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CN-116685639-B - Polypropylene composition for electret melt-blown webs containing novel charge stabilizers

CN116685639BCN 116685639 BCN116685639 BCN 116685639BCN-116685639-B

Abstract

A Polypropylene Composition (PC) comprising a.95.0 to 99.99 wt.% of a polypropylene (PP), preferably a propylene Homopolymer (HPP), and b.0.01 to 5.0 wt.% of a compound according to formula (I), wherein each R is independently selected from C 1 to C 6 alkylene, C 2 to C 6 alkenylene and a single bond, each R 'is independently selected from H and C 1 to C 6 alkyl, each R' is independently selected from H and C 1 to C 22 alkyl, wherein each alkylene, alkenylene and alkyl group may be optionally substituted with deuterium or fluorine, and the two substituents on the central benzene ring may be positioned in ortho, meta or para relationship, wherein MFR 2 of the Polypropylene Composition (PC) is 400 to 5000g/10min and the melting temperature Tm is 140 to 170 ℃.

Inventors

  • WANG JINGBO
  • Marcus Galettner
  • Klaus Bain Wright-tner
  • Joachim Fibbig
  • Henk Van Paridan
  • Wilhelms Sass
  • Gustav Dobson
  • Paulie Lesginan

Assignees

  • 博里利斯股份公司

Dates

Publication Date
20260505
Application Date
20220121
Priority Date
20210121

Claims (20)

  1. 1. A Polypropylene Composition (PC) comprising: i) 95.0 to 99.99 wt% polypropylene (PP) based on the total weight of the polypropylene composition, and Ii) 0.01 to 5.0 wt.%, based on the total weight of the polypropylene composition, of a compound according to formula (I), (I) Wherein each R is independently selected from C 1 to C 6 alkylene, C 2 to C 6 alkenylene, and a single bond, each R' is independently selected from H and C 1 to C 6 alkyl, each R "is independently selected from H and C 1 to C 22 alkyl, wherein each alkylene, alkenylene, and alkyl is optionally substituted with deuterium or fluorine, and the two substituents on the central benzene ring are positioned in an ortho, meta, or para relationship; wherein the respective contents of the polypropylene (PP) and the compound according to formula (I) total to at least 98.0 wt. -%, based on the total weight of the polypropylene composition, and Wherein the melt flow rate MFR 2 of the polypropylene (PP) measured according to ISO 1133 at 230 ℃ under a load of 2.16kg is in the range of 400 to 5000 g/10 min and the melt temperature Tm of the polypropylene (PP) measured according to ISO 11357 by Differential Scanning Calorimetry (DSC) is in the range of 140 to 170 ℃.
  2. 2. Polypropylene Composition (PC) according to claim 1, wherein the polypropylene (PP) is a propylene Homopolymer (HPP).
  3. 3. Polypropylene Composition (PC) according to claim 1 or 2, wherein the respective content of the polypropylene (PP) and the compound according to formula (I) amounts to at least 99.0 wt. -%, based on the total weight of the polypropylene composition.
  4. 4. Polypropylene Composition (PC) according to claim 1 or 2, wherein each R is independently selected from methylene and a single bond, each R' is independently selected from C 1 to C 6 alkyl, each R "is H and the two substituents on the central benzene ring are positioned in meta relationship.
  5. 5. Polypropylene Composition (PC) according to claim 1 or 2, wherein the polypropylene (PP) has a molecular weight distribution (Mw/Mn) in the range of 1.0 to 6.0 as determined by gel permeation chromatography.
  6. 6. Polypropylene Composition (PC) according to claim 1 or 2, wherein the polypropylene (PP) has a weight average molecular weight Mw in the range of 25000 to 85000 as determined by gel permeation chromatography.
  7. 7. Polypropylene Composition (PC) according to claim 1 or 2, wherein the polypropylene (PP) has a content of 2,1 erythro domain defects in the range of 0.01 to 1.5 mol% as determined by 13 C-NMR spectroscopy and/or the polypropylene (PP) has a melting temperature Tm in the range of 151 to 160 ℃ as determined by Differential Scanning Calorimetry (DSC) according to ISO 11357.
  8. 8. Polypropylene Composition (PC) according to claim 1 or 2, wherein the polypropylene (PP) is free of 2,1 erythro region defects as determined by 13 C-NMR spectroscopy and/or the polypropylene (PP) has a melting temperature Tm in the range of 155 to 170 ℃ as determined by Differential Scanning Calorimetry (DSC) according to ISO 11357.
  9. 9. Polypropylene Composition (PC) according to claim 1 or 2, wherein the polypropylene (PP) is the product of visbreaking a precursor polypropylene (PP 2) using a visbreaker.
  10. 10. Polypropylene Composition (PC) according to claim 9, wherein the precursor polypropylene (PP 2) is a precursor propylene homopolymer (HPP 2).
  11. 11. Polypropylene Composition (PC) according to claim 9, wherein the visbreaker is a peroxide radical generator.
  12. 12. Polypropylene Composition (PC) according to claim 9, wherein the visbreaking ratio calculated as the melt flow rate MFR 2 of the polypropylene (PP) divided by the melt flow rate MFR 2 of the precursor polypropylene (PP 2) is in the range of 3.0 to 40, wherein the respective melt flow rate MFR 2 is determined according to ISO 1133 at 230 ℃ under a load of 2.16 kg.
  13. 13. Polypropylene Composition (PC) according to claim 9, wherein the melt flow rate MFR 2 of the precursor polypropylene (PP 2) is in the range of 50 to 399 g/10 min, measured according to ISO 1133 at 230 ℃ under a load of 2.16 kg.
  14. 14. Melt blown web made from the Polypropylene Composition (PC) according to any one of claims 1 to 13.
  15. 15. The meltblown web according to claim 14, which is an electret meltblown web.
  16. 16. A process for preparing the meltblown web according to claim 14 or 15, comprising the steps of: (a.i) providing a polypropylene (PP 1) for preparing a Polypropylene Composition (PC); Or alternatively (A.ii) or providing a precursor polypropylene (PP 2) and a visbreaker; And (B) Providing the compound according to formula (I); (c) Granulating the mixture of components provided in steps (a) and (b) in a granulator to obtain the Polypropylene Composition (PC), the Polypropylene Composition (PC) comprising 95.0 to 99.9 wt% of polypropylene (PP) based on the total weight of the polypropylene composition, and 0.01 to 5.0 wt% of the compound according to formula (I) based on the total weight of the polypropylene composition; (d) And (c) melt-blowing the blended pellets obtained in step (c).
  17. 17. The process according to claim 16, wherein the polypropylene (PP 1) used for preparing the Polypropylene Composition (PC) is a propylene homopolymer (HPP 1) used for preparing the Polypropylene Composition (PC).
  18. 18. The process according to claim 16, wherein the precursor polypropylene (PP 2) is a precursor propylene homopolymer (HPP 2).
  19. 19. The method of claim 16 or 18, wherein the visbreaker is a peroxide radical generator.
  20. 20. The method of any of claims 16 to 18, further comprising: Electrostatically charging the meltblown web obtained in step (d) to obtain an electret meltblown web.

