The properties and operation of adhesives for food packaging

Adhesives are very important materials in food packaging materials and are one of the least noticeable materials. J. Orloff of the National Starch & Chemical Company once said the following paragraph: “Although there is only 1% of the cost of adhesives used in packaging materials, if there is no The remaining 99% will not play a good role in packaging.”

Operational and performance

Matters that need to be studied and discussed in the adhesive can be divided into two categories: "operability" and "performance". The former is about how easy and convenient it can be to use, whether it is possible to use other devices and more convenient operation methods; the latter refers to the problem of how the adhesive can reliably maintain the adhesive force and improve the adhesive ability. In the operational reliability of adhesives, the industry’s most concerned issue is the problem of hot melt, and its research direction can be divided into the security, carbonization, and degradation of the adhesive industry.

In general, for humans and machinery, the low melting point of Hot Melt is more suitable and safe. Almost all EVA (Ethy-lene-Vinylacetate) adhesives are cohesive at temperatures of about 350°F (about 175°C). The melting point of Cool-Lok is about 250°F (about 121°C).

The property of not easily carbonizing is one of the important characteristics of the adhesive. Depending on the needs of different uses, the investment in the use of adhesives is more effective than the investment in equipment and equipment. AStamp of Shure-Glue SysTem believes that even if a system device for applying adhesives is designed for the use of poor adhesives, the residue after the carbonization of the adhesive is still to be removed, the precision of the mechanical equipment is improved, and the display is improved. Additional investment is required for signal devices that exchange the exact time of the adhesive.

Select suitable adhesive

K.Burge, Technical Manager of the hot melt department at HB Fuller, points out that “low-melting adhesives need to be carefully selected to find suitable products. There are also general-purpose adhesives that are not suitable for the application in the market, generally for the temperature We do not recommend using them under rapidly changing environmental conditions. When the temperature of the container holding the adhesive can reach or exceed 140°F (60°C), we recommend the use of adhesive products with a melting point of 350°F."

Heat resistance is a major problem for adhesives, and there is also the issue of impact resistance. Mr. Orloff pointed out two major issues called “Stick” and “Stay Stuck” around adhesives. The so-called "Stick" refers to the problem of adhesion of the adhesive in the equipment device and after leaving the equipment device, and "Stay Stuck" refers to the problem of the extent to which the adhesive can maintain its adhesive ability during the shelf life of the product.

Adhesives for special substrates

For conventional packaging materials such as paperboards and corrugated boxes with wax-coated materials on the outside and bag materials protected with UV-curable coatings, the use of common adhesives can cause problems. This problem also occurs in hot fillable solid foods such as hot filling materials, liquid foods, and cream cheese. The volatile components in the perfume can be transferred through the packaging material, and the hot melt adhesive undergoes a "softening" phenomenon.

In this case, special adhesives are needed. For example, Robond and Robond adhesives based on propylene can be used on sealing tapes and pressure-sensitive labels. According to C.Urheim of Rohm & Haas Company, the greatest advantage of this kind of adhesive is that it will not change yellow under heat and exposure to sunlight. When it is necessary to use new adhesives or when it is necessary to select suitable special adhesives under extremely severe conditions, H.B. Fuller Company usually needs to obtain confirmation from the users of the products and provide accurate information on the conditions in their factories. According to the company, “It is possible to use standard EVA (ethylene-acetic acid)-based hot-melt adhesives that can be used under 90% of the conditions. However, adhesives of various types and properties are also available to meet different product requirements. Customers choose."

Fuller's heat-resistant hot melt adhesive is a polyamide adhesive. There are few problems in practical use, but there are some problems with commonly used adhesives. Fuller also offers another adhesive, Advantra, which is a unique polymer-based adhesive that has been successfully developed by Dow Chemi-cal.

The new adhesive, Aolvantra, is an adhesive commonly used for pallets and other forms of packaging. It is also generally suitable for the sealing of corrugated boxes. Its greatest advantage is bright color and excellent heat resistance, but also can maintain a constant degree of adhesion for a long time, good sealing performance.

Fuller’s Stamp boasts: “When hot melt adhesives are stored in containers, vats or cans, if they are common adhesives, black changes will occur five days later, which means that all carbonization problems have occurred. In actual use, Advantra can be postponed until twenty days later, and the advantages are obvious."

Author: Sheng Guohua

Reprinted from: China Food News