JP2772791B2 - Coating composition for gate roll paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a paper coating composition, and more particularly to a paper coating composition using a gate roll coater. 2. Related Art Coated paper such as art paper and coated paper is often used as printing paper, but uncoated paper such as newsprint and general magazine paper is often used. However, in recent years, in response to the needs of the color visualization era represented by the spread of photo magazines, printing has been accelerated in order to improve its productivity, and precise printing has been required due to the demand for beautiful image quality. In the field of uncoated paper used in magazines, etc., finely coated paper with a few g / m ² of a coating agent applied in solid form has come to be used. . In order to make this finely coated paper, for example, the paper material is supplied from the head box to the wire part, made up, dewatered in the press part, and then dried, and then coated with a gate roll coater. Is applied. The general type of this gate roll coater is an applicator roll that applies a paper coating agent, a metering roll that supplies the applicator roll by controlling the amount of the coating agent, and a coating agent from a bat to the metalling roll. It consists of fountain rolls to be supplied, and these are arranged on both sides, so to speak, in a gate shape for double-sided coating of paper. Such a gate roll coater can apply a high-concentration coating agent as compared with size press coating using two rolls, and can perform drying quickly, so that high-speed coating can be performed. There is an advantage.
Another advantage is that the penetration of the coating agent into the paper is suppressed, and the finished coated paper has excellent surface properties.
Further, this gate roll coater also has features that the apparatus is simpler and lower in cost, and the installation thereof is easier than a blade coater which scrapes a coating agent with a blade. However, the biggest disadvantage of this gate roll coater is that, for example, kaolin clay 60 parts by weight, calcium carbonate
40 parts by weight, styrene-butadiene copolymer latex 12
Parts by weight, 8 parts by weight of starch and 0.4 parts by weight of dispersant, the coating agent is transferred from the applicator roll to the paper, and when the transferred coating agent is torn, a few mm It is easy to generate a myriad of continuous spot-like mottled patterns. When this pattern occurs, the fine smoothness of the surface of the finished paper is lost, and even if printing is performed thereon, a beautiful printed matter cannot be obtained, and the commercial value of the printed matter is reduced. Although the above description has been made on the case where the slightly coated paper is manufactured by the gate roll coater, the same problem occurs when the coated paper having a larger coating amount is manufactured by the gate roll coater. Problems to be Solved by the Invention As described above, conventional coated paper, particularly coated with a gate roll coater, is inevitable in the occurrence of patterns,
The improvement was desired. Means for solving the problems The present invention has a structural unit having an acid group or a salt thereof, and a structural unit composed of a hydrophobic monomer, in order to solve the above problems, the weight ratio of the former and the latter is 54 to 62: 46 to 38 , and a pigment containing at least two pigments, at least 40% of which is heavy calcium carbonate, and having a solid content of at least 60%. An object of the present invention is to provide a coating composition for gate roll paper characterized by the following. Next, the present invention will be described in detail. In the present invention, a copolymer having a structural unit having an acid group or a salt thereof and a structural unit composed of a hydrophobic monomer is used. Examples of the hydrophobic monomer include styrene, α-methylstyrene, vinyltoluene, divinylbenzene, a group of isobutylene and an isobutylene oligomer having a polymerization degree of 2 to 5, and acrylic acid and methacrylic acid having an alkyl group having 1 to 18 carbon atoms. A group of alkyl esters, and one or more compounds selected from one or more than two of dialkyl esters of maleic acid, fumaric acid and itaconic acid having 1 to 18 carbon atoms in the alkyl group, No. Further, the structural unit having an acid group or a salt thereof is obtained, for example, by copolymerization using an unsaturated carboxylic acid as a copolymerization component. Examples of the unsaturated carboxylic acid include acrylic acid,
Group of methacrylic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, and alkyl group having 1 to 18 carbon atoms
