JPH11100799A - Mat coated paper for printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a mat coated paper for printing excellent in white paper gloss or inking properties by coating the top surface of a base paper with a specific water-based pigment composition containing a pigment having a specified particle size distribution and an adhesive. SOLUTION: This mat coated paper for printing is obtained by preparing a water-based pigment composition, consisting essentially of a pigment obtained by compounding a delaminated kaolin capable of manifesting a particle size distribution of 95-100 wt.% particles having <10 μm particle diameter, 80-85 wt.% particles having <5 μm particle diameter, 30-50 wt.% particles having <2 μm particle diameter and 15-30 wt.% particles having <1 μm particle diameter in an amount of 5-50 wt.% solid content ratio to the total pigment and an adhesive such as a styrene-butadiene copolymer latex and having <=60 g/m<2> dynamic water retention degree at 63 wt.% solid concentration (under 1 bar pressurizing conditions), and then coating the top surface of a base paper with the resultant composition in an amount of 2-35 g/m<2> , preferably 3-20 g/m<2> expressed in terms of the solid content based on one surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated paper for printing, and in particular, has excellent printing smoothness, hardly causes stains due to printing ink after printing, and hardly causes streaks or other trace troubles. The present invention relates to a matte coated paper for printing having excellent properties.

[0002]

2. Description of the Related Art In general, a matte coated paper is a coated paper in which the surface gloss of a blank sheet is intentionally reduced to give an elegant and deep tone as a printed matter to give a sense of quality. Such matte coated papers are widely used in high quality art printing, high quality posters, catalogs, calendars and the like.

Heretofore, matte coated paper has been produced in two ways. That is, one of them is to apply a coating composition containing a relatively coarse pigment in comparison with the pigment used in glossy coated paper, and then dry it to produce a product as it is, or It has been commercialized by performing a smoothing process such as super calender. On the other hand, as another method,
There is a method in which the surface of the pigment-coated layer that has been smoothly coated is treated with a roughened calender roll to give a matte surface. In this method, a matte finish is obtained by transferring a micron-order rough surface of a roll to the surface of a coating layer. The matte coated paper thus obtained is generally inferior in print smoothness as compared with a glossy coated paper because the surface is roughened.

[0004] Such matte coated papers also have serious practical difficulties due to their rough surfaces. In other words, the intermediate process and bookbinding process of printing matte coated paper,
Alternatively, there is an ink transfer phenomenon referred to as so-called stain, in which the printing ink is transferred to the blank paper portion due to friction between the printed portion and the blank paper portion in the transport process. The occurrence of such stains reduces the product value, and in severe cases, may cause enormous loss as a user complaint.

[0005] The main cause of the transfer of the printing ink to the blank portion is generally considered as follows. That is, since the matte coated paper has a rough coating layer surface, the rough portion acts like a kind of file, and when the blank portion and the printing portion come into contact, the convex portion of the blank paper becomes It is presumed to be a phenomenon in which the ink is transferred to a blank paper portion by scraping the ink in the printing portion.

Conventionally, in order to solve such stains, in a printing process, a compound containing wax as a main component is added to a printing ink to reduce friction between a printing surface and a blank surface. And other measures have been taken. On the other hand, in the case of coated paper, a method of treating the coated paper with a high-temperature soft calender at a predetermined temperature or higher (Japanese Patent Laid-Open No. 5-1179)
No. 95), and a method of providing a base paper with a coating layer containing 20 to 80% by weight of a delaminated clay having an average particle diameter of 0.4 to 1.0 μm (Japanese Patent Application Laid-Open No. 5-5297). However, the problem has not yet been resolved. Furthermore, a method of forming a coating layer using a coating composition containing a specific amount of a lubricant such as a fatty acid emulsion, a fatty acid salt emulsion, a wax emulsion, or a polyethylene emulsion (JP-A-6-158594)
Publication), but no satisfactory effect has been obtained by using any of the lubricants.

[0007]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems of the matte coated paper for printing, the present inventors have made intensive studies especially on aqueous pigment compositions. As a result, the present invention, by using a pigment having a specific particle size distribution as a pigment of the coating layer, has excellent printing smoothness, and very little stains generated in the printing process and the bookbinding process are likely to occur, Further, the present invention provides a matte coated paper for printing which is less likely to cause operational defects such as streaks.

