Polyester hot melt adhesive for powder coating and preparation method thereof

Abstract

The present invention relates to the field of hot melt adhesives, and specifically discloses a polyester hot melt adhesive for powder coatings and a preparation method thereof. The main ingredients of the polyester hot melt adhesive for powder coatings are composed of polyacids and polyols, and the polyacids are a mixture of terephthalic acid, fumaric acid and succinic acid, the polyols are ethylene glycol and 1,2-pentanediol, and the auxiliary materials include catalysts, modifiers and viscosity regulators. The preparation method of the polyester hot melt adhesive for powder coatings: S1, esterification reaction of polyacids, polyols and catalysts to obtain prepolymers; S2, prepolymers, modifiers and viscosity regulators are subjected to reduced pressure polycondensation reaction; S3, nitrogen is passed to release the vacuum, the material is discharged while hot, and the polyester hot melt adhesive for powder coatings is obtained after pelletizing and drying. The present invention designs raw materials and ratios, and the obtained polyester hot melt adhesive has strong water resistance, heat resistance and toughness, low melt viscosity, is easy to use and process, and broadens its application scenarios and fields for powder coatings.

Description

Technical Field

[0001] The invention relates to the field of hot melt adhesives, and in particular to a polyester hot melt adhesive for powder coatings and a preparation method thereof. Background Art

[0002] Powder coating is a solid powdered synthetic resin coating composed of solid resin, pigment, filler and other additives. It is divided into two categories: thermoplastic powder coating and thermosetting powder coating. Polyester powder coating belongs to thermosetting powder coating. It is widely used in home appliances, furniture, construction and other fields because of its good decorative, anti-corrosion and mechanical properties.

[0003] At present, the commonly used hot melt adhesives are: EVA hot melt adhesive, polyester hot melt adhesive, copolyamide hot melt adhesive and moisture-cured polyurethane hot melt adhesive. Among them, polyester hot melt adhesive plays an important role in the powder coating industry because of its high heat resistance, good weather resistance and elasticity, but its viscosity is large when heated and melted, the melting temperature is high, it is difficult to coat, and the operation is relatively difficult. In addition, polyester hot melt adhesive contains ester bonds in the structural unit and lacks sufficient benzene ring structure, resulting in poor water resistance. In addition, most of the polyester hot melt adhesives currently produced on the market are not easy to degrade and are not friendly to the environment. In recent years, with the development of the market and the improvement of people's living standards, higher requirements are put forward for the performance of polyamide hot melt adhesives. Therefore, the present invention provides a polyester hot melt adhesive for powder coatings with low melt viscosity, strong water resistance, easy degradation, suitable for processing and use, and a preparation method thereof. Summary of the invention

[0004] In order to solve the problems in the related art that polyamide hot melt adhesive has high viscosity, is difficult to coat, and has poor water resistance, the present invention provides a polyester hot melt adhesive for powder coating and a preparation method thereof.

[0005] The invention provides a polyester hot melt adhesive for powder coatings. The preparation raw materials of the polyester hot melt adhesive are composed of a main material and auxiliary materials. The main material is composed of a polyacid and a polyol, wherein the polyacid is composed of a mixture of terephthalic acid, fumaric acid and succinic acid; the polyol is composed of a mixture of ethylene glycol and 1,2-pentanediol; and the auxiliary materials include a catalyst, a modifier and a viscosity regulator.

[0006] Furthermore, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4-6:2-4:1.

[0007] Furthermore, the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3-5:1-3.

[0008] Furthermore, the catalyst is dibutyltin phthalate and / or tetrabutyl titanate.

[0009] Furthermore, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1-0.5:1.

[0010] Further, the modifier is prepared by the following steps:

[0011] (1) Add furfural, vanillin and polyethylene glycol to anhydrous ethanol, stir and dissolve, then add hydrochloric acid solution, control the reaction temperature to 60°C-80°C, stir and react for 3h-5h, after the reaction is completed, wash the reaction product with water, and remove the solvent by vacuum distillation to obtain an acetal product;

[0012] (2) Add the acetal product, lignin and rosin resin into anhydrous ethanol, add glutaraldehyde, stir and react at a temperature of 40°C-60°C for 2-4 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain a modifier.

[0013] Furthermore, in step (1), the mass ratio of furfural, vanillin and polyethylene glycol is 30-50:20-40:18-20.

[0014] Furthermore, in step (2), the mass ratio of the acetal product, lignin and rosin resin is 30-50:3-5:6-8.

