CN112341590B - Waterborne polyurethane and continuous preparation process thereof - Google Patents
Waterborne polyurethane and continuous preparation process thereof Download PDFInfo
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- CN112341590B CN112341590B CN202011253943.7A CN202011253943A CN112341590B CN 112341590 B CN112341590 B CN 112341590B CN 202011253943 A CN202011253943 A CN 202011253943A CN 112341590 B CN112341590 B CN 112341590B
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
- C08G18/66—Compounds of groups C08G18/42, C08G18/48, or C08G18/52
- C08G18/6633—Compounds of group C08G18/42
- C08G18/6659—Compounds of group C08G18/42 with compounds of group C08G18/34
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
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- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
- C08G18/4236—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups
- C08G18/4238—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
- C08G18/66—Compounds of groups C08G18/42, C08G18/48, or C08G18/52
- C08G18/6633—Compounds of group C08G18/42
- C08G18/6637—Compounds of group C08G18/42 with compounds of group C08G18/32 or polyamines of C08G18/38
- C08G18/6648—Compounds of group C08G18/42 with compounds of group C08G18/32 or polyamines of C08G18/38 with compounds of group C08G18/3225 or C08G18/3271 and/or polyamines of C08G18/38
- C08G18/6651—Compounds of group C08G18/42 with compounds of group C08G18/32 or polyamines of C08G18/38 with compounds of group C08G18/3225 or C08G18/3271 and/or polyamines of C08G18/38 with compounds of group C08G18/3225 or polyamines of C08G18/38
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Abstract
The invention relates to the technical field of polyurethane, in particular to waterborne polyurethane and a continuous preparation process thereof. The invention discloses a continuous preparation process of waterborne polyurethane, which comprises the steps of heating a prepolymer with high viscosity in a pre-emulsification system after the raw materials of the waterborne polyurethane form the prepolymer in the first reactor, emulsifying the prepolymer in a short time through high-speed shearing, pre-emulsifying the prepolymer together with a solvent, an emulsifier and a chain extender to reduce the viscosity of the system, then carrying out one-step low-shearing long-time circulating emulsification on a pre-emulsified product through a pipeline type emulsification pump, and controlling the polydispersity of the particle size of the waterborne polyurethane by adjusting the circulating times. The preparation method of the waterborne polyurethane provided by the invention can be used for continuously producing the waterborne polyurethane, and the obtained waterborne polyurethane has wide particle size distribution and meets the quality requirement. And the continuous production process is simple and stable, and does not need to use an organic solvent.
Description
Technical Field
The invention relates to the technical field of polyurethane, in particular to waterborne polyurethane and a continuous preparation process thereof.
Background
The waterborne polyurethane takes water as a dispersion medium, does not contain volatile organic solvent (VOC), is a green and environment-friendly organic polymer material, has the characteristics of no toxicity, energy conservation, safety, difficult combustion and the like, and also has good comprehensive performance. When the waterborne polyurethane is used for construction, a polyurethane film is formed after water volatilizes in the process, and the waterborne polyurethane film has the same excellent performance as a polyurethane material. Common waterborne polyurethane in the market at present mainly comprises single-component waterborne polyurethane, double-component waterborne polyurethane and modified waterborne polyurethane.
The single-component waterborne polyurethane is the most applied waterborne polyurethane, the elongation at break and the strength of the single-component waterborne polyurethane can meet the common requirements, and the single-component waterborne polyurethane can be dried at normal temperature. The main varieties of the polyurethane comprise thermosetting polyurethane, waterborne polyurethane containing blocked isocyanate, room temperature curing waterborne polyurethane, photocuring waterborne polyurethane and polyurethane-acrylate.
The bi-component waterborne polyurethane has the excellent performances of low film forming temperature, strong adhesive force, good wear resistance, high hardness, chemical resistance and the like. In the two components, one component is a curing agent containing active isocyanate groups, and the other component is a water-based polyol capable of chemically reacting with the active isocyanate groups. The curing agent is an important factor affecting the film-forming properties, and should have good solubility, sufficient functionality and reactivity, while having a low viscosity to facilitate mixing with other resins. The aqueous polyol should have a dispersing function to uniformly disperse the hydrophobic curing agent in water with a sufficiently small particle diameter to ensure excellent properties in coating.
