KR20150037050A

KR20150037050A - Method for Preparing PVC resin

Info

Publication number: KR20150037050A
Application number: KR20130116260A
Authority: KR
Inventors: 안병국; 안성용; 황수환; 김경현
Original assignee: 주식회사 엘지화학
Priority date: 2013-09-30
Filing date: 2013-09-30
Publication date: 2015-04-08

Abstract

The present invention relates to a method for producing a polyvinyl chloride resin by suspending a vinyl chloride monomer in a water medium, and the like. According to the present invention, it is possible to suppress the generation of bubbles generated by adding a dispersant to a suspension, A suspension polymerization method of a vinyl chloride polymer which can stabilize a reflux condenser and improve fish-eye, and which can improve an apparent specific gravity, which is an important physical property in vinyl chloride processing, There is provided an effect of providing a vinyl chloride resin for extrusion or a vinyl chloride resin for hard extrusion with an improved apparent specific gravity characteristic.

Description

TECHNICAL FIELD The present invention relates to a method for preparing a polyvinyl chloride resin,

The present invention relates to a method for producing a polyvinyl chloride resin by suspending a vinyl chloride monomer in a water medium, and more particularly, to a method for producing a polyvinyl chloride resin by adding a dispersant to a suspension to suppress foaming, A suspension polymerization method of a vinyl chloride polymer capable of improving stabilization and fish-eye and also improving an apparent specific gravity, which is an important physical property in processing vinyl chloride, and a vinyl chloride polymer for soft extrusion It is possible to provide a vinyl chloride resin for hard extrusion which has improved system resin or apparent specific gravity characteristics.

The vinyl chloride resin is made of vinyl chloride as a main component and can be made by conserving petroleum resources and is called an energy-saving plastic. In general, vinyl chloride polymer is a universal resin used in a wide range of fields worldwide for life and industrial materials such as pipes, window frames, wire covers, sheets, and molded products because of its low cost and easy processing and simple polymerization process.

On the other hand, in order to improve the workability of the vinyl chloride-based polymer and improve the quality, it is important to minimize the scale generation occurring during the reaction. Unlike polyvinyl chloride foam, which has a hydrophilic surface and can be easily removed through water during washing, it is difficult to remove with water, and because of its high internal density, it is one of the main causes of deterioration in quality due to generation of fishy eyes during processing.

The fish eye is the most important quality among the quality of the vinyl chloride resin and is a measure for the workability of the resin. Particularly, polyvinyl chloride is an amorphous product, which is melted by the shear of the extruder at low temperature and processed, and the particles that are not sheared at this time are produced as a glass.

In addition, the apparent specific gravity is one of the important qualities of vinyl chloride resin together with the quality of PVC resin which is directly connected with productivity. Rigid products such as pipes have a lower discharge temperature when the apparent specific gravity during extrusion is higher, thereby reducing the production cost in the manufacturing process of the product.

In order to improve the hydrophilicity, a method of reducing the size of the particles and increasing the porosity by adding a specific protective colloid or changing the process conditions has been tried. In order to improve the apparent specific gravity, a high degree of saponification dispersant is used, And thereafter dividing the vinyl chloride monomer at a specific polymerization conversion rate and continuously adding the vinyl chloride monomer.

In recent years, attempts have been made to obtain a small apparent weight and a high apparent weight by dividing or continuously injecting dispersants having various saponification and molecular weights. However, if a large amount of dispersant is added to increase the porosity or the particle size to obtain a small amount of water, the foam formed during the reaction will rise to the reflux condenser and contaminate the inside of the condenser. The foam generated at this time generates a scale in the polymerizer, Which is a cause of deterioration of physical properties. In addition, since the apparent specific gravity also decreases, there is a problem that it is difficult to obtain a high apparent weight and a high apparent specific gravity at the same time.

