Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M10/00—Physical treatment of fibres, threads, yarns, fabrics, or fibrous goods made from such materials, e.g. ultrasonic, corona discharge, irradiation, electric currents, or magnetic fields; Physical treatment combined with treatment with chemical compounds or elements
  • D06M10/02—Physical treatment of fibres, threads, yarns, fabrics, or fibrous goods made from such materials, e.g. ultrasonic, corona discharge, irradiation, electric currents, or magnetic fields; Physical treatment combined with treatment with chemical compounds or elements ultrasonic or sonic; Corona discharge
  • D06M10/025—Corona discharge or low temperature plasma
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M2200/00—Functionality of the treatment composition and/or properties imparted to the textile material

Definitions

• the present invention relates to a method for processing polymeric yarns and textile materials for modifying their surface resistivity.
• static electricity can be defined as a stationary electric charge due to either an excess or lacking of electrons on the surface of a body.
• the accumulation of electric charges on an article is caused by the movement of the electrons inside the article or by a passage said electrons from a body to another body.
• antistatic indicates the property of a material according to which said material is not electrostatically charged by rubbing, stirring or separating of two surfaces.
• an antistatic material will not be electrostatically charged because of the above mentioned events, owing to a continuous dissipation of the electric charge through the encompassing environment . Accordingly, antistatic materials must both prevent any static electricity from being formed and eliminate, in a nearly instantaneous and safe manner, possibly already present electrostatic charges.
• enforcing rules related to electrostatic discharging products and processes agree in defining antistatic material classes by their surface resistivity (R 3 ) .
• R 3 surface resistivity
• Such a parameter is defined as a ratio of the D. C. voltage and current passing through/over the surface of the body.
• the surface comprises a squared area.
• the surface resistivity corresponds to the resistance between two opposite sides of the square, and is independent from the square size and metering unit thereof.
• the surface resistivity is defined in ohms/square (ohm/square) .
• a further relevant parameter is the so-called surface "conducibility" which is defined as the reverse of the surface resistivity.
• said materials can be classified, as follows : conductive: i.e. those having a Rs ⁇ 1 x 10 5 ⁇ /square; static-dissipative: i.e. those having 1 x 10 5 ⁇ /square ⁇ Rs 1 x 10 12 ⁇ /square; insulating: i.e. those having Rs > 1 x 10 12 ⁇ /square.
• an electrostatic charge is generated each time that, during a processing operation, two surfaces in general are contacted to one another and are then separated from one another again.
• the sensitivity to the above mentioned drawbacks deriving from an electrostatic charge generated on a textile material contacting a part or a component of a processing machine depends on the ratio of the material rate and the diffusion of the surface charge on the material itself.
• the triboelectric charge value accordingly, can greatly change depending on: The material type; The surface type; The contact pressure; The separating speed; - The relative humidity.
• Such a fitting or mating can be achieved by a chemical surface treatment.
• the radioactive substances adapted to eliminate static electricity can be considered as pertaining to two groups: those emitting ⁇ rays and those emitting ⁇ rays. These two groups have specific characteristics and are moreover differentiated from one another in their related apparatus.
• the ⁇ ray emitting apparatus generally use radium as an active material; on the other hand, the ⁇ ray emitting apparatus use thallium- 204 or * strontium-90 and yttrium-90.
• the apparatus are constructionally simple and have a satisfactory efficiency; however, they present dangers, in particular do not allow an immediate detection of possible malfunctions or damages.
• the setting or fixation of the product on the above mentioned fabric materials is achieved by a reaction of the antistatic substance and fiber, or by a polymerization of the water soluble compounds in a water insoluble antistatic film adhering to the fiber.
• Some antistatic products comprise surface active agents, including a water hydrophobic hydrocarbon portion, having an affinity for the fiber, and and end hydrophilic group, projecting from the fiber.
• the individual compounds have very remarkable differences with respect to their use as antistatic materials.
• Molecules having double-bonds or linkages have been found as particularly efficient; moreover, it has been found that an increase of the polarized or polarizable groups and salt bonds contribute to preventing electric charge phenomena from occurring.
• the permanent effect of such a product is based on a forming of a film on its surfaces; moreover, its lightfastness greatly depends on the adhering characteristics of said film, and on the resistance against mechanical actions and solvents.
• a treatment of the above mentioned type causes the product organoleptic and volume properties to change, and, accordingly, such a treatment is not advantageous as applied to textile or yarn materials for making cloth articles.
• the aim of the present invention is to overcome the above mentioned problems, by providing a method for processing polymeric yarns and textile materials to modify their surface resistivity, which does not use conventional chemical products and water, and which, moreover, has a very low environmental impact, without modifying the volume and organoleptic properties of the materials being processed.
