KR890003575B1 - Polymerization of vinylcloride in suspension - Google Patents

Abstract

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Description

Vinyl chloride suspension polymerization method

The present invention relates to a vinyl chloride polymerization method using a complex of clay and a hydrophilic polymer as a suspending agent.

Conventionally, polyvinyl chloride is produced by suspension polymerization, which is a component polymerization method in which droplets composed of vinyl chloride monomer are dispersed in an aqueous solution by stirring with an emulsifier.

The emulsifier has a function of controlling the porosity of the resin and inhibiting the formation of fish eyes. It is described in Patent 2,528,469. However, there are the following problems in this case.

That is, the polymerization initiator that produces free radicals is dissolved in a droplet composed of monomers. The drops are retained as a suspension and a protective colloid.

In general, the polymerization is activated by heat to generate free radicals from the initiator.

The polymerization proceeds in droplets consisting of monomers dispersed in an aqueous solution and impinges on the polymer phase due to collisions during the reaction.

Mechanical agitation is a dynamic equilibrium between droplet formation and coalescence.

In this suspension polymerization, the emulsifier is used to stabilize the monomer droplets in the aqueous dispersion medium and to prevent the coalescence by stabilizing the resulting polymer particles.

In a typical polymerization system, monomer droplets and polymer particles are enclosed in emulsifier molecules with a hydrophilic portion directed to the aqueous dispersion solution.

As the polymerization proceeds, the viscosity of the polymerization system increases and, due to the viscosity of the polymerization medium, it is difficult to maintain the dispersion of the polymer in the droplets by stirring.

The polymerization system, in turn, cannot maintain dispersion by the emulsifier alone, and reaches a limit that cannot prevent the coalescence of polymer particles.

The tendency of the dispersion to coalesce affect the polymerization in various forms.

The coalescence phenomenon adversely affects the particle size distribution and the shape of the polymer product, and also results in poor polymerization efficiency.

When the dispersion is coalesced, the vinyl chloride polymer collects as the inner wall of the reactor blocks the entanglement on the surface and on the propeller of the stirrer. Increasing such composition adversely affects the efficiency of crosslinking, thereby accelerating the coalescence of the polymer.

Since the polymerization is exothermic, a significant amount of heat is generated during the reaction.

In order to remove the heat of reaction, it is common for the polymerization medium to perform indirect heat exchange.

As the polymer droplets coalesce, the polymer attaches to the heat exchange surface of the reactor.

Therefore, the efficiency of heat exchange is reduced and temperature control fails.

This is an accelerating phenomenon and the failure to control the temperature can't control the molecular weight and side reactions and increase the adhesion rate of the polymer on the heat exchange surface.

The deposit of polymer mass in the reactor hinders the shortening of the reaction time since it must be removed from the reactor before the reaction can be resumed. Therefore, it is important to shorten the washing time of the polymerization reactor by minimizing the amount of polymer deposits formed on the surface of the reactor during the polymerization reaction.

In addition, since the polymerization time has a definite effect on the capacity of the polymerization plant, it is preferable to shorten the polymerization time.

Earlier researchers have used protective colloids to stabilize the suspension to prevent coalescence.

Various hydrophilic polymers have been used as suspending agents for vinyl chloride suspension polymerization.

Water-soluble methylcellulose was used in U.S. Patent 3,205,204, and U.S Patent 4,360,651 suggested that crosslinked polyacrylic acid was used as a suspending agent.

Chemical Abst 99: 3894μ reports that polyvinyl alcohol, water soluble seratine and polyacrylic acid are used as preferred suspending agents.

In these cases, however, the polymerization was slightly improved by the use of hydrophilic polymers, but further improvement is required.

Expanding lattice clay (expanding lattice clay, which expands in a lattice form when clay absorbs water, is marketed under the trade name Veegum), and is combined with a hydrophilic polymer to act as a suspending agent. It relates to a vinyl chloride suspension polymerization method characterized in that it makes it as follows.

