A highly phase separated polyurethane emulsion, its preparation method and use

Abstract

The application provides a highly phase-separated polyurethane emulsion and a preparation method and application thereof, and belongs to the technical field of polymer materials, and comprises, in parts by weight, linear polyurethane oligomer 18-42 parts, polymeric diol 30-50 parts, hydrophilic chain extender 3-7 parts, neutralizing agent 2-5.5 parts and catalyst 0.1-0.5 parts, wherein the preparation raw material of the linear polyurethane oligomer comprises diisocyanate monomer and small-molecule diol, and the molar ratio of the small-molecule diol to the diisocyanate monomer is (0.50-0.69):1. The polyurethane emulsion provided by the application has a polyurethane adhesive film with high phase separation, excellent mechanical properties, water resistance and thermal stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer materials, and particularly relates to a highly phase-separated polyurethane emulsion, a preparation method and application thereof, and in particular to a highly phase-separated polyurethane emulsion, a preparation method and application thereof, and a polyurethane adhesive film with a phase-separated structure. BACKGROUND

[0002] Waterborne polyurethane (WPU) is a kind of polyurethane dispersion with water as the dispersion medium, which has excellent flexibility, adhesion and wear resistance of polyurethane materials, and environmental protection, low toxicity, low VOC (Volatile Organic Compounds) emission and other characteristics of water-based system, and is widely used in many fields such as coatings, adhesives, textile coatings, synthetic leather, inks and the like. With the increasingly stringent environmental protection regulations and the continuous increase of demand for sustainable materials, WPU has become an important direction to replace solvent-based polyurethane, and its market demand and technical value continue to grow.

[0003] The final performance of WPU depends largely on its micro-phase structure, especially the degree of micro-phase separation between soft segments and hard segments. The micro-phase separation structure directly affects the key performance indicators of the coating film, such as mechanical strength, elasticity, water resistance, heat resistance and the like. The ideal WPU should have obvious phase separation structure to form a flexible soft segment continuous phase and a highly aggregated hard segment microzone, thereby enhancing rigidity and durability while maintaining flexibility.

[0004] However, the synthesis process of traditional WPU mainly adopts a two-step method, i.e. first reacting isocyanate with polyether or polyester polyol to form a NCO-terminated prepolymer, and then adding a small molecule chain extender to carry out chain extension and introduce hydrophilic groups to realize dispersion in water. In this process, the small molecule chain extender can only connect two or a limited number of prepolymer segments, and the hard segment structure formed is usually composed of di-functional isocyanate and low molecular chain extender (such as 1,4-butanediol, ethylenediamine, etc.). Such hard segment has shorter chain length and poorer regularity, and it is difficult to form an ordered aggregated microzone structure, resulting in that the hydrogen bond or van der Waals force between hard segments cannot be fully exerted, and the degree of micro-phase separation is insufficient.

[0005] Therefore, it is urgent to develop a phase-separated polyurethane material that can effectively improve the chain length and aggregation ability of hard segments, thereby enhancing the phase separation degree of WPU, to further improve the comprehensive performance of waterborne polyurethane material and meet the dual demands of environmental protection and functionality in high-end application fields. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a highly phase-separated polyurethane emulsion, a preparation method and application thereof.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] In one aspect, the present application provides a highly phase-separated polyurethane emulsion, comprising, by weight parts:

[0009] linear polyurethane oligomer 18-42 parts, polymeric diol 30-50 parts, hydrophilic chain extender 3-7 parts, neutralizing agent 2-5.5 parts, and catalyst 0.1-0.5 parts, wherein:

[0010] The raw materials for preparing the linear polyurethane oligomer include diisocyanate monomers and small molecule diols, and the molar ratio of the small molecule diols to the diisocyanate monomers is (0.50-0.69):1, such as 0.50:1, 0.52:1, 0.54:1, 0.55:1, 0.56:1, 0.58:1, 0.60:1, 0.62:1, 0.64:1, 0.65:1, 0.67:1, 0.69:1, etc.

