阅读说明：本技术 氯乙烯聚合物及其制备方法 (Vinyl chloride polymer and method for preparing the same ) 是由 安晟镕 金健地 李世雄 朱镇爀 河玄圭 于 2019-04-29 设计创作，主要内容包括：本发明涉及一种氯乙烯聚合物及其制备方法。更具体地,本发明提供一种多分散指数为2.0至2.3并且孔隙率为60％以上的氯乙烯聚合物,和该氯乙烯聚合物的制备方法。所述氯乙烯聚合物的制备方法具体是如下方法：首先通过预聚合制备转化率为5％至20％的氯乙烯聚合种子,然后将氯乙烯单体引入所述氯乙烯聚合种子中以聚合(主聚合)氯乙烯聚合物,此时,所述预聚合与所述主聚合之间的温度差控制为5℃至15℃。所述制备方法具有改善聚合生产率的效果,并且由于通过所述制备方法制备的氯乙烯聚合物可以表现出期望的物理性能,因此,所述制备方法还具有改善鱼眼质量和初始着色性能以及具有优异的加工性能的效果。(The present invention relates to a vinyl chloride polymer and a method for preparing the same. More specifically, the present invention provides a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3 and a porosity of 60% or more, and a method of preparing the vinyl chloride polymer. The preparation method of the vinyl chloride polymer is specifically as follows: a vinyl chloride polymer seed having a conversion rate of 5 to 20% is first prepared by prepolymerization, and then vinyl chloride monomer is introduced into the vinyl chloride polymer seed to polymerize (main polymerization) a vinyl chloride polymer, at which time a temperature difference between the prepolymerization and the main polymerization is controlled to be 5 to 15 ℃. The preparation method has the effect of improving polymerization productivity, and also has the effect of improving fish-eye quality and initial colorability as well as having excellent processability, since the vinyl chloride polymer prepared by the preparation method can exhibit desired physical properties.)

1. A vinyl chloride polymer having a polydispersity index (PDI) of 2.0 to 2.3 and a porosity of 60% or more.

2. The vinyl chloride polymer according to claim 1, wherein the vinyl chloride polymer has an average pore diameter (4V/a) of 300nm or more.

3. The vinyl chloride polymer of claim 1, wherein the vinyl chloride polymer has a porosity of 60% to 75%.

4. The vinyl chloride polymer of claim 1, wherein the vinyl chloride polymer has an average pore size of 300nm to 600 nm.

5. The vinyl chloride polymer of claim 1, wherein the vinyl chloride polymer is a vinyl chloride homopolymer.

6. A method for preparing a vinyl chloride polymer, the method comprising:

step 1: polymerizing a first vinyl chloride monomer in a prepolymerization reactor to have a polymerization conversion rate thereof ranging from 5% to 20%, thereby preparing a vinyl chloride polymerization seed; and

step 2: transferring the vinyl chloride polymerization seed to a main polymerization reactor, and then polymerizing the vinyl chloride polymerization seed with a second vinyl chloride monomer introduced into the main polymerization reactor, thereby preparing a vinyl chloride polymer, wherein,

the polymerization temperature difference between step 1 and step 2 is from 5 ℃ to 15 ℃,

the vinyl chloride polymer is a vinyl chloride homopolymer.

7. The production method according to claim 6, wherein the polymerization of step 1 and step 2 is suspension polymerization, and the suspension polymerization is carried out in the presence of a protective colloid agent and a polymerization initiator.

8. The production method according to claim 6, wherein the polymerization temperature difference between the step 1 and the step 2 is 10 ℃ to 15 ℃.

9. The preparation method of claim 6, wherein the vinyl chloride polymer seed is prepared by polymerizing such that a polymerization conversion rate is 5 to 15%.

10. The production method according to claim 6, wherein the polymerization temperature in step 1 is higher than the polymerization temperature in step 2.

11. The method of claim 6, wherein the first vinyl chloride monomer and the second vinyl chloride monomer are the same vinyl chloride monomer.

Technical Field

Cross Reference to Related Applications

This application claims the rights of korean patent application No.10-2018-0049563, filed on 30.04.2018, and korean patent application No.10-2019-0048264, filed on 25.04.2019, in korean intellectual property office, the disclosures of both of which are incorporated herein by reference in their entirety.

Background

Vinyl chloride polymers are inexpensive while having an excellent mass balance, and thus, are used in a wide range of fields such as hard materials and soft materials. Specifically, in the hard field, vinyl chloride polymers are used for pipes, films, window frames, and the like, and in the soft field, vinyl chloride polymers are used for electric wire coatings, packaging films, sheets, and the like.