It is characterized by using a mixture of veegum, a composite colloidal magnesium aluminum silicate derived from nature's smectite clay, and a mixture of hydrophilic polymer polyacrylic acid, polyvinyl alcohol and water-soluble cellulose ether. It relates to a vinyl chloride polymerization method.

When a certain amount of the above mixture was used for the polymerization, the inventors found that various experiments have shown that the surface entanglement of the polymerization reactor is significantly reduced and the polymerization time is shortened.

In addition, the above complex was confirmed by various experiments to improve the stability of the droplets in the reactor to make the distribution distribution to form a bell (Bell) and the size of the polymer droplets have the advantage.

A detailed configuration and effect of the present invention are as follows.

The present invention relates to a water-soluble suspension polymerization method of vinyl chloride, a typical suspension polymerization is characterized in that the vinyl chloride is uniformly dispersed throughout the aqueous solution by the action of an emulsifier and agitation, the free radical initiator is included in the polymerization system Soluble on vinyl monomer. The polymerization starts by pyrolyzing the initiator to form free radicals that initiate and deliver the polymerization reaction.

The range of initiator amount that can be used is 0.01-2% by weight relative to the weight of the monomer in the polymerization reactor, 0.02-1.0% by weight is practically applied.

Free radical precursors soluble in vinyl chloride are used as initiators.

Examples of suitable initiators are as follows.

: Dibenzoyl peroxide, dicumyl peroxide 2,2- azo (bis) isobutyronitrile 2,2- azobis (dimethyl valeronitrile) diethyl peroxide, dis Tearyl Peroxide, Tertary-Butyl Peroxide, Di (2,4-Dichlorobenzool) Peroxide Diacetyl Peroxide, Tertary-Butyl Perbenzoate, Tertary-Amyl Perocto Peroctoate di (Turture-butylperoxy cyclohexane, Di (turture-butyl) peroxide, dicumyl peroxide, acetyl cyclohexyl sulfonyl peroxide, di (2-ethyl Hexyl) Peroxy Dicarbonate, Di (Secondary-Butyl) Peroxy Dicarbonate, Diisopropyl Peroxydicarbonate, Tary-butyl PeroxyPibarate, Lauroyl Per Oxide.

The above initiator species di (2-ethyl hexyl) peroxy dicarbonate is the most preferred initiator.

Dispersing the monomer into small droplets and maintaining the dispersion during polymerization is facilitated by adding a suitable emulsifier.

Emulsifiers that may be selected include nonionic, cationic and anionic surfactants.

Representative nonionic emulsifiers used in the present invention are polyol esters such as fatty acids, alcohols, amides, amines, sorbitan fatty acids and axial polymers of various kinds of polyethylenes, Igepal, Triton, Atlas, Tween. A typical surfactant is another type of nonionic emulsifier, which is the commercially available ethylene oxide adduct of acetylene glycol, named sulfinol.

Anionic emulsifiers that can be used are obtained by sulfonation of fatty derivatives.

Sulfated or sulfonated fatty acid esters of tolosan and monopolyalcohol are commercially available under the names Novop, acidazole, and Stantex.

Anionic surfactants used are alkali metal salt ammonium salts of fatty acids consisting of 12-18 carbons, such as sodium laurate sodium stearate.

Useful cationic emulsifiers include Polyethxylated Quaternary Ammonium Salts with trade names such as Xthoquad Variquat.

The emulsifier is used 0.01-2% by weight relative to the water in the polymerization vessel, it is preferable to use 0.05-1% by weight.

The medium of the polymerization reaction is water, and the vinyl chloride monomer is dispersed in the water by the aforementioned emulsifier and stirring.

Normally, vinyl chloride is used at a concentration of about 20-50% of the reaction medium.

The use of less water hinders the heat transfer necessary to remove the heat of polymerization.

Conversely, the use of larger amounts of water has the disadvantage of reducing the concentration of the product and making the recovery of the polymer more difficult and expensive.

The polymerization reaction is initiated by heating the reaction medium to a temperature sufficient to decompose the initiator to produce free radicals.

Usually, the polymerization temperature is in the range of 25-100 ° C, and 30-60 ° C is mainly used.

