JP5471034B2 - Method for producing starch paste liquid, starch paste liquid and coated paper coated or impregnated with the starch paste liquid - Google Patents

Description

The present invention is an enzyme-modified starch paste mainly used in size press solutions and paints for coated paper, has good pH stability when stored in a starch powder suspension slurry, and has a variation in finished paste viscosity due to a stable enzyme reaction. The present invention relates to a method for producing the starch paste liquid with a small amount of the enzyme, an enzyme-modified starch paste solution and a coated paper coated or impregnated with the starch paste solution.

Conventionally, in the paper industry, starch has been used as a raw material for size press liquid, coated paper paint, internal addition, corrugated board processing, paper tube processing, and the like. And when using for these uses, it is common to gelatinize the slurry which disperse | distributed and suspended the starch powder in water by gelatinization, and to prepare and utilize for starch paste liquid.

Starch raw materials include potato, sweet potato, tapioca and the like as underground starch, and rice, wheat and corn as ground starch. Further, when raw starch is gelatinized as it is, the viscosity is high and the quality is inferior, making it unsuitable as a starch paste solution for papermaking. For this reason, enzyme modification, thermochemical modification, acetate ester modification, phosphate ester modification, carboxy ester modification, One or a combination of two or more types of modifications such as etherification modification, hydroxyetherification modification, and cationization modification is used for the viscosity reduction treatment.

When the starch paste solution is used for a size press solution, a coating material for coated paper, and the like, it is called self-modification that the modified gelatinization is performed at a paper mill. Self-denaturation is mostly carried out by enzyme denaturation or thermochemical denaturation. Among them, in recent years, enzyme denaturation has been frequently carried out because the capital investment is small and the cost of chemicals used is low.

In the self-denaturing step, the most basic required quality is that there is little variation in the viscosity of the finished starch paste. This is because the quality of a paper product impregnated and coated with a size press solution using starch paste or coated paper paint depends on variations in the viscosity of the finished starch paste.

In the starch enzyme modification step, the starch powder is suspended in water in a slurry tank, then added with pH-adjusting chemicals and stored at a predetermined pH, and a certain amount of slurry and enzyme solution are added to the steamer as needed. Heating to perform gelatinization and enzyme denaturation. However, when the pH of the slurry fluctuates, the degree of enzyme reaction changes, and the finished viscosity may change even when the same temperature rise curve is used. In the size press, there are occurrences of instability of the application amount of the size press liquid due to variation in viscosity, boiling phenomenon, and clogging of the paint screen due to thickening. In addition, in a coater for applying a coated paper paint, the coating amount becomes unstable due to variations in viscosity, and backflow and bleeding occur due to thickening. In this way, the dispersion of the viscosity of starch paste deteriorates the operability of size presses, coaters, etc., and paper products that use it have reduced surface strength, reduced size, whiteness, glossiness, etc. due to variations in coating amount. In some cases, the quality of the paper product becomes unstable due to fluctuations caused by changes in the coating amount and deterioration of appearance due to deterioration in operability.

Thus, a technique for preventing starch aging by increasing the pH of the starch paste is disclosed (Patent Document 1), but there is no effect of suppressing variations in the finished viscosity itself, and the finished viscosity varies. The product quality could not be reduced. Also disclosed is a paper strength enhancer comprising a water-soluble copolymer obtained by copolymerizing vinyl monomers having (meth) acrylamide as an essential component in an enzyme-modified starch aqueous solution as an active ingredient (Patent Document 2). ) However, if the finished viscosity of the starch varies, the effect of the paper strength enhancer also varies, which is problematic. A heat-modified starch in which starch and organic acid salt are mixed is disclosed (Patent Document 3), which is a technique for suppressing a decrease in the viscosity of the starch, and has nothing to do with variations in the finished viscosity of the starch paste. There is no. A method for producing an enzymatic saccharified solution by pulverizing starch (Patent Document 4) is a method for producing a saccharified solution for the purpose of complete saccharification, and suppresses variations in the finished viscosity of starch paste. I can't. A method of slurrying in an alkaline aqueous solution and filtering the gelatinized liquid after heating and steaming is disclosed (Patent Document 5). This is a method for producing a gelatinized liquid by heating and steaming. Since there is almost no (amylase) activity, it is difficult to apply this method in order to suppress variations in the finished viscosity in enzyme modification of starch.

From the above situation, the enzyme-modified starch paste liquid used in size press liquids and coated paper paints has good pH stability during storage of starch powder suspension slurries, and the finished paste liquid is stabilized by a stable enzyme reaction. There has been a strong demand for an enzyme-modified starch paste with little variation in viscosity.

JP-A-6-248246 Japanese Patent Laid-Open No. 11-241294 JP-A-2005-171112 JP 2001-275893 A Japanese Patent Laid-Open No. 9-194501

The present invention is an enzyme-modified starch paste mainly used in size press solutions and paints for coated paper, has good pH stability when stored in a starch powder suspension slurry, and has a variation in finished paste viscosity due to a stable enzyme reaction. The present invention provides a method for producing an enzyme-modified starch paste having a low content, a starch paste, and a coated paper coated or impregnated with at least one surface of the starch paste.

The present invention includes the following inventions.
(1) In the starch powder manufacturing process, the pH of the starch powder suspension before dehydration and drying is adjusted to 6.0 ± 1.0, and the pH adjusting chemical used in the above adjustment is absorbed into the starch. The starch powder obtained by dehydrating and drying the suspension is resuspended in water without adjusting the pH, and the starch pH is adjusted to 6.0 ± 1.0. Method.

