JP5076541B2 - Multi-layer injection molded product with excellent barrier properties - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-layer injection molded body superior in barrier functionality, peeling resistance, extrusion functionality and moldability. <P>SOLUTION: The multi-layer injection molded body has at least a layer of a resin composition layer having barrier functionality composed of (A) a barrier resin of 50-90 wt.%, (B) a modified polyolefin of 2-45 wt.% and (C) a polyamide of 2-45 wt.% other than a meta-xylylene group-containing polyamide. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

The present invention relates to a multilayer injection molded article excellent in barrier properties and peel resistance. More specifically, it has excellent barrier properties and appearance, and in particular, prevents peeling between the barrier resin layer and its adjacent layer when subjected to an impact during transportation of the molded product or when it is dropped, and has few uneven portions and bent portions. The present invention relates to a multilayer injection molded article that can avoid peeling without having a shape and has a high degree of design freedom.

Injection molding is widely used in mechanical parts, automobile parts, electrical / electronic parts, food / pharmaceutical containers and the like because it can produce a molded body having a complicated shape and has high productivity. In particular, for containers such as beverages, an injection molded body having an excellent screw shape of the cap is often used so that the lid can be sufficiently tightened.
As a material used for injection molding, a general-purpose resin such as polyolefin, polyester, polystyrene, and the like made of polyethylene, polypropylene, etc. are used, among which excellent fluidity and heat resistance during molding, light weight, low moisture absorption, And since it is inexpensive, polyolefins such as polypropylene are widely used in various applications such as containers.
However, since polyolefin is inferior in gas barrier properties such as oxygen, for the storage of contents that are easily affected by oxygen, etc., and for containers such as foods and medicines that require preservation under high temperature environments, It was insufficient. Therefore, a method of improving the barrier property by blending a polyolefin with a barrier material such as polyamide has been disclosed (see Patent Documents 1 and 2). Although the barrier property can be improved by these methods, a special dispersion state of the barrier material is required, so that the barrier property is not sufficiently improved, or the polyamide is unevenly distributed in the vicinity of the surface. Has issues that cause problems.

On the other hand, in the injection molding method, in order to form a multilayer structure having a barrier layer, since there is no adhesion between the polyolefin and the barrier material, an adhesive layer such as polyolefin layer / adhesive layer / barrier layer / adhesive layer / polyolefin layer is provided. At least a five-layer structure is required, but in this case, there are almost no examples because of difficulty in terms of structure and formability. Therefore, a method has been disclosed in which a modified polyolefin having adhesiveness is blended with polyolefin to increase the adhesiveness between the polyolefin layer and the barrier layer, thereby making the adhesive layer unnecessary (see Patent Document 3). Although this method can improve the adhesiveness, it is necessary to add a large amount of expensive modified polyolefin to increase the adhesiveness, and there is a problem that the heat resistance is reduced by the addition of the modified polyolefin. .
JP 2004-292037 A JP 2005-8664 A JP 2006-131275 A

  The present invention is intended to solve the above-described problems in a container obtained from injection molding, and to provide a multilayer injection molded article excellent in barrier properties, peel resistance, heat resistance, extrudability and moldability. .

  As a result of intensive investigations to achieve the above object, the present inventors have used a resin layer comprising a barrier resin having a specific ratio and a modified polyolefin and polyamide as a barrier layer, thereby providing barrier properties, peel resistance, and heat resistance. The inventors have found that a multilayer injection molded article excellent in the above can be obtained, and have completed the present invention.

  That is, the present invention provides a barrier resin comprising 50 to 90% by weight of a barrier resin (A), 2 to 45% by weight of a modified polyolefin (B), and 2 to 45% by weight of a polyamide (C) other than a metaxylylene group-containing polyamide. The present invention relates to a multilayer injection molded article having at least one composition layer.

