KR100301126B1 - Method for producing styrene / acrylic water-soluble resin by continuous bulk polymerization - Google Patents

Abstract

The present invention relates to a method for producing a styrene / acrylic water-soluble resin by continuous bulk polymerization, and more specifically, using a mixed solvent of dipropylene glycol methyl ether / water as a reaction solvent, and cooling coils in an oil jacket and an oil jacket. It relates to a method for producing a styrene / acrylic water-soluble resin using a reactor in the form of controlling the temperature by using, and removing the volatiles in the polymer by using a divolatilizer of the falling strand form. The styrene / acrylic water-soluble resin produced by the method of the present invention has a lower molecular weight, a narrower molecular weight distribution, a higher acid value and a lower volatile content than the conventional resin.

Description

Method for producing styrene / acrylic water-soluble resin by continuous bulk polymerization

The present invention relates to a method for producing a styrene / acrylic water-soluble resin by continuous bulk polymerization, and more particularly, to a styrene / acryl having a low molecular weight, a narrow molecular weight distribution, a high acid value and a low volatile content by continuous bulk polymerization. It relates to a process capable of producing an acrylic water-soluble resin.

At present, most of the ink, paints and coatings used in the country use organic solvents. However, these organic solvents have been recognized as a major cause of air pollution due to the organic substances emitted during use, and because of the flammability, there is a high risk of fire. As one of the proposed methods to solve these shortcomings, high solid liquid coatings using styrene / acrylic water-soluble resins do not cause air pollution, and do not have a problem with paints or inks based on organic solvents. Otherwise, it can reduce the necessary cost in terms of resources, energy, working environment, etc., and there is no risk of fire or explosion.

However, in order to utilize this technique, the problem of viscosity increase due to the increase of solid content must be solved. That is, when the molecular weight of the styrene / acrylic water-soluble resin increases, the viscosity rapidly increases, and as a result, there is a limit in increasing the solid content concentration in the case of a resin having a high molecular weight. For example, when preparing an aqueous ink and an aqueous coating using a styrene / acrylic water-soluble resin having a weight average molecular weight of about 50,000 to 100,000, the maximum solid content is 50% or less, but the weight average molecular weight is about 5,000 to 15,000. However, even if the content of the solid content is about 70 to 80%, there is no problem in producing ink or paint having a high solid content. However, even if the above molecular weight is satisfied, the molecular weight distribution should be narrowed because the higher the molecular weight distribution, the higher the molecular weight of the resin is contained, the higher the viscosity. And to introduce a carboxyl group in order to impart water solubility to the resin, the resin is usually prepared to have an acid value of 200 or more using acrylic acid or methacrylic acid.

On the other hand, if the volatile content in the water-soluble resin is a lot of bubbles generated during the ink or paint production, workability is bad, there is a problem that a large amount of antifoaming agent to be used to remove the foam. Therefore, the lower the volatile content in the water-soluble resin, the better the workability, it is possible to reduce the use of antifoaming agents and the like, the physical properties of the ink and paint is improved.

Therefore, in order to produce a water-soluble ink and an aqueous coating material having a high solid content, it is essential to use a water-soluble resin having a small molecular weight, a narrow molecular weight distribution, and a high acid value and a low volatile content.

As described above, in order to prepare an aqueous ink and an aqueous paint having a high solid content, a styrene / acrylic water-soluble resin having a weight average molecular weight of 4,000 to 16,000, a molecular weight distribution of 22 or less, an acid value of 200 or more and a volatile content of 5% or less is required. . However, styrene / acrylic water-soluble resins satisfying these conditions cannot be manufactured by the solution polymerization method or the emulsion polymerization method which are generally known. That is, the solution polymerization method can usually produce a styrene / acrylic resin having a molecular weight in the range of 10,000 to 100,000, and the emulsion polymerization method can produce a styrene / acrylic water-soluble resin having a molecular weight of about several million.

