[DESCRIPTION]
[invention Title]
METHOD FOR PRODUCING VINYL CHLORIDE-BASED RESIN HAVING SUPERIOR PARTICLE UNIFORMITY AND THERMAL STABILITY
[Technical Field]
The present invention relates to a method for preparing a vinyl chloride-based resin that exhibits superior particle uniformity and thermal stability. More specifically, the present invention relates to a method for preparing a vinyl chloride-based resin that exhibits superior particle uniformity and thermal stability wherein a vinyl chloride resin with superior particle size uniformity and thermal stability can be prepared by using an inorganic compound dispersion that has a specific crystal structure and from which hydrogen chloride can be removed in the process of preparing the vinyl chloride resin, and whiteness and physical properties of products can be improved during processing by increasing the thermal decomposition temperature of the resin.
[Background Art]
In vinyl chloride resins, size and inner structures of particles are considerably essential factors that affect handling of resins, mix level thereof with ancillary materials and processing properties of products and a method for controlling these factors has been researched. The preparation methods of vinyl chloride resins developed to date include bulk polymerization and suspension polymerization used for obtaining particles having a size of about 100 to 200
micrometers, and emulsion polymerization used for obtaining particles having a size smaller than 50 micrometers that are classified depending on the obtained particle size.
The suspension polymerization controls the size and inner structures of monomer droplets using physical stirring and a dispersant, a suspending agent or a protective colloid having a high molecular weight, in which hydrophobicity is suitably balanced with hydrophilicity. Such a method is developed by a variety of companies such as Shin-etsu, Dow chemical, Synthomer, and Nippon Goshei and substances widely used at present include polyvinyl acetate-alcohol copolymers and modified cellulose, polyacrylate resins and the like. However, the methods developed to date are accomplished by controlling properties of the interface between water and vinyl chloride monomers and development of the basic particles of vinyl chloride resins is hardly known.
Also, bulk polymerization controls the shape of particles depending on stirring force without using water, thus disadvantageously causing production of a great amount of abnormal particles. A method for controlling particles using bulk polymerization is hardly known. Korean Patent Laid-open No. 2007-0077246 discloses use of polyethers such as poly(ethylene oxide) and poly(propylene oxide), polymethacrylates such as poly(methyl methacrylate) and poly(n-hexyl methacrylate), polyacrylates such as poly(n-propyl acrylate) and poly(n-butyl acrylate), polyesters such as poly(e-caprolactone) as a dispersant to disperse nano-calcium carbonate on a resin. This dispersant is used only for dispersion of inorganic materials and is not used for controlling the particle size of the resin.
Meanwhile, deterioration in thermal stability of vinyl chloride-based resin limits processing conditions of the resin and causes discoloration or deterioration in physical properties such as tensile strength. For this reason, techniques to solve these problems were actively developed. The fundamental cause of deterioration in thermal stability is known to be low bonding force between carbon and chlorine in molecules. In particular, hydrogen chloride detached from molecular chains is known to accelerate new side reactions through an auto-catalyst reaction and thereby continuously generate hydrogen chloride. Also, double bonds remain in the site from which hydrogen chloride is detached. When a plurality of these double bonds overlap, discoloration is caused and physical properties of products are deteriorated.
In order to solve these problems, most of vinyl chloride-based resin manufacturers remove hydrogen chloride by neutralization using a variety of basic substances, as disclosed in Japanese Patent Publication No. 1997-059327. The neutralizing agents used include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and calcium hydroxide. Water-soluble bases such as ammonia are further used.
At this time, in the process of polymerization of vinyl chloride-based resins using suspension polymerization, excess water is present as a dispersion phase. Accordingly, by using the neutralizing agent described above, advantageously, dispersion can be easily performed and pH can be evenly controlled throughout the atmosphere of the reactor. However, the used neutralizing agent is dispersed in a water phase, thus disadvantageously inhibiting use efficiency of the dispersant, varying particle size and limiting improvement of thermal stability.
Also, a water-soluble neutralizing agent cannot be singly used for bulk polymerization of vinyl chloride resin that does not use water. A water-soluble neutralizing agent should be used in such a manner that it is mixed with water and the mixture is then incorporated after reaction. In this conventional case, it is disadvantageously difficult to homogeneously disperse the neutralizing agent and cost-associated problems occur, for example, a process for drying the resin is inevitably performed, when water is used in a great amount.
