Aqueous polyurethane dispersion and its preparation method and application

Abstract

The present invention provides an aqueous polyurethane dispersion, a preparation method and an application thereof. The raw materials for preparing the aqueous polyurethane dispersion include a combination of polymer diol, diisocyanate, small molecule diol, dimethylol propionate, sulfonic acid surfactant, post-chain extender, acetone and water. By adopting the combination of the raw materials and a specific preparation method, the obtained aqueous polyurethane dispersion has a higher molecular weight and solid content, and also has better stability. At the same time, it is insensitive to various environmental factors such as acid, alkali, electrolyte, etc., is not prone to demulsification, and has good tolerance to fillers and additives added when compounding into slurry.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane dispersion synthesis, and particularly relates to an aqueous polyurethane dispersion and a preparation method and application thereof. Background Art

[0002] Waterborne polyurethane is an environmentally friendly product formed by dispersing polyurethane molecular chains in water through certain technical means. It is primarily used in a variety of applications, including adhesives, coatings, and synthetic leather. Depending on the type of hydrophilic functional groups expressed in the polyurethane segments, waterborne polyurethane systems can be categorized as anionic, cationic, nonionic, and zwitterionic. Common anionic waterborne polyurethanes include carboxylic acid-based and sulfonic acid-based.

[0003] At present, dimethylolpropionic acid (DMPA) and dimethylolbutanoic acid (DMBA) are mainly used in China to synthesize carboxylic acid-type waterborne polyurethane dispersions. Among them, DMPA needs to be added with a solvent to help it melt due to its high melting point (180°C) to achieve homogenization of the reaction system, so as to facilitate the smooth progress of subsequent reactions. The melting point of DMBA is lower than that of DMPA. It can be melted by increasing the reaction temperature in a solvent-free or low-solvent state to achieve homogenization of the reaction system. However, due to its side chain structure -CH2COO-, it affects the aggregation degree and microphase separation of the polyurethane hard segment, resulting in the DMBA system having worse film mechanical properties than the DMPA system under the same formula.

[0004] Carboxylic acid-based waterborne polyurethane dispersions are typically synthesized using methods such as the prepolymer method and the acetone method. The greatest challenge during the prepolymerization process is the dissolution and efficient reaction of the carboxylic acid diol. Therefore, the prepolymerization process requires high temperatures or the addition of organic solvents to achieve optimal dissolution of the carboxylic acid diol in the system. Furthermore, dimethylolpropionic acid exhibits a relatively slow reactivity, requiring the addition of a catalyst or elevated reaction temperature to achieve a faster reaction rate. Waterborne polyurethane dispersions prepared using the prepolymer method often have low prepolymer molecular weight, high levels of backmixing during emulsification and post-chain extension, and batch instability. Furthermore, the conventional acetone method utilizes a large amount of solvent, coupled with the low desolventizing efficiency of the intermittent desolventizing reactor, resulting in high energy consumption and significantly increased manufacturing costs. Furthermore, the emulsification process places high demands on equipment, making large-scale production inefficient.

[0005] CN108424507A reports a solvent-free method for producing aqueous polyurethane dispersions. DMBA is used as a hydrophilic chain extender, mixed with polyglycol, heated to 90°C, thoroughly stirred, and dissolved until clear. Isocyanate is then added to react and prepare a prepolymer. This method is suitable for preparing polyurethane dispersions because DMBA has a melting point of 108-115°C and relatively good solubility in polyglycol. However, this method is not suitable for DMPA systems because DMPA has a melting point of 178-180°C and dissolves poorly in polyglycol.

[0006] CN112266459A reports a high-solid content water-based polyurethane emulsion and a preparation method thereof, comprising mixing poly(hexylene adipate) glycol / diethylene glycol ether glycol, isophorone diisocyanate, and dibutyltin dilaurate at 70-80°C for a period of time, adding a hydrochloric acid solution for reaction, and then slowly adding dimethylolpropionic acid. After a period of reaction, the mixture is cooled to 50-55°C, the pH is adjusted to neutral, and the mixture is added to deionized water to obtain a WPU emulsion. Because the water in the hydrochloric acid solution acts as a solubilizing agent for DMPA, the problem of DMPA dissolution in the absence of an organic solvent and at a suitable temperature is solved. However, this method has the disadvantages of side reactions in the presence of water and is controlled by the viscosity of the prepolymer and the small molecular weight.

[0007] Taking conventional acetone-based batch synthesis and emulsification as an example, DMPA is selected as the raw material and acetone needs to be added to aid dissolution. However, due to the low reactivity of DMPA itself and the presence of large amounts of acetone, the concentration of reactants is low, reducing effective collisions. It is necessary to increase the amount of catalyst used or extend the reaction time to achieve the desired reaction level. Kettle emulsification has high requirements for prepolymer viscosity, requiring the addition of large amounts of acetone to control the prepolymer viscosity. Conventional desolventizing kettle desolventizing methods: high heating medium temperature, high degree of backmixing, and long desolventizing times cause the bound water in the boundary layer between polyurethane particles to volatilize, the emulsion particles to contact each other, and the emulsion viscosity to increase, even becoming a paste, which affects the preparation of high-solids emulsions.

