EP0695384B2 - Process for coating yarns and fibres in textile objects - Google Patents

Abstract

Textile bodies may be coated by physical or chemical vapour deposition in the gaseous phase. The layers deposited on the fibres or filaments have a high quality. It is thus possible to coat filaments or fibres without leaving any pores even with very thin layers, which cause however an imperceptible increase of the total volume of the textile object. Because of the high mobility of the coating material particles, even critical spots, such as the chaining spots in meshed or woven goods, are reliably coated. The same is valid also for complex designed, three-dimensional textile shaped bodies. Besides coatings by simple deposition, surface polymerisations may also be carried out, forming impenetrable layers on the textile material, which either protects it against the environment (allergy, sensitivity to air or light) or confer new properties to it (electric conductivity, antiadhesive coating). Coating in the gaseous phase also prevents in many cases the textile body to be processed from drying out.

Description

The present invention relates to the coating of the surfaces of textile structures, in particular threads, and fibrils in textile articles.

The common technique of surface treatment in the field of textile production is that the filaments or filaments are coated prior to further processing or superficially modified by a chemical or physical process. To a limited extent, these methods are also applicable to textile intermediate or end products. In the chemical treatment and the coating, the usual methods are the application of the coating material or the chemical reagent by brushing, spraying, etc. on the textile material or immersing the textile material in a liquid treatment medium.

Problems arose in these known methods whenever a treatment of the threads prior to processing prohibited, for. B. if the treated threads could no longer be easily spun or entangled and therefore a textile article, whether a semi-finished or an end product, had to be treated. In particular, it could not be ensured that in the mentioned treatment methods, the individual threads were completely and reliably coated or treated. Issues were, for example, the crossover points of the threads in woven or knitted fabric. Similar problems arose with increased demands on the treatment of the filaments in multifilament yarns or twines.

With the increasing importance of ecological aspects, the disadvantage of the known processes came to the fore that spent treatment media were to be disposed of as special waste because of the solvents or other components contained therein.

EP 496 117 A describes a process for producing a sewing yarn provided with an equipment, in particular containing synthetic fibers. Here an equipment is applied directly after spinning on the sewing thread. Here, the equipment itself or monomers or oligomers are applied to the yarn which are radically / ionically oligomerizable / polymerizable and thereby form the equipment. The radical and / or ion-generating treatment may in this case be formed by a low-temperature plasma treatment. However, this process is very time consuming and affects the properties of the yarn in the subsequent production of the textile structure.

EP 492 649 A 3 describes a process for altering the properties of a textile substrate, wherein an initiator which decomposes into radical and / or ions by physical treatment is applied to the substrate. Simultaneously or subsequently, the physical treatment is carried out and brings the resulting radicals with the textile substrate or a substance applied thereto to the reaction. This method has the disadvantage that a chemical initiator is required, which on the one hand requires a greater amount of chemical aids and, on the other hand, is not harmless from the point of view of environmental compatibility. For chemical initiators are usually relatively aggressive substances whose disposal is possible only with considerable effort.

It is therefore an object of the present invention to provide a method for treating the surface of filaments or textile structures, which allows a qualitatively improved surface treatment of the components, by means of which the adhesion of the treatment agent is increased on the surface and which is relatively environmentally friendly.

Such a method is specified in claim 1. Preferred embodiments and applications as well as products are subject of the further claims. Under textile structure is to understand everything that is made of textile material, in particular filaments or fibers or tapes, by one of the usual in the textile industry process, especially weaving, knitting and knitting, so everything from the thread to the textile end product like also, for example, nonwovens. However, the fibers or filaments themselves do not count as textile structures. Threads or yarns are generally linear textile structures, in particular all of fibers or filaments. Textile material is the material from which the textile structures can consist, ie in addition to fibers or filaments made of natural or synthetic fiber, metal threads, stone fibers, glass fibers, etc.

The invention is based on the surprising finding that the coating processes known from the gas phase for coating solid objects made of plastic or metal can be applied to threads or filaments and fibers in a textile structure, and lead to products having properties which have not hitherto or only with disproportionately high effort were available. The treatment medium is produced in the process by chemical (CVD) (Rompp Chemie Lexikon, 9th edition (1990), volume 2) or physical (PVD) processes (Rompp Chemie Lexikon, 9th edition (1992), volume 5). Preliminary tests for modifying the chemical or physical properties of textile materials by a PVD process, the low-temperature plasma process, are known (Y. Rogister, J. Knott, L. Ruys, M. Van Lancker, Etude de l'influence de Nouvelles Techniques de Traitement de Surface sur les Propriétés des Fibres, Techtextil Symposium 1992). In these experiments, a plant for the treatment of plastic films was used, which generated the plasma by electromagnetic excitation. It was in this Plant during the treatment, a negative pressure to 1.33 Pa (10 ^-2 Torr) produced and the influence of the plasma on the textile examined, with changes in the wettability, the surface structure and also the mechanical properties were observed and substantially erosive effects in the foreground stood. Surprisingly, it has now been found that such techniques can also be used for applying layers to textile material.

