Aqueous polyurethane emulsion, method for preparing the same, and two-component polyurethane adhesive

Abstract

The application relates to the technical field of adhesives, and discloses a water-based polyurethane emulsion, a preparation method thereof and a two-component polyurethane adhesive. The preparation method of the water-based polyurethane emulsion comprises the following steps: mixing an oligomer polyol, a first isocyanate, a first chain extender, a second chain extender and water to obtain the water-based polyurethane emulsion; wherein the first chain extender comprises at least one of a polyacrylate carboxylate, a polyacrylate sulfonate and a polyacrylate carboxylate / sulfonate. The method can realize hydrophilic chain extension and acrylate modification of the polyurethane, the hydrophilic chain extension reaction is mild, the solvent consumption can be reduced, the method does not need neutralization, and the obtained water-based polyurethane emulsion is stable in property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to a water-based polyurethane emulsion, a preparation method thereof and a two-component polyurethane adhesive. BACKGROUND

[0002] The water-based polyurethane adhesive has excellent wear resistance, chemical corrosion resistance, better flexibility, better adhesion and higher gloss, is widely used in shoe-making, clothing, building, automobile and food packaging, kitchen supplies, composite film and other industries, and has low content of volatile organic solvents, and has the characteristics of non-toxicity, flame retardancy, no odor, environmental friendliness, no health hazards to operators, etc., and has become the focus of development of polyurethane adhesives. However, the current water-based polyurethane adhesive shows poor adhesion when bonding low surface tension substrates, and the adhesive joint has poor high temperature resistance, the adhesive strength is reduced in high temperature environment, and the hydrolysis resistance is insufficient. In addition, the solid content of the water-based polyurethane is low, thereby increasing the transportation and drying costs.

[0003] Therefore, the research on water-based polyurethane adhesive needs to be further deepened. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0005] In one aspect of the present application, a method for preparing a water-based polyurethane emulsion is provided, which comprises: mixing an oligomer polyol, a first isocyanate, a first chain extender, a second chain extender and water to obtain a water-based polyurethane emulsion; wherein the first chain extender comprises at least one of polyacrylate carboxylate, polyacrylate sulfonate and polyacrylate carboxylate / sulfonate. This method can realize hydrophilic chain extension and acrylate modification of polyurethane, and the reaction of hydrophilic chain extension is mild, which can reduce the amount of solvent, and the method does not need neutralization, and the obtained water-based polyurethane emulsion has stable properties.

[0006] According to the embodiment of the present application, the mixing is carried out according to the following steps:

[0007] (1) first mixing the oligomer polyol and the first isocyanate to obtain a prepolymer;

[0008] (2) second mixing the prepolymer with the first chain extender;

[0009] (3) third mixing the product obtained in step (2) with the second chain extender;

[0010] (4) The product obtained in step (3) is subjected to a fourth mixing with water, so as to obtain an aqueous polyurethane emulsion. In this way, the full reaction of the raw materials can be promoted, and a stable aqueous polyurethane emulsion is formed.

[0011] According to an embodiment of the present application, the molar ratio of the oligomer polyol and the first isocyanate is (0.2-2) : 1. In this way, a prepolymer with active end groups (isocyanate groups) is formed, which facilitates the subsequent chain extension reaction.

[0012] According to an embodiment of the present application, the oligomer polyol comprises a polyester polyol and optionally a polyether polyol.

[0013] According to an embodiment of the present application, the weight average molecular weight of the polyester polyol is 500-10000.

[0014] According to an embodiment of the present application, the polyester polyol comprises at least one of polybutylene adipate glycol, polyhexylene adipate glycol, polycaprolactone glycol and polycarbonate glycol.

[0015] According to an embodiment of the present application, the weight average molecular weight of the polyether polyol is 90-2000.

[0016] According to an embodiment of the present application, the polyether polyol comprises at least one of polytetrahydrofuran ether glycol, polypropylene ether alcohol and polyethylene ether alcohol.

[0017] According to an embodiment of the present application, the first isocyanate monomer comprises at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate and xylylene diisocyanate.

[0018] According to an embodiment of the present application, the weight average molecular weight of the first chain extender is 500-5000.

[0019] According to an embodiment of the present application, the hydroxyl value of the first chain extender is 15 mgKOH / g-77 mgKOH / g.

[0020] According to an embodiment of the present application, the content of carboxylate groups or / and sulfonate groups of the first chain extender is 0.1 mmol / g-2 mmol / g.

[0021] According to an embodiment of the present application, the content of amide groups of the first chain extender is 0.1 mmol / g-1 mmol / g.

[0022] According to the embodiment of the present application, the method for preparing the first chain extender comprises: subjecting an acrylic monomer, an acrylate monomer, a first monomer and a second monomer to a free radical polymerization reaction in the presence of an initiator and a solvent; wherein the first monomer is selected from a hydroxy acrylate monomer and / or an acrylamide monomer; and the second monomer is selected from at least one of sodium acrylsulfonate and sodium acrylate.