[0011] Compared with the existing technology that uses small molecule chain extenders to connect NCO-terminated prepolymers, the hard segment can only be composed of short chain extenders and di-functional isocyanates, and it is difficult to form continuous, regular, and strong aggregation hard segment microdomains. The polyurethane emulsion provided by the present application can make the obtained polyurethane adhesive film have high phase separation, specifically:

[0012] The present application uses linear polyurethane oligomers as hard segments, and the molecular chain of the linear polyurethane oligomers is long and regular, and has strong aggregation ability, thereby improving the microphase separation degree of the polyurethane material, and making the finally obtained polyurethane adhesive film have excellent mechanical properties and water resistance.

[0013] In the present application, the linear polyurethane oligomer 18-42 parts can be 18 parts, 20 parts, 22 parts, 25 parts, 28 parts, 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, etc., the polymeric diol 30-50 parts can be 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 parts, 50 parts, etc., the hydrophilic chain extender 3-7 parts can be 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, etc., the neutralizing agent 2-5.5 parts can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, etc., and the catalyst 0.1-0.5 parts can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, etc.

[0014] Preferably, the average polymerization degree of the linear polyurethane oligomer is 3-5.5, such as 3, 3.5, 4, 4.5, 5, 5.5, etc.

[0015] The molar ratio of the small molecule diol and the diisocyanate monomer is within the limited range of the present application, which can make the linear polyurethane oligomer NCO-terminated, and the average polymerization degree is 3-5.5, the molecular chain length is relatively appropriate, so that the finally obtained phase separation polyurethane adhesive film has relatively optimal tensile strength and elongation at break, and excellent water resistance.

[0016] If the addition amount of the small molecule diol is too low, the polymerization degree of the obtained linear polyurethane oligomer is low, the molecular chain length is short, and the phase separation degree of the polyurethane adhesive film is reduced; if the addition amount of the small molecule diol is too high, the molecular chain of the linear polyurethane oligomer is long, the brittleness of the polyurethane adhesive film is increased, and even the end group of the linear polyurethane oligomer is OH group, which is not conducive to the synthesis of the subsequent polyurethane material.

[0017] The polyurethane material provided by the present application provides a new synthesis route, which constructs a linear polyurethane oligomer with a regular structure as a long hard segment structure in advance, introduces a soft segment structure and a hydrophilic group, and finally makes the obtained waterborne polyurethane adhesive film have high phase separation.

[0018] Preferably, the diisocyanate monomer includes any one or a combination of at least two of 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hexamethylene diisocyanate or diphenylmethane diisocyanate.

[0019] Preferably, the small molecule polyol includes any one or a combination of at least two of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol or 1,6-hexanediol.

[0020] Preferably, the preparation method of the linear polyurethane oligomer includes:

[0021] The small molecule diol and the diisocyanate monomer are mixed in a molar ratio of (0.50-0.69):1, and a polymerization reaction is carried out under the catalysis of a catalyst to obtain the linear polyurethane oligomer.

[0022] Preferably, the temperature of the polymerization reaction is 75-80°C, for example, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, etc., and the time is 1.5-2 h, for example, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h, 2 h, etc.

[0023] Preferably, the relative molecular weight of the polymeric diol is 2000-3000, such as 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, etc.

[0024] Preferably, the hydrophilic chain extender comprises 2,2-dimethylol propionic acid (DMPA) and / or 2-dimethylol butanoic acid (DMBA).

[0025] Preferably, the neutralizing agent comprises triethylamine.

[0026] Preferably, the catalyst comprises an organometallic catalyst, preferably an organotin catalyst.

[0027] Preferably, the highly phase-separated polyurethane material further comprises an organic solvent 10-50 parts, which can be 10 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, etc., and / or deionized water 100-300 parts, which can be 100 parts, 120 parts, 140 parts, 150 parts, 160 parts, 180 parts, 200 parts, 220 parts, 250 parts, 280 parts, 300 parts, etc.

