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
  • D06F58/30—Drying processes 
• • 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
  • F26B3/02—Drying solid materials or objects by processes involving the application of heat by convection, i.e. heat being conveyed from a heat source to the materials or objects to be dried by a gas or vapour, e.g. air
• • 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
  • F26B3/18—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact
  • F26B3/20—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source being a heated surface, e.g. a moving belt or conveyor
  • F26B3/205—Drying solid materials or objects by processes involving the application of heat by conduction, i.e. the heat is conveyed from the heat source, e.g. gas flame, to the materials or objects to be dried by direct contact the heat source being a heated surface, e.g. a moving belt or conveyor the materials to be dried covering or being mixed with heated inert particles which may be recycled
• • 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
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/02—Characteristics of laundry or load
  • D06F2103/08—Humidity
• • 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
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/28—Air properties
  • D06F2103/34—Humidity
• • 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
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/38—Time, e.g. duration
• • 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
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/44—Current or voltage
• • 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
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/46—Drum speed; Actuation of motors, e.g. starting or interrupting
• • 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
  • D06F58/02—Domestic laundry dryers having dryer drums rotating about a horizontal axis
• • 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 

Definitions

• the present invention relates to the drying of textile fibres and fabrics in a tumble dryer using a system which utilises only limited quantities of energy, and which reduces drying-related creasing and associated textile fabric damage.
• the invention provides a method adapted for use in this context.
• Tumble drying processes are a mainstay of both domestic and industrial textile fabric cleaning procedures and typically involve placing the textiles in a container such as a perforated cylindrical drum which is rotated in alternating clockwise and anticlockwise cycles whilst hot air is introduced into the drum through the perforations.
• a container such as a perforated cylindrical drum which is rotated in alternating clockwise and anticlockwise cycles whilst hot air is introduced into the drum through the perforations.
• a combination of the hot air treatment and the mechanical action of the tumbling process causes water to be expelled from the textile materials in order that drying is achieved.
• Performance levels in the domestic sector generally set the highest standard for an efficient fabric drying process. Energy consumption in industrial tumble drying is usually higher, due to the need for faster cycle times. It is also noteworthy that, overall, tumble drying is significantly less efficient than washing as a component part of the laundry process in either sector.
• Heating of the circulating air is the principal use of energy in such tumble dryers and the present inventors have therefore sought to effect improvements in the prior art processes by reducing the temperature levels required in such processes.
• Mechanical action in a conventional, horizontal axis tumble dryer is generated by the forces acting on the fabric through falling and hitting either other fabric or the dryer inner drum surface, whilst the fabric is interacting with the forced hot air flow. This results in release and evaporation of water from within the fabric, and hence drying.
• alteration of the mechanical action of the process in order to promote more localised release and evaporation of water at the fabric surface has resulted in lower drying temperatures.
• the present inventors have sought to devise a new approach to the drying problem, which allows the above deficiencies associated with the methods of the prior art to be overcome.
• the method which is provided eliminates the requirement for the use of high drying temperatures for extended periods of time, but is still capable of providing an efficient means of water removal, so yielding economic and environmental benefits.
• the method which is provided also promotes fabric care through reduced creasing and fewer requirements for subsequent ironing.
• WO-A-2007/128962 there is disclosed a method and formulation for cleaning a soiled substrate, the method comprising the treatment of the moistened substrate with a formulation comprising a multiplicity of polymeric particles, wherein the formulation is free of organic solvents.
• the substrate comprises a textile fibre and the polymeric particles may, for example, comprise particles of polyamides, polyesters, polyalkenes, polyurethanes or their copolymers, but are most preferably in the form of nylon particles.
• the present invention derives from an appreciation on the part of the inventors that optimum drying performance can be achieved as a result of improved mechanical interaction between substrate and physical media. This can be effected by the use of solid particles in the drying process and is a function of the number, size and mass of the particles and the free volume within the vessel in which the drying operation takes place, in addition to the G force dictated by its speed of rotation.
• Free volume in this context refers to the space inside the vessel which remains unoccupied by wet substrate or particulate media, and G force is defined on the basis of the centripetal forces which are acting.
• a method for the drying of a wet substrate comprising treating the substrate with a solid particulate material at ambient or elevated temperature, said treatment being carried out in an apparatus comprising a drum comprising perforated side walls, wherein said drum comprising perforated side walls is rotated so as to facilitate increased mechanical action between said substrate and said particulate material.