The high mobility of the reactive gas particles produced results in that, in textile structures, each individual thread or fiber is reliably superficially applied in its entirety and that the individual fibers are also coated during the treatment of threads or multifilament yarns. Coatings produced by the method according to the invention adhere substantially more firmly than conventional layers and can be produced as a non-porous covering of the textile material. This makes it possible to use filaments of materials whose mechanical properties, while desirable, are superficially undesirable reactions with the environment. Examples which may be mentioned are moisture-sensitive or allergenic materials.

By the method according to the invention, the spectrum of possible surface coatings is also greatly expanded.

It can z. As metal layers are applied to obtain an electrical conductivity or to influence the visual impression. Polymerization may be performed directly on the surface of each fibril of the substrate when the treatment is carried out with a gaseous monomer. It is also possible to carry out in preparation of the coating, first with the same method, an intensive cleaning or preparation of the surfaces, such as. As the dry removal of a lubricant, which over the known methods already significantly better adhesion or treatment intensity can be increased again. Depending on the process conditions, continuous or discontinuous layers can be produced.

With regard to the environmental problem, it should also be emphasized that the process according to the invention requires no solvents or other liquid carriers and that no drying operations have to be carried out, as a result of which the energy consumption is substantially reduced. Because of the high quality of the conversion, it is also possible to reduce the total amount of the coating or reaction material, since the treatment from the gas phase ensures an extremely uniform action on the surfaces to be treated.

The treatment of sensitive materials with highly reactive substances for chemical modification of the surface, which in the known methods usually high temperatures or were not possible at all, can be carried out according to the inventive method, since the thermal load of the object to be treated by adjusting suitable process parameters reduced or can be avoided. In particular, the ions of the plasma have about room temperature in a low pressure plasma treatment.

The present method is also very suitable for impregnating volume-containing or three-dimensionally shaped textile body such. B. spacer fabric, Abstandmaschenware or nonwoven fabrics. The impregnation or the layer structure also takes place in the volume and coated in the interior of the construction all fibers.

A preferred embodiment of the inventive method is to bring a textile body in a conventional chamber for the PVD coating by the low-temperature plasma method. In order to achieve a uniform access of the treatment gas, the textile body is held by a support frame or a clamping frame so that the surfaces are as freely accessible. The process parameters according to the planned coating are set, ie vacuum, gas input and temperature. To be evaporated treatment agents are introduced as usual in this process as a solid or as a powder or granules in the treatment chamber. Suitable gases of the treatment atmosphere are noble gases, for example argon, but also nitrogen and oxygen. The selection depends on the properties of the particular substrate to be coated and the coating material.

When applying a DC Gilmmentladung plasma particles u. a. on the treatment agent in the solid form and lead to its evaporation.

An ionic interaction between the depositing particles and the surface, ie the substrate, leads to particularly adherent and very stable layers. A particularly strong bond between the layer and the substrate occurs when chemical bonds between the substrate and the layer are formed in the course of the deposition, eg. B. by grafting. Very stable layers are obtained when crosslinking the polymerization, in particular resulting in three-dimensionally crosslinked structures. Often, a cleaning process is observed prior to deposition, which can be forced or promoted by appropriate process parameters, creating a thorough cleaning of the surfaces to be treated of the textile body and thus a high quality of the coating is achieved.

An advantage of a coating by surface polymerization according to the present invention is that the activated monomer in spite of their excitation, for. As ionization, only slightly elevated temperature and thus polymerization can also be carried out on temperature-sensitive materials such as thermoplastics. It is also possible to use conventional, chemical type non-polymerizable substances, such as. For example, alkanes, as under the action of a glow discharge, such molecules pass under breaking bonds or cleavage of fragments into reactive forms.

With the method according to the invention, for example, textile bodies made of polyethylene filaments were coated with PTFE, whereby the high tensile strength of the polyethylene could be combined with the anti-adhesive effect of the PTFE. Carbon fibers can be protected by a suitable coating against the oxygen in the air. The deposited layers can be performed cleaning, washing and even boiling and (steam) sterilization resistant.

