JPS6117850B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to molded products and multilayer molded products that have excellent dew condensation prevention properties and gas permeation resistance. More specifically, on one side of an ethylene-vinyl alcohol copolymer resin layer containing 0.5-10% by weight of an alcohol plasticizer, an ethylene content of 25-60 mol%, and a degree of saponification of 90 mol% or more, an HLB value of 4- A molded article having excellent dew condensation prevention properties and gas permeation resistance obtained by coating a nonionic surfactant No. 15 at a rate of 0.01-0.5g/m ² (dry basis), and the nonionic surfactant The present invention relates to a multilayer molded product having excellent dew condensation prevention properties and gas permeation resistance, which is obtained by laminating resin layers coated with a nonionic surfactant so that the surface coated with a nonionic surfactant becomes the innermost surface. 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 the lack of effectiveness in displaying food products, there were other problems such as the water having a negative effect on the packaged foods and accelerating spoilage. 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 terms of anti-condensation properties, a horizontal layer film with an ordinary polyethylene film as an inner layer has the problem of condensation as mentioned above, and when polyethylene films are used for packaging of fruits and vegetables and films for cultivating agricultural crops, etc. Since the surface of the film is essentially hydrophobic, many water droplets adhere to the film surface due to evaporation of water from fruits and vegetables and condensation of moisture in the air due to changes in temperature and humidity, causing cloudiness, especially when packaging fruits and vegetables. In some cases, these water droplets can cause the product to stop decomposing, posing a major problem that shortens 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 Publications No. 34-6539, No. 38-4174, No. 53-
No. 1777, No. 53-6985, and JP-A No. 140549/1977
No. 51-91953, No. 52-104487, No. 53-
No. 9844, No. 53-31749, No. 53-77273, No. 53-
78272 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, making it extremely difficult to produce a film that can exhibit excellent dew condensation prevention properties under any conditions. It shows that something is true. 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. As a surfactant, it can be said that the more hydrophilic the surfactant, the more likely it is to impart properties, ie, anti-condensation properties. However, in the case of polyolefin resins, the compatibility with these hydrophilic surfactants is disadvantageous, so the retention of the surfactants in the resin is insufficient, resulting in insufficient initial and long-term condensation prevention properties. Hateful. In addition, in the case of polyolefin resins, when a surfactant is applied, the coating layer tends to peel off easily, and as water droplets adhere to it, these surfactants tend to be washed away along with the water, eventually reducing the dew condensation prevention effect. will be lost. In addition, when a surfactant is added to the polyolefin resin in order to increase its lasting effect, it tends to bloom easily due to poor compatibility.
Problems such as whitening and adhesion of the film arise. The present inventors developed an ethylene-vinyl acetate copolymer film with the aim of providing a film that has anti-condensation properties not only initially but also over a long period of time, has high moisture permeability, heat sealability, and gas permeation resistance. The copolymerization ratio of ethylene and vinyl acetate in the combined saponified product, the relationship between the degree of saponification and heat sealability, gas permeability, and dew condensation, and changes in moldability and physical properties due to the addition of surfactants, plasticizers, etc. As a result of various studies, we found that by applying a nonionic surfactant on one side of the ethylene-vinyl alcohol copolymer resin layer containing an alcohol-based plasticizer, we found that polyolefin-based dew condensation prevention films, etc. We have now achieved a film that has unattainable excellent dew condensation prevention properties, is beautiful and transparent, can repel moisture to the outside world, and has excellent gas permeability and heat sealability. That is, the molded product and multilayer molded product of the present invention have a specific ethylene-vinyl alcohol copolymer resin layer containing a specific amount of alcohol plasticizer, a specific ethylene content, and a specific degree of saponification.
