JP2502252B2 - Polyvinyl alcohol film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol (PVA) film for forming a film for packaging material.

[0002]

2. Description of the Related Art PVA-based films are tough, have excellent mechanical properties, are transparent and have good luster, have good water vapor permeability, and are resistant to clouding due to humidity. It has gas barrier properties, excellent oil resistance, low chargeability, and stain resistance. It is easy to perform secondary processing such as printing and bag making. As described above, the PVA-based film has excellent characteristics that other synthetic polymer compounds do not have, and is used in various fields. It is filled with a plasticizer and is widely used for packaging.

As plasticizers for PVA-based films, for example, glycols, polyhydric alcohols, specific amines, etc. have been used alone or in admixture with each other. Phosphinic acid compounds, polyalkylene oxide-added glycerin ether compounds, quaternary ammonium compounds, specific amino compounds having a molecular weight of 500 or less, isocyanuric acid alkylene oxide adducts, Michael type reaction products, anhydrohexitol, polyglycidol, etc. A patent application has been filed. Currently the most widely used is glycerin. It is relatively inexpensive, has good compatibility, and has a relatively good plasticizing effect.

A PVA-based film is generally formed by film-forming a PVA-based resin composition containing such a plasticizer. PVA-based films with a high degree of saponification are mainly used for packaging textile products. Textile products may be stored in corrugated cardboard boxes in a warehouse for a long period of time after being packaged until they are displayed in stores. Even when the degree of saponification is high, the PVA-based film absorbs and releases moisture due to changes in ambient humidity. It appears in the nature that it loses its stiffness under high temperature and high humidity in summer and becomes hard and brittle under low temperature and low humidity in winter. When moisture is absorbed and released, the plasticizer also moves in the film. In some cases, it may be scattered in the air, and in the summer, it may stick to the surface and become sticky, and it may be transferred to the inside of the packaged textiles and cardboard boxes and become dirty.
When the plasticizer is lost, the PVA-based film loses flexibility and becomes brittle, and easily breaks.

PVA-based films having a low degree of saponification have high water solubility and are used for packaging water-soluble powders and granules of pesticides, fungicides, insecticides and the like. The packaging materials of these things are especially disliked because they are easily damaged. Even when used, the packaging film is put into water together with the contents without breaking. Such usage is excellent in terms of preventing pollution of the working environment and protecting workers' safety. Water-soluble powders and granules have strong hygroscopicity, and remove water from the surroundings or give water. When it comes into contact with water-soluble powder, the movement of water in the PVA-based film becomes intense, and the plasticizer is more likely to be lost.

The property of the plasticizer that is easily lost also applies to the above-mentioned glycols, polyhydric alcohols, amines and the like. Moreover, these plasticizers have poor compatibility with PVA-based resins and may cause the film to become cloudy. The amount used is naturally suppressed. These properties also apply to other patented plasticizers. Such a plasticizer becomes sticky at high temperature and high humidity and deteriorates flexibility at low temperature and low humidity. In the case of glycerin, which is often used, it disappears over time and the film becomes stiff and the texture may be impaired. If this happens, the bag may break and the contents may pop out.

The PVA-based film is formed by casting an aqueous resin solution on a smooth molded metal surface, or by melt-molding a flake-like substance whose concentration has been adjusted using a metal extruder or the like. PVA-based films have strong adhesion to metal surfaces. In order to manufacture efficiently, it is necessary to make it easy to peel off the film-shaped molded product from the metal surface. Therefore, until now, various hydrophobic substances such as wax, silicone resin and higher aliphatic amine have been applied to the metal surface, and PVA Proposals have been made such as mixing in a resin composition. These substances cause uneven adhesion or surface tension of the resin composition on the metal surface,
The compatibility with PVA-based resins is poor and the film thickness may be non-uniform. In addition, the transparency and glossiness may be lowered, and the film may be whitened during molding.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the flexibility is maintained for a long period of time or under low temperature and low humidity, and stickiness due to exudation of an additive is exhibited even under high temperature and high humidity. It is an object of the present invention to provide a PVA-based film which can be easily peeled off from a molded metal surface during molding without impairing transparency and gloss.

[0009]

The PVA-based film of the present invention made to achieve the above object comprises a PVA-based resin containing an amine acid represented by the following formula.

