Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Sealing compound and its use for producing
pressure-tight containers
The subject of the present invention is a sealing compound
which comprises
A) from 20 to 95% by weight of at least one compound
having on average at least 2 isocyanate groups per molecule)
the isocyanate groups each being blocked,
H) from 1.5 to 30% by weight of at least one di- and/or
polyamine,
C) from 0 to 50% by weight of at least one further organic
polymer,
D) from 0 to 60%. by weight of pigments and/or fillers,
E) from 0 to 50% by weight of one or more reactive
diluents, and
F) from 0 to 35% by weight of auxiliaries and additives.
The present invention relates, furthermore, to processes for
preparing the sealing compound, to processes for producing
closures, especially for the pressure-tight sealing of
packaging containers, using this sealing compound, and to
such closures.
Sealing compounds of the type specified at the outset axe
already known from EP-B-542 766. According to EP-B-542 766,
these sealing compounds are employed in producing closures
for food packaging containers. The use of the sealing
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compounds to produce pressure-tight containers, on the other
hand, is not described in EP-B-542 766.
In the field of pressure-tight containers, especially for
the transportation and storage of liquid goods, for example
paints and inks, and other industrial products subject to
labeling requirements (e. g. chemicals or other
environmentally hazardous goods), there is an increased
requirement for containers which meet the appropriate
standards relating to sealing without an additional clamping
ring. At the same time, however, these containers should
also be easy to open without the use of special tools.
Consequently, EP-B-546 051 proposed applying, to an already
IS applied sealing compound, an adhesive which ensures both the
sealing of the containers without an additional clamping
ring and the trouble-free opening of the containers.
This solution proposed in EP-B-546 051, however, has a
number of disadvantages. For instance, the additional
application of an adhesive requires another process step in
producing the closures, which is associated with further
costs and high time consumption. Furthermore, there is the
possibility that after the containers have been
opened/closed a number of times constituents of the adhering
layer will enter the contents, leading to complaints on the
part of the filling plants.
The present invention is based, accordingly, on the object
of providing a sealing compound which allows the production
of pressure-tight containers, the containers being intended
to meet the corresponding standards (for example German
Hazardous Goods Ordinance Rail and Hazardous Goods Ordinance
Road, Appendix A5) in relation to pressure tightness without
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the use of an additional clamping ring and without the
additional application of an adhesive to the sealing
compound. Furthermore, the sealing compound should show
little or no migration of the constituents of the sealing
compound into the packaged product. In addition, the sealing
compound should also meet the other requirements commonly
set, for example in relation to chemical resistance and
elasticity. Finally, the sealing compound should be able to
be applied and cured on the existing plant.
This object is surprisingly achieved by the sealing compound
of the type specified at the outset, which is characterized
in that it comprises G) from 1 to 40% by weight of at least
one adhesive, the sum of the proportions by weight of all
components (A) to (G) employed in the sealing compound being
in each case 100% by weight.
Further subjects of the present invention are processes for
preparing the sealing compound, processes for producing
closures, especially for the pressure-tight sealing of
packaging containers, using this sealing compound, and such
closures.
It is surprising and was not foreseeable that with the aid
of the sealing compound according to the invention it is
possible to produce pressure-tight containers which comply
with the standards customarily set for such containers, even
without an additional clamping ring and without the
additional application of an adhesive. At the same time it
is also surprising that the sealing compound, and especially
the adhesive component, exhibits extremely little or no
migration into the product - both during storage of the
containers and after the containers have been opened.
Moreover, it is advantageous that by virtue of the addition
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of component (G) the properties of the sealing compound, for
example in respect of chemical resistance and elasticity,
suffer little or no significant adverse effect. Another
advantage, finally, is that the sealing compound can be
applied on the plant which is customarily employed.
In the following text, then, the individual constituents of
the sealing compound according to the invention will first
of all be explained in more detail.
Compounds suitable as component (A) of the sealing compound
are all those having on average at least two isocyanate
groups per molecule. The isocyanates in this case can be
monomers or oligomers and also prepolymers having at least 2
NCO groups per molecule. The prepolymers can have been
prepared, for example, by the reaction of a diisocyanate
with a chain extender. The isocyanate groups of component
(A) are not free but are present in blocked form. It is
preferred to employ blocked isocyanates which at room
temperature are liquid or are present as a solution or
dispersion. It must also be ensured that, in the case of
food packaging, the migration rate of the structural
components of the isocyanate compound, for example blocking
agent, into the product is as low as possible.
