bubble-containing compositions" include additives to be mixed with the bubble-containing composition material (the components of the composition before bubbles are incorporated) during the production of the bubble-containing composition, and additives to be added to the bubble-containing composition. In the former case, the bubble-containing composition material is foamed by stirring or the like after the addition of the additive, thereby forming the bubble-containing composition. In the latter case, the additive is uniformly mixed into the composition by stirring or the like after the addition of the additive. In either case, foaming properties (the ability to form bubbles) and bubble stability (the ability to maintain the formed bubbles) can be imparted to the composition.

[0029] When an additive for producing a bubble-containing composition is added to a bubble-containing composition material (the components of the composition before bubbles are incorporated), the bubble-containing composition material may contain all of the components contained in the final bubble-containing composition, or may contain only a portion of the components contained in the final bubble-containing composition. In the latter case, after the addition of the additive of the present invention, the bubble-containing composition material (a portion of the components of the bubble-containing composition) may be foamed before or during foaming, and the remaining components of the composition may be mixed. Furthermore, the bubble-containing composition material to which the additive of the present invention is added may previously contain a component corresponding to a foaming agent that promotes foam formation and prevents the formed bubbles from coalescing or disappearing. Examples of foaming agents include surfactants such as higher alcohol sulfates, alkyl ether sulfates, N-acyl glutamates, and phosphate esters, as well as proteins such as collagen and keratin, and cellulose compounds such as carboxymethylcellulose and crystalline cellulose.

[0030] The form of the additive for producing a bubble-containing composition is not particularly limited. For example, it may be in the form of a dispersion containing carboxylated CNF and a nonionic water-soluble polymer and / or surfactant, with water or the like as a dispersion medium, or in the form of a dry solid obtained by drying such a dispersion, or in the form of a powder obtained by pulverizing the dry solid. It may also be in the form of a wet solid, which is in an intermediate state between a dispersion and a dry solid. In this specification, the term "dry solid" refers to a dispersion that has been deliquored and dried so that the amount of liquid, such as water, is 12% by mass or less. The amount of liquid in the dry solid can be measured by the following method: The dried solid is dried in an oven at 105°C for 12 hours, and the amount of liquid in the dried solid is calculated from the mass before and after drying. Amount of liquid in dry solids (mass%) = {1 - (mass after drying / mass before drying)} x 100.

[0031] When the additive for producing a bubble-containing composition is in the form of a dispersion, the dispersion medium is preferably water or a mixed solvent of water and a hydrophilic organic solvent, taking into consideration the dispersibility of the carboxylated CNF. The dispersion medium used in the production of the carboxylated CNF may be used as is, or a hydrophilic organic solvent may be added, or a portion of the dispersion medium may be replaced with a hydrophilic organic solvent to form a dispersion medium containing a hydrophilic organic solvent. When a dispersion medium containing both water and a hydrophilic organic solvent is used, the amount of the hydrophilic organic solvent is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, based on the total amount of water and hydrophilic organic solvent. There is no upper limit to this amount, but it is preferably 95% by mass or less, and more preferably 80% by mass or less.

[0032] The hydrophilic organic solvent refers to an organic solvent that dissolves in water. Examples include, but are not limited to, methanol, ethanol, 2-propanol, butanol, glycerin, butylene glycol, propanediol, acetone, methyl ethyl ketone, 1,4-dioxane, N-methyl-2-pyrrolidone, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetonitrile, and combinations thereof. Among these, lower alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, and 2-propanol, and polyols, such as glycerin, butylene glycol, and propanediol, are preferred, with methanol, ethanol, glycerin, butylene glycol, and propanediol being preferred from the standpoints of safety and availability.

[0033] When the additive for producing a bubble-containing composition is in the form of a dry solid, it is preferable to adjust the pH of a dispersion of carboxymethylated CNF and a nonionic water-soluble polymer and / or surfactant to 9 to 11, then deliquoring and drying. Drying after adjusting the pH to 9 to 11 improves dispersibility in the material for a bubble-containing composition or the bubble-containing composition. An alkali such as sodium hydroxide can be used to adjust the pH.

