KR19990010950A - Manufacturing method and apparatus for recovering polymer latex into granular powder - Google Patents

Abstract

The present invention relates to a manufacturing process and apparatus for recovering a polymer latex into granular powder, wherein the weight content of the fine particles from the polymer latex is reduced, has a uniform particle size distribution and a high apparent density of 0.42 or more, and exhibits excellent thermal stability. A method and apparatus for producing granular powder are disclosed. The method for producing granular powder using the apparatus for producing granular powder of the present invention comprising a two-stage first stirring tank or agglomeration tank and a second stirring tank or aging tank is 0.5 to 3 as a flocculant. By weight acid or salt is used, the average residence time in the flocculation tank is 3 to 30 minutes, and the flocculation tank operating conditions are 15-35% of the solid content in the flocculation tank. relative to the transition temperature of T _g to T _g -50≤ features a flocculation temperature ≤T _g and T _g -10 -15≤ aging temperature ≤T _g -5. The stirrer in each agitator tank includes multiple staged paddles, the diameter of which is 30 to 65% of the diameter of the agitator tank, and the linear velocity ranges from 0.5 to 10 m / sec. Is installed.

Description

Manufacturing method and apparatus for recovering polymer latex into granular powder

The present invention generally relates to a manufacturing process and apparatus for recovering polymer latex into granular powder. In particular, the present invention relates to a manufacturing method and apparatus for recovering molecular latex with reduced granular particles, uniform particle size and high apparent density in order to improve the properties of the powder.

The particle size formed in the continuous operation of the latex recovery method has a significant impact on the dehydration performance and drying as well as the productivity of the compounding operation. In addition, the fine particles (typically 70 μm or less) formed in the latex recovery method may block the filter of the dehydrator during the dehydration process, and may reduce the cleaning efficiency and contaminate the workplace during the drying and conveying process. In order to solve these problems, the polymer latex recovery process requires an additional device such as a cyclone bag filter, thereby increasing the facility investment cost. In particular, the fine particles are easily lost during the transfer and extrusion operations, and also may be caused to flow out into the mother liquor through the dehydrator to reduce the yield.

Coarse particles other than fine particles also cause various problems. Residual impurities in the particles are difficult to remove and require a large amount of air to form a fluidized bed during drying. In addition, since the resistance to the removal of water increases, it takes a long time to remove the water, which requires a long residence time in the dryer. This means that it is likely to adversely affect the color of the final powder. In consideration of the above-mentioned problems and mixing with other kinds of resins, the particles formed in the latex recovery method are preferably 0.8 mm or less in size.

In addition, in the case of powders of low apparent density, various problems arise such as an increase in storage and transport costs, and decrease in scattering and flowability of particles during the operation.

The moisture content of the dehydrated particles directly affects the energy consumption of the drying process. Therefore, it is obvious that the lower the moisture content, the lower the energy consumption in the drying process. In addition, if the powder characteristics of the particles are improved, there is an advantage that can be introduced automatic metering to reduce the amount of work that must be performed by the operator.

SUMMARY OF THE INVENTION An object of the present invention is to provide a production method and apparatus for recovering polymer latex with reduced granular particles, uniform particle size and high apparent density in order to improve the properties of the powder.

In order to achieve the object of the present invention, 0.5 to 3 parts by weight of acid or salt is used as a flocculant to recover the polymer latex obtained by emulsion polymerization by grafting to the rubber particles of the present invention to produce granular polymer powder. Forming agglomerated particles having an average residence time of 3 to 30 minutes in a flocculation tank and having a solid content of 15 to 35% in the flocculation tank; Introducing the aggregated particles into a aging tank; Solidifying the aggregated particles by heat treatment in a aging tank; Washing the solidified particles; Dewatering the washed particles; Drying the dehydrated particles; And finally preparing granular polymer powder.