The polymerization temperature determines the molecular weight of the polymer.

In other words, as the temperature increases, the polymerization rate increases, but a resin having a lower molecular weight is produced.

It is generally good to carry out the polymerization at the lowest temperature in order to control to an appropriate polymerization rate.

The polymerization is carried out in a pressure reactor.

Depending on the temperature used, the pressure rises from atmospheric pressure to 115 Psig.

For example, when the polymerization is initiated at 55 ° C., the pressure in the reaction system is almost 115 Psig.

This pressure is constant until the monomer is about 70% converted to polymer, and then the pressure begins to drop as the polymerization proceeds.

The polymerization is usually carried out in a batch reactor which takes 16 hours once and about 13 hours is the actual polymerization time. At 85% conversion, the rate of polymerization actually decreases. And at 95% conversion, the polymerization is actually terminated.

The composition of the suspending agent used as the protective colloid of the above-mentioned polymerization reaction consists of an expanding lattice cray and a hydrophilic polymer.

Expanding Lattice Cray is Montmorillonite, Smectite, Sucinite, Vermiculite, Nontronite, Saponite, Hectorite.

The clays listed above are produced from a mixture of bentonite crays consisting of less than about 20% aluminum oxide.

Bentonitecra also has a high ion exchange capacity between 50-150 Milliequivalent per 100g air dried cray. Other types of expanding lattice cray are produced in Wyoming, South Dakota, Montana, Utah, Nevada and California, USA. In the aforementioned clays, the ion-exchange site is found in the form of alkali alkaline earth metals (ex, sodium, podium, calcium, magnesium).

Clay can be used as it is, but always clean and grind to the desired size. Of the aforementioned expanding lattice cray, Veegum, a complex magnesium aluminum silicate obtained from natural smectite cray, is the most preferred clay.

The chemical composition of the gum is as follows.

TABLE 1

Hydrophilic polymers used in combination with the above-described expanding lattice crayes include cellulose ethyr and alkaline cellulose, such as carboxy methyl cellulose, by reacting with a suitable halide sulfate or epoxide. There are hydroxy alkyl celluloses such as hydroxy methyl cellulose and hydroxyethyl cellulose obtained.

Hydroxypropylmethylcellulose obtained by reacting propelin oxide and methyl chloride with calcareous cellulose is hydroxy butyl methyl cellulose obtained by reacting 1,2-butylene oxide and methyl oxide with alkali cellulose. Can be used as

Hydrophilic polymers used with clays include hydrolyzed polyvinyl alcohols.

Polyvinyl alcohol is prepared by hydrolyzing polyvinyl acetate and changes its physical properties depending on the degree of hydrolysis of the acetate group. Therefore only polyvinyl alcohols with 50-90% acetate groups hydrolyzed are used.

In addition to the foregoing, suitable hydrophilic high-rich polymers include polyacrylic acid and copolymers, cross-linked polyacrylic acid, and the like. However, polyacrylic acid is good and crosslinked polyacrylic acid is best used in combination with cray.

The aforementioned suspending agents may cooperate in a polymerization reactor in separate additions or may be combined to form a composite prior to addition to the polymerization reactor.

The composite may be formed by mixing a hydrophilic polymer to cray weight ratio in the range of 9: 1-1: 1. In a mixture of cray and hydrophilic polymers, either premixed or added as individual compounds, these suspending agents are mixed in an aqueous phase, the polymerization zone, to produce protective colloids that prevent the coalescence of vinyl chloride polymer droplets.

Composites consisting of an expanding lattice cray and a hydrophilic polymer are used in polymerization amounts of 0.01-1% by weight relative to the monomers.

The following examples outline the experimental procedure to demonstrate the present invention and explain the results that can be obtained thereby.

In the following experiments all experimental data were obtained by subjecting the polymerization to reaction using a 1 L reactor. The reactor is equipped with three standard 4-blade vertical curved turvine impellers.

The polymerization reaction was carried out according to the following procedure.

(a) Add distilled water and suspending agent to the reactor.

