KR102235035B1 - Method for preparing polyvinylchloride - Google Patents

Abstract

The present invention relates to a first polymerization step of performing a polymerization reaction while raising a temperature to a first polymerization temperature by first introducing a vinyl chloride-based monomer in the presence of an initiator; And a second polymerization step of performing a polymerization reaction at the first polymerization temperature for 20 to 60 minutes and then secondly introducing an organic peroxide-based material and a vinyl chloride-based monomer to perform a polymerization reaction, wherein the organic peroxide-based material is a polymerization initiator. It relates to a method for producing a vinyl chloride-based polymer having a half-life of 40 minutes or less at the first polymerization temperature.

Description

Manufacturing method of vinyl chloride polymer {METHOD FOR PREPARING POLYVINYLCHLORIDE}

The present invention relates to a method for producing a vinyl chloride-based polymer, and more particularly, to a method for producing a vinyl chloride-based polymer in which an organic peroxide-based material having a half-life of 40 minutes or less at a polymerization temperature and a vinyl chloride-based monomer are additionally added.

Vinyl chloride-based polymers are polymers containing 50% or more of vinyl chloride, and are inexpensive, easy to control hardness, and can be applied to most processing machines, and thus have various fields of application. In addition, it is possible to provide a molded article excellent in physical and chemical properties, such as mechanical strength, weather resistance, chemical resistance, and the like, and is thus widely used in various fields.

On the other hand, the vinyl chloride-based polymer generates dechlorinated hydrogen due to heat or ultraviolet rays applied during processing due to chemical structural defects generated during the polymerization reaction, thereby discoloring the resin or reducing physical properties, and increasing processing load.

Specifically, in the vinyl chloride-based polymer, chemical defects such as allyl chloride or tertiary chlorine are present in the vinyl chloride-based polymer, that is, chemical defects generated during the polymerization reaction. Due to these chemical defects, the binding energy of carbon and chlorine in the vinyl chloride-based polymer has a very low value compared to the binding energy of carbon and chlorine in the normal molecular structure. Therefore, when processing a vinyl chloride-based polymer, the bond between carbon and chlorine is easily released due to external radical transfer, and hydrogen chloride released from the molecular chain accelerates new side reactions through an auto-catalyst reaction and continues to be hydrogen chloride. Will occur. In addition, a double bond is formed at the site where the hydrogen chloride escapes, and because several such double bonds overlap, discoloration of the resin occurs and a problem of deteriorating physical properties occurs. That is, in the vinyl chloride-based polymer or a molded article processed therefrom, a dehydrochlorination reaction occurs due to heat or ultraviolet rays, and as a result, discoloration occurs in the vinyl chloride-based polymer itself, or physical properties are deteriorated or changed.

In order to improve the above problems of the vinyl chloride-based polymer, an organic heavy metal-based thermal stabilizer is mixed with the vinyl chloride-based polymer to suppress the generation of radicals or ions generated when the vinyl chloride-based polymer is thermally decomposed, and thermal decomposition of the resin. I tried to control the speed. However, due to environmental problems and high prices caused when using organic heavy metal stabilizers, there are many restrictions on their use.

JP1997-124711A

An object of the present invention is to provide a method for producing a vinyl chloride-based polymer capable of improving thermal stability and whiteness.

In order to solve the above problems, the present invention is a first polymerization step of performing a polymerization reaction while raising the temperature to the first polymerization temperature by first introducing a vinyl chloride-based monomer in the presence of an initiator; And a second polymerization step of performing a polymerization reaction at the first polymerization temperature for 20 to 60 minutes and then secondly introducing an organic peroxide-based material and a vinyl chloride-based monomer to perform a polymerization reaction, wherein the organic peroxide-based material is a polymerization initiator. It relates to a method for producing a vinyl chloride-based polymer having a half-life of 40 minutes or less at the first polymerization temperature.

The method for preparing a vinyl chloride-based polymer of the present invention provides a vinyl chloride-based polymer having a stable molecular structure and a small residual amount of the initiator by controlling the timing of addition of an initiator having excellent reactivity and a vinyl chloride-based monomer without additional additives. I can.