• said drum comprising perforated side walls has a capacity of between 5 and 50 litres for each kg of substrate.
• said drum is rotated at a speed which generates G forces in the range of from 0.05 to 0.99 G.
• the drum comprising perforated side walls comprises a rotatably mounted cylindrical cage.
• said solid particulate material comprises a multiplicity of particles which may be polymeric, non-polymeric or mixtures thereof, and which may be added at a particle to fabric addition level of 0.1 :1 -10:1 by mass.
• the size of said particles determines the number of particles which are present in a process according to the invention.
• Each particle may have a smooth or irregular surface structure, can be of solid or hollow construction, and is of such a shape and size to allow for good flowability and intimate contact with the soiled substrate, which typically comprises a textile fabric.
• a variety of shapes of particles can be used, such as cylindrical, spherical or cuboid; appropriate cross-sectional shapes can be employed including, for example, annular ring, dog-bone and circular. Most preferably, however, said particles comprise cylindrical or spherical particles.
• Polymeric particles typically have an average density in the range of 0.5-2.5 g/cm 3 , more typically from 0.55-2.0 g/cm 3 , more typically from 0.6-1.9 g/cm 3 .
• Non- polymeric particles generally have an average density in the range of from 3.5-12.0 g/cm 3 , more typically from 5.0-10.0 g/cm 3 , most typically from 6.0-9.0 g/cm 3 .
• the average volume of both the non-polymeric and polymeric particles is typically in the range of 5-275 mm 3 , more typically from 8-140 mm 3 , most typically from 10-120 mm 3 .
• the major cross section axis length, a is typically in the range of from 2.0- 6.0 mm, more typically from 2.2-5.0 mm, most typically from 2.4-4.5 mm
• the minor cross section axis length, b is typically in the range of from 1.3-5.0 mm, more typically from 1.5-4.0 mm, and most typically from 1.7-3.5 mm (a > b).
• the length of such particles, h is typically from 1.5-6.0 mm, more typically from 1.7-5.0 mm, and most typically from 2.0-4.5 mm (h/b is typically in the range of from 0.5-10).
• the typical cross section diameter, d c is in the range of from 1.3-6.0 mm, more typically from 1.5-5.0 mm, and most typically from 1.7-4.5 mm.
• the typical length, h c of such particles is again from 1.5-6.0 mm, more typically from 1.7-5.0 mm, and most typically from 2.0-4.5 mm (hc/d c is typically in the range of from 0.5-10).
• the diameter, d s is typically in the range of from 2.0-8.0 mm, more typically in the range of from 2.2-5.5 mm, and most typically from 2.4-5.0 mm.
• the diameter, d ps is typically in the range of from 2.0-8.0 mm, more typically from 3.0-7.0 mm, and most typically from 4.0-6.5 mm.
• Polymeric particles may comprise either foamed or unfoamed polymeric materials. Furthermore, the polymeric particles may comprise polymers which are either linear or crosslinked.
• Preferred polymeric particles comprise polyalkenes such as polyethylene and polypropylene, polyamides, polyesters or polyurethanes.
• said polymeric particles comprise polyamide or polyester particles, most particularly particles of nylon, polyethylene terephthalate or polybutylene terephthalate.
• copolymers of the above polymeric materials may be employed for the purposes of the invention.
• the properties of the polymeric materials may be tailored to individual requirements by the inclusion of monomeric units which confer particular properties on the copolymer.
• the copolymers may be adapted to attract moisture by comprising monomers which, inter alia, are hydrophilic through being ionically charged or including polar moieties or unsaturated organic groups.
• Non-polymeric particles may comprise particles of glass, silica, stone, wood, or any of a variety of metals or ceramic materials.
• Suitable metals include, but are not limited to, zinc, titanium, chromium, manganese, iron, cobalt, nickel, copper, tungsten, aluminium, tin and lead, and alloys thereof.
• Suitable ceramics include, but are not limited to, alumina, zirconia, tungsten carbide, silicon carbide and silicon nitride. It is seen that non-polymeric particles made from naturally occurring materials (e.g. stone) can have various shapes, depending on their propensity to cleave in different ways during manufacture.
• said non-polymeric particles may comprise coated non-polymeric particles.
• said non-polymeric particles may comprise a non-polymeric core material and a shell comprising a coating of a polymeric material.
