Dye scavenger and method of production of dye scavenger

Abstract

A dye scavenger is provided that comprises a biodegradable hydrogel formed of at least one polymer chemically cross-linked by a cross-linker. The dye scavenger removes dyes rapidly, is prepared in an environmentally friendly manner, is reusable and biodegradable and can optionally incorporate other features of laundry compositions. The dye scavenger is useful for preventing dye transfer between fabrics in laundry and for removing dyes from waste water.

Claims

1. A dye scavenger comprising a biodegradable hydrogel, wherein the hydrogel comprises: a first polymer chemically cross-linked by a cross-linker, a second polymer different from the first polymer, a laundry additive comprising a fragrance, enzyme, fabric softener, water softener, anti-soil re-deposition agent, optical brightener, ethanoic acid and/or 2-hydroxypropane-1,2,3-tricarboxylic acid, wherein the hydrogel has a pore size of from about 0.01 m to about 100 m, and wherein the biodegradable hydrogel has a degree of crosslinking based on a mass ratio of the first polymer to cross-linker from about 30 to about 1.

2. The dye scavenger according to claim 1, wherein the first polymer is a natural polymer.

3. The dye scavenger according to claim 1, wherein the first polymer is selected from alginic acid and salts thereof, cellulose, lignin, bacterial nanocellulose, type A gelatin, type B gelatin, chitin, chitosan, pectin, natural gum, protein, starch, and derivatives thereof.

4. The dye scavenger according to claim 1, wherein the first polymer is chitosan.

5. The dye scavenger according to claim 1, wherein the second polymer is a natural polymer.

6. The dye scavenger according to claim 1, wherein the second polymer is selected from alginic acid and salts thereof, cellulose, lignin, bacterial nanocellulose, type A gelatin, type B gelatin, chitin, chitosan, pectin, natural gum, protein, starch, and derivatives thereof.

7. The dye scavenger according to claim 1, wherein the second polymer is sodium alginate.

8. The dye scavenger according to claim 1, wherein the cross-linker is selected from an acid 1,5-pentanedial, methylene glycol, an epoxy compound, an acrylamide derivative, a polyacid, a saccharide, a plant extract, or derivatives thereof.

9. The dye scavenger according to claim 8, wherein the acid is 2-hydroxypropane-1,2,3-tricarboxylic acid, and wherein the acrylamide derivative is N-[(prop-2 enoylamino)methyl]prop-2-enamide.

10. The dye scavenger according to claim 1, wherein the cross-linker is a plant extract.

11. The dye scavenger according to claim 1, wherein the cross-linker is genipin.

12. The dye scavenger according to claim 1, wherein the laundry additive further comprises a filler, antimicrobial agent, preservative, colour, anionic surfactant, cationic surfactant, non-ionic surfactant, and/or amphoteric surfactant.

13. The dye scavenger according to claim 1, wherein the hydrogel has a pore size from about 1 to 50 m.

14. The dye scavenger according to claim 1 that is in the form of hydrogel beads.

15. A method of preparing the dye scavenger according to claim 1 comprising the steps of: (a) providing a solution of the first polymer and the cross-linker; (b) forming the hydrogel; and (c) isolating the hydrogel; wherein step (a) comprises the steps of: (a1) providing a first solution of the first polymer and the cross-linker; (a2) providing a second solution of the second polymer; and (a3) combining the first solution and the second solution.

16. A method according to claim 15, wherein the first polymer is present in the first solution in a range of from about 0.1 to about 5.0% by mass based on the mass of the first solution and the second polymer is present in the second solution in a range of from about 0.1 to about 5.0% by mass based on the mass of the solution.

17. A method according to claim 15, wherein the cross-linker is present in the first solution in a range of from about 0.05% to about 2.0% by mass based on the mass of the first polymer.

18. A laundry composition comprising the dye scavenger according to claim 1.

19. A dye-scavenging device comprising: a housing that is permeable to a dye solution; the housing containing the dye scavenger according to claim 1.

