JPH0359921B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for separating and recovering a rubbery polymer from a solution or suspension of a rubbery polymer in an inert solvent. More specifically, a solution or suspension of the rubbery polymer is steam-stripped in the presence of the novel dispersant to remove the solvent, the rubbery polymer is separated as an aqueous slurry, and the aqueous slurry is then steam-stripped to remove the solvent. This invention relates to a method for recovering a rubbery polymer by dehydration and drying. Various methods have been proposed for separating a rubbery polymer from a rubbery polymer solution or suspension, including a method of removing the solvent under heating and reduced pressure, and a method of introducing it into a poor solvent. After contacting the solution or suspension with steam and recovering unreacted monomers and polymerization solvent (hereinafter referred to as the steam stripping step), the substantially water-free rubbery polymer is dehydrated from the hot water slurry. , a method of recovering it through a drying process has been implemented industrially. However, the rubber-like polymer particles (crumbs) produced in the steam stripping process have the disadvantage that they coagulate with each other in the hot water slurry, forming large lumps, or adhere to the walls of the apparatus and the stirrer.
As one of the effective methods for solving this drawback in the steam stripping process, various methods have been proposed in which a dispersant is present during the steam stripping process. For example, in Japanese Patent Publication No. 37-17497, (a) zinc oxide, (b) an alkali metal salt of ligninsulfonic acid, and (c) a water-soluble polymeric substance having multiple carboxyl groups and calcium, strontium, and barium are used as dispersants. , discloses the use of metal ions such as aluminum, iron, cobalt, and nickel.
Japanese Patent Publication No. 45-8427 discloses the use of nonionic surfactants, and Japanese Patent Publication No. 44-21346 discloses the use of a combination of anionic surfactants and cationic surfactants, or the use of many other dispersants such as amphoteric surfactants. . The use of dispersants has provided a promising solution to these problems in the steam stripping process. In the dehydration and drying process, various problems occur. For example, (1) the aqueous slurry has poor expeller-type dewatering properties and poor bite into expeller-type and expander-type dryers. (2) Expeller-type dehydrators, expeller-type and expander-type dryers have disadvantages such as sudden increases in load current, die pressure, and temperature. As a result, the operation of the dewatering and drying processes becomes unstable, resulting in a decrease in production speed and widening of variations in quality. Furthermore, when using a band dryer (a type that dries crumbs on a mesh belt with hot air),
Since known dispersants do not improve drying speed,
Improving production speed in the steam stripping process does not lead to improvement in product production speed. A method has been proposed that simultaneously solves the problems of the steam stripping process and the dehydration/drying process as described above. For example, JP-A No. 50-30982 discloses that phosphorus-containing surfactants are selected from (a) specific phosphorus-containing surfactants and (b) water-soluble substances containing hydrocarbon chains having multiple carboxyl groups, or water-soluble derivatives thereof.