Generally, in order to reduce the production cost of vinyl chloride polymers and to improve process efficiency, it is important to increase the polymerization productivity per unit volume of the reaction. As a method for improving the polymerization productivity, there are a method for improving the polymerization conversion while keeping the polymerization reaction time constant to thereby improve the productivity per lot, and a method for shortening the polymerization reaction time.

Among these methods for improving polymerization productivity, as a method for improving polymerization conversion, a method of additionally introducing a vinyl chloride polymer as a polymerization initiator has been proposed. As an example, U.S. patent publication No.2005-008027 discloses a method for increasing the polymerization conversion by additionally introducing an initiator when the internal pressure of a polymerization reactor is reduced. However, although the polymerization conversion rate of the vinyl chloride polymer obtained by the above-described method is slightly improved, since the polymerization conversion rate when the internal pressure of the polymerization reactor is reduced is 70% or more, the effect of improving the polymerization conversion rate by introducing the initiator at this time is insignificant, and there is a problem of increase of fish eyes or increase of fine particles, thereby deteriorating the initial coloring property. Further, when considering the quality of vinyl chloride polymer and considering that the conventional polymerization conversion rate is 83% to 85%, the method for increasing the polymerization conversion rate is not very effective in increasing the polymerization productivity. Therefore, in order to improve the productivity of vinyl chloride resins, many efforts have been made to shorten the polymerization reaction time.

As a method for shortening the polymerization reaction time of vinyl chloride polymers, U.S. Pat. publication No.2005-0054795 discloses a method of introducing an initiator having a short half-life in the middle of the reaction. However, since an initiator having a short half-life is introduced in the middle of the reaction by the above method, there is a problem in that the shape of the inner particles is not uniform due to locally generated reaction heat, and thus fish eyes are increased.

In addition, Japanese patent laid-open No.1998-338701 discloses a method for shortening the polymerization reaction time by using both an oil-soluble initiator and a water-soluble initiator at the initial stage of polymerization, and U.S. Pat. No.6,861,488 discloses a method for preparing a vinyl chloride polymer using an oil-soluble polymerization initiator, i.e., t-amyl peroxyneodecanoate and a peroxide-based polymerization initiator to prevent initial discoloration under suspension polymerization. However, when a vinyl chloride polymer is produced, although the effect of shortening the reaction time by the above-described method can be expected to some extent, vinyl chloride monomer is a substance having oil solubility, which is mainly present in a state of being phase-separated from deionized water as polymerization water in the initial stage of polymerization, and most of unreacted vinyl chloride monomer which is not converted into polymer exists in a state of being dissolved in an aqueous phase when the polymerization reaction proceeds and the polymerization conversion rate is 60% or more in the later stage of polymerization, and therefore, the effect of shortening the reaction time by the water-soluble initiator used together with the oil-soluble initiator is not large in the initial stage of reaction, and there is still a problem of generation of fish eyes due to fine particles generated by the water-soluble initiator in the initial stage of polymerization.

Thus, although the above-mentioned method is a method proposed for improving the polymerization productivity, there is a problem that the quality of the polymer to be produced, such as fish eyes and initial coloring properties, are deteriorated, and further, the processability of the produced polymer cannot be secured.

Therefore, there is a need to develop a method of preparing a vinyl chloride polymer, which can increase polymerization productivity while improving the quality of the polymer in terms of fish eyes and initial coloring properties and improving the processability of the polymer, and a vinyl chloride polymer.

(Prior art document)

(patent document 1)2005-008027A

(patent document 2)2005-0054795A

(patent document 3)1998-338701A

Disclosure of Invention

Technical problem

An aspect of the present invention provides a method for preparing a vinyl chloride polymer, which has excellent processability while solving the problems of low polymerization productivity when preparing a vinyl chloride polymer and deterioration of fish eyes and initial colorability due to undissolved particles of reactants. Specifically, an aspect of the present invention provides a preparation method in which a vinyl chloride polymer seed having a conversion rate of 5% to 20% is prepared in a prepolymerization reactor and then transferred to a main polymerization reactor to polymerize a vinyl chloride polymer by controlling a polymerization temperature difference between prepolymerization and main polymerization.

Another aspect of the present invention provides a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3, a porosity of 60% or more, and an average pore diameter of 300nm or more, which has improved polymer quality in terms of fish eyes and initial colorability, and has excellent processability.

Technical scheme

According to an aspect of the present invention, there is provided a vinyl chloride polymer having a polydispersity index (PDI) of 2.0 to 2.3, a porosity of 60% or more, and an average pore diameter of 300nm or more.