It is also possible to treat webs of textile material. For this purpose, the textile material can be placed on rollers in the treatment chamber and rolled over in this during the treatment time, or the textile material can be pulled through from air to air through the chamber, to which the chamber must have input and output locks.

In summary, therefore, according to the inventive method, a textile body can be holistically equipped with new surface-related properties. The surface treatment is carried out intensively and because of the treatment from the gas phase very evenly in already interwoven or meshed material, and the applied layers can be kept very thin because of the high quality, eg. B. thinner than 1% of the fiber diameter or only a few hundred atomic or molecular layers thick, so that a significant volume increase can be avoided by the coating. Among other things, the following surface properties can be adjusted by choosing the appropriate treatment (s): antibacterial finish, wash and cook resistant; fungicidal properties; wettability; UV-IR absorption; Radiation, in particular IR, UV, light reflection; lubricity; Wrinkle properties; flammability; Anti Pilling; electric conductivity; etc. The layers adhere very well to the surfaces of the textile material and are well formed even in the finest interstices. Thus, a pervasive treatment of voluminous textile structures is also possible, such as spacer fabrics, knitted fabrics, nonwovens and felts. With the method according to the invention, it is also possible to use jackets with materials whose use according to the known methods was too expensive, since only small amounts are necessary in the invention, and thus the importance of the material cost factor is generally also suppressed.

The fiber sheath provided by the invention can be implemented as a process step in existing equipment and coating processes.

The invention applies a technology in the textile sector which hitherto has been used only in other technical fields, e.g. has been used in surface hardening metalworking and in PCBs for CFC-free, reliable cleaning even in the finest boreholes. This technology is made available for area and spatial textiles. The molecules of the monomer are excited and fragmented to a considerable extent by collision with the energetic particles, the electrons present in the gas discharge, i. smashed into pieces of molecule. This allows the monomers and fragments in the gas space to react with each other on all surfaces. These reactions are the very basis of plasma polymerization.

The plasma that stimulates these processes is an ionized gas consisting of ions, electrons, light quanta, atoms, and molecules. Due to the possibility of low-temperature coating, it is possible to coat in a vacuum at room temperature. This may even coat thermoplastics (e.g., polyethylene or polypropylene). The resulting layers are highly cross-linked three-dimensionally and have excellent adhesion to the substrate.

With one and the same system, however, erosive processes are also possible. Thus, e.g. Ignition of an oxygen plasma creates a "cold burn". This removes organic or greasy contaminants without environmentally harmful chemicals. All that remains is an ashen remainder.

Both processes, the removal and application can be done by the appropriate control of the parameters in one operation, i. occur at a reactor charge. This can ensure that a coating matrix is applied only to an absolutely clean substrate.

Another aspect of the up-and-down plasma technology is the hundred percent sterilizing effect of the plasma (destructive effect on organisms). Also by the packaging of e.g. Dressing material can reliably kill off all bacteria.

The coating process of plasma technology is a very economical and environmentally friendly technology. The electrical energy consumption is very low. These are all advantages over the known wet process, which are both time-consuming and energy-consuming and expensive in terms of process steps, since the liquor (water) must be heated and maintained at temperature. Then again is a high energy consumption necessary during drying. These process steps are eliminated. Furthermore, eliminating the disposal of the usual chemical residues in the wet process.

The layers, which can be applied plasma-assisted, have completely new properties due to the high degree of crosslinking, which differ fundamentally from those of a polymer prepared conventionally from monomers. The polymer is always a thermoset, is very temperature resistant and even in a small layer thickness free from pinholds (smallest uncovered areas) and is almost vulnerable to any solvent.

The high-energy particles excited in the plasma therefore trigger intense and profound effects on the monomer (gas). The cold plasma provides high energies in chemically very effective form at room temperature. Similar reactions are e.g. not realizable in the hot flame. Virtually all organic compounds can be made to coat.

According to the invention, each fibril of a thread is encased in the special plasma within the textile surface. The discharge thus also reaches very complicated shaped parts, undercuts and also detects the unexposed contact areas of the fibers. The volume properties of the coated textile are not affected or visibly affected.

The textile is in a vacuum vessel during treatment. The resulting excess or waste gases are sucked off by a vacuum pump and can be easily collected or recycled as a cycle back to the reaction. In principle, in the plasma process an uncontrolled distribution of substances of concern is not to be expected.

Because of the very thin layers, the material costs are very low.

