JP2002037967A - Polyvinyl alcohol-based water soluble film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based water soluble film having characteristics of a water-soluble film comprising a polyvinyl alcohol-based polymer such as high tenacity, transparency, oil resistance, biodegradability and the like. SOLUTION: This polyvinyl alcohol-based water soluble film consists of 100 pts.wt. of a polyvinyl alcohol-based resin having >=2.0 mole % amount of 1,2-glycol bonds and 80-92 mole % degree of saponification and 10-50 pts.wt. of a plasticizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film having excellent water solubility.

[0002]

2. Description of the Related Art In recent years, various chemicals such as pesticides are sealed and packaged in a unit amount in a water-soluble film, and when used, they are poured into water as they are in their packaging form, and the contents are dissolved or dissolved in water together with the packaging film. Dispersion methods have been widely used. The advantage of this unit package is that it can be used without directly touching dangerous chemicals at the time of use, it does not need to be weighed at the time of use because a certain amount is packed, and after use such as containers or bags packed or transported medicines Is unnecessary or simple. Conventionally, an unmodified partially saponified PVA film having a degree of saponification of about 88 mol% has been used as such a water-soluble film for unit packaging. These water-soluble films are easily soluble in cold or hot water and have properties such as excellent mechanical strength. However, in recent years, films having higher water solubility have been demanded from the viewpoint of workability and the like. However, it was difficult to further improve the water solubility of the unmodified partially saponified PVA even if the formulation was modified by adding a plasticizer or the like. For the purpose of improving the water solubility, Japanese Patent Publication No. 6-27205 (JP-A-6-27205)
No. 3,168,437) discloses a method of using a modified PVA into which a sulfonic acid group or the like has been introduced by copolymerization or the like as a water-soluble film. Although the water solubility can be improved by introducing a modifying group, it is generally known that the biodegradability decreases as a comonomer is copolymerized with PVA, and this is particularly remarkable in the case of a comonomer having an ionic group. Therefore, biodegradability is a concern. A film in which an agricultural chemical or the like is packaged needs to have sufficient biodegradability because it may remain in the environment after being dissolved in water.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a PVA-based aqueous solution having a remarkably improved solubility while maintaining the biodegradability of a conventional water-soluble film made of a PVA-based resin. To provide a functional film.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the amount of 1,2-glycol bond is 2.0 mol% or more and the degree of saponification is 80 to 92 mol%. 100 parts by weight of a PVA-based resin and a plasticizer 10 to 50
The present invention has been accomplished by finding that a PVA-based water-soluble film characterized by consisting of parts by weight achieves the above object.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The PVA resin used in the present invention is a saponified vinyl ester polymer. Examples of the vinyl ester used in the present invention include vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl benzoate, vinyl stearate, vinyl pivalate and vinyl versatate. However, vinyl acetate is preferred from the viewpoint of industrial productivity and the easiness of forming a 1,2-glycol bond.

The vinyl ester of the present invention is preferably copolymerized with a small amount of an α-olefin having 4 or less carbon atoms from the viewpoint of improving biodegradability. Examples of the α-olefin having 4 or less carbon atoms include ethylene, propylene, n-butene, isobutylene and the like. Ethylene is particularly preferred from the viewpoint of improving the biodegradability of the obtained polymer film. Also,
Propylene is particularly preferred from the viewpoint of improving water solubility. The content of α-olefin in the copolymerized PVA-based resin is 0.1.
It is 1 to 10 mol%, preferably 0.5 to 5 mol%.
When the content of α-olefin is less than 0.1 mol%, no effect of improving biodegradability is observed, and when it exceeds 10 mol%, the film strength decreases due to a decrease in the degree of polymerization. Not preferred. In particular, when ethylene is copolymerized, the water solubility is reduced, so that it is preferably at most 5 mol%.

