Groz-Beckert KG

Newsletter 2 | 2011

Tri STAR® and Cross STAR® –
Gain ground with Groz-Beckert!

Geotextiles help to save natural resources and landfill capacities. They reduce soil replacement, transport costs and construction expense. They can also be equipped with additional components: special textiles exist with needled-in seeds, for instance. In geotextile production, apart from selection of the most suitable method and the best fibres, powerful precision tools are absolutely indispensable. Here, Groz-Beckert provides specially developed Tri STAR® and Cross STAR® needles.

Geotextile production methods

Description

Basic material

Reinforcement tool

Effect of reinforcement

Product structure

Needlefelt

Transversely oriented web

Barbed hook needle

Barbs catch and entangle the backing material to form a vertical fibre bundle

Compacted fibre nonwoven with vertical fibre plug; fabric weight 100 - 2,000 gsm

Nonwoven stitch-bonded fabric Maliwatt

Transversely oriented web

Slider needle closure wire system

Fibres are clamped together with binder yarn via oversewing

Flat nonwoven, the binder yarn system creates a fabric connection on the top and the underside; fabric weight 100 - 1500 gsm

Nonwoven stitch-bonded fabric Malivlies

Transversely oriented web

Slider needle closure wire system

Tool is used to catch several fibres and form them into fibre bundles

Flat nonwoven, one side shows loops, the other has a flat and fluffy fibre arrangement; fabric weight 100 - 2,000 gsm

Agitated nonwoven

Chaotically oriented web

High pressure water jet

Water jet moves the fibres during collision and discharge; leads to entanglement

Compacted fibre nonwoven with numerous fibre entanglements - fabric weight 30 - 500 gsm

Source: STFI; http://www.nova-institut.de/pdf/schmalz-moe-folien.pdf

The choice of fibre is decisive

Geotextiles filter, reinforce, separate, protect, drain and compensate stress. Because of these diverse characteristics, special requirements are placed on the choice of fibre and the physical properties of the textile.

Natural fibres are mainly used whenever a product has to rot completely, leaving no residue. Water absorption and water discharge capabilities are also important. Hemp and jute fibres are frequently found in geotextiles that can rot.

In addition to natural fibres, a large number of synthetic raw materials are also used, especially if the product needs to be resistant to environmental influences. This is why the fibre used must also be insensitive to water, soils, other construction materials or micro-organisms.

Physical properties

Depending on the function of the geotextile, differing requirements are placed on the physical properties of the nonwoven. This demands intensive and even needling, together with stability and gentleness on the fibres. The requirements placed on felting needles in the production of geotextiles are therefore enormous. For this reason, Groz-Beckert has needles in its product range that have been developed specifically for this sector: the Tri STAR® and the Cross STAR® needles.

Groz-Beckert Tri STAR®

zoom

Tri STAR® needles from Groz-Beckert, the result of a further design development of the standard working component and the barb shape, are distinctive for their even needling effect and their long service life. The needles, which are gentle on the fibres, increase product quality - and the sharply reduced machine downtimes guarantee reliable and economically efficient production processes. The needles are thus ideally suited to the production of typical geo-products. Examples include geo-nonwovens for highway construction, separation and filter felts, coating substrates, safety nonwovens and geo-membranes.

Concave-shaped working-component surfaces with narrower edge angles enable precisely defined fibre looping and better fibre support in the barb. Fibre transport thus increases, leading to more intensive needling and a compact integration of the fibres in the felt. The combination of Groz-Beckert RF barbs with rounded edges and the Tri STAR® working-component cross-section ensures that needling remains gentle on the fibres and simultaneously efficient.

The benefits of a Groz-Beckert Tri STAR® needle over a standard needle are many and varied:

  • more compact felt
  • reduced material thickness with the same weights
  • economically efficient benefits due to longer-running rollers
  • higher line speeds
  • higher productivity
  • reduced downtimes
  • efficient needling even at low needle densities

 

Groz-Beckert Cross STAR®

zoom

Cross STAR® needles are especially suitable with powerfully compacted geo-felts, also in high fabric-weight sectors. They enable constant material properties and highest tensile strengths to be achieved in the transversal and longitudinal direction.  

Cross STAR® needles enable efficient and economical needling. They are successfully used in the production of numerous different applications in the geo-nonwovens sector, e.g. in landscaping, as drainage felts, or as heavyweight compaction mats. The use of the Cross STAR® needles enables the optimal puncture resistance of the product to be achieved.

The Cross STAR® needle has a working component that, in cross-section, resembles a star with four identical edges. The special geometry of the working component with its narrower edge widths enables more effective fibre transport. The use of Cross STAR® needles is thus especially effective during needling of geotextiles with high fabric weights. Apart from this, four edges are also advantageous where more even needling is concerned, especially with regard to isotropy.

Landfills – inconceivable without geotextiles

zoom

In contrast to other application sectors for geotextiles, in which they are needed and integrated as a basic supporting element, modern landfill construction is quite unthinkable without them. Here, geotextiles function as indispensable construction materials, guaranteeing effective watertightness in the lower as well as the upper section of the landfill. Here they fulfil a host of tasks, ranging from separation, filtration and drainage to reinforcement, protection and compaction. This basically involves a so-called "sandwich composite" whereby clay is spread onto a separately pre-needled single layer. After the layer has been spread, a further felt is added as a covering layer and finally needled together with the lower layer.

The separation web – how it is made

zoom
The image shows a production line for needled geotextiles
zoom

For the production of separation webs the main fibres used are PP, PES, PA with staple lengths of 60-90 mm, recycled fibres and spun-bonded fibres (PP). The fibre gauges lie in the region of 1.7-44 dtex, and in special cases up to 200 dtex. The weight area varies depending on the planned application from 80 to 2,000 gsm, and even higher in the sandwich composite. The needling takes place on both sides, whereby the felt is often stretched in the machine direction between the pre-needling and finish needling, in order to achieve optimal lateral and transverse strength conditions (almost 1:1) in the end-product. For the finish needling, the two specially developed Groz-Beckert needle types Tri STAR® and Cross STAR® are available.

Downstream tenter frames or calenders are used to fix the geotextile, to smooth it or to stretch it to the desired width. Generally, parameters between 50 and 250 E/cm2 and a penetration depth of 8-12 mm are selected.

The geotextiles market – more information in this Online Newsletter

Efficient production, nonwovens stability and gentle on fibres - with the Tri STAR® and Cross STAR® needles from Groz-Beckert, no compromises are needed. General information on this topic can also be found in the article "Geotextiles - a diverse market with attractive opportunities".

For more information on everything to do with felting and structuring needles and jetstrips, visit the Groz-Beckert Website.