Adhesive composition for flexible lamination

Abstract

The present invention refers to an adhesive composition for flexible lamination, especially for food packaging, which comprises a vegetable oil-based polyol and an NCO-terminated compound as well as a method of producing the vegetable oil-based polyol. Further, the present invention refers to the use of the inventive adhesive composition in flexible lamination and an article comprising the inventive adhesive composition.

Claims

1. Adhesive composition for flexible lamination comprising: a) a vegetable oil-based polyol and b) an NCO-terminated compound; wherein the vegetable oil-based polyol is a reaction product of a mixture (A) comprising i) unsaturated epoxidized vegetable oil; ii) an alcohol; iii) an organic acid selected from the group consisting of acetic acid, lactic acid, succinic acid, caproic acid, fatty acids and mixtures thereof; and iv) an inorganic acid and wherein the mixture (A) is essentially free of fluoroboric acid.

2. The adhesive composition according to claim 1 wherein the vegetable oil-based polyol is derived from renewable sources and/or the content of renewable materials in the reaction (A) is more than 90 wt. %, based on the total weight of the mixture (A) not including any solvent.

3. The adhesive composition according to claim 1 wherein the mixture (A) comprises: i) 25 to 95 wt. % of an unsaturated epoxidized vegetable oil; ii) 2 to 20 wt. % of an alcohol; iii) 0.5 to 7 wt. % of an organic acid; and iv) 0.5 to 7 wt. % of an inorganic acid, wherein the wt. % are based on the total weight of the mixture (A) not including any solvent.

4. The adhesive composition according to claim 1 wherein the mixture (A) comprises: i) 30 to 95 wt. % of an unsaturated epoxidized vegetable oil; ii) 5 to 15 wt. % of an alcohol; iii) 1 to 5 wt. % of an organic acid; and iv) 1 to 5 wt. % of an inorganic acid, wherein the wt. % are based on the total weight of the mixture (A) not including any solvent.

5. The adhesive composition according to claim 1 wherein the mixture (A) is compliant with the food safety regulations set out EU No. 10/2011 and the US food contact regulations summarized in 21 CFR 175.105 and 21 CFR 182.1073.

6. The adhesive composition according to claim 1 wherein the unsaturated epoxidized vegetable oil is derived from a vegetable oil selected from the group consisting of soybean oil, corn oil, sunflower oil, linseed oil, olive oil, canola oil, sesame oil, cottonseed oil, palm oil, rapeseed oil, tung oil or a blend of any of these oils.

7. The adhesive composition according to claim 1 wherein the unsaturated epoxidized vegetable oil has an epoxy oxygen content of 0.05 to 10%, based on the number of double bonds in the vegetable oil.

8. The adhesive composition according to claim 1 wherein the alcohol is selected from the group consisting of ethanol, second generation ethanol, alcohols and glycols originated from biomass, alcohols and glycols originated from cellulose and its derivates, alcohols and glycols originated from sugar and its derivates and mixtures and blends thereof.

9. The adhesive composition according to claim 1 wherein the organic acid is selected from the group consisting of acetic acid, lactic acid, succinic acid, caproic acid and mixtures thereof.

10. The adhesive composition according to claim 1 wherein the inorganic acid is a mineral acid, selected from the group consisting of nitric acid, phosphoric acid, polyphosphoric acids, sulfuric acid, poly phosphorous acid, hydrochloric acid, perchloric acid and mixtures thereof.

11. The adhesive composition according to claim 1 wherein the NCO-terminated compound is selected from the group consisting of 1,5-Naphthylendiisocyanate (NDI); 2,4- or 4,4-Diphenylmethandiisocyanate (MDI); isomers of Toluylendiisocyanates (TDI); Methylentriphenyltriisocyanate (MIT), hydrated MDI (H12MDI); Tetramethylxylylendiisocyanate (TMXDI); 1-Isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI); Xylylendiisocyanate (XDI); Hexan-1,6-diisocyanate (HDI); Pentamethylendiisocyanate, Dicyclohexylmethandiisocyanate; dimers, trimers, oligomers and polymers of the above; and mixtures of the above.

12. A method for the production of the a) vegetable oil-based polyol of claim 1, comprising: a) providing the mixture (A) comprising the i) unsaturated epoxidized vegetable oil, the ii) alcohol, the iii) organic acid; and the iv) inorganic acid; b) heating the reaction mixture to a temperature of 70 to 130? C.

13. The method according to claim 12, wherein the method does not include a washing step and/or a neutralization step.

14. An article comprising the adhesive composition according to claim 1.

15. A flexible laminate comprising a first film including a surface, a second film including a surface and cured reaction products of the adhesive of claim 1 disposed between the first and second films and bonding the first film surface to the second film surface.

