Sublimation printing of heat sensitive materials

Abstract

The present invention also relates to a sublimation printing process for a multilayer system comprising a polyester top layer and at least one heat-sensitive polymer layer, wherein a temperature gradient is applied during sublimation printing such that the heat-sensitive polymer layer is maintained below its melting temperature and the polyester top layer is maintained above its glass transition temperature to allow diffusion of the sublimable dye into the polyester top layer. The temperature gradient is maintained by using a heat sink element below the heat-sensitive polymer layer. The temperature gradient can also be maintained by cooling the heat sink element. Cooling is preferably achieved using a circulating coolant. The heat sink element comprises a polymer, ceramic, or metal. The present invention also relates to a sublimation printed multilayer system comprising a polyester top layer and at least one heat-sensitive polymer layer. The present invention also relates to multilayer systems in the manufacture of textiles, tents, outdoor gear, apparel, clothing, bags, jackets, and gloves.

Description

Detailed Description of the Invention

[0001] The present invention relates to a sublimation printing process for a multi-layer system comprising a polyester top layer.The present invention further relates to the multi-layer system.The present invention further relates to the use of the multi-layer system.

[0002] Sublimation printing, also called dye sublimation printing, is a printing method for transferring images onto a substrate (usually a fabric material such as polyester fabric). Sublimation refers to the process by which a substance such as a dye goes from a solid state to a gaseous state. Sublimation printing usually involves the use of a digital printer to either produce a mirror image on the transfer medium or to print sublimable dyes directly onto the substrate. The polyester fabric (along with the transfer medium) is exposed to heat and pressure at a temperature of 180-230°C. This causes the dye to go into a gaseous state and open up the polyester fabric structure. Once the dye is in a gaseous state, it penetrates the polyester fabric. When the heat is removed, the dye is permanently fixed in place in the polyester. The best quality of sublimation printing is one that does not fade or crack on polyester. The print is very light and does not have any rough feel to it. In principle, any garment or object with a polyester base or coating can be designed using sublimation printing, but if the substrate contains a heat-sensitive material, it will be destroyed during the fusing process.

[0003] Therefore, dye sublimation printing is a standard process used for customized / patterned sportswear or apparel such as jerseys, trousers or jackets made of polyester fabric. As mentioned before, dye sublimation printing is difficult to apply to fabrics containing heat-sensitive materials due to the high temperatures required for dye sublimation. The high temperatures will damage the heat-sensitive materials. Moreover, this will sacrifice the color depth and color fastness of the print. However, in the textile fabric / fiber industry, coloring of fabrics / fibers is a necessary requirement for many, if not the majority, military, commercial, apparel, industrial, medical and aerospace applications.

[0004] US2011086208 discloses a process for producing waterproof fabrics, in which a heat-sensitive layer including a layer of polypropylene fibers and elastomeric fibers is laminated to a membrane, which is then laminated to a third layer of dye-sublimated polyester elastomeric yarn. In this process, the polyester layer is dye-sublimated before lamination to the membrane and the heat-sensitive layer. Therefore, the object of the present invention is to provide a sublimation printing process on a multi-layer system including a heat-sensitive polymer without damaging the heat-sensitive polymer layer.

[0005] Another object of the present invention is to provide equal print quality on multi-layer systems including a heat sensitive polymer layer.

[0006] It is a further object of the present invention to provide a sublimation printing process onto multi-layer systems including a heat-sensitive polymer layer to produce prints with good color depth and color fastness.

[0007] The object of the present invention is achieved by providing a dye sublimation printing process for a multi-layer system comprising a polyester top layer and at least one thermosensitive polymer layer, where a temperature gradient is applied during sublimation printing such that the thermosensitive polymer layer is maintained at a temperature below its melting temperature and the polyester top layer is maintained at a temperature above its glass transition temperature to allow diffusion of the sublimable dye into the polyester top layer. Preferably, the polyester layer and the layer comprising the thermosensitive polymer are in contact with each other.

