WATER-SOLUBLE PACKAGING FILM

Abstract

The present invention provides a water-soluble packaging film which is capable of packaging chemicals while maintaining appropriate flexibility without changes in the appearance or offensive odors over a long period of time, which takes much less time to dissolve in water, and which can achieve excellent water solubility, excellent visibility, and excellent chemical resistance. The present invention relates to a water-soluble packaging film containing: polyvinyl alcohol; a plasticizer; and an alkali metal, the water-soluble packaging film containing 3 to 15 parts by weight of the plasticizer based on 100 parts by weight of the polyvinyl alcohol, the water-soluble packaging film containing 0.3 to 5% by weight of the alkali metal based on 100% by weight of the water-soluble packaging film.

Claims

1. A water-soluble packaging film comprising: polyvinyl alcohol; a plasticizer; and an alkali metal, the water-soluble packaging film containing 3 to 15 parts by weight of the plasticizer based on 100 parts by weight of the polyvinyl alcohol, the water-soluble packaging film containing 0.3 to 5% by weight of the alkali metal based on 100% by weight of the water-soluble packaging film.

2. The water-soluble packaging film according to claim 1, wherein the alkali metal is sodium.

3. The water-soluble packaging film according to claim 1, wherein the polyvinyl alcohol has a saponification degree of 80.0 to 99.9 mol %.

4. The water-soluble packaging film according to claim 1, wherein the polyvinyl alcohol has a standard deviation (σ) of saponification degree distribution of 0.1 to 1.0 mol %.

5. The water-soluble packaging film according to claim 1, wherein the polyvinyl alcohol is modified with at least one hydrophilic group selected from the group consisting of a sulfonic acid group, a pyrrolidone ring group, an amino group, and a carboxyl group.

6. The water-soluble packaging film according to claim 5, wherein the polyvinyl alcohol contains a constitutional unit having the hydrophilic group in an amount of 0.1 to 15 mol %.

7. The water-soluble packaging film according to claim 1, wherein the water-soluble packaging film has a tensile strength in a tensile test at an elongation of 100% of 5 to 30 MPa.

Description

DESCRIPTION OF EMBODIMENTS

[0087] Embodiments of the present invention are further specifically described in the following with reference to, but not limited to, examples.

Example 1

[0088] An amount of 92.8 parts by weight of polyvinyl alcohol (produced by Sekisui Specialty Chemicals, Selvol513, polymerization degree: 1300, saponification degree: 88.0 mol %, viscosity of 4% by weight aqueous solution: 14 mPa.Math.s, standard deviation of saponification degree distribution: 0.18 mol %), 3.2 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 1.6 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers, and 2.4 parts by weight of sodium acetate (Wako Pure Chemical Industries, Ltd.) were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0089] The standard deviation of the saponification degree distribution of the polyvinyl alcohol was measured as follows.

(Measurement of Standard Deviation of Saponification Degree Distribution)

[0090] Forty polyvinyl alcohol particles were randomly selected, and the acetyl group content of the polyvinyl alcohol was measured with a FT-IR spectrophotometer (produced by Shimadzu Corporation, IRAffinity-1) by ATR method. Based on the measured acetyl group content, the saponification degree of each particle was determined. Based on variations of the obtained saponification degrees, the standard deviation (σ) of the saponification degree distribution was calculated.

[0091] The obtained PVA aqueous solution was applied to a polyethylene terephthalate (PET) film (thickness: 50 μm) as a support member with an auto film applicator (produced by Tester Sangyo Co., Ltd., “PI-1210”), and dried at 80° C. for 5 minutes and then at 100° C. for 20 minutes to give a laminated film including a PVA film (thickness: 50 μm) on a support member.

Examples 2 to 3

[0092] Laminated films including a PVA film (thickness: 50 μm) were prepared in the same manner as in Example 1, except that polyvinyl alcohol, glycerin, trimethylolpropane, and sodium acetate were added each in an amount shown in Table 1.

