JP2013100626A - Coated paper using calcium aluminate compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out decreased blending of clay and increased blending of calcium carbonate while maintaining quality without introducing a complicated device and altering a design of a binder to provide a general-purpose technology for contributing cost reduction in a general coated paper coated with clay and calcium carbonate as principal constituents of a pigment.SOLUTION: The present invention utilizes an effect that blending 1-50 parts of calcium aluminate monocarbonate represented by the chemical formula of 3CaO AlOCaCO11HO in a coated layer containing calcium carbonate develops the interaction of calcium carbonate and calcium aluminate monocarbonate to considerably improve white paper brightness. The present invention allows use of heavy calcium carbonate as calcium carbonate, which is advantageous in cost for solving the above problem.

Description

  The present invention relates to a coating formulation for coated paper, and uses calcium aluminate monocarbonate (hereinafter abbreviated as monocarbonate) (Chemical Formula 1), which is one of calcium aluminate compounds, as a pigment for paper coating. Without introducing complicated equipment or changing the design of the binder, it is possible to reduce the clay and increase the calcium carbonate while maintaining the quality, thereby contributing to the cost reduction of the coated paper.

  Because coated paper has many variations in production equipment and many types of pigments and chemicals to be coated, improvements are constantly being made to improve quality and productivity. The results of the pursuit of quality are reflected in high-white, high-gloss coated paper, which has been used mainly in high-quality publications, such as fashion magazines and automobile magazines, which are frequently used for photo printing. Demand has decreased significantly due to penetration. In addition, the spread of the Internet has changed the competitive landscape of advertising media, and Internet advertising has shown a significant increase, while paper media advertising such as newspapers, flyers and catalogs has decreased.

  With this change in demand structure, paper manufacturers are integrating high-grade grades and special grades, and research on cost reduction that maintains the quality of all coated papers is actively conducted.

  In the past, when papermakers worked to reduce costs, labor costs were reduced by installing large machines and production was increased by speeding up. However, these methods are difficult to handle oversupply of products and small lots. It has become difficult to adapt to changes in the times.

  The only way to reduce costs technically without increasing production is to use inexpensive raw materials. Often, however, design changes in a cheaper direction are accompanied by quality degradation. Common coated paper is composed of 30% by weight of paint and 70% of base paper, and the raw material pulp of coated base paper is usually NBKP (coniferous bleached kraft pulp), LBKP (hardwood bleached kraft pulp), GP (machinery) Pulp) is blended according to purpose. Since all of these are virgin pulp, the cost is high, so it is tried to reduce the cost by blending cheap DIP (waste paper deinked pulp) instead, but simply increasing the blending ratio of DIP In this case, the paper strength such as the tensile strength, tear strength, and bending rigidity is reduced, and there is a concern that the whiteness, opacity, and minute foreign matters are mixed.

  90% of the paint that occupies 30% of the weight of general coated paper is composed of pigment and 10% of binder (adhesive). It can be said that most of the pigments used are heavy calcium carbonate and clay. Both are mass-produced from natural abundant minerals, so the price is much cheaper than pulp. Therefore, reducing pulp and increasing paint will surely lead to cost reductions, but in this case, the paper strength will naturally decrease, and it will be accompanied by dramatic changes in paper quality such as a decrease in paper thickness. It is difficult. As described above, since the design change of the base paper, which is the base material of the coated paper, has a wide influence on the quality, the desire for cost reduction is naturally directed to the pigment.

  Clay, also called kaolin, is a mineral composed of hydrous aluminum silicate produced by the weathering of clay. The greatest feature is high glossiness derived from extremely fine hexagonal plate-like particles. In general coated paper, 30-50% of the pigment is blended. Fine, highly white clay suitable for coated paper is produced only in the US state of Georgia, Brazil, and the United Kingdom, so all Japan must rely on imports.

  On the other hand, heavy calcium carbonate for paper coating is obtained by mechanically pulverizing white limestone produced in Japan to the desired particle size, and can be procured at a lower cost than clay. The shape of heavy calcium carbonate is indefinite, so the gloss performance is inferior to clay, but it is preferred as an extender because of its high whiteness and excellent slurry fluidity. -60% is blended.

  Heavy calcium carbonate is classified into dry pulverized heavy calcium carbonate and wet pulverized heavy calcium carbonate depending on the pulverization method. Dry pulverized heavy calcium carbonate is less expensive than wet pulverized products, but the dry pulverization method has a large pulverization limit particle size in principle, so that no gloss performance can be expected as a coating pigment. Moreover, since the shape is extremely angular, the coating applicator is worn heavily and the coating quality is not stable.

