JP4224691B2 - Polymer recovery method and recovery apparatus - Google Patents

Description

  The present invention relates to a polymer recovery method and recovery apparatus. More specifically, the present invention relates to a polymer recovery method and a recovery apparatus that can recover a high-quality polymer from a polymer solution with high productivity and high yield using a simplified apparatus. About.

  In order to recover a polymer from a polymer solution obtained by solution polymerization, a method using a coagulation / stirring tank has been generally used. That is, a polymer solution is supplied to warm water heated by steam or the like, and the solvent is removed to make the polymer into a crumb-shaped warm water slurry. Next, this slurry is sent to a stripping agitation tank, steam stripping is performed to remove residual solvent, and crumb having a water content of about 50% obtained by dehydrating the slurry with a dehydrator is used as a box dryer or The product was supplied to an extrusion dryer and dried. However, such a method has problems such as a large number of processes, enormous energy required, and an installation area of the apparatus being too large.

  Therefore, in Patent Document 1, the cement-like rubber solution and the coagulating liquid are separately supplied immediately before the inlet of the rotor blade of the crushing function pump, and the generated slurry is continuously supplied to the twin-screw extruder. A method of automatically draining and drying is disclosed. However, in this method, if the amount of coagulation liquid is less than the amount of cementitious rubber solution, coagulation may be incomplete, and a phenomenon in which crumbs adhere to each other and transfer to a twin screw extruder becomes difficult. Had occurred. In order to avoid this phenomenon, it is sufficient to increase the amount of coagulation liquid compared to the amount of cementitious rubber solution, but in that case, the amount of cementitious rubber solution supplied to the pump with crushing function is reduced and the drainage capacity is insufficient. There is a problem in that the production cost increases due to a decrease in productivity and an increase in power consumption.

  Further, in Patent Document 2, in separating the block copolymer from the hydrocarbon solution of the block copolymer, the polymer concentration is concentrated to 80% by weight or more using a flash evaporation method, and then water is added. A method of obtaining polymer pellets by adding them to a vent extruder after the addition is disclosed. However, in this method, a preconcentration facility such as a flash evaporation method must be installed. The preconcentration facility is omitted, and water is added to a polymer having a polymer concentration of 30% by weight or less, and then supplied to a vent extruder. Then, there was a problem that the deaeration vent port was clogged.

JP-A-10-100135 Japanese Patent Publication No.57-51407

  An object of the present invention is to provide a polymer recovery method capable of reducing the number of steps and equipment with a high recovery rate and high productivity when recovering a polymer from a polymer solution obtained by solution polymerization. It is in.

  The inventors of the present invention have made extensive studies in order to achieve the above-mentioned object. As a result, a solidification zone is provided in the barrel of the extruder, and the forward screw element and the reverse feed are provided in a region corresponding to the solidification zone of the screw of the extruder. It has been found that by providing a coagulation screw block having two or more combinations of screw elements, the apparatus is simplified and the polymer can be recovered efficiently even when the amount of coagulation liquid is small relative to the polymer solution. The present invention has been completed.

That is, the present invention
(1) A method of recovering a polymer from a polymer solution using an extruder in which a screw is rotatably arranged inside a barrel having a coagulation zone, wherein the screw corresponds to the coagulation zone. A method for recovering a polymer, comprising a coagulation screw block formed in a region where the coagulation screw block has two or more combinations of a forward feed screw element and a reverse feed screw element;
(2) The method for recovering a polymer according to item 1, wherein the coagulation screw block has a kneading disk for forward or reverse feeding,
(3) The method for recovering a polymer according to item 1 or 2, wherein a screw that is biaxially meshed and rotates in the same direction is used.
(4) An apparatus for recovering a polymer from a polymer solution, comprising an extruder in which a screw is rotatably disposed inside a barrel having a coagulation zone, and the screw corresponds to the coagulation zone. A polymer recovery device comprising a coagulation screw block formed in a region, the coagulation screw block having two or more combinations of a forward feed screw element and a reverse feed screw element;
(5) The polymer recovery apparatus according to item 4, wherein the coagulation screw block has a forward or reverse kneading disk;
(6) The polymer recovery device according to item 4 or 5, which has a drainage zone downstream of the coagulation zone inside the barrel,
(7) The polymer recovery device according to item 6, which has a drying zone downstream of the drainage zone,
(8) The polymer recovery device according to any one of Items 4 to 7, which has a biaxial meshing type and a screw rotating in the same direction.
Is to provide.

