KR100837687B1 - A process for preparing polyvinylalcohol with extruder, and highly saponicated polyvinylalcohol prepared therefrom - Google Patents

Abstract

The present invention relates to a method for producing polyvinyl alcohol using an extruder, and to a high polymerization high gum type polyvinyl alcohol prepared therefrom, and more specifically, to a polyvinylacetate solution and an alkali in an extruder. It relates to a method for producing polyvinyl alcohol comprising the step, and polyvinyl alcohol prepared therefrom.

The polyvinyl alcohol production method of the present invention can obtain a high degree of polymerization and high saponification polyvinyl alcohol in a short time, the productivity and efficiency of the process is increased, and there is an advantage of easy workability.

Polyvinyl acetate, polyvinyl alcohol, saponification, extruder

Description

A process for producing polyvinyl alcohol using an extruder, and a high-tech polyvinyl alcohol prepared therefrom {A PROCESS FOR PREPARING POLYVINYLALCOHOL WITH EXTRUDER, AND HIGHLY SAPONICATED POLYVINYLALCOHOL PREPARED THEREFROM}

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram which shows the saponification process in a twin screw extruder.

[Industrial use]

The present invention relates to a method for producing polyvinyl alcohol using an extruder, and to a high saponified polyvinyl alcohol prepared therefrom, and more particularly, to a method for producing a high polymerization high saponified polyvinyl alcohol in a short time from a polyvinyl acetate and It relates to a polyvinyl alcohol produced therefrom.

[Private Technology]

Polyvinyl alcohol, first discovered in 1924 by WOHerrmann and W. Haehnel (German Patent No. 450,286) during saponification of polyvinylacetate, contains a hydroxyl group produced by saponifying a vinyl ester polymer such as polyvinylacetate. As linear crystalline polymers, they are widely used for the production of scavenger, clothing fibers, industrial fibers, membranes and the like depending on the molecular weight.

In particular, polyvinyl alcohol used as a raw material of high strength and high modulus polyvinyl alcohol fibers should have characteristics of high degree of polymerization and high degree of saponification. In general, the higher the degree of polymerization, the more the number of Tie molecules penetrate through the crystals, thereby obtaining a high-strength high modulus of elasticity.

Methods for producing polyvinyl alcohol include bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and the like.

Bulk polymerization is not industrially applicable because of a large amount of heat of reaction that results in an auto-accelerated reaction [RSSandler and W. Karo, "Polymer Synthesis", vol. 3, p. 197-199, Academic Press, New York , 1980]. Therefore, the polymerization is carried out in an alcohol solvent to undergo a hydrolysis process directly in the presence of alkali [M. Ueda and K. Kajitani, Macromol. Chem., 108, 138 (1967)], however, even if a chain transfer reaction by a solvent is frequently performed during polymerization, the branches are cut off during the hydrolysis process to obtain polyvinyl alcohol having high polymerization degree. Difficult to obtain

Recently, the polymerization mechanism has a bulk characteristic, a method of obtaining a high degree of polyvinyl alcohol through suspension polymerization to control the heat of reaction using water as a dispersion medium [Korea Patent Publication No. 10-0205633, Japanese Patent Laid-Open No. 6-41208 ], But the polymerization rate is very low, the productivity is low. In addition, similar emulsion polymerization reaction mechanism is a method of controlling the heat of reaction using water as a dispersion medium while showing bulk characteristics, but has a very high polymerization rate. However, due to the rapid polymerization rate, branches are formed before the main chain grows, so that it is difficult to obtain polyvinyl alcohol of high polymerization degree by the conventional emulsion polymerization method.

As described above, various special emulsion polymerization methods (Japanese Patent Laid-Open No. 2000-169509) have been attempted to obtain polyvinyl alcohol having a high degree of polymerization, but the polymerization temperature may be lower than 20 ° C and even lower than 0 ° C.

As mentioned above, while the improvement of the polymerization method and the related researches are being actively conducted, attempts to increase and simplify the efficiency of the polyvinyl alcohol manufacturing process have been rarely successful. In particular, research on improving the productivity and efficiency of the process with respect to saponification (saponification) process is insufficient.

The present invention is to solve the above problems, an object of the present invention is to provide a method for producing polyvinyl alcohol to advance the saponification of polyvinyl acetate in the extruder.