According to another aspect of the present invention, there is provided a method of preparing a vinyl chloride polymer, the method comprising: polymerizing a first vinyl chloride monomer in a prepolymerization reactor to have a polymerization conversion rate thereof of 5% to 20% to prepare a vinyl chloride polymerization seed (step 1); and transferring the vinyl chloride polymerization seed to a main polymerization reactor and then polymerizing the vinyl chloride polymerization seed with a second vinyl chloride monomer introduced into the main polymerization reactor to prepare a vinyl chloride polymer (step 2), wherein a polymerization temperature difference between step 1 and step 2 is 5 to 15 ℃, and the vinyl chloride polymer is a vinyl chloride homopolymer.

Advantageous effects

A vinyl chloride polymer according to an embodiment of the present invention satisfies a polydispersity index of 2.0 to 2.3 and a porosity of 60% or more. Therefore, when mixed with a plasticizer or the like, its melt viscosity is low so that processability is excellent, and its plasticizer absorption rate is excellent so that there is an effect that fisheye quality and initial colorability quality are improved.

In addition, the method of preparing vinyl chloride polymer according to one embodiment of the present invention performs polymerization by prepolymerization before main polymerization so that the polymerization conversion rate is 5% to 20% to prepare a vinyl chloride polymerization seed, and then performs main polymerization using the polymerization seed while controlling the conversion rate of the polymerization seed and the polymerization temperature difference between the prepolymerization and the main polymerization to shorten the polymerization reaction time. Therefore, the method has the effect of significantly improving polymerization productivity, and the polymer to be produced is excellent in processability, fish eyes and initial colorability.

Detailed Description

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

It should be understood that the words or terms used in the specification and claims of this invention should not be construed as limited to having the meanings defined in commonly used dictionaries. It should also be understood that the words or terms should be construed as having meanings consistent with their meanings in the context of the related art and in 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.

According to an embodiment of the present invention, there is provided a vinyl chloride polymer having a polydispersity index (PDI) of 2.0 to 2.3 and a porosity of 60% or more.

In addition, the average pore diameter (4V/a) of the vinyl chloride polymer according to one embodiment of the present invention may be 300nm or more.

In the present invention, "vinyl chloride polymer" refers to a compound produced by polymerizing vinyl chloride monomer, and may refer to a polymer chain derived from vinyl chloride monomer.

In the present invention, the "polydispersity index (PDI)" is an index indicating the width of a molecular weight distribution, and is a numerical value indicating the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). That is, the polydispersity index is a value obtained by measuring a weight average molecular weight and a number average molecular weight, and then dividing the weight average molecular weight by the number average molecular weight. At this time, in the present invention, 0.02g of a sample of vinyl chloride polymer was added to 20ml of Tetrahydrofuran (THF) to be dissolved for 24 hours, and then the mixture was filtered with a 0.45 μm filter to measure the number average molecular weight and the weight average molecular weight under the conditions of 25 ℃ and atmospheric pressure (1atm) using a GPC apparatus (Waters 2414 refractive index detector, Waters1525 binary HPLC pump and Waters 717 autosampler, Waters co.). Thereafter, a calibration curve was plotted using standard samples (styrene standards, molecular weights (g/mol) of 1320, 2750, 6760, 19700, 50600, 124000, 279000, 768000, 1540000, 2350000), and then converted.

In addition, in the present invention, surface voids (Pinter), accessible internal voids (Pacc), and inaccessible internal voids (inaccessible internal voids, Pinacc) were measured according to the amount of mercury intruded into vinyl chloride polymer particles under conditions of room temperature (23 ± 2 ℃) and atmospheric pressure (1atm) using a mercury porosity analyzer, specifically Auto Pore IV9520 (Micromeritics corporation), and then the average Pore diameter (4V/a) and porosity were derived from the measurement results.

As in the present invention, a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3, a porosity of 60% or more, and an average pore diameter of 300nm or more has excellent processability, and the quality of fish eyes can be improved, and the problem of deterioration of initial colorability can be solved.

In particular, a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3 has excellent processability and good mechanical strength. In contrast, when the polydispersity index is less than 2.0, since the molecular weight distribution is narrow, a problem of deterioration of processability during processing may occur. When the polydispersity index is more than 2.3, since the molecular weight distribution is too broad, mechanical properties may be deteriorated when the vinyl chloride polymer is mixed with the plasticizer and the processing aid raw material.

