Adhesive resin is often used in multi-layer coextrusion technology and coating composite technology. It is called tie by dumei Guobang company, admer by Mitsui company in Japan, Mitsubishi company in Japan, SK company and atofina company in South Korea, as well as relevant products of Nanjing Aoguang and Nanjing Liuhe company.
Adhesive resin is usually a kind of graft modified polymer. By grafting the monomers onto the main chain of the polymer to form functional branches, the functional branches exposed outside the main chain can react with the bonded materials rapidly and efficiently. The wetting, diffusion, chemical bond and physical entanglement of adhesive materials are the main factors determining the bonding strength.
Common adhesive polymers are anhydride modified ethylene vinyl acetate, polyethylene, polypropylene and some acid copolymers. According to the type of polymer carrier, it can be used to bond PE, PP, sarin, EVA, PA, EVOH, PVC, paper, etc. this kind of adhesive resin can be used for common extrusion and co extrusion equipment processing.
The function of the adhesive resin is to bond together the resin or base material which cannot be bonded to each other. The adhesion effect is usually characterized by peel strength.
1. Anhydride modified ethylene vinyl acetate copolymer (EVA modified adhesive resin for short)
Just like EVA, its modified adhesive resin has the density and melting finger similar to EVA resin, which can bond a variety of materials. For example: PE, EVA, PA6, sarin.
EVA modified adhesive resin must have enough time to activate anhydride during coextrusion to ensure enough adhesion. Therefore, the setting of temperature is very important. In order to ensure the bonding strength, the melt of the adhesive resin should be kept at the melt temperature above 210 ℃ for several minutes before contacting other bonded materials, so as to ensure its adhesion performance during coextrusion processing.
In order to prevent the degradation of EVA due to high processing temperature, the processing temperature should be limited to 238 ℃.
If the adhesion is good, the processing temperature can be reduced to about 230 ℃. The longer the bonding resin is above 210 degrees, the more fully activated anhydride is. However, high temperature or dead corner in extruder may lead to resin aging.
The specific temperature setting should be adjusted according to the screw design, extruder back pressure limit, pressure limit, rheological property matching with other materials during CO extrusion and the influence of other materials' thermal stability. In addition, the retention time of the adhesive resin in the extruder will also affect the quality of the film, so the flow of the adhesive resin in the extruder should be as smooth as possible.
Due to the low softening point of EVA resin modified by anhydride, the temperature of feeding section of extruder should be kept as low as possible during processing, and then the temperature should be raised to the melting point rapidly in the compression section.
Generally, the problem of resin bridging can be avoided by cooling the throat and screw feeding section with water. Standard polyolefin screw can be used to select the appropriate screw according to the need of extrusion amount, but it is necessary to avoid the influence of too deep screw groove on the shear melting of adhesive resin. At the same time, it should avoid using too large screw to extrude adhesive resin at low speed.
2. Linear low density polyethylene polymer modified by anhydride
The density and melt index of LLDPE are similar to those of LLDPE. It can bond a variety of materials, such as ethylene vinyl alcohol copolymer (EVOH), PA6, PE, ionic polymer (sarin) and ethylene copolymer. It has similar physical properties to LLDPE resin. It can be used in blowing film, tape casting film / sheet co extrusion process. The results show that LLDPE adhesive resin has better heat resistance than EVA adhesive resin.
It can also be used in coextrusion coating process. Each grade of resin has different rheological properties, so it has its specific application.
LLDPE adhesive resin has good adhesion to EVOH and excellent adhesion to pa.
Like EVA above, the setting of processing temperature is very important.
Hold for a few minutes at a melting temperature above 200 degrees to activate the anhydride group.
In order to prevent too high temperature of EVA and EVOH, the processing temperature of LLDPE adhesive resin modified by anhydride should not exceed 235 ℃ when CO extrusion with heat sensitive resin materials such as EVA or EVOH.
If the adhesion is good enough, the processing temperature of adhesive resin can be reduced to 210-220 ℃.
When it is coextruded with nylon PA and other heat stable resins, the processing temperature can be higher than 250 ℃. And it can be reduced appropriately. Beyond 260 degrees, the problem of crystal point will appear.
When CO extrusion process is used, the key technology is to control the material and process parameters and match the melt viscosity of different materials.
3. Polypropylene polymer modified by anhydride
The density and melt index of PP are similar to those of PP. It can bond a variety of materials, such as PP, EVOH, PA6.
It has similar physical properties to PP resin. It can be used in blowing film, tape casting film / sheet co extrusion process.

The temperature setting is very important. In order to ensure the bonding strength, the melt of the adhesive resin should be kept at the melt temperature above 210 ℃ for several minutes before contacting other bonded materials, so as to ensure its adhesion performance during coextrusion processing.

In order to prevent too high temperature of EVA and EVOH, the processing temperature of PP adhesive resin modified by anhydride should not exceed 235 ℃ when CO extrusion with heat sensitive resin materials such as EVA or EVOH.
If the adhesion is good enough, the processing temperature of adhesive resin can be reduced to 210-220 ℃.
When it is coextruded with nylon PA and other heat stable resins, the processing temperature can be higher than 250 ℃.
4. High density polyethylene polymer modified by anhydride
It is widely used in coextrusion casting, film blowing, sheet boiling resistance structure, PE and PA, EVOH bonding structure, aluminum plastic bonding structure and so on.
Temperature setting: the processing temperature of anhydride modified HDPE adhesive resin shall not exceed 235 ℃.
If the adhesion is good enough, the processing temperature of adhesive resin can be reduced to 210-220 ℃.
When it is coextruded with nylon PA and other heat stable resins, the processing temperature can be higher than 250 ℃.
5. Copolymer of ethylene and methacrylate (mainly used for coating)
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