Treatment-free CTP plate coating composition and preparation method thereof

Abstract

The present invention discloses a treatment-free CTP plate coating composition and a preparation method thereof, and belongs to the technical field of CTP plates, the coating composition comprises the following raw materials by mass: 20-40 parts of film-forming resin, 1-3 parts of an infrared absorption material, 4-8 parts of a polycarbodiimide cross-linking agent, 0.5-3 parts of an auxiliary agent, and 40-50 parts of a solvent, the film-forming resin comprises an acrylic monomer accounting for 85-90% of the total mass of the film-forming resin and a polyurethane / acrylate hyperbranched polymer accounting for 4-6% of the total mass of the film-forming resin. The film-forming resin takes acrylate resin as a main film-forming component, so that the adhesive force between the coating composition and a base material can be improved, good scratch resistance and ink transfer characteristic can be provided, the image stability can be improved, and the crosslinking density can be improved by adding the polyurethane / acrylate hyperbranched polymer; the rheological property and the material flexibility of the film-forming resin are improved, the pressrun of a CTP plate is improved, and the requirement of long-term continuous operation can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of CTP plates, and in particular relates to a treatment-free CTP plate coating composition and a preparation method thereof. Background Art

[0002] In the modern printing industry, computer-to-plate (CTP) technology has gradually replaced the traditional optical platemaking method and become the mainstream platemaking method. CTP technology mainly uses laser or other forms of energy to directly convert digital files into images on the printing plate, greatly improving work efficiency and accuracy. However, most of the CTPs currently used still require traditional wet development, that is, after exposure, they must be washed with a plate processor and alkaline aqueous solution or organic solvent to remove the soluble part before printing. This not only increases the cost of platemaking, but may also cause certain harm to the environment.

[0003] In order to solve this problem, people have developed a new type of processing-free CTP plate, which can be directly printed on the machine without additional chemical treatment after exposure. This not only reduces equipment costs, reduces operating steps, and improves the working environment, but also can achieve stable plate quality.

[0004] The surface coating of the processing-free CTP plate can help the plate to undergo physical or chemical changes directly under the action of laser or other energy sources, thereby forming a distinction between the image area and the non-image area after exposure. It can also solve various mechanical friction and chemical erosion problems that may occur in most printing processes.

[0005] However, there are still some problems with the surface coating used in the processing-free CTP plate. For example, due to the simplified development and washing steps, it is sometimes difficult to ensure consistent and high-quality image effects after each exposure. Especially when dealing with complex patterns or fine lines, the edges may be blurred; the surface coating will wear or be damaged in the case of long-term continuous operation. Some products show low print durability. The mechanical properties of the surface coating are not high and it is easy to be scratched during transportation or use, affecting the printing quality and causing the printing plate to be scrapped. Summary of the invention

[0006] The object of the present invention is to provide a treatment-free CTP plate coating composition and a preparation method thereof, so as to solve the problems of low mechanical properties, poor printing durability and unstable image quality of the surface coating of the treatment-free CTP plate.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides a treatment-free CTP plate coating composition, comprising the following raw materials in parts by weight:

[0009] 20-40 parts of film-forming resin;

[0010] 1 to 3 parts of infrared absorbing material;

[0011] 4 to 8 parts of polycarbodiimide crosslinking agent;

[0012] 0.5-3 parts of additives;

[0013] 40-50 parts of solvent;

[0014] The film-forming resin comprises 85-90% of the total weight of the film-forming resin acrylic monomer and 4-6% of the polyurethane / acrylate hyperbranched polymer.

[0015] Preferably, the infrared absorbing material includes any one of a cyanine dye and an infrared dye.

[0016] Preferably, the auxiliary agent includes a combination of one or more of an antioxidant, a lubricant and a leveling agent.

[0017] More preferably, the antioxidant includes one or more combinations of antioxidant 1010, antioxidant 1076 and antioxidant 168; the lubricant includes one or more combinations of silicone oil, polyethylene wax, zinc stearate and calcium stearate; the leveling agent includes BYK335, Efka-SL3258, Either FL 3740 or Tech-1355.

[0018] Preferably, the solvent includes any one of ethyl acetate, butyl acetate, isopropyl alcohol, xylene, methyl ethyl ketone and glycol monoethyl ether.

