Patent Publication Number: US-2011070408-A1

Title: Material For Heat Transfer Decoration And Method For Manufacturing Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of pending International patent application PCT/FR2009/050963 filed on May 25, 2009, which designates the United States and claims priority from French patent application 0853590 filed on May 30, 2008, the content of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of decoration using the hot-press transfer technique in which a sheet that carries or defines a decorative pattern is pressed by a heated element such as an iron onto a target base material. In particular, the invention has applications in the field of personalising garments and fabrics. 
     More precisely, the invention relates to a product for decorating a base material by using a hot-press transfer technique and a method for manufacturing such a product. 
     BACKGROUND OF THE INVENTION 
     The hot-press transfer technique is implemented by using special products that are specially developed for this technique where a transferable sheet carries or defines the decorative pattern. This transferable sheet is generally combined with a backing sheet which is hot pressed and can be peeled off once transfer has been obtained. 
     The transferable sheet can be attached to the target base material by a thermofusible bonding layer that is heated during transfer so that it temporarily melts; this bonding layer is located on the opposite side to the peel-off sheet. 
     The decorative pattern can be produced by means of printing on the transferable sheet in which case the latter is, more precisely, a printable sheet. 
     The decorative pattern may also be cut out from the transferable sheet so that it is defined by the cut line once the off cuts have been removed. 
     Currently, the visual appearance of transferable sheets is the result of their colours and, if applicable, the texture of their constituent materials. As far as the Applicant is aware, no currently available transferable sheet is embossed or has any other raised pattern that can withstand hot-pressing at the time of transfer, i.e. is not degraded by being crushed at the time of hot-pressing. 
     SUMMARY OF THE INVENTION 
     The present invention has at least the object of increasing the aesthetic possibilities of decorating base materials such as fabrics by using the hot-press transfer technique by allowing decoration attached using this technique to define a raised pattern such as embossing. 
     According to the invention, this object is achieved thanks to a product for decorating a base material by hot-press transfer comprising a sheet that can be transferred onto such a base material by hot pressing. A raised pattern is defined by the front surface of this transferable sheet which comprises at least one shape-holding layer which is obtained from a polyurethane-based solution having a high solids content having partial, prematurely blocked polymerisation. 
     It has been observed that, for reasons that have not yet been explained, the raised pattern of the sheet of such a product as defined above remains intact after such a sheet has been transferred by hot pressing. Such transfer can be performed onto a fabric, especially onto a garment or another base material such as a motor vehicle dashboard. 
     Advantageously, the sheet comprises a strengthening layer that covers said shape-holding layer and results from the drying of a polyurethane-based fully polymerised resin solution. Such a strengthening layer makes the sheet more resistant to mechanical stresses and, in particular, prevents premature crazing of this sheet. 
     Advantageously, said strengthening layer defines the front surface of the transferable sheet and comprises a superficial portion which is distinguished from an underlying portion of the strengthening layer by having a different colour and is located mainly in those areas that protrude from said front surface. When this is the case, a particular aesthetic effect resulting from a combination of two distinct localised colours having different depths can be obtained. 
     Advantageously, the transferable sheet comprises a bonding layer for attaching it to a target base material by hot-pressing. 
     Advantageously, on one side of the shape-holding layer, namely its side that is opposite the strengthening layer, the bonding layer covers one face of the shape-holding layer. 
     Advantageously, the product for hot-press transfer decoration comprises a backing sheet that carries the transferable sheet without covering the thermofusible bonding layer and can be peeled off in order to separate it from the transferable sheet once transfer has been accomplished. This backing sheet may be transparent in order to facilitate positioning the transferable sheet prior to fixing it by hot-pressing. 
     The object of the invention is also a method for manufacturing a product that is designed to decorate a base material and which comprises a sheet that can be transferred by hot-pressing. The front surface of this transferable sheet defines a raised pattern. The method involves a step in which: 
     b) Using a polyurethane-based solution having a high solids content having partial, prematurely blocked polymerisation, one forms a shape-holding layer for the transferable sheet. 
     Advantageously, in step b), one forms a film with said solution having a high solids content and one then dries said film and continues polymerisation of the polyurethane that is present in this film. 
     Advantageously, in step b), one continues polymerisation of the polyurethane that is present in said film by subjecting the film to heating. 
     Advantageously, this method involves a step in which: 
     a) Using a polymerised polyurethane-based resin solution, one forms a strengthening layer for the transferable sheet. 
     In this case, the shape-holding layer and the strengthening layer are formed on top of each other in steps a) and b). 
     Advantageously, the transferable sheet is formed on an impression that defines a negative of said raised pattern and the method involves a step that takes place after step b) and in which: 
     c) One separates the transferable sheet from said impression. 
