Method for continuously preparing waterborne polyurethane dispersoid through microreactor

Abstract

The invention belongs to the technical field of polymers, and discloses a method for continuously preparing a waterborne polyurethane dispersion through a microreactor. The method comprises a prepolymerization process for generating a polyurethane prepolymer, a primary chain extension process for carrying out primary chain extension on the prepolymer, a polymerization process for polymerizing the prepolymer subjected to chain extension and dihydric alcohol, and a neutralization process which are carried out in sequence, the prepolymerization process, the primary chain extension process, the prepolymer, the polymerization process and the neutralization process are carried out through a micro-channel mixer and a micro-channel reactor which are connected in sequence. According to the method, prepolymerization, chain extension, polymer and neutralization of the dispersion are carried out by adopting a micro-channel mixer and a micro-channel reactor, so that the mass transfer and heat transfer effects can be effectively improved, the polymerization stability is improved, and the obtained waterborne polyurethane has the advantages of concentrated molecular weight distribution, low particle size polydispersity coefficient, controllable structure, stable quality, excellent performance and the like; and the method basically has no amplification effect, is beneficial to industrial amplification and has a good industrial application prospect.

Description

Technical Field

[0001] The invention relates to the field of polymers, and in particular to a method for continuously preparing an aqueous polyurethane dispersion through a microreactor. Background Art

[0002] Waterborne polyurethane dispersion uses deionized water as the dispersion medium, which can greatly reduce the use of volatile organic solvents (VOC). It is a non-toxic, odorless, green and environmentally friendly organic polymer material. During use, water evaporates to form a polyurethane film, which makes the film-forming material of waterborne polyurethane dispersion have the same excellent physical and chemical properties as polyurethane materials. By adjusting the formula and chemical modification, waterborne polyurethane materials can obtain high-performance materials with different hardness and chemical resistance, which are widely used in wood coatings, textile coatings, synthetic leather, plastic coatings, metal coatings, personal care, coatings, adhesives, sealants, water-based inks and other fields.

[0003] At present, the most commonly used production process for waterborne polyurethane is intermittent production, that is, first preparing a polyurethane prepolymer containing hydrophilic groups in the main chain in a prepolymerization reactor, and then transferring the material to a dispersion reactor for neutralization and emulsification. This production process has the following main disadvantages: (1) The reaction time is too long (4-6 hours), the production efficiency is low, and the production cost is high; (2) The production process is overly dependent on manual labor and the degree of automation is low; (3) The temperature distribution in the reactor is uneven, the product quality is unstable, and there is a large difference between batches.

[0004] Continuous production can solve the bottleneck problem of traditional intermittent production. Patent CN202011253943.7 uses a twin-screw extruder as a synthesis reactor for waterborne polyurethane, which can realize the continuous preparation of waterborne polyurethane, but the twin-screw extruder equipment is large in size and complicated to operate, making it difficult to accurately control the reaction conditions, which can easily cause fluctuations in product quality. Patent CN 201711466121.5 uses a tubular reactor as a synthesis reactor for waterborne polyurethane, which can realize the continuous preparation of waterborne polyurethane, but the internal components of this type of reactor are complex, difficult to process and install, and not conducive to industrial scale-up. Summary of the invention

[0005] The purpose of the present invention is to provide a method for continuously preparing an aqueous polyurethane dispersion by a microreactor. The method adopts a microchannel mixer and a microchannel reactor to carry out the prepolymerization, chain extension, polymerization and neutralization processes of the dispersion, which can effectively improve the mass transfer and heat transfer effects and the polymerization stability. The obtained aqueous polyurethane has the advantages of concentrated molecular weight distribution, low particle size polydispersity coefficient, controllable structure, stable quality, excellent performance and the like, and basically has no amplification effect, is conducive to industrial amplification, and has good industrial application prospects.

[0006] To achieve the above objectives, this application discloses:

[0007] A method for continuously preparing an aqueous polyurethane dispersion by a microreactor, the method comprising a prepolymerization process for generating a polyurethane prepolymer, a primary chain extension process for performing a first chain extension on the prepolymer, a polymerization process for polymerizing the chain-extended prepolymer and a diol, and a neutralization process.

[0008] The prepolymerization process, the primary chain extension process, the prepolymer, the polymerization process, and the neutralization process are all carried out through a microchannel mixer and a microchannel reactor connected in sequence.

