GB2094148A - Mouldicidal composition - Google Patents

Abstract

A mouldicidal composition in the form of a low viscosity liquid for application to a substrate such as unseasoned garden fence panels comprises a mouldicide + a colouring agent which is selected to be light fast, storage stable and chemically compatible with the mouldicide. The invention includes apparatus for applying the composition to panels while they held upright.

Description

SPECIFICATION Mouldicidal compositions and apparatus for applying them to substrates The invention relates to mouldicidal compositions for use in the control of moulds and to an apparatus for applying the compositions to substrates to prevent moulds growing theron. More particularly, the invention relates to mouldicidal compositions for use in the control of moulds such as Pencillin spp, Trichoderma spp and Aspergillus spp which tend to grow on substrates such as wood. In particular it relates to compositions for use in the treatment of items of wood to provide a decorative colour and at the same time to prevent the growth of mould especially when the wood is unseasoned and stored in damp conditions.

A specific example of an item of wood to which the invention can be applied is a garden fence panel and for convenience the invention will be described with reference to such a panel but the invention is capable of other uses, e.g. application to porous brick or stonework.

Garden fence panels are frequently made from green (unseasoned) timber. After manufacture they are often stored for some months close piled in large stacks and the humid atmosphere within the stack is an ideal condition for mould growth to occur. Creosote preparations are commonly used to colour fencing panels and these provide some mouldicidal effect but not during a long storage period. These preparations also have the disadvantages of a pungent smell and being dirty to handle.

It is an object of this invention to provide a mould control composition which is substantially odourless and which can colour an item of wood or the like.

According to one aspect of the invention there is provided a substantially odourless mouldicidal composition comprising: (i) a mouldicidal component, comprising one or more mouldicides, and (ii) a colouring component comprising a colouring agent compatible with the mouldicide component.

Typically the composition will be presented in a carrier usually water, and the diluted composition will be of low viscosity.

The mouldicide may be selected from a variety of materials known for the purpose and which can be dissolved or dispersed in water and which, when assessed in comparison with creosote, is substantially odourless or has a slight and/or not unpleasant smell. Examples of preferred mouldicides include methylene bis-thiocyanate, 2-(thiocycanomethylthio) benzothiazole, sodium pentachlorophenoxide, 5-chloro-2-methyl4-isothiazolin-3-one, methyl-4-isothiazolin-3-one, and the like. Preferably the mouldicide is a pentachlorophenoxide and the sodium salt is preferred. More than one mouldicide may be present and mixtures of sodium pentachlorophenoxide with a borate such as sodium dioctoborate or a borax/boric acid blend are preferred.

Preferably the pentachlorophenoxide comprises from about 0.5 to 5% by weight of the composition, most preferably 1.5%, and the disodium octaborate or the borax/boric acid blend slightly less, preferably equal to half the weight of pentachlorophenoxide.

The colouring agent must be one which is chemically compatible with the mouldicide component and which is light fast and storage stable. Chemical compatability means that the colouring agent i.e. the colouring matter or an agent therewith such as a dispersant does not chemically interact with the mouldicide either in the composition or on the treated substrate. By light fastness we mean a colouring agent which, whether in the composition or on the wood will substantially retain its colour i.e. not fade or change in hue for an acceptable period e.g. at least for about nine months. By storage stability we mean that the colouring agent is one which, when blended in a composition with the mouldicide, will not settle out to the extent that use of part of the composition will mean that treated wood may be uncoloured or incorrectly coloured.In general, storage stability and light fastness can be opposing requirements and we have found that of the available colouring agents pigments are more preferred than dyes since although pigment particles tend to settle out from the composition they generally have a reduced tendency to fade. As an empirical way of determining acceptable storage stability of the composition we have found it useful to subject a composition ot periodic agitation e.g. stirring or air blowing: if towards the end of 24 hours following agitation the colouring agent has settled out to the extent that composition drawn off from any position within the vessel is substantially depleted of colouring agent then the colouring agent is not preferred in this invention. It is preferred to include in the composition a binding agent e.g. a polymer to increase the storage stability of a colouring agent.Water soluble dyestuffs may be used but they tend to have insufficient light fastness.

