JPS60127311A - Manufacture of thermoplastic resin powder - Google Patents

Abstract

PURPOSE:To attempt to reduce both operating cost of the equipment and its construction cost along with obtaining, in liquid medium, any size of titled power of good properties, by delivering ABS resin latex through nozzle into coagulating solution at specific temperature. CONSTITUTION:The objective power can be obtained by delivering (A) latex of the thermoplatic resin with butadiene, styrene and acrylonitririle as the monomer components totalling 90wt% or more through nozzle having many capillaries into coagulating solution at 40-88 deg.C (e.g. equeous solution of sulfuric acid). Said capillaries are preferably made of stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention produces a latex by discharging a thermoplastic resin latex composed of a total amount of 90% by weight or more of Petadier, styrene, and acrylonitrile as monomer components into a coagulating liquid from a coagulating nozzle. The present invention relates to a method for producing thermoplastic resin powder, characterized in that the temperature of the coagulating liquid during coagulation is in the range of 40°C to 88°C. In this specification, latex refers to a mixture of a liquid obtained by emulsion polymerization and thermoplastic resin fine particles.The polymerization method used in the polymer industry, which manufactures resins, paints, adhesives, etc. through polymerization reactions, is emulsion polymerization. , bulk polymerization, suspension polymerization and solution polymerization are the most popular.

Among these polymerization methods, the bulk polymerization method, the @turbidity polymerization method8 and the solution polymerization method each have their own advantages and disadvantages, but the polymerization behavior is very similar, so the produced polymers have similar physical properties. In addition, these three polymerization methods have technical and operational difficulties in designing the polymer structure, including the copolymer composition, and are subject to many practical limitations. It is often difficult to apply when trying to obtain resins.

However, the emulsion polymerization method uses an emulsifier to form monomers into extremely small particles and polymerizes them, so it has a completely different polymerization mechanism from the three types of polymerization methods mentioned above, and as a result, free polymerization occurs. Enables the design of combined structures.

From an operational standpoint, the emulsion polymerization method is burdened by the use of emulsifiers, such as countermeasures against foaming and wastewater treatment.Also, from a quality standpoint, there are undesirable problems such as the emulsifier being mixed into the polymer. As mentioned above, this method is a powerful method for producing resins with excellent functions, and has been widely used in the polymerization process of high value-added resins in recent years. For example, Butageno as a monomer component used in the present invention. Thermoplastic resins consisting of 9ON*% or more of styrene and acrylonitrile in total are generally called ABS resins, and are typical high-performance resins manufactured by emulsion polymerization, with good impact resistance, moldability, surface appearance, etc. It is a resin with excellent properties.

The manufacturing process of thermoplastic resin using emulsion polymerization, which is an extremely important polymerization method, usually consists of an emulsion polymerization process, a coagulation process, a washing and dehydration process, a drying process, and a pelletizing process, and the product is in the form of pellets or powder. Will be shipped. Among these steps, the emulsion polymerization step is an important step that determines the physical properties of the produced polymer, but this step hardly affects the subsequent steps. This is because the polymer is obtained as fine particles in an emulsion regardless of the polymerization recipe, and the physical properties of the emulsion have little to do with the polymerization recipe. However, the coagulation process that follows the emulsion polymerization process causes the fine particulate polymers in the emulsion to coalesce and become bulky.
This is the process of extracting it as a powder.

Because the properties of the powder obtained depend on the method, it is necessary to use multiple devices such as dehydrators, dryers, dust collectors, and storage tanks.
The design of equipment will be affected. In other words, it is no exaggeration to say that the coagulation process determines the design of a plant for manufacturing polymers using emulsion polymerization. If it were possible to produce a powder with uniform particle size, close to spherical shape (without fine powder or coarse particles), and excellent bulk specific gravity and dehydration properties during the coagulation process, the operability of the entire manufacturing process 2 Workability and process stability .

It is clear that it contributes greatly to energy costs, environmental measures, labor savings, etc.As mentioned above, the coagulation process is positioned as an important process in the production of thermoplastic resins because it affects the properties of the powder.

