Preparation and use method of ultraviolet curing white codine for tinplate

Abstract

The invention belongs to the field of ultraviolet curing materials, and relates to a preparation method and a use method of ultraviolet curing white codine for tinplate. The white codine disclosed by the invention consists of an oligomer, titanium white color paste, a functional monomer, a photoinitiator and an additive, wherein the oligomer is formed by mixing polymers with different molecular weights and different functional groups. According to the composition, the adhesive force, impact resistance and high-temperature steaming resistance of the ultraviolet curing coating are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of ultraviolet light-curing materials and relates to a preparation method of ultraviolet light-curing white caprolactam for tinplate and a method for using the same. The white caprolactam is composed of oligomers with different molecular weights and functional groups, functional monomers, photoinitiators, and additives. The white caprolactam can be used to prepare a white primer layer on the surface of tinplate with high adhesion, impact resistance, and high-temperature cooking resistance. Background Art

[0002] Tinplate is widely used in food packaging cans and boxes due to its corrosion resistance, non-toxicity, high strength, and good ductility. Before printing and coloring tinplate, a white primer, called white tin, must be applied to the surface. White tin ensures the diversity and fidelity of printed designs and colors, provides the flexibility and stability necessary for printed designs to adhere to the can, and protects the tinplate from physical and chemical corrosion during storage.

[0003] Food packaging has very high requirements for the curing of white caprolactam. The commonly used curing method for white caprolactam is heat curing. The disadvantages of this method are long curing time, high energy consumption, poor environmental protection, and great harm to the human body. UV curing can improve the above disadvantages, but UV-cured coatings usually have poor curing degree and are prone to shrinkage, which reduces the adhesion between the paint film and the substrate, and the impact resistance and high-temperature cooking resistance of the paint film do not meet industrial requirements.

[0004] To address the above issues, researchers have adopted a variety of methods to improve them, such as dual photocuring and thermal curing (CN104178017A), which increases costs and complicates the process; the use of highly corrosive polyester acrylate resins (CN103805040B, CN110982395A) or the introduction of a large number of carboxyl side chains and alicyclic structures into polyurethane resins to improve adhesion and impact resistance (CN114790347B); the above methods have solved the problems of poor adhesion and impact resistance after curing to a certain extent, but obtaining white cotin with good adhesion, impact resistance and excellent high-temperature cooking resistance at the same time remains a challenging task. Summary of the Invention

[0005] A method for preparing and using a UV-curable white caprolactam for tinplate is disclosed. The white caprolactam is prepared by mixing and stirring an oligomer, titanium white paste, a functional monomer, a photoinitiator, and an additive to fully dissolve the mixture, followed by filtration. The white caprolactam is then used by treating the tinplate with plasma, then applying the white caprolactam to the tinplate surface, and then subjecting the tinplate to dual curing by light and heat.

[0006] The specific composition of the white captin is: 3-10wt% of two polyurethane acrylate oligomers with different molecular weights, 1-3wt% of epoxy acrylate oligomers, 25-45wt% of titanium white paste, 40-60wt% of functional monomers, 3-8wt% of photoinitiator and the remainder of additives.

[0007] The polyurethane acrylate oligomer contains two kinds of oligomers, with an average functionality of 2 or more and a number average molecular weight of 300-500 (PU1) and 600-1500 (PU2), and the addition ratio of the two is: PU1:PU2=1:1-1:10.

[0008] The number average molecular weight of the epoxy acrylate oligomer (PEA) is 500-2000, and the addition ratio range is: PEA:PU2=1:1-1:10.

[0009] The titanium white slurry contains 50-70% rutile titanium dioxide, 20-40% diluent monomer and 5-10% dispersion stabilizer.

[0010] The particle size of the rutile titanium dioxide in the titanium white slurry is 100-500 nm, preferably 150-300 nm.

[0011] The diluent monomer in the titanium white slurry is a bifunctional monomer, selected from one or more of diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2 (propoxylated) neopentyl glycol diacrylate, and tricyclodecane dimethanol diacrylate.

[0012] The dispersing stabilizer in the titanium white slurry is selected from one of polyvinyl alcohol, polyvinyl alcohol-polyacrylate copolymer, polycarboxylic acid, and organosilicon dispersant.