The modified waterborne polyurethane has a plurality of modification methods, and the mature method comprises the following steps: acrylic acid modification, epoxy resin modification, organic silicon modification, organic fluorine modification, nano modification, vegetable oil modification, crosslinking modification, multi-element modification and the like.
In the synthesis of the aqueous polyurethane, the curing agent, the aqueous polyol and the chain extender are generally mixed and reacted to prepare a prepolymer having a low molecular weight or a polyurethane resin having a high molecular weight, and then the prepolymer or the polyurethane resin is dissolved or emulsified in water. The synthesis method mainly comprises an acetone method, a prepolymer method, a melt dispersion polycondensation method, a ketimine/ketone nitrogen-linking method and a protective end group emulsification method.
When the waterborne polyurethane is produced by adopting the method, the raw materials are required to be prepolymerized in a reaction kettle. The viscosity of the reaction product increases with the progress of the prepolymerization reaction, and a low-boiling-point organic solvent is usually used for reducing the viscosity for the convenience of subsequent treatment, or a substance with lower molecular weight is selected when the raw materials are added, then the product needs to be transferred to a dispersion kettle for neutralization and dispersion, and finally the organic solvent in the product is removed.
The above process involves stepwise operation, which often results in low production efficiency, unstable product quality, and large batch-to-batch variation. Meanwhile, with the high importance of environmental protection and the gradual implementation of various environmental laws and regulations, the operation of removing the organic solvent cannot meet the requirements, and meanwhile, the reaction temperature in the later stage of synthesis is lower, and the reaction time is prolonged.
The patents and patents overcome the above problems by using a continuous production process. In the patent CN 108097194A, five-section series-connected tubular reactors are adopted to continuously produce the waterborne polyurethane. Firstly, simultaneously adding oligomer polyol into a first-stage tubular reactor through four inlets, and reacting a curing agent and the oligomer polyol in the first-stage tubular reactor to obtain a prepolymer I; simultaneously adding a nonionic hydrophilic compound into a second section of tubular reactor through three inlets, and reacting the prepolymer I with the nonionic hydrophilic compound to obtain a prepolymer II; adding a solvent and/or an acrylate monomer into the third section of tubular reactor to dilute the prepolymer II; adding a hydrophilic chain extender and micromolecular diamine into the fourth section of tubular reactor to carry out chain extension reaction on the diluted prepolymer II to obtain a waterborne polyurethane ionomer; and adding deionized water into the fifth section of tubular reactor to emulsify and disperse the waterborne polyurethane ionomer to obtain the waterborne polyurethane coarse emulsion. Patent CN 109824913a disperses an aqueous polyurethane prepolymer in water by a tubular disperser to prepare aqueous polyurethane. The tubular disperser comprises a feed inlet and a plurality of water inlets, and the water inlets are uniformly distributed on the tubular disperser in the axial direction. The tubular disperser comprises a central shaft, and the central shaft is provided with a plurality of tooth-row dispersing disks. In addition, the tubular disperser contains two inner partition plates, and the inner cavity of the tubular disperser is divided into three areas, namely a premixing area, a phase transition area and a diluting area along the axial direction. And adding water into the tubular disperser in an unequal manner for many times, and dispersing and emulsifying the prepolymer under the rotation action of the dispersing disc.
However, the production method is only suitable for producing the specific type of waterborne polyurethane, the production process is limited by a specific reactor, and the complex structure of the reactor makes the components difficult to process and install. At the same time, relatively high energy input is often required for dispersing the prepolymer, and the polydispersity of the particle size is difficult to control.
Disclosure of Invention
In view of the above, the present invention provides a continuous preparation process of waterborne polyurethane, which adopts high shear and short-time shear dispersion in a high viscosity state after polymerization of a prepolymer, further adopts low shear and long-time cyclic dispersion after the prepolymer is primarily dispersed to a low viscosity state, and does not require high energy input, and the polydispersity of the particle size of the waterborne polyurethane is easy to control.
