GB2294260A - Porous material comprising glass spheres - Google Patents

Porous material comprising glass spheres Download PDF

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Publication number
GB2294260A
GB2294260A GB9421312A GB9421312A GB2294260A GB 2294260 A GB2294260 A GB 2294260A GB 9421312 A GB9421312 A GB 9421312A GB 9421312 A GB9421312 A GB 9421312A GB 2294260 A GB2294260 A GB 2294260A
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GB
United Kingdom
Prior art keywords
porous material
glass
spheres
another
liquid
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Withdrawn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
GB9421312A
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GB9421312D0 (en
Inventor
Alastair Sibbald
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Central Research Laboratories Ltd
Original Assignee
Central Research Laboratories Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Central Research Laboratories Ltd filed Critical Central Research Laboratories Ltd
Priority to GB9421312A priority Critical patent/GB2294260A/en
Publication of GB9421312D0 publication Critical patent/GB9421312D0/en
Publication of GB2294260A publication Critical patent/GB2294260A/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • B01J20/28033—Membrane, sheet, cloth, pad, lamellar or mat
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B1/00—Layered products having a non-planar shape
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B01D39/2003—Glass or glassy material
    • B01D39/2006—Glass or glassy material the material being particulate
    • B01D39/201—Glass or glassy material the material being particulate sintered or bonded by inorganic agents
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
    • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/10—Forming beads
    • C03B19/108—Forming porous, sintered or foamed beads
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B23/00—Re-forming shaped glass
    • C03B23/20—Uniting glass pieces by fusing without substantial reshaping
    • C03B23/203—Uniting glass sheets
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B23/00—Re-forming shaped glass
    • C03B23/20—Uniting glass pieces by fusing without substantial reshaping
    • C03B23/24—Making hollow glass sheets or bricks
    • C03B23/245—Hollow glass sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/02—Cellular or porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/80—Sintered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/73—Hydrophobic

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Analytical Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Vascular Medicine (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Biomedical Technology (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Mechanical Engineering (AREA)
  • Epidemiology (AREA)
  • Dispersion Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Geology (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

A porous material for receiving and retaining liquid by means of capillary action comprising a structure of glass spheres, the glass having a relatively low softening point of preferably less than 800 DEG C, and the glass spheres being thermally fused together, to form a structure having flow paths therebetween permitting smooth capillary flow of liquid. The porous material may be a layer between two sheets of glass.

