JPH0156671B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a laminated plastic web, and more particularly, to a laminated plastic web for producing plastic containers that have a combination of ultraviolet ray barrier properties and gas barrier properties and are capable of preserving foods for long periods of time. Regarding the web. Plastic containers are obtained by melt-extruding thermoplastics such as polyolefin into plate shapes and forming them using plug-assisted air pressure forming.
Because they are lighter than glass containers and have superior impact resistance, they have come to be used in various fields instead of glass containers. Although general-purpose plastics such as polyolefins have excellent moisture resistance and hygienic properties, they have a relatively high oxygen permeability coefficient, and oxygen permeation through the container wall occurs at a non-negligible level, so it is difficult to store food over a long period of time. It is unsuitable for the field of containers for preservation purposes and containers for cosmetics and the like that require fragrance retention. In order to improve this drawback, plastic containers have already been developed whose walls are made of resins with excellent oxygen barrier properties. Currently, the resin with the best oxygen barrier properties among melt-extrudable thermoplastic resins is saponified ethylene-vinyl acetate copolymer (ethylene-vinyl alcohol copolymer), but this saponified copolymer However, they have poor moisture resistance, that is, water vapor barrier properties, and their oxygen permeability coefficients tend to increase significantly as humidity increases.Thus, when used in actual plastic containers, it is necessary to layer them in a sandwich-like manner with moisture-resistant resins such as polyolefins. They are combined to form a multilayer laminated web, which is then molded into containers and the like. Another problem with plastic containers is that the aforementioned polyolefins, ethylene-vinyl alcohol copolymers, etc. have extremely high transmittance to ultraviolet rays. Even when molded from a web,
This means that ultraviolet rays can pass through it to a large extent. For this reason, when the above-mentioned plastic web is used in food containers, although it may be somewhat satisfactory for the purpose of preventing the contents of the food from going rancid, the ultraviolet rays that pass through the container walls may damage pigments, oils, and fats. There is a problem in that food products such as animal proteins, various beverage extracts, etc. are deteriorated and the flavor, appearance, and hygienic characteristics of the food contents are impaired. Conventionally, as a means of blocking ultraviolet rays in plastic containers, it has been known to incorporate an ultraviolet absorber into the resin constituting the plastic container.
There are problems with the hygienic properties of the container, and its ultraviolet blocking effect is still not fully satisfactory. In addition, these plastic containers are inferior to glass containers in terms of transparency and see-through properties, and in particular, the polyolefin resin layer in plastic containers gives a cloudy appearance when the transparent contents are seen through.
There is a problem in that when colored contents are viewed through, they appear dark and muddy (for example,
52-116387). Furthermore, the polyolefin resin used as the inner layer of this plastic container has the ability to adsorb various low-molecular substances, such as dyes, fragrances, vitamins, and beverage extracts from the contents. There is a problem in that the flavor of the container is deteriorated or, conversely, that odor components or monomer components adsorbed during the manufacture of the container are released into the contents, impairing the flavor of the contents. Therefore, an object of the present invention is to provide a laminated plastic web having a combination of barrier properties against ultraviolet rays and gas barrier properties, and in particular to produce plastic containers capable of storing food products for a long period of time without deterioration. To provide laminated plastic web for. Another object of the present invention is to provide a laminated plastic web which, in addition to the above properties, has improved transparency properties. Still another object of the present invention is to provide a laminated plastic web which, in addition to the above properties, prevents polyolefin adsorption. According to the present invention, a laminated plastic substrate comprising a melt-formable moisture-resistant thermoplastic resin layer and a layer mainly composed of an ethylene-vinyl alcohol copolymer is provided with a layer adjacent to the moisture-resistant thermoplastic resin layer. , 99-70% by weight vinylidene chloride, 1-30
% by weight of at least one acrylic or methacrylic monomer and at least one other ethylenically unsaturated monomer in an amount of 0 to 100 parts by weight based on 100 parts by weight of the total amount of the monomers. The oxygen permeability coefficient at 20℃ and 100% RH is 9×10 ^-14 cc・cm/cm ²・sec・cmHg or less and the water vapor permeability coefficient (JIS Z-0208) is 3×
A laminated plastic web is provided, characterized in that it is provided with a coating layer mainly composed of a copolymer having a weight of 10 ^-3 g·cm/m ² ·day or less. In FIGS. 1-A to 1-C showing examples of the layer structure of the laminated plastic web of the present invention, the laminated web of the present invention has layers 1 and 2 of melt-formable moisture-resistant thermoplastic resin and ethylene-vinyl resin. A substrate 4 consisting of a layer 3 mainly composed of an alcohol copolymer, and a vinylidene chloride-acrylic (methacrylic) copolymer (hereinafter also referred to as polyvinylidene chloride resin) applied to at least one surface of the substrate 4. be)
It consists of coating layers 5, 5'. In these preferred embodiments, the laminated substrate 4 includes two moisture-resistant thermoplastic resin layers 1 with a layer 3 mainly composed of ethylene-vinyl alcohol copolymer sandwiched therebetween.