• Beeinflussung der Oberfläche durch Abtragung
• Beeinflussung der Oberfläche durch Beschichtung
• Einstellung der Benetzbarkeit (hydrophil)
• Steigerung/Verminderung der Haftbereitschaft (hierdurch problemlose Färbung)
• Erzeugung elektrisch isolierender/leitfähiger Schichten
• Einstellung der Permeationsdaten für Gase und Flüssigkeiten
• Steigerung der Abrasionsbeständigkeit
• Änderung des Reflexionsverhaltens (UV- und IR-Schutz)
• Änderung des Gleitverhaltens.

Finally, some effects of low-temperature plasma will be listed:

• Influence of the surface by erosion
• Influence of the surface by coating
• Adjustment of wettability (hydrophilic)
• Increase / decrease the readiness to adhere (thus easy coloring)
• Generation of electrically insulating / conductive layers
• Adjustment of permeation data for gases and liquids
• Increase in abrasion resistance
• Change in reflection behavior (UV and IR protection)
• Change of sliding behavior.

The reactor for coating the textile substrate can either be formed as a bell reactor, in which the monomer is supplied from above. The substrate is in the vicinity of the cathode or in the cathode drop region, because there the degree of ionization of the coating monomer is high. The flow form results in a radial overflow of the substrate.

It is also possible to use a tube reactor in which the electrodes are arranged parallel to the tube axis. The substrate is overflowed parallel here by the monomer.

The plasma polymerization can be divided into five steps, which are partially parallel.

In the first step, the initiation, monomers in the gas phase are activated or radicalized by electron impact. In addition, monomers adsorbed on the substrate surface are excited by electron, ion or photon bombardment to react with other monomers.

A second step, adsorption, describes the adsorption of monomers and radical species on the substrate surface. Chain growth is described in a third step. This reaction can occur between radicals and monomers in the gas phase, adsorbed radicals and gaseous monomers, as well as adsorbed radicals and adsorbed monomers.

The fourth step, the termination, leads to the formation of polymeric entities. By reacting longer chain radicals in the gas phase, polymers can be formed in the gas phase. The reaction of radicals from the gas phase with adsorbed radicals or adsorbed radicals with one another produces polymers that are adsorbed on the substrate.

A fifth step, the re-initiation, describes, on the one hand, the repeated fragmentation of the already formed polymer in the gas phase by the action of the plasma and, on the other hand, the process of three-dimensional crosslinking of the polymer on the substrate surface by the action of ions, electrons and photons.

The plasma polymerization is carried out in a pressure range between 0.01 mbar and 10 mbar. At low pressures, the achievable deposition rates are too low, while at higher pressures no transparent continuous layers can be produced with the desired properties.

1. 1) Adhäsive Funktionsschichten, die folgende Eigenschaften beeinflussen: Bedruckbarkeit, Lakkierbarkeit, Metallisierbarkeit Klebbarkeit, Benetzbarkeit, Hydrophilisierung, Hydrophobisierung, Antiadhäsivierung, Schichtverbundfestigkeit, Teilchenverbundfestigkeit und Faserverbundfestigkeit.
2. 2) Optische Funktionsschichten, die folgende Eigenschaften beeinflussen: Farbstabilität, Brechungsindex, Antireflexionswirkung, Antibeschlagwirkung, Entspiegelungswirkung, Adsorptionskoeffizient.
3. 3) Textile Funktionsschichten, die folgende Eigenschaften beeinflussen: Festigkeit, Formbeständigkeit, Bedruckbarkeit, Färbbarkeit, Farbechtheit, Farbhaftung, Klebbarkeit, Flammfestigkeit, statische Aufladbarkeit, Schmutzempfindlichkeit, Wasseraufnahmevermögen, Antifilzwirkung.
4. 4) Biomedizinische Funktionsschichten, die fürTextilien im medizinischen Bereich eingesetzt werden können. Diese beeinflussen z.B. folgende Eigenschaften: Organofilierung, Biokompatibiltät, immunbiologisches Verhalten, Antitoxizität.
5. 5) Elektrische Funktionsschichten, die die elektrischen Eigenschaften der Fasern beeinflussen: Dielektrizitätskonstante, Isolationswiderstand, antistatisches Verhalten, Leitfähigkeit.
6. 6) Chemische Funktionsschichten zur Beeinflussung der folgenden Fasereigenschaften: Migrationsschutz, Diffusionsschutz, Korrosionsschutz, Lösungsmittelresistenz.
7. 7) Mechanische Funktionsschichten zur Steuerung der folgenden Eigenschaften: Verschleißverhalten, Abrasionsschutz, Reibungskoeffizient.
8. 8) Permeable Funktionsschichten zur Steuerung von z.B. Porosität und Permeabilität.
9. 9) Thermische Funktionsschichten zur Beeinflussung der Formbeständigkeit, Haftfähigkeit und Wärmereflektion der textilen Fasern.

