Multilayered container

The present invention relates to the prevention of delamination of a multi-layer container, and more specifically, the interlayer adhesion between the innermost layer and the outermost layer and the intermediate layer when an impact is received during transportation or dropping of the multi-layer container is improved. The present invention relates to a multi-layer container having a large degree of design freedom because it can prevent delamination of the multi-layer container and can avoid delamination without forming a shape having few uneven portions and bent portions.

Currently, plastic containers (bottles, etc.) mainly made of polyester such as polyethylene terephthalate (PET) are widely used for tea, fruit juice drinks, carbonated drinks, and the like. In addition, the proportion of small plastic bottles in plastic containers is increasing year by year. As the bottle becomes smaller, the ratio of the surface area per unit volume increases. Therefore, when the bottle is made smaller, the expiration date of the contents tends to be shorter. In recent years, beer, which is easily affected by oxygen and light, has been sold in plastic bottles and tea in plastic bottles has been sold hot, and as the range of use of plastic containers has expanded, the gas barrier properties of plastic containers have been further improved. It is requested.

In response to the above requirements, as a method of imparting gas barrier properties to bottles, carbon coating, vapor deposition, and barrier resin coating are applied to multi-layer bottles, blend bottles, and thermoplastic polyester resin single-layer bottles using thermoplastic polyester resin and gas barrier resin. Barrier coating bottles and the like have been developed.

As an example of a multi-layer bottle, a thermoplastic polyester resin such as PET forming the innermost layer and the outermost layer and a thermoplastic gas barrier resin such as polymethaxylylene adipamide (polyamide MXD6) are injected to form a mold cavity. A bottle obtained by biaxially stretching blow-molded a parison having a three-layer or five-layer structure obtained by filling has been put into practical use.

Further, a resin having an oxygen trapping function of trapping oxygen inside the container while blocking oxygen from the outside of the container has been developed and applied to a multi-layer bottle. As the oxygen trapping bottle, a multilayer bottle using polyamide MXD6 mixed with a transition metal catalyst as a gas barrier layer is suitable in terms of oxygen absorption rate, transparency, strength, moldability and the like.

The multi-layer bottle is used as a container for beer, tea, carbonated drinks, etc. because of its good gas barrier property. The use of multi-layer bottles for these purposes maintains the quality of the contents and improves shelf life, while delamination occurs between different resins, for example, between the innermost and outermost layers and the intermediate layer, resulting in commodities. There is a problem that the value is lost.

As a method for improving such a problem, a backflow adjusting device capable of causing a certain amount of backflow to the gas barrier layer side when the resin constituting the innermost layer and the outermost layer is finally injected into the mold cavity is provided. Although it is disclosed and described that the delamination resistance is improved by interposing a crude mixed resin between the layers to be used, there is a problem that a special device is used (see Patent Document 1).<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2000-254963</text></patcit>

<p> An object of the present invention is to solve the above problems, in which peeling due to dropping or impact is unlikely to occur in a multi-layer container, and it is not necessary to form a shape with few uneven portions and bent portions in order to prevent peeling, and the degree of freedom in design is increased. The purpose is to provide a large multi-layer container.</p>

<p> As a result of intensive research on the delamination resistance of the multilayer container, the present inventors have enhanced the affinity between the resin constituting the innermost layer and the outermost layer and the resin constituting the intermediate layer, and have a high glass transition temperature. It has been found that by blending the resin, the adhesion between the layers is improved and the delamination can be prevented when the resin is dropped. That is, delamination is suppressed by bringing the solubility index of the resin constituting the intermediate layer close to the solubility index of the resin constituting the innermost layer and the outermost layer, and further increasing the strain of the resin constituting the intermediate layer after blow molding. We have come to the present invention by finding that a multi-layer container is obtained.</p><p> That is, the present invention is a multilayer container composed of an outermost layer, an innermost layer, and at least one intermediate layer located between the outermost layer and the innermost layer, and the outermost layer and the innermost layer contain 80 mol% of terephthalic acid. It is mainly composed of a thermoplastic polyester resin A obtained by polymerizing a dicarboxylic acid component containing 80 mol% or more of the above-mentioned dicarboxylic acid component and a diol component containing 80 mol% or more of ethylene glycol, and at least one of the intermediate layers contains 70 mol% or more of metaxylylene diamine. Polyamide resin C obtained by polymerizing a diamine component containing 70 mol% or more of adipic acid and a dicarboxylic acid component containing 70 mol% or more of adipic acid and the following formula (1): Sa &lt;Sd &lt;Sc (1) (In the formula, Sa is the solubility index of the thermoplastic polyester resin A, Sc is the solubility index of the polyamide resin C, Sd is the solubility index of the polyamide resin D, and each solubility index is calculated by the Small method.) It is mainly composed of a mixed resin B containing a polyamide resin D in a weight ratio of 99.5 / 0.5 to 80/20, and the glass transition temperature of the polyamide resin D is higher than the glass transition temperature of the polyamide resin C and is 130 ° C. Provided is a multilayer container characterized by the following. Further, the present invention uses an injection molding machine having a skin-side injection cylinder and a core-side injection cylinder from the outermost layer, the innermost layer, and at least one intermediate layer located between the outermost layer and the innermost layer. A thermoplastic polyester resin obtained by polymerizing a dicarboxylic acid component containing 80 mol% or more of terephthalic acid and a diol component containing 80 mol% or more of ethylene glycol from the skin-side injection cylinder. A is injected to form the innermost layer and the outermost layer, and a diamine component containing 70 mol% or more of metaxylylene diamine and a dicarboxylic acid component containing 70 mol% or more of adipic acid are polymerized from the core side injection cylinder. Polyamide resin C obtained from the above and the following formula (1): Sa &lt;Sd &lt;Sc (1) (In the formula, Sa is the solubility index of the thermoplastic polyester resin A, Sc is the solubility index of the polyamide resin C, Sd is the solubility index of the polyamide resin D, and each solubility index is calculated by the Small method.) It is characterized by comprising a step of injecting a mixed resin B containing a polyamide resin D satisfying the above conditions at a weight ratio of 99.5 / 0.5 to 80/20 to form at least one layer of the intermediate layer to produce a multilayer parison. Provided is a method for manufacturing a multilayer container.</p>