Example 4

[0093] An amount of 94 parts by weight of sodium sulfonate-modified polyvinyl alcohol (polymerization degree: 1200, R.sup.1=C.sub.4H.sub.8, saponification degree: 95.4 mol %, modification amount with sodium sulfonate: 4 mol %, viscosity of 4% by weight aqueous solution: 12 mPa.Math.s, standard deviation of saponification degree distribution: 0.31 mol %) having a structure represented by the formula (1), 3 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 3 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0094] Using the obtained PVA aqueous solution, a laminated film including a PVA film (thickness: 50 μm) laminated on a support member was produced in the same manner as in Example 1.

Example 5

[0095] A laminated film including a PVA film (thickness: 50 μm) was produced in the same manner as in Example 4, except that polyvinyl alcohol (sodium sulfonate-modified polyvinyl alcohol), glycerin, trimethylolpropane, and sodium acetate were added each in an amount as shown in Table 1.

Example 6

[0096] An amount of 89 parts by weight of pyrrolidone ring-modified polyvinyl alcohol (polymerization degree: 1000, saponification degree: 95.8 mol %, modification amount with pyrrolidone: 4 mol %, viscosity of 4% by weight aqueous solution: 10 mPa.Math.s, standard deviation of saponification degree distribution: 0.21 mol %) having a structure represented by the formula (2), 5.0 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 5.0 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers, and 1 part by weight of sodium acetate (Wako Pure Chemical Industries, Ltd.) were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0097] Using the obtained PVA aqueous solution, a laminated film including a PVA film (thickness: 50 μm) laminated on a support member was produced in the same manner as in Example 1.

Example 7

[0098] An amount of 94 parts by weight of sodium sulfonate-modified polyvinyl alcohol (polymerization degree: 1200, R.sup.1=CH.sub.2, saponification degree: 90.1 mol %, modification amount with sodium sulfonate: 4 mol %, standard deviation of saponification degree distribution: 0.98 mol %) as polyvinyl alcohol, 3 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 3 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0099] The obtained PVA aqueous solution was applied to a polyethylene terephthalate (PET) film (thickness: 50 μm) as a support member with an auto film applicator (produced by Tester Sangyo Co., Ltd., “PI-1210”), and dried at 80° C. for 5 minutes and then at 100° C. for 20 minutes to produce a PVA film (thickness: 50 μm) on the support member.

[0100] After removal of the support member from the obtained PVA film, the PVA film was exposed to an environment at a temperature of 23° C. and a relative humidity of 50% RH for 24 hours, thereby obtaining a water-soluble packaging film.

Example 8

[0101] A water-soluble packaging film was produced in the same manner as in Example 7, except that sodium sulfonate-modified polyvinyl alcohol was changed to amino group-modified polyvinyl alcohol (polymerization degree: 600, R.sup.2=CH.sub.2, saponification degree: 91.8 mol %, modification amount with amino group: 8 mol %, standard deviation of saponification degree distribution: 0.28 mol %) having a structure represented by the formula (3).

Example 9

[0102] A water-soluble packaging film was produced in the same manner as in Example 7, except that sodium sulfonate-modified polyvinyl alcohol was changed to carboxylic acid-modified polyvinyl alcohol A (polymerization degree: 1700, R.sup.3≡CH.sub.2, X.sup.2 and X.sup.3=sodium atoms, saponification degree: 97.5 mol %, modification amount with carboxyl group: 1.5 mol %, standard deviation of saponification degree distribution: 0.12%) having a structure represented by the formula (4-2).

Example 10

[0103] A water-soluble packaging film was prepared in the same manner as in example 7, except that sodium sulfonate-modified polyvinyl alcohol was changed to carboxylic acid-modified polyvinyl alcohol B (polymerization degree: 1700, R.sup.3=CH.sub.2, X.sup.2 and X.sup.3=sodium atoms, saponification degree: 98.2 mol %, modification amount with carboxyl group: 0.5 mol %, standard deviation of saponification degree distribution: 0.25%) having a structure represented by the formula (4-2).

Example 11

[0104] An amount of 89 parts by weight of pyrrolidone ring-modified polyvinyl alcohol (polymerization degree: 1000, saponification degree: 95.8 mol %, modification amount with pyrrolidone: 4 mol %, viscosity of 4% by weight aqueous solution: 10 mPa.Math.s, standard deviation of saponification degree distribution: 0.21 mol %) having a structure represented by the formula (2), 3.0 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 3.0 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers, and 5.0 parts by weight of potassium acetate (Wako Pure Chemical Industries, Ltd.) were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0105] Using the obtained PVA aqueous solution, a laminated film including a PVA film (thickness: 50 μm) laminated on a support member was produced in the same manner as in Example 1.