     Advantageously, step b) takes place after step a) in which one deposits the polyurethane-based polymerised resin solution in the form of a film on said impression and one then dries this film. If this is the case, one forms the shape-holding layer on the strengthening layer in step b). 
     Advantageously, in step a), one first forms a superficial portion of the strengthening layer in the recessed areas of the impression and, on this superficial portion, one then forms an underlying portion of the strengthening layer, with the superficial portion and the underlying portion of the strengthening layer having different colours. 
     Advantageously, this method involves a step which follows step c) and in which: 
     d) One combines the transferable sheet and a peel-off backing sheet with each other so that the peel-off backing sheet is located on the opposite side to a thermofusible bonding layer that is part of the transferable sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be made more readily understandable by the following description which is given merely by way of example and relates to the accompanying drawings in which: 
         FIG. 1  is a schematic cross-sectional view of a portion of a product that is suitable for use with the hot-press transfer technique in accordance with the invention; 
         FIG. 2  is a diagram showing a plant in which a transferable sheet is produced by hot-pressing and is intended to be part of the product shown in  FIG. 1 ; 
         FIG. 3  is a diagram showing a plant in which the product shown in  FIG. 1  is produced from the transferable sheet produced in the plant shown in  FIG. 2 ; 
         FIG. 4  is a schematic perspective view of the product shown in  FIG. 1  before it is used; 
         FIG. 5  is a view similar to  FIG. 4  showing the same product as in  FIGS. 1 and 4  and shows a preparatory step prior to use of the product in a transferable sheet from which a decorative pattern that is to be transferred by hot-pressing has been cut out; and 
         FIG. 6  is a schematic view of a garment provided with the decorative pattern shown in  FIG. 5  and illustrates an operation that follows hot-press transfer of this decorative pattern. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a product  1  which is intended to be used to decorate a garment by means of hot-press transfer and which comprises two sheets combined with each other, back to back, namely a multilayer sheet  2  that can be transferred by hot-pressing and a peel-off backing sheet  3 . 
     In the following text and in the appended claims, the terms “back”, “front” and similar terms refer to transferable sheet  2  after it has been transferred to a fabric as viewed by an observer who is looking at transferable sheet  2 . 
     The front surface  4  of transferable sheet  2  comprises recessed areas  5  and protruding areas  6  which alternate with each other and together form a raised pattern. This raised pattern is defined by two superposed layers  7  and  8  of transferable sheet  2 . In the example suggested here as one possible way of implementing the invention, this pattern is a grain that imitates the grain of natural leather. 
     Layer  7  of transferable sheet  2  is more precisely a shape-holding layer designed to prevent hot-press transfer of this sheet causing this raised to pattern to disappear, i.e. the grain in the example suggested here. It is made of polyurethane (PU) in a manner that is explained below. 
     Layer  8  of transferable sheet  2  is also made of polyurethane (PU). This layer is a strengthening layer which is not manufactured in the same way as shape-holding layer  7  but is intimately bonded to the latter thanks to chemical compatibility and has the function of increasing the strength of transferable sheet  2  in order to withstand mechanical stresses such as tensile forces. The particular role of strengthening layer  8  is to increase the ability of transferable sheet  2  to stretch elastically when subjected to tensile forces, thus preventing crazing of transferable sheet  2  once it has been attached to the target garment. It also defines the front surface  4  to which it gives a smooth, non-tacky touch. 
     Strengthening layer  8  may be the same colour throughout, i.e. be a single colour. It may also be different coloured. This is the case in the example shown where the colour of strengthening layer  8  is not the same at every point. In the protruding areas  6 , a superficial portion  9  of strengthening layer  8  is a first colour. An underlying portion  10  of strengthening layer  8  is a second colour which is different to the first colour. These first and second colours can be chosen so as to accentuate the raised look of front surface  4  and/or so that front surface  4  looks really similar to the external surface of a natural leather. 
     Besides layers  7  and  8 , transferable sheet  2  comprises a thermofusible bonding layer  11  which can, in particular, be copolyester based and covers the back surface of shape-holding layer  7  which is opposite strengthening layer  8 . This bonding layer  11  is designed to securely attach layers  7  and  8  to the target fabric. 
     Backing sheet  3  consists of a transparent film made of polyethylene teraphthalate (PET) and has one side that is tacky, i.e. provided with an adhesive that allows it to be stuck to a surface several times and then detached. In fact, this tacky side is bonded to front surface  4  of transferable sheet  2  so that backing sheet  3  can be peeled off, i.e. be detached from transferable sheet  2 . The other side of backing sheet  3  undergoes a non-stick treatment so that it can be detached easily, thereby allowing product  1  to be wound before use and then easily unwound. 
