Efficient devolatilization process for carbon dioxide-based biodegradable plastics

Abstract

The application discloses a high-efficiency devolatilization process of carbon dioxide-based biodegradable plastics, and provides a method for efficiently and low-costly processing carbon dioxide / epoxide copolymer through a water vapor condensation-stripping devolatilization-extrusion dehydration drying method, which can remove reaction monomers and solvents through condensation stripping at a lower temperature, and can low-costly prepare biodegradable carbon dioxide and aliphatic epoxy copolymer through low-temperature and low-shear extrusion dehydration, compared with the prior art, the processing temperature is low, the shear is small, the molecular weight retention rate is high, and the impurity content of the product is low; since high-energy-consumption vacuum equipment and double-screw equipment are not needed, the energy consumption and production cost can be greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of biodegradable polymer preparation, and in particular relates to a high-efficiency devolatilization process for carbon dioxide-based biodegradable plastics. Background Art

[0002] As the white pollution caused by traditional plastics becomes increasingly serious, degradable plastics are attracting more and more attention. At the same time, as the main greenhouse gas, carbon dioxide has become an important topic in terms of comprehensive utilization as environmental protection requirements increase. The synthesis of polymer materials by reacting carbon dioxide with epoxides can not only make high-value use of carbon dioxide, but also use it to replace non-degradable plastics to solve the "white pollution" problem. It is an important development direction for the future plastics industry.

[0003] The preparation of biodegradable plastics by reacting carbon dioxide with epoxides as substrates is one of the main types of biodegradable plastics in the future. At present, some products have been industrialized. The general production process adopts bulk polymerization or solution polymerization. After the polymerization, the product needs to be separated from the monomer or solvent to prepare high-purity, high-molecular-weight products. Since the reactive epoxy monomer or solvent is generally a good solvent for the polymer, the product separation is generally carried out by adding a precipitant for precipitation or direct devolatilization process.

[0004] Chinese patent CN200910172260A provides a devolatilization method for high-vacuum thin-layer coating, which can devolatilize and recover solvent in a high-vacuum, enclosed space. However, due to the slow diffusion of solvents in polymer materials, trace amounts of solvent and byproducts must be removed under extremely high vacuum, resulting in high equipment investment and energy consumption. Furthermore, high temperatures can easily cause polymer decomposition reactions, making byproduct production difficult to control. Chinese patent application No. 201410231194.6 provides a method for preparing carbon dioxide / propylene oxide copolymers via a tower reactor precipitation process. The product can be directly separated from the solvent by simple filtration, resulting in low cost and high efficiency. However, due to the low solubility of the product in n-hexane or gasoline, precipitation occurs at low molecular weights, making it impossible to produce a high-molecular-weight product. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an efficient devolatilization process for carbon dioxide-based biodegradable plastics.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a high-efficiency devolatilization process for carbon dioxide-based biodegradable plastics, comprising:

[0009] Adding the polymerized carbon dioxide / epoxy monomer copolymer into a viscosity adjustment kettle, adding a solvent, and adjusting the viscosity to a suitable viscosity to obtain a viscosity-adjusted polymer slurry;

[0010] After viscosity adjustment, the polymer slurry enters the termination kettle, where terminator and stabilizer are added to obtain a uniformly mixed polymer slurry;

[0011] The uniformly mixed polymer slurry and water pass through a static / dynamic mixer or directly enter an emulsifier to form a water-in-oil or oil-in-water emulsion;

[0012] After the emulsified emulsion is mixed with the stripping gas, it enters the first coagulation kettle, where the monomer and solvent are removed under the action of temperature and dry steam stripping, and the polymer condenses and precipitates in water to form polymer particles;

[0013] The polymer particles are passed through the second and third coagulation kettles through steam stripping and different temperatures to further remove residual monomers, solvents and by-products to obtain a suspension containing polymer particles. After most of the water is removed by screening / centrifugation, the moisture inside the material is removed by extrusion to obtain a polymer.

[0014] As a preferred embodiment of the high-efficiency devolatilization process of the present invention, the carbon dioxide / epoxide copolymer is a copolymerization product of carbon dioxide and one or more of propylene oxide, butylene oxide or cyclohexene oxide.

