AN IMAGE-RECEPTIVE COATING FOR HIGH-SPEED PRINTING APPLICATIONS

Abstract

A method of preparing a washable durable image on a polyester film from water-based inks using an ink-jet printer, wherein the method comprises providing a substrate having a coating comprising approximately 4% by weight of polyvinyl alcohol as a binder, approximately 30% by weight of Polyethylene powder as an ink absorbing pigment. An image is printed on the coated substrate and is then thermally fused to the coated substrate.

Claims

1. A method of preparing a washable durable image on a polyester film from water-based inks using an ink-jet printer, wherein the method comprises: providing a substrate having a coating comprising: approximately 4% by weight of polyvinyl alcohol as a binder; approximately 30% by weight of Polyethylene powder as an ink absorbing pigment; printing an image on the coated substrate; and thermally fusing the ink jet printed image to the coated substrate.

2. The method according to claim 1, wherein the image is thermally fused at a temperature of between 100° C. and 120° C. for a dwell time of approximately 5 seconds.

3. The method according to claim 1, wherein the coating further includes polyurethane resin or co-polyester resin as a binder.

4. The method according to claim 3, wherein the coating further includes polyvinyl acetate or acrylic as the binder.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0021] The focus on the present invention is to provide a meltable, porous coating which is printable using inkjet inks in a high-speed printing system where the dwell time available to encapsulate the ink into the coating is extremely limited.

[0022] The applicant has undertaken extensive research, development and experimentation to establish the optimum composition of the coating that meets the criteria of printability and protection, after being formed in a high speed printing environment where dwell time is extremely limited.

[0023] The following examples of formula will serve to illustrate the invention and provide formulas that increase the performance of sealable coatings to make them applicable in high-speed printing systems.

TABLE-US-00001 Formula 1 Ethanol (95% solution) 6.40 g demin H.sub.2O 3.20 g Elvamide 8061.sup.1 1.70 g Pre-dissolve at 60° C., then add: Ethanol (H.sub.2-75:25) 8.50 g Isopropanol 1.20 g Orgasol 3501 EXD NAT.1.sup.2 4.00 g .sup.1Polyamide resin/textile adhesive made by Dupont ® .sup.2Polyamide powder made by Arkema ®

[0024] This composition consists of a Polyamide resin as a binder and Polyamide powder as an ink absorbing pigment, which is heat-sealable at or over 140° C.

[0025] The formulation was coated onto a sheet of transparent polyester film. An image was printed with water-based pigmented inks using a photo printer and the printed coating was sealed using an image transfer heat press at 160° C. for 10 seconds. While heating/pressing, the coating was protected by using a sheet of one-sided siliconized polyester film. Tests of the composition found the sealed layer to become transparent. The sealed layer also showed a high degree of water resistance and chemical resistance.

[0026] The layer showed strong resistance to acidic or alkaline exposure thereby allowing the printed product to be washable at common wash temperatures of 40° C. to 60° C.

[0027] The coating would therefore have good applicability in the textile label or carpet tag market for example. The coating would however may not be applicable for the traditional label market that use bi-axially oriented polypropylene films (BOPP) as a substrate as such films would melt or shrink at the melting range of the composition and the pressure sensitive adhesive would be destroyed.

[0028] The applicant has identified that the following formula overcomes these limitations.

TABLE-US-00002 Formula 2 demin H.sub.2O 52.35 g Nolax S35.3031 (37.5%).sup.3 13.42 g Poval R-1130 (9%).sup.4  4.03 g Coathylene HX-1681.sup.5 30.20 g .sup.3Textile adhesive made by Nolax AG .sup.4SI-modified polyvinyl alcohol .sup.5Polyethylene powder made by Axalta Coating Systems

[0029] This composition has a reduced melting range and would therefore be more applicable to the traditional label market. The composition may further include Polyvinyl acetate, Acrylic, Polyurethane or CoPolyester resin as a binder and Polyethylene Powder as the ink absorbing pigment to increase the performance of the formula. Use of Polyethylene as the fusible polymer particles results in lower sealing temperatures which causes an increase in chemical resistance because Polyethyelene is insoluble in most types of organic solvents. This lends the formulation to particular use in production of chemical labels that comply with the Globally Harmonized System (“GHS”).

[0030] The formulation was coated onto a sheet of transparent polyester film (96 micron CF 182 manufactured by Polypex®). An image was printed with water-based pigmented inks using a photo printer (Epson Stylus Photo R2400 printer) and the printed coating was sealed using an image transfer heat press at different temperatures between 110° C. and 120° C. for 5 seconds. While heating/pressing, the coating was protected by using a sheet of one-sided siliconized polyester film (36 micron Siliphan S36M manufactured by Siliconature®).

[0031] In an alternative experiment, the coating was sealed by passing the printed sheet through an office laminator (Olympia S34040, setting 150MIC). The coated/printed side of the sheet was covered by the same type of one-sided siliconized polyester film to prevent from adhering to the heated rubber rollers.

[0032] Tests of this composition have found it to have good sealing properties at temperatures of 110° C. or more. Furthermore, the sealed layer became transparent, and also showed a high degree of water resistance and chemical resistance.

[0033] The layer showed strong resistance to acidic or alkaline exposure thereby allowing the printed product to be washable at normal temperatures of 40 to 60° C.

[0034] The heating time was found to be just as important as the temperature. Increases in temperature, result in a reduction in the dwell time.

[0035] A further important parameter is the applied pressure. In contactless sealing units (for example hot air or infrared radiation units) there is no pressure. The sealing process is defined by the difference in temperature above the melt range of the coating and the dwell time.

[0036] In contact sealing units (for example, heat presses and hot roller type laminators) the required temperature and/or dwell time can be significantly reduced by increasing the pressure.

[0037] Even sealing temperatures below the melt range of the coating are possible.

[0038] Contact sealing can though have undesirable effects such as a lower print resolution caused by pressure induced expansion of the dot sizes of the ink drops, or by changing the adhesive performance of self-adhesive label materials through squeezing of the adhesive layer.