Method for purifying and concentrating polymer semi-finished product

Abstract

The invention provides a method for purifying and concentrating a polymer semi-finished product. A crude product contains a target product polymer and one or more impurities selected from the group consisting of a monomer, an oligomer, a solvent and a by-product. The method comprises the following steps: removing at least part of impurities in the semi-finished product in a film evaporator; the film evaporator comprises a film scraping device, the film scraping device comprises at least one vertically-arranged scraping strip, and each scraping strip is provided with a plurality of scraping plates. The method is carried out in a continuous manner. According to the method disclosed by the invention, the purification and concentration of the polymer semi-finished product can be realized in a simple, efficient and high-production-capacity manner, and the stability of the quality of the polymer product is ensured.

Description

Technical Field

[0001] This application relates to the field of polymers, and more specifically to a continuous process for purifying and concentrating polymer semi-finished products using a scraped thin-film evaporator. Background Technology

[0002] Polymer materials are widely used in various fields of production and daily life, playing an increasingly important role. However, polymer semi-finished products or intermediate products prepared by various polymerization processes (especially solution polymerization) inevitably contain one or more impurities, such as unreacted monomers, oligomers formed by incomplete monomer reaction, residual solvents, small molecule byproducts, and residual additives. These impurities need to be removed first to obtain polymer products with the required purity and concentration before they can be used for their intended purpose. However, existing technologies for the above purification / concentration operations still have serious shortcomings.

[0003] For example, fluoropolymers (also known as fluorocarbon resins) are high-performance polymer materials, including various polyfluorinated olefins, polyfluorinated chloroolefins, polyfluorinated vinyl ethers, polyfluorinated vinyl esters, and mixtures or copolymers of two or more of the above polymers. In particular, FEVE fluoropolymers (specifically composed of fluorinated olefin-vinyl ether / ester copolymers) possess excellent heat resistance, chemical resistance, and weather resistance, and are easy to apply and can be cured at room temperature. This makes solvent-based FEVE fluoropolymers widely used in bridges, ships, and construction. However, fluoropolymers (such as the FEVE fluoropolymers mentioned above) prepared by polymerization of appropriate monomer raw materials (usually solution polymerization) can only be considered semi-finished products. They require treatment with residual initiators, removal of residual monomers, removal of excess solvents, and other component treatments to achieve product purification and concentration. A series of post-processing and analytical tests, such as adjusting the product's solid content and viscosity testing, are then performed to ensure their performance and meet customer requirements before they can be used for their final target application.

[0004] In the prior art, a batch distillation / concentrator is typically used to perform intermittent vacuum distillation / concentration of polymer intermediates or semi-finished products (e.g., fluoropolymers, preferably the FEVE fluoropolymers mentioned above). The specific operation process is usually as follows: the semi-finished product obtained from polymerization (e.g., FEVE resin semi-finished product) is placed in a concentration vessel, and operations such as vacuum distillation, heating, and stirring are performed. Then, distillation begins to remove excess initiator, solvent, and monomer. After collecting the corresponding weight of low-boiling matter, a sample is taken for solid content analysis. If there is a deviation, distillation is continued or solvent is added to dilute to the solid content required by the product specifications, and the solid content test is repeated. If it passes the test, the finished product is bottled. If it fails the test, the above operation is repeated.

[0005] However, since various polymers (such as FEVE fluorocarbon resin) typically have a certain viscosity, they are prone to foaming under vacuum conditions. This limits the concentration rate; otherwise, the material inside the reactor will be unable to defoam in time and will enter the vacuum system, significantly limiting the concentration efficiency. Furthermore, it requires more equipment and wastes more time. In addition, batch concentration reactors have low automation, requiring extensive manual operation. They also have a large resin holdup, poor reliability, and difficulty in accurately controlling the concentration level. They also suffer from low monomer recovery rates and the inability to effectively remove high-boiling-point monomers trapped in viscous resin. For some high-viscosity polymers (especially high-viscosity FEVE fluorocarbon resin), due to their poor flowability, it is difficult to completely drain the concentrated product from the reactor, leading to over-concentration and sticking to the reactor.

[0006] In the existing technology, when using conventional scraped film thin-film evaporators to concentrate polymers (especially FEVE fluoropolymers), problems such as material bridging, cross-contamination, scraper adhesion, material stringing and gel clogging are easily encountered, making it impossible to purify and concentrate the above polymers efficiently and at high throughput.

[0007] Therefore, there is an urgent need in this field to develop a new technology that can solve the above problems. Summary of the Invention

[0008] To address the aforementioned problems, the inventors, through extensive and in-depth research, have developed a novel method for purifying and concentrating polymers (especially FEVE fluoropolymers). This method effectively solves the problems existing in the prior art, achieving continuous, low-hold-time, low-energy-consumption, high-efficiency, and high-reliability purification / concentration processes. Furthermore, the method of this invention can be automated. Specifically, this invention provides a method for purifying and concentrating a polymer semi-finished product, wherein the crude product contains the target product polymer and one or more impurities selected from the following: monomers, oligomers, solvents, byproducts, and additives; the method includes: removing at least a portion of the impurities from the semi-finished product in a thin-film evaporator; the thin-film evaporator includes a scraper, the scraper comprising at least one vertically arranged scraper bar, each scraper bar having multiple scraper blades; the method is performed continuously.

[0009] According to one embodiment of this application, the target product polymer is selected from one or more of the following: fluoropolymers, polyolefins, polyethers, polyesters, polyether ether ketones, acrylic (ester) polymers, epoxy resins, polyurethanes, hydrogenated vegetable oils, and copolymers of two or more of the above polymers.

[0010] According to another embodiment of this application, the target product polymer is selected from the following fluoropolymers: polyfluoroolefins, polychlorofluoroolefins, polyfluorovinyl ethers, polyfluorovinyl esters, and copolymers of two or more of the above polymers.

[0011] According to another embodiment of this application, the target product polymer is prepared by solution polymerization.

[0012] According to another embodiment of this application, a feed controller is used to convey the polymer semi-finished product through the feed port into the thin-film evaporator.

[0013] According to another embodiment of this application, the feed controller includes one or more of the following: a constant pressure valve, a pump, a flow meter, and a regulating valve.

[0014] According to another embodiment of this application, the feed inlet is selected from the following shapes: circular, flat, and conical.

[0015] According to another embodiment of this application, a feeder is provided in the thin film evaporator at a position adjacent to the feed inlet. The feeder is selected from: a hollow disc feeder, a centrifugal feeder, a blade feeder, a hollow cylindrical feeder, a conical feeder, and a cone-shaped feeder.

[0016] According to another embodiment of this application, the scraper of the film scraper has a shape selected from the following: oblique tooth shape, tooth shape, parallelogram shape, wavy shape, roller shape, circular plate shape, rectangle shape, square shape, blade shape, and wavy shape.

[0017] According to another embodiment of this application, the scraper of the film scraper is a serrated scraper with an angle of 10-40 degrees in the material-facing direction. According to another embodiment of this application, multiple scrapers on each scraper bar are arranged obliquely and parallel to each other. According to another embodiment of this application, the tooth angle of the multiple scrapers on each scraper bar gradually increases in the material-facing direction from top to bottom. According to another embodiment of this application, the tooth angle of the multiple scrapers on each scraper bar gradually decreases in the material-facing direction from top to bottom.

