KR20020069054A - Saponification method of poly(vinyl acetate) and poly(vinyl alcohol) of microball-shaped particle prepared thereby - Google Patents

Abstract

PURPOSE: A saponification method of polyacetic acid vinyl and micro spherical granular poly(vinyl alcohol) prepared by the method are provided, to prepare poly(vinyl alcohol) from acetic acid vinyl directly without separation and drying, thereby allowing the continuous process to be carried out. CONSTITUTION: The saponification method comprises the steps of adding polyacetic acid vinyl prepared by suspension polymerization to the mixture comprising 0.01-0.1 mol of methanol, 0.01-0.15 mol of a salt selected from the group consisting of NaOH, KOH, Ca(OH)2 and LiOH, 0.01-0.1 mol of a salt selected from the group consisting of sodium sulfate, sodium sulfite, sodium chloride, calcium sulfate and magnesium sulfate, and 1.0-2.5 mol of H2O based on 1 g of polyacetic acid vinyl particle, without the purification, separation and drying of polyacetic acid vinyl; and saponifying it at 0-90 deg.C. The prepared micro spherical granular poly(vinyl alcohol) has a core/shell dual structure comprising a polyacetic acid vinyl core and a shell whose degree of saponification of polyacetic acid vinyl is 20-99.9%.

Description

Saponification method of poly (vinyl acetate) and poly (vinyl alcohol) of microball-shaped particle prepared hence

The present invention relates to a saponification method of polyvinyl acetate and a fine spherical particulate polyvinyl alcohol produced by the same, and more specifically, to a polyvinyl acetate prepared by high efficiency by suspension polymerization of vinyl acetate (vinyl acetate) The present invention relates to a method for producing fine spherical particulate polyvinyl alcohol having a uniform size distribution by directly saponification without going through.

In 1924, Hermann and W. Haehnel (Germany Patent No. 450,286) first discovered polyvinyl alcohol during the saponification test of poly (vinyl acetate), a vinyl ester polymer such as polyvinyl acetate. It is a hydroxy group-containing linear crystalline polymer produced by saponification of a compound, and has been widely used in the production of scavenger, clothing fibers, industrial fibers and membranes according to its molecular weight.

In such industrial applications, methods for producing polyvinyl alcohol are generally used for polymerization of monomer vinyl acetate, separation, purification and drying of polymerized polyvinyl acetate, dissolution and saponification of dried polyvinyl acetate in methanol, and Only through a complicated process of separation, purification and drying of polyvinyl alcohol prepared by saponification, a polyvinyl alcohol chip capable of the above-described application was obtained. Attempts to simplify the process for producing such polyvinyl alcohol have rarely been successful.

In addition, polyvinyl alcohol is used exclusively as an embolic material compared to other materials due to its biocompatibility, ease of procedure, control of molecular weight and stereoregularity by polymerization, and control of particle size. In addition, polyvinyl alcohol particle embolism is mainly used for embolization of diseases such as malignant liver tumor, hepatic arteriovenous malformation, cerebral arteriovenous malformation, and vascular tumors of various sites, and is the most widely used embolic material among the existing embolic materials. Many studies are in progress.

However, it has been reported that polyvinyl alcohol used in previous studies and clinically causes side effects such as inflammation in the embolized blood vessels. This inflammatory response was expected to be caused by the sharp edges of the materials used. In addition, as a result of embolization with conventional polyvinyl alcohol for neonatal arteriovenous abnormalities with respect to the size of embolic particles, it has been demonstrated that non-uniformity of particle size is related to patient death. Since natural polymers such as gelatin are obtained directly from nature without being synthesized, it is impossible to control their chemical size (molecular weight, molecular weight distribution and branching degree) and physical size (particle size and shape).

Polyvinyl alcohol embolizers (currently: " Contour", "Embosphere", "UltraDrivalon"), which are widely used as embolic materials, are also used for the particle size. Although the uniformity is very low, the size distribution of commercially available samples ranges from 50-150 μm, 150-250 μm, 250-350 μm, and 350-550 μm for excellent products, but in practice, the size range is 1 μm to 1400 μm. It has been reported to have a non-uniform physical size distribution up to larger particles. In addition, it has a very rough and sharp surface, indicating that there is a considerable distance from the spherical particles having a uniform size distribution.

Recently, in order to develop an ideal microspherical embolism, porous cellulose, gelatin,

Research has been conducted to produce spherical particles on various polymer materials except polyvinyl alcohol, such as collagen and collagen coated acrylic, but for the purpose of the procedure, spherical particles having various sizes have a uniform size distribution. Not only are they difficult to obtain, their permanent occlusion effects are still unknown.

