Boiling-resistant bisphenol-A-free stoving varnish protective coating for vacuum cup and preparation method of boiling-resistant bisphenol-A-free stoving varnish protective coating

Abstract

The invention relates to the technical field of coatings, in particular to a boiling-resistant bisphenol-A-free stoving varnish protective coating for a vacuum cup and a preparation method of the boiling-resistant bisphenol-A-free stoving varnish protective coating. Polyester resin and methylated melamino-formaldehyde resin are adopted to form a compact main network, and nano silicon dioxide reinforcing slurry permeates into the network; according to the present invention, based on the two dimensions of the body permeation resistance and the interface stripping resistance, the excellent boiling resistance is achieved, and the coating does not have the blistering or shedding phenomenon after the boiling test.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a water-resistant, bisphenol A-free baking coating for thermos cups and its preparation method. Background Technology

[0002] With the upgrading of consumption, insulated cups have become a necessity in daily life, and consumers have put forward higher requirements for their appearance, durability, and safety. At present, most insulated cups on the market use a baked enamel coating for decoration and protection.

[0003] However, existing baking paint coatings have significant defects in water resistance, especially in high-temperature boiling resistance. After a short period of boiling, the coating is prone to blistering and peeling, which not only affects the appearance of the thermos but also reduces its heat preservation effect and may even cause the metal inner liner to rust, shortening the thermos's lifespan. From a technical perspective, the reasons are: First, insufficient adhesion: The adhesion between the film-forming substance (resin) in the coating and the metal substrate is acceptable at room temperature, but under the corrosive effect of high-temperature water vapor, the interfacial bonding force rapidly weakens, causing the coating to peel off from the substrate. Second, poor chemical bond stability: The cross-linked network of the coating itself is not stable enough under high-temperature boiling conditions. Water molecules can penetrate and break the chemical bonds between polymer molecular chains, leading to coating swelling and performance degradation. In addition, to improve resistance, some manufacturers add special organic additives (such as certain bisphenol A-containing epoxy resins), but this may introduce health risks.

[0004] Therefore, developing a water-resistant, safe, and environmentally friendly paint coating for thermos cups has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a water-resistant, bisphenol A-free baking coating for thermos cups and its preparation method, thereby solving the technical problems mentioned in the background art.

[0006] The objective of this invention is achieved through the following technical solution: a water-resistant, boil-resistant, BPA-free protective coating for thermos cups, which is composed of the following raw materials in parts by weight:

[0007] Polyester resin: 45-50 parts

[0008] 15-25 parts of nano-silica reinforced slurry

[0009] Xylene: 13-16 parts

[0010] n-Butanol: 5-6 parts

[0011] Dispersant: 0.5-1 part

[0012] Matte powder: 8-10 parts

[0013] Leveling agent: 0.1-0.3 parts

[0014] Titanium dioxide: 10-15 parts

[0015] Composite adhesion promoter: 1.5-3.0 parts

[0016] Crosslinking agent: 15-20 parts.

[0017] The polyester resin is a saturated polyester resin with a solid hydroxyl value of 35-55 mgKOH / g and a relative molecular weight of 5000-7000, using DSM's Uralac SN800. The crosslinking agent is a methylated melamine-formaldehyde resin, using Zynx (Cyclad) CYMEL 303LF.

[0018] The preparation method of the nano-silica reinforced paste is as follows:

[0019] (1) Add 10-15 parts of epoxy modified acrylic resin, 4-6 parts of propylene glycol methyl ether acetate, 4-6 parts of xylene, and 0.5-1.0 parts of high molecular weight dispersant BYK-190 to the mixing tank and stir at 600-800 rpm for 5-10 minutes until the mixture is homogeneous.

[0020] (2) Add 6-10 parts of nano silica and 3-5 parts of nano zirconium oxide powder, increase the rotation speed to 1500-1800 rpm, disperse for 20-40 minutes, and perform preliminary dispersion of the slurry;

[0021] (3) Transfer the initially dispersed slurry to a sand mill, add zirconia beads with a particle size of 0.6-0.8 mm, and grind and disperse until the fineness is ≤12 μm;

[0022] (4) Filter the material to obtain the nano-silica reinforced slurry.