<p> According to the present invention, it is possible to obtain a multi-layer container in which delamination is unlikely to occur and the gas barrier property is excellent, and the industrial significance of the present invention is great.</p>

80 mol% of the thermoplastic polyester resin A (hereinafter abbreviated as "polyester resin A"), which may form at least one layer of the outermost layer, the innermost layer, and in some cases, the intermediate layer of the multilayer container of the present invention. As described above, the polyester is obtained by polymerizing a dicarboxylic acid component in which 90 mol% or more is terephthalic acid and a diol component in which 80 mol% or more, preferably 90 mol% or more is ethylene glycol.

As the polyester resin A, polyethylene terephthalate is preferably used. It is possible to exhibit excellent properties in all of the transparency, mechanical strength, injection moldability, and stretch blow moldability of polyethylene terephthalate.

Other dicarboxylic acid components other than terephthalic acid include isophthalic acid, diphenyl ether-4,4-dicarboxylic acid, naphthalene-1,4 or 2,6-dicarboxylic acid, adipic acid, sebacic acid, and decane-1,10-carboxylic acid. Acid, hexahydroterephthalic acid can be used. Other diol components other than ethylene glycol include propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis ( 4-Hydroxyethoxyphenyl) Propane or the like can be used. Further, an oxyacid such as p-oxybenzoic acid can be used as the raw material monomer of the polyester resin A.

The intrinsic viscosity of the polyester resin A is 0.55 to 1.50, preferably 0.65 to 1.40. When the intrinsic viscosity is 0.55 or more, the multilayer parison can be obtained in a transparent amorphous state, and the mechanical strength of the obtained multilayer container is also satisfied. Further, when the intrinsic viscosity is 1.50 or less, it is possible to avoid molding troubles due to the increase in viscosity.

Further, another thermoplastic resin can be blended with the polyester resin A and used as long as the characteristics of the present invention are not impaired. Examples of other thermoplastic resins include thermoplastic polyester resins such as polyethylene-2,6-naphthalenedicarboxylate, polyolefin resins, polycarbonates, polyacrylonitrile, polyvinyl chloride, and polystyrene. The blending amount of the other thermoplastic resin is preferably 10% by weight or less of the polyester resin A.

At least one intermediate layer of the multilayer container of the present invention is formed of a mixed resin B of the following polyamide resin C and polyamide resin D. The polyamide resin C is obtained by polymerizing a diamine component containing 70 mol% or more of m-xylylenediamine and a dicarboxylic acid component containing 70 mol% or more of adipic acid. When the amount of m-xylylenediamine in the diamine component is 70 mol% or more, excellent gas barrier properties can be maintained. When the adipic acid content in the dicarboxylic acid component is 70 mol% or more, it is possible to prevent a decrease in gas barrier property and a decrease in crystallinity.

Polymethoxylylen adipamide (polyamide MXD6) is preferably used as the polyamide resin C because it exhibits excellent properties in co-injection moldability and co-stretch blow moldability with polyester resin A (polyethylene terephthalate). ..

Hexamethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, etc. Aliamine diamines such as 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine; 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1 , 3-Diaminocyclohexane, 1,4-diaminocyclohexane, bis (4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminomethyl) decalin, bis (aminomethyl) tricyclodecane Diamines having an aromatic ring such as bis (4-aminophenyl) ether, paraphenylenediamine, paraxylylenediamine, bis (aminomethyl) naphthalene and the like can be exemplified, but are limited thereto. It's not a thing.

Examples of dicarboxylic acid components that can be used in addition to adipic acid include suberic acid, azelaic acid, sebacic acid, 1,10-decandicarboxylic acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and the like, but are limited thereto. It is not something that will be done. Further, the polyamide resin C may contain a small amount of monoamine and monocarboxylic acid used as a molecular weight modifier at the time of production.

