JP4906426B2 - Corrugated cardboard printed matter and manufacturing method thereof - Google Patents

Description

The present invention relates to a corrugated cardboard printed material that has a clear print image by using an aqueous coating agent in advance when printing on the surface of the corrugated cardboard, and does not cause paper peeling during transportation, and a method for producing the corrugated cardboard printed material. About.

In recent years, dealing with environmental issues is becoming the most important issue that must be addressed by companies regardless of the type of business. For example, in the paper industry that uses wood pulp as a raw material, we are actively engaged in forest resource protection activities to prevent global warming, and pulped and made used paper (such as used paper and paperboard). Using recycled paper is one of those activities. In particular, in the corrugated cardboard industry, the percentage of waste paper used as a raw material exceeds 80%, and the number of times of recycling ranges from four to five times. Cardboard is considered to be used frequently.

However, every time the paper is repeatedly recycled, the strength is weak and the density of the fibers is sparse and the quality of the paper deteriorates. Therefore, usually, high-quality wastepaper is used as a raw material for medium-quality paper and low-grade paper, and that wastepaper is used as a raw material for lower-grade paper. (Cascade use). However, the waste paper used for corrugated cardboard is originally low-quality paper, or the corrugated cardboard itself is often reused repeatedly, and the paper quality is greatly deteriorated when the paper is repeatedly recycled many times.

As printing on such corrugated cardboard, a flexographic printing method is generally used in which water-based ink is printed with a rubber-like flexible letterpress. However, the cardboard that has been repeatedly recycled contains a large amount of paper dust on the paper surface, and if it accumulates on the printing plate surface, the intended cosmetic print cannot be obtained. Then, before paper dust accumulates, the operation | work which interrupts printing, wipes a plate, and removes paper dust is performed, but this operation reduces printing efficiency and becomes a big problem.

In addition to the problem of paper dust, when the degree of paper quality deterioration increases, there are many factors that make cosmetic printing difficult. For example, since low-viscosity ink is used in corrugated cardboard printing, problems such as blurring and faded printed matter occur. In addition, even if a beautiful printed matter is obtained, there is a problem that due to insufficient paper strength, the boxes are rubbed together during transportation, causing paper peeling and the like, resulting in a very unpleasant appearance when lined up at the storefront. .

On the other hand, the corrugated cardboard container functions as a display for enhancing the image of the contents, and the willingness to purchase is often influenced by how the container is printed. For example, in supermarkets and large stores, beverage cans such as beer are usually sold in a box. At this time, it is not difficult to imagine that the willingness to purchase will increase at once if there is a vividly printed pattern that reminds consumers of the thirst and the refreshing feeling when they are drunk. However, it is only possible to obtain a clear print. If the printed matter is blurred and faded, the precious design cannot be used, and the willingness to purchase is reduced. Along with the recent changes in distribution and sales forms, the field in which cardboard printing is strongly required to function as a display is increasing, and the cosmetic decoration of printing has become a very important issue.

As described above, environmental response is a social responsibility, and on the other hand, print quality is an important performance that affects the sales of products. Therefore, a technology that increases the strength of the paper surface is indispensable, using cardboard that has been repeatedly recycled to eliminate printing stains caused by paper dust, enabling clear printing without blurring or fading even with low-density paper. This cannot be done with the current printing method.

Previously, the applicant of the present application mainly used high-quality paper or paper using an aqueous solution containing a dissociable polyvalent metal salt in an aqueous solution in which a water-soluble resin such as water, an alcohol / water mixture, or polyvinyl alcohol is dissolved. The present inventors have found a method for preventing the back-through of an aqueous coating material to be applied and printed later by impregnating the metal salt into a thin paper such as exposed kraft paper (see Patent Document 1). However, even if the same method is used with a thick cardboard liner, there are problems that the effect of preventing bleeding is low and the printed matter is faded. Furthermore, satisfactory performance remains unobtainable, for example, it does not contribute to the enhancement of paper strength at all.
JP 9-31888 A

As explained earlier, in the corrugated cardboard industry, both the recycling of used paper and the decoration of printing must be realized at a higher level. It is extremely difficult at the technical level. Therefore, the problem to be solved by the present invention is to provide a corrugated printed matter that has a clear printed image and does not cause paper peeling even during transportation for a cardboard that has been recycled many times. It is.

