JPS6327964B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to permeators containing hollow fiber membranes, and more particularly to permeators having tube sheets containing a solidified resin made from a polyglycidyl resin and an imidazole curing agent. Hollow fiber membrane-containing permeators are often advantageous because of the high membrane surface area per permeator volume ratio that they can achieve. Therefore, hollow fiber membrane-containing permeators are used in many fluid separation operations,
For example, it may be compact enough to find desirable utility in gas-gas, gas-liquid and liquid-liquid (including liquid-dissolved solids) separations. In these permeators, at least one end of each hollow fiber membrane is embedded (often commonly referred to as "potted") in a tube sheet.
and a hollow fiber membrane extends in fluid connection through the tube sheet. One purpose of this tube sheet is to secure the hollow fiber membrane in an essentially fluid-tight relationship within the tube sheet. This tube sheet can be fixed in an essentially fluid-tight relationship in the permeator so that no fluid can pass from one outside or pore side of the hollow fiber membrane to the other except through the membrane walls. do not. Even a small leak around the tube seat can have a significant negative impact on permeator function. The reason is that non-permeable portions can escape to the permeate side of the hollow fiber membrane through these leakages and reduce the separation selectivity that can be achieved by the permeator. Another purpose of the tube sheet is its integrity to provide a sufficiently strong barrier to fluid flow so that during operating conditions the tube sheet will not rupture or otherwise allow fluid to pass through the tube sheet. The goal is to make sure that you don't lose your identity. Therefore, one must ensure that a fluid-tight relationship is achieved with respect to the hollow fiber membrane and that the tube sheet can withstand any pressure differences to which it may be exposed during the intended separation operation. To provide tightness, this tube sheet is often of substantial thickness. Tube sheets are generally molded using resin, which may be natural or synthetic. The resin can be applied to the hollow fiber membranes which are then assembled into bundles, or the resin can be poured as a liquid around the previously assembled bundles of hollow fiber membranes and then solidified, for example by curing. Can be done. There are many unique considerations in selecting a suitable resin for forming tube sheets. For example, it is usually desirable to: 1. The resin adheres to the hollow fiber membrane sufficiently before and after solidification to be able to achieve the desired fluid-tight relationship between the tube sheet and the hollow fiber membrane; 2. The solidified resin does not adhere to the hollow fiber membrane as intended. exhibit sufficient strength and integrity to withstand the pressure differential expected to exist across the tube sheets during the separation operation being carried out; 3. to avoid creating undue internal stresses within the tube sheets, and The resin shrinks very little during solidification so that it does not separate from the hollow fiber membrane or result in stresses on the hollow fiber membrane that adversely affect the integrity of the hollow fiber membrane. 4. The resin does not unduly dissolve in or otherwise adversely affect the hollow fiber membrane material; 5. The tube sheet does not exhibit solidification, particularly caused by temperature differences during curing of the resin. be relatively free of internal stresses that could be caused by hollow fiber membranes and therefore have different heat generation, heat absorption, or heat transfer properties; (possibly rising in a tube sheet with at least one region that may have different thermal expansion properties than the portion containing the hollow fiber membrane). 6 Polymerization (curing) especially during or after solidification
For resins that undergo polymerization, any heat generated during polymerization should not generate temperatures in the tube sheet that would adversely affect the hollow fiber membrane, and all heat generated during polymerization should The heat should not adversely affect the hollow fiber membrane. 7. Particularly when forming a tube sheet around a pre-assembled bundle of hollow fiber membranes, the viscosity of the fluid resin should be low enough that liquid penetration throughout the bundle can be easily achieved. It should be. 8. The fluid resin is not unduly stretched between the hollow fiber membranes by capillary action (hereinafter referred to as "wicking"), and any possible wicking occurs in a relatively uniform manner over the cross-section of the bundle of hollow fiber membranes. To be something. 9. The tube sheet exhibits sufficient chemical resistance so that it retains sufficient strength and dimensional stability during the intended separation operations. 10. Processing of tube sheets is relatively uncomplicated, does not require the use of complex equipment, and can be produced with a minimum of manufacturing time and a minimum of human training, skill, and time. 11 The solidified resin must be capable of being cut or shaped, for example to expose the pores of a hollow fiber membrane or to accommodate a tube sheet for permeator assembly. 12 The components of the resin do not pose any unreasonable risk of toxicity during the formulation of the liquid resin, during the manufacture of the tube sheet, or after the manufacture of the tube sheet. The performance required for tube sheets depends on the expected operating conditions of the permeator. Hollow fiber membrane containing permeators have found acceptance for use in desalination, engraving and hemodialysis. Generally, these separation operations provide a relatively benign environment. That is, the stream being treated contains only low concentrations, if any, of moieties that could adversely affect the tube sheet material (either through loss of physical strength or integrity, or through swelling). Furthermore, in operations such as in hemodialysis, where little, if any, pressure differential is exhibited per membrane, the strength of the tube sheet is not a major consideration. Therefore, there is a wide degree of freedom in selecting the resin for making the tube sheet. For example, strength and chemical resistance are required to provide a desirable fluidic liquid resin for penetration into the pre-assembled bundle of hollow fiber membranes and to ensure good adhesion of the tube sheet to the hollow fiber membranes. High polymerization temperatures (e.g. exothermic) can be avoided at the cost of this aspect. Even with such permeators operating under relatively mild conditions, considerable difficulties can still be experienced in obtaining resins suitable for making tube sheets. These difficulties are clearly exacerbated when the tube sheet must exhibit high strength and high chemical resistance. For example, in view of the advantages that can be provided by fluid separation provided by membranes, more demanding conditions such as purge streams from chemical plants or refiners that can often contain substances that are degradative to resinous materials. It would be desirable to provide such a tube sheet that would enable permeator technology for use in and waste streams. Such tube sheets have high strength to withstand the high pressure differentials (often 30 or 40 atmospheres, or more than 60 atmospheres) that may be required to achieve favorable permeate flow rates through the walls of the hollow fiber membrane. Should be. Furthermore, the tube sheet should retain its strength and dimensional stability during the long-term operation (eg, two years or more) desired for the permeator. A wide variety of different resins have been proposed for the manufacture of tube sheets for hollow fiber membranes. For example, US Pat. No. 3,499,062 describes solder, cement,
The use of waxes, adhesives, natural and synthetic resins is proposed. US Pat. No. 3,422,008 discloses the use of epoxy resins for the manufacture of tube sheets, and that phenolic-aldehyde resins, melamine-formaldehyde resins, thermoset synthetic rubbers and acrylic resins are also suitable. is proposed. Other materials disclosed for use as materials for forming tube sheets include urethane resins, silicone resins, polysulfides, acetals, cellulose, fluorocarbons, vinyl, styrene, polyethylene and polypropylene. See, for example, US Pat. No. 3,760,949, US Pat. No. 4,049,765, and US Pat. One of the more preferred resins for forming tube sheets is epoxy resin. For example, US Pat. No. 3,728,425 discloses the use of polyepoxides to form tube sheets for permeators. This patent states that polyepoxides include polyhydric phenols such as resorcinol, catechol, hydroquinone, phloroglucinol, 2,
2-bis(4-hydroxyphenyl)propane (bisphenol A), 4,4'-dihydroxybenzophenone, 1,1-bis(4-hydroxyphenyl)ethane, bis(2-hydroxynaphthyl)
Glycidyl polyethers of methane, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-dihydroxyphenyl phenyl sulfone and phenol-formaldehyde condensation products (for the production of novolac resins) may be mentioned. There is. Most commonly, the specifically disclosed epoxy resins include diglydisyl ether of bisphenol A (hereinafter referred to as "DGEBA"). A hardener is used with the epoxy resin. For example, McLain specifically discloses the use of 1.1 parts dimethylaminopropylamine and 6.8 parts soy-1,3-propylene diamine as hardeners for 14.7 parts DGEBA. Schrader
