Dispersants and dispersions for poorly soluble or insoluble substances

Abstract

To provide a dispersant and a dispersion liquid that allows for the dispersion of poorly soluble or insoluble substances by mixing of carboxymethyl cellulose with sodium alginate, ensuring environmental friendliness.SOLUTION: A dispersant for poorly soluble or insoluble substances contains carboxymethyl cellulose and sodium alginate. In such dispersant, carboxymethyl cellulose may have a degree of etherification of 0.1 or more and 0.3 or less. The mixing ratio of carboxymethyl cellulose to sodium alginate, by weight, may be 10 / 1 or more and 1 / 9 or less. The poorly soluble or insoluble substances may be carbon nanotubes, graphene, β-carotene or phthalocyanine.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention mainly relates to a dispersant and a dispersion liquid for dispersing poorly soluble or insoluble substances such as carbon nanotubes in water.

Background Art

[0002] A carbon nanotube (hereinafter referred to as "CNT") is a nanometer-sized cylindrical (tube) substance composed only of carbon, and has a structure in which benzene rings in which carbon atoms are arranged in a hexagonal shape are arranged adjacent to each other on a plane and rolled into a cylinder. A tube with a single layer is called a single-walled carbon nanotube (hereinafter referred to as "SWCNT"), and a structure in which a plurality of tubes with different diameters are layered on top of each other is called a multi-walled carbon nanotube (hereinafter referred to as "MWCNT").

[0003] Carbon nanotubes have high conductivity and high mechanical strength, and their applications to conductive paints, conductive resins, electromagnetic shielding sheets, or heater members are being studied. When applying them to these, the dispersibility of CNTs is important. In the solid state, CNTs form a bundle (bundle) structure due to strong π-π interactions and van der Waals forces, so they are difficult to disperse in many solvents. Therefore, in order to make CNTs dispersible in a solvent and enable various applications, an excellent solubilizing agent to assist this is required.

[0004] For example, as a method for manufacturing an electromagnetic shielding sheet using CNTs, it includes a step of preparing a carbon nanotube aqueous dispersion liquid containing CNTs, carboxymethyl cellulose, and water, and a step of drying the carbon nanotube aqueous dispersion liquid. In the step of preparing the carbon nanotube aqueous dispersion liquid, only carboxymethyl cellulose is used as a dispersant, and in the carbon nanotube aqueous dispersion liquid, the ratio of the mass of carboxymethyl cellulose to the mass of carbon nanotubes is disclosed to be 3 or less (see, for example, Patent Document 1).

[0005] Furthermore, for the purpose of producing a conductive molded article in which a conductive layer is formed on a substrate, a dispersion of a CNT-containing composition is disclosed, which includes a CNT-containing composition, a dispersant made of carboxymethylcellulose or a salt thereof having a degree of etherification of 0.4 or more and less than 0.7, and a dispersion medium (see, for example, Patent Document 2).

[0006] Furthermore, it is disclosed that a sheet with excellent electromagnetic wave suppression and heat generation capabilities can be produced by coating a sheet substrate with an aqueous dispersion obtained by adding and dispersing CNTs in an aqueous solution containing a dispersant consisting of a specific anionic surfactant and a specific polysaccharide. The aqueous dispersion uses one or more of the following as a dispersant: Group A of anionic surfactants consisting of methylnaphthalene sulfonic acid formalin condensate salt, naphthalene sulfonic acid formalin condensate salt, and alkylene maleic acid copolymer salt; and Group B of polysaccharides consisting of water-soluble xylan, xanthan gums, guar gums, gellan gums, and carboxymethylcellulose (see, for example, Patent Document 3).

