JPS6233947B2 - - Google Patents

Description

[Detailed description of the invention]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to plastic containers with improved oxygen barrier properties. The present invention particularly relates to ethylene-
When a layer mainly composed of vinyl alcohol copolymer and a coating layer of vinylidene chloride-acrylic (methacrylic) copolymer (hereinafter also referred to as polyvinylidene chloride resin) are provided in adjacent positions, the This is based on the new finding that an oxygen permeability coefficient lower than the oxygen permeability coefficient can be obtained. still,
The oxygen permeability coefficient is expressed in units of cc·cm/cm ² ·sec·cmHg, and is a coefficient independent of the thickness dimension. Plastic containers allow oxygen to permeate through the container walls to varying degrees, and when this permeation cannot be ignored, they are used in fields such as containers intended for long-term food storage and cosmetics that require fragrance retention. becomes inappropriate. For this reason, the development of plastic containers whose walls are made of resin with excellent oxygen barrier properties is being actively conducted. Currently, the resin with the best oxygen barrier properties among melt-extrudable thermoplastic resins is saponified ethylene-vinyl acetate copolymer (ethylene-vinyl acetate copolymer).
(vinyl alcohol copolymer), but this saponified copolymer has poor moisture resistance, i.e., water vapor barrier properties, and furthermore, its oxygen permeability coefficient tends to increase significantly with increasing humidity, thus making it difficult to use in practical plastics. When used in containers, this drawback is overcome by layering moisture-resistant resins such as polyolefins in a sandwich pattern to form a multilayer laminate. Another disadvantage of plastic containers whose walls are made of ethylene-vinyl alcohol copolymer is that they are highly transparent to ultraviolet rays. Although the purpose of preventing food from going rancid may be somewhat satisfied, the ultraviolet light transmitted through the container wall may alter the quality of pigments, fats and oils, animal proteins, various beverage extracts, etc., resulting in changes in the flavor and appearance of the food contents. , there is a problem of impairing hygienic properties. 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, but such a method has problems with the hygienic properties of the container, and Its ultraviolet blocking effect is still not fully satisfactory. When the present inventors provide a resin layer mainly composed of an ethylene-vinyl alcohol copolymer and a coating layer of a vinylidene chloride-acrylic (methacrylic) copolymer described in detail below in an adjacent position, this lamination It has been found that the plastic container exhibits a lower oxygen permeability coefficient than that of any of the layers, and that the plastic container with this laminated structure is also significantly superior in blocking ultraviolet rays. That is, an object of the present invention is to provide a plastic container that has better barrier properties against gases such as oxygen than conventional plastic containers. Another object of the present invention is to provide a plastic container which, in addition to the above-mentioned low oxygen permeability coefficient, also has UV blocking properties, and therefore allows the contents to be stored stably for a long period of time without deterioration. be. Still another object of the present invention is to provide a multilayer plastic container in which the moisture resistance of the ethylene-vinyl alcohol copolymer and the tendency for oxygen permeation to increase with increase in humidity are also improved. According to the present invention, at least one surface of the plastic container substrate is made of a resin mainly composed of an ethylene-vinyl alcohol copolymer, and the plastic container substrate has a surface adjacent to the resin surface mainly composed of the ethylene-vinyl alcohol copolymer. , (a) 99 to 70% by weight of vinylidene chloride, and (b) 1 to 30% by weight of the following formula: In the formula, R ₁ represents a hydrogen atom or a methyl group, and X represents a nitrile group or a formula, (In the formula, Y is an alkyloxy group, a hydroxyalkyloxy group, or a glycidyloxy group)
A group represented by at least one monomer represented by and (c) containing up to 50 parts by weight of chlorine other than vinylidene chloride per 100 parts by weight of the total amount of the monomers (a) and (b). A copolymer consisting of at least one ethylenically unsaturated monomer, which has an oxygen permeability coefficient of 9×10 ^-14 cc・cm/cm ²・sec・cmHg or less at 20°C and 100%RH and water vapor permeability. Coefficient (JIS Z-0208) is 3×10 ^-3 g・cm/
There is provided a plastic container with improved oxygen barrier properties, characterized in that it is provided with a coating layer of less than m ² ·day. In FIG. 1 showing a bottle-shaped coated plastic container, the bottle 1 has a circumferential wall portion 2 having a circular or elliptical cross section, a bottle mouth portion 3 integrally connected to the circumferential wall portion 2, and a bottom portion 4 continuous to the lower end of the circumferential wall portion. It consists of
The walls of these bottles are all 2-A to 2-D.
As shown in the enlarged sectional view of the figure, at least one surface 5 of the plastic container substrate 6 is made of a resin mainly composed of ethylene-vinyl alcohol copolymer.
and a coating layer 7 mainly composed of vinylidene chloride-acrylic (or methacrylic) copolymer provided in a positional relationship adjacent to the resin surface 5. As shown in Figure 2-A, the plastic container substrate 6 consists of a single layer of resin mainly composed of ethylene-vinyl alcohol copolymer, and as shown in Figure 2-B, both surfaces 5 and 5' are coated with chloride. Vinylidene
Acrylic (methacrylic) copolymer coating 7,7'
may be provided. Further, the plastic container substrate may be made of a laminate of a resin mainly composed of ethylene-vinyl alcohol copolymer and other resins. for example,
As shown in FIG. 2-C, this container substrate 6 includes a resin layer 5 mainly composed of ethylene-vinyl alcohol copolymer (hereinafter simply referred to as ethylene-vinyl alcohol copolymer) and other resins, especially A moisture-resistant thermoplastic resin layer 8 such as a polyolefin resin, and as shown in FIG. 2-C,
It can consist of an ethylene-vinyl alcohol copolymer layer 5 and a moisture-resistant thermoplastic resin layer 8. In any of these cases, the ethylene-vinyl alcohol copolymer layer 5 is coated adjacently thereto, that is, as both surface layers in FIG. 2-B, and as the innermost layer or the innermost layer in FIG. 2-C. As the outermost layer, a vinylidene chloride-acrylic (methacrylic) copolymer coating layer 7, 7' is provided. Furthermore, 2nd-D
In the figure, this container substrate 6 consists of both inner and outer layers 5, 5' of ethylene-vinyl alcohol copolymer and an intermediate layer 8 of thermoplastic resin. Vinylidene chloride-acrylic (methacrylic) copolymer coating layer 7, 7'
will be provided. An important feature of the present invention is that, as already mentioned above, when the ethylene-vinyl alcohol copolymer layer and the vinylidene chloride-acrylic (methacrylic) copolymer coating layer are provided adjacently, this laminate has the same thickness. This is based on the completely unexpected finding that, in comparison, the oxygen permeability is lower than that of either one of the layers. FIG. 3 shows the total thickness tCA, where _tEV is the thickness of the ethylene-vinyl alcohol copolymer layer and _tCA is the thickness of the vinylidene chloride-acrylic (methacrylic) copolymer layer in Example 1, which will be described _later. +t
The relationship between the ratio of t _CA /(t _CA +t _EV ) and the oxygen permeability at 37° C. and relative humidity of 0% to 15% RH is shown, assuming _{that EV} is constant at 15μ. Referring to this FIG. 3, it can be seen that the coated plastic container according to the invention exhibits a significantly lower oxygen permeability, as shown by dashed curve A, than curve B, which is the harmonic mean value of both resin layers, and yet completely Surprisingly, over a fairly wide range of ratios of t _CA /(t _CA + t _EV ), it exhibits an oxygen permeability that is rather smaller than that of the ethylene-vinyl alcohol copolymer, which has a lower oxygen permeability coefficient. I understand. Similarly, Figure 4 shows the ratio of t _CA /(t _CA + t _EV ) when t _CA + t _EV is 15μ, and the relative humidity at 27°C.
The relationship with oxygen permeability at 100%RH and 93%RH is shown. As already mentioned above, ethylene-vinyl alcohol copolymers exhibit relatively high oxygen permeability under conditions of high humidity; even in this case, the coated plastic containers according to the invention can be
As shown in A', the oxygen permeability is significantly lower than the harmonic average value B' of both resin layers, and t _CA /
It can be seen that within a certain range of the ratio of (t _CA +t _EV ), the oxygen permeability is lower at the same thickness than the vinylidene chloride-acrylic (methacrylic) copolymer, which has a smaller oxygen permeability coefficient. The results in Figures 3 and 4 show that the total thickness is 15μ.
