KR20110116552A - Suspension polymerization of methacrylates with alkali water soluble emulsion polymer - Google Patents

Abstract

The present invention relates to a suspension polymerization method of a methacrylic resin using an alkali water-soluble emulsion polymer as a dispersion stabilizer, and has excellent polymerization stability, little scale generation in a reactor, and suppressing the generation of fine particles to maximize reaction yield and productivity. Can improve. In addition, the alkali water-soluble emulsion polymer used as a dispersion stabilizer is recovered from the aqueous medium, thereby providing an economical and simple suspension polymerization method is easy to reuse the solvent used.

Description

Suspension polymerization of methacrylates with alkali water soluble emulsion polymers using alkali water soluble polymer emulsion as dispersion stabilizer

The present invention relates to an economical suspension polymerization method of methacrylic resin, which is excellent in polymerization stability, easy to reuse of solvent, and recoverable of dispersion stabilizer using alkali water-soluble emulsion polymer as dispersion stabilizer.

The composite acrylic resin coating composition based on methyl methacrylate is a special coating product for various purposes such as waterproofing and flooring for special use, and concrete and steel coating and thin film pavement of road asphalt. It is utilized. The composite acrylic resin coating composition may realize various physical properties for use by changing various types of acrylic polymerization compositions, and has great use in the so-called elastic coating field, which is characterized by elasticity according to temperature change.

Methacrylic resin, a composite acrylic resin coating composition, is a polymer of methyl methacrylate, which is a core monomer, and one or more reactive monomers, and then dissolved in a (meth) acrylic monomer. In this case, it is a solvent-free coating that starts curing at a high speed so that both the polymer and the monomer form one polymer.

In US Patent No. 7049355, methyl methacrylate and one or more reactive monomers are polymerized by a bulk polymerization method to prepare a composite acrylic resin coating composition, and unreacted monomers are removed therefrom and purified, followed by (meth) A method of preparing a coating composition by mixing with an acrylic monomer and additives is disclosed. However, due to the characteristics of the bulk polymerization, it is not easy to control the heat of the polymerization reaction. Accordingly, even a minute change in the reaction conditions may cause a large difference in the physical properties of the polymer, particularly the molecular weight. In addition, according to the bulk polymerization method, as the degree of polymerization increases, the viscosity of the polymer increases, so that difficulty in agitation increases and recovery of the final product and separation and purification of unreacted monomers are not easy.

According to general polymer chemistry textbooks, for example, 'Principles of Polymerization (George Odian, 4th ed., Wiley-Interscience, 2004)', alternatives to bulk polymerization can be considered as solution polymerization. Although the physical properties of the polymer can be controlled, most of the solvents that can be used are environmentally harmful and considerable effort is required to remove them from the final product.

In the copolymerization of methyl methacrylate and monomers, an environmentally friendly aqueous phase may be used as the solvent for polymerization. Representative examples include emulsion polymerization and suspension polymerization. According to the emulsion polymerization method, the control of polymerization heat is excellent, a high molecular weight polymer is produced, and the conversion rate of the monomer is very high. However, since fine particles of less than 1 micrometer are formed, it is not easy to separate them by filtration.

In order to solve this problem, Korean Patent Laid-Open Publication No. 2007-0044603 discloses a powdery acrylic copolymer having an average particle diameter of at least 0.3 μm, first prepared by emulsion polymerization, and then spray-dried to obtain a powdery acrylic copolymer having an average particle size of 100 μm or less. Known methods are known, but considering the energy costs for spray drying, it is not economical, and there is a disadvantage in that it is not easy to remove additives such as surfactants.

On the other hand, suspension polymerization is commonly used to industrially polymerize vinyl-based polymers, especially methacrylate and acrylate polymers, styrene-based polymers, and polyvinyl chloride resins. There is an advantage that it is easy to recover and purify the polymer from the aqueous phase of the reaction solvent.

