APPARATUS AND PROCESS FOR DISPERSING FINISHED POLYURETHANE PREPOLIMERS IN ISOCYANATE DESCRIPTION OF THE INVENTION This application is a continuation in part of Copending Application Serial No. 08/528936, filed September 15, 1995. This invention relates to an apparatus and process to • disperse isocyanate-terminated polyurethane prepolymers with water. It is known that dynamic mixers, which have a calibrated vane turbine inside a suction tube generates an axial flow, are useful for the continuous emulsification, homogenization and dispersion of materials. References describing such mixers include: Patent of Japanese Utility Model No. 1148021 (Cañan KK) describes dynamic turbine mixers, which are designed to generate axial flow within the vessel. A product catalog entitled, "T.K. Homomic
Line Flow "from Tokushu Kika Kogyo Co., Ltd, (Osaka, Japan) describes dynamic turbine mixers, which are useful for emulsifying, homogenizing and dispersing materials, which are transferable by metering feeding pumps. describe that they are useful for continuously dissolving various kinds of resin solutions in solvent The reference fails to describe the use of mixers to disperse isocyanate-terminated polyurethane prepolymers in water Generally, isocyanate-terminated polyurethane prepolymers dispersible in water, They are formed by reacting a stoichiometric excess of polyisocyanate with compounds containing active hydrogen atoms, such as polyols and polyamines.The prepolymers are dispersed in water using mechanical stirring and then reacting with compounds such as water soluble amines. Urethane based polyurethane-urea polymer a.The apparatus most frequently used to disperse these prepolymers are dynamic stator-rotor and pivot mixers. Such mixers are designed to rapidly disperse the prepolymers in water using high energy per unit input volume and short resistance times. For example, U.S. Patent No. 4,742,095, Mobay Corporation (Pittsburg, PA) discloses dynamic stator-rotor and pivot mixers operating at a rate of approximately 500 revolutions per minute (rpm) at 8,000 rpm, a wattage of mixed of approximately 0.3 watts / cu. cm at 10.0 watts / cu. cm and a mixing volume of at least about 0.1 liters. The average residence time in the mixers is from about 1 second to 30 seconds. Other related patents, which fail to describe the apparatus and process of the present invention, include British Patent No. 1,414,930, Patent No.
1,432,112, Patent No. 1,428,907 and German Patent No.
2,347,299. A disadvantage with these dynamic mixers is that reduced residence times can not generate a uniform particle dispersion and high energy per unit volume of input, it can cause destabilization induced by shear stress, which generates increased sedimentation. In order to improve the performance characteristics of the water-based polyurethane-urea polymers, it is often necessary to form isocyanate-terminated polyurethane prepolymers, which are characterized by increased hydrophobicity, crystallinity and viscosity. Such prepolymers are not easily dispersed in water, they require long residence times and lower energy per input volume unit, to generate dispersions of uniform particles which are substantially free of sedimentation.
Therefore, there remains a need for an apparatus and process which can disperse isocyanate-terminated polyurethane prepolymers in water using long residence times and lower energy per unit volume of inlet.The present invention is directed to an apparatus and a process for the dispersion in water of isocyanate-terminated polyurethane prepolymers The apparatus comprises: a) at least one reaction vessel containing an NCO-terminated, water-dispersible polyurethane prepolymer, which is the product of the reaction of; 1) at least one polyisocyanate; and 2) at least one polyol and / or polyamine component, which may be substituted with at least one hydrophilic moiety; b) at least one supply container containing at least one compound such as water, organic materials and inorganic materials; c) at least one dynamic mixer, which has a calibrated turbine blade inside a suction tube to generate axial flow, configured to provide: 1) a mixing zone of volume greater than about 0.1 liters; 2) an average tip speed greater than about 100 meters / minute; 3) an average power per input volume unit of less than about 0.60 watts / cu. cm; 4) an average residence time of at least about 10 seconds; with 5) an average of at least about 5 passes through the mixing zone; and d) at least one finishing container, wherein the dispersion is further reacted to form a water-based polyurethane-urea polymer. The invention is further characterized by a process for dispersing the NCO-terminated polyurethane prepolymers comprising the steps of: a) combining an aqueous solution of organic and inorganic ingredients with at least one isocyanate-terminated polyurethane prepolymer, dispersible in water to form a mixture of materials; b) feeding the mixture of materials in at least one dynamic axial flow mixer and using a dispersion process comprising; 1) an average tip speed greater than about 100 meters / minute;