[0019] By adopting the above technical scheme, the coating composition obtained by the present invention uses acrylic resin as the main component of the film-forming resin. The acrylic resin obtained by cross-linking acrylic monomers has good weather resistance and durability compared with other types of film-forming resins, and can maintain good performance in long-term use, and is not easy to cause performance degradation due to environmental factors. At the same time, the acrylic resin has good adhesion and mechanical strength, and has a strong interaction force with the substrate of the CTP plate, which can ensure that the obtained coating composition is firmly attached to the substrate and reduce the impact of shedding or peeling damage on the CTP plate. Acrylic resin can also provide good scratch resistance and good ink transfer characteristics, and improve the stability of the CTP plate image.

[0020] In addition, polyurethane / acrylate hyperbranched polymers are added to the film-forming resin. Due to their highly branched molecular structure, polyurethane / acrylate hyperbranched polymers have the characteristics of low viscosity and high reactivity, which can improve the flow properties of acrylate resins, so that the obtained coating composition can be quickly leveled on the CTP plate substrate, thereby improving the uniformity and adhesion of the formed coating.

[0021] Secondly, the introduction of polyurethane molecular segments can exhibit better weather resistance and help the coating composition remain stable even in harsh environments. And because polyurethane resin has excellent flexibility and wear resistance, it can well regulate the high hardness of acrylic resin, improve the printing resistance of CTP plates, and meet the needs of long-term continuous operation.

[0022] The copolymerization of acrylate segments also enhances the compatibility between polyurethane and film-forming resin, allowing the polyurethane / acrylate hyperbranched polymer to better insert and act on the coating composition, improving the coating performance. In addition, the carbon-carbon double bonds and urethane groups contained in the polyurethane molecular chain can form strong chemical bonds with the film-forming resin, thereby enhancing the adhesion and durability of the coating.

[0023] However, as a film-forming resin, acrylate resin is prone to deformation or performance degradation under high temperature conditions, and is prone to brittle cracking under low temperature conditions, and has poor heat resistance. Therefore, adding a polycarbodiimide crosslinking agent to the coating composition can cause a cross-linking reaction with the carboxyl functional groups in the acrylate to form a more stable and compact three-dimensional network structure in the coating, thereby increasing the glass transition temperature of the acrylate resin and enhancing the heat resistance of the material. In addition, by increasing the cross-linking density, the final coating surface is harder and smoother, which can improve the printing effect, ensure clear reproduction of the pattern, reduce friction resistance during printing, and thus extend the service life of the processing-free CTP plate.

[0024] Preferably, the raw materials of the polyurethane / acrylate hyperbranched polymer include polyurethane prepolymer, hydroxy acrylate and hyperbranched polyester in a molar ratio of 1:(0.8-1):(0.1-0.2).

[0025] Preferably, the R value of the polyurethane prepolymer is 2.2 to 2.4.

[0026] Preferably, the hydroxyacrylate includes one or a combination of hydroxyethyl acrylate and hydroxyethyl methacrylate.

[0027] Preferably, the polyurethane prepolymer is prepared according to the following method:

[0028] Isophorone diisocyanate and dibutyltin dilaurate are added to the dehydrated polypropylene glycol, the solution temperature is maintained at 75-80°C, and the mixture is stirred for 2-3 hours. Then 1,4-butanediol and dihydroxymethylpropionic acid are added, the solution temperature is maintained at 80-85°C, and the mixture is stirred for 1-2 hours to obtain a polyurethane prepolymer.

[0029] Preferably, the polyurethane / acrylate hyperbranched polymer is prepared according to the following method:

[0030] Dissolve the hyperbranched polyester in N,N-dimethylformamide, add it to the polyurethane prepolymer, raise the temperature to 75-80°C, stir and react for 1-2 hours, add hydroxy acrylate, adjust the temperature to 50-60°C, stir and react for 1-2 hours, then add triethylamine and stir to neutralize for 15-20 minutes, finally add distilled water and stir for 30-60 minutes.

[0031] By adopting the above technical scheme, the isocyanate group at the end of the molecular chain of the polyurethane prepolymer can react with the hydroxyl functional group in the hydroxy acrylate to form a copolymer, and then a hyperbranched polyester is added. The molecular end of the hyperbranched polyester contains a large number of hydroxyl groups and has high reactivity, thereby realizing the grafting of the polyurethane and acrylate copolymers to obtain a hyperbranched polymer.

