WO2009136185A1

WO2009136185A1 - Microbiocidal materials

Info

Publication number: WO2009136185A1
Application number: PCT/GB2009/050417
Authority: WO
Inventors: Godfrey Stewart Short
Original assignee: Rocktron Limited
Priority date: 2008-05-07
Filing date: 2009-04-24
Publication date: 2009-11-12
Also published as: GB0808247D0; GB2459948A; EP2331617A1; GB0907005D0

Abstract

A filler for subsequent use with a binder in a binder-and-filler material such as a plastics material, mortar or paint comprises glass beads which are substantially spherical and which are coated with a microbiocide such as zinc pyrithione, the filler being dry. The glass beads have a lower absorption of the microbiocide than most other materials that are conventionally used for this purpose. The glass beads are substantially impervious to microbes so that the required amount of the microbiocide is reduced, for example from about 2 or 3% by volume to about 1% by volume. The glass beads are preferably made from pulverised fly ash having advantages of low cost, low density, high wear resistance, easy dispersion and homogeneousness. The microbiocide disperses with the readily-dispersible beads when the beads are combined with the binder. The coated beads can straightforwardly be used as a replacement for a conventional dry filler when combining with the binder.

Description

[0001 ] MICROBIOCIDAL MATERIALS

Technical Field

[0002] This invention relates generally to microbiocidal materials and in particular to micro- biocidal materials having a filler and a binder, such as plastics, paints, and mortar.

Background Art

[0003] One problem with which the present invention, or at least specific examples of it, is concerned is the persistent global problem of infection of humans and animals from contact with surfaces where microbes such as bacteria, viruses and fungal growth are present. Such places as hospitals, care homes, nurseries, catering establishments, hotels, homes, schools and colleges, sports facilities/changing rooms, public toilets and milking parlours are all potential areas for the growth, transfer and spread of bacteria and viruses.

[0004] Various methods are in use to try to eliminate bacteria, viruses and fungal growth such as cleaning liquids, cleaning cloths impregnated with various chemicals, and coatings and plastics containing antibacterial additives.

[0005] In the case of cleaning liquids and impregnated cloths, the removal of the bacteria, virus or fungal growth is only temporary and needs to be continually repeated to try to provide protection against the growth and spread of these infectious agents.

[0006] Coatings and plastic components are currently produced containing antibacterial, antiviral, antifungal additives such as silver ions. However, they offer a temporary, rather than long-term, solution. Due to their high water solubility the effect of these additives is depleted when coming into contact with water during for example cleaning, or when subjected to ultra violet light such as sunlight, which oxidises the silver or additive on the surface. The silver ions migrate to the surface of the coating or component, where they are depleted, and therefore, in time, the coating or component becomes devoid of any silver ions.

[0007] More recently, substances have been developed which are more effective in the long- term. An example is sold under the registered trade mark Hygienilac by Premier Finishes Limited, NN 15 6AU, GB. Hygienilac is supplied as a clear viscous liquid having a specific gravity of about one. The active ingredient of Hygienilac is zinc pyrithione (CAS no. 13463-41-7). Hygienilac is believed by its manufacturers to act to reduce or eliminate ion gradients in microbial membranes. Bacteria use these ion gradients to store energy, and fungi use them as a source of energy for nutrient transport. Disruption of these ion gradients leads to starvation and death of the microbe. Hygienilac has been shown to offer long term protection and destruction of bacteria, viruses and fungal growth. Its long term effectiveness is due to such factors as low water solubility, ultra violet light stability, non-leaching and non-migratory. Also, Hygienilac is believed not to accumulate significantly in the bacteria and is not destroyed during the process of killing the microbes. [0008] Hygienilac has been tested against the following bacteria: listeria monocytogenes,

Clostridium difficile, staphylococcus aureus, salmonella enteriditis, klebsiella pneumoniae, aspergillus niger, pseudomonas aeruginosa, penicillium purpurogenum, basillus cereus, saccharmyces cerevisiae, escherichia coli and staphylococcus aureus methicillin-resistant strain (MRSA), in each case producing destruction of at least 99.9% in twenty-four hours.

[0009] Another problem with which specific examples of the present invention is concerned is reducing the waste from solid-fuel fired power stations and the amount of landfill that is required to dispose of such waste.