[0028] Preferably, the organic solvent comprises any one or a combination of at least two of N-methyl pyrrolidone (NMP), dimethylformamide (DMF) or acetone.

[0029] In a second aspect, the present application provides a preparation method of the highly phase-separated polyurethane emulsion according to the first aspect, the preparation method comprising:

[0030] S1. polymerizing the polymeric diol with the linear polyurethane oligomer under the catalysis of the catalyst to obtain a prepolymer;

[0031] S2. performing a chain extension reaction on the prepolymer with the hydrophilic chain extender, and after the reaction is completed, adding a neutralizing agent and optionally deionized water to obtain the highly phase-separated polyurethane emulsion.

[0032] Preferably, in step S1, the temperature of the polymerization reaction is 70-80℃, such as 70℃, 71℃, 72℃, 74℃, 75℃, 76℃, 78℃, 80℃, etc., and the time is 1-1.5 h, such as 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, etc.

[0033] Preferably, in step S2, the temperature of the chain extension reaction is 70-80℃, such as 70℃, 71℃, 72℃, 74℃, 75℃, 76℃, 78℃, 80℃, etc., and the time is 2-3 h, such as 2 h, 2.1 h, 2.2 h, 2.4 h, 2.5 h, 2.6 h, 2.8 h, 3 h, etc.

[0034] Preferably, in step S2, the temperature of the addition of the neutralizing agent is 35-45℃, such as 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 42℃, 44℃, 45℃, etc.

[0035] In some embodiments of the present application, the method for preparing the highly phase-separated polyurethane emulsion comprises:

[0036] S1. Under a protective atmosphere, the polymer diol and the linear polyurethane oligomer are subjected to a polymerization reaction at 70-80℃ for 1-1.5 h under the catalysis of a catalyst to obtain an NCO-terminated prepolymer;

[0037] S2. After the polymerization reaction, a hydrophilic chain extender previously dissolved with a solvent is added, and a heat preservation reaction is carried out at 70-80℃ for 2-3 h, and then the temperature is lowered to 35-45℃, and a neutralizing agent is added for neutralization;

[0038] S3. Optionally, after the neutralization reaction is completed, the reaction product is added to deionized water for emulsification and dispersion, preferably the rotation speed of the emulsification and dispersion is 1500-3000 rpm, such as 1500 rpm, 1600 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2500 rpm, 2800 rpm, 3000 rpm, etc., and preferably the time of the emulsification and dispersion is 20-30 min, such as 20 min, 22 min, 24 min, 25 min, 26 min, 28 min, 30 min, etc., to obtain a stable emulsified aqueous polyurethane emulsion.

[0039] In a third aspect, the present application provides a polyurethane adhesive film with a phase separation structure, which is prepared by film coating and drying of the highly phase-separated polyurethane emulsion of the first aspect.

[0040] In the present application, the emulsion is dried into a film, and the hard segment and the soft segment can obviously undergo micro-phase separation, and the obtained polyurethane material has excellent mechanical properties and water resistance.

[0041] In a fourth aspect, the present application provides a use of the highly phase-separated polyurethane emulsion of the first aspect in the preparation of an aqueous coating.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] The polyurethane emulsion provided by the application has high phase separation and excellent mechanical properties, water resistance and thermal stability. DETAILED DESCRIPTION

[0044] The technical solutions of the application are further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0045] In the following specific embodiments of the application, the raw materials are all conventional materials in the art and can be purchased from commercially available products, and part of the raw material information is as follows:

[0046] Polymer diol 1: PTMG2000, purchased from Mitsubishi;

[0047] Polymer diol 2: polypropylene glycol PPG3000, purchased from Nantong Yixun Chemical Industry;

