GB1590818A

GB1590818A - Production of laminated films

Info

Publication number: GB1590818A
Application number: GB15791/78A
Authority: GB
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1977-04-27
Filing date: 1978-04-21
Publication date: 1981-06-10
Also published as: FR2388847A1; ATA300278A; DE2718615C2; SE7803857L; NL7803637A; BE866388A; JPS53134882A; NO781209L; DE2718615A1; ES469154A1; MX147497A; NO148988B; AT372393B; SE444320B; IT1094507B; NO148988C; CA1096764A; FR2388847B1; IT7822539A0; BR7802604A

Abstract

(Composite films) based on thermoplastic films and optionally also cellulose film and metal foils are produced by applying one or more polyethers having at least two terminal isocyanate groups and having molecular weights of between 2000 and 5000 to one of the two films to be bonded and applying one or more relatively long-chain compounds carrying at least two reactive amino groups to the other film, where the molar ratio between the isocyanate groups and the amino groups is between 1:1 and 5:1, and where the two components together are present in an amount of from 0.5 to 5.0 g/m<2>, and pressing the thus-coated film surfaces briefly together.

Description

(54) PRODUCTION OF LAMINATED FILMS (71) We, HENKEL KOMMANDITGESELLSCHAFT AUF AKTIEN, a German company of 67 Henkelstrasse, 4000 Dusseldorf-Holthausen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method for the production of laminated films using solvent-free adhesives comprising at least tone multi-functional isocyanate and at least one multi-functional reactive amine.

Laminated films are generally produced by means of laminating adhesives containing solvents which are applied by rolling onto. a film web. In this case, after evaporation of the solvent, the joining of the film 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 the isocyanates in the terminal position or two-component polyol/polyisocyanate mixtures are used as adhesives. The recent limitations 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 process.

By practice of the present invention there may be provided a method for the production of laminated films using an adhesive system which is free of solvents and can thus be worked with less danger of fire or explosion as well as permitting moreover an economical processing method.

By practice of the present invention there may also be provided a method for the production of laminated films, which gives clear films with an adhesive strength in a manner which is technically inexpensive.

According to the present invention there is provided a method for producing laminated films which comprises applying at least one polyether, said polyether having at least two terminal isocyanate groups and an average molecular weight of between 2000 and 5000, to one of the two films which are to be adhered together, applying at least one amino compound having at least two reactive amino groups to the other film, the molar ratio of isocyanate groups to amino groups being between 1:1 and 5:1 and the two components together being present in an amount of 0.5 to 5.0 gJm2 and pressing the two coated film surfaces together.

The pressing together of the two films need only be effected for a short period of time to achieve satisfactory adhesion.

Isocyanates which are at least bi-functional and suitable for use in the method in accordance with the present invention can be produced in a per se known manner through the conversion of anhydrous polyether diols with at least bifunctional isocyanates. Preferred polyester diols are derived from glycols containing 2 to 4 carbon atoms and accordingly may be polyethylene- and/or polypropylene glycol and/or polytetramethylene glycol (produced by ring opening polymerisation of tetrahydrofuran). The conversion with polyether diols mainly uses relatively low-molecular - weight diisocyanates such as hexamethylenediisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, toluylene diisocyanate (isomeric mixture) among others. For practical, particularly toxicological, reasons diphenylmethane diisocyanate is preferred.

A conversion ratio of 1.8:1 to 2.2:1 is preferably suitable for the formation of the isocyanate adduct, the ratio being of mol diisocyanate to mol diol. A lower conversion ratio is theoretically also possible, on condition that thereby a too high viscous adduct is not produced, the use of which no longer permits satisfactory 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 in that case.

Attention should be paid to the fact that the resulting isocyanate compounds do not exceed a viscosity of approximately 10,000 cP during processing. If desired these reaction components can also be applied at high temperature up to approximately 800 C. In general, however, a temperature of 50 to 650C is preferred.

Applications of laminating adhesives which are carried out only with the adducts, having at least two terminal isocyanate groups, as isocyanate component, in combination with the amine compounds, mentioned below, as amine component, give sufficient adhesiveness. It has, however, been discovered that this 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, whereby the percentages by weight are in relation to the isocyanate adduct.

By means of the isocyanate component modified in this manner a higher initial adhesiveness is particularly achieved as well as, however, an improved final adhesiveness. Conversion products of multi-functional alcohols and diisocyanates (conversion ratio 1 mol diisocyanate per hydroxyl group) are suitable as addition compounds having at least three isocyanate groups, e.g. the conversion product of trimethylolpropane and toluylene diisocyanate, as well as conversion products of one mol water and three mols diisocyanate, e.g., starting from hexamethylene diisocyanate, as well as other aromatic triisocyanates 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 film 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 80"C should not be exceeded. In general a temperature of 60"C is completely sufficient. Up to this temperature it was established that no isocyanate concentration exceeding the MAC (maximum allowable concentration of threshold limit value) of 0.02 ppm occurred in the workplace atmosphere during lamination with the isocyanate component described in the listed Example 1 by measurements taken at the laminating machine.