On the other hand, although the subsequent washing and dehydration process, drying process, and pelletizing process are largely required as unit processes, the quality of these processes rarely has a great influence on other processes.

Therefore, in applying the emulsion polymerization method, not only the establishment of a polymerization method but also the establishment or development of a coagulation method is an extremely important theme. However, regarding the coagulation method, it is not clear whether it is because powder of an acceptable level can be easily obtained, the coagulation mechanism is difficult to understand, or for some other reason, but research and development efforts have not been made in the past. It seems that not much was done. For this reason, the current coagulation technology and coagulation equipment are outdated, and the polymer powder produced is amorphous and has a wide particle size distribution (some coarse particles are included, but a large amount of fine powder is also included). It is usual.

As a result, the polymer powder may scatter (decreased yield or environmental problems, clog in pipes or at the outlet of the storage tank due to the low fluidity of the powder, deteriorate the working environment due to dust generation, or increase the risk of dust explosions, etc.) In addition, the bulk specific gravity of the powder is small, and the dehydration properties during dehydration are poor, resulting in high transportation and storage costs.
Moreover, the dryer consumes a large amount of energy.

In recent years, with the rise in energy prices and the need to reduce manufacturing costs, the importance of the coagulation process, which has the greatest impact on costs, has been recognized, and in order to improve the physical properties of the resin powder obtained in this process. Many methods have been proposed. By the way, excellent powder physical properties mean good fluidity.

It is characterized by its low jetting properties, good dehydration properties, high bulk specific gravity, absence of fine powder, and absence of coarse particles. It can be said that glass beads etc. satisfies these conditions well in terms other than jet property.

In other words, a powder consisting of particles with a uniform particle size (approximately spherical) is ideal.

The methods that have been proposed so far for obtaining such powders belong to a method called the PL mist drying method or the spray coagulation method. The latter is a method of producing spherical powder, and the latter is a method of spraying polymer latex into a coagulation atmosphere to produce a similar coagulated body. Naturally, some proposals include further developments and improvements to these methods, but in any case, the common feature of these methods is that they use a gas phase to fix the shape of the mist droplets. It can be said that Therefore, the powder particles obtained are close to spherical, reflecting the shape of the mist droplets (powder physical properties are also improved to some extent compared to conventional coagulated powders. However, the average particle size is very small, As it falls into the category of fine powder, it is impossible to escape from various problems caused by fine powder.This is due to technological issues such as maintaining the shape of large droplets in space, controlling particle size distribution, and controlling airborne time. This is because there are unresolved problems.In addition, these methods require large equipment due to the use of space, which requires a large amount of construction cost. The operating cost is also enormous because it is necessary to evaporate 1 to 3 times the amount of water than the polymer.For the reasons mentioned above, spray drying is a method for producing powder with better physical properties than polymer latex. Methods that should be referred to as spray coagulation methods or spray coagulation methods are not necessarily excellent measures for improving the coagulation process.

However, the most effective coagulation process and the most excellent emulsion polymerization manufacturing process for thermoplastic resins not only produce powder with excellent powder physical properties as mentioned above, but also have low operating costs and construction costs. Three conditions must be met.

The Ministry of the Invention and others took advantage of this point of view and previously filed a patent application in 1982-73.
We have made several proposals including No. 115, and as a result of further intensive research, we have arrived at the present invention.

The present invention relates to a method for producing powder of arbitrary particle size in a liquid without using a gas phase, and provides significant operating cost benefits with a small investment in equipment.

In the present invention, a coagulation nozzle having a large number of thin tubes is immersed in a coagulation liquid to obtain butadiene as a monomer component.

Production of thermoplastic resin powder characterized in that the temperature of the coagulation liquid is adjusted within the range of 40°C to 88°C when producing thermoplastic resin powder containing 90% by weight or more of styrene and acrylonitrile in total. The present invention provides a method.

Generally, coagulated particles obtained by applying a coagulant to a polymer latex become more solid as the temperature increases, and are completely solidified near the glass transition temperature of the polymer.

If the temperature is further increased, the polymer transitions to a rubber state.