[0008] Surprisingly, it has been found that it is possible to provide a printed multi-layer system comprising at least a heat-sensitive polymer layer without being damaged by heat during a dye sublimation printing process, and that the printed multi-layer system exhibits good print quality, good color depth, good color fastness and / or good resolution.

[0009] Sublimation techniques for the colouring of heat-sensitive materials such as ultra-high molecular weight polyethylene (UHMWPE) are known, for example, from WO 16151409. It is disclosed that UHMWPE materials such as fibres, braids or laminated composites can be coloured by a colouring method which allows the direct infusion of colouring agents into the gel-spun UHMWPE fibres themselves under controlled conditions of heat and pressure.

[0010] WO2011163643 also discloses sublimation printing in which dye is transferred to a composite material. The process includes applying a dye to a transfer medium to form a colored transfer medium, placing the colored transfer medium in contact with a composite material, and using an autoclave to apply at least one of heat, external pressure, and vacuum pressure to infuse the dye into the composite material to form a colored composite material. After sublimation printing, the composite material is cooled to a temperature at which the composite material maintains the desired shape. A drawback of this sublimation printing process is that the cooling is performed after the printing step, which means that if a heat-sensitive polymer layer is used, it will be damaged during the sublimation printing process.

[0011] In contrast, the sublimation printing process of the present invention preferably includes the following steps: Step 1. Providing a multi-layer system comprising a polyester top layer and a heat-sensitive polymer layer comprising a polymer having a melting point below the sublimation temperature. Step 2. Printing a design using one or more sublimable dyes, either via a transfer substrate or directly onto the multi-layer system. Step 3. Placing either the printed multi-layer system or a combination of the printed transfer substrate and multi-layer system and passing it through a heated calender or press while applying a temperature gradient to maintain the sublimation temperature of the polyester top layer above its glass transition temperature while maintaining the temperature of the heat sensitive polymer layer below its melting temperature.

[0012] In step 1 of the process described above, the multi-layer system comprises a polyester fabric top layer, preferably polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). The PET or PBT can be a fiber. The multi-layer system further comprises at least a heat-sensitive polymer layer comprising a polymer having a melting point below the dye sublimation temperature. Examples of polymers having a melting temperature below the sublimation temperature are polyolefins such as polyethylene, polyester block copolymers, polyurethanes or polyamides. Preferably, the heat-sensitive polymer layer comprises a polyethylene or polyester block copolymer. More preferably, the heat-sensitive polymer layer comprises UHMWPE or Arnitel® VT. UHMWPE is a type of polyolefin composed of very long polyethylene chains. Trade names include Dyneema® and Spectra®. UHMWPE is also referred to in the industry as either high modulus polyethylene (HMPE) or high performance polyethylene (HPPE). The molecular weight (MW) of UHMWPE is often expressed as "intrinsic viscosity" (IV) and is typically at least 4 dl / g, preferably at least 8 dl / g. Typically, the IV of the UHMWPE is less than about 50 dl / g, preferably less than about 40 dl / g. In various embodiments, the UHMWPE fibers include extruded polymer chains. In various embodiments, the UHMWPE fibers include pultruded polymer chains.

[0013] In step 2, a digital printer can be used to generate a mirror image on a transfer substrate. The transfer substrate can include at least one of a transfer paper, a transfer laminate, or a transfer film. The dye can be applied to the transfer substrate in the form of a pattern, graphic, or logo. In addition, the dye can be applied to a multi-layer system using direct printing as well.

[0014] In step 3, the printed substrate and the multi-layer system will be passed together through a heated calender (Figure 1) or press (Figure 2) at temperatures up to 230°C, applying a temperature gradient to maintain the sublimation temperature of the polyester top layer above its glass transition temperature, while maintaining the temperature of the heat-sensitive polymer layer below its melting temperature. It is clear that the sublimation temperature of the polyester top layer is below the melting temperature of the polyester.

