CN117645683A - Method for drying and devolatilizing perfluoroether elastomer and method for producing perfluoroether elastomer composition - Google Patents
Method for drying and devolatilizing perfluoroether elastomer and method for producing perfluoroether elastomer composition Download PDFInfo
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- CN117645683A CN117645683A CN202410117351.4A CN202410117351A CN117645683A CN 117645683 A CN117645683 A CN 117645683A CN 202410117351 A CN202410117351 A CN 202410117351A CN 117645683 A CN117645683 A CN 117645683A
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- 229920001774 Perfluoroether Polymers 0.000 title claims abstract description 77
- 238000001035 drying Methods 0.000 title claims abstract description 71
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 14
- 239000003463 adsorbent Substances 0.000 description 10
- 235000011089 carbon dioxide Nutrition 0.000 description 9
- 239000007787 solid Substances 0.000 description 8
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 7
- 238000001816 cooling Methods 0.000 description 7
- 239000003999 initiator Substances 0.000 description 7
- BLTXWCKMNMYXEA-UHFFFAOYSA-N 1,1,2-trifluoro-2-(trifluoromethoxy)ethene Chemical compound FC(F)=C(F)OC(F)(F)F BLTXWCKMNMYXEA-UHFFFAOYSA-N 0.000 description 6
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 6
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- LYIPDZSLYLDLCU-UHFFFAOYSA-N 2,2,3,3-tetrafluoro-3-[1,1,1,2,3,3-hexafluoro-3-(1,2,2-trifluoroethenoxy)propan-2-yl]oxypropanenitrile Chemical compound FC(F)=C(F)OC(F)(F)C(F)(C(F)(F)F)OC(F)(F)C(F)(F)C#N LYIPDZSLYLDLCU-UHFFFAOYSA-N 0.000 description 3
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical group OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
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- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- ABTOQLMXBSRXSM-UHFFFAOYSA-N silicon tetrafluoride Chemical compound F[Si](F)(F)F ABTOQLMXBSRXSM-UHFFFAOYSA-N 0.000 description 3
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- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 1
- 229910000619 316 stainless steel Inorganic materials 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a drying and devolatilizing method of a perfluoroether elastomer and a preparation method of a perfluoroether elastomer composition, which belong to the field of high polymer materials, and specifically comprise the steps of adding a water-soluble organic solvent into emulsion containing the perfluoroether elastomer as a coagulant and stirring to coagulate the perfluoroether elastomer, and centrifugally separating, washing and dehydrating the coagulated perfluoroether elastomer to obtain wet elastomer micropowder coagulate; freezing the wet elastomer micro powder aggregate, and drying and dehydrating the frozen wet elastomer micro powder aggregate to obtain the dried and dehydrated perfluoroether elastomer micro powder; and extracting, devolatilizing and deeply dehydrating the dried and dehydrated perfluoroether elastomer micropowder to obtain the devolatilized perfluoroether elastomer. Through the treatment scheme, the vacuum degree in the drying process is greatly reduced, the drying time is shortened, the drying cost is reduced, and the method is convenient for large-scale commercial application.
Description
Technical Field
The invention relates to the field of high polymer materials, in particular to a drying devolatilization method of a perfluoroether elastomer and a preparation method of a perfluoroether elastomer composition.
Background
The fluorine elastomer is a multifunctional multipurpose sealing material. In high-precision chip production, trace impurities can reduce the performance of the product to a great extent. Only ultra-clean and high-purity environments can meet the requirements of the semiconductor industry. Thus, fluoroelastomer articles used in semiconductor manufacturing must not only have excellent chemical resistance, thermal stability and mechanical properties, but must also have low levels of extractables, low outgassing and low permeability.
Unlike the treatment mode of the thermoplastic resin PFA, the fluoroelastomer such as the perfluoroether elastomer becomes a viscous state when dried at a relatively low temperature (e.g., 120 ℃) and becomes inter-particle adhesion, the void ratio becomes small, and the pressure difference and mass transfer resistance become large, so that the initiator, chain transfer agent, surfactant and small molecular polymer encapsulated therein cannot be thoroughly removed, the devolatilization cannot be effectively performed, and the subsequent effective end group passivation treatment cannot be performed. There is therefore a need for a process that effectively dry devolatilizes fluoroelastomers.
Disclosure of Invention
Accordingly, in order to overcome the above-described drawbacks of the prior art, the present invention provides a method for drying and devolatilizing a perfluoroether elastomer and a method for preparing a perfluoroether elastomer composition.
In order to achieve the above object, the present invention provides a method for drying and devolatilizing a perfluoroether elastomer, comprising the steps of: s1: adding a water-soluble organic solvent as a coagulant into emulsion containing the perfluoroether elastomer, stirring to coagulate the perfluoroether elastomer, and centrifugally separating, washing and dehydrating the coagulated perfluoroether elastomer to obtain wet elastomer micro powder coagulum; s2: freezing the wet elastomer micro powder aggregate, and drying and dehydrating the frozen wet elastomer micro powder aggregate to obtain the dried and dehydrated perfluoroether elastomer micro powder, wherein the drying and dehydrating comprises the following steps: introducing gas with lower dew point temperature, sublimating the frozen wet elastomer micro powder aggregate, and drying and dehydrating, wherein the gas with lower dew point temperature is obtained by gasifying liquid gas, and the dew point temperature is between minus 35 ℃ and minus 80 ℃; s3: and (3) carrying out extraction devolatilization and deep dehydration on the dried and dehydrated perfluoroether elastomer micro powder to obtain the devolatilized perfluoroether elastomer.
In one embodiment, the coalescing agent is acetone.
