JPS6228493A - Production of coated paper - 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 "Industrial Application Field" The present invention relates to a method for producing coated paper, and in particular a method for producing coated paper that is less likely to fade due to light or heat and has excellent whiteness. It is related to.

``Prior art'' Conventional methods for whitening coated paper include washing bulbs, reducing the amount of high-yield bulbs used, adding white fillers internally, and adding blue tints using blue dyes from the surface of the base paper. Countermeasures have been taken from the coating process, in which the surface of the base paper is coated with a coating composition containing white pigments, fluorescent brighteners, dyes, etc. using a size press or coater.

Among these whitening measures, the method of using fluorescent whitening agents is a method commonly used in the paper manufacturing industry as a method to improve the whiteness of printing paper, white paperboard, etc. and increase its commercial value. This is one of the countermeasures.

However, since water-soluble fluorescent brighteners have a strong affinity for bulbs, when a coating composition containing them is coated on a base paper, it penetrates into the base paper along with water at the same time as it is coated. Most of it is adsorbed and fixed to the base paper.

Therefore, the present situation is that satisfactory results are not necessarily obtained in terms of the whitening effect of the coating layer itself.

A method of increasing the whitening effect by using a specific water-soluble polycarboxylate resin and a stilbene-type fluorescent dye in combination [Japanese Patent Publication No. 48-29802], and a method of increasing the whitening effect by using a specific water-soluble polycarboxylate resin together with a stilbene type fluorescent dye, and a method of increasing the whitening effect by using a specific water-soluble polycarboxylate resin together with a stilbene-type fluorescent dye [Japanese Patent Publication No. 48-29802], and a method that uses water-soluble hydroxyethyl cellulose with a specific degree of substitution Fluorescent brightener (
A method of enhancing the whitening effect by using J-L (Japanese Patent Publication No. 57-13678) has also been proposed; As the white effect has been improved, new defects have also been introduced, and the current situation is that satisfactory results have not yet been obtained.

"Problems to be Solved by the Invention" The purpose of the present invention is to provide a method that can extremely efficiently improve the coating layer whitening effect of a water-soluble fluorescent brightener without requiring special materials. That's true.

"Means for Solving the Problems" The present invention contains 0.05 to 2.5 parts by weight of polyvinyl alcohol or a derivative thereof and a water-soluble fluorescent whitening agent based on 100 parts by weight of the pigment. The coating composition obtained was coated on a base paper, and the average evaporation rate was 10 to 60 kg/tl r /
This is a method for producing coated paper characterized by drying at m.

"Action" Polyvinyl alcohol or its derivatives [hereinafter simply referred to as PVA]
] and a water-soluble fluorescent whitening agent are disclosed in, for example, the aforementioned Japanese Patent Publication No. 48-29802 and Japanese Patent Publication No. 57-1.
It is known as No. 3678. However, according to these known documents, even if PVA and a water-soluble fluorescent brightener are used together,
It is said that no excellent whitening effect can be obtained.

However, according to the study results of the present inventors, if the amount of pvA used and the drying conditions of the coating composition are limited to specific conditions, the coating layer whitening effect of the water-soluble fluorescent brightener can be improved. , is expressed extremely efficiently, resulting in less fading due to light and heat.
It has become clear that a coated paper with excellent whiteness can be obtained.

That is, the present inventors have diligently investigated the whitening effect of coated paper obtained by adding a water-soluble fluorescent brightener and various auxiliaries to a coating composition and drying it under various drying conditions. As a result of research, sodium alginate, carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose,
Among various auxiliaries such as cellulose derivatives such as methyl cellulose, PVA, polyacrylate resin, styrene maleic acid copolymer salt resin, melamine formaldehyde resin, starch and its derivatives, urea formaldehyde resin, PV
It has become clear that an extremely significant whitening effect can be obtained only when a specific amount of A is used and drying is carried out under specific drying conditions, which led to the completion of the present invention.

The reason for this effect is not clear, but the inventors' findings suggest that PVA has an excellent fixing effect on water-soluble fluorescent brighteners, and that the brighteners are adsorbed to the bulbs of the base paper. In the process of coating the base paper with the coating composition and drying it, the amount used is set to specific conditions, and the drying conditions are also set to specific conditions. Therefore, the whitening agent is immobilized and migrates to the surface of the coating layer, and as a result, the water-soluble fluorescent brightener is efficiently oriented on the surface of the coating layer, resulting in an excellent whitening effect of the coating layer. It is presumed that this will be the case.