According to the conventional suspension polymerization method, a vinyl monomer such as (meth) acrylate is dispersed in an aqueous medium and then polymerized in the presence of an oil-soluble initiator. In general, as factors for determining the quality of the polymer produced by the suspension polymerization, the conversion rate of the monomer, the ratio of the monomer and water, the polymerization temperature, the type and amount of the initiator, the stirring speed and the form and amount of the dispersion stabilizer may be considered. . Among these, the form of the dispersion stabilizer has the most important influence on the quality of the polymer.

Preferred dispersion stabilizer conditions include: (1) a small amount of sufficient protective colloidal capacity and dispersibility, (2) less foaming during polymerization, and (3) formation of fine particles that are difficult to separate by filtration. (4) It must be possible to completely remove it from the aqueous medium after the end of the polymerization so that the polymerization medium can be reused. It is more preferable if the reaction can be separated and recovered from the medium after completion of the reaction.

As dispersion stabilizers for suspension polymerization of vinyl-based compounds, cellulose derivatives such as methyl cellulose and carboxymethyl cellulose and partially hydrolyzed polyvinyl alcohol (PVA) have been used alone or in combination.

U.S. Patent No. 4868238 discloses that hydrophobically modified nonionic cellulose ethers and copolymers thereof and ethylene oxide can be used to reduce the formation of latex particles during suspension polymerization.

 WO 91/15518 discloses a dispersant for suspension polymerization of vinyl-based compounds having an amino group, an ammonium group, a carboxyl group or a sulfonic acid group at the terminal and containing PVA having a degree of polymerization of 100 or more and a degree of hydrolysis of 50 to 90 mol%. Is described. In addition, U.S. Patent No.5629378 discloses a method of using PVA having a degree of hydrolysis of at least 60 mol% and having a mecaptan group at its end as a dispersion stabilizer for suspension polymerization. It is known to use PVA-based resins containing 1.9 mol% or more of glycol bonds as dispersion stabilizers.

As a dispersion stabilizer for suspension polymerization of a vinyl compound, a method of using a homopolymer of acrylic acid or methacrylic acid or a copolymer of these acids and methyl methacrylate as a dispersion stabilizer is also known (Korea Patent No. 10-0215515). . In addition, a method of using a slurry of poorly soluble inorganic compounds such as calcium phosphate, talc, silica and the like as a dispersion stabilizer is known from US Pat. No. 5,89285.

Meanwhile, Korean Patent No. 10-0926347 discloses a method for preparing amorphous toner particles using an alkali-soluble polymer having an ethylene or styrene monomer and a carboxylic acid group. However, when only ethylene or styrene is used as the hydrophobic monomer, improvement is necessary because it is difficult to provide sufficient dispersion stability in suspension polymerization of the methacrylic resin.

In addition, the problem of completely removing the dispersion stabilizer from the aqueous medium has not been solved so as to completely suppress the formation of fine particles in the suspension polymerization by the dispersion stabilizer and to facilitate the reuse of the aqueous medium after the completion of the polymerization.

In order to solve the problems described above, a suspension polymerization method of excellent polymerization stability and easy reuse of a solvent was found. As a result, a suspension polymerization method of a methacrylic resin using an alkali-soluble emulsion polymer as a dispersion stabilizer was found and the present invention was studied. Completed.

An object of the present invention is to provide a suspension polymerization method of a methacrylic resin using an alkali water-soluble polymer emulsion as a dispersion stabilizer.

In order to achieve the above object, the present invention is a suspension of methacryl-based resin comprising the step of suspending polymerization of methyl methacrylate and at least one reactive monomer using an alkali water-soluble polymer emulsion represented by the formula (1) as a dispersion stabilizer Provide polymerization method:

[Formula 1]

In which R 1 is hydrogen or methyl,

R 2 is straight or branched alkyl having 1 to 4 carbon atoms,

R3 is hydrogen or straight or branched alkyl having 1-18 carbon atoms,

a is a weight fraction of maleic acid or its ester compound,

b is a weight fraction of acrylic acid or methacrylic acid,

c is the weight fraction of alkyl methacrylate or alkyl acrylate,

d is the weight fraction of the styrene monomer,

a + b is 10-40 weight percent,

c + d is from 60 to 90% by weight,

c> 0.

