阅读说明：本技术 从聚碳酸亚烷基酯聚合溶液中分离有机锌催化剂的方法 (Method for separating organic zinc catalyst from polyalkylene carbonate polymerization solution ) 是由 闵庚玟 朴胜莹 金成庚 申相哲 金元硕 禹圆熙 于 2020-09-28 设计创作，主要内容包括：本发明涉及从聚碳酸亚烷基酯聚合溶液中分离有机锌催化剂的方法,并且本发明的方法包括：搅拌包含聚碳酸亚烷基酯树脂、有机锌催化剂、环氧烷和聚合溶剂的聚合溶液并使其老化；以及在完成老化后,过滤聚合溶液。(The present invention relates to a method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution, and the method of the present invention includes: stirring and aging a polymerization solution containing a polyalkylene carbonate resin, an organozinc catalyst, an alkylene oxide, and a polymerization solvent; and filtering the polymerization solution after the aging is completed.)

1. A method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution, the method comprising:

stirring and aging a polymerization solution containing a polyalkylene carbonate resin, an organozinc catalyst, an alkylene oxide, and a polymerization solvent; and

after the aging is completed, the polymerization solution is filtered.

2. The method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, wherein the aging is performed at a temperature ranging from 10 ℃ to 70 ℃.

3. The method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, wherein the aging is performed for 12 hours or more.

4. The method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, wherein polyalkylene glycol is polymerized at the surface of the organozinc catalyst during aging.

5. The method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, wherein the polymerization solution after completion of aging is phase-separated into an upper layer part including the polyalkylene carbonate resin and the solvent and a lower layer part including polyalkylene glycol and the catalyst.

6. The method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, further comprising injecting a flocculant after aging and before filtering.

7. The method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 6, wherein the flocculant is a solid-phase flocculant.

8. The method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 7, wherein the flocculant is one or more selected from the group consisting of Polymethylmethacrylate (PMMA), polymethylmethacrylate copolymers, cellulose, silica, diatomaceous earth, activated carbon, guar gum, alumina, aluminum hydroxide, sodium chloride, sodium sulfate, calcium chloride, and magnesium sulfate.

9. The method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 6, wherein the flocculant is injected into the polymerization solution in an amount of 0.01-10 wt%.

10. The method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution according to claim 1, further comprising centrifuging the polymerization solution after finishing the aging and before the filtering.

Technical Field

[ Cross-reference to related applications ]

This application claims benefit based on priority of korean patent application No. 10-2019-0120841, filed on 30.9.9.2019, the entire contents of which are incorporated herein by reference.

Technical Field

The present invention relates to a method for separating an organozinc catalyst from a polyalkylene carbonate polymerization solution. More particularly, the present invention relates to a method of easily separating an organozinc catalyst by changing the composition of a polyalkylene carbonate polymerization solution.

Background

The polyalkylene carbonate resin is prepared by Ethylene Oxide (EO) and CO₂Biodegradable resins prepared by polymerization in the presence of a catalyst.

As a catalyst for preparing the polyalkylene carbonate resin, an organozinc catalyst of a combination of zinc and dicarboxylic acid, such as a zinc glutarate catalyst, is mainly used.

However, since the organozinc catalyst is uniformly dispersed in the polymerization solution after completion of polymerization, it is difficult to separate the organozinc catalyst from the polyalkylene carbonate polymerization solution. The organozinc catalyst is agglomerated before polymerizing the polyalkylene carbonate, but as the polymerization proceeds, the viscosity increases, the shear stress increases, the organozinc catalyst is dispersed into fine particles, and the polyalkylene carbonate remains on the surface of the catalyst after the polymerization to be emulsified and dispersed in the polymerization solution. Therefore, it is difficult to separate the organozinc catalyst in the polyalkylene carbonate polymerization solution by using a filter such as a metal filter, a polypropylene fiber filter, a cellulose filter paper, or a centrifugal separation method, which is generally used in the removal process of the heterogeneous catalyst.

In order to separate the organozinc catalyst uniformly dispersed in the solution phase, a method of separating the organozinc catalyst by applying silica, a compatible flocculant, and other solvents has been proposed, but there is a limitation that the catalyst particle separation efficiency is poor and causes contamination or decomposition of the finally produced polyalkylene carbonate.

Disclosure of Invention

Technical problem

The present invention has been devised to solve the above-mentioned problems, and provides a method of efficiently separating an organozinc catalyst dispersed in a polyalkylene carbonate polymerization solution.