2) an average power per input volume unit of less than about 0.60 watts / cu. cm; 3) an average residence time of at least about 10 seconds; with 4) an average of at least about
passes through the mixing zone; 5) a higher average flow velocity - about 30 liters / hour; and c) transferring the dispersion to at least one finishing vessel and terminating the isocyanate reaction to form a water-based polyurethane-urea polymer. Surprisingly, the inventive apparatus and process generates uniform prepolymer dispersions using long residence times and lower energy per input volume unit. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary side view, in partial cross section, of a dynamic axial flow mixer using the apparatus and process of the invention. Figure 2 is a schematic diagram of an apparatus of the invention. The present invention is directed to an apparatus and process for dispersing NCO-terminated polyurethane prepolymers. The apparatus is a turbine mixer, which has a calibrated turbine with a suction tube. Turbine mixers, which generate axial flow within the mixing vessel, can be configured to provide less energy per unit volume, extended residence times and multiple passes through the mixing zone. Such mixers have proven to be useful for the processing of prepolymers, which are difficult to disperse in water. Suitable dynamic mixers are commercially available from Tokishu Kika Kogyo Co., Ltd., Osaka, Japan under the product name T.K. Homomic Line Flow. Such mixers are configured to provide: 1) a mixing zone volume greater than about 0.1 liters; 2) a tip speed of about 100 meters / minute to about 5,000 meters / minute and more preferably from about 250 meters / minute to about 1,500 meters / minute; 3) a power per unit input volume of approximately 0.01 watts / cu. cm at approximately 0.60 watts / cu. cm and more preferably approximately 0.10 watts / cu. cm at approximately 0.30 watts / cu. cm; 4) an average residence time of from about 10 seconds to about 120 seconds and more preferably from about 10 seconds to about 60 seconds; with 5) an average number of passes through the mixing zone from about 2 passes to about 150 passes and more preferably from about 10 passes to about 60 passes; and 6) an output flow rate greater than about 100 liters / hour. The average residence time and the average number of passes through the mixing zone can be varied with the feed rates of the material and the speed of the tip. If desired, larger amounts of dispersion can be produced per unit of time using more than one mixer at a time. The Figure illustrates a dynamic mixer of the type used in the apparatus and process of the invention. The mixer includes a motor 12 mounted to a motor base 14, which is connected to a bearing case 16. The bearing case 16 mounts the motor onto the lid of the container 18. A mixing vessel 20 is removably mounted to the lid 18. The calibrated alabe turbine 26 and the suction tube 28 define a mixing zone. The blade is mounted to a shaft 32 operatively connected to the motor shaft by means of a mechanical seal 34. The vessel is a double chamber having a central mixing chamber 21, a "recirculation zone 22 and an additional annular outlet chamber. small 24. An inlet 36 provides the feed access to the mixing chamber 21, while the outlet 38 provides the output of the dispersed product leaving the mixing chamber. In Figure 1, the direction of flow is indicated by the arrows. The material entering the container via the inlet 36 is directed through the mixing zone 21 and the cycles through the suction pipe 28 and the recirculation zone 22 in an axial flow. The dispersed material leaves the recirculation zone through the outlet 38. Figure 2 is a schematic representation of an apparatus according to the invention. An isocyanate-terminated polyurethane prepolymer dispersible in water is prepared in the reaction vessel 100 and fed by means of the metering pump 110 into the dynamic mixer 300. The contents of the supply vessel 200 are fed to the mixer 300 by means of the metering pump 210, which joins the duct 