JPH07179519A - Vinyl alcohol-based polymer - Google Patents

Abstract

PURPOSE:To obtain a polymer, having a specific polymerization degree and a specified distribution thereof, excellent in biodegradability, responsiveness to external stimulation such as heat or light and introduction properties of a functional group into the terminal and useful as a raw material for gelatinous substances responsive to the stimulation, a starting material for graft copolymers, a biodegradability imparter, etc. CONSTITUTION:This polymer has <=50 number-average polymerization degree (Pn and <=1.3 ratio (Pm/Pn) of the weight-average polymerization degree (Pm) to the P. Furthermore, the polymer is obtained by reacting and saponifying a polyaryl vinyl ethereal polymer having <=50 Pn and <=1.3 ratio (Pm/Pn) with metallic sodium in liquid ammonia.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl alcohol polymer having a low degree of polymerization and a sharp degree of polymerization distribution.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as P
The degree of polymerization (abbreviated as VA) is adjusted by adjusting the polymerization conditions such as solvent concentration, polymerization rate, polymerization rate, and polymerization temperature. In the case of solution polymerization, it is difficult to produce an extremely high degree of polymerization PVA, but a desired degree of polymerization can be relatively easily obtained for PVA having a degree of polymerization of about 500 to 2,500. In addition, in the polymerization of polyvinyl acetate (hereinafter, abbreviated as PVAc) obtained by a usual radical polymerization, many kinds of elementary reactions such as an initiation reaction, a growth reaction and a termination reaction occur at the same time. Ratio Pw / of weight average degree of polymerization (Pw) and number average degree of polymerization (Pn) by gel permeation chromatography (GPC) analysis of PVAc
Only Pn (THF solvent system) of about 2.6 can be obtained.

Polymerization of vinyl ether has been studied as a method of synthesizing a precursor of PVA other than radical polymerization. JP-A-60-228509 describes living cationic polymerization of alkenyl ethers with an HI / I ₂ -based initiator, and JP-A-61-1103654, 6
2-57910, JP-A-1-108202 and 1
-108203 describes living cationic polymerization of alkenyl ethers by combining an organoaluminum compound with an ether or ester. It is known that a monodispersed PVA having a high degree of polymerization can be obtained by cleaving the ether bond in the polyvinyl ether obtained by the above synthesis method.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vinyl alcohol polymer having a low degree of polymerization and a sharp degree of polymerization distribution.

[0005]

As a result of intensive studies to solve the above problems, the number average degree of polymerization (Pn) is 50 or less, and the weight average degree of polymerization (Pw) and the number average degree of polymerization (Pn).
The inventors have found a vinyl alcohol polymer having a ratio Pw / Pn of n) of 1.3 or less, and completed the present invention. The number average degree of polymerization (Pn) of the vinyl alcohol polymer in the present invention is 50 or less as measured by ¹ H-NMR (nuclear magnetic resonance). That is, by ¹ H-NMR measurement,
It can be determined by quantifying from the integral ratio of the starting terminal methyl group and the methylene group. The ratio Pw / Pn of the weight average degree of polymerization (Pw) and the number average degree of polymerization (Pn) of the vinyl alcohol-based polymer in the present invention is determined by acetylating the vinyl alcohol-based polymer to obtain a polyvinyl acetate tetrahydrofuran ( Hereinafter, abbreviated as “THF”) as a solvent
It is 1.3 or less in terms of polystyrene conversion by measurement.

The vinyl ether polymer of the present invention may contain units other than vinyl alcohol units within the range not impairing the object of the present invention. Specific examples of these units include, in addition to the vinyl ether monomer as a raw material, a cationic copolymerizable monomer such as other vinyl ether, styrene and its derivatives, and isobutene.