Another object of the present invention is to provide a polyvinyl alcohol having a high degree of polymerization and a high degree of polymerization.

In order to achieve the above object, the present invention provides a polyvinyl acetate solution, and a method for producing polyvinyl alcohol comprising the step of saponification to the alkali in an extruder (extruder).

The present invention also provides a polyvinyl alcohol having a number average degree of polymerization of 1,000 to 10,000 and a degree of saponification of at least 99.8%.

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

In general, polyvinyl alcohol is prepared by polymerizing polyvinylacetate using vinyl acetate, which is a monomer, and separating, purifying, and drying the polymerized polyvinylacetate, followed by saponification (saponification) of the dried polyvinylacetate. .

In particular, the saponification of the polyvinyl acetate in the form of polyvinyl alcohol is a polyvinyl acetate as a whole, since a complex process such as dissolution, saponification, separation, purification, and drying is added separately from the polymerization step of the polyvinyl acetate. The manufacturing process of alcohol is very complicated.

The saponification process is also called a saponification process, and it is common to treat the polymerized polyvinylacetate in the presence of an alkali catalyst, and this method is industrially used. As a method of saponifying polyvinyl acetate, the method of using various saponifiers, such as a belt type, a pipe type, or a slurry type, is common.

In the saponification process, it is important to uniformly mix the polyvinylacetate solution and the saponification catalyst in a short time, and from this point of view, it is preferable to use a reactor that is substantially completely mixed.

A fully mixed reactor is a device that is an ideal extreme state flow through a flow system device, that is, a flow in which the fluid entering the device is uniformly dispersed within the device immediately after inflow. In this state, physical quantities such as concentration and temperature at each instant become completely uniform at one point in time.

As a reactor close to a fully mixed reactor, a mixer having various mixing efficiencies such as a line mixer and a mixing tank having various stirring blades can be exemplified, but a kneader mixer is used. It is known to be preferable.

However, the existing saponification process takes a long time to obtain a high strength PVA-based polymer having a high degree of saponification, and requires a large-scale facility. Therefore, such a general method is disadvantageous in terms of productivity, and in terms of efficiency and workability is poor.

In addition, in the conventional general saponification method, the higher the degree of polymerization of polyvinylacetate, the higher the degree of saponification. When polyvinylacetate is saponified in the presence of an alkali catalyst, partial saponification occurs primarily to precipitate polyvinyl alcohol. At this time, since the precipitated polyvinyl alcohol is in a solid state, it is difficult for the alkali catalyst to penetrate into the polymer chain, and the larger the molecular weight of the polymer, the more the polymer chains are entangled and the more difficult it is for the alkali catalyst to penetrate the inside.

Therefore, if a high-strength polyvinyl alcohol polymer having a higher degree of saponification than the conventional one can be obtained continuously in a short time, it is useful industrially, and it can be seen as a breakthrough in terms of productivity, efficiency, and workability in terms of process. .

In the present invention, polyvinyl acetate solution and alkali are introduced into an extruder and saponified to produce polyvinyl alcohol. When using an extruder as in the manufacturing method of the present invention, it is possible to shorten the saponification process that has been performed for several hours to about a few minutes, and the continuous process is possible to improve productivity and processability. In the case of using a high molecular weight polyvinyl acetate, it is difficult to obtain a high degree of saponification, but in the production method of the present invention, a high degree of high molecular weight polyvinyl alcohol can be obtained.

Although the extruder used for manufacture of the polyvinyl alcohol of this invention is not specifically limited, It is preferable that it is a twin screw extruder.

1 is a schematic diagram showing an example of a twin-screw extruder used in the saponification process of the present invention. Referring to Figure 1, the extruder used in the present invention, the polyvinylacetate solution, and the input portion of the alkali, the mixing portion for mixing the same, the saponification part occurs the saponification reaction, the pulverization unit for grinding the saponified polyvinyl alcohol, and side reactions It can be divided into a crimp to remove the product.

Since the residence time in the extruder can be adjusted according to the rotational speed or L / D of the screw, it is not particularly limited, it is possible to obtain a high saponified polyvinyl alcohol of 99.8% or more in 3 to 30 minutes.