And at least one compound selected from the group consisting of the monoalkyl esters of maleic acid, fumaric acid and itaconic acid, or both. The acid group of these compounds may be converted into a salt before or after copolymerization, or saponified after the copolymer is synthesized. The mixing ratio of the original monomer and the hydrophobic monomer of the structural unit having an acid group or a salt thereof is as follows:
As compared with 70 to 20%, and the latter 30 to 80%, even if the amount of the hydrophobic monomer is large or small, coating unevenness occurs, and a pattern is generated when coating with a gate roll coater as described above. Of the range, the former is 54-62% and the latter is 46
At ~ 38%, these occur less than those outside this range. The copolymer used in the present invention includes those obtained by copolymerizing other copolymerizable components in addition to those exemplified above. For example, acrylamide, methacrylamide, dimethylaminoethyl methacrylate,
Acrylonitrile and the like are exemplified. The total of one or more of these components is 50 parts by weight or less, preferably 30 parts by weight or less, based on 100 parts by weight of the whole copolymer monomer. In order to obtain the above copolymer, a solution polymerization method in which a monomer is uniformly dissolved in an organic solvent and polymerization is performed, and a suspension polymerization method or an emulsion polymerization method in which the monomer is dispersed in water with a dispersant, may be mentioned. A copolymer obtained by a turbid polymerization method or an emulsion polymerization method exhibits an excellent effect in preventing coating unevenness during coating by a gate roll coater. In addition, as a dispersant in the suspension polymerization method or the emulsion polymerization method, natural resin emulsion, synthetic resin emulsion,
Polyvinyl alcohol, fine powder and colloidal inorganics,
Other known emulsifiers can be used. The copolymer used in the present invention can be used by dissolving or dispersing in a solvent, but pigments, adhesives, other dispersants as needed, lubricants such as calcium stearate,
Waterproofing agents, thickeners, thickeners, defoamers, foam inhibitors, preservatives,
It is preferable to appropriately use various auxiliaries such as a fungicide, a water retention agent, a fluorescent brightener, a dye, and a conductive agent. Conventionally known pigments, adhesives and other auxiliaries can be used, but they are used in appropriate amounts according to the solid content concentration, pH, and other conditions. Examples of this pigment include clay, talc, heavy calcium carbonate, light calcium carbonate, satin white, titanium dioxide, aluminum hydroxide, barium sulfate, calcium sulfite, synthetic silica, inorganic pigments such as zinc oxide and styrene-based polymers, There are organic pigments such as urea-based polymers, and at least two of these, including heavy calcium carbonate, can be used as a mixture of two or more. Examples of the adhesive include starch, modified starch (oxidized starch, esterified starch, etherified starch, enzyme-modified starch, pregelatinized starch, cationized starch, etc.), casein,
Gelatin, soy protein, yeast protein, natural polymers such as cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose and the like) or derivatives thereof, and styrene-butadiene-based resins, (meth) acrylate-butadiene-based resins, (meth) acrylate-based resins, Synthetic polymer compounds such as polyvinyl alcohol, vinyl acetate resin, acrylamide resin, styrene- (meth) acrylate resin, styrene-maleic acid resin, and ethylene-vinyl acetate resin are exemplified, and these may be used alone or in combination. These can be used in combination. When a copolymer having a structural unit having the acid group or a salt thereof used in the present invention and a structural unit composed of a hydrophobic monomer is used together with a pigment and an adhesive, for example, a solid content of 100 parts by weight of the pigment is used. Adhesive to solid part 10
When the amount is from 50 to 50 parts by weight, an example in which 0.1 to 5.0 parts by weight of the solid component is blended is shown, but is not limited thereto. When the amount of the copolymer is too small, the occurrence of coating unevenness cannot be suppressed. Also,
If it is too large, coating unevenness does not occur, but the printability at the time of printing, particularly the ink acceptability, becomes poor, and such a coated paper becomes unsuitable as offset printing paper. The solid content concentration of the composition of the present invention is preferably 60 to 70% when coated with a gate roll coater to speed up drying.