He requires an aromatic amine as a curing agent. His suggestions for aromatic amine curing agents were metaphenylene diamine, diaminodiphenylsulfone, 4,4'-methylene dianiline, 2,6-diaminopyridine, 4-chloro-ortho-phenylene diamine, and m-phenylene. These include adducts of diamines and phenyl glycidyl ether of methylene dianiline (disclosed as curing agent Z in U.S. Pat. No. 3,339,633). Mr. Schrader clearly considered Hardener Z to be preferred. Hardener Z has a relatively low viscosity, which allows liquid resin formulation and provides a low viscosity liquid resin suitable for forming tube sheets. However, sclerosing agent Z has been identified as a suspected carcinogen in mammals. Additionally, the nearly stoichiometric amount of curing agent Z required, such as about 20 parts per 100 parts by weight resin (phr), increases the amount required to be processed in the manufacture of tube sheets. Additionally, although aromatic polyamines such as Curing Agent Z are often characterized as providing enhanced strength and chemical resistance to epoxides,
When formulated in a liquid suitable for forming tubesheets, the tubesheets are cured with sufficient chemical resistance to withstand the more severe environments that may be present in gaseous exhaust or waste streams from chemical plants or refiners. There is no basis for the assessment that Agent Z affects tube sheets. Considerable research has been conducted and much literature has been published regarding epoxy technology in general. For example, "Handbook of Epoxy Resins" (1967),
"Epoxy Resins"["Encyclopedia of Polymer"
Science and Technology” Vol. 6, pp. 209-271 (1967)] and “Fpoxy Resins—Chemistry
(1973). Epoxy resins can be used for coating, bonding, electrical encapsulation,
It has found a wide range of applications in tools, flooring, moldings, and more. These various applications may require that the epoxy resin exhibit different properties with respect to its strength, ease of processing, cure time, resistance to heat distortion, and the like. Therefore, many different epoxy resins and hardeners are commercially available to meet the specific needs of a specific application. For example, the Shell Chemical Company product Biurethane (1967) entitled "EPON Resins for Casting" lists 24 hardeners in a table (pages 10-11). Commonly used curing agents can usually be characterized as amines, acid anhydrides, and Lewis acids. One of the available curing agents is 2-ethyl-4-methylimidazole. Although general properties and effects can be attributed to various epoxy resins and curing agents, these general properties and effects are the basis of empirical screening for determining the suitability of an epoxy resin for its intended use. It only serves to guide the selection of candidates. The hollow fiber membrane-containing permeator provided by the present invention exhibits high strength and excellent chemical resistance, yet its tube sheets can be fabricated without the risk of undue damage to the hollow fiber membrane. Additionally, the tube sheet is easy and simple to manufacture, and the manufacturer does not need to be unduly exposed to toxic substances during the manufacture of the tube sheet. The permeator tube sheet of the present invention includes a liquid resin cured epoxy resin containing a polyglycidyl resin and an imidazole hardener. The liquid resin can be applied to the hollow fiber membrane in any suitable manner to form a tube sheet and then cured to solidify the resin. Imidazole curing agents that may be useful in making the tube sheets of the present invention have the following structural formula: It is expressed as In the formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different and hydrogen, alkyl (e.g. 1 to about 12
alkyl containing 1 carbon atoms, preferably 1
lower alkyl containing ~4 or 6 carbon atoms), lower acyl (e.g. containing 1 to about 4 or 6 carbon atoms), and aryl (e.g. monocyclic and bicyclic aryl and aralkyl of approximately 15 carbon atoms). Furthermore, R ₂ , R ₃
and R ₄ can be halogen (eg, chlorine, fluorine or bromine), nitro, hydroxy, alkoxy (eg, alkoxy of 1 to about 6 carbon atoms), or the like. Additionally, R ₃ and R ₄ can be combined to form, for example, benzimidazole.
Each of R ₁ , R ₂ , R ₃ and R ₄ may be substituted, for example with hydroxyl or halogen moieties such as fluorine, chlorine and bromine. Examples of imidazole curing agents are imidazole, N-butylimidazole,
1-acetylimidazole, 1-trifluoroacetylimidazole, 1-perfluorobenzoylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, 2-ethyl-
4-methylimidazole, 2-methyl-5-nitroimidazole, 4-phenylimidazole,
4,5-diphenylimidazole, 4-nitroimidazole and benzimidazole. To facilitate liquid resin formulation, preferably the imidazole curing agent is liquid (including supercooled liquid) at temperatures below about 40°C or at temperatures below about 40°C.
It is soluble in polyglycidyl resins at temperatures below 40°C. As an advantageous imidazole curing agent,
Substituted imidazoles in which at least one of R ₁ , R ₂ , R ₃ and R ₄ is other than hydrogen, such as R ₁ , R ₂ and
Included are substituted imidazoles in which at least one of R ₃ is alkyl, acyl or aryl (including aralkyl). A preferred imidazole curing agent is 2-ethyl-4-methylimidazole.
2-ethyl-4-methylimidazole (e.g.
92% pure) is a supercooled liquid at room temperature and has a viscosity of approximately 4000-6000 centipoise at room temperature. For example, although 2-ethyl-4-methylimidazole has a higher viscosity than certain previously proposed curing agents, such as Curing Agent Z, this imidazole curing agent has a higher viscosity even at slightly higher temperatures. Allow sufficient processing time for the liquid resin before its viscosity begins to increase significantly due to curing. Often, the viscosity of the liquid resin can be reduced at a given temperature for a period of time after its formulation, for example to facilitate penetration into the bundle of hollow fiber membranes. Furthermore, it has been discovered that not only can the imidazole curing agent provide the low viscosity necessary to achieve this penetration of the liquid resin, but also the rheology of the liquid resin can be provided by, for example, centrifugal casting. It may be suitable to achieve penetration through the bundle of hollow fiber membranes without the use of such forcing forces. Apparently highly thixotropic (thixotropic)
Liquid resins that do not penetrate well into the hollow fiber bundle can give highly non-uniform tube sheets.
Another advantage is that unreasonably high peak exotherm temperatures can be avoided. The reason is that liquid resins containing this imidazole curing agent need to be heated, for example to about 40°C or more, for rapid initiation of the curing reaction, which tends to generate high temperatures due to the exothermic curing reaction. This is because it is wet.
For the significant portion of hardening that occurs at lower temperatures,
The ease of maintaining a relatively uniform temperature profile throughout the resin mass during curing is enhanced. Although imidazole curing agents may not eliminate wicking, the amount of wicking is generally not excessive. Furthermore, since good penetration of the liquid resin can often be achieved throughout the bundle, the wicking height per cross-section of the bundle is relatively uniform. A significant advantage of this imidazole curing agent is the ability to vary the degree of overall exotherm of the liquid resin during curing by varying the amount of imidazole used. Imidazole curing agents not only react with epoxy moieties through one or both of the ring nitrogens;
It is believed that the imidazole curing agent also catalyzes the reaction between (1) the alkoxide ion formed by the reaction of the epoxy moiety with the ring nitrogen of the imidazole curing agent and (2) other epoxy moieties. “Imidazole Catalysts in
the Curing of Epoxy Resins” [Journal of
Applied Polymer Science” Volume 12, No. 159-168
(1968) give a more detailed disclosure of the manner in which epoxy moieties are believed to react with imidazole compounds. Therefore, since imidazole curing agents can provide this mechanism for curing epoxy resins, the relative amounts of imidazole curing agents used can affect the relative proportions of these mechanisms that occur in curing epoxy resins. Probably. For example, lower amounts of imidazole curing agent per given amount of epoxy resin tend to promote more cross-linking through the alkoxide ion route. On the other hand, when more imidazole curing agent is used, more epoxy moieties are consumed by reaction with the imidazole nitrogen, and therefore less epoxy moieties are used for cross-linking with any alkoxide ions that may be present. Only part of it will be valid.
It has been found that generally less exothermic reactions occur when higher amounts of imidazole curing agent are used. Accordingly, the amount of imidazole curing agent can be selected to provide a peak temperature that the hollow fiber membrane can withstand, along with sufficient cross-linking to provide advantageous strength and chemical resistance to the tube sheet. According to the invention, it has therefore been found that imidazole curing agents are particularly advantageous for the production of hollow fiber membrane tube sheets. That is, not only can tubular sheets with advantageous strength and chemical resistance be produced, but desirable rheological properties can be achieved with the cured resin to facilitate penetration into the bundle of hollow fiber membranes. Furthermore,
The rate of cure, degree of cure, and peak temperature occurring during cure are sufficiently flexible to enhance the ability to provide a suitable tube sheet. Often, the imidazole curing agent is present in an amount necessary for complete reaction of one ring nitrogen with the epoxy moieties in the liquid resin on a stoichiometric basis (hereinafter referred to as the "stoichiometric reaction requirement"). of at least about 1 or 2%. Often, the imidazole curing agent is present at about 2-40% of the stoichiometric reaction requirement;
For example about 2-30%, and preferably about 5-20%
given in the amount of In common practice, the amount of curing agent in an epoxy resin is expressed in parts by weight per 100 parts by weight of resin ("phr"). Therefore, for ease of understanding the present invention, the imidazole curing agent will often be present in at least about 1 phr, e.g.
