JPH0411109B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides a multilayer resin molded article, particularly an ethylene-vinyl alcohol copolymer layer in the molded article, which is a layer containing a clathrate compound in which a deliquescent substance is encapsulated with cyclodextrin. This invention relates to multilayer resin molded bodies that are protected from influences. (Prior art) Ethylene-vinyl alcohol copolymer is thermoformable and is one of the resins with the best barrier properties (permeation resistance) against gases such as oxygen. It is widely practiced to reduce the gas permeability of packaging containers and improve the shelf life of the contents by incorporating them into molded articles. However, the oxygen gas permeability coefficient (Po ₂ ) of ethylene-vinyl alcohol copolymer alone has a large humidity dependence, and the humidity dependence also varies depending on the vinyl alcohol content. In the case of an ethylene-vinyl alcohol copolymer with about 0 mol%, for example, the temperature is 28°C.
When the relative humidity is 0%, Po ₂ is 10 ^-14 cc・
While it is on the order of cm/cm ²・sec・cmHg,
10 ^-12 at a temperature of 28°C and relative humidity of 95%
It is known that the barrier property decreases by about 100 times, on the order of cc・cm/cm ²・sec・cmHg. In order to protect the ethylene-vinyl alcohol copolymer from humidity, a layer containing a desiccant such as a deliquescent inorganic salt should be provided in the multilayer structure.
It is described in Publication No. 34392. (Problems to be Solved by the Invention) However, when blending such a deliquescent substance into a resin, there are concerns regarding workability, dispersibility in the resin, and the protective effect of the ethylene-vinyl alcohol copolymer. It is recognized that problems still arise. In other words, such deliquescent substances tend to easily absorb moisture from the atmosphere and become sticky when kneaded into a resin, causing them to stick to the vessel walls during dry blending or to cause bridging in the hopper of an extruder. It is often difficult to perform mixing and feeding operations smoothly. In addition, due to deliquescence, the smooth powder state is lost, making it difficult to disperse it evenly and uniformly in the resin, and the deliquescent material is mixed in as foreign matter during molding, causing a loss of continuity and uniformity of the resin layer. You will be killed. Furthermore, due to the attenuation of moisture absorption capacity due to deliquescence and the difficulty in uniformly dispersing deliquescent substances in the resin, moisture-proofing of the ethylene-vinyl alcohol copolymer layer by a resin layer containing a deliquescent substance has become difficult. The effectiveness will also be reduced. Therefore, an object of the present invention is to provide a deliquescent material-containing layer in a multilayer resin molded article comprising an ethylene-vinyl alcohol copolymer and a high-humidity thermoplastic resin layer. The purpose is to eliminate the above-mentioned defects that occur when protecting the product from humidity. Another object of the present invention is to make the ethylene-vinyl alcohol copolymer layer moisture-proof by using a new moisture-absorbing agent that can be easily blended and dispersed into the resin, and as a result, excellent gas barrier properties can be achieved during hot filling and heating. To provide a multilayer resin molded article for packaging that is stably maintained even after sterilization. (Means for Solving the Problems) According to the present invention, a multilayer resin molding comprising at least one layer containing an ethylene-vinyl alcohol copolymer and at least one layer consisting of a moisture-resistant thermoplastic resin. Provided is a multilayer resin molded article, characterized in that a layer containing an clathrate compound in which a deliquescent substance is encapsulated with cyclodextrin is provided in a position that protects the ethylene-vinyl alcohol copolymer layer. Ru. (Function) The moisture absorbent used in the present invention is an inclusion compound in which a deliquescent substance is included in cyclodextrin. Cyclodextrin has a chemical structure in which glucose units are bonded in a ring shape, and more specifically, it has the following formula: In the formula, n is an integer from 6 to 8. The one where n is 6 is α-
Among the cyclodextrins, 7 is known as β-cyclodextrin, and 8 is known as γ-cyclodextrin. This cyclodextrin is known to incorporate other substances (called guest substances) into the central cavity of its cyclic structure, forming an inclusion compound as a whole. In the present invention, when a deliquescent substance is used as a guest substance, a cyclodextrin is used as a host lattice, and an clathrate compound is blended and dispersed as a hygroscopic substance in a resin, the tendency to absorb moisture in the atmosphere is significantly suppressed, and It was found that the tendency to deliquesce was eliminated, workability during compounding and kneading was significantly improved, uniform dispersibility into the resin was improved, and moisture-proofing performance for the ethylene-vinyl alcohol copolymer layer was also significantly improved. It is based on In the present invention, the deliquescent substance used as a guest substance may be an inorganic compound or an organic compound as long as it deliquesces upon moisture absorption. As inorganic compounds, alkali metal salts of various inorganic acids, chlorides, bromides, nitrates of various metals, etc. are used.