In this regard, US Patent No. 3,899,473 discloses a method for homogeneously dispersing an inorganic additive in PVC during bulk polymerization. However, this method does not exhibit effects other than homogeneous mixing of inorganic material.
US Patent No. 4,460,754 discloses that whiteness effects can be improved by adding an organometallic compound-based thermal stabilizing agent at a conversion ratio of 30 to 80% based on the weight of the final product to a resin during bulk polymerization. In this case, the effect on particle size distribution is not disclosed. Similarly, Japanese Patent No. 55,056,108 also discloses incorporation of an inorganic suspending agent in a stage of a conversion ratio of 30 to 80%. However, the purpose of addition is only improvement in flowability of final particles.
[Disclosure! [Technical Problem]
During continuous research associated with a method for improving uniformity of
particle size distribution and thermal stability regardless of polymerization method, the present inventors discovered that, when an inorganic compound having a specific structure in which hydrogen chloride can be removed is used for preparation of vinyl chloride resins, growth of basic particles can be controlled and uniformity of particle size distribution can thus be improved, regardless of the polymerization method, problems such as production of abnormal particles and deterioration in qualities of processed products caused by thermal decomposition can be prevented. The present invention was completed based on this discovery.
That is, it is one object of the present invention to provide a method for preventing deterioration in qualities caused by heating by imparting a uniform particle size distribution to resins and increasing thermal decomposition temperature of the resins through control of formation of inner particles of resins in the process of preparing the resins. Technical Solution]
In accordance with one aspect of the present invention, provided is a method for preparing a vinyl chloride resin with superior particle uniformity and thermal stability by polymerizing a vinyl chloride monomer, wherein an inorganic dispersant having a structure represented by the following Formula 1 is added during the polymerization,
(FARMULA REMOVED)
wherein M(II) is at least one selected from bivalent ions comprising magnesium, nickel and zinc, M(III) is selected from trivalent metal ions comprising aluminum, iron, chromium
and cobalt, Am- is selected from a carbonate ion, a hydroxide ion, a nitrite ion, a sulfate ion and a halogen ion, x is 0 to 1, m is 1 to 2, and n is 0 to 4.
Hereinafter, the present invention will be described in more detail.
First, the polymerization method used for preparation of vinyl chloride resins in the present invention is not particularly limited, but bulk polymerization and suspension polymerization are preferred in view of control of particles, when taking into consideration the fact that it is related to the process for forming first particles in monomer droplets.
The vinyl chloride resin may be a homopolymer of vinyl chloride, a copolymer of vinyl chloride and other monomer copolymerizable therewith, or a copolymer obtained from a monomer selected from an olefin compound such as ethylene and propylene, vinyl ester such as vinyl acetate and vinyl propionate, unsaturated nitrile such as acrylonitrile, vinyl alkyl ether such as vinyl methyl ethyl ether, unsaturated fatty acid such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, and an anhydride of such fatty acid, or a mixture thereof. The inorganic compound that is introduced during polymerization of the vinyl chloride resin is preferably a compound having a structure represented by the following Formula 1 since it can effectively remove hydroxide chloride generated during the polymerization.
(FARMULA REMOVED)

wherein M(II) is at least one selected from bivalent ions comprising magnesium, nickel and zinc, M(III) is selected from trivalent metal ions comprising aluminum, iron, chromium
and cobalt, Am is selected from a carbonate ion, a hydroxide ion, a nitrite ion, a sulfate ion and a halogen ion, x is 0 to 1, m is 1 to 2, and n is 0 to 4.
The kinds of inorganic compound that can be obtained from Formula 1 above include Mg4Al2(OH)12C033H20, Mg2Zn2Al2(OH)12C03-3H20, Mg(OH)2nH20 and the like. Of these, use of hydrotalcite that effectively improves thermal stability of vinyl resins and has a structure of Mg4Al2(OH)i2C03-3H20, or Mg2Zn2Al2(OH)12C03-3H20 in which the part of magnesium is substituted by zinc is more preferred. At this time, when the ratio of zinc is excessive, long-term thermal stability is deteriorated. Accordingly, zinc is preferably 50% or less, based on the amount of magnesium.
