WO2006100279A1

WO2006100279A1 - Method for providing a water-repellent finish on a textile article

Info

Publication number: WO2006100279A1
Application number: PCT/EP2006/060971
Authority: WO
Inventors: Johannes A. Craamer; James E. Fox; Jagvi Ramesh Patel
Original assignee: Ten Cate Advanced Textiles B.V.
Priority date: 2005-03-22
Filing date: 2006-03-22
Publication date: 2006-09-28
Also published as: GB0505893D0; TW200700604A

Abstract

A method of producing a textile article (T) having a water-repellent finish comprising: providing a continuous supply of a textile substrate having a width; providing an array of digital nozzles (12) over the width; supplying a water-repellent formulation to the nozzles; selectively dispensing the water-repellent formulation from the nozzles in a series of droplets to deposit a predetermined pattern of droplets on the substrate; and, drying the formulation to produce a water repellent finish having substantially no hydrophilic residue.

Description

METHOD FOR PROVIDING A WATER-REPELLENT FINISH ON A TEXTILE

ARTICLE

BACKGROUND OF THE INVENTION

1. Field of the Invention [0001] The present invention relates to a process for upgrading a textile article. In particular, the invention relates to a digital procedure for producing a water-repellent textile article and to the water-repellent textile article resulting therefrom.

2. Description of the Related Art

[0002] The production of textiles traditionally takes place in a number of distinct processes. Typically five stages can be distinguished in such production; the fibre production; spinning of the fibres; the manufacture of cloth (for instance woven or knitted fabrics, tufted material or felt and non- woven materials); the upgrading of the cloth; and the production or manufacture of end products. Textile upgrading covers a number of operations such as preparing, bleaching, optically whitening, colouring (dying and/or printing) and finishing. These operations generally have the purpose of giving the textile the appearance and physical and functional characteristics that are desired by the user.

[0003] During dyeing, the textile substrate is usually provided with a single full plane colour. Dyeing presently takes place by immersing the textile article in a dye bath, whereby the textile is saturated with an appropriate coloured chemical substance. During both dyeing and printing the primary goal is to change the colour of the substrate. This is thus an aesthetic effect, characterized by the use of permanent inks and pigments, which have absorption properties at visible light wavelengths between 400 and 700 nm.

[0004] The primary goal of finishing is to use auxiliary chemicals to change the physical and/or mechanical characteristics of the textile. These finishing techniques are meant to improve the properties and/or add properties to the final product. A distinction will henceforth be made between colouring and finishing. Where necessary, finishing may be understood to exclude treatments involving deposition of particles that are applied to the substrate only because of their absorption properties at wavelengths between 400 and 700 nm. [0005] Coating of the textile is one of the more important techniques of finishing and may be used to impart various specific characteristics to the resulting product. It may be used for making the substrate fireproof or flameproof, water-repellent, oil repellent, non-creasing, shrink-proof, rot-proof, non-sliding, fold-retaining, antistatic and the like. Coating of a textile involves the application of a thin layer of an appropriate chemical substance to the surface of the textile substrate. The coating may serve to protect the textile substrate or other underlying layers. It may also be used as a basis or "primer" for subsequent layers or may be used to achieve desired special effects.

[0006] The usual techniques for applying a coating on solvent or water basis are the so-called "knife-over-roller", the "dip" and the "reverse roller" screen coaters. A solution, suspension or dispersion of a polymer substance in water is usually applied to the cloth and any excess coating is then scraped off. For such procedures to be effective, the coating formulation must be in a highly viscous, pasty form. For many functionalities it is not possible to bring the formulation into such a viscous state without affecting the functionality. This may be due to the fact that thickening agents are incompatible with the functional chemical.

[0007] A further procedure sometimes employed for finishing of the textile is the use of immersion or bath techniques known as foularding. The textile is fully immersed in an aqueous solution containing the functional composition that is to be applied. Subsequent repeated cycles of drying, fixation and condensation are required to complete the operation. This leads to considerable use of resources, in particular water and energy. In general, the solutions, suspensions or dispersions used for such techniques have low concentrations of the desired functional composition.

[0008] With respect to imparting water repellency and water proofing to textile products UK Patent No. GB2,221,928 discloses a method of applying a ketene dimer to a fabric using the methods of exhaustion (immersion), padding or spraying. Exhaustion or immersion techniques are inflexible as they necessarily impart a property on the whole of the textile whereas in many practical applications it may be more appropriate only to treat a portion thereof. [0009] The application by padding involves wetting the fabric in a liquid medium having a relatively high concentration, for example, by dipping, followed by squeezing the fabric through a pad mangle, the nip pressure of which is set to permit the retention of the desired proportion of the liquid medium. ROl 17863 describes a process of chemical treatment of a textile by cold-pad finishing in a poly(ester-siloxane) urethane dimethylformamide solution but in which the textile is pretreated using passing cold, pressurized air plasma therethrough. The physical pre-treatment presumably acts to open the weave of the fabric to enable the solution in the later chemical treatment to penetrate to the requisite depth. Although the relaxation of the fabric may act to adequately fix the waterproofing compound in the textile, the process is both a complex and expensive way of achieving this result.