[0023] Epoxy-modified acrylic resin contains polar functional groups such as carboxyl (-COOH) and hydroxyl (-OH), which strongly anchor the surface of nanoparticles (SiO2, ZrO2) and prevent nanoparticle re-aggregation through steric hindrance. The epoxy and carboxyl groups exhibit excellent wet adhesion and corrosion resistance to metal substrates (stainless steel), significantly improving the adhesion durability of the coating under harsh environments (boiling water). Nano-zirconia possesses extremely high chemical inertness and thermal stability, effectively blocking the penetration of water vapor and ions; nano-silica fills the gaps between coating molecules, forming an "organic-inorganic" hybrid network with the resin, greatly enhancing the density, hardness, and stability of the coating. The synergistic effect of these two components allows the coating to pass a ≥4-hour boiling water test at 100°C, far exceeding existing products. Furthermore, the addition of nanoparticles significantly improves the coating's abrasion resistance and scratch resistance.

[0024] The nano-silica has a particle size range of 10-30 nm, and the nano-zirconia has a particle size range of 40-60 nm. The small-sized SiO2 fills the gaps between polymer chains and between slightly larger ZrO2 particles, thereby forming an extremely dense shielding layer with an extremely tortuous penetration path, maximizing the improvement of toughness.

[0025] The dispersant is a polymeric dispersant, specifically BYK-161.

[0026] The matting agent used is a silica matting agent, specifically Grace SYLOID ED 50.

[0027] The leveling agent is a polyether-modified polydimethylsiloxane leveling agent, specifically BYK-331 from BYK.

[0028] The composite adhesion promoter is composed of a phosphate ester promoter, ADP, and an aminosilane coupling agent, KH-540, in a weight ratio of (2:1) to (1:1). This combination forms a robust transition layer at the interface between the coating and the metal, consisting of chemical bonds and strong intermolecular forces. This transition layer effectively prevents moisture from penetrating to the interface and causing a "prying" effect on the coating, thus ensuring that even after prolonged boiling, the coating remains firmly attached to the substrate without blistering or peeling.

[0029] A method for preparing a water-resistant, bisphenol A-free protective coating for thermos cups includes the following process steps:

[0030] Step (1): Add the polyester resin, xylene, n-butanol, dispersant, matting agent, leveling agent, and titanium dioxide in the formula to the reaction vessel in sequence. Stir at a stirring speed of 800-1200 rpm for 40-60 minutes to mix thoroughly and evenly to obtain the main slurry.

[0031] Step (2): Grind the mixed main slurry until the fineness is less than 20μm;

[0032] Step (3): Add the prepared main slurry, nano-silica reinforced slurry, composite adhesion promoter and crosslinking agent in sequence at a stirring speed of 500-600 rpm;

[0033] Step (4): After adding the ingredients, continue stirring for 30-40 minutes to ensure even mixing, thus obtaining the water-resistant, bisphenol A-free baking paint protective coating for thermos cups.

[0034] The beneficial effects of this invention are as follows: The polyester resin and methyl etherified melamine-formaldehyde resin used in this invention form a dense main network. The nano-silica reinforcing paste penetrates into this network, playing a role in enhancing filling and physical barrier. The composite adhesion promoter forms a strong anchor at the interface between the coating and the metal substrate, resisting the peeling of moisture. This invention exerts its strength from two dimensions: the body's anti-permeability and the interface's anti-peeling, achieving excellent water resistance. After the water boiling test, the coating showed no blistering or peeling. Detailed Implementation

[0035] The present invention will be further described in conjunction with the following embodiments.

[0036] Example 1

[0037] A water-resistant, boil-proof, BPA-free protective coating for thermos cups, comprising the following raw materials in parts by weight:

[0038] Polyester resin: 45 parts

[0039] 15 parts of nano-silica reinforced paste

[0040] Xylene: 13 parts

[0041] n-Butanol: 5 parts

[0042] Dispersant: 0.5 parts

[0043] Matte powder: 8 parts

[0044] Leveling agent: 0.1 parts

[0045] Titanium dioxide: 10 parts

[0046] Composite adhesion promoter: 1.5 parts

[0047] Crosslinking agent: 15 parts.

[0048] The polyester resin used is DSM's Uralac SN800, and the crosslinking agent used is Cymex CYMEL 303LF.

