JPH06329709A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To enhance the effect of a suspending agent and facilitate controlling the particle size of the resulting polymer in the suspension polymn. of a vinyl chloride monomer in a water-sol. medium by using a specified amt. of a specific alcohol as a foam breaker. CONSTITUTION:A vinyl chloride polymer is produced by the suspension polymn. of vinyl chloride alone or its mixture with a copolymerizable monomer in a water-sol. medium by using a suspending agent and a foam breaker comprising a 4-18C alcohol satisfying the relationship of formulas I and II wherein gammaF is the surface tension (dyn.cm<-1>) of the medium; gammaD is the surface tension (dyn.cm<-1>) of the foam breaker; and gammaD'F' is the surface tension (dyn.cm<-1>) between the medium and the breaker (e.g. hexyl alcohol) in an amt. of 0.01-10 pts.wt. based on 100 pts.wt. the monomer (mixture). Thus, foaming on the surface of the polymn. fluid is effectively prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl chloride polymer by suspension polymerization of vinyl chloride monomers.

[0002]

2. Description of the Related Art In suspension polymerization of vinyl chloride type, partially saponified polyvinyl alcohol type and cellulose type substances are used as suspending agents. Polymerization proceeds while dispersing by, but since the suspending agent is foamable, foam is generated on the liquid surface during the polymerization reaction, which also hinders the recovery operation of the residual monomer at the end of the reaction. There are many.

Further, the presence of foam during the reaction causes a poor quality vinyl chloride resin to be produced in the foam layer due to the progress of the polymerization reaction, causing fish eyes, resulting in deterioration of the quality, and the polymerization reactor. The scale also adheres to the vessel wall near the liquid surface.

Therefore, in the polymerization vessel provided with a reflux condenser in order to improve the cooling capacity of the reaction heat, this foaming phenomenon becomes an even more serious problem. As methods for preventing foaming on the liquid surface during such a polymerization reaction, two types of methods have conventionally been proposed: mechanical means and chemical means.

As the former mechanical means, there are JP-A-56-26908 and JP-A-58-49710.
In the publication, it is proposed that the rotary vanes of the vapor phase portion or the rotary vanes and their covers are provided to break the bubbles.

As the latter chemical means, in JP-A-61-115908, polyvinyl alcohol as a suspending agent is limited to those having a saponification degree of 85 mol% or more and a saponification degree of 85 mol% or less. It is proposed that defoaming is performed by using together with different mixing ratios.

Further, in JP-A-61-207410 and JP-A-61-207411, it has been proposed to use a nonionic surfactant having an HLB of 6 to 14 as an antifoaming agent. Japanese Patent No. 292310 proposes polyoxyalkylene glycol. Japanese Patent Laid-Open No. 2-18
No. 0908 discloses polysiloxane-based silicone oils as defoaming agents, aliphatic or aromatic alcohols having 10 to 30 carbon atoms, sodium hydroxide, alkaline compounds such as aqueous ammonia, low saponification degree polyvinyl alcohol, etc. Are listed alone or in combination, and the combination of silicone oils and alkali compounds is most preferable.

Further, in JP-A-3-212409, polyvinyl alcohol having a saponification degree of 20 to 50 mol%, polysiloxane silicone oils and aliphatic or aromatic alcohols having 10 to 30 carbon atoms are refluxed. It is proposed to add in the initial stage when the total heat removal amount in the condenser is up to 10%.

However, in these conventional techniques, there is a problem in that bubbles are likely to invade along the gaps of the rotary vanes when mechanical means are used, and in addition, the apparatus becomes complicated and chemical means are used. In this case, there is a problem in the sustainability of the defoaming effect, and it cannot be said that defoaming is sufficiently carried out in the reaction for a long time.

