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, based on the total weight of the laminating adhesive composition, (a) a resin component including at least one NCO-terminated polyurethane prepolymer prepared by reacting at least 40 wt. % diphenylmethane diisocyanate (MDI), wherein the MDI is 4,4-diphenylmethane diisocyanate or a mixture thereof with 2,4-diphenylmethane diisocyanate, and 2 to 20 wt. % polyglycol having a molecular weight (M.sub.w) of 200 to <1,000 g/mol, wherein the polyglycol is polypropylene glycol having a molecular weight of 200 to <1,000 g/mol or polyethylene glycol having a molecular weight of 200 to <1,000 g/mol; and (b) a curing component including a mixture comprising at least two different polyols, wherein the laminating adhesive composition is free of polyester components.

2. The laminating adhesive composition according to claim 1, wherein one of the polyols of the curing component is a trial, to which alkylene oxide (AO) is added and which has a molecular weight M.sub.w of less than 700 g/mol, and which is contained in the curing component in an amount of 5 to 90 wt %.

3. The laminating adhesive composition according to claim 1, wherein one of the polyols of the curing component is an aliphatic, dihydric or polyhydric alcohol having a molecular weight of <150 g/mol and/or a hydroxyl number of 700 to 2,000 mg KOH/g, which is contained in the curing component in an amount of 0.5 to 10 wt. %.

4. The laminating adhesive composition according to claim 1, wherein one of the polyols of the curing component is selected from the group consisting of ethylene glycol, propylene glycol, butanediol-1,4, pentanediol-1,5, hexanediol-1,6, heptanediol-1,7, octanediol-1,8, glycerol, trimethylolpropane and pentaerythritol.

5. The laminating adhesive composition according to claim 1, wherein one of the polyols of the curing component is a triol based on glycerol or trimethylolpropane (TMP) to which propylene oxide (PO) is added and which has a molecular weight M.sub.w of 700 to 1,200 g/mol; or is castor oil; the one of the polyols contained in the curing component in an amount of 5 to 80 wt. %.

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

7. The laminating adhesive composition according to claim 1, wherein the laminating adhesive composition contains: (1) at least one triol selected from glycerol or trimethylolpropane (TMP) to which alkylene oxide (AO) is added and which has a molecular weight M.sub.w of less than 700 g/mol; (2) optionally at least one aliphatic dihydric or polyhydric, monomeric alcohol; and (3) castor oil or at least one trial selected from glycerol or trimethylolpropane (TMP), to which alkylene oxide (AO) is added, and which has a molecular weight M.sub.w of more than 700 g/mol.

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

9. Cured reaction products of the laminating adhesive composition according to claim 1.

10. A method for producing composite films, comprising: providing a first film and a second film; wherein the films can be identical or different plastics; providing the resin component of claim 1; providing the curing component of claim 1; mixing the resin component and the curing component 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 adhesive on the surface of the first film.

11. The method according to claim 10, wherein the laminating adhesive composition is applied in an amount of 1 to 5 g/m.sup.2 to the surface portion of the first film.

12. A composite film produced according to the method of claim 10.

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

Description

EXAMPLES

Example 1 (According to the Invention)

Resin Base:

[0065] 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.

Curing Agent:

[0066] 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.

[0067] Mixing ratio resin: curing agent 100:70 parts by weight.

Example 2 (According to the Invention)

Resin Base:

[0068] 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.

Curing Agent:

[0069] 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.

[0070] Mixing ratio resin: curing agent 100:35 parts by weight.

Example 3 (According to the Invention)

Resin Base:

[0071] 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.

Curing Agent:

[0072] 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.

[0073] Mixing ratio resin: curing agent 100:40 parts by weight.

Example 4 (According to the Invention)

Resin Base:

[0074] 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.

Curing Agent:

[0075] 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.

[0076] Mixing ratio resin: curing agent 100:38 parts by weight.

Example 5 (Comparative Example)

Resin Base:

[0077] 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.

Curing Agent:

[0078] 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.

[0079] Mixing ratio resin: curing agent 100:60 parts by weight.

Example 6 (Comparative Example)

Resin Base:

[0080] 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.

Curing Agent:

[0081] 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.

[0082] Mixing ratio resin: curing agent 100:60 parts by weight.

Example 7 (Comparative Example)

Resin Base:

[0083] 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.

Curing Agent:

[0084] 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.

[0085] Mixing ratio resin: curing agent 100:65 parts by weight.

Composite Film:

[0086] 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).

Adhesion:

[0087] 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.

Composite Materials:

[0088] OPA: oriented polyamide [0089] PE: polyethylene [0090] PET: polyethylene terephthalate [0091] OPP: oriented polypropylene [0092] metOPP: metallized OPP (OPP coated with aluminum) [0093] Al: aluminum foil [0094] CPP: cast polypropylene

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