WO2020002497A1 - Apparatus and method for cross-linking by means of controlled microwaves - Google Patents

Abstract

The invention relates to an apparatus for cross-linking one or more polar materials contained in a product, particularly rubber, wherein the product particularly has the form of a continuous extruded profile (5), having a cavity (1) formed by at least one wall, and having at least one device for generating microwaves (2) in order to heat the material, wherein the microwaves form a radiation field (7) in the cavity. In order to improve the heating of the polar material(s) of the product, it is proposed that the apparatus has means which are designed to modify the radiation field used for heating in the cavity specifically for optimized absorption of the radiation energy. The invention also relates to a method for cross-linking one or more polar materials contained in a product, particularly by means of the apparatus according to the invention.

Description

 DEVICE AND METHOD FOR NETWORKING WITH REGULATED MICROWAVES

The present invention relates to a device for crosslinking one or more polar materials, in particular rubber, contained in a product, the product in particular having the shape of an endless extruded profile, with a cavity formed by at least one wall, and with at least one device for producing of microwaves for heating the material, the microwaves forming a radiation field in the cavity. The invention also relates to a method for crosslinking one or more polar materials, in particular rubber, contained in a product, the product in particular having the shape of an endless extruded profile.

There are a variety of different devices for cross-linking products that are made of or contain polar materials. For vulcanizing endlessly extruded rubber profiles, systems are used, for example, in which the rubber profile is passed through a cavity and heated therein. Hot air, for example, is used to heat the rubber profile and is guided past the rubber profile in the cavity. The heat, which is essentially transferred to the rubber profile by convection, is then conducted from the outside into the interior of the profile.

In order to achieve more uniform heating from the outside and inside, microwaves are used to warm the interior of the rubber profile. The microwaves excite the dipolar molecules of the rubber mixture to vibrate, whereupon the rubber mixture heats up. The microwaves are generated with magnetrons and transmitted to the cavity via hollow waveguides, in order to then, for example, at slot-shaped coupling passages from the

Hollow waveguide to be coupled out and into the cavity. To couple the microwave from the waveguide into the cavity, so-called slides are provided, with which the phase front of the microwave can be adjusted so that the

The microwave couples into the cavity essentially without loss.

The microwaves coupled into the cavity form a radiation field with areas of higher energy density and areas of low energy density, standing waves with intensity maxima and minima being formed in particular. Nevertheless, the heating of the materials to be cross-linked is not always

satisfactory because, for example, certain areas in the cross section of a

Rubber profile are not sufficiently heated and the crosslinking in the less heated areas is not sufficient. So far, attempts have been made to counteract this by increasing the temperature of the hot air.

An object of the invention is to develop a device of the type mentioned at the outset in such a way that it enables better heating of the materials to be crosslinked.

This object is achieved with a device according to claim 1. advantageous

Further developments of the device according to the invention are specified in the subclaims which refer back to claim 1.

In addition, this object is also achieved by a method according to claim 12. Advantageous further developments of the method are specified in the subclaims which refer back to claim 12.

According to the invention, means are provided in a device of the type mentioned at the outset, which are designed to target the radiation field used for heating in the cavity in order to optimize absorption of the radiation

To change radiation energy from the material. It was surprisingly found that the reflections of microwaves on the material can be changed and, in particular, minimized if the radiation field within the cavity can be optimally adjusted to the polar material to be crosslinked

Essentially, the lower the reflection from the polar material, the better the absorption of energy and thus the heating of the polar material. It is thus possible for a larger part of the energy introduced into the cavity via the microwaves to actually be absorbed by the material than in the case of previously known devices. In addition to the resulting energy advantages, the proportion of microwaves that reflect and, for example, in the case of a tubular cavity expand uncontrollably in the longitudinal direction, is lower, so that less microwave energy has to be absorbed in a device according to the invention.

