DE3830223A1 - METHOD FOR DRYING WATER HUMIDIFIER TEXTILES - Google Patents

Description

Clothing textiles in particular have long been more common wise chemically cleaned with the help of perchlorethylene. since however, it is suspected that perchlorethylene is carcinogenic can be gain washing processes without using organic Solvents such as perchlorethylene have increased importance.

In the commercial washing of textiles, such as Be clothing textiles, drying is a special pro is a problem because, on the one hand, it should run as quickly as possible, on the other hand, do not affect the dried textiles may.

Drying especially wool-containing textiles at higher ones Temperatures at which the water evaporates leads to a Shrinkage, in which the tissue becomes matted and shrinked.

If lower drying temperatures are used, for example 70 ° C, in drying chambers through which air flows and in which the textiles are arranged at rest, so the shrinkage is greatly reduced, but the drying lasts Normally over an hour, sometimes four to five hours depending on the type of clothing textiles to be dried. The drying time can be adjusted by rotating drum dryers Type of tumble dryer with gentle program can be shortened, but in such rotating dryers in which the Tex tiles constantly change their position, the shrinkage significantly reinforced.

The object underlying the invention was therefore to a process for drying water-damp textiles, esp special clothing textiles, to get to a possible minimal change in the tissue, such as as little shrinkage as possible, but also with drying times as short as possible.  

The inventive method for drying water humid Textiles by heating the textiles in a resting state in a drying chamber through which air flows indicates that the water present in the textiles evaporated by microwave radiation and thereby the micro wave radiation in the area of falling relative air humidity of the drying chamber exhaust air and before reaching it a residual moisture of the textiles of 7%, based on the text tilie dry weight, finished and then if necessary eating without microwave radiation, but with further notice carry air through the drying chamber to a rest moisture of at least 2%, based on the textile dry weight, dries to the end.

It is surprising that textiles, especially clothing textiles that are usually processed in multiple layers (upper fabric, insert, lining) and often wool and / or relatively never drig melting synthetic fibers contain and metal parts can be dried using microwaves, without attacking the tissue. If you don't have the above designated special conditions of microwave treatment note, you get a quick one when using microwaves complete drying, which leads to the fact that in the final phase se of the drying process, in which only very little or there is no more water in the tissue, one rapid, high-intensity heating takes place so that wool ver is seared and discolored, certain synthetic fibers, such as polyamide fibers, can melt and folds formed in the Tissue to be fixed. If the textiles are metal or too Plastic parts such as zippers, metal buttons, eyelets or Buckles have, so these are in the last phase drying if the claimed special is not observed measures heated by microwave radiation in such a way that the neighboring fabric charred and the textiles completely un become usable. For this reason, drying has been carried out for textiles never applied with the aid of microwaves.

Surprisingly, however, micro according to the invention  use waves to dry water-damp textiles, even if they contain metal parts, if you ge the above additional conditions, i.e. first one Air flow through the drying chamber, secondly the micro wave radiation when the relative humidity drops exhausted air and thirdly the microwave radiation with a certain residual moisture, but this is the case is chosen that the textiles already feel dry. The residual moisture mentioned is suitable for a subsequent one Ironing the textiles, but also evaporates quickly when hanging conditions in normal ambient air.

The use of microwaves to dry textiles leads to very short drying times and intensive processing drying even thick layers of fabric or multi-layer fabrics, what the procedure for drying washed clothing text makes it particularly suitable. By adhering to the shown boundary conditions, the tissue remains intact, and it occurs only a very small and therefore practically unnoticed shrinkage of wool.

If in the present context it is said that the Tex tilts should be warmed up when at rest, so says this is that no violent and permanent change of situation is featured should be taken, as is the case with rotary tumble dryers is. The textiles are useful in the present process ß either lying flat in the drying chamber or hanging dried. Small movements as a result of the flow the air, are not harmful to the process. If arranging the textiles flat in the drying chamber, can NEN they are arranged in stacks, because even then one out sufficient drying of the internal parts up to the he desired residual moisture occurs.

The relative air humidity can be determined by humidity sensors Air output of the drying chamber can be measured. The residual moisture te of textiles can be gravimetric by weight comparison the damp textiles and the completely dried ones  Textiles can be determined. It is average Residual moisture in the entire drying chamber filling, as below different moisture levels occur in different places and different materials can absorb the moisture can keep different. Depending on the size of the drying chamber can be one microwave transmitter or can have multiple microwaves transmitters can be used. For larger systems with relatively large Outside drying chambers it is tick-like, instead of a microwave to arrange several transmitters in the drying chamber. Appropriately the microwave radiation is stopped at 10 to 15% Residual moisture of the textiles and provides the desired residual moisture then with the help of the air flowing on.

You get a shorter drying time if you go with a higher power of the microwave transmitter works. At the process according to the invention can either be carried out that one with essentially constant microwave transmitter types Stung works until you turn it off or that you first with higher microwave transmitter power up to a residual moisture te of textiles works in the range of 10 to 15% and then the performance, e.g. cut in half before after further evaporation of water switches off completely. So you can for example at the beginning of the drying process with a Output of the microwave transmitters work from 650 to 1000 watts and this performance in a second stage when reaching one Residual moisture of the textiles from 10 to 15% to 30 to 50% of the Reduce initial performance. This can be done either through Program process or using moisture sensors in the exhaust air the drying chamber can be controlled.