  The multilayer injection-molded article and multilayer stretch-molded injection-molded article obtained by the present invention are excellent in barrier properties, peel resistance, and heat resistance, and can be used for liquid foods such as beverages and soups, and for processing foods and pharmaceuticals. Suitable as a container.

The barrier resin composition forming the barrier resin composition layer in the present invention can be obtained by mixing the barrier resin (A), the modified polyolefin (B) and the polyamide (C). In the resin composition, the barrier resin (A), the modified polyolefin (B) and the polyamide (C) are added to (A) 50 to 90% by weight, (B) 2 to 45% by weight, and (C) 2 to 2%. 45% by weight, preferably (A) 55-85% by weight, (B) 3-40% by weight and (C) 3-40% by weight, more preferably (A) 60-80% by weight. , (B) 4 to 35% by weight and (C) 4 to 35% by weight. When (A) is less than 50% by weight, there is a problem that the barrier property is insufficient, and when it exceeds 90% by weight, the adhesion with an adjacent layer is lowered, which is not preferable. On the other hand, when (B) is less than 2% by weight, the adhesiveness is low, and when it exceeds 45% by weight, the barrier property is lowered, which is not preferable. On the other hand, when (C) is less than 2% by weight, unevenness of the thickness of the barrier resin composition layer occurs, and when it exceeds 45% by weight, the barrier property is lowered, which is not preferable.

The multilayer injection-molded article of the present invention has at least one layer of the barrier resin composition layer, and layers other than the barrier resin composition layer may be layers made of various thermoplastic resins. it can. Although there is no restriction | limiting in the layer structure of a multilayer injection molding, For example, a thermoplastic resin layer / barrier resin composition layer / thermoplastic resin layer, a thermoplastic resin layer / barrier resin composition layer / thermoplastic resin layer / barrier Resin layer / thermoplastic resin layer and the like. As the thermoplastic resin, polyolefin (polyolefin (D)) is preferable, and a multilayer molded body in which the barrier resin composition layer is sandwiched between polyolefin layers is particularly preferable. Polyolefin (D) includes linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight high density polyethylene, polypropylene, or two or more olefins selected from ethylene, propylene, butene, etc. The copolymer of these, and those mixtures can be illustrated. Of these, polypropylene is preferably used because of its excellent heat resistance. The polyolefin (D) can also be used by mixing with other resins such as elastomers or by mixing with other additives such as carbon black and flame retardant. The multilayer injection-molded article of the present invention comprises a polyolefin (D) layer / barrier resin composition layer / polyolefin (D) layer and a polyolefin (D) layer / barrier resin composition layer / polyolefin (D) layer / barrier resin. It is preferable that the barrier resin composition layer is sandwiched between polyolefin (D) layers as in the composition layer / polyolefin (D) layer.

Examples of the barrier resin (A) used in the present invention include a polyamide (metaxylylene group-containing polyamide), an ethylene-vinyl alcohol copolymer resin, a vinyl alcohol copolymer resin, an acrylonitrile resin, and the like made of metaxylylenediamine and dicarboxylic acid. Among them, a metaxylylene group-containing polyamide is preferably used. As the metaxylylene group-containing polyamide, 70 mol% or more of the structural unit derived from diamine is derived from metaxylylenediamine, and 70 mol% or more of the structural unit derived from dicarboxylic acid is α having 4 to 20 carbon atoms. , Ω-linear aliphatic dicarboxylic acid and isophthalic acid are preferably those derived from dicarboxylic acid having a molar ratio of 30:70 to 100: 0. The polyamide has a molar ratio of a diamine component containing 70 mol% or more (including 100 mol%) of metaxylylenediamine, an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms and isophthalic acid to 30: It can be obtained by polycondensing a dicarboxylic acid component containing 70 to 100 mol% (including 100 mol%) of a dicarboxylic acid that is 70 to 100: 0.