[0023] According to the embodiment of the present application, the weight ratio of the acrylic monomer, the acrylate monomer, the first monomer and the second monomer is (0.3-20):(0.1-21):(0.5-13):1.

[0024] According to the embodiment of the present application, from the perspective of easy availability of raw materials, the acrylic monomer comprises at least one of acrylic acid and methacrylic acid.

[0025] According to the embodiment of the present application, the acrylate monomer comprises at least one of methyl methacrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate and isooctyl acrylate.

[0026] According to the embodiment of the present application, the hydroxy acrylate monomer comprises at least one of hydroxy ethyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl acrylate, hydroxy propyl methacrylate, hydroxy butyl acrylate and hydroxy butyl methacrylate.

[0027] According to the embodiment of the present application, from the perspective of easy availability of raw materials, the acrylamide monomer comprises at least one of acrylamide and methacrylamide.

[0028] According to the embodiment of the present application, the mass ratio of the first chain extender to the prepolymer is 1:(7-40).

[0029] According to the embodiment of the present application, the second chain extender comprises a diamine and / or an alcohol amine.

[0030] According to the embodiment of the present application, the mass content of the second chain extender is 0.5%-5% relative to the total mass of the reactants.

[0031] In another aspect of the present application, an aqueous polyurethane emulsion is provided, which is prepared by the aforementioned method. The aqueous polyurethane emulsion has high stability and adhesion.

[0032] In still another aspect of the present application, a two-component polyurethane adhesive is provided, which comprises a component A and a component B, wherein the component A contains the aforementioned aqueous polyurethane emulsion, and the component B contains a second isocyanate. Thus, the obtained two-component polyurethane adhesive has strong adhesion, good resistance to high temperature and humidity, strong mechanical properties and good hydrophilicity, and the two-component polyurethane adhesive has a large molecular weight, a high solid content and a high crosslinking degree.

[0033] According to an embodiment of the present application, the second isocyanate has a mass content of isocyanate groups of 13% to 25%.

[0034] According to an embodiment of the present application, the mass ratio of the aqueous polyurethane emulsion to the second isocyanate is (12-25) : 1. Thus, after mixing of the two components, a crosslinked product with high crosslinking degree is formed, further improving the adhesion.

[0035] According to an embodiment of the present application, the A component further comprises an additive, which includes at least one of a thickening agent, a defoaming agent and a leveling agent. Thus, the uniformity of the adhesive after film formation can be improved, ensuring the use effect of the adhesive.

[0036] According to an embodiment of the present application, the mass content of the aqueous polyurethane emulsion is 70 parts to 90 parts, based on 100 parts of the total weight of the A component. BRIEF DESCRIPTION OF DRAWINGS

[0037] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the accompanying drawings, in which:

[0038] Figure 1 Flow chart of a method for preparing an aqueous polyurethane emulsion according to some embodiments of the present application;

[0039] Figure 2 Flow chart of a method for preparing a two-component polyurethane adhesive according to some embodiments of the present application. DETAILED DESCRIPTION

[0040] Embodiments of the present application are described in detail below with reference to examples illustrated in the accompanying drawings, in which the same or similar components have the same or similar designations throughout, and in which: the embodiments described below are exemplary, and are intended to explain the present application, and are not to be understood as limiting the present application.

[0041] According to a first aspect of the present application, the present application provides a method for preparing an aqueous polyurethane emulsion, comprising:

[0042] mixing an oligomer polyol, a first isocyanate, a first chain extender, a second chain extender and water to obtain an aqueous polyurethane emulsion;

[0043] In some embodiments, as shown in FIG. 1, the method comprises the following steps:

[0044] In some embodiments, as shown in FIG. 1, the method comprises the following steps: Figure 1 In some embodiments, as shown in FIG. 1, the method comprises the following steps:

[0045] S100: mixing the oligomer polyol and the first isocyanate to obtain a prepolymer.

[0046] In this step, the oligomer polyol and the first isocyanate are allowed to undergo an addition reaction by the first mixing to obtain a prepolymer.

[0047] In some embodiments, the first mixing is performed at a temperature of 40-80°C and under stirring. Specifically, after the oligomer polyol and the first isocyanate are mixed uniformly, the reaction is performed at the above-mentioned temperature, and the isocyanate content in the reaction system is tracked and determined by chemical titration during the reaction. When the isocyanate content reaches the theoretical value, the temperature of the reaction system is lowered to 20-60°C, and acetone is added to adjust the viscosity of the system to obtain the prepolymer.

