Hot melt adhesive, preparation method thereof, and application thereof in card protection film

Abstract

The present invention relates to the technical field of EVA hot melt adhesives, and discloses a hot melt adhesive, a preparation method thereof, and its application in card protection films. The present invention adds EVA resin, EVA-based polyurethane, and an antioxidant to a reactor, heats and stirs to melt, then adds a plasticizer, an auxiliary agent, and a tackifier, and cools to obtain a hot melt adhesive. The EVA-based polyurethane of the present invention contains EVA molecular chains, which improves compatibility between the polyurethane and the EVA resin, provides a better toughening effect, and increases the shear strength and elongation at break of the hot melt adhesive. The EVA-based polyurethane contains hydrophobic fluorinated alkyl chains, which helps to increase the hydrophobicity of the polyurethane, thereby increasing the hydrophobicity of the hot melt adhesive, reducing water absorption, and exhibiting better water resistance. The hot melt adhesive has good practical applications in card protection films and other aspects.

Description

Technical Field

[0001] The present invention relates to the technical field of EVA hot melt adhesives, in particular to a hot melt adhesive and a preparation method thereof and application thereof in card protection films. Background Art

[0002] Card film, also known as plastic film, is widely used in photo, ID card, business card, document protection, and food packaging. Card film is typically composed of a base material such as polyethylene terephthalate (PET) or polyethylene (PE), and a hot-melt adhesive layer such as ethylene-vinyl acetate copolymer (EVA).

[0003] Hot melt adhesive is a plastic adhesive with the advantages of being solvent-free, environmentally friendly, and having a fast curing time. It is widely used in packaging, footwear, medical, metal, and wood applications. EVA hot melt adhesive is currently the most commonly used commercial hot melt adhesive due to its low cost, high chemical resistance, and wide range of applications. Modifying EVA hot melt adhesive to improve its mechanical properties, bonding properties, and water resistance, and to expand its practical application in areas such as card protection films, is a hot topic of research.

[0004] Polyurethane is a polymer material with excellent mechanical properties, high toughness, and excellent elasticity. It is widely used in toughening agents, adhesives, coatings, and other fields. Patent CN110330901 B discloses an EVA hot melt adhesive with high bonding strength. Made from EVA resin, hydroxyl-terminated polyurethane resin, and SBS thermoplastic elastomer, the EVA hot melt adhesive exhibits high bonding strength, excellent high-temperature resistance, and excellent aging resistance. Compared to the hot melt adhesive in the patent, the present invention utilizes EVA-based polyurethane as a modifier, improving the EVA hot melt adhesive's shear strength, bonding properties, toughness, and water resistance. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a method for preparing an EVA hot melt adhesive with high shear strength and water resistance for card protection films.

[0006] The technical solution of the present invention is: a hot melt adhesive and a preparation method thereof and application in card protection film, the preparation method comprising the following steps:

[0007] (1) Nitrogen is introduced into a flask, toluene and maleic anhydride grafted EVA (brand DuPont 30E731) are added, heated to 100-110°C, stirred, fluorinated diol and p-toluenesulfonic acid are added, stirred and reacted for 12-18 hours, condensed and refluxed during the reaction, vacuum distilled, washed with dichloromethane, and dried to obtain fluorinated hydroxyl grafted EVA. The reaction formula is:

[0008]

[0009] (2) Add polyethylene glycol to the flask, vacuum dehydrate, add diisocyanate monomer, carry out polymerization reaction at 70-80°C for 2.5-3h, then add fluorinated hydroxyl grafted EVA and acetone, carry out chain extension reaction at 40-45°C for 1-1.5h, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane.

[0010] (3) Add EVA resin, 15-40% of EVA-based polyurethane by mass of the EVA resin, and antioxidant into the reactor, heat and stir to melt, then add plasticizer, auxiliary agent, tackifier, stir evenly, cool, and obtain hot melt adhesive.

