Patent Application
20170306532
The present invention relates to a card clothing for processing textile fibers.
Flexible and semirigid card clothings are used in various areas of the processing of textile fibers. A flexible or semirigid card clothing essentially consists of a clothing carrier and the clothing tips held therein. The clothing tips are formed by U-shaped wire hooks. In a so-called punching process, the wire hooks are pushed through the clothing carrier in defined intervals and arrangements, with the ends thereof projecting out of the clothing carrier and forming the clothing tips. The wire hooks are held in the clothing carrier and, depending on their shape and length as well as the characteristics of the clothing carrier, have a certain degree of flexibility. Semirigid clothings have stronger wire hooks than flexible clothings. Likewise, in semirigid clothings, the clothing carrier is designed so as to be stronger, in terms of lesser flexibility, than in flexible clothings.
Various embodiments of clothings with clothing carriers having commensurately different designs are known from the prior art, with the clothing carrier generally being multilayered. DE 10 2006 016 832 discloses a clothing carrier composed of at least two layers—an underlayer and a covering layer. The wire hooks are anchored in the underlayer. In contrast, the covering layer enables the wire hooks to swing without hindrance, which is important particularly when used for carding. The underlayer is made of a nonwoven fabric, and the material of the nonwoven fabric is different from the material of the covering layer.
CH 636 134 discloses a clothing with a clothing carrier consisting of a base body with reinforcing insert embedded therein. The base body is made of an elastic plastic, and the reinforcing inserts are made of woven fabric or layers of woven fabric.
In DE 74 14 314, a known embodiment of clothings having a clothing carrier consisting of several woven layers is improved to the effect that at least one layer made of a nonwoven fabric is inserted.
CH 704 412 discloses a clothing with a clothing carrier consisting of a nonwoven that is manufactured from a defined mixture of various types of fiber. Shrinkable fibers, which result in the consolidation of the nonwoven under thermal treatment during the manufacturing process, are particularly used for this purpose.
All clothing carriers known from the prior art have the drawback that they are constructed of several layers or consist of a defined mixture of different fibers, in which case the various layers or various fibers have to be interconnected. The necessity of a layered construction or of the use of different materials in a nonwoven for a clothing carrier appears to be inevitable, since a strong anchoring of the wire hooks in the clothing carrier must be ensured on the one hand, while a certain degree of mobility on the part of the clothing tips as well as the fit in the clothing carrier must be ensured on the other hand. Another drawback of clothing carriers according to the prior art are the relatively weak restorative forces that bring the clothing tips back into the original position after a deflection. This is also due to the fact that known clothing carriers wear out after a short time, thereby resulting in excessive play on the part of the clothing tips in the clothing carrier. This results in the so-called pulling-over of the clothing.
It is the object of the invention to provide a clothing with a clothing carrier in which the clothing carrier has a simple construction and the strength necessary for the anchoring of wire hooks while still permitting the necessary mobility of the wire hooks.
The object is achieved by the features in the characterizing part of the independent claim.
To achieve the object, a clothing for processing textile fibers having a clothing carrier and clothing tips is proposed in which the clothing tips are formed by wire hooks that are pushed through the clothing carrier in a punching process. The clothing carrier is a random, paneled nonwoven formed from continuous fibers or staple fibers that has been consolidated by needling and impregnated with a polymer having a defined specific weight per unit area and a functional layer applied to a side of the clothing carrier facing toward the clothing tips. The polymer has a proportion by weight of 20 to 60 percent of the specific weight per unit area of the random nonwoven. Through the appropriate selection of the combination of random nonwoven and polymer, a proportion by weight of the polymer of up to 70% of the specific weight per unit area of the impregnated random nonwoven is achieved. It was found that the proportion by weight of the polymer to the specific weight per unit area of the impregnated random nonwoven is especially preferably 55% to 70%.
The wire hooks used have a wide variety of shapes, sizes, and lengths. The structure of the wire hooks is dependent on the intended use of the clothing. A great number of shapes for wire hooks is known from the prior art which can be associated with different uses in textile machines. For the present invention, the geometric implementation of the wire hooks does not have a great impact, so it will not be addressed further here.