[0048] In some embodiments, before the first mixing is performed, the method further comprises: pretreating the oligomer polyol to remove small molecules such as water that can exist therein, so as to avoid solidification reaction of water with polyurethane raw materials and affect the stability of the emulsion. The method of pretreatment can comprise: distillation under reduced pressure at a temperature of 100-130°C for 1-3h, with the reduced pressure controlled to be not greater than -0.08MPa, so that the mass content of water in the system is controlled to be below 0.1%, such as 0.05%-0.1%.

[0049] In some embodiments, the oligomer polyol is a polyester polyol. In other embodiments, the oligomer polyol is a polyester polyol and a polyether polyol.

[0050] In some embodiments, the mass ratio of the polyester polyol to the polyether polyol in the oligomer polyol is 1:(0-0.4). Preferably, the mass ratio of the polyester polyol to the polyether polyol is 1:(0.01-0.4). By introducing a small amount of polyether polyol, the solid content of the waterborne polyurethane emulsion can be increased, thereby reducing the storage space and transportation cost of the emulsion, and enabling the polyurethane adhesive layer to have both high elongation at break and tensile strength.

[0051] In some embodiments, the weight average molecular weight (Mw) of the polyester polyol is 500-10000, such as 500, 650, 850, 1000, 2000, 3000, 5000, 8000 and 10000, etc. In this way, the molecular weight of the polyurethane is controlled, and the emulsification effect of the polyurethane is improved. The polyester polyol can be obtained by methods well known in the art, or can be obtained by commercial purchase, such as various polyester polyols available from Huada Chemical Co., Ltd.

[0052] In some embodiments, the polyether polyol has a weight average molecular weight of 90-2000, such as 90, 100, 250, 650, 1000, 2000, etc. In this way, the solubility of the prepolymer in the solvent can be improved, and the subsequent chain extension reaction can be facilitated, the emulsification effect can be improved, and the adhesion can be improved by controlling the ether bond within an appropriate range.

[0053] In some embodiments, the molar ratio of the oligomer polyol to the first isocyanate is (0.2-2) : 1. When the oligomer polyol and the first isocyanate are within the foregoing range, the adhesive strength of the polyurethane prepolymer obtained is greater, and the elongation at break of the adhesive layer is higher.

[0054] Optionally, the polyester polyol includes at least one of polybutylene adipate glycol (PBA), polyhexylene adipate glycol (PHA), polycaprolactone glycol (PCL), and polycarbonate glycol (PCD).

[0055] Optionally, the polyether polyol includes at least one of polytetrahydrofuran ether glycol, polypropylene glycol, and polyethylene glycol.

[0056] Optionally, the first isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, dicyclohexylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and xylylene diisocyanate.

[0057] In some preferred embodiments, the first isocyanate is a combination of hexamethylene diisocyanate and isophorone diisocyanate, and the molar ratio of hexamethylene diisocyanate to isophorone diisocyanate is 90:10 to 70:30. Since hexamethylene diisocyanate has a symmetrical and regular structure, a large proportion thereof is conducive to the rapid crystallization of the waterborne polyurethane, so that the adhesive strength obtained is large; isophorone diisocyanate has a small contribution to the crystallization of the waterborne polyurethane, but due to the large difference in activity of the two isocyanate groups, only one isocyanate group is usually involved in the reaction, which can be used as a blocking agent, and the remaining isocyanate group reacts with the highly active amino group in the post-emulsification stage to further extend the chain, so that the molecular weight of the waterborne polyurethane is further increased. In this way, a polyurethane prepolymer with a high molecular weight can be obtained.

[0058] S200: second mixing of the prepolymer and the first chain extender. Through the second mixing, the prepolymer and the first chain extender are reacted to further increase the molecular weight of the polyurethane.

[0059] According to the embodiment of the present application, the second mixing comprises: adding the first chain extender into the prepolymer obtained in step S100 dropwise under high-speed stirring, for example, for 10-30 min, and then continuing the high-speed stirring for 20-60 min. The high-speed stirring speed is for example 1500-5000 rpm.

[0060] In some embodiments, the mass ratio of the first chain extender to the prepolymer is 1:(7-40). Here, the mass of the prepolymer is determined according to the total amount of the reactants (isocyanate and polyol).

[0061] In the present application, the first chain extender comprises at least one of polyacrylate carboxylate, polyacrylate sulfonate and polyacrylate carboxylate / sulfonate. Here, the polyacrylate carboxylate / sulfonate refers to polyacrylate having both carboxylate and sulfonate groups in the molecular chain.

[0062] In some embodiments, the first chain extender further has hydroxyl and / or amide groups.

