Patent ID: 12202227

EXAMPLES

A series of coated films were prepared by coating a coating composition on a biaxially oriented PET film of thickness 12.5 μm and then dried. The dry coat-weight of the coating composition was 2.3 g/m2. The coating compositions were as follows.

Comparative Example 1

A coating solution was prepared by dissolving copolyester 1 (532 g) and copolyester 2 (133 g) in THF (2,800 g) at 55° C., followed by the addition of slip/anti-blocking ingredients (fatty amide 10.5 g; silica 24.5 g). Copolyester 1 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 45 mol % azelaic acid, and which exhibited a tensile strength of 2700 psi and an elongation of 1000%, measured as defined herein. Copolyester 2 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 33 mol % isophthalic acid, and which exhibited a tensile strength of 11000 psi and an elongation of 5%, measured as defined herein.

Example 1

A coating solution was prepared by dissolving copolyester 1 (476 g) and copolyester 2 (203 g) in THF (2,800 g) at 55° C., followed by the addition of slip/anti-blocking ingredients (fatty amide 10.5 g; silica 10.5 g). Copolyester 1 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 45 mol % azelaic acid, and which exhibited a tensile strength of 2700 psi and an elongation of 1000%, measured as defined herein. Copolyester 2 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 58 mol % sebacic acid, and which exhibited a tensile strength of 1000 psi and an elongation of 1600%, measured as defined herein.

Example 2

A coating solution was prepared by dissolving copolyester 1 (476 g) and copolyester 2 (203 g) in THF (2,800 g) at 55° C., followed by the addition of slip/anti-blocking ingredients (fatty amide 10.5 g; silica 10.5 g). Copolyester 1 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 45 mol % azelaic acid, and which exhibited a tensile strength of 2500 psi and an elongation of 1200%, measured as defined herein. Copolyester 2 was a PET-based copolyester in which the dicarboxylic acid fraction comprised 58 mol % sebacic acid, and which exhibited a tensile strength of 1000 psi and an elongation of 1600%, measured as defined herein.

Cap-Liners

Each of the films was made into a one-piece cap-liner by laminating the film with an aluminium foil layer (of thickness 25.4 μm) followed by laminating with a layer of paper foam (of thickness 127 μm). The cap-liner was inserted into a white 38/400 cap (SKS Bottle & Pkg, Inc.) and induction-sealed to a white PET bottle (Packaging Options Direct, US) having a neck diameter of 38 mm in which the wall thickness of the bottle neck was 2.2 mm. Induction-sealing was performed on an Ifoiler Induction Sealer (Pillar Tech. LLC) using a cap torque of 20 lbf*in (pound-force-inch), an air gap (induction sealer head to bottle cap) of ⅛″ (3.175 mm) and a conveyor line speed 60 feet/min (18.288 m/min).

Table 1 shows the properties of the copolyesters, the films containing them and the cap-liners made therefrom, characterised according to the test methods described hereinabove.

The data in Table 1 show that the variation in heat-seal peel strength over the temperature range of 121 to 204° C. is much larger for Comparative Example 1 and advantageously smaller for Examples 1 and 2. Thus, the inventive examples advantageously exhibit a much lower variation in heat-seal strength with changes in temperature. It will be appreciated that temperatures can be controlled more precisely in a heat-sealing system than in an induction system and that the heat-seal testing was conducted at different temperatures in order to recreate the varying temperature conditions in a conventional induction-sealing system.

The data in Table 1 also show that the variation in heat-seal peel strength after ageing is much larger for Comparative Example 1 and advantageously smaller for Examples 1 and 2. Thus, the inventive examples advantageously exhibit a much smaller increase in heat-seal strength over time.

A similar trend was observed for the induction-seal peel strength data in Table 1. The variation in peel strength after ageing is advantageously much smaller for Example 2 (Example 1 was not tested), compared to Comparative Example 1, which was observed at all power settings tested for each film. The power setting was adjusted to optimise the seal strength of the heat-seal bond. For Comparative Example 1 the optimal setting was 48% of the potential power output of the induction sealing system, whereas for Example 2 the optimal setting was 32% of the potential power output of the induction sealing system in order to provide comparable aged peel strengths to Comparative Example 1. It will be appreciated that the inventive Example also surprisingly allows a reduction in the energy used to make an appropriate heat-seal bond, thereby improving the economy and sustainability of the process.

TABLE 1Induction-seal peel strengthCopolyester 1Copolyester 2Heat-seal peel strength(PS) of cap-liner (g)Co-Co-(PS) of film (g/inch)Δ-PS ondiacidAmountTgTsdiacidAmountTgTsAgedΔ-PS onPowerAgedageing(mol %)(wt %)(° C.)(° C.)(mol %)(wt %)(° C.)(° C.)TeUnaged(24 h)ageingoutputUnaged(24 h)(%)C.Azelaic76 wt %−8150isophthalic19 wt %70150T1711114243144%49675352%Ex. 1acid (45acid (33T2>1078a>1556c478c46%46383981%mol %)mol %)T3>1326b>1600dn/ad48%679102050%Ex. 1Azelaic68 wt %−8150sebacic29 wt %−22100T19291123194————acid (45acid (58T29141092178————mol %)mol %)T311651308143————Ex. 2Azelaic68 wt %−7145sebacic29 wt %−22100T177794116428%50366933%acid (45acid (58T284199014930%914910−4%mol %)mol %)T3897102212532%970110614%Keya1 of 6 samples shredded;b3 of 6 samples shredded;c5 of 6 samples shredded;d6 of 6 samples shreddedeheat-seal temperatures were: T1= 121° C.; T2= 177° C.; T3= 204° C.