JPS62220540A - Polyvinyl alcohol film - Google Patents

Abstract

PURPOSE:The titled film which is suitable for packaging film, is flexible even by no addition of plasticizer, has no reduction in plasticizer content in the case of use of plasticizer and has improved transparency and water resistance, consisting of two kinds of polymers containing specific structural units in specific ratios. CONSTITUTION:(A) 1-50pts.wt., preferably 5-40pts.wt. polymer which consists of A1: 0.5-50mol% structural unit shown by formula I, A2: 0-20mol% structural unit shown by formula II (R<1> is H or 1-10C hydrocarbon), A3: 50-99.5mol% structural unit shown by formula III and A4: 0-30mol% structural unit shown by formula IV (R<2> is H or 1-10C hydrocarbon), has 10-2,000 polymerization degree and correlation ¦X-Y¦<=10 when A+C is >=95mol%, B+C is Xmol% and D is Ymol% is blended with (B) 50-99pts.wt., preferably 60-95pts.wt. polymer which consists of 95-100mol% structural unit shown by the formula III and 0-5mol% structural unit shown by the formula IV and has >=300 polymerization degree and, if necessary, (C) 1-20pts.wt. based on 100pts.wt. total amounts of a plasticizer.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to polyvinyl alcohol films. More specifically, the present invention relates to a polyvinyl alcohol film that has improved flexibility, good transparency, and excellent water resistance.

(However, the term "film" as referred to in the present invention also includes a sheet-like material having a thickness of 5 mm or less.) B. Conventional technology Vinyl esters, especially vinyl acetate, are polymerized and saponified to produce solid polyvinyl alcohol (hereinafter referred to as PVA). In addition to its excellent mechanical properties, the film has excellent properties such as good printability and transparency, so it is used for packaging, mold release, etc.
It is widely used for agriculture, industrial materials, water-soluble films, etc., and is particularly prized as a packaging film.

Since it absorbs moisture during normal use, it has no static charge, and has the excellent characteristics of less adhesion of dust due to static electricity and less deterioration of the appearance of the packaging. In addition, suitable plasticizers (often Grise 11) are used. ) G72pvA film is extremely flexible and does not cause the packaging to bump into other objects, and does not make unpleasant crunchy or rattling sounds when touched by a person, giving it a very soft tactile feel. Because of its good quality, it has succeeded in giving the package a high-class image.

Mayu PVA film has the property of absorbing moisture from the air and this water acts as a plasticizer for the PVA film, but the amount of moisture absorbed changes depending on the humidity in the air. , PVA-based film alone has the property that the flexibility of the film changes depending on humidity.

Particularly under low humidity conditions, the amount of moisture absorbed decreases, making it hard and brittle. Friend, the film tends to harden as the temperature drops, so when the humidity is low in winter, the synergistic effect causes the film to become hard and brittle, making it more likely to cause problems such as film cracking when used as a packaging film. . Therefore, the PVA film alone cannot be used as a packaging film.

To improve this point, conventional methods have been to add polyhydric alcohols such as glycerin as plasticizers.

By adding an appropriate amount of plasticizer, it is possible to obtain a PVA film that is sufficiently flexible and suitable for use even in low humidity conditions in winter, and is widely used.

However, although initial softening can be achieved by adding plasticizers, due to the problem that the content of plasticizers decreases over time, when used for a long time,
The plasticizer content was reduced, and problems such as cracking and cracking of the film due to lack of flexibility under low humidity conditions in winter often occurred. The reason why the plasticizer content decreases over time is not clear, but possible causes include bleeding of the plasticizer onto the film surface, volatilization, and transfer of the plasticizer due to contact between the film and the contents or other articles. Ru.

In recent years, there has been a strong desire to improve this problem of decreasing plasticizer content in PVA-based films, and it is necessary to develop PVA-based films that are flexible even without the addition of plasticizers and PVA-based films whose plasticizer content does not decrease over time. was an urgent matter.

