JPH0354684B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an improved rubbery polymer that efficiently removes catalyst residue contained in a rubbery polymer obtained by slurry polymerization in a poor solvent using a catalyst consisting of a transition metal compound and an organoaluminium compound. This relates to a method for purifying coalescence. Industrial polymerization methods for rubber-like polymers include solutions in which the copolymer is dissolved in normally liquid inert hydrocarbons such as n-pentane, n-hexane, n-heptane, cyclohexane, and toluene to carry out polymerization. There are a polymerization method and a slurry polymerization method in which polymerization is carried out in a state in which a polymer is precipitated and dispersed in a solvent that does not dissolve the polymer, but the latter has many advantages as described below. Even at high polymer concentrations, it can be handled with substantially the same low viscosity as the reaction medium, facilitating mass transfer and mixing. A small reactor volume is required per unit amount of polymer produced. Since a liquid monomer can be used as a solvent, there is no need for a solvent recovery step, as is the case with solution polymerization, and energy consumption can be significantly reduced. Among these, when producing rubber-like polymers by solution polymerization, it is usually necessary to use 10 to 20 times more solvent per unit amount of polymer, and the energy required to recover this solvent is extremely large. In slurry polymerization using polymers as a solvent, this energy can be reduced, and this advantage is industrially extremely large. Although the slurry polymerization method has many advantages as described above, it also has the following disadvantages. That is, (1) since the catalyst is included in the produced polymer particles, it is extremely difficult to remove the residue, and if a large amount remains in the polymer, it will only cause coloring of the polymer. It is known that the development of polymers is facilitated. (2) The presence of residues can also cause corrosion of metal materials such as equipment and instruments used in contact with rubbery polymers during manufacturing and processing processes. As described above, although the slurry polymerization method has many advantages, it also has the above-mentioned serious drawbacks, so that its advantages cannot be fully utilized. Therefore, it has been desired to remove catalyst residues as much as possible by slurry polymerization. In view of this situation, the present inventors conducted extensive research on a method for removing catalyst residue from a rubbery polymer obtained by slurry polymerization, and as a result, discovered an extremely efficient method and completed the present invention. . That is, in the present invention, when removing catalyst residues contained in a rubbery polymer obtained by slurry polymerization using a catalyst consisting of a transition metal compound and an organoaluminum compound, a surfactant is added to the polymer slurry liquid. and water are added and mixed to form an emulsion in which polymer particles surrounded by a slurry solvent are dispersed in water, and then a much smaller amount of polymer than that used in solution polymerization is dissolved in the emulsion. A good solvent (hereinafter sometimes simply referred to as a solvent) is added to form an emulsion in the form of oil-in-water droplets in which droplets of the polymer dissolved in the mixture of the slurry solvent and the solvent are finely dispersed in water; The present invention provides an efficient method for purifying a rubbery polymer, which is characterized in that the catalyst residue is extracted and removed from the droplets in water. The present invention will be explained in detail below. Transition metal compounds used as polymerization catalysts for rubbery polymers include, for example, nickel, cobalt, vanadium,
Compounds such as niobium, tungsten, titanium, rhodium, molybdenum, and zirconium are known. Known organoaluminum compounds include, for example, trialkylaluminum, dialkylaluminum monochloride, alkylaluminum sesquichloride, alkylaluminum dichloride, and the like. Rubbery polymers include polybutadiene, polyisoprene, ethylene-α-olefin copolymers (including ethylene-α-olefin copolymers and ethylene-α-olefin-nonconjugated diene copolymers, hereinafter abbreviated as EPDM). ) etc. In particular, EPDM is strongly required to sufficiently remove catalyst residues in order to ensure its good weather resistance and heat resistance, which are its physical characteristics. In the case of EPDM, as the transition metal compound, vanadium oxytrichloride, vanadium tetrachloride, alcohol (carbon number 1 to 12) modified products of these, or vanadium compounds such as vanadium triacetylacetonate and oxyvanadium diacetylacetonate are used. Generally speaking, when these vanadium compounds are used, vanadium is approximately