The above-mentioned polyamide resin C is produced by melt polycondensation of a diamine component and a dicarboxylic acid component, or by further solid phase polymerization after melt polycondensation. As a melt polycondensation method, for example, there is a method in which a nylon salt composed of metaxylylene diamine and adipic acid is heated in the presence of water under pressure and polymerized in a molten state while removing the added water and condensed water. .. It is also produced by a method in which metaxylylene diamine is directly added to molten adipic acid and polycondensed. In this case, in order to keep the reaction system in a uniform liquid state, metaxylylene diamine is continuously added to the adipic acid, and during that time, the reaction system is raised so that the reaction temperature does not fall below the melting points of the oligoamide and polyamide produced. While warming, polycondensation proceeds.

The relative viscosity of a relatively low molecular weight polyamide obtained by melt polycondensation (a value measured at 25 ° C by dissolving 1 g of a polyamide resin in 100 ml of 96% sulfuric acid, the same applies hereinafter) is usually about 2.28. When the relative viscosity after melt polycondensation is 2.28 or less, a high-quality polyamide with less gel-like formation and good color tone can be obtained. The relatively low molecular weight polyamide obtained by melt polycondensation may then be solid phase polymerized. In solid-phase polymerization, a polyamide having a relatively low molecular weight obtained by melt polycondensation is pelletized or powdered, and the temperature is adjusted to 150 ° C. or higher and the melting point or lower of the polyamide under reduced pressure or an inert gas atmosphere. It is carried out by heating. The relative viscosity of the solid-phase polymerized polyamide is preferably 2.3 to 4.2. Within this range, molding into a hollow container, film, and sheet is good, and the performance of the obtained hollow container, film, and sheet, particularly mechanical performance, is good. Although some of the effects of the present invention can be obtained by using a polyamide having a relatively low molecular weight after melt polycondensation, the mechanical strength, particularly impact resistance, is not sufficient, and it is not practical as a material for a hollow container.

Polyamide resin D is a resin satisfying the following formula (1). Sa &lt;Sd &lt;Sc (1) (In the formula, Sa is the solubility index of the thermoplastic polyester resin A, Sc is the solubility index of the polyamide resin C, and Sd is the solubility index of the polyamide resin D.) The solubility index is calculated by the Small method (see Journal of Japan Adhesive Society, Vol.22, No.10, p.51 (1986)). It is important that the Sd value of the polyamide resin D is between Sa and Sc in order to enhance the affinity between the innermost outer layer (polyester resin A layer) and the intermediate layer (gas barrier layer). When Sd exceeds this range, the affinity between the polyester resin A forming the innermost layer and the outermost layer and the mixed resin B forming the intermediate layer becomes low, and the adhesion between the layers is lowered, which is not preferable for preventing delamination. Such a polyamide resin D can be obtained by designing the skeleton segment in the polymer so as to satisfy the above formula (1) from the solubility indexes of the polyester resin A and the polyamide resin C obtained from the calculation by the Small method. ..

The glass transition temperature of the polyamide resin D is higher than the glass transition temperature of the polyamide resin C and is 130 ° C. or lower. When the glass transition temperature of the polyamide resin D is higher than the glass transition temperature of the polyamide resin C, the stress strain of the polyamide resin B constituting the intermediate layer after blow molding becomes large, and the action of trying to alleviate the strain prevents delamination. Is thought to improve. When the glass transition temperature of the polyamide resin D exceeds 130 ° C, a peeling prevention effect is observed, but molding of a multilayer container becomes difficult, which is not preferable.

As described above, in the present invention, polyethylene terephthalate is preferably used as the polyester resin A because it is excellent in transparency, mechanical strength, injection moldability, and stretch blow moldability. Further, since the co-injection moldability with polyethylene terephthalate and the co-stretch blow moldability are excellent, the polyamide MXD6 is preferably used as the polyamide resin C. When polyethylene terephthalate is used as the polyester resin A and polyamide MXD6 is used as the polyamide resin C, the polyamide resin D preferably contains a unit derived from an aromatic dicarboxylic acid, and the aromatic dicarboxylic acid is terephthalic acid and / or. The one which is isophthalic acid is more preferable. Specific examples thereof include nylon 6IT and nylon 6I6T (I represents isophthalic acid and T represents terephthalic acid), and among these, nylon 6IT is particularly preferable. Further, as the polyamide resin D, a polyamide resin having a solubility index of 11 to 13 is preferable, and a polyamide resin having a solubility index of 12.0 to 12.9 is more preferable.

The mixed resin B is a dry blend method in which pellets of polyamide resin C and polyamide resin D are mixed in a dry manner and repelletized by an injection molding machine hopper, or polyamide resin C and polyamide resin D are melt-extruded and repelletized. It can be produced by any of the melt blending methods. An appropriate compounding formulation is selected according to the application, usage conditions, mechanical performance, and the like.

The weight ratio of the polyamide resin C to the polyamide resin D in the mixed resin B is 99.5 / 0.5 to 80/20, preferably 99/1 to 85/15, and more preferably 95/5 to 90/10. If the weight ratio of the polyamide resin D is less than 0.5%, a remarkable peeling resistance improving effect cannot be obtained. Further, when the weight ratio of the polyamide resin D exceeds 20%, the effect of improving the peel resistance can be seen, but the good barrier property of the polyamide resin C does not contribute to the multilayer container, which is not practical.

