A method for manufacturing an efflorescence-resistant building block and a building block produced thereby

Abstract

A method is disclosed for manufacturing an efflorescence-resistant building block which comprises the steps of: preparing a cementitious mixture comprising a plasticiser, wherein the plasticiser compr

Description

Field of the Invention The present invention relates to a method for manufacturing building blocks, and more particularly, to a method for preventing efflorescence on building blocks during a vapour curing process. Background In the manufacturing of concrete products such as building blocks, pavers, or bricks, it is necessary for the freshly moulded concrete to undergo a curing process to achieve its required structural strength and durability. A simple method for curing is to place the demoulded blocks on open racks in a production hall and allow them to harden in ambient air over several days or weeks. However, this air-curing method is slow and often results in inconsistent hardening and strength development due to variations in air temperature, humidity, and airflow. For large-scale commercial production, such a slow and unreliable process is not viable. To accelerate production, the industry standard is to use a vapour curing process. In this process, uncured building blocks are placed on stacked racks inside a large, enclosed vapour cure chamber. The blocks are then exposed to an environment of elevated temperature and high humidity for a prolonged period, for example, 12 to 24 hours. This accelerated process allows the building blocks to gain a significant portion of their final compressive strength rapidly, enabling faster turnover and consistent quality. However, the vapour curing process suffers from a significant drawback. The high humidity and temperature differentials within the chamber cause water vapour to condense on the internal surfaces of the chamber, including the racks and trays holding the blocks. This condensation forms drips that fall onto the visible top surfaces of the building blocks located on the racks below. These drips penetrate the surface of the fresh concrete and, as they dry, draw soluble salts from the cementitious material to the surface, resulting in a cosmetic defect known as efflorescence. This efflorescence manifests as unsightly white spots or rings, rendering the product visually unappealing and commercially unviable. A critical issue is that this defect may not appear immediately after curing but can develop over a period of up to six months, by which time the product may have already been sold and delivered to a customer. There is therefore a need in the art for a method of manufacturing building blocks that overcomes the problem of efflorescence caused by dripping condensation during a vapour curing process, without compromising the efficiency of the curing process itself. Summary of the Invention According to a first aspect of the invention there is provided a method for manufacturing an efflorescence-resistant building block comprising the steps of: i. preparing a cementitious mixture comprising a plasticiser, wherein the plasticiser comprises: a. ethoxylated nonylphenol; b. polyethylene glycol (PEG); c. sodium polyacrylate copolymer; d. dodecylbenzene sulphonic acid; and e. at least one other component; ii. inserting the cementitious mixture into a mould for forming a building block; iii. allowing the cementitious mixture to harden to form an uncured building block, and demoulding the uncured building block; iv. placing the uncured building block in a vapour cure chamber; and, v. removing the cured building block from the vapour cure chamber after curing. Advantageously, the addition of this specific plasticiser functions to at least temporarily prevent vapour-curing induced efflorescence in the top layer of the building block. This increases the commercial viability of the building blocks produced by this method, as they are not unsightly in comparison to building blocks with efflorescence. Optionally, the method comprises preparing a first cementitious mixture and a second cementitious mixture. Optionally, the method comprises adding the plasticiser to both the first cementitious mixture and the second cementitious mixture. Optionally, the method comprises adding the plasticiser to the second cementitious mixture only. Optionally, the method comprises initially inserting the first cementitious mixture into the mould to form a base layer. Optionally, the method comprises inserting the second cementitious mixture into the mould adjacent the first cementitious mixture for forming a top layer of the building block. Optionally, the step of allowing the cementitious mixture to harden involves allowing both the first and second cementitious mixtures to harden to form an uncured building block. Optionally, the ethoxylated nonylphenol is present in a range of 15% to 17% by weight. Optionally, the polyethylene glycol (PEG) is present in a range of 5% to 7% by weight. Optionally, the sodium polyacrylate copolymer is present in a range of up to 1% by weight. Optionally, the