[0008]

According to the present invention, an aqueous pigment coating composition comprising a pigment and an adhesive as a main component is coated on a base paper.
In a matte coated paper for printing which is dried, the pigment has the following particle size distribution: (a) 95 to 100% by weight of particles smaller than 10 μm (b) 80 to 95% by weight of particles smaller than 5 μm (c) 30 to 50% by weight of particles smaller than 2 μm (d) Delaminated kaolin satisfying 15 to 30% by weight of particles smaller than 1 μm is blended in an amount of 5 to 50% by weight based on the solid content with respect to all pigments. Matt coated paper for printing characterized by the following.

[0009]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present inventors
Intensive research has been conducted to obtain a matte coated paper which is excellent in printing smoothness and in which stains due to printing ink are extremely unlikely to occur. As a result, by including a pigment having a specific particle size distribution, that is, delaminated kaolin in the coating layer, it is possible to obtain a matte coated paper excellent in print smoothness and further significantly reducing stains caused by printing ink. And found that the present invention was completed.

Hereinafter, a specific delaminated kaolin used in the present invention will be described. The specific delaminated kaolin of the present invention is a delaminated kaolin having the following particle size distribution. (A) 95 to 100% by weight of particles smaller than 10 μm; (b) 80 to 95% by weight of particles smaller than 5 μm; (c) 30 to 50% by weight of particles smaller than 2 μm; and (d) 15 to 50% by weight of particles smaller than 1 μm. (A) 95 to 100% by weight of particles smaller than 10 μm, (b) 85 to 95% by weight of particles smaller than 5 μm, and (c) 35 to 45% by weight of particles smaller than 2 μm. d) Delaminated kaolin having a particle size distribution such that particles having a particle size of less than 1 μm is 20 to 30% by weight and having an average particle size of 2 to 4 μm is blended as a pigment of an aqueous pigment composition (hereinafter, simply referred to as a paint). By doing so, the excellent effects desired by the present invention are obtained.

The reason why the use of the delaminated kaolin having such a particle size distribution achieves the excellent effect desired by the present invention is not necessarily clear, but is presumed as follows. That is, the delaminated kaolin having a specific particle size distribution in the present invention has a coarser average particle size than conventionally used pigments such as delaminated kaolin and other kaolins, and has a narrow particle size distribution. Things. Such a delaminated kaolin is difficult to develop the gloss of the coated paper surface,
The compounding amount can be increased and the coatability of the coating layer surface is excellent. As a result, it shows excellent printing smoothness,
It is estimated that friction resistance can be improved. Furthermore, it is presumed that the particles are plate-shaped and that particles having sharp projections are scarcely present, so that it is less likely that ink stains will occur.

When the average particle diameter is smaller than that of the delaminated kaolin specified in the present invention, gloss tends to be developed, and the compounding amount cannot be increased so much. It becomes difficult to improve the suitability for stain resistance. On the other hand, when the average particle diameter is coarse, it is difficult to increase the smoothness of the surface of the coated paper, and it may be difficult to obtain an excellent printing effect. Incidentally, even if the average particle diameter is substantially the same, if the width of the particle size distribution is wider than the delaminated kaolin specified in the present invention, it is difficult to obtain the desired print smoothness and kosle stain suitability of the present invention. Become.

Here, the particle size distribution of the delaminated kaolin referred to in the present invention is all measured using a Sedigraph 5000-01 (sedimentation method) manufactured by Shimadzu Corporation. This device is widely used worldwide to measure the particle size of fillers and pigments. The actual measurement was performed using a dispersion obtained by dispersing the sample in a 0.1% by weight aqueous solution of Na ₄ P ₂ O ₇ by high-speed stirring and ultrasonic waves. The measured particle size distribution was measured using an XY recorder.
The particle diameter of the spherical diameter corresponding to the axis and the percentage (wt%) of the particles on the Y axis are recorded. The particle size distribution specified in the present invention is defined based on a value obtained by reading a curve obtained by the above method.