Not limited to this. In order to produce the composition of the present invention, for example, the pigment is stirred and dispersed in water with a dispersant, an adhesive is added thereto, and, if necessary, an auxiliary agent such as a viscosity modifier is added thereto. A copolymer liquid having a structural unit having the acid group or a salt thereof and a structural unit composed of a hydrophobic monomer, which has been manufactured, is added and stirred. Then, if necessary, the pH is adjusted with caustic soda or the like to complete the process. However, the present invention is not limited to this, and a material other than the pigment may be mixed, and the pigment may be added thereto and mixed. At this time, the pigment may be mixed so as to be fine. When the composition of the present invention is applied to paper by, for example, a gate roll coater, for example, a finely coated paper of 4 g / m ² is obtained, which is a structural unit having an acid group or a salt thereof and a hydrophobic monomer. Coating unevenness can be prevented by the presence of the copolymer having the structural unit consisting of This has a remarkable effect on finely coated paper with a small coating amount in the case of coating with a gate roll coater, but is also effective with coated paper with a larger coating amount. Examples Next, the present invention will be described based on examples. For use in the following Examples and Comparative Examples, a copolymer resin solution composed of a structural unit having a structural unit having an acid group or a salt thereof and a hydrophobic monomer in advance is synthesized as follows. Resin liquid for Reference Example 1 In a reaction flask equipped with a stirrer, a thermometer and a nitrogen inlet tube, 62.4 parts of styrene and 34.4 parts of methacrylic acid were used as monomers.
And 3 parts of sodium dodecylbenzenesulfonate as a dispersant, and 2.3 parts of ammonium persulfate,
2 parts of n-dodecyl mercaptan and 399 parts of water were added, and the mixture was reacted at 80 ° C. for 3 hours to complete the emulsion polymerization. The obtained polymer was neutralized by adding 12.1 parts of 28% aqueous ammonia and 23.1 parts of a 48.5% aqueous potassium hydroxide solution, and further added with water to obtain an aqueous dispersion b- 1 having a solid concentration of 20%. Resin liquid for Example 1 31.2 parts of styrene as monomer, α-methylstyrene
5.9 parts, 6.5 parts of divinylbenzene, 51.6 parts of methacrylic acid were charged, and the same as the resin liquid for Reference Example 1 except that 2.8 parts of ammonium sulfate of polyoxyethylene (n = 6) nonylphenol ether was used as a dispersant. Aqueous dispersion a- 1 having a solid concentration of 20%
I got Resin liquid for Example 2 Reaction and neutralization were carried out in the same manner as for the resin liquid for Reference Example 1 except that 41.6 parts of styrene, 28.4 parts of butyl methacrylate, and 113.6 parts of monododecyl maleate were used as monomers. An aqueous dispersion a- 2 having a concentration of 20% was obtained. Resin liquid for Example 3 The same reaction and neutralization as in the case of the resin liquid for Reference Example 1 were carried out except that 67.2 parts of diisobutylene and 91.2 parts of monobutyl maleate were used as monomers, and the solid content concentration was 20%. Thus, an aqueous dispersion liquid a- 3 was obtained. Resin liquid for Reference Example 2 150 parts of methyl methacrylate and 1.5 parts of sodium styrenesulfonate were placed in the same reaction vessel as in the case of the resin liquid for Reference Example 1.
, 460.3 parts of water and 1.5 parts of sodium lauryl sulfonate, 0.3 parts of ammonium persulfate and 0.2 parts of sodium acid sulfite were added, and the reaction was carried out at 80 ° C for 7 hours to obtain an emulsion composed of fine particles having a solid content of 20%. Obtained. 48.4 parts of the obtained emulsion, 62.4 parts of styrene, 34.4 parts of methacrylic acid and 388 parts of water were added, and ammonium persulfate 2.3 was added.
The polymerization was carried out at 80 ° C. for 3 hours. 12.1 parts of 28% aqueous ammonia and 48.5% aqueous potassium hydroxide solution 2 were added to the obtained polymer.
