H1 TECHNOLOGY - A SUCCESSFUL NEW APPROACH TO NEEDLING

by Dipl.-Ing. Alois Öllinger, Fehrer AG, Linz, Austria

The principle of H1 technology, a Dr. Ernst Fehrer patented invention, is the idea that superior web properties can be obtained by oblique angled needle penetration. Such penetration is achieved by means of an asymmetrically curved needling zone and straight needle movement.

The twenty Dr. Ernst Fehrer needle punching machines which were already delivered with this new feature are mainly used in the following fields of application: synthetic leather, geotextiles, filtration, automotive textiles, nonwoven carpets and shoe linings.


This Dr. Fehrer invention offers the following advantages:

A longer needle path through the web creates better fibre reorientation, randomisation and entanglement than conventional flat needling.

Isotropic web properties can be obtained much easier as a result of fibre orientation in the H1 needling zone.

Identical properties as with conventional needling can be achieved with fewer penetrations, or, using the same number, higher strength and density values can be reached.

In the case of composite products, H1 ensures better entangling of the individual layers.

An H1 production line involves - due to its superior needling which means that fewer machines are needed - reduced investment and service costs and less space.

Increased web stability during needling leads to reduced width shrinkage, because the asymmetric curve of the perforated plates avoids web flutter.

The lower penetration density can be transformed into increased productivity through higher advance per stroke of the material.


The geometry of the needling zone: an asymmetric curve

Several patents regarding modified needling techniques with oblique needling penetration were already claimed in the sixties, but although some encouraging results were obtained the inventors were not able to transform their ideas into industrial operation. Most of the difficulties arose from the fact that it was impossible to use the shown ideas in the field of preneedling - the field in which it was expected to have the most significant effect on felt properties.

A careful analysis of the geometry of the conventional needling system shows why its efficiency is limited.

As is very well known, the principle of needling is to move a loose web or a preneedled felt through a pair of perforated plates of metal. The needles stitch through these perforations into the web and during this operation the barbs of the needles transport some fibres through the web. This results in a certain entanglement between fibres which gives the macroscopic effect of increased strength and delamination resistance of the felt.

The conventional needling technology uses flat plates serving as guides of the web through the machine. This results in every needle making the shortest possible path through the felt which in turn also reduces fibre transportation through the felt to the lowest possible value. The other natural limit of the efficiency of this technology is the parallelism of all needling channels. Especially the needles near the outlet area of the machine do already stitch through pre-consolidated areas of the felt.

The H1 system surpasses those limitations of efficiency of the conventional needling technology and avoids at the same time the disadvantages of the earlier ideas. The asymmetric curve of the needling area with a slight incline at the inlet makes the system usable for preneedling; the subsequent decline of the curve provides a criss - cross of the penetration channels as every single needle passes through the felt at a different angle. As the curve becomes steeper near the outlet - which leads to a much longer path of the needles through the felt - the amount of fibre transportation is very much increased in this critical area.


Effect on web properties

The longer paths of the needles through the web and the criss-cross of the needle channels have a clear effect on fibre entanglement and - as a result - on tensile strength of the felt. The increase of strength during preneedling is much steeper when using the H1 system and also the maximum strength which can be reached is much higher when using this system. Identical strength values as with the conventional system can be obtained with a much lower penetration density.

Since the increase of the length of the needling channels has a clear orientation in MD, the result is a considerably higher re-orientation of fibres and therefore a steeper increase of the strength values in MD. Isotropic felt properties - that means equal properties of a felt in MD and CD - for crosslapped webs can be reached much earlier and much easier by use of H1 needling.

Another clear consequence of the criss-cross of the needling channels is an increase in delamination resistance of multi-layer products.

Since web fluttering is avoided by the curved needling zone, considerable reductions of width shrinkage can be measured.


Test results

Among many test results which show the advantages of the new needling system, three examples - each of them for an important field of application - shall demonstrate the differences of web properties when using either the conventional system or H1 needling.

Comparisons between the mechanical parameters of two automotive carpets show that strength in MD as well as in CD is more or less the same in both samples, also density values do not differ very much. The difference is that the samples deriving from the H1 machines were needled with only 200 p/cm² whereas 400 p/cm² were needed to reach the same entanglement effect by usage of the conventional needling technology.

One of the most important industrial applications of H1 needling is geotextiles. Needling density during production with H1 was 260 p/cm² whereas the sample which was made with the conventional system needed 330 p/cm². The H1 process resulted in a higher MD strength and a more isotropic behaviour of the material, higher values for the puncture resistance and a considerable better drainage effect. The importance of this result for the production of geotextiles is based on the fact that they have to guarantee in many cases a specified minimum for the tensile strength. On the other hand, crosslapped webs always have - due to the specific web structure - a smaller tensile strength in MD as in CD. That means that any increase of MD strength helps the producers to fulfil the guarantees or helps to cut costs by saving of fibres.

In the meantime H1 is already more or less the standard for at least the preneedling process of synthetic leather within this field of industry. The reason for this is the fact that a more isotropic behaviour of the felt can be obtained with a lower punching density and also the delamination resistance of the web and web density can be increased by using H1 needling. An example is given in fig. 7, where two 250 g/m² webs consisting of 70 % PES 1,7 dtex / 38 mm and 30 % PA 2,8 dtex / 40 mm were needled with H1 with 900 p/cm² and with a needling density of 1500 p/cm² when using the conventional process. H1 needling resulted in higher strength values and a considerably higher density of the material.

This may be the reason why one of the leading Asian producers of synthetic leather opted for H1 when they invested in a new production line recently. This 4,0 m wide line consists of an H1 preneedler, a single board H1 upstroke machine and two H1 "Tandem" - machines (i.e. downstroke and upstroke zone in one machine frame).The plates of the last machine in the line - which is only used for surface treatment with very low penetration depths - remain flat by usage of the F9 needle boards, which still adds unsurpassed surface properties to the product.


Summary

The principle of H1 technology, the idea that superior web properties can be obtained by oblique angled needle penetration achieved by means of an asymmetrically curved needling zone and straight needle movement, is explained in detail together with some of the advantages that derive from this new technology, e.g. more isotropic web properties, better fibre entanglement and higher strength values.

Three different test results, for automotive carpets, geotextiles and synthetic leather have been discussed, the latter together with a configuration of an entire production line.

Twenty machines which are already in operation throughout this field of industry are a clear evidence of the acceptance which the H1 technology has already met.