JP7166239B2 - Moisture-absorbing and releasing water-based ink, manufacturing method thereof, and packaging material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a moisture absorbing and releasing aqueous ink, a method for producing the moisture absorbing and releasing aqueous ink, and a packaging material.

Paper packaging materials such as paper and paperboard (hereinafter sometimes simply referred to as "paper") are widely used for packing, transporting, storing, and the like of various products. The outer surface of a paper packaging material is generally printed with printing ink to display various information such as contents, product name, and manufacturer.

The flexographic printing method is mainly used for printing on paperboard such as corrugated cardboard, which is often used as a paper packaging material. Various inks have been proposed so far for packaging materials such as paperboard. For example, Patent Literature 1 proposes an ultraviolet curable ink that is used for flexographic printing on cardboard sheets and that does not contain water or water-soluble solvents.

On the other hand, in recent years, the use of biomass (renewable, biologically derived organic resources excluding fossil resources) has been promoted as a non-exhaustible industrial resource in an effort to deal with the environment. This is no exception in the field of printing inks. For example, Patent Document 2 proposes a printing ink composition containing a biomass-derived alcohol.

JP-A-7-207208 JP 2008-044982 A

A packaging material (paper packaging material) whose main base material is paper (especially paperboard such as corrugated cardboard) can maintain a suitable strength in a low-humidity environment. However, since paper substrates often have hygroscopic properties, in high-humidity environments, paper substrates absorb water and moisture in the air (humidity; gases such as water vapor). The strength of the packaging material gradually decreases, and a situation may arise in which the function as the packaging material becomes insufficient. Such a situation often occurs particularly when paper packaging materials are stored for a long period of time during the rainy season or in a highly humid environment.

On the other hand, in factories that manufacture products such as beverages and foods, by-products including biomass (for example, plant-based biomass and food-based biomass) generated in the manufacturing process of products are generated in large amounts every day and reused. It is desired to develop applications for

Therefore, the present invention aims to provide an ink that is suitable as a printing ink even if biomass is used, has a low environmental load, and is capable of forming a moisture-absorbing and desorbing film. .

According to the present invention, the water-based ink is a moisture-absorbing and desorbing water-based ink containing used tea leaves and diatomaceous earth, and the total dry mass content of the used tea leaves and diatomaceous earth is Moisture-absorbing and desorbing water-based inks are provided that are in the range of 10 to 30% by weight based on the weight of the total solids content of the wet-water-based ink.

According to the present invention, it is possible to provide an ink that is suitable as a printing ink even if biomass is used, has a low environmental load, and is capable of forming a moisture-absorbing and desorbing film.

2 is a graph showing the results of Moisture absorption and desorption test 2 in Examples.

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

<Water-based ink>
The water-based ink of one embodiment of the present invention is a moisture-absorbing and releasing water-based ink containing used tea leaves and diatomaceous earth. In this moisture-absorbing and desorbing water-based ink, the total dry weight content of used tea leaves and diatomaceous earth is in the range of 10 to 30% by mass based on the total solid content of the moisture-absorbing and desorbing water-based ink.

In this specification and the like, "hygroscopic water-based ink" refers to water-based ink that forms a film having moisture-absorbing and desorbing properties. In addition, "hygroscopicity" means a property that has both the property (hygroscopicity) of absorbing moisture in the air (humidity; gas such as water vapor) and the property of releasing the absorbed moisture (moisture releasing property). Hereinafter, the moisture-absorbing and desorbing water-based ink may be simply referred to as "water-based ink", and the film formed from the moisture-absorbing and desorbing water-based ink may be referred to as "moisture-absorbing and desorbing ink layer" or simply "ink layer". I have something to do.

Regarding the used tea leaves and diatomaceous earth contained in the water-based moisture-absorbing and desorbing ink, as will be described later, used tea leaves are extraction residues of tea leaves, and diatomaceous earth is a sediment consisting of fossils of diatom shells, and silicon dioxide (SiO ₂ ). It is an inorganic substance whose main component is Therefore, used tea leaves, which are biomass, and diatomaceous earth, which is an inorganic substance, can be used for moisture absorbing and releasing water-based ink. Water-based inks containing biomass generally tend to be less suitable as printing inks than water-based inks not containing biomass. On the other hand, the water-based moisture-absorbing and desorbing ink contains used tea leaves and diatomaceous earth in a specific content range. It has the advantage of being able to form a moisture-releasing film.

The used tea leaves contained in the water-based moisture-absorbing/releasing ink are extraction residues (extraction residues of tea leaves) obtained by extracting tea leaves (including leaves and stems) with water or the like. Such used tea leaves are generated in large quantities as by-products and waste in factories that manufacture tea-based beverages such as green tea, black tea, and oolong tea, for example. From the viewpoint of such effective utilization of biomass, in the production of tea-based beverages, an extraction process in which tea leaves are extracted with water (preferably 70 to 100 ° C., more preferably 70 to 90 ° C. heated water) using an extraction device. It is preferable to use used tea leaves that are produced later as extraction residues.