[0049] The preparation method of the nano-silica reinforced paste is as follows:

[0050] (1) Add 10 parts (all by weight, the same below) of epoxy modified acrylic resin, 4 parts of propylene glycol methyl ether acetate, 4 parts of xylene, and 0.5 parts of high molecular weight dispersant BYK-190 to the mixing tank and stir at 600 rpm for 5 minutes until they are evenly mixed.

[0051] (2) Add 6 parts of nano silica and 3 parts of nano zirconium oxide powder, increase the rotation speed to 1500 rpm, disperse for 40 minutes, and perform preliminary dispersion of the slurry;

[0052] (3) Transfer the initially dispersed slurry to a sand mill, add zirconia beads with a particle size of 0.6-0.8 mm, and grind and disperse until the fineness is ≤12 μm;

[0053] (4) Filter the material to obtain the nano-silica reinforced slurry.

[0054] The particle size range of the nano-silica is 10-30 nm, and the particle size range of the nano-zirconia is 40-60 nm.

[0055] The dispersant used is BYK-161.

[0056] The matting agent used is Grace SYLOID ED 50.

[0057] The leveling agent used is BYK-331 from BYK.

[0058] The composite adhesion promoter is composed of phosphate ester promoter ADP and aminosilane coupling agent KH-540 in a weight ratio of 2:1.

[0059] A method for preparing a water-resistant, bisphenol A-free protective coating for thermos cups includes the following process steps:

[0060] Step (1): Add the polyester resin, xylene, n-butanol, dispersant, matting agent, leveling agent, and titanium dioxide in the formula to the reaction vessel in sequence. Stir at 800 rpm for 60 minutes to fully mix and obtain the main slurry.

[0061] Step (2): Grind the mixed main slurry until the fineness is less than 20μm;

[0062] Step (3): Add the prepared main slurry, nano-silica reinforced slurry, composite adhesion promoter and crosslinking agent in sequence at a stirring speed of 500 rpm;

[0063] Step (4): After adding the materials, continue stirring for 30 minutes to ensure even mixing, thus obtaining the water-resistant, boil-resistant, BPA-free baking paint protective coating for thermos cups.

[0064] Example 2

[0065] A water-resistant, boil-proof, BPA-free protective coating for thermos cups, comprising the following raw materials in parts by weight:

[0066] Polyester resin: 48 parts

[0067] 20 parts of nano-silica reinforced paste

[0068] Xylene: 15 parts

[0069] n-Butanol: 5 parts

[0070] Dispersant: 0.8 parts

[0071] Matte powder: 9 parts

[0072] Leveling agent: 0.2 parts

[0073] Titanium dioxide: 13 parts

[0074] Composite adhesion promoter: 2.0 parts

[0075] Crosslinking agent: 18 parts.

[0076] The polyester resin used is DSM's Uralac SN800, and the crosslinking agent used is Cymex CYMEL 303LF.

[0077] The preparation method of the nano-silica reinforced paste is as follows:

[0078] (1) Add 12 parts of epoxy modified acrylic resin, 5 parts of propylene glycol methyl ether acetate, 5 parts of xylene, and 0.8 parts of high molecular weight dispersant BYK-190 to the mixing tank and stir at 700 rpm for 8 minutes until the mixture is uniform.

[0079] (2) Add 8 parts of nano silica and 4 parts of nano zirconium oxide powder, increase the rotation speed to 1600 rpm, disperse for 30 minutes, and perform preliminary dispersion of the slurry;

[0080] (3) Transfer the initially dispersed slurry to a sand mill, add zirconia beads with a particle size of 0.6-0.8 mm, and grind and disperse until the fineness is ≤12 μm;

[0081] (4) Filter the material to obtain the nano-silica reinforced slurry.

[0082] The particle size range of the nano-silica is 10-30 nm, and the particle size range of the nano-zirconia is 40-60 nm.

[0083] The dispersant used is BYK-161.

[0084] The matting agent used is Grace SYLOID ED 50.

[0085] The leveling agent used is BYK-331 from BYK.

[0086] The composite adhesion promoter is composed of a phosphate ester promoter ADP and an aminosilane coupling agent KH-540 in a weight ratio of 1:1.

[0087] A method for preparing a water-resistant, bisphenol A-free protective coating for thermos cups includes the following process steps:

[0088] Step (1): Add the polyester resin, xylene, n-butanol, dispersant, matting agent, leveling agent, and titanium dioxide in the formula to the reaction vessel in sequence. Stir at 1000 rpm for 50 minutes to fully mix and obtain the main slurry.

