Laser positioning electrochemical aluminum coating composition and preparation method thereof

Abstract

The present invention relates to the technical field of electrochemical aluminum coatings, and specifically proposes a laser-positioning electrochemical aluminum coating composition and a preparation method thereof. The composition comprises the following components in parts by weight: 35-50 parts of a dicyclopentadiene-maleimide block copolymer, 3-5 parts of sulfonated nano-silica, 1-2 parts of an epoxy silane coupling agent, 2-4 parts of a fluorinated acrylate polymer, 40-60 parts of a butanone / n-propyl acetate mixed solvent, and 0.5-1 parts of a photoinitiator. The laser-positioning electrochemical aluminum coating composition and the preparation method thereof provided by the present invention significantly improve the adhesion and heat resistance of the aluminum coating layer through the synergistic effect of the rigid cyclic structure of the dicyclopentadiene-maleimide block copolymer and the coordination bond of the maleimide group, combined with the ionic bond anchoring effect of the sulfonated nano-silica.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical aluminum coatings, and in particular to a laser positioning electrochemical aluminum coating composition and a preparation method thereof. Background Art

[0002] As the core functional layer of hot stamping materials, laser anodized aluminum coatings must possess high adhesion, excellent heat resistance, and adaptability to precision molding to meet the modern packaging industry's demand for high-precision holographic patterns and durable surface decoration. However, traditional acrylic resins (such as butyl acrylate-acrylonitrile copolymer) are prone to thermal decomposition or softening during high-temperature molding (200-230°C), resulting in a decrease in the adhesion of the aluminum coating.

[0003] Although the styrene-maleic anhydride (SMA) resin system disclosed in patent CN201210115718.6 can improve film-forming properties, its anhydride group has limited chemical bonding ability with the aluminum surface and is easily hydrolyzed at high temperatures, resulting in weak interfacial bonding between the coating and the aluminum plating layer, and prone to peeling or "biting" after molding.

[0004] In response to the above problems, how to enhance the interface bonding strength and provide a laser-positioned electrochemical aluminum coating composition with better interface stability after molding has become one of the technical problems that need to be solved urgently. Summary of the Invention

[0005] In view of this, the present invention proposes a laser-positioned electrochemical aluminum coating composition and a preparation method thereof, which overcomes the core defects of existing coatings in adhesion, heat resistance and environmental protection through the synergistic effect of dicyclopentadiene-maleimide block copolymer and dynamic nanocomposite system.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a laser positioning electrochemical aluminum coating composition, comprising the following components in parts by weight: 35-50 parts of dicyclopentadiene-maleimide block copolymer, 3-5 parts of sulfonated nano-silica, 1-2 parts of epoxy silane coupling agent, 2-4 parts of fluorine-containing acrylate polymer, 40-60 parts of butanone / propyl acetate mixed solvent, and 0.5-1 part of photoinitiator.

[0007] In some embodiments, the method for preparing a dicyclopentadiene-maleimide block copolymer comprises:

[0008] (1) Dicyclopentadiene (DCPD) and maleic anhydride (MAn) were mixed in a molar ratio of 1:1.2, and reacted at 85°C for 4 h in a butanone / propyl acetate solvent with azobisisobutyronitrile (AIBN) as an initiator to form an alternating copolymer;

[0009] (2) reacting the product of step (1) with cyclohexylamine at 120° C. for 2 h to convert the imide structure;

[0010] (3) Styrene monomer was added and RAFT block polymerization was used to form a DCPD-MI-b-PS structure, in which the styrene block accounted for 30%.

[0011] In some embodiments, the chain transfer agent for the RAFT block polymerization is benzylpyridin-2-yl dithiocarboxylate (BPDF), the reaction temperature is 70-90° C., and the molecular weight distribution (PDI) is ≤1.25.

[0012] In some embodiments, the method for preparing the sulfonated nano-silica comprises:

[0013] (1) Disperse fumed silica in concentrated sulfuric acid and ultrasonicate at 60°C for 2 h;

[0014] (2) Add 3-aminopropyltriethoxysilane (APTES) and react at 75-85°C for 2.5-3.5 hours to obtain nano-silica modified with surface sulfonic acid groups, with a Zeta potential of ≤-45 mV.

[0015] In some embodiments, the volume ratio of the butanone and n-propyl acetate mixed solvent is 6:4.

[0016] In some embodiments, the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO-L).

