JP2001200070A - Polyvinyl alcohol resin film - Google Patents

Abstract

[PROBLEMS] To provide a film excellent in water resistance, moisture resistance, hot water solubility, durability and strength. SOLUTION: The content of α-olefin units having 4 or less carbon atoms is 1 to 19 mol%, the degree of polymerization is 200 to 3000, the degree of saponification is 80 to 100 mol%, and the total content of carboxyl groups and lactone rings is 0.02 to 0. A film obtained by hot-melt molding a 4 mol% polyvinyl alcohol-based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film made of a polyvinyl alcohol resin. More specifically, the present invention relates to a film having excellent water resistance, moisture resistance, hot water solubility, durability, and strength.

[0002]

2. Description of the Related Art Films made of polyvinyl alcohol are excellent in mechanical properties, transparency, oxygen barrier properties, oil resistance, etc., and are used for fiber wrapping materials, agricultural films, gas barrier materials, filters, optical films such as polarizing films, and the like. Has been used as In addition, because polyvinyl alcohol has water solubility and biodegradability, packaging, agricultural, civil engineering,
In recent years, it has attracted attention as a water-soluble film and a biodegradable film for medical use, industrial use, daily goods, toys, and the like.

Conventionally, polyvinyl alcohol has a melting point and a decomposition temperature close to each other, so that it has been difficult to produce a film by hot melt molding. Various studies have been made so far to impart thermal fusibility to polyvinyl alcohol. For example, methods of lowering the melting point and melt viscosity and imparting heat fusibility by lowering the degree of saponification, copolymerizing other comonomers, or adding a plasticizer have been studied.

[0004] However, when the degree of saponification is reduced, the thermal stability is reduced, and an acetic acid odor or a decomposed odor is generated at the time of molding. The strength and elastic modulus when the film thus obtained is left under high humidity are greatly reduced. Also, in the case of copolymerization, the strength and elastic modulus when the obtained film is left under high humidity are reduced. Furthermore, when the melting point and melt viscosity are lowered by adding a plasticizer, not only does the strength and elastic modulus of the obtained film left under high humidity decrease, but also the plasticizer oozes out on the film surface. Can often be a problem. Japanese Patent Application Laid-Open No. 8-258145 also considers a method of adding water to a vinyl alcohol-based polymer and molding the same. However, the production cost is high, and water foaming is conspicuous in the film, resulting in poor appearance. There are many.

Further, in recent years, films have been required to have water resistance and cold resistance to cold water.
That is, under cold water conditions or high humidity, there is an increasing demand for a film that can be dissolved in warm or hot water without being broken, eluted, or extremely deteriorated in physical properties. Films made of polyvinyl alcohol with a lower degree of saponification to lower the melting point, or copolymerized with a comonomer, have a reduced water resistance, and currently cannot meet these demands. There has been a demand for a film which is excellent in water resistance and moisture resistance and can be dissolved in warm water or hot water.

[0006]

SUMMARY OF THE INVENTION Under such a background, an object of the present invention is to provide water resistance, moisture resistance, hot water solubility,
It is to provide a film having excellent durability and strength.

[0007]

Means for Solving the Problems The above-mentioned object is to achieve a carbon number 4
The content of the following α-olefin unit is 1 to 19 mol%, the degree of polymerization is 200 to 3000, the degree of saponification is 80 to 100 mol%, and the total content of carboxyl group and lactone ring is 0.1.
This is achieved by providing a film obtained by hot-melt molding a polyvinyl alcohol-based resin in an amount of from 02 to 0.4 mol%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl alcohol resin used in the present invention comprises a vinyl ester and α having 4 or less carbon atoms.
-Saponified copolymers with olefins. Here, as the vinyl ester, vinyl acetate may be mentioned as a representative example, and in addition, vinyl esters such as vinyl propionate, vinyl pivalate, vinyl valerate, vinyl caprate, and vinyl benzoate may also be mentioned. These vinyl esters may be used alone or in combination of two or more.

Examples of the α-olefin having 4 or less carbon atoms include ethylene, propylene, n-butene, isobutylene and the like. Ethylene is preferred in view of water resistance and moisture resistance of the obtained film. It is surprising that by copolymerizing a specific amount of an α-olefin, particularly ethylene, it is possible to impart heat melting property to the polyvinyl alcohol-based resin without significantly impairing the water resistance and moisture resistance of the film. α
-The olefin content needs to be 1 to 19 mol%, preferably 2 to 15 mol%, and 3 to
Particularly preferred is 12 mol%. When the content of the α-olefin is less than 1 mol%, the effect of copolymerization is not remarkably exhibited, and the heat fusibility is reduced. On the other hand, when the content of the α-olefin exceeds 19 mol%, the water solubility of the obtained film decreases, and the film does not dissolve in warm water.

