JPS62177299A - Light weight printing 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 is suitable for printing paper, various types of printer paper,
That is, it relates to a relatively bulky, lightweight printing paper that has printing suitability, paper passing suitability, printing suitability, etc.

More specifically, it relates to a bulky, opaque, and smooth lightweight printing paper made of pulp with a thick fiber wall, such as bleached pulp from southern American hardwoods such as white oak and red gum, and a filler with a low specific gravity, such as a urea resin filler.

[Prior art]

Printing, impact printing, non-impact printing, etc. are methods for recording and transmitting information such as letters and designs on paper, and these methods include gravure printing, offset printing, dot-in-bact gelling, digital printing, etc. Methods include inkjet printing and thermal transfer printing. The paper used for each of these mechanical devices is high-quality paper or plain paper with a basis weight of 65.
~1009/rt are widely used.

In recent years, there has been a social demand for reducing the basis weight of paper due to reductions in material costs, transportation costs, storage volume, and other factors.

[Problem that the invention seeks to solve]

However, if the basis weight of the paper is reduced, the thickness becomes smaller and the stiffness becomes weaker, making it impossible to satisfy paper passing suitability. Various methods have been proposed to solve this problem. For example, Japanese Patent Application Publication No. 54-50605 (% Publication No. 57-1368
No. 0) disclosed a method of agglomerating oblique particles and blending them into paper stock to form thick internal voids in the paper web.

In addition, an inner horizontal paper with excellent rigidity and opacity that contains calcium carbonate of a special shape has been proposed (Japanese Patent Publication No. 56-44198). However, in practical terms, the paper preferably has a smoothness of 50 to 300 seconds (Beck smoothness, hereinafter the same) for offset printing paper, and 8o for gravure printing paper.

It is said that about seconds is preferable. Furthermore, it is said that a smoothness of about 50 to 100 seconds is preferable for various types of printer paper in order to prevent the occurrence of misdots during recording and ensure reproducibility of halftone dots.

In order to meet these demands, it is necessary to smoothen the papermaking base paper using a calender, but since the invention disclosed above relies only on the pore structure of the base paper, the effect is significantly lost compared to calendering. Therefore, at present, low-density, low-smoothness paper, in which the base paper is hardly calendered, or high-density, high-smoothness paper, in which the base paper is calendered, are manufactured and coated only for applications that can withstand their use, and are universally available. A paper with low density and high smoothness that can be used for this purpose has not yet been provided.

[Purpose of the invention]

In view of the problems of the prior art, the present invention has a basis weight of 25 to 60.
17/m'' printing paper, the density K O, 7Vcr/, which is considered to satisfy the above-mentioned paper passing suitability, is as follows: 50
The purpose of the present invention is to provide a white, opaque, lightweight printing paper having a smoothness of at least 2 seconds.

[Means for solving problems]

First, as a result of repeated research on the relationship between the bulk of base paper and the bulk and smoothness of paper, the inventor selected bleached pulp with a thick fiber wall and a bulky filler, and used these as essential ingredients. It was discovered that, depending on the skeletal structure of the base paper, it is possible to obtain a bulky base paper with a void structure added thereto. Secondly, as a result of repeated research on the method of calendering (also referred to as calendering), specifically the conditions for adding moisture to base paper during calendering, we found that we performed moisture coating calendering, which will be described later. After beating each of the pulps listed in columns 1 and 2 of Table 1 to 30°SR to minimize the decrease in bulk, the basis weight was 5.
When the base paper was made using a sheet machine at 0 g/rrl and the density was measured, the paper using the pulp listed in column 1 was 0.
．． 63 to 0.66 Vcd, but those using the pulp described in column 2 showed a lower value of 0.55 to 0.60 E//crd.

In addition, as a filler, urea resin-based pearl ■l (manufactured by Mitsui Toatsu Chemical Co., Ltd., primary particle size 0.1~lμvm, secondary particle size 8~
A comparison was made using K, which had 10 to 20% (solid content weight ts, same hereinafter) added to the pulp (solid content weight ts) (specific gravity 1.45) to 12μ. As the amount of filler added increased, the density of each base paper gradually decreased, but the difference in density due to 2W/D still existed. Considering the decrease in density due to filler addition, the present invention uses pulp with a 2W/D of 0.55 or more.
Pulp with a molecular weight of 0.6 or more is preferred. When thick-walled pulp is used in this way, the bulk of the paper tends to depend more on the base paper, so even if it is calendered by a normal method, it will be bulkier than paper blended with the prior invention or the control pulp. You can get paper. In addition, 0.0 as referred to in the present invention.
2W/D value of 55 or more is 9 according to the measurement method described above, and if the average value of 2W/D of the blended 9 pulps is 0.5
This does not exclude the use of pulps of 5 or less. The beating degree of the pulp can be carried out in the range of 15 to 60°SR, but it is 30
~40°SR is often used. The basis weight of paper is 25~
6011/rrl can be provided, but 40~559/
rrt is often used. As pulp, 2 in Table 1
As shown in the column, both KL pulp and N pulp can be used, but L pulp is preferable because it makes the paper easier to form.

