Thermoplastic, Thermally Bondable Polyolefin Fibre for Production of Nonwovens as Well as a Nonwovens Obtained by Thermal Bonding

Abstract

The invention relates to a thermoplastic, thermally bondable polyolefin fibre for production of nonwovens as well as a nonwovens obtained by thermal bonding of such polyolefin fibres. The production of nonwovens for applications in hygienic end uses have thermal bonding and softness characteristics dependent on the fibres. For improvement the fibre of the invention shows a whole plastic deformability under calendaring process in the thermobonding dot and a low surface degradation during spinning. Therefore the thermobonding dots of a nonwovens are characterized by the whole close packing of the fibres. The thermal bonding behavior of the fibre will be reach with a spinning process with spinning head temperature set up suitable in order to obtain the specified thermal degradation.

1 . Thermoplastic, thermally bondable polyolefin fibre, suitable for production of nonwoven, characterized by whole plastic deformability under calendaring process in the thermo-bonding dot and by a low surface degradation during spinning.  
     
     
         2 . Fibre of  claim 1  characterized by the ratio of the fibre melt flow rate (MFR fibre) to the resin melt flow rate (MFR resin) with its value DI (DI=(MFR fibre)/(MFR resin)) in the range between 1.5 and 3.0.  
     
     
         3 . Fibre of  claim 2  characterized by a value DI of the ration (MFR fibre)/(MFR resin) in the range between 2.0 and 2.5.  
     
     
         4 . Fibre of  claim 2  characterized by made of a first component PP homopolymer and, at least a second component, blend compatible with the first and composed of PP co-polymer with at least one α-olefin co-monomer.  
     
     
         5 . Fibre of  claim 4  characterized by a weight proportion of the blend in the range between 0% and 90% of PP homopolymer and between 100% and 10% of PP-α-olefin co-polymer.  
     
     
         6 . Fibre of  claim 4  characterized by a raw material containing primary antioxidant in the range between 150 and 600 ppm.  
     
     
         7 . Spinning process of polyolefin fibres made according to  claim 1  characterized by a spinning head temperature set up suitable in order to obtain a thermal degradation of fibres, so that the ratio of fibre melt flow rate and resin melt flow rate (MFR fibre)/(MFR resin) has a value DI in the range between 1.5 and 3.0.  
     
     
         8 . Spinning process of  claim 7  characterized by a quenching flow temperature or a quenching flow speed or a quenching distance or a combination of quenching variables suitable to obtain a very low skin degradation at the fibre.  
     
     
         9 . Nonwoven obtained by thermal bonding of polyolefin fibres made according to  claim 1  characterized by the whole close packing of the fibres in the thermally bonded dot after calendering under compression due of the whole plastic deformability of the fibres.  
     
     
         10 . Nonwoven of  claim 9  characterized by a thermal degradation of the fibres by spinning in the higher range of the value DI between 2.5 and 3.0, wherein the best softness is obtained by reducing to the minimum allowed calender temperature.  
     
     
         11 . Nonwoven of  claim 9  characterized by a thermal degradation of the fibres by spinning in the lower range of the value DI between 1.5 and 2.0, wherein the best softness is obtained by increasing the calender temperature until the required tenacity.  
     
     
         12 . Nonwoven of  claim 9  characterized by a thermal degradation of the fibres by spinning in the higher range of the value DI between 2.5 and 3.0, wherein the highest tenacity and the best softness are obtained by increasing the calender temperature.