JPS60199997A - Paper coating liquid composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel coating liquid composition that provides coated paper for offset printing or gravure printing with excellent properties. To be more specific, the requirements for offset printing,
The present invention relates to a novel coating liquid composition that provides coated paper with excellent white paper glossiness and printing glossiness, as well as halftone reproducibility required for gravure printing and printing glossiness.

Technical Background In recent years, along with the rapid increase in the number of printed materials, the demand for offset printing paper and gravure printing paper has also increased significantly.

Coated paper used for offset printing is required to have excellent white paper gloss and printing gloss.

Furthermore, coated paper used for gravure printing is required to have good halftone dot reproducibility and poor printing gloss. Improving the above-mentioned physical properties required of coated paper for printing will improve the finish of printing and significantly increase the commercial value of coated paper.

Prior art Kaolin clay has traditionally been widely used as a pigment for distributing paper coating compositions due to its excellent gloss and printability of coated paper, but in recent years it has been widely used as a pigment for distributing coating compositions. A heavy r that has a great effect on improving the fluidity of the coating liquid when necessary.
(It is used by mixing with calcium carbonate or kaolin clay. However, when mixed with heavy calcium carbonate, the halftone reproducibility and print gloss, which are important characteristics of gravure printing and offset printing, are not good. However, various attempts have been made to solve the drawbacks of adding heavy calcium carbonate.For example, Japanese Patent Application Laid-open No. 5
Publication No. 7-167490 and JP-A-57-77394
According to the publication, when a heavy calcium carbonate pigment is mixed as a paper coating pigment and used in combination with an alkali-sensitive copolymer latex as a binding adhesive, the coated paper has a high degree of adhesion, good halftone reproducibility, and It has been reported that it imparts print gloss. However, there is a limit to increasing the proportion of heavy calcium carbonate pigment only by improving the binding adhesive, and this is insufficient for improving coating workability and achieving high solidity.

Previously, it was reported in Japanese Patent Publication No. 46-6524 that when an organic pigment with a particle size of 0.3 to 0.8 microns is mixed with a lightweight paper coating coating solution, it is significantly effective in improving white paper gloss. ing. In the present invention, the coating liquid composition similarly contains an organic pigment, but the purpose is different, and the effect of significantly improving gravure printing and offset printing characteristics, which was not expected in the above invention, has been obtained. be. Also,
Although the above invention does not mention the particle size distribution, the structure of the present invention is completely different from the above invention in that the particle size distribution is also an important control factor.

Purpose of the Invention The present inventors have carried out various studies on improving coating liquid compositions with the aim of further improving gravure printing characteristics and offset printing characteristics while taking advantage of the characteristics of heavy calcium carbonate such as good flow characteristics. As a result, the use of a new synthetic organic pigment in combination with ground calcium carbonate has shown an unexpected effect: good flow properties and significantly improved gravure and offset printing properties. I found out that it can be done.

Structure of the Invention The present invention consists of: (a) ■ 97 to 60 parts by weight of a mineral pigment containing at least 5 parts by weight of heavy calcium carbonate pigment; ■ An average diameter of 0.5 μm or more, and an average particle diameter of ±20 μm 100 parts by weight of a pigment for paper coating consisting of 3 to 40 parts by weight of a synthetic organic pigment which is an aromatic vinyl compound polymer particle containing 80% or more of particles falling within the above range, and (b) 3 to 40 parts by weight of a pigment binder. This is a paper coating liquid composition containing 30 heavy background parts.

(Mineral pigments) The content of heavy calcium carbonate in mineral pigments is 5 times higher.
It is preferably on a 30-weight board. If the weight ratio is less than 5, the desired fluidity cannot be obtained.

The amount of mineral pigment used is 97 to 60 parts by weight, preferably 95 to 70 parts by weight.

Examples of mineral pigments other than heavy calcium carbonate include clay, talc, satin white, precipitated calcium carbonate, titanium dioxide, zinc oxide, aluminum hydroxide, and lithium sulfate.