Technical scheme

In order to solve these problems, the present invention provides a method of separating an organozinc catalyst from a polyalkylene carbonate polymerization solution, the method comprising: stirring and aging a polymerization solution containing a polyalkylene carbonate resin, an organozinc catalyst, an alkylene oxide, and a polymerization solvent; and filtering the polymerization solution after the aging is completed.

Advantageous effects

In the method of separating an organozinc catalyst of the present invention, after the polymerization of the polyalkylene carbonate resin is completed, an aging step is performed by stirring the polymerization solution. In the case where the aging process is carried out as in the present invention, the unreacted alkylene oxide monomer in the polymerization solution is polymerized into polyalkylene glycol at the surface of the organozinc catalyst. Therefore, when the aging treatment is performed, the surface of the organozinc catalyst is changed from a polyalkylene carbonate-based surface to a polyalkylene glycol-based surface, and the catalyst containing polyalkylene glycol is precipitated at the bottom of the polymerization solution, and as a result, phase separation occurs into an upper layer portion containing a polyalkylene carbonate resin and a solvent and a lower layer portion containing polyalkylene glycol and a catalyst. According to the method of the present invention, a polymerization solution phase-separated into an organozinc catalyst and a polyalkylene carbonate resin may be obtained, and the organozinc catalyst may be easily separated by filtration.

Meanwhile, in the case where a step of injecting a flocculant is additionally performed after the aging step, the organozinc catalyst is coagulated, and phase separation is promoted, thereby further improving the separation efficiency of the organozinc catalyst.

In addition, in the case of separating the organozinc catalyst according to the method of the present invention, the catalyst can be separated into a chemically unchanged state, and there are advantages in that it can be regenerated and the polymerization solution can be reused without separation.

Drawings

Fig. 1 is a photographic image showing the states of the polymerization solutions obtained from example 1 and comparative example 1.

Fig. 2 is a photographic image showing the state of the filtered solutions obtained by filtering the polymerization solutions of example 1 and comparative example 1.

FIG. 3 is a photographic image showing the states of the polymerization solutions obtained in examples 1 to 6.

FIG. 4 is a photographic image showing the states of the polymerization solutions obtained in comparative examples 1 to 5.

Detailed Description

It will be understood that the words or terms used in the specification and claims of this invention should not be construed as meaning defined in commonly used dictionaries. It will be further understood that the words or terms should be interpreted as having a meaning that is consistent with the meaning of the technical idea of the present invention, based on the principle that the inventor can appropriately define the meaning of the words or terms in order to best explain the present invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular is intended to include the plural unless the context clearly dictates otherwise.

It will be further understood that the terms "comprises," "comprising," "has," "having," and the like, when used in this specification, specify the presence of stated features, integers, steps, elements, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, elements, or groups thereof.

Hereinafter, the present invention will be explained in more detail.

The present invention relates to a method for separating an organozinc catalyst from a polymerization solution for preparing a polyalkylene carbonate resin, and the method of the present invention includes (1) a step of stirring and aging a polymerization solution containing a polyalkylene carbonate resin and an organozinc catalyst, and (2) a step of filtering the polymerization solution after completion of aging.

The present inventors found that, if an aging process is performed after the polymerization of the polyalkylene carbonate resin is completed, unreacted alkylene oxide monomer remaining in a polymerization solution of the polyalkylene carbonate resin is also polymerized at the surface of an organozinc catalyst to form polyalkylene glycol during the aging process, and thus, the organozinc catalyst is precipitated to cause phase separation, and the polyalkylene carbonate resin and the organozinc catalyst can be easily separated, thereby completing the present invention.

In the present invention, the polymerization solution is used after completing the polymerization of the polyalkylene carbonate resin and removing CO₂Followed by a solution and comprising a polyalkylene carbonate resin, an organozinc catalyst, unreacted reactants of alkylene oxide, and a polymerization solvent. In addition, in the polymerization solution, a polyalkylene glycol may be included as a reaction by-product.

Generally, the conversion of alkylene oxide reactants to polyalkylene carbonate during the preparation of polyethylene carbonate resins is at a level of 40-60%. Therefore, in the polymerization solution, unreacted alkylene oxide monomer is present in addition to the polyalkylene carbonate resin as a product and the organozinc catalyst as a catalyst. In this case, the alkylene oxide monomer may be, for example, an alkylene oxide having 2 to 20 carbon atoms, particularly ethylene oxide, propylene oxide, butylene oxide, pentane oxide, hexane oxide, octane oxide, decane oxide, dodecene oxide, tetradecene oxide, hexadecene oxide, octadecene oxide, butadiene monoxide, 1, 2-epoxy-7-octene, epihalohydrin, epichlorohydrin, epibromohydrin, isopropyl glycidyl ether, butyl glycidyl ether, tert-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, or the like.