With the device according to the invention, the location of locations can be higher

Change energy density in the radiation field and the location of places with lower energy density. It can be achieved that regions of the microwave field are higher Energy density in areas optimal for heating in the cross section of the

 Workpiece profile are shifted.

In one embodiment, the device for generating microwaves has means for setting the frequency of the microwaves generated within a frequency band. On the one hand, this has the advantage that the microwave frequency can be adapted to the absorption capacity of the material. In addition, since the wavelength of the microwave depends on the frequency, the wave crests of a standing wave forming in the cavity can be compressed or stretched by changing the frequency. This can make the areas higher

 Energy density can be changed in a targeted manner and positioned, for example, in an area through which the material profile runs.

In a further embodiment, the device for generating

 Microwaves Means for shifting the phase of the microwaves generated. The interference pattern of the microwave with other microwaves, for example with waves reflected from walls of the cavity, but especially with microwaves from another neighboring microwave emitter, can be significantly changed in the cavity by a phase shift. This also allows the radiation field for the absorption of the microwaves by the material to be optimized.

A semiconductor microwave generator is particularly preferably provided as the device for generating microwaves. The microwaves generated by a semiconductor microwave generator oscillate at a discrete frequency and not, as in the magnetrons used in known devices, over one

Gaussian bell-shaped frequency range, so that with a

Radiation field generated semiconductor wave element is formed more uniform. The frequency is also not subject to uncontrollable fluctuations, as is the case with a magnetron. Furthermore, the frequency in the generation of microwaves can advantageously be controlled in a simple manner by a semiconductor element and shifted within a frequency range. In contrast to magnetrons, semiconductor elements are not subject to aging, or only very little, so that the properties of the microwave produced can be reproduced safely at any time. The frequency of microwaves generated by semiconductor elements is not dependent on the impedance of the environment of an emitter antenna or the semiconductor element can be adjusted to the impedance of the environment so that it can emit microwaves of any frequency in any environment, so that microwaves generated with a semiconductor element a desired frequency in any Environments can be fed. Ultimately, a semiconductor element has no emitter antenna, which, like a magnetron, is highly susceptible to

Damage caused by reflecting microwaves. On elaborate

Protective devices such as those provided for magnetrons to protect the emitter antennas from reflecting microwaves, such as insulators or

Switch-off devices can be omitted.

In a further embodiment, the cavity has reflection surfaces for microwaves, the position of which is adjustable. For example, one or more reflecting surfaces, the position of which is adjustable, can be provided on the outer wall of the cavity, preferably in the cross section of the cavity opposite the point at which the microwaves are fed in. The reflection surfaces can, for example, be formed by a wall of the cavity itself, provided that its position relative to the microwave feed point can be changed. However, there can also be screens inserted into the cavity, the position of which within the cavity can be changed using suitable facial expressions.

With adjustable reflecting surfaces, the distance between the reflecting surface and the point at which the microwave is fed into the cavity can be exactly a multiple of 1/2 of the wavelength l of the microwave in order to generate a standing wave in the cavity that is as monomodal as possible. However, due to the diverse areas of the cavity from which the microwaves can reflect, it is difficult to achieve a uniform one

Generate radiation field. Therefore, a simple shift from

Reflection surfaces, regardless of the wavelength l of the microwave, lead to a radiation field in the cavity that is better for heating the material.

The radiation field can be adjusted by means of adjustable reflecting surfaces

Heating of the polar material can be optimized regardless of the type of microwave source. Such a means for changing the radiation field can in principle also be used in conjunction with a magnetron. On

Control means for adjusting the frequency or phase of the emitted

Microwave is not absolutely necessary.

With these means, areas of high energy density can be adapted to the position and geometry of the material and held in a corresponding position, for example during a continuous process. In this way, a product made of the material can be specifically heated in certain areas.

In a simple example, the energy density maximum can be exactly in the center of a radiation-field-formed, point symmetrical profile to be placed in cooperation with

 Thermal conduction effects within the profile to achieve the most uniform possible heating of the profile. Another example is the targeted heating of an area, for example a particularly material-rich area in the case of complex ones

 Material geometries with different wall thicknesses or from different materials possible.

