Thermal stamping glue for low-polarity printing substrate with high salt spray corrosion resistance and preparation method thereof

Abstract

The application provides a hot stamping glue for high salt mist erosion resistance of low polarity printing substrate and a preparation method thereof. The hot stamping glue comprises the following raw materials in parts by weight: hydrogenated hydrocarbon resin 20-40 parts, hydrolysis-resistant polyester polyol 20-30 parts, adhesion promoter 5-15 parts, hydrolysis-resistant stabilizer 1-3 parts, tackifying resin 10-25 parts, toughness regulator 5-15 parts, and antioxidant 0.5-1.5 parts. The hot stamping glue can form firm adhesion on the low polarity printing substrate without surface pretreatment, has good hydrolysis resistance and erosion resistance, and makes the hot stamping pattern not easy to fall off and lose luster, effectively solving the problems of poor adhesion and insufficient salt mist resistance of the hot stamping glue in the market for low polarity printing substrate. The preparation method of the hot stamping glue is simple in process and suitable for industrial large-scale production.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and adhesives, specifically to a hot stamping adhesive with high salt spray resistance for low polarity substrates and its preparation method. Background Technology

[0002] Hot stamping is a decorative process that transfers patterns and text from electroplated aluminum foil to the surface of a substrate through heating and pressure; one of the core materials of the foil is hot stamping adhesive. With industrial development, especially in the fields of automotive interior and exterior parts and outdoor durable consumer goods, extremely high requirements have been placed on the durability and corrosion resistance of hot stamped patterns.

[0003] Existing hot melt hot stamping adhesives have significant shortcomings in the following application scenarios: (1) Poor adhesion to low polarity substrates: Materials such as PP, PE, and ABS have low surface energy and strong chemical inertness, making it difficult for ordinary hot stamping adhesives to form a firm bond on their surfaces, resulting in the hot stamping pattern easily falling off and the edges lifting. (2) Poor salt spray resistance: In coastal, high humidity, or winter de-icing agent (salt) environments, traditional hot stamping adhesives are prone to hydrolysis of ester bonds and amide bonds in their polymer structure under the action of humid heat and salt, resulting in powdering of the adhesive layer, loss of adhesion, and consequently, blistering and peeling of the pattern, seriously affecting the appearance and lifespan of the product.

[0004] Currently, methods to improve adhesion often include corona treatment, flame treatment, or the use of primers, but these methods increase process complexity, cost, and environmental impact. Improving salt spray resistance largely relies on using more hydrolysis-resistant resins, but this often comes at the cost of sacrificing flexibility, initial tack, or adhesion to low-polarity substrates. Therefore, developing a hot melt hot stamping adhesive that can be directly applied to low-polarity substrates and possesses both excellent initial adhesion and long-term salt spray resistance has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a hot-melt hot stamping adhesive with high salt spray resistance for low-polarity substrates and its preparation method. This hot-melt hot stamping adhesive can form a strong bond on low-polarity substrates without surface pretreatment. It exhibits excellent resistance to hydrolysis and erosion, making the stamped pattern less prone to peeling and maintaining its gloss. This effectively solves the problems of poor adhesion and insufficient salt spray resistance of existing hot stamping adhesives on the market for low-polarity substrates. The preparation method of this hot stamping adhesive is simple and suitable for large-scale industrial production.

[0006] The objective of this invention is achieved through the following technical solution: a hot stamping adhesive with high salt spray resistance for low polarity substrates, comprising the following raw materials in parts by weight: 20-40 parts of hydrogenated hydrocarbon resin, 20-30 parts of hydrolysis-resistant polyester polyol, 5-15 parts of adhesion promoter, 1-3 parts of hydrolysis-resistant stabilizer, 10-25 parts of tackifying resin, 5-15 parts of toughness modifier, and 0.5-1.5 parts of antioxidant.

[0007] Furthermore, the hydrogenated hydrocarbon resin is at least one of hydrogenated C9 petroleum resin, hydrogenated C5 / C9 copolymer resin, and hydrogenated terpene resin.

[0008] Furthermore, the preparation method of the hydrolysis-resistant polyester polyol includes the following steps: (S1) Feeding: Isophthalic acid and neopentyl glycol are added to the reaction vessel at a molar ratio of 1:1.2-1.5, and esterification catalyst is added at a total feed amount of 0.05-0.1wt%. (S2) Esterification: Under nitrogen protection, the reaction system is heated to 180-220℃ to carry out esterification and dehydration reaction until the amount of water produced reaches more than 95% of the theoretical value and the acid value drops to less than 5 mg KOH / g. (S3) Polycondensation: The reaction system is heated to 230-250℃ and polycondensation is carried out under vacuum to remove residual water and excess diol. (S4) Discharge: When the product viscosity reaches the predetermined value, the reaction is stopped, nitrogen is introduced to release the vacuum, the product is discharged, cooled, and pelletized to obtain hydrolysis-resistant polyester polyol.