Therefore, when performing a dehydration operation in which a strong external force such as centrifugal force or vacuum suction force is applied to a wet polymer powder to separate solid and liquid, the wet polymer powder must be strong enough to withstand the operation. The wet powder must be heated to a certain temperature to solidify it. However, in the conventional coagulation method, the temperature of the slurry obtained after coagulation is performed at a constant temperature is raised to a temperature several tens of degrees below the solidification temperature (1) due to the need to control the properties of the powder. Usually, the user performs the following operations.

However, in the method of producing thermoplastic #B fat powder which has excellent powder physical properties by discharging a polymer into a coagulation liquid from a coagulation nozzle as described in the present invention.

The first factor that determines the properties of the powder is the inner diameter of the capillary, and the second factor is the relative velocity between the latex flow rate and the coagulation fluid flow rate at the tip of the capillary, and the coagulation fluid temperature has almost no effect on this. Therefore, the temperature of the coagulating liquid can be selected arbitrarily, but as mentioned above, the strength of the coagulated particles in the coagulating slurry changes in relation to the temperature of the coagulating liquid. If this operation is performed, particles may be crushed due to lack of mechanical strength following the solidification operation (during operations such as heating and solidification operations or in the piping connecting these devices).
As a result, a large amount of fine powder is generated. Therefore, in order to avoid crushing the coagulated particles of thermoplastic resin latex that are discharged from the coagulation nozzle and are formed into beads to avoid the generation of fine powder, and to solidify them in a good shape, the slurry must be prepared with extreme caution. There are two methods: handling or normal handling under the following conditions, but it goes beyond explanation that the latter is extremely advantageous from an industrial standpoint. This condition means, in the present invention, that the coagulation liquid temperature is 40°C or higher, and the coagulated particles obtained in the coagulation liquid at a low temperature of less than 40°C are very soft and are common in ordinary industry. The resulting thermoplastic resin powder, which cannot withstand physical handling and is crushed before it solidifies, contains a large amount of fine powder.

On the other hand, if the temperature of the coagulating liquid is increased, the coagulated particles will gradually become more solid and will eventually become completely solidified.
As previously proposed by the present researchers in Japanese Patent Application No. 134116/1982,
If it is necessary to perform a treatment such as adjusting the pH of the coagulated slurry for the purpose of improving the physical properties of the resin itself at a temperature of 8°C or lower, the temperature of the coagulating liquid must naturally be kept at 88°C or lower. Furthermore, if the temperature of the coagulation liquid is adjusted to 88℃ or higher, the ABS resin latex discharged from the coagulation nozzle will have a bead-shaped coagulated mother shape, and under normal stirring or transportation conditions, the ABS resin latex will have a bead-like shape in which single particles are connected. Since the particles are not divided into single particles, it is necessary to strengthen the crushing force such as stirring or install a new crusher.

Therefore, the coagulation liquid temperature is 88℃, which is the solidification temperature of ABS resin.
It is preferable that it is below.

The present invention will be explained in more detail.

The thin tube referred to in the present invention is one that satisfies L/D≧0.065Re (L is the tube length, D is the tube inner diameter, and Re is the Reynolds number regarding the latex flow in the tube), and is chemically resistant to polymer latex and coagulation liquid. Anything that is physically stable should not be used. Such materials include stainless steel and titanium.

Hastelloy, metals such as precious metals, polymethyl methacrylate, polyvinyl chloride, nylon, polyester, polycarbonate, polypropylene.

Polyethylene, ABS resin, polyacetal.

Resins such as AS resin and fluororesin, ceramics, and glass are suitable. Further, the coagulation nozzle having such a thin tube is one in which the above-mentioned thin tube is assembled to a substrate having an arbitrary shape.

The substrate and other members can be made of the same material as the capillary.

Coagulating liquids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

Aqueous solution of acids such as sulfite; magnesium sulfate.

Aqueous solutions of polyvalent metal salts such as magnesium chloride, calcium chloride, aluminum sulfate, aluminum chloride, and potassium aluminum sulfate can be used alone or in combination. Furthermore, it goes without saying that chemicals having the ability to coagulate the polymer latex, such as alcohols, can also be used in the same manner as the above-mentioned coagulating liquid.