Further, the PVA of the present invention may contain other monomer units as long as the gist of the present invention is not impaired. Such comonomers include, for example, acrylic acid and its salts with methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-acrylate
-Butyl, 2-ethylhexyl acrylate, dodecyl acrylate, acrylates such as octadecyl acrylate, methacrylic acid and its salts, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,
I-propyl methacrylate, n-butyl methacrylate,
Methacrylic esters such as i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, acrylamide, N-methylacrylamide, N
Acrylamide derivatives such as -ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and salts thereof, acrylamidopropyldimethylamine and salts or quaternary salts thereof, N-methylolacrylamide and derivatives thereof, and methacrylamide Methacrylamide derivatives such as N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and salts thereof, methacrylamidopropyldimethylamine and salts or quaternary salts thereof, N-methylolmethacrylamide and derivatives thereof, N-vinylpyrrolidone,
N-vinylamides such as N-vinylformamide and N-vinylacetamide, allyl ethers having a polyalkylene oxide in the side chain, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-
Propyl vinyl ether, n-butyl vinyl ether,
vinyl ethers such as i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chlorides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; and acetic acid. Allyl compounds such as allyl and allyl chloride; maleic acid and its salts or esters; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; From the viewpoint of biodegradability, the amount of modification is usually 5 mol% or less.

As the polymerization method of the polyvinyl ester polymer of the present invention, conventionally known methods such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method and an emulsion polymerization method can be applied. As the polymerization catalyst, an azo-based catalyst, a peroxide-based catalyst, a redox-based catalyst, or the like is appropriately selected depending on the polymerization method.

For the saponification reaction of the polymer, alcoholysis and hydrolysis with a conventionally known alkali catalyst or acid catalyst can be applied. Among them, N using methanol as a solvent
A saponification reaction using an aOH catalyst is simple and most preferable.

The saponification degree of the PVA of the present invention is from 80 mol% to
It is 92 mol%, preferably 82 to 90 mol%, more preferably 85 to 90 mol%. If the saponification degree of PVA is less than 80 mol%, the water solubility may be reduced, or the PVA may not be completely dissolved and may be in a dispersed state, which is not preferable. Conversely, if it exceeds 92 mol%, the water solubility is undesirably reduced.

The degree of polymerization of the PVA polymer also affects the performance of the water-soluble film of the present invention. The degree of polymerization is appropriately selected depending on the use of the water-soluble film, but the degree of polymerization is 500 or more, preferably 700 or more, more preferably 900 or more from the viewpoint of film strength, and 3000 or less from the viewpoint of industrial productivity. is there. In addition, from the viewpoint of impact resistance required when a water-soluble film is used as a bag, the degree of polymerization is 1
000 or more is particularly preferred.

The amount of 1,2-glycol bond of the PVA of the present invention is 2.0 mol% or more, more preferably 2.2 mol%.
Mol% or more, more preferably 2.5 mol% or more. The 1,2-glycol bond amount can be controlled by various methods such as the type of vinyl ester, solvent, polymerization temperature, and copolymerization of vinylene carbonate. As a simple control method, in the present invention, control by polymerization temperature or copolymerization of vinylene carbonate is preferable. When controlled by the polymerization temperature, the polymerization temperature is 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 180 ° C. or higher.
Although there is no particular upper limit on the amount of 1,2-glycol bond,
-If the polymerization temperature is raised to increase the amount of glycol bonds or if vinylene carbonate or the like is copolymerized, the degree of polymerization will decrease. Therefore, when used as a water-soluble film, it is preferably at most 5 mol%, more preferably at most 4 mol%. Is more preferably 3.5 mol% or less.

The short-chain branching amount of the PVA of the present invention is as follows:
It is at least 0.03 mol%, more preferably at least 0.05 mol%. Short-chain branching can be controlled by various methods such as the type of vinyl ester, solvent, and polymerization temperature. As a simple control method, control at the polymerization temperature is preferred in the present invention. Since the crystallinity of the PVA-based resin is expected to decrease as the amount of short-chain branching increases, the water-solubility is improved and a preferable water-soluble film is obtained. The polymerization temperature is 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher, further preferably 150 ° C. or higher, and particularly preferably 180 ° C. or higher.

The PVA-based water-soluble film of the present invention comprises 1,
It is essential that the composition comprises 100 parts by weight of a PVA resin having a 2-glycol bond amount of 2.0 mol% or more and a saponification degree of 80 to 92 mol%, and 10 to 50 parts by weight of a plasticizer. As the plasticizer used in the present invention, polyhydric alcohols are preferable from the viewpoint of compatibility with the PVA-based resin. Among them, glycerin, trimethylolpropane, diethylene glycol, triethylene glycol, dipropylene glycol, and propylene glycol are preferred from the viewpoint of biodegradability.
In addition, trimethylolpropane is particularly preferred because of its great effect of improving water solubility. The above plasticizers can be used alone or in combination of two or more. The amount of the plasticizer of the present invention is 10 to 10 parts by weight of the PVA resin.
It is 50 parts by weight, preferably 12 to 40 parts by weight. If the amount of the plasticizer is less than 10 parts by weight, the flexibility of the film under low humidity is insufficient, which causes breakage of the bag when used for packaging. Further, the water solubility is not sufficient. From the viewpoint of water solubility, the amount of the plasticizer is preferably as large as possible, but is preferably 50 parts by weight or less, more preferably less than 40 parts by weight, because bleeding occurs.

