CN118812813A - Polyurethane resin for water-based composite ink and preparation method thereof - Google Patents

Abstract

The invention relates to the field of adhesives, and discloses a polyurethane resin for water-based composite ink and a preparation method thereof. The polyurethane resin comprises the following material components: 50-90 parts of an isocyanate component (component A), 10-30 parts of a polyol component (component B), 5-20 parts of a chain extender, 1-5 parts of a catalyst, 50-150 parts of a solvent, 5-20 parts of a heat-resistant polymer, and 5-20 parts of a pH-responsive polymer. In the invention, the heat-resistant polymer is prepared by using 100 g of thiophenol, 20 g of sulfur, 1 g of benzoic acid, and 50 g of a dibasic acid or a diol. The sulfur atom in the thiophenol has a lone pair of electrons and can form a covalent bond with the sulfur atom in the sulfur, thereby constructing the main chain of the polymer. The benzoic acid activates the thiophenol and the sulfur by providing a proton (H+) to promote their reaction. The acidity of the benzoic acid is sufficient to catalyze a polymerization reaction. These substances undergo a polycondensation reaction with a prepolymer to form a network structure, thereby increasing the molecular weight and thermal stability of the polymer.

Description

Polyurethane resin for water-based composite ink and preparation method thereof

Technical Field

The invention relates to the field of adhesives, and in particular to a polyurethane resin for water-based composite ink and a preparation method thereof.

Background Art

Polyurethane resin is a polymer synthetic material. It is a type of resin generated by the reaction of diisocyanate and polyol (or polyamine). This resin has excellent mechanical properties, wear resistance, chemical resistance and adhesion, and is therefore widely used in coatings, plastics, rubber, adhesives, foams and fibers. The properties of polyurethane can be controlled by adjusting the raw materials and reaction conditions. For example, by changing the ratio of hard segments and soft segments, the type of raw materials used and the relative molecular mass, materials with different hardness, elasticity, temperature resistance and chemical resistance can be obtained.

According to the patent authorization publication number: CN114369228B, a polyurethane resin for water-based composite ink is disclosed, which is prepared by mixing the raw materials of the following components: a1, isocyanate; a2, macromolecular polyol; a3, modified intermediate; a4, small molecule chain extender; a5, catalyst; a6, salt-forming agent; the present invention also discloses a preparation method of the polyurethane resin for water-based composite ink. The present invention improves the water resistance, solvent resistance and mechanical properties of the product by introducing the modified intermediate. Therefore, the product obtained by the patented technology of the present invention has excellent water resistance, good alcohol resistance and high peel strength; however, the polyurethane resin for water-based composite ink still has shortcomings. The performance parameters of the polyurethane resin, such as viscosity, hardness and cohesive strength, fluctuate with the change of temperature. Under high temperature conditions, the polyurethane resin may soften, reducing its bonding strength and heat resistance; while at low temperatures, the resin may become harder and more brittle, easily causing cracks and fractures. The performance of the polyurethane resin is also affected by the pH value of the surrounding environment. Under acidic or alkaline conditions, the chemical bonds in the polyurethane molecules may break or form, thereby changing its molecular structure and performance. Therefore, a polyurethane resin for water-based composite ink and a preparation method thereof are needed to increase its temperature resistance and adapt to environmental pH changes.

Summary of the invention

In view of the deficiencies in the prior art, the present invention provides a polyurethane resin for water-based composite ink and a preparation method thereof, which solves the problem that the performance of the polyurethane resin for water-based composite ink is affected by changes in ambient temperature and pH.

To achieve the above purpose, the present invention is implemented by the following technical scheme: a polyurethane resin for water-based composite ink, comprising the following material components: isocyanate component (component A): 50-90 parts, polyol component (component B): 10-30 parts, chain extender: 5-20 parts, catalyst: 1-5 parts, solvent: 50-150 parts, heat-resistant polymer: 5-20 parts, pH-responsive polymer: 5-20 parts;

Wherein, the isocyanate component is a polyisocyanate;

The polyol component is polyester polyol, polyvinyl alcohol or polypropylene alcohol;

