Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
1998-05-20
2001-05-08
Mulcahy, Peter D. (Department: 1713)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S516000, C524S504000, C524S505000, C524S524000
Reexamination Certificate
active
06228504
ABSTRACT:
BACKGROUND OF THE INVENTION
1. (Field of the Invention)
This invention relates to an adhesive composition suitable for the production of a multilayered laminated body, and a laminated body using the above-mentioned adhesive composition.
More specifically, the present invention relates to a composition having excellent adhesiveness to a styrene-type resin layer and a layer of a saponified product of ethylene/vinyl acetate copolymer, and a laminated body equipped with a styrene-type resin layer, an adhesive composition layer, and a layer of a saponified product of ethylene/vinyl acetate copolymer.
2. (Description of the Prior Art)
Since a saponified product of an olefin/vinyl acetate copolymer (to be abbreviated as EVOH) typified by a saponified product of ethylene/vinyl acetate copolymer has excellent gas-barrier property, oil resistance and mechanical strength, but has high water permeability, it has a defect of being unable to be used singly as a food wrapping film or a molded container in which water is contained.
As a method of improving this defect, it has been proposed to laminate a styrene-type resin (to be abbreviated as PS) or a polyolefin-type resin having excellent water resistance. But since these resins do not contain a polar group, even when EVOH is directly laminated on the above resins, an interlayer adhesive force is very small and the resulting product cannot withstand practical use.
Various methods are available to improve the above defects. For example, methods of using a composition comprising an ethylene/vinyl acetate copolymer (to be abbreviated as EVA) and a tackifier are known (Japanese Laid-Open Patent Publication No. 129271/1978, Japanese Laid-Open Patent Publication No. 147733/1978, and Japanese Laid-Open Patent Publication No. 10384/1979).
Furthermore, Japanese Patent Publication No. 67813/1988 discloses a composition comprising an ethylene/vinyl acetate copolymer, a modified polyolefin copolymer, and a tackifier.
Japanese Laid-Open Patent Publication No. 72931/1993 discloses a composition comprising an ethylene/&agr;-olefin copolymer, a modified polyolefin copolymer and a tackifier.
However, in the field of adhesives, a further increase of adhesive force is required between a styrene-type resin and a saponified layer of an ethylene/vinyl acetate copolymer, and an increase in after-processability of an adhered laminated body is also required. The after-processability of the adhered laminated body means that when the laminated body is molded into a cup or a tray, an excellent adhesive force should be maintained, and when cutting is carried out, the cut portion can be cut sharply without threading or peeling.
Conventional adhesive compositions may exhibit excellent properties, but are not satisfactory in such a requirement.
SUMMARY OF THE INVENTION
The present inventors have extensively made investigations, and found that an adhesive composition comprising an ethylene/vinyl acetate copolymer, a modified ethylene/&agr;-olefin copolymer having a degree of crystallinity of not greater than 40%, a tackifier, and a styrene-type polymer meets the above requirement. This finding has led to the present invention.
It is an object of this invention to provide an excellent adhesive composition which has excellent adhesiveness to a styrene-type resin layer and a saponified layer of an ethylene/vinyl acetate copolymer, and also has excellent after-processability.
Another object of this invention is to provide a laminated body equipped with a styrene-type resin layer, an adhesive composition, and a saponified layer of an ethylene/vinyl acetate copolymer and a laminated body having excelllent interlayer adhesiveness and after-processability.
According to this invention, there is provided an adhesive resin composition comprising:
(A) 30 to 70 parts by weight of an ethylene/vinyl acetate copolymer,
(B) 0 to 50 parts by weight of an ethylene/&agr;-olefin copolymer having an ethylene content of 30 to 95 mole % and a degree of crystallinity by X-ray of not higher than 40%,
(C) 0 to 50 parts by weight of a modified ethylene/&agr;-olefin copolymer having an ethylene content of 30 to 95 mole % and a degree of crystallinity of not higher than 40% by X-ray,
(D) 0 to 30 parts by weight of modified polyethylene,
(E) 1 to 20 parts by weight of a tackifier, and
(F) 1 to 20 parts by weight of a styrene polymer,
wherein (B)+(C)=15 to 60%, (C)+(D)≧2% by weight, and (A)/[(B)+(C)]=0.5 to 3.