The type of used tea leaves is not particularly limited. For example, used tea leaves such as green tea, black tea, white tea, yellow tea, blue tea, black tea, and flower tea can be used. One of these used tea leaves may be used, two or more may be used in combination, or a mixture of two or more (mixed used tea leaves) may be used.

Regarding the form of used tea leaves, it is preferable that the used tea leaves are finely divided from the viewpoint of using them as a component of water-based ink. For example, the average particle size of used tea leaves is preferably in the range of 1 to 500 μm, more preferably in the range of 1 to 250 μm, and more preferably in the range of 1 to 150 μm, from the viewpoint of enhancing suitability as a printing ink. is more preferable. The average particle size of used tea leaves and the average particle size of diatomaceous earth, which will be described later, mean the particle size (D ₅₀ ) at which cumulative 50% of the volume-based particle size distribution is measured by a laser diffraction/scattering method.

The diatomaceous earth contained in the moisture-absorbing and releasing water-based ink has a porous structure, and a large number of fine pores of about 1 nm to 1 μm are present on its surface. As diatomaceous earth, diatomaceous earth capable of absorbing and desorbing moisture can be used. Since the above-mentioned used tea leaves are also included in water-based ink, tea liquid (liquid obtained by squeezing used tea leaves or liquid after extracting tea leaves) is mixed with diatomaceous earth, and the fine particles contained in the liquid are filtered through diatomaceous earth. preferably.

As diatomaceous earth, diatomaceous earth ore is generally pulverized and dried, and the pulverized and dried pulverized and dried diatomaceous earth is calcined or calcined with a flux. Furthermore, as the diatomaceous earth contained in the water-based moisture absorbing/releasing ink, it is more preferable to use acid-treated diatomaceous earth, because if catechin reacts with iron to give a black color, it is difficult to adjust the color of the ink. As a method for acid treatment of diatomaceous earth, after contacting diatomaceous earth with acidic water (for example, an aqueous solution of organic acids such as citric acid, lactic acid, and acetic acid, and inorganic acids such as phosphoric acid, nitric acid, and hydrochloric acid), A method of washing with water following liquid separation and using diatomaceous earth in a state of being suspended in water or in a wet state may be mentioned.

There is no particular limitation on the characteristics that represent an index related to the filtration function for allowing fine tea leaves to be adsorbed on diatomaceous earth by passing a liquid obtained by squeezing used tea leaves or a liquid after extracting tea leaves through diatomaceous earth. As a characteristic of diatomaceous earth, for example, the permeability, which is an index representing how easily a fluid can pass, is preferably in the range of 0.01 to 2.0 Darcy, and in the range of 0.02 to 0.5 Darcy more preferably 0.05 to 0.1. In addition, after dispersing diatomaceous earth powder with water, it is packed in a container, and the cake bulk density, which is the density measured considering the gap in the container as a volume, is in the range of 0.2 to 0.5 g / cm ³ . and more preferably in the range of 0.3 to 0.45 g/cm ³ .

Diatomaceous earth that has been passed through the above-mentioned tea liquid generally has tea leaves (extraction residue of tea leaves) attached as filter cake. By using such diatomaceous earth with used tea leaves, biomass can be used more effectively, which also leads to a reduction in the wastewater load during treatment of used tea leaves. Moreover, it can contribute to the improvement of the biomass component (biomass degree) in the solid content of the water-based ink, and the commercial value can be further enhanced.

Diatomaceous earth and used tea leaves can be used in moisture-absorbing and desorbing water-based ink while they are in a water-containing state. The water content in the tea leaves and diatomaceous earth in a hydrated state is the water content of the combined tea leaves and diatomaceous earth, and is preferably in the range of 40 to 90% by mass, more preferably in the range of 50 to 90% by mass. . The used tea leaves and diatomaceous earth may be prepared separately.

Regarding the form of diatomaceous earth, it is preferably finely divided from the viewpoint of use as a component of water-based ink. For example, the average particle size of diatomaceous earth is preferably in the range of 5 to 50 μm, more preferably in the range of 10 to 50 μm, more preferably in the range of 10 to 40 μm, from the viewpoint of enhancing suitability as a printing ink. is more preferable. In addition, when using the diatomaceous earth with used tea leaves, the average particle size measured for the diatomaceous earth with used tea leaves is preferably in the range of 1 to 500 μm, more preferably in the range of 1 to 250 μm. It is more preferably in the range of ~150 μm.

The total dry mass content of tea leaves and diatomaceous earth in the moisture absorbing and desorbing water-based ink is 10 to 30% by mass based on the mass of the total solid content of the moisture absorbing and desorbing water-based ink. When the content of used tea leaves and diatomaceous earth is 10% by mass or more, moisture absorption and desorption properties can be imparted to the film formed from the moisture absorption and desorption water-based ink, and the film is formed as a moisture absorption and desorption ink layer. be able to. From the viewpoint of easily obtaining this effect, the content of used tea leaves and diatomaceous earth is preferably 12% by mass or more, more preferably 15% by mass or more. Moreover, when the content of used tea leaves and diatomaceous earth is 30% by mass or less, a water-based ink having good suitability as a printing ink can be obtained. As will be described later, the water-based moisture-absorbing and desorbing ink preferably contains a coloring agent such as a pigment. is preferably 28% by mass or less, more preferably 25% by mass or less.