A suitable example is: Chlorides such as calcium chloride, magnesium chloride, aluminum chloride, iron chloride; Nitrates such as calcium nitrate, magnesium nitrate, aluminum nitrate; Sulfates such as magnesium sulfate; Sodium carbonate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, etc. Alkali metal salts; phosphorus pentoxide, etc. These inorganic salts may be anhydrous salts or hydrated salts as long as they have deliquescent properties. Further, examples of the deliquescent organic compound include toluenesulfonic acid, naphthalenesulfonic acid ammonium salt, sodium maleate, and the like. The ratio of deliquescent substance to cyclodextrin varies depending on the type of deliquescent substance, and it is difficult to define it unconditionally, but in general, the ratio of deliquescent substance to cyclodextrin per 100 parts by weight of cyclodextrin, which is the host lattice, It is preferable that the amount is included in the range of 5 to 1000 parts by weight. The synthesis of the clathrate compound is carried out by preparing an aqueous solution of cyclodextrin, adding a deliquescent substance to this solution, thoroughly stirring with heating if necessary, and drying this. The alcohol or alcohol-water mixture can also be purified to remove free deliquescent substances. As the resin containing the clathrate compound, any thermoformable thermoplastic resin or a blend of two or more thereof can be used. Generally, an adhesive resin is interposed for the purpose of adhering the moisture-resistant resin layer and the ethylene-vinyl alcohol copolymer, and a resin blend is interposed between the two resin layers for the purpose of reusing the regrind of the molded body. These intervening layers contain clathrate compounds. Of course, the clathrate compound may be contained in the moisture-resistant resin or the ethylene-vinyl alcohol copolymer. The content of the clathrate compound in the resin is preferably 2 to 200 parts by weight, particularly 5 to 100 parts by weight, per 100 parts by weight of the resin. That is, if the amount is less than this range, the provision of moisture proofing properties will not be sufficient, and if it is more than this range, there will be a drawback in terms of moldability. As the ethylene-vinyl alcohol copolymer, an ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, especially 25 to 50 mol%, and a saponification degree of 96 mol% or more, especially 99 mol% A saponified copolymer obtained by saponification as described above is used. The saponified ethylene vinyl alcohol copolymer should have a molecular weight sufficient to form a film, and is generally 0.01/g as measured at 30°C in a mixed solvent with a weight ratio of phenol:water of 85:15. In particular, it is desirable to have a viscosity of 0.05/g or more. As a moisture-resistant resin (low water absorption resin),
Water absorption measured by ASTMD570 is 0.5% or less, especially
Up to 0.1% of thermoplastic resins are used, typically low-, medium-, or high-density polyethylene, isotactic polypropylene, ethylene-propylene copolymers, polybutene-1, ethylene-butene-1 copolymers, etc. polymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, ethylene-vinyl acetate copolymer,
Ionically crosslinked olefin copolymer (ionomer)
Alternatively, blends thereof may include olefin resins, and may also include thermoplastic polyesters and polycarbonates such as polyethylene terephthalate, polyethylene terephthalate isophthalate copolymers, polytetramethylene terephthalate, and blends thereof. In some cases, sufficient adhesiveness cannot be obtained between the ethylene vinyl alcohol copolymer and the moisture-resistant thermoplastic resin during lamination, but in this case, an adhesive resin layer is interposed between the two. Such adhesive resins include carboxylic acid,
Carbonyls based on carboxylic acid anhydrides, carboxylic acid salts, carboxylic acid amides, carboxylic acid esters, etc.

