Monofilament-reinforced hollow fiber membrane

• US 9,561,475 B2
• Filed: 07/14/2014
• Issued: 02/07/2017
• Est. Priority Date: 04/26/2011
• Status: Active Grant

• Current Assignee: Lotte Advanced Materials Co., Ltd. (Lotte Chemical Corporation)
• Original Assignee: Lotte Chemical Corporation, Samsung SDI Company Limited
• Inventors: Seo, Chang Min, Lee, Gyeong Mo
• Primary Examiner(s): Menon, Krishnan S
• Application Number:
  US14/331,100
• Publication Number:
  US 20140339153A1
• Time in Patent Office: 939 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/42 Details of membrane preparation apparatus
• CPC Class Codes: B01D 2325/40 Fibre reinforced membranes
• CPC Class Codes: B01D 61/145 Ultrafiltration
• CPC Class Codes: B01D 61/147 Microfiltration
• CPC Class Codes: B01D 67/0002 Organic membrane manufacture
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 69/10 Supported membranes; Membrane supports
• CPC Class Codes: B01D 69/107 Organic support material
• CPC Class Codes: B01D 71/34 Polyvinylidene fluoride
• CPC Class Codes: B29C 70/222 the structure being shaped to form a three dimensional configuration
• CPC Class Codes: B29K 2027/16 PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2031/04 Polymers of vinyl acetate, e.g. PVAc, i.e. polyvinyl acetate
• CPC Class Codes: B29K 2069/00 Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2225/06 PS, i.e. polystyrene
• CPC Class Codes: B29K 2227/06 PVC, i.e. polyvinylchloride
• CPC Class Codes: B29K 2227/16 PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2231/04 Polymers of vinyl acetate, e.g. PVAc, i.e. polyvinyl acetate
• CPC Class Codes: B29K 2233/08 Polymers of acrylic acid esters, e.g. PMA, i.e. polymethylacrylate
• CPC Class Codes: B29K 2267/00 Use of polyesters or derivatives thereof as reinforcement
• CPC Class Codes: B29K 2269/00 : Use of PC, i.e. polycarbonates or derivatives thereof as reinforcement
• CPC Class Codes: B29K 2277/00 : Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as reinforcement
• CPC Class Codes: B29K 2309/08 : Glass
• CPC Class Codes: B29K 2427/16 : PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2431/04 : Polymers of vinyl acetate, e.g. PVAc, i.e. polyvinyl acetate
• CPC Class Codes: B29K 2469/00 : Use of PC, i.e. polycarbonates or derivatives thereof as filler
• CPC Class Codes: B29K 2627/16 : PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2631/04 : Polymers of vinyl acetate, e.g. PVAc, i.e. polyvinyl acetate
• CPC Class Codes: B29K 2669/00 : Use of PC, i.e. polycarbonates or derivatives thereof for preformed parts, e.g. for inserts
• CPC Class Codes: B29K 2827/16 : PVDF, i.e. polyvinylidene fluoride
• CPC Class Codes: B29K 2831/04 : Polymers of vinyl acetate, e.g. PVAc, i.e. polyvinyl acetate
• CPC Class Codes: B29K 2869/00 : Use of PC, i.e. polycarbonates or derivatives thereof as mould material

Abstract

A hollow fiber membrane is formed by embedding a braid having a spiral open weave of monofilaments only, to avoid a “whiskering” problem common in prior art multifilament braid-supported tubular membranes. The open weave is characterized by contiguous, circumferential, rhomboid-shaped areas of polymer film separated by monofilaments. When the braid is supported on a plasticized PVA cable it can be infiltrated with membrane polymer which, when coagulated embeds the braid positioning it around the lumen. The spiral weave, free of any circumferentially constricting monofilament, when embedded in film, allows the membrane to be biaxially distensible. In other words, the membrane has “give” not only in the axial or longitudinal direction but also in the radial direction. “Give” in the radial direction permits soiled membranes to be backwashed under higher pressure than in a comparable braid which is not radially distensible.

Claims

1. A process for embedding a monofilament, tubular open-weave braid of monofilaments in a membrane polymer, comprising,

weaving an open tubular braid having a recurring rhomboid pattern of synthetic resinous monofilaments in the denier range from 25-250, directly over the surface of and snugly contacting a core cable of poly vinyl alcohol plasticized with from 5-20 weight percent of plasticizer, the cable having a diameter chosen to provide a lumen of desired diameter in the range from 0.5-2.0 mm;

coating the tubular braid with a membrane-forming dope in a coating nozzle until the dope infiltrates into an area below the surface of filaments overlying the cable to form the lumen;

pulling the cable and braid together through the coating nozzle;

coagulating the dope to form a semipermeable membrane embedding the braid as a monolayer which, together with polymer surrounding it, defines the lumen of the membrane;

washing in hot water until at least 99% of the plasticized PVA is removed, and, further washing with an aqueous oxidizing agent chosen from sodium hypochlorite (NaOCl), hydrogen peroxide and potassium hypochlorite (KOCl) to make an asymmetric membrane which tests for eluted water having a total organic carbon (“

TOC”

) of <

0.5 ppm without damaging the lumen of the membrane formed.

2. The process of claim 1 wherein the semipermeable membrane has a wall thickness in the range from 0.2-0.6 mm thick.

3. The process of claim 1 wherein the concentration of NaOCl in the aqueous oxidizing agent is in the range from 0.1-0.5% NaOCl and its temperature is in the range from 20°

C.-80°

C.