[0032] The molecular chain segments of the copolymer with a hyperbranched structure are not easy to entangle, which reduces the viscosity of the film-forming resin and greatly improves the flow properties of the coating composition, facilitating uniform mixing with other components. The free volume within and between molecules increases the toughness of the coating. Coupled with the introduction of flexible polyurethane segments, the coating exhibits better flexibility and wear resistance, thereby solving the problem of poor print durability. A large number of active groups also provide pre-crosslinking density for the film-forming resin, thereby enhancing the stability and density of the coating, as well as the mechanical strength of the coating.

[0033] More importantly, since the present invention uses acrylate resin as the main component of the film-forming resin, although the processing-free CTP plate reduces the development and washing steps, it will still come into contact with some strong solvents or chemicals such as ink and cleaning agents during the image printing process. The acrylate resin has poor solvent resistance, which may cause the formed coating to soften or dissolve, which will cause damage to the surface of the printing plate and affect the printing quality.

[0034] Polyurethane / acrylate hyperbranched polymer has a three-dimensional spherical multi-branch structure, which reduces intermolecular entanglement, can improve the molecular structure of acrylate resin, and can also provide a large number of highly active groups to participate in the cross-linking of the coating to form more cross-linking points. The resulting three-dimensional network structure can effectively prevent solvent molecules from penetrating into the coating, reduce the risk of swelling or dissolution, and significantly improve the coating's resistance to solvents; and through the copolymerization of polyurethane and acrylate, the compatibility between the hyperbranched polymer and the film-forming resin matrix can be significantly improved, ensuring that the various components are closely connected, thereby jointly resisting the effects of external solvents, and also improving the mechanical strength of the coating, reducing the impact of scratches on the surface coating of the untreated CTP board.

[0035] Preferably, the film-forming resin further comprises 3-7% of a cross-linking agent and 1-3% of an initiator.

[0036] Preferably, the cross-linking agent includes any one of an isocyanate cross-linking agent and an amino resin cross-linking agent.

[0037] Preferably, the initiator includes any one of azobisisobutyronitrile, benzoyl peroxide, di-tert-butyl peroxide and ammonium persulfate.

[0038] Preferably, the acrylic monomers include acrylic soft monomers, acrylic hard monomers and acrylic functional monomers in a mass ratio of (45-50):(8-12):(3-6).

[0039] Preferably, the acrylic soft monomer includes a combination of one or more of ethyl acrylate, butyl acrylate, isoamyl methacrylate, isobutyl methacrylate, isoamyl ethacrylate and isooctyl acrylate.

[0040] Preferably, the acrylic hard monomer includes a combination of one or more of methyl methacrylate, styrene and acrylonitrile.

[0041] Preferably, the acrylic functional monomer includes any one of amide acrylic acid, acrylic acid and hydroxyl acrylic acid.

[0042] More preferably, the amide acrylic acid includes a combination of one or more of acrylamide, hydroxymethyl acrylamide, and diacetone acrylamide.

[0043] More preferably, the hydroxy-based acrylic acid includes a combination of one or more of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and hydroxyethyl methacrylate.

[0044] By adopting the above technical solution, adding a crosslinking agent and an initiator to promote the crosslinking and curing process of acrylic monomers, thereby obtaining a coating with higher heat resistance and mechanical strength, and by selecting a combination of different acrylic soft monomers, hard monomers and functional monomers, the problem of high hardness and brittleness of acrylic esters at low temperatures can be effectively improved, thereby extending the service life of the coating composition.

[0045] Preferably, the polycarbodiimide crosslinking agent is modified with sulfonic acid groups.

[0046] Preferably, the raw material of the polycarbodiimide cross-linking agent modified with sulfonic acid groups comprises polycarbodiimide and aminosulfonate in a mass ratio of 1: (0.2-0.3).

[0047] Preferably, the polycarbodiimide crosslinking agent is subjected to sulfonic acid group modification treatment according to the following method:

[0048] Add polycarbodiimide to an organic solvent, adjust the solution temperature to 0-20°C, add aminosulfonate, stir and react for 1-2 hours, then increase the temperature to 25-30°C, continue stirring and mixing for 1-2 hours, and finally centrifuge and dry under reduced pressure to obtain the product.

