JP2020183498A - Ink composition for non-aceous inkjet - Google Patents

Abstract

To provide an ink composition for non-aqueous inkjet which contains a pigment, a water-insoluble resin and a solvent, has good discharge property at the time of printing, enables production of a coated film excellent in scratch resistance after printing, and is suitable for inkjet printing.SOLUTION: An ink composition for non-aqueous inkjet contains a mixed solvent obtained by mixing a first solvent composed of at least a water-insoluble resin, a pigment and ethanol and a second solvent containing at least one selected from aromatic alcohols, propylene glycol, polyethylene glycol and an acetic acid, in which a mass ratio of the water-insoluble resin to the pigment is 2.0-7.5.SELECTED DRAWING: None

Description

Embodiments of the present invention relate to non-aqueous inkjet ink compositions.

In recent years, on the surface of foods, oral drugs, etc., and materials that come into direct contact with them (for example, packaging materials), production information such as production area, producer, production history, quality information such as expiration date and production date, Various indications such as identification information for identifying the type are printed and displayed on a preparation such as a tablet.
Printing on such foods, oral drugs, etc. is made by using an edible material that does not have an adverse effect on the human body because the ink used enters the human body at the same time as the food or the oral drug.

However, since such an edible property is required, there are many restrictions on the ink material used, and the types that can be selected are limited. Therefore, due to the characteristics of the material used, the visibility and stability of the printed portion may not be sufficient.
That is, many of such inks are water-based inks and are inferior in water resistance, so that scratch resistance and the like are not sufficient. For example, in the case of tablets, the printed portion is rubbed off or dropped due to contact between tablets during manufacturing, contact between tablets and a manufacturing machine, contact with the human body during use of tablets, and the like. There were times when I was relaxed.

On the other hand, it is also considered to add a water-insoluble resin to improve water resistance. For example, the ink used for printing on the surface of a tablet includes water, a pigment, a water-insoluble resin, and a water-soluble ink. Inks for inkjet printing, which are composed of a solvent or the like as a material, are known, and various studies have been made to improve printing characteristics (ejection property, stability, viscosity, conductivity, dot formation). ..

By the way, even in such a case, since a water-insoluble resin is used as a resin component, characteristics such as visibility and stability may not yet be sufficient in terms of the content and the mixing ratio with the pigment. There is a demand for inks having even better characteristics.
That is, there is a demand for an ink that is edible, has excellent visibility, scratch resistance, and other stability after printing, and has good ejection properties during inkjet printing.

JP-A-2014-240386 Japanese Unexamined Patent Publication No. 2016-37566 Japanese Unexamined Patent Publication No. 2014-159520

The problem to be solved by the present invention is a coating film containing a pigment, a water-insoluble resin, and a solvent, which has good ejection properties during inkjet printing and has excellent visibility and scratch resistance after printing. The purpose of the present invention is to provide an ink composition for an inkjet in which a film can be obtained.

The non-aqueous inkjet ink composition of the embodiment contains at least one selected from a water-insoluble resin, a pigment, a first solvent consisting of ethanol, aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid. The mass ratio of the water-insoluble resin to the pigment is 2.0 to 7.5, which includes a mixed solvent mixed with a second solvent containing the pigment.

Hereinafter, the non-aqueous inkjet ink composition according to the embodiment will be described.
[Non-aqueous inkjet ink composition]
As described above, the non-aqueous inkjet ink composition of the present embodiment contains a water-insoluble resin, a pigment, and a mixed solvent, and each component will be described below individually.

(Water-insoluble resin)
The water-insoluble resin used in the present embodiment may be a resin capable of forming a dry film by drying, as long as it can impart a predetermined strength to the dried film and adhesion to a printed matter when printed. , A water-insoluble resin known in an ink composition used for inkjet printing. Further, this water-insoluble resin is preferably a resin that is harmless even when applied to foods, oral drugs, etc. and put into the human body, and more preferably an edible resin.