Description

POROUS MATERIALS Field of the Invention The present invention relates to porous materials, and methods of making them, which are capable of receiving and retaining liquid.
Background of the Invention Porous materials occur in many forms: some of these are natural in origin, such as sandstone and wood but many are synthetic such as polyester fabrics, absorbent papers, and granular ceramic materials.
A common feature of porous materials is their relatively open structure, which enables fluids to permeate and percolate throughout the body of the material in a reversible manner, and without changing the chemical properties of the host. If the pore size is relatively small - say less than lmm - then fluids can be drawn into the porous host by capillary action, provided that the host is wettable by the fluid in question. This is dependent upon the surface chemistry of the host material. As the pore size is reduced, the rate of permeation decreases because of the increased flow-resistance of the host material, and also the loading capacity of the host is diminished. In the extreme, an example of this is the workshop "wet-stone" used for sharpening tools: this takes several hours to load with mineral oil after wetting.
Porous materials have widespread applications in industry, medicine and domestic applications, ranging from use in fibre-tip pens to hold ink (and form a nib), through wound dressing, chromatographic analysis, filtration and many fluid-handling situations, especially related to chemical analysis. In this latter application area, it is worth noting that capillary tubes are often used to obtain blood samples, because use of porous materials would tend to separate-out the various elemental constituents, thus degrading the sample. The use of a capillary tube, however, substantially limits the volume size of the sample which can be obtained.
In regard to chemical analysis, in particular chromatography, it is well known to employ columns packed with granules of a small size so that liquid flows therethrough.
DD-A-271650 discloses a structure for use as a catalytic convertor comprising glass spheres, 800-500011m diameter, fused together and coated with a layer of platinum.
Such structure would not be suitable for a porous material, since the interstices are too large to support capillary action.
Summarv of the Invention There is a requirement for a porous material formed synthetically in which the capability for receiving and retaining liquid by means of capillary action can be adjusted to the intended application, and which furthermore has sufficient structural strength to be formed in a desired shape.
The present invention provides in one aspect a porous material for receiving and retaining liquid by means of capillary action comprising a structure of glass spheres, the glass having a relatively low softening point of preferably less than 8000C, and the glass spheres being thermally fused together, to form a structure having capillary flow paths therebetween permitting smooth flow of liquid.
The present invention provides in a further aspect a method of making a porous material, comprising: a) providing a quantity of glass spheres having a relatively low softening point, preferably less than 8000C, b) holding the quantity of spheres in contact with one another while heating the spheres for a predetermined time above their softening point but below their melting point in order to fuse the spheres together and to provide capillary flow paths therebetween permitting smooth flow of liquid of predetermined rates.
Thus the invention provides a synthetic, porous material having superior properties over known alternatives. In particular, the material possesses a very low impedance in respect to fluid flow into and through the bulk, and it is chemically inert and physically robust. An important feature of the invention is that it can be manufactured in the form of elemental components, such as sheets and conduits, which can be used as system components to build other devices and components.
Since most liquids have properties of surface tension and capillarity within an order of magnitude of one another it is possible to define the flow properties of any liquid with the porous material fairly accurately.
The porous material of the invention has particular use where it is desired to bring two liquids into contact with one another at an interface under closely controlled conditions. Essentially, one liquid can be held in the porous material, or caused to flow therethrough at a predetermined rate, while the other liquid flows over a surface of the porous material at a predetermined rate, or is held in contact with the surface. In this way, a stable liquid-liquid interface is formed at the surface on the porous material, allowing a reaction or process to take place at the interface under controlled conditions.
The porous material according to the invention has the feature that the particles from which the bulk material is made are all uniformly smooth and streamlined, and hence the fluid resistance can be made very low. Furthermore, the packing density of a plurality of similar diameter spheres is much lower that of randomly shaped and sized particles, and hence the porous loading capacity is relatively high. The glass is inert and solvent resistant to all but a few liquids. Another feature of the material is that it can be engineered to posses specific properties by selecting an appropriate diameter microsphere for the source material.For example, in respect of biomedical applications, if 200 micron spheres are used, then the inter-sphere percolation pathways will be sufficiently large for whole blood cells to pass though, and the passageways will have smooth walls, thus lessening the likelihood of cell damage or rupture, which would precipitate the clotting process.
By selecting a combination of particular, differing-size sphere diameters, then it is possible to control the porosity and loading capacity. By mixing both high- and lowsoftening point glasses, it is possible to have "trapped", free spheres in the matrix.
It is possible to use materials other than glass, depending on the application, for example plastics, ceramics, metal. The conditions of fusion would depend on the particular material chosen: it might in some applications be necessary to employ an adhesive to bond the spheres together.
The material may be manufactured as bulk material elements, in the form of rods, sheets and cubes, and so on, but also it is possible to manufacture system components of a defined shape. In many fluid-handling applications, it is necessary to contain the porous material, and this can be achieved by manufacturing the material in a form bounded by an impermeable material, such as glass. For example, if a glass tube is packed with the microspheres and thermally cycled, the resultant tube possesses the "suction" properties of a 0.5 mm diameter capillary tube, but can be made to be several cm in diameter. Such rods could be bent and formed into coils and other shapes whilst soft.If the material were to be manufactured bounded between a pair of glass sheets, like a sandwich, then this could be moulded during manufacture, or at a subsequent time, to form a conduit for transporting and exposing fluids in a very precise way.
It is possible by means of the invention to bring two liquids into contact with one another at an interface in a controlled manner, for example to carry out a chemical reaction or a solvent extraction process. Two different liquids held in two elements formed as above may be brought into contact by removing the outer bounding material from the two elements in a predefined region, and bringing the two porous material regions into contact with one another. In other arrangements, two portions of porous material may be provided, one formed of spheres of a hydrophilic substance, for example glass, and the other formed of spheres of a hydrophobic substance such as nylon or stainless steel.In this way, two liquids can be constrained to flow in the two portions and to be brought into contact with one another without providing any external means for holding the two liquids in the two portions.
Preferred embodiments of the invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a schematic view of a first embodiment including porous material according to the invention, bounded on either side by glass walls; Figure 2 is a schematic view of a modified form of the embodiment of Figure 1 which has been moulded to a different shape and with the porous material exposed in one region; Figure 3 is a shematic view of two elements, formed as in Fig. 2, brought together to allow the contacting of two liquids held in the porous material at the common interface; Figure 4 is a schematic view of a second embodiment of the invention comprising a spherical porous glass pellet; and Figure 5 is a schematic view of a third embodiment of the invention, comprising two layers of porous material; Referring to Figure 1, a planar layer of the material 2, which may be of a thickness for example of 5 mm, is bounded on either side by a glass wall 4 to form a plate-like structure. The advantage of placing the material 2 within glass walls is that it adds structural strength to the material, since although the material is strong to compression forces, it is relatively weak as regards bending and stretching forces. The material 2 is bonded to the glass walls by heating the material, and preferably the glass of the glass walls would have a similar low softening point and be formed of soda lime glass or an alkali borosilicate glass.
Referring to Figure 2, the plate structure of Figure 1 has been moulded to form a central angled portion 6, by heating the structure and bending in a suitable mould or vice structure. The glass of the glass wall is removed in the region 8 for example, by grinding so as to expose the inner, porous material 2. It is thus possible, in use of the structure of Figure 2, to feed liquid through the material 2 which will flow at a predetermined rate under the control of the capillary forces within the material, and such liquid will form a stable interface in the region 8 with another liquid in contact with the liquid 8 which may be stationary in a reservoir or may be flowing at a pre-determined rate. Such an arrangement has applications in many areas of chemical technology.
Referring to Fig. 3, two plate structures of the form shown in Fig. 2 are brought together at the regions 8 to enable liquid flowing in the two structures to contact one another at the interface 30 between the two regions 8.
Referring now to Figure 4, a spherical glass pellet 40 comprises microspheres 42 of similar or randomly different sizes. This structure would be formed in the manner of the examples described above. A use for such a sphere would be for hosting whole-cell implants, acting as a freely permeable but robust "trap", allowing relatively free interdiffusion of external fluids and moieties with the absorbate.
Referring now to Figure 5, a third embodiment of the invention is shown comprising, porous material 50 in the form of a planar sheet and composed of hydrophilic glass spheres which permits an aqueous solution to be retained therein by capillary action. This sheet 50 is positioned face to face with a further planar sheet 52 of hydrophobic porous material comprising for example, nylon or stainless-steel spheres fused together to form a porous structure in accordance with the invention which will retain, for example, an organic solution. The two sheets 50, 52 are positioned in contact with one another and their interface constitutes an interface for the two liquids held in the sheets so as to permit a desired reaction or transfer to occur at the interface.