  In recent years, the wet calcium ground heavy calcium carbonate has been remarkably grown by overcoming such problems. With the remarkable progress of the pulverizer, an ultrafine grade containing 100% or less of 2 μm or less has been developed and has come to appeal for high glossiness. As a result, the mixing ratio of heavy calcium carbonate to coated paper has surpassed that of clay, but the glossiness of clay has not been reached, and further increasing the amount of heavy calcium carbonate to be added It will definitely reduce the gloss of the coated paper.

  By the way, calcium carbonate includes light calcium carbonate produced by a chemical method, and has responded to the demand for fine calcium carbonate until high functionality of heavy calcium carbonate is achieved. The chemical synthesis method has been used in a small amount due to its high cost, but in order to improve the ink acceptability by forming a porous coating layer, it is still blended in a small amount according to the purpose.

  Double coating is one of the solutions to these problems by technical innovation in papermaking facilities. Double coating is a two-layer coating. The first layer is for the purpose of smoothing the base, and the second layer is a high-quality coating with expensive pigments. Multi-layer coating is good at producing high-quality coated paper, but it is possible to maintain quality even with the use of less expensive paint, and double coating has been introduced exclusively for the purpose of reducing costs. ing.

  Typical equipment for double coating is blade double coating by an off-machine coater. Although this apparatus requires high technology for controlling the coating amount and the paper run becomes complicated, the equipment cost is high, but it is possible to balance the quality and cost highly. In addition, there are cases in which the paper machine that produces the base paper is remodeled to reduce equipment costs, the first layer of pigment is applied with a gate roll coater, and then the second layer is applied with a normal off-machine single coater. Patent Document 1).

  Non-patent document 2 reports in detail the typical design and quality of coated paper in double coating. The first layer is coated with heavy calcium carbonate containing 60% or less of 2 μm or less, which is coarser than that used for a normal single coat, and the second layer is formulated with the same paint as the single coat. Such double-coated paper can provide good quality with low white paper gloss, printing gloss and opacity, low PPS roughness, and lower production costs than single-coated paper.

  As a method that does not depend on equipment, Non-Patent Document 3 discusses a heavy calcium carbonate single formulation in which water retention and fluidity are devised by chemicals. CMC is used as a water retention agent, the design of the latex is changed, and positive factors such as an increase in paint solids are mobilized to achieve a certain effect. However, although not mentioned in the discussion of this document, in fact, it is considered that the addition of oxidized starch in the comparative study formulation has a significant effect on the gloss of white paper. In any case, an attempt to develop a glossy white paper by thus drastically changing the binder design may affect the adhesive strength, which is the original function of the binder, and further careful consideration is required.

  As can be seen from these non-patent literatures, the coated paper manufacturing site exposed to severe cost reductions has a high increase in the distribution of heavy calcium carbonate (clay blending shift), especially in response to the recent rise in crude oil prices. The trend is getting stronger.

  Monocarbonate, which plays an important role in the present invention, is a crystalline inorganic substance having a layered structure and is a fine hexagonal plate-like crystal similar to clay. Monocarbonate does not exist in nature and is synthesized by a chemical reaction using calcium hydroxide and aluminum hydroxide as raw materials, so it can be obtained with the highest whiteness without containing impurities.

  As a method for synthesizing monocarbonate, for example, 1 to 3 mol of calcium hydroxide is mixed with 1 mol of an aqueous sodium aluminate solution, and the required amount is carbonated by blowing carbon dioxide gas while heating to 50 ° C. or higher. It is disclosed that the synthesis of This method is a relatively simple method, but is a very expensive method because it is necessary to remove and wash sodium carbonate produced as a by-product during carbonation. Moreover, since excessive carbonation decomposes monocarbonate to produce calcium carbonate and gelled aluminum hydroxide, care must be taken in determining the end point of carbonation. The monocarbonate thus obtained has a particle diameter of 2 to 10 μm, which is almost 10 times the size of general clay, so it is clearly disadvantageous for white paper glossiness and fluidity, and is very suitable for paper coating. (Patent Document 1).