[0015] A temperature gradient is essential to achieve printed multi-layer systems comprising heat-sensitive polymers with good print quality, good color depth, good color fastness and / or good resolution. The temperature gradient can be applied passively or actively. In the case of a passive temperature gradient, a heat sink element is used under the heat-sensitive polymer layer. Preferably, the heat sink element comprises a polymer, a ceramic or a metal. More preferably, the heat sink element comprises a metal. Alternatively, the temperature gradient can also be applied actively with additional cooling of the heat sink element. Cooling of the heat sink element can be via a Peltier plate or a plate with a circulating coolant such as oil or water.

[0016] Heat sink element as used in the present invention means an element that provides an efficient path for heat to be transferred to the environment. The general theory behind heat sinks is to increase the surface area of ​​a heat generating device to allow more efficient transfer of heat to the environment. This improved thermal path reduces the temperature rise of the heat sensitive polymer layer.

[0017] In dye sublimation printing from a transfer medium, the parameters that influence the transfer printing process are (a) temperature, (b) time, and (c) the percentage of dye that is actually transferred or printed directly onto the multilayer system. In the case of sublimation printing via a transfer substrate, the sublimation temperature is in the range of 180-230°C, preferably 190-220°C, more preferably 200-210°C, for a period of 10-80 seconds, preferably 20-70 seconds, more preferably 30-60 seconds. In the case of direct printing of dye onto a multilayer system, the sublimation temperature is in the range of 170-230°C, preferably 180-220°C, more preferably 190-210°C, for a period of 10-80 seconds, preferably 20-70 seconds, more preferably 30-60 seconds.

[0018] The multi-layer systems used in the sublimation printing process of the present invention can be in the form of films, fabrics, laminates, felt structures, composite structures and / or combinations thereof. Whatever type of form the multi-layer system may be, it will always include polyester in the top layer.

[0019] The term "composite" is understood herein as a material comprising fibers and a matrix material, e.g. a co(polymer) resin impregnated through the fibers and / or coated on the fibers. The matrix material is typically a liquid (co)polymer resin impregnated between the fibers and optionally subsequently hardened. Hardening or curing can be carried out by any means known in the art, e.g. by chemical reaction or solidification from a molten state to a solid state. Suitable examples include thermoplastic or thermosetting resins, epoxy resins, polyester or vinyl ester resins or phenolic resins. A composite may comprise at least two different types of fibers, the fibers having different chemical structures and properties.

[0020] The term "fiber" is understood herein to mean an elongated body whose length dimension is much greater than the transverse dimensions of width and thickness. Thus, the term fiber includes filaments, ribbons, strips, bands, tapes, etc., having regular or irregular cross-sections. Fibers may have a continuous length, known in the art as filaments or continuous filaments, or discontinuous lengths, known in the art as staple fibers.

[0021] In the context of the present invention, the fabric may be of any type known in the art, such as woven, nonwoven or knitted fabrics. These types of fabrics and their manufacturing methods are already known to those skilled in the art. The areal density of the fabric is preferably between 10 and 2000 g / m 2 , more preferably 100 to 1000 g / m 2 , and even more preferably 100 to 500 g / m 2 , and most preferably 50 to 250 g / m2.

[0022] When the multi-layer system is in the form of a fabric, it preferably comprises a double-face woven or knitted construction, in which case the fabric preferably comprises woven or knitted PET or PBT fibers and UHMWPE fibers.

[0023] The multi-layer system of the sublimation printing process of the present invention may also include a waterproof breathable membrane. The membrane is an additional layer bonded under the outer surface of the multi-layer system. If the multi-layer system is a fabric, the membrane can be bonded to it to form a laminate. Waterproof breathable means that the membrane is resistant to penetration by water but allows water vapor to pass through. Examples of waterproof breathable membranes are PTFE, polyurethane or polyester block copolymers, such as Arnitel® VT.

