GB1588513A

GB1588513A - Heating without drying

Info

Publication number: GB1588513A
Application number: GB2921476A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-14
Filing date: 1976-07-14
Publication date: 1981-04-23
Also published as: FR2358802A1; JPS5331243A; DE2731902A1; IT1079299B

Description

(54) IMPROVEMENTS IN AND RELATING TO HEATING WITHOUT DRYING (71) I, DAVID CAMPBELL FINLAY MAxwELL, a British Subject, of Folley Hall House, Kirkburton, Huddersfield, West Yorkshire, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns improvements in and relating to heating without drying. It relates particularly to processes which comprise applying radio frequency heating to a system in an autoclave, that is a vessel in which pressure and/or vacuum can be controlled.

It is known how to apply radio frequency heating to systems in the wet phase which are not enclosed but it takes a relatively long time to attain an even temperature; the tendency being for evaporation to occur in those areas initially containing less liquid during the period that the wetter areas rise to saturation vapour pressure. Further it is impossible to maintain accurately any temperature either above or below that of normal atmospheric saturation.

I have found unexpectedly that by applying radio frequency heating to a system in an autoclave the required temperature is attained much more rapidly. Further, the temperature can be maintained very accurately by pressure/vacuum monitoring.

According to the present invention, there is provided a process of heating without drying which comprises applying radio frequency heating to textile material in an autoclave, the textile material containing a substance having a molecular structure which responds to radio frequency heating by showing an increase in temperature and which gives off a vapour the pressure of which is proportional to the temperature to which it is heated.

The substance having a molecular structure which responds to radio frequency heating as mentioned above may be solid or liquid and may be for example, water or blood.

The process of the present invention has a wide variety of applications and may be used for example in the flameproofing, waterproofing or sterilisation of fabrics and particularly in the dyeing of fibres. For flameproofing some chemicals have to be applied at a relatively high temperature of the order of 1200C. and this could be achieved by holding the autoclave at pressure and bringing the temperature up to 1200C. using radio frequency heating. Some waterproofing chemicals require heat treatment for wax melting and here again this could be carried out under controlled autoclave conditions.Concerning the sterilisation of fabrics, such as for example hospital bedding or sheets if these were slightly moist then their presence in an autoclave would enable the temperature to be raised and maintained to a bacteria-killing temperature for the required time.

Existing dyeing systems have several disadvantages as follows: Pressure dyeing machines are a relatively poor mechanical answere to the limitations of dyestuffs requiring high temperature for fixation: they are very expensive and consume large amounts of liquid and energy both with heating and cooling and to a lesser extent for pump circulation: furthermore, the machines are very uneconomical on small loads and sampling is difficult.

"Softflow" machines present an attempt to mitigate against the undesirable features of the pressure dyeing machines but they still possess most of the disadvantages of the pressure machines.

Winches run the pieces in rope form and are uneconomical on heat. If they are pressurised, they are expensive and suffer the same disadvantages of the pressure machines, particularly for dyeing.

Beam dyeing machines possess embossing problems due to hydrostatic pressure even if aerated: frequently there is uneven penetration at the lists; there is a high heat consumption and expensive pumping costs.

Pad dyeing systems have the advantages of an excellent liquor ratio (0.8/1 to 1/1), excellent levelness and repeatability and only require low energy. However, pad dyeing systems suffer from the disadvantages that existing International Wool Secretariat cold pad systems are limited to the use of certain dyestuffs, they suffer from an inability to use chrome dyes, there is a difficulty in applying deep shades and there is a long time factor for discovering an error in shade which is generally of the order of 24 hours.

I have found that by using a pad dyeing system and applying radio frequency heating to the package in an autoclave a greater range of dyestuffs can be used, the dyeing time can be reduced and the temperature can be controlled accurately.