[0009] Furthermore, in step (S1), the esterification catalyst is at least one of monobutyltin oxide, dibutyltin oxide, and dibutyltin dilaurate.

[0010] This invention utilizes hydrolysis-resistant polyester polyols to provide hydrolysis-resistant stability and high cohesive strength in hot stamping adhesive systems for low-polarity substrates. It can also form a synergistic effect with hydrogenated hydrocarbon resins, adhesion promoters, and hydrolysis-resistant stabilizers to improve the adhesion and salt spray resistance of hot stamping adhesives.

[0011] Furthermore, the adhesion promoter is at least one of maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, and titanate coupling agent.

[0012] Furthermore, the hydrolysis-resistant stabilizer is at least one of carbodiimide stabilizers and oxazoline stabilizers.

[0013] Furthermore, the tackifying resin is at least one of hydrogenated rosin glycerol ester, hydrogenated disproportionated rosin ester, and terpene phenol resin.

[0014] Furthermore, the toughness modifier is a thermoplastic polyurethane (TPU) elastomer.

[0015] Furthermore, the antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0016] This invention also provides a method for preparing a hot stamping adhesive with high salt spray resistance for low polarity substrates, comprising the following steps: (1) Under nitrogen protection, heat the reactor to 120-130°C, add hydrogenated hydrocarbon resin, hydrogenated rosin glycerol ester and toughness modifier and mix evenly; (2) Raise the system temperature to 150-170℃, add hydrolysis-resistant polyester polyol, adhesion promoter and antioxidant, keep warm and stir evenly; (3) Reduce the system temperature to 130-150℃, add an anti-hydrolysis stabilizer, and continue stirring to homogenize the system.

[0017] The beneficial effects of this invention are as follows: This invention provides a hot stamping adhesive that can form a strong bond on low-polarity substrates without surface pretreatment. The hot stamping adhesive has good resistance to hydrolysis and erosion, ensuring that the stamped pattern does not fall off or lose its gloss, effectively solving the problems of poor adhesion and insufficient salt spray resistance of existing products on low-polarity substrates. The preparation method of the hot stamping adhesive is simple and suitable for large-scale industrial production. Detailed Implementation

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0019] In some embodiments of the present invention, a hot stamping adhesive with high salt spray resistance for low polarity substrates comprises the following raw materials in parts by weight: 20-40 parts of hydrogenated hydrocarbon resin, 20-30 parts of hydrolysis-resistant polyester polyol, 5-15 parts of adhesion promoter, 1-3 parts of hydrolysis-resistant stabilizer, 10-25 parts of tackifying resin, 5-15 parts of toughness modifier, and 0.5-1.5 parts of antioxidant.

[0020] Furthermore, the hydrogenated hydrocarbon resin is at least one of hydrogenated C9 petroleum resin, hydrogenated C5 / C9 copolymer resin, and hydrogenated terpene resin.

[0021] Furthermore, the preparation method of the hydrolysis-resistant polyester polyol includes the following steps: (S1) Feeding: In a reactor equipped with a stirrer, a fractionating column, a nitrogen inlet and a thermometer, isophthalic acid and neopentyl glycol are added at a molar ratio of 1:1.2-1.5, and esterification catalyst is added at a total feed amount of 0.05-0.1% at the same time. (S2) Esterification: Under nitrogen protection, the reaction system is slowly heated to 180-220℃ to carry out esterification and dehydration reaction. This temperature is maintained until the amount of water produced reaches more than 95% of the theoretical value and the acid value drops to less than 5 mg KOH / g. (S3) Polycondensation: The temperature of the reaction system is raised to 230-250℃, and the polycondensation reaction is carried out under the condition that the vacuum degree is gradually reduced to <500 Pa in order to remove residual moisture and excess diol. (S4) Discharge: When the viscosity of the product reaches 8000±2000 mPa·s at 150℃, the reaction is stopped, nitrogen is introduced to release the vacuum, the product is discharged, cooled, and pelletized to obtain hydrolysis-resistant polyester polyol.

[0022] Furthermore, in step (S1), the esterification catalyst is at least one of monobutyltin oxide, dibutyltin oxide, and dibutyltin dilaurate.

[0023] Furthermore, the adhesion promoter is at least one of maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, and titanate coupling agent.