[0007] Furthermore, a CNT dispersant comprising a highly branched polymer obtained by condensation polymerization of a triarylamine compound and an aldehyde compound and / or a ketone compound in the presence of an acid catalyst has also been disclosed (see, for example, Patent Document 4). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2021-57560 [Patent Document 2] Japanese Patent Publication No. 2016-204203 [Patent Document 3] Japanese Patent Publication No. 2013-082610 [Patent Document 4] WO2011 / 065395 [Overview of the project] [Problems that the invention aims to solve]

[0009] The invention described in Patent Document 1 prevents the inclusion of air bubbles by using only carboxymethylcellulose as a dispersant, but it is thought that there are limitations to further improving dispersibility when using only carboxymethylcellulose as a dispersant.

[0010] The electromagnetic shielding material described in Patent Document 2 achieves a dispersion with excellent dispersibility using a small amount of dispersant by using carboxymethylcellulose with an etherification degree of 0.4 or more and less than 0.7 as a dispersant. However, it is thought that further improvement in dispersibility would be difficult if carboxymethylcellulose alone were used.

[0011] The invention described in Patent Document 3 discloses a carbon nanotube aqueous dispersion using one or more specific anionic surfactants from group A and specific polysaccharides from group B as dispersants. This invention aims to suppress the increase in viscosity of the CNT dispersion when the CNT concentration is increased when using a dispersant consisting only of polysaccharides such as carboxymethylcellulose, by mixing in anionic surfactants to enable coating treatment.

[0012] The invention described in Patent Document 4 consists of a highly branched polymer containing a triarylamine structure as a branching point, and therefore exhibits excellent dispersibility of CNTs. However, it has environmental challenges because it uses an organic solvent as a dispersion medium.

[0013] Environmental issues are a very important topic today, and even materials with excellent properties cannot be used if they have a significant environmental impact. When considering environmental impact and biocompatibility, water is the most suitable solvent. Furthermore, it is desirable that dispersants used to dissolve poorly soluble substances be environmentally friendly or biocompatible. For this reason, dispersants used to disperse poorly soluble or insoluble substances are preferably natural products or biodegradable compounds.

[0014] The present invention aims to provide a dispersant and dispersion that can disperse poorly soluble or insoluble substances by mixing carboxymethylcellulose and sodium alginate, and that is also environmentally friendly. [Means for solving the problem]

[0015] To solve the above-mentioned conventional problems, the dispersant for poorly soluble or insoluble substances of the present invention is characterized by containing carboxymethylcellulose and sodium alginate. In such a dispersant, the degree of etherification of carboxymethylcellulose may be 0.1 or higher and 0.3 or lower.

[0016] The degree of etherification of carboxymethylcellulose refers to the number of carboxymethyl groups that replace the three hydroxyl groups present per anhydrous glucose unit of cellulose. In this invention, the degree of etherification was calculated using the following method. Specifically, 200 mg of carboxymethylcellulose was weighed and suspended in 2 mL of 80% ethanol solution. Then, 2 mL of hydrochloric acid (HCl) was added and stirred for 1 hour, after which a precipitate was obtained by centrifugation at 6,000 G for 10 minutes. This precipitate was washed twice with 80% ethanol solution, and then 20 mL of purified water was added and stirred. Furthermore, 25 mL of 0.1 M sodium hydroxide (NaOH) aqueous solution was added and heated for 15 minutes, and 0.1 M hydrochloric acid (HCl) was added to this solution and titrated. The degree of etherification (CM degree) was calculated based on the amount of hydrochloric acid (HCl) added. Furthermore, the mixing ratio of carboxymethylcellulose to sodium alginate may be 1 / 10 or more and 1 / 9 or less by weight.

[0017] In this case, the poorly soluble or insoluble substance may be carbon nanotubes, graphene, β-carotene, or phthalocyanines. Both carboxymethylcellulose and sodium alginate are environmentally friendly materials, and a dispersant mixture of these can not only improve the dispersibility of poorly soluble substances such as carbon nanotubes, graphene, β-carotene, or phthalocyanines, but also result in an environmentally friendly dispersion.