Improved absorption of the microwaves in the product also significantly reduces the reflection of microwaves on the product. In the case of channel-like cavities, which are used, for example, for vulcanizing strand products, also in the longitudinal direction of the channel, the microwave portion that propagates through reflection in the cavity can be significantly reduced, so that absorbers at the ends of the area of microwave heating in the cavity ideally not needed.

In particular, if a semiconductor microwave generator is used, the antenna can be arranged directly on the cavity, since it can emit microwaves of any frequency in any environment. In this case, a waveguide for supplying the microwaves to the cavity, as is necessary, for example, with a magnetron, can be dispensed with, so that the structural complexity of the device is reduced.

Alternatively, microwaves can be transmitted from the device for generating microwaves to the cavity with a hollow waveguide or a coaxial conductor.

For example, it is possible in this way to place the device for generating microwaves on the device regardless of the position of a coupling point at a preferred location, for example an easily accessible location.

A preferred frequency band in which the device for generating microwaves can generate microwaves is the frequency band between 2.4 and 2.5 GHz. This frequency band is for industrial, scientific and medical purposes, e.g. reserved the use of microwaves to heat objects. This frequency band can be used license-free and license-free in many countries.

A further preferred embodiment of the invention is characterized by a plurality of devices for generating microwaves, the microwaves of which are coupled into the cavity in such a way that they generate overlapping microwave fields. The microwaves generated by the individual devices then overlap and generate one common microwave field. This overlay can be used to determine and

Changing the areas of high energy density can be used. If, for example, the phase shift between the microwaves is changed, amplifications and / or extinguishments can be generated, so that the position and the

Energy density of areas of high energy density can be changed in order to specifically heat an area of a product formed by the material.

All devices for generating microwaves preferably have means for shifting the phase of the microwaves generated in order to be able to influence the radiation field in as many different ways as possible.

In a particularly preferred embodiment, the invention

Device has at least one measuring device for determining the microwave energy absorbed by the material, in particular on the basis of a scattering parameter, and / or the material temperature. An optimized formation of the radiation field can be determined from these measured values, for example by determining at which wavelength and / or at which phase shift the product heats up fastest. The position of the product within the cavity as well as the product geometry can also be measured and integrated into one

Control or regulation to generate the radiation field. A sensor, for example for measuring a scattering parameter, can advantageously be installed in a compact manner in the head of a microwave emitter or can be formed by the head of the microwave emitter itself.

A control circuit can preferably be set up with the at least one measuring device, the frequency and / or phase of the emitted microwave and / or the position of one or more reflection surfaces each being a manipulated variable and the

Scattering value and / or a product temperature can be the controlled variable. The heating of the material can then advantageously be carried out automatically and the

Microwave treatment can be automatically adapted to the respective material or its condition. This is particularly advantageous if polar materials of products of different geometries or

Composition should be networked in an alternating sequence.

The device according to the invention is intended, in particular, for vulcanizing rubber-containing products, preferably preferably strand products.

For this purpose, the cavity is designed in a channel-like manner with an opening for supplying the strand product and an opening for discharging the strand product. However, the invention can also be used to vulcanize products containing polar materials in one essentially closed cavity can be used. In both embodiments it is preferred if the cavity has at least one

 Has inlet opening and an outlet opening for supplying and removing hot air, which is guided along the product within the cavity.

A method according to the invention for crosslinking one or more polar materials, in particular rubber, contained in a product, the product in particular having the shape of an endless extruded profile, in a cavity, in particular with a device according to one of the preceding claims, has the following method steps: a) generating a radiation field in the cavity with a device for generating microwaves for heating the material, b) guiding the product through the cavity; c) measuring a size representative of the microwaves reflected in the cavity, d) changing the frequency and / or phase of microwaves and / or the

 Position of reflective surfaces within the cavity to change the radiation field depending on the measured size to reduce the amount of waves reflected in the cavity.