U.S. Patent No. 4,414,370 discloses a continuous bulk polymerization process for preparing styrene / acrylic water-soluble resins, which suggests that a continuous stirred reactor has a residence temperature of at least 2 minutes at a reaction temperature of 235-310 ° C. The monomer was continuously injected to take time, and the polymer was transferred to a devolatitilizer to remove volatiles. The number average molecular weight was 1,000 to 6,000 (about 2,000 to 12,000 in weight average molecular weight), and the molecular weight distribution was It produces styrene / acrylic water-soluble resin of 2.0 or less. The monomer used comprises a mixture of styrene and alpha methyl styrene in a weight ratio of 1: 2 to 2: 1 and acrylic acid in a weight ratio of 60:40 to 80:20. The monomer is used in an amount of 1 to 10 parts by weight of diethylene glycol mono Ethyl ether was used as the solvent. Meanwhile, in the above patent, in order to control the reaction temperature, a heat transfer oil is flowed through the reactor jacket, and a cooling coil is installed inside the reactor to heat the fruit oil to raise / lower the temperature of the reactor. .

However, in the above method, an oil jacket is installed outside the reactor and a cooling coil is installed inside the reactor to control the reaction temperature. In this case, temperature variations occur easily inside the reactor and the outer wall of the reactor, so that uniform temperature control in the reactor is easy. not. In addition, since the reaction temperature is high, the production cost is generated a lot, there is a need for a process capable of producing a styrene / acrylic water-soluble resin having a similar molecular weight and molecular weight distribution even at a low reaction temperature. In the above method, the viscosity of the reaction product was controlled by using diethylene glycol monoethyl ether as a solvent. The diethylene glycol monoethyl ether caused an ester reaction with acrylic acid, which is a reactant, to lower the acid value of the water-soluble resin as a product. Since the solubility in water is lowered, it is necessary to use a substance capable of controlling the viscosity of the reactants as a solvent while less affecting the physical properties of the product.

In the continuous process, the dibolatilizer process, which removes unreacted monomers and solvents from the produced resin, plays an important role not only in terms of overall process efficiency but also in terms of product properties such as volatile content. In the above method, there is no detailed description thereof.

Accordingly, an object of the present invention is to provide a process for preparing a styrene / acrylic water-soluble resin by continuous bulk polymerization which can improve the temperature control method, reaction temperature, solvent used as a viscosity control material, and volatile matter content, which are problems of the prior art. Through this, it is to provide a method for producing a water-soluble resin having a small molecular weight, a narrow molecular weight distribution, high acid value and low volatile content.

The method of the present invention for achieving the above object is 5 to 15 parts by weight of dipropylene glycol methyl ether based on 100 parts by weight of the monomer, initiator and monomer in a continuous bulk polymerization process capable of producing a styrene / acrylic water-soluble resin ( A mixture of dipropylene glycol methyl ether) and water was continuously injected into the reactor, and the temperature was controlled by using an oil jacket and a cooling coil inside the oil jacket. The polymerization is carried out by the residence time, which is transferred to a falling strand type dibolatilizer, which is operated at a temperature of 180 to 210 ° C and a pressure of -500 to -750 mmHg to remove volatiles. It consists of

1 is a schematic view showing a continuous bulk polymerization process of the present invention.

Hereinafter, the present invention will be described in more detail.

1 shows a continuous bulk polymerization process designed to prepare a styrene / acrylic water-soluble resin. As shown in Figure 1, the continuous bulk polymerization process devised in the present invention is composed of two monomer stirring tank, a reactor, a polluting strand type divolatilizer, a distillation column, a monomer recycle tank, and the like.

The monomer is injected into the reactor 3 from the monomer stirring tank 1 or 2 at a constant rate, and the level of the reactor is adjusted to have a residence time of 10 to 20 minutes in the reactor. At this time, the capacity of the reactor is 75 liters, in order to efficiently control the reaction temperature of the continuous bulk polymerization, to install a jacket through which the heat transfer oil (Heat Transfer Oil) flows, the cooling of the low temperature fruit oil can flow inside the jacket The coil was installed. As a result, it was easy to control the reaction temperature, and it was possible to produce a styrene / acrylic water-soluble resin having a weight average molecular weight of 3,000 to 10,000 and a molecular weight distribution of 2.0 or less at a reaction temperature of 150 to 220 ° C, which is a low temperature.

The water-soluble resin that is completed polymerization while passing through the reactor is transferred to the divolatilizer 4 in the form of a falling strand to remove volatile components in the resin. It was installed to maintain a constant temperature by installing a jacket through which the fruit oil can flow to the dibolatilizer, it was possible to maintain a constant vacuum to the dibolatilizer using a vacuum pump (7). As a result, a styrene / acrylic water-soluble resin having a volatile matter content of 2% or less could be produced.

