Pipes and tubular conduits – Flexible – Distinct layers
Reexamination Certificate
1999-12-21
2001-05-08
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Flexible
Distinct layers
C138S141000, C138S174000, C138S132000, C138S153000
Reexamination Certificate
active
06227249
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an abrasion resistant hose in which an inner layer of a hose wall comprising a thermoplastic polyurethane resin, particularly a polyester-series thermoplastic polyurethane resin.
BACKGROUND OF THE INVENTION
Highly pressure-proof abrasion resistant synthetic resin hoses have been used for, e.g., conveyance or transport of powdery or granular particles, and suction and compression-transport of iron powder, sand, ballast. As such synthetic resin hose, Japanese Patent Application Laid-Open No. 141753/1999 (JP-A-11-141753) discloses an abrasion resistant hose comprising an inner layer mainly formed with a polyester-series thermoplastic polyurethane resin, an outer protective layer (hose wall) comprising a soft vinyl chloride resin united with the inner layer by thermal-fusion, and a spiral reinforcement comprising a hard vinyl chloride resin buried in or attached to the outer protective layer.
For improving the moldability or processability of thermoplastic polyurethane resins by making them softer, the inner layer of the above-described abrasion resistant hose is generally formed with an externally-plasticized polyester-series thermoplastic polyurethane resin comprising a polyester-series thermoplastic polyurethane resin and a conventional plasticizer (e.g., a phthalate-series plasticizer) (e.g., E670MNAT manufactured by Nippon Miractran, Co. Ltd.); C70A10W manufactured by Takeda Badische Urethane Industrird, Ltd.).
However, when a powdery substance (e.g., powders or particles capable of absorbing or capturing plasticizer, such as slaked lime or active carbon) are passed through the inside of the abrasion resistant hose, there occurs a phenomenon that the plasticizer (e.g., a phthalate-series plasticizer) added to the thermoplastic polyurethane resin bleeds out from the inner layer to the outer and drained off as the powdery substance is being conveyed because the migration of the platicizer is large. Accompanying or being indifferent to such phenomenon, the conventional plasticizer of large migration, such as a phthalate-series plasticizer [e.g., dioctyl phthalate (DOP)], contained in the soft vinyl chloride resin forming the outer layer migrates to the adjoining inner layer. Therefore, the volume or size of the hose is reduced and the hose contracts, resulting in the hose which is now shorter than as it was.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide an abrasion resistant hose effectively prevented from the bleed migration of plasticizers added to an inner layer and an outer layer.
Another object of the present invention is to provide a synthetic resin pressure-proof hose which is excellent in abrasion resistance, bending resistance, and other characteristics and free from the contraction phenomenon.
The present invention provides the following abrasion resistant hoses to solve the problems described above.
(1) An abrasion resistant hose comprising an inner layer mainly formed with a thermoplastic polyurethane resin, an outer protective layer comprising a soft vinyl chloride resin united with the inner layer by thermal-fusion, and a spiral reinforcement comprising a hard synthetic resin buried in or attached to the outer protective layer, wherein the inner layer is formed with the thermoplastic polyurethane resin containing substantially no migratory plasticizer or an internally-plasticized thermoplastic polyurethane resin (i.e., a thermoplastic polyurethane resin which is not externally-plasticized by a migratory plasticizer), and the outer protective layer is formed with a soft vinyl chloride substantially free from migratory plasticizer.
(2) An abrasion resistant hose comprising an inner layer mainly formed with a thermoplastic polyurethane resin, an outer protective layer comprising a soft vinyl chloride resin united with the inner layer by thermal-fusion, and a spiral reinforcement comprising a hard synthetic resin buried in or attached to the outer protective layer, wherein the inner layer is formed with the thermoplastic resin containing substantially no migratory plasticizer or an internally-plasticized thermoplastic polyurethane resin (i.e., a thermoplastic polyurethane resin which is not externally-plasticized by a migratory plasticizer), and an intermediate layer comprising a soft vinyl chloride resin containing substantially no migratory plasticizer interposed between and united with both the inner layer and the outer protective layer by fusion.
(3) The inner layer may be formed with a polyester-series thermoplastic polyurethane resin containing a non-migration plasticizer.
Polyester-series thermoplastic polyurethane resins usable for the formation of the inner layer of the hose wall are classified by the species of a polyol material as a soft segment for polyurethane and refer to thermoplastic polyurethane resins (TPU) of the type employing a polyester polyol as a polyol component. Thermoplastic polyurethane resins include those blended with a thermoplastic resin(s) such as polyvinyl chloride, polyester, polyamide. with the proviso that the properties of the thermoplastic polyurethane resins are not largely affected.
The thermoplastic polyurethane resin (particularly, a polyester-series thermoplastic polyurethane resin) is internally plasticized by selecting a polyol as a soft segment capable of softening the resin more (particularly, a polyester polyol material), and contains substantially no migratory plasticizer (e.g., a phthalate-series plasticizer) as an additive. Moreover, even in the case where the polyester-series thermoplastic polyurethane resin is externally-plasticized, a non-migration plasticizer is used. Therefore, the polyester-series thermoplastic polyurethane resin shows multiply superior performance in its abrasion resistance than that of a soft vinyl chloride resin, and gives excellent mechanical strength, flexibility, elasticity and others to the hose. Furthermore, the polyester-series thermoplastic polyurethane resin is excellent in adhesion with a vinyl chloride resin and has an advantage of being capable of directly fusing with the outer protective layer comprising a soft vinyl chloride without the aid of an adhesive intermediate resin material.
The phrase “containing no plasticizer for externally-plasticization” refers to both cases where the resin does not contain a plasticizer at all and where the resin contains a plasticizer in such a small amount that nothing will be adversely affected even if the plasticizer bleeds out.
On the other hand, the soft vinyl chloride resin forming the outer protective layer or the intermediate layer contains substantially no migratory plasticizer. The phrase “containing substantially no migratory plasticizer” means (1) a plasticizer having excellent non-migration property, such as a polyester-series plasticizer, is used instead of, e.g., the above-mentioned phthlate-series plasticizer which has been used widely and is of large migration; (2) internally-plasticization by copolymerizing vinyl chloride with a soft monomer; and (3) plasticization by admixing a modifying polymer to a vinyl chloride resin to form a polymer blend.
As was described above, the contraction of the hose can be effectively prevented by the combination of the polyester-series thermoplastic polyurethane resin which is not externally-plasticized with a migratory plasticizer and the soft vinyl chloride resin containing no migratory plasticizer, because the inner layer does not contain a plasticizer to bleed out as well as the outer layer contains no plasticizer to migrate.
Incidentally, even with the combination of the inner layer formed with, instead of the internally-plasticized polyester-series thermoplastic polyurethane resin, a polyester-series thermoplastic polyurethane resin to which a non-migration plasticizer such as a polyester-series plasticizer is added, and the outer layer comprising a migratory plasticizer-free soft vinyl chloride resin, bleed or migration of the plasticizer never occurs and the hose is effectively prevented fr
Akedo Youichi
Hattori Shoji
Inagake Tetsuya
Kodama Hitoya
Morikawa Masataka
Brinson Patrick
Pillsbury & Winthrop LLP
Tigers Polymer Corporation
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