Meanwhile, the organic zinc catalyst may be an organic zinc catalyst used in the art for polymerizing polyalkylene carbonate resins, for example, a compound based on zinc dicarboxylate. In particular, the zinc dicarboxylate-based compound may include a zinc salt of an aliphatic dicarboxylic acid salt having 3 to 20 carbon atoms or a zinc salt of an aromatic dicarboxylic acid salt having 8 to 40 carbon atoms. The aliphatic carboxylic acid salt having 3 to 20 carbon atoms may be, for example, glutarate, malonate, succinate or adipate, and the aromatic dicarboxylic acid salt having 8 to 40 carbon atoms may be, for example, terephthalate, isophthalate, homophthalate or phenyl glutarate, without limitation. The organozinc catalyst may be particularly preferably zinc glutarate in view of its activity.

The organozinc catalyst may include particles having an average particle size of 0.5 μm or less and a standard deviation of particle size of 0.04 μm or less. In particular, the organozinc catalyst may have a uniform particle shape with an average particle size of 0.5 μm or less, or 0.1 to 0.4 μm, or 0.2 to 0.4 μm, and a standard deviation of the particle size of 0.04 μm or less, or 0.01 to 0.03 μm. .

As described above, since the organozinc catalyst has a minute and uniform particle diameter, the surface area of the organozinc catalyst may be 1.8m²More than g, or 1.8 to 2.5m²(ii) in terms of/g. As a result, the contact area of the organozinc catalyst with the reactant may increase during the preparation of the polyalkylene carbonate resin, and may exhibit improved activity.

Meanwhile, as the polymerization solvent, a polymerization solvent used for polymerizing polyalkylene carbonate in the art may be used without limitation. For example, the polymerization solvent may be dichloromethane, dichloroethane, trichloroethane, tetrachloroethane, chloroform, acetonitrile, propionitrile, dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, nitromethane, 1, 4-dioxane, 1, 3-dioxolane, hexane, toluene, tetrahydrofuran, methyl ethyl ketone, methyl aminoketone, methyl isobutyl ketone, acetone, cyclohexanone, trichloroethylene, methyl acetate, vinyl acetate, ethyl acetate, propyl acetate, butyrolactone, caprolactone, nitropropane, benzene, styrene, xylene, and propylene glycol monomethyl ether, or a mixture of two or more thereof, without limitation.

In the above polyalkylene carbonate resin polymerization solution, the organozinc catalyst and the polyalkylene carbonate resin exist in a uniformly dispersed type, and are not easily separated. Therefore, in the present invention, in order to separate the organozinc catalyst from the polymerization solution, after the polymerization of the polyalkylene carbonate is completed, an aging step is performed for a certain time while the polymerization solution is stirred. The aging step may be performed at a temperature ranging from 10 ℃ to 70 ℃, and the aging time may be 12 hours or more, preferably about 12 hours to 144 hours. If the aging temperature and time satisfy the above ranges, the polymerization reaction of the polyalkylene glycol on the surface of the organozinc catalyst can be smoothly performed, and the phase separation of the organozinc catalyst and the polyalkylene carbonate can be well achieved.

If the aging process is performed as described above, the unreacted alkylene oxide monomer remaining in the polymerization solution is polymerized at the surface of the organozinc catalyst to form polyalkylene glycol. By this additional polymerization reaction, the surface composition of the organozinc catalyst is changed from mainly polyalkylene carbonate to mainly polyalkylene glycol, and as the amount of polyalkylene glycol formed on the surface of the catalyst increases, the polyalkylene glycol and the organozinc catalyst are agglomerated and precipitated, thereby causing phase separation. Therefore, the polymerization solution after completion of aging can be separated into an upper layer part containing the polyalkylene carbonate resin and the polymerization solvent and a lower layer part containing the polyalkylene glycol and the catalyst.

Meanwhile, although not necessary, in the method of the present invention, a step of injecting a flocculant after the aging step and before the filtering step may be additionally performed as necessary, which will be described later. In the case where the step of injecting the flocculant is separately performed, the organozinc catalyst can be coagulated, the phase separation of the polymerization solution can be promoted, and the separation efficiency of the catalyst can be further improved.

In this case, as the flocculant, a solid flocculant can be preferably used, and for example, polymethyl methacrylate (PMMA), polymethyl methacrylate copolymer, cellulose, silica, diatomaceous earth, activated carbon, guar gum, alumina, aluminum hydroxide, sodium chloride, sodium sulfate, calcium chloride, magnesium sulfate, or the like can be used without limitation.

