Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1988-02-18
1988-11-29
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
21050038, 521 61, 521 62, 521 63, 521 64, 521183, 521134, 525432, 528335, 528336, C08J 928, C08J 930
Patent
active
047882263
DESCRIPTION:
BRIEF SUMMARY
This invention relates to polyamide membranes, and particularly to alcohol-insoluble membranes and their methods of manufacture.
It is known that alcohol-insoluble microporous polyamide membranes may be made by two different types of process, a so-called wet process wherein a membrane-forming film is cast as a thin layer and passes through a quenching solution to remove non-polyamide ingredients and form a microporous membrane while the material is still in the quench bath, or a dry process in which the membrane is formed by relatively slow evaporation of volatile components from a solution of the polyamide. It is recognised that it is not easy to choose polyamide materials that can be successfully formed into membranes by these methods, if the resultant membranes are to have the required desirable properties of being skinless, hydrophilic, (i.e. capable of being rapidly wetted by water) and capable of use in the filtration of particulate and bacterial contamination from a liquid. Such filtration requires pore sizes in the membrane material within the range of from about 0.1 to about 5 microns, that is to say bubble points in the range of about 690 to 48 kPa, with a membrane thickness within the range of about 0.025 mm to about 0.8 mm.
According to the invention we provide a microporous membrane comprising a hydrophilic, skinless sheet of polytetramethylene adipamide, either alone or in admixture with at least one other polyamide.
It has been found that polytetramethylene adipamide (Nylon 4,6) and mixtures of this material with at least one other polyamide can be formed into a membrane having the desirable qualities referred to above. It is presently preferred that the membranes of the invention be formed by a dry process, the polyamide or polyamides first being formed into a casting liquid by dissolving with a suitable solvent, which will preferably be formic acid: The solvent may be present together with one or more co-solvents (for example water, methanol, glycerol or any other lower molecular weight alcohol), and together with a non-solvent in order to give the casting liquid required viscosity and other properties. Suitable non-solvents include such materials as acetic acid, glycerol, polyethylene glycol and water. Membrane formation by a wet process is also possible.
It has been found that the bubble point of membranes cast from Nylon 4,6 alone is dependent on the molecular weight of the nylon, the bubble point increasing as the molecular weight increases. Molecular weights of not less than 20,000 are preferred. Membranes have been successfully cast from Nylon 4,6 having a molecular weight of approximately 21,000, but these have a relatively low bubble point, and in order to produce a membrane having a pore size capable of absolute removal of bacteria it may be preferred to use Nylon 4,6 of higher molecular weights when that particular polyamide is used alone. However, difficulties may be experienced in dissolving higher molecular weight Nylon 4,6 in formic acid, and other solvent systems may be necessary.
For many membranes it is preferred to use a blend of Nylon 4,6 together with one or more other polyamides, desirably selected from polyhexamethylene adipamide (Nylon 6,6), poly-e-caprolactam (Nylon 6) and polyhexamethylene sebacamide (Nylon 610), the additional nylon in the blend having a higher molecular weight than the Nylon 4,6. The additional polyamides are preferably all alcohol insoluble (as is Nylon 4,6), although small proportions of polyamides having a degree of solubility in alcohol may be tolerated.
Preferred blends are those of Nylon 4,6 and Nylon 6,6. In such blends, the Nylon 4,6 is desirably present in up to 25% by weight in order to give preferred strength and water flow properties. The molecular weight of Nylon 4,6 in the preferred blends may be from approximately 10,000 to approximately 26,500, with the range of approximately 10,000 to 21,000 being preferred. Molecular weight towards the lower end of this latter range are more particularly preferred, as they tend to give a more un
REFERENCES:
patent: 4340480 (1982-07-01), Pall et al.
patent: 4408036 (1983-10-01), Gaymans et al.
patent: 4431545 (1984-02-01), Pall et al.
patent: 4446304 (1984-05-01), Gaymans et al.
patent: 4450126 (1984-05-01), Kesting
patent: 4460762 (1984-07-01), Gaymans et al.
patent: 4693985 (1987-09-01), Degen et al.
patent: 4716214 (1987-12-01), Gaymans et al.
patent: 4719284 (1988-01-01), Nielinger et al.
patent: 4722997 (1988-02-01), Roerdink et al.
Domnick Hunter Filters Limited
Foelak Morton
Lewen Bert J.
Sternberg Henry
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