Next, the method for producing the vinyl alcohol polymer of the present invention will be described. The vinyl alcohol-based polymer of the present invention undergoes living cationic polymerization of a monomer such as benzyl vinyl ether to give a number average degree of polymerization (P
n) is 50 or less, and a ratio Pw / Pn of the weight average polymerization degree (Pw) and the number average polymerization degree (Pn) is 1.3 or less, and a polyaryl vinyl ether (hereinafter abbreviated as PArVE) is synthesized, By reacting the PArVE with sodium in liquid ammonia to saponify the PArVE,
It is obtained by cleaving the ether bond therein. As a method for synthesizing PArVE which is a raw material of PVA of the present invention, a vinyl ether monomer such as benzyl vinyl ether (hereinafter abbreviated as BzVE) is used and an organoaluminum reagent is used as an initiator under a nitrogen atmosphere under complete dehydration Use an initiator concentration of 0.5 (mol / monomer 1
L) It is obtained by setting the above and polymerizing. PA
The method of cleaving the ether bond in rVE is not particularly limited, but a method of deprotecting PArVE using metallic sodium in liquid ammonia can be mentioned.

Next, a method for purifying a vinyl alcohol polymer containing a vinyl alcohol unit of the present invention will be described. Polybenzyl vinyl ether (hereinafter PBzVE
In the deprotection reaction of PArVE (such as abbreviated), sodium or a large amount of salt is used as an activity inhibitor, but these agents need to be purified and removed after the deprotection reaction. As this purification method, a method using an ion exchange resin was found. That is, an aqueous solution of a mixture of a salt and a vinyl alcohol-based polymer is added to a cation exchange resin (50
WX8H ⁺ type, 50 to 100 mesh), 1 to 2 mL
/ Min / cm ² and then anion exchange resin (IRA-400OH ⁻ type).
Ions derived from salts can be completely removed. Further, water is distilled off from the resulting aqueous vinyl alcohol polymer solution using a rotary evaporator to obtain the intended vinyl alcohol polymer of the present invention.

[0009]

The present invention will be further described below with reference to examples, but the present invention is not limited to the examples.

Example 1 A glass reaction vessel equipped with a three-way stopcock was prepared, and after nitrogen substitution, it was heated in a nitrogen gas atmosphere and sucked with a vacuum pump to remove adsorbed water from the glass reaction vessel. . Next, using a syringe that has been replaced with dry nitrogen, toluene 184 mL, ethyl acetate 30 mL, benzyl vinyl ether 30 mL, trifluoroacetic acid in toluene 6
mL (13.5 mL of toluene under a dry nitrogen atmosphere in advance
And a part of the mixed solution obtained by mixing 6 mL of trifluoroacetic acid), and the reaction system was cooled using an ice bath. When the system temperature reached 0 ° C, ethylaluminum dichloride n-hexane solution (1 mol /
L) 50 mL was added to start the polymerization reaction. After 3 minutes, the polymerization reaction was stopped by injecting 50 mL of methanol into the reaction system. After termination of the polymerization reaction, the initiator residue was removed by washing twice with 5% hydrochloric acid, then neutralized with a 2% aqueous sodium hydroxide solution, and the reaction solution was concentrated and dried under reduced pressure to recover PBzVE. . Next, the obtained P
The cleavage reaction of the ether bond of BzVE will be described.
The reaction vessel was sufficiently replaced with nitrogen, cooled to -78 ° C with a dry ice-methanol cooling system, and then 1.2 L of liquid ammonia was introduced. Metal sodium 1 in the reaction vessel
3.2 g of the PBzVE solution (25 g) was added dropwise to a blue-colored liquid ammonia, and the solution was added dropwise. After completion of the dropping, the reaction was carried out by leaving it for 3 hours.

