JPH08100391A - Water-resistant paper for printing and its production - Google Patents

Abstract

PURPOSE: To prepare a sheet of water-resistant paper for printing excellent in printing quality, especially printing finish image quality. CONSTITUTION: This sheet of water-resistant paper for printing uses a paper substrate having <=3.5μm integral value (PY value) of a power spectre at 0.5 to 12.5mm wavelength due to unevenness of thickness thereof. The water- resistant paper is produced under conditions of 1.5-2.5% moisture content of a web just before nipping with an upper wire and 30-50% upper dehydration ratio in the paper substrate to be formed with a two-wire paper machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-resistant paper for printing which is excellent in print quality, especially in printed surface quality, and a method for producing the same.

[0002]

2. Description of the Related Art A method for producing a waterproof paper by coating a surface of a sheet-like substrate with a polyolefin resin is generally well practiced. In addition, a method of laminating a water resistant film on the surface of a sheet-shaped substrate is also used. Paper is most often used as the sheet substrate. Polyolefin is generally used as the coating resin. It is also known that a polyolefin contains an inorganic pigment such as titanium dioxide or zinc oxide. An inorganic pigment-free layer may be provided in order to improve the adhesion between the paper substrate and the inorganic pigment-containing polyolefin layer. With regard to these waterproof papers for printing as well, there is a strong demand for quality improvement. One of them is the print quality. The printed surface quality depends on the smoothness of the waterproof paper for printing, and depends on the smoothness of the paper substrate. JP-A-2-33399 discloses a patent for water-resistant paper for printing, but there is no description about a sheet-like substrate, for example, a smoothness of a paper substrate and a method for producing a paper substrate having good smoothness.

[0003]

The smoothness of the waterproof paper for printing greatly affects the quality of the printed surface after printing. The smoothness of the waterproof paper for printing depends on the smoothness of the paper substrate used. It is an object of the present invention to provide a water resistant paper for printing, which has a good printed surface quality by using a paper substrate having a specific smoothness under specific papermaking conditions of a two-wire paper machine, and a method for producing the same.

[0004]

In the waterproof paper for printing according to the present inventor, at least one surface of a paper substrate is coated with a polyolefin resin, and the uneven thickness of the paper substrate used is continuously measured by a film thickness meter. When the measured signal is obtained by a frequency analyzer, the integrated value (PY value) of the power spectrum in the wavelength 0.5 to 12.5 mm is 3.5 μ.
It is characterized by being m or less. The present invention also provides a wire for forming a web of a Fourdrinier paper machine, which comprises a wire for forming a paper web of a Fourdrinier paper machine, in a method for producing a water resistant paper for printing in which at least one surface of a paper base is coated with a resin containing a polyolefin resin as a main component. When forming with a two-wire paper machine equipped with an endless upper wire so as to sandwich the web from above, the solid content concentration of the web just before being sandwiched by the upper wire is 1.5 to 2.5% by weight. And the total amount of water dewatered by the upper endless wire and the amount of water dewatered by the lower wire of the Fourdrinier in the part sandwiched between the upper wire and the wire of the lower Fourdrinier. A method for producing waterproof paper for printing, characterized in that an upper dehydration rate, which is a ratio of an amount of water dehydrated by an upper endless wire, is set to 30 to 50%.

The inventors of the present invention have found that it is effective to use a paper substrate having a specific surface smoothness in order to obtain a water resistant paper for printing having a good surface smoothness. In this case, the surface of the paper substrate is The present invention has been completed by finding that an integrated value of the power spectrum in the wavelength range of 0.5 to 12.5 mm should be 3.5 μm or less. The PY value on the surface of the paper substrate is the specified wavelength range, that is, 0.5
Is the root mean square value from 12.5 mm. This P
The Y value is obtained by continuously measuring the thickness unevenness of the paper substrate using a film thickness meter (for example, a film thickness meter manufactured by Anritsu Co., Ltd.) and measuring the obtained measurement signal with a frequency analyzer (for example, It can be obtained by frequency analysis using FFT analyzer CF-350 manufactured by Ono Sokki Co., Ltd.

