CONTAMINATION REMOVAL PROCESS

Abstract: A process for facilitating the removal of undesired contamination from a surface, comprising the steps: a) applying a solution containing a polysaccharide and a solvent therefor onto said surface before it is subjected to contamination, said polysaccharide being capable of forming a redissolvable or swelling solid film upon drying; b) allowing the applied solution to dry to form a solid film on said surface; c) treating the coated surface with a liquid capable of redissolving the film or providing for swelling thereof; and d) removing the undesired contamination by removing the dissolved or swelled surface layer of the film.

Description: Contamination removal process. The present invention relates to a process for facili- tating removal of undesired contamination from a surface. In brief, the invention resides in the concept of protecting a clean surface by a polysaccharide film which, after contami¬ nation thereof, can be partly or completely removed by treat «_* ment with a suitable solvent for the polysaccharide in ques- tion. Many surfaces exposed to the environment are continu¬ ously being contaminated by undesired deposits, such as soot grease, dust, traffic pollution etc. Furthermore, accidental stains can be made on items, such as table cloths, carpets, clothes etc. Some types of stains can be extremely difficult or even impossible to remove. Over the last years deliberate scrawling on walls or other structures has become an increas ing problem and has its origin in so called "graffiti". In paint factories, printing works and lacquering industries cleaning of containers, equipment etc. is associated with difficulties and quite generally requires strong alkaline solutions or organic solvents which cause health hazards and environmental inconvenience. Masking procedures in lacquering work are difficult to perform on curved or irregular surfa- ces . The present invention has for an object to provide new techniques by which the above-indicated problems can be cir¬ cumvented or at least greatly reduced. Another object of the invention is to provide for a methodology which does not involve health hazards or other environmental inconvenience. - These and other objects of the invention which will be clear from the following are obtained by first covering the clean surface to be treated with a polysaccharide film which is capable of redissolving or swelling when contacted by a liquid comprising a solvent for said polysaccharide. The po- lysaccharide film thus applied to the surface involved will protect said surface from direct contamination. When contami nated undesired contamination can be easily removed from the surface by treating the contaminated surface with a liquid which is capable of redissolving the film or providing for swelling thereof, whereafter the undesired contamination can be removed by removing at least the dissolved or swelled sur¬ face layer of the film. Such removal can be obtained by any suitable technique, such as spraying, brushing, wiping, rub- bing, washing or the like. Thus, the invention provides for a process for facili¬ tating the removal of undesired contamination from a surface, comprising the following steps: a) applying a solution containing a polysaccharide and a solvent therefor onto said surface before it is subjected to contamina ion, said polysaccharide being capable of forming a redissolvable or swelling solid film upon drying; b) allowing the applied solution to dry to form a solid film on said surface; c) treating the coated surface with a liquid capable of redissolving the film or providing for swelling thereof; and d) removing the undesired contamination by removing the dissolved or swelled surface layer of the film. According to an alternative procedure the facilitated removal of such undesired contamination from a surface may comprise the steps: a) applying a preformed polysaccharide film onto said sur¬ face which film is capable of redissolving or swelling when contacted by a liquid comprising a solvent for said poly— saccharide; b) treating the coated surface with a liquid capable of redissolving the film or providing for swelling thereof; and c) removing the undesired contamination by removing the dissolved or swelled surface layer of the film. In this .alternative procedure there is thus used a pre¬ formed polysaccharide film having the desired properties in regard to being capable of redissolving or swelling when treated with