Combination of each compound (a) and (b), in JP-A-52-74683,
The presence of certain polyethylene oxide-propylene oxide block copolymers during steam stripping is disclosed. However, as shown in Japanese Patent Application Laid-open No. 50-30982,
The combination of (a) certain phosphorus-containing surfactants and (b) water-soluble substances containing hydrocarbon chains with multiple carboxyl groups or their water-soluble derivatives may result in the formation of rubbery polymers during the steam stripping process. Particle agglomeration and adhesion to the walls of the equipment and the stirrer are prevented, and the aqueous slurry is better absorbed into the expeller-type dehydrator, expeller-type and expander-type dryers, but the load current in the dryer , die temperature・
A sudden rise in pressure is likely to occur, and the operational stability of the dryer cannot be said to be sufficient. In addition, in the polyethylene oxide-propylene oxide block copolymer disclosed in JP-A-52-74683, it is possible to prevent rubber-like polymer particles from agglomerating and adhering to the walls of the equipment and the stirrer during the steam stripping process. The effect is remarkable, and there is no sudden rise in the load current of the dryer or die temperature/pressure, but the bite into the expeller type dehydrator, expeller type and expander type dryers is reduced, and the dehydrator and dryer Operational stability cannot be said to be sufficient. The inventors of the present invention have conducted intensive studies on a method that can stably and efficiently operate not only the steam stripping process but also all post-treatment processes including dehydration and drying processes, and have surprisingly found that polyethylene oxide - Only when a propylene oxide block copolymer and a water-soluble polymer compound containing a carboxyl group or a water-soluble salt thereof are used as a dispersant can a rubbery polymer be successfully crumbled in the steam stripping process. The present invention was achieved based on the discovery that not only is this possible, but also that the subsequent dehydration and drying steps can be operated sufficiently stably and efficiently. That is, the purpose of the present invention is to prevent rubber-like polymer particles (crumbs) generated in the steam stripping process from agglomerating and clumping in the aqueous slurry, and to prevent them from adhering to the walls and stirrer of the steam stripping device. At the same time, in the dewatering and drying process, the aqueous slurry is well absorbed into the expeller type dehydrator, expeller type and expander type dryer, and there is no sudden increase in load current, die pressure or temperature, and furthermore, the band type dryer An object of the present invention is to provide a method for producing a rubbery polymer with a high drying rate. That is, in the present invention, when separating and recovering a rubbery polymer from a solution or suspension of a rubbery polymer in an inert solvent, (A) as a dispersant has a molecular weight of 1000 to 1000.
8000, preferably 2000 to 5000, and the ethylene oxide content in the molecule is 15 to 70% by weight, preferably 20
~50% by weight of the polyethylene oxide-propylene oxide block copolymer and (B) a carboxyl group-containing water-soluble polymer compound and/or its water-soluble salt were added to the aqueous slurry after steam stripping at 50% each. ~
It is added to the solution or suspension of the rubbery polymer or the water supplied during coagulation so that the concentration is 1000ppm, 0.01 to 10ppm, and steam stripping is performed to separate the rubbery polymer as an aqueous slurry. Another object of the present invention is to provide a method for producing a rubber-like polymer, which comprises subsequently dehydrating and drying this aqueous slurry. The method for producing a rubbery polymer according to the present invention involves steam stripping in the coexistence of a polyethylene oxide-propylene oxide block copolymer as a dispersant and a water-soluble polymer compound containing a carboxyl group and/or a water-soluble salt thereof. It is characterized by When a polyethylene oxide-propylene oxide block copolymer is used alone, as mentioned above, the ability to feed into an expeller-type dehydrator, an expeller-type dryer, and an expander-type dryer decreases; Using only a polymer compound and/or its water-soluble salt cannot prevent agglomeration and agglomeration of rubbery polymer particles in the steam stripping process, The load current, die pressure, and temperature suddenly increase, making it impossible to operate stably for a long period of time. Furthermore, the drying speed in a band dryer is not improved at all when each of the above surfactants is used alone. That is, the object of the present invention can only be achieved by using a polyethylene oxide-propylene oxide block copolymer together with a water-soluble polymer compound having a carboxyl group and/or a water-soluble salt thereof. When drying rubber in an expander type dryer, the lower the temperature at which the rubber bursts, the more advantageous it will be in terms of energy. A polyethylene oxide-propylene oxide block copolymer lowers the repellency temperature, but a water-soluble polymer compound having a carboxyl group and/or a water-soluble salt thereof tends to slightly increase the repulsion temperature. However, when both are used together, the repellency temperature is lower than when the polyethylene oxide-propylene oxide block copolymer is used alone. This is completely unexpected from known facts, and this is also another effect of the present invention. Polyethylene oxide used in the present invention -
The propylene oxide block copolymer has a molecular weight of 1000 to 8000 and an ethylene oxide content of 15 to 70% by weight in the molecule. If the molecular weight exceeds 8,000 or is less than 1,000, not only will the rubbery polymer particle size increase in the stripping process, but a large amount of the rubbery polymer will adhere to the stripper wall and stirrer, resulting in substantial damage. stripping becomes impossible. Furthermore, if the ethylene oxide content in the molecule is less than 15% by weight, not only will the particle size of the crumb increase in the stripping process, but the amount of rubbery polymer that will adhere to the stripper wall and stirrer will also increase. If the amount exceeds 70% by weight, not only will the particle size of the rubbery polymer increase, but also the amount of rubbery polymer that will adhere to the stripper wall and stirrer will increase, and moreover, foaming within the stripper will become more intense. On the other hand, the carboxyl group-containing water-soluble polymer compound and its water-soluble salt used in the present invention (B) include polyacrylic acid, polymethacrylic acid,
Acrylic acid-styrene copolymer, methacrylic acid-
Butadiene copolymer, maleic acid, -butene-1
Examples include, but are not limited to, copolymers, maleic anhydride-diisobutylene copolymers, maleic anhydride-amylene copolymers, and their sodium, potassium, or ammonium salts. Particularly preferred among these compounds is the sodium salt of maleic anhydride and diisobutylene copolymer. The dispersants (A) and (B) used in the present invention each have a
1000ppm, preferably 100~500ppm and 0.01~
10 ppm, preferably in the range of 0.2 to 2.0 ppm.