Suspension polymerization is not only easy to separate the fine spherical polymer from the reaction system by using an initiator and suspending agent dissolved in the monomer, but also a high molecular weight polyvinyl chloride because the polymerization mechanism of the individual suspended particles is the same as that of the bulk. It is relatively advantageous in producing high molecular weight polyvinyl acetate having excellent linearity for obtaining alcohol. In addition, since the limitation of the conversion rate due to the generation of heat of reaction caused by the method of bulk polymerization or solution polymerization can be overcome, it is possible to polymerize with high efficiency of 80% or more.

Therefore, unlike other polymerization methods, since the amount of monomer and initiator remaining after the reaction is completed can be controlled to be relatively small, it is possible to omit the purification process for saponifying the polymer.

Suspension stabilizers used for suspension polymerization of vinyl acetate are polyvinyl alcohol, arabic gum, hydroxyethyl cellulose, methyl cellulose, and starch with a saponification degree of 88%. , Polyacrylic salt (sodium polyacrylate), polymethacrylic salt (sodium polymethacrylate), gelatin (gelatine) and equimolar copolymer of styrene-maleic anhydride neutralized with sodium hydroxide or ammonia water. Conventionally, high-temperature polyvinyl acetate is prepared at a high efficiency of 80% or more by low-temperature suspension polymerization of vinyl acetate, and then separated and purified, and then saponified by various methods, 50-70 μm, which can be used for occlusion of vascular diseases. 70-90 μm, 90-100 μm, 100-120 μm, 120-150 μm, 150-180 μm, 180-200 μm, 200-220 μm, 220-250 μm, 250-300 μm, 300-350 μm, Particle high molecular weight polyvinyl with sizes of 350-400 μm, 400-450 μm, 450-500 μm, 500-600 μm, 600-700 μm, 700-800 μm, 800-900 μm and 900-1000 μm Alcohol has been prepared. However, this method is obtained by separating and purifying suspension-polymerized polyvinyl acetate and saponifying. It is not known how the polymerization and saponification are continuously performed using one batch.

An object of the present invention is to provide an efficient saponification method of polyvinyl acetate by omitting a separation step and directly performing saponification.

Another object of the present invention is to provide a method for efficiently preparing microspherical particulate polyvinyl alcohol having a uniform size distribution so as to be useful as a medical embolic agent.

The saponification method of polyvinyl acetate of the present invention for achieving the above object is 0.01 to 0.1 mol of methanol to 1 g of the polyvinyl acetate particles, without undergoing purification and separation drying process of the polyvinyl acetate prepared by suspension polymerization 0.01 to 0.15 mol of a salt selected from sodium, potassium hydroxide, calcium hydroxide, and lithium hydroxide, 0.01 to 0.1 mol selected from sodium sulfate, sodium sulfite, sodium chloride, calcium sulfate and magnesium sulfate, and 1.0 to 2.5 mol of water. Methanol, salts and water are added to an alkaline bath of an aqueous solution, characterized in that the continuous batch saponification at 0 to 90 ℃.

In the step, the alkali bath may be added to the polymerization bath of polyvinyl acetate in which the polymerization is completed.

The microspherical particulate polyvinyl alcohol according to the present invention is produced by the saponification method, and the surface is polyvinyl alcohol having a saponification degree of 20 to 99.9% of polyvinyl acetate, and a double structured particle having a polyvinyl acetate inside and uniform. It is characterized by having a size distribution.

Saponification of polyvinyl acetate is generally known by using alkalis, acids, and amines, and the most commonly used method is saponification using an aqueous sodium hydroxide solution as an alkaline agent.

In the present invention, the polymerization before saponification is suspended at 25-50 ° C. with an azobisdimethylvaleronitrile (2,2′-azobis (2,4-dimethylvaleronitrile)) which can initiate the polymerization of vinyl acetate even at 50 ° C. or lower. Polymerized. Azobisdimethylvaleronitrile has the advantage of being capable of polymerization at relatively low initiation temperature (below 50 ℃) compared to the existing azobisisobutyronitrile and benzoyl peroxide, which are widely used as initiators of addition polymerization because of its structural characteristics. Have

In the present invention, continuous saponification in one batch by adding an alkali agent or continuously supplying the polymerization liquid to the alkaline bath without a separate separation process for polyvinyl acetate produced at a high conversion rate of 80% or more by suspension polymerization Was implemented. The present invention, which allows polyvinyl alcohol to be obtained directly from vinyl acetate by performing polymerization and saponification continuously, greatly simplifies the manufacturing process of polyvinyl alcohol, thereby enabling innovative improvements in production time as well as cost reduction. give.