110 to provide a single feed line within the mixer 300. The dispersion of the prepolymer leaving the mixer 300 is fed via the duct 310 to a finishing vessel 500 under agitation. The contents of the supply container 400 can be added to the dispersion in various locations. For example, the contents of the supply container can be fed into the mixing vessel 300 by means of a pumped duct, meter 410 or into the duct 310 by means of the metering duct 420 or into the finishing vessel 500 by way of the duct pumped meter 430. Alternatively, supply container 400, conduit 410, 420 and 430 may be omitted. Once the components are inside the finishing vessel 500, the dispersion of the prepolymer is stirred to complete the reaction of the isocyanate and form a water-based polyurethane-urea polymer. At least one reaction vessel is used in the apparatus and process of the invention. If desired, multiple reaction vessels can be used. Such containers may contain isocyanate terminated polyurethane prepolymers of different composition. At least one axial flow turbine mixer, which is mounted in a suction pipe, is used in the invention. The term "suction tube" refers to an open cylinder, which separates the mixing zone from the recirculation zone. The suction tube generates axial flow and allows recirculation through the mixing vessel. If desired, multiple mixers can be used to disperse large quantities of prepolymer, thereby increasing the total volume of dispersion produced per unit of time. At least one supply container is used. The container contains at least one component, which may include amines, antioxidants, biocides, coalescence aids, coloring agents, defoamers, dispersed pigments, emulsifiable fences, fillers, flame retardants, fungicides, ionic emulsifiers and / or non-ionic emulsifiers. ionic, natural polymer dispersions, emulsifiable synthetic resins that are not based on polyurethane, organic cosolvents, perfume-like materials, plasticizers, sequestering agents, UV stabilizers, water, wetting agents and mixtures thereof. The isocyanate-terminated polyurethane prepolymers and the contents of the supply container can be transferred using metering pumps, which may include centrifugal pumps, or diaphragm pumps, gear pumps, piston pumps, peristaltic pumps, progressive cavity pumps , lobe pumps, screw pumps and vane pumps. Alternatively, the materials can be transferred using gravity feed and / or compressed gases including nitrogen, which will require the use of control valves. Preferably, a duct system comprising pipes or tubes is used to channel the materials through the apparatus of the invention. At least one finishing vessel is used and preferably is equipped with mechanical stirring. As well, multiple finishing containers can be used to react the prepolymer dispersions with different compounds having active hydrogen atoms. Such a process is used to generate water-based polyurethane-urea polymers, which differ in composition. In order to increase the operating characteristics of the water-based polyurethane-urea polymers, it is often necessary to form isocyanate-terminated polyurethane prepolymers having properties such as hydrophobicity, crystallinity and increased viscosity. Examples include the hydrophobic prepolymers described in U.S. Patent No. 5,354,807 (H.B. Fuller Company) and the crystalline polymers described in copending Application Serial No. 08/528936, incorporated herein by reference. The prepolymers can have viscosities in the range from about 10,000 m.Pas to about 100,000 m.Pas and more preferably from about 15,000 m.Pas to about 50,000 m.Pas. These prepolymers are more likely to develop a uniform particle dispersion, when long residence times and lower energy are used per input volume unit. The prepolymers are prepared by reacting a stoichiometric excess of polyisocyanate with at least one polyol compound and / or a polyamine compound, which may be substituted with at least one hydrophilic moiety. The materials can be reacted at a temperature in the range of about 25 ° C to about 100 ° C and more preferably from about 60 ° C to about 90 ° C. The isocyanate percent, present in the finished prepolymer, may be in the range of about 1.0% by weight to about 15.0% by weight and more preferably from about 4.0% by weight to about 8.0% by weight, based on the solids of the total prepolymer. The prepolymers are preferably dispersed using distilled and / or deionized water. The temperature of the water is greater than 0 ° C and preferably in a range from about 5 ° C to about 100 ° C and more preferably from about 25 ° C to about 50 ° C.