[0015] Furthermore, the viscosity modifier is at least one of palm wax, paraffin wax and beeswax.

[0016] Furthermore, the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1-3.

[0017] The present invention also proposes a method for preparing the polyester hot melt adhesive for powder coating, comprising the following steps:

[0018] S1. Add polyacid, polyol and catalyst into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C-200°C for 1h-3h to obtain a prepolymer;

[0019] S2, adding the prepolymer, the modifier and the viscosity regulator into the reactor, and performing a reduced pressure polyurethane reaction at 220° C.-240° C.;

[0020] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, cutting into pellets and drying, thereby obtaining the polyester hot melt adhesive for powder coating.

[0021] Furthermore, in step S1, the mass ratio of the polyacid, the polyol and the catalyst is 100:150-170:4-8.

[0022] Furthermore, in step S2, the mass ratio of the prepolymer, the modifier and the viscosity regulator is 80-100:4-6:10-12.

[0023] In summary, the present invention has the following beneficial effects:

[0024] 1. The present invention designs raw materials and proportions, and adds modifiers and viscosity regulators during the preparation of polyester hot melt adhesives. The prepared polyester hot melt adhesive for powder coatings has strong water resistance, toughness, easy degradation and low melt viscosity, making it more convenient in processing and use and longer in service life.

[0025] 2. The present invention uses terephthalic acid, fumaric acid and succinic acid as polyacids, and ethylene glycol and 1,2-pentanediol as polyols. Among them, terephthalic acid has good chemical stability, which can give polyester materials higher tensile strength and tensile strength, and enhance the wear resistance and weather resistance of the product; fumaric acid and succinic acid are derived from natural substances and have good biodegradability. Their addition can not only synergistically enhance the thermal properties and mechanical properties of polyester materials, but also further improve the environmental friendliness of polyester materials.

[0026] 3. The present invention adds a modifier during the preparation process of the polyester hot melt adhesive. The modifier is obtained by further reacting furfural, vanillin and polyethylene glycol with lignin and rosin resin after an alcohol-aldehyde condensation reaction. The introduction of lignin and rosin resin can improve the adhesion of the polyester hot melt adhesive and enhance the product's high temperature resistance, moisture resistance and corrosion resistance. Glutaraldehyde, as a cross-linking agent, can increase the density of the polyester hot melt adhesive and improve the bonding strength and durability of the polyester hot melt adhesive. The addition of the modifier enhances the bonding strength, heat resistance and cold resistance of the polyester hot melt adhesive. At the same time, this reaction introduces a benzene ring structure, which helps to improve the water resistance of the product and also enhances the toughness and mechanical properties of the product. When the modifier is combined with the prepolymer, the aldehyde ester further undergoes a condensation reaction, and a new carbon-carbon bond is formed again, the carbon chain is increased, and the hydrolysis stability of the product is further improved, which helps to extend the service life.

[0027] 4. The present invention mixes palm wax and beeswax to prepare a viscosity regulator. The compound use of palm wax and beeswax can synergistically adjust the viscosity of polyester hot melt adhesive to meet the needs of different application scenarios. Palm wax and beeswax are both natural waxes. Mixing them can also give polyester hot melt adhesive better gloss and appearance, thereby improving the quality of polyester hot melt adhesive. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the embodiments.

[0029] Rosin resin (purchased from Guangzhou Songbao Chemical Co., Ltd., model SBR-90), lignin (purchased from Leling Chenhao Polymer Technology Co., Ltd., model 1-111), palm wax (purchased from Shanghai Yiba Chemical Raw Materials Co., Ltd., model: T1), beeswax (purchased from Dongguang County Jinsen Wax Products Co., Ltd., model: 002) used in the embodiments of the present invention and the comparative examples.

[0030] Embodiments 1-5 provide a polyester hot melt adhesive for powder coating and a preparation method thereof.

[0031] Example 1

[0032] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0033] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4:2:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0034] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1;

[0035] The modifier is prepared by the following preparation method:

[0036] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 30:20:18, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0037] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 30:3:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0038] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0039] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0040] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0041] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0042] Example 2

[0043] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0044] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4.5:2.5:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3.5:1.5;

[0045] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.2:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1.5; the modifier is prepared by the following preparation method:

[0046] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 35:25:18.5, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 65°C and 450 r / min for 3.5 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0047] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 35:3.5:6.5, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 45°C for 2.5 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0048] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0049] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:155:5, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 185°C for 1.5h to obtain a prepolymer;

[0050] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 85:4.5:10.5, and carry out polycondensation under reduced pressure at 225°C. The polycondensation pressure is controlled to be 170Pa, and the reaction time is 2.5h.

