JPH1150393A - Newspaper paper for offset printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain newspaper paper used for offset printing and excellent in color-printed product quality and printing workability by coating raw paper with a surface-treating agent containing a synthetic resin latex having a specific gel content as a main component and a pigment and subsequently drying the coated paper. SOLUTION: This newspaper paper for offset printing is obtained by coating both the front and back surfaces of newspaper raw paper with a surface-treating agent in an amount of 0.05-2 g/m<2> , preferably 0.1-1 g/m<2> , per one surface. The surface-treating agent contains a synthetic resin latex, such as a styrene- butadiene-methyl methacrylate terpolymer latex, having a gel content of >=90 wt.% and a glass transition point temperature of -10 to 30 deg.C as a main component, and further contains a pigment such as kaolin in a solid content of <=300 pts.wt. per 100 pts.wt. of the total adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to newsprint for offset printing having excellent printing workability and excellent color printing quality.

[0002]

2. Description of the Related Art In recent years, offset printing, color printing, and high-speed printing have been progressing rapidly, and newsprint paper having better color printing suitability and printing workability has been demanded for newsprint as a printing medium. Have been. In offset printing, printing ink having a relatively high tack is used, and therefore, it is required that the strength of the paper surface be high. Also,
The use of dampening water requires surface water resistance. When paper having low surface strength or paper having low or no water resistance is used, there is a problem that paper dust is deposited on a blanket or mixed with ink, so that a so-called blur is generated on a printing surface.

Further, with the recent reduction in weight of newsprint, high opacity after printing on the newsprint is required. Inorganic pigments such as white carbon, titanium oxide, and talc have been widely used as papermaking fillers in order to increase the opacity of paper. These fillers tend to leach out of the paper layer easily by the dampening solution used in the printing process during offset printing, and are one of the main components of the paper powder to be piled on the blanket.

[0004] In order to cope with such a problem of newsprint at the time of offset printing, conventionally, a surface treatment agent containing starch, PVA, polyacrylamide or the like as a component is generally applied to the surface of the newsprint. I have. These surface treatment agents have the function of improving the strength of the paper surface and adhering the fine fibers and fillers on the paper surface to pulp fibers, etc., but all have poor water resistance and are easily released from the paper by dampening water. For this reason, there is a problem that the paper is deposited on a blanket at the time of printing, or the paper surface is sticky, and the paper is easily broken. Furthermore, these surface treatment agents have a drawback that ink absorption unevenness (color unevenness on the printing surface) due to coating unevenness occurs during color printing in order to suppress penetration of the ink into the paper surface.

In view of the above situation, various methods have been proposed for offset printing newsprint in order to suppress the surface tackiness (hereinafter referred to as "Nepari property") and increase the surface strength. For example, a method of increasing the strength of the paper surface by applying a specific polyacrylamide-based compound to the surface, and further increasing the surface water resistance by using polyhydric aldehydes in combination (JP-A-8-13384).
JP-A-5-59689) and a method of improving surface sizing, surface strength, and nap-par by coating a composition obtained by adding a block copolymer of ethylene oxide and propylene oxide to PVA. And a method of applying a specific water-soluble anionic copolymer having a specific polyacrylamide and a hydrophobic substituent (Japanese Patent Laid-Open No.
No. 232193) has been proposed. However, at the same time, it is not always sufficient to achieve both a reduction in nap-paring properties and a surface strength, and there is still no improvement in ink absorption unevenness on a color printing surface.

[0006]

SUMMARY OF THE INVENTION The present inventors have intensively studied to obtain newsprint having excellent offset printing suitability and print quality, particularly excellent color print quality. As a result, by using a specific adhesive as a surface treatment agent applied (externally added) to newsprint, more preferably, in addition to the specific adhesive, a surface treatment further adding a pigment is used. By using the agent, the present invention provides newsprint paper for offset printing which is desired by the present invention.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an offset printing newsprint obtained by applying a surface treatment agent onto base paper and drying the same, wherein the surface treatment agent comprises a synthetic resin latex having a gel content of 90% by weight or more. This is newsprint paper for offset printing, characterized in that the main component is. Further, as a more preferred embodiment, the present invention makes it desirable by using a synthetic resin latex having a glass transition temperature of −10 ° C. to 30 ° C. as the synthetic resin latex, and further adding a pigment in a surface treatment agent. A more excellent action and effect can be obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, starch, PVA, polyacrylamide, and the like are generally applied to the surface of newsprint for offset printing. All of these external coating agents are effective in suppressing paper dust, but they have poor water resistance and accumulate on the blanket due to dampening water during printing, and stick to the blanket called Nepari property There is a problem that ink absorption unevenness is likely to occur in color printing due to troubles and an increased amount of application.

