JP2008255503A - Method for producing coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing coated paper having no difference between inside and outside and excellent high-speed operability in the method for producing the coated paper, which continuously carries out a finish process for coating base paper made by using a gap-former paper machine with a coating liquid containing pigment and an adhesive, drying the coated base paper to form one or more coated layers, passing the coated paper through a soft calender and surface-treating the coated paper. <P>SOLUTION: The method for producing the coated paper comprises passing the coated paper through the soft calender composed of a metal roll and an elastic roll so that the face of the coated paper of the first six nips is brought into contact with the metal roll face in the order of the felt face side of the coated paper, the wire face side, the wire face side, the felt face side, the wire face side and the felt face side in a finish process in which wet paper is subjected to water drainage by using a shoe press in the press part of a paper machine having a papermaking speed of ≥1,300 m/minute, the dried base paper is coated with the coating liquid, dried to provide the coated base paper with one or more coated layers and surface treatment is carried out by the six or more nips in the soft calender. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a coated paper in which there is little difference between the front and the back of the coated paper in the production in which a coating liquid having a pigment and an adhesive is applied to the base paper and then the process of surface finishing by soft calendering is performed at a high temperature. It is related with the manufacturing method.

In recent years, the demand for coated paper for printing has increased in the commercial printing field for the purpose of advertising and advertising such as flyers, catalogs, pamphlets and direct mail. Although these commercial prints have a low commercial value per se, it is important that the purpose is achieved as an advertising medium, and therefore, there is a demand for low cost and good print finishes. In addition, it is an important technical issue for paper makers to increase productivity and reduce costs while maintaining high quality.

The productivity of coated paper is greatly influenced by the surface finishing process. As a means for improving the productivity of the surface finishing process, a soft calendar process under a high temperature condition is known (see Patent Document 1). This is done by winding the coated paper once coated with a conventional coating device (hereinafter referred to as coater) and then using a super calender and processing it at low temperatures and usually in multistage nip conditions of 10 to 14 stages. In this case, smoothness is imparted and the product is commercialized. On the other hand, after applying the coating solution with a coater, the soft calender treatment is performed online and at a high temperature to improve productivity. Cotton rolls used in conventional supercalenders are inferior in heat resistance due to problems of internal heat generation and inferior in pressure resistance and durability, so there is a limit to speeding up, and the maximum speed that can be operated at present is about 800 m / min. . Therefore, in order to use it with a coater exceeding 1000 m / min in recent years, two super calendars are required, which must be taken up once and then applied to the super calendar again, which means further space saving. But it becomes a problem. On the other hand, in the case of a soft calender having a plastic elastic roll excellent in heat resistance and pressure resistance, operation at a speed exceeding 1000 m / min is possible, and productivity can be improved because it can be installed on the coater online.

In addition, by processing with a smaller number of nips at a high temperature, it is possible to save space, and in terms of quality, the surface of the metal roll is transferred to the paper surface with only the paper surface layer being plasticized due to the high temperature. In comparison, when the paper is crushed to the same thickness, excellent surface properties and printability can be obtained.

However, as the processing temperature of the soft calender is increased at a high speed to improve productivity, there are many differences in surface properties such as gloss and smoothness on the felt side and wire side of the coated paper. was there.
In order to solve the problem such as the difference between the front and the back, for example, in a finishing process in which a surface treatment is performed with a soft calender composed of a metal roll and an elastic roll, a 4-nip soft calender is used and the first nip is a metal roll. Pass the paper so that the wire side of the coated paper hits the side, then the felt side of the coated paper hits the metal roll surface at the second and third nips, and the wire side again hits the metal roll at the next fourth nip. By doing so, it has been proposed that there is no difference between the front and the back (see Patent Document 2). However, at a processing speed of 1200 m / min, there is no difference between the front and back surfaces such as glossiness of the blank paper, and an excellent surface wrinkle and package appearance can be obtained, but at a processing speed of 1,300 m / min or more, particularly 1500 m / min or more, blank paper The glossiness was inferior, the difference between the front and back was increased, and the quality such as blister resistance was inferior.