[0015] As a preferred embodiment of the high-efficiency devolatilization process of the present invention, the solvent added to the viscosity adjustment kettle is one or more of dichloromethane, chloroform, carbon tetrachloride, diethyl carbonate, and dioxolane, and the viscosity adjustment range is 10 Pa.s to 300 Pa.s.

[0016] As a preferred embodiment of the high-efficiency devolatilization process of the present invention, the terminator is one or more of anhydride, acyl chloride or isocyanate, and the terminator accounts for 0.05% to 1% of the total amount of the polymerized carbon dioxide / epoxy monomer copolymer.

[0017] As a preferred solution of the efficient devolatilization process of the present invention, the stabilizer is one or more of polyepoxy, antioxidant, and carbodiimide, and the stabilizer accounts for 0.05% to 1% of the total amount of the carbon dioxide / epoxy monomer copolymer.

[0018] As a preferred embodiment of the efficient devolatilization process of the present invention, the particle size of the oil phase formed in the emulsification kettle is controlled to be 10 μm to 500 μm, the emulsification temperature is 50 to 100° C., and the mass ratio of polymer to water in the coagulation kettle is 1:99 to 20:80.

[0019] As a preferred solution of the high-efficiency devolatilization process of the present invention, the stripping gas is one or a combination of nitrogen, carbon dioxide, water vapor, and air.

[0020] As a preferred embodiment of the efficient devolatilization process of the present invention, the temperature of the first condensation kettle is 60-90°C, the temperature of the second condensation kettle is 80-110°C, the temperature of the third condensation kettle is 90-110°C, and the residence time of each condensation kettle is 5-30 minutes.

[0021] As a preferred solution of the high-efficiency devolatilization process of the present invention, the water content of the granular water material coming out of the third coagulation kettle is 20% to 75% after screening or centrifugation.

[0022] As a preferred solution of the high-efficiency devolatilization process of the present invention, the water content of the material after extrusion dehydration is 2% to 15%.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention provides a method for efficiently and cheaply treating a carbon dioxide / epoxide copolymer by steam stripping and devolatilization-water condensation-extrusion dehydration and drying. The method can remove residual reaction monomers and solvents by steam stripping and condensation at a relatively low temperature and combine it with low-temperature and low-shear extrusion dehydration to prepare a biodegradable carbon dioxide and aliphatic epoxy copolymer at a low cost. Compared with the prior art, the method has low processing temperature, low shear, high molecular weight retention rate, and low impurity content of the product; and since high-energy-consuming vacuum equipment and twin-screw equipment are not required, energy consumption and production costs can be greatly reduced.

[0025] (2) The present invention provides a method for treating carbon dioxide / epoxide copolymers with high efficiency and low cost by steam stripping, devolatilization, water condensation and extrusion dehydration and drying. After viscosity adjustment, the polymer slurry enters the termination kettle. If no terminator or stabilizer is added to the termination kettle, the effect is not good. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0027] Figure 1Schematic diagram of the process flow in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0031] The water content in the present invention is determined by Karl Fischer titration; M w The weight average molecular weight and PDI (molecular weight distribution) were determined by GPC using dichloromethane as the mobile phase and narrow distribution styrene as the standard. The residual solvent and monomer content of the product of the present invention were measured by gas chromatography using a hydrogen flame spectrophotometer detector (FID detector) and the external standard method to calculate the content. The by-product content in the present invention was determined by 1 The results were obtained by H-NMR spectral analysis using CDCl3 as solvent.

[0032] Example 1

[0033] This embodiment provides an efficient devolatilization process for carbon dioxide-based biodegradable plastics. The process flow diagram is shown in Figure 1 The main steps are:

[0034] (1) 2000 kg of carbon dioxide / propylene oxide copolymer slurry (solid content 52%, GPC test M) obtained by polymerization was added. w =420kg / mol, PDI=3.23) into the viscosity adjustment kettle; 1000kg of dichloromethane was added to the viscosity adjustment kettle, and the viscosity was 110Pa.s after mixing. The mixture was stirred for 30min until the material in the kettle was uniform and the viscosity was stable, and then the material was discharged to the termination kettle.

[0035] (2) Add 5 kg of phthalic anhydride, 10103 kg of antioxidant, and 1 kg of carbodiimide into the termination kettle, mix well, and discharge into the emulsification kettle;

[0036] 2500 kg of water was added to the emulsification kettle, the stirring speed was 1000 rpm, and a water-in-oil structure was formed. The emulsification temperature was 80°C, and the emulsification was carried out for 20 minutes to form a dispersed phase particle size of about 80 μm.