[Formula] groups in the main chain or side chain, 1 to 700 milli-equivalent (m・eq)/100g resin, especially 10
Examples include thermoplastic resins containing a concentration of 500 meq/100 g resin. Suitable examples of adhesive resins are:
Ethylene-acrylic acid copolymer, ionically crosslinked olefin copolymer, maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene, acrylic acid grafted polyolefin, ethylene-vinyl acetate copolymer, copolymerized polyester,
It is one kind or a combination of two or more kinds of copolymerized polyamides and the like. These resins are useful for lamination by coextrusion, Sand-German lamination, and the like. Further, thermosetting adhesive resin such as isocyanate-based or epoxy-based adhesive resin is also used for adhesive lamination between the preformed ethylene-vinyl alcohol copolymer film and the moisture-resistant resin film. In FIG. 1 showing an example of the cross-sectional structure of the multilayer resin molded article of the present invention, this molded article 1 consists of a moisture-resistant resin inner surface layer 2, a moisture-resistant resin outer surface layer 3, and a sand-chilled ethylene layer between them. It consists of a gas barrier layer 4 of vinyl alcohol copolymer. In the present invention, the inner layer 2, the outer layer 3, or both of the moisture-resistant resin may contain a clathrate compound. In FIG. 2 showing another example of a multilayer resin molded body, an adhesive resin layer 5, 5' is interposed. In one embodiment of the present invention, the adhesive resin layer contains an inclusion compound. Furthermore, in FIG. 3 showing another example of the molded product, the above-mentioned regrind composition of the molded product is added between the moisture-resistant resin layer 2 (or 3) and the adhesive resin layer 5 (or 5'). A layer 6 of a material (a composition mainly composed of a moisture-resistant resin and containing an ethylene-vinyl alcohol copolymer and a small amount of adhesive resin) is provided, and any layer other than the ethylene-vinyl alcohol copolymer layer Contain an clathrate compound. Furthermore, in the example shown in FIG. 4, the moisture-resistant resin layers 2 and 3, the adhesive layer 5,
Regrind layers 6, 6' are provided between the ethylene-vinyl alcohol copolymer layer and the ethylene-vinyl alcohol copolymer layer, and an inclusion compound is contained in any layer other than the ethylene-vinyl alcohol copolymer layer. In order to blend the clathrate compound with the resin, the clathrate compound and the resin are dry blended, and then fed to an extruder, kneader, roll, etc., and kneaded. Of course,
Prior to manufacturing a multilayer molded product, pellets of a resin composition containing a high concentration of clathrate compounds, that is, a masterbatch, are manufactured, and this masterbatch is mixed with a resin that does not contain clathrate compounds, and then put into an injection machine or an extruder. May be supplied. The container of the present invention can be manufactured by a method known per se, except for the layered structure described above. In multilayer simultaneous extrusion, each resin layer is melt-kneaded using an extruder corresponding to the resin layer, and then extruded into a predetermined shape through a multilayer die such as a T-die or a circular die. Furthermore, lamination methods such as dry lamination, sandwich lamination, and extrusion coating may also be employed. The molded article can take the form of a film, a sheet, a parison or pipe for forming bottles or tubes, a preform for forming bottles or tubes, and the like. Formation of bottles from parisons, pipes or preforms is easily accomplished by pinching off the extrudate between a pair of split dies and blowing fluid into the interior. Further, after the pipe or preform is cooled, it is heated to a stretching temperature, stretched in the axial direction, and blow-stretched in the circumferential direction using fluid pressure, thereby obtaining a stretched blown bottle or the like.