The specific technical scheme is as follows:
the invention provides a continuous preparation process of waterborne polyurethane, wherein the waterborne polyurethane is prepared by a waterborne polyurethane production system, and the waterborne polyurethane production system comprises a plurality of first raw material tanks, a mixer, a first reactor, a pre-emulsification system and a pipeline type emulsification pump which are sequentially communicated;
the pre-emulsification system is communicated with a plurality of second raw material tanks;
each of the first stock tanks stores one kind of stock, and each of the second stock tanks stores one kind of stock.
The continuous preparation process of the waterborne polyurethane comprises the following steps:
step 1: respectively inputting polymer dihydric alcohol, diisocyanate, micromolecular alcohols, a first chain extender and a catalyst in a first raw material tank into a mixer for mixing;
step 2: heating the mixer to 80-120 ℃, and inputting the mixture into a first reactor for polymerization reaction to obtain a polyurethane-polyurethane melt;
and step 3: inputting the polyurethane-polyurethane melt into a pre-emulsification system, and simultaneously respectively inputting the solvent, the emulsifier and the second chain extender in the second raw material tank into the pre-emulsification system for mixing and shearing emulsification;
and 4, step 4: inputting a reaction product in the pre-emulsification system into a pipeline type emulsification pump for emulsification to obtain waterborne polyurethane;
the temperature of the shearing emulsification in the step 3 is 60-95 ℃, and the time is 1-3 min;
and 4, the circulating flow rate of the pipeline type emulsification pump is 100-400r/min, the circulating times are 30-100 times, and the emulsification time is 20-40 min.
After the high-viscosity polyurethane melt is formed in the first reactor by the raw materials of the waterborne polyurethane, the polyurethane melt is heated in a pre-emulsification system and is emulsified in a short time by high-speed shearing, the pre-emulsification is realized together with a solvent, an emulsifier and a chain extender, the viscosity of the system is reduced, then a pipeline type emulsification pump is used for carrying out one-step low-shearing long-time circulating emulsification on a pre-emulsified product, and the polydispersity of the particle size of the waterborne polyurethane is controlled by adjusting the circulating times. The preparation method of the waterborne polyurethane provided by the invention can be used for continuously producing the waterborne polyurethane, and the obtained waterborne polyurethane has wide particle size distribution and meets the quality requirement. And the continuous production process is simple and stable, and does not need to use an organic solvent.
In the waterborne polyurethane system provided by the invention, each first raw material tank is provided with a metering pump, and reaction materials in the raw material tanks can be quantitatively input into the mixer. Each of the second feed tanks may also be provided with a metering pump.
In the invention, because the reaction materials in the first reactor can generate high-viscosity prepolymer through polymerization reaction, a booster pump is arranged between the first reactor and the pre-emulsification system and is used for pumping the high-viscosity prepolymer into the pre-emulsification system.
In the step 1 of preparing the waterborne polyurethane, polymer diol, diisocyanate, micromolecular alcohols, hydrophilic chain extender and catalyst are preferably pumped into a mixer through a metering pump to be mixed; the mixer is preferably a casting machine; the casting machine preferably rotates at a speed of 200 rpm.
In the step 2 of the invention, after the mixer is heated to 80-120 ℃, the mixture is input into a first reactor for polymerization reaction to obtain polyurethane melt; the first reactor is preferably a screw extruder which can be a single screw extruder or a double screw extruder, and the screw extruder can fully mix reaction materials by means of pressure shearing force generated by rotation of a screw; the rotation speed of the screw extruder is preferably 30 revolutions per minute; the temperature of the polymerization reaction is 80-120 ℃, preferably 110 ℃, and the time is 20 min; the polymerization reaction yielded a polyurethane melt with a number average molecular weight of 5000-. The applicant has found that when the length-to-diameter ratio (L/D) of the screw extruder is 15-55L/D, the waterborne polyurethane with the solid content of more than 45 percent can be finally obtained. It should be noted that the structure and operating parameters of the screw extruder require the material to have a large shear dispersion function both in the axial direction and in the radial direction of the screw, so that the metering deviation caused by the pulses of the metering device at different times can be ignored.
In step 3 of the invention, the polyurethane-polyurethane melt in the first reactor is preferably pumped into a pre-emulsification system by a booster pump for temperature rise, high shear and short-time emulsification, and the pre-emulsification is realized together with a solvent, an emulsifier and a chain extender, so that the viscosity of the system is reduced; the pre-emulsification system is a high-shear ultra-speed emulsifier.
