JP2002128805A - Method of preparing dispersion and method of manufacturing polyvinyl chloride paste resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preparing a dispersion composed of an aqueous solution of a surfactant and vinyl chloride monomer which realizes a space saving and a reduced cost by simplifying facilities and to provide a method of polymerization in which the dispersion is added during a microsuspension polymerization. SOLUTION: The dispersion composed of the vinyl chloride monomer and the aqueous solution of the surfactant is prepared easily by using a static mixer and the dispersion is added to a polymerization liquid intermittently or continuously while a polymerization reaction is in progress.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preparing a dispersion comprising an aqueous solution of a surfactant and a vinyl chloride monomer during fine suspension polymerization of the vinyl chloride monomer, and adding the dispersion to the polymerization solution. The present invention relates to a method for producing a vinyl chloride paste resin.

[0002]

2. Description of the Related Art In a fine suspension polymerization method, vinyl chloride or a monomer copolymerizable therewith with vinyl chloride (hereinafter referred to as "vinyl chloride monomer"), water, a surfactant, a monomer After dispersing the polymerization initiator and other polymerization auxiliaries soluble in the body with a device other than the polymerization device under high shear, the mixture is transferred to a polymerization device and polymerized under stirring. This is a method for producing fine vinyl chloride resin particles of about 3 μm.

In fine suspension polymerization, droplets homogenized in a homogenization step are heated after being transferred to a polymerization apparatus and polymerized after reaching a predetermined temperature. As the reaction proceeds, the volume of the polymerization solution is increased. Shrinkage is caused and the effective heat removal area of the jacket is reduced, so that the heat removal capability of the polymerization apparatus is reduced. In addition, the cooling water flow level of the jacket is exposed and scale adheres to the polymerization apparatus wall and the stirring blade.

[0004] To solve this problem, Japanese Patent Application 2000
No. -204152 discloses a method of adding a surfactant aqueous solution and a dispersion comprising a vinyl chloride-based monomer to the polymerization solution during the polymerization reaction. Although this means greatly contributes to the improvement of productivity, Japanese Patent Application No. 2000-204152 uses a method in which an additional dispersion is prepared in advance in a pressure vessel provided outside the polymerization vessel. Therefore, in this method,
An extra pressure-resistant container is required, equipment costs are increased, and a space for this is required.

[0005]

SUMMARY OF THE INVENTION The present invention provides an apparatus for preparing and adding a dispersion comprising an aqueous solution of a surfactant and a vinyl chloride monomer during fine suspension polymerization of the vinyl chloride monomer. And realizes space saving and cost reduction, and also reduces the work load.

[0006]

Means for Solving the Problems The present inventors have intensively studied the preparation of a dispersion of a vinyl chloride monomer and an aqueous solution of a surfactant, and as a result, completed the present invention. The present invention provides a vinyl chloride resin characterized in that a static mixer is provided in a pipe connected to a polymerization vessel, and a surfactant aqueous solution obtained therefrom and a dispersion of a vinyl chloride monomer are added during the polymerization reaction. And a method for producing the same. As a method for producing a vinyl chloride paste resin, fine suspension polymerization, emulsion polymerization, seed emulsion polymerization and the like can be mainly used, and this method can be applied to any of them. Particularly, the fine suspension polymerization is effective.

That is, a first aspect of the present invention is to provide an aqueous surfactant solution and a vinyl chloride monomer when the vinyl chloride monomer is homogenized in an aqueous medium together with an oil-soluble polymerization initiator to perform fine suspension polymerization. Is introduced into a static mixer, and a dispersion obtained by dispersing and mixing a vinyl chloride monomer and a surfactant aqueous solution is added during the polymerization from the start of the polymerization to the end of the polymerization. The present invention relates to a method for producing a vinyl chloride paste resin.

[0008] A second aspect of the present invention is the first aspect, wherein a surfactant aqueous solution and a vinyl chloride monomer are mixed in a weight ratio of 75: 2.
The present invention relates to a method for producing a vinyl chloride-based paste resin, which is introduced into a static mixer at a ratio of 5 to 30:70 (claim 2).

In a third aspect of the present invention, in the first or second aspect, the linear velocity of the liquid in the static mixer is 0.5 m / m.
The present invention relates to a method for producing a vinyl chloride-based paste resin, wherein the time is not less than seconds.

