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Co-extruded multilayer structure and method for obtaining thereof

a multi-layer structure and polymer technology, applied in the field of extrusion, can solve the problems of melt breakage, speed and speed limitations of profile extrusion or filament spinning, and the extrusion process is subject to serious limitations in film thickness or filament diameter, and achieves improved critical draw-down ratio and higher elongation or extension

Pending Publication Date: 2021-12-02
KLONER
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a method that involves co-extruding layers of different polymers to create a multilayer structure. The method results in a higher draw-down ratio, which means the structure has a smaller size. This reduces the amount of material that needs to be discarded. In summary, the method saves money and materials, while also minimizing waste.

Problems solved by technology

Polymer extrusion processes like film cast extrusion, extrusion-coating, blown film, profile extrusion or filament spinning are subjected to serious limitations either in speed and in down-gauging film thickness or filament diameter because of process instabilities related to extrusion speed and draw-down.
Extrusion speed limitations are related to shear flow instabilities.
Critical shear stress leads to well-known drawbacks melt shark skin or stick-lip, and finally melt breakage.
In shear flow condition, limitation in extrusion speed is caused by shear stress at the die gap; besides, the polymer rheology itself, the presence of lubricants and the process conditions, the shear stress depends strongly on die gap section area and melt speed at the die exit or the spinneret capillary.
Draw-down limitations are related to extensional flow instabilities.
These instabilities are well-known drawbacks melt draw resonance and gross melt fracture.
Due to experimental and physical limitations, it is difficult to achieve steady state conditions in extensional viscosity measurements; instead we usually have a plot of transient data showing the evolution of extensional viscosity over time for different strain rates.
Further draw down above the critical causes melt breakage.
The draw-down instability is also affecting productivity in extrusion-coating processes where the substrate is covering the required mechanical performance of the product, in this case, high speed and low coating weight is needed.

Method used

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  • Co-extruded multilayer structure and method for obtaining thereof
  • Co-extruded multilayer structure and method for obtaining thereof

Examples

Experimental program
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Effect test

example 3

[0162]Product: Breathable back-sheet for diapers.[0163]Same equipment example 1.[0164]Substrate: Polypropylene homo-polymer spun-bond non-woven 15 g / m2.[0165]Layer structure: A-B-substrate.[0166]A-layer composition: Extensional thinning polymer, Polyether-Ester block co-polymer Dupont Hytrel DYM350 NC010 MFI 15.[0167]B-layer-Tie layer composition: Extensional thickening polymer Low density Polyethylene-Ethylene acrylate co-polymer resin Dupont Bynel 22E804[0168]Process settings at stable running.[0169]Extrusion temperature both layers: 270° C.[0170]Die gap (hot) 0.4 mm.[0171]Vacuum box (cooling on cast roll).[0172]Total Coating thickness 3 μm.[0173]A-layer thickness: 2 μm[0174]B-layer thickness: 1 μm[0175]Line speed: 550 m / min.[0176]Draw down: 133.[0177]Breathability (Mocon test ASTM1249): 5,200 g / m2 day

example 4

[0178]Product: Breathable back-sheet for diapers.[0179]Same equipment example 1.[0180]Substrate: Polypropylene homo-polymer spun-bond non-woven 15 g / m2.[0181]Layer structure: A-B-substrate.[0182]A-layer composition: Extensional thinning polymer, Polyamide 6 Zytel ST7301 NC010.[0183]B-layer-Tie layer composition: Extensional thickening polymer Low density Polyethylene-Anhydride modified Ethylene acrylate co-polymer resin Dupont Bynel 21 E830.[0184]Process settings at stable running.[0185]Extrusion temperature both layers: 265° C.[0186]Die gap (hot) 0.4 mm.[0187]Vacuum box (cooling on cast roll).[0188]Total Coating thickness 2.5 μm.[0189]A-layer thickness: 1.5 μm[0190]B-layer thickness: 1 μm[0191]Line speed: 550 m / min.[0192]Draw down: 160.[0193]Breathability (Mocon test ASTM1249): 4,200 g / m2 day

example 5

[0194]Product: PP Coated raffia for bags.[0195]Same equipment as example 1.[0196]Substrate: woven PP raffia 220 g / m2.[0197]Structure: A-B-Substrate[0198]A-Layer composition: Extensional thinning polymer, polypropylene Homo-polymer Repsol Isplen PP086Y3E MFI 25.[0199]B-Layer composition: 89.5% by weight Extensional thickening polymer Repsol Isplen PP086Y3E MFI 25; crosslinked with 0.5% by weight of Cray valley Dymalink 9200 and 10% by weight Eastman tackifier Regalite R1125.[0200]Process settings at stable running:[0201]Extrusion temperature both layers: 260° C.[0202]Die gap (hot) 0.4 mm.[0203]Air Gap 400 mm.[0204]Total Coating thickness 3 μm.[0205]A-layer thickness: 2 μm[0206]B-layer thickness: 1 μm[0207]Line speed: 550 m / min.[0208]Draw down: 133.

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Abstract

The present invention is directed to a novel co-extruded multilayer structure that possess a draw down ratio superior than the critical draw-down ratio of each one of the polymeric layers, extruded individually. The present invention is also directed to a method for obtaining the co-extruded multilayer structure.The co-extruded multilayer structure obtainable by the method described herein allows preparing films, filaments or spun-melt non-wovens of low weight at high speed using conventional extrusion equipments. The co-extruded multilayer structure is especially suitable as diaper back-sheets or flexible packaging coatings.

Description

FIELD OF THE INVENTION[0001]The present invention is in the extrusion field, particularly, in the extrusion of polymer melts.[0002]The present invention relates to a novel co-extruded multilayer structure as well as to a method for obtaining the co-extruded multilayer structure.[0003]The present invention further relates to the co-extruded multilayer structure for use as a coating. The coating can be a diaper back sheet or a flexible packaging coating.BACKGROUND OF THE INVENTION[0004]Polymer extrusion processes like film cast extrusion, extrusion-coating, blown film, profile extrusion or filament spinning are subjected to serious limitations either in speed and in down-gauging film thickness or filament diameter because of process instabilities related to extrusion speed and draw-down.[0005]Extrusion speed limitations are related to shear flow instabilities. Critical shear stress leads to well-known drawbacks melt shark skin or stick-lip, and finally melt breakage. In shear flow con...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B32B27/08B29C48/00B29C48/08B29C48/21B29C48/22B32B7/12B32B37/15
CPCB32B27/08B29C48/0018B29C48/08B29C48/21B29C48/022B29C48/22B32B2307/7246B32B37/153B32B2555/02B32B2250/02B32B2250/24B32B2307/732B32B7/12B32B7/10B32B27/12B32B5/022B32B27/32B32B27/36B32B27/285B32B27/34B32B21/02B32B21/08B32B33/00A61F13/496A61F13/51401D01D5/08B32B2262/0253B32B2262/067B32B2255/02B32B2255/26B32B2264/02B32B2264/10B32B2270/00B32B2307/514B32B2439/06B32B2439/46B32B7/04B32B2555/00B32B2250/03B32B27/30B29C48/15B29C48/10B29C48/12B29C48/05
Inventor CAMPOS BECEIRO, ALBERTO
Owner KLONER