  In the present invention, as a diamine other than metaxylylenediamine used as a raw material of the metaxylylene group-containing polyamide, tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylene Aliphatic diamines such as diamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, 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) Cyc) propane, bis (aminomethyl) decalin (including structural isomers), alicyclic diamines such as bis (aminomethyl) tricyclodecane (including structural isomers); bis (4-aminophenyl) ether And diamines having an aromatic ring such as paraphenylenediamine, paraxylylenediamine, and bis (aminomethyl) naphthalene (including structural isomers). These can be used in the range of 30 mol% or less in the total diamine component.

  Examples of the α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms include succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid, and dodecanedioic acid. Although aliphatic dicarboxylic acid can be illustrated, adipic acid is preferable among these.

The molar ratio of the C 4-20 α, ω-linear aliphatic dicarboxylic acid unit to the isophthalic acid unit is 30:70 to 100: 0, preferably 30:70 to 95: 5, more preferably 40:60. It is -95: 5, More preferably, it is 60: 40-90: 10.
When the isophthalic acid unit is contained within this range, the barrier property is improved.

In addition, the melting point of the resulting polyamide resin is lower than when only α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms is used, and molding can be performed at a lower temperature, reducing production energy and shortening the molding cycle. Not only can be achieved, but the melt viscosity is increased, and the moldability of the resin against drawdown is improved.

In the present invention, examples of the dicarboxylic acid component other than the α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms and isophthalic acid include phthalic acid compounds such as terephthalic acid and orthophthalic acid; 1,2-naphthalenedicarboxylic acid 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2 , 3-Naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and other isomers such as benzoic acid, propionic acid, butyric acid, etc .; trimellitic acid, pyromellitic Polycarboxylic acids such as acids; Carboxy such as trimellitic anhydride and pyromellitic anhydride You may use an acid anhydride etc. in 30 mol% or less of the total dicarboxylic acid component.

When the above-mentioned metaxylylene group-containing polyamide is obtained by polycondensation, the polycondensation reaction system includes lactams such as ε-caprolactam, ω-laurolactam, ω-enantolactam, 6-aminocaproic acid, 7-aminoheptanoic acid, 11 -Aminoundecanoic acid, 12-aminododecanoic acid, 9-aminononanoic acid, paraaminomethylbenzoic acid and other amino acids may be added as long as the performance is not impaired.

The metaxylylene group-containing polyamide comprises a diamine component containing 70 mol% or more of metaxylylenediamine, an α, ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms and a molar ratio of 30:70 to 100: 0, It is produced by melt polycondensation with a dicarboxylic acid component containing 70 mol% or more of isophthalic acid, and its production method is not particularly limited, and a conventionally known method such as an atmospheric pressure melt polymerization method or a pressure melt polymerization method is used. , Produced according to polymerization conditions. For example, metaxylylenediamine and adipic acid or a nylon salt consisting of metaxylylenediamine, adipic acid and isophthalic acid is heated in the presence of water under pressure, and melted while removing the added water and condensed water. It is manufactured by a method of polymerizing in a state. It can also be produced by a method in which metaxylylenediamine is directly added to molten adipic acid or a mixture of adipic acid and isophthalic acid and polycondensed under normal pressure. In this case, in order not to solidify the reaction system, metaxylylenediamine is continuously added, while raising the temperature of the reaction system so that the reaction temperature therebetween is equal to or higher than the melting point of the generated oligoamide and polyamide, Polycondensation proceeds.

The metaxylylene group-containing polyamide is preferably further heat-treated to increase the melt viscosity. As a heat treatment method, for example, using a batch-type heating device such as a rotating drum, in an inert gas atmosphere or under reduced pressure, it is heated gently in the presence of water, and crystallized while avoiding fusion. Thereafter, a method of further heat treatment; heating in an inert gas atmosphere using a grooved stirring and heating device, and after crystallization, heat treatment in an inert gas atmosphere using a hopper-shaped heating device A method of performing a heat treatment using a batch-type heating device such as a rotating drum after crystallization using a groove type stirring and heating device. Among them, a method of performing crystallization and heat treatment using a batch heating apparatus is preferable. As the treatment conditions, the crystal is obtained by raising the temperature from 70 to 120 ° C. in the presence of 1 to 30% by weight of water and 0.5 to 4 hours with respect to the polyamide (I) obtained by melt polymerization. Then, the conditions of heat treatment in an inert gas atmosphere or under reduced pressure at a temperature of the melting point of polyamide (I) −50 ° C. to the melting point of polyamide (I) −10 ° C. for 1 to 12 hours are preferable.