20. The dye-scavenging device according to claim 19, wherein the housing is a perforated ball.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing the efficiency of dye absorption of a dye scavenger according to the present invention.

DETAILED DESCRIPTION

(2) The dye scavenger according to the invention comprises a biodegradable hydrogel, wherein the hydrogel comprises: a first polymer chemically cross-linked by a cross-linker. The dye scavenger optionally further comprises a second polymer.

(3) Hydrogels according to the present invention can take up large amounts of water and any solutes or particles suspended in it. For example, a hydrogel can take up to 1.1 to 1000 times its dry mass in water, while the shape is kept constant. Depending on the production process and the materials used for preparation, the swelling rate of hydrogels ranges from a fraction of a minute to hours. In addition, monomers and polymers with which cross-linking can be achieved have a very high affinity for dyes and other items present in wash water, increasing the hydrogel efficiency. The dye scavenger can absorb and/or adsorb, trap or make interactions (e.g. via hydrogen bonds, ion-ion, ion-dipole, etc.) with dyes and other items present in wash water.

(4) Examples of polymers suitable as the first polymer and/or the second polymer include linear or branched, condensation or addition polymers and their derivatives. Preferably, hydrophilic polymers are used.

(5) Preferably, a substantial portion of the monomeric units constituting the first polymer and/or the second polymer contain ionic or ionisable groups, or both, which are soluble in aqueous and/or acidic solutions. Examples of ionic or ionisable groups include amine groups, including primary, secondary, tertiary amines and quaternary amine salts, carboxylic acid groups, aromatic hydroxyl groups, such as phenols, sulfonic acid groups, sulfonamide groups, and amide groups. The presence of ionic or ionisable groups increases affinity for dyes and any other solutes or particles suspended in the water, increasing the efficiency of dye uptake. The dye scavenger can thus absorb and/or adsorb dyes and other solutes or particles suspended in wash water via e.g. hydrogen bonds, ion-ion interactions, ion-dipole interactions. The first polymer and/or second polymer may be a polyelectrolyte whose repeating units bear an ionisable group. Alternatively, the first polymer and/or the second polymer may be an ionic polymer. When an ionic polymer is used, provided that ionic groups are present in a sufficient amount, not every repeating unit needs to include an ionic group.

(6) Any polymer is suitable provided that it is capable of forming biodegradable three-dimensional structures. The hydrogel may comprise natural and/or synthetic polymers. Examples of natural polymers are alginic acid and salts thereof, cellulose, lignin, bacterial nanocellulose, type A gelatin, type B gelatin, chitin, chitosan, pectin, natural gum, protein, starch, and derivatives thereof. Examples of synthetic polymers include acrylic polymers, vinyl polymers, poly (ethylene glycols), polyhydroxyalcanoates, polylactides, polycaprolactones, poly(vinyl alcohol) and others. A combination of natural polymers, synthetic monomers and/or synthetic polymers may be used. In a preferred embodiment, the first polymer and/or the second polymer are natural polymers, because they are biodegradable and environmentally friendly. In a preferred embodiment, the first polymer is chitosan. In another preferred embodiment, the second polymer is sodium alginate. In a most preferred embodiment, one of the first polymer or the second polymer is sodium alginate and the other of the first polymer or the second polymer is chitosan.

(7) As used herein, chitosan is a linear polysaccharide composed of -(1.fwdarw.4)-linked D-glucosamine and N-acetyl-D-glucosamine, where D-glucosamine is a compound having the chemical formula (3R,4R,5S)-3-Amino-6-(hydroxymethyl)oxane-2,4,5-triol.

(8) It will be appreciated that it is not particularly important which polymer is designated the first polymer or the second polymer, and any reference to the first polymer shall be construed as including a reference to one of the first polymer or the second polymer and any reference to the second polymer should be construed as including a reference to the other of the first polymer or the second polymer.

(9) Cross-Linking of the Polymer

(10) The dye scavenger according to the invention comprises a hydrogel comprising a first polymer chemically cross-linked by a cross-linker. Such polymers are cross-linked by covalent bonds and are insoluble in water.