a suitable solvent for the polysaccharide. With regard to the polysaccharide solution used in the process of the invention it is preferred to use an aqueous solution. Thus, a water-soluble polysaccharide is preferred to use in such solution. By the term "water-soluble polysaccharide" there is meant polysaccharide which is soluble m water in a liquid state. In order that the polysaccharide used shall perform in a satisfactory manner it shall be capable of forming, when a solution thereof is applied to a surface, a film which is reversably dissolvable or which has the ability to swell when contacted with a solvent for the polysaccharide. Films of the polysaccharide can be produced by solvent evaporation, wet casting or molding. Polysaccharide films can exist as supported or unsupported films. Supported films do not possess sufficient mechanical strength to be used as such but can be produced from low molecular weight carbohydrates supported by a solid substrate. Unsupported films are typical for high molecular weight polysaccharides . Such polysaccharides having molecular weights of from 10^ to 2x10^ daltons generally form unsuppor¬ ted films. Branched polysaccharides need higher molecular weights than linear ones to form unsupported films. Less po- lar polysaccharide derivatives, for example methyl ethers, may form unsupported films at molecular weights of about 8x10^ daltons. Mechanical strength generally increases with increasing chain length up to molecular weights of 10 5 to 10 6 daltons . "Bone dry" polysaccharide films are hard and brittle due to the multiplicity of hydrogen bonding sites, but under normal conditions water is always present m an amount of about 5-20% by weight providing a desired softening effect. To obtain maximum mechanical strength about 5-20% by weight of plasticizer is usually required. On exposure to water most polysaccharide films will be subject to swelling, and the degree of swelling is dependant on the extent of crystalline areas in the film. Most polysaccharides are suitable for use in the pre¬ sent invention in indoor applications, whereas outdoor uses require substantial retrogradation of the polysaccharide n the film. Among suitable polysaccharides the following groups can be mentioned: Hemicelluloses Ce.g. arabinoxylans, glucomannans ) Plant gums Ce.g. Guar gum, Locust bean gum) Cellulose and derivatives thereof Ce.g. ethyl celluloses, hydroxytehyl celluloses, carboxymethyl celluloses) Starch and starch derivatives Ce.g. hydroxyethyl starch) Microbial polysaccharides Ce.g. xanthan gum, curdlan, pullu- lan, dextran) Algal polysaccharides Ce.g. agar, carragenans , alginic acid) Chitin, chitosan and their derivatives. Some polysaccharides are conveniently made into films by precipitation from an aqueous solution under evaporation Ce.g. Locust bean gum, dextran, xanthan). Other polysaccha- rides must be solubilized in alkaline media Ce.g. curdlan and other β-1, 3-glucans) . When neutralized some of these will form supersaturated solutions capable of forming films on evaporation. Some of the polysaccharides will pass over a gel state before forming films. The concentration of the polysaccharide used in the solution thereof may vary within broad limits and the solu¬ tions may contain up to about 25% by weight of a polysaccha¬ ride based on the weight of the solution. It is preferred that the solution does not contain more than about 10% by weight of the polysaccharide and it is particularly preferred to use a concentration of the order of 1 to 2% by weight. Mixtures of two or more polysaccharides may, of course, be used if desired, and such combinations of two polysaccha¬ rides, one of which has a higher dissolvability in water at a certain temperature than the other one at the same tempera¬ ture, are preferred due to advantageous interaction between the two polysaccharide components. Such combination may comprise or essentially consist of: at least a first component a) excluding galactans con¬ stituted by a substituted β-l,4-linked glycan which is dis- solvable in water of a certain temperature and which has a molecular weight CMw) of ∑ 5-10^ Daltons, preferably ∑ 10^ Daltons, particularly __ 10 6 Daltons, and at least a second component b) , also excluding galac¬ tans, constituted by a substituted β-l,4-linked glycan which is more difficult to dissolve than said first component at said temperature, or is agar or a carrageenan. In such composition it is preferred that component a) is