The screw rotation speed of the extruder is preferably 10 to 200 rpm, more preferably 30 to 100 rpm. In order to uniformly mix the alkali and the polyvinylacetate solution, the rotation speed of the screw is preferably 10 rpm or more, and in order to ensure sufficient saponification reaction time to obtain high saponification polyvinyl alcohol, it is preferably 200 rpm or less.

In addition, since L / D of the said extruder may be any thing as long as it satisfy | fills the range of a conventional extruder, it is although it does not specifically limit, It is preferable that it is 20-80. The L / D of the extruder is preferably 20 or more in order to increase the mixing performance, to secure sufficient saponification reaction time, and to obtain polyvinyl alcohol of high saponification degree, and preferably 80 or less in order to increase productivity.

In order to facilitate the saponification reaction in the extruder, it is preferable that the whole section temperature of the extruder is maintained at 10 ° C. or more, preferably 80 ° C. or less, and more preferably 30 to 70 ° C. in terms of stability of the polyvinylacetate solution. .

In addition, the temperature of the entire section of the extruder may be adjusted differently for each section as necessary.

The polyvinylacetate solution used in the production of the polyvinyl alcohol preferably has a concentration of polyvinylacetate of 1 to 40% by weight, more preferably 5 to 10% by weight. In terms of productivity, the concentration of the polyvinylacetate is preferably 1% by weight or more, and in order to obtain a viscosity suitable for the saponification reaction, it is preferably 40% by weight or less.

In addition, the polyvinylacetate may be commercially available polyvinylacetate, but in order to manufacture a polyvinyl alcohol fiber having high strength, high modulus, and excellent hot water resistance properties, polyvinylacetate of high polymerization degree is used. It is preferable. However, it is virtually difficult to polymerize polyvinylacetate having an average degree of polymerization of more than 20,000, and in order to secure high strength properties as fibers, the average degree of polymerization is preferably 2,000 or more.

It is preferable that the polyvinyl acetate of a high degree of polymerization is polyvinylacetate polymerized by the seed emulsion polymerization method. The seed emulsion polymerization method is a technique of increasing the degree of polymerization of a polymer by adding a small amount of emulsifier and monomer first to fix the number of micelles, and then adding an emulsifier and monomer to increase the size of the micelle while fixing the number of micelles.

Since saponification of polyvinylacetate requires alcohol, the polyvinylacetate solution preferably includes an alcohol solvent, and the alcohol solvent is low in cost, low boiling point, and easy to handle. It is more preferable to use.

The alkali is added as a catalyst for the saponification reaction, and the alkali itself may be used as it is, or an alkali solution in which alkali is dissolved in alcohol or water may be used, and an aqueous alkali solution using water as a solvent is more preferable.

The alkali is preferably one or more selected from the group consisting of sodium hydroxide, potassium hydroxide and calcium hydroxide, and more preferably sodium hydroxide. In addition, the alkali concentration in the alkali solution or aqueous solution is preferably 0.1 to 99.9% by weight, more preferably 1 to 20% by weight.

In addition, in order to facilitate the saponification reaction, the ratio of alkali to polyvinylacetate (alkali / polyvinylacetate) is preferably at least 10 ⁻³ in molar ratio, and it is possible to reduce the physical property caused by alkali and waste energy for alkali removal. In order to prevent it, it is preferable that the said input ratio is 10 or less, and it is more preferable that the said input ratio is 0.01-0.2.

According to the manufacturing method of the polyvinyl alcohol of the present invention, it is possible to continuously produce a high saponification degree polyvinyl alcohol in a faster time than the conventional polyvinyl alcohol manufacturing method, the partial saponification of the polyvinyl acetate occurs polyvinyl alcohol partially precipitated Even if the screw is rotated to grind it, it is easy to penetrate the alkali catalyst to the inside of the polymer chain to achieve high gumification.

The polyvinyl alcohol of the present invention produced by the above method has a saponification degree of at least 99.8%, preferably at least 99.9%.

In addition, the polyvinyl alcohol of the present invention is prepared from a high degree of polyvinyl acetate, it may have a number average degree of polymerization of 1,000 to 10,000.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

EXAMPLE

Example 1

The polyvinylacetate having a number average degree of polymerization of 9700 was dissolved in methanol to polymerize by the seed emulsion polymerization to prepare a polyvinylacetate solution having a concentration of 6.25% by weight.