[0013] The functional monomers in the white ketone are selected from monofunctional monomers and difunctional monomers. Specifically, the monofunctional monomer is selected from one or more of acryloylmorpholine, butyl acrylate, octyl acrylate, isobornyl acrylate, benzyl acrylate, tetrahydrofuran acrylate, ethoxyethoxyethyl acrylate, lauryl acrylate, and lauryl methacrylate; and the difunctional monomer is selected from one or more of diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2-(propoxy)neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0014] The photoinitiator is selected from phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide or 2,4,6-trimethylbenzoyl diphenyl phosphine oxide.

[0015] The additives include an adhesion promoter and a wetting and dispersing agent. The adhesion promoter is a phosphate-modified or sulfite-modified polyurethane acrylate with a number average molecular weight of 200-1000; the wetting and dispersing agent is a high molecular copolymer with acidic groups.

[0016] The method for using the white caprolactam is to fully stir and dissolve the oligomer, functional monomer, photoinitiator and additive, filter, and apply the white caprolactam on the surface of the plasma-treated tinplate by a doctor blade method. After drying, the film thickness is 5-20 μm. DETAILED DESCRIPTION

[0017] The present invention is described below by way of specific embodiments, but is not limited to the specific embodiments given below.

[0018] The invention provides a UV-curable white caprolactam for tinplate. The white caprolactam specifically comprises: 3-10 wt% of two polyurethane acrylate oligomers with different molecular weights, 1-3 wt% of epoxy acrylate oligomers, 25-45 wt% of titanium white paste, 40-60 wt% of functional monomers, 3-8 wt% of a photoinitiator, and the remainder of additives.

[0019] In a preferred embodiment, the white caprolactam described in the present invention includes, by weight percentage, PU1: 2wt%, PU2: 5wt%, PEA: 3wt%, titanium white paste: 40wt%, functional monomer: bifunctional monomer: 30wt%, monofunctional monomer: 10wt%, photoinitiator: 5wt%, adhesion promoter: 2wt%, and wetting dispersant: 3wt% (Qingdao Shengshi New Materials Co., Ltd.).

[0020] The polyurethane acrylate oligomer of the present invention is prepared by copolymerizing aliphatic polyurethane and acrylic monomers under certain conditions. It can be prepared in-house or purchased. Examples of commercially available oligomers include CN8010 (fluid viscosity at 25°C is 2000-3000 cps, average functionality is 2) and CN8007 (fluid viscosity at 25°C is 800-1000 cps, average functionality is 4) from Sartomer (Guangzhou) Chemical Co., Ltd.; 6115J from Changxing Materials Industry Co., Ltd. -80 (fluid viscosity at 25°C is 2600-4200cps, average functionality is 2), DR-U299 (fluid viscosity at 25°C is 25000-35000cps, average functionality is 2); 6390 (fluid viscosity at 60°C is 5000-12000cps, average functionality is 4), 6410 (fluid viscosity at 25°C is 2500-6000cps, average functionality is 4) of Guangdong Lankelu New Materials Co., Ltd.

[0021] Average functionality refers to the ratio of the number of functional groups that can actually participate in the reaction to the total amount of monomers in the reaction system during the linear polycondensation stage before reaching the gel point in a mixed polycondensation or co-polycondensation reaction involving two or more monomers.

[0022] In one embodiment, the mixed polyurethane acrylate of the present invention has a fluid viscosity of 2500-3000 cps at 25° C. and an average functionality of 2-4.

[0023] Epoxy acrylate oligomers are prepared by esterification of epoxy resins with acrylic acid or methacrylic acid and are currently one of the most widely used oligomers. Their light-curing speed is the fastest among all oligomers, and the cured film has high hardness, good gloss, and excellent corrosion resistance, heat resistance, and electrochemical properties. Epoxy acrylate oligomers have a wide range of raw material sources, are inexpensive, and have a simple synthesis process, so they are used in large quantities in light-curing coatings. The cured film of this type of oligomer has good adhesion, chemical resistance, and strength, but it also has disadvantages, such as insufficient flexibility and high brittleness of the cured film. Therefore, in order to meet the needs of different fields, the combination of polyurethane acrylate oligomers with excellent flexibility and epoxy acrylate oligomers has become one of the solutions.

[0024] In one embodiment, the epoxy acrylate described herein can be prepared in-house or purchased. Available options include, but are not limited to, CR91192 from Guangdong Haohui New Materials Co., Ltd. (fluid viscosity of 10,000-20,000 cps at 25°C, average functionality of 2), DSM resin 3020 from Shanghai Kaiyin Chemical Co., Ltd. (fluid viscosity of 32-48 s at 60°C, average functionality of 2), and DSM resin 3051 from Shanghai Kaiyin Chemical Co., Ltd. (fluid viscosity of 1-5 s at 60°C, average functionality of 2).

