JP2002030243A - Aqueous ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous ink composition which stably maintains an ink viscosity even after stored for a long period, does not cause the precipitation of a pigment, has good dispersion stability, and a stable quality. SOLUTION: This aqueous ink composition which is used for ball-point pens and comprises a pigment and water, characterized by containing as a thickener a polysaccharide obtained by thermally treating a polysaccharide containing at least glucose, fucose, glucuronic acid and rhamnose as constituting monosaccharides in a >=8 pH aqueous solution at 60 to 180 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous ink composition containing a microbial polysaccharide having excellent viscosity stability and a good thickening property. The present invention relates to an aqueous ink composition having no pigment sedimentation, good dispersion stability, and stable quality.

[0002]

2. Description of the Related Art Water-based inks use water as a main solvent, and various thickeners have been used for the purpose of preventing sedimentation of water-insoluble pigments and imparting an appropriate viscosity that is easy to handle. For example, water-based inks for ballpoint pens are desired to have a high viscosity so that pigments and the like are kept in a stable state during storage and are not exposed from the pen tip, but ink is supplied smoothly and continuously during writing. Need to be done. Therefore, various water-soluble polymers are used as thickeners in inks used in water-based ballpoint pens, so that the ink viscosity is reduced by the shear force generated by the rotation of the ball during writing so that the ink is ejected smoothly. It has been proposed. For example, a composition of xanthan gum (Japanese Patent Publication No. 64-86)
No. 73), blending of welan gum (JP-A-4-214)
No. 782), a combination of succinoglucan (Japanese Unexamined Patent Publication No.
No. 88050) and the combined use of xanthan gum and locust bingham (JP-A-2000-17217).

[0003] However, in xanthan gum, the pigment dispersion tends to be slightly unstable, and the pigment may gradually settle if used in a pigment dispersion for a long period of time. as a result,
When stored for a long period of time, the viscosity of the ink decreases and causes ink leakage, the pigment sediments and the handwriting density at the time of writing becomes uneven, and further, the sedimented pigment clogs the pen tip, Problems such as poor ink followability and inability to write occur.

[0004] Since locust bean gum is generally insoluble in cold water, it must be dissolved in hot water, and
There is a problem that the ink production becomes complicated, the viscosity of the produced ink becomes unstable, and the viscosity of the produced ink becomes complicated, for example, a strict temperature adjustment is required because a significant difference occurs in the viscosity depending on the water temperature at the time of dissolution. In addition, if the amount of locust bean gum is large, the ink fluidity may be lost, which is not preferable.

[0005] In welan gum, it is difficult to maintain the dispersion stability of the pigment as a colorant for a long time, and after storing an aqueous ballpoint pen using an ink using the same for a long time,
When writing is performed, the color of the handwriting may be lightened or, on the contrary, excessively darkened, or the ink may be clogged at the pen tip due to the aggregation of the pigment, and writing may not be performed.

[0006] Similarly, after storing an aqueous ballpoint pen using this succinoglucan for a long period of time, the dispersion state of the pigment becomes worse. , Ink clogging of the pen tip has occurred. As described above, it is still difficult to maintain the dispersion stability of the pigment during long-term storage of the aqueous ink composition for ballpoint pens, and due to sedimentation of the pigment and aggregation of the viscosity modifier,
There are problems such as poor ink followability at the time of writing, heavy writing, and blurring, which makes writing impossible.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous solution having a stable quality, which maintains ink viscosity stably even after long-term storage, has no pigment sedimentation, and has good dispersion stability. It is to provide an ink composition.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on aqueous ink compositions to solve the above problems, and as a result, a specific polysaccharide was obtained by heat treatment in an aqueous alkaline solution. It has been found that the properties of the aqueous ink composition can be improved by blending the polysaccharide as a thickener, and the present invention has been completed based on this finding.

That is, the invention according to claim 1 provides a pigment,
With water, substantially fucose, glucose, glucuronic acid,
A polysaccharide containing rhamnose as a constituent monosaccharide is heat-treated in an aqueous solution having a pH of 8 or more at 60 to 180 ° C., and a thickener comprising a polysaccharide obtained by heating is contained. It is an aqueous ink composition.

