JP4391323B2 - Dispersant for suspension polymerization - Google Patents

Description

  The present invention relates to a dispersion for suspension polymerization mainly comprising a polyvinyl alcohol-based resin.

  Conventionally, polyvinyl alcohol-based resins have been widely used as dispersants for suspension polymerization of vinyl chloride, such as particle size, bulk density, porosity distribution, plasticizer absorbability, and demonomerization properties of the resulting vinyl chloride. It also contributes to improvement.

However, there is a risk that bubbles may be produced during the production (suspension polymerization), leading to a decrease in the physical properties of vinyl chloride, which may cause scale. As a method for suppressing such foaming, an antifoaming agent is used during suspension polymerization. Proposed to be used together. For example, it is known to use a silicone-based antifoaming agent, a polyalkylene glycol-based antifoaming agent, an amide-based antifoaming agent, etc. (for example, see Patent Document 1).
JP-A-9-1000030

However, when the above antifoaming agent is used, foaming and scale during suspension polymerization can be prevented, but the dispersion (liquid) of the polyvinyl alcohol resin before being charged into the polymerization system (can). No consideration is given to suppression of foaming.
That is, when a dispersing agent such as a polyvinyl alcohol resin is charged into a polymerization system, it is generally performed by previously dissolving a polyvinyl alcohol resin or the like in water and charging as an aqueous solution. If the aqueous solution foams, the work efficiency is lowered (it is necessary to wait until the foam disappears), or if the foam cannot be sufficiently removed, bubbles may rise on the upper part of the dissolving can and foreign matter on the upper part of the dissolving can be mixed into the polyvinyl alcohol aqueous solution. There is a need for a dispersion agent for suspension polymerization that can produce polyvinyl chloride with excellent quality, with less foaming during the preparation of aqueous solutions, and less foaming during suspension polymerization of vinyl chloride and defoaming. It is where

（Ｒ１、Ｒ２、Ｒ３はアルキル基、水素または下記一般式（２）で示される官能基のいずれかであって、その少なくとも一つが下記一般式（２）で示される官能基である。）

（Ｒ４はメチル基、エチル基、ｎは５〜５０の整数、ｍは５〜５０の整数）
Therefore, as a result of intensive studies in view of such circumstances, the present inventors have found that a dispersant for suspension polymerization containing a polyvinyl alcohol resin (A) and a compound (B) represented by the following general formula (1) is provided. The present invention was completed by finding out that the above object was met.

(R1, R2, and R3 are either an alkyl group, hydrogen, or a functional group represented by the following general formula (2), at least one of which is a functional group represented by the following general formula (2). )

(R4 is methyl group, ethyl group, n is an integer of 5-50, m is an integer of 5-50)

  Moreover, in this invention, it measures according to JIS K6726 of polyvinyl alcohol-type resin (A) that the average degree of polymerization measured based on JIS K6726 of a polyvinyl alcohol-type resin (A) is 300-5000. The saponification degree is 60 mol% or more, and the content of the compound (B) represented by the general formula (1) is 0.01 to 5% by weight with respect to the polyvinyl alcohol resin (A). This is a preferred embodiment.

  Since the dispersant for suspension polymerization of the present invention contains a specific compound, foaming can be suppressed during preparation of the aqueous dispersant solution before charging into the polymerization system, and the aqueous solution can be efficiently prepared. Foaming at the initial stage of polymerization can also be suppressed, and furthermore, when used for suspension polymerization of vinyl chloride, it is possible to efficiently produce high-quality polyvinyl chloride with very little fish eye at the time of molding.

Hereinafter, the present invention will be described in detail.
The polyvinyl alcohol resin (A) used in the present invention is not particularly limited and can be produced by a known method of saponifying a polyvinyl ester resin and does not hinder the object of the present invention as described later. Within a range, a copolymer of a vinyl ester and another vinyl compound may be saponified, or a compound having a functional group may be added to the resulting polyvinyl alcohol resin by a post reaction.

  Examples of such vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc. Although used in combination, vinyl acetate is preferred for practical use.

  Further, other vinyl compounds can be used preferably within 10 mol%. Examples of such compounds include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene and α-octadecene. , Unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid or their salts or mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as acrylamide and methacrylamide , Olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, di Polyoxyalkylene (meth) allyl ethers such as tildiallylammonium chloride, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, poly Polyoxyalkylene (meth) acrylates such as oxyethylene (meth) acrylate and polyoxypropylene (meth) acrylate, polyoxyalkylene (meth) acrylamides such as polyoxyethylene (meth) acrylamide and polyoxypropylene (meth) acrylamide, poly Oxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polio Shi ethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinyl amine, vinyl ethylene carbonate, and 3,4-diacetoxy-1-butene.