[0011] Preferably, the mass of the fluorinated diol and p-toluenesulfonic acid in (1) is 2-8% and 0.16-0.7% of the mass of the maleic anhydride grafted EVA.

[0012] Preferably, the structural formula of the fluorinated diol is a is any integer from 3 to 8.

[0013] Preferably, the mass of the diisocyanate monomer and the fluorinated hydroxyl-grafted EVA in (2) are 18.4-26.6% and 6-16% of the mass of the polyethylene glycol, respectively.

[0014] Preferably, the diisocyanate monomer is isophorone diisocyanate, hexamethylene diisocyanate, 2,4-toluene diisocyanate or 4,4'-diphenylmethane diisocyanate.

[0015] Preferably, the auxiliary agent is paraffin wax or polyethylene wax; the tackifier is polymerized rosin (model Eastman Dymerex), petroleum resin (hydrogenated C9 resin) or terpene resin (brand Xinghai Chemical XH-022); the plasticizer is dioctyl phthalate or dibutyl phthalate; and the antioxidant is antioxidant 1010 or antioxidant 1076.

[0016] Preferably, the application of hot melt adhesive in the card protection film

[0017] The present invention has the following technical effects: the present invention utilizes a hydroxyl group of a fluorinated diol to react with an anhydride group of maleic anhydride grafted EVA to obtain a fluorinated hydroxyl-grafted EVA, which is then polymerized with polyethylene glycol and a diisocyanate monomer to undergo a chain extension reaction to obtain an EVA-based polyurethane, which is used as a compatibilizer and compounded with an EVA resin, a plasticizer, a tackifier, and the like to obtain a hot melt adhesive.

[0018] The EVA-based polyurethane of the present invention contains EVA molecular chains, thereby achieving better compatibility between the polyurethane and the EVA resin, enabling the polyurethane to play a better toughening role. In addition, the polyurethane itself has excellent bonding properties. When added to the EVA resin hot melt adhesive, the shear strength of the hot melt adhesive is significantly improved, and the polyurethane has good elongation at break and tensile strength, high toughness, and high strength.

[0019] The EVA-based polyurethane of the present invention contains hydrophobic fluorinated alkyl chains, which help improve the hydrophobicity of the polyurethane. When added to EVA hot-melt adhesives, it can improve the hot-melt adhesive's hydrophobicity, reduce water absorption, and exhibit better water resistance. It has good practical applications in card protection films and other fields. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions of the present invention through 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 those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Example 1

[0022] (1) Nitrogen was introduced into the flask, 100 mL of toluene and 6 g of maleic anhydride grafted EVA were added, and the mixture was heated to 100 ° C. After stirring, 0.25 g of decafluoro-1,8-octanediol (CAS No. 90177-96-1) and 23 mg of p-toluenesulfonic acid were added, and the mixture was stirred for 18 hours. During the reaction, the mixture was condensed and refluxed, and the mixture was distilled under reduced pressure, washed with dichloromethane, and dried to obtain fluorinated hydroxyl grafted EVA.

[0023] (2) Add 50g of polyethylene glycol 1000 to the flask, vacuum dehydrate, add 11.7g of isophorone diisocyanate, carry out polymerization reaction at 75℃ for 2.5h, then add 3g of fluorinated hydroxyl grafted EVA and acetone, carry out chain extension reaction at 40℃ for 1h, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane.

[0024] (3) Add 1 kg of EVA resin, 150 g of EVA-based polyurethane, and 25 g of antioxidant 1076 to the reactor, heat and stir to melt, then add 72 g of plasticizer dioctyl phthalate, 190 g of auxiliary agent paraffin, and 32 g of tackifier polymerized rosin, stir evenly, and cool to obtain a hot melt adhesive.

