EP2340332B1 - Device for impregnating a web-type material with thermally curable impregnating resin - Google Patents

Abstract

The invention relates to a device (10) for impregnating a web-type material (12) with thermally curable impregnating resin (16), comprising a resin tank (26), in which the web-type material (12) is brought into contact with the impregnating resin (16), a supply line (30) that leads to the resin tank (26), through which tank the impregnating resin (16) is introduced into the resin tank (26) and a heating device (32) that heats the impregnating resin (16). According to the invention, the heating device (32) is allocated to the supply line (30) and heats the impregnating resin (16) in said line (30).

Description

The invention relates to a device for impregnating web-like material with thermosetting impregnating resin comprising a impregnating trough in which the web-like material is brought into contact with the impregnating resin, a supply line leading to the impregnating trough, through which the impregnating resin is introduced into the impregnating trough, a heating device which heats the impregnating resin.

Such devices are well known in the art.

The impregnation of web-like material with heat-curable impregnating resin, together with the subsequent drying of the impregnated web-shaped material, serves to produce impregnates, such as are used individually or in the form of a laminate formed from such impregnates, for example for coating base bodies formed from wood-based material, for example during manufacture of panels for covering surfaces, for example floors.

As a web material is not only in the prior art, but also in connection with the present invention, in particular a composite of natural fibers and / or synthetic fibers composite into consideration, for example, a scrim, a mat, a fabric or the like. Preferably, the web material is paper whose basis weight in the unimpregnated state can be between about 25 g / m ² and about 300 g / m ² . As is known, the paper layer of an impregnate, which is intended to form a visible surface of the end product, can be printed with a desired décor.

In order to enable penetration of the impregnating resin into the web material, the impregnating resin is mixed with a solvent, for example water, whose function is to lower the viscosity of the synthetic resin. The impregnating liquor thus formed may, if desired, be admixed with further additives, for example a hardener. The finished impregnated web material must be dried before further processing, i. the solvent must be removed from the impregnate again so that only the impregnating resin of the impregnating liquor remains in the finished product.

If, in the context of the present invention, it is mentioned below that the web material is impregnated with impregnating resin or that impregnating resin penetrates into the web material, it is meant that the web material is impregnated with impregnating filament or that the impregnating liquor penetrates into the web material. With regard to the end product, however, ultimately it is only important that the impregnating resin has also penetrated the web material and remains there during subsequent drying. Further, it should be noted at this point that, although in the context of the present invention is always spoken of "the resin" or "the impregnating resin" in the singular, this resin may also be a mixture of different synthetic resins.

As with any other industrially used process, attempts must also be made in the production of impregnates to allow this process to proceed as quickly and effectively as possible in order to keep the cost share of the end product as low as possible. For this purpose, it is of central importance to impregnate the web-like material as quickly and effectively as possible with the impregnating resin and then to be able to dry it. The time required for impregnation is known to be lower, the lower the viscosity of the impregnating liquor. To achieve the lowest possible viscosity of the impregnating liquor can on the one hand their solids content, ie reduced resin content and on the other hand their temperature can be increased.

The solvent, which is based on a given amount of resin and has to be additionally added to reduce the viscosity, must again be removed from the impregnated web-like material in the subsequent drying step. This costs energy and time and thus in turn contributes to an increase in the cost of the impregnate. Overall, therefore, there is no cost advantage.

But the increase in temperature are also limited in practice. Namely, the impregnating resin cures faster at higher temperature, i. it polymerizes faster. However, the higher the molecular weight of the resin, the worse it penetrates into the web-like material and the worse the finished impregnate can be further processed later. Thus, for example, at a temperature of the impregnating trough of more than 35 ° C, the liquor life is reduced to such an extent that in the event of a stoppage of production, the impregnating liquor would become unusable so quickly that disposal of the whole in the production plant, i. especially in the impregnating trough, existing impregnating liquor would be required. Of course, this is not tolerable.

Another problem that already occurs in the prior art at the current tray temperatures of at most 35 ° C, is that the heat exchange rates of up to 2000 kg liquor / h, the heat exchanger surfaces of the impregnation tank must be quite hot to the in To bring the impregnating trough taken on the impregnating trough to the desired trough temperature. Since the geometric design of the troughs naturally laminar flow areas and in unfavorable cases even dead spaces exist, there is always the formation of resin coatings on the heat exchanger surfaces, which worsen the heat transfer over time more and more. This starts a vicious circle of ever-increasing necessary temperatures the heat exchanger surfaces and thus increasingly faster course formation - the tub "grows to".

