KR100513892B1 - Method for Preparing High Macromolecule Latex Resin Powder - Google Patents

Abstract

The present invention relates to a method for producing a polymer latex resin powder, comprising a membrane process for removing water and residual impurities in the polymer latex, and a spray drying process for recovering the latex through the membrane process in powder form, In the method for producing a polymer latex resin powder according to the present invention, the fine powder having a particle size of less than 70 µm is 3% by weight or less, the powder having a diameter of 70 to 400 µm is 95% by weight or more, and the powder having 400 µm or more is 3% by weight or less. The polymer latex resin powder has excellent physical properties such as apparent specific gravity and whiteness, but can be provided at a low production cost by a simple process.

Description

Method for preparing polymer latex resin powder {Method for Preparing High Macromolecule Latex Resin Powder}

The present invention relates to a method for producing a polymer latex resin powder. More specifically, the present invention relates to a method for preparing a powdery polymer latex resin by spray drying after removing impurities from the polymer latex in a membrane process.

In general, the method for preparing the polymer latex powder in the emulsion polymerization process consists of a coagulation process, a aging process and a dehydration / drying process. In the coagulation process, an aqueous solution of a coagulant such as an inorganic salt or an acid is added to the polymer latex, and electrostatic stabilization by the emulsifier is broken, and the polymer particles in the latex are agglomerated with each other by charge neutralization to form flocs. Since these flocs do not form a physical bond and form a kind of multi-particle assemblage, break-up may easily occur due to a disturbance flow caused by an external impeller or the like. Therefore, in order to increase the strength of the floc, the flocculation process is followed by a aging process. The aging process is performed at a high temperature, and the floc forms one particle having a certain strength due to interpenetration between the chains. In addition, the slurry state containing such particles is converted to a powder form having an average particle diameter of 200 to 400 μm through a dehydration / drying process after the aging process. Among these processes, impurities such as residual metal, emulsifier, etc. used in emulsion polymerization in the dehydration process are removed together with water.

However, the conventional method for producing a polymer latex powder as described above must go through four steps of agglomeration, aging, dehydration and drying, so the process is complicated. It is difficult to manage, and there are disadvantages such as an increase in waste water due to the use of flocculant and a large amount of water, an increase in energy consumption, and the like. In spite of these disadvantages, the conventional method is commercialized because of its simple mechanism and easy removal of impurities left in the emulsion polymerization through dehydration.

An alternative to the conventional method for preparing a polymer latex powder consisting of agglomeration, aging, dehydration and drying is a method of applying a spray drying process. Spray drying process is used to disperse latex into droplets of 100-200 μm size using a pressure nozzle or rotary wheel in a dryer operated at high temperature by hot air. After removing the water present in the droplets it is immediately recovered in a powder state. This method is very simple in terms of installation compared to the existing process because there is no need for flocculation, maturation, dehydration and drying processes, thus significantly reducing operating and maintenance costs. However, this method is unable to remove impurities in the latex produced by emulsion polymerization because the process does not include a dehydration process, and eventually impurities remaining in the powder adversely affect the final product. Therefore, in order to solve this fundamental problem, it is possible to minimize the impurity in the latex to change the polymerization formulation, such as changing the amount and type of additives that do not adversely affect the physical properties even without removing impurities through dehydration, but the existing prescription itself There is a difficulty to change completely, and the practical applicability is not great.

Therefore, there is a need for a method for preventing the deterioration of the physical properties of the final article, by minimizing the residual impurity content in the powder produced by removing impurities directly from the latex prepared in the same manner as the conventional method, rather than changing the polymerization prescription.

In order to solve the above problems, the present invention is a polymer latex resin powder having excellent physical properties such as apparent specific gravity, whiteness, etc. from a emulsion-polymerized polymer latex, a simple process that does not require agglomeration, aging, dehydration and drying processes, low cost and energy consumption. It is an object to provide a method for producing a.

The above and other objects of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention is a polymer latex resin, characterized in that it comprises a membrane process for removing water and residual impurities in the polymer latex, and a spray drying process for recovering the latex undergoing the membrane process in powder form It provides a method for producing powder.

The membrane process may be equipped with dilution means for lowering the concentration of residual impurities.

The separator process may be a process by vibrating separator.