[0049] By adopting the above technical scheme, a polycarbodiimide crosslinking agent is also added to the coating composition of the present invention, which can enhance the crosslinking density of the coating. The formed network structure increases the connection points between molecules, thereby increasing the mechanical strength of the obtained coating and helping to obtain high-quality printing effects. At the same time, compared with other crosslinking agents, the ureide bond formed between the polycarbodiimide crosslinking agent and the acrylate molecule is not easily hydrolyzed, so it can effectively prevent solvent penetration and effectively improve the solvent resistance of the acrylate resin when used as a film-forming resin.

[0050] However, the cross-linking reaction of the polycarbodiimide cross-linking agent is rapid, which can increase the cross-linking density but is detrimental to the film-forming process. The resulting coating tends to be brittle. Therefore, the polycarbodiimide cross-linking agent is modified to connect hydrophilic sulfonic acid groups, which can block the activity during the cross-linking process, adjust the cross-linking speed and the film-forming process, thereby improving the mechanical properties of the coating. The introduction of sulfonic acid groups can cooperate with the polyurethane / acrylate hyperbranched polymer in the film-forming resin to form a tighter three-dimensional network structure, thereby improving the adhesion between the coating composition and the CTP sheet substrate, so that the coating composition is not easy to fall off from the substrate under high-speed operation or complex printing conditions. In addition, since the sulfonic acid group carries a negative charge, it can help reduce the problem of image instability caused by electrostatic effects in non-image areas during printing. The polycarbodiimide cross-linking agent can also help adjust the photosensitivity of the coating, so that the CTP plate can capture image details more accurately during exposure, thereby improving printing quality.

[0051] In a second aspect, the present invention provides a method for preparing a treatment-free CTP plate coating composition, comprising the following process steps:

[0052] S1. Adding each raw material of the film-forming resin to the solvent and mixing evenly to obtain a premixed solution;

[0053] S2. Adding polycarbodiimide crosslinking agent, infrared absorbing material and auxiliary agent to the premixed liquid in sequence, mixing evenly and performing three-stage filtration to obtain a treatment-free CTP plate coating composition.

[0054] Beneficial effects of the present invention:

[0055] 1. The film-forming resin in the treatment-free CTP plate coating composition provided by the present invention uses acrylate resin as the main film-forming component, which can improve the adhesion between the coating composition and the substrate, and can also provide good anti-scratch ability and ink transfer characteristics, thereby improving image stability; and a polyurethane / acrylate hyperbranched polymer is added to the film-forming resin, and the hyperbranched structure can effectively improve the rheological properties of the film-forming resin, and can also provide branched cross-linking sites, thereby increasing the cross-linking density of the coating composition, thereby enhancing the mechanical properties and the heat resistance and solvent resistance of the coating composition, and the introduction of the polyurethane chain segment can improve the flexibility of the coating composition, regulate the problem of high hardness of the acrylate resin, thereby improving the printing durability of the CTP plate and meeting the needs of long-term continuous operation.

[0056] 2. The treatment-free CTP plate coating composition provided by the present invention also contains a polycarbodiimide crosslinking agent, which can undergo a crosslinking reaction with the carboxyl group in the acrylate resin to form a more stable and compact three-dimensional network structure, thereby improving the heat resistance and solvent resistance of the coating composition. After being modified with the sulfonic acid group, the crosslinking and film-forming processes can be effectively regulated to improve the mechanical strength and wear resistance of the coating composition. The introduction of the sulfonic acid group can also improve the adhesion of the coating composition and reduce the shedding phenomenon of the coating composition during use. The formed strong and smooth coating can improve the stability of the image. DETAILED DESCRIPTION

[0057] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Preparation Example

[0059] Preparation Example 1

[0060] Preparation Example 1-1, a polyurethane / acrylate hyperbranched polymer, prepared according to the following method:

[0061] Add isophorone diisocyanate and 1 g of dibutyltin dilaurate to 100 g of dehydrated polypropylene glycol, keep the solution temperature at 80° C., stir and mix for 2 hours, then add 9 g of 1,4-butanediol and dimethylolpropionic acid, keep the solution temperature at 85° C., stir and mix for 1 hour to obtain a polyurethane prepolymer; wherein the R value of the obtained polyurethane prepolymer is controlled to be 2.4;

[0062] Take 0.15 mol of hyperbranched polyester (model PFH-16-OH) and dissolve it in 500 mL of N,N-dimethylformamide, add it to 1 mol of polyurethane prepolymer, raise the temperature to 80°C, stir and react for 1 hour, then add 0.9 mol of hydroxyethyl methacrylate, adjust the temperature to 60°C, stir and react for 2 hours, then add 0.015 mol of triethylamine and stir and neutralize for 15 minutes, finally add distilled water and stir at high speed for 40 minutes, wherein the rotation speed is 1200 rpm.

