CN115260976B - Water-soluble polyurethane adhesive and preparation method thereof - Google Patents

Water-soluble polyurethane adhesive and preparation method thereof Download PDF

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CN115260976B
CN115260976B CN202211078656.6A CN202211078656A CN115260976B CN 115260976 B CN115260976 B CN 115260976B CN 202211078656 A CN202211078656 A CN 202211078656A CN 115260976 B CN115260976 B CN 115260976B
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water
carboxymethyl starch
sodium carboxymethyl
polyurethane
polyurethane adhesive
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CN115260976A (en
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袁道升
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Guangxi Zhishan New Material Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes
    • C09J175/08—Polyurethanes from polyethers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C08G18/12—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step using two or more compounds having active hydrogen in the first polymerisation step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/34—Carboxylic acids; Esters thereof with monohydroxyl compounds
    • C08G18/348—Hydroxycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4829—Polyethers containing at least three hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
    • C08G18/66—Compounds of groups C08G18/42, C08G18/48, or C08G18/52
    • C08G18/6666—Compounds of group C08G18/48 or C08G18/52
    • C08G18/6692—Compounds of group C08G18/48 or C08G18/52 with compounds of group C08G18/34
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/08—Macromolecular additives
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Adhesives Or Adhesive Processes (AREA)

Abstract

The application provides a water-soluble polyurethane adhesive and a preparation method thereof. The water-soluble polyurethane adhesive provided by the application comprises the following raw materials: polyurethane prepolymer, acetone, chain extender, ethylenediamine and sodium carboxymethyl starch; because the carboxymethyl starch sodium contains a polyhydroxy five-membered ring structure, the surface of the carboxymethyl starch sodium is rich in a large number of hydroxyl groups, so that the carboxymethyl starch sodium can form hydrogen bond action with active groups in polyurethane, and the carboxymethyl starch sodium plays a good role in enhancing the waterborne polyurethane, so that the thermal stability of the composite material is improved; the preparation method of the water-soluble polyurethane adhesive uses the natural polymer sodium carboxymethyl starch with wide sources, avoids using a large amount of organic reagents, and has wide sources of raw materials and degradability.

Description

Water-soluble polyurethane adhesive and preparation method thereof
Technical Field
The application relates to the technical field of adhesives, in particular to a water-soluble polyurethane adhesive and a preparation method thereof.
Background
Polyurethane adhesive is an important component of polyurethane resin at present, is one of eight synthetic cross-linking agents, but organic solvents are often used for synthesizing traditional polyurethane, so that the traditional polyurethane adhesive is toxic and has strong volatility, can harm human health, has great influence on ecological environment, and in order to avoid the occurrence of the problems, a plurality of researchers concentrate hot spots on high-quality pollution-free waterborne polyurethane.
However, in general, the mechanical properties of the aqueous polyurethane are low, and in order to satisfy more usage scenarios, the aqueous polyurethane needs to be reinforced. For example, the prior art discloses a preparation method of a water-soluble polyurethane adhesive, wherein the mechanical property and the thermal stability of the water-soluble polyurethane are improved by adding bischofite powder, zinc phosphate and gas-phase white carbon black into the water-soluble polyurethane. The prior art also discloses a preparation method of the tannic acid modified waterborne polyurethane, wherein tannic acid is used as a chain extender, a large amount of benzene rings are contained to provide rigidity, the thermal stability of the composite membrane is improved, but the tannic acid is used as a carcinogen and does not accord with the concept of green sustainable development.
In order to improve the mechanical property and the thermal stability of the composite adhesive, the aqueous polyurethane adhesive disclosed above uses non-renewable resources, and causes the waste of the resources.
Disclosure of Invention
In view of the above-mentioned shortcomings in the prior art, the application provides a water-soluble polyurethane adhesive and a preparation method thereof, which solve the problem of lower mechanical property of water-based polyurethane and improve the thermal stability of the water-based polyurethane, thereby meeting more use scenes. The preparation method is simple, avoids using a large amount of organic reagents, and has wide sources of raw materials and degradability.
In a first aspect, the application provides a water-soluble polyurethane adhesive, comprising the following raw materials: polyurethane prepolymer, acetone, chain extender, ethylenediamine and sodium carboxymethyl starch.
Preferably, the water-soluble polyurethane adhesive comprises polyether triol, toluene diisocyanate and citric acid.
Preferably, the water-soluble polyurethane adhesive and the chain extender comprise any one of 2, 3-butanediol, ethylene glycol and 1, 6-hexanediol.
Preferably, the mass ratio of the water-soluble polyurethane adhesive to the polyether triol, the toluene diisocyanate, the citric acid, the acetone, the chain extender, the ethylenediamine and the sodium carboxymethyl starch is (20-30)/(10-15)/(5-15)/(1-5)/(10-15)/(3-10)/(2-20).
In a second aspect, the application also provides a preparation method of the water-soluble polyurethane adhesive, which comprises the following steps:
mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 70-90 ℃ for 1-3 h to obtain polyurethane prepolymer;
adding acetone into polyurethane prepolymer, cooling to 55-65 ℃, continuing stirring for 1-3 h, then adding chain extender, stirring for 1-3 h again, then adding ethylenediamine, continuing stirring for 1-3 h, and finally adding water for emulsification to obtain aqueous polyurethane solution;
adding sodium carboxymethyl starch into the aqueous polyurethane solution, and stirring to obtain mixed emulsion;
coating the mixed emulsion on a substrate, and curing to obtain the water-soluble polyurethane adhesive.
Preferably, in the preparation method of the water-soluble polyurethane adhesive, in the step of coating the mixed emulsion on a substrate and curing, the curing temperature is 40-60 ℃ and the time is 1-3 h.
Preferably, the preparation method of the water-soluble polyurethane adhesive further comprises the following steps before adding sodium carboxymethyl starch into the aqueous polyurethane solution: adding sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, and adding the sodium carboxymethyl starch solution into the aqueous polyurethane solution.
Preferably, the water-soluble polyurethane adhesive is prepared by a method, and the substrate comprises polytetrafluoroethylene substrate.
Compared with the prior art, the water-soluble polyurethane adhesive and the preparation method thereof have the following beneficial effects:
1. the water-soluble polyurethane adhesive comprises sodium carboxymethyl starch, and the surface of the sodium carboxymethyl starch contains a polyhydroxy five-membered ring structure, so that a large number of hydroxyl groups can form hydrogen bond action with active groups in polyurethane, the water-soluble polyurethane is well reinforced, and the thermal stability of a composite material is improved;
2. the preparation method of the water-soluble polyurethane adhesive uses the natural polymer sodium carboxymethyl starch with wide sources, avoids using a large amount of organic reagents, and has wide sources of raw materials and degradability.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the drawings in the following description are only some embodiments of the present application and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
Fig. 1 shows the adhesive strength of the water-soluble polyurethane adhesives prepared in examples 1 to 5 and comparative example 1 according to the present application.
Detailed Description
The following description of the embodiments of the present application will be made in detail and with reference to the embodiments of the present application, but it should be apparent that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to fall within the scope of the present application.
The embodiment of the application provides a water-soluble polyurethane adhesive, which comprises the following raw materials: polyurethane prepolymer, acetone, chain extender, ethylenediamine and sodium carboxymethyl starch.
In some embodiments, the polyurethane prepolymer includes polyether triols, toluene diisocyanate, citric acid.
In some embodiments, the chain extender is an alcohol or amine chain extender, and commonly used alcohol chain extenders are 1, 4-Butanediol (BDO), 2, 3-butanediol, ethylene glycol, 1, 6-hexanediol, glycerol, trimethylolpropane, diethylene glycol (DEG), triethylene glycol, neopentyl glycol (NPG), sorbitol, diethylaminoethanol (DEAE), and the like; examples of the amine chain extender include MOCA, liquid MOCA obtained by modifying with formaldehyde, ethylenediamine (DA), and N, N-dihydroxyl (diisopropyl) aniline (HPA).
In some embodiments, the mass ratio of the polyether triol, the toluene diisocyanate, the citric acid, the acetone, the chain extender, the ethylenediamine and the sodium carboxymethyl starch is (20-30): (10-15): (5-15): (1-5): (10-15): (3-10): (2-20).
Based on the same inventive concept, the embodiment of the application also provides a preparation method of the water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 70-90 ℃ for 1-3 hours to obtain polyurethane prepolymer;
s2, adding acetone into the polyurethane prepolymer, simultaneously cooling to 55-65 ℃, continuously stirring for 1-3 hours, then adding a chain extender, stirring for 1-3 hours again, then adding ethylenediamine, continuously stirring for 1-3 hours, and finally adding water for emulsification to obtain a water-based polyurethane solution;
s3, adding sodium carboxymethyl starch into the aqueous polyurethane solution, and stirring to obtain mixed emulsion;
s4, coating the mixed emulsion on a substrate, and curing to obtain the water-soluble polyurethane adhesive.
Specifically, in the step S2 of the above embodiment, the mass ratio of the water to the polyurethane prepolymer is (0.8-1.2) to (0.8-1.2).
In some embodiments, the mixed emulsion is applied to the substrate and cured at a temperature of 40 to 60 ℃ for a period of 1 to 3 hours.
In some embodiments, the sodium carboxymethyl starch prior to adding to the aqueous polyurethane solution further comprises: dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, and adding the sodium carboxymethyl starch solution into the aqueous polyurethane solution; wherein the mass ratio of the sodium carboxymethyl starch to the water is (0.5-2) to (60-100).
In some embodiments, the substrate comprises a polytetrafluoroethylene substrate.
The water-soluble polyurethane adhesive provided by the application comprises sodium carboxymethyl starch, wherein the carboxymethyl starch is used as water-soluble anionic starch ether, and is generally prepared by reacting starch with chloroacetic acid under alkaline conditions, and after etherification modification, many properties of the sodium carboxymethyl starch are changed, so that the water-soluble polyurethane adhesive has the advantages of strong hydrophilicity, easiness in gelatinization, good film forming property, good freeze-thawing stability and the like. Because the carboxymethyl starch sodium contains a polyhydroxy five-membered ring structure, the surface of the carboxymethyl starch sodium is rich in a large number of hydroxyl groups, so that the carboxymethyl starch sodium can form hydrogen bond action with active groups in polyurethane, and the carboxymethyl starch sodium plays a good role in enhancing the waterborne polyurethane, thereby improving the thermal stability of the composite material.
The process for preparing the water-soluble polyurethane adhesive of the present application is further illustrated in the following specific examples. This section further illustrates the summary of the application in connection with specific embodiments, but should not be construed as limiting the application. The technical means employed in the examples are conventional means well known to those skilled in the art, unless specifically stated. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present application are those conventional in the art. The polyether triols in the examples below are supplied by Asahi chemical (Suzhou) Co.
Example 1
The embodiment of the application provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
s4, dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, wherein the mass ratio of the sodium carboxymethyl starch to the water is 1:80;
s5, adding the sodium carboxymethyl starch solution in the step S4 into the aqueous polyurethane solution in the step S3, and stirring for 2 hours to obtain a mixed emulsion; wherein the mass of sodium carboxymethyl starch in the sodium carboxymethyl starch solution is 5% of the mass of the aqueous polyurethane solution;
s6, coating the mixed emulsion on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Example 2
The embodiment of the application provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
s4, dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, wherein the mass ratio of the sodium carboxymethyl starch to the water is 1:80;
s5, adding the sodium carboxymethyl starch solution in the step S4 into the aqueous polyurethane solution in the step S3, and stirring for 2 hours to obtain a mixed emulsion; wherein the mass of sodium carboxymethyl starch in the sodium carboxymethyl starch solution is 10% of the mass of the aqueous polyurethane solution;
s6, coating the mixed emulsion on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Example 3
The embodiment of the application provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
s4, dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, wherein the mass ratio of the sodium carboxymethyl starch to the water is 1:80;
s5, adding the sodium carboxymethyl starch solution in the step S4 into the aqueous polyurethane solution in the step S3, and stirring for 2 hours to obtain a mixed emulsion; wherein the mass of sodium carboxymethyl starch in the sodium carboxymethyl starch solution is 15% of the mass of the aqueous polyurethane solution;
s6, coating the mixed emulsion on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Example 4
The embodiment of the application provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
s4, dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, wherein the mass ratio of the sodium carboxymethyl starch to the water is 1:80;
s5, adding the sodium carboxymethyl starch solution in the step S4 into the aqueous polyurethane solution in the step S3, and stirring for 2 hours to obtain a mixed emulsion; wherein the mass of sodium carboxymethyl starch in the sodium carboxymethyl starch solution is 20% of the mass of the aqueous polyurethane solution;
s6, coating the mixed emulsion on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Example 5
The embodiment of the application provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
s4, dissolving sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, wherein the mass ratio of the sodium carboxymethyl starch to the water is 1:80;
s5, adding the sodium carboxymethyl starch solution in the step S4 into the aqueous polyurethane solution in the step S3, and stirring for 2 hours to obtain a mixed emulsion; wherein the mass of sodium carboxymethyl starch in the sodium carboxymethyl starch solution is 25% of the mass of the aqueous polyurethane solution;
s6, coating the mixed emulsion on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Comparative example 1
The comparative example provides a preparation method of a water-soluble polyurethane adhesive, which comprises the following steps:
s1, mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 80 ℃ for 2 hours to obtain polyurethane prepolymer; wherein the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid is 14:6:5;
s2, adding acetone into the polyurethane prepolymer in the step S1, simultaneously cooling to 60 ℃, and continuously stirring for 1h at 2000 r/min; wherein the mass ratio of the citric acid to the acetone is 5:1.5;
s3, adding a chain extender 2, 3-butanediol into the mixture in the step S2, stirring for 2 hours again, adding ethylenediamine again after the reaction is finished, stirring for 1 hour again, and finally adding water for emulsification to obtain a water-based polyurethane solution; wherein, the mass ratio of the added chain extender to the ethylenediamine to the acetone is 12:6:3, and the mass ratio of the water to the polyurethane prepolymer is 1:1;
and S4, coating the aqueous polyurethane solution in the step S3 on a polytetrafluoroethylene substrate, and curing for 2 hours at 50 ℃ to obtain the water-soluble polyurethane adhesive.
Performance test:
the water-soluble polyurethane adhesives prepared in examples 1 to 5 and comparative example 1 were peeled off from the polytetrafluoroethylene substrate, and then subjected to the following performance test.
Tensile property test: according to GB/T528 standard, the mechanical properties and the bonding strength of the water-soluble polyurethane adhesive prepared by adding sodium carboxymethyl starch in the comparative example 1 and the water-soluble polyurethane adhesive prepared by adding sodium carboxymethyl starch in different contents in the examples 1-5 are measured by adopting a TA.XT PlusC texture analyzer. The stretching rate was 200mm/min, and each sample was measured at least 5 times, and the results of the experiment were averaged, and the results are shown in Table 1.
Thermal weight loss test: under the condition of nitrogen, the water-soluble polyurethane adhesive prepared by the comparative example 1 without adding sodium carboxymethyl starch and the water-soluble polyurethane adhesive prepared by the examples 1-5 with different contents of sodium carboxymethyl starch are heated from 40 ℃ to 500 ℃ at a heating rate of 20 ℃/min, and the results are shown in table 2.
TABLE 1 mechanical Properties of Water-soluble polyurethane Adhesives prepared in different examples
As is clear from the results in Table 1, the addition of sodium carboxymethyl starch in examples 1 to 5 can significantly improve the mechanical properties of the water-soluble polyurethane adhesive as compared with the water-soluble polyurethane adhesive prepared without the addition of sodium carboxymethyl starch in comparative example 1, but when the addition amount of sodium carboxymethyl starch exceeds 10wt%, the mechanical properties of the water-soluble polyurethane adhesive are lowered, so that the optimum addition amount of sodium carboxymethyl starch should be 10wt%.
TABLE 2 thermal weight loss data for Water-soluble polyurethane Adhesives prepared in different examples
Examples T 5％ (℃) T 10％ (℃) T max (℃)
Comparative example 1 315.9 356.3 409.8
Example 1 318.4 358.5 412.7
Example 2 323.4 360.4 414.8
Example 3 321.8 361.5 415.9
Example 4 319.4 362.8 416.4
Example 5 317.6 360.8 416.9
Note that: t (T) 5％ Is the temperature at which the mass loss is 5%, T 10％ Is the temperature at which the mass loss is 10%, T max Maximum degradation temperature.
As can be seen from Table 2, in examples 1 to 5, T was measured in accordance with the addition of sodium carboxymethyl starch, as compared with the water-soluble polyurethane adhesive prepared in comparative example 1 without the addition of sodium carboxymethyl starch max This indicates that sodium carboxymethyl starch increases the thermal stability of the water-soluble polyurethane adhesive.
The water-soluble polyurethane adhesives prepared in examples 1 to 5 and comparative example 1 were tested for adhesive strength (i.e., ultimate tensile strength), and the standard results according to GB/T528 are shown in FIG. 1.
As can be seen from fig. 1, the adhesive strength of the water-soluble polyurethane adhesives prepared in examples 1 to 5 was enhanced with the addition of sodium carboxymethyl starch, as compared with the water-soluble polyurethane adhesive prepared without the addition of sodium carboxymethyl starch in comparative example 1, but when the content of sodium carboxymethyl starch exceeds 10wt%, the adhesive strength of the water-soluble polyurethane adhesive began to be lowered due to stress concentration caused by the rigid structure of sodium carboxymethyl starch.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application.