Particularly in the field of water-soluble films, films that exclude gold, such as general packaging films, require excellent water resistance.
For this reason, highly saponified PVA, which is highly crystalline, is used as a PVA-based film, but because high saponified PVA is highly crystalline, it has insufficient compatibility with plasticizers. Moreover, the plasticizing effect of the plasticizer is also weakened by the crystallinity. Therefore, a large amount of plasticizer is required to maintain flexibility during low humidity conditions in winter, and due to the poor compatibility between plasticizer and highly saponified PVA, dryness and humidity due to climate changes, It is believed that repeated cooling and heating causes plasticizer bleed, resulting in a significant drop in plasticizer content6. Various attempts have been made to solve this problem, but no satisfactory solution has yet been found. The current situation is that it has not been found. For example, attempts to find plasticizers that are more compatible with highly saponified PVA have not been successful.
Conventionally known polyhydric alcohol plasticizers are currently the best. In addition, in order to increase compatibility with plasticizers, Pv
One possible method is to disrupt the crystallinity of A, but in this case, the compatibility with the plasticizer will certainly improve, but there will be no consequences. Due to the disturbed properties, the PVA-based film loses its water resistance, and its strength is greatly reduced, resulting in a lack of usability.

The inventor has ensured this water resistance and strength (i.e., high crystallinity).
In order to solve the contradictory problem of good compatibility (i.e., low crystallinity) with plasticizers, we considered a method of using a mixture of high-crystalline PVA and low-crystalline PVA'i; However, as a low crystalline PVA, the saponification degree P
If VA or various conventionally known highly modified PVA1 were used,
Poor compatibility with highly crystalline PVA (i.e., highly saponified PVA), phase separation between PVA polymers occurs, resulting in a cloudy film, loss of transparency, and in most cases impractical. .

Problems to be Solved by the C0 Invention Under these circumstances, the present invention provides a PVA-based film that is flexible on its own even without the addition of a plasticizer. It is an object of the present invention to provide a PVA-based film whose content does not substantially decrease over time.

Means for solving the p0 problem As a result of intensive studies to solve the above problems, the inventor found that (a) the content of the following structural unit [A] is 0.5 to 50
and Φ) the following: 5 of polymer II with a content of structural units [CD content of 95 to 100 mol and mol] of O to 5 mol mol
0 to 99 parts by weight, the PVA film is a 37'2 pvA film that is flexible by itself even without the addition of a plasticizer, has good transparency, and has excellent water resistance. Next, when using a plasticizer in combination as necessary, it has the advantage of requiring less plasticizer than conventional PVA-based films, as it is flexible itself, and is compatible with plasticizers. Because of its high quality, there is virtually no decrease in plasticizer content over time, and it also has excellent transparency and water resistance.
He discovered that it was a VA film and completed the present invention.

[A]: (-CI-12-CH-)-easy H [B]: -f-Cf(2-CM) (However, R1 is H or carbon number [CD: (-CH2-CH-
)-H 0 is represented. ) The above structural units [A) to [
In the polymer I containing the structural unit [D] and the polymer (2) containing the structural unit [CD, [D], the structural unit [B] specifically includes allyl formate, allyl acetate, allyl propionate, and the like. Specific examples of the structural unit [D] include vinyl formate, vinyl acetate, and vinyl propionate. Among these, as the structural unit CB), an allyl acetate unit is more preferable, and as the structural unit [D], a vinyl acetate unit is more preferable.

Polymer I consists of structural units [A] to [D], and the content of [A] is 0.5 to 50 mol, or 5 to 50 mol.
It is more than 30 moles. If the content of [A) is too low, the softening effect of the film and the effect of preventing the plasticizer content from decreasing over time are insufficient. Further, the contents of the structural units CB) and CD) of the polymer I are 20 moles or less and 30 moles or less, respectively, and more preferably the sum of the contents of (B) and [D] is 5 moles or less. be. If the content of CH3 and CD) is more than 20 mmol and 30 mmol, respectively, it is not preferable because the solubility in water of polymer I becomes poor during film formation, and the film forming property deteriorates.

Polymer (1) is a conventionally known PVA consisting of the above-mentioned structural units [CD and [D], but in the present invention, it is particularly essential that the content of [CD] be 95 moles or more. If the content of (C) is less than 95 moles, the water resistance of the PVA-based film obtained using heavy components i and lI will be extremely poor and, for example, it cannot be used practically as a general packaging film. It's something you can't get. In this sense, it is more preferable that the content of 1 [C] is 98 moles or more, the sum of the contents of [B] and [D] of the zero-polymer I (X is O), and CD of the polymer II) It is preferable that the content of (Y and 0) be close to each other. When X and Y are significantly flattened, the compatibility between Polymer I and Polymer II deteriorates, and the film tends to become cloudy, resulting in poor transparency. Therefore, it is preferable that the difference between X and Y does not exceed 10 mole, more preferably 5 mole %.