[0009] Preferably, all raw materials must be subjected to ultrasonic degassing treatment before use, the ultrasonic power is preferably 30-180W, more preferably 120-180W; the ultrasonic frequency is preferably 20-100kHz, more preferably 20-60kHz; the ultrasonic time is preferably 10-40min, more preferably 10-20min;

[0010] In the above method, a fluid channel is provided in the microchannel reactor; the fluid channel is formed by alternating a number of thin channels and thick channels; the width of the thick channel is greater than that of the thin channel; a spoiler chip is provided in the middle of the thick channel; the spoiler chip is a structure with thick ends and thin middle; the end of the spoiler chip facing the fluid input has an inner concave portion; the concave direction of the inner concave portion is opposite to the flow direction of the fluid. The cross-section of the thin channel and the thick channel is preferably circular, semicircular, trapezoidal, or rectangular; the material of the microchannel reactor is preferably 304 stainless steel, 316L stainless steel, Hastelloy B, Hastelloy C, titanium alloy, silicon carbide, polyetheretherketone, and more preferably 316L stainless steel.

[0011] Each microchannel reactor and the microchannel mixer are preferably connected in series through microtubes, the inner diameter of the microtubes is preferably 0.5-3mm, more preferably 0.5-2mm, more preferably 0.5-1mm; the outer diameter is preferably 1.5-8mm, more preferably 3-6mm; the material of the microtubes is preferably 304 stainless steel, 316L stainless steel, polytetrafluoroethylene, soluble polytetrafluoroethylene, perfluoroethylene propylene copolymer, more preferably 316L stainless steel, polytetrafluoroethylene.

[0012] In the above method, there is a secondary chain extension process after the neutralization process; the secondary chain extension process uses a diamine chain extender and deionized water to carry out a chain extension reaction; the secondary chain extension process is also carried out through a microchannel mixer and a microchannel reactor connected in sequence or through a reaction kettle; the reaction conditions of the secondary chain extension process include: a reaction temperature of 0-60°C, preferably 5-40°C, more preferably 5-20°C, a mass flow rate of the diamine chain extender and deionized water of 6-10 g / min, and a reaction time of 15-60 min.

[0013] In the prepolymerization process, the reaction raw materials are mixed in a microchannel mixer and then in a static mixer, and finally enter into a corresponding microchannel reactor for reaction.

[0014] In the above method, the microchannel reactor is composed of one or more layers of microchannels connected in series; the microchannels of each layer are arranged in a serpentine shape.

[0015] In the above method, the microchannel reactor is composed of 2 to 5 layers of microchannels; a temperature control structure for controlling the temperature of the microchannels is provided between two adjacent layers of microchannels.

[0016] In the above method, the width ratio of the thin channel and the thick channel is 1:2-3; the width of the widest position of the spoiler chip is 1.3-1.7 times the width of the thin channel; the width of the narrowest position of the spoiler chip is 0.9-1.1 times the width of the thin channel; the diameter of the inner concave portion of the spoiler chip is 0.6-0.9 times the width of the thin channel; the curvature of the inner concave portion of the spoiler chip is 100-140°.

[0017] In the above method, the width of the thin channel is 0.1-1 mm.

[0018] In the above method, the width of the mixing channel of the microchannel mixer is 0.1-1mm; the material of the microchannel mixer is preferably 304 stainless steel, 316L stainless steel, silicon carbide, polytetrafluoroethylene, polyetheretherketone, Hastelloy C, Hastelloy B, and more preferably 316L stainless steel. The static mixer includes a tube body and an inner core arranged in the tube body; the inner core and the tube body constitute a mixing channel; the inner core configuration of the static mixer is preferably SV type, SK type, SX type, SH type, SL type, etc., more preferably SK type and SV type, more preferably SK type; the outer diameter of the inner core is preferably 0.5-3mm, more preferably 0.5-1.5mm; the material of the static mixer is preferably 304 stainless steel, 316L stainless steel, silicon carbide, etc., and more preferably 316L stainless steel.

