JPH1171403A - Low viscosity starch derivative and coating composition blended therewith for coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starch derivative, in a use as an adhesive of a coating compsn. for coated papers, giving good high-speed coatability, rare occurrence of formed ink thickness unevenness, and slight reduction in adhesive strength, and to provide a coating compsn. for coated papers using the starch derivative. SOLUTION: In the starch derivative, which is prepared by heat reaction with urea, the derivative has a combined carbamic acid ester group amount of 0.5 wt.% or more and a solubility in 25 deg.C-water of 15 wt.% or less, and the sizing liquid in the gel state has a viscosity with B-type viscometer of 50-500 mPa.s (measuring condition: solid concentration 35%, temp. 50 deg.C, rotor speed 60 rpm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel starch derivative obtained by heat-reacting urea or urea and phosphoric acid, and a coating composition for coated paper using the starch derivative. The present invention relates to a starch derivative which is excellent in suitability and can impart high gloss, smoothness and good printability to coated paper, and a coating composition for coated paper using the starch derivative.

[0002]

2. Description of the Related Art In order to improve productivity, in the production of coated paper,
Coating machines are becoming faster. However, in high-speed coating with a blade coater exceeding 1000 m / min, a phenomenon in which solidified coating liquid adheres and deposits on the tip of the blade as the coating speed is increased, so-called bleeding, occurs.
If the amount of deposits on the blade tip increases, the coating surface may be scratched to cause streak-like defects on the surface, or the deposits may fall off the blade tip from the coating layer and cause foreign matter defects, resulting in coating defects. It often causes surface defects on the paper.

Although no clear conclusions have been made as to the cause of bleeding, many studies have shown that in high-speed coating, a high shearing force is applied when the coating liquid passes under the blade, and the fluidity at this time is high. Is known to easily occur with coating liquids that are inferior. In order to improve the fluidity of the coating liquid when passing through the blade, it is considered advantageous that the viscosity of the coating liquid under high shearing force is lower.

[0004] Therefore, in high-speed coating, the concentration of the coating liquid must be reduced to perform coating. In this case, in addition to a decrease in gloss and smoothness, a drying load is increased, and quality and economy are reduced. Disadvantaged. The viscosity of the coating solution under high shearing force is greatly affected not only by the pigment used in the coating solution but also by the water-soluble adhesive, that is, the starch derivative. For this reason,
No. 1-162894 discloses a method of reducing the viscosity of acetic acid-esterified starch by enzymatic modification or thermochemical modification and using it for a coating composition. According to the method, although the suitability for high-speed coating is improved to some extent, starch easily migrates in the drying step after coating with the coating liquid, and when the obtained coated paper is printed, unevenness in ink adhesion tends to occur. Problem. Furthermore, JP-A-53-14818, JP-A-7-300799,
A method of using a starch having a specific low size liquid viscosity in a coating composition has been introduced. However, as described above, not only is it easy for ink deposition unevenness to occur, but also the adhesive strength of the coating layer is reduced. There's a problem.

Accordingly, when used as an adhesive for a coating composition for coated paper, a starch derivative which is excellent in suitability for high-speed coating and which causes less unevenness in ink adhesion and lowering of adhesive strength,
It has not been put to practical use yet.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a conventional low-viscosity starch derivative having good suitability for high-speed coating when used as an adhesive for a coating composition for coated paper. It is intended to provide a starch derivative which is less likely to cause non-uniformity in ink adhesion and a decrease in adhesive strength, which is a problem when using the same, and a coating composition for coated paper using the starch derivative.

[0007]

That is, the present invention relates to a starch derivative obtained by heat-reacting urea or urea with phosphoric acid, wherein (a) the amount of bound carbamate groups is 0.5% by weight or more, Viscosity of a paste liquid obtained by gelatinizing the starch derivative with water having a solubility in water of not more than 15% by weight by a B-type viscometer (measurement conditions: solid content concentration 35%, temperature 50 ° C., rotor speed 60 rpm) Is 50 to 500 mPa · s, or a starch derivative (hereinafter also referred to as carbamic acid esterified starch), or (b) the amount of bound carbamic acid ester groups is 0.5% by weight or more, Is 1.0% by weight or less, the solubility in water at 25 ° C. is 15% by weight or less, and the viscosity of the paste liquid obtained by gelatinizing the starch derivative with a B-type viscometer (measurement conditions: solids concentration 35 %, Temperature 50 ℃,
The present invention relates to a starch derivative (hereinafter, also referred to as a carbamic acid phosphorylated ester starch) having a rotor rotation speed of 60 rpm) of 50 to 500 mPa · s. The bound carbamate group amount, the bound phosphate group amount is
Each value is based on the dry weight of the starch. The starch derivative of the present invention can be obtained by performing a heating reaction by gradually increasing the roasting temperature by a dry roasting method.

