JP2012025107A - Gravure printing method and printed material obtained by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gravure printing method which is heated by a dryer of a printer to complete cross-linking (curing) and requires no aging process, and exhibits excellent quick curability, good solvent resistance, and adhesion to a plastic film.SOLUTION: The gravure printing method includes: a process of printing on a printed body with a gravure printing ink composition made of (a) polyurethane/acrylic copolymer resin, (b) vinyl chloride/vinyl acetate copolymer resin, (c) polyisocyanate cross-linking agent, (d) metal chelate compound, and (e) solvent, wherein (a) polyurethane/acrylic copolymer resin and (b) vinyl chloride/vinyl acetate copolymer resin are contained at 70:30-30:70 in terms of weight (in a solid form); and a film cross-linking process by heating and drying a print film at 100-170°C for 10-15 sec. The printed material is obtained by the printing method.

Description

  The present invention is a gravure printing ink composition that has been crosslinked (cured) by a drying device of a printing press, has excellent rapid curability that does not require an aging process, has good solvent resistance, and has adhesion to a plastic film. The present invention relates to a gravure printing method for printed matter and a printed matter obtained by the method.

Conventionally, ink compositions containing polyurethane resins have been widely used for plastic film applications, and polyisocyanates have been used as crosslinking agents (curing agents) in polyurethane resins in order to obtain film properties such as solvent resistance.
Moreover, in order to accelerate | stimulate hardening by a hardening | curing agent, the tin compound etc. of the fatty acid were often mix | blended with resin. However, in order to obtain film properties such as solvent resistance in an ink composition containing a conventional polyurethane resin, it is necessary to manage the aging temperature and the aging time, for example, at room temperature for 7 days or at 40 to 50 ° C. Therefore, an aging process of about 24 to 48 hours was essential. When aging was not sufficient, the desired solvent resistance could not be obtained.

Various methods have been studied to reduce the aging time, such as using highly reactive xylene diisocyanate as a curing agent and increasing the amount of metal catalyst such as dibutyltin dilaurate. There was a drawback that the usage time was shortened.
Japanese Patent Laid-Open No. 5-97952 discloses a curing system using polyisocyanate and a metal chelating agent. Although the pot life is long, the ink film is cured in a short time at the temperature of the dryer. It was difficult.

Japanese Patent Laid-Open No. 5-97952

  Solves the problems of conventional gravure printing ink compositions using polyurethane resin, crosslinks are completed in a drying machine of a printing press, has excellent fast curability that does not require an aging process, has good solvent resistance, and It aims at providing the gravure printing method using the gravure printing ink composition which has adhesiveness to a plastic film, and the printed matter obtained by this method.

  As a result of intensive studies to solve the above problems, the inventors of the present invention include a polyurethane / acrylic copolymer resin and a vinyl chloride / vinyl acetate copolymer resin in a gravure printing ink composition, and a crosslinking agent (curing agent). By using a polyisocyanate and a metal chelate compound in combination, the printing film is heated at a temperature of 100 ° C. to 170 ° C. for 10 seconds to 15 seconds to complete crosslinking in the drying apparatus of the printing press, and does not require an aging process. It has been found that it has excellent curability, good solvent resistance, and adhesion to a plastic film, and has led to the present invention.

  In the present invention, a polyurethane / acrylic copolymer resin (a), a vinyl chloride / vinyl acetate copolymer resin (b), a polyisocyanate crosslinking agent (c), a metal chelate compound (d), a solvent ( e), and a polyurethane / acrylic copolymer resin (a) and a vinyl chloride / vinyl acetate copolymer resin (b) are printed with a gravure printing ink composition having a weight conversion (solid) of 70:30 to 30:70. A gravure printing method comprising: a step of performing coating, and then a step of crosslinking the coating film by heating and drying at a temperature of 100 ° C. to 170 ° C. for 10 seconds to 15 seconds.

The polyurethane / acrylic copolymer resin (a) has a crosslinkable functional group, has a weight average molecular weight of 30,000 to 70,000, a hydroxyl value of 20 to 60 mgKOH / g, and a ratio of polyurethane to acrylic of 30/70. The gravure printing method is characterized by being 50/50.

Further, the gravure printing ink composition having a number average molecular weight of 25,000 to 50,000 and a hydroxyl value of 60 to 180 mgKOH / g of the vinyl chloride / vinyl acetate copolymer resin (b) is used. It is a gravure printing method.