(2) In the starch powder production process, adjust the pH of the starch powder suspension before dehydration and drying to 6.0 ± 1.0, and absorb the pH-adjusting chemical used in the adjustment in the starch. , starch powder obtained by dehydrating and drying the suspension was re-suspended in water without pH adjustment, starch glue optimum pH obtained by steaming added amylolytic enzymes 6.0 ± 1.0 liquid.

(3) A coated paper in which the starch paste liquid according to (2) is applied or impregnated on at least one side of a substrate.

(4) A coated paper in which the coating layer provided on the substrate is a clear coating layer and / or a pigment coating layer containing the starch paste liquid according to (2).

The starch paste liquid according to the present invention has an advantage that the dispersion of the final paste liquid viscosity is small due to a stable enzyme reaction. In addition, the coated paper according to the present invention can be used to obtain a clear coating liquid or a pigment coating liquid having a stable viscosity by using a starch paste liquid with little variation in viscosity. When applied or impregnated on at least one side, it has the advantage that the quality of the coated paper product is stable.

The present inventors have intensively investigated the fluctuation factors of the finished paste viscosity in the enzyme modification step of starch, and the pH fluctuation of the slurry greatly affects the finished viscosity of the starch paste liquid. During the storage of the tank, the starch powder absorbs acid and alkali pH adjusting chemicals to find out that it is generated due to fluctuations in the pH of the liquid phase, and a means for avoiding the pH fluctuation of the slurry was studied. As a result, in the starch powder production process, the pH before dehydration / drying is adjusted to a predetermined range and then dehydrated / dried to form a powder, and the starch powder is used to make a slurry, thereby adjusting the pH in the slurry tank. It was found that fluctuations were suppressed, and that there was almost no variation in the finished viscosity even without the addition of an adjustment chemical, and the present invention was completed.

In order to stabilize the finished viscosity in the enzyme modification step of the starch paste, it is necessary to use starch powder adjusted so that the pH of the starch powder suspension before dehydration and drying is 6.0 ± 1.0. is important. In the final step of starch powder production, the starch suspension is dehydrated and dried to finish as a powder product. The pH of this starch suspension is usually 4.0 to 4 in the case of raw corn starch or acetylated starch. In the case of .5, cationized starch, it is adjusted to about 7.0 to 8.0. In enzyme denaturation, starch-degrading enzymes with an optimum pH ranging from acidic to neutral are usually used. Therefore, starch is suspended in water, and pH adjusting chemicals such as acid and alkali are added to pH from acidic to neutral. The starch slurry is stored in a slurry tank, and the necessary amount is transferred to a steaming tank, and then the enzyme solution is added and steamed by heating to obtain an enzyme-modified starch paste solution. However, when stored in a slurry tank, the pH adjusting chemical is absorbed into the starch over time, so the pH of the slurry often fluctuates, and the amount of the required enzyme varies and the finished viscosity of the starch paste solution varies. Absent. In the present invention, the pH of the starch powder suspension before dehydration and drying is adjusted in the step of producing the powder product, and then the dried starch is used. Therefore, the starch slurry is resuspended in the starch slurry tank. The pH fluctuation at is suppressed, and the finished viscosity of the starch paste is stabilized. If the pH before dehydration / drying is less than 5.0 in the process for producing a powder product, the equipment must be made of an acid-resistant expensive material, which is economically undesirable. On the other hand, if the pH exceeds 7.0, the alkaline component is easily absorbed by the starch in the slurry tank, and the pH fluctuation is easily generated, which is not preferable.

In the starch slurry tank, spoilage tends to occur particularly when rhizome starch such as cassava straw and potato is used. When rot occurs, an organic acid is generated by fungal metabolism, the pH of the starch slurry changes to the acidic side, and the finished viscosity may vary. Therefore, from the viewpoint of preventing spoilage, 0.01 to 1.0% by mass, preferably 0.05 to 0.2% by mass of a preservative, a fungicide, or the like is added to the starch slurry in the starch slurry tank. . As preservatives, isothiazoline compounds, aliphatic nitrogen compounds, organic nitrogen sulfur compounds, organic bromine compounds, sodium benzoate, normal butyl hydroxybenzoate, sodium propionate, potassium sorbate and the like can be used. Two or more types may be used in combination.

Various amylase solutions such as α-amylase, β-amylase, and glucoamylase are used as the starch degrading enzyme. The optimum pH is preferably 6.0 ± 1.0 according to the pH of the starch slurry. By adjusting the optimum pH of the starch-degrading enzyme to the pH of the starch slurry, the enzyme reaction is most efficiently carried out, and the amount of enzyme addition required to obtain a predetermined viscosity is minimized, but particularly in this pH range. If the enzyme activity is 80% or more with respect to the enzyme activity at the optimum pH of the amylolytic enzyme, the amount of enzyme added can be reduced, which is economically preferable. If the pH of the starch slurry deviates from the optimum pH range of the starch degrading enzyme, the activity of the starch degrading enzyme in the enzyme denaturation process in which the starch is heated and steamed becomes low, and the amount of expensive enzyme added is extremely large. Since it is necessary, it is not economically preferable.