In the present invention, the starch derivative is used as an adhesive in a coating composition for coated paper containing a pigment and an adhesive as main components in a solid content ratio of 0.1 to 100 parts by weight of the total pigment. 3 to 1
The present invention relates to a coating composition characterized by using 0 parts by weight.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The starch derivative of the present invention, when used as an adhesive for a coating composition for coated paper, can provide a high balance between high-speed coating suitability and printability. A starch derivative which is suitable as an adhesive for a coating composition, and particularly has a low viscosity liquid paste liquid having a specific amount of a carbamate group bonded thereto while maintaining the solubility of the starch derivative in water at a specific level or less. By doing so, it has been completed based on the knowledge of the present inventors that the above characteristics can be satisfied. Furthermore, by combining a specific amount of a phosphate ester group in addition to a specific amount of a carbamate group, high-speed coating suitability and printability can be more highly balanced.

The starch derivative of the present invention, that is, the starch derivative (a) having an amount of bound carbamate group of 0.5% by weight or more and having the specific solubility and the specific size liquid viscosity is, for example,
To 100 parts by weight of starch, 0.1 to 1.5 parts by weight of 36% by weight hydrochloric acid, 1 to 10 parts by weight of urea and 1 to 60 parts by weight of water are mixed, and the mixture is heated and reacted at 70 to 170 ° C. In roasting, it can be obtained by appropriately selecting the amount of a reaction chemical, the amount of water, the reaction temperature and the reaction time. Preferably, the heating reaction is performed by dividing the roasting temperature into multiple stages such as two stages or three stages. That is, first, to prevent the decomposition of urea,
Roasting is performed at a temperature lower than 0 ° C. to obtain the specific solubility and size liquid viscosity, and then the temperature is raised to 130 ° C. or higher to decompose urea and convert the starch into a carbamic acid ester. By increasing the roasting temperature stepwise, starch is less likely to be decomposed, so that the starch solubility can be kept low.

Further, another starch derivative of the present invention, that is, the amount of bound carbamate group is 0.5% by weight or more,
The starch derivative (b) having the specific solubility and the specific viscosity of the paste liquid having an amount of bound phosphate ester groups of 1.0% by weight or less is, for example, 0.1 to 2 parts by weight of orthophosphoric acid, 1 part by weight of urea and 100 parts by weight of starch. In dry roasting in which 0.5 to 3 parts by weight of sodium chloride and 1 to 60 parts by weight of water are added and mixed as required, and the mixture is heated and reacted at a temperature of 70 to 170 ° C., It can be obtained by appropriately selecting the amount, the amount of water, the reaction temperature and the reaction time. Preferably, the heating reaction is performed by dividing the roasting temperature into multiple stages such as two stages or three stages. That is, to prevent the decomposition of urea,
The roasting is carried out at a temperature lower than the above to obtain the above-mentioned specific solubility and viscosity of the size liquid. Then, the temperature is raised to 130 ° C. or higher to decompose urea, and the starch is carbamate-phosphorylated. By increasing the roasting temperature stepwise, starch is less likely to be decomposed, so that the starch solubility can be kept low.

The dry roasting method referred to in the present invention is described in Japanese Patent Publication No. 45-2
It is a known method described in No. 0512, specifically, impregnating starch with a mixed solution of a reactant and water, or spraying the mixed solution on starch by spraying, After uniformly mixing the starch, the reactants and water by stirring until uniform, the mixture is
The heating reaction is performed using a dry roasting device such as a dryer, a flash dryer, a stirring dryer, or a stationary dryer.