(Synthetic Organic Pigments) The synthetic organic pigments of the present invention are produced by soap-free polymerization or seeding from one or more vinyl monomers, preferably vinyl monomers that are primarily hydrocarbon monomers such as styrene. Norwegian patents ff1780596 and 782920 specification 4I ¥: (
It can be made by the method disclosed in Japanese Patent Application Laid-Open No. 57-24369). The large-particle monodisperse latex according to this specification is produced by first preparing monodisperse polymer particles of 0.3 to 0.6 μm, for example, by a conventional emulsion polymerization method, and then adding an organic substance (with very low solubility in water). Substance I) is dissolved in the polymer particles using acetone or a lower alkanol, and then the polymer particles are dissolved with a suitable aromatic hydrocarbon monomer, such as styrene, which has a water solubility of at least 10 times that of substance I). It can be obtained by expanding the particle size and polymerizing it with an oil-soluble polymerization initiator.

As the synthetic organic pigment of the present invention, polystyrene particles can preferably be used, but a part of styrene, usually less than 80 broomsticks,
It is also possible to substitute other vinyl monomers, preferably up to 30 strands. Vinyl monomers other than styrene that can be used include, for example, t α-methylstyrene, 4
- Vinyl aromatic compounds such as methylstyrene and divinylbenzene, α, β-ethylenically unsaturated carbenoic acid esters such as methyl methacrylate, ethyl acrylate, and dithyl acrylate, halogenated olefins such as vinyl chloride and vinylidene chloride, and unsaturated compounds such as acrylonitrile. Conjugated diolefins such as saturated nitriles and sitadiene are examples. If necessary, acrylic acid, methacrylic acid,
α such as itaconic acid.

Copolymerizing monomers with functional groups such as hydroxyalkyl esters of unsaturated cardinic acids such as β-ethylenically unsaturated carzenic acid, hydroxyethyl acrylate, and hydroxyethyl methacrylate, and unsaturated amides such as acrylamide and methacrylamide. Of course it is also possible. The type and amount of monomers other than styrene should be adjusted so that the polymer and refractive index do not decrease too much in order to maintain white paper gloss, and T2 is 80°C or higher, preferably 90°C or higher. Decide and use.

The synthetic organic pigment particles used in the present invention have white paper gloss and
In order to maintain printability, the surface coated with pigments consisting of organic polymer particles must not form a continuous film when drying or finishing.

Therefore, the acceptable fusing temperature of the polymer particles will vary depending on the method of finishing the surface, but will not form a film at flow rates of 60°C or less if the surface is finished by methods such as calendering or suit-calendering. This is desirable.

More specifically, the synthetic organic pigment used in the present invention has an average particle diameter of 0.5 μm or more, preferably 0.8 μm or more to 3.0 μm, and has an average particle diameter of ±2 μm.
Particles that contain 80% or more of particles in the range of 0 or less, are insoluble in adhesives, and do not form a film under the conditions of contacting and finishing the coated surface, are more suitable for the purpose of the present invention. You can get something with good performance. If less than 80% of the synthetic organic pigment particles have an average particle diameter in the range of ±20%, the effect of improving the suitability for gravure and offset printing of coated paper using the pigment cannot be obtained.

The amount of synthetic organic pigment used is 3 to 40 parts by weight, preferably 5 to 30 parts by weight. The organic pigment plays the role of compensating for the deterioration in printing performance caused by heavy calcium carbonate, which is a mineral pigment, and if it is less than 3 parts by weight, the desired performance of the present invention cannot be brought out, while if it exceeds 40 parts by weight. In addition, organic pigments are expensive and economically unfavorable compared to mineral pigments.

(Pigment binder) As the pigment binder used in the present invention, any binder used in ordinary paper coating liquids can be used. For example, starch, modified starch, natural binders such as casein, styrene-citadiene copolymer latex, cardoxy-modified styrene-butadiene copolymer latex, polyvinyl acetate emulsion, tung fat emulsion, polychloro There are synthetic binders such as zolene latex and polyvinyl alcohol, which can be used alone or in combination of two or more. Among these, it is preferable to use a styrene-citadiene copolymer latex, particularly a calxoxy-modified styrene-butadiene copolymer latex, alone or in combination with a natural binder such as starch or casein.