If the amount of the compound (A) used is less than 50 ppm, mutual agglomeration and agglomeration of the rubber-like polymer cannot be prevented in the stripping process, and if it exceeds 1000 ppm, foaming will become intense and the dehydrator and dryer may become clogged. It becomes defective. In addition, if the amount of compound (B) used is less than 0.01 ppm, the biting properties of dehydrators and dryers will not be improved.
If it exceeds 10ppm, the load current of the dehydrator and dryer will rise rapidly, and the load current of the dryer and die temperature will rise rapidly, making it impossible to control. The dispersant used in the present invention may be used by being dissolved in the water supplied during steam stripping, but it is preferably added to the solution or suspension of the rubbery polymer. In particular, the effects of the present invention can be made even more remarkable by contacting and mixing the polyethylene oxide-propylene oxide block copolymer with the rubbery polymer before the rubber is substantially coagulated in the steam stripping process. be able to. The rubber-like polymer targeted by the present invention is a rubber-like polymer obtained by polymerization or copolymerization of a single monomer or two or more monomers, and an anionic polymerization catalyst such as alkyl lithium or sodium naphthalene. Polybutadiene, polyisoprene, butadiene-styrene copolymer, isobrene-styrene copolymer, butadiene-isoprene copolymer, ethylene-propylene copolymer, isobutylene-isoprene copolymer polymerized using Ziegler type catalyst, Alfyn catalyst, etc. , polypentenamer, polypiperylene, butadiene-piperylene copolymer, etc. are typical examples. The inert polymerization solvent used in the present invention is selected from aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, and compounds that do not inhibit the catalyst activity, such as tetrahydrofuran, tetrahydropyran, and dioxane. atoms 2-12
propane, n-butane, i-butane,
n-pentane, i-pentane, n-hexane, cyclohexane, propene, 1-butene, i-butene, trans-2-butene, cis-2-butene,
1-pentene, 2-pentene, 1-hexene, benzene, toluene, xylene, ethylbenzene and the like are preferred. Moreover, two or more of these solvents can also be used in combination. In the present invention, the concentration of the solution or suspension of the rubbery polymer is preferably 5 to 30% by weight, but there is no need to limit it in particular. The concentration of the aqueous slurry of rubbery polymer dispersed in water is usually 5 to 10% by weight, but there is no need to limit it in particular. On the other hand, the dehydrator and dryer used in the present invention include, but are not limited to, expeller type dehydrators and expander type dryers currently used industrially. Next, one embodiment of the present invention will be explained with reference to FIG. 1 indicates a first stripper, and 2 indicates a second stripper. The rubbery polymer solution or suspension is fed through conduit 10 to the first stripper. Conduit 10 is connected to conduit 20 to 1 from hot water tank 9.
Hot water is supplied via 9 and the dispersant of the invention is supplied via conduit 11. A conduit 12 supplies steam to the first stripper. The hot water slurry of rubbery polymer particles made in the first stripper is transferred to conduit 1.