The polymer latex is 30 to 50 parts by weight of styrene, 50 to 70 parts by weight of butadiene and 0 to 3 parts by weight of a crosslinking agent 20 to 60 parts by weight of butadiene-based rubbery latex prepared by emulsion polymerization 20 to 60 or so alone or a composite monomer of a vinyl aromatic compound Graft by continuously adding 60 parts by weight, 5 to 20 parts by weight of vinyl cyanide compound and 0 to 5 parts by weight of a single or complex monomer of glycidyl acrylate and one or more alkyl acrylates having 1 to 12 carbon atoms It may be prepared by polymerization.

In the spraying process, the spraying method may be sprayed into droplets having a size of 100 to 200 μm by a pressure nozzle method or a rotary wheel method.

Operation conditions of the spray dryer in the spray process may be a temperature of inlet air (inlet air) is 180 to 200 ℃, the feed rate of the latex (feed rate) may be 40 to 80g / min.

Hereinafter, the present invention will be described in detail.

The present invention adopts a spray drying process for preparing a polymer latex resin powder from a emulsion polymerized polymer latex in a simple process that does not require agglomeration, aging, dehydration and drying processes. As impurities such as residual metals and emulsifiers are not removed and the physical properties of the polymer latex resin powder are lowered, the membrane is subjected to a membrane process for removing water and residual impurities in the polymer latex before spray drying.

That is, the present invention includes a membrane process for removing water and residual impurities in the polymer latex, and a spray drying process for recovering the latex that has undergone the membrane process in powder form.

In general, as a method for removing residual impurities in the latex, various methods may be applied according to the type of impurities, and a method of removing residual metal using an ion exchange resin, a method of removing residual monomers by steam stripping, and the like. Among the above methods, residual metal removal method using ion exchange resin is easy to remove residual metal, but is insufficient for removal of other unreacted monomers, and the method by steam stripping removes residual monomers easily, but it is difficult to remove residual metal. Excessive foam is generated, and coagulum is generated due to the deterioration of latex stability.

Thus, the present invention introduces a filtration process to remove impurities in the latex. The membrane process may be a cross-flow filtration or a dead-end filtration depending on the flow direction of the membrane and the fluid. The direct current membrane separation method separates materials smaller than the size of pores in the filter through the filter as the fluid flows perpendicularly to the membrane. Compared with membrane separation efficiency, membrane replacement cycle and washing cycle, the present invention is difficult to apply when the viscosity of the solution to be separated or the solid content is high.

Therefore, the present invention introduces a vibrating membrane separation method that has been commercialized recently and widely used. Unlike the conventional membrane separation method in which the membrane is fixed, the vibration membrane is vibrated at a very high frequency so that the colloid in the latex to be separated is attached to the membrane surface to prevent the pores of the membrane, thereby reducing the membrane separation efficiency. It is excellent in terms of economics because the processing capacity is about 5 to 10 times superior to the DC membrane separation method.

In addition, when the vibrating membrane separation method is introduced into a membrane process for preparing polymer latex powder, a considerable amount of water including residual impurities in the latex is discharged to remove residual impurities in the latex, and the solid content is increased, thereby spraying a subsequent process. Energy consumption is greatly reduced during the drying process. That is, when the solid content is increased from 40% to 50%, since the amount of water to be dried for the same solid content is reduced to 2/3 level, the amount of water to be removed during spray drying is also reduced by the corresponding amount.

The present invention adopts the vibration membrane separation method as described above to remove residual impurities in the polymer latex and removes impurities in water and water while leaving the polymer in the latex as it is, thereby minimizing impurities remaining in the powder after spray drying. . Of course, it is not possible to remove even impurities present at the interface between the polymer phase and the polymer and water phase in the latex, but as can be seen from the results of the following examples, only the residual impurities present in the water can be removed. It has physical properties similar to those of the polymer latex resin powder prepared by the method.

The membrane process of the present invention is equipped with a dilution means for lowering the concentration of residual impurities, by repeating the process of diluting and concentrating the latex through the membrane one or more times to minimize the content of residual impurities, and then spray drying process You can let it through.

As described above, the polymer latex which has undergone the membrane process is lowered to 50% or less of residual impurities in the latex, and improves the solid content by 20% or more. By increasing the solids content in the polymer latex, it is possible to reduce the operating costs and energy consumption in the subsequent spray drying process.

The present invention can use a polymer latex prepared by conventional emulsion polymerization. Preferably 30 to 50 parts by weight of styrene, 50 to 70 parts by weight of butadiene and 0 to 3 parts by weight of a crosslinking agent 20 to 60 parts by weight of butadiene-based rubbery latex prepared by emulsion polymerization 20 or 60 Graft polymerization by continuously adding 0 to 5 parts by weight of single or complex monomers of one or more alkyl acrylates and glycidyl acrylates having 5 to 20 parts by weight of vinyl cyanide compound and an alkyl group having 1 to 12 carbon atoms It is a polymer latex prepared by.