Further, the thermoplastic resin latex that can be used in the present invention is a polymer latex generally called ABS resin produced by an emulsion polymerization method.

It is a polymer latex composed of a total amount of butadiene, styrene and hyacrylonitrile as monomer components of 90 or more by weight. When coagulating such ABS resin latex, the coagulated particles in the slurry obtained by contacting the coagulating liquid with the latex solidify at a temperature higher than 88°C. If so, the temperature of the coagulating liquid must be adjusted to 88°C or less.

The present invention will be specifically described below with reference to Examples.

All numbers in the examples are based on weight.

Example 1 A coagulation solution containing 1% sulfuric acid was poured from the rear end of the nuclide at a rate of 801 per minute into a stainless steel coagulation tank with a width of 30 cm, a depth of 30 cm, and a length of 2 m. After separating the P using mesh wire mesh, it is received in the coagulation liquid receiver 501. The coagulating liquid in the coagulating liquid receiver is circulated to the coagulating tank via a pipe, and the sulfuric acid consumed by the coagulating reaction during operation and the water carried out in the coagulating particles are replenished to keep the coagulating liquid volume and sulfuric acid constant. The concentration was controlled so that it did not fluctuate. Further, water vapor was supplied to the coagulation liquid receiver to heat the coagulation liquid, and the temperature was controlled at 60°C. Next, a coagulation nozzle having 20 glass tubes with an outer diameter of 211 L + an inner diameter of 1 mm and a length of 50 fins was installed in the coagulation tank, and the monomer components were 40% butadiene, 40% styrene, and 20% acrylonitrile.
An ABS resin latex composed of was fed to the nozzle at a rate of 250-min. As a result, the ABS resin latex was vigorously discharged into the coagulation liquid from the tip of the thin tube, coagulated into beads, and was discharged from the coagulation tank along with the flow of the coagulation liquid, which was then collected by a wire mesh installed in the channel. . Next, the obtained ABS resin wet powder was transferred to another stirring tank, water was added to reslurry it, the pH was adjusted by the method described in Japanese Patent Application No. 57-134116, and the temperature of the slurry was lowered to 92°C.
The ABS resin powder was solidified by raising the temperature to .degree. C., and further centrifugally dehydrated to obtain a wet powder containing 18.5% water (dry base). When the physical properties of the ABS dry powder obtained by drying this powder were measured, the average particle size was 0.91, and the bulk specific gravity was 0.45.
The fluidity index was 88.200, and the amount passing through a standard mesh sieve was 0.30% of the total. The coagulation operation was continued for 12 hours, during which time the operating conditions were very stable and no clouding of the coagulation liquid due to the single polymer fine powder was observed.

Example 2 Using the same coagulation tank as in Example 1, a coagulation solution containing 0.8 g of sulfuric acid water bath was circulated through the coagulation tank in the same manner and at the same flow rate as in Example 1. Further, in the same manner as in Example 1, the temperature of the coagulating liquid was adjusted to 70° C., and water and sulfuric acid taken out during operation were replenished. The coagulation tank adjusted as above has an outer diameter of 2.5 mm + an inner diameter of 0.8 mm + a length of 40 mm.
A coagulation nozzle with 50 thin polycarbonate tubes was installed, and the monomer component was 50% butadiene.

A latex of ABS resin consisting of 30% Step 2, 17% acrylonitrile and 3% methacrolein was fed to the nozzle at a rate of 300 d/min. As a result, as in Example 1, the polymer latex was forcefully discharged from the tip of the thin tube into the coagulating liquid, and was coagulated in a beaded shape as it was discharged from the coagulating tank along with the flow of the coagulating liquid. The ABS resin wet powder obtained in Example 1
After adjusting the pH in the same manner as above, the mixture was solidified at 90°C, and further centrifugally dehydrated to obtain a wet resin powder containing 16.4% moisture (dry base). Further, the wet powder was dried in the same manner as in Example 1.

When the powder physical properties were measured, the average particle size was Q, 77 ma.
te bulk specific gravity is 0.48. The liquidity index is 86. The amount passing through the ZOO mesh standard sieve was 0.10% of the total.