Furthermore, by subjecting the film or sheet to vacuum forming, pressure forming, stretch forming, plug assist forming, or the like, packaging containers in the form of cups, trays, etc. can be obtained. Furthermore, in the case of multilayer films, they are stacked or folded into a bag-like shape and the periphery is heat-sealed to form a bag-like container. (Effects of the Invention) According to the present invention, an inclusion compound having a deliquescent substance as a guest substance and a cyclodextrin as a host lattice is blended into a resin as a hygroscopic substance,
By dispersing the resin composition and providing a layer made of this resin composition in a position that protects the ethylene-vinyl alcohol copolymer layer, the tendency to absorb moisture in the atmosphere is significantly suppressed, and the tendency to deliquesce is eliminated.
The workability during blending and kneading is significantly improved, the uniform dispersibility in the resin is also improved, and the moisture-proof performance of the ethylene-vinyl alcohol copolymer layer is also significantly improved. Furthermore, when the above-mentioned clathrate compound is added to the thermoplastic resin constituting the outer surface layer and molded by a heating melt kneading method such as extrusion or injection, the cyclodextrin constituting the host lattice is heated. Due to the browning phenomenon due to
When using a resin that impairs the appearance of the molded product, it also has the effect of significantly improving the color of the molded product. (Example) The present invention will be explained by the following example. Note that the oxygen gas permeability and Qo ₂ in each example were measured and calculated under the following conditions. That is, the inside of the bottle to be measured is replaced with nitrogen gas in a vacuum, and the contact surface between the bottle mouth and the rubber stopper is covered with epoxy adhesive, and then the bottle is placed at a temperature of 30°C and relative humidity. and 20% RH, and 30°C and 80% RH, respectively, for 5 weeks. Thereafter, the concentration of oxygen that permeated into each bottle was measured using a gas chromatograph, and the oxygen gas permeability (Qo ₂ , unit: cc/m ² ·day · atm) was calculated according to the following formula: Qo ₂ = [ m×Ct/100]/t×Op×A Where, m: Amount of nitrogen gas filled in the bottle (ml) t: Storage period in the thermostatic chamber (day) Ct: Oxygen concentration in the bottle after t days (vol.%) A: Effective area of the bottle (m ² ) Op: Oxygen gas partial pressure (=0.209) (atm) Oxygen gas permeability (Qo ₂ ) is for one type of sample and each of the conditions of (a) and (a) above. For each, 10 pieces were measured. For each example described later, the oxygen gas permeability of each 10 tubes, their arithmetic average value, and coefficient of variation (≡100
x standard deviation value/arithmetic mean value). Example 1 A water-soluble emulsion containing 50 wt% cyclodextrin, which is a mixture of 50 wt% α-type, 30 wt% β-type, and 20 wt% γ-type.
After adding 50 parts by weight of calcium chloride to 100 parts by weight, the mixture was stirred at a temperature of 60°C for one day and night.
