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Injection molded body having excellent barrier property

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20120263962 patent thumbnailZoom

Injection molded body having excellent barrier property


An injection molded article comprising: (A) 10 to 60% by mass of a polyamide resin comprising a diamine unit 70 mol % or more of which is one or more m-xylylenediamine units and a dicarboxylic acid unit 70 mol % or more of which is one or more dicarboxylic acid units comprising a C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0; and (E) 40 to 90% by mass of a mixed polyolefin comprising (C) 40 to 100% by mass of a polyolefin and (B) 0 to 60% by mass of a modified polyolefin, wherein at least a part of the polyamide resin (A) is dispersed in a layered state.

Browse recent Mitsubishi Gas Chenical Company, Inc. patents - Chiyoda-ku, JP
Inventors: Kazunobu Sato, Katsuya Maruyama
USPTO Applicaton #: #20120263962 - Class: 4284769 (USPTO) - 10/18/12 - Class 428 
Stock Material Or Miscellaneous Articles > Composite (nonstructural Laminate) >Of Polyamide >Next To Addition Polymer From Unsaturated Monomer(s) >Polymer Of Monoethylenically Unsaturated Hydrocarbon

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The Patent Description & Claims data below is from USPTO Patent Application 20120263962, Injection molded body having excellent barrier property.

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CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims the benefits of priority to U.S. Ser. No. 13/252,302, filed Oct. 4, 2011, which is a continuation of and claims the benefit of priority to U.S. Ser. No. 12/446,111, filed Apr. 17, 2009, which is a national stage of International Application No. PCT/JP2007/070432, filed Oct. 19, 2007. The contents of these applications are incorporated herein by reference in their entireties. The International Application is based on and claims the benefits of priority to Japanese Patent Application Nos. 2006-284766, 2006-284767 and 2007-038070.

TECHNICAL FIELD

The present invention relates to injection-molded articles having excellent barrier property and appearance, etc., and more particularly to multilayer injection molded articles that are excellent in barrier property, appearance, delamination resistance, heat resistance, etc., and single-layer injection-molded articles that are excellent in barrier property, appearance, etc.

BACKGROUND ART

Injection molding has been widely spread and used in various applications such as mechanical parts, automobile parts, electric and electronic parts and containers for food and drugs because it is capable of producing molded articles having a complicated shape with a high productivity. In particular, containers for beverages, etc., have been frequently constructed from an injection molded article because a mouth portion of these containers is formed into an excellent threaded shape in order to ensure sufficient tightening of a cap thereon.

As the material for injection molding articles, there have been used various general resins including polyolefins such as polyethylene and polypropylene, polyesters and polystyrenes. Of these resins, polyolefins such as polypropylene have been extensively used in various applications such as containers because they are excellent in flowability and heat resistance upon molding as well as exhibit a light weight and a low moisture absorption and are available at low costs.

However, the polyolefins tend to be deteriorated in barrier property against gases such as oxygen and are, therefore, unsuitable as containers for preserving contents that are apt to be adversely affected by oxygen, etc., or as containers for food or drugs which are required to exhibit a good keeping property under severe environmental conditions such as high-temperature conditions. In consequence, there are disclosed methods in which a barrier material such as polyamides is blended in the polyolefins to improve a barrier property of the polyolefins (refer to Patent Documents 1 and 2).

These methods might improve a barrier property of the polyolefins to some extent. However, the barrier material to be blended must be dispersed in the polyolefins in a specific condition, so that the polyolefins tend to be improved in barrier property only to an insufficient extent. In addition, these methods also have such a problem that molded articles obtained from the resin mixture tend to have a poor appearance owing to the polyamides that are locally present near a surface thereof. More specifically, the method of the Patent Document 1 requires a biaxial stretch blow molding procedure, and the molded articles obtained without conducting the biaxial stretch blow molding procedure tend to be deteriorated in barrier property. Whereas, the Patent Document 2 discloses the composite molded article made of a polyolefin matrix and an amorphous polyamide in the form of a plurality of masses dispersed in the polyolefin, but is silent about crystalline polyamides and polyamides having a m-xylylene skeleton.