It is a molded product made by coating a specific amount of a nonionic surfactant with an HLB value, and the resin layers are stacked so that the surface coated with the nonionic surfactant becomes the innermost surface. It is a multilayer molded product. Ethylene-vinyl alcohol copolymer resin layer (hereinafter referred to as "copolymer resin") used in the present invention
) needs to have an ethylene content of 25-60 mol % and a saponification degree of 90 mol % or more from the viewpoint of moldability and gas permeation resistance. If the ethylene content exceeds 60 mol %, gas permeation resistance is lost, and therefore it is not suitable for the purpose of the present invention. On the other hand, when the ethylene content is lower than 25 mol%, the number of vinyl alcohol units increases, resulting in a decrease in gas permeability under high humidity conditions and poor melt moldability even when a plasticizer is added. This is undesirable since the heat-sealability also deteriorates. Furthermore, if the degree of saponification of the copolymer resin is less than 90%, the film's water resistance, hot water resistance, gas permeability resistance, and so-called stiffness of the film are reduced, and an acetic acid odor is also produced, which is not preferable. Furthermore, examples of alcoholic plasticizers used in the present invention include glycerin, 1,2 propanediol, 1,2 butanetriol, 1,2,6 hexanetriol, 2,3 butanediol, diglycerin, 1,3 propanediol, 1 , 3-butanediol, 3-methylpentane, 1,3,5-triol, 1,4-butanediol, 2,5-hexanediol, diethanolamine, triethanolamine, 1,5-pentanediol, diethylene glycol, and the like can be used. The above-mentioned alcohol-based plasticizer is used as an internal addition to the copolymer resin, but specifically, for example, it is added and mixed to the copolymer resin pellet before molding, and then added internally after molding. be able to. The amount of alcoholic plasticizer used is 0.5-10% by weight, preferably 1-5% by weight based on the copolymer resin. If it is less than 0.5% by weight, the dew condensation prevention effect including the moisture permeability effect described below will not be sufficient, and if it exceeds 10% by weight, the plasticizer will ooze out, and for example, in films, slippage may occur after film formation. The quality of the film deteriorates and the film becomes wrinkled. As a nonionic surfactant, HLB value is 4-
15, preferably with an HLB value of 7-12. If the HLB value is less than 4, water will not spread sufficiently on the film surface, and if the HLB value is more than 15, it will be undesirable because it will easily dissolve in water and the dew condensation prevention will 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. In the present invention, the nonionic surfactant is used in the form of being coated on the copolymer resin layer containing the alcohol-based plasticizer, so it is a material with particularly good thermal stability, such as when it is internally added and thermoformed. There is no need to select , and in this respect it can be said to be very advantageous compared to internal attachment. When applying a nonionic surfactant, there is no problem in using a solvent such as ethanol, and the amount applied is 0.01-0.5g on a dry basis for the copolymer resin layer containing an alcohol-based plasticizer. It is recommended to apply / ^m2 . If the coating amount is less than 0.01 g/m ² , the effect on preventing dew condensation will not be sufficient, and if it exceeds 0.5 g/m ² , problems will arise with dirt on the surface of the film and slip resistance. In the present invention, in addition to anti-condensation properties, moisture permeability can be adjusted by introducing an alcohol-based plasticizer, and by varying the addition rate of alcohol-based plasticizer, films with various moisture permeability can be manufactured. This is because conventional copolymer resins could not be used as the innermost layer of laminates due to insufficient heat sealability. In contrast, it can be used as the innermost layer, and it can be said to have a major advantage in that it can also provide moisture permeability. Incidentally, the molded article in the present invention includes a container and the like in addition to a film. 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. When the molded product according to (1) of the present invention is used as the innermost layer of a multilayer molded product so that the surface coated with the nonionic surfactant becomes the innermost surface, the other outer layer resin is the multilayer molded product. Various materials can be used depending on the application, but when it is necessary to exclude moisture, nylon, cellophane, moisture-proof cellophane, etc. are useful, and when there is no need to exclude moisture, polypropylene, polyethylene, ethylene-acetic acid, etc. Polyolefins such as vinyl copolymers, stretched polyester, etc. are used as the outer layer resin.
Other resins such as vinyl chloride and polystyrene may also be used as the outer layer resin depending on the purpose. The molded product according to the present invention generally has a significantly higher transparency when compared to conventional polyethylene film, whether it is used as a single film for packaging or as a laminated film with the innermost layer. Shows good performance. In other words, in the case of polyethylene film, approximately 10% of the
The copolymer resin film of the present invention exhibits a haze degree of about 1-2% at a thickness of 30 μm, and as a single film and a laminated film, conventional polyethylene films It brings about a transparent and beautiful packaging effect that has never been available before. As described above, the copolymer resin molded product of the present invention, for example, a film, has a dew condensation prevention function that is useful both as a single film and as a laminated film, and solves problems that could not be achieved with conventional technology. It can be said that this is a new type of film that has succeeded in achieving this goal. Furthermore, various additives such as antioxidants, lubricants, antiblocking agents, etc. may be introduced into the molded product of the present invention, as necessary, to the extent that the effects of the present invention are not adversely affected. In addition, the multilayer molded product of the present invention is not limited to films, but also includes containers and the like, and for molding