The method for producing the PVA-based water-soluble film of the present invention comprising the above-mentioned PVA-based polymer and a specific amount of a plasticizer is not particularly limited, and depends on the required film thickness, film use and purpose. Although it is appropriately selected, a cast film forming method from a solution, a dry film forming method (extrusion into an inert gas such as air or nitrogen), a wet film forming method (forming the PVA polymer into a poor solvent). Extrusion), a dry-wet film forming method, a gel film forming method and the like. As a solvent used at this time, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, ethylene glycol, glycerin, water, hexafluoroisopropanol, or the like is used alone or in combination. Further, an aqueous solution of an inorganic salt such as lithium chloride and calcium chloride can be used alone or as a mixture with the organic solvent. Among them, water, dimethyl sulfoxide, a mixed solution of dimethyl sulfoxide and water, glycerin, ethylene glycol and the like are preferably used. The concentration of the solid content of the stock solution comprising the PVA-based polymer and the plasticizer at the time of film formation varies depending on the film formation method, but is usually from 1 to 60% by weight, and the temperature is usually from room temperature to 250 ° C. The stretching or rolling operation can be performed with dry heat or wet heat,
The temperature is usually in the range from room temperature to 270 ° C. Further, the dissolution rate can be controlled by applying a heat treatment at about 100 to 150 ° C. after the film formation. In addition, in order to improve the anti-blocking property and the water solubility, it is preferable to perform mat processing on the film surface, spraying of an anti-blocking agent and embossing.

The PVA-based water-soluble film of the present invention is not particularly limited in shape and transparency, and may be subjected to uniaxial or biaxial stretching or rolling if necessary.

The PVA-based water-soluble film of the present invention may contain at least one other than the above-mentioned PVA-based polymer and plasticizer as long as the purpose of the present invention is not impaired. And a stabilizer such as an antioxidant or an ultraviolet absorber may be added. In addition, as long as the effects of the present invention are not impaired, the 1,2-glycol bond amount of P is less than 2.0 mol%.
There is no problem even when used by mixing with a VA resin.

The water-soluble rate of the PVA-based water-soluble film of the present invention is preferably 40 seconds or less, more preferably 35 seconds or less, when the film is immersed in stirred water at 20 ° C. Preferably it is 30 seconds or less. Since the water-soluble rate changes depending on the thickness of the film, the thickness may be appropriately adjusted in accordance with the target dissolution time in the present invention. However, in general, in the case of a water-soluble film, a film having a thickness of 40 μm or more is often used due to problems such as impact resistance.
In this case, the above-mentioned dissolution time is preferable. Generally, the larger the amount of plasticizer added, the better the water solubility. Therefore, it is preferable to appropriately adjust the amount of plasticizer in accordance with the target dissolution time.

The PVA-based water-soluble film of the present invention preferably has a Young's modulus of 0.5 kg / mm ² or more, more preferably 1.20 kg under an environment of 20 ° C. and 80% RH from the viewpoint of processability. It is 0 kg / mm ² or more, more preferably 1.5 kg / mm ² or more. The higher the Young's modulus, the higher the stiffness of the film and the better the processability. Since the Young's modulus changes depending on the 1,2-glycol bond amount of the film, the degree of saponification, the amount of the plasticizer, the heat treatment conditions, and the like, it is necessary to appropriately adjust various conditions. Although the reason is unknown, the film having the same composition tends to have a higher Young's modulus as the amount of 1,2-glycol bond increases.
A VA-based water-soluble film has good processability.

The biodegradability of the PVA-based water-soluble film of the present invention after 28 days is 60% by weight or more, preferably 70% by weight.
% By weight or more, more preferably 80% by weight or more.
Although an error in the biodegradation rate occurs due to a variation in sludge activity or the like, the average value of the biodegradation rate of the PVA-based water-soluble film of the present invention is preferably in the above range. The biodegradation rate of the present invention is a biodegradation rate when evaluated according to the biodegradability evaluation method described in ISO14851. The biodegradation rate can be obtained from the amount of carbon dioxide generated or the amount of oxygen consumed during the decomposition.