If more than 50 ppm remains, the polymer will be colored and lose its commercial value, so the purification method of the present invention is a particularly effective means. In addition to vanadium compounds, titanium compounds such as titanium tetrachloride and titanium trichloride can also be used. On the other hand, as the organic aluminum compound, for example, diethylaluminum monochloride, ethylaluminum sesquichloride, ethylaluminum dichloride, triethylaluminum, triisobutylaluminum, and mixtures thereof can be used. In addition, as α-olefin, propylene,
1-Butene is preferred, but 1-hexene, 4-methyl-1-pentene, 1-octene, etc. may also be used. The non-conjugated diene that is the third component of EPDM is a linear or cyclic diene or polyene, such as 5-methylene-2-norbornene,
5-ethylidene-2-norbornene (ENB), 5
-Propylidene-2-norbornene, dicyclopentadiene (DCP), 1,4-hexadiene, 5
-isopropenyl-2-norbornene and the like, among which ENB and DCP are preferred. In addition, as a poor solvent for EPDM slurry polymerization, propylene, 1-butene, halogenated hydrocarbons such as methylene dichloride, methylene dibromide, and ethyl chloride, which do not substantially dissolve EPDM, or those that do not dissolve EPDM There are mixtures of solvents and small amounts of solvents, but as mentioned above, propylene, which is a volatile reactive monomer, 1
- Preference is given to using butene. Next, a method for removing catalyst residue according to the present invention will be explained. After carrying out a copolymerization reaction using the catalyst, monomer, and solvent described above, in the first step, water is added and mixed to the polymerization slurry in the presence of a surfactant to form an emulsion. As the surfactant used in this case, for example, nonionic surfactants of the polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenyl ether type, sorbitan ester type, and polyoxyethylene sorbitan ester type are preferable, but cationic surfactants are preferred. , anionic and amphoteric surfactants may be used in combination. The surfactant may be made into an aqueous solution in advance and added to the rubbery polymer slurry liquid discharged from the polymerization reactor, or it may be added separately from water.
In either method, it is necessary to mix the surfactant, water, and polymerization slurry vigorously to form an emulsion. The amount of surfactant used is usually about 0.01 to 0.3 weight percent based on water. On the other hand, the amount of water to be added may be such that when the solvent is added in the second step, water becomes a continuous phase and an oil-in-water emulsion is formed. Quantitatively, it is preferable to add 0.4 to 2.0 parts by weight per 1.0 parts by volume of the poor solvent used in slurry polymerization and the solvent added in the second stage. Next, in the second step, a solvent is added to the emulsion to form an oil-in-water emulsion, but in order to dissolve the rubbery polymer,
The solvent to be added must be substantially insoluble in water, and solvents such as n-hexane, n-octane, n-nonane, cyclohexane, toluene, methylcyclopentane, benzene, xylene, and ethylbenzene can be used. The amount of these solvents added needs to be such that the rubber-like polymer can be dissolved in a state where the solvent is mixed with the slurry solvent contained in the oil droplets of the oil-in-water emulsion. That is, when the rubbery polymer is EPDM, in order to dissolve it, the solubility parameter (hereinafter abbreviated as S/P value) of the mixture of the slurry solvent and the solvent is required.
It is more preferable that the value is 6.8 or more. When the slurry solvent is propylene and cyclohexane is used as the additive solvent, for 1 part of propylene,
If 0.5 part is added, the S/P value of these mixtures will be 6.8
Therefore, it is suitable for dissolving EPDM. Note that the preferred S/P value for dissolving the rubbery polymer will vary depending on the type of rubbery polymer. Note that the S/P values referred to in the present invention are values at 25°C, and the S/P values of typical solvents (agents) are as follows. Propylene...6.1, Butene...6.7, n-hexane...7.2, n-octane...7.5, n-nonane...7.6, cyclohexane...8.2, toluene...8.9, benzene...9.2, ethylbenzene...8.8 Further, the S/P value of a liquid mixture is generally expressed as the arithmetic mean of the S/P values based on the volume fraction of each component. The type of solvent should be determined based on recovery in later processes.
It is preferable to use a solvent that can dissolve the rubbery polymer in a small amount and has a relatively low boiling point. Among the above-mentioned good solvents, cyclohexane and toluene are preferably used. Next, the temperature at which an oil-in-water emulsion is formed and the catalyst residue is removed is preferably 10 to 70°C; below this range, the viscosity of the droplets will increase significantly, and above this range, the surface activity will increase. This is not preferred because the effect of the agent is significantly reduced. In addition, the oil-in-water type emulsified state can be maintained for about 10 minutes or more, preferably 20 minutes by stirring.
