JPS60163933A - Recovery of polymer - Google Patents

Abstract

PURPOSE:To recover a polymer continuously in a high rate of recovery by a simple process, by coagulating a thermoplastic resin latex, enlarging the coagulated particles and feeding the slurry comprising the particles of a large diameter to a screw squeezer. CONSTITUTION:A thermoplastic resin latex 1 (e.g., a latex of a polymer of styrene or acrylonitrile) is mixed with a coagulant 3 (e.g., CaCl2) to form a highly viscous uniform cream. This cream is fed through a nozzle 6 to a coagulation tank 8, where it is coagulated by the addition of a coagulant 7. The coagulated particles are enlarged by aging them in an aging tank 9. In this way, a slurry containing at least 80%, based on the entire slurry particles, large particles having a diameter >=0.25mm. is formed. The polymer is recovered continuously at a high rate of recovery by feeding the slurry to a screw squeezer 3.

Description

[Detailed Description of the Invention] The present invention relates to a method for continuously recovering a polymer from a thermoplastic resin latex using a scree tie squeeze dehydrator. Conventionally, as a method for recovering a polymer from a thermoplastic resin latex, The most commonly used method is to add a so-called coagulant, which deactivates the emulsifier contained in thermoplastic resin latex, to coalesce and granulate the coagulated and liberated fine polymers. Requiring extremely multiple and diverse processes such as centrifugal dehydration to remove a certain amount of water, drying with hot air in an airflow and fluidized dryer, and then recovering the polymer in an extruder, and requiring a great deal of utility and labor; There are many undesirable points such as large losses during the process, difficulty in preventing foreign matter from entering, and unstable discharge.

Therefore, various studies have been conducted to improve these shortcomings. For example, thermoplastic resin latex is fed into a screw-type squeezing dehydrator in the form of a coagulated ridge or slurry, and then mechanically squeezed inside the screw to create a large Conventional coagulation involves dehydrating the water from the cis slurry using a dehydration mechanism installed at the rear of the screw, then draining the residual water from the pentrol located at the screw type and continuously recovering the molten polymer. - A method has been proposed that allows dehydration, drying, and granulation to be performed all at once among the various processes of soaking, drying, and granulation, thereby simplifying the process.

(Special Publication No. 50-17227, Japanese Patent Publication No. 56-13165
No. 6, etc.). However, when an inorganic acid is used as a coagulant, the coagulated material obtained by the conventional coagulation method described above exhibits a wide particle size distribution in which the recovered particles include coarse particles but also some fine particles. Furthermore, when an inorganic salt is used, the particle size will include many fine particles. Therefore, by using a screw type squeezing dehydrator, there is no problem with the granulation itself.
Although it is excellent in terms of simplifying the process, fine particles may leak along with water from the dehydration mechanism, resulting in loss, and the polymer may not be efficiently recovered or the fine particles leaked out. It requires an additional process of recovering the liquid, and there are disadvantages in that the discharge stability is poor.

Therefore, intensive studies were conducted to find out how to prevent particle leakage, increase collection efficiency, and improve discharge stability, which is the objective of the present invention. As a method, (1) the dehydration mechanism is made to have a filter or slit structure to reduce the opening size, and (2) improvements in the coagulation method were considered in order to enlarge the coagulated particles. However, there are limits to reducing the opening size of the dewatering mechanism described in item (2) due to constraints on mechanical strength and a decrease in capacity due to a decrease in the amount of water removed.

Therefore, the inventors of the present invention conducted various intensive research on improving the coagulation method for enlarging the particles described in item The present invention was achieved by discovering that stability is significantly improved.

In the method for recovering a polymer from a thermoplastic resin latex according to the present invention, the thermoplastic resin latex is coagulated, the coagulated particles are enlarged, and large particles with a particle size of 0.251 m or more account for 80% or more of the total slurry particles. A method for recovering a polymer from a thermoplastic resin latex is provided, the method comprising forming a slurry containing particles with a large particle size and then feeding the slurry containing particles with a large particle size thus obtained to a screw-type squeezing dehydrator. Ru.