[0034] The deliquoring and drying of the dispersion can be performed by known methods, such as spray drying, squeezing, air drying, hot air drying, and vacuum drying. The drying apparatus is not particularly limited, and examples thereof include continuous tunnel dryers, band dryers, vertical dryers, vertical turbo dryers, multi-stage disk dryers, through-flow dryers, rotary dryers, flash dryers, spray dryers, spray dryers, cylindrical dryers, drum dryers, belt dryers, screw conveyor dryers, rotary dryers with heating tubes, vibration transport dryers, batch-type box dryers, through-flow dryers, vacuum box dryers, and agitator dryers, which can be used alone or in combination of two or more.

[0035] Among these, the use of a device that forms a thin film and dries the material is preferred because it can supply heat energy directly and uniformly to the material to be dried, making the drying process more efficient and shorter. This is preferred from the viewpoint of energy efficiency. Apparatuses that form a thin film and then perform drying are also preferred because the dried product can be immediately recovered by a simple means such as scraping off the thin film, and are also preferred because the resulting dried solids are more easily dispersible in the material for a bubble-containing composition or the bubble-containing composition. Examples of apparatuses that form a thin film and then perform drying include drum-type dryers and belt-type dryers that form a thin film on a drum or belt and then dry the film. Among these, drum-type dryers are preferred because they allow for continuous drying and facilitate recovery of the dried product.

[0036] A drum-type dryer is a device that continuously supplies a dispersion to the surface of a rotating heated drum, evaporates and concentrates the dispersion medium, and simultaneously deposits the dispersion in a thin film on the drum surface, drying it, and then scrapes off the dried material formed on the drum surface with a knife to produce a dry solid. Drum-type dryers include double-drum or twin-drum devices that use two drums, and single-drum devices that use one drum, but either can be used. Of these, double-drum devices are preferred because they allow the thickness of the thin film to be adjusted by adjusting the clearance between the drums.

[0037] The thickness of the thin film to be dried is preferably 50 to 1000 μm, more preferably 100 to 300 μm. If it is 50 μm or more, it is easy to scrape off after drying, and if it is 1000 μm or less, the effect of improving dispersibility in the material for a bubble-containing composition or in a bubble-containing composition is observed.

[0038] The drying temperature is not particularly limited. For example, drying can be performed at a temperature of about 200° C. or less. When drying is performed using a drum-type dryer or belt-type dryer that forms and dries a thin film, the drying temperature refers to the temperature of the drum or belt surface.

[0039] Drying may be carried out under normal pressure, vacuum, or reduced pressure, with vacuum or reduced pressure being preferred because it lowers the boiling point of water, accelerates the evaporation rate, and drastically dries the object, while also reducing the thermal impact on the sample.

[0040] When drying is performed in a vacuum or under reduced pressure (hereinafter also referred to as "vacuum drying"), drying is preferably performed within a range of 0 to 50 kPa. Since a lower pressure has the advantage of allowing moisture to evaporate at a lower temperature, the pressure is preferably 50 kPa or less, more preferably 30 kPa or less, and even more preferably 10 kPa or less.

[0041] During drying, it is preferable to obtain a dry solid by vacuum drying the dispersion at a relatively low temperature, such as 40 to 100°C. Since a low drying temperature reduces production efficiency, the drying temperature is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. Furthermore, since a high drying temperature can cause discoloration or damage to the cellulose, the drying temperature is preferably 100°C or lower, more preferably 90°C or lower, more preferably 85°C or lower, and even more preferably 80°C or lower, and may be lower than 80°C.

[0042] The vacuum drying device is not particularly limited, and a vacuum box dryer, a vacuum drum dryer, a vacuum spray dryer, a vacuum belt dryer, etc. can be used alone or in combination of two or more. A vacuum drum dryer is a device in which a heated drum is placed under vacuum or reduced pressure, and a dispersion is continuously supplied to the drum surface while the drum is rotating, and the dispersion medium is evaporated and concentrated while the dispersion is deposited in a thin film on the drum surface and dried, and the dried product formed on the drum surface is scraped off with a knife to produce a dry solid.