[0037] (3) After emulsification, the material enters the coagulation reactor at a constant rate of 1000 kg / h, 200 kg of compressed nitrogen is mixed in per hour through a static mixer, and water is added to the coagulation reactor at a flow rate of 2000 kg / h;

[0038] The temperature of the first coagulation kettle is 80°C and the residence time is 10 minutes. The temperature of the second coagulation kettle is adjusted to 85°C by steam and the residence time is 15 minutes. The temperature of the third coagulation kettle is adjusted to 95°C by steam and the residence time is 20 minutes. The gas phase of the coagulation kettle is connected to a condenser, and the solvent, monomer and by-products are recovered after gas phase condensation.

[0039] Adjust the discharge speed of the three coagulation kettles to maintain a stable liquid level in the coagulation kettles. The water content of the coagulated particles after passing through the screen is 65%.

[0040] (4) The water content of the material after extrusion dehydration is 8.5%, M w =359 kg / mol, PDI =2.95; the residual solvent, monomer, by-product content and molecular weight of the product are shown in Table 1.

[0041] Example 2

[0042] This embodiment provides an efficient devolatilization process for carbon dioxide-based biodegradable plastics, the main steps of which are:

[0043] (1) 2000 kg of carbon dioxide / cyclohexene oxide copolymer slurry (solid content 48%, GPC test M) obtained by polymerization w =372kg / mol, PDI = 2.76) into the viscosity adjustment kettle; 2000kg of dichloromethane was added to the viscosity adjustment kettle, and the viscosity after mixing was 55Pa.s. The mixture was stirred for 30min until the material in the kettle was uniform and the viscosity was stable, and then the material was discharged to the termination kettle.

[0044] (2) Add 3kg of maleic anhydride, 50351kg of antioxidant, and BASF ADR-44681.5kg is mixed evenly and discharged into the emulsification kettle;

[0045] 2000 kg of water was added to the emulsification kettle, the stirring speed was 1200 rpm, an oil-in-water structure was formed, the emulsification temperature was 90°C, and the emulsification was carried out for 30 minutes to form a dispersed phase particle size of about 30 μm.

[0046] (3) After emulsification, the material enters the coagulation reactor at a constant rate of 1000 kg / h, 300 kg of water vapor is mixed in per hour through a static mixer, and water is added to the coagulation reactor at a flow rate of 2300 kg / h at the same time;

[0047] The temperature of the first coagulation kettle is 95°C and the residence time is 5 minutes. The temperature of the second coagulation kettle is adjusted to 105°C by steam and the residence time is 10 minutes. The temperature of the third coagulation kettle is adjusted to 110°C and the residence time is 10 minutes by steam. The gas phase of the coagulation kettle is connected to a condenser, and the solvent, monomer and by-products are recovered after gas phase condensation.

[0048] Adjust the discharge speed of the three coagulation reactors to maintain a stable liquid level. After centrifugal dehydration, the particle content of the coagulated particles is 34%.

[0049] (4) After extrusion dehydration, the water content of the material was 3.6%, Mw = 335 kg / mol, PDI = 2.81; the residual solvent, monomer, by-product content and molecular weight of the product are shown in Table 1.

[0050] Example 3

[0051] This embodiment provides an efficient devolatilization process for carbon dioxide-based biodegradable plastics, the main steps of which are:

[0052] (1) 2000 kg of carbon dioxide / propylene oxide copolymer (solid content 51%, GPC test M) obtained by polymerization w =653kg / mol, PDI=4.36) into the viscosity adjustment kettle; add 1800kg of chloroform into the viscosity adjustment kettle, mix evenly and the viscosity is 250Pa.s, stir for 30min until the material in the kettle is uniform, and after the viscosity stabilizes, discharge the material into the termination kettle.

[0053] (2) Add 10 kg of tetrahydrophthalic anhydride, 50575 kg of antioxidant, and 0.5 kg of diphenylmethane diisocyanate (MDI) into the termination kettle, mix well, and discharge the mixture into the emulsification kettle;

[0054] 3000 kg of water was added to the emulsification kettle, the stirring speed was 800 rpm, and a water-in-oil structure was formed. The emulsification temperature was 90°C, and the emulsification was carried out for 30 minutes to form an oil phase particle size of about 200 μm.