[0019] In the above method, the raw materials of the prepolymerization process are diisocyanate, oligomer diol and catalyst; the reaction temperature of the prepolymerization process is 60-180°C, preferably 80-160°C; the mass flow rate of diisocyanate is 0.50-3.00 g / min, preferably 1.00-2.00 g / min, and the mass flow rate of oligomer diol is 0.50-10.0 g / min, preferably 1.00-8.00 g / min;

[0020] The raw materials of the primary chain extension process are prepolymer, hydrophilic chain extender and solvent, the reaction temperature of the primary chain extension process is 60-180° C., preferably 100-180° C., and the mass flow rate of the hydrophilic chain extender and solvent is 0.60-3.00 g / min, preferably 0.90-2.80 g / min;

[0021] The reaction temperature of the polymerization process is 60-180°C, preferably 80-170°C, and the mass flow rate of the diol is 0.02-0.40 g / min, preferably 0.05-0.35 g / min;

[0022] The reaction temperature of the neutralization process is 50-120° C., preferably 60-100° C.; the mass flow rate of the neutralizer used in the neutralization process is 0.06-0.50 g / min, preferably 0.15-0.45 g / min.

[0023] In the above method, the residence time of the reaction materials in the microchannel reactor during the prepolymerization process, the primary chain extension process, the polymerization process, and the neutralization process is 0.5-5min, 0.5-5min, 0.5-5min, and 1-5min, respectively;

[0024] The diisocyanate is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate;

[0025] The oligomer diol is one or more of polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, polycaprolactone diol, polycarbonate diol and polypropylene carbonate diol with a number average molecular weight of 500-6000;

[0026] The catalyst is one or more of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, bismuth decanoate, and dibutyltin diacetate;

[0027] The hydrophilic chain extender is one or more of dimethylol propionic acid, dimethylol butyric acid, methyldiethanolamine, diethanolamine, triethanolamine, and triisopropanolamine;

[0028] The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, butyl acetate, dipropylene glycol dimethyl ether, N,N-diethylformamide, and N-ethylpyrrolidone;

[0029] The small molecule diol is one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol;

[0030] The neutralizing agent is one or more of triethylamine, dimethylethanolamine, formic acid, and acetic acid;

[0031] The diamine is one or more of ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophoronediamine, and toluenediamine;

[0032] The mass ratio of the catalyst to the oligomer diol is 1:1000-1:20;

[0033] The mass ratio of the hydrophilic chain extender to the solvent is 1:1-1:10;

[0034] The mass ratio of the diamine chain extender to deionized water is 1:40-1:120.

[0035] This application has at least the following beneficial effects:

[0036] The method of the present invention uses a microchannel mixer and a microchannel reactor to carry out the prepolymerization, chain extension, polymerization and neutralization processes of the dispersion, which can effectively improve the mass transfer and heat transfer effects and the polymerization stability. The obtained waterborne polyurethane has the advantages of concentrated molecular weight distribution, low particle size polydispersity coefficient, controllable structure, stable quality, excellent performance, etc., and basically has no amplification effect, which is conducive to industrial amplification and has good industrial application prospects.

[0037] In the preferred embodiment of the present invention, a spoiler chip with a specific structure is used to improve the mixing effect. Specifically, since the polyurethane reaction is a highly exothermic reaction, the strong heat exchange capacity of the microchannel reactor and the short residence time of the material can ensure the uniformity of the temperature of the reaction liquid during the reaction; in the later stage of the polyurethane reaction, the viscosity of the reaction liquid will increase, and the active molecules will mainly diffuse radially. The submicron-level channel ensures a shorter diffusion time, which is beneficial to improving the reaction degree and controlling the molecular weight distribution of the product.

[0038] In a preferred embodiment of the present invention, by controlling the reaction time and the reaction temperature, the side reactions can be effectively controlled, and the microchannel mixer and microchannel reactor used in the present invention can achieve precise control of the reaction time and temperature.

[0039] The present invention adopts distributed and sequential microchannel reaction. During this process, the types of various reaction raw materials can be flexibly adjusted to adapt to the production of different types of polyurethane. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a molecular weight and molecular weight distribution chart of Examples 1 to 3 and Comparative Examples 1 to 6 of the present invention;

[0041] Figure 2 It is a graph of particle sizes and particle size distribution of Examples 1 to 3 and Comparative Examples 1 to 6 of the present invention;

[0042] Figure 3 is a molecular weight and molecular weight distribution chart of Examples 1 to 11 of the present invention;

[0043] Figure 4 is a graph of particle size and particle size distribution of Examples 1 to 11 of the present invention;

[0044] Figure 5 is a flow chart of the present invention;

[0045] Figure 6 is a perspective view of a static mixer of the present invention;

[0046] Figure 7 is an exploded view of the microchannel reactor of the present invention;

[0047] Figure 8 is a schematic diagram of a fluid channel of a microchannel reactor of the present invention;

[0048] Fig. 9 is a partial enlarged view of a fluid channel of a microchannel reactor of the present invention;

[0049] Fig.10 Infrared spectrum of waterborne polyurethane film of Example 1;

[0050] Fig.11 Example 1 waterborne polyurethane film stress-strain curve;

[0051] Fig.12 Thermogravimetric curve of waterborne polyurethane film of Example 1;

[0052] Fig.13 DSC curve of waterborne polyurethane film of Example 1.