The water-based polymers of the present invention may have a solids content in the range of from about 20.0% by weight to about 80.0% by weight and preferably from about 30.0% by weight to about 50.0% by weight. Once the isocyanate-terminated polyurethane prepolymer has been dispersed and transferred to a finishing vessel, the dispersion can be charged with the contents of a second supply vessel, which can contain deionized water and water-soluble amines, to form a dispersion mixture The mixture may or may not be stirred and may be reacted at a temperature from about 5 ° C to about 100 ° C and preferably from about 25 ° C to about 65 ° C. The following description of the compositions is illustrative of the types of dispersible products, which are advantageously prepared using the apparatus and process of the present invention. In the art, they will recognize that alternative products can be formed using other reagents. The polyisocyanates can be linear aliphatics, cyclic aliphatics, aromatics and mixtures thereof. The polyisocyanate is preferably a mixture including hindered polyisocyanate and unimpeded polyisocyanate. The term "hindered polyisocyanate" is defined as an isocyanate portion, which is less sensitive to the water-isocyanate reaction due to the proximity of the adjacent aliphatic character. The hindered polyisocyanate may be present in the polyisocyanate mixture in a range from about 1 part to about 95 parts and more preferably from about 25 parts to about 75 parts, based on 100 parts of total polyisocyanates. Examples of commercially available hindered polyisocyanates include Vestanat® IPDI which is isocyanate of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl from HULS America, Inc. (Piscataway, NJ) and TMXDIR, which is 1,3-bis (1-isocyanato-l-methylethyl) -benzene from Cyanamid (ayne, NJ). Examples of commercially available, non-hindered polyisocyanates include Luxate® HM, which is 1,6-hexamethylene diisocyanate from Olin Corporation (Stamford, CT), diphenylmethane diisocyanate from Upjohn Poymer Chemicals (Kalamazoo, MI), Desmodur® W, which is the 4, 4'-dicyclohexylmethane diisocyanate from Mobay Corporation (Pittsburgh, PA) and toluene diisocyanate (TDI). The presence of hindered polyisocyanate is preferred in the process of the invention. It is assumed that such sterically hindered polyisocyanates are less likely to fully react during the synthesis of the prepolymer. The resulting isocyanate-terminated polyurethane prepolymers, which are less sensitive to the isocyanate / water reaction, may be dispersed in water allowing another reaction with amines. If desired, the isocyanate-terminated polyurethane prepolymers dispersible in water can be subjected to complete hydrolysis. Such prepolymers, which are preferably based on the sulfonate character, generate polyurethane-urea polymers which have increased properties such as water resistance and heat resistance and are described in Copending Application Serial No. 08/528936 mentioned above. previous. Other polyisocyanates which may be used include modified polyisocyanates prepared from hexamethylene diisocyanate, isophorone diisocyanate and toluylene diisocyanate. The modified diisocyanates may have functionalities such as urethanes, uretdiones, isocyanurates, biurets and mixtures thereof. Examples of low molecular weight polyols, which can be used in the preparation of water-dispersible isocyanate-terminated polyurethane prepolymers, can have hydroxyl numbers, as determined by the designation ASTM E-222-67 (Method B), in the range from about 130 to about 1250 and preferably from about 950 to about 1250. Examples of low molecular weight polyols include trimethylolpropane, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol and the aliphatic diols described in U.S. Patent No. 5,039,732, of Sherwin-Williams Company (Baltimore, MD), incorporated herein by reference. The prepolymer of the invention can be made dispersible in water by the chemical incorporation of anionic portions, nonionic portions, cationic portions and mixtures thereof. Anionic polyurethane-urea polymers are preferred and prepolymers containing a combination of sulfonate and carboxylate groups are more preferred. Examples of ionic portions which can be incorporated into the prepolymer include dimethylolpropionic acid and 1,4-dihydroxybutane sulfonic acid described in U.S. Patent No. 3,412,054 and U.S. Patent No. 4,108,814, incorporated herein by reference. reference. The anionic groups can be neutralized with bases such as alkali metal hydroxides, organic tertiary amines, ammonia and mixtures thereof. The conversion of the anionic groups to ionic groups (salts) can be carried out before, during or after the prepolymer has been dispersed in water.
