CA1080600A - Production of laminates employing solvent-free adhesives - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method for the production of laminated films employing a two component non-solvent adhesive system comprising the steps of applying a thin film of a polyether having at least two terminal isocyanate groups to one of the films to be bonded, applying a thin film of a long chain compound having at least two terminal primary amino groups and a molecular weight of from 300 to 2000 to the other of the films to be bonded, the application of both thin films being in such amounts that the molar ratio of isocyanate groups to amino groups is from 1:1 to 2:1, the two component adhesive having a combined coating thickness of from 1 to 6 µ, pressing the coated sides of the two coated films together, and recovering said laminated films.

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Description

Laminated films are generally manufactured by me~ns of laminating adhesives which contain solvents and which are applied to a length of filrn by means of rollers. After the solvent has evaporated, the two len~ths of fi~n are united under pressure which is applied for a short period of time. In this mRthod~ known as "dry laminating", the adhesives used are almost exclusively solvent~containing polyurethane systems in the form of moisture-hardening prepolyrners having terminal isocyanate groups or two-component polyol/polyisocyanate mix-tures. Recent restrictions with respect to the emission of sol-vents into the atmosphere render it necessary to perform expen-sive processing steps for the absorption or after-burning of the solvent/air mixture.

r. An object of the present invention is the develop-ment of a method of manufacturing laminated`fi~ns by using sol-vent free adhesives based on polyfunctional isocyanQtes andpoly-functlonal primary amines.
Another ob~ect of the present invention is the devel-opment of a method of manufacturing laminated films by using an adhesive system which is free from solvents and which can thus be processed without the risk of fire or explosion and which also - -permits a more economical method of manufacture.
A further object of the present invention is the development of a method for the production of laminated films employing a two component non-solvent adhesive system comprisin~
the steps of applying a thin film of a polyether having at least two texminal isocyanate groups to one ol the ~ilms to be bonded, applying a thin film of a long chain compound ha~ing at least two terminal primary amino groups and a molecular ., ~

' : - - - : . ~

wcigllt of from 300 ~o 2000 to thc other of the film~ to be bonded, thc applica~ion of both thin films being in such amounts that the molar ratio of isocyanate groups to umino groups is from 1:1 to 2:1, the two component adhesive having a combined thickness o~ from 1 to 6~, pressing the coated sides of the two coated films together, and recovering said laminated films.
These and other objects of the invention will become more apparent as the description thereof proceeds.
1-0 In one particular aspect the present invention provides a method for the production of laminated films employing a two component non-solvent adhesive system comprising the steps of applying a thin film of a first reaction product of i mol of polyoxyalkylene glycol having 2 to 4 carbon atoms in the alkylene and a molecular weight of from 200 to lS00 with 2 mols of a diisocyanate, said first reaction product having a viscosity of under 9000 cP, to one of the films to be bonded,`applying a thin film of a second reaction product of 1 mol of polyoxyalkylene glycol having 2 to 4 carbon atoms in the alkylene with 2 mols of acrylonitrile, which was subsequently catalytically hydro-genated, said second reaction product having a viscosity of 50 to 1200 cP and a molecular weight of from 300 to 2000 to the other of the films to be boided, the application of both thin films belng in such amounts that the molar ratio of isocyanate groups to amino groups is from 1:1 to 2:1, the two component adhesive having a combined coating thickness of from 1 to 6~, pressing the coated sides of the two coated films together, and recovering said laminated films.
By the practice of the invention, the drawbacks of the prior art are overcome and a method of manufacturing laminated films i8 provided which produces clear, adherent laminated foils at low technologlcal expense.

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~ lore pal-t;.cularly, the present invention relates to n method for the production of laminated films employing a two component non-so].vent adhesive system comprising the steps of applying a thin film of a polyether having at least two terminal isocyanate groups to one of the films to be bonded, applying a thin film of a long chain compound having a. least two terminal primary amino groups and a mo~lecular .~ ..

