Polyester-free laminating adhesive composition

Abstract

The invention relates to a two-component polyurethane adhesive, in particular for laminating films, wherein the PU adhesive, based on the total weight of the laminating adhesive composition, (a) contains as resin component at least one NCO-terminated polyurethane pre-polymer having a content, based on the total weight of the resin component, of at least 40 wt % of diphenylmethanedi-isocyanate (MDI), wherein the MDI is 4,4-diphenylmethanediisocyanate or a mixture thereof with 2,4-diphenylmethanediisocyanate, and 2 to 20 wt % of polyglycol having a molecular weight Mw of 200 to <1000 g per mol, and (b) contains as hardener component a polyol mixture comprising 2, 3, or more different polyols and is free of polyesters. The invention further relates to the use of the adhesive for bonding films, to methods for producing composite films, and to composite films bonded with the adhesive described.

Claims

1. A polyurethane two-component laminating adhesive composition comprising: (a) a resin component including at least one NCO-terminated polyurethane prepolymer prepared by reacting a reaction mixture consisting of: at least 40 wt. % by weight, based on the total weight of the reaction mixture, of diphenylmethane diisocyanate (MDI), wherein the MDI is 4,4-diphenylmethane diisocyanate or a mixture of 4,4-diphenylmethane diisocyanate and 2,4-diphenylmethane diisocyanate; 2 to 20 wt. % by weight, based on the total weight of the reaction mixture, of polypropylene glycol having a molecular weight of from 200 to <1,000 g/mol or polyethylene glycol having a molecular weight of from 200 to <1,000 g/mol; and one or more components selected from the group consisting of additional polyisocyanates and polyglycols selected from the group consisting of polypropylene glycol having a molecular weight of from 1,000 to 4,000 g/mol, polyethylene glycol having a molecular weight of from 1,000 to 4,000 g/mol, copolymers of polypropylene glycol having a molecular weight of from 1,000 to 4,000 g/mol, and copolymers of polyethylene glycol having a molecular weight of from 1,000 to 4,000 g/mol; and (b) a curing component consisting of a mixture of a trifunctional polypropylene glycol having a molecular weight Mw of <700 g/mol and castor oil, wherein the polyurethane two-component laminating adhesive composition is free of polyester components and does not contain any solid particulate filler particles in which at least 90% of the filler particles have a particle size of 4 m or less and which have a Mohs hardness of 3 or less.

2. The polyurethane two-component laminating adhesive composition of claim 1, wherein the molar NCO: OH ratio of resin component to curing component is less than 1.4.

3. The polyurethane two-component laminating adhesive composition of claim 1, wherein: (a) the polyurethane two-component laminating adhesive composition further comprises at least one catalyst selected from the group consisting of a Sn-based metal catalyst, a Ti-based metal catalyst, and an amine catalyst; (b) the polyurethane two-component laminating adhesive composition has a viscosity of from 500 to 5,000 mPas at a temperature of 40 C.; (c) the polyurethane two-component laminating adhesive composition is substantially free of organic solvents; or (d) any combination of (a), (b), and (c).

4. The polyurethane two-component laminating adhesive composition of claim 1, wherein all of the polyglycols reacted with the diphenylmethane diisocyanate (MDI) have a molecular weight Mw of 2,000 or less.

5. The polyurethane two-component laminating adhesive composition of claim 1, wherein the polyurethane two-component laminating adhesive composition is substantially free of filler particles.

6. A cured reaction product of the polyurethane two-component laminating adhesive composition of claim 1.

7. A method for producing a composite film, the method comprising: providing a first film and a second film, wherein the first and second films are identical or different plastic films; mixing the resin component and the curing component of the polyurethane two-component laminating adhesive composition of claim 1 at a predetermined NCO:OH ratio to form a laminating adhesive; applying the laminating adhesive over some portion of a surface of the first film; and disposing the second film over the laminating adhesive on the surface of the first film.

8. The method of claim 7, wherein the laminating adhesive is applied in an amount of from 1 to 5 g/m.sup.2 to the portion of the first film.

9. A composite film produced by the method of claim 7.

10. A package comprising a composite film produced by the method of claim 7, the package sealingly disposed around a food product or medicament.