Inorganic pigments (e.g. transparent iron oxides) may be used but they have a high specific gravity and tend to settle out of the composition on storage unless additives are included. Most preferably the colouring agent is an aqueous dispersion or colloidial suspension of an organic pigment e.g. finely ground azo or phthalo cyanine pigments dispersed in water and stabilised with anionic or non-ionic surfactants, since these are effective in terms of colour and light fastness. Glycols such as methylene glycol and ethylene glycol may be present for improved resistanc to freeze/thaw cycling. The pigment may be adapted to any colour for the item of wood and since consumers are used to garden fence panels coloured from yellow or gold to brown, pigments which give these colours are preferred.Where, as has sometimes proved desirable, a darker colour is preferred, carbon black dispersions may be included in the colouring agent. The pigments may be in paste form and of the type which are high strength aqueous dispersions and used for paper coating and aqueous printing inks. Such dispersions are available from several commercial sources. Our investigations have shown that if the pigment dispersion contains a surfactant which is not completely compatible with the mouldicide it is possible to reduce the incompatibility by preblending the dispersion with a resin or synthetic polymer. A high solids acrylic emulsion has been found to be especially suitable for this purpose.

The composition may include additives to enhanve its storage properties or effectiveness in use. Wetting agents, dispersants and anti-foaming agents and a resin binder or synthetic polymer may be included, preferably in the form of an aqueous acrylate emulsion, since this tends to prevent the pigment from flocculating and can assist in binding pigment and mouldicide to the wood. Synthetic polymer solutions or water thinnable alkyd resins may be included.

A preferred range of compositions is as follows (parts by weight); sodium pentachlorophenoxide 0.5 to 5.0 disodium octaborate or other borate 0.25 to 2.5 wetting agent 0.1 to 1.0 acrylic emulsion 0.75 to 10.0 pigment paste 0.5 to 6.0 antifoaming agent 0.1 to 1.0 water to 100 A composition of this invention may be applied to a substrate by a variety of ways including spray, brush or dip. As the composition is a low viscosity liquid it tends to run off vertical surfaces quickly and the invention further provides a method and apparatus for the application of such low viscosity liquids.

According to another aspect of the invention there is provided a method of applying a composition as disclosed herein to a substrate held in substantially vertical condition, comprising passing the substrate through apparatus comprising a chamber housing spray means for applying the composition on to the substrate passed through the chamber on conveyor means, spraying the composition on to the substrate, and removing surplus liquid from the wetted item by blowing means at the exit end of the chamber.

According to yet another aspect of this invention there is provided apparatus for the purpose specified comprising a chamber housing spray means for applying treatment liquid on to items passed through the chamber, conveyor means for passing items through the chamber and blowing means for removing surplus liquid from the wetted items. Typically the items will be panels.

Most preferably a second set of blowing means is present at the entrance side of the chamber to blow off the panels surface deposits or contamination. Preferably the blowing means is an air knife or the like. The blowing means is preferably air delivered at an appropriate pressure. The air may be heated.

The chamber may have a roof mounted spray system such as spray head. The liquid may be delivered at high or low pressure. The floor preferably has a tank to receive run-off and blown off surplus liquid for recirculating.

The conveyor means is preferably a chain conveyor or a conveyor belt.

In order that the invention may be well understood it will now be described with reference to the accompanying diagrammatic drawings, in which Figure 1, is an partial perspective view of one apparatus, Figure 2 is an end view of the apparatus, and Figure 3 is a partial plan view of another apparatus.

The apparatus comprises a chain or belt conveyor 1 located between the side walls 2 defining a passageway or treatment chamber. A pressure spray head system 3 is mounted above the conveyor in the chamber. The system 3 is arranged to deliver a cascade or spray deluge of composition on to garden fence panels P pulled or driven in series along the conveyor 1. The system is preferably a low pressure one, liquid being supplied and recirculated by a pump, not shown. The rate of flow of the pump is adjusted to ensure that the panels P are completely covered with liquid as they pass through the chamber. Below the conveyor 1 in alignment with the system 3 is a tank 4 to receive liquid from the system 3 and to recirculate it by pumps, not shown, to the spray system 3. The conveyor 1 is arranged to pass the panels P through the apparatus from right to left as shown in Figure 1. A set of air knives 5 is located on each side of the spray system 3, the knives 5 at the entrance side being arranged to blow dust and sawdust off the panels P before they reach the system 3 and knives Sat the exit side to drive or scour surplus liquid off the panels afterthey have been treated. The knives comprise tubes having air holes 6 or they may have slits instead through which air is driven. The air may be heated and it may be replaced by another gas e.g. nitrogen. The knives are connected to blower units, not shown. The dimensions of the knives will depend on the nature of the liquid and the rate of travel of the panels P etc. In the case of knives about 2.44 cm high the air delivery is preferably about 500 cu. ft/min (28316.8 cu. cm/min).