Therefore, since the vinyl chloride-based polymer prepared by the production method of the present invention has excellent thermal stability and whiteness without additional additives, the production cost can be reduced and environment-friendly.

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

The terms or words used in the specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

In the present invention, the half-life of the organic peroxide-based material and the half-life of the initiator represent the decomposition rate of the initiator at the polymerization temperature, and refer to the time required for the content of the initiator introduced at the polymerization temperature to be reduced to 50%.

The half-life of the initiator can be determined by differential scanning calorimetry-thermal activity monitoring (DSC) of a dilute solution of the initiator in monochlorobenzene.

In addition, the half-life of the initiator can be calculated by the Arrhenius equation.

k _d = A e ^{- Ea /RT}

t _1/2 = ln2/k _d

k _d = rate constant for the initiator dissociation in s ^-1

A = Arrhenius frequency factor in s ^-1

E _a = Activation energy for the initiator dissociation in J/mole

R = gas constant (8.3142 J/mole K)

T = temperature in K

t _1/2 = half-life in s

On the other hand, the residual concentration of the initiator can be calculated by the following equation.

[I] = [I ₀ ]· e ^-kd·t

[I ₀ ] = original initiator concentration

[I] = initiator concentration at time t

t = time measured from the start of decomposition in s

A method of preparing a vinyl chloride-based polymer according to an embodiment of the present invention includes a first polymerization step of performing a polymerization reaction while raising a temperature to a first polymerization temperature by first introducing a vinyl chloride-based monomer in the presence of an initiator; And a second polymerization step of performing a polymerization reaction at the first polymerization temperature for 20 to 60 minutes and then secondly introducing an organic peroxide-based material and a vinyl chloride-based monomer to perform a polymerization reaction, wherein the organic peroxide-based material is a polymerization initiator. The half-life at the first polymerization temperature is 40 minutes or less.

The time point of the second addition of the organic peroxide-based material and the vinyl chloride-based monomer is preferably a time point in which 20 to 50 minutes have elapsed from the start of the second polymerization reaction, and more preferably a time point in which 20 to 40 minutes have elapsed. . When the organic peroxide-based material and the vinyl chloride-based monomer are secondarily added at the above point in time, there is an advantage in that the polymerization reaction is stabilized and thermal stability is improved. If it is added below the above-described time point, the polymerization reaction is unstable, and if it is added beyond the above-described time point, thermal stability is not improved.

When the organic peroxide-based material and the vinyl chloride-based monomer are added for a second time at the same time, the organic peroxide-based material is stably decomposed into reactive radicals to proceed with the polymerization reaction, so that a vinyl chloride-based polymer having a stable molecular structure can be prepared. Therefore, the whiteness and thermal stability of the vinyl chloride-based polymer may be improved.

However, if only the organic peroxide-based material is added in the second polymerization reaction, the amount of the vinyl chloride-based monomer capable of reacting with the organic peroxide-based material becomes insufficient, so that the organic peroxide-based material is prepared in the previous step. It will react with the polymer. Accordingly, a vinyl chloride-based polymer having an unstable molecular structure and a large residual amount of an organic peroxide-based material is produced, and as a result, the whiteness and thermal stability of the vinyl chloride-based polymer are deteriorated.

The half-life of the organic peroxide-based material is 40 minutes or less at the first polymerization temperature, preferably 3 to 40 minutes, and more preferably 20 to 40 minutes. If the organic peroxide-based material has the above-described half-life, appropriate reactivity with the vinyl chloride-based monomer can be maintained, and a vinyl chloride-based polymer having a stable molecular structure can be prepared, thereby making the whiteness and thermal stability of the vinyl chloride-based polymer. This can be improved. However, if the half-life of the organic peroxide-based material is less than the above-described range, the reactivity of the organic peroxide-based material becomes too large, so that radical growth occurs rapidly, and a runaway reaction occurs at the same time as the injection, and thus the process itself may become unstable. In addition, since the reaction rapidly weakens as the reaction time elapses, the initial colorability may be deteriorated due to an increase in fisheye or an increase in fine particles in the vinyl chloride-based polymer. If the above-described range is exceeded, the polymerization reaction is delayed due to low reactivity, and thus the reaction time is lengthened, and thus process efficiency may be deteriorated. In addition, since the residual amount of the initiator in the vinyl chloride-based polymer increases, mechanical properties in addition to the thermal stability of the vinyl chloride-based polymer may be deteriorated.