dodecylbenzene sulphonic acid is present in a range of 4% to 6% by weight. Advantageously, the specific concentration ranges of ethoxylated nonylphenol, PEG, sodium polyacrylate copolymer and dodecylbenzene sulphonic acid have been demonstrated to be particularly effective in reducing or eliminating efflorescence. Optionally, the at least one other component is present in a range of 69% to 76%. Optionally, the other component of the plasticiser is or comprises liquid carrier. Optionally, the liquid carrier is water. Optionally, the method comprises heating the vapour cure chamber after the uncured building block has been added. Optionally, the method comprises heating the vapour cure chamber to a maximum temperature of between 30°C and 50°C. Optionally, the method comprises controlling the relative humidity within the vapour cure chamber after the building block has been added. Optionally, the vapour cure chamber has a relative humidity of between 80% and 100% during curing. Optionally, the method comprises curing for up to 96 hours in the vapour cure chamber. Optionally, the vapour cure chamber comprises a plurality of racks for holding the building blocks, wherein the racks are arranged in a vertical stack. Optionally, the building block is a brick, a paver, or a kerbstone. Optionally, the top layer has a thickness that is less than the thickness of the base layer. In embodiments where the plasticiser-containing mixture is only present in a thinner top layer, the method provides the full protective benefit in a cost-effective manner, as the additive is used only where it is needed on the visible surface. Further, additives such as pigments may be added to the top layer. Again, by only adding such additives to a smaller portion of the entire block this reduces cost and improves the quality of the final product. Optionally, the thickness of the top layer is between 5% and 30% of the total thickness of the building block. Optionally, the second cementitious mixture further comprises a pigment. According to a second aspect of the invention there is provided a building block prepared by the method of any preceding claim. Advantageously, the building block produced by this method has the benefits of being vapour cured, which is known to reduce permeability and enhance surface finish, whilst also avoiding the unsightly efflorescence that results from the vapour curing process. According to a third aspect of the invention there is provided a use of a plasticiser comprising: i. ethoxylated nonylphenol; ii. polyethylene glycol (PEG); iii. sodium polyacrylate copolymer; iv. dodecylbenzene sulphonic acid; and v. at least one other component; wherein the use comprises adding the plasticiser to a cementitious mixture in the manufacture of an efflorescence-resistant building block. This defines a new and non-obvious use for a specific class of plasticisers, applying them not for their conventional purpose of improving workability, but to solve the distinct technical problem of preventing surface efflorescence. Optionally, the ethoxylated nonylphenol is present in a range of 15% to 17% by weight. Optionally, the polyethylene glycol (PEG) is present in a range of 5% to 7% by weight. Optionally, the sodium polyacrylate copolymer is present in a range of up to 1% by weight. Optionally, the dodecylbenzene sulphonic acid is present in a range of 4% to 6% by weight. Optionally, the at least one other component is present in a range of 69% to 76%. Optionally, the other component of the plasticiser is or comprises liquid carrier. Optionally, the liquid carrier is water. Features of the various aspects of the invention are interchangeable between the aspects. List of Figures Specific implementations of the present disclosure will now be described, by way of example only, and with reference to the accompanying drawings in which: Figure 1 is a flow chart of the method according to the invention. Figure 2 is a side view of a building block according to the invention. Detailed Description Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains. The meaning and scope of these terms should be clear, but in cases of ambiguity, the definitions articulated herein supersede any definitions found in dictionaries or external sources. Within the specification and the appended claims, unless explicitly stated otherwise, the ensuing terms are ascribed the meanings outlined: As used herein, the term "building block" refers to any precast concrete or cementitious article that can be used in construction or landscaping. This includes, but is not limited to, products such as bricks for walling, pavers for walkways and driveways, and kerbstones for edging. As used herein, the term "cementitious mixture" refers to a composition used to form concrete products, which may comprise a cementitious binder (such as cement), an aggregate (such as sand and / or stone), and water. The mixture may optionally include other admixtures or pigments. As used herein, the terms "base layer" and "top layer" refer to the distinct layers of a dual-layer building block. The "base layer" constitutes