[0025] Example 2

[0026] (1) Nitrogen was introduced into the flask, 100 mL of toluene and 6 g of maleic anhydride grafted EVA were added, and the mixture was heated to 110°C. After stirring, 0.48 g of hexafluoro-1,10-decanediol (CAS No. 754-96-1) and 42 mg of p-toluenesulfonic acid were added. The mixture was stirred for 12 hours. During the reaction, the mixture was condensed and refluxed, and the mixture was distilled under reduced pressure. The mixture was washed with dichloromethane and dried to obtain fluorinated hydroxyl grafted EVA.

[0027] (2) Add 50g of polyethylene glycol 1000 to a flask, dehydrate under vacuum, add 9.7g of 2,4-toluene diisocyanate, carry out polymerization reaction at 70°C for 3h, then add 4.5g of fluorinated hydroxyl-grafted EVA and acetone, carry out chain extension reaction at 40°C for 1.5h, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane.

[0028] (3) Add 1 kg of EVA resin, 230 g of EVA-based polyurethane, and 25 g of antioxidant 1010 to the reactor, heat and stir to melt, then add 75 g of plasticizer dioctyl phthalate, 210 g of auxiliary agent polyethylene wax, and 37 g of tackifier terpene resin, stir evenly, and cool to obtain a hot melt adhesive.

[0029] Example 3

[0030] (1) Nitrogen was introduced into the flask, 80 mL of toluene and 6 g of maleic anhydride grafted EVA were added, and the mixture was heated to 100 ° C. After stirring, 0.12 g of hexafluoro-1,5-pentanediol (CAS No. 376-90-9) and 9.6 mg of p-toluenesulfonic acid were added, and the mixture was stirred for 12 hours. During the reaction, the mixture was condensed and refluxed, and the mixture was distilled under reduced pressure, washed with dichloromethane, and dried to obtain fluorinated hydroxyl grafted EVA.

[0031] (2) Add 50g of polyethylene glycol 1000 to the flask, vacuum dehydrate, add 13.3g of 4,4'-diphenylmethane diisocyanate, carry out polymerization reaction at 70℃ for 3h, then add 6g of fluorinated hydroxyl grafted EVA and acetone, carry out chain extension reaction at 45℃ for 1h, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane.

[0032] (3) Add 1 kg of EVA resin, 320 g of EVA-based polyurethane, and 30 g of antioxidant 1010 to the reactor, heat and stir to melt, then add 81 g of plasticizer dibutyl phthalate, 180 g of auxiliary agent paraffin, and 40 g of tackifier hydrogenated C9 petroleum resin, stir evenly, and cool to obtain a hot melt adhesive.

[0033] Example 4

[0034] (1) Nitrogen was introduced into the flask, 90 mL of toluene and 6 g of maleic anhydride grafted EVA were added, and the mixture was heated to 110 ° C. After stirring, 0.37 g of perfluoro-1,9-nonanediol (CAS No. 203303-01-9) and 35 mg of p-toluenesulfonic acid were added, and the mixture was stirred for 12 hours. During the reaction, the mixture was condensed and refluxed, and the mixture was distilled under reduced pressure. The mixture was washed with dichloromethane and dried to obtain fluorinated hydroxyl grafted EVA.

[0035] (2) Add 50g of polyethylene glycol 1000 to the flask, vacuum dehydrate, add 9.2g of hexamethylene diisocyanate, carry out polymerization reaction at 80℃ for 2.5h, then add 8g of fluorinated hydroxyl grafted EVA and acetone, carry out chain extension reaction at 45℃ for 1h, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane.

[0036] (3) Add 1 kg of EVA resin, 400 g of EVA-based polyurethane, and 30 g of antioxidant 1076 into the reactor, heat and stir to melt, then add 76 g of plasticizer dioctyl phthalate, 190 g of auxiliary agent polyethylene wax, and 30 g of tackifier terpene resin, stir evenly, and cool to obtain a hot melt adhesive.