  According to the polymer recovery method and recovery apparatus of the present invention, a polymer can be recovered with high recovery rate and high productivity from a polymer solution obtained by solution polymerization, with omitted equipment and a small number of steps. I can do it. In particular, when recovering a polymer from a cement-like rubber solution, it is useful because the polymer can be recovered efficiently even when the amount of coagulating liquid is small relative to the amount of rubber solution.

The polymer recovery method of the present invention is a method for recovering a polymer from a polymer solution using an extruder in which a screw is rotatably disposed inside a barrel having a coagulation zone, the screw Has a coagulation screw block formed in a region corresponding to the coagulation zone, and the coagulation screw block has two or more combinations of a forward feed screw element and a reverse feed screw element. It is.
The combination of the forward screw element and the reverse screw element used in the method of the present invention includes a combination of the forward screw element and the reverse screw element, or irrelevant to the feed action between the forward screw element and the reverse screw element (neutral). ) Can be used as appropriate.
In the screw block for solidification of the method of the present invention, one or two of the above two combinations are combined and used in total of two or more.
A known screw element, for example, a forward feed screw element (or a reverse feed screw element) having a different pitch or a neutral kneading disk or the like can be appropriately inserted between and before and after the plurality of sets, and the structure of such a screw block. This is a preferred embodiment in that the function and effect of the present invention can be appropriately adjusted depending on the design.
The form of the coagulation zone is not limited as long as it is an area where coagulation is performed, but usually means from the tip of the screw on the supply side to just before the first drainage means.
Moreover, in this invention, it is preferable to have a drainage zone in the downstream of a coagulation zone, and it is preferable to have a drying zone in the downstream of a drainage zone. Furthermore, it is preferable from the viewpoint of drying efficiency that the drying zone is divided into an atmospheric drying zone and a reduced pressure drying zone.
FIG. 1 is an explanatory view of an embodiment of an extruder used in the method of the present invention. The extruder of this aspect is comprised from the screw which consists of the barrel which consists of 12 barrel units, 3 types of screw elements, and 3 types of kneading discs. The coagulation zone is composed of No. 1 to 3 barrel units and a part of No. 4 barrel unit. The drainage zone consists of part of No. 4-6 barrel unit and No. 7 barrel unit. The drying zone consists of a normal pressure drying zone consisting of No. 7-8 barrel units and a reduced pressure drying zone consisting of No. 9-12 barrel units. The No. 1 barrel unit is a supply unit having a supply port to which a coagulating liquid and a polymer solution are supplied. The barrel unit No. 4 is a drainage unit having a drainage slit through which the solidified drainage separated by the solidification of the polymer solution is discharged. The interval between the drainage slits is usually 0.05 to 0.20 mm, preferably 0.08 to 0.15 mm. The barrel units of No. 7, No. 9 and No. 11 are vent units in which the solvent (including water) contained in the polymer is volatilized and removed by heating. The vent unit may have a vent slit. The barrel unit other than the above is a cylindrical standard unit.

The screw of the extruder shown in FIG. 1 includes a fine pitch forward screw element A, a coarse pitch forward screw element B, a reverse feed screw element C, a forward feed kneading disc D, a neutral kneading disc E, and a reverse feed kneading disc F. It is comprised by arrangement | positioning. The arrangement of C to F is shown in the figure. All elements without symbols are progressive screw elements A or B. In the extruder according to this aspect, the coagulation screw block formed in the region corresponding to the coagulation zone has two sets of combinations of forward feed screw elements and reverse feed screw elements arranged alternately. By alternately arranging the forward feed screw element and the reverse feed screw element, the slurry that has been coagulated with the coagulating liquid is kneaded more finely and the coagulation is completed, and the polymer and coagulated waste liquid are separated. Is done.
The extruder shown in FIG. 1 has two combinations of forward screw elements and reverse screw elements, and the fine mixing is repeated twice. Therefore, two stages of complete mixing are performed for the solidification of the polymer solution. Exhibits the same effect as the tank. That is, the extruder used in the method of the present invention has the original extrusion function and the complete mixing function of the complete mixing tank, and can efficiently coagulate the polymer solution with a small scale facility and a small amount of power.
The reverse feed screw element used in the present invention preferably has a length / pitch ratio of 0.5 and a pitch / diameter ratio of 0.4 to 1.5, preferably 0.6 to 1.2. More preferably. If the pitch / diameter ratio is less than 0.4 or exceeds 1.5, the effects of damming and kneading may not be sufficiently exhibited.