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned laser-positioned electrochemical aluminum coating composition, comprising the following steps:

[0018] (1) Ultrasonic dispersion of sulfonated nano-silica and epoxy silane coupling agent in butanone for 30 min;

[0019] (2) Add dicyclopentadiene-maleimide block copolymer and fluorinated acrylate polymer and stir at 1200 r / min for 2 h;

[0020] (3) After coating on the PET base film, pre-bake at 80°C for 5 minutes and cure under ultraviolet radiation to form a cross-linked coating.

[0021] In some embodiments, the coating process uses a 200 mesh anilox roller, a dry film thickness of 1.2-1.5 μm, a molding temperature of 180-200°C, and a molding pressure of 3.5-4.0 kg / cm 2 .

[0022] In some embodiments, the UV curing energy is 1000-1500 mJ / cm 2 .

[0023] In some embodiments, after UV curing, heat treatment at 120° C. for 10-20 minutes is further included.

[0024] The present invention has the following beneficial effects compared to the prior art:

[0025] The laser positioning electrolytic aluminum coating composition and preparation method provided by the present invention significantly improve the adhesion and heat resistance of the aluminum coating layer through the synergistic effect of the rigid cyclic structure of the dicyclopentadiene-maleimide block copolymer and the coordination bond of the maleimide group, combined with the ionic bond anchoring effect of sulfonated nano-silica; a thiol-ene click reaction is used to construct a dynamic reversible cross-linking network to achieve a microcrack self-repair effect; and a butanone / propyl acetate low-VOCs solvent and ultraviolet light curing process are used to improve coating efficiency while reducing energy consumption, which has good application prospects. DETAILED DESCRIPTION

[0026] 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 embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0028] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0029] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0030] Example 1

[0031] A laser positioning electrochemical aluminum coating composition, the raw materials of which include the following components in parts by weight:

[0032] 45 parts of dicyclopentadiene-maleimide block copolymer (DCPD-MI)

[0033] 4 parts of sulfonated nanosilica (SN-Si) (Zeta potential -48mV)

[0034] 1.5 parts of epoxy silane coupling agent (KH-560)

[0035] 3 parts of fluorinated acrylate polymer (FA)

[0036] 50 parts of a mixed solvent of butanone and n-propyl acetate (6:4)

[0037] Photoinitiator (TPO-L) 0.8 parts.

[0038] Preparation method:

[0039] DCPD-MI synthesis:

[0040] Step (1): DCPD and maleic anhydride (1:1.2 molar ratio) were reacted in butanone / n-propyl acetate at 85°C for 4 h, with an AIBN dosage of 1.5%;

[0041] Step (2): Cyclohexylamine was reacted at 120°C for 2 h, and the imide conversion rate was ≥95% (FTIR detection);

[0042] Step (3): Styrene RAFT polymerization (BPDF chain transfer agent, 80°C), PS block accounted for 30%, PDI = 1.20.

[0043] SN-Si preparation:

[0044] The gas-phase SiO2 was ultrasonically treated in concentrated sulfuric acid at 60℃ for 2h and modified with APTES at 80℃ for 3h. The sulfonic acid group density was 1.2 mmol / g.

[0045] Coating preparation:

[0046] SN-Si and KH-560 were ultrasonically dispersed in butanone for 30 min;

[0047] Add DCPD-MI and FA, and stir at 1200 r / min for 2 h;

[0048] Coated on PET base film (200 mesh anilox roller, dry film 1.3μm), pre-baked at 80℃ for 5min, and UV cured (1300mJ / cm 2 ), post-treatment at 120℃ for 15min.

[0049] Example 2

[0050] This embodiment is based on the embodiment 1, except that the feeding amount of dicyclopentadiene-maleimide block copolymer (DCPD-MI) is 35 parts, the feeding amount of sulfonated nano-silica (SN-Si) is 5 parts, and the UV curing energy is 1000mJ / cm 2 . Other conditions remain unchanged.

[0051] Example 3

[0052] This embodiment is based on the embodiment 1, except that the amount of dicyclopentadiene-maleimide block copolymer (DCPD-MI) is 50 parts, the amount of sulfonated nano-silica (SN-Si) is 3 parts, and the UV curing energy is 1500mJ / cm 2 . Other conditions remain unchanged.

[0053] Comparative Example 1

[0054] This comparative example adopts the traditional SMA system

[0055] The raw materials include: 40 parts of styrene-maleic anhydride resin (SMA), 5 parts of nitrocellulose, and 60 parts of toluene solvent.

