One-component laminating adhesive having silane cross-linking

Abstract

The invention relates to a crosslinkable one-component laminating adhesive containing 25 to 80 wt. % of polyester prepolymers, polyether prepolymers and/or polyurethane prepolymers, which have at least two cross-linkable alkoxysilane groups and have a molecular weight of 2000 to 30,000 g/mol, 75 to 19 wt. % of organic solvent having a boiling point up to 130 C., 1 to 20 wt. % of polymers which contain anhydride groups, and 0 to 15 wt. % of additives, wherein the viscosity of the adhesive is between 50 and 20,000 mPas (according to DIN ISO 2555), measured at 15 to 45 C.

Claims

1. A crosslinkable one-pack adhesive for bonding flexible multi-layer films, containing: a) 25 to 80 wt. % of a prepolymer selected from polyester prepolymers, polyurethane prepolymers, and mixtures thereof, wherein the prepolymer has at least two crosslinkable alkoxysilane groups and possesses a molecular weight of 2000 to 30000 g/mol, and wherein at least of the prepolymer is based on polyester polyol, b) 75 to 19 wt. % of organic solvents with a boiling point of up to 130 C. selected from esters, alcohols or combinations thereof, c) 1 to 20 wt. % polymers, oligomers and/or monomers which contain one or more anhydride groups, wherein the polymers, oligomers and/or monomers are solid compounds at 25 C. and contain 5 mole % to 60 mole % anhydride groups, d) 0 to 15 wt. % additives, wherein the viscosity of the adhesive is between 50 and 20000 mPas (according to DIN ISO 2555), measured at 15 to 45 C. and the adhesive does not contain any catalysts.

2. The one-pack adhesive according to claim 1, wherein the polyester prepolymer or polyurethane prepolymer is produced from polyester polyols having a molecular weight of 400 to 25000 g/mol, which comprise at least two OH groups.

3. The one-pack adhesive according to claim 1, wherein the prepolymer contains trialkoxysilane groups.

4. The one-pack adhesive according to claim 1, wherein the prepolymer contains triethoxysilane groups or trimethoxysilane groups.

5. The one-pack adhesive according to claim 1, wherein the polymers, oligomers and/or monomers with anhydride groups have cyclic anhydride groups.

6. The one-pack adhesive according to claim 5, wherein the adhesive contains 2 to 15 wt. % polymers with maleic anhydride (MA) groups.

7. The one-pack adhesive according to claim 5, wherein the adhesive contains 2 to 15 wt. % MA/styrene copolymers or MA/(meth)acrylate copolymers.

8. A flexible multi-layer film comprising a plurality of films selected from polymer films, paper, foils, metal foils and surface-treated films bonded together by cured reaction products of the one-pack adhesive of claim 1.

9. The one-pack adhesive according to claim 1, wherein the glass transition temperature (T.sub.g) of the crosslinked adhesive is between 15 and +30 C.

10. A flexible multi-layer film for the production of food packaging comprising a first film layer selected from polyolefin; polyvinyl chloride; polystyrene; polyester; polyamide; cellophane; metal foil or paper; a second film layer selected from polyolefin; polyvinyl chloride; polystyrene; polyester; polyamide; cellophane; metal foil or paper; and a crosslinkable one-pack adhesive disposed between the first and second layers, the adhesive containing: a) 25 to 80 wt. % of a prepolymer selected from polyester prepolymers, polyurethane prepolymers, and mixtures thereof, wherein the prepolymer has at least two crosslinkable alkoxysilane groups and possesses a molecular weight of 2000 to 30000 g/mol, and wherein at least 50% of the prepolymer is based on polyester polyol, b) 75 to 19 wt. % of organic solvents with a boiling point of up to 130 C., the solvents selected from esters, alcohols or combinations thereof, c) 1 to 20 wt. % polymers, oligomers and/or monomers which contain one or more anhydride groups, wherein the polymers, oligomers and/or monomers are solid compounds at 25 C. and contain 5 mole % to 60 mole % anhydride groups, d) 0 to 15 wt. % additives, wherein the viscosity of the crosslinkable adhesive is between 50 and 20000 mPas (according to DIN ISO 2555), measured at 15 to 45 C. and the adhesive does not contain any catalysts.

11. The flexible multi-layer film of claim 10 wherein the first layer is polyolefin.

12. The flexible multi-layer film of claim 10 wherein the first layer is polyolefin and forms one exterior surface of the multi-layer film and the second layer is polyester and forms an opposing exterior surface of the multi-layer film.

13. The flexible multi-layer film of claim 10, comprising a third film layer selected from polyolefin; polyvinyl chloride; polystyrene; polyester; polyamide; cellophane; metal foil or paper bonded to the first film layer and the second film layer.

14. The flexible multi-layer film of claim 10 comprising a third barrier layer bonded to the first film layer and the second film layer.

15. The flexible multi-layer film of claim 10 wherein cured reaction products of the adhesive bond the first film layer to the second film layer.