[0018] Furthermore, the carbon nanotube dispersion of the present invention is characterized by containing the dispersant described above, a sparingly soluble or insoluble substance consisting of carbon nanotubes, and water. Such a carbon nanotube dispersion can be used for purposes such as conductive coatings, electromagnetic shielding materials, field emission materials, and negative electrode materials for batteries.

[0019] Furthermore, the graphene dispersion of the present invention is characterized by containing the dispersant described above, a poorly soluble or insoluble substance made of graphene, and water. Such a graphene dispersion can be used by coating it onto a substrate surface for purposes such as conductive coatings, electromagnetic shielding materials, and electrolytic emission materials.

[0020] Furthermore, the β-carotene dispersion of the present invention is characterized by containing the dispersant described above, a poorly soluble or insoluble substance consisting of β-carotene, an organic solvent, and water. Since both carboxymethylcellulose and sodium alginate are materials used in food and cosmetics and their safety has been confirmed, the β-carotene dispersion can also be applied as a cosmetic ingredient or food additive.

[0021] Furthermore, the phthalocyanine dispersion of the present invention is characterized by containing the dispersant described above, a poorly soluble or insoluble substance consisting of phthalocyanines, an organic solvent, and water. Phthalocyanines are commonly used as pigments, but using a dispersion with improved dispersibility makes it easier to apply them to various dyes.

[0022] Phthalocyanines are chemically cyclic compounds containing four isoindole groups. When there is no metal at the center, it is chemically called phthalocyanine, but there are many that do have a metal at the center, with copper phthalocyanine being a typical example. In this invention, copper phthalocyanine, cobalt phthalocyanine, zinc phthalocyanine, magnesium(II) phthalocyanine, tin(II) phthalocyanine, metal-free phthalocyanines, low-chlorinated phthalocyanines, etc., will be referred to as phthalocyanines.

Advantages of the Invention

[0023] The dispersant and dispersion liquid for poorly soluble or insoluble substances of the present invention can easily disperse poorly soluble or insoluble substances such as CNTs. In particular, the dispersion liquid in which CNTs are dispersed has a great effect in the field of electronic components.

Brief Description of the Drawings

[0024] [Figure 1] It is a diagram showing the relationship between the degree of etherification of carboxymethyl cellulose used as the dispersant according to Example 1 of the present embodiment and the degree of MWCNT dispersion when MWCNT is used as CNT. [Figure 2] It is a diagram showing the relationship between the degree of MWCNT dispersion and the viscosity of the dispersion liquid when sodium alginate is mixed with carboxymethyl cellulose for the dispersant according to Example 1 of the same embodiment. [Figure 3] It is a diagram showing the result of dispersion using SWCNT according to Example 2 of the same embodiment in comparison with the MWCNT dispersion result. [Figure 4] It is a diagram showing the result of dispersion using graphene according to Example 3 of the same embodiment in comparison with the MWCNT dispersion result. [Figure 5] It is a diagram in which the absorption spectrum of the result of dispersion using β-carotene according to Example 4 of the same embodiment is measured by an ultraviolet-visible spectrophotometer. [Figure 6] It is a diagram in which the absorption spectrum of the result of dispersion using copper phthalocyanine according to Example 5 of the same embodiment is measured by an ultraviolet-visible spectrophotometer.

Modes for Carrying Out the Invention

[0025] (Embodiment)

[0026] The following describes a dispersant for sparingly soluble or insoluble substances according to an embodiment of the present invention. Figure 1 shows the relationship between the degree of etherification of carboxymethylcellulose used as a dispersant according to this embodiment and the degree of MWCNT dispersion when MWCNTs are used as CNTs. Figure 2 shows the relationship between the degree of MWCNT dispersion and the viscosity of the dispersion when sodium alginate is mixed with carboxymethylcellulose. The dispersant for sparingly soluble or insoluble substances and the dispersion according to this embodiment will be described using these figures and the table described later.