As for the ratio of used tea leaves and diatomaceous earth contained in the moisture-absorbing and desorbing water-based ink, it is preferable that the ratio of the dry weight of used tea leaves to the dry weight of diatomaceous earth is within the range of used tea leaves:diatomaceous earth=20:80 to 40:60. As a result, suitability as a printing ink tends to be better.

Moisture-absorbing and desorbing water-based ink preferably contains a binder resin in addition to used tea leaves and diatomaceous earth. Moisture-absorbing and desorbing water-based ink can form a moisture-absorbing and desorbing ink layer without containing a binder resin. It is possible to enhance the film-forming ability by

Any binder resin that can be used for water-based ink can be used as the binder resin. Suitable binder resins include, for example, (meth)acrylic resins (polymers or copolymers of (meth)acrylic acid esters), urethane-modified (meth)acrylic resins, silicone-modified (meth)acrylic resins, styrene-(meth)acrylic resins, ) Acrylic copolymer resin, styrene-acrylic acid copolymer resin, styrene-maleic acid copolymer resin, ethylene-(meth)acrylic copolymer resin, polyurethane resin, polyester resin, polystyrene resin, rosin-modified maleic acid resin, vinyl chloride- Vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl acetate-vinyl chloride copolymer resin, vinyl acetate-(meth)acrylic acid copolymer resin, ethylene-vinyl chloride copolymer resin, ethylene-vinyl acetate- (Meth)acrylic copolymer resins, polyvinyl acetal resins, polyamide resins, cellulose resins, and the like can be mentioned. These 1 types can be used individually or in combination of 2 or more types. As used herein, the term "(meth)acrylic" includes both the terms "acrylic" and "methacrylic".

Examples of the form of the binder resin include an aqueous solution type, an emulsion type, and a dispersion type. Among these, it is preferable to use an aqueous solution type or emulsion type binder resin from the viewpoint of enhancing suitability as a printing ink.

When a binder resin or a resin dispersant is included in the water-absorbing and desorbing ink, the content of the resin in the water-absorbing and desorbing water-based ink (nonvolatile content) is the mass of the total solid content of the water-absorbing and desorbing water-based ink. As a standard, it is preferably in the range of 20 to 70% by mass, more preferably in the range of 30 to 50% by mass.

Moisture-absorbing and desorbing water-based ink preferably contains coloring agents such as pigments and dyes in addition to used tea leaves and diatomaceous earth. By including a colorant in the moisture-absorbing and desorbing water-based ink, it is possible to suppress the influence of tea leaves and diatomaceous earth, which are contained as essential components, on the hue of the ink layer. In addition, the moisture-absorbing and desorbing water-based ink containing the colorant is applied to the base material, for example, the content, product name, place of production, place of manufacture, place of processing, producer, manufacturer, processor, barcode, two-dimensional It can be suitably used as a printing ink for displaying various information such as codes, marks and designs. It is also possible to form a moisture absorbing/releasing ink layer having a hue derived from tea leaves and diatomaceous earth with the moisture absorbing/releasing aqueous ink. In this case, the moisture absorbing/releasing aqueous ink does not contain a coloring agent. may

It is more preferable that the moisture-absorbing and desorbing water-based ink contains a pigment as a coloring agent. Examples of pigments include titanium oxide, zinc oxide, lead oxide, zinc sulfide, aluminum, mica, titanium oxide-coated mica (pearl pigment), bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine blue, and Prussian blue. , red iron oxide, yellow iron oxide, iron black, and carbon black; extender pigments (inorganic pigments) such as barium sulfate, calcium carbonate, magnesium carbonate, aluminum hydroxide, silica, mica, kaolin, and clay; monoazo Pigments, disazo pigments, condensed azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindoline pigments, isoindolinone pigments, thioindigo pigments, pyrrolopyrrole pigments, azomethine azo pigments, perinone pigments organic pigments such as pigments and perylene-based pigments; These 1 type(s) or 2 or more types can be used.

When the pigment is contained in the moisture absorbing and desorbing aqueous ink, the content of the pigment in the moisture absorbing and desorbing aqueous ink is in the range of 10 to 70% by mass based on the total solid content of the moisture absorbing and desorbing aqueous ink. preferably in the range of 20 to 60% by mass, even more preferably in the range of 30 to 50% by mass. The amount of pigment to be used can be appropriately adjusted according to the use of water-based ink, the type of pigment, and the like.

Moisture-absorbing and desorbing water-based ink contains at least water. The content of water in the moisture-absorbing and desorbing water-based ink can be appropriately adjusted according to the printing method of the water-based ink, the printing machine used for printing, and the like. For example, the water content can be in the range of about 30 to 80% by mass based on the total mass of the moisture-absorbing and desorbing water-based ink.

Moisture-absorbing and desorbing water-based ink may contain a water-soluble organic solvent in addition to water. Any water-soluble organic solvent that can be used for aqueous ink can be used as the organic solvent, and examples thereof include alcohols, polyhydric alcohols, and glycol ethers. One or two or more of such organic solvents may be contained in the water-based moisture absorbing/releasing ink.