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~ 2a~

,~ .
,D''' ' . ' -- , ' . ' . ' : , . - . .

~eight of from 300 to 2000 to the other of ~he lîl~s to be bonded, the application of both thin films being in such amounts that the molar ratio o- isocyan~te groups to amLno ~roups .s ~rom 1:1 to 2:1, the ~YO component adhesive having a ccmbined coating thickness of ~rom 1 to 6 u, pressin~ ihe C32 ted sides ol ihe two coated films together, and recovering said laminated films.
The polyekher having at least two terminal iso-cyanate groups suitable for the method in accordance with tne present invention can be produced by reacting anhydrous poly-ether diols with at least bifunctional isocyanates in a manner known per se, in a i~olar ratio whereby one mol of said at least bifunctional isocyanate is employed per hydroxyl group. Pre-ferred polyether diols are the polyoxyalkylene glycols derived .
- from alkylene glycols containing 2 to 4 carbon atoms. Conse-~ quently, polyoxyethylene glycol and/or polyoxypropylene glycol i and/or polyoxytetramethylene glycol (produced by ring-opening polymerization of tetrahydrofuran) are suitable. Pre~erab_y, these polyether diols have average molecular t~eights o~ betw~en 200 and 1500, preferably 300 to 1000. Relatively low m~lecular weight isocyanates, preferably alkylene diis~cyanates having

3 to 12 carbon atoms in the alkylene, cycloalkylene diisocyanates having 5 to 12 carbon atoms in the cycloalkyl andaromatic hydro- -carbon diisocyanates having 6 to 15 carbon ato~s in the aro~atic hydrocarbon, such as hexamethylene diisocyanate, trime~hyl-hexamethylene diisocyanate, isophorone diisocyanate, tolu~lene diisocyanate (isomeric mixture) and others, are primarily sui~-able for the reaction with ~he polyether diols. Care must be taken that the isocyanate compounds obtained do not exceed a viscosity of approximately 8000 to 9000 cP during processing.
I~ required, this reaction component can also be applied ~ith , 1(~8~)600 slightly increased temperatures of up to 50C t~ 60C. In general, however, temperatures of from 20 C to 30C will be preferred.
The second reaction component use~ f3r the mRthod in acc~rdance ~ith the inventi~n is an at least bifunctional amine. Tne componen~ is a lo~g chain-compound ha~-ing at le2s~
- ~wo terminal primary amine groups and a molecular weight o fro~ 300 to 20~0. It can be built up from the same basic starting compo~nd, i.e. polyether diols or polyoxyalkylene glycols having from 2 to 4 carDon atoms in the alkylene. Advan-tageously, acrylonitrile is added to the polyether diols. This adduct is then h~rdrogenated in a kno~ mannex, primary amino groups being formed from the nitrile groups. Po~yether glycols, - derived from polyoxyethylene glycol~ polyoxypropylene ~l~col and polyoxytetramethylene glycol having a molecular weight between approximately 200 and 1500, preferably 300 to 1000, axe pre~erred for the manufacture of the two reaction components o~ the solvent-free laminating adhesive ~uI~he~20re~ it is possible to procee~ ~rom relati~el~ 1O~T molecul æ weight di~mines habnu~ a ch~;n - ~ ¦
g~h o~ lro~ 2 to 18 c~rbon a~oms whlch m~ also be partially rDpiaced b~ ox~gen atoms~ ana to reac~ ~hese diami~es with compou~ds con~ainin~ at least t;lJO ~m~lona~
groups ~ h ~e capable o~ reaction. with an amine (cha~n . .
len~hen~g). Amines.o~ this type are, :Eor e.~le:. -: !
~2-- ~2~ ~ (C~2) ~--~H ~ G~ ~ ~