[0018] According to another embodiment of this application, the thin-film evaporator is further provided with a nitrogen supply device, which supplies nitrogen gas into the thin-film evaporator in an upward direction. According to another embodiment of this application, the flow rate of the nitrogen gas is 0.5-10% of the crude product flow rate. The inlet of the nitrogen supply device is located near the central longitudinal axis of the thin-film evaporator. The vertical height of the inlet of the nitrogen supply device is between 1 / 10 and 1 / 2 of the height of the scraper.

[0019] According to another embodiment of this application, a low-boiling-point component outlet is provided at the top of the thin-film evaporator, and a polymer outlet is provided at the bottom of the thin-film evaporator.

[0020] According to another embodiment of this application, impurities separated from the semi-finished product are discharged from the outlet of the low-boiling-point component, monomers are separated from the impurities in a separation device, and the separated monomers are recycled for polymer synthesis.

[0021] According to another embodiment of this application, the purified polymer is discharged from the polymer outlet.

[0022] According to another embodiment of this application, the polymer outlet is connected to a discharge pump for continuous polymer discharge, wherein the discharge pump is selected from one or more of the following: cycloidal pump, screw pump, gear pump, centrifugal pump, peristaltic pump.

[0023] According to another embodiment of this application, a heating-temperature control device is provided on the outer periphery of the thin film evaporator, wherein the heating-temperature control device is selected from one or more of the following: water bath device, oil bath device, electric heating device, electromagnetic induction heating device.

[0024] According to another embodiment of this application, it further includes at least one detector for online detection of the input semi-finished product, the material in the thin film evaporator, and / or the polymer output from the polymer outlet, and the detector is data-connected to the feed controller to perform online control of the feed of the feed controller based on the detection result of the detector.

[0025] According to another embodiment of this application, the detector is selected from one or more of the following: viscometer, pressure gauge, differential pressure gauge, density meter, refractometer, and spectrometer.

[0026] In the detailed description section below, the method and polymer product of this application will be further described with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 A schematic diagram of the process flow of a method according to one embodiment of this application is shown; Figure 2A The arrangement of the feed inlet on the sidewall of a thin-film evaporator according to an exemplary embodiment of this application is shown; Figure 2B This illustrates the arrangement of the feed inlet at the top of a thin-film evaporator according to another exemplary embodiment of this application; Figure 3A A schematic diagram of a film scraper according to an exemplary embodiment of this application is shown; Figure 3B A schematic diagram of scrapers mounted on the same scraper according to an exemplary embodiment of this application is shown, wherein the scrapers are rectangular and each scraper is parallel and aligned with each other, and the angle of attack of the scrapers remains unchanged; Figure 3C A schematic diagram of scrapers mounted on the same scraper according to an exemplary embodiment of this application is shown, wherein the scrapers are rectangular and the angle of attack of each scraper gradually decreases from top to bottom; Figure 3D A schematic diagram of scrapers mounted on the same scraper according to an exemplary embodiment of this application is shown, wherein the scrapers are rectangular and the angle of attack of each scraper gradually increases from top to bottom; Figure 3E A schematic diagram of scrapers mounted on the same scraper according to an exemplary embodiment of this application is shown, wherein the scrapers are obliquely toothed and each scraper is parallel and aligned with each other, and the angle of attack of the scrapers remains unchanged; Figure 3F A schematic diagram of scrapers mounted on the same scraper according to an exemplary embodiment of this application is shown, wherein the scrapers are obliquely toothed and the angle of attack of each scraper gradually increases from top to bottom; Figure 4The image shows a thin-film evaporation apparatus used according to a specific embodiment of this application. Detailed Implementation

[0028] The “range” disclosed in this document takes the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges that can be defined in this way are inclusive and composable; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is also expected that ranges of 60-110 and 80-120 are also included. Furthermore, if the minimum range values ​​are listed as 1 and 2, and if the maximum range values ​​are listed as 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0029] In this application, unless otherwise stated, the numerical range "ab" is a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this document, and "0-5" is simply a shortened representation of these numerical combinations.

[0030] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0031] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0032] In this application, unless otherwise specified, the term "comprising" as used herein can be either open-ended or closed-ended. For example, "comprising" may mean that it may also include other components not listed, or it may only include the listed components.

[0033] In this invention, the terms "crude product", "intermediate product", and "semi-finished product" can be used interchangeably to refer to the processing objects of the method of this invention.

[0034] Furthermore, in this invention, "purification" and "concentration" are carried out simultaneously. By using the method of this invention to process the semi-finished product, impurities are removed from the semi-finished product, thereby improving the purity of the polymer and increasing the concentration of the polymer.

[0035] According to one embodiment of this application, the polymer semi-finished product is obtained through a polymerization reaction and has not been purified, or has only undergone preliminary purification. The polymer semi-finished product of the present invention is preferably obtained by solution polymerization. In addition to the target polymer, the polymer semi-finished product contains a relatively large amount of impurities, which may include one or more of the following: monomers, oligomers, solvents, byproducts, additives, etc. Examples of additives may include one or more of the following: initiators, stabilizers, emulsifiers, surfactants, activators, promoters, accelerators, catalysts, pH adjusters, reaction aids, etc. The synthesis process of the polymer semi-finished product (especially the solution polymerization synthesis process) is known in the art.

[0036] According to one embodiment of this application, since the target polymer in the semi-finished product is solid, while other low molecular weight impurities are mostly in liquid form, the relative content of the target polymer can be expressed by the solid content of the semi-finished product (and thus can also be used to express the content of impurity components). For example, based on the total weight of the semi-finished product, the solid content of the semi-finished product can be 30-60% by weight, for example 40-55% by weight, or 42-54% by weight. According to another embodiment of this application, the polymer product obtained after processing by the method of this application can have the following solid content: based on the total weight of the polymer product, the solid content of the polymer product can be 62-80% by weight, for example 64-75% by weight, or 65-72% by weight.

[0037] In this invention, the polymer includes one or more of the following: fluoropolymers, polyolefins, polyethers, polyesters, polyether ether ketones, acrylic (ester) polymers, epoxy resins, polyurethanes, hydrogenated vegetable oils, and copolymers of two or more of the above polymers. According to a preferred embodiment of this application, the polymer is a fluoropolymer, such as polyfluorinated olefins, polychlorofluoroolefins, polyfluorinated vinyl ethers, polyfluorinated vinyl esters, and copolymers of two or more of the above polymers. According to an exemplary embodiment of this application, examples of the fluoropolymer include polyvinyl fluoride (polyvinyl fluoride), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoropropylene (FEP), polychlorotrifluoroethylene, trichlorotrifluoroethylene-vinyl ether / ester copolymer (FEVE), fluoroethylene-vinyl ether / ester copolymer (FEVE), or mixtures or copolymers of two or more of the above fluoropolymers. According to a preferred embodiment of this application, the fluoropolymer described above is prepared by solution polymerization. According to a most preferred embodiment of this application, the polymer is FEVE; particularly preferred is FEVE prepared by solution polymerization.

