Caustic washable printing compositions

Abstract

The present invention provides a printing composition that offers sufficient adhesion to the substrate surface and can be effectively removed by caustic cleaning. [Solution] A chemically ray-curable composition comprising a carboxyl group-containing acrylate, a urethane acrylate, a monomer, and a photoinitiator is provided. A printing method is provided, comprising applying the chemically ray-curable composition onto the surface of a substrate, curing the applied composition, and applying ink onto the cured composition.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 041,011, filed on June 18, 2020, the content of which is hereby incorporated by reference in its entirety.

Background Art

[0002] Printable compositions such as inks, primers, coatings, etc. are widely used for commercial product labels and packaging. Generally, printable compositions need to have strong adhesion to the substrate surface. On the other hand, one issue when recycling packaging materials is to effectively remove printed colors, labels, and / or coatings from the substrate material. Printable compositions such as inks and primers are desired to provide good adhesion to the substrate surface (e.g., plastic surface) so that the substrate can be safely reused and be removable by caustic cleaning. Therefore, effective printable products such as energy - curable inks and primers that meet both requirements are needed.

Summary of the Invention

[0003] In one aspect, the present disclosure provides a radiation - curable composition useful for printing applications, which has good adhesion to the substrate surface and can be effectively removed by caustic cleaning.

[0004] In one embodiment, a radiation - curable composition includes a carboxylated acrylate, a urethane acrylate, a monomer, and a photoinitiator, which is applied to a surface and cured, and the composition (1) maintains at least 80% adhesion to the surface in a tape adhesion test and (2) is at least 80% removed from the surface by caustic cleaning.

[0005] In another embodiment, a chemically ray curable composition is provided comprising about 35% to about 55% by weight of a carboxylated acrylate, about 15% to about 45% by weight of a urethane acrylate, about 5% to about 15% by weight of a monomer, about 2% to about 10% by weight of an adhesion promoter, and about 5% to about 15% by weight of a photoinitiator.

[0006] In another embodiment, the present disclosure provides a printing method comprising applying a chemically curable composition, such as those disclosed herein, onto the surface of a substrate, curing the applied composition, and applying an ink to the cured composition. [Modes for carrying out the invention]

[0007] This disclosure relates to chemically ray curable compositions suitable for printing applications. Notably, the compositions can provide both good adhesion to substrate surfaces and effective removal during caustic cleaning, and due to their advantageous adhesive and caustic removal properties, the compositions may be particularly useful for ink printing and deinking applications on reusable plastic substrates.

[0008] As used herein, the terms “comprise(s),” “include(s),” “having,” “have,” “can,” “contain(s),” and their variants are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms (a), (an), and (the) include plural references unless the context explicitly indicates otherwise. This disclosure also considers other forms of “comprising,” “consisting of,” and “essentially consisting of,” which, whether explicitly indicated or not, are embodiments or elements presented herein.

[0009] The modifier "about," used in relation to quantity, includes the stated number and has a meaning determined by the context (e.g., including the degree of error related to the measurement of at least a particular quantity). Furthermore, the modifier "about" should be considered to indicate a range defined by the absolute values ​​of two endpoints. For example, the expression "about 2 to about 4" also discloses a range from 2 to 4. The term "about" can refer to plus or minus 10% of the stated number. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1" may mean 0.9 to 1.1. Other meanings of "about" are evident from contexts such as rounding; for example, "about 1" may mean 0.5 to 1.4.

[0010] In this specification, when enumerating numerical ranges, each number that lies between similar degrees of precision is explicitly considered. For example, in the range 6–9, the numbers 7 and 8 are considered in addition to 6 and 9. In the range 6.0–7.0, the numbers 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly considered.

[0011] As used herein, the term “chemical radiation” includes all electromagnetic radiation that induces chemical reactions, such as polymerization reactions between curable compounds described herein. Preferred chemical radiation includes, but is not limited to, ultraviolet (UV) radiation, light-emitting diode (LED) radiation, electron beam (EB) radiation, and other emission or transmission of energy in the form of waves or particles through space or a material medium.

[0012] As used herein, the term "chemically beam curable" refers to curing in response to exposure to suitable chemical radiation, such as UV radiation, LED radiation, and EB radiation.