The second reaction component which is used for the method in accordance with the present invention is an at least bi-functional amine. At least two amino groups must be present and each group may be either primary or secondary.

Compounds of this type are known and produced in a known manner.

A preferred basic framework for the amino compound is the polyether diols or also oligomeric glycols. In accordance with an advantageous embodiment one proceeds so that acrylonitrile is added onto the polyether diols. The adducts which thereby result are then hydrogenated in a known manner, whereby primary amino groups are formed from the nitrile group. For the production of the two reaction components of the solvent-free laminating adhesive oligomeric glycols or polyether glycols are preferred, which are derived from polyethylene glycol, polypropylene glycol and polytetramethylene glycol of a molecular weight of between 200 and 4500, particularly 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 convert these diamines by means of compounds containing at least two functional groups, capable of reacting with an amine (chain lengthening). Amines of this type are for example: H2N-CH2-CH2-CH2-O-(CH2)24-O-CH2-CH2-CH2-NH2 H2N-CH2-CH2-CH2-O(-CH2-CH2-O)1CH2-CH2-CH2-NH2 or also

or H2N-(CH2)68-NH2 The functional groups of the chain lengthening agents can thereby be, for example, epoxide or isocyanate radicals or also a, P 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 favourable effect on the adhesion or strength of the adhesive bond under certain circumstances.

In the case of diepoxide or diglycidyl compound

where R is an aliphatic or cycloaliphatic radical with up to 25 carbon atoms, as for example, methylene, ethylene, propylene, neopentylene, hexamethylene, dodecamethylene, cyclohexylene, dicyclohexyl, methylene dicyclohexyl or also a diethylene or triethylene glycol ether radical, and the di-primary amine corresponds to the general formula H2N-R'-N112, where R' denotes, for example, an ethylene, tetramethylene, hexamethylene, diethylene glycol ether, dipropylene glycol ether or also a triethylene glycol ether, radical, one obtains compounds containing two terminal primary amines of the general formula

In the case of chain lengthening with isocyanates, as for example, toluylene, hexamethylene and isophorone diisocyanate, one obtains compounds containing two terminal amino groups as well as urea groups of the general formula

in which R' has the meaning given above whilst R denotes the radical of the isocyanate used.

German Patent Application P 25 49 371.4 gives a further description of the reactions of chain-lengthening of suitable amines.

In many cases it may be advantageous to add 1 to 50% by weight, preferably 1 to 15% by weight, of water to the amine compounds carrying at least two reactive amino groups. This causes an increase in or earlier attainment of the final strength and affects, in a favourable manner, the sealing ability of the laminated film.

During machine lamination a sufficiently high initial adhesiveness is formed spontaneously so that Jelamination or "telescoping" of the laminated film does not occur whilst 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 cros-linked and exhibit a behaviour which satisfies all requirements of packing technology with regard to laminar adhesion and thermal stability, which is a prerequisite for its sealability. The finished laminates are further distinguished by very good optical properties. Very frequently.

occurring laminating errors such as "fish eyes" or "orange peel structure" cannot be detected in the laminates.

By means of the twin-component lamination glue all laminates of plastic films such as polyethylene, polypropylene, polyester, polyvinyl chloride, polystyrene or polyamide films, can be manufactured. Furthermore the production of laminated films is possible using metal films e.g. aluminium film, or by using various cellophanes or paper.

The present invention will now be further illustrated by way of the following examples, without it being limited thereto. The compounds designated as "aminopropylised" polypropylene glycols in the examples were produced by addition of acrylonitrile to the glycol and subsequent catalytic hydrogenation.

Example 1 Component A 2000 g Isocyanate adduct of polypropylene glycol with the molecular weight 2000 and diphenylmethane-4,4'-diisocyanate, in the molar ratio 1:2, and 100 g conversion product of 3 mol hexamethylene diisocyanate and I mol water.