• said core may comprise a metal core, typically a steel core, and said shell may comprise a polyamide coating, for example a coating of nylon.
• the selection of specific particle type (polymeric and non-polymeric) for a given drying operation is particularly important in optimising fabric care.
• particle size, shape, mass and material must all be considered carefully in respect of the particular substrate which is to be dried, so that particle selection is dependent on the nature of the garments to be dried, i.e. whether they comprise cotton, polyester, polyamide, silk, wool, or any of the other common textile fibres or blends which are commonly in use.
• G is a function of the drum size and the speed of rotation of the drum and, specifically, is the ratio of the centripetal force generated at the inner surface of the cage to the static weight of the wet substrate.
• the claimed method additionally provides, on completion of the drying process, for separation and recovery of the particles comprised in the solid particulate material, which are then re-used in subsequent drying procedures.
• Said rotatably mounted cylindrical cage is comprised in any suitable tumble drying apparatus comprising a housing and access means, allowing access to the interior of said cylindrical cage.
• said apparatus may comprise:
• said rotatably mounted cylindrical cage comprises a drum comprising perforated side walls, wherein up to 60% of the surface area of said side walls comprises perforations, and said perforations comprise holes having a diameter of no greater than 25.0 mm.
• Said drying process also comprises the introduction of either ambient or heated air into said drum comprising perforated side walls. If said air is heated, this is achieved by means of any commercially available air heater and circulated using a fan so as to achieve a temperature of between 5° and 120°C, preferably between 10° and 90°C, most preferably between 20° and 80°C in the apparatus.
• the temperature of ambient air is dependent on the surroundings in which the drying process is running, but this can typically vary from 5-20°C.
• drying operations according to the invention are typically carried out at temperatures which are 20°C lower than with prior art processes, whilst achieving equivalent drying performance for the same time of treatment.
• Figure 1 is a diagrammatic representation of particles which are employed in the method of the invention.
• Figure 2 is a graphical representation of the efficiency of the drying process according to an embodiment of the invention.
• Figure 3 a graphical representation of the efficiency of the drying process according to a further embodiment of the invention.
• said access means typically comprises a hinged door mounted in the casing, which may be opened to allow access to the inside of the cylindrical cage, and which may be closed in order to provide a substantially sealed system.
• the door includes a window.
• Said rotatably mounted cylindrical cage is mounted horizontally within said housing means. Consequently, in preferred embodiments of the invention, said access means is located in the front of the apparatus, providing a front-loading facility.
• Rotation of said rotatably mounted cylindrical cage is effected by use of drive means, which typically comprises electrical drive means, in the form of an electric motor. Operation of said drive means is effected by control means which may be programmed by an operative.
• drive means typically comprises electrical drive means, in the form of an electric motor.
• control means which may be programmed by an operative.
• Said rotatably mounted cylindrical cage is of the size which is to be found in most domestic or industrial tumble driers, and may have a capacity in the region of 50 to 7000 litres.
• a typical capacity for a domestic machine would be in the region of 80 to 140 litres and, for an industrial machine, this range would typically be from 170 to 2000 litres.
• Said rotatably mounted cylindrical cage is located within a first upper chamber of said housing means and beneath said first upper chamber is located a second lower chamber which functions as a collection chamber for said solid particulate material.
• Said housing means is connected to standard plumbing features, thereby providing recirculation means, for returning said solid particulate material from said lower chamber, and delivery means, by virtue of which said solid particulate material may be returned to said cylindrical cage.
• said apparatus additionally comprises means for circulating air within said housing means, and for adjusting the temperature therein.
• Said means may typically include, for example, a recirculating fan and an air heater.
• sensing means may also be provided for determining the temperature and humidity levels within the apparatus, and for communicating this information to the control means.
• Said apparatus comprises recirculation means, thereby facilitating recirculation of said solid particulate material from said lower chamber to said rotatably mounted cylindrical cage, for re-use in drying operations.
• said recirculation means comprises ducting connecting said second chamber and said rotatably mounted cylindrical cage.
• said ducting comprises control means, adapted to control entry of said solid particulate material into said cylindrical cage.
• said control means comprises a valve located in feeder means, preferably in the form of a feed tube attached to the apex of a receptor vessel located above, and connected to the interior of, said cylindrical cage.