[0010] The application of waterproofing agents by padding is further complicated by the tendency of the agents to adhere to the padding rollers. After prolonged operating times the rollers have to be cleaned which means an expensive interruption of the production process.

[0011] In an attempt to improve the continuity of the finishing operation, European Patent No. 0109872 describes a method and apparatus for waterproofing sheet-like materials that are supple and / or risk being deformed by stretching. In this method a sheet is made to unwind onto a conveyor; above the conveyor a single extrusion ramp that deposits an aqueous emulsion of acrylic resin on the sheet. It is noted however that the resin is only deposited as a uniform layer thereon. This citation thus fails to provide a process for finishing a textile article wherein a water repellent formulation can be precisely coated thereon without compromising the functionality of the remaining article portions or the article as a whole.

[0012] The use of inkjet printing techniques to apply functional compositions to textile substrates is suggested in Japanese Unexamined Patent Application No. JP61-152874 (Toray Industries). [0013] InkJet printers of various types are generally known for providing graphic images. Such printers may be desktop inkjet printers such as used in the office or home and are generally used for printing onto a particular type of paper substrate (printer paper), using small droplets (<20 pL) of water based inks containing colorants. Larger, industrial inkjet printers also exist for printing graphic images or date/batch codes onto products; these -A-

printers are typically printing onto non-porous substrates using solvent based inks containing colorants pigments. Such formulations are not however suitable for application to most textiles in particular due to lack of colour fastness. In order to print onto textiles using inkjet techniques, textile articles have in the past been pretreated with a coating onto which ink droplets may be applied. For upgrading purposes, most currently used coatings and finishing compositions are unsuitable for deposition using inkjet techniques. Industrial inkjet printers and nozzles that produce large droplets are generally designed for use with solvent based, coloured inks. Furthermore, the droplet volumes that can be jetted are extremely low, in the order of 50 pL and mostly insufficient for textile finishing, where a significant penetration into the fabric is necessary. Typical finishing formulations are mostly water based and generally have particle sizes that can cause clogging of the nozzles. Additional problems with foaming, spattering and encrustation have been encountered. When working with large numbers of nozzles operating continuously at up to 100 KHz, reliability and fault free operation are of prime importance. While indicating that conventional inkjet devices are unsuitable for applying finishing compositions, JP61-152874 fails to provide teaching regarding how this could be improved.

[0014] That document proposes impregnating a textile with a functional composition in the form of 'dots', wherein a mean dot diameter is between 30 and 500 μm. It is concerned primarily with maintaining an identifiable droplet structure and with preventing the droplets running together. In providing a coverage between 3 and 95 % of the available surface area, the disclosed method attempts to prevent droplets from spreading by pre-treating the textile prior to depositing the droplets. Such process related pre-treatment adds an additional step to the procedure and is generally undesirable. Furthermore, although the document provides examples regarding the use of solutions, it fails to address the problems of inkjet deposition of dispersions or suspensions, and the practical problems of foaming, sputtering and encrustation at the nozzles.

[0015] There is also a need for a formulation which can be successfully and accurately applied using inkjet deposition technology and which does not leave a hydrophilic residue on the textile on drying. BRIEF SUMMARY OF THE INVENTION

[0016] According to the present invention there is provided a method of producing a textile article having a water-repellent finish comprising: providing a continuous supply of a textile substrate having a width; providing a first array of digital nozzles over the width; supplying a water-repellent formulation to the nozzles; selectively dispensing the water-repellent formulation from the nozzles in a series of droplets to deposit a predetermined pattern of droplets on the substrate; and, drying the formulation to produce a water repellent finish having substantially no hydrophilic residue.

[0017] According to the present invention there is also provided a water-repellent formulation for application by digital droplet deposition to a textile substrate, the formulation comprising: i) 1 to 30 wt.% of a water-repellent agent preferably selected from the group consisting of acrylic resins, ketene dimers, paraffins, paraffins admixed with aluminium or zirconium salts, fluorocarbons, silicone, fatty hydrophobic compounds, alkanolamides, diakylketones and polymeric formaldehydes; ii) 50 to 95 wt.% of water; iii) 0.01 to 1 wt.% of a water-repellent anti-foaming agent; and, optionally, iv) at least one compound selected from the group consisting of co-solvents, humectants, viscosity control agents, conductivity agents, surfactants, biocides, pH modifiers, corrosion inhibitors and wetting agents, and wherein the dispersed droplets have a surface tension in the range between 20 and 50 dynes/cm and more preferably 25 and 40 dynes/cm and dry to produce a water repellent finish having no hydrophilic residue.

[0018] In this context, the value of 1 to 30 wt.% of the water-repellent agent is intended to refer to the quantity of the active component even though this may be commercially supplied in a formulation already combined with water and other additional components.

[0019] The surface tension of the droplet is critical to the wetting of the fluid inside the nozzle. If the surface tension is too high the formulation will not wet the internal surface of the nozzles properly leaving air pockets that prevent reliable release of the droplets. If the surface tension is too low the meniscus at the nozzle aperture will not form properly and the formulation will spontaneously flow therefrom.

