JPH0141171B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides dew condensation prevention and gas barrier properties by applying a solution of ethylene-vinyl alcohol copolymer resin (hereinafter referred to as EVOH) containing a nonionic surfactant to the surface of the base film or sheet and drying it. This invention relates to a method for producing a laminate with excellent performance. One of the characteristics required of packaging materials, especially food packaging materials, is gas permeation resistance. EVOH is Tokko Akira
As shown in No. 46-21941, it is a resin with excellent gas barrier properties, and is mainly used in food packaging materials when laminated with other polyolefin resins. Extrusion lamination and dry lamination of melt extrusion film products as a method of lamination with other materials;
Alternatively, there is simultaneous melt coextrusion, etc., but EVOH
When hot melt molded, it tends to thermally decompose and also has problems in blocking resistance. In order to eliminate these drawbacks, Japanese Patent Publication No. 1983-30600 (coating an EVOH solution containing polyethyleneimine to the base material of polyolefin moldings) and Japanese Patent Publication No. 46-23911 (EVOH (dissolving EVOH in a solvent or dispersing it in water and applying it to packaging materials), Japanese Patent Publication No. 47-48489 (applying EVOH dissolved in an alcohol-water mixed solvent at a temperature from 50°C to below the boiling point), etc. . The present invention is based on these technologies, and relates to a laminate that not only has excellent gas barrier properties but also has high added value, is beautiful, and has excellent dew condensation prevention properties, and a method for producing the same. Anti-condensation property is also expressed as droplet resistance or anti-fogging property.
A physical property that depends on how much water adhering to the surface of a film or sheet spreads, and is a property related to the hydrophilicity of the surface of the film or sheet. Conventionally, when contents with a high moisture content are packaged with a laminated film that has a polyethylene film with excellent sealing properties as the innermost layer, when the inside of the package becomes humid and supersaturated, water condenses and the contents are damaged. In addition to lacking the effect of displaying food products, the water had a negative effect on the packaged foods, causing them to deteriorate more quickly. In other words, films (including containers) used to package meat products such as Wiener sausages and frankfurter sausages, fish paste products such as chikuwa, kamaboko, and hanpen, as well as low-temperature distribution foods such as fresh noodles, shiyu mai, and gyoza. In order to prevent condensation, laminated films with ordinary polyethylene film as an inner layer have the problem of condensation as mentioned above, and polyvinyl chloride and polyethylene films are also used for packaging of fruits and vegetables and films for cultivating agricultural crops. When the surface of the film is essentially hydrophobic, a large number of water droplets adhere to the film surface due to evaporation of water from the fruits and vegetables and condensation of moisture in the air due to changes in temperature and humidity, causing cloudiness. In the case of packaging, these water droplets can cause spoilage and become a major problem, shortening the product's lifespan. Furthermore, in the case of agricultural films, etc., there arise problems such as the inability to maintain a sufficient function as a greenhouse due to blocking of sunlight and diffused reflection. In order to improve these problems, many proposals have been made so far, such as Special Publication No. 34-6539, No. 38-
No. 4174, No. 53-1777, No. 53-6985, and JP-A-50-140549, No. 51-91953, No. 52-104487
No. 53-9844, No. 53-31749, No. 53-78272
No. 53-77273, etc. All of these are aimed primarily at improving the anti-condensation properties of polyolefin films, and despite the many patent applications that have been filed, no one has been satisfied with both the initial anti-condensation effect and its sustained effect. The reality is that this cannot be said to be possible. This is because when using a polyolefin film, the resin itself is inherently hydrophobic, so it is extremely difficult to provide excellent dew condensation prevention performance under any conditions. This shows that. Generally speaking, imparting dew condensation prevention properties to a film, etc. refers to ensuring that water adhering to the surface of the film, etc. spreads uniformly over the surface of the film so that it does