  The gravure printing method is characterized in that the polyisocyanate crosslinking agent (c) is a burette type of hexamethylene diisocyanate, and its blending amount is 20 to 50% by weight based on the resin solid content in the ink. .

  The metal chelate compound (d) is titanium tetrakisacetylacetonate, and the amount of the chelate compound is 1.5 to 6.0% by weight based on the resin solid content in the ink. It is a gravure printing method.

  Moreover, it is a gravure printed matter obtained by the gravure printing method.

  In the gravure printing ink composition of the present invention, crosslinking (curing) of the printed film is completed by applying heat of 100 ° C. to 170 ° C. with a drying device of a printing press, and the aging process required for conventional products is not necessary. It is useful for improving productivity.

The gravure printing ink composition of the present invention comprises 70/70 polyurethane / acrylic copolymer resin (a) and vinyl chloride / vinyl acetate copolymer resin (b) in order to develop solvent resistance only with a drying device on a printing press. : Used in an amount to give a weight ratio of 30 to 30:70. Preferably, the weight ratio of polyurethane / acrylic copolymer resin (a) and vinyl chloride / vinyl acetate copolymer resin (b) is 50:50 to 70:30. By blending at this weight ratio, the cross-linking (curing) property becomes the highest, and sufficient solvent resistance is exhibited by heating in a short time.
When the polyurethane / acrylic copolymer resin (a) and the vinyl chloride / vinyl acetate copolymer resin (b) are in a weight ratio of 100: 0 to 70:30, it is difficult to obtain sufficient solvent resistance.
When the weight ratio of the polyurethane / acrylic copolymer resin (a) and the vinyl chloride / vinyl acetate copolymer resin (b) is 30:70 to 0: 100, the ink composition becomes a gel state in a short time after the curing agent is blended. .

Examples of the polyurethane / acrylic copolymer resin (a) used in the present invention include Polym. Bull. , 8, 239 (1982), a polyurethane / acrylic graft copolymer resin which can be used as a one-component type by chemically bonding a polyurethane segment and an acrylic segment, ethylene disclosed in JP-A-10-1524 A polyurethane / acrylic copolymer resin in which a vinyl monomer containing a (meth) acrylic acid ester is polymerized with a polymer linear polyurethane having an unsaturated double bond group at both ends can be used.
As the polymer component of the polyurethane, polycarbonate polyol, polyether polyol, polyester polyol and the like can be used.

The polyurethane / acrylic copolymer resin preferably has a crosslinking group, and the crosslinking group is a hydroxyl group or a carboxyxyl group, preferably a hydroxyl group.
The hydroxyl value is preferably 20 to 60 mgKOH / g. If it is 20 mgKOH / g or less, it becomes difficult to obtain sufficient solvent resistance, and if it is 60 mgKOH / g or more, the pot life after blending the curing agent is shortened.
The weight average molecular weight of the polyurethane / acrylic copolymer resin (a) is preferably 30,000 to 70,000. If it is 30,000 or less, transfer (blocking) of the ink film to the printed back surface occurs, and it becomes difficult to obtain sufficient solvent resistance, and if it is 70,000 or more, the usable time after blending the curing agent is shortened.
The ratio of polyurethane / acryl is preferably 50:50 to 30:70. Polyurethane /
When the acrylic ratio is 100: 0 to 50:50, the ink film is transferred (blocked) to the back side of the print, and when the polyurethane / acryl ratio is 30:70 to 0: 100, the plastic film as a printing medium is sufficient. It becomes difficult to obtain a good adhesion.

The vinyl chloride / vinyl acetate copolymer resin (b) used in the present invention includes vinyl chloride / vinyl acetate copolymer resin, vinyl chloride / vinyl acetate / polyvinyl resin copolymer resin, vinyl chloride / vinyl acetate / maleic acid copolymer. Examples thereof include resins and vinyl chloride / vinyl acetate / acrylic acid copolymer resins, and one or more of them are used. In particular, it preferably has a crosslinking group such as a carboxyl group or a hydroxyl group, and a vinyl chloride / vinyl acetate / polyvinyl resin copolymer resin containing a hydroxyl group is suitable.
The hydroxyl value is preferably 60 to 180 mgKOH / g. If it is 60 mg KOH / g or less, it will be difficult to obtain sufficient solvent resistance, and if it is 180 mg KOH / g or more, the viscosity of the ink composition will increase markedly, and the ink composition will gel in a short time after blending the curing agent. It becomes a state.
The number average molecular weight of the vinyl chloride / vinyl acetate copolymer resin (b) is preferably 25,000 to 50,000. If it is 25,000 or less, transfer (blocking) of the ink film to the back side of the print occurs and it becomes difficult to obtain sufficient solvent resistance. If it is 50,000 or more, the usable time after blending the curing agent is short. Become.