Upon producing a molded article having a multilayer structure including polyolefin layers and a barrier layer by injection molding method, since a material for the barrier layer exhibit no adhesion to the polyolefin layers, the molded article is required to have, for example, a structure having at least five layers, i.e., a layer structure of polyolefin layer/adhesive layer/barrier layer/adhesive layer/polyolefin layer. The production of the molded article having such a multilayer structure tends to be accompanied with difficulties in view of its structure and moldability and, therefore, has been rarely practiced from industrial viewpoints. In consequence, there is disclosed a method in which a polyolefin is compounded with a modified polyolefin to enhance adhesion of a polyolefin layer to a barrier layer and necessitate no adhesive layer therebetween (refer to Patent Document 3). The method of the Patent Document 3 improves adhesion between the polyolefin layer and barrier layer, but requires a large amount of the expensive modified polyolefin to ensure sufficient adhesion between these layers. In addition, this method has such a problem that the resulting molded article tends to be deteriorated in heat resistance owing to addition of the modified polyolefin thereto.

The present inventors have previously proposed the polyamide resin obtained by polycondensation of a diamine component containing 70 mol % or more of m-xylylenediamine and a mixed dicarboxylic acid component containing an α,ω-linear aliphatic dicarboxylic acid and isophthalic acid (refer to Patent Document 4). The polyamide resin exhibits an excellent barrier property. However, it has been still required that a multilayer injection molded article produced using the polyamide resin is further improved in delamination resistance. Patent Document 1: JP 2004-292037A Patent Document 2: JP 2005-8664A Patent Document 3: JP 2006-131275A Patent Document 4: JP 2004-352985A

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

An object of the present invention is to solve the above conventional problems encountered in containers obtained by injection molding, and provide a multilayer injection molded article that is excellent in barrier property, appearance, delamination resistance and heat resistance, as well as a single-layer injection molded article that is excellent in barrier property, appearance, etc., which is capable of being produced in an economically advantageous manner.

Means for Solving the Problem

As the result of extensive and intensive researches for achieving the above object, the present inventors have found that the object is suitably achieved by a multilayer injection molded article including a resin layer composed of a specific polyamide resin and a modified polyolefin or a resin layer composed of the polyamide resin, the modified polyolefin and the other polyamide resin as a barrier layer, or by an injection molded article in which the above specific polyamide resin is dispersed in a layered state in a mixed polyolefin. The present invention has been accomplished on the basis of the above finding.

Thus, the present invention relates to the injection molded articles as described in the following aspects.

1. An injection molded article with a multilayer structure including at least one layer of a barrier resin composition including (A) 10 to 70% by mass of a polyamide resin including a diamine constitutional unit 70 mol % or more of which is derived from m-xylylenediamine and a dicarboxylic acid constitutional unit 70 mol % or more of which is derived from a dicarboxylic acid containing a C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0; (B) 90 to 30% by mass of a modified polyolefin; and (C) 0 to 50% by mass of a polyolefin.

2. An injection molded article with a multilayer structure including at least one layer of a barrier resin composition including (A) 50 to 90% by mass of a polyamide resin including a diamine constitutional unit 70 mol % or more of which is derived from m-xylylenediamine and a dicarboxylic acid constitutional unit 70 mol % or more of which is derived from a dicarboxylic acid containing a C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0; (B) 2 to 45% by mass of a modified polyolefin; and (D) 2 to 45% by mass of a m-xylylene group-free polyamide (D).

3. An injection molded article including (A) 10 to 60% by mass of a polyamide resin including a diamine constitutional unit 70 mol % or more of which is derived from m-xylylenediamine and a dicarboxylic acid constitutional unit 70 mol % or more of which is derived from a dicarboxylic acid containing a C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0; and (E) 40 to 90% by mass of a mixed polyolefin including (C) 40 to 100% by mass of a polyolefin and (B) 0 to 60% by mass of a modified polyolefin, wherein at least a part of the polyamide resin (A) is dispersed in a layered state.

4. The injection molded article according to the above aspect 1 or 2, wherein the polyamide resin (A) has a relative viscosity of 2.5 or more as measured at 25° C. in 96% by mass concentrated sulfuric acid as a solvent with a concentration of 1 g/100 mL.

5. The injection molded article according to any one of the above aspects 1 to 3, wherein the modified polyolefin (B) is obtained by graft-modifying the polyolefin (C) with an unsaturated carboxylic acid or an anhydride thereof.

6. The injection molded article according to the above aspect 2, wherein the m-xylylene group-free polyamide (D) is an aliphatic polyamide selected from the group consisting of nylon-6, nylon-66 and nylon-666.

7. The injection molded article according to the above aspect 2, wherein the m-xylylene group-free polyamide (D) is an aliphatic polyamide having a relative viscosity of less than 5 as measured at 25° C. in 96% by mass concentrated sulfuric acid as a solvent with a concentration of 1 g/100 mL.

8. The injection molded article according to the above aspect 1 or 2, wherein the article has a multilayer structure in which the layer of the barrier resin composition is sandwiched between thermoplastic resin layers (F) each made of a polyolefin.