The metaxylylene group-containing polyamide preferably has a relative viscosity (measured under the conditions of 96 mass% concentrated sulfuric acid as a solvent, temperature 25 ° C., concentration 1 g / 100 ml) of 2.5 or more, more preferably 3 or more. belongs to. When the relative viscosity is less than 2.5, there is a problem that moldability is lowered.

The melting point of the metaxylylene group-containing polyamide is preferably controlled in a range of 160 ° C to 240 ° C, more preferably 170 to 235 ° C, and further preferably 180 to 230 ° C. By bringing the melting point of the polyamide close to the melting point of the thermoplastic resin such as polyolefin (D), the occurrence of defects such as thickness unevenness due to the molding temperature difference between the resins during the production of the multilayer molded body, and the odor and coloring due to the resin deterioration. It becomes possible to suppress.

The glass transition point of the metaxylylene group-containing polyamide is preferably in the range of 80 to 130 ° C. By setting the glass transition point of polyamide to 80 ° C. or higher, a polyamide having excellent barrier properties at high temperatures can be obtained.

  The metaxylylene group-containing polyamide preferably has a terminal amino group concentration of less than 40 μequivalent / g, preferably 10 to 30 μequivalent / g, more preferably a carboxyl group concentration of 40 to 100 μequivalent / g or more. When the end group exceeds the above range, there is a problem that the resulting barrier layer is colored yellow.

The metaxylylene group-containing polyamide may contain a phosphorus compound in order to enhance processing stability during melt molding or to prevent coloring of the polyamide. As the phosphorus compound, a phosphorus compound containing an alkali metal or an alkaline earth metal is preferably used. Examples thereof include phosphates such as sodium, magnesium and calcium, hypophosphites and phosphites, and alkali metals. Alternatively, a material using an alkaline earth metal hypophosphite is preferably used because it is particularly excellent in the anti-coloring effect of the polyamide. The concentration of the phosphorus compound in the polyamide is desirably 200 ppm or less, preferably 160 ppm or less, and more preferably 100 ppm or less as phosphorus atoms. In addition to the above phosphorus compounds, the polyamide used in the present invention includes a lubricant, matting agent, heat stabilizer, weathering stabilizer, ultraviolet absorber, nucleating agent, plasticizer, difficulty as long as the effects of the present invention are not impaired. Additives such as a flame retardant, an antistatic agent, an anti-coloring agent, and an anti-gelling agent can be added, but the present invention is not limited to those described above, and various materials may be mixed.

It is desirable to dry the metaxylylene group-containing polyamide before use so that the moisture content is 0.10% or less, preferably 0.08% or less, more preferably 0.05% or less. If the water content is higher than 0.10%, bubbles may be generated by water generated from the polyamide during melt mixing, which is not preferable. When drying polyamide, it can carry out by a publicly known method. For example, a method in which polyamide is charged in a heatable tumbler (rotary vacuum tank) equipped with a vacuum pump or in a vacuum dryer, and dried by heating at a temperature not higher than the melting point of the polymer, preferably not higher than 160 ° C., under reduced pressure. However, it is not limited to this.