[0089] Step (2): Grind the mixed main slurry until the fineness is less than 20μm;

[0090] Step (3): Add the prepared main slurry, nano-silica reinforced slurry, composite adhesion promoter and crosslinking agent in sequence at a stirring speed of 550 rpm;

[0091] Step (4): After adding the materials, continue stirring for 35 minutes to ensure even mixing, thus obtaining the water-resistant, boil-resistant, BPA-free baking paint protective coating for thermos cups.

[0092] Example 3

[0093] A water-resistant, boil-proof, BPA-free protective coating for thermos cups, comprising the following raw materials in parts by weight:

[0094] Polyester resin: 50 parts

[0095] 25 parts of nano-silica reinforced paste

[0096] Xylene: 16 parts

[0097] n-Butanol: 6 parts

[0098] Dispersant: 1 part

[0099] Matte powder: 10 parts

[0100] Leveling agent: 0.3 parts

[0101] Titanium dioxide: 15 parts

[0102] Composite adhesion promoter: 3.0 parts

[0103] Crosslinking agent: 20 parts.

[0104] The polyester resin used is DSM's Uralac SN800, and the crosslinking agent used is Cymex CYMEL 303LF.

[0105] The preparation method of the nano-silica reinforced paste is as follows:

[0106] (1) Add 15 parts of epoxy modified acrylic resin, 6 parts of propylene glycol methyl ether acetate, 6 parts of xylene, and 1 part of polymeric dispersant BYK-190 to the mixing tank and stir at 800 rpm for 5 minutes until the mixture is homogeneous.

[0107] (2) Add 10 parts of nano silica and 5 parts of nano zirconium oxide powder, increase the rotation speed to 1800 rpm, disperse for 20 minutes, and perform preliminary dispersion of the slurry;

[0108] (3) Transfer the initially dispersed slurry to a sand mill, add zirconia beads with a particle size of 0.6-0.8 mm, and grind and disperse until the fineness is ≤12 μm;

[0109] (4) Filter the material to obtain the nano-silica reinforced slurry.

[0110] The particle size range of the nano-silica is 10-30 nm, and the particle size range of the nano-zirconia is 40-60 nm.

[0111] The dispersant used is BYK-161.

[0112] The matting agent used is Grace SYLOID ED 50.

[0113] The leveling agent used is BYK-331 from BYK.

[0114] The composite adhesion promoter is composed of phosphate ester promoter ADP and aminosilane coupling agent KH-540 in a weight ratio of 2:1.

[0115] A method for preparing a water-resistant, bisphenol A-free protective coating for thermos cups includes the following process steps:

[0116] Step (1): Add the polyester resin, xylene, n-butanol, dispersant, matting agent, leveling agent, and titanium dioxide in the formula to the reaction vessel in sequence. Stir at 1200 rpm for 40 minutes to fully mix and obtain the main slurry.

[0117] Step (2): Grind the mixed main slurry until the fineness is less than 20μm;

[0118] Step (3): Add the prepared main slurry, nano-silica reinforced slurry, composite adhesion promoter and crosslinking agent in sequence at a stirring speed of 500 rpm;

[0119] Step (4): After adding the materials, continue stirring for 40 minutes to ensure even mixing, thus obtaining the water-resistant, bisphenol A-free baking paint protective coating for thermos cups.

[0120] Comparative Example 1

[0121] The difference between Comparative Example 1 and Example 2 is that nano-silica reinforcing paste was not used.

[0122] Comparative Example 2

[0123] The difference between Comparative Example 1 and Example 2 is that no composite adhesion promoter was used, but only the phosphate ester promoter ADP was used.