[0010]

Among many synthetic resins, vinyl chloride resin is the most versatile among the many synthetic resins because of its low price, excellent mechanical properties such as tensile strength, and good weather resistance. This is the resin used. In the vinyl chloride-based suspension polymerization for producing this vinyl chloride resin, the foaming phenomenon on the liquid surface of the polymerization vessel is unavoidable, and due to the polymerization reaction in the foamed layer, particles with poor morphology and the cause of fish eyes are caused. As a result, the homogeneity of the vinyl chloride resin produced in the entire system is deteriorated. Therefore, it is necessary to prevent this foaming phenomenon over the entire time from the start of the polymerization reaction to the recovery of the residual monomer at the end. Also,
Due to foaming during the reaction, the suspending agent used is concentrated and unevenly distributed in the foam layer, resulting in a decrease in suspension efficiency that acts on the suspension system. As a result, there has been a drawback that prediction and control of the particle size of the vinyl chloride resin produced is hindered.

An object of the present invention is to propose a suspension polymerization method which overcomes such drawbacks and facilitates control of the particle size of the produced vinyl chloride resin. Therefore, in the present invention, to improve the homogeneity of the quality of this vinyl chloride resin,
In addition, by making it easier to control the particle size, which is important in the production of vinyl chloride resin, it is possible to greatly contribute to the field of powder molding as well as conventional kneading molding.

[0012]

Means for Solving the Problems As a result of earnest research on the foaming phenomenon on the liquid surface of a polymerization vessel, which is the problem,
The present invention was completed by investigating according to the mechanism of foam breaking on the liquid surface, discovering a persistent foam breaking agent, and confirming its effect.

In suspension polymerization of vinyl chloride type monomers,
In the foam layer, a large number of bubbles are connected and adjacent to each other, having a portion where adjacent bubbles are in contact with each other, that is, a plateau boundary.

In order to break the foam, it is an absolute condition that both the spreading and penetration effects of the foam breaker on the plateau boundary are active and rapid. Therefore, S _DF for the function of spreading the coefficient of expansion (Spreading Coefficient) is the coefficient of penetration for intrusion (Enterin
It is a necessary condition that all E _DFs that are g Coefficient) are positive (plus).

Γ _F : surface tension of water-soluble medium
(dyne ・ cm ^-1 ), γ _D : Surface tension of the defoaming agent (dyne ・ cm ^-1 ), γ _{D'F '} : Interfacial tension between the water-soluble medium and the defoaming agent (dyne ・ c
m ^-1 ), by satisfying γ _F + γ _{D'F '} > γ _D , the bubbles are coalesced and coalesced as the bubbles are drawn to the plateau boundary of the adjacent bubbles. To do.

Therefore, S, which is the coefficient of spread of the defoaming agent,
_DF is S _DF = γ _F −γ _{D′ F ′} −γ _D > 0 (1) and must be S _DF > 0.

Further, the invasion coefficient E _DF is E _DF = γ _F + γ _D' F'-γ _D > 0 (2) and must be E _DF > 0.

As the suspending agent in the polymerization of vinyl chloride type monomers, various grades of partially saponified polyvinyl alcohol type and cellulose type are used. In order to break the robust foam layer that is formed, by selecting a foam breaking agent that satisfies S _DF > 0 and E _DF > 0 in the above formulas (1) and (2), The present inventors have found that the foam on the liquid surface is broken.

The case of suspension polymerization of vinyl chloride will be described based on specific numerical values. The surface tension of the partially saponified polyvinyl alcohol aqueous solution used as a suspending agent is naturally different depending on the saponification degree and the concentration to be used, but at a general use concentration in a general-purpose grade,
It is considered that γ _F is in the range of 60 to 70 dyne · cm ⁻¹ . Explaining hexyl alcohol as an example of a defoaming agent, the interfacial tension between hexyl alcohol and water is γ _{D'F '} = 6.8 dyne · cm ^-1 (25 ° C),
The surface tension of hexyl alcohol is γ _D = 24.4dyne
・ Since it is cm ⁻¹ (25 ° C.), applying these specific numerical values to the above equations (1) and (2), S _DF and E
It can be seen that the _DFs are clearly positive (plus).

