Compositions – Compositions containing a single chemical reactant or plural... – Organic reactant
Reexamination Certificate
2001-07-25
2003-11-18
Sergent, Rabon (Department: 1711)
Compositions
Compositions containing a single chemical reactant or plural...
Organic reactant
C252S182200, C252S182210, C528S028000, C528S049000, C528S069000
Reexamination Certificate
active
06649084
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a polyisocyanate curing agent for laminate adhesive, as well as to a laminate adhesive using the curing agent. More particularly, the present invention relates to a polyisocyanate curing agent for laminate adhesive, having a particular nonionic hydrophilic group, as well as to a laminate adhesive comprising the curing agent and an active hydrogen group-containing resin.
(2) Related Prior Art
Recently, as a packaging method, complex flexible packaging has been remarkably developed for reasons such as strength of package, protectability for goods packed, workability during packaging, propaganda effect of package, reduction of packaging cost caused by the use of a film supplied in a large amount at a low cost, and the like. In the complex flexible packaging, there is used a laminated film produced using an adhesive. The current main stream of such a laminate adhesive is a two-pack type polyurethane adhesive composed of a base resin having active hydrogen group and a curing agent having isocyanate group, because the two-pack type polyurethane adhesive is excellent in adhesivity, durability and heat resistance and further it can be widely applied to various kinds of films.
As such a laminate adhesive, there is disclosed in, for example, JP-A-5-112766, a solvent type two-pack adhesive comprising a hydrophilic group-containing polyurethane compound and a polyisocyanate compound. Also in JP-A-7-48429 is disclosed a hydrophilic group-containing, self-emulsifiable polyisocyanate composition and an aqueous adhesive composition using the polyisocyanate composition.
When the polyisocyanate compound described in JP-A-5-112766 is combined with the hydrophilic group-containing polyurethane compound (a base resin) described in the same literature, however, the resulting adhesive is insufficient in adhesivity to metal foils, metal-deposited films and polyolefin films. Further, the aqueous adhesive composition described in JP-A-7-48429 requires a large amount of energy for vaporizing the water contained therein.
Meanwhile, use of a coupling agent for adhesivity improvement is proposed in, for example, JP-A-63-110272. That is, in this literature is proposed a composite laminate adhesive composition comprising:
a polyol such as polyether polyol, polyester polyol, polyether urethane polyol, polyester urethane polyol or the like,
an isocyanate group-containing silane coupling agent, and
a polyisocyanate compound.
Owing to the diversification of eating habits in recent years, the quality requirements for the laminated films used for packaging of various foods have become higher, and, for example, resistance to severe retort treatment is required. The technique described in JP-A-63-110272, however, has been unable to provide a laminated film satisfying the above requirement.
SUMMARY OF THE INVENTION
The present invention aims at providing a polyisocyanate curing agent used in a laminate adhesive superior in storage stability, heat resistance, durability and adhesivity particularly to metallic films and polyolefin films; and a laminate adhesive using the curing agent.
The present invention lies in the following (1) to (4).
(1) A polyisocyanate curing agent for laminate adhesive, comprising:
(A) an isocyanate group-terminated prepolymer obtained by reacting an organic polyisocyanate containing at least (c) an aliphatic polyisocyanate and/or an alicyclic polyisocyanate, with (a) a block polyether monool represented by the following formula (1) wherein the oxypropylene group content is larger than the oxyethylene group content, and
(B) a silane coupling agent represented by the following formula (2).
(wherein R is an alkyl group having 1 to 5 carbon atoms, and m and n are each an integer of 1 or more).
OCN—(CH
2
)
r
—Si(OR′)
3
(2)
(wherein R′ is a methyl group or an ethyl group, and r is an integer of 1 to 5).
(2) A polyisocyanate curing agent for laminate adhesive, comprising:
(A′) an isocyanate group-terminated prepolymer obtained by reacting an organic polyisocyanate containing at least (c) an aliphatic polyisocyanate and/or an alicyclic polyisocyanate, with (a) a block polyether monool represented by the following formula (1) wherein the oxypropylene group content is larger than the oxyethylene group content and (b) an active hydrogen group-containing aliphatic compound other than the compound (a), and
(B) a silane coupling agent represented by the following formula (2).
(wherein R is an alkyl group having 1 to 5 carbon atoms, and m and n are each an integer of 1 or more).
OCN—(CH
2
)
r
—Si(OR′)
3
(2)
(wherein R′ is a methyl group or an ethyl group, and r is an integer of 1 to 5).
(3) A laminate adhesive comprising a polyisocyanate curing agent set forth in the above (1) and an active hydrogen group-containing resin.
(4) A laminate adhesive comprising a polyisocyanate curing agent set forth in the above (2) and an active hydrogen group-containing resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
In the present invention, the isocyanate group-terminated prepolymer (A) or (A′) can be obtained by reacting an organic polyisocyanate containing at least (c) an aliphatic polyisocyanate and/or an alicyclic polyisocyanate, with (a) a block polyether monool represented by the following formula (1) wherein the oxypropylene group content is larger than the oxyethylene group content by weight basis and, optionally, (b) an active hydrogen group-containing aliphatic compound other than the compound (a).
(wherein R is an alkyl group having 1 to 5 carbon atoms, and m and n are each an integer of 1 or more).
When in the block polyether monool (a) of the formula (1), R is an alkyl group having 6 or more carbon atoms, the polyisocyanate curing agent obtained from such a block polyether monool tends to give an adhesive low in adhesivity to adherend. When in the block polyether monool (a), the weight proportion of the oxyethylene group is larger than the weight proportion of the oxypropylene group, the resulting curing agent tends to give an adhesive low in water resistance.
The block polyether polyol (a) has a number-average molecular weight of preferably 800 or more, more preferably 800 to 5,000, particularly preferably 1,000 to 3,000. When the number-average molecular weight of (a) is smaller than the lower limit, the polyisocyanate curing agent obtained from (a) tends to give an adhesive low in adhesivity. When the number-average molecular weight of (a) is larger than the upper limit, the polyisocyanate curing agent obtained from (a) has an increased viscosity and tends to have lower workability.
The block polyether monool (a) can be obtained by a known method. That is, first, a monool and ethylene oxide are subjected to a ring-opening addition reaction to form a poly(oxyethylene)monool; then, the poly(oxyethylene)monool and propylene oxide are subjected to a ring-opening addition reaction.
As the monool as a starting material, there are preferably used aliphatic monools such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol and the like. Of these, methanol and ethanol are used more preferably.
In the present invention, it is possible to use, in combination with the block polyether monool (a), an active hydrogen group-containing aliphatic compound (b) other than (a) as necessary, in view of the affinity between curing agent and base resin and the adhesivity between different adherends.
As the active hydrogen group-containing aliphatic compound (b), there can be mentioned low-molecular monools such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, pentanol, hexanol, heptanol, octanol, 2-ethylhexanol, benzyl alcohol, alkylene glycol monoalkyl ether and the like; low-molecular primary monoamines such as ethylamine, butylamine and the like; low-molecular secondary monoamines such as diethylamine, dibutylamine and the like; active hydrogen group-containing polyes
Higashikubo Ichiro
Morikawa Yukihiro
Sasahara Toshiaki
Yoshida Kouji
Browdy and Neimark , P.L.L.C.
Nippon Polyurethane Industry Co., Ltd.
Sergent Rabon
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