The PVA used in the present invention is not only polyvinyl alcohol obtained by hydrolysis from vinyl acetate polymer, but also modified polyvinyl alcohol that has undergone modification treatments such as esterification, etherification, urethanization, acetalization, crosslinking, and copolymerization. It also includes rest induced by polyvinyl alcohol and the like.

The degree of polymerization of PVA is desirably in the range of about 100 to 3,000, and in particular, a degree of polymerization of about 200 to 2,000, so that appropriate migration occurs in the coated layer under specific drying conditions and contributes to the whitening effect. Preferably, PVA is used. In addition, the degree of saponification of PVA affects the fixation of the water-soluble fluorescent whitening agent in the coating layer, and the brightening effect of PVA with a higher degree of saponification is greater, so it is preferably 20 mol% or more. PVA having a degree of saponification of 60 mol% or more is preferably used.

In the present invention, the proportion of PVA used is extremely important, and the amount used is less than 0.
If the amount is less than 0.5 parts by weight, the desired whitening effect of the present invention cannot be expected. However, when compounding at a high ratio of 3 to 5 parts by weight or more, which is normally used as an adhesive, the viscosity of the coating composition increases due to the shock phenomenon caused by the strong bond between PVA and pigment. Since appropriate migration of PVA in the coated layer during the drying process is inhibited, the desired effects of the present invention are also impaired. Therefore, the ratio of PVA used is 10 parts pigment.
The amount should be adjusted within the range of 0.05 to 2.5 parts by weight, more preferably 0.05 to 1.0 parts by weight.

As mentioned above, the water-soluble fluorescent brightener to be incorporated into the coating composition of the present invention containing PVA in a specific proportion is a stilbene type such as diaminostilhene disulfonic acid derivative commonly used for paper manufacturing. A whitening agent is preferably used, but any water-soluble whitening agent can be used, and it is of course possible to use two or more types in combination.

The pigments used in the coating composition are not particularly limited, and include kaolin, hydrated halloysite, clay, heavy calcium carbonate, light calcium carbonate, barium sulfate, aluminum hydroxide, satin white, titanium dioxide, and talc. Ordinary pigments for coated paper such as , calcium sulfite, zinc sulfate, and plastic pigments are blended as appropriate depending on the properties of each pigment.

Adhesives are also not particularly limited, including casein, soybean protein, yeast protein, starch, oxidized starch, esterified starch,
Etherified starch, modified starch such as cationic starch, natural adhesives such as cellulose derivatives, conjugated diene copolymer latex such as styrene/butadiene copolymer, methyl methacrylate/butadiene copolymer, acrylic and/or methacrylate ester Alkali-insensitive synthetic adhesives such as acrylic polymer latex such as polymers or copolymers of Alkali-sensitive synthetic adhesives such as alkali-sensitive synthetic resin emulsions whose main component is carboxylic acid and aqueous emulsions made by blending alkali-insensitive styrene-butadiene copolymer latex with alkali-sensitive copolymer latex. , 1 of ordinary coated paper adhesives
The above types are appropriately selected and used depending on the purpose of the coated paper.

The blending ratio of the adhesive is generally adjusted within the range of 3 to 25 parts by weight based on 100 parts by weight of the pigment, but in order to provide excellent smoothness, opacity, white paper gloss, and ink gloss, it is necessary to In order to increase the amount and obtain coated paper with improved printability, it is desirable to adjust the amount within a range of about 5 to 20 parts by weight.

In addition, various auxiliary agents, such as dispersants, flow modifiers, antifoaming agents, dyes, lubricants, waterproofing agents, and water retention agents, which are generally added to coated paper compositions, may of course be added as necessary. It is possible.

The coating composition thus prepared is coated on one or both sides of the base paper using an on-machine or off-machine coater, and the coating composition is coated in a single layer or on both sides so that the coating amount is about 3 g/rrr or more. Multilayer coating is desirable.

In that case, the formulations of the coating compositions for both sides and the coating compositions forming each layer in multilayer coating can be changed as appropriate according to conventional methods.

Furthermore, the coating method is not particularly limited; air knife coaters, roll coaters, paddle and inverter type blade coaters, blade coaters, Hebel and Hen 1 type coaters, bill blades, twin blade coaters, etc. , short dwell blades, rod blades, various blade coaters such as chambrax, etc.
Various conventional coating devices can be used as appropriate. Among these various coating devices, blade coaters in particular have traditionally been preferably used to produce high-quality coated paper because they can provide smoother coated surfaces.