[0043] When the obtained dried solid is pulverized to obtain a powder, the median diameter of the powder is preferably about 10.0 to 150.0 μm, more preferably 25.0 to 100.0 μm, and even more preferably 35.0 to 70.0 μm. If the median diameter is 10.0 μm or more, problems such as flying powder are unlikely to occur, and if it is 150.0 μm or less, the powder has an appropriate bulk, which makes the packing work of the powder easier, and is therefore preferable. The median diameter of the powder can be adjusted by adjusting the pulverization and classification conditions. The median diameter can be measured by the following procedure: Using methanol as a dispersion medium, a sample is prepared so that the scattering intensity is 0.1 to 20%, and is measured using a laser diffraction particle size distribution analyzer (Malvern Instruments, Mastersizer (registered trademark) 3000).

[0044] <Material for bubble-containing composition or addition to bubble-containing composition> A bubble-containing composition can be produced by mixing the additive for producing a bubble-containing composition of the present invention with a bubble-containing composition material (composition components before bubbles are incorporated) and stirring to foam it. The additive of the present invention imparts good foaming properties to the bubble-containing composition material and can also increase the persistence of the formed bubbles (bubble stability). The bubble-containing composition material may contain all of the components contained in the final bubble-containing composition, or it may only contain a portion of the components contained in the final bubble-containing composition. In the latter case, after adding the additive of the present invention, the remaining components of the composition may be mixed after or while foaming the bubble-containing composition material (a portion of the components of the bubble-containing composition).

[0045] Furthermore, by adding the additive for producing a bubble-containing composition of the present invention to the bubble-containing composition, foaming can be further promoted and bubble stability can be improved.

[0046] After adding the additive of the present invention to the material for the bubble-containing composition or the bubble-containing composition, it is preferable to stir using a known mixing and stirring device to promote foaming. The stirring conditions at this time may be appropriately determined according to the type of the bubble-containing composition and the desired degree of foaming, and are not particularly limited. For example, it is stirred at about 100 to 15000 rpm, preferably about 500 to 10000 rpm, for about 1 to 30 minutes, preferably about 1 to 15 minutes.

[0047] The content of the additive of the present invention in the final bubble-containing composition may be appropriately changed according to the type of the bubble-containing composition and the desired degree of foaming, and is not particularly limited. For example, it is preferable to add the amount of CMized CNF derived from the additive so that it is 0.05% by mass or more with respect to the amount of the bubble-containing composition, and it is more preferable to add it so that it is 0.1% by mass or more.

Examples

[0048] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0049] <Production of CMized CNF> To a twin-screw kneader with the rotation speed adjusted to 100 rpm, 620 parts of isopropanol (IPA) and a solution of 10 parts of sodium hydroxide dissolved in 30 parts of water were added, and 100 parts by dry mass when hardwood pulp (manufactured by Nippon Paper Industries Co., Ltd., LBKP) was dried at 100 ° C for 60 minutes was charged. It was stirred and mixed at 30 ° C for 90 minutes to prepare mercerized cellulose. While further stirring, 15 parts of IPA and 12 parts of monochloroacetic acid were added, stirred for 30 minutes, then heated to 70 ° C and subjected to a CMization reaction for 90 minutes. After the reaction was completed, it was neutralized with acetic acid until the pH reached 7, washed with hydrous methanol, de-liquored, dried, and pulverized to obtain carboxymethyl cellulose with a carboxymethyl substitution degree of 0.18.

[0050] The carboxymethylated cellulose obtained in the above process was adjusted to 1.0 mass% with water and treated three times with an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain a carboxymethylated CNF dispersion. The obtained fibers had an average fiber diameter of 5 nm, an aspect ratio of 150, and a crystallinity of cellulose type I of 72%.

[0051] Example 1 A 1.0% by mass aqueous dispersion of the carboxymethylated CNF obtained above was prepared. Hydroxyethyl cellulose (manufactured by Daicel Corporation, product name SE550) was selected as the nonionic water-soluble polymer (hereinafter, "hydroxyethyl cellulose" will be abbreviated as "HEC"), and a 2.0% by mass aqueous dispersion of HEC was prepared to have a viscosity similar to that of the 1.0% by mass aqueous dispersion of carboxymethylated CNF. The resulting 1.0% by mass aqueous dispersion of carboxymethylated CNF and a 2.0% by mass aqueous dispersion of HEC were mixed in a 250 ml lidded polypropylene container (manufactured by AS ONE Corporation, product name: Pack Clean) at the mass ratio listed in Table 1. Each sample was stirred at 3000 rpm for 10 minutes using a homodisper. To evaluate foamability and foam stability, the height from the bottom of the container to the top of the dispersion was measured both immediately after stirring and after leaving it at room temperature for 1 day. Photographs were also taken. The photographs are shown in Figure 1.