[0063] In some embodiments, the first chain extender has a weight average molecular weight of 500-5000, for example, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 and 5000, etc.; a hydroxyl value of 15-77 mgKOH / g, for example, 15, 30, 45, 60 and 77 mgKOH / g, etc.; a content of carboxylate groups or / and sulfonate groups of 0.1-2 mmol / g, for example, 0.1, 0.5, 1, 1.5 and 2 mmol / g, etc.; and a content of amide groups of 0.1-1 mmol / g, for example, 0.1, 0.2, 0.4, 0.6, 0.8 and 1 mmol / g, etc. Under the above conditions, the first chain extender can be uniformly and effectively mixed with the prepolymer obtained in step S100 to perform chain extension, to obtain acrylate-modified polyurethane, and to increase the molecular weight of the final obtained waterborne polyurethane.

[0064] In the present application, the "content of carboxylate groups or / and sulfonate groups" refers to the total content of carboxylate groups and sulfonate groups on the first chain extender, and is selected according to the specific type of the first chain extender. For example, when the first chain extender is a polyacrylate carboxylate, the "content of carboxylate groups or / and sulfonate groups" refers to the content of carboxylate groups; when the first chain extender is a polyacrylate sulfonate, the "content of carboxylate groups or / and sulfonate groups" refers to the content of sulfonate groups; when the first chain extender is a combination of a polyacrylate carboxylate and a polyacrylate sulfonate or a polyacrylate carboxylate / sulfonate, the "content of carboxylate groups or / and sulfonate groups" refers to the total content of carboxylate groups and sulfonate groups.

[0065] In some embodiments, the method for preparing the first chain extender described above comprises mixing an initiator, an acrylic monomer, an acrylate monomer, a first monomer (a hydroxy acrylate monomer and / or an acrylamide monomer), a second monomer (at least one of sodium acrylsulfonate and sodium acrylate) with a solvent, performing a free radical polymerization reaction, and removing the solvent under reduced pressure after the polymerization reaction is completed. The weight ratio of the acrylic monomer, the acrylate monomer, the first monomer, and the second monomer is (0.3-20):(0.1-21):(0.5-13):1.

[0066] The temperature of the free radical polymerization reaction can be 60-80°C, and the reaction time can be 2-4h.

[0067] As an example, the acrylic monomer can be selected from one or more of monomers having a carbon atom number of 3-8. Alternatively, the acrylic monomer includes acrylic acid and / or methacrylic acid.

[0068] As an example, the acrylate monomer can be selected from one or more of monomers having a carbon atom number of 4-12. Alternatively, the acrylate monomer includes at least one of methyl methacrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, and isooctyl acrylate.

[0069] As an example, the hydroxy acrylate monomer can be selected from one or more of monomers having a carbon atom number of 5-12. Alternatively, the hydroxy acrylate monomer includes at least one of hydroxy ethyl acrylate, hydroxy ethyl methacrylate, hydroxy propyl acrylate, hydroxy propyl methacrylate, hydroxy butyl acrylate, and hydroxy butyl methacrylate.

[0070] As an example, the acrylamide monomer can be selected from one or more of monomers having a carbon atom number of 3-6. Alternatively, the acrylamide monomer includes acrylamide and / or methacrylamide.

[0071] In the present application, the initiator can be various free radical initiators that initiate polymerization of the above monomers. In some embodiments, the initiator includes dibenzoyl peroxide, tert-butyl peroxybenzoate, azobisisobutyronitrile, azobisisoheptyl nitrile, cyclohexanone peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, hydrogen peroxide, persulfate, dimethyl azobis isobutyrate, azobis isobutyl amide hydrochloride, 2,2 ， - at least one of azobis (2-methyl-4-carboxybutyronitrile) and 2,2 ， - at least one of azobis (2-methyl-4-carboxybutyronitrile) and 2,2

[0072] S300: The product obtained in step S200 is mixed with a second chain extender for a third time. As a result, the second chain extender further extends the chain, so that the molecular weight of the waterborne polyurethane is further increased.

[0073] In this step, the product obtained in step S200 can be post-extended by adding a second chain extender under stirring. In some embodiments, the second chain extender includes at least one of a diamine and an alcohol amine. The diamine is, for example, ethylenediamine, and the alcohol amine is, for example, ethanol amine. The mass amount of the second chain extender can be 0.5% to 5% relative to the total amount of reactants. Here, the total amount of reactants is determined based on the total amount of reactants (oligomer polyol, first isocyanate, first chain extender, second chain extender, and water).

[0074] In this step, the temperature of the third mixing (i.e., the chain extension reaction) can be 20°C to 40°C, and the time can be 10 min to 50 min.

[0075] S400: The product obtained in step S300 is mixed with water for a fourth time. The polyurethane is dispersed at high speed by adding water (e.g., dropwise) as an emulsifying agent, so that emulsification is achieved. Through the emulsification, a waterborne polyurethane emulsion with a solid content of 40% to 75% can be obtained.

[0076] In some embodiments, the method can further include removing the acetone under reduced pressure. The acetone evaporated under reduced pressure can be recycled.