6 to the second stripper. The second stripper is supplied with steam via conduit 12' to control the temperature of the slurry tank. Unreacted monomers and solvent pass through conduits 13, 14, heat exchanger 4, and conduit 15, and are recovered by decanter 3 together with entrained steam. Unreacted monomer and solvent are sent via conduit 27 to the purification system for reuse. The separated hot water is reused in conduits 18-19. on the other hand,
The hot water slurry of rubbery polymer particles is withdrawn from the second stripper in conduit 17, and screen 5 separates the hot water and crumbs. Hot water is in hot water tank 9
will be collected. Crumbs separated by a screen are
It contains 30-60% water and is fed to the dehydrator 6, where the squeezed water is collected via conduit 26 into a hot water tank. The moisture content of the rubber that comes out of the dehydrator is 10~
20, and the rubber particles are fed to the dryer 7 to obtain dried rubber with a moisture content of 1% or less. Here, the dryer may be an expander type, an expeller type, a band type, or a combination thereof. The present invention will be specifically explained below with reference to Examples, but the scope is not limited to these Examples. Example 1 Two polymerization reactors with an internal volume of 200 were connected to produce a 1.3-
1,3-butadiene with 25% by weight of butadiene and n-
The hexane mixture was continuously fed at a rate of 80Kg/Hr, and at the same time divinylbenzene and n-butyllithium were each added per 100 parts by weight of 1,3-butadiene.
0.542 parts by weight and 0.027 parts by weight (as active amount) were continuously supplied, and the reaction was carried out at 40°C. After the reaction was completed, 2.6-di-t-butyl-P-cresol (BHT) was added to the polymer solution in an amount of 1 part by weight per 100 parts by weight of the polymer. Next, add (A) a polyethylene oxide-propylene oxide block copolymer having a molecular weight of 3000 and an ethylene oxide content of 40% by weight in the molecule and (B) sodium maleic anhydride and diisobutylene copolymer to the polymer solution. Salt is added as a dispersant and the internal volume is increased with the polymer solution at a rate of 250/Hr.
800 first strippers were continuously fed.
At the same time, steam 250Kg/Hr to the first stripper.
Hot water of 1200 Kg/Hr was continuously supplied, and steam stripping was carried out continuously at a temperature of 110° C. using two strippers: a first stripper and a second stripper with an internal volume of 800 mm. The crumb concentration in the resulting aqueous slurry was 5.0%. The dispersant in the aqueous slurry was continuously added so that (A) was 200 ppm and (B) was 0.4 ppm. The aqueous rubbery polymer slurry was then passed through a screen to separate most of the water, and the rubbery polymer crumb was dehydrated and then dried in an expander dryer. The results of steam stripping, dehydrator, and dryer are shown in Table 1. As is clear from Table 1, the crumb particles of the aqueous slurry in the stripper were fine and uniformly dispersed, and there was no adhesion to the walls or stirrer in the stripper. In addition, when the crumbs were fed to a dehydrator and an expander type dryer, there was no abnormal increase in the load, die temperature, or die pressure in the dehydrator or dryer, and the crumbs were well chewed, resulting in stable operation. I was able to do it. Furthermore, in expander dryers, the rubber bursts at a relatively low temperature, and the dried rubber that bursts out is extremely porous.