Therefore, the oxygen permeability shown in these drawings can be considered to be the oxygen permeability coefficient itself, excluding the thickness factor. For example, according to page 287 of "Polymer and Moisture" published by Koshobo on September 1, 1971, the oxygen permeability of a laminate is generally calculated as the harmonic average value of the oxygen permeability of each layer (the 7.16 on page), the significant reduction in oxygen permeability in the coated plastic container of the present invention is not caused by the mere lamination effect of both resin layers, but is due to the physical and It will be understood that it is based on chemical interactions. According to the invention, it is thus possible to significantly reduce the oxygen permeability of the container wall, in particular by applying a thin coating of vinylidene chloride-acrylic (methacrylic) copolymer to the surface of the ethylene-vinyl alcohol copolymer. By providing this, it becomes possible to reduce the humidity dependence of oxygen permeability. In the present invention, both resin layers satisfy the following inequality: 0.95≧t _CA /(t _CA +t _EV )≧0.005, especially 0.75≧t _CA /(t _CA +t _EV )≧0.008, t _CA ≧0.5 μ, especially t _CA ≧1.0 It is desirable to provide it so that μ, is satisfied. In addition, the thickness (t _EV ) of the ethylene-vinyl alcohol copolymer layer varies depending on its ethylene content and degree of saponification, but generally, t _EV ≧3.0μ, especially t _EV ≧5.0. It is desirable to provide it so that μ, is satisfied. According to the present invention, excellent ultraviolet blocking properties can also be obtained by providing a vinylidene chloride-acrylic (methacrylic) copolymer coating layer on the ethylene-vinyl alcohol copolymer layer. The fact that the container wall of the present invention has excellent UV blocking properties is immediately apparent by reference to FIG. That is, curve A in FIG.
The relationship between wavelength and transmittance is shown for a container wall made only of vinyl alcohol copolymer. According to this curve A, it can be seen that the above-mentioned plastic container 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 a case in which a 30μ thick coating of vinylidene chloride-acrylic (methacrylic) copolymer is provided on the ethylene-vinyl alcohol copolymer layer of the plastic container substrate. Curve B shows that ultraviolet light blocking properties can be obtained by simply applying a coating of only 30 microns to the ethylene-vinyl alcohol copolymer layer of the plastic container substrate. The coated plastic containers of the present invention also have the unexpected advantage of providing permanent UV protection. That is, curves C and D in FIG. 5 represent the coated plastic container of curve B.
60℃, 25 hours and 60℃ with Weatherometer, respectively.
This is a wavelength-transmittance curve of a sample exposed to ultraviolet light for 50 hours. According to these curves C and D, in the coated plastic container of the present invention, the more it is irradiated with ultraviolet rays, the more its transmittance to ultraviolet rays is suppressed to a lower level, and the more it shifts to the absorption wavelength side. It is clear that there are. Thus, the more a coated plastic container according to the invention is irradiated with UV light, the more it acts to prevent the transmission of UV light, and even when subjected to prolonged UV exposure, the overall UV light is reduced. This makes it possible to suppress the amount of transmission to a significantly low level. The reason for this is thought to be that conjugated diene bonds are formed in the vinylidene chloride-acrylic (methacrylic) copolymer layer as the layer is irradiated with ultraviolet rays, and these conjugated diene bonds act to absorb more ultraviolet rays. The vinylidene chloride-acrylic (methacrylic) copolymer used as the coating layer in the present invention contains (a) 99 to 70% by weight, especially 96 to 80% by weight of vinylidene chloride, (b) 1 to 30% by weight, especially 4 to 80% by weight. 220% by weight of the following formula, In the formula, R ₁ represents a hydrogen atom or a methyl group, and X represents a nitrile group or a formula, (wherein, Y is an alkyloxy group, a hydroxyalkyloxy group, or a glycidyloxy group); at least one acrylic or methacrylic monomer represented by the following; and (c) an optional component. as the total amount of monomers (a) and (b) above.
A copolymer comprising up to 50 parts by weight per 100 parts of at least one chlorine-containing ethylenically unsaturated monomer other than vinylidene chloride, the copolymer having an oxygen permeability coefficient of 9 x 10 ^- at 20°C and 100% RH. ¹⁴ cc・cm／ ^cm2・sec・
cmHg or less and water vapor permeability coefficient (JIS Z-0208)
is 3×10 ^-3 g・cm/m ²・day or less. Specifically, the acrylic or methacrylic monomer (b) includes acrylic acid, acrylonitrile, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, and acrylic. Cyclohexyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, monoglyceride acrylate, methacrylic acid, methacrylonitrile, methyl methacrylate, amyl methacrylate, glycidyl methacrylate, monoglyceride methacrylate,
Examples include 2-hydroxypropyl methacrylate and β-methoxyethyl methacrylate. These acrylic or methacrylic monomers can be used alone or in combination of two or more. Acrylic or methacrylic monomers (b) particularly suitable for the purpose of the present invention include (i) nitrile monomers such as acrylonitrile and methacrylonitrile, (ii) methyl acrylate, ethyl acrylate, and methacrylic acid. methyl,
Ester monomers such as 2-hydroxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylic acid monoglyceride, methacrylic acid monoglyceride, methoxyethyl acrylate, methoxyethyl methyl methacrylate, and (iii) combinations of (i) and (ii) above. It is. Examples of the chlorine-containing ethylenically unsaturated monomer (c) as an optional component other than vinylidene chloride include vinyl chloride, ethylene trichloride, ethylene tetrachloride, etc. These monomers may be used singly or in combination. The above combinations can be used. 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/acrylonitrile/ethylene trichloride copolymer, vinylidene chloride/acrylonitrile/vinyl chloride copolymer Polymer, vinylidene chloride/acrylonitrile/monoglyceride methacrylate/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 containers 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 bottle substrates, formula In the formula, each of R ₂ and R ₃ is a hydroxyl group, where these two hydroxyl groups may be dehydrated to form an oxirane ring. The monomers are preferably used in an amount of 0.5 to 15% by weight based on total monomers. Furthermore, in order to further improve the coating performance on plastic bottles, 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 plastic containers by the method described below. Ethylene-vinyl alcohol copolymers forming plastic container substrates include ethylene-acetic acid with 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. Saponified vinyl copolymers are 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. The moisture-resistant thermoplastic resin used in combination with ethylene vinyl alcohol copolymer has a water vapor permeability coefficient of 5×10 ^-1 g・cm/m ²・day (JIS Z
-0208) The following thermoplastic resins, especially low-, medium-,
Or high-density polyethylene, polypropylene,
Olefin polymers such as ethylene-propylene copolymer, ethylene-butene copolymer, ionomer, ethylene-vinyl acetate copolymer, ethylene-acrylic ester copolymer; polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate/ Polyester such as isophthalate; Polyamide such as nylon 6, nylon 6,6, nylon 6,10; Polystyrene, styrene-butadiene block copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer (ABS resin) )
Styrenic copolymers such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymers; acrylic copolymers such as polymethyl methacrylate and methyl methacrylate-ethyl acrylate copolymers; polycarbonates etc.
These thermoplastic resins may be used alone or in the form of a blend of two or more. As the moisture-resistant thermoplastic resin, it is desirable to use polyolefins such as polyethylene and polypropylene from the viewpoints of economy and moldability. 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. This plastic bottle substrate can be manufactured by molding methods known per se, such as blow molding, biaxial stretch blow molding, injection molding, and the like. Bottles are formed by blow molding, in which a single thermoplastic resin or a combination of thermoplastic resins mentioned above is melt-extruded into a parison, the extruded parison is supported in a split mold, and a fluid is blown into the contents. Therefore, it is easily obtained. In addition, in order to improve the impact resistance and transparency of the bottle, a parison or preform is produced in advance by melt extrusion or injection molding, and the parison or preform is stretched at a stretching temperature below its melting point. It is also possible to make a plastic bottle which is mechanically stretched in the axial direction and also stretched in the circumferential direction by blowing fluid into it to form a biaxially molecularly blended plastic bottle. Furthermore, bottles can also be made by injection molding. The plastic container substrate used in the present invention can be in the form of a cup or jar. This cup or wide mouth bottle is made of a single layer film or sheet formed in advance by single extrusion, or a multilayer film or sheet formed by coextrusion molding, dry lamination, sandwich lamination, etc. is obtained by subjecting the sheet to drawing or stretch forming, which is known per se, such as vacuum forming, pressure forming, plug-assist forming, or the like. At this time, if the single-layer or multi-layer film or sheet is subjected to pressure molding, plug assist molding, etc. at a temperature that allows stretching of the constituent resin layers, uniaxial or biaxial molecular orientation can be imparted to the container wall. can. Furthermore, the plastic container substrate used in the present invention can also be an extrudable tube container. This tube container is, for example, published in JP-A-55-5311.
As described in the publication, a thin-walled single- or multi-layer plastic bottle with a threaded opening is manufactured by blow molding, the bottom of the bottle is cut off, and the tip of the body wall is heat-sealed. Manufactured by The texture of plastic container substrates can vary widely from relatively thin walls such as extruded tubes to relatively thick walls such as rigid containers. Generally, the wall thickness of the container substrate is between 0.05 and 2.5
