A kind of blocked waterborne polyisocyanate curing agent and its preparation

Abstract

The present invention belongs to the technical field of polymer materials, and in particular to a closed water-based polyisocyanate curing agent and its preparation. Based on a total mass of 100 parts, each component is: 20-30 parts of isocyanate polymer, 3-10 parts of aminosulfonate, 8-15 parts of sealing agent, 0-4 parts of polyethylene glycol monoether, and 50-65 parts of water. The present invention uses aminosulfonate as a hydrophilic group to prepare a water-based polyisocyanate curing agent, which has excellent storage stability and water-based resin compatibility, and excellent aging resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to a blocked water-based polyisocyanate curing agent and a preparation method thereof. Background Art

[0002] Inkjet printing is a new printing method that is fast and easy to operate. The adhesive, as a major component, plays a decisive role in the color fastness, printing feel, and color development of inkjet printing. As a commonly used inkjet adhesive, two-component water-based polyurethane is generally composed of a water-based resin main agent and a curing agent. The water-based polyisocyanate curing agent generally reacts with the groups on the main agent molecular chain to cross-link, thereby improving the color fastness performance of inkjet printing.

[0003] Conventional water-based polyisocyanate curing agents contain isocyanate groups (-NCO), which are very easy to react with water and are difficult to preserve. Therefore, general curing agents are prepared before the use of two-component water-based polyurethane, which is a cumbersome process. During the preparation process, some organic solvents are often added to reduce the viscosity, which will cause volatile organic compound (VOC) pollution, which is not conducive to the cleanliness of the fabric, and the residual organic solvents are also harmful to human health.

[0004] Blocked polyisocyanate curing agent is a kind of polyisocyanate curing agent that uses a blocking agent to protect the highly active isocyanate group, so that it can be stored for a long time in the water-based emulsion. When using, the curing agent is heated to a certain temperature to release the blocking of the isocyanate group and cause a curing reaction. This method can reduce the reaction between the isocyanate group and water, effectively extend the storage time of the polyisocyanate curing agent, reduce the ink preparation process, and increase the stability of the ink.

[0005] The aminosulfonic acid used in patent CN116209692A is a secondary amine group, which is grafted with a cyclohexyl group to reduce the polarity of aminosulfonic acid, so that it can react with isocyanate at high temperature. Its raw material structure is relatively complex and difficult to synthesize, and it requires high temperature to be processed, which increases energy consumption and reduces profits. The above patent does not block the isocyanate group, and it needs to be prepared with resin to form an emulsion when used, which increases the difficulty of operation for operators and increases the process steps.

[0006] In patent CN113508150, Mitsui Chemicals only uses polyoxyethylene methyl ether as the hydrophilic group, and the hydrophilic group content is higher than 10% to obtain a stable self-emulsifying blocked polyisocyanate. In this case, the high content of hydrophilic groups will reduce the rubbing color fastness of the printing and dyeing ink on the fabric, especially the wet rubbing color fastness. Summary of the invention

[0007] The purpose of the utility model is to provide a closed water-based sulfonate polyurethane curing agent, which is used as an adhesive for pigment ink for digital inkjet printing, and solves the problem that the curing agent of the two-component water-based polyurethane in the prior art needs to be configured on site before use, and the prepared water-based polyisocyanate curing agent has good storage stability and thermal stability.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A blocked waterborne polyisocyanate curing agent with sulfonate as the hydrophilic group.

[0010] A closed water-based sulfonate polyisocyanate curing agent contains isocyanate polymer, aminosulfonate, a sealing agent, polyethylene glycol monoether and water.

[0011] Furthermore, based on 100 parts by total weight, the components are: 20-30 parts of isocyanate polymer, 3-10 parts of aminosulfonate, 8-15 parts of blocking agent, 0-4 parts of polyethylene glycol monoether, and 50-65 parts of water.

[0012] The isocyanate polymer is selected from one or two of a trimer of diisocyanate and a reaction prepolymer of diisocyanate and a polyhydroxy compound.

[0013] The trimer of diisocyanate is one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and 4,4'-dicyclohexylmethane diisocyanate trimer;

[0014] The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, 4,4-diphenylmethane diisocyanate and 2,2,4-trimethyl-hexamethylene diisocyanate;

[0015] The polyhydroxy compound is one or more of trimethylolpropane, pentaerythritol and glycerol.

[0016] The structural formula of the aminosulfonate is NH2-R1-SO3 - wherein R1 is a linear or branched aliphatic group having 2 to 10 carbon atoms, preferably a linear or branched aliphatic group having 2 to 4 carbon atoms.