The phenomenon of such bubble breaking is that the bubble breaking agent spreads in a thin film of bubbles in a double layer to bring two bubbles close to each other, the liquid is extruded from between them, and the tension of the liquid film is lowered. As the curvature of the bubbles increases, the thickness of the bubble film decreases, and as a result, the bubbles are destroyed.

Therefore, in order for the thin film of the defoaming agent to cover the surface of the foam, the spreading coefficient S _DF and the penetration coefficient E _DF are
Both need to be large. As described above, the method of the present invention is based on an idea which is basically different from the conventional method by the chemical method using various antifoaming agents shown as the prior art.

The method of the present invention exhibits a particularly remarkable effect when a vinyl chloride monomer is polymerized in an aqueous medium, particularly when a suspension polymerization method is used. Examples of alcohols defined as a foam breaking agent in the present invention include, for example, n
-Hexyl alcohol, n-heptyl alcohol, 2-
Ethyl - hexyl alcohol, 3,5,5-trimethyl-1-hexanol _{[CH 3 C (CH 3)} 2 CH 2 CH (CH 3) CH 2 C
H ₂ 0H], n-decyl alcohol, n-dodecyl alcohol 2,6,8-trimethyl-nonanol [CH ₃ CH (C
H ₃ ) CH ₂ CH (OH) CH ₂ CH (CH ₃ ) CH ₂
CH (CH ₃ ) CH ₃ ], tetradecanol [CH _{3
(CH 2) 3 CH (C} 3 H 7) CH 2 CH (OH) CH
_{2 CH (CH 3) CH 3} ] di -tert- amyl phenoxyethanol _{[2,4- (tert-C 5 H} 11) 2 -C 6 H 3 O-C 2 H 4 O
[H] and the like.

As exemplified herein, as the foam breaking agent of the present invention, rucols having 4 to 18 carbon atoms can be used, but alcohols having 4 to 14 carbon atoms are particularly used. It is preferable.

In the method of the present invention, the above formula (1) is used.
The expansion coefficient S _DF and the intrusion coefficient E _DF of the formula (2) are both positive (plus), and the addition amount of the foam breaking agent to the polymerization system is 100 parts by weight of the vinyl chloride monomer. 0.
The amount is 01 parts by weight to 10 parts by weight, preferably 0.1 parts by weight to 5 parts by weight.

The polymerization of the present invention is not limited to vinyl chloride monomers, but a mixture of vinyl chloride containing vinyl chloride as a main component and a copolymerizable monomer, particularly vinyl chloride, is preferably used.
It can also be applied to a monomer mixture of 0% or more. Examples of the comonomer include olefins such as ethylene and propylene, vinyl acetates such as vinyl acetate and vinyl stearate,
Examples thereof include esters and anhydrides of acids such as maleic acid and fumaric acid, nitrile compounds such as acrylonitrile, and vinyl chloride copolymerizable monomers such as vinylidene compounds such as vinylidene chloride.

As the suspending agent used in the suspension polymerization of the present invention, those generally known in the art can be used. Partially saponified polyvinyl alcohols, methyl cellulose, ethyl cellulose, carboxymethyl cellulose,
Water-soluble celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose, water-soluble polymers such as acrylic acid polymers and gelatin, and the like can be used alone or in combination of two or more.

Examples of the polymerization initiator used in the suspension polymerization of the present invention include diacyl peroxides such as lauroyl peroxide, peroxydicarbonates such as di-2-ethylhexyl peroxydicarbonate, and dicumyl peroxide. Dialkyl peroxides, peroxyesters such as t-butylperoxypivalate and cumylperoxyneodecanoate, azo compounds such as azobisisobutyronitrile, etc., which have been conventionally used for vinyl chloride-based polymerization. An oil-soluble catalyst can be mentioned, and these can be used individually or in combination of 2 or more types.