The amount of the specific delaminated kaolin in the paint is 5 to 50% by weight, preferably 10 to 3% by weight, based on the total solids in the paint.
It is adjusted in the range of 0% by weight. By the way, when the content is less than 5% by weight, the effect desired by the present invention, that is, the elimination of stains caused by friction between the printed portion and the blank portion is reduced.
No reduction effect or improvement effect on print smoothness can be obtained. on the other hand,
If the content exceeds 50% by weight, it is not possible to prepare a high-concentration paint, and as a result, the operability during the production of coated paper is reduced, and the printing smoothness of the obtained matt coated paper cannot be increased.

In the present invention, as a more preferred embodiment for obtaining the desired effect, the dynamic water retention of the paint used (pressurizing condition at measurement = 1 bar, solid content concentration of paint = 63 wt. %) Is 60 g / m ² or less, preferably 55 g / m ² or less, and more preferably 30 to 55 g / m ^2.
By using the paint which is ² , the printing smoothness is further improved, and not only the effect of reducing or eliminating stains on the stain is obtained, but also when applying using a blade coater, the streak and the like may be reduced. Trace troubles are reduced and stable operation is possible.

Here, the dynamic water retention refers to AA-GWR
(Kaltec Scientific Inc./U.S.A.) And refers to a value obtained by measuring the amount of water transfer (g / m ² ) from a paint to base paper under pressurized conditions. In the present invention, the dynamic water retention when the pressurizing condition is 1 bar and the solid content concentration of the paint is 63% by weight has a correlation with the printing smoothness and the abrasion resistance suitability (rub resistance). It was found that the pressure was large, and the pressure condition: 1 bar and the paint concentration: 63% by weight were used as the measurement conditions. By the way, when the dynamic water retention exceeds 60 g / m ² , the permeability of the coating material to the base paper becomes high, and it becomes difficult to obtain the printing smoothness desired by the present invention, and furthermore, defects such as streaks are reduced. It is easy to occur. On the other hand, if it is less than 30 g / m ² , it becomes difficult for the paint to adhere, and there is a concern that operability in blade coating may be poor.

There are various methods for adjusting the dynamic water retention of the paint. For example, the combination of the kind and amount of the pigment to be mixed in the paint, the kind and the amount of the adhesive, the addition of the water retention agent, the size of the base paper, and the combination of the coating temperature and the base paper temperature at the time of coating are appropriately selected. By doing so, the dynamic water retention can be adjusted.

When the matte-coated paper of the present invention is used for gravure printing, the effect of eliminating printing defects such as missing dots and the like specific to gravure printing is recognized.

Examples of the pigment include delaminated kaolin, kaolin, talc, heavy calcium carbonate, light calcium carbonate, satin white, calcium sulfite, gypsum, barium sulfate, white carbon, calcined kaolin, and structures other than those specified above. Inorganic pigments such as kaolin, diatomaceous earth, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, magnesium oxide, bentonite, sericite, polystyrene resin fine particles, and urea formalin resin fine particles And organic pigments such as fine hollow particles and porous fine particles. One or more of these can be used in appropriate combination.

Examples of the adhesive used together with the pigment include proteins such as casein and soybean protein, styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and styrene-methyl methacrylate-butadiene copolymer latex. Such as conjugated diene latex, acrylic latex such as acrylate and / or methacrylate ester polymer or copolymer latex, vinyl latex such as ethylene-vinyl acetate polymer latex, or various copolymers thereof Synthesis of partially soluble or non-soluble latex modified by modifying a latex with a monomer containing a functional group such as a carboxyl group, polyvinyl alcohol, olefin-maleic anhydride resin, melamine resin, urea resin, urethane resin, etc. Fatty adhesives, oxidized starch, positive starch, esterified starch, ordinary adhesives for coated paper such as starches such as dextrin, and cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose. One or more of the agents can be used as appropriate. The amount of the adhesive is not particularly limited, and is 2 to 50 in terms of solid content with respect to all pigments.
%, Preferably in the range of 5 to 30% by weight.

In the coating material constituting the coating layer, in addition to the above-mentioned pigments and adhesives, polyolefin resins, lubricants such as fatty acid emulsions, fatty acid salt emulsions and wax emulsions, and alkali thickening acrylic emulsions A water-retaining agent such as a polyacrylate, and various assistants such as an antifoaming agent, a coloring agent, a flow modifier, and a water-proofing agent can be added as needed.