For example, in US Patent No. 5,096,988 to Shinetsu, suspension polymerization of vinyl chloride monomer was carried out batchwise. After adding the vinyl chloride monomer and the initiator additive, an attempt was made to add a dispersant having a degree of saponification of 75% or more and 85% or less at the beginning and the middle of the reaction. As a result, a high apparent specific gravity was obtained. However, when the polymerization is carried out according to the conventional method as described above, physical properties such as low apparent specific gravity of the final polyvinyl chloride are lowered.

Likewise, US Pat. No. 5,204,421 to Shinetsu also discloses that a dispersant having a degree of saponification of 20% or more and 55% or less in saponification degree is separately added in the early stage and middle stage of the reaction to obtain a vinyl chloride resin having a high plasticizers But the productivity was low due to the low apparent weight.

Therefore, the inventors of the present invention have found that, in order to solve the problems of the prior art as mentioned above, the vinyl chloride polymer improved in fish eye can be obtained for the soft extrusion application, and the method for improving the apparent specific gravity property for the hard extrusion , The addition of a dispersant with a low degree of saponification to the middle stage of the reaction suppresses foaming of the reactor and formation of scale in the reflux condenser, thereby improving workability and solving the above-mentioned problems. For soft extrusion applications, A vinyl polymer can be obtained, and for the purpose of hard extrusion, stable specific quality can be ensured by improving apparent specific gravity, and the present invention has been accomplished.

That is, an object of the present invention is to provide a process for producing a vinyl chloride resin by suspension polymerization of a vinyl chloride monomer in the presence of a protective colloid assistant and a polymerization initiator, wherein a dispersant having a degree of saponification of 55% % At the point of time to reduce foaming, thereby suppressing scale adhesion of the reactor, thereby improving the characteristics of the fish eye and increasing the apparent specific gravity to improve the productivity.

That is, in the present invention, a polyvinyl chloride resin is produced by suspension polymerization,

Wherein the suspension polymerization is carried out by introducing a dispersant having a degree of saponification of 30 to 55% at a polymerization conversion rate of 20 to 60%.

Further, according to the present invention, there is provided a vinyl chloride resin for soft extrusion, which is obtained by the above-mentioned method and is improved in the softness.

Further, according to the present invention, there is provided a vinyl chloride resin for hard extrusion obtained by the above-mentioned method and having improved apparent specific gravity characteristics.

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

In the present invention, polymerization of vinyl chloride monomer by suspension polymerization is started, polymerization is started in the presence of a suspension stabilizer, polymerization initiator and vinyl chloride monomer, and the polymerization is started at a point of polymerization conversion rate of 20 to 60% By weight of a dispersant having a low degree of saponification of 30% or more and 55% or less.

Specifically, a polyvinyl chloride resin is produced by suspension polymerization,

The suspension polymerization is characterized in that a dispersant having a degree of saponification of 30 to 55% is introduced at a conversion rate of 20 to 60% of the polymerization.

The time point of introduction of the dispersant is characterized by a point of 20 to 60% conversion of the suspension polymerization.

This may affect the stability of the polymerization reaction before the addition of the dispersant before or at the beginning of the reaction, which may result in changes in the particle, plasticizer absorption, fine particle content and overall physical properties.

If the amount of the vinyl chloride monomer to be added at the initial stage of the reaction is less than 50% of the total amount of the vinyl monomer to be added, the fine particles may increase and the initial coloring property may become poor. In this case, Because.

Further, if the vinyl chloride monomer is added continuously after the polymerization conversion rate of 60%, it is difficult to control the physical properties of the final vinyl chloride polymer, and it may be difficult to produce a high quality vinyl chloride polymer having stable quality such as fish eye and initial coloring property. Further, when the dispersing agent is added after the polymerization conversion rate of 60%, since the reaction has already proceeded to a considerable extent, the scale inhibition effect may not be obtained since much scale is generated in the reactor or the reflux condenser due to the bubbles generated.

The dispersant having a degree of saponification of 30 to 55% may be polyvinyl alcohol having a degree of saponification of 30 to 55%, for example. If the amount is less than the above range, solubility in water is very low and viscosity is high, and therefore, it may be difficult to handle. When the above range is exceeded, intergranular aggregation may occur or the effect of improving initial apparent specific gravity may be insufficient.

