WO2002059421A2 - Cast coated paper and method of producing the same - Google Patents

Cast coated paper and method of producing the same

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Publication number
WO2002059421A2
WO2002059421A2 PCT/ID2002/000001 ID0200001W WO2002059421A2 WO 2002059421 A2 WO2002059421 A2 WO 2002059421A2 ID 0200001 W ID0200001 W ID 0200001W WO 2002059421 A2 WO2002059421 A2 WO 2002059421A2
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WO
Grant status
Application
Patent type
Prior art keywords
coated
paper
layer
cast
coating
Prior art date
Application number
PCT/ID2002/000001
Other languages
French (fr)
Other versions
WO2002059421A3 (en )
Inventor
Ali Alimsyah
Sanjung Sungkarto
Horiuchi Muneyoshi
Okada Haruo
Original Assignee
Pt. Pindo Deli Pulp And Paper Mills
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/46Non-macromolecular organic compounds
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/64Inorganic compounds
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H25/00After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
    • D21H25/08Rearranging applied substances, e.g. metering, smoothing; Removing excess material
    • D21H25/12Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod
    • D21H25/14Rearranging applied substances, e.g. metering, smoothing; Removing excess material with an essentially cylindrical body, e.g. roll or rod the body being a casting drum, a heated roll or a calender

Abstract

A cast coating composition contains either of calcium formate and calcium acetate and any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc., as air permeability modifiers respectively, so that the cast coating composition is applied onto a base paper (1). Next, the base paper (1) is dried by a drying machine (3) until the base paper (1) contains a predetermined rate of moisture. A rewetting liquid is applied from a nozzle (4) to the dried base paper (1) so as to moisten the base paper (1) and plasticize the coated material. The paper is then brought into contact with the surface of a mirror-finished drum (7) which is heated to a high-temperature, and pressed by a press roll (5) so as to be finished to be glossy. Particularly, as for the quantities of the air permeability modifiers to be added, it is preferably that the quantity of either of calcium formate and calcium acetate is in a range of from 0.2 parts to 1.8 parts by weight, and further the quantity of any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc., is in a range of from 0.1 part to 3.0 parts by weight, per 100 parts by weight of the pigment. Thus, high-quality cast coated paper having a high gloss without any surface defect such as pin-holes can be produced at a high speed under the production conditions having a comparatively acceptable and reasonable range in manufacturing.

Description

CAST COATED PAPER AND METHOD OF PRODUCING THE SAME

BACKGROUND OF INVENTION

Field of the Invention The present invention relates to cast coated paper and a method of producing the same, and particularly relates to cast coated paper having a high gloss peculiar to cast coated paper and having excellent printability without any surface defect such as pin-holes, and a method for producing such cast coated paper at a high speed-

Description of the Related Art

Known methods of producing high gloss paper for printing, called cast coated paper, include (1) a wet casting method in which paper coated with a cast coating composition having a pigment and an adhesive as its principal components is pressed against the mirror-finished surface of a heating drum while the coated layer of the paper is in the wet state, so that the coated layer is dried and finished to be glossy, (2) a gel-casting method in which the coating layer is dipped with specular acid or salt and pressed against the mirror-finished surface of a heating drum while the coated layer in the wet state is set to the gel state, so that the coated layer is dried and finished to be glossy, and (3) a rewet coating method in which the coated layer in the wet state is once dried, then moistened and plasticized with a re-wetting liquid, and then pressed against the mirror-finished surface of a heating drum.

These methods for producing cast coated paper have a point in common as follow. That is, in each of the methods, the surface of a coated layer of paper in a plasticized state is pressed against the mirror-finished surface of a heating drum so as to be dried, and then released from the heating drum as a replica of the mirror-finished surface. However, since the surface of the coated layer is dried in contact with the surface of the heating drum in such a producing method, the moisture in the coated layer or the moisture of the re-wetting Tiquid must all pass through the paper layer to the opposite side and be evaporated. As a result, pin-holes or unevenness in the gloss are apt to appear in the surface of the coated layer of the cast coated paper obtained thus. It is necessary to solve such troubles by changing the operating conditions .

