DE102012015128A1 - Producing resin-based foams by foaming and curing aqueous or alcoholic solution or dispersion, comprises supplying solution or dispersion in microwave heater, applying the solution onto conveyor belt, and moving solution to conveyor belt - Google Patents

Abstract

Producing resin-based foams by foaming and curing an aqueous or alcoholic solution or dispersion comprising a blowing agent and/or a chemical compound, which is reacted or decomposed to form a gas, comprises supplying the solution or dispersion in a microwave heater (16) with a pre-determined amount of energy by microwave irradiation, applying the solution or dispersion onto a continuously running conveyor belt (14) in a first chamber (12) in a row-wise manner, and moving the solution or dispersion to the conveyor belt under irradiation with microwaves through a second chamber (34). Producing resin-based foams by foaming and curing an aqueous or alcoholic solution or dispersion comprising a blowing agent and/or a chemical compound, which is reacted or decomposed to form a gas, comprises supplying the solution or dispersion in a microwave heater (16) with a pre-determined amount of energy by microwave irradiation, applying the solution or dispersion onto a continuously running conveyor belt (14) in a first chamber (12) in a row-wise manner, and moving the solution or dispersion on the conveyor belt under at least intermittent irradiation with microwaves through a second chamber (34). An independent claim is also included for a device for carrying out the above mentioned method, comprising the first chamber, the continuous running conveyor belt, which is arranged in the chamber, at least one microwave generator (36) for irradiating at least part of the interior of first chamber with microwaves, and a microwave heater, which is connected upstream to the chamber.

Description

The present invention relates to a method and an apparatus for producing resin-based foams by foaming and subsequent curing of an aqueous or alcoholic solution or dispersion containing a blowing agent and / or a chemical compound which reacts or decomposes to form gas.

For example, from the DE 10 2005 027 552 A1 thermoformable melamine / formaldehyde foams with low formaldehyde emission are known. These are prepared by heating to froth and cross-link a mixture containing a melamine / formaldehyde (MF) precondensate, a hardener and a blowing agent, adding a formaldehyde scavenger before heating. The heating of the blowing agent-containing solution or dispersion can be carried out by microwave irradiation. The microwave irradiation of the mixture to be foamed takes place immediately after it has emerged from a foaming nozzle. The existing microwave systems used for this purpose have the disadvantage that the heating and reactive foaming takes place in a multimode microwave chamber. That is, the wavelength of the coupled microwave power is many times smaller than the dimensions of the chamber. This results in an electric field strength distribution of different field minima and maxima. By suitable arrangements of microwave couplings, although the distribution of field minima and maxima can be improved, inhomogeneities can not be (completely) avoided. In particular, the reactive resin mixture entering the chamber must be heated very uniformly from the ambient temperature to a temperature, such as boiling temperature or reaction temperature, of, for example, 100 ° C. Due to the inhomogeneous field distribution in the multimode microwave chamber, this is only possible to a limited extent. This can result in a very different temperature profile along a transport direction in the chamber. These differences in temperature and energy can have great negative effects on the foaming and the ongoing reaction of the resin mixture. Desired are a very uniform heating and energetic loading of the resin mixture.

In order to improve the uniformity of the microwave energy distribution, the microwave chamber can be segmented into sections to better control these sections energetically. This is operationally complex. Likewise, the energy density can be reduced, resulting in small deviations between the field minima and maxima. As a result, however, the length of the microwave chamber or system is increased and thus increase the cost and the footprint. Likewise, the process control is impaired. Desirable is a targeted and rapid heating to boiling or reaction temperature.

Common inlet temperatures are in the range of 20-30 ° C. The mixture or the solution or dispersion is then increased to about 60-80 ° C, in which case the foaming begins. The foaming is strongly dependent on the temperature. If differences in temperature occur in the temperature profiles along the transport direction, differences in the foam structure and in the crosslinking of the foam are visible. This leads to inhomogeneities. About 30% of the total length of a microwave chamber equipment is usually required for the reaction heating.

The present invention is therefore based on the object to achieve a more uniform foaming with a homogeneous pore structure and uniform crosslinking of the foam by means of microwaves.

According to the invention this object is achieved in the method of the type mentioned in that the solution or dispersion in a microwave water heater a predetermined amount of energy is supplied by microwave irradiation and then the solution or dispersion on a, preferably continuously running, conveyor belt in a chamber, preferably line by line, applied and moved on the conveyor belt under at least temporary irradiation with microwaves through the chamber. Instead of a conveyor belt, another suitable conveyor may be provided.

Furthermore, this object is achieved by a device for producing resin-based foams by foaming and subsequent curing of an aqueous or alcoholic solution or dispersion containing a blowing agent and / or a chemical compound which reacts or decomposes to form gas, comprising: a chamber, in which a, preferably continuously running, conveyor belt is arranged, at least one microwave generator for irradiating at least a portion of the interior of the chamber with microwaves, and a chamber of the microwave upstream water heater.