Examples of the thermoplastic resin latex that can be applied to the present invention include (1) a polymer latex of alkenyl aromatic monomers such as styrene and α-methylstyrene obtained by a general emulsion polymerization method, (2) acrylonitrile, methacrylonitrile,
Polymer latex of acrylic monomers such as methyl acrylate, methyl methacrylate, butyl methacrylate, ■ Copolymer latex consisting of a mixture of two or more of the above monomers, ■ At least one of the above monomers and polybutadiene or a graft polymer latex of butadiene and a butadiene yarn copolymer of a heptadolefin yarn monomer,
■Graft polymer latex of at least one of the above monomers and a mixture of polybutadiene and butadiene yarn copolymer; ■Mixed latex of two or more of the above polymer latex, copolymer latex, and graft polymer latex. It will be done.

In the present invention, one preferable embodiment of the coagulation method is the coagulant divided addition coagulation method, in which a part of a coagulant suitable for coagulating the thermoplastic resin latex is added to the thermoplastic resin latex, and the coagulant is added to the thermoplastic resin latex during supply. Mix to create a uniform high viscosity cream.

This high viscosity cream is then fed in the form of a strand from a feed nozzle to a coagulation tank. At this time, it is desirable to have a scraping mechanism inside the nozzle to prevent the nozzle from clogging.

The remaining amount of the coagulant is further added to the coagulation tank and heated and stirred, whereby the strand-shaped high viscosity cream is coagulated. Furthermore, the particles are aged in a maturing tank which is heated and stirred in the same manner as the coagulation tank to obtain strong, large-sized particles. When the slurry containing almost no fine particles obtained by this coagulation method is supplied to the Scree-Tino squeezing dehydrator, particle leakage from the dehydration mechanism is significantly reduced.
A new and efficient continuous polymer recovery process with less loss and simplified steps becomes possible. The present invention provides a method for recovering a polymer, which is characterized by a combination of a coagulation method that generates a small amount of fine particles as described above, and a scree type wringer dehydrator.

The coagulant used in the coagulation method of the present invention is an inorganic salt such as CaCl2. BaCl2. MgCl2
゜ZiCZ2j Az2(so4)3 and MgSO4:
Examples of inorganic acids include compounds selected from HCl, H2SO4, etc., or mixtures thereof. In the above-mentioned coagulation method, there is no significant difference in the particle size obtained whether the coagulant is an inorganic salt or an inorganic acid.Since acids are concerned about corrosion of equipment and equipment due to sulfate groups remaining in the particles, inorganic salts are preferred.

The amount of coagulant is determined by the type and amount of emulsifier used during polymerization of thermoplastic resin latex, but it is generally 0.5 to 5.0% by weight based on the polymer, which is better. is from 1.0 to 303. If it is less than 0.5% by weight, the coagulation of the latex will be insufficient, and the amount used will be less than 5% by weight.
Even if it exceeds 0% by weight, there is almost no change in the coagulation state or particle size, which is uneconomical.

The dividing ratio of the amount of coagulant is important in order to produce a uniform high viscosity cream in the first stage of addition; if it is too small, the viscosity will not reach a level that can be extruded into strands, and if it is too large, the cream will not be creamy. It becomes moxa-like with no fluidity.

Therefore, in order to obtain a uniform and highly viscous cream, 30 to 60 g of the total amount should be added in the first step, but it is best to determine the optimum amount based on the viscosity and properties of the cream by testing in advance. . A mixer such as a line mixer may be used to generate the high viscosity cream, if necessary.

This high viscosity cream is discharged from the feed nozzle in the form of a strand, and it is appropriate that the nozzle diameter of the feed nozzle for discharging the cream in the form of a strand is μ2 to 10s+iφ. If it is less than 2nφ, the cream will be injected from the feed nozzle and fine particles will not be generated (if it exceeds 101mφ, it will become coarse particles and will be easily broken by stirring in the coagulation tank.The preferred nozzle diameter is 3 to 5 With a diameter of this size, high viscosity cream can be discharged uniformly, and if the scraping mechanism provided inside the feed nozzle is constantly rotating, it can be discharged smoothly without clogging the nozzle.