15 phr especially about 2 to 12 phr, and most often about 3 to
Used in an amount of 7phr. Other suitable hardeners and modifiers may be useful in combination with the imidazole hardener.
Examples of curing agents and modifiers include polyamine curing agents and amine modifiers such as isopropylamine, polymethylene diamine, polyalkyl ether diamines, dialkylene triamines (e.g. diethylene triamine), trialkylenetetramines (e.g. triethylenetetramine), diethylaminopropylene. , N-aminoethylethanolamine, 1,3-bis(dimethylamino)-2-
Propanol, menthanediamine, aminoethylpiperazine, 1,3-diaminocyclohexane,
Bis(p-aminocyclohexyl)methane, m-
Phenylene diamine, m-xylylene diamine,
4,4'-diaminodiphenylmethane, diaminodiphenyl sulfone, piperazine, N-methylpiperazine, piperidine, 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30),
Tri-2-ethylhexanoate salt of DMP-30,
halohydrin ethers of modified aliphatic polyamines such as glycol polyamine adducts,
Dimethamine adducts of allocimene diepoxide, aminoalkoxysilane adducts of propylene oxide, hydroxypolyamines and others, acidic curing agents (generally not preferred as they may be reactive with imidazole curing agents) such as boron trifluoride, Aluminum chloride, boron trifluoride monoethylamine, sleic anhydride, phthalic anhydride, chlorendic anhydride, pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, dodecenylsuccinic anhydride, Nadizku methyl anhydride, Tetrahydrophthalic anhydride, hexahydrophthalic anhydride and others, amides such as amide polyamines, fatty polyamines, vicinal amides such as p-phenylene bis(anilinophenylphosphine oxide), urea (including substituted ureas and urea-formaldehyde) , N,N-diallylmelamine, triallyl cyanurate, hydrazide, aminoacetal such as bis(2-dimethylaminoethoxy)
Methane, bis(1-dimethylamino-2-propoxy)methane, 1,6-bis(2-dimethylaminoethoxy)hexane, α,α′-bis(2-dimethylaminoethoxy)-p-xylene, bis(3
-dimethylamino-1-propoxy)methane,
2,6-bis(2-dimethylaminoethoxy)pyridine, 2,6-bis(1-dimethylamino-2
-propoxy)pyridine, 2,6-bis(3-dimethylamino-1-propoxy)pyridine, bis(2-dimethylaminoethoxy)methane, bis(2-N-morpholinoethoxy)methane, 1,1
-Bis(2-dimethylaminoethoxy)propane, 2,2-bis(2-dimethylaminoethoxy)propane, α,α′-bis(2-dimethylaminoethoxy)toluene, 1,1-bis(2-dimethylamino) ethoxy)butane, 1,1-bis(2
-dimethylaminoethoxy)ethane and 1,
Examples include 1,2,2-tetrakis(2-dimethylaminoethoxy)ethane and others. If one or more other curing agents are used in the curing composition in combination with the imidazole curing agent, the total reactive sites provided on the curing agent (the imidazole curing agent has 1 It is preferred that the amount of reactive sites (considered to have 100 reactive sites) is no more than about 30% or 40% of the stoichiometric reaction requirement, such as about 5 or 10-30%. Typically, the imidazole curing agent will be present in an amount of at least about 1%, such as about 2-20%, of the stoichiometric reaction requirement. Thus, other hardeners are typically used in amounts up to about 10-12 phr, such as about 1 or 2-12 phr, and imidazole hardeners are used in amounts of at least about 2 phr, such as about 2 phr.
Used in amounts of ~6 phr. Most often, the imidazole curing agent comprises at least about 40%, such as about 50-95%, by weight of the total cured composition. A particularly attractive advantage offered by imidazole hardeners is that a wider range of polyglycidyl resins can be used in the manufacture of tube sheets. The polyglycidyl resins are therefore primarily chosen to facilitate the production of tube sheets, for example with respect to low viscosity, low wicking, low shrinkage, high adhesion and low solvation on hollow fiber membranes. be able to. Moreover, the imidazole curing agent allows tube sheets to be formed without undue exothermic reactions and can provide tube sheets exhibiting the desired strength and chemical resistance. The liquid resin polyglycidyl resin preferably contains 1
species or more diglycidyl compounds (including glycidyl-terminated prepolymers). Optionally, the polyglycidyl resin may also contain tri- or higher functional glycidyl compounds. Triglycidyl and higher functional compounds (such as novolaks) are generally not required to impart advantageous strength and chemical resistance to tubesheets. This is because imidazole curing agents often provide sufficient cross-linking to achieve the desired properties. However, when used, triglycidyl and higher functional compounds are often less than about 10% by weight of the polyglycidyl resin, such as about 5% by weight.
For example, it constitutes about 0.01 to 2% by weight. Typically, the diglycidyl compound will be at least about 75% by weight of the polyglycidyl resin, such as about 90 or 95% to essentially
Consists of 100% by weight. Polyglycidyl resins useful in providing the tube sheets of this invention are often obtained as glycidyl reaction products between glycidyl group-forming compounds such as epihalohydrins such as epichlorohydrin and organic compounds. An example of such a glycidyl-forming reaction is, for example, a reaction involving epichlorohydrin carried out in two steps: (1) formation of a chlorohydrin intermediate and (2) formation of a glycidyl compound by dehydrohalogenation of the intermediate. It is. Such reactions are generally described in the epoxy technology literature. For example, "Handbook of Epoxy Resins"
(1967). Polyglycidyl resin generally has the following structure can be characterized by the presence of multiple glycidyl groups. The organic compound forming the glycidyl resin can be an aliphatic hydrocarbon and it may contain aromatic hydrocarbon groups or even have a heterocyclic structure. Organic compounds can be characterized by having active hydrogen groups, such as alcohol or amine groups, which hydrogens are replaced by glycidyl groups. Such active hydrogen alcohol and/or amine groups can even be present in heterocyclic structures such as triazines or hydantoins. Among the more preferred polyglycidyl resins useful for obtaining the tube sheets of the present invention, glycidyl-forming compounds such as epichlorohydrin and bisphenol A, resorcinol, catechol, hydroquinone, phloroglucinol, 4,4'-dihydroxy Benzophenone, 1,1-bis(4-hydroxyphenyl)ethane, bis(2-hydroxynaphthyl)methane, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-dihydroxydiphenylsulfone , ethylene glycol, propylene glycol, butanediol, pentanediol, isopentanediol, linoleic acid dimer,
poly(oxypropylene) glycol, 2,4,
4'-trihydroxybisphenyl, 2,2',4,
4'-tetrahydroxybisphenyl, bisresorcinol F, 2,2',4,4'-tetrahydroxybenzophenone, bisphenol hexafluoroacetone, aniline, p-aminophenol, isocyanuric acid, hydantoin, 1, 1', 2,
2'-tetra(p-hydroxyphenyl)ethane,
Phenol-formaldehyde novolac, o-
All polyglycidyl resins including glycidyl reaction products with any compound selected from cresol-formaldehyde novolaks, cycloaliphatic alcohols and mixtures thereof.