[0013] As used herein, the terms “cure” and “curing” refer to the process of polymerization, curing, and / or crosslinking of monomer and / or oligomeric units to form a polymer.

[0014] As used herein, the term "monoma" refers to a material having a viscosity less than that of an oligomer, a molecular weight less than 1000 g / mol or about 1000 g / mol, and a viscosity less than 500 cps or about 500 cps at 25°C. A monoma may contain one or more unsaturated groups that can be polymerized to form an oligomer or polymer.

[0015] As used herein, the term "oligopolymer" refers to a material having a viscosity greater than that of a monomer and a molecular weight of approximately 5,000 g / mol to 200,000 g / mol. Oligomers can be polymerized to form polymers with higher molecular weights. Oligomers can be cured upon application of UV, LED, or EB radiation.

[0016] Caustic cleaning refers to the process of partially or completely removing ink, marks, or labels printed on a substrate surface by contacting the substrate surface with an aqueous solution of a strong base. For example, an ink composition may be printed onto the surface of a plastic substrate to form a printed film, and the ink composition may be partially or completely removed by contacting the surface with an aqueous caustic solution as described herein. Caustic cleaning may also be a standard caustic cleaning process of the Plastic Recycling Association (APR) suitable for the reuse of plastic materials. See, for example, APR document number PET-P-00, section PET-P-04 (shown at http: / / plasticrecycling.org / images / pdf / design-guide / test-methods / PET_Practices_PET-P-00.pdf). Caustic cleaning can be carried out in an aqueous solution containing at least 0.1% by weight, at least 0.5% by weight, or at least 1.0% by weight of a strong base such as sodium hydroxide or potassium hydroxide. The aqueous solution may further contain a detergent such as Triton X-100 nonionic surfactant in an amount of at least 0.1% by weight, at least 0.3% by weight, or at least 0.5% by weight. In some embodiments, the caustic cleaning is carried out in an aqueous solution containing about 0.3% by weight of detergent and about 1% by weight of sodium hydroxide. The caustic cleaning can be carried out with stirring and at a high temperature. For example, in some embodiments, the temperature may be about 60°C, about 65°C, about 70°C, about 75°C, about 80°C, or about 85°C, or about 90°C. In some embodiments, the caustic cleaning is carried out at a temperature of about 85°C with stirring.

[0017] The term "tape adhesion test" refers to the measurement of the adhesion level of a composition applied to a surface. Appropriate test methods include those well known in the art. Typically, the composition is applied to a surface and cured, then adhesive tape is applied to the composition, and the tape is then peeled off. The adhesion level is measured by the amount of composition remaining on the substrate after the tape is peeled off. For example, "80% adhesion," as demonstrated by a tape adhesion test, means that 80% of the applied composition remains adhered to the substrate surface.

[0018] [Composition]

[0019] In one embodiment, the disclosure provides a chemically laser-curable composition useful for printing applications. In particular, the chemically laser-curable composition can be used as a primer composition that imparts caustic washability to energy-curable ink systems. Notably, the primer composition can enable ink adhesion to reusable plastic substrates (e.g., plastic films), be resistant to steam / heat treatment used in shrink packaging systems, ensure proper handling of substrates and label lines, and be removable using standard caustic washing methods suitable for recycling purposes, such as the APR standard process.

[0020] The chemically ray-curable composition of the present invention is more useful than known water and / or solvent-based primers and can be fully compatible with energy-curable inks. In particular, laboratory tests have shown faster curing, better adhesion, and printability of energy-curable inks on existing primers.

[0021] In a first embodiment, the present disclosure provides a chemically radiation-curable composition comprising a carboxylated acrylate, a urethane acrylate, a monomer, and a photoinitiator, wherein the composition, when applied to a surface and cured, (1) maintains at least 80% adhesion to the surface in a tape adhesion test, and (2) is removed from the surface by at least 80% by caustic cleaning.

[0022] In a second embodiment, the present disclosure provides a chemically curable composition comprising from about 35 wt% to about 55 wt% carboxylated acrylate, from about 15 wt% to about 45 wt% urethane acrylate, from about 5 wt% to about 15 wt% monomer, from about 2 wt% to about 10 wt% adhesion promoter, and from about 5 wt% to about 15 wt% photoinitiator. When the composition of the second embodiment is applied and cured on a surface, it (1) maintains at least 80% adhesion to the surface in a tape adhesion test and (2) is removed from the surface by at least 80% by caustic cleaning.