[0077] According to a second aspect of the present application, the present application provides a waterborne polyurethane emulsion prepared by the method.

[0078] In some embodiments, the waterborne polyurethane emulsion has a solid content of 50% to 75% and an average particle size of 100 nm to 150 nm.

[0079] The waterborne polyurethane emulsion also has high stability, such as no delamination after being placed at room temperature for a long time (e.g., ≥ 180 days or more).

[0080] According to a third aspect of the present application, there is provided a two-component polyurethane adhesive comprising a component A and a component B, wherein the component A comprises the waterborne polyurethane emulsion according to the second aspect of the present application, and the component B comprises a second isocyanate.

[0081] According to the present application, the component A can further comprise additives, which can be selected according to existing two-component polyurethane adhesives. In some embodiments, the additives comprise at least one of a thickening agent, a defoaming agent, and a leveling agent. The additives are typically waterborne materials.

[0082] Further, in the component A, the mass content of the waterborne polyurethane emulsion is 70-90 parts per 100 parts of the total weight of the component A.

[0083] As an example, in the component A, the waterborne polyurethane emulsion is 85-99 parts, the waterborne thickening agent is 0.05-5 parts, the waterborne defoaming agent is 0.03-6 parts, the waterborne leveling agent is 0.02-4 parts, and the total amount of the component A is 100 parts by mass.

[0084] According to the present application, the component B can further comprise a waterborne color paste and water. The waterborne color paste can be a window pigment, which is used to facilitate the judgment of whether the components A and B are mixed uniformly by an operator during the mixing process.

[0085] In some embodiments, in the component B, the second isocyanate is 80-90 parts, the waterborne color paste is 0-1 parts, the water is 10-19 parts, and the total amount of the component B is 100 parts by mass.

[0086] In some embodiments, the two-component polyurethane adhesive is prepared by separately preparing the component A comprising the waterborne polyurethane emulsion and the component B comprising the second isocyanate to obtain the two-component polyurethane adhesive.

[0087] In other embodiments, the two-component polyurethane adhesive is prepared by separately preparing the component A comprising the waterborne polyurethane emulsion and the component B comprising the second isocyanate; and then, as shown in S500, mixing the component A comprising the waterborne polyurethane emulsion and the component B comprising the second isocyanate to obtain the two-component polyurethane adhesive. The mixing can be performed at room temperature. Figure 2

[0088] In some embodiments, the mass ratio of the component A to the component B is (10-20) : 1. Thus, after mixing the component A and the component B, the two-component polyurethane adhesive can be prepared. The mass ratio of the waterborne polyurethane emulsion to the second isocyanate is (12-25) : 1.

[0089] ​Further, the second isocyanate is an isocyanate curing agent, such as an isocyanate polymer. The cured isocyanate is commercially available, including, for example, at least one selected from BASF Desmodur DN, Desmodur N3600, Bayhydur 3100, Bayhydur XP2547, Bayhydur XP2451, and NPU AQ-140. Additionally, the isocyanate curing agent may contain 13%-25% by mass of isocyanate groups (NCO).

[0090] Those skilled in the art will understand that the adhesive of the present invention is a two-component reactive curing adhesive, that is, when the adhesive is applied to the surface of the objects to be bonded, the polyurethane in component A and the second isocyanate in component B can undergo a curing reaction to form a cured film on the surface of the objects to be bonded. The curing conditions may include: a temperature of 20℃-50℃ and a time of 24h-168h.

[0091] The two-component polyurethane adhesive of the present invention has the advantages of strong adhesion, high temperature and high humidity resistance, strong mechanical properties, high hydrophilicity, large molecular weight, high solid content, and high degree of crosslinking.

[0092] The embodiments of the present invention are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known to others. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0093] In the following examples and comparative examples,

[0094] The leveling agent is BYK-301 from BYK, the thickener is TEGO ViscoPlus3030 from TEGO, the defoamer is BYK-028 from BYK, and the water-based colorant is B6153-SA from KODI.

[0095] The preparation examples are used to illustrate the first chain extender and its preparation method.

[0096] Preparation Example 1

[0097] To a solution of 20 g of ethyl acetate dissolved with azobisisobutyronitrile (0.08 g) at 70 °C, a monomer mixture containing 2.3 g of methacrylic acid, 1 g of methyl methacrylate, and 3 g of ethyl acrylate, 0.53 g of hydroxyethyl methacrylate, 1.42 g of acrylamide, 1.44 g of sodium acrylsulfonate, and 0.9 g of sodium acrylate was added dropwise for 90 min, and then the polymerization was performed at 70 °C for 3 h. After the reaction was completed, the solvent was removed under reduced pressure to prepare a polyacrylate sulfonate, which was designated as Al. The characterization results thereof are shown in Table 1.