In addition, when the porosity is less than 60%, the porosity is too low, so that the absorption rate of the plasticizer and the auxiliary raw material added during the process may be reduced. Therefore, the mixed material is unevenly dispersed, so that the quality of fish eyes and the quality of initial coloring performance may be deteriorated. Further, when the average pore diameter is less than 300nm, the diameter is too small, so that the absorption rate of the plasticizer and the auxiliary raw material may be lowered, causing the same problems as described above.

Here, the fish eye refers to white transparent particles generated due to undissolved reactant particles, and is an index for determining the protrusion quality of the polymer. The more fish eyes, the lower the quality of the polymer.

Specifically, according to an embodiment of the present invention, the vinyl chloride polymer may have a porosity of 60% to 75%, more preferably 60% to 70%, while satisfying the polydispersity index within the above range. Further, the average pore diameter thereof may be 300nm to 600nm, and more preferably, the average pore diameter thereof may be 300nm to 500 nm. When the above numerical range is satisfied, the above-described mixed physical properties can be further maximized.

In addition, the polymerization degree of the vinyl chloride polymer according to one embodiment of the present invention may be 700 to 1300, preferably 1000 to 1200. In the present invention, "degree of polymerization" refers to the number of repeating units (monomers or monomers) constituting a polymer, and may be a numerical value measured according to ASTM D1243-79.

In addition, the vinyl chloride polymer according to an embodiment of the present invention may be a homopolymer. The homopolymer is a polymer formed from a single type of monomer, and the vinyl chloride polymer of the present invention may be a polymer polymerized using only vinyl chloride monomer.

According to the vinyl chloride polymer of one embodiment of the present invention, a vinyl chloride polymer exhibiting the above-described physical properties may be prepared by a seed polymerization method. At this time, the vinyl chloride polymer seed may be prepared by performing polymerization in a prepolymerization reactor such that the polymerization conversion rate is 5% to 20%, and the polymerization temperature difference between prepolymerization for polymerizing the seed and main polymerization for polymerizing the finally prepared vinyl chloride polymer may be 5 ℃ to 15 ℃. Therefore, according to another embodiment of the present invention, there is provided a method of preparing a vinyl chloride polymer.

That is, the method of preparing a vinyl chloride polymer according to an embodiment of the present invention may include: a step of polymerizing a first vinyl chloride monomer in a prepolymerization reactor to have a polymerization conversion rate thereof of 5% to 20% to prepare a vinyl chloride polymerization seed (step 1); and a step of transferring the vinyl chloride polymerization seed to a main polymerization reactor and then polymerizing the vinyl chloride polymerization seed with a second vinyl chloride monomer introduced into the main polymerization reactor to prepare a vinyl chloride polymer (step 2). At this time, the polymerization temperature difference between step 1 and step 2 is 10 ℃ to 15 ℃, and the vinyl chloride polymer is a vinyl chloride homopolymer.

In addition, the method of preparing a vinyl chloride polymer according to one embodiment of the present invention may be a method of preparing the above-described vinyl chloride polymer, specifically, a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3 and a porosity of 60% or more. Alternatively, the method may be a method of preparing a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3, a porosity of 60% or more, and an average pore diameter of 300nm or more.

In addition, the polymerization of step 1 and step 2 may be performed by suspension polymerization, and suspension polymerization may refer to polymerization performed in the presence of a protective colloid agent and a polymerization initiator. That is, the method of preparing a vinyl chloride polymer according to one embodiment of the present invention may be a method of preparing a polymer by suspension seed polymerization.

The method for preparing vinyl chloride polymer using suspension polymerization seed as described above is the following method: vinyl chloride polymerization seeds are polymerized in a prepolymerization reactor before main polymerization and then transferred to a main polymerization reactor to be subjected to suspension polymerization with vinyl chloride monomer, to shorten polymerization reaction time, thereby remarkably increasing polymerization productivity, preventing fish eyes due to undissolved particles of reactants, and improving initial colorability. Further, when a specific polymerization conversion ratio and a temperature difference between the prepolymerization and the main polymerization are satisfied, not only the above-mentioned improving effect but also the polydispersity index of the polymer to be produced is improved, and thus, there is an effect of improving processability.

Hereinafter, each step will be described in detail.

Step 1

Step 1 according to one embodiment of the present invention is a step of preparing a vinyl chloride polymerization seed using a prepolymerization reactor. Specifically, a first vinyl chloride monomer is polymerized in a prepolymerization reactor to have a polymerization conversion rate thereof ranging from 5% to 20%, thereby preparing a vinyl chloride polymerization seed. Step 1 may refer to a prepolymerization step. The vinyl chloride polymerization seed of step 1 may be prepared by suspension polymerization carried out in the presence of a polymerization initiator and a protective colloid agent. In addition, the vinyl chloride polymer seed is insoluble in Vinyl Chloride Monomer (VCM), and the size of the seed particle is 100 μm to 120 μm.