Examples of suitable blocking agents of component (A) are,
in particular, compounds unobjectionable from the standpoint
of foodstuffs law, for example amino acids, cyclized amino
acids and sugars, and also, for example, malonic acid and
malonic esters. Other possible blocking agents are oximes,
for example acetoxime, diethyl ketoxime, acetophenone oxime,
cyclohexanone oxime, cyclopentanone oxime, formaldoxime,
acetaldoxime, and also phenols and caprolactams. When these
blocking agents are employed, however, it should be ensured
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that no problems occur as a result of migration of residues
of blocking agent into the product.
Isocyanates suitable as the isocyanate component are, in
5 particular, all those which, in the form in which they have
been fully reacted with one of the above-mentioned blocking
agents, are preferably liquid and lead to systems which
preferably have Shore A hardnesses (DIN 53 505) of between
20 and 80. Preferably, furthermore, the isocyanate component
should not be readily volatile at room temperature.
Examples of suitable isocyanates are di- and/or trimerized
2,4- and 2,6-tolylene 'diisocyanate, di- and/or trimerized
hexamethylene diisocyanate, alone or in a mixture with small
amounts of monomeric tolylene or hexamethylene diisocyanate,
respectively. Also suitable are chain-extended
diisocyanates, especially chainextended tolylene or
hexamethylene diisocyanate. Chain extenders employed are
diols and/or triols and/or polyols and also mixtures of
diols with tri- and/or polyols. It is preferred to. employ
di- and/or trimerized tolylene diisocyanate or tolylene
diisocyanate which has been chain-extended with a diol
and/or triol.
Component (A) is employed in the sealing compound in an
amount of from 20 to 95o by weight, preferably from 25 to
90o by weight, based in each case on the overall weight of
the sealing compound.
Compounds (component (B)) suitable for crosslinking the
blocked isocyanates, which are employed in an amount of from
1.5 to 30o by weight, preferably from 2 to 20% by weight,
based in each case on the overall weight of the sealing
compound, are di- and/or polyamines, especially diamines
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which are liquid at room temperature, particularly
preferably liquid cycloali.phatic diamines, for example 4,4-
diamino-3,3-dimethyldicyclohexylmethane, 4,4-diaminodicyclo-
hexylmethane, polyoxypropylenetriamine having a mean
molecular weight MW of from 400 to 450, and also liquid
polyaminoamides such as) for example, the commercial product
"Versamid 100" from the company Schering AG, and liquid
polyaminoamides prepared by condensation of di- and trimeric
fatty acids with aliphatic amines, and also amines having a
low melting point. The amino groups of the amino compounds
employed are generally primary and/ or secondary in nature.
By means of the ratio of isocyanate component (A) and amine
component (B) established in each case in the sealing
compound it is possible, as by appropriate choice of
components (C) and (G) and the selection of the particular
auxiliaries and additives employed, to influence the tack of
the sealing compounds within certain limits. The isocyanate
component (A) and the amine component (B) are therefore
employed in the sealing compounds according to the invention
preferably in amounts such that the proportion of component
(A) to component (B) is between 7 . 1 and 15 . 1,
particularly preferably between 10 . 1 and 14 . 1.
As a further constituent (C) the sealing compound may also,
if desired, include at least one further organic polymer,
preferably at least one further plastic and/or elastic
and/or reactive organic liquid and/or pulverulent polymer.
This component (C) is employed in the sealing compound in an
amount of from 0 to 50% by weight, preferably from 1 to 350
by weight, based in each case on the overall weight of the
sealing compound.
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Examples of suitable modifiers (component (C)) are styrene-
butadiene copolymers, styrene-butadiene-styrene rubber,
relatively high molecular mass polyethylene homo- and
copolymers, relatively high molecular mass ethylene-vinyl
acetate copolymers, relatively high molecular mass vinyl
acetate-ethylene copolymers, polystyrene, polyvinyl
alcohols, polyamides, acrylate polymers, nitrile rubbers,
polyurethane precondensates, epoxy resins, polyesters,
sugars, etc.
Through the selection of the nature and amount of these
modifiers it is possible to control specifically the
properties of the sealing compound, for example the
flexibility. This, however, is known to the skilled worker,
and the most favorable type and amount of these modifiers in
each case can readily be determined with the aid of a few
routine experiments.
As a further constituent the sealing compound also contains
from 0 to 60% by weight, preferably from 0 to 30o by weight,
based in each case on the overall weight of the sealing
compound, of pigments and/or fillers, such as, for example,
titanium dioxide, synthetic iron oxides, organic pigments,
for example phthalocyanines, tartrazines, ultramarine blue,
Pigment Yellow 83, Pigment Orange 43, Pigment Orange 5,
Pigment Red 4, and also magnesium silicates and aluminum
silicates, amorphous and pyrogenic silica, barium sulfate,
carbon black, talc, kaolin and chalk (component (D)).