The modified polyolefin (B) used in the present invention is obtained by graft-modifying the above polyolefin (polyolefin (D)) with an unsaturated carboxylic acid or its anhydride, and is generally widely used as a compatibilizing agent or an adhesive. Is. Specific examples of unsaturated carboxylic acids or anhydrides include acrylic acid, methacrylic acid, α-ethylacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, chloromaleic acid, butenyl succinic acid, and the like These acid anhydrides are mentioned. Of these, maleic acid and maleic anhydride are preferably used. As a method for obtaining a modified polyolefin by graft copolymerization of the unsaturated carboxylic acid or its anhydride onto a polyolefin, various conventionally known methods can be used. For example, a method in which a polyolefin is melted using an extruder and a graft monomer is added and copolymerized, or a method in which a polyolefin is dissolved in a solvent and a graft monomer is added and copolymerized, and the polyolefin is mixed with an aqueous suspension. Examples thereof include a method in which a graft monomer is added and copolymerized.

The modified polyolefin (B) used in the present invention preferably has a melt flow rate (MFR) at a load of 190 ° C. and a load of 2.16 kgf in the range of 0.5 to 50 g / 10 min. When it comes off, since adhesiveness and a moldability fall, it is unpreferable.

The polyamide (C) used in the present invention is a polyamide other than the polyamide used as the barrier resin (A), and is a polyamide other than the metaxylylene group-containing polyamide. The polyamide (C) is preferably a softer polyamide than the barrier resin (A), such as nylon-4, nylon-6, nylon-12, nylon-66, nylon-46, nylon-610, nylon-612, nylon 666, etc. Among them, nylon-6, nylon-66 and nylon-666 are preferably used.
The polyamide (C) preferably has a relative viscosity of less than 5 and more preferably less than 4 when measured under the conditions of 96 mass% concentrated sulfuric acid as a solvent, temperature 25 ° C. and concentration 1 g / 100 ml. . When the relative viscosity is 5 or more, when premixing is performed with an extruder, problems such as fluctuations in extrusion and breakage of strands may occur.
The relative viscosity can be measured by the following method.
<Measurement method of relative viscosity>
1 g of polyamide is precisely weighed and dissolved in 100 ml of 96% by mass sulfuric acid at 20-30 ° C. with stirring. After complete dissolution, immediately take 5 cc of the solution in a Cannon-Fenceke viscometer, leave it in a constant temperature bath at 25 ° C. for 10 minutes, and then measure the drop rate (t). The dropping rate (t0) of 96% by mass sulfuric acid itself is also measured in the same manner. The relative viscosity is calculated from t and t0 by the following equation (A).
Relative viscosity = t / t0 (A)

You may mix resin other than said (A), (B), (C) in the said barriering resin composition in the range which does not impair the effect of this invention. The amount of these resins used is usually 30 parts by weight or less with respect to the total of 100 parts by weight of (A), (B) and (C). Examples of the resin include polyolefin (E), elastomer, ionomer, polyester resin, styrene resin, polycarbonate, and the like, and polyolefin (E) is particularly preferable.
The polyolefin (E) used in the present invention includes various types, but preferably low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, 1-polybutene, 1-polymethyl. Homopolymer of ethylene hydrocarbon having 2 or more carbon atoms, preferably 2 to 8, such as pentene; homopolymer of α-olefin having 3 to 20 carbons; copolymer of α-olefin having 3 to 20 carbons (Ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, ethylene / 1-butene copolymer, ethylene / 4-methyl-1-pentene copolymer, ethylene / 1-hexene copolymer, Ethylene / 1-octene copolymer, ethylene / 1-decene copolymer, propylene / 1-butene copolymer, propylene / 4-mer Til-1-pentene copolymer, propylene / 1-hexene copolymer, propylene / 1-octene copolymer, propylene / 1-decene copolymer, etc.), C3-C20 α-olefin and cyclic olefin (For example, a copolymer with norbornene). These polyolefins can be used alone or as a mixture of two or more. Among these polyolefins, resins having a high glass transition point such as resins such as polyethylene, polypropylene, 1-polybutene, or copolymers of α-olefin and cyclic olefin are preferable, and among them, polypropylene having excellent heat resistance is preferable. Used. The polyolefin (E) used in the present invention preferably has a melt flow rate (MFR) in the range of 1 to 100 g / 10 min at 190 ° C. and a load of 2.16 kgf. If the MFR is smaller than 1 g / 10 min, there is a problem that moldability such as thickness unevenness occurs, which is not preferable.

