A ONE-LAYER TRANSFER FOR DECORATING TEXTILES WITH COLOURED PATTERNS

Abstract: The invention relates to a heat application transfer for decorating textiles and similar substrates with coloured patterns. The transfer comprises a carrier sheet, which carries a one- or multi-coloured pattern layer obtainable by printing using a digitally controlled colour printer; and a transparent or white-pigmented elastomer layer printed onto the pattern layer, said elastomer layer being obtainable by printing onto the pattern layer a mixture comprising a thermosplastic polymer having essentially no free hydroxylgroups available for cross linking and having a softening point in the range of 120-180 DEG C and 5-12 % by weight of isocyanate. The transfer is simple to produce and provides patterns on textile with high resolution and long durability.

Description: A one-layer transfer for decorating textiles with coloured patterns The invention relates to a heat application transfer for decorating textiles and similar substrates with designs m the form of coloured patterns having good washing properties and durability, wherein the design is produced by means of a digitally controlled colour printer. BACKGROUND OF THE INVENTION The most common way of making transfers for application on textiles is by means of silkscreen printing where each individual colour is applied to a sheet of silicone paper. Some colours, such as vinyl and plastisol colours, are heat-activatable, but are then not very durable without further treatment. To improve the durability, the colours are usually provided with a hot melt granulate layer m the form of a powder or a fine-grained granulate mixed m an extender base which is applied to the colours and serves as a special glue layer between textile and colours, thereby considerably improving the durability. At high tempera- tures, however, e.g. during tumbling processes which in certain cases use temperatures up to 140 °C, the colours will get loose from the textile or a possible glue layer. Solvent-based two-component colours will be more stable against the action of temperature, but, when subjected to industrial washing and tumbling for an extended period of time, they will dry out and peel off from the textile. A number of available data-controlled colour printers of various types reproduce four-coloured raster images with a resolution of 600 dpi or more with an almost photographic appearance. In a pure silk screen-printing process it is not possible to achieve a resolution of more than 100 dpi, and consequently fine details are lost m the reproduction. Accordingly, it is desirable to use such colour printers for the production of coloured and particularly multicoloured configurative transfers for the textile industry. Thereby, data programs for the editing of images and designs, and the use of scanners, which transfer original im- ages to data will also by available tools in the production of transfers. The use of data-controlled colour printers in the production of transfers is not simple, particularly due to problems relating to washing and cleaning weaknesses, as the coloured image after being transferred to a textile can only stand washing at temperatures up to about 40 °C for a limited number of times. The reason is primarily that the colour toners are relatively unprotected against mechanical impacts, and that the colour types used are thermoplastic resins that remain heat-activatable at temperatures as low as about 90 °C. Attempts to print a coloured image or pattern on a carrier sheet (e.g. silicone paper) and cover it by a conventional thermoplastic adhesive to form a transfer have also been unsuccessful because the thermoplastic toners are partly absorbed into and partly smeared out on the adhesive layer. Further, such a coloured pattern is usually applied from the transfer to a textile by heating to 130-200 °C, generally 160-190 °C, under pressure, and at this temperature the toners will melt to such a low viscosity that they pass through the thermoplastic adhesive layer and into the fabric whereby the image will be distorted and fine details lost. The international patent application WO 92/07990 mentions a possible use of a colour copier with a two-component colour toner system in the production of a transfer for textiles. This, however, is pure speculation as two-component toners for a colour copier do not exist. Also, the idea of using two-component toners is contradictory to the function of the toners m a colour copier because the toners used with a digital colour printer must have a low melting point (approx. 