The weight of the heavy content l is not particularly limited, but it is preferably 1
It is 0-2000. When the degree of polymerization is extremely low, migration of the polymer in the obtained film,
The polymerization degree of ON aggregate II, which is undesirable because it causes plasticizer-like behavior such as bleeding and migration to other substances, is not particularly limited, but is preferably 300 or more. If the degree of polymerization is lower than this, the strength of the film tends to decrease, which is not preferable.

The fecal amounts of the conjugate I and the polymer II are 1 to 50 parts by weight, and 50 to 99 parts by weight, preferably 5 to 40 parts by weight, and 60 to 95 parts by weight, respectively. If the amount of polymer 1 used is small, the desired softening effect of the film and, if a plasticizer is used, the effect of preventing the content of plasticizer from decreasing over time will be insufficient. Moreover, if the amount of heavy content I is used is too large, the film becomes too flexible, water resistance is impaired, and strength decreases significantly, which is not preferable.

Furthermore, if Polymer I is used alone, only a film with almost no water resistance and low strength can be obtained, so that it is not very practical.

Polymer! and () may each contain a small amount of other components within a range that does not impede the compatibility of the polymers I and II and does not hinder the softening of the film, which is the object of the present invention. I can't help it. As such a component, a method of copolymerizing monomers that can be copolymerized can be considered.

Such monomers include, for example, olefins such as ethylene, propylene, butylene, α-hexene, (meth)
Unsaturated acids such as acrylic acid, phosphoric acid, (anhydrous) maleic acid, 7-malic acid, itaconic acid, and their alkyl esters, alkali salts, (meth)acrylamide%UN-dimethyl acrylamide, alkyl vinyl ether, 2- Acrylamide - Unsaturated sulfonic acids and their alkali salts such as 2-methylglobasosulfonic acid and allylsulfonic acid, trimethyl-2-(1-(meth)acrylamide-
Cationic monomers such as 1,1-dimethylethyl) ammonium chloride, silyl group-containing monomers such as vinyltrimethoxysilane and allyltriethoxysilane, acetic acid f-7
"Lopenyl, impropenyl alcohol, 2-methyl-
Examples include 4-acetoxy-1-butene, 2-methyl-1-buten-4-ol, α-methylallyl acetate, α-methylallyl alcohol, and the like.

The PV of the present invention comprising the above-mentioned polymer (1) and polymer (2)
A-type film does not use plasticizers, and is made of its own material that is already light-flexible. However, when a higher degree of flexibility is desired, such as for general packaging, It goes without saying that various plasticizers can be used in combination as appropriate.

In this way, when a higher degree of flexibility is required, (a) the content of the above structural unit [A] is 0.5 to 50
(b) 1 to 50 parts by weight of a polymer 1 in which the content of mole B] is 0 to 20 mol and the content of C] is 50 to 99.5 mol, and gold coins of 0 to 30 mol CD; 50-99 of polymer II having a content of 95-100 mol and 0-5 mol of the structural unit [C]
Parts by weight, and (C) A PVA-based film comprising 1 to 20 parts by weight of a plasticizer per 100 parts by weight of the sum of the weights of polymers I and II (C) is exemplified as a preferable film. In particular, the plasticizer is the sum of the weights of polymers ① and Ⅰ 10
Particularly suitable is one containing 2 to 15 parts by weight per 0 parts by weight. If the amount of plasticizer is too large, problems such as the film becoming too flexible and flattening occur.

The plasticizer is not particularly limited and any known plasticizer can be used, but polyhydric alcohol plasticizers are particularly preferred. Examples of polyhydric alcohol plasticizers include ethylene glycol, trimethylene glycol, tetophmenalene glycol, glycerin, butanediol, diethylene glycol, triethylene glycol, and trimethylolpropane. Of these, glycerin is Most preferred from the viewpoint of plasticizing effect, compatibility with polymers, high boiling point, etc.

There are no particular restrictions on the method for producing Polymer 1, but a method is to subject vinyl acetate and allyl acetate, or vinyl acetate (2) and allyl alcohol to radical synthesis, and to saponify the resulting rt symbiotic substance using an alkali catalyst. is convenient and preferable. Copolymerization includes bulk polymerization, solution polymerization, suspension M, 7x, emulsion polymerization, etc.
Conventionally known methods can be applied. As the Me catalyst, an azo peroxide catalyst, a redox catalyst, or the like is appropriately selected depending on the polymerization method.

For the saponification reaction of the copolymer, conventionally known alkali catalyst or acid catalyst alcoholysis, hydrolysis, etc. can be applied. Among these, the saponification reaction using an NaOH catalyst using methanol as a solvent is simple and most preferred.