Examples of the water-insoluble resin used here include cellulose, cellulose derivatives, brazing materials, xanthan gum, starch, processed starch, amylopectin, gum arabic, gelatin, processed gelatin, silicone resin, canten, vinyl polymer, polyethylene and polyethylene. Examples thereof include derivatives, acrylic resins, and other natural polymers derived from animals and plants.

Cellulose is a processed product of a water-insoluble fibrous substance mainly collected from plants. As the cellulose, those having various molecular weights, particle sizes, and crystals can be used, but they can be appropriately selected according to the purpose of use, the dispersibility of the pigment in the dry film is good, and the physical properties of the dry film are good. From the viewpoint of good results, low molecular weight ones are preferable. Examples of this cellulose include crystalline cellulose, cellulose nanofibers, cellulose nanocrystals, and the like.
Cellulose is a preferable component in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

Cellulose derivatives are modified celluloses in which the functional groups of cellulose are replaced with organic groups. As this cellulose derivative, those having various molecular weights and substitution rates can be used, but they can be appropriately selected according to the purpose of use, the dispersibility of the pigment in the dry film is good, and the physical properties of the dry film are good. From the viewpoint, the one having a low molecular weight is preferable. Examples of this cellulose derivative include methyl cellulose, ethyl cellulose, ethyl methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, carboxymethyl ethyl cellulose, carmellose potassium salt, carmellose calcium salt, and carmellose sodium. Examples thereof include salts, cellulose acetate, hypromellose acetate succinate, hypromellose phthalate, and croscarmellose sodium salt.
The water-insoluble cellulose is a preferable component in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

Wax is a water-insoluble oil-like substance with a high melting point. In addition to being collected from animal and plant oils and fats, waxy paraffin-based wax obtained during fractional distillation of crude oil, synthetic materials from paraffin, and animal and plant-derived oils and fats are used. Includes processed materials. As the brazing material, those having various molecular weights can be used, and can be appropriately selected depending on the purpose of use. Examples of this wax material include carnauba wax, honey wax, sardine wax, serrac, white serrac, micro serrac, hazerou, urshiro, palm wax, sugar cane, candelilla wax, mokuro, bita chocolate, whale wax, vine oil, yomo wax, synthetic wax, and monttan. Wax, paraffin, hard wax, hardened oil, soybean hardened oil, polyethylene hardened castor oil, cacao butter, caster wax, cetanol, stearyl alcohol, cetostearyl alcohol, stearic acid, stearate, glycerin monooleate, sorbitan monooleate , Aluminum monostearate, glycerin monostearate, sorbitan monostearate, sorbitan monolaurate, montanic acid ester wax, glycerin fatty acid ester and the like.
The brazing material is a preferable component in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

Shellac resins such as shellac, white shellac, and micro shellac are edible resins obtained by purifying a resinous substance derived from shellac worms, and are mixed with various kinds of resin acids and their esterified products, waxes, pigments, and the like. It is preferable to use an alcohol-soluble type. As the shellac resin, it is preferable to use a purified shellac resin from which wax and pigments have been removed in advance from the viewpoint of having stable quality, and further, bleached white shellac is also preferable.

The shellac resin is a preferable resin in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

Modified starch is a processed material of starch collected from animals and plants. As the processed starch product, those having various molecular weights can be used, and can be appropriately selected depending on the purpose of use. Examples of this processed starch product include soluble starch, wheat starch, rice starch, potato starch, dried potato starch, corn starch, corn starch granules, pregelatinized starch, partially pregelatinized starch, and hydrolyzed starch-added light anhydrous silica. Examples thereof include acid, dried starch hydrolyzed product, sodium starch glycolate, and spherical starch granules.
The modified starch is a preferable component in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

The processed gelatin product is a processed material of gelatin collected from animals and plants. As the processed gelatin product, those having various molecular weights can be used, and can be appropriately selected depending on the purpose of use. Examples of this processed gelatin product include hydrolyzed gelatin, hydrolyzed gelatin powder, amberized gelatin, purified gelatin and the like.
The processed gelatin product is a preferable component in the present embodiment because the dispersibility of the pigment is good, the dry film thereof can be made to have water resistance, and the scratch resistance can be improved. It is also a component that is dissolved in a mixed solvent to adjust the viscosity of the ink composition.