On the other hand, in the present circumstances, for such cast coated paper, the speed of the operation is extremely low unavoidably, as compared to the speed of the production of general art paper or general coated paper, which is dried from both sides and further from the coated layer side. That is, in the wet casting method, the coated paper is pressed against the surface of the heating drum immediately after being coated with a coating composition. Accordingly, since the coated paper is pressed in the state where the coating composition is plasticized, a mirror- finished gloss can be obtained easily. However, if the coated paper is dried rapidly with much moisture contained in the coating composition, the moisture cannot move following the drying, so that surface defects such as blisters are produced. Therefore, even if the drying load is reduced by adopting a double coating process while the drum temperature is set at 90°C or lower, the manufacturing speed cannot be increased to 80 m/min or higher. In the gel-casting method, the coating composition applied is coagulated with an aqueous solution of specific acid or salt, and then pressed against the surface of the heating drum. Accordingly, the drying load is reduced in comparison with that in the wet casting method. Thus, the air permeability is improved so that the operation can be carried out at a drum temperature of 100 C or higher. However, since surface defects such as pin-holes are produced easily, the limit of the manufacturing speed is 90 m/min .

With respect to this point, in the rewet casting method, the coated layer dried once is moistened and plasticized with a re-wetting liquid, and then pressed against the mirror-finished surface of the heating drum. Accordingly, the moisture dried is less than that in either of the wet casting method and the gel-casting method. In addition, in the rewet casting method, the surface of the coated layer is pressed against the surface of the heating drum while only surface of the coated layer is in the wet state. Thus, this method has a big potential for production at a high speed, as compared to those in the other two methods. However, because of the poverty of plasticity in the coated layer when it is pressed against the heating drum, the limit of the manufacturing speed is 60 m/min or a value near 60 m/min.

In addition, in this rewet casting method, it is necessary to rewet the dried coated layer and further give the coated layer enough plasticity to make a replica of the mirror-finished surface of the casting drum (above-mentioned heating drum) thereon during an instantaneous time of pressure contact between the surface of the casting drum and a press roll. At the same time, it is necessary to evaporate the moisture chiefly coming from the re-wetting liquid through a layer of base paper smoothly. Thus, the manufacturing conditions cannot help being complicated in comparison with those in the other methods, that is, the wet casting method and the gel-casting method.

Conventionally, as for methods for solving such problems, various researches have been made on the base paper, the coating composition, the composition and the concentration of the re-wetting liquid, the drying temperature, the contact pressure, the drum temperature, and so on. For example, a coating composition which often uses calcium carbonate having high air permeance as a white pigment of the coating, and a coating composition which uses synthetic rubber latex as a principal component of an adhesive are disclosed in JP-B-1-2815 and JP-B-8-26274 respectively. A re-wetting liquid using a dispersant, a release agent, a PH adjuster, etc., alone or combination, is disclosed, for example, in JP-B-4-15315. As for the drum temperature and the contact pressure, in some cases, the casting drum is heated to 100 C or higher, and the operation is carried out at a high pressure of 180 kg/cm or higher between the casting drum and the press roll. As a result, even in the rewet casting method, the manufacturing speed in a factory reaches approximately 90 m/min. Thus, the operation can be carried out at a high speed to some extent. However, in these production methods, there still remains problems about stability in a long-term operation, quality of finished products, ephemeralization of parts used, limitation of the manufacturing speed, and so on. Thus, many improvements have been demanded.

The present invention was brought to completion as a result of consideration of such problems from entirely new points of view. That is, diligent researches were carried on consideration of the following two points: one was to keep the plasticity of the coated layer due to the re-wetting liquid maximal at the time of instantaneous pressure contact between the casting drum and the press roll; and the other was to maximize the air permeance of the dried coated layer in order to release the moisture efficiently. As a result, there was found cast coated paper with a high gloss and an excellent printability without any surface defect such as pin-holes, by containing a proper quantity of calcium formate or calcium acetate, and a proper quantity of a mixture of any one of zinc oxide, zinc chloride, zinc sulfate, and so on, in the cast coating composition at the same time, and a production method in which such paper can be produced efficiently, stably and a high speed.

