JPH03124734A - Water-soluble film - Google Patents

Abstract

PURPOSE:To reduce the rate of moisture absorption and improve the morphological stability by partially acetalizing a pyrrolidone-modified polyvinyl alcohol and forming it into a film. CONSTITUTION:A monomer having a pyrrolidone unit and a polymerizable double bond (e.g. N-vinylpyrrolidone) is copolymerized with a vinyl ester of a fatty acid (e.g. vinyl acetate), and the reaction product is saponified to give a pyrrolidone-modified polyvinyl alcohol having a degree of polymn. of 200-2000, a degree of saponification of 95mol% or higher, and a content of pyrrolidone unit of 1-20mol%. The modified polyvinyl alcohol is acetalized by the reaction of it with a 1-5C aldehyde in the presence of an acid catalyst in water to give an acetalized pyrrolidone-modified polyvinyl alcohol having a degree of acetalization of 1-30mol%, which is formed into a film to give a water-sol. film of 5-200mum thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to water-soluble films. More specifically, the present invention relates to a water-soluble film with excellent cold water solubility, alkali resistance, and morphological stability obtained by partially acetalizing pyrrolidone-modified polyvinyl alcohol.

1-"L Kei" mouth-water-soluble film is used for laundry detergent unit packaging, insecticides, etc.
It is widely used for packaging bleach and cleaning agents, short-term storage bags for clothes to be washed (laundry bags), and packaging for gardening seeds and seedlings. If a substance that is harmful to the human body is packaged using a water-soluble film, humans will not come into direct contact with the substance, and the water-soluble film will quickly dissolve or disperse in water during use, making it extremely easy to handle. . Laundry bags have excellent features such as being suitable for short-term storage of clothes to be washed, preventing the generation of odors, being highly portable, and being easy to handle as all the bags can be loaded in at once when washing. . When packaging garden seeds and seedlings, a water-soluble film acts as a spacer, and the distance between the seeds is preset, so you can just plant them as they are, which improves work efficiency. It is prized because the packaging dissolves quickly and has no effect on the growth of seedlings.

Conventionally, polyvinyl alcohol films, particularly partially saponified polyvinyl alcohol films, have been used as water-soluble films.

Polyvinyl alcohol films have excellent properties such as strong coatings, excellent transparency, good printability, and when the degree of saponification is adjusted to an appropriate level, they have good solubility in cold water.

Problem to be Solved by the Invention However, as the degree of saponification of polyvinyl alcohol increases, its crystallinity increases, and the crystalline portion does not dissolve in cold water, so polyvinyl alcohol with a high degree of saponification has the property of being insoluble in cold water. are doing. For this reason, completely saponified polyvinyl alcohol films have not been used as cold water-soluble films, and partially saponified polyvinyl alcohols with a degree of saponification of 80 to 90 mol % have been used. However, partially saponified polyvinyl alcohol does not suppress crystallinity sufficiently, and although sufficient cold water solubility is obtained when the film is initially prepared, crystals gradually grow when stored for a long period of time. There was a drawback that the sexiness decreased. Furthermore, when the content of the film is an alkaline or acidic substance such as a detergent, the degree of saponification of the partially saponified polyvinyl alcohol gradually increases, resulting in a disadvantage that the solubility in cold water decreases when stored for a long period of time.

In order to suppress crystal growth over time or to delay the increase in the degree of saponification with alkali or acid, it is effective to lower the degree of saponification of partially saponified polyvinyl alcohol. If the degree of saponification is lowered to 80 mol% or less, the hydrophobicity of the partially saponified polyvinyl alcohol becomes strong, the cloud point decreases, and it becomes insoluble in hot water.If the degree of saponification is further lowered, it becomes insoluble in water. The current situation is that the method does not give a satisfactory result.

