JPH1112328A - Carboxylate oligomer, latex composition using the same and paper coating composition using the same latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject particles hardly generating a bleeding phenomenon, and improving coating efficiency, also printability and strength of a coated paper by incorporating a water soluble oligomer having a specific composition, production method, and molecular weight, with a latex and a pigment. SOLUTION: This latex composition is obtained by incorporating a carboxylate oligomer having >=1,000 and <=1,500 weight averaged molecular weight and obtained by copolymerizing 30-95 wt.% unsaturated carboxylate monomer with 5-50 wt.% vinylcyanate-based monomer, 0-10 wt.% (meth) acrylamide-based monomer and 0-65 wt.% other vinyl-based monomer by using water as a solvent, with a latex (the solid portion of the above oligomer is 0.5-30 wt.% based on the solid portion thereof) and a pigment as necessary (the solid portion of the above oligomer based on 100 pts.wt. pigment is 0.02-6 pt.wt.).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving the coating operability of coated paper, and more specifically, to a method of adding a latex or a paper coating composition using the same to form a paper coating composition. The present invention relates to a specific water-soluble oligomer having improved high-speed coating properties, a latex composition using the same, and a paper coating composition using the same.

[0002]

2. Description of the Related Art Coated paper is used to improve the printability and optical properties of paper, and to apply pigments such as kaolin clay, calcium carbonate, satin white, talc, titanium oxide, etc. And a paper coating composition containing water-soluble polymers such as starch, polyvinyl alcohol, and carboxymethyl cellulose as main components, and a polymer latex as a binder and a viscosity modifier or an auxiliary binder. Here, as a polymer latex as a binder, a styrene-butadiene copolymer latex emulsion-polymerized with styrene and butadiene as main monomer components, a so-called SB latex, has been widely used.

[0003] In recent years, the production of coated paper has increased remarkably along with the increase in demand for color printed magazines, direct mails, pamphlets and advertisements. On the other hand, offset printing is increasing in the printing of coated paper. However, demand for the paper is increasing, and the productivity of the paper is required to be improved. One of the problems in coating operability is a phenomenon called bleeding that occurs during coating with a blade coater. This is a phenomenon in which foreign matter generated at the blade edge grows. If the foreign matter grows so much that it adheres to the coated paper, there is a problem that the yield of the product is reduced and the coating speed cannot be increased. Therefore, there is a demand for a paper coating composition that does not easily cause a bleeding phenomenon even under high-speed coating conditions (hereinafter referred to as having good high-speed coating properties).

Although many studies have been made on the bleeding phenomenon, it has heretofore been considered that the lower the apparent viscosity of the paint under high shear, the less likely it is for the bleeding phenomenon to occur. For example, Japan Pulp and Paper Technical Association (published by Japan Pulp and Paper Technology Association), Vol. 49, No. 2 (published in February 1995)
From pages 391 to 397, entitled "A Study on Bleeding Phenomena in Blade Coating"
A bleeding phenomenon is described. Part 39
On page 5, FIG. 5 shows the result that the lower the viscosity at the blade edge, the less bleeding occurs.

As described above, conventionally, it has been considered that the bleeding phenomenon is hardly caused by reducing the viscosity (high shear viscosity) when a shearing force corresponding to immediately below the blade is applied. To reduce the viscosity during high shear while maintaining printability, various measures were taken, such as changing the shape (aspect ratio) of the pigment and reducing the particle size of the binder latex. Coated paper strength often changes at the same time, and it is often difficult to achieve a balance between operability, printability, and strength at the same time at a high level. In particular, it has been difficult to improve high-speed coating properties while maintaining printing performance.

[0006] On the other hand, there have been studies to add operability and printability by adding additives without changing the latex or the content components. For example, Japanese Patent Application Laid-Open No. 60-224896 discloses a paper coating method containing a latex containing a water-soluble oligomer selected from alkali metal salts or ammonium salts of polycarboxylic acids with the aim of improving coating operability. It is disclosed that the composition has good water retention and dispersibility, stability, and low high shear viscosity. It can be said that the invention according to the conventional concept is described in that the high shear viscosity is reduced. However, this publication does not disclose a specific method for producing an alkali metal salt of a polycarboxylic acid and could not carry out additional tests. JP-A-53-12
Japanese Patent No. 9200 discloses an invention relating to an oligomer composed of only acrylic acid and maleic acid and aimed at obtaining printability equivalent to that of a conventional dispersant in a small amount, but is effective in improving operability. Can not be seen.

JP-A-53-85828 discloses an oligomer comprising a hydroxyacrylic ester of acrylic acid or methacrylic acid and a half ester or half amide of acrylic acid, methacrylic acid, itaconic acid or itaconic acid for the purpose of improving gloss. Is described. Although the purpose of the invention is different, no operability improvement effect is seen with the oligomers described.

