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
2000-09-08
2002-05-21
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S232000, C525S240000
Reexamination Certificate
active
06391974
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to pressure-sensitive adhesives, pressure-sensitive adhesive sheets or films, and hot-melt adhesives. Specifically, the present invention relates to pressure-sensitive adhesives which are useful such as for pressure-sensitive adhesive films which pressure-sensitively adhere to the surfaces of a synthetic resin plate, decorative plywood, metal plate, coated steel plate and the like to protect the surfaces from dust adhesion and scratching. The present invention also relates to pressure-sensitive adhesive sheets and films which are useful such as for masking tapes used for baking coatings on automobiles and the like, and as masking tapes used for solder immersion of printed wiring boards and the like, as well as other uses. The present invention further relates to hot-melt adhesives useful for adhesion of a polyolefin resin, mutual adhesion of rubber, adhesion between different materials such as rubber and metal, and the like.
BACKGROUND OF THE INVENTION
Conventionally, pressure-sensitive adhesive sheets or films have been used to protect the surface of a coated body, such as a coated body used for working, storage and transportation of building materials, electric insulation, electronic products, and automobiles and the like. Such pressure-sensitive adhesive sheets or films should have excellent pressure-sensitive adhesion and, simultaneously, they should be able to be peeled off easily after use thereof without contaminating the surface of the coated body with the pressure-sensitive adhesive. Recently, pressure-sensitive adhesive sheets or films comprising a substrate made of a polyolefin-based resin are increasingly being used instead of pressure-sensitive adhesive sheets or films comprising a substrate made of a plastic vinyl chloride resin. The pressure-sensitive adhesive sheets or films comprising a substrate made of a polyolefin-based resin that mainly have been used in that manner are those integrally formed by co-extrusion of a pressure-sensitive adhesive layer made of a low crystalline or amorphous pressure-sensitive adhesive such as ethylene vinylacetate copolymer (EVA), low density polyethylene and the like, or a pressure-sensitive adhesive layer made of an elastomer such as styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS) and the like, with a substrate. However, the above-mentioned pressure-sensitive adhesive sheets or films have problems in that when they are left under a high temperature environment, a change occurs with the lapse of time, causing an increase in pressure-sensitive adhesion force leading to difficulties when later peeling the adhesive sheet or film from the coated body, leaving behind pressure-sensitive adhesive material as a contaminant on the surface of the body, and the like. Japanese Patent Application Laid-Open (JP-A) No. 4-55488 discloses a pressure-sensitive adhesive sheet or film causing no change with the lapse of time even under high temperature environment, in which a pressure-sensitive adhesive film comprising a pressure-sensitive adhesive layer made of a polyethylene or ethylene/&agr;-olefin copolymer having a density of 0.92 g/cm
2
or less and a melt index of 1 to 20 g/10 minutes is formed on one surface of a substrate layer made of a thermoplastic resin. Further, JP-A No. 8-157791 discloses a pressure-sensitive adhesive film composed of a pressure-sensitive adhesive layer made of an ethylene-&agr;-olefin copolymer having a weight-average molecular weight Mw of 5×10
4
or more, Mw/Mn of 3 or less in which “Mw/Mn” is a ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), a melting peak temperature in DSC analysis of 110° C. or more, and a heat of fusion of 100 J/g or less, and a substrate made of another polyolefin-based resin. However, these pressure-sensitive adhesive films have low pressure-sensitive adhesion, and in particular, extremely lowered pressure-sensitive adhesion at lower temperature.
On the other hand, hot-melt adhesives containing EVA and the like have been developed. However, they have disadvantageous properties such as insufficient flexibility, crystalline property, and the like. Therefore, the pressure-sensitive adhesion changes significantly, depending on the temperature of usage. In particular, sufficient pressure-sensitive adhesion is not obtained under a low temperature environment. Further, since an adhesion temperature is required that is not lower than the melting temperature, these hot-melt adhesives are not suitable for a material to be adhered which tends to show thermal deformation.
Further, rubber adhesion complexes, such as used in a tire, conveyer belt, hose, lining product and the like, are produced by laminating un-vulcanized rubber materials and then vulcanizing for adhesion. However, a problem arises in that a strongly adhered rubber adhered complex is not obtained, and this occurs because when the above-mentioned rubber materials are laminated, compatibility between un-vulcanized rubber materials maybe poor, and the vulcanization speeds may vary significantly, and the forms of cross-linking and the like may vary significantly as between the rubber materials, leading to an absence of co-vulcanizing property. Moreover, it is known to use a rubber sheet as a water-proof sheet in the water proofing of concrete buildings and the like. However, since the size of the rubber sheet obtained by molding, vulcanization and the like is limited as compared with a sheet otherwise used for such a purpose in the construction field, a considerable number of rubber sheets have to be added and assembled along the length and breadth directions at the construction site. Conventionally, therefore, many pieces of rubber sheets are spread out at the construction site, and edge portions thereof are overlapped and an adhesive is applied on the edge portions, to adhere the rubber sheets together. As the above-mentioned adhesive, a solvent type polychloroprene adhesive is primarily used. Since an organic solvent is used in the above-mentioned polychloroprene adhesive, the organic solvent is vaporized in execution, causing undesirable effects from the standpoints of safety and hygienics for humans, and environmental protection. On the other hand, an aqueous adhesive prepared by compounding tackifier resin into rubber latex is suggested as an adhesive using no organic solvent; however, this aqueous adhesive has problems in terms of adhesion force in that strong adhesion is not obtained easily and peeling tends to occur. Further, a method is known for mutual adhesion of rubbers in which a plastic material, such as a high-pressure polyethylene, polypropylene, polystyrene and the like, is provided so as to intervene between rubbers to be adhered; however, this method has a drawback in that the flexibility of a rubber-adhered complex is lowered due to hardening of the adhered portion.
SUMMARY OF THE INVENTION
Under these circumstances, the present inventors have found that the above-mentioned problems are solved by using a unique olefin-based copolymer having certain specific physical properties and a thermoplastic resin composition obtained by using this olefin-based copolymer.
The present invention relates to a unique pressure-sensitive adhesive comprising a specific polymer which can provide a thermoplastic resin composition having an excellent balance of flexibility, heat-resistance, cold-resistance and weather-resistance. The present invention also relates to an adhesive sheet or film composed of this pressure-sensitive adhesive. The present invention also relates to a unique hot-melt adhesive. More particularly, the present invention relates to a pressure-sensitive adhesive which pressure-sensitively adheres or adheres without using an organic solvent, and also maintains suitable pressure-sensitive adhesion without causing extreme change with the lapse of time, even under a low temperature environment or a high temperature environment and irrespective of the environ
Hozumi Hidetake
Jyouhouji Hirofumi
Ogawa Atsuko
Sassa Tatsuo
Fitch Even Tabin & Flannery
Nutter Nathan M.
Sumitomo Chemical Co,. Ltd.
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