Method for preparing a water-based adhesive for labels

Abstract

The application discloses a preparation method of a water-based adhesive for labels and belongs to the technical field of adhesives. The method comprises the following steps: in step S1, after oligomer polyol, isophorone diisocyanate and 2,2'-dihydroxymethyl butyric acid are stirred and mixed, the mixture is reacted by adding dibutyltin dilaurate under heating, then 1,4-butanediol is added for reaction after cooling, then dimethyl ethanedione is added, and the mixture is reacted at 80-85 DEG C for 4-6 h to obtain a capped prepolymer; in step S2, the capped prepolymer is cooled to 45-50 DEG C, and the viscosity is adjusted by adding acetone; when the temperature is reduced to 30 DEG C, triethylamine is added for neutralization, deionized water is added for emulsification, ethylenediamine is added for chain extension reaction, the temperature is increased to 60 DEG C for aging for 4 h, and acetone is removed by vacuum distillation to obtain the water-based adhesive for labels. The adhesive for labels prepared by the method has good fluidity, strong initial adhesion, fast drying speed and good storage stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesives, and particularly relates to a preparation method of a water-based adhesive for labels. BACKGROUND

[0002] The water-based adhesive is an environmentally friendly adhesive prepared by using natural polymers or synthetic polymers as adhesive materials and water as a solvent or dispersant. Since the volatility of water is poorer than that of organic solvents, the water-based adhesive dries more slowly. In addition, due to the large surface tension of water, the wetting ability of the water-based adhesive on a hydrophobic substrate is poor, and the initial adhesion is low. When most of the water in the adhesive layer is not volatilized into the air or absorbed by a porous substrate, and then heated for drying, it is not easy to obtain a continuous adhesive layer. When the water-based adhesive is used for label pasting, the label may be wrinkled, the edges may be curled, or the label may be detached, and the like. SUMMARY

[0003] The application aims to provide a preparation method of a water-based adhesive for labels to solve the problems in the background art.

[0004] The object of the application can be achieved by the following technical solutions.

[0005] A preparation method of a water-based adhesive for labels comprises the following steps.

[0006] In step S1, an oligomeric polyol, isophorone diisocyanate, 2,2'-dihydroxymethyl butyric acid, and dibutyltin dilaurate are added into a three-necked flask, and then stirred at a speed of 400 r / min. After that, the mixture is heated to 60 DEG C, and then dibutyltin dilaurate is added. Then, the mixture is heated to 80-90 DEG C and reacted for 4 h. After that, the mixture is cooled to 70 DEG C, and then 1,4-butanediol is added and reacted for 1-2 h. Then, dimethyl ethanedione is added, and the mixture is reacted at 80-85 DEG C for 4-6 h to obtain a capped prepolymer.

[0007] In step S2, the capped prepolymer is cooled to 45-50 DEG C, and then acetone is added to adjust the viscosity. After that, the temperature is reduced to 30 DEG C, and then triethylamine is added and neutralized for 5-7 min. Then, deionized water is added to emulsify. After the emulsification is completed, ethylenediamine is added and reacted for 30 min. Then, the mixture is heated to 60 DEG C and aged for 4 h. Finally, the acetone is removed by distillation under reduced pressure to obtain the water-based adhesive for labels.

[0008] Further, the mass ratio of the oligomeric polyol, isophorone diisocyanate, 2,2'-dihydroxymethyl butyric acid, dibutyltin dilaurate, 1,4-butanediol, dimethyl ethanedione, triethylamine, and ethylenediamine is 40-50:35-45:3-4:0.2-0.5:1.2-1.5:5-7:2.5-3:0.5-1.

[0009] Further, the rotation speed of the emulsification is 10000-20000r / min, and the emulsification time is 10-20min.

[0010] Further, the oligomer polyol is dehydrated in a vacuum drying oven at 80-85℃ for 2-3h.

[0011] Further, the oligomer polyol is a mixture of polyether triols and polybutylene glycol adipate with a mass ratio of 3-5:45.

[0012] Further, the polyether triols are prepared by the following steps:

[0013] Propylene oxide, citric acid and DMC catalyst are added into the dried high-pressure reaction kettle, the pressure in the high-pressure reaction kettle is balanced at 4-5MPa by introducing carbon dioxide in a water bath at 70℃, and the polymerization reaction is stirred for 10-12h, then cooled in an ice water bath, and the excess carbon dioxide is released, and the polyether triols are obtained after post-treatment. The polyether triols contain carbonate groups and ether groups.