Although there are no particular restrictions on the method for producing Polymer (1), a method conventionally known as a method for producing PvA, in which vinyl acetate is radically polymerized and then saponified is simple and preferred. The same method as for producing Polymer I, in which vinyl acetate is polymerized alone, is preferably used for the production of Polymer I. The method used as is preferably used. That is, using water as a solvent,
A casting method in which casting is performed on a drum 11 and a belt and drying, a melt extrusion method in which pellets impregnated with water are melt-extruded, etc. can be applied. The film after film formation may be subjected to heat treatment depending on the purpose, or may not be subjected to machete heat treatment. There is also nothing wrong with carrying out stretching.

The PVA film of the present invention has excellent flexibility.

Due to its transparency and water resistance, it can be used in various fields such as release films for various plastics, prize packaging films, agricultural films, and films for industrial materials, but it is especially suitable for general packaging films. used.

90 Actions and Effects of the Invention The PVA film of the present invention has excellent flexibility, transparency, and water resistance, and when a plasticizer is used in combination, the plasticizer content changes over time. Although the reason why it is so effective in preventing a decline in performance is not clear, it is presumed as follows.

Firstly, the polymer I used in the PVA film of the present invention tends to have crystallinity due to the presence of structural units [A], [B], and [D], and is a flexible polymer; Secondly, it is a highly hygroscopic polymer compared to ordinary PVA, and has a high moisture content even at low humidity, and has a large plasticizing effect due to moisture 4, so it is advantageous for softening the film at low humidity. Third, it has good compatibility with plasticizers, especially polyhydric alcohol plasticizers such as glycerin, and the presence of Polymer I reduces the bleed rate of the plasticizer. Surprisingly, the presence of [A) does not impair compatibility with ordinary PVA (polymer II).

The first and second points show the effect of softening the film, that is, compared to conventional plasticizer-added PVA films, it is possible to reduce the amount of plasticizer added or eliminate the use of plasticizer. . The third point shows that even when a plasticizer is used, it is possible to prevent the plasticizer content from decreasing over time. The fourth point shows that it can be used in blends with ordinary PVA, which is extremely important in obtaining a PVA-based film with excellent transparency.

Although a film obtained using Polymer I alone is highly flexible, it has poor water resistance and a large decrease in strength, making it impractical. Therefore, the flexible and strong film of the present invention , and has good transparency and excellent water resistance.
In addition, in order to obtain an LfcPV A film that is extremely practical, as described in detail above, the above-mentioned specific polymer 11 and the above-mentioned specific high degree of saponification polymer It is essential to use blended formulations according to the above specific amount allocation.

By the way, in Japanese Patent Publication No. 30-6485, PVA alone or with PVA having a small amount of allyl alcohol units is disclosed.
Synthetic fibers, membranes, and other base materials made of mixtures with VA are described, and a friend film is disclosed that looks similar to unexploded PVA-based films, however, The film described in Japanese Patent Publication No. 30-6485 is simply a water-soluble film that easily dissolves in water at room temperature, in other words, it has no water resistance. The described invention is completely different from the present invention in its purpose, and also in the water resistance of the obtained PVA film, that is, the practicality of ft #110 for use as a general packaging film, etc. However, the purpose of the present invention cannot be achieved with the invention described in the publication. is not limited to these in any way. Note that "part" and "chi" mean "heavy electrical department" and "weight t%J" unless otherwise specified.

Example of g preparation method for Polymer I'M@-2400 parts of vinyl acetate, 310 parts of allyl acetate in a can
After charging 301 parts of methanol and heating to 60°C and purging with nitrogen, 6.7 parts of 2.2'-azobisisobutyronitrile was added.
6 parts were added and polymerized at 60°C for 6 hours. The polymerization rate is 52
．． I'm sorry for the 5th one.

After expelling unreacted vinyl acetate monomer by introducing methanol vapor, a 50% methanol solution of the copolymer was obtained. While stirring this solution at 40° C., 1.4% of sodium hydroxide based on the weight of the copolymer was dissolved in the solution, and 9 methanol J solution was added to perform a saponification reaction. The obtained white gel was pulverized, thoroughly washed with methanol, and then dried to obtain a polymer (1) (referred to as polymer A) consisting of the following structural units (A) to (El)).