9. The injection molded article according to the above aspect 1 or 2, wherein the article is in the form of a multilayer stretched injection molded article obtained by subjecting a multilayer injection molded article to biaxial stretch blow molding.

Effect of the Invention

The injection molded article with a multilayer structure according to the above aspect 1 of the present invention (hereinafter occasionally referred to merely as the “multilayer injection molded article I”) and the injection molded article with a multilayer structure according to the above aspect 2 of the present invention (hereinafter occasionally referred to merely as the “multilayer injection molded article II”) are excellent in barrier property, delamination resistance, heat resistance and appearance. In particular, the multilayer injection molded articles I and II are prevented from suffering from delamination between a barrier resin layer and adjacent layers even when exposed to severe impact upon transportation or drop thereof, are capable of avoiding occurrence of the delamination even though they are not formed into such a shape having less irregular and flexed portions, and therefore exhibit a large freedom of design.

The injection molded article according to the above aspect 3 of the present invention (hereinafter occasionally referred to merely as the “single-layer injection molded article”) is excellent in barrier property and appearance, and can be produced in an economically advantageous manner.

Therefore, the multilayer injection molded articles I and II and the single-layer injection molded article are suitably used as containers for liquid food such as beverages and soups or for food and drugs capable of being subjected to retort treatment, etc.

BEST MODE FOR CARRYING OUT THE INVENTION

The polyamide resin (A) used in the multilayer injection molded articles I and II and the single-layer injection molded article according to the present invention includes a diamine constitutional unit and a dicarboxylic cid constitutional unit in which 70 mol % or more of the diamine constitutional unit is derived from m-xylylenediamine, and 70 mol % or more of the dicarboxylic acid constitutional unit is derived from a dicarboxylic acid containing a C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0.

The multilayer injection molded articles I and II of the present invention includes at least one layer of a barrier resin composition containing the polyamide resin (A) as a main component, and preferably has such a multilayer structure in which the layer of the barrier resin composition is sandwiched between thermoplastic resin layers (E) each made of a polyolefin.

The single-layer injection molded article of the present invention has such a structure in which at least a part of the polyamide resin (A) is dispersed in a layered state in a molded body containing a polyolefin (C).

Examples of diamines other than m-xylylenediamine which may be used as a raw material for production of the polyamide resin (A) include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methyl pentane diamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine and 2,4,4-trimethyl-hexamethylenediamine; alicyclic diamines such as 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 (including structural isomers thereof) and bis(aminomethyl)tricyclodecane (including structural isomers thereof); and aromatic ring-containing diamines such as bis(4-aminophenyl)ether, p-phenylenediamine, p-xylylenediamine and bis(aminomethyl)naphthalene. These diamines other than m-xylylenediamine may be used in an amount of 30 mol % or less on the basis of the whole diamine components.

Examples of the C4 to C20 α,ω-linear aliphatic dicarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, adipic acid, sebacic acid, undecanedioic acid and dodecandioic acid. Of these acids, especially preferred is adipic acid.

The molar ratio of the C4 to C20 α,ω-linear aliphatic dicarboxylic acid to isophthalic acid in the mixed dicarboxylic acid is from 30:70 to 100:0, preferably from 30:70 to 95:5, more preferably from 40:60 to 95:5 and still more preferably from 60:40 to 90:10. When using the mixed dicarboxylic acid containing isophthalic acid in the above specified range, the resulting polyamide resin is enhanced in barrier property. In addition, the polyamide resin produced by using the mixed dicarboxylic acid not only has a lower melting point, is shaped at a lower temperature, and is therefore capable of being produced with a less energy and shortened in molding cycle, but also exhibits a higher melt viscosity and is therefore improved in moldability without occurrence of drawdown of the resin, etc., as compared to the polyamide resin produced from the C4 to C20 α,ω-linear aliphatic dicarboxylic acid solely.

Examples of dicarboxylic acids other than the C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid which may be used as a dicarboxylic acid component of the polyamide resin (A) in the present invention include phthalic acid compounds such as terephthalic acid and orthophthalic acid; naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalene dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalene dicarboxylic acid, 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid; monocarboxylic acids such as benzoic acid propionic acid and butyric acid; polycarboxylic acids such as trimellitic acid and pyromellitic acid; carboxylic acid anhydrides such as trimellitic anhydride and pyromellitic anhydride.

In the polyamide resin (A) used in the present invention, the content of the constitutional unit derived from these dicarboxylic acids other than the C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid is in the range of 30 mol % or less on the basis of the whole dicarboxylic acid constitutional units.