[0023] The surface described herein may include a plastic material. In some embodiments, the surface includes polyethylene terephthalate (PET), high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), polycarbonate (PC), or combinations thereof. In some embodiments, the surface includes crystalline polyethylene terephthalate (CPET).

[0024] The adhesion level may be at least 80% adhesion, at least 85% adhesion, at least 90% adhesion, at least 95% adhesion, or at least 99% adhesion, as demonstrated by the tape adhesion test described herein.

[0025] When the chemically curable composition of the present invention is applied and cured on a surface, it may be removed from the surface by at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% by the caustic cleaning described herein.

[0026]

[0027] ​The radiation-curable composition of the present invention can have a viscosity of about 200 cps to about 1000 cps at 25°C. The viscosity of the composition may be at least 200 cps, at least 400 cps, at least 600 cps, or at least 800 cps at 25°C. The viscosity of the composition may be at most 900 cps, at most 700 cps, at most 500 cps, or at most 300 cps at 25°C. In some embodiments, the viscosity of the composition is about 200 cps to about 800 cps, about 200 cps to about 600 cps, or about 400 cps to about 800 cps at 25°C.

[0028] The radiation-curable composition of the present invention may contain about 35 wt% to about 55 wt% of carboxylated acrylate. The composition may contain at least 35 wt%, at least 40 wt%, at least 45 wt%, or at least 50 wt% of carboxylated acrylate. The composition may contain carboxylated acrylate at most 55 wt%, at most 50 wt%, at most 45 wt%, or at most 40 wt%. In some embodiments, the composition contains about 35 wt%, about 40 wt%, about 45 wt%, about 50 wt%, or about 55 wt% of carboxylated acrylate. In some embodiments, the composition contains about 35 wt% to about 45 wt% of carboxylated acrylate.

[0029] Suitable carboxylated acrylates include, but are not limited to, various carboxylated polyester acrylate oligomers. These compounds may have carboxyl groups (-COOH) attached to the ends or backbone of the polymer or oligomer. The carboxylated acrylates may be alkali-exfoliable or removable under alkaline conditions. The carboxylated acrylates may have an acid value of about 100 mg KOH / g to about 300 mg KOH / g, for example, about 150 mg KOH / g to about 300 mg KOH / g, about 200 mg KOH / g to about 280 mg KOH / g, or about 240 mg KOH / g to about 270 mg KOH / g. In some embodiments, the carboxylated acrylates have an acid value of about 150 mg KOH / g, about 200 mg KOH / g, about 250 mg KOH / g, or about 270 mg KOH / g. Carboxylated acrylates can have viscosities of approximately 200 cps to 50,000 cps at 25°C, for example, approximately 200 cps to 30,000 cps, approximately 200 cps to 10,000 cps, or approximately 200 cps to 6,000 cps.

[0030] Suitable carboxylated polyester acrylate oligomers include, for example, DOUBLEMER 272 (acid value 200 mg KOH / g, viscosity 10,000-30,000 cps at 25°C) from Double Bond Chemical (Taiwan) Co., Ltd., SP 270 (acid value 200 mg KOH / g, viscosity 1,500 cps at 25°C), SP 271 (acid value 180 mg KOH / g, viscosity 14,000 cps at 25°C), SP 277 (acid value 200 mg KOH / g, viscosity 6,500 cps at 25°C) from Soltech Ltd., and Miramer SC 6640 (acid value 240-270 mg KOH / g, viscosity 200 cps at 25°C) from Miwon Specialty Chemical Co., Ltd. In certain embodiments, the carboxylated acrylate includes alkali-release polyester acrylates such as Miramer SC 6640.

[0031] The chemically curable composition of the present invention may contain about 15% to about 45% by weight of urethane acrylate. The composition may contain at least 15% by weight, at least 20% by weight, at least 25% by weight, at least 30% by weight, at least 35% by weight, or at least 40% by weight of urethane acrylate. The composition may contain up to 45% by weight, up to 40% by weight, up to 35% by weight, up to 30% by weight, up to 25% by weight, or up to 20% by weight of urethane acrylate. In some embodiments, the composition contains about 20% by weight, about 25% by weight, about 30% by weight, about 35% by weight, or about 40% by weight of urethane acrylate. In some embodiments, the composition contains about 25% to about 40% by weight of urethane acrylate.

