JPH04361686A - Production of newspaper blank form and the same - Google Patents

Abstract

PURPOSE:To obtain the title blank form excellent. in printability and workability by imparting the surface of a newspaper blank form with low-pressure, mild heated steam to heat and humidify the blank form followed by calendering at a specified range of temperatures. CONSTITUTION:Just before the soft calendering for a newspaper blank form, it is imparted with low-pressure, mild heated steam to heat and humidify its surface, and it is put to calendering, using a soft calendering equipment with its roll's temperature between 100 and 150 deg.C, so as to come to pref. 40-200sec in the smoothness after calendering (determined by an Oken-type smoothness tester, JAPAN-Tappi-No.5), thus obtaining the objective newspaper blank form.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is used in the production of newsprint to achieve a predetermined static smoothness. The present invention relates to a method for producing newsprint, which improves printing suitability (ink receptivity) and improves printing workability (paper dust, tensile strength, etc.), and to newsprint produced by the method.

0002

BACKGROUND OF THE INVENTION In recent years, newspaper printing has progressed from letterpress rotary printing to offset rotary printing, and color printing and increased page size are also progressing.

[0003] In general, the necessary characteristics of newsprint include workability and printability. Newspapers are most disliked due to their breaking news, and the workability of newspapers, such as wrinkles and doubling, is strictly controlled. In addition, the characteristics required for printing suitability are diversifying along with the recent trends toward emphasis on public notices, colorization, and weight reduction. Particularly in letterpress printing, post-print opacity and ink receptivity are issues, while in offset printing, surface strength (paper powder), ink receptivity, and post-print opacity are issues.

[0004] In particular, paper dust poses a very big problem when offset printing uses dampening water. This is mainly caused by fine fibers taken from the surface of the base paper getting mixed into the ink or depositing on the blanket, causing scratches, stains, etc. on printed matter. There are also problems in terms of workability such as blanket cleaning and maintenance. Therefore, in order to solve the problem of printing surface strength, it is generally done by coating the newsprint with starch using a coating device such as a gate roll.

Furthermore, ink receptivity is more often a problem in direct letterpress printing than in offset printing using a soft blanket, but this is due to the surface properties of the paper (smoothness,
Dynamic smoothness under printing pressure), texture, etc. influence this.

[0006] As a measure in the papermaking process to increase the printed surface strength of newsprint, starch coating is carried out as described above, but the calender part, which is essential to the papermaking process, tends to reduce the surface strength. This is thought to be because the calendering process crushes the paper with a certain pressure and breaks the bonds between fibers. In particular, this tendency increases as the calendering process is performed at higher pressure and lower moisture content. Furthermore, the lower the calendering temperature, the more intense pressure is required to finish the paper to a predetermined surface property, resulting in a decrease in surface strength. In addition, other general strength properties (tensile strength,
The rigidity, etc.) also decreases, which has a negative impact on the suitability for tasks such as breaking newsprint.

[0007] Furthermore, when trying to increase the smoothness of newsprint in order to improve ink receptivity, it is still necessary to perform calender treatment at high linear pressure, resulting in the same problem as above. At the same time, the density of the paper increases, leading to a decrease in bulk, opacity, and stiffness, which reduces the printability of newsprint.
This results in poor work suitability.

From the above points of view, as a more preferable calendering method that improves the surface properties by processing with a lower linear pressure, thermal calendering using a high-temperature roll or applying water or heating steam to the paper surface immediately before calendering is recommended. Possible methods include granting. Humidification is generally considered to be more effective than heating in order to improve the surface properties of paper (M. Agrouts; Tappi J. 66
(10), 96 (1983)). Therefore, humidified calendering is considered more advantageous in maintaining surface strength than thermal calendering, since a lower linear pressure is required to finish the paper to the same surface properties. In addition, in the case of humidification by water application, the average moisture content of the paper increases by at least about 1.5%, and the increase in density becomes too large.
Excessive humidification also causes problems such as the adhesion of paper powder to the calender rolls.