mm, particularly preferably in the range of 0.1 to 1.5 mm, and in the case of multilayers, the ratio of the moisture-resistant resin layer and the ethylene-vinyl alcohol copolymer layer is 1:10 to 1:1.
It is desirable to have a thickness ratio of 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 coated plastic container according to the present invention is formed by applying an aqueous latex or organic solvent solution of the aforementioned copolymer to at least one surface of the plastic container substrate thus produced, and then drying the formed coating film. be done. At this time, it is desirable to apply the vinylidene chloride copolymer in the form of an aqueous latex. 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. To apply the above-mentioned latex or solution to the plastic container substrate, dip coating, spray coating, brush coating, roller coating, slush coating, flow coating, electrostatic coating, centrifugal coating, Coating methods known per se can be used, such as casting 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,
A pretreatment such as a chemical etching treatment may be performed, and a conductive treatment or the like may be performed to impart conductivity. Drying of the applied copolymer layer varies depending on the thickness of the coating film, but generally drying at a temperature of 40 to 150°C 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 30 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. An alternative method of manufacturing the plastic bottles of the invention includes a parison of thermoplastic resin from which the bottle is to be made;
A latex or organic solvent solution of the above-mentioned copolymer is applied to a preform, sheet, film, etc., and then dried to form a coating layer, and this coating structure is then molded by the above-mentioned method to form a coated plastic container. Manufacture. The copolymer coating layer used in the present invention can withstand these treatments, and
It exhibits the excellent advantage of not losing adhesion to the substrate. When forming the coating layer, the copolymer may contain, if desired, a compounding agent known per se. 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, the above-mentioned moisture-resistant thermoplastic resin may contain one or more additives such as pigments, antioxidants, antistatic agents, ultraviolet absorbers, and lubricants, if desired, per 100 parts by weight of the resin. It can also be added in an amount of 0.001 part to 5.0 parts. For example, in order to reinforce this bottle, fiber reinforcing materials such as glass fiber, aromatic polyamide fiber, carbon fiber, bulb, cotton linter, etc., powder reinforcing materials such as carbon black and white carbon, or glass flakes, One or more types of flaky reinforcing materials such as aluminum flakes can be blended in a total amount of 2 to 150 parts by weight per 100 parts by weight of the thermoplastic resin. calcium carbonate, mica,
Talc, kaolin, gypsum, clay, barium sulfate,
1 such as alumina powder, silica powder, magnesium carbonate, etc.
There is no problem in blending one or more types in a total amount of 5 to 150 parts by weight per 100 parts by weight of the thermoplastic resin according to a known formulation. The plastic container of the present invention takes advantage of the above-mentioned advantages and is useful as a lightweight plastic container for storing various foods, seasonings, beverages, medicines, cosmetics, agricultural chemicals, etc. over a long period of time. The invention is illustrated by the following example. The oxygen permeability (Q _O2 -D and Q _O2 -W) and wavelength under each humidity condition described in each example are
The ultraviolet transmittance (UVT) at 280 mμ was measured in accordance with the method described below, and the results were calculated. (i) Oxygen permeability (Q _O2 -D) under low humidity (0%RH/15%RH): The inside of the empty container to be measured is replaced with nitrogen gas in a vacuum, and the mouth of the container is sealed with a rubber stopper. After sealing and covering the contact interface between the mouth and the rubber stopper with epoxy adhesive, the container was stored for a certain period of time in a constant temperature and humidity chamber at a temperature of 27℃ and a humidity of 15%RH. The concentration of oxygen permeated into the container is determined using a gas chromatograph, and according to the following formula, the inside of the container is 0%RH and the outside of the container is 0%RH.
We calculated the oxygen gas permeability at 15% RH (hereinafter referred to as low humidity) and a temperature of 27°C, and further utilized the fact that the thickness and oxygen permeability are inversely proportional to the polyvinylidene chloride resin. coating thickness (t _CA ) and ethylene vinyl alcohol copolymer thickness (t _EV )
The oxygen gas permeability was converted so that the sum of Therefore, Q _O2 -D means the value of oxygen gas permeability at t _CA +t _EV =15 (μ). The result is N
= Average value of three measurement results. Here, 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 [m ² ], Op; oxygen gas partial pressure (=0.209) [atm]. (ii) Oxygen permeability (Q _O2 -W) under high humidity (100% RH/93% RH): Fill the empty container to be measured with 200 c.c. of distilled water in advance, and then vacuum the inside of the container. After replacing the inside with nitrogen gas, sealing the mouth of the container with a rubber stopper, and covering the interface between the mouth and the rubber stopper with epoxy adhesive, the temperature of the container was set at 27°C. And the humidity is reduced to 93% by the saturated aqueous solution of potassium nitrate.
After storing for a certain period of time in a constant temperature and humidity chamber controlled at %RH, the concentration of oxygen that permeated into the container was determined using a gas chromatograph, and calculated using the formula described in the section on oxygen permeability under low humidity in (i). Therefore, the oxygen gas permeability was calculated under conditions of 100% RH inside the container and 93% RH outside the container (hereinafter referred to as high humidity) and a temperature of 27°C, and furthermore, the thickness and oxygen permeability were reversed. Utilizing the proportional relationship, the coating thickness of polyvinylidene chloride resin (t _CA ) and ethylene-
The oxygen gas permeability was converted so that the sum with the thickness of the vinyl alcohol copolymer ( _tEV ) was 15μ.
Therefore, Q _O2 -W means the value of oxygen gas permeability at t _CA +t _EV =15 (μ). The results are the average values of N=3 measurements. (iii) 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 5, the wavelength is between 210 and 700.
Measurements were made over mμ, and the wavelength was 280mμ.
(arrow in Figure 5)
It was expressed as Example 1 A moisture-resistant thermoplastic resin that can be melt-extruded and has a melt index (ASTM D-1238) of 0.3.
g/10min, density (ASTM D-1505) 0.95
g/cc of high-density polyethylene as the inner layer, maleic anhydride-modified high-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd.;
-31B) as the adhesive layer, and the outer layer is a saponified ethylene-vinyl acetate copolymer (ethylene-vinyl alcohol copolymer) with an ethylene content of 30 mol% and a degree of saponification of 99%. A bottle (inner volume: 50 ml) was molded by a known coextrusion blow molding method (component ratio: outer layer: adhesive layer: inner layer = 1:0.5:20, and the average thickness of the ethylene vinyl alcohol copolymer was 14.4 μm). . Next, on the outer surface of the obtained laminated bottle, ethylene trichloride was added to 100 parts by weight of a total of 83% by weight of vinylidene chloride, 14% by weight of methoxyethyl methyl acrylate, and 3% by weight of methyl acrylate.
A polyvinylidene chloride resin latex (dispersion medium: water, solid content concentration: 47% by weight) having a composition ratio of 40 parts by weight was applied by a known dip coating method, and a perfect oven (air circulation type) was used. After heating at 70°C for 5 minutes, aging (heat treatment) was performed at 80°C for 4 minutes in an air constant temperature system. The drying and heat treatment operations described above were repeated 1 to 10 times. Then, a coated laminated bottle having a layer structure as shown in FIG. 2-C (the outer surface was the above-mentioned polyvinylidene chloride resin and the inner surface was the above-mentioned high-density polyethylene) was obtained. The average film thickness (coat thickness) of the polyvinylidene chloride resin applied to the outer surface of the obtained bottle was 2.9μ when the above drying and heat treatment operations were performed once, and the same was repeated twice. 6.4μ when applied repeatedly, 9.7μ when applied 3 times, and 38.3μ when applied 10 times.
It was hot. In addition, the temperature of this polyvinylidene chloride resin at 20℃,
The oxygen permeability coefficient at 100%RH is 1.42×10 ^-14
The cc·cm/cm ² ·sec·cmHg and water vapor permeability coefficient (JIS Z-0208) are 1.02×10 ⁻³ g·cm/m ² ·day. The oxygen permeability Q under each humidity condition was determined using the method described in the text for the four types of coated laminated bottles obtained and, for comparison, the laminated bottle substrate to which the polyvinylidene chloride resin was not coated. _O2 −D and Q _O2 −W) and wavelength are
Each measurement of ultraviolet transmittance (UVT) at 280 mμ was performed. The results are shown in Table 1. The presence of the polyvinylidene chloride resin improves the oxygen gas permeability value of the ethylene vinyl alcohol copolymer, eliminates its dependence on humidity, and further improves the wavelength of 280.
It is known from Table 1 that the ultraviolet transmittance at mμ is reduced and the ultraviolet barrier effect is exhibited.