In addition, the present invention further comprises the step of separating the polymer by filtration after the reaction is completed, and additionally adjusting the pH of the filtered aqueous medium to have a value of 3-5 to recover the alkaline water-soluble polymer from the aqueous medium. It provides a suspension polymerization method characterized in that.

Furthermore, the present invention provides an alkali water-soluble polymer emulsion represented by the formula (1) as a dispersion stabilizer used in the suspension polymerization method of methacryl resin.

In the method according to the present invention, the alkali water-soluble emulsion polymer is used as a dispersion stabilizer, which is excellent in polymerization stability, generates little scale in the reactor, and can suppress generation of fine particles that are difficult to filter. In addition, the alkali water-soluble emulsion polymer used as a dispersion stabilizer is recovered from the aqueous medium together with the polymerized copolymer, thereby providing an economical and convenient suspension polymerization method for easy reuse of the solvent used.

The present invention provides a suspension polymerization method of a methacrylic resin comprising a step of suspending polymerizing methyl methacrylate and at least one reactive monomer using an alkali water-soluble polymer emulsion represented by the following formula (1) as a dispersion stabilizer.

In which R 1 is hydrogen or methyl,

R 2 is straight or branched alkyl having 1 to 4 carbon atoms,

R3 is hydrogen or straight or branched alkyl having 1-18 carbon atoms,

a is a weight fraction of maleic acid or its ester compound,

b is a weight fraction of acrylic acid or methacrylic acid,

c is the weight fraction of alkyl methacrylate or alkyl acrylate,

d is the weight fraction of the styrene monomer,

a + b is 10-40 weight percent,

c + d is from 60 to 90% by weight,

c> 0.

Hereinafter, the present invention will be described in more detail.

In the suspension polymerization method according to the present invention, the alkali water-soluble polymer emulsion generally contains a large amount of acrylic acid, methacrylic acid or maleic acid in the molecular structure, and alkyl methacrylates such as methyl methacrylate and alkyl acrylate as comonomers. Or styrene-based monomers. The molecule contains in the range of 10-40% by weight of at least one monomer of acrylic acid, methacrylic acid, maleic acid or maleic acid ester compound, and at least one of alkyl methacrylate, alkyl acrylate or styrene monomer The copolymer alkali water-soluble polymer emulsion which comprises in the range of weight% is used.

In order to improve dispersion stability in suspension polymerization of the methacrylic resin, it is advantageous to include alkyl methacrylate in the structure of the alkali-soluble polymer emulsion, and preferably 50-80 wt%.

Alkali-soluble polymer emulsions are dispersed in the form of latex particles in an aqueous medium having an acidic or neutral pH, but are characterized by dissolving when the pH of the aqueous medium is alkaline to form a uniform phase. In this case, various acid groups included in the molecular structure may be neutralized by the cation to serve as a polymer anionic surfactant. Once dissolved, the alkaline water-soluble polymer emulsion may reduce the solubility in the medium to be recovered as solid particles by reducing the pH of the aqueous medium back to acidic.

The alkali water-soluble polymer emulsion may be prepared by an emulsion polymerization method using a surfactant or no surfactant. Alternatively, you can choose from one of a variety of products on the market. For example, Ciba Specialty Chemicals Inc. The DISPEX G40 or DISPEX GA40, Rohm and Haas's ACRYSOL ™ ASE, RHOPLEX ™ I-2426D, or RHOPLEX ™ 1531, Sartomer Company's SMAResin, Rohm and Haas's Morez101 or Morez300.

It is preferable to use the alkali water-soluble polymer emulsion having a weight average molecular weight in the range of 3,000-30,000. In order to synthesize an emulsion polymer of less than 3,000, a large amount of chain transfer agent must be included, which is not preferable to obtain an alkali water-soluble emulsion polymer itself because it significantly lowers the conversion of monomers. In addition, if it exceeds 30,000, even if the same amount is used, there is a problem that the viscosity of the polymerization medium is excessively increased and the filtration rate is lowered when the polymer is recovered from the polymerization medium.