[0014] Further, the molar ratio of propylene oxide and citric acid is 6-6.5:1, and the amount of DMC catalyst is 50-70ppm of the mass sum of propylene oxide and citric acid.

[0015] Further, the post-treatment includes dissolving the reaction product with dichloromethane, filtering to remove the DMC catalyst, and rotary evaporation to remove dichloromethane.

[0016] The beneficial effects of the present application are:

[0017] In the present application, carbon dioxide, propylene oxide and citric acid are polymerized under the catalysis of DMC catalyst to prepare polyether triols containing carbonate groups and ether groups. The prepared polyether triols and polybutylene glycol adipate are mixed as soft segments. The polyether triols contain carbonate groups and ether groups in the molecular chain, and the soft ether group segments are easily folded and aggregated into small particles during the emulsification process, thereby promoting the small and uniform emulsion particles after emulsification, improving the stability of the water-based adhesive, and improving the flowability of the water-based adhesive and the toughness of the film after curing, making the adhesive film smooth and flat, and having good wettability. When applied to label pasting, it can effectively prevent the label paper from wrinkling and warping. The ether group segment also has excellent hydrolysis resistance. The polyether triols react with isophorone diisocyanate to form a network cross-linked structure, which can inhibit the penetration and diffusion of water molecules in the adhesive film on the basis of the good water resistance of the ether group, increase the water resistance of the polyurethane, and prevent the label from falling off after being pasted in water.

[0018] The present application uses isophorone diisocyanate, 2,2'-dimethylol butyric acid and dimethyl ethanedione as hard segments, the molecular formula of dimethyl ethanedione contains imine groups, which can effectively form hydrogen bonding between molecular chains, making up for the negative impact of polyether triols on the crystallization performance of soft segments in polyurethane, together with the network structure formed by polyether triols, the density of the water-based sealant at the bonding point is improved, and then the initial adhesion of the water-based adhesive is improved;

[0019] The label adhesive prepared by the present application has good flowability, strong initial adhesion, fast drying speed and good storage stability. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] Embodiment 1

[0022] The polyether triol is prepared by the following steps:

[0023] Propylene oxide, citric acid and DMC catalyst are added to a dried high-pressure reaction kettle according to a molar ratio of 6:1, and the amount of DMC catalyst is 50ppm of the mass sum of propylene oxide and citric acid. In a water bath at a temperature of 70℃, carbon dioxide is introduced to balance the pressure in the high-pressure reaction kettle to 4MPa. The stirring polymerization reaction is carried out for 12h, then cooled in an ice water bath, and the excess carbon dioxide is released. The reaction product is dissolved with dichloromethane, filtered to remove the DMC catalyst, and rotary evaporated to remove dichloromethane, to obtain the polyether triol. The polyether triol contains carbonate groups and ether groups.

[0024] Embodiment 2

[0025] The polyether triol is prepared by the following steps:

[0026] Propylene oxide, citric acid and DMC catalyst are added to a dried high-pressure reaction kettle according to a molar ratio of 6.2:1, and the amount of DMC catalyst is 60ppm of the mass sum of propylene oxide and citric acid. In a water bath at a temperature of 70℃, carbon dioxide is introduced to balance the pressure in the high-pressure reaction kettle to 4.5MPa. The stirring polymerization reaction is carried out for 11h, then cooled in an ice water bath, and the excess carbon dioxide is released. The reaction product is dissolved with dichloromethane, filtered to remove the DMC catalyst, and rotary evaporated to remove dichloromethane, to obtain the polyether triol. The polyether triol contains carbonate groups and ether groups.

[0027] Embodiment 3

[0028] The polyether triol is prepared by the following steps:

[0029] The propylene oxide, citric acid and DMC catalyst are added into the dried high-pressure reaction kettle in a molar ratio of 6.5:1, and the amount of the DMC catalyst is 70 ppm of the total mass of the propylene oxide and the citric acid. The pressure in the high-pressure reaction kettle is balanced at 5 MPa by introducing carbon dioxide in a water bath at a temperature of 70°C. The polymerization reaction is stirred for 10 h, then cooled in an ice water bath, and the excess carbon dioxide is released. The reaction product is dissolved in dichloromethane, filtered to remove the DMC catalyst, and rotary evaporated to remove the dichloromethane, to obtain the polyether triol. The polyether triol contains carbonate groups and ether groups.

