JP5926630B2 - Liquid ink - Google Patents

Description

The present invention relates to a liquid ink composition excellent in printability, storage stability, laminate properties, and two-component stability without using toluene as a solvent in gravure printing or flexographic printing, and a printed matter using the liquid ink.

  The liquid ink for laminating mainly used for the production of soft packaging materials mainly uses urethane resin or urethane urea resin as a main component as a resin binder. Furthermore, in recent years, the use of toluene is being restricted from the viewpoints of both occupational hygiene during printing and the harmfulness of packaging materials. This toluene-free liquid ink has adhesiveness to various film materials and suitability for lamination, Polyurethane polyurea resin is used as a resin main component from the viewpoint of printability, and instead of toluene, acetates such as ethyl acetate and propyl acetate or mixed solvents of acetates and ketones tend to be used. is there.

  For example, a binder for printing ink that contains phosphate esters in a polyurethane resin solution and is excellent in stability over time is disclosed (for example, see Patent Document 1). However, it is difficult to obtain sufficient aging stability and two-component stability with phosphate esters, and more effective improvement measures have been demanded in recent years when it is essential to use a toluene-free ink.

JP 2002-284984 A

  An object of the present invention is to provide a liquid ink generically called gravure ink and flexo ink, which are low-viscosity liquid inks that are excellent in printability, storage stability, laminate physical properties, and two-component stability without using toluene as a solvent. It is in. Moreover, it is providing the printed material using this ink.

  The present invention examines the blending components and balance of resin and volatile solvent components, and is a liquid ink that satisfies the basic properties of ink at the time of printing without using toluene from the environmental, hygiene and safety aspects. Is found. As a result of intensive studies to solve the above-mentioned problems, the present inventor did not use toluene while satisfying the printability and basic characteristics of the ink at the time of printing, when a specific binder resin was added to the liquid ink. Both found that storage stability, laminate physical properties, and two-component stability were improved, and the invention was completed.

  That is, the present invention is firstly a liquid ink having a binder resin and a solvent, wherein the binder resin is a polyurethane resin and / or a polyurethane polyurea resin, and the above-mentioned binder resin component contains styrene-free maleic anhydride. A liquid ink containing 0.01 to 5.0% by weight of an acid resin, and a printed matter obtained by printing using the liquid ink are provided.

  According to the present invention, it is possible to obtain a liquid ink that can be printed without using toluene while maintaining excellent printability, storage stability, laminate physical properties, and two-component stability.

  The present invention is a liquid ink having a binder resin and a solvent, wherein the binder resin is a polyurethane resin and / or a polyurethane polyurea resin, and a styrene maleic anhydride resin is 0.01 to in the binder resin component. A liquid ink containing 5.0% by weight is provided.

  The binder resin component used in the liquid ink of the present invention is a polyurethane resin and / or a polyurethane urea resin having a urea bond, and a styrene maleic anhydride resin in the binder resin component is 0.01 to It is essential to use 5.0% by weight. These resins may be of a single type or a plurality of types.

  The number average molecular weight of the polyurethane resin and the polyurethane polyurea resin used in the liquid ink of the present invention is preferably in the range of 15,000 to 100,000. When the number average molecular weight of the polyurethane resin is less than 15,000, the resulting ink composition tends to have low blocking resistance, laminate strength, chemical resistance, and the like. There is a tendency that the viscosity of the obtained ink composition becomes high and a predetermined printing density cannot be obtained.

  When a specific anhydrous styrene maleic resin, which is essential as a binder resin component used in the liquid ink of the present invention, is added to the polyurethane polyurea resin, the viscosity of the ink is stabilized and the two-component stability can also be improved. In the past, it was possible to suppress viscosity reduction by adding malic acid, phosphoric acid ester, etc., but addition of an appropriate amount of a specific styrene maleic anhydride resin improves viscosity reduction and in addition isocyanate Viscosity stability (two-component stability) when a curing agent is added is also improved.

Suitable anhydrous styrene maleic resin for use in the liquid ink of the present invention includes an acid value of 95 to 120 (mg KOH / g), a glass transition point (Tg) of 95 to 120 ° C.,
A number average molecular weight in the range of 3,000 to 20,000 is preferred. If the number average molecular weight is less than 3,000, the film strength after printing tends to decrease. Conversely, if the number average molecular weight is 20,000 or more, the adhesion to the substrate is inhibited and the laminate strength decreases. . Furthermore, the addition amount of the styrene maleic anhydride resin in the binder resin is preferably in the range of 0.01 to 5.0% by weight. When the amount of the styrene maleic anhydride resin is less than 0.01% by weight or more than 5.0% by weight, the stability of the ink itself and the storage stability of the two liquids are reduced due to a decrease in viscosity over time. However, there is a tendency that the printing quality and the retort resistance such as scum and plate fog are lowered. The styrene maleic anhydride resin may be added during the synthesis of the polyurethane resin to prevent the viscosity of the resin itself from being lowered, or may be added simultaneously with the raw materials during the production of the ink.