  As another monocarbonate synthesis method, a combination of alkali aluminate, alkali carbonate and calcium hydroxide, or aluminum hydroxide or aluminum oxide, alkali hydroxide, alkali carbonate and calcium hydroxide, respectively A method of mixing the theoretical amount of a product and heating and stirring to 60 ° C. or higher is disclosed. This method is intended to promote the reaction by dissolving low-reactivity aluminum hydroxide with a strong alkali, and is essentially the same as the synthesis method described above. Since alkali carbonate is used instead of carbon dioxide, there is no concern about excessive carbonation, but it can be said to be a more expensive method. This method is intended for an anion adsorbent, and there is no description regarding the particle size of monocarbonate (Patent Document 2).

  As a method for synthesizing fine monocarbonate excellent in white paper glossiness and fluidity as a paper coating pigment, a method utilizing a mechanochemical developed by the present inventors is suitable. In this method, a mechanochemical treatment (grinding treatment) is applied to aluminum hydroxide to distort the crystal structure of aluminum hydroxide, leading to a reaction with calcium hydroxide. Calcium carbonate is used as the carbonate ion source, and it does not contain unnecessary elements such as sodium. Therefore, the reaction formula is extremely simple (Formula 1). Since this method is excellent in reaction controllability, it is possible to stably synthesize fine monocarbonate having a width of 1 μm or less (Patent Document 3).

Formula 1

3Ca (OH) ₂ + 2Al (OH) ₃ + CaCO ₃ + 5H ₂ O → 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O

Paper PA Technical Journal December 2006 P12-23 Papa Gikyo Magazine August 2009 P44-48 Papa Gikyo Magazine August 2008 P30-34 JP-A-5-147930 JP 9-241919 JP 2008-37664 A

  The monocarbonate used in the present invention is a completely new pigment, but is represented by a chemical formula similar to that of satin white, which was often used in the past as a pigment for paper coating (Chemical Formula 2). Satin white is synthesized by a neutralization reaction between aluminum sulfate and calcium hydroxide, and needle crystals having a length of 1 to 5 μm can be synthesized relatively easily. Satin white is a pigment that is indispensable for the production of art paper in blade coating because it is easy to obtain high gloss due to the immobilization promoting effect of the paint that seems to be derived from sulfate ions, but on the other hand, paint storage stability (stable It is almost no longer used due to the poor quality and handling.

  In that respect, monocarbonate is a carbonate ion type, so there is no difficulty in handling such as satin white, and it has lightness in addition to the high glossiness unique to plate-like particles. Monocarbonates whose particle size is controlled to a width of 1 μm or less exhibit an unparalleled gloss, such as a commercially available high gloss clay. Regarding lightness, the true specific gravity of monocarbonate by the pycnometer method is 2.1 g / cc, which is considerably smaller than 2.6 g / cc of clay and 2.7 g / cc of calcium carbonate.

  The object of the present invention is to reduce the amount of clay and reduce the amount of calcium carbonate while maintaining the quality without introducing complicated equipment or changing the design of the binder in general coated paper mainly composed of clay and calcium carbonate. The purpose is to provide general-purpose technology that can increase dividends and contribute to cost reduction.

  In the present invention, by incorporating 1 to 50 parts of monocarbonate into the calcium carbonate-containing coating layer, the interaction between calcium carbonate and monocarbonate is expressed, and the effect of greatly improving the white paper gloss of the coating layer is utilized. In order to solve the above problems, heavy calcium carbonate that is advantageous in terms of cost can be selected as calcium carbonate.

  The present invention not only provides high-quality coated paper by using monocarbonate excellent in whiteness, white paper glossiness, and light weight, but is not limited to monocarbonate quality superiority, monocarbonate and calcium carbonate It is the greatest feature to use a synergistic effect of white paper gloss expression that is not in the conventional concept by using together. Rather, since the effect becomes more remarkable as the calcium carbonate is increased, the glossiness of the white paper can be maintained even if the clay is reduced, and at the same time, the cost is reduced. It can also be said that the whiteness is surely improved by replacing clay and calcium carbonate.

  As described above, the present invention enables cost reduction of the coated paper while maintaining the quality, and does not require the introduction of complicated equipment or the design change of the binder, so that it can be introduced in any existing coating equipment. High technology.

  The monocarbonate used in the present invention may be produced by any method as long as it achieves the object of the present invention, and is characterized by using the mechanochemically treated aluminum hydroxide introduced above. It is desirable in terms of cost and quality to use fine monocarbonate produced by the method described above. The particle size of the monocarbonate obtained by the above method is usually 1 μm or less, and almost no aggregation occurs. In practice of the present invention, it is needless to say that the particle size of monocarbonate is preferably small, but if it is 1 μm or less, a sufficient effect can be expected.