SUMMARY OF THE INVENTION The present invention provides cast coated paper constituted by base paper; a cast coating composition containing a pigment and an adhesive as a principal component and applied onto the base paper, the applied cast coating composition being dried to form a coated layer on the base paper; and a re-wetting liquid applied to the coated layer to thereby moisten and plasticize the coated layer, the coated layer being pressed against a mirror- finished and heated surface of a drum to thereby finish the paper with a gloss; wherein the coated layer contains either of calcium formate and calcium acetate, and any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc.

Particularly, of the zinc compounds, a proper quantity of zinc oxide together with calcium formate may be added to the cast coating composition at the same time. In this case, the air permeance of the coated layer is improved dramatically. At the same time, the dried coated layer is plasticized smoothly with the re-wetting liquid when the coated layer is instantaneously pressed against the surface of the heating drum. Thus, it is possible to obtain cast coated paper having a high gloss but without any surface defect such as pin-holes .

According to a preferred embodiment, the coated layer contains, per 100 parts by weight of the pigment, 0.2 to 1.8 parts by weight of either of calcium formate and calcium acetate, and 0.1 to 3.0 parts by weight of any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc.

In addition, the present invention has a feature in a method of producing cast coated paper, comprising the steps of: (a) coating base paper with a cast coating composition which contains a pigment and an adhesive as a principal component, the cast coating composition being made to contain either of calcium formate and calcium acetate, and further any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc; (b) drying the coated base paper until the coated base paper contains a predetermined rate moisture; (c) applying a re-wetting liquid to the dried base paper to thereby moisten the coated base paper; and (d) plasticizing the applied cast coating composition with the re-wetting liquid, and then pressing the coated base paper against a mirror-finished drum surface which is heated to a predetermined temperature so as to gloss-finish the coated base paper to thereby obtain cast coated paper. Particularly, of the zinc compounds, a proper quantity of zinc oxide together with calcium formate may be added to the cast coating composition. In this case, the air permeance of the coated layer is improved dramatically. At the same time, the dried coated layer is plasticized smoothly with the re- wetting liquid when the coated layer is instantaneously pressed against the surface of the heating drum. Thus, the operation of production of cast coated "paper having a high gloss but without any surface defect such as pin-holes can be carried out at a high speed.

According to a preferred embodiment, the above- mentioned method of producing cast coated paper has a feature that a portion where the coated paper is dipped in the re-wetting liquid is located in a nip portion formed by the drum and a press roll. Thus, it is possible to prevent the re-wetting liquid from penetrating the paper layer excessively.

According to another preferred embodiment, the above- mentioned method of producing cast coated paper has a feature that the cast coating composition contains, per 100 parts by weight of the pigment, 0.2 to 1.8 parts by weight of either of calcium formate and calcium acetate, and 0.1 to 3.0 parts by weight of any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc. According to another preferred embodiment, the above- mentioned method of producing cast coated paper has a feature that the coated layer is dried to reduce moisture contained in the coated layer to 2% to 10%.

The contents of the present invention will be described below in detail. As for the coated layer in the rewet casting method, it is important to know how the moisture is evaporated through the coated paper layer and the coated layer is dried efficiently when the coated layer is instantaneously pressed against the casting drum through the press roll, and how the plasticity of the coated layer is kept to be large enough to perform a smooth mirror-finishing of the coated layer by the pressure contact. Both the processes area often contradictory to each other as measures. It is the chief object of the present invention how both the processes can be attained simultaneously.

First, for the efficient removal of moisture, the quantity of the re-wetting liquid sufficient to plasticize the coated layer is required because the coated layer is plasticized essentially by the re-wetting liquid in the rewet casting method. On the other hand, reduction in this required quantity depends on a large faculty of the re- wetting liquid to moisten and plasticize the dried coated layer, and above-mentioned method of producing cast coated paper has a feature that the coated layer is dried to reduce moisture contained in the coated layer to 2% to 10%.