The suspension polymerization of a general vinyl chloride-based monomer is carried out using these typical polymerization raw materials, and the particle diameter of the produced vinyl chloride resin or its copolymer is determined by It is traditionally said that it is determined by the stirring strength, Weber number, and the type and amount of suspending agent, but the suspension used due to the presence of a foam layer on the liquid surface that is constantly generated during the reaction. The result was that the turbidity agent did not work efficiently.

However, in the method of the present invention, since the suspension agent efficiency is improved by the use of the foam breaking agent, the correlation between the suspension agent concentration and the particle size of the produced polymer is obtained under each stirring strength. It was found that more clear linearity was recognized as compared with the suspension polymerization by the conventional method. That is, it was possible to easily control the particle size of the polymer, which is important in the production of the vinyl chloride polymer, by the method of the present invention.

Further, in the method of the present invention, a polymerization degree adjusting agent, a chain transfer agent, a pH adjusting agent, an antioxidant, an antiscaling agent, which are generally used for producing vinyl chloride polymers,
Stabilizers and the like can be optionally added as needed.

The present invention improves the efficiency of the suspending agent by breaking the bubbles generated on the liquid surface during the production of the vinyl chloride polymer in this way, and produces a more homogeneous polymer. However, a method for producing a vinyl chloride resin that enables easy control of the particle size has been established, and its industrial value is extremely large.

[0032]

EXAMPLES Next, the present invention will be explained by showing concrete examples and comparative examples, but the present invention is not limited to these. Example 1 A glass lining polymerization vessel having an inner volume of 300 liters equipped with a stirrer and a jacket was charged with 150 kg of deionized water, 150 g of partially saponified polyvinyl alcohol, 65 g of lauroyl peroxide and 70 g of t-butylperoxypivalate, and the inside of the vessel was removed. After care, vinyl chloride monomer 100Kg
And hot water is passed through the jacket with stirring.
The temperature was raised to ℃ and the polymerization was started.

Ten minutes after the start of heating, a solution of 300 g of n-dodecyl alcohol in ethanol (400 g) was added three times at intervals of 30 minutes, the reaction was continued for 9.8 hours, and the internal pressure of the polymerization vessel was 5.0 kg /. After the unreacted monomer was recovered when the pressure was lowered to cm ² , the polymer slurry was taken out of the system. Comparative Example 1 The same method as in Example 1 was carried out except that no ethanol solution of n-decyl alcohol was used.

By comparing the results of Example 1 and Comparative Example 1 as follows, the effect of using the defoaming agent according to the method of the present invention was confirmed. That is, when the foaming state of the liquid surface during the reaction was observed from two sight glasses on the upper part of the polymerization vessel, no foaming was observed in Example 1, whereas in Comparative Example 1, on the liquid surface. Foaming was observed throughout.

Regarding the condition of the scale on the vessel wall near the liquid surface boundary of the polymerization reactor after the reaction, the scale adhesion was very small in Example 1, but the scale near the gas-liquid boundary was found in Comparative Example 1. Was clearly higher than in Example 1.

Further, the average particle diameter of the produced vinyl chloride resin was 72 μm in Example 1, but was 1 in Comparative Example 1.
The particle shape of the produced vinyl chloride resin was substantially circular in Example 1, but was irregular in Comparative Example 1. Example 2 200 kg of deionized water in a polymerization vessel having an internal volume of 300 liters,
85 g of polyvinyl alcohol having a degree of saponification of 87 mol%, 154 g of lauroyl peroxide, 11 g of octyl peroxydicarbonate, 412 g of trichloroethylene and 18 kg of vinyl acetate monomer were charged, and after degassing the inside of the vessel, 82 kg of vinyl chloride monomer was charged. 6 with hot water in the jacket
Heat to 3 ° C. Five minutes after the start of heating, a solution of 500 g of benzene (500 g) in 500 g of n-dodecyl alcohol was added.
The copolymerization reaction was continued while adding four times at minute intervals. The residual vinyl chloride monomer was recovered when the internal pressure of the polymerization vessel dropped to 1.5 kg / cm ² , and then the copolymer slurry was taken out of the system. Comparative Example 2 The same method as in Example 2 was carried out except that the benzene solution of n-dodecyl alcohol was not used.