In order to produce recycled paper, waste paper is disaggregated until it becomes fibrous (disaggregation process), foreign matter that causes dust is removed (dust removal process), and ink is peeled off and removed (deinking process). There are five steps: bleaching the fibers (bleaching step) and then making paper with a paper machine (paper making step). At this time, since the fibers of the paper are thinned and shortened mainly in the disaggregation step, the degree of adsorption between the fibers is weakened, and the strength and density of the recycled paper are both reduced. The specific compressive strength and wax pick value of the liner defined in the present invention are typical values of paper that has been repeatedly recycled many times.
In such a paper, at the stage of manufacturing corrugated cardboard, fibers on the surface of the paper are rubbed to generate a large amount of paper powder. This paper dust becomes scumming or uneven when it collects in the image area (part where the ink adheres) of the plate, and it becomes printing stains when it accumulates in the non-image area (area where the ink does not adhere). It causes deterioration of quality. Further, if the strength of the paper is weak, the paper may be peeled off due to the rubbing of the surface during transportation.

Therefore, first, in the present invention, before printing ink, using a method of applying a nonionic water-soluble resin to the paper surface, the paper powder is adhered to the paper surface, and the paper is not peeled off. Strengthen the paper surface. Furthermore, in the present invention, a dissociable polyvalent metal salt is used together, but the following effects can be obtained in combination with a water-soluble resin.
The ink used in the corrugated board printing has a very low viscosity so that the fluid component penetrates and quickly dries. Accordingly, in a liner having a weak paper fiber adsorption force and a low density, the ink penetrates deeply between the fibers over a wide range. As a result, there is a problem that bleeding easily occurs and the amount of the colorant component remaining on the paper surface decreases, resulting in a faded printed matter.

For a long time, for thin paper, by cross-linking and precipitating the acid group-containing binder resin of the water-based ink composition with a dissociable polyvalent metal salt, the solid content is partly retained on the paper surface to prevent back-through. Technology is known. However, in thick paper such as a liner, the aqueous solution of the dissociable polyvalent metal salt itself penetrates deeply into the paper, so the amount of active ingredient that acts as a cross-linking agent on the paper surface is reduced, and the expected effect is obtained. Results in not. In particular, if the density of paper fibers is sparse, this tendency becomes remarkable, and bleeding and fading are likely to occur.
In contrast, an aqueous solution containing a water-soluble resin and a dissociable polyvalent metal salt can be set to have a high viscosity, so that it can suppress penetration and act as a cross-linking agent closer to the surface of the paper, causing blurring and fading. Can be prevented. Further, by filling the water-soluble resin in the gaps between the paper fibers, the penetration of the ink can be further suppressed, and a printed matter having a clear and high color density can be obtained.

As described above, when printing on corrugated cardboard that has been regenerated a number of times and applying an aqueous solution of a nonionic water-soluble resin and a dissociable polyvalent metal salt in advance, bleeding and fading will occur even when printing with normal printing ink. It has been found that there is an effect that the strength of the paper surface can be greatly increased and paper dust does not adhere to the plate surface. And since it has all the conditions for solving said subject, this invention was completed.
That is, the present invention relates to (1) a cardboard printed matter in which at least one liner surface of a corrugated cardboard composed of a core and a liner is printed with an aqueous printing ink composition, wherein the liner has a specific compressive strength of 11 to 11. 13N · m ² / g, wax pick value is 20 or less, and after applying or printing an aqueous coating agent containing a cellulose derivative or an alkyl ketene dimer and a calcium salt as a dissociable polyvalent metal salt, an acid group-containing resin It is related with the corrugated cardboard printed matter printed by the water-based printing ink composition which uses as a binder.
The present invention also relates to (2) the corrugated cardboard printed matter according to the above (1), wherein calcium formate is used as the calcium salt.
In the present invention, the surface of the liner of the corrugated cardboard composed of ( 3 ) a core and a liner having a wax pick value of 20 or less and a specific compressive strength of 11 to 13 N · m ² / g, After coating or printing a cellulose derivative or an alkyl ketene dimer and an aqueous coating agent containing a calcium salt as a dissociable polyvalent metal salt, printing an aqueous printing ink composition using an acid group-containing resin as a binder. The present invention relates to a method for producing a featured cardboard printed matter.