[0051] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 85° C. and the drying time is 40 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0052] Example 3

[0053] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0054] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 5:3:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 4:2;

[0055] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.3:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:2; the modifier is prepared by the following preparation method:

[0056] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 40:30:19, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 70°C and 500 r / min for 4 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0057] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 40:4:7, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 50°C for 3 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0058] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0059] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:160:6, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 190°C for a reaction time of 2h to obtain a prepolymer;

[0060] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 90:5:11, and carry out polycondensation under reduced pressure at 230°C, controlling the polycondensation pressure to 190Pa and the reaction time to 3h;

[0061] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 90° C. and the drying time is 45 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0062] Example 4

[0063] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0064] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 5.5:3.5:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 4.5:2.5;

[0065] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.4:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:2.5; the modifier is prepared by the following preparation method:

[0066] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 45:35:19.5, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 75°C and 550 r / min for 4.5 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0067] (2) The acetal product, lignin and rosin resin were added to anhydrous ethanol (the amount was 10 times the amount of the acetal product) in a mass ratio of 45:4.5:7.5, and glutaraldehyde (the amount was 10% of the amount of the acetal product) was added. The mixture was stirred at 55°C for 3.5 hours, and then the solvent was removed by reduced pressure distillation to obtain a modifier.

[0068] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0069] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:165:7, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 195°C for a reaction time of 2.5h to obtain a prepolymer;

[0070] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 95:5.5:11.5, and carry out polycondensation under reduced pressure at 235°C. The polycondensation pressure is controlled to be 210Pa, and the reaction time is 3.5h.

[0071] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 95° C. and the drying time is 50 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0072] Example 5

[0073] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0074] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 6:4:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 5:3;

[0075] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.5:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:3; the modifier is prepared by the following preparation method:

[0076] (1) Furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural) in a mass ratio of 50:40:20, stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 80°C and 600 r / min for 5 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0077] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 50:5:8, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 60°C for 4 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0078] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0079] S1. Add polyacid, polyol and catalyst into a reaction kettle in a mass ratio of 100:170:8, and carry out esterification reaction at a reaction temperature of 200°C for 3 hours to obtain a prepolymer;

[0080] S2. Add the prepolymer, modifier and viscosity modifier into the reactor at a mass ratio of 100:6:12, and carry out polycondensation under reduced pressure at 240°C. The polycondensation pressure is controlled to be 230 Pa, and the reaction time is 4 hours.

[0081] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 100° C. and the drying time is 55 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0082] Comparative Example 1

[0083] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0084] Among the main ingredients, the polyacid is terephthalic acid; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0085] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0086] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 30:20:18, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0087] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 30:3:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0088] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0089] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:0.4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0090] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0091] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0092] Comparative Example 2

[0093] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0094] Among the main ingredients, the polyacid is composed of terephthalic acid and fumaric acid mixed in a mass ratio of 4:2; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0095] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0096] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 30:20:18, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0097] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 30:3:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0098] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0099] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0100] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0101] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0102] Comparative Example 3

[0103] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0104] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4:2:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0105] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0106] (1) According to the mass ratio of furfural to polyethylene glycol 200 of 50:18, furfural and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 12 times the amount of furfural), stirred and dissolved, and then a hydrochloric acid solution with a mass concentration of 60% (the amount is 6% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0107] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 30:3:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0108] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0109] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0110] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0111] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0112] Comparative Example 4

[0113] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0114] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4:2:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0115] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0116] (1) According to the mass ratio of furfural, 3-methylbutyraldehyde and polyethylene glycol 200 being 30:20:18, furfural, 3-methylbutyraldehyde and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a hydrochloric acid solution with a mass concentration of 60% (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0117] (2) The acetal product, lignin and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) in a mass ratio of 30:3:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0118] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0119] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0120] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0121] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0122] Comparative Example 5

[0123] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0124] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4:2:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0125] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0126] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 30:20:18, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0127] (2) The acetal product and lignin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) at a mass ratio of 30:3, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0128] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0129] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0130] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0131] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0132] Comparative Example 6

[0133] The invention discloses a polyester hot melt adhesive for powder coating, the raw materials of which are composed of main materials and auxiliary materials.