In addition, an aqueous sodium hydroxide solution having a concentration of 20% by weight was prepared.

The twin screw extruder of EM Korea Co., Ltd. was used for the production of polyvinyl alcohol of the present invention.

While adjusting the entire length of the extruder to 60 ℃, while slowly increasing the rotational speed of the screw to 50 rpm, the aqueous solution of sodium hydroxide in NaOH to the second input while introducing a polyvinylacetate solution at a rate of 30 kg per hour to the first input of the extruder / PVAc was added at a molar ratio of 0.2.

By obtaining and drying the polyvinyl alcohol discharged from the extruder, polyvinyl alcohol was prepared.

Example 2

Polyvinyl alcohol was prepared in the same manner as in Example 1 except that the rotation speed of the extruder screw was 20 rpm.

Example 3

Polyvinyl alcohol was prepared in the same manner as in Example 1 except that the amount of polyvinylacetate added to the extruder was 15 kg per hour.

Comparative Example 1

A polyvinylacetate solution having a concentration of 6.25 wt% was prepared by dissolving polyvinylacetate having a number average degree of polymerization of 9700 in methanol by polymerization by a seed emulsion polymerization method.

In addition, an aqueous sodium hydroxide solution having a concentration of 20% by weight was prepared.

140 kg 1 batch of said polyvinylacetate solution was put into the saponification reactor (large diameter precision) which is a mixing type stirring tank, and the sodium hydroxide aqueous solution was made so that the molar ratio of NaOH / PVAc might be 0.2.

The saponification temperature was 60 ° C., the stirring speed was 150 rpm, and the saponification reaction was carried out for 7 hours. Then, the discharged polyvinyl alcohol was obtained and dried to prepare polyvinyl alcohol.

1. Measurement of safflower degree

The saponification degree of the polyvinyl alcohol prepared according to Examples 1 to 3 and Comparative Example 1 was measured by the method of JIS K 6726. However, in the case of saponification degree of 97 mol% or more, it was measured according to the following saponification method measuring method I, and in the case of saponification degree of less than 98 mol%, it measured in accordance with the following saponification method measuring method II, and the result was calculated according to the following formula 1 It summarized in Table 1.

[Calculation 1]

A (%) = [0.60 × (a-b) × F × 100] / (S × P)

B (%) = (44.05 × A) / (60.5-0.42 × A)

C (%) = 100-B

P = 100-[R + N + (K-N × 0.378)]

A: weight of remaining acetic acid (%)

B: mol (%) of residual acetic acid

C: saponification degree mol (%)

S: weight of raw material (g)

P: net content (%)

F: Concentration coefficient of 0.1N NaOH solution

R: Volatilization (%)

N: sodium acetate (%)

K: ash content (%)

1) Method of measuring safflower degree I (when saponification degree is more than 97 mol%)

About 3 g of raw material was precisely taken in a 300 ml Erlenmeyer flask, about 100 ml of water was added to dissolve and cooled (95-98 ° C.), and then 25.0 ml of 0.1N NaOH solution was added thereto and left at room temperature for 2 hours or more.

Next, 25.0 ml of 0.1NH ₂ SO ₄ was added, the excess sulfuric acid was titrated with 0.1N NaOH solution until the pale yellow color appeared using phenolphthalein as an indicator, and the appropriate amount was made a ml.

Separately, the blank test was carried out in the same manner as in the present test, and the saponification degree was calculated from the above formula 1 using b ml as an appropriate amount of the 0.1N NaOH solution required for the blank test.

2) Method of measurement of safflower degree II (if safflower is less than 97 mol%)

About 0.5 g of the raw material was accurately taken in a 300 ml Erlenmeyer flask, about 100 ml of water was added to dissolve and cooled (95-98 ° C.), and then 25.0 ml of 0.2N NaOH solution was added and allowed to stand at room temperature for 2 hours or more.

Next, 25.0 ml of 0.2NH ₂ SO ₄ is added, the phenolphthalein is used as an indicator, and the excess sulfuric acid is titrated with 0.1 N NaOH solution until a light red color appears, and the appropriate amount is a ml.

Separately, the blank test was carried out in the same manner as in the present test, and the saponification degree was calculated from the above formula 1 using b ml as an appropriate amount of the 0.1N NaOH solution required for the blank test.