the main structural body of the block. The "top layer" is formed adjacent to the base layer and constitutes the primary visible and aesthetic surface of the block when installed. The top layer is formed from the second cementitious mixture containing the plasticiser. As used herein, the term "plasticiser" refers to a chemical admixture added to a cementitious mixture. While traditionally used to improve the workability and flow of the mixture, in the context of the present invention, the term specifically refers to an additive formulated to impart efflorescence resistance to the hardened surface of the building block, particularly against defects caused by dripping condensation during a vapour curing process. As used herein, the term "vapour cure chamber" refers to an enclosed environment or oven used for the accelerated curing of concrete products. Such a chamber is capable of maintaining an atmosphere of elevated temperature and high relative humidity (water vapour) to promote the rapid hydration of cement. As used herein, the term "efflorescence-resistant" describes the property of a building block’s surface to prevent or substantially reduce the formation of efflorescence, which is the crystalline deposit of soluble salts that appears as white spots or rings on the surface, especially when caused by water penetrating the surface during the curing process. Figure 1 outlines the method for manufacturing a building block according to the invention. In this particular example, the building block comprises two layers, but in other embodiments the building block may have a single layer. The building block may be a brick, a block, a paver, or a kerbstone, for example. The method comprises providing a cementitious mixture which is then inserted into a mould. In the particular example in Figure 1, there is a first and second cementitious mixture. Optionally, the cementitious mixture, the first cementitious mixture or second cementitious mixture, or both the first and second cementitious mixtures, comprises sand and cement. Optionally, the cementitious mixture, the first cementitious mixture or second cementitious mixture, or both the first and second cementitious mixtures, comprises aggregates. The aggregates may be pebbles. The pebbles may have a maximum sie of 15 mm, 12.5 mm, 10 mm, or 7.5 mm. The sand may have a maximum particle size of 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, or 2 mm. The cement may be present in a range of 8% to 25% by weight, or 10% to 20%. The sand may be present in a range of 70% to 90% by weight, or 80% to 90%. In one embodiment, the first cementitious mixture has a sand content of 84% to 86% by weight, and cement content of 10% to 12% by weight. In one embodiment, the first cementitious mixture comprises sand with a particle size of no greater than 5 mm. In one embodiment, the first cementitious mixture comprises pebbles at 14% to 16% by weight of the mixture. In one embodiment, the first cementitious mixture comprises pebbles having a size of no greater than 10 mm. In one embodiment, the second cementitious mixture comprises a sand content of 81% by weight, and cement content of 19% by weight. In one embodiment, the second cementitious mixture comprises sand with a particle size of no greater than 3 mm. In step i. a first cementitious mixture is prepared. The first cementitious mixture is inserted, in particular by pouring, although any suitable method may be used, into a mould. This forms a base layer of the building block. Next, in step ii, a second cementitious mixture is prepared. The second cementitious mixture may include a pigment for decorative purposes, such that the second cementitious mixture provides a different colour than the first cementitious mixture. The second cementitious mixture also includes a plasticiser comprising ethoxylated nonylphenol, polyethylene glycol (PEG), sodium polyacrylate copolymer, dodecylbenzene sulphonic acid and at least one other component. The volume of plasticiser added may vary. At least the top 10% of the building block may comprise at least 0.1 ml of plasticiser. At least the top 15% of the building block may comprise at least 0.2 ml of plasticiser. At least the top 15% of the building block may comprise at least 0.3 ml of plasticiser. At least the top 15% of the building block may comprise at least 0.4 ml of plasticiser. The top 20% may comprise approximately 0.5 ml of plasticiser. The ethoxylated nonylphenol may comprise a branched nonyl moiety. The ethoxylated nonylphenol may comprise variable ethoxylation. The ethoxylated nonylphenol may have an amphiphilic structure. The ethoxylated nonylphenol may conform to the general formula: R-C6H4-O-(CH2CH2O)n-H. R may be a branched nonyl group (C9H19). R may be attached predominantly at the para position of the phenol ring. The hydrophilic portion may be a polyoxyethylene chain, (CH2CH2O)n. The number of repeating ethoxy units, n, may be 1 to 15, 1 to 10, or 1 to 5. The ethoxylated nonylphenol may be present in a range of 15% to 17% of the plasticiser by weight. In other embodiments, this range may be