The specific components of the heat-resistant polymer include: 100g of thiophenol, 20g of sulfur, 1g of benzoic acid, and 50g of dibasic acid or diol. The heat-resistant polymer is obtained by polymerizing thiophenol and sulfur under the action of benzoic acid to form a prepolymer of polyphenylene sulfide, and the polyphenylene sulfide prepolymer is subjected to a condensation reaction with a dibasic acid or diol to form a heat-resistant polymer. The thiophenol and sulfur are polymerized under the action of an acid catalyst to form a polyphenylene sulfide prepolymer having high thermal stability. After the prepolymer is subjected to a condensation reaction with a dibasic acid or diol, the formed heat-resistant polymer can maintain stable performance under high temperature environment without softening or decomposition, thereby ensuring the bonding strength and durability of the polyurethane resin. The heat-resistant polymer accounts for 2-10% of the total material mass fraction;

The specific components of the pH responsive polymer include: 20g of acrylic acid, 0.5g of potassium persulfate, and 100mL of water. The pH responsive polymer is formed by polymerization of acrylic acid under the action of a catalyst (potassium persulfate K2S2O8). The polymerization reaction is carried out in water, and persulfate or azo compound is used as an initiator. The pH responsive polymer usually contains functional groups that can change with changes in pH value, such as acrylic acid, methacrylic acid, etc. These polymers will change their solubility, morphology or physical properties at different pH values, and their performance at specific pH values. Adding this polymer to the polyurethane resin for water-based composite ink can ensure that the ink can still maintain good adhesion and adaptability when encountering environments with different pH values. The pH responsive polymer accounts for 4-8% of the total material mass.

Preferably, the chain extender is one or both of 1,6-hexanediol and 1,4-butanediol.

Preferably, the catalyst is dibutyltin dilaurate.

Preferably, the solvent is one or both of isopropanol or ethanol.

A method for preparing a polyurethane resin for water-based composite ink comprises the following steps:

Step 1: Preparation of isocyanate component (component A): 50 parts of polyisocyanate and 75 parts of isopropanol were mixed and stirred at 25°C for 10 minutes to reduce its viscosity;

Step 2: Preparation of polyol component (component B): 10 parts of polyester polyol, 10 parts of polyvinyl alcohol and 10 parts of polypropylene alcohol were mixed with 20 parts of ethanol and stirred at 25°C for 15 minutes;

Step 3: Preparation of heat-resistant polymer: 5 parts of thiophenol and 1 part of sulfur are polymerized under the action of benzoic acid to form a prepolymer of polyphenylene sulfide, and then the polyphenylene sulfide prepolymer is subjected to polycondensation reaction with 5 parts of dibasic acid or diol to form a heat-resistant polymer, and 5 to 20 parts of the heat-resistant polymer are taken, wherein the weight of one part of the heat-resistant polymer accounts for 0.5% of the total weight of the isocyanate and the polyol;

Step 4: Preparation of pH-responsive polymer: 5 parts of acrylic acid are polymerized under the action of potassium persulfate K2S2O8 to form a pH-responsive polymer, and 5 to 20 parts of the pH-responsive polymer are taken, wherein one part of the pH-responsive polymer accounts for 0.8% of the total weight of the isocyanate and the polyol;

Step 5: Preparation of water-based composite ink polyurethane resin: Mix the components prepared in steps 1, 2, 3 and 4 in the following proportions: isocyanate component (component A): 50 parts, polyol component (component B): 10 parts, chain extender: 15 parts, catalyst: 2 parts, solvent: 60 parts, heat-resistant polymer: 10 parts, pH-responsive polymer: 10 parts, stir evenly at 70°C until a uniform polyurethane resin solution is formed, then add an appropriate amount of solvent to adjust the viscosity and ensure that all components are fully mixed.

Preferably, the heat-resistant polymer is prepared by a high temperature polymerization reaction, wherein the polymerization reaction temperature is 100°C to 120°C.

Preferably, the pH-responsive polymer adjusts its molecular weight and properties by controlling the pH value of the polymerization reaction, and the pH value is between 4.0 and 10.0.

Preferably, in step five, the water-based composite ink polyurethane resin mixing process includes a pre-mixing stage, a mixing stage, adding a pH-responsive polymer, and final mixing and stirring.

Preferably, in the pre-mixing stage, the isocyanate component (component A) is stirred at a low speed for 10 minutes to ensure that it is fully dispersed, the polyol component (component B), the chain extender, the catalyst and the heat-resistant polymer are added, and the stirring is continued at a low speed for 20 minutes to allow initial reaction and mixing between these components. In the mixing stage, the stirring speed is gradually increased to a medium speed, and the stirring is continued for 30 minutes to ensure that all the ingredients in the mixture are fully mixed and dispersed. During this process, the amount of the solvent can be appropriately adjusted to achieve the desired viscosity.