JP 54-125712 A Japanese Patent Laid-Open No. 10-331095

In view of the situation as described above, the object of the present invention is to apply a coating solution containing a pigment and an adhesive onto a base paper that has been made using a gap former type paper machine and to dry the coating layer. Provided is a coated paper manufacturing method in which a finishing process in which a surface treatment is performed by passing through a soft calender is continuously performed after providing more than one layer, and there is no difference between the front and back sides and excellent in high-speed operability. There is.

As a result of intensive studies, the present inventors have applied and dried a coating liquid containing a pigment and an adhesive on a base paper made using a gap former type paper machine to provide one or more coating layers. After that, in the coated paper manufacturing method in which the finishing process of surface treatment by passing through a soft calender is continuously performed, wet paper is applied to the press part of a paper machine with a paper making speed of 1300 m / min or more using a shoe press. Finishing process of surface treatment of soft calenders composed of metal rolls and elastic rolls at 6 nips or more after applying and drying coating liquid on dried and dried base paper to provide one or more coating layers Then, the coating paper passes so that the surface of the coated paper hitting the first 6-nip metal roll surface is in the order of the felt surface side, the wire surface side, the wire surface side, the felt surface side, the wire surface side, and the felt surface side. By manufacturing paper, Reached Ming.

  There is no difference between the front and back, coated paper having excellent high-speed operability and excellent blister resistance during offset printing can be produced, and the effect can be exerted more particularly on lightweight coated paper.

In the present invention, a coating liquid containing a pigment and an adhesive is applied and dried on a base paper made using a gap former type paper machine to provide one or more coating layers, and then passed through a soft calender. In the method for producing coated paper in which the finishing process of paper and surface treatment is continuously performed, wet paper is applied using a shoe press to a press part of a paper machine having a paper making speed of 1300 m / min or more, preferably 1500 m / min or more. Finishing process that coats and dries the coating liquid on the base paper that has been squeezed and dried to provide one or more coating layers, and then surface-treats a soft calender composed of a metal roll and an elastic roll at 6 nips or more. Then, pass the paper so that the surface of the coated paper that hits the metal roll surface of the first 6 nips is in the order of the felt surface side, the wire surface side, the wire surface side, the felt surface side, the wire surface side, and the felt surface side. This is a paper manufacturing method.
The coated base paper of the present invention uses a gap former type paper machine in which the stock jetted from the head box runs between two wires and dehydrates almost evenly from both sides of the wet paper. By using a gap-former type paper machine of the roll-and-blade former type having a dewatering mechanism with a dewatering blade immediately after the initial dewatering with the forming roll, it is possible to obtain a surface with no difference between the front and back, and 1300 m / min or more It is more suitable for high paper making speed. The forming part in the manufacturing method of the present invention is a roll-and-blade type former, and the initial dewatering is performed in the lap area of the forming roll having a vacuum, and immediately after that, the blade is dewatered by the pressure blade module. This mechanism makes it possible to dewater more slowly than the conventional former, so that paper having a uniform paper layer structure and texture can be obtained. If the diameter of the forming roll used at this time is small, a sufficient holding angle cannot be obtained, and it is desirable that the forming roll is 1500 mm or more because the dehydration adjustment is insufficient. In addition to a dewatering mechanism using a forming roll or a blade, dryness can be adjusted by appropriately using a dewatering device such as a suction unit or a high vacuum suction box in the subsequent stage.
The press part of the present invention uses a shoe press. When the paper making speed is high, it is preferable to process a tandem type shoe press in one or more stages, more preferably two or more stages in consideration of moisture after pressing. By treating with, interlayer strength and blister resistance are improved. The shoe press has a nip width generally in the range of 150 to 250 mm, and the processing conditions are preferably 100 KN / m to 1100 KN / m, more preferably 500 KN / m to 1100 KN / m.
Further, when two or more shoe presses are used, passing the paper so that the transfer belt comes into contact with the shoe press on the dryer part side is less likely to cause paper breakage and has excellent high-speed operability.