The amount of the alkali water-soluble polymer emulsion is preferably used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of methyl methacrylate and at least one reactive monomer. The alkali water-soluble polymer emulsion added in the form of latex particles is dissolved in an aqueous medium at the same time as adding an aqueous alkali solution such as sodium hydroxide, potassium hydroxide, or ammonia water to form a homogeneous phase and serve as an ionic dispersion stabilizer.

In the suspension polymerization method according to the present invention, one or more of the reactive monomers may be used all the reactive monomers which are usually suspended, such as acrylic acid, esters of methacrylic acid or vinylaromatic monomers. For example, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, Stearyl (meth) acrylate, styrene, alpha-methyl styrene, vinyltoluene and the like can be used, and esters of acrylic acid or methacrylic acid are preferably used.

The suspension polymerization method according to the present invention uses an aqueous medium containing an aqueous alkali solution, the pH of the aqueous medium is preferably 6.5 ~ 12. If the pH of the aqueous medium is lower than the suggested range due to the insufficient amount of the aqueous alkali solution, the solubility of the alkaline water-soluble polymer emulsion is low so that it cannot fully serve as a dispersion stabilizer, and the addition of an excessively large amount does not help the dispersion stability, but the reaction process It is not preferable because a large amount of raw material must be added additionally.

In addition, in addition to the suspension polymerization reaction, a free radical initiator catalyst, a chain transfer agent or both may be used. As the free radical initiator catalyst, a 10-hour half-life, peroxides and azo compounds having a temperature of 120 ° C. or less can be used as a polymerization initiator, and preferably a 10-hour half-life and a peroxide-type polymerization initiator having a temperature of 90 ° C. or less can be used.

Such polymerization initiators include 1,1-bis (t-butylperoxycyclohexane), isobutyl peroxide, lauroyl peroxide, succinic acid peroxide, 3,5,5-trimethylhexanoyl peroxide, di-2 Ethoxyethyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, di-methoxybutyl peroxy dicarbonate, t-butyl peroxy isobutyrate, t-butyl per Oxy neodecanoate, t-butyl peroxy 2-ethylhexanoate, t-butyl peroxy pivalate, a, a-bis neodecanoyl peroxy diisopropyl benzene, cumyl peroxy neodecanoate, t -Hexyl peroxy neodecanoate, t-hexyl peroxy pivalate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy 2- Ethylhexanoate, t-amyl peroxy pivalate, t-amyl peroxy 2-ethylhexanoate, t-amyl Peroxy neodecanoate and benzoyl peroxide, and the like. In a general manner, one of the above polymerization initiators, or two or more initiators in combination is used in an amount of 0.1 to 5% by weight, preferably 0.2 to 2% by weight, based on the monomers.

It is possible to control the molecular weight of the methacrylic resin to be polymerized by adding, in a known manner, at least one chain transfer agent of 0.01-10% by weight to the suspension polymerization reaction on a monomer basis. The chain transfer agent may use any one selected from n-octyl mecaptan, alkyl mecaptan such as n-dodecyl mecaptan, ester compound of thioglycolic acid or thioglycolic acid, dimer of alpha-methyl styrene, and the like.

The suspension polymerization method of the present invention can be carried out in a classical manner. In a batch reaction, an aqueous medium comprising a dispersion stabilizer and an aqueous alkali solution is prepared and introduced into an appropriate reactor. An organic phase is prepared which contains dissolved additives in methyl methacrylate and at least one monomer, such as polymerization initiators, chain transfer agents and the like, in dissolved form, which are then added to the aqueous medium with stirring. Suspension is carried out according to known techniques. In order to obtain a polymer powder of methacrylic resin having a particle size of 20 µm or more, an impeller or anchor type stirring device is generally used. The reaction medium is then heated to initiate the polymerization.

The ratio of organic phase / aqueous medium is usually between 1/10 and 1/1, preferably between 1/5 and 1/1. It is customary for the polymerization temperature to be determined between approximately 40 ° C. and 90 ° C., depending on the polymerization initiator used.