The mixed resin B may contain a layered silicate. The layered silicate is a 2-octhedral or 3-octhedral layered silicate having a charge density of 0.25 to 0.6, and the 2-octhedral type includes montmorillonite, biderite, etc. as a 3-octhedral type. Examples include Hectrite and Savonite. Of these, montmorillonite is preferred.

It is preferable that an organic swelling agent such as a polymer compound or an organic compound is brought into contact with the layered silicate in advance to expand the layers of the layered silicate. As the organic swelling agent, a quaternary ammonium salt can be preferably used, but more preferably, a quaternary ammonium salt having at least one alkyl group or alkenyl group having 12 or more carbon atoms is used.

4-Amino-n-butyric acid, 6-amino-n-caproic acid, 8-aminocapricic acid, 10-aminodecanoic acid, 12-aminododecanoic acid, 14-aminotetradecanoic acid, 16-aminohexadecanoic acid, 18-aminooctadecane Examples include ω-amino acids such as acids. In addition, ammonium salts containing hydroxyl groups and / or ether groups, among them, methyldihydroxyethyl hydrogenated beef ammonium salt, methyldialkyl (PAG) ammonium salt, ethyldialkyl (PAG) ammonium salt, butyldialkyl (PAG) ammonium salt, Dimethylbis (PAG) ammonium salt, diethylbis (PAG) ammonium salt, dibutylbis (PAG) ammonium salt, methylalkylbis (PAG) ammonium salt, ethylalkylbis (PAG) ammonium salt, butylalkylbis (PAG) ammonium salt, methyltri (PAG) ammonium salt, ethyltri (PAG) ammonium salt, butyltri (PAG) ammonium salt, tetra (PAG) ammonium salt (however, alkyl is an alkyl group with 12 or more carbon atoms such as dodecyl, tetradecyl, hexadecyl, octadecyl, and eicosyl. Representing, PAG represents a polyalkylene glycol residue, preferably a quaternary ammonium salt containing at least one alkylene glycol residue such as a polyethylene glycol residue having 20 or less carbon atoms or a polypropylene glycol residue) is also organically swollen. It can be used as an agent. Among them, trimethyl dodecyl ammonium salt, trimethyl tetradecyl ammonium salt, trimethyl hexadecyl ammonium salt, trimethyl octadecyl ammonium salt, dimethyl didodecyl ammonium salt, dimethyl ditetradecyl ammonium salt, dimethyl dihexadecyl ammonium salt, dimethyl dioctadecyl ammonium salt, dimethyl Quaternary ammonium salt and methyldihydroxyethyl hydrogenated beef fat ammonium salt are preferable. These organic swelling agents can be used alone or as a mixture of a plurality of types. Umm salt, dimethyldihexadecylammonium salt, dimethyldioctadecylammonium salt, dimethylditaroammonium salt, and methyldihydroxyethyl hydrogenated beef fat ammonium salt are preferable. These organic swelling agents can be used alone or as a mixture of a plurality of types. Umm salt, dimethyldihexadecylammonium salt, dimethyldioctadecylammonium salt, dimethylditaroammonium salt, and methyldihydroxyethyl hydrogenated beef fat ammonium salt are preferable. These organic swelling agents can be used alone or as a mixture of a plurality of types.

The blending ratio of the layered silicate treated with the organic swelling agent in the mixed resin B is preferably 0.5 to 8% by weight, more preferably 1.5 to 5% by weight, based on the total amount of the polyamide resin C and the polyamide resin D. When the blending ratio of the layered silicate treated with the organic swelling agent is within the above range, the effect of improving the gas barrier property of carbon dioxide gas, oxygen and the like can be obtained, and the transparency is not impaired.

The layered silicate treated with the organic swelling agent is preferably uniformly dispersed in the mixed resin B without locally agglutinating. The term "uniform dispersion" as used herein means that the layered silicates are separated into flat plates in the mixed resin B, and 50% or more of them have an interlayer distance of 5 nm or more. Here, the interlayer distance means the distance between the centers of gravity of the flat plate-shaped object. The larger the distance, the better the dispersed state, the better the appearance such as the transparency of the molded product, and the better the barrier property against gaseous substances such as oxygen and carbon dioxide.

The method for dispersing the layered silicate treated with the organic swelling agent in the mixed resin B is not particularly limited. For example, a method of adding and stirring a layered silicate treated with an organic swelling agent during polycondensation for producing polyamide resin C and / or polyamide resin D, various commonly used methods such as a single-screw or twin-screw extruder. A known method such as a method of melt-kneading a layered silicate treated with a polyamide resin C and / or a polyamide resin D and an organic swelling agent using an extruder can be used. Among these, the method of melt-kneading using a twin-screw extruder is the preferred method in the present invention.

