Melt-Blown Webs Without Shots and With Improved Barrier Properties

• US 20190323155A1
• Filed: 06/25/2019
• Published: 10/24/2019
• Est. Priority Date: 12/15/2014
• Status: Active Grant

• Current Assignee: Borealis AG (Government of ABU Dhabi)
• Original Assignee: Borealis AG (Government of ABU Dhabi)
• Inventors: Fiebig, Joachim, Van Paridon, Henk, Wang, Jingbo, Gahleitner, Markus, Sars, Wilhelmus Henricus Adolf, Tynys, Antti
• Granted Patent: US 10,870,937 B2
• Time in Patent Office: Days
• CPC Class Codes: A41D 13/1209 Surgeons' gowns or dresses
• CPC Class Codes: A61B 46/40 Drape material, e.g. laminates; Manufacture thereof
• CPC Class Codes: A61F 13/51 characterised by the outer layers wicking or transfer layers A61F13/537
• CPC Class Codes: C08F 110/06 Propene
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 2810/10 including a reactive processing step which leads, inter alia, to morphological and/or rheological modifications, e.g. visbreaking
• CPC Class Codes: C08F 4/651 Pretreating with non-metals or metal-free compounds
• CPC Class Codes: C08F 4/6546 organo-magnesium compounds
• CPC Class Codes: C08F 8/50 Partial depolymerisation
• CPC Class Codes: C08K 5/098 Metal salts of carboxylic acids
• CPC Class Codes: C08K 5/103 with polyalcohols
• CPC Class Codes: C08K 5/3435 Piperidines
• CPC Class Codes: C08L 23/12 Polypropene
• CPC Class Codes: D01F 1/10 Other agents for modifying properties
• CPC Class Codes: D01F 6/06 from polypropylene
• CPC Class Codes: D04H 1/4291 Olefin series
• CPC Class Codes: D04H 1/544 Olefin series
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: D04H 3/007 Addition polymers
• CPC Class Codes: D04H 3/16 : with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
• CPC Class Codes: D10B 2321/022 : polypropylene

Abstract

Melt-blown webs having no shots and improved barrier properties, whereby the melt-blown webs are made out of a so-called “controlled rheology” propylene (CR-PP), which was visbroken without any peroxide.

Claims

1. A method of preparing a melt-blown web which is free of shots, the method comprising blowing a molten polypropylene composition from an extruder die tip onto a conveyer or take-up screen, wherein the polypropylene composition comprises

(A) a polypropylene polymer and

(B) optionally a polymeric nucleating agent,

wherein the polypropylene composition has

(i) a melt flow rate MFR2 (230°

C./2.16 kg) measured according to ISO 1133 of 20 to 5000 g/10 min and

(ii) a melting temperature Tm between ≥

130°

C. and ≤

170°

C. and

(iii) a molecular weight distribution (MWD)>

2 and

(iv) wherein the polypropylene composition has been visbroken without the use of peroxides.

2. The method of preparing a melt-blown web according to claim 1, wherein the polypropylene polymer is a propylene homopolymer.

3. The method of preparing a melt-blown web according to claim 1, wherein the polypropylene composition has been visbroken by using a hydroxylamine ester, a sulphur compound, or by purely thermal degradation.

4. The method of preparing a melt-blown web according to claim 3, wherein the polypropylene composition has been visbroken by using a hydroxylamine ester.

5. The method of preparing a melt-blown web according to claim 1, wherein the polypropylene composition is free of phthalic compounds as well as their respective decomposition products.

6. The method of preparing a melt-blown web according to claim 1, wherein the melt-blown web is characterized by the following ratios:

(a) a molecular weight (Mw) ratio of Mw of the web to Mw of the polypropylene composition Mw(web)/Mw(PP)<

1 and

(b) a molecular weight distribution (MWD) ratio of MWD of the web to MWD of the polypropylene composition MWD(web)/MWD(PP)<

1.

7. The method of preparing a melt-blown web according to claim 6, wherein the melt-blown web is characterized by the following ratios:

(a) a molecular weight (Mw) ratio of Mw of the web to Mw of the polypropylene composition Mw(web)/Mw(PP) is ≤

0.90, and

(b) a molecular weight distribution (MWD) ratio of MWD of the web to MWD of the polypropylene composition MWD(web)/MWD(PP) is ≤

0.95.

8. The method of preparing a melt-blown web according to claim 7, wherein the melt-blown web is characterized by the following ratios:

(a) a molecular weight (Mw) ratio of Mw of the web to Mw of the polypropylene composition Mw(web)/Mw(PP) is <

0.85, and

(b) a molecular weight distribution (MWD) ratio of MWD of the web to MWD of the polypropylene composition MWD(web)/MWD(PP) is ≤

0.90.

9. The method of preparing a melt-blown web according to claim 7, wherein the melt-blown web is characterized by the following ratios:

(a) a molecular weight (Mw) ratio of Mw of the web to Mw of the polypropylene composition Mw(web)/Mw(PP) is ≤

0.80, and

(b) a molecular weight distribution (MWD) ratio of MWD of the web to MWD of the polypropylene composition MWD(web)/MWD(PP) is ≥

0.85.

10. The method of preparing a melt-blown web according to claim 1, 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), b) optionally a co-catalyst (Co), and c) optionally an external donor (ED).

11. The method of preparing a melt-blown web according to claim 10, wherein the internal donor (ID) is selected from the group consisting of optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates, derivatives thereof and mixtures thereof;

and the molar ratio of co-catalyst (Co) to external donor (ED) [Co/ED] is 5 to 45.

12. The method of preparing a melt-blown web according to claim 10, wherein the Ziegler-Natta catalyst (ZN-C) is produced by a process comprising the steps of

a)

a₁) providing a solution of at least a Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound (MC) and a monohydric alcohol (A) comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium;

or

a₂) a solution of at least a Group 2 metal alkoxy compound (Ax′

) being the reaction product of a Group 2 metal compound (MC) and an alcohol mixture of the monohydric alcohol (A) and a monohydric alcohol (B) of formula ROH, optionally in an organic liquid reaction medium;

or

a₃) providing a solution of a mixture of the Group 2 alkoxy compound (Ax) and a Group 2 metal alkoxy compound (Bx) being the reaction product of a Group 2 metal compound (MC) and the monohydric alcohol (B), optionally in an organic liquid reaction medium;

or

a₄) providing a solution of Group 2 alkoxide of formula M(OR₁)_n(OR₂)_mX_2-n-m or mixture of Group 2 alkoxides M(OR₁)_n·

X_2-n′

and M(OR₂)_m·

X_2-m′

, where M is Group 2 metal, X is halogen, R₁ and R₂ are different alkyl groups of C₂ to C₁₆ carbon atoms, and 0≤

n<

2, 0≤

m<

2 and n+m+(2−

n−

m)=2, provided that both n and m≠

0, 0<

n′

≤

2 and 0<

m′

≤

2; and

b) adding said solution from step a) lo at least one compound (TC) of a transition metal of Group 4 to 6 and

c) obtaining the solid catalyst component particles,

and adding a internal electron donor (ID), at any step prior to step c).