JP2737897B2 - Transfer roll coating paint and coated paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention uses a novel composition to provide high solids content, low viscosity, and the advantages of transfer roll coating during operation, especially on-line high speed and stable operation. A transfer roll coating paint that can be applied without impairing the properties, and a coated paper having a high coating amount and excellent gloss, smoothness and printing performance comparable to blade coating. Things.

[0002]

2. Description of the Related Art Paints used for transfer roll coating, like other coating paints, are mainly composed of a pigment and an adhesive, have a high viscosity, and have a low coating amount. It was characterized. As a pigment,
Inorganic pigments such as kaolin, clay, light calcium carbonate, heavy calcium carbonate, titanium oxide, aluminum hydroxide, satin white, barium sulfate, magnesium oxide, talc and colloidal silica, or organic pigments such as plastic pigment and white urea resin pigment Are used, and usually two or more kinds are used in combination. Examples of the adhesive include water-soluble polymers such as casein, oxidized starch, phosphated starch, soybean protein, carboxymethyl cellulose, and SBR.
Synthetic latex or acrylic latex, which is referred to as a polymer, MBR, or MSBR, which is usually a water-soluble polymer 10 to 5 based on 100% by weight of a pigment.
0% by weight, 10-30% by weight of latex is used,
Usually used together. Further, if necessary, an antifoaming agent, a dispersant,
A coating agent was prepared by adding auxiliaries such as a waterproofing agent, a preservative, a coloring agent, and a release agent.

The solid content of the transfer roll coating thus obtained is 40 to 55% by weight, and the ratio of the pigment to the adhesive (binder ratio) is 30 to 50% by weight of the pigment to the adhesive. The ratio of the adhesive was quite high. In many cases, the adhesive is a combination of a starch-based adhesive and a latex, and the starch-based adhesive is characterized by a high use ratio of 20 to 50% by weight based on the pigment. The viscosity of the starch-based adhesive is at least 3,000 cps when measured at a temperature of 50 ° C. and a No. 4 rotor of a B-type viscometer at 60 rpm at a solid content concentration of 30% by weight, usually 10,
000 cps or more is used. In addition, a large feature is that a coating amount of usually less than 5 g / m ² per side, particularly a low coating amount of 3 g / m ² or less can be efficiently applied.

[0004] As described above, transfer roll coating is known to be suitable for coating of a size liquid because it is extremely light-weight coating. However, even though the apparatus is compact, it has a wide width. Against the web
It has many advantages that it can be operated continuously for several days with few paper breaks on-machine, can be easily coated on both sides, and has little difference between the front and back of the product. However, on the other hand, the coating surface feeling is inferior to blade coating, there are limitations on coating properties,
There were drawbacks such as the need for roll maintenance.

[0005] The transfer roll coating surface has a unique streak-like coating pattern, and it is not possible to obtain a uniform, smooth and glossy coating surface as obtained by blade coating. This streak pattern can be improved by increasing the amount of application, but this time, a split pattern such as satin appears, so when printing on transfer roll-coated paper, excellent print quality is obtained. Can not get. Therefore, in spite of having many advantages as described above, transfer roll coating is used for size liquid coating or lightweight coating that does not require a high coating amount, or for low-grade coated paper where print quality is not required. Used only for manufacturing.

[0006]

In recent years, there has been an increasing desire to upgrade the quality of coated paper in general. For example, in the case of art paper, a so-called super art paper having higher gloss and excellent print quality has emerged, and a super-grade paper which is a general-purpose grade has been developed. Higher opacity, rigidity, and glossiness are also required for lightweight coated paper. This tendency is the same in low-grade coated paper. Conventionally, a super calender or a machine calender has been used to improve the smoothness and glossiness of coated paper, and a means of increasing calender pressure and temperature has been used to obtain a coated paper having higher gloss. However, when these means are applied to transfer roll coated paper, although the gloss is slightly improved, the bulk of the paper is lost, and the opacity, whiteness,
The stiffness, ink acceptability, and other qualities are degraded, and no solution can be made.