[0027] This invention relates to a dispersant for poorly soluble or insoluble substances using polysaccharides, carboxymethylcellulose and sodium alginate. The invention was developed based on the discovery that high dispersion ability can be obtained by mixing carboxymethylcellulose, a polysaccharide, with sodium alginate, another anionic polysaccharide. In particular, a dispersant prepared by mixing sodium alginate with carboxymethylcellulose whose etherification degree is controlled to be between 0.1 and 0.3 has the characteristic of achieving high dispersion and maintaining stable dispersibility of CNTs when formed into a dispersion. While a etherification degree of carboxymethylcellulose between 0.1 and 0.3 is preferable, the range of 0.1 to 0.2 is more preferable.

[0028] Furthermore, by mixing carboxymethylcellulose and sodium alginate in a weight ratio of 10 / 1 or more and 1 / 9 or less, a dispersion for sparingly soluble or insoluble substances with high dispersibility and low viscosity can be produced. In particular, when the concentration of the insoluble substance to be dispersed is 0.1 to 0.2%, a mixing ratio of 10 / 1 to 1 / 1 is preferable, and when the concentration of the insoluble substance is 1% or more, a mixing ratio of 10 / 1 to 2 / 1 is preferable.

[0029] Carboxymethylcellulose is generally colored and semi-transparent when its degree of etherification is around 0.3 or less, but it is water-soluble and transparent when it is 0.4 or higher. In many cases where carboxymethylcellulose is used as a dispersant, it is used in a water-soluble and transparent state. Sodium alginate is a neutral salt in which the carboxyl group of alginic acid is bonded to a Na ion. Alginic acid is insoluble in water, but sodium alginate dissolves well in cold and hot water to form an aqueous solution.

[0030] Furthermore, the molecular weight of carboxymethylcellulose can be used without particular restrictions as long as it is in the range of 10 to 2 million. Similarly, the molecular weight of sodium alginate can be used without restrictions as long as it is in the range of 10 to 2 million. In particular, a molecular weight of carboxymethylcellulose between 10,000 and 200,000 and a molecular weight of sodium alginate between 1,000 and 40,000 are more preferable. Alternatively, a ratio of the weight-average molecular weights of carboxymethylcellulose to sodium alginate between 100 / 1 and 5 / 1 is more preferable.

[0031] In this embodiment, carboxymethylcellulose with different degrees of etherification was prepared by carboxymethylating cellulose as follows. First, 100 g of cellulose slurry was replaced with isopropanol. Next, 10 g of 30% sodium hydroxide (NaOH) aqueous solution and 5 g of sodium monochloroacetate were added and stirred at 45°C. After stirring for 15 minutes, 60 minutes, and 180 minutes, a portion of the reaction solution was taken, and ethanol was added to obtain a precipitate. This precipitate was washed with 90% ethanol and then dried at 70°C to obtain carboxymethylcellulose with different degrees of etherification. The method for evaluating the degree of etherification of these carboxymethylcelluloses is as described above, so the explanation is omitted here.

[0032] While cellulose is known as a major component of plants, this invention also includes holocellulose, cellulose fibers, cellulose nanofibers, oxidized cellulose, oxidized cellulose nanofibers, bacterial cellulose, and microcrystalline cellulose. (Example 1)

[0033] This example describes the case where MWCNTs are used as CNTs. Figure 1 shows the relationship between the degree of etherification of carboxymethylcellulose used as a dispersant in this example and the degree of MWCNT dispersion. The degree of dispersion of CNTs was evaluated as follows. 50 mg of MWCNTs were added to 50 mL of aqueous solutions of carboxymethylcellulose with different degrees of etherification as described above, and dispersed using an ultrasonic homogenizer (600 W). Then, the mixture was separated using a centrifuge (Eppendorf Hi-Mac Technologies, CT18R) at 10,000 G for 1 hour, and the supernatant was used as the sample. The absorbance of this supernatant at a wavelength of 500 nm was measured using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-1900), and the value calculated based on the obtained absorbance was defined as the degree of dispersion.