[0022]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified.

[Method of Analyzing PVA] The method of analyzing PVA was in accordance with JIS-K6726 unless otherwise specified. The content of the 1,2-glycol bond and the short-chain branch of the PVA of the present invention is 500 MHz proton NMR (JEOL GX-
500) It was determined as follows from the measurement by the apparatus. (1) The 1,2-glycol bond amount of PVA can be determined from the NMR peak. Saponification degree 99.9 mol%
After saponification as described above, the sample was thoroughly washed with methanol, dried at 90 ° C. under reduced pressure for 2 days, dissolved in DMSO-d6, and added with a few drops of trifluoroacetic acid.
Hz at 80 ° C. using proton NMR (JEOL GX-500). The peak derived from methine in the vinyl alcohol unit is 3.2 to 4.0 ppm (integral value A),
The peak from one methine with a 2-glycol bond is 3.
It is assigned to 25 ppm (integral value B), and the 1,2-glycol bond content can be calculated by the following equation. 1,2-glycol bond amount (mol%) = (B / A) × 1
(2) The short-chain branching amount (consisting of two monomer units) of PVA can be determined from the NMR peak. After saponification to a degree of saponification of 99.9 mol% or more, the sample was thoroughly washed with methanol, dried at 90 ° C. under reduced pressure for 2 days, and dissolved in DMSO-d6.
NMR and 125.65 of the sample dissolved in D ₂ O.
It is measured at 80 ° C. using 13 C NMR (JEOL GX-500) of MHz. From the sample, the peak derived from methine in the vinyl alcohol unit was 3.2 to 4.0 ppm (integral value C), and the peak derived from methylene in the terminal alcohol was 3.0.
52 ppm (integral value D), and the peak derived from methylene of all terminal alcohols was 60.95 to 6
1.65 ppm (integral value E), the peak derived from methylene of the short-chain branched terminal alcohol being 60.95 to 61.18 pp
m (integral value F), and the short-chain branch content can be calculated by the following equation. Short chain branch content (mol%) = [(D / 2) / C] ×
(F / E) × 100

[Method of Measuring Water-Solubleness of Water-Soluble Film] A film sample having a thickness of 40 μm was cut into a square of 40 mm × 40 mm, and this was cut into a slide mount.
The film was immersed in water with stirring at a temperature of ° C., and the time (seconds) until the film was completely dissolved was measured and evaluated. Stir 1L
1 L of distilled water was put into a beaker, the temperature was kept at 20 ° C. in a thermostat, and the rotation was performed at 250 rpm using a 5 cm stirrer. The complete dissolution time was measured five times, and the average was determined.

[Biodegradability evaluation method] Inorganic medium 300m
Sample No. 3 was prepared by mixing 30 mg of acclimated sludge (a mixture of sludge obtained from the sewage treatment plant on the day of the test start and sludge acclimated for one month in an aqueous solution of polyvinyl alcohol at 1: 1) and Sample 3.
0 mg, and add a coulometer (Okura Electric OM3001)
(Type A) and cultured at 25 ° C. for 28 days, and the biodegradation rate was determined by measuring the amount of oxygen consumed for biodegradation.