As described above, the latex from which impurities are removed through the separator is converted into a powder phase through a spray drying process. As shown in FIG. 1, the latex that has undergone the vibration separation membrane process 20 passes through a spray drying process 40 equipped with a spray dryer, through a polymer latex powder recovery line 50, and finally a polymer in a powder form. Switch to As a spray method that can be used in the spray drying process, there are a pressure nozzle method and a rotary wheel method. Both of these methods spray latex into droplets of 100 to 200 μm in the dryer, but pressure nozzles in the case of products requiring a larger particle size because the average nozzle diameter of the droplets is larger than that of the rotary wheels. It is preferable to select and use the method.

In addition, the operating conditions of the spray dryer can be adjusted according to the product to be applied, but maintains the inlet air temperature conditions at 180 to 200 ℃, the latex feed rate (Feed rate) is adjusted to 40 to 80g / min It is desirable to. In the spray dryer, the average size of the particles can be controlled by adjusting the injection pressure of the latex in the case of the pressure nozzle method, and the rotary wheel method is performed by adjusting the rotational speed of the wheel. In the case of the pressure nozzle, the operating pressure is 2 to 3KG. In the case of the wheel system, it is preferable to adjust the rotational speed to 10,000 to 15,000 rpm.

The polymer latex resin powder, which has undergone the spray drying process after the separation membrane process as described above, has a particle size of less than 70 μm of fine powder powder of 3 wt% or less, 70 to 400 μm of 95 wt% or more, and 400 μm or more of powder. It consists of 3 weight% or less. In addition, as the residual impurities in the powder are lowered to 10% or less, physical properties such as apparent specific gravity and whiteness of the powder are excellent.

 Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the examples.

Examples 1-3 and Comparative Examples 1-2

Example 1

Latex with a solid concentration of 40% was injected at the inlet of the membrane process at a rate of 100 g / min. The membrane process was carried out using the VSEP process of NRI, USA. Polysulfone was used, and a membrane having a molecular weight cutoff of 100,000 was used to remove water and other impurities in latex having a molecular weight of 100,000 or less. The solids content of the latex through the membrane was 60%. The latex through the membrane was immediately transferred to a spray dryer, which was sprayed using a Niro's Spray Dryer (Model: Mobile Minor). The temperature of the inlet air was maintained at 180 ° C., the latex feed rate was 80 g / min, and the spraying method was a rotary wheel method, and the rotation speed of the wheel was 10,000 rpm. The polymer latex resin powder produced by passing through the spray dryer was recovered. Particle size distribution and physical properties of the recovered polymer latex resin powder are shown in Table 1 below.

Example 2

After dilution, additional dilution water was added to the latex with 50% solids to reduce the solids content to 40%, and then passed through the membrane process to transfer the latex with 50% solids to the spray dryer. Was carried out in the same manner as in Example 1 to recover the polymer latex resin powder. Particle size distribution and physical properties of the recovered polymer latex resin powder are shown in Table 1 below.

 Example 3

After adding the dilution water to the latex of 50% of the solid content after passing through the membrane to reduce the solids content to 40%, and then passing the membrane process again to transfer the latex of 50% of the solid content to the spray dryer. In the same manner as in Example 1 to recover the polymer latex resin powder. Particle size distribution and physical properties of the recovered polymer latex resin powder are shown in Table 1 below.

Comparative Example 1

Agglomeration tank with a 40% solids concentration of latex at a flow rate of 132 L / hr, a calcium salt coagulant diluted to 10% at a flow rate of 23.5 L / hr (4.5 parts by weight relative to a polymer resin), and water at a flow rate of 263 L / hr. Simultaneously supplied to the bottom, the retention time of the flocculation tank was 2 minutes 30 seconds, the temperature was adjusted to 37 ℃ to complete the aggregation. The agglomerated latex was transferred to the aging tank by the overflow method. The aging tank is separated into primary and secondary aging tanks. The operating temperature of the primary aging tank is 60 ° C and the residence time is 30 minutes, and the temperature of the secondary aging tank is 90 ° C and the residence time is 30 minutes. Allow sufficient maturation. The polymer latex after aging was dehydrated and dried to recover the powdery polymer latex. Particle size distribution and physical properties of the recovered polymer latex resin powder are shown in Table 1 below.

