JPH11269798A - Coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for improving a surface processing suitability of a coated paper (coat paper, white paperboard, etc.), to decrease the missing dots in gravure printing, improve the water-resistance in offset printing, decrease the surface tackiness of coated layer and improve the surface slipperiness in filling. SOLUTION: A coated layer of a coated paper having a pigment-coated layer is compounded with a sizing agent composed mainly of an alkyl ketene dimer and having a zeta potential of -5 mV to +5 mV. The compounding amount of the sizing agent is 0.2-0.8 pt.wt. of the alkyl ketene dimer based on 100 pts.wt. of the pigment. The zeta potential of the sizing agent composed mainly of an alkyl ketene dimer is adjusted to -5 mV to +5 mV by adjusting the addition amount of a cationic emulsifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the printing processability of coated paper,
More specifically, the present invention relates to a coated paper having excellent ink depositing property during solid printing, halftone dot reproducibility during gravure printing, and excellent paper filling suitability.

[0002]

2. Description of the Related Art Coated paper and white paperboard used for printed matter, book covers, paper containers, and the like are required to have higher print finish and better abrasion resistance with the trend toward higher quality. Characteristics required for the coating layer of paperboard and coated paper include: a: wet strength, water resistance, b: surface processing / printing suitability (smoothness, gloss, break / crack suitability, calendar stain prevention, etc.). It was necessary to add a water-proofing agent to obtain the characteristic a, and to add a release agent to obtain the characteristic b.

[0003] In these methods, the types of added chemicals are increased and the management is complicated. In addition, for example, the addition of a release agent tends to lower the surface strength of the coating layer. There is a problem that it is necessary to add a chemical or change the adhesive.

Further, in offset printing, which occupies most of the printing methods, ink receptivity under the influence of dampening water,
Improvement and improvement of water resistance of wet picks and the like have become important issues in the industry. Traditionally, to address these issues,
Melamine-formaldehyde resin, urea-formaldehyde resin, or polyamide polyurea-formaldehyde resin, for example, JP-B-44-11667 and JP-B-5
There is known a method of adding a waterproofing agent, a printability improving agent, and the like as disclosed in JP-A-9-32597.

[0005] However, these conventional water-proofing agents and printability improving agents all have effective properties, but have serious disadvantages or insufficient effects in some of the properties. It was not always satisfactory.

For example, aminoplast resins such as melamine formaldehyde resin and urea-formaldehyde resin not only generate a large amount of formaldehyde during work or from coated paper, but also have little effect of improving ink receptivity. When the pH of the coating composition is high, there is a problem that the water-resistant effect is hardly exhibited.

The disadvantage of the release agent is that the foaming is remarkable when the coating liquid has a low viscosity (B type viscosity of 10 to 100 cp) due to the influence of the release agent containing calcium stearate as a main component.
There was a drawback that the fixability of dyes and organic pigments to paints was poor.

[0008]

SUMMARY OF THE INVENTION The present invention reduces the number of missing dots in gravure printing and improves water resistance in offset printing.
It is an object of the present invention to provide a method for improving the surface processing suitability of coated paper (coated paper, white paperboard, etc.) which reduces the adhesiveness of the surface of a coating layer and improves the surface slippage during filling.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an alkyl ketene dimer (hereinafter referred to as AKD) added for the purpose of improving the sizing degree of ordinary paper is used as a main component. The sizing agent to be adjusted is adjusted to a specific zeta potential, and the AKD active ingredient is added to 100 parts by weight of the pigment in the top coat paint of the paper (the paint in the case of one layer coating, or the outermost layer in the case of multilayer coating). It has been found that the above object can be achieved by adding 0.2 to 0.8 parts by weight.