[0037] Comparative Example 1

[0038] (1) Add 1 kg EVA resin and 25 g antioxidant 1076 into the reactor, heat and stir to melt, then add 72 g plasticizer dioctyl phthalate, 190 g auxiliary agent paraffin, 32 g tackifier polymerized rosin, stir evenly, and cool to obtain hot melt adhesive.

[0039] Comparative Example 2

[0040] (1) Add 50g of polyethylene glycol 1000 to a flask, dehydrate under vacuum, add 11.7g of isophorone diisocyanate, carry out polymerization reaction at 75℃ for 2.5h, then add 3g of 1,4-butanediol and acetone, carry out chain extension reaction at 40℃ for 1h, remove acetone by vacuum distillation, and dry to obtain polyurethane.

[0041] (2) Add 1 kg EVA resin, 150 g polyurethane, and 25 g antioxidant 1076 into the reactor, heat and stir to melt, then add 72 g plasticizer dioctyl phthalate, 190 g auxiliary agent paraffin, and 32 g tackifier polymerized rosin, stir evenly, and cool to obtain hot melt adhesive.

[0042] Comparative Example 3

[0043] (1) Nitrogen was introduced into the flask, 100 mL of toluene and 6 g of maleic anhydride grafted EVA were added, and the mixture was heated to 100 ° C. After stirring, 0.25 g of 1,8-octanediol (CAS No. 629-41-4) and 23 mg of p-toluenesulfonic acid were added, and the mixture was stirred for 18 hours. During the reaction, the mixture was condensed and refluxed, and the mixture was distilled under reduced pressure, washed with dichloromethane, and dried to obtain hydroxyl grafted EVA.

[0044] (2) Add 50g of polyethylene glycol 1000 to the flask, vacuum dehydrate, add 11.7g of isophorone diisocyanate, carry out polymerization reaction at 75℃ for 2.5h, then add 3g of hydroxyl-grafted EVA and acetone, carry out chain extension reaction at 40℃ for 1h, remove acetone by reduced pressure distillation, and dry to obtain EVA-based polyurethane.

[0045] (3) Add 1 kg of EVA resin, 150 g of EVA-based polyurethane, and 25 g of antioxidant 1076 to the reactor, heat and stir to melt, then add 72 g of plasticizer dioctyl phthalate, 190 g of auxiliary agent paraffin, and 32 g of tackifier polymerized rosin, stir evenly, and cool to obtain a hot melt adhesive.

[0046] Dumbbell-shaped specimens were made of hot-melt adhesive, and tensile properties were tested according to GB / T 1040.1-2018. The tensile rate was 100 mm / min, and five samples were tested in each group, and the average value was taken.

[0047] Hot melt adhesive was applied to two steel surfaces, heated to 160°C, then cooled and solidified for 24 hours. Tensile shear strength was tested according to GB / T 7124-2008. Five samples were tested per set, and the average value was calculated.

[0048] The hot melt adhesive was made into a sample of 8cm×8cm×1cm, weighed after drying (m0), and then soaked in water for 48 hours. The sample was taken out, the surface moisture was absorbed with filter paper, and the sample was weighed (m1). The water absorption rate W was calculated.

[0049] W = (m1 - m0) / m0 × 100%.

[0050] The performance test results are shown in Table 1.

[0051] Table 1 Performance test

[0052]

[0053] Compared to Comparative Example 1, Examples 1-4 incorporate EVA-based polyurethane. Because the polyurethane contains EVA molecular chains, it enhances compatibility with the EVA resin, resulting in a more robust toughening effect. Furthermore, the polyurethane itself possesses excellent bonding properties. When added to the EVA resin hot melt adhesive, it significantly improves the hot melt adhesive's shear strength, exhibits good elongation at break and tensile strength, and exhibits high toughness and strength. EVA-based polyurethane contains hydrophobic fluorinated alkyl chains, which contribute to the polyurethane's hydrophobicity. Adding it to the EVA hot melt adhesive enhances its hydrophobicity, reduces water absorption, and exhibits improved water resistance.