The kneading disc used in the present invention has a configuration in which a plurality of substantially elliptical disc plates are combined at different angles. Although only one disk plate is neutral with respect to feeding, a progressive kneading disk, neutral kneading disk, or reverse feeding kneading disk can be obtained by combining a plurality of disk plates at different angles. . Here, the neutral kneading disk is formed by shifting a plurality of disk plates perpendicular to the axial direction by 90 degrees and parallel to the axial direction.
If the pitch is the same, the effect of kneading becomes stronger in the order of a forward feed screw element, a forward feed kneading disc, a neutral kneading disc, a reverse feed kneading disc, and a reverse feed screw element. By providing a kneading disk on the coagulation screw block, the polymer solution and the coagulation liquid can be mixed efficiently, and the polymer solution can be coagulated and slurried.
The extruder used in the method of the present invention is preferably a twin screw type extruder, and particularly preferably a twin screw type extruder having a screw rotating in the same direction. A twin-screw meshing extruder rotating in the same direction has good self-cleaning properties and excellent kneading performance and extrusion performance, and can knead and extrude solvent-containing slurry without causing slippage.
The polymer solution to which the polymer recovery method of the present invention can be applied is not particularly limited as long as the polymer is dissolved in an organic solvent. SBR (styrene-butadiene copolymer rubber) solution, NBR (Acrylonitrile-butadiene copolymer rubber) solution, hydrogenated NBR solution, maleated NBR solution, cemented rubber solution such as maleated hydrogenated NBR solution; resin solution such as acrylic resin solution, polyacetal resin solution, vinyl chloride resin solution; Among these, a cemented rubber solution is preferable, a cemented rubber solution using acetone as a solvent is more preferable, and a hydrogenated NBR solution using acetone as a solvent is particularly preferable.
In the method of the present invention, there is no particular limitation on the coagulation liquid added to the polymer solution, and any coagulation liquid may be used as long as it acts as a poor solvent. It is done. The value of the weight of the coagulating liquid / the weight of the polymer solution is generally in the range of 0.01 to 5, preferably 0.05 to 1, and particularly preferably 0.1 to 0.5.

The polymer recovery apparatus of the present invention is an apparatus for recovering a polymer from a polymer solution, and comprises an extruder in which a screw is rotatably disposed inside a barrel having a coagulation zone. And a coagulation screw block formed in a region corresponding to the coagulation zone, wherein the coagulation screw block has two or more combinations of forward feed screw elements and reverse feed screw elements.
In the apparatus of the present invention, the solidification block preferably has a kneading disk.
The apparatus of the present invention preferably has a drainage zone downstream of the coagulation zone inside the barrel, and further preferably has a drying zone downstream of the drainage zone.

The recovery apparatus shown in FIG. 1 has No. 4 to No. 3 on the downstream side of the solidification zone constituted by part of No. 1 to No. 3 barrel units and No. 4 barrel unit. 6 has a drainage zone constituted by a part of the barrel unit No. 7 and part of the barrel unit No. 7. The polymer slurry produced by the solidification of the polymer solution in the coagulation zone is pressurized by a reverse feed kneading disk provided in the standard unit No. 5 in the drainage zone, and discharged from the No. 4 drainage unit. The coagulated waste liquid separated from the liquid slit is discharged.
The polymer from which the solidified waste liquid of the slurry has been discharged in the drainage zone is extruded into a drying zone constituted by No. 7 to No. 12 barrel units. The solvent ratio of the polymer extruded from the drainage zone to the drying zone is usually 20 to 50% by weight.
In the apparatus of this embodiment, No. 7 unit, No. 9 unit and No. 11 unit of the drying zone are vent units, and No. 8 unit, No. 10 unit and No. 12 are standard units. The solvent contained in the polymer kneaded and uniform by the progressive kneading disk, reverse feed kneading disk and reverse feed screw element provided from the standard unit No. 8 to the vent unit No. 9 is No. It volatilizes from the vent slit of the vent unit 9 (the opening if no vent slit is used). A reverse feed screw element is provided immediately before the vent slit.

