JPH09277698A - Manufacture and apparatus for paper web having cb layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform coated layer by mutally pressing two rolls so that a surface surface pressure exists in a roll gap. SOLUTION: A web is guided through a roll gap formed between a covered roll 2 and an opposed roll 1. A CB layer is continuously applied to the covered roll 2 and is then proportioned on the above-mentioned roll by a proportioning unit 4 to be transferred to a paper web 3 in a roll gap. In this case, the two rolls 1, 2 are mutually pressed so that a mean surface pressure of not exceeding 2N/mm<2> exists in the roll gap.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a paper web having a so-called CB layer, having the features of the preamble of claim 1. The invention further relates to an apparatus for performing the above method. As is well known,
The CB layer applied to the paper comprises a microencapsulated chromophore, which is a so-called CF layer (comprising chromogenic pigment) of another paper (eg of a set of copy paper). , And thus the visible character appears due to pressure effects (eg, during handwriting).

[0002]

2. Description of the Related Art For the prior art, reference is made to DE 42 24 718 A1 and the publications mentioned therein.

In the known method, the roll gap through which the paper web passes is adjusted to a gap not less than the thickness of the uncoated paper. With this known method, it is expected that it will be very difficult or even impossible to transfer the coating compound to the paper web surface in the required uniform state. That is,
Full web width (up to several meters, maximum of about 10
Exactly the same adjustment over m) is extremely difficult. Thus, for example, a change in temperature and a local change in diameter due to this change in the temperature change the spacing between the two roll peripheral surfaces.

[0004]

SUMMARY OF THE INVENTION The object of the invention is therefore to provide a method according to the preamble of claim 1 so that the finished paper web with the pressure-sensitive CB layer fulfills higher quality requirements than before. To improve. It is likewise intended to improve the device according to the preamble of claim 4.

[0005]

This setting task is based on the characterizing part of claim 1 (that is, a maximum of 2 N / mm ^2).
5. Pressing the two rolls 1, 2 against each other such that the average surface pressure of the rolls is in the roll nip), and the characterizing part of claim 4 (ie any linear force of 80).
A pressing device suitable for adjusting in the range of kN / m or less,
The device is characterized in that it is arranged on two rolls 1,2).

The present inventor has confirmed that the microcapsules contained in the CB coating ink can completely withstand a certain pressure as long as they are suspended in the coating ink liquid. Therefore, according to the invention, the CB-coated ink can be transferred to the paper web without risk in the roll gap. In this case, of course, structural measures must also be used to establish a mean surface pressure in the roll gap which is not too great. Thus, a coating layer that is substantially more uniform than before can be obtained. The fringe formation expected in the prior art is avoided. This is because, in particular, the risk of slippage that is conventionally present between the paper web and the roll surface is eliminated. In other words, a certain force bond is formed between the paper web and the two driven rolls. Thus, in particular,
The risk of tearing the paper web is much less than before. That is, the method according to the present invention can be operated with higher efficiency than known methods.

The above-mentioned structural measures are particularly relevant to claim 3.
(I.e. at least 5 mm measured in the web running direction,
Selecting a linear force appearing in the roll gap, taking into account the material of the roll coating, the hardness and the elastic modulus and the roll diameter so that there is a gap length (a) of preferably 10 to 20 mm), or Item 5 (ie, there is a roll gap length (a) of at least 5 mm, preferably 10 to 20 mm, measured in the direction of web travel,
Based on the material of the roll coating, the hardness and the elastic modulus and the selection of the roll diameter), a strategy for obtaining the minimum length of the roll gap is included. That is, the paper web is in contact with both roll peripheral surfaces at the same time in the roll gap over a certain running section. Thus, the average surface pressure is kept at a relatively low value. Further, the expected length of the roll gap in the web running direction can be obtained by a known calculation method (Hertz's equation), that is, in consideration of the roll diameter, the linear force, the material of the roll peripheral surface and the elastic modulus.

If one of both rolls is constructed as a shoe press roll, a particularly suitable value can be obtained. In this case, as is well known, the pressing force is distributed over a particularly large area. As in the known shoe press rolls (on a paper machine), the pressing force can be increased particularly precisely and gradually when introducing the paper web and the CB layer to be applied into the roll gap. At the same time, a rapid or steep pressure drop can be achieved on withdrawal from the roll gap. Thus, the uniformity (in other words, smoothness) of the CB layer surface is further improved. Thus, the conventionally recognized stripe formation is almost completely avoided.

In some cases, it is advantageous to adjust the roll gap to a particularly small linear force (approximately 0-10 kN / m). This is difficult or impossible to achieve with conventional pressing devices. However, this makes claim 7 (the pressing device comprises a variable force generator (13) which is counteracted by a force store (spring 14, back pressure cylinder, etc.).
This is possible due to the special configuration of.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1, a coating roll 2 and an opposing roll 1 mutually form a roll gap (a) through which a paper web 3 to be coated passes. A CB coating ink supply / dispensing device (generally,
(Indicated by CB). This device comprises a known ink roller 6 which delivers ink from a storage container 12 to a coating roll 2. The coating roll 14 is a metering roll 14
Together with this, a precise metering gap is formed. Thus, a thin coating ink film is formed on the peripheral surface of the coating roll 2 from the supplied CB coating ink, and then this film is transferred to the paper web 3 in the roll gap (a).