and 2, and coating layers 5 and 5' of vinylidene chloride-acrylic (methacrylic) copolymer are provided on both surfaces of this laminated substrate 7. An important feature of the present invention is that the vinylidene chloride-acrylic (methacrylic) copolymer detailed below is
In addition to exhibiting excellent adhesion to plastic substrates with a laminated structure, this new finding shows that the ultraviolet blocking properties of the entire web can be significantly improved by simply providing a coating layer of the copolymer layer on the plastic substrate. It is based on The fact that the plastic web of the present invention has excellent UV blocking properties is readily apparent by reference to FIG. That is, curve A in FIG.
shows the relationship between wavelength and transmittance for a plastic substrate 4, namely a plastic web consisting only of polyolefin (low density polyethylene)/ethylene-vinyl alcohol copolymer system mixture/polyolefin (low density polyethylene). According to this curve A, it can be seen that the plastic web exhibits a considerably high transmittance for ultraviolet light having a wavelength of 210 to 400 mμ, similar to visible light. On the other hand, curve B is a wavelength-transmittance curve for the plastic substrate 4 coated with a 30μ thick coating of vinylidene chloride-acrylic (methacrylic) copolymer. It can be seen that ultraviolet blocking properties can be obtained by simply providing a coating with a thickness of only 30μ. The plastic web of the present invention also has the unexpected advantage of permanently providing this UV protection. That is, curves C and D in FIG. 2 are wavelength-transmittance curves of the plastic substrate of curve B exposed to ultraviolet light for 25 hours at 60°C and 50 hours at 60°C using a weatherometer, respectively. . According to these curves C and D, in the plastic web of the present invention, the more it is irradiated with ultraviolet rays, the more the transmittance of ultraviolet rays is suppressed to a lower level and the absorption wavelength shifts to the longer wavelength side. It is clear that you are doing so. Thus, the more the plastic web according to the invention is irradiated with UV rays, the more it acts to prevent the transmission of UV rays, and even when exposed to UV rays for a long time, the overall UV ray transmission decreases. This makes it possible to suppress the amount to a significantly low level. The reason for this is that as UV irradiation increases,
This is thought to be because conjugated diene bonds are formed in the vinylidene chloride-acrylic (methacrylic) copolymer layer, and these conjugated diene bonds act to absorb more ultraviolet rays. In the present invention, this ultraviolet blocking effect is achieved while actually improving oxygen barrier properties, moisture resistance, and humidity dependence of oxygen barrier properties.
