Note: Descriptions are shown in the official language in which they were submitted.
10967S4
The invention relates to a method for the production of laminated
films using solvent-free adhesives comprising at least one multi-functional
isocyanate and at least one multi-functional reactive amine.
Laminated films are generally produced by means of laminating
adhesives containing solvents which adhesives are applied by rolling onto a
sheet web. In this method of production, after evaporation of the solvent,
~oining of one sheet web to the second web is effected under pressure for a
short period of time.
In this method, which is known as dry lamination, almost
exclusively polyurethane systems, containing solvents, in the
form of moisture-hardening prepolymers with isocyanates in the
terminal position or two-component polyol-polyisocyanate mixtures,
are used as adhesives. The recent restrictions on the release
of solvents into the atmosphere require the absorption or after-
burning of the solvent-air mixture as a costly step in the pro-
cess.
It is an object of the present invention to provide an improved
method for the production of laminated films using an adhesive system which
which is free of solvents and can thus be worked with less danger of fire or
explosion, as well as a more economical processing method.
It is another object of the present invention to provide a
method for the production of laminated films, which gives clear films
with good adhesive strength in a manner which is technically inexpensive.
~k
10~67Ç~
It is a further object of the present invention to
provide a process for producing laminated films employing a
two component non-solvent adhesive system, which comprises the
steps of applying a thin film of at least one polyether having
at least two terminal isocyanate groups and a molecular weight
between 2000 and 5000 to one of two films to be bonded together,
applying a thin film of at least one long chain compound
having at least two reactive terminal amino groups to the other
film to be bonded, the application of both thin fi~ms being
in such amounts that the molar ratio of isocyanate groups to
amine groups is from 1:1 to 5:1 and the two components together
being present in an amount of 0.5 to 5.0 gm/m2, pressing the
coated sides of the two coated films together and recovering
said laminated films.
In one particular aspect the present invention provides
a method for the production of laminated films employing a
two-component non-solvent adhesive system, which comprises
the steps of
applying a thin film of a mixture of (a) the reaction
product of 1 mole of polyoxyalkylene glycol having 2 to 4
carbon atoms in the alkylene and 2 moles of a diisocyanate,
said reaction product having a molecular weight of from 2000 -
to 5000, and (b) a compound selected from the group consisting
of (i) the reaction product of an alkanepolyol having 3 to
10 carbon atoms and 3 to 6 hydroxyl groups or a cycloalkane
polyol having 6 to 8 carbon atoms and 3 to 6 hydroxy groups
with a diisocyanate, wherein 1 mole of diisocyanate is
reacted per hydroxy group of said polyol; (ii) the reaction
product of one mole of water and three moles of a diisocyanate;
(iii) an aromatic triisocyanate; and (iv) a polyisocyanate,
said compound (b) having at least three isocyanate groups
being present in an amount of 0.5 to 20% by weight, relative
jl/. .. ~ -2-
~0~6764
to said reaction product (a), to one of two films to be
bonded together,
applying to the other film to be bonded a thin film of
at least one second reaction product of 1 mole of polyoxyalkylene
glycol having 2 to 4 carbon atoms in the alkylene with 2
moles of acrylonitrile, which was subsequently catalytically
hydrogenated, said reaction product having a molecular
ueight of from 300 to 2000, the application of both thin
films being in such amounts that the molar ratio of isocyanate
groups to amine groups is from 1:1 to 5:1 and the two components
together being present in an amount of 0.5 to 5.0 gm/m2,
pressing the coated sides of the two coated films
together whereby adhesion between the coated films is initiated,
anl
recovering said laminated films.
In another particular aspect the present invention
provides a method for the production of laminated films
employing a two-component non-solvent adhesive system, which
comprises the steps of
applying a thin film of at least one reaction product
(a) of 1 mole of polyoxyalkylene glycol having 2 to 4 carbon
atoms in the alkylene and 2 moles of a diisocyanate, said
reaction product (a) having a molecular weight of from 2000
to 5000, to one of two films to be bonded together,
applying to the other film to be bonded a thin film of
at least one reaction product (b) of 1 mole of polyoxyalkylene
glycol having 2 to 4 carbon atoms in the alkylene with 2
moles of acrylonitrile, which was subsequently catalytically
hydrogenated, said reaction product (b) having a molecular
weight of from 300 to 2000, the application of both thin
films being in such amounts that the molar ratio of isocyanate
groups to amine groups is from 1:1 to 5:1 and the two components
~ 2a-
l~q6764
together being present in an amount of 0.5 to 5.0 gm/m2,
pressing the coated sides of the two coated films
together whereby adhesion between the coated films is initiated,
and
recovering said laminated fil~s.
