Synthesis and preparation method of EB-curing coating for metal coil

Abstract

The present invention is a synthesis and preparation method of a metal coil EB curing coating. The hyperbranched poly (ester-acrylic acid) resin is composed of a hyperbranched polyester, a vinyl group and a vinyl group, and the hyperbranched (ester-acrylic acid) resin number average molecular weight Mn is distributed in 3000-15000, and the polymer branching degree is 0.15-0.8. The preparation method comprises the following steps: pentaerythritol and maleic anhydride are placed in a reactor, and the temperature is raised to 90-120°C for reaction for 1-3 hours; ethylene glycol or glycidol and a catalyst are added to the reactant of step 1) in sequence for 2-3 hours, and the water produced by the reaction is vacuumed and removed. The resin contains a hyperbranched structure and a large amount of vinyl, and can be used as a base resin for preparing a metal coil EB curing coating, with the advantages of fast reaction, multiple cross-linking points, no solvent, and low volume shrinkage after curing; on the basis of this resin, pigments, fillers, additives, etc. are added, and the fineness reaches the specified requirements after sand milling, and a metal coil EB coating can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical curing material preparation, and specifically relates to a synthesis and preparation method of an EB curing coating for a metal coil. Background Art

[0002] Electron beam (EB) curing is a curing process that uses electron beam radiation at room temperature to achieve the conversion of chemical formulas (coatings) from liquid to solid. It is an important radiation curing technology. EB curing provides an advanced processing method for curing the surface of materials. This type of curing technology is different from traditional curing technology (such as thermal curing, UV curing). Its biggest feature is that the former uses high-efficiency energy (electron beam) as a triggering method, which can achieve rapid curing of the coating. Its curing time is in the millisecond level, and it has many advantages such as low energy consumption and high efficiency. The solid content of the resin before and after curing is close to 100%, usually does not contain VOC, and is more environmentally friendly. At the same time, compared with other radiation curing, electron beam can also penetrate the inorganic fillers in the coating to completely cure the resin. It is a new environmentally friendly and energy-saving curing technology with great potential.

[0003] Previous researchers have studied the EB curing of epoxy resins. This technology uses cationic ring-opening reactions to complete resin curing. Compared with the curing mechanism of free radical polymerization, cationic polymerization systems do not require the protection of inert gas during the curing process, and the performance of the coating is also better. Cationic curing reactions are based on cationic initiated polymerization, and cationic polymerization usually requires low temperature and anhydrous conditions. Although cationic polymerization is prone to chain termination in the presence of water and room temperature, new active centers (protons or other cations) can still be generated during chain termination, which can still react with monomers to initiate new polymerization reactions. Unlike free radical polymerization, due to the mutual repulsion between cations, double ion chain termination reactions cannot occur, so cationic polymerization reactions can proceed more easily. Therefore, this also leads to the cationic epoxy resin system. After being separated from the radiation source, the resin will continue to react, that is, the cationic curing resin system has a post-radiation curing effect, which will lead to some uncontrolled situations.

[0004] Therefore, the EB-induced free radical polymerization reaction is generally more widely used. The earliest composite resin matrix used in electron beam curing is the unsaturated polyester resin system. Different types of vinyl resins and acrylic resins with double bonds at the end are easy to achieve radiation curing, but their relatively low Tg, high porosity, low fracture toughness, and large shrinkage during curing limit their application. Summary of the invention

[0005] The present invention aims at solving the above technical problems and provides a method for synthesizing and preparing an EB-cured coating for metal coils. The method first prepares an EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin, which is a poly(ester-acrylate) polymer containing a hyperbranched structure and vinyl groups in the skeleton and the end groups, and utilizes its special structure and large vinyl density to achieve good EB curing, thereby avoiding the shortcomings of the prior art, especially avoiding defects such as orange peel, sand eyes, and fish eyes on the surface of the resin after curing.

[0006] In order to achieve the above invention object, the specific technical solution of the present invention is:

[0007] An EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin, wherein the hyperbranched poly(ester-acrylic acid) resin is composed of a hyperbranched polyester, a vinyl group and a vinyl-containing group, and has the following hyperbranched molecular structure (the circle is a branching point):

[0008]

[0009]

[0010] Preferably, the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin has a number average molecular weight Mn ranging from 3000 to 15000, and a polymer branching degree ranging from 0.15 to 0.8.

[0011] Furthermore, the resin skeleton contains vinyl groups, which are provided by reaction with maleic anhydride; and the resin end groups contain vinyl groups, which are provided by reaction with (meth)acrylic anhydride.

[0012] "Hyperbranching" relates to the degree of branching (DB), i.e. a branched polymer can be characterized by its degree of branching (DB). The degree of branching DB is defined as DB=(T+Z) / (T+Z+L), where T is the average number of terminally connected monomer units, Z is the average number of branched monomer units, and L is the average number of linearly connected monomer units.

