KR20000000782A - Process for preparing granular polymer from latex in sequence and apparatus thereof - Google Patents

Abstract

PURPOSE: A preparation method of thermoplastic polymer resin power from latex continuously and its apparatus are provided which can produce a product having a high apparent density and a low content of fine and coarse particle and increase its productivity. CONSTITUTION: Polymer latex having a glass transition temperature of 80-110°C obtained by emulsion polymerization is poured in a pair of agitators(5) with a series connection, added with 0.5-5 wt% of coagulant based on the total weight of resin composition to give coagulated particles, which are heat-treated, washed, dehydrated, and dried to give granular resin powder. The agitators(5) contain a multistage pitched paddle having 30-67% of agitator diameter and a linear velocity of agitation is 0.5-20 m/sec and a recirculation rate is 0.05-1.5 cubic meter. Heating source is saturated and unsaturated aqueous vapor having a temperature of 80-250°C and a pressure of 1-10 kgf/cm¬2 and is moved in the agitator directly.

Description

Process and apparatus for producing polymer latex continuously in granular form

The present invention relates to a method and apparatus for producing a thermoplastic polymer resin in powder from latex obtained by emulsion polymerization. The present invention relates in particular to a technique for achieving the goal of increasing the yield with the achievement of low powder properties, with both high apparent density and both fine and coarse particle contents. The present invention also aims to provide a process for the production of polymer powder with high properties which is operated with a short residence time.

Polymer latex in the present invention can be obtained through the grafting reaction of the vinyl monomer to the rubber particles in general emulsion polymerization. Such polymer resins are often produced in the form of powder finally dried through a polymerization step, agglomeration step, aging step, washing and dehydration step, and drying step.

Among these various steps, the step after the polymerization step is generally carried out continuously. Among them, the coagulation step is the first step in which the polymer latex is mixed with the coagulant to form a coagulation slurry, and the coagulation slurry is heated and solidified in the next aging step.

In the washing and dewatering step, the slurry of solidified polymer particles is continuously dehydrated as water, and at the same time, a solid-liquid separation unit process is performed.

This coagulation / maturation step plays an important role in the overall process flow as an important process linking the subsequent washing / dehydration step and drying step with the previous batch polymerization step process.

In other words, the coagulation and aging process not only affects the yield of the final polymer powder, but also affects the apparent specific gravity and particle size distribution of the powder.

In the final powder produced during this process, fine particles may be lost during transport and extrusion, causing environmental problems, and also acting as a factor to reduce the yield by flowing out during dehydration. In addition, packaging may cause loss of resin due to the scattering of fine powder, and dust generation may worsen the surrounding working environment.

Coarse particles as well as fine particles also cause various problems. That is, due to the coarse particles, it is difficult to remove residual impurities mixed in the particles, and a large amount of air is required to form a fluidized bed during the drying process. In addition, low apparent densities cause problems of increased storage and transport costs.

Various prior arts are known to solve the problems caused by the occurrence of such fine powders, non-uniformity of particle size distribution and low apparent density.

For example, Japanese Laid-Open Patent Publications No. 53-33244, No. 53-187873, No. 56-41227, No. 57-59929, and the like, spray the aqueous solution of the flocculant into the gas phase to release the polymer latex in a flocculating atmosphere. To induce agglomeration through contact with a flocculant, and then recover the powder through a aging tank. This has the disadvantage of having a problem of particle adhesion on the coagulation tank wall and the use of a facility which occupies a very large space. European patent application EP0101576 also discloses a process for neutralizing agglomerated slurries having a low pH with an aqueous alkali solution. However, during this process, fine powder may increase, which may cause problems in the dehydration process. In addition, European patent application EP0611788 describes a method of inducing agglomeration continuously through a multistage agglomeration process and agglomerating a polymer having a weight of 40 to 80 in the first step. This approach has the disadvantage of having to be accompanied by excessive installation and operation.

In order to solve the problems in the prior art, the present invention provides a method for producing a polymer powder having a high apparent specificity and reducing the content of fine particles and coarse particles with increasing the production of the polymer powder.

1 is a schematic diagram of an apparatus and process for recovering a polymer latex according to the present invention into granular powder.