[0056] Preparation method:

[0057] In a four-necked flask equipped with a stirrer and a condenser, 12 g of maleic anhydride and 100 mL of xylene were added and heated to 80°C to dissolve.

[0058] Dissolve 13 g of styrene and 0.3 g of dibenzoyl peroxide in 50 mL of xylene and add dropwise to the reaction flask (35 minutes) while controlling the temperature to ≤90°C.

[0059] The temperature was raised to 103°C and the reaction was carried out for 2 hours to generate a white precipitate (alternating copolymer).

[0060] After cooling, the mixture was filtered, washed with petroleum ether and dried to obtain SMA resin powder.

[0061] SMA resin and nitrocellulose were added to toluene solvent in sequence and stirred at 50°C until completely dissolved.

[0062] Coated on PET base film, pre-baked at 80℃ for 5 minutes, thermal curing process (no UV curing)

[0063] Comparative Example 2

[0064] This comparative example uses a traditional high acrylic acid system

[0065] The raw materials include: 40 parts of isobutyl methacrylate copolymer, 5 parts of mastic resin, and 50 parts of toluene solvent.

[0066] Preparation method:

[0067] Acrylic resin synthesis:

[0068] Methyl methacrylate and cyclohexyl methacrylate were mixed in a ratio of 1:3, and 20 parts of methacrylic acid, 25 parts of styrene, and an initiator (4 parts of dibenzoyl peroxide) were added.

[0069] In a mixed solvent (polyvinyl alcohol: water = 1:40), the reaction is carried out at 90°C until polymerization is completed to produce a thermoplastic acrylic resin.

[0070] Coating preparation:

[0071] Acrylic resin, mastic resin and toluene solvent were mixed and stirred at a high speed of 5000 rpm for 1.5 hours.

[0072] After coating, a thermal curing process (120°C x 1.5 hours) is used without dynamic cross-linking or UV triggering steps.

[0073] Comparative Example 3

[0074] This comparative example is based on Example 1, using:

[0075] 45 parts of maleic anhydride-dicyclopentadiene alternating copolymer (no block structure)

[0076] 4 parts of unsulfonated nano-SiO2

[0077] Other conditions are the same as in Example 1.

[0078] Comparative Example 4

[0079] This comparative example is based on Example 1, using:

[0080] 45 parts of dicyclopentadiene-styrene random copolymer (without maleimide group)

[0081] Other conditions are the same as in Example 1.

[0082] The coating compositions prepared in the above examples and comparative examples and attached to the surface of the PET substrate were subjected to performance tests.

[0083] 1. Peel strength test:

[0084] Cut the coated composite material into a standard size of 130mm×30mm, clean the surface (wipe with ethanol), apply adhesive (such as PU glue) after drying, pressurize for 30 seconds after lamination, let it stand for 24 hours, use a tensile testing machine (accuracy 0.01kgf), set the clamp spacing to 25mm, test speed to 100mm / min, fix the sample, stretch it at a peel angle of 180° or 90°, record the force-displacement curve, eliminate the first and last 1 / 4 data segments, take the average peel force of the 10 points in the middle segment, and calculate the peel strength per unit width.

[0085] 2. Self-repair rate test:

[0086] Prepare scratch samples, place them in a 40°C environment for a certain period of time, use a microscope or profilometer to measure the change in scratch size before and after repair, and calculate the healing rate.

[0087] 3. Wet and hot adhesion retention test:

[0088] The coating composite material was cut into a standard size of 50 mm × 50 mm, and the surface was cleaned (wiped with ethanol). Before the wet heat treatment, the initial adhesion was tested by the pull-off method and the data was recorded. A constant temperature and humidity test chamber was used with a temperature control accuracy of ±1°C and a humidity control accuracy of ±2%. The temperature was 47°C, the humidity was 96% RH, and the simulation time was 240 h.

[0089] Hang the samples vertically or lay them flat in the test chamber to avoid contact with each other.

[0090] Start the device, gradually increase the temperature to the target temperature and maintain the set humidity.

[0091] Regularly check the operating status of the equipment and record temperature and humidity fluctuations

[0092] Then, using a pull-off tester, bond the aluminum pull-off head to the coating surface and apply a pull vertically until the coating peels off, and record the maximum destructive force.