Example 1 3000 g of vinyl acetate and 0.090 g of tartaric acid were placed in a 5 L pressure reactor equipped with a stirrer, a nitrogen inlet and an initiator inlet.
The reaction vessel pressure was raised to 2.0 MPa while bubbling with nitrogen gas at room temperature, and the mixture was allowed to stand for 10 minutes. The operation of releasing the pressure was repeated three times to replace the system with nitrogen. A 0.1 g / L concentration solution of 2,2'-azobis (N-butyl-2-methylpropionamide) dissolved in methanol as an initiator was prepared, and nitrogen was replaced by bubbling with nitrogen gas. Next, the temperature in the polymerization tank was set to 1
The temperature was raised to 50 ° C. The reaction tank pressure at this time is 0.8MP
a. Next, 8.0 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 150 ° C., and 2,2′-azobis (N-butyl-2-methylpropionamide) was continuously added at 13.6 ml / hr using the above initiator solution to carry out the polymerization. Carried out. The reactor pressure during the polymerization was 0.8 MPa. After 3 hours, the mixture was cooled to stop the polymerization. At this time, the solid content concentration was 25%. Then, unreacted vinyl acetate monomer was removed while occasionally adding methanol at 30 ° C. under reduced pressure to obtain a methanol solution of polyvinyl acetate (concentration: 33%). Methanol was added to the obtained polyvinyl acetate solution to adjust the concentration to 25.
% To 400 g of a methanol solution of polyvinyl acetate (100 g of polyvinyl acetate in the solution) adjusted to be 40%.
Saponification was carried out by adding 2.3 g of an alkali solution (10% methanol solution of NaOH) at 2.3 ° C. (molar ratio (MR) 0.005 to vinyl acetate unit in polyvinyl acetate). The gel that was gelled in about 20 minutes after the addition of the alkali was pulverized by a pulverizer and left for 1 hour to progress the saponification. Then, 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the completion of the neutralization using a phenolphthalein indicator, 1000 g of methanol was added to white solid polyvinyl alcohol (hereinafter abbreviated as PVA) obtained by filtration, and the mixture was allowed to stand at room temperature for 3 hours for washing. After repeating the above washing operation three times, the PV obtained by centrifugal drainage was obtained.
A in a dryer at 70 ° C. for 2 days to dry PVA (PV
A-1) was obtained.

The degree of saponification of the obtained PVA (PVA-1) was 88 mol%. Further, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization is saponified at an alkali molar ratio of 0.5, and the pulverized one is left at 60 ° C. for 5 hours to advance saponification. After
Soxhlet washing with methanol was performed for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the degree of polymerization of the PVA was measured according to JIS-K6726 of a usual method, it was 1200. The amount of 1,2-glycol bound to the purified PVA was changed to 500 MHz proton NM.
It was 2.5 mol% when determined as described above from the measurement with an R (JEOL GX-500) apparatus.

To 100 parts by weight of the obtained PVA, 20 parts by weight of glycerin as a plasticizer and 900 parts by weight of water were added and stirred at 90 ° C. to prepare an aqueous solution having a PVA concentration of 9.8% by weight. After sufficiently defoaming the aqueous solution at 60 ° C, it was cast on a polyester film and dried at 90 ° C. Thereafter, a heat treatment was performed at 100 ° C. for 10 minutes. The thickness of the obtained film was 40 μm. Using the obtained film, water solubility at 20 ° C. and biodegradability were evaluated. The results obtained are shown in Table 3.

Example 2 Polymerization and saponification were carried out in the same manner as in Example 1 except that the polymerization temperature was changed to 180 ° C. Table 1 shows the conditions for PVA synthesis, and Table 2 shows the analysis values of the obtained resin (PVA-2). Then, the same operation as in Example 1 was performed to prepare a film having the composition shown in Table 3, and the water solubility and biodegradability were evaluated. The results are shown in Table 3.

Example 3 29.4 kg of vinyl acetate and 0.6 kg of methanol were charged into a 50 L pressure reactor equipped with a stirrer, a nitrogen inlet, an ethylene inlet, an initiator addition port and a delay solution addition port. After the temperature was raised, the system was purged with nitrogen for 30 minutes by bubbling nitrogen. Next, the reaction tank pressure was 1.8 MPa.
Was introduced so that A 0.1 g / L solution of 2,2′-azobis (N-butyl-2-methylpropionamide) dissolved in methanol as an initiator was prepared, and nitrogen replacement was performed by bubbling with nitrogen gas. After adjusting the internal temperature of the polymerization tank to 150 ° C., 45 ml of the above initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to raise the reaction tank pressure to 1.8 MPa,
The polymerization temperature was maintained at 150 ° C., and 2,2′-azobis (N-butyl-2-methylpropionamide) was continuously added at 185 ml / hr using the above initiator solution to carry out polymerization. After 3 hours, when the degree of polymerization reached 25%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled through to completely remove ethylene. Next, unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of polyvinyl acetate. Methanol was added to the resulting polyvinyl acetate solution to give a concentration of 30.
% To 333 g of a polyvinyl acetate methanol solution (100 g of polyvinyl acetate in the solution) adjusted to be
9.3 g (molar ratio (MR) 0.006 with respect to vinyl acetate units in polyvinyl acetate) of an alkaline solution (Na
(10% methanol solution of OH) was added for saponification. After about 5 minutes from the addition of the alkali, the gelled system was pulverized with a pulverizer and left at 40 ° C. for 1 hour to progress the saponification. Then, 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the completion of neutralization using a phenolphthalein indicator, a white solid PVA obtained by filtration is obtained.
Was added and methanol was added and washed at room temperature for 3 hours. After repeating the above washing operation three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain a dried PVA (PVA-3). The obtained ethylene-modified P
The above analysis of VA revealed that the degree of polymerization of PVA-3 was 1150, the degree of saponification was 88 mol%, and the amount of ethylene modification was 3 mol%. The analytical values of the obtained resin (PVA-3) are shown in Table 2. Then, the same operation as in Example 1 was performed to prepare a film having a composition shown in Table 3 and having a thickness of 40 μm, and water solubility and biodegradability were evaluated. The results are shown in Table 3.