In one embodiment, the step S2 includes: freezing the wet elastomer micro powder condensate by adopting a refrigerant; introducing a gas having a lower dew point temperature at a temperature to sublimate the frozen wet elastomer micro powder condensate; and after the moisture in the frozen wet elastomer micro powder aggregate is dried, heating for the second step to ensure that the product is raised to the highest temperature below the viscous flow state temperature of the polymer, and performing secondary drying.
In one embodiment, freezing the wet elastomeric micropowder agglomerate with a refrigerant comprises: spraying and freezing the wet elastomer micro powder condensate by adopting a refrigerant, and transferring the frozen wet elastomer micro powder condensate into a freeze drying box after the temperature is raised to a preset transfer temperature; or spraying the wet elastomer micro powder condensate into a receiver containing a refrigerant in a high-pressure air flow entrainment mode, and then transferring the frozen wet elastomer micro powder condensate into a freeze drying box, wherein the pressure range of the high-pressure air flow is 1-40 MPa.
In one embodiment, the gas having a lower dew point temperature is provided by pressure swing or temperature swing adsorption of the gas.
In one embodiment, the gas comprises at least one of air, nitrogen, carbon dioxide, argon.
In one embodiment, the extractant employed in the extractive devolatilization comprises liquid CO 2 Or supercritical CO 2 And (3) extracting and devolatilizing the dried and dehydrated perfluoroether elastomer micropowder.
In one embodiment, the liquid CO 2 Or supercritical CO 2 The temperature and pressure of the fluid are 25-120deg.C, 6-20 MPa, and the water removal and devolatilization time is 1hr-24hr; CO at normal temperature and pressure 2 The apparent flow rate of (2) is 0.01m/s-1m/s.
In one embodiment, the polymer micropowder is obtained by precipitation and centrifugation, and free water is removed by centrifugation after repeated washing.
A method for preparing a perfluoroether rubber composition comprising: the perfluoro ether elastomer is pretreated by adopting the drying devolatilization method of the perfluoro ether elastomer; and (3) carrying out fluorination and/or amination treatment on the pretreated perfluoroether elastomer, and mixing, thin-pass molding and secondary vulcanization to obtain the perfluoroether elastomer composition.
Compared with the prior art, the invention has the advantages that: the devolatilized perfluoroether elastomer is dried to produce a high purity low release perfluoroether elastomer composition subsequently. In the drying and devolatilizing process, the gas with lower dew point temperature is adopted for freeze drying and a heat source is provided, so that the vacuum degree in the drying process is greatly reduced, the drying time is shortened, the drying cost is reduced, and the large-scale commercial application is facilitated.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a process for the dry devolatilization purification of perfluoroether elastomers in an embodiment of the present invention;
FIG. 2 is a flow chart of the preparation of a gas having a lower dew point temperature in an embodiment of the invention.
Detailed Description
Embodiments of the present application are described in detail below with reference to the accompanying drawings.
Other advantages and effects of the present application will become apparent to those skilled in the art from the present disclosure, when the following description of the embodiments is taken in conjunction with the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. The present application may be embodied or carried out in other specific embodiments, and the details of the present application may be modified or changed from various points of view and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.
It is to be noted that various aspects of the embodiments within the scope of the present invention are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms and that any specific structure and/or function described herein is merely illustrative. Based on the present application, one skilled in the art will appreciate that one aspect described herein may be implemented independently of any other aspect, and that two or more of these aspects may be combined in various ways. For example, apparatus may be implemented and/or methods practiced using any number and aspects set forth herein. In addition, such apparatus may be implemented and/or such methods practiced using other structure and/or functionality in addition to one or more of the aspects set forth herein.
It should also be noted that the illustrations provided in the following embodiments merely illustrate the basic concepts of the application by way of illustration, and only the components related to the application are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complicated.
In addition, in the following description, specific details are provided in order to provide a thorough understanding of the examples. However, it will be understood by those skilled in the art that aspects may be practiced without these specific details.
As shown in fig. 1, an embodiment of the present application provides a method for drying and devolatilizing a perfluoroether elastomer, which includes the following steps:
and step 1, adding a water-soluble organic solvent serving as a coagulant into emulsion containing the perfluoroether elastomer, stirring to coagulate the perfluoroether elastomer, and centrifugally separating, washing and dehydrating the coagulated perfluoroether elastomer to obtain wet elastomer micro powder coagulant.
The emulsion (A) containing the perfluoroether elastomer is obtained by emulsion polymerization, and for example, a synthetic emulsion can be synthesized by polymerizing 55% Tetrafluoroethylene (TFE), 43% perfluoromethyl vinyl ether (PMVE) and 2% perfluoro-8-cyano-5-methyl-3, 6-dioxa-1-octene (8-CNVE) in combination with a usual surfactant, initiator and the like. The surfactant may be an aqueous solution of perfluorosilane at a concentration of 1wt% to 2 wt%. The initiator may be any one of sodium persulfate, potassium persulfate, and ammonium persulfate. A water-soluble organic solvent is added to the emulsion containing the perfluoroether elastomer as a coagulant and vigorously stirred during coagulation, so that the perfluoroether elastomer is coagulated. Vigorous stirring can result in a small agglomerated particle size, facilitating the subsequent lyophilization process. And then centrifugally separating, washing and dehydrating the coagulated perfluoroether elastomer to obtain wet elastomer micro powder condensate (B), wherein most of water carried in the coagulated perfluoroether elastomer can be removed.
And 2, freezing the wet elastomer micro powder aggregate, and drying and dehydrating the frozen wet elastomer micro powder aggregate to obtain the dried and dehydrated perfluoroether elastomer micro powder, wherein the drying and dehydrating comprises the following steps: introducing gas with lower dew point temperature, sublimating the frozen wet elastomer micropowder aggregate, drying and dehydrating, wherein the gas with lower dew point temperature is obtained by gasifying liquid gas, and the dew point temperature is-35 ℃ to-80 ℃.