The starch raw material used in the present invention is not particularly limited, but corn and cassava-derived starch that has not been subjected to viscosity reduction treatment can be preferably used because it is economically advantageous. For example, in raw corn starch that has not been chemically modified, a starch slurry is obtained from raw material grains through water immersion, dehydration, coarse pulverization, germ separation, fine pulverization, hull / fiber separation, protein separation, and washing steps. The starch slurry is dehydrated and dried to form raw corn starch. Since this starch slurry is added with sodium sulfite for preventing oxidation, the pH of the slurry becomes acidic. In the present invention, the pH can be adjusted to 6.0 ± 1.0 by adding an inexpensive pH adjusting chemical solution such as sodium hydroxide to the starch slurry before the drying step. Since the starch-adjusting chemicals are absorbed in the starch granules before entering, even if the starch powder after drying is resuspended in water, there is almost no change in the pH of the slurry. Chemically modified starch uses reactive chemicals based on the starch slurry and is modified by oxidation, acetylation, phosphate esterification, cationization, etc., so expensive chemical costs and reaction / washing steps are required. The increase in price due to the increase is inevitable, but these chemically modified starches can be used as appropriate depending on the required characteristics.

The temperature raising conditions in the enzyme-modifying step of starch in the present invention are not particularly limited, but if the rate of temperature rise is too fast, the amount of enzyme required to adjust to a predetermined viscosity increases, and if the rate of temperature rise is too slow, the equipment It is important to keep a balance because the productivity will decrease. In general, during the temperature increase, stop the temperature increase in the temperature range near the optimal temperature of the enzyme or close to the optimal temperature above the gelatinization temperature, take a holding time at a constant temperature, and perform the enzyme reaction. In the present invention, it is a starch slurry and pH condition that suppress variation in the finished viscosity, so it is sufficient that the temperature rise time is constant, and the holding time is The necessity of taking can be determined as appropriate according to the situation.

Although it does not specifically limit about the starch slurry density | concentration in this invention, 5-50 mass% is preferable if it can disperse | distribute uniformly by gentle stirring, and the range of 7-40 mass% is further more preferable. If the starch slurry concentration is too low, the productivity of the equipment will be lowered, and if it is too high, uniform dispersion and mixing will not be possible, causing unevenness in the enzyme reaction during heating and cooking, and causing variations in viscosity. Absent.

The viscosity of the starch paste liquid of the present invention is not particularly limited, but it is preferably 100 to 10000 mPa · s, more preferably 200 to 3000 mPa · s, as a B-type viscosity at a temperature of 80 ° C. and a concentration of 28%. If the viscosity is less than 100 mPa · s, the surface strength of the coated paper when used as a size press solution or when blended in a pigment coating solution is low, and print quality may be insufficient. On the other hand, when the viscosity exceeds 10,000 mPa · s, the circulation pump load and the agitator load become extremely large especially in the enzyme denaturation process using a high-concentration starch slurry, which not only requires large-scale equipment but also coating. In the process as well, boilers and splashes in size presses or streaks in blade coaters are likely to occur, which often adversely affects operability and print quality.

  The present invention has a great feature that variation in finished viscosity after enzyme treatment is reduced. Unmodified corn starch, which is commonly used, adjusts the pH of the starch slurry with a pH-adjusting chemical when the powder is resuspended at the place of use without adjusting the pH in the powder manufacturing process. In such a case, the pH of the slurry starts to change in about 1 to 3 hours, and when stored for about 6 hours, it may change from pH immediately after pH adjustment to over 1.0. Depending on the enzyme used, when the pH changes by 1.0, the enzyme activity changes by about 20-30%. With this change in enzyme activity, the finished viscosity measured by a B-type viscometer is about 100-500%. Variations may occur. On the other hand, in the present invention, the change with time of the pH of the starch slurry is 0.5 or less even after storage for 6 hours, the change in enzyme activity is extremely small, the finished viscosity hardly varies, and the coefficient of variation is 0.1. It becomes as follows.

The coated paper according to the present invention is obtained as follows. First, as a raw material pulp, one or more kinds of chemical pulp (NBKP, LBKP, etc.), mechanical pulp (GP, CGP, RGP, PGW, TMP, etc.), waste paper pulp (DIP, etc.) are appropriately mixed to prepare a stock. Is done. Although there is no restriction | limiting in particular about mixing | blending of each pulp, It is preferable to mix | blend 30 mass% or more of mechanical pulp and waste paper pulp with a high yield from the point of effective utilization of resources. Next, fillers such as white carbon, clay, amorphous silica, talc, titanium oxide, heavy calcium carbonate, and light calcium carbonate are added as needed to the paper material, and paper strength enhancers, yield improvers, Commonly known and commonly used papermaking chemicals such as reinforced rosin sizing agents, emulsion sizing agents, internal sizing agents, water resistance agents, UV absorbers and the like are added, and conventionally used paper machines such as circular nets, long The base material according to the present invention is manufactured by making paper using various types of paper machines such as a net, on-top, and twin wire.

The basis weight of the base material is not particularly limited, is preferably about 25 to 150 g / ^{m 2,} more preferably about 40 to 100 g / ^{m 2.}

(About coating layer)
In the coated paper of the present invention, the coating layer containing the enzyme-modified starch paste provided on the substrate is composed of a clear coating layer containing no pigment and / or a pigment coating layer containing a pigment. Is done. The clear coating layer is formed by coating and drying the enzyme-modified starch paste liquid of the present invention.
Examples of the pigment constituting the pigment coating layer include kaolin, aluminum hydroxide, heavy calcium carbonate, light calcium carbonate, titanium dioxide, barium sulfate, zinc oxide, satin white, calcium sulfate, talc, and plastic pigment. A species or two or more species can be selected and used.

