JP7010396B1 - Water-based coating varnish and printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve blocking resistance and abrasion resistance, high glossiness, and suppression of thickening with time. Another issue is the improvement of press suitability in addition to the above. A water-based coating varnish containing zinc oxide, polyolefin resin particles, and styrene or acrylic resin particles, wherein the content of the zinc oxide is 0.075 to 0.3 mass in the total amount of the water-based coating varnish. %, The 70% diameter of the polyolefin resin particles is 5 μm or less, and the content of the polyolefin resin particles is 0.1 to 2% by mass in the total amount of the water-based coating varnish. be. Further, a water-based coating varnish containing 0.3 to 0.8% by mass of a phosphoric acid ester in the total amount of the water-based coating varnish is preferable. [Selection diagram] None

Description

The present invention relates to a water-based coating varnish and a printed matter obtained by using the water-based coating varnish.

Generally, a coating layer obtained by using a water-based coating varnish used for carton paper containers, wrapping paper, etc. is required to have excellent gloss, abrasion resistance, blocking resistance, and the like.

Styrene, acrylic resin, or polyolefin resin is used as a general method for imparting high gloss, abrasion resistance, and blocking resistance (see Patent Documents 1 and 2). Further, by increasing the content of these resins or reducing the particle size of the polyolefin resin, both of the above characteristics are achieved. However, when the content of the resin is increased, blocking property and thickening with time may occur depending on the type of the resin used. Further, when the particle size of the polyolefin resin is reduced, the friction resistance and the blocking resistance are deteriorated.

Further, as a method for improving the blocking resistance of printed matter, there is a method of adding a cross-linking agent such as a carbodiimide, an isocyanate or an epoxy compound to an aqueous coating varnish (see Patent Documents 3 and 4). However, in this case, there is a drawback that the tendency of thickening and gelation becomes strong, and stable storage becomes difficult.

In response to the demand for higher gloss, varnishes suitable for press working are also required. However, in press working, it is necessary to adjust so that the coating layer made of water-based coating varnish does not peel off during roll pressing where high temperature and high pressure are applied. That is, if the peeling resistance is too weak, the printed matter will fall off immediately after the roll press, and conversely, if the peeling resistance is too strong, the printed matter cannot be discharged from the roll.

As described above, there has never been a water-based coating varnish in which the coating layer has a suitable level of blocking resistance, abrasion resistance, glossiness, and suppression of thickening over time. rice field.

Japanese Unexamined Patent Publication No. 2007-45773 Japanese Unexamined Patent Publication No. 02-1697797 Japanese Unexamined Patent Publication No. 07-316470 Japanese Unexamined Patent Publication No. 2006-206802

The present invention has been made to solve the above problems, and an object thereof is to obtain a coating layer having excellent blocking resistance and abrasion resistance and high glossiness, and further causing thickening with time. The purpose is to provide a water-based coated varnish that has never been used. Further, an object of the present invention is to provide the above-mentioned water-based coating varnish, which can obtain a coating layer having good press suitability in addition to the above.

As a result of diligent research to obtain a water-based coating varnish that meets the above-mentioned object, the present inventors have found a water-based coating varnish having the following constitution and completed the present invention.

That is, the present invention is an aqueous coating varnish containing zinc oxide, polyolefin resin particles, and styrene or acrylic resin particles.
The zinc oxide content is 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish.
The 70% diameter of the polyolefin resin particles is 5 μm or less.
The present invention relates to a water-based coating varnish, wherein the content of the polyolefin resin particles is 0.1 to 2% by mass based on the total amount of the water-based coating varnish.

Further, the present invention further contains a phosphoric acid ester, and the present invention further contains a phosphoric acid ester.
The present invention relates to the water-based coating varnish, wherein the content of the phosphoric acid ester is 0.3 to 0.8% by mass in the total amount of the water-based coating varnish.

The present invention also relates to a printed matter obtained by using the above-mentioned water-based coating varnish.