The polymerization takes place in an adiabatic manner or by removing at least a portion of the heat of polymerization by cooling, depending on the ratio of organic phase / aqueous medium used. Suspension polymerization generally lasts from 1 hour to 3 hours. Thereafter, the temperature of the reactant is increased to sufficiently decompose the polymerization initiator, so that the polymerization initiator is substantially free from residual polymer particles. The polymerization initiator decomposition temperature at this time is terminated within 2 hours by adopting a temperature at which the half-life of the initiator is approximately 10 minutes.

After the suspension polymerization reaction is completed, the polymer is separated by filtration, and an aqueous solution of an inorganic acid such as hydrochloric acid or sulfuric acid is slowly added to the filtrate to adjust the pH of the aqueous medium to a weak acid, preferably pH 3-5. Alkali-soluble polymers can be recovered from the aqueous medium.

Alkali-soluble polymers dissolved in an aqueous medium are precipitated in the form of particles due to a decrease in solubility with decreasing pH. The polymerized methacrylic resin and the alkali water-soluble polymer precipitate are separated by filtration or centrifugation. Various salts and the like can be removed by washing with water directly on a filter paper or in a centrifuge. And recovered by drying in a suitable drying apparatus, for example in a drying furnace or in a dryer having a fluidized bed.

The average diameter of the methacrylic resin powder obtained by the above method depends on the amount of the dispersion stabilizer used, preferably having a pearl-like bead having an average diameter of 100 μm or more.

On the other hand, in the aqueous medium after filtration, the monomers and various additives used in the polymerization, in particular the alkali water-soluble polymer emulsions used as dispersion stabilizers, remain and only inorganic salts generated during the neutralization process of the alkaline aqueous medium, for example, the aqueous alkaline solution used. Depending on the type of aqueous solution and inorganic acid, sodium chloride, potassium chloride, ammonium chloride, sodium sulfide, potassium sulfide, or ammonium sulfide may remain in a small amount, which may be removed using a general wastewater treatment process such as ion exchange or water purification.

In another aspect, the present invention provides an alkali water-soluble polymer emulsion represented by the following formula 1 as a dispersion stabilizer used in the suspension polymerization method of the methacrylic resin:

[Formula 1]

In which R 1 is hydrogen or methyl,

R 2 is straight or branched alkyl having 1 to 4 carbon atoms,

R3 is hydrogen or straight or branched alkyl having 1-18 carbon atoms,

a is a weight fraction of maleic acid or its ester compound,

b is a weight fraction of acrylic acid or methacrylic acid,

c is the weight fraction of alkyl methacrylate or alkyl acrylate,

d is the weight fraction of the styrene monomer,

a + b is 10-40 weight percent,

c + d is from 60 to 90% by weight,

c> 0.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited to the following examples.

Example  1-1: Alkali Water Soluble Polymer emulsion  Using dispersion stabilizer Methacryl  Resin Suspension polymerization  One

(1) Synthesis of Alkali Water Soluble Polymer Emulsion

392 g of distilled water was added to a 1 L four-neck glass reactor equipped with a stirrer, a thermometer, and a reflux condenser, 1.2 g of sodium bicarbonate (Sigma-Aldrich) and 1.6 g of sodium persulfate (Sigma-Aldrich) were dissolved. The temperature in the reactor was raised to 60 ° C using. A monomer mixture consisting of 48 g of acrylic acid, 130 g of methyl methacrylate, and 22 g of alpha-methyl styrene was charged to the reactor over 100 minutes. After the stirring was continued for 6 hours to complete the reaction. The solid content measured after evaporation of the aqueous medium and the volatile component was 30% by weight, and gel permeation chromatography was measured using tetrahydrofuran as a mobile phase to confirm that the weight average molecular weight was 18,500.