[0013] Another object of the present invention is to provide a method for preparing the above-mentioned EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin, comprising the following steps:

[0014] 1) Place pentaerythritol and maleic anhydride in a reaction kettle, heat to 90-120°C and react for 1-3 hours;

[0015] 2) adding ethylene glycol or glycidol and a catalyst to the reactant of step 1) in sequence and reacting for 2-3 hours, and removing the water generated by the reaction by vacuuming;

[0016] 2) adding (meth)acrylic anhydride to the material after the reaction in step 2), reacting for 1-2 hours, and removing unreacted monomers by vacuuming;

[0017] 3) adding (meth)acrylic anhydride to the material after the reaction in step 2), reacting for 1 to 2 hours, and removing unreacted monomers by vacuuming;

[0018] 4) adding any one or a mixture of several monomers containing active vinyl functional groups as active diluent monomers to obtain a hyperbranched vinyl-containing poly(ester-acrylic acid) resin containing vinyl groups in both the backbone and the end groups, which is an EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin.

[0019] Preferably, during the above reaction process, nitrogen is introduced into the reaction system from the bottom of the reactor throughout the whole process.

[0020] The nitrogen is used as a protective gas to isolate oxygen and also as a water-carrying agent. The hyperbranched polyester produced in steps 1) and 2) has a carboxyl end group, which reacts with the alcohol compound for dehydration. The nitrogen flows to carry out the water produced by the reaction and promote the reaction to occur in the forward direction. The temperature at which the nitrogen is heated is the same as the temperature of the reaction system.

[0021] Preferably, the molar ratio of pentaerythritol, maleic anhydride, ethylene glycol and (meth)acrylic anhydride is 1:4:4:3-6, more preferably 1:4:4:4; or the molar ratio of pentaerythritol, maleic anhydride, glycidol and (meth)acrylic anhydride is 1:4:4:3-8, more preferably 1:4:4:8.

[0022] Preferably, the catalyst is selected from any one of concentrated sulfuric acid, concentrated phosphoric acid or p-toluenesulfonic acid or a mixture of several thereof; and the added amount thereof is 0.5-5.0% of the mass of all additives before the addition of the substance.

[0023] Preferably, the monomer containing active vinyl functional group (active diluent) is selected from any one or a mixture of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triethylene glycol divinyl ether, cyclohexyl vinyl ether, vinyl caprolactam, etc.; and its added amount is 20-60% of the mass of all additives before the addition of the substance.

[0024] Another invention object of the present application is to protect an EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin obtained by any of the above methods or any combination of steps.

[0025] The third invention object of the present application is to protect the application of an EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin obtained by any of the above methods or any combination of steps, wherein the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin is used as a resin in an EB-cured coating.

[0026] A method for preparing an EB coating for a metal coil comprises the following steps: adding a pigment, an inorganic filler and an auxiliary agent to an EB-cured hyperbranched poly(ester-acrylic acid) resin containing vinyl groups obtained by the above method, grinding the mixture with a sand mill to a required fineness, then mixing the EB-cured hyperbranched poly(ester-acrylic acid) resin containing vinyl groups obtained by the above method again, and stirring the mixture at a high speed to obtain the EB coating for the metal coil.

[0027] Preferably, the mass ratio of the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin, pigment, inorganic filler, additive added for the first time and the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin added for the second time is 40:5 to 20:5 to 20:1 to 10:60.

[0028] Preferably, the pigment can be any one or more of aniline yellow, permanent yellow, permanent orange, golden red, light-fast phthalocyanine blue, phthalocyanine green, etc. to prepare the required color; the inorganic filler can be any one or more of carbon black, iron oxide powder, titanium dioxide, kaolin, light calcium carbonate, etc. to prepare the required color and hiding power; the additive can be any one or more of dispersant, defoamer, wetting agent, surface-reducing agent, adhesion promoter, film-forming agent, multifunctional additive, etc. Dispersant, defoamer, wetting agent, surface-reducing agent, adhesion promoter, film-forming agent, multifunctional additive are commonly used products in this field.

[0029] Compared with the prior art, the positive effects of the present invention are embodied in:

[0030] (i) In the present invention, a hyperbranched polyester is used as the skeleton design, and vinyl groups are introduced into the hyperbranched skeleton and peripheral end groups. The polyester skeleton forms a hyperbranched structure, and a large number of vinyl groups participate in EB curing polymerization. The hyperbranched polymer of the present invention has a high vinyl density and is regularly distributed in the skeleton and peripheral end groups, and has both a large number and good reactivity, and can obtain a product with excellent performance.

[0031] (ii) The inventors combined vinyl groups with hyperbranched polyesters, introduced vinyl groups into the hyperbranched polyester backbone and peripheral end groups, increased the local concentration of vinyl groups, and effectively improved the EB curing reaction performance of the hyperbranched polymer.

