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hot air vulcanization of rubber profiles ...

by:DMS Seals     2020-06-30
In the automotive industry, elastic profiles are heavily deployed on buses as seals and waterproof materials.
High standards required by the industry;
Weather protection, noise reduction, improvement of tolerance limits, and strong demand for B-C rubber forced the development of the rubber processing industry, especially elastic materials.
A complex proofing system must also be realized through an extremely complex form factor.
These profiles usually have a very large surface and a lower CrossSection density.
They are usually composed of two or three rubber compounds and reinforced by steel bars.
Sometimes they are flocked with a low friction coating. Such high-
The vulcanization method needs to be adjusted for technical seals.
For more than 90 years, with the reduction of the number of rubber in each sealing device and the decrease of the dielectric coefficient, especially the use of B-C rubber, this consistent trend once again highlights the old-fashioned vulcanization method, A method that has developed to a very high standard in the past few years is hotair method.
Curing Method and its importance in autoclave (steam-bath)
This is a very old method that has nothing to do with today\'s manufacture of sealed profiles.
It still holds a place in the manufacture of profiles with woven components, such as cables, pressure hoses and manifold tubes for vehicles.
The internal structure of this product should not be required to be completely free of moisture and air, as people work under high pressure steam.
The peroxide vulcanization system is possible during this process.
Very laborious treatment-
Dense and therefore very expensive.
The modern appearance is almost impossible --
Due to the long curing time, keep the geometry of the profile shape when packing in the autoclave.
In most cases, 20 minutes or more.
This vulcanization method is completely out of date.
Hot air is blown into a whirlpool-
The speed of this air must be strictly controlled so that the glass beads that make up the Whirlpool bed will not be discharged.
The outline slides on the moving glass beads, just heated on the side.
Form a superficial impression.
Glass beads can easily be embedded in a sunken surface
Lip print and cleaning are very difficult.
Because a lot of air has to be heated, a lot of energy is used for curing.
It is difficult to achieve such necessary environmental protection measures.
In addition, the recycling of the remaining energy becomes extremely difficult, among other things, due to the condensation of softening steam.
This is of course the dirtiest of all curing methods.
Only a limited running speed can be achieved. Infra-
These factories are rarely used to heat rubber profiles today.
Due to known energy consumption problems at long distances, their disadvantage is that it is almost impossible for the profile to be heated evenly.
Therefore, this method is also rarely used for adhesives now.
Drying of flocking profiles.
The energy consumption is relatively low, but unfortunately the same is true for throughput speed.
Even today, it is common for Vulcanization to install Vulcanization in molten salt.
The excellent heat transfer performance between salt and vulcanization rubber makes it possible to cure the peroxide, even if salt granular oxygen is obtained on the surface of the profile.
Due to the average contact of molten salt to all surfaces, the heating of the profiles is very uniform.
When this contact occurs in a few seconds, one can think that the surface of the sponge is very smoothrubber.
The energy needed to keep the molt at 240 to 248 [degrees]
C is not very large, although one should remember that the salt bath is usually electric heating, nevertheless, the salt bath will also bring considerable operating costs.
The large consumption of salt has significantly increased these costs.
In addition to the obvious advantages of the system, the following disadvantages must be considered. Large cross-
The part of sponge rubber is difficult to make, because as the cell structure deteriorates, uniformity is lost when it approaches the center.
If the metal conveyor belt is used, it must be prepared for the change of the lip
The position of the profile due to buoyancy.
Admittedly, due to very narrow operating speed tolerances, excellent heat transfer can hardly be changed in the length of the plant.
If sulfur is used for curing, it is almost impossible to prevent dangerous gases
Contains a large number of nitrosamines.
The salt used for purification according to current environmental requirements can only be achieved with huge capital expenditures.
Over time, the importance of vulcanization will become smaller and smaller.
It is almost impossible to meet always stricter environmental requirements.
The curing method of shear head vulcanization was promoted in 1979, while gaining a place in the industry.