[0025] Preferably, the epoxy acrylate of the present invention has a fluid viscosity of 32-48s at 25°C.

[0026] The role of titanium white paste in white varnish is to improve the covering power and color stability of white varnish, prevent the white varnish from flowing, make the coating wear-resistant, and protect the clarity and durability of printed products. The rutile titanium white paste in titanium white paste has a bright color and strong covering power, while also preventing surface contamination and oxidation. The titanium white paste used in the present invention is rutile titanium white paste, wherein the rutile titanium dioxide content is 50-70%, the diluent content is 20-40%, and the dispersion stabilizer content is 5-10%.

[0027] In one embodiment, the titanium white paste of the present invention can be prepared by yourself or purchased. The purchase includes but is not limited to the oily titanium white paste from Guangdong Kedi New Material Technology Co., Ltd.

[0028] In one embodiment, the functional monomers described in the present invention are selected from monofunctional monomers and bifunctional monomers. Specifically, the monofunctional monomer is selected from one or more of acryloylmorpholine, butyl acrylate, octyl acrylate, isobornyl acrylate, benzyl acrylate, tetrahydrofuran acrylate, ethoxyethoxyethyl acrylate, lauryl acrylate, and lauryl methacrylate; and the bifunctional monomer is selected from one or more of diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2-(propoxy)neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

[0029] The functional monomer of the present invention is a combination of a monofunctional monomer and a difunctional monomer in a certain ratio.

[0030] Preferably, the monofunctional monomers of the present invention are acryloylmorpholine and butyl acrylate, and the bifunctional monomers are dipropylene glycol diacrylate.

[0031] In a preferred embodiment, the weight ratio of the functional monomers of the present invention is: monofunctional monomer: difunctional monomer = 1: (3-4).

[0032] Photoinitiators are compounds that absorb energy of a certain wavelength in the ultraviolet (250-420 nm) or visible (400-800 nm) region, generating free radicals, cations, and the like, thereby initiating polymerization, crosslinking, and curing of monomers and oligomers. Examples of photoinitiators used in the present invention include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0033] In one embodiment, the photoinitiator of the present invention is used in an amount of 4-8 wt %.

[0034] The additives include an adhesion promoter and a wetting and dispersing agent. The adhesion promoter is a phosphate-modified or sulfite-modified polyurethane acrylate with a number average molecular weight of 200-1000; the wetting and dispersing agent is a high molecular copolymer with acidic groups.

[0035] The present invention provides a method for preparing the above-mentioned UV-curable white caprolactam for tinplate, comprising the following steps: Add the initiator to a certain amount of mixed monomers and stir magnetically for 30 minutes to fully dissolve.

[0036] Add oligomer, titanium white slurry and additives to the mixture and stir magnetically for 3-5 hours.

[0037] Use medium-speed filter paper to vacuum filter and remove undissolved matter.

[0038] The present invention provides a method for using the UV-curable white tin for tinplate, comprising the following steps: After spraying ethanol on the surface of the dust-free cloth, wipe the tinplate surface.

[0039] After the surface is dry, place it in a plasma treatment device with the treatment conditions: 100W, 100S.

[0040] After the treatment is completed, apply the white paint on the tinplate surface with a wire rod.

[0041] Use a 495nm LED lamp to cure for 5-10s, and then bake in a 150℃ oven for 10min.

[0042] Adhesion was tested using a paint film cross-hatch tester; impact resistance was tested using a 1000g, 50cm hammer; and boiling resistance was observed by heating in a 105°C water bath for 30 minutes. Example

[0043] The present invention is described in detail below by way of examples. The following examples are only intended to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by professionals in this field based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0044] PU1: polyurethane acrylate oligomer The polyurethane acrylate oligomer is an aliphatic polyurethane acrylate oligomer, which is purchased from Guangdong Lankelu New Materials Co., Ltd. as 6390.

[0045] PU2: polyurethane acrylate oligomer The polyurethane acrylate oligomer is an aliphatic polyurethane acrylate oligomer, purchased from Sartomer (Guangzhou) Chemical Co., Ltd. as CN8007.

[0046] PEA: Epoxy Acrylate Oligomer The epoxy acrylate oligomer is DSM resin 3020 purchased from Shanghai Kaiyin Chemical Co., Ltd.