[0048] Polymer diol 3: polycarbonate diol PCDL 2000, purchased from Shanghai Shurui Chemical Industry;

[0049] Preparation Example 1

[0050] The preparation example provides a preparation method of a linear polyurethane oligomer, as follows:

[0051] In a four-necked flask with a stirring device, a temperature control system and nitrogen protection, 45 parts of 1,4-butanediol and 222.3 parts of isophorone diisocyanate (molar ratio 0.50:1) were mixed, heated to 75°C, and reacted for 2 h under the catalysis of 0.3 parts of dibutyltin dilaurate to obtain a linear polyurethane oligomer with an average polymerization degree of 3.

[0052] Preparation Example 2

[0053] The preparation example provides a preparation method of a linear polyurethane oligomer.

[0054] The difference from Preparation Example 1 is that in the present preparation example, the molar ratio of small molecule diol and diisocyanate is 0.60:1 by changing the amount of 1,4-butanediol added, and the linear polyurethane oligomer obtained has an average polymerization degree of 4.

[0055] Preparation Example 3

[0056] The preparation example provides a preparation method of a linear polyurethane oligomer.

[0057] The difference from Preparation Example 1 is that, in the present preparation example, the molar ratio of small molecule diol and diisocyanate is 0.67:1 by changing the addition amount of 1,4-butanediol, and the average polymerization degree of the linear polyurethane oligomer obtained is 5.

[0058] Preparation Example 4

[0059] The difference from Preparation Example 1 is that, in the present comparative preparation example, the molar ratio of small molecule diol and diisocyanate is 0.69:1 by changing the addition amount of 1,4-butanediol, and the average polymerization degree of the linear polyurethane oligomer obtained is 5.5.

[0060] Preparation Example 5

[0061] The present preparation example provides a preparation method of a linear polyurethane oligomer as follows:

[0062] In a four-necked flask with stirring device, temperature control system and nitrogen protection, 31 parts of ethylene glycol and 262.4 parts of 4,4'-dicyclohexylmethane diisocyanate (H 12 MDI) (molar ratio 0.50:1) were mixed, heated to 75°C, and reacted for 2 h under the catalysis of 0.3 parts of dibutyltin dilaurate to obtain a linear polyurethane oligomer with an average polymerization degree of 3.

[0063] Comparative Preparation Example 1

[0064] The present preparation example provides a preparation method of a linear polyurethane oligomer.

[0065] The difference from Preparation Example 1 is that, in the present comparative preparation example, the molar ratio of small molecule diol and diisocyanate is 0.33:1 by changing the addition amount of 1,4-butanediol, and the average polymerization degree of the linear polyurethane oligomer obtained is 2.

[0066] Comparative Preparation Example 2

[0067] The difference from Preparation Example 1 is that, in the present comparative preparation example, the molar ratio of small molecule diol and diisocyanate is 0.71:1 by changing the addition amount of 1,4-butanediol, and the average polymerization degree of the linear polyurethane oligomer obtained is 6.

[0068] Examples 1-3

[0069] The present examples provide a highly phase-separated polyurethane emulsion, the constituent ingredients of which are shown in Table 1:

[0070] Table 1

[0071]

[0072] Note: Linear polyurethane oligomer is provided by Preparation Example 1, and the organotin catalyst is dibutyl tin dilaurate.

[0073] The preparation method is as follows:

[0074] S1. Under a protective atmosphere, the polymer diol and the linear polyurethane oligomer are subjected to a polymerization reaction under the catalysis of a catalyst to obtain an NCO-terminated prepolymer;

[0075] S2. After the polymerization reaction, a hydrophilic chain extender previously dissolved in an organic solvent is added for a holding reaction, and after the reaction is completed, the temperature is lowered to 40°C, and a neutralizing agent is added for neutralization;

[0076] S3. After the neutralization reaction is completed, the reaction product is added to deionized water for emulsification and dispersion to obtain a highly phase-separated polyurethane emulsion.