[0024] In another embodiment of the invention, the multi-layer system may comprise a polyester top layer and a composite comprising at least two unidirectional layers (UD layers) comprising a thermosensitive material, the first layer comprising high performance fibers aligned in a parallel direction in a first matrix material, and the second layer comprising high performance fibers aligned in a parallel direction in a second matrix material. The second fiber direction is preferably offset by up to 90 degrees with respect to the first fiber direction. The high performance fibers of the first and second layers may be the same or different. However, the composite may also comprise one or more additional polymer layers bonded to the UD layers.

[0025] The high performance fibers of the first and second layers can be the same or different. The high performance fibers used in the first and second layers typically have a melting point below the sublimation temperature up to 220°C. Preferably, they have a tensile strength of at least 0.5 GPa, more preferably at least 0.6 GPa, most preferably at least 0.8 GPa. The fibers preferably have a tensile strength of 3.1 to 4.9 GPa, more preferably 3.2 to 4.7 GPa, most preferably 3.3 to 4.5 GPa.

[0026] The fiber load of the first and second layers is generally between 1 and 50 grams per square meter. The fiber load may also be referred to as the fiber density of the layers. Preferably, the fiber load of the layers is between 2 and 30 grams per square meter, more preferably between 3 and 20 grams per square meter. It has been found that fiber densities within these ranges help maintain the flexibility of the multilayer composite.

[0027] The most preferred high performance fibres are polyethylene fibres, also referred to as highly drawn or oriented polyethylene fibres, consisting of polyethylene filaments prepared by a gel spinning process, as described, for example, in GB 2042414A or WO 01 / 73173. The advantage of these fibres is that they have a very high tensile strength combined with a light weight, so that they are suitable for use in very thin layers. Preferably, fibres of ultra-high molecular weight polyethylene (UHMWPE) are used, having an intrinsic viscosity of at least 4 dL / g, more preferably at least 8 dL / g.

[0028] The first and second matrix materials are preferably selected from polyacrylates, polyurethanes such as Hysol US0028, polyesters such as thiokol Adcote, silicones such as DOW-96-083, -X3-6930, -6858 (UV curable), polyolefins, modified polyolefins, ethylene copolymers such as ethylene vinyl acetate, polyamides, polypropylene or thermoplastics such as PEEK, PPS, Radel, Ryton. The first and second matrix materials can be the same or different.

[0029] Preferably, the first and second matrix materials comprise polyurethanes. The polyurethanes may comprise polyether-urethanes or polyester-urethanes based on polyether diols. The polyurethanes are preferably based on aliphatic diisocyanates, as this further improves product performance, including color stability.

[0030] In a further preferred embodiment, the matrix material may comprise an acrylic resin or a polymer containing acrylate groups.

[0031] In the case of polyolefins, the matrix material preferably comprises a homopolymer or copolymer of ethylene and / or propylene, the polymeric resin having a modulus of 860 to 930 kg / m, as measured according to ISO 1183.3 , a peak melting temperature in the range of 40°-140° C., and a heat of fusion of at least 5 J / g. Further details of the matrix material and the monolayer having unidirectional fibers can be found, for example, in U.S. Pat. No. 5,470,632, which is incorporated herein by reference in its entirety.

[0032] The amount of matrix material in the first or second layer is typically 10-95 wt%, preferably 20-90 wt%, more preferably 30-85 wt%, and most preferably 35-80 wt% to ensure adequate bond strength between the layer and other components, thereby reducing the chance of premature delamination of the composite after repeated bending cycles.

[0033] The invention also relates to a sublimation printed multi-layer system obtainable by the process of the invention.

[0034] The present invention also relates to such a printed multi-layer system. The printed multi-layer system comprises a polyester top layer and at least one heat-sensitive polymer layer, providing a color difference (CMC-ΔE) of less than 1 when compared to a multi-layer system without a heat-sensitive polymer layer. Preferably, the polyester layer and the heat-sensitive layer are in contact with each other. The printed multi-layer system preferably comprises a color fastness to dry and wet rubbing of at least 3, preferably 4, more preferably 5. The color fastness is measured according to ISO105-X12:2016. The burst strength of the multi-layer system is preferably at least 90% compared to a non-printed multi-layer system, more preferably 95% compared to a non-printed multi-layer system, and most preferably 100%.