The binder is usually used in an amount of 3 to 30 parts by weight per 100 parts by weight of the pigment. If the amount is less than 3 parts by weight, no effect as a binder can be obtained, while if it is less than 30 parts by weight, the viscosity of the coating liquid composition will increase and the coating workability will be poor.

(Coating method) Each component of the present invention is mixed and prepared by a conventional method, and applied by a conventional coating method such as an air knife coater, a blade coater,
It is applied to paper substrates using a roll coater, etc.

EXAMPLES Next, the present invention will be explained in detail with reference to examples, but the present invention is not limited to these examples.

[Example of production of synthetic organic pigment]

(a) 175 parts by weight of distilled water, 1.0 parts by weight of potassium persulfate, 2.0 parts by weight of methacrylic acid, and 98 parts by weight of styrene were placed in a reactor that had been purged with nitrogen gas in advance, and
The temperature was raised to 0°C and the reaction was continued for 8 hours. As a result, a monodispersed latex (A) having a styrene polymerization rate of 99 or higher and an average particle diameter of 0.9 μm was obtained.

(b) Dry weight 40 using latex prisoners as seed particles
Remove the heavy part and add 0.6M sodium lauryl sulfate to it.
Then, 8 parts by weight of l-chlordodecane, 12 parts by weight of acetone and 40 parts by weight of distilled water were mixed, and 25 parts by weight were added.
Stir for 2 hours at ~30°C to absorb 1-chlordodecane into the seed particles. Diacetone was then removed by vacuum evaporation to obtain a seed solution. Divide the seed solution into four equal parts and use each as a base for the following (0), (d), (e
), (f) was polymerized.

(C) Pour the seed solution into a reaction vessel and add 190% water to it.
Add 3.7 parts by weight of heavy weight styrene and 0.3 mg# part of azoisozoteronitrile, stir well, and then heat to 70°C.
The temperature was raised to 1, and the reaction was continued for 8 hours. According to this, the polymerization rate is 99
% or more and a monodisperse latex with an average particle size of 1.5 μm (B
I got l.

(d) Also, in the same manner as in (e) above, put the seed solution into a reaction container, add 190 parts by weight of water, 36 parts by weight of styrene,
Add 0.4 parts by weight of azoisobutyronitrile (AIBN), stir well, raise the temperature to 70°C, and react for 8 hours to obtain a monodispersed latex with an average particle size of 3.0 μm and a polymerization rate of 99% or more ( I got 01.

(el In (C) above, the reaction was carried out in exactly the same manner as in (C) except that 3.7 parts by weight of methyl methacrylate was used in place of 3.7 parts of styrene, and the polymerization rate was 99.
A monodispersed latex pile with a particle size of 1.5 μm or more was obtained.

(f) The reaction was carried out in exactly the same manner as in (d) except that 34.5 parts by weight of styrene and 1.5 parts by weight of methacrylic acid were used instead of 36 parts of stycine in the above (dl). A monodisperse latex (El) with a particle size of 3.0 μm and a coefficient of 99 or higher was obtained.

The above latex (A), (B) l (0),
(DJ and (El) were dried to give synthetic organic pigments (A), (13), (0), (D) and (B), respectively.The size of these particles was measured using an electron microscope, and the results were as follows. This is Tooshi in Table 1.

Table 1 Examples 1 to 5 Preparation A composition of the following composition (solid content 65%) using (Bl, (0), (mouth) and (El)
), then adjust the pH with ammonia water! ! 1111
1! L. A coating liquid for gravure printing was obtained.

Table 2 Table 3 (Comparative Examples 1 to 3) The formulations of Examples 1 to 3 (Table 3) were used, but the compositions shown in Table 4 were applied without using the synthetic organic pigment of the present invention. A coating solution for gravure printing was obtained by preparing a composition in which the composition ratio of pigments in the coating solution was changed.

