Hot melt adhesive, preparation method thereof and application of hot melt adhesive in card protecting film

Abstract

The invention relates to the technical field of EVA (Ethylene Vinyl Acetate) hot melt adhesives, and discloses a hot melt adhesive, a preparation method thereof and an application of the hot melt adhesive in a card protecting film. The preparation method comprises the following steps: adding EVA resin, EVA-based polyurethane and an antioxidant into a reaction kettle, heating, stirring and melting, then adding a plasticizer, an auxiliary agent and a tackifier, and cooling to obtain the hot melt adhesive. The EVA-based polyurethane contains an EVA molecular chain, so that the polyurethane and EVA resin have better compatibility, a better toughening effect is achieved, the shear strength and the elongation at break of the hot melt adhesive are improved, the EVA-based polyurethane contains a hydrophobic fluorine-containing alkyl chain, the hydrophobicity of the polyurethane is improved, the hydrophobicity of the hot melt adhesive is improved, and the hot melt adhesive has a good application prospect. The water absorption rate is reduced, and better water resistance is shown. Good practical application is realized in the aspects of card protecting films and the like.

Description

Technical Field

[0001] The 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 a card protection film. Background Art

[0002] Card protection film, also known as plastic film, is widely used in photo, ID card, business card, document protection, food packaging, etc. Card protection film is usually composed of a base material such as polyethylene terephthalate, polyethylene, 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, green and environmentally friendly, and having a short curing time. It is widely used in packaging, shoemaking, medical treatment, metal, wood and other fields. Among them, EVA hot melt adhesive has the advantages of low cost, high chemical resistance and a wide range of applications. It is one of the most commonly used commercial hot melt adhesives. Modifying EVA hot melt adhesive, improving its mechanical properties, bonding properties, water resistance and other properties, and expanding its practical application in card protection films and other fields are research hotspots.

[0004] Polyurethane is a polymer material with good 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. The EVA hot melt adhesive prepared by using EVA resin, hydroxyl-terminated polyurethane resin, SBS thermoplastic elastomer and the like as raw materials has the advantages of high bonding strength, good high temperature resistance and excellent aging resistance. Compared with the hot melt adhesive of the patent, the present invention uses EVA-based polyurethane as a modifier to improve the shear strength, bonding performance, toughness and water resistance of the EVA hot melt adhesive. Summary of the invention

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

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

[0007] (1) Nitrogen is introduced into a flask, toluene and maleic anhydride grafted EVA (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 a 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 the mass of EVA resin and EVA-based polyurethane, and antioxidant into the reaction kettle, heat and stir to melt, then add plasticizer, auxiliary agent, and tackifier, stir evenly, and cool to obtain hot melt adhesive.

[0011] Preferably, the mass of the fluorinated diol and p-toluenesulfonic acid in (1) is 2-8%, 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, in (2), the mass of the diisocyanate monomer and the fluorinated hydroxyl-grafted EVA 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 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 fluorinated hydroxyl grafted EVA, and then polymerizes 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, etc. to obtain a hot melt adhesive.

[0018] The EVA-based polyurethane of the invention contains EVA molecular chains, so that the polyurethane and the EVA resin have better compatibility, so that the polyurethane plays a better toughening role, and the polyurethane itself has good bonding performance. 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 a hydrophobic fluorinated alkyl chain, which is beneficial to improving the hydrophobicity of the polyurethane. When added to the EVA hot melt adhesive, the hydrophobicity of the hot melt adhesive can be improved, the water absorption rate can be reduced, and better water resistance can be exhibited. It has good practical applications in card protection films and the like. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0021] Example 1

[0022] (1) Nitrogen was introduced into a 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 distilled under reduced pressure. The mixture was washed with dichloromethane and dried to obtain fluorinated hydroxyl grafted EVA.

[0023] (2) Add 50 g of polyethylene glycol 1000 into a flask, vacuum dehydrate, add 11.7 g of isophorone diisocyanate, and carry out polymerization reaction at 75°C for 2.5 hours. Then add 3 g of fluorinated hydroxyl-grafted EVA and acetone, and carry out chain extension reaction at 40°C for 1 hour. Remove acetone by reduced pressure 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 a 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 a 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, 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.

[0027] (2) Add 50 g of polyethylene glycol 1000 to a flask, dehydrate under vacuum, add 9.7 g of 2,4-toluene diisocyanate, and carry out polymerization reaction at 70°C for 3 hours. Then add 4.5 g of fluorinated hydroxyl-grafted EVA and acetone, and carry out chain extension reaction at 40°C for 1.5 hours. Remove the 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 a 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 a 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. The mixture was washed with dichloromethane and dried to obtain fluorinated hydroxyl grafted EVA.