[0038] According to a specific embodiment of this application, the polymer semi-finished product contains the fluoropolymer described above, and the impurities contained therein are mainly solvents, unreacted monomers, and initiator decomposition products. Non-limiting examples of the solvent include one or more of the following: C6-C16 straight-chain alkanes, C6-C16 cycloalkanes, C6-C16 aromatics, and C1-C16 carboxylic acids (C1-C12 alkyl esters); for example, the solvent may include benzene, toluene, xylene, and C1-C6 carboxylic acids (C1-C6 alkyl esters). The unreacted monomers contained in the semi-finished product depend on the raw materials and specific processes used to synthesize the polymer, and may include one or more of the following: vinyl fluoride (i.e., monofluoroethylene), vinylidene fluoride, tetrafluoroethylene, perfluoropropylene, trifluorochloroethylene, vinyl ethers, vinyl esters, HFO-1234ze, and HFO-1234yf.

[0039] In related fields, viscosity (rather than molecular weight) is typically used to characterize semi-finished products or finished products treated with the methods of this application. The viscosity of the semi-finished product can be 30-10000 mPa·s (25°C); after treatment with the methods of this invention, the viscosity of the finished product will increase, for example, to 100-15000 mPa·s (25°C). In this invention, the viscosity of the polymer can be detected using techniques and equipment known in the art.

[0040] According to one embodiment of this application, the method is carried out continuously. Specifically, the semi-finished product is continuously fed into a thin-film evaporator, while the purified and concentrated polymer and the separated impurities are continuously output from the thin-film evaporator. The continuous method of this invention avoids the aforementioned defects of the batch concentration vessels of the prior art, achieving a more stable process, ensuring the stability of the finished product quality, better controlling the degree of product concentration, improving the efficiency of material concentration operations, reducing the number of equipment and floor space, saving operating time, preventing the processed polymer material from remaining in the equipment (sticking to the vessel), and improving the recovery of monomeric impurities.

[0041] According to one embodiment of this application, such as Figure 1As shown, the method of the present invention may include the following steps: The previously synthesized polymer semi-finished product a (e.g., FEVE fluoropolymer semi-finished product synthesized by solution polymerization) is continuously and stably fed into the thin-film evaporator 3 through the feed inlet via the feed controller 1. After passing through the distributor, it is dispersed in the thin-film evaporator. Temperature, vacuum degree, and feed rate are controlled within the thin-film evaporator for vacuum distillation. During vacuum distillation, the scraper 2 continuously rotates, controlling the material to be uniformly dispersed on the inner wall of the thin-film evaporator. Low-boiling-point residual monomers and solvents, and other impurities b, are separated from the semi-finished product and continuously discharged from the low-boiling-point component outlet at the top of the thin-film evaporator, flowing into a separation device 8 (e.g., a degassing tower, distillation tower, or other separation device) where the impurities b are separated, for example, unreacted monomers e, which are recycled back to the polymer synthesis process. Other impurities can be recovered as needed, or further purified (e.g., distillation) and reused. The processed polymer c (e.g., purified FEVE resin) is continuously discharged from the polymer outlet at the bottom of the thin-film evaporator 3 using the discharge pump 4. Figure 1 The implementation includes a product monitoring component 5, which monitors the properties (e.g., resin concentration) of the material flowing out of the polymer outlet online. When the measured properties meet the requirements, the material is input as a finished product into a product collection container to obtain the finished polymer 6. Additionally, in Figure 1 The illustrated embodiment also includes a vacuum control component 7 for real-time control of the vacuum level in the thin-film evaporator.

[0042] According to one embodiment of this application, the semi-finished polymer obtained by polymerization reaction is temporarily stored in a semi-finished material tank, and then drawn out from the semi-finished material tank and continuously transported to the downstream thin-film evaporator when the method of this application is implemented.

[0043] According to another embodiment of this application, a feed controller is provided upstream of the thin-film evaporator. This controller can actively control the feed rate, eliminating the effects of viscosity, pipe resistance, air resistance, etc., and can perform interlocking control based on the discharge conditions. The feed controller can be selected from one or more of the following: a constant pressure valve, a pump, a flow meter, a regulating valve, preferably a constant pressure valve or a combination of other devices and a constant pressure valve.

[0044] According to another embodiment of this application, the feed controller works in conjunction with the feed inlet to achieve the best fabric distribution effect. The feed inlet is generally circular, flat, or conical.

[0045] In the method of this invention, the feed controller mainly serves three purposes. First, it feeds the material at a constant and uniform rate during the continuous reaction process, ensuring the purification and concentration processes proceed as stably as possible. Second, it flexibly adjusts to accommodate polymer materials of varying viscosities and potential process fluctuations by providing external force to counteract factors such as material viscosity, pipeline resistance, and gas resistance, ensuring that the inlet pressure and velocity remain constant, further guaranteeing process stability. Third, the feed controller is connected to a detector at the downstream product outlet of the thin-film evaporator (allowing data exchange between them), enabling timely adjustment of the feed rate (even real-time adjustment) based on fluctuations and changes in the discharge, either manually or automatically, thereby improving process stability, product concentration, and purification quality. Compared to existing thin-film evaporator purification processes, the method of this invention, through the use of a feed controller and a distributor, achieves excellent constant compensation and flow rate correction.

[0046] According to another embodiment of this application, the feed controller cooperates with the feed inlet to control the feed flow rate into the thin-film evaporator within the range of 40%-90% of the thin-film evaporator's processing capacity. For example, if the processing capacity of the thin-film evaporator is 5 kg / h, the feed rate is controlled at 2~4.5 kg / h; while if the processing capacity of the thin-film evaporator is 500 kg / h, the feed rate is controlled at 200~450 kg / h.

[0047] The feed inlet can be located on the upper part of the side wall of the thin-film evaporator. Figure 2A (in the case of) or set on top of the thin film evaporator ( Figure 2B (The situation). For the purpose of clarity, in Figure 2A and 2B The image only shows the feed inlet and the thin-film evaporator in a schematic form, while omitting other components (such as the feeder, bottom outlet, etc.). Figure 2A The left, middle, and right sides of the figure show circular, flat, and conical feed inlets extending into the upper part of the thin-film evaporator through its sidewall, respectively. As shown, the circular feed inlet is in the form of a circular pipe, the flat feed inlet is a flat and slender slot device at the end of the feed pipe, and the conical feed inlet is a conical flared component at the end of the feed pipe, with a truncated cone-shaped flow-blocking component concentrically arranged inside the flared component, preferably a conical valve core.

[0048] exist Figure 2B In the alternative embodiment shown, the feed inlet is a circular feed inlet that can be located at the top of the thin-film evaporator and extend into it through the top of the thin-film evaporator.

[0049] According to another preferred embodiment of this application, when the feed inlet is a circular feed inlet, it can be located at the top or upper part of the side wall of the thin film evaporator; when the feed inlet is a flat feed inlet or a conical feed inlet, it can only be located at the upper part of the side wall of the thin film evaporator.

[0050] Furthermore, the devices, apparatuses, and components in all the accompanying drawings of this invention are merely schematic and not drawn to scale. The actual dimensions and proportions of these devices, apparatuses, and components are as defined in this specification. Additionally, due to... Figure 2A and Figure 2B The purpose is mainly to show the structural design of the feed inlet, so the scraper of the present invention is simply shown as several triangles in these two figures.

[0051] This invention uses a thin-film evaporator to process polymer semi-finished products, for example, see [link to relevant documentation]. Figure 1 In the embodiment shown, the feed inlet (circular feed inlet) is located at the top of the thin-film evaporator, and a low-boiling-point component outlet is also located at the top, while a polymer outlet is located at the bottom of the thin-film evaporator.