The paper machine pre-dryer and after-dryer can also use a public apparatus, and the drying conditions are not particularly limited, and can be appropriately set within the normal operating range.
The pulp raw material for coated base paper is not particularly limited and is generally used as a paper raw material for printing paper such as mechanical pulp (MP), deinked pulp (DIP), and softwood kraft pulp (NKP). Any one of these may be used, and one or two or more of these may be used as appropriate. Examples of mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), and semi-chemical pulp (SCP). . The deinked pulp may be any deinked pulp made from high-quality paper, medium-quality paper, low-grade paper, newspaper, flyers, magazines, etc. Absent. In the present invention, even when the deinked pulp is 30% by weight or more with respect to the pulp, effects such as no difference in front and back and good interlayer strength can be exhibited.

  The filler used in the present invention can be arbitrarily selected from known fillers such as heavy calcium carbonate, light calcium carbonate, clay, silica, light calcium carbonate-silica composite, kaolin, calcined kaolin, deramikaolin, magnesium carbonate. Inorganic fillers such as amorphous silica produced by neutralization by mineral production of barium carbonate, barium sulfate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, zinc oxide, titanium oxide, sodium silicate, Organic fillers such as urea-formalin resin, melamine resin, polystyrene resin and phenol resin can be used alone or in combination. Among these, calcium carbonate and light calcium carbonate-silica composite, which are typical fillers for neutral papermaking and alkaline papermaking, are preferably used. The filler content in the paper is 1 to 40% by weight. In papermaking, the yield decreases as the filler content in the paper increases. Therefore, the effect of the present invention is greater when the present invention is applied to the production of a printing base paper having a high filler content in the paper. From this viewpoint, the filler content in the paper is preferably 10 to 40% by weight, and more preferably 12 to 35% by weight.

As the internal additive, chemicals such as a dry paper strength improver, a wet paper strength improver, a drainage improver, a dye, and a neutral sizing agent may be used as necessary. Examples of the dry paper strength improver include polyacrylamide and cationized starch, and examples of the wet paper strength improver include polyamidoamine epichlorohydrin. These chemicals are added within a range that does not affect the formation and operability. Examples of neutral sizing agents include alkyl ketene dimers, alkenyl succinic anhydrides, and neutral rosin sizing agents.
Further, a coating liquid containing a pigment and an adhesive is coated on the base paper made as described above, dried to provide a coating layer, and then passed through a soft calender to perform a smooth finish.
Prior to the formation of the coating layer, a base paper or the like that is subjected to a surface treatment by appropriately applying an adhesive or the like to the base paper using a 2-roll size press coater, a rod metering size press coater, a gate roll coater or the like is used. Is also possible. Further, it is particularly preferable to smooth the base paper in advance using an on-line soft calendar before coating in order to make the coating layer after coating uniform.

As the pigment used in the coating liquid of the present invention, pigments used in the ordinary coated paper production field can be used as appropriate. Specifically, one or more of kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum oxide, calcium carbonate, satin white, aluminum silicate, magnesium silicate, magnesium carbonate, plastic pigment and the like are appropriately used. Use by mixing.

In addition, as an adhesive used in the coating liquid, an adhesive used in a normal coated paper manufacturing field can be appropriately used. For example, various starches such as starch and oxidized starch, casein, soy protein, synthetic protein, etc. Proteins, polyvinyl alcohol, cellulose derivatives such as carboxymethyl cellulose and methyl cellulose, styrene-butadiene copolymer, conjugated diene polymer latex of methyl methacrylate-butadiene copolymer, acrylic polymer latex, ethylene-vinyl acetate copolymer Vinyl polymer latex such as coalescence is used alone or in combination of two or more. In addition, the compounding quantity of an adhesive agent adjusts 5-50 weight part with respect to 100 weight part of pigments, More preferably, it is 10-30 weight part. In addition to pigments and adhesives, the coating liquid contains various types of dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives, etc. used in the general coated paper manufacturing field. Auxiliaries can be added as appropriate.