The dry air flow used in the process chamber is essential to the evaporated from the textiles To drain the amount of water and thus relatively short drying times to enable. A constant air flow can be used for this lig be passed through the drying chamber. If he desires, the air flow can also at least partially circulated, i.e. several times through the drying chamber leads, but this requires that the recirculated air  dried before reintroducing them into the drying chamber is what makes the process more complex than if the Ab air from the drying chamber is blown directly into the atmosphere becomes. Since the exhaust air only contains water vapor, this is for the Environment unproblematic.

In the drying chamber there is no very significant flow air speed needed. Preferably the flow air flow rate as it passes through the drying chamber set so that the air volume of the dry came mer per minute at least 10 times, preferably 25 to 50 times is exchanged.

Through the following examples and comparative examples the subject of the invention further explained.

Example 1 and Comparative Examples 1 to 5 1. Test fabric

Fabric pieces 30 × 30 cm made of cotton, wool, polyester, buttocks Lyamide and acrylic were 5 layers together with metal clips stapled. The individual weight of this test tacked together fabric was 32 g.

2. Pretreatment

12 of these test fabrics were made into 4 stacks of 3 fabric series each folded and wetted for 5 minutes in water at 30 ° C and then to a moisture absorption of 80 to 85% squeezed.

A total of 384 g textile dry weight therefore came per experiment, which after wetting and squeezing approx. 310 to 320 g contained.

3. Experimental setup

The test fabric series were folded in the middle and over one Wire frame with which they are vertically Drying cabinet with 37 l drying chamber content were given.  

Test target

Determination of

• a) drying speed,
• b) uniformity of drying, especially in the inner fabric layer,
• c) Risk of burns at textile contact points with metal.

The drying cabinet was in addition to the convection heating with a Microwave transmitter with a max. Power of 650 watts.

4. Experimental alternatives

Table I

5. Results

Table II

In Example 1, depending on the Exhaust air drying temperature, the relative humidity exhaust air and the residual moisture of the tissue samples.

Table III

When the experiment was repeated, the drying process was carried out run so that when the values for the relative humidity in the exhaust air from the microwave transmitter was switched off and the drying process another 3 min. was continued in recirculated air without microwave radiation.

With a drying process analogous to Table III, the Mi crown wave irradiation in the 18th minute after the start of drying when the relative humidity drops from 91 to 87% below chunk. After a total drying time of 22 minutes, the Ab was air temperature 55 ° C, the relative humidity 62%, the Residual moisture 7%. The fabric layers were the same on the outside and inside moderately dried, they felt due to the residual moisture no longer clammy, but a bit cool on. Burning certificate Nothing was mentioned anywhere.  

Example 2 and Comparative Examples 6 and 8

In this experimental set-up the influence of drying procedure for the shrinkage of wool fabrics.

IWS felt shrinkage test fabrics were washed with a mild detergent Wet 1 g / l wet for three minutes, then on one Squeezed out residual moisture of 120% and after one of the follow dried the process. Then by measuring the Test fabric determined the area loss.

In Comparative Example 6, the drying was carried out lying flat at room temperature for 24 hours. The loss of area was at 2.4%. With regard to the long drying time is depending but a commercial application is not possible.

In Comparative Example 7, the drying was carried out lying flat at 80 ° C in the circulating air used in Examples 1 and 2 drying cabinet without microwave radiation for 2 hours. The area loss was 3.0%. Even such a drying time is not suitable for commercial use.

In comparative example 8, the drying took place in a house Holding tumble dryer with rotating drum in a gentle program for 45 minutes. The area loss was 18.2% and is not acceptable at this level.

In example 2 according to the invention, in example 1 used drying cabinet with microwave radiation under Application of the drying conditions of Example 1 during Dried for 20 minutes. The area loss was in this case at only 1.8%. Despite the slight shrinkage, it is invented in accordance with this example with a very short dry time from what the process is for commercial use extremely suitable.

Claims (8)

1. A method for drying water-damp textiles by heating the textiles in the quiescent state in a drying chamber through which air flows, characterized in that the water present in the textiles is evaporated by means of microwave radiation and the microwave radiation in the region of the drop in the relative atmospheric humidity the exhaust air from the drying chamber and before reaching a residual moisture of 7%, based on the textile dry weight, ended and, if necessary, subsequently without microwave radiation, but with further passage of air through the drying chamber to a residual moisture of at least 2%, based on the textiles dry weight, dries to the end. 2. The method according to claim 1, characterized in that one microwave radiation in the area of residual moisture of textiles from 10 to 15%, based on the textiles dry weight, finished. 3. The method according to claim 1, characterized in that one the power of the microwave transmitter when reaching a rest moisture of the textiles from 10 to 15%, based on the text dry weight, reduced and the microwave irradiated before reaching the residual moisture of 7% completed. 4. The method according to claim 1 to 3, characterized in that you can get a residual moisture without microwave radiation te of textiles dries from 4 to 6% to the end. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the microwave radiation is stopped, if the relative humidity of the exhaust air the dry chamber by 1 to 10, preferably 2 to 6% over that maximum value reached has dropped. 6. The method according to any one of claims 1 to 5, characterized records that one with a microwave transmitter power above half a 400 watt the drying process begins and ends phase lowered. 7. The method according to any one of claims 1 to 6, characterized records that the air with such flow velocity through the drying chamber that the air volume of the drying chamber at least 10 times per minute, is preferably exchanged 20 to 50 times. 8. The method according to any one of claims 1 to 7, characterized records that the textiles are flat in the drying chamber dries lying or hanging.