[0093] Retention rate = (adhesion after treatment / initial adhesion) * 100%

[0094] The test results are shown in the following table:

[0095]

[0096] Peel strength and adhesion

[0097] Example 1-3: The maleimide group of DCPD-MI forms a coordination bond with the aluminum surface, combined with the sulfonic acid group of SN-Si for ion anchoring, and the peel strength reaches 25.3 MPa (the traditional SMA system is only 18.2 MPa).

[0098] Comparative Example 3-4: The alternating / random copolymer lacks the ability of block-directional bonding, and the adhesion decreases by 20-30%.

[0099] Dynamic self-repair

[0100] Example: The thiol-ene dynamic network achieves microcrack self-repair (≥90%) under UV curing. Comparative Examples 3-4 have no cross-linked network and the self-repair rate is <30%.

[0101] Weather resistance

[0102] Example: The adhesion retention rate in a hot and humid environment is ≥98%, thanks to the interface stabilization effect of the epoxy silane coupling agent.

[0103] Comparative Example 1-2: SMA / acrylic resin is easily hydrolyzed and adhesion fails after 500 hours of wet heat

[0104] Comparison shows that Examples 1-3, through the innovative design of a DCPD-MI block copolymer + SN-Si + dynamic crosslinking network, significantly outperform traditional systems in adhesion, heat resistance, environmental friendliness, and self-healing capabilities. The alternating / random copolymers of Comparative Examples 3-4 demonstrate the irreplaceable nature of the block structure and functional group (maleimide).

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A laser positioning electrochemical aluminum coating composition, characterized in that: The invention comprises the following components in parts by weight: 35-50 parts of a dicyclopentadiene-maleimide block copolymer, 3-5 parts of sulfonated nano-silica, 1-2 parts of an epoxy silane coupling agent, 2-4 parts of a fluorine-containing acrylate polymer, 40-60 parts of a butanone / n-propyl acetate mixed solvent, and 0.5-1 part of a photoinitiator. The preparation method of the dicyclopentadiene-maleimide block copolymer comprises: (1) Dicyclopentadiene (DCPD) and maleic anhydride (MAn) were mixed in a molar ratio of 1:1.2, and reacted at 85°C for 4 h in a butanone / propyl acetate solvent with azobisisobutyronitrile (AIBN) as an initiator to form an alternating copolymer; (2) reacting the product of step (1) with cyclohexylamine at 120°C for 2 h to convert the imide structure; (3) Styrene monomer was added and RAFT block polymerization was used to form a DCPD-MI-b-PS structure, in which the styrene block accounted for 30%.

2. The laser positioning electrochemical aluminum coating composition according to claim 1, characterized in that: The chain transfer agent for the RAFT block polymerization is benzylpyridin-2-yl dithiocarboxylate (BPDF), the reaction temperature is 70-90° C., and the molecular weight distribution (PDI) is ≤1.

25.

3. The laser positioning electrochemical aluminum coating composition according to claim 1, characterized in that: The preparation method of the sulfonated nano-silica comprises: (1) Disperse fumed silica in concentrated sulfuric acid and ultrasonicate at 60°C for 2 h; (2) Add 3-aminopropyltriethoxysilane (APTES) and react at 75-85°C for 2.5-3.5 hours to obtain nano-silica modified with surface sulfonic acid groups, with a Zeta potential of ≤-45 mV.

4. The laser positioning electrochemical aluminum coating composition according to claim 1, characterized in that: The volume ratio of the butanone and n-propyl acetate mixed solvent is 6:

4.

5. The laser positioning electrochemical aluminum coating composition according to claim 1, characterized in that: The photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO-L).

6. The method for preparing the laser positioning electrochemical aluminum coating composition according to any one of claims 1 to 5, characterized in that: The steps include: (1) Ultrasonic dispersion of sulfonated nano-silica and epoxy silane coupling agent in butanone for 30 min; (2) Add dicyclopentadiene-maleimide block copolymer and fluorinated acrylate polymer and stir at 1200 r / min for 2 h; (3) After coating on the PET base film, pre-bake at 80°C for 5 minutes and cure under ultraviolet radiation to form a cross-linked coating.

7. The preparation method according to claim 6, wherein The coating process uses a 200 mesh anilox roller, the dry film thickness is 1.2-1.5μm, the molding temperature is 180-200℃, and the molding pressure is 3.5-4.0kg / cm 2 .

8. The preparation method according to claim 6, wherein UV curing energy is 1000-1500mJ / cm 2 .

9. The preparation method according to claim 6, wherein After UV curing, it also includes heat treatment at 120°C for 10-20 minutes.

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