[0009] From the above, it is considered most preferable to perform calender treatment using heated steam that has both heating and humidifying effects on paper.

[0010] A method of applying mildly heated steam to paper and then calendering the paper has been developed in recent years, and its effectiveness has been recognized (Japanese Unexamined Patent Publication No. 2-160993). However, this is applied to coated lightweight printing paper, and is fundamentally different from the present invention in the following points.

(1) The newsprint used in the present invention naturally has different surface properties because no coating liquid is applied to the paper. Therefore, when the paper is humidified with steam, the moisture and heat plasticity of the paper surface differ.

(2) In the present invention, the quality improvement described in the present invention is achieved only when the calender treatment conditions after applying steam to the paper are limited to a treatment temperature of 100 to 150°C as described in the above claim. It has been recognized that the same effect can be obtained (the same effect cannot be obtained with the method of JP-A-2-160993).

[0013] Furthermore, it is only possible to carry out calender treatment under the above-mentioned high temperature conditions by using a soft calender having a highly heat-resistant resin roll. The soft calendering method basically combines a metal roll and a soft roll on-machine (sometimes off-machine) and calenders with a small number of nips.The soft roll is coated with a special resin with high heat resistance. In this method, a metal roll is used as a humidifying type.

[0014]

[Problem to be Solved by the Invention] The present inventors have conducted intensive studies to solve the problems of printing suitability and work suitability of newsprint as described above, and as a result, the inventors have found that the paper surface is pre-humidified using heated steam. Moreover, by calendering at a specific temperature after heating, it is possible to improve printability without improving static smoothness as in conventional techniques, and it also enables new printing workability ( printing surface strength,
It is also recognized that tensile strength, stiffness, etc.), bulk, and opacity are improved, and the present invention provides a method for producing newsprint and newsprint obtained by the method, which has unprecedentedly excellent quality.

[0015]

[Means for Solving the Problems] The present invention provides a method for producing newsprint, in which slightly heated steam is ejected at low pressure parallel to the paper immediately before calendering, and after humidifying and heating the paper surface, This is a method for producing newsprint, characterized by soft calendering within a temperature range of .degree.

[0016] The present invention also provides newsprint obtained by the above-mentioned manufacturing method, and further provides smoothness (
JAPAN Tappi No5 Oken type smoothness tester measurement value) is typical of newsprint in the range of 40 to 200 seconds.

A feature of the present invention is that immediately before calendering the newsprint, mildly heated steam is applied to the surface of the paper at low pressure, and the calendering is carried out under specific temperature conditions.

Regarding the steam humidifier, the following problems have been pointed out when it is used continuously in actual equipment. That is, (
1) Steam drain falls or is blown away on the paper surface,
(2) Steam scatters around, condenses on surrounding equipment, and condensed water falls on the paper. (3) There are problems such as steam leaking into the surrounding area and deteriorating the working environment.

In order to solve the above problems, an apparatus has been proposed in which steam is caused to flow parallel to and opposite to the paper by utilizing the Coanda effect. The advantages of this are that the contact time between the paper and steam can be extended, that air can be prevented from entering along with the paper, and that the running stability of the paper is improved.

The main concept of this device is as follows.

The thermal energy of the steam is transmitted by the steam condensing as fine particles on the paper surface due to the temperature difference between the paper and the steam. At this time, if air is present, the air acts as a heat insulator, and the efficiency of heat transfer and reception is significantly reduced. At the same time, the condensed water becomes large particles, and the condensed water adheres to the paper unevenly. , moisture, and temperature variations. By solving these operational problems and improving thermal efficiency, it became possible to use the machine before the calender.

[0022] Conventional calendering is performed at approximately 50-80°C.
In order to obtain the desired surface properties, the paper is crushed under fairly high linear pressure. In order to obtain the same surface quality at a lower linear pressure and to minimize the decrease in print surface strength, it is necessary to improve the surface quality by densifying only the very surface layer of the paper. As a method for this, the so-called temperature gradient calender method has been proposed, which develops surface properties by crushing only the surface layer of paper by heating (
M. F. Gratton et. al. ;Pulp
and Paper Can. ,88(12),
T461 (1987) etc.).