  Coating liquids prepared using the above materials include blade coaters, bar coaters, roll coaters, air knife coaters, reverse roll coaters, curtain coaters, rod metering size press coaters, blade metering size press coaters, gate roll coaters, etc. Using one or two or more layers on a base paper, it is coated on one side or both sides and dried. The solid content concentration of the coating liquid is adjusted to about 30 to 68% by weight. In addition, when providing the coating layer in multiple layers, considering the quality characteristics of the final product, the type of the upper layer and lower layer pigments, adhesives, etc. can be changed, or the blending ratio etc. can be changed as appropriate. .

In the present invention, when coating on a layer adjacent to the base paper, a film transfer system such as a gate roll coater, a blade or a rod metering size press coater is preferable, but from the viewpoint of high-speed operability of 1300 m / min or more, In particular, a rod metering size press coater in which a coating layer with a low coating amount is provided at a high speed, and a blank paper surface feeling and a surface property of the front and back are good. The coating amount in this case, base paper per side 1 to 6 g / m ^2, more preferably from 2 to 4 g / m ^2. In the case of further overcoating, a blade system using a flooded nip type blade coater, a jet fountain type blade coater, a short dwell time application type blade coater or the like is preferable, and in particular, from the viewpoint of suitability for high speed coating, a jet fountain type blade It is preferable to employ a coater. Moreover, you may perform a soft calendar process after undercoat coating.
In the present invention, papermaking, coating, and calendar treatment are integrated, and the coated paper is manufactured by continuously passing paper, thereby providing excellent operability at a high speed of 1300 m / min or more, and the front and back sides of the coated paper. There is no difference, and a highly smooth coated paper can be obtained, preferably 1500 m / min or more, more preferably 1600 m / min or more and about 2500 m / min. That is, one or more coating layers are provided by coating and drying a coating solution containing a pigment and an adhesive on a base paper that is made using a tandem shoe press in the press part of a gap former type paper machine. Then, when finishing the coated paper at a high speed of 1300 m / min or more, the finishing process of passing the surface through a soft calender is continuously performed. There is a problem that the smoothness and the like are increased, and there is a difference between the front and the back in the surface property. In order to solve this problem, the paper feeding conditions of the soft calendar were studied repeatedly. As a result, at least 6 nips are required to eliminate the difference between the front and back sides, and the first nip is coated on the metal roll surface with the felt surface side of the coated paper, and then the second and third nips are coated on the metal roll surface. Pass the paper so that the wire side of the paper touches the metal roll, then the fourth nip again hits the metal roll on the felt side and the fifth nip hits the metal roll on the wire side, and the sixth nip hits the metal roll on the felt side. I found out that there was no difference between the two sides.