Further, as the binder, in addition to enzyme-modified starch, conjugated diene copolymer latex such as styrene-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, styrene-methyl methacrylate-butadiene copolymer latex, Acrylic (co) polymer latex such as acrylic ester and / or methacrylic ester polymer or copolymer latex, vinyl (co) polymer latex such as ethylene-vinyl acetate copolymer, or various of these (Co) polymer latex modified with a functional group-containing monomer such as carboxyl group or water-dispersible binder such as copolymer latex, synthetic resin binder such as polyvinyl alcohol, olefin-maleic anhydride resin, Carboxymethyl cellulose , Water-soluble binders such as cellulose derivatives such as hydroxyethyl cellulose and the like, can be used to select one or two or more of these water-dispersible and / or water-soluble binders as appropriate. In addition, 15-100 mass% is preferable, and, as for the mixture ratio of the enzyme modified starch in a binder, More preferably, it is 20-60 mass%.

Here, the blending ratio of the pigment and the binder is generally 5 to 150 parts by mass of the binder with respect to 100 parts by mass of the pigment.
In the present invention, the pigment coating layer may be a single layer or a multilayer. However, regardless of whether the coating layer is a single layer or multiple layers, when forming the coating layer, the binder is adjusted so that the binder is 5 to 150 parts by mass per 100 parts by mass of the pigment as the binder of the entire coating layer. That's fine. When the amount of the binder is less than 5 parts by mass, the strength of the pigment coating layer that can withstand various types of printing cannot be obtained. There is a risk of failure.
The pigment coating solution may further contain auxiliary agents such as water retention agents, thickeners, antifoaming agents, and various dyes as necessary.

The apparatus for applying or impregnating the coating liquid composition containing the enzyme-modified starch paste liquid of the present invention to the substrate is not particularly limited. For example, an ink line or a party-to-roll size press, Roll coater such as blade metering size press, rod metering size press, gate roll coater, trailing, flexible, roll application, fountain application, short dwell and other bevel type, bent type blade coater, rod blade coater, bar coater Well-known and publicly used coating devices such as an air knife coater, curtain coater, spray coater, and gravure coater are appropriately used.

Moreover, when providing a coating layer by the said size press process, in addition to the starch by this invention, polyvinyl alcohol, polyacrylamide type resin, etc. can be used. In addition, wax, styrene resin, olefin resin, styrene-acrylic resin, styrene-maleic acid resin, styrene-maleic acid-acrylic resin, higher fatty acid resin, polyamide polyamine epichlorohydrin are added to the size press liquid. Materials, pigments and the like can be added as appropriate. Examples of the pigment include ordinary coated paper pigments such as kaolin, barium sulfate, light calcium carbonate, heavy calcium carbonate, aluminum hydroxide, satin white, titanium dioxide, calcium sulfite, zinc sulfate, and plastic pigment. It is done. Of these, use of heavy calcium carbonate is preferable because the air permeability of the base paper can be lowered and blister trouble can be suppressed when printed on an offset rotary printing press. When a pigment is blended in the size press liquid, the blending ratio is preferably 5 to 200 parts by mass, more preferably 10 to 100 parts by mass of the polymer resin mainly composed of enzyme-modified starch with respect to 100 parts by mass of the pigment. The solid concentration of the size press liquid is preferably about 2 to 12% by mass. In addition, although there is no restriction | limiting in particular about the adhesion amount in the case of performing a size press process, Generally 0.1 to 13 g / m < ² > is preferable at the dry adhesion amount of both surfaces total.

Furthermore, although the solid content concentration of the pigment coating solution can be selected in the range of 10 to 75% by mass, it is preferably in the range of 45 to 70% by mass in consideration of operability. The coating amount per coating layer is generally selected in the range of 0.5 to 20 g / m ² per side in terms of dry mass. In addition, as a method of drying the wet coating layer after coating with a coating liquid composition, various systems, such as steam drying, gas heater drying, electric heater drying, infrared heater drying, etc., are employable, for example.

As for the production of coated paper containing the enzyme-modified starch of the present invention, after forming the coating layer of the coating liquid composition, smoothing treatment may be carried out in various calendar devices. Generally used calendar devices such as a super calender, soft calender, gloss calender, compact calender, mat super calender, and mat calender are appropriately used. The conditions for calendar finishing are appropriately selected according to the required quality, such as the temperature of the rigid roll, the calendar pressure, the number of nips, the roll speed, and the moisture before the calendar. Furthermore, the calendar device has an off type that is different from the coater and an on type that is integrated with the coater, but can be used in either case. As the material of the calendar device to be used, the rigid roll is a roll whose surface is mirror-finished with metal or hard chrome plating. As the elastic roll, a roll obtained by molding a resin roll such as urethane resin, epoxy resin, polyamide resin, phenol resin, polyacrylate resin, cotton, nylon, aramid resin or the like is used as appropriate. In addition, it is also possible to use suitably combining the water coating apparatus, electrostatic humidification apparatus, steam humidification apparatus, etc. for humidity control and humidification of the coated paper after finishing with a calendar.

The present invention will be specifically described below with reference to examples and comparative examples. Of course, the present invention is not limited to these examples. Moreover, unless otherwise indicated, the part and% in an example show a mass part and mass%, respectively.
The following physical properties were measured for starch pastes and coated papers as Examples and Comparative Examples obtained as described below, and the results are shown in Tables 1 and 2.