By adding AKD, the a,
The characteristics described above can be obtained, and the drawbacks caused by the water-proofing agent can be avoided. Furthermore, the above-mentioned property b (the suitability of sliding on the surface) is obtained, and the above-mentioned drawbacks can be avoided because a release agent is not required.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As sizing agents for internal addition, rosin sizing agents, AKD sizing agents and the like are known.
It is characterized in that KD is used not as an internal additive but as an externally added sizing agent (surface sizing agent). However, if AKD is added too much, the viscosity increases, so the zeta potential is -5 mV to 5 mV.
Use those. The amount of addition is 0.1 to the pigment.
2 to 0.8% by weight is required.

As described above, when the amount of AKD is less than 0.2% by weight, the effect of water resistance is insufficient, and when it exceeds 0.8% by weight, the viscosity of the paint is remarkably increased and coating cannot be performed. This is not preferable because the surface strength is reduced. Similarly, when the zeta potential of AKD is less than -5 mV, the expression of water resistance is insufficient, and when it is more than 5 mV, the viscosity of the paint is remarkably increased, coating cannot be performed, and the surface strength is reduced. Not preferred.

The zeta potential of AKD may be adjusted during the synthesis of AKD by selecting the amount and / or degree of cationicity of the cationic emulsifier or by mixing and using the nonionic emulsifier. At the time of addition to the paint, it can be easily performed by means such as stirring and mixing. Preferred cationic emulsifiers include, but are not limited to, amine hydrochlorides, such as monoalkylammonium chlorides, dialkylammonium chlorides, trialkylammonium chlorides, and tetraammonium chlorides. An appropriate selection may be made in consideration of the occupation ratio.

The other components of the paint used in the present invention are not particularly limited. In addition to known pigments and adhesives, pH adjusters, dispersants, defoamers, preservatives, colorants, fluorescent brighteners. And an antistatic agent and the like are used as needed. For example, pigments include kaolin, aluminum hydroxide, satin white, barium sulfate, talc, heavy calcium carbonate, light calcium carbonate, plastic pigment, calcined clay, zinc oxide, titanium dioxide, etc., and adhesives such as SBR latex And water-soluble polymers such as synthetic rubber-based latex such as MBR latex, oxidized starch, phosphorylated ester starch, soybean protein, casein, carboxymethylcellulose, and hydroxymethylcellulose. The amount of the adhesive used was pigment 1
It is adjusted in the range of about 10 to 30 parts by weight with respect to 00 parts by weight.

The coating composition composed of the above materials is generally adjusted to about 35 to 65% by weight. The coating method of the paint is applied by a commonly used method such as various known blade coater, air knife coater, roll coater, bar coater, gravure coater, gate roll coater, champion coater, and any of on-machine coating and off-machine coating It may be.

The base paper for coating is not particularly limited, but is generally 50 to 500 g / m ² depending on the use.
Acid paper or neutral paper of a certain degree is used, and bleached or unbleached wood pulp, waste paper pulp, deinked waste paper pulp, high yield pulp and non-wood pulp, and various additives such as internal fillers and paper strength agents are appropriately used. What was mixed and made paper is used. The base paper may be undercoated, and the top coat is coated so as to have a dry weight per side of 1 to 40 g / m ² , preferably about 5 to ²⁰ g / m ² , and a machine calendar or super coat. Perform a smoothing process using a calendar or the like.

[0017]

The mechanism developed by adding AKD to a paint is considered as follows. That is, by adding 0.2 to 0.8 parts by weight of AKD having a zeta potential of -5 mV to 5 mV to the pigment parts by weight, the AKD and the anionic paint form an aggregate, and the apparent viscosity increases. . When this coating is applied, the coating layer becomes porous, and the cushioning property increases by 20 to 30%.

If solid printing is performed on the surface of the microporous coating layer, the ink deposition of the second and subsequent colors is improved, that is, the suitability for fountain solution is improved. Further, if the cushioning property of the coating layer is high, the number of halftone dots missing during gravure printing also decreases.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. %
And parts are numerical values based on weight or active ingredient, respectively. Was dispersed and mixed to obtain a basic slurry.