not form into droplets, and is used for this purpose. It can be said that the more hydrophilic the surfactant is, the more likely it is to provide better properties, ie, anti-condensation properties. However, in the case of polyolefin resins, the disadvantage is that they have poor compatibility with these hydrophilic surfactants, making it difficult to provide initial dew condensation prevention properties, and the long-term retention of surfactants in general is also insufficient. Moreover, when the amount added is increased, so-called embossing properties become stronger, leading to problems such as whitening and adhesion of the film. The present inventors have investigated the copolymer composition of EVOH, the relationship between the degree of saponification and dew condensation, and the surface activity of EVOH in order to provide a laminate that has long-term anti-condensation properties and gas permeation resistance. Changes in moldability, changes in physical properties, thermal deterioration, etc. due to the addition of agents were investigated. Simply coating the surface of an EVOH film with a nonionic surfactant has a drawback in terms of sustainability, and an EVOH composition containing a nonionic surfactant is melt-extruded to form a base film. In the method of extrusion lamination to a sheet or melt extrusion film formation and then lamination with a base film and sheet, not only EVOH, which is easily thermally decomposed, but also a nonionic surfactant with poor thermal stability is exposed to high temperature (200~200℃). 250°C), the thermal deterioration of the EVOH composition further progresses, resulting in problems such as discoloration, increased sticking eyes, poor blocking resistance, and deterioration of recovered resin compositions.
As a result of various studies, we solved these problems by dissolving a specific amount of nonionic surfactant and EVOH in a solvent, applying this solution to another thermoplastic resin, laminating it, and then drying it. It has excellent dew condensation prevention properties that cannot be achieved with polyolefin-based dew condensation prevention films, and has good gas barrier properties.
Compared to the case where the EVOH composition is hot melt molded,
It was discovered that a transparent and beautiful laminate with few visible eyes can be obtained, and the present invention was achieved. That is, an ethylene content of 25 to 60 containing 0.1 to 3% by weight of a nonionic surfactant with an HLB value of 4 to 16.
Manufacture of a laminate with excellent dew condensation prevention and gas permeation resistance, characterized by coating the surface of a thermoplastic film or sheet with an ethylene-vinyl alcohol copolymer resin having a mole% saponification degree of 96% or more. It is the law. However, the HLB value is an index of hydrophile-lipophile-balance. The present invention will be explained in further detail below. The EVOH used in the present invention has an ethylene content of 25 to 25% from the viewpoint of water resistance and gas permeability.
It is necessary to have a saponification degree of 60 mol% or more and a saponification degree of 96% or more. If the ethylene content exceeds 60 mol %, gas permeation resistance will be lost and this will not be suitable for the purpose of the present invention. On the other hand, when the ethylene content is lower than 25 mol %, the vinyl alcohol units increase, resulting in poor water resistance and reduced gas permeability under high humidity conditions. In addition, the degree of saponification of the copolymer is 96
If it is less than %, the film's water resistance, gas permeability resistance, and so-called stiffness of the film are deteriorated, and an acetic acid odor is produced, which is not preferable. The nonionic surfactant used must have an HLB value of 4 to 16, preferably 7 to 12, in an amount of 0.1 to 3% by weight based on the copolymer resin. If the HLB value is less than 4, water will not spread sufficiently on the film surface, and
If the HLB value is greater than 16, it is undesirable because it becomes easily soluble in water and the dew condensation prevention does not last long. Specific examples of nonionic surfactants used in the present invention include sucrose fatty acid esters, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene oxide adducts thereof, and polyoxyethylene alkyls. Nonionic surfactants such as ether type and polyoxyethylene alkyl allyl ether type can be used, and these may be used alone or as a mixture of two or more types. The amount of nonionic surfactant used is 0.1 to 3% by weight based on the copolymer resin, but the amount added is 0.1% by weight.