[0020] Foam generation is often an issue with water based formulations due to the high surface tension of water and the presence of surfactants. (This problem is not encountered with traditional inks as these fluids are solvent based.). However, this issue cannot be resolved by merely including any defoaming agent in the aqueous fluid as the agent must show water-repellency. Preferred anti-foam agents in this regard comprise silicone resins, silicone gum, precipitated silica, fumed silica, polydiorganosiloxane and mixtures thereof. More preferably, the anti-foaming agents comprise the silicone based agents BYK 022™ (available from BYK-Chemie) and Respumit S™ (available from Bayer).

[0021] In accordance with a still further embodiment of the invention there is provided a textile substrate provided with a substantially continuous water-repellent finish by the digital deposition of a water-repellent formulation thereon. [0022] The term 'textile' is used herein for any substrate in general, or more specifically any fabric, and then in particular clothing flags, tent-cloths and the like on which the operations of painting, coating and / or finishing (and printing) can be performed. The term is not intended to include paper and cardboard. These fibrous articles, although sometimes referred to as textiles, are internally linked in such a way that they maintain a substantially fixed two- dimensional form. Even though they may be flexible in a third dimension they are not generally free to stretch or distort as is inherent in a true textile. Preferably the textile substrate is more than 100 meters in length and may be provided having a width of greater than 1 meter. Preferred textiles comprise cotton and/or other treated cellulosic fibres and also polyesters, polyamides, polyacrylnitril and acetates and triacetates. [0023] The term 'formulation' herein encompasses aqueous solutions, dispersions or suspensions that comprise the active component. According to an important advantage of the invention, the formulation may be non-reactive with the substrate. In this manner, the formulation may be applied to a greater diversity of substrates than would otherwise be the case. [0024] As used herein the term 'water repellent' is defined as having a degree of resistance to permeability by and damage caused by water in liquid form and therefore encompasses the common terms of water-resistant, 'waterproof and hydrophobic. It is intended to cover materials meeting, for example, the ISO 4920-1981 (E) and ISO 811 - 1981 (E) test standards. It is to be noted that a fabric can only be regarded as "waterproof when it is shown to be impermeable to water in the performance of a 'Static Head Test': although it is possible to generate waterproof fabrics using this invention, it is often preferred that the textiles are not 100% waterproof in order to allow the fabrics to breathe, that is to allow excess humidity to escape therefrom. [0025] The term 'digital nozzle' is intended to refer to a device for emitting a defined droplet from a supply of agent in response to a digital signal and depositing the droplet at a defined and controllable position. The term includes inkjet printing heads working on both the continuous flow and drop-on-demand principles. It also includes both piezoelectric and thermal inkjet heads and encompasses other equivalent devices capable of digital droplet deposition. Digital nozzles are generally well known to the skilled person in the field of graphic printing. It is envisaged that nozzles of this invention can have an outlet diameter between 10 and 150 microns, preferably around 90 microns. The advantage of such selective dispensation of the water-repellent formulation is that it provides the possibility of on- demand delivery and importantly very specific patterned layers of the finishing formulation can be applied due to the very precise dosage and control of the nozzles which are possible; the nozzles can position drops very accurately onto the substrate with placement errors of only + / - 10 microns. This accuracy of placement substantially eliminates the possibility of producing a substrate having regions that are uncovered, even when a minimum of the finishing formulation is applied. Nevertheless, the ability to form a patterned surface is highly advantageous in that, should it be desired, different parts of a textile can be imparted with different levels of resistance to water depending on the function to which the article is put. For example, those parts of textiles that may be folded to yield seams can be imparted with improved water repellency.

[0026] The ability to form a patterned surface is also highly advantageous when the water- repellent agent comprises a hydrophobic formulation. When hydrophobic molecules are applied to the fibers of a textile, they arrange themselves such that the hydrophobic parts thereof are perpendicular to the fibre surface. In this way the tendency of the water to spread over the entire surface is reduced. Under the effect of cohesion forces the water assumes the form of spheres and runs off the textile in beads. A patterned hydrophobic surface would compliment this by further localizing bead formation and partially controlling the run-off pathways. In clothing applications this could, for example, prevent the beads moving towards functional features such as zips, pockets and the like where water can more easily penetrate.

[0027] It is considered that the array of nozzles can selectively dispense the water proofing agent over the width of the textile with sufficient resolution to mimic natural water resistant surfaces, membranes, cuticles or skins (i.e. to form biomimetic surfaces).

[0028] The ejection of the formulation from the digital nozzles may additionally be controlled accurately to thereby control the penetration of the formulation into the textile. In accordance with a preferred embodiment the formulation is dispensed onto only one side of the substrate and, further, such that it penetrates the textile substrate to a maximum depth of ¹A of the thickness of said substrate. This allows for the possibility of treating only one side of the textile substrate, allowing the other side thereof to better retain its original properties and / or functionality.