[0008] Therefore, developing an aqueous polyurethane dispersion with high solid content, high molecular weight and high product batch stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the present invention aims to provide an aqueous polyurethane dispersion machine, a preparation method and application thereof. The aqueous polyurethane dispersion uses dimethylol propionate as a preparation raw material, which effectively reduces the amount of acetone added. At the same time, the addition of a surfactant further provides hydrophilicity, ultimately obtaining an aqueous polyurethane dispersion with high solid content, high molecular weight and high product batch stability.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides an aqueous polyurethane dispersion, wherein the raw materials for preparing the aqueous polyurethane dispersion include the following components in parts by weight:

[0012]

[0013] The amount of the polymer diol may be 42 parts by weight, 44 parts by weight, 46 parts by weight, 48 parts by weight, or 50 parts by weight.

[0014] The diisocyanate may be in an amount of 18 parts by weight, 20 parts by weight, 22 parts by weight, 24 parts by weight, 26 parts by weight, or 28 parts by weight.

[0015] The small molecule diol can be 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight or 3.5 parts by weight.

[0016] The dimethylol propionate may be 2.2 parts by weight, 2.4 parts by weight, 2.6 parts by weight, 2.8 parts by weight, 3 parts by weight, 3.2 parts by weight, 3.4 parts by weight, 4.6 parts by weight, 5.8 parts by weight, etc.

[0017] The amount of the sulfonic acid surfactant may be 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, or 1.8 parts by weight.

[0018] The amount of the post-chain extender can be 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, 0.7 parts by weight, 0.8 parts by weight, or 0.9 parts by weight.

[0019] The amount of acetone can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, or 9 parts by weight.

[0020] The amount of water may be 60 parts by weight, 70 parts by weight, 80 parts by weight, 90 parts by weight, 95 parts by weight, 105 parts by weight, 115 parts by weight, or 120 parts by weight.

[0021] First, the raw material used in the preparation of the aqueous polyurethane dispersion provided by the present invention is neutralized dimethylolpropionic acid, i.e., dimethylolpropionate, which can effectively reduce the amount of acetone added. At the same time, the dimethylolpropionate can also play a catalytic role, which can increase the reactivity of isocyanate groups and hydroxyl groups, thereby greatly shortening the reaction time.

[0022] Secondly, the dimethylolpropionate and the sulfonic acid surfactant in the raw materials for preparing the aqueous polyurethane dispersion provided by the present invention can play a synergistic role. The two can jointly improve the hydrophilicity of the aqueous polyurethane dispersion. Furthermore, under the premise of the same hydrophilicity, the usage amount of the dimethylolpropionate can be effectively reduced, thereby increasing the solid content of the emulsion. Therefore, the prepared aqueous polyurethane dispersion has a higher molecular weight and solid content, and also has better stability. At the same time, the aqueous polyurethane dispersion is insensitive to various environmental factors such as acids, alkalis, and electrolytes, is not prone to demulsification, and has good tolerance to fillers and additives added when compounding into slurry.

[0023] Preferably, the polymer diol includes any one of polytetramethylene glycol, polyoxypropylene glycol or polyoxyethylene glycol, or a combination of at least two thereof.

[0024] Preferably, the number average molecular weight of the polytetrahydrofuran diol is 1000-3000, for example, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600 or 2800.

[0025] Preferably, the number average molecular weight of the polyoxypropylene glycol is 1000-2000, for example, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600 or 2800.

[0026] Preferably, the number average molecular weight of the polyethylene glycol is 500 to 2000, for example, 700, 900, 1100, 1300, 1500 or 1800.

[0027] Preferably, the diisocyanate comprises any one or a combination of at least two of isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI) or toluene diisocyanate (TDI), more preferably a combination of isophorone diisocyanate and hexamethylene diisocyanate, and even more preferably a combination of isophorone diisocyanate and hexamethylene diisocyanate in a mass ratio of 1:(0.2-3) (e.g., 10.5, 1:0.7, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6 or 1:2.8, etc.).

[0028] Preferably, the small molecule diol includes any one or a combination of at least two of 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol.

[0029] Preferably, the raw materials for preparing the dimethylolpropionic acid salt include dimethylolpropionic acid and a neutralizing agent.

[0030] Preferably, the neutralizing agent comprises any one of triethylamine, N-methyldiethanolamine, N-methylmorpholine or N-ethylmorpholine, or a combination of at least two thereof.

[0031] Preferably, the sulfonic acid surfactant comprises sodium dodecylbenzenesulfonate.

[0032] Preferably, the post-chain extender includes any one of isophorone diamine, ethylenediamine, diethylenetriamine or hydrazine hydrate, or a combination of at least two thereof.

[0033] Preferably, the solid content of the aqueous polyurethane dispersion is 40-50%, for example, 42%, 44%, 46% or 48%.

[0034] Preferably, the raw materials for preparing the aqueous polyurethane dispersion further include a catalyst.

[0035] Preferably, the content of the catalyst in the preparation raw material is 0.03 to 0.05 parts by weight, for example, 0.032 parts by weight, 0.034 parts by weight, 0.036 parts by weight, 0.038 parts by weight, 0.04 parts by weight, 0.042 parts by weight, 0.044 parts by weight, 0.046 parts by weight or 0.048 parts by weight.

[0036] Preferably, the catalyst comprises an organobismuth catalyst.