[0052] A material distributor is installed in the upper part of the internal space of the thin-film evaporator, preferably near the feed inlet. The material distributor is used to quickly and evenly disperse the material onto the inner wall of the evaporator, while also suppressing phenomena such as foaming, bridging, or climbing. The material distributor is selected from: a perforated disc distributor, a centrifugal distributor, a blade distributor, a hollow cylindrical distributor, a conical distributor, and a spiked conical distributor; preferably, the material distributor is a perforated disc distributor or a hollow cylindrical distributor; for polymers with high viscosity, especially for fluoropolymers with high viscosity, the material distributor is a spiked conical distributor.

[0053] The feeder can be installed horizontally or vertically to suit the specific location and structure of the feed inlet. When the feeder is installed horizontally, the feed inlet is located above the feeder, and the material entering through the feed inlet moves downwards, rapidly spreading across the feeder due to gravity and centrifugal force. When the feeder is installed vertically, the feed inlet is located on the side of the feeder, and the material enters the evaporator and is diffused by the feeder and the active scraper.

[0054] According to a preferred embodiment of this application, the hollow disc feeder and the hollow cylindrical feeder can separate the air channels, ensuring that the evaporating airflow rises in the central area of ​​the evaporator, while the concentrated material descends on the surface of the evaporator, avoiding the unfavorable phenomenon of the concentrated material being blown upwards after foaming. On the other hand, the conical and cone-shaped feeders can prevent high-viscosity materials from climbing the rods during feeding.

[0055] According to one embodiment of this application, a circular feed inlet can be located at the top or upper side wall of the thin film evaporator, thereby being used in conjunction with a horizontal feeder or a vertical feeder respectively, suitable for processing medium and low viscosity materials.

[0056] According to another preferred embodiment of this application, a flat feed inlet is provided on the upper part of the side wall of the thin film evaporator. It is in the form of a horizontal or inclined flat groove for side wall feeding, which is suitable for use with a vertical feeder and is suitable for medium to high viscosity materials.

[0057] According to another preferred embodiment of this application, the conical inlet is in the form of a conical valve core installed at the end of the feed pipe, which is used to ensure that the material does not foam before entering the evaporator, and is suitable for medium to high viscosity or easily foaming materials.

[0058] The thin-film evaporator of the present invention also includes a film scraper, such as... Figure 1 As shown, the film scraper includes a rotating shaft arranged along the central longitudinal axis of the thin-film evaporator, a motor disposed outside the thin-film evaporator and connected to the rotating shaft, a bracket connected to the rotating shaft inside the thin-film evaporator, and at least one scraper strip mounted on the bracket, for example, 1-6 scraper strips, 2-4 scraper strips, or 3-4 scraper strips. Multiple scraper blades are mounted on the scraper strips. According to one embodiment of this application, the bracket is provided with a groove and a fixing element, and a spring is provided in the groove so that after the scraper strip is installed in place, the scraper blades on the scraper strip are pressed against the inner wall of the film by the action of the spring, ensuring the film scraping effect. In this invention, the film scraper is used to quickly disperse materials, make the materials uniformly distributed, and control the material residence time.

[0059] Figure 3A A side view and a corresponding top view of a specific exemplary scraper of the present invention are shown. A centrally located stirring shaft is connected to a motor located above and outside the thin-film evaporator, for driving the rotation of the support and scraper. The upper part of the support is a disc with a through-hole, the central through-hole allowing polymer material and gas to flow through, while the scraper is vertically connected to a top disc and a bottom ring, the center of which is hollow to avoid interfering with material flow and the arrangement of the gas delivery conduits described below. For clarity and simplicity, Figure 3A The scraper mounted on the scraper blade is not shown in the image.

[0060] According to one embodiment of this application, the scraper is a thin plate having a cross-sectional shape of oblique teeth, tooth shape, parallelogram shape, wave shape, roller shape, circle shape, rectangle shape, square shape, blade shape, or wave shape, preferably a rectangular shape, tooth shape, or oblique tooth shape, and particularly preferably a thin plate with a rectangular or oblique tooth cross-sectional shape.

[0061] According to one embodiment of this application, the plurality of scrapers mounted on each scraper strip have identical dimensions and shapes. According to one embodiment of this application, the length-to-width ratio of each scraper can be from 10:1 to 1:0.9, or from 6:1 to 2:1; the length-to-thickness ratio of each scraper can be from 40:1 to 1:0.8, preferably from 20:1 to 5:1, or from 10:1 to 6:1. When the scale of the thin-film evaporator equipment is increased or decreased, the size of the scrapers can be proportionally increased or decreased.

[0062] Figure 3B The image shows a view taken from a direction perpendicular to the sidewall of the thin-film evaporator (perpendicular to the longitudinal axis of the thin-film evaporator). The scrapers of this invention are positioned relative to the horizontal direction (e.g., Figure 3B The coating material in the thin-film evaporator is mounted on the scraper at an angle c (referred to as the "feeding angle" in this invention) as the scraper rotates. When the scraper rotates, the coating material in the thin-film evaporator contacts the scraper at the angle c in the direction indicated by the arrow. The feeding angle can be 10-40 degrees or 15-40 degrees.

[0063] According to one embodiment of this application, the scrapers mounted on the same scraper are parallel to each other and have the same angle of attack.

[0064] According to another embodiment of this application, the angle of approach of the scrapers mounted on the same scraper gradually increases (in order from top to bottom).

[0065] According to another embodiment of this application, the angle of approach of the scrapers mounted on the same scraper gradually decreases (in order from top to bottom).

[0066] According to another embodiment of this application, the scrapers are arranged such that for each pair of adjacent scrapers, the lowest point of the upper scraper is lower than the highest point of the lower scraper. According to another embodiment of this application, the geometric centers of all scrapers connected on the same scraper are located on the same straight line (which is parallel to the scraper and also parallel to the central longitudinal axis of the thin-film evaporator).

[0067] According to one embodiment of this application, all scrapers are arranged parallel to the central longitudinal axis of the thin-film evaporator.

[0068] According to another embodiment of this application, the scraper strips may not be parallel to the central longitudinal axis of the thin-film evaporator, but rather, for example, the upper ends of each scraper strip may be inclined in the same direction (e.g., the material-facing direction, i.e., the rotation direction of the scraper strip), thereby forming a spiral shape. In this case, all scrapers on the same scraper strip may be arranged parallel to each other, or the material-facing angle may gradually increase or decrease in a top-to-bottom order as described above.

[0069] exist Figure 3B In the exemplary embodiment shown, the scrapers have a rectangular cross-sectional shape, all scrapers are aligned parallel to each other, and the angle of attack is fixed at approximately 30 degrees.

[0070] exist Figure 3C In the embodiment shown, the scrapers have a rectangular cross-sectional shape, and the angle of attack of these scrapers gradually decreases from top to bottom.

[0071] exist Figure 3D In the illustrated embodiment, the scrapers have a rectangular cross-sectional shape, and the angle of attack of these scrapers gradually increases from top to bottom. The applicant unexpectedly found that this rectangular scraper design with an increasing angle of attack is particularly suitable for the purification of high-viscosity and heat-sensitive fluoropolymers.