thereof, conventional methods such as lamination, extrusion lamination, simultaneous melt coextrusion molding, etc. can be used. , it can be used in multiple layers of two or more layers. Further, if necessary, a blend layer of various polymers in addition to the resins mentioned above as the outer layer resin may be adopted for the outer layer, and the outer layer may be provided via an adhesive layer using an adhesive. Further, among the multilayer molded products of the present invention, the film can be used not only for food packaging but also as agricultural sheets. For example, when the ethylene-vinyl alcohol copolymer resin film of the present invention is used as a film for cultivating agricultural crops, it may swell and elongate due to water, causing a change in form. However, by laminating a polyolefin film or the like on the outside of the copolymer resin film, it is possible to prevent the ethylene-vinyl alcohol copolymer resin film from changing its shape. Further, in this case, the dew condensation prevention properties of the ethylene-vinyl alcohol copolymer resin film are not hindered by the lamination. Furthermore, the effect of water on the other side of the film for lamination,
It is desirable to select an appropriate material by taking into consideration the strength, moisture permeability, etc. of the film. Hereinafter, the present invention will be explained in more detail with reference to Examples. Incidentally, the degree of haze, which indicates transparency, and the charging property were measured by the following method. How to measure haze degree Instrument: Integrating sphere HTR meter, Model name: SEP-H, Manufacturer: Japan Precision Optical Co., Ltd., Standard: JIS KOIOI Transmitted light passing through the sample is scattered forward by 2.5 degrees or more It is expressed as a percentage of the total transmittance of light that deviates from the incident light. The smaller the number, the better the transparency. Measuring method of electrostatic property Equipment: Honest meter, manufacturer: Shishido Shokai, measurement conditions: Discharge electrode distance 20 mm, receiving electrode distance
15mm, applied voltage 10Kv Measurement is performed by applying a voltage of 10Kv to a 3cm x 4cm film using an honest meter, charging the film, measuring the time (half-life; t1/2) until the amount of charge is reduced to half, and determining the charge. We conducted a sex evaluation. If the half-life is 30 seconds or less, the antistatic effect is excellent, and the smaller the number, the better the antistatic effect. Example 1 Ethylene content 44 mol%, degree of saponification 99.5 mol%, melting index at 190°C with a load of 2160 g is 5.5
2 g/10 minutes of glycerin to the ethylene-vinyl alcohol copolymer resin.
Pellets were prepared by melt-mixing at 220° C. using a 60 mmφ extruder at a ratio of % by weight. This glycerin-containing pellet was melt-extruded through a T-die using a 115 mmφ extruder to produce a film with a thickness of 20 μm. A 1% by weight ethanol solution of sucrose fatty acid ester with an HLB value of 11 was coated on one side of this film using a 150-mesh gravure roll and dried in a dryer at 60°C, resulting in a dry coating amount of 0.07 g/m2. ²
It was hot. First, about the various performances of this film.
Shown in the table.

[Table] Comparative Example 1 The ethylene-vinyl alcohol copolymer resin used in Example 1 was melt-extruded with a T die using a 115 mmφ extruder without adding the alcohol plasticizer shown in the present invention to form a film with a thickness of 20 μm. Created. Table 1 shows the performance of this film without coating with a nonionic surfactant. Comparative Example 2 HLB instead of the surfactant shown in Example 1
Table 1 shows the performance of the glycerin-containing ethylene-vinyl alcohol copolymer coated with 0.07 g/m ² of polyoxyethylene nonyl phenyl ether having a value of 18. Comparative Example 3 Table 1 shows the performance of the ethylene-vinyl alcohol copolymer film containing 2% by weight of glycerin prepared in Example 1 when no nonionic surfactant was applied. Comparative Example 4 Using the coating liquid used in Example 1, a dry coating amount of 0.07 g/m ² was applied to one side of a 50μ thick low-density polyethylene film in the same manner as in Example 1.
The sugar fatty acid ester was applied so that
Table 1 shows various performances of this film. Comparative Example 5 Table 1 shows the performance of a 50μ thick low density polyethylene film. In Table 1, it can be seen that in Example 1, no clouding occurred at all in both the dew condensation test using hot water and the test of leaving it in the refrigerator, indicating that it had excellent dew condensation prevention properties. In addition, in Example 1, the moisture permeability was increased and the heat sealability was also improved compared to the ethylene-vinyl alcohol copolymer film (Comparative Example 1) which had no additives and was not coated with a surfactant. Furthermore, there is almost no difference in gas permeation resistance between the two, indicating good gas permeation resistance. Comparative Example 3 is an example in which a plasticizer is added and no surfactant is applied to the surface, but in this case, almost no effect of the plasticizer on the anti-condensation property is observed. Comparative Example 4 shows a case in which a surfactant was applied to a low-density polyethylene film, but the major difference from the present invention is that the same nonionic surfactant was used, as is clear from the results of the durability test and the refrigerator storage test. It can be seen that even when the same amount of the film is applied, there is a large difference in performance, indicating that the film of the present invention has extremely excellent performance. Example 2 A two-layer composite film was obtained by dry laminating moisture-proof cellophane with a thickness of 20μ on the opposite side to the nonionic surfactant coated side of the film produced in Example 1, and using this composite film. We conducted a bag making test using a three-sided seal. When the ethylene-vinyl alcohol copolymer resin layer was used as a heat-sealing layer (inner layer) in a 20cm x 10cm bag, 50
Bags could be made without any problems at the processing speed of bags/minute. Approximately 100 g of wiener sausage with water droplets on the surface was placed in this bag, and after purging with nitrogen gas, it was left in a refrigerator at 5° C. for 3 weeks.
During this time, it became clear that the dew condensation inside the bag showed a completely beautiful packaging effect. The amount of water evaporated from inside the bag during the past three weeks is
3.3g, and the concentration of nitrogen gas inside after 3 weeks remained the same as at the start of the 99.5% cm ² test. Comparative Example 6 Wiener sausages were placed in a two-layered bag with an outer layer of biaxially oriented polypropylene with a thickness of 20μ and an inner layer of low-density polyethylene with a thickness of 50μ in the same manner as in Example 2, and then replaced with nitrogen and placed in a refrigerator. I left it there. Water droplets started forming immediately after the bag was placed in the refrigerator, and while the bag was left for three weeks, minute water droplets adhered to the entire inner surface of the bag, making it difficult to see the Vienna sausage inside. The amount of water evaporated from inside the bag during the past three weeks is
0.2g, and the nitrogen gas concentration inside the bag after 3 weeks was 79.5%, indicating that the gas had been almost completely replaced with the atmosphere, indicating that oxygen had entered the packaging bag. . Example 3 Ethylene content 32 mol%, degree of saponification 98.5 mol%, melting index at 190°C with a load of 2160 g is 1.7
3-methylpentane-1,3,5-triol was melt-mixed with the copolymer resin at a ratio of 4% by weight at 220°C using a 60mmφ extruder. Pellets were made. Thereafter, the plasticizer-containing ethylene-vinyl alcohol copolymer resin was melt-extruded using a T-die using a 60 mmφ extruder to obtain a film with a thickness of 20 μm. Next, stearic acid monoglyceride with an HLB value of 5.0 and polyoxyethylene nonyl phenyl ether with an HLB value of 12.4 were added in a weight ratio of 95:5.
A 1% by weight ethanol solution of this mixture was applied to one side of the film using a coater equipped with a 150-mesh gravure roll. The coating amount after drying in a 60°C dryer was 0.04 g/m ² . Table 2 shows various performances of this film.

[Table] Comparative Example 7 The surfactant used in Example 3 was applied to a 50μ thick low-density polyethylene film using the same method as in Example 1, and the dry coating amount of the surfactant was 0.04.
It was coated so that it was applied at a concentration of g/m ² . Table 2 shows various performances of this film. As shown in Table 2, even when the same amount of the same surfactant is applied, the ethylene
It shows better performance when applied to a vinyl alcohol copolymer film. Example 4-6, Comparative Examples 8 and 9 Ethylene content 50 mol%, saponification degree 98 mol%,
The melting index at 190℃ and a load of 2160g is 20g/
Pellets were prepared by melt-mixing diethylene glycol with an ethylene-vinyl alcohol copolymer resin at a ratio of 1% by weight based on the copolymer resin for 10 minutes. The pellets were melted and formed into a film using a T-die using a 90 mmφ extruder to produce a film with a thickness of 20 μm. This film was coated with an ethanol solution of polyoxyethylene glycerin monooleate having an HLB value of 13 in the same manner as in Example 1 to obtain films with different dry coating weights. The performance of these films is shown in Table 3.

[Table] As is clear from Table 3, if the amount of nonionic surfactant applied is less than 0.01 g/m ² on a dry basis, the dew condensation prevention effect will not be sufficient, and if it is more than 0.5 g/m ² In some cases, dirt may appear on the film exterior,
In addition, the slip property becomes worse. Application amount is 0.01−0.5
When the amount is within the range of g/m ² , a film with good anti-condensation properties and good appearance can be obtained as shown in Example 4-6.

Claims (1)

[Claims] 1. Ethylene content 25-60 mol%, including 0.5-10% alcohol plasticizer, saponification degree 90 mol%
Condensation prevention is achieved by coating a nonionic surfactant with an HLB value of 4-15 on one side of the above ethylene-vinyl alcohol copolymer resin layer at a rate of 0.01-0.5 g/m ² (dry basis). Molded product with excellent durability and gas permeability. 2 Ethylene content 25-60 mol%, saponification degree 90 mol%, including alcohol plasticizer 0.5-10% by weight
A resin layer formed by coating a nonionic surfactant with an HLB value of 4-15 at a rate of 0.01-0.5 g/m ² (dry basis) on one side of the above ethylene-vinyl alcohol copolymer resin layer. A multilayer molded product having excellent dew condensation prevention properties and gas permeation resistance, which is obtained by laminating the above nonionic surfactant-coated surfaces such that the innermost surface thereof is the surface coated with the nonionic surfactant.