The moisture-absorbing and desorbing water-based ink may contain various additives other than the components described above. Additives include, for example, dispersants, surfactants, antifoaming agents, pH adjusters, curing agents, cross-linking agents, lubricants, waxes, matting agents, antiblocking agents, leveling agents, coupling agents, antioxidants. , ultraviolet absorbers, light stabilizers, preservatives, rust inhibitors, anti-mold agents, anti-settling agents, plasticizers, flame retardants, color developers and the like.

Moisture-absorbing and desorbing water-based inks can be suitably used for packaging materials, as will be described later. Therefore, among the above additives, it is preferable to use wax from the viewpoint of improving the abrasion resistance of the ink layer. From this point of view, a hydrocarbon wax can be used as a suitable wax. Hydrocarbon waxes include, for example, polyethylene wax, polypropylene wax, Fischer-Tropsch wax, paraffin wax, and microcrystalline wax. One or more of these can be used. Further, the penetration of the hydrocarbon wax at 25° C. measured according to JIS K 2207 is preferably in the range of 1 to 20, more preferably in the range of 1 to 15. more preferred.

From the viewpoint of facilitating the formation of a moisture absorbing/releasing ink layer by applying the moisture absorbing/releasing water-based ink to the base material, the moisture absorbing/releasing ink is preferably used for printing, that is, it is preferably a printing ink. Among them, from the viewpoint of great significance of providing a moisture absorbing and releasing ink layer on a paper substrate, the moisture absorbing and releasing aqueous ink is used for flexographic printing suitable for printing on a paper substrate, that is, flexographic printing It is preferably an ink for industrial use, and it is preferably used for paper substrates. Various types of paper can be used as the paper substrate, and among them, cardboard such as corrugated base paper (medium base paper, front liner, and back liner) and corrugated cardboard sheets in which these are combined are more preferable.

The manufacturing method of the moisture-absorbing and desorbing water-based ink is not particularly limited, and the essential ingredients such as used tea leaves and diatomaceous earth, water, and if necessary, a binder resin, a coloring agent, and other additives are blended and mixed. , moisture absorption and desorption water-based ink can be produced.

Since used tea leaves and diatomaceous earth are preferably finely divided, it is preferable to use an aqueous dispersion containing at least used tea leaves and diatomaceous earth in the production of moisture-absorbing and desorbing water-based ink. That is, in the method for producing a moisture-absorbing and desorbing water-based ink according to one embodiment of the present invention, a step of preparing a water dispersion containing used tea leaves and diatomaceous earth (step of preparing a water dispersion), and using the water dispersion, It is preferable to include a step of preparing a moisture-absorbing and releasing water-based ink containing used tea leaves and diatomaceous earth (ink preparation step).

In the step of preparing the aqueous dispersion, a step of mixing water, used tea leaves, and diatomaceous earth, finely pulverizing the used tea leaves and diatomaceous earth in the mixture (in water), and dispersing them in water (dispersion step) can be performed. more preferred. In this dispersing step, various dispersing machines such as ball mills, attritors, sand mills, bead mills, colloid mills, roll mills, homodispers, dissolvers, homomixers, high-pressure homogenizers, and ultrasonic homogenizers can be used. One of these dispersers may be used to perform the dispersion treatment once or multiple times, or two or more dispersers may be used in combination to perform the dispersion treatment multiple times. Moreover, in the dispersing step, the mixture may contain additives such as a dispersant and an antifoaming agent.

When a pigment is contained as a coloring agent in the water-absorbing/desorbing water-based ink, the pigment can be blended in the aqueous dispersion. At that time, in the dispersing step, water, used tea leaves, and diatomaceous earth are mixed, and in the mixture (in water), the used tea leaves and diatomaceous earth are finely pulverized and dispersed. It is more preferable to include a second dispersion step of mixing the obtained liquid (aqueous dispersion containing used tea leaves and diatomaceous earth) with the pigment, and finely dispersing the used tea leaves, diatomaceous earth, and the pigment in water. The various dispersing machines described above can also be used in the second dispersing step. By performing the dispersing step including the first and second dispersing steps, the used tea leaves and diatomaceous earth can be sufficiently finely divided, and the prepared water-based ink is more likely to be suitable as a printing ink. In the dispersing step, water, used tea leaves, diatomaceous earth, and pigment may be mixed together, and the used tea leaves, diatomaceous earth, and pigment may be finely dispersed in the mixture (in water).

In the ink preparation process, as described above, the total content of used tea leaves and diatomaceous earth as a dry mass is in the range of 10 to 30% by mass based on the mass of the total solid content of the water-based ink. A moisture-releasing water-based ink is prepared. When the above-mentioned binder resin is contained in the moisture-absorbing and desorbing water-based ink, in the ink preparation process, the aqueous dispersion containing used tea leaves and diatomaceous earth (more preferably used tea leaves, diatomaceous earth, and It is preferable to mix the aqueous dispersion containing the pigment) and the binder resin.