  For example, in the case of gravure printing, the content of the binder resin component in the liquid ink of the present invention is 5% by weight or more based on the total weight of the ink from the viewpoint of sufficient adhesion to the printing body of the gravure ink, From the viewpoint of moderate ink viscosity and work efficiency at the time of ink production and printing, it is preferably 25% by weight or less, and in the case of flexographic printing, it should be 5% by weight or more and 30% by weight or less based on the total weight of the flexographic ink. preferable.

The liquid ink of the present invention can contain water with a content of less than 10% by weight in the ink composition together with an organic solvent as a volatile component. Further, the range of 1 to 5% by weight is particularly preferable because printability is improved.
In this case, the water may be added to an organic solvent to form a water-containing organic solvent, or a specific amount of water may be added separately.

Further, in order to obtain heat resistance for the ink film, a resin having a urea bond such as the above-described resin is effective. At that time, urea bonds are bonded to each other by hydrogen bonds, so that the viscosity of the ink is increased and printability tends to be deteriorated. In order to prevent such a phenomenon, water is preferably contained in the ink composition at a content of less than 10% in order to reduce the viscosity of the resin bonded with urea bonds and hydrogen bonds. Moreover, it is also possible to reduce the used organic solvent component by addition of such water.
Furthermore, there is also a function of controlling the drying property of the ink by adding water. In particular, in the case of gravure printing, it is possible to clearly reproduce a gradation portion having a low ink transfer amount, which is a feature of the ink.

Furthermore, as the binder resin component used in the liquid ink of the present invention, a vinyl chloride-vinyl acetate copolymer resin can be added.
The vinyl chloride vinyl acetate copolymer resin used in the liquid ink of the present invention is obtained, for example, by copolymerizing vinyl chloride and vinyl acetate, and the resin may have a hydroxyl group. Such vinyl chloride vinyl acetate copolymer resin having a hydroxyl group is obtained by copolymerizing vinyl chloride and vinyl acetate resin and then introducing a hydroxyl group by partially hydrolyzing, or at the time of polymerization, vinyl chloride or vinyl acetate. It can be obtained by introducing a hydroxyl group by adding and copolymerizing a component having a hydroxyl group other than the above, for example, 2-hydroxyethyl methacrylate. A commercially available product may be used as the vinyl chloride / vinyl acetate copolymer resin having a hydroxyl group.
In the vinyl chloride vinyl acetate copolymer resin having a hydroxyl group, the properties of the resin film and the resin dissolution behavior are determined by the content ratio of the hydroxyl group-containing structure such as vinyl chloride skeleton, vinyl acetate skeleton, and vinyl alcohol skeleton. That is, vinyl chloride imparts toughness and hardness of the resin coating, vinyl acetate imparts adhesiveness and flexibility, and hydroxyl groups such as vinyl alcohol impart good solubility in polar solvents. In addition, it is preferable to contain 0.1 to 5.0 weight% in the said binder resin component.

  Examples of the colorant used in the liquid ink of the invention include organic and inorganic pigments and dyes used in general inks, paints, and recording agents. Organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dictopyrrolopyrrole, isoindoline, etc. Pigments. Indigo ink is copper phthalocyanine, and transparent yellow ink is C.I. I. Pigment No Yellow 83 is preferably used.

  For example, pigment C.I. I. Black7, Y12, Y13, Y14, Y17, Y83, Y74, Y-154, Y180, R57: 1, R122, R48: 1, R48: 2, R48: 3, R53: 1, R146, R-150 R-166, R170, R184, R185, V19, V23, V32, O13, O16, O34, G7, G36, B15: 3, B15: 4, W6 and the like.

  Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, bengara, aluminum, mica (mica), and the like. From the viewpoints of cost and coloring power, it is preferable to use titanium oxide for white ink, carbon black for black ink, aluminum for silver ink, and mica for pearl ink. Aluminum is in the form of powder or paste, but is preferably used in the form of paste from the viewpoint of handling and safety, and whether to use leafing or non-leafing is appropriately selected from the viewpoint of brightness and concentration. The colorant is preferably contained in an amount sufficient to ensure the density and coloring power of the ink, that is, in a proportion of 1 to 50% by weight based on the total weight of the ink. Moreover, a coloring agent can be used individually or in combination of 2 or more types.

  These organic pigments and inorganic pigments also have the effect of improving the drying properties and printing characteristics of the ink by the addition of the moisture described above.