Electric energy is converted from the motor directly before the extrusion die to the rotation of the shear head core shaft.
The rubber is processed through the extruder barrel into a shear head space, which is generated from the space between the rotating core shaft and the stationary and central cylinder.
The electrical energy converted into molecular friction heat is adjusted by changing the speed of the core rod.
Therefore, the elastic temperature can be much higher than the typical extrusion temperature and remain the same when exiting the mold.
These facts have brought important advantages to users;
Start vulcanization immediately before the formation process.
Therefore, with the reduction of viscosity, the compound is partially crossed
Link, can achieve the height shape definition and stability of sealed profiles.
The electricity used for heating is little or no waste, and the cost is relatively low due to low consumption.
As with each curing method, there are some shortcomings to consider when deploying this method.
The adjustment of the elastic compound may be problematic, because only after the rubber is removed from the mold can the focus of the compound be determined.
Due to the reasons determined by the composite technology, it is usually only possible to work at low outlet temperature, which again places the responsibility for most of the vulcanization on the following mandatory heat-air channel.
Increased production
It is possible to seal the components and sponge rubber, but the same problem still exists.
One particular drawback is the expansion of rubber when subject to variable temperature.
Therefore, this curing method requires a special extrusion mold that cannot be used with a normal extruder.
On the other hand, of course, introduction-
The tool of the previous extruder cannot be used with the shear head system.
However, for rubber sealed profiles that are not important for most forms and compound changes, shear head vulcanization seems to provide a favorable technique.
A uhf device that uses a UHF energy of 2 for vulcanization.
45 GHz is common.
If the dielectric loss or polarity of the compound can be set high enough, then the microwave energy can be directly converted into heat inside the vulcanization rubber.
Unfortunately, however, the physical properties of the B-C rubber formulation often do not adapt well to the UHF.
The polarity may be low due to the filler or other reagents in the composite formula.
However, this can be overcome by adding special reagents, which will make it easier for the formulation to accept UHF.
The downside to this is that it makes the rubber compound more expensive.
Most importantly, the high-tech requirements of the automotive industry have led to a declining deployment of the UHF plant.
However, it is also because modern elastic seals require only a limited amount of unit raw glue while maximizing the shapeseal surface.
The applied heat is reflected back very quickly because the radiation emission coefficient is 0,95 W/m * d 253 * K * d 253 * and the total radiation grows to the power temperature of the four contours.
Already installed, below, hot-air-
Channels are increasingly inclined to take over the task of heating the profile, a task that naturally requires it-specific quality.
Then, it must be noted here that the UHF machine can only be deployed wisely if the compound has a high polarity and the profile has a small surface relative to the crosssectional mass.
However, one may try to prove that, on the contrary, the operating costs of microwave devices are relatively high.
For example, under the UHF output with a rated power of 24 kw, the total electrical requirements (
Including support hot air is too weak)is 80 kw.
This does not include the energy of heat-air-
Channel after microwave.
Only the UHF part is considered-
For example, only in the United States
Running for more than a year, running three shifts a day, a person can expect an energy cost of $35,000 for UHF only ($. 05/Kw).
Additives that increase the polarization of rubber compounds will increase the compound cost by an average of $0. 05 per kilogram
At an extrusion rate of 300 kilograms per working hour, we spend an additional $131,400 per year.
The heated post-curing Channel uses an additional $63,000 in energy costs, so in the case of the most favorable calculation and excluding maintenance costs, the annual cost is approximately $229,400.
Are we going to compare this to 180 KW of gas demand? air-
In the same performance channel, we will find an immediate savings of $205,700, which is $23,700 in energy costs per year ($0. 015/Kw).
This calculation has very similar results when applied to our European neighbors.
Extra savings in economic calculations
No, the \"profit\" of the installation is $205,000 per year.
This should be a good reason to consider the vulcanization method. Hot-
30 years ago, the rubber had been subjected to continuous hot vulcanization. air-method.
However, due to the fact that the development of the machine cannot overcome the inferior heat exchange between the well-known gas and vulcanization rubber, the success is limited.