The contents of the invention will be described below in detail. As for the coated layer in the rewet casting method, it is important to know how the moisture is evaporated trough the coated paper layer and the coated layer is dried efficiently when the coated layer is instantaneously pressed against the casting drum through the press roll, and how the plasticity of the coated layer is kept to be large enough to perform a smooth mirror-finishing of the coated layer by the pressure contact. Both the processes are often contradictory to each other as measures. It is the chief object of the present invention how both the processes can be attained fulfillment of the following condition. That is, re-wetting liquid is effective if the re-wetting liquid required for plasticization is retained only in the surface of the coated layer, but not allowed to penetrate the paper layer excessively in vain. In addition, the coated layer itself must have high moisture permeance (hereinafter referred to as "permeance") , and this is the quality essential for the coating composition. It is important to know how this permeance can be made to fall in a range in which high quality and high speed production can be attained, without sacrificing properties required for manu acturing and using a product, for example, without sacrificing operating performance in the manufacturing process, printability of a finished product, and so on.

As a specific method for optimizing the pigment component and the kind and loading of the adhesive in the coating composition as described above, and further for improving the permeance of the coated layer itself aggressively, methods in which calcium formate conventionally used as a coagulating agent in a coagulating liquid in the gel-casting method was added to the coating composition itself were conceived of variously. For example, JP-B-28-15751 disclose a hot gel casting method in which a so-called coagulating agent is added to a cast coating . composition. In addition, as a method aimed at achieving a similar affect, JP-A-51-40410 discloses a method in which a large quantity of satin white is added, and JP-C- 2987528 discloses a method in which a small quantity of satin white is added. However, each method is not suitable for high-speed operation because a coated layer in a semidry state is pressed against a heating drum, that is, a casting drum, or because a coated layer is pressed against a casting drum in a state of not being dried beforehand.

On the other hand, according to the present invention, high-speed operation can be carried out if the coated layer is moistened with the re-wetting liquid and then finished after the coated layer is dried to reduce the moisture contained therein to a predetermined rate. At this time, calcium formate gelatinizes the coated layer while a meshwork formed in the coated layer improves the permeance of the coated layer at the same time. On the other hand, if calcium formate is added directly to the coating composition, not to say, the viscosity of the coating composition is increased, and further the coating composition is destabilized due to consideration or the like. Thus, at the same time, it is expected that excessive use also gives a bad influence such as deterioration of surface strength to the quality of a finished product.

As a result of comprehensive consideration of these points, it was found that the permeance could be improved without sacrificing the operating performance and the quality of a finished product if the quantity of calcium formate to be added was set in a range of from 0.2 part to 1.8 parts by weight per 100 parts by weight of the pigment after the coated layer was dried to reduce the moisture contained therein in a range of from 2% to 10%, preferably in a range of from 3% to 8%. This quantity to be added generally corresponds to 3.0 to 30 parts by weight per 100 parts by weight of a protein adhesive. On the other hand, as a result of researches, it was found that zinc compounds such as zinc chloride, zinc sulfate, zinc oxide, etc., which were usually used as water resistant agents, also had a large effect on such improvement of permeance. That is, such a zinc compound lowered an immovable point of the coating composition due to reaction or aggregation in the step of drying after coating, so that the micro-porous property of the coated layer was improved. Further, in the rewet casting method, various researches were made on the use of zinc compounds. As a result, when a proper quantity of a zinc compound was added to the coating composition, the increase in the viscosity of the coating composition was low, and there was a water-proof effect. However, it was not possible to obtain an expected effect to produce, at a high speed, cast coated paper having a high glossy surface without any surface defect such as pin-holes. On the contrary, when a large quantity of a zinc compound was added, the permeance was indeed improved, but there appeared a surface defect such as pin-holes if a production machine for cast paper was operated at a high speed not lower than 80 m/min for a test. In this case, it is considered that the permeance is indeed improved, but the water resistance is however increased to deteriorate another requirement, that is, to deteriorate the effect of plasticization of the dried coated layer with the re-wetting liquid in the instantaneous pressure contact between the casting drum and the press roll. Therefore, though production high in speed could be carried out to some extent by adding a proper quantity of calcium formate to the cast coating composition as described above, various researches were made on further improvement. As a result, among zinc compounds, particularly the addition of a proper quantity of zinc oxide together with calcium formate to the cast coating composition not only could improve the permeance of the coated layer dramatically, but also could plasticize the dried coated layer smoothly with the re-wetting liquid when the coated layer was instantaneously pressed against the surface of the heating drum. Thus, the operation of production of cast coated paper having a high gloss without any surface defect such as pin- holes could be carried out at a high speed not lower than 120 m/min. The quantity of calcium formate to be added to the cast coating composition is in a range of from 0.2 to 1.8 parts by weight, preferably in a range of from 0.5 to 1.2 parts by weight per 100 parts by weight of the pigment. This quantity to be added generally corresponds to 3.0 to 30 parts by weight per 100 parts by weight of a protein adhesive. If the quantity exceeds this range, the viscosity of the coating composition increases, and the coating composition will be gelatinized at last so that the operation cannot be carried out. On the contrary, if the quantity is below this range, an expected effect cannot be obtained. On the other hand, the quantity of zinc oxide is in a range of from 0.1 to 3.0 parts by weight, preferably in a range of from 0.3 to 2.0 parts by weight, per 100 parts by weight of the pigment. This quantity to be added generally corresponds to 1.5 to 40 parts by weight per 100 parts by weight of a protein adhesive. If the quantity exceeds this range, there will occur a problem such as the lowering of a white paper gloss as soon as the effect reaches its saturated state. On the contrary, if the quantity is below this range, an expected effect cannot be obtained.

