JP5699694B2 - Low basis weight printing paper - Google Patents

Description

The present invention relates to a printing paper having a low basis weight, a high opacity after printing, a high surface strength, and a good ink landing property.

There has been a demand for lighter paper from the viewpoint of resource saving. In reducing the weight of paper, it is required to reduce the weight while maintaining the thickness of the paper, or to reduce the weight while maintaining the opacity. In particular, since printing paper used for comics, magazines, books, and the like is printed on both sides, it is required that the opacity is maintained even when the weight is reduced and there is no show-through. Patent documents related to paper weight reduction include the following.

In patent document 1, 65 to 95% by weight of mechanical pulp and 20 to 80% by weight of mechanical pulp are pine as printing papers that are bulky and have good surface strength and ink inkability and excellent printability. For bulky offset printing, which is composed of a pine-based thermomechanical pulp, has a clear size of 0.5 to 1.5 g / m ² applied on both sides, and a tension of 0.40 to 0.50 g / cm ³ Medium quality paper has been proposed. However, opacity and post-print opacity have not been studied.

Patent Document 2 discloses an amorphous form having a bulk density of 0.1 to 2 g / ml and containing 0.1 to 2% by weight of a low-density chemical as a printing paper having a high bulk strength and excellent offset printability and high printing strength. Low density papers containing 1 to 9% by weight of silica or amorphous silicate per paper weight have been proposed. However, opacity and post-print opacity have not been studied.

Patent Document 3 proposes a low-density printing paper containing 1 to 25 solids by weight of light calcium carbonate-silica composite as a low-density printing paper that is bulky and excellent in opacity and opacity after printing. ing. However, it is a special filler in which the surface of light calcium carbonate particles is coated with silica, and opacity after printing has not been studied in detail.

In Patent Document 4, whiteness is 75% or more, density is 0. 5% as a printing paper having high whiteness, excellent fading, light weight, bulkiness, excellent printability, no paper dust, and good touch feeling. Printing paper having 50 g / cm ³ or less and fading of 6 or less has been proposed. However, opacity after printing has not been studied.

Patent Document 5 discloses a paper density reducing agent as a low density printing paper having a low density, a soft paper, a good ink-inking property, and a low density printing paper excellent in printability with little adhesion of paper dust to a blanket. A low density printing paper to which 3 to 2.0% by mass and 0.05 to 2.0% by mass of carboxymethylcellulose are added has been proposed. However, opacity and post-print opacity have not been studied.

JP-A-5-98593 (Japanese Patent No. 2650533) JP 2000-282392 A JP 2005-281915 A JP 2007-262587 A JP 2008-88582 A

When reducing the weight of paper, the opacity decreases when the basis weight is lowered.
In order to maintain the thickness, as a means other than using the above-described bulking agent, there is a method of increasing the bulk by weakening the beating of the raw material pulp. However, if this is done, the fiber-to-fiber bond of the pulp becomes weak, so that the surface strength is lowered, and there is a problem that troubles such as paper dust and paper peeling occur during printing. Furthermore, it is possible to increase the bulk by weakening the pressurization of the calendar for performing the smoothing treatment, but at the same time, the smoothness is deteriorated and the ink inking property is deteriorated.

The object of the present invention is intended to solve the above problems. That is, it is to provide a printing paper having a low basis weight, a high opacity, a high surface strength and a good ink landing property.

The inventors of the present invention have made intensive investigations on a means for making a printing paper that maintains opacity, has a high surface strength, and has a good ink setting property when the basis weight of the printing paper is reduced. As a result, the mechanical pulp is 65 to 90 mass. %, The pulp composition is adjusted so that the softwood kraft pulp contains 5 to 20% by mass, 0.5 to 2.0% by mass of white carbon is added as a filler, and the base paper to which 10 to 20% by mass of calcium carbonate is added, printing paper paper strength agent is at least one surface 0.5 to 1.0 g / m ² coating, particular whiteness, opacity, opacity after printing, basis weight, thickness, smoothness, Clark stiffness transverse As a result, the present inventors have found that the above problems can be solved, and have completed the present invention.

The invention of claim 1 is a printing paper in which waste paper deinking pulp having the following characteristics (1) to (7) is blended.
(1) The pulp composition is adjusted so that the mechanical pulp in the total pulp obtained by disaggregating the printing paper contains 65 to 90 mass% and the softwood kraft pulp contains 5 to 20 mass%.
(2) As a filler, white carbon 0.5-2.0 mass% and calcium carbonate 10-20 mass% are added, and it is set as ash content 5-15%.
(3) Whiteness 65-75%, opacity 87-97%, post-print opacity 85-95%
(4) Basis weight 50-60 g / m ² , thickness 120-140 μm
(5) A paper strength enhancer is applied to at least 0.5 to 1.0 g / m ^{2 on} one side.
(6) smoothness 5-20 seconds (7) Clark stiffness transverse 20 to 50 cm ^3/100

The invention according to claim 2 is the printing paper according to claim 1, wherein the difference between the opacity and the opacity after printing is 3% or less.