JP-A-56-89827, JP-A-5-9827
In JP-A-6-89828, from the viewpoint that it is necessary to improve the dispersibility of the pigment in order to improve the coating operability,
An invention using a copolymer of polyethylene glycol monoallyl ether and a (meth) acrylic acid monomer as a dispersant is described. The operability cannot be improved with the oligomer having this composition.

JP-A-56-118730 describes a dispersant for inorganic pigments obtained by copolymerizing an acrylic acid monomer, a sulfonic acid monomer, a maleic acid monomer and the like. However, this dispersant has no effect on improving operability. Japanese Patent Application Laid-Open No. 5-125122 discloses an oligomer using an organic initiator in an organic solvent system. This oligomer was synthesized according to the description in the specification and a supplementary test was conducted. Improvement was insufficient.

In Japanese Patent Application Laid-Open No. 5-222696, in order to increase the water retention of a paper coating composition as a printability improver,
25-75 mol of (meth) acrylamide monomers
% Oligomers, 5 to 25 mol% vinyl cyanide monomer, and 20 to 50 mol% unsaturated carboxylic acid monomer. This was additionally tested, but no effect of improving the coating operability was found.

[0011]

DISCLOSURE OF THE INVENTION The present invention relates to a latex or a paper coating composition using the same, which maintains the printability and strength of the coated paper while maintaining the printability and strength of the coated paper. An object of the present invention is to provide a specific water-soluble oligomer capable of improving coating operability.

[0012]

Means for Solving the Problems In view of the problems of the prior art as described above, the present inventors have made intensive studies and as a result, have been manufactured according to a specific manufacturing method and have a specific composition, manufacturing method,
When a water-soluble oligomer having a molecular weight is used for a paper coating composition, the bleeding phenomenon is less likely to occur even though the high shear viscosity of the paper coating composition may increase, and as a result, the coating operability is remarkable. The present inventors have found a surprising fact that overturns the conventional knowledge that coated paper coated with the improved paper does not cause deterioration in printability and coated paper strength, and has reached the present invention.

That is, the present invention provides: (A) 30 to 95% by weight of an unsaturated carboxylic acid monomer, (b) 5 to 50% by weight of a vinyl cyanide monomer,
(C) 0 to 10% by weight of (meth) acrylamide monomers and (d) 0 to 65% by weight of other vinyl monomers
Is a carboxylic acid oligomer having a weight average molecular weight of 1,000 or more and 15,000 or less, obtained by copolymerization of A latex composition comprising the carboxylic acid oligomer according to the above and a latex, wherein the solid content of the carboxylic acid oligomer is 0.5 to the solid content of the latex.
2. 30% by weight of a latex composition; Pigment and 1. A paper coating composition containing the carboxylic acid oligomer and a latex according to the above, wherein the carboxylic acid oligomer has a solid content of 0.0
2 to 6 parts by weight of a paper coating composition.

[0014] It is unknown what effect the water-soluble oligomer of the present invention can improve the high-speed coating property, but contrary to the conventional idea, the addition of the oligomer makes the paper coating composition highly efficient. Although the shear viscosity may increase, there is an unexpected effect of improving high-speed coating properties. The present invention will be described in more detail below.

Conventionally, in order to evaluate coating operability, a coating test had to be actually performed using an actual machine or a pilot coater, which required time and effort. Accordingly, the present inventors reexamined the operability improvement technology developed by the conventional researchers, and described in Japanese Patent Application Laid-Open No. Hei 8-266998 as an evaluation means for examining new technology development. We decided to use a technology that simply evaluates coating operability. The gist of the technology is to evaluate the bleeding phenomenon by observing the occurrence of bleeding when the paper coating composition is applied directly to the backing roll and the speed is increased by a device that scrapes with a blade. To
BC evaluation (backing roll / coating evaluation)
). It has been confirmed that there is a correlation between the result of the actual machine test using the pilot coater and the result of this BC evaluation.

Using this evaluation technique, various additives described in the prior art were evaluated, but their effects were insufficient as described above. The inventors have conducted extensive studies using this evaluation technique, and have reached the present invention. Examples of the (a) unsaturated carboxylic acid monomer used in the present invention include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, and the like. Among them, it is preferable to use an unsaturated dibasic carboxylic acid such as maleic acid, itaconic acid, fumaric acid, since the reaction is relatively mild and an oligomer having a low molecular weight and a high solid content is easily polymerized. These unsaturated carboxylic acids can be used alone or in combination of two or more kinds. The usage ratio is 30 to 95% by weight based on 100% by weight of all monomers, and the amount of carboxylic acid used is 30% by weight. The above dissolves in water, and the coating operability can be exhibited. The coating operability can be exhibited at 95% by weight or less. It is more preferably 50 to 80% by weight from the viewpoint of improving the coating operability.