<Explanation of symbols for main parts of drawing>

1. Water inlet

2. Polymer latex inlet

3. Coagulant Inlet

4. Heating source inlet

5. Stirrer

6. Slurry overflow tube

The present invention relates to a process for producing a polymer powder finally through a two-stage continuous stirring tank to improve the coagulation step and the aging step of the polymer latex prepared by emulsion polymerization. In more detail, the process used in the method of the present invention is composed of two stages of a series of stirring tanks connected in series, the first stirring tank is called agglomeration tank, and the second stirring tank is called a maturing tank. The coagulation tank is operated for the purpose of inducing particle formation by mixing the polymer latex and coagulant injected into the top of the coagulation tank through a stirrer in a strong turbulent flow through the stirrer. It acts to increase.

Latex and flocculant are added to the flocculation tank, and water is added to control the amount of solids in the flocculation tank. The slurry in the coagulation tank flows into the second aging tank by overflow, and the slurry solidifies through heat treatment in the stirring tank. The slurry in the aging tank flows into the next reservoir by overflow. It is transferred to the dehydrator by a pump to obtain particles from which water has been removed. The powder passed through the dehydrator is obtained as a final granular powder through drying.

As a heating source of each stirring vessel, saturated steam or unsaturated steam having a temperature of 80 to 250 ° C. and a pressure of 1 to 10 kgf / cm ² is used, and is directly introduced into the stirring vessel. The higher the temperature of the heating source, the smaller the amount of steam for maintaining each stirring vessel at a constant temperature.

Such a heating source is effectively dispersed so that the effective vapor surface area is increased and heat transfer in the agitation tank should be smoothly performed.

The above-described goal is a process in which agglomerated slurry of a mixture of polymer latex and a flocculant is stirred at a constant temperature for a predetermined time, and the slurry undergoes a solidification step while being stirred at a constant temperature higher than the agglomeration temperature in the next stage of aging. It can be achieved through the improvement of various factors and device improvement.

As the type of flocculant, sulfuric acid, hydrochloric acid, phosphoric acid and the like are used, and as the type of salt, calcium chloride and magnesium sulfate are used. The heating source was added directly so as to be sufficiently dispersed. In addition, latex was introduced at the top of the coagulation tank to circulate in the coagulation tank for a predetermined time.

The stirring characteristic of the present invention is made under a disturbing flow and has a great feature of vertical stirring. The circulation flow rate of the fluid in the agitation tank through such agitation is a very important factor. And the general pattern of circulation is downward near the agitator shaft and upward near the agitator wall. This circulation flow rate is 0.01 to 2 m ³ / sec in the flocculation tank and preferably should be operated in the range of 0.01 to 1.5 m ³ / sec.

When the agitation force is high, the shear force of the outside is increased rather than the bonding force between particles, thereby causing particle crushing to increase the content of the fine particles. However, when the stirring force is weak, the particles stagnate at the top, making continuous operation impossible.

And, when the operating temperature of each stirring tank is low, the content of fine particles is large, the apparent specific gravity is low. And when the slurry content in the coagulation tank is high, the viscosity in the coagulation tank is increased, so that it is difficult to maintain a uniform shear force as a whole. In this case, continuous operation for a long time is impossible.

In addition, when the residence time decreases, that is, when the flow rate of the input material increases, the upper stagnation part is formed, and it is difficult to maintain a uniform shear force as a whole.

Increasing the amount of production, the residence time in the coagulation tank continuously operated as the flow rate of the input latex increases, it is necessary to make this residence time more uniform. In addition, the contact between the inlet flocculant and latex was improved, and the agitation in the flocculation tank was improved.

There is a balance between agglomeration between particles in the agglomeration tank and dispersion by agitation forces, thereby determining the particle diameter. The cohesive force is affected by the amount and temperature of the coagulant, and in the case of the dispersion force, the stirring properties and the residence time are affected.

Through the following examples and comparative examples will be described in detail the present invention. The conditions and results of the examples are shown in Tables 1 and 2, and the conditions and results of the comparative examples are shown in Table 3.

The polymer latex used in the present invention is prepared by emulsion polymerization and the solid content is 30 to 45%, the rubber content of the butadiene component is 25 to 60% by weight of styrene 15 to 55 parts by weight, and acrylonitrile 10 to 40 It is prepared by emulsion polymerization by grafting parts by weight. In the polymerization, rosin-based surfactants are used. The average particle diameter is 0.1 to 0.42 µm, and the pH is 9 to 11. Glass transition temperature is 80-110 degreeC.