The present invention is described in detail below.
In the present invention, the corrugated cardboard used as the printing medium is composed of a core and a liner. The liner has a specific compressive strength of 11 to 13 N · m ² / g and a wax pick value of 20. The following are used.
The specific compressive strength is a numerical value defined by the following formula using a test piece of 6 inches in the traveling direction when the liner is made and 1/2 inch in the direction perpendicular to the traveling direction.
Specific compressive strength (A) = S / W × 10
Here, S is JIS P 8126 (Paper and paperboard - compressive strength test method -) is a strong compression of the resulting test piece based on is, W is per 1 m ² of liner weight (basis weight).
The wax pick value is a value measured based on JIS P 8129 (paper and paperboard-paper peeling test method).
Corrugated cardboard usually has a structure in which both sides of a core are sandwiched between liners. The corrugated cardboard printed matter of the present invention is obtained by printing at least one liner surface with an aqueous printing ink composition.

Next, the aqueous coating agent applied in advance to the liner surface of the cardboard will be described.
As the nonionic water-soluble resin blended in the aqueous coating agent, a cellulose derivative or an alkyl ketene dimer is preferable. Examples of cellulose derivatives include lower alkyl group-substituted products such as methyl cellulose and ethyl cellulose, lower acyl group-substituted products such as cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate, and alkylene oxides such as cellulose ethylene oxide adducts. Cellulose alkylene oxide adducts added to can be used, and these can be used alone or in combination of two or more. Among the cellulose derivatives, a cellulose alkylene oxide adduct is preferable. There are various cellulose derivatives having different molecular weights and substitution degrees with respect to hydroxyl groups, and various cellulose derivatives are appropriately selected and used in accordance with the viscosity of the target aqueous coating agent.
The alkyl ketene dimer is represented by the following formula (1).

[Wherein, R ¹ and R ² each independently represent a hydrocarbon group having 8 to 30 carbon atoms. ]
Specific hydrocarbon groups of R ¹ and R ² in the general formula (1) include, for example, alkyl groups such as decyl, dodecyl, tetradecyl, hexadecyl, octadecyl; alkenyl groups such as eicosyl group; octylphenyl, nonylphenyl, etc. Examples thereof include an alkyl-substituted phenyl group; a nonylcyclohexyl group and the like.
The nonionic water-soluble resin is preferably used in an amount of 1 to 10% by mass in the aqueous coating agent.

Calcium salts to be blended as dissociable polyvalent metal salts in the aqueous coating agent of the present invention include inorganic acid salts such as calcium chloride, sulfate and nitrate, or organic acid salts such as acetate and formate. can give. Specifically, calcium acetate, calcium chloride, calcium formate, calcium nitrate, calcium sulfate and the like can be exemplified, and these can be used alone or in combination of two or more. The calcium salt is preferably calcium formate.
It is preferable to use 1 to 15% by mass of the calcium salt in the aqueous coating agent.

Furthermore, various additives, such as an antifoamer, a rust preventive agent, a water-miscible solvent, a plasticizer, and a wax, can be used as appropriate for the aqueous coating agent.
The aqueous coating agent contains a nonionic aqueous resin and a calcium salt in an aqueous medium. The aqueous medium may be water alone or in combination with a water-miscible organic dispersion medium.
The viscosity of the aqueous coating agent is not particularly limited as long as it can be applied or printed by a usual method such as flexographic printing. 4 is preferably 7 to 14 seconds.
The method for preparing the aqueous coating agent is not particularly limited, and a calcium salt and a cellulose derivative or an alkyl ketene dimer may be sequentially added and mixed in an aqueous medium.