The wet elastomer fine powder aggregate (B) may be frozen directly or by precooling or freezing the wet elastomer fine powder aggregate (B). And freeze-drying and dehydrating the wet elastomer micro powder aggregate in a frozen state to obtain the dried and dehydrated perfluoroether elastomer. The wet elastomer micro powder agglomerate (B) may be frozen in the open receiver by using a refrigerant such as liquid nitrogen. The refrigerant can be selected from common liquid refrigerants such as liquid nitrogen or liquid carbon dioxide, or liquid refrigerants such as fluorine-chlorine carbide which are adopted in industry for indirect heat exchange and refrigeration.
The gases having a lower dew point temperature being obtained by vaporisation of a cryogenic liquid, e.g. CO 2 Boiling point at 527kPa at-56.6 ℃, N 2 The boiling point at 101.3kPa was-195.6 ℃. The gas having the lower dew point temperature is heated to a certain temperature and then serves as a drying and heat source providing gas.
By drying with a gas having a lower dew point temperature at a temperature, the dew point temperature and flow rate of the drying gas depend on the temperature of the sample to be dried and the quality of the dried sample. To ensure successful freeze-drying, the temperature of the freeze-drying chamber is maintained at the temperature level of the sample to be dried.
The input gas and sublimated water vapor are timely discharged by a vacuum pump. The lower the sublimation temperature, the higher the vacuum level required, and the indirectly reduced the vacuum level required due to the use of a gas having a lower dew point temperature as the heat source.
Taking liquid nitrogen as an example, the micro powder of the wet elastomer micro powder aggregate (B) can be dispersed into liquid nitrogen, and the liquid nitrogen cools and freezes the polymer particles and absorbs heat to gasify, so that the low-temperature nitrogen overflows and plays a certain role in precooling the descending polymer particles. The amount of total liquid nitrogen required, which includes the amount of liquid nitrogen that cools the container and is lost to the environment, depends primarily on the amount of polymer and the water content in the condensate (B). In one embodiment, dewars (Dewars) may be used as freezing containers for the condensate (B), which may ignore the cooling container and the amount of liquid nitrogen that is lost to the environment. The grain size of the micro powder can be controlled between 0.01mm and 1mm.
And (3) controlling the water in the wet elastomer micro powder aggregate (B) in a frozen state to sublimate, thereby drying and dehydrating the wet elastomer micro powder aggregate (B) to obtain the dried and dehydrated perfluoroether elastomer. For example, the agglomerate (B) frozen in the dewar is taken out and put on a support net of a low-temperature drying oven, which may employ a single-layer or multi-layer support net. And then drying and dehydrating the condensate on the support net through a refrigerant to obtain the dried and dehydrated perfluoroether elastomer. Specifically, a certain temperature of gas with a lower dew point temperature can be introduced into the lower part of the supporting net of the low-temperature drying box, so that ice in the frozen material sublimates.
And step 3, extracting, devolatilizing and deeply dehydrating the dried and dehydrated perfluoroether elastomer micro powder to obtain the devolatilized perfluoroether elastomer.
When the volatile components such as chain transfer agent, surfactant, small molecular polymer, etc. remaining in the fine powder in step 2 cannot be removed effectively, the volatile components remaining in the fine powder can be removed by devolatilization by extraction at this time. Specifically, liquid or supercritical fluid can be adopted to further remove moisture and volatile matters, so that the dried and dehydrated perfluoroether elastomer is extracted and devolatilized, and the treated perfluoroether elastomer is obtained.
Supercritical fluid (supercritical fluid) refers to a fluid that has a temperature and pressure above its critical point, both above the critical point. The physicochemical properties of supercritical fluids are very different from those of liquids and gases in the non-critical state. By supercritical CO 2 The viscosity of the fluid is about one percent of that of the liquid, and the self-diffusion coefficient is about 100 times of that of the liquid, so that the fluid has good mass transfer characteristics, can greatly shorten the time required by phase equilibrium, and is an ideal medium for efficient mass transfer; has a much faster diffusion rate than liquids, and has a much greater dissolution and carrying capacity for solid substances than gases; has high compressibility, and small changes in pressure and temperature near the critical point can cause CO 2 The density of (2) is greatly changed, so that the CO can be simply changed 2 The dissolution capacity of the catalyst is regulated by the pressure and the temperature of the catalyst, so that the extraction selectivity is improved; by reducing the pressure of the systemTo separate CO 2 And the dissolved product, the process of eliminating the solvent is omitted.
In one embodiment, the extractant includes liquid CO 2 Or supercritical CO 2 A fluid.
In one embodiment, the extractant may also contain an entrainer by which the CO is enhanced 2 Selectivity, solvency and extraction efficiency of the extraction process. Entrainers, also known as carryover agents, are substances which are added to supercritical fluid solvents and which have a high affinity for the extracted substance, are miscible with the fluid solvents and have a volatility intermediate between that of the extracted substance and the supercritical component, so as to increase the selectivity and solubility of the substance to the extracted component, and can be either a pure substance or a mixture of two or more substances.
Polymer devolatilization is an important process in the process of processing and producing high molecular materials. In particular embodiments, the extractant employed in the extractive devolatilization may be CO 2 Fluid or supercritical CO 2 A fluid. In order to effectively remove a portion of the polar small molecules, in some embodiments, the extractant employed in the extractive devolatilization contains not only CO 2 Fluid or supercritical CO 2 The fluid is also added with entrainer, and the dosage of the entrainer is CO 2 The entrainer can be methanol or ethanol with a mass of 0.5-10%. The addition of polar entrainers can improve the selectivity to polar volatile components during extraction. The entrainer used in this example was ethanol.
