Abstract: This article mainly introduces the performance and application of the special adhesive for alcohol-soluble polyurethane aluminum plating film newly developed by Occidental Industries (Shenzhen) Co., Ltd. The adhesive is an environmentally friendly product with high initial tack and short maturation time. The low maturation temperature and the small amount of glue can effectively avoid the aluminum plating transfer phenomenon and the composite product has higher strength.

Keywords: alcohol-soluble polyurethane adhesive aluminum film

With the development of society and the improvement of people’s living standards, the application of aluminized films in flexible packaging has become more widespread. There are two commonly used aluminized film materials, one is polypropylene aluminized film, abbreviated as VMCPP, one is aluminized aluminized film, abbreviated as VMPET, and the two kinds of aluminized films have the following characteristics: 1  appearance has metallic luster, Has a strong reflection of light, increasing the visual effect of the package. 2 After the aluminum plating film, it can greatly improve its barrier properties, can extend the shelf life of packaged goods. 3  good processing performance. Compared with aluminum foil, aluminum-plated film is not easy to wrinkle and break.

Although there are many advantages in the application of aluminized films on flexible packaging, there are also certain deficiencies. The author believes that there are two points: 1 The aluminum layer of aluminized aluminum is easy to transfer, resulting in a decrease in the composite strength of the composite film. This is because domestic aluminizing film manufacturers generally do not apply primer to the surface of plastic film when producing aluminized films. The combination between aluminum and film depends only on the polarity of the molecules, and the binding force of the polarity itself is very low. , so the aluminum layer is easy to fall off. Because the polarity of PET is higher than that of CPP, the composite strength of VMPET and other films is higher than that of VMCPP and other films. Another reason is the use of the adhesive itself. I have done experiments with the same aluminized film and the same production process. As a result, it has been found that the degree of transfer of the aluminum layer is not the same and there is a large difference in the composite strength. When the aluminum alloy film is dry-type composite processing, white spots may occur easily, especially at the white ink and the yellow ink. One of the most important reasons is the poor leveling property of the adhesive. For the ester soluble adhesive, if the quality of the adhesive is good, the dry basis weight of the adhesive should be 2.5 to 3 grams. / Square meters, can achieve the desired surface effect. If the adhesive quality is poor, the dry basis weight of the glue should reach 2.8-3.5 g/m2 in order to achieve the desired apparent effect.

In view of the fact that the aluminized film is liable to cause the transfer of the aluminum layer during the compounding process, thus reducing the composite strength, many adhesive manufacturers with research and development capabilities have conducted many years of research and have successively introduced different brands of ester-soluble aluminum plating. Film special glue, some brands can play a certain effect, and some of the effects are not obvious.

The author of the five domestic brands of ester-soluble adhesive aluminum coating on the experiment. The three brands A, B and C are common ester-soluble binders, and the D and E brands are ester-soluble aluminum-plated adhesives. The experimental process, materials and strength are as follows:

Experimental equipment and materials: OPP printing (chlorinated polypropylene ink), VMCPP, VMEPT, dry laminating machine (Japan Fuji), network roller (120#, 60μ), tensile machine (Shimadzu, Japan).

Experimental process: glue concentration 30%, compound pressure 5 kg, three-stage drying temperature 60, 70, 80°C, compound temperature 70°C, machine speed 90m/min, aging temperature 50°C, aging time 48 hours.

Phenomenon: The aluminum layer of the aluminized film of the A brand adhesive composite product is severely transferred, and the white ink has white spots. B and C brand adhesive composite product aluminum film transfer 80% of the aluminum layer, white ink position is not white, D brand adhesive composite product aluminum film aluminum layer is hardly transferred, white ink position There is no white spot, but the aged colloids are sticky and somewhat similar to single-component stickers. E brand adhesive composite product aluminum film transfer of 20% of the aluminum layer, white ink does not have white spots.

Europe and the United States Branch Industrial (Shenzhen) Co., Ltd. as a well-known adhesive manufacturer in the flexible packaging industry, is also the only manufacturer of alcohol-soluble two-component polyurethane adhesive, the company's R & D center according to the characteristics of aluminum film and alcohol-soluble type The characteristics of the adhesive, starting from the reaction mechanism of the adhesive, are adjusted on the molecular structure. This adhesive retains the advantages of the alcohol-soluble adhesive and achieves the effect of avoiding the aluminum layer transfer of the aluminum coating. . The following two tables list the physical characteristics of the two varieties.

The author conducted experiments on the above two varieties. The experimental results are as follows:

Experimental equipment and materials: OPP printing (chlorinated polypropylene ink), VMCPP (Toujin), VMPET, dry laminating machine (Japan Fuji), screen roller (120#, 60μ), tension machine (Shimadzu, Japan).

Experimental procedure: glue concentration 30% and 25%, compound pressure 4 kg, drying temperature 60, 70, 80°C, compound temperature 60°C, machine speed 90m/min, aging temperature 40°C, aging time 48 hours.

Phenomenon: A small amount of local aluminum transfer, no white spots at the ink.

Summary: Alcohol-soluble adhesives produced by the Occidental Company, with a dry basis weight of 1.9 g/m2, can effectively eliminate the white point phenomenon and have a higher composite strength. From the perspective of application cost, due to the low coating amount, the final use cost is effectively reduced by about 15%, bringing real benefits to the majority of users. (Text/Feng Xinping)