As the starch substrate that can be used in the present invention, all known starches are used, for example, corn starch, potato starch, sweet potato starch, tapioca starch, wheat starch,
Sago starch, starches such as rice starch, and polysaccharides containing amylose, amylopectin and the like, for example, arabic gum,
Plant mucilage such as locust bean gum;
Depending on the purpose, starch derivatives such as acid-treated starch, enzyme-treated starch, oxidized starch, etherified starch, and esterified starch of starches can be used.

In the starch derivative (a) of the present invention, the amount of the bound carbamate group is 0.5% by weight or more, particularly preferably 0.8% by weight or more. If the amount of the bound carbamic acid ester group is less than 0.5% by weight, good printability may not be obtained when used as an adhesive for a coating composition for coated paper. On the other hand, the upper limit of the amount of the bound carbamate group is not particularly limited, but is preferably 2.0% by weight or less in order to suppress the coloring of starch and the increase in solubility. In addition, the solubility of starch in water at 25 ° C is 15
When it is used as an adhesive of a coating composition for coated paper, it is important to balance it with good printability and adhesive strength, and it is preferably 13% by weight or less. . That is, the solubility of starch in water at 25 ° C. is an index indicating the ratio of the very low molecular weight of the starch derivative. These very low molecular weight components not only easily migrate in the coating liquid drying step but also have an adhesive strength. Is extremely small, and if the solubility exceeds 15% by weight, unevenness in ink deposition may easily occur, or the adhesive strength may be significantly reduced. On the other hand, the lower limit of the solubility is not particularly limited, but is preferably 5% by weight or more from the viewpoint of the effect as an adhesive. In the starch paste viscosity, the viscosity of the paste liquid by a B-type viscometer (measurement conditions: solid content concentration 35%, temperature 50 ° C., rotor rotation speed 60 rpm) needs to be 50 to 500 mPa · s,
Particularly, 100 to 300 mPa · s is preferable. When the viscosity is less than 50 mPas, the water retention of the coating liquid is reduced when used as an adhesive of the coating composition for coated paper, while when the viscosity exceeds 500 mPas, the viscosity of the coating liquid is reduced. In any case, the applicability of high-speed coating may be deteriorated.

[0015] In the starch derivative (b) of the present invention, the amount of the bound carbamate group is 0.5% by weight or more, and particularly preferably 0.8% by weight or more. If the amount of the bound carbamic acid ester group is less than 0.5% by weight, good printability may not be obtained when used as an adhesive for a coating composition for coated paper. On the other hand, the upper limit of the amount of the bound carbamate group is not particularly limited, but is desirably 2.0% by weight or less in order to suppress the coloring of starch and the increase in solubility. Further, the amount of the bound phosphate group is 1.0% by weight or less, particularly preferably 0.50% by weight or less. When the amount of the bound phosphate group exceeds 1.0% by weight,
When used as an adhesive for a coating composition for coated paper, the viscosity of the coating liquid may increase and the suitability for high-speed coating may deteriorate. Further, the lower limit of the amount of the bound phosphate group is not particularly limited.
% By weight or more is preferred. Further, when the solubility of starch in water at 25 ° C. is set to 15% by weight or less, when used as an adhesive of a coating composition for coated paper, in order to balance good printability and adhesive strength. Important, preferably 13
% By weight or less. That is, the solubility of starch in water at 25 ° C. is an index indicating the ratio of the very low molecular weight of the starch derivative. These very low molecular weight components not only easily migrate in the coating liquid drying step but also have an adhesive strength. Is extremely small, and if the solubility exceeds 15% by weight, unevenness in ink deposition may easily occur, or the adhesive strength may be significantly reduced. On the other hand, the lower limit of the solubility is not particularly limited, but is preferably 5% by weight or more from the viewpoint of the effect as an adhesive. The starch paste viscosity is required to be 50 to 500 mPa · s, especially 100% by a B-type viscometer (measurement conditions: solids concentration 35%, temperature 50 ° C., rotor speed 60 rpm). ~ 300 mPa · s is preferred. Viscosity 50mPa ・ s
When the viscosity is less than 500 mPas, the viscosity of the coating liquid increases, and when the viscosity exceeds 500 mPas, the viscosity of the coating liquid increases. There is a possibility that the suitability for high-speed coating may deteriorate.