It is therefore an object of the present invention to develop a device of the generic type such that the impregnation of sheet material with thermosetting impregnating resin can be made more effective.

This object is achieved by a device of the type mentioned, in which the heating device is associated with the feed line and heated the impregnating resin in the feed line. According to the invention, therefore, the impregnating resin is no longer heated in the impregnating trough, but in a heating device upstream of the impregnating trough. As a result, the wall surfaces of the impregnating trough no longer need to be used as heat exchanger surfaces for heating the impregnating resin, so that the risk of formation of coatings on these walls is at least reduced, if not completely excluded.

Thus, it is possible to supply the impregnating resin, more precisely the impregnating liquor, to the impregnating trough having a higher temperature, in particular a temperature of between approximately 50 ° C. and approximately 80 ° C., and thus lower viscosity than was possible in the prior art. As a result, the penetration of the impregnating resin into the web-shaped material can be improved. Alternatively, however, the impregnating liquor may also contain less solvent and, due to the elevated temperature, have a viscosity which corresponds to that of a prior art impregnating liquor with a higher solvent content and lower temperature. This allows the subsequent drying to run more effectively. Of course, these two effects can also be used together. In whatever form one makes use of the advantageous consequences of the temperature increase made possible by the present invention, in each case the impregnation process is carried out Use of the impregnating device according to the invention run off more effectively. In the former case, the impregnation process itself is faster, thereby increasing the amount of sheet-like material impregnated per unit time. In the other case, the drying of the impregnated web-shaped material can be done faster and with the use of less energy.

In order to prevent the formation of deposits in the impregnation tank upstream of the impregnation tank, it is proposed in a further development of the invention that the heating device is a non-contact heating device. For this purpose, the heating device can heat the impregnating resin, for example using microwave radiation.

Furthermore, it may be advantageous if a control device is provided, which ensures that the heating device is supplied only to the amount of impregnating resin required for impregnation. As a result, in particular, the amount of energy expended for heating the impregnating resin can be reduced to a minimum. The control device may operate in response to the detection signal of at least one sensor detecting at least one operating parameter of the impregnation device, for example, depending on the engine speed, i. depending on the speed with which the sheet material is fed to the impregnating trough. The control device can also be connected to a pump, which supplies the heating device with the amount of impregnating resin required for impregnation, or further functional units of the impregnating device.

In a further development of the invention, it is proposed that the impregnating trough be provided with a cooling device. This cooling device can be used, for example in the case of a production stoppage, to cool the impregnating resin in order to reduce its polymerization rate and thereby increase the liquor service life in such a way that that the resin can still be used after the resumption of production.

This cooling device may comprise an integrated cooling unit. For example, according to the invention, the heat exchanger device already present in impregnating tanks of the prior art can no longer be used for heating but rather for cooling the impregnating liquor.

Additionally or alternatively, however, it is also possible that the cooling device comprises an external cooling unit. This can be particularly advantageous if particularly high cooling capacities are required. In this case, the impregnating liquor or the impregnating resin is pumped out of the impregnating trough and through the external cooling unit in order to be able to achieve an even more effective cooling.

In a further development of the invention, it is further proposed that the impregnation tank is subdivided into at least two sub-tanks. This makes it possible to use a first part-tub for pre-impregnation and a second part-tub for main impregnation, wherein the impregnating resin can be kept preferably only in the first part-tub at the elevated temperature compared to the prior art, while in the second part-tub at a temperature which corresponds, for example, to the temperature used in the prior art. This development makes use of the fact that the actual penetration of the impregnating liquor into the web-like material takes place already in the preimpregnation step and in the main impregnation step mainly involves the correct metering of the basis weight of the impregnating resin relative to the basis weight of the weblike material.

Therefore, it is also possible for a first sub-trough connected to the feed line to have a smaller volume than a further sub-trough arranged further downstream in the flow direction of the resin. Is advantageous it further, if between the two sub-wells, a further cooling unit is arranged. If desired, the further cooling unit can be assigned to a third part trough serving as a transition part trough, wherein this transition part trough, for example, can still be attributed to the preimpregnation step.

Advantageously, the receiving volumes of the plurality of sub-pans can be formed separately from each other, in such a way that on the one hand a transition of impregnating from an upstream sub-tub to a downstream sub-tub can be done, but on the other hand, a transition of impregnating from a downstream sub-tub to one upstream arranged sub-tub is not possible.

In a further development of the invention may finally also be provided a spraying device which moistens the sheet-like material, for example with water, preferably hot water or steam. By this measure, the penetration of the impregnating liquor in the web-shaped material can be further improved. It is particularly advantageous in this case if the web-like material is both pre-moistened and preheated.