The polyisocyanate crosslinking agent (c) is used for the curing agent of the present invention. Examples thereof include adduct types such as hexamethylene diisocyanate, isopolone diisocyanate, and xylene diisocyanate, polyisocyanate prepolymers such as a burette type and a trimer type, and one or more of these are used.
From the viewpoint of solvent resistance and pot life, hexamethylene diisocyanate is preferred as the isocyanate. The blending ratio of the polyisocyanate crosslinking agent (c) is preferably 20 to 50% by weight based on the resin solid content in the ink.
If it is 20% by weight or less, it becomes difficult to obtain sufficient solvent resistance, and if it is 50% by weight or more, the usable time after blending the curing agent becomes extremely short, causing problems in practical use.

Examples of the metal chelate compound (d) used in combination with the polyisocyanate crosslinking agent (c) include tetraisopropoxy titanium, tetra-n-butoxy titanium, and titanium tetrakis acetylacetonate.
Titanium tetrakisacetylacetonate is preferred from the standpoint of solvent resistance and stability when blended with a crosslinking agent (curing agent). The compounding ratio of the metal chelate compound (d) is desirably 1.5 to 6.0% by weight based on the resin solid content in the ink. If it is 1.5% by weight or less, it becomes difficult to obtain sufficient solvent resistance, and if it is 6.0% by weight or more, the ink composition becomes a gel state in a short time after blending the curing agent.

In the combination of the polyisocyanate crosslinking agent (c) and the metal chelate compound (d), it is necessary to cure the resin at a predetermined temperature in a short time. For this purpose, it is necessary that the polyisocyanate crosslinking agent (c) and the metal chelate compound (d) are uniformly dispersed in the ink film in a short time and the reaction with active hydrogen such as a hydroxyl group proceeds smoothly. In particular, even after the solvent is volatilized, an appropriate resin flexibility is required, and the metal chelate compound (d) and the polyisocyanate crosslinking agent (c) are sufficiently uniformly dispersed in the resin while the ink film is cured. It is necessary to
In general, the crosslinking and curability of the resin are expressed by the crosslinking density per unit volume and depend on the addition amount of the curing agent, the number of functional groups of the curing agent, the amount of binder resin used as a reaction partner of the curing agent, the number of functional groups, and the like. However, in order to crosslink at a predetermined temperature and time, not only the crosslinking density but also the flexibility derived from the chemical structure of the resin itself is effective.
In the present invention, the use of the urethane / acrylic resin (a) and the vinyl chloride / vinyl acetate copolymer (b) enables the ink film to be cured in a short time at a specific temperature.

  Examples of the solvent (d) used in the ink composition of the present invention include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and organic solvents such as esters such as ethyl acetate and N-propyl acetate. Available. In order to develop stable solvent resistance, it is desirable that the ink composition does not contain an alcohol solvent such as isopropanol or normal propanol.

The gravure printing ink composition used in the present invention can contain a wax component for the purpose of improving film physical properties such as friction resistance. Various known waxes such as polyethylene wax and paraffin wax can be used as the wax.
Furthermore, various ink additives such as a pigment dispersant, a leveling agent, and a surfactant can be added.

In gravure printing, ink is filled in the recesses that become the image areas carved on the surface of the cylindrical cylinder, and after removing the ink in the non-image areas with a metal plate called a doctor, the ink remaining in the cylinder recesses is printed on paper. Or a printing method in which an image is formed by transferring to a printing material such as a plastic film.
The amount of ink is controlled by the depth of the recess to express the shade of the printed image, and it is widely used for printing food packaging.
A conventional gravure printing method can be used as it is for the gravure printing ink composition of the present invention.

