Poly(ethylene chlorotrifluoroethylene) membranes

• US 20070216057A1
• Filed: 01/31/2007
• Published: 09/20/2007
• Est. Priority Date: 02/12/2002
• Status: Active Grant

• Current Assignee: Evoqua Water Technologies LLC (Xylem, Inc.)
• Original Assignee: Seimens Water Technologies Corporation
• Inventors: Mullette, Daniel, Muller, Heinz-Joachim
• Granted Patent: US 7,632,439 B2
• Time in Patent Office: Days
• US Class Current: 264/45.100
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/18 Pore-control agents or pore formers
• CPC Class Codes: B01D 2323/22 Specific non-solvents or non-solvent system
• CPC Class Codes: B01D 2325/0231 Dense layers being placed on the outer side of the cross-section
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/36 Hydrophilic membranes
• CPC Class Codes: B01D 2325/38 Hydrophobic membranes
• CPC Class Codes: B01D 67/0018 Thermally induced processes [TIPS]
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 67/0031 by elimination of at least one of the blocks of a block copolymer
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 71/32 containing fluorine atoms
• CPC Class Codes: B29C 67/202 comprising elimination of a solid or a liquid ingredient
• CPC Class Codes: D01D 5/24 with a hollow structure; Spinnerette packs therefor D01D5/38 takes precedence; producing tubes of plastic material B29D; addition of agents forming hollow filaments D01F1/08
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers

Abstract

Porous polymeric membranes including HALAR® (poly(ethylene chlorotrifluoroethylene)) and related compounds and the methods of production thereof which avoid the use of toxic solvents. Preferred solvents, coating agents and pore forming agents are citric acid ethyl ester or glycerol triacetate. The membranes may be in the form of a hollow fibre or flat sheet, and may include other agents to modify the properties of the membranes, such as the hydrophilic/hydrophilic balance. Leachable agents may also be incorporated into the membranes.

Claims

1-76. -76. (canceled)

77. A method of forming a membrane comprising casting a membrane from poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II:

78. The method of claim 77, wherein the solvent according to formula I is citric acid ethyl ether.

79. The method of claim 77, wherein the solvent according to formula II is glycerol triacetate.

80. The method of claim 77, wherein the act of casting the membrane comprises inducing a phase separation of poly(ethylene chlorotrifluoroethylene) and the solvent.

81. The method of claim 80, wherein the act of casting a membrane comprises contacting a first surface with a lumen forming fluid.

82. The method of claim 81, wherein the act of contacting a first surface with the lumen forming fluid comprises contacting the surface with diethylene glycol.

83. The method of claim 81, wherein the act of casting the membrane comprises contacting a second surface with a coating fluid.

84. The method of claim 83, wherein the act of contacting the second surface with the coating fluid comprises contacting the surface with a fluid selected from the group consisting of glycerol triacetate, citric acid ethyl ester, diethylene glycol, and mixtures thereof.

85. The method of claim 80, further comprising removing the solvent from the membrane.

86. The method of claim 80 wherein R₁, R₂, and R₃ are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl, and hexyl.

87. A method of forming a hollow fiber membrane comprising:

forming a blend comprising poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II;

wherein R₁, R₂, and R₃ are alkyl;

R₄ is selected from the group consisting of H, OH, OR₅, OCOR₅, an alkyl, and an alkoxy; and

R₅ is an alkyl;

forming the blend into a hollow fiber shape;

contacting a first surface of the hollow fiber shape with a lumen forming fluid;

inducing a phase separation in the hollow fiber shape to form a hollow fiber membrane; and

removing the solvent from the membrane.

88. The method of claim 87, wherein the solvent according to formula I is citric acid ethyl ether.

89. The method of claim 87, wherein the solvent according to formula II is glycerol triacetate.

90. The method of claim 87, wherein the blend is maintained at a temperature greater than 200°

C.

91. The method of claim 87, wherein the blend comprises about 14-25% poly(ethylene chlorotrifluoroethylene).

92. The method of claim 87, further comprising an act of removing the solvent from the membrane.

93. The method of claim 87, further comprising an act of contacting a second surface of the hollow fiber shape with a coating fluid.

94. The method of claim 93, wherein the coating fluid is selected from the group consisting of glycerol triacetate, citric acid ethyl ester, diethylene glycol, and mixtures thereof.

95. The method of claim 87, wherein the lumen forming fluid comprises diethylene glycol.

96. The method of claim 87, wherein the blend further comprises a pore controlling agent.

97. The method of claim 96, wherein the pore controlling agent comprises glycerol triacetate.

98. The method of claim 96, wherein the pore controlling agent comprises citric acid ethyl ester.

99. The method of claim 87, wherein the blend further comprises a pore forming agent.

100. The method of claim 99, further comprising an act of removing the pore forming agent from the hollow fiber with a leachant.

101. The method of claim 100, wherein the leachant comprises a caustic solution.

102. The method of claim 99, wherein the pore forming agent is an inorganic solid with a particle size of less than 1 micron.

103. The method of claim 99, wherein the pore forming agent comprises silica.

104. The method of claim 103, further comprising an act of preparing from the blend, a dope comprising from about 3 weight percent to about 9 weight percent silica.

105. A method of preparing a porous polymeric material comprising:

heating a mixture comprising poly(ethylene chlorotrifluoroethylene) and at least one solvent selected from the group consisting of a compound according to formula I and formula II;

wherein R₁, R₂, and R₃ are alkyl;

R₄ is selected from the group consisting of H, OH, OR₅, OCOR₅, an alkyl, and an alkoxy; and

R₅ is an alkyl;

forming a polymer rich phase and a polymer lean phase, wherein the polymer rich phase and the polymer lean phase form a matrix;

cooling the matrix to form a solid polymeric material; and

removing the polymer lean phase from the solid polymeric material.

106. The method of claim 105, wherein R₁, R₂, and R₃, are selected from the group consisting of methyl, ethyl, propyl, butyl, pentyl and hexyl.