According to one embodiment of the present invention there is provided a process for pad dyeing, spray dyeing or printing fibres, thereafter using radio frequency to fix the dyestuff in an autoclave by heating the package to a selected temperature of for example 75 C. to 130C The fibres may be used as piece goods, woven, non-woven or knitted or yarns and these fibres may be composed of natural or synthetic fibres, for example protein, polyester, polyamide or polyacrylic fibres, especially-cotton or wool.

The package may conveniently be a roll of fabric on a former of low dielectric constant for example having a power factor at 1 MHz of better than 0.02 our it may be loose stock packed into a hollow core low dielectric container with perforated ends for steam difussion. Alternatively, sliver or tops may be wound onto a standard type of former manufactured from materials of low dielectric constant.

The package is introduced into the vessel and radio frequency heated to the pre-set saturation pressure. The rate of rise of temperature may conveniently be of the order of 25 CC. per minute; dependent only on the size of package related to the radio frequency output capacity of the generator.

The dyeing temperatures can be maintained to an accuracy within 2 C. throughout the package by pressure monitoring.

When the required temperature for dyeing has been reached the electrical energy can be removed and the radiation losses made up by the injection of steam during the fixation period.

Afterwards, the temperature can be reduced extremely rapidly to for example about 70"C. at little cost by applying a vacuum; the package is then removed for washing.

In another embodiment of this invention, the fabric can be padded to treat it in preparation for transfer print dyeing and the transfer print paper run onto the~batching roll simultaneously and then introduced into the autoclave fro printing. This method removes any chance of print diffusion likely to occur due to differential movement be tween fabric and paper which sometimes occurs with conventional machines.

Sampling may be carried out in a small pressure vessel by inserting a dye-padded strip and raising to fixation temperature at a rate of conveniently say 100"C. per minute permitting an assessment of colour to be made within about two to three minutes.

The method of the present invention in the embodiment described namely the dyeing of fibres has the following advantages: (a) low energy costs.

(b) none of the effluent problems associated with the normal carrier liquid disposal.

(c) minimum effluent problems due to the small amount of liquid that is required for washing off fabric in rolled form.

(d) minimum water requirements.

(e) a wide range of dyes can be used en abling virtually all fibres to be pro cessed.

(f) the rate of dyeing can be enormously accelerated since current additives are normally designed to delay the fixation of dyestuff to permit levelness to occur.

(g) improved quality of work due to the elimination of the need to run in rope form and due also to the substantially reduced time during which the material is maintained at an elevated tempera ture.

(h) small packages heat more quickly show ing a saving in energy and time during this period of the process and, (i) virtually no additional steam load is required for the dyehouse.

The invention is illustrated by the following Examples. In each of these Examples the radiation was effected in the autoclave and the radio frequency field is provided either by a parallel plate type of oven or by an apparatus comprising a radio frequency generator and a coupling network feeding through an insulator to a central spigot. In the latter case the radio frequency field radiates outwards from the spigot.

In each example a 40 KW generator was employed. 66 Ibs of cloth were treated.

Example 1 Nylon material was impregnated with liquor containing 40 g/kg Avilon Dark Brown GRW (C.I. Acid Brown 282) 8 g/kg glacial acetic acid 4 g/kg Solvitose Gum OFA (Scholten) as a thickener and padded to give 100% liquor retention. The dye was fixed by raising the material to the fixation temperature of 100"C. in the R.F. field and maintaining this temperature for a further five minutes by steam. The time taken to raise to the fixation temperature was- 4.7 mins.

Example 2 Acrylic material was impregnated with liquor containing 10- g/kg Maxilon Red GRL (C.I. Basic Red 46) 5 g/kg Indalca PAl as a thickener pH 4.5-5.0 with acetic acid and padded to give 96% liquor retention; The dye was fixed by raising the material to the fixation temperature of 100 C. in the R.F. field and maintaining this temperature for a further 6 minutes by'steam. The time taken to raise to the fixation temperature was 4.5 mins.

