EP0454761A1 - Heteropolycondensats d'acide silicique modifies organiques - Google Patents

Heteropolycondensats d'acide silicique modifies organiques

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Publication number
EP0454761A1
EP0454761A1 EP90902451A EP90902451A EP0454761A1 EP 0454761 A1 EP0454761 A1 EP 0454761A1 EP 90902451 A EP90902451 A EP 90902451A EP 90902451 A EP90902451 A EP 90902451A EP 0454761 A1 EP0454761 A1 EP 0454761A1
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EP
European Patent Office
Prior art keywords
groups
fluid
silicic acid
formula
organic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90902451A
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German (de)
English (en)
Inventor
Bradley Keith Coltrain
William Edward Pascoe
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Eastman Kodak Co
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Eastman Kodak Co
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Publication of EP0454761A1 publication Critical patent/EP0454761A1/fr
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28042—Shaped bodies; Monolithic structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/262—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon to carbon unsaturated bonds, e.g. obtained by polycondensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
    • B01J20/28011—Other properties, e.g. density, crush strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28064—Surface area, e.g. B.E.T specific surface area being in the range 500-1000 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/281—Sorbents specially adapted for preparative, analytical or investigative chromatography
    • B01J20/282—Porous sorbents
    • B01J20/283—Porous sorbents based on silica
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
    • C03C1/006—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route
    • C03C1/008—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route for the production of films or coatings
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C11/00—Multi-cellular glass ; Porous or hollow glass or glass particles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/02—Polysilicates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
    • C08G77/04—Polysiloxanes
    • C08G77/06—Preparatory processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/80—Aspects related to sorbents specially adapted for preparative, analytical or investigative chromatography
    • B01J2220/82—Shaped bodies, e.g. monoliths, plugs, tubes, continuous beds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Definitions

  • This invention relates to improved silicic acid heteropolycondensates which contain organic radicals. It also pertains to a method for their formation, and the use of such condensates.
  • Silicic acid heteropolycondensates have been known in the art for quite some time. In general, these products are produced by a low or mild temperature process, which comprises hydrolysis and condensation. The process is performed using one or more silanes (having 2-4 hydrolyzable groups) as the starting material. The process is illustrated below using a triethoxysilane as the raw material on which the process is conducted. In the equations which follow, R is a non-hydrolyzable organic group, such as an alkyl or aryl group.
  • Equation (1) illustrates complete hydrolysis of the triethoxysilane. As shown, for each molar equivalent of trialkoxysilane which is completely hydrolyzed, three molar equivalents of water are consumed. The hydrolyzed product is comparatively unstable; it tends to rapidly undergo the condensation process illustrated by Equation (2). It is known in the art that condensation can begin to occur before all three alkoxide groups are hydrolyzed. Equation (2) is an oversimplification. It illustrates condensation between two silanol groups, each of which were formed in step (1). As shown by the unsatisfied valences, further condensation between other groups can occur. It is known in the art that such continued condensation results in products known as sol—gels.
  • the term "sol— el” refers to a glassy solid mixture of organic-modified silicic acid heteropolycondensates formed by the hydrolysis and condensation of one or more silanes which contain one or two non—hydrolyzable groups (such as R in the equations above), and in which the remainder of silicon valences are satisfied by hydrolyzable groups.
  • these polycondensate products comprise a network of interconnected silicon-containing chains, wherein the silicon atoms are connected by oxygen. These products are polymeric; but because they are in the solid state, molecular weight determinations cannot be made.
  • Equation (2) each condensation of two silanol groups results in the splitting out of one molecule of water.
  • Linear polycondensates are produced from reactants solely composed of silanes having two hydrolyzable groups per molecule.
  • starting materials which contain one or more silanes with three or four hydrolyzable groups yield crosslinked polycondensates.
  • crosslinked, silicic acid condensates can contain residual hydrolyzable groups (e.g., alkoxy radicals) or residual silanol groups. It is known in the art that silicic acid heteropoly ⁇ condensates (which are not organic modified, i.e., which do not contain organic groups) can be dried using fluids above their supercritical temperatures; Tewari et al, Materials Letters, Vol. 3, number 9, 10, pp.