If the amount is less than 3% by weight, it is difficult to provide anti-condensation properties that meet the purpose of the present invention;
If the amount is more than 20%, problems such as so-called embossment caused by the activator, whitening of the film, adhesion, etc. occur, and the gas barrier performance deteriorates, which is undesirable. When EVOH is mixed with a nonionic surfactant and applied to a substrate, the solvents used are a mixture of normal propanol and water, a mixture of isopropanol and water, a mixture of tertiary butyl alcohol and water, and a mixture of methanol and water. A mixture of ethanol and water,
Dimethyl sulfoxide, dioxane, ethylene chlorohydrin, etc. can be used. A coating solution is prepared by dissolving EVOH in these solvents and adding a nonionic surfactant. Depending on the solvent, this solution may gel at room temperature, so it should be kept at an appropriate temperature before use. It is preferable that the substrate to be coated is coated with an adhesive in advance, and the solution is applied to a thermoplastic resin film or sheet coated with the adhesive, such as polypropylene,
Applies to surfaces such as polystyrene, polyester, nylon, cellophane, polyethylene, and vinyl chloride. If the solvent is removed after drying, a laminated structure with good dew condensation prevention and gas permeation resistance in which the base material and the coating layer are adhered can be obtained. In this case, it is preferable to heat-treat at a temperature of 80 to 170°C for several seconds to several minutes after removing the solvent. This increases the crystallinity of EVOH and improves its anti-condensation properties, gas permeability, strength, slip resistance, etc. Improve further. If necessary, various additives such as antioxidants, lubricants, anti-blocking agents, etc. may be added to this coating liquid within a range that does not adversely affect the effects of the present invention. There are no particular limitations on the film or sheet used, but various types can be used depending on the purpose of the laminate. There are no particular limitations on the coating method, including gravure roll coating, Meyer bar coating, doctor blade coating, reverse roll coating, dip coating,
Methods such as air knife coating can be employed. According to the present invention, when producing an EVOH laminate having anti-condensation properties without using melt extrusion film formation, there are the following advantages in addition to thermal decomposability. (1) The amount of surfactant contained in the dissolved EVOH is larger than that in the case of melt kneading, and therefore it can provide higher anti-condensation properties than a film obtained by melt extrusion. (2) Intra-molecular crosslinking occurs in EVOH through thermal history. Therefore, in the case of melt-forming, film formation is likely to cause fisheyes, but when coating is performed by melting, there are no fisheyes and a beautiful film can be obtained. (3) When EVOH is extruded into a film using a T-die, the edges cannot be commercialized due to poor thickness. Therefore, it is necessary to collect and reuse that part, but if the surfactant is contained in a few percent, the resulting film will have a significant increase in the film's structure, resulting in poor quality. According to the coating method of the present invention, a laminated film of good quality can be efficiently obtained by slitting the end of the roll of laminated film by a small amount and discarding it. The molded articles obtained by the present invention include containers as well as films and sheets. Further, as another feature of the copolymer resin film of the present invention, antistatic properties can be mentioned. For example, in the case of a multilayer film in which an ethylene-vinyl alcohol copolymer resin layer is used as an intermediate layer and polyolefin is arranged as the innermost layer, an antistatic agent is added to the polyolefin for ease of lamination process and continuous packaging work. Generally, no antistatic agent is used in the ethylene-vinyl alcohol copolymer resin layer, which is the intermediate layer, except in special cases. However, when an ethylene-vinyl alcohol copolymer resin layer is used as the innermost layer as in the present invention instead of the conventional polyolefin layer to which an antistatic agent is added as the innermost layer, the charging property is Although this is a problem, the present invention has the great advantage