Example 4 Polymerization and saponification were carried out in the same manner as in Example 3 except that propylene was used instead of nitrogen as the replacement gas in the reaction vessel, and the conditions during the polymerization were changed as shown in Table 1. . The analytical values of the obtained resin (PVA-4) are shown in Table 2. However,
The amount of propylene modification was determined by measuring the DSC of a polymer saponified to a saponification degree of 99.9 mol% and determining the melting point. The amount of modification [式 (mol%)] was determined from the melting point [Tm (° C.)] using the following equation. Δ = (234.1-Tm) /7.55 Then, the same operation as in Example 1 was performed to prepare a film having a composition shown in Table 3 and having a thickness of 40 μm, and the evaluation of water solubility and biodegradability was performed. Table 3 shows the results.

Example 5 Polymerization and saponification were carried out in the same manner as in Example 1 except that the polymerization temperature was changed to 120 ° C. Table 1 shows the conditions for PVA synthesis, and Table 2 shows the analysis values of the obtained resin (PVA-5). Then, the same operation as in Example 1 was performed to prepare a film having a composition shown in Table 3 and having a thickness of 40 μm, and water solubility and biodegradability were evaluated. The results are shown in Table 3.

Example 6 Vinyl acetate 20 was placed in a 5 L four-neck separable flask equipped with a stirrer, a nitrogen inlet, an initiator inlet, and a reflux condenser.
00 g, methanol 400 g, vinylene carbonate 7
8.8 g was charged, and the system was replaced with nitrogen while bubbling nitrogen at room temperature for 30 minutes. The internal temperature of the above polymerization tank is 60 ° C.
Then, 0.9 g of α, α'-azobisisobutyronitrile was added as an initiator to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60 ° C., and after 4 hours, the polymerization was stopped by cooling. At this time, the solid content concentration was 55%. Then, unreacted vinyl acetate monomer was removed while occasionally adding methanol at 30 ° C. under reduced pressure to obtain a methanol solution of polyvinyl acetate (concentration: 33%). Methanol was added to the obtained polyvinyl acetate solution to adjust the concentration to 25% by adding methanol.
0 g (100 g of polyvinyl acetate in the solution) and 46.4 g (molar ratio (MR) 0.005 to vinyl acetate unit in polyvinyl acetate) of alkali solution (N) at 40 ° C.
(10% methanol solution of aOH) was added to perform saponification. The gel that was gelled in about 1 minute after the addition of the alkali was pulverized with a pulverizer and left for 1 hour to progress the saponification. Then, 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the completion of the neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration and washed at room temperature for 3 hours. After the above washing operation was repeated three times, P
VA is left in a dryer at 70 ° C. for 2 days to dry PVA (P
VA-6) was obtained. The degree of saponification of the obtained PVA (PVA-6) was 88 mol%. Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5,
After the pulverized product was left at 60 ° C. for 5 hours to progress saponification, Soxhlet washing with methanol was carried out for 3 days, followed by drying at 80 ° C. for 3 days under reduced pressure to purify the purified PV.
A was obtained. The degree of polymerization of the PVA is determined according to the standard method of JIS K672.
It was 1700 when measured according to 6. The purified P
The 1,2-glycol bond amount of VA was determined as described above from the measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, and it was 3.0 mol%.
Then, the same operation as in Example 1 was performed to prepare a film having a composition shown in Table 3 and having a thickness of 40 μm, and water solubility and biodegradability were evaluated. The results are shown in Table 3.