100 °C) m order to be melted and fixed by passage of hot rollers for a fraction of a second. The above problems have practically been solved by the invention disclosed m the international patent application WO 97/21867, by a method comprising the use of a two or further layer transfer system comprising the steps of 1) printing on a carrier sheet a one-or multi-coloured pattern layer using a digitally controlled colour printer; 2) printing configuratively on the pattern layer a transparent or white-pigmented elastomer layer of a polymer having a high plasticizmg point and optionally comprising isocyanate; and 3) applying by printing a heat-activable thermoplastic polymeric glue layer on the elastomer layer or by sprinkling a heat-activable hot melt granulate on the elastomer layer while this is still wet. This method is as mentioned designated a two layer transfer system because two layers are required onto the colour pattern layer. In connection with the invention disclosed m WO 97/21867 it was observed that the polymer/isocyanate mixture combines with the toner to form a homogeneous unit, which hardens at room temperature. Thereby the washing and cleaning resistance at elevated temperatures of a print or colour pattern provided by a transfer on a textile is highly improved, and further it has been found that the ability of the thermoplastic toners to be partly absorbed into and partly smeared out on the adhesive layer is virtually gone and similarly is the tendency of the image to be distorted and loos details. OBJECT OF THE INVENTION Thus the above disclosed transfers and the method for the production thereof is highly acceptable, but still there is need for improvements. By using the method according to WO 97/21867 the different layers normally will protrudes beyond each other. Due to inaccuracies m the register when applying the elastomer layer onto the colour pattern layer, and when applying the glue layer onto the elastomer layer, the elastomer layer will at least partly protrudes beyond the colour pattern layer, and further the glue layer normally should be ap- plied so that it protrudes 1-2 mm beyond the elastomer layer due to make sure that the adhesion along the periphery of the colour pattern layer is sufficient. The glue layer on the textile is m most case visible due to a slight change of colour. Thus it would be desirable to avoid or minimize the protruding of the glue layer beyond the configuration of the other layers, while still maintaining a safe adherence along the periphery of the colour pattern layer. Also, it will be desirable to provide a method for produc- mg a transfer exhibiting the same good properties as the transfers disclosed m WO 97/21867 with respect to providing coloured image of high resolution, and with a high resistance against washing at elevated temperature, which method is easier, faster and more cost effective than the method disclosed m WO 97/21867. Thus, an objective of the invention is to provide a coloured configurative transfer, and a method for its production which transfer and which method fulfil the above desires . This and other objectives have been achieved by the transfer and the method as defined in the claims. The one layer system method defined in the claims for the production of the transfer is very attractive to the manufacturer of digital/screen printed transfer. Not only does this method reduces the production time substantially, but also it saves all the additional costs in preparation of screens and subsequent cleaning thereof. Further, it reduces the registration problem that always follows a multilayer transfer production. SUMMARY OF THE INVENTION The transfer according to the invention for decorating textiles and similar substrates with image in the form of col ¬ oured patterns is unique in that it comprises a carrier sheet, which carrier carries (a) a one- or multi-coloured pattern layer obtainable by printing using a digitally controlled colour printer; (b) a transparent or white-pigmented elastomer layer printed onto the pattern layer, said elastomer layer being obtainable by printing preferably configuratively onto the pattern layer a mixture containing a thermoplastic polymer having essentially no free hydroxyl groups available for cross linking and having a softening point in the range of 120-180 °C and 5-12 c = by weight of isocyanate. As it appear from the above the transfer comprises only one layer besides the coloured pattern layer and thus the pro- trudmg of the glue layer beyond the configuration of the colour pattern layer has been minimized, while still maintain a safe adherence along the periphery of the pattern layer . Further the method as claimed is much faster and more cost effective than the method disclosed m WO 97/21867. As mentioned above the toners used with a digital colour printer e.g. an electrostatic laser colour printers must have a low melting point (approx. 