Preferably, the vinyl chloride polymerization seed is prepared by performing polymerization using a prepolymerization reactor so that the polymerization conversion rate is 5% to 20%. More preferably, however, the vinyl chloride polymer seed is prepared by polymerization so that the polymerization conversion rate is 5% to 15%, more preferably 10% to 15%.

In the present invention, the polymerization conversion rate may be a value measured by gas chromatography using a butane tracer. Specifically, the polymerization conversion may be a value obtained by: a polymerization conversion curve is made according to a change over time in a ratio of vinyl chloride monomer to butane under predetermined polymerization conditions whenever the respective polymerization conditions are satisfied, and a polymerization conversion according to the polymerization conditions is measured based on the made polymerization conversion curve.

In the step 1), when vinyl chloride polymerization seeds are prepared such that the polymerization conversion rate is less than the above range, the polymerization seeds are not sufficiently polymerized. Therefore, the amount of the polymerization seeds to be introduced into the main polymerization reactor is too small, so that the effect of improving the polymerization productivity is insignificant. When the vinyl chloride polymer seed is prepared such that the polymerization conversion rate is greater than the above range, the polymer seed grows to a certain extent and the stability is increased. Therefore, coalescence/redispersion with vinyl chloride monomer introduced from the main polymerization reactor is difficult to occur, so that it may be difficult to control the internal shape of the polymer particles and the molecular weight of the polymer. Therefore, it is difficult to control the polydispersity index, porosity, average pore diameter, etc., so that it may be difficult to prepare a high quality vinyl chloride polymer having stable quality of fish eyes, initial coloring property, etc. In addition, the processability is also deteriorated.

The polymerization of step 1) can be carried out by conventional suspension polymerization at the polymerization temperature of vinyl chloride polymer. In particular, the suspension polymerization can be carried out at a temperature of from 30 ℃ to 80 ℃, preferably at a temperature of from 45 ℃ to 75 ℃. The temperature during suspension polymerization can be appropriately controlled within the above range depending on the desired polymerization degree and polymerization time (productivity). For example, in terms of degree of polymerization, the higher the desired degree of polymerization, the lower the temperature. The lower the desired degree of polymerization, the higher the temperature.

In addition, the stirring rate of the suspension polymerization may be a rate generally used for preparing a vinyl chloride polymer. The size of the reactor, the shape and kind of the stirrer, and the stirring rate may be controlled according to the desired physical properties of the vinyl chloride polymer. Therefore, although not particularly limited, in one example of the present invention, 1m is³The stirring rate in the reactor (2) may be from 180rpm to less than 250 rpm.

Step 1) according to one embodiment of the present invention includes, specifically, preparing a reaction mixture by mixing a protective colloid agent, a first vinyl chloride monomer, and a polymerization initiator in polymerization water. Here, the first vinyl chloride monomer refers to a vinyl chloride monomer which may be the same as a second vinyl chloride monomer described later, or may be a number used to determine the order of introduction.

At this time, the polymerization water is a polymerization solvent, and various polymerization waters such as distilled water or deionized water may be used as the polymerization water. Preferably, deionized water may be used. The temperature of the polymerization water may be appropriately determined in consideration of the temperature at which the suspension polymerization is carried out, and the amount of the polymerization water may also be appropriately determined according to the polymerization conditions. For example, the total content of the polymerization water of step 1) and step 2) may be 70 parts by weight or more based on 100 parts by weight of the first vinyl chloride monomer and the second vinyl chloride monomer.

The protective colloid agent can be used for the purpose of maintaining the stability of vinyl chloride monomer during the preparation of vinyl chloride polymer and obtaining a desired degree of physical properties of vinyl chloride polymer, such as average particle diameter, apparent specific gravity (B.D.), particle diameter distribution, and plasticizer absorption rate (CPA). The protective colloid agent may be, for example, selected from vinyl alcohol resins having a degree of hydration of 30% to 90% and a viscosity of 5cps to 100cps in a 4% aqueous solution at room temperature; cellulose having 15 to 40% by weight of a methoxy group and 3 to 20% by weight of a propylhydroxy group, and having a viscosity of 10 to 20,000cps in a 2% aqueous solution measured at 23 ± 5 ℃; and unsaturated organic acids. Preferably, the protective colloid agent may be a vinyl alcohol resin having a degree of hydration of 30% to 90% and a viscosity of 5cps to 100cps in a 4% aqueous solution at room temperature; cellulose having 15 to 40% by weight of methoxy groups and 3 to 20% by weight of propylhydroxy groups, and having a viscosity of 10 to 20,000cps in a 2% aqueous solution measured at room temperature (20 ± 5 ℃); or mixtures thereof. In this case, the unit% of the degree of hydration may be understood as% by weight.

