Focus on the textile world: from recycling to networking

From bottle to needled textile

The billions of polyethylene terephthalate (PET) water bottles worldwide represent a vast source of secondary raw materials that can be recycled several times over. Thanks to its high quality, the bottle material can be reintroduced into the production process – and the raw material for the bottles can be reused several times over without any significant loss in terms of quality.

In addition to the ecological benefits, this also has a positive effect on costs: The cost of recycling old PET bottles is significantly lower than for new PET, which has to be obtained from crude oil.

According to market analyses, Germany produces 470,200 tons of PET bottles annually, around 97 percent of which can be recycled. Roughly one third of that amount (about 152,000 tons) goes to the textile industry, a further third is used again for the production of PET bottles, and the final third is distributed across several different fields of application such as plastic film manufacture or the packaging industry.

The PET bottle – reborn as fiber

Polyester is one of the most popular fiber materials. Its special characteristics, such as its high formability, enable numerous applications. Moreover, the thickness of the fibers and the feel of the fabric can be brought into line with the end-product requirements. Polyester also has the highest tear and abrasion resistance as well as dry and wet strength, and is extremely resistant to breakage and bleaching.

The potential of recycled PET bottles for production of (needled) nonwovens is huge: Experts believe that a 2-liter PET bottle (about 40 grams) can be turned into around 1 square meter of nonwoven fabric. A typical application for nonwovens of such weight range are coverstocks for sanitary products and incontinence articles.

So if the approximately 152,000 tons of PET bottles supplied to the textile industry in Germany were used to produce nonwoven fabric of around 40 gsm, that fabric would cover a total area of ​​3,800,000 square kilometers – even larger than the surface area of India (3,287,590 sq km).

The above reasons clearly show that because of its high availability, its properties and its lower price, recycled PET is a very interesting raw material for the production of nonwovens – indeed, it has already become an indispensable part of it.

Polyester fibers from PET bottles

Polyester fibers are produced by a melt spinning process. Here, the virgin pellets are mixed together with the recycled flakes. The material is then fed to an extruder and melted, until a viscous mass is formed that can be spun. The extruder pushes the spun material through a spinning beam with spinnerets. Depending on the gauge that needs to be achieved in the subsequent fiber product, the spinnerets have a suitably predefined nozzle diameter. During this process step it is also possible to give the fiber strands special cross-sections, such as a triangle or star shape.

The filaments are then passed through a cooling shaft. Here, the spinning process is completed and the filaments are cooled.

Now the fiber cable is fed into several pairs of rollers running at different speeds, so that the fibers are stretched. The interaction between the hole size of the spinneret, the stretching in the cooling shaft, and the pairs of rollers ultimately results in the final level of fiber fineness and crystallinity.

After this production step it is also possible to crimp the fiber cable, using a crimping chamber. Following these process steps, the fiber cables are cut to the desired staple length and compressed into bales.

A second life for environmental protection

The recycled PET flakes processed into polyester fibers are now ready to complete an additional lifecycle in a manufacturing process of the nonwoven industry. Through the use of recycled PET bottles, manufactured textiles can make a significant contribution to climate protection and to conservation of resources.

Moreover, the fibers can be integrated into products that are already making a contribution to environmental protection. Examples here include needled air filters for cleaning, or high-density geotextiles for counteracting erosion.

Other fields of application are also conceivable, of course, such as:

Groz-Beckert also offers a felting needle with a projectile point, especially for needling of abrasive fibers and recycled polyester. The advantage of this shape and geometry is that it specifically counteracts bifurcation of the needle point.