Description

EXAMPLES

Example Polyester 1

(1) A polyester was prepared from adipic acid and isophthalic acid together with ethylene glycol.

(2) The polyester had a molecular weight of approx. 2000 g/mol. The OH value was approx. 58, and the acid value was less than 2.

Example Polyester 2

(3) A polyester was prepared from adipic acid, isophthalic acid, azelaic acid and phthalic acid together with diethylene glycol, ethylene glycol, propylene glycol and neopentyl glycol.

(4) The polyester had a molecular weight of 5100 g/mol. The OH value of the polyester was approx. 22.

Examples of Adhesives

Example 3a

(5) 51.5 parts of polyester 1 were dissolved in 38.5 parts of ethyl acetate and then reacted with 6 parts of TDI 80. 4.3 parts of bis(3-triethoxysilylpropyl)amine were then added.

(6) The resulting product had a solids content of 62%. It contained no further isocyanate groups. The viscosity was approx. 1400 mPas (20 C.). The T.sub.g (crosslinked) was 2 C.

Example 3b

(7) To the adhesive of example 3a, 1.6 parts (approx. 2.5% based on solids) of a styrene copolymer containing approx. 50 wt. % MA building blocks were added and the mixture was homogenized.

Example 4a

(8) 63.0 parts of polyester 2 were dissolved in 30.0 parts of ethyl acetate and then reacted with 3.45 parts of TDI 100 and 4.15 parts of bis(3-triethoxysilylpropyl)amine.

(9) The resulting product had a solids content of 70%. It contained no further isocyanate groups. The viscosity was approx. 7750 mPas (20 C.).

(10) The T.sub.g (crosslinked) was +4 C.

Example 4b

(11) To the adhesive of example 4a, 1.7 parts (approx. 2.5% based on solids) of a styrene copolymer containing approx. 50 wt. % MA building blocks were added and the mixture was homogenized.

Example 5a

(12) 61.2 parts of polyester 2 were dissolved in 34.5 parts of ethyl acetate and then reacted with 5.0 parts of TDI 100 and 1.4 parts of n-cyclohexylaminomethylmethyldiethoxysilane. The resulting product had a solids content of 65%. It contained no further isocyanate groups. The viscosity was approx. 6700 mPas (20 C.).

Example 5b

(13) To the adhesive of example 5a, 3.5 parts (approx. 5% based on solids) of a styrene copolymer containing approx. 50 wt. % MA building blocks were added and the mixture was homogenized. The viscosity was approx. 6800 mPas (20 C.).

Example 5c

(14) To the adhesive of example 5a, 2 parts (approx. 3% based on solids) of phthalic anhydride were added and the mixture was homogenized. The viscosity was approx. 6700 mPas (20 C.).

(15) All of the adhesives were diluted with ethyl acetate before application (series 1) to a solids content of approximately 31%.

(16) The viscosity here was less than 800 mPas (20 C.).

(17) The adhesives of examples 3a, 3b, 5a, 5b were diluted with a mixture of ethyl acetate/ethanol in such a way that a total of 10% ethanol was contained in the solvent (series 2), solids content approx. 33%.

(18) Bonding:

(19) Films based on polyethylene (PE) were coated with the adhesives according to the invention of test series 1 using a knife. The layer thickness was 5 m.

(20) Another film was similarly coated with a layer thickness of 10 m. The coated surface was dried in air at 30 C. for approx. 1 min. Then, a second film based on OPP was squeezed onto each coated film using a roller.

(21) PET films were coated with adhesive from test series 2 with a layer thickness of 3 g/m.sup.2 using a knife. After drying in air, these films were bonded with an Al foil.

(22) After 6 days and 14 days, the bonding of the film substrates was determined. In all cases, good adhesion with one another was determined.

(23) From the bonded films, the content of ethyl acetate and ethanol was determined by headspace GC after 24 hours.

(24) TABLE-US-00001 Examples (series 1) EtOH EtOAc 3a 30 2 mg/m.sup.2 3b 5 2 4a 20 2 4b 7 2 5a 15 2 5b 5 2

(25) The tests show that, with the addition of the MA-containing components, the alcohol content is reduced.

(26) TABLE-US-00002 Examples (series 2) EtOH EtOAc 3a (bonded immediately after mixing) 50 3 mg/m.sup.2 3b 15 2 3a (bonded 2 h after mixing) 50 3 mg/m.sup.2 3b 14 3 3a (bonded 4 h after mixing) 40 3 mg/m.sup.2 3b 16 3 3a (bonded 24 h after mixing) 34 4 mg/m.sup.2 3b 12 2 5b (bonded immediately after mixing) 50 3 5a 14 3 5b (bonded 24 h after mixing) 45 3 5a 14 3

(27) The tests show that, with a proportion of EtOH in the solvent, the measured values in the bonded film are nevertheless reduced. There is also a sufficiently long stability of these adhesives for processing, the effect of the reduction of alcohols being maintained.