阅读说明：本技术 氯乙烯基聚合物的制备方法 (Process for producing vinyl chloride-based polymer ) 是由 李光珍 全亮俊 朴宰贤 河玄圭 于 2020-09-07 设计创作，主要内容包括：本发明涉及一种氯乙烯基聚合物的制备方法。在根据本发明的氯乙烯基聚合物的制备方法中,通过在聚合过程中顺序地加入彼此不同的第一乳化剂和第二乳化剂,并且使用琥珀酸酯化合物作为第一乳化剂来制备氯乙烯基聚合物,使得当使用制备的聚合物混合增塑溶胶时,可以通过实现低粘度性能来改善加工性能,并且通过抑制挥发性有机化合物的产生来改善雾化性能。(The present invention relates to a method for producing a vinyl chloride-based polymer. In the method for preparing a vinyl chloride-based polymer according to the present invention, a vinyl chloride-based polymer is prepared by sequentially adding a first emulsifier and a second emulsifier different from each other during polymerization and using a succinate compound as the first emulsifier, so that when a plastisol is mixed using the prepared polymer, processability can be improved by achieving low viscosity properties, and fogging properties can be improved by suppressing the generation of volatile organic compounds.)

1. A method for producing a vinyl chloride-based polymer, comprising the steps of:

1) adding a vinyl chloride-based monomer to the reactor to initiate polymerization;

2) continuously adding a first emulsifier to the reactor from the time of initiation of polymerization to the time when the polymerization conversion rate reaches 35% to 52%; and

3) after the addition of the first emulsifier is finished, continuously adding a second emulsifier,

wherein the first emulsifier and the second emulsifier are different from each other, and the first emulsifier is a succinate compound.

2. The method for preparing a vinyl chloride-based polymer according to claim 1, wherein the second emulsifier is continuously added until a polymerization conversion rate reaches 70 to 95%.

3. The method for producing a vinyl chloride-based polymer according to claim 1, wherein the second emulsifier is added immediately after the end of the addition of the first emulsifier.

4. The method for preparing a vinyl chloride-based polymer according to claim 1, wherein the first emulsifier and the second emulsifier are added in a weight ratio of 5:5 to 9: 1.

5. The method for preparing a vinyl chloride-based polymer according to claim 1, wherein the second emulsifier has a higher Critical Micelle Concentration (CMC) than the first emulsifier.

6. The method for producing a vinyl chloride-based polymer according to claim 1, wherein the second emulsifier comprises a sulfate compound.

7. The method for preparing a vinyl chloride-based polymer according to claim 1, wherein the total amount of the first emulsifier and the second emulsifier added is 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the vinyl chloride-based monomer.

8. The method for preparing a vinyl chloride-based polymer according to claim 1, wherein the first emulsifier includes at least one succinate compound selected from the group consisting of dioctyl sodium sulfosuccinate, ditridecyl sodium sulfosuccinate, disodium lauryl polyether sulfosuccinate, and sodium lauryl sulfosuccinate.

9. The method for producing a vinyl chloride-based polymer according to claim 1, wherein the second emulsifier comprises at least one selected from the group consisting of alkyl sulfate, alkyl ether sulfate, alkanolamide sulfate, monoglyceride sulfate, glycerol ether sulfate, fatty acid ether sulfate and fatty acid amide ether sulfate.

10. The method for producing a vinyl chloride-based polymer according to claim 1, wherein in step 1), a carbonate-based metal salt is further added.

11. The method for producing a vinyl chloride-based polymer according to claim 1, wherein in step 1), an initiator and polymerization water are further added.

12. The method for producing a vinyl chloride-based polymer according to claim 1, wherein the polymerization is carried out by an emulsion polymerization method.

Technical Field

Cross Reference to Related Applications

This application claims the benefit of korean patent application No.10-2019-0113003, filed by the korean intellectual property office at 11.9.2019, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a method for preparing a vinyl chloride-based polymer having excellent processability by realizing not only low viscosity properties but also stable viscosity and excellent fogging properties by reducing the generation of volatile organic compounds.

Background

The vinyl chloride-based polymer is a resin containing 50% or more of vinyl chloride, is inexpensive, easily controls hardness, and is suitable for most processing apparatuses, thereby having various application fields. In addition, since a vinyl chloride-based polymer can provide molded articles having excellent physical and chemical properties, such as mechanical strength, weather resistance, and chemical resistance, the vinyl chloride-based polymer is widely used in various fields.

Such a vinyl chloride-based polymer is prepared in various forms depending on its use. For example, vinyl chloride-based polymers used for direct processing such as extrusion processing, calendering processing and plunge processing are generally prepared by suspension polymerization, and vinyl chloride-based polymers used for paste processing such as dipping, spraying and coating are prepared by emulsion polymerization.