Preferably, in the adding of the pH responsive polymer, the pH responsive polymer is added to the mixture and stirred again for 20 minutes to ensure that the pH responsive polymer is fully mixed with the mixture. In the final mixing and stirring, the mixture is transferred to a larger stirring container and continued to be stirred at a medium speed while gradually adding the remaining solvent (such as isopropanol or ethanol) until the desired viscosity is reached. The prepared polyurethane resin solution is stored in a sealed container to prevent volatilization and contamination.

Beneficial Effects

The present invention provides a polyurethane resin for water-based composite ink and a preparation method thereof. Compared with the prior art, the polyurethane resin has the following beneficial effects:

In the present invention, a heat-resistant polymer is prepared by using 100g of thiophenol, 20g of sulfur, 1g of benzoic acid, and 50g of dibasic acid or diol. The sulfur atom in thiophenol has a lone pair of electrons and can form a covalent bond with the sulfur atom in sulfur to construct the main chain of the polymer. Under the action of an acidic catalyst, thiophenol and sulfur undergo a condensation polymerization reaction to form a prepolymer of polyphenylene sulfide. This reaction is reversible, but at high temperature, the prepolymer further reacts with the dibasic acid or diol to form a more stable cross-linked structure and improve heat resistance. Benzoic acid activates thiophenol and sulfur by providing protons (H+) to promote their reaction. The acidity of benzoic acid is sufficient to catalyze the polymerization reaction, but not so strong as to cause uncontrolled chain transfer or degradation reactions. These substances undergo a condensation polymerization reaction with the prepolymer to form a network structure, thereby increasing the molecular weight and thermal stability of the polymer.

In the present invention, by preparing pH responsive polymer by 20g of acrylic acid, 0.5g of potassium persulfate, 100mL of water, 3g of sulfate or azo compound, acrylic acid contains carbon-carbon double bonds, and is easy to form long-chain polymers by free radical polymerization. Its carboxyl group gives the polymer pH responsiveness, because the dissociation state of the carboxyl group changes with the pH value, thereby changing the solubility and charge of the polymer, and potassium persulfate decomposes in water to produce sulfate radicals, which attack the double bonds of acrylic acid and start free radical polymerization chain reaction. This reaction is exothermic, and the reaction conditions need to be controlled to avoid violent polymerization. These substances, as co-initiators, can synergize with potassium persulfate to improve the generation efficiency of free radicals and the uniformity of polymerization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system flow chart of a polyurethane resin for water-based composite ink and a preparation method thereof proposed by the present invention.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Please refer to FIG1 , the present invention provides three technical solutions, specifically including the following embodiments:

Embodiment 1:

A polyurethane resin for water-based composite ink, comprising the following material components: isocyanate component (component A): 50-90 parts, polyol component (component B): 10-30 parts, chain extender: 5-20 parts, catalyst: 1-5 parts, solvent: 50-150 parts, heat-resistant polymer: 5-20 parts, pH-responsive polymer: 5-20 parts;

Wherein, the isocyanate component is a polyisocyanate;

The polyol component is polyester polyol, polyvinyl alcohol or polypropylene alcohol;

The specific components of the heat-resistant polymer include: 100g of thiophenol, 20g of sulfur, 1g of benzoic acid, and 50g of dibasic acid or diol. The heat-resistant polymer is polymerized by thiophenol and sulfur under the action of an acid catalyst (benzoic acid) to form a prepolymer of polyphenylene sulfide, and the polyphenylene sulfide prepolymer is subjected to a condensation reaction with the dibasic acid or diol to form a heat-resistant polymer. 20 parts of the heat-resistant polymer are taken, and the heat-resistant polymer accounts for 10% of the total weight of the isocyanate and the polyol.

The specific ingredients of the pH responsive polymer include: 20 g of acrylic acid, 0.5 g of potassium persulfate, and 100 mL of water. The pH responsive polymer is formed by polymerization of acrylic acid under the action of a catalyst (potassium persulfate K2S2O8). The polymerization reaction is carried out in water, and persulfate or azo compound is used as an initiator. 10 parts of the pH responsive polymer are taken, and the pH responsive polymer accounts for 8% of the total weight of the isocyanate and the polyol.

Preferably, the chain extender is one or both of 1,6-hexanediol and 1,4-butanediol.