The base paper for matte-coated paper according to the present invention is not particularly limited, but from the viewpoint of obtaining a desired and superior effect, the coating paint for the matte-coated paper specified in the present invention is used. It is desirable to appropriately adjust the sizing degree and the like so as to obtain the water retention.

The rice tsubo of the base paper is not particularly limited.
But generally 30-400 g / m ^TwoSomething used
Is done. The method of making the base paper and the paper machine are also particularly limited.
Not specified, for example, acidic paper, alkali paper
Machine, round netting machine, combination net and round netting machine
Thin or twin wire machine, on top twin
Paper making method using wire machine etc. can be adopted as appropriate
You. Wood is one of the main pulp fibers of base paper
Chemical pulp, mechanical pulp and waste paper made from non-wood materials
Pulp can be used. In addition, with size press
Starch, polyvinyl alcohol, surface sizing agent applied
Pre-applied paint consisting of things and pigments and adhesives,
Patterned blankets, etc. in the pressing process of the machine
And those made by embossing roll after paper making
Used as appropriate.

The coating amount of the coating material on the base paper is not particularly limited.
5 g / m ^2, it is preferably adjusted in the range of about 3 to 20 g / m ^2. By the way, when it is less than 2 g / m ² , it is difficult to obtain the printing smoothness desired by the present invention.

A coating apparatus for forming a coating layer also includes:
There is no particular limitation, and generally known and publicly-known coating apparatuses can be appropriately used. Specific examples include an air knife coater, blade coater, roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, gravure coater, champlex coater, gate roll coater, size press coater, or bill blade coater. One or more coating layers can be provided on base paper by an on-machine or off-machine coater having one or more of these coaters.

The solid content concentration of the coating material is generally 20 to 75% by weight, but is adjusted in the range of 40 to 67% by weight in consideration of the obtained quality, coating suitability, or operability.
In addition, as a drying method of the paint applied on the base paper, conventionally used steam heating, hot air heating, gas heater heating, high frequency heating, electric heater heating, infrared heater heating, laser heating, electron beam heating, etc. Can be used as appropriate. The coated paper thus obtained can be passed through a soft calender, a super calender or the like to be subjected to a smoothing treatment as required.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. Of course, the present invention is not limited to these. Unless otherwise specified, parts and% in the examples indicate parts by weight and% by weight, respectively.

Example 1 The following particle size distribution was used as the pigment for the paint: (a) 98% by weight of particles smaller than 10 μm (b) 89% by weight of particles smaller than 5 μm (c) 40% by weight of particles smaller than 2 μm (D) Delaminated kaolin having 25% by weight of particles smaller than 1 μm (average particle size 2.5 μm)
m: 20 parts of pigment A) having an average particle size of 0.55 μm
Kaolin (trade name: HT / EC Co., Ltd. Pigment B) 30 parts, flat
Heavy calcium carbonate having a uniform particle size of 0.57 μm (quotient)
Product name: Hydrocurve 90 / Bikita Powder Co., Ltd .... Pigment C)
40 parts, light carbonic acid calcium carbonate having an average particle size of 1.0 μm
Um (trade name: TP-121 / Okutama Kogyosha ... Pigment D)
10 parts, styrene-butadiene copolymer as adhesive
Latex 11 parts, oxidized starch 3 parts (solid fractionation
Calculation), dispersant (trade name: Aron T-40 / Toa Gosei Co., Ltd.)
Add 0.2 parts (solids) and stir with a Coreless disperser.
The mixture was stirred and mixed to obtain a coating having a solid content of 64%. This paint
90g / m^TwoDry weight per side to high quality base paper
15g / m ^TwoUsing a blade coater so that
Both sides were coated and dried to obtain a matte coated paper for printing.

Example 2 A matte coated paper for printing was obtained in the same manner as in Example 1 except that pigment A was changed to 8 parts and pigment B was changed to 42 parts. Table 1 shows the quality and operability of the obtained coated paper.

Example 3 A matte coated paper for printing was obtained in the same manner as in Example 1 except that Pigment A was changed to 45 parts and Pigment B was changed to 5 parts. Table 1 shows the quality and operability of the obtained coated paper.