By the way, synthetic resin latex, which is widely used as an adhesive for coating compositions (paints) in the field of production of general coated paper, has been studied as a surface treating agent for newsprint so far. Since the adhesiveness of the dried film of the latex was higher than that of starch or polyacrylamide, it was said that there was a problem in the nepari property, and the use was not actively performed. The present inventors have reviewed and studied the use of this highly water-resistant synthetic resin latex as a surface treatment agent for newsprint. As a result, when a synthetic resin latex having a gel content of 90% by weight or more is used as a surface treatment agent, the nepari property is not significantly increased, the water resistance is improved, the generation of paper powder is effectively suppressed, and color printing is performed. It was found that the quality was improved, and the present invention was completed.

Here, the gel content of the synthetic resin latex is generally known as an indicator of the degree of crosslinking of the latex as a toluene-insoluble matter, and the gel content in the present invention is measured by the following method. , Calculated. That is, a synthetic resin latex was dried at room temperature to prepare a latex film, and about 1.0 g of the dried latex film was accurately weighed (Bg), placed in 400 cc of toluene and left for 48 hours, and then subjected to a 300 mesh wire mesh. After filtration, the undissolved material on the wire mesh was dried at room temperature, weighed (Ag), and the gel content [(A / B) × 100: unit...% By weight] was calculated.

The gel content is appropriately adjusted by adjusting the monomer composition of the synthetic resin latex, the type and amount of the chain transfer agent during polymerization, and the like. For example, examples of the monomer include styrene, butadiene, methyl methacrylate, and acrylonitrile. By the way, the gel content of general-purpose latex widely used in the production field of general coated paper is usually about 30 to 80% by weight, and the gel content (rate) of 90% by weight or more specified in the present invention. ) Is in a fairly high area. The reason that the use of the synthetic resin latex having a high gel content reduces the nepari property is not necessarily clear, but due to the advanced degree of crosslinking of the latex, the latex is dried once and the film is dried. It is presumed that even if the dry film is re-wetted with a fountain solution, the nepari property is not strongly exhibited. By the way, when the gel content is less than 90% by weight,
It is not preferable because it has a strong tendency to induce paper breakage or the like during offset printing due to the appearance of sliminess.

Another factor affecting the Neppari (tackiness) is the Tg (glass transition temperature) of latex. Generally, the higher the Tg, the lower the Neppari, but the lower the adhesive strength. Usually -3
It is used in the range of 0 to 50C, preferably -10 to 30C.

In the present invention, in addition to the above-mentioned synthetic resin latex having a high gel content as a surface treating agent,
Other adhesives can be used in combination as long as the effects of the present invention are not impaired. Incidentally, examples of such an adhesive include starches such as corn starch, oxidized starch, and cationized starch, carboxymethyl cellulose, methyl cellulose, water-soluble cellulose compounds such as hydroxyalkyl cellulose, polyvinyl alcohol compounds and polyacrylamides, and casein. Is exemplified. In this case, the proportion of the synthetic resin latex having a high gel content specified in the present invention in the total adhesive is 30% by solid content.
More than% by weight is required. If the amount is less than 30% by weight, the effect of improving blanket piling and the effect of eliminating ink absorption unevenness in color printing as desired in the present invention may not be obtained. In addition, as a surface treatment agent,
In addition to the above adhesives, surface sizing agents, defoamers, preservatives, thickeners, and the like commonly used in the papermaking field and coated paper manufacturing field are appropriately used in combination.

Further, in order to further improve the color printing quality, a pigment for coated paper used in the field of producing general coated paper may be appropriately used in the surface treating agent. Examples of the pigment in this case include kaolin, clay, calcined kaolin, amorphous silica, zinc oxide, aluminum oxide,
Inorganic pigments such as aluminum hydroxide, calcium carbonate, satin white, aluminum silicate, magnesium silicate, magnesium carbonate and the like, and one or more kinds of plastic pigments and the like can be appropriately mixed and used. In this case, the pigment is blended in a range of 300 parts by weight or less in terms of solid content based on 100 parts by weight of the total adhesive in the surface treatment agent. If the amount exceeds 300 parts by weight, paper dust may be generated.

The surface treating agent thus obtained is adjusted to a solid concentration of 1 to 20% by weight and coated on newsprint base paper. The coating amount is usually 0.05% by dry weight per side.
To 2 g / m ^2, preferably is coated on both surfaces of the base paper in the range of 0.1 to 1 g / m ^2. By the way, the coating amount is 0.05 g
/ In the case of m less than ² hardly sufficient surface strength can be obtained, whereas, if it exceeds 2 g / m ^2, came out Neppari resistance, sticking, etc. of the blanket is concerned.