To establish a favorable application viscosity the sealing
compound may also comprise from 0 to 50% by weight,
preferably from 0 to 20% by weight, based in each case on
the overall weight of the sealing compound, of one or more
reactive diluents (component (E)).
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Examples of suitable compounds are preferably polyfunctional
amines, especially cycloaliphatic diamines, for example
cyclohexylpropylenediamine etc. In addition, however, it is
also possible to employ polyols, for example propylene
glycol and diethylene glycol and also reactive oils, for
example vegetable oils containing OH groups, as reactive
diluents. However, they have the 'disadvantage of a lower
reactivity in comparison with polyamines.
Finally, the sealing compound according to the invention may
also comprise from 0 to 35% by weight, preferably from 1 to
20% by weight, based on the overall weight of the sealing
compound, of other auxiliaries and additives (component
(F)). Examples thereof are, in particular, low molecular
mass plasticizers, for example phthalates, citrates,
sebacates, octoates and the like, and also other customarily
employed auxiliaries and additives, for example silicone
oils.
Further examples of compounds employed as component F are
waxes and silicas for obtaining specific flow properties
(thixotropic agents) and, in the case of foamed sealing
compounds, blowing agents, for example azodicarboxamides or
sulfohydrazides.
Preferably, however, the sealing compound according to the
invention contains less than to by weight, with particular
preference essentially no lubricants, since the customarily
employed lubricants reduce the tack of the sealing compound.
The sealing compound is employed primarily for use in
closures for pressure-tight containers of the type specified
at the outset. Alternatively, it can be employed as a foamed
sealing compound. In general the foaming of the sealing
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compounds brings about a reduction in the Shore A hardness
(measured in accordance with DIN 53 505), an increase in the
flexibility, a more favorable weight/volume ratio, and the
obtention of a better sealing function as a result of better
deformability. The tack of the sealing compound is affected
only slightly, in general, by the addition of foaming
agents.
It is essential to the invention that the sealing compound
contains from 1 to 40% by weight, preferably from 5 to 25 0
by weight, based in each case on the overall weight of the
sealing compound, of at least one adhesive.
Adhesives suitable in principle for use in the sealing
compound according to the invention are all adhesives,
especially all adhesives which at room temperature are
liquid or highly viscous. In this case, component (G) can
also be employed in the form of a liquid or highly viscous
solution or dispersion. Also suitable in principle are so
called hotmelt adhesives.
Component (G) is generally selected such that at least some
of component (G) is located on the surface of the sealing
compound, after the sealing compound has been applied, and
ensures heightened adhesion or adhesion promotion of the
sealing compound relative to the counterpart of the closure
(for example metal or further sealing compound).
In the sealing compound according to the invention it is
possible, for example, to employ adhesives based on tall
resins and/or colophony resins and the like. The adhesives
preferably employed in the sealing compound according to the
invention are low molecular mass, branched or, preferably,
linear or substantially linear homo- and/or copolymers of
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aliphatic, ethylenically unsaturated hydrocarbons having 2
to 6 C atoms, for example polybutene and/or polyisobutylene
or polyisobutene and/or ethylene-propylene copolymers and/or
ethylene-vinyl acetate copolymers.
The preparation of the sealing compound takes place by
mixing the individual components, with or without first
adding the insoluble components, for example pigments, to
component (A) and - where necessary - carrying out
dispersion using the dispersing equipment customary in the
coating industry. In the case of the preparation of non-
foamed sealing compounds, mixing or dispersing is usually
carried out under vacuum. The sealing compound prepared in
this way generally has Shore A hardnesses (DIN 53 505) of
between 20 and 80, preferably between 25 and 70.
The amount in which the sealing compound is applied depends
on the geometry of the closure part, on the intended use of
the packaging and whether the sealing compound is foamed or
not. For use in pressure-tight containers, the sealing
compound according to the invention is usually applied in a
coat thickness of from 0.2 to 20 mm, preferably from 1 to
10 mm.
To produce the closures in accordance with the process
according to the invention the above-described sealing
compound is applied to the closures, preferably by means of
the known "injection process". In this process, the sealing
compound is injected or pressed at slightly elevated
temperature, usually from about 30 to 70°C, in the uncured,
pastelike state, from one or more nozzles, into the closure
parts, which are set in rotation using a suction cup or the
like at high rotational speed. Owing to the centrifugal
forces, the sealing composition is transferred in the
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desired contour and form. After this inflow is complete,
curing of the sealing compound takes place at temperatures
between 150°C and 240°C for a drying time of from 1 to 5 min
(conditions depending on recipe). Drying, and the equipment
employed for it, are likewise known and therefore require no
further explanation here.