On-line high temperature soft calendering process that integrates papermaking, coating and calendering processes and manufactures coated papers by continuously passing paper, the metal roll side at the first nip that can be processed with the highest moisture content. The surface of the coated paper that hits the surface is more easily plasticized than the subsequent nip, and the smooth metal roll surface is easily copied, so that the glossiness and smoothness of white paper are the highest. In the present invention, in the base paper made by using a tandem shoe press in the press part of the gap former type paper machine, the shoe press on the dryer part side is used in order to achieve both water squeezing and running performance in a balanced manner. It is preferable that the transfer belt comes into contact. At this time, since the transfer belt is smoother than a normally used blanket, the surface property on the side in contact with the transfer belt is good. Therefore, it is necessary to pass the first nip so that the felt surface, which is inferior in surface property, is brought into contact with the metal roll surface. Next, for the second nip, the wire surface side touches the metal roll, and for the third nip, the wire surface side is applied to the metal roll surface, the fourth nip is the felt surface side, the fifth nip is the wire surface side, and the sixth nip is the felt. By applying a metal roll to the surface side, a coated paper with no difference between the front and the back can be obtained. In addition, even if the number of nips is increased from 7 nips, after 7 nips, calendar processing will be performed in the area where the moisture of the coated paper is low, and the order of the coated surfaces corresponding to the metal roll surface will be different from the front and back. The effect is small, and no matter what kind of paper is passed, there is no problem.
The surface temperature of the metal roll at the 1st to 6th nips of the soft calender is preferably 100 to 250 ° C, more preferably 100 to 200 ° C. Moreover, it is preferable that the calender linear pressure to 1st-6th nip is 100-600 kN / m, More preferably, it is 150-450 kN / m.

  The paper moisture when entering the first nip of the soft calender is preferably 5% to 12%, more preferably 7% to 10%, in order to achieve both glossiness and operability. The material of the elastic roll used in pair with the metal roll of the soft calender is not particularly limited, but generally at high temperature and high pressure such as modified urethane resin, epoxy resin, polyamide resin, phenol resin, polyether resin, polyacrylate resin, etc. A resin roll exhibiting durability is preferably used. Moreover, as the hardness of the resin roll, excellent surface smoothness can be obtained by using a shear D hardness of 85 degrees or more. The type of soft calendar used in the present invention is preferably 6 stacks of 2 rolls of tandem type in consideration of easy paper passing and space saving. The tandem type is a soft calendar of a type in which two rolls obtained by overlapping a pair of metal rolls and elastic rolls are arranged in parallel.

In the present invention, a coating layer containing a pigment and an adhesive is coated and dried on a base paper that has been made using a gap former type paper machine using a shoe press as a press part. After providing the above, there is no difference between the front and back by producing coated paper at a high speed of 1300 m / min or higher, continuously performing the finishing process of passing the surface of the soft calender through 6 nips or more. In addition, it can produce coated paper with excellent surface wrinkles and package appearance (bulkyness, gloss, whiteness, blank paper feel) and excellent high-speed operability, especially for lightweight coated paper. can do. Specifically, the basis weight of the coated paper is preferably 30 to 80 g / m ² , more preferably 40 to 65 g / m ² , and the coating amount per side of the base paper is 3 to 15 g / m ^2. Is more preferable, more preferably 4 to 12 g / m ² , still more preferably 4 to 10 g / m ² , and the effect of the present invention is more exhibited.

The present invention will be specifically described below with reference to examples. In the examples, parts and% indicate parts by weight and% by weight, respectively. The quality evaluation method is as follows.