  As an example of producing the multilayer injection molded body of the present invention, a thermoplastic resin and a barrier resin composition are transferred from the injection cylinders on the skin side and the core side to the mold using an injection molding machine having two injection cylinders. There is a method of obtaining a multilayer injection molded product obtained by injection into a mold cavity through a hot runner, and a multilayer stretched injection molded product is obtained by biaxial stretch blow molding of the multilayer injection molded product. The multilayer injection molded article may be blow molded by a conventionally known method. For example, a method of blow molding after heating the surface of the multilayer injection molded article to 120 to 170 ° C. is employed. The blow pressure is usually 0.1 to 4 MPa.

  In the step of injecting a thermoplastic resin such as polyolefin constituting the innermost layer and outermost layer from the skin side injection cylinder, and injecting the barrier resin composition constituting the barrier resin composition layer from the core side injection cylinder, By injecting a thermoplastic resin, then injecting a barrier resin composition, and then injecting the required amount of thermoplastic resin to fill the mold cavity, a three-layer structure (thermoplastic resin / barrier resin composition / Thermoplastic resin) can be produced. The method for producing the multilayer parison is not limited to the above method.

The thickness of the layer made of the thermoplastic resin composition in the multilayer injection molded article is preferably 0.01 to 3.0 mm on average, and the thickness of the barrier resin composition layer is 0.005 on average. 2 mm is preferable. Moreover, the thickness of the multilayer container which consists of a multilayer injection-molded body does not need to be constant throughout the container, and is usually in the range of 0.01 to 5.0 mm on average.

By biaxially stretching the multilayer injection molded product obtained in the present invention, a multilayer stretched injection molded product can be obtained. The biaxial stretching method can be performed by a general blow molding machine.
For example, by using a biaxial stretch blow molding machine, the injection molded body is heated for about 15 seconds to 5 minutes with a far infrared heater or the like, and blow molded with a stretch rod and a pressure of 0.1 to 4 MPa. .

In the multilayer injection molded product of the present invention, burrs and defective products at the time of molding can be melted again and introduced as a recycled layer. In this case, it is preferable to arrange in the outer layer from the barrier resin composition layer from the viewpoint of strength.

Unless the object of the present invention is impaired, each resin layer includes a lubricant, a mold release agent, an antioxidant, a processing stabilizer, a heat stabilizer, an ultraviolet absorber, a layered silicate, a crystal nucleating agent, Co, and Mn. Inorganic or organic metal salts such as Zn, complexes and the like can be added.

The multilayer injection molded article or multilayer stretched injection molded article thus obtained is excellent in gas barrier properties, peel resistance, and appearance, such as carbonated beverages, juice, water, milk, sake, whiskey, shochu. , Coffee, tea, jelly drinks, health drinks and other liquid drinks, seasonings, sauces, soy sauce, dressings, liquid soup, mayonnaise, miso, grated spices, etc., pasty foods such as jam, cream, chocolate paste , Liquid soup such as liquid soup, boiled food, pickles, stew, and other processed foods, raw noodles such as buckwheat noodles, noodles and ramen, boiled noodles, polished rice, moisture-conditioned rice, and unwashed rice Cooked rice, cooked rice, processed rice products such as gomoku rice, red rice, rice bran, high-moisture foods such as powdered soups, powdered seasonings such as dashi stock, dried vegetables, coffee beans, rice Low-moisture foods, such as honey powder, tea, cereals and other sweets, solid and solution chemicals such as agricultural chemicals and insecticides, liquid and paste pharmaceuticals, lotions, cosmetic creams, It can be used as a container for storing various articles such as cosmetic emulsion, hair conditioner, hair dye, shampoo, soap, detergent and the like.