Example 12

[0106] An amount of 86 parts by weight of pyrrolidone ring-modified polyvinyl alcohol (polymerization degree: 1000, saponification degree: 95.8 mol %, modification degree with pyrrolidone: 4 mol %, viscosity of 4% by weight aqueous solution: 10 mPa.Math.s, standard deviation of saponification degree distribution: 0.21 mol %) having a structure represented by the formula (2), 3.0 parts by weight of glycerin (Wako Pure Chemical Industries, Ltd.) and 2.0 parts by weight of trimethylolpropane (Wako Pure Chemical Industries, Ltd.) as plasticizers, and 9.0 parts by weight of potassium acetate (Wako Pure Chemical Industries, Ltd.) were dissolved in 600 parts by weight of water to prepare a 14.3% by weight aqueous solution.

[0107] Using the obtained PVA aqueous solution, a laminated film including a PVA film (thickness: 50 μm) on a support member was produced.

Comparative Examples 1 to 3

[0108] Laminated films including a PVA film (thickness: 50 μm) were produced in the same manner as in Example 1, except that polyvinyl alcohol, glycerin, trimethylolpropane, and sodium acetate were added each in an amount as shown in Table 1.

Comparative Example 4

[0109] A laminated film including a PVA film (thickness: 50 μm) was produced in the same manner as in Example 1, except that polyvinyl alcohol, glycerin, trimethylolpropane, sodium sulfite (Wako Pure Chemical Industries, Ltd.) were added each in an amount as shown in Table 1.

TABLE-US-00001 TABLE 1 Composition Polyvinyl alcohol resin Standard deviation of Saponi- distribution of Amount of Amount Polymer- fication Saponification modifying added ization degree degree group Viscosity (parts by degree (mol %) σ(mol) Modifying group (mol %) (mPa .Math. s) weight) Example 1 1300 88 0.18 — — 14 92.8 Example 2 1300 88 0.18 — — 14 88.1 Example 3 1300 88 0.18 — — 14 83.8 Example 4 1200 95.4 0.31 Sulfonic acid group 4 12 94 Example 5 1200 95.4 0.31 Sulfonic acid group 4 12 89 Example 6 1000 95.8 0.21 Pyrrolidone ring group 4 10 89 Example 7 1200 90.1 0.98 Sulfonic acid group 4 11 94 Example 8 600 91.8 0.28 Amino group 8 6 94 Example 9 1700 97.5 0.12 Craboxyl group 1.5 31 94 Example 10 1700 98.2 0.25 Craboxyl group 0.5 30 94 Example 11 1000 95.8 0.21 Pyrrolidone ring group 4 10 89 Example 12 1000 95.8 0.21 Pyrrolidone ring group 4 10 86 Comparative 1300 88 0.18 — — 14 95.1 Example 1 Comparative 1300 88 0.18 — — 14 80 Example 2 Comparative 1300 88 0.18 — — 14 72.7 Example 3 Comparative 1300 88 0.18 — — 14 94.0 Example 4 Composition Plasticizer content* Metal salt (parts by weight) Plasticizer (parts by weight) (parts by Sodium Sodium Potassium Lithium Glycerin Trimethylolpropane weight) acetate sulfite acetate acetate Example 1 3.2 1.6 5.2 2.4 0 0 0 Example 2 3.1 1.4 5.1 7.4 0 0 0 Example 3 2.9 1.4 5.1 11.9 0 0 0 Example 4 3 3 6.4 0 0 0 0 Example 5 1.5 1.5 3.4 8 0 0 0 Example 6 5 5 11.2 1 0 0 0 Example 7 3 3 6.4 0 0 0 0 Example 8 3 3 6.4 0 0 0 0 Example 9 3 3 6.4 0 0 0 0 Example 10 3 3 6.4 0 0 0 0 Example 11 3 3 6.7 0 0 5 0 Example 12 3 2 5.8 0 0 0 9 Comparative 3.3 1.6 5.2 0 0 0 0 Example 1 Comparative 10 10 25.0 0 0 0 0 Example 2 Comparative 2.3 1 4.5 24 0 0 0 Example 3 Comparative 3.3 1.7 5.3 0 0.5 0 0 Example 4 *Amount added based on 100 parts by weight of polyvinyl alcohol resin