Comparative Example 1 Water was added to 100 parts by weight of polyvinyl alcohol (PVA-7) having a 1,2-glycol bond content of 1.6 mol%, a polymerization degree of 1700 and a saponification degree of 88 mol%, polymerized at a polymerization temperature of 60 ° C. Add 900 parts by weight, stir at 90 ° C, and add 10% by weight.
An aqueous solution was made. After sufficiently defoaming the aqueous solution at 60 ° C, it was cast on a polyester film and dried at 90 ° C. Thereafter, a heat treatment was performed at 100 ° C. for 10 minutes. Table 3 shows the water solubility and biodegradability of the obtained film having a thickness of 40 μm.
It was shown to.

COMPARATIVE EXAMPLE 2 Plasticization was carried out with respect to 100 parts by weight of polyvinyl alcohol (PVA-7) having a 1,2-glycol bond content of 1.6 mol%, a polymerization degree of 1700 and a saponification degree of 88 mol% polymerized at a polymerization temperature of 60 ° C. As an agent, 20 parts by weight of glycerin and 900 parts by weight of water were added, and the mixture was stirred at 90 ° C. to prepare an aqueous solution having a PVA concentration of 9.8% by weight. After sufficiently defoaming the aqueous solution at 60 ° C,
It was cast on a polyester film and dried at 90 ° C.
Thereafter, a heat treatment was performed at 100 ° C. for 10 minutes. Table 3 shows the water solubility and biodegradability of the obtained film having a thickness of 40 μm.

Comparative Examples 3 to 7 Polymerization and saponification were carried out in the same manner as in Example 1 except that the synthesis conditions were changed as shown in Table 1. The analytical values of the obtained resin are shown in Table 2. Then, the same operation as in Example 1 was performed to prepare a film having a composition shown in Table 3 and having a thickness of 40 μm, and water solubility and biodegradability were evaluated. The results are shown in Table 3.

Comparative Example 8 Polyvinyl alcohol (PVA-1) synthesized in Example 1
70 parts by weight of glycerin as a plasticizer and 900 parts by weight of water were added to 100 parts by weight, and the mixture was stirred at 90 ° C. to prepare an aqueous solution having a PVA concentration of 9.3% by weight. 60 ° C
After defoaming enough, cast on a polyester film,
Dried at 90 ° C. Thereafter, a heat treatment was performed at 100 ° C. for 10 minutes. The obtained film having a thickness of 40 μm had severe bleed-out of the plasticizer, was blocked, and was not practically usable. The water solubility and biodegradability are shown in Table 3.

Comparative Example 9 Sulfonic acid-modified 3 mol% polymerized at a polymerization temperature of 60 ° C.
1.5 mol% of 1,2-glycol bond, degree of polymerization 140
0, polyvinyl alcohol having a saponification degree of 88 mol% (PV
A-11) 20 parts by weight of glycerin as a plasticizer and 900 parts by weight of water were added to 100 parts by weight, and the mixture was stirred at 90 ° C. to prepare an aqueous solution having a PVA concentration of 9.8% by weight. After sufficiently defoaming the aqueous solution at 60 ° C, it was cast on a polyester film and dried at 90 ° C. Then, at 100 ° C, 1
Heat treatment was performed for 0 minutes. The water solubility and biodegradability of the obtained film having a thickness of 40 μm are shown in Table 3.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

As is clear from the above examples, the polyvinyl alcohol-based water-soluble film of the present invention has extremely good water-solubility as compared with the conventional polyvinyl alcohol-based polymer film while having biodegradability. . This is a water-soluble film comprising a polyvinyl alcohol resin having a 1,2-glycol bond amount of 2.0 mol% or more and a saponification degree of 80 to 92 mol% and a specific amount of a plasticizer as a polyvinyl alcohol polymer. It has been achieved by use.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shintaro Hikasa 1621 Sazu, Kurashiki-shi, Okayama F-term in Kuraray Co., Ltd.

Claims (3)

[Claims] 1. A composition comprising 100 parts by weight of a polyvinyl alcohol resin having a 1,2-glycol bond amount of 2.0 mol% or more and a saponification degree of 80 to 92 mol%, and 10 to 50 parts by weight of a plasticizer. Polyvinyl alcohol-based water-soluble film. 2. The polyvinyl alcohol-based water-soluble film according to claim 1, wherein the polyvinyl alcohol-based resin has a short-chain branching of 0.03 mol% or more. 3. The polyvinyl alcohol-based water-soluble film according to claim 1, wherein the film having a thickness of 40 μm has a dissolution time in water at 20 ° C. of 40 seconds or less.