[0034] As can be seen from Figure 1, in this embodiment, the carboxymethylcellulose showed greater dispersion at etherification degrees of 0.2 and 0.3 than at 0.5. Setting the optimal range for the etherification degree of carboxymethylcellulose requires not only high dispersion of MWCNTs, but also important factors such as solubility in water and viscosity of the dispersion. Therefore, to determine the optimal range for the etherification degree, carboxymethylcellulose with various etherification degrees was prepared, and its solubility in water, dispersion degree, and viscosity of the dispersion were evaluated.

[0035] These evaluations were all made by visual inspection for simplification and indicated with ○, ×, etc. However, the evaluations were based on experience with previous measurement values ​​and visual evaluations. For dispersion, ○ corresponds to approximately 29 or higher in visual evaluation, ◎ to approximately 36 or higher, △ to approximately less than 29, and × to approximately 10 or lower in visual evaluation. For viscosity, △ corresponds to approximately 7 mPa·s or higher in visual evaluation, ○ to approximately 6 mPa·s or lower, and × to approximately 10 mPa·s or higher or when measurement was not possible in visual evaluation. Furthermore, for solubility in water, × was evaluated if clumps of MWCNT were visible, ◎ if they were not visible and the mixture was black but a clean liquid overall, and ○ for intermediate cases. The same applies to Tables 2 and 3. Note that in Table 1, the concentration of carboxymethylcellulose in water was 0.2%, and 0.1% MWCNT was mixed in. Table 3 shows both the results of visual evaluation and viscosity measurement, confirming that viscosity can be adequately evaluated visually.

[0036] [Table 1]

[0037] As can be seen from Table 1, solubility in water was judged as ○ if the degree of etherification was 0.1 or higher, but 0.4 or higher was judged as ◎ as it indicates even better solubility. On the other hand, for the dispersion of MWCNTs, a degree of etherification of 0.1 or higher and 0.3 or lower was judged as ○, and 0.4 or higher was judged as △. The viscosity of the dispersion was △ for all except a degree of etherification of 0. However, a viscosity evaluation of △ was considered to be higher than the target viscosity, but still usable for coating, etc. Overall, it was found that a degree of etherification of 0.1 or higher and 0.3 or lower is preferable.

[0038] Table 2 shows the results of evaluating the solubility in water, MWCNT dispersion, and dispersion viscosity when sodium alginate is mixed with carboxymethylcellulose having various degrees of etherification. In Table 2, the mixing ratio of carboxymethylcellulose to sodium alginate was set to 5 / 1, and the concentration of the dispersant in water was set to 0.2%. 50 mg of MWCNTs were added to 50 mL of this dispersion and dispersed using an ultrasonic homogenizer (600 W). Viscosity was measured using the solution with the MWCNTs dispersed.

[0039] [Table 2]

[0040] As can be seen from Table 2, better results were obtained in both dispersion and viscosity compared to the case using carboxymethylcellulose alone. In particular, it was found that all evaluation items for solubility in water, dispersion, and viscosity could be cleared when the degree of etherification was 0.1 or higher and 0.3 or lower. In particular, when the viscosity of the dispersion is 6 mPa·s or lower, the fluidity is high, which improves work efficiency during application and makes it easy to handle, making it preferable.