Gerlach Limited.
Participate in the heat-
Especially in the last 18 years, in the past seven years, it has been improved to such a high technical standard that in most cases it is superior to the above methods both technically and economically.
Not only high recommended hot production standards-
Air vulcanization.
As has been discussed, now users of elastic profile seals need compounds and forms that can be passed through the heat-air method.
The purpose of transferring heat to rubber profiles as soon as possible depends on three criteria: * temperature difference between heat
Conveying air and rubber profiles should be as large as possible.
Technically, it\'s easy to implement this \"delta T.
\"* In order to store and release a lot of heat, hot air must be as heavy as possible.
It should also be as wet as possible.
* Heat-absorbing elastic profiles should be exposed to the air in such a way that the high-energy air molecule is exposed to its surface as much as possible.
Finally, the heat exchange should be linear throughout the heat-heat periodair-
Channel, dela T sinks due to the heating of the profile, which is difficult to obtain.
The possible working principle and its renderings 1 show a very old method in which cold air is extracted from the working channel and then re-introduced through the electric air heater. The air-
The flow direction is 90 degrees angle with the contour axis. [
Slightly] Illustrations
The effects of constant temperature and constant temperature on profile warming are very limited.
As shown in the figure, the profile can only be weakly heated on one side, while releasing a large part of the energy obtained (
See UHF installation).
The air is permanently contaminated by the softener, which condenses or gathers in the work channel and supply route, resulting in a marked deterioration in the quality of the process. This so-called cross-
The current recycling principle comes from the textile industry and was originally developed for the drying of fabrics.
It is completely unsuitable for vulcanization of rubber profiles, but unfortunately it is used for this purpose again and again.
A similar principle is shown in figure 2.
Here, the cold air is drawn from the working channel and finally delivered through the weak current air heater. [
Slightly] Illustrations
Then the heating process air returns to the working channel through infrared
Complete the red stick of the heating process before re-heatingentry. The infra-
The red heating rod is located at the back of the narrow grid performance plate pulled out in length, which is understandable and hardly allows infrared
Red energy enters the working channel.
The air is guided in a relatively long process parallel to the contour axis and recycled.
And every one of you
However, a lot of air enters the factory, which must be handled.
Compared with the method described earlier, the efficiency of this method is significantly improved.
Nevertheless, the heating efficiency is still too limited.
In the criteria previously listed, only the first point is covered.
So in the best case this machine can only be deployed as an afterthought
If the required profile temperature can be reached with UHF, it is the heater of the UHF factory.
However, this is exactly what the problem is (
See UHF installation)
There is no reason to think that it will become easier over time.
The pollution of the installation limits convenience.
In order to solve this problem, the heat was installed-
An exchange plate that has been tried with a moisturizer that can be partially concentrated.
However, as maintenance is now focused on the day-to-day cleaning of the exchange board, this has not been fully successful.
This also creates problems because cleaning is done with compressed water, which creates environmental problems. Hot-
Unfortunately, air facilities based on this principle have still been deployed, although few.
This method has been in existence for more than 20 years and at this time it has never met the expectations of profile producers.
The concept of air meets the criteria listed earlier.
To achieve the best Delta T, the air is wet.
The hot air-carrying molecules provide the best heat exchange directly on the surface of the profile through their extremely high cross-action.
By modifying the molecular motion, the linear heat transfer over the total length is realized throughout the duration.
As shown in figure 3, the process air is forced into the air/air heat exchanger through the ventilator.
Here, it absorbs a large part of the exhaust heat and is delivered to the burner unit 5 through pipes 3 and 4.
This gas heating can be achieved with natural gas or propane gas. [
Slightly] Illustrations
Air further into the working Channel 6.
It is expected that there will be an air intake booster jet every 3 kilometers.
Remove air in different quantities at stages 7, 8, 9 and 10 and cause a heat exchanger 2.