When the PY value of the paper substrate used exceeds 3.5 μm, it is difficult to obtain a water-resistant printing paper having good smoothness. To obtain water-resistant printing paper with good smoothness, 3.
It must be 5 μm or less. Preferably 3.0
μm or less. In this case, the printed surface becomes a smooth and glossy surface, and has a good-looking so-called printed surface quality. A water-resistant printing paper using a paper substrate having a PY value of more than 3.5 μm is inferior in smoothness of printing and causes wrinkle-like flicker, resulting in poor appearance and so-called printed surface quality.

Further, in order to obtain a paper substrate having a PY value defined in the present invention, the paper substrate is provided with a wire forming a web of a Fourdrinier paper machine and an endless upper portion so that the web is sandwiched from the wire. When forming with a two-wire paper machine equipped with wires, the solid content concentration of the web just before being sandwiched by the upper wire is 1.5 to 2.5% by weight, and the Fourdrinier paper machine of the upper wire and the lower part Amount of water dewatered by the upper endless wire and the amount of water dewatered by the lower wire of the Fourdrinier in the part sandwiched between the wires The upper dehydration rate is 30 to 50%.

In the present invention, when a paper substrate is formed by a two-wire paper machine in which a wire for forming a web of a Fourdrinier paper machine and an endless wire for sandwiching the web from above are provided on the paper substrate, Immediately before the stock is sandwiched between the upper endless wires, the solid content of the web should be 1.5 to 2.5% by weight. Regarding the formation that is most related to the PY value of the paper substrate, if the solid content concentration is less than 1.5%, the improvement effect in the portion sandwiched by the upper wires is not exhibited and the target PY value cannot be obtained. .. A water-resistant printing paper using this paper substrate causes wrinkle-like flicker, resulting in poor printed surface quality. When the solid content concentration of the web just before being sandwiched by the upper wire exceeds 2.5%, the formation already formed in the portion sandwiched by the upper wire is destroyed and the formation is deteriorated. As a result, the target PY value cannot be obtained. Water-resistant printing papers using this paper substrate also have wrinkle-like flickering, resulting in poor printed surface quality.

In addition, when a web is formed by a two-wire paper machine in which a paper base is provided with a wire for forming a web of a Fourdrinier and an endless wire so as to sandwich the web from above, the upper wire is used. Upper endless wire to the total amount of water dewatered by the upper endless wire and the amount of water dewatered by the lower wire of the Fourdrinier in the part sandwiched between the wire of the lower and fourdrinier The upper dehydration rate, which is the ratio of the amount of water dehydrated in, must be 30 to 50%. If the upper dehydration rate is less than 30%, the effect of homogenizing the sandwiched webs in the thickness direction is small and the target P
I can't get the Y value. The waterproof paper for printing using this paper substrate also has poor printed surface quality and cannot attain its purpose as described above. When the upper dehydration rate is more than 50%, the strength of the paper layer is lowered, which causes a problem in printability such as occurrence of blisters during printing. Further, wire marks are also likely to appear, which is reflected on the surface of the waterproof paper for printing, and the printing surface quality is impaired.

The paper substrate used in the present invention is made of wood pulp, synthetic pulp, synthetic fiber or the like. Among these, the softwood pulp, the hardwood pulp, and the hardwood mixed pulp wood pulp are effective. These pulps may contain various additives. For example, as a dry paper strengthening agent, cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxyl-modified PVA, gelatin and the like, and as a sizing agent, a fatty acid salt, a rosin derivative, an alkyl ketene dimer,
Petroleum resin emulsions, higher fatty acid amides, etc. as pigments, kaolin, barium sulfate, titanium oxide, etc., wet paper strength enhancers, urea resins, epoxidized polyamide resins, etc., fixing agents, polyvalent metal salts such as aluminum chloride, cations, etc. Cation-modified polymers such as modified starch, caustic soda and sodium carbonate as pH adjusters, sodium chloride as inorganic electrolyte, sodium sulfate and the like, other dyes, optical brighteners and the like can be added in appropriate combination. Further, after being made into paper, size press, tab size, spray size, etc. can be applied.

The basis weight of the paper substrate is not particularly limited, but is usually 50 to 250 g / m ² . The density is also not particularly limited, but 0.8 to 1.2 g / cm ³ is preferable.
The paper substrate obtained in the present invention is coated with a polyolefin resin. The resin is coated by a general method such as extrusion coating or solvent coating. Depending on the resin, a treatment such as electron beam curing may be used. Further, the polyolefin resin may contain titanium oxide, a colorant, a conductive agent, a stabilizer and the like. Hereinafter, the present invention will be described in detail with reference to examples, but the examples do not limit the present invention.