A fourth aspect of the present invention is the method according to the first, second or third aspect, wherein the polymerization conversion rate is 30% of the initially charged monomer amount.
A vinyl chloride-based paste resin characterized in that the addition is started when it is less than 10% by weight and the addition of the dispersion is completed during the polymerization until the conversion reaches 95% by weight of the initially charged monomer. (Claim 4).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the method of the present invention, if the concentration of the vinyl chloride-based monomer in the added dispersion is too low, the solid content concentration after polymerization is reduced, and the load of the drying step is increased. This tends to result in phase separation before the polymer solution enters the polymerization solution, resulting in a decrease in the stability of the polymerization solution. In order to prevent this, the proportion of the vinyl chloride-based monomer in the additional dispersion may be set in the range of 25% or more and 70% or less, preferably 45% or more and 60% or less.

On the other hand, if the linear velocity of the fluid in the static mixer is too low, the dispersion is insufficient, and the dispersion tends to be phase-separated before reaching the polymerization reactor, and the dispersion tends to be unstable. Therefore, the linear velocity in the static mixer may be set to 0.5 m / sec or more, preferably 0.8 m / sec or more.

The linear velocity in the static mixer can be calculated by the following equation.

[0014]

(Equation 1) Also, when the surfactant aqueous solution and the vinyl chloride monomer are phase-separated in the flow direction as shown in FIG. 2 when introduced into the static mixer, the dispersion in the static mixer becomes insufficient and Stability tends to decrease. For this purpose, a chamber is used as a pump for sending the monomer and the surfactant aqueous solution, or a pulsating flow is eliminated by using a pump having a plurality of liquid sending sections, so that the surfactant aqueous solution and the monomer aqueous solution are removed. May be separated into two layers perpendicularly to the flow direction before introduction into the static mixer, and then introduced into the static mixer. Alternatively, as shown in FIG. 3, a converging portion of the monomer and the surfactant aqueous solution may be used in which the monomer solution sending tube is inserted into the surfactant solution sending tube,
As shown in FIG. 4, a premixing tank may be provided before the introduction of the static mixer, and the surfactant aqueous solution and the monomer may be premixed and then introduced into the static mixer.

If the number of elements of a static mixer (also called a static mixing stirrer or a mixer in a pipe) to be used is small, the stability of the dispersion tends to decrease. It is recommended to use

The amount of the surfactant constituting the dispersion is not particularly limited, but it is usually 0.1 to 3 parts by weight based on 100 parts by weight of the monomer in the additional dispersion. The type of the surfactant is not particularly limited, and may be the same as the surfactant contained in the polymerization liquid, or another emulsifier may be used. This surfactant may be supplied from a surfactant storage tank while being mixed with water in a line and diluted to an appropriate concentration, or may be supplied by dissolving in a simple tank.

When the dispersion liquid is added to the polymerization liquid, if the time to start adding the dispersion liquid to the polymerization liquid is too late, the heat removal area of the jacket is already reduced. When the water is closed, the area for the original heat removal cannot be secured. In order to avoid these problems, it is preferable that the polymerization conversion rate is not more than 30% of the initially charged monomer amount after the initiation of the polymerization, more preferably 2%.
The addition may be started while it is below 0%, most preferably below 10%.

If the time for ending the addition of the dispersion to the polymerization liquid is too long, the polymerization time may be delayed and the polymerization productivity may be reduced. To avoid this, the addition may be terminated while the amount of polymer produced is less than 95% of the initially charged monomer, preferably less than 90%.

If the amount of the vinyl chloride-based monomer in the added dispersion is too small, an increase in the amount of the produced polymer cannot be expected and it is difficult to improve the productivity. If the amount is too large, the polymerization time is delayed. Instead, the polymerization productivity tends to decrease. Therefore, the amount of the vinyl chloride-based monomer in the added dispersion is preferably 3 to 30 parts by weight, and more preferably 5 to 20 parts by weight, based on 100 parts by weight of the initially charged vinyl chloride-based monomer.

