JPS6228239B2 - - Google Patents

Description

[Detailed description of the invention]

An object of the present invention is to provide paper of a suitable size as a base paper for offset rotary printing. Conventional paper surface sizing agents include oxidized starch, sodium alginate, carboxymethyl cellulose,
Polyacrylamide, polyvinyl alcohol, and the like are used alone or in combination of two or more, but as offset rotary printing becomes more widespread, several problems have arisen. The biggest one is the lack of blister resistance. In other words, if a coat of base paper with the above surface size and an air-permeable coating layer is subjected to continuous offset rotary printing and then immediately dried by direct heating (approximately 350°C), the Water vapor and air caused by moisture do not escape to the surface and accumulate inside, causing blistering. Therefore, in offset rotary printing, in order to prevent the paper layer from blistering when heated by direct flame, it is necessary to (a) have high Z-axis strength (strength in the direction perpendicular to the paper surface) of the paper, and (b) resist water vapor. - High air permeability is particularly required, but conventional surface sizing agents have not been able to sufficiently meet these requirements. The present invention solves the problem of conventional offset rotary printing base paper by "dialkali maleic acid salt unit 0.5 to This problem was solved by using as a sizing liquid an aqueous solution of a saponified product with a degree of saponification of vinyl acetate units of 20 mol % or more and 97 mol % or more. By using an aqueous solution of the above-mentioned highly saponified product as a sizing liquid, the Z-axis strength increases by about 40 to 80% compared to using general-purpose oxidized starch, and about 30% more than polyvinyl alcohol. make it big In a comparison of air permeability, both the sized paper of the present invention and the oxidized starch sized paper give good results, while the polyvinyl alcohol sized paper has inferior air permeability. The overall result is as follows. Z-axis strength Air permeability Saponified products of the present invention ○ ○ Oxidized starch × ○ Polyvinyl alcohol △ △ The saponified products used in the present invention include maleic acids such as monomethyl maleate, monoethyl maleate, monopropyl maleate, and monobutyl maleate. Copolymers of maleic acid esters and vinyl acetate, representative examples of which are monoesters, maleic diesters such as dimethyl maleate, diethyl maleate, dipropyl maleate, and dibutyl maleate, are saponified under severe alkaline saponification conditions. It is manufactured for the first time by doing so. That is, if the above copolymer is simply saponified by a conventional method in the presence of a caustic alkali or alkali metal alcoholate catalyst in a solvent such as methanol, the maleic acid units in the copolymer will not convert to the dialkali salt type, and the vinyl acetate units will not change to the dialkali salt type. The degree of saponification increases to only about 95 to 96% at most, and saponification beyond that level is extremely difficult. This is thought to be because saponification of the vinyl acetate units on both sides of the maleic acid unit does not proceed easily. Therefore, in order to convert the maleic acid unit into a dialkali salt and to make the degree of saponification of the vinyl acetate unit 97 mol% or more as shown in the above formula, the partially saponified product obtained by the above conventional method is further mixed with an alkaline aqueous solution, such as caustic soda. It is necessary to further advance the saponification reaction by adding the partially saponified product into an aqueous solution or aqueous caustic potassium solution, or by attaching an alkaline aqueous catalyst to the partially saponified product and heating it. If a large amount of maleic acid ester remains without being converted into dialkali salt units, the gas permeability is low and there is a risk of blistering when heated over an open flame. Furthermore, even if dialkali salt units are present, if the molar fraction is less than 0.5 mol%, the Z-axis strength will be poor;
On the other hand, when it exceeds 20 mol%, the degree of polymerization decreases, resulting in insufficient strength. The sum of the mole fraction m of vinyl acetate units and the mole fraction n of vinyl alcohol units is the remaining 80 to 99.5 mol%, but 100n/m+n is 97 to 100, that is, the degree of saponification of vinyl acetate units is 97. Must be greater than or equal to mol%,
If the degree of saponification of vinyl acetate units is less than 97 mol%, air permeability will be poor and cause blisters. Particularly favorable results are obtained when the degree of saponification of vinyl acetate units is 98 mol % or more. When sizing base paper for offset rotary printing using the sizing agent of the present invention, the sizing agent should be dissolved in the above-mentioned saline water to have a solid content of about 0.5 to 10%. All conventional surface sizing methods are adopted, in which the viscosity of a 4% aqueous solution at 20°C is adjusted to about 5 to 100 cps, and the solution is coated on the paper surface by size press coating, calendar stack coating, roll coating, etc., and then dried. I can do it. In addition to using the above saponified products alone,
It may be used in combination with conventionally known surface sizing agents such as oxidized starch and polyvinyl alcohol, as well as a small amount of sulfuric acid. In particular, the combination with oxidized starch is economically and qualitatively useful. Further, it is preferable that the base paper to which the method of the present invention is applied contains a small amount of alumina (aluminium sulfate, etc.) in order to fully exhibit its effects. Next, the present invention will be further explained with reference to Examples.
Hereinafter, "parts" and "%" are expressed on a weight basis unless otherwise specified. Example 1 A monomethyl maleate-vinyl acetate copolymer with a monomethyl maleate content of 3.0 mol% was saponified in methanol in the presence of a caustic soda catalyst to obtain a monomethyl maleate-vinyl acetate copolymer with a degree of saponification of vinyl acetate units of 95.0 mol%. Vinyl alcohol copolymer particles were obtained, and then the particles were poured into a 5% aqueous solution of caustic soda and heated and stirred at a temperature of 85° C. for 2 hours.
The product thus obtained contained 3.0 mol% of disodium maleate units, and the degree of saponification of vinyl acetate units was 99.5 mol%. Next, a 3% aqueous solution of the saponified product thus obtained was prepared (viscosity 18.5 cps at 20°C), and the solid content was coated on high-quality paper with a basis weight of 60 g/m ² containing some sodium sulfate using a size press coater. After coating and drying to a concentration of 1.0 g/m ² , the surface was sized by passing it once through a super calender at a temperature of 80 to 85°C. This size paper was left for 72 hours at a temperature of 20℃ and relative humidity of 65%, and then Z-axis strength, air permeability, oil absorption, and IGT were measured.
Pick strength and Steckigt sizing were measured.
In addition, after coating layers were provided on the front and back sides of this size paper, continuous offset rotary printing was performed, and then drying was performed by direct heating (approximately 350°C) to see whether or not blistering occurred. The results are shown in Table 1. Control Example 1 Size press was carried out in the same manner as in Example 1 except that a 6% aqueous solution of oxidized starch was used. (3
% aqueous solution has inferior properties, so a 6% aqueous solution was used. ) Control Example 2 Example 1 except that a 3% aqueous solution of polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 99.5 mol% was used.
Size press was performed in the same manner as above. Control example 3 Example 1 except that a 3% aqueous solution of polyvinyl alcohol with a degree of polymerization of 500 and a degree of saponification of 88.0 mol% was used.
Size press was performed in the same manner as above. The results of Control Examples 1 to 3 are also shown in Table 1.