In use, panels Pare assembled at a station not shown and then fed onto the chain 1. The belt brings the panels to the apparatus where knives 5 blow off sawdust and surface deposits. (The blown off matter is drawn off to a dust collection unit not shown). The cleaned panel is then passed under the spray system 3 by which it is deluged with a low viscosity treatment liquid, preferably the water based mouldicide composition identified above. The panels then pass through knives 5 by which surplus liquid is driven off and the panels P, treated and dry to touch are then stacked and moved to store. Surplus liquid is drained off into the tank 4 for reuse. The apparatus is clean and simple to use, and enables panels to be treated with a non-smelling mouldicide with little or no pollution risk.

In the embodiment of Figure 3, the apparatus has side walls 2 between which pass the panels P on a chain conveyor. A pair of spray pipes 7 is mounted at the entrance side of the passageway. The pipes have spray hole outlets 8 and these are arranged to spray a mist of the low viscosity liquid composition on to the panel.

At the exit side is a pair of air knives and these comprise a pivotally mounted square tube 9 having a slit 10 through which air is blown. The tubes may be pivoted to an appropriate angle to blow liquid off the panels P.

(Extra air knives may be present at the entrance side to blow off sawdust etc. before the panels reach the spray pipes 7). The apparatus operates in the same way as that of Figures 1 and 2 but is of simpler construction.

The invention is further illustrated by the following Examples in which all parts are by weight.

Example 1 A composition was made of the following ingredients: sodium pentachlorophenoxide 1.5 aqueous dispersion of yellow pigment 1.0 acrylic emulsion 1.0 disodium octaborate 0.75 antifoaming agent 0.3 anionic wetting agent 0.5 water, balance to 100 The composition was made by dissolving in water at 40 C the borate, the pentachlorophenoxide and the wetting agent. The pigment and the antifoaming agent were mixed into the acrylic emulsion and the resulting dispersion let down with the mouldicide solution.

Fencing panels were treated with the composition using the apparatus described in Figures 1 and 2 described above. Tests carried out on fluid uptake by panels indicated a typical loading of 250 g fluid per sq.

m. They were stacked out of doors exposed to the weather and examined at intervals for visible mould growth. No visible mould was present after 4 months.

Slats from panels subjected to accelerated weathering on a QUV weatherometer (4 hours UV/4 hrs condensation alternating cycle) for periods in excess of 450 hours showed no change in hue but there was a slight darkening of the wood substrate.

Exterior exposure for period of 6 months had negligible effect on colour.

Exampe II The composition was evaluated for storage stability. Samples of the composition prepared as in Example I were stored in both metal and glass containers over a range of temperature from below 0 C to 40"C.

At temperatures in excess of 0 C up to 400C the composition was stable and retained its application capability during storage over a period of five weeks. Some settlement of pigment and binder was evident at all temperatures and such settlement increased with time. Periodic agitation obviated hard settlement and coalescence of the binder.

At 0 C and below, the composition exhibited a tendency to freeze and crystallisation of one or more of the solid components was evident.

A 400 Kg batch of the composition was prepared and stored overwinter in an outside metal tank. Hard settlement was prevented by periodic agitation and the level of settlement was low. Sub-zero overnight temperatures did, on occasion, lead to partial freezing and crystallisation. Judicious application of heat restored homogeneity and the composition appeared to suffer no lasting effects in terms of applicability.

Microscopic examination of samples taken at various times during storage revealed no change in the degree of pigment dispersion.

Corrosion tests in mild steel containers indicated that corrosive attack by the fluid did not exceed that due to water alone.

Example III The apparatus of Figure 3 was used to appiy a primer to a moulded timber window frame section and a satisfactory coating was obtained.

Example IV A range of compositions was made and applied to unseasoned slats as used for garden fence panels. The treated panels were stacked under plastics sheeting for 16 weeks during which time they were kept moist to encourage the growth of mould. The compositions were separately tested for storage stability. The results are reported in the accompanying Table I.

The results show that the preferred compositions of the invention have the desired properties of being mouldicidal, storage stable, and light-fast. The selected mouldicides had little or no smell compared to Creosote.