[0010] Pulverised fly ash is produced from the combustion of coal in electricity generating power stations. It is collected from the exhaust gas stream of the furnace either in electrostatic precipitators or sometimes in a filter. It is estimated that in excess of 500 million tonnes of fly ash was produced globally during 2005. Rather than dispose of the fly ash in landfill, techniques have been developed for processing the fly ash economically, as described, for example, in patent documents GB2320245A, US6269952B and EP0948410B to produce useful products such as cement constituents, carbon for fuel use, carbon for use in industrial processes, magnetite, and solid or hollow spheres of alumino- silicate glass. These glass spheres or beads find uses, for example, as fillers in plastics and paints and have several advantages. They have a lower cost and lower density than many other fillers. They produce a higher wear resistance than other fillers. They readily disperse uniformly throughout the filled material. Also, when used as a filler in moulded plastics, the glass beads produce a lower melt viscosity of the molten filled plastic than many other fillers, due to the spherical shape of the beads, enabling thinner wall thicknesses to be moulded. These glass spheres beads therefore provide excellent functionality as fillers.

Disclosure of Invention

[0011] In accordance with a first aspect of the present invention, there is provided a filler for subsequent use with a binder in a binder-and- filler material, the filler comprising glass beads which are preferably substantially spherical and which are coated with a mi- crobiocide, the filler being dry. In accordance with a second aspect of the present invention, there is provided a binder-and-filler material comprising a filler of glass beads which are preferably substantially spherical and which are preferably coated with a microbiocide, and a binder which binds together the glass beads. [0012] The glass beads have a lower absorption of the microbiocide than most other materials that are conventionally used as fillers, such as calcium carbonate, talc and clays. Furthermore, the glass beads are substantially impervious to microbes. As a result, the amount of the microbiocide that is required in order to be effective is reduced, for example from about 2 or 3% by volume to about 1% by volume. Furthermore, the glass beads provide or produce the other advantages discussed above, such as low cost, low density, high wear resistance, easy dispersion and homoge- neousness. In the case where the glass beads are coated with the dry microbiocide, the microbiocide disperses with the readily-dispersible beads when the beads are combined with the binder. Also, in the case where the coated beads are supplied dry, they can straightforwardly be used as a replacement for a conventional dry filler when combining with the binder.

[0013] The microbiocide is preferably antibacterial and/or antiviral and/or antifungal. The microbiocide preferably has low water solubility and/or is substantially unaffected by ultraviolet light. The microbiocide is preferably substantially non-leaching and/or is substantially non-migratory in the binder-and-filler material. Accordingly, an article or coating produced from the filler- and-binder material can remain microbiocidally active for a long time despite washing, exposure to sunlight or wear.

[0014] In one example, the microbiocide acts to reduce or eliminate ion gradients in microbial membranes. Zinc pyrithione (for example in the form of Hygienilac) may be employed as the microbiocide.

[0015] At least the majority of the beads preferably each have a maximum dimension of no more than 100 micrometres. At least some of the glass beads may be nanospheres, i.e. having a maximum dimension that is less than 1 micrometre.

[0016] The glass beads are preferably formed from alumino- silicate and are preferably formed from pulverised fly ash.

[0017] The glass beads preferably constitute no more than about 75% by volume of the binder-and-filler material so that the glass beads can be completely bound by the binder. In some embodiments of the invention, the coated glass beads form the primary or sole filler in the binder-and-filler material. In other embodiments, the filler is formed by the coated glass beads, together with other glass beads which are similar except that they are not coated with microbiocide. In this case, the coated and uncoated glass beads are preferably mixed well before being combined with the binder. The proportions of the coated and uncoated glass beads may be chosen so as to provide an appropriate proportion of filler in the material, without producing an excessive proportion of the microbiocide in the material.

[0018] The proportion of microbiocide in the material is preferably at least Vi% by volume and more preferably between about 1 and 2% by volume. [0019] In one example, the binder comprises a plastics resin, such as (i) a mouldable plastics resin, so that the binder and filler can be moulded, for example by injection moulding or extrusion, to produce a microbiocidal article, in which case the glass beads provide the advantage of low melt viscosity, or (ii) a powdered plastics resin, so that the binder and filler can be used to powder coat an article.

[0020] In another example, the binder comprises Portland cement, so that the binder- and-filler material takes the form of a mortar or concrete.

[0021] In a further example, the binder comprises gypsum plaster, and the binder and filler may be supplied in the form of a powder ready for mixing with water.

[0022] In yet another example, the binder- and-filler material takes the form of a paint or lacquer.

[0023] In accordance with a third aspect of the invention, there is provided a method of manufacture of a filler as described above, or the filler of a binder- and-filler material as described above.

[0024] The method preferably includes the step of forming the glass beads from pulverised fly ash, for example using a method as described in patent documents GB2320245A, US6269952B and EP0948410B. Accordingly, waste material which would otherwise need to be disposed of can be economically processed to provide the glass beads.

[0025] The method may include the step of coating the glass beads with the microbiocide wet, and then allowing or causing the microbiocide to dry so that it adheres to the glass beads, or coating the glass beads with the microbiocide in dry powdered form in such a way that the microbiocide adheres to the beads..