[0037] In a second aspect, the present invention provides a method for preparing the aqueous polyurethane dispersion as described in the first aspect, the preparation method comprising the following steps:

[0038] (1) reacting a polymer diol, a diisocyanate, a small molecule diol, and optionally a catalyst to obtain a polyurethane prepolymer;

[0039] (2) reacting the polyurethane prepolymer obtained in step (1), dimethylol propionate and acetone to obtain an intermediate product;

[0040] (3) adding an aqueous solution of a surfactant and an aqueous solution of a post-chain extender to the intermediate product obtained in step (2) in sequence and mixing them to obtain an aqueous polyurethane emulsion;

[0041] (4) removing acetone from the aqueous polyurethane emulsion obtained in step (3) to obtain the aqueous polyurethane dispersion.

[0042] Preferably, the step (1) further comprises removing water from the polymer diol before the reaction, and the removal method is to remove water under reduced pressure at 100-110°C (for example, 102°C, 104°C, 106°C or 108°C, etc.).

[0043] Preferably, the reaction temperature in step (1) is 80-90°C, such as 82°C, 84°C, 86°C or 88°C.

[0044] Preferably, the reaction time of step (1) is 2 to 3 hours, for example, 2.2 hours, 2.4 hours, 2.6 hours or 2.8 hours;

[0045] In fact, during the reaction of step (1), the mass percentage of the NCO group in the system was tested, and the test result was 1.7±0.2%, so the reaction can be stopped.

[0046] Preferably, the specific method of the reaction in step (1) includes: cooling the polymer diol to 65-70°C (for example, 66°C, 67°C, 68°C or 69°C, etc.) in a protective gas atmosphere, adding a small molecule diol and optionally a catalyst to react to obtain a polyurethane prepolymer.

[0047] Preferably, the protective gas comprises nitrogen.

[0048] Preferably, the reaction temperature in step (2) is 70-75°C, such as 71°C, 72°C, 73°C or 74°C.

[0049] Preferably, the reaction time of step (2) is 0.5 to 1 h, such as 0.6 h, 0.7 h, 0.8 h or 0.9 h.

[0050] In fact, the reaction in step (2) can be stopped when the mass percentage of isocyanate groups in the system is 1.55±0.2%.

[0051] Preferably, the specific method of the reaction in step (2) comprises: adding a mixed solution of dihydroxymethylpropionate and acetone to the polyurethane prepolymer obtained in step (1) at 50-55° C. to react and obtain an intermediate product.

[0052] Preferably, the dispersing equipment used in step (3) is a homogenizer.

[0053] Preferably, the rotation speed of the homogenizer is 4000-7000 rpm / min, for example, 4000 rpm / min, 5000 rpm / min, 6000 rpm / min, 6500 rpm / min or 7000 rpm / min.

[0054] As a preferred technical solution of the present invention, the present invention provides a continuous emulsification method. In order to achieve better physical properties, the molecular weight of the polyurethane prepolymer obtained in step (1) needs to be increased. Therefore, only a small amount of solvent (acetone) is added to the raw materials for preparation. As a result, the viscosity of the intermediate product prepared from the polyurethane prepolymer is relatively high. The general dispersion device cannot meet the requirements. Therefore, a high-speed homogenizer with a rotation speed of 4000 to 7000 rpm / min is used, and graded feeding is adopted to achieve a continuous emulsification and post-chain extension process combining internal and external emulsification.

[0055] Preferably, the mixing time in step (3) is 3 to 10 seconds.

[0056] Preferably, the mass percentage of acetone in the aqueous polyurethane emulsion in step (3) is 3-5%, for example, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6% or 4.8%.

[0057] Preferably, the removal in step (4) is carried out in a removal device, which comprises a combination of a falling film evaporator, a vapor-liquid separator, a heat exchanger and an emulsion collecting kettle with an atomizing nozzle.

[0058] Preferably, the removal method specifically comprises the following steps:

[0059] (4A) feeding the aqueous polyurethane emulsion obtained in step (3) into the top of a falling film evaporator, and flowing downward from the top of the falling film evaporator, and performing gas-liquid separation in a vapor-liquid separator to obtain a liquid phase material and a gas phase;

[0060] (4B) The liquid phase material obtained in step (4A) is heat exchanged in a heat exchanger and then enters an emulsion collection kettle with an atomizing nozzle to further remove acetone to obtain the aqueous polyurethane dispersion.

[0061] As a preferred technical solution of the present invention, a high-efficiency continuous desolventizing method is adopted in step (4) of the preparation method provided by the present invention, and a desolventizing device including a falling film evaporator, a vapor-liquid separator, a heat exchanger and an emulsion collecting kettle with an atomizing nozzle is adopted. The falling film evaporator and the emulsion collecting kettle nozzle with an atomizing nozzle are combined, and a desolventizing device is used to cooperate with the decompression device to realize a high-efficiency production mode of continuous emulsification and continuous desolventizing. Specifically, under a certain vacuum degree, the acetone-containing aqueous polyurethane emulsion flowing out of the homogenizer is distributed by the liquid distributor in the falling film evaporator and flows downward along the tube side of the falling film evaporator in a film shape. The liquid film in the tube side and the hot water in the shell side undergo heat exchange, so that the acetone is vaporized, and the vapor-liquid separator separates the gas and the emulsion. The outflowing emulsion then passes through a heat exchanger to heat the emulsion, and then enters the decompression collecting kettle through the atomizing nozzle, and the acetone in the liquid phase is further removed to obtain an aqueous polyurethane dispersion.