The first polymerization temperature may be preferably 55 to 65°C, specifically 57 to 62°C, and more specifically 58 to 60°C. When the above-described polymerization temperature is satisfied, a polymerization degree of 900 to 1,100 and an average particle diameter of 140 to 170 μm can be prepared.

The organic peroxide-based material may be at least one selected from the group consisting of t-amyl peroxy neodecanoate having a half-life of 30 to 40 minutes at the first polymerization temperature and diisopropyl peroxy dicarbonate having a half-life of 20 to 30 minutes. have. The organic peroxide-based material is preferably t-amyl peroxy neodecanoate.

The organic peroxide-based material may be added in an amount of 0.003 to 0.12 parts by weight, preferably in an amount of 0.004 to 0.10 parts by weight, and more preferably in an amount of 0.005 to 0.08 parts by weight, based on 100 parts by weight of the first amount of the vinyl chloride-based monomer. desirable. In addition, the secondary amount of the vinyl chloride-based monomer may be 3 to 20 parts by weight, preferably 5 to 15 parts by weight, and more preferably 7 to 12 parts by weight, based on 100 parts by weight of the first amount of the vinyl chloride-based monomer. Do. If the above-described range is satisfied, the organic peroxide-based material reacts with a vinyl chloride-based monomer rather than a vinyl chloride-based polymer, so that the molecular structure is stable, so that a vinyl chloride-based polymer having improved thermal stability and whiteness can be prepared.

On the other hand, the secondly introduced organic peroxide-based material and vinyl chloride-based monomer may be batch-injected, periodic-injected, or continuously injected, and specifically, may be continuously injected. And due to the continuous injection, the polymerization reaction can be stably maintained and thermal stability can be further improved.

Meanwhile, in the first polymerization reaction, the vinyl chloride-based monomer is first added, dispersed in water using a dispersant, and then polymerization reaction is performed while raising the temperature to the first polymerization temperature in the presence of an initiator.

The vinyl chloride-based monomer may be a vinyl chloride monomer or a mixed monomer including the same. The mixed monomer may include a vinyl-based monomer copolymerizable with the vinyl chloride monomer. The mixed monomer may include 1 to 50 parts by weight of the vinyl-based monomer based on 100 parts by weight of the vinyl chloride monomer. If the above-described range is satisfied, the suspension polymerization is performed stably, and further, there is an effect of stabilizing the processability of the obtained vinyl chloride-based resin. The vinyl-based monomers include olefin compounds such as ethylene and propylene; Vinyl esters such as vinyl acetate and vinyl propionate; Unsaturated nitriles such as acrylonitrile; Vinyl alkyl ethers such as vinyl methyl ether and vinyl ethyl ether; Unsaturated fatty acids such as acrylic acid, methacrylic acid, itaconic acid and maleic acid; And it may be one or more selected from the group consisting of anhydrides of these fatty acids.

The dispersant may be included in an amount of 0.03 to 0.2 parts by weight, preferably 0.05 to 0.15 parts by weight, and more preferably 0.06 to 0.12 parts by weight, based on 100 parts by weight of the vinyl chloride-based monomer. If the above-described range is satisfied, the stability of the process during polymerization is excellent, and unreacted monomers can be easily recovered after polymerization, resulting in excellent productivity.