[0029] According to an important aspect of the present invention, a transport surface may be provided for moving the textile substrate past the array of nozzles, the substrate being retained by the transport surface for movement therewith. Because of the ability of textiles to stretch or distort, the use of such a transport surface may ensure that the substrate remains flat and that no relevant movement takes place during the process. As machine and staging errors can contribute to placement error, the flatness of the substrate allows for small standoff distances that can lessen the impact of trajectory errors. The transport surface may be in the form of a conveyor belt, to which the substrate is temporarily affixed e.g. by a release adhesive or by vacuum. Alternatively, the transport surface may be a shape-retaining carrier layer to which the textile is affixed, e.g. a backing film. Within such an arrangement, the textile substrate may be considered analogous to a flat, pixilated screen on which the droplets of the finishing formulation can be deposited in a square matrix or other controlled format. [0030] The nozzles of the device have a preferably static position, wherein the textile is guided past the nozzles. In this way substantially higher speeds can be achieved for the transport of the textile compared to spraying systems where the nozzles are required to traverse the moving substrate. More preferably the array of nozzles are provided as parallel rows thereof; this arrangement enables effective coverage of the textile substrate as it is positioned - or moves - below the array. It does not necessarily have to be the case that the dispensing of the formulation is carried out by each row or each nozzle of each row. Equally, each row and /or constituent nozzle can be used to dispense the formulation at a different time. [0031] Dispensing materials from digital nozzles, in particular under conditions of continuous flow, is a high shear technique and materials that are not stable to shear may decompose within the nozzle or print head, blocking it. Consequently this limits the formulations particularly in respect to the viscosity of the carrier. Shear thickening fluids should be avoided. In accordance with this invention it is preferable that the formulation has a viscosity less than 25 centipoise, but more than 3 centipoise (as measured with a Brookfield viscometer) at the temperature of operation which is typically between 10°C and 60°C.

[0032] With respect to solutions and dispersions, the solids content thereof in part determines the pressure required both to eject a droplet from the digital nozzle and then break it up to achieve effective deposition; the solids act to dampen the pressure pulse used to eject the droplet. Conversely, however, it is advantageous to have a high solids' content as this will limit the amount of drying or other post-treatment required to release the active component from the formulation. Accordingly, the formulation is preferably provided having a residual solids content of greater than 2%, more preferably greater than 5% and most preferably greater than 15%. [0033] Related to the property of the solids content of the formulation is the particle size of these solids i.e. the dimensions of any crystalline structure, polymer micelle or nanoparticle included therein. As inkjet nozzles are so small there is a maximum size of particle that can be borne within the formulation and that can fit through the aperture of the nozzle. This maximum particle size is substantially smaller than the nozzle diameter due to crowding effects. Accordingly in this invention, it is preferable that any particles of formulation have a diameter less than 5 microns, more preferably less than 2 microns and most preferably less than 0.5 microns. It has been found most significant that the formulation is of a consistent quality in this respect. Reference to particle size smaller than a given diameter is thus intended to refer to the D₉₉ diameter or better. The formulation should also not be subject to flocculation or sedimentation. This is intended to mean that the composition does not form particles greater than the given values during prolonged use or when the inkjet device is idle during its normal use. It is understood that many compositions may e.g. form sediment during prolonged storage but that this may be overcome by appropriate mixing arrangements.

[0034] Although it is envisaged that the method of this application may be performed by providing each droplet of formulation on demand, it is preferable that the printing head is of the continuous inkjet flow type (sometimes herein denoted as 'CIJ') and the functional formulation is deposited by continuous inkjet flow deposition. In the continuous flow method, pumps or other pressure sources carry a constant flow of agent to one or more very small nozzle outlets. Under the influence of an excitation mechanism such a jet breaks up into a constant flow of droplets of the same size. One or more inkjets of agent are ejected through these outlets. The most used excitator is a piezo-crystal although other forms of excitation or cavitation may be used. From the constant flow of droplets generated only certain droplets are selected for application to the substrate of the textile. For this purpose the droplets are electrically charged or discharged. There are two variations for arranging droplets on the textile; binary CIJ and multi-deflection CIJ. According to the binary deflection method, drops are either charged or uncharged. The charged drops are deflected as they pass through an electric field in the print head. Depending on the configuration of the specific binary CIJ printer, the charged drops may be directed to the substrate whilst the uncharged droplets are collected in the print head gutter and re-circulated, or vice versa . According to a more preferred method known as the multi-deflection method, the droplets are applied to the substrate by applying a variable level of charge to them before they pass through a fixed electric field, or conversely by applying a fixed level of charge before they pass through a variable electric field. The ability to vary the degree of field/charge interaction on the drops means the level of deflection they experience (and thus their position on the substrate) can be varied, hence 'multi-deflection'. Uncharged droplets are collected by the print head gutter and re-circulated. More specifically this method comprises of: feeding the formulation to the nozzles in almost continuous flows; breaking up the continuous flows in the nozzles to form respective droplets, whilst simultaneously applying an electric field, as required, to charge the droplets; and applying a second electric field so as to deflect the droplets such that they are deposited at suitable positions on the textile article. [0035] Using this method of deflection the final position at which the different droplets come to lie on the substrate can be finely adjusted.

[0036] Use of the continuous inkjet method makes it possible to generate between 64,000 and 125,000 droplets per second per jet. This large number of droplets and a number of mutually adjacent heads over the whole width of the cloth results in a relatively high productivity: in view of the high spraying speed, a production speed can moreover be realized in principle of about 20 metres per minute using this technology, and in view of the small volume of the reservoirs associated with the nozzles, changeover between one finishing regime and another may be realized within a very short time. However, it is a requirement of continuous inkjets that the formulation has a conductivity to allow the droplets to be charged so that they can be deflected by the electric field. Accordingly it is preferable that the water-repellent formulation has a conductivity greater than 500μS/cm.