In the paste processing, a vinyl chloride-based polymer latex for paste processing, which is generally obtained by emulsion polymerization, is spray-dried to form final resin particles. The particles are dispersed in a solvent or plasticizer and applied to products such as flooring materials, wallpaper, tarpaulins, raincoats, gloves, automotive body undercoats, sealants, and carpet tiles by processes such as coating (reverse roll coating, knife coating, screen coating, spray coating), gravure and screen printing, spin casting, and shell casting and dip coating. Such a vinyl chloride-based polymer for paste processing is difficult to be used alone due to its poor processability, and therefore, the vinyl chloride-based polymer is generally processed and used in the form of a plastisol composed of various additives such as a heat stabilizer and a plasticizer. In this case, in order to improve the processability of the vinyl chloride polymer, it is important to reduce the viscosity of the plastisol to maintain good fluidity.

Therefore, in order to improve the processability of the vinyl chloride-based polymer, the content of the plasticizer is adjusted and mixed. However, if the content of the plasticizer is increased, the plasticizer itself is separated inside the resin due to migration, volatility and extractability after processing, thereby causing deterioration in properties and accelerated aging.

In another case, the processing viscosity of the plastisol may be significantly reduced when the content of the plasticizer is increased. In this case, the processability may be deteriorated due to the sol dripping phenomenon during the coating process.

In addition, in recent years, demands for non-toxicity to humans and the environment and performance of the vinyl chloride-based polymer are increasing. Therefore, many studies are being conducted to reduce volatile organic compounds generated in molded articles manufactured using a vinyl chloride-based polymer, and studies are being conducted on various additives such as plasticizers, which are mainly used as secondary materials.

For example, european patent application EP2039718 describes a method of using a plasticizer mixture based on alkyl sulfonates and glycol dibenzoates instead of phthalate plasticizers, and US7973194 discloses a highly solvated plasticizer mixture for polyvinyl chloride plastisols comprising dibutyl, dibenzyl and butyl benzyl esters of 1, 4-cyclohexanedicarboxylic acid.

However, the above-mentioned method cannot sufficiently reduce the generation of volatile organic compounds, and in particular, with various regulations on the environment being increased, there is a limitation in reducing the degree of generation of volatile organic compounds below an appropriate level only by replacing plasticizers used as secondary materials.

Accordingly, there is a need for a method capable of reducing volatile organic compounds generated from a vinyl chloride-based polymer itself while maintaining effective physical properties of the vinyl chloride-based polymer.

Therefore, it is necessary to conduct research on a method for preparing a vinyl chloride-based polymer, in which, even though the content of a plasticizer is not significantly increased when a plastisol is mixed, the process viscosity is reduced to improve processability, the process viscosity is not rapidly reduced due to the addition of the plasticizer, thereby stably maintaining the process viscosity, and volatile organic compounds generated from the vinyl chloride-based polymer are reduced, thereby securing excellent fogging properties.

Documents of the prior art

(patent document 1) EP 2039718B 1(2009.03.25)

(patent document 2) US 7973194B 1(2011.07.05)

Disclosure of Invention

Technical problem

An aspect of the present invention provides a method for preparing a vinyl chloride-based polymer having a low viscosity to improve processability during mixing of plastisol, excellent foaming properties, and excellent fogging properties due to high density of foam cells.

Technical scheme

In order to solve the above problems, according to one aspect of the present invention, a method for preparing a vinyl chloride-based polymer comprises the steps of: 1) adding a vinyl chloride-based monomer to the reactor to initiate polymerization; 2) continuously adding a first emulsifier to the reactor from the time of initiation of polymerization to the time when the polymerization conversion rate reaches 35% to 52%; and 3) continuously adding a second emulsifier after the addition of the first emulsifier is finished, wherein the first emulsifier and the second emulsifier are different from each other, and the first emulsifier is a succinate compound.

According to another aspect of the invention, the first emulsifier and the second emulsifier are added in a weight ratio of 5:5 to 9: 1.

According to another aspect of the invention, the second emulsifier comprises a sulfate compound.

Advantageous effects

The vinyl chloride-based polymer prepared by the preparation method according to the present invention can exhibit low viscosity properties even when the content ratio of the plasticizer is not significantly increased, and thus has excellent processability. In addition, since the viscosity does not greatly change even if the content of the plasticizer is changed, the vinyl chloride-based polymer can have a stable processing viscosity.

In addition, the method for producing a vinyl chloride-based polymer according to an embodiment of the present invention can suppress the generation of volatile organic compounds, and can produce a vinyl chloride-based polymer having excellent fogging properties compared to conventional vinyl chloride-based polymers.

In addition, the method for preparing a vinyl chloride-based polymer according to an embodiment of the present invention can prepare a vinyl chloride-based polymer having further improved foaming properties due to the dense formation of foam units while satisfying the above-mentioned processability and fogging properties.

Drawings

The following drawings attached to the present specification illustrate preferred embodiments of the present invention by way of example and serve to enable the technical concept of the present invention to be further understood together with the detailed description of the invention given below, and the present invention should therefore not be construed as limited to the matters in the drawings.

FIG. 1 is a photograph showing a cross-section of a foam prepared from the polymer of example 1 of the present invention taken with an optical microscope;

FIG. 2 is a photograph showing a cross section of a foam prepared from the polymer of comparative example 2 of the present invention taken with an optical microscope.

Detailed Description

Hereinafter, preferred embodiments are presented to understand the present invention. However, the following examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.

