JPH10212684A - Finishing of paper and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject device having a calendering device and a brushing and spraying device which are mutually independently driven, capable of transferring liquid mist imparted to the transfer roll of the calendering device to a web, capable of improving the stiffness of the web, while minimizing the losses of the thickness and volume of the web such as a paper board. SOLUTION: This method for finishing paper comprises using at least one roll of a calendering device as a transfer roll, disposing a brushing and spraying device at a place just adjacent to the transfer roll, and imparting liquid mists to be imparted to a web in a transfer nip to the surface of the transfer roll. The calendering device and the brushing and spraying device can mutually independently be driven to control the amount of the liquid mists imparted to the transfer roll without relating to the operation characteristics of the calendering device. The minimum amount of water can uniformly be imparted to the web to highly compact and stiffen only the outside layer of the web by a calendering operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the finishing of paper and paperboard. More specifically, the present invention provides a conventional waterbox calender for finishing paperboard to improve stiffness or stiffness while minimizing loss of thickness or bulk. Regarding improvement.

[0002]

2. Description of the Related Art It is common practice in the papermaking industry to impart moisture to a paper web during mechanical calendering in the papermaking process. Although other methods have been proposed as a method for imparting moisture, a method using water box calendering is used as the most common method. A typical example of a conventional water box calendar is, for example, Fletch.
er) in U.S. Pat. No. 2,130,530. However, an inherent problem with the use of a water box calender is that the amount of liquid drawn up by the web at the calender nip is uncontrollable. In conventional waterbox calendering, the amount of liquid supplied to the calender nip is such that the nip is submerged. For this reason, the amount of liquid sucked up by the web depends on the calender roll diameter, operating speed,
It depends on the calender nip pressure and the properties of the web (thickness, sizing level and roughness). Therefore, the amount of water applied to the web using a water box calendar cannot be controlled independently of the operating characteristics of the calendar. The operating characteristics of the calendar are selected to achieve the desired paper or paperboard characteristics. For example, a typical papermaking machine is used to obtain a predetermined range of paper thickness or basis weight. However, if the operating characteristics of the water box calendar are selected to provide the desired paper characteristics for a particular basis weight, the operating characteristics are not suitable for products of other basis weights. This is a decisive drawback. Because the stiffness of the paper web depends on the fiber densification rate during calendering.
on), and it is known to be related to the moisture content of the web during calendering. In this connection, during calendaring, especially during waterbox calendaring,
As the density of virtually similar structures such as paper and paperboard increases,
Generally, the stiffness decreases. On the other hand, when the densification rate is controlled, for example, in the case of a composite structure, the outer layer has a higher elastic modulus than the central layer, and the density increases until the so-called I-beam effect is obtained. If
The stiffness can be improved. Thus, for a typical papermaking machine, a method for moistening the web prior to mechanical calendering to obtain the I-beam effect compared to what is currently possible by using a conventional water box Thus, it is desirable to provide a more flexible method.

[0003] Other methods for imparting moisture to the paper web include using steam or spraying water. Although it is possible to use steam in the web to increase its moisture content, it is necessary to cool the web so that the steam is sufficiently liquefied. Furthermore, in addition to the need for a device to cool the web, it is difficult to liquefy the amount of water vapor required to achieve a smoothness comparable to that achievable by waterbox calendering. . Spraying the liquid directly onto the web is another way to increase the moisture content of the web. However, conventional spray systems for spraying water directly onto the web do not have the uniformity required to form a smooth surface. In addition, the lack of cross direction uniformity and the occurrence of wet streaks due to the overlap of spray water from adjacent nozzles, the non-uniformity in smoothness and thickness distribution Cause. A third method for applying moisture to the web is to apply the liquid directly to the web using an offset roll or the like. An example of this method is described in U.S. Pat.
No. 73,441. Disclosed herein is an apparatus for applying a liquid or plasticizer directly to a web by an offset method and then calendering to achieve a compression gradient in the web. However, in this method, as in the case of using steam, it is necessary to add a predetermined device to the papermaking machine before performing the mechanical calendar. It is also known that in practice such offsetting devices are not sufficient to achieve a uniform cross-directional moisture distribution on the web.