A good result can be obtained by maintaining it for ~120 minutes. To summarize the features of the rubber-like polymer purification method according to the present invention explained above, the slurry liquid after the polymerization reaction is kept in an emulsified state in advance. Next, a small amount of solvent is added to the emulsion containing the slurry solvent to form an oil-in-water emulsion, and the catalyst is removed. The following effects can be obtained by the method of the present invention. By keeping the slurry liquid in an emulsified state in advance,
In the oil-in-water emulsion formed in the next step, oil droplets can be finely dispersed in water. In other words, the polymer particles discharged from the polymerization reactor are extremely small, so by emulsifying them in advance, they can maintain this microscopic state, and when a solvent is added,
The morphology changes into minute oil droplets, which promotes mass transfer and allows the catalyst to be easily extracted into the aqueous phase. On the other hand, if a method is used in which a solvent is added prior to emulsification, an oil-in-water emulsion will be formed after passing through a high viscosity state, which will prevent the oil droplets from being minutely dispersed and ensure sufficient catalyst extraction. Obstructed and undesirable. Note that when the slurry liquid is emulsified, the state is such that fine particles of the polymer surrounded by the slurry solvent are dispersed in water. Since the polymerization reaction is in a slurry state and the catalyst removal is in an oil-in-water type emulsified state, operations such as stirring and transfer can be performed while maintaining a low viscosity state from polymerization to catalyst removal. On the other hand, if a solvent is added prior to emulsification, stirring and mixing operations are required in a highly viscous state, which is undesirable in terms of energy consumption. Since a good solvent is added to a state where a slurry solvent, which is a poor solvent that does not dissolve the polymer, is present, a solvent that is relatively similar to a poor solvent that can dissolve the polymer is generated, resulting in the formation of a polymer. The viscosity of the oil droplets in the solution is reduced and mass transfer is promoted. When a solvent is added to an emulsified slurry liquid, the solvent is rapidly incorporated into the slurry solvent, so that the polymer can be dissolved in a short time and oil droplets can be formed. Another method to make oil droplets is to emulsify the solvent with water and add it to the slurry liquid, but this method requires a long time to dissolve the polymer, as shown in the examples below. Undesirable. Forming a mixed solvent that dissolves a polymer with a slurry solvent and a solvent means, in other words, that the slurry solvent can be used as a solvent, and therefore, the amount of newly added solvent can be reduced. Specifically, EPDM is slurry polymerized using propylene as a solvent,
When comparing the amount of solvent used per unit weight of EPDM, which is a polymer, when cyclohexane is used as a solvent for dissolving the polymer and when EPDM is produced by solution polymerization, the ratio by weight of the latter is 10 to 20. On the other hand, the former has a much lower weight ratio of 1.5 to 3, which makes the catalyst removal method of the present invention advantageous. In addition, if a polymerization terminator is added to the polymerization slurry before adding water to form an emulsion,
The present inventors have also discovered that even higher catalyst removal effects can be obtained, and this method also
It is within the scope of the present invention. in this case,
Polymerization terminators that can be suitably used include polyethylene glycol alkyl ester derivative compounds;

[Formula] A structure having a group (R is a _C1 to _C20 alkyl group, n is an integer of 3 to 200), such as polyoxyethylene monoalkylate, polyoxyethylene sorbitate tetraoleate, polyoxy Examples include ethylene sorbitan trialkylate and polyoxyethylene dialkylate, among which polyoxyethylene sorbitate tetraoleate is particularly preferred. The amount of these compounds added is 0.5 to 10 times the weight of the transition metal compound as a polymerization catalyst, preferably 1 to 10 times the weight of the transition metal compound as a polymerization catalyst.
It is 5 times the weight. Also, by removing part of the slurry solvent before or at the same time as adding the solvent,
Substantially lower amounts of solvent can be added and this method is also within the scope of the present invention. Further, in order to shorten the extraction time of the catalyst residue and the dissolution time of the polymer, an emulsifier or a crusher which applies high shear force can be appropriately arranged and used. EXAMPLES Next, the present invention will be specifically explained using Examples, but the present invention is not limited to the Examples in any way. In addition, in the examples, the amount of catalyst residue was measured by atomic absorption spectrometry. Example 1 1.5 times the mole of dehydrated and dried n-butyl alcohol was gradually added to vanadium oxytrichloride at room temperature to produce ethylene and propylene in liquid propylene in the presence of the modified vanadium compound and diethylaluminium chloride. and ENB to a propylene slurry of EPDM obtained by copolymerizing 1 part of liquid propylene,
One part of a 0.08 weight percent aqueous solution of the surfactant polyoxyethylene nonyl phenyl ether (trade name, Neugen EA-80) was stirred vigorously (approx.