Thereafter, the aqueous solution was concentrated using a flask equipped with a refluxer, and vacuum-dried at a temperature of 70° C. for 4 days and nights to produce a powder of an clathrate compound in which the guest substance was calcium chloride and the host lattice was the cyclodextrin. . On the other hand, there is an extruder for the inner and outer layers (moisture-resistant resin layer) equipped with a full-flight screw with a diameter of 65 mm and an effective length of 1430 mm, and a regrind machine with a full-flight screw with a diameter of 90 mm and an effective length of 1980 mm. Adhesive layer extruder with full-flight screw 50 mm diameter and 1000 mm effective length Ethylene-vinyl alcohol adhesive layer extruder with full-flight screw 50 mm diameter and 1000 mm effective length An extruder group consisting of an extruder for copolymer layers and a multilayer die for coextrusion with a seven-layer configuration, and a
A seven-layer bottle as shown in FIG. 4 was molded using a blow molding machine equipped with a mold for a 1000 ml cylindrical bottle. In this case, the following thermoplastic resins constituting the multilayer were used: ) Inner and outer layers (moisture-resistant resin layers), 2 and 3; density (ASTM D-1505) of 0.922 g/cc, melt index (ASTM D-1238) is 0.50g/
10min, water absorption rate (ASTM D-570) is 0.09wt%
low-density polyethylene, ) ethylene-vinyl alcohol copolymer layer,
4; Ethylene content is 45 mol%, saponification degree is
98.6%, ethylene-vinyl alcohol copolymer with a viscosity of 0.07/g, ) Adhesive layer, 5 and 5'; carbonyl group concentration
A mixture of 60 parts by weight of the clathrate compound added to 100 parts by weight of 450meq/100g maleic anhydride-modified low-density polyethylene;) regrind layers, 6 and 6'; the low-density polyethylene, the ethylene-vinyl A blend of the alcohol copolymer, the maleic anhydride-modified low-density polyethylene, and the clathrate compound at a mixing ratio of 10:1:2 (weight ratio) (no burrs or molding defects that occur during molding). crushed matter). The weight (fabric weight) of the molded bottle is approximately 35
g, the layer composition ratio (weight ratio) is according to the symbols in Figure 4: 2 layers; 6 layers: 5 layers: 4 layers: 5' layer: 6' layer: 3 layers = 5:10:1: The ratio was 1:1:10:5. Hereinafter, this bottle will be referred to as "A". For comparison, a mixture obtained by adding 30 parts by weight of non-clathrated calcium chloride to 100 parts by weight of the maleic anhydride-modified low-density polyethylene was used for the adhesive layer, and the multilayer extruder group and blow molding described above were used. Depending on the machine, a 7-layer bottle (hereinafter referred to as
This is written as "B". ), using only the maleic anhydride-modified low-density polyethylene in the adhesive layer, and having the same full pour volume, basis weight, and layer composition ratio as above, using the multilayer extruder group and blow molding machine described above. A seven-layer bottle (hereinafter referred to as "C") was molded. Next, for each of these three types of bottles A, B, and C, the oxygen gas permeability of each bottle stored in the atmosphere under the two conditions described above, Qo ₂ [unit: cc/
m ² ·day · atm] was calculated according to the method described above. The results for Bottle A are shown in Table 1, the results for Bottle B are shown in Table 2, and the results for Bottle C are shown in Table 3. From Table 3, it can be seen that for multilayer bottles (C bottles) that do not contain deliquescent substances such as calcium chloride in any layer, storage conditions are 30°C and relative humidity 20% RH, that is, low humidity conditions. Below, N=
The arithmetic mean value and coefficient of variation (dispersion) of oxygen gas permeability and Qo ₂ obtained from the 10 tubes were all small, but under storage conditions of a temperature of 30°C and a relative humidity of 80% RH, that is, high humidity. Although the coefficient of variation of Qo ₂ is small under these conditions, it is known that the homogeneous arithmetic mean value clearly shows a larger value than in the case of low humidity storage. Also, from Table 2, the results of the multilayer bottle (B bottle) whose adhesive layer mainly contains only a deliquescent substance such as calcium chloride are not much different from the results of the C bottle under the storage conditions at low humidity mentioned above. However, it is known that the coefficient of variation (dispersion) of Qo ₂ is particularly large under storage conditions of high humidity of 30°C and 80% RH. In contrast to these results, a multilayer bottle (A bottle) in which the adhesive layer mainly contained calcium chloride clathrated by the cyclodextrin
It is clear from Table 1 that the arithmetic mean value of Qo ₂ does not change much under both the low humidity and high humidity storage conditions mentioned above, and the coefficient of variation is also small.

