Research and Application of New Aluminized Composite Film Adhesive

Beijing Gaomeng Chemical Co., Ltd. has been dedicated to the development of special adhesives in order to serve the packaging industry. The special glues that have been completed include 135°C high-temperature cooking glue, 121°C cooking glue, anti-media glue, aluminized composite glue, and fast. Curing adhesives, special adhesives for washing powder bags, and other adhesives designed specifically for packaging companies. This article describes the latest development of our company's new aluminum film adhesive. 

The aluminized composite film is a combination of aluminized films (VMPET, VMBOPP, VMCPP and VMCPE) and a plastic film to form a packaging material with aluminum luster. Because of its good barrier properties, puncture resistance, high and low temperature resistance, boiling resistance and opaque, impervious, and airtight, it has been widely used in food, health care products, pharmaceuticals and cosmetics and other packaging. In the past, the peeling strength of the aluminized composite film on the market was too low. In 1998, Beijing Gaomeng Chemical Co., Ltd. introduced the YH501S special adhesive for aluminized film, which greatly improved the strength of the aluminized composite film, but there was a plastic/plastic composite strength. Not as good as ordinary glue, high system activity, inconvenient operation, and resistance to water boiling at 100°C. In order to meet the needs of the market, on the basis of YH501S aluminum-plated film adhesive, we redesigned the molecular structure and developed a new multi-purpose, high-strength, water-resistant boiled aluminum composite film adhesive. 

First, test part

1. The main raw materials
Dimethyl terephthalate, industrial grade (Beijing Chemical Plant); isophthalic acid, industrial grade (Yanshan Petrochemical); adipic acid, industrial grade (Liaoning Chemical Plant); diethylene glycol, industrial grade (Jinshan Petrochemical) Ethylene glycol, industrial grade (Jinshan Petrochemical); diisocyanate, industrial grade (Bayer); ethyl acetate, industrial grade (Tianjin); catalyst (homemade); VM10 curing agent (homemade). 1# material is full-print BOPP film (20μ)/aluminum-coated CPP (VMCPP) film, which is provided by Qingdao factory; 2# material is full-print BOPP film (28μ)/aluminum-coated CPP (VMCPP) film, which is provided by Beijing manufacturer; The 3# material is a full-print BOPP film (35μ)/aluminum-coated CPP (VMCPP) film, which is provided by Hebei manufacturers;
2. Equipment and instruments
HIROSHIMA laminating machine (Japan), compound speed 50 ~ 70m/min; BLD-200s electronic peeling tester. 

3. Synthesis of Polyester Polyols
Measured dimethyl terephthalate, diethylene glycol and catalyst for transesterification reaction until the methanol to the theoretical amount, then add the measured isophthalic acid, adipic acid, ethylene glycol for esterification reaction After reaching the theoretical amount of water, the polycondensation was performed in a vacuum state. The acid value and hydroxyl value were sampled and analyzed at regular intervals. After passing, the polyester polyol was obtained with a molecular weight of about 2000. 

4. Synthesis of adhesive main agent
The measured amount of polyester polyol, diisocyanate and part of ethyl acetate were added into the reaction vessel, heated to a certain temperature and kept at the temperature for several hours. Samples were analyzed for viscosity, solid content, and hydroxyl value. After passing the test, the temperature was lowered and the auxiliary agent and acetate were added. The ester was stirred evenly to obtain the main adhesive agent. The trade name is YH501SL. 

5. Performance Test
1 Solvent residue test. According to YY0235-1996 drug packaging composite film (General) 5.5 solvent residue test. 
2 peel strength. According to GB2790-81, 180°C peel strength was measured. 