Meanwhile, the particle size of the inorganic compound is preferably 10 n (micrometers) or less and more preferably 0.5 µm (micrometers) or less in order to maintain dispersability. Of these, the particle size is most preferably 0.2 µm (micrometers) or less in view of deterioration in transparency.
The inorganic compound is preferably incorporated in an early or middle stage of polymerization, more preferably, when the conversion ratio is 10% or less based on the weight of the finally produced vinyl chloride-based resin, in view of particle size uniformity or thermal stability. The reason for this is that, when the conversion ratio exceeds the standard value, although an inorganic compound is added, it does not participate in production of initial particles, and control and uniformity of particle sizes cannot be increased. In particular, addition of inorganic compound in the process of preparing seeds is more preferred in that the inorganic
compound mediates production of initial particles and thus increases particle size uniformity of final products.
Meanwhile, the inorganic compound is more preferably surface-treated with an organic modifier in view of improvement of dispersability of vinyl chloride monomers. The organization may be carried out by coating one or more of an anionic surfactant, fatty acid, silane, polyorganosiloxane, polyorganohydrogensiloxane and higher fatty acid ester, more specifically, stearic acid, on the surface of the inorganic compound, or reacting the surface of the inorganic compound with polyvalent alcohol or polyvalent alcohol ester, more specifically, glycol monostearate by heating. Of these, reaction of polyvalent alcohol ester with the surface of the inorganic compound is most preferred in view of compatability with vinyl chloride-based resin.
Meanwhile, the organic modifier is used at an amount of 1 to 10 parts by weight, based on 100 partsby weight of the inorganic compound. When the amount exceeds the value defined above, the inorganic compound may disadvantageously deteriorate thermal stability although it is added during polymerization of vinyl chloride-based resins.
The organized inorganic compound is added at an amount of 0.01 to 0.2 parts by weight, based on 100 parts by weight of the vinyl chloride monomer during bulk polymerization, 0.01 to 0.2 parts by weight to 0.4 parts by weight, based on 100 parts by weight of the vinyl chloride during suspension polymerization. The amount of the incorporated organized inorganic compound can be changed according to the desired particle size. For example, the
organized inorganic compound is added at an amount of 0.01 parts by weight with respect to the total parts by weight of the initial monomer, particles shaving a particle size of 150 µm (micrometer) can be obtained during bulk polymerization. Meanwhile, when the added amount exceeds the range defined above, small particles are produced, an inorganic compound that is not bonded to the monomer is present and scales are disadvantageously thus formed. Also, if the inorganic compound is incorporated at an amount lower than the range, particle size increases and uniformity improvement effect is disadvantageously decreased.
When a vinyl chloride-based resin is used for hard extruded or injected articles, specifically for profiles for construction applications, the average particle size of the vinyl chloride-based resin is preferably 100 to 250 µm (micrometers), and when the vinyl chloride-based resin is used for soft calendar products, specifically, food wraps or sheets, the average particle size of vinyl chloride-based resin is preferably 50 to 200 µm (micrometers), production for plastisol products, specifically, wallpapers or primers and flooring materials, the average particle size of vinyl chloride-based resin is preferably 1 to 50 p (micrometers).
Specifically, in the preparation method using bulk polymerization according to the present invention, for example, a first reaction pressure is set, a first reaction initiator is added, and a first vinyl chloride monomer is polymerized at a first reaction temperature and at a second reaction pressure for a first reaction time (first step). The inorganic compound of formula 1 that is surface-treated with an organic modifier is added to produce a seed (second step) in the early reaction stage or the first step before a polymerization conversion ratio is higher than 10%. Then,
a second vinyl chloride monomer and a second reaction initiator are added to the produced seed, reaction is performed at a second reaction temperature and at a third reaction pressure for a second reaction time and the unreacted monomer is harvested while the temperature is decreased to obtain a resin (third step).
As described above, the vinyl chloride monomer for production of seeds is used in the first step at an amount of 10 to 90 parts by weight, with respect to 100 parts by weight, and the remaining amount of the vinyl chloride monomer is separately added during preparation of the resin in the third step.
Furthermore, the reaction pressure is controlled via three steps, specifically, the first reaction pressure is 4.5 to 8.5 K/G, the second reaction pressure is 9 to 13 K/G, and the third reaction pressure is 7 to 8 K/G.
