Guowang Forum • You Ask, I Answer • QQ Group Questions

Yongsheng Packaging - Julia: For a two-layer laminated film, apart from the thickness of the film materials, roughly how thick are the ink and adhesive?

Shanghai Yiguang Packaging Equipment: About 1 si, that is, 10um.

Yongsheng Packaging - Julia: For a four-layer structure laminated three times, is it about 3um added for ink and adhesive?

Dong, Guangzhou Tongze Machinery: I think they should be calculated separately, based on the coating weight of ink and adhesive; each 1g/m² of adhesive applied increases thickness by 1um.

Engineer Li: For dry lamination, the total thickness of ink and adhesive should be close to 10um.

Xiao Ke, Jinan: How could it be that thick? At most 3um.

1. Frozen Packaging Structure for Duck Feet

Zhongbu Printing: For frozen food bags for duck feet, with deboned duck feet and water inside, stored at -4℃, what structure is suitable? OPP//PE or nylon//PE, or another structure? 40um on one side.

Harbin Botai: Nylon//PE! PE is more suitable for frozen packaging; CPP is too brittle at low temperatures. How heavy is the content?

Song Kai, Guangzhou Bostik: I suggest NY//RCPP.

Zhongbu Printing: Estimated 200g, bag size 22*18cm.

Harbin Botai: If you want premium quality, NY//PE; if you want cost control, single-layer PE with surface printing.

Zhongbu Printing: That makes sense; 40um on one side is a bit thin.

Harbin Botai: Quick-frozen cut chicken all uses single-layer PE, 140um total, with freeze-resistant ink for surface printing.

Zhongbu Printing: How about OPP//frozen PE?

Harbin Botai: No, you can try PET/PE; low cost and decent results.

Zhongbu Printing: Will PET//PE side seams crack at low temperatures, since PET is also brittle?

Xiao Xia, Hubei Dry Lamination: Your structure is not reliable; the PE is a bit thin.

Zhongbu Printing: Which structure is not reliable? The customer wants it thin to save cost.

Harbin Botai: At least 60um would be better.

Xiao Xia: If that's the case, just use 10um nylon.

Zhongbu Printing: Where can I buy 10um nylon?

Xiao Xia: If you want it even cheaper, use 15um OPP.

Zhongbu Printing: What are the pros and cons of PET//PE?

Xiao Xia: PET is fine too, but its density is a bit higher. Calculate which is cheaper; it's really hard to say at this thickness—there is a risk of breakage.

1. Solventless Lamination Not Curing

A Flexible Packaging Company: With Nordmeccanica solventless lamination equipment, several meters of each film roll do not cure—sometimes in the middle of the roll, sometimes at the edge. The uncured width is about 4~5cm. What is the cause?

Song Kai, Yidebang Adhesive: It is caused by too long a stoppage in the middle of the run.

A Flexible Packaging Company: Why?

Song Kai: When the machine stops, the adhesive inside the static mixer has already been mixed together; over time it begins to react and its viscosity increases. By the time it is pumped out the second time, the adhesive at the front is not mixed evenly enough, causing local non-curing. Choosing a solventless adhesive with a long pot life can overcome this problem.

A Flexible Packaging Company: But it is not that there is too little adhesive—it does not cure. When torn open there is adhesive, but it just does not cure. The stoppage was just a roll change.

Song Kai: The non-curing phenomenon is caused by uneven mixing of the A and B components—there is no NCO component.

Dong Wentao, Guangzhou Tongze: Are the temperatures set the same for the A and B adhesive tanks?

A Flexible Packaging Company: No, B is 40℃, A is 30℃.

Dong Wentao: At room temperature, is B adhesive more viscous or A adhesive?

A Flexible Packaging Company: B adhesive. There are 7 rolls of material in total; some rolls have two sections that do not cure, while some rolls have only one section that does not cure.

Dong Wentao: Then it may be that the adhesive output is not synchronized.

Song Kai: The core in the middle of the static mixer was installed backwards; it rotates as the adhesive is pumped.

Dong Wentao: Clean the adhesive output pipeline.

A Flexible Packaging Company: It can't be installed backwards. Do you mean the core of the adhesive mixer rotates?

Dong Wentao: Clean the A adhesive pipeline, including the mixing head.

A Flexible Packaging Company: Okay.

Song Kai: Yes.

1. Ink Peeling

Lanhai Printing: When printing BOPP heat-seal film with high-temperature ink, some ink still peels off onto the heat-sealing knife of the packaging machine and sticks to it. What is the cause? How can it be solved?

Harbin Botai: Is Teflon tape applied to the heat-sealing knife? It still feels like the ink is not temperature-resistant.

Xiao Ke, Jinan: Generally, designs are not recommended at the sealing position.

Color Printing & Aluminum Coating Consultant: Inks used for printing on OPP are not resistant to high temperatures; temperature-resistant inks generally require high-temperature baking or are two-component.

1. Wrinkles in Lamination Winding

Xin, Dalian Jutong Plastics: May I ask, how can wrinkles caused by lamination winding be controlled?