This synergistic effect obtained by mixing and using calcium formate and zinc oxide has not been grasped clearly yet. It is, however, estimated that the effect of increase of the meshwork of zinc oxide is added to the expansion of the permeance caused by the meshwork of the coated layer appearing due to the use of calcium formate, while the effect of immobilization appears synergistically, and the plasticization of the coated layer required in the press nip portion is also kept sufficiently at the same time.

The composition of the re-wetting liquid is not limited especially. For example, the re-wetting liquid may contain about 0.01% to 3.0% by weight of a release agent such as polyethylene emulsion, fatty acid soap, calcium stearate, micro-crystalline wax, a surface active agent, Turkey red oil, or the like. In addition, the re-wetting liquid may contain 0.01% to 3.0% of inorganic salts such as zinc sulfate, calcium phosphate, sodium polyphosphate, sodium hexametaphosphate, sodium formate, ammonium formate, potassium tartrate, sodium citrate, potassium citrate, dioctyl sodium sulfosuccinate, etc. Of them, particularly, sodium polyphosphate, sodium citrate, etc., such as sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, or the like, are suitable for use due to their excellent dispersion effect.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.l and Fig. 2 show the data of the test result of air permeability modifiers. Fig. 2 is a schematic view of an example of a cast coating apparatus to which a method of producing cast coated paper according to Japan Patent Application No. 2001-016334.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below more specifically in accordance with embodiments. Not to say, however, the present invention is not limited to these embodiments .

Base paper to be used may include: so-called acidic paper using clay, talc, or the like, as a filler and using a rosin size or aluminum sulfate as a fixing agent; or neutralized or alkaline paper using clay, talc, calcium carbonate, or the like, as a filler and using a size such as

AKD or ASA, cationic starch or the like, as a fixing agent. The coating composition may use a white pigment usually for coated paper, such as clay, kaolin, precipitated or ground calcium carbonate, barium sulfate, plastic pigment, or the like. The white pigment is chosen in consideration of the quality of a finished product and the suitability for casting. Particularly, satin white is not used because it reacts to calcium formate to thereby increase the viscosity. The adhesive usually includes a mixture of a protein adhesive such as casein, soya bean protein, or the like, and synthetic rubber latex having butadiene-styrene, methyl methacrylate, acrylic acid, or the like, as its principal component. Each adhesive is chosen in consideration of the quality of a finished product and the suitability for casting in the same manner as the pigment. The mixture of a protein adhesive and a synthetic rubber latex adhesive, particularly the synthetic rubber latex adhesive has a large influence on the suitability of high-speed operation such as permeance, or the quality of a finished product. Thus, the selection of the adhesives is important. Further, as a dispersant for the pigment, sodium polyphosphate or sodium polyacrylate is generally added. In addition, in order to improve the stripping quality of the cast coated layer from the casting drum, a proper quantity of a lubricant such as metal salt of fatty acid, a polyethylene compound, or the like, is added. Moreover, an antifoaming agent and a water resistant agent are added in accordance with necessity.