The volatiles removed from the dibolatilizer are composed of unreacted monomer, oligomer and dipropylene glycol methyl ether used as solvent, water and the like. The volatiles are transferred to the distillation column (5) for purification. After separation and storage in the monomer recycle tank 6, a certain ratio is injected into the reactor and recycled to prepare a styrene / acrylic water-soluble resin.

Meanwhile, US Pat. No. 4,414,370 used diethylene glycol monoethyl ether as a solvent in order to absorb heat of reaction and control the viscosity of the reactants in the preparation of water-soluble resins. However, since this substance has a hydroxyl group, the carboxyl group of the water-soluble resin is esterified to chemically bond in the molecules of the water-soluble resin, thereby losing its function as a solvent, increasing the viscosity of the reactant, and making it difficult to control the temperature inside the reactor. In addition, the acid value of the water-soluble resin is dropped to reduce the physical properties of the product. Therefore, in the present invention, by using a mixture of 5 to 15 parts by weight of dipropylene glycol methyl ether and water with respect to 100 parts by weight of the monomer as a solvent, not only the effect of controlling the viscosity of the reactant, but also reduces the ester reaction with acrylic acid, A styrene / acrylic water-soluble resin having an acid value of 200 to 230 could be produced. At this time, the content of water in the solvent mixture is preferably 20 to 45% by weight, if the water content is less than 20% by weight, a lot of esterification reaction of dipropylene glycol methyl ether and acrylic acid occurs a problem that the acid value of the final product falls When the content exceeds 45% by weight, the amount of evaporation of water increases, thereby increasing the internal pressure of the reactor and causing a problem in that the viscosity of the reactants cannot be effectively controlled.

On the other hand, the monomer used in the present invention is made by mixing a styrene monomer and an acrylic monomer in a weight ratio of 60 to 80:20 to 40, the styrene monomer is styrene alone or a styrene of a mixed weight ratio of 50 to 90: 10-50 And an alpha methyl styrene monomer, wherein the acrylic monomers include acrylic acid and alkyl acrylate monomers alone or in a mixed weight ratio of 80 to 90: 10 to 20.

In addition, the initiator used in the present invention is a low-temperature initiator is used because the reaction takes place at a low temperature, t-butyl peroxy benzoate (t-butyl peroxy benzoate) is preferred, the amount used is 3 to 6 weight based on the total amount of the monomer Addition is preferred.

In the present invention, in order to remove volatiles in the polymer, a divolatilizer in the form of a falling strand is used, and the method is higher than in the case of using a dibolatilizer in the form of a stirred tank used in US Pat. No. 4,414,370. It is advantageous in that the volatile matter in the resin can be easily removed by increasing the surface area of the resin.

On the other hand, the temperature condition of the falling strand debolilatilizer of the present invention is preferably 180 to 210 ° C, and if the temperature is less than 180 ° C, a problem of hardly removing volatile matter in the resin occurs, and if it exceeds 210 ° C, Deterioration of the resin causes a problem of poor physical properties. In addition, the pressure condition of the falling strand debolilatilizer is preferably -750 to -500 mmHg, when the pressure is less than -750 mmHg, the flow of the resin is rapidly worsened, the problem of very difficult to transfer the resin occurs More than -500 mmHg, it becomes difficult to sufficiently remove volatile matter in the resin.

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

Examples 1-5

The styrene-based monomers (styrene and alpha methyl styrene) and the acrylic monomers (in the amount shown in Table 1) are continuously stirred in an oil jacket installed outside and a cooling coil installed inside the oil jacket to control the temperature. Acrylic acid) to prepare a styrene / acrylic water-soluble resin.

Example 1 Example 2 Example 3 Example 4 Example 5 Styrene (parts by weight) 35 35 35 35 35 Alphamethylstyrene (parts by weight) 32 32 32 32 32 Acrylic acid (parts by weight) 33 33 33 33 33 Reaction temperature (℃) 150 180 200 210 220 Number average molecular weight 5,000 4,800 4,400 3,600 3,100 Weight average molecular weight 9,800 8,700 7,500 6,200 5,200 Molecular weight distribution 1.9 1.8 1.7 1.7 1.7 Acid 223 223 225 225 226 Volatile Content (%) 1.5 1.5 1.3 1.2 1.2

In this case, the polymerization initiator used was t-butylperoxybenzoate, and the amount used was 3.5 parts by weight based on the total amount of the monomers. In addition, 15 parts by weight of a mixture of dipropylene glycol methyl ether and water was used with respect to 100 parts by weight of the monomer, and the content of water in the mixed solvent was 35%. The reaction temperature was changed to 150 ° C to 220 ° C. On the other hand, in order to remove the volatile components of the water-soluble resin produced by passing through the divolatilizer device in the form of a stranding strand finally obtained a water-soluble resin from which the volatile components were removed. At this time, the operating conditions of the dibolatilizer was 195 ° C, -750 mmHg.