The dispersant may be in the range of 0.001 to 0.01 part by weight based on 100 parts by weight of the vinyl chloride monomer used in the suspension polymerization. If the upper limit is exceeded, the plasticizer absorption rate is lowered and the plasticizer can be increased.

It is preferable that the above-mentioned input is intermittent input or batch input rather than continuous input.

The suspension polymerization is, for example, characterized in that a high-temperature polymerized water at 70 to 100 ° C is prepared in a reactor and then polymerized by the introduction of a polymerization initiator.

As a specific example, the suspension polymerization is started by using a vinyl chloride monomer, a high-temperature polymerized water and a protective colloid preparation, mixing the high-temperature polymerized water with a vinyl chloride monomer and a protective colloid assistant, introducing a polymerization initiator into the mixed solution May be polymerized.

A degree of saponification of 30% or more and 55% or less is mixed with the above-mentioned protective colloid assistant, or they are put in the middle of the polymerization reaction and polymerized.

At this time, the dispersant of the additionally added low saponification degree lowers the interfacial tension between the water and the protective colloid, loosens the chain of the already formed protective colloid, and consequently increases the apparent specific gravity by allowing the penetration into the protective colloid of the additional vinyl chloride monomer .

In addition, the low-saponification dispersant serves as a defoaming agent, and the scale introduced into the reflux condenser and the reactor can be converted into a foam form which can be easily removed with water, thereby preventing formation of scales and effectively reducing the number of fish eyes.

The addition of a dispersant with a low degree of saponification is limited to a polymerization conversion rate of 20 to 60% at the point of time when the dispersant is added before the reaction or at the beginning of the reaction, which affects the overall polymerization stability, , It is preferable that the polymerization conversion rate is at least 10%.

In view of the fact that accurate measurement of the polymerization conversion time point is not possible, it is preferable to start and end the injection within approximately ± 3% in actual application. When the reaction is carried out at a later time than the proper conversion rate, the reaction proceeds considerably, so that the bubbles generated during the polymerization have a large particle size and a large scale attached to the inside of the reactor or the reflux condenser, and the risk of obtaining a polyvinyl chloride- have.

Examples of the protective colloid assistant include a polyvinyl alcohol resin having a degree of saponification of 30 to 90% by weight and a viscosity of 5 to 100 cps at 4% aqueous solution at room temperature, a propylenic resin having a methoxy group content of 15 to 40% % By weight and a viscosity of 2% aqueous solution measured at room temperature of 10 to 20,000 cps, and an unsaturated organic acid.

As a specific example, the protective colloid assistant may include a vinyl alcohol resin having a degree of saponification of 85 to 98% and a vinyl alcohol resin having a degree of saponification of 50 to 60%.

As another example, the protective colloid assistant may be a mixture of a vinyl alcohol resin having a degree of saponification of 85 to 98% and a vinyl alcohol resin having a degree of saponification of 50 to 60%.

As another example, the suspension polymerization may be carried out with 120 to 150 parts by weight of high-temperature polymerization water, 0.02 to 0.2 parts by weight of a polymerization initiator, and 0.03 to 5 parts by weight of a protective colloid preparation, based on 100 parts by weight of the vinyl chloride monomer.

The vinyl chloride-based resin of the present invention is a mixture of a resin composed mainly of a vinyl chloride monomer and a vinyl monomer mainly composed of a vinyl chloride monomer and copolymerizable with the vinyl monomer, wherein the content of the vinyl chloride monomer in the resin composition is 50% ).

In the present invention, the protective colloid preparation used for the purpose of stably maintaining the process for producing polyvinyl chloride resin and obtaining stable particles has a degree of saponification of 30 to 90% by weight and a viscosity of 4% aqueous solution at room temperature of 5 to 100 cps Vinyl alcohol resin, cellulose having a methoxy group content of 15 to 40% by weight, a propylhydroxyl group content of 3 to 20% by weight and a 2% aqueous solution viscosity measured at room temperature of 10 to 20,000 cps. It is preferable that the protective colloid assistant comprises a vinyl alcohol resin having a degree of saponification of 85 to 98% and a vinyl alcohol resin having a degree of saponification of 30 to 55%. Within this range, . In the present invention, a dispersant having a degree of saponification of 85% or more and a dispersant having a degree of saponification of 55% or less are mixed in a weight ratio of 0.3 to 1.5, and the mixture is used .

