Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-12
2004-09-21
Sellers, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S403000, C525S407000, C525S410000, C525S523000, C528S408000, C528S411000, C528S412000, C528S416000, C528S417000, C528S418000, C528S419000, C528S421000
Reexamination Certificate
active
06794451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cationically polymerizable liquid composition that, without containing an organic solvent, can be coated easily on a substrate and can be polymerized by light or heat after the coating so that it can be used as a pressure-sensitive adhesive having good tack properties. The present invention also relates to a tacky polymer that can be obtained by cationic polymerization of the above-mentioned cationically polymerizable liquid composition.
2. Description of the Related Art
With regard to conventional pressure-sensitive adhesives, a solvent type in which a rubber or acrylic material is dissolved in an organic solvent, and an emulsion type in which the material is dispersed in water have been used. Currently, solvent type pressure-sensitive adhesives are most widely used, but the release of the organic solvent has become an issue recently. The emulsion type has the drawbacks of poor water resistance, long drying time, etc. A hot-melt type, which has been proposed as a method for resolving the above-mentioned problems, still has poor coating performance, poor tack properties and, in particular, poor heat resistance.
Recently, a solvent-free liquid curable pressure-sensitive adhesive has been proposed that is formed mainly from a polymerizable monomer, and a large number of proposals have been made regarding a radically photocurable solvent-free liquid composition employing a radically polymerizable acrylate. However, since it is difficult to complete the radical polymerization in air due to the polymerization inhibiting effect of oxygen, the remaining monomer causes problems such as an unpleasant odor and skin irritation. In order to improve the above-mentioned polymerization, it has been proposed that irradiation with light should be carried out under an atmosphere of nitrogen, but the equipment cost is too high.
A large number of cationically photopolymerizable compositions have been proposed as having good photopolymerization properties in air. For example, JP-A-5-78639 (JP-A denotes Japanese unexamined patent application publication) discloses a pressure-sensitive adhesive comprising a polymer obtained by the copolymerization of acrylic vinyl monomers having a hydroxy group, a bi- or poly-functional epoxy compound, and a cationic polymerization initiator. JP-A-8-60127 discloses a UV curable hot-melt pressure-sensitive adhesive composition comprising a cyclohexene monoepoxide group-containing thermoplastic acrylic polymer, a polyol, and a cationic polymerization photoinitiator. JP-A-11-166168 discloses an acrylic pressure-sensitive adhesive composition comprising an acrylic oligomer obtained by polymerizing specified monomer components, and a cationic photocatalyst. However, since all of these compositions have low polymerizability, a large amount of light is needed when they are cured at room temperature, and the low polymerizability might cause a problem in practice. It is surmised that, since these compositions contain an ester group ascribable to the acrylic group, the presence of the ester group retards the ring-opening polymerization of the cyclic ether, thereby lowering the polymerizability. Furthermore, when the acrylic oligomer has a high molecular weight, the composition becomes highly viscous, thus making it difficult to coat the composition.
In order to avoid the retardation in polymerization due to the ester group, a cationically photopolymerizable composition has been disclosed (Eric-Jack Gerard and Jurgen Schneider, Rad. Tech. Europe 97, 175, 1997), the composition employing a material into which an epoxy group had been incorporated by oxidation of a block polymer having an unsaturated bond in its main chain. JP-A-2000-26830 discloses a UV curable pressure-sensitive adhesive composition formed by mixing a specified epoxy compound, a compound having a functional group that reacts with an epoxy group, a compound having rubber elasticity, and a cationically curing catalyst. However, all of the compositions are very highly viscous; it is proposed in the former that the composition is heated during coating, and in the latter that a solvent is used.
JP-A-11-80681 discloses a foamed pressure-sensitive adhesive tape employing a cationically photoreactive oligomer type pressure-sensitive adhesive composition. Only two types of the composition are disclosed, one of which is the same as that above disclosed by Gerard, et al. and is highly viscous so that it is difficult to coat. The other composition is the same as one disclosed in JP-A-11-166168, and it can be easily expected that its curing speed will be low.
JP-A-11-158437 discloses an adhesion method wherein a pressure-sensitive adhesive material containing a cationically polymerizable compound and a cationic photopolymerization initiator is discharged from a head of an ink-jet printer, coated, and then polymerized by irradiation with light. Although the composition disclosed in the example of the above-mentioned publication has low viscosity, since its polymerizability is low and little polymerization takes place with the level of irradiation described in the publication, it is of no practical utility.
As hereinbefore described, among the solvent-free liquid curable pressure-sensitive adhesives reported so far, there are no reports of a pressure-sensitive adhesive that has ease of coating, can be rapidly polymerized in air and can form a coating of the pressure-sensitive adhesive having good tack properties by irradiation with light.
BRIEF SUMMARY OF THE INVENTION
The present invention has been carried out in view of the above-mentioned circumstances.
It is an object of the present invention to provide a novel cationically polymerizable liquid composition that has ease of coating and high polymerizability in air, and can give a tacky coating having excellent tack properties such as adhesion, holding power, and tack after cationic polymerization. It is another object of the present invention to provide a tacky polymer having excellent tack properties such as adhesion and holding power.
As a result of an intensive investigation by the present inventors in order to achieve ease of coating, high polymerizability in air, and good tack properties after polymerization, the present invention has been accomplished. That is to say, the above-mentioned objects can be realized by a low viscosity cationically polymerizable liquid composition comprising a polymerizable mixture (A) comprising a monofunctional monomer, a polyfunctional monomer and a latent cationic polymerization initiator, the monomers having as a cationically polymerizable group in the molecule a cyclic ether having ring-opening polymerizability; and a solid resin (B) having compatibility with the polymerizable mixture (A). The solid resin (B) here preferably has a softening point of at least 40° C. The above-mentioned ‘low viscosity’ means that the viscosity at 25° C. is 20 Pa·sec or below.
One aspect of the present invention relates to a cationically polymerizable liquid composition, which is a liquid resin having a viscosity at 25° C. of 20 Pa·sec or below, comprising a cationically polymerizable mixture (A) comprising a monofunctional monomer (A-1) having only one cyclic ether structure represented by formula (1) below in the molecule (hereinafter, also simply called ‘monofunctional monomer’), a polyfunctional monomer (A-2) having in the molecule at least two groups derived from a cyclic ether structure represented by formula (1) below (hereinafter, also simply called ‘polyfunctional monomer’), and a latent cationic polymerization initiator (A-3); and a solid resin (B) that is compatible with the above-mentioned mixture (A) at room temperature and has a softening point of at least 40° C.
In the formula, n denotes 0, 1, or 2, and R
1
to R
6
independently denote hydrogen atoms or hydrocarbon groups, which may have a substituent.
Another aspect of the present invention relates to a tacky polymer that can give excellent tack properties and a polymerizable liquid composition f
Sasaki Hiroshi
Yoneda Koutarou
Sellers Robert
Sughrue & Mion, PLLC
Toagosei Co. Ltd.
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