Another method is to crush only the surface layer of paper by humidification. This method has basically the same mechanism of action as the temperature gradient calendar method, with the only difference being that heating or humidification is used. That is, the mechanism is such that only the surface layer of the paper is plasticized by humidification, and then calender treatment is performed immediately to transfer the calender roll surface to the plasticized paper surface.

[0024] These calendering methods are compared with conventional calendering methods, and when paper is finished to the same density (bulk),
Higher surface properties will be obtained.

As a result of intensive research into this humidifying calendar method, the present inventors found that when humidifying with a water shower, the amount of humidification increases (1.5% as the average moisture content of paper).
Calendering greatly improves the surface properties, but at the same time, the increase in density becomes too large, making it impossible to maintain the desired paper thickness. He acknowledged that there would be problems with the roll being taken. The excessive increase in density is thought to be due to moisture penetrating not only the surface layer of the paper but also the middle layer.

This method also has problems such as difficulty in controlling the moisture profile of the paper. It was also found that in this case, water adhering to the paper surface lowered the temperature of the calender roll.

As mentioned above, in order to plasticize the paper surface, it is preferable to treat the calender roll at a higher temperature, but in the humidification method using a water shower, the temperature of the calender roll is lowered, so there is a negative effect. This results in the effect of

From the above studies, the inventors of the present invention have recognized that the humidification method using steam is the best method. Since the steam used in the present invention has a high temperature (100° C. or higher), the paper surface is simultaneously humidified and heated to plasticize it. Therefore, when calendering is carried out immediately after steam humidification, only the surface layer of the paper increases in density and the surface properties are improved, but the density does not increase in the middle layer of the paper, and the average density of the paper as a whole does not increase much, resulting in low lines. Pressure treatment provides a predetermined surface quality, resulting in newsprint with excellent printing surface strength and workability.

Furthermore, if the paper is finished to the same density and bulk as in the case of the conventional calendering method, highly smooth newsprint with excellent ink receptivity can be obtained.

[0030] In addition, prior art (Japanese Patent Application Laid-Open No. 2002-110002) discusses the effects of using a calendering method using steam similar to the present invention.
160993) in the following points. First, in the present invention, the calendering temperature after applying steam to the paper is defined as 100 to 150°C, as described in the above claims.

[0031] In the above-mentioned prior art, by calendering using steam humidification, it is possible to improve the Oken type smoothness (static smoothness) while minimizing the increase in paper density and the decrease in bulk. It is argued that it is only through this that it is possible to improve printability. However, according to this method, the dynamic smoothness is improved even if the Oken type smoothness does not change, making it possible to improve the printability.

Furthermore, in the above prior art, the bulk (reciprocal of density),
While stiffness and opacity tend to decrease, the method of the present invention improves bulk, opacity, and rigidity, and can also improve printing workability (printing surface strength, tensile strength). Admitted.

[0033] The reason for this is that the mechanism of the appearance of paper surface properties is influenced by complex factors such as paper's plasticity against heat and moisture, paper's thermal conductivity, elastic modulus, paper layer structure, and elastic roll's elastic modulus. Although it is not certain because it is thought that
The following differences can be considered as the main reasons.

First, when the calendering temperature is 100°C or less as described above, the temperature of the calender roll is lower than the temperature of the surface layer of the paper, so the temperature of the surface layer of the paper, which has been heated in advance by steam, is reversed. This results in a negative effect on the effect of plasticizing only the surface layer of the paper, and as a result, even if the paper is finished to the same density, the Oken type smoothness will not improve.

[0035] Furthermore, when processing at a high temperature of 150°C or higher, heating and humidification by steam become excessive, and although the surface properties are greatly improved due to the synergistic effect, the density increases extremely as described above. The result is a reduction in bulk, opacity, and stiffness.