[0004]

Thus, while the use of a water box calendar is generally considered to be a preferred method for moisturizing a paper web, the problems inherent in conventional water box calendering are still solved. Must be done. In addition, other conventional methods, known as methods for applying moisture to the web, are less capable. Nevertheless, it is useful to produce the same structural characteristics (i.e., the I-beam effect) within virtually the same type of structure, such as paper, paperboard, and the like. Such properties can be achieved in a composite structure having an outer densified layer and a large volume inner layer. Now, the goal is to uniformly apply a minimum amount of moisture across the web and in the direction of calendering, only the outer layers of the web are densified (similar to a composite structure), The stiffness is thereby improved. This result is achieved by practicing the invention. In the present invention, the means for imparting moisture to the web is of a new type, in particular, a brush sprayer capable of generating water mist. This brush spray device is disclosed in U.S. Pat. No. 5,314,119, whose spray volume can be controlled independently of the operating characteristics of the calendar. Accordingly, the novelty of the present invention is that the water box commonly used for mechanical calendars has been replaced with a brush sprayer to achieve the desired results. The brush spray device will be described in detail below.

[0005]

SUMMARY OF THE INVENTION A modification of an existing water box calendar to include a brush spraying device as disclosed herein provides for a calender roll diameter, operating speed, calender nip pressure, or substrate characteristics. Independently controls the amount of liquid applied to the surface of the substrate, thereby
A means is provided by which the final product with increased stiffness while maintaining volume can be achieved. By replacing the water box adjacent to the transfer roll of the mechanical calendar with a brush sprayer, a minimal amount of moisture can be applied to one or both sides of the web. This results in a stiff web having a densified thin surface layer and a large volume of inner layer when compressed in a calendar device.
In this way, an amount of liquid is applied to the web that does not exceed the amount needed to achieve the desired smoothness. This method reduces the occurrence of damage to the web due to uncontrolled watering from a conventional water box, while reducing the amount of product that would normally be possible using a conventional water box calendar. To produce products with a wide range of basis weights. Thus, in the present invention, it is possible to control the location and depth of the impregnation of moisture into the substrate, thereby reducing the thickness loss during calendaring, while at the same time increasing the desired stiffness with improved stiffness. Can be produced.

The present invention relates to bleached or unbleached paper and paperboard,
In particular, it is applicable to the production of high-rigidity grade paper and paperboard. The increased rigidity grade provided by the present invention provides additional opportunities for reducing the fiber content of the web in papermaking machines, thereby reducing costs. The paperboard or cover and label grade paper used in the manufacture of the container is a product that can benefit from the practice of this invention.

[0007]

DETAILED DESCRIPTION The following is the best mode currently conceivable in the practice of the invention. This description has been made in order to explain the general principles of the present invention and should not be taken in a limiting sense. The scope of the present invention is limited only by the appended claims.

The present invention can be practiced with a typical calender having a plurality of nip rolls arranged in a row, that is, a calender of the type previously used in waterbox calendering of paper and paperboard webs. The invention may also be practiced with other so-called non-conventional calendaring devices, such as the one shown in U.S. Pat. No. 4,670,102, owned by the present assignee. It is. Regardless of the shape of the calendar, the essence of the invention resides in the use of a brush spray type watering device instead of the typical waterbox used in the past. Examples of brush sprayers that can be used in the present invention include Latanic Equipment, Inc.
k Equipment, Inc. ). In this regard, see "Method and Apparatus for Applying Thin Coatings of Fluid Droplets (Method
and Apparatus for Applyin
g Thin Coings of Fluid Dr
opplets) in US Pat.
No. 119, the disclosure of which is incorporated herein by reference. Other brush spray devices are known. For example, U.S. Pat.
No. 069,063.
However, the Latanic device and U.S. Pat.
In any of the devices shown in No. 3, moisture is applied directly to the substrate web. When moisture is provided in this manner, it is difficult to achieve a uniform moisture distribution, especially in the width direction of the web. For this reason, in contrast to such known watering methods, the brush sprayer used in the present invention applies water to a transfer roll of a calendar device and transfers the water to a web at a transfer nip. Are located in
In operation, the brush spray device used here is operated independently of the calendar device, and the amount of water applied to the transfer roll is controlled independently of the operating characteristics of the mechanical calendar. Thus, cross direction uniformity can be controlled while constantly applying only a thin film of water to the web.
In operation, in contrast to the typical operation of the spray nozzle, the brush spray device has almost no "bounce back" effect,
It is known that virtually all of the mist generated by the rotating brush is applied to the web.