[0017] More preferably, the aminosulfonate is one or more of sodium 3-aminoisobutanesulfonate, sodium 4-amino-n-butanesulfonate, sodium 3-aminopropanesulfonate, and sodium 2-aminoethanesulfonate.

[0018] The polyethylene glycol monoether is one or more polyethylene glycols synthesized with a monohydric alcohol as an initiator, and the monohydric alcohol is a linear or branched aliphatic monohydric alcohol with 1 to 4 carbon atoms.

[0019] The number average molecular weight of the polyethylene glycol monoether is 300-1500 g / mol, such as 300, 500, 750, 1000, 1200, etc.;

[0020] Preferably, the polyethylene glycol monoether is polyethylene glycol monobutyl ether or polyethylene glycol monomethyl ether;

[0021] The blocking agent is one or more of 2-methylimidazole, 3,5-dimethylpyrazole, butanone oxime, acetone oxime, caprolactam, ethyl acetoacetate, diethyl malonate and phenol.

[0022] A method for preparing a blocked water-based polyisocyanate curing agent comprises the following steps: mixing an isocyanate polymer with a polyethylene glycol monoether to carry out a first step reaction, adding a blocking agent after the reaction is completed to carry out a second step reaction, cooling to room temperature after the reaction is completed, adding aminosulfonate to carry out a third step reaction, and emulsifying with water to obtain a water-based polyisocyanate curing agent with a solid content of 30%-50%.

[0023] The specific steps include:

[0024] (1) mixing an isocyanate polymer with polyethylene glycol monoether to obtain an isocyanate prepolymer;

[0025] (2) adding a blocking agent to the isocyanate prepolymer obtained in step (1) to react to obtain a blocked isocyanate prepolymer;

[0026] (3) adding aminosulfonate to the blocked isocyanate prepolymer obtained in step (2) for reaction at room temperature;

[0027] (4) adding water to step (3) for emulsification to obtain a blocked water-based polyisocyanate for curing.

[0028] The reaction temperature of step (1) is 70-90° C., the reaction time is 1-5 h, and the reaction is carried out under the protection of nitrogen.

[0029] When the blocking agent is 2-methylimidazole or 3,5-dimethylpyrazole, the reaction temperature of step (2) is 0-30°C, the blocking agent is added for 0.5-3h, and the reaction is carried out for 1h-3h;

[0030] When the blocking agent is butanone oxime, acetone oxime, caprolactam, ethyl acetoacetate, diethyl malonate, or phenol, the reaction temperature of step (2) is 80-100° C., the blocking agent is added for 1-3 hours, and the reaction is carried out for 1-3 hours.

[0031] The reaction temperature of step (3) is 20-30° C., the aminosulfonate is added for 10-30 min, and the reaction lasts for 20-40 min.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention uses aminosulfonate as a hydrophilic group to prepare a water-based polyisocyanate curing agent, which has excellent storage stability and compatibility with water-based resins and excellent aging resistance.

[0034] (2) The aqueous sulfonic acid type polyisocyanate curing agent of the present invention has low viscosity and excellent filterability. When used in inkjet printing resin adhesives, it has good color fastness and abrasion resistance and has almost no effect on the color development of the pigment.

[0035] (3) The water-based sulfonic acid type polyisocyanate curing agent of the present invention gets rid of the traditional water-based polyisocyanate curing agent which needs to be prepared on site before use, thus simplifying the operation of construction personnel; and can be mixed with resin for storage, thus reducing costs.

[0036] (4) The water-based sulfonic acid type polyisocyanate curing agent of the present invention has a simple synthesis process and can be produced on a large scale.

[0037] (5) The present invention can obtain a stable water-based polyisocyanate curing agent by using aminosulfonate alone, which is applied to inkjet printing adhesives; at the same time, a small amount of polyethylene glycol monoether can be added to adjust the filterability and viscosity of the water-based polyisocyanate curing agent.

[0038] (6) The raw materials used in the present invention are easy to obtain, the reaction temperature is low and the reaction rate is fast, which reduces energy consumption; and the product of the present invention can be directly mixed with resin for storage, without the need for on-site preparation when used, thereby reducing cumbersome preparation process steps. DETAILED DESCRIPTION

[0039] The methods and results of the present invention are further described in conjunction with specific examples. The following examples do not constitute any limitation on the scope of protection claimed by the present invention.