The present inventors have already discovered that a water-soluble film made of polyvinyl alcohol containing pyrrolidone groups can improve the above-mentioned drawbacks, and filed a patent application (Japanese Patent Application No. 63-1891).
No. 48, Japanese Patent Application No. 1-181380). A water-soluble film made of polyvinyl alcohol containing pyrrolidone groups has excellent water solubility, alkali resistance, and acid resistance, and provides an extremely excellent water-soluble film, but perhaps because it is too hydrophilic, the moisture absorption rate is is large,
For example, when exposed to hot and humid conditions such as during the rainy season or summer, there is a drawback that the morphological stability is slightly reduced.

D. In order to solve the problem, the present inventors solved the above-mentioned drawbacks of a water-soluble film made of polyvinyl alcohol containing pyrrolidone groups (as a result of repeated studies, it was found that a water-soluble film containing 1 to 20 mol% of pyrrolidone units, The present invention was completed by discovering a water-soluble film made of acetalized pyrrolidone-modified polyvinyl alcohol having a degree of acetalization of 1 to 30 mol%.

The pyrrolidone unit used in the present invention is not particularly limited, and any pyrrolidone unit represented by the general formula (wherein R1 to R8 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms) All of them can be suitably used.

There are no particular restrictions on the method for producing the pyrrolidone-modified polyvinyl alcohol used in the present invention, but the method includes copolymerizing a monomer containing a bi0ridone unit and having a polymerizable double bond with a fatty acid vinyl, and then saponifying it. The method is simple and preferred. Among these monomers containing a pyrrolidone unit and having a polymerizable double bond, the double bond portion is vinyl, allyl, styryl, acryloxy, methacryloxy,
Examples include groups such as vinyl ether and allyl ether, among which vinyl and allyl groups are preferred from the viewpoint of copolymerizability with fatty acid vinyl and alkali resistance during saponification. Two specific examples of such monomers include N-vinyl-2-pyrrolidone, N-vinyl-5-methyl-2-pyrrolidone, N-vinyl-5,5-dimethyl-
Examples include 2-pyrrolidone, N-allyl-2-pyrrolidone, and the like. Among these, N-vinyl-2-pyrrolidone is the most preferred monomer. Further, specific examples of vinyl fatty acids include vinyl formate, vinyl acetate, vinyl oxate, vinyl pivalate, vinyl persatate, etc.
Among these, vinyl acetate is industrially the most preferred monomer.

For copolymerization, conventionally known bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. can be used, but solution polymerization using methanol as a solvent is industrially optimal.

Various conventionally known saponification methods can be applied to the saponification reaction, but among these, the method of alcoholysis using an alkali hydroxide in methanol is simple and preferred.

The content of pyrrolidone units in the pyrrolidone-modified polyvinyl alcohol used in the present invention is 1 to 20 mol%,
More preferably, it is 2 to 12 mol%.

If the content of pyrrolidone units is too low, N8H
The effect of improving the shortcomings of partially saponified polyvinyl alcohol, such as crystallization over time and lack of alkali resistance and acid resistance, is too small.On the other hand, if the amount is too high, the hygroscopicity of the film becomes too large and the film cannot be used under high humidity conditions. It is undesirable because it tends to be sticky and become hard and brittle in low humidity.

The degree of polymerization of the pyrrolidone-modified polyvinyl alcohol used in the present invention is not particularly limited, but is usually 200 to 2000.
is preferably used.

The degree of saponification of the pyrrolidone-modified polyvinyl alcohol to be acetalized used in the present invention (the degree of saponification in the present invention refers to the unit excluding pyrrolidone units)
It refers to the proportion of vinyl alcohol units when it is set to 0. ) is 50 to 100 mol%, more preferably 80 to 1
00 mol%, more preferably 95 to 100 mol%. If the degree of saponification is too low, the strength of the film tends to be insufficient and the water solubility tends to be low, which is not preferable.