The discharged cream is fed into the above-mentioned coagulation tank as a second stage, where the remaining coagulant is added and stirred at high temperature, where it is coagulated. Next, it is sent to an aging tank which is also stirred at a high temperature, where it is further aged to form strong, large-sized particles. The temperature in the tank depends on the thermoplastic resin latex, but is generally preferably 70° C. or higher. Further, stirring may be performed at a rotational speed such that the slurry particles in the tank are uniformly dispersed.

When the slurry made of strong, large-sized particles obtained by this coagulation method is fed to a scree-type squeezing dehydrator,
The slurry is mechanically squeezed in the wringer dehydrator, and the squeezed out water is discharged from a dewatering mechanism provided in the wringer dehydrator. By making the slurry particle size larger and stronger,
At this time, there are very few particles entrained in the discharged water, and almost all of the slurry is wrung out and melted in the dehydrator, the remaining small amount of water is discharged from the vent, and the dried resin is extruded from the tip. . In this way, by combining the coagulant division addition coagulation method and the squeezing dehydrator, 1. An efficient collection process with very little loss and simplified steps can be achieved. Furthermore, the quality of the recovered polymer is no different from that obtained by conventional coagulation methods.

In the present invention, the pressure coagulation method, which is another embodiment of the coagulation method, refers to the instantaneous coagulation method in which the thermoplastic resin latex and coagulation liquid are brought into contact with each other under pressure in a pressure-resistant coagulation tank in a temperature range equal to or higher than the heat distortion temperature of the polymer. This is a coagulation method to obtain particles by coagulating the particles. As for the conditions, it is desirable to solidify under a pressure of 05 to 1.8 Kf7cm G and a solidification temperature in the range of 110 to 130°C. For example, when coagulating using a conventional coagulation method using an inorganic salt as a coagulant, the resulting coagulated particles will contain many fine particles and the recovery rate will be very poor, but when coagulating using the pressure coagulation method described above, A sharp particle size distribution with fewer fine particles can be obtained, and the recovery rate can therefore be improved.

In addition, when recovering the polymer, when the solidified slurry is fed to a screw-type wringer dehydrator, the slurry is dehydrated, dried, and melted inside the machine, so that other i+++ raw materials (such as acrylonitrile-styrene copolymer, etc.) It is also possible to apply it as a process in which blending is performed simultaneously by supplying additives, etc.

The present invention will be explained in detail below using Examples and Comparative Examples. Note that parts and parts in the following Examples and Comparative Examples mean parts by weight and weight % unless otherwise specified. Further, the type of the screw type wringer dewatering machine is not limited to those described in the examples, and there are no particular restrictions on the type of screw type, such as single screw or double screw, meshing of the screws, presence or absence of non-meshing vents, number of stages, etc.

Example 1 (Manufacture of thermoplastic resin latex I) 25 parts of polybutadiene latex (solid content) were mixed with 1 part of sodium stearate, 200 parts of distilled water, and a catalytic amount of a radical polymerization catalyst, and 53 parts of styrene, A thermoplastic resin latex with a solids content of aO* is produced by dropping a mixture of 22 parts of acrylonitrile and emulsion polymerizing it.
I got it.

(Coagulation) Using the above latex, a coagulant-divided addition coagulation method was carried out as follows under the coagulation conditions shown in Table 1 and the coagulation interior shown in FIG.

Thermoplastic resin latex is supplied from a storage tank 1 to a feed starch 2. The first stage coagulant aqueous solution is supplied from a storage tank 3 by a feed pump 4. A high viscosity cream is generated at the confluence section 5 of the latex and coagulant aqueous solution, and is discharged from a feed nozzle 6 (scraping type) into a strand shape into a coagulation tank 8. A second-stage coagulant aqueous solution is added into the coagulation tank from the storage tank 7, and is heated and stirred by the heating steam pipe 10 and stirring blades 12 to coagulate the Shifreem. Next, it is sent to the aging tank 9, where it is also heated by a heating steam pipe 11 and a stirring blade 13.
While being stirred, the coagulated material is further matured to form strong, large-sized particles.