[0040] Example 1

[0041] A blocked water-based sulfonate polyisocyanate curing agent, the total weight of raw materials is measured as follows: 26.7 parts of hexamethylene diisocyanate trimer, 8.7 parts of 2-methylimidazole, 9.6 parts of sodium 3-aminoisobutanesulfonate, and 55 parts of water.

[0042] The preparation method is:

[0043] (1) Hexamethylene diisocyanate trimer was placed in a four-necked flask, and 2-methylimidazole was added at 25° C. for 1 hour. The reaction was continued for 1 hour to obtain a blocked isocyanate prepolymer.

[0044] (2) Sodium 3-aminoisobutanesulfonate was dissolved in water of equal mass and slowly added dropwise into the above four-necked flask at an increased speed at 25° C. The addition time was 10 min and the reaction was continued for 30 min.

[0045] (3) Finally, the remaining mass of water is added thereto for emulsification to obtain a blocked water-based polyisocyanate curing agent with a solid content of 45%.

[0046] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 9.9% of the solid content.

[0047] Example 2

[0048] A closed water-based sulfonate polyisocyanate curing agent, the total weight of raw materials is measured as 100 parts: 25.6 parts of isophorone diisocyanate trimer, 7.9 parts of 3,5-dimethylpyrazole, 5.6 parts of sodium 3-aminobutanesulfonate, 0.9 parts of polyethylene glycol monobutyl ether (number average molecular weight is 500), and 60 parts of water.

[0049] The preparation method is:

[0050] (1) Under nitrogen conditions, isophorone diisocyanate trimer and polyethylene glycol monobutyl ether were mixed and reacted at 85° C. for 2 h to obtain a polyurethane prepolymer.

[0051] (2) The prepolymer obtained in the above step was cooled to 25° C., 3,5-dimethylpyrazole was added for 1 hour, and the mixture was reacted at room temperature for another 1 hour.

[0052] (3) Add 50% sodium 3-aminobutanesulfonate aqueous solution to the reactant obtained in the above step at 25°C for 10 min and continue the reaction for 30 min.

[0053] (4) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 40%.

[0054] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 8.7% of the solid content.

[0055] Example 3

[0056] A blocked water-based sulfonate polyisocyanate curing agent comprises 100 parts of raw materials by total weight: 5.7 parts of trimethylolpropane, 22.7 parts of pentamethylene diisocyanate, 10.1 parts of butanone oxime, 4.4 parts of sodium 3-aminopropanesulfonate, 2.1 parts of polyethylene glycol monomethyl ether (number average molecular weight 1000), and 55 parts of water.

[0057] The preparation method is:

[0058] (1) Under nitrogen conditions, pentamethylene diisocyanate, trimethylolpropane and polyethylene glycol monomethyl ether were mixed and reacted at 85°C for 5 hours to obtain a polyurethane prepolymer.

[0059] (2) The prepolymer obtained in the above step was cooled to 80°C and butanone oxime was added for 1 hour.

[0060] The reaction was continued at 60°C for 2 h.

[0061] (3) The blocked prepolymer was cooled to room temperature, and a 50% aqueous solution of sodium 2-aminoethanesulfonate was added for 10 minutes, and the reaction was continued for 30 minutes.

[0062] (4) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 45%.

[0063] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 10.1% of the solid content.

[0064] Example 4

[0065] A closed water-based sulfonate polyisocyanate curing agent, the total weight of raw materials is measured based on 100 parts: 10.7 parts of hexamethylene diisocyanate trimer, 14.1 parts of isophorone diisocyanate trimer, 13.2 parts of ethyl acetoacetate, 4 parts of sodium aminopropanesulfonate, and 58 parts of water.

[0066] The preparation method is:

[0067] (1) Ethyl acetoacetate was added to a mixture of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer, and the temperature was raised to 100° C. under nitrogen protection. The addition time was

[0068] 1h, react for 3h to obtain a blocked isocyanate trimer.

[0069] (2) Cool the above-mentioned blocked isocyanate trimer to room temperature and add 30% sodium aminopropanesulfonate.

[0070] The aqueous solution was added for 10 min and the reaction was continued for 30 min.

[0071] (3) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 42%.

[0072] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 10.2% of the solid content.

[0073] Example 5

[0074] A closed water-based sulfonate polyisocyanate curing agent, the total weight of raw materials is measured as 100 parts: 30 parts of 4,4'-dicyclohexylmethane diisocyanate trimer, 8.5 parts of phenol, 3.6 parts of sodium 2-aminoethanesulfonate, 1.9 parts of polyethylene glycol monomethyl ether (number average molecular weight 1000), and 56 parts of water.