3 2 ~ C82 o7 ~l~er~t,iv~ly --4_ - CEt3 .. ~3 ~

- . 3 . - 3 or ~2h~ - (C~ 2 6-~3 ,, -., : The function3.1 groups in the co~3unds contain-ng at least t'.Jo functional groups may be epoxide or isocyana~e radicals or a,~~unsaturated esters or halogen atoms. The OH groups, secondary amino groups or urea groupings fo~med during this re-action or the ester groupings introduced tend to promote the adhesion or strength of the glued joint.
The compound containing at least two epoxide radi-cals can be a diepoxide or diglycidyl compound having the formulae C~ R C~ CH2 or ~ / C~2 CR ~2 - wherein R is an aliphatic or cycloaliphatic radical with up to approximately 25 carbon atoms, for example, alkylene having ~
to 25 carbon atoms or cycloalkylene having 5 to 25 carbon ato~s, such as methylene, ethylene, propylene, neopentyl, hexylene, dodecylene, cyclohexylene, dicyclohexyl, methylene - dicyclo-. hexyl or, alternatively, polyoxyalkylene having 2 to 4 carbon : atoms in the alkylene such as radicals derived ~rom dioxyethylene -~ 20 glycol or trioxyethylene..glycol. The:dia~ines can be diprimary amines corresponding to the general ~ormula H2N-Rl-I~H2, wherein Rl represents, ~or example, alkylene havin~ 2 to 18 carbon atoms such as ethylene, butylene, hexylene, polyoxyalkylene having 2 to 4 carbon atoms in the alkylene~ such as dioxyethylene, ~ .

.. . .

lQ81)600 dioxypropylene, or, alternatively, trioxvethylene. On chain len~thening of the amines using 2 mols o~ a dianine for each mol o~ die~oxide, one obtains compounds containing two terminal primary amino groups, of the general for~ula:

. . . ~ 0~
~ " - r~ - ~ ~ C~ G~ - C~2 - ~- R~

Tn the case o~ chain lengthening with isocyanates, such as-the above-indicated diisocyanates, for example, ~oluylene diisocyanate, hexamethylene diisocyanate, isophoronediiso-cyanate, using again 2 mols of diamine to 1 mol of diisocyanate, one obtains c3mpounds containing two-terminal amino groups and urea groups, of the general ~ormula:

~N - Ri _ N~ N~ - Rt _ ~ -f - -in which R' has the above significance, while R'r represents th~ radical of the isocyanate used. -I~hen using (meth) acrylic acid esters of glycols (for example tri- or tetraoxyethylene glycol di(meth)acrylic ester) ~or chain lengthening, one obtains compounds of the general formula:

.

~C--o _ ~ I O ~
R~ 2 (~a33 ~( ~ ) .
in ~hich R' again has the same significance as a~ove, and R'lt represents the dialcohol radical of the (meth) acrylic es~er~

-6_ lQ806~0 i.e. the tri-, or tetraoxyethylene glycol radical in the case mentioned by way o~ example. The indication H(CH3) shows the con~igurati3n 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 13 carbon atoms, for example, ethylene glycol, propylene glycol, butylene glycol, decane diol, etc.
Finally, it is also possible to e~fect a chain lengthening with a,~-dihalides, this being effected in accord-ance with the same principle in a known manner. In this case,compounds o~ the general formula H N -R'--NH- RiV- ~H - R' NH2 are produced, in which RiV repxesents a radical of up to 12 carbon atoms and which can optionally contain oxygen, for example, alkylene having l to 12 carbon atoms or polyoxyalkylene 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 dipr~mary amines to the chain-lengthening agent should be chosen such that approximately l mol o~ di~unctional epoxide, isocyanate, (meth)acrylic ester or dihalide is allotted to 2 mols of amine. The reaction ~orms substantially the desired compounds containing at least two end position primary amino groups and having a molecular weight of approxlmately 300 to 2000. Advantageously, the viscosity of the aminic component is somewhat less than that of the iso-cyanate component. It has proved to be practicable to work towards a viscosity o~ approximately 50 to 1200 cP at 20C to 30C.
The two reaction components are applied each to one of the ~ilms by means o~ rollers ln such amounts that the . .