[0031] (2) Add 50 g of polyethylene glycol 1000 to a flask, vacuum dehydrate, add 13.3 g of 4,4'-diphenylmethane diisocyanate, and carry out polymerization reaction at 70°C for 3 hours. Then add 6 g of fluorinated hydroxyl-grafted EVA and acetone, and carry out chain extension reaction at 45°C for 1 hour. Remove acetone by reduced pressure 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 a 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 a 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. The mixture was stirred for 12 h. During the reaction, the mixture was condensed and refluxed, and distilled under reduced pressure. The mixture was washed with dichloromethane and dried to obtain fluorinated hydroxyl grafted EVA.

[0035] (2) Add 50 g of polyethylene glycol 1000 to a flask, dehydrate under vacuum, add 9.2 g of hexamethylene diisocyanate, and carry out polymerization reaction at 80°C for 2.5 hours. Then add 8 g of fluorinated hydroxyl-grafted EVA and acetone, and carry out chain extension reaction at 45°C for 1 hour. 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 to a 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 of EVA resin and 25 g of antioxidant 1076 to a reactor, heat and stir to melt, then add 72 g of plasticizer dioctyl phthalate, 190 g of auxiliary paraffin, and 32 g of tackifier polymerized rosin, stir evenly, and cool to obtain a hot melt adhesive.

[0039] Comparative Example 2

[0040] (1) Add 50 g of polyethylene glycol 1000 to a flask, dehydrate under vacuum, add 11.7 g of isophorone diisocyanate, carry out polymerization reaction at 75°C for 2.5 hours, then add 3 g of 1,4-butanediol and acetone, carry out chain extension reaction at 40°C for 1 hour, 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 to a 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 a hot melt adhesive.

[0042] Comparative Example 3

[0043] (1) Nitrogen was introduced into a 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 h. During the reaction, the mixture was condensed and refluxed, and distilled under reduced pressure. The mixture was washed with dichloromethane and dried to obtain hydroxy-grafted EVA.

[0044] (2) Add 50 g of polyethylene glycol 1000 into a flask, vacuum dehydrate, add 11.7 g of isophorone diisocyanate, and carry out polymerization reaction at 75°C for 2.5 hours. Then add 3 g of hydroxy-grafted EVA and acetone, and carry out chain extension reaction at 40°C for 1 hour. 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 a 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] The hot melt adhesive was made into dumbbell-shaped specimens, and the tensile properties were tested according to the GB / T 1040.1-2018 method. The tensile rate was 100 mm / min, and 5 samples were tested in each group of specimens to take the average value.

[0047] Place the hot melt adhesive on the surface of two steel plates, heat to 160°C, then cool and solidify, and place for 24 hours. The tensile shear strength is tested according to the GB / T 7124-2008 method. Test 5 samples in each group of samples and take the average value.

[0048] The hot melt adhesive was made into a sample of 8cm×8cm×1cm, weighed after drying (m0), and then soaked in water for 48h. The sample was taken out, the surface moisture was absorbed with filter paper, and 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 with Comparative Example 1, EVA-based polyurethane is added to Examples 1-4. Since the polyurethane contains EVA molecular chains, the polyurethane and the EVA resin have better compatibility, so that the polyurethane plays a better toughening role, and the polyurethane itself has good bonding properties. When added to the EVA resin hot melt adhesive, the shear strength of the hot melt adhesive is significantly improved, and it has good elongation at break and tensile strength, high toughness and high strength. EVA-based polyurethane contains hydrophobic fluorinated alkyl chains, which is beneficial to improving the hydrophobicity of polyurethane. When added to the EVA hot melt adhesive, the hydrophobicity of the hot melt adhesive can be improved, the water absorption rate can be reduced, and better water resistance can be shown.

[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 relatively 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 is reacted with 1,8-octanediol to obtain hydroxyl-grafted EVA, which is 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 them 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 above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

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 a flask, toluene is added, maleic anhydride is grafted onto EVA, the mixture is heated to the reaction temperature, fluorinated diol is added after stirring, p-toluenesulfonic acid is stirred to react, vacuum distillation is performed, dioxane is washed, and drying is performed to obtain fluorinated hydroxyl-grafted EVA; (2) Add polyethylene glycol to a 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 the mass of EVA resin and EVA-based polyurethane, and antioxidant into the reaction kettle, heat and stir to melt, then add plasticizer, auxiliary agent, and tackifier, stir evenly, and cool to obtain hot melt adhesive.

2. The method for preparing hot melt adhesive according to claim 1, characterized in that: 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 hot melt adhesive according to claim 2, characterized in that: The structural formula of the fluorinated diol is a is any integer from 3 to 8.

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

5. The method for preparing hot melt adhesive according to claim 1, characterized in that: 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.

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

7. 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 h; the chain extension reaction temperature is 40-45° C., and the reaction time is 1-1.5 h.

8. The method for preparing hot melt adhesive according to claim 1, characterized in that: The auxiliary agent is paraffin 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.

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

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

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