(11) The cross-linker may be any cross-linker that provides a biodegradable hydrogel. For example, the cross-linker may be an inorganic or organic molecule, and may be a multi-functional monomer or natural or synthetic polymer. The cross-linker may be selected from an acid such as 2-hydroxypropane-1,2,3-tricarboxylic acid, 1,5-pentanedial, methylene glycol, an epoxy compound, an acrylamide derivative such as N-[(prop-2-enoylamino)methyl]prop-2-enamide, a polyacid, a saccharide, a plant extract, and derivatives thereof. Preferably, the cross-linker is a natural compound. Preferably, the cross-linker is a plant extract. Most preferably, the cross-linker is genipin.

(12) Cross-linkers also include monomers from which cross-linking can be achieved, including vinyl and acrylic monomers such as prop-2-enamide, 1-propene-2-3-dicarboxylic acid, 2-methyl-2-propenoic acid, prop-2-enoic acid and derivatives of the aforementioned monomers.

(13) Genipin is an extract from the fruit Gardenia Jasminoides Ellis. It is known to react with primary and secondary amine groups. It degrades slowly and is non-toxic relative to other known cross-linkers. One molecule of genipin forms a single bifunctional cross-link between two chains of polymer.

(14) An important property that influences the efficiency of dye uptake by the dye scavenger is the degree of swelling. The degree of swelling is the amount by which the hydrogel can swell in water relative to a dry sample. The degree of swelling of a hydrogel sample can be expressed in terms of the ratio of the mass of the swollen hydrogel sample to the mass of the dry hydrogel sample. Preferably, the degree of swelling is from about 50 times to about 150 times with respect to the mass of the dry sample. More preferably, the degree of swelling is from about 60 times to about 100 times with respect to the mass of the dry sample.

(15) Another important property that influences the efficiency of dye uptake by the dye scavenger is the average pore size of the pores defined by the hydrogel network. The average pore size according to the equilibrium swelling theory is 0.01 m to 100 m, preferably from 1 m to 50 m. The equilibrium swelling theory is well known in the field of polymer science (see, for instance, L. Brannon-Peppas et al., Chemical Engineering Science 46 (1991) 0.715-722, and L. M. Lira et al., European Polymer Journal, 45 (2009), 1232-1238).

(16) The degree of swelling and the average pore size are influenced by the degree of cross-linking in the hydrogel, i.e. the amount of cross-linkers. Increasing the degree of cross-linking generally decreases the degree of swelling and the pore size, and vice versa. The degree of cross-linking can be expressed in terms of the mass ratio of polymer to cross-linker and is preferably from about 30 to about 1, more preferably from about 6 to about 1.

(17) Additional Laundry Additives

(18) In addition to a being a dye scavenger, the dye scavenger of the invention can also act as a fabric softener and/or water softener and/or optical brightener and/or redeposition agent and/or antimicrobial agent by including one or more additional laundry additives. Laundry additives are well known in the art, and can be selected from a filler, fragrance, antimicrobial agent, enzyme, fabric softener, water softener, anti-soil re-deposition agent, preservative, colour, optical brightener, anionic surfactant, cationic surfactant, non-ionic surfactant, amphoteric surfactant, ethanoic acid, and 2-hydroxypropane-1,2,3-tricarboxylic acid.

(19) The dye scavenger can also act as a colour catcher and an antimicrobial agent, where the antimicrobial agent is released from the hydrogel during the washing process and affects microbes present in the wash water. This improves the efficiency of a detergent throughout the wash process, especially at low washing temperatures. The microbial agent can be selected from titanium dioxide, zinc oxide, silver ions, zinc ions, silver nanoparticles, zinc nanoparticles and others. Preferably, the antimicrobial agent is silver or zinc ions.