3.1 parts were added and neutralized to obtain an aqueous dispersion b-2 having a solid content of 20%. Resin liquid for Reference Example 3 In a reaction vessel similar to that for the resin liquid for Reference Example 1, 62.4 parts of styrene, 34.4 parts of methacrylic acid, 96.8 parts of 10% PVA (polyvinyl alcohol), and 290 parts of water were added, and benzoylpar was added. 2.4 parts of oxide was added and polymerization was carried out at 80 ° C. for 3 hours. The obtained polymerization product was filtered and thoroughly washed with water, after which 12.1 parts of 28% aqueous ammonia and 48.5% aqueous potassium hydroxide solution 2
3.1 parts and 390 parts of water were added, and the mixture was heated at 70 ° C. for 1 hour and dissolved to obtain an aqueous dispersion b-3 having a solid concentration of 20%. Resin liquid for Reference Example 4 In the same reaction vessel as for the resin liquid for Reference Example 1, 62.4 parts of styrene, 34.4 parts of methacrylic acid, 96.8 parts of isopropyl alcohol, 1.6 parts of azobisisobutyronitrile and n
-2 parts of dodecyl mercaptan was added, solution polymerization was carried out at 80 ° C for 4 hours, 23.1 parts of a 48.5% aqueous potassium hydroxide solution and 416.5 parts of water were added, and isopropyl alcohol was distilled off. To the obtained polymer, 12.1 parts of 28% aqueous ammonia was added, and water was further added to obtain an aqueous dispersion b-4 having a solid matter concentration of 20%. Resin liquid for Reference Example 5 67.2 parts of diisobutylene, 39.2 parts of maleic anhydride, and 106.4 parts of toluene were added to a reaction vessel similar to that for the resin liquid for Reference Example 1 except that a dropping funnel was provided. Then, a mixed solution of 3 parts of t-butyl peroxybenzoate and 20 parts of toluene was dropped by a dropping funnel over 30 minutes. Further, the reaction was carried out at 110 ° C. for 3 hours to complete the polymerization. After completion of polymerization, 33 parts of 48.5% aqueous sodium hydroxide solution at 80 ° C, water
After adding 268 parts and distilling off toluene, 24.3 parts of 28% aqueous ammonia was added, and further water was added to obtain an aqueous dispersion b-5 having a solid concentration of 20%. Resin Liquid for Comparative Example A resin liquid for Reference Example 4 except that 25 parts of styrene, 75 parts of methacrylic acid, and 100 parts of isopropyl alcohol are used in the same reaction vessel as that for the resin liquid for Reference Example 1. The reaction and neutralization were carried out in the same manner as in the above to obtain an aqueous dispersion c-1 having a solid concentration of 20%. Examples 1 to 4 using the above resin liquid as a coating unevenness preventing agent
3. The paper coating compositions of Reference Examples 1 to 5 were prepared. Examples 1 to 3 and Reference Examples 1 to 5 After dispersing kaolin clay and heavy calcium carbonate in water with a dispersing agent, a pregelatinized aqueous solution of a phosphorylated starch and a styrene-butadiene latex were added, followed by further coating. Aqueous resin solution a as unevenness inhibitor
-1 to a- 3 and b-1 to b-5 are added respectively, and 30%
The composition was prepared with an aqueous solution of caustic soda and water to a pH of 9 and a solid concentration of 60%. The proportions of the pigment, adhesive, dispersant and coating unevenness inhibitor are as shown in Table 1. Comparative Example 1 A paper coating shown in Table 1 was performed in the same manner as in Examples 1 to 3 and Reference Examples 1 to 5, except that the resin liquid c-1 for the comparative example was used as the coating unevenness inhibitor. A working composition was obtained. Comparative Example 2 Examples 1 to 3 and Reference Examples 1 to 3 except that no coating unevenness preventing agent was used in Examples of Table 1 and Comparative Examples.
By performing the same operation as in Example 5, a coating composition for paper shown in Table 1 was obtained. Coating Test Using Gate Roll Coater The coating compositions for paper obtained in Examples 1 to 3, Reference Examples 1 to 5 and Comparative Examples 1 and 2 were prepared using a gate roll coater.