A random nonwoven is to be understood as a textile fabric composed of fibers or filaments that is created through the loose stringing-together and layering of unordered fibers or filaments. No distinction is made in the present invention between the use of staple fibers and continuous filaments. A nonwoven can consist of longitudinal, longitudinal and transverse, or transverse fibers or filaments, or of a completely randomly aligned layer, with the nonwoven being referred to as a random nonwoven in the case of a randomly aligned layer. If the fibers or filaments are aligned in one direction, a unidirectional nonwoven is formed.
Polyester (PES) fibers or polyamide (PA) fibers have proven to be suitable for forming random nonwovens in order to achieve the characteristics that are essential for the clothing carrier. The fibers are preferably used as staple fibers with a staple length from 30 mm to 80 mm and a fiber fineness from 1.0 dtex to 5.0 dtex. The specific strength is 25 cN/tex to 60 cN/tex. Alternatively, continuous filaments having the same fiber fineness and strength can also be used.
The random nonwoven is preferably made from polyamide fibers. In comparison to polyester fibers, polyamide fibers have a greater ability to absorb moisture, which also manifests itself in a higher level of wettability. Increased adhesion of the polymer used during impregnation to the individual fiber is thus achieved. The polyamide fiber also exhibits greater resilience after mechanical loading than the polyester fiber. This means that, after mechanical stress, the polyamide fiber returns more quickly to its original state than the polyester fiber. In the present application, these mechanical restorative forces result in an increased service life of the clothing carrier.
As is known from the prior art, the fibers used to form the random nonwoven are placed after the carding process onto a belt as a random nonwoven layer and then stacked using a nonwoven crosslapper. Through the crosslapping of several random nonwoven layers, a paneled random nonwoven is formed in which the fibers run predominantly in the transverse direction. The transverse direction is to be understood as the direction orthogonal to a direction of travel of the belt on which the random nonwoven layer is placed. Through the paneling (doubling), the desired weight per unit area of the random nonwoven fraction of the clothing carrier is achieved. In a preferred embodiment, the random nonwoven is constructed from at least 30-60 panels, preferably 40 panels.
A paneled random nonwoven has only limited inherent cohesiveness. In order to improve this limited cohesiveness, the random nonwoven is subjected to a needling process, thereby achieving consolidation of the nonwoven. Needling can be performed in one or also multiple passes. Furthermore, it is also possible to influence the orientation of the fibers in the nonwoven through targeted drawing (stretching) of the nonwoven before or after the needling process. This enables defined stress-strain characteristics of the nonwoven in the longitudinal and transverse direction to be clothing. The needling results in an increase in the density of the random nonwoven, and densities of up to 0.3 g/cm3 are achieved. Using the high-performance needling machines known today, the density of the random nonwoven can be increased to up to 0.4 g/cm3.
After needling, the random nonwoven is fed a first time through calender rolls. Differences in thickness are thus evened out and a defined thickness and/or density is set.
One important characteristic of the clothing carrier is permanent elasticity. The clothing tips used later are stressed such that the wire hooks move back and forth. In order to prevent the wire hooks from wearing out in their mounts, the clothing carrier must have a high level of permanent elasticity. To increase the permanent elasticity, the clothing carrier is impregnated with a polymer after the first calendering step.
The polymer—such as latex (acrylonitrile), for example—is made available in the form of an aqueous dispersion. The water content is preferably 50 to 70 percent, preferably less than 60 percent. In an alternative embodiment, the polymer can also consist of over 95% synthetic rubber dissolved in gasoline. The random nonwoven is dipped into this dispersion or solution, whereby the random nonwoven takes the dispersion or solution up into its hollow spaces. The random nonwoven is then pressed off in a second calendering step in order to remove excess dispersion, and then it is stabilized and dried in another step. An infrared field is usually used for the stabilization, thereby preventing sedimentation of the polymer. The stabilizing and drying of the random nonwoven can be performed in a heated space through which the random nonwoven is transported. The random nonwoven can be conveyed through the heated space on belts, rollers, or other suitable means, such as suctioned drums of a perforated drum dryer, for example.
In another embodiment, heated rollers can also be used to stabilize and dry the random nonwoven. The heating makes it possible to produce smooth surfaces or to establish the surface characteristics of the clothing carrier.