According to the present invention, even with a low basis weight and a low density, it is possible to provide a printing paper that has high opacity, high surface strength, and good ink deposition.

Embodiments of the present invention will be described below.
For the production of the printing paper of the present invention, a paper machine comprising each process of a wire part, a press part, a dryer part, and a reel part is used.

In the printing paper according to the present invention, kraft pulp, waste paper pulp, mechanical pulp, and the like can be used as raw material pulp. As the kraft pulp, softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), and the like can be used. In addition, as waste paper pulp, deinked pulp (DIP) such as newspaper waste paper deinked pulp and high-quality waste paper deinked pulp can be used. As the mechanical pulp, stone ground pulp (SGP), pressurized stone ground pulp (PGP), refiner ground pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), or the like can be used.

In the printing paper according to the present invention, the pulp composition is adjusted so that the mechanical pulp in the total pulp obtained by disaggregating the printing paper contains 65 to 90% by mass and the softwood kraft pulp contains 5 to 20% by mass. . Bulkiness can be obtained by containing 65 mass%-90 mass% of mechanical pulp. When the blending ratio of mechanical pulp is high, the wet paper strength at the time of papermaking becomes low, and paper breakage trouble is likely to occur. In particular, since the printing paper of the present invention has a low basis weight and this concern is great, the wet paper strength is ensured by containing 5 to 20% by mass of softwood kraft pulp, and papermaking operability is improved. If there is more softwood kraft pulp, the texture will be poor and the opacity after printing will be low.

The printing paper of the present invention contains waste paper pulp. A higher recycled paper pulp content is desirable in terms of recycling, but the upper limit is determined by the pulp content and the opacity and whiteness required for printing paper. If the fiber composition of the used paper pulp is determined by JISP8120: 1998 paper, paperboard and pulp-fiber composition test method, the fiber composition of the pulp obtained by releasing the printing paper containing the used paper pulp can be predicted. In the case of newspaper waste paper deinked pulp, the fiber composition (%) of the finished pulp is about NBKP / LBKP / mechanical pulp = 10/50/40.

A filler is added to the printing paper of the present invention. Specifically, it is desirable to add 0.5 to 2.0% by mass of white carbon, and it is desirable to add 10 to 20% by mass of calcium carbonate. Since white carbon has a high ink absorption capability, it contributes particularly to improvement in opacity after printing, and calcium carbonate contributes to improvement in opacity, so that a printing paper with little show-through can be obtained.

In addition, the type of filler used is not particularly limited, and fillers generally used for printing paper such as inorganic fillers such as titanium dioxide, talc, clay and silica, and plastic pigments can be used as necessary. The ash content of the printing paper of the present invention is 5 to 15%. If the ash content is too high, the surface strength becomes low, and paper dust and picking troubles are likely to occur.
Since the filler fills the gaps between the pulp fibers, smoothness can be imparted to the paper without smoothing by calendering, and the ink inking property is improved. Therefore, ink inking property can be improved while maintaining the bulk.

The opacity of the printing paper thus obtained is 87 to 97%, and the opacity after printing is 85 to 95%. More preferably, the opacity after printing is 89 to 95%.
General printing paper has a higher basis weight than newsprint (basis weight 43 g / m ² ), and it is not necessary to consider so much ink penetration. However, since the printing paper of the present invention has a basis weight that is lower than that of the conventional one and is lighter, the influence of ink permeation on the back-through is increased, and thus the opacity after printing becomes important.
Comic paper is printed on an offset rotary press or offset sheet-fed press. The ink drying method is a heat set method using a drying device in a rotary press, and a cold set method without a drying device in a sheet-fed machine. In general, the cold setting method has a larger ink penetration.
As printing paper becomes lighter in the future, the effect of ink penetration on the back-through will increase, so the opacity after printing of printing paper will be important even in heat-set rotary presses. It can be said that it is very important for the sheet-fed machine.
In the present invention, when measuring the opacity after printing, the opacity after printing, which is important for reducing the weight of the printing paper, is measured under more severe conditions by using the newspaper offset ink used in the cold set method, which has a large ink penetration. doing.