Hereinafter, the present invention will be specifically described with reference to examples and the like. In Examples and the like, the evaluation methods for polyamide and molded body were as follows.
(1) 1 g of relative viscosity polyamide was precisely weighed and dissolved in 100 ml of 96% by mass sulfuric acid at 20-30 ° C. with stirring. After completely dissolving, 5 cc of the solution was quickly taken into a Cannon Fenceke viscometer, and allowed to stand in a constant temperature bath at 25 ° C. for 10 minutes, and then the dropping speed (t) was measured. Further, the dropping speed (t0) of 96% by mass sulfuric acid itself was measured in the same manner. The relative viscosity was calculated from t and t0 by the following formula (A).
Relative viscosity = t / t0 (A)
(2) Extrudability After dry blending each resin pellet of the barrier resin composition, it is a twin screw extruder set with a cylinder diameter of 37 mm and a hardened type screw having a retention part by a reverse main element. The extrusion stability was evaluated when extrusion kneading was performed under the conditions of 100 RPM per hour / hour.
A: Extrusion stability, B: Slightly unstable, X: Unstable.
(3) Formability The body portion of the multilayer injection molded product container was cut to evaluate the uniformity of the thickness of the barrier resin composition layer.
(Circle): Thickness uniformity, (triangle | delta): Thickness unevenness is some, x: Thickness unevenness is large. The peeled state when the layer was peeled off by hand was evaluated.
A: There is a feeling of resistance at the time of peeling, ○: A little feeling of resistance at the time of peeling, ×: There is no feeling of resistance at the time of peeling.
(5) Oxygen barrier property The oxygen transmission rate of the injection molded article was measured in accordance with ASTM D3985 in an atmosphere of 23 ° C., 60% relative humidity inside the multilayer injection molded article, and 50% relative humidity outside. The measurement used OX-TRAN 10 / 50A made by Modern Controls.
(6) Heat resistance 500 ml of water was put into a bottle, the cap was capped, and retort treatment was performed at 121 ° C./30 minutes in an autoclave (manufactured by Tommy Industry Co., Ltd.).

The multilayer molded body container was manufactured by the following method.
Three-layer injection-molded body shape: total length 95 mm, outer diameter 25 mm, wall thickness 3.0 mm. For the production of the three-layer injection molded body, an injection molding machine (model: M200, 4 pieces) manufactured by Meiki Seisakusho Co., Ltd. was used.
Three-layer injection molded body molding conditions Skin side injection cylinder temperature: 240 ° C
Core side injection cylinder temperature: 260 ° C
Resin channel temperature in mold: 260 ° C
Mold cooling water temperature: 15 ° C
Ratio of barrier resin composition layer in multilayer molded body container: 10% by weight

<Examples 1-5>
Using the materials shown in Table 1, a multilayer molded container having a three-layer structure was produced by the method described above, and the peel resistance, oxygen barrier property and heat resistance were evaluated. The results are shown in Table 1.

<Comparative Examples 1-4>
Using the materials shown in Table 2, a multilayer molded container having a three-layer structure was produced and evaluated by the above method. Note that the multilayer molded body container obtained in Comparative Example 2 was not evaluated for oxygen barrier properties and heat resistance because the barrier resin composition layer (intermediate layer) and the adjacent layer were easily separated. The results are shown in Table 2.