According to the present invention, a proper quantity of calcium formate or calcium acetate, and a proper quantity of a zinc compound such as zinc oxide, zinc chloride, zinc sulfate, or the like, are added in order to obtain the high speed workability in the rewet casting method and the excellent quality of a finished product without any surface defect such as pin-holes. The effects of this addition are to improve the permeance of the coated layer as described previously, and to keep plasticity of the coated layer enough to obtain smoothness and a high gloss when the coated 10

layer is brought into instantaneous pressure contact between the casting drum and the press roll.

The method of addition and the order of addition have to be chosen carefully because calcium formate or calcium acetate causes an effect to coagulate the coating composition when it is added to the coating composition. For example, PH of the coating composition is adjusted while a quantity of calcium formate or calcium acetate is divided and added. Then, these materials are dispersed, for example, with a high-speed agitator such as a Cowless dissolver, a Cellier mixer, or the like, so as to form a coating composition. The coating composition is filtered with a screen so as to be prepared. The coating composition is suitably selected in a range of 38% to 65% in solid content, and in a range of from 50 cps to 1,500 cps in viscosity. As for the method of coating, the coating composition is applied to the surface of base paper having a basis weight of 40 to 350 g/m by use of an air coater, a blade coater, a roll coater, a rod coater, or the like, so as to apply coating in a range of from 10 to 30 g/m . Thus, the coated layer is formed.

Next, the coated layer is dried at a temperature of 100 to 200°C by means of an air drier using gas or steam as a heat source or an infrared drying machine, which is suitable for high-speed operation. The coated layer provided thus on the base paper is re-wetted with the re-wetting liquid so as to be plasticized, and pressed against the mirror-finished drum under the nip pressure of 100 to 250 kg/cm so as to be dried by the drum heated to 90 to 150°C. Thus, cast coated paper having a high gloss without any surface defect such as pin-holes or adhesion unevenness and having excellent surface strength can be produced at a high speed. Incidentally, the work of smoothing with a gloss calender, a soft calendar, a super-calender, or the like, which has been required after coating and drying in a conventional rewet casting method, is not required any more in the present invention because the coated layer is plasticized sufficiently at the time of pressure contact. In addition, such a work of smoothing is undesirable because it blocks the permeance of the coated layer.

More specific Examples 1 to 8 and Comparison Examples corresponding to these Examples will be described below sequentially. The numerical values and percentages (%) of materials in Tables 1 and 2 show by parts by weight and percent (%) by weight. Example 1 A white pigment composed of 75 parts of kaolin (UW90 made by Engelhard Minerals and Chemicals Corporation) for coating and 25 parts of calcium carbonate (Brilliant N15 from Shiraishi Kogyo Kaisha Ltd.) for coating, to which 0.8 parts of sodium polyacrylate was added as a dispersant, was dispersed in water by means of a Cowless dissolver so as to prepare a pigment dispersion (concentration 60%) . To this pigment dispersion, added were 7 parts by solid content of alkali-dissolved casein (added and dissolved with 3 parts of sodium hydroxide and 10 parts of 28% ammonia liquid so as to obtain a concentration of 16%) , and 19 parts of denatured styrene-butadiene synthetic rubber latex (LX1385 from Asahi Kasei Corporation) .

Next, 1.0 part by solid content (10% aqueous solution) of calcium formate was first added to this mixture liquid as an air permeability modifier A. The air permeability modifier A was added carefully, otherwise the viscosity would be increased suddenly. Further, 0.5 part of zinc oxide was added as an air permeability modifier B. Moreover, 1 part of a lubrication/release agent (PEM17 from NOPCO Chemical Company), 0.05 part of tributyl phosphate as an anti-foaming agent, and a proper quantity of ""complementary dye were added. The mixture was screened to complete the coating composition. The completed coating composition was 45% in concentration, 300 CP in viscosity, 9.5 in PH, and 25°C in temperature.