[0077] Examples 4-7

[0078] This example provides a highly phase-separated polyurethane emulsion.

[0079] The difference from Example 1 is that in this example, the linear polyurethane oligomer is provided by Preparation Examples 2-5, wherein the molar number of the linear polyurethane oligomer is the same as that of the linear polyurethane oligomer used in Example 1.

[0080] Comparative Examples 1-2

[0081] This comparative example provides a highly phase-separated polyurethane emulsion.

[0082] The difference from Example 1 is that in this comparative example, the linear polyurethane oligomer is provided by Comparative Preparation Examples 1-2, wherein the molar number of the linear polyurethane oligomer is the same as that of the linear polyurethane oligomer used in Example 1.

[0083] Comparative Example 3

[0084] This comparative example provides a phase-separated polyurethane emulsion.

[0085] The difference from Example 1 is that in this comparative example, the linear polyurethane oligomer is replaced by an equal molar number of isophorone diisocyanate.

[0086] Performance test

[0087] The sample emulsions provided by the examples and comparative examples are dropped into clean glassware, the thickness is controlled to be about 1 mm, and after a uniform gel film is formed at room temperature, the following performance tests are performed on the gel film, and the method is as follows:

[0088] (1) Phase separation degree:

[0089] The degree of phase separation is detected and calculated by FT-IR (Fourier transform infrared spectroscopy), specifically: the characteristic peaks of the sample in the ester carbonyl absorption region are fitted by Gaussian method, and the hydrogen bonding index HBI is calculated according to the absorption peak area of free carbonyl, disordered hydrogen-bonded carbonyl and ordered hydrogen-bonded carbonyl; the greater the HBI value, the higher the degree of hydrogen bonding, which shows a higher degree of microphase separation, and the calculation method of HBI value is:

[0090]

[0091] Wherein: S A is the peak area of hydrogen-bonded C=O, S B is the peak area of free C=O.

[0092] (2) Tensile strength and elongation at break: the sample is cut into dumbbell shape, and tested according to GB / T 528-2009, the tensile rate is 100 mm / min.

[0093] (3) Water absorption: the adhesive film is cut into a sample piece of 3 cm x 3 cm, and the mass of the sample piece is weighed as m0 according to T / CWA 206-2021, immersed in deionized water for 24 h, taken out and the surface water is absorbed with filter paper, and the mass is weighed as m1, and the water absorption is calculated according to the following formula:

[0094]

[0095] The test results are shown in Table 2:

[0096] Table 2

[0097]

[0098] It can be known from the examples and performance tests that by introducing linear polyurethane oligomers and other components, polyurethane materials with high phase separation can be obtained, and the adhesive film obtained by coating has excellent mechanical properties and water resistance, wherein the HBI is above 0.9, and the optimal can reach above 1, the tensile strength is above 50 MPa, the elongation at break is above 420%, and the water absorption is below 7%.

[0099] From the comparison of Examples 1, 4-6, it can be seen that in the linear polyurethane oligomer defined in the application, as the molar ratio of small molecule diol to diisocyanate increases from 0.50 to 0.67 (the average polymerization degree increases from 3 to 5), the oligomer chain segment growth enhances the regularity of hard segment and the degree of hydrogen bonding, the HBI increases significantly, the tensile strength increases synchronously, the elongation at break decreases, the water absorption decreases, and the microphase separation significantly enhances; when the molar ratio further increases to 0.69, the hard segment aggregation tends to be saturated and the packing frustration / free carbonyl increases, the HBI and the tensile strength no longer increase and decrease, the water absorption increases from the minimum value, but the phase separation degree of the obtained adhesive film is still high, and the performance can still meet the application requirements.

[0100] From the comparison of Example 1 and Comparative Examples 1-2, it can be seen that in the linear polyurethane oligomer defined in the application, when the molar ratio of small molecule polyol to diisocyanate is in the range of (0.5-0.69):1, the obtained polyurethane material has a higher phase separation degree, and excellent mechanical properties and water resistance.