[0098] Preparation Example 2-7

[0099] The first chain extender was prepared according to the method of Preparation Example 1, except that the amounts of the reactants were adjusted, and the characterization results of the prepared products are shown in Table 1. The prepared products were A2 to A7, respectively.

[0100] Table 1

[0101]

[0102]

[0103] In Table 1, the test method for the hydroxyl value: acetic anhydride-pyridine method.

[0104] The test method for the content of sulfonate groups and carboxylate groups: the content of sulfonate groups and carboxylate groups in the system was determined by the thymol blue-methylene blue acid phase separation titration method.

[0105] The test method for the content of amide groups: the first chain extender was dissolved in dimethyl sulfoxide (DMSO) solvent and subjected to nuclear magnetic resonance hydrogen spectrum (frequency 600 MHz) test, and the content of amide groups was calculated according to the characteristic peak area of the amide groups.

[0106] Example 1

[0107] 1) Preparation of an aqueous polyurethane emulsion

[0108] (1) At a temperature of 120 °C, 80 g of polybutylene adipate glycol (Mw = 2000) was subjected to water removal under reduced pressure for 3 h, with the reduced pressure being controlled to be -0.06 MPa, and then the temperature was lowered to 50 °C. 4.46 g of isophorone diisocyanate and 10.12 g of hexamethylene diisocyanate were added to the system and stirred. After the isocyanate content in the reaction system reached the theoretical value (-NCO content of 2.9%) was determined by chemical titration, the temperature was lowered to 40 °C, and 80 g of acetone was added to adjust the viscosity of the system, to obtain a prepolymer.

[0109] (2) Under high speed stirring, control the dropping rate to be finished within 30 min, drop 10 g of polyacrylate sulfonate obtained in Preparation Example 1 into the above pre-polymer, after the dropping is finished, continue to stir for 50 min.

[0110] (3) Add 1.20 g of ethylenediamine and 1.28 g of ethanolamine to the product obtained in step (2) to perform post-chain extension, and stir at 30°C for 25 min.

[0111] (4) Emulsify the product obtained in step (3) by dropping 60 g of deionized water to form an emulsion, and remove acetone under reduced pressure to obtain an aqueous polyurethane emulsion with a solid content of 57%.

[0112] 2) Preparation of two-component polyurethane adhesive

[0113] Prepare A component: according to parts by mass, 90 parts of aqueous polyurethane emulsion, 3 parts of thickening agent, 5 parts of defoaming agent, 2 parts of leveling agent;

[0114] Prepare B component: according to parts by mass, 85 parts of BASF Desmodur DN, 1 part of aqueous color paste, and 14 parts of water.

[0115] Mix the above A component and B component at a mass ratio of 20:1 at room temperature.

[0116] Example 2-7

[0117] Prepare the aqueous polyurethane emulsion and two-component polyurethane adhesive according to the method of Example 1, except that in the preparation of the aqueous polyurethane emulsion, the amount of oligomeric polyol, the type and amount of the first chain extender are adjusted, as shown in Table 2.

[0118] Comparative Example 1

[0119] 1) Preparation of aqueous polyurethane emulsion

[0120] (1) At a temperature of 120°C, mix 80 g of polybutylene adipate diol with a weight average molecular weight of 650 and 1.5 g of polytetrahydrofuran ether diol with a weight average molecular weight of 650, remove water and small molecules in the polyol under reduced pressure for 3 h, control the reduced pressure to be -0.06 MPa, and control the water content in the system to be 0.08%, after the water removal is finished, cool to 50°C, add 2.25 g of isophorone diisocyanate and 13.46 g of hexamethylene diisocyanate into the system and mix uniformly, use chemical titration method to track the isocyanate content in the reaction system to reach the theoretical value (-NCO content is 3.7%), cool to 40°C, and add 160 g of acetone to adjust the viscosity of the system to obtain a pre-polymer.

[0121] (2) Under high speed stirring, control the dropping rate to end within 30 min, drop 4.75 g of 2-(2-aminoethyl) aminoethanesulfonic acid sodium into the above pre-polymer for mixing, after the dropping ends, continue to react for 50 min under high speed stirring.

[0122] (3) Under high speed stirring, add 0.24 g of ethylenediamine and 1.58 g of ethanolamine to the product of step (2) for post chain extension, the reaction temperature is 30℃, the reaction time is 25 min, and 260 g of deionized water is dropped for emulsification, mix uniformly to form an emulsion, after the emulsion is formed, remove the acetone under reduced pressure to prepare a waterborne polyurethane emulsion with a solid content of 37%.