(A): (-C)i2-C)l+disturbance H [B]: (-CH2-CH+ H2 ■ 0-C-CH3 [C]: (-C ratio-CH-)-H [D]: ( -(&-CH)- 0-C-CH3 Polymer A A tri DMSO O, -d6 te O'H
-NMRL t), the content of structural units [A] to [1)) is A, 9.9 mol%, 0.1 mol%, 88.2
It was calculated as 0.8%/l/%. In addition, Polymer 711A was reacetylated with a mixture of acetic anhydride and pyridine, and It aggregates 4B to 4F were synthesized using a method similar to that of Polymer 4A, which was measured in acetone at 30°C. The degree of polymerization can be adjusted by using methanol in the polymerization system.
This was done by changing the . Table 1 shows the types of comonomers and the yield of 7t! The analysis results of coalescence I are shown.

Table 1: Analysis results of Polymer I Preparation method of Polymer H Polymer (1) was synthesized in the same manner as the preparation method of Polymer I, except that allyl acetate was not used all around. The obtained polymer AG-
The analysis results of L are shown in Table 2.

Table 2=Analysis results of polymer H Example 1 After dissolving 30 parts of polymer A and 70 parts of polymer X in 900 parts of water, 5 parts of glycerin was added. This solution was heated to 70°C.
The mixture was cast onto a rotating drum to form a film, and dried to obtain a film with a thickness of 75 μm. Table 3 shows the results of visually determining the transparency of this film. This film was heat treated at 120°C for 10 minutes, left in an atmosphere of 20°C and 65% RH for 7 days, and then cut into 5 square pieces.
Moved to. After standing in a desiccator for one day, the film surface was visually inspected to observe the state of plasticizer bleed. The results are also shown in Table 3. .

Examples 2 to 8, Comparative Examples 1 to 5 Table 3 shows the results of testing films of various compositions in the same manner as in Example 1.

From Table 3, it is clear that the film of the present invention has excellent transparency like conventional PVA films, has good compatibility with plasticizers, and is highly effective in preventing plasticizer bleeding.

The following is a summary of Example 9 A film that was formed into a film and heat-treated in the same manner as in Example 1 was left in an atmosphere of 20°C and 4Q% RH for 7 days, and then subjected to a tensile test using an autograph. The results are shown in Table 4. Table 4 shows the results of tests conducted in the same manner except for the holes with different amounts of glycerin added.

Autograph measurement conditions Similar to Example 9, tensile tests were conducted on films with different polymer compositions and with different amounts of glycerin added. The results are shown in Table 4.

From Table 4 below, the film of the present invention is more flexible (i.e., Young's modulus is lower and elongation is higher) when compared with the same amount of glycerin under low humidity, or conversely, it has the same degree of flexibility. It is clear that a small amount of glycerin is sufficient for the whole process. This indicates that in addition to the film of the present invention exhibiting the effect of suppressing glycerin bleed as shown in the results of Examples 1 to 6, it is even more effective in preventing bleed by reducing the amount of glycerin added. It shows that.

Well, even if glycerin is not added to the film of the present invention, or even if glycerin is added and the film completely loses glycerin for some reason, the films of Comparative Examples 6 to 8 will not lose glycerin. It is clear from Table 4 that the films are more flexible than the films of Comparative Examples 6 to 8.

Example 15 After forming a film in the same manner as in Example 1 except for changing the amount of glycerin, the heat-treated film was cut into a size of t-10 m square, and then a commercially available thinly torn cloth (size 12 cIn
Sandwiched between two sheets (four sides, thickness l■). Furthermore, the top and bottom of the cloth are sandwiched between glass plates to ensure good contact between the cloth and film.
20°C, 95% [i] for 1 day, then 5°C, 3
Place on a flat surface for a 1 day cycle under 0SRH. After a total of 10 days, take out the film and store at 5°C and 30SRH.
At the bottom, fold the film in half at the center and observe whether the film cracks or not.The 7'co results are shown in Table 5.

Examples 16 and 17, Comparative Example 9 Table 5 shows the results of a similar test conducted in parallel with Example 15.
Shown accordingly. From Table 5, it is clear that the film of the present invention has a better flexibility retention effect than the comparative example.

Margin below Table 5: Film flexibility retention test 1) ○: Does not break even when bent.

×: Breaks when bent.

! The same method as in Example 1 was used except that glycerin was not used. The film was made into a film and heat treated. The film was immersed in water at 20°C, and the temperature of the water was raised at a rate of 1°C per minute t-1, until the film was completely formed. The temperature of the water dissolved in the water was determined visually. The results are shown in Table 6.