The polymeric diols used in the preparation of the prepolymers can have hydroxyl numbers, as determined by ASTM designation E-222-67 (Method B), in a range from about 20 to about 140 and preferably from about 55 to about 110. The polymer polyols can have melting temperatures from about 10 ° C to about 200 ° C and more preferably from about 25 ° C to about 95 ° C. The polyols can be selected from the group consisting of polyols, polyether polyols, polycarbonate polyols, polyurethane polyols, polyacetal polyols, polyacrylate polyols, polycaprolactone polyols, polyesteramide polyols, polythioether polyols and mixtures thereof. Preferred polymeric polyols are those described in copending application Serial No. 08/528936 mentioned in the foregoing and U.S. Patent No. 5,334,690 (Hoechst Aktiengesellschaf, Fed.), Incorporated herein by reference. The inventive process generates water-based polyurethane-urea polymers, which are characterized in that they have increased properties that include heat resistance and water resistance. The process is also useful in the preparation of water-based polyurethane-urea polymer blends and hybrids containing poly-acrylic and / or polyvinyl polymers. Examples include the compositions described in co-pending US Application 08/561197, filed November 21, 1995, H.B. Fuller Company (St. Paul, MN) incorporated herein by reference. The invention is illustrated by the following non-limiting examples. Example 1 Example 1 describes the preparation of highly crystalline, water-based polyurethane-urea polymer. To a reaction vessel are charged 45.39 kg (44.5 hydroxyl equivalents) Rucoflex® XS-5483-55 which is a sulfonated polyester polyol from Ruco Polymer Corporation (Hicksville, NY). 2.13 kg of dimethylolpropionic acid (15.9 hydroxyl equivalency), 2.39 kg of 1,4-butanediol (53.0 equivalence hydroxyl), 6.60 kg of isophorone diisocyanate (59.4 isocyanate equivalence), 9.99 kg of hexamethylene diisocyanate (118.8 equivalence) isocyanate) and 4.24 kg of anhydrous acetone. The mixture is stirred gently and heated to 70 ° C for about 2.5 hours, then loaded with 1.27 kg of triethylamine and stirred an additional 15 minutes before dispersion.
The prepolymer (80 ° C) and the deionized water (60 ° C) are combined in lines and transferred to a dynamic axial flow mixer T.K. Homonic Line Flow model 100S from Tokushu Kika Kogyo Co., Ltd. (Osaka, Japan). The prepolymer is transferred from the reaction vessel using a gear pump set at a speed of 3.60 kg per minute, while the water is transferred from a supply vessel using a progressive gravity pump set at a speed of 6.40 kg per minute. The mixer is configured to provide an average residence time of 61 seconds using an axle speed of 3,600 rpm and a tip speed of 1,000 meters / minute. The dispersion is transferred to a finishing vessel equipped with a turbine stirrer and operated at a circulation speed of about 10 min "1 for about 20 minutes.A mixture containing ethylenediamine in deionized water is charged to the dispersion. stir an additional 30 minutes at 60 ° C to generate water-based polyurethane-urea polymer The properties of the polymers are described as follows: pH = 7.9 Solids = 31.38% Average diameter particle size = 189 nm Viscosity = 40 m.Pas Example 2 Examples 2 describes the preparation of a water-based, hydrophobic polyurethane-urea polymer.A 28.53 kg of Rucoflex® S-102-10 is charged to a reaction vessel, which is a polyester polyol of Ruco Polymer Corporation (Hicksville, NY), 0.348 kg of trimethylolpropane (7.8 hydroxyl equivalency), 3.48 kg of dimethylolpropionic acid (50.0 hydroxyl equivalency), 30.18 kg of TMXDIR, the ual is tetramethylxylene diisocyanate of Cyanamid (Wayne, NJ), 0.362 kg of Irganox® 1076, which is a phenol hindered antioxidant from Ciba-Geigy Corporation (Hawthorne, NY) and 2.50 kg of triethylamine. The mixture is gently stirred and heated at 90 ° C for 2 hours. The prepolymer is charged with 6.60 kg of TomahR-14
(47.0 amine equivalence), which is isodecyloxypropyl-1,3-diaminopropane from Tomah Products (Milton, Wl). The amine is charged to the reactor over a period of 1 hour keeping the temperature below 90 ° C. The prepolymer, which has a viscosity of about 15,000 m.Pas at 90 ° C, is processed as described similarly in Example 1. The exception is that the prepolymer is dosed at 4.4 kg / minute, water (62 ° C) ) was dosed at a rate of 7.0 kg / minute, the speed of the turbine tip was 1,000 meters / second and the average resistance time was 53 seconds. The dispersion is transferred to a finishing vessel equipped with a turbine agitator and operated at a circulation speed of about 10 min. "1 for about 20 minutes.The dispersion is charged with a diluent solution of the chain consisting of 12.65. % Diethylenetriamine, 39.62% ethylenediamine and water The dispersion is stirred an additional 30 minutes to generate a water-based polyurethane-urea polymer The properties of the polymers are described as follows: pH = 9.12 Solids = 36.7% Viscosity = 20 m.Pas