(20) The addition of fillers to the dye scavenger can enhance its efficiency and/or mechanical properties. The fillers can be selected from natural and synthetic zeolites, fullerenes, nanotubes, talc, chalk, kaolin, titanium dioxide, zinc oxide, zinc ions, silver ions, silver nanoparticles, zinc nanoparticles, hydroxyapatite, sodium carbonate, sodium bicarbonate, sodium sulphate, sodium chloride, potassium carbonate, potassium bicarbonate, potassium sulphate, potassium chloride and others. Preferably, the filler is a synthetic zeolite, such as hydrophilic zeolite A or hydrophobic ZSM-5.

(21) Shape of the Hydrogel

(22) The dye scavenger according to the invention can be provided in the form of hydrogel beads. The beads are preferably substantially spherical or spherical in shape. The diameter of the beads can be tuned according to need, and may for example be from about 1 mm to about 10 mm in diameter. However, the dye scavenger can be provided in various shapes, for example hydrogel discs, sheets, films etc. without substantially affecting its properties, function and efficiency. The precise shape, size and amount of the dye scavenger will depend on the application.

(23) Preparation of Dye Scavenger

(24) A method of preparing a dye scavenger comprising a biodegradable hydrogel according to the invention comprises the steps of: (a) providing a solution of a first polymer and a cross-linker; (b) forming the hydrogel; and (c) isolating the hydrogel. The method preferably comprises the steps of: (a) providing a solution of a first polymer, a second polymer and a cross-linker; (b) forming the hydrogel; and (c) isolating the hydrogel.

(25) In one embodiment, step (a) comprises the steps of: (a1) providing a first solution of a first polymer and a cross-linker; (a2) providing a second solution of a second polymer; and (a3) combining the first solution and second solution.

(26) The first polymer, second polymer and cross-linker are as described above.

(27) The concentrations of the first polymer in the first solution and/or the second polymer in the second solution range from about 0.1% to about 5.0% by mass based on the mass of the solution, preferably from about 0.5% to about 3.0%, more preferably from about 1.5% to about 2.5%.

(28) In the above embodiments, the solutions of the first polymer and/or the second polymer may be provided by dissolving a preformed polymer. Alternatively, the solutions of the first polymer and/or the second polymer may be provided by dissolving monomers and an initiator, which react to provide the first polymer and/or the second polymer. When monomers are used, they may be selected from vinyl and acrylic monomers such as prop-2-enamide, 1-propene-2-3-dicarboxylic acid, 2-methyl-2-propenoic acid, prop-2-enoic acid and related derivatives of the aforementioned monomers.

(29) When monomers are used instead of a preformed polymer, the concentration of monomer in solution ranges from about 0.1% to about 5.0% by mass based on the mass of the solution, preferably from about 0.5% to about 3.0%, more preferably from about 1.5% to about 2.5%. When monomers are used instead of preformed polymer, initiator is included in the solution in an amount of from 0.1% to 1.0% by mass based on the mass of the solution.

(30) It will be appreciated that it is not particularly important which solution is designated the first solution or the second solution, and any reference to the first solution shall be construed as including a reference to one of the first solution or the second solution and any reference to the second solution should be construed as including a reference to the other of the first solution or the second solution.

(31) In an embodiment, the cross-linker is added in an amount of from about 0.05% to about 2.00% by mass based on the mass of the first polymer, for example from about 0.5% to about 1.5%.

(32) In step (b), the dye scavenger can be formed immediately upon providing a solution of a first polymer and a cross-linker; a solution of a first polymer, second polymer and a cross-linker; a solution of a monomer, an initiator and a cross-linker; or a solution of a monomer, an initiator, a first polymer and a cross-linker. Alternatively, the hydrogel may take time to form by cross-linking and/or polymerisation. In either case, the hydrogel may be agitated, for example, by stirring or shaking for a period of time. An air shaker can be used. The period of time can range from 30 minutes to 48 hours, preferably 1 hour to 36 hours, more preferably 20 to 28 hours. The hydrogel can be formed at any temperature, such as 5 C. to 90 C., preferably 10 C. to 40 C., more preferably 15 C. to 30 C., most preferably room temperature (i.e. 20 C. to 25 C.). An advantage of the invention is that the dye scavenger can be formed at room temperature or ambient temperature.

