Melt-blown webs with improved properties

Patent metadata

Field	Value
Publication number	US-11053371-B2
Application number	US-201615753654-A
Country	US
Kind code	B2
Filing date	Sep 23, 2016
Priority date	Oct 2, 2015
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

Melt-blown webs having a widened process window and better barrier properties (3rd drop, cm H2O resp. mbar). The melt-blown webs are made from so-called “controlled rheology” propylene (CR-PP), which has been visbroken without the use of peroxide but with a specific type of visbreaking additive.

First claim

What is claimed is:

1. Melt-blown webs comprising melt-blown fibers made of at least 80 wt % of a polypropylene composition comprising
(A) a propylene polymer being a propylene homopolymer or a random propylene copolymer having a comonomer content in the range of 3.0 to 8.5 wt % and
(B) optionally a polymeric nucleating agent,
whereby the polypropylene composition has been visbroken with at least one compound
(C) being capable of thermally decomposing into carbon-based free radicals of formula (I) by breaking at least one single bond:

wherein in the formula (I)
R 1 , R 2 and R 3 can be independently selected from hydrogen, substituted and unsubstituted straight chain, branched and cyclic saturated or mono-unsaturated hydrocarbons with 1 to 12 C-atoms, substituted and unsubstituted aromatic hydrocarbons with 5 to 12 C-atoms or carboxylate group COOX, with X being a C 1 -C 6 -alkyl group, whereby at least one of R 1 , R 2 and R 3 is a substituted or unsubstituted aromatic hydrocarbon with 5 to 12 C-atoms,
wherein the obtained melt flow rate MFR 2 (230° C., 2.16 kg) measured according to ISO 1133 of the polypropylene composition is in the range of 150 to 2500 g/10 min,
wherein the amount of compound(s) (C) being added to the polypropylene composition for visbreaking is in the range of 0.01 to 10 wt % based on the polypropylene composition,
wherein the polypropylene polymer has been polymerized in the presence of a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a non-phthalic compound; b) optionally a co-catalyst (Co), and c) optionally an external donor (ED).

2. Melt-blown webs according to claim 1 wherein the carbon-based free radicals of formula (I) are generated from one or more compounds (C) of the formula (II)

wherein each of R 1 , R 3 , R 4 and R 6 independently is selected from the group consisting of hydrogen, substituted and unsubstituted straight, branched and cyclic hydrocarbons with 1 to 12 C-atoms and substituted and unsubstituted aromatic hydrocarbons with 5 to 12 C-atoms, and each of R 2 and R 5 independently is selected from the group consisting of substituted and unsubstituted straight, branched and cyclic hydrocarbons with 1 to 12 C-atoms and substituted and unsubstituted aromatic hydrocarbons with 5 to 12 C-atoms and wherein at least one of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 is a substituted or unsubstituted aromatic hydrocarbon with 5 to 12 C-atoms.

3. Melt-blown webs according to claim 2 wherein in the formula (II) of compound (C) R 2 and R 5 independently are selected from the group consisting of substituted and unsubstituted aryl groups with 6 to 10 C-atoms and each of R 1 , R 3 , R 4 and R 6 independently is selected from the group consisting of hydrogen and C 1 -C 6 alkyl groups.

4. Melt-blown webs according to claim 1 wherein the at least one compound (C) has formula (III)

wherein each of R 7 , R 8 , R 9 and R 10 independently is selected from a group consisting of hydrogen atom, C 1-6 alkyl groups, C 1-2 alkoxy groups, a nitrile group and a halogen atom, and wherein each of R 1 , R 3 , R 4 and R 6 independently is selected from group consisting of hydrogen and C 1-6 alkyl groups.

5. Melt-blown webs according to claim 4 , wherein the at least one compound (C) is selected from the group consisting of 2,3-dimethyl-2,3-diphenylbutane, 2,3-dipropyl-2,3-diphenylbutane, 2,3-dibutyl-2,3-diphenylbutane, 2,3-dihexyl-2,3-diphenylbutane, 2-methyl-3-ethyl-2,3-diphenylbutane, 2-methyl-2,3-diphenylbutane, 2,3-diphenylbutane, 2,3-dimethyl-2,3-di-(pmethoxyphenyl)-butane, 2,3-dimethyl-2,3-di-(pmethylphenyl)-butane, 2,3-dimethyl-2-methylphenyl-3-(p 2′3′-dimethyl-3′-methylphenyl-butyl)-phenyl-butane, 3,4-dimethyl-3,4-diphenylhexane, 3,4-diethyl-3,4-diphenylhexane, 3,4-dipropyl-3,4-diphenylhexane, 4,5-dipropyl-4,5-diphenyloctane, 2,3-diisobutyl-2,3-diphenylbutane, 3,4-diisobutyl-3,4-5 diphenylhexane, 2,3-dimethyl-2,3-di p(t-butyl)-phenyl-butane, 5,6-dimethyl-5,6diphenyldecane, 6,7-dimethyl-6,7-diphenyldodecane, 7,8-dimethyl-7,8-di(methoxyphenyl)-tetra-decane, 2,3-diethyl-2,3-diphenylbutane, 2,3-dimethyl-2,3-di(p-chlorophenyl)butane, 2,3-dimethyl-2,3-di(p-iodophenyl)butane, and 2,3-dimethyl-2,3-di(p-nitrophenyl) butane.

6. Melt-blown webs according to claim 5 , wherein the at least one compound (C) is selected from the group consisting of 2,3-dimethyl-2,3-diphenylbutane and 3,4-dimethyl-3,4-diphenylhexane.

7. Melt-blown webs according to claim 6 , wherein the at least one compound (C) is 2,3-dimethyl-2,3-diphenylbutane.

8. Melt-blown webs according to claim 1 , wherein the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and one or more of derivatives or mixtures thereof; and the molar ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

9. Melt-blown webs according to claim 1 , whereby the polypropylene composition is free of phthalic compounds as well as their respective decomposition products.

10. Melt-blown webs according to claim 1 , wherein webs being free of shots can be produced within a process temperature window of from 250° C. to 320° C.

11. An article comprising melt-blown webs according to claim 1 , wherein said article is selected from the group consisting of filtration media, diapers, sanitary napkins, panty liners, incontinence products for adults, protective clothing, breathing protection masks, surgical drapes, surgical gowns, and surgical wear.

12. Melt-blown webs according to claim 1 , wherein said internal donor (ID) is a non-phthalic acid ester.

13. Melt-blown webs according to claim 8 , wherein the internal donor (ID) is a citraconate.

Assignees

• Borealis Ag

Inventors

• Wang Jingbo
• Fiebig Joachim
• Van Paridon Henk
• Gahleitner Markus
• Grestenberger Georg
• Vanhoutte Jeroen

Classifications

• C08L23/10

  Homopolymers or copolymers of propene · CPC title

• D04H1/4291 Primary

  Olefin series · CPC title

• D04H1/544

  Olefin series · CPC title

• D04H1/56

  in association with fibre formation, e.g. immediately following extrusion of staple fibres · CPC title

• C08K5/0083

  Nucleating agents promoting the crystallisation of the polymer matrix · CPC title