This coagulation operation was continued for 20 hours, during which time the operating condition was very stable and reached 69. No clogging of the nozzle or clouding of the coagulated liquid due to fine resin powder was observed.

Example 3 A coagulation nozzle having 300 stainless steel thin tubes with an outer diameter of 0.81 mm, an inner diameter of 0.51 mm, and a length of 100 mm was installed at the bottom of a glass coagulation tank with an outer diameter of 100 mm and a height of 1 m. A coagulating liquid containing 0.5% aluminum sulfate and having a temperature of 40° C. was flowed through the gap between each capillary tube at a rate of 40 A' per minute. The entire amount of the coagulation liquid overflowing from the top of the coagulation tank was led to the solidification tank, and the temperature of the assimilation tank was adjusted to 90° C. by blowing steam into the tank. Now, in the coagulation nozzle installed in this coagulation device, 30% butadiene and Stereph 4 were added as monomer components.
ABS composed of 5% and 25% Hyacronitrile
A coagulation operation was performed by supplying resin latex at a rate of li/min. As a result, the ABS resin latex was discharged into the coagulation liquid with force from the tip of the tube, coagulated into beads, rose inside the coagulation tower together with the coagulation liquid, and was discharged from the top of the column.Then, the ABS resin particles were in the form of a slurry. It flowed down together with the coagulation liquid and entered an assimilation tank where it was heated and solidified. Since it overflowed the solidification tank, it was centrifugally dehydrated to obtain a wet resin powder containing 21.1% moisture (dry base). After drying the wet powder, we measured the powder properties of the ABS resin powder, and found that the average particle diameter was 0.47+++m, the bulk specific gravity was 0.43°, the fluidity index was 82,200, and the amount that passed through a standard mesh sieve was 0.33% of the total.
Met.

Comparative Example 1 The same experiment as in Example 1 was conducted except that the temperature of the coagulation liquid was adjusted to 20°C. As a result, it was possible to collect the coagulated particles with the wire mesh installed in the slurry flow path, and although the operating conditions were good during 8 hours of continuous operation and no nozzle clogging was observed, the coagulated particles were considerably crushed and solidified. When the liquid became cloudy with fine polymer powder, the fine powder floated to the surface and accumulated in other dead spaces of the ICL solidification tank. Further, the coagulated powder collected with a wire mesh was solidified in the same manner as in Example 1, and then centrifugally dehydrated to obtain a wet powder containing 25.1% moisture (dry base).

Furthermore, after drying the wet powder, the physical properties of the powder were measured and found that the average particle diameter was 0.75, and the bulk specific gravity was 0.36. The fluidity index is 80,200 mesh standard sieve passing amount is 1.6 overall.
%Met. It seemed that stable operation for a longer period of time would be impossible unless the fine polymer powder accumulated in the so-called dead space where the flow was slow was removed by some method.

Comparative Example 2 A coagulation operation was performed using a conventional method of dropping polymer latex into a container equipped with a stirrer and a heater.

First, put the same coagulating liquid 51 as in Example 1 into the container 65
After the temperature was raised to ℃, the same latex 51 used in Example 1 was slowly poured into the slurry while stirring vigorously so that the slurry temperature did not drop. After all the latex was poured into the stirring tank. The particles in the slurry obtained by heating the slurry formed in the tank and raising the temperature to 92°C are completely solidified.
This was centrifugally dehydrated to obtain a wet polymer powder containing 32.4% moisture (dry base). When this was dried and the physical properties of the powder were measured, the average particle size was 0.15, and the bulk specific gravity was 0.27.
The fluidity index is 73° and the amount passing through the 200 mesh standard sieve is 8.2% of the total. Ta. The method of this comparative example is a conventional method.

Claims (1)

[Claims] Powder with excellent powder physical properties produced by discharging thermoplastic resin latex consisting of 90% by weight or more of butadiene, styrene, and acrylonitrile as monomer components into a coagulation liquid from a coagulation nozzle having a large number of thin tubes. A method for producing thermoplastic resin powder, characterized in that the temperature of the coagulating liquid is in the range of 40°C to 88°C.