Device and method for continuously removing solvent from waterborne polyurethane emulsion

Abstract

The invention provides a device and a method for continuously removing a solvent from a waterborne polyurethane emulsion. The device comprises a desolventizing tower, a cooling device and a vacuum device which are connected in sequence, a heating device is arranged outside the desolventizing tower; a plurality of tower trays are arranged in the desolventizing tower, one end of each tower tray is fixed on the inner wall of the desolventizing tower, and the other end of each tower tray is provided with an overflow weir. According to the device and the method provided by the invention, the problems of low efficiency, high vacuum degree, easiness in skinning, deslagging, bubbling, heater blockage and the like in the traditional process of removing the solvent from the waterborne polyurethane emulsion are effectively solved; the device can automatically, efficiently, quickly and continuously remove the organic solvent in the waterborne polyurethane emulsion, the water content in the removed organic solvent is low, and the water can be used for subsequent production without being separated and purified by a refining system again.

Description

Technical Field

[0001] The invention belongs to the technical field of removing solvent from waterborne polyurethane emulsion, and in particular relates to a device and a method for continuously removing solvent from waterborne polyurethane emulsion. Background Art

[0002] Waterborne polyurethane emulsion uses water to replace organic solvents as the dispersion medium through certain technical means. It contains a small amount of volatile organic solvents (VOC) and is a low-odor, non-toxic, green and environmentally friendly organic polymer material. During its use, the dispersion medium water is volatilized to form a polyurethane film. Therefore, the film-forming material of the waterborne polyurethane emulsion has the same excellent physical and chemical properties as the polyurethane material. Waterborne polyurethane materials can be adjusted by formula and chemical modification to obtain high-performance materials with different hardness and chemical resistance. They 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 industrial production process for removing organic solvents from waterborne polyurethane emulsions is mainly based on the intermittent process. The intermittent process refers to a process in which prepolymerization, chain extension, dispersion, and solvent removal are carried out step by step in the reactor in chronological order after a single feed. However, the intermittent removal process has significant disadvantages in the production of waterborne polyurethane emulsions, such as low production efficiency, high equipment vacancy rate, high production cost, low degree of production automation, large quality fluctuations between product batches, and high defective rate.

[0004] In particular, the current industry mainly uses kettle-type intermittent desolventizing to remove acetone solvents, which has industry problems such as long time consumption, low efficiency, high vacuum degree, easy skinning, slag discharge, foaming, and heater blockage. The residual organic solvents such as acetone after the desolventizing process of water-based polyurethane emulsion in the current industry are still at a high level (about 500-3000ppm). In addition, the acetone solvent obtained by removal also contains a high content of water and cannot be directly used for production. A set of acetone solvent refining system is still required, resulting in large equipment investment and high operating costs.

[0005] CN110193312A discloses a water-based polyurethane high-efficiency desolventizing device, including a thermal insulation layer, the thermal insulation layer includes a vacuum layer, a vitrified micro-bead thermal insulation sand layer and an XPS polyurethane foam layer, the vitrified micro-bead thermal insulation sand layer is provided with a vacuum layer inside, the vacuum layer is provided with an XPS polyurethane foam layer on the side away from the vitrified micro-bead thermal insulation sand layer, the thermal insulation layer is provided with a desolventizing kettle body, the inner middle position of the desolventizing kettle body is provided with a stirring shaft, three stirring rods are evenly provided below the stirring shaft, and four stirring blades are provided on each stirring rod, and the solvent is removed by strong stirring. However, this method is prone to foaming during the stirring process, and a large amount of crusting is easily generated on the kettle wall, which requires shutdown for cleaning, and continuous production is not possible, which affects the production efficiency of the equipment.

[0006] In summary, providing a device and method for removing solvent from an aqueous polyurethane emulsion with high efficiency and energy saving, high degree of automation, continuous production and high product yield is a problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0007] The object of the present invention is to provide a device and method for continuously removing solvents from an aqueous polyurethane emulsion, which can automatically, efficiently and quickly remove organic solvents from the aqueous polyurethane emulsion continuously, while having a low water content in the removed organic solvent, and can be used for subsequent production without the need for separation and purification through a refining system again.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a device for continuously removing solvent from an aqueous polyurethane emulsion, the device comprising a desolventizing tower, a cooling device and a vacuum device connected in sequence;

[0010] A heating device is provided outside the desolventizing tower;

[0011] A plurality of tower plates are arranged in the desolventizing tower, one end of the tower plate is fixed to the inner wall of the desolventizing tower, and the other end is provided with an overflow weir.