When N-wood pulp is used, it is preferable to use one having thicker fiber walls than North Pacific wood, such as American southern pine.

In some cases, it is possible to increase the bulk by adding mechanical pulp such as thermomechanical pulp, ground wood pulp, waste paper pulp, or recycled pulp, but since the strength and printability are inferior, the combination of 20%
% or less.

(Filler) As the filler, mainly organic or inorganic fillers having a specific gravity of 1.0 to 2.0 are used. As an organic filler, urea resin filler (
Specific gravity 1.45), foamed resin (specific gravity 1.10), plastic pigments such as polystyrene, and as inorganic fillers, synthetic silica (specific gravity 1.95), nacreous materials, etc. can be used. The reason why the specific gravity is limited to 1.0 to 2.0 is that materials in this range are suitable as bulking materials for paper. The particle size may be within a range that can be used as an internal additive in paper manufacturing, that is, an average particle size of 1 to 20 μm. Although white fillers are usually used, colored fillers may also be used depending on the purpose. The various fillers described above can be used alone or in combination. The amount of filler added is 20% of the filler content in the base paper that is made.
Adjust so that the opacity is 80 or higher. When the filler ratio is 20% or more, the contribution rate of the void structure increases, and the volume tends to decrease significantly due to calendering.

Among the fillers mentioned above, the filler with the best bulking properties, opacity, yield, etc. is the urea resin filler.

The urea resin filler is produced, for example, by the method disclosed in JP-A-54-135893. In this method, after mixing formaldehyde aqueous solution, urea, carboxymethyl cellulose and water, the pH is adjusted to 7 with caustic soda water,
The reaction yields an initial condensate. This initial condensate liquid is continuously mixed with several liters of sulfuric acid aqueous solution using an in-line mixer, and before the mixture begins to solidify, it is fed onto an endless belt of acid-resistant rubber, and the mixed liquid solidifies on the belt. .

Water is added to the solidified product obtained in this way, the mixture is stirred to form a slurry, and after being neutralized, it is finely pulverized in a colloid mill to form a dispersion of cross-linked urea formaldehyde polymer powder (
Filler dispersion) is obtained. The product form is a cake-like product with a solid content of, for example, 25 ts, which is obtained by dehydrating this product by f. Furthermore, a method for recovering and utilizing dehydrated waste fluid is also disclosed (
(Japanese Unexamined Patent Publication No. 57-53519), quality characteristics and product form are the same as above. In addition, in order to improve the strength while maintaining the bulk and opacity of the paper, 40% or less of the filler specified in the present invention may be replaced with other fillers such as precipitated calcium carbonate (specific gravity 2.6 to 2.8). One of the preferred embodiments of the present invention is to use it as such. If it exceeds 40%, the bulking effect of urea resin fillers and the like is likely to be hindered. There are no restrictions on the crystal form or particle form, and any of calcite, aragonite, block form (Japanese Patent Publication No. 44198/1983), etc. can be used.

(Method for producing base paper) Pulp is prepared by beating L material pulp alone or by mixing it with a required amount of N material pulp, or by mixing the separately beaten products of each material to obtain a pulp paper stock with a beating degree of 15 to 60"SR. A predetermined filler is added to the paper stock, which is then made into paper with a basis weight of 25 to 601/rrl using a Fourdrinier paper machine.The paper stock is made with a number of additives that improve paper strength, printability, writability, yield, etc. For this purpose, neutral sizing agents such as alkyl ketene dimer-based and petroleum resin-based sizing agents, other acidic sizing agents, cationized starch, cationized polyacrylamide, and other ordinary internal additives can be added. Also, starch, casein, gelatin, etc. A known surface sizing agent such as , polyvinyl alcohol, or a waterproofing agent can be applied using a size press, an on-machine coater, etc. The surface sizing agent is usually applied at 0.3 to 31/rrl per side of the paper. paper weight 2-6
Adjust the paper to the correct size and use it as base paper. The density of the base paper produced in this way varies from υ0.5 to 0.617 cr depending on the composition of the paper stock.
d bulky product is obtained.