[0123] 2) Preparation of two-component polyurethane adhesive

[0124] Prepare A component: according to mass parts, waterborne polyurethane accounts for 90 parts, waterborne thickening agent accounts for 3 parts, waterborne defoamer accounts for 5 parts, and waterborne leveling agent accounts for 2 parts;

[0125] Prepare B component: according to mass parts, Basf Desmodur DN accounts for 85 parts, waterborne color paste accounts for 1 part, and water accounts for 14 parts.

[0126] Mix the above A component and B component according to a mass ratio of 20:1 at room temperature uniformly.

[0127] Comparative Example 2

[0128] 1) Preparation of waterborne polyurethane emulsion

[0129] (1) At a temperature of 120℃, mix 80 g of polybutylene adipate glycol with a weight average molecular weight of 2000 and 32 g of polytetrahydrofuran ether glycol with a weight average molecular weight of 250, remove water and small molecules in the polyol under reduced pressure for 3 h, control the reduced pressure to be -0.06 MPa, and control the water content in the system to be 0.08%, after the water removal ends, cool to 50℃, add 3.03 g of isophorone diisocyanate and 16.84 g of hexamethylene diisocyanate into the system for mixing uniformly, use chemical titration method to track and determine the isocyanate content in the reaction system to reach the theoretical value (-NCO content is 2.3%), cool to 40℃, and add 200 g of acetone to adjust the viscosity of the system, so as to obtain a pre-polymer.

[0130] (2) Under high speed stirring, control the dropping rate to end within 30 min, drop 3.36 g of dimethylpropionic acid into 85 mass parts of the pre-polymer for mixing, after the dropping ends, continue to react for 50 min under high speed stirring.

[0131] (3) Under high speed stirring, add 0.24 g of ethylenediamine and 1.58 g of ethanolamine to the product obtained in step (2) to perform post chain extension, and add 100 g of deionized water dropwise to emulsify, mix uniformly to form an emulsion, and remove the acetone under reduced pressure after the emulsion is formed to prepare an aqueous polyurethane emulsion with a solid content of 59%.

[0132] 2) Preparation of two-component polyurethane adhesive

[0133] Prepare component A: 90 parts of aqueous polyurethane; 3 parts of aqueous thickening agent; 5 parts of aqueous defoaming agent; and 2 parts of aqueous leveling agent.

[0134] Prepare component B: 85 parts of BASF Desmodur DN; 1 part of aqueous color paste; and 14 parts of water.

[0135] Mix the above-mentioned component A and component B at a mass ratio of 20:1 at room temperature.

[0136]

[0137]

[0138] In Table 2, the test method for the average particle size of the aqueous polyurethane emulsion: a small amount of component A of the aqueous polyurethane emulsion is added to deionized water for dilution, and then the particle size of the emulsion is tested by a laser particle size analyzer, the test temperature is (23±2) °C, and the relative humidity is (50±5) %.

[0139] The test method for emulsion stability: simulate the storage stability by centrifugal acceleration sedimentation test, after centrifugal sedimentation at 3000 r / min in a centrifuge for 15 min, if there is no sedimentation, it can be considered that there is a storage stability period of more than 6 months.

[0140] Test example

[0141] 1. Test of peel strength

[0142] The above-mentioned two-component adhesive is coated on one side of ABS plate and soft leather, after coating (coating amount is 120 g / m 2 ), the soft leather is bonded to the ABS plate, and the peel strength is tested according to the adhesive 180° peel strength test method of GB / T2790 at room temperature (25 °C, 50% humidity) after applying pressure of 0.05 MPa at 90 °C for 3 min, the peel speed is 300 mm / min.

[0143] i.e. peel strength: test the peel strength within 0.5 h after coating;

[0144] peel strength: test the peel strength after 72 h at room temperature;

[0145] 100℃ heat aging peel strength: after the soft leather bonded on the ABS plate was completely cured, the leather was cut into a sample with a width of 25±0.5mm and a length of more than 200mm, and then the sample was placed in a 100℃ air oven, taken out after aging for 168h, cooled for 0.5h, and then the peel strength was tested.

[0146] 2. Test of resistance to creep deformation

[0147] The completely cured soft leather (25±0.5mm wide) bonded on the ABS plate was manually peeled off 10mm from the bonding interface of one end of the sample, and a line was drawn at the end of the peeling. Then the sample was placed in an environmental chamber at 90℃ for 30min, and a 100g weight was placed on the surface of the peeling end for 24h. After the test was completed, the sample was taken out, and the distance from the line to the end of the peeling was measured using a ruler.

[0148] 3. Tensile strength and elongation at break were tested according to GB / T 1040.3 2006

[0149] Preparation of the sample: the A component was poured into a polytetrahydrofuran mold on a water platform, and a film was cast. The film was placed at room temperature for 3h, and then was placed in a 60±2℃ air drying oven for 6h, and then was naturally cooled at room temperature to prepare a glue film. The prepared glue film was cut into a sample with a width of 25±0.5mm, a thickness of 4±0.5mm, and a length of 200mm according to GB / T 1040.3.