[0032] Suitable urethane acrylates include, but are not limited to, various urethane (meth)acrylate oligomers. The urethane acrylate may have a molecular weight of less than approximately 75,000 g / mol and a viscosity of less than approximately 50,000 cps at 25°C. For example, the urethane (meth)acrylate oligomer may have a molecular weight of approximately 500 g / mol to approximately 50,000 g / mol and a viscosity of approximately 100 cps to approximately 40,000 cps at room temperature (25°C). The urethane acrylate may be an aromatic urethane acrylate, an aliphatic urethane acrylate, or a combination thereof. Suitable urethane acrylates include monofunctional, difunctional, trifunctional, tetrafunctional, pentafunctional, hexafunctional compounds, or combinations thereof.

[0033] Suitable aromatic urethane (meth)acrylate oligomers include, but are not limited to, trade names CN-131, CN9782, CN9783, CN992, CN975, and CN972, commercially available from Sartomer Chemical Co., or trade names Genomer4622 and Genomer4217, commercially available from Rahn Corp. Suitable aliphatic urethane (meth)acrylate oligomers are available from Sartomer Chemical Co. Trademarks sold by Co., CN9004, CN9005, CN9006, CN9023, CN9028, CN9178, CN969, CN9788, CN986, CN989, CN9893, CN996, CN2920, CN3211, CN9001, CN9009, CN9010, CN9011, CN9071, CN9070, CN929, CN962, CN9025, CN9026, CN968, CN965, CN964, CN991, CN980, CN981, CN983, CN9029, CN9030, CN9031, CN9032, CN9039, CN9018, CN9024, and CN9013, or Rahn Examples of trade names sold by Corp. include Genomer4188, Genomer4215, Genomer4230, Genomer4267, Genomer4269, Genomer4312, Genomer4316, Genomer4425, Genomer4590, and Genomer4690, but are not limited to these. Other suitable urethane (meth)acrylate oligomers include Miramer PU2252 and Miramer PU212, marketed by Miwon Specialty Chemical Co., Ltd., or Ebecryl 271, Ebecryl 242, Ebecryl 1291, Ebecryl 4100, Ebecryl 4200, Ebecryl 5129, Ebecryl 8210, Ebecryl 8296, Ebecryl 8402, Ebecryl 8411, Ebecryl 8465, Ebecryl 8604, Ebecryl 220, Ebecryl 4500, and Ebecryl 4849, marketed by Allnex.In some embodiments, the urethane acrylate is a commercially available aromatic urethane acrylate (e.g., RAHN GENOMER 4622), an aliphatic urethane acrylate (e.g., MIWON MIRAMER PU2552, MIWON MIRAMER PU212), or a combination thereof. Various other types of urethane acrylates may be used. A suitable urethane acrylate product may be modified, for example, in a diluent used to reduce the viscosity of the urethane.

[0034] The chemically curable composition of the present invention may contain about 5% to about 25% by weight of monomer. The composition may contain at least 5% by weight, at least 10% by weight, at least 15% by weight, or at least 20% by weight of monomer. The composition may contain up to 25% by weight, up to 20% by weight, up to 15% by weight, or up to 10% by weight of monomer. In some embodiments, the composition may contain about 5% by weight, about 8% by weight, about 10% by weight, about 12% by weight, about 15% by weight, or about 20% by weight of monomer. In some embodiments, the composition contains about 5% to about 15% by weight of monomer.

[0035] Suitable monomers include, but are not limited to, monofunctional monomers, difunctional monomers, trifunctional monomers, tetrafunctional monomers, or combinations thereof. Suitable monomers include, for example, 2-(2-ethoxyethoxy)ethyl acrylate (EOEOEA), propoxylated neopentyl glycol diacrylate (PONPGDA), ethoxylated 1,6-hexanediol diacylate (EOHDODA), tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), trimethylolpropane triacrylate (TMPTA), or combinations thereof. Suitable monomers include commercially available products such as SARTOMER SR502 EO9 TMPTA, SARTOMER SR351H TMPTA, SARTOMER SR 9003B POPGDA, or IGM PHOTOMER 4172F EOPETA. In some embodiments, the monomer includes a free radical polymerization monomer such as propoxylated neopentyl glycol diacrylate (PONPGDA). Various other known monomers may also be used.