[0041] Next, we will explain the properties of the dispersion when sodium alginate is mixed. Figure 2 shows the relationship between the degree of dispersion and the viscosity of the dispersion when sodium alginate is mixed with carboxymethylcellulose in various proportions. The degree of etherification of carboxymethylcellulose was set to 0.3, the concentration of the dispersant in water to 0.2%, and the relationship between the degree of dispersion and viscosity was determined when 0.1% MWCNT was dispersed by changing the mixing ratio of carboxymethylcellulose and sodium alginate. Dispersants with mixing ratios of carboxymethylcellulose and sodium alginate varied from 10 / 0 (carboxymethylcellulose only) to 1 / 1 were used. When carboxymethylcellulose and sodium alginate were mixed in a 10 / 1 ratio, the degree of dispersion improved by 25% compared to when carboxymethylcellulose alone was used. The degree of dispersion was almost the same up to a mixing ratio of 2 / 1, but a slight decrease was observed at 1 / 1. However, even at a mixing ratio of 1 / 1, it was found that there was a 20% improvement compared to when carboxymethylcellulose alone was used. On the other hand, the viscosity of the dispersion decreased from 8 mPa·s when only carboxymethylcellulose was used (10 / 0) ​​as the mixing ratio of sodium alginate increased, and it was found that a viscosity suitable for coating work could be achieved.

[0042] Table 3 shows the results of visually evaluating the degree of dispersion and the viscosity of the dispersion by varying the mixing ratio of carboxymethylcellulose with sodium alginate. In this table, as in Figure 2, the degree of etherification of carboxymethylcellulose was set to 0.3, the concentration of the dispersant relative to water was set to 0.2%, and 0.1% MWCNTs were dispersed by varying the mixing ratio of carboxymethylcellulose to sodium alginate.

[0043] [Table 3]

[0044] As can be seen from Table 3, it was found that mixing sodium alginate in a range of 1 / 10 to 1 / 9 improved the dispersion and maintained that dispersed state. Furthermore, it was found that the dispersion could be further improved in the range of 1 / 10 to 1 / 1. In addition, it was found that the viscosity could be made suitable for coating and other applications when sodium alginate was mixed in a range of 1 / 10 to 1 / 9. However, at a mixing ratio of 1 / 10, aggregation occurred after ultrasonic treatment, the fluidity was lost, and neither the dispersion nor the viscosity could be measured.

[0045] The improved dispersion and reduced viscosity resulting from mixing carboxymethylcellulose with sodium alginate are presumed to be due to the interaction between the carboxymethylcellulose physically adsorbed on the surface of the MWCNTs and the sodium alginate suspended in the water, which prevents the MWCNTs from aggregating. As a result, the dispersion is improved, the dispersed state can be maintained, and the viscosity is reduced. (Example 2)

[0046] This example describes the case where SWCNTs are used as CNTs. Figure 3 shows the dispersion results using SWCNTs in comparison with the dispersion results using MWCNTs. A dispersant was used with a degree of etherification of carboxymethylcellulose of 0.3, a concentration of the dispersant relative to water of 0.2%, and a mixing ratio of carboxymethylcellulose to sodium alginate of 2 / 1. 50 mg of SWCNTs were added to 50 mL of the dispersion and dispersed using an ultrasonic homogenizer (600 W). This procedure is the same as for MWCNTs, so the explanation is omitted. Figure 3 also shows the dispersion degree of MWCNTs for comparison, which is the same as the data for the mixing ratio of 2 / 1 in Figure 2. As can be seen from Figure 3, the dispersion degree of SWCNTs is about 29, which is lower than that of MWCNTs, but a dispersion degree sufficient for practical use was obtained. SWCNTs with an aspect ratio in the range of 5,000 to 100,000 are particularly preferred. (Example 3)

[0047] This example describes the case using graphene. Figure 3 shows the results of dispersion using graphene in comparison with the MWCNT dispersion results. A dispersant was used with a degree of etherification of carboxymethylcellulose of 0.3, a concentration of the dispersant relative to water of 0.2%, and a mixing ratio of carboxymethylcellulose to sodium alginate of 2 / 1. 50 mg of graphene was added to 50 mL of the dispersion and dispersed using an ultrasonic homogenizer (600 W). This procedure is the same as for MWCNT, so the explanation is omitted. Figure 4 also shows the dispersion degree of MWCNT for comparison, which is the same as the data for the mixing ratio of 2 / 1 in Figure 2. As can be seen from Figure 4, the dispersion degree of graphene is about 27, which is lower than that of MWCNT, but a dispersion degree that is suitable for practical use was obtained. (Example 4)