In step 4 of the invention, the reaction product in the pre-emulsification system is input into a pipeline type emulsification pump for low-shear long-time circulating emulsification to obtain the waterborne polyurethane.
In the invention, the polymer diol is 500-600 parts;
50-60 parts of diisocyanate;
0-5 parts of micromolecular alcohols;
1-2 parts of a first chain extender;
0-3 parts of a second chain extender;
0.01-0.03 part of catalyst;
0-55 parts of an emulsifier;
3000 portions of solvent and 6000 portions of solvent.
In the invention, the polymer dihydric alcohol comprises one or more than two of polyether dihydric alcohol, polyester dihydric alcohol and polycarbonate dihydric alcohol.
The polyether diol adopts polyether oligomer with terminal hydroxyl group and number average molecular weight of 500-10000, and comprises one or more than two of polytetrahydrofuran diol, polyoxypropylene diol, polyoxyethylene diol and polyoxypropylene oxyethylene copolymerized diol, and the proportion of the mixture is not particularly limited;
the polyester diol is an oligomer containing 2 terminal hydroxyl groups and a polyester structure, has the number average molecular weight of 500-10000, and comprises one or more than two of poly (1, 4-butanediol adipate) diol, poly (ethylene glycol adipate) diol, poly (propylene glycol adipate), poly (1, 6-hexanediol adipate) diol, poly (neopentyl glycol adipate) diol, poly (ethylene glycol adipate) butanediol diol, poly (ethylene glycol adipate) propylene glycol diol, poly (hexanediol adipate) neopentyl glycol diol, poly (butanediol adipate) hexanediol diol, poly (butanediol neopentyl glycol adipate) diol and polycaprolactone diol, and the proportion of the mixture is not particularly limited;
the polycarbonate diol adopts an oligomer containing a carbonate structure with a terminal hydroxyl group, has the number average molecular weight of 500-4000, is synthesized by exchanging carbonic diester with diol ester, and comprises one or a mixture of more of poly (hexanediol carbonate diol), poly (pentanediol carbonate diol), poly (butylene carbonate diol) and poly (propylene carbonate diol).
In the present invention, the diisocyanate includes one or more of 4, 4-diphenylmethane diisocyanate, toluene diisocyanate, xylylene diisocyanate, 1, 5-naphthalene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated 4, 4-diphenylmethane diisocyanate.
In the present invention, the small molecule alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 5-pentanediol, neopentyl glycol, 1, 6-hexanediol, 1, 8-octanediol, hydroquinone hydroxyethyl ether, cyclohexyldimethanol, 2-ethyl-2-butylpropanediol, 2,3, 4-trimethylpentanediol, positionally isomeric diethyloctanediols, cyclohexanediol, cyclohexane-1, 2-diol, cyclohexane-1, 4-dimethanol, trimethylolethane, trimethylolpropane, glycerol, hydrogenated bisphenol A, 2-dimethyl-3-hydroxypropionic acid and 2, one or more than two of 2-dimethyl-3-hydroxypropyl, preferably one or more than two of trimethylolpropane, 1, 4-butanediol, cyclohexane-1, 4-dimethanol and 1, 6-hexanediol.
In the present invention, the catalyst is an organotin catalyst, preferably dibutyltin dilaurate;
the solvent is water and/or acetone, preferably pure water, and a mixed solution of acetone and water;
the emulsifier comprises an external emulsifier and an internal emulsifier; 0-25 parts of the external emulsifier, and 0-20 parts of the external emulsifier; the external emulsifier is selected from castor oil, ethylene oxide-propylene oxide copolymer or bisphenol A-epichlorohydrin-polyethylene glycol oxide adduct; the internal emulsifier is selected from dihydroxypropionic acid, dimethylolbutyric acid or tartaric acid, and is preferably dihydroxypropionic acid. It should be noted that when the internal emulsifier is sufficient, the emulsifier may not be added.