In addition, the total content of the protective colloid agent of step 1) and step 2) may be 0.03 to 5.0 parts by weight, preferably 0.05 to 2.5 parts by weight, based on 100 parts by weight of the first vinyl chloride monomer and the second vinyl chloride monomer. When the total amount of the protective colloid agent used is less than 0.03 parts by weight, the droplet stability is lowered, and the particle diameter of the polymerization seed and the particle diameter of the finally polymerized vinyl chloride polymer are excessively increased, so that fish eyes may be generated. When more than 5.0 parts by weight, initial coloring properties may be deteriorated due to the increase of fine particles.

Meanwhile, in one example of the present invention, the protective colloid agent may include a mixture of two or more vinyl alcohol resins having different degrees of hydration. For example, the protective colloid agent may include a mixture of a vinyl alcohol resin having a hydration degree of more than 50% to 90% or less (high hydration resin) and a vinyl alcohol resin having a hydration degree of 30% to 50% (low hydration resin).

In addition, the protective colloid agent may include cellulose in addition to the vinyl alcohol-based resin. At this time, the total content of the cellulose may be 0.001 parts by weight to 0.5 parts by weight based on 100 parts by weight of the first vinyl chloride monomer and the second vinyl chloride monomer. Examples of the cellulose may include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and the like, and any one of them or a mixture of two or more of them may be used. Wherein the protective colloid agent may be hydroxypropylmethyl cellulose, and the cellulose may be, more specifically, cellulose having a methoxyl group of 15 to 40 wt% and a propylhydroxyl group of 3 to 20 wt%, and a viscosity of 10 to 20,000cps in a 2% aqueous solution measured at 20 ± 5 ℃.

In addition, examples of the unsaturated organic acid polymer may include acrylic acid polymers, methacrylic acid polymers, itaconic acid polymers, fumaric acid polymers, maleic acid polymers, succinic acid polymers, and the like, and any one of them or a mixture of two or more of them may be used.

In addition, the total content of the polymerization initiators of step 1) and step 2) according to one embodiment of the present invention may be 0.02 parts by weight to 0.2 parts by weight based on 100 parts by weight of the first vinyl chloride monomer and the second vinyl chloride monomer used in the polymerization. Specifically, the polymerization initiator may be used in an amount of 0.03 parts by weight to 0.12 parts by weight, based on 100 parts by weight of the first vinyl chloride monomer and the second vinyl chloride monomer. If the total content of the polymerization initiators is less than 0.02 parts by weight, the polymerization reaction time increases and the conversion rate to the vinyl chloride polymer decreases, so that productivity may deteriorate. When more than 0.2 parts by weight, the polymerization initiator is not completely consumed during the polymerization to remain in the finally produced vinyl chloride polymer, so that the thermal stability and color quality of the polymer may be deteriorated.

The polymerization initiator is not particularly limited, and may be, for example, diacyl peroxide-based initiators such as dicumyl peroxide, dipentyl peroxide, di-3, 5, 5-trimethylhexanoyl peroxide, and dilauryl peroxide; peroxydicarbonate-type initiators such as diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and cumyl peroxydicarbonate; peroxyester type initiators such as t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-amyl peroxyneodecanoate, cumyl peroxyneoheptanoate, 1,3, 3-tetramethylbutyl peroxyneodecanoate and hydroxy-dimethylbutyl peroxide; azo compounds such as azobis-2, 4-dimethylvaleronitrile; sulfate type initiators, such as potassium persulfate and ammonium persulfate. Any one of them or a mixture of two or more of them may be used.

The method of preparing a vinyl chloride polymer according to one embodiment of the present invention may include stirring the reaction mixture prepared above, and the suspension polymerization may be performed by stirring.

In addition, if necessary, the method for preparing a vinyl chloride polymer according to one embodiment of the present invention may further include sodium bicarbonate (NaHCO)₃) Sodium borate (Na)₂B₄O₇) Disodium hydrogen phosphate (Na)₂HPO₄) Sodium carbonate (Na)₂CO₃) Potassium dihydrogen phosphate (KH)₂PO₄) Ammonium hydroxide (NH)₄OH), potassium tartrate (KHC)₄H₄O₆) Potassium hydrogen phthalate (KHC)₈H₄O₄) And calcium hydroxide (Ca (OH)₂) As a hydrogen ion concentration control agent, either one or a mixture of two or more thereof.