[0062] The above-mentioned desolventizing process has the characteristics of uniform heating of the emulsion, large evaporation area, and low temperature requirement for the heating medium. It can effectively shorten the desolventizing time of the solvent and improve production efficiency. Furthermore, the above-mentioned solvent desolventizing process is more suitable for removing solvents from high-solid content emulsions. The low temperature difference between the emulsion and the heating medium and the short residence time of the emulsion are conducive to keeping the bound water in the boundary layer between the polyurethane particles from being vaporized and reducing the outward migration of bound water inside the particles, thereby improving the stability of the emulsion during the desolventizing process, facilitating the preparation of high-solid content emulsions, and obtaining water-based polyurethane dispersions with high solid content and batch stability.

[0063] Preferably, the shell side temperature of the falling film evaporator in step (4A) is 50-55°C, such as 51°C, 52°C, 53°C or 54°C.

[0064] Preferably, the shell side pressure of the falling film evaporator in step (4A) is -0.085 to -0.095 MPa, for example, -0.087 MPa, -0.089 MPa, -0.091 MPa or -0.093 MPa.

[0065] Preferably, the shell side temperature of the heat exchanger in step (4B) is 50-55°C, such as 51°C, 52°C, 53°C or 54°C.

[0066] In a third aspect, the present invention provides a use of the aqueous polyurethane dispersion as described in the first aspect in adhesives, coatings or synthetic leather.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] (1) The raw materials for preparing the aqueous polyurethane dispersion provided by the present invention include a combination of polymer diols, diisocyanates, small molecule diols, dimethylol propionate, sulfonic acid surfactants, post-chain extenders, acetone and water. The aqueous polyurethane dispersion prepared using the above raw materials has a higher molecular weight and solid content, and also has better stability. At the same time, the aqueous polyurethane dispersion is insensitive to various environmental factors such as acids, alkalis, and electrolytes, is not prone to demulsification, and has good tolerance to fillers and additives added when compounding into slurry.

[0069] (2) The preparation method of the aqueous polyurethane dispersion provided by the present invention includes the steps of continuous emulsification, post-chain extension and continuous rapid solvent removal, which effectively improves the production efficiency and stability of product batches, so that the aqueous polyurethane prepared by the preparation method can be used in the fields of synthetic leather, adhesives, coatings and fabric coatings. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0071] Preparation Example 1

[0072] A dimethylol propionate, the preparation method of which comprises: adding 2 parts by weight of dimethylol propionic acid and 3 parts by weight of triethylamine to 10 parts by weight of acetone, and reacting at 30° C. for 5 minutes to obtain the dimethylol propionate.

[0073] Preparation Example 2

[0074] A dimethylol propionate, the preparation method of which comprises: adding 3 parts by weight of dimethylol propionic acid and 4.5 parts by weight of N-methyldiethanolamine to 10 parts by weight of acetone, and reacting at 35° C. for 5 minutes to obtain the dimethylol propionate.

[0075] Preparation Example 3

[0076] A dimethylol propionate, the preparation method of which comprises: adding 3 parts by weight of dimethylol propionic acid and 4.5 parts by weight of N-methylmorpholine to 10 parts by weight of acetone, and reacting at 25° C. for 5 minutes to obtain the dimethylol propionate.

[0077] Example 1

[0078] A waterborne polyurethane dispersion, prepared from raw materials comprising the following components in parts by weight: 40 parts by weight of polytetramethylene glycol (number average molecular weight of 2000), 10 parts by weight of polyoxypropylene glycol (number average molecular weight of 1000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.4 parts by weight of 1,4-butanediol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 3 parts by weight of dimethylolpropionate (Preparation Example 1), 5 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of isophorone diamine, and 69 parts by weight of water;

[0079] The preparation method of the aqueous polyurethane dispersion provided in this embodiment comprises the following steps:

[0080] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding 1,4-butanediol, hexamethylene diisocyanate, isophorone diisocyanate and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0081] (2) Cooling the polyurethane prepolymer obtained in step (1) to 55° C., adding dimethylolpropionate (Preparation Example 1) and acetone, and heating to 75° C. for reaction for 0.5 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0082] (3) cooling the intermediate product obtained in step (2) to 55° C. and continuously injecting it into a shear pump at a flow rate of 3.5 kg / min at a speed of 4000 r / min, and injecting an aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing isophorone diamine (the mass percentage of isophorone diamine is 2%) into the shear pump in a graded manner for dispersion to obtain an aqueous polyurethane emulsion having a mass percentage of acetone of approximately 3%;

[0083] (4) feeding the aqueous polyurethane emulsion obtained in step (3) into the top of a falling film evaporator, and after the emulsion is distributed by a liquid distributor, flowing downward from the top of the film evaporator in a film-like manner along the tube side. Under the conditions of a pressure of -0.085 MPa and a shell side temperature of 55° C., acetone is vaporized, and a gas-liquid mixture is drawn out from the lower end and separated by a gas-liquid separator to obtain a liquid phase material and gaseous acetone;

[0084] (5) The liquid phase obtained in step (4) is passed through the tube side of a heat exchanger with a shell side temperature of 55° C. The liquid phase heated by the heat exchanger enters a vacuum collection kettle through an atomizing nozzle to further remove acetone from the liquid phase to obtain an aqueous polyurethane dispersion with a solid content of 50%.

