Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-01-27
2002-03-05
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C525S440030, C525S457000, C156S307100, C528S905000
Reexamination Certificate
active
06353078
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyurethane adhesive, a method of using it for adhesion, and a use of the mixture; and in particular, the present invention relates to a polyurethane adhesive that is useful in adhering plastics, metals, and the like, a method of using it for adhesion, and a use of the mixture.
BACKGROUND ART
In recent years, multi-layered composite films in which plastic films such as polyethylene, polypropylene, polyamide, polyester, vinyl chloride, vinylidene chloride, or the like, or alternatively, a combination of a plastic film and metallic foil such as aluminium foil are laminated in two-, three-, or four-plus layers, have been developed and used in various ways as a packaging material for food and luxuries.
Furthermore, in order to keep the freshness and flavor of food products and preserve these food products over a long period of time, higher performance, multi-layered composite films are required, and therefore, improvements for an adhesive used in laminating are strongly desired.
In particular, an adhesive for use in multi-layered composite films for packaging retort food products or food products requiring high-temperature sterization, must exhibit superior properties with regard to an initial adhesion strength, permanent adhesion strength, hot water resistance, fatigue resistance, acid resistance, and the like, as well as high-speed lamination.
Hitherto, a polyurethane adhesive has been used for the aforementioned purposes, however, its properties in hot water resistance, heat resistance, and resistance to contents, are inferior. For example, when food containing vinegar is packaged and disinfected with water at a high temperature, the adhesion strength between the aluminium foil and plastics weakens, leading to peeling and loss of function as a multi-layered composite film.
As the aforementioned polyurethane adhesive, Japanese Published Examined Patent Application, No. 25989/92 discloses a polyurethane adhesive comprising a poly(&bgr;-methyl-&dgr;-valerolactone)polyol and the like, and an organic polyisocyanate.
Additionally, Japanese Published Unexamined Patent Application, No. 6075/88 discloses a polyurethane adhesive comprising a polymer polyol derived from 3-methyl-1,5-pentanediol, and an organic polyisocyanate.
In addition, Japanese Published Unexamined Patent Application, No. 182387/88 discloses a polyurethane adhesive comprising a polymer polyol derived from 2-methyl-1,8-octanediol, and an organic diisocyanate.
Additionally, Japanese Published Unexamined Patent Application, No. 262859/93 discloses an adhesive comprising a polyester polyol derived from a diol possessing an alkyl side chain, and a hardening agent; and Japanese Published Unexamined Patent Application, No. 81414/92 discloses an adhesive comprising a polyester polyol polyurethane derived from a diol possessing an alkyl side chain. However, the aforementioned publications neither disclose concrete technological details nor disclose any specific disclosure with regard to a polyurethane derived from a 2,4-dialkyl-1,5-penetanediol.
In addition, WO96/09334 discloses a polyurethane comprising a polyester polyol derived from a 2,4-dialkyl-1,5-pentanediol, and an organic polyisocyanate; however, this document does not disclose its use as an adhesive.
It is an object of the present invention to provide a polyurethane adhesive that is particularly useful in manufacturing multi-layered composite films which are formed by means of laminating various plastic films, metallic foil, and the like.
DISCLOSURE OF THE INVENTION
The present invention provides an adhesive comprising a polyester polyol or polyurethane polyol possessing structural units represented by the following general formula (I) within its molecular structure, and an organic polyisocyanate in which the isocyanate groups may be protected (hereinafter, said organic polyisocyanate in which the isocyanate groups are unprotected is sometimes referred to simply as an organic polyisocyanate):
wherein R
1
and R
2
are the same or different and each represents lower alkyl.
Additionally, the present invention provides a method of mixing a polyester polyol or polyurethane polyol, possessing the structural units represented by the aforementioned general formula (I), and an organic polyisocyanate in which the isocyanate groups may be protected, and using the mixture for adhesion. Furthermore, the present invention provides a use of a mixture of a polyester polyol or polyurethane polyol, possessing the structural units represented by the aforementioned general formula (I), and an organic polyisocyanate in which the isocyanate groups may be protected.
BEST MODES FOR CARRYING OUT THE INVENTION
In the definition of the aforementioned general formula (I), the lower alkyl means a linear or branched chain alkyl having 1 to 8 carbon atoms, examples of which may include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isoamyl, neopentyl, 2-pentyl, 3-pentyl, hexyl, heptyl, octyl, and the like.
The polyester polyol, a component of the adhesive of the present invention, is a polyester possessing the structural units represented by the aforementioned general formula (I) as repeating units in the main chain. Preferably, both terminal groups of said polyester are normally hydroxyl groups.
The structural units represented by the aforementioned general formula (I) are formed by esterification of a 2,4-dialkyl-1,5-pentanediol and a dicarboxylic acid, or transesterification of a 2,4-dialkyl-1,5-pentanediol and a dicarboxylic acid ester, or the like.
In other words, an example of the method for preparation is a method carrying out esterification of a diol containing a 2,4-dialkyl-1,5-pentanediol, which is a constituent that provides structural units represented by the general formula (I), and a dicarboxylic acid, according to a conventional method. For example, a diol containing a 2,4-dialkyl-1,5-pentanediol and a dicarboxylic acid is heated to 150-250° C. in the presence of a catalyst for esterification, if necessary. The pressure is reduced to 10-15 mmHg at the same temperature when the acid number of the reaction mixture reaches about 15 (KOH mg/g), and the esterification reaction is further continued. When the acid number of the reaction mixture reaches about 0.3 (KOH mg/g), the reaction is stopped and the mixture is cooled, to obtain the desired polyester polyol.
Additionally, the other example of the method for preparing the polyester polyol is a method carrying out transesterification of a diol containing a 2,4-dialkyl-1,5-pentanediol and a lower alkyl ester of dicarboxylic acid such as a methyl ester, an ethyl ester, or the like, according to a conventional method.
In the starting materials for the esterification reaction, when adding an organic polyisocyanate to a polyester polyol for a use as an adhesive, the molar ratio of all dicarboxylic acids or the lower alkyl esters of the dicarboxylic acids to all diols is 0.90-1.20, and preferably 0.95-1.10. Additionally, when preparing the polyester polyol as a starting material of the polyurethane polyol, the molar ratio of all dicarboxylic acids or the lower alkyl esters of the dicarboxylic acids to all diols is 0.1-1.0, and preferably 0.5-1.0, while the preferred terminal groups of the polyester are normally hydroxyl groups.
Specific examples of the 2,4-dialkyl-1,5-pentandiol may include 2,4-dimethyl-1,5-pentanediol, 2-ethyl-4-methyl-1,5-pentanediol, 2-methyl-4-propyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-4-propyl-1,5-pentanediol, 2,4-dipropyl-1,5-pentanediol, 2-isopropyl-4-methyl-1,5-petanediol, 2-ethyl-4-isopropyl-1,5-pentanediol, 2,4-diiosopropyl-1,5-pentanediol, 2-isopropyl-4-propyl-1,5-pentanediol, 2,4-dibutyl-1,5-pentanediol, 2,4-dipentyl-1,5-pentanediol, 2,4-dihexyl-1,5-pentanediol, and the like. Among these examples, 2,4-diethyl-1,5-pentanediol is preferably used.
The 2,4-dialkyl-1,5-pentandiol can be prepared according to a known method such as the method disclosed in Japanese Published Unexamined Patent Application, No. 48642/
Murata Shigeru
Nakajima Tetsuya
Yasuda Masahiko
Gorr Rachel
Kyowa Yuka Co., Ltd.
White & Case LLP
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