The protective colloid aid is preferably included in an amount of 0.03 to 5 parts by weight, more preferably 0.05 to 2.5 parts by weight, based on 100 parts by weight of the total monomers. When used in the above amount, no coarse particles are formed and no fish eye is generated.

Further, as the polymerization initiator, diacyl peroxides such as dicumyl peroxide, dipentyl peroxide, di-3,5,5-trimethylhexanoyl peroxide and diaryl peroxide, diisopropyl peroxydicarbonate, Di-sec-butyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and other peroxydicarbonates, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t- Peroxyesters such as neodecanoate, cumyl peroxyneodecanoate, cumyl peroxyneoheptanoate and 1,1,3,3-tetramethylbutyl peroxyneodecanoate, azobis-2,4 Azo compounds such as dimethylvaleronitrile, and sulfates such as potassium persulfate and ammonium persulfate, and they may be used alone or in combination of two or more thereof.

The amount of the polymerization initiator to be used is determined by factors such as the production process, productivity, quality, etc. The total amount of the polymerization initiator may be 0.02 to 0.2 parts by weight or 0.04 to 0.12 parts by weight based on 100 parts by weight of the total charged monomers. If the amount is less than the above range, the reaction time is delayed to deteriorate the productivity. If the content exceeds the above range, the initiator may not be completely consumed during the polymerization process, and may remain in the final resin product to deteriorate the initial coloring property of the resin.

Examples of the antioxidant that can be used before the reaction is stopped in the present invention include a triethylene glycol-bis-3- (3-t-butyl Hydroxyphenyl) propionate, hydroquinone, p-methoxyphenol, t-butylhydroxyanisole, n-octadecyl-3- (4- t-butylphenyl) propionate, 2,5-di-t-butylhydroquinone, 4,4-butylidenebis (3-methyl- Phenol compounds such as 4-thiobis (6-t-butyl-m-cresol) and tocopherol, amines such as N, N-diphenyl-p-phenylenediamine and 4,4-bis (dimethylbenzyl) Sulfur compounds such as dodecyl mercaptan, 1,2-diphenyl-2-thiol, and the like, or a mixture of two or more thereof.

As the reactor usable in the present invention, it is sufficient to use an agitator generally used for suspension polymerization of a vinyl chloride resin, and as a specific example, a stirrer may be a paddle type, a pitched paddle type A blender gin type, a pfaudler type, a turbine type, a propeller type and the like, or an agitator combined with two or more agitating blades may be used. The baffle may be a plate, A cylindrical shape, a D shape, a loop shape, a finger shape, or the like can be used.

The vinyl chloride resin slurry may be dried under a normal reaction condition with a fluidized bed dryer to produce a final vinyl chloride resin. According to the above-described method, it is possible to provide a vinyl chloride resin having improved characteristics in soft extrusion, or to provide a vinyl chloride resin having improved apparent specific gravity characteristics during hard extrusion.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a suspension polymerization method for producing an excellent high-quality polyvinyl chloride resin having a low viscosity and a high apparent specific gravity. Furthermore, stabilization of the reflux condenser and improvement of the fish-eye are suppressed by suppressing the generation of bubbles generated by adding a dispersant to the suspension, suppressing the generation of scales in the reactor, and furthermore, an apparent specific gravity A vinyl chloride resin for soft extrusion or a vinyl chloride resin for hard extrusion having an improved apparent specific gravity property can be provided by the suspension polymerization method of the vinyl chloride polymer which can be improved.