The method can be used both in continuously operated devices with an open, preferably channel-shaped cavity on opposite sides through which a strand product can be passed, and in devices operated in batch mode with a cavity closed on all sides. In a preferred method form, steps c) and d) are carried out repeatedly within a control loop, in particular continuously around the position of the radiation field, which changes with the temperature of the material

changing and optimizing the changing dipolarity of the material or - for example in the case of a continuously operated device - to a changing geometry of the material.

In a preferred embodiment of the method, the radiation field is changed continuously. In this way, areas of high energy density of the radiation field can be moved continuously within the product, for example, moving back and forth. In this way, each area of the workpiece absorbs the same amount of energy from the radiation field averaged over time Workpiece can be heated particularly evenly. A hiking of the

Energy density maximums can be generated, for example and particularly preferably, by continuously changing the frequency of the microwaves generated. In particular, the frequency for this can oscillate within a certain frequency band, for example between the frequencies 2.4 and 2.5 GHz.

The microwaves can also be pulsed, for example with a pulse frequency greater than 1 kHz. Thus, for a given power of the device for generating microwaves, the energy introduced into a region of a workpiece formed from the material can be reduced over time. In this way, for example in the case of materials with a low thermal conductivity, areas of the product which pass through the radiation field in areas of high energy density are prevented from being overheated, and the heat is achieved within the product via thermal conduction, even if they should be comparatively bad, can distribute evenly.

The object on which the invention is based, as is evident from the above, is also achieved by using a semiconductor microwave generator for crosslinking one or more polar elements contained in a product

Materials solved.

In the following, the invention is based on figures in which preferred

Embodiments of the invention are shown, explained in more detail.

Show it :

Fig. 1 is a schematic representation of a vulcanization device for

 Extruded rubber profiles;

Fig. 2 is a schematic representation of a cavity with a schematic

 shown standing microwave with poor energy transfer into a rubber profile to be vulcanized;

Fig. 3 is a schematic representation of a cavity with a schematic

 illustrated standing microwave with an improved

 Energy transfer into the rubber profile to be vulcanized;

Fig. 4 is a schematic representation of a cavity with a schematic

shown standing microwave, also with one opposite Microwave in Figure 2 improved energy transfer into the rubber profile to be vulcanized; and

Fig. 5 is a schematic representation of a cavity with two side by side

 arranged coupling points for microwave.

In Fig. 1 are the essential elements of a device for

 Vulcanization of strand products with a cavity 1, a microwave generator 2 arranged outside the cavity 1 for generating microwaves and a waveguide 3, through the microwaves from the microwave generator 2 to one

 Coupling point 4 for coupling the microwaves out of the waveguide 3 and coupling the microwave into the cavity 1 is shown. An endless rubber profile 5 is passed through the cavity 1 on a conveyor belt 6. The cavity 1 is designed like a channel, so that a hot air stream for heating the rubber profile can flow past it. The rubber profile is additionally exposed in the area of the coupling point 4 to microwave radiation 7, which is ideally formed by monomodal, standing microwaves running transversely to the transport direction of the rubber profile. However, the microwaves within the cavity are often reflected on the rubber profile itself and also on the side walls of the cavity, so that a pattern of overlapping microwaves is formed and some of the microwaves also spread along the cavity, as indicated by the arrows 8.

2 schematically shows a bad arrangement of the radiation field for heating the extruded profile. The rubber profile 5 passes through the microwave radiation 7 in a region of low energy density (shown here as the node of the wave). In addition, the wavelength and height of the cavity are not optimally coordinated with one another, so that the coupled-in microwave cannot form a monomodal standing wave with the wave reflected on the underside of the cavity 1.