(Evaluation)

(1) Measurement of Alkali Metal (Sodium, Potassium, Lithium) Content

[0110] The support member was peeled off from the obtained laminated film to prepare a water-soluble packaging film (200 mm×200 mm). The obtained water-soluble packaging film was exposed to an environment at a temperature of 23° C. and a relative humidity of 50% RH for 24 hours.

[0111] Then, the alkali metal (sodium, potassium, lithium) content (% by weight) based on 100% by weight of the water-soluble packaging film was measured with an ICP-MS (Hitachi High-Technologies Corporation, Z2310).

[0112] The alkali metal content (g/m.sup.2) per unit area was also calculated.

(2) Tensile Strength

[0113] The support member was peeled off from the obtained laminated film to prepare a water-soluble packaging film. The obtained water-soluble packaging film was exposed to an environment at a temperature of 23° C. and a relative humidity of 50% RH for 24 hours.

[0114] Then, the water-soluble packaging film was cut to a size of 100 mm×15 mm, and the resulting film piece was subjected to a tensile test under the conditions of a temperature of 23° C., a humidity of 50%, and a peeling rate of 100 mm/min, thereby determining the tensile strength (Mpa) at an elongation of 100%.

∘∘ (Excellent): 5 MPa or higher but lower than 15 MPa.
∘ (Good): 15 MPa or higher but lower than 30 MPa.
x (Poor): Lower than 5 MPa, or, 30 MPa or higher.

(3) Water Solubility (Dissolution Time)

[0115] The support member was peeled off from the obtained laminated film to prepare a water-soluble packaging film. The obtained water-soluble packaging film was exposed to an environment at a temperature of 23° C. and a relative humidity of 50% RH for 24 hours.

[0116] Then, the water-soluble packaging film was cut to a size of 35 mm×40 mm, and the obtained film piece was fixed to a jig. The film fixed to the jig was immersed in water (500 ml) in a 500-ml beaker under stirring (in such a manner that the bottom of a vortex reaches the metering line of 400 ml) with a stirrer while the water temperature was maintained at 23° C. The time until residues of the film was not any more observed visually on the jig was measured.

∘∘ (Excellent): Shorter than 20 seconds.
∘ (Good): Shorter than 30 seconds.
x (Poor): 30 seconds or longer.

(4) Long-Term Storability

[0117] The support member was peeled off from the obtained laminated film to prepare a water-soluble packaging film. The obtained packaging film was put into an aluminum zipper bag and left to stand in an environment at a temperature of 23° C. and a relative humidity of 50% RH for a month.

[0118] Then, the water-soluble packaging film was taken out and visually observed to check the presence of bleeding of the plasticizer or the additives from the film after the standing for a month.

[Evaluation Criteria of Appearance]

[0119] ∘ (Good): Film was transparent and had no bleeding therefrom.
x (Poor): Film was turbid and had bleeding therefrom.

(5) Chemical Resistance

[0120] The obtained water-soluble packaging film was formed into a bag in a size of 5 cm×4 cm and allowed to contain 20 g of sodium trichloroisocyanurate therein. The package was further put into an aluminum bag and sealed therein. The bag was left in a constant temperature/humidity oven at a temperature of 40° C. and a humidity of 70% RH for a month. Then, the appearance of the water-soluble packaging film was visually observed.

∘ (Good): The appearance was not changed.
x (poor): The appearance was colored yellow or brown.

(6) Visibility

[0121] The haze of the obtained water-soluble packaging film was measured with a haze meter (produced by Tokyo Denshoku Co., Ltd. TC-H3DPK) at 20° C., and evaluated based on the following criteria.