Also, the reaction temperature is preferably controlled via two steps, specifically, the first reaction temperature is 60 to 75°C, and the second reaction temperature is 50 to 55°C.
As the first reaction initiator used for production of seeds, one or more selected from the group consisting of t-butyl peroxyneodecanoate, octyl peroxydicarbonate and hexyl peroxypivalate may be used at an amount of 0.01 to 0.2 parts by weight and, as the second reaction initiator used for production of the resin, tetramethylbutyl peroxydecanoate or cumyl peroxypivalate may be used in an amount of 0.01 to 0.4 parts by weight.
Preferably, the polymerization time taken for production of seeds is 15 to 25 minutes which is enough to obtain homogeneously dispersed particle nuclei and the polymerization time
taken for production of the resin is 160 to 200 minutes, which enables production of resins having a conversion ratio of 60% or more.
Also, the inorganic compound of Formula 1 that is added in the second step is added in an initial reaction stage or in the first step before the polymerization conversion ratio exceeds 10%, the particle size thereof is 0.05 to 10 µm (micrometers), and the inorganic compound is added at an amount of 0.01 to 0.2 parts by weight based on the total 100 partsby weight of the vinyl chloride monomer. At this time, preferably, the inorganic compound previously treated with an organic modifier is added.
Meanwhile, in accordance with a preparation method using suspension polymerization, for example, a protective colloid, a vinyl chloride monomer, an inorganic compound and an initiator were added, stirred and polymerized at a first reaction temperature for a first reaction time. Then, the reaction products are neutralized, sodium hydrogen carbonate is added thereto to protect equipment and the unreacted and remaining monomer is removed while a temperature is decreased to obtain a resin. At this time, the inorganic compound having a structure of Formula 1 added in the initial reaction stage or before the polymerization conversion ratio exceeds 10% has a particle size of 0.05 to 10 µm (micrometer) and is added at an amount of 0.01 to 0.4 parts by weight, based on 100 parts by weight of the vinyl chloride monomer. At this time, the inorganic compound previously treated with an organic modifier is preferably added.
Also, preferably, as the protective colloid, a first dispersant composed of polyvinyl(acetate-alcohol) having a hydration degree of 80%, or a secondary dispersant
composed of polyvinyl(acetate-alcohol) having a hydration degree of 40% is added at an amount of 0.01 to 0.2 parts by weight based on 100 parts by weight of the vinyl chloride monomer, and as the initiator, at least one selected from the group consisting of t-butyl peroxyneodecanoate, octyl peroxydicarbonate, hexyl peroxypivalate, tetramethylbutyl peroxydecanoate and cumyl peroxypivalate is added at an amount of 0.02 to 0.2 parts by weight.
Preferably, the first reaction temperature is 55 to 60°C and reaction time is 4 to 6 hours in that a resin having a conversion ratio of 75% or more can be prepared.
[Advantageous Effects]
In accordance with the method described above, by using an inorganic compound dispersion which has a specific crystal structure, and from which hydrogen chloride can be removed in the process of preparing a vinyl chloride resin, a vinyl chloride resin with superior particle size uniformity and thermal stability can be prepared, the thermal decomposition temperature of the resin can be increased, and whiteness and physical properties of products can thus be improved during processing.
[Brief description of the drawings]
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:
FIG. 1 shows optical microscope images that are obtained to confirm particle shape and distribution of respective vinyl chloride-based resins produced by bulk polymerization according to the present invention and conventional bulk polymerization. Specifically, FIG. 1A is an optical microscope image (x200) illustrating seeds in accordance with Comparative Example 1, FIG. 1B is an optical microscope image (x200) illustrating final particles produced from the seeds of FIG. 1 A, FIG. 1C an optical microscope image (x200) illustrating seeds in accordance with Example 1, and FIG. 1D is an optical microscope image (x200) illustrating final particles produced from the seeds of FIG. 1C. [Best Mode]
Hereinafter, configuration and effects of the present invention will be described in more detail with reference to the following examples and comparative examples. However, these examples are provided only for illustration and should not be construed as limiting the technical scope of the present invention.