Accordingly, the present invention provides the advantages of transfer roll coating, in particular, provides a uniform coating surface without coating unevenness without impairing the on-machine high-speed and stable workability, and at the same time, provides high coating performance under low calender conditions. The challenge is to provide a stable supply of transfer roll coating paint that provides a glossy and smooth coating surface, and coated paper that is coated with this paint and provides excellent print quality comparable to blade coating. And

[0008]

Generally, in coated paper, a smooth surface can be obtained when the coating amount of the coating layer is increased. However, the adjustment of the coating amount in the transfer roll coating is performed by adjusting the nip pressure between the rolls. The adjustment is performed by adjusting the peripheral speed of each roll and the solid content concentration of the paint.

Therefore, it was considered that increasing the amount of coating would solve the above-mentioned problem, and the nip pressure between rolls, the peripheral speed, and the solid content of the paint were examined. When the nip pressure is reduced and the gap between the rolls is increased, the coating amount increases, but a ring-shaped pattern is likely to be generated, and if the peripheral speed difference is given, the coated surface feeling deteriorates. It was found that only a small amount of coating could be adjusted. Therefore, the adjustment of the coating amount is mainly a function of the solid content concentration of the paint, and in order to apply a high coating amount, the solid content concentration of the paint must be increased. However, if the solids concentration is increased in the range of the materials used for the conventional transfer roll coating paint, the viscosity increases, and a split pattern of the paint is generated on the applicator roll, and the pattern appears on the coating surface and the coating is applied. Not only does the work feel deteriorate, but paint boil-up, gum-up, and paint mist splatters occur, making it impossible to perform on-machine wide, high-speed, and stable operations, a major advantage of transfer roll coating. .

Therefore, as a result of further study, the solid content concentration was 58% by weight or more, and the viscosity of the coating material having the solid concentration was 60 rpm using a No. 4 rotor of a B-type viscometer.
If it is 1,500 cps or less as measured in m, the advantages of transfer roll coating, particularly high-speed and stable on-machine workability, are not impaired, and uniform coating without coating unevenness can be achieved. Under the conditions, a high gloss and a smooth coated surface were obtained, and it was found that coated paper of excellent print quality comparable to the blade coating method was obtained, and the present invention was completed.

When the solid content concentration is 58% by weight or more,
A paint having a viscosity of 1,500 cps or less (hereinafter, the viscosity of the paint is always the viscosity measured under these conditions) measured using a No. 4 rotor of a type viscometer at 60 rpm requires the use of a low-viscosity adhesive. It has also been found that by using a pigment having a small aspect ratio, a coated paper having good viscosity and coated surface can be obtained.

The adhesive that can be used in the present invention is:
A water-soluble adhesive capable of increasing the concentration without increasing the viscosity when mixed with a pigment must exhibit sufficient adhesive strength of the pigment. After examining the properties of the paint and the properties of the coated surface after transfer roll coating, the adhesive solids concentration was 30% by weight.
Use a starch-based adhesive having a viscosity of 570 or more and less than 3,000 cps (B-type viscometer, 60 rpm, 50 ° C .; the viscosity of the starch-based adhesive is measured under these conditions). Have been found necessary for the present invention. The viscosity of a conventionally used starch-based adhesive at a solid content of 30% by weight is at least 3,000 cps.
In many cases, the viscosity is extremely low as compared with 10,000 cps or more. Such low-viscosity starch-based adhesives include modified starches such as ethyl etherified starch, hydroxyethyl etherified starch, and low-viscosity oxidized starch, and modified starch-based adhesives such as starch latex copolymers. Also, from the viewpoint of the strength of the coated surface and the printing glossiness, rather than using this low-viscosity starch-based adhesive alone, other adhesives, especially a latex-based adhesive having a relatively low viscosity and a large adhesive force, are used in combination. Is preferred. The amount of adhesive used depends on the type of adhesive and pigment used,
In addition, since it varies depending on the required quality of coated paper, it is not limited to a fixed one.
The viscosity of the completed paint at a solid content of 58% by weight should be 1,500 cps or less. In general,
When used in combination with latex, low-viscosity modified starch is preferably used in an amount of about 1 to 15% by weight based on the weight of the pigment. Since the starch latex copolymer can be used alone, it is appropriate to use about 20 to 50% by weight based on the pigment.