[Table] As is clear from Table 1, the present invention shows favorable results such as good releasability from the roll when drying size paper, particularly high Z-axis strength, and high air permeability. In addition, the oil absorption, IGT pick strength, and Steckigt size do not pose any practical problems. Furthermore, even if coated paper is made from the size paper of the present invention, subjected to offset rotary printing, and heated over direct flame, no blistering phenomenon occurs at all. On the other hand, in Comparative Example 1 using oxidized starch, the Z-axis strength of the sized paper was insufficient, so a blistering phenomenon was observed during direct heating during offset rotary printing. Furthermore, Comparative Example 2, which used completely saponified polyvinyl alcohol, was slightly inferior in both N-axis strength and air permeability, and therefore caused some blistering when heated over an open flame. Note that Comparative Example 3 using a partially saponified polyvinyl alcohol has poor Z-axis strength and extremely poor air permeability, resulting in significant blistering. Furthermore, when polyvinyl alcohol is used, whether it is a completely saponified product or a partially saponified product, there is a drawback that the releasability from the drying roll when drying size paper is poor. Example 2 A monomethyl maleate-vinyl acetate copolymer with a monomethyl maleate content of 10.0 mol% was once saponified in a methanol solvent in the presence of a caustic soda catalyst to obtain monomethyl maleate-vinyl acetate with a degree of saponification of vinyl acetate units of 90.0 mol%. - After obtaining vinyl alcohol copolymer particles, sprinkle a 40% caustic soda aqueous solution on the particles, and then uniformly mix with a Henschel mixer to obtain 9.0 mol% of disodium maleate units, 1.0 mol% of monomethyl maleate units, and acetic acid. A saponified copolymer with a degree of saponification of vinyl units of 99.5 mol% was obtained. This saponified copolymer was heated and dissolved in water to prepare a 3% aqueous solution, and Example 1
Size press was performed in the same manner as above. Control Example 4 The saponified product in the first stage in Example 1, that is, the monomethyl maleate-vinyl acetate-vinyl alcohol copolymer 3 with a monomethyl maleate content of 3.0 mol% and a degree of saponification of vinyl acetate units of 95.0 mol%.
Size press was carried out in the same manner as in Example 1 using a % aqueous solution. Example 3 A monobutyl maleate-vinyl acetate copolymer having a monobutyl maleate content of 5.0 mol% was first saponified in methanol and then in water in the presence of a caustic soda catalyst to obtain disodium maleate units.
A saponified copolymer was obtained with a degree of saponification of 4.8 mol%, monobutyl maleate units: 0.2 mol%, and vinyl acetate units: 99.5 mol%. 3 of this saponified copolymer
Size press was carried out in the same manner as in Example 1 using a % aqueous solution. Example 4 A monomethyl maleate-vinyl acetate copolymer having a monomethyl maleate content of 3.0 mol % was obtained by polymerizing maleic anhydride and vinyl acetate in methanol. Maleic anhydride is converted into monomethyl maleate units in the polymer. Next, this copolymer was saponified first in methanol and then in water using a caustic soda catalyst to obtain a copolymer having a degree of saponification of 3.0 mol% of disodium maleate units and 99.7 mol% of vinyl acetate units. Size pressing was carried out in the same manner as in Example 1 using a 3% aqueous solution of this copolymer. The results of Examples 2 to 4 and Control Example 4 are shown in Table 2.

[Table] As is clear from Table 2, good results similar to those in Example 1 are obtained in Examples 2 to 4, but the maleic acid units are not converted to the disodium salt type and the vinyl acetate units are In Control Example 4, which has a slightly lower degree of saponification, the air permeability is poor, and a blistering phenomenon occurs when heated over a direct flame.

Claims (1)

[Claims] 1 Maleic acid dialkali salt unit 0.5 obtained by secondary saponification of the maleic acid ester-vinyl acetate copolymer saponified product in the presence of an alkaline aqueous solution
~20 mol%, saponification degree of vinyl acetate unit 97 mol%
A surface sizing agent for base paper for offset rotary printing, characterized in that an aqueous solution of the above saponified substance is used.