The base paper for newsprint in the present invention may be a chemical pulp (such as NBKP or LBKP), a mechanical pulp (such as GP, CGP, RGP, PGW, or TMP) as a raw material pulp.
Pulp in which waste paper pulp (DIP or the like) or the like is used alone or mixed at an arbitrary ratio is used. Also, white carbon,
Fillers such as clay, amorphous silica, talc, titanium oxide, and calcium carbonate are added to the stock, and further, a paper strength agent,
A generally known papermaking chemical such as a sizing agent such as a retention aid, a reinforced rosin sizing agent, or an emulsion sizing agent, a waterproofing agent or an ultraviolet ray inhibitor is internally added, and the paper is made by a known and publicly available paper machine. The basis weight of the base paper is not particularly limited, but is generally in the range of 35 to 50 g / m ² .

The above-mentioned base paper is coated and dried with the surface treatment agent which is a feature of the present invention. The coating apparatus in this case is not particularly limited. A ring size press, a rod metaling size press, a gate roll coater, a blade coater, a bar coater, a rod blade coater, an air knife coater and the like are appropriately used.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the present invention. Parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

EXAMPLE 1 (Making of base paper) A mixture of 15 parts of softwood kraft pulp, 40 parts of thermomechanical pulp (TMP), 10 parts of ground pulp (GP), and 35 parts of deinked waste paper pulp was mixed.
Disintegrated, 150 ml freeness in refiner.
S. F. (Canadian Standard Freeness) White carbon with an average particle size of 1.5 μm was added as a filler to a pulp stock prepared to have a freeness of 1% based on the absolute dry pulp, and the pulp was made with a twin-wire paper machine. A newsprint base paper having a basis weight of 42 g / m ² was obtained.

(Application of Surface Treatment Agent) As a surface treatment agent,
100 parts of a styrene-butadiene-methyl methacrylate copolymer latex (trade name: PKC1008 / Zeon Corporation) having a gel content of 95% and a glass transition temperature of 3 ° C., and 10 parts of carboxymethyl cellulose as a thickener (each , Solid content) and diluted with water to obtain a surface treatment agent having a solid content concentration of 5%. This surface treatment agent was applied to both sides of the above newsprint base paper (42 g / m ² ) using a gate roll coater so that the weight after drying on one side was 0.2 g / m ² , followed by drying. After that, calendering was performed under the condition of a linear pressure of 150 kg / cm to obtain newsprint for offset printing.

Example 2 In Example 1, instead of styrene-butadiene-methyl methacrylate copolymer latex (PKC1008) as a surface treating agent, the gel content was 91%,
Newsprint paper for offset printing was obtained in the same manner as in Example 1 except that a styrene-butadiene copolymer latex having a glass transition temperature of -30 ° C (trade name: L-1392 / Asahi Kasei Corporation) was used. At this time, the coating amount after drying was 0.08 g / m ² per one side.

Example 3 Styrene-butadiene copolymer latex having a gel content of 91% and a glass transition temperature of 30 ° C. (trade name: P-583)
8 / Sumitomo ABS Latex Co.), 100 parts of an oxidized modified starch aqueous solution (trade name: Ace A / Oji Cornstarch) dissolved in hot water, kaolin (trade name: UW)
-90 / Engelhard) 50 parts, light calcium carbonate (trade name: Brilliant S-15 / Shiroishi Kogyo) 50
Parts (each in terms of solid content) was added and diluted with water to prepare a paint having a solid content of 15%. Example 1
Using a gate roll coater on both sides of the base paper (42 g / m ² ) used in the above step, the base paper was applied so as to be 1 g / m ² per side, dried, and then pressed under a linear pressure of 150 kg / cm under one nip. A calender passing process was performed to obtain newsprint paper for offset printing.

Example 4 Styrene having a gel content of 91% and a glass transition temperature of -3 ° C.
-Butadiene copolymer latex (trade name: L-128)
8 / Asahi Kasei Co., Ltd.) 100 parts of oxidized modified starch dissolved with hot water
Powder aqueous solution (trade name: Ace C / Oji Cornstarch)
60 parts, kaolin (UW-90 / above) 50 parts (each
And converted to solids), diluted with water,
A 15% paint was prepared. This paint was used in Example 1
Base paper (42g / m^TwoGate roll coater on both sides
1g / m per side using ^TwoCoating so that
After drying, 1 nit under a pressure of 150 kg / cm
Paper for the offset printing.
I got a question paper.

Example 5 Newspaper for offset printing was obtained in the same manner as in Example 1, except that the concentration of the surface treating agent was changed to 3%. However, the coating amount at this time was 0.08 g / m ^{2 on} one side in dry weight.