Examples

Example 1

175kg of polymerization water, 125g of potassium persulfate (KPS) and 140g of sodium carbonate (Na) were added₂CO₃) After charging into a 500L high-pressure reactor, the reactor was subjected to vacuum treatment while stirring the resulting mixture. After 175kg of vinyl chloride monomer was added to the reactor in a vacuum state, the temperature of the reactor was increased to 52 ℃ and polymerization was performed. When the polymerization was initiated, 1.40kg of dioctyl sodium sulfosuccinate (DOSS) was continuously added to the reactor over 4 hours. At this time, the time when the addition of dioctyl sodium sulfosuccinate was completed was a time when the polymerization conversion rate reached 45%. Immediately after the end of the addition of dioctyl sodium sulfosuccinate, 0.35kg of Sodium Lauryl Sulfate (SLS) was continuously added to the reactor over 4 hours. At this time, the time when the addition of sodium lauryl sulfate was completed was the time when the polymerization conversion rate reached 90%. At the end of the addition of sodium lauryl sulfate, the reaction was terminated, and unreacted vinyl chloride monomer was recovered and removed to obtain a vinyl chloride polymer latex. The resulting vinyl chloride polymer latex was sprayed and dried to prepare a powdery vinyl chloride polymer.

Example 2

A vinyl chloride polymer was prepared in the same manner as in example 1, except that 1.05kg of dioctyl sodium sulfosuccinate and 0.7kg of sodium lauryl sulfate were added.

Example 3

A vinyl chloride polymer was prepared in the same manner as in example 1, except that the time at the end of the addition of dioctyl sodium sulfosuccinate was a time when the polymerization conversion rate reached 52%.

Example 4

A vinyl chloride polymer was prepared in the same manner as in example 1, except that 0.875kg of dioctyl sodium sulfosuccinate and 0.875kg of sodium lauryl sulfate were added.

Example 5

A vinyl chloride polymer was prepared in the same manner as in example 1, except that 0.7kg of dioctyl sodium sulfosuccinate and 1.05kg of sodium lauryl sulfate were added.

Comparative example 1

A vinyl chloride polymer was prepared in the same manner as in example 1, except that dioctyl sodium sulfosuccinate was not added, but 1.75kg of sodium lauryl sulfate was continuously added to the reactor from the start of polymerization over 8 hours until the conversion rate reached 90%.

Comparative example 2

A vinyl chloride polymer was prepared in the same manner as in example 1, except that sodium lauryl sulfate was not added, but 1.75kg of dioctyl sodium sulfosuccinate was continuously added to the reactor from the start of polymerization over 8 hours until the conversion rate reached 90%.

Comparative example 3

A vinyl chloride polymer was prepared in the same manner as in example 1, except that sodium lauryl sulfate was used instead of sodium dioctyl sulfosuccinate, and sodium dioctyl sulfosuccinate was used instead of sodium lauryl sulfate.

Comparative example 4

A vinyl chloride polymer was prepared in the same manner as in example 2, except that sodium lauryl sulfate was used instead of sodium dioctyl sulfosuccinate, and sodium dioctyl sulfosuccinate was used instead of sodium lauryl sulfate.

Comparative example 5

A vinyl chloride polymer was prepared in the same manner as in example 2, except that the dioctyl sodium sulfosuccinate and the sodium lauryl sulfate were not sequentially added, but mixed and continuously added to the reactor over 8 hours from the start of the polymerization (until the conversion rate reached 90%).

Comparative example 6

A vinyl chloride polymer was prepared in the same manner as in example 1, except that dioctyl sodium sulfosuccinate was added until the conversion rate reached 25%, followed by immediately adding sodium lauryl sulfate.

Comparative example 7

A vinyl chloride polymer was prepared in the same manner as in example 1, except that dioctyl sodium sulfosuccinate was added until the conversion rate reached 60%, followed by immediately adding sodium lauryl sulfate.

Experimental example 1: measurement of fogging Properties of vinyl chloride Polymer

In order to analyze the fogging properties of the vinyl chloride polymers prepared in examples and comparative examples, the generation degree of volatile organic compounds was measured. The degree of volatile organic compound production was measured according to DIN 75-201B (horizons-FTS, manufactured by Thermo Fisher Scientific Inc.) using an atomization tester, and the results thereof are shown in Table 1 below.

Specifically, 10g of each vinyl chloride polymer was added to a fogging cup, and the top of the fogging cup was covered with an aluminum foil, followed by heating at 100 ℃ for 16 hours. Thereafter, the volatile organic compounds collected on the surface of the aluminum foil were measured by the following equation 1. The lower the measured value, the less the amount of volatile organic compounds produced, and the more excellent the atomization performance.

[ equation 1]

Atomization performance (mg) mass of aluminum foil after atomization test-mass of aluminum foil before atomization test

Experimental example 2: measurement of physical Properties of plastisol

Viscosity properties of plastisols comprising the respective vinyl chloride polymers prepared in the above examples and comparative examples and foam cells of the foams were measured, and the results thereof are shown in the following table 1.