The invention according to claim 2 is the invention wherein the constituent monosaccharides of the polysaccharide are fucose: glucose: glucuronic acid: rhamnose = 1 to 2: 1 to 4: 1: 1-2: 1-2 in a molar ratio. 2. The aqueous ink composition according to item 1.

The invention according to claim 3 is the aqueous ink composition according to claim 1, wherein the polysaccharide is composed of glucose, glucuronic acid, and rhamnose as a main chain, and further has a structure in which fucose is bonded to a side chain. It is.

The invention according to a fourth aspect is the aqueous ink composition according to the first, second or third aspect, wherein the polysaccharide is a polysaccharide produced by Alcaligenes L. strain B-16.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The thickener used in the aqueous ink composition of the present invention is substantially fucose, glucose, glucuronic acid,
Polysaccharides containing rhamnose as a constituent monosaccharide are dispersed or dissolved in an aqueous alkali solution and heat-treated.

The polysaccharide used in the present invention is a polysaccharide substantially containing fucose, glucose, glucuronic acid, and rhamnose as constituent monosaccharides, and is preferably glucose, glucuronic acid, rhamnose represented by the following formula (1): This is a polysaccharide comprising a main chain having a repeating structure consisting of: and a structure in which one fucose is branched into one glucose.

[0016]

Embedded image

The polysaccharide of the present invention is obtained as a polysaccharide produced by a microorganism. Generally, microorganisms often produce two or more kinds of polysaccharides. Therefore, even if other microorganisms are contained in addition to the polysaccharide used in the present invention, the effect of the polysaccharide of the present invention is hindered. If not, it does not preclude the inclusion of other polysaccharides.

The microorganism producing the polysaccharide of the present invention is not particularly limited.
Laterus B-16 strain bacteria (FERM BP-2015)
No.). For example, Alcaligenes Latus B-1
In the case of polysaccharides produced by 6 strains of bacteria, the procedure is as follows.

Alkagenes strain B-16 strain bacteria are cultivated by a usual method of culturing microorganisms. For example, monosaccharides such as fructose, glucose and sucrose, natural polymers such as hemicellulose, starch and corn starch, and olive Oils such as fats and oils, nitrogen sources such as urea, ammonium chloride, ammonium nitrate, inorganic nitrogen sources such as ammonium sulfate, tripton, yeast extract, meat extract, peptone, malt extract, etc. Initial p using a medium supplemented with inorganic salts such as magnesium sulfate and sodium chloride
The aeration and agitation liquid culture is performed for 3 to 10 days at H of 4 to 10 and a culture temperature of 15 to 40 ° C. After the culture, about twice (volume) or more of an organic solvent such as acetone, ethanol, isopropyl alcohol and the like is added to the culture solution, and the culture product is collected as insoluble aggregates.

It has been confirmed that at least two types of polysaccharides are contained in the polysaccharide produced by the Alcaligenes strain B-16 bacterium. One of the polysaccharides is the polysaccharide of the present invention, A polysaccharide having a structure in which one fucose is branched from one glucose in a repeating structure comprising glucose, glucuronic acid, and rhamnose as shown in 1), and the other is represented by the following formula (2): Is a polysaccharide having a repeating structure substantially consisting of fucose and mannose as constituent monosaccharides [see Abstracts of 1998 Annual Meeting of the Japanese Society of Agricultural Chemistry, page 371]. Y. Nohata, J .; Azu
ma, R .; Kurane, Carbohydrate
Research 293 , (1996) 213-22
2).

[0021]

Embedded image

Even if the polysaccharide represented by the formula (2) is contained in the polysaccharide of the formula (1) which is the polysaccharide of the present invention, its effect is not impaired. Without removing the saccharides, polysaccharides produced by the bacterium Alcaligenes latus B-16 can be used.

The concentration of the polysaccharide when heat-treated in an aqueous alkaline solution is 0.01 to 3% by weight, preferably 0.1 to 3% by weight.
It is a concentration of 1% to 1% by weight. If the concentration exceeds 1% by weight, the viscosity of the aqueous solution may be so high that handling may be poor. A concentration of 0.01% by weight or less is not preferable because the concentration is low and the efficiency is low.