a substituted β-l,4-linked glucan, gluco annan, xylan, mannan or a β-l,4-linked polysaccharide consisting of 2-acet- amido-2-deoxy-D-glucopyranos- or 2-amino-2-deoxy-D-glucopyra- nos entities. The substitution of the glycan of component a) is preferably constituted by mono- or oligosaccharide groups or hydroxyalkyl , carboxyalkyl, aminoalkyl, alkyl, acyl or hydroxyalkylCalkyloxy)alkyl . Component b) in the composition of the present inven¬ tion is preferably a substituted β-l,4-linked glucan, gluco¬ mannan, xylan, mannan or a β-l,4-linked polysaccharide con¬ sisting of 2-acetamido-2-deoxy-D-glucopyranos- or 2-amino-2- -deoxy-D-glucopyranos entities, or agar or carrageenan. The substitution of the glycan of component b) may be the same as that of component a) . In a preferred embodiment of the composition of this invention component b) is a substituted β-i,4-linked glucan, glucomannan, xylan, mannan or a β-l,4-linked polysaccharide consisting of 2-acetamido-2-deoxy-D-glucopyranos or 2-amino- -2-deoxy-D-glucopyranos entities, or agar or carrageenan, the substitution consisting of mono- or oligosaccharide groups or hydroxyalkyl, carboxyalkyl, aminoalkyl, alkyl, acyl or hyd- roxyalkylCalkyloxy)alkyl . According to yet another embodiment of the invention component a) is a substituted β-l,4-linked glucan or mannan, chitin or chitosan-, component b) also being a polysaccharide selected from these or from agar and carrageenan. In such composition the substitution is preferably mono- or oligo¬ saccharide groups, hydroxyalkyl, carboxyalkyl, alkyl, acyl or hydroxymethyl methyloxy)methyl . According to another embodiment of the invention compo¬ nents a) and b) are selected from galactomannans , cellulose derivatives, chitin derivatives and chitosan derivatives. In such composition components a) and b) are suitably selected from galactomannans, hydroxyethyl celluloses and carboxy- ethyl celluloses. Components a) and b) are particularly se¬ lected from galactomannans, such as Guar gums and Locust bean gums . In regard to the character of components a) and b) as concerns their dissσlvability in water of a certain tempera¬ ture, such temperature is not critical as to its level but constitutes a demarcation line between the two components in regard to dissolvability in water. However, for normal uses of the composition of the present invention at normal envi- ronmental temperatures, a practical temperature range would be from about 30 to about 50°C although still not a limiting range. At normal, room temperature a practical demarcation temperature would be about 40°C. It is important to note that the process of the inven- tion when practically utilized results in a solid film, wherein the polysaccharides are present m an essentially amorphous state. The present invention is particularly suitable to use in regard to the removal of non-covering undesired contamma- tion, such as a graffiti or scrawl type of contamination, in particular ink or paint type of contamination, especially of the lacquer based type, or environmental precipitation, such as soot, dust etc. The structure of the surface to be treated can vary between glossy surfaces, such as glass or metal, to highly porous surfaces, such as concrete or mortar surfaces. When used on porous surfaces, the cleaning of which normally is virtually impossible, the invention greatly facilitates removal of contamination therefrom and one could say m fact that the invention is the first practical solution to the problem of removal of such contamination. The invention will in the following be further descri¬ bed by specific examples of a non-limiting character. EXAMPLE 1 This example illustrates the use of the invention for the removal of undesired scrawl or graffiti from a concrete wall. In the example there is used an aqueous polysaccharide solution containing about 1% by weight of a mixture of 20% by weight of Guar gum and 80% by weight of Locust bean gum. Lo¬ cust bean gum is sold by Sigma Chemical Corporation, St. Louis, USA and is a galactomannan polysaccharide originating from seeds of Seratonia siliqua. The Guar gum used is sold by the same company. The solution described above is applied onto a concrete wall in three layers in a quantity of about 11/m^. After each application the layer applied is allowed to dry. After drying of the last layer the underlying concrete wall was fully vi¬ sible due to the transparence of the film. The protected wall was then sprayed with lacquer