Preferably, polymethyl methacrylate is used as the flocculant, in which case the polymethyl methacrylate may have a weight average molecular weight (Mw) of 50,000g/mol to 200,000g/mol, preferably 70,000g/mol to 150,000g/mol, more preferably 90,000g/mol to 100,000g/mol, and a melt index (MI, measurement conditions: 230 ℃, load of 3.8kg) of 10g/10min to 30g/10min, preferably 15g/10min to 25g/10 min.

In addition, the flocculant may be injected in the polymerization solution in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, more preferably 0.1 to 2% by weight. If the amount of the flocculant is too small, the separation efficiency of the catalyst is not significant, and if the amount of the flocculant is too large, an additional process for separating the flocculant is required and the process efficiency may be reduced.

In addition, the method of the present invention may further include a step of performing centrifugation of the polymerization solution before the filtration step, as will be described later, if necessary.

The centrifugal separation is for promoting the phase separation of the polymerization solution, and may be performed, for example, at a relative centrifugal force of 100G to 50,000G, or 1,000G to 30,000G, or 2,000G to 20,000G for 0.1 minute to 10 minutes, or 0.1 minute to 5 minutes. The relative centrifugal force is a value in the case where the centrifugal force is represented by a ratio with respect to the gravity of the earth, and may represent a force applied during centrifugal separation. If the relative centrifugal force is too small and less than 100G, or if the time for performing centrifugal separation is too short and less than 0.1 minute, the agglomeration effect of the organozinc catalyst particles may be reduced.

Examples of the specific method for performing centrifugation are not particularly limited, and various centrifugation apparatuses widely used in the art may be used without limitation.

If a phase-separated polymerization solution is obtained by the above method, the polymerization solution is filtered to separate the organozinc catalyst from the polyalkylene carbonate resin polymerization solution. In this case, the filtration may be performed by using a filtration method commonly used in the art, by using a filter such as a polypropylene fabric filter and a cellulose filter paper, and the method is not particularly limited.

According to the method of the present invention, the polyalkylene glycol and the organic zinc catalyst formed on the surface of the catalyst by the aging step are mostly coagulated and precipitated and move toward the lower layer portion of the polymerization solution, while the polyalkylene carbonate resin and the polymerization solvent remain in the upper layer portion of the polymerization solution. In case a flocculant injection and/or centrifugation step is performed, this phase separation may be further facilitated.

According to the method of the present invention as described above, the polyalkylene carbonate resin and the organozinc catalyst exist in a separated state by phase separation, and the organozinc catalyst can be easily separated by filtration.

Modes for carrying out the invention

Hereinafter, the present invention will be specifically explained by specific embodiments.

Example 1

Carbon dioxide and ethylene oxide are polymerized in the presence of an organozinc catalyst to synthesize a polyalkylene carbonate resin solution.

Then, carbon dioxide was removed from the polymerization reactor, and the polyalkylene carbonate resin including the solvent, the polyalkylene carbonate resin, the organic zinc catalyst, etc. was additionally aged for one additional day while being stirred at 25 ℃.

Comparative example 1

A polyalkylene carbonate resin polymerization solution containing a solvent, a polyalkylene carbonate resin, and an organic zinc catalyst was obtained by the same method as example 1, except that the aging treatment was not performed.

Experimental example 1

The state of the polymerization solutions obtained according to comparative example 1 and example 1 was visually checked. In fig. 1, photographic images showing the states of the polymerization solutions of comparative example 1 and example 1 are shown. As shown in fig. 1, in the solution of comparative example 1 which was not subjected to the aging treatment, the components were uniformly dispersed without phase separation, but in contrast, in the solution of example 1 which was subjected to the aging treatment, phase separation was exhibited.

In addition, in order to confirm the composition, NMR analyses were performed on samples of the upper layer solution and the lower layer solution taken from the polymerization solution of comparative example 1 and the polymerization solution of example 1. The analysis results are shown in the following [ Table 1 ].

[ Table 1]

And (3) PEC: polyethylene carbonate, PEG: polyethylene glycol

As shown in [ table 1], it can be confirmed that the polymerization solution of example 1 subjected to the aging treatment showed a high polyethylene glycol content as compared to comparative example 1, indicating that polyethylene glycol was additionally polymerized by the aging process.

In addition, it was confirmed that polyethylene carbonate was present as a main component in the upper layer solution of the polymerization solution of example 1, and polyethylene glycol was present as a main component in the lower layer solution.