[0037] Typically the water-repellent formulation is provided as a solution or dispersion in water to the extent that this is compatible with the textile and with regulatory requirements. Therein, the pH of the formulation will influence the solubility or dispersion stability of the components in the fluid. Although the pH range may be limited by the tolerance of the digital nozzle to corrosion it is preferable herein that the formulation has a pH in the range between 4 and 10, and more preferably between 5 and 7.5.

[0038] On the basis of the determined properties of the water-repellent formulation chosen the droplets form a pixel of a given diameter, preferably between 120 and 500 microns on impinging on and perhaps penetrating the substrate surface.

[0039] In accordance with a preferred embodiment the individual nozzles are directed with a central control, formed for instance by a computer. The computer may preferably employ a drop and position visualization system that can be used to establish the optimum print-head operating conditions and verify the quality of the droplet formation.

[0040] As already stated herein this invention also provides a water-repellent formulation for application by digital droplet deposition to a textile substrate, the formulation comprising: i) 1 to 30 wt.% of a water-repellent agent preferably selected from the group consisting of acrylic resins, ketene dimers, paraffins, paraffins admixed with aluminium or zirconium salts, silicone, fatty hydrophobic compounds, alkanolamides, diakylketones and polymeric formaldehydes; ii) 50 to 95 wt.% of water; iii) 0.01 to 1 wt.% of a water-repellent anti- foaming agent; and, optionally, iv) at least one compound selected from the group consisting of co-solvents, humectants, viscosity control agents, conductivity agents, surfactants, biocides, pH modifiers, corrosion inhibitors and wetting agents, and wherein the dispersed droplets have a surface tension in the range between 20 and 50 dynes/cm and more preferably 25 and 40 dynes/cm and dry to produce a water repellent finish having no hydrophilic residue.

[0041] The water-repellent finish may be applied directly to the substrate. However, the textile article that is finished in accordance with this invention is preferably pretreated. The skilled reader would be aware that the pretreatment steps that can be applied to textiles before finishing are numerous and that the appropriate steps to be employed will depend on the types of fibers in the textile and the fabric construction. However, in the present invention, it is preferable that the pretreating of the textile article includes at least one processing step selected from the group consisting of hydrophilic treatments, bleaching, optically whitening, painting, printing and coating of the textile. Where pretreatment is required, it is further preferred that the chemical agents used therein are applied to the substrate by second or further arrays of nozzles disposed before the first array. Pretreatment of the textile may be divided into functional and process pretreatments. Functional pretreatments are those steps that are provided to impart additional functionality to the textile. Process pretreatments are those steps that may be additionally required or desired in order to effectively perform the process step of digital deposition of a flame retardant. According to an important aspect of the present invention, no additional process pretreatments may be required over and above the steps used in pretreating conventionally finished textiles. [0042] Concomitantly, after the water-repellent finish has been applied, the finished substrate may be subjected to post-treatment which includes at least the step of drying the substrate. Further post-treatment steps will be apparent to a person of ordinary skill in the art and would, by way of example only, include curing by the use of UV radiation or heat treatment, fixing, washing, stretching and brushing. It is perceived that the water repellent finish may be overcoated with one or more further layers of coating using second or further arrays of nozzles to provide an enhanced durability finish, which is less susceptible to abrasion.

[0043] The water-repellent finishing formulation for the application to the substrate preferably comprises a waterproofing agent selected from the group consisting of acrylic resins, ketene dimers, paraffins, paraffins admixed with aluminium or zirconium salts, silicone, fatty hydrophobic compounds, alkanolamides, diakylketones and polymeric formaldehydes. More preferably the water-repellent formulation comprises dialkyl ethers having from 8 to 50 carbon atoms, esters of branched or unbranched fatty acids, branched or unbranched fatty alcohols and halogen substituted acrylic resins. Most preferably, the water- repellent agent comprises fluoroalkylacrylate.

[0044] In order to achieve effective application by digital deposition the agent or carrier should preferably be formulated in accordance with Table 1 below, wherein the reader is asked to note that that some of the compounds are optional therein. Equally, the formulations may be varied depending on the mode of droplet deposition employed. Droplet deposition by drop-on-demand, for example, subjects the formulations to a much lower shear than continuous inkjet methods and therefore slightly different operable viscosities, solids' content and particle sizes may be considered for the formulations.

Table 1

Water Based Carrier

Formulations defined by % By weight

Binary Multideflection CIJ Thermal InkJet Piezo DOD CIJ (TIJ)

Water 70-95 50-90 70-95 60-90

Anti-Foaming Agent 0.01-1 0.01-1 0.01-1 0.01-1

Co-solvent 0 0-20 0-3 0-5

Humectant 0-3 0-5 10-30 10-35

Viscosity control agent 0-2 0-25 0-25

Conductivity agent 0-0.5 0-0.5

Surfactant 0-0.5 0-0.5

Biocide 0-0.5 0-0.5 0-0.5 0-0.5 pH modifier 0-1 0-1 0-1 0-1

Corrosion inhibitor 0-0.2 0-0.2 0-0.2 0-0.2

Wetting Agent 0 0.01-0.3 0.01-0.3

Active component(s) 5-20 5-30 1-5 5-30 [0045] The aqueous solutions or dispersions of the active components are preferably in deionised water to limit the influence of inorganic ions on the compounds.