The starch derivative of the present invention is usually prepared in a slurry of 20 to 45%, and then the slurry is kept at 85 to 95 ° C. for a certain period of time in a heating vessel equipped with a stirrer. Gelatinization can be performed by adding the slurry and heated steam to a so-called apparatus and passing the slurry while heating to 130 to 160 ° C. The obtained gelatinized starch is added to a pigment slurry for coated paper prepared in advance together with a synthetic adhesive and various auxiliaries to form a coating liquid. The amount of the gelatinized starch to be added to the pigment is 0.3 to 10 parts by weight, preferably 2 to 9 parts by weight, based on 100 parts by weight of the pigment.
Parts by weight. If the amount is less than 0.3 part by weight, the desired effects of the present invention cannot be obtained. If the amount exceeds 10 parts by weight, the viscosity of the coating liquid becomes high, and the suitability for high-speed coating may be deteriorated.

Examples of the pigment used in the coating composition include coated paper pigments such as heavy calcium carbonate, light calcium carbonate, kaolin, aluminum hydroxide, titanium dioxide, satin white, calcium sulfate, talc, and plastic pigment. Can be illustrated. Examples of the synthetic adhesive used as an adhesive together with the starch derivative of the present invention include, for example, styrene-butadiene copolymer, conjugated diene-based copolymer latex such as methyl methacrylate-butadiene copolymer, acrylic ester or Examples include a vinyl-based copolymer latex of methacrylic acid ester, or an alkali partially soluble or alkali-insoluble copolymer latex obtained by modifying these various copolymer latexes with a monomer containing a functional group such as a carboxyl group. I can do it. Also,
As the starch derivative of the present invention and the adhesive used in combination with the synthetic adhesive, as long as the desired effect of the present invention is not impaired,
Various starch derivatives other than the present invention, or celluloses such as carboxymethylcellulose and hydroxymethylcellulose, and water-soluble adhesives such as polyvinyl alcohol and olefin-maleic anhydride resin can be appropriately added. Further, in the coating liquid, various auxiliary agents such as a dispersant, a thickener, a water retention agent, a defoaming agent, a water-proofing agent, a lubricant, a dye, and a pH adjuster, if necessary, besides the pigment and the adhesive. It is appropriately blended and adjusted to a solid concentration of about 50 to 70%.

[0018]

The present invention will be described in more detail with reference to the following examples, which, of course, are not intended to limit the scope of the present invention. Parts and% in Examples are parts by weight and% by weight, respectively, unless otherwise specified. The properties of the starch derivative and the coating composition using the same, and the method for evaluating the quality of the obtained coated paper are as follows.

Example 1 (Preparation of carbamate-phosphorylated starch) 1 g of orthophosphoric acid, 2 g of urea, and 100 g of commercially available corn starch
1 g of sodium chloride and 50 g of water were mixed and mixed by stirring. The mixture is heated at 70 ° C for 30
After drying to reduce the water content to 4% or less, 110
Heated at ℃ for 30 minutes, and further heated at 140 ℃ for 30 minutes. The amount of bound phosphate groups of the obtained carbamic acid phosphorylated starch was 0.43% by weight, and the amount of bound carbamic acid ester groups was 0.88% by weight.

The solubility of the carbamic acid phosphorylated starch in water at 25 ° C. was 12% by weight. The carbamic acid phosphorylated starch was made into a 35% slurry, which was heated at 95 ° C. for 30 minutes to gelatinize, and then cooled to 50 ° C. When the viscosity of the size liquid was measured by a B-type viscometer at a rotor rotation speed of 60 rpm, it was 260 mPa · s. Table 2 shows the results.

(Preparation and Coating of Coating Liquid) A coating liquid was prepared in accordance with the blending amount shown in Table 1 using the paste liquid of the carbamic acid phosphorylated ester starch obtained by the above method.

[0022]

[Table 1]

The above coating solution is applied to a base paper for high quality coated paper of 50 g / m ² in basis weight of 50 g / m ² at a coating speed of 1000 m / min by a blade coater so that the double-side coating amount is 22 g / m ² (in terms of solid content). Side and W side in this order and dried to obtain a double-sided coated paper having a water content of 5.5%. Then, it was subjected to a super calender treatment under the conditions of a linear pressure of 250 kg / cm and a speed of 600 m / min to finish a printed double coated paper.