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

* Explanation of symbols for main parts of the drawings

1, 4: water inlet

2: polymer latex inlet

3: flocculant inlet

5: slurry outlet

6, 6 ': Stirrer

7, 8: slurry overflow pipe

In the present invention, finally, the polymer powder is prepared from the polymer latex prepared by emulsion polymerization through a continuous stirring tank of two stages. More specifically, the production apparatus for recovering the polymer latex of the present invention into granular powder includes a stirring tank connected in two stages in series. The first stirring tank of the stirring tank is called agglomeration tank, and the second stirring tank is called a maturing tank. The coagulation bath basically has a driving purpose for stirring the polymer latex and the coagulant and also inducing collisions between the latex particles. The aging tank is operated at high temperature and serves to increase the strength of the particles through heat treatment.

When acid, such as sulfuric acid or hydrochloric acid, and salts such as sodium chloride, magnesium sulfate, and calcium chloride are added to the polymer latex, electrostatic repulsion is reduced to induce agglomeration between particles, thereby increasing the size of the particles. The particles produced through such agglomeration process do not have strong bonds between particles, and are not themselves resistant to external forces, and have a sponge-like porous structure. The particles thus formed are treated as a group of multiplexes, each of which does not form a physical bond and is separated by a thin water film of 0.1-1 nm. Agglomerated particles are disorderedly distributed and contain water in the particles. The structure of the floc is determined by the alignment of each individual particle.

In order to increase the strength of the flocs, the particles undergo a aging process. The aging process is generally performed at a high temperature and the particles form a single particle due to interpenetration between the chains. However, if the degree of aging is weak, the particles may break up at a later stage of aging.

The present inventors improved the operating conditions and agitation performance, such as the average residence time, the amount of flocculant, the slurry content, and the temperature in each stirring vessel, and the granular polymer having excellent particle size distribution and showing high apparent density and thermal stability. It was found that the powder can be obtained. Specifically, according to the present invention, it is possible to obtain a powder having a uniform particle size distribution with a small content of fine particles of 100 μm or less and a significant decrease in the content of coarse particles of 0.8 mm or more, and having a high apparent density and excellent thermal stability. Can be.

There is a balance between the cohesive force between the particles in the coagulation tank and the dispersion force by stirring, and by adjusting this, the distribution of the particle diameters can be controlled. The cohesive force is governed by the amount of flocculant, the slurry pentant, the temperature and the like, and the dispersing force is controlled by the stirring characteristic and the residence time.

The polymer latex (about 38% solids) of the present invention obtained by emulsion polymerization is prepared by emulsion polymerization by grafting styrene 5 to 55 parts by weight of styrene and 10 to 40 parts by weight of acrylonitrile to 25 to 60 parts by weight of butadiene rubber. will be. The surfactant used in the polymerization is a rosin series. The average particle diameter is 0.28 mu m and the pH is 10.3.

The latex produced by the emulsion polymerization as described above together with the coagulant is introduced into the coagulation tank, and water is added to adjust the amount of solids in the coagulation tank. Each inflow is fed through a pump. In the present invention, the temperature of the coagulation bath is preferably T _g- 50 ≤ coagulation temperature ≤ T _g- 10, where T _g is a glass transition temperature. The slurry agglomerated in the coagulation tank which is the primary stirring tank is introduced into the aging tank which is the secondary stirring tank by overflow (Over-Flow), and the slurry is solidified through heat treatment in the secondary stirring tank. In the present invention, the aging temperature of the aging tank is preferably T _g -15 ≤ aging temperature ≤ T _g -5. Solidified slurry is also introduced into the slurry tank by overflow. It is then transferred to a dehydrator by a pump to obtain particles from which water is removed by centrifugal force of the dehydrator. The dehydrated slurry sample is dried at 60 ° C. for about 3 hours to finally obtain granular polymer powder. A manufacturing process and apparatus for recovering the polymer latex of the present invention into granular powder is shown in FIG.