[0063] Preparation Example 1-2, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of the hyperbranched polyester is 0.1 mol, and the added amount of hydroxyethyl methacrylate is 0.8 mol.

[0064] Preparation Example 1-3, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of the hyperbranched polyester is 0.2 mol, and the added amount of hydroxyethyl methacrylate is 1 mol.

[0065] Preparation Example 1-4, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of hydroxyethyl methacrylate is 0.6 mol.

[0066] Preparation Example 1-5, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of hydroxyethyl methacrylate is 1.2 mol.

[0067] Preparation Example 1-6, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of the hyperbranched polyester is 0.05 mol.

[0068] Preparation Example 1-7, a polyurethane / acrylate hyperbranched polymer, is different from Preparation Example 1-1 only in that the added amount of the hyperbranched polyester is 0.25 mol.

[0069] Preparation Example 1-8, a polyurethane hyperbranched polymer, was prepared according to the following method:

[0070] Add isophorone diisocyanate and 1 g of dibutyltin dilaurate to 100 g of dehydrated polypropylene glycol, keep the solution temperature at 80° C., stir and mix for 2 hours, then add 9 g of 1,4-butanediol and dimethylolpropionic acid, keep the solution temperature at 85° C., stir and mix for 1 hour to obtain a polyurethane prepolymer; wherein the R value of the obtained polyurethane prepolymer is controlled to be 2.4;

[0071] Take 0.15 mol of hyperbranched polyester (model PFH-16-OH) and dissolve it in 500 mL of N,N-dimethylformamide, add it to 1 mol of polyurethane prepolymer, raise the temperature to 80°C, stir and react for 3 hours, then add 0.015 mol of triethylamine and stir and neutralize for 15 minutes, finally add distilled water and stir at high speed for 40 minutes, where the rotation speed is 1200 rpm.

[0072] Preparation Example 1-9, a polyurethane / acrylate polymer, was prepared according to the following method:

[0073] Add isophorone diisocyanate and 1 g of dibutyltin dilaurate to 100 g of dehydrated polypropylene glycol, keep the solution temperature at 80° C., stir and mix for 2 hours, then add 9 g of 1,4-butanediol and dimethylolpropionic acid, keep the solution temperature at 85° C., stir and mix for 1 hour to obtain a polyurethane prepolymer; wherein the R value of the obtained polyurethane prepolymer is controlled to be 2.4;

[0074] Add 1 mol of polyurethane prepolymer to 500 mL of N,N-dimethylformamide, raise the temperature to 80°C, stir and react for 1 hour, then add 0.9 mol of hydroxyethyl methacrylate, adjust the temperature to 60°C, stir and react for 2 hours, then add 0.015 mol of triethylamine and stir and neutralize for 15 minutes, finally add distilled water and stir at high speed for 40 minutes, wherein the rotation speed is 1200 rpm.

[0075] Preparation Example 1-10, a polyurethane, is prepared according to the following method:

[0076] Isophorone diisocyanate and 1 g of dibutyltin dilaurate were added to 100 g of dehydrated polypropylene glycol, the solution temperature was maintained at 80° C., and the mixture was stirred for 2 h. Then, 9 g of 1,4-butanediol and dihydroxymethylpropionic acid were added, the solution temperature was maintained at 85° C., and the mixture was stirred for 1 h to obtain a polyurethane. The R value of the obtained polyurethane was controlled to be 2.4.

[0077] Preparation Example 2

[0078] Preparation Example 2-1, a polycarbodiimide crosslinking agent modified with sulfonic acid groups, is prepared according to the following method:

[0079] 10g polycarbodiimide (model CA-01) was added to 250 mL of acetone, the solution temperature was adjusted to 10°C, 2 g of sodium aminosulfonate was added, the reaction was stirred for 2 h, and then the temperature was raised to 30°C, the stirring was continued for 1 h, and finally centrifuged and dried under reduced pressure to obtain the product.