[0101] From the comparison of Example 1 and Comparative Example 3, it can be seen that when the linear polyurethane oligomer is not introduced into the polyurethane material as a hard segment building unit, but the isocyanate is directly reacted with the polyether polyol to form a prepolymer, the hard segment chain in the structure is short, the distribution is disordered, and there is a lack of effective aggregation; from the comparison of the test results, it can be seen that the HBI of Comparative Example 3 is 0.78, which is significantly lower than 0.95 of Example 1, indicating that the microphase separation degree is lower and the hard segment aggregation ability is insufficient; at the same time, the tensile strength decreases to 44.6 MPa, and the water absorption increases to 8.2%, indicating that the structure has poor compactness and water resistance, although the elongation at break is slightly higher, but the overall performance is not as good as Example 1, which verifies the significant effect of pre-constructing linear hard segment structure on improving the performance of polyurethane.

[0102] The applicant declares that the technical solutions of the application are illustrated by the above examples, but the application is not limited to the above examples, that is, it does not mean that the application must rely on the above examples to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of each raw material of the product of the application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. A highly phase-separated polyurethane emulsion, characterized in that, By weight, it includes: The composition includes 18-42 parts of linear polyurethane oligomer, 30-50 parts of polymeric diol, 3-7 parts of hydrophilic chain extender, 2-5.5 parts of neutralizing agent, and 0.1-0.5 parts of catalyst, wherein: The raw materials for preparing the linear polyurethane oligomer include diisocyanate monomers and small molecule diols, wherein the molar ratio of the small molecule diols to the diisocyanate monomers is (0.50-0.69):

1. The linear polyurethane oligomer has an average degree of polymerization of 3.5-5.5; The small molecule diol is selected from any one or a combination of at least two of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol or 1,6-hexanediol.

2. The highly phase-separated polyurethane emulsion according to claim 1, characterized in that, The diisocyanate monomer is selected from any one or a combination of at least two of 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, phenyl dimethyl diisocyanate, tetramethylphenyl dimethyl diisocyanate, hexamethylene diisocyanate or diphenylmethane diisocyanate.

3. The highly phase-separated polyurethane emulsion according to claim 1 or 2, characterized in that, The relative molecular weight of the polymer diol is 2000-3000; And / or, the hydrophilic chain extender includes 2,2-dimethylolpropionic acid and / or 2-dimethylolbutyric acid; And / or, the neutralizing agent includes triethylamine; And / or, the catalyst includes an organometallic catalyst.

4. The highly phase-separated polyurethane emulsion according to claim 1 or 2, characterized in that, The highly phase-separated polyurethane material further includes 10-50 parts of organic solvent and / or 100-300 parts of deionized water.

5. A method for preparing a highly phase-separated polyurethane emulsion according to any one of claims 1-4, characterized in that, The preparation method includes: S1. Polymer diol and linear polyurethane oligomer are polymerized under the catalysis of a catalyst to obtain a prepolymer; S2. The prepolymer undergoes a chain extension reaction with a hydrophilic chain extender. After the reaction is complete, a neutralizing agent and deionized water are added to obtain the highly phase-separated polyurethane emulsion.

6. The preparation method according to claim 5, characterized in that, In step S1, the polymerization reaction is carried out at a temperature of 70-80°C for 1-1.5 hours. And / or, in step S2, the chain extension reaction is carried out at a temperature of 70-80°C for 2-3 hours; And / or, in step S2, the temperature at which the neutralizing agent is added is 35-45°C.

7. A polyurethane film with a phase separation structure, characterized in that, The polyurethane film is prepared by coating and drying the highly phase-separated polyurethane emulsion according to any one of claims 1-4.

8. The use of a highly phase-separated polyurethane emulsion as described in any one of claims 1-4 in the preparation of waterborne coatings.

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