In addition, the symbol in Tables 1-2 shows the following.
A1: MX nylon S6121 (Mitsubishi Gas Chemical Co., Ltd. polymetaxylylene adipamide, relative viscosity = 3.8).
A2: Polyamide 2 obtained by the following method.
Weigh 14.2 kg (97.1 mol) of adipic acid and 1.0 kg (6.2 mol) of isophthalic acid in a 50 L reactor equipped with a stirrer, a condenser, a cooler, a dripping tank, and a nitrogen gas introduction tube. The mixture was sufficiently purged with nitrogen and further made into a uniform slurry of molten adipic acid and isophthalic acid at 160 ° C. under a small amount of nitrogen stream. To this, 14.0 kg (102.6 mol) of metaxylylenediamine was added dropwise over 1 hour with stirring. During this time, the internal temperature was continuously increased to 247 ° C. Water distilled with the addition of metaxylylenediamine was removed out of the system through a condenser and a condenser. After completion of the dropwise addition of metaxylylenediamine, the internal temperature was raised to 260 ° C. and the reaction was continued for 1 hour. The obtained polymer was taken out as a strand from the nozzle at the bottom of the reaction can, cooled with water and then cut into pellets.
Next, the pellets were charged in a stainless steel drum-type heating device and rotated at 10 rpm. The atmosphere in the reaction system was raised from room temperature to 150 ° C. under a small nitrogen flow. When the internal temperature of the reaction system reached 150 ° C, the pressure was reduced to 1 torr or less, and the internal temperature was further increased to 210 ° C in 110 minutes. From the time when the system temperature reached 210 ° C., the reaction was continued at the same temperature for 180 minutes. After completion of the reaction, the pressure reduction was terminated and the system temperature was lowered under a nitrogen stream. When the temperature reached 60 ° C., the pellets were taken out to obtain polyamide 2.
The obtained polyamide 2 had a relative viscosity of 2.7 and a melting point of 207 ° C.

B1: Modic AP-P565 (modified polyolefin MFR = 5.7, density = 0.89 manufactured by Mitsubishi Chemical Corporation).

C1: UBE nylon-1030B (Ube Industries, Ltd. nylon-6, relative viscosity = 4.1).
C2: UBE nylon-1024B (Ube Industries, Ltd. nylon-6, relative viscosity = 3.5).

D1: Novatec MG03E (Nippon Polypro Corp. polypropylene, random polymer, MFR = 30).

  The injection-molded article obtained in the present invention has excellent barrier properties, peel resistance, extrudability and moldability, and is suitable as a food / medicine container capable of processing liquid food such as beverages and soups and retort. is there.

Claims (8)

At least one barrier resin composition layer comprising 50 to 90% by weight of the barrier resin (A), 2 to 45% by weight of the modified polyolefin (B), and 2 to 45% by weight of the polyamide (C) other than the metaxylylene group-containing polyamide. And a multilayer injection molded article having at least one thermoplastic resin layer adjacent to the barrier resin composition layer . The multilayer injection molded article according to claim 1, wherein the barrier resin (A) is a metaxylylene group-containing polyamide. In the barrier resin (A), 70 mol% or more of the structural unit derived from diamine is derived from metaxylylenediamine, and 70 mol% or more of the structural unit derived from dicarboxylic acid is α, ω having 4 to 20 carbon atoms. The multilayer injection molded article according to claim 1, which is a polyamide derived from a dicarboxylic acid having a molar ratio of linear aliphatic dicarboxylic acid to isophthalic acid of 30:70 to 100: 0. The multilayer injection-molded article according to claim 1, wherein the modified polyolefin (B) is obtained by graft-modifying polyolefin with an unsaturated carboxylic acid or an anhydride thereof. The multilayer injection molded article according to claim 1, wherein the polyamide (C) is an aliphatic polyamide selected from nylon-6, nylon-66 and nylon-666. The multilayer injection-molded article according to claim 1, wherein the polyamide (C) is a polyamide having a relative viscosity of less than 5 when measured under the conditions of 96 mass% concentrated sulfuric acid as a solvent, a temperature of 25 ° C, and a concentration of 1 g / 100 ml. The multilayer injection-molded article according to claim 1, wherein the barrier resin composition layer is sandwiched between polyolefin layers. A multilayer stretch injection-molded product obtained by biaxially stretching blow-molding the multilayer injection-molded product according to claim 1.