greater, for example 12% to 20% or 10% to 30%. The ethoxylated nonylphenol may be present at a concentration of 16% or approximately 16%. The polyethylene glycol (PEG) component may be any linear or branched polyether diol derived from ethylene oxide, generally represented by the formula HO(CH2CH2O)nH, where ‘ri is an integer that yields an average molecular weight suitable for the intended application. Typically, the PEG will have a number average molecular weight ranging from about 200 to 2,000 g / mol, such as PEG 400, PEG 600, or PEG 1000. Additionally, the PEG may be capped or modified to alter its polarity, compatibility, or volatility. Such modifications include, but are not limited to, PEG mono- or diesters (e.g., acetate, laurate, or phthalate esters), PEG ethers (e.g., methyl, ethyl, or butyl ethers), or mixed functionalised PEGs. The PEG may be present in a range of 5% to 7% of the plasticiser by weight. In other embodiments, this range may be greater, for example 2% to 10% or 1% to 20%. The PEG may be present at a concentration of 6% or approximately 6%. The sodium polyacrylate copolymer may be any water-soluble or water-swellable synthetic polymer derived from acrylic acid and its salts, specifically comprising a sodium. This includes polymers resulting from the co-polymerisation of sodium acrylate (or acrylic acid neutralised with sodium hydroxide). Additionally, it includes polymers resulting from the co-polymerisation of one or more co-monomers selected from the group consisting of: carboxylate-containing monomers (e.g., methacrylic acid, maleic acid, or their salts), acrylamides (e.g., acrylamide, methacrylamide, N-isopropylacrylamide), hydrophobic monomers (e.g., vinyl acetate, styrene, alkyl acrylates, or hydrophobic / V-alkyl acrylamides), sulphonate-containing monomers (e.g., 2-acrylamido-2-methylpropanesulphonicacid, or AM PS), or nonionic monomers (e.g., hydroxyethyl acrylate, polyethylene glycol acrylates). The polymer can be linear or cross-linked. The cross-linking agent may be a polyfunctional vinyl monomer (e.g., divinyl glycol or methylene-bis-acrylamide). The molecular weight of the copolymer may be from 500 g / mol up to about 25,000 g / mol. The molecular weight of the copolymer may be from 1,000 g / mol up to about 10,000 g / mol. The molecular weight of the copolymer may be from 2,000 g / mol up to about 5,000 g / mol. The sodium polyacrylate copolymer may be present in a range of up to 4% by weight. The sodium polyacrylate copolymer may be present in a range of 0.01% to 1%, 2%, 3% or 4% by weight. The sodium polyacrylate copolymer may be present in a range of 0.1% to 1%, 2%, 3% or 4% by weight. The dodecylbenzene sulphonic acid component may be present as a linear alkylbenzene sulphonic acid (LABSA) homologue. The dodecylbenzene sulphonic acid may comprise a mixture of C10 to C14 alkyl chains attached to a benzene ring that is functionalised with a sulphonic acid group. The dodecylbenzene sulphonic acid may be an anionic surfactant or wetting agent, or both. Advantageously, this molecule exhibits strong dispersing and emulsifying properties to ensure the homogeneous blending of all components within the plasticiser. The dodecylbenzene sulphonic acid may be present in a range of 4% to 6% of the plasticiser by weight. In other embodiments, this range may be greater, for example 2% to 10% or 1% to 20%. The dodecylbenzene sulphonic acid may be present at a concentration of 5% or approximately 5%. The at least one other component of the plasticiser may be a liquid carrier. The carrier may be a polar protic solvent like water, a polar aprotic solvent, or a hydrocarbon solvent (e.g., mineral spirits, toluene, or xylene). The carrier may be a polyol liquid such as propylene glycol, glycerine, ora low-molecular-weight Polyethylene Glycol (as previously described). The at least one other component is present in a range of 69% to 76%. In other embodiments, this range may be greater, for example 60% to 80%. The at least one other component may be present at a concentration of 72% or 73% or approximately 72% or approximately 73%. The at least one other component may be only the liquid carrier. The total sum of ethoxylated nonylphenol, polyethylene glycol (PEG), sodium polyacrylate copolymer, dodecylbenzene sulphonic acid and at least one other component is 100% by weight of the plasticiser. Next, in step iii, the second cementitious mixture is inserted, for example, by pouring, into the mould adjacent the first cementitious mixture for forming a top layer of the building block. Then, in step iv, the first and second cementitious mixtures are allowed time to harden to form an uncured building block, which is then subsequently demoulded. In step v, the uncured building block is placed in a vapour cure chamber to undergo an accelerated curing process. The vapour cure chamber is a large, enclosed environment designed to maintain a controlled atmosphere of elevated temperature and high humidity. The uncured building blocks are typically arranged on a plurality of shelves of a transportable rack, with the top layer of the