The method for adding the dispersion to the polymerization liquid may be continuous or intermittent. Also, if the liquid level is higher than the liquid level at the start of polymerization due to the addition of the dispersion liquid during polymerization, the internal pressure may rise and become dangerous, so the dispersion liquid should not be higher than the liquid level at the start of polymerization. It is preferable to add. The liquid level during polymerization can be easily calculated from the amount of raw materials charged and the conversion rate, and the conversion rate can be obtained by sampling the latex during polymerization and using the gravimetric method, or can be calculated from the heat removal from the jacket It is. The monomer that can be used in the polymerization method of the present invention is vinyl chloride alone or a mixture of vinyl chloride and a monomer copolymerizable therewith. In the present specification, these are collectively referred to as "vinyl chloride monomers".

The monomers which can be copolymerized are not particularly limited, but olefins such as ethylene, propylene and butene, vinyl esters such as vinyl acetate, vinyl propionate and vinyl stearate, methyl vinyl ether and ethyl Vinyl ether, octyl vinyl ether,
Vinyl ethers such as lauryl vinyl ether; vinylidenes such as vinylidene chloride; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride; Methyl, ethyl acrylate, monomethyl maleate, dimethyl maleate, unsaturated carboxylic esters such as butyl benzyl maleate, styrene,
All known monomers copolymerizable with vinyl chloride, such as aromatic vinyl compounds such as α-methylstyrene and divinylbenzene, unsaturated nitriles such as acrylonitrile, and crosslinking monomers such as diallyl phthalate can be used. The amount of these monomers used is preferably less than 50% by weight in the mixture with vinyl chloride.

The surfactant used in the fine suspension polymerization is not particularly limited, but an anionic surfactant is usually used in an amount of about 0.1 to 3 parts by weight per 100 parts by weight of the monomer. Examples of the anionic surfactant include potassium, sodium, and ammonium salts such as fatty acids, alkyl sulfates, alkyl benzene sulfonic acids, alkyl sulfosuccinic acids, α-olefin sulfonic acids, and alkyl ether phosphates.

As the dispersing aid, higher alcohols such as lauryl alcohol, myristyl alcohol, cetyl alcohol and stearyl alcohol, and higher fatty acids such as lauric acid, myristic acid, palmitic acid and stearic acid can be used. Other polymerization aids include aromatic hydrocarbons, polyvinyl alcohol, gelatin, particle size modifiers (such as sodium sulfate and sodium bicarbonate),
Chain transfer agents, antioxidants and the like. These can be used alone or in combination of two or more.

The oil-soluble initiator used in the fine suspension polymerization includes diacyl peroxides such as dilauroyl peroxide, di-3,5,5, trimethylhexanoyl peroxide, diisopropyl peroxydicarbonate, and di-2. Organic peroxide initiators such as peroxydicarbonates such as -ethylhexylperoxydicarbonate, and peroxyesters such as t-butylperoxypivalate and t-butylperoxyneodecanoate; and 2,2 ' -Azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-
An azo initiator such as azobis (4-methoxy-2,4-dimethylvaleronitrile) can be used. The amount of these initiators used is 0.01 to the total charged monomers.
The amount is generally about 3% by weight, but it is also possible to increase the amount of the charged initiator or add it during the polymerization as needed in order to prevent the polymerization time from being extended by the addition.

In the homogenization at the time of fine suspension polymerization, a one-stage or two-stage pressurized high-pressure pump, a colloid mill,
Known methods such as a centrifugal pump, a homogenizer (homomixer), a vibratory stirrer, high-pressure ejection from a nozzle or an orifice, and ultrasonic waves can be used. The polymerization reaction is carried out by a usual method.
７５75 ° C., and the amount of water for polymerization ranges from 0.6 to 3 times the weight of all monomers. The amount of the dispersing aid or other polymerization aid used may be an ordinary amount. In order to prevent the scale from adhering, it is desirable to apply a scale inhibitor to the inner wall surface of the polymerization vessel in advance, or to pressurize nitrogen before raising the temperature of the homogenizing solution.

[0026]

The present invention will be described below in detail with reference to examples and comparative examples.