Preferably, the catalyst is dibutyltin dilaurate.

Preferably, the solvent is one or both of isopropanol or ethanol.

A method for preparing a polyurethane resin for water-based composite ink comprises the following steps:

Step 1: Preparation of isocyanate component (component A): 50 parts of polyisocyanate and 75 parts of isopropanol were mixed and stirred at 25°C for 10 minutes to reduce its viscosity;

Step 2: Preparation of polyol component (component B): 10 parts of polyester polyol, 10 parts of polyvinyl alcohol and 10 parts of polypropylene alcohol were mixed with 20 parts of ethanol and stirred at 25°C for 15 minutes;

Step 3: Preparation of heat-resistant polymer: polymerize 5 parts of thiophenol and 1 part of sulfur under the action of an acid catalyst (benzoic acid) to form a prepolymer of polyphenylene sulfide, and then carry out a condensation reaction of the polyphenylene sulfide prepolymer with 5 parts of a dibasic acid or a diol to form a heat-resistant polymer;

Step 4: Preparation of water-based composite ink polyurethane resin: Mix the components prepared in steps 1, 2, 3 and 4 in the following proportions: isocyanate component (component A): 50 parts, polyol component (component B): 10 parts, chain extender (1,6-hexanediol and 1,4-butanediol): 15 parts, catalyst (dibutyltin dilaurate): 2 parts, solvent (isopropanol and ethanol): 60 parts, heat-resistant polymer: 10 parts, pH-responsive polymer: 10 parts, stir evenly at 70°C until a uniform polyurethane resin solution is formed, then, add an appropriate amount of solvent (such as isopropanol or ethanol) to adjust the viscosity and ensure that all components are fully mixed.

Embodiment 2:

A polyurethane resin for water-based composite ink, comprising the following material components: isocyanate component (component A): 50-90 parts, polyol component (component B): 10-30 parts, chain extender: 5-20 parts, catalyst: 1-5 parts, solvent: 50-150 parts, heat-resistant polymer: 5-20 parts, pH-responsive polymer: 5-20 parts;

Wherein, the isocyanate component is a polyisocyanate;

The polyol component is polyester polyol, polyvinyl alcohol or polypropylene alcohol;

The specific components of the heat-resistant polymer include: 100g of thiophenol, 20g of sulfur, 1g of benzoic acid, and 50g of dibasic acid or diol. The heat-resistant polymer is polymerized by thiophenol and sulfur under the action of an acid catalyst (benzoic acid) to form a prepolymer of polyphenylene sulfide, and the polyphenylene sulfide prepolymer is subjected to a condensation reaction with the dibasic acid or diol to form a heat-resistant polymer. 12 parts of the heat-resistant polymer are taken, and the heat-resistant polymer accounts for 6% of the total weight of the isocyanate and the polyol.

The specific ingredients of the pH responsive polymer include: 20 g of acrylic acid, 0.5 g of potassium persulfate, and 100 mL of water. The pH responsive polymer is formed by polymerization of acrylic acid under the action of a catalyst (potassium persulfate K2S2O8). The polymerization reaction is carried out in water, and persulfate or azo compound is used as an initiator. The pH responsive polymer is taken in 7.5 parts, and the pH responsive polymer accounts for 6% of the total weight of isocyanate and polyol.

Preferably, the chain extender is one or both of 1,6-hexanediol and 1,4-butanediol.

Preferably, the catalyst is dibutyltin dilaurate.

Preferably, the solvent is one or both of isopropanol or ethanol.

A method for preparing a polyurethane resin for water-based composite ink comprises the following steps:

Step 1: Preparation of isocyanate component (component A): 50 parts of polyisocyanate and 75 parts of isopropanol were mixed and stirred at 25°C for 10 minutes to reduce its viscosity;

Step 2: Preparation of polyol component (component B): 10 parts of polyester polyol, 10 parts of polyvinyl alcohol and 10 parts of polypropylene alcohol were mixed with 20 parts of ethanol and stirred at 25°C for 15 minutes;

Step 3: Preparation of heat-resistant polymer: polymerize 5 parts of thiophenol and 1 part of sulfur under the action of an acid catalyst (benzoic acid) to form a prepolymer of polyphenylene sulfide, and then carry out a condensation reaction of the polyphenylene sulfide prepolymer with 5 parts of a dibasic acid or a diol to form a heat-resistant polymer;