The paper samples were conditioned in a constant temperature and humidity room at 20 ° C. and 65% RH for 24 hours or more, and then evaluated for paper quality and printability. Separately, while keeping the coating amount constant with the blade coater, the coating speed is increased from 1000 m / min by 100 m at a time, and the coating speed at which the bleeding starts to rapidly increase is checked. The suitability for high-speed coating was evaluated.

Example 2 (Preparation of carbamate phosphate esterified starch) Carbamate phosphate was prepared in the same manner as in Example 1 except that 1.2 g of orthophosphoric acid, 2.4 g of urea and 1.2 g of sodium chloride were used. An esterified starch was prepared. The amount of bound phosphate groups of the obtained carbamic acid phosphate esterified starch was 0.45% by weight,
The bound carbamate group amount was 1.00% by weight.
The solubility of the obtained carbamic acid phosphorylated starch in water at 25 ° C. was 13% by weight. The obtained carbamic acid phosphorylated esterified starch was gelatinized in the same manner as in Example 1 and the viscosity was measured. Size liquid viscosity is 185mPa
・ It was s.

(Preparation and Coating of Coating Solution) Coating was performed in the same manner as in Example 1 except that the paste solution of the carbamic acid phosphorylated starch obtained by the above method was used as the starch shown in Table 1. The solution was prepared, coated and finished to obtain a double coated paper for printing. In addition, the suitability for high-speed coating of the coating liquid was determined in Example 1.
Was evaluated in the same way as

Example 3 (Preparation of carbamic esterified starch) Carbamate-esterified starch was prepared in the same manner as in Example 1 except that 0.90 g of 36% by weight hydrochloric acid and 6 g of urea were used without using phosphoric acid and sodium chloride. Was prepared. The amount of bound carbamic acid ester groups in the obtained carbamic acid-esterified starch was 1.8% by weight. The solubility of the obtained carbamate-starch in water at 25 ° C. was 11% by weight. The obtained carbamate-esterified starch was gelatinized by the same method as in Example 1 and the viscosity was measured. The viscosity of the size liquid was 285 mPa · s.

(Preparation and Coating of Coating Liquid) The coating liquid of the coating liquid was prepared in the same manner as in Example 1 except that the paste liquid of the carbamate-esterified starch obtained by the above method was used as the starch shown in Table 1. Preparation, coating and finishing were performed to obtain a double-side coated paper for printing. Further, suitability for high-speed coating of the coating liquid was evaluated in the same manner as in Example 1.

Comparative Examples 1 and 2 (Preparation of Oxidized Starch) In this Comparative Example, a commercially available oxidized starch was used. Ace A (Oji Cornstarch) in Comparative Example 1 and Ace C (Oji Cornstarch) in Comparative Example 2.
Was used. Gelatinization was carried out in the same manner as in Example 1 except that the slurry at the time of gelatinization was 25%. Comparative Example 1
And in Comparative Example 2, they were 4000 mPa · s and 140 mPa · s, respectively.

(Preparation and Coating of Coating Liquid) A coating liquid was prepared in the same manner as in Example 1 except that the commercially available oxidized starch paste obtained by the above method was used as the starch shown in Table 1. Coating and finishing were performed to obtain a double-side coated paper for printing. Further, suitability for high-speed coating of the coating liquid was evaluated in the same manner as in Example 1.

Comparative Examples 3 to 5 (Preparation of Carbamate Phosphated Starch) In this Comparative Example, a commercially available carbamic acid phosphated starch was used. Ace P-260 (Oji Cornstarch) was used in Comparative Example 3, Ace P-150 (Oji Cornstarch) was used in Comparative Example 4, and Ace P-140 (Oji Cornstarch) was used in Comparative Example 5. Gelatinization was carried out in the same manner as in Example 1 except that the slurry at the time of gelatinization was 25%. The B-type viscosity at 50 ° C. was 50 mPa · m in Comparative Example 3, Comparative Example 4 and Comparative Example 5, respectively.
s, 65 mPa · s and 130 mPa · s.