This is a significant advantage. When containing an ultraviolet absorber or the like in the resin in an amount that provides the same ultraviolet blocking effect as in the present invention, by mixing the ultraviolet absorber,
Naturally, the gas barrier properties of the resin layer deteriorate. On the other hand, the vinylidene chloride-acrylic (methacrylic) copolymer used in the present invention has a remarkable combination of oxygen barrier properties and moisture resistance, and is said to have extremely low humidity dependence of oxygen barrier properties. It has characteristics. That is, this copolymer is heated at 20℃,
Oxygen permeability coefficient at 100%RH is 9×10 ^-14 cc・
cm/cm ²・sec・cmHg or less, and the water vapor permeability coefficient (JIS Z-0208) is 3×10 ⁻³ g・cm/m ²・day or less. Furthermore, this vinylidene chloride-acrylic (methacrylic) copolymer is provided so as to cover the multilayer plastic substrate serving as the base so as to overlap in the gas permeation direction. Thus, according to the present invention, the above-mentioned gas barrier properties can be further improved due to this lamination effect. In addition to the features described above, the plastic web of the present invention provides several additional advantages. That is, the coating solution of vinylidene chloride-acrylic (methacrylic) copolymer has the characteristics that it has excellent wettability and adhesion to the surface of the plastic substrate and forms a dense and smooth film on the substrate. ing. Thus, when a coating of the copolymer is provided on the outer surface of a substrate, for example, when this laminated web is formed into a container, when the contents are viewed through the container wall, the contents appear cloudy or darkened. The tendency is eliminated and the significant advantage of significantly improving the see-through properties or even transparency of the container is achieved. In addition, vinylidene chloride-acrylic (methacrylic) copolymer has significantly lower adsorption to the above-mentioned components than polyolefin resins, so when this copolymer is molded into a container, the inner surface of the container substrate When provided in such a manner, it is possible to prevent adsorption by polyolefin and the like and release of adsorbed components from polyolefin and the like, thereby significantly improving the flavor retention of the contents. The copolymer used as the coating layer in the present invention is 99%
Contains as an essential component at least one of vinylidene chloride in an amount of 70% to 70% by weight, particularly 96% to 80% by weight, and 1 to 30% by weight, particularly 4 to 20% by weight of an acrylic or methacrylic monomer, and optionally the above. It optionally contains up to 100 parts by weight of other ethylenically unsaturated monomers per 100 parts by weight of the total amount of monomers. As the above-mentioned acrylic or methacrylic monomer, acrylic acid, methacrylic acid or derivatives thereof are used, and preferred examples include the following formula: In the formula, R ₁ represents a hydrogen atom, a halogen atom, or a methyl group, and X represents a nitrile group (-C≡N) or a (In the formula, Y is an amino group, a hydroxyl group, an alkyloxy group, a cycloalkyloxy group, an aminoalkyloxy group, a hydroxyalkyloxy group, an alkoxyalkyloxy group, a haloalkyloxy group, a glycidyloxy group, an aryloxy group, an aralkyloxy group) is a group represented by ), especially acrylic acid, acrylonitrile,
Acrylamide, methyl acrylate, ethyl acrylate, methyl α-chloroacrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, cyclohexyl acrylate, glycidyl acrylate, -2 acrylate
-Hydroxyethyl, acrylic acid monoglyceride, phenyl acrylate, methacrylic acid, methacrylonitrile, methacrylamide, methyl methacrylate, amyl methacrylate, glycidyl methacrylate, methacrylic acid monoglyceride, 2-hydroxypropyl methacrylate, beta methacrylate
-methoxyethyl, β-aminoethyl methacrylate, and γ-N,N-diethylaminopropyl methacrylate. These acrylic or methacrylic monomers can be used alone or in combination of two or more. Particularly suitable acrylic or methacrylic monomers for the purpose of the present invention include (i) nitrile monomers such as acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile, (ii) methyl acrylate, ethyl acrylate, Methyl methacrylate, methacrylic acid-2
- Ester monomers such as hydroxyethyl, glycidyl acrylate, glycidyl methacrylate, acrylic acid monoglyceride, methacrylic acid monoglyceride, methoxyethyl acrylate, methoxyethyl methyl methacrylate, and (iii) the above (i) and (ii)
It is a combination monomer of Ethylenically unsaturated monomers other than vinylidene chloride and acrylic or methacrylic monomers include:
Vinyl aromatic monomers such as styrene and vinyltoluene; vinyl esters such as vinyl acetate and vinyl propionate; diolefins such as butadiene and isoprene; methyl vinyl ether, glycidyl allyl ether, vinyl chloride, ethylene trichloride,
Ethylene tetrachloride, vinyl fluoride, vinylidene fluoride, ethylene trifluoride, ethylene tetrafluoride, maleic anhydride, fumaric acid, vinyl succinimide,
