JPS60250040A - Production of film having improved gas-barrier properties - Google Patents

Abstract

PURPOSE:To obtain a film having improved gas-barrier properties and blocking resistance, by applying a vinylidene chloride copolymer latex to the surface of a film, heat-treating the resulting coated layer and again applying said, latex to the surface through said layer. CONSTITUTION:The surface of a film is coated with a vinylidene copolymer latex contg. 60-94wt% vinylidene chloride and dried. Immediately after the film is heat-treated at a temp. not lower than the m.p. of the copolymer, the surface is again coated with said latex and dried. The quantity of the vinylidene chloride copolymer to be applied to the first layer is 1-20g/m<2> (on a solid basis) which can be applied by one coating. The copolymers having an m.p. of 90- 170 deg.C are preferred.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention involves heat-treating a film coated with a vinylidene chloride copolymer latex at a temperature higher than the melting point of the vinylidene chloride copolymer. The present invention relates to a method for producing a composite film with excellent gas barrier properties, which comprises further coating a vinylitine chloride copolymer latex on the combined film and drying it.

[Prior art]

It is already known that vinylidene chloride copolymer latex can significantly improve the gas barrier properties of thermoplastic films, especially polyolefin, polyamide and polyester films, when applied to the films.

A coating film obtained from this vinylidene chloride copolymer 2-tex is obtained by evaporating water from the latex and drying it. This film is formed when one coalesced particle in the latex is filled and deformed mainly by capillary pressure, and the particles come into close contact with each other and are fused.

The film obtained from this latex is compared to films obtained by other film processing methods, such as a method in which the resin is heated and melted and then extruded and stretched, or a method in which the resin is dried and formed from a solution in a soluble solvent. The resin composition of the film is not homogeneous (and contains impurities such as emulsifiers).

That is, it contains a crystalline vinylidene chloride copolymer which has a high softening temperature and has almost no plasticizing fluidity at room temperature. In a film obtained by coating and drying latex, the latex particles are only adhered to each other at their interfaces, and it is thought that the resin is hardly completely melted and homogenized between the particles. Therefore, in such a film, it is easily observed with a microscope that there are many minute pores, cracks, etc. in the film. This means that when comparing a film formed from latex with a film of the same thickness formed from a solution of the same copolymer composition as the latex in an organic solvent, the gas barrier properties of the former film are inferior. This is a big reason why.

On the other hand, vinylidene chloride copolymer solutions using organic solvents have high viscosity even at low solids concentrations, which greatly limits the amount that can be coated, and the disadvantages of using solvents are significant in film formation. This is a drawback. When forming a film from latex, there are fewer restrictions on the amount that can be coated, but as mentioned above, the material of the film obtained is non-uniform and the gas barrier
Their disadvantage is that they are inferior in gender.

On the other hand, it may be possible to improve the gas barrier properties by applying a vinylidene chloride copolymer latex to the base film and then heat-treating it to a temperature at which the vinylidene chloride copolymer softens and flows. A locking phenomenon occurs, and when the latex coated film is rolled up, the films stick together, making subsequent operations difficult.

[Summary of the invention]

The inventors of the present invention have conducted intensive studies on a method for eliminating the above-mentioned drawbacks and improving the gas barrier properties of the film.
We have arrived at the present invention.

That is, the present invention uses 60 to 94% by weight of vinylidene chloride.
Immediately after coating and drying a vinylidene chloride copolymer latex containing the following on the surface of the film and heat-treating at a temperature higher than the melting point of the copolymer, further coating and drying the vinylidene chloride copolymer latex on the surface. The present invention relates to a method for producing a film with improved gas barrier properties.

According to the present invention, the coated vinylidene chloride copolymer latex particles are melted together and formed into a uniform film by heat treatment, so that the gas barrier properties of the resulting film are significantly improved compared to when no heat treatment is performed. improves. That is, the oxygen permeability, which is a measure of gas barrier properties, decreases to 70 degrees or less of the latex coated film that has not been heat treated.

Further, after the heat treatment, the vinylidene chloride copolymer latex is coated on the surface again, so that no blocking occurs when winding into a four-ring shape, making subsequent operations easier.

[Detailed description of the invention]

As the base film used in the method of the present invention, commonly used films are used. Here, the term "film" includes not only so-called films but also sheet-like materials.

Since the film used in the present invention is heat treated at a temperature higher than the melting point of the vinylidene chloride copolymer, thermoplastic resin films with relatively high heat resistance, such as films of polyethylene terephthalate, polyamide and polypropylene, regenerated cellulose such as cellophane, etc. films are preferably used. In the case of a thermoplastic resin film, a biaxially stretched film is particularly preferably used.

Anchor coat (hereinafter referred to as AC agent) is applied to the surface of these base films or their oxidized surface as necessary.
Apply. As the AC agent, a commonly used acrylic resin emulsion, an organic solvent solution, or an organic solvent solution of polyurethane or polyester adhesive can be used. Note that if the vinylidene chloride copolymer latex has good adhesive properties, it is not necessary to use the above-mentioned AC agent. Vinylidene chloride copolymer latex is applied as a first layer to the surface of this base film, the oxidation-treated surface, or the AC agent-coated surface and dried.

The amount of vinylidene chloride copolymer applied in the first layer is not particularly limited, but it is usually 1 to 20 #1, which is the amount that can be applied in one coat.
/m2 (solid content) is suitable. The vinylidene chloride copolymer to be applied to this first layer is vinylidene chloride 60.
-94% by weight, preferably 70-92% by weight, and a small amount (both 6-4% by weight of one monomer) copolymerizable with vinylidene chloride.
0% by weight, preferably 8 to 30% by weight. If the content of vinylidene chloride in the vinylidene chloride copolymer is 9.4% by weight or more, it is undesirable because it becomes difficult to form a film from latex and the melting point of the copolymer becomes excessively high. do not have.

On the other hand, if it is less than 60% by weight, the resulting film will have poor gas barrier properties.

The melting point of vinylidene chloride copolymer is 90 to 170
Those within the range of C can be preferably used.

When a biaxially oriented polypropylene film is used as the base film, it is desirable to use a vinylidene chloride copolymer coated in the first layer with a melting point of 120C or less.

Examples of monomers copolymerizable with vinylidene chloride include vinyl chloride, vinyl acetate, acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate, methyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate. , methyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, sodium styrene sulfonate, methoxypolyethylene glycol methacrylate, and the like.

A conventional emulsion polymerization method is used to polymerize the vinylidene chloride copolymer latex. As the emulsifier, an anionic emulsifier, a nonionic emulsifier, or a mixed emulsifier thereof is used, and polymerization is usually carried out at a temperature of 40 to 80C.

The film coated with the first layer of vinylidene chloride copolymer as described above is heat-treated at a temperature equal to or higher than the melting point of the vinylidene chloride copolymer without causing thermal deformation of the base film. Usually, the heat treatment temperature is preferably in the range of 90 to 190C. For example, when the base film is a biaxially oriented polyethylene terephthalate film or a biaxially oriented polyamide film, the temperature range is approximately 140 to 180 C, although it varies somewhat depending on the melting point of the vinylidene chloride copolymer coated in the first layer. is suitable. On the other hand, in the case of biaxially oriented polypropylene film, it rapidly shrinks due to heat at a temperature of 1000 or more.
Above the melting point of the vinylidene chloride copolymer used and 120C
It is desirable to perform heat treatment at a temperature below.

As a heat treatment method, hot air, infrared irradiation, a roll, etc. are used, but the most effective method is to contact and heat the surface coated with the first layer of vinylidene chloride copolymer with a heating roll. The heat treatment time varies depending on the heat treatment method, the type and thickness of the base film, and it is necessary to heat the film until at least the applied first layer of vinylidene chloride copolymer melts. Generally, about 0.1 to 20 seconds is preferred, particularly 0.1 to 10 seconds. Excessively long heat treatment should be avoided since the vinylidene chloride copolymer will be colored. After this heat treatment,
Immediately, a second layer of vinylidene chloride copolymer latex is applied to the surface of the first layer of vinylidene chloride copolymer film, dried, cooled, and then wound into a roll.

The vinylidene chloride copolymer latex applied to the second layer is obtained by polymerization in the same manner as the vinylidene chloride copolymer latex used in the first layer. The copolymer for this second layer is 60 to 94% by weight of vinylidene chloride, preferably 70 to 9% by weight.
A copolymer is used consisting of 6 to 40% by weight, preferably 8 to 30% by weight of at least one monomer copolymerizable with vinylidene chloride and a 2M amount. As the monomer copolymerizable with vinylidene chloride, the above-mentioned monomers used in the first layer copolymer are preferably used. The composition of the vinylidene chloride copolymer applied to the second layer may be the same as that of the first layer, or may be different. However, the usefulness of the present invention is increased by using a material that has good blocking resistance when wound into a roll and also has good post-processability, that is, good suitability for printing and lamination with a polyolefin film.