As described in detail above, the water-based moisture absorbing/releasing ink of one embodiment of the present invention contains used tea leaves and diatomaceous earth in a total of 10 to 30% by mass in terms of dry mass based on the mass of the total solid content of the water-based ink. Therefore, even when diatomaceous earth with used tea leaves, which is biomass, is used as used tea leaves and diatomaceous earth in this water-absorbing and desorbing water-based ink, this water-absorbing and desorbing water-based ink has good aptitude as a printing ink and has low environmental load. It is possible to form a hygroscopic coating with a small amount.

The hygroscopic water-based ink can form a hygroscopic film (hygroscopic ink layer), so it is particularly significant to use it for printing on paper substrates. Paper substrates retain moderate strength in low-humidity environments, but many of them have hygroscopic properties, and in high-humidity environments they absorb moisture (humidity) such as water and water vapor in the air. This is because the strength may gradually decrease over time. That is, by printing the moisture absorbing/releasing water-based ink on such a paper substrate and providing a moisture absorbing/releasing ink layer, the moisture absorbing/releasing ink layer positively absorbs moisture rather than the paper substrate absorbs moisture. Since it can absorb and release moisture, it can be expected to maintain the strength of the paper substrate.

It is considered that the above-described reduction in strength due to moisture absorption of the paper base material is particularly likely to occur when paperboard such as corrugated board as the paper base material is used as a packaging material. This is because paperboard such as corrugated board has strength in a dry state due to its thickness, but may also absorb a large amount of moisture, and it is considered that strength reduction is conspicuous in the moisture absorption state. In addition, packaging materials based on paperboard such as corrugated board are widely used for packaging, transportation, and storage of various products, and it is thought that there are many opportunities to come into contact with water and moisture in the air. is. Under these circumstances, it is preferable that the moisture-absorbing and desorbing water-based ink is used for paper substrates (more preferably paperboard such as corrugated cardboard) that constitute packaging materials. By using this moisture absorbing and desorbing water-based ink, it is possible to provide the packaging material described below.

<Packaging material>
A packaging material of one embodiment of the present invention comprises a paper base material and a moisture absorbing/releasing ink layer provided on the paper base material. The moisture-absorbing/releasing ink layer in this packaging material contains used tea leaves and diatomaceous earth, and the content of the total dry weight of used tea leaves and diatomaceous earth in the moisture-absorbing/releasing ink layer is in the range of 10 to 30% by mass.

The moisture-absorbing/releasing ink layer in the packaging material can be formed using the moisture-absorbing/releasing water-based ink according to the above embodiment, and can be a dry film of the moisture-absorbing/releasing water-based ink described above, for example. As a method for providing a moisture-absorbing/releasing ink layer on a paper-made base material, a method of printing the moisture-absorbing/releasing water-based ink described above on a paper-made base material can be employed, and among these, a flexographic printing method is preferable. The printing of the moisture-absorbing and desorbing water-based ink on the paper base material may be performed on a part of the surface of the paper base material, or may be performed on the entire surface. Therefore, the hygroscopic ink layer in the packaging material may be provided partially or entirely on the surface of the paper base material.

Various types of paper can be used as the paper base material in the packaging material, and among them, cardboard such as corrugated cardboard base paper (medium base paper, front liner, and back liner) and corrugated cardboard sheets in which these are combined are preferable. . The form of the packaging material is not particularly limited, and various forms such as sheet-like, label-like, bag-like, and box-like can be employed.

In addition, as described above, an embodiment of the present invention can have the following configuration.
[1] A water-based ink, wherein the water-based ink is a moisture-absorbing and desorbing aqueous ink containing used tea leaves and diatomaceous earth, and the total dry mass content of the used tea leaves and the diatomaceous earth is equal to the moisture-absorbing and desorbing water-based ink Moisture-absorbing and desorbing water-based ink in the range of 10 to 30% by mass based on the mass of the total solid content.
[2] The moisture-absorbing/releasing water-based ink according to [1] above, wherein the ratio of the dry mass of the used tea leaves to the dry mass of the diatomaceous earth is in the range of used tea leaves:diatomaceous earth=20:80 to 40:60.
[3] The hygroscopic water according to [1] or [2] above, wherein diatomaceous earth with used tea leaves is contained as the used tea leaves and the diatomaceous earth, and the average particle size of the diatomaceous earth with used tea leaves is in the range of 1 to 500 μm. ink.
[4] The moisture-absorbing and desorbing water-based ink according to any one of [1] to [3], further containing a binder resin.
[5] Moisture-absorbing and desorbing water-based ink according to any one of [1] to [4], which is used for flexographic printing.
[6] Moisture-absorbing and desorbing water-based ink according to any one of [1] to [5], which is used for a paper substrate.
[7] A step of preparing an aqueous dispersion containing used tea leaves and diatomaceous earth; As a standard, a method for producing a moisture absorbing and desorbing water-based ink, comprising a step of manufacturing a moisture absorbing and desorbing water-based ink in the range of 10 to 30% by mass.
[8] A paper substrate and a moisture absorbing/releasing ink layer provided on the paper substrate, wherein the moisture absorbing/releasing ink layer contains used tea leaves and diatomaceous earth, and the moisture absorbing/releasing ink layer contains The content of the used tea leaves and the diatomaceous earth as a total dry mass is in the range of 10 to 30% by mass.
[9] A paper substrate and a moisture absorbing/releasing ink layer provided on the paper substrate, wherein the moisture absorbing/releasing ink layer is the moisture absorbing/releasing ink layer according to any one of [1] to [6] above. A packaging material made of moisture-absorbing and desorbing water-based ink.

