JPH0811766B2 - Method of recovering block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a hydrocarbon solution of a block copolymer obtained by anionic block copolymerizing an aromatic vinyl compound and a conjugated diene in a hydrocarbon solvent. The present invention relates to a method for efficiently recovering the copolymer after distilling out most of the solvent by pouring into hot water.

[Prior art]

It is conventionally known that block copolymers of various structures are obtained by performing block copolymerization of an aromatic vinyl compound and a conjugated diene in the presence of an anionic polymerization initiator. When producing these copolymers, it is usual to carry out the polymerization in a hydrocarbon solvent which is active with respect to the catalyst system, and the produced copolymer is either uniformly dissolved in the solvent or suspended. Since it is obtained in a turbid state, a step of separating the copolymer and the solvent and recovering the copolymer is required. Generally, a method of recovering a copolymer that is uniformly dissolved in a solvent is to add a large amount of a non-solvent to a copolymer such as a lower alcohol and separate and recover the copolymer Copolymer solution The method of recovering the copolymer by directly concentrating and desolvating the copolymer is a method of recovering the copolymer by steam-stripping the copolymer solution to remove the solvent, followed by dehydration and drying. There are three known methods.

[Problems to be solved by the invention]

However, this method requires a third component called lower alcohol, and further requires a separation operation of the lower alcohol and the copolymer, which is economically extremely disadvantageous in comparison with other aspects in terms of equipment and operation.

It has been conventionally considered that the method of (1) is economically advantageous both in terms of equipment and operation. However, this is because the amount of solvent contained in the recovered copolymer is a relatively high residual solvent concentration of several thousand to 1,000 ppm, and in recent years, the residual solvent in the copolymer was As demand for a low concentration range of several hundreds to several tens of ppm has emerged, it has been found that this method is extremely disadvantageous, especially because of high cost in terms of equipment.

Regarding one method, the steam hot-spun copolymer hot water slurry was conventionally made to have a water content of 20 to 40 wt% with a centrifugal dehydrator, etc., and then dried with a band hot air dryer or the like to give a crumb-shaped intermediate product. Then, it was molded in an extruder, but it had the drawback of requiring complicated operations as described above.

[Means for solving problems]

The present inventors have conducted intensive studies as a result of developing a method for recovering a copolymer that solves the above-mentioned drawbacks of the prior art, and as a result, completed the present invention. That is, the present invention is that a hydrocarbon solution of a block copolymer obtained by copolymerizing an aromatic vinyl compound and a conjugated diene in a hydrocarbon solvent at 120 ° C or lower is injected into hot water to form a hydrocarbon solvent. After distilling off, the block copolymer was made into a slurry, and then the water content of the slurry was adjusted to 5 to 60% by weight with a dehydrator, and then kneaded with a vent extruder having two or more axes to remove volatile components. Disclosed is a method for recovering a block copolymer, which comprises removing the block copolymer.

 The present invention will be specifically described below.

The block copolymer used in the present invention is not particularly limited, but it is a block copolymer of an aromatic vinyl compound and a conjugated diene and has the general formula (AB) n, (AB) n- A
Alternatively, it is preferably at least one represented by (AB) mX. (In the formula, A is an aromatic vinyl compound, B is a conjugated diene, n is an integer of 1 to 10, m is an integer of 2 to 6, and X is a coupling agent residue.) As the aromatic vinyl compound, styrene, α- Methyl styrene, paramethyl styrene and the like can be mentioned, and among them, styrene is preferable. As a conjugated diene,
Examples thereof include butadiene, isoprene, piperylene, etc. Among them, butadiene and isoprene are preferable.

The block copolymer in the present invention is obtained by block-copolymerizing an aromatic vinyl monomer and a conjugated diene monomer in a hydrocarbon solvent in the presence of an anionic polymerization initiator.

The aromatic vinyl and the conjugated diene monomer are used alone or in combination of two or more. The content of the aromatic vinyl compound unit in the block copolymer is preferably 10 to 90% by weight, more preferably 15 to 85% by weight, and the number average molecular weight is
It is preferably 50,000 to 500,000, more preferably 100,000 to 200,000. The polymerization method is a conventionally known method, for example, JP-B-48-4106, JP-A-52-59698, and JP-A-59.
Various methods are performed in addition to the method shown in -166518.
By selecting the polymerization method, the block structure of the produced copolymer can have various structures.