[Table] Furthermore, the polyvinylidene chloride resin was coated once on the inner surface (high-density polyethylene side) of the laminated bottle substrate. The coating method, drying and aging method and conditions were the same as above, and the average coating thickness of the polyvinylidene chloride resin coated on the inner surface was 3.1μ. The oxygen permeability of the obtained laminated bottle with the inner surface coated was also measured under various conditions according to the method described in the specification. Q _O2 −D is 0.54cc/
m ²・day・atm (converted to t _CA + t _EV = 15 μ), Q _O2
−W is 11.48cc/m ²・day・atm (t _CA +t _EV = 15
(converted to μ), and the coated laminated bottle with a layer structure in which the polyvinylidene chloride resin layer and the ethylene-vinyl alcohol copolymer layer are in an adjacent positional relationship is better. Tables 1 and 2 show that both Q _O2 -D and Q _O2 -W are clearly smaller than the coated laminated bottle with a layered structure in which the polyethylene layer (including the adhesive layer) is interposed between the polyethylene resin layer and the polyethylene layer (including the adhesive layer). It is known from the comparison of the above results. Example 2 A saponified ethylene-vinyl acetate copolymer (ethylene-vinyl alcohol copolymer) with an ethylene content of 59 mol% and a saponification degree of 96% was molded to a diameter (inner diameter) by a known injection molding method. 4cm, height 11cm,
It was molded into a cylindrical cup with a wall thickness of 0.4 mm. Next, a polyvinylidene chloride system having a composition ratio of 89% by weight of vinylidene chloride, 4% by weight of acrylonitrile, 5% by weight of methyl methacrylate, and 2% by weight of methyl acrylate is applied to the inner and outer surfaces of the obtained cup. Applying resin latex (dispersion medium: water, solid content concentration: 52% by weight) to the outer surface of the cup by a known flow coating method,
After drying in an air circulation oven at 80°C for 2 minutes, it was applied to the inner surface of the cup by a known slush coating method and further dried in the open oven at 80°C for 3 minutes. Then, a coated cup having a layer structure as shown in FIG. 2-B (the base material was the above-mentioned ethylene/vinyl alcohol copolymer, and the inner and outer surfaces were the above-mentioned polyvinylidene chloride resin) was obtained. The average film thickness (coat thickness) of the polyvinylidene chloride resin applied to the outer surface of the resulting cup was 10.7μ, and the coat thickness on the inner surface of the cup was 7.4μ (total thickness;
18.1μ). In addition, the temperature of this polyvinylidene chloride resin at 20℃,
The oxygen permeability coefficient at 100%RH is 1.33×10 ^-14
cc·cm/cm ² ·sec·cmHg and water vapor permeability coefficient (JIS Z-0208) are 0.97×10 ⁻³ g·cm/m ² ·day. Next, the coated laminated tube was heated at 60°C using a sunshine-type weatherometer manufactured by Suga Test Instruments Co., Ltd.
Irradiation was performed for 50 hours (irradiation energy = 1.2 × 10 ⁷
joule/ ^m2 ). The thus obtained coated laminated cups, and for comparison, cups made of the ethylene-vinyl alcohol copolymer alone, which were not coated with the polyvinylidene chloride resin, were each treated according to the method described in the text. Oxygen permeability (Q _O2 -D and Q _O2 -W) and wavelength under humidity conditions are 280 mμ
Various measurements of ultraviolet transmittance (UVT) were carried out. The results are shown in Table 2. Furthermore, after filling the above two types of cups (single cup and coated cup) with 135 c.c. of tap water and sealing the mouth with laminated film containing aluminum foil,
It was left in a constant temperature bath adjusted to ℃ and 10% RH for 21 days. After 21 days, reduce the amount of tap water in each cup.
It was weighed using a top plate balance capable of weighing up to 500 mg, and the moisture loss (=1 - moisture content after standing/moisture content immediately after filling) was determined. The moisture loss was 0.84 for the ethylene-vinyl alcohol copolymer cup, whereas it was 0.84 for the ethylene-vinyl alcohol copolymer cup coated with polyvinylidene chloride resin of the above thickness on the inner and outer surfaces. It was impossible to measure weight loss within the range that the balance could detect.