The above and other objects of the present invention will
become more apparent as the description thereof proceeds.
In order to obtain the above objects and to overcome the
drawbacks of the prior art, the present invention provides a
method for producing laminated films by applying a solvent-free
adhesive comprising at least one multi-functional isocyanate
to one of two films to be bonded together and a solvent-free
adhesive comprising at least one multi-functional reactive amine
to the other film and pressing the two coated films surfaces
formed together for a short period of time.
More particularly, the present invention provides a
process for producing laminated films employing a two component
non-solvent adhesive system, which comprises the steps of
applying a thin film of at least one polyester having at least
two terminal isocyanate groups and a molecular weight between
2000 and 5000 to one of two films to be bonded together,
applying a thin film of at least one long chain compound having
at least two
~ 2b-
l~g~764
reactive terminal amino groups to the other film to be bonded,
the application of both thin films being in such amounts that the
molar ratio of isocyanate groups to amine groups is from l:l to
5:1 and the two components together being present in an amount
of 0.5 to 5.0 gm/m2, relative to the area of contact of the two
films, t~ pressing the two coated sides of the two coated films
together and recovering said laminated films.
The pressing together of the two films need only be
effected for a short period of time to achieve satisfactory
`lO adhesion.
Isocyanates which are at least bi-functional and suit-
able for use in the method of the present invention can be pro-
duced in a manner known per se through the conversion or reaction
of anhydrous polyether diols with at least bi-functional isocyan-
ates in a molar ratio whereby one mole of said at least bi-
functional isocyanate is employed per hydroxyl group. Preferred
polyether diols are the polyoxyalkylene glycols derived from
alkylene glycols containing 2 to 4 carbon atoms. Consequently,
polyoxyethylene glycol and/or polyoxypropylene glycol and/or
polyoxytetramethylene glycol (produced by ring-opening polymeriza-
tion of tetrahydrofuran) are suitable. For the reaction with
polyether diols mainly relatively low-molecular weight isocyan-
ates, preferably alkylene diisocyanates having 3 to 12 carbon
atoms in the alkylene, cycloalkylene diisocyanates having 5 to
12 carbon atoms in the cycloalkyl and aromatic hydrocarbon diiso-
cyanates having 6 to 15 carbon atoms in the aromatic hydrocarbon)
such as hexamethylenediisocyanate, trimethylhexamethylene diiso-
cyanate, dicyclohexylmethane diisocyante, diphenylmethane diiso-
cyanate, isophorone diisocyante, toluylene diisocyanate(isomeric
mixture), and others~are primarily suitable for the reaction with
the polyether diols. For practical, particularly toxicological,
reasons, diphenylmethane diisocyanate is preferred.
1096764
A reaction or conversion ratio of 1.8:1 up to 2.2:1 :i5
preferably suitable for the formation of the isocyanate poly-
ether diol adduct, the ratio being of moles diisocyanate to
moles diol. A lower conversion ratio is theoretically also
possible, on the condition that a too highly viscous adduct is
not thereby produced, the use of which no longer perrnits satis-
factory machine lamination. A possibly higher conversion ratio
than 2.2:1 would also be tolerable in principle, if there were
no doubts on toxicological grounds regarding the high content
of free diisocyanate inthiscase.
Attention should be paid to the fact that the resulting
isocyanate compounds do not exceed a viscosity (Brookfield) of
approximately 10,000 cP during processing. If required, this
reaction component can also be applied at high temperature up
to approximately 80C. In general, however, a temperature of
50 to 65C is preferred.