There is no problem with the pyrrolidone-modified polyvinyl alcohol of the present invention containing a small amount of other components within the molecule, as long as it does not interfere with the gist of the present invention. Specific examples of methods for introducing such other components include carboxylic acid-containing monomers such as (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, and itaconic acid, or salts thereof, acrylamide, etc. - Monomers containing sulfonic acid groups such as sodium 2-methylpropanesulfonate, sodium allylsulfonate, and sodium vinylsulfonate, monomers containing quaternary ammonium salts such as (meth)acrylamide-propyl-trimethylammonium chloride, etc. There is a method in which an anionic or cationic monomer is allowed to coexist during copolymerization. However, when such an ionic monomer is copolymerized in a large amount, the humidity dependence of the obtained film increases, and the film tends to be hard under low humidity and sticky under high humidity, which is not preferable. Therefore, the content of such monomers should be less than 2 mol%, more preferably less than 1 mol%. Other specific examples of small amounts of pond components include α-
Olefins, (meth)acrylic acid esters, amide group-containing monomers such as acrylamide, dimethylacrylamide, N-methylolacrylamide, alkyl vinyl ethers, silyl group-containing monomers such as trimethoxyvinylsilane, allyl alcohol, dimethylallyl Hydroxyl group-containing monomers such as alcohol and isopropenyl alcohol,
A method in which acetyl group-containing monomers such as allyl acetate, dimethylallyl acetate, and isopropenyl acetate, halogen-containing monomers such as vinyl chloride and vinylidene chloride, and aromatic monomers such as styrene are allowed to coexist during copolymerization. There is.

However, based on the spirit of the present invention, the copolymerized amount of these monomers should be less than 2 mol%, more preferably less than 1 mol%.

The aldehyde compound used for acetalizing the pyrrolidone-modified polyvinyl alcohol of the present invention has 1-i carbon atoms.
The aldehyde compound of o is preferable, and when the aldehyde compound has 11 or more carbon atoms, the water solubility of the resulting film may decrease, which is not preferable. More preferred are aldehyde compounds having 1 to 5 carbon atoms.

Specific examples of aldehydes having 1 to 10 carbon atoms include formaldehyde, acetaldehyde, propionaldehyde,
Examples include butyraldehyde, isobutyraldehyde, octylaldehyde, and the like. These may be used alone or in combination. It is also possible to use dialdehydes such as glyoxal and succindialdehyde, and unsaturated aldehydes such as acrolein, but since the resulting acetalized product is easily crosslinked and gelled, it is necessary to use a small amount or to adjust the acetalization conditions. need to be chosen carefully.

Acetalization can be easily carried out by conventionally known methods. Industrially, the best method is to react pyrrolidone-modified polyvinyl alcohol with an aldehyde compound in an aqueous solution in the presence of an acid catalyst.

In the water-soluble film of the present invention, the degree of acetalization is defined as the molar percentage of structural units containing acetalized hydroxyl groups among all structural units excluding pyrrolidone units. The degree of acetalization is preferably 1 to 30 mol%, preferably 5 to 20 mol%. If the degree of acetalization is less than 1 mol%, the morphological stability of the obtained film will be poor, and if the degree of acetalization exceeds 30 mol%, the water solubility of the obtained film will decrease or the strength will decrease. Therefore, it is undesirable.

Conventionally known film manufacturing methods such as a casting method and a melt molding method can be suitably applied to the water-soluble film of the present invention. In particular, since the melting temperature is lowered by the pyrrolidone units contained in the pyrrolidone-modified polyvinyl alcohol of the present invention, melt molding, which is unsuitable for conventional partially saponified polyvinyl alcohol, is easy.

There is no particular limit to the thickness of the film obtained, but it is usually 5 to 50% thick.
A material having a diameter of 200μ is preferably used. Furthermore, the obtained film may be subjected to surface treatments such as embossing, plasma treatment, and adhesion prevention treatment.