EXAMPLES Hereinafter, the water-based ink of one embodiment of the present invention will be described more specifically with reference to examples and comparative examples, but the water-based ink is not limited to the following examples. In the following text, "parts" and "%" are based on mass ("parts by mass" and "% by mass", respectively) unless otherwise specified.

<Example 1>
(Preparation of used tea leaves and diatomaceous earth)
A liquid obtained by extracting tea leaves with hot water at a rate of 10 g / L for 10 minutes and a pressed liquid obtained by pressing the tea leaves at 90 kg / cm ² were filtered through a mesh with an opening of 500 μm, and the permeability was 0.08 Darcy. , diatomaceous earth with used tea leaves was prepared by mixing diatomaceous earth having a cake bulk density of 0.4 g/cm ³ and then removing the liquid with a cloth. The water content of used tea leaves and diatomaceous earth was 58%, and the dry mass ratio of used tea leaves and diatomaceous earth was 30 (used tea leaves):70 (diatomaceous earth). In addition, for diatomaceous earth with used tea leaves (mixture of used tea leaves and diatomaceous earth), a particle size distribution measuring device using a laser diffraction/scattering method (trade name “Laser diffraction particle size distribution measuring device SALD-2300”, manufactured by Shimadzu Corporation) As a result of measuring the volume-based particle size distribution, the average particle size (D ₅₀ ) was 125 μm.

(Preparation step of aqueous dispersion)
18.8 parts of water, a resin dispersant (30% aqueous solution of styrene-acrylic copolymer resin; trade name "Joncryl 70J", manufactured by BASF Japan) 20.0 parts, and an antifoaming agent (solid content: more than 96%, 10.0 parts of diatomaceous earth with used tea leaves in a water-containing state was added to a liquid containing 0.2 parts of BYK-024 (trade name, manufactured by BYK-Chemie Japan) to obtain a mixed liquid. This mixture was sufficiently stirred with a homomixer until coarse particles disappeared to obtain a uniform dispersion of used tea leaves and diatomaceous earth dispersed in water. To the resulting dispersion containing used tea leaves and diatomaceous earth, a copper phthalocyanine blue pigment (trade name: "Cyanine Blue ZCA-350EP", manufactured by Dainichiseika Kogyo Co., Ltd.), which is an organic pigment as a coloring agent, is added, and sufficiently stirred with a stirrer. After stirring, dispersion treatment was performed using a horizontal bead mill type disperser (dispersion step). In this way, an aqueous dispersion of used tea leaves, diatomaceous earth, and pigment in water was obtained.

(Ink preparation process)
In the aqueous dispersion containing used tea leaves, diatomaceous earth, pigments, etc. obtained in the above aqueous dispersion preparation process, a core-shell type styrene-methacrylic acid copolymer emulsion (solid content: 34%, theoretical Tg: 17° C.) 37.0 parts, water 2.0 parts, aqueous dispersion of low molecular weight polyethylene wax (solid content: 40%, penetration according to JIS K 2207: 10, trade name “Chemipearl W500”, Mitsui Chemicals ) and 0.3 parts of an antifoaming agent (solid content: more than 96%, trade name “BYK-024”, manufactured by BYK-Chemie Japan) are added and thoroughly stirred, and the water-based ink of Example 1 was prepared.

<Examples 2 to 4 and Comparative Examples 1 to 3>
Compared with Example 1, each amount of water and diatomaceous earth with used tea leaves in a hydrated state used in the "process for preparing aqueous dispersion" was changed to the amount shown in the upper row of Table 1 ("process for preparing aqueous dispersion" column). In the same manner as in Example 1, except that the amount of the resin emulsion used in the "Ink preparation process" was changed to the amount shown in the middle row of Table 1 ("Ink preparation process" column). , Examples 2-4 and Comparative Examples 1-3 were prepared.

<Moisture absorption and desorption test 1>
(Production of packaging material)
Water was added to each of the water-based inks obtained in Examples 1-4 and Comparative Examples 1-3, and the viscosity of each water-based ink was adjusted to 13-15 seconds at 25°C with a Zahn cup #4 (manufactured by Rigosha). adjusted to A diluted water-based ink was solidly printed on both sides of a plain corrugated cardboard sheet by a flexographic printing method and dried to form an ink layer. Thus, for each of Examples 1 to 4 and Comparative Examples 1 to 3, a packaging material (packaging material) having ink layers provided on both sides of the corrugated cardboard sheet was produced.