FIG. 1 is a schematic diagram illustrating the method for producing the dispersion of the present invention. 1 is a surfactant tank, 2 is a vinyl chloride monomer tank, 3 and 4 are pumps, 5 is a static mixer, 6 is a polymerization vessel, and 7 is a pressure resistant glass tube. In Examples and Comparative Examples, the prepared dispersion liquid was collected in a pressure-resistant glass tube of No. 7, and the separation behavior of the dispersion liquid was observed, and the separation in the glass tube as shown in FIG. Surfacing)
The stability of the dispersion was compared according to the following criteria. ：: No separation was observed even after 30 minutes had passed after the dispersion was collected. X: Separation was observed by 30 minutes after the dispersion was collected. (Reference Example) 825 kg of vinyl chloride monomer, 825 kg of ion-exchanged water,
5.8 kg of sodium dodecylbenzenesulfonate and 8.25 kg of cetyl alcohol were charged and homogenized with a pressure homogenizer. Then, 2,2'-azobis-
0.75 kg of 2,4-dimethylvaleronitrile was added to the above 2
It was transferred to a 500 L polymerization reactor, and the temperature was raised to 45 ° C. to initiate polymerization. Four hours after the start of the polymerization, the flow of water through the upper jacket was stopped. The polymerization pressure is 1.5 times the initial pressure.
Polymerization was carried out until the weight decreased to kg / cm ³ , and the remaining monomers were removed from the polymerization vessel.

The scale was rubbed off from the latex after polymerization with a 32 mesh standard sieve, and the weight was measured after drying.
The latex was spray-dried by a conventional method, and the obtained powder was pulverized with a bandam mill to obtain a paste resin. Table 1 shows the results.

Example 1 Polymerization was started in the same manner as in Reference Example 1. However, 3 hours after the internal temperature of the polymerization vessel reached 45 ° C., a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate and a 2% vinyl chloride monomer were added.
The mixture was introduced into a static mixer having an inner diameter of 3.4 mm and 18 elements at a rate of 0.9 kg / hour and 23.9 kg / hour, and the resulting dispersion was continuously added to the polymerization solution. Finished continuous addition. In this case, the linear velocity in the static mixer was 1.45 m / sec, the ratio of the aqueous surfactant solution: vinyl chloride monomer was 47:53, and the total amount of additional monomers was 119.5 kg. When the addition was started, the polymerization conversion rate with respect to the initially charged monomer was 25.
%, And the polymerization conversion at the end of the addition was 88%. Further, the conversion rate with respect to all the monomers after the completion of the polymerization was 93%. Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results.

(Example 2) In the same manner as in Example 1, a 2% by weight aqueous solution of sodium dodecylbenzenesulfonate and a vinyl chloride monomer were added after 2 hours from the time when the internal temperature of the polymerization reactor reached 45 ° C. 19.3 kg / hour and 20.
The dispersion was introduced into the same static mixer as in Example 1 at a rate of 7 kg / hour, and the resulting dispersion was continuously added to the polymerization liquid, and the continuous addition was completed at 8 hours. In this case, the linear velocity in the static mixer was 1.29 m / sec, the aqueous surfactant solution: vinyl chloride monomer was 48:52,
The total amount of additional monomers is 124.2 kg. The polymerization conversion rate with respect to the initially charged monomer at the start of the addition was 17%, and the polymerization conversion rate at the end of the addition was 86%.
Further, the conversion rate with respect to all the monomers after the completion of the polymerization was 92%. Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results.

Example 3 As in Example 1, one hour after the internal temperature of the polymerization vessel reached 45 ° C., a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate and a vinyl chloride monomer were added. 13.2 kg / hour, 2 each
The mixture was introduced into the same static mixer as in Example 1 at a rate of 6.4 kg / hour, and the resulting dispersion was continuously added to the polymerization solution, and the continuous addition was completed at 8 hours. In this case, the linear velocity in the static mixer was 1.30 m / sec,
Surfactant aqueous solution: vinyl chloride monomer is 33:67, and the total amount of additional monomer is 184.8 kg. The polymerization conversion with respect to the initially charged monomer at the start of the addition was 6%, and the polymerization conversion at the end of the addition was 82%. Further, the conversion rate with respect to all the monomers after the completion of the polymerization is 91%.
Met. Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results.

Example 4 In the same manner as in Example 1, one hour after the internal temperature of the polymerization vessel reached 45 ° C., a 1% by weight aqueous solution of sodium dodecylbenzenesulfonate and a vinyl chloride monomer were added. 9.2 kg / hour, 10.1
The dispersion was introduced at a rate of kg / hour into the same static mixer as in Example 1, and the obtained dispersion was continuously added to the polymerization liquid, and the continuous addition was completed at 8 hours. In this case, the linear velocity in the static mixer was 0.62 m / sec, the ratio of the aqueous surfactant solution: vinyl chloride monomer was 48:52, and the total amount of additional monomers was 70.7 kg. When the addition was started, the polymerization conversion rate for the initially charged monomer was 6%.
The polymerization conversion rate at the end of the addition was 90%. Further, the conversion rate with respect to all the monomers after the completion of the polymerization was 94%.
Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results.