The above method, drying and devolatilizing the perfluoroether elastomer to prepare a high purity and low release perfluoroether elastomer composition. In the drying and devolatilizing process, the gas with lower dew point temperature is adopted for freeze drying and a heat source is provided, so that the vacuum degree in the drying process is greatly reduced, the drying time is shortened, the drying cost is reduced, and the large-scale commercial application is facilitated.
In one embodiment, the coalescing agent is acetone. Acetone may be a commercially available analytically pure reagent.
In one embodiment, the wet elastomer micro powder aggregate is freeze-dried and dehydrated in a frozen state to obtain the dried and dehydrated perfluoroether elastomer micro powder, which comprises the following steps:
and 2-1, freezing the wet elastomer micro powder condensate by adopting a refrigerant.
The wet elastomer fine powder aggregate (B) may be frozen by a freezing chamber or may be frozen by a refrigerant. In one embodiment, the refrigerant may be a direct contact refrigerant, preferably liquid carbon dioxide or liquid nitrogen. As in fig. 2, the wet elastomer micro powder agglomerates are first frozen by liquid nitrogen. For example, the refrigerating fluid is liquid carbon dioxide and spray-frozen. CO 2 It is not possible to exist in a liquid state at atmospheric pressure, but only in a gas or a solid. During the freezing process, liquid CO 2 After being ejected from the nozzle, the mixture became snow-like solid dry ice (43%) and CO 2 The gases (57%) were all at-78.5 deg.c, with the latent heat of sublimation of dry ice accounting for about 84% of the total refrigeration. In one embodiment, to facilitate handling of the fluoroelastomer, the lyophilized micropowder may be placed in a stainless steel inner cylinder using a 2000 mesh stainless steel screen (Taylor mesh, about 6.5 microns), the inner cylinder placed in the extraction device with the gap between the inner cylinder and the extraction device sealed with a PTFE gasket to prevent CO 2 The fluid flow is shorted.
Liquid CO 2 Spray freezing is directly in contact with condensate, and its refrigerating capacity depends on the latent heat of vaporization and the sensible heat of temperature rise, and thus has a direct relation with the amount of usage. Liquid CO 2 The larger the flow, the larger the refrigerating capacity, the lower the refrigerating temperature, the larger the temperature difference and the faster the cooling speed, the condensate exchanges heat through conduction and convection. Liquid CO 2 During spraying, dry ice and gas are formed after high-pressure spraying, at the moment, heat exchange is strongest, but spraying time is short (0.5-20 min), and the drying chamber can maintain low temperature by means of sublimation refrigeration of dry ice after spraying.
And 2-2, introducing a gas with a certain temperature and a lower dew point temperature to sublimate the frozen wet elastomer micro powder aggregate.
And introducing a gas with a certain temperature and a lower dew point temperature, and performing freeze drying to ensure that the temperature of the product is far lower than the viscous flow state temperature of the polymer, thereby performing sublimation drying. The drying rate at which freeze-drying is performed is a function of the freezing temperature and the vapor pressure gradient between the water vapor formation site and the drying medium, rather than the total pressure in the drying chamber, i.e., freeze-drying may be performed by circulating a convective freeze-drying medium (e.g., cold air stream) under atmospheric conditions, which is kept dry by a molecular sieve desiccant or freeze-condenser, even though freeze-drying may be performed without a vacuum pump, provided that the water vapor pressure at the sample surface is lower than the saturated vapor pressure of ice at the temperature of the dried sample. In fig. 2, the gas having the lower dew point temperature is dry air.
And 2-3, drying the moisture in the frozen wet elastomer micro powder aggregate, heating for the second step, raising the product to the highest temperature lower than the viscous flow state temperature of the polymer, and performing secondary drying.
When the mass of the perfluoroether elastomer is unchanged at high temperature for a certain period of time by sampling analysis, the moisture in the frozen condensate is judged to be basically dried. And (3) basically drying the moisture in the frozen aggregate, then heating the product for the second time, and raising the product to the highest temperature below the viscous flow state temperature of the polymer for secondary drying. In this case, the removed water vapor or the like may be adsorbed by a desiccant, a molecular sieve, an adsorbent bed or the like.
The desiccant may be selected from activated alumina desiccants. The active alumina drier is spherical active alumina prepared through special process. The water-absorbing agent has the characteristics of no toxicity, no odor, no pulverization, water insolubility, white spherical appearance and strong water absorbing capacity; under certain operation condition and regeneration condition, its drying depth is up to below dew point temperature-40 deg.C, so that it is a high-effective drying agent for drying trace water.
The 13X type molecular sieve and the CaX type molecular sieve are widely applied to a pre-treatment unit in air separation, and can be used for removing impurities such as water vapor, carbon dioxide and the like in compressed air so that the concentration of the impurities is lower than a certain limit value.
The 13X type molecular sieve is used for drying the air under the working pressure of 0.5MPa, the dew point temperature can reach below minus 60 ℃, and the CaX type molecular sieve is used for drying the air, the dew point temperature can reach minus 70 ℃.
According to one embodiment, an adsorbent bed is employed, the adsorbent being activated alumina, a 13X type molecular sieve, or a CaX type molecular sieve. In order to improve the adsorption efficiency and the adsorbent utilization rate, a mixed bed can be adopted, activated alumina, a 13X type molecular sieve and a CaX type molecular sieve are sequentially filled in an adsorption tower, and inert porcelain balls with certain thickness are placed on the adsorption tower.
In one embodiment, the gas having the lower dew point temperature is provided by pressure swing or temperature swing adsorption of the gas. Generally, pressure swing adsorption achieves a higher gas dew point temperature and temperature swing adsorption achieves a lower gas dew point temperature. The temperature swing adsorption (Temperature Swing Adsorption) process is characterized in that the characteristic that the equilibrium adsorption capacity of the adsorbent is reduced along with the temperature rise is utilized, and the operation method of normal temperature adsorption and temperature rise desorption is adopted. Besides adsorption and desorption, the whole temperature swing adsorption operation also comprises auxiliary links such as cooling the desorbed adsorbent. Temperature swing adsorption is used for dehumidifying atmospheric gas and air, recovering solvent vapor in air, and the like. If the adsorbent is water, the adsorbent may be heated with hot gas for desorption.