Particle size was measured by a sieve method. 100 g of powder is weighed and placed at the top of 20, 40, 50, 100, 140, 200, mesh and vibrated for 15 minutes, and then the particle size distribution is determined as the difference between the weight of each mesh and the weight of the powder filtered through the mesh. Measure The apparent specific gravity was measured according to JIS-K-6721.

Example 1

The polymer latex recovery apparatus according to the present invention was used.

The polymer latex, flocculant and water are all transferred to the flocculation tank via a pump. 10% dilute sulfuric acid was used as flocculant, and the slurry content was maintained at 20-30%. The residence time was 10 minutes, and the sulfuric acid flow rate was set under the condition of 1.0 to 2.5 parts by weight.

The agitator in the coagulation tank was comprised in multiple stages. Agitator diameter (d) is 35 to 75% of the total agitator diameter (T), it was operated so that the linear velocity is 2.17 m / sec. In addition, the input position of the heating source was put at 15% of the total length of the stirring vessel, and the polymer latex was put at 80% of the stirring center axis with respect to the radius of the stirring vessel.

The stirrer in the aging tank consisted of multiple stages. The stirrer diameter (d) is 30 to 65% of the total stirring tank diameter (T), and this was operated so that the linear velocity is 3.4 m / sec. And the heating source was put into 30% from the bottom compared with the full length of the stirring vessel.

Under these conditions, the coagulation aging process can be stably operated continuously.

Example 2

The injection position of the latex was changed to 40% under the conditions of Example 1. The linear velocity of the stirrer in the coagulation tank is 3.5 m / sec.

Example 3

In the conditions of Example 1, the input position of the heating source was changed to 25%. And residence time was reduced to 7 minutes.

Example 4

The loading position of the latex was changed to 40% under the conditions of Example 3. The linear velocity of the stirrer in the coagulation tank is 5.83 m / sec.

Example 5

The linear velocity is 1.2 m / sec under the conditions of Example 1. The residence time was reduced to 7 minutes.

The linear velocity of the aging stirrer was operated to be 6.7 m / sec. And the heating source was put into 15% from the bottom compared with the full length of the stirring vessel.

Example 6

In the conditions of Example 5, the injection position of the latex was changed to 40%. The linear velocity of the agitator in the coagulation tank is 6.05 m / sec.

Example 7

The linear velocity of the flocculation tank stirrer under the conditions of Example 5 is 2.17 m / sec. The residence time was reduced to 4 minutes.

The linear velocity of the aging stirrer was operated to be 8.3 m / sec.

Example 8

In the conditions of Example 7, the linear velocity of the coagulation tank stirrer is 1.2 m / sec, and the linear velocity of the aging tank stirrer is 13.2 m / sec.

Comparative Example 1

It carried out by changing the linear velocity of the agitator in agglomeration tank to 8.42 m / sec on the conditions of Example 1.

Comparative Example 2

It carried out by changing the input position of the heating source to 5% on the conditions of Example 1.

Comparative Example 3

In the condition of Example 1, the input position of the heating tank heating source was introduced at 5% and operated so that the linear velocity of the heating tank stirrer was 6.8 m / sec.

Comparative Example 4

The residence time in the conditions of Example 1 was reduced to 4 minutes.

Conditions and Results of the Examples Example 1 Example 2 Example 3 Example 4 Coagulation tank Heating source input position ^* 15% → 25% → Latex injection position ^** 80% 40% 80% 40% Retention time (minutes) 10 → 7 → Linear velocity (m / sec) 2.17 3.5 2.17 5.82 Aging degree Heating source input position ^** 30% → → 30% Linear velocity (m / sec) 3.4 → → → Powder Characteristics Particle size (% weight) 20 mesh or more 5.3 6.7 5.8 6.7 20-40 mesh 8.5 7.8 7.9 7.9 40-50 mesh 20.8 18.3 19.5 23.2 50-100 mesh 25.9 29.0 15.2 22.4 100-140 mesh 33.6 30.5 35.3 35.7 140-200 mesh 4.8 5.9 10.8 8.9 200 mesh or less 1.1 1.8 0.5 1.0 Apparent specific gravity (g / cc) 0.4 0.42 0.43 0.43