[0030] Example 4

[0031] The present embodiment provides a preparation method of a water-based adhesive for labels, comprising the following steps:

[0032] Step S1, the polyether triol prepared in Example 1 is mixed with polybutylene glycol adipate at a mass ratio of 3:45 to form an oligomer polyol. 40 parts by weight of the oligomer polyol, 35 parts by weight of isophorone diisocyanate, and 3 parts by weight of 2,2'-dimethylol butyric acid are added into a three-necked flask, and then stirred and mixed at a speed of 400 r / min. Then the temperature is raised to 60°C, 0.2 parts by weight of dibutyltin dilaurate is added, and then the temperature is raised to 80°C for reaction for 4 h. After cooling to 70°C, 1.2 parts by weight of 1,4-butanediol is added for reaction for 1 h, and then 5 parts by weight of dimethylglyoxime is added for reaction for 6 h at 80°C, to obtain a capped prepolymer.

[0033] Step S2, the capped prepolymer is cooled to 45°C, and then acetone is added to adjust the viscosity. When the temperature is reduced to 30°C, 2.5 parts by weight of triethylamine is added for neutralization for 5 min, and then deionized water is added for emulsification at a speed of 10,000 r / min for 20 min. After the emulsification is completed, 0.5 parts by weight of ethylenediamine is added for chain extension reaction for 30 min, and then the temperature is raised to 60°C for curing for 4 h. Finally, the acetone is removed by distillation under reduced pressure, to obtain the water-based adhesive for labels.

[0034] Example 5

[0035] The present embodiment provides a preparation method of a water-based adhesive for labels, comprising the following steps:

[0036] Step S1, the polyether triol prepared in Example 2 was mixed with polybutylene glycol adipate in a mass ratio of 4:45 to form an oligomer polyol, 45 parts by weight of the oligomer polyol, 40 parts by weight of isophorone diisocyanate, 3.5 parts by weight of 2,2'-dimethylol butyric acid were added to a three-necked flask, mixed by stirring at a speed of 400 r / min, then heated to 60°C and 0.4 parts by weight of dibutyltin dilaurate was added, then heated to 85°C and reacted for 4h, cooled to 70°C and then 1.3 parts by weight of 1,4-butanediol was added and reacted for 1.5h, then 6 parts by weight of dimethylglyoxime was added and reacted for 5h at 83°C to obtain a capped prepolymer;

[0037] Step S2, the capped prepolymer was cooled to 48°C, acetone was added to adjust the viscosity, and when the temperature dropped to 30°C, 2.8 parts by weight of triethylamine was added and neutralized for 6min, then deionized water was added and emulsified at a speed of 15000 r / min for 15min, after the emulsification was completed, 0.8 parts by weight of ethylenediamine was added and chain-extended for 30min, then heated to 60°C and aged for 4h, and finally distilled under reduced pressure to remove acetone to obtain a water-based adhesive for labels.

[0038] Example 6

[0039] The present embodiment provides a preparation method of a water-based adhesive for labels, comprising the following steps:

[0040] Step S1, the polyether triol prepared in Example 3 was mixed with polybutylene glycol adipate in a mass ratio of 1:9 to form an oligomer polyol, 50 parts by weight of the oligomer polyol, 45 parts by weight of isophorone diisocyanate, 4 parts by weight of 2,2'-dimethylol butyric acid were added to a three-necked flask, mixed by stirring at a speed of 400 r / min, then heated to 60°C and 0.5 parts by weight of dibutyltin dilaurate was added, then heated to 90°C and reacted for 4h, cooled to 70°C and then 1.5 parts by weight of 1,4-butanediol was added and reacted for 2h, then 7 parts by weight of dimethylglyoxime was added and reacted for 4h at 85°C to obtain a capped prepolymer;

[0041] Step S2, the capped prepolymer was cooled to 50°C, acetone was added to adjust the viscosity, and when the temperature dropped to 30°C, 3 parts by weight of triethylamine was added and neutralized for 7min, then deionized water was added and emulsified at a speed of 20000 r / min for 10min, after the emulsification was completed, 1 part by weight of ethylenediamine was added and chain-extended for 30min, then heated to 60°C and aged for 4h, and finally distilled under reduced pressure to remove acetone to obtain a water-based adhesive for labels.

[0042] Comparative Example 1

[0043] The comparative example is compared with Example 5, and an equal amount of polybutylene adipate glycol is used to replace the oligomer polyol, i.e., the polyether triol prepared in Example 2 is replaced with an equal amount of polybutylene adipate glycol, and the remaining raw materials and preparation methods are the same.

[0044] Comparative Example 2

[0045] The comparative example is compared with Example 5, and an equal amount of butanone oxime is used to replace dimethylglyoxime, and the remaining raw materials and preparation methods are the same.