[0010]

Embedded image

In the formula, R ¹ and R ² are hydrogen or an organic group, and one or both of them must be at least one of-(CH ₂ CH ₂ O) _m H and-(CHCH ₃ CH ₂ O) _n H. It is. In addition, m and n are polymerization degrees and are integers of 1 to 10. When m and n are 11 or more, the compatibility with the PVA-based resin deteriorates and the film is whitened, which is not preferable. R
³ is a carboxy aliphatic group represented by -RCOOH, a carboxy aromatic group, or a carboxy heterocyclic compound group, and has 2 to 12 carbon atoms.

In RCOOH, the aliphatic group, aromatic group or heterocyclic compound group represented by R may be a group having a hydroxyl group, an amino group or a mercapto group.

Examples of the amine acid represented by the formula 1 are N-hydroxyethyl-2-aminoacetic acid, N-hydroxyethyl-3-aminopropionic acid, N-hydroxyethyl-6-aminocaproic acid and N-hydroxyethyl-
12-aminolauric acid, N-hydroxyethyl-2-
Amino-3-methylbutyric acid, N-hydroxypropyl-2
-Aminoacetic acid, N-hydroxypropyl-6-aminocaproic acid, N, N-bis (hydroxyethyl) -2-aminobutyric acid, N, N-bis (hydroxyethyl) -3-aminopropionic acid, N, N-bis (Hydroxyethyl)
-2-Amino-3-hydroxypropionic acid, N, N-
Bis (hydroxypropyl) -2-amino-4-carboxybutyric acid, N, N-bis (hydroxyethyl) -p-aminobenzoic acid, N, N-bis (polyoxyethylene)-
2-aminoacetic acid (degree of polymerization = 10), N, N-bis (polyoxypropylene) -2-aminopropionic acid (degree of polymerization = 4), N, N-bis (polyoxyethylene) -2-amino-3 -Phenylpropionic acid (degree of polymerization = 6), N,
N-bis (polyoxyethylene) -2-amino-3-mercaptopropionic acid (degree of polymerization = 3), N, N-bis (polyoxypropylene) -2-amino-3- (4-imidazolyl) -propionic acid (Polymerization degree = 8), N, N-
Examples thereof include bis (polyoxyethylene) -2-amino-6-aminocaproic acid (degree of polymerization = 2). These amine acids may be used alone or in a mixture.

Such an amine acid is added to the P
It is used by being contained in a VA resin. PVA resin is
It may be PVA, a vinyl alcohol copolymer, or a derivative thereof. In that case, as PVA,
For example, PVA having a saponification degree of 70 mol% or more, a polymerization degree of 300 or more, preferably 75 mol% or more, and a polymerization degree of 500 or more may be used. Examples of the vinyl alcohol copolymer include a saponified product of an unsaturated carboxylic acid-vinyl acetate copolymer. Examples of the unsaturated carboxylic acid in that case include acrylic acid, maleic acid, itaconic acid, fumaric acid, and allyl acetate. Examples of the PVA derivative include such an esterified product of PVA or a vinyl alcohol copolymer. Examples of the acid forming the ester include acid anhydrides such as succinic anhydride, phthalic anhydride and maleic anhydride.

The amount of the amine acid added may be appropriately selected depending on the use of the PVA type film. Generally 2-40 parts,
It is often 5 to 30 parts in many cases.

These may be used as additives together with glycols, polyhydric alcohols, amines, etc. which have been conventionally known as plasticizers, and if necessary, activators, fragrances, pigments and the like may be added. It may be added.

Examples of the plasticizer used include glycols such as ethylene glycol, diethylene glycol, triethylene glycol and low molecular weight polyethylene glycol. Glycerin, polyglycerin, sorbit, trimethylolpropane, 1,3,5-pentane-
Examples of polyhydric alcohols such as triol include ethanolamine, triethanolamine, ethyleneamine,
Examples include amines such as diethyleneamine and ethylenediamine. In addition, a phosphinic acid compound described in JP-B-46-2944, a polyalkylene oxide-added glycerin ether compound described in JP-B-46-35972, and a hydroxyl group described in JP-B-50-35543. Quaternary ammonium compound possessed, JP-B-51-456
Amino compounds having a molecular weight of 500 or less obtained by adding an alkylene oxide to ammonia as described in JP-B-20, JP-B-55
Alkylene oxide adduct of isocyanuric acid described in JP-A-30019, Michael type reaction product of polyhydric alcohol or alkanolamine and acrylic acid ester described in JP-B-58-12301, JP-A-60-156741 Examples thereof include mono- or dianhydrohexitol described in JP-A No. 61-98752 and water-soluble polyglycidol having an arer group at the terminal described in JP-A-61-98752. These may be used alone or in combination.