  • a problem with prior art silicic acid heteropolycondensates is they contain residual silanol groups and residual hydrolyzable groups of the type discussed above. Such groups can have a deleterious effect on the materials of the prior art.
  • this problem can be solved by removal of such groups by treating heteropolycondensates with a fluid in the supercritical state.
  • use of the supercritical liquid does not remove organic groups which are bonded to silicon atoms in such condensates by a silicon—to—carbon bond.
  • the organic modified silicic acid heteropolycondensates produced by our upgrading process have enhanced oxygen permeability, which makes them useful for forming films for use in oxygen permeable systems.
  • monolithic glassy, porous solids can be produced by a process which comprises contacting an organic modified silicic acid sol in a mold with a fluid above its critical temperature and pressure.
  • this invention has several aspects. First, it pertains to a method of upgrading an organic modified silicic acid heteropolycondensate by removal of residual silanol and/or hydrolyzable groups, said method comprising contacting the polycondensate to be upgraded with a fluid above the critical temperature and pressure of the fluid, for a time sufficient to remove silanol or hydrolyzable groups from the condensate.
  • the hydrolyzable groups that are removed are alkoxide groups
  • the supercritical fluid is the alcohol corresponding to the alkoxide radicals.
  • the products of the upgrading process are free or substantially free of silanol and hydrolyzable groups.
  • substantially free means that no more than about 5% of the groups bonded to silicon are hydrolyzable or silanol groups.
  • this invention comprises a preparative process.
  • the preparative process of this invention comprises a hydrolysis/condensation reaction of the type exemplified by Equations (1) and (2) above, followed by an upgrading process which removes residual hydrolyzable and silanol groups from the polycondensate intermediate.
  • the upgrading process of this embodiment is of the type described above.
  • the preparative and upgrading embodiments of this invention are directed to the preparation of organic modified, silicic acid heteropolycondensates products of two types which comprise a third embodiment of the invention, the first type of product are powders.
  • the first type of product are powders.
  • at least about 90% of the repeating silicon-containing units have at least one organic group (R) bonded to the silicon atom.
  • the second type of products are porous, glassy monolithic solids.
  • “monolithic” means cast or otherwise formed in a single piece.
  • the monoliths of this invention can be in the form of rods or have another shape, e.g., lenticular.
  • the monoliths of this invention are glass-like, (i.e., non-crystalline) opaque or transparent solid bodies.
  • a typical rod has a diameter of 0.5 to 25 millimeters and a length of 10 to 125 millimeters. Products outside of the size range can be produced.
  • the monoliths of this invention can be used as adsorbents, e.g., as substrates for chromatographic separations.
  • the Figure in the drawing is a plot, graphically comparing oxygen permeability of a non-monolithic product of this invention, with a similar material which has not upgraded by the process provided herein.
  • Oxygen permeability values are on the "y" axis, while the oxygen concentration values are plotted along the "x" axis.
  • an organic modified silicic acid heteropolycondensate (i) containing phenyl groups, and (ii) produced by the process of this invention has a much greater oxygen permeability when compared to the permeability of a similar material not subjected to the upgrading process of this invention.
  • the linearity of response with the product of this invention appears to be slightly less than with the comparison material. This slight decrease in linearity does not materially detract from the utility of the product.
  • this invention comprises a method for upgrading an organic modified silicic acid heteropolycondensate by reducing the number of hydrolyzable groups and/or silanol radicals in the condensate.
  • This method comprises heating said condensate at an elevated temperature, in contact with a fluid which is under high pressure, for a time sufficient to remove such groups.
  • the process is conducted above the critical temperature and pressure of the fluid.
  • the product can be recovered by separating the fluid and the volatile product(s) formed during removal of the hydrolyzable groups.
  • the process of this embodiment is referred to as the "upgrading process" of this invention.
  • the upgrading process can be conducted on a wide variety of organo odified silicic acid heteropolycondensates.
  • the applicability of the upgrading process of this invention is independent of the method employed for producing the condensate to be upgraded, provided that the polycondensate to be treated contains hydrolyzable and/or silanol groups which can be removed.
