CH707323A2 - Method and apparatus for coating of textile fibers by means of plasma treatment. - Google Patents

Abstract

A process for coating textile fibers by plasma treatment, wherein the textile fiber to be coated is wound on a first bobbin and the textile fiber is rewound onto a second bobbin, is used to achieve improved fissile property and durability of the functionalized surface. For this purpose, the plasma treatment is carried out such that the plasma acts directly on the wound on the first bobbin textile fiber and the textile fiber is rewound during the plasma treatment of the first to the second reel.

Description

Technical Background and Prior Art:

The treatment of whole bobbins (wound on a core threads or textile fibers) has long been known in the textile industry for wet-chemical dyeing and cleaning steps (DE 461 456, DE 505 471). Since the 1990s, the possibility of dry cleaning based on CO2 purification has also been investigated. Again, threads or textiles can be wound on a core and treated with good depth effect (US 5,863,298). During the treatment no rewinding takes place. For a dry treatment by plasma technology, however, this method has not yet been considered because the penetration (fissuring) of a plasma treatment is limited. All patents and publications known to us consider it necessary that the surfaces of the textile and thread-like structures to be coated are as freely accessible as possible (EP 0 695 384 B1, EP 0 451 425 B1). This is due to the fact that the plasma is generated outside the textile structure and the layer-forming species must be transported to the surfaces. Especially at high pressures (near atmospheric pressure), numerous impacts prevent penetration into open structures.

US 4,328,324 (1982) describes the plasma treatment of PA fibers drawn through a plasma chamber (low pressure). This improves adhesion in a matrix for composite materials. US4606930 (1984) describes a bobbin in low pressure and the winding of the fibers in air, the plasma treatment is, however, brought about (by rolling) several times by passing the drawn thread through the plasma zone.

Fig. 1 shows a plasma coating of textile fibers according to the known prior art.

US Pat. No. 6,497,954 (2002) describes the plasma coating on textiles with partial coating of the fibers for textile-reinforced composites. Penetration in columns (fissuring of plasmas) is already described in the literature, without anticipating the possibility of coating a bobbin in the plasma. Poll et al. (Surf. Coat, Technol., 142-144, 2001, 489) describe the O 2 plasma treatment of up to four textile layers, wherein the wettable surface (capillary effects) clearly decreases already in the fourth layer.

Disadvantages of the prior art

By the use of plasma coatings instead of a plasma treatment (without layer formation) an improved fissile property and durability of the functionalized surface is achieved. For plasma coating on threads, it is currently only known to pull the threads over rollers through the plasma zone. This is associated with a high expenditure on equipment and the threads can lose strength due to shearing. The inventive design in the form of the coating of the thread directly on the reel during rewinding reduces the mechanical stress on the threads and simplifies the experimental design. This can be expected both lower investment and production costs.

Description of the invention

Surprisingly, we have found that a coating by plasma polymerization under suitable conditions many layers can penetrate into superimposed textile structure. Not only exposed surfaces are reached, but also hidden ones, presumably due to collisions of the layer-forming species with a mean free path in the order of the thread distances and surface diffusion. Therefore, it is also possible to coat directly overlying threads. The idea underlying the invention therefore provides for textile or thread-like structures to be coated directly on the roll on which they are wound. In particular, bobbins (wound-up filaments) can be coated directly in the low-pressure plasma while being wound on a second roll.

Fig. 2 shows an inventive plasma coating of textile fibers. FIG. 3 shows a further plasma coating of textile fibers according to the invention (alternative solution).

If a bobbin provided directly with a about 100 nm thick hydrophilic plasma polymer layer (layer thickness on the outside threads), we could prove the functionalization of the threads up to more than 10 layers deep on the reel, which in the example about 4 km thread length corresponds. The coating thickness decreases approximately exponentially with the depth. If the thread is then pulled off the reel while it is plasma-coated and wound on a second reel (rewound), not only the freely accessible thread (outermost layer) is coated, but also the underlying layers (with reduced intensity). However, a steady state results which, in the example given, applies three times more layer compared to the coating of only one layer (e.g., freely tensioned threads between two rolls or on a tenter). This can increase the process speed by a factor of 3.

