Resin composition of good long-run workability comprising ethylene-vinyl alcohol copolymer

Abstract

Disclosed are a resin composition comprising an ethylene-vinyl alcohol copolymer and a multi-layered structure comprising the resin composition. The resin composition comprises an ethylene-vinyl alcohol copolymer, and is characterized in that, when it is heated in a nitrogen atmosphere at 220° C., its MFR (at 230° C. under a load of 10.9 kg) shows a minimum value within 10 hours after the start of heating it, and shows a maximum value (MFRmax) within 100 hours after showing its minimum value, that it contains from 0.05 to 4 μmols / g of a carboxylic acid (A), and that it satisfies the following formulae (1) and (2): 0.5≦MFRmax / MFR0≦45   (1) 0.1≦(a1) / (A)≦1.0   (2) wherein MFRmax indicates the maximum value of MFR (at 230° C. under a load of 10.9 kg) of the resin composition heated in a nitrogen atmosphere at 220° C.; MFR0 indicates MFR (at 230° C under a load of 10.9 kg) of the resin composition not heated; (A) indicates the total content (μmol / g) of the carboxylic acid (A) and its salt in the resin composition; (a1) indicates the content (μmol / g) of a carboxylic acid (a1) having a molecular weight of at least 75 and its salt in the resin composition. The resin composition has good interlayer adhesiveness when fabricated into laminates, and its moldings are yellowed little and have good appearances with few fish eyes (gels or hard spots) and streaks. While molded in melt, the resin composition ensures good long-run workability not smelling so much, and when recycled, it is yellowed little.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a resin composition comprising an ethylene-vinyl alcohol copolymer (EVOH) and a multi-layered structure comprising the resin composition. The resin composition has good interlayer adhesiveness when fabricated into laminates, and its moldings are yellowed little and have good appearance with few fish eyes (gels or hard spots) and streaks. While molded in melt, the resin composition ensures good long-run workability, and when recycled, it is yellowed little. [0003] 2. Description of the Related Art [0004] EVOH is a useful polymer material having good oxygen barrier properties, oil resistance, antistatic properties and mechanical strength, and is widely used for various wrapping and packaging materials such as films, sheets, containers, etc. Such wrapping and packaging materials are generally produced by molding polymers in melt. Therefore, the polymers for them are required to have goo...

AI Technical Summary

Benefits of technology

[0124] Of those, preferred is the method of dipping EVOH in a solution of the additive compounds for more favorably ensuring the effect of the invention. The treatment for the method may be effected in any mode of batch operation or continuous operation. For the treatment, the morphology of EVOH is not limited, including, for example, powders, granules, spherical pellets, columnar pellets, etc.

[0125] In the method where EVOH is dipped in a solution containing a carboxylic acid (A) and optionally an alkali metal salt (B), an alkaline earth metal salt (C), a phosphate compound (D) and a boron compound (E), the concentration of the carboxylic acid (A) and optionally alkali metal salt (B), alkaline earthmetal salt (C), phosphate compound (D) and boron compound (E) to be in the solution is not specifically defined. The solvent for the solution is also not specifically defined. In view of its handlability, preferred is an aqueous solution. The dipping time will vary, depending on the morphology of EVOH, but is preferably not shorter than 1 hour, more preferably not shorter than 2 hours, for EVOH pellets having a size of from 1 to 10 mm or so.

[0126] Regarding the dipping treatment of EVOH in the solution of the compounds, EVOH may be dipped in a plurality of different solutions separately containing any of the compounds, or may be dipped in one solution containing all the compounds. In particular, especially preferred is dipping EVOH in one solution containing all of a carboxylic acid (A) and optionally an alkali metal salt (B), an alkaline earth metal salt (C), a phosphate compound (D) and a boron compound (E), as the treatment in that manner is simple. After having been dipped in the solution, EVOH is finally dried and the intended EVOH composition is thus obtained.

[0127] The EVOH resin composition obtained in the above manner is molded in melt into various moldings such as films, sheets, containers, pipes, fibers, etc. The moldings can be recycled by grinding and re-molding them. The films, sheets and fibers of the composition may be uniaxially or biaxially stretched. For molding the composition in melt, employable is any mode of extrusion, inflation extrusion, blow molding, melt spinning, injection molding, etc. The temperature at which the resin composition is melted varies, depending on the melting point of EVOH in the composition, but preferably falls between 150 and 270° C. or so.

[0128] The EVOH resin composition of the invention may be molded into single-layered moldings of the composition alone, but, in practical use, it is often molded into multi-layered structures comprising at least one layer of the composition in which the layer of the composition may be in any form of film, sheet or the like. The layer constitution of the multi-layered structures includes, for example, E / Ad / T, T / Ad / E / Ad / T, etc., in which E indicates the EVOH resin composition of the invention, Ad indicates an adhesive resin, and T indicates a thermoplastic resin. However, these are not limitative. In the multi-layered structures, each layer may be single-layered, or, as the case may be, multi-layered.

[0129] The method of producing the multi-layered structures as above is not specifically defined. For example, employable are a method of melt-extruding a thermoplastic resin onto a molding (e.g., film, sheet, etc.) of the EVOH resin composition; a method of co-extruding the EVOH resin composition along with any other thermoplastic resin, etc.; a method of co-injecting the EVOH resin composition along with any other thermoplastic resin; a method of laminating films or sheets of a molding of the EVOH resin composition and any other substrate via a known adhesive of, for example, organotitanium compounds, isocyanate compounds, polyester compounds and the like, therebetween. Of those, preferred is the method of co-extruding the EVOH resin composition along with any other thermoplastic resin.

Problems solved by technology

In the related art disclosures (1) to (5), however, no one can find out an EVOH composition satisfying all the necessary requirements of long-run workability in melt molding, good appearance of moldings, recyclability, yellowing resistance in recycling, and interlayer adhesiveness in laminates.

Highly functional EVOH moldings of high quality are needed these days, but, at present, none of known moldings are on the satisfactory level that meets the requirements.

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