Experimental example 2

A filter pad of cellulose material was installed in a filter press and the polymerization solutions of comparative example 1 and example 1 were passed therethrough to perform a filtration experiment. The polymerization solution was injected under a pressure of 7 bar, and the filtered solution was put into a glass vial to compare transparency. In fig. 2, a photographic image showing the state of the solution after filtration and put into a glass vial is shown. As shown in fig. 2, it can be confirmed that the solution of example 1 was transparent after filtration, but the solution of comparative example 1 was opaque after filtration because the organozinc catalyst was not separated but remained.

In addition, in order to check the remaining amount of the catalyst in the filtered solution, the Zn metal content in the filtered solution was measured using an Inductively Coupled Plasma (ICP) apparatus. The measurement results are shown in the following [ Table 2 ].

[ Table 2]

	Zn content (ppm)
		Example 1	40
Comparative example 1	1450

As shown in table 2, the polymerization solution of example 1, which was subjected to the aging process, showed a significant decrease in the Zn content in the solution after filtration, as compared to the solution after filtration of the polymerization solution of comparative example 1, and the separation efficiency of the organozinc catalyst was very excellent according to the method of example 1.

Example 2

A polyethylene carbonate resin was prepared by the same method as example 1, and was aged. By performing NMR analysis on the composition of the polymerization solution after aging, it was found that the content of polyethylene glycol in the polymerization solution was 1.5 parts by weight based on 100 parts by weight of polyethylene carbonate.

Then, after completion of aging, 0.1% by weight of polymethyl methacrylate (melt index (MI) 23G/10min, weight average molecular weight Mw 90,000-100,000G/mol) was added as a flocculant to the polymerization solution, and centrifugation was performed at 3000G for 3 minutes in a centrifuge.

Example 3

The same procedure as in example 2 was conducted, except that 0.2% by weight of polymethyl methacrylate (melt index (MI) 23g/10min, weight average molecular weight Mw 90,000-100,000 g/mol) was added as a flocculant.

Example 4

The same procedure as in example 2 was conducted, except that 0.3% by weight of polymethyl methacrylate (melt index (MI) 23g/10min, weight average molecular weight Mw 90,000-100,000 g/mol) was added as a flocculant.

Example 5

The same procedure as in example 2 was conducted, except that 0.4% by weight of polymethyl methacrylate (melt index (MI) 23g/10min, weight average molecular weight Mw 90,000-100,000 g/mol) was added as a flocculant.

Example 6

The same procedure as in example 2 was conducted, except that 0.5% by weight of polymethyl methacrylate (melt index (MI) 23g/10min, weight average molecular weight Mw 90,000-100,000 g/mol) was added as a flocculant.

Comparative example 2

A polyethylene carbonate resin was prepared by the same method as comparative example 1. Then, 5 wt% of polyethylene glycol having a weight average molecular weight of 200G/mol was added to the polymerization solution containing the polyethylene carbonate resin, and centrifugation was performed at 3000G in a centrifuge for 3 minutes.

Comparative example 3

The same procedure as in comparative example 2 was conducted, except that polyethylene glycol having a weight average molecular weight of 600g/mol was added.

Comparative example 4

The same procedure as in comparative example 2 was conducted, except that polyethylene glycol having a weight average molecular weight of 2,000g/mol was added.

Comparative example 5

The same procedure as in comparative example 2 was conducted, except that polyethylene glycol having a weight average molecular weight of 10,000g/mol was added.

Experimental example 3

The state of the solutions obtained from examples 1 to 6 and comparative examples 1 to 5 was visually checked. In FIG. 3, photographic images showing the state of solutions of examples 1 to 6 are shown, and in FIG. 4, photographic images showing the state of solutions of comparative examples 1 to 5 are shown.

As shown in fig. 3, the solutions of examples 2 to 6 in which the flocculant was injected were higher in transparency when compared with the solution of example 1 in which the flocculant was not injected, and it was confirmed that the transparency was improved as the amount of the flocculant injected was increased. This indicates that the separation effect of the organozinc catalyst is improved by injecting the flocculant.

In contrast, as shown in FIG. 4, in comparative examples 2 to 5 in which polyethylene glycol was injected instead of being produced by the aging process, the solution was opaque as in comparative example 1, indicating that the organozinc catalyst was in a dispersed state in the polymerization solution after the centrifugal separation. That is, the separation effect of the organozinc catalyst is not achieved by the method of adding polyethylene glycol, and polyethylene glycol is not formed on the surface of the catalyst through an aging process.