In addition, to the vinylidene chloride copolymer latex used in the second layer, inorganic powders or waxes such as silica, calcium carbonate, talc, clay, etc. can be added as anti-blocking agents, as well as pigments, dyes, etc. The coating amount of the vinylidene chloride copolymer used in this second layer must be at least an amount that can improve the blocking resistance, and is usually used in the range of 1 to 201/m2c (solid content). A thickness of about 1 to 517 m, which is smaller than that of the first layer, is economically preferable.

If this second layer of vinylidene chloride copolymer is not applied, the first layer of vinylidene chloride copolymer is heat-treated, so the copolymer becomes amorphous and becomes flexible. However, if the film is wound into an X-roll, it will block and become unusable, so there is no practical point in producing such a film.

The usefulness of the present invention will be illustrated below by way of examples. The parts and parts shown are percent by weight and parts by weight, respectively.

First, the evaluation test method will be explained below.

(1) Oxygen permeability: ゛The sample composite film was measured at 200.90 SRH
Measured with OCON 0X-TRAN 100 type testing machine,
Compared to the sample without heat treatment, the transmittance value is 7.
It was determined that there was an effect when it became 0% or less.

(2) Blocking resistance: After applying 2 layers of the second layer of vinylidene chloride copolymer and drying, a 2 cm x 2 cm film was prepared by directly contacting the base film surface and the second layer of vinylidene chloride copolymer surface. A load of 1 Yu was applied to a flat surface of the same size, and the sample was left open for 20 hours at 40C. Thereafter, the blocking strength of the sample film was measured as the peel strength by pulling both ends of the sample in opposite directions under the condition of 23C1'60 inch RH. The tolerance for blocking strength differs depending on the film strength of the base film, so if the base film is biaxially oriented polyethylene terephthalate, the tolerance is 1500.
I! The following is good, and 1 in the case of biaxially stretched nylon film.
A value of 8009 or less was determined to be good, and in the case of a biaxially oriented polypropylene film, a value of 900F or less was determined to be good.

(3) Printing suitability: Moisture-proof cellophane printing ink GNC-8T and its diluting bath agent GN are applied to the second layer coated with vinylidene chloride copolymer.
-102 (manufactured by Toyo Ink Co., Ltd.) at a ratio of 2:1 was applied so that the solid content was 217 m2, and 60C
It was dried for 1 minute in a hot air oven. Thereafter, a cellophane adhesive tape was brought into close contact with the printed ink surface and peeled off at a high speed, and the degree of peeling of the printed ink surface was determined. A case where the width of the peeled surface of the printing ink was 20% or less was judged as good. Moreover, this film with good printability also had good lamination suitability.

Next, the monomer composition (wt%) of the vinylidene chloride copolymer used in the examples and comparative examples and the DS of the copolymer
The melting point (Tm) measured with (3' (differential scanning calorimeter)) is shown below.

Copolymer A: Tm: 160C Vinylidene chloride 91.5% Methyl methacrylate 8% Methacrylic acid 0.5% Copolymer B; 'rm: 140C Vinylidene chloride 91% ' Methyl acrylate 5% Acrylonitrile 3% Acrylic acid 1 % C Copolymer: T77L: 155t:' Vinylidene Chloride 89.8 Methyl Thiacrylate 7.2% Acrylic Acid 3.0 T D Copolymer: 'I'm: 105C Vinylidene Chloride 86.5 Methyl Thiacrylate 11. 0 Methyl methacrylate 2.0% Acrylic acid 0.5% E copolymer: 'rm: 160C Vinylidene chloride 91,5 Methyl methacrylate 6 Thiacrylonitrile 2 Acrylic acid 0.5 Example 1 12μ door Atocoat AD-503 and AT-1 were applied to the oxidized surface of the biaxially stretched polyethylene terephthalate film.
0 (manufactured by Toyo Morton Co., Ltd.) and diluted to approximately 5% with ethyl acetate was applied as an AC agent so that the solid content was 0.317 m2. A as the first layer on the OAC agent surface.
The copolymer latex was applied to a solid content of 311/m 2 and dried with 80υ hot air for 30 seconds. After heating this copolymer surface at 180C for 2 seconds in contact with a hot roll, apply B copolymer latex on this surface at a solid content of 3.
y/m2 and dried for 30 seconds with 8 liters of hot air. Immediately, this composite film was used as a sample for measuring the blocking resistance.

On the other hand, this composite film was aged at 40C for 2 days, and its gas barrier properties and printability were tested. The results are shown in Table 1.