[0124]

[0125]

[0126] Data analysis shows that Comparative Example 1, lacking nano-silica reinforcement, had a less dense coating structure, failing to effectively block water vapor penetration, resulting in a sharp deterioration in water resistance and adhesion. The absence of epoxy-modified acrylic resin, which provides excellent metal adhesion, and the lack of the filling and shielding effects of nano-silica and zirconium oxide, which effectively fill the micropores in the polyester / amino resin crosslinking network, making the coating denser and significantly increasing the difficulty of water molecule penetration, further exacerbated the problem. Simultaneously, the nanoparticles possess high hardness, and their uniform dispersion in the paint film significantly improves the overall hardness and scratch resistance of the coating; without them, the hardness drops from 2H to H. Comparative Example 2, lacking KH-540 and using only ADP, showed a decrease in water resistance and adhesion. This is because the synergistic effect of the composite adhesion promoter was disrupted. While ADP primarily provides initial adhesion, its molecules strongly adsorb onto the metal surface, but its bonding with the resin is mainly through physical adsorption and hydrogen bonding, making it unstable under high temperature and humidity conditions. Aminosilane (KH-540) is key to water resistance. Its alkoxy groups, after hydrolysis, can form strong Si-O-Me (Me representing metal) covalent bonds with the hydroxyl groups on the metal surface; its amino groups can also react with resin systems (especially the carboxyl groups of epoxy carriers and polyesters) or form strong hydrogen bonds. This creates a chemically bonded, hydrolysis-resistant bridge between the coating and the metal. Therefore, initial adhesion may be good. However, once exposed to boiling water, water molecules will penetrate the coating / metal interface, disrupting the relatively weak physical adsorption and hydrogen bonds between ADP and the metal, leading to loss of adhesion and blistering and peeling starting from weak points such as edges.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A water-resistant, boil-resistant, BPA-free protective coating for thermos cups, characterized in that: It consists of the following raw materials in parts by weight: Polyester resin: 45-50 parts 15-25 parts of nano-silica reinforced slurry Xylene: 13-16 parts n-Butanol: 5-6 parts Dispersant: 0.5-1 part Matte powder: 8-10 parts Leveling agent: 0.1-0.3 parts Titanium dioxide: 10-15 parts Composite adhesion accelerator: 1.5-3.0 parts Crosslinking agent: 15-20 parts. The polyester resin is a saturated polyester resin with a solid hydroxyl value of 35-55 mgKOH / g and a relative molecular weight of 5000-7000, and the crosslinking agent is methylated melamine-formaldehyde resin.

2. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 1, characterized in that: The preparation method of the nano-silica reinforced paste is as follows: (1) Add 10-15 parts of epoxy modified acrylic resin, 4-6 parts of propylene glycol methyl ether acetate, 4-6 parts of xylene, and 0.5-1.0 parts of high molecular weight dispersant BYK-190 to the mixing tank and stir at 600-800 rpm for 5-10 minutes until the mixture is homogeneous. (2) Add 6-10 parts of nano silica and 3-5 parts of nano zirconium oxide powder, increase the rotation speed to 1500-1800 rpm, disperse for 20-40 minutes, and perform preliminary dispersion of the slurry; (3) Transfer the initially dispersed slurry to a sand mill, add zirconia beads with a particle size of 0.6-0.8 mm, and grind and disperse until the fineness is ≤12 μm; (4) Filter the material to obtain the nano-silica reinforced slurry.

3. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 2, characterized in that: The particle size range of the nano-silica is 10-30 nm, and the particle size range of the nano-zirconia is 40-60 nm.

4. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 1, characterized in that: The dispersant is a polymeric dispersant.

5. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 1, characterized in that: The matting agent is a silica matting agent.

6. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 1, characterized in that: The leveling agent is a polyether-modified polydimethylsiloxane leveling agent.

7. The water-resistant, bisphenol A-free protective coating for thermos cups according to claim 1, characterized in that: The composite adhesion promoter is composed of a phosphate ester promoter and an aminosilane coupling agent in a weight ratio of (2:1) to (1:1).

8. The preparation method of a water-resistant, bisphenol A-free protective coating for thermos cups as described in claim 1, characterized in that: It includes the following process steps: Step (1): Add the polyester resin, xylene, n-butanol, dispersant, matting agent, leveling agent, and titanium dioxide in the formula to the reaction vessel in sequence. Stir at a stirring speed of 800-1200 rpm for 40-60 minutes to mix thoroughly and evenly to obtain the main slurry. Step (2): Grind the mixed main slurry until the fineness is less than 20μm; Step (3): Add the prepared main slurry, nano-silica reinforced slurry, composite adhesion promoter and crosslinking agent in sequence at a stirring speed of 500-600 rpm; Step (4): After adding the ingredients, continue stirring for 30-40 minutes to ensure even mixing, thus obtaining the water-resistant, bisphenol A-free baking paint protective coating for thermos cups.

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