The dispersant is water-soluble polyvinyl alcohol, oil-soluble partially saponified polyvinyl alcohol, polyacrylic acid, a copolymer of vinyl acetate and maleic anhydride, hydroxypropyl methylcellulose. , Gelatin, calcium phosphate, hydroxyapatite, sorbitan monolaurate, sorbitan trioleate, polyoxyethylene, sodium lauryl sulfate ( sodium lauryl sulfate), dodecylbenzene sulfonic acid (sodium salt), and sodium dioxtylsulfosuccinate.

The water may be deionized water or pure water.

The initiator is not particularly limited, but dicumyl peroxide, dipentyl peroxide, di(3,5,5-trimethylhexanoyl) peroxide (di(3,5,5-trimethylhexanoyl) ) peroxide), dilauroyl peroxide, and other diacyl peroxides; Diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, etc. Peroxy carbonates; t-butylperoxy neodecanoate, t-butylperoxy neoheptanoate, t-amyl peroxy neodecanoate, cumyl Peroxyneodecanoate (cumyl peroxy neodecanoate), cumyl peroxy neoheptanoate (cumyl peroxy neoheptanoate), 1,1,3,3-tetramethylbutyl peroxyneodecanoate (1,1,3,3 peroxy esters such as -tetramethylbutyl peroxy neodecanoate); Azo compounds such as azobis-2,4-dimethylvaleronitrile; It may be one or more selected from the group consisting of sulfates such as potassium persulfate and ammonium persulfate.

The initiator may be included in an amount of 0.03 to 0.15 parts by weight, preferably 0.05 to 0.12 parts by weight, and more preferably 0.06 to 0.1 parts by weight, based on 100 parts by weight of the vinyl chloride-based monomer. If the above-described range is satisfied, the stability of the process during polymerization becomes excellent.

The second polymerization reaction may be terminated at the beginning of polymerization, that is, when a pressure difference occurs by 1.0 to 1.5 kg/cm 2 compared to the reaction pressure of the reactor at the start of the first polymerization reaction.

The vinyl chloride-based polymer prepared according to an embodiment of the present invention may have a number average degree of polymerization of preferably 900 to 1,100, specifically 950 to 1,050, and more specifically 990 to 1,010. In addition, the average particle diameter of the vinyl chloride-based polymer may be preferably 140 to 170 μm, specifically 145 to 165 μm, and more specifically 150 to 160 μm.

The number average degree of polymerization refers to the average number of repeating units in the polymer chain, and may be calculated as a ratio of the number average molecular weight to the molecular weight of the repeating unit.

The average particle diameter is an average particle diameter measured from the size of the angle of light diffracted according to the size of the particle when the powder, which is a sample unit, passes through the cell using an optical laser particle measuring device, and It may be a particle size distribution value.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Example One

1㎥ polymerization reactor, agitator located inside the polymerization reactor, a reflux condenser connected to the polymerization reactor to heat the temperature of the polymerization reaction, and vinyl chloride recovery connected to the reflux condenser to discharge unreacted vinyl chloride monomer Using a polymerization apparatus including a pipe, a vinyl chloride-based monomer was polymerized in the following manner.

In the polymerization reactor, 100 parts by weight of a vinyl chloride monomer as a vinyl chloride-based monomer, 0.06 parts by weight of t-butyl peroxy neodecanoate as an initiator, 120 parts by weight of deionized water, and 0.08 parts by weight of polyvinyl alcohol as a dispersing agent were added at once. Vacuum was applied to the polymerization reactor, and the first polymerization reaction was performed while raising the temperature to 58° C. while stirring, and after reaching 58° C. for 30 minutes, t-amyl peroxy neodecano was used as an organic peroxide-based material. A second polymerization reaction was carried out while 0.005 parts by weight of 8 was added to 100 parts by weight of the vinyl chloride-based monomer, and 20 parts by weight of the vinyl chloride-based monomer was added secondarily, and continuously added for 3 hours at a constant rate. When the pressure in the polymerization reactor reached 7.0 kg/cm 2, the second polymerization reaction was stopped. Then, the polymerization reactor was cooled, and the unreacted monomer and vinyl chloride polymer slurry were recovered from the polymerization reactor. The vinyl chloride polymer slurry was stripped and dehydrated to separate unreacted vinyl chloride-based monomer and moisture, dried with hot air at 60° C. in a fluidized bed dryer, and sorted to obtain a vinyl chloride-based polymer.