In addition, if necessary, the method of preparing a vinyl chloride polymer according to an embodiment of the present invention may further include any one or a mixture of two or more of diallyl maleate (DAM), diallyl phthalate (DAP), Ethylene Glycol Dimethacrylate (EGDMA), and triallyl isocyanurate (TAIC) as a crosslinking agent.

In addition, at a specific point within the polymerization conversion range specified in step 1), the prepared vinyl chloride polymerization seed and unreacted monomers may be all transferred to the main polymerization reactor to perform main polymerization.

Step 2

Step 2) according to an embodiment of the present invention is a step of preparing a vinyl chloride polymer through main polymerization using the vinyl chloride polymer seed prepared in step 1). Specifically, the vinyl chloride polymerization seed of step 1) is transferred to a main polymerization reactor, and then polymerized with a second vinyl chloride monomer introduced into the main polymerization reactor to prepare a vinyl chloride polymer. Further, step 2) may refer to a main polymerization step. Further, the vinyl chloride polymer prepared after performing the step 2) may be a homopolymer.

That is, the step 2) may be a step of transferring the vinyl chloride polymerization seed of the step 1) to a main polymerization reactor, and then polymerizing the transferred vinyl chloride polymerization seed with a second vinyl chloride monomer introduced into the main polymerization reactor to prepare a vinyl chloride polymer.

The method of preparing a vinyl chloride polymer according to one embodiment of the present invention produces a vinyl chloride homopolymer, and since compatibility between monomers is excellent when compared to a method of preparing a copolymer, polymerization productivity can be significantly improved.

In addition, in the case of the copolymer, the structure and properties of the entire polymer may vary according to the type and content ratio of the comonomer copolymerized with vinyl chloride monomer, so that it is not easy to control the degree of polymerization. Further, it is difficult to ensure the reliability of the degree of polymerization determined by the measuring method of the present invention due to the influence of the comonomer, and therefore, an accurate degree of polymerization cannot be determined. Further, even when mixed with a resin composition, as described above, physical properties greatly vary depending on the type and content ratio of the comonomer, and therefore, when compared with a homopolymer, it is difficult to predict the mixed physical properties, and thus, it is not easy to control the quality and the like of a molded product. Accordingly, the vinyl chloride polymer of the present invention is characterized by being specified as a vinyl chloride homopolymer to solve the above-mentioned problems of the copolymer and to ensure excellent polymerization productivity and mixing physical properties.

According to an embodiment of the present invention, the order of the time point of transferring the vinyl chloride polymerization seed prepared in step 1) and the time point of introducing the second vinyl chloride monomer into the main polymerization reactor is not particularly limited. For example, the vinyl chloride polymerization seed may be transferred to the main polymerization reactor while the main polymerization reactor is filled with the second vinyl chloride monomer, or the vinyl chloride polymerization seed may be transferred to the main polymerization reactor, and then the second vinyl chloride monomer may be introduced into the main polymerization reactor. In another example, the transfer of the vinyl chloride polymerization seed and the introduction of the second vinyl chloride monomer into the main polymerization reactor may be performed simultaneously.

Step 2) may employ the same suspension polymerization method as described in step 1). Specifically, the suspension polymerization may be performed in the presence of a protective colloid agent and a polymerization initiator, in addition to the vinyl chloride polymerization seed prepared in step 1). At this time, the protective colloid agent and the polymerization initiator may be introduced into the main polymerization reactor simultaneously with the second vinyl chloride monomer, or may be introduced into the main polymerization reactor before the second vinyl chloride monomer is introduced. Further, the protective colloid agent and the polymerization initiator may be selected from the types of the protective colloid agent and the polymerization initiator described in step 1), and the protective colloid agent and the polymerization initiator used in step 2) may be the same as or different from those in step 1). In addition, in step 2), the polymerization water described in step 1) may also be contained in the reaction mixture, and if necessary, a hydrogen ion concentration controlling agent and a crosslinking agent may also be incorporated. At this time, the polymerization water, the hydrogen ion concentration controlling agent and the crosslinking agent used in step 2) may be the same as or different from those in step 1).

In addition, the polymerization temperature of step 2) may be a temperature different from the polymerization temperature of step 1) by 5 ℃ to 15 ℃, and preferably, the polymerization temperature difference between step 1) and step 2) may be 10 ℃ to 15 ℃. When the polymerization temperature difference between step 1) and step 2) satisfies the range of 5 ℃ to 15 ℃, a vinyl chloride polymer having a polydispersity index of 2.0 to 2.3 can be prepared, and has an effect of improving processability since the vinyl chloride polymer has a polydispersity index of the above range.