This coating composition was applied onto base paper having a basis weight of 60 g/m2 by an air coater 2 shown in Fig. 3, so as to apply 20 g/m2 of coating on one side. Coated paper was dried by a hot air drying machine 3 using gas or steam as a heat source, so as to reduce the content of moisture to about 6%. In a pressure contact portion between a chromium-plated casting drum 7 and a press roll 5 coated with urethane rubber or the like, this dried coated paper was dipped into a re-wetting liquid of sodium hexametaphosphate with a concentration of 0.5% supplied from a nozzle 4. After that, the paper was pressed instantaneously and smoothed in a high-temperature and high- pressure nip 6 formed between the casting drum 7 and the press roll 5, and then dried by the casting drum 7. The cast coated paper obtained thus was then stripped from the casting drum 7. Here, because the portion where the paper was dipped into the re-wetting liquid was located in the nip portion 6 formed by the casting drum 7 and the press roll 5, only the surface of the coated layer could be plasticized so that the re-wetting liquid was prevented from penetrating the paper layer excessively. Incidentally, in Fig. 3 the reference numeral 1 represents base paper, and 8 represents cast coated paper. The production speed of 120 m/min could be attained with the casting drum 7 set at the temperature of 120°C and the nip pressure set at 200 kg/cm. The production speed could be made even higher than 120 m/min. As shown in Figure 1, in terms of quality, the cast coated paper obtained thus had an excellent gloss without any surface defect such as pin-holes and also had excellent printability such as surface strength. Example 2

Cast coated paper was produced in the same manner as in Example 1 except that another coating composition shown for Example 2 in Figure 1 was used. As shown in Figure 1, in terms of quality, the cast coated paper obtained thus had an excellent gloss without any surface defect such as pin-holes and also had excellent printability. Example 3 Cast coated paper was produced in the same manner as in Example 1 except that another coating composition shown for Example 3 in Figure 1 was used. Denatured protein (made by Protein Chemical Co., Ltd.) for the adhesive was used in form of a 30% aqueous solution. As shown in Figure 1, in terms of quality, the cast coated paper obtained thus had an excellent gloss without any surface defect such as pin-holes and also had excellent printability such as surface strength . Example 4 to 8 Cast coated paper was produces in the same manner as in Example 1 except that different coating compositions shown for Examples 4 to 8 in Figure 1 were used, particularly the rates of the air permeability modifiers A and B were varied. As shown in Figure 1, in terms of quality, the cast coated paper obtained thus had an excellent gloss without any surface defect such as pin-holes and also had excellent printability. [ Figure 1 ]

A method for measurement was adopted as follows :

Gloss : Measured in accordance with JIS P8142

TAPPI T480om-92. Specular Gloss of Paper and Paperboard at 75°.

Printed gloss Measured in a test method using an RI printing test machine. Ink used : High Eco Blue 0.4 cc made by Toyo Ink MFG. Co., Ltd.

Permeance Measured in accordance with ISO 5636 (Air permeance) ml/min

Surface strength Evaluated by degree of picking in a coated layer with ink (ink quantity 0.6 cc) of "Ink Tack No. 18" made by Toyo Ink MFG. Co., Ltd. by means of an RI printing machine (made by Ishikawajima Industrial Machinery Co., Ltd.).

Pin-holes Observed over the surface of the coated paper with a 10-power loupe.

5 : nothing ©

4.5 : few O

4.0 : here and there Δ~O

3.5 : many Δ

3.0 : very many X General judgement

excellent

O good

Δ with trouble x unacceptable

Comparison Examples 1 to 8

Comparison Examples 1 to 8 correspond to Examples 1 to 8 respectively. Cast coated paper was produced in the same manner as in Example 1 except that the rates of the air permeability modifiers A and B were varied. The cast coated paper obtained thus had qualities as shown in Figure 2.

In comparison Examples 1 to 3, the air permeability modifiers were added alone respectively. In Comparison Examples 4 and 6, the air permeability modifiers were added excessively. In comparison Examples 5 and 7, the air permeability modifiers were added insufficiently. Further, in Comparison Example 8, no air permeability modifier was added.

[Figure 2]

The present invention was developed with diligent researches focused on two points, that is, improvement of permeance and improvement of plasticity of a coated layer at the time of pressure contact. As a result, as is apparent from the results of Figure 1, by adding two kinds of air permeability modifiers to a cast coating composition, high- quality cast coated paper having a high gloss without any surface defect such as pin-holes could be manufactured at a high speed of 120 m/min or higher under the production conditions having a comparatively acceptable and reasonable range in manufacturing.