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

Example One

320 kg of deionized water at 80 ° C was charged into a 1 m ³ internal volume reactor equipped with a reflux condenser, 102 g of polyvinyl alcohol having a degree of saponification of 88%, 50 g of polyvinyl alcohol having a degree of saponification of 52% 14 g of cellulose was added to the reactor in a batch, 300 kg of vinyl chloride monomer was added, and then 120 g of t-butylperoxyneodecanonate was added to initiate the reaction.

During the entire polymerization reaction, the reaction was allowed to proceed while maintaining the reaction temperature at 64 占 폚. When the polymerization conversion reached approximately 20%, 22 g of polyvinyl alcohol having a degree of saponification of 52% was further added thereto. Then, (2,2,6,6-tetramethylpiperidin-1-yl) propane was used as an antioxidant at the time when the pressure of the polymerization reactor reached 8.0 kg / cm < ² > 5 g of oxyl and 36 g of triethylene glycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate were added and the unreacted monomer was recovered. Respectively. The slurry thus obtained was dried in a fluidized bed drier by a conventional method to obtain a vinyl chloride resin.

Example 2

In Example 1, polymerization was carried out under the same conditions as in Example 1 except that 22 g of polyvinyl alcohol having a degree of saponification of 52% was added at a conversion of about 40%.

Example 3

In Example 1, polymerization was carried out under the same conditions as in Example 1 except that 22 g of polyvinyl alcohol having a degree of saponification of 52% was added at a conversion of about 60%.

Example 4

In Example 1, the initial amount of polyvinyl alcohol having a degree of saponification of 52% was reduced to 22 g, and the amount of polyvinyl alcohol dispersant having a degree of saponification of 52% was increased to 50 g when the polymerization conversion reached 60% The polymerization was carried out under the same conditions as in Example 1 and evaluated.

Example 5

Except that polyvinyl alcohol having a degree of saponification of 52% was not initially charged and the amount of polyvinyl alcohol dispersant having a degree of saponification of 52% was increased to 72 g when the polymerization conversion was 60% The polymerization was carried out under the same conditions as in Example 1 and evaluated.

Example 6

In Example 1, polymerization was carried out under the same conditions as in Example 1 except that 22 g of polyvinyl alcohol having a degree of saponification of 38% was added.

Example 7

Polymerization was carried out under the same conditions as in Example 1 except that 22 g of polyvinyl alcohol having a degree of saponification of 38% was added at the conversion rate of 40% in Example 1, and the evaluation was carried out.

Example 8

Polymerization was carried out under the same conditions as in Example 1 except that 22 g of polyvinyl alcohol having a degree of saponification of 38% was added at a conversion rate of 60% in Example 1.

Comparative Example One

320 kg of deionized water at 80 ° C was charged into a 1 m ³ internal volume reactor equipped with a reflux condenser, 102 g of polyvinyl alcohol having a degree of saponification of 88%, 72 g of polyvinyl alcohol having a degree of saponification of 52% 14 g of cellulose was added to the reactor in a batch, 300 kg of vinyl chloride monomer was added, and then 120 g of t-butylperoxyneodecanonate was added to initiate the reaction.

While maintaining the reaction temperature at 64 ℃ during the polymerization reaction before the process advances to reaction, as an antioxidant at the time the pressure reaches 8.0 kg / cm ^2, the polymerization reactor (the time of the polymerization conversion rate is equivalent to approximately 85%) of (2 , 5 g of 2,6,6-tetramethylpiperidin-1-yl) oxyl and 36 g of triethylene glycol-bis-3- (3-t- butyl-4-hydroxy-5-methylphenyl) propionate The unreacted monomers were recovered and the resin slurry was recovered in a polymerization reactor. The slurry thus obtained was dried in a fluidized bed drier by a conventional method to obtain a vinyl chloride resin.

Comparative Example 2

Except that 22 g of a polyvinyl alcohol dispersant having a degree of saponification of 52% was additionally added when the initial charging amount of polyvinyl alcohol having a degree of saponification of 52% was reduced to 50 g and the polymerization conversion rate reached 5% Was subjected to polymerization under the same conditions as in Example 1 and evaluated.