[0053] Specific embodiment

[0054] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that, if no specific conditions are specified in the embodiments, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0055] Example 1

[0056] Before describing the specific production method of the present invention, the system of the present invention is first described. Figure 3 , the system comprises a micro mixer 1 and a static mixer, MR1, a micro mixer 2, MR2, a micro mixer 3, MR3, a micro mixer 4, MR4, and a high-speed disperser connected in sequence;

[0057] MR1, MR2, MR3, and MR4 are all microchip reactors; Figures 4 to 7 Each microchip reactor has three layers of microchannels; the microchannel reactor is composed of three layers of microchannels connected in series; there is a temperature control structure 17 for controlling the temperature of the microchannels between two adjacent layers of microchannels. Each layer of microchannels is serpentine; the fluid channel constituting the microchannel is formed by alternating a number of thin channels 11 and thick channels 12, and the width of the thick channel is greater than that of the thin channel; a spoiler chip 13 is provided in the middle of the thick channel; the spoiler chip is a structure with thick ends and thin middle; the end of the spoiler chip facing the fluid input has an inner concave portion 14; the concave direction of the inner concave portion is opposite to the flow direction of the fluid. The cross-section of the thin channel and the thick channel is circular; the width ratio of the thin channel to the thick channel is 1:2.5; the width of the widest position of the spoiler chip is 1.5 times the width of the thin channel, the width of the narrowest position of the spoiler chip is 1 times the width of the thin channel, the diameter of the inner concave portion of the spoiler chip is 0.8 times the width of the thin channel, the arc of the inner concave portion of the spoiler chip is 120°; the width of the thin channel is 0.8mm. The static mixer includes a tube body 15 and an inner core 16 arranged in the tube body; the inner core and the tube body constitute a mixing channel; the width of the mixing channel is 0.8mm, the inner core is SK type, and the outer diameter of the inner core is 1mm;

[0058] Raw material preparation: isophorone diisocyanate is raw material A, a mixture of stannous octoate and polypropylene glycol (Mn=2000) is raw material B, wherein the mass ratio of stannous octoate to polypropylene glycol (Mn=2000) is 1:200, a mixture of dimethylolpropionic acid and N,N-dimethylformamide is raw material C, wherein the mass ratio of dimethylolpropionic acid to N,N-dimethylformamide is 1:3, 1,4-butanediol is raw material D, triethylamine is raw material E, a mixture of ethylenediamine and deionized water is raw material F, wherein the mass ratio of ethylenediamine to deionized water is 1:100, raw materials A~E are stored in raw material tanks A~E respectively, after being ultrasonically treated at 150W, 60kHz for 20min, the temperature is raised to 40°C for standby use, raw material F is stored in raw material tank F, after being ultrasonically treated at 150W, 60kHz for 10min, the temperature is lowered to 15°C for standby use;

[0059] Preparation method: First, raw material A and raw material B are respectively fed into micro mixer 1 and static mixer through feed pumps to be mixed, and mixed solution I is obtained. The flow rates of feed pump A and feed pump B are 1.44 g / min and 2.67 g / min, respectively. Mixed solution 1 is reacted in MR1 set at 140°C, and the residence time is 1 min to obtain prepolymer I.

[0060] Then, the raw material C is mixed with the prepolymer I in the micro mixer 2 through the feed pump to obtain the mixed liquid II. The flow rate of the feed pump C is 1.27 g / min. The mixed liquid II enters the MR2 set at 150°C for reaction. The residence time is 2 minutes to obtain the prepolymer II.

[0061] Then, the raw material D is mixed with the prepolymer II in the micro mixer III through a feed pump to obtain a mixed solution III. The flow rate of the feed pump D is 0.07 g / min. The mixed solution III enters the MR3 set at a temperature of 140°C for reaction. The residence time is 2 minutes to obtain a prepolymer III.

[0062] Then, the raw material E is mixed with the prepolymer III in the micro mixer IV through a feed pump to obtain a mixed liquid IV. The flow rate of the feed pump E is 0.20 g / min. The mixed liquid IV enters the MR4 set at a temperature of 60°C for reaction. The residence time is 2 minutes to obtain a prepolymer IV.