Here it is cooled to the temperature of 65 [degrees]
C. A moisturizer with exhaust gas.
Through the cooling of one side of the air and the diversion of the air-
Separation effect, so
On the other hand, a large amount of condensate is called separated and can be taken away.
The air that is still contaminated enters the cooler and the strengthening separator through the pipe 11.
Here it is cooled further and another part of the moisturizer can be condensed and taken away.
The air is then further converted into a centrifugal filter for 99.
Remove 7% of the remaining impurities.
One of the features of this filter is that it is self-cleaning.
Finally, the air is fed into the No. 14 exhaust ventilator and 85% of the air is returned from there to a single burner.
The way the burner 5 is constructed can burn the remaining impurities.
Heat efficiency-
The concept of air can be summarized as: the system is actually closed, and environmental protection is completely indispensable.
Since a single burner is delivered with relative cold air, there is a strong differential pressure between the burners
Take and exit, which makes it possible to modify the air in the working channel so that different pressures can also be obtained.
Figure 3 shows very clearly that the pressure value Δp is larger at the end of the installation.
Air system determined, parallel to pressure increase, cross pressure increase
Movement of molecules in contact with the surface of the profile.
Due to the decrease of Δts between air temperature and profile temperature, a significant increase in heat exchange value is achieved.
Heat transfer runs from the beginning to the end of the channel, parallel to the pressure curve.
The burner unit can be built in such a way that a large amount of water can be released into the working passage.
Therefore, as mentioned above, the air becomes particularly heavy and the heat transfer performance is improved again.
In theory, the working temperature can be increased to 500 [degrees]C.
It is regulated to a maximum of 340 [for security reasons [degrees]C.
Air concept provides a modular system in which software can be modified to handle the hardware as needed.
For the user, this offers the possibility of growth in the next few years, whether in the special elastic field or in the specific profile field. The hot-
Air installation concept, when we are fully aware of the product range that is cured by heat
Air vulcanization plant, then it is very simple to create a working concept for installation.
Figure 4 shows the heat-
Air devices with average operating speed and expected energy consumption. [
Slightly] Illustrations
Each installation assumes that there is a vacuum extruder at the front and a regulation and measurement unit at the back, which is able to measure the profile and adjust the raw material feed to the extruder.
However, it must be noted that it is not possible to adjust the material in this way if there is coextrusion.
After measuring and adjusting the device, highspeed-hot-
Air channels are basically always deployed for heating the rubber temperature from the extrusion temperature to the desired vulcanization temperature.
The running speed \"V\" shown in the table is from the installation of Gerlach hot-air channels.
In order to determine these values, the PDM profile-
Overall use in automobile tradewere used.
In the case that the rubber profile is rigid due to its steel bars, two kinds of heat
Air channels are often deployed in sequence.
In this case, the second machine always consumes less energy than the first one.
Steel bar profiles can usually be transferred to the corresponding minimum radius.
In this case, the second machine should be threebanked hot-
Air passage with overall cooling system.
This machine is shown in the picture; marked 114.
The most compact installation in global deployments is a combination of 109 and 114.
Elastic seals in the automotive industry are often solidified on systems indexed in Figures 5, 6 and 7.
Installation 9 is very commonly used in the production of bulk profile seals in the construction industry.
Due to the compact structure of the machine, very good operating speed can be achieved, such as a total length of 25 m mm, a heating channel of 50 m mm, and a cooling device of 25 m mm.
The throughput number given is the average, and if the relationship between the profile surface area and the cross section is changed, it is easy to adjust up or down.
The installation shown does not include special requirements.
However, due to the modular structure, there are few special orders that cannot be completed.
What compounds and profiles can be cured with a hot air vulcanization device?
Here we can give a very simple answer: all the contours of sulfur
Curing compound and heating
Hot vulcanization can be used for curingair channel.
Sealed profiles with silicon base can be cured very quickly with heat
Type 109 air channel.
Low textile or metal reinforcementmiddle-and high-
Pressure hose can be very effective at high temperatureair channel.
There are special aggregates that can control the form of these supports, such as adjusting the air content to eliminate moisture.
