Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/20—General details of domestic laundry dryers 
  • D06F58/26—Heating arrangements, e.g. gas heating equipment
  • D06F58/266—Microwave heating equipment
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
  • F26B3/34—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects
  • F26B3/343—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action by using electrical effects in combination with convection

Definitions

• Drying is a particular problem in the commercial washing of textiles, such as clothing textiles in particular, since on the one hand it should run as quickly as possible and on the other hand it must not adversely affect the dried textiles.
• drying temperatures e.g. 70 ° C
• drying chambers through which air flows and in which the textiles are arranged at rest
• the drying time can be shortened by rotating drum dryers in the manner of a tumble dryer with a gentle program, but in those rotating dryers in which the textiles constantly change their position, the shrinkage is considerably increased.
• the object underlying the invention was therefore to obtain a method for drying water-damp textiles, in particular clothing textiles, which leads to the least possible change in the fabric, such as, for example, the least possible shrinkage, but on the other hand works with the shortest possible drying times.
• the process according to the invention for drying water-moist textiles by heating the textiles in the quiescent state in a drying chamber through which air flows is characterized in that the water present in the textiles is evaporated by microwave radiation and the microwave radiation in the region of the drop in the relative atmospheric humidity of the exhaust air from the drying chamber and before reaching a residual moisture of 7%, based on the dry weight of the textile, and if necessary subsequently drying without microwave radiation, but with further passage of air through the drying chamber until a residual moisture of at least 2%, based on the dry weight of the fabric, finally dries.
• the textiles have metal or plastic parts, such as zippers, metal buttons, eyelets or buckles, they are heated in the last phase of drying, if the special measures claimed are not observed, by microwave radiation in such a way that the neighboring fabric is charred and the textiles become completely unusable . Therefore, drying with the aid of microwaves has never been used for textiles.
• micro according to the invention use waves to dry water-damp textiles, even if they contain metal parts, if the additional conditions mentioned above are observed, i.e. firstly an air flow through the drying chamber, secondly the microwave radiation stops when the relative humidity of the exhaust air drops and thirdly the microwave radiation at a certain level Residual moisture ends, but is chosen so that the textiles already feel dry.
• the residual moisture mentioned is suitable for subsequent ironing of the textiles, but also evaporates quickly when hanging in normal ambient air.
• the textiles are expediently dried either lying flat in the drying chamber or hanging. Small movements, for example as a result of the air flowing through them, are not harmful to the process. If the textiles are laid flat in the drying chamber, they can be arranged in stacks, since even then the interior parts are adequately dried to the desired residual moisture.
• the relative air humidity can be measured by humidity sensors at the air outlet of the drying chamber.
• the residual moisture of the textiles can be determined gravimetrically by comparing the weight of the moist textiles and the completely dried ones Textiles can be determined. It is an average residual moisture of the entire drying chamber filling, since different moisture contents can occur at different points and different materials can hold the moisture differently.
• one or more microwave transmitters can be used. In larger systems with relatively large drying chambers, it is advisable to arrange several in the drying chamber instead of one microwave transmitter.
• the microwave irradiation is expediently ended at 10 to 15% residual moisture in the textiles and the desired residual moisture is then set with the aid of the air flowing on.
• the air flow through the drying chamber used in the process is essential in order to remove the amount of water evaporated from the textiles and thus enable relatively short drying times.
• a constant air flow can be passed through the drying chamber once.
• the air flow can, however, also be at least partially circulated, ie passed through the drying chamber several times, but this requires that the recirculated air is dried before it is reintroduced into the drying chamber, which makes the process more complex than if the exhaust air from the drying chamber is blown off directly into the atmosphere. Since the exhaust air contains only water vapor, this is not a problem for the environment.
• the flow velocity of the air as it passes through the drying chamber is preferably set so that the air volume of the drying chamber is exchanged at least 10 times, preferably 25 to 50 times per minute.
• Tissue pieces 30 x 30 cm made of cotton, wool, polyester, polyamide and acrylic were attached to each other in 5 layers with metal clips.
• the individual weight of these test fabrics stapled together was 32 g.
• a total of 384 g of dry textile weight were thus obtained per test, which contained about 310 to 320 g of water after wetting and squeezing.
• test fabric series were folded in the middle and hung over a wire rack, with which they were placed vertically in a circulating air drying cabinet with 37 l drying chamber content.
• the drying cabinet was in addition to the convection heating with a microwave transmitter with a max. Power of 650 watts.
• Example 1 depending on the drying temperature of the exhaust air, the relative humidity of the exhaust air and the residual moisture of the tissue samples were determined first.
• Table III Drying process Exhaust air temperature r. Humidity Residual moisture in the tissue 0 42 ° C 55% 100% 1 min. 48 ° C 60% 3 min. 50 ° C 82% 5 min. 54 ° C 88% 75% 7 min. 59 ° C 91% 10 min. 60 ° C 91% 46% 12 min. 60 ° C 91% 15 minutes. 60 ° C 91% 23% 16 min. 60 ° C 90% 17 min. 60 ° C 89% 18 min 59 ° C 87% 12% 19 min. 59 ° C 82% 20 min. 58 ° C 74% 3% smell of fire in exhaust air
• the drying process was controlled in such a way that when the values for the relative humidity in the exhaust air began to drop, the microwave transmitter was switched off and the drying process was continued for a further 3 minutes with recirculated air without microwave radiation.
• the microwave radiation was interrupted in the 18th minute after the start of drying when the relative atmospheric humidity fell from 91 to 87%. After a total drying time of 22 minutes, the exhaust air temperature was 55 ° C, the relative humidity 62%, the residual moisture 7%.
• the fabric layers were evenly dried on the outside and inside, they no longer felt clammy due to the residual moisture, but felt a bit cool. There were no signs of burns anywhere.
• IWS felt shrinkage test fabrics were wetted cold with a mild detergent liquor of 1 g / l for three minutes, then squeezed to a residual moisture of 120% and dried by one of the following methods. The area loss was then determined by measuring the test fabric.
• Comparative Example 6 the drying was carried out lying flat at room temperature for 24 hours. The area loss was 2.4%. Given the long drying time, however, commercial use is not possible.
• Example 2 drying was carried out for 20 minutes in the drying cabinet used in Example 1 using microwave radiation using the drying conditions of Example 1.
• the area loss in this case was only 1.8%.
• the drying time in this example is very short, which makes the process extremely suitable for commercial use.

Landscapes

• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Biotechnology (AREA)
• Molecular Biology (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Drying Of Solid Materials (AREA)
• Treatment Of Fiber Materials (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (5)

• 1988
  • 1988-09-06 DE DE3830223A patent/DE3830223A1/de not_active Withdrawn
• 1989
  • 1989-07-14 EP EP89112893A patent/EP0359929A1/de not_active Withdrawn
  • 1989-09-05 DK DK437689A patent/DK437689A/da not_active Application Discontinuation

Patent Citations (5)

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