Comparative Examples 1 to 3

In order to show how effectively the reactor designed in the present invention controls the temperature inside the reactor, under the same conditions as in Examples 1 to 5, the heating oil inside the reactor oil jacket does not flow, and the cooling coil is temporarily cooled inside the reactor. Was prepared to prepare a styrene / acrylic water-soluble resin. The results are shown in Table 2 below.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Reaction temperature 180 210 220 Number average molecular weight 4,500 3,250 2,750 Weight average molecular weight 10,550 7,850 6,700 Molecular weight distribution 2.34 2.41 2.43 Acid 220 222 222 Volatile Content (%) 1.5 1.4 1.4

As shown in Table 2, it can be seen that the molecular weight distribution of the styrene / acrylic water-soluble resin adjusted at the same reaction temperature is wider than the result shown in Table 1, which means that the average reaction temperature is the same due to the temperature deviation inside the reactor. This is in part because the reaction temperature is different. That is, it can be seen that the reaction temperature control is not easy with the reactor having the oil jacket outside the reactor and the cooling coil inside the reactor.

Examples 6-9

Styrene / acrylic water-soluble resins were prepared while changing the operating conditions of the divolatilizer under the same conditions as in Example 4 above in order to examine the effect of the operating conditions of the divolatilizer, which is a volatile removal device. The results are shown in Table 3 below.

Example 4 Example 6 Example 7 Example 8 Example 9 Divolatilizer Temperature (℃) 195 210 180 210 180 Dibolatilizer Pressure (mmHg) -750 -750 -750 -500 -600 Number average molecular weight 3,600 3,600 3,600 3,600 3,600 Weight average molecular weight 6,200 6,200 6,200 6,200 6,200 Molecular weight distribution 1.7 1.7 1.7 1.7 1.7 Acid 225 225 226 225 224 Volatile Content (%) 1.2 1.1 1.5 1.7 1.8

Comparative Examples 4 to 5

Styrene / acrylic water-soluble resin was prepared while changing the operating conditions under the same conditions as in Example 4 in order to examine the effect on the operating conditions of the dibolatilizer in more detail. The results are shown in Table 4 below.

Example 4 Comparative Example 4 Comparative Example 5 Divolatilizer Temperature (℃) 195 170 235 Dibolatilizer Pressure (mmHg) -750 -350 -750 Number average molecular weight 3,600 3,600 2,800 Weight average molecular weight 6,200 6,200 5,850 Molecular weight distribution 1.7 1.7 2.1 Acid 225 225 214 Volatile Content (%) 1.2 3.8 0.6

As shown in Table 4, when the temperature of the dibolatilizer is low and the pressure is high, the volatile matter content is high. When the temperature and the pressure of the dibolatilizer are high, the volatile content is low, but the molecular weight distribution is It can be seen that it widens and the mountain falls slightly.

Examples 10-13

In order to examine the influence of the mixed solvent used, under the same conditions as in Example 4, the amount of mixed solvent (mixture of dipropylene glycol methyl ether and water) and the composition of the mixed solvent were changed to prepare a styrene / acrylic water-soluble resin. .

The results are shown in Table 5 below.

Example 4 Example 10 Example 11 Example 12 Example 13 Amount of Mixed Solvent (parts by weight) 15 10 15 5 10 Water content in mixed solvents (%) 35 35 45 20 25 Number average molecular weight 3,600 3,500 3,600 3,200 3,600 Weight average molecular weight 6,200 6,300 6,200 6,500 6,200 Molecular weight distribution 1.7 1.8 1.7 1.8 1.8 Acid 225 220 230 205 203 Volatile Content (%) 1.2 1.1 1.3 1.1 1.2

Examples 14-17

In order to determine the effect of the used styrene monomer content, the styrene / acrylic water-soluble resin was prepared under varying amounts of styrene and alpha ethyl styrene under the same conditions as in Example 4. The results are shown in Table 6 below.