[0026] EXAMPLES

[0027] A number of examples of the invention will now be described. The microbiocide Hy- gienilac is used in the examples, but other generally similar microbiocides may be substituted. It is to be noted that Hygienilac should not be heated to a temperature above 240⁰C, otherwise the zinc pyrithione decomposes and its beneficial effects are destroyed.

[0028] Example 1

[0029] Pulverised fly ash collected from a coal-fired power station is processed for example employing the methods described in patent document GB2320245A, US6269952B and EP0948410B to produce smooth solid spherical glass beads of alumino- silicate having diameters ranging from less than 1 micrometre to about 100 micrometres, a density in the range of about 2000 to 2350 kg/m³ and a Mohs hardness of about 5 to 6. Hygienilac microbiocide in viscous liquid form is then diluted with alcohol in a high speed mixer. The dilute microbiocide is then mixed with the glass beads in a planetary mixer for sufficient time to allow thorough dispersion. The beads are then dried in any of a variety of ways such a flash or spray drying, vacuum drying, oven drying or natural evaporation, leaving the glass beads coated with dry microbiocide having a coating thickness of several micrometres. The beads are then mixed as a filler with a pelletised binder of thermoplastic resin having a melting point of less than 240⁰C in the proportion 70:30 bindeπfiller by weight, the proportion of Hygienilac in the mixture being about 1% by volume. The mixture is then fed into a conventional injection- moulding machine operating at a temperature above the melting point of the binder but below 240⁰C to mould a desired article.

[0030] Example 2

[0031] Example 2 is similar to Example 1, except that (i) the glass beads are hollow (also known as cenospheres) having diameters ranging from less than 1 micrometre to about 100 micrometres and a density of about 750 kg/m³, and (ii) the glass beads are mixed with a thermosetting resin before placing in a mould.

[0032] Example 3

[0033] Example 3 is similar to Example 1, except that the mixture of binder and filler is fed into a conventional extruding machine operating at a temperature above the melting point of the binder but below 240⁰C to extrude a desired article such as a pipe or a floor covering.

[0034] Example 4

[0035] Example 4 is similar to Examples 1 to 3, except that the glass beads are coated with Hygienilac in dry powder form in a heated high-speed mixer so that the Hygienilac adheres uniformly to the glass beads.

[0036] Example 5

[0037] Pulverised fly ash collected from a coal-fired power station is processed for example employing the methods described in patent document GB2320245A , US6269952B and EP0948410B to produce glass cenospheres of alumino- silicate having diameters ranging from less than 1 micrometre to about 100 micrometres and a density of about 750 kg/m³. The cenospheres are then wetted with liquid Hygienilac and allowed to dry so that the cenospheres are coated with dry Hygienilac having a coating thickness of several micrometres. The cenospheres are then mixed as a filler with a powdered binder of thermosetting resin having a melting point of less than 240⁰C to produce a Hygienilac content of about 1% by volume. The mixture is then applied by a conventional powder coating technique to an article to be coated and baked to a temperature above the melting point of the binder but below 240⁰C so that the binder flows and bonds to the coated cenospheres and the article.

[0038] Example 6

[0039] Beads coated with Hygienilac are produced as described in Example 1. The beads are then added to a pigmented binder and a solvent or vehicle to form a paint.

[0040] Example 7 [0041] Hygienilac microbiocide in viscous liquid form is diluted with water in a high speed mixer. The dilute microbiocide is then mixed with glass beads as described in Example 1 in a planetary mixer for sufficient time to allow thorough dispersion. The beads are then dried in any of a variety of ways such a flash or spray drying, vacuum drying, oven drying or natural evaporation, leaving the glass beads coated with dry microbiocide having a coating thickness of several micrometres. The beads are then mixed with sand, and the mixture of coated beads and sand is then mixed as a filler with Portland cement as a binder and water to form a mortar. The proportion of glass beads in the mix is such that the Hygienilac content is about 1% by volume. The mortar may then be used for any suitable purpose such as rendering a wall or screeding a floor.

[0042] Example 8

[0043] Example 8 is similar to Example 7 except that the coated beads are mixed with sand and a coarser aggregate such as gravel, so that when combined with cement and water, concrete is formed.

[0044] Example 9

[0045] In Example 9, coated glass beads are prepared in the manner described in Example 7. The beads are then mixed with dry plaster of Paris powder. The proportion of glass beads in the mix is such that the Hygienilac content is about 1% by volume. The mixture can then be used, when mixed with water, in a similar manner to conventional plaster of Paris powder, for example to form a coating for a wall of a building, or a plaster cast for a broken limb.