[Table] Example 3 A rectangular laminated cup (inner volume: 540 ml) having the following three-layer structure was molded by known coextrusion and solid state air pressure forming methods. Outer layer: Melt index is 1.4g/10min,
Isotactic polypropylene with a density of 0.91 g/cc Adhesive layer: Maleic anhydride modified polypropylene (manufactured by Mitsubishi Yuka Co., Ltd., P-40B) Inner layer: ethylene content 25 mol% saponification degree
99.6% ethylene/vinyl alcohol copolymer In this case, the composition ratio of each layer is outer layer: adhesive layer: inner layer = 1:0.1:1, and the average thickness of the ethylene vinyl alcohol copolymer layer (inner layer) is 148μ It was hot. Next, a polyvinylidene chloride resin latex (dispersion medium: water, solid content concentration: 30% by weight) having a composition ratio of 90% by weight of vinylidene chloride and 10% by weight of acrylonitrile is applied to the inner surface of the obtained laminated cup.
was applied by a known dip coating method and dried at 60° C. for 30 minutes using a circulating air oven. Furthermore, aging (heat treatment) was performed for 2 days at 40°C in an air constant temperature bath. And the second-C
A coated laminated cup having the layer structure shown in the figure (the outer surface was made of the above-mentioned isotactic polypropylene, and the inner surface was made of the above-mentioned polyvinylidene chloride resin) was obtained. The average film thickness (coat thickness) of the polyvinylidene chloride resin coated on the inner surface of the resulting cup was 1.4 μm. In addition, the temperature of this polyvinylidene chloride resin at 20℃,
The oxygen permeability coefficient at 100%RH is 1.25×10 ^-14
cc·cm/cm ² ·sec·cmHg and water vapor permeability coefficient (JIS Z-0208) are 0.89×10 ⁻³ g·cm/m ² ·day. The oxygen permeability (Q
_O2 -D and Q _O2 -W) and ultraviolet transmittance (UVT) at a wavelength of 280 mμ were measured. The results are shown in Table 3.