Example 4 In Example 1, Pigment C was replaced with heavy calcium carbonate having an average particle diameter of 1.2 μm (trade name: Hydrocarb-60)
/ Bihoku Powder Chemical Industry Co., Ltd. A matte coated paper for printing was obtained in the same manner as in Example 1 except that the pigment was changed to E). Table 1 shows the quality and operability of the obtained coated paper.

Comparative Example 1 Matte coated paper for printing was prepared in the same manner as in Example 1 except that Pigment A was not added, Pigment B was changed to 50 parts, and Pigment C was changed to Pigment E. I got Table 1 shows the quality and operability of the obtained coated paper.

Comparative Example 2 In Example 1, the following particle size distribution was used instead of Pigment A: (a) 100% by weight of particles smaller than 10 μm (b) 95% by weight of particles smaller than 5 μm (c) Particles smaller than 2 μm 73% by weight (d) Delaminated kaolin (trade name: Capine DL) having 54% by weight of particles smaller than 1 μm
/ Chuo Kaolin-average particle size 0.88 μm ... Pigment F)
Except for changing to, a matte coated paper for printing was obtained in the same manner as in Example 1. Table 1 shows the quality and operability of the obtained coated paper.

Comparative Example 3 In Example 1, the following particle size distribution was used instead of Pigment A: (a) 90% by weight of particles smaller than 10 μm (b) 67% by weight of particles smaller than 5 μm (c) Particles smaller than 2 μm 42% by weight (d) A matte coated paper for printing was obtained in the same manner as in Example 1 except that kaolin (average particle size: 3.0 μm ... Pigment F) having 33% by weight of particles smaller than 1 μm was used. Was. Table 1 shows the quality and operability of the obtained coated paper. The quality evaluation of the coated paper obtained as described above was performed according to the following, and the obtained results are shown in Table 1.

[Quality Evaluation] (Glossy) Measured according to JIS P8142. The gloss value at 75 ° was obtained using a gloss meter manufactured by Murakami Color Research Laboratory.

(Print Smoothness: Evaluated by Ink Adhesion) RI
Using a type II printability tester, offset printing ink (F-gloss / ink) 0.15 manufactured by Dainippon Ink and Chemicals, Ltd.
Printing was performed in cc, and the appearance was evaluated according to the following criteria. ◎: The ink is uniformly printed on the paper surface. ：: There are some parts where the ink density is low. Δ: Ink deposition was inferior, and there were portions with low ink density. ×: Ink deposition was very poor, and unevenness of ink density was remarkable.

(Friction resistance) Using an RI-II type printability tester, printing was performed using 0.35 cc of offset printing ink (F-gloss / black ink) manufactured by Dainippon Ink and left overnight. After that, the test paper printed by Toyo Seiki Seiza Land Lab Tester and the white paper were brought into contact with each other under certain conditions, and rubbed reciprocally 20 times under a load of 1 lb. The ink density transferred from the printed paper to the white paper was determined according to the following criteria. evaluated. ◎: Almost no transfer of ink. ：: Slight transfer of ink. Δ: There is considerable ink transfer. ×: very much ink transfer.

(Coater operability) The occurrence of streaks when coating was performed at a speed of 800 m / min using a blade coater was observed. : Almost no streaks occurred. Δ: Streak is slightly observed, but there is no practical problem. ×: Many streaks are generated.

[0039]

[Table 1]

[0040]

As is evident from the results in Table 1, the matte coated paper according to the present invention is excellent in glossiness of white paper, ink adhesion, and abrasion resistance (excellent in ink stain resistance). Was.

Claims (2)

[Claims] 1. A matte coated paper for printing, which is obtained by coating and drying an aqueous pigment composition containing a pigment and an adhesive as main components on a base paper, wherein the pigment has the following particle size distribution: 95-100% by weight of particles smaller than 10 μm (b) 80-95% by weight of particles smaller than 5 μm (c) 30-50% by weight of particles smaller than 2 μm (d) 15-30% by weight of particles smaller than 1 μm A matte coated paper for printing, characterized in that the content of the delaminated kaolin is 5 to 50% by weight, based on the total solid content, of the total pigment. 2. The aqueous pigment composition has a dynamic water retention of 60 g / m ^{2 at} a solid content of 63% by weight (pressurizing condition: 1).
2. The aqueous pigment composition of claim 1, wherein
Matte coated paper for printing as described.