[0024] Furthermore, the hydrolysis-resistant stabilizer is at least one of carbodiimide stabilizers and oxazoline stabilizers.

[0025] Furthermore, the tackifying resin is at least one of hydrogenated rosin glycerol ester, hydrogenated disproportionated rosin ester, and terpene phenol resin.

[0026] Furthermore, the toughness modifier is a thermoplastic polyurethane elastomer.

[0027] Furthermore, the antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants.

[0028] In some embodiments of the present invention, a method for preparing a hot stamping adhesive with high salt spray resistance for low polarity substrates includes the following steps: (1) Premixing: Under nitrogen protection, heat the reactor to 120-130℃, add hydrogenated hydrocarbon resin, hydrogenated rosin glycerol ester and toughness modifier in sequence, stir at 300-500 rpm until completely melted into a uniform liquid base. (2) Main mixing: Raise the system temperature to 150-170℃, and slowly add the self-made hydrolysis resistant polyester polyol, adhesion promoter and antioxidant under stirring. Keep stirring at this temperature for 60-90 minutes to ensure that each component is fully melted, mixed and undergoes some interfacial reaction. (3) Homogenization and stabilization: Reduce the system temperature to 130-150℃, add anti-hydrolysis stabilizer to avoid premature failure due to high temperature; continue stirring for 10-60 minutes to make the system completely homogenized. Example 1

[0029] In this embodiment, a hot stamping adhesive with high salt spray resistance for low polarity substrates comprises the following raw materials in parts by weight: 32 parts hydrogenated hydrocarbon resin, 30 parts hydrolysis-resistant polyester polyol, 10 parts adhesion promoter, 2 parts hydrolysis stabilizer, 15 parts tackifying resin, 10 parts toughness modifier, and 1 part antioxidant.

[0030] Furthermore, the hydrogenated hydrocarbon resin is a hydrogenated C9 petroleum resin (Regalite™ R1125, Eastman).

[0031] Furthermore, the preparation method of the hydrolysis-resistant polyester polyol includes the following steps: (S1) Feeding: In a reactor equipped with a stirrer, a fractionating column, a nitrogen inlet and a thermometer, add 332g of isophthalic acid (IPA) and 208g of neopentyl glycol (NPG) (molar ratio 1:1.4) and 0.3g of esterification catalyst; (S2) Esterification: Under nitrogen protection, the temperature is programmed to 210℃ for esterification reaction until the water output reaches more than 95% of the theoretical value and the acid value drops to less than 5mg KOH / g; (S3) Polycondensation: The temperature of the reaction system is raised to 240°C and the vacuum is gradually reduced to below 200 Pa to carry out the polycondensation reaction; (S4) Discharge: When the product viscosity (150℃) reaches 8000±1000mPa.s, stop the reaction, purge with nitrogen to release the vacuum, discharge the product, cool it, and granulate it to obtain hydrolysis-resistant polyester polyol.

[0032] Furthermore, the adhesion promoter is maleic anhydride-grafted polypropylene (PP-g-MAH, Amplify TY1053H, Dow).

[0033] Furthermore, the hydrolysis stabilizer used is Lanxess Stabaxol® P hydrolysis stabilizer.

[0034] Furthermore, the tackifying resin is hydrogenated rosin glycerol ester (Sylvalite™ RE 100L, Kronen).

[0035] Furthermore, the toughness modifier is thermoplastic polyurethane (Elastollan® 1185A, BASF).

[0036] Furthermore, the antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0037] In this embodiment, a method for preparing a hot stamping adhesive with high salt spray resistance for low polarity substrates includes the following steps: (1) Premixing: Under nitrogen protection, the reactor is heated to 125°C, and hydrogenated hydrocarbon resin, hydrogenated rosin glycerol ester and toughness modifier are added in sequence. The mixture is stirred at 400 rpm until it is completely melted into a uniform liquid base. (2) Main mixing: Raise the system temperature to 160℃, and slowly add the self-made hydrolysis resistant polyester polyol, adhesion promoter and antioxidant under stirring. Keep stirring at this temperature for 90 minutes to ensure that each component is fully melted, mixed and undergoes some interfacial reaction. (3) Homogenization and stabilization: Reduce the system temperature to 140℃, add an anti-hydrolysis stabilizer to avoid premature failure due to high temperature; continue stirring for 40 minutes to make the system completely homogenized. Example 2

[0038] In this embodiment, a hot stamping adhesive with high salt spray resistance for low polarity substrates comprises the following raw materials in parts by weight: 37 parts hydrogenated hydrocarbon resin, 30 parts hydrolysis-resistant polyester polyol, 5 parts adhesion promoter, 2 parts hydrolysis stabilizer, 15 parts tackifying resin, 10 parts toughness modifier, and 1 part antioxidant.

