Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1998-10-01
2001-05-15
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
active
06232382
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a saponified ethylene-vinyl acetate copolymer (i.e. ethylene-vinyl alcohol copolymer; hereinafter abbreviated as EVOH”) resin composition and a laminate having a layer of said resin composition.
PRIOR ART
EVOH is a resin very excellent in such properties as transparency, gas barrier property, aroma-retaining property, solvent resistance and oil resistance, among others. Making the best use of such characteristics, EVOH is molded into and used as films, sheets, or bottles or other containers for packaging foodstuffs, drugs, industrial chemicals, agrochemicals and the like.
EVOH is generally molded by melt molding and, by such molding, it is processed into such forms as films, sheets, bottles, cups, tubes, pipes and the like for putting to practical use. For EVOH, its molding processability (long-run moldability, appearance of moldings, etc.) is very important. In particular, in molding EVOH, it is often coextruded into laminates together with a substrate such as a polyolefin resin and an adhesive layer to provide the laminates with mechanical strength, moisture resistance and heat sealability, among others. Therefore, a low extent of odor emanation in the step of producing laminates from EVOH as well as interlayer adhesion is important.
Thus, in molding EVOH, the appearance of moldings (i.e. obtainability of moldings without fish eyes, striation or discoloration, among others), long-run processability in melt molding (i.e. obtainability of moldings without fish eyes or striation even in a long period of molding) and, further, low odor emanation from and interlayer adhesion of laminates should be fully satisfactory.
Various proposals have been made for improving the heat stability of EVOH. In Japanese Kokai Tokkyo Koho S51-91988, it is proposed that the sodium or potassium salt of an acid satisfying specific pKa conditions should be added. In Japanese Kokai Tokkyo Koho S56-41204, it is proposed that EVOH should contain calcium acetate or magnesium acetate in combination with a specific organic acid. In Japanese Kokai Tokkyo Koho S64-66262, an EVOH composition is proposed which contains a specific metal salt and two acidic substances and has a specific viscosity behavior. Japanese Kokai Tokkyo Koho H07-80954 describes an EVOH composition which contains a polymerization degree adjusting agent and satisfies a specific conditional formula concerning the change in viscosity average degree of polymerization in the step of heat treatment.
PROBLEMS WHICH THE INVENTION IS TO SOLVE
However, the market is demanding EVOH compositions of still higher quality. Detailed studies made by the present inventors have shown that the technologies disclosed in Japanese Kokai Tokkyo Koho's S51-91988, S56-41204 and H07-80954 still have room for improvement with respect to long-run moldability and that the technology disclosed in Japanese Kokai Tokkyo Koho S64-66262 shows a considerable improvement in long-run moldability but still has room for improvement concerning the odor of laminates and concerning interlayer adhesion.
OBJECTS OF THE INVENTION
Accordingly, it is an object of the present invention to provide an EVOH resin composition excellent in long-run moldability in the step of melt molding, hardly causing fish eye formation, striation, discoloration or the like, thus excellent in appearance characteristics, capable of giving laminates with reduced odor emanation and, further, excellent in interlayer adhesion. Another object is to provide a laminate having a layer of such resin composition.
SUMMARY OF THE INVENTION
The saponified ethylene-vinyl acetate copolymer (EVOH) resin composition of the present invention is a composition comprising a saponified ethylene-vinyl acetate copolymer (EVOH) (A) having an ethylene content of 20-60 mole percent and a saponification degree of not less than 90 mole percent, magnesium acetate or/and calcium acetate (B) as an essential component and at least one of acetic acid (C) a boron compound (D) and sodium acetate (E) as an optional component, and is characterized in that the contents of the respective components in said composition, relative to 100 parts by weight of EVOH (A), are as follows: magnesium acetate or/and calcium acetate (B) 0.001-0.02 part by weight on the metal basis; acetic acid (C) 0-0.05 part by weight; the boron compound (D) 0-1 part by weight on the boron basis; and sodium acetate (E) 0-0.1 part by weight on the metal basis; and that the weight loss when said composition is maintained at a temperature (T+70)° C. higher by 70° C. than the melting point T° C. of said EVOH (A) for 1 hour is not more than 10% by weight.
The laminate of the present invention is characterized in that a layer of a thermoplastic resin is disposed at least one side of a layer consisting of the EVOH resin composition mentioned above.
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention is described in detail.
In accordance with the present invention, the EVOH (A) to be used has an ethylene content of 20-60 mole percent (preferably 25-55 mole percent) and a saponification degree of not less than 90 mole percent (preferably not less than 95 mole percent). If the ethylene content is lower than 20 mole percent, the gas barrier property will be low under high moisture conditions and the melt moldability also will be low. If, conversely, the ethylene content exceeds 60 mole percent, satisfactory gas barrier properties will not be obtained. If the degree of saponification is lower than 90 mole percent, decreased gas barrier property, heat stability and moisture resistance will result, hence the objects of the present invention cannot be attained.
As the EVOH (A), two or more EVOH species differing in composition may be used. In this case, by using a blend of EVOH species differing in ethylene content by not less than 5 mole percent and/or in saponification degree by not less than 1 mole percent, the fabrication qualities such as drawability in high-degree drawing, vacuum pressure forming or deep draw forming qualities, among others, can further be improved while retaining the gas barrier properties.
The above-mentioned EVOH (A) preferably has a melt index (MI) (210° C., load 2160 g) of 0.1-100 g/10 minutes (in particular 0.5-50 g/10 minutes). If the melt index is below this range, the extruder inside will reaches a high torque state in the step of molding and therefore the extrusion processing becomes difficult. If it is larger than said range, the mechanical strength of moldings will be insufficient.
Such EVOH (A) can be obtained by saponification of an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer can be produced by any of the known polymerization processes, for example suspension polymerization, emulsion polymerization or solution polymerization, among others. The saponification of the ethylene-vinyl acetate copolymer can be performed by the well-known method.
The EVOH may be “modified by copolymerization” with a small amount of one or more other comonomers selected from among &agr;-olefins, unsaturated carboxylic acid compounds, unsaturated sulfonic acid compounds, (meth)acrylonitrile, (meth)acrylamide, vinyl ethers, vinylsilane compounds, vinyl chloride, styrene, polyoxyalkylene (meth)allyl ether, polyoxyalkylene (meth)acrylate, polyoxyalkylene (meth)acrylamide, polyoxyalkylene vinyl ether, polyoxyalkylene allylamine, polyoxyalkylene vinylamine and the like. It may be “post-modified” by urethane formation, acetalization or cyanethylation, for instance, within limits within which the effects of the present invention are not sacrificed.
In accordance with the present invention, the EVOH (A) contains, as an essential component, magnesium acetate or/and calcium acetate (B). In addition, it is preferred that it contain at least one of acetic acid (C), a boron compound (D) and sodium acetate (E) as an optional component.
The content of component (B), namely magnesium acetate or/and calcium acetate contained in EVOH (A) is 0.001-0.02 part by weight, preferably 0.0015-0.0
Kita Koji
Kunieda Makoto
Ninomiya Kenji
Armstrong Westerman Hattori McLeland & Naughton LLP
Michl Paul R.
Nippon Gohsei Kagaku Kogyo Kabushiki Kaisha
LandOfFree
Saponified ethylene-vinyl acetate copolymer resin... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Saponified ethylene-vinyl acetate copolymer resin..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Saponified ethylene-vinyl acetate copolymer resin... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2544450