The use of the impregnating device according to the invention enables the impregnation at a significantly higher solids content of the impregnating liquor, which can be saved in the subsequent drying considerable amounts of energy or allow existing drying capacities higher production speeds. For example, it is possible to work with a solids content of about 60% of impregnating resin in the impregnating liquor.

In addition, it was surprisingly found that the rheology of the impregnating liquor changes favorably at higher temperatures. So it came in conventional impregnating by the spraying around the Resin in the impregnation constantly to dirt and damage. According to the invention, it has now surprisingly been found that at higher temperatures, the tendency of the impregnation of the impregnating liquor decreases and thus significantly longer maintenance intervals of the impregnating become possible.

It should also be added that aminoplast and phenoplast resins are usually used as impregnating resins. For example, the following resins may be considered as impregnating resins: urea-formaldehyde resin, melamine-formaldehyde resin, melamine-urea-formaldehyde resin (MUF), melamine-urea-phenol-formaldehyde resin (MUPF), phenol-formaldehyde Resin (PF), tannin resins, resorcinol-formaldehyde resins, silicone resins.

Fig. 1

eine schematische Darstellung des Aufbaus einer erfindungsgemäßen Imprägniervorrichtung.

The invention will be explained in more detail below using an exemplary embodiment with reference to the attached drawing. It shows:

Fig. 1

a schematic representation of the structure of an impregnating device according to the invention.

In Fig. 1 is a device for impregnating a sheet material 12, for example a paper web, generally designated 10. The impregnating device 10 comprises an impregnating trough 14, in which the paper web 12 is impregnated with impregnating resin 16, more precisely, impregnating liquor 16a.

The impregnating trough 14 is subdivided in the illustrated embodiment into three sub-troughs 18, 20 and 22, which are passed through in succession from the material web 12 along a predetermined path of deflection rollers 24. With regard to their structure and arrangement, and also with regard to the question of whether some or more of these guide rollers are driven, the guide rollers 24 correspond to those of an impregnating device of the prior art. Therefore, a more detailed explanation in this regard will be omitted here.

In the illustrated embodiment, the impregnation device 10 includes a tub body 26 having a well volume 26a. In the tub body 26, an insert body 28 is inserted, in which the first part trough 18 and the second part trough 20 are formed. The partial volume of the tub volume 26a not occupied by the insert body 28 forms the third part tub 22. According to the invention, the volume of the first part tub 18 is smaller than the volume of the second part tub 20, and the latter is again smaller than the volume of the third part tub 22.

During operation of the impregnating device 10, the first part trough 18 is supplied via an inlet line 30 to the impregnating liquor 16a, which has previously been heated without contact in a heating device 32, preferably by means of microwave radiation. The inlet of the feed line 30 into the first part of the trough 18 is shown at 34. According to the invention, the impregnating liquor 16a may comprise about 60% solids content of impregnating resin 16, for example melamine resin, in a solvent, for example water, and be introduced into the first part trough 18 at a temperature of about 50 ° C. to 80 ° C. Due to this high temperature, the impregnating liquor 16a, despite the high solids content, has such a low viscosity that it can easily penetrate into the material web 12 in the first sub-tub 18 in order to impregnate it. To facilitate penetration, the material web 12 may be moistened before entry into the first part trough 18 by means of a spray device 36 and, if desired, also preheated.

The impregnating liquor passes from the first part-trough 18 into the second part-trough 20 via an overflow 38. The boundary walls 20a of the second part-wall 20 are designed as heat-exchanging surfaces of a cooling unit 40, which cools the impregnating liquor 16a to a temperature of about 30 ° C., for its service life to increase significantly. In addition, will the web 12 in the second sub-tub 20 soaked again with impregnating liquor 16 a.

Via an overflow 42, the impregnating liquor 16a passes from the second sub-tub 20 into the third sub-tub 22, in which a dip section 44 is provided for the material web 12. While the actual impregnation of the material web 12 takes place with impregnating liquor 16a in the first two sub-troughs 18 and 20, the main function of the immersion path 44 in the third sub-trough 22 is to ensure that the material web 12 is loaded with the desired amount of impregnating liquor 16a.

Although in Fig. 1 At various points doctor blades 46 are provided, the task of which is to remove excess impregnating liquor 16a from the surface of the material web 12 and / or evenly distribute and / or smooth the impregnating liquor 16a applied to the material web 12, the present invention is not concerned with this aspect. Therefore, a more detailed explanation will be omitted in this regard.