【table】

【table】

[Table] Example 2 The cyclodextrin described in Example 1
After adding 25 parts by weight of sodium dihydrogen phosphate to 100 parts by weight of a 50 wt% water-soluble emulsion, the mixture was stirred at a temperature of 60°C for one day and night. after that,
After concentrating the aqueous solution in a flask equipped with a refluxer, vacuum drying was performed at a temperature of 70°C for 4 days and nights to create a powder of an clathrate compound in which the guest substance was sodium dihydrogen phosphate and the host lattice was the cyclodextrin. did. And, the density (ASTM D-1505) is 0.907 g/cc, the melt index (ASTM D-1238) is 1.41 g/10 min, based on 100 parts by weight of the clathrate compound powder.
A dry blend containing 100 parts by weight of isotactic polypropylene with an absorption rate (ASTM D-570) of 0.06 wt% was processed using a pelletizer equipped with a full-flight screw with a diameter of 65 mm and an effective length of 1300 mm. A masterbatch pellet of the above mixture was prepared. On the other hand, using the coextrusion multilayer extruder group also described in Example 1 and a blow molding machine with a full pouring volume of 1000 ml and equipped with a mold for cylindrical bottles, a mold as shown in FIG. A seven-layer bottle was molded. In this case, the following thermoplastic resins were used to constitute each layer: ) Inner and outer layers (moisture-resistant resin layers), 2 and 3; Mixing ratio of the isotactic polypropylene and the masterbatch pellets. is 50:50
(weight ratio) dry blend product, ) ethylene-vinyl alcohol copolymer layer,
4; Ethylene content is 28mol%, saponification degree is
99.6%, ethylene-vinyl alcohol copolymer with a viscosity of 0.19/g, ) Adhesive layer, 5 and 5'; carbonyl group concentration
50 meq/100 g of maleic anhydride-modified high-density polyethylene;) regrind layers 6 and 6'; a mixture of the isotactic polypropylene and the masterbatch pellets, the ethylene-vinyl alcohol copolymer and the maleic anhydride; A blend of modified high-density polyethylene in a mixing ratio of 10:1:2 (weight ratio) (ground material of burrs and molding defects generated during molding). The weight (fabric weight) of the molded bottle is approximately 32
g, the layer composition ratio (weight ratio) is according to the symbols in Figure 4: 2 layers: 6 layers: 5 layers: 4 layers: 5' layers: 6' layers: 3 layers = 5:10:1: The ratio was 1:1:10:5. Hereinafter, this bottle will be referred to as "D". For comparison, a mixture obtained by adding 15 parts by weight of non-clathrated sodium dihydrogen phosphate to 100 parts by weight of the isotactic polypropylene was used for the inner and outer layers, and the multilayer extruder group and blow molding described above were used. Depending on the machine, a bottle with a seven-layer structure (hereinafter referred to as "E") having the same fill volume, basis weight, and layer composition ratio as above, with only the isotactic polypropylene in the inner and outer layers. A bottle with a seven-layer structure (hereinafter referred to as "F") having the same fill volume, basis weight, and layer composition ratio as above was made using the multilayer extruder group and blow molding machine described above. , respectively. Next, for each of these three types of bolts D, E, and F, the oxygen gas permeability of each bottle stored in the atmosphere under the two conditions described above, Qo ₂ [unit: cc/
m ² ·day · atm] was calculated according to the method described above. The results for the D bottle are shown in Table 4, the results for the E bottle are shown in Table 5, and the results for the F bottle are shown in Table 6. From Table 6, it can be seen that for a multilayer bottle (F bottle) that does not contain a deliquescent substance such as sodium dihydrogen phosphate in any layer, the temperature is 30°C and the relative humidity is 20°C.