EXAMPLE 6 15 parts of softwood kraft pulp, 35 parts of thermomechanical pulp, 10 parts of ground pulp, deinked waste paper pulp 40
Parts, mix and disintegrate, freeness 1 in refiner
10 ml C.I. S. F. (Canadian Standard Freeness) Pulp adjusted to 1% per bone dry pulp with light calcium carbonate having an average particle size of 2 μm as filler,
A base paper for newsprint of 43 g / m ² was obtained. Except for using this base paper, newsprint paper for offset printing was obtained in the same manner as in Example 3. The amount of the surface treatment agent applied at this time was 1 g / m ² per one surface in terms of dry weight.

Comparative Example 1 In Example 1, 100 parts of an oxidized modified starch (Ace A / described above) was dissolved in hot water at 90 ° C. as a surface treating agent.
After dilution, an aqueous starch solution having a solid content of 5% was used, and the base paper (42 g / m ² ) used in Example 1 was coated on both sides with a gate roll coater so that the coating amount after drying was 0.1% on one side. Newspaper for offset printing was obtained in the same manner as in Example 1 except that the coating was performed so as to have a coating weight of 3 g / m ² and dried.

Comparative Example 2 In Example 1, the styrene-butadiene-methyl methacrylate copolymer latex used in the surface treatment agent was replaced with a gel content of 70% and a glass transition temperature of 12
° C styrene-butadiene copolymer latex (trade name: SN-123H / Sumika ABS latex)
Was used in the same manner as in Example 1 except for using, to obtain newsprint paper for offset printing. At this time, the applied amount of the surface treatment agent after drying was 0.1 g / m ² per one surface.

Comparative Example 3 In Example 3, a gel content was 80% and a glass transition temperature was 10 ° C. instead of the copolymer latex of the surface treating agent.
Styrene-butadiene copolymer latex (trade name:
SN-307 / Sumitika ABS latex) was used to obtain newsprint paper for offset printing in the same manner as in Example 3. At this time, the applied amount of the surface treatment agent after drying was 1 g / m ² per one surface.

Comparative Example 4 In Example 1, a polyacrylamide resin (trade name: Santax NP-10 / Mitsui Toatsu Chemicals) was used instead of styrene-butadiene-methyl methacrylate copolymer latex as a surface treatment agent. Except for
Newsprint paper for offset printing was obtained in the same manner as in Example 1. At this time, the applied amount of the surface treatment agent after drying was 0.1 g / m ² per one surface.

Comparative Example 5 In Example 1, a calendering treatment was performed directly under the condition of a linear pressure of 150 kg / cm without performing the treatment with the surface treating agent to obtain newsprint paper for offset printing.

The quality of the thus-obtained newsprint paper for offset printing in Examples and Comparative Examples was evaluated, and the results are summarized in Table 1.

"Ink Density (Absorption) Unevenness" Using an offset printing machine (Komori SYSTEM C-20), four-color printing was performed, and the ink density unevenness of the indigo / red overlapping portions was visually determined. ◎: No ink density unevenness was observed at all, the ink density was high, and the image was uniform and clear. ：: There is almost no ink density unevenness, and the ink density is normal, but the image is uniform. Δ: An image in which unevenness in ink density was observed and was slightly uneven.

Using a "blanket paper powder piling" offset printing machine (Komori SYSTEM C-20),
After printing 5,000 copies, color four-color printing,
The state of accumulation of the paper powder in the blanket non-image area was visually determined. : No paper dust was observed. C: Slight generation of paper dust is observed. ×: A lot of paper powder is deposited on the blanket.

"Nippari (adhesive)" Two newspaper paper samples were cut to an appropriate size and immersed in water for 10 seconds.
After passing the paper at g / cm and drying at room temperature for 24 hours, the peel strength of the two sheets of paper was measured using a tensile tester. The larger the value, the stronger the adhesiveness (Nepari property).

[0035]

[Table 1]

[0036]

As is clear from the results in Table 1, the newsprint paper for offset printing obtained in the examples according to the present invention is:
It had excellent color printing quality and had no blanket paper powder piling or blanket sticking, and was excellent in printing workability.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiro Nojima 4-3-1 Jokoji, Amagasaki-shi, Hyogo Oji Paper Co., Ltd. Amagasaki Research Center

Claims (3)

[Claims] An offset printing newsprint obtained by applying and drying a surface treating agent on a base paper, wherein the surface treating agent is mainly composed of a synthetic resin latex having a gel content of 90% by weight or more. Newspaper for offset printing. 2. The offset printing newsprint according to claim 1, wherein a synthetic resin latex having a glass transition temperature of -10 ° C. to 30 ° C. is used as the synthetic resin latex. 3. The newsprint for offset printing according to claim 1, further comprising a pigment in the surface treating agent.