Such a film containing the amine acid represented by the formula 1 may be molded as follows.
For example, a PVA-based resin composition aqueous solution or slurry having a concentration of 10 to 30% by weight is prepared and cast on a smooth metal surface such as a roll, a drum, an endless belt. Alternatively, 30 to 50% by weight of flakes are prepared by adding water or the like, and melt-molded with an extruder or the like.

The PVA-based film thus formed is used for packaging textile products such as cutter shirts, sweaters, underwear, sheets, blankets, duvets, and wool systems when PVA has a high degree of saponification. When the degree of saponification is low, it is used for packaging water-soluble pesticides, fungicides, insecticides, herbicides, detergents, dyes, pigments and the like.

[0020]

The amine acid represented by the above formula has a plasticizing action for improving the flexibility of the PVA type film even at low temperature and low humidity. It has good compatibility with PVA resin and does not exude even under high temperature and high humidity. It also has a function of easily peeling off from the metal surface of a roll, a drum, an endless belt, a die, a screw and the like of a molding machine when the film is formed. There is almost no loss of transparency and gloss peculiar to PVA-based films. Both are findings that the present inventor found experimentally.

[0021]

As described above in detail, the P of the present invention
The VA-based film maintains flexibility even under low temperature and low humidity. The additive does not exude even under high temperature and high humidity, and there is no stickiness. Therefore, the package is not soiled. There is no possibility that the filling material disappears, becomes brittle, and easily breaks. Almost always, it exhibits the toughness unique to PVA-based films. It has excellent releasability, can be easily peeled off from the metal surface of the molding machine, can be manufactured industrially efficiently, has no cracks or scratches, is smooth and transparent, and has good gloss.

[0022]

Embodiments of the present invention will be described below.

Example 1 Completely saponified PV having a polymerization degree of 1700 and a saponification degree of 99 mol%.
Water was added to A (“Shin-Etsu Poval A” manufactured by Shin-Etsu Chemical Co., Ltd.) and stirred while heating to prepare an aqueous solution having a concentration of 10% by weight. As shown in Table 1, 20 parts by weight of N-hydroxypropyl-3-aminopropionic acid (50% aqueous solution) was added to 100 parts by weight of this aqueous solution, and the mixture was cast on a chromium plating drum heated to 80 ° C. for 3 minutes. Dry and thickness 0.
A 04 mm colorless, transparent and flexible film was obtained.

[0024]

[Table 1]

In the PVA type column in the table, Shin-etsu A is completely saponified PVA, saponification degree 99 mol%, polymerization degree 175.
0 (“Shin-Etsu Poval A” manufactured by Shin-Etsu Chemical Co., Ltd.) is shown. Shin-Etsu P-20 shows a partially saponified PVA, a saponification degree of 89 mol% and a polymerization degree of 2000 (Shin-Etsu Poval P-20 manufactured by Shin-Etsu Chemical Co., Ltd.). Kuraray KM-118 is an itaconic acid-modified PVA (“Poval KM” manufactured by Kuraray Co., Ltd.
-118 ''). The amount of PV added is 10% by weight of PV
The parts by weight of the amine acid additive added to 100 parts by weight of the solution A are shown. The number in parentheses indicates the active ingredient concentration of the amine acid additive.

With respect to the film thus obtained, the transparency, compatibility, breaking strength, breaking elongation, Young's modulus,
The bleeding in the high temperature and high humidity state, the flexibility in the low temperature and low humidity state, the transferability of the additive, the water content, and the releasability were evaluated as follows. Table 2 shows the results.

