Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2002-02-26
2004-12-21
Yao, Sam Chuan (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S331700, C156S332000, C156S324000, C524S589000, C528S052000
Reexamination Certificate
active
06833044
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a solvent-free curable adhesive composition and a process of lamination with use of the adhesive composition. In further detail, the present invention relates to a solvent-free two-component curable adhesive composition for lamination useful in producing materials for packaging food, necessaries of life, and others, and to a process of lamination.
BACKGROUND OF THE INVENTION
Currently, composite laminated films have been widely used in the field of packaging materials, and these composite films are produced by bonding various plastic films and metal foil, and others by using an adhesive. As the adhesive for lamination, an organic solvent-based two-component curable adhesive comprising a mixture of an organic polyisocyanate compound and a polyester polyol, a polyether polyol, a polyurethane polyol or any mixture of these polymers has been used.
However, in recent years, for improving working environment and regulation of the use of solvents, the organic solvent-based adhesives have been replaced gradually with solvent-free adhesives in the production of composite laminated films. As such solvent-free adhesives for lamination, an adhesive composition comprising a polyol component and a polyisocyanate component has been used.
Composite laminated films using solvent-free adhesive compositions are produced with use of a laminator (for a solvent-free adhesive). A process for producing composite laminated films with use of the laminator is illustrated with referring to FIG.
1
.
A polyol component and a polyisocyanate component are usually supplied from tanks
1
and
2
, respectively, and the components are mixed by a mixer
3
before the components reach at coating part (area) of a laminator. The resultant adhesive
4
is supplied between a doctor roll
5
and a metering roll
6
which are rotated in the opposite direction each other. The adhesive
4
is transferred from the metering roll
6
to a coating roll
7
, and is coated on a film
9
which is supplied between the coating roll
7
and a impression roll
8
. The film
9
on which the adhesive is coated, and the other film
10
are supplied between a laminating roll
11
and a nip roll
12
, to bond or adhere the coating surface of the film
9
with the film
10
, and then rolled up by a winding unit to produce a composite laminated film
13
having two layers structure. Furthermore, if necessary, a composite laminated film composed of three or more layers may be sometimes produced in the same manner. The respective shapes of coating parts of the doctor roll
5
, the metering roll
6
and the coating roll
7
and the impression roll
8
are different depending on equipment, and this figure shows just one embodiment thereof.
The conventional solvent-free adhesives, depending on the laminating conditions, is liable to cause deterioration (detraction) of the external appearance due to unevenness of coating surface caused by forcibly peeling the coating layer on the film
9
from the coating roll
7
or non-uniformity of thickness of the coated adhesive. In particular, there has propensity to cause deterioration of the external appearance when laminating at high speed and laminating a film having high rigidity such as polyethylene terephthalate film and others. Thus, a low coating speed (e.g., 100 m/minute or less of a lamination speed) is required, and causes reduction in working efficiency.
Moreover, in the case of lamination with the conventional solvent-free adhesives by a laminator, in most cases, foam comes to be contained in the adhesive accumulated between the doctor roll
5
and the metering roll
6
, the foam is transferred to the coating layer as such on the film, and the film is laminated. As a result, in most cases, the initial external appearance of the composite laminated film makes worse.
Moreover, usually, for accelerating reaction of an isocyanate group with a hydroxyl group and improving conformability of the adhesive to the film after lamination as well, the composite laminated film often allows to warm at 30 to 60° C. for one or more days (hereinafter, referring as aging (or aging step)). However, when the external appearance of the film at the time immediately after lamination deteriorates and remarkably differs from that of the film at the time after aging step, quality (appearance) of the composite laminated film as the final product obtained from aging step can not be evaluated (imaged) immediately after laminating step. Furthermore, as a lamination speed is faster, large foam generated in the film remains intact. Part of the foam remains without disappearance even after aging step, as a result, deterioration of the external appearance sometimes occurs in the film.
On the other hand, a coating amount and an initial adhesive strength (or adhesive properties) depend on the viscosity of the solvent-free adhesive. Thus, for overcoming the above-mentioned problems, if the viscosity of the adhesive allows lower, it becomes difficult to keep an amount of coating and the initial adhesive strength. As a result, there has propensity to deteriorate the external appearance due to blur and tunneling (embossment) to the composite laminated film, and there has propensity to delaminate if three or more layer are laminated.
Japanese Patent Application Laid-open No. 181393/1999 (JP-11-181393A) discloses a solvent-free two-component curable adhesive composition comprising a hydroxyl group-containing compound such as a crystalline polymer polyol, and an isocyanate-containing compound, wherein a mixture of both compounds is solid or semisolid state. Even if the adhesive composition is used, however, when a film having high rigidity is laminated at high speed, the external appearance of the composite laminated film is remarkably deteriorated.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a solvent-free curable adhesive composition (a solvent-free two-component curable adhesive composition) capable of producing a composite laminated film having the superior external appearance simply and efficiently, and a process of lamination using such a adhesive composition.
It is another object of the present invention to provide a solvent-free two-component curable adhesive composition capable of having an improved initial adhesive strength, and a process of lamination using such a adhesive composition.
It is further another object of the present invention to provide a solvent-free two-component curable adhesive composition and a process of lamination capable of producing a composite laminated film having the good external appearance at the time both immediately after lamination and after aging step, even when laminating at high speed or laminating with a film having high rigidity such as polyethylene terephthalate.
The inventors of the present invention made intensive studies to achieve the above objects, and finally found that use of a component containing a specific crystalline polyol component at certain ratio as a polyol component and/or a polyisocyanate component enables to produce a composite laminated film having high initial adhesive strength and having superior appearance even when laminated at high speed simply. The present invention was accomplished based on the above findings.
That is, the solvent-free two-component curable adhesive composition of the present invention comprises (A) a polyol component and (B) a polyisocyanate component, wherein at least one component of the components (A) and (B) comprises at least one polyol component having crystallinity at room temperature and selected from the group consisting of a polyester polyol, a polyether polyol, a polycarbonate polyol and a polyurethane polyol, and an amount of the crystalline polyol component is 3 to 50% by weight (particularly, 3 to 45% by weight) relative to the total weight of the components (A) and (B). The polyol component may be crystalline, or the crystalline polyol component may be contained in the polyol component and/or the isocyanate component as a constru
Imai Akihiro
Imamura Kazuaki
Morimoto Taiji
Mitsui Takeda Chemicals Inc.
Wenderoth , Lind & Ponack, L.L.P.
Yao Sam Chuan
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