Development of High Strength Water-resistant Corrugated Paperboard Starch Adhesive (I)

Corrugated paperboard occupies an extremely important position in the entire packaging paper container material. This is because the corrugated paper box is not only flexible in shape, but also suitable for automatic high-speed production. The appearance of the paperboard display is good, and it can effectively protect the goods. The price is low, and the recycling is easy. Use, will not cause pollution to the environment, is environmentally friendly packaging materials. In China, almost all corrugated board production currently uses starch adhesives. The common problems are: starch adhesives tend to thin during recycling; unstable performance leads to easy delamination of storage, easy precipitation and can not be used continuously; The corrugated cardboard tends to be soft and soft, resulting in a decrease in the adhesive strength and side pressure strength of the cardboard. In response to the above problems, the author developed a high-strength, water-resistant corrugated cardboard starch adhesive. The starch adhesive was tried in Guangdong Zhongwei Wacho Paperboard Co., Ltd. The effect was very good, which brought considerable economic benefits to the company and had great social promotion value.

1 experiment
1.1 Experimental materials Starch (industrial grade); Multifunctional suspending agent (developed by Zhuzhou Institute of Technology); Borax (industrial grade); Hydroxymethylurea (Zhuzhou Institute of Technology); Sodium hydroxide (industrial grade); Water (drinking water) .

1.2 Proportioning of Adhesive: The ratio of starch to water is 1:5 in winter and 1:4.5 in summer. The balance is calculated based on the weight of starch. The mass percentages are: borax 2%, multifunctional suspension agent 5%, and hydroxide Sodium 2.8% to 3.0% and methylolurea 10%. 1.3 Preparation of High-strength Water-resistant Starch Adhesive Add 200ml of water, 30g of starch and sodium hydroxide solution (5.6g of NaOH+100mlH2O) in a 400ml beaker and mix well as a carrier glue; add 600ml of water, 170g of starch and 10g of suspension agent in a 1000ml beaker. The main starch liquid is stirred evenly; then the carrier rubber is slowly added into the main starch liquid and stirred to obtain a starch adhesive; 20 g of methylol urea is added into the starch adhesive, and the starch adhesive is evenly mixed to obtain a high-strength water-resistant starch adhesive.

2 Results and Discussion
2.1 Effect of multifunctional suspending agent on the performance of starch adhesive According to the preparation process of starch adhesive mentioned above, starch adhesives were prepared by adding different weights of multifunctional suspending agent to the main starch glue, and the viscosity of the starch adhesive was measured and made of the adhesive. Corrugated paperboards are used to test the adhesive strength and side pressure strength of corrugated board. The results are shown in Figures 1 and 2.

As can be seen from the figure, the viscosity of the starch adhesive and the adhesive strength of the corrugated cardboard increased with the increase of the amount of the multifunctional suspending agent, but when the amount of the suspending agent exceeded 10 g, the adhesive strength of the corrugated cardboard decreased. This is because the suspending agent consists of a variety of substances (including inorganics and organics) and has a variety of functional roles. The increased adhesive strength of corrugated cardboard is the result of the combined effect of various functional groups of the suspending agent: some of the components of the suspending agent can be coordinated with the polar groups of the starch, such as the nucleus of some of the constituent substances in the suspending agent. The free orbits of the outer electron layer can accept the lone electron pairs of the hydroxyl groups in the starch molecules to form complexes. This complex has two functions. One is to improve the viscosity of the adhesive, and the other is to increase the adhesive force and the drying speed of the adhesive. Stiffness; some of the composition of the suspension can also be linked with the polar groups of the paper fiber through the coordination bond, forming a strong chemical bond between the adherends, and the suspension agent and the main starch aggregate penetrate into the paper fiber at the same time. In the surface voids, a mechanical fitting force is generated after curing, and a large physical adhesion force can be generated, so that firm adhesion is obtained between the adherends, thereby improving the adhesive strength of the corrugated cardboard. However, with the increase of the suspending agent, the solid content of the starch adhesive increases, so that the viscosity of the adhesive exceeds the optimum range of use (30-40 s), the viscosity is large, the wettability to the adherend (paper) is poor, and the adhesive force of the corrugated cardboard is decreased. Therefore, when preparing the starch adhesive, the amount of the suspension agent is controlled to be 10 g (5% of the amount of starch), the viscosity of the prepared starch adhesive is suitable, and the adhesive strength of the corrugated cardboard made from the starch glue is large.