As shown in fig. 2, a gas having a lower dew point temperature is produced using dual bed pressure swing/temperature swing adsorption.
The adsorbent filled in the bed layer A and the bed layer B can be at least one of activated alumina, a 13X type molecular sieve or a CaX type molecular sieve, for example, a mixed adsorption bed can be adopted, and the added adsorbent is the activated alumina, the 13X type molecular sieve and the CaX type molecular sieve from bottom to top.
In one embodiment, the gas comprises at least one of air, nitrogen, carbon dioxide, argon.
In one embodiment, freezing the condensate using a refrigerant includes:
spraying a refrigerant to freeze the condensate, and transferring the frozen condensate into a freeze drying box after the temperature is raised to a preset transfer temperature; or alternatively
Spraying the condensate into a receiver containing a refrigerant in a high-pressure air flow entrainment mode, and transferring the frozen condensate into a freeze drying box, wherein the pressure range of the high-pressure air flow is 1-40 MPa, and preferably 6-20 MPa.
In one embodiment, liquid CO is employed 2 Or supercritical CO 2 And (3) taking the fluid as an extracting agent, and extracting and devolatilizing the dried and dehydrated perfluoroether elastomer.
In one embodiment, the liquid CO 2 Or supercritical CO 2 The temperature and pressure of the fluid are 25-120deg.C, 6-20 MPa, and the water removal and devolatilization time is 1hr-24hr; CO at normal temperature and pressure 2 The apparent flow rate of (2) is 0.01m/s-1m/s.
In one embodiment, in step 1, wet aggregate with most of the water removed is obtained by centrifugation, polymer micropowder is obtained by precipitation and centrifugation, and free water is removed by centrifugation after repeated washing. The emulsion is condensed into water-containing perfluoroether elastomer micropowder, part of impurities are removed by repeatedly washing the micropowder, and part of water is centrifugally separated, wherein the part of water is free water and is water existing in pores or gaps of the micropowder. Removing bound water in micropowder by freeze drying method, and supercritical CO 2 Extracting to remove volatile components contained in the perfluoroether elastomer.
In one embodiment, there is also provided a method for preparing a perfluoroether rubber composition, comprising the steps of:
pretreating the perfluoroether elastomer by adopting a drying devolatilization method of the perfluoroether elastomer;
and (3) carrying out fluorination and/or amination treatment on the pretreated perfluoroether elastomer, and mixing, thin-pass, mould pressing and secondary vulcanization to obtain the perfluoroether elastomer composition with high cleanliness and low release.
Example 1
The embodiment of the application provides a drying devolatilization method of a perfluoroether elastomer, which comprises the following steps:
s1, adding a water-soluble organic solvent into the emulsion (A) containing the perfluoroether elastomer as a coagulant, stirring to coagulate the perfluoroether elastomer, and centrifugally separating to obtain wet elastomer micro powder coagulum (B) with most of water removed.
The emulsion (A) containing the perfluoroether elastomer is obtained by emulsion polymerization, and for example, a synthetic emulsion can be synthesized by polymerizing 55% Tetrafluoroethylene (TFE), 43% perfluoromethyl vinyl ether (PMVE) and 2% perfluoro-8-cyano-5-methyl-3, 6-dioxa-1-octene (8-CNVE) in combination with a usual surfactant, initiator and the like. The surfactant may be an aqueous solution of perfluorosilane at a concentration of 1wt% to 2 wt%. The initiator may be any one of sodium persulfate, potassium persulfate, and ammonium persulfate. Stirring 20L of the emulsion (A) of the perfluoroether elastomer, adding an acetone coagulant with the solid content of about 30 percent and the solid content of about 1.5 percent, precipitating and centrifugally separating to obtain a solid polymer, repeatedly washing and centrifugally dewatering to obtain about 6kg of wet elastomer micro powder coagulant with most of water removed, wherein the water content is about 8-10 percent and the particle size is about 0.01-1 mm.
Taking 1kg of wet polymer therein and using high pressure N 2 The gas stream is entrained by the jet of gas which is slowly dispersed into a dewar (de wars) receiver containing liquid nitrogen.
A10L Dewar flask was filled with about 2L (about 1.6 kg) of liquid nitrogen, and the frozen polymer was cooled to about-50℃to obtain a wet elastomer micro powder agglomerate (B) by pre-cooling and freezing.
S2, freeze-drying and dehydrating the frozen wet elastomer micro powder aggregate (B) by using a gas with a lower dew point temperature to obtain the dried and dehydrated perfluoroether elastomer micro powder (C).
The drying gas may be selected from air, nitrogen, carbon dioxide, argon, for example, in fig. 2, drying air. The drying gas (dried air) with lower dew point temperature is prepared by adopting temperature swing adsorption as shown in fig. 2, the dew point temperature is about t1= -60 ℃, t2= 25 ℃ is reached after the drying gas is heated by a heater, the freezing temperature of the polymer to be frozen and dried is t3= -50 ℃, and the sensible heat which can be released by the drying gas is mC p (t2-t3)=75mC p Wherein m is the mass of the input dry gas per unit time, C p The specific heat is the average constant pressure of the dry gas over the operating temperature range.
Freeze-drying oven model JK-II-50L, jiang Kai (Suzhou) instruments and technologies Co., ltd.
When the dew point temperature is t1= -60 ℃, the vapor pressure of water is 0.0107mbar, and when the vapor pressure of water is 0.0300mbar, and when t3= -50 ℃, the pressure difference Δp=0.0300 mbar-0.0107 mbar=0.0193 mbar is about the driving force of freeze drying.