  In the polymerization or copolymerization of vinyl ester compounds and other vinyl compounds, there is no particular limitation, and any known polymerization method can be arbitrarily used. Usually, however, a solution using methanol, ethanol or isopropyl alcohol as a solvent. Polymerization is carried out. Of course, emulsion polymerization and suspension polymerization are also possible.

  The polymerization reaction is carried out using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, and the polymerization catalyst is not limited. The reaction temperature is selected from the range of about 35 ° C. to the boiling point (more preferably 50 to 80 ° C.), and the reaction temperature can be set to 70 to 120 ° C. using a pressure resistant reactor.

  When the obtained vinyl ester polymer is saponified, the polymer is dissolved in alcohol and the reaction is carried out in the presence of an alkali catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like. The concentration of the polymer in the alcohol is selected from the range of 20 to 65% by weight. Furthermore, it is possible to improve the blocking property of the remaining acetic acid groups by saponifying alcohol in the presence of a solvent having a low dielectric constant such as methyl acetate, ethyl acetate or benzene. It is also possible to lower the blocking property of the remaining acetic acid groups by carrying out the saponification reaction in the presence of water or the like.

  As the saponification catalyst, alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate can be used. What is necessary is just to make the usage-amount of this catalyst 1-100 millimol equivalent with respect to vinyl ester. In some cases, it can be saponified with an acid catalyst such as sulfuric acid or p-toluenesulfonic acid.

  Thus, the polyvinyl alcohol-based resin (A) is obtained. In the present invention, the average degree of polymerization of the polyvinyl alcohol-based resin (A) measured in accordance with JIS K6726 is 300 to 5000 (more preferably 300 to 4500). In particular, when the average degree of polymerization is less than 300, the effect of suppressing coarsening is reduced, and when the average degree of polymerization exceeds 5000, the porosity of the obtained polyvinyl chloride is reduced. It is not preferable.

Moreover, the saponification degree measured based on JIS K6726 of polyvinyl alcohol-type resin (A) is 60 mol% or more (more preferably 65-99.5 mol%, especially 68-99 mol%), and this takes If the degree of saponification is less than 60 mol%, the effect of suppressing coarsening is reduced, which is not preferable.

Furthermore, the 1,2-glycol bond amount of the polyvinyl alcohol-based resin (A) is 1.5 to 2.5 mol% (more preferably 1.6 to 2.2 mol%, particularly 1.6 to 1.8 mol%). If the amount of the bond is less than 1.5 mol%, the stability of the aqueous solution tends to be lowered. Conversely, if the amount exceeds 2.5 mol%, the adsorption to the vinyl chloride monomer is poor, which is preferable. Absent.
Moreover, the block character measured by ¹³ C-NMR of the polyvinyl alcohol resin (A) is 0.1 to 0.7 (more preferably 0.2 to 0.6, particularly 0.3 to 0.5). It is preferable that the polyvinyl chloride particles are coarsened outside the range of the block character.

（Ｒ１、Ｒ２、Ｒ３はアルキル基、水素または下記一般式（２）で示される官能基のいずれかであって、その少なくとも一つが下記一般式（２）で示される官能基である。）

（Ｒ４はメチル基、エチル基、ｎは５〜５０の整数、ｍは５〜５０の整数）

The compound (B) used in the present invention is represented by the following general formula (1).

(R1, R2, and R3 are either an alkyl group, hydrogen, or a functional group represented by the following general formula (2), at least one of which is a functional group represented by the following general formula (2). )

(R4 is methyl group, ethyl group, n is an integer of 5-50, m is an integer of 5-50)

Specifically, the compound (B) is preferably a compound in which R1 to R3 are represented by the formula (2) [wherein R4 is a methyl group], and a product containing such a compound is “SN deformer” manufactured by San Nopco. 777 ”and the like. In addition, a compound in which R1 is C ₁₀ H ₂₁ , R2 is H, and R3 is the formula (2) [wherein R4 is a methyl group] is also preferable. As a product containing such a compound, “SN deformer 444” manufactured by San Nopco Etc. can be illustrated.