16. A food package comprising a foodstuff contained within a pouch comprising the flexible laminate of claim 15.

17. An adhesive composition for flexible lamination comprising: a) a vegetable oil-based polyol and b) an NCO-terminated compound; wherein the vegetable oil-based polyol is a reaction product of a mixture (A) comprising i) 25 to 95 wt. % of an unsaturated epoxidized vegetable oil; ii) 2 to 20 wt. % of an alcohol; iii) 0.5 to 7 wt. % of an organic acid; and iv) 0.5 to 7 wt. % of an inorganic acid.

18. Cured reaction products of the adhesive composition according to claim 17.

19. A flexible laminate comprising a first film including a surface, a second film including a surface and the adhesive of claim 17 disposed between the first and second films and in contact with the first film surface and the second film surface.

Description

EXAMPLES

(1) Vegetable Oil-Based Polyol

(2) Unsaturated vegetable oil which had previously been partially epoxidized was introduced into a reaction reactor, followed by the addition of the alcohol. The reaction mixture was heated in the reactor to a temperature in the range of 80 to 110? C. and a batch of the organic acid and the inorganic acid was added, the batch making up 10 to 40 wt.-% of the total amount of organic and inorganic acid, respectively. The reaction mixture was maintained at a temperature in the range of 80 to 110? C. for 2 hours before another batch of the organic acid and the inorganic acid was added. The reaction mixture was again kept in the prescribed temperature range before the final batch of organic and inorganic acid was added. The reaction mixture was then kept at a temperature of 80 to 110? C. for a period of 20 to 35 hours. After completion of the reaction, the desired vegetable oil-based polyol was obtained by distillation. The obtained polyol had an average molecular weight M.sub.n of 1131 g/mol and a polydispersity of 1.56, determined according to the above-mentioned methods. Hydroxyl value and acidity number were determined to be 117 mg KOH/g and 0.71 mg KOH/g, respectively. The viscosity was measured to be 0.4 Pas, determined according to ASTM D-4878 at 25? C., using a Brookfield RTV.

Inventive Example

(3) A 1200 ml round bottomed flask equipped with a thermometer, a heating mantle, a stirrer and nitrogen gas flush inlet was charged as follows: an aromatic isocyanate was added into the reactor and followed by sequential addition of the vegetable oil-based polyol. The reactor temperature was set to 75? C. and the reaction was carried out for 2 hours. Solvent-free adhesive 02 was discharged from the reactor and isocyanate level and viscosity were measured following the above-mentioned testing methods.

Comparative Example

(4) A 1200 ml round bottomed flask equipped with a thermometer, a heating mantle, a stirrer and nitrogen gas flush inlet was charged as follows: an aromatic isocyanate was added into the reactor, followed by sequential addition of propylene glycols (molecular weight 1000 to 2000 g/mol) and vegetable oil. The reactor temperature was set to 75? C. and the reaction was carried out for 2 hours. Solvent-free adhesive 01 was discharged from the reactor and isocyanate level and viscosity were measured following the above-mentioned testing methods.

(5) Application Tests:

(6) Comparative adhesive 01 was mixed with a commercially available hardener in a fixed proportion of 10 parts of adhesive 01 and 8 parts of hardener to run lamination described below.

(7) Solvent free adhesive 02 was mixed with a commercially available hardener in a fixed proportion of 10 parts of adhesive 02 and 8 parts of hardener to run lamination described below.

(8) The mixture was applied on different films (see table below) in a Nordmeccanica Labo Combi Lamination Machine and laminated to standard flexible packaging films.

(9) TABLE-US-00001 Adhesive 01 Test Unit (comp.) Adhesive 02 Average bond strength gf/inch 902 984 (flexible laminate 1) Average bond strength gf/inch 290 307 (flexible laminate 2) Average bond strength gf/inch 297 211 (flexible laminate 3) Maximum Sealing strength gf/inch 6160 5760 (flexible laminate 1) Maximum Sealing strength gf/inch 2495 2488 (flexible laminate 2) Maximum Sealing strength gf/inch 490 391 (flexible laminate 3)

(10) Flexible laminate 1: PET Film (12 microns)/adhesive/Polyethylene film (60 microns), adhesive coating weight: 2.1 g/m.sup.2,

(11) Flexible laminate 2: PET metalized (12 microns)/Adhesive/Polyethylene film (60 microns): adhesive coating weight: 2.1 g/m.sup.2,

(12) Flexible Laminate 3: BOPP metalized (14 microns)/Adhesive/BOPP (14 microns): adhesive coating weight: 2.1 g/m.sup.2.

(13) The adhesion and sealing strength results obtained clearly show that the inventive adhesive composition comprising a polyol based on renewable sources can be used to replace adhesive compositions comprising synthetic polyols for lamination.