[0039] In this embodiment, a hot stamping adhesive with high salt spray resistance for low-polarity substrates includes the following steps: (1) Premixing: Under nitrogen protection, the reactor is heated to 125°C, and hydrogenated hydrocarbon resin, hydrogenated rosin glycerol ester and toughness modifier are added in sequence. The mixture is stirred at 400 rpm until it is completely melted into a uniform liquid base. (2) Main mixing: Raise the system temperature to 160℃, and slowly add the self-made hydrolysis resistant polyester polyol, adhesion promoter and antioxidant under stirring. Keep stirring at this temperature for 90 minutes to ensure that each component is fully melted, mixed and undergoes some interfacial reaction. (3) Homogenization and stabilization: Reduce the system temperature to 140℃, add an anti-hydrolysis stabilizer to avoid premature failure due to high temperature; continue stirring for 40 minutes to make the system completely homogenized.

[0040] The rest of this embodiment is the same as that in Embodiment 1.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that: in this comparative example, a hot stamping adhesive includes the following raw materials in parts by weight: 34 parts of hydrogenated hydrocarbon resin, 30 parts of hydrolysis-resistant polyester polyol, 10 parts of adhesion promoter, 15 parts of tackifying resin, 10 parts of toughness modifier, and 1 part of antioxidant.

[0042] The rest of this comparative example is the same as in Example 1.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that: in this comparative example, a hot stamping adhesive includes the following raw materials in parts by weight: 32 parts of ordinary C9 petroleum resin (unhydrogenated), 30 parts of hydrolysis-resistant polyester polyol, 10 parts of adhesion promoter, 2 parts of hydrolysis-resistant stabilizer, 15 parts of tackifying resin, 10 parts of toughness modifier, and 1 part of antioxidant.

[0044] The rest of this comparative example is the same as in Example 1.

[0045] The raw material composition of the hot stamping adhesives in Examples 1-2 and Comparative Examples 1-2 is shown in Table 1 below: The hot stamping adhesives prepared in Examples 1-2 and Comparative Examples 1-2 were stamped onto PP plastic sheets with a film thickness of 0.2 mm. After stamping, the samples were left to stand at 23°C and 50% RH for 24 hours, then cut into 100×25 mm samples for performance testing. The test results are shown in Table 2 below. The initial adhesion test, conforming to GB / T9286-2021, was conducted using the cross-cut test method with a 1mm grid spacing, using 3M 600 tape for vertical peeling. The alcohol resistance test involved immersing the sample in a 50% ethanol aqueous solution at room temperature for 24 hours, drying it, and then testing the adhesion. The water resistance test involved immersing the sample in a 40℃ constant temperature water solution for 72 hours, drying it, and then testing the adhesion. The salt water resistance test involved immersing the sample in a 5% NaCl aqueous solution at room temperature for 72 hours, drying it, and then testing the adhesion.

[0046] Salt spray resistance was tested according to GB / T 1771-2007, under continuous spraying conditions of 35℃ and 5% NaCl solution for 500 hours. Appearance was checked and adhesion was tested. The test results show that the adhesive layer of Example 1 was intact after treatment, without blistering or cracking, and the edges of the hot stamping pattern were clear. The adhesive layer of Example 2 was basically intact, with slight lifting at the edges. The adhesive layer of Example 3 blistered, with lifting at the edges and fine cracks. The adhesive layer of Example 4 slightly blistered, with lifting at the edges and fine cracks.

[0047] The artificial sweat resistance test involved immersing the sample in artificial sweat at 37°C for 48 hours, removing and drying it, and then testing the adhesion. The artificial sweat was prepared according to ISO 105-E04. Comparing Example 2 with Example 1, it can be seen that the reduced amount of adhesion promoter in Example 2 resulted in decreased interfacial bonding strength and insufficient durability of the hot stamping adhesive in more demanding humid and corrosive media (such as sweat). Therefore, regarding its impact on adhesion to PP substrates, maleic anhydride-grafted polyolefin is a crucial raw material for achieving high initial adhesion to low-polarity substrates such as PP, and its dosage significantly affects the strength and durability of the adhesion.