Example 4 Example 14 Example 15 Example 16 Example 17 Styrene (part by weight) 35 43 52 60 67 Alphamethylstyrene (parts by weight) 32 24 15 7 0 Acrylic acid (parts by weight) 33 33 33 33 33 Number average molecular weight 3,600 3,200 3,750 3,800 4,100 Weight average molecular weight 6,200 5,750 6,800 7,500 8,150 Molecular weight distribution 1.7 1.8 1.8 2.0 2.0 Acid 225 223 225 227 227 Volatile Content (%) 1.2 1.4 1.3 1.3 1.3

Examples 18-20

In order to determine the effect of the used acrylic monomer content, the amount of acrylic acid and methyl acrylate was changed under the same conditions as in Example 4 to prepare a styrene / acrylic water-soluble resin. The results are shown in Table 7 below.

Example 4 Example 18 Example 19 Example 20 Styrene (part by weight) 35 35 35 35 Alphamethylstyrene (parts by weight) 32 32 32 32 Acrylic acid (parts by weight) 33 29.5 28.5 27 Methyl acrylate (parts by weight) 0 3.5 4.5 6 Number average molecular weight 3,600 3,650 3,700 3,700 Weight average molecular weight 6,200 6,600 6,700 7,350 Molecular weight distribution 1.7 1.8 1.8 2.0 Acid 225 220 213 204 Volatile Content (%) 1.2 1.3 1.4 1.4

Comparative Example 6

According to the method disclosed in US Pat. No. 4,414,370, a styrenic monomer in an amount of the amount shown in the following Table 8 in a continuous stirring reactor capable of flowing the fruit oil in the reactor jacket, installed a cooling coil inside the reactor to control the temperature (Styrene and alphamethylstyrene) and an acrylic monomer (acrylic acid) were used, and styrene / acrylic water-soluble resin was prepared at a temperature shown in the following table using diethylene glycol monoethyl ether as a reaction solvent. The results are shown in Table 8 below.

Comparative Example 6 Styrene (parts by weight) 31 Alphamethylstyrene (parts by weight) 37 Acrylic acid (parts by weight) 32 Reaction temperature (℃) 263 Solvent content (parts by weight) 20 Divolatilizer Temperature (℃) 263 Number average molecular weight 1,700 Weight average molecular weight 2,650 Molecular weight distribution 1.56 Acid 160

As described above, in a continuous bulk polymerization process for producing a styrene / acrylic water-soluble resin, a mixture of dipropylene glycol methyl ether and water is used as a solvent, and a reaction method for controlling the reaction temperature and polling is different from the conventional technique. The styrene / acrylic water-soluble resin of the present invention prepared through the form and operation method of the strand dibolatilizer has a low molecular weight, a narrow molecular weight distribution, a high acid value and a low volatile content even at a lower temperature than the resin prepared by the conventional method. It is very useful for industrial use.

Claims (5)

In the continuous bulk polymerization process for producing a styrene / acrylic water-soluble resin, 5-15 parts by weight of a mixed solvent of dipropylene glycol methyl ether and water is continuously injected into the reactor with respect to 100 parts by weight of the monomer, the initiator and the monomer, and In the reactor in which the temperature is controlled using a cooling coil inside the jacket and the oil jacket, the polymerization is carried out at a reaction temperature of 150 to 220 ° C. and a residence time of 10 to 20 minutes, and then the polymer is divolatile in the form of a falling strand. A method for producing a styrene / acrylic water-soluble resin by continuous bulk polymerization, which is transported to a riser and operated at a temperature of 180 to 210 ° C. and a pressure of -500 to -750 mmHg to remove volatile matter. The method of claim 1, wherein the content of the water in the mixed solvent is 20 to 45% by weight. The method for producing a styrene / acrylic water-soluble resin according to claim 1, wherein the monomer is a mixture of a styrene monomer and an acrylic monomer in a weight ratio of 60 to 80:20 to 40. The method for producing styrene / acrylic water-soluble resin according to claim 3, wherein the styrene monomer is a mixture of styrene alone or a mixture of styrene and alpha methyl styrene monomer in a weight ratio of 50 to 90: 10 to 50. The method of claim 3, wherein the acrylic monomer is a mixture of acrylic acid alone or a mixture of acrylic acid and an alkyl acrylate monomer in a weight ratio of 80 to 90: 10 to 20.