(33) The method of preparing the dye scavenger may be carried out at any pH. In a preferred embodiment, the pH of the solution will be from about 3.0 to about 9.0, preferably from about 3.5 to about 6.0.

(34) Although specific embodiments of the invention are described by reference to solution-phase polymerisation, the preferred solvent being water, the dye scavenger could be prepared by suspension or emulsion polymerisation with the appropriate equipment.

(35) The composition of the dye scavenger is determined by the relative amounts of each component included in the solution. In general, from about 80% to about 95% of the initial amount of the first polymer and the cross-linker and the second polymer, when present, is incorporated into the hydrogel.

(36) Dye-Scavenging Device

(37) The invention also provides a dye-scavenging device comprising: a housing that is permeable to a dye solution; the housing containing a dye scavenger comprising a hydrogel.

(38) The precise shape of the housing is not particularly limited, provided that it is configured to be permeable to a dye solution and retain the hydrogel. In a preferred embodiment, the housing is a perforated ball, although the housing may also be in the shape of a cube, block, bag or any other shape. The one or more perforations may be any shape or size, provided that they are configured to be permeable to a dye solution and retain the hydrogel. The one or more perforations may be uncovered holes or they may be covered with mesh or fabric. When the one or more perforations are uncovered holes, they should not exceed the diameter of the hydrogel pieces contained within.

(39) The housing may be made of any material, such as plastics or fabric.

(40) The dye-scavenging device preferably contains a dye scavenger as described above.

(41) In use, the dye-scavenging device is placed in the washing machine drum with the fabrics to be washed. During washing, dyes may be released from the fabric into the wash water to form a dye solution. The dye solution can permeate through the housing of the dye-scavenging device and contact the dye scavenger. The dye scavenger can absorb and/or adsorb, trap or make interactions (e.g. via hydrogen bonds, ion-ion, ion-dipole, etc.) with the dye to remove it from the wash water, and thereby prevent transfer onto the source fabric or other fabrics.

(42) Laundry Composition

(43) The invention also provides a laundry composition comprising a dye scavenger according to the invention. The laundry composition may be in the form of a laundry powder, laundry liquid, or laundry tablet. The laundry composition may comprise any one or more of the additional laundry additives as described above.

EXAMPLES

(44) The present invention will now be described by reference to the following non-limiting examples.

Example 1: Preparation of Dye Scavenger

(45) A dye scavenger comprising a biodegradable hydrogel can be prepared according to the following method. A first solution is provided containing a first polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution and a cross-linker in an amount of from 0.05% to 2.00% based on the mass of the first polymer. A second solution is provided containing a second polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution. The first solution is added to the second solution in a ratio of 1:1 by volume. Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The dye scavenger is ready to use.

Example 2: Preparation of an Antimicrobial Dye Scavenger

(46) An antimicrobial dye scavenger comprising a biodegradable hydrogel can be prepared according to the following method. A first solution is provided containing a first polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution and a cross-linker in an amount of from 0.05% to 2.00% based on the mass of the first polymer. A second solution is provided containing a second polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution and an antimicrobial agent in an amount of from 1% to 10% by mass based on the mass of the solution. The first solution is added to the second solution in a ratio of 1:1 by volume. Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The dye scavenger is ready to use.

Example 3: Preparation of Dye Scavenger with Filler

(47) A dye scavenger comprising a biodegradable hydrogel and a filler can be prepared according to the following method. A first solution is provided containing a first polymer in an amount of from 0.5% to 3.0% by mass based on the mass of the solution and a cross-linker in an amount of from 0.05% to 2.00% based on the mass of the first polymer. A second solution is provided containing a second polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution and zeolite as filler in an amount of from 1% to 10% by mass based on the mass of the solution. The first solution is added to the second solution in a ratio of 1:1 by volume. Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The dye scavenger is ready to use.