(Moisture-coated calendering) The base paper used in the present invention employs the moisture-coated calendering method described below, which results in a smooth and bulky paper with less volume loss than normal calendering. be able to. It is generally known that increasing the nip pressure, passage time, moisture content, temperature, etc. of calender cooling reduces the bulk of paper.

Furthermore, the smoothing effect of a calendar is explained as follows for printing paper containing groundwood pulp (S-8e
hmldt and R-Kirbis, The role of temperature in the flattening process of paper webs, Guochien Platfahr Aprication 23/24, 1979.

P, 933-P, 940). To summarize, 1) The glass transition temperature of cellulose and lignin present in the outer layer of the paper web is significantly lowered in the presence of water. For example, the glass transition point of pure cellulose in a dry state is 220°0, but upon crystallization containing 5% moisture, the glass transition point of pure cellulose at 55% drops to about 100°0. In addition, the glass transition point of lignin is 80 to 90° in the presence of water.
It is 0. Above the glass transition point, the surface of the base paper becomes plastic and becomes susceptible to the smoothing effect of linear pressure. However, if the temperature of the base paper is too high, this effect is no longer confined to its outer layers, and experience shows that opacity, porosity, whiteness, picking strength, etc. are impaired. For this reason, calendering is usually operated at a maximum roll surface temperature of about 95°0. 2) When the linear pressure is constant, the higher the roll surface temperature, the higher the smoothness can be obtained, and the smaller the decrease in bulk. Therefore, K, which has a certain level of smoothness, can prevent a decrease in bulk by increasing the roll surface temperature and reducing the linear pressure.

3) Even when the rolls are not heated, the desired smoothness can be obtained by the crushing action, but the volume decreases significantly compared to when the rolls are heated.

However, the S-8e5-8eh and RsKlr
With BIM, the temperature-moisture effect mentioned above is effective only when the customer requires a high smoothness of 800 seconds, such as gravure printing paper, and when the required smoothness is low (100 seconds), such as offset paper. ~300 seconds) K states that it is difficult to control smoothness and bulk. For example, roll temperature 30-60゛0, linear pressure 180-210
It is said that a smoothness of 100 to 300 seconds is obtained with an input moisture content of 6 to 8% and an exit moisture content of 4 to 6%, but the base paper is compressed over the entire profile.

The present inventor focused on moisture coating calendering mainly for the purpose of obtaining lightweight printing paper with a smoothness of 50 to 300 seconds. Moisture coating calendering refers to applying moisture during calendering so that the moisture on the paper surface is high and the moisture inside the paper layer is low. Generally, when water is added to the paper surface, the water begins to seep into the paper after a certain wetting time. This wetting time is the time during which water flows into the recesses on the paper surface and the time during which the fiber surface is chemically wetted.

Therefore, if the paper passes through the roll nip during this wetting time, the paper surface will decrease in volume with a smaller amount due to the lowering of the glass transition point of cellulose, etc. in the outer layer of the base paper, which has increased moisture, or the softening of the pulp fibers that have absorbed moisture. Smoothed. The wetting time is controlled by the manufacturing conditions of the base paper, especially the amount of surface sizing agent in the base paper, and is calendered within 10-100 milliseconds after application of moisture. As mentioned above, the surface sizing agent is 0.3 to 3 per side of the paper web! il/m (solid content, hereinafter the same) is applied. If it is less than 0.31//rrl, the coating water will easily permeate into the inner layer and the coating operation will be difficult. Also 3
g/? If it exceeds the above range, the water absorption of the pulp fibers will be hindered, making it difficult to plasticize the fibers, making it difficult to achieve the effects of the present invention. The preferred amount of the surface sizing agent is 0.5 to 21/m'' per side.The surface sizing agent has the above-mentioned effect, and the hydrophilic surface sizing agent itself swells and improves smoothness. Therefore, it may be possible to increase the smoothness by adding a part of the surface sizing agent to the coating moisture.The amount of moisture to be coated varies depending on the condition of the paper surface, and mainly reduces the amount of moisture present on the paper surface. It can be calculated from the number and volume of recesses, but
In practice, a moisture content of 91 to 10 fi/rrl is applied to one side. 0.0 from the viewpoint of coating equipment, ease of coating work, etc.
A water amount of 5 to 5 Vnl is suitable. There are no restrictions on the coating device as long as it can uniformly add water. A roll coater is preferred, but a method in which water is discharged under pressure through a slit or nozzle, a dew-blowing method, etc. can also be used. Heating during calendering is usually carried out at a roll surface temperature of 80 to 150°0 in order to plasticize and dry the cellulose and the like. However, the method of the present invention is effective even at room temperature in some cases. The pressure conditions are the roll's own weight or 40 kg.
This can be done with a linear pressure of ycIIL. By using the base paper specified by the present invention and performing moisture coating calendering, the density can be reduced to 0.71/cd or less, especially 0.55 to 0.6 s.
l1cr& smoothness is 50 seconds or more, especially 100-30
You can walk around the paper for 0 seconds.