In the present invention, the first chain extender and the second chain extender are both hydrophilic chain extenders, the chain extender is a compound containing one or more of carboxyl group, carboxylate group, sulfonate group and ammonium group, preferably monohydroxy carboxylic acid, dihydroxy dicarboxylic acid, monoamino carboxylic acid, diamino carboxylic acid, monohydroxy sulfonic acid, dihydroxy sulfonic acid, monoamino sulfonic acid, diamino sulfonic acid, monohydroxy bony acid, dihydroxy phosphoric acid, monoamino phosphoric acid, diamino phosphoric acid and salts thereof, such as dimethylol propionic acid, dimethylol butyric acid, hydroxypivalic acid, N- (2-aminoethyl) alanine, 2- (2-aminoethyl amino) ethane sulfonic acid, ethylenediamine propyl sulfonic acid or ethylenediamine butyl sulfonic acid, 1, 2-propane diamine, 1, 3-propane diamine ethyl sulfonic acid, malic acid, ammonium group, One or more than two of citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, lysine, 3, 5-diaminobenzoic acid, p-phenylene diisocyanate, acrylic acid and alkali metal salt and/or ammonium salt thereof, polyether sulfonate and N-methyldiethanolamine.
The invention also provides the waterborne polyurethane prepared by the continuous preparation process, wherein the solid content of the waterborne polyurethane is 20-55%, the average particle size is 80-400 nm, and the viscosity is 480-1200 mPas.
According to the technical scheme, the invention has the following advantages:
the invention provides a continuous preparation process of waterborne polyurethane, which comprises the steps of heating a prepolymer with high viscosity in a pre-emulsification system after the raw materials of the waterborne polyurethane form a prepolymer with high viscosity in a first reactor, emulsifying the prepolymer in a short time through high-speed shearing, pre-emulsifying the prepolymer together with a solvent, an emulsifier and a chain extender to reduce the viscosity of the system, then carrying out one-step low-shearing long-time circulating emulsification on a pre-emulsified product through a pipeline type emulsification pump, and controlling the polydispersity of the particle size of the waterborne polyurethane by adjusting the circulating times. The preparation method of the waterborne polyurethane provided by the invention can be used for continuously producing the waterborne polyurethane, the obtained waterborne polyurethane has wide particle size distribution and high solid content, the quality meets the requirement, and the continuous production process is simple and stable and does not need to use an organic solvent.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
FIG. 1 is a schematic structural diagram of an aqueous polyurethane production system provided in an embodiment of the present invention;
FIG. 2 is a graph showing the relationship between the particle size distribution of the aqueous polyurethane emulsion provided in example 1 of the present invention and the number of cycles of an in-line emulsification pump;
FIG. 3 is a particle size distribution diagram of the aqueous polyurethane emulsions provided in example 1 of the present invention and comparative example 1;
FIG. 4 is a graph showing the viscosity of the aqueous polyurethane emulsion according to the present invention in example 1 and comparative example 1 as a function of the solid content;
wherein the illustration is as follows:
1. a first raw material tank; 2. a metering pump; 3. a mixer; 4. a first reactor; 5. a booster pump; 6. A pre-emulsification system; 7. an in-line emulsion pump; 8. a second material tank.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it should be apparent that the embodiments described below are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the examples of the present invention, the molecular weight of polybutylene adipate was 2000, and the molecular weight of the ethylene oxide-propylene oxide copolymer was 1500.
In the examples of the present invention, the high shear ultra-speed emulsifier is available from Nantong Rickett fluid Equipment, Inc.
Example 1
In the embodiment, the waterborne polyurethane is prepared by using a waterborne polyurethane production system, and the preparation steps are as follows:
1) a metering pump is adjusted, 524 parts of polybutylene adipate, 51 parts of hexamethylene diisocyanate and 0.015 part of dibutyltin dilaurate are quantitatively input into a casting machine from a first raw material tank and mixed;
2) heating a casting machine (200 r/min) to 110 ℃, inputting the mixture in the casting machine into a screw extruder (30 r/min, L/D is 19) to react for 20min at 110 ℃ to obtain polyurethane melt with the number average molecular weight of 20000;
3) pumping the polyurethane-polyurethane melt into a pre-emulsification system through a booster pump, quantitatively inputting 10 parts of dihydroxypropionic acid, 16 parts of ethylene oxide-propylene oxide copolymer, 1.2 parts of ethylenediamine and 4000 parts of water into a high-shear ultra-speed emulsifying machine from a second raw material tank, adjusting the temperature of the pre-emulsification system to 95 ℃, and staying for 3 min;
4) inputting a reaction product in the high-shear ultra-speed emulsifying machine into a pipeline type emulsifying pump for emulsifying, wherein the circulating flow rate of pipeline type emulsifying is 80 rpm, the circulating frequency is 15-90 times, staying for 20 minutes, and discharging to obtain the waterborne polyurethane emulsion.