If in the broadest sense, we can consider the fire.
The hose, with or without a polyester sheath, must be a perfect example of hot air heating as a profile.
Unfortunately, if it does not help, Peroxide curing in hot air is not possible, due to the affinity between the peroxide particles on the surface of the profile and the oxygen in the process air vulcanization, almost impossible.
Vulcanization in an inert environment is also impractical, as inevitable traces of oxygen can detect an uncured profile surface, resulting in a volatile surface.
In the past, attempts to maintain a distance between oxygen and the profile surface by powdered oxygen failed.
A surface chemical treatment method has recently been developed, which speeds up the curing process, among other things.
We are involved in research projects and are confident that these results will be ready for the release of the technology market in a few months.
Can the transport marks on the surface be eliminated?
When the conveyor belt reaches the highest plasticity, the elastic profile is located on the conveyor belt, and the contact surface obtains any irregularities inherent to the above conveyor belt.
These unnecessary irregularities can be eliminated using an absolutely smooth conveyor belt.
Unfortunately, the market has not yet provided such a belt, which can resist extremely high temperatures at the same time.
This surface marking can also be reduced by using a coating on the profile-
For example, with talcum-
However, it is well known that this creates other problems.
Particularly balanced cross profile
It is possible to hang parts on the air cushion, but it is very difficult to handle.
Excellent results can be achieved by deploying a conveyor belt consisting of rollers.
The development of this solution is complete and very interesting.
This new method not only eliminates the belt marking, but also helps with more uniform heating around the part.
Without the obstruction of the belt, the lower side can be heated more directly.
Curing sponge rubber through hot air is crucial, when curing sponge rubber, to achieve a good cellular structure across the cross section and to produce a smooth surface area possible.
Of course, to a large extent, both of the above criteria depend on the compound used.
However, the type and adjustment of the installation is also a problem.
Index 9 in Figure 4 shows a typical hotspot
Air device for sponge rubber.
Here, the rubber profile is powered by a high-speed Channel of Type 109 and is 12,000mm in length.
The channel is set in such a way that a very large heat transfer from air to the rubber profile occurs in the first channel area so that the surface can be heated and cured as soon as possible.
After about 3.
5 m then, the heat transfer rate is increased again in the third and fourth channel regions to initiate the foaming process.
In this installation, The Blowing Point is set at the end of the machine, which can balance the expansion of the profile by increasing the conveying speed of the following machines.
After this, the machine, by the way, a-type 114 12 m cm long, three-in-one memory machine has an overall heat dissipation device below.
This manufacturing process ensures a uniform honey profile
Comb over the entire cross section and the surface is quite smooth.
The larger cooling plant under the machine (
No extra floor space required)
Providing good cooling of the product, it is well known that sponge rubber cannot achieve this without the corresponding long stay in the cooling medium. In a twelve-
The cooling device of the meter machine is 20-
5 m long
For large cross-section profiles, place a very low output between the High Speed Channel and the triplebanked device below or the straight one-way oven, possibly a very short UHF machine for 3kw is
This UHF back can now be integrated-up in a high-
Speed installation.
This low KW microwave is possible because the energy that can now be put into the profile through the surface is very high.
Since rapid skin curing can be achieved, the addition of the new super jet air channel can now greatly improve the surface of the sponge profile.
Further possibilities for thermal deployment
The Air factory not only needs to heat the vulcanization of the elastic profile, but it usually dries from the primer of the rubber coated steel bar.
For this application, a short device needs to be queued in front of the extruder.
In the best case, they are heated by gas and the temperature of the process air can be set to 400 [degrees]F (248[degrees]C).
The coachman seals are often gathered together by polyester fiber.
For safety reasons, it is better to use the adhesive that is particularly fast in drying, provided that it has a temperature of 170 [degrees]F 248[degrees]
The air around is wet. A high-
Speed Channel, Type 109, can meet all expectations, at the same time it can aggregate adhesive faster and more evenly than infrared technology
Red device.
