Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2002-07-02
2004-06-15
Buttner, David J. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S448000, C428S3550RA, C525S440030, C525S458000, C528S028000, C528S059000
Reexamination Certificate
active
06749943
ABSTRACT:
The invention relates to a moisture curable, hot melt composition, to a method for the manufacture of the moisture curable, hot melt composition, to a cured adhesive composition based on the moisture curable, hot melt composition and to articles bonded with the moisture curable, hot melt composition.
BACKGROUND OF THE INVENTION
Isocyanate-terminated polyurethane prepolymers (sometimes referred to hereinafter as “polyurethane prepolymers” or “prepolymers”) are desirable in a variety of applications. For example, they can be used in reactive hot melt urethane adhesive, coating and/or sealant systems. Hot melt urethane systems are solid at room temperature, melt to a viscous liquid when heated to moderate temperatures (e.g., 55° C.-121° C.), and are applied in a molten state to an appropriate substrate. On the substrate, the adhesive cools to a solid state to provide an initial bond strength (sometimes referred to as “green strength”), and eventually the adhesive will achieve its ultimate bond strength in a curing reaction with ambient moisture. In the presence of an appropriate catalyst, typically a tin-based catalyst, urethane hot melts have rapid rates of cure and provide excellent final properties when cured. Other advantages associated with hot melt adhesives include rapid green strength, bonding without fixturing, and adhesion to a wide variety of substrates While widely used, hot melt urethanes have not been problem-free. These adhesive systems may contain a level of free monomeric isocyanate that can raise concerns regarding possible toxicity. Toxicity issues may become especially important in the application of hot melt adhesives to substrates using spraying and other dispensing methods for applying a hot melt adhesive to a substrate at high temperatures (>275° F.). Because of the foregoing concerns, the use of urethane hot melts has been banned from some industrial sites. In addition to toxicity issues, urethane hot melt adhesives emit carbon dioxide during the curing process. The generation of carbon dioxide in amorphous adhesives can cause undesired bubble formation in the body of the adhesive during the curing process. Problems have also been noted in the otherwise accepted use of tin based catalysts for catalyzing the curing reaction of polyester urethane hot melts. For example, the presence of tin in a urethane hot melt that is based on one or more polyester monomers can adversely affect the hydrolytic stability of the polyester and the thermal stability of the prepolymer.
In one approach to addressing the foregoing toxicity issue, some urethane hot melt adhesives have been end capped with an organo-functional silane to reduce the potential for significant isocyanate toxicity. Such adhesives still require the use of tin-based catalysts to generate acceptable cure rates through the organo-silane groups.
It is desirable to provide a polyester based hot melt adhesive that can be manufactured without the need for a tin-based catalyst but which also has an acceptable and relatively rapid rate of cure.
SUMMARY OF THE INVENTION
In a first aspect, the invention provides a moisture curable, hot melt composition comprised of the product of reacted components, the components comprising:
(a) a semi-crystalline polyol;
(b) an essentially amorphous polyol selected from the group consisting of polyols having branched primary hydroxyl groups, polyols having secondary hydroxyl groups, and combinations of the foregoing;
(c) a secondary aminosilane endcapper comprising secondary amnino functionality;
(d) an isocyanate; and
(e) substantially no tin.
In another aspect, the invention provides a method for the manufacture of a moisture curable, hot melt adhesive and/or sealant composition, the method comprising:
(a) preparing a prepolymer by:
(i) mixing a semi-crystalline polyol, an essentially amorphous polyol, an isocyanate and, optionally, a non-tin catalyst, the essentially amorphous polyol selected from the group consisting of polyols having branched primary hydroxyl groups, polyols having secondary hydroxyl groups and combinations thereof;
(ii) reacting the mixture to provide the prepolymer;
(b) reacting the prepolymer with a secondary aminoalkoxysilane endcapper comprising secondary amino functionality to provide the moisture curable, hot melt adhesive and/or sealant composition; and
the steps (a) and (b) are accomplished in the absence of tin catalyst.
In the foregoing aspects of the invention, the semi-crystalline polyol may be a polyester-based polyol selected from a variety of materials including polyhexamethylene sebacate, polyhexamethylene adipate, polybutylene adipate, polyhexamethylene dodecanedioate, poly-epsilon-caprolactone, and combinations thereof. The semi-crystalline polyol comprises the reaction product of a diol and a polyacid (e.g., a dicarboxylic acid). The essentially amorphous polyol may comprise a copolymer of ethylene oxide and propylene oxide, partially end capped with ethylene oxide and having a hydroxyl number between about 10 and about 100. The amorphous polyol can have a crystallinity index less than or equal to about 0.25. In some embodiments, the essentially amorphous polyol comprises a mixture of primary hydroxyl-containing and secondary hydroxyl-containing materials. The isocyanate may comprise a material selected from the group consisting of aliphatic isocyanates, aromatic isocyanates, derivatives of aliphatic isocyanates, derivatives of aromatic isocyanates and combinations of the foregoing. The foregoing adhesive may be provided in a variety of configurations such as a film, for example.
The secondary arninosilane endcapper may comprise any of a variety of silane including N-alkyl-aminoalkyl-alkoxysilane selected from the group consisting of N-methyl-3-amino-2-methylpropyltrimethoxysilane; N-ethyl-3-anino-2-methylpropyltrimethoxysilane; N-ethyl-3-amino-2-methylpropyldiethoxymethylsilane; N-ethyl-3-amino-2-methylpropyltriethoxysilane; N-ethyl-3-amino-2-methylpropyldimethoxymethylsilane; N-butyl-3-amino-2-methylpropyltrimethoxysilane; N-ethyl4-amino-3,3-dimethylbutyldimethoxymethylsilane; N-ethyl-4-amino-3,3-dimethylbutyltrimethoxysilane and combinations of the foregoing. In general, the secondary aminosilane endcapper comprises a material having the formula:
R
0
—NR
1
—R
2
—Si(OR
3
)
m
(R
4
)
n
where R
0
is aliphatic,
R
1
is hydrogen,
R
2
is a straight, branched, or cyclic aliphatic chain,
R
3
and R
4
are C
1
-C
6
alkyl,
m=1-3, and
n=0-2.
In one preferred embodiment, the (a) the semi-crystalline polyol is polyhexamethylene adipate; (b) the essentially amorphous polyol is a polyoxypropylene glycol comprising secondary hydroxyl groups; (c) the secondary aminosilane endcapper is N-ethyl-3-amino-propyltrimethoxysilane; and (d) the isocyanate is 4,4′-diphenylmethane diisocyanate.
In another aspect of the invention, a cured adhesive and/or sealant composition is provided, derived from the curable, hot melt adhesive and/or sealant composition described above.
In still another aspect of the invention, a curable, hot melt adhesive is provided by the foregoing method of manufacture, and upon curing, provides a cured adhesive derived therefrom.
In still another embodiment of the invention, a bonded article is provided, comprising:
a first substrate;
a second substrate; and
the foregoing cured adhesive composition (derived from the foregoing moisture curable, hot melt composition) between the first substrate and the second substrate and affixing the first and second substrates to one another.
In still another aspect, the invention provides a tape comprising a backing and having the aforementioned moisture curable, hot melt composition associated with at least one major surface of the backing.
Other features of the invention will be more fully appreciated by those skilled in the art upon consideration of the remainder of the disclosure including the Detailed Description of the Preferred Embodiment, including the Examples and the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates t
Tangen John C.
Waid Robert D.
3M Innovative Properties Company
Buttner David J.
Keehan Christopher
Pastirik Daniel R.
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