Claims

Claims
1. Cast coated paper comprising: base paper; a cast coating composition containing a pigment and an adhesive as a principal component and applied onto said base paper, said applied cast coating composition being dried to form a coated layer on said base paper; and a re-wetting liquid applied to said coated layer to thereby moisten and plasticize said coated layer, said coated layer being pressed against a mirror-finished and heated surface of a drum to thereby finish said paper with a gloss; wherein said coated layer contains either one of calcium formate and calcium acetate, and any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc.
2. Cast coated paper according to Claim 1, wherein said coated layer contains, per 100 parts by weights of said pigment, 0.2 to 1.8 parts by weight of either of calcium formate and calcium acetate, and 0.1 to 3.0 parts by weights of any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc.
3. A method of producing cast coated paper, comprising the steps of:
(a) coating base paper with a cast coating composition which contains a pigment and an adhesive as a principal component, said cast coating composition being made to contain either of calcium formate and calcium acetate, and further any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc; (b) drying said coated base paper until said coated base paper contains a predetermined rate of moisture;
(c) applying a re-wetting liquid to said dried coated base paper to thereby moisten said coated base paper; and ξd) (d) plasticizing said applied cast coating composition with said re-wetting liquid, and then pressing said coated base paper against a mirror-finished drum surface heated to a predetermined temperature so as to gloss-finish said coated base paper to thereby obtain cast coated paper. 0
4. A method of producing cast coated paper according to Claim 3, wherein a portion where said coated base paper is dipped in said re-wetting liquid is located in a nip portion formed by said drum and a press roll. 5
5. A method of producing cast coated paper according to Claim 3 or 4, wherein said cast coating composition contains, per 100 parts by weight of said pigment, 0.2 to 1.8 parts by weight of either of calcium formate and calcium 0 acetate, and 0.1 to 3.0 parts by weight of any one of zinc compounds such as zinc oxide, zinc chloride, zinc sulfate, etc.
6. A method of producing cast coated paper according to any 5 one of Claims 3 to 5, wherein said coated layer is dried to reduce moisture contained in said coated layer to 2% to 10%.
0
PCT/ID2002/000001 2001-01-24 2002-01-24 Cast coated paper and method of producing the same WO2002059421A3 (en)

Priority Applications (2)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1923505A1 (en) * 2006-11-20 2008-05-21 Rohm and Haas Company Coated paper and paperboard
EP1923504A1 (en) * 2006-11-20 2008-05-21 Rohm and Haas France SAS Coated paper and paperboard

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4562305B2 (en) * 2001-03-15 2010-10-13 日本製紙株式会社 Method for producing a cast coated paper
JP2013148700A (en) * 2012-01-19 2013-08-01 Hokuetsu Kishu Paper Co Ltd Printing paper for wet electrophotography

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3356517A (en) * 1963-12-17 1967-12-05 Scott Paper Co Heat coagulatable paper coating composition
US4620992A (en) * 1983-12-29 1986-11-04 Kanzaki Paper Mfg. Co., Ltd. Method of producing cast coated paper
EP0796947A1 (en) * 1996-03-22 1997-09-24 Nippon Paper Industries Co., Ltd. Cast-coated paper and production method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3356517A (en) * 1963-12-17 1967-12-05 Scott Paper Co Heat coagulatable paper coating composition
US4620992A (en) * 1983-12-29 1986-11-04 Kanzaki Paper Mfg. Co., Ltd. Method of producing cast coated paper
EP0796947A1 (en) * 1996-03-22 1997-09-24 Nippon Paper Industries Co., Ltd. Cast-coated paper and production method thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1923505A1 (en) * 2006-11-20 2008-05-21 Rohm and Haas Company Coated paper and paperboard
EP1923504A1 (en) * 2006-11-20 2008-05-21 Rohm and Haas France SAS Coated paper and paperboard
US8043476B2 (en) 2006-11-20 2011-10-25 Rohm And Haas Company Coated paper and paperboard

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JP2002227091A (en) 2002-08-14 application

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