[0080] Preparation Example 2-2, a polycarbodiimide crosslinking agent modified with sulfonic acid groups, is different from Preparation Example 2-1 only in that the amount of sodium aminosulfonate added is 3 g.

[0081] Example

[0082] Example 1, a treatment-free CTP plate coating composition, is prepared according to the following process steps:

[0083] 88g of acrylic monomer, 5g of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1, and 5g of an isocyanate crosslinking agent (model BI7963) and 2g of azobisisobutyronitrile, wherein the acrylic monomers include isobutyl methacrylate, methyl methacrylate and hydroxymethyl acrylamide in a mass ratio of 48:10:5;

[0084] Take 30g of the film-forming resin raw material obtained above, add it to 45g of ethyl acetate and mix well to obtain a premixed solution;

[0085] 6 g of the polycarbodiimide crosslinker prepared in Preparation Example 2-1, 2 g of cyanine dye and 2 g of auxiliary agent (antioxidant 1010 and leveling agent BYK335 in a mass ratio of 1:1) were added to the premixed liquid in sequence, mixed evenly and then subjected to three-stage filtration to obtain a treatment-free CTP plate coating composition.

[0086] Example 2 and Example 3 are a treatment-free CTP plate coating composition, which differs from Example 1 only in that the raw material ratio of the film-forming resin is adjusted, as shown in Table 1:

[0087] Table 1 Ratios of film-forming resin raw materials in Examples 1 to 3

[0088]

[0089] The acrylic monomers in Example 2 include isobutyl methacrylate, methyl methacrylate and hydroxymethyl acrylamide in a mass ratio of 45:12:6; the acrylic monomers in Example 3 include isobutyl methacrylate, methyl methacrylate and hydroxymethyl acrylamide in a mass ratio of 50:8:3.

[0090] Example 4, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-2.

[0091] Example 5, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-3.

[0092] Example 6 and Example 7 are a treatment-free CTP plate coating composition, which differs from Example 1 only in that the composition ratio of the coating composition is adjusted, as shown in Table 2:

[0093] Table 2 Coating composition ratios of Example 1, Example 6 and Example 7

[0094] Example 1 Example 6 Example 7 Film-forming resin / g 30 20 40 Ethyl acetate / g 45 40 50 Cyanine dye / g 2 1 3 Polycarbodiimide crosslinking agent / g 6 4 8 Additives / g 2 2 3

[0095] Example 8, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polycarbodiimide cross-linking agent prepared in Preparation Example 2-1 is replaced by an equal amount of the polycarbodiimide cross-linking agent prepared in Preparation Example 2-2.

[0096] Example 9, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-4.

[0097] Example 10, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-5.

[0098] Example 11, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-6.

[0099] Example 12, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-7.

[0100] Example 13, a treatment-free CTP plate coating composition, which is different from Example 1 only in that an equal amount of polycarbodiimide (model CA-01) replaces the polycarbodiimide crosslinking agent prepared in Preparation Example 2-1.

[0101] Comparative Example

[0102] Comparative Example 1, a treatment-free CTP plate coating composition, which is different from Example 1 only in that the addition amounts of each raw material in the film-forming resin are: 88g acrylic monomer, 2g polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1, 7g isocyanate crosslinking agent (model BI7963) and 3g azobisisobutyronitrile.

[0103] Comparative Example 2, a treatment-free CTP plate coating composition, which is different from Example 1 only in that the addition amounts of each raw material in the film-forming resin are: 85g acrylic monomer, 8g polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1, 5g isocyanate crosslinking agent (model BI7963) and 2g azobisisobutyronitrile.

[0104] Comparative Example 3, a treatment-free CTP plate coating composition, is different from Example 1 only in that the polyurethane hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane hyperbranched polymer prepared in Preparation Example 1-8.

[0105] Comparative Example 4 is a treatment-free CTP plate coating composition, which is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane / acrylate polymer prepared in Preparation Example 1-9.

[0106] Comparative Example 5 is a treatment-free CTP plate coating composition, which is different from Example 1 only in that the polyurethane / acrylate hyperbranched polymer prepared in Preparation Example 1-1 is replaced by an equal amount of the polyurethane prepared in Preparation Example 1-10.