1) Cross-sectional properties of foams (foam cells)

Each plastisol was prepared by stirring 100g of each vinyl chloride polymer prepared in example 1 and comparative example 2, 100g of diisononyl phthalate (DINP), 3g of Ba — Zn stabilizer and 3g of AZO type foaming agent at 800rpm for 10 minutes using a Werke mixer (eurosar IKA). Each prepared plastisol was coated on a release paper, coated with a 0.5mm bar, and then dried at 150 ℃ for 45 seconds using a Mathis oven to prepare a pre-gel sheet, which was then heated to 210 ℃ for 100 seconds. After that, the final gel sheet (foam) was cut, and a cross section of the foam was observed using an optical microscope (NIKON SMZ 1500).

Fig. 1 is a photograph showing a cross section of the foam of example 1, and fig. 2 is a photograph showing a cross section of the foam of comparative example 2. As shown in fig. 1 and 2, it can be observed that, in example 1 using an emulsifier other than a succinate compound, specifically a sodium lauryl sulfate emulsifier, as a second emulsifier, foam units are formed more densely, compared to comparative example 2 continuously using a succinate compound as a first emulsifier without changing the second emulsifier.

2) Measuring General Viscosity (General viscocity)

Each plastisol was prepared by stirring 100g of each of the vinyl chloride polymers prepared in examples and comparative examples and 100g of diisononyl phthalate (DINP) at 800rpm for 10 minutes using a Werke mixer (eurosar IKA), and the viscosity of the plastisol was measured at room temperature (23 ± 3 ℃) after mixing the plastisol for 1 hour. At this time, the viscosity was measured using a Brookfield viscometer (Brookfield, DV-1 viscometer) under the conditions of #64 spindle and 12rpm, and the results thereof are shown in Table 1 below.

3) Measurement of Process viscocity

Each plastisol was prepared by stirring 100g of each of the vinyl chloride polymers prepared in examples and comparative examples and 100g of diisononyl phthalate (DINP) at 800rpm for 10 minutes using a Werke mixer (eurosar IKA), and after 1 hour of mixing the plastisol, the viscosity was measured in the same manner as in the viscosity measuring method in the above 1), the results of which are shown in the following table 1.

[ Table 1]

As shown in table 1, it can be seen that examples 1 to 5, in which a succinate compound is used for the first emulsifier, an emulsifier different from the first emulsifier is used for the second emulsifier, and the addition period of the first emulsifier satisfies the scope of the present invention, stably provide low viscosity and exhibit excellent atomization performance, as compared to comparative examples 1 to 7, in which at least one of these conditions is not satisfied.

Specifically, it can be confirmed that examples 1 to 5 achieve low viscosity performance, and in particular, examples 1 to 5 exhibit remarkably improved atomization performance, as compared to comparative example 1 in which only a single type of emulsifier, specifically only sodium lauryl sulfate, is used throughout the polymerization reaction. It was confirmed that, in examples 1 to 5, rapid viscosity reduction due to the addition of the plasticizer did not occur, compared to comparative example 2 using only dioctyl sodium sulfosuccinate as a single type of emulsifier, thereby realizing stable viscosity performance. In the case of comparative example 2, the addition of the plasticizer causes a significant decrease in viscosity, thereby causing a sol dripping phenomenon during processing, and thus, the viscosity of the vinyl chloride polymer is too low to be processed.

In addition, it can be confirmed that examples 1 to 5 exhibited improved atomization performance while achieving low viscosity performance, as compared to comparative examples 3 and 4 in which the addition order of the emulsifiers was changed. It can also be expected that in examples 1 to 5, the processability was improved by achieving the low viscosity property, as compared with comparative example 5 in which the first emulsifier and the second emulsifier were mixed and added simultaneously from the beginning. Specifically, it can be seen that the atomization performance of examples 1 to 5 is greatly improved as compared with comparative example 5.

In addition, it was confirmed that in examples 1 to 5, normal latexes having stable viscosity properties could be obtained, as compared with comparative examples 6 and 7 in which the addition period of the first emulsifier falls outside the range of the present invention. Among them, it was confirmed that in comparative example 6, since the addition period of the first emulsifier was too short to ensure polymerization stability, and it was difficult to obtain a normal latex.

In the present invention, it was confirmed that the atomizing property of the vinyl chloride-based polymer and the viscosity property of the plastisol were affected depending on the type of the emulsifier, the addition period and the addition method. Further, it was confirmed that the use of a succinate compound as a first emulsifier, added during a certain period of time, and then a second emulsifier different from the first emulsifier allows the preparation of a polymer that can achieve excellent atomization properties and stable low viscosity properties.

The foregoing description of the present invention has been presented for purposes of illustration, and it will be appreciated by those skilled in the art that embodiments of the inventive concept may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments are therefore illustrative in all respects and should be understood as non-limiting.

Hereinafter, the present invention will be described in more detail so that the present invention can be more clearly understood.

It should be understood that the words or terms used in the specification and claims should not be construed as meaning defined in commonly used dictionaries. It should also be understood that these words or terms should be interpreted as having meanings consistent with their meanings in the background of the related art and the technical idea of the present invention, based on the principle that the inventor can appropriately define the meanings of the words or terms to best explain the present invention.