[0012] In the present invention, a cooling device is connected to the top of the desolventizing tower; the vacuum device includes a vacuum pump and auxiliary devices, and the top pressure of the desolventizing tower is adjusted by the vacuum device according to actual needs; and a heating device is arranged outside the kettle of the desolventizing tower.

[0013] The device provided by the present invention adopts a tower plate with a specific structure and is provided with a heating device outside the tower kettle of the desolventizing tower. The desolventizing tower is sequentially connected with a cooling device and a vacuum device, and has the functions of emulsion desolventizing and organic solvent refining at the same time, effectively solving the problems of low efficiency, high vacuum degree, easy skinning, slag discharge, foaming, heater blockage, etc. in the process of traditional water-based polyurethane emulsion desolventizing, realizing automatic, rapid and efficient continuous desolventizing of the water-based polyurethane emulsion, reducing the energy consumption of desolventizing, less organic solvent loss in the desolventizing process, stable product quality of the water-based polyurethane emulsion, and low water content in the desolventized organic solvent.

[0014] As a preferred technical solution of the present invention, a feed inlet is provided on the side wall of the desolventizing tower.

[0015] Preferably, a product discharge port is provided at the bottom of the desolventizing tower.

[0016] As a preferred technical solution of the present invention, the side wall of the desolventizing tower is provided with an air inlet.

[0017] In the present invention, the gas introduced through the air inlet includes any one of nitrogen, carbon dioxide, air or oxygen, or a combination of at least two of them, preferably nitrogen; introducing nitrogen can also avoid the generation of an explosive atmosphere.

[0018] Preferably, a distribution device is provided in the desolventizing tower kettle, and the distribution device is arranged at 5%-50% of the liquid holding height in the desolventizing tower kettle, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable, preferably 10%-20%.

[0019] In the present invention, the distribution device is used to evenly disperse the gas introduced into the desolventizing tower. Firstly, the desolventizing efficiency can be improved by utilizing the effect of gas lift, and secondly, it is also beneficial to the pressure regulation and stabilization of the system under different operating conditions.

[0020] In the present invention, the distribution device is horizontally arranged in the kettle of the desolventizing tower, at a certain height from the bottom of the desolventizing tower, specifically at 5%-50% of the liquid holding height of the kettle of the desolventizing tower, which is conducive to the uniform dispersion and function of the gas in the desolventizing tower. The liquid holding height is the liquid level height reached by the aqueous polyurethane emulsion in the kettle of the desolventizing tower.

[0021] Preferably, the distribution device is connected to a pipeline of the air inlet.

[0022] As a preferred technical solution of the present invention, a plurality of tower plates are alternately arranged on the left and right inner walls of the desolventizing tower, and the tower plates are all arranged below the feed port.

[0023] In the present invention, the left-right alternation specifically refers to adjacent trays being staggered left-right on the inner wall of the desolventizing tower. The trays are all arranged above the distribution device.

[0024] Preferably, the diameter ratio of the tower plate to the desolventizing tower is (0.85-0.92):1, for example, it can be 0.86:1, 0.87:1, 0.88:1, 0.89:1, 0.9:1 or 0.91:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the spacing between adjacent tower plates is 200-700 mm, for example, it can be 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, 600 mm or 650 mm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 400-600 mm.

[0026] The present invention needs to control the distance between adjacent trays. If the distance between adjacent trays is too small, mist entrainment will occur. If the distance between adjacent trays is too large, foaming will occur easily. Moreover, too large a flow rate will also cause demulsification, thus affecting product quality.

[0027] Preferably, the number of the tower plates is 3-15, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 6-10.

[0028] The present invention needs to control the number of tower plates. If too many tower plates are provided, it will lead to high production energy consumption and a large amount of liquid in the desolventizing tower; if too few tower plates are provided, it will lead to insufficient desolventizing efficiency and a large amount of solvent will remain in the bottom of the desolventizing tower.

[0029] As a preferred technical solution of the present invention, a plurality of holes are provided on the tower plate.

[0030] Preferably, the hole diameter is 2-20 mm, for example, it can be 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm or 19 mm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 3-10 mm.

