Composition and method for making ultra-fine, high tenacity and high toughness polymeric multifilaments

Patent metadata

Field	Value
Publication number	US-2024110315-A1
Application number	US-202318457479-A
Country	US
Kind code	A1
Filing date	Aug 29, 2023
Priority date	Sep 30, 2022
Publication date	Apr 4, 2024
Grant date	—

Abstract

The present invention provides a composition and method for forming polymeric multifilaments having a filament diameter of no more than 10 μm with a high tensile strength and toughness. The composition includes at least one semi-crystalline thermoplastic polymer and a nucleating agent to stabilize the multifilaments during melt-spinning and facilitate phase transformation of the thermoplastic polymer in subsequent drawing and annealing cycles. The method includes a quenching step for the melt-spun filaments immediately after the melt-spinning and collection of the quenched filaments with a specific winding speed to decrease the filament diameter. The subsequent drawing and annealing cycles further enhance the mechanical properties of the filaments after the quenching.

First claim

What is claimed is:

1 . A melt-spinnable or melt-extrudable polymeric composition for forming polymeric multifilaments with a small average filament diameter, high tensile strength and tensile toughness, the composition comprising:
at least one semi-crystalline thermoplastic polymer; a nucleating agent; and one or more anti-oxidants.

2 . The polymeric composition of claim 1 , wherein the at least one semi-crystalline thermoplastic polymer comprises polypropylene, polyethylene, polyethylene terephthalate, and polyamide 6.

3 . The polymeric composition of claim 2 , wherein the polypropylene is one or both of isotactic polypropylene having a molecular weight of about 341 kDa and a polypropylene having a melt flow index (MFI) of 1500.

4 . The polymeric composition of claim 3 , wherein the isotactic polypropylene has a melt index of 4 g/10 minutes at about 230° C. under 2.16 kg load.

5 . The polymeric composition of claim 3 , wherein the isotactic polypropylene and the polypropylene with the MFI of 1500 are in a weight ratio of 10:0 to 7:3.

6 . The polymeric composition of claim 1 , wherein the nucleating agent is a sorbitol-based nucleating agent.

7 . The polymeric composition of claim 6 , wherein the sorbitol-based nucleating agent is selected from 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol or 1,3:2,4-dibenzylidene-D-sorbitol.

8 . The polymeric composition of claim 1 , wherein the one or more antioxidants is a blend of two different anti-oxidants.

9 . The polymeric composition of claim 8 , wherein the two different anti-oxidants are selected from a phenolic antioxidant and a hydrolytically stable phosphite processing stabilizer in a weight ratio of 1:2.

10 . The polymeric composition of claim 9 , wherein the phenolic antioxidant is selected from pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate); the hydrolytically stable phosphite processing stabilizer is selected from tris(2,4-di-tert-butylphenyl) phosphite.

11 . The polymeric composition of claim 1 , wherein the at least one semi-crystalline thermoplastic polymer, the nucleating agent, and the one or more anti-oxidants in the composition are in a weight ratio of 993:4:3.

12 . A polymeric multifilament formed from the polymeric composition of claim 1 , having an average filament diameter of 4 to 10 μm, tensile strength of greater than 1 GPa, tensile toughness of greater than 100 MJ/m 3 , and an elongation at break of at least 15%.

13 . A method for forming a polymeric multifilament comprising:
providing the composition of claim 11 ; melt-spinning said composition under an inert gas environment on a multiple orifice die to generate a plurality of filaments; quenching the plurality of the filaments at a first temperature within a range higher or lower than a glass transition temperature of the at least one semi-crystalline thermoplastic polymer in the composition to obtain a plurality of quenched filaments; collecting the quenched filaments with a winder at a winding speed to obtain a plurality of as-spun filaments; drawing the plurality of as-spun filaments on a multiple furnace platform at a second temperature and with a second winding ratio; repeating said drawing for at least five times to obtain a plurality of drawn filaments; annealing the plurality of drawn filaments at a third temperature on a multiple furnace platform as in said drawing and with a third winding ratio; and repeating said annealing for at least twice to obtain a plurality of annealed filaments.

14 . The method of claim 13 , wherein the inert gas environment is provided by supplying an inert gas comprising nitrogen and argon at a pressure from 1,000 to 2,000 kPa.

15 . The method of claim 13 , wherein the multiple orifice die for said melt-spinning has an orifice number between 10 and 20.

16 . The method of claim 15 , wherein each of the orifices of the multiple orifice die for said melt-spinning has an average size of about 0.15 mm.

17 . The method of claim 13 , wherein the first temperature for said quenching is about 15 to 25° C. higher or lower than the glass transition temperature of the at least one semi-crystalline thermoplastic polymer in the composition.

18 . The method of claim 17 , wherein the at least one semi-crystalline thermoplastic polymer is one or both of isotactic polypropylene with the other polypropylene having an MFI of 1500 such that the first temperature is about 0° C. to 8° C. for said quenching.

19 . The method of claim 18 , wherein a melt extrusion temperature of about 205 to 250° C. is used in said melt-spinning.

20 . The method of claim 13 , wherein the first winding speed of the winder used for said collecting the quenched filaments is up to 200 m/min and not below 100 m/min.

21 . The method of claim 13 , wherein the second temperature for said drawing is lower than the third temperature for said annealing.

22 . The method of claim 13 , wherein the second temperature for said drawing is about 140° C. to 155° C.

23 . The method of claim 13 , wherein the second winding ratio for said drawing is higher than the third winding ratio for said annealing.

24 . The method of claim 13 , wherein the second winding ratio for said drawing is up to 6.

25 . The method of claim 13 , wherein the multiple furnace platform comprises at least three furnaces each having an equal length and spacing to the other furnace.

26 . The method of claim 25 , wherein each of the at least three furnaces has the length of about 40.5 cm and the spacing of about 6.5 cm between two of the furnaces.

27 . The method of claim 13 , wherein said drawing is repeated for at least five times before said annealing.

28 . The method of claim 13 , wherein the third temperature for said annealing is about 160° C. to 170° C.

29 . The method of claim 13 , wherein the third winding ratio is up to 1.2.

30 . The method of claim 13 , wherein said annealing is repeated for at least twice before obtaining said plurality of annealed filaments.

31 . The method of claim 13 , wherein said annealing is performed on the same multiple furnace platform as that for said drawing.

32 . The method of claim 13 , wherein said plurality of annealed filaments are the polymeric multifilaments with an average diameter of 4 to 10 μm, tensile toughness of at least 100 MJ/m 3 , tensile strength of greater than 1 GPa, an elongation at break of at least 15%, and a filament count of at least 10 per batch.

Assignees

• Nano & Advanced Materials Inst Ltd

Inventors

• Zhang Kang
• Yec Christopher Cheung
• Zhang Shilong
• Li Jifan

Classifications

• C08K5/1575

  Six-membered rings · CPC title

• C08K5/1345

  Carboxylic esters of phenolcarboxylic acids · CPC title

• C08K5/526

  with hydroxyaryl compounds · CPC title

• D01F1/10 Primary

  Other agents for modifying properties · CPC title

• D01F6/46

  of polyolefins · CPC title