Under the storage condition of %RH, that is, under low humidity conditions, the oxygen gas permeability obtained from N = 10 bottles, Qo ₂
Both the arithmetic mean value and the coefficient of variation (dispersion) of Qo ₂
It is known that although the coefficient of variation is small, the arithmetic mean value is clearly larger than that in the case of low humidity storage. Furthermore, from Table 5, it can be seen that the multi-layer bottle (E-bottle) containing only a deliquescent substance, such as sodium dihydrogen phosphate, mainly in the inner and outer layers, does not have the same results as the F-bottle under the above-mentioned storage conditions at low humidity. However, it is known that the coefficient of variation (dispersion) of Qo ₂ is particularly large under storage conditions of high humidity of 30°C and 80% RH. In contrast to these results, in the multilayer bottle (D bottle) whose inner and outer layers mainly contain sodium dihydrogen phosphate clathrated by the cyclodextrin, it was found that the multilayer bottle (D bottle) contained neither the above-mentioned low humidity nor high humidity storage conditions. It is clear from Table 4 that the arithmetic mean value of Qo ₂ does not change much even in the lower case, and the coefficient of variation is also small. In addition, after filling the bottles D, E, and F with tap water to their full capacity and capping them,
A panel of 11 people (humans) conducted pairwise comparisons of [] D bottle vs. E bottle, [] D bottle vs. F bottle, and [] E bottle vs. F bottle.
The participants were asked to judge which bottle was "better" (less cloudy, in other words, better in color). [] In the results of a pairwise comparison between D bottle and E bottle, 11 out of 11 panelists answered that the color of D bottle was better. 10 panelists answered that D bottle was better, and 1 panel member answered that F bottle was better in color. [] In the results of pairwise comparison of E bottle and F bottle, 4 panelists out of 11 answered that E bottle was better. Six people answered that the color of the F bottle was better, and one person answered that there was no difference.

【table】

【table】

[Table] Example 3 The cyclodextrin described in Example 1
After adding 100 parts by weight of sodium maleate to 100 parts by weight of a 50 wt% water-soluble emulsion (containing 5 wt% ethyl alcohol), 50 parts by weight of sodium maleate was added.
The mixture was stirred for one day and night at a temperature of .degree. Thereafter, the aqueous solution was concentrated in a flask equipped with a refluxer, and vacuum-dried at a temperature of 70°C for 4 days and nights to produce a powder of an clathrate compound in which the guest substance was sodium maleate and the host lattice was the cyclodextrin. did. Then, the density (ASTM D-
A dry blend to which 200 parts by weight of high-density polyethylene with a melt index (ASTM D-1238) of 0.955 g/cc, a melt index (ASTM D-1238) of 0.35 g/10 min, and a water absorption rate (ASTM D-507) of 0.04 wt% was added.
The pelletizer has a built-in full-flight screw with a diameter of 65 mm and an effective length of 1300 mm.
Masterbatch pellets of the above mixture were prepared. On the other hand, using the coextrusion multilayer extruder group also described in Example 1 and a blow molding machine with a full pouring volume of 1000 ml and equipped with a mold for a cylindrical bottle, as shown in FIG. A seven-layer bottle was molded. In this case, the following thermoplastic resins were used to constitute each layer: ) Inner and outer layers (moisture-resistant resin layers), 2 and 3; the above-mentioned high-density polyethylene; ) Ethylene-vinyl alcohol copolymer layer;
4; Ethylene content is 37mol%, saponification degree is
99.4% ethylene-vinyl alcohol copolymer with a viscosity of 0.17/g;) Adhesive layer, 5 and 5'; Maleic anhydride modified high density polyethylene as described in Example 2;) Regrind layer, 6 and 6'; The mixing ratio of the high-density polyethylene, the ethylene-vinyl alcohol copolymer, and the maleic anhydride-modified high-density polyethylene is 10:1:2, respectively.