[0063] Finally, the raw material F is emulsified and dispersed with the prepolymer IV in a high-speed disperser through a feed pump. The flow rate of the feed pump F is 8.89 g / min, the emulsification temperature is 10° C., and the emulsification time is 30 min to obtain an aqueous polyurethane dispersion.

[0064] Example 2

[0065] Raw material preparation: Raw materials were prepared as described in Example 1, except that: Raw material A was dicyclohexylmethane diisocyanate;

[0066] Preparation method: Prepare according to Experimental Example 1, except that: the flow rate of feed pump A is 1.49 g / min, the temperature of MR1 is 150°C; the temperature of MR2 is 160°C; the flow rate of feed pump D is 0.02 g / min, the temperature of MR3 is 150°C; the flow rate of feed pump F is 8.08 g / min.

[0067] Example 3

[0068] Raw material preparation: Raw materials were prepared as described in Example 1, except that: Raw material A was hexamethylene diisocyanate;

[0069] Preparation method: Prepare with reference to Experimental Example 1, except that: the flow rate of feed pump A is 1.36 g / min; the flow rate of feed pump D is 0.15 g / min; the flow rate of feed pump F is 8.51 g / min.

[0070] Example 4

[0071] Raw material preparation: Prepare raw materials as per Example 1;

[0072] Preparation method: Prepare according to Experimental Example 1, except that: the flow rate of feed pump A is 1.00 g / min; the flow rate of feed pump B is 1.85 g / min; the flow rate of feed pump C is 0.90 g / min; the flow rate of feed pump D is 0.05 g / min; the flow rate of feed pump E is 0.14 g / min; the flow rate of feed pump F is 6.17 g / min.

[0073] Example 5

[0074] Raw material preparation: Prepare raw materials as per Example 2;

[0075] Preparation method: Prepare according to Experimental Example 2, except that: the flow rate of feed pump A is 1.00 g / min; the flow rate of feed pump B is 1.79 g / min; the flow rate of feed pump C is 0.85 g / min; the flow rate of feed pump D is 0.01 g / min; the flow rate of feed pump E is 0.13 g / min; the flow rate of feed pump F is 5.42 g / min.

[0076] Example 6

[0077] Raw material preparation: Prepare raw materials as per Example 3;

[0078] Preparation method: Prepare according to Experimental Example 3, except that: the flow rate of feed pump A is 1.00 g / min; the flow rate of feed pump B is 1.96 g / min; the flow rate of feed pump C is 0.93 g / min; the flow rate of feed pump D is 0.11 g / min; the flow rate of feed pump E is 0.15 g / min; the flow rate of feed pump F is 6.26 g / min.

[0079] Example 7

[0080] Raw material preparation: Prepare raw materials as per Example 1;

[0081] Preparation method: Prepare according to Experimental Example 1, except that: the flow rate of feed pump A is 3.00 g / min; the flow rate of feed pump B is 5.56 g / min; the flow rate of feed pump C is 2.65 g / min; the flow rate of feed pump D is 0.15 g / min; the flow rate of feed pump E is 0.42 g / min; the flow rate of feed pump F is 18.52 g / min.

[0082] Example 8

[0083] Raw material preparation: Prepare raw materials as per Example 2;

[0084] Preparation method: Prepare according to Experimental Example 2, except that: the flow rate of feed pump A is 3.00 g / min; the flow rate of feed pump B is 5.38 g / min; the flow rate of feed pump C is 2.56 g / min; the flow rate of feed pump D is 0.04 g / min; the flow rate of feed pump E is 0.40 g / min; the flow rate of feed pump F is 16.27 g / min.

[0085] Example 9

[0086] Raw material preparation: Prepare raw materials as per Example 3;

[0087] Preparation method: Prepare according to Experimental Example 3, except that: the flow rate of feed pump A is 3.00 g / min; the flow rate of feed pump B is 5.89 g / min; the flow rate of feed pump C is 2.80 g / min; the flow rate of feed pump D is 0.33 g / min; the flow rate of feed pump E is 0.44 g / min; the flow rate of feed pump F is 18.77 g / min.

[0088] Example 10

[0089] Raw material preparation: Prepare raw materials as per Example 1;

[0090] Preparation method: The preparation was carried out according to Experimental Example 1, except that the width of the fine channel inside the microchannel reactor was 0.5 mm.