3 schematically shows a radiation field that is optimized for the energy input into the rubber profile. The wavelength of the microwave was changed (enlarged here), so that on the one hand the area of high energy density

Microwave radiation 7 (shown here as the belly of the wave) is shifted into an area through which the rubber profile passes. On the other hand, the wavelength is matched to the height of the cavity 1, so that in the ideal case a monomodal standing wave can form. Fig. 4 shows schematically a radiation field that is also optimized for the energy input into the rubber profile. The wavelength of the microwave was shortened here and the reflection surface opposite the coupling point 4, which is formed by the lower wall of the cavity 1, was shifted downward. Here too, it is achieved that, on the one hand, the area of high energy density of the microwave radiation 7 (shown here as the belly of the wave) is shifted into an area through which the rubber profile runs. On the other hand, the wavelength is matched to the height of the cavity 1, so that in the ideal case a monomodal standing wave can form.

5 shows a cavity 11 with two coupling points 12, 13 for microwaves, which lie next to one another, so that the microwave fields emanating from the coupling points overlap. A phase adjustment of the microwaves coupled into the cavity at the coupling points 12, 13 can produce a radiation field 14 with an interference pattern in which as many areas of high energy density as possible lie in the area of the rubber profile 15 passed through the cavity 11. The coupling points do not have to lie directly next to one another, for example they can also be at different points

Walls of the cavity may be arranged or face each other. More than two coupling points can also be provided. Important for one

The variability of the radiation field in this exemplary embodiment is such that the microwaves coupled into the cavity from the coupling points overlap.

Claims

claims 1. Device for networking one or more in one product  contained polar materials, in particular rubber, the product in particular having the shape of an endless extruded profile, with a cavity formed by at least one wall, and with at least one  Device for generating microwaves for heating the material, the microwaves forming a radiation field in the cavity, thereby  characterized in that means are provided which are designed to specifically change the radiation field used for heating in the cavity for an optimized absorption of the radiation energy. 2. Device according to claim 1, characterized in that the device for generating microwaves has means for adjusting the frequency of the microwaves within a frequency band, in particular in a frequency band between 2.4 and 2.5 GHz. 3. Device according to claim 1 or 2, characterized in that the device for generating microwaves has means for shifting the phase of the microwaves. 4. Device according to one of the preceding claims, characterized in that a semiconductor microwave generator is provided as a device for generating microwaves. 5. Device according to one of the preceding claims, characterized in that a device for generating microwaves is arranged directly on the cavity. 6. Device according to one of the preceding claims, characterized in that the cavity has reflection surfaces for microwaves, the position of which is adjustable. 7. Device according to one of the preceding claims, characterized by a hollow waveguide between a device for generating microwaves and the cavity. 8. Device according to one of the preceding claims, characterized by several devices for generating microwaves, the microwaves of which are coupled into the cavity in such a way that they generate overlapping microwave fields. 9. Device according to one of the preceding claims, characterized by  at least one measuring device for determining the microwave energy absorbed by the material, in particular using a scattering parameter, the material geometry, the material position and / or the material temperature. 10. The device according to claim 9, characterized by means for changing the radiation field depending on the absorbed by the material  Microwave energy or material temperature. 11. Device according to one of the preceding claims, characterized in that the cavity at least one inlet opening and at least one  Outlet opening for supplying and removing hot air, which is guided along the product inside the cavity. 12. A method for crosslinking one or more polar materials contained in a product, in particular rubber, the product  has in particular the shape of an endless extruded profile, in a cavity, in particular with a device according to one of the preceding claims, comprising the following method steps: a) generating a radiation field in the cavity with a device for  Generating microwaves to heat the material, b) guiding the product through the cavity; c) measuring a size representative of the microwaves reflected in the cavity, d) changing the frequency and / or phase of microwaves and / or the  Position of reflective surfaces within the cavity to change the radiation field depending on the measured size to reduce the amount of waves reflected in the cavity. 13. The method according to claim 12, characterized in that the radiation field with step d), in particular the frequency of the microwaves generated, is continuously changed. 14. Use of a semiconductor microwave generator for cross-linking one or more polar materials contained in a product.