[0085] Example 2

[0086] A waterborne polyurethane dispersion, prepared from raw materials comprising the following components in parts by weight: 33 parts by weight of polytetramethylene glycol (number average molecular weight of 2500), 20 parts by weight of polyoxypropylene glycol (number average molecular weight of 2000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.5 parts by weight of neopentyl glycol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 4 parts by weight of dimethylolpropionate (Preparation Example 2), 7.5 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of ethylenediamine, and 109 parts by weight of water;

[0087] The preparation method of the aqueous polyurethane dispersion provided in this embodiment comprises the following steps:

[0088] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding neopentyl glycol, hexamethylene diisocyanate, isophorone diisocyanate, and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0089] (2) Cooling the polyurethane prepolymer obtained in step (1) to 50° C., adding dimethylolpropionate (Preparation Example 2) and acetone, and heating to 75° C. for reaction for 1 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0090] (3) cooling the intermediate product obtained in step (2) to 50° C. and continuously injecting it into a shear pump at a flow rate of 3 kg / min at a speed of 5000 r / min, and injecting an aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing ethylenediamine (the mass percentage of ethylenediamine is 2%) into the shear pump in a graded manner for dispersion to obtain an aqueous polyurethane emulsion having a mass percentage of acetone of approximately 6%;

[0091] (4) feeding the aqueous polyurethane emulsion obtained in step (3) into the top of a falling film evaporator, and after the emulsion is distributed by a liquid distributor, flowing downward from the top of the film evaporator in a film-like manner along the tube side. Under the conditions of a pressure of -0.095 MPa and a shell side temperature of 50° C., acetone is vaporized, and a gas-liquid mixture is drawn out from the lower end and separated by a gas-liquid separator to obtain a liquid phase material and gaseous acetone;

[0092] (5) The liquid phase obtained in step (4) is passed through the tube side of a heat exchanger with the shell side at 50° C. The liquid phase heated by the heat exchanger enters a vacuum collection kettle through an atomizing nozzle to further remove acetone from the liquid phase to obtain an aqueous polyurethane dispersion with a solid content of 40%.

[0093] Example 3

[0094] A waterborne polyurethane dispersion, wherein the raw materials for preparing the dispersion include the following components in parts by weight: 40 parts by weight of polytetramethylene glycol (number average molecular weight of 2000), 20 parts by weight of polyoxypropylene glycol (number average molecular weight of 1000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.5 parts by weight of neopentyl glycol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 4 parts by weight of dimethylol propionate (Preparation Example 3), 7.5 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of ethylenediamine, and 120 parts by weight of water;

[0095] The preparation method of the aqueous polyurethane dispersion provided in this embodiment is the same as that in Example 1.

[0096] Example 4

[0097] A waterborne polyurethane dispersion is disclosed, which differs from Example 1 in that hexamethylene diisocyanate is not added, the added amount of isophorone diisocyanate is 17.9 parts by weight, and the other components, amounts and preparation methods are the same as those in Example 1.

[0098] Example 5

[0099] A waterborne polyurethane dispersion is disclosed, which differs from Example 1 in that isophorone diisocyanate is not added, the added amount of hexamethylene diisocyanate is 14.0 parts by weight, and the other components, amounts used, and preparation methods are the same as those in Example 1.

[0100] Example 6

[0101] A waterborne polyurethane dispersion is disclosed, which differs from Example 1 only in that the rotation speed of the shear pump in step (3) of the preparation method is 1000 r / min, and the other components, amounts and preparation method are the same as those in Example 1.

[0102] Example 7

[0103] A waterborne polyurethane dispersion, which differs from Example 1 only in that the speed of the shear pump in step (3) of the preparation method is 500 r / min, and the other components, amounts and preparation method are the same as those in Example 1.

[0104] Example 8

[0105] A waterborne polyurethane dispersion, wherein the raw materials for its preparation include the following components in parts by weight: 40 parts by weight of polytetramethylene glycol (number average molecular weight of 2000), 10 parts by weight of polyoxypropylene glycol (number average molecular weight of 1000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.4 parts by weight of 1,4-butanediol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 3 parts by weight of dimethylolpropionate (Preparation Example 1), 5 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of isophorone diamine, and 69 parts by weight of water;

[0106] The preparation method of the aqueous polyurethane dispersion provided in this embodiment comprises the following steps:

[0107] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding 1,4-butanediol, hexamethylene diisocyanate, isophorone diisocyanate and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0108] (2) Cooling the polyurethane prepolymer obtained in step (1) to 55° C., adding dimethylolpropionate (Preparation Example 1) and acetone, and heating to 75° C. for reaction for 0.5 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0109] (3) cooling the intermediate product obtained in step (2) to 55° C. and continuously injecting it into a shear pump at a flow rate of 3.5 kg / min at a speed of 4000 r / min, and injecting an aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing isophorone diamine (the mass percentage of isophorone diamine is 2%) into the shear pump in a graded manner for dispersion to obtain an aqueous polyurethane emulsion having a mass percentage of acetone of approximately 3%;

[0110] (4) The aqueous polyurethane emulsion obtained in step (3) is sent to a desolventizing kettle for collection, the temperature is raised to 55° C., and acetone is removed at a pressure of -0.085 MPa to obtain an aqueous polyurethane dispersion with a solid content of 50%.