[0054] The polyurethane in Comparative Example 2 does not contain EVA molecular chains, the compatibility between polyurethane and EVA resin is relatively low, the toughening effect of polyurethane is poor, and the dispersibility in EVA hot melt adhesive is poor, resulting in low shear strength, tensile strength and elongation at break of the hot melt adhesive. In addition, polyurethane has strong hydrophilicity, which leads to increased hydrophilicity and water absorption of the hot melt adhesive, which is not conducive to improving the water resistance of the hot melt adhesive.

[0055] In Comparative Example 3, maleic anhydride-grafted EVA was reacted with 1,8-octanediol to obtain hydroxyl-grafted EVA, which was then subjected to a polymerization chain extension reaction with polyethylene glycol and isophorone diisocyanate. The obtained EVA-based polyurethane has good compatibility with the EVA resin, and the EVA hot melt adhesive has excellent shear strength, tensile strength and elongation at break. However, the EVA-based polyurethane does not contain hydrophobic fluorinated alkyl chains. Adding it to the EVA hot melt adhesive will increase its hydrophilicity and water absorption, which is not conducive to improving the water resistance of the hot melt adhesive.

[0056] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a hot melt adhesive, characterized in that: The preparation method comprises the following steps: (1) nitrogen is introduced into the flask, toluene is added, maleic anhydride grafted EVA is added, heated to the reaction temperature, stirred, fluorinated diol is added, p-toluenesulfonic acid is stirred to react, vacuum distilled, washed with dioxane, and dried to obtain fluorinated hydroxyl grafted EVA; (2) Add polyethylene glycol to the flask, vacuum dehydrate, add diisocyanate monomer, carry out polymerization reaction, then add fluorinated hydroxyl-grafted EVA and acetone, carry out chain extension reaction, remove acetone by vacuum distillation, and dry to obtain EVA-based polyurethane; (3) Add EVA resin, 15-40% of EVA resin mass of EVA-based polyurethane, and antioxidant into the reactor, heat and stir to melt, then add plasticizer, additive, and tackifier, stir evenly, and cool to obtain hot melt adhesive; The structural formula of the fluorinated diol is , a is any integer between 3 and 8.

2. The method for preparing the hot melt adhesive according to claim 1, wherein: The mass of the fluorinated diol and p-toluenesulfonic acid in (1) is 2-8% and 0.16-0.7% of the mass of the maleic anhydride grafted EVA.

3. The method for preparing the hot melt adhesive according to claim 1, wherein: The reaction temperature in (1) is 100-110° C., and the reaction time is 12-18 h.

4. The method for preparing the hot melt adhesive according to claim 1, wherein: The mass of the diisocyanate monomer and the fluorinated hydroxyl-grafted EVA in (2) is 18.4-26.6% and 6-16% of the mass of the polyethylene glycol respectively.

5. The method for preparing the hot melt adhesive according to claim 4, characterized in that: The diisocyanate monomer is isophorone diisocyanate, hexamethylene diisocyanate, 2,4-toluene diisocyanate or 4,4'-diphenylmethane diisocyanate.

6. The method for preparing hot melt adhesive according to claim 1, characterized in that: The polymerization reaction temperature is 70-80° C., and the reaction time is 2.5-3 hours; the chain extension reaction temperature is 40-45° C., and the reaction time is 1-1.5 hours.

7. The method for preparing hot melt adhesive according to claim 1, characterized in that: The auxiliary agent is paraffin wax or polyethylene wax; the tackifier is polymerized rosin, petroleum resin or terpene resin; the plasticizer is dioctyl phthalate or dibutyl phthalate; and the antioxidant is antioxidant 1010 or antioxidant 1076.

8. A hot melt adhesive obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the hot melt adhesive obtained by the preparation method according to claim 7 in card protection film.

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