Comparative Example 1 (bulk polymerization)
Oxygen and other impurities were removed by degassing an inner pressure of a reactor to a high vacuum lower than 70 torr using a general bulk polymerization. 60 parts by weight of a first vinyl chloride monomer was added thereto. The resulting mixture was heated with stirring, 0.02 parts by weight of t-butyl peroxyneodecanoate as a first reaction initiator was added thereto when the reaction pressure was 4.5 to 8.5 K/G, and polymerization was performed for 15 to 25 minutes until the reaction temperature became 60 to 75°C and the reaction pressure became 9 to
13 K/G, to form particle nuclei.
40 parts by weight of a second vinyl chloride monomer and 0.03 parts by weight of tetramethylbutyl peroxydecanoate as a second reaction initiator were added to particle nuclei, and reaction was performed at a reaction temperature of 50 to 55°C and at a reaction pressure 7 to 8 K/G for 160 to 200 minutes. At this time, the stirring speed was lower than in the process of forming the particle nuclei.
Then, the remaining and unreacted monomer was removed while the temperature was decreased to obtain a final resin. At this time, an optical microscope image of the obtained seeds is shown in FIG. 1A and an optical microscope image of final particles is shown in FIG. IB.
Comparative Example 2 (suspension polymerization)
Using a general suspension polymerization method, a dispersant having a hydration degree of 80% and a dispersant having a hydration degree of 40% were added to a reactor as protective colloid at a ratio of 3:1 at an amount of 0.06 parts by weight with respect to the monomer, and 0.03 parts by weight of t-butylperoxy neodecanoate with respect to the monomer was added as an initiator. Then, the inner pressure of the reactor was degassed to a high vacuum lower than 70 torr to remove oxygen and other impurities. 100 partsby weight of a vinyl chloride monomer was added thereto. The resulting mixture was stirred at a speed of 180 rpm and reacted at a temperature of 58°C for 5 hours. Then, 0.008 parts by weight of sodium hydrogen carbonate was added to the obtained reaction product with respect to 100 partsby
weight of the monomer. Then, the remaining and unreacted monomer was removed while the temperature was decreased to obtain a slurry and the slurry was dried to obtain a final resin.
Preparation Example 1 (Preparation example 1 of inorganic compound surface-treated with organic modifier)
Glycerin monostearate was added at an amount of 10 parts by weight, based on 100 partsby weight of the inorganic compound, to hydrotalcite having a structure of Mg4Al2(OH)12C03-3H20 or Mg4Zn2A2(OH)CO33H2O, and a size of 0.5 µm (micrometers) or 10 \an (micrometers), respectively, followed by heating at 180°C to prepare an inorganic compound surface-treated with an organic modifier.
Preparation Example 2 (Preparation example 2 of inorganic compound surface-treated with organic modifier) An inorganic compound surface-treated with an organic modifier, having a structure of Mg4A12(OH)12CO3 3H2 or Mg4Zn2Al2(OH)12CO3 3H2O, and a size of 0.5 µm (micrometers) or 10 µm (micrometers), respectively, was prepared in the same manner as Preparation Example 1 except that stearic acid was used at an amount of 1 part by weight, based on 100 partsby weight of the inorganic compound, instead of glycerin monostearate.
Example 1 (inorganic compound 1 that undergoes bulk polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of hydrotalcite surface-treated with an organic modifier, having a size of 0.5 [Ml
(micrometers) and a structure of Mg4Al2(OH),2C03-3H20 prepared in Preparation Example 1 was added when the polymerization conversion ratio was 10% or less. The optical microscope image of the obtained seeds is shown in FIG. 1C and the optical microscope image of final particles is shown in FIG. 1D.
Example 2 (inorganic compound that undergoes suspension polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 2 was repeated except that 0.01 parts by weight of hydrotalcite surface-treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12C03 3H20 prepared in Preparation Example 2, was added when the polymerization conversion ratio was 10% or less.
Example 3 (inorganic compound that undergoes bulk polymerization without surface-treatment with organic modifier)
The same process as Example 1 was repeated except that 0.01 parts by weight of hydrotalcite not-treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12C03 3H2O, was added.
Example 4 (inorganic compound 2 that undergoes bulk polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 0.01 parts by
weight of hydrotalcite treated with an organic modifier, having a size of 10 µm (micrometers) and a structure of Mg4Al2(OH)12C03 3H20 prepared in Preparation Example 2 was added.