Comparative Example 2

The polymer latex resin powder was recovered in the same manner as in Example 1 except that the latex having a solid content concentration of 40% was immediately transferred to the spray dryer without undergoing a membrane process. Particle size distribution and physical properties of the recovered polymer latex resin powder are shown in Table 1 below.

division Example Comparative example One 2 3 One 2 Content of latex solids after process (%) 50 50 50 40 40 Particle size distribution (% by weight) 400㎛ or more One 2 2 8 2 200 ~ 400㎛ 11 13 8 22 13 70 ~ 200㎛ 85 82 88 62 82 Less than 70㎛ 3 3 2 8 3 Apparent specific gravity (gr / cc) 0.51 0.52 0.51 0.43 0.52 Whiteness of powder 46 49 52 55 25 Residual Metals in Powder (ppm) 1,520 830 570 420 4830

As shown in Table 1, the specific gravity of the particle size distribution and powder of Comparative Example 2, which is subjected to a dry spray process but not subjected to a separation membrane process, is compared with Comparative Example 1 prepared by conventional agglomeration, aging, dehydration and drying processes. Although high, the whiteness value of the powder of Comparative Example 2 can be seen that the 50% lower than that of Comparative Example 1. This result is due to the fact that Comparative Example 2, which has not undergone the impurity removal process, contains about 10 times as much residual metal in the polymer latex powder as compared to Comparative Example 1 in which the impurity is removed by the dehydration process, which affects the polymer latex properties. Can be estimated.

In contrast, Example 1, which was spray-dried after removing impurities by a separation membrane process, showed a particle size distribution and apparent specific gravity similar to that of Comparative Example 2, while improving whiteness by about 80% or more compared to Comparative Example 2. These results can be presumed that a considerable amount of impurities are removed during the membrane process, and the amount of residual metal in the polymer latex powder is greatly reduced.

Examples 2 and 3, which were subjected to the dilution and concentration of the latex through the membrane once and twice, respectively, followed by the spray drying process, showed that the amount of residual metal in the polymer latex powder was higher than that of Example 1, which did not undergo the dilution and concentration process. Decreased, and whiteness increased. In addition, in Example 3, in which the dilution and concentration processes were performed twice, the amount of residual metal in the polymer latex powder was reduced and the whiteness was increased as compared with Example 2, which was performed once.

As described above, the method for producing the polymer latex resin powder according to the present invention has a fine powder having a particle diameter of less than 70 μm of 3% by weight or less, a powder having 70 to 400 μm of 95% by weight or more, and a powder having a size of 400 μm or more. It is a useful invention that the polymer latex resin powder consisting of 3% by weight or less can be provided at a low production price by a simple spray drying process while having excellent physical properties such as apparent specific gravity and whiteness.

While the invention has been described in detail above with reference to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope and spirit of the invention, and such modifications and variations fall within the scope of the appended claims. It is also natural.

1 is a schematic diagram of the entire process for recovering the polymer latex resin powder from the polymer latex according to the present invention.

Brief description of the main parts of the drawing

10: polymer latex supply line

20: vibrating membrane process

30: treated water supply line via membrane

40: spray drying process

50: polymer latex resin powder recovery line

Claims (6)

(A) a vibration membrane process for removing water and residual impurities in the polymer latex; And (B) a spray drying step for recovering the latex that has been subjected to the vibration separation membrane process in powder form. The method of claim 1, A method for producing a polymer latex resin powder, characterized in that the separation membrane process of (a) is equipped with dilution means for lowering the concentration of residual impurities. delete The method of claim 1, The polymer latex of (A) is 30 to 50 parts by weight of styrene, 50 to 70 parts by weight of butadiene and 0 to 3 parts by weight of a crosslinking agent 20 to 60 parts by weight of a butadiene-based rubbery latex prepared by emulsion polymerization alone or 20 to 60 parts by weight of a composite monomer, 5 to 20 parts by weight of a vinyl cyan compound and one or more alkyl acrylates and glycidyl acrylates having an alkyl group having 1 to 12 carbon atoms, or 0 to 5 parts by weight of a composite monomer continuously Method for producing a polymer latex resin powder, characterized in that prepared by graft polymerization by addition. The method of claim 1, The method of manufacturing a polymer latex resin powder, characterized in that the spraying method in the spraying step (b) is sprayed into droplets of 100 to 200μm size by a pressure nozzle method or a rotary wheel method. The method of claim 1, In the spraying process of (b), the operating conditions of the spray dryer are inlet air at a temperature of 180 to 200 ° C., and a latex feed rate is 40 to 80 g / min. Production method of powder.