[0052] [Table 1]

[0053] The photograph in Figure 1 shows that in the case of HEC alone, foaming can be confirmed immediately after stirring, but after leaving it to stand for one day, the formed bubbles almost completely disappear. On the other hand, in the case of carboxymethylated CNF alone, foaming ability immediately after stirring is low. In contrast, it can be seen that in the samples containing a mixture of HEC and carboxymethylated CNF, foaming ability and bubble stability were improved.

[0054] Furthermore, when the above-mentioned 1.0 mass% aqueous dispersion of carboxymethylated CNF and 2.0 mass% aqueous dispersion of HEC were mixed in a mass ratio ranging from 90:10 to 30:70 (i.e., 22 to 467 mass parts of HEC per 100 mass parts of carboxymethylated CNF), placed in a vial, and left to stand at room temperature, it was confirmed that bubbles remained even after one week. From the above, it was found that the use of a mixture of HEC and carboxymethylated CNF provides high initial foaming properties and high foam stabilization effect over time.

[0055] <Example 2> A 1.0 mass% aqueous dispersion of the carboxymethylated CNF obtained above was prepared. A 1.0 mass% aqueous dispersion of polyethylene glycol (molecular weight 4,000,000) (hereinafter, "polyethylene glycol" will be abbreviated as "PEG") was also prepared as a nonionic water-soluble polymer. 100 g of each of the obtained 1.0 mass% aqueous dispersion of carboxymethylated CNF and 1.0 mass% aqueous dispersion of PEG was added to a 250 ml lidded polypropylene container (manufactured by AS ONE Corporation, product name: Pack Clean) at the mass ratio shown in Table 2. Each sample was stirred at 3,000 rpm in a Homo Disper for 10 minutes. To evaluate foamability and foam stability, the height from the bottom of the container to the top of the dispersion was measured immediately after stirring, after leaving it at room temperature for 10 minutes, and after leaving it for 1 hour. Photographs were also taken. The photographs are shown in Figure 2.

[0056] [Table 2]

[0057] From the photograph in Figure 2, it can be seen that in the case of PEG alone, foaming can be confirmed immediately after stirring, but defoaming progresses after 10 minutes. In contrast, it can be seen that in the samples containing a mixture of PEG and carboxymethylated CNF, both foaming ability and foam stability have improved.

[0058] <Comparative Example 1> A 1.0% by mass aqueous dispersion of the carboxymethylated CNF obtained above was prepared. A 0.08% by mass aqueous dispersion of carbomer was also prepared using a carboxyvinyl polymer (manufactured by Iwase Cosfa Co., Ltd., product name: Carbopol® 940 Polymer) as an anionic water-soluble polymer (hereinafter, "carboxyvinyl polymer" will be abbreviated as "carbomer") to achieve a viscosity similar to that of the 1.0% by mass aqueous dispersion of carboxymethylated CNF. 100 g of each of the obtained 1.0% by mass aqueous dispersion of carboxymethylated CNF and the 0.08% by mass aqueous dispersion of carbomer was added to a 250 ml polypropylene container with a lid (manufactured by AS ONE Corporation, product name: Pack Clean) at a mass ratio shown in Table 3. Each sample was stirred at 3,000 rpm for 10 minutes using a homodisper. For the samples immediately after stirring, the height from the bottom of the container to the top of the dispersion was measured as in Examples 1 and 2. Photographs were also taken. The photographs are shown in Figure 3.

[0059] [Table 3]

[0060] The photograph in Figure 3 shows that in both the case of carbomer alone and the case of a mixture of carbomer and carboxylated CNF, there was almost no foaming, indicating low foaming properties.

[0061] <Comparative Example 2> The PEG in Example 2 was replaced with carboxymethylcellulose (F350HC-4, manufactured by Nippon Paper Industries Co., Ltd.) (hereinafter, "carboxymethylcellulose" will be abbreviated as "CMC"), an anionic water-soluble polymer. Similar to Example 2, a 1.0% by mass aqueous dispersion of carboxymethylated CNF and a 1.0% by mass aqueous dispersion of CMC were mixed in the mass ratio shown in Table 4, placed in a polypropylene container, and each sample was stirred at 3000 rpm for 10 minutes using a homodisper. For the samples immediately after stirring, the height from the bottom of the container to the top of the dispersion was measured, similar to Examples 1 and 2. Photographs were also taken. The photographs are shown in Figure 4.