Zeta potential list of AKD Symbol A: 20 mV Addition of 1.0% cationic emulsifier B: 10 mV Addition of 0.5% cationic emulsifier C: 5 mV Addition of 1.0% fine cationic emulsifier D: -5 mV Fine cationic Addition of 0.5% of emulsifier E; −10 mV Addition of 0.1% of fine cationic emulsifier These two kinds of ionization degrees of the emulsifier are used. Was adjusted.

The measurement of the zeta potential is performed using LASER ZEE.
Using MODEL 500 (manufactured by PEN KEM),
The zeta potential of the AKD colloid particles was measured.

Examples 1 to 4 and Comparative Examples 1 to 8 AKD shown in Table 1 was added to the basic slurry in accordance with the amount of addition, and the mixture was stirred well to form a coating material. so that the coating amount 18 g / m ² in / m ² at a coating speed of 200 meters / min to give a coating with a pigment coated white paperboard. This was humidified so that the water content became 9%, and then subjected to a two-pass process using a test gloss calendar. The processing conditions are as follows: the first pass has a steel roll temperature of 70 ° C
Nip pressure 75 kg / cm, processing speed 50 m / min, 2
Pass is steel roll temperature 110 ° C, nip pressure 100
kg / cm, processing speed 50 m / min.

Evaluation Method 1 These pigment-coated white paperboards were humidified under the conditions of JIS-P8111 and then subjected to gravure printing, fountain solution suitability, and surface strength. Gravure printing uses the Ministry of Finance gravure printing machine,
The number of missing dots of 25% gradation per 100 mm ² was visually measured. Suitable for fountain solution is RI printing tester (Meiji Seisakusho)
Ink HYPLUS Red M (Toyo Ink) 0.5m
1 is supplied, water is applied with a Molton roll before printing, printing is performed, and after air drying, the ink density is measured with a Macbeth densitometer. As for the surface strength, IPI No. 7
Supply 0.5 ml instead of ink, print at a speed of 60 rpm, and visually evaluate paint removal after printing on a five-point scale (5 is good with few surface picking, 1 is poor with picking occurring on the entire surface) .

Evaluation method 2 The starting angle of the slip was determined according to JIS-P8111 using pigment-coated white paperboard.
After adjusting the humidity under the conditions described above, an inclined table is set on a Tensilon tensile tester, and the surface of the white paperboard is placed thereon, and the surface of the sample piece is placed thereon. 200mm
By lowering the table at a speed of / min, the tilt table moves and the sample piece slides down. The angle at which the sliding starts at this time is measured.

[0025]

[Table 1] The water-proofing agent of Comparative Example 7 was a polyamide urea / formaldehyde resin (Epinox S-982: manufactured by Dick Hercules), and the release agent of Comparative Example 8 was an emulsion of calcium stearate (DEF-922F: manufactured by Nissin Chemical Laboratory). It was used.

[0026]

As shown in Table 1, the zeta potential is -5.
By adding 0.2 to 0.8 parts by weight of the AKD sizing agent adjusted to the range of mV to 5 mV to 100 parts by weight of the pigment, the number of halftone dots missing during gravure printing is reduced, and fountain solution during offset printing Printability improvement effects, such as improved suitability,
Furthermore, it was possible to obtain the effect of improving the suitability for automatic box making and the suitability for filling machines, which are the main uses of white paperboard, as indicated by the decrease in the angle at which sliding starts.

Claims (2)

[Claims] In a coated paper provided with a pigment coating layer, a sizing agent having an alkyl ketene dimer as a main component and having a zeta potential of -5 mV to 5 mV is added to the coating layer with 100 parts by weight of the pigment. 0.2-0.8 with ketene dimer component
Coated paper characterized by blending in parts by weight. 2. The coated paper according to claim 1, wherein the zeta potential of the sizing agent containing an alkyl ketene dimer as a main component is -5 mV to 5 mV depending on the amount of the cationic emulsifier added.