Step 4: Preparation of pH-responsive polymer: 5 parts of acrylic acid are polymerized under the action of a catalyst (potassium persulfate K2S2O8) to form a pH-responsive polymer;

Step 5: Preparation of polyurethane resin for water-based composite ink: Mix the components prepared in steps 1, 2, 3 and 4 in the following proportions: isocyanate component (component A): 50 parts, polyol component (component B): 10 parts, chain extender (1,6-hexanediol and 1,4-butanediol): 15 parts, catalyst (dibutyltin dilaurate): 2 parts, solvent (isopropanol and ethanol): 60 parts, heat-resistant polymer: 10 parts, pH-responsive polymer: 10 parts, stir evenly at 70°C until a uniform polyurethane resin solution is formed, then, an appropriate amount of solvent (such as isopropanol or ethanol) can be added to adjust the viscosity and ensure that all components are fully mixed.

Embodiment three:

A polyurethane resin for water-based composite ink, comprising the following material components: isocyanate component (component A): 50-90 parts, polyol component (component B): 10-30 parts, chain extender: 5-20 parts, catalyst: 1-5 parts, solvent: 50-150 parts, heat-resistant polymer: 5-20 parts, pH-responsive polymer: 5-20 parts;

Wherein, the isocyanate component is a polyisocyanate;

The polyol component is polyester polyol, polyvinyl alcohol or polypropylene alcohol;

The specific components of the heat-resistant polymer include: 100g of thiophenol, 20g of sulfur, 1g of benzoic acid, and 50g of dibasic acid or diol. The heat-resistant polymer is polymerized by thiophenol and sulfur under the action of an acid catalyst (benzoic acid) to form a prepolymer of polyphenylene sulfide, and the polyphenylene sulfide prepolymer is subjected to a condensation reaction with the dibasic acid or diol to form a heat-resistant polymer. 8 parts of the heat-resistant polymer are taken, and the heat-resistant polymer accounts for 2% of the total weight of the isocyanate and the polyol;

The specific ingredients of the pH responsive polymer include: 20 g of acrylic acid, 0.5 g of potassium persulfate, and 100 mL of water. The pH responsive polymer is formed by polymerization of acrylic acid under the action of a catalyst (potassium persulfate K2S2O8). The polymerization reaction is carried out in water, using persulfate or azo compounds as initiators. Five parts of the pH responsive polymer are taken, and the pH responsive polymer accounts for 4% of the total weight of the isocyanate and the polyol.

Preferably, the chain extender is one or both of 1,6-hexanediol and 1,4-butanediol.

Preferably, the catalyst is dibutyltin dilaurate.

Preferably, the solvent is one or both of isopropanol or ethanol.

A method for preparing a polyurethane resin for water-based composite ink comprises the following steps:

Step 1: Preparation of isocyanate component (component A): 50 parts of polyisocyanate and 75 parts of isopropanol were mixed and stirred at 25°C for 10 minutes to reduce its viscosity;

Step 2: Preparation of polyol component (component B): 10 parts of polyester polyol, 10 parts of polyvinyl alcohol and 10 parts of polypropylene alcohol were mixed with 20 parts of ethanol and stirred at 25°C for 15 minutes;

Step 3: Preparation of pH-responsive polymer: 5 parts of acrylic acid are polymerized under the action of a catalyst (potassium persulfate K2S2O8) to form a pH-responsive polymer;

Step 4: Preparation of polyurethane resin for water-based composite ink: Mix the components prepared in steps 1, 2 and 3 in the following proportions: isocyanate component (component A): 50 parts, polyol component (component B): 10 parts, chain extender (1,6-hexanediol and 1,4-butanediol): 15 parts, catalyst (dibutyltin dilaurate): 2 parts, solvent (isopropanol and ethanol): 60 parts, heat-resistant polymer: 10 parts, pH-responsive polymer: 10 parts, stir evenly at 70°C until a uniform polyurethane resin solution is formed, then add an appropriate amount of solvent (such as isopropanol or ethanol) to adjust the viscosity and ensure that all components are fully mixed.

Test: The polyurethane resins prepared in Example 1, Example 2, and Example 3 were subjected to heat resistance test and pH responsiveness test respectively;

Heat resistance test

Thermogravimetric analysis (TGA)

Prepare about 10-20 mg of polyurethane resin sample, place the sample in the sample pot of the TGA instrument, set the temperature range from room temperature to 500°C at a rate of 10°C/min, record the relationship between the mass change of the sample and the temperature, analyze the curve, and determine the initial thermal decomposition temperature of the resin, the maximum weight loss rate, and the final residue mass.