Furthermore, the plasma system can be made compact and the thread does not have to be deflected. At each deflection shear forces occur, which affect the strength of the thread, which is particularly in high-strength thread materials such u.a. Carbon fiber, UHMWPE, Aramid, Vectran and PBO represents a problem. In the direct coating of the reel only a minimum deflection (a few degrees) is required by two rollers, as the thread when pulling on the width of the bobbin wanders (charged) and is led out centrally through an opening in the plasma chamber. The winding can then be carried out by known methods in air. Furthermore, the thread can also be removed overhead or from the inside with a coreless winding. In the latter embodiment, the plasma can be generated inside the coil. Consideration must be given to crossing points at which the threads on the reel lie in contact one above the other. An ideal cross winding (90 ° between the threads) in the bobbin production results in a coverage of 25% per layer (crossing points), but also an open area of 25%. In practice, the fraction of open area can be affected by the type of winding: typically between 35% (through multiple crossing points) and near 0% (in a parallel winding). In essence, the open area allows the coating of the lower layers. The crossing points, however, receive less coating. Since these points are stable until the thread is pulled off, results in this method, an uneven layer thickness along the thread. For many applications (e.g., hydrophilic, hydrophobic, adhesion mediation, friction reduction) this is insignificant, e.g. however, in the area of electrical conductivity or barrier effect are impaired. It has been found experimentally that the splitting action actually increases with the angle of the crossing threads on the bobbin. In addition to the plasma coating during the removal of the thread - which is a preferred embodiment, since this is easily possible in low pressure - but also the plasma coating during winding on a bobbin is equally possible. Thus, a two-stage system is also possible, which provides for two plasma treatments when rewinding from one reel to a second reel, whereby in each case according to the invention the reel is treated, e.g. Combination of 2 coatings or 1x plasma cleaning + 1x plasma coating. Other combinations with the treatment of the thread on the bobbin and with a further treatment on the withdrawn thread (according to the prior art) is also possible. Also, the pressure range (low pressure to atmospheric pressure) is not limited in principle. However, there is an optimal pressure range (in low pressure) depending on the textile structure and the type of plasma treatment. Independently of this, however, an atmospheric plasma treatment according to the invention could also be of interest, as a result of which vacuum technology is eliminated. By different types of winding and unwinding can continue to influence the density of the thread-like structures and thus the open area and the penetration of the plasma treatment.

Industrial Applicability of the Invention:

High-strength thread materials such as carbon fibers, UHMWPE, aramid, Vectran, PBO, etc. obtained their properties essentially by high crystallinity (alignment of polymer chains). As a result, however, these thread materials contain no functional (terminal) groups on the surface and are thus inert. The binding of chemical or biological groups on the surface or the incorporation into a matrix is thus difficult. Wet-chemical activation usually leads to a significant decrease in strength. The plasma coating reduces these disadvantages and allows surface functional groups to be stable even in an aqueous environment. In addition, plasma technology is a dry technology. Possible commercial use therefore arises in fiber-reinforced composites and in medical technology.

Claims (4)

1. A method for coating textile fibers by means of plasma treatment, wherein the textile fiber to be coated is wound on a first reel and the textile fiber is rewound on a second reel, characterized in that during the plasma treatment, the plasma acts directly on the wound on the first reel textile fiber and that the textile fiber is rewound from the first to the second reel during the plasma treatment. 2. The method according to claim 1, characterized in that the rewinding takes place on the second reel with only a single pair of guide rollers without multiple deflection. 3. The method according to claim 1 or 2, characterized in that the textile fibers are high-strength thread materials such as carbon fibers, UHMWPE, aramid, Vectran or PBO. 4. Apparatus for carrying out the method according to claim 1 with a first bobbin for receiving the textile fiber to be coated and a second bobbin for receiving the finished coated textile fiber, wherein the textile fiber from the first bobbin on the second bobbin is rewindable, characterized in that the Device for the direct plasma action is formed on the wound on the first reel textile fiber during rewinding.