[0091] Embodiment 11

[0092] Raw material preparation: Prepare raw materials as per Example 1;

[0093] Preparation method: The preparation was carried out according to Experimental Example 1, except that the width of the fine channel inside the microchannel reactor was 1.2 mm.

[0094] Comparative Example 1

[0095] In this comparative example 1, a tubular reactor was used to prepare an aqueous polyurethane dispersion, and the method was as follows:

[0096] Raw material preparation: Prepare raw materials as per Example 1;

[0097] Preparation method: First, raw material A and raw material B are respectively fed into mixer 1 through feed pumps to obtain mixed solution I. The flow rates of feed pump A and feed pump B are 1.44 g / min and 2.67 g / min, respectively. After preheating to 60° C., mixed solution 1 enters into a first tubular reactor (VR1) set at 85° C. for reaction. The residence time is 30 min to obtain prepolymer I.

[0098] Then, the raw material C is mixed with the prepolymer I in the mixer 2 through the feed pump to obtain the mixed liquid II. The flow rate of the feed pump C is 1.27 g / min. The mixed liquid II enters VR2 set at 75°C for reaction. The residence time is 60 minutes to obtain the prepolymer II.

[0099] Then, the raw material D is mixed with the prepolymer II in the micro mixer III through a feed pump to obtain a mixed solution III. The flow rate of the feed pump D is 0.07 g / min. The mixed solution III enters VR3 set at a temperature of 75°C for reaction. The residence time is 30 minutes to obtain a prepolymer III.

[0100] Then, the raw material E is mixed with the prepolymer III in the micro mixer IV through a feed pump to obtain a mixed liquid IV. The flow rate of the feed pump E is 0.20 g / min. The mixed liquid IV enters VR4 set at a temperature of 40° C. for reaction. The residence time is 10 min to obtain a prepolymer IV.

[0101] Finally, the raw material F is emulsified and dispersed with the prepolymer IV in a high-speed disperser through a feed pump. The flow rate of the feed pump F is 8.89 g / min, the emulsification temperature is 10° C., and the emulsification time is 30 min to obtain an aqueous polyurethane dispersion.

[0102] Comparative Example 2

[0103] This comparative example 2 adopts the batch method to prepare the aqueous polyurethane dispersion, and the implementation is as follows:

[0104] First, 40.00 g of polypropylene glycol (Mn=2000) and 21.67 g of isophorone diisocyanate were added to an intermittent reactor, and the mixture was reacted at 75°C for 1 h. Then, 4.00 g of dihydroxymethylpropionic acid and 0.06 g of stannous octoate were added, and the temperature was raised to 85°C for reaction for 1.5 h. Then, 1.00 g of 1,4-butanediol was added, and the reaction was continued for 1 h. During the reaction, an appropriate amount of N,N-dimethylformamide was added to reduce the reaction viscosity. Then, the temperature was lowered to 50°C, 3.02 g of triethylamine was added, and the reaction was carried out for 0.5 h to obtain a polyurethane prepolymer. Then, the polyurethane prepolymer was slowly poured into a jacketed dispersion barrel filled with 132 g of deionized water and 1.32 g of ethylenediamine, and the mixture was dispersed at high speed at 15°C for 30 min to obtain an aqueous polyurethane dispersion.

[0105] Comparative Example 3

[0106] This comparative example 3 uses a tubular reactor to prepare an aqueous polyurethane dispersion, and the implementation is as follows:

[0107] Raw material preparation: Raw materials were prepared as in Comparative Example 1, except that: Raw material A was dicyclohexylmethane diisocyanate;

[0108] Preparation method: Prepare with reference to Comparative Example 1, except that: the flow rate of feed pump A is 1.49 g / min; the flow rate of feed pump D is 0.02 g / min; and the flow rate of feed pump F is 8.08 g / min.

[0109] Comparative Example 4

[0110] This comparative example 4 adopts the batch method to prepare the aqueous polyurethane dispersion, and the implementation is as follows:

[0111] The test was carried out with reference to Comparative Example 2, except that: the diisocyanate was dicyclohexylmethane diisocyanate, and the added amount was 22.36 g; the added amount of 1,4-butanediol was 0.31 g; the amounts of deionized water and ethylenediamine were 115 g and 1.15 g, respectively.