These reactant compounds can be substituted, for example, with hydroxyl groups or halogen groups such as fluorine, chlorine and bromine. One such substituted organic compound is tetrabrominated bisphenol-A. Preferably, the polyglycidyl resin includes a glycidyl-forming compound such as the glycidyl reaction product of epichlorohydrin and phenol-formaldehyde novolak or bisphenol-A. Polyglycidyl resin reaction products based on phenol-formaldehyde novolacs are sometimes referred to as polyglycidyl ethers of bisphenol-F, as bisphenol-F epoxy resins, or as polyglycidyl ethers of phenol-formaldehyde novolacs. Most preferably, the polyglycidyl resin includes a glycidyl reaction product of bisphenol-A and a glycidyl-forming compound. The preferred polyglycidyl resin is commonly referred to as diglycidyl ether of bisphenol-A (DGEBA) or bisphenol-A epoxy resin, and it generally has the structural formula (where n is often between 0 and 1, such as between 0.01 and 0.5). In the epoxy art, polyglycidyl resins are commonly characterized by "epoxide equivalent weight" or "epoxy equivalent weight," which is the weight in grams of polyglycidyl resin containing one gram equivalent of epoxy. Therefore, in a diglycidyl compound, the "epoxy equivalent weight" is half the molecular weight of the compound. Often the polyglycidyl resins used in making the tube sheets of the present invention have an "epoxy equivalent weight" of about 75 to 300 grams, such as about 125 to 250 grams, and most often about 150 to 200 grams. Attractive polyglycidyl resins have an "epoxy equivalent weight" of about 165-185 grams. In general, an important consideration in the selection of polyglycidyl resins is to ensure that the liquid resin has appropriate rheology (viscosity and flow) to enable formation of tube sheets. Therefore, the polyglycidyl component is often selected to have an "epoxy equivalent weight" such that it provides a liquid resin with suitable rheology. The liquid resin may also contain monoglycidyl compounds. Commercially available polyglycidyl resins often contain monoglycidyl compounds as impurities or additives. Monoglycidyl compounds often serve to reduce the viscosity of liquid resins. Because monoglycidyl compounds are reactive with the curing agent, they are included in the cured epoxy structure. Monoglycidyl compounds also serve to stop the curing reaction. Therefore, if high strength and chemical resistance tube sheets are essential, all monoglycidyl compounds should be no more than about 10% by weight of the polyglycidyl resin, e.g., essentially 0 to 5% by weight. is preferred. Examples of monoglycidyl compounds are butane glycidyl ether, pentane glycidyl ether, phenyl glycidyl ether, glycidyl ether of 2-ethoxyhexanol, and others. The liquid resin may contain other polymeric materials such as phenolic resins, polycarbonates, polysulfones, polyimides, polyamides, and the like. However, these polymeric materials may be less than about 50% by weight of the polyglycidyl resin, e.g.
Preferably, it is present in an amount up to % by weight, such as from about 0 to 10%. This liquid resin contains other ingredients such as plasticizers, bonding promoters, curing accelerators, thickeners,
Dyes, pigments and inorganic or organic fillers may be included. Plasticizers include phthalate esters (eg, dioctyl phthalate), tricresyl phosphate, and others. Bonding promoters include tertiary amines such as benzyldimethylamine, N-methylmorpholine, dimethylaminopropylamine, and others. Accelerators include resorcinol, nonylphenol, bisphenol-A, triphenyl phosphate, toluenesulfonic acid, lactic acid, salicylic acid, and others. Thickening agents include very finely divided solids such as colloidal silica, clays, and the like. Fillers can be used to reduce the amount of polyglycidyl resin required per unit volume of liquid resin. If used, the filler may often constitute up to about 70% by volume of the liquid resin, such as about 2-60%, such as about 5-50%. The filler should not be of such small particle size or high surface area per unit volume that it unduly increases the viscosity of the liquid resin. Therefore, most often the filler is at least about 2 or 5μ,
For example, it has an average particle size of about 5 to 150 or 200 microns. Examples of fillers include inorganic materials such as silica, alumina, aluminum, iron, iron oxide, ceramics, etc., chemically combined inorganic and organic materials such as organically modified silica, or organic materials such as phenols, polycarbonates, polyurethanes,
Mention may be made of solid polymers including polyureas, polysulfones and others. The filler should not unduly settle out of the liquid resin during tube sheet formation. Preferably the density of this filler is about 7
g/cm ³ or less, for example about 1 to 5 g/cm ³ . Preferably, the liquid resin has a viscosity sufficient to maintain the filler in suspension at least for a sufficient period of time to form the liquid resin into a substantially tube sheet form. If desired, the curing composition can contain at least one other curing agent in addition to the imidazole curing agent. Such other curing agents have greater reactivity with glycidyl moieties than imidazole curing agents have. This other curing agent is preferably non-reactive with the imidazole curing agent. The other curing agent in this curing composition is sufficient to increase the viscosity of the liquid resin to maintain the filler in suspension without undue settling prior to curing of the remainder of the resin with the imidazole curing agent. It is made to exist in a large amount. Therefore, the viscosity of the liquid resin is low enough for tube sheet formation, and the viscosity of the liquid resin is rapidly increased after the liquid resin is placed in tube sheet form to eliminate undue filler loading. Sedimentation can be excluded. Preferably, the amounts of other components in the curing agent are insufficient to result in undue exotherm of the resin and undue reduction of cross-linking provided by the imidazole curing agent. Often, the weight ratio of other curing agent to imidazole curing agent in the curable composition is from about 0.01:1 to 1:1, such as from about 0.1:1 to 0.75:
It is 1. Any suitable curing agent may find use as another curing agent in the total curable composition. Polyamines and modified polyamine curing agents are generally preferred. The liquid resin can be formed into tube sheets by any suitable method. For example, a liquid resin may be placed on the ends of a plurality of hollow fiber membranes and the hollow fiber membranes may then be assembled, such as in U.S. Pat.
It can be in the form of a bundle as disclosed in each specification of No. 3690465. In this type of assembly, the ends of the hollow fiber membranes are joined together to form an integral resin tube sheet. Generally, in these methods, the liquid resin has a temperature of about 5000 ~
Preferably it exhibits a viscosity of 100,000, preferably about 5,000 to 50,000 centipoise. A thickening agent is often desirable in order to produce a mixture that is sufficiently thixotropic to prevent undue flow of liquid resin when it is placed at the end of a hollow fiber membrane.
For example, thickeners can be used in amounts of 0.01 to 0.5% by weight of the liquid resin. A more preferred method of tube formation, due to the simplicity of the process and the absence of complex molding equipment, is to mold the liquid resin around a preformed bundle of hollow fiber membranes. In these methods, the ends of the hollow fiber membrane holes are generally sealed to prevent liquid resin from being drawn into the holes, for example, or the hollow fiber membranes are looped and the bundle of hollow fiber membranes is placed in a mold. . The liquid resin can then be introduced into the mold and formed into a substantially tube sheet configuration. This resin is then allowed to solidify. When molding a liquid resin to form a tube sheet, the viscosity of the liquid resin at 25°C is approximately
Below 15,000 centipoise, often around 200 or 500 ~
15,000, such as about 500 to 1200 centipoise. Molding can be carried out at elevated temperatures to reduce the viscosity of the liquid resin. However, excessively high temperatures may accelerate the curing reaction of the resin, and this may result in undesirable temperatures resulting in a rapid curing rate. Therefore, the temperature of the liquid resin during molding is approximately 45℃
For example, the temperature is about 15° to 40°C. Any suitable curing schedule for the resin can be applied to the tube sheet production of the present invention. Curing of liquid resins often proceeds in three stages: a first initiation of curing, a second solidification, and a third final cross-linking. In these cases, the conditions to which the resin is exposed during curing can affect the rate of curing, the peak temperature that appears during curing of the resin, and the degree of crosslinking of the resin. Often hardening is e.g. 10
Although starting at ambient temperatures of ~30°, it may be desirable to supplement the liquid resin with heat during the early stages of curing to help initiate the curing reaction. Preferably, the temperature is less than a temperature such that the reaction rate is so fast that very little of the heat generated cannot be dissipated and unreasonably high temperatures are generated which further accelerate the reaction rate. It is low. This phenomenon is referred to herein as exotherm, and the peak temperature during curing is referred to as the peak exotherm temperature. The rate at which curing is initiated can affect the peak temperature achieved during the exotherm. Preferably, the temperature of the liquid resin during the initial stages of curing is such that undesirable peak exothermic temperatures are not produced. The peak exotherm temperature of the curing reaction should be below the temperature at which the hollow fiber membrane is unduly affected with respect to strength, chemical resistance and/or permeability. Often, the peak exothermic temperature of the curing reaction is at least 10°C or 20°C below the glass transition temperature of the hollow fiber membrane. When supplemented with heat, the temperature of the liquid resin is typically up to about 45°C, such as about 25°C or 30° to 40°C. The solidification stage of the curing reaction is usually carried out at elevated temperatures due to the heat generated during the curing reaction. If necessary, heat can be supplemented to the cured resin to provide the desired reaction rate. However, once initiated, the curing reaction usually proceeds to solidification of the resin without the need for heat supply. Advantageously, the peak temperature during solidification is at least 10°C or 20°C lower than the glass transition temperature of the hollow fiber membrane. Sometimes the peak exothermic temperature during solidification is about 100℃ or less,
For example, about 90°C or less, such as about 25-90°C. The curing reaction slows down as it approaches completion. The reason is that the concentration of the reaction components is substantially reduced. Optionally, in the final cross-linking step, the temperature of the resin is increased, for example, to facilitate reaction component migration and to accomplish additional cross-linking (curing). This additional cross-linking, even though the amount of cross-linking is small, provides a substantial increase in the strength and chemical resistance of the tube sheet. The temperature generally used for final cross-linking is
At least as high as the peak temperature during solidification, but about 10 or 20 degrees Celsius below the glass transition temperature of the hollow fiber membrane. In the case of highly temperature stable hollow fiber membranes, the curing mass may be up to about 150°C or 170°C.