The water-soluble oligomer of the present invention needs to contain (b) a vinyl cyanide monomer. Examples of the vinyl cyanide-based monomer include acrylonitrile, methacrylonitrile and the like. The amount of the vinyl cyanide monomer used is 5 to 50% by weight. When the amount is 5% by weight or more, the coating operability is improved, and when the amount is 50% by weight or less, the solubility of the oligomer is maintained and the coating operability is good. Become. Preferably it is 15 to 40% by weight.

In the present invention, (c) a (meth) acrylamide monomer can be used. Examples of the (meth) acrylamide monomer include (meth) acrylamide and N
-Methylol (meth) acrylamide, N-alkoxy (meth) acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and the like. In the present invention, the effect can be enhanced by adding a (meth) acrylamide monomer, but the amount used is 10%.
% By weight or less. Use of more than 10% by weight is not preferred because it increases the low shear viscosity of the latex and paper coating composition and deteriorates workability. Preferably it is 1 to 5% by weight.

In the present invention, (d) other vinyl monomers can be used. (D) Other vinyl monomers include (a) an unsaturated carboxylic acid monomer, and (b)
It is a monomer that can be copolymerized with a vinyl cyanide monomer or (c) a (meth) acrylamide monomer that is optionally added, and is a (meth) acrylate, a vinyl ester, a vinyl ether, an unsaturated dibasic acid. Esters, basic vinyl monomers having amino groups, conjugated dienes, silicon-containing α, β-ethylenically unsaturated monomers, aromatic (di) vinyl compounds, vinyl halides, olefins, allyl compounds, and others Copolymerizable monomers can be mentioned.

The (meth) acrylates include:
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate,
Isobutyl (meth) acrylate, n-amyl (meth)
Acrylate, isoamylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate , Benzyl (meth) acrylate, 2-ethyl-hexyl (meth) acrylate, glycidyl (meth) acrylate, ethylene glycol di (meth) acrylate, ethylene glycol di (meth)
Acrylate, 1,3-butylene glycol di (meth)
Acrylate, 1,4-butylene glycol di (meth)
Acrylate, propylene glycol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, Diethylene glycol ethoxy acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (Meth) acrylate, tetramethylolmethanetetra (meth) acrylate, allyl (meth) acrylate,
Bis (4-acryloxypolyethoxyphenyl) propane, methoxypolyethylene glycol (meth) acrylate, stearyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, 2,2-bis [4-
((Meth) acryloxyethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxydiethoxy) phenyl] propane, 2,2-bis [4-
((Meth) acryloxy.polyethoxy) phenyl] propane, isobornyl (meth) acrylate, and the like.

Examples of the vinyl ester include vinyl acetate, vinyl butyrate, vinyl stearate, vinyl laurate, vinyl myristate, vinyl propionate, and vinyl versatate. As vinyl ethers, methyl vinyl ether, ethyl vinyl ether,
Examples thereof include propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, and hexyl vinyl ether.

Examples of the unsaturated dibasic acid alkyl ester include crotonic acid alkyl ester, itaconic acid alkyl ester, fumaric acid alkyl ester, and maleic acid alkyl ester. Examples of the basic monomer having an amino group include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and diethylaminoethyl (meth) acrylate.

Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene and 2-methyl-
Examples thereof include 1,3-butadiene, 1,3-pentadiene, chloroprene, 2-chloro-1,3-butadiene, and cyclopentadiene. Examples of the silicon-containing α, β-ethylenically unsaturated monomer include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinylbis (β-methoxyethoxy) silane.

Examples of the aromatic (di) vinyl compound include styrene, α-methylstyrene, o-methylstyrene and m-methylstyrene.
Examples thereof include methylstyrene, p-methylstyrene, ethylstyrene, vinyltoluene, vinylxylene, bromostyrene, vinylbenzyl chloride, pt-butylstyrene, chlorostyrene, alkylstyrene, divinylbenzene, and trivinylbenzene.

Examples of the vinyl halide include vinyl chloride,
Examples thereof include vinyl bromide, vinyl fluoride, vinylidene chloride, and vinylidene fluoride. Examples of the olefin include ethylene and the like. Examples of the allyl compound include allyl ester and diallyl phthalate.

In addition, three or more monomers having a sulfonic acid group such as sodium styrenesulfonate, sodium methallylsulfonate, sodium allylsulfonate and sodium vinylsulfonate, acrolein, and triallylisocyanurate. A monomer having a double bond can also be used. These vinyl monomers (d) can be used alone or in combination of two or more. The usage ratio of these vinyl monomers (d) is 0 to 65% by weight.

The weight average molecular weight of the carboxylic acid oligomer in the present invention is from 1,000 to 15,000.
Within this range, the effect of improving the coating operability is exhibited. Also,
When it is 15,000 or less, the solubility of the oligomer in water is maintained. Preferably it is 1000 or more and 9000 or less, more preferably 1000 or more and 4000 or less. The molecular weight of the carboxylic acid oligomer of the present invention is preferably controlled by the amount of the initiator. The polymerization can be controlled by the amount of a molecular weight regulator such as a chain transfer agent instead of the amount of the initiator, but the coating operability may be difficult to exert.

