First, the basic principle of flexible packaging adhesive

There are many kinds of composite adhesives and their shapes are different. It is necessary to adopt suitable methods for sizing according to actual requirements. There are many methods in post-printing compounding, and now the roll coating method is mainly introduced: That is, a rubber roller or a metal anilox roller performs the sizing with a rolling method. The thickness of the adhesive layer is controlled by adjusting the gap or pressure of the rubber roller or metal anilox roller. The method is glued, the glue layer is even, and the production efficiency is high. A series of questions surrounding the definition of the compound glue and the formula design are roughly explained as follows: Glue Bond Definition: Bonding refers to the use of solid materials of the same species or different species, which are linked together by a substance to form an interface. One of the substances used is an adhesive, also called an adhesive or a compound adhesive. The formation of composite bond: When the adherends I and III are bonded, the bond strength is mainly determined by the adhesive force between the adhesive (adhesive) and the adherend and the cohesive force of the adhesive, and the cohesive force is the adhesive. The force between the molecules themselves, however, the size of the cohesive force (composite peel force) cannot be regarded as merely the sum of cohesion and adhesion.

First, the bond strength depends on the smallest of the factors. When the body of I and III is destroyed, it is called the cohesive destruction of the adherend. When the interface between the I and III phases of the II is destroyed, it is called interface failure and is usually called cementation. When the body breaks down, the cohesion called adhesive breaks down. We know that when the two solid surfaces are close to 0.411m or less, that is, when the effective distance between the intermolecular forces is reached, there is no sticky adhesive, and the two can also achieve bonding. In order to make the surface of the adherend uneven to achieve a full real touch, adhesive must be used to achieve. Bonding Mechanism: The bonding process is a complex physicochemical process. The generation of adhesive force depends not only on the structure and properties of the adhesive (composite) and the surface of the adherend—hydrogen bonding force, solubility, surface tension, but also closely related to the operating conditions of the bonding (composite) process.

Indeed, for example, the bonding and wetting, the composition of the adhesion force, the coupling theory (which is divided into adsorption theory, diffusion theory, electrostatic theory, chemical bonding theory, mechanical bonding theory), are the basic theory of compound (adhesive) glue. Secondly, the factors affecting the bond strength are: (1) the impact of the properties of the composite glue: (2) the influence of the solvent: (3) the influence of the temperature and length of the drying tunnel; (4) the influence of the surface properties of the composite (its criticality The surface tension value can generally reflect the size of the solid surface free energy, such as PE3lXlO N, solubility of 8, PVC3.9xiO N, solubility of 9.6); (5) the influence of other factors (such as the plasticization in the composite rubber system The dosage of the agent, the amount of filler, the surface treatment of the base film, the size of the glue, the amount of foam in the compound, the degree of release of the solvent, the length of the curing time, the speed of the cooling coil, etc.). Soft-pack composite adhesives are often divided into two categories: dry and wet methods: one is aluminum foil adhesive, the other is aluminum-plastic composite adhesive, third is water-based paper-plastic composite adhesive, and fourth is alcohol-soluble polyvinyl chloride adhesive to further illustrate the above-mentioned adhesives (composite Glue), now its use, formula, component adjustment, preparation methods are briefly introduced.

Second, compound rubber formula design

2.1.1 Formula design of environment-friendly aluminum foil compound adhesive

(VAC) Vinyl Acetate 23.57%
(BA) Butyl Acrylate 4.71%
(AA) Acrylic 0.34%
(PVA1799) Polyvinyl alcohol 4.71%
(APS) 0.12% ammonium persulfate
(Emulsifier OP) Polyethylene Glycol Octyl Phenyl Ether 0.79%
(SDS) Sodium dodecyl sulfate 0.4%
(DBP) o-Benzo Z-dicarboxylate 2.36%
(TDP) Tributyl phosphate 0.16%
Water 62.84%

2.1.2 Component Adjustment

A. Monomer composition: In the composition of this product, acrylic acid and butyl ester account for about 15 总量 of the total amount of comonomers, which makes the adhesion of the emulsion and the flexibility of the film improve. The introduction of acrylic acid can improve the stability of the emulsion polymerization, improve the adhesion of the emulsion and the adhesion of the metal (composite), but if the amount is too large, the water resistance of the film decreases, and at the same time, the decomposition rate of the initiator is faster. , hindering the normalization of the copolymerization reaction, so the amount of acrylic acid added is generally controlled at about 1.5% of the total amount of monomers.

B. Influence of polyvinyl alcohol: As the protective colloid of the copolymer emulsion, the degree of polymerization, solubility and the amount of the material have an influence on the viscosity of the emulsion. The use of 17-99 polyvinyl alcohol increases the viscosity of the emulsion as its amount increases. It usually occupies a total amount of 5.5 茗 and the viscosity is more suitable.