(viscosity)
The starch paste liquid of each Example and Comparative Example was produced for 10 batches continuously for 10 days, and the viscosity of the starch paste liquid of each batch was measured using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. according to JIS Z 8803-1991. Measured. At that time, the concentration of the paste liquid was 28% by mass, and the measurement temperature was 80 ° C. The average value from the measured values of the viscosity of the 10 batches (the arithmetic average obtained by adding all the measured values and dividing by the number thereof was used (Chemical Dictionary Editor's Committee “Chemical Dictionary 8”, page 223, reduced edition) 34th edition (1993))), using the square root of the standard deviation (dispersion (mean of the square of the difference between each measured value and the average value)) (Chemical Dictionary Dictionary, "Chemical Dictionary 7"), 533, reduced edition 34th edition (1993))), coefficient of variation (standard deviation divided by average value, relative variation expressed) Dictionary 8 ”, page 666, reduced edition No. 34 (1993))).

(Splash evaluation)
The degree of splash of the coating solution when it was coated at 1000 m / min with a gate roll coater was visually evaluated. Evaluation was carried out by a three-step evaluation.
3: There is very little splash and it is a level which does not have any problem in operation.
2: There is a little splash, but the product quality is satisfactory and is at an operational level.
1: There is a lot of splash and it is a level where product quality and operational problems occur.

(Surface strength of coated paper)
A sample strip having a width of 2 cm and a length of 20 cm was cut from the coated paper obtained in each of the examples and comparative examples, and this was pasted on a sample mount (“OK Special Art Post” manufactured by Oji Paper Co., Ltd., 256 g / m ² ), and RI printing was performed. Printing was performed using 0.4 cc of printing ink (“SD50 Red B” for paper test made by T & K TOKA Co., Ltd.) with a testing machine (Ishikawajima Sangyo Co., Ltd.), and the degree of picking on the printed surface was visually evaluated. Evaluation was carried out by a five-step evaluation.
5: No fiber is removed and no white spots occur.
4: A slight amount of fiber was removed and white spots were slightly observed (about 1 to 5 locations / 36 cm ² ).
3: Fibers are partially removed, but at a level that does not cause any practical problems. White spots are about 6 to 20 places / 36 cm ² .
2: Fibers are observed on the entire surface, and the area ratio of white spots is less than 5%.
1: Fibers are removed from the entire surface and the paper surface is peeled off, and the area ratio of white areas is 5% or more.
Those with an evaluation of less than 3 have practical problems.

(Print gloss)
A sample strip having a width of 2 cm and a length of 20 cm was cut from the coated paper obtained in each of the examples and comparative examples, and this was pasted on a sample mount (“OK Special Art Post” manufactured by Oji Paper Co., Ltd., 256 g / m ² ), and RI printing was performed. Printing was performed using 0.1 cc of printing ink (Values-G type, manufactured by Dainippon Ink & Chemicals, Inc.) with a tester (Ishikawajima Industrial Machinery Co., Ltd.), and the printing gloss was visually evaluated.
A: The printing glossiness is particularly excellent.
○: Excellent print gloss.
(Triangle | delta): Although printing glossiness is a little inferior, it is a level which is satisfactory practically.
X: The printing glossiness is inferior, and is a level causing a practical problem.

(Ink setting)
A sample strip having a width of 2 cm and a length of 20 cm was cut from the coated paper obtained in each of the examples and comparative examples, and this was pasted on a sample mount (“OK Special Art Post” manufactured by Oji Paper Co., Ltd., 256 g / m ² ), and RI printing was performed. Printing was performed using 0.5 cc of printing ink (“SD50 Crimson B” for paper test made by T & K TOKA Co., Ltd.) with a testing machine (Ishikawajima Industrial Machinery Co., Ltd.). Printing was performed 2 to 3 cm at regular intervals from when the sample touched the ink roll, and the ink roll after printing was copied onto another sheet of paper, and the density change was visually evaluated. Evaluation was performed by the following five-step evaluation.
<Evaluation criteria>
5 (excellent) → 1 (inferior)
5: The ink setting property was extremely high.
4: The ink setting property was high.
3: Practical ink setting was ensured.
2: The ink setting property was low.
1: The ink setting property was extremely low.
Those with an evaluation of less than 3 have practical problems.

<Example 1>
(Manufacture of base material for starch paste clear liquid coated paper)
Cationized starch (product) Name: “P3Y”, PIRAAB STARCH Co. Ltd. 0.5%, neutral rosin sizing agent (trade name: “N815”, Arakawa Chemical Co., Ltd.) 0.8%, white carbon as filler 2. 0%, all of these were added at a rate of mass% per dry pulp, and after adjusting the papermaking pH to 6.5 with a sulfuric acid band, the resulting stock was made with a gap former type paper machine, A base material for starch paste clear liquid coated paper having a basis weight of 43.0 g / m ² was obtained.

In the process of producing unmodified corn starch powder, NaOH aqueous solution is added to the starch slurry (concentration 40%) before dehydration and drying, and adjusted so that the pH of the slurry becomes 6.0, followed by dehydration and drying (conditions: after dehydration) A spray dryer was used so that the water content was 60% and the water content was 88%. The pH-adjusted starch powder A was resuspended in water to obtain a starch slurry before cooking. After storing in a slurry tank at 25 ° C. for 6 hours, a part is transferred to a steaming tank, and starch degrading enzyme (trade name: “Spytase LH” (α-amylase), manufactured by Nagase ChemteX Corporation) per starch solids After the addition to 800 ppm, the temperature was raised to 95 ° C. in 28 minutes, and then kept at 95 ° C. for 15 minutes for enzyme deactivation to obtain starch paste A. A clear coating material prepared by diluting starch paste A to a concentration of 10% is prepared, and this is applied to both sides of the base material using a gate roll coater, and the coating amount after drying is 0.3 g / m ² per side. It was coated and dried as described above to obtain 43.6 g / m ² of starch paste liquid clear liquid coated paper as an actual amount.