[0048] Comparing Comparative Example 1 with Example 1 shows that, without an anti-hydrolysis stabilizer, the polyester segments of the hot stamping adhesive in Comparative Example 1 hydrolyze under the catalysis of warm water, salt water, and sweat, resulting in a significant reduction in the cohesive strength of the adhesive layer and adversely affecting its functionality. This demonstrates the indispensable role of the anti-hydrolysis stabilizer. Therefore, this invention, by combining an anti-hydrolysis stabilizer with hydrolytically resistant polyester and other raw materials in the hot stamping adhesive system, helps improve the resistance of hot stamping adhesive to complex media. Carbodiimide anti-hydrolysis agents are crucial raw materials for resisting polymer hydrolysis caused by media such as warm water, salt water, and sweat. Without the aforementioned anti-hydrolysis stabilizer, the entire adhesive system will rapidly fail in these media.

[0049] Comparing Comparative Example 2 with Example 1 reveals that the hot stamping adhesive in Comparative Example 2 uses a non-hydrogenated resin instead of the hydrogenated hydrocarbon resin in Example 1. The non-hydrogenated resin is easily oxidized and corroded, leading to a significant decrease in the overall weather resistance and media resistance of the system, and affecting its appearance. Therefore, this invention, by combining hydrogenated hydrocarbon resin with the remaining raw materials of the hot stamping adhesive system, effectively avoids performance degradation and yellowing caused by the oxidation and corrosion of the unsaturated bonds of the resin itself, thus helping to improve the stability of the hot stamping adhesive system.

[0050] In summary, this invention, through the combination of hydrogenated hydrocarbon resins, hydrolysis-resistant polyester polyols, adhesion promoters, and hydrolysis-resistant stabilizers, effectively solves the problem of achieving high initial adhesion of hot stamping adhesives on low-polarity substrates such as PP, while simultaneously resisting the erosion of various complex chemical media such as alcohols, warm water, salt water, and artificial sweat, thus exhibiting excellent comprehensive performance.

[0051] The specific embodiments described above are further illustrations of the technical solution and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A hot stamping adhesive with high salt spray resistance for low-polarity substrates, characterized in that, The raw materials include the following parts by weight: 20-40 parts hydrogenated hydrocarbon resin, 20-30 parts hydrolysis-resistant polyester polyol, 5-15 parts adhesion promoter, 1-3 parts hydrolysis-resistant stabilizer, 10-25 parts tackifying resin, 5-15 parts toughness modifier, and 0.5-1.5 parts antioxidant.

2. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The hydrogenated hydrocarbon resin is at least one of hydrogenated C9 petroleum resin, hydrogenated C5 / C9 copolymer resin, and hydrogenated terpene resin.

3. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The preparation method of the hydrolysis-resistant polyester polyol includes the following steps: (S1) Feeding: Isophthalic acid and neopentyl glycol are added to the reaction vessel at a molar ratio of 1:1.2-1.5, and esterification catalyst is added at a total feed amount of 0.05-0.1wt%. (S2) Esterification: Under nitrogen protection, the reaction system is heated to 180-220℃ to carry out esterification and dehydration reaction until the amount of water produced reaches more than 95% of the theoretical value and the acid value drops to less than 5 mg KOH / g. (S3) Polycondensation: The reaction system is heated to 230-250℃ and polycondensation is carried out under vacuum to remove residual moisture and excess diol. (S4) Discharge: When the product viscosity reaches the predetermined value, the reaction is stopped, nitrogen is introduced to release the vacuum, the product is discharged, cooled, and pelletized to obtain hydrolysis-resistant polyester polyol.

4. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 3, characterized in that: In step (S1), the esterification catalyst is at least one of monobutyltin oxide, dibutyltin oxide, and dibutyltin dilaurate.

5. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The adhesion promoter is at least one of maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, and titanate coupling agent.

6. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The hydrolysis-resistant stabilizer is at least one of carbodiimide stabilizers and oxazoline stabilizers.

7. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The tackifying resin is at least one of hydrogenated rosin glycerol ester, hydrogenated disproportionated rosin ester, and terpene phenol resin.

8. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The toughness modifier is a thermoplastic polyurethane elastomer.

9. The hot stamping adhesive with high salt spray resistance for low polarity substrates according to claim 1, characterized in that: The antioxidant is at least one of hindered phenolic antioxidants and phosphite antioxidants.

10. The method for preparing a hot stamping adhesive with high salt spray resistance for low polarity substrates as described in any one of claims 1-9, characterized in that: Includes the following steps: (1) Under nitrogen protection, heat the reactor to 120-130°C, add hydrogenated hydrocarbon resin, hydrogenated rosin glycerol ester and toughness modifier and mix evenly; (2) Raise the system temperature to 150-170℃, add hydrolysis-resistant polyester polyol, adhesion promoter and antioxidant, keep warm and stir evenly; (3) Reduce the system temperature to 130-150℃, add an anti-hydrolysis stabilizer, and continue stirring to homogenize the system.

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