Examples include vinylpyrrolidone, and these monomers may be used alone or in combination of two or more. Examples of suitable copolymers include, but are not limited to: Vinylidene chloride/acrylonitrile copolymer, vinylidene chloride/acrylonitrile/methacrylonitrile copolymer, vinylidene chloride/methacrylonitrile copolymer, vinylidene chloride/acrylonitrile/glycidyl acrylate copolymer, vinylidene chloride/acrylonitrile/glycidyl methacrylate Copolymer, vinylidene chloride/acrylonitrile/monoglyceride acrylate copolymer, vinylidene chloride/ethyl acrylate/glycidyl acrylate copolymer, vinylidene chloride/methyl methacrylate/styrene copolymer, vinylidene chloride/acrylonitrile/styrene copolymer combination, vinylidene chloride/acrylonitrile/ethylene trichloride copolymer, vinylidene chloride/acrylonitrile/vinyl chloride copolymer, vinylidene chloride/acrylonitrile/methacrylic acid monoglyceride/ethylene trichloride copolymer, vinylidene chloride/methoxyethyl methyl methacrylate/ Methyl methacrylate/ethylene trichloride copolymer. In the copolymer used in the present invention, it is important to have 70% by weight or more of vinylidene chloride units in terms of UV blocking properties and gas barrier properties; In order to be able to coat plastic substrates without causing damage, it is important to contain at least 1% by weight of acrylic monomer or methacrylic monomer. Additionally, to improve adhesion to various plastic substrates, the formula In the formula, each of R ₂ and R ₃ is a hydroxyl group, and these two hydroxyl groups may be dehydrated to form an oxirane ring in an amount of 0.5 to 15% by weight based on the total monomers. It is desirable to use it in Furthermore, for the purpose of further improving the coating performance on plastic substrates, up to 100 parts by weight of other ethylenically unsaturated monomers may be added per 100 parts by weight of the total amount of vinylidene chloride and acrylic or methacrylic monomers. is allowed to contain. The copolymer used in the present invention is generally prepared by emulsifying or suspending the constituent monomers in an aqueous medium by the action of an emulsifier and a dispersant, and then carrying out emulsion polymerization or suspension polymerization in the presence of a radical initiator. can be easily obtained by As the radical initiator, peroxides, azo compounds, or redox catalysts, which are known per se, are used. The copolymer used in the present invention generally has a molecular weight sufficient to form a film. The polymer used in the present invention is generally difficult to mold by hot melting, and is used in the form of an organic solvent solution or in the form of an aqueous emulsion or latex to coat a plastic substrate by the method described below. The plastic substrate 4 used in the present invention has a multilayer structure consisting of a moisture-resistant thermoplastic resin layer that can be melt-molded and a layer mainly composed of an ethylene-vinyl alcohol copolymer, and also has gas barrier properties when molded into a container. , which is extremely important in terms of storage stability. Moisture-resistant thermoplastic resins include thermoplastic resins with a water vapor permeability coefficient of 5×10 ^-1 g・cm/m ²・day (JIS Z-0208) or less, especially low-, medium-, or high-density polyethylene, polypropylene. , ethylene-propylene copolymer, ethylene-butene copolymer,
Ionomer, ethylene-vinyl acetate copolymer,
Olefin polymers such as ethylene-acrylic acid ester copolymers; polyethylene terephthalate,
Polyesters such as polybutylene terephthalate, polyethylene terephthalate/isophthalate;
Polyamides such as nylon 6, nylon 6,6, and nylon 6,10; styrene copolymers such as polystyrene, styrene-butadiene block copolymer, styrene-acrylonitrile copolymer, and styrene-butadiene-acrylonitrile copolymer (ABS resin) Polymers; vinyl chloride copolymers such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymers; acrylic copolymers such as polymethyl methacrylate and methyl methacrylate/ethyl acrylate copolymers; polycarbonates, and the like. These thermoplastic resins may be used alone or in the form of a blend of two or more. The effects of the present invention are remarkable when an olefin polymer such as polyethylene or polypropylene is used as the moisture-resistant thermoplastic resin. As the ethylene-vinyl alcohol copolymer, a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 80 mol%, especially 25 to 60 mol%, and a saponification degree of 90% or more, especially 95% or more, is used. Preferably used. Instead of using this ethylene-vinyl alcohol copolymer alone, other resins such as olefin resins and polyamides may be used within a range that does not impair gas barrier properties, that is, within a range that does not exceed 50% by weight of the total. etc. can be used by blending them. If there is no adhesiveness between the moisture-resistant resin layer and the ethylene-vinyl alcohol copolymer layer, a known adhesive layer may be interposed between the two layers. Examples of such an adhesive layer include olefinic resins graft-modified with ethylenically unsaturated carboxylic acids such as acrylic acid, maleic acid, and maleic anhydride or their anhydrides. Alternatively, instead of interposing an adhesive between the two, at least one of the moisture-resistant resin layer or the ethylene-vinyl alcohol copolymer layer may contain a thermoplastic material, as disclosed in Japanese Patent Publication No. 11263/1983. A carbonyl group polymer may be included to improve the adhesion between the two. In the present invention, a latex or an organic solvent solution of the above-mentioned copolymer is applied to a multilayer film or sheet formed by laminating the above-mentioned plastic substrate by coextrusion molding, dry lamination, sandwich lamination, etc. Apply,