The term "vinyl chloride-based polymer" used herein includes compounds prepared by polymerizing a vinyl chloride-based monomer alone or a mixture of a vinyl chloride-based monomer and a vinyl-based monomer copolymerizable with the vinyl chloride-based monomer, and may represent a polymer chain derived from the vinyl chloride-based monomer.

The term "plastisol" as used herein refers to a mixture of a resin and a plasticizer which can be shaped, molded, or processed into a continuous film by heating, and for example, may refer to a paste form in which a vinyl chloride-based polymer and a plasticizer are mixed.

The term "plasticizer" used herein may mean an organic additive material for improving the moldability of a resin at high temperature by being added to a thermoplastic resin to improve the thermoplastic properties.

According to an embodiment of the present invention, a method for preparing a vinyl chloride-based polymer may include the steps of: 1) adding a vinyl chloride-based monomer to the reactor to initiate polymerization; 2) continuously adding a first emulsifier to the reactor from the time of initiation of polymerization to the time when the polymerization conversion rate reaches 35% to 52%; and 3) continuously adding a second emulsifier after the addition of the first emulsifier is finished. Here, the first emulsifier and the second emulsifier may be the same as each other, and the first emulsifier may be a succinate compound.

Hereinafter, each step will be described in detail.

Step 1

According to one embodiment of the present invention, step 1) of the method for producing a vinyl chloride-based polymer is a step of adding a vinyl chloride-based monomer to a reactor and initiating polymerization, and forming the vinyl chloride-based polymer from the vinyl chloride-based monomer. Further, according to an embodiment of the present invention, the polymerization may be preferably performed by an emulsion polymerization method.

Specifically, the polymerization in step 1) may be performed by adding a vinyl chloride-based monomer to a polymerization reactor filled with polymerization water and a polymerization initiator, and performing a polymerization reaction. In this case, the polymerization reactor filled with the polymerization water and the polymerization initiator may mean a polymerization reactor containing a mixed solution containing the polymerization water and the polymerization initiator. The mixed solution may further include a dispersant, a molecular weight regulator, an electrolyte, and a reaction inhibitor in addition to the polymerization water and the polymerization initiator, but the present invention is not limited thereto. Preferably, a carbonate metal salt may also be added to the reactor in step 1).

According to an embodiment of the present invention, the polymerization initiator may be used in an amount of 0.01 parts by weight to 2.0 parts by weight, relative to 100 parts by weight of the vinyl chloride-based monomer. Although not particularly limited, the polymerization initiator may be at least one selected from the group consisting of peroxycarbonates, peroxyesters, and azo compounds. Specifically, the polymerization initiator is Lauryl Peroxide (LPO), di-2-ethylhexyl peroxycarbonate (OPP), diisopropyl peroxydicarbonate, tert-butyl peroxypivalate, tert-butyl peroxyneodecanoate, 2-azobisisobutyronitrile, or the like, and may be used alone or may be used in combination of two or more.

In addition, the polymerization initiator may be a water-soluble initiator. When the polymerization initiator is a water-soluble initiator, although not particularly limited, the polymerization initiator may be at least one selected from the group consisting of potassium persulfate KPS, ammonium persulfate, and hydrogen peroxide. In the present invention, preferably, a water-soluble initiator may be used as the polymerization initiator, and specifically, potassium persulfate may be used.

In addition, the polymerization water may be used in an amount of 70 parts by weight to 150 parts by weight, and the polymerization water may be deionized water, with respect to 100 parts by weight of the vinyl chloride-based monomer.

In addition, according to an embodiment of the present invention, the vinyl chloride monomer may refer to a vinyl chloride monomer alone, or a mixture of a vinyl chloride monomer and a vinyl-based monomer copolymerizable with the vinyl chloride monomer. That is, the vinyl chloride-based polymer according to an embodiment of the present invention may be a vinyl chloride homopolymer, or a copolymer of a vinyl chloride monomer and a vinyl-based monomer copolymerizable therewith. If the vinyl chloride-based polymer is the copolymer, the vinyl chloride-based polymer may contain 50% or more of vinyl chloride.

Although not particularly limited, the vinyl-based monomer copolymerizable with the vinyl chloride monomer may be, for example: olefinic compounds, such as ethylene, propylene, butylene; vinyl esters such as vinyl acetate, vinyl propionate, and vinyl stearate; unsaturated nitriles such as acrylonitrile; vinyl alkyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl octyl ether, vinyl lauryl ether; vinylidene halides, such as vinylidene chloride; unsaturated fatty acids and anhydrides of these fatty acids, such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, and itaconic anhydride; unsaturated fatty acid esters such as methyl acrylate, ethyl acrylate, monomethyl maleate, dimethyl maleate and butyl benzyl maleate; and crosslinkable monomers such as diallyl phthalate. Further, the vinyl-based monomer may be used alone or in combination of two or more.

In addition, the method for preparing a vinyl chloride-based polymer according to an embodiment of the present invention may start with controlling the pH to 8 or more in step 1), and may be performed by adding a carbonate-based metal salt to the polymerization mixture.