Claims (3)

1. The preparation method of the water-soluble polyurethane adhesive is characterized by comprising the following raw materials: polyurethane prepolymer, acetone, chain extender, ethylenediamine and sodium carboxymethyl starch;
the polyurethane prepolymer comprises polyether triol, toluene diisocyanate and citric acid;
the chain extender comprises any one of 2, 3-butanediol, ethylene glycol and 1, 6-hexanediol;
the mass ratio of the polyether triol to the toluene diisocyanate to the citric acid to the acetone to the chain extender to the ethylenediamine to the sodium carboxymethyl starch is (20-30): (10-15): (5-15): (1-5): (10-15): (3-10): (2-20);
the preparation method of the water-soluble polyurethane adhesive comprises the following steps:
mixing polyether triol, toluene diisocyanate and citric acid, and stirring at 70-90 ℃ for 1-3 h to obtain polyurethane prepolymer;
adding acetone into polyurethane prepolymer, cooling to 55-65 ℃, continuing stirring for 1-3 h, then adding chain extender, stirring for 1-3 h again, then adding ethylenediamine, continuing stirring for 1-3 h, and finally adding water for emulsification to obtain aqueous polyurethane solution;
adding sodium carboxymethyl starch into the aqueous polyurethane solution, and stirring to obtain mixed emulsion;
coating the mixed emulsion on a substrate, and curing to obtain a water-soluble polyurethane adhesive;
in the step of coating the mixed emulsion on the base material for curing, the curing temperature is 40-60 ℃ and the curing time is 1-3 h.
2. The method for preparing the water-soluble polyurethane adhesive according to claim 1, wherein the method further comprises the steps of: adding sodium carboxymethyl starch into water to obtain sodium carboxymethyl starch solution, and adding the sodium carboxymethyl starch solution into the aqueous polyurethane solution.
3. The method of preparing a water-soluble polyurethane adhesive of claim 1, wherein the substrate comprises a polytetrafluoroethylene substrate.
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JP2009235275A (en) * 2008-03-27 2009-10-15 Nicca Chemical Co Ltd Aqueous polyurethane resin composition, one-pack type adhesive using the same, laminate and method for producing aqueous polyurethane resin composition
CN103450837A (en) * 2013-09-03 2013-12-18 山东天庆科技发展有限公司 Waterborne polyurethane adhesive for synthetic leather and preparation method thereof

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JP2009235275A (en) * 2008-03-27 2009-10-15 Nicca Chemical Co Ltd Aqueous polyurethane resin composition, one-pack type adhesive using the same, laminate and method for producing aqueous polyurethane resin composition
CN103450837A (en) * 2013-09-03 2013-12-18 山东天庆科技发展有限公司 Waterborne polyurethane adhesive for synthetic leather and preparation method thereof

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