The water content was extremely low, resulting in a well-dried rubber. Example 2 When steam stripping the rubber solution of Example 1, a polyethylene oxide-propylene oxide block copolymer with a molecular weight of 4600 and an ethylene oxide content of 50% was mixed with maleic anhydride and diisobutylene copolymer Na. The process was carried out in exactly the same manner as in Example 1 except that it was used in combination with a salt. The results are also shown in Table 1. Comparative Example 1 1,3-Butadiene was polymerized in exactly the same manner as in Example 1, and steam stripping, dehydration, and drying were performed in the same manner as in Example 1 without adding any dispersant. The results are shown in Table 1. Comparative Example 2 Same as Example 1 except that only the polyethylene oxide-propylene oxide block copolymer among the dispersants used in Example 1 was added as a dispersant during steam stripping using the rubber solution of Example 1. Rubber was recovered in exactly the same manner. The results are shown in Table 1. When only the polyethylene oxide-propylene oxide block copolymer is added, crumb dispersion in steam stripping and rubber adhesion to the walls and stirrer in the stripper are improved, but the dehydrator and expander are improved. The biting property in the mold dryer was markedly poor and productivity was reduced. Comparative Example 3 Rubber was recovered in exactly the same manner as in Example 1, except that only sodium salt of maleic anhydride and diisobutylene copolymer was added as a dispersant. The results are shown in Table 1. In this case, not only the dispersion of crumbs during steam stripping and the adhesion of rubber to the wall in the stripper and the agitator are not improved at all, but also the load in the dehydrator and expander dryer, the die temperature, A sudden rise in die pressure occurred and the operation became extremely unstable.

【table】

[Table] Examples 3 to 5 In the polymer solution of Example 1, the compounds listed in Table 2 were used as the dispersant (B) instead of the Na salt of maleic anhydride and diisobutylene copolymer, and Example 1 Coagulation, dehydration, and drying were performed in the same manner as above. The results are also shown in Table 2. As is clear from Table 2, good results similar to those of Example 1 were obtained with other salts of water-soluble polymer compounds containing carboxyl groups.

【table】

[Table] Comparative Examples 4 to 6 A polyethylene oxide-propylene oxide block copolymer having the molecular weight or ethylene oxide content in the molecule shown in Table 3 was mixed with a sodium salt of maleic anhydride and diisobutylene copolymer. Rubber was recovered in exactly the same manner as in Example 1 using the rubber solution of Example 1, except that it was added in combination. If a material with a molecular weight exceeding 8000 or an ethylene oxide content of less than 15% is used, the dispersion of crumbs during steam stripping and the adhesion of rubber to the walls inside the stripper and the stirrer will be improved. On the other hand, the ethylene oxide content is 70
%, foaming in the stripper became intense. The results are shown in Table 3.

[Table] Comparative Examples 7 to 9 Amount of polyethylene oxide-propylene oxide block copolymer used in Example 1,
Alternatively, rubber was recovered in exactly the same manner as in Example 1, except that the amount of sodium salt of maleic anhydride and diisobutylene copolymer used was as shown in Table 4. If the amount of polyethylene oxide-propylene oxide block copolymer used is less than 50 ppm, the dispersion of crumbs in steam stripping and the adhesion of rubber to the walls and stirrer in the stripper will not be improved at all. On the other hand, when the amount exceeded 1000 ppm, foaming was severe, and the ability to chew crumbs in dehydrators and expander dryers became significantly worse. In addition, if too much sodium salt of maleic anhydride and diisobutylene copolymer is used, the load on the dehydrator and dryer will increase, and the die temperature and die pressure in the dryer will also rise sharply, causing operational became unstable.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 shows a flow diagram representing one example of the present invention. 1... First stripper, 2... Second stripper, 3... Decanter, 4... Heat exchanger, 5...
... Screen, 6 ... Dehydrator, 7 ... Dryer, 9
...Hot water tank, 10...Rubber-like polymer supply port,
11... Surfactant supply port, 12, 12'... Steam supply port, 13-27... Conduit.

Claims (1)

[Claims] 1 When separating and recovering a rubbery polymer from a solution or suspension of a rubbery polymer in an inert solvent, use a dispersant (A) with a molecular weight of 1000 to 8000 and an ethylene oxide content of 15 to 70% in the molecule. 50 to 1000 ppm of each of the polyethylene oxide-propylene oxide block copolymer and (B) the water-soluble polymer compound containing a carboxyl group and/or its water-soluble salt to the aqueous slurry after steam stripping. The rubbery polymer is added to the solution or suspension of the rubbery polymer or the water supplied during coagulation to a concentration of 0.01 to 10ppm, and steam stripping is performed to separate the rubbery polymer as an aqueous slurry. A method for producing a rubbery polymer, which comprises dehydrating and drying an aqueous slurry.