The present invention is a method for producing an aqueous coating varnish in which zinc oxide, an aqueous dispersion of polyolefin resin particles, and an aqueous dispersion of styrene or acrylic resin particles are mixed.
The zinc oxide content is 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish.
The 70% diameter of the polyolefin resin particles is 5 μm or less.
The present invention relates to a method for producing a water-based coating varnish, wherein the content of the polyolefin resin particles is 0.1 to 2% by mass in the total amount of the water-based coating varnish.

Further, in the present invention, the aqueous dispersion of the polyolefin resin particles is an aqueous dispersion of polyolefin resin particles having an average particle size of 1 to 5 μm and an aqueous dispersion of polyolefin resin particles having an average particle size of 50 to 500 nm. The present invention relates to the above-mentioned method for producing a water-based coated varnish, including.

INDUSTRIAL APPLICABILITY According to the present invention, it has become possible to obtain a coating layer having excellent blocking resistance and abrasion resistance and having high gloss, and to provide a water-based coating varnish that does not cause thickening with time. Further, according to the present invention, in addition to the above, it has become possible to provide the above-mentioned water-based coating varnish, which can obtain a coating layer having good press suitability.

First, the reason why the water-based coating varnish of the present invention can solve the above problems will be described below. However, the following is a guess and does not limit the technical scope of the present invention.

In general, when an aqueous coating varnish containing only styrene or acrylic resin particles is used, the obtained coating layer tends to obtain gloss due to the styrene or acrylic resin. However, the abrasion resistance and the blocking resistance may not meet the generally required performance standards.

Therefore, in the present invention, polyolefin resin particles are further used in order to improve friction resistance and blocking resistance. Generally, the polyolefin resin particles are used as an aqueous medium (at least a solvent containing water) in the form of an aqueous dispersion. Further, there are polyolefin resin particles having various particle diameters. However, for example, when polyolefin resin particles having an average particle diameter of 5 μm or more are used, although the abrasion resistance and the blocking resistance are improved, the glossiness of the coating layer is significantly reduced, and these characteristics cannot be compatible with each other. By reducing the average particle size (for example, setting the average particle size to 1 to 4 μm), the decrease in glossiness can be suppressed to some extent, but the friction resistance and the blocking resistance are deteriorated instead. Further, when only fine polyolefin resin particles having an average particle diameter of about 50 to 500 nm are used, the glossiness does not decrease, but the amount added in order to obtain sufficient abrasion resistance and blocking resistance. Need to be increased. Generally, an aqueous dispersion of polyolefin resin particles is often marketed and provided with a solid content concentration of 50% by mass or less, and if the amount of the polyolefin resin particles added is too large, it is suitable for printing as a water-based coating varnish. It becomes difficult to maintain the viscosity, and there is a risk of a decrease in viscosity.

Therefore, as a result of repeated studies to solve the above problems, zinc oxide is further added in an amount of 0.075 to 0.3% by mass based on the total amount of the aqueous coating varnish, and the 70% diameter and blending amount of the polyolefin resin particles are specified. I found that.

First, in the present invention, the 70% diameter of the polyolefin resin particles is 5 μm or less, and the blending amount is 0.1 to 2% by mass in the total amount of the aqueous coating varnish. This is a balance of glossiness, abrasion resistance, blocking resistance, and thickening with time when used in combination with styrene or acrylic resin particles, but as described above, this alone is desirable for all of the above. You can't get the quality. In particular, since the average particle size of the polyolefin resin particles in the water-based coating varnish becomes small, it becomes very difficult to secure blocking resistance.

Therefore, the present invention is further characterized in that a certain amount of zinc oxide is used. In addition to the small average particle size of the polyolefin resin particles, it is conceivable that the hydrophilic groups present in the styrene or acrylic resin take in water as a factor that causes blocking, but zinc oxide is a styrene or acrylic resin. Since it is considered to inhibit dissolution in water, the influence of the styrene or acrylic resin can be blocked by adding 0.075% by mass or more of the zinc oxide. Further, by setting the blending amount to 0.3% by mass or less, the adverse effect of zinc oxide on the thickening of the water-based coating varnish over time can be suppressed.