Next, the aqueous printing ink composition will be described.
The aqueous printing ink composition used in the present invention contains an acid group-containing resin as a binder. As said acid group containing resin, what precipitates by presence of the calcium salt contained in the above-mentioned aqueous coating agent, for example is mentioned. Examples of such a resin include an aqueous resin that can be dissolved or dispersed in water in the presence of a basic compound and that can be dispersed in water in the presence of an emulsifier, as described in JP-A-09-31888. An aqueous resin is mentioned.

Specific examples of the aqueous resin that can be dissolved or dispersed in water in the presence of a basic compound include carboxyl group-containing resins having an acid value of 30 to 350, casein, and the like. Examples of the carboxyl group-containing resin include conventionally used styrene-maleic acid copolymers having an acid value of 30 to 350, styrene-acrylic copolymers, styrene-acrylic-maleic acid copolymers, acrylic resins, and the like. . Examples of basic compounds for dissolving or dispersing the carboxyl group-containing resin having an acid value of 30 to 350 of the present invention in water include ammonia, diethylethanolamine, dimethylethanolamine, triethylamine, tributylamine, morpholine, diethanolamine, and triethanolamine. Alternatively, a mixture of two or more of these can be used, but ammonia or a volatile amine is preferably used from the viewpoint of the drying property and water resistance of the aqueous coating agent. As casein, a conventionally known casein aqueous solution can be used.

As an aqueous resin dispersible in water in the presence of an emulsifier, a low molecular emulsifier (anion type, nonion type, cationic type) in which the interfacial potential of particles decreases or salting out in the presence of a dissociable polyvalent metal salt. Any of them may be used), and an aqueous resin dispersible in water in the presence of a polymer emulsifier (the carboxyl group-containing resin having an acid value of 30 to 350) can be used.

Furthermore, the above-mentioned water-based printing ink composition includes, if necessary, a printing ink such as a colorant; a gloss-imparting coating such as a high-gloss emulsion resin; a coating that imparts friction resistance such as a film-forming emulsion resin or wax. Agents; coating agents for imparting anti-slip properties such as inorganic anti-slip materials; pressure-sensitive adhesives, organic solvents, leveling agents, viscosity modifiers and the like can be appropriately blended.

The aqueous printing ink composition includes an acid group-containing resin in an aqueous medium, and examples of the aqueous medium include the same ones that can be used for an aqueous coating agent.
The aqueous printing ink composition of the present invention is prepared by mixing a colorant and various additives, if necessary, with an acid group-containing resin that precipitates due to the presence of a calcium salt, and using a disperser and a grinder. It can be performed according to conventional methods.

The corrugated cardboard printed matter of the present invention is coated or printed with a nonionic aqueous resin and an aqueous coating agent containing a calcium salt as a dissociable polyvalent metal salt in advance on the liner surface of the corrugated cardboard composed of a core and a liner. Then, it can be manufactured by printing an aqueous printing ink composition using an acid group-containing resin as a binder.
The method for coating or printing the aqueous coating agent and the aqueous printing ink composition is not particularly limited, and examples include air knife, roll coater, spray, gravure printing, flexographic printing and the like.
In the method of the present invention, it is preferable to print the aqueous printing ink composition after applying or printing the aqueous coating agent and then drying.