[0010] The polyvinyl alcohol resin of the present invention comprises:
Modifications other than α-olefins may be made as long as the effects of the present invention are not impaired. Vinyl monomers copolymerizable with vinyl esters include acrylamide, N-methylacrylamide, N-ethylacrylamide, N,
Acrylamide monomers such as N-dimethylacrylamide; methacrylamide, N-methylmethacrylamide,
Methacrylamide monomers such as N-ethyl methacrylamide and N, N-dimethyl methacrylamide; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, t-butyl vinyl ether and dodecyl vinyl ether Allyl alcohol; vinyltrimethoxysilane; N-vinyl-2-pyrrolidone, isopropenyl alcohol, 7-octen-1-ol, allyl acetate, isopropenyl acetate, and the like.

The degree of polymerization of the polyvinyl alcohol resin used in the present invention needs to be from 200 to 3000, preferably from 250 to 2500, and more preferably from 300 to 2,500.
It is particularly preferred that it is ２０００2000. 200 degree of polymerization
If it is lower, the physical properties of the obtained film, particularly impact resistance and mechanical physical properties, decrease. On the other hand, when the degree of polymerization is higher than 3000, the melt viscosity becomes high, and hot melt molding becomes extremely difficult.

The degree of saponification of the polyvinyl alcohol resin used in the present invention must be 80 to 100 mol%, preferably 85 to 100 mol%, and more preferably 90 to 100 mol%. Particularly preferred. If the saponification degree is less than 80 mol%, not only the water resistance and moisture resistance of the film are lowered, but also the thermal stability at the time of molding becomes poor,
Odor of acetic acid may be generated, and a large amount of dust or gel may be generated on the film.

Further, the polyvinyl alcohol resin is
Polyvinyl alcohol-based resins differing in at least one of the type and amount of these comonomers, the degree of saponification, and the degree of polymerization may be used as a mixture.

The polyvinyl alcohol resin used in the present invention needs to be heat fusible. The heat-fusibility is one that can set molding conditions that do not cause remarkable deterioration or deterioration such as gelation during hot-melt molding,
A polyvinyl alcohol resin having a melting point of 170 to 230 ° C is preferable. When the melting point is lower than 170 ° C., the thermal stability and heat resistance of the polyvinyl alcohol-based resin, as well as the water resistance and the moisture resistance, are reduced, which may cause a problem. On the other hand, when the melting point exceeds 230 ° C., the temperature becomes close to the thermal decomposition temperature of the polyvinyl alcohol-based resin, so that molding may be difficult. Further, those having a melt flow index of 0.1 to 500 g / 10 min at a load of 2160 g at any temperature in the range of 190 ° C. to 230 ° C. are generally used.

Further, the total content of carboxyl groups and lactone rings of the polyvinyl alcohol resin of the present invention must be 0.02 to 0.4 mol%, and 0.022 to 0.37 mol. % Is preferred, and 0.0
24 to 0.33 mol% is more preferable, and 0.025 to
0.3 mol% is particularly preferred. The carboxyl group in the present invention includes a carboxyl group or a metal salt thereof, and examples of the alkali metal include potassium and sodium. When the total content of the carboxyl group and the lactone ring is less than 0.02 mol%, the viscosity increase and gelation when the polyvinyl alcohol-based resin is hot-melt-molded become remarkable, and the melt-moldability may decrease. is there. On the other hand, when the total content of the carboxyl group and the lactone ring exceeds 0.4 mol%, not only the melt moldability may be deteriorated due to the thermal decomposition of the polyvinyl alcohol-based resin, but also the water resistance and moisture resistance of the obtained film. Performance may be reduced.

As a method for producing an α-olefin-modified vinyl alcohol resin having a carboxyl group and a lactone ring, a vinyl ester monomer such as vinyl acetate is used.
-A method of saponifying a vinyl ester resin obtained by copolymerizing an olefin with a monomer capable of forming a carboxyl group and a lactone ring in an alcohol or dimethyl sulfoxide solution, mercaptoacetic acid,
-In the presence of a thiol compound containing a carboxylic acid such as mercaptopropionic acid, a method of saponifying it after polymerizing an α-olefin and a vinyl ester monomer,
When polymerizing a vinyl ester monomer such as vinyl acetate, a chain transfer reaction to the alkyl group of the vinyl ester monomer and the vinyl ester resin occurs, and saponification is performed after obtaining a highly branched vinyl ester resin. Method, a method of reacting a co-resin of a monomer having an epoxy group and a vinyl ester monomer with a thiol compound having a carboxyl group, followed by saponification, by acetalization reaction of PVA with an aldehyde having a carboxyl group And the like.