[Table] Example 4 Laminated bottle with the following two-layer structure (inner volume:
1000 ml) was molded by known coextrusion and biaxial stretching blow molding methods. Outer layer: ethylene content is 50 mol%, saponification degree is
98.2% saponified ethylene vinyl acetate copolymer (ethylene/vinyl alcohol copolymer) Inner layer: 97% by weight polyvinyl chloride with an average degree of polymerization of 850 and 3% by weight acrylonitrile.
Blend product with styrene-butadiene copolymer. In this case, the composition ratio of each layer is outer layer: inner layer = 1:50
The average thickness of the ethylene vinyl alcohol copolymer layer (outer layer) was 9.7 μm. Next, a polyvinylidene chloride resin latex having a composition ratio of 70% by weight vinylidene chloride, 10% by weight methyl acrylate, and 20% by weight glycidyl acrylate (dispersion medium: water , solid content concentration: 64% by weight) was applied by a known spray coating method, and dried at 100° C. for 10 seconds using an air circulation oven. Furthermore, aging (heat treatment) was performed at 100°C for 15 seconds in an air constant temperature bath. A coated laminated bottle having a layer structure as shown in FIG. 2-C (the inner surface was made of the polyvinyl chloride resin and the outer surface was made of the polyvinylidene chloride resin) was obtained. The average film thickness (coat thickness) of the polyvinylidene chloride resin coated on the outer surface of the resulting bottle was 22.1 μm. In addition, the temperature of this polyvinylidene chloride resin at 20℃,
The oxygen permeability coefficient at 100%RH is 2.49×10 ^-14
cc·cm/cm ² ·sec·cmHg and water vapor permeability coefficient (JIS Z-0208) are 1.76×10 ⁻³ g·cm/m ² ·day. Next, this coated laminated bottle was irradiated using the weatherometer described in Example 2 under the same conditions as in Example 2. The oxygen permeability ( Q _O2 -D and Q _O2 -W) and ultraviolet transmittance (UVT) at a wavelength of 280 mμ were measured. The results are shown in Table 4.