Although the water-soluble film of the present invention exhibits sufficient performance even with pyrrolidone-modified polyvinyl alcohol alone,
If necessary, polyesters such as glycerin, diglycerin, ethylene glycol, diethyl glycol, triethylene glycol, polyethylene glycol, trimethylolpropane, pentaerythritol, mannitol, sorbitol, 2.3-butanediol, 1.3-butanediol, etc. It is also possible to add alcohol as a plasticizer and moisture absorbent. It is also possible to add known plasticizers for acetalized polyvinyl alcohol, such as dibutyl terephthalate and dioctyl terephthalate. Further, amides such as dimethylacetamide, amines such as triethanolamine, sulfoxides such as dimethyl sulfoxide, etc. may be added as plasticizers and moisture absorbers. Furthermore, normal PV
A, polyacrylic acid or its salt, polyacrylamide, starch, cellulose, etc. may be used in combination. Furthermore, since pigments such as clay talc, titanium oxide, and calcium carbonate, dyes, surfactants, and slip property imparting agents may be blended, the present invention is not limited to these in any way. In addition, in the following, "part" or "%"
” means “parts by weight” or “% by weight” unless otherwise specified.

2,800 parts of vinyl acetate was placed in a polymerization vessel equipped with a reflux condenser.
650 parts of methanol and 54.3 parts of N-vinylpyrrolidone were charged, heated to 60°C, and then replaced with nitrogen.

Polymerization was initiated by adding 0.23 parts of 2-mercaptoethanol, 2.53 parts of α,α゛-azobisisobutyronitrile, and 50 parts of methanol. After the start of polymerization, the temperature inside the polymerization tank was increased to 6
While maintaining the temperature at 0°C, 106 parts of N-vinylpyrrolidone and 85.5 parts of a 6% methanol solution of 2-mercaptoethanol were uniformly added over 4 hours. After the start of polymerization, 1000 parts of methanol was added to the tube for 4 hours, and the polymerization was stopped by cooling. The polymerization rate of vinyl acetate at this time was 60%.
Met. Remaining vinyl acetate was distilled off while methanol vapor was added to the mixture to obtain a 50% methanol solution of pyrrolidone group-containing polyvinyl acetate. To 500 parts of these, 323 parts of methanol and 58 parts of a 4% methanol solution of sodium hydroxide were added, and a saponification reaction was carried out at 40°C. The resulting gel was pulverized, thoroughly washed with methanol, and then dried to obtain pyrrolidone group-containing polyvinyl alcohol. The degree of polymerization of this product was 430, the content of pyrrolidone groups was 6.0 mol% Tearly based on NMR, and the degree of saponification was 98.8 mol%.

To 100 parts of a 10% aqueous solution of this product, 0.1 part of concentrated hydrochloric acid and 2.5 parts of butyraldehyde were added and reacted at 70°C for 4 hours. This product was poured into a large amount of acetone to precipitate the reaction product, which was washed repeatedly with acetone and dried.

The obtained butyralized product (hereinafter abbreviated as [polymer A]) was found by NMR measurement to be a butyralized polyvinyl alcohol containing 6.0 mol% of pyrrolidone groups with a degree of butyralization of 21 mol%. .

Polymers [B] to [F] were synthesized using the same method. The structures of the obtained polymers [A] to [F] are summarized in Table 1.

Example 1 A 10% aqueous solution of polymer [A] was cast into a film using a drum film forming machine at a drum temperature of 75° C. to obtain a film with a thickness of 40 μm. Make a sx 5ca+ bag with this film, put 15g of sodium carbonate decahydrate inside, seal the opening with a heat sealer, and make a 3.5X 3.5c+ bag.
Place it on a stainless steel plate with n holes and heat at 40℃ x 90℃.
After the plate was left horizontally for 3 days under %RH, the morphology of the bag was observed. (This test will be referred to as the morphological stability test.) In addition, a film separately conditioned at 20°C and 65% RH was tested for 3
It was sandwiched between two pieces of paperboard with ×3CI11 holes and fixed with a stapler. This was immersed in distilled water at 20°C, and the time required for the film to completely dissolve was measured (hereinafter referred to as the water solubility test).
Heat treatment was performed for 0 minutes to promote crystallization.

This film was also subjected to the above water solubility test.