[0031] The present invention needs to control the pore size of the hole. If the pore size of the hole is too large, it will cause leakage, which is not conducive to forming a good liquid film; if the pore size of the hole is too small, the emulsion will foam and mist will be entrained due to the too fast gas speed.

[0032] Preferably, the shape of the hole includes a round hole shape and / or a square hole shape, preferably a round hole shape.

[0033] Preferably, the porosity of the tower plate is 3-30%, for example, it can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or 28%, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 10-20%.

[0034] In the present invention, the opening rate of the tower plate is controlled within the range of 3-30%, thereby ensuring good film-forming property and desolventizing efficiency.

[0035] Preferably, the tower tray and the overflow weir are arranged vertically.

[0036] Preferably, the height of the overflow weir is 5-50 mm, for example, it can be 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm or 45 mm, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 10-30 mm.

[0037] In the present invention, an overflow weir is provided at one end of the tower plate to ensure good film formation of the emulsion and efficient separation of the solvent. In addition, the height of the overflow weir needs to be controlled. If the height of the overflow weir is too low, the separation efficiency of the desolventizing tower will be low. If the height of the overflow weir is too high, liquid leakage and excessive tower pressure drop will occur, which is not conducive to desolventizing.

[0038] As a preferred technical solution of the present invention, the heating device includes a thermal insulation jacket.

[0039] In the present invention, a heating device is arranged outside the kettle of the desolventizing tower, which can reduce the operation cost on the one hand, and avoid the problems of emulsion crusting, particle size increase, etc. on the other hand, and avoid affecting the product quality.

[0040] In the present invention, the heat medium in the heat-insulating jacket includes hot water or steam, preferably hot water. The temperature of the material in the bottom of the desolventizing tower is controlled by controlling the flow rate of the heat medium.

[0041] Preferably, the outlet of the cooling device is connected to an organic solvent storage tank.

[0042] In a second aspect, the present invention provides a method for continuously removing solvent from an aqueous polyurethane emulsion, the method being carried out using the device described in the first aspect, and comprising the following steps:

[0043] (1) conveying the crude aqueous polyurethane emulsion to a desolventizing tower through a feed port, wherein the crude aqueous polyurethane emulsion is distributed in a film on a tower plate and flash separated to obtain a flash gas phase and a flash liquid phase;

[0044] (2) The flash vapor phase in step (1) is led out to a cooling device through a vacuum device, and the organic solvent is collected after condensation by the cooling device. The flash liquid phase in step (1) is downward through the tower plates one by one, and the water-based polyurethane emulsion product is obtained in the bottom of the desolventizing tower.

[0045] In the present invention, a certain liquid level of crude aqueous polyurethane emulsion can be introduced into the bottom of the desolventizing tower in advance.

[0046] The method provided by the present invention can automatically, efficiently and rapidly remove organic solvents from aqueous polyurethane emulsions continuously, while removing low water content in the organic solvents, and can be used for subsequent production without the need for separation and purification by a refining system.

[0047] As a preferred technical solution of the present invention, the organic solvent in the crude aqueous polyurethane emulsion in step (1) includes acetone.

[0048] In the present invention, the crude aqueous polyurethane emulsion includes a crude aqueous polyurethane dispersion (PUD) and / or a crude aqueous polyurethane / acrylate composite emulsion (PUA); the crude aqueous polyurethane emulsion is prepared by reacting isocyanate with polyol and a hydrophilic chain extender in an organic solvent environment.

[0049] In the present invention, the isocyanate includes any one of dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI) or toluene diisocyanate (TDI) or a combination of at least two thereof, preferably dicyclohexylmethane diisocyanate and / or hexamethylene diisocyanate; the polyol includes poly(1,4-butylene adipate) diol (PBA-2000), poly(neopentyl adipate) diol and poly(1,6-hexanediol adipate) copolymer (CMA654). or polycaprolactone diol (CAPA2209), any one or a combination of at least two thereof, preferably poly 1,4-butylene adipate diol; the chain extender includes any one or a combination of at least two thereof including 2,2-dihydroxymethylpropionic acid (DMPA), 1,4-butanediol (BDO), sodium ethylenediamine sulfonate (A95), isophorone diammonium (IPDA), hydroxyethylethylenediamine or polyethylene glycol monomethyl ether (MPEG1200), preferably any one or a combination of at least two thereof including 2,2-dihydroxymethylpropionic acid, isophorone diammonium, hydroxyethylethylenediamine or polyethylene glycol monomethyl ether.