When the polysaccharide is heat-treated in an aqueous alkaline solution, the pH is 8 or more, preferably 11 or more, more preferably 12 or more. Under acidic conditions where the pH of the aqueous solution is less than 7, the molecular chain of the polysaccharide is severely cut, and the intended thickening effect may not be obtained.

The temperature at which the polysaccharide is heat-treated in an aqueous alkaline solution is 60 to 180 ° C., preferably 80 to 180 ° C.
The temperature is 160 ° C, more preferably 100 to 140 ° C. 6
If it is lower than 0 ° C., the polysaccharide of the present invention may not be obtained even if the heating time is extended. If the temperature is 180 ° C. or higher, the decomposition of the polysaccharide may proceed excessively, which is not preferable. Heat treatment at 100 ° C. or higher requires the use of a heat-resistant container. The heating time is appropriately determined depending on the pH, the treatment temperature, and the desired viscosity characteristics, but is usually 10 to 3 times.
0 minutes. After the heat treatment, the alkali aqueous solution of the polysaccharide is cooled to room temperature, neutralized by adding an aqueous solution of an inorganic acid (for example, sulfuric acid or hydrochloric acid), and about 3 times (volume) of acetone, ethanol, An organic solvent such as isopropyl alcohol is added to precipitate the heat-treated polysaccharide as an aggregate, which is filtered and dried under reduced pressure to obtain the thickener of the present invention.

The rotational viscosity of a 0.1% by weight aqueous solution of the polysaccharide before the heat treatment is 310 mPa · s.
At 120 ° C. for 120 minutes, the rotational viscosity of the aqueous solution having the same concentration was 410 mPa · s, and the pH was 13, 13, 120 ° C.
The viscosity is greatly improved to 1,310 mPa · s by the heat treatment for 20 minutes. The viscosity of the thickener of the present invention is increased by heating in an alkaline aqueous solution because a part of the molecular chain of the polysaccharide is cut, and the viscosity is increased by improving the solubility in water. It is thought that it became.

The amount of the thickener of the present invention is 0.001 to 0.5% by weight, preferably 0.03% by weight in the aqueous ink composition.
Between 0.5 and 0.1% by weight. If the blending amount is less than 0.001% by weight, the blended effect cannot be obtained. If the blending amount is more than 0.5% by weight, the effect can be improved, but the effect corresponding to the blending amount can be improved. In some cases, there are few economic benefits.

The thickener of the present invention comprises a conventional synthetic thickener,
Compared to natural thickeners, small amounts have high viscosity, large thixotropy, high water retention and sustained release of water according to the surrounding environment, and the effect on viscosity is small even when inorganic substances and inorganic salts are present. The effect of temperature on the viscosity is small and the viscosity can be maintained stably, so that the polysaccharide of the present invention is used in an aqueous ink composition to disperse dyes, pigments, colored resin emulsions, etc. It improves stabilization and stability over time, and furthermore improves stability of ink viscosity depending on temperature.
As a result, long-term storage, especially in summer, improved storage stability,
High print quality such as prevention of clogging at the tip of a water-based ballpoint pen using this water-based ink composition and improvement of ejection stability, improvement of printing unevenness and color density or bleeding of printed matter, and improvement of drying property of characters after printing. Can be realized.

In addition, other water-soluble polymers such as xansan gum, welan gum, ramzan gum, guar gum, locust bean gum and the like, as long as the effect of the thickener of the present invention is not impaired, can be used. It does not hinder the use of a mixture with synthetic high molecular weight polyvinyl alcohol (PVA), such as hydroxyethyl cellulose and carboxymethyl cellulose (CMC).

The pigment used in the present invention is used as a main colorant, and those conventionally used in aqueous ink compositions can be used. Specifically, inorganic pigments such as carbon black, titanium oxide, cobalt blue, iron oxide, ultramarine, navy blue, etc., organic pigments, aluminum powder, gold powder, silver powder, copper powder, tin powder, metal powder pigments such as brass powder, Fluorescent pigments, mica pigments and the like can be used. Further, an aqueous ink composition base of a dispersed pigment in which a pigment is dispersed in an aqueous medium can also be used. These can be used alone or in combination.