Applications of laminating adhesives which are carried
out only with the adducts, having at least two terminal iso-
cyanate groups, as isocyanate component, in combination with
the amine compounds described below, as amine component, give
sufficient adhesiveness. It has, however, been discovered that
this adhesiveness can be considerably increased if 0.5 to 20%,
preferably 1.0 to 10%, by weight of a compound having at least
three isocyanate groups is added to the isocyanate adduct,
wherein said percentages by weight are in relation to the iso-
cyanate adduct. By modifying the isocyanate component in this
manner a higher initial adhesiveness is, in particular,achieved
as well as, moreover, an improved final adhesiveness. The
reaction products of multi-functional alcohols,such as alkane-
polyols having 3 tolo carbon atoms and 3 to 6 hydroxyl groups
6764
and cycloalkane polyols having 6 to 8 carbon atoms, and 3 to 6
hydroxy groups,and diisocyanates, such as the above-indicated
diisocyanates, (using a conversion ratio of 1 mol diisocyanate
per hydroxyl group in the alcohol) are suitable as the addition
compounds having at least three isocyanate groups, as e.g.~the
conversion product of trimethylolpropane and toluene diiso-
cyanate, as well as the reaction products of one mole water and
three moles diisocyanate, such as the above-indicated diiso-
cyanates, as e.g., hexamethylene diisocyanate, as well as other
aromatic triisocyanates, preferably phenyl or phenyl alkane
triisocyanates containing from 6 to 22 carbon atoms and 1 to 3
phenyl groups, such as 4,4',4"-triisocyanatotriphenylmethane,
and also polyisocyanates such as polymethylenepolyphenyl
isocyanate.
In order that the resulting isocyanate mixtures can be
easily applied to the sheet web during machine lamination they
should be heated in the coating pan to lower the working
viscosity. When heating the isocyanate mixtures, a maximum
temperature of 80C should not be exceeded. In general a
temperature of 60C is completely sufficient. Up to this
temperature it was established by measurements taken at the
laminating machine that no isocyanate concentration exceeding
the MAK value of 0.02 ppm occurred in the workplace atmosphere
during lamination with the isocyanate component described in
Example 1 below of this application.
The second reaction component which is used for the
method of the present invention is an at least bi-functional
amine. At least two amino groups must be present which can be
both primary and secondary. Compounds of this type are known
and can be produced in a known manner.
l~q6764
A preferred basic framework upon which this amino
compound can be built up is the polyether diols or oligomeric
glycols such as the polyoxyalkylene glycols having from 2 to 4
carbon atoms in the alkylene. In accordance with an advant-
ageous embodiment one proceeds by adding acrylonitrile onto the
polyether diols. ~he adducts which thereby result are then
hydrogenated in a known manner, whereby primary amino groups
are formed from the nitrile groups. For the production of the
two reaction components of the solvent-free laminating adhesive
those oligomeric glycols or polyether glycols are preferred,
which are derived from polyoxyethylene glycol, polyoxypropylene
glycol, and polyoxytetramethylene glycol of a molecular weight
of between 200 and 4500, preferably between 300 and 2000.
It is further possible to start from relatively low- -
molecular weight diamines having a chain length of 2 to 18
carbon atoms, which can also be partially replaced by oxygen
atoms, and to react these diamines with compounds containing at
least two functional groupsX which are capable of reacting with
an amine (to thereby effect a chain lengthening~. Amines of
this type are, for example:
2 2 ~ 2 (CH2)2-_4 n_ CH2_ CH2_ CH _ NH
2 2 2 2 ( CH2_ CH2- )1 3 CH _ CH _ CH _ NH
or alternatively
CH CH3
H2~ CH2-- -- 'H2
CH3 H3
or H2N - (CH2)6-8 NH2
1~6764
The functional groups of the chain lengthening agents
can be, for example, epoxide or isocyanate radicals or also
~,~ unsaturated esters or halogen atoms. The OH groups,
secondary amino groups or urea groupings which form during this
reaction or the ester groupings introduced may have a favorable
effect on the adhesion or strength of the adhesive bond under
certain circumstances.