Example 4: Preparation of Dye Scavenger with Fragrance

(48) A dye scavenger comprising a biodegradable hydrogel and fragrance can be prepared according to the following method. A first solution is provided containing a first polymer in an amount of from 0.5% to 3.0% by mass based on the mass of the solution and a cross-linker in an amount of from 0.05% to 2.00% based on the mass of the first polymer. A second solution is provided containing a second polymer in an amount of from 0.1% to 5.0% by mass based on the mass of the solution. The first solution is added to the second solution in a ratio of 1:1 by volume: Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The beads are immersed in a fragrance solution and left for 1 hour. The dye scavenger is ready to use.

Example 5: Preparation of Dye Scavenger from a Monomer Solution and a Polymer Solution

(49) A dye scavenger comprising a biodegradable hydrogel can be prepared according to the following method. A monomer solution is provided containing a monomer in an amount of from 0.5% to 3% by mass based on the mass of the solution and an initiator in an amount of from 0.1% to 1.0% by mass based on the mass of the solution. A polymer solution is provided containing a polymer in an amount of from 0.5% to 3% by mass based on the mass of the solution and a cross-linker in an amount of from 0.05% to 2.00% based on the mass of the first polymer. The monomer solution is added to the polymer solution in a ratio of 1:1 by volume. Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow polymerisation and cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The dye scavenger is ready to use.

Example 6: Preparation of a Dye Scavenger

(50) A dye scavenger comprising a biodegradable hydrogel can be prepared according to the following method. A first solution is provided containing chitosan in an amount of 2% by mass based on the mass of the solution. A second solution is provided containing a sodium alginate in an amount of 1% by mass based on the mass of the solution and a cross-linker in an amount of 0.5% based on the mass of the first polymer. The first solution is added to the second solution in a ratio of 1:1 by volume. Beads of hydrogel are formed immediately and left on an air shaker for 24 hours at 25 C. to allow cross-linking to occur. The beads of dye scavenger are removed and rinsed in water. The dye scavenger is ready to use.

Example 7: Dye Scavenging Properties of Dye Scavenger

(51) Hydrogel beads prepared according to Example 6 were tested for removal of dye C.I. Acid Orange 7 (AO7) from solutions prepared in tap water. Four different dye solutions were tested: a) AO7 in tap water in an amount of 10 ppm; b) AO7 in tap water in an amount of 10 ppm with the addition of washing powder (Persil Expert Regular ColdZyme, Stain Removal Booster by Henkel) in an amount of 3.32 mL of washing powder per 1 L of water; c) AO7 in tap water in an amount of 10 ppm with the addition of liquid detergent for coloured clothes (Perwoll Color Magic by Henkel) in an amount of 2 mL of liquid detergent per 1 L water); and d) AO7 in tap water in an amount of 10 ppm with the addition of liquid detergent for dark clothes (Perwoll Black Magic by Henkel) in an amount of 2 mL of liquid detergent per 1 L water.

(52) Dye C.I. Acid Orange 7 (AO7) was selected because it is commonly used in dying of fabrics. An initial dye concentration of 10 ppm was selected because this is typically the maximum dye concentration that is found in the wash water of a typical washing machine. The typical dye concentration is between 1 and 10 ppm.

(53) The dye concentration was observed over 60 minutes. The results are shown in FIG. 1. After 60 minutes, the hydrogel beads absorbed almost all of the dye.

INDUSTRIAL APPLICABILITY AND ALTERNATIVE APPLICATIONS

(54) The dye scavenger according to the present invention is useful for preventing dye transfer between fabrics in laundry and for removing dyes from waste water. The dye scavenger may be used in a dye-scavenging device or it may be added to a laundry composition.

(55) Although the present invention is described as being useful in washing or laundry processes, it will be apparent to those skilled in the art that it can also be used in situations other than in laundry where dyes are present. For example, the dye scavenger of the present invention could be used to clean up waste streams from industrial waste flows comprising dyes. The present invention may be used as part of waste water treatment equipment, for example in a semi-permeable membrane of filter.