In the gravure printing ink composition of the present invention, the crosslinking (curing) of the gravure-printed film is completed by heating and drying at a temperature of 100 ° C. to 170 ° C. for a time of 10 seconds to 15 seconds with a drying device of a printing press. . When the drying temperature is 100 ° C. or lower, it is difficult to obtain sufficient solvent resistance, and when the drying temperature is 170 ° C. or higher, the plastic film as the printing medium may be deformed.
As an example of the drying device, when the printing speed is 150 m / min, the drying device of the printing machine needs to have a length of 30 m or more. The inside of the drying device is divided into 5 to 6 zones, and it is desirable that the temperature gradient be provided. Although the cured state varies depending on the thickness of the ink film, a film thickness of 2 μm or less / layer by normal gravure printing is preferable.

As the printing material to which the gravure printing method of the present invention is applied, it is desirable that there is no deformation due to heat, and for example, a polyethylene terephthalate (PET) film which is a general-purpose plastic film is suitably used. Other plastic films include polybutylene terephthalate (PBT). It is preferable that the air volume in drying is 30 to 70 m ³ / min.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In this example, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.

Example 1
<Preparation of vinyl chloride / vinyl acetate copolymer resin (b) varnish>
25 parts of vinyl chloride / vinyl acetate / polyvinyl alcohol copolymer resin (= 88/1/11, hydroxyl value 166 mgKOH / g, number average molecular weight 28,000) are mixed and dissolved in 75 parts of ethyl acetate to give a test chloride. A vinyl / vinyl acetate copolymer resin varnish (resin varnish b1, solid content 25% by weight) was obtained.
25 parts of vinyl chloride / vinyl acetate copolymer resin (= 86/14, hydroxyl value 0 mgKOH / g, number average molecular weight 25,000) are mixed and dissolved in 75 parts of ethyl acetate, and vinyl chloride / vinyl acetate copolymer resin for test is used. A varnish (resin varnish b2, solid content 25% by weight) was obtained.

Examples 2-7, Comparative Examples 1-4
For Examples 2 to 7 and Comparative Examples 1 to 4, in the same manner as in Example 1, the above vinyl chloride / vinyl acetate copolymer resin and polyurethane / acrylic copolymer resin were used. The materials shown were kneaded with a sand mill, and further a curing agent and a crosslinking agent were blended to obtain a printing ink composition of the present invention.
In addition, the following were used as a polyurethane / acrylic copolymer resin varnish (resin varnish a1), (resin varnish a2), a pigment, a lubricant, a solvent, a curing agent, and a crosslinking agent.

Resin varnish a1: Polyurethane (polyester) / acryl = 30/70, solid content 40%, hydroxyl value 42.5 mgKOH / g (solid content conversion), weight average molecular weight 30,000, manufactured by Taisei Fine Chemical Co., Ltd. Resin varnish a2 : Polyurethane (polyester) / acrylic = 50/50, solid content 40%, hydroxyl value 0 mgKOH / g (solid content conversion), weight average molecular weight 30,000, “Acryt 8UA-140” manufactured by Taisei Fine Chemical Co., Ltd.
Pigment: Lionol Blue 7358 (Toyo Ink Manufacturing Co., Ltd.)
Lubricant: High flat T10P4 (Gifu Shellac Manufacturing Co., Ltd.)
Solvent: Methyl ethyl ketone Polyisocyanate crosslinking agent A: Burette type of hexamethylene diisocyanate Polyisocyanate crosslinking agent B: Bullet type of hexamethylene diisocyanate Metal chelate compound: Titanium tetrakisacetylacetonate

  Using the adjusted test gravure printing ink composition, a corona discharge-treated polyester film (Lumirror S10, manufactured by Toray Industries, Inc.) is printed using a gravure proofing machine, and 90 ° C, 105 ° C, 120 ° C in a drying oven. After heating at each temperature of 165 ° C. for 12 seconds, re-solubility, solvent resistance, and pot life were evaluated by the following methods.

The test gravure printing ink composition diluted with a mixed solvent of methyl ethyl ketone and toluene was allowed to stand at room temperature for 6 hours in a sealed state at room temperature, and pot life was evaluated by the following method.
The evaluation results of each test gravure printing ink composition are shown in Table 1.