The moisture application using a calendar has been described above, but it goes without saying that the calendar may be either a paper machine calendar made of chilled rolls or a supercalender made of chilled rolls and elastic rolls. In the paper manufacturing industry, various mechanical devices for smoothing paper are known, such as those using chrome-plated heating cylinders, and one-gross calenders that combine calender rolls and large-diameter heating cylinders. It includes any method as long as it falls within the scope of the technical concept.

〔Effect of the invention〕

The present invention is characterized by: (1) pulp with a thick fiber wall was used as pulp, so the skeletal structure of the base paper itself became bulky; (2) addition of filler that contributes to the void structure was kept to a minimum; It is possible to make base paper with high compression resistance.

In addition, the moisture added to the base paper by moisture coating calendaring remains on the base paper surface9 and passes through the roll nip before seeping into the interior, so only the base paper surface becomes plastic and has a high density, while the inner layer has a low density. An effect can be obtained in which the structure of the base paper is hardly destroyed. That is, the present invention has a three-layer structure in which the front and back sides of the paper are high-density and the inner layer is low-density, and this makes it possible to provide a lightweight printing paper that is bulky and low-density as a whole. The lightweight printing paper of the present invention can be universally used in the various printing methods described above, but is particularly suitable for rich multicolor printing.

[Example 1] LB of southern American wood such as white oak and red gum
After beating KP Alabama River (trade name, manufactured by Alabama Reper Pulp Co., Ltd., fiber wall/fiber width ratio 0.667) to 30'SR, a urea resin-based organic filler with a secondary particle size of 8 to 12 μm was used. 901 (manufactured by Shinsan Kagaku Co., Ltd.) as a neutral sizing agent was added to 0.5% of the pulp as a neutral sizing agent.
After adding 1.0% of Polystron (81PS619 (manufactured by Fubuyou Rinsan Kagaku Co., Ltd.) as a paper strength enhancer, paper was made using a sheet machine with a target basis weight of SO9/rn: , 5511/rr? and dried.

Corn starch 5K-100 as a surface sizing agent
(I1 product name, manufactured by Nippon Corn Starch) 4% concentration, polyvinyl alcohol (Denkasaisu A-50, manufactured by Denki Kagaku) 1.17% concentration, surface sizing agent MS-501 (trade name, manufactured by Sanyo Kasei) 0.18% concentration , a total of 5.35% aqueous solution was prepared. The solid content of this paper was reduced to 0.0% by using the sheet machine paper VCf'' size press machine.
A base paper was prepared by uniformly coating 51 layers each on the front and back sides and drying.

Table 2 shows the necessary physical properties of the base paper. This base paper was heated on one side at a point 70 milliseconds before the nip between the chilled roll and asbestos roll of a test supercalender D29/
rrl of water using a gravure roll at a speed of 200 m.
1t.

After adhesion, the finished paper was passed through a roll nip at a linear pressure of 20 kg/2 and a roll surface temperature of 140°0. The paper quality is shown in Table 2.

Table 2 According to Table 2, there was only a slight decrease in bulk (increase in density) of the finished paper, and a paper with high smoothness and opacity was obtained. When the cross-sectional structure of the finished paper was observed using an electron microscope, it was confirmed that it had a three-layer structure consisting of a high-density outer layer and a low-density inner layer. The finished paper of this example was tested using a Fogura printability tester and good results were obtained. On the other hand, when the base paper of 55111rr1 in Table 2 was processed under normal calendering conditions of 50° and 0.20 kg/cIrL without any moisture coating, the density was 0.68. S! Drip smoothness 7
A finished paper of 0 seconds/1 oad was obtained. This shows that if the base paper specified by the present invention is used, it is effective without special calendering operations, and that the effect is further enhanced by moisture coating. By the way, the density of commercially available lightweight printing paper is 0.64 ~
At 0.6517 cd, the smoothness is low at 40 seconds/10 d@.
It was difficult to recognize that the cross-sectional profile structure was differentiated into three layers.

Claims (1)

[Claims] (1) For printing paper with a basis weight of 25 to 60 g/m^2, the average ratio of fiber wall thickness to fiber width is 0.55.
A filler with a specific gravity of 1.0 to 2.0 is mainly dispersed between the above pulp stock, and the density is 0.7 g/cm.
A lightweight printing paper characterized by a smoothness of ^3 or less and a smoothness of 50 seconds or more according to the Beck method.