The dispersant for suspension polymerization of the present invention contains the polyvinyl alcohol resin (A) and the compound (B) as described above, and the content ratio is not particularly limited, but the polyvinyl alcohol resin (A) On the other hand, the compound (B) is preferably contained in an amount of 0.01 to 5% by weight (more preferably 0.05 to 3% by weight, particularly 0.1 to 2% by weight). If it is less than%, the effects of the present invention may not be sufficiently obtained. Conversely, if it exceeds 5% by weight, the surface activity of the polyvinyl alcohol-based resin may be adversely affected.
In addition to the above compound (B), the dispersant for suspension polymerization of the present invention preferably contains a siloxane compound such as polydimethylsiloxane, mineral oil, hydrophobic silica, etc., and the content thereof is polyvinyl alcohol. It is preferable to contain 0.00001 to 2% by weight (more preferably 0.0001 to 1% by weight, particularly 0.0002 to 0.7% by weight) with respect to the resin (A). If the amount is less than 0.0001% by weight, a sufficient defoaming effect may not be obtained. On the other hand, if it exceeds 2% by weight, various physical properties of the resulting polyvinyl chloride may be adversely affected.
Furthermore, diethylene glycol, 1,4-dioxane, propylene glycol monomethyl ether, polyoxypropylene butyl ether, polyethylene glycol and the like may be contained.

The suspension polymerization using the dispersant for suspension polymerization of the present invention thus obtained will be described.
In preparing the suspension polymerization dispersant of the present invention in a polymerization system (can), an aqueous solution is prepared in advance. At this time, the suspension polymerization dispersant is added to a predetermined amount of deionized water with stirring. After sufficiently dispersing, the temperature is raised to 70 to 90 ° C., and stirring is continued for about 1 to 3 hours at the same temperature, followed by cooling to room temperature while stirring to prepare an aqueous solution. The concentration of the aqueous solution cannot be generally specified by the viscosity or cloud point of the aqueous solution, but is usually 0.5 to 12% by weight (more preferably 1 to 10% by weight, particularly 2 to 8% by weight). Preferably, when the concentration is less than 0.5% by weight, the effect of hot water charge is poor. On the other hand, when the concentration exceeds 12% by weight, the viscosity of the aqueous solution is excessively increased and the workability is lowered, and the accuracy of the charged amount is lowered. It is not preferable.

The dispersant for suspension polymerization of the present invention can obtain the effects of the present invention more remarkably when it is previously charged into the polymerization system as an aqueous solution, but it can also be added as it is without forming an aqueous solution.
In addition, the target suspension polymerization is useful for suspension polymerization of various vinyl compounds such as vinyl chloride, vinylidene chloride, styrene, (meth) acrylate, vinyl acetate, and is particularly useful for suspension polymerization of vinyl chloride. The application will be described below, but the application is not limited thereto.

In carrying out suspension polymerization, the suspension polymerization dispersant of the present invention (preferably in an aqueous solution) of the present invention is added to the polymerization system to disperse vinyl chloride and polymerize in the presence of an oil-soluble catalyst. Do.
The amount of the dispersing agent charged at this time is preferably 0.01 to 0.15 parts by weight, more preferably 0.01 to 0.1 parts by weight, particularly 0, relative to 100 parts by weight of vinyl chloride. .01 to 0.08 parts by weight are preferred. If the charged amount is less than 0.01 parts by weight, it is difficult to control the particle size due to insufficient protective colloid properties at the time of polymerization. Conversely, if the charged amount exceeds 0.15 parts by weight, the particle size becomes too small. Absorbability is lowered, which is not preferable.
The dispersant may be charged all at the beginning of the polymerization or may be divided and charged in the middle of the polymerization.

The polymerization is preferably carried out while removing heat with a polymerization can equipped with a reflux condenser (RC). During the polymerization, the RC cooling water temperature and reactor jacket temperature are controlled, and the polymerization reaction heat is removed by the RC and reactor jacket.
After completion of the polymerization reaction, for example, the following post-treatment is performed. First, unreacted vinyl chloride monomer is recovered. The monomer is used during or after the transfer of the polyvinyl chloride slurry. More specifically, the transfer is usually carried out by reducing the pressure of the unreacted vinyl chloride monomer recovery container under a reduced pressure from the pressure of the reaction vessel, and during or after the transfer, the unreacted vinyl chloride monomer is used in the reaction vessel or unreacted vinyl chloride monomer. It is collected in the gas holder connected to the collection container. The demonomerized polyvinyl chloride slurry is further dehydrated and dried to obtain polyvinyl chloride particles.