In addition to the above components, various additives conventionally used in aqueous ink compositions can also be used. For example, a water-soluble organic solvent may be added for the purpose of preventing drying of the ink and preventing freezing of the ink at a low temperature. Specifically, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, 1,3-butylene glycol, thiodiethylene glycol, 1,5-pentanediol, and glycerin; Monomethyl ether, diethylene glycol monomethyl ether, 2-
One or more kinds of pyrrolidone, N-methyl-2-pyrrolidone, triethanolamine and the like can be used as a mixture.

In addition, a resin may be added for improving the fixability of the ink on the surface to be written. Examples of the resin include a styrene-acrylic resin emulsion, an acrylic resin emulsion, a styrene-butadiene resin emulsion, an alkali-soluble resin, and a betaine acrylic resin.

Further, known water-soluble dyes such as acid dyes, basic dyes and direct dyes can also be used as the colorants for complementary colors.
In addition, benzothiazoline-based, omazine-based preservatives, rust preventives such as benzotriazole and various chelating agents,
Various additives such as anionic and nonionic surfactants, defoamers and dispersants can also be used.

The production of the aqueous ink composition of the present invention is not particularly limited, and may be carried out by various conventional methods. For example, the above-mentioned components are mixed by a stirrer such as a turbo mixer or a Henschel mixer. It is easily obtained by stirring and mixing, and mixing and grinding with a disperser such as a ball mill.

The aqueous ink composition according to the present invention comprises a polysaccharide having at least glucose, fucose, glucuronic acid and rhamnose as constituent monosaccharides in an aqueous solution having a pH of 8 or more.
A polysaccharide obtained by heat treatment at ~ 180 ° C is blended as a thickener, whereby the thixotropic properties of the ink are increased, the ink viscosity is stable even after long-term storage, and the sedimentation of the pigment is prevented. Becomes possible. Therefore, when used for a ballpoint pen or the like, even if the pen tip is left down, it is possible to prevent blurring of the handwriting and impossibility of writing due to sedimentation of the pigment on the pen tip.

[0035]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. [Preparation of B-16 polysaccharide] According to the method described in JP-A-2-291292, alkaligene streasus strain B-16 (FERM BP-2015) is cultured. A volume of isopropyl alcohol was added and mixed with stirring. The precipitated aggregate was filtered and collected, and dried under reduced pressure to obtain B-16 polysaccharide. [Preparation of Thickeners 1-3 Used in the Present Invention] (Preparation of Thickener-1) The B-16 polysaccharide obtained by the above method was made into a 0.5 wt% aqueous solution, and 1 mol / L water was used. The pH was adjusted to 11.5 with sodium oxide, left at room temperature overnight, and further kept in an autoclave at 120 ° C. for 60 minutes, cooled to room temperature, and neutralized with 1 mol / L sulfuric acid. After neutralization, about 3 times the volume of isopropyl alcohol of the aqueous polysaccharide solution was added, and the precipitated aggregate was filtered,
Drying under reduced pressure gave the thickener-1 of the present invention. (Preparation of Thickener-2) Similarly to Thickener-1, the B-16 polysaccharide obtained by the above method was adjusted to pH 12.0,
The mixture was kept at 0 ° C. for 20 minutes to obtain a thickener-2. (Preparation of Thickener-3) Similarly to Thickener-1, the B-16 polysaccharide obtained by the above method was adjusted to pH 13.0,
The mixture was kept at 0 ° C. for 20 minutes to obtain a thickener-3.

Thickener-1 to Thickener-3, xanthan gum and locust bingham each in 0.1% by weight aqueous solution (p
H: 6.9) The viscosities at 30 ° C., 50 ° C. and 80 ° C. are shown in Table 1.