[0046] The water-based adhesives prepared in Examples 4-6 and Comparative Examples 1-2 are tested for performance:

[0047] The water-based adhesives are poured into a polytetrafluoroethylene tray, dried at room temperature for 7 days, dried in a vacuum oven at 40°C for 24h, and then the adhesive film is made into a dumbbell shape, and its elongation at break and tensile strength are tested on a universal testing machine;

[0048] The peel strength of the water-based adhesive is tested according to the GB / T 2941-2006 standard;

[0049] The peel strength of the water-based adhesive after soaking in water at 25°C for 5 days is tested according to the GB / T 532-2008 standard;

[0050] The initial adhesion of the water-based adhesive is tested according to the GB / T 2791-1995 standard.

[0051] The results are shown in Table 1:

[0052] Table 1

[0053] Test item Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Tensile strength MPa 17.8 18.3 18.1 17.7 14.3 Elongation at break % 958 995 1050 475 736 Peel strength N / cm 90.5 92.2 92.6 86.8 66.9 Water resistance N / cm 81.7 82.5 83.2 44.3 74.8 Initial tack N / cm 8.3 8.6 8.8 8.9 6.2

[0054] As can be seen from the data in Table 1, the water-based adhesives prepared in Examples 4-6 have excellent tensile strength and elongation at break compared with Comparative Examples 1-2, and also have higher initial adhesion and peel strength, and even after water soaking, still maintain a relatively high peel strength, with excellent water resistance.

[0055] It should be noted that in this document, relational terms such as first and second and the like can only be used to distinguish one entity or action from another entity or action, without necessarily requiring or implying that there is any such actual relationship or order between these entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof are intended to cover non-exclusive inclusions, so that a process, method, article, or apparatus that includes a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0056] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing an aqueous adhesive for labels, characterized by, The method comprises the following steps: Step S1, adding oligomer polyol, isophorone diisocyanate, 2,2'-dimethylol butyric acid into a three-mouth flask, mixing at a stirring speed of 400 r / min, then heating to 60 DEG C and adding dibutyltin dilaurate, further heating to 80-90 DEG C and reacting for 4 h, cooling to 70 DEG C and adding 1,4-butanediol and reacting for 1-2 h, then adding dimethylglyoxime and reacting for 4-6 h at 80-85 DEG C to obtain a capped prepolymer; Step S2, cooling the capped prepolymer to 45-50 DEG C, adding acetone to adjust the viscosity, cooling to 30 DEG C, adding triethylamine and neutralizing for 5-7 min, then adding deionized water to emulsify, after the emulsification is completed, adding ethylenediamine and chain extending for 30 min, further heating to 60 DEG C and aging for 4 h, and finally distilling and removing acetone under reduced pressure to obtain a water-based adhesive for labels; The oligomer polyol is a mixture of polyether triol and polybutylene glycol adipate in a mass ratio of 3-5:45; The polyether triol is prepared by the following steps: Adding propylene oxide, citric acid and DMC catalyst into a dried high-pressure reaction kettle, balancing the pressure in the high-pressure reaction kettle to 4-5 MPa by introducing carbon dioxide in a water bath at 70 DEG C, stirring and polymerizing for 10-12 h, then cooling in an ice water bath and releasing excess carbon dioxide, and after treatment, obtaining the polyether triol.

2. The method for preparing a water-based adhesive for labels according to claim 1, characterized in that, The mass ratio of the oligomer polyol, isophorone diisocyanate, 2,2'-dimethylol butyric acid, dibutyltin dilaurate, 1,4-butanediol, dimethylglyoxime, triethylamine and ethylenediamine is 40-50:35-45:3-4:0.2-0.5:1.2-1.5:5-7:2.5-3:0.5-1.

3. The method for preparing a water-based adhesive for labels according to claim 1, characterized in that, The emulsification speed is 10000-20000 r / min and the emulsification time is 10-20 min.

4. The method for preparing a water-based adhesive for labels according to claim 1, characterized in that, The oligomer polyol is dehydrated in a vacuum drying oven at 80-85 DEG C for 2-3 h before use.

5. The method for preparing a water-based adhesive for labels according to claim 1, characterized in that, The molar ratio of propylene oxide and citric acid is 6-6.5:1, and the amount of DMC catalyst is 50-70 ppm of the mass sum of propylene oxide and citric acid.

6. The method for preparing a water-based adhesive for labels according to claim 1, characterized in that, The after-treatment comprises dissolving the reaction product with dichloromethane, filtering and separating to remove the DMC catalyst, and rotary evaporation to remove dichloromethane.