[0075] The preparation method is:

[0076] (1) Under nitrogen conditions, 4,4'-dicyclohexylmethane diisocyanate trimer and polyethylene glycol monomethyl ether were mixed and gradually heated to 85°C and reacted for 1 hour to obtain an isocyanate polymer.

[0077] (2) When the temperature of the isocyanate polymer is raised to 95° C., phenol is slowly added dropwise for 2 hours and the reaction is continued for 2 hours to obtain a blocked isocyanate polymer.

[0078] (3) The above isocyanate polymer was cooled to room temperature, and a 50% aqueous solution of sodium 2-aminoethanesulfonate was added for 10 minutes, and the reaction was continued for 30 minutes.

[0079] (4) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 44%.

[0080] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 9.0% of the solid content.

[0081] Comparative Example 1

[0082] A closed water-based sulfonate polyisocyanate curing agent, the total weight of the raw materials is measured based on 100 parts: 4.2 parts of polyethylene glycol monomethyl ether, 18.6 parts of hexamethylene diisocyanate trimer, 7.2 parts of 3,5-dimethylpyrazole, 70 parts of water

[0083] (1) Under nitrogen conditions, hexamethylene diisocyanate trimer and polyethylene glycol monomethyl ether were mixed and the temperature was gradually raised to 85° C. and reacted for 2 h to obtain an isocyanate polymer.

[0084] (2) The prepolymer obtained in the above step was cooled to 25° C., 3,5-dimethylpyrazole was added for 1 hour, and the mixture was reacted at room temperature for another 1 hour.

[0085] (3) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 30%.

[0086] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 10.5% of the solid content.

[0087] Comparative Example 2

[0088] A closed water-based sulfonate polyisocyanate curing agent, the total weight of the raw materials is measured based on 100 parts: 1.5 parts of polyethylene glycol monobutyl ether, 24.7 parts of hexamethylene diisocyanate trimer, 9.7 parts of 3,5-dimethylpyrazole, 2.1 parts of sodium alanine, 62 parts of water

[0089] (1) Under nitrogen conditions, hexamethylene diisocyanate trimer and polyethylene glycol monobutyl ether were mixed and the temperature was gradually raised to 85° C. and reacted for 2 h to obtain an isocyanate polymer.

[0090] (2) The prepolymer obtained in the above step was cooled to 25° C., 3,5-dimethylpyrazole was added for 1 hour, and the mixture was reacted at room temperature for another 1 hour.

[0091] (3) The above isocyanate polymer was cooled to room temperature, and a 50% aqueous solution of sodium alanine was added for 10 minutes, and the reaction was continued for 30 minutes.

[0092] (4) Finally, the remaining mass of water is added thereto to obtain a blocked water-based polyisocyanate curing agent with a solid content of 38%.

[0093] The effective blocked NCO content of the blocked waterborne polyisocyanate curing agent is 10.0% of the solid content.

[0094] Evaluation experiment:

[0095] Under the same test conditions, the performance of the water-based sulfonic acid type polyisocyanate curing agent of Examples 1-5 and Comparative Examples 1-2 was tested, and the test method was as follows:

[0096] (1) Viscosity test, test method: rotational viscometer, 25°C, rotor No. 0

[0097] (2) Particle size test, test method: nanoparticle size analyzer, 25℃

[0098] (3) Thermal stability test, test method: forced air oven, 60°C, 7 days

[0099] (4) Friction resistance test: After mixing with the laboratory-made water-based polyurethane resin, refer to GB / T 3920 Textile Color Fastness Test for Friction Color Fastness. The friction resistance grade of pure resin is 2-3, and the dry friction color fastness grade is 3-4.

[0100] The test results are shown in Table 1.

[0101] Table 1

[0102] Viscosity / mpas Particle size / nm Thermal stability Wet friction resistance / grade Dry friction resistance / grade Example 1 16.32 94 excellent 3～4 4～5 Example 2 24.50 108 excellent 3～4 4～5 Example 3 44.60 54 excellent 3～4 4～5 Example 4 19.38 120 excellent 3～4 4～5 Example 5 10.05 168 good 3 4 Comparative Example 1 6800 359 generally 3 4 Comparative Example 2 109 158 Difference 3～4 4

[0103] As shown in Table 1, Comparative Example 1 does not add sulfamic acid salt, and a large amount of polyethylene glycol monoether is introduced in order to obtain a stable emulsion, which increases the difficulty of emulsification, resulting in that the solid content of the emulsion is difficult to improve, and the viscosity is relatively large, and the color fastness to rubbing is not improved much compared to pure resin. Comparative Example 2 uses sodium alanine to replace sulfamic acid salt, which is excellent in color fastness to rubbing, but there is a phenomenon of emulsion stratification in the thermal stability test. It can be seen that the reaction conditions have a significant effect on the performance of the closed water-based polyisocyanate curing agent. The embodiment of the present invention uses sulfamic acid salt as a hydrophilic group, and the degree of ionization of the sulfonate is higher, and the obtained water-based polyisocyanate curing agent has a higher solid content. Sulfamic acid salt is added to the isocyanate prepolymer in the form of an aqueous solution. The water solubility of sulfamic acid salt is crucial. The temperature at which sulfamic acid salt is added is room temperature. Too high a temperature may cause water to react with the isocyanate group, and too low a temperature may cause the amino group to not react completely. At the same time, according to different reaction volumes, the addition speed of aminosulfonate is appropriately adjusted, and the addition time should be controlled within 10 to 30 minutes. According to different application requirements of the curing agent, those skilled in the art can control the solid content between 30% and 50%.

[0104] In summary, the water-based polyisocyanate curing agent of the present invention has good thermal stability and low viscosity. After being mixed with water-based polyurethane resin, it has excellent wet friction resistance after testing, and has certain application prospects in inkjet printing resin curing agent.

Claims

1. A blocked waterborne polyisocyanate curing agent, characterized in that: Based on 100 parts of total weight, the components are: 20-30 parts of isocyanate polymer, 3-10 parts of aminosulfonate, 8-15 parts of blocking agent, 0-4 parts of polyethylene glycol monoether, and 50-65 parts of water.

2. The blocked water-based polyisocyanate curing agent according to claim 1, characterized in that: The isocyanate polymer is selected from one or two of a trimer of diisocyanate and a reaction prepolymer of diisocyanate and a polyhydroxy compound.

3. The blocked water-based polyisocyanate curing agent according to claim 2, characterized in that: The trimer of diisocyanate is one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and 4,4'-dicyclohexylmethane diisocyanate trimer; The diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, toluene diisocyanate, 4,4-diphenylmethane diisocyanate and 2,2,4-trimethyl-hexamethylene diisocyanate; The polyhydroxy compound is one or more of trimethylolpropane, pentaerythritol and glycerol.

4. The blocked water-based polyisocyanate curing agent according to claim 1, characterized in that: The structural formula of the aminosulfonate is NH2-R1-SO3 - One or more of Wherein, R1 is a linear or branched aliphatic group having 2 to 10 carbon atoms.

5. The blocked water-based polyisocyanate curing agent according to claim 1, characterized in that: The blocking agent is one or more of 2-methylimidazole, 3,5-dimethylpyrazole, butanone oxime, acetone oxime, caprolactam, ethyl acetoacetate, diethyl malonate and phenol.

6. The blocked water-based polyisocyanate curing agent according to claim 1, characterized in that: The polyethylene glycol monoether is one or more polyethylene glycols synthesized with a monohydric alcohol as an initiator, and the monohydric alcohol is a linear or branched aliphatic monohydric alcohol with 1 to 4 carbon atoms.

7. A method for preparing the blocked waterborne polyisocyanate curing agent according to claim 1, comprising the following steps: (1) mixing an isocyanate polymer with polyethylene glycol monoether to obtain an isocyanate prepolymer; (2) adding a blocking agent to the isocyanate prepolymer obtained in step (1) to react to obtain a blocked isocyanate prepolymer; (3) adding aminosulfonate to the blocked isocyanate prepolymer obtained in step (2) for reaction at room temperature; (4) Add water to step (3) for emulsification to obtain a blocked water-based polyisocyanate curing agent.

8. The preparation method according to claim 7, characterized in that: The reaction temperature of step (1) is 70-90° C., the reaction time is 1-5 h, and the reaction is carried out under the protection of nitrogen.

9. The preparation method according to claim 7, characterized in that: When the blocking agent is 2-methylimidazole or 3,5-dimethylpyrazole, the reaction temperature of step (2) is 0-30°C, the blocking agent is added for 0.5-3h, and the reaction is carried out for 1h-3h; When the blocking agent is butanone oxime, acetone oxime, caprolactam, ethyl acetoacetate, diethyl malonate, or phenol, the reaction temperature of step (2) is 80-100° C., the blocking agent is added for 1-3 hours, and the reaction is carried out for 1-3 hours.

10. The preparation method according to claim 7, characterized in that: The reaction temperature of step (3) is 20-30° C., the aminosulfonate is added for 10-30 min, and the reaction lasts for 20-40 min.