building block facing upwards. These racks are configured to be arranged in a vertical stack inside the chamber to maximise production capacity. It is this industrially necessary arrangement, however, that gives rise to the technical problem solved by the present invention. During the high-humidity curing cycle, condensation inevitably forms on the underside of each shelf or tray of a rack. This condensation then drips down onto the exposed top surface of the building blocks positioned on the rack immediately below, which in the prior art leads to the formation of efflorescence. By placing the uncured building block, which includes the plasticiser in its top layer, into this environment, the present invention provides resistance to this damaging dripping effect. During curing, the vapour cure chamber may have an internal maximum temperature of between 30°C and 50°C, or between 34 and 42°C. The vapour cure chamber may have an internal maximum temperature of 38°C, or approximately 38°C. During operation, the temperature may fluctuate, for example, during the initial heating and then during cooling at the end of the curing process. During curing, the vapour cure chamber may have an internal relative humidity of between 80% and 100%, or between 80% and 90%, or even between 82.5% and 87.5%. The curing process within the vapour cure chamber is ideally at least 24 hours. However, the curing process may last up to 96 hours, up to 72 hours, or up to 48 hours. Finally, in step vi, the cured building block is then removed from the vapour cure chamber. Figure 2 illustrates a building block 1 as prepared by the present method comprising a top layer 2 and bottom layer 3. In this particular example, the building block comprises two layers, but in other embodiments the building block may have a single layer. The top layer has a thickness that is less than the thickness of the base layer. The thickness of the top layer may be between 5% and 30% of the total thickness of the building block. The thickness of the top layer may be between 10% and 25% of the total thickness of the building block. The building block 1 is efflorescence-free for at least 7 days, at least 14 days, at least 28 days, at least 2 months, at least 3 months, at least 4 months, at least 5 months, or at least 6 months after curing. The use of a vapour cure chamber subjects the building block to a fundamentally different and more aggressive environment compared to a block left to cure in ambient air. While air curing relies on slow, passive evaporation which, as noted in the prior art, can lead to insufficient strength, lower durability, and increased porosity, the vapour curing process is an active method. It intentionally introduces high levels of external moisture at elevated temperatures, creating a saturated atmosphere. This controlled, high-humidity environment is crucial for achieving rapid strength gain -reaching 70-90% of design strength in under 24 hours - and improved early durability by reducing permeability, making it essential for viable commercial-scale production. However, these conditions of high heat and saturated water vapour create the secondary problem of intense condensation and dripping, a phenomenon not present in air curing. The inventive step of the present invention lies in this specific context. Plasticisers are conventionally understood in the art to be rheology-modifying agents, used to improve the flow and workability of the wet cementitious mixture. It was entirely unexpected that such an additive would also function as a protective agent, creating a surface that is uniquely resilient to the efflorescence caused by the specific mechanism of condensation dripping within a hot, saturated vapour environment. Therefore, the combination of subjecting the block to a vapour curing process while simultaneously protecting its top layer with a plasticiser represents a non-obvious solution to a long-standing and commercially significant problem inherent to this essential manufacturing technique. Where a range of values is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter. It should be understood that the terms “a” and “an” as used above and elsewhere herein refer to “one or more” of the enumerated components. It will be clear to one of ordinary skill in the art that the use of the singular includes the plural unless specifically stated otherwise. Therefore, the terms “a,” “an” and “at least one” are used interchangeably in this application. Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as size, weight, reaction conditions and so forth used in the specification and claims are to the understood as being modified in all instances by the term “about”. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present subject matter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Throughout the application, descriptions of various embodiments use "comprising" language; however, it will be understood by one of skill in the art, that in some instances, an embodiment can alternatively be described using the language "consisting essentially of or "consisting of."