Comparative Example 3

Except that 22 g of a polyvinyl alcohol dispersant having a degree of saponification of 52% was additionally added when the initial charging amount of polyvinyl alcohol having a degree of saponification of 52% was reduced to 50 g and the polymerization conversion rate reached 80% Was subjected to polymerization under the same conditions as in Example 1 and evaluated.

Comparative Example 4

In Comparative Example 1, polymerization was carried out under the same conditions as in Comparative Example 1 except that the degree of saponification was changed to 28% of polyvinyl alcohol having a degree of saponification of 72% instead of 52% of polyvinyl alcohol.

Comparative Example 5

In Comparative Example 1, polymerization was carried out under the same conditions as in Comparative Example 1 except that the degree of saponification was changed to 63% of polyvinyl alcohol in place of 52% of polyvinyl alcohol.

Comparative Example 6

Polymerization was carried out under the same conditions as in Comparative Example 1, except that the degree of saponification in Comparative Example 1 was continuously increased from 52% polyvinyl alcohol to 50% after the polymerization conversion rate was 30%.

Properties of the vinyl chloride resin prepared in Examples 1-8 and Comparative Examples 1-6 and physical properties such as polymerization conversion rate during polymerization were measured in the following manner, and the results are shown in Tables 1 and 2 below .

&Lt; Measurement of physical properties &

* Measurement of polymerization conversion ratio: Measurement was carried out using a butane tracer equipped with gas chromatography. If the polymerization conversion curve according to the ratio of the vinyl chloride monomer to the butane over time under the constant polymerization conditions is prepared every polymerization conditions, the polymerization conversion ratio according to the polymerization conditions can be measured with high accuracy.

* Measurement of polymerization degree: Measured by ASTM D1 243-79.

* Apparent Specific Gravity: Measured according to ASTM D1 895-89.

* Plasticizer absorption rate : The amount of DOP absorbed by the sample in accordance with ASTM D3367-95 is expressed in weight% with respect to the sample before absorption.

* Particle distribution measurement: The weight% of the sample passed through the sieve # 200 according to the particle distribution measurement method of ASTM D1705 was determined and measured.

* Fish eye (fish - eye) can: by using a vinyl chloride resin 100 parts by weight DOP 45 parts by weight of stearic acid, barium, 0.1 part by weight of tin based stabilizer, 0.2 parts by weight of 6-inch roll of carbon black 0.1 parts by weight of 140 ℃ The mixture was blended for 5 minutes, and then a sheet having a thickness of 0.3 mm was prepared. The sheet was expressed by the number of white transparent particles in 400 cm ² of the sheet.

Metrics unit Example One 2 3 4 5 6 7 8 Degree of polymerization 802 800 805 803 801 800 800 800 Apparent specific gravity g / cc 0.511 0.524 0.535 0.485 0.479 0.515 0.517 0.521 Plasticizer absorption rate % 23.6 22.7 20.9 20.4 21.4 20.3 19.3 18.3 Average particle diameter ㎛ 171 178 181 162 156 162 159 167 Particle Size Distribution # 200 % 1.44 1.18 0.71 5.17 2.21 4.46 1.16 2.70 Fishie Eye Ea 6 8 7 9 8 8 7 9 Initial coloring degree ○ ○ ◎ ○ ○ ○ ○ ○

Metrics unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Degree of polymerization 800 800 800 800 Apparent specific gravity g / cc 0.473 0.480 0.474 0.498 Plasticizer absorption rate % 19.5 20.7 19.5 20.3 Particle Size Distribution # 200 % 4.71 5.69 4.37 5.81 Average particle diameter ㎛ 149 150 147 146 Fishie Eye Ea 18 15 31 14 Initial coloring degree ○ X ○ ○ Metrics unit Comparative Example 5 Comparative Example 6 Degree of polymerization 800 800 Apparent specific gravity g / cc 0.425 0.515 Plasticizer absorption rate % 19.3 22.1 Particle Size Distribution # 200 % 6.56 5.43 Average particle diameter ㎛ 142 150 Fishie Eye Ea 25 19 Initial coloring degree X X

As shown in Table 1, in the case of Examples 1 to 3 in which the polymerization was started using the high-temperature polymerized water and the low-saponification dispersant was added and added at the time of 20 to 60% The apparent specific gravity was increased and the plasticizer absorption ratio was improved, as compared with Comparative Example 1 in which no dispersant was added. In addition, it was confirmed that scale formation inside the reactor was significantly suppressed, and improvement of fish eye was possible.