The hydrocarbon solvent used in the method of the present invention is preferably a paraffinic, naphthenic or aromatic inactive hydrocarbon having 3 to 10 carbon atoms, which facilitates removal and recovery of the solvent by evaporation from the copolymer. Therefore, a solvent having a boiling point of 120 ° C. or less at atmospheric pressure is preferable, and more preferably 60
Those at -100 ° C are used. As a specific example, use of benzene, toluene, hexane, heptane, cyclohexane, and a mixture thereof is particularly preferable. The amount of the solvent used in the polymerization step is preferably in the range such that the polymer concentration is 15 to 50% by weight, more preferably 25 to 40% by weight.

 The method of the present invention will be described with reference to FIG. 1 as an example.

The polymer solution in which the polymerization reaction is completed is pressurized by the pump 2 from the intermediate tank or the polymerization tank 1 and enters the stripper 3. Steam or hot water is introduced into the stripper from the conduit 4. From the top of the stripper 3, the evaporated solvent vapor and steam enter the condenser 7 through the conduit 6, where they are cooled and liquefied, stored in the tank 8 and then recovered via the conduit 9.

The copolymer that has been almost desolvated in the stripper 3 becomes fine particles, which are dispersed in hot water to form a slurry, and enter the dehydrator 10 via the conduit 5. At this time, the polymer concentration of the slurry is preferably 3 to 15% by weight, more preferably 4 to
It is preferably kept at 10% by weight, particularly preferably 3-8% by weight. Water is separated from the slurry in the dehydrator 10. The water content at the outlet 12 of the dehydrator is set to an economically optimum value in consideration of the capacity of the dehydrator and the load of the extruder at the subsequent stage, but is preferably 5 to 60% by weight, more preferably 10 to
It is 40% by weight, particularly preferably 10 to 35% by weight.

As the dewatering device 10, specifically, a vibrating screen, a centrifugal dewatering machine, a screw-type dewatering machine, etc. are preferable. Considering the overall system configuration, these dewatering machines may be used alone or in combination of two or more. You can The hot water 11 discharged from the dehydrator 10 recovers heat and then is drained or circulated to the stripper 3 for reuse (not shown).

The copolymer exiting the dehydrator 10 is usually in the form of particles and fed to the extruder 13. In the example shown in FIG. 1, the extruder 13 is provided with a dehydration slit 14 and deaeration vents 16 and 17.

The extruder usually has 1 to 2 stages of dehydration slits and 1 to 3 stages.
It is possible to use a biaxial or more vent extruder equipped with a step vent. If the number of vents is one stage, the deaeration capacity is insufficient and the moisture is not sufficiently dried. It is not desirable except for foaming and drying at the tip of the extruder to obtain crumbs. Further, the single-screw extruder is also unfavorable because the surface renewal in the vent is insufficient and the deaeration capacity becomes insufficient, resulting in the same result. The structure of the extruder having two or more screws may be either non-meshing or meshing, and the rotation direction may be the same direction or different directions.

The L / D (length / diameter) of the screw is preferably about 15 to 45.

The screw rotation speed of the vent extruder and the heating conditions of the barrel are determined in consideration of the extrusion capacity, degassing capacity, and product properties, but the screw rotation speed is 10 to 400 rotations / minute, and the temperature is 130
It is usually selected from the range of up to 230 ° C.

The dewatering slit is used to further squeeze and release water that could not be separated by the dewatering device and remove it. The position of the slit may be on the upstream side, downstream side or both sides of the feed port. However, the wake side is more preferable. Regarding the number and length of the dehydration slits, the optimum one will be selected depending on the water content, but usually one or two places and a length L / D = 0.8 to 5 are selected. From the copolymer dehydrated to a water content of 2 to 15% by weight with a dehydration slit, the remaining water and solvent are evaporated by degassing vents 16 and 17, and the water content and residual solvent content are reduced to the specified levels. A copolymer 20 extruded from the tip die of the extruder 13 and molded is obtained. The pellets are usually molded, but the pelletizer is usually selected from underwater cutting, air cutting, and strand cutting. In some cases,
It is also possible to take out crumbs by closing the vent ports 16 or 17 and foaming and drying at the tip of the extruder.