[0032] (III) The synthesis method of the present invention is simple, the experimental conditions are mild, and it is easy to industrialize.

[0033] (IV) The EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared by the present invention has excellent adhesion and shrinkage resistance as coatings and inks, and can also be used in combination with other additives, and can be widely used in the preparation of coatings and inks. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is an infrared image of the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared in the example. DETAILED DESCRIPTION

[0035] In order to make the content of the present invention easier to understand, the present invention is further described below in conjunction with specific embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0036] All substances used in this application are commercially available products. For example, triethylene glycol divinyl ether was purchased from Hubei Zhenbo Chemical Co., Ltd., and trimethylolpropane triacrylate was purchased from Hefei Anbang Chemical Co., Ltd.

[0037] Unless otherwise specified, % in this application refers to the mass percentage.

[0038] Embodiment 1:

[0039] The preparation method of EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin comprises the following steps:

[0040] 1 mol of pentaerythritol and 4 mol of maleic anhydride are placed in a reaction kettle, nitrogen is introduced to replace the air in the kettle, and the temperature is raised to 100°C for reaction for 2 hours. Then 4 mol of ethylene glycol is added, and 3% of the total mass of all the above monomers (additives) of concentrated sulfuric acid is added, and the reaction is carried out for 2 hours. Stop the introduction of nitrogen, vacuumize to remove the moisture produced by the reaction, and finally add 4 mol of (methyl) acrylic anhydride, react for 1 hour, and vacuumize to remove unreacted monomers. Add 50% of the total mass of all the above chemicals as a diluent monomer for active vinyl ether functional groups to obtain a hyperbranched vinyl-containing poly (ester-acrylic acid) resin containing vinyl groups in the skeleton and end groups, which is an EB-cured vinyl-containing hyperbranched poly (ester-acrylic acid) resin.

[0041] Embodiment 2:

[0042] The preparation method of EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin comprises the following steps:

[0043]

[0044] 1 mol of pentaerythritol and 4 mol of maleic anhydride are placed in a reaction kettle, nitrogen is introduced to replace the air in the kettle, and the temperature is raised to 120°C for reaction for 2.5 hours. Then 4 mol of propylene glycol and 4% of p-toluenesulfonic acid by mass of all the above monomers are added, and the reaction is carried out for 2 hours. Stop introducing nitrogen, vacuumize to remove the moisture produced by the reaction, and finally add 8 mol of (methyl) acrylic anhydride, react for 1 hour, and vacuumize to remove unreacted monomers. Add 50% of the mass fraction of all the above chemicals as a diluent monomer for active vinyl ether functional groups to obtain a hyperbranched vinyl-containing poly(ester-acrylic acid) resin containing vinyl groups in the skeleton and end groups, which is an EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin.

[0045] Example 3

[0046] The preparation method of EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin comprises the following steps:

[0047] 1 mol of pentaerythritol and 4 mol of maleic anhydride are placed in a reaction kettle, nitrogen is introduced to replace the air in the kettle, and the temperature is raised to 110°C for reaction for 3 hours. Then 2 mol of ethylene glycol and 2 mol of propylene glycol are added, and then concentrated phosphoric acid accounting for 2% of the mass fraction of all the above monomers (reactants) is added, and the reaction is carried out for 2 hours. Stop the introduction of nitrogen, vacuumize to remove the moisture produced by the reaction, and finally add 6 mol of (methyl) acrylic anhydride, react for 1 hour, and vacuumize to remove the unreacted monomers. Add 60% of the mass fraction of all the above chemicals (additives) of cyclohexyl vinyl ether and vinyl caprolactam as active vinyl ether functional group diluent monomers (the mass ratio of cyclohexyl vinyl ether and vinyl caprolactam is 6:4), and obtain a hyperbranched vinyl-containing poly (ester-acrylic acid) resin containing vinyl in the skeleton and end groups, which is an EB-cured vinyl-containing hyperbranched poly (ester-acrylic acid) resin.

[0048] Determination:

[0049] The EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin synthesized in Example 1 was characterized by infrared spectroscopy. Figure 1 .from Figure 1 It can be seen that at 3515.1cm -1 The characteristic peak of hydroxyl group can be seen at 1724.8cm -1 (wave number) a strong ester carbonyl resonance characteristic absorption can be seen at 1268.5cm -1 The CO vibration of the ester connected to the carbonyl group can be observed at 1070.4 cm -1 The characteristic vibration absorption peak of CO in RCO can be seen. The above information can accurately determine the esterification structure contained. In addition, 1646.9cm-1 Unsaturated C=C vibration and fingerprint area 978.4cm -1 The double bond characteristic peak indicates that the compound contains a double bond structure.