  When the dispersant for suspension polymerization of the present invention is used separately for the main dispersant and the dispersion aid, both of them can be used, but the main dispersant is preferred. Examples of the dispersant include a polyvinyl alcohol resin having a polymerization degree of 1800 to 3000 and a saponification degree of 78 to 82 mol%, or a polyvinyl alcohol resin having a polymerization degree of 1800 to 4500 and a saponification degree of 88 to 99 mol%, and further polymerization. Polyvinyl alcohol resins having a degree of saponification of 500 to 1000 and a degree of saponification of 68 to 82 mol%, heat-treated products thereof, and the like can be used.

  The weight ratio of the main dispersant to the dispersion aid (main dispersant / dispersion aid) is preferably in the range of 100/0 to 30/70 (more preferably 90/10 to 50/50). If the weight ratio is less than 30/70, the effect of suppressing coarsening during suspension is lowered, which is not preferable.

Hereinafter, the present invention will be described in more detail with reference to examples.
In the examples, “%” and “parts” are based on weight unless otherwise specified.

Example 1
(Preparation of dispersant)
In a dissolving can (200 liters), 100 parts of polyvinyl alcohol (A) having a saponification degree of 79 mol% and an average degree of polymerization of 2000 and 1 part of “SN deformer 777” (B) manufactured by San Nopco are added to 2400 parts of room temperature water. The mixture was heated to 80 ° C. in about 1.5 hours, then mixed and stirred for about 1.5 hours, and cooled to room temperature to obtain an aqueous dispersant solution.
<Foaming state during preparation>
The foaming state at the time of preparation of the aqueous dispersant solution was observed through the observation window of the dissolution can and evaluated as follows.
◎ ・ ・ ・ The distance from the water surface to the top surface of foam (bubble thickness) is less than 5cm ○ ・ ・ ・ 〃 5cm or more and less than 30cm × ・ ・ ・ ・ ・ ・ 30cm or more

(Suspension polymerization)
After both degassed equipped with 1.5 m ³ reactor and RC interior reflux condenser (RC), 500 parts of vinyl chloride in the reaction can, supplying degassed deionized water 500 parts, 100 parts of further vinyl chloride After introducing 1.5 parts (0.06 part in terms of solid content) of the above dispersant aqueous solution and raising the internal temperature of the polymerization can to 57 ° C., G-2-ethylhexyl-oxydicarbonate as a polymerization initiator And 0.03 part of t-butylperoxyneocarbonate was added to 100 parts of vinyl chloride, respectively, and at the same time, RC was operated and polymerization was performed for 4 hours while stirring at 400 rpm to obtain polyvinyl chloride.

During the polymerization, the RC cooling water temperature and the reactor jacket temperature were controlled, and the polymerization reaction heat was removed by the RC and reactor jacket.
After completion of the polymerization reaction, the polyvinyl chloride was transferred to an unreacted monomer recovery container having the same size as the reaction vessel. This transfer was carried out with the pressure of the recovery container being reduced under a pressure of the reaction vessel. There was almost no foaming in the reaction can at the time of transfer, and the transfer was completed in less than 25 minutes. During and after the transfer, unreacted monomer was recovered in a gas holder connected to the reactor and the unreacted monomer recovery container, and the transferred polyvinyl chloride slurry was dehydrated and dried to obtain polyvinyl chloride.

  The foamability at the time of suspension polymerization and the obtained fish eye of polyvinyl chloride were evaluated in the following manner.

<Foaming properties>
(1) Wet forming The state of foaming 1 hour after the start of polymerization was observed through a viewing window on the side of the polymerization can, and the height of the foam from the liquid level was measured.
The evaluation criteria are as follows.
◎ ・ ・ ・ less than 7cm ○ ・ ・ ・ less than 7-10cm × ・ ・ ・ 10cm or more

(2) Polyvinyl chloride transfer time In order to evaluate foamability when recovering the unreacted vinyl chloride monomer after completion of the polymerization, the time for transferring the polyvinyl chloride slurry to the recovery container was measured. That is, the more foaming, the longer it takes to transfer the slurry.
The evaluation criteria are as follows.
◎ ・ ・ ・ less than 40 minutes ○ ・ ・ ・ less than 40-60 minutes × ・ ・ ・ 60 minutes or more

<Fisheye>

100 parts of the obtained polyvinyl chloride, 30 parts of dioctyl phthalate, 30 parts of adipic acid ester plasticizer ("Diasizer D409" manufactured by Mitsubishi Chemical Corporation), 4.5 parts of lead-based powder stabilizer, 0.15 part of carbon A sheet having a thickness of 0.3 mm was prepared by roll kneading at 155 ° C. for 5 minutes, and the number of fish eyes per 50 mm × 50 mm was measured. The evaluation criteria are as follows.
◎ ... 0-4 pieces ○ ... 5-19 pieces × ... 20 pieces or more

Example 2
In Example 1, an aqueous dispersant solution was obtained in the same manner except that the amount of “SN deformer 777” (B) manufactured by San Nopco was changed to 0.1, and suspension polymerization was performed in the same manner. Evaluation was performed.