Claims (8)

1. A porous material for receiving and retaining liquid by means of capillary action comprising a structure of glass spheres, the glass having a relatively low softening point of preferably less than 8000C, and the glass spheres being thermally fused together, to form a structure having flow paths therebetween permitting smooth capillary flow of liquid.
2. A structure including first and second sheets of glass disposed face to face and including a layer of material disposed therebetween, the material being porous material as claimed in claim 1.
3. A structure according to claim 2, which is moulded in a desired shape.
4. A structure according to claims 2 or 3, wherein a region of glass is removed in a sheet to expose the porous material.
5. Apparatus for bringing first and second liquids in contact with one another, including first and second structures each as claimed in claim 4, with their respective regions of exposed porous material are disposed adjacent one another.
6. Apparatus for bringing first and second liquids in contact with one another including first and second sheets of material disposits adjacent one another, the first sheet comprising porous material as claimed in claim 1 and the second sheet comprising a porous material comprising spheres of a hydrophobic material bonded together.
7. A method of making a porous material, comprising: a) providing a quantity of glass spheres having a relatively low softening point preferably of less than 8000C, b) holding the quantity of spheres in contact with one another while raising the temperature the spheres for a predetermined time above their softening point but below their melting point in order to fuse the spheres together and to provide flow paths therebetween permitting smooth flow of liquid of predetermined rates.
8. Porous materials and methods of making them substantially as described with reference to the accompanying drawings and examples herein.
GB9421312A 1994-10-22 1994-10-22 Porous material comprising glass spheres Withdrawn GB2294260A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9421312A GB2294260A (en) 1994-10-22 1994-10-22 Porous material comprising glass spheres

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9421312A GB2294260A (en) 1994-10-22 1994-10-22 Porous material comprising glass spheres

Publications (2)

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GB9421312D0 GB9421312D0 (en) 1994-12-07
GB2294260A true GB2294260A (en) 1996-04-24

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GB9421312A Withdrawn GB2294260A (en) 1994-10-22 1994-10-22 Porous material comprising glass spheres

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1210702A (en) * 1967-03-21 1970-10-28 Gruenzweig & Hartmann A light transmissive acoustic plate
WO1986001147A1 (en) * 1984-08-09 1986-02-27 Torobin Leonard B Hollow microspheres made from dispersed particle compositions and methods and apparatus for producing them

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1210702A (en) * 1967-03-21 1970-10-28 Gruenzweig & Hartmann A light transmissive acoustic plate
WO1986001147A1 (en) * 1984-08-09 1986-02-27 Torobin Leonard B Hollow microspheres made from dispersed particle compositions and methods and apparatus for producing them

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Publication number Publication date
GB9421312D0 (en) 1994-12-07

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