The amounts of the bound phosphate groups in Comparative Examples 3, 4 and 5 were 2.47% by weight, 1.26% by weight and 1.14% by weight, respectively.
% By weight. Comparative Example 3, Comparative Example 4, Comparative Example 5
Are 2.67% by weight, respectively.
1.38% by weight and 1.47% by weight.

The solubility of Comparative Examples 3, 4 and 5 in water at 25 ° C. was 45% by weight, 17% by weight and 21% by weight, respectively.
Met.

(Preparation and Coating of Coating Liquid) Example 1 was repeated except that the paste liquid of the commercially available carbamic acid phosphorylated starch obtained by the above method was used as the starch shown in Table 1.
Preparation, coating, and finishing of a coating liquid were performed in the same manner as in the above to obtain a double-side coated paper for printing. Further, suitability for high-speed coating of the coating liquid was evaluated in the same manner as in Example 1.

Comparative Example 6 (Preparation of Carbamate Phosphated Starch) Carbamate phosphorylated ester starch was prepared in the same manner as in Example 1 except that the amount of orthophosphoric acid was changed to 0.25 g and the amount of urea was changed to 1.5 g. .
The amount of bound phosphate group of the obtained carbamic acid phosphorylated starch was 0.09% by weight, and the amount of bound carbamic acid ester group was 0.40% by weight.

The solubility of the resulting carbamic acid phosphorylated starch in water at 25 ° C. was 3% by weight. Gelatinization was carried out in the same manner as in Example 1 except that the slurry at the time of gelatinization was 25%. The B-type viscosity at 50 ° C. was 360 mPa · s.

(Preparation and Coating of Coating Solution) Coating was performed in the same manner as in Example 1 except that the paste solution of the carbamic acid phosphorylated starch obtained by the above method was used as the starch shown in Table 1. The solution was prepared, coated and finished to obtain a double coated paper for printing. In addition, the suitability for high-speed coating of the coating liquid was determined in Example 1.
Was evaluated in the same way as

The characteristic values of the starch derivative and the characteristics and quality of the coating liquid and coated paper using the starch derivative were determined as follows. <Type B viscosity> Using a BM type viscometer manufactured by Tokyo Keiki Co., Ltd.
The coating liquid was measured at 50 ° C. and 60 rpm at 30 ° C. and 60 rpm.

<High Shear Viscosity> Using a Hercules high shear viscometer manufactured by Kumagai Riki Co., Ltd., using an F bob, 88
It was measured at a rotation speed of 00 rpm. The smaller the value, the lower the viscosity under high shear. <Amount of bound phosphate group> The starch was washed with a mixture of methanol and water, decomposed into glucose with a saccharifying enzyme (dextrozyme), and quantified by a molybdenum blue colorimetric method. The obtained phosphorus was converted to the amount of a phosphate group and determined. Amount of bound phosphate group (% by weight) = Amount of bound phosphorus × 98/3
1

<Amount of Bound Carbamate Group> After the starch was washed with a mixture of methanol and water, the bound nitrogen was measured by the Kjeldahl method. The obtained nitrogen was converted to the amount of the bound carbamate group and determined. Bound carbamate group amount (% by weight) = Bound nitrogen × 44 ÷ 14 <Solubility in water at 25 ° C.> 25 ° C. in 2 g of dry weight starch
Of distilled water to make 100 g, and leave it at 25 ° C for 30 minutes.
The mixture was centrifuged at 4500 rpm at 30 ° C. for 30 minutes, and the supernatant was dried at 105 ° C. to obtain a solid content. Solid content in supernatant (g) / 2 = Solubility (% by weight)

<High-speed coating property> The coating speed was increased from 1000 m / min by 100 m while the coating amount was kept constant, and the coating speed at which bleeding began to increase sharply was recorded. The higher the coating speed, the better the coating suitability. <Blank glossiness> Measured according to JIS P-8142. <Smoothness> JAPAN TAPPI paper pulp test method N
The measurement was performed using an Oken type smoothness meter according to B of o5.

<Ink deposition unevenness> Using an offset sheet-fed printing press (Dia E4 / Mitsubishi Heavy Industries), print four colors at a printing speed of 6000 sheets / hour, and solid weight of the second color (cyan) and the third color (magenta). The unevenness of the color portion was visually evaluated based on the following criteria.