(Test/evaluation method)
A certain area is cut out from each of the prepared packaging materials to obtain a specimen, and each specimen is cured in a constant temperature and humidity chamber at a temperature of 25 ° C and a relative humidity of 50% RH until the mass of the specimen reaches a constant weight, The mass m ₀ (g) of the specimen after curing was measured as the initial mass before testing. The specimen after curing was placed in a constant temperature and humidity chamber at a temperature of 40° C. and a relative humidity of 90% RH for 48 hours to absorb moisture (moisture absorption process). After the moisture absorption process, the specimen was removed from the constant temperature and humidity chamber, and immediately after measuring the mass ma (g) of the specimen after moisture absorption, the specimen after moisture absorption was placed at _a temperature of 25 ° C. and a relative humidity of 50. It was transferred to a constant temperature and humidity bath of % RH and allowed to release moisture (moisture releasing process). The masses m _d (m _d10 , m _d30 , m _d45 and m _d60 respectively) of the specimens were measured 10 minutes, 30 minutes, 45 minutes and 60 minutes after the start of the moisture release process.

The mass increase rate ([m _d −m ₀ ]/m ₀ ) was calculated and evaluated for each elapsed time from the start of the moisture desorption process of the test body after moisture absorption. Moisture in the specimen that absorbs moisture in a high-humidity environment is released into the air over time, approaching the surrounding environmental humidity. The amount of moisture that has increased from the initial mass of the specimen is the moisture absorbed by the specimen. represents that

In addition, the moisture absorption and desorption area _A (m ² ) of the specimen, the mass m ₀ (g) of the specimen after curing, the mass ma (g) of the specimen at the end of the moisture absorption process, and the time of the moisture desorption process From the mass m _d (g) of the specimen, the moisture absorption amount W _a (g/m ² ) of the specimen is calculated based on the following formula (1), and the moisture desorption process of the specimen is calculated based on the following formula (2) The moisture release amount W _d (g/m ² ; W _d10 , W _d30 , W _d45 , W _d60 ) per hour was calculated. Furthermore, the moisture release rate (%) for each hour of the moisture release process was calculated based on the following formula (3). The results of Moisture Absorption/Desorption Test 1 are shown in the upper part of Table 2.
W _a =(m _a −m ₀ )/A (1)
W _d =(m _a −m _d )/A (2)
Moisture release rate (%) = ( _Wd /Wa) _x 100 (3)

<Moisture absorption and desorption test 2>
(Production of packaging material)
Water was added to each of the water-based inks obtained in Examples 1-4 and Comparative Examples 1-3, and the viscosity of each water-based ink was adjusted to 13-15 seconds at 25°C with a Zahn cup #4 (manufactured by Rigosha). adjusted to A diluted water-based ink was solidly printed on both sides of the front liner paper for corrugated board by a flexographic printing method, and dried to form an ink layer. Thus, for each of Examples 1 to 4 and Comparative Examples 1 to 3, a packaging material (packaging material) having ink layers provided on both sides of the liner paper was produced.

(Test/evaluation method)
A certain area is cut out from each of the prepared packaging materials to obtain a specimen, and each specimen is cured in a constant temperature and humidity chamber at a temperature of 25 ° C and a relative humidity of 50% RH until the mass of the specimen reaches a constant weight, The mass m ₀ (g) of the specimen after curing was measured. The initial mass per unit area (m ₀ /specimen area A; g/m ² ) of the specimen after this curing (specimen before test) was calculated. Next, each specimen was stored in a room at a temperature of 26 ° C. and a relative humidity of 76% _RH , and the mass (g) after 10 minutes, 30 minutes, and 45 minutes was measured. m _b10 , m _b30 , m _b45 ). The amount of increase in mass per unit area ([m _b −m ₀ ]/A; g/m ² ) and the rate of increase in mass (%) of the specimen upon moisture absorption during the predetermined time were calculated.

A specimen stored in a high-humidity environment absorbs moisture and its weight increases from the initial weight before the test. Humidity also occurs at the same time. Therefore, it can be said that the more gradual the amount of increase in mass, or the more the amount of increase in mass remains almost unchanged or decreases with the elapsed time of the moisture absorption process, the higher the moisture releasing effect of the ink layer. The results of Moisture absorption and desorption test 2 are shown in the middle part of Table 2 and in FIG.

<Friction resistance test>
(Production of packaging material)
Water was added to each of the water-based inks obtained in Examples 1-4 and Comparative Examples 1-3, and the viscosity of each water-based ink was adjusted to 13-15 seconds at 25°C with a Zahn cup #4 (manufactured by Rigosha). adjusted to A diluted water-based ink was solidly printed on one side of a plain unbleached liner paper with a coating weight of 300 LPI anilox by a flexographic printing method using a flexo hand proofer and dried to form an ink layer. Thus, for each of Examples 1 to 4 and Comparative Examples 1 to 3, a packaging material (packaging material) having an ink layer provided on one side of unbleached liner paper was produced. Each prepared packaging material was placed in a constant temperature and humidity chamber at a temperature of 25° C. and a relative humidity of 50% RH for 24 hours for curing, and each packaging material after curing was used as a test specimen.