Example 5 In the same manner as in Example 1, a 3% by weight aqueous solution of sodium dodecylbenzenesulfonate and a vinyl chloride monomer were added after 3 hours from the time when the internal temperature of the polymerization reactor reached 45 ° C. 10.5kg / hour, 3 each
The mixture was introduced into the same static mixer as in Example 1 at a rate of 2.4 kg / hour, and the resulting dispersion was continuously added to the polymerization solution, and the continuous addition was completed at 8 hours. In this case, the linear velocity in the static mixer was 1.42 m / sec,
Surfactant aqueous solution: vinyl chloride monomer is 24:76, and the total amount of additional monomer is 162 kg. Further, the polymerization conversion rate with respect to the initially charged monomer at the start of the addition was 25%, and the polymerization conversion rate at the end of the addition was 84%.
Further, the conversion rate with respect to all the monomers after the completion of the polymerization was 91%. Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results. The jacket behavior was good, but the amount of coarse particles in the latex was large.

Example 6 Polymerization was started in the same manner as in Example 1 except that a static mixer having an inner diameter of 7.0 mm and the number of elements was 18, and a dispersion was prepared and added. The linear velocity in the static mixer at that time was 0.34
m / sec. The polymerization conversion rate with respect to the initially charged monomer at the start of the addition was 25%, and the polymerization conversion rate at the end of the addition was 87%. Further, the conversion rate with respect to all the monomers after the completion of the polymerization was 91%. Also, the upper jacket remained watered. A latex after polymerization was used to obtain a paste resin in the same manner as in Reference Example. Table 1 shows the results. The jacket behavior was good, but the amount of coarse particles in the latex was large.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to save space and simplify equipment in the preparation of a dispersion comprising a surfactant and a vinyl chloride monomer, and in the polymerization method of adding the dispersion to the polymerization liquid. became.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a method for producing a dispersion of the present invention.

FIG. 2 shows a case where a surfactant aqueous solution and a vinyl chloride monomer are phase-separated in a flow direction when introduced into a static mixer.

FIG. 3 is an enlarged view of the confluence of the aqueous surfactant solution and the vinyl chloride monomer of FIG. 2;

FIG. 4 A preliminary mixing tank is provided before introducing a static mixer, and a surfactant aqueous solution and a monomer are premixed.

FIG. 5 shows separation (floating of vinyl chloride monomer droplets) in a glass tube.

[Description of Signs] 1: Surfactant tank, 2: Vinyl chloride monomer tank, 3: Pump, 4: Pump, 5: Static mixer, 6: Polymerizer, 7: Pressure-resistant glass tube 8: Surfactant Aqueous solution, 9: vinyl chloride monomer, 10: static mixer, 11: flow direction of vinyl chloride monomer, 12: flow direction of surfactant 13: premix tank

Claims (4)

[Claims] 1. A surfactant aqueous solution and a vinyl chloride-based monomer are introduced into a static mixer when a vinyl chloride-based monomer is homogenized with an oil-soluble polymerization initiator in an aqueous medium to perform fine suspension polymerization. A vinyl chloride-based paste resin characterized in that a dispersion obtained by dispersing and mixing a vinyl chloride-based monomer and a surfactant aqueous solution is added during the polymerization from the start of the polymerization to the end of the polymerization. Manufacturing method. 2. The vinyl chloride paste according to claim 1, wherein the aqueous surfactant solution and the vinyl chloride monomer are introduced into a static mixer in a weight ratio of 75:25 to 30:70. Method of manufacturing resin. 3. The method for producing a vinyl chloride paste resin according to claim 1, wherein the linear velocity of the liquid in the static mixer is 0.5 m / sec or more. 4. Addition is started when the polymerization conversion rate is 30% by weight or less of the initially charged monomer amount, and the polymerization is continued until the conversion rate becomes 95% by weight of the initially charged monomer. 4. The method for producing a vinyl chloride-based paste resin according to claim 1, wherein the addition of the dispersion liquid is terminated halfway.