[0036] The chemically curable composition of the present invention may contain about 5% to about 15% by weight of a photoinitiator. The composition may contain at least 5% by weight, at least 8% by weight, at least 10% by weight, or at least 12% by weight of a photoinitiator. The composition may contain up to 15% by weight, up to 12% by weight, up to 10% by weight, up to 8% by weight, or up to 6% by weight of a photoinitiator. In some embodiments, the composition contains about 5% by weight, about 8% by weight, about 10% by weight, about 12% by weight, or about 15% by weight of a photoinitiator. In some embodiments, the composition contains about 6% to about 10% by weight of a photoinitiator.

[0037] Various known photoinitiators may be used, and the chemically beam-curable compositions of the present invention can be cured under various light sources, including, but not limited to, mercury bulbs, LEDs, energy beams, or long-wavelength lamps. Suitable photoinitiators include, for example, commercially available diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2-hydroxy-2-methylpropiophenone (HMPP), 1-hydroxycyclohexylphenyl ketone (HCPK), and combinations thereof.

[0038] The chemically curable composition of the present invention may further contain at least one additive component selected from adhesion promoters, matting agents, stabilizers, and defoaming agents.

[0039] Adhesion promoters can increase the adhesion between the chemically curable composition and the substrate to which the composition is applied. The chemically curable composition may contain about 2% to about 10% by weight of the adhesion promoter. The composition may contain at least 2% by weight, at least 4% by weight, at least 6% by weight, or at least 8% by weight of the adhesion promoter. The composition may contain up to 10% by weight, up to 8% by weight, up to 6% by weight, or up to 4% by weight of the adhesion promoter. In some embodiments, the composition contains about 4% by weight, about 6% by weight, about 8% by weight, or about 10% by weight of the adhesion promoter. In some embodiments, the composition contains about 6% to about 10% by weight of the adhesion promoter. Suitable adhesion promoters may contain polymerizable groups such as vinyl groups. In some embodiments, the adhesion promoter is considered a monomer in the ink composition. In some embodiments, the ink composition contains a monomer described herein (e.g., an acrylate monomer) and an adhesion promoter different from the monomer. Suitable adhesion promoters include, but are not limited to, N-vinyl-2-caprolactam, N-vinyl-2-pyrrolidone, and combinations thereof. Examples of commercially available adhesion promoters include V-Pyrol®RC and V-Cap®RC (Ashland).

[0040] The chemically ray-curable composition of the present invention may contain about 0.1% to about 2% by weight of a matting agent. Suitable matting agents include, for example, commercially available precipitated silica products.

[0041] The chemically curable composition of the present invention may contain about 0.1% to about 2% by weight of a stabilizer. A suitable stabilizer is, for example, the commercially available product XAMCHEM XC-SB302.

[0042] The chemically curable composition of the present invention may contain about 0.05% to about 0.5% by weight of an antifoaming agent. A suitable antifoaming agent is, for example, the commercially available product Evonik 971.

[0043] 〔method〕

[0044] In another embodiment, the Disclosure provides a printing method comprising applying a chemically curable composition disclosed herein onto the surface of a substrate, curing the applied composition, and applying an ink to the cured composition.

[0045] A favorable feature is that the chemically curable composition used in the method of the present invention, once applied to a surface and cured, can maintain at least 80% of its adhesive strength to the surface in a tape adhesion test and can be removed from the surface by caustic cleaning at least 80%. Therefore, the printing method of the present invention can be particularly useful for decorating or labeling reusable substrates as printed compositions, and the printed compositions and inks can be easily removed by caustic cleaning to facilitate the reuse of the substrate.

[0046] In some embodiments, the ink is a chemically laser-curable ink. For example, the ink may contain a formulation that can be cured by UV, LED, or EB radiation. In these embodiments, the method may further include a step of curing the applied ink.

[0047] The chemically laser-curable composition may be applied to the entire or partial surface of a substrate. The surface may include the outer surface, inner surface, or both. The surface or area on the surface to which the composition is applied may be of any shape or size.