The water-insoluble resin used here is preferably one whose use is permitted by the Food Sanitation Law or the Pharmaceutical Machinery Law. The water-insoluble resin preferably contains the above-mentioned shellac resin. When the shellac resin is contained in the resin, the content ratio of the shellac resin in the total material components other than the solvent is preferably 90% by mass or more, more preferably 92% by mass or more, still more preferably 95% by mass or more. At this time, water-insoluble cellulose is preferable as the resin component to be used in combination.

(Pigment)
As the pigment used in the present embodiment, a pigment known in the ink composition for an inkjet used for inkjet printing can be used. Further, this pigment is preferably a pigment that is harmless even when applied to foods, oral medicines and the like and put into the human body, and more preferably an edible pigment.

Examples of such pigments include black materials such as carbon powder (carbon powder), squid pigments, activated carbon and iron oxide; white materials such as titanium oxide and calcium carbonate; and aluminum lakes (red lakes and yellows) as food dyes. Lake, blue lake) and the like.

When a black material is used as the pigment, it is good for the pigment concentration and reflection concentration of the dry film, the identification of the dry film, the hardness of the dry film, and the printing effect (visibility by comparing the color of the base material). preferable. These pigments are preferably edible, and more preferably those permitted to be used by the Food Sanitation Law or the Pharmaceutical Machinery Law.

As the black material, charcoal powder pigment can be preferably exemplified as an edible pigment and an opaque material, and is preferable. The charcoal powder pigment is not particularly limited as long as it is approved as a food additive, and for example, one containing carbon obtained by carbonizing a plant as a main component can be used. As such a plant-derived charcoal powder pigment, roasted cacao fruit shells are generally known. And, for example, those obtained by heating a plant to a high temperature by a steam activation method and carbonizing it are also recognized as food additive pigments, and bamboo charcoal, which is a charcoal of bamboo, charcoal such as hardwood and conifer, etc. Can also be used as a vegetable charcoal powder pigment.

In the present embodiment, among the plant-derived charcoal powder pigments, those using broad-leaved trees such as oak, sardine, and kashiwa as raw materials are particularly preferable. In particular, it is more preferable to use Bincho charcoal obtained by using Umebakashi or the like. This Bincho charcoal is produced in Kishu and Tosa, and has a structure with many holes. It is presumed that this is related to the structure of the plant before carbonization, but due to having such a porous structure, the pigment required for printing by an inkjet printer despite being a very hard material. Can be made relatively easy. In addition, since Bincho charcoal has a large amount of carbon, it is easy to obtain a black feeling when it is made into ink. Bincho charcoal is also a material that has been used in foods and has a long history of culture. Therefore, it is also a valuable material that gives a sense of security when used in foods. Bincho charcoal is a material having a lower electrical resistance than bamboo charcoal, and is also a material that is not easily affected by static electricity in the production of an ink composition for an inkjet and is easy to handle.

Since such charcoal powder pigments such as Bincho charcoal are generally obtained in the form of lumps, they are roughly crushed by a crusher, and then finely divided for easy dispersion and used as carbon powder. To do. As such a miniaturization method, various general-purpose crushers due to mechanical impact can be used. Further, in order to further miniaturize, it is desirable to use a fine pulverizer such as a jet mill or a bead mill. In order to use it in an inkjet ink composition for inkjet printing, the charcoal powder dye finely pulverized in this way is used and dispersed in the above resin.