As the solvent used in the polymerization of the carboxylic acid oligomer of the present invention, it is necessary to use water.
For unknown reasons, oligomers polymerized using water as a solvent can achieve the object of the present invention. However, it is possible to use an appropriate amount of a solvent that is soluble in water. For example, a mixed solvent of alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and pentanol and water can also be used. However, when a solvent is used, at least the polymerization initiator needs to be dissolved in the mixed solvent.

The polymerization initiator used for synthesizing the carboxylic acid oligomer of the present invention is a compound that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing substance, and is a water solvent. It is necessary to dissolve in Specific examples include potassium peroxodisulfate, sodium peroxodisulfate, persulfates such as ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, And peroxides such as cumene hydroperoxide. It is also possible to use a combination of a persulfate and a peroxide, or a combination of a reducing agent such as sodium bisulfite and sodium bisulfite with a polymerization initiator. Persulfate initiators such as peroxodisulfate can be used alone or in combination, and further combined with reducing agents such as sulfites. In particular, when using persulfate or sulfite or hydrogen sulfite as a reducing agent,
The coating operability can be significantly improved, which is preferable. It is not clear why persulfates and the like are preferable as the polymerization initiator, but it is thought that the presence of a predetermined amount of sulfate groups in the oligomer may further improve the coating operability of the paper coating composition. ing. The amount of the polymerization initiator used was 10 for all monomers.
It is preferably 0.1 to 40.0 parts by weight based on 0 parts by weight. The timing of the addition is not particularly limited.

In the polymerization of the oligomer of the present invention, a chain transfer agent may be added as a molecular weight regulator during the polymerization. As the chain transfer agent, mercaptan, α-methylstyrene dimer and the like can be used. Specific examples of the mercaptan include n-hexyl mercaptan, 2-ethylhexyl mercaptan, n-octyl mercaptan, lauryl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, t-hexadecyl mercaptan, cetyl mercaptan, Stearyl mercaptan and the like can be mentioned.

These are used in an amount of 5 parts by weight or less based on 100 parts by weight of the total monomers. The polymerization temperature of the oligomer of the present invention is 50 to 95 ° C, preferably 70 to 90 ° C. At 50 ° C. or higher, the reaction time is short and the productivity is good. Also,
The molecular weight can be easily controlled at 95 ° C or lower. The latex composition of the present invention is a composition containing the above-mentioned specific carboxylic acid oligomer in a solid content of 0.5 to 30% by weight based on the solid content of the latex. The timing of addition of the oligomer to the latex is determined during the emulsion polymerization of the latex and / or
Alternatively, it may be after completion of emulsion polymerization. When the carboxylic acid oligomer is added during the emulsion polymerization of the latex, it can be added in the state of being dissolved in water or the like at the start of the polymerization and / or during the polymerization. When the polymerization is carried out after the completion of the emulsion polymerization, it may be carried out before or after the pH is adjusted after the completion of the polymerization.

The timing of adding the carboxylic acid oligomer to the paper coating composition is not particularly limited. It is also possible at the stage of actually preparing the paper coating composition. The carboxylic acid oligomer latex composition may be added, or the latex and carboxylic acid oligomer may be added at another time. The latex used in the latex composition of the present invention is not particularly limited, and any latex having a conventionally known composition such as SB latex, MB latex, acrylic latex, EVA latex, and vinyl acetate latex can be used. Especially SB commonly used for paper coating
Desirable for latex.

As the polymerization method of the latex, a conventionally known method can be applied, and it does not matter whether it is a one-stage polymerization or a multi-stage polymerization. As the monomer that can be used for polymerization, a conventionally known monomer can be used and is not particularly limited. For example, those exemplified as monomers that can be used for producing a carboxylic acid oligomer can be used.

Examples of the conjugated diene include butadiene and isoprene. As the unsaturated carboxylic acid, the same ones as those exemplified in the production of the carboxylic acid monomer of the present invention can be used. Specific examples of other monomers include vinyl cyanide monomers, (meth) acrylamide monomers, (meth) acrylates, vinyl esters, vinyl ethers, unsaturated dibasic esters, and bases having an amino group. Vinyl monomer, conjugated diene, silicon-containing α, β-ethylenically unsaturated monomer, aromatic (divinyl compound, vinyl halide, olefin,
Examples include allyl compounds and other copolymerizable monomers conventionally used in the production of latex.

The particle size of the latex is from 50 nm to 200 n.
It can be applied to those having a general size of m, but is not limited thereto. The carboxylic acid oligomer of the present invention can also exert an effect when the latex is a latex having a composition mainly composed of a conjugated diene, styrene, and an unsaturated carboxylic acid. The term mainly used herein means that the ratio of the monomer other than the conjugated diene, styrene and unsaturated carboxylic acid to the whole monomer is 10% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less. It means something. In addition, even with such a latex, the production method is not particularly different from that of the conventional latex, and it can be produced by a conventionally known production method.