[0048] The substrate may include reusable materials such as plastic materials. In some embodiments, the substrate is a plastic substrate, which includes a substrate made of reusable plastic. In some embodiments, the substrate includes plastic and at least one other material, such as metal, alloy, paper, porcelain, or a combination thereof. For example, the substrate may be a container such as a reusable plastic bottle, can, jar, or box.

[0049] The substrate surface to which the chemically radiation-curable composition is applied may include reusable materials such as plastic materials. For example, the surface may include the inner wall of a plastic substrate, or a plastic layer on a substrate containing at least one other material such as metal, alloy, paper, porcelain, or a combination thereof.

[0050] In some embodiments, the substrate surface to which the chemically curable composition is applied includes polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), polycarbonate (PC), or a combination thereof. In some embodiments, the substrate surface to which the chemically curable composition is applied includes crystalline polyethylene terephthalate (CPET).

[0051] The chemically curable compositions of the present invention can be applied by known printing methods such as flexographic printing. In some embodiments, the composition is applied as a primer composition. For example, the composition may be applied as a primer composition in a flexographic printing method using known techniques. The applied primer may be cured, for example, using UV light (in the range of 200 nm to 400 nm). Once the primer is cured, a suitable, commercially available UV flexographic printing ink or offset printing ink may be printed on the primer. These inks may be cured using appropriate known methods for these processes.

[0052] The chemically curable compositions of the present invention may also be applied for use in various other printing methods, such as digital and offset printing. For example, the composition may be adjusted to prepare a low-viscosity, sprayable composition for use as a primer in digital printing. The composition may also be applied as an offset primer, which may be applied to a coating unit at the start of the press or converted into a first down varnish layer. Suitable printing processes may also include screen or gravure processes known in the art. In some embodiments, the composition is applied as a spray (e.g., for a low-viscosity sprayable primer) or as a coating (e.g., an offset primer).

[0053] A chemically curable composition applied to the surface of a substrate may form a film or thin film on the surface. In some embodiments, the applied composition forms a film on the substrate surface having a thickness of about 2 μm to about 25 μm. The thickness may be about 5 μm, about 10 μm, about 15 μm, or about 20 μm.

[0054] [Examples]

[0055] The primer formulation was prepared and tested according to the following examples. Printed samples were prepared for each example by applying the primer formulation to shrink plastic packaging material via flexographic printing, curing the primer formulation with UV light, and printing flexographic UV ink onto the primer. The printed samples were shrunk by steam by holding them over a beaker of boiling water. The samples shrunk to approximately 75%. After shrinking, the adhesion of the samples was confirmed by tape tests and fingernail scratch tests.

[0056] Tape adhesion was measured using commercially available tape products (e.g., 3M 610, 3M 810) as a quality test of the primer formulations. Typically, the primer and ink were applied to a substrate to form a print, the tape was attached to the print, and then the tape was removed. The "adhesion level" of the primer was measured by visually estimating the percentage of ink (adhesion to the primer) remaining on the substrate after the tape was removed. For example, in the tape adhesion tests described herein, an 80% adhesion means that approximately 80% of the ink remains attached to the primer on the substrate, as estimated by visual inspection. For the primer formulations disclosed herein, an adhesion level of 90-100% measured by the tape adhesion tests is considered acceptable or good adhesion, while an adhesion level of 50% or less is considered weak or insufficient adhesion.

[0057] Furthermore, printed samples were tested using a caustic washing method adapted from the procedure specified by APR. Typically, printed samples (e.g., shrink plastic labels) were washed in a hot caustic aqueous solution and a detergent solution. The caustic aqueous solution may contain, for example, Triton X-100 nonionic surfactant (approximately 0.3 wt%) and sodium hydroxide (approximately 1 wt%). After placing the printed sample in the caustic aqueous solution in the sample at a solution weight ratio of approximately 1:4, the solution was stirred at 85°C for 15 minutes (e.g., using an impeller with an impeller tip speed of at least 240 m / min). In some tests, the printed samples became granular, consisting of plastic fragments, before coming into contact with the caustic aqueous solution. The washed samples were then rinsed for approximately 5 minutes in 45°C water (four times the weight of the sample) stirred (e.g., at an impeller tip speed of at least 240 m / min). The rinsed samples were further rinsed with water (8 to 10 times the weight of the sample) under gentle agitation conditions and collected. The collected samples were dried with air or in a laboratory oven at a temperature of 60°C or less. Next, the samples were visually inspected to estimate the amount of ink remaining on the samples. For example, a washed sample with an ink remaining of approximately 20% or less indicates that at least 80% of the ink printed on the sample was removed by the caustic cleaning process. In the caustic cleaning tests described herein, "pass" indicates that at least 85% of the ink was removed by the caustic cleaning process.