The opacity after printing is lower than the opacity. When compared with papers having the same opacity, paper having a smaller difference between opacity and post-printing opacity (opacity−post-printing opacity) suppresses ink penetration in the thickness direction of the paper. It is more difficult to reduce this difference as the paper has a lower basis weight. However, the printing paper of the present invention has the above-described configuration, so that the difference between opacity and post-printing opacity is 3% or less, preferably 2%. It is as follows. By reducing the difference between opacity and opacity after printing in this way, without increasing the opacity excessively, the opacity after printing, which is important for comic paper with a low basis weight, was increased, preventing the show-through. Printing paper can be obtained.
That is, it is possible to prevent adverse effects such as a decrease in strength due to the addition of a filler, a deterioration in ink deposition due to an increase in the blending of mechanical pulp, and a decrease in blending of used paper pulp in order to improve opacity.

In the printing paper of the present invention, a sulfuric acid band, a sizing agent, a paper strength enhancer, a yield improver, a dye, and the like can be added to the raw material pulp. As the sizing agent, a sizing agent such as rosin sizing agent, alkyl ketene dimer, alkenyl succinic anhydride can be used. As the paper strength enhancer, cationized starch, polyacrylamide resin and the like can be used. In addition, additives such as a slime control agent, a pitch control agent, and an antifoaming agent can be used.

The printing paper of the present invention is coated with a surface treatment agent containing a paper strength enhancer on at least one side for the purpose of improving the surface strength. Usually it is applied at the same coating amount on both sides. The coating amount of the paper strength enhancer is 0.5 to 1.0 g / m ² on one side. Since the paper strength enhancer is applied, the surface strength can be increased even when the blending ratio of mechanical pulp and the addition ratio of filler are high. If the coating amount of the paper strength enhancer is less than 0.5 g / m ² on one side, the surface strength is insufficient, and if it is greater than 1.0 g / m ² , no further effect can be expected.

As a device for applying the surface treatment agent, a commonly used roll coater such as a two-roll size press coater or a gate roll coater, a blade coater, or a spray coater can be used.
As the paper strength enhancer to be applied, oxidized starch, cationized starch, polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose, styrene maleic acid copolymer, styrene acrylic acid copolymer and the like can be used.
In addition to the paper strength enhancer, chemicals such as surface sizing agents, lubricants, and anti-slip agents can be mixed and applied to the surface treatment agent.

The coating concentration of the surface treatment agent is desirably 5 to 10% by mass. In order to increase the paper thickness, it is preferable that the coating concentration is low. However, if the coating concentration is lower than 5% by mass, it is difficult to secure the coating amount. If the coating concentration exceeds 10% by mass, uneven coating tends to occur, which is undesirable in terms of surface strength.
The moisture content of the wet paper when applying the surface treatment agent is preferably 5 to 15%, more preferably 5 to 10%. If it is lower than 5%, the rapid expansion of the printing paper in the papermaking process due to a rapid change in the moisture content due to the application of the surface treatment agent will cause wrinkles, and papermaking stability will deteriorate. When the wet paper moisture at the time of application is higher than 15%, the penetration of the surface treatment agent into the paper layer increases, and the moisture content after application increases, resulting in a poor moisture profile and wrinkles. is there.

In the production of the printing paper of the present invention, the paper is usually smoothed by a calender device after being dried by a dryer. As such a calendar device, a commonly used calendar device such as a chilled calendar, a soft calendar, or a gloss calendar can be used. The number of nips, nip pressure, roll temperature, roll material, roll hardness, etc. are set according to the required smoothness.

The basis weight of the printing paper of the present invention is 50 to 60 g / m ² . If it is 60 g / m < ² > or less, it will become a basis weight lower than the conventional comic paper, and it is still more preferable that it is 50-58 g / m < ² >. If the basis weight is less than 50 g / m ² , the thickness or opacity is insufficient, making it difficult to use for comics. The thickness of the printing paper of the present invention is 120 to 140 μm. Preferably it is 120-135 micrometers. If it is this range, as a comic, a hand feeling and the ease of turning of a page will become favorable.

The whiteness of the printing paper of the present invention is preferably 65 to 75%. This range is suitable for comics.
If the whiteness is less than 65%, the contrast with the printed image is weak and the printing effect is low. If the whiteness is higher than 75%, it becomes difficult to ensure opacity at a low basis weight. The smoothness of the printing paper of the present invention is preferably 5 to 20 seconds on both the front and back surfaces, and more preferably 10 to 20 seconds. If the smoothness is low, the ink inking property is inferior, and if it exceeds 20 seconds, the ink inking property is good but the density becomes high, and the thickness required for comic paper cannot be ensured with a low basis weight.