The vents 16 and 17 are normally operated under atmospheric pressure to atmospheric pressure of about 50 mmHg to vacuum system.

The opening length of the vent port is usually preferably L / D = 0.8 to 8 in consideration of the degassing rate. The water and the solvent evaporated from the vent port are cooled and condensed in the condenser 21 through the conduit 18, stored in the liquid receiving tank 22, and then extracted from the system through the conduit 24. If it is necessary to maintain a vacuum at the vent port, connect a vacuum pump or ejector (neither shown) through conduit 18.

It is possible to add an appropriate conversion agent 19 to the extruder 13 as needed, and optionally water may be injected to accelerate desolvation.

〔Example〕

 Embodiments of the present invention will be described below with reference to examples.

Example 1 Styrene content of 80% by weight copolymerized with n-butyllithium as an initiator in a cyclohexane solvent as a number average molecular weight 12
An experiment was carried out using a 35 wt% solution of an ABA type styrene / butadiene block copolymer of 0.000 as a sample.

 As an antioxidant, octade
Syl-3- (3 ', 5'-di-tert-butyl-4'-hydro
Xyphenyl) propionate (Geigy Irgannot
Cous 1076) is added and mixed evenly, and the pressure is increased by a pump.
The stripper was shaded at a flow rate of 450 kg / h. Strip
Par is controlled by steam at 105 ℃
From the bottom of the top, add hot water slurry with a copolymer concentration of 5% by weight.
It was taken out continuously. Evaporated from the top of the stripper
The solvent and water vapor were extracted. Screw this slurry
-Squeeze dewatering with a squeezing machine
It was fed to a twin-screw extruder with a vent. The extruder used is
Clew diameter 70m / m, L / D ratio 30 is used, and the cylinder is
Heated to 160 ° C with heat transfer oil. Every screw rotation
50 to 250 revolutions per minute, the pressure of the vent is 400mmHg for the first step
Absolute pressure, reduced to 200 mmHg absolute pressure in the second stage with a vacuum pump.
Was. Cut into pellets from the tip of the extruder and make a sample
Got

Under these conditions, the amount of drainage water from the slit, the amount of polymer outflow, the amount of residual water, and the amount of residual solvent were as shown in Table 1, and the residual water / solvent amount was 300 weight ppm or less, which was satisfactory.

Example 2 In Example 1, the dehydration apparatus was replaced with a squeezing dehydrator, and a centrifugal dehydrator was used. Other conditions were the same as in Example 1. The results are shown in Table 1. By selecting the conditions, it became 300 ppm by weight or less as in Example 1.

Example 3 In Example 1, the dehydration apparatus was replaced with a squeezing dehydrator, and a vibrating screen was used. Other conditions were the same as in Example 1. The results are shown in Table 1. By selecting the conditions, it became 300 ppm by weight or less as in Example 1.

Example 4 In Example 1, the second vent of the extruder was closed and foamed at the tip of the extruder to form a crumb. Other conditions were the same as in Example 1. The results are shown in Table 1. A dry crumb with little residual water and solvent was obtained.

Example 5 In Example 1, 1.3 was used as the conjugated diene monomer and iprene was used instead of butadiene, and a styrene-isoprene block copolymer having a styrene content of 15% was used as a sample. Other conditions were the same as in Example 1. The results are shown in Table 1. Similar to Example 1, dry pellets with less residual solvent were obtained.

Comparative Example 1 The polymer solution shown in Example 1 was used as a sample, and the solution was directly heated to distill off a part of the solvent, and then an experiment was conducted in which the remaining solvent was deaerated and removed using an extruder. The flow sheet is shown in FIG.