As described above, the water-based coating varnish containing a certain amount of zinc oxide, polyolefin resin particles having a specific 70% diameter and blending amount, and styrene or acrylic resin particles provides gloss, abrasion resistance, and blocking resistance. , Suppression of thickening over time can be realized at the same time.

Although the details will be described later, it is also possible to add 0.3 to 0.8% by mass of a phosphoric acid ester to the water-based coating varnish to adjust the peelability necessary for press working or the like.

Subsequently, the components constituting the water-based coating varnish of the present invention will be described in detail below.

The zinc oxide used in the aqueous coating varnish of the present invention is preferably used in a state of being dissolved in a basic aqueous solution. For example, it can be used in the form of an aqueous solution complexed with aqueous ammonia. The amount of zinc oxide added is 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish. By adding 0.075% by mass or more of zinc oxide, the influence of styrene or acrylic resin, which may adversely affect the blocking property, can be blocked. Further, when the blending amount is 0.3% by mass or less, the thickening of the water-based coating varnish over time can be suppressed.

As an aqueous dispersion of polyolefin resin particles used in the aqueous coating varnish of the present invention, a polyolefin such as polyethylene, polyethylene oxide, polypropylene, polypropylene oxide, etc. is simply dispersed in water together with a surfactant and other emulsions. Alternatively, an emulsion dispersion or the like can be used.

The average particle diameter in the present invention represents a 50% diameter, and the 70% diameter and the average particle diameter are the Coulter counter method (when the average particle diameter of the target aqueous dispersion is 1 μm or more) and Microtrack. It is a value based on the number measured by the method (when the average particle size of the target aqueous dispersion is less than 1 μm).

The optimum particle size of the polyolefin resin particles is 70% with a diameter of 5 μm or less. When the 70% diameter is 5 μm or less, sufficient friction resistance can be imparted without excessively increasing the addition amount, and deterioration of gloss can be suppressed.

In order to reduce the 70% diameter to 5 μm or less, for example, only one type of polyolefin resin particles having an average particle diameter (50% diameter) of 4 μm or less and a 70% diameter of 5 μm or less may be used. However, in the case of the present invention, from the viewpoint of improving the abrasion resistance while suppressing the decrease in gloss, the polyolefin resin particles having an average particle diameter of 1 to 5 μm and the polyolefin resin particles having an average particle diameter of 50 to 500 nm are used. It is preferable to use them together. When the polyolefin resin particles having an average particle diameter close to 5 μm are used, the polyolefin resin particles having a small average particle diameter (for example, the average particle diameter is 50 to 500 nm) so that the 70% diameter is 5 μm or less. It is necessary to adjust the blending amount.

The total content of the polyolefin resin particles is 0.1 to 2% by mass, more preferably 1 to 2% by mass, based on the total amount of the aqueous coating varnish.

Examples of the styrene or acrylic resin particles constituting the aqueous coating varnish of the present invention include styrene-based copolymers, acrylic-based copolymers, styrene-acrylic acid-based copolymers, and styrene-maleic acid-based copolymers. ..
The monomers used when synthesizing the resin are not particularly limited, and are aromatic vinyl monomers such as styrene, ethylenically unsaturated carboxylic acid esters such as acrylic acid esters, ethylenically unsaturated carboxylic acid amides, and malein. Ethylene unsaturated carboxylic acids such as acids can be used.

The styrene or acrylic resin particles used in the present invention are described above in the presence of a surfactant such as an anionic activator, a nonionic activator, and a polymer active agent (alkali-soluble water-soluble resin, etc.). It can be obtained by emulsifying and polymerizing the monomer of. Above all, from the viewpoint of glossiness, leveling property, fluidity, and resolubility, it is preferable to use an emulsion produced by using an alkali-soluble water-soluble resin.

Examples of the aromatic vinyl monomers include styrenes such as styrene, α-methylstyrene, and vinyltoluene.
These can be used as one kind or a mixture of two or more kinds.

Examples of the ethylenically unsaturated carboxylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth). ) Alkyl esters of (meth) acrylic acid such as acrylate,
Hydroxyl-containing ethylenically unsaturated compounds such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate,
Examples thereof include epoxy group-containing ethylenically unsaturated compounds such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate.
These can be used as one kind or a mixture of two or more kinds.