[0112] Comparative Example 5

[0113] This comparative example 5 uses a tubular reactor to prepare an aqueous polyurethane dispersion, and the implementation is as follows:

[0114] Raw material preparation: Raw materials were prepared as in Comparative Example 1, except that: Raw material A was hexamethylene diisocyanate;

[0115] Preparation method: Prepare with reference to Comparative Example 1, except that: the flow rate of feed pump A is 1.36 g / min; the flow rate of feed pump D is 0.15 g / min; the flow rate of feed pump F is 8.51 g / min.

[0116] Comparative Example 6

[0117] This comparative example 6 adopts the batch method to prepare the aqueous polyurethane dispersion, and the implementation is as follows:

[0118] The test was carried out with reference to Comparative Example 2, except that: the diisocyanate was hexamethylene diisocyanate, and the added amount was 20.34 g; the added amount of 1,4-butanediol was 2.32 g; and the amounts of deionized water and ethylenediamine were 164 g and 1.64 g, respectively.

[0119] Results

[0120] The dispersions of the above-mentioned embodiments and comparative examples were sent for testing of molecular weight, molecular weight distribution, particle size, and polydispersity coefficient;

[0121] Test results such as Figure 1 , Figure 2 , Figure 3 and Figure 4 ;

[0122] pass Figure 1 and Figure 2 It can be seen that the method of the present invention has a narrower molecular weight distribution, a smaller dispersion coefficient and a relatively smaller particle size compared with the tubular reactor reaction method and the intermittent kettle reaction method.

[0123] pass Figure 3 and Figure 4 It can be seen that in Examples 1, 4, and 7 (or Examples 2, 5, and 8 or Examples 3, 6, and 9) of the present invention, by changing the mass flow rate of the raw materials, different flow rates are obtained. The higher the flow rate, the more evenly the reaction materials are mixed, and a narrower molecular weight distribution and a smaller dispersion coefficient can be obtained, but the flow rate cannot be too high. Too high a flow rate will cause excessive pressure drop inside the reactor. At the same time, too high a flow rate will greatly shorten the residence time, and too short a residence time will make the reaction incomplete; in Examples 1, 10, and 11 of the present invention, by changing the size of the fine channel inside the microchannel reactor, it can be seen that the size of the fine channel is reduced, the radial diffusion of the materials in the fine channel is more uniform, the reaction will be more sufficient, which is conducive to increasing the molecular weight and reducing the particle size, but the size of the fine channel cannot be too small. Too small a size will cause excessive pressure drop inside the reactor, and severe cases may even cause channel blockage, making it impossible for the reaction to proceed continuously.

[0124] Fig.10 , Fig.11 , Fig.12 , Fig.13 They are infrared spectra, stress and strain curves, thermogravimetric curves, and differential scanning calorimetry curves of Example 1 and Comparative Example 1, respectively.

[0125] pass Fig.10 The characteristic functional groups in the infrared spectrum show that the experimental methods of Example 1 and Comparative Example 1 successfully synthesized waterborne polyurethane; Fig.11The stress-strain curve shows that the waterborne polyurethane in Example 1 has a higher tensile strength than that in Comparative Example 1. Fig.12 The thermogravimetric curve shows that the waterborne polyurethane in Example 1 has better heat resistance than that in Comparative Example 1. Fig.13 It can be seen from the differential scanning calorimetry curve that Example 1 and Comparative Example 1 have similar glass transition temperatures (Tg).

[0126] This shows that the prepolymerization, chain extension, polymerization and neutralization processes are all carried out using microchannel mixers and microchannel reactors, which can effectively improve the mass transfer and heat transfer effects and improve the polymerization stability. The obtained water-based polyurethane has the advantages of concentrated molecular weight distribution, low particle size polydispersity coefficient, controllable structure, stable quality, excellent performance, etc., and there is basically no amplification effect, which is conducive to industrial amplification and has good industrial application prospects.

[0127] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for continuously preparing an aqueous polyurethane dispersion by a microreactor, characterized in that: The method comprises a prepolymerization process for generating a polyurethane prepolymer, a primary chain extension process for performing a first chain extension on the prepolymer, a polymerization process for polymerizing the chain-extended prepolymer and a diol, and a neutralization process. The prepolymerization process, the primary chain extension process, the prepolymer, the polymerization process, and the neutralization process are all carried out through a microchannel mixer and a microchannel reactor connected in sequence.