[0012]

【Example】

Examples 1 to 4 and Comparative Examples 1 to 12 Mixed pulp of 50 parts of hardwood bleached kraft pulp (LBKP) and 50 parts of hardwood sulfite pulp (LBSP) was beaten to 320 ml with Canadian standard freeness, and this pulp slurry was prepared. , Alkyl ketene dimer as a sizing agent (AS-24 manufactured by Japan PMC Co., Ltd.)
To pulp solids 0.5%, polyacrylamide (Stargaku Chemical Co., Ltd. Stargum-A-15) 0.5% as a strength agent, cationized starch (Nissho Kako Co., Ltd. Neotac 130) Was also added 2.0%, and polyamide epichlorohydrin resin (WS525 manufactured by Japan PMC Co., Ltd.) 0.5% was also added to make 1% paper stock.

10 m of paper stock is placed on the wire of the Fourdrinier
Paper was made by a two-wire paper machine having an upper wire at the position. During the drying, a size press treatment was carried out using a modified Poval coating liquid in order to provide surface strength. The water content of the dried paper substrate was 8%, the basis weight was 110 g / m ² , and the thickness was 115 μm. The solid content concentration of the web just before being sandwiched between the Fourdrinier paper machine and the upper wire, and the upper dehydration rate were adjusted as shown in Table 1. The PY values of the obtained paper substrates were as shown in Table 1.

One side of the paper substrate is pre-corona treated and then high density polyethylene (density 0.96 g / cm ³ ) 5
0 parts by weight and low density polyethylene (density 0.92 g / cm
³ ) A mixture of 50 parts by weight and 5 parts by weight of anatase-type titanium oxide was melted at a temperature of 320 ° C. and coated by extrusion coating to a thickness of 15 μm. The roughness of the chill roll surface used is the RZ value according to JIS-B-0601.
The one having a thickness of 1.0 μm was used. The reason why the chill roll having a surface close to a mirror surface is used is that the printed surface quality of the waterproof paper for printing after printing is easy to see. When the surface roughness of the chill roll to be used is high, the quality of the printed surface is deteriorated as a whole, and it becomes difficult to determine wrinkle-like flicker. Then, the same amount was applied to the surface on the opposite side by the same method to obtain a waterproof paper for printing.

The water-resistant printing paper thus obtained was cut into a flat sheet by a cutter and printed by a Roland offset printing machine. The degree of wrinkle-like flicker of print quality was visually graded. Grade 1 was the best and Grade 5 was the worst. Grades 1 to 2 are acceptable. The results are shown in Table 1.

[0016]

[Table 1]

[0017]

The water-resistant printing paper obtained by the production method according to the present invention using a paper substrate having a specific smoothness has a good printed surface quality without wrinkle-like flicker.

Claims (2)

[Claims] 1. In a waterproof paper for printing in which at least one surface of a paper base is coated with a resin containing a polyolefin resin as a main component, the thickness unevenness of the paper base is continuously measured by a film thickness gauge and the measurement is performed. When the signal is analyzed and obtained by a frequency analyzer, the integrated value (PY value) of the power spectrum in the wavelength range of 0.5 to 12.5 mm is 3.5 μ.
A waterproof paper for printing, characterized by having a thickness of m or less. 2. A method for producing a waterproof paper for printing in which at least one surface of a paper substrate is coated with a resin containing a polyolefin resin as a main component, the wire being used to form the web of a Fourdrinier and the wire from above the paper substrate. When forming by a two-wire paper machine provided with an endless upper wire so as to sandwich the web, the solid concentration of the web just before being sandwiched by the upper wire is 1.5 to 2.5% by weight, and The amount of water dehydrated by the upper endless wire in the part sandwiched between the upper wire and the lower Fourdrinier wire and the total amount of water dewatered by the lower wire of the Fourdrinier A method for producing waterproof paper for printing, characterized in that an upper dehydration rate, which is a ratio of the amount of water dehydrated by an endless wire, is set to 30 to 50%.