Examples of the ethylenically unsaturated carboxylic acid amides and their derivatives include N-methylol (meth) acrylamide, N-dimethylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and N-methoxymethyl (meth) acrylamide. , N-ethoxymethyl (meth) acrylamide and the like.
These can be used as one kind or a mixture of two or more kinds.

Further, examples of the ethylenically unsaturated carboxylic acids include (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid, crotonic acid and their anhydrides.
These can be used as one kind or a mixture of two or more kinds.

Further, as the polymerization initiator used in emulsion polymerization, ordinary radical polymerization initiators, for example, persulfates such as ammonium persulfate, organic peroxides such as t-butyl peroxide and the like can be used. The amount of the polymerization initiator used is appropriately 0.1 to 5 parts by mass with respect to the total amount of the monomers.

The glass transition point of the styrene or acrylic resin is preferably in the range of 20 to 100 ° C. When press working is required, the glass transition point is more preferably 30 to 100 ° C, more preferably 50 to 100 ° C, from the viewpoint of sufficiently exhibiting heat resistance.

Here, the glass transition point refers to the value of the contact point between the tangent line of the heat absorption curve near the glass transition temperature and the baseline when measured at a temperature rise temperature of 10 ° C./min using a differential scanning calorimeter.

The aqueous coating varnish of the present invention may contain a phosphoric acid ester. As the phosphoric acid ester, it is preferable to use one having an alkyl group having 4 to 13 carbon atoms and having an HLB value of 5 to 13 from the viewpoint of press suitability. Further, from the viewpoint of press suitability, the blending amount is preferably 0.3 to 0.8% by mass in the total amount of the water-based coating varnish. If it is 0.3% by mass or more, it will be easy to peel off from the press machine during endless press processing, and if it is 0.8% by mass or less, the peelability from the press machine will be excessively strong. It is preferable because there is no more.

The HLB value is a value experimentally obtained by the water number method. For example, the phosphate ester of interest is dissolved in a benzene / dioxane mixed solvent and titrated with water until turbidity occurs. Then, the HLB value can be calculated by 0.89 × WN + 1.11 from the amount of water (water number, WN) added until turbidity occurs.

In addition to the above components, the coating varnish of the present invention has additives such as a defoaming agent, a surfactant, a thickener, a leveling agent, a high boiling point solvent, and an aqueous dispersion, if necessary. It may contain a water-soluble resin other than the resin.

The coating varnish of the present invention can be produced by blending a predetermined amount of the above components, mixing them well, and then adjusting the viscosity and pH.

Further, the coating varnish of the present invention can be applied onto a recording medium to be a printed matter by, for example, offset inline coating printing or flexographic printing. Further, as the recording medium, a medium having a coated layer such as coated paper or coated balls can be preferably used. The coating varnish of the present invention may be applied onto a recording medium on which characters and images are printed.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Hereinafter, in the examples and the table, “part” means “part by mass” and “%” means “% by mass”.

[Examples 1 to 17 and Comparative Examples 1 to 7]
With the formulation shown in Table 1, each material was placed in a mixing container equipped with a disper and stirred well to prepare water-based coated varnishes of Examples 1 to 17 and Comparative Examples 1 to 7.

In Table 1, Zinc Oxide Solution No. Reference numeral 1 is an aqueous solution of zinc oxide manufactured by BASF (solid content: 15%). Chemipearl W300, WF640, and W200 are aqueous dispersions of polyolefin resin particles manufactured by Mitsui Chemicals Co., Ltd .; JONCRYL WAX26 DMAE, Holder PE03, AQUASER513 are aqueous dispersions of polyolefin resin particles manufactured by BYK; An aqueous dispersion of polyolefin resin particles. The solid content and average particle size of the aqueous dispersion of each of the above-mentioned polyolefin resins are as shown in Table 1. Further, JONCRYL PDX-7677 is an aqueous dispersion (solid content 46%) of BASF-made styrene or acrylic resin particles. Phosphanol ML-220 is a phosphoric acid ester manufactured by Toho Chemical Industry Co., Ltd. (solid content 93%), and Sanmorin OT-70 is an anionic surfactant manufactured by Sanyo Chemical Industries Co., Ltd. (solid content 70%). ..