Second, the results and discussion

1. Adhesive design principle

The aluminum-plated composite film is a composite of aluminum-plated film and plastic film. The structure is schematically shown in Figure 1 (slightly). 
 According to the diagram, it can be seen that there are mainly several factors affecting the peeling strength of aluminum-coated composite films: 1 adhesive body strength and the nature of the adhesive; 2BOPP or PET film and adhesive interface strength; 3 adhesive and VM interface strength; 4VM and CPP or PET Film interface strength. 
With the ordinary two-component polyurethane adhesive bond aluminum composite film, composite film peel strength is very low, the peeling failure occurs mainly in the VM-CPP interface, complete transfer of aluminum film, 180 °C peel strength less than 0.3N. This shows that the adhesive body strength, BOPP or PET film and adhesive interface strength, adhesive and VM interface strength are higher than the VM and CPP interface strength. In fact, the interface strength between VM and CPP or PET film is much larger than 0.3N before composite. Therefore, the nature of the adhesive, that is, the nature of the adhesive, the composition, molecular structure, molecular weight distribution, and monomer residual amount of the adhesive have a great influence on the aluminum plating layer, thereby affecting the peel strength and the residual solvent amount. If the molecular structure of the adhesive is unreasonable, the ratio of soft and hard segments is unreasonable, the molecular weight distribution is too wide, and the residual monomer content is high, not only affects the strength of the adhesive, the interface between BOPP and adhesive, the strength of the adhesive and the VM interface, but also affects the VM and CPP interfaces. Strength and residual solvent.
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The two-component polyurethane adhesive is composed of a main agent composed of a hydroxyl group-OH and a curing agent composed of an isocyanate group-NCO. When used, the main agent and the curing agent are mixed in a certain proportion, and after the molecules are extended by the chemical reaction, a high molecular weight polymer is formed. As an adhesive, the composition, molecular structure, and molecular weight distribution of the polyurethane have an important influence on the bonding. Polyurethane can be considered as a block copolymer containing a soft segment and a hard segment. The soft segment is composed of oligomer segments such as polyester, polyether, and polyolefin, and is very compliant and assumes a random curl state due to its The glass transition temperature is lower than room temperature, and it is called rubber phase; the hard segment is composed of aromatic group, substituted urea group, urethane group, allophanate, biuret and other groups, and it is stretched into a rod shape at room temperature. It is easy to change its conformational conformation and the cohesive energy is very large. They associate with each other to form many microcells. The microspheres have a glass transition temperature much higher than room temperature, and they are glassy, ​​cold or microcrystalline at room temperature. Crystal, called the plastic phase. Due to the incompatibility of the thermodynamics of the two segments, microscopic phase separation occurs and phase or microphase regions form within the polymer matrix. The excellent properties of polyurethane can be solved by two-phase morphologies: The hard segment phase provides multi-functional physical cross-linking, ie, the formation of hydrogen bonds and cross-linking, plays a reinforcing role; the soft segment is reinforced by the hard segment region. Because the physical properties of aluminum, plastic film, etc. vary greatly, if the adhesive structure design is not reasonable, the stress concentration will occur during the curing process; in addition, the two-component polyurethane adhesive is formed by the chemical reaction after the main agent and the curing agent are mixed. Molecular polymer (curing) bonding, this process takes a long time, usually requires 48h at room temperature. During this period, residual monomers and small molecules in the adhesive will enter the interface between the VM layer and the CPP layer through the aluminum plating layer. The VM layer and CPP will be reduced due to the curing shrinkage of the adhesive and the stress caused by the aluminum and CPP wire expansion coefficients. The bond strength of the layer. 

2. Effect of material properties and aging conditions on peel strength

Three different thicknesses of the film were compounded and cured under different conditions. The peel strength is shown in Table 1 (slightly) (unit: N/15mm). o
It can be seen from the table that the YH501SL/VM10 adhesive has a higher initial tack; composite films of different thicknesses have slightly different peel strengths; the film thickness is greater and the peel strength is also slightly larger. After 24 hours aging, the peel strength was very high. After aging for 48 hours, the peel strength reached the maximum, and the aging strength continued to decrease, and the aluminum layer was partially transferred. It is recommended that the aging time at 50°C should not exceed 48 hours.
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3. Effect of coating amount
The effect of compound film composites is related to factors such as the amount of adhesive applied, the aging temperature and the time, and also related to factors such as humidity in the production environment, compound temperature, and film tension control. The factors affecting the aging temperature and time have been discussed above. The effect of the coating amount on the peel strength of full-print BOPP/VMCPP is shown in Table 2 (abbreviated). 
It can be seen from the table that when the coating weight is greater than 2.0 g/m2, the peel strength of YH501SL/VM10 composite full-print BOPP/VMCPP reaches and exceeds that of YH501S and imported glue D, but it is recommended that if the peel strength is maximized, it is recommended. The amount of cloth is not less than 3.0g/m2. 

4. Influence of the amount of curing agent
The results of the peel strength of YH501SL and VM10 with different mass ratios (with different -OH/NCO) are shown in Table 3 (abbreviated).

5. Boil resistance performance
YH501S and imported rubber D are not resistant to boiling at 100°C. The composite films of YH501SL compounded were aged at 50° C. for 48 hours and then boiled in boiling water at 100° C. The peel strength was measured immediately after boiling. The results are shown in Table 4 (omitted). 
According to the data in the table, YH501SL/VM10 composite film adhesive has good boiled performance, but different films have different boiling resistance performance. The smaller the thickness of the film used, the better the resistance to boiled water. 

6. Plastic/plastic composite YH501SL is used for compounding PET/PEP, PET/CPP and NNNY/PE composite films. After aging for 48 hours at 50°C, the peel strength is measured. The results are shown in Table 5 (omitted). 
From the table it can be seen that YH501SL is used for plastic/plastic composites and has a high peel strength. 

7. Performance comparison
The performance comparison of YH501S, imported rubber D and YH501SL is shown in Table 6 (omitted). 

As can be seen from the table, the YH501SL performs better than the YH501S and imported glue D. 
Through the adhesive composition, molecular structure, molecular weight distribution design and control, developed the excellent performance of aluminum alloy composite film adhesive YH501SL; the adhesive used in aluminum composite film has good initial tack, excellent peel strength and boiling resistance For plastic / plastic composite also has a higher peel strength.

Source: Chemical Fine Network