The carbonate-based metal salt is used to control the pH of the polymerization mixture and is required to be a material capable of raising the pH to a certain level. In particular, the carbonate-based metal salt may include sodium carbonate (Na)₂CO₃) Sodium bicarbonate (NaHCO)₃) And potassium carbonate (K)₂CO₃) At least one of (1). As described above, in terms of reducing the number of defects in the polymer, it is preferable to add a material capable of raising the pH of the polymerization mixture to a certain level, for example, raising the pH to 8 or more.

The carbonate-based metal salt may be added in an amount of 100ppm to 1500ppm, preferably 200ppm or more, or 300ppm or more, and 1300ppm or less, 1200ppm or less, 1000ppm or less, or 800ppm or less, relative to the total weight of the vinyl chloride-based monomer. If the content of the carbonate type metalloid salt falls within the range, not only can the pH of the mixture be controlled to 8 or more, but also a significant reduction in the number of olefin type defects and chlorine type defects in the final polymer can be affected.

In addition, it is effective to add the carbonate metalloid salt at the initial stage of the polymerization, and specifically, the carbonate metalloid salt may be added before the polymerization is started, that is, before the conversion is considered to be 0%. In other words, the polymerization may be started from the addition of the carbonate-based metal salt, and the addition method is not particularly limited, and for example, continuous addition, divided addition, and batch addition may be used. The addition of the carbonate metal salt at the above time while satisfying the above content affects the achievement of the above effects.

Therefore, if the pH of the reaction is appropriately controlled when a carbonate metal salt is added during the polymerization, the number of defects in the final vinyl chloride-based polymer may be reduced, and in particular, the proportion of pseudo-terminal trans-type defects among olefin-type defects may be maintained, and the proportion of terminal-symmetrical chlorine-type defects among chlorine-type defects may be maintained, thereby finally contributing to a great improvement in heat resistance.

In addition, according to an embodiment of the present invention, although not particularly limited, a reaction inhibitor may be used, for example, p-benzoquinone, hydroquinone, butylated hydroxytoluene, monomethyl ether hydroquinone, tetrabutylcatechol, diphenylamine, triisopropanolamine, triethanolamine, etc. Although not particularly limited, the dispersant may use a higher alcohol such as lauryl alcohol, myristyl alcohol, or stearyl alcohol, or a higher fatty acid such as lauric acid, myristic acid, palmitic acid, or stearic acid.

In addition, although not particularly limited, the molecular weight regulator may be, for example, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, or the like. The electrolyte may be, for example, one or more selected from the group consisting of potassium chloride, sodium chloride, potassium bicarbonate, sodium carbonate, potassium bisulfite, sodium bisulfite, tetrapotassium pyrophosphate, tetrasodium pyrophosphate, tripotassium phosphate, trisodium phosphate, dipotassium phosphate, and disodium phosphate. Although not particularly limited, the electrolyte may be one or more selected from the group consisting of potassium chloride, sodium chloride, potassium bicarbonate, sodium carbonate, potassium bisulfite, sodium bisulfite, tetrapotassium pyrophosphate, tetrasodium pyrophosphate, tripotassium phosphate, trisodium phosphate, dipotassium phosphate, and disodium phosphate.

Step 2

In the method for preparing a vinyl chloride-based polymer according to an embodiment of the present invention, step 2) is a step of effecting addition of the first emulsifier, and may be a step of continuously adding the first emulsifier to the reactor from the polymerization initiation time to the time when the polymerization conversion rate reaches 35% to 52%. Further, the first emulsifier may be a succinate compound.

The first emulsifier may be continuously added from the polymerization initiation time to the time when the polymerization conversion rate reaches 35% to 52%, preferably 35% to 48%, more preferably 40% to 46%. Here, the polymerization initiation time may mean a time when the polymerization conversion rate is considered to be 0%, for example, a time when the internal temperature of the reactor in which the reaction mixture exists reaches the polymerization temperature and the polymerization reaction starts. When the first emulsifier is added until the time when the polymerization conversion rate is less than 35%, the type of the emulsifier changes before all the initial polymer particles are formed, which makes it difficult to control the particle size of the polymer particles and the viscosity of the resulting polymer exceeds the desired viscosity property level. Furthermore, when the second emulsifier is added too quickly as a polymerization reactant, the time during which the second emulsifier is exposed to hydrolysis conditions increases, thereby increasing the likelihood of hydrolysis. Therefore, there may be a problem that the atomization performance of the polymer resulting from the hydrolysis product of the second emulsifier is deteriorated. For example, when a succinate compound is added until a time when the conversion rate is less than 35%, then the type of the emulsifier is changed to a sulfate compound or the like as the second emulsifier, and the second emulsifier is added, the change time of the emulsifier is too early, thereby increasing the possibility of hydrolysis of the-SO-bond in the sulfate compound as the second emulsifier. Therefore, a large amount of alcohol compounds that deteriorate the atomization performance are generated, thereby greatly reducing the atomization performance of the produced polymer. Further, the amount of the first emulsifier added per hour is smaller when the first emulsifier, i.e., the succinate compound, is continuously added until the time when the conversion rate exceeds 52% than when the first emulsifier is added until the time when the conversion rate is 52% or less under the condition that the same amount of the first emulsifier is added in the entire reaction system. Therefore, coarse particles are formed during the generation of the initial particles, or the number of particles is significantly small, thereby significantly reducing the viscosity of the prepared polymer. Further, the succinate compound highly compatible with the plasticizer is added in an excessively large amount without controlling the addition amount, and thus, the viscosity may be significantly reduced to such an extent that it is difficult to process when mixing the plastisol. In addition, the influence of the second emulsifier is reduced in the produced polymer, which causes a problem of deteriorating foaming properties, such as lowering the density of foam units during foaming.