It is then dried to form a coating layer to form a laminated plastic web. As the aqueous latex of the copolymer, one having a solid content concentration of 20 to 65% and a viscosity of 3 to 500 centipoise is preferably used, while as an organic solvent solution, tetrahydrofuran, ethyl acetate, methyl ethyl ketone, cyclohexane are used. , dimethyl formamide, dimethyl sulfoxide,
Solid content concentration in organic solvent such as dioxane is 5 to 60
% solution is used. The above-mentioned latex or solution can be applied to a plastic substrate by dip coating, flow coating, spray coating, brush coating, roller coating, electrostatic coating, slush coating, centrifugal coating, or casting. Coating methods known per se can be used, such as coating methods, electrophoretic coating methods, and combinations thereof.
The application may be carried out in a single application or in a multi-stage application method of two or more stages.Furthermore, in order to improve the wetting properties of the plastic container substrate, the plastic container substrate may be pre-treated with a frame treatment or an anchoring agent, if necessary. , corona discharge treatment, surfactant coating treatment, chemical etching treatment, etc. may be performed, and conductive treatment etc. may be performed to impart electrical conductivity. Drying of the applied copolymer layer varies depending on the thickness of the coating film, but it is generally dried at a temperature of 40 to 150°C.
Drying for about 2 seconds to 60 minutes is sufficient. In addition, in the present invention, the gas and fragrance blocking effect is sufficiently exhibited by the above-mentioned drying alone; however,
If necessary, aging (heat treatment) at a temperature of 30° C. to 120° C. for 10 seconds to 7 days after drying will further enhance the effect. In the present invention, satisfactory results can be obtained if the vinylidene chloride copolymer is provided at a thickness of generally 0.5 to 50 μm, particularly 1 to 40 μm. The wall thickness of the plastic substrate 4 varies depending on the type of container etc. to be molded, but generally the wall thickness of the plastic substrate is 0.05 to 2.5 mm, particularly 0.1 to 1.5 mm.
It is preferable that the moisture-resistant resin layer and the ethylene-vinyl alcohol copolymer layer are in the range of 1: mm.
It is desirable to have a thickness ratio of 10 to 200:1, especially 1:2 to 150:1. The present invention is particularly useful for blocking ultraviolet light in plastic containers that require transparency. The laminated plastic web of the present invention can be formed into a container such as a cup or a bottle by applying a forming method known per se, such as drawing or stretch forming such as vacuum forming, pressure forming, plug assist forming, etc. can. In this case, by performing pressure molding, plug assist molding, etc. at a temperature at which the constituent resin layer can be stretched, it is possible to impart monoaxial or biaxial molecular orientation to the container wall. When the laminated plastic web of the present invention is molded into a container or the like, it is desirable to form the copolymer layer on both surfaces of the wall surface. On the other hand, for the purpose of blocking the release of gas and aroma from the contents or odor components from the plastic layer, the layer structure should have a copolymer layer only on the inner surface. You can also do it. The copolymer layer used in the present invention exhibits the excellent advantage of being resistant to these processes and of not losing its adhesion to the substrate. In the present invention, when forming the copolymer layer,
If desired, compounding agents known per se can be included in the copolymer. For example, reinforcing agents, fillers, plasticizers, heat stabilizers,
One or more of antioxidants, ultraviolet absorbers, thickeners, thinners, antiblocking agents, lubricants, leveling agents, colorants, etc. are added to the copolymer according to known formulations. Can be mixed. Of course, additives such as pigments, antioxidants, antistatic agents, ultraviolet absorbers, and lubricants may be added to at least one of the melt-moldable moisture-resistant thermoplastic resin and the ethylene-vinyl alcohol copolymer, as desired. One or more of these may be added in a total amount of 0.001 to 5.0 parts per 100 parts by weight of the resin. For example, glass fibers, aromatic polyamide fibers, carbon fibers,
One or more types of fiber reinforcing materials such as bulbs, cotton linters, etc., powder reinforcing materials such as carbon black and white carbon, or flaky reinforcing materials such as glass flakes and aluminum flakes are added to 100% of the thermoplastic resin by weight. It can be blended in a total amount of 2 to 150 parts by weight, and for the purpose of increasing the amount, heavy to soft calcium carbonate, mica, talc, kaolin, gypsum, clay, barium sulfate, alumina powder, silica powder, carbonic acid can be added. One or more types of magnesium etc. are added to the thermoplastic resin.