The latex composition of the present invention contains a carboxylic acid oligomer and a latex. In this case, the amount of the carboxylic acid oligomer is 0.5 to 0.5% of the solid content of the latex. ~ 30% by weight
It is necessary to be. When the carboxylic acid oligomer is 0.
When the content is 5% by weight or more, the effect of improving the coating operability is exhibited, and when the content is 30% by weight or less, the ability as a latex binder is exhibited, and the printability is good. From the balance between effects such as printability and coating operability, the content is more preferably 0.5 to 15% by weight.

The paper coating composition of the present invention comprises a pigment, a carboxylic acid oligomer and a latex.
The solid content of the carboxylic acid oligomer is required to be 0.02 to 6 parts by weight with respect to 0 parts by weight. The coating operability is improved by setting the solid content of the carboxylic acid oligomer to be more than 0.02 part. When the content is 6 parts by weight or less, an effect excellent in printability can be obtained. More preferably, it is 0.02 to 3 parts by weight.

As the pigment, conventionally known pigments can be used, and there is no particular limitation. For example, kaolin clay, calcium carbonate, satin white, aluminum hydroxide, titanium oxide, plastic pigment and the like can be exemplified. In producing the paper coating composition, a latex and a carboxylic acid oligomer may be added to make a latex composition and then a pigment may be added, or a carboxylic acid oligomer and a pigment may be mixed and then a latex may be added. The carboxylic acid oligomer may be added after mixing the latex and the pigment. It does not particularly depend on the mixing order.

The solid content concentration of the paper coating composition is not particularly limited, and can be appropriately adjusted according to the purpose. The paper coating composition of the present invention can be used not only with a blade coater but also with an air knife coater, a roll coater, a bar coater and the like. If necessary, other additives such as a printability improving agent, a coloring agent, a water-proofing agent, and a preservative can be added to the paper coating composition.

[0040]

Next, an embodiment of the present invention will be described. First, a test method and a sample preparation method used in Examples will be described in detail. (1) Preparation of Latexes L1 to L4 Aqueous dispersion of seed particles having a diameter of 35 nm (solid concentration 3
0% by weight) was placed in a pressure-resistant reaction vessel equipped with a stirrer and a jacket for temperature control, and 70 parts by weight of water, 0.2 parts by weight of sodium lauryl sulfate, 2 parts by weight of itaconic acid, and 1 part by weight of fumaric acid were added. The internal temperature was raised to 80 ° C., 26 parts by weight of styrene, 42 parts by weight of butadiene,
10 parts by weight of methyl methacrylate, acrylonitrile 1
8 parts by weight, a monomer mixture consisting of 1 part by weight of hydroxyethyl acrylate, an oily mixture of t-dodecyl mercaptan and α-methylstyrene dimer, 15 parts by weight of water, 1 part by weight of sodium peroxodisulfate, 0 part of sodium hydroxide An aqueous solution consisting of 0.2 parts by weight and 0.1 parts by weight of sodium lauryl sulfate was added at a constant flow rate over 4 hours and 5 hours, respectively. Then, the temperature of 80 ° C.
After completion of the polymerization reaction, the mixture was cooled. The resulting copolymer latex was adjusted to pH 7 with sodium hydroxide to remove unreacted monomers by a steam stripping method, and filtered through a 200-mesh wire gauze. The concentration was adjusted to 50% by weight to obtain a copolymer latex L1. The particle size determined by light scattering was 113 nm.

Similarly, copolymer latexes L2 to L4 were synthesized with the monomer compositions shown in Table 1. Table 1 shows the particle size of each latex. (2) Preparation of paper coating composition A paper coating composition was prepared according to the formulation shown in Table 2. Ion-exchanged water having a weight calculated in advance so that the final solid content is constant is put in a container, and then Alon T-40 (trade name, manufactured by Toa Gosei Chemical Co., Ltd.) as a dispersant is 0.1 to 0.2 pph.
(Meaning 0.1 to 0.2 part with respect to 100 parts of the total pigment), and 0.1 to 0.2 part of sodium hydroxide as an alkali.
2 pph was dissolved and then the pigment was introduced with stirring with a stirrer. As a pigment, clay (trade name: KCS, E
CC International), clay (product name; UW-)
90, manufactured by ENGEL HARD CORP) and calcium carbonate (trade name: Carbital CB-90, manufactured by EC International Corporation). Thirty minutes later, cooked starch (trade name; Oji Ace A or Oji Ace B, manufactured by Oji Corn Starch Co., Ltd.) was charged. Twenty minutes later, the latex polymerized by the method described above and the synthesized carboxylic acid oligomer were added. The latex was prepared to be 11 to 12 pph including the carboxylic acid oligomer.
After a further 20 minutes, a bactericide (trade name: Somasite AT, manufactured by Somar Co., Ltd.) was added and stopped after a few minutes. High-speed coatability evaluation described below using this paper coating composition,
Capillary viscosity measurement and printability evaluation were performed. (3) Evaluation of high-speed coating property Evaluation was performed using an apparatus and a method described in JP-A-8-266988. The apparatus includes a coating device including a backing roll, a color applicator, a coater head, a blade, and the like, a coating thickness sensor, a blade goniometer, and a blade surface observation device. The paper coating composition is applied to a backing roll by an applicator roll, and is controlled to have a constant thickness by a thickness sensor. The roll speed is increased while scraping the paper coating composition with a blade. At this time, the blade surface is enlarged and observed, and foreign matter starts to be generated, that is, the speed at which bleeding occurs is determined by Vc.
(Critical coating speed) is determined. It is determined that the higher the Vc, the better the high-speed coating property. A series of measurements were performed in an environment controlled at 23 ° C. The blade was measured at a bevel angle of 35 °, a set angle of 37.5 °, and a new blade to prevent disturbance of wear.