After centrifugation, the wet elastomeric micropowder agglomerate (B) has a water content psi of about 8% to about 10%, i.e. 1kg of the polymer to be freeze-dried has a water content of about 100g and a latent heat of ice sublimation of about 3.35X 10 5 J/kg, the specific heat capacity of the rubber is about 1700J/kg.K, and when the temperature of the polymer is raised from t3= -50 ℃ to 25 ℃, the input (3.35 multiplied by 10) is needed to freeze-dry 1kg of wet elastomer micro powder aggregate in consideration of the heat absorption condition of the polymer 5 J/kg×0.1kg +1700J/kg•K×75K×0.9kg）=（33.5+114.8）×10 3 J=148.3 kJ heat.
Assuming a freeze drying time of 10 hours, the heat input was required to be 14.8kJ/hr. Constant pressure specific heat capacity of air is about C p The theoretical input gas amount was found to be m=14.8 kJ/hr/(1.005 kJ/kg.kx 75K) =0.196 kg/hr=196 g/hr.
The volume of the drying oven is 50L, the exhaust gas amount of the vacuum pump is approximately equal to the input air volume plus the sublimated water vapor amount=196 g air/hr+10 g water vapor/hr= 151.4L/hr+12.4L/hr=163.8L/hr=45.5 mL/s, and if the sublimated water vapor amount is required to be removed in time, the vacuum degree is maintained at 91.0Pa (absolute pressure).
The vacuum levels that t2 and t3 in example 1 need not be maintained at the same time are shown in Table 1.
And S3, extracting, devolatilizing and deeply dehydrating the dehydrated perfluoro ether elastomer micro powder (C) to obtain the devolatilized perfluoro ether elastomer (D).
About 0.9kg of perfluoroelastomer micro powder (C) which needs deep dehydration and devolatilization is filled into a stainless steel inner cylinder, the cylinder adopts a 2000-mesh stainless steel screen mesh (Taylor mesh, about 6.5 microns), the inner cylinder is placed in an extraction device, and a gap between the inner cylinder and the extraction device is sealed by a PTFE sealing gasket. By CO 2 The flushing is repeated to remove air. When in operation, the valve of the gas cylinder is firstly opened to intake air, and the cooling device is started to cool down to enable CO 2 Liquefying, boosting the high-pressure pump, regulating the pressure to a preset pressure by a back pressure valve, and extracting and removingVolatilizing, desorbing the extracted volatile matters in the extracted high-pressure fluid into the separator through the throttle back pressure valve, releasing the devolatilized matters from the bottom of the separator, processing the low-pressure gas through the vent valve by the tail gas processing device, and measuring the flow by the flowmeter. The fluid absorbs heat during throttling, and the throttling back pressure valve and the separator are required to be heated to maintain a certain temperature. In the extraction process, the extraction pressure, the separation pressure and the CO passing through in the extraction process are adjusted by adjusting each valve 2 The flow rate is stabilized in a required range.
The temperature and pressure of the liquid or supercritical fluid are 25-120deg.C, 6-20 MPa, and the time for removing water and volatilizing is 1hr-24hr; CO 2 The apparent flow rate of (C) is 0.01m/s-1m/s (measured at normal temperature and pressure).
After the detection of the deeply dehydrated devolatilized tail gas meets the requirements (the concentration of organic matters is less than 0.1 mg/kg; PE company GC-MS), decompressing and using CO 2 Purging, and taking out the stainless steel inner cylinder to obtain the deep dehydrated and devolatilized perfluoroether elastomer (D).
Example 2
The embodiment of the application provides a drying devolatilization method of a perfluoroether elastomer, which comprises the following steps:
s1, adding a water-soluble organic solvent as a coagulant into emulsion (A) containing the perfluoroether elastomer, stirring to coagulate the perfluoroether elastomer, and centrifugally separating to obtain wet elastomer micro powder coagulum (B) with most of water removed.
The emulsion (A) containing the perfluoroether elastomer is obtained by emulsion polymerization, and for example, a synthetic emulsion can be synthesized by polymerizing 55% Tetrafluoroethylene (TFE), 43% perfluoromethyl vinyl ether (PMVE) and 2% perfluoro-8-cyano-5-methyl-3, 6-dioxa-1-octene (8-CNVE) in combination with a usual surfactant, initiator and the like. The surfactant may be an aqueous solution of perfluorosilane at a concentration of 1wt% to 2 wt%. The initiator may be any one of sodium persulfate, potassium persulfate, and ammonium persulfate. Stirring 20L of emulsion (A) of perfluoro ether elastomer, adding acetone coagulant with solid content of about 30%, precipitating, centrifuging to obtain solid polymer, repeatedly washing, and centrifuging to remove waterAbout 6kg of wet elastomer micro powder agglomerate (B) with most of the water removed is obtained, wherein the water content is about 8% -10% and the particle size is about 0.01mm-1mm. By liquid CO 2 Spraying frozen wet elastomer micro powder aggregate (B).
Selected liquid CO 2 The storage tank is of the DPL450-175-2.0 type and manufactured by Zhejiang plain yang cryogenic equipment Co., ltd.
A hollow cone nozzle of the spay system (Shanghai) limited company was selected. The model is as follows: LN-4W series, interface size 1/4NPT external screw thread, the material is 316 stainless steel material. The nominal orifice diameter was 1.5mm, mass flow m=3 g/s (1.5 bar), and the injection angle was 60 degrees.