[0050] As a preferred technical solution of the present invention, before the transportation in step (1), the method further includes: regulating the bottom temperature of the desolventizing tower by a heating device, regulating the top pressure of the desolventizing tower by a vacuum device, and then opening the air inlet.

[0051] Preferably, the bottom temperature of the desolventizing tower is 35-45°C, for example, it can be 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C or 44°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] Preferably, the absolute pressure at the top of the desolventizing tower is 30-80 kPa, for example, it can be 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa or 75 kPa, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 40-55 kPa.

[0053] As a preferred technical solution of the present invention, the temperature of the cooling medium in the cooling device in step (2) is -5 to 15°C, for example, it can be -4°C, -3°C, -2°C, -1°C, 0°C, 1°C, 2°C, 3°C, 5°C, 6°C, 8°C or 9°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 0 to 5°C.

[0054] In the present invention, the cooling medium includes water and / or ethylene glycol; the amount of the cooling medium is adjusted according to the gas phase temperature in the cooling device.

[0055] Preferably, the water content in the organic solvent in step (2) is less than 100 ppm, for example, it can be 90 ppm, 80 ppm, 70 ppm, 60 ppm, 50 ppm, 40 ppm or 20 ppm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the organic solvent content in the aqueous polyurethane emulsion product of step (2) is less than 10 ppm, for example, it can be 9 ppm, 8 ppm, 7 ppm, 6 ppm, 5 ppm, 4 ppm or 2 ppm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The device provided by the present invention adopts a tower plate with a specific structure and is provided with a heating device outside the tower kettle of the desolventizing tower. The desolventizing tower is connected with a cooling device and a vacuum device in sequence. The emulsion film is used to stably and efficiently remove the organic solvent in the desolventizing tower. The emulsion has stable properties and is not easy to foam. No additional defoaming agent is required. Under preferred conditions, the residual organic solvent in the emulsion is reduced to less than 10 ppm, thereby achieving green and environmentally friendly products. At the same time, the device has the function of refining organic solvents. Under preferred conditions, the water content in the organic solvent is as low as less than 100 ppm, and it can be used for subsequent production without separation and purification by a refining system, which greatly saves equipment investment costs and operating costs.

[0059] (2) The device and method provided by the present invention effectively solve the problems of low efficiency, high vacuum degree, easy skinning, slag, foaming, and heater clogging in the traditional aqueous polyurethane emulsion solvent removal process, and realize rapid, efficient, continuous, automatic and stable solvent removal. The quality of the emulsion product is stable, the solvent removal efficiency is improved, and the energy consumption and operating costs of the removal are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic diagram of the structure of the device for continuously removing solvent from the aqueous polyurethane emulsion provided in Example 1;

[0061] Figure 2 This is a schematic diagram of the structure of the holes on the tower plate in Example 1;

[0062] Among them, 1-feed port, 2-tower tray, 3-desolventizing tower, 4-heating device, 5-distribution device, 6-product discharge port, 7-air inlet, 8-organic solvent storage tank, 9-cooling device, 10-vacuum device. DETAILED DESCRIPTION

[0063] It should be understood that, in the description of the present invention, the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0064] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0065] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0066] A method for preparing an aqueous polyurethane emulsion is provided in a specific embodiment of the present invention. The method comprises: firstly heating a synthesis kettle to 60°C, then adding poly(1,4-butylene adipate diol), dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, 2,2-dimethylol propionic acid, polyethylene glycol monomethyl ether and acetone into the synthesis kettle in proportion, then starting stirring at a stirring speed of 200 rpm / min, heating to 85-90°C for reaction for 3h, when the NCO% (isocyanate group) content is 2.10%, cooling to 50°C, adding acetone for dilution, then adding chain extenders isophorone diammonium and hydroxyethylethylenediamine, raising the stirring speed to 1000 rpm / min, maintaining the temperature at 40-45°C for reaction for 20min, then gradually adding water for dispersion for 10min, sampling and measuring the particle size until the particle size is qualified, and obtaining a crude aqueous polyurethane emulsion. The proportion of the synthetic raw materials is specifically defined according to needs.

[0067] In the specific implementation manner of the present invention, the raw materials for synthesizing the aqueous polyurethane emulsion are all commercially available products; the crude aqueous polyurethane emulsion to be processed is all the same material.