A dry blend in which 100 parts by weight of the above masterbatch pellets is added to 100 parts by weight of a mixture (pulverized material of burrs and molding defects generated during molding) of (weight ratio). The weight (fabric weight) of the molded bottle is approximately 41
g, the layer composition ratio (weight ratio) is according to the symbols in Figure 4: 2 layers: 6 layers: 5 layers: 4 layers: 5' layers: 6' layers: 3 layers = 5:10:1: The ratio was 1:1:10:5. Hereinafter, this bottle will be referred to as "G". For comparison, a mixture in which 65 parts by weight of non-clathrated sodium maleate was added to 100 parts by weight of the high-density polyethylene was used in the regrind layer, and the mixture was processed using the multilayer extruder group and blow molding machine described above. Therefore, a bottle with a 7-layer structure (hereinafter referred to as "H") having the same full filling volume, basis weight and layer composition ratio as above, using only the high-density polyethylene in the regrind layer, A seven-layer bottle (hereinafter referred to as "I") having the same fill volume, basis weight, and layer composition ratio as described above was molded using the multilayer extruder group and blow molding machine described above. . Next, for each of these three types of G, H, and I bottles, the oxygen gas permeability of each bottle stored in the atmosphere under the two conditions described above, Qo ₂ [unit: cc/
m ² ·day · atm] was calculated according to the method described above. The results for the G bottle are shown in Table 7, the results for the H bottle are shown in Table 8, and the results for the I bottle are shown in Table 9. From Table 9, it can be seen that for multilayer bottles (I bottles) that do not contain deliquescent substances such as sodium maleate in any layer, the temperature is 30°C and the relative humidity is 20%.
Under storage conditions of RH, that is, low humidity conditions, the oxygen gas permeability obtained from N = 10 bottles, Qo ₂
Both the arithmetic mean value and the coefficient of variation (dispersion) of Qo ₂
It is known that although the coefficient of variation is small, the arithmetic mean value is clearly larger than that in the case of low humidity storage. Furthermore, from Table 8, the results of the multilayer bottle (H bottle) in which only a deliquescent substance such as sodium maleate is contained in the regrind layer are not much different from the results of the I bottle under the above-mentioned storage conditions at low humidity. However, it is known that the coefficient of variation (dispersion) of Qo ₂ is particularly large under storage conditions of high humidity of 30°C and 80% RH. In contrast to these results, the multilayer bottle (G bottle) in which the regrind layer contained sodium maleate clathrated by the cyclodextrin did not perform well under both the low humidity and high humidity storage conditions described above. It is clear from Table 7 that the arithmetic mean value of Qo ₂ does not change much, and the coefficient of variation is also small. On the other hand, 10 bottles each of G, H, and I were filled with 5 wt% saline solution, capped at the bottle mouth, and left in a refrigerator at 5°C for 7 days. A drop test was conducted in the refrigerator room from a height of 120 cm so that the bottom of the bottle hit the concrete floor in the room. The test was repeated 10 times for each bottle. Regarding the bottles G and I, no breakage or delamination was observed in the drop test. However, in the case of H-bottles, although no bottle damage was observed in such a drop test, observation after the test concluded that granular delamination was observed in all 10 bottles. .

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a multilayer resin molded article having two types and three layers according to the present invention, and FIG.
FIG. 3 is a cross-sectional view of a multilayer resin molded body having a 5-layer structure according to the present invention; FIG.
FIG. 2 is a cross-sectional view of a multilayer resin molded body having a layered structure. 1 is a molded product, 2 is a moisture-resistant resin inner surface layer, 3 is a moisture-resistant resin outer surface layer, 4 is an ethylene vinyl alcohol copolymer layer, 5, 5' is an adhesive resin layer, 6,
6' indicates a regrind layer.

Claims (1)

[Claims] 1 In a multilayer resin molded article consisting of at least one layer containing an ethylene-vinyl alcohol copolymer and at least one layer consisting of a moisture-resistant thermoplastic resin, a deliquescent substance is included in a cyclodextrin. A multilayer resin molded article, characterized in that a layer containing a compound is provided in a positional relationship that protects the ethylene-vinyl alcohol copolymer layer.