The use of the brush spray device of the present invention, that is, the brush spray device which is driven independently of the calendar device, makes it possible to uniformly distribute a minimum amount of water to one or both surfaces of a web such as paper. With good reproducibility. Required to increase stiffness during calendering, regardless of the speed of operation of the calendar or the thickness of the web (ie, I-beam effect), by moisturizing the transfer rolls of the calender rather than the paper. A very thin and dense surface layer can be achieved.

FIG. 1 shows an example of an apparatus useful for the present invention. A typical mechanical calender 10 suitable for pressing a web 12 of calenderable material, such as paper, includes a plurality of hard rolls 14 of steel arranged in series. In this case, the paper web 12 is almost "S"
It passes between calendar rolls in a letter-shaped path. Idler rolls 16 can be placed on each side of the row and easily moved without wrinkling the paper. Further, a pair of brush spray devices 18 and 20 are shown in the figure. These are for moisturizing the web and are located on each side of a row of calendars. Each brush spraying device is composed of a brush 22, a liquid pump 2
4 and a liquid storage tank 26. As the brush 22 rotates relative to the liquid pumping roll 24, a liquid mist 28 is generated. This liquid mist is directly deposited as fine droplets on the transfer rolls 15 and 17 in the calendar row. The positions are approximately 2 o'clock and 10 o'clock. The transfer rolls 15 and 17 are the same roll,
It usually includes a water box device for a water box calendar. Each roll 15,1
7 transports a thin film of water or other liquid directly into the respective transfer nips 13, 19, where the liquid is transferred to the paper web 12. The amount of liquid applied to the transfer rolls 15 and 17 is adjusted by adjusting the speed of the pumping roll 24 or the brush roll 22 independently of the operation speed of the calendar so that a predetermined amount of water is applied to one or both surfaces of the web. It can be changed by allowing it to be applied to only

In operation, the brush sprayers 18, 20
The amount of water given to the transfer rolls 15 and 17 by
It may be desirable to incrementally increase until a micro-flooded nip is formed. Preliminary tests have uncovered facts that were discovered unintentionally.
It is the mechanical calendering that results in a very thin densified layer on one or both sides of the web, as controlled by micro-flooding so that only one side of the web 12 is uniformly moistened. This means that the desired I-beam effect with the volume layer is achieved and the stiffness can be maximized. The results of this test are shown in the examples below.

[0012]

EXAMPLE Ratanikku Equipment, Inc. made of brush spray device is mounted adjacent to the steel roll machine calender for finishing one surface of the paperboard web. A conventional water box mixture is used
m) in steps of 2 pounds (0.9 kg) using a brush spray unit. The size of the run is 278.7 m ² (3000 square feet).
Met. The applied amount is 0 to 4.54 kg / 278.7.
m ² (0-101 lb / ream). The calendar load is 181.44 kg per 2.54 cm of straight line
(400 pli) and the calendar was operated at 216.41 m (710 fpm) per minute. 2
About 2.99 kg (6.6 1 b / r) per 78.7 m ²
At the application level of eam), the micro-inundation was prominent in the fluid transfer nip. The data in this test was compared to data in a control treated with a conventional water box. The results are shown in the table below.

[0013]

The data in the table show that the test conditions using the brush sprayer of the present invention exhibit at least a 20% higher CD (cross direction) Taber stiffness as compared to the water boxed control. Was. In that case, the decrease in volume (thickness) was negligible, but in the control treated in the water box,
The thickness was reduced by about 1 point. In summary, these results demonstrate that mechanical calendering using the brush spray apparatus disclosed herein can increase stiffness while effectively maintaining the volume of the web. Furthermore, when compared with the conventional water box calendering, the immersion nip (micro immersion) obtained by the brush spraying device is small and the rate of water application is low, so that the possibility of damage to the web is reduced,
A better product will be obtained. Also, since the brush spray device for applying moisture to the web is driven independently of the means for driving the calendar, achieving the most favorable density distribution in the web regardless of the thickness of the web. Becomes possible.