The compound containing at least two epoxide radicals
can be a diepoxide or diglycidyl compound having the formulae
CH CH-R-CH - CH or C ~ CH-CH2-0-R-0CH2-cH / H2
O O O O
wherein R is an aliphatic or cycloaliphatic radical with up to
25 carbon atoms, as for example, a~lene having 1 to 25 carbon
atoms or cycloalkylene having 5 to 25 carbon atoms, such as
methylene, ethylene, propylene, neopentylene, hexylene, dodecy-
lene, cyclohexylene, dicyclohexyl, methylene dicyclohexyl or,
alternatively, polyoxyalkylene having 2 to 4 carbon atoms in
the alkylene elements such as radicals derived from dioxyethy-
lene glycol or trioxyethylene glycol. The diamines can be di-
primary amines corresponding to the general formula
H2N--- R' NH2, where R' represents, for example, alkylene
having 2 to 18 carbon atoms such as ethylene, butylene,hexylene
polyoxyalkylene having 2 to 4 carbon atoms in the alkylene,
such as dioxyethylene, dioxypropylene, or, alternatively, tri-
oxyethylene. On chain lengthening of the amines using 2 moles
of a diamine for each mole of diepoxide, oneobtains compounds
containing two terminal primary amino groups of the general --:
formula
~)9676~
OH OH
H2N-R'-NH-CH2-CH-R-CH-CH2-NH-R'-NH2
In the case of chain lengthening with isocyanates, such
as the above-indicated diisocyanates, as for example, toluene
diisocyanate,hexamethylene diisocyanate and isophorone diiso-
cyanate, using again 2 moles of diamine to 1 mole diisocyanate,
one obtains compounds containing two terminal amino groups and
urea groups, of the general formulas
H2N-R'-NH-C-NH-R"-NH-C-NH-R'-NH2
O O
in which R' has the meaning given above, while R" represents
the radical of the isocyanate used.
When using (meth) acrylic acid esters of glycols (for
example tri- or tetraoxyethylene glycol di(meth)acrylic ester)
for chain lengthening, one obtains compounds of the general
formula ~
f -0-R"'-0-C~
NH2-R'-NH-CH2-CH CH-CH -NH-R'-NH
(H) (CH3) H(CH3)
in which R' again has the same significance as above, and R"'
represents the dialcohol radical of the (meth) acrylic ester,
i.e. the tri-, or tetraoxyethylene glycol radical in the case
mentioned by way of example. The indication H(CH3) shows the
configuration with a diacrylate (H) or a dimethacrylate (CH3).
It will be appreciated that one can also proceed from other
di(meth)acrylic acid esters of glycols, such as alkylene
glycols containing 2 to 18 carbon atoms, for example, ethylene
glycol, propylene glycol, butylene glycol, decane diol, etc.
--8--
1~9676g
Finally, it is also possible to effect a chain lengthen-
ing with a,~-dihalides, this being effected in accordance with
the same principle in a known manner. In this case, compounds
of the general formula
H2N-R'-NH-RiV-NH-R'-NH2
are produced, in which RiVrepresents a radical of up to 12
carbon atoms and which can optionally contain oxygen, for
example, alkylene having 1 to 12 carbon atoms or polyoxyalkyler.e
having 2 to 4 carbon atoms in the alkylene, such as in the case
of the tetraoxyethylene radical or trioxypropylene radical,
and R' has the same significance as before.
The ratio of diprimary amines to the chain-lengthening
agent shouldbe chosen such that approximately 1 mol of difunc-
tional epoxide, isocyanate, (meth)acrylic ester or dihalide is
allotted to 2 moles of amine. The reaction forms substantially
the desired compounds containing at least two end position
primary amino groups and having a molecular weight of approxi-
mately 300 to 2000. Advantageously, the viscosity of the
aminic component is somewhat less than that of the isocyanate
component. It has proved to be practicable to work towards a
viscosity of approximately 50 to 1200 cP at 20C to 30C.
The two reaction components are applied each to one
of the films by means of rollers in such amounts that the molar
ratio of the isocyanate groups of the isocyanate component on
one film to the amino groups of the amine component on the other
film lies between approximately 1:1 and 5:1. The amount is
otherwise measured such that the two components together are
present in an amount of 0.5 to 5.0 gm/m , relative to the area
of contact of the two films.
_g_
~q6764
The surfaces of the films coated with the two components
are pressed together between a pair of rollers which may also
be partially heated. The pressure required is nominal, only
that sufficient to bring the two films in contact. Adequate
primary adhesion (initial adhesion) is formed on the way to the
rolling-up arrangement and, if required, can be increased by
applying heat by, for example, hot air.