However most often the temperature is around 40°C to 80°C
℃ or 100℃. The duration of heat during the final cross-linking step of the curing reaction generally depends on the degree of cross-linking desired. The use of excessive cross-linking can make the tube sheet undesirably brittle. Frequently, the duration of this heating is sufficient to provide a substantially uniform temperature throughout the tube sheet.
Often this duration will be at least about 1 hour, such as at least about 2 hours. Duration of more than about 24 or 36 hours may be undesirable due to the time required for tube sheet forming. Preferably the duration of this heating is about 1 to 24 hours, such as about 1 to 16 hours. After a bundle of hollow fiber membranes with liquid resin at the ends is assembled or cast into a tube sheet, the tube sheet is generally cut to open the holes in the hollow fiber membrane. expose. Provides a tube sheet which exhibits highly advantageous properties, namely high strength, good chemical resistance, low and uniform wicking, etc., and which can still be formed into an acceptable tube sheet without risk of damage to the hollow fiber membrane. For this purpose, liquid resins can be formulated using a wide range of polyglycidyl resins and additive selections. For example, the tube sheets of the present invention can exhibit highly advantageous strength and chemical resistance. For example, tube sheets made from bisphenol-A and diglycidyl ether of 2-ethyl-4-methylimidazole,
It exhibits virtually no volume change when exposed to liquid ammonia, toluene, xylene or diethylbenzene. At least about 350 or 400 ^per cm2
Tensile strengths of Kg can be achieved. This tube sheet can be rigid. That is, it exhibits sufficient strength to hold its structure under stress. Often, the cured resin exhibits a Shore A hardness (ASTMD 2240) of at least about 70, such as at least about 80 or 90, and often up to about 120 or 130. Resin shrinkage during curing is generally 2 or 3
volume% or less. If even slight resin shrinkage during curing is undesirable, additional liquid resin can be added to the solid resin to provide the desired dimensions and structure. Resins typically exhibit sufficient adhesion to a wide range of materials suitable for hollow fiber membranes without unduly adversely affecting them. Since a wide range of curing conditions may be suitable for curing liquid resins with imidazole curing agents, curing conditions can be chosen to avoid undue stress in the tube sheet. Hollow fiber membrane-containing permeators in which tube sheets are commonly used generally have at least one membrane-containing permeator adapted to accept tube sheets.
an elongated tubular shell having an open end, an essentially fluid-impermeable end closure cap secured to and overlying the elongated tubular shell at the open end and having at least one fluid connection port; a plurality of generally parallel and longitudinally extending hollow fiber membranes forming at least one bundle in an elongated tubular shell, with at least one end of each hollow fiber membrane being connected in fluid-tight relation; a tube sheet embedded therein and such that the holes in the hollow fiber membrane are in fluid communication through the tube sheet;
and at least one fluid inlet port connected via an elongated tubular shell.
It is characterized by having two fluid outlet ports.
The elongated tubular shell can be of any suitable cross-sectional configuration to hold a bundle of hollow fiber membranes.
Conveniently the tubular shell has a circular cross section and the bundle of hollow fiber membranes substantially fills the cross section of the tubular shell. However, other cross-sectional configurations may also be suitable, such as rectangular, elliptical, free-form, etc. The permeator can be a single-ended or a double-ended permeator. Single-ended permeators have a tube sheet at only one end, and one or both ends of the hollow fiber membrane are embedded in the tube sheet. If only one end of each hollow fiber membrane is embedded in the tube sheet, the other end must be plugged or otherwise obstructed. In a double-ended permeator, each end of the tubular shell is provided with a tube sheet, and the hollow fiber membrane can extend from one tube sheet to the other tube sheet. Alternatively, the permeator can contain at least two separate bundles of hollow fiber membranes, with at least one bundle extending into only one tube sheet. Often, a single hollow fiber membrane bundle is used in a permeator, and at least one end of the hollow fiber membranes in the bundle is embedded in a tube sheet. The opposite end of the hollow fiber membrane may be looped back. That is, the bundle is generally U-shaped and may be embedded in the same tube sheet or the other end of the hollow fiber membrane may be plugged or embedded in another tube sheet. It's okay. If the hollow fiber membranes in the bundle are U-shaped, their ends may be segmented. As a result, a different location on the tube sheet contains each end of the hollow fiber membrane. Each of these regions on the tube sheet can be held in an essentially fluid-tight relationship, so that fluid connections between these regions can only be made by passage of fluid through the pores of the hollow fiber membrane. . This permeator can be operated in any desired manner. For example, the fluid feed mixture can be introduced into the shell and first contact the shell side of the hollow fiber membrane or it can be introduced into the pores of the hollow fiber membrane. The fluid flow pattern on the shell side of the hollow fiber membrane is either primarily transverse to the longitudinal orientation of the hollow fiber membrane or it is primarily axial to the orientation of the hollow fiber membrane. It can be a direction. If the flow on the shell side of the hollow fiber membrane is axial, it may generally be cocurrent or countercurrent to the flow in the pores of the hollow fiber membrane. The tube sheet is in a fluid tight relationship with the tube shell. This fluid-tight relationship is usually achieved by a tube seat and sealing means located between the at least one end closure cap and the tube-like shell. For example, the sealing means may be an o-ring or a gasket positioned between the side surface of the tube sheet and the inner surface of the tube shell [see, for example, U.S. Pat.
3422008, 3528553, 3702658, and 4061574]. Alternatively, a fluid-tight relationship can be provided by placing an o-ring or other gasket between the end face of the tube seat or a lateral protrusion from the tube seat and the end sealing cap [e.g., U.S. Pat. Application No. 151003, Application No. 972642 and Application No.
See each specification of No. 086211]. of the tubesheet to ensure that each hollow fiber membrane is embedded within the tubesheet and to provide a section of sufficient thickness in the tubesheet to receive, for example, a sealing o-ring or other gasket. The peripheral dimension typically extends outside the tube sheet zone through which the bundle of hollow fiber membranes extends.
That is, the tube sheet includes regions with a high density of hollow fiber membranes and regions with relatively little hollow fiber membranes. These regions may exhibit different curability, including different peak exotherm temperatures during the solidification stage of curing, due to differences in resin density between the regions, for example. The liquid resin used in the manufacture of the tube sheets of the present invention is of sufficient size to ensure the desired embedment of the hollow fiber membranes by leaving areas relatively free of hollow fiber membranes and the tube sheets are It is possible to provide sufficient area to enable a fluid-tight relationship. Most preferably,
The average circumferential dimension around the tube sheet is at least about 2% greater, such as about 5-50%, such as about 5-25%, greater than the average circumferential dimension of the tube sheet zone through which the bundle of hollow fiber membranes passes. Often, the difference between these margins is about 1 to about 15 or 20 cm. The tube sheet region containing hollow fiber membranes may contain a relatively high density of hollow fiber membranes. Typically, the density of hollow fiber membranes is expressed in terms of the packing factor, which is the percentage of a given cross-sectional area occupied by the hollow fiber membrane based on the cross-sectional dimensions of the hollow fiber membrane. Advantageously, the invention provides a high packing factor in terms of the peripheral dimensions of the bundles in tube sheets;
For example, it may be possible to produce desirable tube sheets having a bundle of packing factors of often at least about 40 or 45%, such as about 65 or 70%, and most often about 50-60%. Frequently, the tube sheets have an average cross-sectional dimension (eg, diameter for tube sheets having a circular cross-sectional configuration) of at least about 1 or 2 cm. Although this average cross-sectional dimension can be up to 1 m or more, many tube sheets are at least about 0.02 m, preferably at least about 0.05 to 1.0 m.