paints of differents brands including both two component lacquers and three component lacquers. Other parts of the wall was subjected to scrawl using a water-proof felt pen. After seve¬ ral days of drying the contaminated wall could be easily cleaned by scrubbing with water or by using a high pressure hose. Heating the water to an increased temperature made the cleaning even easier. After drying no contamina ion could be seen on the concrete wall . EXAMPLE 2 The experiment of Example 1 is repeated using Guar gum in a 1% Cw/w) aqueous solution and similar results were ob¬ tained. EXAMPLE 3 The experiment of Example 1 is repeated using a solu¬ tion of Locust bean gum Cl% w/w) , similar results being ob¬ tained. EXAMPLE 4 Example 1 is repeated while applying the polysaccharide solution onto a brick wall. Similar results are obtained. EXAMPLE 5 Example 2 is repeated using galvanized steel as a test surface. The same useful results are obtained. EXAMPLE 6 Example 1 is repeated using soluble potatoe starch CSigma) in a concentration of about 2% by weight. Similar results are obtained. EXAMPLE 7 Example 1 is repeated using chitosan CSigma) as a 1% by weight solution in 0,5N AcOH. S-ubstantially the same results are obtained. EXAMPLE 8 Example 1 is repeated using hydroxyethyl cellulose CCellosize WP-40) as a polysaccharide. Similar results are obtained . EXAMPLE 9 Example 1 is repeated using native dextran CPharmacia, Sweden) as a 5% by weight solution. Substantially equal re¬ sults are obtained. EXAMPLE 10 Example 1 is repeated using xanthan gum CSigma) as an aqueous solution at 1% by weight. Similar results are obtai¬ ned. EXAMPLE 11 Example 1 is repeated using Pullulan CSigma) as a 1% by weight aqueous solution. Substantially equal results are ob¬ tained . EXAMPLE 12 Example 1 is repeated using Pectin CSigma) in a concen¬ tration of 2% by weight, aqueous solution. Similar results are obtained .

Claims: CLAIMS 1. A process for facilitating the removal of undesired contamination from a surface, comprising the steps: a) applying a solution containing a polysaccharide and a 5 solvent therefor onto said surface before it is subjected to contamination, said polysaccharide being capable of forming a redissolvable or swelling solid film upon drying; b) allowing the applied solution to dry to form a solid film on said surface; 1.0; c) treating the coated surface with a liquid capable of redissolving the film or providing for swelling thereof; and d) removing the undesired contamination by removing the dissolved or swelled surface layer of the film. 2. A process for facilitating the removal of undesired 1.5 contamination from a surface, comprising the steps: a) applying a preformed polysaccharide film onto said sur¬ face which, film is capable of redissolving or swelling when contacted by a liquid comprising a solvent for said poly¬ saccharide; 20 b) treating the coated surface with a liquid capable of redissolving the film or providing for swelling thereof; and c) removing the undesired contamination by removing the dissolved or swelled surface layer of the film. 3. A process according to claim 1 or 2, wherein under 25 the removal step Cd and c, respectively) said removal is pro¬ vided by spraying, brushing, wiping, rubbing, washing or the like. 4. A process according to claim 1, 2 or 3, wherein said solution is an aqueous solution. 0 5. A process according to any preceding claim, wherein there is used a polysaccharide having a molecular weight of at least about 1000. 6. A process according to any preceding claim, wherein the solution contains up to about 25% by weight of the poly- 35 saccharide. 7. A process according to claim 5, wherein the solution contains up to about 10% by weight of the polysaccharide. 8. A process according to any preceding claim, wherein the polysaccharide is selected from the group comprising: celluloses and derivatives thereof, starches and derivatives thereof, plant gums, capsular microbial polysaccharides, pec- tins, inulins, and algal polysaccharides. 9. A process according to any preceding claim for faci¬ litating the removal of graffiti type undesired contamination on a surface . 10. A process according to any of claims 1-8 for faci- litating the removal of undesired contamination in the form of environmental precipitation on a surface.

Inventors: SVENSSON SIGFRID, SVENSSON, SIGFRID
Applicants: BIOBOAT AB
Application year: 1988
Main classification: B05D5
IPC codes: B05D1, B05D5, B08B17, C09D5, C09K3