Content of free isocyanate groups 4.2% or 1.0 m equivalents/g Viscosity at 230C: 25,000cP Viscosity at 500 C: 8,000 cP Viscosity at 600 C: 2,500 cP (In each case Brookfield viscosity) Component B 300 g aminopropylised polypropylene glycol (average molecular weight 400) 500 g of aminopropylised polypropylene glycol (average molecular weight 2000) Amine content 2.5 m equivalents/g 1.68 g/m2 dfcbmponent A, which was heated to 600C, was applied by machine to a polyester film (film thickness 12 ,um) and 0.35 g/m2 of the component B, at room temperature, was applied to polyethylene film of low density (film thickness 50 ,um) which has been pre-treated by a corona discharge. The molar ratio of isocyanate to amine component was 1.9:1 relative to isocyanate to amine groups.

The coated sides of the films where pressed together over rollers.

The adhesive film showed a high spontaneous initial adhesiveness (30 seconds after application a peel adhesiveness of 30 g/15 mm at a withdrawal speed of 100 mm/Min. was measured).

After lamination lasting eight hours the components could also be processed satisfactorily with the formation of a constantly high initial adhesiveness. Due to the increase in viscosity the application quantity of the isocyanate component rose to 1.92 g/m2 whilst the application quantity of the amine component remained constant at 0.35 g/m2, thus giving a molar application ratio of 2.2:1.

After storing for seven days at room temperature a peel adhesiveness of 350 g/15 mm occurred. This value was found in 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.

Example 2 Component A: Isocyanate adduct of polypropylene glycol (average molecular weight 2000) and diphenylmethane-4,4'-diisocyanate, in the molar ratio 1:2.

Content of free isocyanate groups: 3.4% or 0.81 m equivalents/g Viscosity at 230C: 20,000 cP Viscosity at 600 C: 2,000 cP Component B 300 g aminopropylised polypropylene glycol (average molecular weight 400) 500 g aminopropylised polyDropyleneglycol (average molecular weight 2000) Amine content: 2.5 m equ valents/g ~ 2.1 g/m2 of component A, heated to 600C, was applied to an aluminium film (film thickness 12 ,um) and 0.4 g/m2 of component B to a polyethylene film of low density (film thickness 50 ,um which had been pre-treated by means of a corona discharge. The molar ratio of the components was 1.7:1 (Isocyanate: amine group).

In drawing together the coated film sides a sufficiently high initial adhesiveness was reached. (Tensile peel strength: 6 g/15 mm at a withdrawal speed of 100 mm/min 30 seconds after manufacture.) After storing for seven days the final strength (250 g/15 mm) was attained.

Example 3 Component A 2000 g isocyanate adduct of polypropylene glycol (average molecular weight 3000) and diphenylmethane-4,4'-diisocyanate, in the molar ratio 1:2, and 100 g of conversion product of 3 mols of hexamethylene diisocyanate and I inol water.

Content of free isocyanate groups: 3.3% or 0.79 m equivalents/g Viscosity at 230C: 29,000 cP Viscosity at 600 C: 6,000 cP Component B Aminopropylised polypropylene glycol (average molecular weight 400) Amine content: 5 m equivalents/g 2.56 g/m2 of component A, heated to 600 C, was applied to polyester film (film thickness 9 m) and 0.2 g/m2 of component B to an aluminium film (film thickness 12 ,lem). The molar ratio thereby was 2:1 relative to isocyanate and amine groups.

Initial adhesiveness (30 seconds after sticking together) 15 g/15 mm. Final strength (after seven days): 300 g/15 mm.

Example 4 Component A 2000 g of isocyanate adduct of polypropylene glycol (average molecular weight 2000) and diphenyl-4,4'-diisocyanate, in the molar ratio 1:2, and 100 g of conversion prdduct of 3 mols of hexamethylene diisocyanate and I mol water.

Content of free isocyanate groups 4.2% or 1.0 m equivalents/g Viscosity at 230C 25,000 cP Viscosity at 600C 2,500 cP Component B 300 g aminopropylised polypropylene glycol (average molecular weight 400) 500 g. of aminopropylised polypropylene glycol (average molecular weight 2000) and 20 g water.

Amine content 2.44 m equivalents/g.

2.17 g/m2 of component A, heated to 600C, was applied to polyester film (film thickness 12 m) and 0.41 g/m2 -of component B, at room temperature, to polyethylene film of low density (film thickness 40 Mm) which was pre-treated by means of a corona discharge. The molar ratio of the components was2.2:1 (isocyanate to amine).

Initial adhesiveness (30 seconds after sticking together): 10 g/15 mm. Final strength (after three days): 380 g/l 5 -mm.

WHAT WE CLAIM IS: 1. A method of producing a laminated film, which comprises applying at least one polyether, said polyether having at least two terminal isocyanate groups and an average molecular weight between 2000 and 5000, to one of two films to be adhered together, applying at least one amino compound having at least two reactive amino groups to the other film, the molar ratio of isocyanate groups to amino groups being between 1:1 and 5:1 and the two components together being present in an amount of 0.5 to 5.0 g/m2, and pressing the two coated film surfaces formed together.