  Monocarbonate is used in the same manner as light calcium carbonate for general coating, once dehydrated and concentrated, then re-liquefied using a powerful shearing stirrer with the addition of polyacrylic dispersant, and a solid content of 50%. It is desirable to finish as the above high concentration slurry.

  In the present invention, in order to enhance the gloss development effect by the interaction of monocarbonate and calcium carbonate, they must be blended in the same coating layer. For example, in the case of applying a plurality of times such as double coating, if the coating is performed separately, no effect is exhibited.

  The preferable blending number of monocarbonate and calcium carbonate is 1 to 50 parts, more preferably 3 to 20 parts, for monocarbonate. If it is 1 part or less, the synergistic effect is small, and if it is 50 parts or more, the cost is high, which is not preferable. About 20 parts or more is preferable about calcium carbonate, and 50 parts or more are still more preferable. If it is 20 parts or less, the synergistic effect of the corner can hardly be enjoyed.

  With regard to calcium carbonate, the same effect is exhibited by both heavy calcium carbonate and light calcium carbonate. However, cheap heavy calcium carbonate is preferable from the gist of solving the problem, and wet ground heavy calcium carbonate is most preferable.

  Although the mechanism of the interaction and synergistic effect of monocarbonate and calcium carbonate, which is a feature of the present invention, is not clear, the calcium aluminate ion acts on the surface of the calcium carbonate particles, and the rheology of the calcium carbonate particles is glossy. It is presumed to change to a state favorable for expression.

  In the present invention, the combined use of monocarbonate and calcium carbonate is essential, but commercially available coating pigments can be used without any problem. Examples of commercially available coating pigments include clay, talc, plastic pigment, titanium oxide, aluminum hydroxide, and satin white, and one or more of them may be used in combination.

  As the binder used in the coating layer of the present invention, styrene / butadiene copolymer latex and modified starch used for the production of general coated paper are suitable. Either of them may be used, but it is usually better to use them together. Chemically modified starch not only serves as a binder, but also has the role of imparting water retention to coatings, suppressing migration (inhibiting fluidization), and imparting rigidity to the coating layer. Phosphate esterified starch is suitable for coating. Although used, oxidized starch, etherified starch, enzyme-modified starch and the like can also be used. These binders are preferably used in an amount of 5 to 15 parts by weight for latex and 1 to 10 parts by weight for modified starch with respect to 100 parts by weight of pigment.

  In the coating material of the present invention, various auxiliary agents such as a dispersant, an antifoaming agent, a water-resistant agent, a water retention agent, a thickening agent and the like are suitably used as in the case of a normal coating paper coating.

  The coating material thus adjusted can be applied in the same manner as ordinary coated paper by various coating methods such as a blade coater, an air knife coater, a roll coater, a rod coater, and a curtain coater.

  Other conditions such as base paper conditions, paint concentration, pigment dispersion conditions, coating speed, drying conditions, supercalender or soft calender conditions may be appropriately adjusted within the range of normal coated paper manufacturing conditions. In the invention, no special consideration is required except for the combined use of monocarbonate and calcium carbonate, and an excellent effect is exhibited only by use under normal conditions.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the following Example. Unless otherwise specified, “parts” and “%” in the examples represent “parts by weight” and “% by weight”, respectively, and are values in terms of solid content. In addition, it evaluated based on the test method as shown below about a coating liquid and the obtained coated paper.

(Test method)
(1) Blank paper glossiness: measured based on JIS P8142. Measuring device: Nippon Denshoku Industries Co., Ltd. VG7000
(2) ISO whiteness: measured based on JIS P8148. Measuring device: Konica Minolta Sensing Co., Ltd. CM-3500d
(3) Color difference value (a value / b value): Konica Minolta Sensing Co., Ltd. CM-3500d The larger the a value, the stronger the reddishness, and the larger the b value, the stronger the yellowishness.
(4) Particle size measurement: Nippon Laser Co., Ltd. SIMPATE HELOS SYSTEM Laser Laser Diffraction Particle Size Analyzer By a wet dispersion method.