Advantageously, in the method, the solution or dispersion in the microwave water heater is passed through a through pipe made of plastic, ceramic, glass ceramic o. Ä.

Conveniently, the solution or dispersion is pumped through the passageway at a pressure in the range of about 1 to about 20 bar.

Particularly preferably, the microwave water heater is operated in the single mode. In a cylindrical waveguide, there are different fundamental waves. The E01 (also called TM01) fundamental has an electric field strength amplitude which is maximum in the central axis of the cylindrical waveguide and decreases toward the wall of the cylindrical waveguide. If a tube (through-tube) is now placed in the central axis of the cylindrical waveguide and evenly promotes product through this tube, the product absorbs microwave energy on the dwell line, which leads to a uniform heating of the product volume at the outlet of the microwave instantaneous heater.

According to a particular embodiment, the residence time of the solution or dispersion in the microwave instantaneous water heater is in the range from about 0.1 s to about 10 s.

According to another particular embodiment of the present invention, the supply of energy is such that the temperature of the solution or dispersion does not exceed the pressure-dependent boiling temperature in the microwave water heater.

Alternatively, the temperature is the reaction temperature of the chemical compound which reacts or decomposes to form gas.

Advantageously, the temperature is in the range of about 60 ° C to 200 ° C.

According to a particular embodiment of the invention, the solution or dispersion by means of a relaxation device, in particular a nozzle, applied to the conveyor belt.

Furthermore, it can be provided that the chamber has a multi-mode microwave sub-chamber.

Conveniently, the residence time in the multimode microwave sub-chamber is in the range of about 5 seconds to about 40 seconds.

Advantageously, in the device between the microwave water heater and the microwave chamber, a relaxation device, such as a nozzle, for, preferably line by line, application of the output from the microwave water heater solution or dispersion interposed on the conveyor belt.

Finally, the microwave instantaneous water heater advantageously has a through pipe made of plastic, ceramic, glass ceramic or the like.

The invention is based on the surprising finding that in the upstream microwave instantaneous water heater so much energy is supplied by means of microwaves that the solution / dispersion or the product in the downstream microwave chamber immediately starts to foam up in the atmosphere. Since a large part of the energy required for foaming has already been introduced by the upstream microwave instantaneous water heater, the microwave energy density in the microwave chamber can be reduced, which leads to fundamentally better microwave energy distributions. In addition, the length of the microwave chamber or system can be shortened. Since the product already enters the microwave chamber at a high temperature of, for example, 60 ° C. to 100 ° C., a much more uniform foaming takes place with a homogeneous pore structure and uniform crosslinking of the foam. The energetic loading by means of the microwave instantaneous heater significantly shortens the residence time in the downstream microwave chamber for foaming (for example, 1 to 5 minutes reduced to 5 to 40 seconds) and the length of the microwave chamber or chamber for foaming and curing be shortened by about 30 to 50%.

Since, at least in a particular embodiment, a proportion of water is also present in the reaction mixtures, the process temperature in the liquid phase can be increased significantly above 100 ° C. by higher pressures in the microwave instantaneous water heater (water in the liquid phase and energetically charged) (typically 130 ° C.) ° C to 150 ° C). This leads after exiting the solution / dispersion or the foam mixture of, for example, a nozzle (Schäumdüse) at the conveyor belt of the microwave chamber to a flash expansion flash (Flash) and supports rapid foaming (foaming) and that a part of the water containing immediately atmospheric pressure evaporates. With this targeted process control of the upstream microwave continuous flow heater can be targeted quality characteristics of the foam control, such as density on pore size, foam height, mechanical strength, etc. This targeted influence is poor or hardly possible with a simple microwave chamber or -kammeranlage.

In addition to hardeners, catalysts are also used to accelerate the "chemical foam reaction". The catalysts undergo the critical phase of foaming and curing faster. The catalysts however, often affect the long-term properties and are expensive. As experiments have shown, it takes about 20-50% less catalysts when using a microwave water heater. This improves long-term stability and reduces costs.

Further features and advantages of the invention will become apparent from the appended claims and the following description, in which an embodiment will be described with reference to the single drawing. The single drawing shows schematically a device 10 for producing resin-based foams by foaming and subsequent curing of an aqueous or alcoholic solution or dispersion according to a particular embodiment of the present invention.

The device 10 has a chamber 12 in which is a conveyor belt 14 and an upstream single-mode microwave instantaneous water heater 16 on. A single mode microwave instantaneous water heater is known, for example, from US Pat EP 1 839 741 B1 known. As by two pipes 18 and 20 indicated, a mixture is produced in the form of a solution or dispersion and via a pipeline 22 with mixer 23 and a pump 24 , preferably high-pressure pump, in a passage tube 26 made of plastic, ceramic, glass ceramic or similar, of the single-mode microwave continuous flow heater 16 pumped. When flowing through the passage tube 26 the mixture is made by means of a microwave generator 28 , Of course, as required, several microwave generators can be used, irradiated with microwaves and thereby heated. About a pipeline 30 then passes the mixture to the chamber 12 , There she is using a nozzle 32 , which generates a corresponding spray cone or a corresponding spray lamella and / or is movable, line by line on the conveyor belt 14 , which preferably consists of plastic, applied. The conveyor belt 14 is running continuously in this case. Of course, the entire system can also work discontinuously.