[0035] The invention also relates to the use of the printed multi-layer system according to the invention in the manufacture of textiles, tents, outdoor products, apparel, clothing, bags, jackets, gloves.

[0036] The present invention is illustrated by the following examples without being limited thereto. [Brief description of the drawings]

[0037] [Figure 1] Color intensity as a function of sublimation temperature. [Diagram 2] 1 shows a sublimation apparatus equipped with a cooling zone (calendar). [Diagram 3] Shown is a sublimation apparatus equipped with a cooling area (flat press).

[0038] [Measurement method] Below are the test methods referenced herein.

[0039] Color fastness is measured using a dry rubbing cloth and a wet rubbing cloth in accordance with ISO105-X12:2016, which measures color fastness to rubbing.

[0040] Bursting strength is measured according to ISO 13938-1 (1999) using an Autoburst SDL-Atlas M229 and a test surface of 50 cm2 at 20 degrees Celsius and 65% relative humidity.

[0041] The color difference CMC-ΔE is measured according to ISO11664-4, and a ΔE (color difference from the reference) of less than 1 is good.

[0042] Colour strength is measured according to ISO 11664-4 and is defined as [((K / S)batch / (K / S))standard] x 100.

[0043] [Example 1] A double knit fabric is provided, comprising 30% UHMWPE fibers (55 dtex SK75 140TZ) and 70% polyester fibers (110 dtex textured PET), the polyester fibers being a top layer interconnected with an inner layer of UHMWPE fibers. The areal density of the fabric is 125 g / m2.

[0044] Sublimation printing uses a heat press (Collin PV400 2019) with individually temperature controlled upper and lower metal plates with a surface of 40 x 40 cm. The upper plate of the heat press is heated to a temperature of 230 °C and the bottom plate is maintained at a temperature of 70 °C with circulating coolant. The double knit fabric was placed with the UHMWPE fibre side facing the 70 °C metal plate and the printed transfer substrate was placed on top of the polyester top layer. The press is closed for 60 seconds at a pressure of 2 bar.

[0045] [Example 2] In Example 2, the fabric of Example 1 is used. The heat press is a flat press for sublimation printing known to those skilled in the art. The heat press is heated to a temperature of 230°C, and in addition, a stainless steel metal plate (thickness 3 mm) with an initial temperature of 25°C is placed under the heat-sensitive UHMWPE fiber layer, and no active cooling by coolant is applied. The press is closed for 60 seconds at a pressure of 2 bar.

[0046] [result]

[0047] [Table 1]

[0048] It is clear from Table 1 that sublimation printing of the fabric shown in Example 1, where active cooling of the bottom plate is applied, results in fabrics with good CMC dE and good color strength when compared to Reference A. The same is true for Example 2, where there was no active cooling, but the starting temperature of the bottom plate was 25°C. Also, good burst strengths are achieved in Examples 1 and 2, compared to the burst strength of Reference B. References A and B relate to the double knit fabric disclosed in Example 1. In Reference A, the fabric is sublimation printed at 200°C without cooling during printing. In Reference B, the fabric is not printed and shows the original burst strength of the fabric.

[0049] [Comparative Experiments I-II] A double knit fabric is provided, comprising 30% UHMWPE fibers (55 dtex SK75 140TZ) and 70% polyester fibers (110 dtex textured PET), the polyester fibers being a top layer interconnected with an inner layer of UHMWPE fibers. The areal density of the fabric is 125 g / m2.

[0050] Sublimation printing uses a heat press.

[0051] [Comparative Experiment I] The heat press is heated to a temperature of 150° C. The press is closed for 60 seconds at a pressure of 2 bar.

[0052] [Comparative Experiment II] The heat press was heated to a temperature of 200 degrees and no cooling was performed during the sublimation printing.