Example 1
10 parts of monocarbonate (manufactured by Kotegawa Sangyo: Monocarbonate V60: average particle size 0.7 μm), 90 parts of heavy calcium carbonate (manufactured by Kotegawa Sangyo: wet pulverized product: 97% below 2 μm), and 100 parts of pigment as a binder An aqueous coating material having a solid content of 59% was prepared by mixing 11 parts of latex (manufactured by JSR: product number 0695: SB latex) and 3 parts of starch (manufactured by Oji Cornstarch: HSS # 100: phosphate esterified starch). By combining a plain bar with Imoto Seisakusho automatic coating machine IMC-70F0 to 20μm clearance it was applied to a coating weight 10 ± 0.3g / ^{m 2} on one surface of woodfree paper of 64 g / ^{m 2} . Subtle adjustment of the coating amount was performed by adjusting the coating speed. The wet paper immediately after coating was fixed on a backing paper and dried in a shelf dryer set at 120 ° C. for 90 seconds. The masses of the base paper and the coated paper were measured after aging at 25 ° C. and 50% humidity using a constant temperature and humidity machine. The coated paper prepared in this way was tested at a test super calendar 25FC-200E manufactured by Kumagai Riki Kogyo Co., Ltd., with a roll temperature of 40 ° C., a linear pressure of 50 kgf / cm, a paper feeding speed of 10 m / min, and two passes. The target coated paper was completed by polishing.

Example 2
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 50 parts monocarbonate and 50 parts heavy calcium carbonate.

Example 3
Coated paper in the same manner as in Example 1 except that the composition of the pigment was changed to 10 parts monocarbonate, 60 parts heavy calcium carbonate, and 30 parts light calcium carbonate (Okutama Kogyo Co., Ltd .: TP-123: Aragonite needle shape). It was created.

Example 4
A coated paper is prepared in the same manner as in Example 1 except that the pigment composition is changed to 10 parts monocarbonate, 80 parts heavy calcium carbonate and 10 parts clay (manufactured by Engelhard: UW-90: primary particle size distribution). did.

Example 5
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 10 parts monocarbonate, 20 parts heavy calcium carbonate, and 70 parts clay.

Comparative Example 1
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 10 parts monocarbonate, 5 parts heavy calcium carbonate, and 85 parts clay.

Comparative Example 2
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 10 parts monocarbonate and 90 parts clay.

Comparative Example 3
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 50 parts monocarbonate and 50 parts clay.

Comparative Example 4
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 50 parts of heavy calcium carbonate and 50 parts of clay.

Comparative Example 5
A coated paper was prepared in the same manner as in Example 1 except that the pigment composition was changed to 30 parts of heavy calcium carbonate and 70 parts of clay.

Reference Example A coated paper was prepared in the same manner as in Example 1 using monocarbonate, heavy calcium carbonate, light calcium carbonate and clay alone. The results are shown in (Table 1).

  The test results of Examples 1 to 5 and Comparative Examples 1 to 5 are shown in (Table 2). The actual measured value of white paper gloss is a value actually measured with a gloss meter. The blank paper gloss calculation value is a value obtained by multiplying the white paper gloss of each pigment by the blending ratio and summing them. The synergistic effect is a value obtained by subtracting the calculated value of the blank paper gloss from the measured value of the blank paper gloss.

  In Comparative Examples 2 to 5 in which monocarbonate and calcium carbonate are not used in combination, the actual measured value and the calculated value of white paper gloss are substantially the same, whereas in Examples 1 to 5, the actual measured value is higher than the calculated value. A synergistic effect of combining calcium carbonate with calcium carbonate is observed. The effect was almost the same for both heavy calcium carbonate and light calcium carbonate.

  From Examples 4 and 5 and Comparative Example 1, it can be seen that the greater the amount of calcium carbonate blended, the greater the synergistic effect, which becomes more pronounced with 20 parts or more of calcium carbonate.

  From Examples 1-5, it turns out that it is the tendency for whiteness to become high, so that a synergistic effect is large.

Industrial applicability

  In this way, the technology that uses monocarbonate and calcium carbonate together in the paper coating industry exhibits glossiness not seen in the conventional inorganic pigment concept, so a considerable amount of clay is converted into heavy calcium carbonate while maintaining the quality. It can be transferred and is expected to meet the demand for cost reduction.

Claims (2)

Calcium represented by the chemical formula of 3CaO · Al ₂ O ₃ · CaCO ₃ · 11H ₂ O with respect to 100 parts by weight of pigment in coated paper in which a paint mainly composed of a pigment and an adhesive is applied on the base paper. A coated paper comprising 1 to 50 parts by weight of aluminate monocarbonate and 20 parts or more of calcium carbonate at the same time.   The coated paper according to claim 1, wherein the calcium carbonate is particularly heavy calcium carbonate.