In many cases it may be advantageous to add l to 50% by
weight, preferably l to 15% by weight, relative to the weight
of the long chain compounds carrying the amino groups, of
water to said long chain compounds carrying the amino groups.
This causes an increase in or earlier attainment of the final
strength and affects, in a favorable manner, the sealing ability
of the laminated sheet.
The method in accordance with the present invention
enables the laminating operation to be carried out at relatively
high speeds. There is no need to use drying channels. After
the films have been pressed together during machine lamination
a sufficiently high initial adhesiveness is formed spontaneous~
so that the webs do not slip or slide relative to one another
and delamination or "telescoping" of the laminated sheet does
not occur while it is being wound on. Within seven days after
manufacture the adhesiveness reaches its final value during
storage at room temperature. The adhesive films are thereafter
chemically cross-linked and exhibit a behavior which satisifes
all the requirements of packing technology with regard to
laminar adhesion and thermal stability, which is a prerequisite
for its sealability. The finished laminates are further distin-
guished by very good optical properties. Very frequently occur-
3o ring laminating flaws such as "fish eyes" or "orange peel
structure" cannot be detected in the laminates.
--10--
~q6764
By means of the twin-component laminating adhesive of
the invention all laminates of plastic sheets such as poly-
ethylene, polypropylene, polyester (e.g. polyethylene tereph-
thalate),polyvinyl chloride, polystyrene, polyamide sheet
(e.g. polycaprolactam) etc., can be manufactured. Furthermore
the production of laminated films is possible by using metal
foils, e.g. aluminum foil, and, moreover, by using, various
cellulose glasses and paper.
Preferably the films have a thickness of from 6~ to 1 mm. The
laminates can be of different film components.
While the description discusses production of film
laminates, it is obvious that other materials can be bonded by
the adhesive system discussed, utilizing the conditions above.
The present invention will now be further illustrated by
references to the following examples:
EXAMPLES
The compounds designated as "aminopropylized" poly-
propylene glycols in the following examples were produced by
addition of acrylonitrile to the polypropylene glycol and sub-
sequent catalytic hydrogenation.
EXAMPLE 1
Component A
Component A consisted of:
2000 gm of the isocyanate adduct of polypropylene glycol, having
molecular weight 2000 and diphenylmethane-4,4'-diisocyanate, in
the molar ratio 1:2, and
100 gm of the reaction product of 3 moles hexamethylene diiso-
cyanate and 1 mole water.
--11--
~96764`
Physical Characteristics of Component A:
Content of free isocyanate groups: 4.2% or lO m.-eq./gm
Viscosity (Brookfield) at 23C : 25,000 cP
" " at 50C : 8,ooo cP
" " at 60C : 2,500 cP
Component B
Component B consisted of:
300 gm aminopropylized polypropylene glycol (average molecular
weight 400) and
500 gm of aminopropylized polypropylene glycol (average molecu-
lar weight 2000)
The amine content of component B was 2.5 m.-e~./gm
1.68 gm/m of the above component A, which was heated
to 60C, was applied by machine to a polyester sheet (sheet
thickness 12~m) and 0.35 gm/m of the above component B, at
room temperature, was applied to a polyethylene sheet of low
density polyethylene (sheet thickness 50~m), which had been
pre-heated by a corona discharge. The molar ratio of the
isocyanate to the amine component was l.9:1 (with respect to
isocyanate to amine groups). The coated sides of the sheets
were pressed together over rollers.
The adhesive film showed a high spontaneous initial
adhesiveness (30 seconds after application a peel adhesiveness
of 30 p/15 mm at a withdrawal speed of lO0 mm/min. was measured).
After a lamination lasting eight hours the above com-
ponents could also be processed satisfactorily with the forma-
tion of a consistently high initia~ adhesiveness. Due to the
-12-
1~6764
increase in viscosity in this case the application quantity of
the isocyanate component rose to 1.92 gm/m2 while the applica-
tion quantity of the amine component remained constant at
0.35 gm/m2, thus resulting in a molar application ratio of
2.2:1.
After storing the laminate for seven days at room
temperature a peel adhesiveness of 350 p/15mm was obtained.
This value was found for a section of the laminate which was
produced at the start of the eight-hour period of lamination as
well as in one which was produced at the end of the period.