In general, saponification of polyvinyl acetate is performed by completely dissolving polyvinyl acetate in methanol and then dropping an alkaline solution. The polyvinyl alcohol produced by this process has a very irregular surface in appearance and a very wide size distribution. Recently, polyvinyl acetate is used as a particulate embolic agent, but its biocompatibility has not been recognized, and it is not widely used clinically.

In addition, the saponification of the existing polyvinyl acetate has a disadvantage that the separation and purification process must be accompanied, and the complexity of the process and the increase in production costs are accompanied. There is a need for the development of an economical saponification method that can maintain particle size, prevent particle association, and omit separation and purification processes.

The saponification method of polyvinyl acetate has conventionally realized a heterogeneous saponification of the suspension polymer of polyvinyl acetate, and this method converts polyvinyl acetate particles prepared by suspension polymerization into sodium sulfate, sodium sulfite, calcium sulfate, and sulfuric acid. Various types of salts such as magnesium and sodium chloride are used as dispersants and antistatic agents, and then separated into individual particles, followed by non-uniform surface saponification to maintain the shape of the sphere. Polyvinyl alcohol / poly saponified only the surface of polyvinyl acetate The preparation of a particulate embolic agent having a core / shell dual structure of vinyl acetate, which also involves separation and purification, which is a necessity of increasing the complexity and cost of the production process.

In the present invention, the fine spherical particulate polyvinyl acetate obtained by the suspension polymerization of vinyl acetate in a high yield of 70% or more is added or polymerized into an alkaline aqueous bath containing an alkali, a swelling agent, and a dispersant without undergoing purification and separation drying. By adding the above-mentioned aqueous alkali solution preparation to the liquid and saponifying continuously, the saponification is carried out while maintaining the swelling state.

The present invention considers that the swelled polyvinyl acetate particles immediately after suspension polymerization do not occur with the electrostatic attraction of the particles unlike the dried particles. By adjusting the concentration, it was confirmed that the association between the particles can be minimized in the aqueous dispersion state after polymerization. In general, particulate polyvinyl acetate produced by suspension polymerization loses its swelling state due to dehumidification in the separation and purification process and subsequent drying process, so as to swell it in a state capable of performing non-uniform saponification. This requires a lot of time and money, with careful attention to the concentration of solvents and non-solvents.

The present invention provides a polyvinyl acetate polymer solution prepared by suspension polymerization, which is not isolated and purified, 0.01 to 0.1 mol of sodium, 0.01 to 0.15 mol of salt selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide, sodium sulfate. Or a dispersant salt selected from sodium sulfite, sodium chloride, calcium sulfate and magnesium sulfate in an alkali bath comprising an aqueous solution in which the methanol, salts and water are mixed at a ratio of 0.01 to 0.1 mol and water 1.0 to 2.5 mol, or the alkali The bath is continuously batch saponified at 0 to 90 ° C. by adding the polymerizer to the polymerization complete.

In the present invention, continuous saponification is carried out while maintaining and expanding the swelling state of the polyvinyl acetate particles obtained by suspension polymerization.

The present invention is expected to improve the cost competitiveness and production efficiency of polyvinyl alcohol products including polyvinyl alcohol adjuvant, film and fiber in the future by manufacturing polyvinyl alcohol having excellent properties at a low price and in a short time. .

The present invention will be described in more detail below.

The saponification process of the high molecular weight polyvinyl acetate of the present invention has a significant difference from the two known methods.

The existing two saponification methods of polyvinyl acetate are as follows.

First, polyvinyl acetate is completely dissolved in methanol, and then a high-molecular weight polyvinyl alcohol in a precipitated state can be obtained by dropwise addition of a high concentration alkali agent in an aqueous sodium hydroxide solution.

Second, the spherical polyvinyl acetate obtained by suspension polymerization is separated into individual particles by using various salts as dispersant and antistatic agent, and then the shape of the sphere is maintained by uneven surface saponification, and the surface of polyvinyl acetate is saponified. Particles having a core / shell dual structure of alcohol / polyvinyl acetate can be obtained.