FIG. 2 is a graph showing the relationship between the particle size distribution of the aqueous polyurethane emulsion obtained in this example and the number of cycles of the inline emulsification pump. As shown in FIG. 2, the abscissa is the cycle number and the ordinate is the average particle diameter and dispersion index of the particles of the aqueous polyurethane emulsion, which shows that the particle diameter of the emulsion can be controlled within a certain range by different cycle numbers.
FIG. 3 is a graph showing the particle size distribution of the aqueous polyurethane emulsion of this example (cycle number 80) and the aqueous polyurethane emulsion of comparative example 1. As shown in fig. 3, compared with the aqueous polyurethane emulsion obtained by the conventional batch stirring process in comparative example 1, the continuous aqueous polyurethane preparation process used in this embodiment can obtain a smaller average particle size and a wider particle size distribution under the same formulation, which is beneficial to increase of the limit solid content after concentration.
FIG. 4 is a graph showing the viscosity of the aqueous polyurethane emulsion of this example (cycle number 80) and that of the aqueous polyurethane emulsion of comparative example 1 as a function of the solid content. As shown in FIG. 4, when the solid content of the waterborne polyurethane is increased to different degrees after evaporation and concentration, the viscosity is changed along with the increase of the solid content. Compared with the viscosity change values of the waterborne polyurethane with different solid contents obtained by the conventional stirring process of the batch method in the comparative example 1, the waterborne polyurethane with better dispersibility and high solid content can be obtained by adopting the continuous preparation process of the embodiment under the same formula.
When the number of cycles is 80, the number average molecular weight of the aqueous polyurethane emulsion prepared in this example is 45000, the average particle size is 80nm, the solid content after solvent removal is 53%, and the viscosity is 480 mpa sec.
Example 2
This example is the preparation of aqueous polyurethane
This example differs from example 1 in that:
20 parts of dihydroxypropionic acid, 1 part of ethylenediamine and acetone and water as solvents, wherein 1226 parts of acetone and 588 parts of water are contained;
the high-shear overspeed emulsifying machine maintains the temperature at 60 ℃, the circulating flow rate of the tubular emulsification is 50 r/min, and the circulating times are 30 times.
The number average molecular weight of the aqueous polyurethane emulsion prepared in the example was 62000, the average particle diameter was 150nm, the solid content after solvent removal was 55%, and the viscosity was 550 mpa-sec.
Comparative example 1
The formula of the aqueous polyurethane emulsion of the comparative example is the same as that of example 1.