EXAMPLE 2
Component A
Component A consisted of:
2000 gm of the isocyanate adductof polypropylene glycol (average
molecular weight2000) and diphenylmethane-4,4'-diisocyanate,
in the molar ratio 1:2.
Physical Characteristics of Component A:
Content of free isocyanate groups: 3.4% or 0.81 m.-eq./gm
Viscosity (Brookfield) at 23C: 20,000 cP
tl at 60C: 2,000 cP
Component B
Component B consisted of:
300 gm aminopropylized polypropylene glycol (average molecular
weight 400) and
500 gm aminopropylized polypropylene glycol (average molecular
weigh 2000)
-13-
~Q'~676~
The amine content of component B was 2.5 m.-eq./gm
2.1 gm/m2 of the above component~A heated to 60C, was
applied to an aluminum foil (foil thickness 12 mm) and 0.4
gm/m2 of the above component B at room temperature was applied
to a polyethylene sheet of low density polyethylene (sheet
thickness 50~m), which had been pre-treated by means of a
corona discharge. The molar ratio of the components was 1.7:1
(isocyanate: amine groups).
By pressing together the coated sheet sides a sufficiently
high initial adhesiveness was reached. (Tensile peel strength:
6 p/15 mm at a withdrawal speed of 100 mm/min obtained 30
seconds after preparation).
After storing the laminate for seven days at room
temperature the final strength of (250 p/15 mm) was attained.
EXAMPLE 3
Component A
Component A consisted of:
2000 gm of the isocyanate adduct of polypropylene glycol (aver-
age molecular weight 3000) and diphenylmethane-4,4'-diisocyanate,
in the molar ratio 1:2, and
100 gm of the reaction product of 3 moles of hexamethylene
diisocyanate and 1 mole water.
Physical Characteristics of Component A:
Content of free isocyanate groups: 3.3% or 0.79 m.-eq./gm
Viscosity (Brookfield) at 23C: 29,000 cP
" at 60C: 6,ooo cP
-14-
~96764
Component B
Component B consisted of:
300 gm Aminopropylized polypropylene glycol (average molecular
weight 400)
The amine content of component B was 5 m.-eq./gm
2.56 gm/m2 of component A, heated to 60C, was applied
to a polyester sheet (sheet thickness 9~m) and 0.2 gm/m2 of
component B at room temperature was applied to an aluminum foil
(foil thickness 12~m). The molar ratio of the components was
2:1 (isocyanate: amine groups).
The initial adhesiveness (30 seconds after sticking
together) was 15 p/15 mm. The final strength (after seven
days ) was 300 p/15 mm.
EXAMPLE 4
Component A
Component A consisted of:
2000 gm of the isocyanate adduct of polypropylene glycol (aver-
age molecular weight 2000) and diphenyl-4,4'-diisocyanate, in
the molar ratio 1:2, and
100 gm of the reaction product of 3 moles of hexamethylene
diisocyanate and 1 mole water.
Physical characteristics of Component A:
Content of free isocyanate groups: 4.2% or 1.0 m.-eq./gm
Viscosity (Brookfield) at 23C: 25,000 cP
" " at 60C: 2,500 cP
-15-
764
Component B
Component B consisted of:
300 gm aminopropylized polypropylene glycol (average molecular
weight 400),and
500 gm of aminopropylized polypropylene glycol (average mole-
cular weight 2000),and
20 gm water.
The amine content of component B was 2.44 m.~eq./gm
2.17 gm/m of the above component A, heated to 60C,
was applied to a polyester sheet (sheet thickness 12~m) and 0.41
gm/m2 of the above component B, at room temperature, was applied
to a polyethylene sheet of low density polyethylene (sheet
thickness 40~m), which had been pre-treated by means of a
corona discharge. The molar ratio of the components was 2.2:1
(isocyanate to amine groups).
The initial adhesiveness (30 seconds after sticking
together) was 10 p/15mm. The final strength (after three days)
was 380 p/15mm.
The preceding specific embodiments are illustrative
of the practice of the invention. It is to be understood,
however, that other expedients known to those skilled in the
art, or given herein, may be employed without departing from
the spirit of the invention or the scope of the appended claims.
-16-