[0107] Comparative Example 6, a treatment-free CTP plate coating composition, is different from Example 1 only in that the addition amount of each raw material in the film-forming resin is: 90g acrylic monomer, 7g isocyanate crosslinking agent (model BI7963) and 3g azobisisobutyronitrile.

[0108] Comparative Example 7 is a treatment-free CTP plate coating composition, which is different from Example 1 only in that the polycarbodiimide crosslinking agent prepared in Preparation Example 2-1 is not added to the treatment-free CTP plate coating composition.

[0109] Comparative Example 8, a treatment-free CTP plate coating composition, which is different from Example 1 only in that an equal amount of polyisocyanate crosslinking agent (model BI7982) replaces the polycarbodiimide crosslinker prepared in Preparation Example 2-1.

[0110] Performance testing

[0111] Sample preparation:

[0112] The coating composition obtained in the embodiment and the comparative example was coated on an aluminum substrate to obtain a treatment-free CTP plate, and then an 830 nm infrared laser was used for exposure and development in a conventional manner, and performance testing was performed.

[0113] Performance Test:

[0114] According to the relevant records in HG / T 4865-2015 "Positive Thermal Computer-to-Plate (CTP) Plates for Ultraviolet Curing (UV) Inks", the obtained experimental samples were tested for coating photosensitivity and solvent resistance loss rate, and the results are shown in Table 3.

[0115] Table 3 Performance test results

[0116]

[0117] According to Table 3, in combination with Example 1, Example 9, Example 10 and Comparative Example 3, it can be seen that the post-development density of Example 9, Example 10 and Comparative Example 3 is lower than that of Example 1, and the solvent resistance loss rate is increased, indicating that the image stability and solvent resistance of Example 9, Example 10 and Comparative Example 3 are lower. The reason is that the amount of acrylate added in the polyurethane / acrylate hyperbranched polymer used in Example 9 is reduced during the preparation process, which will lead to a decrease in the compatibility of the obtained hyperbranched polymer with the acrylate resin matrix, and the hyperbranched polymer cannot be evenly dispersed in the coating composition, affecting the stability of the final image development, solvent resistance and mechanical strength, while the polyurethane in Comparative Example 3 is not copolymerized with acrylate, and the performance degradation is more obvious. In Example 10, the amount of acrylate added is increased, which will affect the improvement of the flexibility of the polyurethane / acrylate hyperbranched polymer and is not conducive to the improvement of the print run.

[0118] Combining Example 1, Example 11, Example 12 and Comparative Example 4, it can be seen that the developed density of Example 11, Example 12 and Comparative Example 4 is lower than that of Example 1, and the solvent resistance loss rate is increased, among which the change in Comparative Example 4 is more obvious. The reason is that in Example 11, the amount of hyperbranched polyester added in the preparation process of polyurethane / acrylate hyperbranched polymer is reduced, resulting in a decrease in hyperbranching degree, a decrease in hyperbranching sites, a decrease in rheological properties, and a decrease in cross-linking sites, resulting in a decrease in solvent resistance. In Comparative Example 4, no hyperbranching treatment is performed, and the performance decrease is more obvious. In Example 12, the amount of hyperbranched polyester added is increased, resulting in a decrease in the intermolecular force of the coating composition, which in turn leads to a decrease in the density of the formed cross-linked network structure, a decrease in the mechanical strength of the formed coating, and a decrease in solvent resistance.

[0119] Combining Example 1 and Example 13, it can be seen that the post-development density of Example 13 is slightly decreased, and the solvent resistance loss rate is increased. The reason is that compared with Example 1, the polycarbodiimide cross-linking agent added in Example 13 has not been modified with sulfonic acid groups, which will affect the mechanical properties of the coating, reduce flexibility, and lead to reduced printing resistance. In addition, due to the lack of the effect of the sulfonic acid group, the image stability of the material is also slightly reduced.

[0120] Combining Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 6, it can be seen that the post-development density of Comparative Example 1, Comparative Example 2 and Comparative Example 6 is reduced compared with Example 1, and the solvent resistance loss rate is increased. The reason is that the addition amount of polyurethane / acrylate hyperbranched polymer in the film-forming resin is reduced in Comparative Example 1, and the regulation of hyperbranched structure and polyurethane segment is lacking, and the flexibility of the material will decrease significantly, resulting in a decrease in the printing resistance of the coating composition. In addition, with the reduction of hyperbranched polymer, the cross-linking site and cross-linking density of the coating composition will decrease, and the solvent resistance performance will also decrease accordingly. In Comparative Example 6, no polyurethane / acrylate hyperbranched polymer is added, and the performance decrease is more obvious. In Comparative Example 2, the addition amount of polyurethane / acrylate hyperbranched polymer is increased. On the one hand, the large amount of flexible structure added will affect the mechanical strength of the coating, resulting in a decrease in the wear resistance of the coating. On the other hand, the excessive hyperbranched polymer will interfere with the normal cross-linking and curing process, and the processing performance of the coating composition is affected.