108~600 molar retio of` the isocyanate groups of ~he isocyanate com-ponent on one film to the amino groups of the amine componen~
~n the other film lies `oetween approximately 1:1 and 2:1. The amount is otherwise r.leasured such that a film o~ adhesive ha~ing a total thickness of 1.0 to 6.o~ is formed.
The surfaces of the films coated with the two componen~s are pressed t~gether bet~:een a pair of roller~ hich may also be partially heated. The pressure required is nominal, only that sufficient to br~ng the two ~ilms in contact. Adequa~e pr'mary adhesion (initial adhesion) is f~rmed on the way to the rolling-up arrangement andJ if required, can be increased by applying heat by, for example, hot air.

-- ~he method ~ accordance ~i~h ~he presen~ Inv~ o~
enables the la~ina~in~ opera~ion ~o be carriea ou~ rela~l~el~ -high speeds. ~here is no need to ~se arylng cha~els,. ~e~
! the ~ilms have been pressed together, the uebs do ~o~ s~;.p or -slide rela~l~e to one ano~her and p~rtial delamLna~i~ does not e~en occur . After the ~ll m~c have been wouna o~to rolls ,, ~he ~ilms nave ~o be s~,orea ~or appro}~ima~ely ~ ~o ~ ~a~s a~ -20 room ~em~era~ure ~ccord~ to ~he ~hic~ess o:f ~he ~i~ o~
adhesi~e ~d the reac~ivit;s~ of ~,he react2:n~s~ ~he ~
s~e~,~h is fo~med dur~ ~his perioa o~ time.- ~he peel 2~re~ h of the ,la~nates ob~ai~ed is usuall~ so high ~a~
. 1~ is ~ -possible ~o del~mi~ate ~hem ~Jithou~ ~ear~ ~he ma~eTrial.
ated ~ilms made from the compo:~e~ po.l~Fe~lene (pre~reated), pol;7prop;~ Le (pretreated~, cellulose El;ydra..e n a lac~uered and ~o~-lacquered ~or~ polye~h~lene ~ereph~hala~e, polycaprolac~2m, alu~iDlu~ ana o~her me~als~-30 can be ~an~factured b~ ~ea~s o~ the me~hod ~n acco~a~ce ~h .

the rresent invention. Preferably the films have a thicknessof from 6~ to 1 mm. The laminates can be of different film com~onents.
While the description discusses production of film laminates, it is obvious that other materials can be bonded by the adheslve system discussed, utilizing the condi-tions above.
The present invention will now be further illus-trated by reference to the following examples: -Component A: Isocyanate adduct from polyoxypropylene glycol (average molecular weight 410) and trimethylhexamethylene diisocyanate in the molar ratio 1:2 (molecular weight 830).
Content of free isocyanate groups: 10.1~ -! Viscosity at 25C: 3,500 cP ~Brook~ield) , Com~onent B: Aminopropylated polyoxypropylene glycol (average molecular weight 410), obtained by adding acrylonitrile to the glycol and subsequent catalytic hydrogenation (theoretical molecular weight 524).
Amine number 170 - 180 Viscosity 60 cP (Brookfield) 2.5 gm of component A were applied to 1 square meter of a polyethylene film of low densit~ which had been pre-treated by corona discharge (film thic~ness 50~ ), and 1.56 gm of the component B were applied to 1 square meter of a polyester film (film thickness 12~ ), the molar ratio of A to B being ` 1.2:1. The coating thicknesses of the two components corres-pond approximately to 2.5 and 1.56~ respectivel~. m e coated sides of the films were joined together by means of rollers.
The bonded film exhibited spontaneous initial ad-hesiveness, and a peel strength of 3 to 5 p/15 mm was measured ':
.. . ..
,~.......................................... , ` .