[0134] Among the main ingredients, the polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4:2:1; the polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3:1;

[0135] Among the auxiliary materials, the catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1:1; the viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1; the modifier is prepared by the following preparation method:

[0136] (1) According to the mass ratio of furfural, vanillin and polyethylene glycol 200 being 30:20:18, furfural, vanillin and polyethylene glycol 200 are added to anhydrous ethanol (the amount is 20 times the amount of furfural), stirred and dissolved, and then a 60% hydrochloric acid solution (the amount is 10% of the amount of furfural) is added, and stirred at 60°C and 400 r / min for 3 hours. The reaction product is washed with water and then distilled under reduced pressure to obtain an acetal product;

[0137] (2) The acetal product and rosin resin are added to anhydrous ethanol (the amount is 10 times the amount of the acetal product) at a mass ratio of 30:6, and glutaraldehyde (the amount is 10% of the amount of the acetal product) is added. The mixture is stirred and reacted at 40°C for 2 hours, and then the solvent is removed by reduced pressure distillation to obtain a modifier.

[0138] A method for preparing a polyester hot melt adhesive for powder coatings comprises the following steps:

[0139] S1. According to the mass ratio of polyacid, polyol and catalyst of 100:150:4, polyacid, polyol and catalyst are added into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C for 1 hour to obtain a prepolymer;

[0140] S2. Add the prepolymer, modifier and viscosity modifier into the reactor in a mass ratio of 80:4:10, and carry out polycondensation under reduced pressure at 220°C, controlling the polycondensation pressure to 150 Pa and the reaction time to 2 h;

[0141] S3, releasing the vacuum by passing nitrogen, discharging the material while hot, and then pelletizing and drying the material. The drying temperature is controlled to be 80° C. and the drying time is 35 min, thereby obtaining the polyester hot melt adhesive for powder coating.

[0142] Performance Testing

[0143] The comprehensive properties of the polyester hot melt adhesives for powder coatings prepared in Examples 1-5 of the present invention and Comparative Examples 1-6 were tested respectively.

[0144] 1. Melt viscosity test

[0145] The melt viscosity of the sample was tested using a Brookfield DV-E rotational viscometer. 10 g of the polyamide hot melt adhesive sample prepared in Examples 1-5 and Comparative Examples 1-6 was weighed. During the test, a rotor of model S27 was selected, the temperature was controlled at 220° C., and the rotation rate was continuously adjusted so that the test value was within the linear range of 20%-90%. The measured value was recorded after stabilization. The results are shown in Table 1.

[0146] 2. Peel strength test

[0147] According to the standard GB / T 2790-1995 "Adhesive 180 degree peel strength test method - Flexible material to rigid material", the polyester hot melt adhesives prepared in Examples 1-5 and Comparative Examples 1-6 were preheated at 100°C for 2h, and then evenly coated on the surface of polypropylene plastic to obtain a 5mm thick adhesive layer. After aging for 24h, the peel strength was measured. The measurement results are shown in Table 1.

[0148] 3. Softening point test

[0149] The softening points of the polyester hot melt adhesives prepared in Examples 1-5 and Comparative Examples 1-6 were measured according to the standard GB-T15332-1994. The measurement results are shown in Table 1.

[0150] 4. Water resistance determination

[0151] The polyester hot melt adhesives prepared in Examples 1-5 and Comparative Examples 1-6 were preheated at 100°C for 2h, and then evenly coated on the surface of polypropylene plastic to obtain an adhesive layer with a thickness of 5mm. After aging for 24h, the adhesive layer was immersed in deionized water at 70°C for 10d and dried at room temperature. The peel strength retention rate was tested according to the standard GB / T 2790-1995 "Test method for 180 degree peel strength of adhesives - flexible materials to rigid materials". The test results are shown in Table 1.

[0152] 5. Determination of elongation at break

[0153] According to the standard GB / T 1040.1-2018 "Determination of tensile properties of plastics Part 1: General", the elongation at break of the polyester hot melt adhesives prepared in Examples 1-5 and Comparative Examples 1-6 was measured, and the measurement results are shown in Table 1.

[0154] Table 1 Performance data of examples and comparative examples

[0155]

[0156] It can be seen from the data in Table 1 that compared with Comparative Examples 1-2, Example 3 replaces the polyacid with a polyester hot melt adhesive for powder coating prepared by only terephthalic acid or a mixture of terephthalic acid and fumaric acid in Comparative Examples 1-2. The test result is worse than that of Example 3, indicating that the use of terephthalic acid, fumaric acid and succinic acid as polyacids can improve the heat resistance, water resistance and toughness of the polyester hot melt adhesive, and has good environmental protection, thereby expanding its application range.