2. The method according to claim 1, characterized in that A fluid channel is arranged in the microchannel reactor; the fluid channel is formed by a plurality of thin channels and thick channels connected alternately; the width of the thick channel is greater than that of the thin channel; a spoiler chip is arranged in the middle of the thick channel; the spoiler chip has a structure with thick ends and a thin middle; the end of the spoiler chip facing the fluid input has an inner recess; the recessed direction of the inner recess is opposite to the flow direction of the fluid.

3. The method according to claim 1, characterized in that After the neutralization process, there is a secondary chain extension process; the secondary chain extension process uses a diamine chain extender and deionized water to carry out a chain extension reaction; the secondary chain extension process is also carried out through a microchannel mixer and a microchannel reactor connected in sequence, or through a reaction kettle, or through a disperser; In the prepolymerization process, the reaction raw materials are mixed in a microchannel mixer and then in a static mixer, and finally enter into a corresponding microchannel reactor for reaction.

4. The method according to claim 2, characterized in that: The microchannel reactor is composed of one or more layers of microchannels connected in series; the microchannels of each layer are arranged in a serpentine shape.

5. The method according to claim 3, characterized in that: The microchannel reactor is composed of 2 to 5 layers of microchannels; a temperature control structure for controlling the temperature of the microchannels is provided between two adjacent layers of microchannels.

6. The method according to claim 2, characterized in that The width ratio of the thin channel and the thick channel is 1:2-3; the width of the widest position of the spoiler chip is 1.3-1.7 times the width of the thin channel; the width of the narrowest position of the spoiler chip is 0.9-1.1 times the width of the thin channel; the diameter of the inner concave portion of the spoiler chip is 0.6-0.9 times the width of the thin channel; the curvature of the inner concave portion of the spoiler chip is 100-140°.

7. The method according to claim 6, characterized in that The width of the thin channel is 0.1-1 mm.

8. The method according to claim 2, characterized in that: The microchannel mixer comprises a tube body and an inner core arranged in the tube body; the inner core and the tube body constitute a mixing channel; the width of the mixing channel is 0.1-1 mm.

9. The method according to claim 3, characterized in that: The raw materials of the prepolymerization process are diisocyanate, oligomer diol and catalyst; the reaction temperature of the prepolymerization process is 60-180°C; the mass flow rate of diisocyanate is 0.50-3.00 g / min; the mass flow rate of oligomer diol is 0.50-10.0 g / min; The raw materials of the primary chain extension process are prepolymer, hydrophilic chain extender and solvent, the reaction temperature of the primary chain extension process is 60-180° C., and the mass flow rate of the hydrophilic chain extender and solvent is 0.60-3.00 g / min; The reaction temperature of the polymerization process is 60-180°C, preferably 80-170°C, and the mass flow rate of the diol is 0.02-0.40 g / min; The reaction temperature of the neutralization process is 50-120° C.; the mass flow rate of the neutralizer used in the neutralization process is 0.06-0.50 g / min.

10. The method according to claim 9, characterized in that In the prepolymerization process, the primary chain extension process, the polymerization process, and the neutralization process, the residence time of the reaction materials in the microchannel reactor is 0.5-5min, 0.5-5min, 0.5-5min, and 1-5min, respectively; The diisocyanate is one or more of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate; The oligomer diol is one or more of polyethylene glycol, polypropylene glycol, polybutylene adipate diol, polyethylene adipate diol, polycaprolactone diol, polycarbonate diol and polypropylene carbonate diol with a number average molecular weight of 500-6000; The catalyst is one or more of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, bismuth decanoate, and dibutyltin diacetate; The hydrophilic chain extender is one or more of dimethylol propionic acid, dimethylol butyric acid, methyldiethanolamine, diethanolamine, triethanolamine, and triisopropanolamine; The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, butyl acetate, dipropylene glycol dimethyl ether, N,N-diethylformamide, and N-ethylpyrrolidone; The small molecule diol is one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, and 1,8-octanediol; The neutralizing agent is one or more of triethylamine, dimethylethanolamine, formic acid, and acetic acid; The diamine is one or more of ethylenediamine, hydrazine hydrate, 2-methyl-1,5-pentanediamine, 2-[(2-aminoethyl)amino]ethanesulfonic acid sodium salt, triethylenetetramine, diethylenetriamine, diaminodicyclohexylmethane, isophoronediamine, and toluenediamine; The mass ratio of the catalyst to the oligomer diol is 1:1000-1:20; The mass ratio of the hydrophilic chain extender to the solvent is 1:1-1:10; The mass ratio of the diamine chain extender to deionized water is 1:40-1:120.

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