DE3544523C2 - - Google Patents

Description

The invention relates to a method for producing Bicomponent fibers from polyolefin blends and those made from them produced fibers and their use for thermobonded Nonwovens with a soft handle, high bulk, good thermal bonding properties and high elongation.

Bicomponent fibers are usually made by that two material components separately in individual extruders are melted and brought together in the nozzle and be spun together. Bicomponent fibers have consequent their inhomogeneous structure a curl across the thread direction behave on. You can also use the material combinations influence the physical and textile properties. So far, bicomponent fibers with an asymmetric are known core made of polypropylene (PP) and a jacket made of polyethylene len (PE). This allows a soft grip and high bulk achieve. These fibers are very expensive and therefore for one wide use in the hygiene area not suitable. This is true also for the bicomponent threads according to US Pat. No. 4,469,540, which in addition to a core / shell arrangement of the PE and PP components a side-by-side arrangement was also disclosed. Here comes added that both material components on the thread surface lie. The thermal and textile-physical properties  Both components therefore affect both the thread processing processing to the flat structure as well as in the properties of the Finished products. A fleece made of such fibers therefore has a harder grip than a fleece made exclusively of PE fibers with appropriate titer. Pure PP fibers make it softer Handle achieved by using fibers with a very fine titer (approx. 1.7 dtex) and high strains. Despite fine These fibers do not have the titer and high elongation soft grip and high bulk, which meet the requirements in Hygiene area is sufficient.

The invention has for its object a method for Production of fibers with a soft feel, high bulk and high Stretch, good curling properties and good thermal bonding to create properties. In particular, fibers should be created which have the same or better properties than the known ones Own bicomponent fibers, but in their manufacture are cheaper and therefore also for a wide application, are particularly suitable in the hygiene area.

The object is achieved in that a PP PE funnel mixture with up to 20% PE is produced. By a mixer located at the screw tip of the extruder a finely dispersed distribution of the PE in the PP is obtained, so that a fine spin titer can be spun. The material will extruded and spun at 180 to 280 ° C and slowly at 20 up to 120 m / min through the first extraction device, the one Temperature over 100 and up to 140 ° C, deducted. Between the first and second trigger device Fibers stretched. The stretching that takes place is preferred wise lower than usual and below natural Draw ratio (VVnat), i.e. within the flow line ches (cf. H. Ludewig, polyester fibers, Akademie-Verlag, Berlin (1965), p. 197). It has been found that the PE  Components in the fiber in melt form at 120 to 140 ° C are available. It was found that the PP components during the Crystallization process at 120 to 140 ° C. start and be oriented towards molecular chains. It will assumed that the crystal nuclei begin to grow and grow at the same time by stretching in the longitudinal axis of the thread align. By growing from the core of the fiber Crystals are likely to have PE components on the outer edge of the fiber be pressed. The material migration is caused by the preferred low aspect ratio even easier. At the Passing through the convection oven heated to 150 to 170 ° C can be introduced by the orientation of the molecular chains Tensions relax, and the crystal growth of the PP should be accelerated. At the same time, more and more PE Components pressed against the edge of the fiber. After leaving the The convection oven finds one on a second extractor further heating to 110 to 140 ° C instead. The PP matrix should continue to crystallize, and the PE component also crystallizes at  simultaneous stretching and stabilization by the Trigger device. The outside of the PP fibers components of the PE are given a volume menu alignment in the longitudinal axis of the thread. It becomes a fiber with Preserved bicomponent structure, with a PP core and a Jacket area with accumulations of the PE component.

First of all, this shows that a fiber with soft handle typical of PE is obtained. Second the fibers show the herbs typical of bicomponent threads selection which may be mechanical, e.g. through upsetting brought in ripple, superimposed and to a high Bulky and the special softness of the manufactured Flat structures, especially fleeces leads. Show finally the threads during calendering for the production of thermally bonded (melt-glued) fleece a very wide, towards PE showing softening area of their outer skin. Thereby the temperature control of the calender rolls becomes crucial simplified. In addition, the melting temperature is outside skin much lower than with PP, so that the Fusion of the fibers in the fleece to the outer skin limited and the strength-determining fiber core is not damaged by heat.