[0068] The test method for acetone content in a specific embodiment of the present invention is as follows: 50 g of sample is taken and headspace injection gas chromatography is used; gas chromatograph model: Agilent Technologies 7890B; parameters: chromatographic column model: DB WAX (30m×0.25mm×0.25μm); injection port temperature: 200°C, split ratio: 50:1, pressure: 76.025psi, septum purge flow: 3mL / min; chromatographic column flow: 1mL / min and the flow is constant.

[0069] The test method of water content in the specific embodiment of the present invention is as follows: take 1 mL of sample into a gas chromatography vial, and use gas-TCD to quantify the water content. Gas chromatograph model: Agilent 7890B, parameters: chromatographic column model: HP-PLOT / Q (30m×0.53mm×40um), injection port temperature: 250°C, injection volume: 0.5μL, split ratio: 10:1, chromatographic column flow: 4mL / min, constant flow mode, detector TCD, detector temperature: 270°C.

[0070] In the following embodiments of the present invention, the diameter ratio of the tower plate to the desolventizing tower is 0.9:1.

[0071] Example 1

[0072] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion (such as Figure 1 As shown), the device comprises a desolventizing tower 3, a cooling device 9 and a vacuum device 10 connected in sequence;

[0073] The side wall of the desolventizing tower 3 is provided with a feed inlet 1; the bottom of the desolventizing tower 3 is provided with a product discharge port 6;

[0074] The inner wall of the desolventizing tower 3 is alternately provided with 10 trays 2 (such as Figure 2 As shown), one end of the tower tray 2 is fixed to the inner wall of the desolventizing tower 3, and the other end is provided with an overflow weir; the tower tray 2 is vertically arranged with the overflow weir; the height of the overflow weir is 10 mm;

[0075] The trays 2 are all arranged below the feed port 1; the spacing between adjacent trays 2 is 600 mm; holes are provided on the trays 2; the hole diameter is 3 mm; the shape of the holes includes a circular hole; the opening rate of the trays 2 is 20%;

[0076] The side wall of the desolventizing tower 3 is provided with an air inlet 7; a distribution device 5 is horizontally provided in the kettle of the desolventizing tower 3, and the distribution device 5 is arranged at 15% of the liquid holding height in the kettle of the desolventizing tower 3; the distribution device 5 is connected with the pipeline of the air inlet 7;

[0077] The desolventizing tower 3 is provided with a heating device 4 outside the kettle;

[0078] The outlet of the cooling device 9 is connected to an organic solvent storage tank 8 .

[0079] Example 2

[0080] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion, the device comprising a desolventizing tower, a cooling device and a vacuum device connected in sequence;

[0081] The side wall of the desolventizing tower is provided with a feed inlet; the bottom of the desolventizing tower is provided with a product discharge port;

[0082] The inner wall of the desolventizing tower is provided with 6 tower plates alternately on the left and right sides, one end of the tower plate is fixed to the inner wall of the desolventizing tower, and the other end is provided with an overflow weir; the tower plate is vertically arranged to the overflow weir; the height of the overflow weir is 30 mm;

[0083] The tower plates are all arranged below the feed port; the spacing between adjacent tower plates is 400 mm; holes are provided on the tower plates; the hole diameter is 10 mm; the shape of the holes includes a circular hole; the opening rate of the tower plates is 10%;

[0084] The side wall of the desolventizing tower is provided with an air inlet; a distribution device is horizontally arranged in the kettle of the desolventizing tower, and the distribution device is arranged at 20% of the liquid holding height in the kettle of the desolventizing tower; the distribution device is connected to the pipeline of the air inlet;

[0085] A heating device is provided outside the desolventizing tower kettle;

[0086] The outlet of the cooling device is connected to an organic solvent storage tank.

[0087] Example 3

[0088] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion, the device comprising a desolventizing tower, a cooling device and a vacuum device connected in sequence;

[0089] The side wall of the desolventizing tower is provided with a feed inlet; the bottom of the desolventizing tower is provided with a product discharge port;

[0090] The inner wall of the desolventizing tower is provided with 8 trays alternately on the left and right sides, one end of the tray is fixed to the inner wall of the desolventizing tower, and the other end is provided with an overflow weir; the tray is vertically arranged to the overflow weir; the height of the overflow weir is 20 mm;

[0091] The tower plates are all arranged below the feed port; the spacing between adjacent tower plates is 500 mm; holes are provided on the tower plates; the hole diameter is 6 mm; the shape of the holes includes a circular hole; the opening rate of the tower plates is 15%;

[0092] The side wall of the desolventizing tower is provided with an air inlet; a distribution device is horizontally arranged in the kettle of the desolventizing tower, and the distribution device is arranged at 10% of the liquid holding height in the kettle of the desolventizing tower; the distribution device is connected to the pipeline of the air inlet;

[0093] A heating device is provided outside the desolventizing tower kettle;

[0094] The outlet of the cooling device is connected to an organic solvent storage tank.