[0037]

[Table 1]

[Raw materials for aqueous ballpoint pen ink] Aluminum paste: trade name of "WXMU75", aluminum powder content 60% by weight, Toyo Aluminum Co., Ltd.
Titanium oxide: "Kronos KR380" (trade name) (manufactured by Titanium Industry Co., Ltd.) Colorant-1: "EM Green G" (trade name), green dispersion pigment, 44% by weight of nonvolatile matter (Toyo Ink Co., Ltd.)
Colorant-2: "NKW-2107" (trade name), pink fluorescent pigment, non-volatile content 53% by weight (manufactured by Nippon Fluorescent Chemical Co., Ltd.) Colorant-3: "NKW-2167" (trade name), Purple fluorescent pigment, nonvolatile content 54% by weight (Nippon Fluorescent Chemical Co., Ltd.)
Resin emulsion-1: "Johncryl 450" (trade name), styrene-acrylic resin emulsion (manufactured by Johnson Polymer Co., Ltd.) Resin emulsion-2: "Movinyl DM774" (trade name), acrylic resin emulsion (Hoechst Gosei Co., Ltd.) Resin aqueous solution-1: "John Krill 61J" (trade name),
Ammonium salt of styrene-acrylic acid ester copolymer (manufactured by Johnson Polymer Co., Ltd.) Dispersant-1: Mixture of oleic acid ester of polyoxyethylene diglycerin borate and oleic acid ester of diglycerin borate Dispersion Agent-2: Polyoxyethylene diglycerin borate laurate dispersant-3: "TL10" (trade name) (manufactured by Nikko Chemicals Co., Ltd.) Preservative: 1,2-benzoisothiazolin-3-one ( "Proxel GXL" (trade name) (manufactured by ICI Japan) Defoaming agent: "formclean S" (trade name), silicone emulsion (manufactured by Hakuto Co., Ltd.) Xanthan gum: "Roadpol 23" (trade name) (Rhone Poulin Japan Co., Ltd.) Locust Bean Gum: "Mayprodin 200" (Trade name) (manufactured by May Hall Chemical Co., Ltd.) (Example 1) Thickener-1 and water are mixed in the following formulation 1 to prepare a dispersion of thickener-1, and other components are mixed with this. And
Dispersed for 5 minutes with a turbo mixer. The mixture was further stirred for 30 minutes with a propeller stirrer, and further subjected to a centrifugal defoaming machine to remove fine bubbles, thereby obtaining a glossy green ink. (Formulation 1) Aluminum paste 6.0 parts by weight Colorant-1 12.0 parts by weight Water 64.4 parts by weight Ethylene glycol 6.0 parts by weight Glycerin 6.0 parts by weight Thickener-1 0.2 parts by weight Resin Emulsion-1 4.0 parts by weight Preservative 0.2 parts by weight Dispersant-1 1.0 part by weight Antifoaming agent 0.2 parts by weight (Example 2) In the following formulation 2, in the same manner as in Example 1 It was produced to obtain a glossy pink ink. (Formulation 2) Aluminum paste 4.0 parts by weight Colorant-2 11.0 parts by weight Water 62.6 parts by weight Propylene glycol 15.0 parts by weight Glycerin 5.0 parts by weight Thickener -1 0.2 parts by weight Resin Emulsion-2 1.0 part by weight Preservative 0.2 part by weight Dispersant-2 1.0 part by weight (Example 3) In the following formulation 3, a glossy pink ink produced in the same manner as in Example 1 I got (Formulation 3) Aluminum paste 4.0 parts by weight Colorant-2 11.0 parts by weight Water 62.7 parts by weight Propylene glycol 15.0 parts by weight Glycerin 5.0 parts by weight Thickener-2 0.1 part by weight Resin Emulsion-2 1.0 part by weight Preservative 0.2 part by weight Dispersant-2 1.0 part by weight (Example 4) In the following formulation 4, a pink ink produced in the same manner as in Example 1 and having a gloss I got (Formulation 4) Aluminum paste 4.00 parts by weight Colorant-2 11.00 parts by weight Water 62.75 parts by weight Propylene glycol 15.00 parts by weight Glycerin 5.00 parts by weight Thickener-3 0.05 parts by weight Resin Emulsion-2 1.00 parts by weight Preservative 0.20 parts by weight Dispersant-2 1.00 parts by weight (Example 5) In the following formulation 4, dispersion treatment was performed for 24 hours by a ball mill instead of the turbo mixer of Example 1. Was carried out in the same manner as in Example 1 except that the above process was carried out to obtain a glossy purple ink. (Formulation 5) Titanium oxide 20.0 parts by weight Colorant-3 10.0 parts by weight Water 50.6 parts by weight Ethylene glycol 5.0 parts by weight Glycerin 5.0 parts by weight Thickener-1 0.2 parts by weight Resin Aqueous solution-1 7.0 parts by weight Dispersant-4 2.0 parts by weight Preservative 0.2 parts by weight (Comparative Example 1) 0.2 parts by weight of thickener-1 of Example 1 and 0.2 parts by weight of water A glossy green ink was obtained in the same manner as in Example 1 except that the parts were changed to 0.4 parts by weight of xanthan gum. (Comparative Example 2) Glossy green in the same manner as in Example 1 except that 0.2 part by weight of thickener-1 and 0.6 part by weight of water were changed to 0.8 part by weight of xanthan gum. An ink was obtained. (Comparative Example 3) Same as Example 1 except that 0.2 parts by weight of thickener-1 and 0.2 parts by weight of water in Example 1 were changed to 0.32 g of xanthan gum and 0.08 g of locust bean gum. A glossy green ink was obtained. (Comparative Example 4) Same as Example 1 except that 0.2 part by weight of thickener-1 and 0.4 part by weight of water in Example 1 were changed to 0.45 g of xanthan gum and 0.15 g of locust bean gum. A glossy green ink was obtained. (Comparative Example 5) A glossy pink ink was prepared in the same manner as in Example 2 except that 0.2 part by weight of the thickener-1 and 0.4 part by weight of water in Example 2 were changed to 0.6 g of welan gum. Obtained. Comparative Example 6 A purple ink was obtained in the same manner as in Example 3, except that 0.05 parts by weight of thickener-1 and 0.55 parts by weight of water in Example 4 were changed to 0.6 g of locust bean gum. Was.