[0058] [Formulation 1A] TIFF2026086738000001.tif61145

[0059] [Formulation 1B] TIFF2026086738000002.tif42166

[0060] [Formulation 1C] TIFF2026086738000003.tif68166

[0061] [Formulation 1D] TIFF2026086738000004.tif93165

[0062] The above primer formulations were prepared and tested using the caustic cleaning method described herein. The tests revealed that these formulations were not removed during the caustic cleaning.

[0063] [Composition 2] TIFF2026086738000005.tif41148

[0064] The above primer formulation was specifically prepared using Miramer SC6640 (Miwon), a commercially available carboxylated polyester acrylate designed to be alkali-peelable. However, it was found that this primer formulation did not provide sufficient adhesion, and the primer and ink could be removed during the shrinking process of the printed shrink plastic packaging material.

[0065] [Formulations 3-9] TIFF2026086738000006.tif120168TIFF2026086738000007.tif100164

[0066] The above primer formulations were prepared and tested for their sensitivity to steam to maintain adhesion during the shrinkage process. The test results for these formulations are shown in Table 1. [Table 1] TIFF2026086738000008.tif48144

[0067] Formulas 3-8 exhibited weak or insufficient adhesion and were not subjected to caustic cleaning tests. In contrast, Formula 9 exhibited acceptable adhesion, allowed for good printing and shrinkage, and passed the caustic cleaning tests described herein. The addition of a matting agent (sedimented silica) to Formula 9 showed some improvement in adhesion levels. However, the adhesion level of Formula 9 is considered to be improved by controlling, for example, the curing level, the amount of primer / ink printed, and the accumulation of the formula, providing consistent results between laboratory tests and commercial press settings.

[0068] [Formulation 10-14] TIFF2026086738000009.tif126162

[0069] The effects of reducing the amount of carboxylated acrylate in the above formulations were tested. It is assumed that moisture resulting from the shrinkage process may interfere with adhesion. Urethane acrylate is included to increase the flexibility of the primer and enhance its adhesive strength. While reducing the carboxylate acrylate content may help improve adhesion after shrinkage, the results demonstrated that it is not necessarily required to pass (95% adhesion or better adhesion as measured by the tape adhesion test described herein). The test results for these formulations are shown in Table 2. [Table 2] TIFF2026086738000010.tif41153

[0070] [Formulations 15-17] TIFF2026086738000011.tif107158

[0071] The above primer formulations were prepared, and the effect of carboxylated acrylate content ranging from approximately 35% to 55% by weight was tested. Formulations 15 to 17 all showed good adhesion, or adhesion of 95% or more, even after shrinkage and the caustic cleaning test described herein.

[0072] Lab prints were prepared using formulation 15 as a primer on the INX UV Flexo Shrink 70 system under commercial printing conditions, and satisfactory results were obtained. Lab test results showed that the primer / ink combination exhibited good adhesion before and after shrinkage, and that the ink and primer were removed from the substrate by cleaning with the APR caustic cleaning method. Therefore, formulations 15-17 may be suitable as primers in commercial printing, for example.

[0073] An additional formulation containing carboxylated acrylate was developed. Notably, this formulation was observed to correct the curl problem that typically occurs when printed samples are washed, thereby improving the efficiency of caustic washing.

[0074] [Formulations 18-24] TIFF2026086738000012.tif139155TIFF2026086738000013.tif107149

[0075] As shown in Table 3, formulation 24 exhibited good adhesion and very little curling during the wash cycle in laboratory testing. Furthermore, the primer had excellent adhesion during the shrinkage process. Press tests were then performed on this formulation. The press tests showed similar results to the laboratory tests, with some curling during the wash cycle, which trapped ink particles inside the curled plastic piece. As a result, 92% of the printed ink was removed from the substrate after caustic cleaning. [Table 3] TIFF2026086738000014.tif49147