Description

Polypropylene composition for electret melt-blown webs containing novel charge stabilizers Technical Field The present invention relates to a polypropylene composition comprising a specific charge stabilizer, to a meltblown web and an electret meltblown web made from said composition, to a process for preparing said meltblown web and electret meltblown web and to the use of the specific charge stabilizer for stabilizing the charge of an electret material. Background Meltblown webs, a nonwoven structure comprised of meltblown fibers, are typically made in a one-step process in which high velocity air blows molten thermoplastic resin from an extruder die (die tip) onto a conveyor belt or take-up screen to form a fine fiber self-adhesive web. While many types of polymers are available for melt blown fibers and fabrics, polypropylene is one of the most commonly used polymers. Meltblown webs are often employed due to their filtration characteristics. While optimized filtering performance is very important in many long-history areas, it has become increasingly important since COVID-19 pandemic transmission, with masks having beneficial filtering characteristics being particularly valuable. In this case, and in fact in most applications, beneficial filtration characteristics include having a high filtration efficiency (i.e., removing a high proportion of the particles) and a low pressure drop (i.e., allowing a relatively easy passage of a gas, such as air, through the filter, thereby enabling the user of the mask to breathe more easily). Face masks with particularly high filtration efficiency (e.g., N95 masks) typically comprise polypropylene meltblown webs that have been electrostatically charged. Polypropylene is a natural electret, which means that it is capable of supporting a permanent electric dipole due to its dielectric properties. Electrostatically charged filters have significantly improved filtration efficiency without concomitant increase in pressure drop. Factors known to affect the filtration performance of such melt blown webs include the selection of suitable polypropylene substrates, optimization of the charging process, and the use of charge stabilizing additives. Charge stabilizing additives are particularly important because it is particularly economical to add very small amounts of compounds which have a great influence on the final properties. Many charge stabilizing additives are known in the art. Exemplary charge stabilization additives include magnesium stearate (RSC ADVANCE,2018,8,7932), triamide derivatives (EP 2 294 257 A2), hydroxyamides (EP 2005 453 A1), F-free heterocyclic imides (EP 2 414 573 A2), arylamino-substituted benzoic acids/salts (EP 2 986 354 A2) and substituted mercaptobenzimidazole salts (substituted-mercaptobenizidyolate salts) (EP 2 938 420 A1), and multicomponent systems (EP 2 609 238 A1). While many of these additives are useful charge stabilizers, some also have other functions (e.g., visbreaking agents), which place a limit on the choice of polypropylene substrate. In view of the importance of these additives, it has been desired to develop new charge stabilizers, especially if improved filtration properties (indicating good charge retention) can be obtained both immediately after charging and after a period of time. Disclosure of Invention The present invention is based on the discovery that certain charge stabilizers, previously known only for their use as heat and UV/light stabilizers for polyamides, especially for nylon, surprisingly act as effective charge stabilizers for polypropylene-based electrets. The present invention thus relates to a Polypropylene Composition (PC) comprising: i) 95.0 to 99.99 wt% of a polypropylene (PP), preferably a propylene Homopolymer (HPP), based on the total weight of the composition, and Ii) 0.01 to 5.0% by weight, based on the total weight of the composition, of a compound according to formula (I) Wherein each R is independently selected from C 1 to C 6 alkylene, C 2 to C 6 alkenylene, and a single bond, each R' is independently selected from H and C 1 to C 6 alkyl, each R "is independently selected from H and C 1 to C 22 alkyl, wherein each alkylene, alkenylene, and alkyl may be optionally substituted with deuterium or fluorine, and the two substituents on the central benzene ring may be positioned in an ortho, meta, or para relationship; Wherein the respective contents of polypropylene (PP), more preferably propylene Homopolymer (HPP) and of the compound according to formula (I) amounts to at least 98.0 wt%, more preferably at least 99.0 wt%, and Wherein the melt flow rate MFR 2 of the polypropylene (PP), more preferably of the propylene Homopolymer (HPP) measured according to ISO 1133 at 230 ℃ under a load of 2.16kg is in the range of 400 to 5000g/10min, and the melt temperature Tm of the polypropylene (PP), more preferably of the propylene Homopolymer (HPP) measured according to ISO 11357 by Differential Scanning Calorimetr