The polymer devolatilized in the No. 9 vent unit is heated in the No. 10 standard unit, and the progressive kneading disc and reverse feed knee provided from the No. 10 standard unit to the No. 11 vent unit. The mixture is kneaded and heated by the ding disk and the reverse feed screw element to be uniform, and the solvent contained in the polymer is volatilized from the vent slit of the No. 11 vent unit. A reverse feed screw element is provided immediately before the vent slit. Due to the devolatilization in the three vent units, the solvent ratio of the polymer is usually reduced to 1% by weight or less.
The polymer from which the solvent has been removed in the drying zone is extruded from a die provided at the outlet of the extruder.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples and comparative examples, a twin screw extruder having a screw diameter of 56 mm, a total screw length of 2,340 mm, and a screw rotation direction rotating in the same direction toward the front of the outlet was used. In addition, the slit interval of the drainage slit was 0.1 mm, and the vent slit was not used for the vent unit. The screw elements and kneading discs used are shown in Table 1. The 12 barrel units used are shown in Table 2.
In the following Examples and Comparative Examples, the loss on heating of the dry rubber was determined by the following formula by leaving about 5 g of the dry rubber in a hot air dryer at 105 ° C. for 90 minutes.
Dry rubber heat loss = (weight before hot air drying treatment−weight after hot air drying treatment) / (weight after hot air drying treatment) × 100 (wt%)

[Example 1]
A screw in which a screw element and a kneading disk were arranged as follows was used in an area corresponding to each zone. As the coagulation screw block, two combinations of the forward feed screw element A and the reverse feed screw element C were used and A and C were alternately arranged as follows.
Coagulation zone BBBADECADADEADC
Drainage zone BBBBBEBACCCC
Normal pressure drying zone BBBBADFCC
Vacuum drying zone BBBADBFCCBBBBDBB
The length of the feed process, ie the distance from the No. 1 supply unit to the first reverse feed screw element is 195 mm. From No. 1 supply unit to the first reverse feed screw element, it consists of a forward feed screw element, a forward feed kneading element, a neutral kneading element, a forward feed screw element, a forward feed kneading element, and a reverse feed screw element. The coarsely coagulated slurry is further finely kneaded to complete coagulation. Since this is repeated twice, it is similar to a mechanism in which two continuous complete mixing tanks are connected in series.
No. The temperature from No. 1 supply unit to No. 5 standard unit was 20 ° C. No. 6 standard units to No. 12 standard units were heated to 180 ° C. In addition, the No. 7 vent unit was connected to a ventilator of an activated carbon adsorption tower exhausted to the atmosphere via a water-cooled condenser. The No. 9 vent unit and No. 11 vent unit were connected to a water-sealed vacuum pump via a water-cooled condenser, and the pressure was reduced.
Water as a coagulation liquid was sent to the supply port of the No. 1 supply unit of the twin screw extruder at a flow rate of 80 parts / hr by a plunger pump. Next, ZP-2020 (hydrogenated NBR manufactured by Nippon Zeon Co., Ltd.) acetone solution (hereinafter abbreviated as “cement”) with a concentration of 14.5% by weight is No. 1 of a twin screw extruder using a plunger pump. It was fed into the supply port of the supply unit at a flow rate of 576 parts / hr (water / cement ratio = 0.14). The rotational speed of the biaxial screw was 440 rpm, and the pressure at the supply port was 0.8 MPa.
As a result, a dry rubber was obtained at a dry rate of 83 parts / hr. The loss on heating of this dry rubber was 0.22% by weight. Further, when the dry rubber was dissolved in tetrahydrofuran and analyzed by gas chromatography, the residual acetone content in the dry rubber was 1700 ppm. Further, the process loss at this time was 1.0% by weight and the specific power = 0.458 Kwh / Kg.