1000 rpm) to form an emulsion and stirring was maintained for 10 minutes. This emulsion contained propylene and EPDM particles finely dispersed in water. Next, 0.6 parts of cyclohexane (a mixed solvent of S and P) was added to the emulsion to 1 part of liquid propylene.
6.9) and was stirred vigorously (approximately 1000 rpm) while maintaining the temperature at 30-35°C. After stirring for 60 minutes, it was confirmed that the EPDM had dissolved and was finely dispersed as droplets in the water, and the stirring was stopped. After stopping stirring, let this emulsion stand for about 1 hour.
It was separated into an EPDM solution and water containing a surfactant. Table 1 shows the analysis results of EPDM obtained by removing the solvent and drying the EPDM solution separated from water by well-known steam stripping.
Shown below. The polymerization temperature was 33℃, and the catalyst yield was 446g−
EPDM/g-Al2720g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 31% by weight. Example 2 A propylene slurry of EPDM obtained by copolymerizing a vanadium compound as vanadium oxytrichloride in liquid propylene in the same manner as in Example 1 was added with the same surface activity as in Example 1 for 1 part of liquid propylene. 1.5 parts of a 0.10 weight percent aqueous solution of the agent was slowly added with vigorous stirring (approximately 1000 rpm) to form an emulsion and stirring was maintained for 10 minutes. Next, 0.4 parts of toluene (S/P value of mixed solvent 6.9) per 1 part of liquid propylene was added to the emulsion, and the mixture was vigorously stirred (approximately 1000 rpm) for 60 minutes while maintaining the temperature at 30 to 35°C. I went. The subsequent operations were carried out in the same manner as in Example 1, and the analysis results of the obtained polymer are shown in Table 1. The polymerization temperature was 27℃ and the catalyst yield was 571g−
The EPDM/g-Al was 3220 g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 34 weight percent. Example 3 Obtained by copolymerization under the same setting conditions as Example 1
Half of the liquid propylene solvent was added to the EPDM propylene slurry by heating it in a jacket for 30 minutes.
It was removed by evaporation while maintaining at ~35°C. Next, the same surfactant as in Example 1 was added to 1 part of the liquid propylene of the EPDM slurry that remained without evaporation.
1.5 parts of the 0.08 weight percent aqueous solution was added and stirred vigorously to form an emulsion and stirring was maintained for 10 minutes. Next, to this emulsion, 0.5 parts of cyclohexane (a mixed solvent of S and P) was added to 1 part of liquid propylene.
value 6.8) and keeping the temperature at 30-35℃.
Vigorous stirring was performed for 60 minutes. The subsequent operations were the same as in Example 1. The analysis results of the obtained polymer are shown in Table-1. The polymerization temperature was 30℃ and the catalyst yield was 481g−
EPDM/g-Al, 2930 g-EPDM/g-V, and the EPDM concentration in the liquid propylene was 34 weight percent before half of the propylene was removed.
Since 1/2 of the liquid propylene, which is the slurry solvent, has been evaporated, the amount of cyclohexane added to achieve the S/P value that dissolves EPDM can be reduced to 1/2, and as shown in Table 1, the amount of cyclohexane added can be reduced to 1/2. The catalyst residue inside could be reduced to the same level as in Examples 1 and 2. Example 4 Obtained by copolymerization under the same setting conditions as Example 1
To the propylene slurry of EPDM, polyoxyethylene sorbitate tetraoleate (trade name, Rheodol) was added as a polymerization terminator by 2.5 times the weight of the vanadium compound used in the copolymerization, and the mixture was stirred for 5 minutes. Next, the slurry was emulsified, EPDM was dissolved, droplets were formed, the catalyst residue was extracted, the solvent was removed, and the polymer was dried in the same manner as in Example 1, and the polymer was analyzed. The analysis results are shown in Table-1. The polymerization temperature was 33℃ and the catalyst yield was 398g−
The EPDM/g-Al was 2515 g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 29 weight percent. Comparative Example 1 Obtained by copolymerization under the same setting conditions as Example 1.