The pigment that can be used in the present invention is not particularly limited as long as it has a small aspect ratio, and is selected from pigments conventionally used for transfer roll coating. Several kinds of pigments can be used in combination according to the required quality. As the aspect ratio increases, the surface coverage improves, but the fluidity of the paint deteriorates, and when applying the transfer roll, a split pattern such as a satin finish occurs on the applicator roll, making it difficult to obtain a uniform and smooth coating surface. Due to the tendency, the use of pigments with too high an Arpect ratio is not preferred. If the average particle size is large, the viscosity of the coating will be small, but the uniformity and smoothness of the coated surface will be impaired. If the average particle size is too small, the viscosity of the coating material increases and a split pattern such as a satin finish is formed on the applicator roll during transfer roll coating, so that a uniform and smooth coating surface may not be obtained. It is necessary to select a pigment of ratio and average particle size. In this regard, kaolinite clay and talc, which have been awarded as coating pigments, have an average aspect ratio of about 2%.
It is as large as 0 or 30 and cannot be used alone. The smaller the aspect ratio, the more uniform and even the coated paper with good printing quality can be obtained even when a pigment having a small particle size is used.

The pigment suitable for use in the present invention must have an aspect ratio of 10 or less , such as heavy calcium carbonate, light calcium carbonate, calcium sulfite, pyrophyllite, and plastic pigment. Having an average particle size of about 0.1 to 5 μm. Among these, it is preferable to use calcium carbonate having an average aspect ratio of 5 or less, more preferably 3 or less, and an average particle size of about 0.5 to 2 μm. Other pigments which can be used in combination with the calcium carbonate are preferably as small as possible in aspect ratio, and in this regard, the combination with an organic pigment is preferable. If the gloss or opacity of the coated surface is high, a pigment having a relatively large aspect ratio, such as kaolin, can be used in combination within a range that does not impair the transfer roll coating characteristics. Even in such a case,
The aspect of the pigment as a whole must be 10 or less.
It is important . When a pigment is used in combination, the calcium carbonate is preferably used in an amount of 30% by weight or more of the total pigment, more preferably 40% by weight or more.

The pigment and the adhesive are mixed, and if necessary, auxiliary agents such as a water-proofing agent, an antifoaming agent, a dispersant, a preservative, a colorant, and a release agent are added in an amount of about 0.1 to 2% by weight. To obtain the final paint. The paint thus obtained has a paint concentration of 5
Even if it is as high as 8% by weight or more, the viscosity becomes 1,500 cps or less, and it becomes a paint suitable for transfer roll coating.

In the present invention, the transfer roll coating means that the paint supplied by the paint supply means is transferred to an applicator roll via a metering means and, if necessary, a smoothing means, and the paint on this roll is transferred to a support. On the other hand, this is a coating method characterized in that transfer is performed in a forward rotation.
The paint supply means, the metering means, and the smoothing means are basically constituted by a plurality of rolls rotating forward with respect to the applicator roll. However, for the purpose of more advanced metering or smoothing, a counter-rotating roll or rod, or a blade or air may be attached in the opposite direction. The present invention can be applied to any of these without hindrance.

The coating of the coating material of the present invention is performed, for example, by setting two gate rolls at a constant interval so as to obtain a desired coating amount, and adjusting the relative speed of the rolls. The paint splits the surface of the roll through the gate, half of which is transferred to the web along the transfer roll, and the other half of the paint returns to the paint tank. When the paint of the present invention is used, a high coating amount of 5 g / m ² or more, which cannot be obtained by the conventional transfer roll coating, can be obtained without impairing the high speed of the transfer roll coating. By applying ^two or more, a coated surface with high smoothness, high gloss and good print quality can be obtained. The preferred coating amount is 5 to 15 g / m ² , more preferably 6 to 12 g / m ² on one side.

[0018]

The reason why high gloss, high smoothness and high print quality coated paper can be obtained by using the transfer roll coating composition of the present invention is not clear, but is considered as follows.