In the method of the present invention, the specific coating composition thus coated on the base paper has an average drying rate of 10 to 60 kg/Hr/
It is necessary to dry under specific drying conditions such as %.

In general, there are cylinder dryers, tunnel dryers, floater dryers, air cap dryers, infrared dryers, etc. as drying devices after coating the coating liquid, and their evaporation capacity varies greatly depending on the scale and type of the device. ing.

In the present invention, the amount of PVA in the coating composition is at least LO kg/llr/rr so that it can efficiently migrate to the surface of the coating layer and contribute to the whitening effect on the surface of the coating layer. It is necessary to dry at a higher average evaporation rate.

Under drying conditions below 10 kg/llr/m, the desired whitening effect of the present invention cannot be expected.

However, the average evaporation rate is 60 kg/fir/m
Excessive drying in excess of 10% will result in rapid evaporation of the water in the coating composition, resulting in rapid and uneven migration of PVA, reducing the printability of the resulting coated paper and making it difficult to print. Unevenness occurs. In addition, there is a risk that the surface of the coating layer may become rough or that a shaky phenomenon may occur. For this reason, the quality of the coated paper is extremely low.

Therefore, in the method of the present invention, it is necessary to dry the coating composition by adjusting the capacity of the drying device so that the average evaporation rate falls within a specific range of 1O to 60 kg/Ilr/rd. .

After coating and drying, the coated paper is processed into a coated paper with excellent white gloss, smoothness, and printability using a finishing device such as a machine calender, super calender, or gloss calender according to a conventional method. I can do it.

"Effect" The thus obtained coated paper of the present invention has an extremely efficiently improved whitening effect on the surface of the coated layer, and moreover, the b value of the color difference expressed by Hunter's chromaticity coordinates has a bluish tendency. It has extremely excellent properties, such as preventing fading and yellowing due to light and heat, and causing little change in the appearance of blank paper and printed matter after long-term storage. In addition, because the whitening effect is significant,
It was also possible to reduce the amount of fluorescent whitening agent used depending on the intended use of the coated paper, and it was also economically advantageous.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Note that parts and % in the examples indicate parts by weight and % by weight, respectively, unless otherwise specified.

Examples 1 and 2, Comparative Examples 1 to 7 A valve composition consisting of 50 parts of NBKP, 20 parts of LBKP, and 30 parts of 5GP, 0.5 part of rosin size, and 3 parts of sulfuric acid
1.0 parts, 0.6 parts of an internal paper strength agent, and 10 parts of talc as a filler were added to obtain a base paper for coated paper with a weight of 40 g/n.

70 parts of kaolin (manufactured by EMC, UW-90) and 3 parts of heavy calcium carbonate (manufactured by Bihoku Funka Kogyo, Softon 2200)
Separate 0 parts using 0.2 parts of sodium polyacrylate.
L, 6 parts of oxidized modified starch (manufactured by Clove Cornstarch Co., Ltd., AceΔ), styrene-butadiene copolymer latex (
Manufactured by Sumitomo Naugatuck.

SN308) 10 parts, 0.5 part of a water-soluble fluorescent brightener (Whitex BB, manufactured by Sumitomo Chemical Co., Ltd.), and 0.5 part of various brightening aids listed in Table 1 were added. A coating composition with a mold concentration of 62% was obtained.

Note that in Comparative Example 1, no fluorescent brightener or whitening aid was added, and in Comparative Example 2, no brightening aid was added. Further, the whitening aids used in each example and other comparative examples are as follows.

・Example 1: PVA (manufactured by Kuraray Co., Ltd., PVA117) ・Example 2: PVA (manufactured by Nippon Gosei Kagaku Co., Ltd., Gosselan F-7
8) Comparative Example 3 Sodium nyalginate (manufactured by Sanshinsha Co., Ltd., Kelgin R
L) - Ratio 92 Example 4: Carboxymethyl cellulose (Daiichi Kogyo Seiyaku Co., Ltd., Celogen 7A) - Comparative example 5: Hydroxyethyl cellulose (Fushi Chemical Co., Ltd., Fuji HEC-AL15) - Comparative example 6: Polyamide polyurea-formaldehyde resin ( Manufactured by Sumitomo Chemical Co., Ltd., 5
R636)・Comparative Example 7: Styrene maleic anhydride copolymer (manufactured by Arayo Kagaku Co., Ltd., Polymalon 353) The obtained coating composition was coated on both sides of the base paper (1) and one side using a barironoto blade coater. Dry coverage per unit is 1
3 g/r+ (coated so that it becomes), 4.4 kg
After drying at an average evaporation rate of /llr/m, nine coated papers were produced by supercalendering.