The closure which is to be coated with the sealing compound
is understood as being all parts of the packaging material
which are connected to the body of the packaging. In
particular, however, the sealing compounds are applied in
pressure-tight containers as are employed for the
transportation and the storage of liquid products, for
example paints and inks, or other chemicals (for example
goods subject to labeling requirements, which in some
circumstances may be environmentally hazardous). The sealing
compound according to the invention is suitable, for
example, for application in the containers described in EP-
B-546 051, with sealing being ensured without an additional
clamping ring and without the additional application of an
adhesive.
These closures may consist of metals, such as aluminum,
black plate, tinplate and various ferrous alloys, to which a
passivating layer based on nickel compounds, chromium
compounds and tin compounds may have been applied. In the
process according to the invention the sealing compound can
be applied to coated closures, but in particular, owing to
the good adhesion to metals, can also be applied to uncoated
closures.
Suitable coating compositions are the coating materials,
customary in the packaging industry, based on epoxy-phenolic
resin, acrylate resin or polyester, or organosols. However,
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these coating materials are known (cf. e.g. H. Kittel,
Lehrbuch der Lacke and Beschichtungen [Textbook of Paints
and Coatings), Volume IV, Lack- and Beschichtungssysteme,
Formulierung [Paint and coating systems, formulation),
Verlag W.A. Colomb in der H. Heenemann GmbH, Berlin-
Oberschwandorf 1976) and therefore require no more detailed
description here.
The invention is illustrated in more detail below with
reference to working examples. Unless expressly stated
otherwise, all indications as to parts and percentages are
by weight.
First of all, the sealing compounds of Examples 1 to 5 and
of Comparison Example 1 are prepared from the components
indicated in Table 1 by mixing. The tack (manually} and the
exudation behavior (manually and visually) of these sealing
compounds are assessed. The results of these investigations
are likewise shown in Table 1.
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Table 1: Composition of the sealing compounds in parts, and
properties of the sealing-compounds
Ex. Ex. Ex. Ex. Ex. Comp.
1 2 3 4 5 1
Isocyanate 1~ 46.8 46.8 46.8 42.9 41.6 52.0
Polyamine 2~ 3.6 3.6 3.6 3.3 3.2 4.0
BaS04 4.5 4.5 4.5 5.0 4.0 5.0
TiOz 1.0 1.0 1.0 1.0 0.8 1.0
Polymer 3~ 4.1 4.1 4.1 4.5 3.7 4.5
Talc 9.0 9.0 9.0 10.3 8.0 10.4
Plast. 4~ 21.0 21.0 21.0 23.0 18.7 23.0
Silicone oil 5~ - - - - - 0.1
PIB 1 6~ 10.0 - - - 20.0 -
PIB 2 ~~ - 10.0 - - - -
PIB 3 e~ - - 10.0 - - -
PB 1 9 ~ - _ _ _ _
10.0
Tack 1~ sat. sat. sat. sat. sat. unsat.
Exud. 11~ sat. sat. sat. 12) sat -----
Key to Table 1:
1): commercial, s-caprolactam-blocked polyisocyanate
(commercial product Desmodur~ BL 1100 from the company Bayer
AG )
2): 4,4 diamino-3,3-dimethylcyclohexylmethane [sic]
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3): commercial polymethyl methacrylate having a softening
temperature of about 130°C and a Tnmax of about 136°C
4): commercial plasticizer based on diisononyl phthalate
5): commercial silicone oil having a viscosity of 340 cPs at
25°C
6): commercial, low molecular mass, room-temperature-liquid
polyisobutylene having a number-average molecular weight of
1300, a density at 20°C of 0.89 g/cm3 and a viscosity at
100°C of about 500 mm2/s
7): commercial, low molecular mass, room-temperature-liquid
polyisobutene having a kin. viscosity at 100°C of 180 -240
mm2/s , a density at 20°C of 0.887 g/cm3 and having a number-
average molecular weight of 940
8): commercial, low molecular mass, room-temperature-liquid
polyisobutene having a kin. viscosity at 100°C of 570 -650
mm2 / s
9): commercial, room-temperature-liquid, low molecular mass
polybutene having a viscosity at 99°C of 635 - 690 cSt
10): The tack was assessed manually (finger test) (sat. -
satisfactory; unsat. - unsatisfactory).
11): The exudation was assessed manually and visually (sat.
- satisfactory; unsat. - unsatisfactory).
12): Very severe exudation
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