The coating material of the present invention is excellent in fluidity because of its low viscosity in spite of its high solid content concentration, and it can be applied uniformly by forming a uniform coating film between the transfer rolls. 5g by adjusting the gap between the rolls and the peripheral speed
/ M ² or more. Also,
Since the solid content concentration of the paint is high, the penetration of the liquid component containing the binder into the base paper is small, and a bulky coating layer is formed. Therefore, the opacity is increased, and the streak-like coating unevenness peculiar to the transfer roll coating can be eliminated by the low calendering treatment, so that high glossiness and smoothness can be obtained. Furthermore, a high-concentration coating forms a porous coating layer, which can compensate for a decrease in ink set due to an increase in the coating amount, and also increases rigidity, so that coated paper with good printability and excellent print quality can be obtained. Becomes

Further, the paint of the present invention has a viscosity in a range suitable for transfer roll coating, so that there is no boiling or paint mist of the paint at the time of coating, and the solid content concentration is high, so that the paint of the present invention is compared with a low solid content paint. As the absolute moisture content decreases, the stains on the lead-out roll, expander roll, and after-dryer immediately after coating decrease, and the amount of moisture permeating into the coating base paper decreases, and the drying load decreases. High-speed coating can be performed despite the large amount of coating.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. First, a method for adjusting the adhesive solution to be used will be described, and then, a method for adjusting a transfer roll coating paint and a coated paper manufacturing example will be described. In the following examples, parts and% are% by weight and% by weight, respectively, unless otherwise specified. In addition, all the blending parts in the table are on a solid content basis.

[Adjustment of Adhesive Solution] Water was added to the adhesive to adjust the solid concentration to 30%, and the mixture was stirred and dissolved while maintaining the temperature at 95 ° C. or higher. After dissolution, the temperature was adjusted to 50 ° C., and the viscosity was measured at 60 rpm using a B-type viscometer. Low viscosity starch-based adhesive (1) used in Examples
(3), the normal starch-based adhesive (1) used in Comparative Examples
Table 1 shows the type (2) and the measurement results of the viscosity.

[0023]

[Table 1]

[Preparation of Transfer Roll Coating Paint] To a specified pigment formulation, 0.1 part of a dispersant and 0.04 part of sodium hydroxide were added to the pigment, and dispersed in water using a Serie disperser. A pigment slurry having a concentration of 73% was prepared.
Next, as the adhesive, the adhesive solution prepared above and SB latex having a solid content of 50% were added, and as other additives, a lubricant and a waterproofing agent were added. Finally, water was added to the target concentration. This was adjusted to give a transfer roll coating composition. A preferred pigment used in the following examples and comparative examples is heavy calcium carbonate having an average aspect ratio of 2 to 5.

[Production of Coated Paper] Fine coating base paper of 64 g / m ² using the paint obtained as described above and adjusting the gap and peripheral speed of the rolls so as to obtain a desired coating amount. To 60
Transfer roll coating was performed at a speed of 0 m / min.
The coated paper thus obtained is subjected to the following conditions at 20 ° C. and a relative humidity of 65%.
Seasoning was performed day and night, and then calendar processing was performed.

[Examples 1 and 2, Comparative Examples 1 and 2] Examples 1 and 2 and Comparative Examples 1 and 2 were prepared according to the above-mentioned coating paint preparation method using the pigments and adhesives shown in Table-2. Was obtained. Coated paper was manufactured for each coating material by the above coated paper manufacturing method. Table 2 shows the results of measurement or evaluation of the viscosity of the coating material, the smoothness of the coated paper, and the printing quality (glossiness, unevenness of the inlay) by the following measuring methods and evaluation methods.