[0053] [result]

[0054] [Table 2]

[0055] It is clear from Table 2 that a sublimation temperature of 150° C. has a significant negative effect on the color depth. However, the burst strength is comparable to that of Reference B. In the case of sublimation printing without cooling during printing, the color depth is good, but the burst strength is significantly reduced and the heat-sensitive polymer layer is destroyed.

Claims

1. 1. A dye sublimation printing process for a multi-layer system comprising a polyester top layer and at least one heat-sensitive polymer layer comprising a polymer having a melting point below its sublimation temperature, wherein a temperature gradient is applied during dye sublimation printing such that the heat-sensitive polymer layer is maintained at a temperature below its melting temperature and the polyester top layer is maintained at a temperature above its glass transition temperature to allow diffusion of a sublimable dye into the polyester top layer.

2. The sublimation printing process of claim 1 , wherein the temperature gradient is maintained by using a heat sink element beneath the heat sensitive polymer layer.

3. The sublimation printing process of claim 2 , wherein the temperature gradient is maintained by cooling the heat sink element beneath the heat sensitive polymer layer.

4. The sublimation printing process of claim 3 , wherein the cooling is accomplished using a circulating coolant.

5. The sublimation printing process of any one of claims 2 to 4, wherein the heat sink element comprises a polymer, a ceramic or a metal.

6. The sublimation printing process of claim 5 , wherein the heat sink element comprises a metal.

7. The sublimation printing process of any one of claims 1 to 6, wherein the polyester top layer comprises polyethylene terephthalate (PET) or polybutylene terephthalate (PBT).

8. A sublimation printing process according to any one of claims 1 to 7, wherein the heat sensitive polymer can be any polymer having a melting temperature at least below the sublimation temperature of the dye, which is 190°C.

9. A sublimation printing process according to any one of claims 1 to 8, wherein the heat sensitive polymer is selected from the group consisting of polyolefins, polyamides, polyester block copolymers or polyurethanes.

10. 10. Sublimation printing process according to claim 9, wherein the heat sensitive polymer is selected from polyethylene, preferably ultra-high molecular weight polyethylene (UHMWPE).

11. A sublimation printing process according to any one of claims 1 to 10, wherein the multi-layer system can be in the form of a multi-layer film, a laminate, a knitted fabric, a woven fabric, a non-woven or felt structure or a composite structure and / or combinations thereof.

12. 12. The sublimation printing process of claim 11, wherein the multi-layer system is in the form of a fabric comprising a double-face woven or knitted construction.

13. 12. The sublimation printing process of claim 11, wherein the multi-layer system is in the form of a laminate structure further comprising a waterproof breathable membrane.

14. 14. The sublimation printing process of claim 13, wherein the waterproof, breathable membrane comprises PTFE, polyurethane, or block copolyester.

15. 12. The sublimation printing process of claim 11, wherein the multi-layer system is in the form of a composite comprising at least two unidirectional layers, a first layer comprising parallel aligned high performance fibers in a first matrix material and a second layer comprising parallel aligned high performance fibers in a second matrix material.

16. 16. The sublimation printing process of claim 15, wherein the fiber direction of the high performance fibers in the second layer is offset by up to 90 degrees relative to the fiber direction of the high performance fibers in the first layer.

17. 16. The sublimation printing process of claim 15, wherein the high performance fibers of the first and second layers are the same or different and are selected from UHMWPE.

18. 16. The sublimation printing process of claim 15, wherein the first and second matrix materials can be the same or different and are selected from the group consisting of polyacrylates, polyurethanes, polyesters, silicones, polyolefins, modified polyolefins, ethylene copolymers, polyamides, polypropylene.

19. A method for producing a printed multi-layer system, comprising the step of sublimation printing a multi-layer system by a process according to any one of claims 1 to 18.

20. A method for producing a textile, tent, outdoor product, apparel, clothing, bag, jacket, or glove using a printed multi-layer system produced by the method of claim 19.

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