300 meters / minute at a coating speed of basis weight 75 g / m ² wood-containing base paper 8 g /
Coating was performed so that the coating amount was m ² . The temperature of the coated paper is
The calender treatment was performed twice under the condition of 60 ° C. and a linear pressure of 75 kg / cm. The resulting coated paper was conditioned at 20 ° C and 65% RH (relative humidity) for 24 hours, followed by observation of coating unevenness, gravure printing suitability, and ink acceptability.
The suitability for RI printing such as wet pick and dry pick and paper quality such as whiteness, glossiness, smoothness and air permeability were measured. Further, the viscosity of the coating liquid was measured. Table 2 shows the measurement results. Each test method is as follows. 1) Viscosity of coating liquid The viscosity of the coating liquid was measured at 25 ° C at 60 rpm using a B-type viscometer (model: BM type, manufactured by Tokyo Keiki Seisakusho). 2) Coating unevenness Using a RI printing machine, perform solid printing with a small amount of ink, observe the state of ink deposition, and evaluate the degree of coating unevenness on a five-point scale. Inferior ”. 3) Suitability for gravure printing A gravure printing tester of the Ministry of Finance, Ministry of Finance was used to observe the occurrence rate of 15% halftone dot misdots. The smaller the value, the better the gravure printing suitability. 4) Ink acceptability Using a RI printing tester, wet the coated surface with a water supply roll, print, and visually observe the ink acceptability with the naked eye. 5 is “excellent” and 1 is “poor”. And a five-step evaluation was performed. 5) Wet pick Using a RI printing tester, wet the coated surface with a water supply roll and then print, observe the peeling state with the naked eye, set the wet pick resistance to 5 as “excellent” and set 1 Was evaluated as "poor" and a five-step evaluation was performed. 6) Dry pick A print was printed with an RI printing tester, the paper peeling state was observed with the naked eye, and the dry pick resistance was evaluated in the same manner as the above wet pick resistance. From the results of the above Examples, Reference Examples, and Comparative Examples, those of Examples, Reference Examples, and Comparative Examples show that the ratio of the unsaturated carboxylic acid as the monomer serving as the structural unit having an acid group to the ratio of the hydrophobic monomer used (weight ratio) ), Example 1 is 54.2 / 45.8 , Example 2 is 61.9 / 38.1 , Example 3 is 57.6 / 42.4 , and Reference Example 1 is
35.5 / 64.5, Reference Example 2 is 32.4 / 67.6, Reference Example 3 is 35.5 / 64.
5, Reference Example 4 is 35.5 / 64.5, Reference Example 5 is 36.8 / 63.2, and Comparative Example 1 is 75/25, but the amount of unsaturated carboxylic acid used exceeds 54% and does not exceed 62%. 1, 2, 3
Comparative Example 1 in which the amount of unsaturated carboxylic acid used is 75%
Of course, the amount of unsaturated carboxylic acid used is
Compared to those of Reference Examples 1, 2, 3, 4, and 5 which are less than 37%, they are excellent in that both coating unevenness and wet pick are improved at the same time. If the amount is not too large, such as 75%, the larger the amount of the unsaturated carboxylic acid used, the better. In addition, in view of their viscosities, all of the examples not only have sufficient fluidity and stability at the time of coating, but also have no coating unevenness, ink receptivity and wet /
It shows that it is also excellent in pick resistance. Compared to this,
In Comparative Examples 1 and 2, not only the degree of coating unevenness was large, but also the ink receptivity and wet pick resistance were particularly poor.