Comparative Example 1 A composite film sample identical to Example 1 was prepared except that the heat treatment was not performed.

Example 2 A composite film sample identical to Example 1 was prepared except that the heat treatment conditions were changed to 180C for 4 seconds.

Example 3 5117WL of C copolymer latex was applied as a solid content to the oxidized surface of a 15 μm biaxially stretched 6-nylon film.
2 and dried with hot air at 80C for 30 seconds. The C side of this copolymer was placed on a heating roll at 180C for 4 hours.
After contacting for seconds and cooling, B copolymer latex was applied as a second layer in the same manner as in Example 1 to a solid content of 317 m 2 and dried with hot air at 80 C for 30 seconds.

Comparative Example 2 The same sample was produced except that the heat treatment of Example 3 was not performed.

Example 4 The same AC agent as in Example 1 was applied to the oxidized surface of a 20P77L biaxially stretched polypropylene film in the same manner. This ACC screen D copolymer latex has a solid content of 5
g/m2 and dried with hot air at 80C for 30 seconds.

The surface of this copolymer was brought into contact with a 115C heating roll for 4 seconds and then cooled. Copolymer B was coated on the surface of copolymer D in the same manner as in Example 1 and dried.

Comparative Example 3 A composite film sample identical to Example 4 was prepared except that the heat treatment was not performed.

Example 5 Using a biaxially stretched polyethylene terephthalate film with a 12μ door, the A copolymer used in Example 1 was replaced with an E copolymer, and the solid content was coated with s, oy/-2 to form the second layer. A composite film sample was prepared by applying, drying, and heating in the same manner as in Example 1, except that the B copolymer was replaced with the above E copolymer.

Comparative Example 4 A composite film sample identical to Example 5 was produced except that the heat treatment of Example 5 was not performed.

Comparative Example 5 The AC agent and the first layer A copolymer were applied in the same manner as in Example 1, and the heat treatment was also performed under the same conditions as in Example 1.
A second layer of B copolymer was not applied. The blocking strength of this composite film sample was 2500 g or more, and it did not peel off easily.

Comparative Example 6 After applying the AC agent and the first layer of E copolymer in the same manner as in Example 5, heat treatment was performed under the same conditions as in Example 5, but the second layer of E copolymer was not applied. . The blocking strength of this composite film sample was 25009 or higher, and it did not peel off easily.

Table 1 shows the structure and physical properties of the composite films obtained in the above Examples and Comparative Examples. As is clear from the results in Table 1, the samples subjected to heat treatment in Examples 1 to 5 were
Comparative example 1 using conventional processing method without heat treatment
Compared to Sample No. 4, the oxygen permeability was 70% or less even with the same vinylidene chloride copolymer thickness, indicating that the barrier properties were improved.

Comparative Examples 5 and 6 are examples in which the second layer of vinylidene chloride copolymer was not applied after heat treatment, and when wound up into a roll, blocking occurred between the base film and the vinylidene chloride copolymer. This resulted in poor practicality.

Procedural amendment July 31, 1980 Patent Application No. 106450 of 1988 2, Title of invention: Process for producing a film with improved gas barrier properties 3, Relationship with the person making the amendment, Patent applicant name: Kureha Kagaku Kogyo Co., Ltd. Kasumigaseki Building Post Office P.O. Box No. 49 Eiko Patent Office Telephone (581)-96Q 1 (Representative) The column for detailed description of the invention in the specification will be amended as follows.

1) In the first line of page 6, "Including coalescence. From latex" is corrected to "From latex containing coalescence."

2) Correct "printability" in the 5th line from the bottom of page 12 to "printability".

6) On page 19, line 1, “AT-10J is CAT-1”
0”.

4) "〃" in the Comparative Example 1 Comprehensive Evaluation column of Table 1 on page 19 is corrected to "-".

Procedural amendment September 1980/g Date Patent Application No. 106450 of 1982 2, Name of the invention - Method for manufacturing a film with improved gas barrier properties 3, Person making the amendment Relationship to the case ``Name of patent applicant Kureha Chemical Industry Co., Ltd. Kasumigaseki Building Post Office PO Box No. 49

Claims (1)

[Claims] Immediately after coating a vinylidene chloride copolymer latex containing 60 to 94% by weight of vinylidene chloride on the film surface and drying it, and heat-treating it at a temperature higher than the melting point of the copolymer, the vinylidene chloride copolymer latex is further applied to the surface. Method for producing a film with improved gas barrier properties characterized by coating and drying