Description

EXAMPLES

Example 1 (According to the Invention)

(1) Resin Base:

(2) NCO-terminated MDI-prepolymer having an NCO content of 13-15 wt. % and an NCO:OH ratio of 4.3:1, obtainable from 50 wt. % 4,4-diphenylmethane diisocyanate (MDI); 15 wt. % polypropylene glycol (PPG) having Mw=400 g/mol; 25 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 10 wt. % hexane-1,6-diisocyanate (HDI) trimer.

(3) Curing Agent:

(4) Polyol mixture having an OH value of 210-250 mgKOH/g and a functionality f=3, consisting of 30 wt. % trifunctional polypropylene glycol (PPG) having Mw=450 g/mol; 70 wt. % castor oil.

(5) Mixing ratio resin: curing agent 100:70 parts by weight.

Example 2 (According to the Invention)

(6) Resin Base:

(7) NCO-terminated MDI-prepolymer having an NCO content of 13-15 wt. % and an NCO:OH ratio of 4.0:1, obtainable from 50 wt. % 4,4-diphenylmethane diisocyanate (MDI); 10 wt. % polypropylene glycol (PPG) having Mw=400 g/mol; 30 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 10 wt. % toluylene diisocyanate (TDI) prepolymer*. *TDI-prepolymer: Reaction product of 2,4-TDI having a polyether diol having Mw=400 . . . 1,000, demonomerized.

(8) Curing Agent:

(9) Polyol mixture having an OH value of 330-370 mgKOH/g and a functionality f=3, consisting of 5 wt. % trimethylolpropane; 70 wt. % trifunctional polypropylene glycol (PPG) having Mw=450 g/mol; 25 wt. % castor oil.

(10) Mixing ratio resin: curing agent 100:35 parts by weight.

Example 3 (According to the Invention)

(11) Resin Base:

(12) NCO-terminated MDI-prepolymer having an NCO content of 12-14 wt. % and an NCO:OH ratio of 3.9:1, obtainable from 50 wt. % 4,4-diphenylmethane diisocyanate (MDI); 5 wt. % polypropylene glycol (PPG) having Mw=400 g/mol; 25 wt % polypropylene glycol (PPG) having Mw=1,000 g/mol; 10 wt. % polypropylene glycol (PPG) having Mw=2,000 g/mol; 10 wt. % hexane-1,6-diisocyanate (HDI) trimer.

(13) Curing Agent:

(14) Polyol mixture having an OH value of 330-370 mgKOH/g and a functionality f=3, consisting of 5 wt. % trimethylolpropane; 70 wt. % trifunctional polypropylene glycol (PPG) having Mw=450 g/mol; 25 wt. % castor oil.

(15) Mixing ratio resin: curing agent 100:40 parts by weight.

Example 4 (According to the Invention)

(16) Resin Base:

(17) NCO-terminated MDI-prepolymer having an NCO content of 11-13 wt. % and an NCO:OH ratio of 4.3:1, obtainable from 55 wt. % 4,4-diphenylmethane diisocyanate (MDI); 5 wt. % polypropylene glycol (PPG) having Mw=400 g/mol; 30 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 10 wt. % polypropylene glycol (PPG) having Mw=2,000 g/mol.

(18) Curing Agent:

(19) Polyol mixture having an OH value of 330-370 mgKOH/g and a functionality f=3, consisting of 5 wt. % trimethylolpropane; 70 wt. % trifunctional polypropylene glycol (PPG) having Mw=450 g/mol; 25 wt. % castor oil.

(20) Mixing ratio resin: curing agent 100:38 parts by weight.

Example 5 (Comparative Example)

(21) Resin Base:

(22) NCO-terminated MDI-prepolymer having an NCO content of 11-13 wt. % and an NCO:OH ratio of 4.3:1, obtainable from 50 wt. % 4,4-diphenylmethane diisocyanate (MDI); 10 wt. % hexane-1,6-diisocyanate (HDI) trimer; 20 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 20 wt. % polypropylene glycol (PPG) having Mw=2,000 g/mol.

(23) Curing Agent:

(24) Polyol mixture having an OH value of 210-250 mgKOH/g and a functionality f=3, consisting of 30 wt. % trifunctional polypropylene glycol (PPG) having Mw=450 g/mol; 70 wt % castor oil.

(25) Mixing ratio resin: curing agent 100:60 parts by weight.