Example 5 (inorganic compound 3 that undergoes bulk polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12CO3 3H2O prepared in Preparation Example 2, was added.
Example 6 (inorganic compound 4 that undergoes bulk polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 1 part by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12CO3 3H2Oprepared in Preparation Example 2, was added.
Example 7 (inorganic compound 5 that undergoes bulk polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12CO3 3H2O prepared in Preparation Example 2, was added when
the polymerization conversion ratio was 10% or less.
Example 8 (inorganic compound 2 that undergoes suspension polymerization and surface-treatment with organic modifier)
The same process as Comparative Example 2 was repeated except that 0.01 parts by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)I2C033H20 prepared in Preparation Example 1, was added when the polymerization conversion ratio was 10% or less.
Example 9 (inorganic compound 5 that undergoes suspension polymerization without surface-treatment with organic modifier)
The same process as Comparative Example 2 was repeated except that 0.01 parts by weight of hydrotalcite non-treated with an organic modifier, having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12C033H20, was added when the polymerization conversion ratio was 10% or less.
Comparative Example 3 (bulk polymerization and variation of conversion ratio at which inorganic compound is added)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometers)
and a structure of Mg4Al2(OH)I2C033H20 prepared in Preparation Example 1, was added when the polymerization conversion ratio was 10% to 20%.
Comparative Example 4 (suspension polymerization and variation of conversion ratio at which inorganic compound is added)
The same process as Comparative Example 2 was repeated except that 0.01 parts by weight of hydrotalcite treated with an organic modifier, having a size of 0.5 µm (micrometer) and a structure of Mg4Al2(OH)I2C033H20 prepared in Preparation Example 1, was added when the polymerization conversion ratio was 10% to 20%.
Comparative Example 5 (bulk polymerization and addition of other inorganic compound)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of titanium dioxide having a size of 0.5 p (micrometers) that had been prepared and treated with an organic modifier in the same manner as in Preparation Example 1 was added when the polymerization conversion ratio was 10% or less.
Comparative Example 6 (suspension polymerization and addition of other inorganic compound)
The same process as Comparative Example 2 was repeated except that 0.01 parts by
weight of titanium dioxide having a size of 0.5 µm (micrometers) that had been prepared and treated with an organic modifier in the same manner as in Preparation Example 1 was added when the polymerization conversion ratio was 10% or less.
Comparative Example 7 (bulk polymerization and variation in content of added inorganic compound 1)
The same process as in Example 1 was repeated except that the organized inorganic compound was added at an amount of 0.001 parts by weight.
Comparative Example 8 (bulk polymerization and variation in content of added inorganic compound 2)
The same process as in Example 1 was repeated except that the organized inorganic compound was added at an amount of 0.5 parts by weight.
Comparative Example 9 (suspension polymerization and variation in content of added inorganic compound 1)
The same process as in Example 1 was repeated except that the organized inorganic compound was added at an amount of 0.001 parts by weight in Example 2.
Comparative Example 10 (suspension polymerization and variation in content of
added inorganic compound 2)
The same process as in Example 1 was repeated except that the organized inorganic compound was added at an amount of 0.5 parts by weight in Example 2.
Comparative Example 11 (inorganic compound that undergoes bulk polymerization and excessive surface-treatment with organic modifier)
The same process as Comparative Example 1 was repeated except that 0.01 parts by weight of hydrotalcite having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12C033H20, which had been treated with an organic modifier by adding 20 parts by weight of stearic acid, based on 100 partsby weight of the inorganic compound in Preparation Example 2, was added when the polymerization conversion ratio was 10% or less.
Comparative Example 12 (inorganic compound that undergoes suspension polymerization and excessive surface-treatment with organic modifier)
The same process as Comparative Example 2 was repeated except that 0.01 parts by weight of hydrotalcite having a size of 0.5 µm (micrometers) and a structure of Mg4Al2(OH)12C033H20, which had been treated with an organic modifier by adding 20 parts by weight of stearic acid, based on 100 partsby weight of the inorganic compound in Preparation Example 2, was added when the polymerization conversion ratio was 10% or less.