• a main object of the invention is to provide such a method allowing to obtain a quick charge dissipation, to be easily fitted to a broad range of fabric material products to be processed, thereby providing said products with novel functional properties.
• a further object is to provide such a method which ⁇ s not related to any modifications of the material surface static charge, i.e. of the material contact potential, but to a reduction of the surface resistivity or, equivalently, an increase of the surface conducibility, thereby, each time electric charges are created on the material surface because of rubbing or contacting with other charged bodies, said surface charges do not accumulate, but are dissipated owing to said increased surface electric conducibility.
• a further object of the present invention is to provide such a method for processing polymeric yarns and textile materials which, owing to its specifically designed characteristics, is very reliable and safe in operation.
• Yet another object of the present invention it to provide such a method which can be easily carried out and which, moreover, is very competitive from a mere economic standpoint.
• the above mentioned aim and objects, as well as yet ' other objects, which will become more apparent hereinafter, are achieved by a method for processing polymeric yarns and textile materials to modify their surface resistivity, characterized in that said method comprises a step of directly processing by a plasma the textile material fibers.
• said plasma is a "cold" plasma, i.e. a mixture of charged particles (electrons and ions) and neutral species (atoms, molecules, radicals), the temperature of which is of the same order as the environment temperature.
• said plasma can be generated under vacuum, or in suitable plasma generating chambers containing gases at pressures less than the atmospheric pressure, and preferably from 0.1 to 20 mbars, or equal to the atmospheric pressure, while using gas control chambers .
• the plasma can be generated by different electromagnetic plasma generating sources, i.e different frequency and different geometrical shape sources .
• the physical-chemical processes occurring on the surface of the materials to be processed mainly depend on the plasma parameters, i.e. the plasma gas, gas pressure, unit surface power, plasma material exposition time, and residue pressure of the evacuation step fo'r evacuating the material to be processed vacuum chamber.
• the typical operating parameters are as follows : - gas: CO 2 , SF 6 , hydrocarbons, acrylic acid, ammonia, fluorocarbons, even in mixtures thereof, noble gases, nitrogen, oxygen, hydrogen; - operating gas pressure: 10 2 mbars at an atmospheric pressure
• the plasma processing method can be carried out either in vacuum or at an atmospheric pressure.
• the plasma can be generated by any plasma generating source (low frequency, radio frequency, high frequency) .
• the plasma process does not depend on the geometric shape or frequency of the plasma source, and, moreover, does not depend on the vacuum chamber geometric shape and configuration, but on the above specified operating or working parameters.
• two plasma processing methods will be hereinafter disclosed, i.e. a vacuum processing method and an atmospheric pressure processing method. Treatment under vacuum
• a polymeric textile material sample is supplied to a cylindric reactor (having for example a diameter of 20 cm and a height of 40 cm) and is arranged in front of the operating antenna, at a distance therefrom from 2 to 10 cm.
• Evacuation and degassing step A pumping step is at first performed, in which the overall system is evacuated and brought to a low pressure, in each case however larger than 10 "6 mbars. In this step, the polymeric sample is degassed, thereby- removing therefrom air and moisture contained therein. Filling-in step
• a filling-in step is carried out, in which the reactor is filled-in by the process gas (CO 2 , SF 6 , CH 4 ) .
• the target or desired processing pressure (from 10 ⁇ 2 mbars and 1 mbar) is achieved under flow conditions inside the reactor.
• Plasma generation step The plasma is supplied through a RF generator or source (for example: Huettinger PFG-300, 13.56 MHz) coupled to the antenna through a semi-automatic matching device.
• the RF generator or source can be used both in a continuous mode of operation and in a pulse mode of operation. In this latter case, it is possible to change the times t on (plasma switching on time) and toff (plasma switching-off time) .
• the applied powers are varied from 0.1 W/cm 2 to 1 W/cm 2 .
• Processing step The polymeric fabric sample is exposed to the plasma for a time variable from 1 second to 15 minutes. Filling-in step
• a chamber filling ' -in step is carried out, after having switched- off the radiofrequency, and the filling-in step can be carried out by using different types of gases, air, from air to inert or noble gases. At atmospheric pressure
• the sample is entrained between two electrodes coated by a ceramics material, spaced from one another at 1 mm to 5 mm.
• the samples are cyclically processed, each processing cycle comprising a treatment having a duration of fractions of second.
• the typical speeds or processing rates, under continuous-regimen roll-to-roll conditions vary from 1 m/minute to 100 m/minute.
• the gases used in noble gas, air or nitrogen mixtures are CO 2 , SF 6 , CH 4 , fluorocarbons, acrylic acid.