[0072] exist Figure 3E In the exemplary embodiment shown, the scraper has a serrated cross-sectional shape, all scrapers are aligned parallel to each other, and the angle of attack is fixed at approximately 30 degrees. In this invention, "serrated" means that the cross-sectional shape of the scraper is a non-isosceles trapezoid, and the base angle on one side of the trapezoid is smaller than the angle on the other side. Correspondingly, "toothed" means that the cross-sectional shape of the scraper is an isosceles trapezoid.

[0073] exist Figure 3F In the illustrated embodiment, the scrapers have a serrated cross-sectional shape, with the angle of attack gradually increasing from top to bottom. This serrated scraper design with an increasing angle of attack is particularly suitable for the purification of high-viscosity and / or heat-sensitive fluoropolymers.

[0074] It should be noted that in the above Figure 3C , 3D In 3F, for the purpose of highlighting and emphasizing, the change of the scraper's angle of attack is exaggerated. In some exemplary experiments of this invention, dozens, more than a hundred, or even hundreds of scraper blades are set on a scraper bar. In this case, the change of the angle of attack of adjacent scrapers is almost imperceptible to the naked eye.

[0075] According to another embodiment of this application, the purification / concentration method of the present invention also uses a nitrogen supply device, which may include a nitrogen source and a pump disposed outside the thin-film evaporator, and a pipe extending into the interior of the thin-film evaporator. Preferably, the pipe is disposed close to the central longitudinal axis of the thin-film evaporator, for example, designed to be flush with the central longitudinal axis, or integrated with the central longitudinal axis (using a hollow longitudinal axis as a nitrogen delivery pipe, with an opening at a suitable height to output nitrogen). According to another embodiment of this application, the pipe opening (nitrogen inlet) is vertically upward, for example, the height of the opening may be located at 1 / 20 to 1 / 2 of the scraper height, for example, at 1 / 10 to 1 / 5 of the scraper height. According to another embodiment of this application, nitrogen is continuously input into the thin-film evaporator during the purification and concentration process of the method of the present invention. The temperature of the nitrogen can be from room temperature to 80°C. According to another embodiment of this application, the flow rate of the nitrogen may be 0.5-10% of the flow rate of the material (crude product) input from the feed inlet, for example, 1-5%.

[0076] The applicant unexpectedly discovered that by adopting this nitrogen input operation, the concentration efficiency of various materials can be significantly improved. In the scheme of inputting nitrogen and gradually increasing the angle of attack, the processing efficiency can be improved by at least 10% (compared to the scheme of not inputting nitrogen and keeping the angle of attack unchanged). For low viscosity materials, the concentration efficiency can be improved by up to 25%. For heat-sensitive materials, the change in molecular weight of heat-sensitive resin before and after treatment can be significantly reduced.

[0077] According to another embodiment of this application, a heating-temperature control device is provided on the outer periphery of the thin-film evaporator. The heating-temperature control device is selected from one or more of the following: a water bath device, an oil bath device, an electric heating device, and an electromagnetic induction heating device. According to another embodiment of this application, for cases where the concentration range of the composition is large or the viscosity varies significantly, multiple heating-temperature control devices can be used to apply segmented temperature control within the thin-film evaporator.

[0078] According to another embodiment of this application, the temperature in the thin-film evaporator is 70-90°C, preferably 75-80°C.

[0079] According to another embodiment of this application, at least a portion of the height of the thin-film evaporator is affected by the aforementioned heating-temperature control device, forming a "heating zone," which may, for example, occupy 60-100%, or even 70-90%, of the height of the thin-film evaporator. Figure 2A The heating area is shown in the middle with a dashed box.

[0080] According to another embodiment of this application, the upper and lower ends of the stirring rack extend beyond the heating area.

[0081] According to another embodiment of this application, the method of the present invention further includes at least one detector for online detection of the input semi-finished product, the material in the thin-film evaporator, and / or the polymer output from the polymer outlet. The target parameters for detection may include one or more of the following: viscosity, pressure (including absolute pressure and pressure difference), density, refractive index, retention time, nuclear magnetic resonance signal, mass spectrometry signal, etc. According to another embodiment of this application, the detector is selected from one or more of the following: viscometer, pressure gauge, differential pressure gauge, densitometer, refractometer, spectrometer. The spectrometer includes one or more of the following: infrared spectrometer, nuclear magnetic resonance spectrometer, gas chromatograph, gas chromatography-mass spectrometry, liquid chromatograph, and liquid chromatography-mass spectrometry.

[0082] According to one embodiment of this application, the vacuum degree in the thin-film evaporator is 10-500 mbar, for example 50-300 mbar, or 80-150 mbar.

[0083] According to another embodiment of this application, the discharge pump continuously and stably draws the processed material from the thin-film evaporator. The discharge pump is selected from one or more of the following: cycloidal pump, screw pump, gear pump, centrifugal pump, peristaltic pump; preferably, the discharge pump is a gear pump.

[0084] According to another embodiment of this application, the aforementioned detector is connected to at least one of a temperature control device, a pressure control device, and a feeding device, thereby automatically adjusting and controlling the vacuum degree, temperature, feeding rate, scraper rotation speed, etc., based on the parameters measured by these detectors. Online monitoring enables precise and controllable finished product indicators, stable process, and fully automated control, maintaining the stability of finished product quality.

[0085] According to another embodiment of this application, a finished product filling device is provided at the outlet of the thin film evaporator to fill the continuously output qualified polymer finished products (e.g., FEVE fluorocarbon resin finished products) into product containers, thereby establishing a complete continuous automated production line.

[0086] According to another embodiment of this application, before the equipment is fully stable or when there are fluctuations in the equipment, there may be insufficient polymer purification / concentration, which may not meet the quality requirements of the finished product. In this case, the polymer material output from the bottom of the thin film evaporator is recycled back to the feed inlet, and the above concentration operation is repeated.

[0087] Not wishing to be limited to any particular theory, the method of this invention can achieve one or more of the following advantages: 1. Compared with the prior art using batch concentration vessels, the method of the present invention can purify and concentrate polymer materials with higher efficiency and throughput, and avoids problems such as foaming, adhesion, cross-contamination, stringing, and gel clogging that occur in polymers during the concentration process in the prior art.

[0088] 2. The technology of this invention can be used to process a large number of polymers of different types and properties that are particularly difficult to process with existing technologies, such as FEVE resin with a particularly large viscosity change before and after concentration, FEVE resin with a particularly high viscosity, FEVE resin with a high degree of concentration requirement, FEVE resin that is prone to foaming, FEVE resin that is prone to gelling when over-concentrated, and FEVE fluorocarbon resin with viscoelastic properties, etc.

[0089] 3. The technical solution of the present invention is designed with automation, which can respond sensitively and conveniently to changes in polymer properties, further improving the stability of the process and the stability of the polymer finished product properties.

[0090] 4. The technical solution of the present invention ensures the stability of high viscosity materials during concentration by combining the three aspects of feed control, feed inlet structure, and material distribution tray design.

[0091] 5. Furthermore, the present invention also considers further design of the scraper shape and the angle of attack, which can achieve further significant improvements for purification processes of, for example, heat-sensitive crude fluoropolymers and / or high-viscosity crude fluoropolymers.

[0092] 6. The present invention also unexpectedly discovers that by introducing nitrogen into the thin-film evaporator in a specially designed manner, the concentration efficiency can be further improved, and the negative impact on the molecular weight of heat-sensitive polymers can be further significantly reduced.