  • the preparative method comprises: (a) formation of an organic modified silicic acid condensate by a reaction which comprises hydrolysis and condensation of an organosilane, followed by (b) removal of residual hydrolyzable and/or silanol groups with a supercritical fluid. Step (b) comprises the upgrading process of this invention.
  • a preferred process within the preparative embodiment of this invention comprises: a method for preparing an organic modified silicic acid heteropolycondensate (i) having repeating silane units with the formula RSi ⁇ such that the free valences in said formula are interconnected by oxygen, and (ii) being characterized by being substantially free of hydrolyzable and silanol groups, said method comprising:
  • Step (A) comprises a preparative process of this invention.
  • Step (B) is an upgrading process of the type referred to above.
  • Step (C) comprises a product recovery step. Such a step is a desirable, but not a critical feature of the invention.
  • the third embodiment of this invention comprises an organic group—containing, porous monolithic glassy body containing the repeating units Si ⁇ and RS ⁇ , wherein R is a stable organic group, such that (a) from about 5 to about 35 mole percent of said units are RSi ⁇ , (b) said RSi ⁇ units are substantially uniformly dispersed throughout said body, and (c) said repeating units are interconnected by oxygen; said body having a surface area of from
  • this invention provides a process for producing a monolithic body of the type described above, said process comprising contacting a precursor polycondensate in a mold with a fluid above the critical temperature and pressure of said fluid, for a time sufficient to remove substantially all residual silanol and hydrolyzable groups from said sol, and subsequently venting and cooling to separate said body from said fluid and volatile by-products formed upon removal of said groups from said precursor polycondensate; said precursor condensate having been produced by hydrolysis and condensation of a mixture of silanes having the formula SiX and the formula
  • RSiX 3 wherein from about 5 to about 35 mole percent of said silanes in said mixture have the formula RSiX 3 , and wherein each X in said formulae is a hydrolyzable group, and R is a non-hydrolyzable organic group.
  • the products of this invention are organic modified; i.e., they contain organic groups. They are polymeric in nature. Linear polymers produced by this invention generally are composed of repeating
  • crosslinked, organic modified silicic acid heteropolycondensates which are upgraded by a process of this invention, have the repeating unit RSiE, wherein the unsatisfied valences are interconnected through oxygen.
  • these repeating units can be formed by a hydrolysis and condensation reaction using one or more silanes having the formula:
  • R is an organic radical bonded to silicon through carbon
  • the radicals indicated by X are alike or different and selected from hydrolyzable groups, such as alkoxides, (e.g., the alkoxide radicals referred to above), aryloxides, alkylalkoxide, alkoxyalkoxides, halides, and the like.
  • the heteropolycondensates may also contain groups derived from one or more silanes having the formulas:
  • the organic radical can be a short or long alkyl chain, either branched or unbranched, unsubstituted or substituted with groups such as alkoxy, halogen (Cl, Br or I), or amine, or the like. More typically, they are short, unbranched, or slightly branched lower hydrocarbyl alkyl groups, i.e., alkyl groups that are solely composed of carbon and hydrogen, and which contain up to about 4 carbon atoms.
  • alkoxide groups within materials of Formula II are illustrated by the following non-limiting examples: methoxide ethoxide iso-propoxide tert—butoxide sec—butoxide
  • a most preferred alkoxide of this type is tetramethoxysilane; however, other compounds of this type, such as tetraethoxysilane, can also be used.
  • Compounds of Formula II which are useful in this invention include aryloxides. Thus, compounds such as tetraphenoxysilane and diethoxydiphenoxy— silane can be used in this invention. Generally speaking, the aryloxy groups can be the phenoxy group or alkylphenoxy groups having up to about 14 carbon atoms. The alkyl substituents may be of the types discussed above. For powdered, i.e., non-monolithic, products the amount of Formula II compounds used in this invention is set forth in Table I.
  • One or more materials having Formula III can be added. These materials can be included within the reaction mixture to add linearity to the resultant heteropolycondensate, or to add more organic groups to the finished product.
  • materials of Formula III to add organic groups
  • the combination of one molecule of Formula II and one molecule of Formula III contains two organic groups (indicated by R above).