When melt-kneading using a twin-screw extruder, it is preferable to set the melt-kneading temperature in the range from near the melting point of the polyamide resin to the melting point + 60 ° C, and to shorten the residence time of the resin in the extruder as much as possible. .. In addition, the screw installed in the extruder is provided with a part where polyamide resin and layered silicate treated with an organic swelling agent are mixed, and parts such as a reverse screw element and a kneading disk are combined in that part. The layered silicate can be easily dispersed efficiently if it is used.

In the melt-kneading method, if the melt viscosity of the polyamide resin C or D is too low, the layered silicate is difficult to disperse, and agglomerates thereof are likely to be formed, which impairs the appearance when molded. Further, if the melt viscosity is too high, a special device may be required when performing melt kneading. By appropriately controlling the melt viscosity (for example, controlling the melt viscosity of polyamide resin C to 200 to 1000 Pa · s and the melt viscosity of polyamide resin D to 100 to 900 Pa · s), an appropriate pressure is applied to the resin during extrusion kneading. Therefore, the dispersibility of the layered silicate is improved, and it becomes easier to mold at the time of injection molding or extrusion molding.

The water content of the polyamide resin C and the polyamide resin D is preferably less than 0.2%. When the water content is 0.2% or more, not only the dispersibility of the layered silicate treated with the organic swelling agent at the time of melt-kneading is lowered, but also the molecular weight of the polyamide resin is greatly lowered, or a gel-like substance is formed in the molded product. It is not preferable because it tends to occur.

The mixed resin B may contain one or more metal elements selected from Group VIII transition metals, manganese, copper and zinc in the Periodic Table of the Elements. By containing the metal element, the oxidation of the mixed resin B is promoted and the oxygen absorption function is exhibited.

The metal element is preferably added to the polyamide resin C and the polyamide resin D as an inorganic acid salt, an organic acid salt or a complex salt (hereinafter collectively referred to as a metal catalyst compound) having a low acid value of the metal element. Examples of the inorganic acid salt include halides such as chlorides and bromides, sulfates, nitrates, phosphates, silicates and the like. Examples of the organic acid salt include carboxylates, sulfonates, phosphonates and the like. Examples of the complex salt include a transition metal complex with β-diketone, β-keto acid ester and the like. Since the oxygen absorption function is good, it is preferable to use the carboxylate, halide, and acetylacetonate complex of the metal element, and it is more preferable to use the stearate, acetate, or acetylacetonate complex. Further, as a metal element, cobalt is particularly preferable because it has an excellent oxygen absorption function. One or more of the above metal catalyst compounds can be added.

The amount of the metal element added is preferably 0.01 to 0.10% by weight, more preferably 0.02 to 0.08% by weight, based on the total amount of the polyamide resin C and the polyamide resin D. When the addition amount is less than 0.01% by weight, the oxygen absorption function is not sufficiently exhibited, and the effect of improving the oxygen barrier property of the multi-layer container is also low. Further, even if more than 0.10% by weight is added, the oxygen barrier effect of the multilayer container is not further improved, which is uneconomical.

In the multi-layer container of the present invention, a portion having a low draw ratio (1 to 2.5 times) may occur depending on the shape of the parison and the container. Whitening may occur when the intermediate layer of the low draw ratio portion absorbs water. By adding an anti-whitening agent to the mixed resin B as needed, whitening is suppressed and a multi-layer container with good transparency can be obtained.

The anti-whitening agent used in the present invention is a fatty acid metal salt having 18 to 50 carbon atoms, preferably 18 to 34 carbon atoms. It can be expected to prevent bleaching when the number of carbon atoms is 18 or more. Further, when the number of carbon atoms is 50 or less, uniform dispersion in the mixed resin B becomes good. Fatty acids may have side chains or double bonds, but are linearly saturated with stearic acid (C18), eicosanoic acid (C20), behenic acid (C22), montanic acid (C28), triaconic acid (C30), etc. Fatty acid is preferred. The metal forming the salt with the fatty acid is not particularly limited, but sodium, potassium, lithium, calcium, barium, magnesium, strontium, aluminum, zinc and the like are exemplified, and sodium, potassium, lithium, calcium, aluminum and zinc are particularly examples. preferable.

The fatty acid metal salt may be used alone or in combination of two or more. In the present invention, the particle size of the fatty acid metal salt is not particularly limited, but the smaller the particle size, the easier it is to uniformly disperse in the mixed resin B. Therefore, the particle size is preferably 0.2 mm or less.

The amount of the fatty acid metal salt added is preferably 0.005 to 1.0 parts by weight, more preferably 0.05 to 0.5 parts by weight, and particularly preferably 0.12 to 0.5 parts by weight, based on 100 parts by weight of the total amount of the polyamide resin C and the polyamide resin D. is there. An anti-whitening effect can be expected by adding 0.005 parts by weight or more to 100 parts by weight of the total amount. Further, when the addition amount is 1.0 part by weight or less with respect to 100 parts by weight of the total amount, the cloudiness value of the obtained multilayer container can be kept low.

Instead of the fatty acid metal salt, a compound selected from the following diamide compounds and diester compounds may be added as an anti-whitening agent. One or more diamide compounds may be added, one or more diester compounds may be added, one or more diamide compounds and one or more diamide compounds Diester compounds may be used in combination.