(Normal production method)
The liquid ink of the present invention can be produced, for example, by adding a coloring pigment, an extender pigment, a solvent, and, if necessary, additives such as an antistatic agent, an antiblocking agent, a plasticizer, ink flowability, and the like to a polyurethane resin. Normal printing inks such as ball mills, attritors, and sand mills that use surfactants to improve dispersibility or resins that are compatible with polyurethane resins in a range where thickening and gelation do not occur over time. This is done by kneading using a production apparatus. In particular, the addition of an antistatic agent is effective in suppressing static electricity troubles during printing, called whiskers and lightning stripes, which are likely to occur when using ester solvents and ketone solvents.

  Examples of resins that can be used in combination with the binder resin include nitrified cotton, chlorinated polyethylene, chlorinated polypropylene, chlorinated polyolefins such as chlorinated ethylene / propylene, ethylene / vinyl acetate copolymers or chlorinated resins thereof, and vinyl chloride / acetic acid. Examples thereof include vinyl copolymers, rosin resins and modified products thereof, ketone resins, and cellulose resins.

  The present invention provides a printed matter obtained by printing the above-described liquid ink.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, "part" in an Example represents a mass part.

(Preparation of polyurethane resin A)
Number average obtained by reacting a mixture of ethylene glycol and neopentyl glycol (molar ratio = 1/1) with adipic acid in a four-necked flask equipped with a stirrer, thermometer, reflux condenser and nitrogen gas inlet tube A polyester diol having a molecular weight of 1,800 (605.9 parts) and isophorone diisocyanate (94/1 part) were charged and reacted at 90 ° C. for 10 hours under a nitrogen stream to produce a prepolymer having a free isocyanate value of 1.02% by weight. 300 parts of ethyl acetate was added to make a uniform solution of urethane prepolymer. Next, the urethane prepolymer solution was added to a mixture composed of 18.1 parts of isophoronediamine, 873 parts of ethyl acetate and 503 parts of IPA, and stirred and reacted at 45 ° C. for 8 hours to obtain a polyurethane polyurea resin solution. The resulting polyurethane polyurea resin solution (hereinafter referred to as polyurethane polyurea resin solution A) has a resin solid content concentration of 30.5% by weight, a viscosity of 850 mPa · S (25 ° C.), and the resin solid content Mw is 58,000. there were.

Examples 1-10, Comparative Examples 1-4
(Ink preparation method)
Mixtures mixed at the blending ratios shown in Tables 1 and 2 were kneaded using a dyno mill (manufactured by Willy et Bacofen) to prepare inks described in Examples 1 to 10 and Comparative Examples 1 to 4. .

  The following evaluation was implemented about Example 1-10 ink and Comparative Examples 1-4 which were obtained above.

(Viscosity measurement)
The ins described in Table 1 and Table 2 were used as Zaan Cup No. 4 was used to measure the viscosity at a liquid temperature of 50 degrees immediately after ink production.

(Viscosity stability)
The inks listed in Tables 1 and 2 were collected in glass bottles and stored at 50 degrees for 28 days. Thereafter, the viscosity was measured to evaluate the change in viscosity before storage.
(Evaluation)
5: No viscosity change Viscosity change is less than 2 seconds 4: Viscosity change is small Viscosity difference is 2 seconds or more and less than 5 seconds 3: Viscosity change is slightly large Viscosity difference is 5 seconds or more and less than 10 seconds 2: Viscosity change is large Viscosity Difference is 10 seconds or more and less than 15 seconds 1: Viscosity change is very large Viscosity difference is 15 seconds or more

(2 liquid stability)
The inks listed in Table 1 and Table 2 were collected in glass bottles, and CVL NO. 4 wt% of 10 hardener (isocyanate curing agent: manufactured by DIC) was added and stored at 50 degrees for 28 days. Thereafter, the viscosity was measured to evaluate the change in viscosity before storage.
(Evaluation)
5: No viscosity change Viscosity change is less than 2 seconds 4: Viscosity change is small Viscosity difference is 2 seconds or more and less than 5 seconds 3: Viscosity change is slightly large Viscosity difference is 5 seconds or more and less than 10 seconds 2: Viscosity change is large Viscosity Difference is 10 seconds or more and less than 15 seconds 1: Viscosity change is very large Viscosity difference is 15 seconds or more