[0047] TS: Titanium white paste The titanium white slurry is an oily titanium white slurry purchased from Guangdong Kedi New Material Technology Co., Ltd.

[0048] S1: Monofunctional monomer The monofunctional monomer is n-butyl acrylate.

[0049] S2: Monofunctional monomer The monofunctional monomer is acryloylmorpholine.

[0050] S3: Monofunctional monomer The monofunctional monomer is isobornyl acrylate.

[0051] S4: Bifunctional monomer The monofunctional monomer is hydroxypropyl acrylate.

[0052] S5: Bifunctional monomer The bifunctional monomer is hydroxyethyl methacrylate.

[0053] S6: Bifunctional monomer The bifunctional monomer is dipropylene glycol diacrylate.

[0054] S7: Bifunctional monomer The bifunctional monomer is diethylene glycol diacrylate.

[0055] I: Photoinitiator The photoinitiator is TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0056] A1: Adhesion promoter The adhesion promoter is phosphate-modified polyurethane acrylate.

[0057] A2: The wetting and dispersing agent is a high molecular weight copolymer with acidic groups.

[0058] The wetting and dispersing agent was purchased from Qingdao Shengshi New Materials Co., Ltd.

[0059] Table 1 (Contents are in weight percentage: wt%) Example 1 2 3 4 5 6 7 8 9 10 PU1 1 2 1 2 4 1 3 1 0.8 2.5 PU2 2 8 4 3 7 3 6 6 8 7.5 PEA 2 0.8 2 1 2 1 4 5 2 3 TS 45 25 30 35 29 40 36 25 38 29 S1 5 - 10 10 - 20 10 12 - 12 S2 5 - 10 10 10 - - - 5 2 S3 5 20 - - 20 25 30 36 20 30 S4 5 10 5 - 2 4 3 1 6 8 S5 10 10 20 10 5 - - 5 5 - S6 10 20 10 15 10 - - - - - S7 - - - - - - - 5 - I 8 3 5 6 7 5 6 7 6 5 A1 1 0.6 3 5 3 0.8 2 1.2 3 0.75 A2 1 0.6 - 3 1 0.2 - 0.8 1.2 0.25

[0060] The tinplate coated with white corundum was subjected to light curing and heat curing treatment to obtain the finished product as a sample for performance testing.

[0061] Adhesion: The sample provided in the example was scratched with a paint crosshatch to create 10 equal-sized squares on the coating, serving as the test area. 3M-600 tape was applied to the test area and then removed rapidly and continuously. The cutting edge of the tape was maintained at a 35-45 degree angle to the coating surface and penetrated the coating. The cutting was continuous and constant, and the coating was evaluated based on the area of ​​coating removal. Grade 1 indicates no coating removal, Grade 2 indicates a coating removal area of ​​1% or greater but less than 5%, Grade 3 indicates a coating removal area of ​​5% or greater but less than 20%, Grade 4 indicates a coating removal area of ​​20% or greater but less than 50%, and Grade 5 indicates a coating removal area of ​​50% or greater. The results are shown in Table 2.

[0062] Impact resistance: The sample provided in the embodiment is placed on one end of the impact table. After releasing the heavy hammer from the top (50 cm), the impacted sample is immersed in a copper sulfate solution for 20 minutes, taken out, washed with clean water, and then wiped dry. The paint film on the sample is observed to see if it is broken, wherein the broken area of ​​the folded or bent paint film appears as a black or red line or continuous dot. The mass of the heavy hammer is 1000 g. The percentage of the area of ​​the broken paint film of the sample to the total area is calculated as the paint explosion rate, and a rating is performed, wherein level 1 is a paint explosion rate of less than 0.1%, level 2 is a paint explosion rate of less than 0.2% and greater than or equal to 0.1%, level 3 is a paint explosion rate of less than 0.5% and greater than or equal to 0.2%, and level 4 is a paint explosion rate of greater than or equal to 0.5%. The results are shown in Table 2.

[0063] Boiling resistance: Hang the sample in a 105℃ water bath and heat for 30 minutes. After the test, the printed surface should not fade, blur, fall off, wrinkle, bubble, or particle, and there should be no whitening or obvious reduction in gloss.

[0064] Table 2 Evaluation results Example Adhesion Impact resistance Retort resistance 1 1 2 good 2 1 1 excellent 3 1 2 excellent 4 1 2 good 5 1 1 excellent 6 2 2 good 7 2 1 excellent 8 1 1 excellent 9 1 1 good 10 2 1 excellent

[0065] It can be seen from the test results in Table 2 that the UV-curable white tin for tinplate provided by the present invention has excellent adhesion, impact resistance and boiling resistance.