100 °C) m order to be melted and fixed by passage of hot rollers m a fraction of a second. The toners used by an electrostatic laser colour printers which is a preferred printer for the production of the transfer according to the invention are normally powder toner systems with low melting point, about 100 °C, and a very fast melting index m order to adhere to the substrate m a fraction of a second. Further, the toners are generally non-elastic and have no elongation property. Surprisingly, according to the invention, the colour toners are cross linked by the content of isocyanate, having there melting point raised to above 210 °C, whereas the thermoplastic sealant quality of the polymer resin is substan ¬ tially unaffected by the isocyanate due to the lack of free OH groups. It is a necessity that the melting point of the toners is increased to the mentioned temperature as, other- wise, they will melt down into the thermoplastic polymer resin, and/or even down into the fabric, during the heat/press application of the transfer to a textile fabric. In this case the image will be blurred and fine details lost. It is even more surprising that not only does the toner resin obtain a high melting point, but also the relative high content of isocyanate provides the toner with elastic properties, which is very desirable when the colour pattern has been applied on elastic and/or flexible substrates such as a textile. Depending on the type of thermoplastic m the elastomer layer it may be desired to incorporate an anti-cross- linking agent for preventing or reducing cross-linking of the elastomer layer. Is certain situation depending on the thermoplastic m the elastomer as well as the substrate to oe decorated it may however be preferred to allow a certain cross-linking of the elastomer. Thus, the non-reacted por- tion of the isocyanate may contribute to a better adherence to the substrate. This quality may be of especial advantage on substrates such as polyamide 6 and 6.6 textiles (nylon), which substrates are usually considered to be difficult to decorate by use of prior art transfer. Under heat and pres- sure during the application process the free isocyanate m the polymer will react with the surface of the textile by cross linking and create a stronger adhesion between the transfer and the substrate. Other digital colour printers using liquid toners - mk]et - might not require an increase of the melting temperature of the colour toners, as they may not consist of thermoplastic resins. There are solvent- as well as water-based inks used m mk ets. There are also digital colour printers using dye inks and pigmented inks, both dissolved m either a solvent or water, together with a binder. When the solvent/water is evaporated the binder glues the pigment or dye to the carrier sheet. During drying and curing the thermoplastic layer printed on top of the colour print will adhere to the dried binder containing the dyes or pigments, and form a uniform coloured layer, which is still thermoplastic. The image of the transfer can then be applied to a substrate m the usual manner. The invention is not limited to applying the resins to the digital image on paper sheets by screen printing, but can also be carried out by coating a coloured pattern printed digitally on a release liner m the form of a roll, for m- stance printed on a XEIKON electrostatic colour printer. In this case the printed coloured pattern can be coated by either a reel-to-reel screen-printing machine - manufactured by "KLEMM SIEBDRUCKMASCHINEN GmbH in Germany. Further, the coating process can be carried out as an ordinary direct roll-to-roll coating, covering the printed release liner m full width and therefore not obtaining any configuration m the thermoplastic layer. This process may be carried out as a continuous process with a coater unit followed by a tunnel dryer. DETAILED DESCRIPTION OF THE INVENTION The invention will be illustrated more fully by the following detailed description, including practical examples. The carrier sheet of the transfer according to the inven ¬ tion may m principle be any type of carrier sheet, e.g. a sheet having a non-bmdmg surface defined as a surface from which it is possible to remove the essentially part of the colour pattern layer by transferring it to a textile using heat e.g. up to about 200 °C and a pressure up to about 500 kPa. The carrier sheet may e.g. m the form of a roll. Further information concerning useful carrier can be found in WO 97/21867. Any digitally controlled colour printer my m principle be used, but it is preferred that the toner used is a dry toner powder of a thermoplastic polymer type e.g. a one component. Printer using such toners e.g. an electrostatic laser colour printer, make prints with a desirable high resolution . The pattern layer may have any size and shape. It is