(Printability test: Scratch test)
The inks listed in Tables 1 and 2 were diluted with the mixed organic solvent having the same ratio used for ink preparation, and diluted with Zaan Cup No. 3 manufactured by Koiso Co., Ltd. so as to be 16 seconds. Using a gravure printing machine (manufactured by DIC Engineering Co., Ltd.) to which a gravure plate having a plate depth of 3 μm is attached, biaxially stretched polyester film (Toyobo Co., Ltd., E-5100 thickness) The printing was performed on the treated surface having a thickness of 12 μm. And the transfer degree (scratch degree) of the ink to the printing part of printed matter was evaluated. In the blur test, evaluation was performed at a printing speed of 300 m / min at a circumference of 600 mmφ of the gravure plate. For the purpose of investigating changes over time, each of the ink immediately after production and the ink stored at 50 ° C. for 28 days were subjected to the test.
(Evaluation)
5: No blurring 4: Slightly blurring 3: Slight blurring, practical range 2: Scratching can be remarkably confirmed 1: Scratching occurs frequently

(Printability test: Plate fog test)
Of the printed matter when printed under the above-described blur test conditions, the degree of stain (plate fog) of the non-printed area was evaluated. For the purpose of investigating changes over time, each of the ink immediately after production and the ink stored at 50 ° C. for 28 days were subjected to the test.
(Evaluation)
5: Print stains None 4: Print stains can be confirmed slightly 3: Print stains Slightly confirmed, practical range 2: Print stains Remarkably occurring 1: Print stains

(concentration)
Using printed matter when printed under the above-mentioned blur test conditions, the reflection density of each printed matter was compared with a reflection densitometer X-RITE530.
For the purpose of investigating changes over time, each of the ink immediately after production and the ink stored at 50 ° C. for 28 days were subjected to the test.
(Evaluation)
○: Reflection density value is 2.0 or more Δ: Reflection density value is 1.5 or more and less than 2.0 ×: Reflection density value is less than 1.5

(Lamination strength)
A urethane-based adhesive is used for the printed matter, and an unstretched polypropylene film (Toray Synthetic Film ZK-) is produced by a dry laminating machine (manufactured by DIC Engineering) with a dry laminating adhesive Dick Dry LX-703VL / KR-90 (manufactured by DIC Engineering). 75 50 μm) was laminated, and the peel strength was measured after aging at 40 ° C. for 5 days. The determination criteria were as follows.
○: The laminate strength is 500 (g / 15 mm) or more, and the strength is sufficient.
(Triangle | delta): Laminate intensity | strength is 300 or more-less than 500 (g / 15mm), and intensity | strength is a little insufficient.
X: The laminate strength is less than 300 (g / 15 mm) and the strength is insufficient.

(Retort resistance)
After the above-mentioned printed matter was dry laminated, the laminate was made into a bag, and a water / salad oil mixture was added as the contents. After sealing, the laminate was heated at 120 ° C. for 30 minutes. The determination criteria were as follows.
For the purpose of investigating changes over time, each of the ink immediately after production and the ink stored at 50 ° C. for 28 days were subjected to the test.
○: There is no Lami float.
(Triangle | delta): Only a part was delaminated or the blister produced slightly.
X: Full surface delamination occurred.

The raw materials in the table are as follows.
Fastogen Blue 5380 (manufactured by DIC Corporation): C.I. I. Pig.
No. = B-15: 3
R-780 (Ishihara Sangyo Co., Ltd.) titanium oxide pigment: average particle size 0.24 μm, oil absorption 33
Solvein A (Nissin Chemical Industry Co., Ltd.) Vinyl chloride vinyl acetate copolymer resin:
Number average molecular weight 30,000, glass transition point 76 ° C., K value = 48
Resin composition; vinyl chloride / vinyl acetate / vinyl alcohol = 92/3/5 (weight ratio)
High loss X-228 (manufactured by Seiko PMC) Styrene maleic acid resin: acid value 140 (mg KOH / g), number average molecular weight 16,000, glass transition point 83 ° C.

  From the above results, it can be seen that the liquid ink of the present invention can maintain excellent printability, storage stability, laminate physical properties, and two-component stability without using toluene.

  The liquid ink of the present invention is a low-toluene type low-viscosity liquid ink in consideration of environmental and hygiene in gravure printing or flexographic printing, and flexible packaging for industrial products such as food packaging materials, sanitary products, cosmetics, and electronic parts. Can be widely deployed in applications.

Claims (4)

A liquid ink having a binder resin and a solvent, wherein the binder resin is a polyurethane resin and / or a polyurethane polyurea resin, and a styrene maleic anhydride resin is 0.01 to 5.0 weight in the binder resin component. % Liquid ink. The liquid ink according to claim 1, wherein the liquid ink contains less than 10% by weight of water in the composition of the liquid ink. The liquid ink according to claim 1, further comprising 0.1 to 5.0% by weight of vinyl chloride-vinyl acetate copolymer resin in the binder resin. The printed matter obtained by printing the liquid ink in any one of Claims 1-3.