When using the printing paper of the present invention to comics, Clark stiffness (JISP8143: 2009 Paper - stiffness test method - Clark stiffness tester method) horizontal is preferably 20 to 50 cm ^3/100. If less than 20cm ^3/100, to thereby provide an inexpensive impression there is no firm hand Nikkan, less likely to turn the page after bookbinding. After binding and higher than 50cm ^3/100, naturally close tendency to open the book there is a problem that is strongly handling becomes worse.
The range required for the stiffness of the printing paper differs depending on the application. Paper used for flyers and catalogs with a small number of pages requires a hand feeling and is preferred to be more stiff. On the other hand, in the case of printing paper to be bound, the required range varies depending on the book size and the number of pages. Paperback books (mainly A6 size) are relatively small in size and have a large number of pages, so paper with low stiffness is preferred. Weekly magazines and magazines (mainly B5 size, A4 size) are desirable because they are large in size and high in stiffness. For these intermediate size comics (mainly B6 size), when the sheet of a low basis weight of the present invention preferably Clark stiffness transverse described above is 20 to 50 cm ^3/100.

Hereinafter, the effects of the present invention will be specifically described by Examples and Comparative Examples. In addition, unless otherwise indicated,% represents the mass%, and the addition amount is represented by solid content or an active ingredient with respect to 100 mass parts of absolutely dry pulp.

Example 1
White carbon (Maruzumi Engineering Co., Ltd.) was added to the raw material pulp dispersion consisting of 65 parts by weight of thermomechanical pulp (95 ml CSF), 10 parts by weight of softwood bleached kraft pulp (480 ml CSF) and 25 parts by weight of newspaper waste ink deinked pulp (200 ml CSF). 0.5% by mass (made by company), 17% by mass calcium carbonate (made by Okutama Kogyo Co., Ltd., trade name: Tama Pearl 121-6S), and a yield improver (trade name: Hymo Lock ND-260, made by Hymo Co., Ltd.) ) 200 ppm was added to make paper.
Oxidized starch (product name: Oji Ace A, manufactured by Oji Cornstarch Co., Ltd.) dissolved in a wet roll with a gate roll coater to a concentration of 8% is applied to wet paper that has been dried to a moisture content of 11% at a rate of 0.8 g / m ² per side. After being applied to both sides of the paper as described above, it was dried and calendering was not carried out to obtain a printing paper having a moisture content of 6.5%, a basis weight of 59.8 g / m ² , and a whiteness of 70%.

(Example 2)
A printing paper was obtained in the same manner as in Example 1 except that the calendar 1 nip treatment (nip pressure 10 kN / m) was performed.

(Example 3)
Example 1 except that the amount of white carbon added was 2.0 mass%, the amount of calcium carbonate added was 10 mass%, and the coating amount of the surface treatment agent was 1.0 g / m ² per side. A printed paper was obtained in the same manner.

Example 4
The blending ratio of the thermomechanical pulp was 80 parts by mass, the blending ratio of the waste paper deinked pulp was 10 parts by mass, the amount of white carbon added was 1.0% by mass, and the amount of calcium carbonate added was 20% by mass. and it has, and that the coating amount of the surface treating agent was per side 1.0 g / m ^2, except that the basis weight and 56.0 g / m ^2, to obtain a printing paper in the same manner as in example 1 .

(Example 5)
A printing paper was obtained in the same manner as in Example 4 except that the addition amount of calcium carbonate was 20% by mass and the basis weight was 53.0 g / m ² .

(Comparative Example 1)
A printing paper was obtained in the same manner as in Example 1 except that no white carbon was added and the amount of calcium carbonate added was 24% by mass.

(Comparative Example 2)
Example 1 except that no white carbon was added, the addition amount of calcium carbonate was 5.0 mass%, and the coating amount of the surface treatment agent was 0.6 g / m ² per side. Similarly, a printing paper was obtained.

(Comparative Example 3)
Except that the blending ratio of the thermomechanical pulp is 40 parts by mass, the blending ratio of the used newspaper deinked pulp is 50 parts by mass, and the coating amount of the surface treatment agent is 0.3 g / m ² per side, A printing paper was obtained in the same manner as in Example 1.

(Comparative Example 4)
The mixing ratio of thermomechanical pulp is 40 parts by mass, the mixing ratio of softwood bleached kraft pulp is 20% by mass, the mixing ratio of waste newspaper deinked pulp is 40 parts by mass, white carbon is not added, calcium carbonate A printing paper was obtained in the same manner as in Example 4 except that the addition amount of 22 wt% and the coating amount of the surface treatment agent was 0.8 g / m ² per side.