* Input distance from bottom to full length

** Distance from stirring center axis to stirring tank radius

Conditions and Results of the Examples Example 5 Example 6 Example 7 Example 8 Coagulation tank Heating source input position ^* 15% → → → Latex injection position ^** 80% 40% 80% → Retention time (minutes) 7 → 4 → Linear velocity (m / sec) 1.2 6.05 2.17 1.2 Aging degree Heating source input position ^** 15 → → → Linear velocity (m / sec) 6.7 → 8.3 13.2 Powder Characteristics Particle size (% weight) 20 mesh or more 4.8 1.8 2.5 3.3 20-40 mesh 9.8 5.9 15.8 16.3 40-50 mesh 9.5 30.5 20.2 25.1 50-100 mesh 35.6 32.6 33.8 28.1 100-140 mesh 30.8 9.8 18.1 16.5 140-200 mesh 5.9 0.5 5.1 7.2 200 mesh or less 3.6 1.8 4.5 3.5 Apparent specific gravity (g / cc) 0.43 0.42 0.39 0.38

* Input distance from bottom to full length

** Distance from stirring center axis to stirring tank radius

Conditions and Results of Comparative Examples Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Coagulation tank Heating source input position ^* 15% 5% 15% → Latex injection position ^** 80% → → → Retention time (minutes) 10 → → → Linear velocity (m / sec) 8.42 2.17 → → Aging degree Heating source input position ^** 30% → 5% 30% Linear velocity (m / sec) 3.4 → 6.8 3.4 Powder Characteristics Particle size (% weight) 20 mesh or more 15.3 6.1 15.8 1.2 20-40 mesh 17.8 4.3 96.3 5.3 40-50 mesh 15.4 15.1 16.0 10.1 50-100 mesh 18.7 3.8 21.6 9.2 100-140 mesh 24.1 32.3 20.3 30.3 140-200 mesh 6.8 20.3 6.7 18.8 200 mesh or less 1.9 18.1 10.3 25.1 Apparent specific gravity (g / cc) 0.4 0.35 0.4 0.38

* Input distance from bottom to full length

** Distance from stirring center axis to stirring tank radius

Claims (10)

A polymer latex obtained by grafting polymer particles having rubber characteristics and emulsion polymerization is introduced into a plurality of stirring tanks having a glass transition temperature of 80 ° C to 110 ° C in a plurality of serially connected agitators. A method for producing granular powder, characterized by washing, dehydrating and drying the solidified particles by heat treatment after formation. The method of claim 1, The flocculant is sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, magnesium sulfate, calcium chloride, sodium chloride. The method according to claim 1 or 2, A method for producing a polymer powder, wherein the amount of the flocculant is 0.5 to 5% by weight based on the total resin composition. The method of claim 1, The stirring tank comprises a multi-stage pitched paddle, the diameter of the paddle is 30 to 67% of the diameter of the stirring tank. The method of claim 4, wherein Agitation linear velocity is 0.5 to 20 and m / sec, the circulation rate is method of producing a polymer powder having a stirring property of 0.05~1.5 m ³ / sec. The method of claim 1, A method for producing a polymer powder, wherein the residence time during formation of the flocculation slurry in the flocculation tank is 3 to 20 minutes. The method of claim 1, Method for producing a polymer powder in which the polymer latex is placed in the stirring tank 20 to 90% from the center of the stirring tank radius. The method of claim 1, A method for producing polymer powder by heating a stirring vessel using saturated steam or unsaturated steam having a pressure of 1 to 10 kgf / cm ² . The method of claim 8, A method for producing a polymer powder in which a heating source is introduced at a position of 1 to 70% from a lower part of the stirring tank in relation to the total length of the stirring tank. a) a plurality of stirring vessels each comprising a polymer latex air apparatus, a flocculant supply apparatus and a water supply apparatus; b) an agitator installed in the agitation vessel, the agitator comprising a plurality of paddles, wherein the diameter of the paddles is 30-67% of the stirrup diameter; c) a slurry overflow tube connecting a plurality of stirring vessels; And d) a heating source capable of maintaining the stirring vessel at the desired temperature Polymer powder production apparatus comprising a.