• Recirculation of solid particulate matter from said lower chamber to said rotatably mounted cylindrical cage is achieved by the use of pumping means comprised in said recirculation means, wherein said pumping means are adapted to deliver said solid particulate matter to said control means, adapted to control the re-entry of said solid particulate matter into said rotatably mounted cylindrical cage.
• said recirculation means comprises a vacuum pumping system.
• cleaned garments containing residual moisture are first placed into said rotatably mounted cylindrical cage.
• the cylindrical cage is caused to rotate and ambient or heated air is introduced via the perforations in the cage before the solid particulate material is added.
• water is caused to be removed from the garments by evaporation and a quantity of the solid particulate material falls through the perforations in the cage and into the second chamber of the apparatus.
• the solid particulate material is re-circulated via the recirculation means such that it is returned, in a manner controlled by said control means, to the cylindrical cage for continuation of the drying operation. This process of continuous circulation of the solid particulate material occurs throughout the drying operation until drying is completed.
• the solid particulate material which exits through the perforations in the walls of said rotatably mounted cylindrical cage and into said second chamber is carried to the top side of said rotatably mounted cylindrical cage, wherein it is caused, by means of gravity and operation of the control means, to fall back into said cage, thereby to continue the drying operation.
• pumping of fresh and recycled solid particulate material proceeds at a rate sufficient to maintain approximately the same level of material in said rotatably mounted cylindrical cage throughout the drying operation, and to ensure that the ratio of particulate material to substrate stays substantially constant until the cycle has been completed.
• any remaining solid particulate material on said at least one substrate may be easily removed by shaking the at least one substrate. If necessary, however, further remaining solid particulate material may be removed by suction means, preferably comprising a vacuum wand.
• Said rotatably mounted cylindrical cage more preferably has a volume of between 5 and 50 litres for each kg of fabric in the load. Preferred rates of rotation of said rotatably mounted cylindrical cage are sufficient to give G forces of between 0.05 and 0.99 G. Typically the drying process and the subsequent separation of the particles from the fabric are both carried out within this G range. After separation, the particles are recovered for use in subsequent drying procedures.
• said apparatus operates in conjunction with wet substrates and drying media comprising a solid particulate material, which is most preferably in the form of a multiplicity of particles which may be polymeric, non-polymeric, or mixtures of both polymeric and non-polymeric particles. All particles may be solid or hollow in their structure and the polymeric particles may be foamed or unfoamed and linear or crosslinked. These particles are required to be efficiently circulated to promote optimum performance and the apparatus, therefore, preferably includes circulation means.
• the inner surface of the cylindrical side walls of said rotatably mounted cylindrical cage preferably comprises a multiplicity of spaced apart elongated protrusions affixed essentially perpendicularly to said inner surface.
• said protrusions additionally comprise air amplifiers which are typically driven pneumatically and are adapted so as to promote circulation of a current of heated air within said cage.
• said apparatus comprises from 3 to 10, most preferably 4, of said protrusions, which are commonly referred to as lifters.
• the method of the invention may be applied to the drying of any of a wide range of substrates including, for example, plastics materials, leather, metal or wood.
• said method is principally applied to the drying of wet substrates comprising textile fibres and fabrics, and has been shown to be particularly successful in achieving efficient drying of textile fabrics which may, for example, comprise either natural fibres, such as cotton, or man-made and synthetic textile fibres, for example nylon 6,6, polyester, cellulose acetate, or fibre blends thereof.
• the solid particulate material comprises a multiplicity of particles which may be polymeric, non-polymeric, or mixtures thereof.
• Typical polymeric particles may comprise polyamide or polyester particles, most particularly particles of nylon, polyethylene terephthalate or polybutylene terephthalate, or copolymers thereof, most preferably in the form of beads, which may be solid or hollow in their structure.
• the polymers may be foamed or unfoamed, and may be linear or crosslinked.
• Various nylon or polyester homo- or co-polymers may be used including, but not limited to, Nylon 6, Nylon 6,6, polyethylene terephthalate and polybutylene terephthalate.
• the nylon comprises Nylon 6,6 homopolymer having a molecular weight in the region of from 5000 to 30000 Daltons, preferably from 10000 to 20000 Daltons, most preferably from 15000 to 16000 Daltons.
• the polyester will typically have a molecular weight corresponding to an intrinsic viscosity measurement in the range of from 0.3-1.5 dl/g as measured by a solution technique such as ASTM D-4603.