<Example 2>
A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that the starch powder A of Example 1 was changed to starch powder B adjusted to pH 5.5, and the amylolytic enzyme addition amount was 850 ppm.

<Example 3>
A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that the starch powder A of Example 1 was changed to starch powder C adjusted to pH 6.5, and the amylolytic enzyme addition amount was 850 ppm.

<Example 4>
The starch powder raw material of Example 1 is starch powder D made from cassava-derived tapioca starch, the starch degrading enzyme is changed (trade name: “Fungamil L800” (α-amylase), manufactured by Novozymes Japan), and added. A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that the amount was 150 ppm.

<Example 5>
A starch paste clear liquid coated paper was obtained in the same manner as in Example 4 except that the starch powder D of Example 4 was changed to starch powder E adjusted to pH 5.2 and the amount of added starch degrading enzyme was 170 ppm.

<Example 6>
A starch paste clear liquid coated paper was obtained in the same manner as in Example 4 except that the starch powder D of Example 4 was changed to starch powder F adjusted to pH 6.7 and the amount of added starch degrading enzyme was 170 ppm.

<Example 7>
(Preparation of pigment coating solution for undercoat layer)
Into a pigment slurry made of heavy calcium carbonate (trade name: “Hydrocurve 60”, manufactured by Bihoku Flour Industry Co., Ltd.), 100 parts of the pigment, 4 parts of the enzyme-modified starch of Example 1 as a binder, and styrene-butadiene 5 parts of polymer latex (trade name: “OJ-2000”, manufactured by JSR) was added, and antifoaming agent and dye were sequentially added as auxiliary agents, and finally an undercoat coating layer having a solid content concentration of 67%. A pigment coating solution was prepared.

(Preparation of pigment coating solution for top coating layer)
To an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate (trade name: “Aron T-50”, manufactured by Toagosei Co., Ltd.) is added as a dispersant is added to kaolin (trade name: “Hydra Gloss 90”, 50 parts of Huber Co., Ltd. and 50 parts of heavy calcium carbonate (trade name: “Hydro Curve 90”, manufactured by Bihoku Powder Chemical Co., Ltd.) were added and dispersed with a Coreless disperser to prepare a pigment slurry. In this pigment slurry, 3 parts of the enzyme-modified starch of Example 1 with respect to 100 parts of pigment, 8.4 parts of styrene-butadiene copolymer latex (trade name: “OJ-2000”, manufactured by JSR), and auxiliary agent As a result, an antifoaming agent and a dye were sequentially added to finally prepare a pigment coating solution for a top coating layer having a solid content concentration of 66.5%.

(Manufacture of base materials)
To the pulp slurry mixed so as to be 30 parts of LBKP (CSF 450 ml) and 70 parts of NBKP (CSF 480 ml), 0.5% of aluminum sulfate (vs. pulp, solid content conversion), cationized starch (trade name: “ACE K”) , Manufactured by Oji Cornstarch Co., Ltd.) 0.9% (vs. pulp, solid content conversion), AKD sizing agent (trade name: “Size Pine K-902”, manufactured by Arakawa Chemical Co., Ltd.) 0.03% Pulp, solid content) is added to the machine chest sequentially, and then the recovered white water and the above pulp slurry are mixed, and heavy calcium carbonate (trade name: “Hydrocurve 60”, manufactured by Bihoku Flour Industries Co., Ltd.) is used as a filler. It was added before the fan pump so that the paper ash content was 15%. Furthermore, 0.016% of a cationic acrylic resin (trade name: “DR-3015”, manufactured by Hymo Co., Ltd.) was added in front of the screen to prepare a paper stock (concentration: 1.01%). The paper stock is formed with a gap former at a J / W ratio of 0.995 and a paper making speed of 1500 m / min. After squeezing with two continuous shoe presses, squeezing and smoothing with a roll press are performed. After drying with a one-stage array dryer, the starch paste solution A of Example 1 is diluted to a concentration of 4.0% using a rod metering size press device so that the solid content becomes 2.5 g / m ^2. performs size press treatment, and then dried by a two-step sequence dryer and passed through a machine calender, which is on the machine specifications, moisture 4.5%, the substrate having a basis weight of 47.4 g / m ² Obtained.

(Manufacture of coated paper)
Using a blade coater that supplies the base material with a pigment coating solution for the undercoat coating layer by a jet fountain method, the dry coating amount per side is 7.5 g / m ^2. Coating and drying were performed to obtain a double-sided primer-coated paper. Subsequently, a dry coat amount per side of 9.5 g / m is used by using a blade coater that supplies the above-mentioned pigment coating solution for the top coating layer to the double-sided undercoating paper by a jet fountain method. ^The coated paper was dried to obtain 2 to obtain a coated paper. The coated paper obtained in this way was adjusted for temperature, linear pressure, and paper feeding conditions with a multi-nip calender in which metal rolls and resin rolls were inclined, and the basis weight was 81.4 g / m ^2. A coated paper for printing was obtained.