It has an average cross-sectional dimension of m. The length of the tube sheet (measured in a direction parallel to the general orientation of the bundle of hollow fiber membranes through the tube sheet) is generally adequate to withstand the total pressure differential to which the tube sheet may be subjected in the intended separation operation. It is sufficient to provide strength. That is, the length used may depend on the strength of the resin. Additionally, the tube sheet should be of sufficient length to provide sufficient contact between the tube and the resin to ensure an essentially fluid-tight relationship. Therefore, the adhesion between the tube and tube sheet material also affects the desired tube sheet length. Often,
This tube sheet has a length of at least approximately 2
cm, e.g. about 2-100 cm, e.g. about 2-30 or
It is 50cm long. The volume of liquid resin used to make the tube sheets of the present invention will vary depending on the size of the tube sheets and the proportion of the tube sheet volume occupied by the hollow fiber membrane. Often times more than about 1000 or 1500 g of liquid resin is required for the manufacture of tube sheets, which minimize the risk of unacceptably high peak exotherm temperatures during the solidification stage of the curing reaction. manufactured in two or more stages. Alternatively and more preferably, fillers and the like are used to reduce the amount of polyglycidyl resin and curing composition required to form the tube sheet and to absorb the heat generated by the curing reaction. Hollow fiber membranes can be made from any synthetic or natural material suitable for fluid separation or for supporting materials that perform fluid separation.
The selection of materials for the hollow fibers is governed by the heat-resistant chemical resistance and/or mechanical strength of the hollow fiber membrane and the fluid separation to which it is intended for use, and the operating conditions to which it is subjected. It may be based on other factors. The hollow fiber forming material can be inorganic, organic or an organic-inorganic mixture. Typical inorganic materials include glasses, ceramics, celmets, metals, and others. Organic materials are usually polymers. Typical polymers that may be suitable for hollow fiber membranes include substituted and unsubstituted polysulfones, styrene-containing copolymers such as acrylonitrile-styrene copolymers, styrene-butadiene copolymers, and styrene-vinylbenzyl halide copolymers. poly(styrene), polycarbonate, cellulose copolymers such as cellulose acetate, butyrate, cellulose propionate, ethylcellulose, methylcellulose, nitrocellulose and others, polyamides and polyimides including aryl polyamides, polyimides and polyamide copolymers, polyethers, polyacetals, poly(arylene oxides) such as poly(phenylene oxide), and poly(xylylene oxide),
poly(esteramide-diisocyanate), polyurethane, polyester (including polyarylate) such as poly(ethylene terephthalate),
Poly(alkyl methacrylate), poly(alkyl acrylate), poly(phenylene terephthalate) and others, polysulfides, polymers from monomers having α-olefinic unsaturation other than those mentioned above, such as poly(ethylene), poly(propylene) ), poly(butene-1), poly(4-methylpentene-1), polyvinyl such as poly(vinyl chloride), poly(vinyl fluoride), poly(vinylidene chloride), poly(vinylidene fluoride), poly(vinyl poly(vinyl esters) such as poly(vinyl acetate) and poly(vinyl propionate), poly(vinyl pyridine), poly(vinyl pyrrolidone), poly(vinyl ether), poly(vinyl ketone), poly(vinyl aldehyde) For example poly(vinyl formal) and poly(vinyl butyral), poly(vinylamine), poly(vinyl phosphate) and poly(vinyl sulfate), polyallyl, poly(benzobenzimidazole), polyhydrazide, polyoxadiazole, polytriazole , poly(benzimidazole), polycarbodiimide, polyphosphazine, etc., and copolymers containing repeating units from the foregoing, such as terpolymers of acrylonitrile-vinyl bromide-p-sulfophenyl methalylether sodium salt. and grafts and blends containing any of the foregoing. Typical substituents to provide substituted polymers include halogens such as fluorine, chlorine and bromine, hydroxyl groups, lower alkyl groups, lower alkoxy groups, monocyclic aryls, lower acyl groups, and the like. One preferred polymer for hollow fiber membranes in environments requiring strength and/or chemical resistance is a polysulfone polymer. In particular, polysulfones with aromatic hydrocarbyl-containing moieties generally have good thermal stability, are stable to chemical attack, and have an excellent combination of toughness and flexibility. Useful polysulfones are sold, for example, under the trade names "P-1700" and "P-3500" (Union Carbide), but these commercially available products have the general formula A polysulfone derived from bisphenolmethane (particularly derived from bisphenol-A) having a linear chain of (where n represents the degree of polymerization and is about 50 to 80). Another useful polysulfone is manufactured by 3M under the trade name "ASTREL 360 PLASTIC".
It is released by the company. Poly(arylene ether) sulfones are often preferred. repeating structure The poly(arylene ether) sulfone with
It is available from ICI (UK) and is also useful. Still other useful polysulfones can be prepared by polymer modification, such as by cross-linking, grafting, quaternization, and the like. Another group of polymers that may be attractive for hollow fiber membranes are copolymers of styrene and acrylonitrile or terpolymers containing styrene and acrylonitrile. Often, styrene is up to about 60 or 70 mole percent of the total monomers in the polymer, such as about 10 to 50 mole percent. Advantageously, the acrylonitrile monomer comprises at least about
20 mol% e.g. about 20 to 90 mol% often about 30 to 90 mol%
Consists of 80 mol%. Other monomers that may be used with styrene and acrylonitrile, for example to form terpolymers, include olefin monomers such as butene, butadiene, vinyl chloride, and the like. The copolymer or terpolymer of styrene and acrylonitrile is at least about
It has a weight average molecular weight of 25,000 or 50,000, such as about 75,000 to 500,000 or more. Still other groups of polymers that may be particularly attractive are polymers and copolymers derived from hexamethylene diamine, including copolymers with dicarboxylic acids such as terephthalic acid, and substituted poly(phenylene oxides) such as Alkylated, alkylbrominated, arylbrominated and brominated substituents on poly(phenylene oxide) and primary and secondary
Polymers and copolymers of phenylene oxide, including reaction products between phenylene oxide and bases. The cross-sectional dimensions of this hollow fiber membrane can be selected from a wide range. However, the hollow fiber membrane should have sufficient wall thickness to provide sufficient strength and the pores (bore) should be sized so as not to impose an unreasonably high pressure drop on the fluid passing through the pores. It should be large enough so that no embolization occurs due to the presence of solids in the fluid passing through it. Often the outer diameter of the hollow fiber membrane is at least about 20μ, such as at least about 30μ, and fibers of the same or different outer diameters can be included in the bundle. The outer diameter of hollow fiber membranes is often around 800μ or 1000μ
cannot be exceeded. This is because such large diameter hollow fibers can provide a less desirable hollow fiber surface area ratio per unit volume of permeator. Preferably the outer diameter of the hollow fiber membrane is about 50-800μ,
and most preferably about 150 or 300 to 600 or 800μ. Generally, the wall thickness of hollow fiber membranes is at least 5μ, and in some hollow fiber membranes, the wall thickness can be up to about 200 or 300μ.