[0150] Test conditions: the sample to be tested was placed in a standard environment (23±2)℃ and (50±5)% relative humidity specified in GB / T 2918 for more than 24h, and the test was performed in the environment, wherein the tensile speed was 100mm / min.

[0151] The results are shown in Table 3.

[0152] Table 3

[0153]

[0154] As shown in Table 3, the tensile strength, elongation at break of the A component containing the polyurethane emulsion prepared in Examples 1 to 7, and the peel strength, peel strength, 100℃ heat aging peel strength, and resistance to creep of the two-component polyurethane adhesive were higher than those of the adhesive prepared in Comparative Examples 1 and 2.

[0155] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples, without contradiction.

[0156] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0157] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

Claims

1. A method for preparing an aqueous polyurethane emulsion, characterized in that, include: Oligomeric polyol, first isocyanate, first chain extender, second chain extender and water are mixed to obtain an aqueous polyurethane emulsion; The first chain extender includes at least one of polyacrylate carboxylate, polyacrylate sulfonate, and polyacrylate carboxylate / sulfonate. The method for preparing the first chain extender includes: In the presence of an initiator and a solvent, acrylic monomers, acrylate monomers, a first monomer, and a second monomer undergo free radical polymerization; wherein, The first monomer is selected from hydroxy acrylate monomers and acrylamide monomers; The second monomer is selected from at least one of sodium propylene sulfonate and sodium acrylate; The mixing is performed according to the following steps: (1) The oligomeric polyol and the first isocyanate are first mixed to obtain a prepolymer; (2) The prepolymer is mixed with the first chain extender in a second mixing process; (3) The product obtained in step (2) is mixed with the second chain extender in a third mixing process; (4) The product obtained in step (3) is mixed with water for a fourth time to obtain an aqueous polyurethane emulsion.

2. The method according to claim 1, characterized in that, The molar ratio of the oligomeric polyol to the first isocyanate is (0.2-2):1; Optionally, the oligomeric polyol includes polyester polyols and optionally polyether polyols; Optionally, the weight-average molecular weight of the polyester polyol is 500-10000; Optionally, the polyester polyol includes at least one of polybutylene adipate diol, polyhexyl adipate diol, polycaprolactone diol, and polycarbonate diol; Optionally, the weight-average molecular weight of the polyether polyol is 90-2000; Optionally, the polyether polyol includes at least one of polytetrahydrofuran ether diol, polypropylene diether alcohol, and polyethylene diether alcohol; Optionally, the first isocyanate includes at least one of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylphenyl diisocyanate, polymethylene polyphenyl polyisocyanate, and phenyl diisocyanate.

3. The method according to claim 1, characterized in that, The first chain extender satisfies at least one of the following conditions: The weight-average molecular weight is 500-5000; The hydroxyl value ranges from 15 mg KOH / g to 77 mg KOH / g. The content of carboxylate groups and / or sulfonate groups is 0.1 mmol / g to 2 mmol / g; The content of amide groups is 0.1 mmol / g-1 mmol / g.

4. The method according to claim 3, characterized in that, The weight ratio of the acrylic monomer, the acrylate monomer, the first monomer, and the second monomer is (0.3-20):(0.1-21):(0.5-13):1; Optionally, the acrylic monomer includes at least one of acrylic acid and methacrylic acid; Optionally, the acrylate monomers include at least one of methyl methacrylate, butyl methacrylate, ethyl acrylate, ethyl methacrylate, and isooctyl acrylate; Optionally, the hydroxy acrylate monomers include at least one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and hydroxybutyl methacrylate; Optionally, the acrylamide monomer includes at least one of acrylamide and methacrylamide.

5. The method according to claim 1, characterized in that, The mass ratio of the first chain extender to the prepolymer is 1:(7-40).

6. The method according to claim 1, characterized in that, The second chain extender includes diamines and / or alcoholamines; Optionally, the mass content of the second chain extender is 0.5%-5% relative to the total mass of the reactants.

7. An aqueous polyurethane emulsion, characterized in that, It is prepared using the method described in any one of claims 1-6.

8. A two-component polyurethane adhesive, characterized in that, It includes component A and component B, wherein component A contains the aqueous polyurethane emulsion of claim 7, and component B contains a second isocyanate.

9. The two-component polyurethane adhesive according to claim 8, characterized in that, The isocyanate group content in the second isocyanate is 13%-25% by mass; Optionally, the mass ratio of the aqueous polyurethane emulsion to the second isocyanate is (12-25):1; Optionally, component A further comprises additives, said additives including at least one of thickeners, defoamers, and leveling agents; Optionally, the waterborne polyurethane emulsion contains 70-90 parts by mass, based on a total weight of 100 parts of component A.

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