In Examples 1 to 3 and Comparative Examples 1 to 3, the solid content was 6%.
At 5%, Examples 4 to 14 and Comparative Examples 4 to 10 have a solid content of 6%.
A value of 7.8% was read. (4) Capillary viscosity measurement Capillary viscometer (trade name: HOCHDRACK K)
APILAAR VISKOSIMETER HVA
6, ANTON PAAR K. G. FIG. Was used for the measurement. Capillary inner diameter 0.305mm, length 10m
m, the paper coating composition prepared in (3) was filtered through a 325 mesh wire mesh and then measured in an environment of 23 ° C. The value measured in this way corresponds to the high shear viscosity, which is the cause of bleeding. (5) Preparation of Coated Paper for Printability Evaluation Coated paper for printability evaluation is applied to a coating device (Cyclical Laboratory Coater CLC-
6000). Using a roll paper having a basis weight of 70.3 g / m ² at a speed of 1600 m / min and a coating amount of 16 to
A paper coating composition adjusted to a solid content of 64% so as to have a dry content of 18 g / m ² was applied. The thickness of the blade mounted on a pound having a blade installation angle of 50 degrees (a container for storing the paper coating composition) was 0.508 mm, and the blade angle was 45 degrees. Drying conditions were according to the manufacturer's manual, without preheating, with an infrared dryer output of 100% for 30 seconds, and with a run of 10 m. The resulting coated paper is 25 ° C, humidity 65%
After curing in a constant temperature room for 24 hours, 50 ° C, linear pressure 100kgf /
Super calendar treatment was performed twice under the condition of cm to obtain a coated paper for evaluation of printability. (6) Evaluation of Printing Gloss (IG) A 0.6 cc printing ink GEOS-G (blue) (manufactured by Dainippon Ink and Chemicals, Inc.) was used for an RI printing machine (manufactured by Akira Seisakusho Co., Ltd., RI-1). Place on a rubber roll and knead for about 5 minutes until uniform. Next, set the base paper on which the reference paper and the test coated paper with the changed conditions were affixed to the RI printing machine,
Printed once. It was dried in a constant temperature and humidity room at 23 ° C and a constant temperature and humidity of 65% all day and night, and a gloss meter (trade name: GM-26D, M
URAKAMI COLOR RESEARCH LA
BORATORY) under the condition of 75 degrees. (7) Evaluation of Ink Set (IS) 0.3 cc of the printing ink GEOS-G (blue) (manufactured by Dainippon Ink and Chemicals, Inc.) was placed on a rubber roll of an RI printing machine, and about 5 cm was obtained. Mix for a minute. Next, the base paper with the reference paper and the test coated paper with the changed conditions
I was set on the printing press, and the backing sheet was set on the 4th roll, and printing was performed. As the evaluation result, the degree of transfer of the ink to the backing sheet is visually evaluated, and the lower the transfer density, the higher the score. The standard of the visual evaluation was 3.0, and 1.0 to
The rank was determined within a range of 5.0.

Specifically, coated papers coated with various paper coating compositions were arranged on the same backing paper, and Examples 1 to 3 corresponded to Comparative Examples 1 to 3, Examples 4 to 14, respectively. In Examples 5 to 9, each score was determined based on the coated paper coated with the paper coating composition of Comparative Example 4 (point: 3.0). This test is a total of 3
The test was repeated twice, and the average value of these test results was set as a score. (8) Measurement of molecular weight GPC (Gel Permeation Chroma)
Water (borate pH 9.18 buffer, manufactured by Kishida Chemical Co., Ltd.) was used as a carrier according to the method of graphography. Polyacrylic acid standard reagent (POLYMER LAB)
ORATORIES) molecular weight 1250, 296
Calibration curves were prepared using 5,18000 samples. The column is Asahipak GS-510 (manufactured by Showa Denko KK)
It was used. In the apparatus used for the GPC measurement, the controller was LC-6A manufactured by Shimadzu Corporation and the UV detector was SPD-6A manufactured by Shimadzu Corporation.