Example 3 Wool material was impregnated with liquor containing 30 g/kg Lanacron Scarlet s-2G (C.I. Acid Red 383) 10 g/kg glacial acetic acid.

4 g/kg Solvitose Gum OFA (Scholten) as a thickener and padded to give 85% liquor retention. The dye was fixed by raising the temperature to 100"C. in the R.F. field and maintaining this temperature for a further 4 minutes by steam. The time taken to raise to the fixation temperature was 4.0 mins.

The present invention in general terms has the following advantages.

(1) the ability to heat any material without the loss of weight or vapour.

(2) the acceleration of heating time due to the fact that any vapour that is created from the liquid phase recondenses onto the cooler parts of the load, evening out the heat distribution.

(3) temperatures either below or above nor mal saturation temperatures at atmos pheric pressure can be achieved by selecting appropriate vacuum/pressure settings which then control the tempera ture of the package by monitoring the vapour pressure. This enables excep tionally high accuracy of heat control to be maintained.

(4) reduced energy consumption in the case where the material is rolled on a former or arranged concentrically about a cen tral radiating spigot since as soon as the temperature is achieved from heat gene rated in the package the surrounding material is of the same temperature so that there is no temperature gradient and therefore no heat loss from the bulk of the material but only from the outside areas and this can be made good by periodical application of a small amount of radio frequency energy or by steam injection.

Where the apparatus used to provide the radio frequency field involves the use of a central spigot there are considerable problems in obtaining an even temperature distribution.

Energy distribution along the length of the spigot is influenced by two - significant factors, namely the energy being absorbed in the load as the wave travels towards the end and the standing wave effect as the radio frequency wave is reflected from the open circuit end of the element. A solution to this uneven distribution has been found by so shaping the diameter of the spigot that it assumes a small diameter towards the open circuit end and becomes larger in diameter as the voltage reduces along the spigot, in other words the spigot diameter is tapered axially, thus evening up the energy radiation distribution within the surrounding package.

WHAT I CLAIM IS:- 1. Process of heating without drying which comprises applying radio frequency heating to textile material in an autoclave, the textile material containing a substance having a molecular structure which responds to radio frequency heating by showing an increase in temperature and which gives off a vapour the pressure of which is proportional to the temperature to which it is heated.

2. Process as claimed in claim 1 in which the substance is solid or liquid.

3. Process as claimed in claim 1 in which the substance is water.

4. Process as claimed in claim 1 in which the textile material is impregnated with dyestuff.

5. Process as claimed in claim 4 in which the textile material is in the form of piece goods, woven, non-woven or knitted or yarns.

6. Process as claimed in claim 4 in which the textile material is a natural or synthetic fibre.

7. Process as claimed in claim 6 in which the fibres are protein, polyester, polyamide or polyacrylic fibres.

8. Process as claimed in claim 6 in which the fibres are cotton or wool fibres.

9. Process as claimed in claim 4 in which the dyestuff is fixed on the textile material by radio frequency heating to a temperature of 75"C to 130 C.

10. Process as claimed in claim 9 in which, when the required temperature has been reached, the radio frequency heating is stopped and any radiation losses made up by steam during fixation.

11. Process as claimed in claim 9 or 10 in which, after fixation, the temperature is reduced by applying a vacuum.

12. Process as claimed in any of claims 4 to 11 in which the textile material is in the form of sliver or tops or a roll of fabric on a former having a power factor at 1 MHz of better than 0.02.

13. Process as claimed in any of claims 4 to 11 in which the textile material is in the form of loose stock packed in a hollow

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Example 2 Acrylic material was impregnated with liquor containing

10- g/kg Maxilon Red GRL (C.I. Basic Red 46) 5 g/kg Indalca PAl as a thickener pH 4.5-5.0 with acetic acid and padded to give 96% liquor retention; The dye was fixed by raising the material to the fixation temperature of 100 C. in the R.F. field and maintaining this temperature for a further 6 minutes by'steam. The time taken to raise to the fixation temperature was 4.5 mins.

