Patent Grant
7666805
1. Field of the Invention
The present invention relates generally to a process and the product produced therefrom for constructing spunbond fabrics or laminates using a raw material of ultra low viscosity resins. An apparatus and process for producing such a fabric is to use the spunbond process described in Applicant's U.S. Pat. No. 5,688,468 entitled Process for Producing Non-Woven Webs, issued Nov. 18, 1997, and U.S. Pat. No. 6,183,684, which are hereby incorporated by reference. The process is required to provide filaments from the ultra low viscosity resins with high spinning speed above 4,000 meters per minute.
2. Description of Related Art
The term R.V. shall mean relative viscosity and is a ratio. The term PA6 refers to nylon 6. The unit for melt flow rate is given in grams/10 minutes at 230 degrees Centigrade. The inherent viscosity of the polyester for the present invention is determined in a 0.5 wt. % (percentage) solution in a 60/40 phenol/tetrachloroethane solvent mixture. The determined inherent viscosity is then converted to intrinsic viscosity (I.V.) using an established formula.
It has been known in the prior art that different processes for making fabrics and laminates require different polymeric resins to be used as feedstock or raw materials with certain aspects such as viscosity or molecular weight. The fact that polypropylene (PP) resins with a melt flow rate (MFR) ranging from 25 to 40 are most widely used in the spunbond industry and no PP resins with an MFR over 100 have ever been attempted in the spunbond process is well known. However, high MFR resins up to 1500 have been commercially available for the melt blowing process and hence have been referred to as meltblown grade resins.
It is believed in the prior art that the fabrics produced by the spunbond process possess properties distinctively different from that produced from the melt blown technology in terms of the range of filament size (denier), fabric strength, softness and barrier properties. Therefore, the fabrics produced by spunbond process are used in different products for different applications from the products produced by the melt blown technology.
At some point the “SMS” (Spunbond/Meltblown/Spunbond) technology was then created to produce “SMS” composite laminated fabrics where the “S” layer serves the role of support with tenacity and the “M” layer serves the role of improving the appearance and the barrier properties of the composite with its ultra fine filaments. It is well known that there are drawbacks of the “SMS” composites, such that while the barrier property is improved, the composite fabric looses its softness and breathability because of the “M” layer acting like a layer of glue. The “SMS” composite is very susceptible of being damaged when stretched during converting due to the brittleness of “M” layer resulting in the barrier property being destroyed.
Applicant has determined that ultra low viscosity resins with a melt flow rate over 100 can be used successfully for improved spunbond fabrics and laminates with a process able to spin filaments at high speed of above 4,000 meters per minute.
This invention relates to a new non-woven fabric or laminate produced in a spunbond process such as that disclosed in Applicant's U.S. Pat. No. 5,688,468 and U.S. Pat. No. 6,183,684, incorporated herein by reference, that employs as raw material ultra low viscosity polymeric resins for polypropylene (PP) with an MFR over 100 and polyethylene terephthalare (PET) resins with I.V. (intrinsic viscosity) less than 0.55 or other fiber forming polymers with viscosity lower than that of fiber grade resins that are generally low molecular weight and low crystallinity materials. Thus, the resulting resins with ultra low viscosity can be processed at lower temperature and the filaments can be spun at higher velocity than that of the resins with a high viscosity (low MFR), resulting in filaments of finer diameters produced (as low as 0.2 dpf or lower). Even though the filament tenacity is normally lower with lower viscosity resins, the strength of fabric produced can be compensated by the bonding strength due to the fact that bonding only occurs in the amorphous phase of the filaments which is in favor of the lower viscosity resins.
The fabric or laminates produced in the spunbond process in accordance with this invention using ultra low viscosity resins can be a single layer of “S” or multiple layers of “SS” or “SMS” and so on and so forth, with each layer having different characteristics in terms of filament size and basis weight.
It is an object of this invention to provide a new non-woven fabric or laminate produced in a spunbond process that uses ultra low polymeric resins as the raw materials utilizing a spunbond process as described in U.S. Pat. No. 5,688,468 and U.S. Pat. No. 6,184,183 using high filament speeds above 4,000 M/min.
It is another object of the invention to provide improved spunbond fabrics and laminates produced with ultra low viscosity resins such as PP with MFR over 100, PET resins with an I.V. (intrinsic viscosity) of less than 0.55, and polyamide (PA6) of R.V. below 2.2 and polyethylene (PE) with MFR over 50 in the form of either mono or multi-component filaments in a spunbond process using high filament speeds above 4,000 M/min.
In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.
A spunbond fabric or laminate that utilizes ultra low polymeric resins as a raw material can be manufactured and produced with an apparatus and process such as described in U.S. Pat. No. 5,688,468 and U.S. Pat. No. 6,183,684 that provides high filament speeds. The ultra low viscosity polymer resins could be PP resins with a MFR over 100 in one example.
In another embodiment the raw material can be PET resins with an intrinsic viscosity of less than 0.55. In yet another embodiment other fiber forming polymers with viscosities lower than that of regular fiber grade resins could be used.
A fabric or laminate produced in a process using the ultra viscosity resins could be a single layer of “S” or multiple layers of “SS”, or “SMS” and so on, and the layers can have different characteristics in term of filaments size and basis weight.
The filaments used can be mono-component (one material) or multiple components that are made up of two or more different resins or the same resin with different viscosities weights.
The following is a comparison of the new spunbond ultra low viscosity resin fabrics and laminates with prior art spunbond fabrics or SMS.
A garment such as a surgical gown could be made of this fabric or laminate and have excellent water/liquid barrier properties required for protection against blood penetration, while having good air permeability. The filaments of 0.6 denier and below have been produced and filament speeds well above 6,000 M/min reached. The resin melt flow rate of well over 100 for polypropylene can be used.
The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5476911 | Morini et al. | Dec 1995 | A |
| 5688468 | Lu | Nov 1997 | A |
| 6268302 | Ofosu et al. | Jul 2001 | B1 |
| 6548431 | Bansal et al. | Apr 2003 | B1 |
| Number | Date | Country |
|---|---|---|
| 03146756 | Jun 1991 | JP |
| WO 9629460 | Sep 1996 | WO |