For example, it can be about 50-200μ. For hollow fiber membranes made from materials with lower strength, it may be necessary to use larger hollow fiber diameters and wall thicknesses to impart sufficient strength to the hollow fiber membrane. Although the walls of hollow fiber membranes are essentially solid, they may also have substantial void volume. If voids are desired, the density of the hollow fiber membrane can be essentially the same across its walls, i.e. the hollow fiber membrane can be isotropic, or the hollow fiber membrane can be The hollow fiber membrane can be characterized in that it has at least one relatively dense region within its wall thickness in the barrier flow relationship of the membrane, ie the hollow fiber membrane is anisotropic. The hollow fiber membranes are generally arranged in parallel in one or more bundles within the shell. Generally, at least about 10,000 hollow fibers, and often a substantially larger number, such as up to 1 million or more, are contained in the permeator. For example, the fibers in the bundle may be relatively linear, or they may be spirally wound, as disclosed, for example, in US Pat. No. 3,422,008. The following examples are given to further illustrate the invention and are not intended to limit it. In the examples, all parts and percentages of liquids and solids are by weight and parts and percentages of gases are by volume, unless otherwise stated. Example 1 An outer skin having an outer diameter of approximately 450μ, an inner diameter of approximately 150μ and polysulfone (P-3500, Union
About 1,500 to 1,600 anisotropic hollow fiber membranes, about 37 cm long, made from Carbide Corporation (available from Carbide Corporation) are assembled into bundles having a generally circular cross-sectional structure. A section of plastic pipe with an internal diameter of about 2.5 cm and a length of about 25 cm is placed on one end of the bundle to fix the hollow fiber membrane in the form of a bundle with a circular cross-sectional structure. A similar pipe, but having a length of about 2-3 cm, is placed at the other end of the bundle. A gap of about 6-7 cm exists between these pipes. The area of the hollow fiber membrane in the gap is sprayed with a 2% by weight solution of Sylgard 184 (poly(dimethylsiloxane), available from Dow Corning) in isopentane. Remove the short piece of pipe and trim the ends of the bundle with a sharp razor blade so that they are perpendicular to the orientation of the bundle. Household waterproofing cement (DUCO Cement, available from DuPont) is applied to each exposed end of the hollow fiber membrane bundle to seal the pores in the hollow fiber membrane. The cement is then allowed to dry. Prepare a mold for forming tube sheets. The mold has a recess approximately 5.6 cm in diameter and approximately 4.4 cm deep. A concentric hole approximately 2.5 cm in diameter and 2.5 cm in length extends from this recess. At the bottom of the concentric hole is an aluminum plug with a thickness of approximately 0.75 cm. The outside of the mold is surrounded by an electrical heating unit. The mold recess and concentric holes are prepared for casting by coating with a silicone-based mold release agent. The exposed end of the bundle is inserted into the mold recess so that the end of the bundle extends into the concentric hole and contacts the aluminum plug. Heat the mold to about 35℃
Heat to. The liquid resin has an "epoxy equivalent weight" of 185 and
The diglycidyl ether of bisphenol-A (Ciel.
2-Ethyl-4-methylimidazole (available as Epon 826 from Huaique Chemical Company) having a viscosity of approximately 6000 centipoise at 25°C and a purity of approximately 90-92% (available as Epon 826 from Huaique Chemical Company) Contains. This liquid resin is poured into the mold recess and an insulator is placed around the bundle at the top of the mold. This liquid resin solidifies overnight (about 16 hours or more). The temperature of the mold is then gradually increased to about 150° C. over about 5 hours. The temperature of about 150℃ is about 3
Hold for a period of time to achieve the desired cross-linking, and then allow the mold to cool to normal room temperature conditions (approximately 25°C). The cast tube sheet was removed from the mold and the protrusions for the tube sheet created by the concentric holes in the mold were cut with a hack saw and then trimmed with an electric planer and then a razor blade to form hollow fibers. Expose the membrane pores. This tube sheet exhibits good strength and chemical resistance. This resin adheres to the hollow fiber membrane. A particularly useful method for evaluating the potential suitability of a curable composition for use in forming tube sheets is to cast a resin mass approximating the amount needed to form tube sheets and observe the curing characteristics of the resin mass. It is to be. For example, the resin may be less desirable if relatively low temperatures produce accelerated reaction rates that result in excessively high peak exothermic temperatures. Also,
The resin may be less desirable if high temperatures are required to initiate the cure reaction or produce solidification. Advantageously, the imidazole curing agents of the present invention provide resins that can be cured without unduly high onset temperatures or unduly excessive peak exotherm temperatures. The following examples illustrate the suitability of compositions containing various polyglycidyl resins and imidazole curing agents for the formation of tube sheets. Examples 2-18 Various polyglycidyl resins and imidazole curing agents are mixed and cured to determine their suitability for forming tube sheets. In one aspect, these examples illustrate the ability of a liquid resin to substantially cure at a temperature below that which produces rapid acceleration of the curing reaction, and thus the temperature that produces rapid acceleration of the curing reaction. . That is, for example, a certain liquid resin may be heated to a lower temperature during the solidification stage, e.g.
C. or below 40.degree. C. and can then be subjected to further curing in a cross-linking step at higher temperatures without the risk of producing an unduly high peak exotherm temperature. The results are given in the table. The following abbreviations are used in the tables: 826: "Epon 826", an unmodified bisphenol-A epoxy resin available from Shell Chemical Company having a viscosity of about 65-95 poise at 25°C and an epoxy equivalent weight of about 180-190. Epon 828'', unmodified bisphenol-A epoxy resin XD7817, available from Schiel Chemical Company, having a viscosity of about 100-160 poise at 25°C and an epoxy equivalent weight of about 185-192: from Dow Chemical Company. Available epoxy novolak resins (bisphenol-F epoxy resins) EMI: 2-ethyl-4-methylimidazole PDF: Bis(2-dimethylaminoethoxy)methane BDMAP: 1,3-bis(dimethylamino)-
2-propanol TETA: triethylenetetramine IMD: imidazole 2EI: 2-ethylimidazole 4PI: 4-phenylimidazole 4NI: 4-nitroimidazole 1AI: 1-acetylimidazole ND: undissolved imidazole hardener Temperature program: ambient temperature is not necessarily the temperature of the resin.

[Table] Examples 19 to 21 Tube sheets are prepared by substantially repeating the procedure of Example 1, except that the polyglycidyl resin and imidazole curing agent listed in the Table are used. In all examples the curing agent is approximately 7 phr.

[Table] Midazole

Table: Le Epon 8132 is a glycidyl ether of bisphenol-A, available from Siel Chemical Company, having a viscosity of about 170 to 225 poise at 25°C and an epoxy equivalent weight of about 190 to 198, by weight. % and a viscosity of 5 to 7 poise at 25°C and approximately 195
A 20% by weight mixture of monofunctional reactive diluent components with an epoxy equivalent weight of ~215. Example 22 An outer skin having an outer diameter of approximately 560μ and manufactured from polysulfone (P-3500, available from Union Carbide Corporation)
A bundle of 66,000 hollow fiber membranes is placed into an aluminum mold sprayed with silicone mold release agent. The hollow fiber membrane is sealed by melting at the ends of the bundle placed in the mold. This mold has a slightly tapered cylindrical upper chamber with a maximum diameter of approximately 24.5 cm and a depth of 10 cm at the top, and a concentric lower chamber with a diameter of 20.3 cm and a depth of 7.6 cm. ing. This mold has a diameter of about 10cm at the bottom
It has concentric plug holes. This mold is electrically heated. Orient the bundle vertically and fit the bottom edge of the bundle into the lower chamber of the mold (approximately 55% packing factor based on the diameter of the lower chamber) and bend out at the top of the mold. Heat this mold to approximately 35°C. Approximately 5400 g Epon 826600 g neopentyl glycol diglycidyl ether and 3900 g finely divided (-325 US standard mesh) aluminum powder (available as Reynolds #120 Aluminum Powder from Reynolds Metal Company)
and heat this to about 35°C.
about 240 g of Versamide 140 (a polyamide reactive resin having a viscosity of about 2 to 6 poise at 75°C and an amine number of about 370 to 400 and available from General Mills) and 210 g of 2-ethyl-4 - Methylimidazole (EMI-24, available from Huaique Chemical Company) separately at approximately 35°C.
and then mixed with a polyglycidyl resin-containing mixture to form a liquid resin. Mixing takes approximately 5-10 minutes. Then pour this liquid resin into the mold. Approximately 3 to 4 injections of liquid resin are required to fill the mold recesses. This is because the liquid resin permeates into the bundle. Approximately 100g
Place the remaining liquid resin in the refrigerator. Above the level of the liquid resin in the mold, tie a thick cord around the bundle so that the diameter of the bundle is approximately 20-22 cm. The cord is then slid down the bundle to just below the level of the liquid resin. The mold is kept at 35°C for 18-20 hours during which time the resin solidifies and shrinks slightly. Place the refrigerated liquid resin on top of the solidified resin and hide the tube sheet. Next, increase the mold temperature to 45℃.
time, then 2 hours at 55°C, then 2 hours at 65°C, then 2 hours at 75°C, and finally 2 hours at 100°C. The mold is allowed to cool to room temperature and the tube sheet is removed from the mold. The sides of the bundle of tube sheets exhibit moderate wicking, eg, less than about 5 cm, which is relatively uniform throughout the bundle. The tube sheet portion formed by the lower chamber is sectioned with a hand saw approximately 3-7 cm from the portion formed by the larger chamber of the mold to expose the hollow fiber membrane. That is, the surface of the tube sheet is formed.