After the reaction was completed, 45 g of ammonium acetate was added to the reaction vessel to stop the reaction. Next, after passing nitrogen through the reaction vessel to completely distill off ammonia, about 2
After adding 00 mL of distilled water into the reaction vessel and performing filtration, the solvent of the filtrate was distilled off using a rotary evaporator. The white solid obtained by the above operation was dissolved in 150 mL of distilled water, and the solution was filtered and then added to 1 L of a cation exchange resin (DOWEX50WX8, H ⁺ type).
It was passed at a rate of 1 to ² mL / min / cm ² to convert sodium ion and ammonium ion in the aqueous solution into hydrogen ion. Next, anion exchange resin (IRA-4
00, OH ⁻ type) 1 L to remove acetate ion in the aqueous solution and further neutralize hydrogen ion. Next, water was distilled off from the ion-exchanged solution using a rotary evaporator, and vacuum drying was performed at 40 ° C. to obtain PVA. The number average degree of polymerization (Pn) of the PVA obtained from the value measured by ¹ H-NMR (nuclear magnetic resonance) was 9. Also, the P
Polyvinyl acetate T obtained by acetylating VA by a conventional method
The ratio (Pw / Pn) between the weight average polymerization degree and the number average polymerization degree in terms of standard polystyrene determined by GPC measurement at 40 ° C. using HF as a solvent was 1.26.

Example 2 In the same manner as in Example 1, toluene 212 mL, ethyl acetate 30 mL, benzyl vinyl ether 30 mL, trifluoroacetic acid toluene solution 3 mL (toluene 13.5 mL and trifluoroacetic acid 6 m were previously prepared under a dry nitrogen atmosphere.
The mixture was added to the reaction vessel in this order, and the reaction system was cooled using an ice bath. When the temperature in the system reached 0 ° C., 25 mL (1 mol / L) of ethylaluminum dichloride n-hexane solution was added to start the polymerization reaction. After 30 minutes, the polymerization reaction was stopped by injecting 20 mL of methanol into the reaction system. Then, PBzVE was recovered by performing the same purification as in Example 1. Next, the cleavage reaction of the ether bond of the obtained PBzVE will be described. The reaction vessel was sufficiently replaced with nitrogen, cooled to -78 ° C with a dry ice-methanol cooling system, and 1.2 L of liquid ammonia was introduced. 13.2 g of metallic sodium was placed in a reaction vessel, and a solution of 25 g of PBzVE obtained above in 10% dimethoxyethane was added dropwise to liquid ammonia showing a blue color. After the dropping is completed,
The reaction was allowed to stand for 3 hours. Next, PVA was obtained by purifying in the same manner as in Example 1. With respect to the PVA, Pn determined in the same manner as in Example 1 was 18, and Pw / Pn was 1.27.

Example 3 In the same manner as in Example 1, toluene 228 mL, ethyl acetate 30 mL, benzyl vinyl ether 30 mL, trifluoroacetic acid toluene solution 6 mL (toluene 18.9 mL and trifluoroacetic acid 0.
(6 mL of a mixed part) was sequentially added to the reaction vessel, and the reaction system was cooled in an ice bath. When the system temperature reached 0 ° C, ethylaluminum dichloride n-hexane solution (1mo
1 / L) 25 mL was added to start the polymerization reaction. After 30 minutes, the polymerization was stopped by injecting 20 mL of methanol into the reaction system. Then, PBzVE was recovered by performing the same purification as in Example 1. Next, the obtained P
The cleavage reaction of the ether bond of BzVE will be described.
The reaction vessel was sufficiently replaced with nitrogen, cooled to -78 ° C with a dry ice-methanol cooling system, and 1.2 L of liquid ammonia was introduced. Metal sodium 13.
A solution of 25 g of the PBzVE obtained above in a concentration of 10% in dimethoxyethane was added dropwise to 2 g of liquid ammonia that was blue. After completion of the dropping, the reaction was carried out by leaving it for 3 hours. Next, PVA was obtained by purifying in the same manner as in Example 1. With respect to the PVA, Pn determined in the same manner as in Example 1 was 46, and Pw / Pn was 1.12.