(b) Add no gum or a fixed amount to the reactor.

(c) Tween (polysorbate 8) is added to the reactor.

(d) Sealed in the reactor and vacuumed for 30 minutes.

(e) A monomer and di-2-ethylhexyl peroxy dicarbonate are placed in a reactor.

(f) Stir for 15 minutes.

(g) Maintain RPM 500.

(h) Raise the reaction temperature to 55 ° C.

(i) The reaction is continued until the reaction pressure drops to 95 Psig.

(j) Quickly cool and leak the contents of the reactor.

(k) Recover the resin in the usual way.

(l) Wash the reactor with secondary distilled water about three times.

(m) The polymer build-up is determined by removing the polymer scale attached to the reactor inner wall, the stirring shaft, and the stirring blade, and weighing it.

The reaction time was based on the time when the pressure of the reactor dropped to 95 Psig from the start of stirring.

The polymer product was analyzed according to ASTM and the following items were tested.

Particle size distribution, bulk density, plasticizer absorption, degree of polymerization, intrinsic viscosity, feed rate

Example 1

The protective colloid used in the first experiment was divided into the case of adding crosslinked polyacrylic acid and expanding lattice cray and the case of no test. The results are shown in Table 2 below.

TABLE 2

The combination of expanding lattice cray and polyacrylic acid was able to observe the following improvements during polymerization.

That is, the reaction time was shortened, the amount of scale formation during polymerization was reduced, and the particle size distribution and feed rate were improved.

Example 2

The following example was done following the experimental procedure of Example 1 with only hydroxy propylmethyl cellulose gum being used as a protective colloid.

The experimental results are shown in Table 3.

TABLE 3

The combination of hydrooxypropylmethyl cellulose and expanding lattice cray reduced the polymerization time.

Example 3

According to the experimental procedure of Example 1 was used as a suspension and gum and polyvinyl alcohol, the results are shown in Table 4.

TABLE 4

The combination of hydroxypropylmethyl cellulose and expanding laticray increased the bell-shaped product.

This can be seen from the measurement of particle size distribution and average particle size. Vinyl chloride polymerization was estimated by use as a suspending agent of the present invention. In most cases the polymerization time was significantly shortened.

Suspensions also enhanced the formation of bell-shaped polymeric products and increased particle size.

In the first experiment where the amount of polymerization scale formed on the surface of the reactor apparatus was measured, it was observed that the protective colloid played a role in reducing the amount of polymer accumulated on the surface of the reactor and the apparatus. In addition, the reactor cleaning time required before the polymerization was reduced to allow for an effective polymerization.

Claims (7)

A vinyl chloride suspension polymerization method using a polymerization initiator using a mixture of smectite clay and hydrophilic polymer water in a vinyl chloride suspension polymerization method. The vinyl chloride suspension polymerization method according to claim 1, wherein the polymerization initiator and the suspending agent used are as follows. [next] A. Smectite clay: Expanding lattice magnesium, aluminum, silicate cray. N. Polymers: selected from the group consisting of polyacrylic acid, polyvinyl alcohol and carboxyalkyl cellulose esters. The vinyl chloride suspension polymerization method according to claim 1, wherein the experimental composition of smectite is as follows. A. Silicon dioxide 56.9-69.1% N. Magnesium oxide 2.9-13.0% C. Aluminum oxide 8.9-17.0% D. Iron oxide 0.7- 1.3% M. Calcium Oxide 1.1- 2.0% Iii. Sodium Oxide 2.1- 3.8% G. Potassium oxide 0.2- 1.0% 2. The vinyl chloride suspension polymerization method according to claim 1, wherein the polyacrylic acid in the hydrophilic polymer is crosslinked. The vinyl chloride suspension polymerization method according to claim 1, wherein the polymerization temperature is 30-60 ° C. The vinyl chloride suspension polymerization method according to claim 1, wherein the initiator of suspension polymerization is di-2 (ethylhexyl) peroxydicarbonate. 4. The method of claim 1, wherein the cray and the hydrophilic polymer form a complex before being added to the polymerization reactor.