[Measurement Method of Paint Viscosity, White Paper Smoothness, Print Quality Evaluation Method] <Paint Viscosity> The viscosity at the adjusted paint concentration was measured at room temperature at a rotation speed of a B-type viscometer of 60 rpm. <Coating unevenness> The coating unevenness of the coated surface of the coated paper was evaluated by visual evaluation. ◎ No coating unevenness is observed. The smoothness of the coated surface of the coated paper was measured by an Oken type smoothness meter. <Print Gloss> Using an RI-II type printing tester, printing was performed using 0.4 cc of ink (trade name: TK Mark Eye, manufactured by Toyo Ink Co., Ltd.) on the coated surface of the coated paper, and the printing was performed day and night After seasoning, 75 ° gloss was measured using a gloss meter manufactured by Murakami Color Research Laboratory. <Ink unevenness> Using an RI-II type printing tester, 0.4 cc of ink (trade name: TK Mark Eye, manufactured by Toyo Ink Co., Ltd.) was used to print on the coated surface of the coated paper.
After seasoning day and night, visually observe the ink
It was evaluated by the point method (5 good to 1 bad).

[0028]

[Table 2]

As is evident from these Examples and Comparative Examples, the coated paper using the transfer roll coating composition according to the present invention was excellent in print quality, and particularly excellent in unevenness in ink adhesion. The paint of the comparative example is 10 g / m on one side.
^{Although two} coatings were possible, even at 10 g / m ² , coating unevenness (split pattern) peculiar to transfer roll coating occurred, and ink was uneven. In addition, since the paint viscosity was high, boiling occurred and workability during coating was poor.

[Examples 3 and 4, Comparative Examples 3 to 8] The paints were prepared by mixing the pigments and the adhesives shown in Table 3, and the coating amount on one side of each paint was 5 g / m ² , 7 0.5 g / m
^Two coated papers were produced. Example 1 Regarding the viscosity of the paint, the smoothness of the coated paper, and the print quality (glossiness, unevenness of the inking)
Measurement or evaluation was carried out by the same measurement method and evaluation method as those described above, and the results are shown in Table 3.

[0031]

[Table 3]

As is apparent from these examples, the coated paper using the coating material of the present invention was excellent in print quality, and particularly excellent in uneven ink deposition. In Comparative Examples 4, 6, and 8, coating unevenness occurred, and therefore, the smoothness and the print gloss could not be measured. Further, in the comparative example, streaky ink deposition unevenness peculiar to transfer roll coating was observed. In particular, Comparative Example 3,
In No. 5, the streaky coating unevenness was intense, and the unevenness in ink deposition was also remarkable.

Examples 5-6, Comparative Examples 9-14 Table-4
The coating materials were prepared by the blending of the pigment and the adhesive shown in (1) above, coated paper was manufactured for each of the coating materials, and then calendering was performed at a higher linear pressure. Example 1 Regarding the viscosity of the paint, the smoothness of the coated paper, and the print quality (glossiness, unevenness of the inking)
The measurement and evaluation were carried out by the same measuring method and evaluation method as described above, and the results are shown in Table-4.

[0034]

[Table 4]

As is clear from these examples, the coated paper using the transfer roll coating composition according to the present invention has excellent print quality even when subjected to a calendering treatment under a high linear pressure, and particularly has good ink adhesion. It was excellent for meat unevenness. On the other hand, in Comparative Examples 4, 6, and 8, coating unevenness occurred, and therefore, the smoothness and the print gloss could not be measured. Further, in the comparative example, streaky ink deposition unevenness peculiar to transfer roll coating was observed, and even when calendering was performed at a high linear pressure, it was not improved and the printing quality was poor. In particular, in Comparative Examples 3 and 5, streak-like coating unevenness was severe, and unevenness in ink deposition was also remarkable.

[Examples 7 to 9 and Comparative Examples 15 to 20] In Examples 7 to 9 and Comparative Examples 15 to 17, paints were prepared by blending pigments and adhesives shown in Table 5 and applied by an actual machine. Speed 1000m
/ Min transfer roll coating at a linear pressure of 75 kg / c
m for soft calendering. Comparative Examples 18 to 20 are commercially available products by blade coating of the same grade as the examples. The viscosity of the coating material, the smoothness of the coated paper, and the printing quality (glossiness, unevenness in the thickness) were measured or evaluated by the same measuring method and evaluation method as in Example 1. The results are shown in Table-5.