Comparative Example 1 Toluene 39.5 was prepared using the same reaction vessel as in Example 1.
mL, ethyl acetate 60 mL, benzyl vinyl ether 6
0 mL and a trifluoroacetic acid toluene solution 6 mL (a part of toluene 97 mL and trifluoroacetic acid 0.6 mL were mixed in advance under a dry nitrogen atmosphere) were added in this order, and the reaction system was cooled in an ice bath. When the temperature in the system reached 0 ° C, ethyl aluminum dichloride n-hexane solution (1 m
ol / L) 6 mL was added to start the polymerization reaction. After 30 minutes, 20 mL of methanol was injected into the reaction system to stop the polymerization. Next, PBzVE was recovered by purification in the same manner as in Example 1. Next, the obtained P
The cleavage reaction of the ether bond in BzVE is described. After thoroughly replacing the reaction vessel with nitrogen, dry ice-
It cooled to -78 degreeC with the methanol cooling system, and introduced 1.2 L of liquid ammonia. Into a reaction vessel, 13.2 g of metallic sodium was added, and a solution of 25 g of PBzVE obtained above in 10% dimethoxyethane was added dropwise to liquid ammonia that was blue. After completion of the dropping, the reaction was carried out by leaving it for 3 hours. 45 g of ammonium acetate after the reaction
Was added to the reaction vessel to stop the reaction. Next, nitrogen is passed through the reaction vessel to completely distill off the ammonia, and then about 200 mL of distilled water is added to the reaction vessel, and after filtration, the filtrate is distilled to remove the solvent using a rotary evaporator. When it is removed, it is concentrated to a white suspension. This was put into 4.5 L of methanol for reprecipitation. After air-drying, methanol Soxhlet extraction was carried out for 2 days for the purpose of completely removing a salt contained in a trace amount. After finishing, vacuum drying for 2 days
A was obtained. With respect to the PVA, Pn determined in the same manner as in Example 1 was 528, and Pw / Pn was 1.19.
Met.

Examples 1 to 3 and Comparative Example 1 Next, in order to confirm the effectiveness as the biodegradable polymer of the present invention, the biodegradability of the single PVA of the present invention was evaluated by PVA oxidation isolated from PVA-degrading bacteria. Enzyme (PVA Dehydro
genase). The PVA dehydrogenase activity measurement method is the method of Shimao et al. {M. Shimao et al. Applied and Environmental
Microbiology 51,268-275
(1986). }, The composition was optimized. The composition is shown below. Final concentration (same below) 50 mM phosphate buffer pH 7.
2 1 mM phenazine ethosulfate (PES) 0.1 mM 2,6-dichlorophenol indophenol (DCPIP) 10 mM KCN 0.5% Tween 80 1 mM MgCl ₂ 0.5 mM CaCl ₂ 1 μg / mL PQQ 0.01% BSA PVA (degree of polymerization) 1700, saponification degree 99.9 mol%)
(7.5 mg / mL) A solution having the above composition was prepared, pre-incubated at 30 ° C., and the enzyme reaction was started by adding the enzyme solution also pre-incubated. The reaction was carried out in a disposable cell, and the mixture was mixed by inversion immediately after the addition of the enzyme solution, and the decrease in absorbance at 600 nm was observed. At the same time, a solution using distilled water instead of PVA was used as a blank, and the same measurement was performed. The enzyme activity is defined as the activity that changes 1 μmol of DCPIP per minute.
Unit (U). The amount of change in DCPIP was calculated from the molecular extinction coefficient = 1.91 × 10 ⁻³ (1 / M).

A vinyl alcohol polymer was used by preparing it into a 7.5% aqueous solution (w / v) (it can be heated). Further, those having a low solubility and incapable of preparing a 7.5% aqueous solution were those having a maximum solubility. A 7.5% aqueous solution is diluted 2-fold with distilled water to give 7.5% (75 mg / mL) to 0.1%.
Dilute up to about 2% (1.2 mg / mL) for each 1.2
Prepare each mL and pre-incubate (1
Substrate solution (A) was prepared by performing the treatment for 5 minutes or more.