preferred that the transparent or white-pigmented elastomer layer printed onto the pattern layer is obtained or obtainable by printing onto the pattern layer a mixture which besides solvents and minor amount of additives e.g. additives up to about 5 * by weight, preferably up to about 1 by weight consisting essentially of a thermoplastic polymer having essentially no free hydroxyl groups available for cross linking and having a softening point in the range of 120-180 °C and 5-12% by weight of isocyanate. The thermoplastic polymer in the elastomer layer may be any thermoplastic polymer or mixture of polymers having essentially no free hydroxyl groups available for cross linking and having a softening point in the range of 120-180 °C. The thermoplastic polymer may e.g. be selected from the group consisting of PVC, polyolefins, polyesters, (PET or PBT) , polyamide, polycarbonate and mixtures thereof. Preferably the thermoplastic polymer includes at least 40 % by weight, preferably at least 80 % by weight of thermo- plastic PVC adhesive. The thermoplastic polymers should preferably be solvent- based. Any weight % or amount relating to the elastomer is relating to the elastomer without solvent. The thermoplastic polymer may further comprises 10-60 % by weight, preferably 20-40 % by weight of one or more white- pigmented or transparent thermoplastic granulates, which preferably should have an average particle size of less than 100 μm measured by sieving, meaning that at least 50 % by weight of the particles should have a particle size less than 100 μm. Preferred solvent-based thermoplastic polymers having a softening point of 120-160 °C include one component PVC without free OH groups, e.g. "TF Printable Adhesive 10210TF" from Wilflex Inc. or "ZE 591" from Sericol Ltd. These PVC adhesives consist of copolyester 15-40%, phtha- late esters mix 15-40%, polyvinyl chloride 15-40% and additives. Preferred water-based PVC dispersions are "VYCAR 576" and "VYCAR 577" which are plasticized vinyl chloride polymers using polyacrylates as thickener and anionic syn- thetic emulsifier. Generally, it is preferred to incorporate an anti-cross- linking agent for preventing or reducing cross-linking of the elastomer layer. The anti-cross-linking agent prevent or reduce any substantial cross-linking in the elastomer layer after the hardening of the colour toner has been completed and the elastomer has become substantially dry from solvent. Particularly, any significant cross-linking of the thermoplastic polymer with it self should be avoided, as such cross-linking may reduce the adhesiveness of the elas- tomer layer severely. The anti-cross-linking agent may be any component which terminates cross-linking activities e.g. components which prevent reaction between isocyanate molecules or which prevent reaction between isocyanate molecules and oxygen. Preferred anti-cross-linking agent may e.g. be a high molecular alcohol. High molecular alcohols includes any alcohols having a volatility which is sufficient low, preferably at least as low as the volatility of the solvent in the elastomer if such a solvent is used during the application of the elastomer layer. The high molecular alcohols may preferably include propanols and glycols, such as monopropylene glycol. The amount of anti-cross-linking agent largely depends on the type of thermoplastic polymer and the type of isocyanate. Generally, the amount of anti-cross-linking agent may be up to about 4% by weight of the elastomer, preferably between 1 and 3% by weight of the elastomer. The isocyanate acting as a catalyst may be any isomer thereof or mixtures. The HDI dnsocyanates of the type "Hexamethylene Dl-Isocyanate" , xylene (mixture of isomers) is recommended as regards solvent-based PVC adhesives. With regard to water-based PVC a water-soluble HDI trimmer is preferred. Both isocyanates are manufactured by "BAYER". In a preferred method of the production of the transfer a silicone paper or a heat-resistant plastic sheet coated with a thin release layer of silicone or fluorocarbon, serves as carrier, and a single- or multi-coloured pattern is printed mirror-mversed with a digitally controlled printer. On top of the coloured pattern a transparent or white-pigmented thermoplastic polymer is printed preferably configuratively by silk screen-printing using a 54-27T mesh. Prior to the printing, a cross linking agent is mixed and stirred into the thermoplastic polymer m a dosage from 5 to 12 . The polymer layer is then dried and cured m an mfrared/hot air-drymg tunnel at about 110-150 °C for about 30-150 s depending on the energy from the heat source . The image of the transfer may now be applied to any ordinary textile or other substrate m the usual manner at 170- 200 °C and a pressure of about 310 kPa for 