Fl, Dongguan Jinheng Packaging: They can be controlled by adjusting the winding curve of the equipment.

Liu, Xiamen Jinyuan: Adjust the winding tension.

Walking My Own Road: It is poor control of winding tension.

Chengdu Color Printing Management: Are they wrinkles at the bottom of the laminated roll or surface wrinkles?

Xiao Xia: Soft wrinkles.

Yang, Guangzhou Dry Lamination: If the take-up can be run manually, run it manually; once adjusted, do not increase it again, and minimize the number of stoppages.

Lida: Automatic winding tension is indeed rather difficult to control. Tension and the winding curve should be adjusted according to the width and thickness of the film.

Wang, Jinyu Packaging: Winding wrinkles include bottom-of-roll wrinkles, splice wrinkles and surface wrinkles. Bottom-of-roll wrinkles are controlled by initial tension, the tension taper curve setting, a large paper core, and the regularity and smoothness of the paper core; for splice wrinkles, pay attention to the flatness of the splice tape and the rationality of tension switching (equipment performance); surface wrinkles are mostly related to bottom-of-roll wrinkles in the raw material, especially thick film—pay attention to early roll-change splicing.

Gazing at the Starry Sky: Change the core to a larger one.

1. Coffee Packaging Structure

Mr. Hu, Taishan Malaysia: Does anyone know the material specification of the roll film used for Nescafé coffee's automatic inner packaging recently? It is an easy-tear material, and every part can be easily torn.

Packaging Rookie: It is made by extrusion lamination, PET/AC/LDPE-LDPE+AE/AL/EAA-MLLDPE, using twin-screw co-extrusion.

Jiang, Guangdong Lamination: PET//PE//AL//PE//PE.

1. Blank Doctor Lines

Yang Zibiao: May I ask everyone, why do blank doctor lines always appear during lamination? The adhesive and the adhesive pan are both clean.

Yang, Wuhan Printing: If there are blank doctor lines, it is definitely not clean.

Xiao Xia: Check the blade edge—what adhesive are you using?

Yang Zibiao: Lihe.

Yang, Wuhan Printing: If it always appears, it should not be the blade.

Xiao Xia: Have you used alcohol-soluble and water-based adhesives?

Yang Zibiao: The adhesive is not dirty—no, I haven't; the doctor blade is also quite normal.

Xiao Xia: If it always appears, you need to check whether the blade edge has been wiped clean.

Yang Zibiao: It has been wiped clean.

Liu Liufang: It may be the rubber roller.

Xiao Xia: Put stockings over both ends of the adhesive suction pipe, and rub the blade edge with sandpaper.

Yang, Wuhan Printing: It is definitely caused by debris; find a way to filter the adhesive.

Yang Zibiao: We add adhesive manually. Why should the blade edge be rubbed with sandpaper?

Xiao Xia: If you add adhesive manually, you should store the adhesive properly yourself! Cover it with a lid to reduce dust ingress.

Yang Zibiao: The adhesive is not dirty; it is clean.

Xiao Xia: Why rub the blade edge with sandpaper? To prevent dried adhesive under the blade edge from softening again in the adhesive.

Jingbao—RH: Adjust the doctor blade angle and filter the adhesive. Xiao Xia makes sense.

Yang, Wuhan Printing: Clean thoroughly before use, and filter with a 120-mesh or finer filter screen before use.

Jiangxi Yunlong Color Printing: The adhesive must contain particles; pay attention to the blade angle.

Xiao Xia: A blank doctor line means there is impurity!

Jiangxi Yunlong Color Printing: The anilox roller should also be wiped clean.

Yang Zibiao: The blade angle is basically parallel.

Xiao Xia: You can check for yourself—is there a lot of impurity in the adhesive left in the pan at the end of the shift?

Yang Zibiao: We use a 140-mesh filter screen; after work there is a little impurity in the adhesive.

Xiao Xia: Lower the adhesive pan a bit.

Jiangxi Yunlong Color Printing: There is too much old adhesive stuck under the blade.

Jingbao—RH: There is definitely impurity; the only way to keep impurity from getting stuck in the doctor blade is to adjust the doctor blade angle.

Xiao Xia: If you are in the same workshop as printing, it is best to use fewer poor-quality blankets.

Yang Zibiao: There is no adhesive under the blade; the new machine has only run a few times.

Yang, Wuhan Printing: Find a way to filter the adhesive.

Jingbao—RH: In spring, floating dust, catkins and fibers are all impurities—they can give you a headache.

Engineer Li: Change the blade first and see; go from simple to complex. Then check the thickness and position of the lines and whether continuity changes. Try changing the pressure roller.

Zhang, Shangpin Printing: I think the working concentration of the adhesive is a bit high, and there is impurity in the adhesive; add solvent to reduce the concentration.

(Note: The above are some technical questions discussed in the group. Readers who have different opinions or additions are welcome to submit to us: fanjunhong@126.com or ss8996@126.ccom. You are also welcome to join our flexible packaging technical exchange QQ groups: Main Group: 121451012; Group I: 64311965; Group II: 37848282; Group III: 119411638; Group IV: 116162302; Group V: 256925591).