  • a molar equivalent of a compound of Formula III can (optionally) be added so that the resultant product has as many organic groups as a condensate made solely from RSiX com ⁇ ound(s).
  • the amounts set forth in Table 1 are generally useful when it is desirable to prepare organic modified silicic acid heteropoly ⁇ condensates in the form of a powder or similar comminuted material.
  • a silane starting mixture which contains compound(s) of Formula II in an amount of at least about 65 mole percent, more preferably at least about 70 mole percent.
  • the remainder of the silane mixture is preferably one or more compounds of Formula I.
  • a small amount say up to about 5 mole percent, can be selected from compounds of Formula HI.
  • the monolithic products of this invention are not limited to rods or rod-like shapes.
  • the shaped articles of this invention generally conform to the shape of the vessel in which the reaction mixture is subjected to the hypercritical drying step illustrated by Example 3- Use of vessels (with other than a tubular shape) to hold the reaction mixture will result in different shaped products, e.g., spheres.
  • the rods or other shaped products can be comminuted after preparation by hammering, grinding or similar techniques, if desired.
  • the silanes of Formulas I and III all contain at least one organo group bonded to silicon through a carbon bond.
  • the organic group employed in general, there is no limitation on the size or type of the organic group employed.
  • the group is "stable"; i.e., it does not undergo an untoward amount of decomposition during the preparative or upgrading process of this invention. More preferably, the organic group is relatively inexpensive.
  • the organic group be not so bulky as to unduly retard the process by steric hindrance, or by entering into an untoward amount of undesirable side reactions.
  • Alkyl radicals of the straight- or branched- chain type represent one type of organic group which can be present within the silanes employed in this invention. More preferably, the alkyl radicals contain from about 1 to about 20 carbon atoms, and most preferably from 1 to about 10 carbon atoms. Of particular interest are the lower alkyl radicals in which the radicals contain up to about 6 carbon atoms. Examples of lower alkyl radicals which may appear within the silanes employed in this invention are methyl, ethyl, isopropyl, n-butyl, &££-butyl, texi-butyl, n— entyl, and n—hexyl.
  • Aryl radicals represent another type of organic group which may be bonded to silicon in the silanes employed in this invention.
  • hydrocarbyl aryl radicals which contain from about 6 to about 20 carbon atoms, more preferably from 6 to about 14 carbon atoms, and even more preferably from 6 to about 10 carbon atoms.
  • phenyl, naphthyl, biphenyl, and the like are phenyl, naphthyl, biphenyl, and the like.
  • the radical(s) indicated by R in the above formulas may also be an alkenyl radical, e.g., a straight- or branched-chain radical containing from 2 to about 20 carbon atoms, and more preferably, 1 carbon—to-carbon double bond.
  • alkyl radicals of this type are the ethylenyl, allyl, and vinyl groups.
  • the starting component (or mixture of starting components) is contacted with water.
  • the silane or mixture of silanes is first dissolved in an organic solvent.
  • Suitable solvents are alcohols, preferably the lower alcohols having from 1 to about 4 carbon atoms and exemplified by ethanol, ethanol, isopropanol, and isobutyl alcohol.
  • the solvent may also be selected from ketones, particularly from lower dialkyl ketones. Solvents of this type include acetone and methyl isobutyl ketone.
  • the solvent may be an ether, such as diethyl ether or another lower dialkyl ether.
  • the solvent may be an amide, such as dimethylamide.
  • the solvent is a lower alcohol.
  • the starting material(s), preferably in an organic solvent, is mixed with water in order to cause the reaction to proceed.
  • the amount of water is at least the quantity required to hydrolyze the hydrolyzable groups that are present.
  • the silane starting material used in the preparation process of this invention is composed of one or more compounds of Formula I, i.e., compounds having the formula RSiX 3 , then at least three moles of water is used, even though 1.5 mole equivalents of water are theoretically required to be added. Although three moles of water are required to hydrolyze each of the hydrolyzable groups, Equation 2 shows that in each condensation between silanol groups one mole equivalent of water is formed. This mole of water formed in the overall hydrolysis- condensation process is available for the hydrolysis step. Hence, in this example, the amount of water to be added to the reaction mixture is two thirds of the amount required to hydrolyze the hydrolyzable groups within the materials to be reacted.
