Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-08-27
2003-06-03
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C206S568000, C252S183110, C528S053000
Reexamination Certificate
active
06572729
ABSTRACT:
The invention relates to the field of polyurethane formulations and, in particular, to polyurethane formulations based on hydroxylated polybutadienes, which are catalysed so as to have an extended pot life and rapid setting.
Generally speaking, the catalysis chosen for this type of formulation permits a slow increase in the viscosity of the formulation over a sufficiently long time, followed by a rapid increase. The person skilled in the art renders this, respectively, by prolonged pot life and rapid setting.
The polyurethane material is obtained by reaction between a part A comprising at least one compound having at least two alcohol functions, designated hereinafter as polyol, and a part B, comprising at least one compound having at least two isocyanate functions, designated hereinafter as polyisocyanate.
The formulations which lead to the polyurethane material therefore consist of two parts A and B which, once intimately mixed, crosslink in accordance with a particular viscosity-rise profile. Generally speaking, the catalyst system is present in part A.
Generally speaking, each part can comprise different elements, such as mineral fillers, plasticizers, stabilizers, etc.
It is found that catalysis with mercury salts, which is employed in general, meets the requirements perfectly. For example, the person skilled in the art knows that organomercury salts have a capacity to give an extended pot life and rapid setting.
However, the mercury salts pose an obvious environmental problem, and the use of these compounds is increasingly deprecated.
The problem, therefore, which the applicant is proposing to solve is to substitute the catalysts based on mercury salt by another compound which allows an extended pot life and rapid setting and which does not pose an environmental or ecotoxicological problem.
The applicant has found that an ingenious solution to this problem involves the substitution of the catalysts based on mercury salt by an at least N-substituted imidazole derivative.
Indeed, at least N-substituted imidazole derivatives contain no environmentally harmful heavy metals and, as catalysts of polyurethane formulations, allow an extended pot life and rapid setting. Furthermore, they are stable and retain their catalytic activity even in the course of prolonged storage.
The said catalyst system is used in a conventional polyurethane formulation including optionally a filler, a plasticizer and/or an adhesion promoter.
One of the subjects of the invention is a formulation which leads to a polyurethane material and consists of two parts A and B which, once intimately mixed, crosslink in accordance with a particular viscosity-rise profile, characterizing the invention as described below.
Generally speaking, the catalyst system is present in part A. However, in accordance with another variant, it may be present in part B.
In accordance with one embodiment of the invention, the part A comprising the polyol or polyols consists of:
from 5 to 99.99% by weight and, preferably, from 10 to 50% of at least one polyol,
from 0 to 50% by weight and, preferably, from 10 to 50% of at least one plasticizer,
from 0 to 90% by weight and, preferably, from 40 to 90% of at least one mineral filler,
from 0 to 20% by weight and, preferably, from 0 to 10% of at least one dehydrating agent of the molecular sieve type,
from 0 to 5% by weight and, preferably, from 0 to 1% of at least one tackifying resin,
from 0 to 5% by weight and, preferably, from 0 to 1% of at least one UV stabilizer and/or one antioxidant,
from 0.01 to 1% by weight and, preferably, from 0.01 to 0.1% of the catalyst system according to the invention.
The polyols which can be used are, generally, polymers having a number-average molecular mass Mn ranging from 500 to 15,000 and, preferably, ranging from 1000 to 5000.
In accordance with the invention, the polyols are preferably polydiene polyols having number-average masses of less than 7000 and, preferably, of between 1000 and 5000.
They exhibit average functionalities ranging from 1 to 5 and, preferably, of between 1.8 and 3.
In accordance with the present invention, the conjugated diene of the polydiene polyol is selected from the group consisting of butadiene, isoprene, chloroprene, 1,3-pentadiene and cyclopentadiene.
Also suitable are the copolymers of conjugated dienes and vinyl and acrylic monomers, such as styrene and acrylonitrile.
By way of illustration of polydiene polyols, mention may be made of the hydroxylated polybutadienes marketed by the company ELF ATOCHEM S.A. under the tradenames POLY BD®R-45HT and POLY BD®R-20LM.
These polyols can be used in a mixture with polyether polyols or polyester polyols.
It would not be departing from the scope of the invention to use hydroxytelechelic diene oligomers epoxidized on the chain or else hydrogenated hydroxytelechelic oligomers of conjugated dienes.
In accordance with the invention, a polyol with a mass of less than 500, referred to as chain extender, can be mixed with the polyol.
By way of illustration of such compounds, mention may be made of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, N,N-bis(2-hydroxypropyl)aniline and 2-methyl-1,5-pentanediol.
It would not be departing from the scope of the invention to add to the polyol a polyamine as chain extender, such as isophoronediamine. hexamethylenediamine or amine-modified ethylene glycol oligomers, such as the Jeffamine® products from the company HUNTSMAN.
The plasticizers which can be used in accordance with the present invention are plasticizers known to the person skilled in the art, namely esters of divalent or polyvalent carboxylic acids, naphthenic oils, and mixtures thereof. By way of example, preference is given to the use of dialkyl phthalates, such as di(2-ethylhexyl)phthalate and di(undecyl)phthalate, benzyl alkyl phthalates, and cycloaliphatic compounds obtained from the distillation of naphthenic cuts.
The mineral fillers, whose function is to regulate the viscosity and rheological profile of the mixture, can be selected from treated or untreated carbonates, treated or untreated silicates, treated or untreated oxides of titanium, of aluminium or of other metals, and carbon blacks.
The liquid tackifying resins which are used in order to improve the adhesion can be brought in as esters, hydrogenated or unhydrogenated terpene resins, or a mixture thereof.
The UV stabilizers and antioxidants are, generally, those used in the polyurethanes industry.
The dehydrating agent, whose function is to limit or even eliminate the harmful effect of moisture, is selected, for example, from the range of the molecular sieves.
The catalyst system will be selected from the chemical class of the substituted imidazoles, alone or in a mixture with tertiary amines in order to permit suitable ultimate crosslinking kinetics, such as triethyldiamine.
The imidazoles of the invention correspond to the following general formula:
in which
R
1
is a C
1
-C
4
alkyl group such as methyl or ethyl,
R
2
, R
3
and R
4
, which are identical or otherwise, are selected from the group of:
hydrogen,
C
1
-C
6
cyclic or branched or linear aliphatic alkyl radicals.
According to the invention, the catalyst is chosen so as to provide an extended pot life and rapid setting. This is measured by an apparatus of the TROMBOMAT type. In particular, the slope of the curve at the point of inflection must be at least 50 Pa.s/min (see attached FIG.
1
).
Part B comprising the polyisocyanate consists of
from 5 to 100% by weight and, preferably, from 20 to 40% of at least one polyisocyanate,
from 0 to 80% by weight and, preferably, from 20 to 60% of at least one plasticizer,
from 0 to 80% by weight and, preferably, from 5 to 40% of at least one mineral filler, which acts as pigment,
from 0 to 20% by weight and, preferably, from 0 to 10% of at least one dehydrating agent of the molecular sieve type, and
from 0 to 50% by weight and, preferably, from 10 to 30% of at least one adhesion promoter.
The polyisocyanates whi
Auvray Josée
Flat Jean-Jacques
Pradel Jean-Laurent
Renouard Philippe
Elf Atochem
Gallagher John J.
Smith , Gambrell & Russell, LLP
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