In addition, the first emulsifier may be a succinate compound, and the succinate compound collectively refers to a compound including a succinate functional group. Specifically, the succinate compound may include a sulfosuccinate compound, and more specifically, include at least one selected from the group consisting of dioctyl sulfosuccinate, ditridecyl sulfosuccinate, lauryl ether sulfosuccinate (lauryl polyether sulfosuccinate), and lauryl sulfosuccinate. Among them, the succinate compound may preferably include dioctyl sulfosuccinate from the viewpoint of further improving the stability of the polymerization reaction and further improving the viscosity property of the prepared polymer.

In this case, the succinate compound may be used in the form of a salt bonded with an alkali metal, alkaline earth metal, ammonium ion, amine and/or amino alcohol ion, for example, the succinate compound may be used in the form of a salt with sodium ion (Na)⁺) The form of the ionically bonded salt is used. As an example, the succinate compound may be used in the form of dioctyl sodium sulfosuccinate, ditridecyl sodium sulfosuccinate, disodium lauryl sulfosuccinate (sodium laureth sulfosuccinate), or sodium lauryl sulfosuccinate.

In one embodiment of the present invention, the succinate compound used as the first emulsifier has excellent compatibility with the plasticizer, so that low viscosity properties can be achieved during mixing of the plastisol, thereby greatly improving processability of the plastisol. Further, the succinate compound can stably maintain its structure as compared with other types of emulsifiers, whereby generation of causative substances that may be converted into volatile organic compounds can be suppressed. Thus, polymers with improved atomisation properties can be prepared.

In contrast, when other types of compounds other than the succinate compound, such as a sulfate compound, are used as the first emulsifier, since the structural stability is lower than that of the succinate compound, the possibility of hydrolysis increases. Specifically, when the sulfate compound is added from the polymerization initiation time, the proportion of the hydrolysis product increases because the compound is exposed to the hydrolysis conditions for a long period of time. At this time, the hydrolyzate causes a problem of deteriorating the fogging property of the produced polymer. For example, since the bonding strength of the S — O bond in the structure is low, a sulfate ester emulsifier such as sodium lauryl sulfate changes the bonding structure to R — OH (in the case of sodium lauryl sulfate, R means lauryl (dodecyl)), and the changed compound becomes a substance causing a decrease in atomization performance. Further, since the sulfate ester emulsifier has poorer compatibility with a plasticizer than the succinate ester compound, there is a problem that, when a plastisol is prepared from a polymer obtained by using the sulfate ester emulsifier alone, the sulfate ester emulsifier cannot secure low viscosity properties, causing poor processability. If the content of the plasticizer is increased to improve processability during mixing of the plastisol, processability may be improved, but there is a problem in that the migration phenomenon is deteriorated as the plasticizer is increased. Thus, it is preferable to use the succinate compound during step 2) in order to not only improve the atomization property, but also to achieve a low viscosity property to improve the processability.

In addition, the continuous addition of the first emulsifier during polymerization makes it easier to adjust the particle size of the polymer particles than in the case of batch addition, so that latex stability and viscosity stability during mixing of plastisol can be further improved. This feature can be achieved because the concentration of the emulsifier is rapidly increased in a short time at the initial stage of polymerization, thereby preventing the formation of particles having an excessively small size and irregular polymer particles, and the concentration of the emulsifier in the polymerization reactant can be maintained at a predetermined level.

Step 3

Step 3) according to an embodiment of the present invention may be a step of continuously adding the second emulsifier after the end of the addition of the first emulsifier added in step 2). At this time, the first emulsifier and the second emulsifier are different from each other.

There is no limitation on the type of the second emulsifier according to an embodiment of the present invention as long as it is different from the first emulsifier. For example, the second emulsifier may have a higher Critical Micelle Concentration (CMC) than the first emulsifier described above.

When an emulsifier having a higher CMC than the first emulsifier is used as the second emulsifier, it is possible to prevent continuous generation of particles except for the initial stage of polymerization, which would occur in the case where an emulsifier having a lower CMC is continuously used during the polymerization reaction.

In addition, it is more preferable to use a high CMC emulsifier because a vinyl chloride-based polymer exhibiting low viscosity properties can be prepared by preventing the formation of additional particles.

Specifically, the second emulsifier may comprise a sulfate compound, and may include, for example, alkyl sulfates, alkyl ether sulfates, sulfated alkanolamides, monoglyceride sulfates, glycerol ether sulfates, fatty acid ether sulfates, and fatty acid amide ether sulfates. More specifically, the second emulsifier may include one or more selected from lauryl sulfate, dodecylbenzene sulfate, cetyl stearyl sulfate, and lauryl ether sulfate (laureth sulfate).