• Suitable non-polymeric particles may comprise particles of glass, silica, stone, wood, or any of a variety of metals or ceramic materials.
• Suitable metals include, but are not limited to, zinc, titanium, chromium, manganese, iron, cobalt, nickel, copper, tungsten, aluminium, tin and lead, and alloys thereof.
• Suitable ceramics include, but are not limited to, alumina, zirconia, tungsten carbide, silicon carbide and silicon nitride. It is seen that non-polymeric particles made from naturally occurring materials (e.g. stone) can have various shapes, depending on their propensity to cleave in different ways during manufacture.
• Said solid particulate cleaning material may be comprised entirely of polymeric particles or entirely of non-polymeric particles, or may comprise mixtures of both types of particles.
• the ratio of polymeric particles to non-polymeric particles may be anywhere from 99.9%:0.1% to 0.1%:99.9% w/w.
• the ratio of solid particulate material to substrate is generally in the range of from 0.1 :1 to 10:1 w/w, preferably in the region of from 1.0:1 to 7:1 w/w, with particularly favourable results being achieved using polymeric particles at a ratio of between 3:1 and 5:1 w/w, and especially at around 4:1 w/w.
• polymeric particles at a ratio of between 3:1 and 5:1 w/w, and especially at around 4:1 w/w.
• 20 g of polymeric particles would be employed in one embodiment of the invention.
• the ratio of solid particulate material to substrate is maintained at a substantially constant level throughout the drying cycle.
• the method of the present invention may be used for either small or large scale batchwise processes and finds application in both domestic and industrial drying processes.
• the method of the invention finds particular application in the drying of textile fabrics.
• the conditions employed in such a system do, however, allow the use of significantly reduced temperatures from those which typically apply to the conventional tumble drying of textile fabrics and, as a consequence, offer significant environmental and economic benefits.
• typical procedures and conditions for the drying cycle require that fabrics are generally treated according to the method of the invention at, for example, temperatures of between 20 and 80°C for a duration of between 5 and 55 minutes. Thereafter, additional time is required for the completion of the particle separation stage of the overall process, so that the total duration of the entire cycle is typically in the region of 1 hour.
• the method of the invention also shows benefits in terms of reducing drying- related fabric damage.
• fabric creasing readily occurs in conventional tumble drying, and this acts to concentrate the stresses from the mechanical action of the drying process at each crease, resulting in localised fabric damage.
• Prevention of such fabric damage (or fabric care) is of primary concern to the domestic consumer and industrial user.
• the addition of particles according to the method of the invention effectively reduces creasing in the process by acting as a pinning layer on the fabric surface in order to help prevent the folding action.
• the particles also inhibit interaction between separate pieces of fabric in the drying process by acting as a separation or spacing layer, thereby reducing entanglement which is another major cause of localised fabric damage.
• mechanical action is still present but, critically, this is much more uniformly distributed as a result of the action of the particles. It is the localised aspect of the damage that determines the lifetime of a garment under multiple drying processes.
• the method of the present invention provides for enhanced performance in comparison with the methods of the prior art under equivalent energy conditions; alternatively, equivalent drying performance may be achieved at lower levels of energy, together with reduced fabric damage.
• the solid particulate material is continually falling out of the rotatably mounted cylindrical cage through its perforations, and is being recycled and added, together with fresh material, via the control means. This process may either be controlled manually, or operated automatically.
• the rate of exit of the solid particulate material from the rotatably mounted cylindrical cage is essentially controlled by means of its specific design.
• the key parameters in this regard include the size of the perforations, the number of perforations, the arrangement of the perforations within the cage and the G force (or rotational speed) which is employed.
• the perforations should be sized so as to be at least the size of the largest dimension of the particles comprised in the solid particulate material, in order that these particles are able to exit from the cage.
• optimum separation of particles from fabric is achieved when the perforations are sized at around 1-3 times the largest particle dimension which, typically, results in perforations having a diameter of between 2.0 and 25.0 mm.
• a rotatably mounted cylindrical cage would be drilled so that only around 34% of the surface area of the cylindrical walls of the cage comprises perforations. Whilst restricting air flow, this allows for greater retention of solid particulate material in the drying load.
• the perforations may be banded in stripes or distributed evenly over the cylindrical walls of the rotatably mounted cylindrical cage, or could even be exclusively located, for example, in one half of the cage.