[0062] [Table 4]

[0063] From the photograph in Figure 4, it can be seen that in both the case of CMC alone and the case of a mixture of CMC and carboxylated CNF, there was almost no foaming, and the foaming ability was low.

[0064] <Comparative Example 3> Similar to Example 2, the PEG in Example 2 was replaced with xanthan gum (Keltrol (registered trademark) CG-T, manufactured by Sansho Co., Ltd.), an anionic water-soluble polymer. A 1.0% by mass aqueous dispersion of carboxymethylated CNF and a 1.0% by mass aqueous dispersion of xanthan gum were mixed in the mass ratio shown in Table 5, and the mixture was placed in a polypropylene container. Each sample was stirred at 3000 rpm for 10 minutes using a homodisper. The height from the bottom of the container to the top of the dispersion was measured for the samples immediately after stirring and one day later, similar to Examples 1 and 2. Photographs were also taken. The photographs are shown in Figure 5.

[0065] [Table 5]

[0066] From the photograph in Figure 5, it can be seen that in the case of xanthan gum alone, foaming can be confirmed immediately after stirring, but the bubbles have disappeared after one day. In addition, in the sample in which xanthan gum and carboxymethylated CNF were mixed, foaming can be confirmed immediately after stirring, but no clear improvement in foaming ability was observed, and after one day the bubbles have disappeared, just like in the case of xanthan gum alone.

[0067] Example 3 100 g of the aqueous dispersion containing 0.2% by mass of carboxymethylated CNF and 0.01% by mass of sodium lauryl sulfate obtained above was placed in a 600 ml lidded polypropylene container (manufactured by AS ONE Corporation, product name: Pack Clean) and stirred at 3000 rpm for 5 minutes using a Homo Disper. For comparison, an aqueous dispersion containing only 0.01% by mass of sodium lauryl sulfate was also placed in the same container and stirred. To evaluate foamability and foam stability, the height from the bottom of the container to the top of the dispersion was measured immediately after stirring, after standing at room temperature for 5 minutes, and after standing for 10 minutes. Photographs were also taken. The photographs are shown in Figure 6.

[0068] The photograph in Figure 6 shows that in the case of sodium lauryl sulfate alone, separation of the foam layer and liquid phase is observed immediately after stirring. On the other hand, in the sample containing sodium lauryl sulfate and carboxylated CNF, foaming ability is improved immediately after stirring, and foam stability also improves over time.

[0069] Example 4 A 1.0 mass% aqueous dispersion of the carboxymethylated CNF obtained above was prepared. A 1.0 mass% aqueous dispersion of methyl cellulose (7000-10000 mPa·s, 2% in water at 20°C, Tokyo Chemical Industry Co., Ltd.) (hereinafter, "methyl cellulose" will be abbreviated as "MC") was also prepared as a nonionic water-soluble polymer. 100 g of each of the obtained 1.0 mass% aqueous dispersion of carboxymethylated CNF and 1.0 mass% aqueous dispersion of MC was added to a 250 ml polypropylene container with a lid (manufactured by AS ONE Corporation, product name: Pack Clean) at the mass ratio shown in Table 6. Each sample was stirred at 3000 rpm for 5 minutes using a homodisper. To evaluate foamability and foam stability, the height from the bottom of the container to the top of the dispersion was measured for samples left at room temperature for 10 minutes immediately after stirring, 1 day at room temperature, and 4 days at room temperature. Photographs were also taken. A photograph is shown in Figure 7.

[0070] [Table 6]

[0071] The photograph in Figure 7 shows that in the case of MC alone, foaming can be confirmed immediately after stirring, but after leaving it to stand for one day, the formed bubbles almost completely disappear. On the other hand, in the case of carboxymethylated CNF alone, foaming ability immediately after stirring is low. In contrast, it can be seen that in the samples that mixed MC and carboxymethylated CNF, foaming ability and bubble stability were improved.