2. Measurement of the number average polymerization degree of PVA

1) Acetylating PVA with PVAc

Into a 250 ml three-necked flask, 3 g of PVA, 60 ml of acetic acid, 60 ml of acetic anhydride, and 6 ml of pyridine, prepared according to the above Examples and Comparative Examples, were reacted at 100 ° C. for 24 hours under a nitrogen stream.

The product of the reaction is filtered and purified by repeating dissolution and precipitation twice with 500 ml of methanol and 500 ml of water.

The product purified in the above process is filtered and dried at 60 ° C. under vacuum.

By comparing the area of the PVAc of CH ₂ peak indicated by the area of the acetyl CH ₂ peak Chemistry of PVA 95% or more was confirmed to be acetylated.

2) Measurement of intrinsic viscosity (IV)

After the sample was pulverized and vacuum dried at 60 ° C., three samples were each taken at a concentration of 0.2 w / v%, 0.4 w / v%, and 0.6 w / v% with respect to 25 ml of benzene as a solvent.

The sample solution was stirred until dissolved in a 30 ° C. shaking incubator. At this time, the rotation speed was adjusted so that benzene does not splash. After all of the polymer was dissolved, it was transferred to a thermostat at 30 ° C. and incubated for at least 30 minutes, and about 7 ml of the sample solution was put into a mebel pipette in a Ubelodoh viscometer (Ubbelohde Size 0B), and the number of seconds of the current was measured. In addition, inherent viscosity (Inherent Viscosity, IV) was calculated according to the following equation 2 by measuring the number of seconds of the current (sec) of benzene as a solvent under the same conditions.

[Calculation 2]

IV = ln (η _rel ) / C

Where η _rel is the sample solution falling water number / benzene solution falling water number, C is the concentration, and ln is the natural logarithm.

3) Calculation of number average degree of polymerization by viscosity method

After describing the measured intrinsic viscosity value as a graph of viscosity according to each concentration, extrapolating the graph to obtain the intrinsic viscosity [η] of PVAc at the concentration of 0 w / v%, and obtaining the intrinsic viscosity of the obtained PVAc. It was converted into a number average degree of polymerization according to the Mark-Houwink equation of the equation (3).

[Calculation 3]

[η] = 8.91 x 10 ^-3 [Pn] ^0.62

In the above formula, Pn represents the number average degree of polymerization of PVAc, 8.91 × 10 ^−3, and 0.62 are constants determined according to the type and solvent of the polymer.

 TABLE 1

Example 1 Example 2 Example 3 Comparative Example 1 Safflower process Extruder Extruder Extruder Mixed Stirring Tank PVAc solution input 30 kg / hr 30 kg / hr 15 kg / hr 140 kg / Bx. Screw rotation speed 50 rpm 20 rpm 50 rpm 150 rpm (stirring speed) Saponification reaction time 5 minutes 7 minutes 5 minutes 7 hours Safflower 99.9 99.8 99.9 99.8 Number average polymerization degree of PVA 4450 4400 4500 4300

As shown in Table 1, the polyvinyl alcohol of Examples 1 to 3 saponified using an extruder is treated with high molecular weight polyvinylacetate for 5-7 minutes to at least 99.8%, whereas general mixing and stirring It can be seen that the polyvinyl alcohol of Comparative Example 1 obtained by saponification using a tank obtained saponification degree of 99.8% after 7 hours.

 The polyvinyl alcohol production method of the present invention can obtain a high degree of polymerization and high saponification polyvinyl alcohol in a short time, the productivity and efficiency of the process is increased, and there is an advantage of easy workability.

Claims (8)

Polyvinylacetate solution and alkaline solution, Polyvinylacetate solution and alkaline solution inlet; Mixing unit for mixing the two solutions; Saponification unit in which a saponification reaction occurs; Grinding unit for grinding the saponified polyvinyl alcohol; And a step of injecting and saponifying into a twin screw extruder including a pressing part for removing a side reaction product. The polyvinylacetate solution has a concentration of 5 to 40% by weight of polyvinylacetate, The charge ratio of the alkali / polyvinylacetate is 10 ^-3 to 10 in molar ratio, The total section temperature of the twin screw extruder is 10 to 80 ℃ manufacturing method of polyvinyl alcohol. delete delete delete delete delete delete delete

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