It was found that with common market qualities of Spinning material with the selection of correct mixing ratios the bicomponent fiber described is obtained. The Experiments were carried out with a commercially available LLDPE (linear low density polyethylene) and HDPE (high density polyethylene) carried out. It could be a fiber with a very soft feel, high bulk, good crimp and very high stretch and good thermal bonding properties will. The filament titer of the fiber was 1.7 dtex and Elongation at about 370%. Through the fiber according to the invention Areas of application are opened that are otherwise only essential expensive bicomponent fibers were accessible.  

It was also found that when mixed with only 5% by weight of PE has no bicomponent properties to step. Distinctive and industrially usable bike components properties occur with a PE content of more than 10% on. With a funnel mixture with more than 20% PE, that will be Spinning the mixture is problematic because of the melt temperature of the PP the already molten PE component is damaged.

Further details and features of the invention emerge from the following description in conjunction with FIG. 1, which schematically shows a device for carrying out the method:

A PP-PE funnel mixture with up to 20% by weight of PE granulate is produced, which is melted in the extruder 1 . The melt is passed through a dynamic mixer 10 , so that a finely dispersed mixture is formed in which the PE phase is distributed in small particles. This mixture is pressed out and spun into fibers. They emerge from the spinnerets 2 and are guided over a heated to 100 to 140 ° C first take-off device 3 , consisting of seven rollers, which preferably run about 1% faster in the thread running direction, and drawn off at an increased speed. The stretching of the fibers is such that it is below the natural stretching ratio. The fibers then pass through a hot air oven 4 at a temperature of 150 to 170 ° C and are drawn off from it by a second take-off device 5 which consists of seven rollers which are heated to a temperature of 110 to 140 ° C and which are driven more slowly in the direction of the thread will. The fibers pass through a Stauchkräu selkammer (crimper) 6 , are then cut on a fiber cutting edge 7 and pressed into bales by a baler 8 or wound up as continuous fibers according to FIG. 1A (winding devices 9 ).

Fig. 2 shows a stuffer box crimped polypropylene fiber. The flat, relatively coarse crimp is typical.

Figure 3 shows a stuffer box crimped fiber according to this invention. The typical stuffer box crimp has been preserved, but this is overlaid with a fine-arched, three-dimensional crimp.

Claims (13)

1. A method for producing bicomponent fibers from polyolefin mixtures, characterized in that
the fibers are spun from a finely dispersed mixture of polyethylene and polypropylene with more than 5 and up to 20% by weight of polyethylene,
that the fibers are drawn in a take-off device heated to over 100 ° C. at a speed of 20 to 120 m / min and pass through a hot air oven at a temperature of 150 to 170 ° C. and from a second take-off device at a temperature of 110 to 150 ° C. 2. The method according to claim 1, characterized in that a funnel mix of polyethylene and polypropylene will be produced. 3. The method according to claim 1 and 2, characterized in that 10 to 20 wt.% PE can be added. 4. The method according to claim 1 to 3, characterized in that that PE is an HDPE. 5. The method according to claim 1 to 3, characterized in that that PE is an LDPE.   6. The method according to any one of claims 1 to 3, characterized in that that PE is an LLDPE. 7. The method according to any one of the preceding claims, characterized in that the temperature of the first fume cupboard above 100 ° C and is at most 140 ° C. 8. The method according to any one of the preceding claims, characterized in that the temperature of the convection oven at 160 to 170 ° C lies. 9. The method according to any one of the preceding claims, characterized in that the temperature of the second trigger device at 110 to 140 ° C. 10. The method according to any one of the preceding claims, characterized in that the first and second trigger device each there are several partially wrapped rollers and that the rollers of the first and / or second take-off Run slower in the direction of the thread. 11. The method according to any one of the preceding claims, characterized in that the stretching of the fibers is less than the natural one Aspect ratio is.   12. Bicomponent fibers made of polypropylene-polyethylene of 0.6 up to 5 dtex, characterized in that the polyethylene component 10 to 20% of the polypropylene com component and irregular in the polypropylene matrix ßig and especially in the peripheral areas of the fiber cross cut as material oriented in the longitudinal direction collections occurs. 13. Use of the bicomponent fibers according to claim 12 for Nonwovens with high bulk and soft handle for the Hygiene area.