[0046] Co-solvent may often be required to improve the solubility of the active component(s) and its compatibility with the conductivity agent (as incompatibility between these materials is a common formulation issue). Typically the co-solvents are low boiling point liquids that can evaporate from the surface of the substrate after acting as the carrier of the active component. It is preferable to use a co-solvent selected from the group consisting of ethanol, methanol and 2-propanol.

[0047] Humectant is usually a low volatility, high boiling point liquid that is used to prevent crusting of the nozzle when the jet(s) are not active. The compound polyethylene glycol

(PEG) which is a known humectant for a plurality of applications is, however, not suitable for use in this invention. Preferably the humectants are selected from the group consisting of polyhydric alcohols, glycols, glycerol, n-methyl pyrrolidone (NMP). Although with certain formulations it may appear that more than 5 wt.% humectant is being used, it is in fact the case that the same material may also be present as a viscosity modifier.

[0048] Viscosity control agents or complex binders are the key ingredient for inkjet printing reliability and quality as it controls the droplet formation and break up process. Preferred viscosity control agents include polyvinylpyrrolidone (PVP), polyethylene oxide, polypropylene glycol, acrylics, styrene acrylics, polyethyleneimine (PEI), polyacrylic acid (PAA). K-30 grade PVP has been found particularly useful due to its low bacterial sensitivity and its non-ionic nature.

[0049] Conductivity is required to allow the droplets to be charged and therefore deflected and conductivity agents are used when insufficient conductivity is naturally present in the ink. Conductivity agents must be selected that are compatible with the other components of the formulation and do not promote corrosion. Known conductivity agents suitable in this regard include: lithium nitrate; potassium thiocyanate; dimethylamine hydrochloride; thiophene-based materials, for example polythiophene or thiophene copolymers including 3,4-ethylenedioxythiophene (EDT) and polyethylenethiophenes; and, phosphoric acid esters such as Avistat 3P ™ which also exhibits antistatic effects on synthetic fibres and imparts a neutral handle. Potassium thiocyanate has been found particularly useful for jetting purposes as relatively little is required to achieve the desired conductivity.

[0050] Surfactants are typically included either to reduce foaming of the formulation and release dissolved gases or to lower the surface tension of the droplet and thereby improve wetting. Preferable surfactants for the finishing formulation of the present invention include Surfynol DF75™, Surfynol 104E™, Dynol 604™ (all available from Air Products) and Zonyl FSA™ (available from Du Pont).

[0051] pH modifiers are used to maintain a pH at which the solids of the formulation are soluble (or stably dispersed); typically this is pH>7, so most are alkaline. Preferred pH modifiers include ammonia, morpholine, diethanolamine, triethanolamine and acetic acid.

[0052] Corrosion inhibitors are used to prevent unwanted ions present in the fluid (usually as impurities coming from the active components) from causing corrosion of the printer. The preferred corrosion inhibitor herein comprises tolytriazole or ethylenediaminetetraacetic acid (EDTA). [0053] Degassing agents can be oxygen scavengers such as cyclohexanone oxime which will remove dissolved oxygen or gas release agents such a Surfynol DF75™ (available from Air Products) which will act to encourage gases to be released from the fluid and not reabsorbed. They are preferably used in high surface tension fluids which are more likely to absorb gas and release it during jetting (particularly at high firing frequency). [0054] Wetting agents are utilized to improve the surface wetting of the fluid on the internal capillaries of the digital nozzle. Preferred wetting agents include acetylinic diols. Surfactants and co-solvents may also act as wetting agents.

[0055] In addition to the above-mentioned agents, the water-repellent formulation may optionally comprise a dispersant and / or a penetrant. [0056] In accordance with a preferred embodiment of the invention the finishing formulation further includes a biocide. Many aqueous dispersions and emulsions can be seriously impaired during storage and use due to the growth of bacteria and fungi such as: Staphylococcus aureus, Salmonella typhosa, Klebsiella pneumoniae, Bacillus subtilis, Escheridia coli, Proteus vulgaris, Pseudomonas aeruginosa, Rhizopus stolonifer, Aspergillus penicilloides, Apergillus niger, Altemaria radicina and Trichophyton mentagrophytes. The inclusion of a biocide may prevent or reduce degradation by these organisms.

[0057] As used herein the term biocide refers to chemical substances intended to control insects or their larva, or to act as a bactericide, fungicide or virucide. By providing for the controlled and effective distribution of the biocide, this acts to delimit the influence of microbes before, during and after the finishing process for the textile. The nature of the substrate may also be a factor in determining the optimum amount of biocide in the finishing formulation; for example, natural fibers such as cotton are more susceptible to microbial growth due to their porous, hydrophilic structure retains water, oxygen and nutrients and may require enhanced levels of biocide.