There is no problem even if the total amount is 5 to 150 parts by weight per 100 parts by weight according to a known recipe. The laminated plastic web of the present invention takes advantage of the above-mentioned advantages and is useful as a raw material for lightweight plastic containers for storing various foods, seasonings, beverages, pharmaceuticals, cosmetics, agricultural chemicals, etc. over long periods of time. The invention is illustrated by the following example. Here, in each example described later, the laminated plastic web of the present invention is molded into the shape of a container,
The following characteristic values were measured. Further, measurements of ultraviolet transmittance (UVT), oxygen permeability (Qo ₂ ), flavor test (FLR), and transparency characteristic (doc) described in each example were carried out according to the methods described below. (i) Ultraviolet transmittance (UVT): The body or bottom of the obtained container was cut into a predetermined size, and a recording spectrophotometer manufactured by Hitachi, Ltd. was used. As in the case of Figure 2, the wavelength is
Measurements were made over a wavelength range of 210 to 700 mμ.
The ultraviolet transmittance at 280 mμ (arrow in Figure 2) is expressed in UVT. (ii) Oxygen permeability (Qo ₂ ): After filling the empty container to be measured with 20 c.c. of water in advance, the container is replaced with nitrogen gas in a vacuum,
After sealing the mouth of the container with a rubber stopper and covering the contact surface between the mouth and the rubber stopper with epoxy adhesive, the container was placed in a constant temperature and humidity chamber at a temperature of 27°C and a humidity of 15% RH. After storage for a certain period of time, the concentration of oxygen permeated into the container was determined using a gas chromatograph, and the oxygen gas permeability (Qo ₂ ) was calculated according to the following formula. Results are average values of N=3. Qo ₂ = m x ct/100/t x Op x A [cc/m ²・day・atm] where m: Amount of nitrogen gas filled into the container [ml] t: Storage period in the hot tank [day], ct: oxygen concentration in the container after t days [Vol%], A: effective surface area of the container [m ² ], Op: oxygen gas partial pressure (=0.209) [atm]. (iii) Flavor test (FLR): Laminated containers with the polyvinylidene chloride resin applied to the inner or outer surfaces of the container, and laminated containers (container substrate) to which the polyvinylidene chloride resin was not applied for comparison. Two types of containers were filled with distilled water, the mouths of which were sealed, and then left at a temperature of 50°C for 3 days. Thereafter, a panel of 24 people tasted the distilled water and compared and judged the tasteless and less odor containers to be better. The numerical values in each table in Examples represent the number of panels judged to be good. (iv) Transparency characteristics (doc): 10 people (panel) for laminated containers coated with the above-mentioned polyvinylidene chloride resin on the outer or inner and outer surfaces of the container and uncoated containers (container substrate) for comparison. First, show the two types of empty containers (unfilled containers) to be compared.
Pairwise comparisons were made using a visual judgment method, and participants were asked to select the container with the better appearance, such as transparency and gloss. Next, in the two types of containers that were visually judged,
Filled with tap water in which 1% by weight of Congo Red, a type of dye, had been dissolved, each filled container was shown to the same panel of 10 people as before, and a paired comparison was performed using the same visual judgment method to determine the contents of the container. Participants were asked to select a container with good visibility (that is, a container with less cloudy or different color appearance of the contents). In such a two-step visual judgment method, one panel member gives one point to a designated container, and through pairwise comparison, it is determined that there is "no difference" in the appearance or perspective of the contents between the two types of containers. If it was, 0.5 points were given to both containers, and the total score for each of the two types of containers was calculated. The transparency characteristic (doc) was calculated using the following formula. doc=(B-A)+(C-D)/2N =(B-A)+(C-D)/2×10...(2) In the formula, N is the number of panel members (10 people in this case) represents. Furthermore, A, B, C, and D each mean the total score of each container shown in the following table (Table-REF.) (A+B=C+D=10 points).