∘ (Good): Haze of less than 3.5%.
x (Poor): Haze of 3.5% or more.
(7) Visibility after Durability Test

[0122] The obtained water-soluble packaging film was formed into a bag in a size of 5 cm×4 cm and allowed to contain 20 g of sodium trichloroisocyanurate therein. The bag was further put into an aluminum bag and sealed therein. The obtained bag was left in a constant temperature/humidity oven at a temperature of 40° C. and a humidity of 70% RH for a month. Then, the film portion was cut out from the bag, and the haze thereof was measured with a haze meter (produced by Tokyo Denshoku Co., Ltd., TC-H3DPK) at 20° C. The obtained haze was evaluated based on the following criteria. In addition, the change in haze was calculated based on the difference from the haze measured in “(6) visibility”.

∘ (Good): Haze was less than 3.5% and change in haze was less than 20%.
x (Poor): Haze was 3.5% or more, or change in haze was 20% or more.

TABLE-US-00002 TABLE 2 Evaluation Alkali metal content Tensile strength Water solubility Long-term Potassium Content per Tensile Dissolu- storability Sodium or lithium unit area strength tion time Evaluation of (wt %) (wt %) (g/m.sup.2) (MPa) Evaluation (sec.) Evaluation appearance Example 1 0.85 0 0.51 14.7 ∘∘ 23 ∘ ∘ Example 2 2.1 0 1.26 13.2 ∘∘ 19 ∘∘ ∘ Example 3 3.2 0 1.92 12.8 ∘∘ 16 ∘∘ ∘ Example 4 1.6 0 0.96 10.5 ∘∘ 18 ∘∘ ∘ Example 5 4.1 0 2.46 22 ∘ 14 ∘∘ ∘ Example 6 0.5 0 0.30 8.3 ∘∘ 27 ∘ ∘ Example 7 1.5 0 0.90 10 ∘∘ 13 ∘∘ ∘ Example 8 1.3 0 0.78 6.5 ∘∘ 14 ∘∘ ∘ Example 9 0.9 0 0.54 15 ∘∘ 21 ∘ ∘ Example 10 0.9 0 0.54 16 ∘∘ 16 ∘∘ ∘ Example 11 0 1.2 0.72 9.3 ∘∘ 22 ∘ ∘ Example 12 0 3 1.80 13 ∘∘ 18 ∘∘ ∘ Comparative 0.2 0 0.12 15 ∘ 31 x ∘ Example 1 Comparative 0.1 0 0.06 3 x 28 ∘ x Example 2 Comparative 6.5 0 3.90 20 ∘ 14 ∘∘ x Example 3 Comparative 0.25 0 0.15 14.6 ∘ 32 x ∘ Example 4 Evaluation Visibility after durability test Visibility Change Chemical resistance Haze Haze in haze Appearance Evaluation (%) Evaluation (%) (%) Evaluation Example 1 Colored brown x 2.3 ∘ 3.3 43.5 x Example 2 Colored brown x 2.8 ∘ 4 42.9 x Example 3 Colored brown x 3.4 ∘ 5 47.1 x Example 4 No change ∘ 2.2 ∘ 2.3 4.5 ∘ Example 5 No change ∘ 2.8 ∘ 3 7.1 ∘ Example 6 No change ∘ 2.4 ∘ 2.6 8.3 ∘ Example 7 No change ∘ 2.5 ∘ 2.6 4.0 ∘ Example 8 No change ∘ 3 ∘ 3.1 3.3 ∘ Example 9 No change ∘ 2.8 ∘ 3 7.1 ∘ Example 10 No change ∘ 2.3 ∘ 2.7 17.4 ∘ Example 11 No change ∘ 2.5 ∘ 2.7 8.0 ∘ Example 12 No change ∘ 3 ∘ 3.3 10.0 ∘ Comparative Colored brown x 2.1 ∘ 3.5 66.7 x Example 1 Comparative Colored brown x 2.3 ∘ 3.9 69.6 x Example 2 Comparative Colored brown x 3.6 x 6.2 72.2 x Example 3 Comparative Colored brown x 2.2 ∘ 3.7 68.2 x Example 4

INDUSTRIAL APPLICABILITY

[0123] The present invention can provide a water-soluble packaging film which is capable of packaging chemicals while maintaining appropriate flexibility without changes in the appearance or offensive odors over a long period of time, which takes much less time to dissolve in water, and which can achieve excellent water solubility, excellent visibility, and excellent chemical resistance.