As in Example 1, 1 part by weight of a 0.08 weight percent aqueous solution of surfactant polyoxyethylene nonyl phenyl ether is added to 1 part of liquid propylene to the propylene slurry of EPDM to form an emulsion, and the temperature is raised to 30 to 35. The mixture was vigorously stirred (approximately 1000 rpm) for 2 hours while maintaining the temperature at °C. Stirring was then stopped, the entire amount of liquid propylene was evaporated off, and the mixture was allowed to stand for 1 hour to separate the polymer and water. EPDM, which had been separated from water in this manner, was dried by steam stripping to remove a very small amount of propylene and the solvent for diluting the catalyst. Table 1 shows the analysis results of the obtained EPDM. The polymerization temperature was 33℃ and the catalyst yield was 415g−
EPDM/g-Al, 2620 g-EPDM/g-V, and the EPDM concentration in the polymerization solution was 30 weight percent. Comparative Example 2 Obtained by copolymerization under the same setting conditions as Example 1.
0.6 parts of cyclohexane was added to 1 part of liquid propylene to the propylene slurry of EPDM, and the mixture was stirred for about 1 hour while maintaining the temperature at 30 to 35°C. Approximately 1
After a period of time, the state was a highly viscous homogeneous solution in which EPDM was completely dissolved. Then, a 0.08 weight percent aqueous solution of the same surfactant as in Example 1 was added to 1 part of liquid propylene.
The mixture was stirred vigorously (approximately 1000 rpm) for 60 minutes while maintaining the temperature at 30-35°C. The subsequent operations were the same as in Example 1. The analysis results of the obtained polymer are shown in Table-1. The polymerization temperature was 33℃ and the catalyst yield was 498g−
EPDM/g-Al, 3026 g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 33 weight percent. Comparative Example 3 The amount of cyclohexane added was reduced to 0.3 parts per 1 part of liquid propylene (the S/P value of the mixed solvent was
6.6), and other conditions were the same as in Example 1 for polymerization and catalyst residue removal. When the emulsion was collected and observed 60 minutes after the addition of cyclohexane, it was found that the oil droplets were finely dispersed in the water, but the EPDM was not dissolved in each oil droplet and was in a swollen state. The polymerization temperature was 33℃ and the catalyst yield was 465g−
The EPDM/g-Al was 2910 g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 32 weight percent. Comparative Example 4 Obtained by copolymerization under the same setting conditions as Example 1.
Add a pre-prepared emulsion of water and cyclohexane to the EPDM propylene slurry and bring the temperature to 30°C.
Stir vigorously for 60 min while maintaining ~35°C (approx.
1000rpm) and leave it for about 1 hour.
The solution and water were separated. The EPDM solution separated from the water in this manner was collected and observed. Although a portion of the EPDM had been dissolved, a large amount of undissolved EPDM remained. The above emulsion of water and cyclohexane is a 0.08 weight percent aqueous solution of the surfactant used in Example 1.
It was prepared by adding 0.6 parts of cyclohexane to 1 part of cyclohexane and stirring vigorously. The amount of the emulsion of water and cyclohexane added was 1.6 parts per part of liquid propylene. The polymerization temperature was 35℃ and the catalyst yield was 362g−
The EPDM/g-Al was 2320 g-EPDM/g-V, and the EPDM concentration in the polymerization slurry was 26 percent by weight.

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Claims (1)

[Scope of Claims] 1. When removing catalyst residues contained in a rubbery polymer obtained by slurry polymerization in a poor solvent using a catalyst consisting of a transition metal compound and an organoaluminum compound, in the first step, the polymer is removed. After preliminarily forming an emulsion by mixing a surfactant and water with the combined slurry, a good solvent for the polymer is added to the emulsion in a second step to form an oil-in-water emulsion. 1. A method for purifying a rubbery polymer, which comprises extracting a catalyst residue into an aqueous phase. 2. Claims in which the surfactant is a nonionic surfactant selected from polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenyl ether type, sorbitan ester type, and polyoxyethylene sorbitan ester type surfactants. Purification method according to item 1. 3. The purification method according to claim 1, wherein the good solvent is cyclohexane and/or toluene.