In addition, as long as the polymerization temperature of step 1) and the polymerization temperature of step 2) satisfy the temperature difference of the above range, there is no particular limitation on whether the polymerization temperature of step 1) is higher or lower than the polymerization temperature of step 2). When considering the improvement of the physical properties of the vinyl chloride polymer to be produced, the polymerization temperature of step 2) may be controlled to be higher than that of step 1). However, when considering improvement of polymerization productivity and shortening of polymerization time, it is preferable that the polymerization temperature of step 1) is higher than that of step 2). In addition, the first vinyl chloride monomer and the second vinyl chloride monomer described above are terms for distinguishing the order of introduction only. To prepare a vinyl chloride homopolymer, preferably, the first vinyl chloride monomer and the second vinyl chloride monomer are the same vinyl chloride monomer.

In addition, the second vinyl chloride monomer of step 2) may be introduced more than the first vinyl chloride monomer of step 1), and the weight ratio of the first vinyl chloride monomer to the second vinyl chloride monomer may be, for example, 1:1.2 to 1:10, preferably 1:2 to 1: 8.

In addition, step 2) of the method of preparing a vinyl chloride polymer according to one embodiment of the present invention may further include terminating the polymerization and recovering the product (vinyl chloride polymer).

At this time, the suspension polymerization may be terminated by introducing a reaction terminator, and the time point of the termination may be when the pressure in the reactor is 6kgf/cm²To 8kgf/cm²When (or when the polymerization conversion is greater than 85%).

The reaction terminator is not particularly limited. For example, the reaction terminator may be a phenol compound, an amine compound, a nitrile compound, a sulfur compound, or the like. Specifically, the reaction terminator may be any one selected from the following: phenolic compounds, such as triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, hydroquinone, p-methoxyphenol, tert-butylhydroxyanisole, n-octadecyl-3- (4-hydroxy-3, 5-di-tert-butylphenyl) propionate, 2, 5-di-tert-butylhydroquinone, 4 '-butylidenebis (3-methyl-6-tert-butylphenol), tert-butylcatechol, 4' -thiobis (6-tert-butyl-m-cresol), and tocopherol; amine compounds such as N, N '-diphenyl-p-phenylenediamine and 4,4' -bis (dimethylbenzyl) diphenylamine; nitrile compounds such as 2-phenylnitroxyl nitroxide (2-phenylnitroxide), 3-imidazoline nitroxide, 4-hydroxy-2, 2',6,6' -tetramethyl-piperidine-1-oxyl; sulfur compounds such as dodecyl mercaptan and 1, 2-diphenyl-2-thiol; phosphoric acid-based compounds, such as triphenyl phosphite, diphenyldecyl phosphite, phenylisodecyl phosphite, tris (nonylphenyl) phosphite and trilauryl trithiophosphite. Preferably, the reaction terminator may include triethylene glycol-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate.

The vinyl chloride polymer prepared according to the above-mentioned termination of polymerization may be in the form of a slurry, and the slurry may be prepared in the form of a finally prepared vinyl chloride polymer by removing moisture using a fluidized bed dryer under conventional reaction conditions.

In addition, in the polymerization of step 1) and step 2), additives such as a polymerization control agent, a chain transfer agent, a pH control agent, an antioxidant, a crosslinking agent, an antistatic agent, a scale inhibitor, a surfactant, and the like may be additionally added, if necessary, in addition to the above-mentioned active ingredients, and the type and content of the additives are not particularly limited. Additives of known types may be used at levels well known in the art. The additives may be added at any point in the suspension polymerization, such as at the beginning of the suspension polymerization, during the suspension polymerization or after the suspension polymerization. The additives may all be added simultaneously or continuously.

The reactor used in the present invention is not particularly limited in the shape of stirring means such as a stirrer and a baffle. Any stirring device commonly used for suspension polymerization of vinyl chloride polymers may be used. Specifically, as the agitator, an agitator having a single agitating blade such as a paddle blade, a pitched paddle blade, a bloomers gin blade, a paudora blade, a turbine blade, and a propeller blade, or two or more of them may be used. As the baffle, a baffle having a plate shape, a cylindrical shape, a D shape, a ring shape, or a finger shape may be used.

Hereinafter, the present invention will be described in more detail with reference to examples and experimental examples. However, the following examples and experimental examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention.