JPH01249342A - Polyvinyl alcohol film with coated surface and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. PRODUCT 1 The present invention relates to a polyvinyl alcohol film and a method for producing the same. More specifically, the present invention relates to a polyvinyl alcohol film that has excellent flexibility, good transparency, and water resistance, and a method for producing the same. (However, the film referred to in the present invention also includes sheet-like materials with a thickness of 51 mm or less.) B. Conventional techniques (- Polyvinyl alcohol obtained by polymerizing and saponifying vinyl esters, particularly vinyl acetate (hereinafter referred to as PVA (abbreviated as PVA) type film has excellent properties such as good printability and transparency in addition to its excellent mechanical properties, so it is used for packaging, mold release, agriculture, and industrial materials. , is widely used for water-soluble films, etc., and is particularly prized as a packaging film.In particular, PVA-based materials softened with an appropriate plasticizer (usually a polyhydric alcohol-based plasticizer) The film is extremely pliable, has a good texture, has excellent transparency, and is beautiful, so it has been successfully used as a packaging film to give a high-class image to the package.

PVA-based film absorbs moisture from the air and this water acts as a plasticizer, but since the absorption rate of 1 m changes depending on the humidity in the air, PVA-based film alone cannot The film has the property that its flexibility changes depending on the humidity.In particular, under low humidity, the amount of moisture absorbed decreases, making it hard and brittle.
The film tends to become hard even when the degree of a decreases, so during low humidity in winter, the synergistic effect causes the film to become hard and brittle, and when used as a packaging film, problems such as film cracking are likely to occur. Therefore P
VA film alone cannot be used as a packaging film.

In order to improve this point, a method has conventionally been adopted in which polyhydric alcohol such as glycerin is added as a plasticizer.

By adding a suitable plasticizer, a PVA film that is sufficiently flexible and suitable for use even at low humidity in winter can be obtained, and has been put into widespread practical use.

However, although initial softening can be achieved through the addition of plasticizers, the problem of decreasing plasticizer content over time causes problems when used for long periods of 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 migration of the plasticizer due to contact between the film and the contents or items in the pond.

In recent years, there has been a strong desire to improve the problem of a decrease in the plasticizer content of PVA-based films, and there has been an urgent need to develop a PVA-based film whose plasticizer content does not decrease over time.

Various attempts have been made to solve this problem, but no satisfactory solution has yet been found.

C8B tries:.

Under these circumstances, the present invention aims to provide a PVA-based film and a method for producing the same in which the content of polyhydric alcohol-based plasticizer does not substantially decrease over time.

00 Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has determined that the surface of a polyvinyl or alcohol-based film containing a polyhydric alcohol-based plasticizer can be coated with an organic solvent-soluble material capable of forming 111. An organic solvent solution of a polymer compound, the coating of which has a weight swelling degree of 200% or less in water, and the weight swelling degree of the coating film of a polyhydric alcohol plasticizer of 400% or less. Alternatively, it has been discovered that the above problems can be solved by using a polyvinyl alcohol film characterized by coating with a dispersion liquid, and the present invention has been completed.

The present invention will be explained in detail below.

First, the polyvinyl alcohol of the polyvinyl alcohol film containing the polyhydric alcohol plasticizer used in the present invention is not particularly limited as long as it is a polyvinyl alcohol polymer compound, but preferably has a degree of polymerization of 100 or more. 10000 or less, more preferably polymerization degree 10
00 or more and 3000 or less, and the degree of saponification is preferably 5
It is preferably 0 mol% or more, more preferably 95 mol% or more.

If the degree of polymerization is too low, the strength of the polyvinyl alcohol film containing the polyhydric alcohol plasticizer will tend to be insufficient, and if it is too high, the film will have high viscosity during film formation, which will reduce workability, which is undesirable. . Furthermore, if the degree of saponification is too low, the strength of the film tends to be insufficient. Particularly in applications where water resistance is required, a saponification degree of 95 mol % or more is desirable because the higher the saponification degree, the higher the crystallinity and the water resistance.

Although the method for producing polyvinyl alcohol used in the present invention is not particularly limited, a conventionally known method of polymerizing fatty acid vinyl (particularly vinyl acetate) and then saponifying it is preferably used.

Furthermore, there is no problem with the polyvinyl alcohol used in the present invention containing small amounts of other components. Examples of such components include olefins such as ethylene, propylene, methylene, and l-hexene, unsaturated acids such as (meth)acrylic acid, crotonic acid, maleic acid (anhydride), fumaric acid, and itaconic acid, and alkyl thereof. Unsaturated sulfonic acids and their alkalis such as esters and alkali salts, (meth)acrylamide, N,N-dimethylacrylamide, N-vinylpyrrolidone, al-cow rubinyl ether, 2-acrylamido-2-methylpropanesulfonic acid and allylsulfonic acid. salts, cationic monomers such as trimethyl-3-(1-(meth)acrylamidopropyl)ammonium chloride, silyl group-containing monomers such as vinyltrimethoxysilane, allyl acetate, impropenyl alcohol, dimethylallyl alcohol, etc. A possible method is to copolymerize the monomer with vinyl fatty acid and then saponify it.

Next, the polyhydric alcohol plasticizer used in the present invention refers to a compound that has two or more hydroxyl groups and exhibits a plasticizing effect when added to the polyvinyl alcohol polymer compound. Specific examples of such compounds include ethylene glycol, trimethylene glycol, tetramethylene glycol, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, glycerin, diglycerin, butanediol, diethylene glycol, triethylene glycol, trimethylolpropane. etc. can be mentioned. Among these, glycerin and diglycerin are most preferred in view of their plasticizing effect, compatibility with polyvinyl alcohol-based polymer compounds, and high boiling point.

There is no particular restriction on the amount of polyhydric alcohol plasticizer added, but it is preferably 1 part by weight per 100 parts by weight of PVA.
~50 parts by weight, more preferably 5 to 20 parts by weight.

If the amount of polyhydric alcohol plasticizer added is too small, the film will become hard and brittle, whereas if it is too much, the film will become hard and brittle.
It tends to become too flexible and lose its firmness.

PV containing polyhydric alcohol plasticizer used in the present invention
A-type films include sheets with a thickness of 51 μm or less, and those with a thickness of 5 to 200 μm are usually preferably used.

PV containing polyhydric alcohol plasticizer used in the present invention
As a method for manufacturing the A-based film, a method conventionally used for manufacturing a PVA-based film is suitably used. That is, a casting method that uses water as a solvent, casts it on a drum or belt, and dries it;
A melt extrusion method in which a pellet impregnated with water is melt-extruded can be applied.The film after forming may or may not be heat-treated depending on the purpose.

There is also nothing wrong with stretching.

An organic solvent-soluble polymer compound capable of forming a film used in the present invention, the film having a weight swelling degree in water of 200% or less, and a weight swelling degree of the film in a polyhydric alcohol plasticizer. As for the polymer compound having 400% or less (hereinafter referred to as ?ti, polymer compound for covering polymer), there is no limitation at all as long as it satisfies the above requirements. It is essential that the coating polymer compound of the present invention is capable of forming a film. Polymerized a-products that do not have the ability to form a film cannot cover the surface of a polyvinyl alcohol film, and cannot exhibit the effect of preventing the polyhydric alcohol plasticizer from bleeding or migrating to other substances. Furthermore, the coating polymer compound of the present invention is soluble in organic solvents and has a coating film with a weight swelling degree of 200% or less in water, and has a low affinity for water, so when coated on the surface of a polyvinyl alcohol film, It has the characteristics of improving the water resistance of polyvinyl alcohol films and reducing the rate of moisture absorption and desorption, resulting in films with low humidity dependence.

Furthermore, the polymer compound for coating of the present invention has a weight swelling degree of 400% or less with respect to a polyhydric alcohol plasticizer, and when the surface of a polyvinyl alcohol film is coated, the polyhydric alcohol plasticizer penetrates into the coating layer. As a result, the polyvinyl alcohol-based film overturned the polyhydric alcohol-based plasticizer, which bleeds out or migrates to other substances.The total weight of the swollen coating polymer compound after equilibrium is reached.

B: Among the coating polymer compounds swollen after being immersed in a polyhydric alcohol plasticizer at 20°C to reach equilibrium,
Weight of coating polymer compound only.

That is, if there is no swelling at all, A = 8, and the weight swelling degree of the coating polymer compound relative to the polyhydric alcohol compound must be 400% or less, but the effect of preventing plasticizer bleed and migration is If it is expressed, a smaller value is more preferable, and a value of 100% or less is desirable.

The coating polymer used in the present invention is not limited in any way as long as it satisfies the above requirements, but preferably includes phenol resin, polyethylene, polypropylene, polystyrene, polyisobutyne, fluorine thread resin, lincone resin, urea resin, Melamine resin, alkyd resin, unsaturated polyester resin, epoxy resin, polyurethane resin, aldehyde resin, ketone resin, coumaron resin, maleic acid resin, polyvinyl acetate resin, polyvinyl chloride resin, poly(meth)acrylate resin, butyral Resins, rubber resins, cellulose derivatives, etc. are used. Among these, polyurethane resin, polyvinyl acetate resin, poly(meth)
Acrylic acid ester resin, butyral resin, etc. are most preferably used.

The coating polymer used in the present invention only needs to be capable of forming a film by itself, but preferably the glass transition temperature of the film is within the range of 120°C to 150°C. . If the glass transition temperature is lower than this, the formed film will be too soft and the resulting polyvinyl alcohol films will have strong mutual adhesion, making them unusable. On the other hand, if the glass transition temperature is higher than 150° C., the obtained polyvinyl alcohol film becomes hard and has reduced flexibility, which is not preferable.

The coating polymer compound used in the present invention may have a transparent or opaque coating, but if transparency is required such as in packaging film applications, a transparent coating may be used. It is preferable to use a coating polymer compound that provides an opaque coating, or to use a thin layer of a coating polymer compound that provides an opaque coating.

The coating polymer compound used in the present invention is sufficiently effective even when used alone, but it can also be used to improve the adhesion to the PVA film containing a polyhydric alcohol plasticizer, which is the base material. For the purpose of improving the solvent resistance of the coating layer, a crosslinking agent such as a reactive polyvalent isocyanate compound or a polyvalent epoxy compound may be used in combination. In particular, a polymer compound containing 30 mol% or less of one or more of carboxyl groups, amino groups, and hydroxyl groups is selected as the coating polymer compound, and a polyfunctional isocyanate having two or more isocyanate groups in one molecule is selected. When used in combination so that the isocyanate group is in excess of the sum of the carboxy group, amine group, and hydroxyl group, what happens? 111 polymer compound layer and PVA base material
A PVA-based film can be obtained which has excellent bone adhesion properties with the PVA-based film and also has excellent solvent resistance. Specific examples of such coating polymer compounds include acrylic resins containing carboxyl groups and hydroxyl groups, two-component type and L-wave type polyurethane resins, and the like.

The number of coating polymer compounds used in the present invention may be one type, or two or more types may be used in combination.

Further, when used in combination, they may be mixed and coated, or two or more layers may be provided separately.

In particular, if the adhesion between the coating polymer used and the PVA film that is the base material is a problem, it is necessary to
It is also possible to coat the surface of the VA film with a layer that acts as an adhesive, and then coat the polymer compound for wear. As the adhesive layer, a conventionally known compound called a brimer is suitably used. Specific examples of the primer include a mixture of polyester polyol or polyether polyol and a polyfunctional isocyanate.

It is of course possible to add other components to the coating polymer used in the present invention, such as pigments, plasticizers, slip agents, surfactants, anti-adhesion agents, antistatic agents, and the like.

Regarding the PVA film of the present invention, the relationship between the total thickness of the coating polymer compound layer [A] and the thickness of the PVA film containing the polyhydric alcohol plasticizer [B] is preferably [A/[ B]=0.0001 to 0.5, more preferably [A/[B]=0. Ol-0,2 is good. If the thickness of the coating layer is too thin, it will not be effective in preventing the polyhydric alcohol plasticizer from bleeding, volatilizing, or coming into contact with other articles, and if it is too thick, the P
This is not preferable because the original flexibility of the VA film is lost.

Regarding the present invention, the method for forming a layer of a coating polymer compound on a PVA film containing a polyhydric alcohol plasticizer is to apply a solution or dispersion of a coating polymer compound in an organic medium using a conventionally known coating method. A method of engineering is preferably used. Note that the organic medium here includes all conventionally known organic solvents, and specific examples include aliphatic, aromatic, vegetable, and naphthenic hydrocarbon solvents, and alcohols such as methanol and ethanol. ester solvents such as l-agents, tu acid, ethyl, and ethyl acetate, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as ether and butyl cellosolve, halogen solvents such as methylene chloride, and nitrosols such as 2-nitropropane. Examples include solvents. In addition, if the amount is small, water may be added. Specific examples of coating methods include brush coating, dip coating, spin coating, flow coating, spray coating,
Methods include roll coating, air knife coating, and blade coating. The film of the present invention is obtained by drying after coating, but heat treatment, stretching, etc. may be performed as necessary. Further, coating may be performed on only one side, or may be applied on both sides.

The PVA film of the present invention is used for packaging, mold release, agriculture,
It is suitably used for industrial materials, water-soluble films, etc.

The PVA-based film of the present invention has a low content of polyhydric alcohol-based plasticizer that decreases over time, and is less prone to cracking in winter (
stomach. Although the detailed reason for this is not clear, '?' is used in the present invention. The reason for this is that the polyhydric alcohol plasticizer does not substantially penetrate into the polymer compound for covering the polymer, and the polyhydric alcohol plasticizer does not bleed onto the surface of the PVA film of the present invention. It can be considered as

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these in any way. In the following, "parts" and "%" are "parts by weight" unless otherwise specified.
Means "% by weight".

Example 1 100 parts of polyvinyl alcohol with a degree of polymerization of 1750 and a degree of saponification of 99.9 mol% and 12 parts of glycerin were mixed with 10 parts of water (10
It was then cast onto a rotating drum at a drum temperature of 70° C. to obtain a PVA film with a dry thickness of 40 μm. Polymethyl methacrylate-butyl acrylate copolymer (molecular weight 50,000, methyl methacrylate 50
An ethyl acetate solution (mol%) was applied to only one side using an applicator type coater at a drying temperature of 80°C. The dry thickness of the coating layer of the obtained film was 1 μm.

After cutting this film into 10cm squares, 20℃, 65%R
11 for one week to adjust the humidity. Place this on a 15cm square glass plate with the coated side facing up, place a 12cm square cotton cloth (gyun cloth No. 19A) on top, and then place a 15cm square glass plate on top. A 2 kg weight was placed on top of it. This product was left standing at 20° C. under 65% R)I for 20 days. The content of glycerin in the film before and after this test was determined using gas chromatography. (This test will be referred to as the plasticizer migration test.)
The results are shown in Table 1.

Separately, an ethyl acetate solution of polymethyl methacrylate-butyl acrylate copolymer (molecular weight 50,000, methyl methacrylate 50 mol%) was cast onto a polytetrafluoroethylene sheet, and allowed to stand at room temperature to dry. Thereafter, it was peeled off and further dried at 120° C. for 10 minutes to obtain a single polyacrylic resin film.

The thickness of this material was 55μ. 5X this film
After cutting it into loam and measuring its weight (denoted as Wl), it was immersed in glycerin at 20°C for 72 hours, pulled out, and the adhering glycerin was thoroughly wiped off with a filter paper, and its weight was measured (W ). Furthermore, after dissolving this film in acetone, glycerin was quantified by gas chromatography. The glycerin content in this film at this time is assumed to be X%.

Next, the weight swelling degree in glycerin and the solubility in glycerin of the polyacrylic resin alone film were calculated using the following formula.

The results are shown in Table 1.

In addition, a similar test was conducted on the single polyacrylic resin film described above using water instead of glycerin.
The weight swelling degree in water and the solubility in water were determined. In this case, the evaporation to dryness method was used to determine the water content in the swollen film. The results are shown in Table 1.

Examples 2 to 6 Example 1 except that the coating polymer compound and its thickness were changed.
The test was conducted in the same manner. The results are also shown in Table 1.

Comparative Example I P before coating with the polyacrylic resin obtained in Example 1
A plasticizer migration test similar to that in Example 1 was conducted using a VA film. The results are shown in Table 1.

Comparative Example 2 Instead of the acrylic resin used in Example 1, acrylic acid-
The test was conducted in the same manner as in Example 1, except that a butyl acrylate copolymer (molecular weight 55,000, acrylic acid 30 mol %) was used. The results are shown in Table 1.

Below is the margin Example 7 Degree of polymerization 1750. 100 parts of polyvinyl alcohol with a degree of saponification of 98.5 mol % and 15 parts of glycerin were dissolved in 800 parts of water and cast onto a rotating drum at a drum temperature of 70° C. to obtain a PVA film with a dry thickness of 70 μm.

This film was coated with polyester polyol (Atocoat A D-335A, manufactured by Toyo Morton Co., Ltd.) and polyvalent isocyanate (CAT-10, manufactured by Toyo Morton Co., Ltd.).
were diluted with methyl ethyl ketone and toluene at a solid weight ratio of 100:6 and coated on one side with a bar coater so that the thickness after drying was 0.3 μm. 1 at 80℃
After drying for several minutes, the surface was coated with an ethyl acetate solution of the copolymer used in Example 1 using a bar coater so that the thickness after drying was 3 μm, and dried at 120° C. for 10 minutes. Furthermore, a similar two-stage coating was applied to the back side.

This film and the 70μ PVA film before coating were suspended and stored in a desiccator kept at 20°C and 95% R, and after 3 days, the states of the coated film and the uncoated film were observed. . The coated film did not change at all, while the uncoated film was completely sticky due to bleeding glycerin.

Example 8 vll Synthetic leather SSO, 100 parts of polyvinyl alcohol with saponification degree of 95 mol% and 9710 parts of glycerin are dissolved in 1000 parts of water, and cast on a rotating drum at a drum temperature of 70°C to form a PVA film with a dry thickness of 40μ I got it.

A 5% ethyl acetate solution of the acrylic resin used in Example 1 was applied to this film using a dip nip coater at a temperature of 1.
Both sides were coated at 00°C. The thickness of the coat layer after drying was 1 μm per side, and 2 μm in total. The transparency of this film was visually judged, and the flexibility was judged by touch. The results are shown in Table 2.

In addition, use this film to make wool yarn balls (commercially available for handicrafts, 5
0 g (manufactured by Hamanaka Co., Ltd.) was wrapped, placed in a paper bag, and allowed to stand at 20° C. and 65% R11 for 3 months. After 3 months, the film was taken out and placed in an environment of 5°C and 40% RH for 1 day, then folded at 5°C and observed whether it would crack.

The results are also shown in Table 2.

Examples 9 to 12 Example 8 except that the coating polymer compound and its thickness were changed.
The test was conducted in the same manner. The results are shown in Table 2.

Comparative Example 3 PV before coating with acrylic resin produced in Example 8
A test similar to Example 8 was conducted using Film A. The results are shown in Table 2.

Comparative Example 4 A test was conducted in the same manner as in Example 8, except that the acrylic resin used in Comparative Example 2 was used as the coating polymer compound. The results are shown in Table 2.

From the results described below, it is clear that the PVA-based film of the present invention is an excellent film that has excellent transparency and flexibility, and shows little decrease in the content of polyhydric alcohol-based plasticizer over time.

Patent applicant RiRashi Co., Ltd.

Claims (6)

[Claims] (1) An organic solvent-soluble polymer compound containing a polyhydric alcohol plasticizer and capable of forming a film on at least one side, and the weight swelling degree of the film in water is 200.
% or less, and the film has a coating layer made of a polymer compound whose degree of weight swelling with respect to a polyhydric alcohol plasticizer is 400% or less. (2) The polyvinyl resin according to claim (1), wherein the organic solvent-soluble polymer compound is at least one selected from polyurethane resin, polyvinyl acetate resin, poly(meth)acrylate resin, and butyral resin. alcohol film. (3) The total thickness of the coating on the organic solvent-soluble polymer compound is 0.0 relative to the thickness of the polyvinyl alcohol film containing the polyhydric alcohol plasticizer as the base material;
001 to 0.5, the polyvinyl alcohol film according to claim 1. (4) The polyvinyl alcohol film according to claim 1, wherein the polyhydric alcohol plasticizer is glycerin or diglycerin. (5) The surface of the polyvinyl alcohol film containing a polyhydric alcohol plasticizer is made of an organic solvent-soluble polymer compound capable of forming a film, and the weight swelling degree of the film in water is 200% or less, A method for producing a polyvinyl alcohol film, characterized in that the film is coated with an organic solvent solution or dispersion of a polymer compound whose weight swelling degree relative to a polyhydric alcohol plasticizer is 400% or less. (6) Isocyanate is a polyfunctional isocyanate in which the organic solvent-soluble polymer compound contains 30 mol% or less of one or more of carboxyl groups, amino groups, and hydroxyl groups, and has two or more isocyanate groups in one molecule. 6. The method for producing a polyvinyl alcohol film according to claim 5, wherein the groups are used together in excess of the total of carboxyl groups, amino groups, and hydroxyl groups. (7) Coating in advance a mixture of polyester polyol or polyether polyol and a polyfunctional isocyanate having two or more isocyanate groups per molecule on the surface of a polyvinyl alcohol film containing a polyhydric alcohol plasticizer, The method for producing a polyvinyl alcohol film according to claim 5, wherein the film is coated with an organic solvent-soluble polymer compound.