[0111] Comparative Example 1

[0112] A waterborne polyurethane dispersion, the preparation raw materials of which include the following components in parts by weight: 40 parts by weight of polytetramethylene glycol (number average molecular weight of 2000), 10 parts by weight of polyoxypropylene glycol (number average molecular weight of 1000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.4 parts by weight of 1,4-butanediol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 2 parts by weight of dimethylolpropionic acid, 3 parts by weight of triethylamine, 16 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of isophorone diamine, and 71 parts by weight of water;

[0113] The preparation method of the aqueous polyurethane dispersion provided in this comparative example comprises the following steps:

[0114] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding 1,4-butanediol, hexamethylene diisocyanate, isophorone diisocyanate and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0115] (2) cooling the polyurethane prepolymer obtained in step (1) to 55° C., adding dimethylolpropionic acid and acetone, raising the temperature to 75° C. and reacting for 5 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0116] (3) cooling the intermediate product obtained in step (2) to 45° C., adding triethylamine for neutralization for 10 minutes, and then continuously injecting the intermediate product into a shear pump at a flow rate of 3.5 kg / min and a rotation speed of 4000 r / min. An aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing isophorone diamine (the mass percentage of isophorone diamine is 2%) are sequentially injected into the shear pump for dispersion to obtain an aqueous polyurethane emulsion having a mass percentage of acetone of approximately 3%;

[0117] (4) feeding the aqueous polyurethane emulsion obtained in step (3) into the top of a falling film evaporator, and after the emulsion is distributed by a liquid distributor, flowing downward from the top of the film evaporator in a film-like manner along the tube side. Under the conditions of a pressure of -0.085 MPa and a shell side temperature of 55° C., acetone is vaporized, and a gas-liquid mixture is drawn out from the lower end and separated by a gas-liquid separator to obtain a liquid phase material and gaseous acetone;

[0118] (5) The liquid phase obtained in step (4) is passed through the tube side of a heat exchanger with a shell side temperature of 55° C. The liquid phase heated by the heat exchanger enters a vacuum collection kettle through an atomizing nozzle to further remove acetone from the liquid phase to obtain an aqueous polyurethane dispersion with a solid content of 50%.

[0119] Comparative Example 2

[0120] A waterborne polyurethane dispersion, the preparation raw materials of which include the following components in parts by weight: 40 parts by weight of polytetramethylene glycol (number average molecular weight of 2000), 10 parts by weight of polyoxypropylene glycol (number average molecular weight of 1000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.4 parts by weight of 1,4-butanediol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 2 parts by weight of dimethylolpropionic acid, 3 parts by weight of triethylamine, 16 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of isophorone diamine, and 71 parts by weight of water;

[0121] The preparation method of the aqueous polyurethane dispersion provided in this embodiment comprises the following steps:

[0122] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding 1,4-butanediol, hexamethylene diisocyanate, isophorone diisocyanate and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0123] (2) cooling the polyurethane prepolymer obtained in step (1) to 55° C., adding dimethylolpropionic acid and acetone, raising the temperature to 75° C. and reacting for 5 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0124] (3) cooling the intermediate product obtained in step (2) to 45° C., adding triethylamine for neutralization for 10 minutes, and then continuously injecting the intermediate product into a shear pump at a flow rate of 3.5 kg / min and a rotation speed of 4000 r / min. An aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing isophorone diamine (the mass percentage of isophorone diamine is 2%) are sequentially injected into the shear pump for dispersion to obtain an aqueous polyurethane emulsion having a mass percentage of acetone of approximately 8%;

[0125] (4) The aqueous polyurethane emulsion obtained in step (3) is sent to a desolventizing kettle for collection, the temperature is raised to 55° C., and acetone is removed under a pressure of −0.085 MPa to obtain an aqueous polyurethane dispersion with a solid content of 50%.

[0126] Comparative Example 3

[0127] A waterborne polyurethane dispersion, wherein the raw materials for preparing the dispersion include the following components in parts by weight: 33 parts by weight of polytetramethylene glycol (number average molecular weight of 2500), 20 parts by weight of polyoxypropylene glycol (number average molecular weight of 2000), 9 parts by weight of isophorone diisocyanate (IPDI), 7 parts by weight of hexamethylene diisocyanate (HDI), 0.5 parts by weight of neopentyl glycol, 0.03 parts by weight of an organic bismuth catalyst (DY-20 from Deyin Chemical), 3 parts by weight of dimethylolpropionic acid, 4.5 parts by weight of N-methyldiethanolamine, 24 parts by weight of acetone, 2 parts by weight of sodium dodecylbenzenesulfonate, 0.5 parts by weight of ethylenediamine, and 115 parts by weight of water;

[0128] The preparation method of the aqueous polyurethane dispersion provided in this embodiment comprises the following steps:

[0129] (1) heating polytetrahydrofuran diol and polyoxypropylene diol to 100° C. and removing the contained water under reduced pressure, cooling to 65° C. in nitrogen, adding neopentyl glycol, hexamethylene diisocyanate, isophorone diisocyanate, and an organic bismuth catalyst, and reacting at 80° C. for 3 h. During the reaction, the mass percentage of NCO groups was measured to be 1.70±0.2%, thereby obtaining a polyurethane prepolymer;

[0130] (2) cooling the polyurethane prepolymer obtained in step (1) to 50° C., adding dimethylolpropionic acid and acetone, raising the temperature to 75° C. and reacting for 5 h. During the reaction, the mass percentage of NCO groups was measured to be 1.55±0.2%, thereby obtaining an intermediate product;

[0131] (3) After cooling the intermediate product obtained in step (2) to 45° C., N-methyldiethanolamine was added for neutralization for 10 minutes, and then continuously injected into a shear pump at a flow rate of 3.5 kg / min and a rotation speed of 5000 r / min. An aqueous solution containing sodium dodecylbenzenesulfonate (the mass percentage of sodium dodecylbenzenesulfonate is 23%) and an aqueous solution containing ethylenediamine (the mass percentage of ethylenediamine is 2%) were sequentially injected into the shear pump for dispersion to obtain an aqueous polyurethane emulsion with a mass percentage of acetone of about 12%;

[0132] (4) The aqueous polyurethane emulsion obtained in step (3) is sent to a desolventizing kettle for collection, the temperature is raised to 55° C., and acetone is removed under a pressure of −0.085 MPa to obtain an aqueous polyurethane dispersion with a solid content of 40%.