Test items:
* Measurement of processing whiteness index:
3 parts by weight of a lead-based stabilizing agent, 0.3 parts by weight of barium stearate and 0.1 parts by weight of titanium dioxide were added to 100 partsby weight of the vinyl chloride-based resin obtained in Examples and Comparative Examples, and kneaded at 185°C for 5 minutes using a roll-mill to obtain a sheet with a thickness of 0.5 mm. Then, whiteness index (W.I) was measured using NR-3000 produced by Nippon Denshoku and the results are shown. From the whiteness index, thermal stability was evaluated. As whiteness index increases, thermal stability improves.
*Measurement of thermal decomposition temperature:
A variation in weight of the resin was measured while heating at a speed of 10 degrees per minute from 40°C to 400°C at a nitrogen atmosphere using a Q50 model produced by the TA instrument company. A thermal decomposition temperature was defined as a temperature at which a decomposition ratio reached 70%.
* Measurement of particle size and particle size distribution:
The particle sizes of obtained resins were measured using a HELOS particle size meter produced by the Sumpatec company and the span value was defined as a particle size distribution. As span decreases, deviation decreases.
TABLE 1
(TABLE REMOVED)

As can be seen from Table above, as compared to Comparative Example 1 in which a resin was prepared using bulk polymerization without adding an inorganic compound, Examples 1, 3, 4, 5 and 6 in which resins were prepared using bulk polymerization exhibited improved
processing whiteness index, thermal decomposition temperature, particle size uniformity and particle size. Also, as compared to Example 3 which was not surface-treated with an organic modifier, Examples 1, 4, 5 and 6 exhibited improved processing whiteness index, thermal decomposition temperature and particle size.
Meanwhile, as compared to Comparative Example 2 in which a resin was prepared without adding an inorganic compound, not bulk polymerization, using suspension polymerization, Example 2 in which a resin was prepared using suspension polymerization by adding an inorganic compound exhibited deteriorated particle size uniformity, but exhibited considerably improved processing whiteness index and thermal decomposition temperature and particle size.
As can be seen from FIG. 1 showing an optical microscope image in brief, the seeds and final particles prepared in Example 1 of the present invention (FIGS. 1C and ID) exhibited more uniform particle shape and distribution, as compared to the seeds and final particles prepared in Comparative Example 1 (FIGS. 1A and IB).
Furthermore, it could be seen that Comparative Examples 3 and 4 in which an inorganic compound was added too late exhibited bad processing whiteness index and particle size uniformity, while Comparative Examples 5 and 6 in which titanium dioxide was used as an inorganic compound exhibited bad processing whiteness index and thermal decomposition temperature. Also, it could be seen that Comparative Examples 7 to 10 in which the content of added inorganic compound was not preferred had problems of excessive large or small particle
sizes, while Comparative Examples 11 and 12 in which the surface of inorganic compound was excessively treated exhibited bad processing whiteness index.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[CLAIMS] [Claim1 ]
A method for preparing a vinyl chloride resin with superior particle uniformity and thermal stability by bulk- or suspension-polymerizing a vinyl chloride monomer,
wherein a dispersion of inorganic compound represented by the following Formula 1 is added during the polymerization,
(FARMULA REMOVED)
wherein M(II) is at least a bivalent ion selected from the group consisting of magnesium, nickel and zinc, M(III) is a trivalent metal ion selected from the group consisting of aluminum, iron, chromium and cobalt, Am is one selected from the group consisting of a carbonate ion, a hydroxide ion, a nitrite ion, a sulfate ion and a halogen ion, x is 0 to 1, m is 1 to 2, and n is 0 to 4. [Claim 2]
The method according to claim 1, wherein the vinyl chloride resin is at least one selected from the group consisting of a homopolymer of vinyl chloride; a copolymer of vinyl chloride and other monomer copolymerizable therewith; and a copolymer obtained from a monomer selected from an olefin compound of ethylene and propylene, vinyl ester of vinyl acetate and vinyl propionate, unsaturated nitrile of acrylonitrile, vinyl alkyl ether of vinyl methyl ethyl ether, unsaturated fatty acid of acrylic acid, methacrylic acid, itaconic acid, maleic acid, and
an anhydride of a fatty acid, or a mixture thereof.