[0048] This example describes the case using β-carotene. In this example, a dispersant was prepared using carboxymethylcellulose with a degree of etherification of 0.3, with a mixing ratio of carboxymethylcellulose to sodium alginate of 2:1. A 0.2% aqueous solution was prepared by adding 0.2% of this dispersant to water. 10 mg of β-carotene was added to this aqueous solution and dispersed using an ultrasonic homogenizer (600 W). In this example, instead of determining the degree of dispersion, the absorption spectrum was measured and evaluated using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-1900). The results are shown in Figure 5.

[0049] As can be seen in Figure 5, when β-carotene was added directly to water without a dispersant, no absorption occurred in the UV-Vis spectrophotometer measurement because β-carotene does not dissolve in water. However, in the case of the dispersion with a dispersant added, the absorbance at a wavelength of 500 nm was 0.317, indicating that good dispersion was achieved. (Example 5)

[0050] This example describes the case where copper phthalocyanine(II) (β-type) is used as the phthalocyanine. In this example, a dispersant was prepared using carboxymethylcellulose with a degree of etherification of 0.3, with a mixing ratio of carboxymethylcellulose to sodium alginate of 2:1. A 0.2% aqueous solution was prepared by adding 0.2% of this dispersant to water. 1 mg of copper phthalocyanine(II) (β-type) was added to this aqueous solution and dispersed using an ultrasonic homogenizer (600 W). In this example, instead of determining the degree of dispersion, the absorption spectrum was measured and evaluated using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-1900). The results are shown in Figure 6.

[0051] As can be seen in Figure 6, when copper phthalocyanine(II)(β-type) was added directly to water without a dispersant, the copper phthalocyanine(II)(β-type) did not dissolve in water, and therefore no absorption was observed in the UV-Vis spectrophotometer measurement. However, in the case of the dispersion with a dispersant added, the absorbance at a wavelength of 500 nm was 0.3, indicating that good dispersion was achieved.

[0052] Although this embodiment and the examples described use carboxymethylcellulose, other salts such as sodium carboxymethylcellulose (sodium salt of carboxymethylcellulose), calcium carboxymethylcellulose (calcium salt), potassium carboxymethylcellulose (potassium salt), and ammonium carboxymethylcellulose (ammonium salt) may also be used. Sodium carboxymethylcellulose, in particular, is preferred. [Industrial applicability]

[0053] The dispersant and dispersion for poorly soluble or insoluble substances of the present invention are useful in the field of electronic components such as electromagnetic wave shielding sheets that take advantage of conductivity when using CNTs, in the food and cosmetics fields when using β-carotene, and in the paint field when using phthalocyanine.

Claims

1. A dispersant for poorly soluble or insoluble substances, comprising carboxymethylcellulose and sodium alginate, wherein the carboxymethylcellulose has a degree of etherification of 0.1 or more and 0.3 or less.

2. The dispersant according to claim 1, characterized in that the mixing ratio of the carboxymethylcellulose and the sodium alginate is 10 / 1 or more and 1 / 9 or less by weight.

3. The dispersant according to claim 1 or 2, characterized in that the poorly soluble or insoluble substance is carbon nanotubes, β-carotene, or phthalocyanines.

4. A carbon nanotube dispersion comprising the dispersant according to claim 1 or 2, a poorly soluble or insoluble substance consisting of carbon nanotubes, and water.

5. A graphene dispersion comprising the dispersant according to claim 1 or 2, a poorly soluble or insoluble substance consisting of graphene, and water.

6. A β-carotene dispersion comprising the dispersant according to claim 1 or 2, a poorly soluble or insoluble substance consisting of β-carotene, and water.

7. A phthalocyanine dispersion comprising the dispersant according to claim 1 or 2, a sparingly soluble or insoluble substance consisting of phthalocyanines, and water.

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