(Test/evaluation method)
For each specimen, using a Gakushin type rubbing fastness tester, the ink layer on the specimen was rubbed 100 times with a white cloth (cotton No. 3-1) with a load of 200 gf. The appearance was visually confirmed, and the abrasion resistance of the ink layer was evaluated according to the following evaluation criteria. The results of this evaluation are shown in the "wear resistance" column of Table 2.
A: Fouling due to friction was hardly observed.
B: Fouling due to friction was not so much observed, but was partially observed.
C: Conspicuous dirt due to friction was confirmed.

<Evaluation of color development of water-based ink>
(Preparation of printed matter)
Water was added to each of the water-based inks obtained in Examples 1-4 and Comparative Examples 1-3, and the viscosity of each water-based ink was adjusted to 13-15 seconds at 25°C with a Zahn cup #4 (manufactured by Rigosha). adjusted to A diluted water-based ink was solidly printed on one side of art paper with a coating amount of 300 LPI anilox by a flexographic printing method using a flexo hand proofer, and dried to form an ink layer. In this manner, prints were produced by providing an ink layer on one side of art paper for each of Examples 1 to 4 and Comparative Examples 1 to 3. Each of the produced prints was placed in a constant temperature and humidity chamber at a temperature of 25° C. and a relative humidity of 50% RH for 24 hours to cure, and the prints after curing were used as test specimens.

(Evaluation method)
For each specimen, the values of L ^* , a ^* , and b ^* in the CIELAB color system were measured using a spectrophotometer (trade name “X-Rite eXact”, manufactured by X-Rite). Also, using these measured values, the ΔE ^* values of Examples 1 to 4 and Comparative Examples 2 and 3 were calculated based on the L ^* , a ^* , and b ^* values of Comparative Example 1. . These results are shown in the lower part of Table 2.

As shown in Table 2, the water-based inks of Examples 1 to 4 are better than the water-based ink containing no used tea leaves and diatomaceous earth (Comparative Example 1) and the water-based ink containing too little used tea leaves and diatomaceous earth (Comparative Example 2). , it was confirmed that an ink layer having good moisture absorption and desorption properties could be formed. Moreover, it was confirmed that the water-based inks of Examples 1 to 4 were capable of forming ink layers with good abrasion resistance. Furthermore, the ink layers of Examples 1 to 4 with the water-based inks had a ΔE ^* value of less than 5 based on the ink layer with the water-based ink containing no used tea leaves and diatomaceous earth (Comparative Example 1). From this, it was confirmed that the water-based inks of Examples 1 to 4 were capable of forming an ink layer in which the change in hue due to the inclusion of used tea leaves and diatomaceous earth was suppressed, and that the suitability as a printing ink was good. confirmed. From the above results, like the water-based inks of Examples 1 to 4, moisture-absorbing and desorbing water-based inks containing specific amounts of used tea leaves and diatomaceous earth have less environmental impact and are suitable as printing inks even when biomass is used. , it was confirmed that a moisture-absorbing and desorbing film can be formed.

Claims (7)

water-based ink,
The water-based ink is a moisture-absorbing and releasing water-based ink containing used tea leaves and diatomaceous earth,
The content as a total dry mass of the used tea leaves and the diatomaceous earth is in the range of 10 to 30% by mass based on the mass of the total solid content of the moisture-absorbing and desorbing water-based ink ,
Moisture-absorbing and desorbing water-based ink , wherein the ratio of the dry mass of the used tea leaves to the dry mass of the diatomaceous earth is in the range of used tea leaves:diatomaceous earth=20:80 to 40:60 . Containing diatomaceous earth with used tea leaves as the used tea leaves and the diatomaceous earth,
The water-based moisture absorbing and desorbing ink according to claim 1, wherein the diatomaceous earth with used tea leaves has an average particle size in the range of 1 to 500 µm. Moisture-absorbing and desorbing water-based ink according to claim 1 or 2 , further comprising a binder resin. Moisture-absorbing and desorbing water-based ink according to any one of claims 1 to 3 , which is used for flexographic printing. Moisture-absorbing and desorbing water-based ink according to any one of claims 1 to 4 , which is used for paper substrates. A step of preparing an aqueous dispersion containing used tea leaves and diatomaceous earth;
Moisture-absorbing and desorbing water-based ink in which the content of the used tea leaves and the diatomaceous earth as a total dry mass is in the range of 10 to 30% by mass based on the mass of the total solid content of the ink using the aqueous dispersion. and
A method for producing a moisture-absorbing and desorbing water-based ink, wherein the ratio of the dry mass of the used tea leaves to the dry mass of the diatomaceous earth is in the range of used tea leaves:diatomaceous earth=20:80 to 40:60 . a paper substrate;
a hygroscopic ink layer provided on the paper substrate,
The moisture absorbing/releasing ink layer contains used tea leaves and diatomaceous earth, and the total dry mass content of the used tea leaves and diatomaceous earth in the moisture absorbing/releasing ink layer is in the range of 10 to 30% by mass , The packaging material , wherein the ratio of the dry mass of the used tea leaves to the dry mass of the diatomaceous earth is within the range of used tea leaves:diatomaceous earth=20:80 to 40:60 .

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