The polyamide resin (A) is produced by polycondensing a diamine component containing m-xylylenediamine in an amount of 70 mol % or more with a dicarboxylic acid component containing the mixed dicarboxylic acid composed of the C4 to C20 α,ω-linear aliphatic dicarboxylic acid and isophthalic acid at a molar ratio of from 30:70 to 100:0, in an amount of 70 mol % or more. The production method is not particularly limited. The polyamide resin (A) may be produced by conventionally known methods such as atmospheric melt polymerization and pressure melt polymerization.

For example, the polyamide resin (A) may be produced by heating a nylon salt produced from m-xylylenediamine and adipic acid or from m-xylylenediamine, adipic acid and isophthalic acid under pressure in the presence of water, and polymerizing the nylon salt while being kept in a molten state and removing water added and condensed water produced, from the reaction system. Alternatively, the polyamide resin (A) may be produced by directly adding m-xylylenediamine to adipic acid or a mixture of adipic acid and isophthalic acid which is kept in a molten state, and polycondensing these compounds with each other under normal pressures. In the latter method, in order to prevent the reaction system from being solidified, m-xylylenediamine is continuously added to the dicarboxylic acid component, and the polycondensation reaction therebetween proceeds while heating the reaction system to keep the reaction temperature during the addition at such a temperature not lower than melting points of oligoamides and polyamides produced.

Upon the polycondensation for production of the polyamide resin (A), lactams such as ε-caprolactam, ω-laurolactam and ω-enanthlactam, amino acids such as 6-aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, 9-aminononanoic acid and p-aminomethylbenzoic acid, etc., may be added to the polycondensation reaction system unless the addition thereof adversely affects the properties of the obtained polyamide resin.

The polyamide resin (A) is preferably further subjected to heat treatment after the above polycondensation to enhance a melt viscosity thereof. The heat treatment may be conducted, for example, by a method in which the polyamide resin is gently heated in the presence of water in an inert gas atmosphere or under reduced pressure using a batch type heater such as a rotary drum and crystallized while avoiding fusion thereof, followed by subjecting the resulting resin to further heat treatment; a method in which the polyamide resin is heated and crystallized in an inert gas atmosphere using a groove type stirring heater, and then the resulting resin is heat-treated in an inert gas atmosphere using a hopper-shaped heater; or a method in which the polyamide resin is crystallized using a groove type stirring heater, and then the resulting resin is heat-treated using a batch type heater such as a rotary drum. Among these methods, preferred is the method in which the crystallization and heat treatment are conducted using the batch type heater. The conditions of the treatments are preferably controlled such that the polyamide resin (A) obtained by the melt polymerization is heated from 70° C. to 120° C. over 0.5 to 4 h in the presence of water in an amount of 1 to 30% by mass based on the polyamide resin and crystallized, and then further heat-treated at a temperature of from [melting point of polyamide resin (A)-50° C.] to [melting point of polyamide resin (A)-10° C.] over 1 to 12 h in an inert gas atmosphere or under reduced pressure.

The polyamide resin (A) used in the multilayer injection molded articles I and II preferably has a relative viscosity of 2.5 or more and more preferably 3 or more as measured at 25° C. in 96% by mass concentrated sulfuric acid as a solvent with a concentration of 1 g/100 mL. When the relative viscosity of the polyamide resin (A) is less than 2.5, the polyamide resin (A) tends to be insufficient in adhesion property, thereby causing delamination of the resulting article.

The polyamide resin (A) used in the single-layer injection molded article preferably has a relative viscosity of 2.5 or less and more preferably 2.3 or less as measured under the same conditions as described above. When the relative viscosity of the polyamide resin (A) is more than 2.5, the polyamide resin (A) tends to be insufficient in barrier property.

The melting point of the polyamide resin (A) used in the multilayer injection molded articles I and II and the single-layer injection molded article of the present invention is preferably controlled to a temperature range of from 160 to 240° C., more preferably from 170 to 235° C. and still more preferably from 180 to 230° C.

Meanwhile, when the melting point of the polyamide resin (A) used in the multilayer injection molded article I is controlled to be close to the melting point of the modified polyolefin (B) or the polyolefin (C), it is possible to prevent occurrence of defects such as unevenness in thickness owing to difference in molding temperature between resins upon production of the multilayer molded article, or suppress generation of off-odor and undesirable coloration owing to deterioration of the resins.



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stats Patent Info
Application #
US 20120263962 A1
Publish Date
10/18/2012
Document #
13531825
File Date
06/25/2012
USPTO Class
4284769
Other USPTO Classes
International Class
32B27/08
Drawings
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