Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-06-21
2003-12-30
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S338000, C528S339000, C528S339300, C528S340000, C528S341000, C528S349000, C526S317100, C526S318200, C526S935000, C156S060000, C156S325000, C156S326000, C156S330900
Reexamination Certificate
active
06670442
ABSTRACT:
FIELD OF THE INVENTION
Background of the Invention
The present invention relates to polyamide compositions which are useful as hotmelt adhesives, in particular the invention relates to polyamide compositions which are suitable for bonding nonpolar substrates such as poly-&agr;-olefin substrates. More specifically, the compositions of the present invention are thermoplastic polyamides derived from the polymerized fatty acid components.
Hotmelt adhesives are thermoplastic adhesive compositions, which are solid at room temperature. Prior to application of these adhesives, they are heated to become viscous fluids which solidify rapidly on cooling after the assembly of the substrates to be bonded. Hotmelt adhesives have acquired increasing significance in numerous areas of bonding technology. The advantages of hotmelts lay in the fact that they develop the necessary bond strength by cooling from the melt and, accordingly, are suitable for high-speed production processes. Since these adhesives do not contain volatile solvents, there is no need for exhaust equipment and no long drying times are required as for water-based adhesives.
Polyamides are an important class of hotmelt adhesives. Among polyamides, those based on dimeric fatty acids are particularly important because these polyamides on the one hand have a relatively narrow softening range and, on the other hand, show no tendency towards crystallization and resulting embrittlement, even at temperatures below 0° C.
Although adhesives based on polyamides derived from dimeric fatty acids show excellent properties in numerous applications, efforts are still being made to develop special hotmelt adhesives having even better adhesion properties. Thus, attempts have been made to modify the polyamides to adapt them to application involving bonding of nonpolar substrates such as poly-&agr;-olefin substrates, in particular the frequently used polyethylene, polypropylene and corresponding copolymer substrates.
According to Gerd Habenicht “Kleben, Grundlagen, Technologie, Anwendungen”, 3
rd
edition, 1997 it is still necessary to surface treat polyethylene or polypropylene substrates before bonding by mechanical pretreatments like sanding or sanding and coating (SACO-process), flaming, corona-treatment, low pressure plasma, fluorinating, chemical etching or preapplying of primers.
U.S. Pat. No. 4,791,164 discloses hotmelt adhesives compositions which may be used for bonding nonpolar polymers like polyethylene or polypropylene with considerable strength without the otherwise usual pretreatments as mentioned above. These hotmelt adhesives comprise blends of polyamides consisting essentially of the reaction product of dimerized fatty acid, aliphatiac dicarboxylic acid, monomeric fatty acid and aliphatic diamines plus terpolymer based on ethylene. This terpolymer is based on ethylene and/or propylene, an ethylenically unsaturated anhydride of carboxylic acid and a C
1
-C
18
alkyester of acrylic or methacrylic acid.
U.S. Pat. No. 4,912,196 suggests hotmelt adhesives compositions for difficult-to-bond plastic materials such as polyvinyl chloride, polyesters, polyethylene and metals. According to U.S. Pat. No. 4,912,196 blends of thermoplastic polyamide resins consisting of polycondensates of a dimer fatty acid or mixture of such acids, a polyoxyalkylene urea diamine, aliphatic C
6
-C
40
diamine or a mixture of such diamines result in suitable hotmelt adhesive compositions for such substrates. Polyoxyakylene urea diamines are difficult to obtain in the market. Moreover, although these compositions give good adhesion to polyethylene in shear, their peel adhesion is poor.
U.S. Pat. No. 5,548,027 discloses hotmelt compositions for bonding non-pretreated polyethylene. In this reference compatible mixtures of at least one polyamide based on dimerized fatty acid, at least one copolymer of ethylene with at least one member selected from the group consisting of vinylacetate, acrylate and copolymers, block copolymers of styrene with ethylene isoprene butadiene and butylene and at least one plasticizer are suggested to solve this problem. The polyamide based on dimerized fatty acid may contain only very small amounts of trimeric fatty acid. This implies that only distilled dimer acid can be used. Although these adhesive compositions display very good adhesive properties both in tensile strength as well as in peel strength, they are expensive due to the fact that specific copolymers and purified dimer acids are required for making these adhesives.
According to EP-A-0 045 383, it is essential to use dimerized fatty acid with a very high content, preferably more than 90% by weight of dimer fatty acid and only a very small amount of trimeric fatty acid. According to EP-A-0 045 383 no more than 6% by weight of trimeric fatty acid should be present in the mixture.
“Dimerized fatty acids” are obtained by oligomerizing or polymerizing unsaturated long-chain monobasic fatty acids such as for example linoleic acid.or oleic acid. These polymeric acids have long been known and are commercially available. They are known to be a mixture of several isomers and oligomers. Prior to purification, such crude mixtures of polymeric fatty acids have approximately the following composition:
monomeric acids
5-15 % by weight
dimeric acids
60-80 % by weight
trimeric acids
10-35 % by weight
These crude polymeric fatty acids are normally purified by distillation and sometimes subsequent hydrogenation. However, these purification steps add to the costs of the final product. It is highly desirable to find demanding uses for crude polymeric fatty acids.
BRIEF DESCRIPTION OF THE INVENTION
It has now surprisingly been found that polyamide adhesive compositions based on crude polymeric fatty acids are useful for making adhesive compositions for bonding nonpolar substrates like poly-&agr;-olefins without prior pretreatment of the surface. Thus hotmelt adhesives with good adhesion to non-treated polyethylene are obtained from polyamides based on crude polymeric fatty acids with a trimer fatty acid content of up to 20% by weight and a proper balance of several organic diamines which avoids the presence of short polar segments in the polymer chain.
It has now surprisingly been found that polyamide adhesive compositions based on crude polymeric fatty acids are useful for making adhesive compositions for bonding unpolar substrates like poly-&agr;-olefins without prior pretreatment of the surface. Thus hotmelt adhesives with good adhesion to non-treated polyethylene are obtained from polyamides based on crude polymeric fatty acids with a trimer fatty acid content of up to 20% by weight and a proper balance of several organic diamines which avoids the presence of short polar segments in the polymer chain.
More specifically, the compositions of the present invention comprise the condensation product of
a) an acid component consisting essentially of one or more crude polymeric fatty acids and one or more dicarboxylic acids and optionally a monocarboxylic fatty acid
b) an amine component, consisting of
i) one or more aliphatic diamines in which the amine groups are bonded to the aliphatic chain with a number of carbon atoms equal to or higher than 4 and,
ii) one or more cyclic aliphatic diamines and optionally
iii) one or more polyoxyalkylene diamine.
These polyamide condensation products are solid at room temperature, having a softening point of at least 80°, preferably above 100° C. These solid polyamides are either acid terminated or amine terminated.
DETAILED DESCRIPTION OF THE INVENTION
The softening point is determined by the standard Ring and Ball method according to ASTM E 28.
The reactants employed to prepare the polyamide adhesive compositions of the present invention are well known as are the methods of their preparation. The crude polymeric fatty acids are complex mixtures resulting from the polymerization of fatty acids. Representative of crude polymeric fatty acids are those commercially available from the polymerization of tall oil fatty acids, linoleic or oleic acid. These p
Meda Francesco
Rossini Angela
Hampton-Hightower P.
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Ortiz Daniel S.
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