[Table] In the above formula showing the degree of perspective characteristic (doc),
If the value of doc is a + (plus) sign, "Container-I" is more likely to be "Container-I" due to the filling of the contents.
The see-through properties of the contents are better than that of
This means that the effect is most significant when doc=+1.0. On the other hand, if the value of doc is - (minus) sign, it means that the see-through characteristics of the contents are poor, and if doc = 0, even if the contents are filled, two types of containers (Container-I, Container-I, This means that the see-through properties of the container and container-) remained unchanged. Example 1 Melt index (ASTM D-1238) was used as a moisture-resistant thermoplastic synthetic resin (1 and 2 in Figures 1-A to 1-C) that can be melt-extruded.
Outer layer of 0.3g/10min high density polyethylene resin,
A saponified ethylene-vinyl acetate copolymer (ethylene-vinyl acetate copolymer with an ethylene content of 30 mol% and a saponification degree of 99%) is made of maleic anhydride-modified high-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd.: H-31B) as an adhesive layer. A three-layer plastic web with an inner layer of vinyl alcohol copolymer (vinyl alcohol copolymer) has a diameter of 65 mm and an effective length of 1430 mm.
Extruder for high-density polyethylene with built-in metering screw of mm, diameter 40 mm, effective length
An extruder for ethylene vinyl alcohol copolymer equipped with a metering type screw of 800 mm, an extruder for adhesives having a built-in metering type screw with a diameter of 32 mm and an effective length of 704 mm, and 3 with a lip width of 520 mm. Obtained by a known coextrusion method using a flat die for layers (total thickness of the web: 0.8 mm, composition ratio: high density polyethylene layer: adhesive layer: ethylene vinyl alcohol copolymer layer =
5:0.5:1). Next, a polyvinylidene chloride resin latex (dispersion medium: water, solid content concentration: 30% by weight) having a composition ratio of 95% by weight of vinylidene chloride and 5% by weight of acrylonitrile is applied to the high-density polyethylene side of the obtained laminated web. %) by a known dip coating method, dried at 50℃ for 55 minutes using a Perfect Oven (explosion-proof type), and then aged (heat treated) at 90℃ for 3 minutes in an air thermostat. Konatsuta. Then, a laminated web having a layered structure as shown in FIG. 1-B was obtained. The film thickness of the polyvinylidene chloride resin coated on the high-density polyethylene side of the obtained laminated web was 1.5 μm. Then, a cylindrical laminated cup having an outer surface of the polyvinylidene chloride resin layer and an inner surface of the ethylene-vinyl alcohol copolymer layer was molded from the laminated web by a known plug-assisted vacuum-pressure forming method. . Hereinafter, this laminated cup will be referred to as A. The ultraviolet transmittance at a wavelength of 280 mμ (UVT ) and oxygen permeability (Qo ₂ ) measurement results are shown in Table 1. Table 2 shows the results of measuring the degree of perspective characteristic (doc).

【table】

[Table] Tables 1 and 2 show that by applying the polyvinylidene chloride resin to the laminated cup substrate, the barrier properties against ultraviolet rays (UVT) and oxygen (Qo ₂ ) are improved, and the transparency properties (doc) are also improved. It is known that this has been significantly improved. Example 2 As a moisture-resistant thermoplastic synthetic resin (1 and 2 in Figures 1-A to 1-C) that can be melt-extruded, the inner layer was made of attack polystyrene with a melt index of 3.2, and the ethylene content was A two-layer laminated web with an outer layer of saponified ethylene/vinyl acetate copolymer (ethylene/vinyl alcohol copolymer) with a saponification degree of 35 mol% and 96%.