The corrugated cardboard printed matter of the present invention has a paper surface reinforced by coating or printing an aqueous coating agent containing a calcium salt and a nonionic water-soluble resin on the corrugated cardboard in advance, and the water-soluble resin is placed in the gap between the fibers of the paper. By clogging, the yield of a water-based printing ink composition to be printed later can be improved, and the water-based printing ink composition can be prevented from penetrating into the cardboard. Even if it is used, it has a clear printed image and does not peel off during transportation.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” means “mass%” and “parts” represents parts by mass.
(Examples 1-2, Comparative Examples 1-2)
Aqueous coating agents 1 to 4 were prepared according to the formulation in Table 1 and evaluated for viscosity, stability, and the like. The results are shown in Table 1.
<Evaluation method>
(viscosity)
The viscosity of water-based coating agents 1 to 4 was adjusted to the Zahn Cup No. The measurement was performed at 4 (manufactured by Koseisha Co., Ltd.), and ○ was the number of seconds (7 to 14 seconds) in which flexographic printing was possible, and x was the others.
(Stability)
The aqueous coating agents 1 to 4 were stored at 40 ° C. for 1 week.

Next, the above aqueous coating agents 1 to 4 are applied to low-grade paper (trade name: ETS160, manufactured by Rengo) with a glass bar, dried, and then an aqueous flexographic ink FK-99 (as an aqueous printing ink composition). Sakata Inx Co., Ltd.) was applied with a 165 line hand proofer, and the water rub resistance and yield were evaluated. The results are shown in Table 1.
<Evaluation method>
(Water and friction resistance)
Gakushin friction tester, using 5 drops of water on gauze as a friction material, a friction test is performed under a load of 200 g and 10 reciprocations, and no aqueous coating agent is applied. Based on the above, the water rub resistance was evaluated as ◯, and the same or lower than the standard as x.
(Yield)
The yield was confirmed by visual observation, and the case where the aqueous printing ink composition had an effect of suppressing the penetration into the corrugated cardboard was rated as ◯, and the case where it was not was rated as x.

From the results in Table 1, the following was found.
Example 1 using an aqueous coating agent 1 containing a calcium salt and a cellulose derivative as an aqueous coating agent, and Example 2 using an aqueous coating agent 2 containing a calcium salt and an alkyl ketene dimer, It was excellent in evaluation items.
On the other hand, Comparative Example 1 using an aqueous coating agent 3 containing polyvinyl alcohol instead of a cellulose derivative or an alkyl ketene dimer is inferior in water rub resistance and yield when an aqueous printing ink composition is applied, The comparative example 2 using the aqueous coating agent 4 which mix | blended polyacrylamide instead of the cellulose derivative or the alkyl ketene dimer had the bad viscosity and stability of an aqueous coating agent, and is a case where the aqueous printing ink composition is applied. The yield was also inferior.

The corrugated cardboard printed matter of the present invention has a paper surface reinforced by coating or printing an aqueous coating agent containing a calcium salt and a nonionic water-soluble resin on the corrugated cardboard in advance, and the water-soluble resin is placed in the gap between the fibers of the paper. By clogging, the yield of a water-based printing ink composition to be printed later can be improved, and the water-based printing ink composition can be prevented from penetrating into the cardboard. Even if it is used, it has a clear printed image and does not peel off during transportation.

Claims (3)

In the corrugated cardboard printed matter in which at least one liner surface of the corrugated cardboard composed of the core and the liner is printed with the aqueous printing ink composition,
The liner has a specific compressive strength of 11 to 13 N · m ² / g and a wax pick value of 20 or less.
After coating or printing an aqueous coating agent containing a calcium salt as a cellulose derivative or alkyl ketene dimer and a dissociable polyvalent metal salt, it is printed with an aqueous printing ink composition having an acid group-containing resin as a binder. Characteristic cardboard printed matter. Claim 1, wherein the cardboard printed matter obtained by using calcium formate as the calcium salt. Cellulose derivative or alkyl ketene dimer and dissociation in advance on the liner surface of the corrugated cardboard composed of a core and a liner having a wax pick value of 20 or less and a specific compressive strength of 11 to 13 N · m ² / g A method for producing a corrugated cardboard printed matter comprising printing an aqueous printing ink composition containing an acid group-containing resin as a binder after coating or printing an aqueous coating agent containing a calcium salt as a functional polyvalent metal salt.