of being able to solve these antistatic problems at the same time. Incidentally, the charging property will be explained in further detail in Examples. Furthermore, the laminated sheet of the present invention can be used as an agricultural sheet in addition to food packaging. For example, when used as a sheet for cultivating agricultural crops, by applying the EVOH solution according to the present invention to the inner layer or inner or outer layer of the base sheet, it can also be used as an agricultural sheet with excellent dew condensation prevention properties. The present invention will be specifically explained below using Examples. Test details in Examples and Comparative Examples Condensation test Pour 200 c.c. of water into a cylindrical glass container (capacity 265 c.c.) with a diameter of 75 mm and a height of 60 mm, and apply EVOH (or polyvinyl alcohol (PVA)). A film was placed on top of the container with the side facing downward and left in a refrigerator (5 to 6°C).The degree of haze on the inside of the film was observed after 30 minutes and 24 hours.One or two points were minute water droplets. is adhered to the entire surface and is opaque. 3-4 points are water droplets that do not fuse with other water droplets at all and are opaque or translucent. 5-6 points are water droplets that do not uniformly fuse with other water droplets and are translucent. 7-4 8 points indicate that some parts are not wet enough and are almost transparent. 9-10 points indicate that the entire surface is almost uniformly wet and there are no water droplets, making it safe and transparent. Amount of oxygen permeation: EVOH layer or PVA layer with a length x width of 20 cm x 20 cm inside. 200 c.c. of N ₂ gas was injected into the bag with a syringe, and the bag was completely heat-sheeted for one week and one month later, the gas inside the bag was removed and the bag was subjected to gas chromatography to calculate the amount of O ₂ permeation. It was left at 20℃ and 65%RH. Slip angle The friction angle between the base film surface and the EVOH layer surface or PVA layer surface was measured at 20℃ and 65%RH using a friction angle measuring machine manufactured by Toyo Seiki Seisakusho Co., Ltd. .Surface specific resistance Resistance meter (model
4329A) was used to measure the surface resistivity of the EVOH layer surface or PVA layer surface at 20°C and 65%RH. Examples 1 to 3 Ethylene content 32 mol%, saponification degree 99.5%
100 parts by weight of EVOH, 350 parts by weight of water, 350 parts by weight of normal propanol, and a saccharide fatty acid ester with an HLB value of 11 (DK Ester F manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
-110) in 0.2, 1.5, and 2.5 parts by weight, and
A transparent coating solution was prepared by stirring and dissolving for a period of time. A biaxially stretched polyester film (20 μm) coated with an isocyanate-based anchor coating agent was coated with the coating solution at a speed of 50 m/min at a temperature of 65° C. using a gravure coater. Immediately after coating, it was passed through a drying oven adjusted to 100 to 130°C for drying and heat treatment. As a result, a transparent and beautiful laminated film having a 2 μm EVOH layer containing sucrose fatty acid ester was obtained. Table 1 shows various physical properties. Comparative Example 1 Table 1 shows the physical properties of the biaxially stretched polyester film (20μ) used in Example 1, which was coated with an isocyanate-based anchor coating agent and dried in a solvent. Various tests were conducted using surfaces to which no adhesive was applied. Comparative Example 2 Among the coating liquids of Example 1, a coating liquid containing no sucrose fatty acid ester was used.
A laminated film was produced in exactly the same manner. Various physical properties are shown in Table 1. Comparative Examples 3 to 4 A laminated film was produced in exactly the same manner as in Example 1 using a coating liquid containing 0.05 and 3.5 parts by weight of sucrose fatty acid ester based on 100 parts by weight of EVOH used in Example 1. did. Table 1 shows various physical properties. Comparative Examples 5 to 7 In Example 1, a coating solution consisting of PVA (saponification degree 99%), water, and sucrose fatty acid ester was used instead of the coating solution consisting of EVOH, water, normal propanol, and sucrose fatty acid ester. A laminated film was obtained in the same manner as in Example 1 except that .
Table 1 shows various physical properties.