  • the water be slowly added to be reaction zone. Accordingly, it is preferred that the water be added as a slow stream or in a drop-wise fashion. Addition of the water in this manner helps prevent unchecked hydrolysis and/or condensation of the more reactive groups within the material being reacted.
  • the preparative process of this invention can be conducted with water alone, or in the presence of a catalyst.
  • Suitable catalysts are acidic or basic substances.
  • suitable acid catalysts are strong, non-oxidizing, inorganic acids, such as hydrochloric acid, sulfuric acid, acetic acid, and the like. These preferred acids have a pK of at least about 5.
  • a catalyst may be a non—oxidizing alkaline substance, such as sodium hydroxide, potassium hydroxide, or a lower alkylamine, such as triethylamine having a pK, of at least 5.
  • a non—oxidizing alkaline substance such as sodium hydroxide, potassium hydroxide, or a lower alkylamine, such as triethylamine having a pK, of at least 5.
  • reaction be conducted in the presence of a catalyst. It is also preferred that an acidic catalyst be employed. When a catalyst is used, it is usually employed in an amount up to about 5 weight percent based on the total weight of the reaction mixture.
  • reaction is conducted at a temperature within the range of from about 10 ⁇ C to about 130°C.
  • reaction is conducted at a temperature within the range of from about 25°C to about 65°C.
  • organic modified silicic acid heteropolycondensate by hydrolysis/condensation is preferentially conducted at atmospheric pressure. However, it is to be understood that other pressures can be employed. Thus, for example, it is possible to use slightly lower or higher pressures, say, pressures within the range from about 0.5 to 5 atmospheres.
  • the formation of organic modified silicic acid heteropolycondensates in this invention is conducted for a time which affords a desired state of reaction. In a preferred embodiment the process is conducted for from about 1 minute to 24 hours. When a catalyst is employed, the reaction can be completed in a shorter time.
  • the condensate to be upgraded is treated with an extractant fluid at a supercritical temperature and pressure above atmospheric, so that silanol groups and hydrolyzable groups are removed from the polycondensate.
  • an extractant fluid at a supercritical temperature and pressure above atmospheric, so that silanol groups and hydrolyzable groups are removed from the polycondensate.
  • By-products which are produced e.g., water and alcohol, become admixed with, absorbed, or dissolved in the extractant fluid.
  • the pressure is reduced and the fluid removed from the condensate so that the by-products are separated with the extractant fluid.
  • the operating temperature is at or preferably somewhat above the critical temperature of the fluid which is used, e.g., methanol or ethanol.
  • the operating pressure is also above the critical pressure of the fluid.
  • the upgrading is conducted at a temperature within the range of from about 200 ⁇ C to the decomposition temperature of the heteropolyconden ⁇ sate, more preferably at a temperature of from about 250°C to about 350°C. It is to be understood that temperatures outside of this range can be used. The operator will select a temperature which is sufficient to give a reasonable process rate, but not so high as to cause an intolerable amount of unwanted decomposition.
  • the upgrading process is also conducted at an elevated pressure.
  • the upgrading is usually conducted at a pressure of from about 1000 to about 5000 psi.
  • the upgrading may be conducted in the presence of a small amount of water to remove any hydrolyzable groups which may still remain in the polycondensate.
  • a small amount of water to remove any hydrolyzable groups which may still remain in the polycondensate.
  • greater or lesser amounts of water can be used. In general, one uses enough water to conduct the desired amount of hydrolysis, but not so much water as to cause the process to proceed in an undesirable manner.
  • the upgrading step is conducted for a time sufficient to give the desired amount of hydrolysis or condensation.
  • a reaction time of rom about 3 to about 20 hours.
  • the reaction time is not a truly independent variable, but is dependent at least to some extent on the other reaction conditions employed. For example, higher reaction temperatures generally require shorter reaction times.
  • the processes of this invention involve a considerable number of process and composition variables to select from. Consequently, the invention includes an ability to "tailor—make” or “fine—tune” a heteropolycondensate composition so that it has a desired set of properties. This offers considerable advantage when it is desired to produce a composition having preselected performance criteria.