• the above disclosed plasma processing method can be applied after any desired yarn or fabric enhancing or nobilitating step.
• This parameter is defined as the ratio of the D. C. voltage and current passing on a surface of a body.
• the surface comprises a square area.
• the surface resistivity corresponds to the resistance between the two opposite sides of a square and is independent from the square size and size unit thereof.
• the surface resistivity is measured in ohms/square.
• the surface resistivity is calculated by using a measurement of the electric resistance of the sample on which are arranged two concentric ring elements operating as electrodes and therebetween a potential difference of 100 V is applied.
• the used measurement method measures the resistance of a material as a current intensity between the two electrodes.
• the sample, having a size of 12 x 12 2 is held in e fixed position by a metal clamping plate.
• the used measurement instrument is a Agilent ohmeter, Model 4339B, with a measurement cell Model 16008B • including concentric rings for measuring the surface resistivity and volume of insulating materials.
• the samples are preserved under relative humidity and temperature controlled conditions for at least 24 hours, before and after the measurement. Said conditions correspond to 20 + 2°C and 65 ⁇ 2% RH.
• the measurement range varies from 1 x 10 3 to 1.6 x 10 16 ohm/square.
• the surface resistivity is calculated by using the following Formula:
• the measurements have been performed under the following operating conditions: the sample is arranged in the measurement cell and clamped or locked between the electrodes and a metal plate under a load of 5 kg.
• the measurement is performed on a non-plasma processed sample, and on the plasma processed sample, immediately after the processing or treatment and then at time intervals of the order of weeks.
• the antistatic property providing method is carried out under a vacuum at a pressure from 0.1 to 10 mbars, preferably 0.2 mbars to 2 mbars, more preferably from 0.-2 mbars to 0.6 mbars .
• the used gases comprise: CO 2 , air, noble gases,
• the operating residue pressures were larger than 10 "6 mbars, to reduce the degassing effect of the material during the surface plasma applying step.
• the typical operating or working power densities vary from 0.1 W/cm 2 to 1 W/cm 2 and the plasma can be generated with a pulsed manner of generation.
• the treatment or processing times i.e. the time for which the material surface is exposed to the plasma, are less than 15 minutes, preferably than 8 minutes, and more preferably from 1 second to 2 minutes .
• the surface resistivity value decreases by at least four orders: from a value for a not processed material NT, of 1.5 x 10 15 ohms/square to values, for a processed PET material, of at least 1.0 x 10 11 ohms/square.
• the surface property is, in most cases, a permanent one, i.e. the surface resistivity measurement remains unaltered for the plasma processed sample, after several weeks from the processing time.
• the fluorurated gas is herein used not for providing the textile material surfaces with hydrophobic properties, but for modifying their surface conducibility, while holding unaltered, or at most modified in a hydrophilic sense, their surface properties.
• the plasma processing is efficient for all the materials (polyester, nylon, acrylic, poplypropylene and mixed materials, and in general on all the synthetic fabric and yarn materials.
• materials polymers, nylon, acrylic, poplypropylene and mixed materials, and in general on all the synthetic fabric and yarn materials.
• a PET polymeric fabric material is herein considered.
• the samples were arranged in front of a flat antenna at a distance variable from 3 cm to 10 cm, and the plasma was supplied either under a continuous or a pulsed regimen.
• NT Not-Treated material
• Cons the contact angle expressed by degrees
• Time means the time interval of the plasma treatment, as measured in seconds;
• P means the process gas pressure providing the cold plasma, as measured in mbars;
• “imp” means the pulsed mode of operation of the generator used for supplying the source
• Ton means the on-time of the generator in a pulsed mode of operation
• Toff means the off-time of the generator in a pulsed mode of operation
• PET means the PET polymeric fabric material
• the samples have been analyzed after the plasma treatment or process, and it has been found that the surface resistivity values were constant for months after the treatment.
• the sample processed by SF6 PET#9 has been analyzed after several months, and the surface resistivity value after three months was of 2.190E + 12.
• inventive method is adapted to provide textile and yarn polymeric materials with target conducibility properties, without using chemical products and water, with a consequent very low environmental impact.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Textile Engineering (AREA)
• Chemical Or Physical Treatment Of Fibers (AREA)

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• 2005
  • 2005-05-04 IT ITMI20050813 patent/ITMI20050813A1/it unknown
• 2006
  • 2006-05-04 WO PCT/IT2006/000311 patent/WO2006117829A1/en not_active Application Discontinuation
  • 2006-05-04 EP EP06745321A patent/EP1880050A1/en not_active Withdrawn

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