[0058] Although it is envisaged that any biocide that is selective to such organisms may be suitable for inclusion in this invention, it is preferable that the biocides employed are selected from the group consisting of isothiazolinones, aldehydes, diacylhydrazine, triazines, quaternary ammonium compounds, hydroxymethyl ureide derivatives, etheramines, ethernitriles, hydantoins, alkylmetatoluamides, alkyl phthalates, chloronicotinyl compounds, n-methlycarbamates, organochlorine compounds, organophosporous compounds, pheromones, pyrazoles, pyrethroids, halogenated phenols, azoles, benzinidiazoles, carboxamides, dicarboxamides, dithicarbamates and substitutes benzenes. More preferably, the biocides are selected from the group consisting of N-N-diethylmetatoluamide (DEET), 3- Bromo-l-chloro-5,5-dimethyl-2,4-imidazolinedione (BCDMH), 5-Chloro-2- methylisothiazol-3-one (CMI), 2-Methyl-2,3-dihydroisothiazol-3-one (MI), 1,2- Benzisothiazolin-3-one, l,3-Dichloro-5,5-Dimethylhydantoin (DCDMH), l,3-Dibromo-5,5- Dimethylhydantoin (DBDMH), 2,2-Dibromo-2-Nitroethanol (DBNE), tetradecyl dimethyl ammonium bromide, tetradecyl dimethly benzyl ammonium bromide. Selection and use of the biocide is subject to regulatory requirements. l,2-Benzisothiazolin-2-one has been found particularly appropriate for this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Further advantages, features and details of the present invention will be elucidated on the basis of the following description for a preferred embodiment thereof. Reference is made to the following figures in which: [0060] FIG. 1 shows a schematic block diagram of the process of upgrading a substrate;

[0061] FIG. 2 shows a view in perspective of a textile finishing device according to a first preferred embodiment of the invention;

[0062] FIG. 3 is a schematic side view of the textile finishing device of figure 2; [0063] FIG. 4 is a schematic front view of the textile finishing device of figure 2; [0064] FIG. 5 is a schematic plan view of the textile finishing device of figure 2; and

[0065] FIG. 6 is a schematic side view of the textile finishing device of figure 2 showing the presence of IR heaters.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0066] The following is a description of certain embodiments of the invention, given by way of example only and with reference to the drawings. Referring to figures 2 to 6 show a textile finishing device 1 according to a preferred embodiment of the invention. Textile finishing device 1 is built up of an endless conveyor belt 2 driven using electric motors (not shown). On conveyor belt 2 can be arranged a textile article T which can be transported in the direction of arrow Pl along a housing 3 in which the textile may undergo a number of operations. Finally, the textile is discharged in the direction of arrow P2 (as shown in figure 4) for post-treatment. A large number of nozzles 12 are arranged in housing 3. The nozzles are arranged on successively placed parallel beams 4, 5, 6, 7. A first row 4, a second row 5, a third row 6 and so on are thus formed. The number of rows is variable (indicated in figure 5 with a dotted line) and depends among other factors on the desired number of operations. The number of nozzles per row is also variable and depends among other things on the desired resolution of any designs to be applied to the textile. In a particular preferred embodiment, the effective width of the beams is about 1 m, and the beams are provided with about 29 fixedly disposed spray heads, each having about eight nozzles of 50 μm per head. Each of the nozzles 12 can generate one or more jets of droplets of the finishing formulation.

[0067] In the preferred continuous inkjet method, pumps carry a constant flow of ink through one or more very small nozzles. One or more jets of ink, inkjets, are ejected through these holes. Under the influence of an excitation mechanism such an inkjet breaks up into a constant flow of droplets of the same size. The most used excitator is a piezo-crystal. From the constant flow of droplets generated only certain droplets are selected for application to the substrate of the textile. For this purpose, the droplets are electrically charged or discharged. The uncharged droplets are undeflected and are collected by a collector or gutter. The charged droplets are directed onto the substrate using an electric field whereby either the charge or the field is varied such that the final position at which the different droplets come to lie on the substrate can be adjusted. Although in figure 2, the droplets are shown being deflected in the direction of movement of the substrate it is understood that this deflection could occur also in the transverse direction. [0068] In figure 5 is indicated with dotted lines that the different nozzles 12 are connected electrically or wirelessly) by means of a network 15 to a central control unit 16, which comprises for instance a micro-controller or a computer. The drive of the conveyor belt 2 is also connected to the control unit via network 15'. The control unit can now actuate the drive and the individual nozzles as required. [0069] Also arranged per row of nozzles 4-7 is a double reservoir in which the finishing formulation substance to be applied is stored. The first row of nozzles 4 is provided with reservoirs 14a, 14b, the second row 5 is provided with reservoirs 15a, 15b, the third row 6 is provided with reservoirs 16a, 16b and so on. The appropriate formulation is arranged in at least one of the two reservoirs of a row. The nozzles 12 connected to each reservoir and disposed in different rows are directed such that the textile article undergoes the correct treatment with the finishing formulation. In this embodiment the textile article T is preferably treated with infrared radiation from light sources 13 in order to influence the coating of the finishing. [0070] It is possible to treat different successively transported textile articles in different ways, in some cases even without transport of the textile therein having to be interrupted. It is for instance possible to have different finishing formulations applied to the textile through a correct choice of the reservoirs. The first reservoirs (14a, 15a, 16a) are for instance used in each case for a first type of textile, while the second reservoirs ( 14b, 15b, 16b) are used for a second type of textile.