<Quality evaluation method>
(1) Glossiness of blank paper: measured at an angle of 75 degrees according to JIS P-8142.
(2) Blister resistance: Using a RI-I type printer (Ming Seisakusho), using Toyo Ink (TK Mark V617), printing on both sides with a constant ink amount of 0.8 cc and adjusting the humidity all day and night, this The test piece was immersed in a constant temperature oil bath set at a temperature of 140 ° C., and the occurrence of blisters was visually determined.
◎ = Not generated at all, ○ = Not generated at all, △ = Generated, X = Significantly generated (3) High-speed operability: Paper breakage at the press part is difficult to occur, and no mist is generated during coating. The suitability of high-speed operability without the occurrence of shrinkage wrinkles during calendaring was evaluated.
◎ Very good, ○ Good, △ Slightly poor, × Poor [Example 1]
Add 30 parts of waste paper pulp, add 70 parts of LBKP light pulp gallium carbonate as a filler so that the ash content in the paper is 11%, and add 4 parts of cationized starch as an internal paper strength agent. It was adjusted. Using this stock, two tandem shoe presses (pressing line pressure 1000 KN / m, second paper wire on the press part in a gap-former type paper machine of roll and blade former type with a paper making speed of 1600 m / min. The wet paper is squeezed using the transfer belt on the front side and made into a dry base paper, and then oxidized starch with a solid content of 6% on both sides using an on-machine rod metering size press coater. The solution was coated and dried at 1.6 g / m ² to obtain 45.6 g / m ² of medium-quality coated base paper. Next, 100 parts of pigment containing 73 parts of heavy calcium carbonate and 27 parts of kaolin were mixed with 4.5 parts of oxidized starch and 8.2 parts of carboxy-modified styrene / butadiene copolymer latex as an adhesive. A coating solution having a partial concentration of 64% was prepared, and 8.3 g / m ² per side of the base paper was overcoated on both sides and dried.
Subsequently, using a 2-roll / 6-stack high-temperature soft calender having a resin roll with a Shore D hardness of 91 °, all the 1 to 6 nips were continuously calendered under conditions of a metal roll surface temperature of 150 ° C. and a linear pressure of 400 kN / m. did. At that time, the coated paper was manufactured by passing the coated surface in order of the F, W, W, F, W, and F surfaces in the 1 to 6 nips so as to contact the metal roll surface of each nip. Since papermaking, coating, and calendaring were integrated and performed continuously, the coating speed and calendar speed were also 1600 m / min.

[Comparative Example 1] Using a 2-roll, 4-stack high-temperature soft calender having a resin roll with a Shore D hardness of 91 °, the 1-3 nip is a metal roll surface temperature of 160 ° C, the linear pressure is 250 kN / m, and the 4 nip is a metal Continuous calendering was performed under conditions of a roll surface temperature of 40 ° C. and a linear pressure of 100 kN / m. At that time, the coated paper is manufactured in exactly the same manner as in Example 1 except that the coated surface is passed through the nips in the order of W, F, F, and W surfaces in the 1 to 4 nips. did.
[Comparative Example 2] Coated paper was produced in the same manner as in Example 1 except that a hybrid former in which only the rear part of the long-mesh wire was a twin wire was used.
[Comparative Example 3] When performing continuous calendering, the above except that the coated surface was passed in order of F, W, W, F, F, W surface side in order of the nips 1 to 6 so as to contact the metal roll surface of each nip. Coated paper was produced in exactly the same manner as in Example 1.
[Comparative Example 4] Coated paper was produced in exactly the same manner as in Example 1 except that the press treatment was carried out with four roll presses at a linear pressure of 1 to 4 nips of 70 KN / m.

Claims (5)

Apply a coating liquid containing pigment and adhesive on a base paper that has been made with a gap former type paper machine and dry it to provide one or more coating layers. In a coated paper manufacturing method in which the finishing process is continuously performed, wet paper is squeezed using a shoe press at the press part of a paper machine with a papermaking speed of 1300 m / min or more, and the coating liquid is applied to the dried base paper. The first 6-nip metal roll surface is a finishing process in which a soft calender composed of metal rolls and elastic rolls is surface-treated at 6 nips or more after coating and drying to provide one or more coating layers. A method for producing a coated paper, characterized in that the coated paper is applied so that the surface of the coated paper hitting the felt surface side, the wire surface side, the wire surface side, the felt surface side, the wire surface side, and the felt surface side in this order. The method for producing coated paper according to claim 1, wherein the gap former type paper machine is of a roll and blade former type having a dewatering mechanism with a dewatering blade immediately after initial dewatering with a forming roll.   The method for producing coated paper according to claim 1 or 2, wherein the shoe press has one or more tandem shoe presses.   The method for producing a coated paper according to any one of claims 1 to 3, wherein an apparatus for first coating on the base paper is a metering size press coater. The metal roll surface temperature from the 1st to 6th nip of the soft calender is 100 to 250 ° C.