The diamide compound is obtained from a fatty acid having 8 to 30 carbon atoms and a diamine having 2 to 10 carbon atoms. When the carbon number of the fatty acid is 8 or more and the carbon number of the diamine is 2 or more, the whitening prevention effect can be expected. Further, when the carbon number of the fatty acid is 30 or less and the carbon number of the diamine is 10 or less, the uniform dispersion in the mixed resin B is good. The fatty acid may have a side chain or a double bond, but a linear saturated fatty acid is preferable.

Examples of the fatty acid component of the diamide compound include stearic acid (C18), eicosanoic acid (C20), behenic acid (C22), montanic acid (C28), and triaconic acid (C30). Examples of the diamine component of the diamide compound include ethylenediamine, butylenediamine, hexanediamine, xylylenediamine, and bis (aminomethyl) cyclohexane. The diamide compound obtained by combining these is used in the present invention. A diamide compound obtained from a fatty acid having 8 to 30 carbon atoms and a diamine mainly composed of ethylenediamine, or a diamide compound obtained from a fatty acid mainly composed of montanic acid and a diamine having 2 to 10 carbon atoms is preferable. The diester compound is obtained from a fatty acid having 8 to 30 carbon atoms and a diol having 2 to 10 carbon atoms. When the fatty acid has 8 or more carbon atoms and the diol has 2 or more carbon atoms, an anti-whitening effect can be expected. Further, when the fatty acid has 30 or less carbon atoms and the diol has 10 or less carbon atoms, uniform dispersion in the mixed resin B becomes good. The fatty acid may have a side chain or a double bond, but a linear saturated fatty acid is preferable.

Examples of the fatty acid component of the diester compound include stearic acid (C18), ecoic acid (C20), behenic acid (C22), montanic acid (C28), and triaconic acid (C30). Examples of the diol component of the diester compound include ethylene glycol, propanediol, butanediol, hexanediol, xylylene glycol, cyclohexanedimethanol and the like. The diester compound obtained by combining these is used in the present invention. Particularly preferred are diester compounds obtained from fatty acids predominantly composed of montanic acid and diols predominantly composed of ethylene glycol and / or 1,3-butanediol.

The amount of the diamide compound and / or the diester compound added is preferably 0.005 to 1.0 parts by weight, more preferably 0.05 to 0.5 parts by weight, particularly preferably 0.12 to 100 parts by weight, based on 100 parts by weight of the total amount of the polyamide resin C and the polyamide resin D. 0.5 parts by weight. An anti-whitening effect can be expected by adding 0.005 parts by weight or more to 100 parts by weight of the total amount. Further, when the addition amount is 1.0 part by weight or less with respect to 100 parts by weight of the total amount, the cloudiness value of the obtained multilayer container can be kept low.

A conventionally known mixing method can be applied to the addition of the anti-whitening agent to the mixed resin B. For example, pellets of polyamide resins C and D, a metal catalyst compound, and an anti-whitening agent may be put into a rotating hollow container and mixed for use. Further, a method of producing a polyamide resin composition containing a high concentration of anti-whitening agent, diluting it with a polyamide resin pellet containing no anti-whitening agent at a predetermined concentration, and melt-kneading this, followed by melt-mixing. , A method of molding by injection molding or the like is adopted.

When an anti-whitening agent is used, it is possible to prevent the intermediate layer made of the mixed resin B from whitening immediately after the multilayer container is manufactured. Further, it is possible to prevent the intermediate layer made of the mixed resin B from whitening after the multilayer container is stored for a long period of time under the condition that the whitening does not occur or the whitening does not increase. That is, after long-term storage in a condition where whitening does not occur or does not increase whitening without adding an anti-whitening agent, for example, in a temperature of 23 ° C and a humidity of 50% RH, the multi-layer container is exposed to high humidity, or is exposed to water or boiling. Even if it is brought into contact with water or heated above the glass transition temperature, whitening is suppressed as in the case immediately after molding.

The multi-layer container of the present invention uses an injection molding machine having two injection cylinders, and molds polyester resin A and mixed resin B having gas barrier properties from the skin side and core side injection cylinders through a mold hot runner. It is obtained by further biaxially stretching blow molding the multilayer parison obtained by injecting into the cavity. Blow molding of the multi-layer parison may be performed by a conventionally known method. For example, a method of blow molding after heating the surface of the multi-layer parison to 80 to 120 ° C, crystallizing the mouth of the multi-layer parison and making the surface 80 to 80 to A method of blowing molding in a mold of 90 to 150 ° C after heating to 120 ° C is adopted. The blow pressure is usually 2-4 MPa.

In the process of injecting polyester resin A constituting the innermost layer and outermost layer from the skin-side injection cylinder and injecting mixed resin B constituting the intermediate layer from the core-side injection cylinder, first, polyester resin A is injected and then mixed. By injecting resin B and polyester resin A at the same time, and then injecting the required amount of polyester resin A to fill the mold cavity, a multi-layer parison with a three-layer structure (polyester resin A / mixed resin B / polyester resin A) is created. Can be manufactured.