According to the method of the present invention, one of the
By processing at higher temperatures, the same Oken type smoothness (
Static smoothness) can be processed with low linear pressure,
Improves bulk and opacity. Furthermore, since the paper does not need to be subjected to strong ironing, the stiffness, tensile strength, and printing surface strength are improved (there is no effect at all below 100°C). Note that the temperature of the roll of the soft calender is preferably set higher than the temperature of the paper.

[0037] Further, calendering at the above-mentioned high temperature becomes possible only by employing a soft calendering method having a special resin roll having excellent heat resistance and pressure resistance. This is because in the case of commonly used super calendars, the internal heat generation of the elastic cotton roll is large and there are limits to heat and pressure resistance, so the maximum operating temperature of the roll is generally limited to approximately 85°C or less. This is to be done. In addition, in the case of gloss calenders commonly used in the manufacture of paperboard, the metal roll side can be used at high temperatures of over 100°C, but the rubber rolls, which are elastic rolls, have significantly inferior durability and are generally used in high-speed paper machines. Not applicable to coaters. Therefore, it is only possible to use the calender at high temperatures and pressures by using a soft calender having a special resin roll with excellent heat resistance and pressure resistance.

The device of the present invention for jetting a low-pressure, mildly heated steam stream onto paper includes a device that jets steam parallel to the paper;
A device that sprays water from a nozzle onto the paper surface at a fixed angle.
Any device can be used as long as it allows steam to adhere to the paper surface and adjust the temperature and moisture of the paper to an appropriate level.

The steam used in the present invention is low-pressure, mildly heated steam, and when applied to paper, the steam pressure used is 1k.
g/cm2 or less, steam flow rate is 15 to 80 kg/Hr
It is desirable to apply steam within the range of paper moisture increase rate of 0.3 to 1.2% with a width of /m. The reason for this is that, as mentioned above, if the vapor pressure is high and the flow rate is too large, excess moisture will penetrate into the middle layer of the paper, greatly reducing the bulk after calendering. Furthermore, if the amount of vapor adhering to the paper is too large, there will be a problem in the case of coated paper that the surface of the coating layer will be taken away by the calender roll. On the other hand, if the steam flow rate is too small, there is a risk of uneven paper smoothness and gloss, and the effects of humidification and heating will be reduced, and the effect of improving smoothness and printability will also be reduced.

[0040] Therefore, as appropriate moisture imparting conditions, it is desirable to apply steam so that the paper moisture increase rate is within the range of 0.3 to 1.2%.

[0041] The time after steam application until it enters the calender roll nip should be as short as possible, and should be between 0.01 and 0.
．． It is desirable that the time be within the range of 25 seconds. If the time is longer than this, steam particles will penetrate into the middle layer of the paper, greatly reducing the bulk after calendering.

Further, as a result of this study, it was found that the hardness of the elastic roll used is preferably within the range of Shore D 87 to 93.

Although the reason is not clear, when the hardness of the elastic roll is lower, the nip width becomes wider and the surface pressure against the paper becomes larger. In this case, the time required to transfer the surface of the metal roll onto the paper surface becomes longer and the linear pressure becomes smaller as opposed to the surface pressure. The Oken type smoothness, which measures smoothness close to the surface, does not show much of an improvement.

On the other hand, when the elastic roll hardness is high, the nip width is narrow and the linear pressure applied to the paper is high, so it is thought that the improvement in Oken type smoothness will be large. However, if the roll hardness is excessively high, the roll will be damaged when foreign objects pass through it, and its recovery performance will be poor, making it impractical.
There is no difference between this method and the calender method, which uses a combination of metal rolls. Therefore, it is necessary to use an elastic roll with a suitable hardness range.

The newsprint of the present invention has a basis weight of 40 to 5.
Smoothness after calendering (J
APAN Tappi No. 5 Oken type smoothness tester measurement value) is typically in the range of 40 to 200 seconds.

[0046] Furthermore, the newsprint of the present invention contains additives commonly used in paper making, such as a sizing agent, a dry paper strength enhancer, a wet paper strength enhancer, a fixing agent, and a yield improver, as required.