     A plant for manufacturing transferable sheet  2  is shown in  FIG. 2  where the arrows indicate the directions of the various feed or rotation movements. Layers  7  and  8  of sheet  2  are produced first using a technique known as “transfer coating” in which a coating is applied to a temporary base material. In the example shown, this temporary base material consists of grained paper  12 , which is commonly referred to as transfer paper, one side of which  13  defines a mould impression. This mould impression comprises indentations that match protruding areas  6  and protrusions that match indentations  5 . Its shape is therefore a negative of the embossing that is intended to be defined by front surface  4 . In other respects, paper  12  is a conventional transfer paper such as that marketed under the brand name EMBOSSED DOLARO by the firm FAVINI CARTIERA, via 4 novembre, 276—28882 CRUSINALLO/OMEGNA (VB)—ITALY. 
     A first coating station  20  of the system shown in  FIG. 2  is used to deposit solution  21  on surface  13  of transfer paper  12 . This solution  21  contains a fully polymerised polyurethane-based resin that is a first colour and is dissolved in a solvent. A doctor blade  22  determines the quantity of solution  21  left on surface  13  of transfer paper  12 . The blade is adjusted so that solution  21  is only left in the indentations defined by surface  13 , i.e. in the indentations that match protruding areas  6 . 
     After coating station  20 , transfer paper  12  goes into a first drying oven  23  where the solvent in solution  21  is evaporated. When it leaves oven  23 , superficial portion  9  of strengthening layer  8  is formed in the indentations in surface  13 . It consists of the non-volatile matter in solution  21 , i.e. the polyurethane-based resin contained in solution  21 . After drying, superficial portion  9  is distributed with a surface density which can, for example, be of the order of 10 g/m 2 . A solution  21  consisting of 59% by weight Larithane marketed under the brand name MS 128 by the firm NOVOTEX ITALIANA SPA, 39.4% by weight dimethylformamide (DMF), 0.44% by weight Norene black marketed under the brand name S1052 by aforementioned firm NOVOTEX ITALIANA SPA, 1.06% by weight Norene orange marketed under the brand name S3188 by aforementioned firm NOVOTEX ITALIANA SPA and 0.1% by weight Noresil marketed under the brand name S 900 by aforementioned firm NOVOTEX ITALIANA SPA, whose address is via Enrico Fermi, 20—20083 GAGGIANO (MI)—ITALY, has produced good results. 
     Drying in oven  23  is followed by a second coating operation. This takes place at a second coating station  24  where solution  25  is deposited on superficial portion  9  and on those areas of surface  13  of transfer paper  12  that are still exposed. This solution  25  has substantially the same chemical composition as solution  21 , but the colour of its non-volatile matter is nevertheless different. A doctor blade  26  on coating station  24  determines the quantity of solution  25  that is deposited and the assembly is then moved into second drying oven  27  where the solvent is evaporated from solution  25 . After drying, the solid content of deposited solution  25  forms underlying portion  10  of strengthening layer  8 . Its surface density can then be, for example, of the order of 30 g/m 2 . 
     When strengthening layer  8  has been formed on transfer paper  12 , the assembly is transported to third coating station  28  where polyurethane-based solution  29  is deposited on the exposed side of strengthening layer  8 . This solution  29  has a high solid content and is also referred to as a “high-solid solution” in which the polyurethane-based solid content is high compared to that of a normal polyurethane solution such as solutions  21  and  25 . 
     The proportion of non-volatile matter in the high-solid solution is advantageously in excess of 70% by weight and preferably in excess of 85% by weight, for instance of the order of 95% by weight. 
     For example, solution  29  may contain only 5% solvent by weight whereas the proportion of solvent in solutions  21  and  25  is of the order of 70% by weight. The polyurethane in solution  29  is partially polymerised which means that its polymerisation has been prematurely blocked. A solution  29  consisting of 91.41% by weight UCECOAT SV 201, 6.76% by weight UCECOAT IT 131, 0.46% by weight UCECOAT AS 20, 0.46% by weight UCECOAT R446/50, 0.46% by weight UCECOAT AS 41 and 0.46% by weight flatting agents, marketed under the brand name TS 100 by the firm SAFIC-ALCAN, 3, rue Bellini—92806 PUTEAUX—FRANCE, has produced good results. Solution  29  has the composition defined above and is colourless. Solution  29  may also be coloured in which case the colorants are part of its composition. Products UCECOAT SV 201, UCECOAT IT 131, UCECOAT AS 20, UCECOAT R446/50 and UCECOAT AS 41 are available from the firm CYTEC—Anderlecht Str 33—1620 DROGENBOS—BELGIUM. 