(Comparative Example 5)
A printing paper was obtained in the same manner as in Example 4 except that the basis weight was 49.0 g / m ² .

Table 1 shows the evaluation results of the printing papers of Examples 1 to 5 and Comparative Examples 1 to 5. The test method and evaluation method are as follows.
(Basis weight) JISP 8124: 1998 paper and paperboard-basis weight measurement method (whiteness) JISP8148: 2001 paper, paperboard and pulp-measurement method of ISO whiteness (diffuse blue light reflectance) (fiber composition) JISP8120: 1998 paper, Paperboard and Pulp-Fiber Composition Test Method (Thickness) JISP 8118: 1998 Paper and Paperboard-Thickness and Density Test Method (Ash) JISP8251: 2003 Paper, Paperboard and Pulp-Ash Test Method-525 ° C Combustion Method (Opacity) JISP8149: 2000 paper and paperboard-Opacity test method (paper backing)-Diffuse illumination method (opacity after printing) "Newspaper-Opacity test method after printing" (Japan Tappi paper pulp test method No. 45) The average of the measured values on the front and back surfaces was obtained. In addition, in order to evaluate the penetrability of ink, newspaper ink for offset printing was used.
(Smoothness) JISP8119: 1998 paper and paperboard-Smoothness test method with Beck smoothness tester (Clark stiffness) JISP8143: 2009 paper-stiffness test method-Clark stiffness tester method (surface strength evaluation, ink inking property evaluation) Using an RI printing aptitude tester, solid printing was performed with offset ink, and the dry pick and ink inking property were relatively evaluated in the following three stages. ◎ Excellent ○ Good × Inferior

As shown in Table 1, according to the examples of the present invention, a printing paper having high opacity and post-printing opacity, and excellent evaluation of surface strength and ink landing property is obtained.
In Comparative Example 1, since white carbon was not added, the ink did not stay on the surface, but permeated into the paper and the opacity after printing was low, and the difference between opacity and opacity after printing was 3.3%. It is getting bigger. By setting the added amount of calcium carbonate to 24% by mass, the opacity after printing is 88.7%, which is a fairly high value, but the evaluation of the surface strength is poor due to the high ash content.
In Comparative Example 2, white carbon was not added and the amount of calcium carbonate added was as low as 5.0% by mass, so the ash content was as low as 4.7%. Both the opacity and the opacity after printing were low. The difference between transparency and opacity after printing is as large as 3.1%. In addition to the low ash content, the smoothness is as low as 8 seconds for the front and 7 seconds for the back, so that the ink adhesion evaluation is poor.
In Comparative Example 3, the content of mechanical pulp is as low as 60% by mass and the basis weight is 59.8 g / m ^2. Among the Comparative Examples, the opacity and the opacity after printing are low, The difference in opacity after printing is as large as 3.1%. Moreover, since the coating amount of the paper strength enhancer is as small as 0.3 g / m ^{2 on} one side, the surface strength evaluation is poor.
In Comparative Example 4, the content of mechanical pulp is as low as 55% by mass, and the content of NBKP is as high as 25%, resulting in poor texture, low opacity and opacity after printing, and opacity and post-printing. The difference in opacity is as large as 3.7%. Further, since the amount of calcium carbonate added is as large as 22% by mass and the ash content is as high as 15.2%, the surface strength evaluation is poor.
Comparative Example 5, since the basis weight as low as 49.0 g / ^{m 2,} a thickness of 110 [mu] m, Clark stiffness transverse are as low as 19cm ^3/100, has become unsuitable as comic paper.

The printing paper of the present invention can be preferably used as comic paper, but can also be used for printing paper for other purposes.

Claims (2)

A printing paper containing waste paper deinked pulp having the following characteristics (1) to (7).
(1) The pulp composition is adjusted so that the mechanical pulp in the total pulp obtained by disaggregating the printing paper contains 65 to 90 mass% and the softwood kraft pulp contains 5 to 20 mass%.
(2) As a filler, white carbon 0.5-2.0 mass% and calcium carbonate 10-20 mass% are added, and it is set as ash content 5-15%.
(3) Whiteness 65-75%, opacity 87-97%, post-print opacity 85-95%
(4) Basis weight 50-60 g / m ² , thickness 120-140 μm
(5) A paper strength enhancer is applied to at least 0.5 to 1.0 g / m ^{2 on} one side.
(6) smoothness 5-20 seconds (7) Clark stiffness transverse 20 to 50 cm ^3/100 The printing paper according to claim 1, wherein a difference between the opacity and the opacity after printing is 3% or less.