[0072] <Example 5> 100 g of the aqueous dispersion containing 0.2% by mass of the obtained carboxymethylated CNF and 0.01% by mass of lauramidopropyl hydroxysultaine (Kawaken Fine Chemicals Co., Ltd., product name: Softazoline® LSB-R) was placed in a 600 ml lidded polypropylene container (manufactured by AS ONE Corporation, product name: Pack Clean) and stirred at 3000 rpm for 5 minutes using a Homo Disper. For comparison, an aqueous dispersion containing only 0.01% by mass of lauramidopropyl hydroxysultaine was also placed in the same container and stirred. To evaluate foamability and bubble stability, the height from the bottom of the container to the top of the dispersion and the height from the bottom of the container to the bottom of the bubbles were measured immediately after stirring, after standing at room temperature for 5 minutes, and after standing for 10 minutes. Photographs were also taken. The photographs are shown in Figure 8.

[0073] The photograph in Figure 8 shows that when only lauramidopropyl hydroxysultaine was used, foaming was low and foam stability was also low. On the other hand, the sample containing lauramidopropyl hydroxysultaine and carboxylated CNF showed improved foaming immediately after stirring, and foam stability over time also improved.

[0074] Example 6 Foaming ability and foam stability were evaluated in the same manner as in Example 5, except that 0.01% by mass of lauramidopropyl hydroxysultaine was replaced with 0.2% by mass of decyldimethylamine oxide (Lion Specialty Chemical Co., Ltd., trade name: Cadenax (registered trademark) DM10D-W). Photographs are shown in Figure 9.

[0075] The photograph in Figure 9 shows that when only decyldimethylamine oxide was used, no foaming occurred. On the other hand, when decyldimethylamine oxide was mixed with carboxymethylated CNF, foaming occurred and foam stability was also good.

[0076] Example 7 The foaming ability and foam stability were evaluated in the same manner as in Example 5, except that 0.01% by mass of lauramidopropyl hydroxysultaine was replaced with 0.003% by mass of lauramine oxide (Lion Specialty Chemical Co., Ltd., trade name: Cadenax (registered trademark) DW12D-W(C)). Photographs are shown in Figure 10.

[0077] The photograph in Figure 10 shows that when lauramine oxide and carboxylated CNF are mixed, the height from the bottom of the container to the bottom of the bubbles is less likely to increase over time than when lauramine oxide is used alone. This indicates that the foamed dispersion is less likely to return to a liquid state, and that mixing lauramine oxide and carboxylated CNF improves bubble stability. Furthermore, when lauramine oxide and carboxylated CNF are mixed, the bubbles appear to be finer than when lauramine oxide is used alone.

[0078] Example 8 Foaming properties and foam stability were evaluated in the same manner as in Example 5, except that 0.01% by mass of lauramidopropyl hydroxysultaine was changed to 0.03% by mass of sodium oleate. Photographs are shown in Figure 11.

[0079] The photograph in Figure 11 shows that the height from the bottom of the container to the bottom of the bubbles is less likely to increase over time when sodium oleate and carboxylated CNF are mixed, compared to when sodium oleate alone is used. This indicates that the foamed dispersion is less likely to return to a liquid state, and that mixing sodium oleate and carboxylated CNF improves bubble stability. Furthermore, it was observed that the bubbles became finer when sodium oleate and carboxylated CNF were mixed, compared to when sodium oleate alone was used.

Claims

1. The present invention comprises carboxymethylated cellulose nanofibers having a degree of carboxymethyl substitution per glucose unit of 0.01 to 0.50 and a degree of cellulose type I crystallinity of 40% or more, and a nonionic water-soluble polymer, the nonionic water-soluble polymer is at least one selected from hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, polyvinylpyrrolidone, a copolymer of vinylpyrrolidone and vinyl acetate, galactan, pullulan, mannan, sclerotium gum, and guar gum; An additive for producing a bubble-containing composition, comprising a nonionic water-soluble polymer in an amount of 1 to 5,000 parts by mass per 100 parts by mass of carboxymethylated cellulose nanofibers.

2. A method for producing an aerated composition, comprising mixing the additive for producing aerated compositions according to claim 1 with a material for the aerated composition and stirring the material to foam it.

3. A method for stabilizing bubbles in an aerated composition, comprising adding the additive for producing aerated compositions according to claim 1 to the aerated composition.

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