The impregnation also results in increased density. By changing the polymer fraction in the aqueous dispersion, the embedded quantity of polymer in the clothing carrier can be determined. This affects the elasticity and the density of the clothing carrier, and densities of 0.4 g/cm3 to 0.5 g/cm3 are achieved. Through the use of highly compacted random nonwovens, the impregnation can increase the density of the impregnated random nonwoven to up to 0.6 g/cm3.
Advantageously, the impregnated random nonwoven reaches a specific weight per unit area of greater than 1,400 g/m2. It was found that impregnated random nonwovens having a lower specific weight per unit area result in a reduction in the cohesion of the wire hooks pushed into them and thus promote faster wearing-out of the wire hooks. The specific weight per unit area of the impregnated random nonwoven is preferably greater than 1,600 g/m2.
The functional layer applied to the side of the clothing carrier facing toward the clothing tips has the purpose of achieving a structural evening-out of the surface of the random nonwoven. The functional layer advantageously has a thickness of 0.05 mm to 0.5 mm. Thin functional layers are achieved through the application of a rubber coating. Such functional layers are produced, for example, through the multiple application of a small quantity of rubber.
In another embodiment, the application of a functional layer is provided for through lamination with a polyurethane (PUR) film. Through the lamination, the PUR film is joined with the random nonwoven. One process that is particularly suitable for this purpose if thermolamination, in which the PUR film is applied to the clothing carrier under heat and pressure, for example with the aid of heated rollers. The PUR film used has a thickness of 0.1 mm to 0.5 mm, with PUR films with a thickness of 0.2 mm to 0.3 mm preferably being used.
This functional layer created by the coating or the film has the advantage that the surface of the clothing carrier is easy to clean and fibers conducted past the clothing during use result in fewer adhesions. What is more, the PUR film preferably used contributes to improving the permanently elastic characteristics of the clothing carrier. The PUR film applied to the random nonwoven also increases the retaining force of the clothing carrier in relation to the inserted wire hooks. This represents another difference between the known prior art, with the use of a covering layer, and the application of a functional layer. The functional layer performs several tasks, thereby making a substantial contribution to improving the performance of the clothing. The increase in retaining force with flexibility that is stable over a longer service life and good cleaning characteristics cannot be achieved by a clothing with a simple covering layer.
Through the use of heated rollers or belts during thermolamination, the PUR film is provided with a surface structure. As a result of the pressure exerted by the rollers or belts onto the PUR film, a structure present on the rollers or belts is transferred to the film.
The friction of the fibers is also substantially less on a structured surface than on a smooth surface—the reason for this being that the actual contact surface between a fiber and the surface of the clothing carrier is reduced by the structuring of the surface. The surface of the functional layer preferably has a wavy structure. The wavy structure is transferred by the heated rollers or belts to the surface of the PUR film during lamination.
The surface of the functional layer preferably has a surface roughness Ra from 5 μm to 30 μm, especially preferably 7 μm to 20 μm. The greatest height difference Rz is greater than 30 μm. The key data for surface roughness Ra and Rz are determined using the profile method according to the standard DIN EN ISO 4287 (1998 edition). The nominal characteristics of the profiling device used are defined by the standard EN ISO 3274 (1997 edition). öhendifferenz H
It was found that a structured surface of the functional layer or even an increased roughness of the surface compared to a smooth surface of the functional layer results in improved slipping of the fibers on the surface and to a reduction in the adhesion of contaminants. This also contributes to improving the cleaning of the clothing.
The invention is explained in further detail below with reference to an exemplary embodiment and by drawings.
Clothing carriers 1 are generally manufactured as continuous webs having a defined web length and a web width corresponding to the later length of the clothing strips and are equipped by means of the punching process with wire hooks 4 to form the clothing tips 2. After the entire manufacturing process is concluded, the clothing carriers 1 equipped with wire hooks 4 are cut transversely to the longitudinal direction of the web into ready-to-use clothing strips having the width b. In that case, the width b is between 15 mm and 150 mm, depending on the intended use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01537/14 | Oct 2014 | CH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2015/000874 | 6/8/2015 | WO | 00 |