Table 1 shows the coagulation conditions.

As a result of carrying out the coagulation under the coagulation conditions shown in Table 1 or higher, particles having a particle size distribution as shown in Table 2 were obtained.

(Pelletization using a screw-type wringer dehydrator) The particles obtained by the above coagulation method were adjusted to a slurry concentration of 2°, and granulated using a wringer dehydrator.

The scree type squeezing dewatering machine is shown in Fig. 2, and the scree has two shafts meshing in the same direction, 50nφ, i=28
．． 4. Vent: 2 stages, double dehydration slit opening O-25m
m (equivalent to 60m@i+h).

In FIG. 2, slurry introduced from a feed hopper 1 is supplied to a screw type wringer dehydrator 3 via a screw feeder 2. The slurry is mechanically squeezed in a squeezing dehydrator, and most of the squeezed water is discharged from the dewatering slit 4. The opening of this dehydration slit is 0.25 ram, which corresponds to 60 m@sh. The slurry from which most of the water has been discharged from the dehydration slit 4 is then kept in a molten state, and the remaining small amount of water is discharged from the vent 5, and the polymer is continuously recovered. The obtained polymer has no foaming, dries well, and is comparable to that obtained by conventional coagulation-dehydration-drying-granulation method.

The particle size of the slurry obtained in the coagulation of Example 1 is as shown in Table 2 above (0.25 mm or larger particles accounted for 83 mm of the total particles). The leaked particles and their particle size distribution are shown in Table 6.

Example 2 (Production of thermoplastic resin latex ■) 18 parts of polybutadiene latex (solid content) was mixed with 1 part of sodium stearate, 200 parts of distilled water, and a catalytic amount of a radical polymerization catalyst, and 60 parts of styrene and A mixture consisting of 22 parts of acrylonitrile was added dropwise to obtain a thermoplastic resin latex (2) with a solids content of 32'%.

(Coagulation) Using the above latex, a pressure coagulation method was carried out in the coagulation apparatus shown in FIG. 3 as follows.

In FIG. 3, the coagulation tank 1 is a pressure-resistant stirring tank with an internal volume of 7 J, and the stirring blades 2 are three paddle blades with a diameter of 110 m1 and inclined at 45°, and are installed in three stages. The stirring shaft was adjusted to 1200 rpm using a continuously variable transmission 9. The latex is supplied to the coagulation machine through piping 4 at the bottom of the coagulation tank. The coagulant solution and heating steam are supplied from piping at the bottom of the coagulation tank 5 and 6, and the solidified slurry is discharged from the horizontal pipe 7 at the top of the coagulation tank. In this case, a pressure regulating valve 10 was installed in the coagulation slurry discharge pipe 7 to keep the internal pressure of the coagulation tank constant. The temperature of the liquid in the coagulation tank is detected by a thermometer 8, and can be adjusted to a predetermined temperature by adjusting the water vapor flow rate.

During coagulation, the rotation of the coagulation tank stirring shaft was set at 120° rpm (
Adjust the thermoplastic resin latex to 1,000 m
/hr, Q, 1.2 m of 5% CaC12 aqueous solution
/hr was supplied to the coagulation tank using a metering pump. At the same time, water vapor at a pressure of 3 kg/cm2G was introduced into the coagulation tank, and the liquid temperature in the coagulation tank was adjusted to 105°C. In addition, in order to adjust the coagulation tank internal pressure to 0.5 Kg/cm ・c, the slurry discharge pipe pressure NIl! I activated the valve control.

The particle size distribution of the particles obtained by the above coagulation method was as shown in Table 3.

No. 3 (Pelletization using a screw tights wringer dehydrator) The particles obtained by the above coagulation method were granulated using a wringer dehydrator under the same conditions as in Example-1. The results, as shown in Table 6, were the same as in Example-1.

Comparative Example 1 Using the thermoplastic resin latex summer obtained in Example 1,
Coagulation was performed by a conventional coagulation method using the coagulation apparatus shown in FIG.