[0093] The following embodiments illustrate the methods of this application in detail, with the aim of providing a better understanding of the content of this application. It should be understood that these embodiments are merely illustrative and not restrictive. Unless otherwise stated, the reagents used in the embodiments are commercially available. Unless otherwise specified, the methods and conditions used in the embodiments are conventional methods and conditions.

[0094] Example

[0095] In the following examples, three FEVE fluoropolymer semi-finished products were purified and concentrated using the method of the present invention. Resin 1, Resin 2, Resin 3, and Resin 4, processed in the examples, were all different FEVE fluoropolymer semi-finished products produced by the fluoropolymer production workshop of Changshu Sanai Fuzhonghao Chemical New Materials Co., Ltd.

[0096] Resin 1 is synthesized using trifluorochloroethylene and vinyl ethers (hydroxybutyl vinyl ether, cyclohexyl vinyl ether and ethyl vinyl ether) as copolymer raw materials, with xylene as the solvent, a solid content of 51.6% by weight, a viscosity of 500 mPa.s ± 50 (25℃), and a number-average molecular weight of 12000 ± 1000. It is a thermosensitive polymer. Resin 2 is synthesized using trifluorochloroethylene and vinyl ethers (hydroxybutyl vinyl ether, cyclohexyl vinyl ether and ethyl vinyl ether) as copolymer raw materials, with butyl acetate as the solvent. The solid content is 53.2% by weight, the corresponding viscosity is 260 mPa·s ± 50 (25℃), and the corresponding number-average molecular weight is 15000 ± 1000. It is a non-thermal-sensitive polymer. Resin 3 was synthesized using tetrafluoroethylene and vinyl ethers (hydroxybutyl vinyl ether, cyclohexyl vinyl ether and ethyl vinyl ether) as copolymer raw materials. The solvents used were butyl acetate and xylene. The solid content was 42.3% by weight, the corresponding viscosity was 90 mPa·s ± 30 (25℃), and the corresponding number average molecular weight was 10000 ± 1000. Resin 4 is synthesized using trifluorochloroethylene and vinyl ethers (hydroxybutyl vinyl ether and ethyl vinyl ether) as copolymer raw materials, with xylene as the solvent. The solid content is 52.1% by weight, the corresponding viscosity is 3300 mPa.s ± 100 (25℃), and the corresponding number average molecular weight is 33000 ± 1000. It is a thermosensitive polymer.

[0097] The following techniques are used for testing: (1) Method for determining polymer solid content: The solid content of the polymer was determined using a Mettler HC103 moisture analyzer, with the test temperature set at 175°C and the sample size at 0.5–1 gram.

[0098] (2) Install a bypass path at the polymer outlet. Install the pump, pressure gauge, stainless steel pipe (approximately 15 cm long x 4 mm inner diameter), pressure gauge, and tee in sequence along the bypass path. Monitor the flow rate, temperature, and pressure difference in real time to help determine the concentration status of the material.

[0099] (3) Polymer viscosity test

[0100] At regular intervals, samples were taken from the polymer outlet and kept at a constant temperature of 25°C. The actual viscosity of the product was then analyzed using a DV2TLV viscosity meter provided by Bollefeld Corporation of the United States.

[0101] (4) Polymer molecular weight detection

[0102] The molecular weight of the polymer was determined using Waters' ACQUITY APC (Ultra-High Performance Polymer Chromatography) system.

[0103] Example 1

[0104] In this embodiment, using according to Figure 1 The device constructed as shown, the specific device is as follows Figure 4 As shown. This embodiment uses a thin-film evaporator designed by the inventor. The thin-film evaporator employs a conical feed inlet mounted on the upper side wall of the evaporator. This conical feed inlet includes a feed pipe with an inner diameter of 8 mm and a conical valve core at the end of the feed pipe. A perforated disc-shaped distributor is vertically installed, facing the conical feed inlet on the side, and its height is higher than the feed inlet. The scraper includes a rotating shaft arranged along the central longitudinal axis of the thin-film evaporator. The rotating shaft extends to three circumferentially symmetrical supports. The supports have grooves containing springs and fixing elements to fix three 50 cm long scraper strips parallel to the rotating shaft to the supports. Each scraper strip has a large number of parallel and aligned scraper blades. The scraper blades are rectangular, each with a thickness of 2 mm, a spacing of 2 mm, a length of 10 mm, a width of 5 mm, and an angle of attack of 30 degrees. The pressure provided by the springs causes the scraper blades to adhere to the inner wall of the thin-film evaporator.

[0105] Resin 1 (fluororesin semi-finished product) was fed into the thin-film evaporator. A gear pump was used as the feed controller, with its speed set to 800 rpm. The back pressure valve was set to 0.05 MPa, the feed rate was 80 g / min, the jacket water temperature was 80 ± 0.2℃, the scraper speed was controlled at 20 Hz, and the vacuum degree inside the thin-film evaporator was controlled at 100 mbar.

[0106] After the device stabilized, sampling was performed. Based on the differential pressure data from the outlet monitoring, the control conditions were fine-tuned in real time, maintaining the differential pressure of resin 1 at the outlet at 0.22 bar (with the monitoring bypass flow rate set at approximately 1 L / h). Additionally, samples were taken every hour for solid content analysis to verify the accuracy of the online monitoring data. Continuous concentration was performed for at least 24 hours per run. In Example 1, the overall fluctuation in the solid content data of the finished product was less than 0.8%. The average solid content of the product resin was approximately 70.2%, the viscosity was approximately 3300 mPa·s ± 70 (25°C), and the number-average molecular weight was 11000 ± 1000.

[0107] Table 1: Solid content and real-time differential pressure monitoring data of FEVE resin 1

[0108] Example 2

[0109] In this embodiment, a device constructed in the same manner as in Embodiment 1 is used, except that this embodiment uses a circular feed inlet with an inner diameter of 8 mm and a hollow disc feeder is used.

[0110] Resin 2 (fluororesin semi-finished product) was fed into the thin-film evaporator, using a gear pump as the feed controller, with its speed set to 800 rpm. The back pressure valve was set to 0.05 MPa, the feed rate to 100 g / min, the jacket water temperature to 75 ± 0.2℃, the scraper speed to 20 Hz, and the vacuum level inside the thin-film evaporator to 120 mbar.

[0111] After the device has stabilized, sampling is performed. Based on the differential pressure data fed back from the outlet monitoring, the control conditions are finely adjusted in real time. The differential pressure of the FEVE resin at the outlet is maintained at 0.13 bar (the flow rate of the monitoring bypass is set to about 2 L / h). In addition, samples are taken every hour for solid content analysis to verify the accuracy of the online monitoring data. Continuous concentration is carried out for at least 24 hours per run. The average solid content of the product resin is about 65.5%, the viscosity is about 1000 mPa·s ± 50 (25℃), and the number average molecular weight is 15000 ± 1000.

[0112] Example 3

[0113] In this embodiment, a device constructed in the same manner as in Embodiment 2 is used.

[0114] Resin 3 (fluororesin semi-finished product) was fed into the thin-film evaporator, using a gear pump as the feed controller, with its speed set to 800 rpm. The back pressure valve was set to 0.05 MPa, the feed rate to 100 g / min, the jacket water temperature to 80 ± 0.2℃, the scraper speed to 20 Hz, and the vacuum level inside the thin-film evaporator to 100 mbar.