The transparency evaluation method was as follows. -2
After leaving for 5 days in an atmosphere of 3 ° C and 50% relative humidity,
It was decided that the sample was evaluated as ◯ if it remained transparent without turbidity, Δ if slightly clouded white, and x if it was clouded white semi-transparently. The compatibility was evaluated as follows. -23 ° C, relative humidity 50
Allowed to stand for 5 days under%, if there is no repelling or unevenness of moisture in the appearance ○, if the repelling or unevenness of slightly moisture occurs △, if that occurred many repelling or unevenness is evaluated as × I decided. The breaking strength, breaking elongation, and Young's modulus were measured under a temperature of 23 ° C. and a relative humidity of 50% for 5 days, and then a tensile tester “Autograph A” manufactured by Shimadzu Corporation.
G-500C ”. The bleeding evaluation in the high temperature and high humidity state was as follows. The film was allowed to stand for 10 days at a temperature of 40 ° C. and a relative humidity of 85%, and then the stickiness of the film surface was examined. When the appearance did not change at all, it was evaluated as ○, when the film surface was slightly sticky, it was evaluated as △, and when the film surface was considerably sticky, it was evaluated as ×. The flexibility of the low temperature and low humidity condition was evaluated as follows. Put the film in a desiccator containing silica gel and leave it in an atmosphere at 20 ° C for 5 days, then at -10 ° C.
The film was taken out under the above atmosphere and the state when the film was bent was observed. When the sheet was not broken even when it was bent and the fold was pressed strongly, it was evaluated as ○, when the sheet was broken when the sheet was bent and the fold was pressed strongly, and × when the sheet was cracked only by bending. The transferability of the additive was evaluated as follows. Sandwich the film from both sides with absorbent cotton,
After leaving it at a temperature of 40 ° C. and a relative humidity of 30% for 10 days, the film is taken out and the amount of the plasticizer in the film is measured.
The residual ratio of the additive was calculated and evaluated by the following formula.

Residual rate of additive (%) = (amount of additive after test ÷ added amount of initial additive) × 100 ◯ when the residual rate of additive was 81% or more, residual of additive When the ratio was 30 to 80%, it was evaluated as Δ, and when the residual ratio of the additive was 29% or less, it was evaluated as ×. The film moisture content was evaluated as follows. The temperature was 23 ° C and the relative humidity was left in each atmosphere of 33%, 65% and 80% for 5 days and weighed, then dried at 105 ° C for 2 hours, weighed again and the moisture content was calculated by the following formula. It was calculated.

Moisture content of film = {(weight before drying−weight after drying) ÷ weight before drying} × 100 The releasability between the film and the metal surface at the time of molding was evaluated by obtaining the shrinkage rate by the following formula. Shrinkage (%) = (width of film cast-width of film after peeling) / width of film cast x 100 When the shrinkage is 0 to less than 5%, the shrinkage is 5 to 1
When it was less than 0%, it was evaluated as Δ, and when the shrinkage ratio was 10% or more, it was evaluated as ×.

[0030]

[Table 2]

Examples 2-7, Comparative Examples 1-7 Films were prepared using the PVA and plasticizer compositions shown in Table 1 in the same manner as in Example 1, and the same criteria as in Example 1 were used. evaluated. The physical properties of the film are shown in Table 2.

From these results, the following was found. When the carboxyl group of the amine acid is neutralized with sodium, potassium, etc., the film has high hygroscopicity, and the additive easily oozes out, which is not preferable. If the amine acid forms an ester bond with alcohol, PV
The compatibility with the A-based resin deteriorates and the film does not repel
It becomes a cause for Luo. If an amino acid is used as an additive, the compatibility with the PVA-based resin is poor even if it is filled, and it easily exudes from the inside, which is not preferable. The releasability from the film forming die also becomes weak. When the degree of polymerization of the alkylene group substituted for the amino group is 11 or more, the compatibility with the PVA-based resin is poor and the film is whitened.

Claims (1)

(57) [Claims] 1. A polyvinyl alcohol-based resin having the following formula: [In the formula, R ¹ and R ² are hydrogen or an organic group, and one or both of them is — (CH ₂ CH ₂ O) _m H or / and-
(CHCH ₃ CH ₂ O) _n H, m and n are polymerization degrees and are integers of 1 to 10, R ³ is a carboxy aliphatic group, a carboxy aromatic group or a carboxy heterocyclic compound group represented by —RCOOH. And the aliphatic group, aromatic group, or heterocyclic compound group represented by R having 2 to 12 carbon atoms may have a hydroxyl group, an amino group, or a mercapto group.] A polyvinyl alcohol film characterized by being formed.