<Example 8>
(Preparation of size press solution)
35 parts of the enzyme-modified starch of Example 1 as a polymer resin with respect to 100 parts of the pigment, styrene-butadiene, in a pigment slurry made of heavy calcium carbonate (trade name: “Hydrocurve 60”, manufactured by Bihoku Powder Chemical Co., Ltd.) Add 5 parts of copolymer latex (trade name: “OJ-2000”, manufactured by JSR), add antifoaming agent and dye sequentially as auxiliary agents, and finally size press liquid with a solid content concentration of 28% Was prepared.

(Preparation of pigment coating solution for top coating layer)
To an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate (trade name: “Aron T-50”, manufactured by Toagosei Co., Ltd.) is added as a dispersant is added to kaolin (trade name: “Hydra Gloss 90”, 50 parts of Huber Co., Ltd. and 50 parts of heavy calcium carbonate (trade name: “Hydro Curve 90”, manufactured by Bihoku Powder Chemical Co., Ltd.) were added and dispersed with a Coreless disperser to prepare a pigment slurry. In this pigment slurry, 3 parts of the enzyme-modified starch of Example 1 with respect to 100 parts of pigment, 8.4 parts of styrene-butadiene copolymer latex (trade name: “OJ-2000”, manufactured by JSR), and auxiliary agent As a result, an antifoaming agent and a dye were sequentially added to finally prepare a pigment coating solution for a top coating layer having a solid content concentration of 66.5%.

(Manufacture of base materials)
To the pulp slurry mixed so as to be 10 parts of LBKP (CSF 450 ml) and 90 parts of NBKP (CSF 480 ml), 0.5% aluminum sulfate (vs. pulp, solid content conversion), cationized starch (trade name: “ACE K”) , Manufactured by Oji Cornstarch Co., Ltd.) 0.9% (vs. pulp, solid content conversion), AKD sizing agent (trade name: “Size Pine K-902”, manufactured by Arakawa Chemical Co., Ltd.) 0.03% Pulp, solid content) was sequentially added to the machine chest, and then the recovered white water and the above pulp slurry were mixed, and amphoteric polyacrylamide (trade name: “Polystron 1280”, manufactured by Arakawa Chemical Industries, Ltd.) 0.1% ( Added to the pulp, solid content), then heavy calcium carbonate (trade name: “Hydrocurve 60”, manufactured by Bihoku Flour Industry Co., Ltd.) as a filler, with a paper ash content of 15 It was added before the fan pump in such a way that. Furthermore, 0.016% of a cationic acrylic resin (trade name: “DR-3015”, manufactured by Hymo Co., Ltd.) was added in front of the screen to prepare a paper stock (concentration: 1.01%). The paper stock is formed with a gap former at a J / W ratio of 0.995 and a paper making speed of 1500 m / min. After squeezing with two continuous shoe presses, squeezing and smoothing with a roll press are performed. After drying with a single-stage array dryer, the size press liquid is subjected to a size press treatment so that the solid content becomes 6.0 g / m ² using a rod metalling size press apparatus. After drying, the paper was passed through a machine calendar having an on-machine specification to obtain a base material having a moisture content of 4.5% and a basis weight of 55.4 g / m ² .

(Manufacture of coated paper)
Using a blade coater that supplies the above-mentioned base material with the above-mentioned pigment coating solution for the top coating layer by a jet fountain method, the dry coating amount per side becomes 13 g / m ^2. Coated and dried to obtain a coated paper. The coated paper obtained in this way was adjusted for temperature, linear pressure, and paper feeding conditions with a multi-nip calender in which metal rolls and resin rolls were inclined, and the basis weight was 81.4 g / m ^2. A coated paper for printing was obtained.

<Example 9>
(Preparation of pigment coating solution for top coating layer)
To an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate (trade name: “Aron T-50”, manufactured by Toagosei Co., Ltd.) is added as a dispersant is added to kaolin (trade name: “Hydra Gloss 90”, 50 parts of Huber Co., Ltd. and 50 parts of heavy calcium carbonate (trade name: “Hydro Curve 90”, manufactured by Bihoku Powder Chemical Co., Ltd.) were added and dispersed with a Coreless disperser to prepare a pigment slurry. In this pigment slurry, 3 parts of the enzyme-modified starch of Example 1 with respect to 100 parts of pigment, 8.4 parts of styrene-butadiene copolymer latex (trade name: “OJ-2000”, manufactured by JSR), and auxiliary agent As a result, an antifoaming agent and a dye were sequentially added to finally prepare a pigment coating solution for a top coating layer having a solid content concentration of 66.5%.

(Manufacture of coated paper)
Using a blade coater that supplies the above-mentioned pigment coating solution for the top coating layer to the base material produced in Example 7 by the jet fountain method, the dry coating amount per side is 17 g / m ² . Coated and dried as described above to obtain a coated paper. The coated paper obtained in this way was adjusted for temperature, linear pressure, and paper feeding conditions with a multi-nip calender in which metal rolls and resin rolls were inclined, and the basis weight was 81.4 g / m ^2. A coated paper for printing was obtained.

<Comparative Example 1>
The starch powder A of Example 1 was used as starch powder G having a pH of 4.5 obtained without adjusting the pH of the starch slurry before dehydration and drying, and the resuspended starch slurry was adjusted to pH 6 using NaOH in a slurry tank. 0.0 and a starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that the amount of starch degrading enzyme added was 850 ppm.

<Comparative example 2>
The starch powder A of Example 1 was changed to starch powder H adjusted to pH 4.8, the resuspended starch slurry was adjusted to pH 6.0 using NaOH in the slurry tank, and the starch degrading enzyme addition amount was 850 ppm. A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that.