Example 2

After the polymerization reaction was carried out for 20 minutes after reaching 58° C., the polymerization reaction was carried out in the same manner as in Example 1 except that t-amyl peroxy neodecanoate and a vinyl chloride-based monomer were secondarily added to obtain vinyl chloride. System polymer was obtained.

Example 3

After the polymerization reaction was carried out for 40 minutes after reaching 58° C., the polymerization reaction was carried out in the same manner as in Example 1, except that t-amyl peroxy neodecanoate and a vinyl chloride-based monomer were secondarily added to obtain vinyl chloride. System polymer was obtained.

Comparative example One

A vinyl chloride-based polymer was obtained in the same manner as in Example 1, except that the organic peroxide-based material and the vinyl chloride-based monomer were not added.

Comparative example 2

A vinyl chloride-based polymer was obtained in the same manner as in Example 1, except that 2-ethylhexyl peroxy dicarbonate having a half-life of 45 minutes) was added instead of t-amyl peroxy neodecanoate.

Comparative example 3

In place of t-amyl peroxy neodecanoate, t-butyl peroxy neodecanoate having a half-life of 42 minutes and a vinyl chloride-based monomer were added at 58° C. A vinyl chloride-based polymer was obtained in the same manner.

Comparative example 4

After the polymerization reaction was carried out for 90 minutes after reaching 58° C., a vinyl chloride-based polymer was obtained in the same manner as in Example 1 except for the second addition of t-butyl peroxy neodecanoate and a vinyl chloride-based monomer. .

The polymerization conditions of the Examples and Comparative Examples are summarized in Table 1 below.

division Initiator Monomer Organic peroxide-based substances Monomer input
Point of view
(min) Kinds content
(Part by weight) Primary
input
(Part by weight) Kinds Half-life content
(Part by weight) Secondary
input
(Part by weight) Example 1 tBPND 0.06 100 tAPND 40 minutes 0.005 20 30 Example 2 tBPND 0.06 100 tAPND 40 minutes 0.005 20 20 Example 3 tBPND 0.06 100 tAPND 40 minutes 0.005 20 40 Comparative Example 1 tBPND 0.06 100 - - - - - Comparative Example 2 tBPND 0.06 100 EHPDC 45 minutes 0.005 20 30 Comparative Example 3 tBPND 0.06 100 tBPND 42 minutes 0.005 20 0 Comparative Example 4 tBPND 0.06 100 tBPND 42 minutes 0.005 20 90

* tBPND: t-butyl peroxyneodecanoate

* tAPND: t-amyl peroxyneodecanoate

* EHPDC: 2-ethylhexyl peroxy dicarbonate

* The unit of the content of the initiator, monomer and organic peroxide-based material is parts by weight, and is the content based on 100 parts by weight of the primary input amount of the vinyl chloride-based monomer.

* Input point (min): The time from the point at which the first polymerization temperature is reached to the second point of addition of the organic peroxide-based material and the vinyl chloride-based monomer

* Half-life measurement method: Calculated by Arrhenius equation.

k _d = A e ^{- Ea /RT}

t _1/2 = ln2/k _d

k _d = rate constant for initiator decomposition

A = Arrhenius frequency factor

E _a = decomposition activation energy of the initiator

R = gas constant (8.3142 J/mole K)

T = absolute temperature

t _1/2 = half-life

Experimental example One

The average particle diameter and polymerization degree of the vinyl chloride-based polymers of Examples 1 to 3 and Comparative Examples 1 to 4 were measured, and are shown in Table 2 below.

1) Method of measuring average degree of polymerization: It was measured according to ASTM D1243-79.