[0037]

[Table 5]

As is evident from these examples, the coated paper using the transfer roll coating composition according to the present invention is superior in print quality to the comparative example produced by the same coating method, and is particularly excellent in ink application. Excellent in meat unevenness, and compared with commercial products by blade coating, which is generally said to be superior to transfer roll coated products, it has the same or better print quality Was what it was. In addition, the stencil production process in normal blade coating
It can be manufactured without dividing the coating process. Further, the speed of the on-machine transfer roll coating of the present invention was equal to or higher than the speed of the blade coating, and a wide high-speed coating could be performed.

Examples 10 to 13 and Comparative Examples 21 to 24
The paint was adjusted by the blending of the pigment and the adhesive shown in Table 6 and the coating amount on one side of each paint was 5 g / m ² and 8 g.
/ M ² coated paper was produced. The viscosity of the paint, the smoothness of the coated paper, and the print quality (glossiness, unevenness in the thickness) were measured or evaluated by the same measuring method and evaluation method as in Example 1, and the results are shown in Table-6.

[0040]

[Table 6]

As is clear from these examples, it can be said that the coated paper using the transfer roll coating composition according to the present invention is excellent in printing quality, and particularly excellent in unevenness in ink adhesion. In Comparative Examples 21 and 24, the coating amount of 8 g / m ² could not be applied due to the structure of the transfer coating machine. In Comparative Examples 22 and 23, coating unevenness occurred, and streak-like ink unevenness peculiar to transfer roll coating was observed.

Examples 14 to 17, Comparative Examples 25 to 30
The paint was adjusted by the blending of the pigment and the adhesive shown in Table 7, and the coating amount on one side of each paint was 6 g / m ² , and 7.
A coated paper of 5 g / m ² was produced. About the viscosity of the paint, the smoothness of the coated paper, and the print quality
It was measured or evaluated by the same measuring method and evaluation method as in Example 1, and the results are shown in Table-7.

[0043]

[Table 7]

As is clear from these examples, it can be said that the coated paper using the transfer roll coating composition according to the present invention is excellent in print quality, and particularly excellent in uneven ink adhesion. Further, in Comparative Examples 25 to 30, coating unevenness occurred, and streaky ink deposition unevenness peculiar to transfer roll coating was observed.

[0045]

By using the transfer roll coating composition of the present invention, it is possible to increase the coating amount without causing coating unevenness peculiar to transfer roll coating. And on-machine high-speed and stable operation can be realized without impairing the advantages of transfer roll coating. In addition, coated paper obtained by applying such a transfer roll coating paint has high smoothness under low calendar conditions,
Achieved high gloss, high opacity, high rigidity, and high print quality, and especially excellent print gloss and uneven ink coverage, and can provide coated paper of high print quality comparable to blade coating. . As a result, a remarkable effect was obtained in that high-grade printing paper could be obtained using transfer roll coating, which was conventionally known as a method for obtaining low-grade printing paper. Furthermore, since a coating layer having excellent coatability can be obtained by on-machine high-speed and stable coating, it is excellent for undercoating when performing multilayer coating on-machine.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-143598 (JP, A) JP-A-56-68187 (JP, A) JP-A-63-264996 (JP, A) JP-A-1- 156595 (JP, A) JP-A-2-80694 (JP, A)

Claims (3)

(57) [Claims] 1. A transfer roll coating composition comprising a pigment and an adhesive as main components, wherein the adhesive is a starch-based adhesive.
Wherein the starch-based adhesive has a viscosity of 30% solids
%, The temperature of 50 ℃ and the No.4 rotor of B-type viscometer
570 or more and 3,000 when measured at 60 rpm using
A low-viscosity starch adhesive having a viscosity of less than 0 cps;
The average aspect ratio is 10 or less, the solid content of the paint is 58% by weight or more, and the viscosity of the paint measured at 60 rpm using a No. 4 rotor of a B-type viscometer is 1,500.
A transfer roll coating composition having a cps or less. 2. The pigment has an average aspect ratio of 5 or less;
Calcium carbonate having an average particle size of 2 μm or less
The transfer roll coating composition according to claim 1, wherein the coating composition contains at least% by weight . 3. The method according to claim 1, wherein the paint is a transformer.
Coated paper made by fur-roll coating.
Coating characterized by being at least 5 g / m2 per surface
paper.