The total content of carboxyl groups and lactone rings in the polyvinyl alcohol resin can be determined from the peak of proton NMR. After complete saponification to a degree of saponification of 99.95 mol% or more, washing with methanol was sufficient, followed by drying at 90 ° C. under reduced pressure for 2 days to analyze PVA for analysis.
And In the above case, the created analytical PVA is
It was dissolved in O-D6 and proton NMR at 500 MHz (J
EOL GX-500) at 60 ° C. Acrylic acid, acrylic acid esters, acrylamide and acrylamide derivative monomers were prepared using methacrylic acid,
The content of the monomers of methacrylic acid esters, methacrylamide and methacrylamide derivatives was calculated by a conventional method using a peak (0.6 to 1.1 ppm) derived from a methyl group directly connected to the main chain. A monomer having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, or the like is obtained by dissolving the prepared PVA for analysis in DMSO-D6, adding a few drops of trifluoroacetic acid, and adding 500 MHz. NMR (J
EOL GX-500) at 60 ° C. For quantification, the content was calculated by an ordinary method using the methine peak of the lactone ring attributed to 4.6 to 5.2 ppm. In the cases of and, the content was calculated using the peak (2.8 ppm) derived from methylene bonded to the sulfur atom.
In the case of the above, the prepared analytical PVA was replaced with methanol-D4 / D
2O = 2/8 dissolved, 500 MHz proton NMR
(JEOL GX-500) at 80 ° C. The peak derived from methylene of the terminal carboxylic acid or an alkali metal salt thereof (the following chemical formulas 1 and 2) is 2.2 p.
pm (integral value A) and 2.3 ppm (integral value B), the peak derived from the methylene of the terminal lactone ring (the following formula 3) is 2.6 ppm (integral value C), and the peak derived from methine as a vinyl alcohol unit Peak is 3.5 to 4.15 ppm
(Integral value D), and the total content of the carboxyl group and the lactone ring is calculated by the following formula. Here, △ indicates the amount of modification (mol%). Total content of carboxyl groups and lactone rings (mol%) = 50 × (A + B + C) × (1
00- △) / (100 × D)

[0018]

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[0019]

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[0020]

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In the case of (1), the prepared analysis PVA is
It was dissolved in O-D6 and proton NMR at 500 MHz (J
EOL GX-500) at 60 ° C. Peak 4.8 to 5.2 derived from methine in the acetal moiety
The content was calculated by the usual method using ppm (the following chemical formula 4).

[0022]

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The film of the present invention contains glycerin,
Those to which known plasticizers such as diglycerin and derivatives thereof, polyethylene glycol, and water are added are also included. The added amount of the plasticizer is polyvinyl alcohol resin 10
The amount is preferably 0 to 30 parts by weight, more preferably 0 to 25 parts by weight, based on 0 parts by weight. If the amount of the plasticizer exceeds 30 parts, the water resistance and moisture resistance of the film may be reduced, or the plasticizer may bleed to the surface, which may cause problems. Further, other additives (a heat stabilizer, an ultraviolet absorber, an antioxidant, a coloring agent, a lubricant, a release agent, a filler, a surfactant, and the like) can be used as long as the object of the present invention is not hindered.

The film of the present invention is produced by hot-melt molding the polyvinyl alcohol resin. The hot melt molding method is inexpensive in manufacturing cost as compared with other film forming methods, and furthermore, the film is crystallized in a process of cooling from a molten state, thereby improving water resistance, strength, etc. There are advantages. The type of the hot-melt molding method is not particularly limited, and any known method can be used as long as the resin is heated to a temperature equal to or higher than the melting point or softening point and shaped into a film. As an example, T-die extrusion molding, inflation molding, calendar molding and the like can be mentioned. Also,
The thickness of the film is not particularly limited and can be appropriately selected depending on the application. However, it is usually used in a range of usually 1 to 1000 μm.