2) Average particle diameter: It was measured using a HELOS particle size analyzer (Sympatec).

division Degree of polymerization Average particle diameter (㎛) Example 1 995 154 Example 2 1,000 160 Example 3 1,000 164 Comparative Example 1 1,000 166 Comparative Example 2 1,000 145 Comparative Example 3 1,010 150 Comparative Example 4 1,000 155

Referring to Table 2, it was confirmed that the polymerization degree of the vinyl chloride-based polymer of Examples 1 to 3 according to the present invention was 995 to 1,000, which is the same level as that of the vinyl chloride-based polymer of Comparative Examples 1 to 4 . In addition, the average particle diameter of the vinyl chloride-based polymer of Examples 1 to 3 differs due to the type of additionally added initiator, but is equivalent to the average particle diameter of the vinyl chloride-based polymer of Comparative Examples 1 to 4 Was able to confirm.

Experimental example 2

100 parts by weight of a vinyl chloride polymer of Examples 1 to 3 and Comparative Examples 1 to 4, and 0.1 parts by weight of a calcium-based heat stabilizer were mixed, and kneaded at 185° C. for 3 minutes using a roll mill, and the thickness was 0.5 mm. A thick preliminary sheet was obtained. The preliminary sheet was cut and 10 sheets overlapped, put in a 3 mm thick frame and compressed, preheated at 185° C. for 2 minutes, heated at 185° C. for 3 minutes at a pressure of 10 kg, and pressure of 15 kg, 25 It was compressed at °C for 2 minutes to prepare a sheet having a thickness of 3 mm.

The whiteness and thermal stability were evaluated, and the results are shown in Table 3 below.

3) Whiteness: The degree of whiteness compared to the standard white plate was measured.

4) Thermal stability: The sheet was put in an oven at 195°C and the time until it turned black was measured.

division Whiteness Thermal stability (min) Example 1 73 22.0 Example 2 73 21.5 Example 3 72 21.0 Comparative Example 1 70 20.0 Comparative Example 2 68 18.0 Comparative Example 3 69 18.4 Comparative Example 4 67 19.0

Referring to Table 3, it was confirmed that the sheets of Examples 1 to 3 according to the present invention have excellent whiteness and thermal stability compared to Comparative Examples 1 to 4.

On the other hand, in the case of Comparative Example 1, the organic peroxide-based material and the vinyl chloride-based monomer were not additionally added, and in the case of the sheet of Comparative Example 2, the timing of the additionally added initiator was appropriate, but an initiator with a long half-life was used. To Example 3, both whiteness and thermal stability were not excellent.

In the case of Comparative Examples 3 and 4, not only the organic peroxide-based material having a half-life exceeding 40 minutes was added, but also the timing of the second addition of the organic peroxide-based material and the vinyl chloride-based monomer was not appropriate. For this reason, the sheets of Comparative Example 3 and Comparative Example 4 were not excellent in whiteness and thermal stability compared to the sheets of Examples 1 to 3.

Claims (8)

A first polymerization step of performing a polymerization reaction while raising a temperature to a first polymerization temperature by first introducing a vinyl chloride-based monomer in the presence of an initiator; And
After the polymerization reaction at the first polymerization temperature for 20 to 60 minutes, a second polymerization step of polymerization reaction by secondly introducing an organic peroxide-based material and a vinyl chloride-based monomer,
The organic peroxide-based material is t-amyl peroxy neodecanoate is a method for producing a vinyl chloride-based polymer.
delete The method according to claim 1,
The first polymerization temperature is 55 to 65 ℃ method for producing a vinyl chloride-based polymer.
delete The method according to claim 1,
The method for producing a vinyl chloride-based polymer wherein the organic peroxide-based material is added in an amount of 0.003 to 0.12 parts by weight based on 100 parts by weight of the first amount of the vinyl chloride-based monomer.
The method according to claim 1,
The second input amount of the vinyl chloride-based monomer is 3 to 20 parts by weight based on 100 parts by weight of the first input amount.
The method according to claim 1,
The organic peroxide-based material and the secondary input vinyl chloride-based monomer are continuously added for 1 to 4 hours.
The method according to claim 1,
The polymerization is a method for producing a vinyl chloride-based polymer that is suspension polymerization.