[0133] Performance testing:

[0134] (1) Solid content: Take 1.0-1.3 g of aqueous polyurethane dispersion, dry it at 150°C for 1 h, and calculate the mass percentage of the remaining part in the total amount;

[0135] (2) Viscosity: The aqueous polyurethane dispersion was placed at room temperature for 24 h before testing using a digital rotational viscometer with an S62 rotor and a speed of 30 r / min.

[0136] (3) Total prepolymerization time: the total time of step (1) and step (2) in the preparation method;

[0137] (4) Desolventization time at high temperature: the cumulative time during the desolventization process when the material temperature is ≥40°C;

[0138] (5) Acetone content: Tested according to the method provided in ASTM D6133-2002 (2014), Standard Test Method for Acetone and Methyl in Solvent- and Water-Containing Paints, Coatings, and Resins by Direct Injection Gas Chromatography.

[0139] (6) Centrifugal stability: 4 g of aqueous polyurethane dispersion was placed in a 5 mL centrifuge tube and centrifuged at a speed of 3000 r / min. After 30 min, the centrifuge tube was taken out, slowly inverted, and allowed to stand for 10 min. The bottom of the centrifuge tube was observed to see if there was any sediment.

[0140] The aqueous polyurethane dispersions provided in Examples 1 to 8 and Comparative Examples 1 to 3 were tested according to the above test method. The test results are shown in Table 1:

[0141] Table 1

[0142]

[0143]

[0144] According to the data in Table 1, we can see that:

[0145] The aqueous polyurethane dispersions provided in Examples 1 to 3 have excellent comprehensive properties, a solid content of 40 to 50%, a viscosity of ≤1000 cp, an acetone usage of 5 to 7.5 parts by weight, a total prepolymerization time of 3.5 to 4 hours, a desolvation time at high temperature of 3 to 5 minutes, an acetone content of <500 ppm, and no stratification in the centrifugal stability test.

[0146] By comparing the data of Example 1 and Comparative Examples 1 to 3, it can be seen that the use of dimethylolpropionic acid in the prepolymerization stage greatly shortens the prepolymerization reaction time (3.5 h), while adding dimethylolpropionic acid first and then the neutralizer in the prepolymerization stage will increase the total prepolymerization time (8 h). At the same time, Comparative Examples 2 to 3 use conventional desolvation methods, which also results in a very long desolvation time.

[0147] Comparing the data of Example 1 and Examples 4 to 8, it can be seen that the aqueous polyurethane dispersion obtained in Example 4 has a lower viscosity and poorer stability; while Examples 5 to 7 fail to emulsify and no aqueous polyurethane dispersion can be obtained; and the desolvation time in the preparation method provided in Example 8 is too long.

[0148] In summary, the use of dihydroxymethylpropionate can effectively reduce the duration of the prepolymerization reaction, achieve the effects of efficient dissolution and rapid reaction, and the centrifugal stability of the emulsion can be improved by matching the types of isocyanates. The high-speed shearing of the homogenizer helps to smoothly emulsify the high-viscosity prepolymer. Combined with a complete set of continuous desolventizing equipment, it solves the process problem of rapid solvent removal, thereby improving production efficiency and product batch stability.

[0149] The applicant declares that the present invention, through the above-described embodiments, illustrates a waterborne polyurethane dispersion, its preparation method, and its application. However, the present invention is not limited to the above-described embodiments, and this does not necessarily mean that the present invention must rely on the above-described embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. An aqueous polyurethane dispersion, characterized in that The raw materials for preparing the aqueous polyurethane dispersion include the following components in parts by weight: The diisocyanate is a combination of isophorone diisocyanate and hexamethylene diisocyanate; The preparation method of the aqueous polyurethane dispersion comprises the following steps: (1) reacting a polymer diol, a diisocyanate, and a small molecule diol in the presence of an optional catalyst to obtain a polyurethane prepolymer; (2) reacting the polyurethane prepolymer obtained in step (1), dimethylol propionate and acetone to obtain an intermediate product; (3) adding an aqueous solution of a sulfonic acid surfactant and an aqueous solution of a post-chain extender to the intermediate product obtained in step (2) in sequence and mixing them to obtain an aqueous polyurethane emulsion; (4) removing acetone from the aqueous polyurethane emulsion obtained in step (3) to obtain the aqueous polyurethane dispersion; The equipment used for the mixing in step (3) is a homogenizer, and the rotation speed of the homogenizer is 4000-7000r / min.

2. The aqueous polyurethane dispersion according to claim 1, characterized in that The polymer diol includes any one of polytetramethylene glycol, polyoxypropylene glycol or polyoxyethylene glycol, or a combination of at least two of them.

3. The aqueous polyurethane dispersion according to claim 2, characterized in that The number average molecular weight of the polytetrahydrofuran diol is 1000-3000.

4. The aqueous polyurethane dispersion according to claim 2, characterized in that The number average molecular weight of the polyoxypropylene glycol is 1000-2000.