<Comparative Example 3>
In Comparative Example 2, the starch paste clear liquid coated paper was prepared in the same manner as in Comparative Example 2 except that the pH of the resuspended starch slurry was not adjusted in the slurry tank and the starch degrading enzyme addition amount was 1500 ppm. Obtained.

<Comparative Example 4>
The starch powder A of Example 1 was used as starch powder I adjusted to pH 7.6, the resuspended starch slurry was adjusted to pH 6.5 using dilute sulfuric acid in the slurry tank, and the starch degrading enzyme addition amount was 850 ppm. A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that.

<Comparative Example 5>
A starch paste clear liquid coated paper was obtained in the same manner as in Comparative Example 3 except that the starch powder G of Comparative Example 3 was changed to starch powder J adjusted to pH 7.2.

<Comparative Example 6>
A starch paste clear liquid coated paper was obtained in the same manner as in Example 1 except that the starch powder D of Example 4 was changed to starch powder K adjusted to pH 8.0 and the starch degrading enzyme addition rate was 170 ppm.

<Comparative Example 7>
(Preparation of pigment coating solution for undercoat layer)
In a pigment slurry composed of heavy calcium carbonate (trade name: “Hydrocurve 60”, manufactured by Bihoku Flour Industry Co., Ltd.), 100 parts of pigment, 4 parts of enzyme-modified starch of Comparative Example 1 as a binder, and styrene-butadiene 5 parts of polymer latex (trade name: “OJ-2000”, manufactured by JSR) was added, and antifoaming agent and dye were sequentially added as auxiliary agents, and finally an undercoat coating layer having a solid content concentration of 67%. A pigment coating solution was prepared.

(Preparation of pigment coating solution for top coating layer)
To an aqueous solution in which 0.1 part of kaolin in which sodium polyacrylate (trade name: “Aron T-50”, manufactured by Toagosei Co., Ltd.) is added as a dispersant is added to kaolin (trade name: “Hydra Gloss 90”, 50 parts of Huber Co., Ltd. and 50 parts of heavy calcium carbonate (trade name: “Hydro Curve 90”, manufactured by Bihoku Powder Chemical Co., Ltd.) were added and dispersed with a Coreless disperser to prepare a pigment slurry. In this pigment slurry, 3 parts of the enzyme-modified starch of Comparative Example 1 with respect to 100 parts of pigment, 8.4 parts of a styrene-butadiene copolymer latex (trade name: “OJ-2000”, manufactured by JSR), and an auxiliary agent As a result, an antifoaming agent and a dye were sequentially added to finally prepare a pigment coating solution for a top coating layer having a solid content concentration of 66.5%.

(Manufacture of coated paper)
Dry coating amount per side using a blade coater that supplies the above-mentioned pigment coating liquid for the undercoat coating layer to the starch paste liquid clear liquid coated paper produced in Comparative Example 1 by the jet fountain method Was coated and dried so as to be 7.5 g / m ² to obtain a double-sided primer-coated paper. Subsequently, a dry coat amount per side of 9.5 g / m is used by using a blade coater that supplies the above-mentioned pigment coating solution for the top coating layer to the double-sided undercoating paper by a jet fountain method. ^The coated paper was dried to obtain 2 to obtain a coated paper. The coated paper thus obtained was subjected to adjustment of temperature, linear pressure, and paper feeding conditions in a multi-nip calender in which a metal roll and a resin roll were inclined, and a coated paper for printing was obtained.

  As apparent from Tables 1 and 2, the coated paper according to the examples of the present invention had extremely excellent performance as a printing paper. Comparative Examples 1 to 3 are not preferable because the pH of the starch slurry before dry powdering is lower than the optimum pH range, so that enzyme denaturation is unstable or the amount of enzyme added must be increased. Further, Comparative Examples 4 to 6 are not preferable because the starch slurry has a pH higher than the optimum pH, so that enzyme denaturation is unstable or the amount of enzyme added must be increased. Since Comparative Example 7 contains enzyme-modified starch having a large viscosity variation in the coating layer coating solution, when the coated paper is formed using the starch paste solution, a coated paper having inferior printing quality is obtained. .

  According to the present invention, the enzyme-modified starch paste liquid used in size press liquids and coatings for coated paper has good pH stability during storage of starch powder suspension slurry, and the viscosity of the finished paste liquid is stabilized by a stable enzyme reaction. It is possible to supply an enzyme-modified starch paste liquid with little variation.

Claims (4)

In the starch powder manufacturing process, the pH of the starch powder suspension before dehydration and drying is adjusted to 6.0 ± 1.0, and the pH adjusting chemical used in the above adjustment is absorbed into the starch, A starch paste obtained by resuspending starch powder obtained by dehydrating and drying a turbid solution in water without adjusting pH, and adding starch-degrading enzyme having an optimum pH of 6.0 ± 1.0 and steaming. Manufacturing method. In the starch powder manufacturing process, the pH of the starch powder suspension before dehydration and drying is adjusted to 6.0 ± 1.0, and the pH adjusting chemical used in the above adjustment is absorbed into the starch, The starch powder obtained by dehydrating and drying the suspension is resuspended in water without adjusting the pH, and obtained by steaming the starch-degrading enzyme having an optimum pH of 6.0 ± 1.0. Starch paste liquid.   A coated paper, wherein the starch paste solution according to claim 2 is coated or impregnated on at least one surface of a substrate.   A coated paper, wherein the coated layer provided on the substrate is a clear coated layer and / or a pigment coated layer containing the starch paste liquid according to claim 2.