Various qualities of the obtained coated paper were measured and listed in Table 1. The whitening effect of the coated paper obtained in the examples of the present invention was particularly excellent, and the yellowing after the weathering test was It exhibited excellent fading resistance.

The contents of the various quality tests are as follows.

[Fluorescence reaction]: Displayed according to the following evaluation criteria.

-+ ++ +++ None...
[Fluorescence reaction] ... Strong [whiteness]: Elleho whiteness measured with a xenon lamp (wavelength 457 m, i)).

[b value]: Shown in Hunter chromaticity coordinates.

(+: Stronger yellowness; -: stronger blueness) [Weather resistance test]: Indicated by the quality measurement results after 3 hours of arc discharge irradiation.

Examples 3 and 4, Comparative Examples 8 to 1O To a valve composition consisting of 20 parts of NBKP and 80 parts of LBKP, 1 part of rosin size, 3 parts of sulfuric acid hand, and 15 parts of talc as a filler were added to make paper, and the paper was oxidized and modified in a size press. 2.5 g of starch/rti coating and 52 g/
A base paper for coated paper of m was obtained.

Kaolin (manufactured by EMC Co., Ltd., UW-90) 80 parts, heavy calcium carbonate (manufactured by Fuji Kaolin Co., Ltd., Carbital 90)
20 parts of sodium polyacrylate was dispersed using 0.2 parts of sodium polyacrylate to obtain oxidatively modified starch (manufactured by Tamago Cornstarch Co., Ltd., Ace A).
) 5 parts, styrene-butadiene copolymer Latinx (manufactured by Sumitomo Naugatuck Co., Ltd.).

5N307) 12 parts, water-soluble fluorescent brightener (Sumitomo Chemical Co., Ltd., Whitex BK) 0.3 parts, PVA (Kuraray Co., Ltd.).

Add 0.5 part of PVAI 17) to make the solid content concentration 60
% coating composition was obtained, but no PVA was added in Comparative Example 8.

The obtained coating composition was coated on both sides of the base paper using a Bicono 1-blade coater, with a dry coating amount of 16 g per side.
/m, dried at the average evaporation rate as shown in Table 2, and then subjected to supercalender treatment to form 5 types<
A coated paper of p was produced.

Various qualities of the obtained coated paper were measured and listed in Table 2. The whitening effect of the coated paper obtained in the examples of the present invention was exceptional.

In Comparative Example 8, in which PVA was not added as a whitening aid, and in Comparative Example 9, in which drying conditions were insufficient, a satisfactory whitening effect could not be obtained, and in Comparative Example 10, in which rapid drying was performed, unevenness was observed. Due to the migration of PVA, the brightening effect was uneven. In addition, scratches appeared on the coated paper, and uneven ink transfer and poor printing smoothness after printing were observed.

Table 2 Evaluation Criteria ○...Excellent △...Slightly Inferior ×...Very Inferior Example 5.6, Comparative Example 11.12 Using a brightening aid in the proportions shown in Table 3. Example 1 except that a certain PVA (manufactured by Kuraray Co., Ltd., PVA105) was added.
Four types of coating compositions were obtained in the same manner as above.

This coating composition was coated on both sides of the same base paper as in Example 1 using a pilot blade coater, with a dry coating amount of 1% per side.
3 g/n (coated to give 11.0 kg/n)
After drying with an average evaporation rate of llr/rd, four types of coated paper were prepared by supercalendering. Various qualities of the obtained coated paper were measured and listed in Table 3, and the whitening effect of the coated paper obtained in the examples of the present invention was particularly excellent, and the coating suitability was also good. there were.

Table 3

Claims (1)

[Claims] A coating composition containing 0.05 to 2.5 parts by weight of polyvinyl alcohol or a derivative thereof and a water-soluble fluorescent brightener per 100 parts by weight of the pigment is coated on a base paper, and the average A method for producing coated paper, characterized by drying at an evaporation rate of 10 to 60 kg/Hr/m^2.