[Table] As shown in Examples 1 to 3, laminates with good dew condensation prevention properties, oxygen barrier properties, slip properties, surface resistivity, etc. can be produced. As shown in the comparative examples, the cases of Comparative Examples 2 and 3 (when the amount of sucrose fatty acid ester used is 0 or small) lack dew condensation prevention properties, and the case of Comparative Example 4 (when the amount of sucrose fatty acid ester used is 0 or small). If a large amount is used), too much surfactant oozes out onto the coated surface, resulting in poor slip properties and problems during winding and subsequent processing. Furthermore, in the case of Comparative Examples 5 to 7 (EVOH
When PVA is used instead of PVA), the anti-condensation properties are not sufficient, the oxygen barrier properties are also poor, and
The PVA coating layer swells with water and has extremely poor slip resistance. Examples 4 to 6 Ethylene content 48 mol%, saponification degree 99.0%
100 parts by weight of EVOH, 350 parts by weight of water, 450 parts by weight of isopropanol, polyoxyethylene nonyl phenyl ether with an HLB value of 7.8 (Kao Matras
0.2, 1.5, and 2.5 parts by weight of Emulgen 903) (manufactured by Co., Ltd.) were mixed and dissolved with stirring at 75°C for 2 hours to prepare a transparent coating solution. Using a gravure coater, apply the above coating solution to biaxially oriented polypropylene (30μ) coated with an isocyanate-based anchor coating agent at a temperature of 65°C for 50m/min.
It was applied at a speed of 1 minute. 100-130 immediately after application
It was passed through a drying oven adjusted to a temperature of 0.degree. C. for drying and heat treatment. As a result, a transparent and beautiful laminated film having an EVOH layer of 2 μm containing polyoxyethylene nonyl phenyl ether was obtained. Table 2 shows various physical properties. Comparative Example 8 Table 2 shows the physical properties of the biaxially stretched polypropylene film (30μ) coated with the isocyanate-based anchor coating agent used in Example 4. Various tests were performed using surfaces to which no adhesive was applied. Comparative Example 9 A laminated film was manufactured in exactly the same manner as in Example 4 using the coating liquid of Example 4 in which polyoxyethylene nonyl phenyl ether was not blended. Various physical properties are shown in Table 2. Comparative Examples 10 to 11 Using a coating liquid containing 0.05 and 3.5 parts by weight of polyoxyethylene nonyl phenyl ether to 100 parts by weight of EVOH used in Example 4,
A laminated film was produced in exactly the same manner as in Example 4. Table 2 shows various physical properties.

[Table] As shown in Examples 4 to 6, laminates with good dew condensation prevention properties, oxygen barrier properties, slip properties, surface resistivity, etc. can be produced. Comparative Example 12 In the coating solution of Example 1, sorbitan fatty acid ester (Solgen 30 manufactured by Dai-ichi Kogyo Seiyaku) with an HLB value of 3.7 was used instead of the sucrose fatty acid ester.
A laminated film was manufactured in the same manner as in Example 1 using the coating liquid containing the following parts by weight. Table 3 shows its physical properties.
Shown below. Comparative Example 13 Using the coating solution of Example 1, a coating solution containing 1.5 parts by weight of polyoxyethylene nonylphenol ether (Emulgen 950 manufactured by Kao Soap Co., Ltd.) having an HLB value of 18.2 instead of the sucrose fatty acid ester was used. A laminated film was produced in the same manner as in Example 1. Its physical properties are shown in Table 3.

[Table] As shown in Comparative Examples 12 and 13, when a nonionic surfactant whose HLB value is outside the range of the present invention is used, sufficient anti-condensation properties cannot be obtained as shown in Table 3. .

Claims (1)

[Claims] 1. A nonionic surfactant with an HLB value of 4 to 16, 0.1 to 1.
25-60 mol% ethylene content, including 3% by weight;
A method for producing a laminate with excellent dew condensation prevention and gas permeation resistance, which comprises applying a solvent solution of ethylene-vinyl alcohol copolymer resin with a degree of saponification of 96% or more to the surface of a thermoplastic film or sheet. . However, the HLB value is an index of hydrophile-lipophile-balance.