[Table] Example 5 Laminated bottle with the following three-layer structure (inner volume:
500 ml) was molded by known coextrusion and biaxial stretching blow molding methods. Outer layer: Ethylene with an ethylene content of 5% by weight.
Propylene copolymer Adhesive layer: Maleic anhydride-modified high-density polyethylene (manufactured by Showa Denko, ER-403) Inner layer: 45 mol% ethylene content, degree of saponification
98.5% ethylene/vinyl alcohol copolymer In this case, the composition ratio of each layer is outer layer: adhesive layer: inner layer = 20:0.1:1, and the thickness of the ethylene/vinyl alcohol copolymer layer (inner layer) is the average 25.2μ
It was hot. Next, on the inner surface of the obtained laminated bottle, a total amount of 80% by weight vinylidene chloride, 10% by weight methyl methacrylate, and 10% by weight glyceride acrylate.
A polyvinylidene chloride resin latex (dispersion medium: water, solid content concentration: 45% by weight) having a composition ratio of 50 parts by weight of vinyl chloride to 100 parts by weight was applied by a known slush coating method, and air circulation was applied. It was dried at 80° C. for 2 minutes using an oven. After that, aging (heat treatment) was performed at 30°C for 7 days in an air constant temperature bath. A coated laminated bottle having a layer structure as shown in FIG. 2C (the outer surface was made of the above-mentioned ethylene propylene copolymer and the inner surface was made of the above-mentioned polyvinylidene chloride resin) was obtained. Average film thickness (coat thickness) of the polyvinylidene chloride resin applied to the inner surface of the obtained bottle
was 11.3μ. In addition, the temperature of this polyvinylidene chloride resin at 20℃,
The oxygen permeability coefficient at 100%RH is 6.80×10 ^-14
cc·cm/cm ² ·sec·cmHg and water vapor permeability coefficient (JIS Z-0208) are 2.96×10 ⁻³ g·cm/m ² ·day. The oxygen permeability (Q
_O2 -D and Q _O2 -W) and ultraviolet transmittance (UVT) at a wavelength of 280 mμ were measured. The results are shown in Table 5.

[Table] Example 6 A laminated tube (inner volume: 200 ml) having the following three-layer structure was molded by known coextrusion and blow molding methods. Inner and outer layers: 70% by weight of the ethylene/vinyl alcohol copolymer in Example 1, with a density of
0.922g/cc, melt index
0.5g/10min low density polyethylene
A blend consisting of 20% by weight and 10% by weight of an ionomer with an ion type of Na ⁺ .Intermediate layer: Low density polyethylene with a density of 0.922g/cc and a melt index of 0.5g/10min. : Middle class =
1:10, and the average thickness of the blend layers (inner and outer layers) mainly composed of the ethylene/vinyl alcohol copolymer was 29.6 μm as a total amount. Next, a polyvinylidene chloride resin latex having the composition ratio described in Example 1 (dispersion medium: water, solid content concentration: 47
% by weight) by a known dip coating method and dried at 50° C. for 1 hour using a circulating air oven. After that, it was heated to 40℃ in an air constant temperature bath.
Aging (heat treatment) was performed for one day. A coated laminated tube having the layer structure shown in FIG. 2-D (the inner and outer surfaces were made of the polyvinylidene chloride resin) was obtained. The average film thickness (coat thickness) of the polyvinylidene chloride resin applied to the inner and outer surfaces of the obtained tube was 3.4μ on the outer surface and 3.4μ on the inner surface.
It was 3.1μ (total amount: 6.5μ). Next, this coated laminated tube was irradiated using the weatherometer described in Example 2 under the same conditions as in Example 2. Regarding the coated laminated tube thus obtained and the laminated tube substrate not coated with the polyvinylidene chloride resin for comparison,
According to the method described in the text, oxygen permeability (Q _O2 -D and Q _O2 -W) under each humidity condition and ultraviolet transmittance (UVT) at a wavelength of 280 mμ were measured. The results are shown in Table 6.

[Table] Example 7 The five types of bottles described in Example 1 were filled with 18 cans of commercially available soybean oil, and the mouth was sealed with a laminated film containing aluminum foil.
℃, 80% RH constant temperature bath (hereinafter referred to as dark place), and 30 ℃, 80% RH adjusted and 1000 Lux
Each of the five types of filled bottles was placed in a constant temperature bath (hereinafter referred to as a light place) equipped with a light source and stored for two months. After that, the soybean oil filled in each bottle was taken out and the peroxide value of each soybean oil was measured according to the standard oil and fat analysis test method (Japan Oil Chemists Association). /peroxide value immediately after filling) was calculated. The results are shown in Table 7. All values are average values of n=3.

[Table] It is known from Table 7 that the presence of the polyvinylidene chloride resin reduces the peroxide value of soybean oil, and also suppresses the tendency for the peroxide value to increase due to light rays. Example 8 The two types of laminated cups described in Example 2 were filled with 18 cans of commercially available grape concentrate, and the openings were sealed with a laminated film containing aluminum foil. The above two types of filled cups were placed in a constant temperature bath adjusted to %RH (hereinafter referred to as dark place) and a constant temperature bath adjusted to 30℃, 80%RH and equipped with a 1000 Lux light source (hereinafter referred to as bright place). were left standing and stored for 3 months. After that, take out the grape concentrate filled in each cup, measure the absorbance of each grape concentrate at a wavelength of 520 mμ using a spectrophotometer, and calculate the rate of change in absorbance (= absorbance after storage / absorbance immediately after filling). I calculated it. The results are shown in Table 8. All values are average values of n=3.