The tube sheet surface is then smoothed with an electric planer and trimmed with a reggie knife to ensure that the holes in the hollow fiber membrane are open to fluid flow. EXAMPLE 23 The procedure of Example 22 is essentially repeated, except that epoxysilane-coupled silica having a surface area of about 2 cm ² per gram is used in place of the aluminum powder.

Claims (1)

Claims: 1. Embedded therein are a plurality of hollow fiber membranes suitable for fluid separation, adapted to be positioned in fluid-tight relationship in a permeator, and having a structural formula of polyglycidyl resin. (wherein R ₁ is hydrogen, alkyl of 1 to about 12 carbon atoms, aralkyl of 6 to about 15 carbon atoms, lower acyl or monocyclic or bicyclic aryl, and R ₂ , R ₃ and R ₄ are hydrogen, halogen, hydroxy, nitro, alkoxy of 1 to about 6 carbon atoms, alkyl of 1 to about 12 carbon atoms, or aralkyl of 6 to about 15 carbon atoms , lower acyl or monocyclic or bicyclic aryl) and on a stoichiometric basis from about 2 to about the amount required for complete reaction of the epoxy moiety of the liquid resin with one ring nitrogen. A tube sheet containing a liquid resin cured epoxy resin containing an imidazole curing agent provided in an amount of 40%. 2. The tube sheet according to claim 1, wherein at least one of R ₁ , R ₂ , R ₃ and R ₄ is other than hydrogen. 3. The tube sheet according to claim 2, wherein the imidazole curing agent is 2-ethyl-4-methylimidazole. 4 Imidazole curing agent is polyglycidyl resin
A tube sheet according to claim 1, 2 or 3, provided in an amount of about 2 to 12 parts by weight per 100 parts by weight. 5 The polyglycidyl resin contains a glycidyl-forming compound, bisphenol A, resorcinol, catechol, hydroquinone, phloroglucinol,
4,4'-dihydroxybenzophenone, 1,1-
Bis(4-hydroxyphenyl)ethane, bis(2-hydroxynaphthyl)methane, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-
Dihydroxydiphenyl sulfone, ethylene glycol, propylene glycol, butanediol, pentanediol, isopentanediol,
Linoleic acid dimer, poly(oxypropylene) glycol, 2,4,4'-trihydroxybisphenyl, 2,2',4,4'-tetrahydroxybisphenyl, bisresorcinol F, 2,2' ,4,
4′-tetrahydroxybenzophenone, bisphenol-hexafluoroacetone, aniline, p
- selected from aminophenol, isocyanuric acid, hydantoin, 1,1',2,2'-tetra(p-hydroxyphenyl)ethane, phenol-formaldehyde novolac, o-cresol-formaldehyde novolac, or mixtures thereof. 2. A tube sheet according to claim 1, comprising a glycidyl reaction product with a compound containing a glycidyl compound. 6. The tube sheet of claim 5, wherein the polyglycidyl resin comprises a glycidyl reaction product of a glycidyl-forming compound and bisphenol-A or phenol-formaldehyde novolak. 7. The tube sheet of claim 6, wherein the polyglycidyl resin comprises a mixture of diglycidyl ethers of bisphenol-A. 8. Claim 1, wherein the polyglycidyl resin has an epoxy equivalent weight of about 150-200 g.
The tube sheet according to item 5 or 7. 9. The tube sheet according to claim 1, 3 or 7, wherein the liquid resin contains another curing agent. 10. The tube sheet according to claim 1, wherein the liquid resin contains aminoacetal. 11. The tube sheet according to claim 10, wherein the aminoacetal is bis(2-dimethylaminoethoxy)methane. 12. The tube sheet of claim 1, wherein the hollow fiber membranes are arranged in bundles and the packing factor of the bundle in the tube sheet, based on the circumference of the bundle, is at least about 45%. 13. The tube sheet of claim 1, wherein the tube sheet has regions relatively free of hollow fiber membranes and regions with hollow fiber membranes. 14. The tube sheet of claim 12, wherein the average circumferential dimension around the tube sheet is greater than about 5 to 50% greater than the average circumferential dimension of the tube sheet area through which the bundle of hollow fiber membranes passes. 15 Average cross-sectional dimension of approximately 0.05 to 1.0 m and approximately 2
Claims 1 and 3 having a length of ~50 cm
Or the tube sheet described in item 7. 16. The tube sheet of claim 1, wherein the hollow fiber membrane has a diameter of about 150 to 800 microns. 17 The hollow fiber membrane is made of polysulfone, polyamide,
The tube sheet according to claim 1 or 16, comprising poly(phenylene oxide) or a copolymer of acrylonitrile and styrene. 18 by introducing a plurality of hollow fiber membranes and a liquid resin into a mold and then curing the liquid resin so that the liquid resin has the structural formula of a polyglycidyl resin. (wherein R ₁ is hydrogen, alkyl of 1 to about 12 carbon atoms, aralkyl of 6 to about 15 carbon atoms, lower acyl or monocyclic or bicyclic aryl, and R ₂ , R ₃ and R ₄ are hydrogen, halogen, hydroxy, nitro, alkoxy of 1 to about 6 carbon atoms, alkyl of 1 to about 12 carbon atoms, or aralkyl of 6 to about 15 carbon atoms; lower acyl or monocyclic or bicyclic aryl) and about 2 to 40% of the amount required for complete reaction of the epoxy moiety of the liquid resin with one ring nitrogen on a stoichiometric basis. 1. A process for producing a tube sheet having a plurality of hollow fiber membranes suitable for fluid separation embedded therein, characterized in that it includes a given amount of an imidazole curing agent. 19. The method of claim 18, wherein the liquid resin has a viscosity of less than 15,000 centipoise at 25°C when introduced into the mold. 20. The method of claim 18, wherein the liquid resin is introduced into the mold at a temperature of about 45°C or less. 21. The method of claim 18, wherein the temperature of the resin is increased to achieve additional cross-linking as the curing reaction approaches completion. 22 The temperature used for final cross-linking is approximately 40° ~
22. The method according to claim 21, wherein the temperature is 100°C. 23. The method of claim 18, wherein at least one of R ₁ , R ₂ , R ₃ and R ₄ is other than hydrogen. 24 Claim 19, wherein the imidazole curing agent is 2-ethyl-4-methylimidazole
The method described in section. 25 Imidazole curing agent is polyglycidyl resin
Provided in an amount of about 2 to 12 parts by weight per 100 parts by weight,
The method according to claim 20. 26 The polyglycidyl resin contains a glycidyl-forming compound, bisphenol A, resorcinol, catechol, hydroquinone, phloroglycinol,
4,4'-dihydroxybenzophenone, 1,1-
Bis(4-hydroxyphenyl)ethane, bis(2-hydroxynaphthyl)methane, 2,2-bis(4-hydroxyphenyl)butane, 4,4'-
Dihydroxydiphenyl sulfone, ethylene glycol, propylene glycol, butanediol, pentanediol, isopentanediol,
Linoleic acid dimer, poly(oxypropylene) glycol, 2,4,4'-trihydroxybisphenyl, 2,2',4,4'-tetrahydroxybisphenyl, bisresorcinol F, 2,2' ,4,
4'-tetrahydroxybenzophenone, bisphenol-hexafluoroacetone, aniline, p
- selected from aminophenol, isocyanuric acid, hydantoin, 1,1',2,2'-tetra(p-hydroxyphenyl)ethane, phenol-formaldehyde novolac, o-cresol-formaldehyde novolac, or mixtures thereof. 19. The method of claim 18, comprising a glycidyl reaction product with a compound that is 27. The method of claim 26, wherein the polyglycidyl resin comprises a reaction product of a glycidyl-forming compound and bisphenol-A or phenol-formaldehyde novolak. 28 Polyglycidyl resin is bisphenol-A
28. The method of claim 27, comprising a mixture of diglycidyl ethers. 29 Claim 1, wherein the polyglycidyl resin has an epoxy equivalent weight of about 150 to 200 g.
The method described in Section 8. 30. The method of claim 18, wherein the liquid resin contains other curing agents. 31. The method of claim 18, wherein the liquid resin contains an aminoacetal. 32. The method of claim 18, wherein the aminoacetal is bis(2-dimethylaminoethoxy)methane.