The preparation method of the waterborne polyurethane emulsion comprises the following specific steps:
524 parts of polybutylene adipate, 51 parts of hexamethylene diisocyanate and 0.015 part of dibutyltin dilaurate are mixed and reacted at 75 ℃, the mixture is cooled to 65 ℃ after reacting for 1 hour, 146 parts of acetone is added and uniformly stirred, the reaction is continued for 50 minutes, the temperature is reduced to 60 ℃, 76 parts of acetone is added, the reaction is continued for 40 minutes, 826 parts of acetone is added, the temperature is continuously reduced to 50 ℃, the material is discharged, 218 parts of acetone is used for cleaning a reactor and then is combined, 10 parts of dihydroxypropionic acid, 16 parts of ethylene oxide-propylene oxide copolymer, 1.2 parts of ethylenediamine and 588 parts of water are added, the mixture is stirred and emulsified at 40 ℃ for 30 minutes, and finally the acetone is evaporated at low pressure to obtain the waterborne polyurethane.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. The continuous preparation process of the waterborne polyurethane is characterized in that the waterborne polyurethane is prepared by a waterborne polyurethane production system, wherein the waterborne polyurethane production system comprises a plurality of first raw material tanks, a mixer, a first reactor, a pre-emulsification system and a pipeline type emulsification pump which are sequentially communicated;
the pre-emulsification system is communicated with a plurality of second raw material tanks;
each of the first stock tanks storing one stock and each of the second stock tanks storing one stock;
the continuous preparation process of the waterborne polyurethane comprises the following steps:
step 1: respectively inputting polymer dihydric alcohol, diisocyanate, micromolecular alcohols, a first chain extender and a catalyst in a first raw material tank into a mixer for mixing;
step 2: heating the mixer to 80-120 ℃, and inputting the mixture into a first reactor for polymerization reaction to obtain a polyurethane-polyurethane melt;
and step 3: inputting the polyurethane-polyurethane melt into a pre-emulsification system, and simultaneously respectively inputting water, an emulsifier and ethylenediamine in a second raw material tank into the pre-emulsification system for mixing and shearing emulsification;
and 4, step 4: inputting a reaction product in the pre-emulsification system into a pipeline type emulsification pump for low-shear long-time circulating emulsification to obtain waterborne polyurethane;
3, the temperature of the shearing emulsification is 60-95 ℃, and the time is 1-3 min;
the pre-emulsification system is a high-shear overspeed emulsifying machine;
the emulsifier comprises an external emulsifier and an internal emulsifier; the external emulsifier is selected from castor oil, ethylene oxide-propylene oxide copolymer or bisphenol A-epichlorohydrin-polyethylene glycol oxide adduct, and the internal emulsifier is selected from dihydroxypropionic acid, dimethylolbutyric acid or tartaric acid;
and 4, the circulating flow rate of the pipeline type emulsification pump is 100-400r/min, the circulating times are 30-100 times, and the emulsification time is 20-40 min.
2. The continuous production process according to claim 1, wherein the first reactor is a screw extruder;
the length-to-diameter ratio L/D of the screw extruder is more than or equal to 15 and less than or equal to 55.
3. The continuous production process according to claim 1, wherein the catalyst is prepared by mixing, in parts by weight,
500-600 parts of polymer diol;
50-60 parts of diisocyanate;
0-5 parts of micromolecular alcohols;
1-2 parts of a first chain extender;
0-3 parts of ethylenediamine;
0.01-0.03 part of catalyst;
0-55 parts of an emulsifier;
3000 portions of water and 6000 portions of water.
4. The continuous preparation process according to claim 1, wherein the polymer diol comprises one or more of polyether diol, polyester diol and polycarbonate diol;
the diisocyanate comprises one or more than two of 4, 4-diphenylmethane diisocyanate, toluene diisocyanate, benzylidene diisocyanate, 1, 5-naphthalene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and hydrogenated 4, 4-diphenylmethane diisocyanate.
5. The continuous production process according to claim 1, the small molecular alcohols comprise one or more than two of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 5-pentanediol, neopentyl glycol, 1, 6-hexanediol, 1, 8-octanediol, hydroquinone hydroxyethyl ether, cyclohexyl dimethanol, 2-ethyl-2-butyl propanediol, 2,3, 4-trimethylpentanediol, positionally isomeric diethyl octanediols, cyclohexanediol, cyclohexane-1, 2-diol, cyclohexane-1, 4-dimethanol, trimethylolethane, trimethylolpropane, glycerol and hydrogenated bisphenol A.
6. The continuous production process according to claim 1, wherein the catalyst is an organotin catalyst.
7. The continuous production process according to claim 1, wherein the polymerization reaction in step 2 is carried out at a temperature of 80-120 ℃ for 20 min.
8. The continuous production process according to claim 1, wherein a booster pump is arranged between the first reactor and the pre-emulsification system for pumping the reaction product in the first reactor into the pre-emulsification system.
9. The continuous production process according to claim 1, wherein each of the first raw material tanks and each of the second raw material tanks are provided with a metering pump for quantitatively feeding a reaction raw material.
10. The waterborne polyurethane prepared by the continuous preparation process of any one of claims 1 to 9, wherein the waterborne polyurethane has a solid content of 20 to 55%, an average particle size of 80 to 400 nm, and a viscosity of 480 to 1200 mPas.
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