Both of the above methods require separation and purification of polymerized polyvinyl acetate, and polymerization and saponification reactions are performed in separate processes, and thus continuous processing is impossible. In particular for the second method, a milling process must be involved to prevent and dissociate the particles between the particles due to electrostatic attraction of the polyvinyl acetate on the dried microspherical particles.

Hereinafter, specific examples and comparative examples of the present invention will be described.

However, the following examples should not be construed as limiting the scope of the invention as they are for illustration only.

Example 1

In a 250 ml four-necked flask equipped with a thermometer, nitrogen inlet, cooling tower, and anchor type stirrer, 10 mol of distilled water and suspension stabilizer for polyvinyl alcohol 7.9 × 10 ^-4 mol (saturation degree: 88%,) for 1 mol of vinyl acetate. Number average molecular weight: 127,000), dissolved by stirring at 50 ° C, cooled to room temperature, passed through pyrogallol-alkali aqueous solution trap and dryer light trap to remove oxygen, and then passed through nitrogen for 2 hours to remove oxygen and acetic acid. 0.11 mol of vinyl and azobisdimethylvaleronitrile as an initiator were added to 1.0 × 10 ⁻³ mol / mol _VAc , and oxygen was removed for 1 hour. Then, the temperature was raised to 50 ° C., the polymerization temperature. Polymerized for 48 hours.

To 1 g of polymerized polyvinyl acetate, 0.09 mol of sodium hydroxide, 0.009 mol of sodium sulfate, and 0.06 mol of methanol were added dropwise with stirring to the alkaline bath in an alkaline bath of 1.13 mol of distilled water, followed by saponification at 50 ° C. for 24 hours. % Polyvinyl alcohol was obtained.

Example 2

The alkaline liquid having the same composition as in Example 1 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 73%.

Example 3

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was an alkali in which 0.06 mol of sodium hydroxide, 0.017 mol of sodium sulfate and 0.06 mol of methanol were dissolved in 1.13 mol of distilled water with respect to 1 g of the polymerized polyvinyl acetate. The polymerization solution was added dropwise to the bath with stirring, followed by saponification at 60 ° C. for 16 hours to obtain polyvinyl alcohol having a saponification degree of 97%.

Example 4

An alkaline liquid having the same composition as in Example 3 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 60 ° C. for 16 hours to obtain polyvinyl alcohol having a saponification degree of 96%.

Example 5

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkali bath as the composition in Example 3, followed by 24 hours at 50 ° C. Saponification gave polyvinyl alcohol having a saponification degree of 66%.

Example 6

An alkaline liquid having the same composition as in Example 3 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 61%.

Example 7

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkali bath as the composition in Example 3, and then at 40 ° C. for 32 hours. Saponification gave polyvinyl alcohol having a saponification degree of 42%.

Example 8

An alkaline liquid having the same composition as in Example 3 was added dropwise to the reactor in which the polymerization of Example 1 was completed while stirring, followed by saponification at 40 ° C. for 32 hours to obtain polyvinyl alcohol having a saponification degree of 43%.

Example 9

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkali bath as the composition in Example 1, followed by saponification at 40 ° C. for 32 hours to obtain polyvinyl alcohol having a saponification degree of 52%.

Example 10

The alkaline liquid having the same composition as in Example 1 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 40 ° C. for 32 hours to obtain polyvinyl alcohol having a degree of saponification of 53%.

Example 11

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkaline bath as in the composition of Example 1, followed by saponification at 65 ° C. for 15 hours to obtain polyvinyl alcohol having a saponification degree of 99.9%.

Example 12

Alkaline liquid having the same composition as in Example 1 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 65 ° C. for 15 hours to obtain polyvinyl alcohol having a saponification degree of 99.9%.

Example 13

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was an alkali in which 0.12 mol of sodium hydroxide, 0.009 mol of sodium sulfate, and 0.06 mol of methanol were dissolved in 1.13 mol of distilled water with respect to 1 g of polymerized polyvinyl acetate. The polymerization solution was added dropwise to the bath with stirring, followed by saponification at 55 ° C. for 22 hours to obtain polyvinyl alcohol having a saponification degree of 99.9%.

Example 14

An alkaline liquid having the same composition as in Example 13 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 55 ° C. for 22 hours to obtain polyvinyl alcohol having a saponification degree of 84%.

Example 15

Suspension polymerization of vinyl acetate was carried out as in Example 1. The saponification of the polymerized polyvinyl acetate was an alkali in which 0.09 mol of sodium hydroxide, 0.026 mol of sodium sulfate and 0.09 mol of methanol were dissolved in 1.13 mol of distilled water with respect to 1 g of the polymerized polyvinyl acetate. The polymerization solution was added dropwise to the bath with stirring, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 99%.