2. A method as claimed in claim 1, in which a compound having at least three isocyanate groups is added to the polyether(s) having isocyanate groups and wherein the compound having at least three isocyanate groups is added in an amount of 0.5 to 20% by weight relative to the polyether(s) having isocyanate groups.

3. A method as claimed in claim 2, in which the compounds having at least three isocyanate groups is added in an amount of I to 10% by weight relative to the polyether(s) having isocyanate groups.

4. A method as claimed in any one of claims 1 to 3, in which the compounds having reactive amino groups are products obtained by the conversion of polyethers with acrylonitrile with subsequent hydrogenation.

5. A method as claimed in any one of claims 1 to 4, in which 1 to 50% by weight, relative to the compound(s) having amino groups, of water is added to the compound(s) having amino groups.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

Example 3 Component A

2000 g isocyanate adduct of polypropylene glycol (average molecular weight 3000) and diphenylmethane-4,4'-diisocyanate, in the molar ratio 1:2, and

100 g of conversion product of 3 mols of hexamethylene diisocyanate and I inol water.

Content of free isocyanate groups: 3.3% or 0.79 m equivalents/g Viscosity at 230C: 29,000 cP Viscosity at 600 C: 6,000 cP Component B Aminopropylised polypropylene glycol (average molecular weight 400) Amine content: 5 m equivalents/g 2.56 g/m2 of component A, heated to 600 C, was applied to polyester film (film thickness 9 m) and 0.2 g/m2 of component B to an aluminium film (film thickness 12 ,lem). The molar ratio thereby was 2:1 relative to isocyanate and amine groups.

Initial adhesiveness (30 seconds after sticking together) 15 g/15 mm. Final strength (after seven days): 300 g/15 mm.

Example 4 Component A

2000 g of isocyanate adduct of polypropylene glycol (average molecular weight 2000) and diphenyl-4,4'-diisocyanate, in the molar ratio 1:2, and

100 g of conversion prdduct of 3 mols of hexamethylene diisocyanate and I mol water.

Content of free isocyanate groups 4.2% or 1.0 m equivalents/g Viscosity at 230C 25,000 cP Viscosity at 600C 2,500 cP Component B

300 g aminopropylised polypropylene glycol (average molecular weight 400)

500 g. of aminopropylised polypropylene glycol (average molecular weight 2000) and

20 g water.

Amine content 2.44 m equivalents/g.

2.17 g/m2 of component A, heated to 600C, was applied to polyester film (film thickness 12 ssm) and 0.41 g/m2 -of component B, at room temperature, to polyethylene film of low density (film thickness 40 Mm) which was pre-treated by means of a corona discharge. The molar ratio of the components was2.2:1 (isocyanate to amine).

Initial adhesiveness (30 seconds after sticking together): 10 g/15 mm. Final strength (after three days): 380 g/l 5 -mm.

WHAT WE CLAIM IS: 1. A method of producing a laminated film, which comprises applying at least one polyether, said polyether having at least two terminal isocyanate groups and an average molecular weight between 2000 and 5000, to one of two films to be adhered together, applying at least one amino compound having at least two reactive amino groups to the other film, the molar ratio of isocyanate groups to amino groups being between 1:1 and 5:1 and the two components together being present in an amount of 0.5 to 5.0 g/m2, and pressing the two coated film surfaces formed together.
2. A method as claimed in claim 1, in which a compound having at least three isocyanate groups is added to the polyether(s) having isocyanate groups and wherein the compound having at least three isocyanate groups is added in an amount of 0.5 to 20% by weight relative to the polyether(s) having isocyanate groups.
3. A method as claimed in claim 2, in which the compounds having at least three isocyanate groups is added in an amount of I to 10% by weight relative to the polyether(s) having isocyanate groups.
4. A method as claimed in any one of claims 1 to 3, in which the compounds having reactive amino groups are products obtained by the conversion of polyethers with acrylonitrile with subsequent hydrogenation.
5. A method as claimed in any one of claims 1 to 4, in which 1 to 50% by weight, relative to the compound(s) having amino groups, of water is added to the compound(s) having amino groups.
6. A method as claimed in claim 5, in which 1 to 15% by weight, relative to the

compound(s) having amino groups, is added.
7. A method as claimed in any one of claims 1 to 6, in which the two films are selected from polyethylene, polypropylene, polyester, polyvinyl chloride, polystyrene and polyamide films.
8. A method as claimed in claim 1 and substantially as hereinbefore described with reference to any one of the examples.
9. A laminated film whenever produced by a method as claimed in any one of claims 1 to 8.