(2) Suspension Polymerization of Methacrylic Resin Using Alkali Water Soluble Polymer Emulsion Dispersant

250 g of distilled water was added to a 1 L four-necked glass reactor equipped with a stirrer, a thermometer, and a reflux condenser, and the alkali water-soluble polymer emulsion (A) obtained as a dispersion stabilizer was neutralized with ammonia water, and 4 g of a 15 wt% aqueous solution was added thereto. This includes 35 g of methyl methacrylate (MMA), 15 g of butyl methacrylate (BMA) and 0.5 g of alpha-methyl styrene dimer (a-MSD, Sigma-Aldrich), a chain transfer agent, and benzoyl peroxide (BPO, 1 g of Arkema Inc, Luperox A75) was mixed to prepare an organic phase and then charged into a reactor. The temperature in the reactor was raised to 80 ° C. using an oil bath. The polymerization was carried out over about 3 hours and then stirred at a temperature of 90 ° C. for 6 hours to induce decomposition of the residual polymerization initiator. Thereafter, the temperature of the reactant was cooled to room temperature, filtered to separate the polymer, and 3 g of 1 N aqueous hydrochloric acid solution was slowly added with stirring to recover the alkali water-soluble polymer.

Example  1-2-1-10: Alkali-soluble polymer emulsion  Using dispersion stabilizer Methacryl  Resin Suspension polymerization  One

Copolymer suspension of methyl methacrylate (MMA) and butyl methacrylate (BMA) was carried out in the same manner as in Example 1-1, wherein the used methyl methacrylate (MMA) and butyl methacrylate ( The amount of BMA) and the amount of the aqueous alkali solution, the type and amount of the chain transfer agent, the type and amount of the initiator, the amount of aqueous hydrochloric acid solution and the like are summarized in Table 1.

Example  2-1: alkali water-soluble polymer emulsion  Using dispersion stabilizer Methacryl  Resin Suspension polymerization  2

(1) Synthesis of Alkali Water Soluble Polymer Emulsion

392 g of distilled water was added to a 1 L four-neck glass reactor equipped with a stirrer, a thermometer, and a reflux condenser, 1.2 g of sodium bicarbonate (Sigma-Aldrich) and 1.6 g of sodium persulfate (Sigma-Aldrich) were dissolved. The temperature in the reactor was raised to 80 ° C using. A monomer mixture consisting of 36 g of acrylic acid, 12 g of maleic acid, 130 g of methyl methacrylate, 22 g of alpha-methyl styrene, and 1 g of octyl mecaptan was charged to the reactor over 100 minutes. After the stirring was continued for 6 hours to complete the reaction. The solid content measured after evaporation of the aqueous medium and the volatile component was 30% by weight, and gel permeation chromatography was measured using tetrahydrofuran as a mobile phase to confirm that the weight average molecular weight was 8,500.

(2) Suspension Polymerization of Methacrylic Resin Using Alkali Water Soluble Polymer Emulsion Dispersant

250 g of distilled water was added to a 1 L four-necked glass reactor equipped with a stirrer, a thermometer, and a reflux condenser, and the alkali water-soluble polymer emulsion (B) obtained as a dispersion stabilizer was neutralized with ammonia water, and 4 g of a 15 wt% aqueous solution was added thereto. This includes 35 g of methyl methacrylate (MMA), 15 g of butyl methacrylate (BMA) and 0.5 g of alpha-methyl styrene dimer (a-MSD, Sigma-Aldrich), a chain transfer agent, and benzoyl peroxide (BPO, 1 g of Arkema Inc, Luperox A75) was mixed to prepare an organic phase and then charged into a reactor. The temperature in the reactor was raised to 80 ° C. using an oil bath. The polymerization was carried out over about 3 hours and then stirred at a temperature of 90 ° C. for 6 hours to induce decomposition of the residual polymerization initiator. Thereafter, the temperature of the reactant was cooled to room temperature, filtered to separate the polymer, and 3 g of 1 N aqueous hydrochloric acid solution was slowly added with stirring to recover the alkali water-soluble polymer.

Example  2-2 to 2-3: alkali water-soluble polymer emulsion  Using dispersion stabilizer Methacryl  Resin Suspension polymerization  2

Copolymer suspension of methyl methacrylate (MMA) and butyl methacrylate (BMA) was carried out in the same manner as in Example 2-1, wherein the used methyl methacrylate (MMA) and butyl methacrylate ( The amount of BMA) and the amount of the aqueous alkali solution, the type and amount of the chain transfer agent, the type and amount of the initiator, the amount of aqueous hydrochloric acid solution and the like are summarized in Table 1.