Final concentration (same below) 125 mM phosphate buffer (pH 7.2) 2.5 mM phenazine ethosulfate (PES) 0.25 mM 2,6-dichlorophenol indophenol (DCPIP) 25 mM KCl 1.25% Tween80 The above composition About 1.2 times the required amount of aqueous solution (0.4 mL was used for 1 assay, each substrate concentration was measured at 2 points) was prepared, and pre-incubated at 30 ° C. in the dark to prepare a buffer solution (B). .

Final concentration 10 mM MgCl ₂ 5 mM CaCl ₂ 10 μg / mL PQQ 1% BSA Purified PVA Dehydrogenase About 1.2 times the required amount of the aqueous solution of the above composition (0.1 mL was used for one assay, each substrate concentration was measured at 2 points) ) Prepare 3
An enzyme solution (C) was prepared by preincubation at 0 ° C.

A disposable cell (for 1 mL) was prepared by adding 0.5 mL of the substrate solution (A), 0.4 mL of the buffer solution (B) and 0.1 mL of the enzyme solution (C) (finally adding the enzyme solution to start the reaction). , Made of plastic), mix quickly by inversion with the lid on, and monitor the decrease in absorbance at 600 nm (monitor the absorbance value every 30 seconds) until the amount of change in absorbance reaches about 0.2 to 0.3. Observe that the initial rate of reduction of DCPIP (= v, μM / mi
n. ) Was asked. At this time, the change amount of 600 nm and the DCP
The initial rate of change in DCPIP concentration was obtained from the molecular extinction coefficient of IP, and two points were measured at each substrate concentration, and the average was taken as the initial rate.

A plot derived from the Michaelis-Menten equation (we used the Lineweaver-Burk plot, vertical axis: 1 / v, horizontal axis: 1 / s, X intercept: -1 / K
m, Y intercept: 1 / Vmax. ) From Km and Vma
x. Was calculated. However, the substrate concentration (s) was expressed by weight concentration (mg / mL). As an index of the reactivity between the substrate and the enzyme, Vmax. / Km (the higher the value, the higher the reactivity).

Comparative Example 2 A biodegradation activity test was conducted in the same manner as in Examples 1 to 3 and Comparative Example 1 except that PVA obtained by radical polymerization shown in Table 1 was used. The results are shown in Table 1.

[0022]

[Table 1]

[0023]

According to the present invention, a vinyl alcohol polymer having an extremely low degree of polymerization and a sharp degree of polymerization distribution is provided. The PVA of the present invention has a remarkable biodegradation rate as a biodegradable polymer. Further, the vinyl alcohol-based polymer obtained by the production method of the present invention is very easy to control the degree of polymerization as compared with the conventional vinyl alcohol-based polymer, and has a response to external stimuli such as heat and light. It is characterized by its sharpness and can be suitably used not only for conventional vinyl alcohol-based polymer applications but also for applications utilizing the characteristics of the vinyl alcohol-based polymer of the present invention. Examples of these applications include raw materials for external stimuli-responsive polymers such as heat and light, or stimuli-responsive gels, which have extremely high industrial value. Further, the vinyl alcohol polymer obtained by the production method of the present invention is easy to control the degree of polymerization, and it is easy to introduce a functional group at one end or both ends of the polymer. It is useful as a starting material for a graft copolymer or a block copolymer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yuji Hatanaka, Kuraray Co., Ltd., 2045, Satsuki, Kurashiki City, Okayama Prefecture (72) Masao Tsuji, 1) 2045, Sakurazu City, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd.

Claims (2)

[Claims] 1. A vinyl alcohol polymer having a number average degree of polymerization (Pn) of 50 or less and a ratio Pw / Pn of the weight average degree of polymerization (Pw) to the number average degree of polymerization (Pn) of 1.3 or less. . 2. A polyaryl vinyl ether-based polymer having a number average degree of polymerization (Pn) of 50 or less and a ratio Pw / Pn of the weight average degree of polymerization (Pw) and the number average degree of polymerization (Pn) of 1.3 or less. The method for producing a vinyl alcohol polymer according to claim 1, wherein the combined product is reacted with sodium in liquid ammonia to be saponified.