Example 6 (Comparative Example)

(26) Resin Base:

(27) NCO-terminated MDI-prepolymer having an NCO content of 12-14 wt % and an NCO:OH ratio of 3.4:1, obtainable from 55 wt. % 4,4-diphenylmethane diisocyanate (MDI); 15 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 15 wt % polypropylene glycol (PPG) having Mw=400 g/mol; 15 wt. % bifunctional polyester*. *Polyester based on isophthalic acid, adipic acid, 1,2-propanediol, diethylene glycol.

(28) Curing Agent:

(29) Polyol mixture having an OH value of 200-230 mgKOH/g and a functionality f2 or 3, consisting of 75 wt. % bifunctional polyester*; 22 wt % polypropylene glycol (PPG) triol having Mw=450 g/mol; 3 wt. % trimethylolpropane.

(30) Mixing ratio resin: curing agent 100:60 parts by weight.

Example 7 (Comparative Example)

(31) Resin Base:

(32) NCO-terminated MDI-prepolymer having an NCO content of 13-15 wt. % and an NCO:OH ratio of 3.7:1, obtainable from 51 wt. % 4,4-diphenylmethane diisocyanate (MDI); 10 wt. % hexane-1,6-diisocyanate (HDI) trimer; 13 wt. % polypropylene glycol (PPG) having Mw=1,000 g/mol; 13 wt. % polypropylene glycol (PPG) having Mw=400 g/mol; 13 wt. % bifunctional polyester*. *Polyester based on isophthalic acid, adipic acid, 1,2-propanediol, diethylene glycol.

(33) Curing Agent:

(34) Polyester mixture having an OH value of 200-230 mgKOH/g and a functionality f2 or 3, consisting of 75 wt. % bifunctional polyester*; 22 wt. % polypropylene glycol (PPG) triol having Mw=450 g/mol; 3 wt. % trimethylolpropane.

(35) Mixing ratio resin: curing agent 100:65 parts by weight.

(36) Composite Film:

(37) Composite films are produced using a laminating device of the Super Combi 2000 type, for example. In the process, the adhesive composition is applied in an amount of approximately 2 g/m.sup.2 to one of the films to be adhesively bonded (OPA or metOPP) and this film is then laminated to the second film (PE or OPP) under pressure. In this case, the acting roller pressure of the laminating machine corresponds to a force of up to 200 N (20 kg).

(38) Adhesion:

(39) The adhesion is determined in accordance with the standard DIN 53357 after 14 days of curing at room temperature by means of a tensile testing machine from the company Instron (Instron 4301). For this purpose, test strips of the composite film (sample width of 15 mm) are clamped between clamping jaws, which are then pulled apart at a pulling speed of 100 m/min, a pulling angel of 90 and for a pulling length of 5 to 10 cm. The average of a three-fold determination of the maximum force to be applied based on the sample width of 15 mm is given.

(40) Composite Materials:

(41) OPA: oriented polyamide PE: polyethylene PET: polyethylene terephthalate OPP: oriented polypropylene metOPP: metallized OPP (OPP coated with aluminum) Al: aluminum foil CPP: cast polypropylene

(42) TABLE-US-00001 TABLE 1 Experimental parameters Parameter Widest range Narrowest range 1 Adhesion spectrum: >3N/15 mm after 14 days 3-9N/15 mm after 14 days bond strength on >3N/15 mm 3-4N/15 mm PET/Al/PE >2N/15 mm 2-6N/15 mm PET . . . Al >4N/15 mm after 14 days 4-6N/15 mm after 14 days Al . . . PE PET/Al/CPP 2 Running time: a. Initial mixing a. 600-900 mPas at 40 C. viscosity <1,000 mPas at 40 C. a. Pot life curve (viscosity b. Super combi machine b. V = 300-350 m/min increase over time) >300 m/min without misting b. Experimental test: on laminating equipment 3 Bond strength after heat >3N/15 mm without any 3-5N/15 mm without any treatment: delamination after delamination after OPA.sub.pr 14/PE.sub.50 pasteurization 30 min 90 C. pasteurization 30 min 90 C. 4 Filler resistance: Foam bath: >1N/15 mm Foam bath: 1-3N/15 mm Bond strength on after 14 days/40 C. Olive oil: 2-5N/15 mm PET/AI/PE in chambers, Olive oil: >2N/15 mm after 14 days/40 C. in chambers