Table 4 Examples 6 to 12 After preparing compositions using the synthetic organic pigment (B) in which the composition ratio of the synthetic organic pigment in the coating solution was changed as shown below,
A coating liquid for gravure printing was obtained by adjusting H with aqueous ammonia. Dispersants and binders not listed in Table 5 were as listed in Table 3.

Table 5 (Application Example 1) The coating liquids obtained in Examples 1 to 2 and Comparative Examples 1 to 3 were coated on one side on medium base paper, immediately placed in a hot air dryer, and heated to 150 ml.
Dry for 30 seconds at 50C, 100Kf/
C++! The suit was calendered twice and then left in a constant temperature room (20° C., 65% RH). The physical properties of the coated paper thus obtained are shown in Tables 6 and 7 together with the physical properties of the coating solution. The following methods were used to measure each physical property: (11 pH: 6+2 when measured at 25C) Viscosity: Measured using a BL type viscometer (60 rpm, A4 spindle).

(3) Drybic: Using an R, I printing machine, print several times with tack A8 ink, and visually judge the pitching condition of the printed surface. The smaller the number, the better.

(4) White paper gloss = 75° Murakami color gloss meter The larger the value, the better.

(5) Gravure printing suitability: Gravure printing facultability tester (
Using the Ministry of Finance Printing Bureau method], the printed test pieces are judged with the naked eye to determine their superiority or inferiority.

◎Best, ○Good, ΔTown, ), (D) and (E) to prepare the following composition (solid content: 64%).
) was prepared, and then H was prepared with aqueous ammonia to obtain a coating liquid for offset printing.

Table 8 Table 9 (Comparative Examples 4 to 6) The formulations of Examples 3 to 17 (Table 9) were used, but
A composition in which the composition ratio of the pigment in the coating liquid is changed as shown in No. 1 O without using the synthetic organic pigment of the present invention is prepared! 3 to obtain a coating liquid for offset printing.

Table 1O Examples 18 to 24 Preparation of compositions using synthetic organic pigments (Bl) in which the composition ratio of the synthetic organic pigments in the coating liquid was changed as shown below After L4,
The pH was adjusted with aqueous ammonia to obtain a coating solution for offset printing. Dispersants and binders not listed in Table 11 were omitted from Table 9.

Table 11 (Application Example 2) The coating liquids obtained in Examples 13 to 24 and Comparative Examples 4 to 6 were coated on one or both sides of high-quality base paper, and after drying, supercalendering was performed. was measured. The results are shown in Tables 12 and 13 along with the physical properties of the coating fluid used.
Shown in the table. The following methods were used to measure each physical property.

(11,H: Measured at 25°C.

(2) Viscosity: Same as Reference Example 1.

(3) Dry Vic 1 (4) Wet Vic: Evaluated by point method using R, I printing tester.

The smaller the number, the better.

(5) White paper glossiness: Same machine as application example ■.

(6) Print gloss level = 75° using Murakami Color gloss meter.

The ink is Toyo Jet Kixmi ( 0,20C) used.

The larger the number, the better.

(7) Trapping property: Using Mei Seisakusho's RI printing tester, the printed test pieces were judged visually to determine their superiority or inferiority.

◎Best, ○Good, ΔTown, x Poor Table 12 Physical properties of coating liquid Table 13 Coated paper properties (Note) * indicates dissatisfaction.

Effects of the Invention As is clear from a comparison of the above embodiments, comparative examples, and applied examples, the present invention can achieve its objectives.

applicant Nippon Kai Sei Rubber Co., Ltd. Agent: Patent Attorney Minoru Isaka

Claims (1)

[Scope of Claims] (A) ■ 97 to 60 parts by weight of a mineral pigment containing at least 5% by weight of heavy calcium carbonate pigment; ■ An average diameter of 0.5 μm or more, and an average particle diameter of ±20 100 parts by weight of a paper coating pigment consisting of 3 to 40 parts by weight of a synthetic organic pigment which is an aromatic vinyl compound-based polymer particle containing 80% or more of particles in the range of A coating liquid composition for paper containing parts by weight.