[0095] Example 4

[0096] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion, and further defines the heating device as a heat-insulating jacket on the basis of Embodiment 1.

[0097] Example 5

[0098] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the number of the tower plates is 2, other conditions are the same as those in Embodiment 1.

[0099] Example 6

[0100] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the number of the tower plates is 15, other conditions are the same as those in Embodiment 1.

[0101] Example 7

[0102] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the spacing between adjacent trays is 100 mm, other conditions are the same as those in Embodiment 1.

[0103] Example 8

[0104] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the spacing between adjacent trays is 700 mm, other conditions are the same as those in Embodiment 1.

[0105] Example 9

[0106] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the diameter of the holes is 1 mm, other conditions are the same as those in Embodiment 1.

[0107] Example 10

[0108] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the diameter of the holes is 20 mm, other conditions are the same as those in Embodiment 1.

[0109] Embodiment 11

[0110] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the height of the overflow weir is 5 mm, other conditions are the same as those in Embodiment 1.

[0111] Example 12

[0112] This embodiment provides a device for continuously removing solvent from an aqueous polyurethane emulsion. Except that the height of the overflow weir is 60 mm, other conditions are the same as those in Embodiment 1.

[0113] Comparative Example 1

[0114] The present comparative example provides a device for removing solvent from an aqueous polyurethane emulsion, which adopts a general intermittent kettle type desolventizing device. A stirring device is arranged in the desolventizing kettle, a product discharge port is arranged at the bottom of the desolventizing kettle, and the top of the desolventizing kettle is connected to a gas phase condensation system and a vacuum system in sequence, and an outlet of the gas phase condensation system is connected to an acetone storage tank.

[0115] Comparative Example 2

[0116] This comparative example provides a device for removing solvent from an aqueous polyurethane emulsion. Except that the tray in the desolventizing tower is replaced with Sulzer Mellapak 202Y structured packing, other conditions are the same as those in Example 1.

[0117] Application Example 1-12

[0118] This application example provides a method for continuously removing solvent from an aqueous polyurethane emulsion, the method being carried out using the apparatus provided in Examples 1-12, comprising the following steps:

[0119] (1) introducing a crude aqueous polyurethane emulsion having a liquid holdup height of 60% into a desolventizing tower, adjusting the bottom temperature of the desolventizing tower to 40° C. by a heating device, and adjusting the top pressure of the desolventizing tower to 40 kPa by a vacuum device, and then opening the air inlet to introduce nitrogen;

[0120] (2) conveying the crude aqueous polyurethane emulsion to a desolventizing tower through a feed port, wherein the crude aqueous polyurethane emulsion is distributed on a tower plate in a film-forming manner, and flash separation is performed at a temperature of 40° C. and a pressure of 40 kPa to obtain a flash gas phase and a flash liquid phase;

[0121] (3) The flash vapor phase in step (2) is led out to a cooling device through a vacuum device, and acetone is collected after being condensed by the cooling device. The feed flow rate of the feed inlet is controlled to ensure that the liquid holdup height in the desolventizing tower is 60%. The flash vapor phase in step (2) flows downward through the tower plates one by one, and the water-based polyurethane emulsion product is obtained in the bottom of the desolventizing tower.

[0122] Comparative Application Example 1-2

[0123] This comparative application example provides a method for removing solvent from an aqueous polyurethane emulsion. The method is carried out using the device provided in Comparative Example 1-2, and the temperature of the desolventizing kettle is 40° C. and the pressure is 40 kPa.

[0124] The problems and desolventizing efficiencies in the desolventizing process of the above application examples and comparative application examples were recorded, the aqueous polyurethane emulsion products obtained in the above application examples and comparative application examples were tested for acetone residue, and the obtained acetone was tested for water content. The results are shown in Table 1.