[Claim 3]
The method according to claim 1, wherein the inorganic compound is Mg4Al2(OH)12C03-3H20 or Mg2Zn2Al2(OH)12C03-3H20. [Claim 4]
The method according to claim 1, wherein the particle size of the inorganic compound is 0.05 to lOp. [Claim 51
The method according to claim 1, wherein the inorganic compound is added to the reaction system at the initial stage of polymerization or when a polymerization conversion ratio is 10% or less. [Claim 61
The method according to claim 1, wherein the surface of the inorganic compound is coated with an organic modifier or is reacted by heat with the organic modifier to organize the surface of the inorganic compound prior to using. [Claim 7]
The method according to claim 6, wherein the organic modifier is at least one selected from an anionic surfactant, fatty acid, silane, polyorganosiloxane, polyorganohydrogensiloxane, higher fatty acid ester, and polyvalent alcohol and polyvalent alcohol ester, and is used at an amount of 1 to 10 parts by weight, based on 100 partsby weight of the inorganic compound.
I Claim 8]
The method according to claim 1, wherein the organized inorganic compound is added at an amount of 0.01 to 0.2 parts by weight, based on 100 parts by weight of the vinyl chloride monomer during bulk polymerization. [Claim 9 J
The method according to claim 1, wherein the organized inorganic compound is added at an amount of 0.01 to 0.4 parts by weight, based on 100 parts by weight of the vinyl chloride monomer during suspension polymerization. [Claim 101
The method according to claim 1, wherein the bulk polymerization comprises:
a) a first step of setting a first reaction pressure, adding a first reaction initiator and polymerizing a first vinyl chloride monomer at a first reaction temperature and at a second reaction pressure for a first reaction time;
b) a second of adding the inorganic compound of formula 1 of which surface is treated with an organic modifier in an early reaction stage or the first step before a polymerization conversion ratio is higher than 10%, to produce a seed; and
c) a third of adding a second vinyl chloride monomer and a second reaction initiator to the seed, performing reaction at a second reaction temperature and at a third reaction pressure for a second reaction time, and removing an unreacted monomer at a decreased temperature to obtain a resin.
[Claim 11]
The method according to claim 10, wherein the vinyl chloride monomer for producing seeds is used an amount of 10 to 90 parts by weight, with respect to 100 parts by weight in the first step and the remaining amount of the vinyl chloride monomer is separately added during preparation of the resin in the third step. [Claim 12l
The method according to claim 10, wherein the first reaction pressure is 4.5 to 8.5K/G, the second reaction pressure is 9 to 13K/G, and the third reaction pressure is 7 to 8K/G. [Claim 131
The method according to claim 10, wherein the first reaction temperature is 60 to 75D and the second reaction temperature is 50 to 55D, and the first reaction time is 15 to 25minutes and the second reaction time is 160 to 200 minutes. [Claim 14]
The method according to claim 10, wherein the first reaction initiator is at least one selected from t-butyl peroxyneodecanoate, octyl peroxydicarbonate and hexyl peroxypivalate, and is used at an amount of 0.01 to 0.2 parts by weight, and the second reaction initiator is tetramethylbutyl peroxydecanoate or cumyl peroxypivalate, and is used at an amount of 0.01 to 0.4 parts by weight. [Claim 15]
The method according to claim 1, wherein the suspension polymerization is carried out
by adding a protective colloid, a vinyl chloride monomer, an inorganic compound and an initiator, stirring, performing polymerization at a first reaction temperature for a first reaction time and adding sodium hydrogen carbonate thereto,
wherein the inorganic compound having a particle size of 0.05 to 10 um is added at an amount of 0.01 to 0.4 parts by weight, based on 100 parts by weight of the vinyl chloride monomer, in an initial reaction stage or before a polymerization conversion ratio is higher than 10%. [Claim 16]
The method according to claim 15, wherein 0.01 to 0.2 parts by weight of a first dispersant having a hydration degree of 80% and a secondary dispersant having a hydration degree of 40% is added as the protective colloid, 100 parts by weight of the vinyl chloride-based monomer, and at least one selected from the group consisting of t-butyl peroxyneodecanoate, octyl peroxydicarbonate, hexyl peroxypivalate, tetramethylbutyl peroxydecanoate and cumyl peroxypivalate is added as an initiator at an amount of 0.02 to 0.2 parts by weight. [Claim 17]
The method according to claim 15, wherein the first reaction temperature is 55 to 60D and the reaction time is 4 to 6 hours.