The particle size of the recovered powder in the present invention was measured by a sieving method. Particle distribution was obtained by weighing 100 g of powder and shaking in 20. 40, 50, 100, 140, 200 mesh (mesh) for 15 minutes and measuring the difference between each mesh weight and total weight. The apparent density was measured according to JIS K-6721. Then, after the powder was left in an oven at a constant temperature of 20 ° C., the color change due to heat was visually observed, and thermal stability was determined. There are three stages of color change:

-Almost no color change

-Turned yellow

-Turning brown

Divided into.

The manufacturing method and the experimental method of the polymer latex described above are similarly applied to all the Examples and Comparative Examples. Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The conditions and results of the examples are shown in Tables 1, 2, and 3.

Example 1

Example 1 used a polymer latex recovery apparatus according to the invention shown in FIG. Water, polymer latex, and sulfuric acid as a flocculant are all at room temperature, and are introduced into the flocculation tank through a pump at the water inlet 1, the polymer latex inlet 2 and the flocculant inlet 3, respectively. Sulfuric acid was used diluted to 5%, slurry content was 25%, residence time was 10 minutes, and the amount of sulfuric acid was set at the flow rate conditions 0.5 parts by weight.

The impeller in the first agitation tank or the coagulation tank is composed of multiple-stage pitched paddles, and the diameter of the impeller is designed to be 61% of the diameter T of the first agitation tank. The linear velocity of the impeller is 2.17 m / sec. The diameter and linear velocity of the impeller were based on the maximum value among the stages. These criteria apply equally to all the following examples and comparative examples.

The impeller in the second agitation tank or the aging tank was designed to be 42% of the diameter T of the multi-stage pitched paddle and the second agitation tank. The linear velocity of the impeller is 3 m / sec. In addition, the temperature of a coagulation tank is 80 degreeC, and the temperature of a aging tank is 94 degreeC.

Example 2

In the conditions of Example 1, the slurry tentent was 18%, and changed to a condition in which 2 parts by weight of sulfuric acid, a flocculant, was introduced. The remaining conditions were the same as in Example 1.

Example 3

In the conditions of Example 1, the residence time in the flocculation tank was 20 minutes, the linear velocity of the impeller was 2.41 m / sec, the diameter of the impeller was changed to 42% of the diameter of the stirring vessel, and the remaining conditions were Example 1 Is the same as

Example 4

In the conditions of Example 1, the linear velocity of the impeller was 5.82 m / sec, and the diameter of the impeller was changed to 42% of the diameter of the stirring vessel, and the remaining conditions were the same as in Example 1.

The results of Examples 1 to 4 are shown in Table 1.

Example 5

Under the conditions of Example 1, the residence time in the coagulation tank is 10 minutes, the linear velocity of the impeller is 1.20 m / sec, and the linear velocity of the agitator 6 'in the aging vessel is changed to the condition of 6.7 m / sec. And the remaining conditions are the same as in Example 1.

Example 6

Under the conditions of Example 1, the residence time in the flocculation tank was 5 minutes, the linear velocity of the impeller was 6.05 m / sec, and the linear velocity of the agitator 6 'in the aging vessel was changed to 6.7 m / sec. The diameter of the stirrer 6 'was changed to 55% of the diameter of the aging tank, and the remaining conditions were the same as in Example 1.

Example 7

In the conditions of Example 1 was carried out by introducing water into the aging tank, the remaining conditions are the same as in Example 1.

Example 8

In the conditions of Example 5 was carried out by adding water into the aging tank, the remaining conditions are the same as in Example 5.

The results of Examples 5-8 are shown in Table 2.

Example 9

In the conditions of Example 1, the temperature of the coagulation bath was changed to 70 ° C., and the temperature of the aging bath was changed to 90 ° C., and the remaining conditions were the same as in Example 1.