5. The aqueous polyurethane dispersion according to claim 2, characterized in that The number average molecular weight of the polyethylene glycol is 500-2000.

6. The aqueous polyurethane dispersion according to claim 1, characterized in that The diisocyanate is a combination of phorone diisocyanate and hexamethylene diisocyanate in a mass ratio of 1:(0.2-3).

7. The aqueous polyurethane dispersion according to claim 1, characterized in that The small molecule diol includes any one of 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol, or a combination of at least two thereof.

8. The aqueous polyurethane dispersion according to claim 1, characterized in that The raw materials for preparing the dimethylol propionate include dimethylol propionic acid and a neutralizing agent.

9. The aqueous polyurethane dispersion according to claim 8, characterized in that The neutralizing agent includes any one of triethylamine, N-methyldiethanolamine, N-methylmorpholine or N-ethylmorpholine, or a combination of at least two thereof.

10. The aqueous polyurethane dispersion according to claim 1, characterized in that The sulfonic acid surfactant includes sodium dodecylbenzenesulfonate.

11. The aqueous polyurethane dispersion according to claim 1, characterized in that The post-chain extender includes any one of isophorone diamine, ethylenediamine, diethylenetriamine or hydrazine hydrate, or a combination of at least two thereof.

12. The aqueous polyurethane dispersion according to claim 1, characterized in that The solid content of the aqueous polyurethane dispersion is 40-50%.

13. The aqueous polyurethane dispersion according to claim 1, characterized in that The raw materials for preparing the aqueous polyurethane dispersion also include a catalyst.

14. The aqueous polyurethane dispersion according to claim 13, characterized in that The content of the catalyst in the preparation raw material is 0.03 to 0.05 parts by weight.

15. The aqueous polyurethane dispersion according to claim 13, characterized in that The catalyst includes an organic bismuth catalyst.

16. A method for preparing the aqueous polyurethane dispersion according to any one of claims 1 to 15, characterized in that: The preparation method comprises the following steps: (1) reacting a polymer diol, a diisocyanate, and a small molecule diol in the presence of an optional catalyst to obtain a polyurethane prepolymer; (2) reacting the polyurethane prepolymer obtained in step (1), dimethylol propionate and acetone to obtain an intermediate product; (3) adding an aqueous solution of a sulfonic acid surfactant and an aqueous solution of a post-chain extender to the intermediate product obtained in step (2) in sequence and mixing them to obtain an aqueous polyurethane emulsion; (4) removing acetone from the aqueous polyurethane emulsion obtained in step (3) to obtain the aqueous polyurethane dispersion; The equipment used for the mixing in step (3) is a homogenizer, and the rotation speed of the homogenizer is 4000-7000r / min.

17. The preparation method according to claim 16, characterized in that Before the reaction in step (1), the step of removing water from the polymer diol is also included.

18. The preparation method according to claim 16, characterized in that The reaction temperature in step (1) is 80-90°C.

19. The preparation method according to claim 16, characterized in that The reaction time of step (1) is 2 to 3 hours.

20. The preparation method according to claim 16, characterized in that The specific method of the reaction in step (1) includes: cooling the polymer diol to 65-70° C. in a protective gas environment, adding a small molecule diol and optionally a catalyst to react to obtain a polyurethane prepolymer.

21. The preparation method according to claim 20, characterized in that The protective gas includes nitrogen.

22. The preparation method according to claim 16, characterized in that The reaction temperature in step (2) is 70-75°C.

23. The preparation method according to claim 16, characterized in that The reaction time of step (2) is 0.5 to 1 h.

24. The preparation method according to claim 16, characterized in that The specific method of the reaction in step (2) includes: adding a mixed solution of dihydroxymethyl propionate and acetone to the polyurethane prepolymer obtained in step (1) at 50-55° C. to react and obtain an intermediate product.

25. The preparation method according to claim 16, characterized in that The mixing time in step (3) is 3 to 10 seconds.

26. The preparation method according to claim 16, characterized in that The mass percentage of acetone in the aqueous polyurethane emulsion in step (3) is 3-5%.

27. The preparation method according to claim 16, characterized in that The removal in step (4) is carried out in a removal device, which includes a combination of a falling film evaporator, a vapor-liquid separator, a heat exchanger and an emulsion collecting kettle with an atomizing nozzle.

28. The preparation method according to claim 16, characterized in that The method for removing specifically comprises the following steps: (4A) feeding the aqueous polyurethane emulsion obtained in step (3) into the top of a falling film evaporator, and flowing downward from the top of the falling film evaporator, and performing gas-liquid separation in a vapor-liquid separator to obtain a liquid phase material and gaseous phase acetone; (4B) The liquid phase material obtained in step (4A) is heat exchanged in a heat exchanger and then enters an emulsion collection kettle with an atomizing nozzle to further remove acetone to obtain the aqueous polyurethane dispersion.

29. The preparation method according to claim 28, characterized in that The shell side temperature of the falling film evaporator in step (4A) is 50-55°C.

30. The preparation method according to claim 28, characterized in that The shell side pressure of the falling film evaporator in step (4A) is -0.085 to -0.095 MPa.

31. The preparation method according to claim 28, characterized in that The shell side temperature of the heat exchanger in step (4B) is 50-55°C.

32. Use of the aqueous polyurethane dispersion according to any one of claims 1 to 15 in adhesives, coatings or synthetic leather.

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