TABLE I Mouldicide colouring storage first mould light agent stability growth after fastness water only 0 N/A 1 week N/A KALCIOL 10 0 good 1 week N/A KALCIOL10 cationic fair/good 1 week fair/good dye KALCIOL 10 basic dye fair/good 1 week fair/good PARMETOL DF 12 (3%) acid dye good 1 week fair/good sodium pentachlorophenoxide (2%) acid dye poor no growth poor + POLYBOR (1%) sodium pentachlorophenoxide (2%) iron oxide rapid pigment no growth excellent + POLBOR (1%) pigment settlement sodium pentachloropenoxide (2%) organic acceptable no growth excellent + POLYBOR (1%) pigment dispersion 2-thiocyanomethyl thio)- organic acceptable no growth excellent benzothiazole (0.9%) pigment dispersion In the Table N/A means not applicable; KALCIOL is available from Protim Ltd., and comprises a mixture of amines and a quaternary ammonium compound; ; PARETOL DF 12 is available from Sterling Industrial Ltd. and comprises halogenated acid amine derivatives and heterocyclic compounds; and POLYBOR is available from Borax Consolidated Ltd. and comprises disodium octaborate tetrahydrate.

Claims (22)

1. A substantially odourless mouldicidal composition comprising: (i) a mouldicide component comprising one or more mouldicides, and (ii) a colouring component comprising a colouring agent chemically compatible with the mouldicide component.

2. A composition according to Claim 1, in which the colouring agent is sufficiently light fast to retain its colour for about nine months.

3. A composition according to Claim 2, in which the colouring agent does not fade or change in hue.

4. A composition according to any of Claims 1,2 or 3, in which the colouring agent is storage stable with the mouldicide component.

5. A composition according to Claim 4 in which the colouring agent is one which, when the composition is agitated daily when stored, is substantially uniformly present throughout the composition.

6. A composition according to any preceding Claim, presented in an aqueous carrier and of low viscosity.

7. A composition according to any preceding Claim, in which the mouldicide component comprises methylene bisthiocyanate, 2-(thiocyanomethylthio) benzothiazole, a pentachlorophenoxide, a borate or a mixture of these.

8. A composition according to Claim 7, in which the mouldicide component comprises a pentachlorophenoxide in a concentration from about 0.5 to 5% by weight of the composition, and disodium octaborate or a borax/boric acid blend equal to substantially half the weight of pentachlorophenoxide.

9. A composition according to any preceding Claim, in which the colouring agent comprises a water soluble dyestuff or an inorganic pigment.

10. A composition according to any preceding Claim, in which the colouring agent is an aqueous dispersion or suspension of an organic pigment.

11. A composition according to Claim 10, in which the colouring agent comprises a paste of finely divided pigment comprising a high strength aqueous dispersion containing anionic and non-ionic surfactants.

12. A composition according to any preceding Claim, including wetting agent, dispersants or anti-foaming agents.

13. A composition according to any preceding Claim, including sufficient resin binder or synthetic polymer in the form of an aqueous emulsion to enhance the chemical compatibility of the colouring agent.

14. A composition according to any preceding Claim, comprising (parts by weight): sodium pentachlorophenoxide 0.5 to 5.0 disodium octaborate or other borate 0.25 to 2.5 wetting agent 0.1 to 1.0 acrylic emulsion 0.75 to 10.0 pigment paste 0.5 to 6.0 antifoaming agent 0.1 to 1.0 water to 100

15. A composition according to any preceding Claim, substantially as described with reference to any of the Examples.

16. A method of applying a composition according to any preceding Claim to a substrate held in substantially vertical condition, comprising passing the substrate through apparatus comprising a chamber housing spray means for applying the composition on to a substrate passed through the chamber on conveyor means and spraying the composition on to the substrate and removing surplus liquid from the wetted items by blowing means at the exit end of the chamber.

17. A method according to Claim 16, in which the apparatus includes a second set of blowing means at the entrance side of the chamber, and the second blow means is arranged to blow surface deposits or contamination off the substrate before it reaches the spray means.

18. A method according to Claim 16 or 17, in which the conveyor comprises a chain or belt conveyor.

19. A method according to any of Claims 16 to 18 substantially as described with reference to the drawings.

20. Apparatus for use in applying a low viscosity liquid composition to a substrate in substantially vertical condition, comprising a chamber housing spray means for passing the items through the chamber and blowing means for removing surplus liquid from the wetted items.

21. Apparatus according to Claim 20, including a second set of blow means at the entrance side of the chamber to blow surface deposits or contamination off the items.

22. Apparatus according to Claim 20, substantially as described with reference to the drawings.