[0044]

Example 1 Itaconic acid 7 was placed in a 1-liter flask equipped with a stirrer capable of controlling the stirring speed, a cooling pipe, and a thermometer.
5 g, acrylonitrile 25 g, ion exchange water 400
g and 0.5 g of sodium hydroxide at room temperature, followed by stirring while introducing nitrogen gas, and the temperature in the system was raised to 85 ° C. in a water bath. Next, a solution prepared by dissolving 10 g of sodium peroxosulfate in 20 g of ion-exchanged water was added to the system, and stirring was continued at 85 ° C. After one hour, the same amount of sodium peroxosulfate and ion-exchanged water are added,
Stirring was continued at 85 ° C. for 3 hours 30 minutes. 4 hours and 30 minutes after the start of the reaction, the temperature was raised to 93 ° C. and maintained for 1 hour, then cooled to room temperature and neutralized to obtain a dark brown carboxylic acid oligomer. The molecular weight was 2756.

The obtained carboxylic acid oligomer 0.03p
ph and latex L1 were used at 11.7 pph to prepare a paper coating composition having a solid content of 65% according to the above-described paper coating composition preparation procedure and Table 2. Table 3 shows the results of high-speed coating property evaluation and printability test. Compared to Comparative Example 1, high-speed coatability was obtained, and there was no problem in printability.

[0046]

Comparative Example 1 Using L1 as a latex, each paper coating composition was prepared according to the formulation in Table 2 so that the final solid content was 65%. The amount of latex L1 was 12 pph and no carboxylic acid oligomer was added. Using this paper coating composition, each test for high-speed coating property evaluation and printability was performed. Table 4 shows the evaluation results.

[0047]

Embodiments 2 and 3 L2 and L3 are used as latex.
Using 7 pph each and 0.3 pph of the carboxylic acid oligomer synthesized in Example 1, each paper coating composition was prepared to a final solids content of 65% according to the formulation in Table 2 and used in Example 2. No. 3 was obtained as a paper coating composition.

Using these paper coating compositions, high-speed coating property evaluation and various tests on printability were performed. Table 3 shows the results of the evaluation. Regardless of the type of the monomer composition of the latex, the high-speed coatability is improved as compared with the proportions 2 and 3 containing no carboxylic acid oligomer while using the same latex, indicating that there is no problem in printability.

[0049]

Comparative Examples 2 and 3 L2 and L as latexes for evaluating physical properties
Except for using Sample No. 3, a paper coating composition was obtained in the same manner as in Comparative Example 1. Using this paper coating composition, high-speed coating property evaluation,
Each test for printability was performed. Table 4 shows the evaluation results.

[0050]

Examples 4 to 6 A paper coating composition was prepared in the same manner as in Example 1 except that L4 was used as the latex and the amount of the carboxylic acid oligomer obtained in Example 1 was changed as shown in Table 3. Obtained and evaluated. Table 3 shows the contents and evaluation results.

[0051]

Comparative Example 4 A paper coating composition was prepared in the same manner as in Example 4 except that the carboxylic acid oligomer was not added and the amount of latex was changed to 11 pph. Table 4 shows the results of high-speed coating property evaluation, capillary viscosity measurement, and printability test.

[0052]

Example 7 A paper coating composition was obtained in the same manner as in Example 4 except that the carboxylic acid oligomer obtained in Example 1 was previously mixed with the latex L4 one week before. Table 3 shows the results of high-speed coating property evaluation, capillary viscosity measurement and printability test. Compared with Comparative Example 4, higher high-speed coatability was obtained.

[0053]

Examples 8 to 13 As shown in Table 3, carboxylic acid oligomers were produced in the same manner as in Example 1 except that the monomer composition and the amount of the initiator added were changed. Using the obtained carboxylic acid oligomer and latex L4, a paper coating composition having a solid content of 67.8% was prepared according to the paper coating composition preparation procedure and Table 2. High-speed coating property evaluation, capillary viscosity measurement, and printability test were performed. Table 3 shows the results. It can be seen that the carboxylic acid oligomer of the present invention shows excellent performance even when the capillary viscosity is high.

[0054]

Comparative Examples 5 and 6 Except for using the monomer composition shown in Table 4,
A carboxylic acid oligomer was polymerized in the same manner as in Example 1. Using the obtained oligomer and latex L4,
A paper coating composition was prepared according to the paper coating composition preparation procedure and Table 2. Table 4 shows the results. Although the capillary viscosity was lower than that of Comparative Example 4 in which none of the oligomers were added, the value of Vc was low, indicating that the high-speed coating property was inferior.