  • a practitioner wishes to produce a heteropolycondensate according to the teachings of this invention, he or she can be guided by the description above and the examples which follow.
  • the procedure described above can be modified to produce a variety of compositions simply by varying the monomers.
  • the amount of ethanol which is added may be in equal volume to the silane monomers.
  • the amount of water added, in the form of 0.15 M HCl, for example, may be equal to the number of moles of hydrolyzable groups on the silane monomers.
  • the organic modified silicic acid heteropolycondensates produced by the above process were isolated from the ethanol solution in which they were made. This was accomplished by pouring the ethanol solution of the condensate into an excess of water. The condensate separated as a viscous oil which could be collected, dried (in a vacuum oven), and dissolved in methylene chloride.
  • a suitable reaction time is employed. In general, three hours of stirring at 60°C after addition of the aqueous HCl was sufficient.
  • Heteropolycondensates made according to the process illustrated by this Example can be upgraded by heating them at an elevated temperature and pressure as (discussed above and) illustrated by the following Example:
  • Example 2 Phenyltriethoxysilane (60 ml, 0.25 mol) was polymerized according to the procedure set forth in Example 1 using 46.7 ml of ethanol and 13.4 ml (0.75 mol) of water. No acid catalyst was employed.
  • the ethanolic solution of the silicic acid heteropolycondensate produced was transferred to a stainless steel reaction vessel and dried by heating above the critical temperature of ethanol as in Example 3.
  • the phenyl group-containing silicic acid heteropolycondensate produced by the process of this Example is a product of this invention.
  • a method of upgrading an organic modified silicic acid heteropolycondensate, such that a product in the form of a rod is obtained is illustrated by the following example.
  • Esaro le 3 In a 250 ml, 3-neck, round—bottom flask equipped with a mechanical stirrer and reflux condensor were placed 30 ml of tetramethoxysilane, 8.6 ml of phenyltriethoxysilane, and 30 ml of methanol. The flask was placed in a 60°C constant temperature bath and 26.5 ml of distilled water were added dropwise with stirring. After the H 2 0 addition, stirring was maintained for two hours at 60°C before removing from the bath. The reaction mixture contained 15 mole percent phenyltriethoxy ⁇ silane based on the total moles of silane employed.
  • the solution of organic modified silicic acid heteropolycondensate was added to a glass tube 25.2 cm long with a 7 mm inner diameter.
  • the tube was placed in a stainless steel reactor and charged with N 2 to about 800 psi.
  • the temperature of the vessel was then increased at a rate of 100'C/hr. to 240-250°C with a resulting pressure of 2000 psi. This created a supercritical fluid (above the critical point of methanol).
  • the reactor was vented and swept five times with 2 and then slowly allowed to cool to ambient temperature.
  • the product was isolated in the form of a rod which readily separated from the walls of the glass tube. The rod was slightly opaque.
  • Example 4 To demonstrate utility of the non-monolithic products of this invention, stock solutions were prepared by dissolving one gram of organic modified silicic acid heteropolycondensates in 10 mL of CH 2 C1 2 in which one milligram of PtOEP was added. Light was excluded from the stock solution.
  • an optical fiber spectrometer (Guided Wave Model 200) was used to measure the phosphorescence intensity. This commercial instrument is equipped with a bifurcated fiber with one input fiber in the center axis to guide light to the sample and six output fibers along the edge to collect the scattered light and guide it back to the spectrometer. The fibers are terminated in a stainless steel probe.
  • a polycarbonate or polymethacrylate barrel was screwed with dichloromethane.
  • the 25 mil thick plate places the dye in the cross section of the exciting beam and the field of view defined by the numerical aperture of the optical fibers, maximizing the observable phosphorescence.
  • the PtOEP/sol—gel was first drop coated on the circular glass plate. This coating was then processed at 60 ⁇ C to 120 ⁇ C for one to four hours. After cooling to room temperature, this glass plate was "glued" to the barrel.
  • the fiber was kept in a glass bottle which is connected to two flowmeters. The two flowmeters were used to control the ratio of compressed nitrogen and air partial pressure, while keeping the total pressure constant.