[0055] (3) After emulsification, the material enters the coagulation reactor at a constant rate of 1000 kg / h, 500 kg of compressed carbon dioxide is mixed in per hour through a static mixer, and water is added to the coagulation reactor at a flow rate of 1000 kg / h at the same time;

[0056] The first coagulation kettle has a temperature of 60°C and a residence time of 20 minutes. The second coagulation kettle has a temperature of 80°C and a residence time of 30 minutes. The third coagulation kettle has a temperature of 90°C and a residence time of 15 minutes. The gas phase of the coagulation kettle is connected to a condenser, and the solvent, monomer and by-products are recovered after gas phase condensation.

[0057] Adjust the discharge speed of the three coagulation reactors to maintain a stable liquid level. The water content of the coagulated particles after passing through the screen is 69%.

[0058] (4) The water content of the material after extrusion dehydration is 13.2%, M w =593 kg / mol, PDI =2.95; the residual solvent, monomer, by-product content and molecular weight of the product are shown in Table 1.

[0059] Example 4

[0060] This embodiment provides an efficient devolatilization process for carbon dioxide-based biodegradable plastics, the main steps of which are:

[0061] (1) 2000 kg of carbon dioxide / propylene oxide / cyclohexene oxide terpolymer obtained by polymerization (solid content 44%, GPC test M w =287kg / mol, PDI=2.96) into the viscosity adjustment kettle; 2000kg of dichloromethane and 800kg of dioxolane were added to the viscosity adjustment kettle, and the viscosity after mixing was 21Pa.s. The mixture was stirred for 30min until the material in the kettle was uniform and the viscosity was stable, and then the material was discharged to the termination kettle.

[0062] (2) Add 0.5 kg of acetyl chloride and 48303 kg of antioxidant into the termination kettle, mix well and discharge into the emulsification kettle;

[0063] 3200 kg of water was added to the emulsification kettle, the stirring speed was 1200 rpm, and an oil-in-water structure was formed. The emulsification temperature was 95°C, and the emulsification was carried out for 30 minutes to form a water phase particle size of about 20 μm.

[0064] (3) After emulsification, the material enters the coagulation reactor at a constant rate of 1000 kg / h, 200 kg of water vapor is mixed in per hour through a static mixer, and water is added to the coagulation reactor at a flow rate of 1800 kg / h simultaneously;

[0065] The first coagulation kettle is at 83°C with a residence time of 10 minutes. The second coagulation kettle is adjusted to 93°C with steam and a residence time of 30 minutes. The third coagulation kettle is adjusted to 95°C with steam and a residence time of 5 minutes. The gas phase of the coagulation kettle is connected to a condenser, and the solvent, monomer and by-products are recovered after gas phase condensation.

[0066] Adjust the discharge speed of the three coagulation kettles to maintain a stable liquid level. After the coagulated particle water is centrifuged and dehydrated, the particle content is 45%.

[0067] (4) The water content of the material after extrusion dehydration is 6.3%, M w =265 kg / mol, PDI=2.88; the residual solvent, monomer, by-product content and molecular weight of the product are shown in Table 1.

[0068] Comparative Example 1

[0069] (1) 2000 kg of carbon dioxide / propylene oxide copolymer slurry (solid content 52%, GPC test M) was obtained by the same polymerization as in Example 1. w =420kg / mol, PDI=3.23) into the viscosity adjustment kettle; 1000kg of dichloromethane was added to the viscosity adjustment kettle, and the viscosity was 110Pa.s after mixing. The mixture was stirred for 30min until the material in the kettle was uniform and the viscosity was stable, and then the material was discharged to the termination kettle.

[0070] (2) No additives are added to the termination kettle;

[0071] 2500 kg of water was added to the emulsification kettle, the stirring speed was 1000 rpm, and a water-in-oil structure was formed. The emulsification temperature was 80°C and the emulsification was carried out for 20 minutes.

[0072] (3) After the emulsification is completed, the material enters the coagulation kettle at a constant rate of 1000 kg / h, 200 kg of compressed nitrogen is mixed into the coagulation kettle per hour through a static mixer, and water is simultaneously added to the coagulation kettle at a flow rate of 2000 kg / h; the coagulation kettle conditions are the same as those in Example 1.