The aqueous ink compositions for ballpoint pens obtained from Examples 1 to 4 and Comparative Examples 1 to 4 were tested. The test method is as follows. (Stability Evaluation Test: Ink Viscosity) The ink composition for aqueous ball-point pens prepared by the above method and the viscosity after being left closed for 6 months at room temperature were measured under the following conditions.・ Measurement temperature: 25 ° C. ・ Viscometer used: E-type viscometer (manufactured by Tokimec Co., Ltd.) ・ Rotor used: ST ・ Rotor rotation speed: 1 rotation / min The results are shown in Table 1. (Stability evaluation test: writing test) Using “Hybrid K105” (trade name) manufactured by Pentel Co., Ltd., ink storage in a hollow hollow cylinder made of transparent polypropylene connected to a stainless steel ballpoint pen tip (ball material: cemented carbide). A tube was filled with the ink composition for an aqueous ballpoint pen of the present invention, and filled with an ink backflow preventer to prepare a ballpoint pen for a writing test. Using this ballpoint pen for writing test, put one eye on the commercially available copy paper.
Fifty characters were written, and the number of writable characters without blurring was confirmed. After the test, the ballpoint pen was left for 6 months at room temperature with the tip of the ballpoint pen facing down. Six months later, a similar writing test was performed again. When 150 characters were written and writing was possible without blurring, "150" was described. In the case of less than 150 characters, the writing was cut off in units of 10 characters and evaluated as the number of writing characters. The test results are shown in Table 1.

[0040]

[Table 2]

[0041]

The aqueous ink composition of the present invention maintains a stable viscosity even after long-term storage, has no sedimentation of the pigment, has no reduction in the number of characters that can be written without causing blurring, and has stable quality. .

Claims (4)

[Claims] 1. A pigment and water and a polysaccharide substantially containing fucose, glucose, glucuronic acid and rhamnose as constituent monosaccharides are obtained by heat-treating an aqueous solution having a pH of 8 or more at 60 to 180 ° C. A water-based ink composition comprising a thickener composed of a polysaccharide. 2. The constituent monosaccharides of the polysaccharide are fucose: glucose: glucuronic acid: rhamnose = 1 to 2:
The aqueous ink composition according to claim 1, wherein the ratio is 1 to 4: 1 to 2: 1 to 2. 3. The aqueous ink composition according to claim 1, wherein the polysaccharide is composed of glucose, glucuronic acid, and rhamnose as a main chain, and has a structure in which fucose is bonded to a side chain. 4. The method according to claim 1, wherein the polysaccharide is alkaligenes latus.
4. A polysaccharide produced by the B-16 strain.
The aqueous ink composition as described in the above.