[0115] After the device has been running stably, sampling is carried out. Based on the differential pressure data fed back from the outlet monitoring, the control conditions are finely adjusted in real time. The differential pressure of FEVE resin at the outlet is maintained at 0.1 bar (the flow rate of the monitoring bypass is set to about 3 L / h). In addition, samples are taken every hour for solid content analysis to verify the accuracy of the online monitoring data. The continuous concentration is run for at least 24 hours at a time. The average solid content of the product resin is about 65.3%, the viscosity is about 500 mPa·s ± 50 (25℃), and the number average molecular weight is 10000 ± 1000.

[0116] Example 4

[0117] In this embodiment, a device constructed in the same manner as in Embodiment 1 is used, except that a flat feed inlet is used. The flat feed inlet includes a circular tube with an inner diameter of 8 mm and a flat slot device with dimensions of 6 mm × 30 mm is provided at the end of the tube. The scraper is oblique toothed, each scraper is 3 mm thick, 3 mm apart, 12 mm long, and 6 mm wide. The angle of attack of the top scraper is 30 degrees. The angle of attack of the scraper gradually increases from top to bottom, until the angle of attack of all scrapers in the range of 15% of the height of the bottom scraper is 40 degrees.

[0118] Resin 4 (fluoropolymer semi-finished product) is fed into the thin-film evaporator using a gear pump as the feed controller, with its speed set to 800 rpm. The back pressure valve is set to 0.07 MPa, the feed rate is 42 g / min, the jacket water temperature is 70 ± 0.2℃, the scraper speed is controlled at 8 Hz, and the vacuum degree inside the thin-film evaporator is controlled at 150 mbar. This feed rate is the optimal feed rate for resin 4, confirmed after multiple experiments using the equipment of this embodiment. If the feed rate is lower than this, the average solid content of the product resin will decrease unfavorably. If the feed rate is increased to a level higher than this optimal feed rate, the material inside the thin-film evaporator will exhibit stringing and adhesion phenomena, and the equipment will produce abnormal noises (indicating the risk of equipment instability and malfunction). Therefore, a feed rate of 42 g / min is the optimal / maximum allowable material processing load achievable under the equipment design conditions of this embodiment.

[0119] After the device stabilizes, sampling is performed. Based on the differential pressure data from the outlet monitoring, the control conditions are finely adjusted in real time. The differential pressure of the FEVE resin at the outlet is maintained at 0.21 bar (the flow rate of the monitoring bypass is set to about 0.5 L / h). In addition, samples are taken every hour for solid content analysis to verify the accuracy of the online monitoring data. Continuous concentration is carried out for at least 24 hours per run. The average solid content of the product resin is about 59.9%, the viscosity is about 6400 mPa·s ± 100 (25℃), and the number average molecular weight is 33000 ± 1000.

[0120] Example 5

[0121] In this embodiment, the steps of Embodiment 4 are completely repeated, except that a nitrogen input device is added. This device includes a nitrogen tank, a nitrogen pressure reducing valve, and a flow meter located outside the thin-film evaporator. The nitrogen delivery pipe enters from the bottom center of the thin-film evaporator, close to the central rotating shaft of the thin-film evaporator, with an opening 5 cm from the bottom of the rotating shaft. The nitrogen exits the pipe at this point and enters the thin-film evaporator. Ten minutes after the thin-film evaporator begins processing the resin material, the vacuum degree and water temperature inside the thin-film evaporator reach and stabilize at the set values, and the descending material begins to form a complete liquid film. At this point, nitrogen input begins, with a nitrogen flow rate of approximately 1 L / min. Furthermore, although the equipment and conditions of Embodiment 5 are almost identical to those of Embodiment 4, because Embodiment 5 uses nitrogen purging, its feed rate can be maintained stably at 50 g / min for a long period. That is to say, by adopting nitrogen purging, a significant improvement in resin processing efficiency is achieved without causing a decrease in product solids content, material stringing or adhesion, or equipment failure. After the device has stabilized, sampling is performed. Based on the differential pressure data fed back from the outlet monitoring, the control conditions are finely adjusted in real time. The differential pressure of the FEVE resin at the outlet is maintained at 0.2 bar (the flow rate of the monitoring bypass is set to about 0.5 L / h). In addition, samples are taken every hour for solid content analysis to verify the accuracy of the online monitoring data. Continuous concentration is carried out for at least 24 hours at a time. The average solid content of the product resin is about 60.5%, the viscosity is about 6100 mPa·s ± 100 (25℃), and the number average molecular weight is 33000 ± 1000.

[0122] Do we need to add supplementary explanations regarding viscosity and molecular weight? It should be noted that after adding nitrogen in Example 5, the viscosity of the final product increased less than that in Examples 4 and 6.

[0123] Example 6

[0124] In this embodiment, the steps of Example 4 are completely repeated, except that the oblique toothed scraper of Example 4 is replaced with a rectangular scraper of the same size, and the angle of attack of all scrapers is fixed at 35 degrees. Although the equipment and conditions of Example 6 are almost identical to those of Example 4, the feed rate of Example 6 can only be maintained stably at 40 g / min for a long period of time because the scraper of Example 6 adopts the above design. That is to say, by adopting this scraper design, the resin processing efficiency is significantly lower than that of Examples 4 and 5 without causing a decrease in the solid content of the product, material stringing and sticking, or equipment failure.

[0125] After the device stabilizes, sampling is performed. Based on the differential pressure data from the outlet monitoring, the control conditions are finely adjusted in real time. The differential pressure of the FEVE resin at the outlet is maintained at 0.22 bar (the flow rate of the monitoring bypass is set to about 0.5 L / h). In addition, samples are taken every hour for solid content analysis to verify the accuracy of the online monitoring data. Continuous concentration is carried out for at least 24 hours per run. The average solid content of the product resin is about 60.3%, the viscosity is about 6500 mPa·s ± 100 (25℃), and the number average molecular weight is 33000 ± 1000.

[0126] Comparative Example 1

[0127] In this comparative example, resin 1 was concentrated intermittently: A 29L reactor was used for vacuum concentration. 17.1 kg of resin 1 was added, and the mixture was stirred at 300 rpm to maintain the reactor temperature below 45°C. The reactor was then sealed, and a vacuum was slowly applied to remove low-boiling-point residual monomers. The pressure inside the reactor was allowed to drop to 100 mbar, and this vacuum was maintained until the internal temperature decreased at a rate less than 0.5°C / 20 min. The internal temperature was then increased to 75°C at a rate less than 10°C / h and maintained for 2 h. The vacuum was then slowly increased to 50 mbar, and the distilled components were collected until 4.51 kg of solvent was collected. Theoretically, the solid content at this point was 70%. The vacuum was then stopped, and cooling began. The solid content measured after discharge was 72.2%, which was 2.1% higher than the theoretical value.