Separately, make a 5 x 10 cm bag with film, put 30 g of sodium carbonate decahydrate or 30 g of citric acid inside, seal the bag with a heat sealer, and store at 40°C.
It was left standing at 80% RH for 2 months. After 2 months, each bag was opened, the contents were thoroughly removed, and the water solubility test was conducted at 20°C. The results are summarized in Table 2.

Examples 2 to 6 Tests were conducted in the same manner as in Example 1 except that polymer [A] was changed to polymers [B] to [F]. The results are shown in Table 2.

Comparative Example 1 A test similar to Example 1 was conducted using polyvinyl alcohol with a degree of polymerization of 550 and a degree of saponification of 80 mol%. The results are shown in Table 2.

Comparative Example 2 Polymerization degree 1750. A test similar to Example 1 was conducted using polyvinyl alcohol with a saponification degree of 89 mol%. The results are shown in Table 2.

Comparative Examples 3 to 5 Pyrrolidone-modified polyvinyl alcohol before butyralization obtained during the synthesis of polymers [A], [B], and [D] (polymer [G], [H], and [T], respectively) A test similar to that of Example 1 was conducted using

The results are shown in Table 2. Below is the margin Example 7 100 parts of polymer [A] and 5 parts of pentaerythritol,
After mixing 7 parts of glycerin, the mixture was melt-extruded using an extruder at a temperature of 170°C, and pelletized using a pelletizer.

This pellet was subjected to inflation molding using an inflation molding machine at an inflation die temperature of 170° C. to obtain a film in the form of a folded tube with a folding width of 10 cm and a thickness of 35 μm per sheet.

After cutting this into a length of 10 cm, one opening was sealed by heat-sealing, 30 g of a commercially available powdered detergent (Kao "Zabu") was put inside, and the opening was heat-sealed and the opening was sealed. This product was left standing at 40° C. and 90% RH for 3 days. There was no change in the shape of the bag and no abnormalities were observed. Separately, this product was allowed to stand at 40° C. and 60% RH for 3 months, then taken out and poured into stirring water to observe water solubility. The water solubility was good, and the film was completely dissolved within 1 minute, and foaming caused by the detergent was intense.

Comparative Example 6 Polyvinyl alcohol with a degree of polymerization of 450 and a degree of saponification of 82 mol % was used instead of the polymer [A] of Example 7, and instead of inflation molding, drum film forming was performed as in Example 1 (thickness The test was carried out in the same manner as in Example 7, except that the test sample was tested in the same manner as in Example 7.

The shape of the tri-riki moon stationary ornament under 40°C and 90% RH was considerably distorted. Further, the water solubility at 40° C. and 60% RH was poor, and the film did not tear even after 1 minute, and no foaming occurred due to the detergent.

As is clear from the above examples, the water-soluble film of the present invention has good morphological stability even when exposed to high temperature and high humidity conditions, and is also resistant to alkaline and acidic substances. Even if the degree of saponification of polyvinyl alcohol increases due to contact, crystallization is suppressed by the pyrrolidone group, so the drop in water solubility is small, so it has excellent alkali resistance and acid resistance.

The water-soluble film of the present invention can be used for detergent packaging, insecticides, bleach, etc.
It can be used for a wide range of purposes, including packaging for cleaning products, bath additives, and toiletry products, as well as packaging for laundry bags and gardening seeds.It is especially suitable for packaging detergents due to its excellent alkali and acid resistance. It is something that can be done.

Claims (3)

[Claims] (1) A water-soluble film made of acetalized pyrrolidone-modified polyvinyl alcohol having a content of pyrrolidone units of 1 to 20 mol% and a degree of acetalization of 1 to 30 mol%. (2) Claim 1 wherein the degree of saponification of the pyrrolidone-modified polyvinyl alcohol before acetalization is 95 mol% or more.
The water-soluble film described. (3) The water-soluble film according to claim 1 or 2, wherein the acetalization uses an aldehyde compound having 1 to 5 carbon atoms.