By comparing the results of Example 2 and Comparative Example 2 as follows, the effect of using the defoaming agent according to the method of the present invention was confirmed in this case as well. That is, when the foaming state of the liquid surface during the reaction was observed, foaming was not observed in Example 2, whereas foaming was observed throughout the liquid surface in Comparative Example 2.

Regarding the recovery operation of the residual monomer after completion of the reaction, the recovery operation was quick and easy in Example 2 because the foaming at the time of recovery was extremely small, whereas in Comparative Example 2, recovery operation was performed at the time of recovery. Due to the large amount of foaming, it took a long time to collect.

Further, the average particle diameter of the produced vinyl chloride resin was 115 microns in Example 2, but Comparative Example 2
The particle size was 156 microns and large particles were mixed on the beads. Example 3 170 Kg of deionized water was added to a polymerization vessel having an internal volume of 300 liters.
40 g of polyvinyl alcohol having a saponification degree of 88 mol%, 80 g of methylcellulose-based suspension agent, 200 g of crosslinking agent, 85 g of polymerization initiator cumylperoxyneodecanoate and 45 g of di-2-ethylhexylperoxydicarbonate, 2-ethylhexyl Alcohol 60
After charging 0 g and degassing the inside of the vessel, vinyl chloride monomer 1
00 kg was charged, the reaction temperature was raised to 45 ° C. with stirring, polymerization was carried out at a reaction pressure of 5.5 kg / cm ² for 9 hours, and a slurry was taken out by a conventional method. Comparative Example 3 The same method as in Example 3 was carried out except that 2-ethylhexyl alcohol was not used.

As shown below, the effect of using 2-ethylhexyl alcohol which is a defoaming agent in the method of the present invention,
It was confirmed by comparing the results of Example 3 and Comparative Example 3.

That is, when the foaming state of the liquid surface during the reaction was observed, no foam on the liquid surface was observed in Example 3, whereas foaming was observed throughout the liquid surface in Comparative Example 3. . Regarding the condition of the scale near the liquid surface boundary of the polymerization vessel after the reaction, the scale adherence was small in Example 3, but the scale adherence was obviously higher in Comparative Example 3 than in Example 3. Further, the average particle diameter of the produced vinyl chloride resin was 75 microns in Example 3, but Comparative Example 3
Was 118 microns.

[0042]

EFFECTS OF THE INVENTION According to the present invention, since the foaming on the liquid surface of the polymerization vessel during the production of the vinyl chloride polymer is effectively broken, the effect of the suspending agent to be used can be enhanced, and the vinyl chloride produced can be produced. The industrial value of the resin is very large because the particle size of the resin can be controlled more easily, and since no extraneous vinyl chloride resin is formed in the liquid foam layer.

Claims (1)

[Claims] 1. When suspension polymerization of a vinyl chloride monomer alone or a mixture of a vinyl chloride monomer and a monomer copolymerizable with vinyl chloride in a water-soluble medium is carried out against bubbles on the surface of the polymerization liquid. As a defoaming agent, the following formulas: γ _F −γ _{D'F '} −γ _D > 0 (1) and γ _F + γ _D'F' −γ _D > 0 (2) [wherein, γ _F is water-soluble] The surface tension of the medium (dyne ・ cm ^-1 ), γ _D is the surface tension of the foam breaker (dyne ・ cm ^-1 ), γ _{D'F '} is the interfacial tension between the water-soluble medium and the foam breaker. (dyne ・ c
m ^-1 ). ], And the number of carbon atoms is 4-18
Alcohol is 0.0 per 100 parts by weight of the monomer
A method for producing a vinyl chloride polymer, which is used in the range of 1 to 10 parts by weight.