[0046] Example 10

[0047] Example 10 is similar to Example 9 except that the mixture of plaster and coated glass beads is used in the manufacture of plasterboard (also known as drywall).

[0048] Example 11

[0049] Example 10 is similar to Examples 1 to 3, except that the glass beads are not coated with Hygienilac prior to mixing with the binder. Instead, Hygienilac is incorporated into a polymer in a compounding extruder and pelletised to produce a masterbatch containing about 10% by volume of Hygienilac. The beads, pelletised masterbatch and pelletised binder are then mixed in the required proportions to produce a mixture containing about 1% of Hygienilac before feeding to the injection moulding or extruding machine.

[0050] Modifications and developments

[0051] In the examples described above, the proportion by volume of Hygienilac in the finished product is dependent on the proportion by volume of the coated beads in the finished product and on the average proportion by volume of Hygienilac in a coated bead. In order to permit variations in the proportion of filler in the finished product whilst maintaining the proportion of Hygienilac in the finished product at about 1% by volume, and without the need to provide different coating thicknesses on the glass beads, in each of Examples 1 to 10 above a mixture of coated glass beads and uncoated glass beads may be used instead of solely glass beads which are coated. The ratio of coated to uncoated glass beads may therefore be chosen so as to provide the required proportion of Hygienilac in the finished product. It should be noted that the above examples have been described purely by way of illustration and that many modifications and developments may be made without departing from the scope of the invention.

Claims

[0001] A filler for use in a binder- and-filler material, the filler comprising glass beads which are coated with a microbiocide, and the filler being dry.

[0002] A binder- and- filler material comprising a filler of glass beads, a microbiocide, and a binder which binds together the glass beads.

[0003] A binder-and-filler material as claimed in claim 2, wherein the glass beads are coated with the microbiocide.

[0004] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the microbiocide is antibacterial and/or antiviral and/or antifungal.

[0005] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the microbiocide has low water solubility and/or is substantially unaffected by ultraviolet light.

[0006] A binder-and-filler material as claimed in any of claims 2 to 5, wherein the microbiocide is substantially non-leaching and/or is substantially non-migratory in the binder-and-filler material.

[0007] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the microbiocide acts to reduce or eliminate ion gradients in microbial membranes.

[0008] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the microbiocide comprises zinc pyrithione.

[0009] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the beads are substantially spherical.

[0010] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein at least the majority of the beads each have a maximum dimension of no more than 100 micrometres.

[0011] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the glass beads are formed of alumino-silicate.

[0012] A filler, or a binder-and-filler material, as claimed in any preceding claim, wherein the glass beads are formed from pulverised fly ash.

[0013] A binder-and-filler material as claimed in any of claims 2 to 12, wherein the glass beads constitute no more than 75% by volume of the material.

[0014] A binder-and-filler material as claimed in any of claims 2 to 13, wherein the glass beads form the primary or sole filler in the material.

[0015] A binder-and-filler material as claimed in any of claims 2 to 13, wherein the material also includes a filler of glass beads which are similar to the first- mentioned glass beads but which are not coated with microbiocide.

[0016] A binder-and-filler material as claimed in any of claims 2 to 15, wherein the proportion of microbiocide in the material is no less than Vi% by volume.

[0017] A binder-and-filler material as claimed in any of claims 2 to 16, wherein the binder comprises a plastics resin.

[0018] A binder-and-filler material as claimed in any of claims 2 to 16, wherein the binder comprises Portland cement.

[0019] A binder-and-filler material as claimed in any of claims 2 to 16, wherein the binder comprises gypsum plaster.

[0020] A binder-and-filler material as claimed in any of claims 2 to 16, in the form of a paint or lacquer.

[0021] A method of manufacture of a filler as claimed in claim 1 or any of claims 4, 5 and 7 to 12 when directly or indirectly dependent on claim 1, or a method of manufacture of a filler of a material as claimed in any of claims 2 to 20, the method including the step of forming the glass beads from pulverised fly ash.

[0022] A method of manufacture of a filler as claimed in claim 1 or any of claims 4, 5 and 7 to 12 when directly or indirectly dependent on claim 1, or a method of manufacture of a filler of a material as claimed in any of claims 2 to 20, or a method as claimed in claim 21, the method including the step of coating the glass beads with the microbiocide wet, and then allowing or causing the microbiocide to dry.

[0023] A method of manufacture of a filler as claimed in claim 1 or any of claims 4, 5 and 7 to 12 when directly or indirectly dependent on claim 1, or a method of manufacture of a filler of a material as claimed in any of claims 2 to 20, or a method as claimed in claim 21, the method including the step of coating the glass beads with the microbiocide in dry powdered form.