As shown diagrammatically, one of both rolls (for example the coating roll 2) is supported on a stationary bearing. On the other hand, the bearing of another roll (opposing roll 1) is movable. That is, the bearings are provided, for example, on the swiveling lever 4 which can be actuated by a load device (for example, the hydraulic cylinder 13). The hydraulic cylinder presses both rolls 1 and 2 against each other. Accumulator (eg compression spring 1
4) acts against the hydraulic cylinder in the opposite way. Thus, the pressing force acting in the roll gap is, if necessary,
It can be adjusted very precisely, for example to very low values.

The diameters of the two rolls 1 and 2, the material of the roll peripheral surface or the roll coating, the elastic modulus and hardness, and the magnitude of the linear force acting in the roll gap are: -measured in the running direction-the roll gap. Has a length of at least 5 mm
(Preferably 10-20 mm).

The other side of the paper web 3 (the upper side in FIG. 1) is held unchanged during the application of the CB layer to the lower side. As another measure, as shown in FIGS. 2, 3 and 4, an auxiliary feeding / dispensing device is used to apply an arbitrary medium such as water or starch or an arbitrary coating ink (for example, CF coating ink) to the facing roll 1. The media can be applied and then transferred from the opposing roll to another side of the paper web 3.

As shown in FIG. 1, the peripheral speed v ₁ of the metering roll 14 is smaller than the working speed v of the entire apparatus. Thus,
The CB layer to be applied can be dispensed particularly precisely.

The embodiment of FIG. 2 essentially differs from that of FIG. 1 only in that a shoe press roll 1 is provided instead of the usual counter roll. This shoe press roll has a continuous flexible press sleeve 1a surrounding a stationary support member 7. The radially movable press shoe 5 has a concave (and adapted to the coating roll 2) sliding surface for the pressing sleeve 1a. The press shoe is guided by the support member 7 and covers the press sleeve 1a with the coating roll 2
Can be pressed precisely. Movable press shoe 5
Unlike, a stationary sliding shoe 8 with a convex sliding surface is provided on the support member 7. In this case, the auxiliary supply / dispensing device 16 can be provided on the outer surface of the press sleeve 1a.

In Figures 1 and 2, the paper web essentially runs from top to bottom through the roll gap. In this case, the feeding / dispensing device CF or 16 or 16 'is used. The supply / dispensing device is structurally configured so that it can be installed on the side of the roll shell facing downward. Feeding / dispensing device 16 'provided on the facing roll 1 of FIG.
Forms a liquid pool with the roll shell, while
A separate feeding and metering device CF; 16 avoids this kind of pool and is therefore suitable for higher speed work.

In contrast to FIGS. 1-4, the CB-coated ink (and / or the medium, which is optionally coated on the opposite side) can be fed to the roll 2; 1 by means of a free-spray nozzle known per se. . The excess CB coated ink (or excess media) can then be scraped off the roll if desired.

[Brief description of drawings]

FIG. 1 is a schematic side view of an apparatus according to the present invention used to manufacture a CB layer.

FIG. 2 is a schematic side view of an apparatus according to the present invention used to manufacture a CB layer.

FIG. 3 is a schematic side view of an apparatus according to the present invention used to manufacture a CB layer.

FIG. 4 is a schematic side view of an apparatus according to the present invention used to manufacture a CB layer.

[Explanation of symbols]

 1 Opposing Roll 2 Coated Roll 3 Paper Web 11 Roller Doctor 12 Storage Container 13 Hydraulic Cylinder 14 Metering Roll

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michael Trefts Germany 89522 Heidenheim bei Ernweg 9

Claims (7)

[Claims] 1. A method for producing a paper web having a so-called CB layer on one side of the web, comprising: a) coating a rough paper web produced by a paper machine on a roll (2).
And guiding through a roll gap (a) formed by the opposing roll (1), and b) a CB containing a colorant encapsulated in microcapsules.
A step of continuously applying the coating ink on the rotating peripheral surface of the coating roll (2), and then metering it by a metering device (for example, metering roll 14, roller-type doctor 11, coating blade or the like). , C) CB thus dispensed in the roll gap
Of the type comprising transfer of the applied ink to the paper web (3) by means of a rotating coating roll (2): d) two rolls such that an average surface pressure of at most 2 N / mm ² is present in the roll gap. The method described above, characterized in that (1, 2) are pressed against each other. 2. The method according to claim 1, wherein the average surface pressure is at most 1 N / mm ² . 3. At least 5 as measured in the direction of web travel.
The linear force appearing in the roll gap is selected in consideration of the material of the roll coating, the hardness and the elastic modulus and the roll diameter so that the gap length (a) of mm, preferably 10 to 20 mm exists. The method according to claim 1 or 2. 4. An apparatus for carrying out the method according to claim 1, wherein the coating roll (2) forms a roll gap with the counter roll (1), and the coating roll (CB). Of the type having a CB coating ink supply / dispensing device arranged on the free peripheral surface of: a pressing device suitable for adjusting an arbitrary linear force in a range of 80 kN / m or less, two rolls ( 1, 2) are arranged. 5. At least 5 as measured in the direction of web travel.
5. Device according to claim 4, characterized in that the material of the roll coating, the hardness and the elastic modulus and the roll diameter are chosen such that there is a roll gap length (a) of mm, preferably 10 to 20 mm. 6. One of both rolls has an elastically deformable press peripheral surface (1a) which slides on the press shoe (5) so that there is a roll gap extending in the web running direction. The apparatus of claim 4. 7. A variable force generator (1) in which the pressing device receives a reverse action from a force accumulator (spring 14, back pressure cylinder, etc.).
Device according to one of claims 4 to 6, characterized in that it comprises 3).