The film of the present invention is excellent in water resistance and moisture resistance and is soluble in warm water or hot water. Specifically, the elution rate when the film is immersed in cold water at 30 ° C. for 10 minutes is preferably 40% or less, more preferably 30% or less, and particularly preferably 20% or less. It is preferable that the film does not break or melt when it is pulled up after further immersion for 10 minutes.
The elution rate when immersed in 80 ° C. warm water for 10 minutes is 7%.
0% or more, preferably 90% or more, more preferably 95%
% Or more.

The film of the present invention is excellent in water resistance, moisture resistance and hot water solubility while maintaining the excellent durability and strength of the polyvinyl alcohol resin, and is suitable for packaging, agriculture, civil engineering, and medical use. It is used for various applications such as water-soluble films or sheets, biodegradable films or sheets for industrial use, industrial use, daily goods, toys and the like.

[0027]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. In the following Examples and Comparative Examples, “parts” and “%” mean on a weight basis unless otherwise specified. The PVA was analyzed in the following manner.

Analysis method for PVA The analysis method for PVA is JIS-K6 unless otherwise specified.
726. The amount of ethylene modification of the present invention is a modified polyvinyl ester, and the total content of carboxyl groups and lactone rings is 500 MHz 1H-NMR (JEOL) using PVA.
GX-500). The melting point of the PVA of the present invention is determined by DSC (Mettler, TA300).
0) at 250 ° C. in nitrogen at a rate of 10 ° C./min.
After the temperature was raised to room temperature, the temperature was raised to 250 ° C. again at a rate of 10 ° C./min, and the peak endothermic temperature indicating the melting point of PVA was examined.

Examples 1 to 7 A twin screw extruder using various polyvinyl alcohol resins having different degrees of polymerization, degree of saponification, degree of modification, and total contents of carboxyl groups and lactone rings as they are or after adding a plasticizer (glycerin). And melt-kneaded at 225 ° C. to produce pellets. Further, the pellets were subjected to inflation molding at a cylinder temperature of 225 ° C. and a die temperature of 220 ° C. to obtain a film having a thickness of 30 μm and a folding width of 18 cm. The moldability and the water solubility of the film were evaluated according to the following criteria. Table 1 shows the results.

Evaluation method (1) Formability The appearance of the film was visually evaluated. The evaluation was performed according to the following criteria. ：: No coloring or gel was observed in the film, and there was no smoke or decomposition odor due to deterioration of the resin. ：: Coloring or gel is slightly observed in the film, but there is almost no smoke or decomposition odor due to deterioration of the resin. Fair: Coloring or gel was considerably observed in the film, and smoke and decomposition odor due to deterioration of the resin were observed. X: The resin cannot be melt-molded due to severe deterioration of the resin or the high melting point of the resin. Alternatively, since the obtained film is brittle, the film breaks when it is wound, and a film cannot be obtained continuously. (2) Water solubility (elution rate) The film was immersed in water at 30 ° C. or 80 ° C. for 10 minutes, and the elution rate was measured.

Comparative Examples 1 to 3 Molding was carried out in the same manner as in Example 1 except that the degree of polymerization, degree of saponification, degree of modification and the total content of carboxyl groups and lactone rings of the polyvinyl alcohol resin were different, but the resin deteriorated severely. Or, the resin could not be melt-molded due to its high melting point, or the obtained film was brittle, so that no film could be obtained.

Comparative Examples 4 to 8 Films were prepared in the same manner as in Example 1 except that the degree of polymerization, degree of saponification, degree of modification, content of carboxyl group and lactone ring of polyvinyl alcohol resin were different, and moldability and water solubility Was evaluated. Table 1 shows the results.

[0033]

[Table 1]

[0034]

According to the present invention, a film having excellent water resistance, moisture resistance, hot water solubility, durability and strength can be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4F071 AA15X AA29 AA81 AF02 AF07 AF14 AF30 AF53 AH04 AH19 BB06 BC01 BC17 4J100 AA01Q AA02Q AD02P AG02P AG04P AG08P BA03H BA16H BC43P BC53H CA04 CA31 DA01 DA29 HA32 JA33

Claims (2)

[Claims] 1. A content of an α-olefin unit having 4 or less carbon atoms of 1 to 19 mol%, a polymerization degree of 200 to 3000, a saponification degree of 80 to 100 mol%, and a total content of carboxyl groups and lactone rings of 0.02 to 0.02. A film obtained by hot-melt molding a 0.4 mol% polyvinyl alcohol-based resin. 2. The film according to claim 1, wherein the α-olefin unit is an ethylene unit.