Example 19, Comparative Examples 1o and 11 Tests were conducted in the same manner as in Example 18 except for the following changes, except that the degree of saponification of Polymer II used in Example 18 was changed. Result t-
It is also shown in Table 6. From Part 6, it is clear that the film of the present invention has excellent water resistance.Table 6: Water resistance test of film

Claims (18)

[Claims] (1) (a) Content of the following structural unit [A] is 0.5 to 5
0 mol%, the content of [B] is 0 to 20 mol%, the content of [C] is 50 to 99.5 mol%, and the content of [D] is 0 to 30
1 to 50 parts by weight of Polymer I, which is mol%, and (b) a polymer in which the content of the following structural units [C] is 95 to 100 mol% and the content of [D] is 0 to 5 mol% II-5
A polyvinyl alcohol film comprising 0 to 99 parts by weight. [A]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [B]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R^
1 represents H or a hydrocarbon group having 1 to 10 carbon atoms. ) [C]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [D]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R^
2 represents H or a hydrocarbon group having 1 to 10 carbon atoms. ) (2) Content of structural unit [C] of polymer II is 98 to 100
The polyvinyl alcohol film according to claim 1, which is mol%. (3) The polyvinyl alcohol film according to claim 1, wherein the sum of the contents of structural units [A] and [C] in polymer I is 95 mol% or more. (4) If the sum of the contents of structural units [B] and [D] in polymer I is X mol%, and the content of structural units [D] in polymer II is Y mol%, |X-Y|≦ 10. The polyvinyl alcohol film according to claim 1, wherein (5) The polyvinyl alcohol film according to claim 1, wherein the content of the structural unit [A] in the polymer I is 5 to 30 mol%. (6) The polyvinyl alcohol film according to claim 1, wherein the polymer I has a polymerization degree of 10 to 2,000, and the polymer II has a polymerization degree of 300 or more. (7) The polyvinyl alcohol film according to claim 1, wherein R^1 of the structural unit [B] is a methyl group, and R^2 of the structural unit [D] is a methyl group. (8) 5 to 40 parts by weight of Polymer I and 60 parts by weight of Polymer II
The polyvinyl alcohol film according to claim 1, comprising 95 parts by weight. (9) (a) The content of the following structural unit [A] is 0.5 to 5
0 mol%, the content of [B] is 0 to 20 mol%, the content of [C] is 50 to 99.5 mol%, and the content of [D] is 0 to 30
(b) 1 to 50 parts by weight of Polymer I, which is mol%; 5
and (c) 1 to 20 parts by weight of a plasticizer based on 100 parts by weight of the sum of the weights of polymers I and II. [A]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [B]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R^
1 represents H or a hydrocarbon group having 1 to 10 carbon atoms. ) [C]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [D]: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, R^
2 represents H or a hydrocarbon group having 1 to 10 carbon atoms. ) (10) Content of structural unit [C] of polymer II is 98 to 10
The polyvinyl alcohol film according to claim 9, which has a content of 0 mol %. (11) The polyvinyl alcohol film according to claim 9, wherein the sum of the contents of structural units [A] and [C] in polymer I is 95 mol% or more. (12) If the sum of the contents of structural units [B] and [D] in polymer I is X mol%, and the content of structural units [D] in polymer II is Y mol%, |X-Y|≦ 10. The polyvinyl alcohol film according to claim 9. (13) The content of structural unit [A] in polymer I is 5 to 30
The polyvinyl alcohol film according to claim 9, which is mol%. (14) The degree of polymerization of the polymer I is 10 to 2000,
The polyvinyl alcohol film according to claim 9, wherein the polymer II has a degree of polymerization of 300 or more. (15) The polyvinyl alcohol film according to claim 9, wherein R^1 of the structural unit [B] is a methyl group, and R^2 of the structural unit [D] is a methyl group. (16) 5 to 40 parts by weight of Polymer I, 60 parts by weight of Polymer II
10. The polyvinyl alcohol film according to claim 9, comprising 1 to 20 parts by weight of a plasticizer per 100 parts by weight of the sum of the weights of Polymers I and II. (17) The polyvinyl alcohol film according to claim 9, wherein the plasticizer is a polyhydric alcohol plasticizer. (18) The polyhydric alcohol plasticizer is glycerin,
18. The polyvinyl alcohol film according to claim 17, which contains 2 to 15 parts by weight of glycerin per 100 parts by weight of the sum of the weights of polymers I and II.