[0073] Adjust the discharge speed of the three coagulation kettles to maintain a stable liquid level in the coagulation kettles. The water content of the coagulated particles after passing through the screen is 70%.

[0074] (4) The water content of the material after extrusion dehydration is 11.5%, M w =192 kg / mol, PDI =2.21; the content of residual solvent, monomer, by-product and their molecular weight are shown in Table 1.

[0075] Table 1

[0076]

[0077] As can be seen, the present invention provides a highly efficient and low-cost method for treating carbon dioxide / epoxide copolymers by steam stripping and devolatilization-water condensation-extrusion dehydration and drying. Residual reaction monomers and solvents can be removed by steam stripping and condensation at a relatively low temperature, combined with low-temperature, low-shear extrusion dehydration to prepare biodegradable carbon dioxide and aliphatic epoxy copolymers at a low cost. Compared with the prior art, the low treatment temperature and low shear rate result in high molecular weight retention and low product impurity content. Furthermore, since high-energy-consuming vacuum equipment and twin-screw equipment are not required, energy consumption and production costs can be significantly reduced.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. An efficient devolatilization process for carbon dioxide-based biodegradable plastics, characterized by: include, Adding the polymerized carbon dioxide / epoxy monomer copolymer to a viscosity adjustment kettle, adding a solvent, and adjusting the viscosity to 10 Pa.s to 300 Pa.s to obtain a viscosity-adjusted polymer slurry; After adjusting the viscosity, the polymer slurry enters the termination kettle, and a terminator and a stabilizer are added to the termination kettle to obtain a uniformly mixed polymer slurry, wherein the terminator is one or more of anhydride, acyl chloride or isocyanate, and the stabilizer is one or more of an antioxidant and carbodiimide; The uniformly mixed polymer slurry and water pass through a static / dynamic mixer or directly enter an emulsifier to form a water-in-oil or oil-in-water emulsion; After the emulsified emulsion is mixed with the stripping gas, it enters the first coagulation kettle, where the residual monomers and solvent are removed under the action of temperature and stripping gas, and the polymer condenses and precipitates in water to form polymer particles; The polymer particles are passed through the second and third coagulation kettles at different temperatures and pressures to further remove monomers, solvents and by-products to obtain polymer-containing particles. After most of the water is removed by screening / centrifugation, the moisture inside the material is removed by extrusion to obtain the polymer.

2. The high-efficiency devolatilization process according to claim 1, wherein: The carbon dioxide / epoxide copolymer is a copolymerization product of carbon dioxide and one or more of propylene oxide, butylene oxide or cyclohexene oxide.

3. The efficient devolatilization process according to claim 1 or 2, wherein: The solvent added to the viscosity adjusting kettle is one or more of dichloromethane, chloroform, carbon tetrachloride, diethyl carbonate and dioxolane.

4. The high-efficiency devolatilization process according to claim 1, wherein: The terminator is 0.05% to 1% of the total amount of the polymerized carbon dioxide / epoxy monomer copolymer.

5. The efficient devolatilization process according to claim 4, wherein: The stabilizer is 0.05% to 1% of the total amount of the carbon dioxide / epoxy monomer copolymer.

6. The high-efficiency devolatilization process according to claim 5, wherein: The particle size of the oil phase formed in the emulsification kettle is controlled at 10um~500um, the emulsification temperature is 50~100℃, and the mass ratio of polymer to water in the coagulation kettle is 1:99~20:

80.

7. The efficient devolatilization process according to claim 6, wherein: The stripping gas is one or a combination of nitrogen, carbon dioxide, water vapor and air.

8. The efficient devolatilization process according to claim 1, wherein: The temperature of the first coagulation kettle is 60-90° C., the temperature of the second coagulation kettle is 80-110° C., the temperature of the third coagulation kettle is 90-110° C., and the residence time of each coagulation kettle is 5-30 minutes.

9. The high-efficiency devolatilization process according to claim 8, wherein: The water content of the granular water material coming out of the third coagulation reactor is 20%~75% after screening or centrifugation.

10. The high-efficiency devolatilization process according to any one of claims 1, 2, 4 to 9, characterized in that: The moisture content of the material after extrusion dehydration is 2%~15%.

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