In addition, in the case of Comparative Example 2 and Comparative Example 3 in which the dispersing agent was added at a point of time when the polymerization conversion ratio was less than 5 to 10% and 60%, it was confirmed that the apparent specific gravity and the visual acuity were worsened compared with Example 1.

On the other hand, in Examples 4 to 5, in which the ratio of the dispersant was different from that in Example 1, and the other polymerization conditions were the same, the effect of improving the quality of fish eye was improved compared to Comparative Example 1, I could.

In Examples 6 to 8 using polyvinyl alcohol having a degree of saponification of 38% as compared with Examples 1 to 3 in which polyvinyl alcohol having a degree of hydration of 52% was used, the apparent specific gravity was slightly improved.

In the case of Comparative Example 4 and Comparative Example 5 in which the degree of saponification of the chlorinated polyalcohol used as the dispersant was less than 25 to 30% and the dispersant having a degree of saponification of more than 60% was added, the apparent specific gravity and / .

Particularly, in Comparative Example 6 in which the dispersing agent was continuously added at a conversion rate of 30 to 50% at the time of occurrence of bubbles, the apparent specific gravity was slightly increased compared with Example 1 which was intermittently injected, but the scale of the reactor was accelerated, I was able to confirm.

Claims

A polyvinyl chloride resin is produced by suspension polymerization,
Wherein the suspension polymerization is carried out by adding a dispersant having a degree of saponification of 30 to 55% at a conversion rate of 20 to 60% of the polymerization.

The method according to claim 1,
Wherein the dispersant having a degree of saponification of 30 to 55% is polyvinyl alcohol having a degree of saponification of 30 to 55%.

The method according to claim 1,
Wherein the dispersant is present in an amount of 0.001 to 0.01 part by weight based on 100 parts by weight of the vinyl chloride monomer used in the suspension polymerization.

The method according to claim 1,
Wherein the dispersant is partly introduced into the polyvinyl chloride resin one or more times within the polymerization conversion rate range.

The method according to claim 1,
Wherein the suspension polymerization is carried out by preparing a high-temperature polymerized water at 70 to 100 ° C in a reactor, and then polymerizing the polymerized polyolefin resin by the introduction of a polymerization initiator.

6. The method of claim 5,
Wherein the protective colloid preparation has a degree of saponification of 30 to 90% by weight and a viscosity of 5 to 100 cps at 4% aqueous solution at room temperature, a methoxy group content of 15 to 40% by weight and a hydroxyl group content of 3 to 20% Wherein the 2% aqueous solution measured at room temperature has a viscosity of 10 to 20,000 cps and at least one selected from the group consisting of cellulose and unsaturated organic acid.

6. The method of claim 5,
Wherein the protective colloid assistant comprises a polyvinyl alcohol resin having a degree of saponification of 85 to 98% and a polyvinyl alcohol resin having a degree of saponification of 50 to 60%.

8. The method of claim 7,
Wherein the protective colloid preparation is blended with a polyvinyl alcohol resin having a degree of saponification of 85 to 98% and a vinyl alcohol resin having a degree of saponification of 50 to 60%.

The method according to claim 1,
Wherein the suspension polymerization is carried out in an amount of 120 to 150 parts by weight of high-temperature polymerization water, 0.02 to 0.2 part by weight of a polymerization initiator and 0.03 to 5 parts by weight of a protective colloid preparation, based on 100 parts by weight of the vinyl chloride monomer. Gt;

A vinyl chloride resin for soft extrusion obtained by the method of claim 1, wherein the vinyl chloride resin is improved.

A vinyl chloride resin for hard extrusion obtained by the method of claim 1 and having improved apparent specific gravity characteristics.