Dynamic Thermal Analysis (DMA)

Prepare about 10-20 mg of polyurethane resin sample and stick it on the sample holder of the DMA instrument, set the frequency to 1 Hz, and the temperature range starts from room temperature and rises to 150°C at a rate of 10°C/min. Record the dynamic modulus and Tg of the sample, analyze the curve, determine Tg and its corresponding temperature range, softening point test, prepare a certain amount of polyurethane resin sample, and put it into the mold, put the mold into the softening point tester, heat it at an appropriate heating rate, observe the resin sample, and record the temperature when the sample is completely softened. Repeat the experiment at least three times and take the average value to obtain the softening point of the resin;

The following are the heat resistance test results of the above examples:

pH responsiveness test

Prepare a series of solutions with different pH values (e.g. pH 3, 5, 7, 9, 11), and soak the resin samples in these solutions respectively. Measure and record the pH values of the resin samples at regular intervals. Continue soaking for at least 24 hours and observe the changes in the pH value of the resin samples.

Expansion coefficient test

Prepare a certain amount of polyurethane resin sample and fix it on the expansion coefficient testing device, gradually change the surrounding pH value, record the change in resin volume, measure and calculate the volume expansion coefficient of the resin at different pH values.

Optical microscope observation

Place the resin sample under an optical microscope, adjust the distance between the lens and the sample, gradually change the pH value, observe the changes in the appearance of the resin sample, and record and describe the changes in the color, morphology, etc. of the resin sample.

Spectral analysis

Prepare a certain amount of polyurethane resin sample and place it in a UV-visible spectrometer or infrared spectrometer to measure the spectral changes of the resin at different pH values, analyze the spectral curve, and observe the relationship between the resin structure and pH value.

The following are the pH responsiveness test results of the above example:

Based on the above experimental data results, in the preparation process of water-based composite ink polyurethane resin, the polyurethane resin with added heat-resistant polymers and pH-responsive polymers can withstand high temperatures and changes in the pH value of the surrounding environment, so that it can maintain the bonding effect under temperature changes and changes in the pH value of the surrounding environment, thereby improving the application range and flexibility of the adhesive.

The following are the performance test results of the polyurethane resin for water-based composite ink prepared by the heat-resistant polymer and the pH-responsive polymer at different ratios in the above examples:

In summary of the above embodiments, Example 2 shows excellent heat resistance. After a series of heat resistance tests, the polyurethane resin of Example 2 shows better stability and ability to maintain hardness under high temperature environment. Example 2 also performs well in the bonding strength test, and its bonding strength exceeds that of other embodiments, which shows that the formula of Example 2 provides good heat resistance while maintaining high bonding performance.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the application should be included in the protection scope of the present application.

Claims (10)

1. A polyurethane resin for water-based composite ink is characterized in that: the material comprises the following components in parts by weight: isocyanate component (component a): 50-90 parts of a polyol component (B component): 10-30 parts of chain extender: 5-20 parts of a catalyst: 1-5 parts of solvent: 50-150 parts of heat-resistant polymer: 5-20 parts of pH-responsive polymer: 5-20 parts of a lubricant;

Wherein the isocyanate component is a polyisocyanate;

The polyol component is polyester polyol, polyvinyl alcohol or polyacrylate;

The heat-resistant polymer comprises the following specific components: 100g of thiophenol, 20g of sulfur, 1g of benzoic acid and 50g of dibasic acid or dihydric alcohol, wherein the heat-resistant polymer is prepared by polymerizing thiophenol and sulfur under the action of benzoic acid to form a prepolymer of polyphenylene sulfide, and performing polycondensation reaction on the prepolymer of polyphenylene sulfide and dibasic acid or dihydric alcohol to form a heat-resistant polymer, wherein the heat-resistant polymer accounts for 2-10% of the total material in parts by weight;

The pH response type polymer comprises the following specific components: 20g of acrylic acid, 0.5g of potassium persulfate, 100mL of water and 3g of sulfate or azo compound, wherein the pH-responsive polymer is formed by the polymerization of acrylic acid under the action of potassium persulfate K2S2O8, the polymerization is carried out in water, and the persulfate or azo compound is used as an initiator, wherein the pH-responsive polymer accounts for 4-8% of the total material in parts by weight.