In order to use it as a material for an ink composition used for inkjet printing, the average particle size of the pigment used here is preferably 10 μm or less, more preferably 0.01 μm or more and 10 μm or less. By setting the average particle size to 10 μm or less, dispersion in the water-insoluble resin can be performed satisfactorily, and by setting the average particle size to 0.01 μm or more, the density in the printed portion after printing is secured and visibility is ensured. Can be good.
In the present specification, the average particle size means a volume average value in a volume-based particle size distribution obtained by using a laser diffraction / scattering type particle size distribution measuring device.

(Mixed solvent)
The mixed solvent used in the present embodiment includes a first solvent composed of ethanol and a second solvent containing at least one selected from aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid. , A solvent in which these are mixed is used. In addition, the inkjet ink composition of the present embodiment is a non-aqueous inkjet ink composition that does not contain water in the mixed solvent.

Here, the term "non-aqueous (not containing water)" means that the ink composition for an inkjet ink contains water that is inevitably contained, and does not contain any more water. Specifically, for a non-aqueous inkjet. It means that the water content in the ink composition is 5% by mass or less. The content of this water is preferably 3% by mass or less, and more preferably 1% by mass or less.

The first solvent composed of ethanol is mainly for dissolving a water-insoluble resin component, and is also a component for adjusting the viscosity of a non-aqueous inkjet ink composition. Ethanol has a viscosity of 1 mPa · s and a boiling point of 78 ° C.

The second solvent containing at least one selected from aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid dissolves the water-insoluble resin component in the same manner as ethanol, and makes the viscosity of the non-aqueous inkjet ink composition. It is also an ingredient to adjust.

The viscosity of this second solvent is preferably 2 to 100 mPa · s, more preferably 3 to 40 mPa · s. With such a viscosity, the viscosity of the mixed solvent mixed with the first solvent can be easily adjusted.

The boiling point of the second solvent is preferably 90 to 250 ° C, more preferably 100 to 150 ° C. By setting such a boiling point, the drying property of the mixed solvent mixed with the first solvent can be easily adjusted.

As the second solvent, aromatic alcohols are particularly preferable. Aromatic alcohols are compounds having an aromatic ring and an alcoholic hydroxyl group, and a compound having an organic group in which one or more hydrogens of alkyl groups having 1 to 10 carbon atoms are substituted with hydroxyl groups in the benzene ring is preferable, for example. Examples thereof include benzyl alcohol, phenethyl alcohol, 3-phenyl-1-propanol, phenoxyethanol, anis alcohol, and cinnamyl alcohol.

Then, by mixing these first solvent and the second solvent to prepare a mixed solvent, the resin component can be sufficiently dissolved, the viscosity of the non-aqueous inkjet ink composition is adjusted, and the drying property is further improved. Can be preferred. That is, a first solvent having a low boiling point and a second solvent having a higher boiling point can be mixed to have desired properties in terms of solubility, viscosity and drying property.

As the mixed solvent, when the mixed solvent is 100% by mass, it is preferable that the first mixed solvent is contained in the range of 5 to 80% by mass and the second mixed solvent is contained in the range of 20 to 95% by mass. By setting it in such a range, the balance of the above characteristics can be made good. In this content ratio, it is more preferable that the first solvent is 10 to 70% by mass and the second solvent is 30 to 90% by mass.

(Preparation of non-aqueous inkjet ink composition)
A non-aqueous inkjet ink composition can be obtained by mixing the water-insoluble resin, the pigment, the mixed solvent and other additive components to be blended as necessary, which have been described above individually. Examples of the additive component include talc, sugar, amino acid, silicate and the like. The content of the additive component is usually 20% by mass or less in the non-aqueous inkjet ink composition.

Further, the content ratio of each component contained in the non-aqueous inkjet ink composition is preferably in the following range.