As can be further seen from the single figure, the chamber is 12 in the longitudinal direction of the conveyor belt 14 divided by a sheet into two sub-chambers. In the first compartment 34 that are on the side of the nozzle 32 is the mixture or the foam by means of the present example, three microwave generators 36 for foaming and subsequent drying and curing. It works in multimode mode.

In the second compartment 38 there is no irradiation with microwaves. Rather, there is a cooling of the resulting foam.

On top of the multimode microwave chamber 12 are also 4 air exhaust pipes 40 shown over a common pipe 42 with a fan 44 keep in touch.

In addition to the single-mode microwave instantaneous water heater 16 is also an example of the temperature profile of the mixture when passing through the passage tube (reactor tube) 26 shown.

Furthermore, in the single figure below the chamber 12 also shown by way of example the electric field distribution, which results from a multi-mode cavity (first sub-chamber).

The features of the invention disclosed in the present description, in the drawings and in the claims may be essential both individually and in any desired combinations for the realization of the invention in its various embodiments.

LIST OF REFERENCE NUMBERS

10

contraption

12

chamber

14

conveyor belt

16

Single-mode microwave water heater

18, 20, 22

piping

23

mixer

24

pump

26

Through pipe

28

Microwave generator

30

pipeline

32

jet

33

sheet

34

first compartment

36

Microwave generator

38

second sub-chamber

40

Air flues

42

pipe

44

fan

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005027552 A1 [0002]
• EP 1839741 B1 [0024]

Claims (14)

A process for the production of resin-based foams by foaming and subsequent curing of an aqueous or alcoholic solution or dispersion containing a blowing agent and / or a chemical compound which reacts or decomposes to form gas, characterized in that the solution or dispersion in a microwave Water heater ( 16 ) a predetermined amount of energy is supplied by microwave irradiation and then the solution or dispersion on a, preferably continuously running, conveyor belt ( 14 ) in a chamber ( 12 ), preferably line by line, and on the conveyor belt with at least temporary irradiation with microwaves through the chamber ( 34 ) is moved. Process according to claim 1, characterized in that the solution or dispersion in the microwave instantaneous water heater ( 16 ) through a passageway ( 26 ) made of plastic, ceramic, glass ceramic o. Ä., Is passed. A method according to claim 2, characterized in that the solution or dispersion at a pressure in the range of about 1 to about 20 bar through the passageway ( 26 ) is pumped. Method according to one of the preceding claims, characterized in that the microwave instantaneous water heater ( 16 ) is operated in single mode. Method according to one of the preceding claims, characterized in that the residence time of the solution or dispersion in the microwave instantaneous water heater ( 16 ) is in the range of about 0.1 s to about 10 s. Method according to one of the preceding claims, characterized in that the supply of energy is such that the temperature of the solution or dispersion, the pressure-dependent boiling temperature in the microwave water heater ( 16 ) does not exceed. Method according to one of claims 1 to 4, characterized in that the temperature is the reaction temperature of the chemical compound which reacts or decomposes to form gas. Method according to one of the preceding claims, characterized in that the temperature is in the range of about 60 ° C to about 200 ° C. Method according to one of the preceding claims, characterized in that the solution or dispersion by means of a relaxation device, in particular a nozzle, on the conveyor belt ( 14 ) is applied. Method according to one of the preceding claims, characterized in that the chamber ( 12 ) a multimode microwave sub-chamber ( 34 ) having. Method according to claim 10, characterized in that the residence time in the multimode microwave sub-chamber ( 34 ) is in the range of about 5 seconds to about 40 seconds. Contraption ( 10 ) for producing resin-based foams by foaming and then curing an aqueous or alcoholic solution or dispersion containing a blowing agent and / or a chemical compound which reacts or decomposes to form gas, comprising: a chamber ( 12 ), in which a, preferably continuously running, conveyor belt ( 14 ), at least one microwave generator ( 36 ) for irradiating at least a part of the interior of the chamber ( 12 ) with microwaves, and a microwave instantaneous water heater ( 16 ). Contraption ( 10 ) according to claim 12, characterized in that between the microwave instantaneous water heater ( 16 ) and the microwave chamber a relaxation device, such as a nozzle ( 32 ), for, preferably line by line, application of the output from the microwave water heater solution or dispersion is interposed on the conveyor belt. Apparatus according to claim 12 or 13, characterized in that the microwave instantaneous water heater ( 16 ) a passage tube ( 26 ) made of plastic, ceramic, glass ceramic o.

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