2. The polyurethane resin for aqueous composite ink according to claim 1, wherein: the chain extender is one or two of 1, 6-hexanediol and 1, 4-butanediol.

3. The polyurethane resin for aqueous composite ink according to claim 1, wherein: the catalyst is dibutyl tin dilaurate.

4. The polyurethane resin for aqueous composite ink according to claim 1, wherein: the solvent is one or two of isopropanol and ethanol.

5. A method for preparing a polyurethane resin for water-based composite ink, based on the polyurethane resin for water-based composite ink as claimed in any one of claims 1 to 4, characterized in that: the method comprises the following steps:

step one: preparation of isocyanate component (a component): 50 parts of polyisocyanate are mixed with 75 parts of isopropanol and stirred for 10 minutes at 25 ℃ to reduce the viscosity thereof;

step two: preparation of polyol component (B component): 10 parts of polyester polyol, 10 parts of polyvinyl alcohol and 10 parts of polypropylene alcohol are mixed with 20 parts of ethanol and stirred for 15 minutes at 25 ℃;

Step three: preparation of heat resistant polymers: polymerizing 5 parts of thiophenol and 1 part of sulfur under the action of benzoic acid to form a prepolymer of polyphenylene sulfide, and then carrying out polycondensation reaction on the prepolymer of polyphenylene sulfide and 5 parts of dibasic acid or dihydric alcohol to form a heat-resistant polymer, wherein 5-20 parts of heat-resistant polymer are taken, and the weight of one part of heat-resistant polymer accounts for 0.5% of the total weight of isocyanate and polyol;

Step four: preparation of pH-responsive polymers: carrying out polymerization reaction on 5 parts of acrylic acid under the action of potassium persulfate K2S2O8 to form a pH-responsive polymer, and taking 5-20 parts of the pH-responsive polymer, wherein one part of the pH-responsive polymer accounts for 0.8% of the total weight of isocyanate and polyol;

Step five: preparation of aqueous composite ink polyurethane resin: mixing the components prepared in the first step, the second step, the third step and the fourth step according to the following proportion: isocyanate component (component a): 50 parts of a polyol component (B component): 10 parts of chain extender: 15 parts of catalyst: 2 parts of solvent: 60 parts of heat-resistant polymer: 10 parts of pH-responsive polymer: 10 parts, stirred uniformly at 70 ℃ until a uniform polyurethane resin solution is formed, followed by addition of an appropriate amount of solvent to adjust the viscosity and ensure adequate mixing of all components.

6. The method for producing a polyurethane resin for aqueous composite ink according to claim 5, characterized in that: the heat resistant polymer is prepared by high temperature polymerization, wherein the temperature of the polymerization is 100 ℃ to 120 ℃.

7. The method for producing a polyurethane resin for aqueous composite ink according to claim 5, characterized in that: the pH responsive polymer adjusts its molecular weight and properties by controlling the pH of the polymerization reaction, which is between 4.0 and 10.0.

8. The method for producing a polyurethane resin for aqueous composite ink according to claim 5, characterized in that: in the fifth step, the mixing process of the aqueous composite ink polyurethane resin comprises a premixing stage, a mixing stage, adding the pH responsive polymer and finally mixing and stirring.

9. The method for producing a polyurethane resin for aqueous composite ink according to claim 8, characterized in that: in the pre-mixing stage, the isocyanate component (a component) is stirred at a low speed for 10 minutes to ensure adequate dispersion thereof, the polyol component (B component), the chain extender, the catalyst and the heat-resistant polymer are added, and stirring is continued at a low speed for 20 minutes to allow preliminary reaction and mixing between these components, and in the mixing stage, the stirring speed is gradually increased to a medium speed, and stirring is continued for 30 minutes to ensure adequate mixing and dispersion of all the components in the mixture.

10. The method for producing a polyurethane resin for aqueous composite ink according to claim 8, characterized in that: in the addition of the pH-responsive polymer, the pH-responsive polymer is added to the mixture and stirred again for 20 minutes to ensure adequate mixing of the pH-responsive polymer with the mixture, and in the final mixing and stirring, the mixture is transferred to a larger stirring vessel, stirring is continued at a medium speed while gradually adding the remaining solvent until the desired viscosity is reached, and the prepared polyurethane resin solution is stored in a sealed vessel to prevent volatilization and contamination.