Example 16

Alkaline liquid having the same composition as in Example 15 was added dropwise while stirring to the reactor in which the polymerization of Example 1 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 99%.

Example 17

Suspension polymerization of vinyl acetate was carried out in the same manner as in Example 1 except that azobisdimethylvaleronitrile, which was an initiator, was set to 2.0 × 10 ⁻⁴ mol / mol _VAc . The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkali bath as in the composition of Example 3, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 68%.

Example 18

An alkaline liquid having the same composition as in Example 3 was added dropwise while stirring to the reactor in which the polymerization of Example 17 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 68%.

Example 19

Suspension polymerization of vinyl acetate was carried out in the same manner as in Example 1 except that azobisdimethylvaleronitrile, which was an initiator, was set to 5.0 × 10 ⁻³ mol / mol _VAc . The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkaline bath as in the composition of Example 3, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 79%.

Example 20

Alkaline liquid having the same composition as in Example 3 was added dropwise while stirring to the reactor in which the polymerization of Example 19 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 80%.

Example 21

Suspension polymerization of vinyl acetate was carried out as in Example 1 except that 0.22 mol of vinyl acetate was added. The saponification of the polymerized polyvinyl acetate was added dropwise while stirring the polymerization solution to the same alkaline bath as in the composition of Example 3, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 80%.

Example 22

An alkaline liquid having the same composition as in Example 3 was added dropwise while stirring to the reactor in which the polymerization of Example 21 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 79%.

Example 23

Suspension polymerization of vinyl acetate was carried out as in Example 1. The alkali bath for saponification of the polymerized polyvinyl acetate was the same as in Example 3 except that potassium hydroxide was used as the alkali. The polymerization solution was added dropwise to the alkali bath with stirring, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 86%.

Example 24

An alkaline liquid having the same composition as in Example 23 was added dropwise while stirring to the reactor in which the polymerization of Example 3 was completed, followed by saponification at 50 ° C. for 24 hours to obtain polyvinyl alcohol having a saponification degree of 88%.

Comparative Example 1

In a 200 ml two-necked flask equipped with a thermometer and a cooling tower, 2 g of polyvinyl acetate particles prepared by suspension polymerization were completely dissolved in 100 ml of methanol, and 2.5 ml of 40% sodium hydroxide solution was slowly dropped, followed by stirring at room temperature for 5 hours. After filtration, the mixture was washed thoroughly with methanol to remove sodium acetate and dried at 50 ° C. under vacuum to obtain polyvinyl alcohol having a saponification degree of 99.9%.

The comparative example method is a general saponification method of polyvinyl acetate, although it is possible to obtain a high degree of saponification of 99.9%, but the process of re-dissolution for the separation, purification and saponification of the polymer is essential. There is a big difference from the invention.

According to the present invention, the polyvinyl acetate prepared by suspension polymerization is added without an additional purification and separation process, or by continuously supplying the polymerization solution to the alkaline bath to achieve continuous saponification in one batch. , Polyvinyl alcohol can be obtained directly from vinyl acetate by continuous polymerization and saponification, thereby simplifying the production process of polyvinyl alcohol, thereby achieving innovative improvements in production time as well as cost reduction. There is.

While the invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims. .

Claims (3)

0.01 to 0.1 mol of methanol, 0.01 to 0.1 mol of sodium, sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide, 0.01 to 0.1 g of the polyvinyl acetate prepared by suspension polymerization, without undergoing purification and separation and drying. 0.15 mol, sodium sulfate, sodium sulfite, sodium chloride, calcium sulfate and magnesium sulfate in a ratio of 0.01 to 0.1 mol, and water 1.0 to 2.5 mol in an alkaline bath made of an aqueous solution mixed with methanol, salts and water A method of saponification of polyvinyl acetate, characterized in that it is subjected to continuous batchwise saponification at 0 to 90 ° C. The method of claim 1, Said alkali bath is put into the polyvinyl acetate polymerization bath which completed the superposition | polymerization, and saponification method of the said polyvinyl acetate characterized by continuous batch saponification at 0-90 degreeC. A polyvinyl alcohol having a saponification degree of 20 to 99.9% of polyvinyl acetate, the inside of which is a core / shell dual structure particle of polyvinyl acetate, and is uniformly distributed in size according to the saponification method of claim 1 or 2. Microspherical particulate polyvinyl alcohol having a.