According to this invention, there is a laminated body in which the layer composed of the adhesive resin composition is formed between a styrene-resin layer and a saponified layer of an ethylene/vinyl acetate copolymer.
DETAILED DESCRIPTION OF THE INVENTION
The adhesive composition of this invention is prepared from (A) to (F), but is characterized in that the ethylene/vinyl acetate copolymer, a modified or unmodified lowly crystalline ethylene/&agr;-olefin copolymer, a modified polyethylene, a tackifier and a styrene-resin layer are combined in specified proportions. As a result, the adhesiveness to the styrene-type resin and the saponified layer of an ethylene/vinyl acetate copolymer can be markedly increased, and in addition, the after-processability of the laminated body formed can be improved.
Compounded Components
(A) Ethylene/vinyl acetate copolymer
The ethylene/vinyl acetate copolymer used in this invention is a known ethylene/vinyl acetate copolymer (EVA). Usually, this ethylene/vinyl acetate copolymer has a melt flow rate [MFR(E): ASTM D 1238.E] of 0.1 to 50 g/10 minutes, preferably 1 to 30 g/10 minutes, and a vinyl acetate content of 5 to 50% by weight, preferably 15 to 40% by weight, especially preferably 20 to 30% by weight. By using this ethylene/vinyl acetate copolymer, there can be obtained an adhesive resin composition having excellent extrusion moldability and adhesiveness.
(B) Ethylene/&agr;-olefin copolymer
The ethylene/&agr;-olefin copolymer (B) used in this invention is a random copolymer of ethylene and an &agr;-olefin having the following characteristics.
Melt flow rate [MFR (E): ASTM D 1238 .E]: 0.1 to 50 g/10 minutes, preferably 0.3 to 30 g/10 minutes.
Density: 0.850 to 0.900 g/cm
3
, preferably 0.850 to 0.890 g/cm
3
.
Ethylene content: 30 to 95 mole %, preferably 75 to 95 mole %, especially preferably 75 to 90 mole %.
Degree of crystallinity by X-ray: 40% or below, preferably 30% or below, especially preferably less than 25%.
If an ethylene/&agr;-olefin copolymer having the characteristic values within the above ranges is used, an adhesive resin composition having excellent adhesiveness can be obtained.
As the &agr;-olefin constituting such an ethylene/&agr;-olefin copolymer (B), &agr;-olefins containing 3 to 20 carbon atoms may be used. Specific examples of such &agr;-olefins include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene. These &agr;-olefins may be used singly or as mixtures of at least two monomers.
Such an ethylene/&agr;-olefin copolymer (B) has a melting point (ASTM D3418) of usually 100° C. or below.
(C) Modified ethylene/&agr;-olefin copolymer
The modified ethylene/&agr;-olefin copolymer (C) used in this invention is obtained by graft-reacting a monomer selected from unsaturated carboxylic acids or derivatives thereof. In the present invention, the graft-modified amount of the unsaturated carboxylic acids or derivatives thereof is usually 0.001 or 10% by weight, preferably 0.01 to 10% by weight, especially preferably 0.1 to 5% by weight, in the graft modified ethylene/&agr;-olefin copolymer.
The unsaturated carboxylic acids or the derivatives thereof may include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, Nadic acid® (endo-cis-bicyclo[2,2,1]hepto-5-ene-2,3-dicarboxylic acid), and the derivatives thereof, for example, acid halides, amides, imides, anhydride, and esters, specifically chlorinated maleanil, maleim
Kitahara Kouji
Sawada Yuji
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Mulcahy Peter D.
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