[0157] By comparing Example 3 with Comparative Examples 3-6, it can be seen that the polyester hot melt adhesive for powder coating prepared in Comparative Examples 3-6 without adding vanillin or replacing vanillin with 3-methylbutyraldehyde or without adding rosin resin or without adding lignin, the test results are worse than those of Example 3, indicating that furfural, vanillin and polyethylene glycol 200 first undergo an alcohol-aldehyde condensation reaction, and then further react with lignin and rosin resin, which can not only extend the carbon chain and improve the water resistance and heat resistance of the polyester hot melt adhesive, but also adjust the fusion viscosity of the polyester hot melt adhesive and enhance the toughness and mechanical properties of the polyester hot melt adhesive.

[0158] It can be seen from Table 1 above that the polyester hot melt adhesive for powder coating prepared in Examples 1-5 has better comprehensive performance than the polyester hot melt adhesive for powder coating prepared in Comparative Examples 1-6, and can meet the performance requirements. This shows that the prepared polyester hot melt adhesive for powder coating has strong water resistance, heat resistance, toughness, environmental protection and low melt viscosity, and has high application value.

[0159] The specific embodiments of the present invention are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A polyester hot melt adhesive for powder coating, characterized in that: The raw materials for its preparation are composed of main materials and auxiliary materials. The main materials are composed of polyacids and polyols, wherein the polyacids are a mixture of terephthalic acid, fumaric acid and succinic acid; the polyols are a mixture of ethylene glycol and 1,2-pentanediol; the auxiliary materials include catalysts, modifiers and viscosity regulators; The catalyst is composed of dibutyltin phthalate and tetrabutyl titanate mixed in a mass ratio of 0.1-0.5:1; The modifying agent is prepared by the following steps: (1) Add furfural, vanillin and polyethylene glycol to anhydrous ethanol, stir and dissolve, then add hydrochloric acid solution, control the reaction temperature to 60°C-80°C, stir and react for 3h-5h, after the reaction is completed, wash the reaction product with water, and remove the solvent by vacuum distillation to obtain an acetal product; (2) adding the acetal product, lignin and rosin resin into anhydrous ethanol, adding glutaraldehyde, stirring and reacting at a temperature of 40°C-60°C for 2-4 hours, and after the reaction is completed, removing the solvent by reduced pressure distillation to obtain a modifier; The viscosity regulator is composed of palm wax and beeswax mixed in a mass ratio of 1:1-3.

2. The polyester hot melt adhesive for powder coating according to claim 1, characterized in that: The polyacid is composed of terephthalic acid, fumaric acid and succinic acid mixed in a mass ratio of 4-6:2-4:

1.

3. The polyester hot melt adhesive for powder coating according to claim 1, characterized in that: The polyol is composed of ethylene glycol and 1,2-pentanediol mixed in a mass ratio of 3-5:1-3.

4. The polyester hot melt adhesive for powder coating according to claim 1, characterized in that: In step (1), the mass ratio of furfural, vanillin and polyethylene glycol is 30-50:20-40:18-20.

5. The polyester hot melt adhesive for powder coating according to claim 1, characterized in that: In step (2), the mass ratio of the acetal product, lignin and rosin resin is 30-50:3-5:6-8.

6. A method for preparing a polyester hot melt adhesive for powder coatings according to any one of claims 1 to 5, characterized in that: The steps include: S1. Add polyacid, polyol and catalyst into a reaction kettle to carry out esterification reaction at a reaction temperature of 180°C-200°C for 1h-3h to obtain a prepolymer; S2, adding the prepolymer, the modifier and the viscosity regulator into the reactor, and performing a reduced pressure polyurethane reaction at a temperature of 220° C. to 240° C.; S3, releasing the vacuum by passing nitrogen, discharging the material while hot, cutting into pellets and drying, thereby obtaining the polyester hot melt adhesive for powder coating.

7. The method for preparing a polyester hot melt adhesive for powder coating according to claim 6, characterized in that: In step S1, the mass ratio of the polyacid, the polyol and the catalyst is 100:150-170:4-8.

8. The method for preparing a polyester hot melt adhesive for powder coating according to claim 6, characterized in that: In step S2, the mass ratio of the prepolymer, the modifier and the viscosity regulator is 80-100:4-6:10-12.

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