The content ratio of the water-insoluble resin is preferably 0.5 to 30% by mass, more preferably 1 to 20% by mass in the non-aqueous inkjet ink composition. By setting this content ratio to 0.5% by mass or more, the dry film after printing can be thickened, and the fixability and scratch resistance of the pigment can be improved. By setting this content to 30% by mass or less, the water-insoluble resin can be sufficiently dissolved in the mixed solvent, and the viscosity of the non-aqueous inkjet ink composition can be adjusted within a dischargeable range.

The content ratio of the pigment is preferably 0.2 to 10% by mass, more preferably 1 to 5% by mass in the non-aqueous inkjet ink composition. By setting this content ratio to 0.2% by mass or more, the visibility of the printed portion can be sufficiently ensured and can be identified. By setting this content to 10% by mass or less, the pigment can be sufficiently dissolved in the mixed solvent, and the viscosity of the non-aqueous inkjet ink composition can be adjusted within a dischargeable range.

The content ratio of the mixed solvent is preferably 60 to 99.3% by mass, more preferably 80 to 99.3% by mass in the non-aqueous inkjet ink composition. By setting this content to 60% by mass or more, the resin component can be sufficiently dissolved in the mixed solvent, the pigment can be sufficiently dispersed, and the viscosity of the non-aqueous inkjet ink composition can be adjusted within a dischargeable range. it can. By setting this content ratio to 99.3% by mass or less, the ratio of the water-insoluble resin forming the coating film is secured, the amount of the dry film to be the printed portion is sufficient, and the desired printing is possible. it can.

Further, the present embodiment is characterized in that the mass ratio of the water-insoluble resin and the pigment described above is within a predetermined range. That is, the ratio of the mass of the water-insoluble resin to the mass of the pigment (mass of the water-insoluble resin / mass of the pigment) is set to 2.0 to 7.5. By setting this mass ratio to 2.0 or more, the strength of the dry film after printing can be increased, and the fixability and scratch resistance of the pigment can be improved. By setting it to 7.5 or less, the printed portion of the printed portion can be improved. Sufficient visibility can be ensured and can be identified.

By setting this mass ratio within the above range, the adhesion of the dry film of the ink on the surface of the printed matter and the hardness of the dry film are excellent, and transfer to the transfer machine and generation of stains in the transfer process of other printed matter and printed matter are suppressed. it can.

The non-aqueous inkjet ink composition obtained by mixing each of the above components preferably has a viscosity of 4 to 20 mPa · s, more preferably 5 to 15 mPa · s. Within such a range, the ejection stability by the inkjet can be improved and printing can be performed satisfactorily. The viscosity can be measured with a rotary viscometer, a vibration viscometer, or the like. In this specification, the viscosity is a value at 23 ° C.

Further, the surface tension of this non-aqueous inkjet ink composition is preferably 25 to 40 mN / m, more preferably 30 to 40 mN / m. Within such a range, the ejection stability by the inkjet can be improved and printing can be performed satisfactorily. The surface tension can be measured by a plate method, a ring method, a Young-Laplace method, a ds / de method, or the like. In this specification, the surface tension is a value at 23 ° C.

In producing the non-aqueous inkjet ink composition of the present embodiment, each of the above-described components may be mixed by a known method. As this mixing method, for example, a known kneader such as a pot mill, a ball mill, a bead mill, a roll mill, a homogenizer, a super mill, or a Raikai machine is used to knead the mixture at room temperature or under heating, and then dilute the solvent as necessary. And get it.

In the present embodiment, by making the ink composition non-aqueous, scratching caused by the printed ink composition being dissolved in water is suppressed, and scratch resistance is improved.
As described above, a non-aqueous solvent is used in this embodiment in order to dissolve the water-insoluble resin that can obtain scratch resistance after printing.