Comparative example

1 g of 2-hydroxy ethyl cellulose (HEC, Sigma-Aldrich) (Comparative Example 1), polyvinyl alcohol resin (PVA, Sigma-Aldrich) having a degree of hydrolysis of 99% instead of the alkali water-soluble polymer emulsion used in the examples. 1 g (Comparative Example 2) and a copolymer of acrylic acid and styrene neutralized with aqueous ammonia (average molecular weight 25,000) were used as a dispersion stabilizer using 2 g (Comparative Example 3) of 30 wt% aqueous solution of methyl methacrylate and butyl methacrylate. Suspension polymerization was carried out. Table 1 shows the amount of distilled water, methyl methacrylate (MMA) and butyl methacrylate (BMA) used, the type and amount of chain transfer agent, the type and amount of initiator, and the like.

Example Dispersion
stabilizator Distilled water MMA BMA Chain transfer agent Initiator 1N-NH4OH 1N-HCl 1-1 4 g
(A) 250 g 40 g 10 g 0.5 g
(MSD) 1 g
(BPO) 2 g 3 g 1-2 4 g
(A) 250 g 35 g 15 g 0.5 g
(MSD) 1 g
(BPO) 2 g 3 g 1-3 4 g
(A) 250 g 30 g 20 g 0.5 g
(MSD) 1 g
(BPO) 2 g 3 g 1-4 4 g
(A) 250 g 25 g 25 g 0.5 g
(OM) 1 g
(LPO) 2 g 3 g 1-5 2 g
(A) 250 g 40 g 10 g 0.5 g
(OM) 1 g
(LPO) 2 g 3 g 1-6 1 g
(A) 250 g 40 g 10 g 0.5 g
(OM) 1 g
(LPO) 2 g 3 g 1-7 2 g
(A) 250 g 50 g 20 g 0.7 g
(OM) 1 g
(LPO) 2 g - 1-8 2 g
(A) 250 g 35 g 15 g 0.5 g
(OM) 1 g
(LPO) 4 g - 1-9 2 g
(A) 250 g 35 g 15 g 0.5 g
(OM) 1 g
(LPO) 6 g 3 g 1-10 2 g
(A) 250 g 35 g 15 g 1.0 g
(OM) 1 g
(LPO) 2 g 3 g 2-1 4 g
(B) 250 g 35 g 15 g 0.5 g
(MSD) 1 g
(BPO) 2 g 3 g 2-2 4 g
(B) 250 g 30 g 20 g 0.5 g
(OM) 1 g
(LPO) 2 g 3 g 2-3 4 g
(B) 250 g 25 g 25 g 0.5 g
(OM) 1 g
(LPO) 2 g 3 g Comparative Example 1 1 g 250 g 35 g 15 g 0.5 g
(MSD) 1 g
(BPO) - - Comparative Example 2 1 g 250 g 35 g 15 g 0.5 g
(MSD) 1 g
(BPO) - - Comparative Example 3 2 g 250 g 35 g 15 g 0.5 g
(MSD) 1 g
(BPO) - -

MSD: alpha-methyl styrene dimer

OM: Octyl Mecaptan

LPO: lauroyl peroxide

BPO: Benzoyl Peroxide

Experimental Example  1: polymerized Methacryl  Analysis of resin

For Examples 1-1 to 1-10 and 2-1 to 2-3, after completion of the reaction, the resultant was filtered through filter paper under reduced pressure, washed with distilled water, and dried to obtain a polymer. The mass was measured after drying and the polymerization yield was calculated by comparison with the theoretical yield. The weight average molecular weight was measured by gel permeation chromatography using tetrahydrofuran as a mobile phase. 1N hydrochloric acid aqueous solution was added to the filtered aqueous medium, and the precipitate was filtered to recover the alkali water-soluble polymer. Analysis of the filtrate using liquid chromatography and gel permeation chromatography with water as the mobile phase revealed no residual alkali-soluble polymers or other reaction raw materials.

On the other hand, the polymerization stability was excellent for the comparative example, but after the filtration of the polymer particles, a large amount of fine particles were present in the filtrate. It was hard to do. Therefore, reuse of the aqueous medium is not easy.

