Flash-spinning

Commercial spun bonded or flash spun products have been made primarily from PE plexifilamentary film-fibril strands and have typically been produced using trichlorofluoromethane as a spin agent. 

However, trichlorofluoromethane is an atmospheric ozone depletion chemical, and therefore, alternatives have been under investigation. There have been many other agents used for flash spinning PE to either minimize or eliminate the potential for ozone depletion. 

Plexifilamentary film-fibril strands of fiber-forming TPX having a tenacity of 1 p den-1 have been produced. Also blends of TPX with PE and PP can be fabricated (12). 

It is known that TPX has a higher melting point than either PE or PP (235°C - versus 140°C and 165°C, respectively) and as such can provide a flash spun product usable at higher temperatures. Rather the copolymers with around 85% 4-methyl-l-pentene are in use than the pure homopolymer. In addition, it can be blended with either PE or PP or both. 

The flash spun TPX exhibits a very good fibrillation, but it does not have the strength of PE. However, the plexifilamentary fibers made from TPX have a strength of greater than 0.5 pden-1, which is sufficient for many purposes. At the most, a strength greater than 1 p den-1 can be achieved. 

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Flash spinning Flat-bed screen printing Flat film Flat glass... 

By special processes, like polymerization under shear conditions or flash-spinning of polymer solutions, it is furthermore possible to obtain materials which do not only have this new shish-kebab micro-morphology, but also a new macro-morphology, namely the polymer fibrids.35... 

Microcellular foams can be obtained by flash spinning and are usually prepared at relatively high polymer concentrations in the spinning solution, i.e., at least 40% synthetic fiber-forming polyolefin. 

R. Akki and H. Shin, Flash spinning polymethylpentene process and product, US Patent 6352773, assigned to E. I. du Pont de Nemours and Company (Wilmington, DE), March 5,2002. 

Nonwoven flash-spuns Flash-spinning is a radical departure from the conventional melt spinning methods to produce nonwoven fabrics. In flash-spinning a 10-15 wt% solution of, for example HDPE in trichlorofluoromethane or methylene chloride. It is heated to 200C (392F) and pressurized to at least 4500 kPa (650 psi). This pressurized vessel is connected to a spinneret containing a single... 

The diameter of natural and synthetic fibres usually ranges from 7 to 20 xm. Microfibres and bicomponent split fibres allow a range of 3-7 pm and finer. Tightly woven textiles made of fine microfibres are watertight, but are permeable to water vapour. Melt-blow and flash spinning fibres have a 1 pm diameter. With electro-spinning, a diameter of 100 nanometres or lower can be produced. These fine fibres are very suitable for the filtering of small particles. 

A distinction is made between synthetic papers and plastic papers with papers from synthetic materials. Synthetic papers are fiber mats or fleeces, whereas plastic papers are films. Poly(ethylene), poly(propylene), polyamides, or polyesters are used to make synthetic papers. These are converted to filaments by, for example, flash spinning. The filaments are then cut into short fibers. Fiber-like products from poly(ethylene) or poly(propylene) which can be processed like cellulose pulp on conventional paper making machinery are also known as synthetic pulp synthetic pulp is consequently not a cellulose product. Synthetic papers are often coated to improve printability. 

Anderson, R.D. and J.E. Ramano, Process and apparatus for flash spinning of fibrillatedflexifilamenlary material. 1966. 

Fibrids Short, irregular fibrous products, made by mixing a dilute polymer solution with a non-solvent with agitation. They can also be made by flash spinning and breaking up the resulting filaments. Used in felts, in papermaking, for filtration product, etc. Also see fibrets. 

Spun bonded media production processes exploit the thermosetting properties of polymers, to form fibres that can be bonded by combinations of heat, pressure and chemical activation. Melt spinning, using conventional synthetic fibre technology, was the earliest method used for producing spun bonded filter media and continues to be of major importance, but finer fibres are produced by melt blowing and flash spinning processes. 

An overview of flash-spinning technologies is presented by Wehman. Flashspun nonwovens made from fibers with very low linear density, which can be obtained using splittable fibers as a raw material for production of conventional webs [4]. 

Flash spinning High production rate Economic process Short fibre lengths (3—10 pm) Solvent recovery Proprietary technology Limited range of polymers High fibre diameter distribution... 

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