When used for lithographic printing paper using dampening water, excellent printed matter may not be obtained. In addition, as the structural unit having an acid group or a salt thereof, an acid other than a carboxylic acid such as styrenesulfonic acid and a salt thereof and a salt thereof can be used. Effects of the Invention As described above, according to the present invention, a coating composition for a gate roll paper containing a copolymer having a structural unit having an acid group or a salt thereof and a structural unit composed of a hydrophobic monomer is provided. Since this can be provided, when this is applied to paper by a gate roll coater, the occurrence of a pattern due to uneven coating can be prevented. When coating unevenness is prevented in this way, ink receptivity at the time of printing is improved, and the pick resistance of the paper is also increased, so that printing is performed at high speed like a photo magazine,
Further, it is possible to further enhance the value of printed matter requiring beautiful image quality as paper, and to provide a finely coated paper having excellent surface properties similar to coated paper. Further, since at least two kinds of pigments are used and at least 40% of them are made of heavy calcium carbonate, it is possible to provide a gate roll paper having the characteristics of other pigments to be used in combination, and at the same pigment concentration, The viscosity can be lower than that of a coating liquid composition using light calcium carbonate instead of heavy calcium carbonate or a coating liquid composition using other pigments other than these calcium carbonates. At least 60% solids concentration
As a result, it is possible not only to increase the certainty of high-speed coating because drying can be performed quickly, but also to provide a gate roll paper having excellent surface properties by suppressing the penetration of the coating agent into the paper, and at the same time, providing high In the case of a coating solution having a concentration, the weight ratio of the structural unit having an acid group or a salt thereof to the structural unit including a hydrophobic monomer is 54 to 100, although a pattern due to coating unevenness is easily generated in a gate roll coater. 62:
This can be prevented by using a copolymer having a unique composition which is 46 to 38 and has a selective effect on the former amount, and the characteristics of the gate roll coater can be utilized to the maximum.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kaoru Kondo               Dick Ha 17-2 Yawata Kaigandori, Ichihara-shi               ー Cures Co., Ltd. (72) Inventor Hiroshi Sonobe               Dick Ha 17-2 Yawata Kaigandori, Ichihara-shi               ー Cures Co., Ltd.                (56) References JP-A-58-31195 (JP, A)                 JP-A-61-43607 (JP, A)                 JP-A-53-51234 (JP, A)                 JP-A-61-97497 (JP, A)                 JP-A-57-161194 (JP, A)                 JP-A-49-31902 (JP, A)                 JP-A-61-63795 (JP, A)

Claims (1)

(57) [Claims] Having a structural unit having an acid group or a salt thereof, and a structural unit composed of a hydrophobic monomer, the weight ratio of the former to the latter is 54 to
62: 46-38 and a pigment comprising at least two pigments, at least 40% of which is heavy calcium carbonate and having a solids concentration of at least 40%.
A coating composition for gate roll paper, which is 60%. 2. 2. The composition according to claim 1, wherein said copolymer is contained in an amount of 0.1 to 5.0 parts by weight on a solid basis in a liquid containing 10 to 50 parts by weight of an adhesive based on 100 parts by weight of a pigment. The coating composition for gate roll paper according to the above. 3. Hydrophobic monomer is styrene, α-methylstyrene,
A group of vinyltoluene, divinylbenzene, isobutylene and an isobutylene oligomer having a polymerization degree of 2 to 5, a group of alkyl esters of acrylic acid and methacrylic acid having an alkyl group having 1 to 18 carbon atoms, and a group of 1
2. The compound according to claim 1, wherein the compound is one or more compounds selected from one or more of dialkyl esters of maleic acid, fumaric acid and itaconic acid. Or the coating composition for gate roll paper of Claim 2. 4. The structural unit having an acid group or a salt thereof is constituted by using an unsaturated carboxylic acid monomer as a copolymer component,
This unsaturated carboxylic acid monomer includes acrylic acid, methacrylic acid, maleic anhydride, maleic acid, fumaric acid and itaconic acid, and maleic acid, fumaric acid and itaconic acid having 1 to 18 carbon atoms in the alkyl group. 4. The gate according to claim 1, wherein the compound is one or two or more compounds selected from either one or both groups of the alkyl ester group. Coating composition for roll paper. 5. The coating composition for gate roll paper according to claim 1, 2, 3, or 4, wherein the copolymer is an emulsion polymer or a suspension polymer.