In the process of injecting the polyester resin A constituting the innermost layer and the outermost layer from the skin-side injection cylinder and injecting the mixed resin B constituting the intermediate layer from the core-side injection cylinder, the polyester resin A is first injected, and then the mixed resin is injected. By injecting B alone and finally injecting polyester resin A to fill the mold cavity, a five-layer structure (polyester resin A / mixed resin B / polyester resin A / mixed resin B / polyester resin A) Multi-layer parison can be manufactured. The method for manufacturing the multilayer parison is not limited to the above method.

The thickness of the layer made of the polyester resin A in the multilayer container is preferably 0.01 to 1.0 mm, and the thickness of the layer made of the mixed resin B is preferably 0.005 to 0.2 mm. Further, the thickness of the multilayer container does not have to be constant in the entire container, and is usually in the range of 0.2 to 1.0 mm.

In a multi-layer container obtained by biaxially stretching blow molding a multi-layer parison, gas barrier performance can be exhibited if at least an intermediate layer made of mixed resin B is present in the body of the multi-layer container, but the tip of the spout of the multi-layer container can be exhibited. The gas barrier performance is even better when the intermediate layer extends to the vicinity.

In the multilayer container of the present invention, the weight of the layer made of the mixed resin B is preferably 1 to 20% by weight, more preferably 2 to 15% by weight, based on the total weight of the multilayer container. If the weight of the layer made of the mixed resin B is less than 1% by weight, the gas barrier property of the multilayer container may not be sufficient, which is not preferable. Further, if the weight of the layer made of the mixed resin B is more than 20% by weight, it may be difficult to form the precursor multi-layer parison into a multi-layer container, which is not preferable.

The multilayer container of the present invention is unlikely to be delaminated due to dropping or impact. Further, since delamination is unlikely to occur even in a shape including uneven portions and bent portions, the shape of the multilayer container is not limited to a shape having few uneven portions and bent portions, and the degree of design freedom is increased. The multi-layer container of the present invention includes, for example, liquid beverages such as carbonated beverages, juices, water, milk, Japanese sake, whiskey, shochu, coffee, tea, jelly beverages, health beverages, seasonings, sauces, soy sauce, dressings, liquid sauces, etc. It is suitable for storing and preserving various articles such as seasonings, liquid foods such as liquid soup, liquid medicines, lotions, cosmetic emulsions, hairdressing agents, hair dyes, and shampoos.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The measurement method of the characteristics measured in Examples and the like is shown below. (1) Intrinsic viscosity of polyethylene terephthalate [η]: Uses a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio). Measurement temperature 30 ° C. (2) Relative viscosity of polyamide MXD6 [η_rel]: Resin 1g / 96% sulfuric acid 100ml, measurement temperature 25 ° C. (3) Calculation of solubility index: Calculated by the Small method (see Journal of Japan Adhesive Association, Vol.22, No.10, p.51 (1986)). (4) Glass transition temperature: Measured with a heat flow flux differential scanning calorimeter (model: DSC-50) manufactured by Shimadzu Corporation. Heating rate 10 ° C / min (5) Cloud value: Measured by a cloud value measuring device (model: COH-300A) manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with JIS K-7105 and ASTM D1003. (6) Delaminability: Evaluated by a drop test of the container. Drop test method: After filling the multi-layer container with water and capping it, the multi-layer container that had been allowed to stand for 24 hours was dropped and the presence or absence of delamination was visually determined. The multi-layer container was dropped vertically so that the bottom touched the floor. Drop height 75 cm. Delamination property is evaluated by the number of delaminated bottles when 50 bottles are dropped. (7) Oxygen permeability of the multi-layer container: Measured according to ASTM D3985 in an atmosphere of 23 ° C, 100% relative humidity inside the multi-layer container, and 50% relative humidity outside. For the measurement, OX-TRAN 10 / 50A manufactured by Modern Controls was used.

The multilayer containers used in Examples 1 to 5 and Comparative Examples 1 and 2 were produced by the following methods. 3-layer parison shape: Overall length 95 mm, outer diameter 22 mm, wall thickness 4.2 mm. An injection molding machine (model: M200, 4 pieces) manufactured by Meiki Co., Ltd. was used to manufacture the 3-layer parison. 3-layer parison molding conditions Skin side injection cylinder temperature: 280 ° C Core side injection cylinder temperature: 260 ° C Resin flow path temperature in the mold: 280 ° C Mold cooling water temperature: 15 ° C Percentage of mixed resin B in parison: 8% by weight Multi-layer container shape: total length 223 mm, outer diameter 65 mm, internal volume 500 ml, polyester resin A layer / mixed resin B layer / polyester resin A layer = 0.28 mm / 0.056 mm / 0.10 mm, bottom shape is champagne type. A blow molding machine (manufactured by KRUPP CORPOPLAST, model: LB-01) was used for biaxial stretch blow molding. Biaxial stretch blow molding conditions Parison heating temperature: 100 ° C Blow pressure: 2.7MPa