Example 3
In Example 1, a polyvinyl alcohol (A) was used except that polyvinyl alcohol having a saponification degree of 72 mol% and an average degree of polymerization of 800] was used to obtain a dispersant aqueous solution in the same manner, followed by suspension polymerization. Evaluation similar to Example 1 was performed.

Example 4
In Example 1, an aqueous dispersant solution was similarly used except that 17 parts of a polyvinyl alcohol resin having a saponification degree of 42 mol% and an average polymerization degree of 250 was used as a dispersion aid with respect to 100 parts of the polyvinyl alcohol resin (A). The suspension polymerization was performed in the same manner, and the same evaluation as in Example 1 was performed.

Example 5
In Example 4, a dispersion aqueous solution was similarly obtained except that a polyvinyl alcohol-based resin having a saponification degree of 48 mol% and an average polymerization degree of 250 was used as a dispersion aid, and suspension polymerization was carried out in the same manner. The same evaluation was performed.

Example 6
In Example 4, a dispersion aqueous solution was similarly obtained except that a polyvinyl alcohol resin having a saponification degree of 58 mol% and an average polymerization degree of 250 was used as a dispersion aid, and suspension polymerization was carried out in the same manner. The same evaluation was performed.

Example 7
In Example 1, an aqueous dispersion solution was similarly obtained except that the same amount of “SN deformer 444” manufactured by San Nopco was used instead of “SN deformer 777” manufactured by San Nopco, and suspension polymerization was similarly performed. Evaluation similar to Example 1 was performed.

Example 8
In Example 3, an aqueous dispersion solution was similarly obtained except that the same amount of “SN deformer 444” manufactured by San Nopco was used instead of “SN deformer 777” manufactured by San Nopco, and suspension polymerization was similarly performed. Evaluation similar to Example 1 was performed.

Comparative Example 1
In Example 1, a dispersion aqueous solution was obtained in the same manner as in Example 1 except that the “SN deformer 777” (B) manufactured by San Nopco was not added. Similar evaluations were made.

  The evaluation results of Examples and Comparative Examples are shown in Table 1.

[Table 1]
Foaming state foaming at the time of preparation
(1) (2) Fisheye
Example 1 ◎ ○ ○ ○
〃 2 ○ ○ ○ ○
３ 3 ◎ ○ ○ ◎
４ 4 ◎ ○ ○ ◎
〃 5 ◎ ○ ○ ◎
６ 6 ◎ ○ ○ ○
７ 7 ◎ ○ ○ ○
８ 8 ◎ ○ ○ ◎
Comparative Example 1 × × × ×

  The dispersant for suspension polymerization of the present invention is excellent in foaming suppression effect at the time of aqueous solution preparation, and further excellent in foaming suppression effect and scale prevention effect during suspension polymerization. Vinyl chloride, vinylidene chloride, styrene, (meth) It is useful for suspension polymerization of various vinyl compounds such as acrylate and vinyl acetate, and particularly useful for suspension polymerization of vinyl chloride. At this time, the fish eye suppression effect of the obtained polyvinyl chloride can also be exhibited.

Claims (5)

A dispersant for suspension polymerization comprising a polyvinyl alcohol-based resin (A) and a compound (B) represented by the following general formula (1).

(R1, R2, and R3 are either an alkyl group, hydrogen, or a functional group represented by the following general formula (2), at least one of which is a functional group represented by the following general formula (2). )

(R4 is methyl group, ethyl group, n is an integer of 5-50, m is an integer of 5-50) The dispersant for suspension polymerization according to claim 1, wherein the average degree of polymerization of the polyvinyl alcohol-based resin (A) measured in accordance with JISK6726 is 300 to 5,000. The dispersant for suspension polymerization according to claim 1 or 2, wherein the degree of saponification of the polyvinyl alcohol-based resin (A) measured according to JIS K6726 is 6 mol% or more. The content of the compound (B) represented by the general formula (1) is 0.01 to 5% by weight based on the polyvinyl alcohol resin (A). Dispersant for suspension polymerization. The dispersant for suspension polymerization according to any one of claims 1 to 4, wherein the dispersant is used for suspension polymerization of vinyl chloride.