More uniform because the hot air is evenly transported to all surfaces, even in deep cracks
There are special problems with red radiation ,(
In addition, the intensity of the infrared ray decreases to a cubic ratio of the radiation distance, which leads to different degrees of aggregation).
Thanks to better heat transfer and very high air humidity, the production speed is faster.
The fact that the process air is clean allows removal by evaporation of the adhesive solvent.
Although there is a high airflow in one channel, the flock-
The fibers remain very stable. Hot-
Air device as back
Ultra-high frequency machines such as cutting head presses require heat-
As an air device on the back-
Ups in order to keep the heat obtained unchanged within the necessary time.
However, in general, it is not enough to just keep the heat and need extra heat, which is a fact.
It has been explained so far.
High throughput speed
It is recommended to use the air device as shown in Figure 4 and index 9.
If the high volume profile is cured, then the installation of the 114 type is enough --
The total length is 12 m and the heating length is 30 m.
The cooling length of 8 m and 25 m because the extrusion speed has been controlled by the extruder. The hot-air channel -
Usually there is only one unit on a long line.
The air vulcanization plant is only a small unit on a long production line.
More importantly, it has to be designed in a way that is compatible with other machines, with performance close to 100%.
For example, a universally compatible computer control is now provided, which can identify and handle problems before causing the entire factory to crash.
Here, we can\'t forget, the fault in the heat-
The air curing device can stop the whole production line. In our hot-
Air vulcanization unit we measure not only the temperature but also the actual experience of the rubber profile --
Successful vulcanization is acceptable.
Siemens SPS control can be spliced into the main computer through RS-splicinginterface.
Applications for storing data-
The value occurs automatically.
We believe that one of the most basic human demands can no longer be ignored --
Breathe clean air.
So Gerlach is currently working on a collection filter that is envisioned to remove mechanically.
3% of the pollutant and return it to the burner to be burned.
The resistance of this centrifugal filtration device is to produce the aerosol phase and then collect the fine spray mechanically.
However, since the entire filtration unit has a centrifugal movement, the collected steam can be discharged immediately after entering the filtration layer.
Therefore, the filter unit is largely self-
Clean to maximize efficiency. Energy costs -
A concept of saving, if we use less, we will naturally spend less energy.
If we can save energy, it\'s obviously very positive.
However, if productivity drops at the same time as these energy savings, then the process has generally been degraded to low efficiency.
We insist that energy should never be wasted, and the main energy we use in the process must be the cheapest in the market and the cleanest.
So, let\'s get gas.
Since we use direct heat rather than indirect heat, we find it particularly easy to meet the emission requirements set by law.
For most countries in the world, the cost of natural gas or propane gas is only ten to twenty pounds.
5% of electricity.
Small side effects, I . e. extremely fast heating of process air from 20 to 340 [degrees]
C in 30 to 60 seconds, relative to the cost advantage, is often almost ignored.
As mentioned earlier, a thoughtful investment cost
By saving energy costs in a relatively short period of time, the vulcanization unit can be recovered.
The waste heat has to be recovered, and we do this because if it flows into our heat exchanger, we will have it carried in the most complicated way, clean process air.
It is obvious that condensation is formed.
However, this can be allowed to run freely and cleaning may only be required every 6-
It only takes 30 minutes for 12 months.
The future development, the introduction trend of the limited number of ternary rubber sealing profiles per rubber and the future demand for complex sealing devices forced the pace of hot air treatment devices into the industry.
To be more flexible with future complex seals, Gerlach is working to support high-speed thermal seals
Air channels with extra UHF.
In this concept, the polarity of the compound plays a less important role, because the dielectric loss is usually significantly increased by heating through hot air.
With computer control, the magnetic field can be moved on the cross section of the channel so that the profile can be optimally adapted.
There are only about 2 very low-power UHF units.
Most need 4 kw as one heating is still by heat-
Air installation.
We used superjet air oven to remove the belt markings and play a huge role in better sponge surface conditions.
It also reduces the requirement for line length, which is a big problem in many old factories.
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