[0015]

In summary, the present invention finishes a web, such as paper, paperboard, or the like by controlling the moisture applied to the web, so that the web has a minimum level across the width of the web regardless of the speed of the calendar. And a method for uniformly applying water. According to this process, a density gradient is formed in the web, and an I-beam effect is achieved by one or two densified layers and an inner layer having a large volume. As a result, a web having high rigidity and a desired volume is formed. Although only one embodiment of the invention is fully disclosed and described, those skilled in the art will depart from the spirit and scope of the invention as set forth in the appended claims. It can be understood that various modifications can be made without any change.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus suitable for practicing the invention.

Claims (9)

[Claims] 1. A device for finishing a web of paper or the like to improve rigidity while minimizing a decrease in volume, comprising: a calender device including at least two calender rolls abutted on a nip; and the calender device. At least one brush sprayer associated with: one of said at least two calender rolls is a transfer roll, said at least one brush sprayer later comprising a web transfer device at a first transfer nip. The calendar device and the brush spray device are arranged independently of and adjacent to a transfer roll of the calendar device for applying a mist of liquid transferred to the first surface to the surface of the transfer roll. The amount of liquid mist applied to the web after being driven and deposited on the transfer roll of the calendar device is controlled by the operation of the calendar device. A device that can be controlled regardless of its operating characteristics. 2. The apparatus according to claim 1, wherein the calendar device has a plurality of nip-contacted calendar rolls, and at least two of the calendar rolls are transfer rolls. 3. A second brush sprayer is associated with a second transfer roll of the calendar device, the second brush sprayer for supplying a mist of liquid to a surface of the second transfer roll. , Disposed adjacent to a second transfer roll and disposed on the opposite side of the first brush spray device with the calendar device interposed therebetween, wherein the second brush spray device includes the calendar device and the first brush spray device. Driven independently of the brush sprayer, the amount of liquid mist transferred to the opposing surface of the web at the second transfer nip after being applied to the second transfer roll is determined by the calendar device and the first brush sprayer. 2. The device according to claim 1, wherein the device is controllable independently of operating characteristics. 4. The apparatus according to claim 3, wherein the liquid mist is applied to each transfer roll at approximately 2 o'clock and 10 o'clock. 5. Each of the brush spraying devices has a liquid storage tank, a liquid pumping roll, and a brush member, and at least a part of the liquid pumping roll is immersed in the liquid in the liquid storage tank, and the brush member 5. The apparatus according to claim 4, wherein the brush is in contact with the liquid pumping roll and each of the liquid pumping roll and the brush member is rotatable independently of each other. 6. A method for finishing a web of paper or the like to improve rigidity while minimizing volume loss, comprising:
(A) feeding a web such as paper to a calender having a plurality of nip abutting rolls including at least one transfer roll; and (b) at least one brush sprayer capable of generating a liquid mist. (C) driving the brush spraying device independently of the calendar device to apply the liquid mist to the transfer roll in a minimum amount and substantially uniformly to the paper at the transfer nip; Transferring the web treated in step (c) in one or more nips of the calendering apparatus, including a transfer nip, to substantially reduce the original size of the web. Forming a density gradient in the web with a thin densified layer at the treated surface of the web while maintaining volume. 7. A calender device is disposed on at least two transfer nips and on the opposite side of the first brush spray device across the calender device for transferring a film of liquid to the opposing surface of the paper web. A second brush sprayer, wherein the web is compressed in a calendering device to form a web structure having a density gradient with a thin densified layer on each side and a bulky inner layer. 7. The method of claim 6, wherein a web having enhanced I-beam effect and enhanced stiffness is produced. 8. The amount of liquid applied to each side of the web is from about 0.997 to 4.535 kg / 278.7 m ^2.
(Dimensions of 2-10 1b / ream, ream 3000
The method according to claim 7, wherein the value is within the range of (square foot). 9. An apparatus for finishing a web of paper or the like to improve rigidity while minimizing volume reduction, comprising: a series of calenders including two pairs of calender rolls abutted on a nip; One of a pair of calendar rolls is a transfer roll, and the brush sprayer transfers a mist of liquid that is subsequently transferred to the surface of the web at a transfer nip. In order to apply to the surface of the roll, the brush sprayer is driven independently of each other, being associated with each pair of calendar rolls and disposed immediately adjacent to the transfer roll of each pair of rolls. The amount of liquid mist applied to the web in each in-line calender can be controlled independently of the operating characteristics of the in-line calender Equipment that has been enabled.