     A doctor blade  30  determines the quantity of solution  29  that is deposited in the form of film  31  on strengthening layer  8 . The assembly is then transported to drying oven  32  where the solvent in solution  29  is evaporated. After drying, film  31  may, for example, have a surface density of the order of 80 to 100 g/m 2 . 
     The conveyor belt from oven  32  is driven by two heated calendaring rollers  33  between which the belt passes. Thermofusible bonding layer  11  carried on temporary polyethylene film  34  also passes between calendaring rollers  33  which attach it by heating it and pressing it against dry film  31 . A thermofusible layer marketed under the brand name FAITERM 104 by Italian firm FAITPLAST, Via industriale—25060 CELLATICA (BR)—ITALY has produced good results when used as bonding layer  11 . 
     The heat provided by oven  32  and/or provided by calendaring rollers  33  causes polymerisation of the polyurethane in film  31  to continue so that this polymerisation is finished after film  31  has been formed. Once the polyurethane it contains has been polymerised, film  31  constitutes shape-holding layer  7 . 
     The penultimate operation is performed by plant as shown in  FIG. 2  and involves releasing transferable sheet  2  from the impression by separating it from transfer paper  12  in  35 . Transferable sheet  2  can then be wound, cut into sheets or packaged in other ways. 
     Product  1  can be produced from transferable sheet  2  obtained from a plant as shown in  FIG. 2  and from a strip of backing sheet  3  obtained from a plant as shown in  FIG. 3  where the arrows indicate the directions of feed or rotation movements. In  FIG. 3 , transferable sheet  2  and backing sheet  3  together pass through two calendaring rollers  40  which press them against each other so as to stick the adhesive side of backing sheet  3  against front surface  4  of transferable sheet  2 . The two calendaring rollers  40  are heated in order to heat the adhesive that is present on the adhesive side of backing sheet  3 . A polythene terephthalate sheet marketed under the brand name ETL115142 by the firm BISCHOF+KLEIN GmbH—Rahestraβe 47 —49525 LENGERICH—GERMANY has given good results when used as backing sheet  3 . 
     When transferable sheet  2  and backing sheet  3  have been attached to each other, temporary film  34  is removed, after which product  1  is finished. 
       FIGS. 4 and 5  illustrate the first steps in using product  1 .  FIG. 4  shows a sample of product  1 , on the transferable sheet  2  whereof the outline  50  of a decorative pattern that is to be cut out  51  is marked in a dotted line. Using an appropriate device such as a graphic cutter, one cuts out decorative pattern  51  from transferable sheet  2  without cutting peel-off backing sheet  3 . Following this, only decorative pattern  51  that is to be transferred is left on peel-off backing sheet  3 , the off cuts  52  produced by cutting having been removed, as shown in  FIG. 5 . 
     The transparency of backing sheet  3  makes it easier to position decorative pattern  51  prior to attaching it to a garment such as a T-shirt. It is attached by hot-pressing. In a manner that is known in itself, attachment involves pressing decorative pattern  51  complete with peel-off backing sheet  3  against the garment, using a hot press or an electric iron. During this process, bonding layer  11  of decorative pattern  51  softens or even melts, thus allowing it to attach to the fibres of the target garment. 
     In  FIG. 6 , decorative pattern  51  has been attached to garment  53  by hot-pressing. Bonding layer  11 , once cooled and solidified, attaches decorative pattern  51  to the fabric of garment  53 . Peel-off backing sheet  3  can be removed and separated from decorative pattern  51 , as illustrated in  FIG. 6 . 
     It has been demonstrated that, surprisingly, the embossing of front surface  4  withstands hot-press transfer thanks to the presence of shape-holding layer  3  in transferable sheet  2 . 
     The invention is not confined to the embodiment described above. In particular, the plant shown in  FIG. 2  can be broken down into several separate subassemblies, even though grouping these subassemblies together enables continuous operation. 
     In addition, hot-press transfer of transferable sheet  2  or part thereof can be achieved on a target base material other than a fabric by making a few adjustments that are within the ability of those skilled in the art. For example, the target base material can be a dashboard, an interior trim component or a passenger compartment shelf of a motor vehicle or some other accessory such as a passenger compartment. 
     In addition, shape-holding layer  7  can be made of a foamed plastic and have a cellular structure. To achieve this, a foaming agent can be incorporated in solution  25 . For example, this can be azodicarbonamide which reacts with the heating drying oven  27  by releasing a blowing gas. Roughly 5 to 6% by weight azodicarbonamide of the mass of resin in solution  25  has given good results. Foaming of the material of shape-holding layer  7  can be obtained in another way other than by using azodicarbonamide. For example, this can be obtained by microspheres that are added to solution  25  and contain a gas that is intended to cause them to dilate due to the effect of a temperature rise.