In this case, the sulfate ester compound may be used in the form of a salt ionically bonded to an alkali metal, alkaline earth metal, ammonium ion, amine and/or aminoalcohol, and, for example, the sulfate ester compound may be used in the form of a salt ionically bonded to sodium ion (Na)⁺) The form of the ionically bonded salt is used. For example, the sulfate compound may be used in the form of sodium lauryl sulfate, sodium dodecylsulfate, sodium hexadecylstearyl sulfate, sodium lauryl ether sulfate (sodium laureth sulfate), or ammonium lauryl sulfate. Among them, the sulfate compound may preferably contain sodium lauryl sulfate in supplementing compatibility with a plasticizer to prevent a sudden decrease in viscosity even when the plasticizer is added, to provide more stable viscosity properties, and to densely form foam cells during foaming, and to further improve foaming properties. Here, the supplementary compatibility with the plasticizer means the viscosity according to the addition of the plasticizer due to the use of the first emulsifier having excellent plasticizer compatibilityThe decrease in the degree is appropriately controlled to prevent the viscosity from abruptly decreasing to such an extent that it cannot be processed.

As described above, by further adding a second emulsifier of a different type from the first emulsifier compound after the first emulsifier has been added, the compatibility with the plasticizer can be supplemented to prevent the viscosity from suddenly decreasing even when the plasticizer is added. Therefore, a stable processing viscosity can be ensured. In addition, the density and foaming properties of the foam unit can be further improved, which is difficult to achieve by using only the first emulsifier.

In addition, the second emulsifier is specifically added from a time after the end of the addition of the first emulsifier, and is continuously added until a time when the polymerization conversion rate reaches 70% to 95%, preferably 75% to 92%, more preferably 84% to 92%. Further, the time after the end of the addition of the first emulsifier may specifically mean a time immediately after the end of the addition of the first emulsifier, in which case the second emulsifier may be added immediately after the end of the addition of the first emulsifier, and the addition termination time may specifically be a time when the reaction is terminated.

In addition, the first emulsifier and the second emulsifier may be added in a weight ratio of 5:5 to 9:1, specifically in a weight ratio of 6:4 to 9:1, more specifically in a weight ratio of 6:4 to 8:2, respectively. When the above weight ratio is satisfied, the low viscosity property can be easily achieved and the atomization property can be further improved; and when the weight ratio of the second emulsifier is too low, the stability of the initially produced particles may be deteriorated.

In addition, the total amount of the first emulsifier and the second emulsifier added may be 0.1 to 5.0 parts by weight, specifically 0.1 to 3.0 parts by weight, more specifically 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the vinyl chloride-based monomer.

In addition, when the first emulsifier and the second emulsifier are mixed and continuously added, there may be a problem in that the second emulsifier having poor structural stability is added from an initial stage of polymerization, thereby causing an increase in the proportion of a hydrolysate of the second emulsifier, so that the atomization performance of the polymer may be deteriorated. Further, when the first emulsifier and the second emulsifier are mixed and continuously added, there is a problem that low viscosity property cannot be achieved, and thus processability improving effect cannot be secured. Therefore, when the first emulsifier and the second emulsifier are sequentially added, the desired effects of the present invention, improved processability, and improved atomization can be achieved by achieving low viscosity properties.

In addition, the method for preparing a vinyl chloride-based polymer according to an embodiment of the present invention uses two types of emulsifiers in a single reactor. Therefore, even if the polymer is produced by a single polymerization reaction, a vinyl chloride-based polymer can be prepared, which exhibits viscosity properties to greatly improve processability, has stable viscosity properties such that the viscosity does not sharply decrease according to the amount of plasticizer added, and has excellent fogging properties and foaming properties. Further, unlike the case of mixing polymers having different viscosity properties and foaming properties, respectively, the above method has advantages in that since a reservoir (reservoir) for storing each polymer, weighing for uniform mixing, and a mixing container are not additionally required, the manufacturing apparatus is relatively simplified, and a separate mixing process is not included, thereby improving process efficiency. Further, in the case where the polymers are separately prepared and mixed, since the content of the total emulsifier in the mixed polymers should be controlled in order to ensure excellent latex stability and atomization performance, the content of the emulsifier that can be used in the preparation process of each polymer is relatively small, there may be a problem in that it is difficult to ensure polymerization stability in each polymerization. However, the preparation method according to the present invention can employ a single polymerization reaction, and thus has an advantage in that an emulsifier can be used in an amount sufficient to maintain stability during the polymerization reaction, thereby having excellent polymerization stability.

The polymerization carried out according to one embodiment of the present invention may be carried out with the internal pressure of the reactor up to 3.0kgf/cm²To 5.0kgf/cm²Or when the conversion rate reaches 90 +/-5%.

In addition, according to the present invention, a step of drying the prepared vinyl chloride-based polymer may also be included, in which case, the drying is not particularly limited and may be performed by a method well known in the art, specifically, by a spray drying method. Before drying, dehydration and washing steps can also be included.