Example 10

Hydrochloric acid was used as the flocculant in the conditions of Example 4, and the rest of the conditions were the same as in Example 4.

Example 11

In the conditions of Example 10, the residence time in the flocculation tank was 10 minutes, the temperature was 75 ° C, the linear velocity of the impeller was 2.17 m / sec, and the diameter of the impeller was changed to 61% of the flocculation tank. The remaining conditions are the same as in Example 10.

The results of Examples 9-11 are shown in Table 3.

Table 1

Conditions and Results of the Examples

TABLE 2

Conditions and Results of the Examples

TABLE 3

Conditions and Results of the Examples

Comparative Example 1

In the conditions of Example 1, the linear velocity of the impeller in the flocculation tank was changed to 8.42 m / sec, and the remaining conditions were the same as in Example 1.

Comparative Example 2

In the conditions of Example 1, the flocculant was changed to 4 parts by weight, and the remaining conditions were the same as those in Example 1.

Comparative Example 3

In the conditions of Example 4, the residence time in the coagulation bath was changed to 30 minutes, and the remaining conditions were the same as in Example 4.

Comparative Example 4

In the conditions of Example 5, the residence time in the coagulation tank was changed to 5 minutes, and the linear velocity of the impeller in the aging tank was changed to 3.4 m / sec, and the remaining conditions were the same as in Example 5.

Comparative Example 5

In the conditions of Example 9, the temperature of the coagulation bath was changed to 65 ° C., and the temperature of the aging tank was changed to 85 ° C., and the remaining conditions were the same as in Example 9.

Comparative Example 6

In the conditions of Example 9, the temperature of the coagulation bath was changed to 60 ° C., and the temperature of the aging tank was changed to 80 ° C., and the remaining conditions were the same as in Example 9.

Comparative Example 7

Under the conditions of Example 10 0.5 parts by weight of hydrochloric acid as a flocculant, the linear velocity of the impeller in the flocculation tank was changed to 2.17m / sec, the temperature of the maturation tank was changed to 90 ℃, the remaining conditions are the same as in Example 10.

Comparative Example 8

3 parts by weight of a flocculant was used in the conditions of Example 11, and the remaining conditions were the same as in Example 11.

The conditions and results of the comparative example are summarized in Tables 4 and 5.

Table 4

Conditions and Results of Comparative Examples

Table 5

Conditions and Results of Comparative Examples

Claims (5)

In the method for producing the granular polymer powder by recovering the polymer latex obtained by grafting on the rubber particles by emulsion polymerization, Forming agglomerated particles using 0.5 to 3 parts by weight of an acid or salt as a flocculant, having an average residence time of 3 to 30 minutes in a flocculation tank, and having a solid content of 15 to 35% in the flocculation tank ; Introducing the aggregated particles into the aging tank; Solidifying the aggregated particles by heat treatment in a aging tank; Washing the solidified particles; Dewatering the washed particles; Drying the dehydrated particles; And Converting the dried particles into granular polymer powder Granular polymer powder production method comprising a. The method of claim 1, wherein the temperature range of the agglomeration temperature and the maturation temperature in the flocculation tank and the maturation tank is T _g- 50 ≤ agglomeration temperature ≤ T _g- 10 and T _g- 15 ≤ aging temperature ≤ T _g -5, respectively , T _g is a glass transition temperature). A first stirring bath; And 2nd stirring tank Including, The first and second stirring vessels are connected in series in two stages, each having a stirrer therein, each stirrer including a plurality of pitch paddles, the diameter of each of the stirrers, respectively 30 to 65% of the diameters of the first and second stirring vessels, and the linear velocities of the respective agitators are 0.5 to 10 m / sec, respectively. The granular polymer powder production apparatus according to claim 3, wherein the first stirring tank is an agglomeration tank and the second stirring tank is a aging tank. The granular polymer powder production apparatus according to claim 3 or 4, wherein the second agitator tank includes a water inlet pipe therein.