~080600 30 seconds after gluing (draw-off speed 100 mm/min). After ~our days stora~e, it was impossible to delaminate the film without tearing the material.

Component A: Isocyanate adduct from polyoxypropylene glycol (average molecular weight 630) and trimethylhexamethylene diisocyanate in the molar ratio 1:2 (molecular weight 1050).
Gontent o~ free isocyanate groups: 8.0~
Viscosity at 25C: 5,000 cP (Brook~ield) Viscosity at 50C: 1,000 cP (Brookfield) Component B: Aminopropylated polyoxypropylene glycol (average molecular weight 630), obtained by adding acrylonitrile to the glycol and subsequent catalytic hydrogenation (theoretical molecular weight 744).
t Amine number 142 Viscosity: 130 cP (Brookfield) 1.0 gm of component ~ was applied to 1 square meter of pretreated polyethylene film (fil~ thickness 50~u ), and 0.74 gm of component B was applied to 1 square meter of cellulose glass film (film weight 31.5 gm/m ), molar ratio of A to B being 1.02;1. The coating thicknesses of the two com-ponents correspond approximately to 1 and 0.75 ~ respectively.
The coated sides were united by means o~ rollers. The laminated film was then immediately heated to 50C for 10 seconds.
The peel strength subsequently measured is 5 to 6 p/15 mm (draw-of~ speed 100 ~m/min.). After four days storage, it was impossible to delaminate the film without destroying the material.
.~ .

: ' ~ , -~ XA MPIE 3 Component A: Isocyanate adduct from po.lyoxytetramethylene glycol (average molecular weight 980) and toluylene diiso-cyanate in the molar ratio 1:2 (molecular weight 1328).
Content of free isocyanate groups: 6.33~
Viscosity at 25C: 7,000 cP (Brookfield) Component B: The diamine in accordance with Example 1.
1.38 gm of component A were applied to 1 square meter of pretreated polyethylene film (film thickness 50~ ) and o.6 gm of component B were applied to 1 square meter of poly-; amide film (film thickness 60~ ), approximate molar ratio of A to B being 1.1:1. The coating thic~nesses of the two com~ -- ponents correspond to 1.38 and o.6~ respectively. The coated sides of the ~ilm were united by means of rollers The bonded ~ilm was heated to 50C for a short period of tLme.
The peel strength subsequently measured is B to 10 p/15 mm ~draw-off speed 100 mm/min.). After four days storage, it was impossible to delaminate the film without destroying the material The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, how-ever, that other e~pedients known to those skilled in the art, or disclosed herein, may be employed without departing ~rom the spirit of the invention or the scope of the appended claims.
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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for the production of laminated films employing a two component non-solvent adhesive system comprising the steps of applying a thin film of a first reaction product of 1 mol of polyoxyalkylene glycol having 2 to 4 carbon atoms in the alkylene and a molecular weight of from 200 to 1500 with 2 mols of a diisocyanate, said first reaction product having a viscosity of under 9000 cP, to one of the films to be bonded, applying a thin film of a second reaction product of 1 mol of polyoxyalkylene glycol having 2 to 4 carbon atoms in the alkylene with 2 mols of acrylonitrile, which was subsequently catalytically hydrogenated, said second reaction product having a viscosity of 50 to 1200 cP and a molecular weight of from 300 to 2000 to the other of the films to be bonded, the application of both thin films being in such amounts that the molar ratio of isocyanate groups to amino groups is from 1:1 to 2:1, the two component adhesive having a combined coating thickness of from 1 to 6µ, pressing the coated sides of the two coated films together, and recovering said laminated films.

2. The method of Claim 1 wherein said glycol has a molecular weight of from 300 to 1000.

3. The method of Claim 1 wherein said diisocyanate is trimethyl hexamethylene diisocyanate.

4. The method of Claim 1 wherein said diisocyanate is toluylene diisocyanate.