As described above, the present inventors have conducted various studies on the calendering method using heating or humidification as a means of plasticizing only the surface layer of paper, and as a result, the present inventors applied mild heated steam at low pressure to the surface of newsprint, After humidifying and heating the paper surface, soft calendering is performed at a specific temperature range.
It is now possible to improve printability without improving static smoothness as with conventional technology, and new printing workability (printing surface strength, tensile strength, stiffness, etc.), bulk, and opacity can also be improved. It was also recognized that newsprint of unprecedented quality could be obtained.

[0048]

[Example] Examples of the present invention are shown below.

[0049] For calendering, a 2-stage soft nip consisting of a combination of chilled rolls and resin rolls is used.
Using a stack of soft calenders, before each nip, use a humidifier (steam foil from Aikawa Tekko Co., Ltd.) so that steam is ejected onto the paper surface on the side that hits the chilled rolls.
was installed and the following experiment was conducted.

[0050] Details of the soft calender used in the present examples and comparative examples are as follows.

Main unit manufacturer: Minamisenju Seisakusho Co., Ltd. Roll surface length: 1050 mm Heating roll: Induction heating jacket roll (manufactured by Tokuden)
Soft roll: Eraglass RE (manufactured by Kinyosha) Shore hardness D89, etc. Example 1 Newspaper with a basis weight of 48 g/m2, steam pressure used of 0.8 k
Steam was applied under constant conditions at a width of g/cm2 and a steam flow rate of 50 kg/Hr/m, and calendering was performed so that it entered each calender nip after 0.03 seconds. At that time, the calender roll temperature was 120°C.

Comparative Example 1 Calendar treatment was carried out under the same conditions as in Example 1 above, except that the calender roll temperature was 70°C.

Comparative Example 2 No steam was used and the calender roll temperature was 70°C.
All the same as Example 1 above except for calendering at °C.
Calendar processing was carried out under the same conditions.

<Quality evaluation method> Static smoothness: JAPA
Measured using N Tappi No5 Oken type smoothness tester.

Dynamic smoothness: Expressed as roughness in μ units using a Parker Print Surf surface roughness (PPS) meter (model PPS-78, manufactured by Nomura Corporation). The smaller the number, the higher the dynamic smoothness.

- Printing surface strength (paper powder): After printing 1000 sheets of B4 size samples using a Roland offset printing machine, the paper powder deposited on the blanket was collected, quantified, and expressed in mg.

- Ink receptivity: After printing using a letterpress printing machine (Kurosawa Printing Seiki Delmax Printing Machine), the uniformity of ink coverage on the printed surface was visually judged on a five-point scale.

- Stiffness: Measured using a Clark stiffness tester according to JIS P-8143.

- Tensile strength: Measured using a JIS P-8114 Schopper type tester.

・Opacity (%): JIS P-813
Measured according to 8.

[0061]

[0062]

[Effects of the Invention] As is clear from the table, unlike the conventional steam humidification calendering technique, the calendering conditions after applying steam to the paper are as described in the above claims, and the calendering temperature is set at 100 to 150°C. By the method of the present invention, which performs defined soft calendering, the dynamic smoothness is improved even if the Oken type smoothness is not changed, so that it is possible to improve the printability (ink receptivity). Furthermore, the bulk and opacity are improved, and new printing workability (paper powder, stiffness, tensile strength) can also be improved.

[0063] Therefore, the newsprint produced by the newsprint production method of the present invention has excellent quality characteristics never seen before, and its product value is extremely high.

Claims (3)

[Claims] Claim 1. In a method for producing newsprint, immediately before soft calendering of newsprint, mildly heated steam is applied at low pressure to humidify and heat the paper surface, and then the temperature of the soft calender roll is 100 to 150°C. 1. A method for producing newsprint, characterized in that calendering is carried out using a soft calendering device within a range. 2. Newspaper produced by the production method according to claim 1. [Claim 3] Smoothness after calendering (JAPA
3. The newsprint according to claim 2, wherein the N Tappi No. 5 Oken smoothness tester measurement value is in the range of 40 to 200 seconds.