Liquid CO 2 Spray freezing is a direct contact with the polymer, and its refrigeration capacity depends on the latent heat of vaporization and the sensible heat of temperature rise, and thus has a direct relation to the amount used. Clearly, liquid CO 2 The larger the flow, the larger the refrigerating capacity, the lower the refrigerating temperature, and the temperature difference is large and the cooling speed is high through conduction and convection heat exchange of the perfluoroether elastomer. Liquid CO 2 During spraying, dry ice and gas are formed after high-pressure spraying, at the moment, heat exchange is strongest, but spraying time is short (0.5-20 min), low temperature can be maintained in a drying chamber after spraying by means of sublimation refrigeration of dry ice, sublimation latent heat of the dry ice is 573kJ/kg, and sensible heat of the dry ice heated to-20 ℃ is 50kJ/kg. About 0.51kg of dry ice is required to be converted into liquid CO 2 1.2kg (about 1.3L).
Liquid CO 2 Spraying for about 400s, and transferring to a freeze drying box after the temperature is raised to-20 ℃.
S2, freeze-drying and dehydrating the frozen wet elastomer micro powder aggregate (B) by using a gas with a lower dew point temperature to obtain the dried and dehydrated perfluoroether elastomer micro powder (C).
The drying gas can be selected from air, nitrogen, carbon dioxide and argon, and is dry air. The dew point temperature of the drying gas with lower dew point temperature is about t1= -30 ℃, t2=25 ℃ is reached after the drying gas is heated by the heater, the freezing temperature of the polymer to be frozen and dried is t3= -20 ℃, and the sensible heat which can be released by the drying gas is mC p (t2-t3)=45mC p Wherein m is the mass of the input dry gas per unit time, C p The specific heat is the average constant pressure of the dry gas over the operating temperature range.
When the dew point temperature is t1= -30 ℃, the vapor pressure of water is 0.3874mbar, and when the vapor pressure of water is 1.032mbar, the pressure difference Δp=1.032 mbar-0.3874 mbar= 0.6446mbar is about the driving force of freeze drying.
1kg of the wet elastomer micro powder agglomerate to be freeze-dried in example 2 had a water content of about 100g and a latent heat for ice sublimation of about 3.35X 10 5 J/kg, the specific heat capacity of the rubber is about 1700J/kg.K, and when the temperature of the polymer is raised from t3= -20 ℃ to 25 ℃, the input (3.35 multiplied by 10) is needed to freeze-dry 1kg of wet elastomer micro powder aggregate in consideration of the heat absorption condition of the polymer 5 J/kg×0.1kg+1700J/kg•K×45K×0.9kg）=102.4×10 3 J=102.4 kJ heat.
Assuming a freeze drying time of 10 hours, the amount of heat required to be input is 10.2kJ/hr. Constant pressure specific heat capacity of air is about C p The theoretical input gas amount was found to be m=10.2 kJ/hr/(1.005 kJ/kg.kx45K) =0.226 kg/hr=0.063 g/s.
The volume of the drying oven is 50L, the exhaust gas amount of the vacuum pump is approximately equal to the input air volume plus the sublimated water vapor amount=226 g air/hr+10 g water vapor/hr=174.6L/hr+12.4L/hr=187.0L/hr=51.9 mL/s, and if the sublimated water vapor amount is required to be removed in time, the vacuum degree is maintained to be 103.9Pa (absolute pressure).
The vacuum levels that t2 and t3 in example 2 need not be maintained at the same time are shown in Table 2.
S3, extracting, devolatilizing and deeply dehydrating the dehydrated perfluoro ether elastomer micro powder (C) to obtain the devolatilized perfluoro ether elastomer (D).
About 0.9kg of perfluoroelastomer micro powder (C) which needs deep dehydration and devolatilization is filled into a stainless steel inner cylinder, the cylinder adopts a 2000-mesh stainless steel screen mesh (Taylor mesh, about 6.5 microns), the inner cylinder is placed in an extraction device, and a gap between the inner cylinder and the extraction device is sealed by a PTFE sealing gasket. By CO 2 The flushing is repeated to remove air. When in operation, the valve of the gas cylinder is firstly opened to intake air, and the cooling device is started to cool down to enable CO 2 Liquefying and pumping up high pressureAnd the pressure is regulated by a back pressure valve to rise to a preset pressure for extraction and devolatilization, the extracted volatile matters are desorbed and extracted from the high-pressure fluid which enters the separator through a throttling back pressure valve, devolatilization matters are discharged from the bottom of the separator, and the low-pressure gas is treated by a tail gas treatment device through a blow-down valve and then the flow is measured by a flowmeter. The fluid absorbs heat during throttling, and the throttling back pressure valve and the separator are required to be heated to maintain a certain temperature. In the extraction process, the extraction pressure, the separation pressure and the CO passing through in the extraction process are adjusted by adjusting each valve 2 The flow rate is stabilized in a required range.
In a specific embodiment of the present invention, the liquid or supercritical fluid temperature and pressure are respectively 25-120 ℃, 6-20 MPa, and the water removal and devolatilization time is 1hr-24hr; CO 2 The apparent flow rate of (C) is 0.01m/s-1m/s (measured at normal temperature and pressure).
After the detection of the deeply dehydrated devolatilized tail gas meets the requirements (the concentration of organic matters is less than 0.1 mg/kg; PE company GC-MS), decompressing and using CO 2 Purging, and taking out the stainless steel inner cylinder to obtain the devolatilized fluoroelastomer (D).
The following is a summary of the results of examples 1 and 2 described above, which is intended to illustrate the present application, but is not intended to limit the scope of the present application. Each table is given by way of example for 3 different cases.