The 70% diameter of the water-based coating varnishes of Examples 1 to 17 and Comparative Examples 1 to 7 was confirmed by the above-mentioned method. As a result, it was confirmed that the 70% diameter was 5 μm or less except for the water-based coating varnish of Comparative Example 1.

[Evaluation of Examples 1 to 17 and Comparative Examples 1 to 7]
Evaluation tests of the time-dependent thickening (storage stability) of the aqueous coating varnishes of Examples 1 to 17 and Comparative Examples 1 to 7 were carried out by the methods shown below. Further, on an offset printing machine with a water-based coater (Komori Corporation, Lithrone 26), the water-based coating varnishes of Examples 1 to 17 and Comparative Examples 1 to 7 were overcoated at a printing speed of 8000 sheets / hour to print printed matter. Made. The overcoat printing was performed on a coated cardboard (Maricoat F270 manufactured by Hokuetsu Corporation) printed with offset sheet-fed ink (TKNEX-PR indigo MZ manufactured by Toyo Ink Co., Ltd.). Then, the obtained printed matter was evaluated for blocking resistance, glossiness, and abrasion resistance by the methods shown below. The evaluation results are as shown in Table 1.

[Evaluation of thickening over time]
The viscosities of each of the water-based coating varnishes of Examples 1 to 17 and Comparative Examples 1 to 7 were measured at 60 rotations using a B-type viscometer. Then, it was sealed and stored in an oven at 35 ° C. for 30 days, and the viscosity was measured again using a B-type viscometer. Then, the viscosity increase with time was evaluated by comparing the changes in viscosity before and after storage. The evaluation criteria are as follows, and a score of 3 or higher was considered acceptable.
4: No change in viscosity (pass)
3: Viscosity change is less than + 10% (pass)
2: Viscosity change is + 10% or more and less than + 20% (failure)
1: Viscosity change is + 20% or more (failure)

[Evaluation of blocking resistance]
The printed matter of the water-based coated varnishes of Examples 1 to 17 and Comparative Examples 1 to 7 produced by the above method was pressed at 49 kN / m ² facing each other so that the printed surfaces were in contact with each other, and had a temperature of 50 ° C. and a humidity of 50 ° C. Stored under 80% for 24 hours. Then, the blocking resistance was evaluated from the strength of the peeling resistance (confirmed by touch) and the peeling marks (confirmed visually) when the printed matter was peeled off after storage. The evaluation criteria are as follows, and 2 points or more were accepted.
4: No peeling resistance (pass)
3: There was slight peeling resistance, but there were no peeling marks on the printed matter (passed).
2: There was slight peeling resistance, and there were peeling marks on the printed matter, but it was slight (passed).
1: The peeling resistance is strong, and the peeling marks on the printed matter can be easily confirmed visually (failure).

[Evaluation of gloss]
The gloss on the surface of the printed matter produced by the above method was measured with a gloss meter (GM-26D manufactured by Murakami Color Research Institute, 60 ° incident light). The evaluation criteria are as follows, and 2 points or more were accepted.
4: Gloss value 70 or more (pass)
3: Gloss value 60 or more and less than 70 (pass)
2: Gloss value 50 or more and less than 60 (pass)
1: Gloss value less than 50 (failure)

[Evaluation of abrasion resistance]
The printed matter produced by the above method was rubbed 500 times with high-quality paper to which a load of 1000 g was applied using a Gakushin type friction tester, and the degree of scratches was visually evaluated. The evaluation criteria are as follows, and 2 points or more were accepted.
4: The printed matter was not scratched (passed)
3: The printed matter was scratched but slight, and the indigo ink in the lower layer did not adhere to the woodfree paper (passed).
2: The printed matter was scratched, and the indigo ink in the lower layer slightly adhered to the high-quality paper (passed).
1: The printed matter was scratched, the indigo ink in the lower layer was also removed, and the paper fibers of the base paper were exposed (non-conforming).