As in Fig. 1 indicated schematically, a cooling device 48 is provided in the bottom of the impregnating trough 26, the task of which is to keep the impregnating liquor 16a in the third partial volume 22 at the desired temperature of about 30 ° C, which in the case of a production standstill on the other hand but also is used to cool the impregnating liquor 16a even further, in order to increase their service life so far that they can be used loss-free after resumption of production. If necessary, an external cooling device 50 can also be provided for this purpose, which pumps and cools the impregnating liquor 16a from the trough volume 26a.

Even in normal production operation, the impregnating liquor 16a is pumped around. In fact, it is removed via a drain 52 from the tub volume 26a and via a line 54 from a pump 56 to the microwave heating device 32 and passed via the supply line 30 on to the inlet 34 into the first part trough 18. In this case, the pump 56 and the microwave heating device 32 preferably operate under the control of a control unit 58, so that on the one hand it is ensured that always exactly the amount of impregnating liquor 16a is introduced into the first part pan 18, depending on the production speed, in particular the running speed the material web 12 is required, and that the impregnating liquor 16a is introduced into the first part trough 18 at the desired temperature.

Furthermore, a metering device 60 ensures that via a line 62 and an inlet 64 always exactly the amount of impregnating liquor 16 is replenished into the tub volume 26a, which removes the material web 12 as a result of impregnation from the impregnating device 10. In this way it can be ensured that the mirror of the impregnation liquor 16 in the sub-tanks 18, 20 and 22 can always be kept at the same height. The metering device 60 also preferably operates under the control of the control device 58.

Further, the control device 58, the detection signals of a plurality of sensors S are supplied, for example, a sensor for detecting the speed of the web 12, a sensor for detecting the temperature of the introduced into the first sub-tub 18 impregnating liquor 16a, a sensor for detecting the level of the impregnating liquor 16a in the sub-wells 18, 20 and 22 and the like sensors more. These sensors and their connection lines to the control device 58 are in Fig. 1 not shown for reasons of clarity of presentation.

It is still to be added that the in Fig. 1 illustrated embodiment for retrofitting to existing impregnation devices of the prior art. In addition to the provision of a microwave heating device 32, only the insert body 28, in which the first two sub-wells 18 and 20 are formed, needs in the Tray volume 26a of the impregnating trough 26 to be used to make a impregnating device of the prior art, an impregnating device 10 according to the invention. In principle, however, it is also possible to provide a specially trained impregnating trough.

Claims (12)

1. An apparatus (10) for impregnating web-like material (12) with thermally curable impregnating resin (16), comprising:

   an impregnating trough (26) in which the web-like material (12) is brought into contact with the impregnating resin (16),

   an inlet line (30) which leads to the impregnating trough (26) and through which the impregnating resin (16) is introduced into the impregnating trough (26),

   a heating device (32) which heats the impregnating resin (16), characterised in that the heating device (32) is associated with the inlet line (30) and heats the impregnating resin (16) in the inlet line (30).
2. An apparatus according to Claim 1,
   characterised in that the heating device (32) is a heating device operating in a non-contact manner.
3. An apparatus according to Claim 1 or 2,
   characterised in that the heating device (32) heats the impregnating resin (16) using microwave radiation.
4. An apparatus according to any one of Claims 1 to 3,
   characterised in that a control device (58) is provided which ensures that the amount of impregnating resin (16) required for the impregnation is fed to the heating device (32).
5. An apparatus according to any one of Claims 1 to 4,
   characterised in that the impregnating trough (26) is provided with a cooling device (48,50,40).
6. An apparatus according to Claim 5,
   characterised in that the cooling device (48,50,40) comprises an integrated cooling unit (48).
7. An apparatus according to Claim 5 or 6,
   characterised in that the cooling device (48,50,40) comprises an external cooling unit (50).
8. An apparatus according to any on of Claims 1 to 7,
   characterised in that the impregnating trough (26) is divided into at least two trough sections (18,20,22).
9. An apparatus according to Claim 8,
   characterised in that a first trough section (18) connected to the inlet line (30) has a smaller volume than a further trough section (22) arranged further downstream in the flow direction of the resin.
10. An apparatus according to Claim 8 or 9,
    characterised in that a cooling unit (40) is arranged between the two trough sections (18,22).
11. An apparatus according to any one of Claims 8 to 10,
    characterised in that at least one of the trough sections (18,20,22) is formed in a trough body (28) which can be inserted into a larger trough body (26), the remaining trough volume (26a) of which forms at least one further trough section (22).
12. An apparatus according to any one of Claims 1 to 11,
    characterised in that a spraying device (36) is provided which moistens the web-like material (12), for example with water, preferably hot water or steam.

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