[0066] The foregoing embodiments are merely illustrative and serve to illustrate some features of the method of the present invention. The appended claims are intended to claim the widest possible scope that can be envisioned, and the embodiments presented herein are merely illustrative of the selection of combinations of all possible embodiments. Therefore, it is the applicant's intention that the appended claims are not limited by the selection of examples illustrating the features of the present invention. Some numerical ranges used in the claims also include subranges therein, and variations in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A preparation method of a UV-curable white tin for tinplate and a method for using the same, characterized by: The preparation method of the white caprolactam comprises mixing and stirring an oligomer, titanium white paste, a functional monomer, a photoinitiator, and an additive to fully dissolve the mixture and filtering the mixture. The use method of the white caprolactam comprises treating tinplate with plasma, then applying the white caprolactam on the tinplate surface, and then subjecting the tinplate to a dual curing treatment using light and heat.

2. The preparation and use method of a UV-curable white alkali-based tinplate according to claim 1, wherein the white alkali-based tinplate comprises: 3-10 wt% of two polyurethane acrylate oligomers with different molecular weights, 1-3 wt% of epoxy acrylate oligomers, 25-45 wt% of titanium dioxide paste, 40-60 wt% of functional monomers, 3-8 wt% of a photoinitiator, and the remainder of additives.

3. The preparation of the ultraviolet-cured tinplate according to claim 1 and 2, characterized in that: The polyurethane acrylate oligomer contains two kinds of oligomers, with an average functionality of 2 or more and a number average molecular weight of 300-500 (PU1) and 600-1500 (PU2), and the addition ratio of the two is: PU1:PU2=1:1-1:

10.

4. The preparation of the UV-curable white tinplate according to claim 1 and 2, characterized in that: The number average molecular weight of the epoxy acrylate oligomer (PEA) is 500-2000, and the addition ratio range is: PEA:PU2=1:1-1:

10.

5. The preparation of ultraviolet-cured tinplate according to claim 1, characterized in that: The titanium white slurry contains 50-70% rutile titanium dioxide, 20-40% diluent monomer and 5-10% dispersion stabilizer.

6. The preparation of the UV-curable white tinplate according to claims 1 and 5, characterized in that: The particle size of the rutile titanium dioxide is 100-500 nm, preferably 150-300 nm.

7. The preparation of the UV-curable white tinplate according to claims 1 and 5, characterized in that: The diluent monomer is a bifunctional monomer, selected from one or more of diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2 (propoxylated) neopentyl glycol diacrylate, and tricyclodecane dimethanol diacrylate.

8. The preparation of the UV-curable white tinplate according to claims 1 and 5, characterized in that: The dispersion stabilizer is selected from one of polyvinyl alcohol, polyvinyl alcohol-polyacrylate copolymer, polycarboxylic acid, and organosilicon dispersant.

9. The preparation of the ultraviolet-cured white tinplate according to claim 1, characterized in that: The functional monomer is selected from monofunctional monomers and bifunctional monomers. Specifically, the monofunctional monomer is selected from one or more of acryloylmorpholine, butyl acrylate, octyl acrylate, isobornyl acrylate, benzyl acrylate, tetrahydrofuran acrylate, ethoxyethoxyethyl acrylate, lauryl acrylate, and lauryl methacrylate; and the bifunctional monomer is selected from one or more of diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 2-(propoxy)neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate.

10. The preparation of the ultraviolet-cured white tin for tinplate according to claim 1, characterized in that: The photoinitiator is selected from phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide or 2,4,6-trimethylbenzoyl diphenyl phosphine oxide.

11. The preparation of the ultraviolet-cured white tin for tinplate according to claim 1, characterized in that: The additives include an adhesion promoter and a wetting and dispersing agent. The adhesion promoter is a phosphate-modified or sulfite-modified polyurethane acrylate with a number average molecular weight of 200-1000; the wetting and dispersing agent is a high molecular copolymer with acidic groups.

12. The method for using the UV-curable whitening agent for tinplate according to claim 1, wherein: The oligomer, functional monomer, photoinitiator and additive are fully stirred and dissolved, and then filtered. The white caprolactam is coated on the plasma-treated tinplate surface by a doctor blade method. After drying, the film thickness is 5-20 μm.