Example 3 Wool material was impregnated with liquor containing 30 g/kg Lanacron Scarlet s-2G (C.I. Acid Red 383) 10 g/kg glacial acetic acid.

4 g/kg Solvitose Gum OFA (Scholten) as a thickener and padded to give 85% liquor retention. The dye was fixed by raising the temperature to 100"C. in the R.F. field and maintaining this temperature for a further 4 minutes by steam. The time taken to raise to the fixation temperature was 4.0 mins.

The present invention in general terms has the following advantages.

(1) the ability to heat any material without the loss of weight or vapour.

(2) the acceleration of heating time due to the fact that any vapour that is created from the liquid phase recondenses onto the cooler parts of the load, evening out the heat distribution.

(3) temperatures either below or above nor mal saturation temperatures at atmos pheric pressure can be achieved by selecting appropriate vacuum/pressure settings which then control the tempera ture of the package by monitoring the vapour pressure. This enables excep tionally high accuracy of heat control to be maintained.

(4) reduced energy consumption in the case where the material is rolled on a former or arranged concentrically about a cen tral radiating spigot since as soon as the temperature is achieved from heat gene rated in the package the surrounding material is of the same temperature so that there is no temperature gradient and therefore no heat loss from the bulk of the material but only from the outside areas and this can be made good by periodical application of a small amount of radio frequency energy or by steam injection.

Where the apparatus used to provide the radio frequency field involves the use of a central spigot there are considerable problems in obtaining an even temperature distribution.

Energy distribution along the length of the spigot is influenced by two - significant factors, namely the energy being absorbed in the load as the wave travels towards the end and the standing wave effect as the radio frequency wave is reflected from the open circuit end of the element. A solution to this uneven distribution has been found by so shaping the diameter of the spigot that it assumes a small diameter towards the open circuit end and becomes larger in diameter as the voltage reduces along the spigot, in other words the spigot diameter is tapered axially, thus evening up the energy radiation distribution within the surrounding package.

WHAT I CLAIM IS:- 1. Process of heating without drying which comprises applying radio frequency heating to textile material in an autoclave, the textile material containing a substance having a molecular structure which responds to radio frequency heating by showing an increase in temperature and which gives off a vapour the pressure of which is proportional to the temperature to which it is heated.
2. Process as claimed in claim 1 in which the substance is solid or liquid.
3. Process as claimed in claim 1 in which the substance is water.
4. Process as claimed in claim 1 in which the textile material is impregnated with dyestuff.
5. Process as claimed in claim 4 in which the textile material is in the form of piece goods, woven, non-woven or knitted or yarns.
6. Process as claimed in claim 4 in which the textile material is a natural or synthetic fibre.
7. Process as claimed in claim 6 in which the fibres are protein, polyester, polyamide or polyacrylic fibres.
8. Process as claimed in claim 6 in which the fibres are cotton or wool fibres.
9. Process as claimed in claim 4 in which the dyestuff is fixed on the textile material by radio frequency heating to a temperature of 75"C to 130 C.
10. Process as claimed in claim 9 in which, when the required temperature has been reached, the radio frequency heating is stopped and any radiation losses made up by steam during fixation.
11. Process as claimed in claim 9 or 10 in which, after fixation, the temperature is reduced by applying a vacuum.
12. Process as claimed in any of claims 4 to 11 in which the textile material is in the form of sliver or tops or a roll of fabric on a former having a power factor at 1 MHz of better than 0.02.
13. Process as claimed in any of claims 4 to 11 in which the textile material is in the form of loose stock packed in a hollow

core container having a power factor at 1 MH of better than 0.02 with perforated ends for steam diffusion.
14. Process as claimed in any of the preceding claims in which the radio frequency field radiates outwards from a central spigot, the spigot increasing in diameter from the open circuit end as the voltage reduces along the spigot.
15. Process of dyeing textile material substantially as herein described with reference to and as illustrated in any of the Examples.