The thermoplastic resin latex is introduced from the storage tank 1 into the coagulation tank 5 through the feed pump 7°2. The coagulant 3 is mixed with dilution water 4 in a pipe, and is also introduced into the coagulation tank as an aqueous coagulant solution. The coagulation tank is heated and stirred by steam 9 and stirring blades 7, and the latex introduced therein and the aqueous coagulant solution are contacted and mixed to form a coagulation slurry. Next, the slurry (17) is introduced into the ripening tank 6 from the overflow chute of the coagulation tank, and the maturing tank is heated and stirred by steam lO and stirring blades 8, like the coagulation tank, to ripen the particles.

As a result of coagulation under the coagulation conditions shown in Table 4, particles having the particle size distribution shown in Table 5 were obtained.

Table 4 Table 5 (Pelletization using a scree type squeezing dehydrator) Example-1
Example-1 using the Scrier type wringer dehydrator used in
Granulation was carried out under the same conditions as above, but the particles obtained by the above coagulation method were mostly fine particles and the opening of the dehydration slit (0, 25
(equivalent to mII s 60ml 5h) Larger particles are 60
%, which is lower than in Examples-1 and 2. Regarding the granulation itself, the discharge was somewhat unstable, and a large amount of particles leaked from the dehydration slit, making the dehydration liquid cloudy. The solid content is 6 to 8 inches, and the leakage rate is 18q6 to the feed.
This is a very inefficient method for recovering polymers.

Comparative Example-2 Using the coagulated slurry obtained in Comparative Example-1, the dewatering slit opening was made as small as 0.1 mm (150 mesh) and the same conditions as in Example-1 were used in a screw-type squeezing dehydrator. As a result, the granulation itself was not particularly problematic, but as the operating time progressed, the dehydration slits became clogged, the amount of dewatering decreased, the capacity decreased, and the discharge became unstable.
It was not possible to efficiently and continuously recover the polymer.

The results of Comparative Examples 1 and 2 are also shown in Table 6.

Regarding Examples 1 and 2 and Comparative Example 1, the operation time was 5 to 6 hours, but there was almost no clogging of the dehydration slit and no decrease in performance was observed.

However, in Comparative Example-2, the dehydration slit opening was 0.1 Im.
Because of this, the dewatering slits became clogged as the operating time increased, and the amount of dewatering decreased, resulting in a gradual decline in capacity. (*Feed amount 72 Kf/hr for 4 hours of operation →
(reduced to 50 Kp/hr)

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of one embodiment of the coagulation device according to the present invention. l... Latex storage tank, 3... Coagulant storage tank, 6... Feed nozzle, 8... Coagulation tank, 10
゜11... Steam piping for heating, 9... Aging tank Figure 2 is a schematic diagram of a scree-type diaphragm dehydrator. 2.-Screen feeder, 3. Squeezing dehydrator, 4.
...Dewatering mechanism section, FIG. 3 shows a schematic diagram of another specific example of the coagulation device in the present invention. l... Coagulation tank, 4... Latex piping, 5... Coagulant piping, 6... Steam piping for heating, 2... Stirring blade,
8...Thermometer Figure 4 is a schematic diagram of a conventional coagulation device.

Claims (3)

[Claims] (1) In a method for recovering a polymer from thermoplastic resin latex, the thermoplastic resin latex is coagulated, the coagulated particles are enlarged, and large particles with a particle size of 0.25111 or more are added to 80% of the entire slurry particles. A method for recovering a polymer from a thermoplastic resin latex, which comprises forming a slurry containing the above particles, and then supplying the slurry containing large particles thus obtained to a screen-tie squeezer dehydrator. . (2) the enlargement of the coagulated particles causes the coagulant to mix with the thermoplastic latex to form a uniform high viscosity cream;
1 coalescence according to claim 1, which is carried out by supplying the cream through a nozzle to a coagulation tank, further adding a coagulant to the coagulation tank to coagulate the high viscosity cream, and then ripening the coagulated particles. collection method. (3) Enlargement of the coagulated particles described above can be prevented by mixing the thermoplastic resin latex and coagulant at a temperature above the softening point of the polymer under pressure in a coagulation tank and fusing the coagulated particles. A method for recovering a polymer according to claim 1.