8-15 s. EXAMPLES Example 1 A four-coloured pattern or image was printed directly on a 105 g silicone paper m a "DC12 Xerox" colour printer. Sub- sequently, a white-pigmented thermoplastic PVC adhesive "TF Super Opaque Ink" from "Wilflex Inc" with added 10% HDI trimmer from "BAYER" was silk screen printed on top of the toner pattern, using a 32T mesh. The transfer was dried and cured m an infrared-heated tunnel dryer at 130 °C for 2 minutes. The image of the finished transfer was applied to a cotton textile at 180 °C and a pressure of 310 kPa for 12 seconds. This type of transfer has a soft hand and is suitable for most types of textiles including elastic fabrics. Example 2 Like m the preceding example, a coloured pattern or image was printed on a carrier sheet, and then a transparent thermoplastic PVC layer was screen printed on top of the colour print m the described manner. This time a water- based PVC "VYCAR 576" was prepared by adding 0,5% "BYK 19" defoamer, 0,6- "BYK 346" levelling agent, 1% "COATEX 125P" thickener, "Additive N" 8% wetting agent, "Additive SLF" flow agent. After stirring for 10 minutes a viscosity of 12000 Brookfield was obtained, then 10% HDI isocyanate "Bayhydur 3100" was added, and the mixture stirred for 3 minutes. After printing, the transfer was dried and cured m an infrared-heated tunnel oven at 120 °C for 2 minutes. The image of the finished transfer was applied to a white cotton/polyester blend textile m the usual manner. This kind of transfer is only intended for white substrates, but has a particularly good adhesion to the textile due to the absence of pigment. Example 3 As m Example 1, but adding 20% (by weight) of a white- pigmented fine thermoplastic granulate with a particle size of less than 100 μm to the white-pigmented thermoplastic PVC adhesive. The granulate, "Estane T5258", is a thermoplastic polyurethane compound having good adhesion properties towards textiles. It contributes to improve the dura- bility of the transfer and enhance opaqueness of the layer on dark substrates.

Claims: CLAIMS 1. A heat application transfer for decorating textiles and similar substrates with coloured patterns, said transfer comprising a carrier sheet, which carries (a) a one- or multi-coloured pattern layer obtainable by printing using a digitally controlled colour printer; (b) a transparent or white-pigmented elastomer layer printed onto the pattern layer, said elastomer layer being obtainable by printing onto the pattern layer a mixture comprising a thermoplastic polymer having essentially no free hydroxyl groups available for cross linking and having a softening point m the range of 120-180 °C and 5-12% by weight of isocyanate. 2. A transfer according to claim 1 wherein the one- or multi-coloured pattern layer (a) is obtainable by using a powder toner printer, preferably m the form of an electrostatic laser colour printer. 3. A transfer according to any one of the claims 1 and 2 wherein the thermoplastic polymer comprises one or more polymers including at least 40 % by weight, preferably at least 80 % by weight of a thermoplastic PVC adhesive to which 5-12% isocyanate has been added prior to use. 4. A transfer according to any one of claims 1-3 wherein the thermoplastic polymer comprises 10-60 % by weight, preferably 20-40 % by weight of one or more white-pigmented or transparent thermoplastic granulates, said granulates preferably having an average particle size of less than 100 μm. 5. A transfer according to any one of claims 1-4 wherein the carrier sheet is m the form of a sheet of release pa- per which is removable from the pattern layer and elastomer layer, and preferably the transparent or white-pigmented elastomer layer has been printed configuratively on the coloured pattern layer. 6. A transfer according to any one of claims 1-4 wherein the carrier sheet is m the form of a roll. 7. A method of making a heat application transfer for decorating textiles and similar substrates with coloured patterns having good washing and durability, which comprises (a) printing a one- or multi-coloured pattern on a carrier sheet using a digitally controlled colour printer; and (b) printing on top of the coloured pattern a transparent or white-pigmented elastomer layer comprising a mixture of thermoplastic polymer having no free hydroxyl groups avail- able for cross linking and having a softening point m the range of 120-180 °C and 5-12% by weight of isocyanate. 8. A textile or similar product onto which a one- or multicoloured pattern is attached by application of a transfer according to any one of claims 1-5.

Inventors: FRANKE KELL ERIK, FRANKE, KELL, ERIK
Applicants: FRANKE KELL ERIK, STRAND EILIF, FRANKE, KELL, ERIK, STRAND, EILIF
Application year: 2001
Main classification: D06Q1
IPC codes: D06P5, D06Q1