[0076] [Formulation 25-26] TIFF2026086738000015.tif101147

[0077] Formulations 25 and 26 both showed excellent resistance to substrate curling during the washing cycle (Table 4). This allowed for complete (100%) removal of the primer and printed ink. Formulation 25 was slightly modified to enhance robustness and scratch resistance. Further press testing was performed on formulation 26. [Table 4] TIFF2026086738000016.tif15147

[0078] Furthermore, primers produced by formulations 15-26 may be modified for use in various other printing methods, such as digital and offset printing. For example, a low-viscosity, sprayable primer produced by formulations 15-26 may be used as a digital primer. An offset primer produced by formulations 15-26 may be applied to a coating unit at the start of the press, or it may be converted into a varnish version. Such a varnish version of an offset primer produced in connection with formulations 15-26 is resistant to spray solutions used in offset presses.

[0079] It will be understood that the foregoing description and examples are merely illustrative and not limiting to the scope of the invention. Various changes and modifications to the disclosed embodiments can be made without departing from the spirit and scope of the invention.

Claims

1. 35% to 55% by weight of carboxylated acrylate, 15% to 45% by weight of urethane acrylate, Monomas in a 5% to 15% weight range, A chemically ray curable composition comprising 5% to 15% by weight of a photoinitiator.

2. The chemically curable composition according to claim 1, wherein the composition has a viscosity of 200 cps to 1000 cps at 25°C.

3. A chemically ray curable composition according to any one of claims 1 to 2, comprising 35% to 45% by weight of the carboxylated acrylate.

4. The carboxylated acrylate has an acid value of 100 mg KOH / g to 300 mg KOH / g, as described in any one of claims 1 to 3, for the chemically laser curable composition.

5. The chemically curable composition according to any one of claims 1 to 4, wherein the urethane acrylate is an aromatic urethane acrylate, an aliphatic urethane acrylate, or a combination thereof.

6. The chemically wire-curable composition according to any one of claims 1 to 5, wherein the monomer is a monofunctional monomer, a difunctional monomer, a trifunctional monomer, a tetrafunctional monomer, or a combination thereof.

7. The chemically ray curable composition according to any one of claims 1 to 6, wherein the photoinitiator is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, or a combination thereof.

8. The chemically ray curable composition according to claim 1, wherein the composition, when applied to the surface of a substrate and cured, (1) maintains at least 80% adhesion to the surface in a tape adhesion test, and (2) is removed at least 80% from the surface by caustic cleaning, the tape adhesion test being performed by applying the composition to the substrate made of shrink plastic, further printing a flexo UV ink to form a printed material, attaching tape to the printed material, and measuring the adhesion based on the percentage of the ink remaining on the substrate after the tape is removed, and the caustic cleaning being performed in accordance with the test method specified in APR.

9. 35% to 55% by weight of carboxylated acrylate, 15% to 45% by weight of urethane acrylate, Monomas in a 5% to 15% weight range, 2% to 10% by weight of an adhesion promoter, A chemically ray curable composition comprising 5% to 15% by weight of a photoinitiator.

10. The chemically ray curable composition according to claim 9, wherein, when applied to a surface and cured, (1) maintains at least 80% adhesion to the surface in a tape adhesion test, and (2) is removed from the surface by caustic cleaning by at least 80%.

11. A step of applying the chemically ray curable composition according to any one of claims 1 to 8 to the surface of a substrate, A step of curing the coated composition, A printing method comprising the step of applying ink onto the cured composition.

12. The method according to claim 11, wherein the ink is a chemically wire-curable ink, and the method further comprises the step of curing the applied ink.

13. The method according to any one of claims 11 to 12, wherein the surface includes plastic.

14. The method according to any one of claims 11 to 13, wherein the surface comprises polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PP), polystyrene (PS), polycarbonate (PC), or a combination thereof.

15. The method according to any one of claims 11 to 14, wherein the surface comprises crystalline polyethylene terephthalate (CPET).

16. The method according to any one of claims 11 to 15, wherein the composition is applied by flexographic printing.

17. The method according to any one of claims 11 to 16, wherein the coated composition forms a film having a thickness of 2 μm to 25 μm.

18. A step of applying the chemically curable composition according to any one of claims 9 to 10 onto the surface of a substrate, A step of curing the coated composition, A printing method comprising the step of applying ink to the cured composition.

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