The polystyrene was passed through an extruder with a diameter of 65 mm in Example 1, and the ethylene-vinyl alcohol copolymer was passed through an extruder with a diameter of 32 mm in Example 1 into a two-layer flat die with a lip width of 600 mm. was obtained by a known coextrusion method. (Total thickness of the web: 0.7 mm, composition ratio: polystyrene layer: ethylene/vinyl alcohol copolymer layer = 20:1). Next, on the polystyrene side of the obtained laminated web, 80% by weight of vinylidene chloride, 10% by weight of methyl acrylate, and 10% by weight of acrylic acid monoglyceride were added.
A polyvinylidene chloride resin latex (dispersion medium: water, solid content concentration: 22% by weight) having a composition ratio of 50 parts by weight of vinyl chloride to 100 parts by weight of the total amount of was applied by a known slush coating method. , and dried for 2 minutes at 80°C using a Perfect Oven.
Such coating and drying operations were repeated three times. Then, aging (heat treatment) was performed at 30°C for 7 days in an air constant temperature bath. And the first
A laminated web having a layer structure as shown in Figure -B was obtained. The film thickness of the polyvinylidene chloride resin applied to the polystyrene side of the obtained web is
It was 9.6μ. Then, a rectangular laminated cup having the outer surface of the ethylene/vinyl alcohol copolymer layer and the inner surface of the polyvinylidene chloride resin layer was molded from the laminated web by a known solid phase pressure forming method. Hereinafter, this laminated cup will be referred to as B. The ultraviolet transmittance at a wavelength of 350 mμ (UVT ), and the measurement results of oxygen permeability (Qo ₂ ) are shown in Table 3. In addition, Table 4 shows the results of flavor test (FLR) measurements.

【table】

[Table] Next, each cup of B and nB was filled with commercially available tomato puree just after opening, and the mouth was sealed with a laminated film containing aluminum foil. It was left at a location (1000 Lux) for 14 days. After that, the a value of each tomato puree filled in each pot was measured using a color difference meter, and the discoloration rate (= a value after standing / a value immediately after opening the can) was measured.
value) was calculated. The color change rate of the tomato puree filled in the B cup was 0.97, while the color change rate of the puree filled in the nB cup was 0.70. Furthermore, each of these tomato purees left to stand was tasted by the 24 panelists and they were asked to judge the flavor and taste. All 24 panelists answered that the tomato puree filled in the B cup had better flavor and taste.

[Brief explanation of drawings]

1-A to 1-C are enlarged sectional views showing examples of the layer structure of the laminated plastic web of the present invention, and FIG. It is a diagram showing the relationship between the ratio and the reference numerals are 1, 2... a moisture-resistant thermoplastic resin that can be melt-molded, 3... a layer mainly composed of an ethylene/vinyl alcohol copolymer, 4... a plastic substrate,
5, 5'... Indicates a vinylidene chloride/acrylic (methacrylic) copolymer coating layer, respectively.

Claims (1)

[Scope of Claims] 1. A laminated plastic substrate including a melt-moldable moisture-resistant thermoplastic resin layer and a layer mainly composed of an ethylene-vinyl alcohol copolymer, in a positional relationship adjacent to the moisture-resistant thermoplastic resin layer. and 99 to 70% by weight of vinylidene chloride, 1 to 30% by weight of at least one of acrylic or methacrylic monomers, and 0 to 0 to 100 parts by weight of the total amount of the monomers.
consisting essentially of 100 parts by weight of at least one other ethylenically unsaturated monomer;
Oxygen permeability coefficient at ℃ and 100%RH is 9×10 ^-14
A coating layer mainly made of a copolymer with a water vapor permeability coefficient (JIS Z-0208) of cc・cm/cm ²・sec・cmHg or less and a water vapor permeability coefficient (JIS Z-0208) of 3×10 ^-3 g・cm/m ²・day or less was provided. A laminated plastic web characterized by: 2. The web according to claim 1, wherein the moisture-resistant thermoplastic resin is an olefin resin. 3 The ethylene-vinyl alcohol copolymer has an ethylene content of 20 to 80 mol% and a saponification degree of
The web of claim 1 which is 90% or more ethylene-vinyl alcohol copolymer. 4. The web of claim 1, wherein the laminated plastic substrate comprises inner and outer surface layers of olefinic resin and an intermediate layer of ethylene-vinyl alcohol copolymer located between these layers. 5. The web of claim 1, wherein the coating layer has a thickness of 0.5 to 50 microns.