Claims

1. A method for manufacturing an efflorescence-resistant building block comprising the steps of:i. preparing a cementitious mixture comprising a plasticiser, wherein the plasticiser comprises:a. ethoxylated nonylphenol;b. polyethylene glycol (PEG);c. sodium polyacrylate copolymer;d. dodecylbenzene sulphonic acid; ande. at least one other component;ii. inserting the cementitious mixture into a mould for forming a building block;iii. allowing the cementitious mixtures to harden to form an uncured building block, and demoulding the uncured building block;iv. placing the uncured building block in a vapour cure chamber; and,v. removing the cured building block from the vapour cure chamber aftercuring.

2. The method of claim 1 further comprising preparing a first cementitious mixture and a second cementitious mixture, wherein initially the first cementitious mixture is inserted into the mould to form a base layer, and the second cementitious mixture is inserted into the mould adjacent the first cementitious mixture for forming a top layer of the building block, and wherein the step of allowing the cementitious mixture to harden involves allowing both the first and second cementitious mixtures to harden to form an uncured building block.

3. The method of claim 1 or claim 2 wherein the ethoxylated nonylphenol is present in a range of 15% to 17% by weight.

4. The method of any preceding claim wherein the polyethylene glycol (PEG) is present in a range of 5% to 7% by weight.

5. The method of any preceding claim wherein the sodium polyacrylate copolymer is present in a range of up to 1% by weight.

6. The method of any preceding claim wherein the dodecylbenzene sulphonic acid is present in a range of 4% to 6% by weight.

7. The method of any preceding claim wherein the at least one other component is present in a range of 69% to 76%.

8. The method of any preceding claim wherein the other component of the plasticiser is or comprises liquid carrier.

9. The method of claim 8 wherein the liquid carrier is water.

10. The method of any preceding claim comprising heating the vapour cure chamber after the uncured building block has been added, wherein the vapour cure chamber is heated to a maximum temperature of between 30°C and 50°C.

11. The method of any preceding claim comprising controlling the relative humidity within the vapour cure chamber after the building block has been added, wherein the vapour cure chamber has a relative humidity of between 80% and 100% during curing.

12. The method of any preceding claim comprising curing for up to 96 hours in the vapour cure chamber.

13. The method of any preceding claim wherein the vapour cure chamber comprises a plurality of racks for holding the building blocks, wherein the racks are arranged in a vertical stack.

14. The method of any preceding claim, wherein the building block is a brick, a paver, or a kerbstone.

15. The method of claim 2, wherein the top layer has a thickness that is less than the thickness of the base layer.

16. The method of claim 15, wherein the thickness of the top layer is between 5% and 30% of the total thickness of the building block.

17. The method of claim 2 wherein the second cementitious mixture further comprises a pigment.

18. A building block prepared by the method of any preceding claim.

19. Use of a plasticiser comprising:i. ethoxylated nonylphenol;ii. polyethylene glycol (PEG);iii. sodium polyacrylate copolymer;iv. dodecylbenzene sulphonic acid; andv. at least one other component;wherein the use comprises adding the plasticiser to a cementitious mixture in the manufacture of an efflorescence-resistant building block.

20. The use of claim 19 wherein the ethoxylated nonylphenol is present in a range of 15% to 17% by weight.

21. The use of claim 19 or claim 20 wherein the polyethylene glycol (PEG) is present in a range of 5% to 7% by weight.

22. The use of any one of claims 19 to 21 wherein the sodium polyacrylate copolymer is present in a range of up to 1% by weight.

23. The use of any one of claims 19 to 22 wherein the dodecylbenzene sulphonic acid is present in a range of 4% to 6% by weight.

24. The use of any one of claims 19 to 23 wherein the at least one other component is present in a range of 69% to 76%.

25. The use any one of claims 19 to 24 wherein the other component of the plasticiser is or comprises liquid carrier.17A

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