(Resolubility evaluation)
Re-solubility: Using a prepared test gravure printing ink composition, it was applied to a polyester film treated with corona discharge (Lumirror S10, manufactured by Toray Industries, Inc.) with a # 6 Miya bar, and 50 ° C.
After drying in an oven for 20 seconds, a mixed solvent of methyl ethyl ketone: toluene = 50: 50 was sprayed with a Komagome pipette to evaluate the degree of dissolution of the ink film.
The standard of solubility is shown.
◯: Ink film dissolves easily when sprayed with solvent △: Ink film dissolves after a while after spraying solvent ×: Ink film does not dissolve at all even when sprayed with solvent

(Solvent resistance evaluation)
Solvent resistance: Using a Gakushin type friction tester, the printed surface was rubbed with a cotton cloth moistened with a mixed solvent of ethyl acetate: isopropyl alcohol = 50: 50, and the number of printed designs was evaluated.
The standard of solvent resistance is shown.
◯: The printed pattern does not disappear unless it is rubbed 70 times or more. Δ: The printed pattern disappears if it is rubbed 50 to 60 times. ×: The printed pattern disappears if it is rubbed 30 to 40 times.

(Evaluation of pot life)
Pot life: after diluting a test printing ink composition containing a curing agent and a cross-linking agent with a solvent of methyl ethyl ketone: toluene = 65: 35, the solution viscosity after 6 hours at room temperature storage is Zaan Cup # 3 manufactured by Kouaisha Measured with
The evaluation standard of pot life is shown.
○: Almost no change in viscosity even after 6 hours of blending of curing agent and crosslinking agent Δ: Thickening of about 5 to 10 seconds is observed after 6 hours of blending of curing agent and crosslinking agent ×: 1 hour after blending of curing agent and crosslinking agent By the time the ink becomes extremely thick or gelled

  In Table 1, the resin composition ratio indicates polyurethane / acrylic copolymer resin (a) / vinyl chloride / vinyl acetate copolymer resin (b), * 1 is 27.8% by weight based on the resin solid content in the ink, * 2 is 5.5% by weight based on the solid content of the resin in the ink.

In the gravure printing method of the present invention, as a gravure printing ink composition, a polyisocyanate crosslinking agent (c) and a metal chelate compound (c) are added to a polyurethane / acrylic copolymer resin (a) and a vinyl chloride / vinyl acetate copolymer resin (b). d), using the solvent (d), after printing, is heated and dried at a temperature of 100 ° C. to 170 ° C. for a time of 10 seconds to 15 seconds, and is excellent in rapid curability as compared with an ink composition containing a conventional polyurethane resin, Crosslinking (curing) is completed by the drying device of the printing press.
In order to obtain film properties such as solvent resistance with an ink composition containing a conventional polyurethane resin, an aging step necessary is eliminated. Therefore, in addition to cost reduction by improving productivity, it is useful for shortening the delivery time by eliminating the aging process.

Claims (6)

  It consists of polyurethane / acrylic copolymer resin (a), vinyl chloride / vinyl acetate copolymer resin (b), polyisocyanate crosslinking agent (c), metal chelate compound (d), and solvent (e) on the substrate. A step of printing with a gravure printing ink composition in which the polyurethane / acrylic copolymer resin (a) and the vinyl chloride / vinyl acetate copolymer resin (b) are 70:30 to 30:70 in terms of weight (solid), A gravure printing method characterized by comprising a film crosslinking step by heating and drying a printed film at a temperature of 100 ° C to 170 ° C for a time of 10 seconds to 15 seconds. The polyurethane / acrylic copolymer resin (a) has a crosslinkable functional group, has a weight average molecular weight of 30,000 to 70,000, a hydroxyl value of 20 to 60 mgKOH / g, and a ratio of polyurethane to acrylic of 30/70 to 50 The gravure printing method according to claim 1, which is / 50. A gravure printing ink composition having a number average molecular weight of 25,000 to 50,000 and a hydroxyl value of 60 to 180 mgKOH / g of the vinyl chloride / vinyl acetate copolymer resin (b) is used. The gravure printing method as described. The gravure printing method according to claim 1, wherein the polyisocyanate crosslinking agent (c) is a burette type of hexamethylene diisocyanate, and the blending amount thereof is 20 to 50% by weight with respect to the resin solid content in the ink. .   2. The metal chelate compound (d) is titanium tetrakisacetylacetonate, and the amount of the chelate compound is 1.5 to 6.0% by weight based on the resin solid content in the ink. The gravure printing method as described.   A gravure print obtained by the gravure printing method according to claim 1.