[0055]

Comparative Example 7 Commercially available dispersant Aron T-40 (manufactured by Toa Gosei Chemical Co., Ltd.) instead of carboxylic acid oligomer
Except for using, a paper coating composition was prepared in the same manner as in Comparative Example 5. Table 4 shows the results of high-speed coating property evaluation, capillary viscosity measurement, and printability test.

[0056]

Comparative Example 8 140.6 g of isopropanol was charged into a 500 cc separable flask, and 30 g of methyl methacrylate, 45 g of methacrylic acid, and 7.5 g of t-dodecyl mercaptan were put into the flask and capped. 1.5 g of lauroyl peroxide was added, and the vessel was purged with nitrogen for 5 minutes. 7
Place in a 5 ° C water bath and stir at 200 rpm.
Allowed to react for hours. After completion of the reaction, the pH was adjusted to 8 by adding 55 g of a 25% aqueous sodium hydroxide solution at 75 ° C. without removing isopropanol, and 150 g of water was further added, followed by cooling. When the molecular weight was measured in the same manner, 96
30. A paper coating composition was prepared according to the paper coating composition preparation procedure and Table 2. High-speed coating property evaluation, capillary viscosity measurement, and printability test were performed. Table 4 shows the results.
Vc was equivalent to Comparative Example 4.

[0057]

Comparative Example 9 Water 15 was placed in a 500 cc separable flask.
0.6 g was charged, and 22.7 g of acrylamide, 4.2 g of acrylonitrile, and 13.1 g of acrylic acid were put therein and capped. 3.2 g of a 25% aqueous sodium hydroxide solution was added dropwise to adjust the pH to 3.6. The vessel was purged with nitrogen for 30 minutes. 1 g of sodium peroxosulfate was dissolved in 30 g of water and injected. 200 rpm for water bath at room temperature
And after 5 minutes, add 1.2 g of sodium bisulfite in 2 portions.
A solution dissolved in 4 g of water was injected and observed for 10 minutes. As a result, the temperature rose to about 40 ° C. 8 in 30 minutes from here
The temperature rose to 5 ° C. After 2 hours, the reaction was completed, and after cooling, 25% aqueous sodium hydroxide was added to add p.
H was set to 9.4. Its molecular weight was 76800.
A paper coating composition was prepared according to the paper coating composition preparation procedure and Table 2. High-speed coating property evaluation, capillary viscosity measurement, and printability test were performed. Table 4 shows the results. Vc is Comparative Example 4.
Worse.

[0058]

Example 14 Water 20 was placed in a 500 cc separable flask.
0 g, acrylonitrile 25 g, itaconic acid 7
5 g and 0.5 g of sodium hydroxide were put therein and capped.
An aqueous ferric nitrate solution was added so that 0.0025 g of iron was contained. 10 g of 69% perbutyl H was added. 200
The temperature was raised to 80 ° C. while stirring at rpm, and 3.5 g of an aqueous solution in which 11 g of sodium ascorbate was dissolved in 50 g of water.
It continued to drip over time. It was left for 30 minutes, and after 4 hours from the start of the reaction, it was cooled and 39.4 g of a 25% aqueous sodium hydroxide solution was added dropwise to adjust the pH to 8.1. Its molecular weight was 3085. A paper coating composition was prepared according to the paper coating composition preparation procedure and Table 2. High-speed coating property evaluation, capillary viscosity measurement, and printability test were performed. Table 4 shows the results
Shown in High-speed coatability was slightly improved.

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

[0062]

[Table 4]

[0063]

The carboxylic acid oligomer of the present invention is added to a paper coating composition using a latex,
The high-speed coatability of the paper coating composition can be improved without lowering printability. Specifically, the occurrence of bleeding during coating with a blade coater can be suppressed.

Even when the latex used in the paper coating composition is a latex having a relatively simple composition, the addition of the carboxylic acid monomer of the present invention allows the high-speed coating while maintaining printability. Properties can be improved.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 35/00 C08L 35/00 D21H 19/44 D21H 1 / 28Z // (C08F 222/02 5 / 00Z 220: 44 220 : 56)

Claims (3)

[Claims] 1. An unsaturated carboxylic acid monomer (a)
95% by weight, (b) 5 to 50 vinyl cyanide monomers
% By weight, (c) (meth) acrylamides monomer 0
10% by weight and (d) other vinyl monomers 0-6
A carboxylic acid oligomer having a weight average molecular weight of 1,000 or more and 15,000 or less, obtained by copolymerizing 5% by weight of water as a solvent. 2. A latex composition comprising the carboxylic acid oligomer according to claim 1 and a latex, wherein the solid content of the carboxylic acid oligomer is 0.5 to 30% by weight based on the solid content of the latex. Latex composition. 3. A paper coating composition containing a pigment, the carboxylic acid oligomer according to claim 1 and a latex, wherein the carboxylic acid oligomer is contained in a solid content of 0.02 to 100 parts by weight of the pigment. A paper coating composition containing 6 parts by weight.