<Dry Pick> The degree of picking after the printing of the coating layer was repeated a predetermined number of times using an ink of tack value 13 with an RI printing machine (manufactured by Meiji Seisakusho) was visually evaluated according to the following criteria. Evaluation criteria: ＝= no picking occurred and strong adhesive strength. ○ = Picking occurs slightly, but there is no practical problem. Δ = Picking occurs frequently and adhesive strength is weak. Table 2 shows the characteristic values of the starch derivatives obtained in these Examples and Comparative Examples, and the characteristics and quality of coating liquids and coated papers using the starch derivatives.

[0044]

[Table 2]

As is apparent from Table 2, in Examples 1 to 3 of the present invention, good results were obtained in all properties. On the other hand, in Comparative Examples 1 to 6, it was revealed that the glossiness and smoothness of the white paper were inferior, and the suitability for high-speed coating was inferior.

Example 4 and Comparative Example 7 The starches prepared in Example 2 and Comparative Example 2 were used, and the number of starches was increased from 3 parts to 8 parts to be Example 4 and Comparative Example 7, respectively. Preparation of coating liquid in the same manner as in Example 1,
Coating and finishing were performed to obtain a double-side coated paper for printing. Also,
The suitability for high-speed coating was evaluated in the same manner as in Example 1. Table 3 shows the properties and qualities of the coating liquids and coated papers of the examples and the comparative examples.

[0047]

[Table 3]

As is clear from Table 3, the starch of the present invention has a small reduction in high-speed coating suitability and paper quality even when the amount of added starch is increased, and is still excellent in high-speed coating suitability as compared with the starch of the comparative example. It turned out that the paper quality was obtained.

[0049]

According to the present invention, by using urea or a starch derivative obtained by heat-reacting urea and phosphoric acid as an adhesive for a coating composition for coated paper, good high-speed coating suitability can be obtained. A coated paper having high white paper gloss and smoothness can be obtained, and the occurrence of unevenness in ink adhesion and a decrease in adhesive strength can be suppressed.

Continued on the front page (72) Inventor Toshio Hinako 9th Yawata Kaigandori, Ichihara-shi, Chiba Prefecture Inside the Research Laboratory of Oji Corn Starch Co., Ltd. Inside the laboratory (72) Inventor Miwa Sunada 9th Yawata Kaigandori, Ichihara City, Chiba Prefecture Inside the Oji Cornstarch Development Laboratory (72) Inventor Mitsuo Ishida 9th Yawata Kaigandori, Ichihara City, Chiba Prefecture Inside the Oji Cornstarch Development Laboratory (72) Inventor Naoto Arai 9th, Yawata Kaigandori, Ichihara City, Chiba Pref.

Claims (4)

[Claims] 1. A starch derivative obtained by heating and reacting urea with an amount of bound carbamate groups of 0.5% by weight or more and a solubility in water at 25 ° C. of 15% by weight or more.
% By weight and the viscosity of the size liquid obtained by gelatinizing the starch derivative with a B-type viscometer (measurement condition: solid content concentration 35
%, Temperature 50 ° C, rotor speed 60 rpm)
A starch derivative having 0 mPa · s. 2. In a starch derivative obtained by heating and reacting urea and phosphoric acid, the starch derivative has a bound carbamate group content of 0.5% by weight or more and a bound phosphate ester group content of 1.0% by weight. Hereinafter, the solubility in water at 25 ° C. is 1
5% by weight or less, and the viscosity of the size liquid obtained by gelatinizing the starch derivative with a B-type viscometer (measurement conditions: solid content concentration 35
%, Temperature 50 ° C, rotor speed 60 rpm)
A starch derivative having 0 mPa · s. 3. The starch derivative according to claim 1, wherein the heating reaction is carried out by increasing the roasting temperature stepwise by a dry roasting method. 4. A coating composition for coated paper comprising a pigment and an adhesive as main components, wherein the starch derivative according to any one of claims 1 to 3 is used as the adhesive in 100 parts by weight of the pigment. The coating composition containing 0.3 to 10 parts by weight based on the solid content.