[0128] Comparative Example 2

[0129] In this comparative example, resin 2 was concentrated intermittently: A 29L reactor was used for vacuum concentration. 17.5 kg of resin 2 was added, and the mixture was stirred at 300 rpm to maintain the reactor temperature below 45°C. The reactor was then sealed, and a vacuum was slowly applied to remove low-boiling-point residual monomers. The pressure inside the reactor was allowed to drop to 100 mbar, and this vacuum was maintained until the internal temperature decreased at a rate less than 0.5°C / 20 min. The internal temperature was then increased to 70°C at a rate less than 10°C / h and maintained for 2 h. The vacuum was then slowly increased to 50 mbar, and the distilled components were collected until 3.2 kg of solvent was collected. Theoretically, the solid content at this point was 65%. The vacuum was then stopped, and cooling began. The solid content measured after discharge was 67.7%, which was 2.6% higher than the theoretical value.

[0130] Comparative Example 3

[0131] In this comparative example, resin 3 was concentrated intermittently: A 29L reactor was used for vacuum concentration. 17.2 kg of resin 3 was added, and the mixture was stirred at 300 rpm to maintain the reactor temperature below 45°C. The reactor was then sealed, and a vacuum was slowly applied to remove low-boiling-point residual monomers. The pressure inside the reactor was allowed to drop to 100 mbar, and this vacuum was maintained until the internal temperature decreased at a rate less than 0.5°C / 20 min. Then, the internal temperature was raised to 70°C at a rate less than 10°C / h and maintained for 2 h. The vacuum was then slowly increased to 50 mbar, and the distilled components were collected until 6.1 kg of solvent was collected. Theoretically, the solid content at this point was 65.5%. Afterward, the vacuum was stopped, and cooling began. The solid content measured upon discharge was 68%, which was 2.5% higher than the theoretical value.

[0132] Comparative Example 4

[0133] In this comparative example, resin 4 was concentrated intermittently: a 29L reactor was used for vacuum concentration. 17.0 kg of resin 4 was added, and the mixture was stirred at 300 rpm. The temperature inside the reactor was maintained below 45°C. The reactor was sealed, and then a vacuum was slowly applied to remove residual low-boiling-point monomers. The pressure inside the reactor was allowed to drop to 100 mbar, and this vacuum was maintained until the internal temperature decreased at a rate less than 0.5°C / 20 min. Then, the internal temperature was raised to 70°C at a rate less than 10°C / h, and attempts were made to collect the distilled components. However, due to the high viscosity of the material inside the reactor, foaming easily occurred during the concentration process, causing the liquid level to rise and eventually block the vacuum pipes. Therefore, the experiment had to be stopped. This experiment fully demonstrates that the existing distillation process is fundamentally unsuitable for purifying and concentrating high-viscosity resins.

[0134] Table 2: Concentration effect of comparative examples 1-3

[0135] In the comparative examples 1-3 described above, unfavorable phenomena such as foaming and bubbling occurred during the concentration process. Moreover, when the state of the material inside the vessel could not be determined, the rate of heating and vacuum lifting had to be strictly controlled to limit the concentration efficiency.

[0136] Furthermore, in the intermittent concentration processes of Comparative Examples 1-3, the material was under vacuum and subjected to high-speed stirring, making real-time viscosity monitoring and sampling impossible. Sampling could only be performed after concentration was complete. The analysis results then determined whether to continue distillation or add more solvent to correct the concentration. However, different brands or batches of resin have varying residual compositions, and factors such as condensation effects and vacuum losses can cause significant discrepancies between the actual concentration results and calculated results for some batches. Comparative Example 4, on the other hand, could not be performed normally.

[0137] Overall, compared with conventional thin-film evaporation processes in the prior art, the method of the present invention achieves significantly improved feed stability, stable product quality with no large fluctuations during continuous production, excellent adjustability, and the actual processing capacity is basically equivalent to the ideal design estimate. During long-term continuous processing, no problems such as material pulling, rod climbing, bridging into the vacuum zone, or over-concentration occurred.

Claims

1. A method for purifying and concentrating a polymer semi-finished product, wherein the crude product contains a target product polymer and one or more impurities selected from the group consisting of monomers, oligomers, solvents, byproducts, and additives; the method comprising: In a thin-film evaporator, at least some of the impurities in the semi-finished product are removed; The thin-film evaporator includes a scraper, which includes at least one vertically arranged scraper bar, and each scraper bar is provided with multiple scraper blades; The method is performed continuously.

2. The method according to claim 1, characterized in that, The target product polymer is selected from one or more of the following: fluoropolymers, polyolefins, polyethers, polyesters, polyether ether ketones, acrylic (ester) polymers, epoxy resins, polyurethanes, hydrogenated vegetable oils, and copolymers of two or more of the above polymers.

3. The method according to claim 1, characterized in that, The target product polymer is selected from the following fluoropolymers: polyfluoroolefins, polychlorofluoroolefins, polyfluorovinyl ethers, polyfluorovinyl esters, and copolymers of two or more of the above polymers.

4. The method according to claim 1, characterized in that, The polymer semi-finished product is fed into the thin-film evaporator through the feed inlet using a feed controller; The feed controller includes one or more of the following: a constant pressure valve, a pump, a flow meter, and a regulating valve; The feed inlet is selected from the following shapes: round, flat, and conical.

5. The method according to claim 1, characterized in that, A feeder is provided in the thin film evaporator adjacent to the feed inlet. The feeder is selected from: a hollow disc feeder, a centrifugal feeder, a blade feeder, a hollow cylindrical feeder, a conical feeder, and a cone-shaped feeder.

6. The method according to claim 1, characterized in that, The scraper blade of the film scraper has a shape selected from the following: oblique tooth, tooth, parallelogram, wavy, roller, circular plate, rectangle, square, blade, wavy; The angle of the scraper blade in the material-facing direction of the film scraper is 10-40 degrees; Multiple scrapers on each scraper are arranged at an angle parallel to each other, or the tooth angle of the scrapers in the material-facing direction gradually increases from top to bottom, or the tooth angle of the scrapers in the material-facing direction gradually decreases from top to bottom.

7. The method according to claim 1, characterized in that, It also includes using a nitrogen supply device to deliver nitrogen into the thin-film evaporator from bottom to top; The flow rate of nitrogen is 0.5-10% of the crude product flow rate; The nitrogen supply device has its inlet located near the central longitudinal axis of the thin-film evaporator. The vertical height of the air inlet of the nitrogen supply device is between 1 / 10 and 1 / 2 of the height of the scraper.

8. The method according to claim 1, characterized in that, A low-boiling-point component outlet is provided at the top of the thin-film evaporator, and a polymer outlet is provided at the bottom of the thin-film evaporator; Impurities separated from the semi-finished product are discharged from the outlet of the low-boiling-point component. Monomers are separated from the impurities in the separation device and the separated monomers are recycled for polymer synthesis. The purified polymer is discharged from the polymer outlet.

9. The method according to claim 8, characterized in that, The polymer outlet is connected to a discharge pump for continuous polymer discharge. The discharge pump is selected from one or more of the following: cycloidal pump, screw pump, gear pump, centrifugal pump, peristaltic pump; and / or A heating and temperature control device is provided on the outer periphery of the thin film evaporator. The heating and temperature control device is selected from one or more of the following: water bath device, oil bath device, electric heating device, and electromagnetic induction heating device.

10. The method according to any one of claims 1-9, characterized in that, It also includes at least one detector for online detection of the input semi-finished product, the material in the thin film evaporator and / or the polymer output from the polymer outlet, and the detector is connected to the feed controller for online control of the feed based on the detection results of the detector; The detector is selected from one or more of the following: viscometer, pressure gauge, differential pressure gauge, density meter, refractometer, and spectrometer.

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