Table 2 summarizes the weight average molecular weight of the polymerized methacrylic resin, the aqueous medium state after filtration, and the recovery rate for each Example.

Weight average molecular weight Aqueous medium after filtration Recovery rate (%) 1-1 78,000 transparent 94.1 1-2 73,000 transparent 97.1 1-3 73,000 transparent 96.8 1-4 69,000 transparent 93.1 1-5 81,000 transparent 94.4 1-6 77,000 transparent 97.6 1-7 71,000 transparent 95.2 1-8 66,000 Blue and transparent 97.3 1-9 68,000 Blue and transparent 94.6 1-10 52,000 transparent 94.3 2-1 54,000 transparent 95.5 2-2 61,000 transparent 96.2 2-3 58,000 transparent 93.8 Comparative Example 1 80,000 White and opaque 88.1 Comparative Example 2 75,000 White and opaque 92.8 Comparative Example 3 110,000 White and opaque 89.2

Claims (11)

A suspension polymerization method of a methacrylic resin comprising the step of suspending polymerizing methyl methacrylate and at least one reactive monomer using an alkali water-soluble polymer emulsion represented by the following formula (1) as a dispersion stabilizer:
[Formula 1]

In which R 1 is hydrogen or methyl,
R 2 is straight or branched alkyl having 1 to 4 carbon atoms,
R3 is hydrogen or straight or branched alkyl having 1-18 carbon atoms,
a is a weight fraction of maleic acid or its ester compound,
b is a weight fraction of acrylic acid or methacrylic acid,
c is the weight fraction of alkyl methacrylate or alkyl acrylate,
d is the weight fraction of the styrene monomer,
a + b is 10-40 weight percent,
c + d is from 60 to 90% by weight,
c> 0.
The suspension polymerization method of methacryl-based resin according to claim 1, wherein c in Formula 1 is 50 to 80% by weight.
The method according to claim 1, wherein the alkali water-soluble polymer emulsion of Formula 1 has a weight average molecular weight in the range of 3,000-30,000 suspension polymerization method of methacryl-based resin.
The suspension polymerization method of methacrylic resin according to claim 1, wherein 0.01 to 5 parts by weight of an alkali water-soluble polymer emulsion of Formula 1 is used based on 100 parts by weight of methyl methacrylate and at least one reactive monomer.
The suspension polymerization method of methacrylic resin according to claim 1, wherein the one or more reactive monomers are acrylic acid, methacrylic acid esters or vinyl aromatic monomers.
The method of claim 5, wherein the one or more reactive monomers are ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate And lauryl (meth) acrylate, stearyl (meth) acrylate, styrene, alpha-methyl styrene, and vinyltoluene monomers.
The suspension polymerization method of methacrylic resin according to claim 5, wherein the reactive monomers are esters of acrylic acid or methacrylic acid.
The suspension polymerization method according to claim 1, wherein the suspension polymerization method uses an aqueous medium containing an aqueous alkali solution, and the pH of the aqueous medium is 6.5 to 12.
The suspension polymerization method of methacrylic resin according to claim 1, wherein a free radical initiator catalyst, a chain transfer agent, or both are used.
The method of claim 1, further comprising filtering the polymerized methacrylic resin after the polymerization reaction is completed, and additionally adjusting the pH of the aqueous medium to 3-5 to recover the alkali-soluble polymer from the aqueous medium. Suspension polymerization method of methacrylic resin.
An alkali water-soluble polymer emulsion represented by the following Chemical Formula 1 as a dispersion stabilizer used in the suspension polymerization method of the methacryl-based resin of claim 1:
[Formula 1]

In which R 1 is hydrogen or methyl,
R 2 is straight or branched alkyl having 1 to 4 carbon atoms,
R3 is hydrogen or straight or branched alkyl having 1-18 carbon atoms,
a is a weight fraction of maleic acid or its ester compound,
b is a weight fraction of acrylic acid or methacrylic acid,
c is the weight fraction of alkyl methacrylate or alkyl acrylate,
d is the weight fraction of the styrene monomer,
a + b is 10-40 weight percent,
c + d is from 60 to 90% by weight,
c> 0.