[0050] The appearance and performance of the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resins prepared in Examples 1-3 were measured. The specific results are shown in Table 1:

[0051] Table 1 Quality indexes of resins in Examples 1 to 3

[0052]

[0053]

[0054] Example 4

[0055] In parts by weight, 10 parts of light-fast phthalocyanine blue pigment, 20 parts of titanium dioxide, 2 parts of leveling agent, 3 parts of defoaming agent and 5 parts of wetting agent were added to 40 parts of the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared in Example 1, and after grinding with a sand mill to reach the required fineness (15μ), 60 parts of the EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared in Example 1 were added, stirred evenly at high speed, and ground with a sand mill until the fineness reached the specified requirement (15μ), thereby obtaining a metal coil EB light blue coating.

[0056] The added leveling agent, defoaming agent and wetting agent are conventional technologies and are not protected in this application.

[0057] Example 5

[0058] In parts by weight, 20 parts of pigment aniline yellow, 20 parts of light calcium carbonate, 5 parts of leveling agent, 5 parts of defoamer and 10 parts of wetting agent were added to 60 parts of EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared in Example 2, and after grinding with a sand mill to reach the required fineness, 40 parts of EB-cured vinyl-containing hyperbranched poly(ester-acrylic acid) resin prepared in Example 2 were added, stirred at high speed and ground with a sand mill until the fineness reached the specified requirement, thereby obtaining a metal coil EB light yellow coating.

[0059] The leveling agent, defoamer and wetting agent added are conventional.

[0060] The metal coil EB coatings prepared in Example 4 and Example 5 were tested, and the specific results are shown in Table 2:

[0061] Table 2 Quality indicators of the coatings obtained in Examples 4 to 5:

[0062]

[0063] As can be seen from the above table, the resin prepared by this method is used for metal coil coatings, which solves the problems that may exist in existing coatings, such as "defects such as orange peel, fish eyes, sand holes on the coating surface and indicators not meeting the standards", and is more convenient to use, without the need to use or with reduced use of various additives.

[0064] The above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing an EB-cured vinyl-containing hyperbranched polyester acrylic resin, characterized in that: The hyperbranched polyester acrylic resin comprises the following hyperbranched molecular structure: or ， The preparation method thereof comprises the following steps: 1) Place pentaerythritol and maleic anhydride in a reactor, heat to 90-120°C and react for 1-3 hours; 2) Add ethylene glycol or glycidol and a catalyst to the reactant in step 1) in sequence and react for 2 to 3 hours, and then evacuate the reactant to remove the water produced by the reaction; 3) adding methacrylic anhydride to the material after the reaction in step 2), reacting for 1 to 2 hours, and removing unreacted monomers by vacuuming; 4) adding any one or a mixture of several monomers containing active vinyl functional groups as active diluent monomers to obtain a hyperbranched vinyl-containing polyester acrylic resin containing vinyl groups in both the backbone and the end groups, which is an EB-cured vinyl-containing hyperbranched polyester acrylic resin; The resin skeleton contains vinyl groups, which are provided by the reaction of maleic anhydride; the resin end groups contain vinyl groups, which are provided by the reaction of methacrylic anhydride; the resin is used for EB curing coatings; The monomer containing active vinyl functional groups is selected from any one of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triethylene glycol divinyl ether, cyclohexyl vinyl ether and vinyl caprolactam, and the amount of the monomer containing active vinyl functional groups is 20-60% of the mass of all additives before adding the monomer containing active vinyl functional groups; The catalyst is any one of concentrated sulfuric acid, concentrated phosphoric acid, and p-toluenesulfonic acid or a mixture of the two or more thereof, and the amount of the catalyst used is 0.5-5.0% of the mass of all additives before the catalyst is added; the molar ratio of pentaerythritol, maleic anhydride, ethylene glycol, and methacrylic anhydride is 1:4:4:3-6; or the molar ratio of pentaerythritol, maleic anhydride, glycidol, and methacrylic anhydride is 1:4:4:3-8.

2. A method for preparing EB coating for metal coil, characterized in that The EB-cured hyperbranched polyester acrylic resin containing vinyl groups obtained by the method as claimed in claim 1 is prepared by the following steps: adding pigment, inorganic filler and auxiliary agent to the EB-cured hyperbranched polyester acrylic resin containing vinyl groups, grinding the resin to a required fineness with a sand mill, then mixing the EB-cured hyperbranched polyester acrylic resin containing vinyl groups, stirring the resin at high speed to obtain a metal coil EB coating; the mass ratio of the EB-cured hyperbranched polyester acrylic resin containing vinyl groups, the pigment, the inorganic filler and the auxiliary agent added for the first time to the EB-cured hyperbranched polyester acrylic resin containing vinyl groups added for the second time is 40:5-20:5-20:1-10:60.

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