[Example 2]
The experiment was performed in the same manner as in Example 1 except that the amount of coagulated water was increased to 150 parts / hr (water / cement ratio = 0.26).
As a result, a dry rubber was obtained at a dry rate of 83 parts / hr. The loss on heating of this dry rubber was 0.18% by weight. Further, when the dry rubber was dissolved in tetrahydrofuran and analyzed by gas chromatography, the residual acetone content in the dry rubber was 1200 ppm. Further, the process loss at this time was 0.5% by weight, and the specific power was 0.506 Kwh / Kg.

[Example 3]
The experiment was performed in the same manner as in Example 1 except that the amount of the coagulant water was increased to 260 parts / hr (water / cement ratio = 0.45). As a result, a dry rubber was obtained at a dry rate of 83 parts / hr. The loss on heating of this dry rubber was 0.15% by weight. Further, when the dry rubber was dissolved in tetrahydrofuran and analyzed by gas chromatography, the residual acetone content in the dry rubber was 1000 ppm. Further, the process loss at this time was 0.3% by weight and the specific power = 0.578 Kwh / Kg.

[Example 4]
The experiment was performed in the same manner as in Example 1 except that the amount of the coagulant water was increased to 350 parts / hr (water / cement ratio = 0.45). As a result, power shortage occurred, so the operation was performed with the drying rate reduced to 50 parts / hr. The weight loss on heating of the obtained dry rubber was 0.10% by weight. Further, when the dry rubber was dissolved in tetrahydrofuran and analyzed by gas chromatography, the residual acetone content in the dry rubber was 700 ppm. Furthermore, there was no process loss at this time, and the specific power was 0.920 Kwh / Kg.

[Comparative Example 1]
The experiment was performed in the same manner as in Example 2 except that only the coagulation screw block was changed as follows.
Coagulation zone BBBBADADADADB
As a result, a dry rubber was obtained at a dry rate of 83 parts / hr. The loss on heating of this dry rubber was 0.17% by weight. Further, when the dry rubber was dissolved in tetrahydrofuran and analyzed by gas chromatography, the residual acetone content in the dry rubber was 1200 ppm. Furthermore, the process loss at this time was as bad as 4.8% by weight, and the specific power was 0.468 Kwh / Kg.

  As described above, the coagulation screw block has two or more combinations of the forward feed screw element and the reverse feed screw element, so that the process loss can be suppressed and the polymer can be efficiently recovered.

FIG. 1 is an explanatory view of an embodiment of an extruder used in the method of the present invention.

Claims (8)

  A method for recovering a polymer from a polymer solution by using an extruder in which a screw is rotatably arranged inside a barrel having a coagulation zone, wherein the screw is placed in a region corresponding to the coagulation zone. A method for recovering a polymer, comprising a coagulation screw block formed, wherein the coagulation screw block has two or more combinations of a forward feed screw element and a reverse feed screw element.   The method for recovering a polymer according to claim 1, wherein the coagulation screw block has a kneading disk for forward or reverse feeding.   The method for recovering a polymer according to claim 1 or 2, wherein a screw that is biaxially engaged and rotates in the same direction is used.   An apparatus for recovering a polymer from a polymer solution, comprising an extruder in which a screw is rotatably arranged inside a barrel having a coagulation zone, and the screw is formed in a region corresponding to the coagulation zone A polymer recovery apparatus comprising: a solidified screw block, wherein the solidifying screw block has two or more combinations of a forward feed screw element and a reverse feed screw element.   The polymer recovery apparatus according to claim 4, wherein the coagulation screw block has a kneading disk for forward or reverse feeding.   6. The polymer recovery apparatus according to claim 4 or 5, wherein a drainage zone is provided downstream of the coagulation zone inside the barrel.   The polymer recovery apparatus according to claim 6, further comprising a drying zone downstream of the drainage zone.   The polymer recovery apparatus according to any one of claims 4 to 7, which has a biaxial meshing type and a screw rotating in the same direction.

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