With ordinary inkjet inks, if the boiling point is too low, the ink dries and causes clogging in the head, and if the boiling point is too high, the ink does not dry quickly after printing, so the boiling point is in an appropriate range. Is required to have. Although it is possible to use an appropriate inkjet head that can handle inks having a low boiling point such as ethanol, a first containing at least one selected from ethanol and aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid as a non-aqueous solvent. A mixture of the two solvents is used, or a second solvent containing at least one selected from aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid is used as the non-aqueous solvent to have a boiling point in an appropriate range. May be adjusted to have.

Next, the present embodiment will be described based on the examples, but the present embodiment is not limited thereto.
(Examples 1 to 7, Reference Examples 1 to 4)
As raw materials, the materials shown below were weighed so as to have the compositions shown in Tables 1 and 2, mixed and stirred to produce a non-aqueous inkjet ink composition.

[Pigment]
Bincho charcoal (charcoal powder pigment, carbon powder) (average particle size: 0.7 μm)
[solvent]
Ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Benzyl alcohol (manufactured by Sankyo Chemical)
[Water-insoluble resin]
Shellac (manufactured by Japan Shellac Industry, product name: dry transparent white rack)

The obtained non-aqueous inkjet ink composition was printed and applied to the surface of a sugar-coated tablet using an inkjet printer, and dried at 40 ° C. to form a dry film.

[Characteristic]
(Visibility)
The printed performance of the obtained dry film was confirmed visually and with a microscope, and the visibility was evaluated according to the following criteria.
◯: Characters and round dot shapes can be recognized, ×: Characters and round dot shapes cannot be recognized due to bleeding (scratch resistance)
The obtained dry film was rubbed with a constant load and the scratch resistance was evaluated according to the following criteria.
◯: Dry film does not peel off or fall off, ×: Dry film peels off or falls off (IJ ejection property)
The obtained ink was ejected by an inkjet and the IJ ejection property was evaluated according to the following criteria.
◯: Can continue to discharge for a certain period of time, ×: Cannot discharge or cannot discharge within a certain period of time

From the results of the above Examples, it was confirmed that in Examples 1 to 7, all of the visibility, the scratch resistance and the IJ ejection property were good.

Although some embodiments of the present invention have been described above, these embodiments are shown as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

Claims (9)

A mixed solvent in which at least a water-insoluble resin, a pigment, a first solvent composed of ethanol, and a second solvent containing at least one selected from aromatic alcohols, propylene glycol, polyethylene glycol and acetic acid are mixed. , Including
A non-aqueous inkjet ink composition, wherein the mass ratio of the water-insoluble resin to the pigment is 2.0 to 7.5. The non-aqueous inkjet ink composition according to claim 1, wherein the pigment is an edible pigment selected from charcoal powder pigment, iron oxide, calcium carbonate, and aluminum lake as an edible pigment. The non-aqueous inkjet ink composition according to claim 2, wherein the average particle size of the pigment is 10 μm or less. The non-aqueous inkjet ink composition according to any one of claims 1 to 3, wherein the water-insoluble resin contains a brazing material and / or water-insoluble cellulose. The non-aqueous inkjet ink composition according to claim 4, which comprises any of shellac, white shellac, and micro shellac as the wax material. The non-aqueous inkjet ink composition according to any one of claims 1 to 5, which contains an aromatic alcohol having a boiling point of 90 to 250 ° C. as the second solvent. The mixed solvent is any one of claims 1 to 6, which contains 5 to 80% by mass of the first solvent and 20 to 95% by mass of the second solvent, assuming that the mixed solvent is 100% by mass. The non-aqueous inkjet ink composition according to the section. The water-insoluble resin is contained in an amount of 0.5 to 30% by mass, the pigment is contained in an amount of 0.2 to 10% by mass, and the mixed solvent is contained in an amount of 60 to 99.3% by mass in the non-aqueous inkjet ink composition. The non-aqueous inkjet ink composition according to any one of claims 1 to 7. The non-aqueous inkjet ink composition according to any one of claims 1 to 8, wherein the non-aqueous inkjet ink composition is edible.