&lt;Example 1&gt; Using the following materials, a multi-layer container with a three-layer structure was molded. Innermost layer and outermost layer Polyester resin A: Polyethylene terephthalate with an intrinsic viscosity of 0.75 (RT543C manufactured by Nippon Unipet). The solubility index is 11.1. Middle layer Mixed resin B: 90/10 (weight ratio) dry blend of polyamide resin C and polyamide resin D Polyamide resin C: Polyamide MXD6 with a relative viscosity of 2.70 (MX Nylon S6007 manufactured by Mitsubishi Gas Chemical Company). The solubility index is 13.0 and the glass transition temperature is 80 ° C. Polyamide resin D: Nylon 6IT (Selar PA 3426 manufactured by Mitsui / DuPont Polychemical Co., Ltd.). The solubility index is 12.6 and the glass transition temperature is 125 ° C. Table 1 shows the evaluation results of delamination.

&lt;Example 2&gt; A multi-layer container having a three-layer structure was formed in the same manner as in Example 1 except that the polyamide resin C and the polyamide resin D were mixed at 95/5 (weight ratio). Table 1 shows the results of delamination evaluation of the obtained three-layer container.

&lt;Example 3&gt; A multi-layer container having a three-layer structure was molded in the same manner as in Example 1 except that the polyamide resin C and the polyamide resin D were mixed at 99/1 (weight ratio). Table 1 shows the evaluation results of the delamination property of the obtained three-layer container.

&lt;Comparison example 1&gt; A multi-layer container having a three-layer structure was formed in the same manner as in Example 1 except that the polyamide resin D was not used and the intermediate layer was composed of the polyamide resin C alone. Table 1 shows the evaluation results of the delamination property of the obtained three-layer container.

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&lt;Example 4&gt; Polyamide MXD6 with a relative viscosity of 2.70 (MX Nylon S6007 manufactured by Mitsubishi Gas Chemical Company) and layered silicate treated with an organic swelling agent (Kunipia manufactured by Kunimine Kogyo Co., Ltd., layered silicate containing 30% by weight of octadecylammonium as an organic swelling agent) Salt) was dry-blended at 97/3 (weight ratio). The obtained mixture is supplied at a speed of 6 kg / hr to a co-rotating twin-screw extruder with a cylinder diameter of 20 mm and equipped with a screw having a retention part by a reverse element, and melt-kneaded at a cylinder temperature of 270 ° C. Then, it was extruded into a strand shape from the extruder head, cooled, and pelletized. A multi-layer container having a three-layer structure was formed in the same manner as in Example 2 except that this was used as the polyamide resin C. Table 2 shows the evaluation results of the oxygen permeability and delamination property of the obtained three-layer container.

&lt;Example 5&gt; Polyamide MXD6 (MX nylon S6007 manufactured by Mitsubishi Gas Chemicals Co., Ltd.) with a relative viscosity of 2.70 and cobalt stearate are dry-blended at 99.5 / 0.5 (weight ratio), and then melt-kneaded with a twin-screw extruder at a cylinder temperature of 270 ° C. , Extruded into strands from the extruder head, cooled and pelletized. A multi-layer container having a three-layer structure was molded in the same manner as in Example 2 except that this was used as the polyamide resin C. Table 2 shows the evaluation results of the oxygen permeability and delamination property of the obtained three-layer container.

&lt;Comparative example 2&gt; The oxygen permeability of the three-layer container molded in Comparative Example 1 was measured. The results are shown in Table 2.

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&lt;Example 6&gt; When mixing polyamide resin C and polyamide resin D, 0.2 parts by weight of sodium montanate (trade name: Hostamont NaV101, manufactured by Clariant Japan Co., Ltd.) was added as an anti-whitening agent to 100 parts by weight of the total amount of polyamide resin. A multi-layered container having a three-layer structure was formed in the same manner as in Example 1 except that the shape of the container was changed as follows. Multi-layer container shape: total length 170 mm, volume 330 ml, neck diameter 25 mm, body diameter 66 mm, polyester resin A layer / mixed resin B layer / polyester resin A layer = 0.33 mm / 0.066 mm / 0.12 mm, bottom shape is champagne type. After evaluating the delamination property of the obtained three-layer container and storing the three-layer container filled with 330 ml of water at 40 ° C / 80% RH for 6 months, the low stretch ratio portion of the container (stretch ratio). Table 3 shows the results of measuring the cloudiness value of the intermediate layer taken out from 1 to 1.5 times).

&lt;Example 7&gt; A multi-layer container having a three-layer structure was formed in the same manner as in Example 6 except that the anti-whitening agent was changed to ethylene bisstearylamide (trade name: Alflow H-50T, manufactured by Nippon Yushi Co., Ltd.). Table 3 shows the evaluation results obtained in the same manner as in Example 6.

&lt;Comparative example 3&gt; A multilayer container having a three-layer structure was molded in the same manner as in Example 6 except that the polyamide resin D was not used and the intermediate layer was used alone with the polyamide resin C. Table 3 shows the evaluation results obtained in the same manner as in Example 6.

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