• Conventional commercial vented tumble dryers e.g. DanubeTM - Model Number TD2005/10E
• Conventional commercial vented tumble dryers typically have perforations of 6.5 mm diameter, and these are drilled at maximum areal density, such that they are distributed closely packed (1 mm apart) over the cylindrical cage wall. This equates to some 56% of the surface area of the cylindrical walls of the cage comprising perforations which ensures good air flow through the drying load, and this cage geometry is also found to be suitable for the successful performance of the method of the present invention.
• the rate of exit of the solid particulate material from the rotatably mounted cylindrical cage is also affected by the speed of rotation of said cage, with higher rotation speeds increasing the G force, although at G > 1 the fabric adheres to the sides of the cage and prevents exit of the particulate material.
• slower rotational speeds have been found to provide optimum results in this regard, as they allow the particles to fall from the fabric and through the perforations as the fabric opens out more during tumbling.
• Rotational speeds resulting in a G force of ⁇ 1 are therefore required ( ⁇ 42 rpm in a 98 cm diameter cage, for example).
• the G force (or rotational speed) is also controlled so as to maximise the beneficial effect of the mechanical action of the particulate material on the substrate, and the most suitable G is generally found to be in the region of 0.9 G (e.g. 40 rpm in a 98 cm diameter cage).
• the method of the invention has been shown to be successful in the removal of particulate material from the dried substrate after processing and tests with cylindrical polyester particles, and nylon particles comprising either Nylon 6 or Nylon 6,6 polymer, have indicated particle removal efficacy such that on average ⁇ 5 particles per garment remain in the load at the end of the particle separation cycle. Generally, this can be further reduced to an average of ⁇ 2 particles per garment and, in optimised cases wherein a 20 minute separation cycle is employed, complete removal of particles is typically achieved.
• the method of the invention is believed to comprise the mechanical action of the particles against a cloth so as to liberate the moisture trapped between fibres, and the pick up of this moisture on the particle surface, wherein rapid evaporation occurs of the thin film of water which is formed.
• Certain polymeric particles also have the ability to absorb moisture to a larger extent (Nylon 6 and Nylon 6,6 being examples). It may be the case, therefore, that some such absorption is also contributing to the drying mechanism.
• a drying procedure was carried out by adding a solid particulate material comprising 4 kg of Nylon 6,6 particles (DuPont Zytel ® 101 NC010) to a mesh bag with 1 kg (dry mass) of a cloth substrate, which had been wetted with 10°C water. Details of the particles are set out in Table 1 and an illustration of these cylindrical particles is provided in Figure 1.
• the substrate was made up of the same type of article in each case (cotton pillowcases). This bag was then loaded into a conventional commercial vented tumble dryer (DanubeTM - Model Number TD 2005/10E). The dryer was set to rotate at 48 rpm which, with a drum diameter of 74 cm, resulted in a centripetal force on the bag and its contents of 0.95 G. The dryer operating temperature was set to 20°, 30°, 40°, or 60°C for individual separate drying tests, and repeat experiments were performed without particles present (i.e. fabric only) to act as controls. The heat up rate programmed into the dryer was 2.0°C/min.
• Table 3 and Figure 3 provide a comparative illustration of the drying efficacy which is achieved when heated particles are employed. These data effectively provide an illustration of the benefits associated with heat retention in the particles for a subsequent drying process.
• the particles were pre-heated in a separate tumble dryer to 60°C (measured by an in-situ remote temperature recorder) in order to simulate heated particles from a previous cycle.
• These hot particles were then quickly added to the mesh bag with wet cloth as before, and tumbled in the DanubeTM dryer at 20°C (the test denoted 'Particles 60°C/Dryer 20°C). As previously therefore, this was effectively ambient temperature with the heaters in the dryer switched off. With heated particles, the drying efficiency increased to 0.48% water removed/minute, vs. the test from Example 1 with the particles at 20°C, which gave only 0.28% water/min.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Drying Of Solid Materials (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)
• Treatment Of Fiber Materials (AREA)

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• 2011
  • 2011-01-19 GB GBGB1100918.0A patent/GB201100918D0/en not_active Ceased
• 2012
  • 2012-01-19 TW TW101102295A patent/TWI561785B/zh not_active IP Right Cessation
  • 2012-01-19 BR BR112013018255A patent/BR112013018255A2/pt not_active Application Discontinuation
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