[Table] Example 9 The two types of laminated cups described in Example 3 were filled with commercially available white miso, and after sealing the mouth with a laminated film containing aluminum foil, they were heated at 30°C and 80°C.
%RH (hereinafter referred to as dark place) and a constant temperature chamber adjusted to 30℃, 80%RH and equipped with a 1000 Lux light source (hereinafter referred to as bright place).
Each type of filled cup was left standing and stored for 4 months. After that, we took out the white miso filled in each cup and measured the brightness of each white miso using a color difference meter.
The rate of change in brightness (=brightness after storage/brightness immediately after filling) was calculated. The results are shown in Table 9. All values are average values of n=3.

[Table] Example 10 The two types of laminated bottles described in Example 5 were filled with 18 cans of commercially available Piure, and after sealing the mouth with a laminated film containing aluminum foil, they were heated at 30°C. Fill the above two types in a constant temperature bath adjusted to 80% RH (hereinafter referred to as dark place) and a constant temperature bath adjusted to 30°C, 80% RH and equipped with a 1000 Lux light source (hereinafter referred to as bright place). Each bottle was left standing and stored for 6 months. Thereafter, the tomato puree filled in each bottle was taken out, the a value of each puree was measured using a color difference meter, and the rate of change in the a value (=a value after storage/a value immediately after filling) was calculated. The results are shown in Table 10. All values are average values of n=3.

[Table] Example 11 The two types of laminated tubes described in Example 6 were filled with 18 cans of commercially available soybean oil, and
After sealing the mouth with a laminated film containing aluminum foil, it was placed in a constant temperature bath (hereinafter referred to as a dark place) adjusted to 30°C and 80% RH, and in a thermostatic chamber adjusted to 30°C and 80% RH.
The two types of filled tubes were placed in a constant temperature bath (hereinafter referred to as a light place) equipped with a 1000 Lux light source and stored for 3 months. After that, take out the soybean oil filled in each tube, measure the absorbance of each soybean oil at a wavelength of 470 mμ using a spectrophotometer, and calculate the rate of change in absorbance (= absorbance combination after storage / absorbance immediately after opening the can). I calculated it. The results are shown in Table 11. All values are average values of n=3.

【table】 [Brief explanation of the drawing]

FIG. 1 is a side view showing a plastic container of the present invention in partial cross section, FIG. 2-A, FIG. 2-B, and FIG.
Figures -C and 2-D are enlarged cross-sectional views showing several examples of the cross-sectional structure of the container wall of the container shown in Figure 1, and Figure 3 shows a resin layer mainly composed of ethylene vinyl alcohol copolymer and a chloride layer. Total thickness with vinylidene resin layer (t
The thickness (t _CA ) of the vinylidene chloride resin layer per _CA + t _EV ) and the oxygen permeability (measurement temperature 27°C, relative humidity: 0% RH inside the container, 15% RH outside the container, t _CA +
t _EV is a diagram showing the relationship between the actual value and the value of 15μ, where curve A is the measured value, curve B is the harmonic mean theoretical value,
Figure 4 shows t _CA / (t _CA + t _EV ) and oxygen permeability under high humidity conditions (measured temperature 27°C, relative humidity; inside the container).
100% RH, 93% RH outside the container, t _CA + t _EV is shown converted to 15μ).
A' is an actual measured value, curve B' is a harmonic average theoretical value, and Figure 5 is a diagram showing the relationship between wavelength and transmittance in plastic containers.Curve A is a container made of polyolefin/ethylene vinyl alcohol copolymer. Wall transmittance; curve B is the transmittance of container wall A with a coating of vinylidene chloride/acrylic (methacrylic) copolymer; curves C and D are transmittance of container wall B exposed to ultraviolet light; The rates are shown respectively. The reference number 1 is the entire bottle, 2 is the peripheral wall of the bottle, 3 is the mouth of the bottle, 4 is the bottom of the bottle, and 5 and 5' are the ethylene.
A vinyl alcohol copolymer resin surface, 6 a plastic container substrate, 7 and 7' a coating layer of vinylidene chloride/acrylic (methacrylic) copolymer, and 8 a moisture-resistant thermoplastic resin.

Claims (1)

[Scope of Claims] 1. A plastic container substrate in which at least one surface is made of a resin mainly composed of an ethylene-vinyl alcohol copolymer, and a positional relationship in which it is adjacent to the resin surface mainly composed of the ethylene-vinyl alcohol copolymer. (a) 99 to 70% by weight vinylidene chloride;
and (b) 1 to 30% by weight of the following formula: In the formula, R ₁ represents a hydrogen atom or a methyl group, and X represents a nitrile group or a formula, (In the formula, Y is an alkyloxy group, a hydroxyalkyloxy group, or a glycidyloxy group)
A group represented by at least one monomer represented by and (c) containing up to 50 parts by weight of chlorine other than vinylidene chloride per 100 parts by weight of the total amount of the monomers (a) and (b). A copolymer consisting of at least one ethylenically unsaturated monomer, which has an oxygen permeability coefficient of 9×10 ^-14 cc・cm/cm ²・sec・cmHg or less at 20°C and 100%RH and water vapor permeability. Coefficient (JIS Z-0208) is 3×10 ^-3 g・cm/
A plastic container with improved oxygen barrier properties characterized by having a coating layer of less than m ² ·day.