C. Polyethylene glycol octyl phenyl ether is a type of emulsifier. The amount of poly(ethylene glycol) octyl phenyl ether has a great influence on the particle size and stability of the copolymer emulsion. Therefore, sodium lauryl sulfate is often used as a complex emulsifier. The ratio of the former to the latter is generally 1:2. However, as the dosage increases, the stability of the emulsion will increase, but the fluidity and bond strength of the adhesive will decrease. After a lot of experiments and use, it is proved that when the amount of the two is about 5 总量 of the total amount of the copolymer, there is no agglomeration and the stability is good.

D. The amount of ammonium persulfate has a certain influence on the conversion rate of the monomer and the viscosity of the emulsion. During the production, the amount of polymerization is incomplete, the solid content does not meet the formula design requirements, the viscosity of the composite rubber is low, and the odor Large, on the contrary, it will cause explosions, and the polymerization reaction will be difficult to control.

2.1.3 Production Method

Distilled water, polyvinyl alcohol, and tributyl phosphate were added to a reaction cup equipped with an adjusting stirrer, a thermometer, and a reflux condenser. After soaking for 3 minutes, the temperature was gradually raised to about 93° C. to fully dissolve the polyvinyl alcohol and reduce the temperature to 60° C. Add PEG octyl phenyl ether and persulfate compound to stir and disperse for about 13 min, then add the total amount of monomer 13 茗 mixed monomer to emulsify for 15 min, add sodium lauryl sulfate and stir for 15 min. A total of one-third to one-half of the total sodium phosphate solution of sodium superphosphate. The reaction was carried out at 65°C for about 1 h until the material was slightly blue. After no significant reflux, the temperature was raised to 73°C. The remaining mixed monomers were added dropwise, and additional ammonium persulfate solution was added periodically. When the monomer mixture is dropped, it is left to stand for 1 Omin and the remaining ammonium persulfate solution is added. Continue the heat preservation reaction. When there is no obvious reflux, raise the internal temperature to 83°C for 1 hour. Add dibutyl phthalate, cool down to 60°C, and adjust the pH to 5 with saturated sodium bicarbonate to cool the material.

Description: (1) The adhesive is firmly bonded, aluminum foil and liner cannot be torn open, and it can meet the composite use requirements of high-speed aluminum foil machine above 15Om/min.

(2) According to the above production process, the yield is about 90%.

2.2.1 Formulation Design Example of Aluminum Plastic Composite Adhesive

1, vinyl chloride vinyl acetate 4.6%
2,401 resin 18.3%
3, C9 tree refers to 7.5%
4, coupling agent TM-P 0.6%
5, mixed solvent 79.0%
Total 100%

2.2.2 Component Adjustment

A. The effect of the amount of aluminum-plastic composite adhesive on the bonding performance: The formula is mainly composed of linear 2 resin, 1 is the auxiliary resin, and is dissolved and mixed with a suitable 5 . With the increase of the amount of 2, the adhesive force will also increase, but when it reaches a certain amount, the adhesive force will decrease, the film brightness will decrease, and the viscosity will also increase and affect the sizing (composite ). The addition of 3 is to increase the holding power. If the amount is too large, the viscosity will decrease, the cohesion will increase, and the surface tension will become smaller. When sizing coating, wrinkles are easily generated, resulting in compound unevenness (clothing).

Effect of B, 4 dosage on heat seal strength: The most ideal coating film state is to form molecular layer on the surface of ink and aluminum foil to ensure that the ink molecule can be connected with 4 and aluminum foil. Therefore, the amount of 4 is used for bonding. Intensity has an effect. Usually adding a coupling agent can significantly improve the performance of inks and adhesives on aluminum foils and plastic films, and increase their bonding strength. On the other hand, when using a coupling agent, the appropriate coupling agent should be selected in consideration of various ink colors.

C. The higher the ink film thickness of the ink, the lower the bond strength. This is because the ink and the composite adhesive have poor permeability to each other, so that the ink and the composite adhesive show different wet affinity to the aluminum foil, resulting in low composite adhesive strength.

2.3.1 Water-based paper plastic compound formula design:

1, liquid acrylic resin 70.0%
2. Vinyl acetate 20.0%
3, waterborne rosin emulsion 4.5%
4, styrene emulsion 4.3%
5, coupling agent 1.0%
6, XH-24 silicone oil 0.2%

2.3.2 Component Adjustments:

A. The influence of pre-emulsification on the mixing reaction: This formulation uses commercially-available liquid acrylic resin for relatively stable reaction in emulsion polymerization, but the time for direct emulsification and aggregation of water, each emulsion and acrylic resin is significantly shortened.

B. The effect of tackifier resin on the properties of the composite rubber:

Styrene-based resins are most often used. In terms of the adhesive strength around the sticky and sticky, especially the peel strength, most of the self-made rosin is used as a tackifier for the composite adhesive system, and the cost is low.

C. According to the adhesive application, it is recommended that: (1) 30% acrylic resin; (2) 40% styrene emulsion; (3) 30% rosin emulsion.