Table 1 results of liquid nitrogen freezing, air drying and vacuum drying in example 1
Conditions are as follows: freeze drying for 10hr, oven volume 50L, and water content 10%
TABLE 2 liquid CO in example 2 2 Spray freeze drying and air drying results
Conditions are as follows: freeze drying for 10hr, oven volume 50L, and water content 10%
TABLE 3 weight loss of perfluoroether elastomer after devolatilization by supercritical extraction
Conditions are as follows: w1 as such, w2 after lyophilization, w3 after devolatilization by extraction
The test results show that the use of a gas with a lower dew point temperature for lyophilization, whether liquid nitrogen leach freezing (table 1) or carbon dioxide spray freezing (table 2), requires a vacuum level at the time of drying that is comparable to conventional vacuum lyophilization methods (vacuum level at the required absolute pressure is about mPa,1 mpa=10) -3 Pa) is greatly reduced by several orders of magnitude, and the water content of the perfluoroether elastomer is reduced, and the obtained perfluoroether elastomer can be used for preparing a high-cleanness low-release perfluoroether rubber composition after being subjected to fluorination and amination treatment.
The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions easily conceivable by those skilled in the art within the technical scope of the present application should be covered in the scope of the present application.
Claims (10)
1. A method for drying and devolatilizing a perfluoroether elastomer, comprising the steps of:
s1: adding a water-soluble organic solvent as a coagulant into emulsion containing the perfluoroether elastomer, stirring to coagulate the perfluoroether elastomer, and centrifugally separating, washing and dehydrating the coagulated perfluoroether elastomer to obtain wet elastomer micro powder coagulum;
s2: freezing the wet elastomer micro powder aggregate, and drying and dehydrating the frozen wet elastomer micro powder aggregate to obtain the dried and dehydrated perfluoroether elastomer micro powder, wherein the drying and dehydrating comprises the following steps: introducing gas with lower dew point temperature, sublimating the frozen wet elastomer micro powder aggregate, and drying and dehydrating, wherein the gas with lower dew point temperature is obtained by gasifying liquid gas, and the dew point temperature is between minus 35 ℃ and minus 80 ℃;
s3: and (3) carrying out extraction devolatilization and deep dehydration on the dried and dehydrated perfluoroether elastomer micro powder to obtain the devolatilized perfluoroether elastomer.
2. The dry devolatilization process of claim 1, in which the coagulant is acetone.
3. The dry devolatilization process as claimed in claim 1, wherein the S2 step comprises:
freezing the wet elastomer micro powder condensate by adopting a refrigerant;
introducing a gas having a lower dew point temperature at a temperature to sublimate the frozen wet elastomer micro powder condensate;
and after the moisture in the frozen wet elastomer micro powder aggregate is dried, heating for the second step to ensure that the product is raised to the highest temperature below the viscous flow state temperature of the polymer, and performing secondary drying.
4. The dry devolatilization process as claimed in claim 3, wherein freezing the wet elastomer micro powder agglomerate with a refrigerant comprises:
spraying and freezing the wet elastomer micro powder condensate by adopting a refrigerant, and transferring the frozen wet elastomer micro powder condensate into a freeze drying box after the temperature is raised to a preset transfer temperature; or alternatively
Spraying the wet elastomer micro powder condensate into a receiver containing a refrigerant in a high-pressure air flow entrainment mode, and transferring the frozen wet elastomer micro powder condensate into a freeze drying box, wherein the pressure range of the high-pressure air flow is 1-40 MPa.
5. The dry devolatilization process as claimed in claim 1, wherein the gas having a lower dew point temperature is provided by pressure swing adsorption or temperature swing adsorption of the gas.
6. The dry devolatilization process of claim 1, wherein the gas comprises at least one of air, nitrogen, carbon dioxide, argon.
7. The method of claim 1, wherein the extractant used in the extractive devolatilization comprises liquid CO 2 Or supercritical CO 2 And (3) extracting and devolatilizing the dried and dehydrated perfluoroether elastomer micropowder.
8. The dry devolatilization process of claim 7, in which the liquid CO 2 Or supercritical CO 2 The temperature and pressure of the fluid are 25-120deg.C, 6-20 MPa, and the water removal and devolatilization time is 1hr-24hr; CO at normal temperature and pressure 2 The apparent flow rate of (2) is 0.01m/s-1m/s.
9. The method for drying and devolatilizing according to claim 1, wherein the polymer micropowder is obtained by centrifugal separation after precipitation, and free water is removed by centrifugation after repeated washing.
10. A process for producing a perfluoroether rubber composition, comprising:
the perfluoroether elastomer is pretreated by adopting the drying devolatilization method of the perfluoroether elastomer micropowder according to any one of claims 1 to 9;
and (3) carrying out fluorination and/or amination treatment on the pretreated perfluoroether elastomer, and then carrying out mixing, thin-pass, compression molding and secondary vulcanization to obtain the perfluoroether elastomer composition.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009280687A (en) * | 2008-05-21 | 2009-12-03 | Asahi Glass Co Ltd | Fluorine-containing elastic copolymer |
| CN116118045A (en) * | 2023-03-02 | 2023-05-16 | 上海森桓新材料科技有限公司 | Recovery method and recovery system for fluorine-containing rubber waste |
| CN116426024A (en) * | 2023-06-14 | 2023-07-14 | 上海森桓新材料科技有限公司 | Method for passivating end group of fluorine elastomer |
| CN116751428A (en) * | 2023-08-23 | 2023-09-15 | 上海森桓新材料科技有限公司 | Preparation method of high-temperature low-compression permanent deformation perfluoroether elastomer composition |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009280687A (en) * | 2008-05-21 | 2009-12-03 | Asahi Glass Co Ltd | Fluorine-containing elastic copolymer |
| CN116118045A (en) * | 2023-03-02 | 2023-05-16 | 上海森桓新材料科技有限公司 | Recovery method and recovery system for fluorine-containing rubber waste |
| CN116426024A (en) * | 2023-06-14 | 2023-07-14 | 上海森桓新材料科技有限公司 | Method for passivating end group of fluorine elastomer |
| CN116751428A (en) * | 2023-08-23 | 2023-09-15 | 上海森桓新材料科技有限公司 | Preparation method of high-temperature low-compression permanent deformation perfluoroether elastomer composition |
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