Adhesive composition and adhesive composition-applied laminate

Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers

Reexamination Certificate

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Reexamination Certificate

active

06333119

ABSTRACT:

DETAILED DESCRIPTION OF THE INVENTION:
The present invention relates to an adhesive composition and a laminate formed by the application of the adhesive composition. More specifically, it relates to an adhesive composition which exhibits excellent processability and adhesion properties particularly when a saponification product of an ethylene/vinyl acetate copolymer is laminated on paper, and a laminate formed by the application of the adhesive composition.
When a saponification product of an ethylene/vinyl acetate copolymer is laminated on paper, it is conventional practice to use a composition containing a substantially linear, low-density polyethylene and a modified ethylene polymer as an adhesive.
However, the above composition is insufficient in adhesion to paper, and it is being desired to improve its adhesion properties.
The formation of a laminate is industrially advantageously carried out by a method in which an adhesive composition and, for example, a saponification product of an ethylene/vinyl acetate copolymer are co-extruded in such a manner that a layer of the adhesive composition is brought into contact with paper, whereby the saponification product, the adhesive composition and the paper are combined in this order. However, the above composition is liable to cause necking or wavy edges (periodical changes in width and thickness of the extruded film). In particular, when the extrusion rate increases, these phenomena occur to a greater extent, and these problems remain to be solved.
It is an object of the present invention to provide an adhesive composition.
It is another object of the present invention to provide an adhesive composition having improved adhesion properties particularly to paper.
It is further another object of the present invention to provide an adhesive composition which exhibits improved extrusion processability, i.e., remarkable improvement in the degrees of necking and wavy edges when it is co-extruded, for example, together with a saponification product of an ethylene/vinyl acetate copolymer.
It is still further another object of the present invention to provide a laminate formed by the application of the adhesive composition of the present invention.
Other objects and advantages of the present invention will be apparent from the following description.
According to the present invention, first, the above objects and advantages of the present invention are achieved by an adhesive composition comprising
(A) a substantially linear, low-density polyethylene,
(B) a high pressure low-density polyethylene,
(C) an ethylene-based polymer modified with an unsaturated carboxylic acid or a derivative thereof, the ethylene-based polymer being an ethylene homopolymer or a random copolymer formed from ethylene and an &agr;-olefin other than ethylene in which the &agr;-olefin makes up not more than 10 mol % based on the total molar amount of the ethylene and the &agr;-olefin, and
(D) a tackifier,
the amount of each of Components (A), (B), (C) and (D) being respectively 30 to 80% by weight, 1 to 50% by weight, 1 to 30% by weight and 1 to 30% by weight, based on the total amount of Components (A), (B), (C) and (D).
The adhesive composition of the present invention comprises four components, Components (A) to (D), as specified above.
The substantially linear, low-density polyethylene as Component (A) preferably has a density of not more than 0.94 g/cm
3
and a melt index value of 1 to 50 g/10 minutes. This linear, low-density polyethylene is a copolymer formed from ethylene and an &agr;-olefin, and the &agr;-olefin content is not more than 10 mol %. The &agr;-olefin is generally selected from those having 3 to 20 carbon atoms such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octane and 1-decene.
The high pressure low-density polyethylene as Component (B) preferably has a density of not more than 0.93 g/cm
3
and a melt index value of 0.1 to 50 g/10 minutes.
The ethylene-based polymer as Component (C) is a product obtained by modifying an ethylene homopolymer or a random ethylene/&agr;-olefin copolymer with an unsaturated carboxylic acid or a derivative thereof, the random ethylene/&agr;-olefin copolymer being formed from ethylene and &agr;-olefin other than ethylene in which the content of the &agr;-olefin based on the total molar amount of ethylene and the &agr;-olefin is not more than 10 mol %, preferably not more than 5 mol %.
Examples of the unsaturated carboxylic acid or the derivative thereof include unsaturated carboxylic acids such as acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid and Nadic acid (endo-cis-bicyclo[2,2,1]hept-5-ene2,3-carboxylic acid); or derivatives thereof such as acid halides, amides, imides, anhydrides and esters. Specific examples of the above derivatives include malenyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate and glycidyl maleate. Of these, particularly preferred are unsaturated dicarboxylic acids or anhydrides thereof, and particularly preferred are maleic acid, Nadic acid or anhydrides of these.
The random ethylene/&agr;-olefin copolymer before the modification is a random copolymer formed from ethylene and &agr;-olefin other than ethylene, in which the content of the &agr;-olefin based on the total molar amount of ethylene and the &agr;-olefin is not more than 10 mol %.
The &agr;-olefin other than ethylene is preferably selected from &agr;-olefins having 3 to 20 carbon atoms such as propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-tetradecene and 1-octadecene. These &agr;-olefins may be used alone or in combination.
The above &agr;-olefin makes up not more than 10 mol %, preferably not more than 5 mol %, of the total molar amount of ethylene and the &agr;-olefin which form the random copolymer.
When the amount of the &agr;-olefin exceeds 10 mol %, undesirably, blocking occurs due to stickiness, and it is difficult to handle the copolymer.
The ethylene-based polymer modified with an unsaturated carboxylic acid or a derivative thereof as Component (C) is that which is graft-modified with preferably 0.05 to 15% by weight, more preferably 0.1 to 10% by weight, based on the ethylene-based copolymer before the modification, of an unsaturated carboxylic acid or a derivative thereof.
Further, the modified ethylene-based polymer as Component (C) preferably exhibits a melt flow rate (MFR), measured according to ASTM D1238 (190° C., a load of 2,160 g), of 0.1 to 50 g/10 minutes, and more preferably, 0.3 to 30 g/10 minutes.
The tackifier as Component (D) is preferably a solid amorphous polymer, and is selected from those which are usually used as a tackifier resin in the fields of adhesive tapes, coating compositions and hot melt adhesives.
The tackifier is exemplified as below depending upon a difference in monomer sources which are polymerized. For example, the tackifier includes aliphatic hydrocarbon resins formed mainly from C
4
fractions, C
5
fractions, mixtures of these, which are obtained by decomposition of petroleum and naphtha, e.g., isoprene and 1,3-pentadiene contained in C
5
fractions; aromatic hydrocarbon resins formed mainly from an styrene derivative and indenes contained in C
9
fractions obtained by decomposition of petroleum and naphtha; an aliphatic aromatic hydrocarbon resin obtained by copolymerization of a C
9
fraction and either or both of C
4
and C
5
fractions; an alicyclic hydrocarbon resin obtained by hydrogenation of an aromatic hydrocarbon resin; a synthetic terpene hydrocarbon resin having a structure containing aliphatic, alicyclic and aromatic moieties; a terpene hydrocarbon resin formed from &agr;,&bgr;-pinenes contained in terpene oil; a cumarone-indene hydrocarbon resin formed from indene and styrenes contained in coal tar; a low molecular weight styrene resin; and a rosin hydrocarbon resin.
The adhesive composition of the present invention contains, based on the total amount of Components (A) to (D), 30 to 80% by we

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