  • the dye/polymer was excited with a tungsten lamp and an Ealing interference filter which passed wavelengths ⁇ 550 nm.
  • the phosphorescence was monitored at 642 nm with a bandwidth of 10 nm.
  • Phosphorescence lifetimes were estimated from recorded decay curves by nonlinear curve fitting. Visible absorption spectra were taken with an HP-4850A UV-VIS spectrometer.
  • the slope of a plot of [I(N 2 )/I(0 2 )-1] vs. P is proportional to the product of the lifetime ⁇ . and the permeability P .
  • the drawing in the Figure shows that an organic modified silicic acid heteropolycondensate made from phenyltriethoxysilane according to the method of Example 2, is significantly more permeable to oxygen than a polycondensate material made from the same silane but which was not upgraded by the process of this invention.
  • the material made by the process of Example 2 has some nonlinear response in permeability to oxygen relative to oxygen concentration over the range examined.
  • the materials of this invention need not be solely composed of silicic acid heteropolycondensates such as described above. They may also be modified to contain other metal oxide units in the polymeric matrix.
  • the raw material composition used in the preparative process of this invention may be modified to contain up to about 80 mole percent, and more preferably up to about 50 mole percent of one or more hydrolyzable materials, such as the alkoxides of titanium, molybdenum, lead, geranium, zironium or vanadium.
  • Modified condensates comprising metal oxide units derived from such materials have utilities similar to those discussed above.
  • the method in accordance with this invention removes residual silanol groups and hydrolyzable groups, it improves the properties of silicic acid condensates. For example, because the method of this invention improves the oxygen permeability of such condensates, it makes such materials more useful in applications such as oxygen sensing, where it is necessary to have utilize a substance that is permeable to oxygen. Also, since the upgrading method of this invention does not remove organic groups bonded to silicon through Si-C bonds, it can be used to improve the oxygen permeability of organic modified silicic acid heteropolycondensates without decomposition of their organic substituents.

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Abstract

On peut valoriser des hétéropolycondensats d'acide silicique modifiés organiques en retirant le silanol résiduel ou les groupes hydrolisables. Le procédé de valorisation consiste à mettre en contact le condensat avec un fluide surcritique à une température et une pression élevées. Les produits valorisés, qui se présentent sous la forme de poudre, peuvent être dissous dans un solvant organique et utilisés pour produire des revêtements présentant une perméabilité améliorée à l'oxygène. Les produits valorisés peuvent également être fabriqués sous forme solide non pulvérisée, par exemple sous forme de barres. Ces articles sont utiles comme adsorbants.
EP90902451A 1989-01-19 1990-01-16 Heteropolycondensats d'acide silicique modifies organiques Withdrawn EP0454761A1 (fr)

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DE19545042A1 (de) * 1995-12-02 1997-06-05 Studiengesellschaft Kohle Mbh Amorphe mikroporöse Mischoxidkatalysatoren mit kontrollierter Oberflächenpolarität für die selektive heterogene Katalyse Adsorption und Stofftrennung

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US2680696A (en) * 1951-02-14 1954-06-08 Du Pont Method of esterifying the surface of a silica substrate having a reactive silanol surface
US2967168A (en) * 1954-11-12 1961-01-03 Gen Electric Vinyl-substituted silica aerogels
DE2357184A1 (de) * 1973-11-16 1975-05-22 Merck Patent Gmbh Verfahren zur herstellung von organisch modifizierten siliciumdioxiden
DE2758415A1 (de) * 1977-12-28 1979-07-12 Fraunhofer Ges Forschung Kieselsaeureheteropolykondensate, verfahren zu deren herstellung und deren verwendung als membranen und adsorbentien
US4402927A (en) * 1980-04-22 1983-09-06 Dardel Guy Von Silica aerogel
FR2601017B1 (fr) * 1986-07-02 1988-09-23 Centre Nat Rech Scient Nouvelles compositions a base de derives de silice modifiee par des groupements organiques, leur preparation et leur application, notamment comme conducteurs protoniques

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CA2045511A1 (fr) 1990-07-20
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