Further, regarding the press suitability, Examples 1, 14 and 16 in which the amount of the phosphoric acid ester added was different were evaluated. The evaluation results are shown in Table 2.
[Evaluation of press aptitude]
Using a roll press machine (SA-1010 manufactured by Tester Sangyo Co., Ltd.), the printed matter of the water-based coating varnish of Examples 1, 14 and 16 was pressed at 70 ° C., 10 m / min and 500 N / cm. By confirming the peelability at that time, the press suitability was evaluated. The evaluation criteria are as follows, and 3 points or more are considered to be particularly excellent in terms of quality.
4: It could be peeled off from the metal roll of the roll press machine with a light peeling resistance, and no peeling mark was left on the roll. In addition, the gloss of printed matter was improved by pressing.
3: At the time of peeling, the metal roll of the roll press machine had peeling resistance, but the roll could be peeled without leaving any peeling marks. In addition, the gloss of printed matter was improved by pressing.
2: At the time of peeling, the metal roll of the roll press machine had peeling resistance, and peeling marks remained on the roll, or the peeling resistance was light, but the gloss of the printed matter did not change before and after pressing 1: The printed matter was metal. It stuck completely to the roll and could not be peeled off from the roll unless the printed matter was torn, or the printed matter did not stick to the metal roll at all and the printed matter fell off at the roll exit.

As a result of the evaluation, zinc oxide was contained in 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish, and the polyolefin resin particles were contained in 0.1 to 2% by mass in the total amount of the aqueous coating varnish, and 70% of the polyolefin resin particles. It was confirmed that the water-based coated varnishes of Examples 1 to 17 having a diameter of 5 μm or less had acceptable levels of quality in all of the thickening with time, blocking resistance, glossiness, and abrasion resistance. ..
Further, the aqueous coating varnishes of Examples 1 and 16 containing 0.3 to 0.8% by mass of a phosphoric acid ester in the total amount of the aqueous coating varnish were particularly excellent in press suitability.

On the other hand, Comparative Example 1 in which the 70% diameter of the polyolefin resin particles was larger than 5 μm, Comparative Examples 2 to 3 in which the content of the polyolefin resin particles was out of the above range, and the content of the zinc oxide were described above. For Comparative Examples 5 to 6 which were out of the range and Comparative Examples 4 and 7 which did not use zinc oxide, one or more of the above evaluations were rejected levels. From this result, the aqueous coating varnish containing a certain amount of zinc oxide, polyolefin resin particles having a specific 70% diameter and blending amount, and styrene or acrylic resin particles was used to suppress thickening with time, blocking resistance, and glossiness. It was confirmed that abrasion resistance can be realized at the same time.

Claims (5)

A water-based coating varnish containing zinc oxide, polyolefin resin particles, and styrene or acrylic resin particles.
The zinc oxide content is 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish.
The 70% diameter of the polyolefin resin particles is 5 μm or less.
A water-based coating varnish, wherein the content of the polyolefin resin particles is 0.1 to 2% by mass based on the total amount of the water-based coating varnish. In addition, it contains a phosphate ester,
The water-based coating varnish according to claim 1, wherein the content of the phosphoric acid ester is 0.3 to 0.8% by mass in the total amount of the water-based coating varnish. A printed matter obtained by using the water-based coating varnish according to claim 1 or 2. A method for producing an aqueous coating varnish in which zinc oxide, an aqueous dispersion of polyolefin resin particles, and an aqueous dispersion of styrene or acrylic resin particles are mixed.
The zinc oxide content is 0.075 to 0.3% by mass in the total amount of the aqueous coating varnish.
The 70% diameter of the polyolefin resin particles is 5 μm or less.
A method for producing a water-based coating varnish, wherein the content of the polyolefin resin particles is 0.1 to 2% by mass in the total amount of the water-based coating varnish. A claim that the aqueous dispersion of the polyolefin resin particles includes an aqueous dispersion of polyolefin resin particles having an average particle size of 1 to 5 μm and an aqueous dispersion of polyolefin resin particles having an average particle size of 50 to 500 nm. 4. The method for producing a water-based coated varnish according to 4.