Among the functional layers applied to the textiles by plasma technology, nine groups can be distinguished:

1. 1) Adhesive functional layers which influence the following properties: printability, lacqurability, metallizability bondability, wettability, hydrophilization, hydrophobization, antiadhesion, composite bond strength, particle bond strength and fiber composite strength.
2. 2) Optical functional layers, the following characteristics influence: color stability, refractive index, antireflection effect, antifogging effect, antireflection effect, adsorption coefficient.
3. 3) Textile functional layers which influence the following properties: strength, dimensional stability, printability, dyeability, color fastness, ink adhesion, adhesiveness, flame resistance, static chargeability, dirt sensitivity, water absorption capacity, anti-fouling effect.
4. 4) Biomedical functional layers that can be used for textiles in the medical field. These influence, for example, the following properties: organofilament, biocompatibility, immunobiological behavior, anti-toxicity.
5. 5) Electrical functional layers that influence the electrical properties of the fibers: dielectric constant, insulation resistance, antistatic behavior, conductivity.
6. 6) Chemical functional layers to influence the following fiber properties: migration protection, diffusion protection, corrosion protection, solvent resistance.
7. 7) Mechanical functional layers for controlling the following properties: wear behavior, abrasion protection, friction coefficient.
8. 8) Permeable functional layers for controlling eg porosity and permeability.
9. 9) Thermal functional layers for influencing the dimensional stability, adhesion and heat reflection of the textile fibers.

Each coating monomer has its own polymerization kinetics because of its chemical composition and structure as well as the required process parameters. The rate of polymerization and thus the rate of growth of layers of different monomers differ significantly. Thus, e.g. In the case of monomers having high molecular weights, the coating rates are generally higher, since larger low molecular weight fragmentation products can form and attach. To achieve different desired properties, several monomers can be applied to the textile substrate simultaneously or in succession by plasma technology.

Claims (12)

1. A method of treating the surface of threads, consisting of one or more filaments, and of threads in textile structures with a treatment agent comprising the step of activating said treatment agent in a plasma in which said treatment agent is translated into a gaseous or plasma state and deposited on the surface of said threads or filaments, said treatment agent being translated into a reactive form by the effect of glow discharge and in the course of the deposition chemical bonds being formed between said filament or thread and the coating of said treatment agent to be deposited whereby said treatment agent is made available by evaporating a solid body of a coating material.
2. The method as set forth in claim 1, characterized in that the treatment is implemented at a total gas pressure of maximally approx. 10 kPa.
3. The method as set forth in any of the claims 1 to 2, characterized in that said treatment agent in the gaseous state is translated into a chemically reactive state by an electric discharge or interaction with plasma particles of the environment generated by irradiation with energy, more particularly by electromagnetic fields.
4. The method as set forth in any of the claims 1 to 2, characterized in that said treatment agent is translated by the effect of radiation and/or heat into a state in which said treatment agent is capable of being deposited on the surface to be coated.
5. The method as set forth in claim 3 or 4, characterized in that said treatment agent is polymerizable and caused to polymerize indirectly, via energized or reactive particles in the atmosphere of the treatment space, or directly.
6. The method as set forth in any of claims 1 to 5, characterized in not the structure to be cooled or heated by micro waves.
7. The method as set forth in any of the claims 1 to 6 for coating textile material and structures consisting at least in part thereof, characterized in that said threads or filaments of said textile material are homogenously sheathed by a coating generated from said treatment agent by surface deposition or polymerization.
8. The method as set forth in any of the claims 1 to 6 for coating textile material, characterized in that the threads or filaments of said textile structure are homogenously provided with a surface comprising one or more of the following properties: electrically conductive, electrically insulating, metallic, gas-impermeable, radiation reflective, light-reflective, antibacterial, fungicidal, cleansing compatible, sterilization-compatible.
9. The method as set forth in one of claims 1 to 6,
   characterized in that a plasma coating is effected at room temperature.
10. The method as set forth in claim 9,
    characterized in that the plasma coating is effected by PVD or CVD process.
11. The method as set forth in one of the preceding claims, characterized in that before the coating by the ignition of an oxygen plasma a cold burning is effected for removing organic impurities of the substrate.
12. The method of claim 11, characterized in that the ignition of the oxygen plasma and the subsequent coating are effected in one step.