Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-20
2004-06-08
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S261000, C528S066000, C427S385500, C049S475100
Reexamination Certificate
active
06747093
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a moisture-curing reactive hot-melt adhesive for weather strip flocking, a flocked weather strip, and a process for producing the flocked weather strip. The weather strip is obtained by flocking on a sliding side thereof to a glass or the like, and is especially suitable for use in motor vehicles.
DESCRIPTION OF THE RELATED ART
In a general technique for weather strip production, weather strips having a side on which a glass is to be slid are flocked on the sliding side in order to reduce sliding resistance and secure sealing properties.
Adhesives for flocking generally include an emulsion type and a solvent-based type. However, adhesives used for weather strip flocking are generally of a two-pack solvent-based type and a one-pack solvent-based type from the standpoints of adhesion to substrates and water resistance.
Conventional processes for producing a flocked weather strip using those adhesives comprise applying an adhesive in a given thickness to a substrate on its side to be the sliding side of a weather strip, electrostatically flocking piles in the adhesive layer, cutting the pile-flocked substrate into strips of a given size while being nipped in areas along the cutting lines, heating the adhesive to remove a solvent and cure the adhesive, and then cutting off both edges of each strip which have been impaired in the raised state as a result of the deformation caused by nipping during the cutting.
The reason why cutting is conducted before drying is that since drying requires about 10 minutes, a drying oven necessitates a large space and should be as long as 100 m when line speed is, for example, 10 m/min. Usually, a drying line having a width such that flocked weather strips cut into a given size can be transported thereon extends perpendicularly to the flocking line.
JP-A-5-96670 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a flocked material obtained by electrostatically flocking a substrate with piles through an adhesive comprising a urethane prepolymer. However, the urethane prepolymer described in the above publication is unclear in crystallinity.
In the case where the solvent-based adhesives are used, the flocked substrate is cut before drying while being nipped in areas along the cutting lines, so that both edges of each resulting strip, which have deformed during the cutting, should be cut off and discarded. These edges to be discarded account for about 10% of the total production of locking. Consequently, the conventional process not only has a loss of about 10% in variable cost and processing cost, but also yields wastes.
In addition, since a solvent is handled, the conventional process always has problems concerning worsening of the working atmosphere and possibility of catching fire and necessitates a high cost of light and heat for drying the adhesive.
In the case of using a two-pack type adhesive, there also is a problem concerning curing failures attributable to hardener mixing errors.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide a flocked weather strip free from the problems described above.
Another object of the invention is to provide a process for producing the weather strip.
Still another object of the invention is to provide an adhesive composition for use in flocking.
As a result of intensive investigations to overcome the problems described above, it has been found that a specific moisture-curing reactive hot-melt adhesive comprising as the main component a urethane prepolymer containing isocyanate groups is useful for the electrostatic flocking of weather strip substrates made of PVC or another material with piles. The invention has been completed based on this finding.
According to a first embodiment of the invention, there is provided a moisture-curing reactive hot-melt adhesive for weather strip flocking, which comprises as the main component a urethane prepolymer containing isocyanate groups, the hot-melt adhesive having a dielectric constant at 25° C. of 3 to 10 and a melting point of 40° C. to 150° C.
In one preferred embodiment of the moisture-curing reactive hot-melt adhesive for weather strip flocking of the invention, it has a tack-free time of 10 minutes or shorter as measured by the following test method:
Test Method
An adhesive melted by heating at 120±5° C. is uniformly applied to a 100 &mgr;m-thick poly(ethylene terephthalate) film in a thickness of 100±10 &mgr;m to form a square adhesive layer having dimensions of 1 cm by 1 cm. The film having the adhesive layer is immediately placed in a thermostatic chamber maintained at 25±1° C. and allowed to stand therein. The time required for the adhesive layer to become tack-free is measured based on touching to the surface thereof with a finger.
In another preferred embodiment of the moisture-curing reactive hot-melt adhesive for weather strip flocking of the invention, it contains a silane coupling agent in an amount of 1 to 20% by weight based on the total weight of the adhesive.
According to a second embodiment of the invention, there is provided a flocked weather strip comprising a substrate flocked through the moisture-curing reactive hot-melt adhesive described above.
According to a third embodiment of the invention, there is provided a process for producing a flocked weather strip which comprises thermally melting the moisture-curing reactive hot-melt adhesive described above, applying the melt to a substrate in a thickness of 40 to 150 &mgr;m, electrostatically flocking the resulting layer of the molten adhesive with piles, cooling the adhesive to solidify the same, thereby fixing the piles to the substrate, and then cutting the substrate into a given size.
The adhesive of the invention is suitable for use in the flocking of a weather strip substrate and enables the piles flocked in a melt of the adhesive to strongly bond to the weather strip substrate in a short period of time.
The weather strip of the invention has excellent sliding resistance and is especially suitable for use in motor vehicles.
The process for producing a flocked weather strip according to the invention gives a flocked weather strip in which piles after flocking have a sufficient strength with respect to the retention of the raised state and, hence, do not deform when a nipping stress is applied thereto in cutting. Because of this, the process is free from the losses and wastes accompanying the use of a solvent-based adhesive. Since the process uses a solvent-free adhesive, it not only is free from worsening of the working atmosphere and possibility of catching fire, but also is effective in reducing the cost of light and heat because no drying step is necessary. Furthermore, since the adhesive is of the one-pack type, the process is free from curing failures attributable to hardener mixing errors which may occur in the case of using a two-pack type solvent-based adhesive.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
1. Adhesive
The adhesive used in the invention is a moisture-curing reactive hot-melt adhesive for weather strip flocking which comprises as the main component a urethane prepolymer containing isocyanate groups.
The adhesive used in the invention has a content of the urethane prepolymer containing isocyanate groups of preferably 60% by weight or higher, more preferably 70% by weight or higher, based on the total weight of the adhesive.
The urethane prepolymer containing isocyanate groups is an isocyanate-terminated urethane prepolymer obtained by reacting one or more polyols having two or more hydroxyl groups in the molecule with one or more polyisocyanates having two or more isocyanate groups in the molecule. The urethane prepolymer has a weight average molecular weight of 2,000 to 50,000. Such urethane prepolymers may be used alone or in combination of two or more thereof.
1.1. Polyols
The polyols used as a starting material for the urethane prepolymer are compounds having two or m
Takahashi Shin
Yamada Masashi
Sughrue & Mion, PLLC
Toagosei Co. Ltd.
Yoon Tae H.
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