Example 1

[0071] A formulation "Man 93" according to Table 2 was prepared.

Table 2

[0072] The formulation was found to have the physical properties according to Table 3.

Table 3

[0073] The Man 93 formulation was jetted twice through a 62 micron Linx 6000 CIJ printer nozzle without failure or noticeable change in the fluid physical properties.

Example 2

[0074] A formulation "Man 89" according to Table 4 was tested in a Linx 6000 CIJ printer using a 62 μm nozzle.

Table 4

[0075] The formulation was found to have the physical properties according to Table 5.

Table 5

[0076] The Man 89 formulation was jetted onto a cotton substrate and showed sufficient reliability for continuous jetting up to 2 hours.

Example 3

[0077] A formulation "Man 118" according to Table 6 was tested in a Linx 6000 CIJ printer using a 62 μm nozzle. Table 6

[0078] The formulation was found to have the physical properties according to Table 7.

Table 7

[0079] The Man 118 formulation was jetted onto cotton textile and was found to exhibit excellent results. [0080] The invention is not limited to the above described embodiments thereof. The rights sought are rather defined in the following claims, within the scope of which many modifications can be envisaged.

Claims

WHAT IS CLAIMED IS:

1. A method of producing a textile article having a water-repellent finish comprising: providing a continuous supply of a textile substrate having a width; providing an array of digital nozzles over the width; supplying a water-repellent formulation to the nozzles; selectively dispensing the water-repellent formulation from the nozzles in a series of droplets to deposit a predetermined pattern of droplets on the substrate; and drying the formulation to produce a water repellent finish having substantially no hydrophilic residue.

2. The method according to claim 1, wherein the array of digital nozzles is static and wherein the textile substrate is provided by guiding it past said array.

3. The method according to claim 1 or claim 2, wherein said textile substrate is provided on an endless conveyor belt.

4. The method according to any one of claims 1 to 3, wherein said array of nozzles comprises a plurality of parallel rows.

5. The method according to any one of claims 1 to 4, wherein said formulation is supplied as a solution or dispersion in water.

6. The method according to claim 5, wherein said dispensing of the water-repellent formulation is effected by a device of the continuous inkjet and multi-level deflection type, the method comprising: feeding the formulation to the nozzles in an almost continuous flow; breaking up the continuous flows in the nozzles to form respective droplets, whilst simultaneously applying an electric field, as required, to charge the droplets; applying a second electric field so as to deflect the droplets such that they are deposited at suitable positions on the textile article.

7. The method according to any one of claims 1 to 6, wherein the formulation is dispensed only onto one side of the textile substrate.

8. The method according to claim 7, wherein the formulation is dispensed such that it penetrates the textile substrate to a maximum depth of ¹A of the thickness of said substrate.

9. The method according to any one of claims 1 to 8, wherein the droplets are deposited at a temperature in the range between 10° and 60°C.

10. A water-repellent formulation for application by digital droplet deposition to a textile substrate, the formulation comprising:

1 to 30 wt% of a water-repellent agent preferably selected from the group consisting of acrylic resins, ketene dimers, paraffins, paraffins admixed with aluminium or zirconium salts, silicone, fatty hydrophobic compounds, alkanolamides, diakylketones and polymeric formaldehydes; 50 to 95 wt% of water;

0.01 to 1 wt% of a water-repellent anti-foaming agent; and optionally at least one compound selected from the group consisting of co- solvents, humectants, viscosity control agents, conductivity agents, surfactants, biocides, pH modifiers, corrosion inhibitors and wetting agents, wherein the dispensed droplets have a surface tension in the range between 20 and 50 dynes/cm and more preferably between 25 and 40 dynes/cm and dry to produce a water repellent finish having substantially no hydrophilic residue.

11. The formulation according to claim 10 having a pH in the range between 4 and 10 and more preferably between 5 and 7.5.

12. The formulation according to claim 10 or claim 11, having a viscosity between less than 25 centipoise, more preferably less than 15 centipoise but preferably greater than 3 centipoise as measured with a Brookfield viscometer at the temperature of operation.

13. The formulation according to any one of claims 10 to 12, having a residual solids content of greater than 2%, more preferably greater than 5% and most preferably greater than 10%.

14. The formulation according to any one of claims 10 to 13, wherein said formulation has a conductivity greater than 500μS/cm.

15. The formulation according to any one of claims 10 to 14, wherein on being dispensed from said digital nozzle.

16. The formulation according to any one of claims 10 to 15, wherein particles within said formulation have a maximum diameter of less than 5 μm, more preferably less than 2 μm and most preferably less than 0.5 μm.

17. A textile substrate provided with a patterned water-repellent finish by the digital deposition of a water-repellent formulation thereon.

18. A textile substrate according to claim 17, wherein said pattern imparts different repellent properties to different parts of the substrate.

19. A textile substrate according to claim 17 or claim 18, wherein said pattern acts to concentrate the formation of beads of water when said water impinges on the substrate, thereby facilitating the run-off of those beads from the substrate.