The polymer was pressurized with a pump, heated to 180 ° C. in a heat exchanger, and then fed to a concentrator at 210 to 420 Kg / h. The pressure inside the concentrator was maintained at about atmospheric pressure. The solvent concentration at the outlet of the concentrator was 15 wt%, and this solution was supplied to a twin-screw two-stage vent extruder. The extruder used had a screw diameter of 70 m / m and an L / D ratio of 36, and the cylinder was heated to 160 ° C with a heat transfer oil.
The screw rotation speed was 50 to 250 rotations per minute, and the pressure at the vent port was reduced to 200 mmHg absolute / 100 mmHg absolute for each of the first and second stages with a vacuum pump. Under these conditions, the amount of pellet polymer discharged from the tip and the amount of residual solvent were as shown in Table 2, and both were unsuitable as products because the amount of residual solvent did not fall below 3000 ppmwt.

Comparative Example 2 Comparative Example 1 was carried out in the same manner as Comparative Example 1 except that the polymer was the styrene / iprene block copolymer in Example 5 used as a sample. The results are shown in Table 2. As in Comparative Example 1, the residual solvent amount was high.

Comparative Example 3 In Example 1, the efficiency of the dehydrator before being fed to the twin-screw extruder was reduced, the water content of the fed polymer was raised to 70%, and the polymer was fed to the extruder to perform an experiment. However, the undried water in the polymer was evaporated at the tip of the extruder, the polymer foamed and was not sufficiently dried, and it was unsuitable as a product.

[Effect of the Invention] The boiling point of the styrene-based monomer and the conjugated diene monomer group is 12
In order to recover the block copolymer obtained by anion-block copolymerization in a hydrocarbon solvent at 0 ° C or lower, the copolymer solution was poured into hot water, and the solvent was distilled off.
According to the present invention in which the water content is dewatered to 5 to 60% by a dewatering device and then degassed and dried by a vent extruder having two or more shafts, the drying and pelletizing steps which are conventionally performed are
The copolymer containing substantially no solvent or water can be efficiently recovered in the form of pellets or crumbs.

[Brief description of drawings]

FIG. 1 is a flow sheet of the method of the present invention, and FIG. 2 is a flow sheet of the method of the comparative example. 1 ... Intermediate tank or polymerization tank, 2 ... Pump 3 ... Stripper, 4 ... Steam or hot water 5 ... Copolymer hot water slurry, 6,18,23 ... Conduit 7,21 ... Condenser , 8,22 …… Storing tank 9 …… Solvent and water discharge pipe, 10 …… Dehydration device 11 …… Drainage, 12 …… Dehydration device outlet pipe 13 …… 2-axis 1-stage slit 2-stage vent extruder 14 …… Dehydration slit, 15,24 …… Drainage 16,17… Vent port, 19 …… Additive or water 20 …… Product 51 …… Intermediate tank or polymerization tank, 52 …… Pump 53 …… Heat exchanger, 54 …… Concentrator 55 …… Condenser, 56 …… Recovered solvent storage tank 57 …… Recovered solvent discharge pipe, 60 …… Two-axis two-stage vent extruder 61 …… Supply nozzle, 62,63 …… Vent port 64 …… Product, 65 …… Conduit 66 …… Condenser, 67 …… Recovered solvent storage tank 68 …… Vent discharge port (vacuum pump connection) 69 …… Recovered solvent discharge pipe

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mikio Takeuchi 2-11-24 Tsukiji, Chuo-ku, Tokyo Inside Nippon Synthetic Rubber Co., Ltd. (56) References Japanese Patent Publication Sho 58-11477 (JP, B2) Japanese Patent 57-51407 (JP, B2)

Claims (3)

[Claims] 1. A hydrocarbon solution of (a) a block copolymer of an aromatic vinyl compound and a conjugated diene having a boiling point of 120 ° C. or less is poured into hot water to distill off the hydrocarbon solvent, and (b) ) The water content of the block copolymer is 10 to 40% by weight in a dehydrator.
And (c) kneading with a twin-screw or more vent extruder to remove volatile components, and the residual hydrocarbon solvent content in the copolymer is adjusted to 790 ppm or less. 2. The recovery method according to claim 1, wherein the block copolymer is recovered in the form of pellets from the vent extruder. 3. The recovery method according to claim 1, wherein the block copolymer is recovered in the form of foamed crumb from the vent extruder.