[0121] Combining Example 1, Comparative Example 7 and Comparative Example 8, it can be seen that the post-development density of Comparative Example 7 and Comparative Example 8 is lower than that of Example 1, and the solvent resistance loss rate is increased. The reason is that in Comparative Example 8, no polycarbodiimide crosslinking agent is added, the crosslinking density of the coating composition is reduced, the stability is reduced, and the printing effect is also reduced; Comparative Example 7 uses a conventional crosslinking agent, and the solvent resistance is reduced compared with the polycarbodiimide crosslinking agent, and the photosensitivity effect of the CTP plate coating is reduced.

[0122] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0123] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A treatment-free CTP plate coating composition, characterized in that: Including the following raw materials by mass: 20-40 parts of film-forming resin; 1 to 3 parts of infrared absorbing material; 4 to 8 parts of polycarbodiimide crosslinking agent; 0.5-3 parts of additives; 40-50 parts of solvent; The film-forming resin comprises 85-90% of the total mass of the film-forming resin acrylic monomer and 4-6% of polyurethane / acrylate hyperbranched polymer.

2. The treatment-free CTP plate coating composition according to claim 1, characterized in that: The raw materials of the polyurethane / acrylate hyperbranched polymer include polyurethane prepolymer, hydroxy acrylate and hyperbranched polyester in a molar ratio of 1:(0.8-1):(0.1-0.2).

3. The treatment-free CTP plate coating composition according to claim 2, characterized in that: The R value of the polyurethane prepolymer is 2.2-2.

4.

4. The treatment-free CTP plate coating composition according to claim 2, characterized in that: The polyurethane / acrylate hyperbranched polymer is prepared according to the following method: Dissolve the hyperbranched polyester in N,N-dimethylformamide, add it to the polyurethane prepolymer, raise the temperature to 75-80°C, stir and react for 1-2 hours, add hydroxy acrylate, adjust the temperature to 50-60°C, stir and react for 1-2 hours, then add triethylamine and stir to neutralize for 15-20 minutes, finally add distilled water and stir for 30-60 minutes.

5. The treatment-free CTP plate coating composition according to claim 1, characterized in that: The film-forming resin also includes 3-7% of a cross-linking agent and 1-3% of an initiator.

6. The treatment-free CTP plate coating composition according to claim 1, characterized in that: The acrylic monomers include acrylic soft monomers, acrylic hard monomers and acrylic functional monomers in a mass ratio of (45-50):(8-12):(3-6).

7. The treatment-free CTP plate coating composition according to claim 1, characterized in that: The polycarbodiimide cross-linking agent is modified with sulfonic acid groups.

8. The treatment-free CTP plate coating composition according to claim 7, characterized in that: The raw materials of the polycarbodiimide cross-linking agent modified with sulfonic acid groups include polycarbodiimide and aminosulfonate in a mass ratio of 1: (0.2-0.3).

9. The treatment-free CTP plate coating composition according to claim 8, characterized in that: The polycarbodiimide crosslinking agent is subjected to sulfonic acid group modification treatment according to the following method: Add polycarbodiimide to an organic solvent, adjust the solution temperature to 0-20°C, add aminosulfonate, stir and react for 1-2 hours, then increase the temperature to 25-30°C, continue stirring and mixing for 1-2 hours, and finally centrifuge and dry under reduced pressure to obtain the product.

10. A method for preparing a treatment-free CTP plate coating composition according to any one of claims 1 to 9, characterized in that: The process steps include: S1. Adding each raw material of the film-forming resin to the solvent and mixing evenly to obtain a premixed solution; S2. Adding polycarbodiimide crosslinking agent, infrared absorbing material and auxiliary agent to the premixed liquid in sequence, mixing evenly and performing three-stage filtration to obtain a treatment-free CTP plate coating composition.

Images