[0125] Table 1

[0126]

[0127]

[0128] It can be seen from Table 1 that the device and method provided by the present invention adopt a tower plate of a specific structure and a heating device is arranged outside the tower kettle of the desolventizing tower. The desolventizing tower is connected in sequence with a cooling device and a vacuum device, and the emulsion film is used to realize stable and efficient removal of the organic solvent in the desolventizing tower. The emulsion has stable properties and is not easy to foam. No additional defoaming agent is required. Under preferred conditions, the residual organic solvent in the emulsion is reduced to below 10 ppm, realizing the green and environmental protection of the product, and at the same time having the function of refining the organic solvent. Under preferred conditions, the water content in the organic solvent is as low as below 100 ppm, and it can be used for subsequent production without separation and purification through the refining system again, which greatly saves the equipment investment cost and operating cost, and has broad application prospects.

[0129] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A device for continuously removing solvent from an aqueous polyurethane emulsion, characterized in that: The device comprises a desolventizing tower, a cooling device and a vacuum device connected in sequence; A heating device is provided outside the desolventizing tower; A plurality of tower plates are arranged in the desolventizing tower, one end of the tower plate is fixed to the inner wall of the desolventizing tower, and the other end is provided with an overflow weir.

2. The device according to claim 1, characterized in that The side wall of the desolventizing tower is provided with a feed inlet; Preferably, a product discharge port is provided at the bottom of the desolventizing tower.

3. The device according to claim 1 or 2, characterized in that: The side wall of the desolventizing tower is provided with an air inlet; Preferably, a distribution device is provided in the desolventizing tower kettle, and the distribution device is arranged at 5%-50% of the liquid holding height in the desolventizing tower kettle, preferably at 10%-20%; Preferably, the distribution device is connected to a pipeline of the air inlet.

4. The device according to any one of claims 1 to 3, characterized in that: The inner wall of the desolventizing tower is provided with a plurality of tower plates alternately on the left and right sides, and the tower plates are all arranged below the feed port; Preferably, the diameter ratio of the tower tray to the desolventizing tower is (0.85-0.92):1; Preferably, the spacing between adjacent trays is 200-700 mm, preferably 400-600 mm; Preferably, the number of the tower trays is 3-15, preferably 6-10.

5. The device according to any one of claims 1 to 4, characterized in that: The tower plate is provided with a plurality of holes; Preferably, the hole has a diameter of 2-20 mm, preferably 3-10 mm; Preferably, the shape of the hole includes a circular hole shape and / or a square hole shape, preferably a circular hole shape; Preferably, the opening rate of the tray is 3-30%, preferably 10-20%; Preferably, the tower tray and the overflow weir are arranged vertically; Preferably, the height of the overflow weir is 5-50 mm, preferably 10-30 mm.

6. The device according to any one of claims 1 to 5, characterized in that: The heating device comprises a heat-insulating jacket; Preferably, the outlet of the cooling device is connected to an organic solvent storage tank.

7. A method for continuously removing solvent from an aqueous polyurethane emulsion, characterized in that: The method is carried out using the device according to any one of claims 1 to 6, and comprises the following steps: (1) conveying the crude aqueous polyurethane emulsion to a desolventizing tower through a feed port, wherein the crude aqueous polyurethane emulsion is distributed in a film on a tower plate and flash separated to obtain a flash gas phase and a flash liquid phase; (2) The flash vapor phase in step (1) is led out to a cooling device through a vacuum device, and the organic solvent is collected after condensation by the cooling device. The flash liquid phase in step (1) is downward through the tower plates one by one, and the water-based polyurethane emulsion product is obtained in the bottom of the desolventizing tower.

8. The method according to claim 7, characterized in that The organic solvent in the crude aqueous polyurethane emulsion in step (1) includes acetone.

9. The method according to claim 7 or 8, characterized in that: Before the transportation in step (1), the method further includes: regulating the temperature of the bottom of the desolventizing tower by a heating device, regulating the pressure at the top of the desolventizing tower by a vacuum device, and then opening the air inlet; Preferably, the bottom temperature of the desolventizing tower is 35-45°C; Preferably, the absolute pressure at the top of the desolventizing tower is 30-80 kPa, preferably 40-55 kPa.

10. The method according to any one of claims 7 to 9, characterized in that: The temperature of the cooling medium in the cooling device in step (2) is -5 to 15°C, preferably 0 to 5°C; Preferably, the water content in the organic solvent in step (2) is less than 100 ppm; Preferably, the organic solvent content in the aqueous polyurethane emulsion product in step (2) is less than 10 ppm.

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