A new method for quickly cold-sealing corrugated cartons

Nowadays, there are many manufacturers of corrugated cartons in the country that generally use inexpensive corn starch adhesives. In the late 1970s, some domestic units started to study corn starch as a raw material for corrugated paperboard adhesives. However, there are widespread phenomena such as long reaction time, uncontrollable oxidation degree, instable quality, short storage period, and slow natural drying. , resulting in corn starch adhesives has not been widely applied. For this reason, we refer to the relevant literature. After more than 10 years of trial and error, we have obtained an ideal new method for fast-cooling corrugated cardboard cornstarch adhesives. This method is described below for reference by our colleagues.

(I) Raw materials and recipes

(B) Preparation of Adhesives

First, in a reactor equipped with an electric stirrer, put in a good amount of corn starch. Add a suitable amount of water and stir it to make it fully wet. Adjust the pH to be alkaline. Under constant stirring, add the catalyst and NaCLO solution, stir for 40 minutes, and measure the fluidity (by inserting a 4 mm diameter round bar into the middle of the deep liquid, and then provoke it, you can see that the glue droplet breaks 2-3 cm long) Add appropriate amount of water, add borax and reducing agent, add antifoaming agent and driers after mixing evenly to obtain finished product.

(III) Performance Indicators of Products

(d) Discussion

4.1 Selection and dosage of oxidants

The choice and amount of oxidant is the key to making the adhesive. For a certain starch, the degree of oxidation is different and the resulting product has different properties. Commonly used oxidants are H2O2, Na2O2, NaCLO, KMnO4 and so on. Due to the deep coloration of the binder made with KMnO4, the cost of H2O2 and Na2O2 is higher, the degree of oxidation is not easy to control, and the melon time is long. In the experiment, NaCLO was decided. If the amount of oxidizing agent is too large, the starch may be degraded too much, the viscosity is too large, the fluidity is poor, and the storage stability is poor. After repeated experiments and comparisons, it was found that at room temperature alkaline conditions, the amount of NaCLO is preferably 7-10%.

4.2 Effect of the catalyst

Although NaCLO naturally decomposes atomic state (O) at room temperature, it proceeds slowly at room temperature. If a catalyst is added to reduce the activation energy of the reaction, the decomposition of the oxidant is accelerated, and the oxidation reaction time can be shortened. NiSO4 is particularly effective in accelerating the decomposition of NaCLO, and it can increase the solubility of starch in water, improve the permeability and film forming ability, and improve the bonding ability, but the amount needs special attention, otherwise it will not be catalytic.

4.3 Effect of Adhesive

The amount of gelatinizer NaOH has a great influence on the adhesive fluidity and depth of gelatinization. The amount is too little, the gelatinization is not complete, the glue is turbid, the fluidity is poor, and it is difficult to store; when the amount is too large, the hydrogen bonds of a large number of starch molecules are destroyed, the adhesive force and the moisture resistance are reduced, and the glue is not easy to apply, or the glue appears. Paper products are highly corrosive. The appropriate amount to control in 10-13% is appropriate.

4.4 Effect of Complexing Agents

The complexing agent borax has the effect of increasing the cylinder, increasing the initial tack, and shortening the drying time, but the amount of borax has to be strictly controlled. More, it will produce a larger network structure with starch, enveloping the water molecules into a gel, making the adhesive's fluidity worse, making it difficult to sizing, making the adhesive layer brittle, etc.; less, gluing Not enough, poor adhesive power, easy to cause corrugated cardboard degumming after the machine.

4.5 Effect of terminating agent

The terminating agent can stop the continuous reaction of the oxidizing agent with the adhesive so that the adhesive can be stored for a longer period of time. The amount of terminator should be appropriate, too much, the cost will increase accordingly; too little, the adhesive will freeze and the storage period will be too short. Through experimental exploration, we have chosen sodium sulfate, the amount of 0.3-0.4%.

(5) Handling of product quality problems

Adhesive common quality problems are dealt with as follows:

(6) Conclusion

The corn starch adhesive produced by the method described above has not only good performance, simple process, low equipment investment, no “three wastes”, but also the paperboard, carton, and carton bonded with the product have a smooth surface and no yellowing. Moisture absorption, firm bonding, no degumming, no running, etc., and has high compressive strength, puncture strength, peel strength, and its main technical quality indicators meet or exceed the requirements of export packaging cartons. For a factory producing 6 tons of corn starch glue per day, the equipment investment is only 3,000 yuan, the plant area is 30m2, the operating workers are 1-2, the production cost is 320 yuan/ton-400 yuan/ton, the sales price is 550-650 yuan/ Tons, the monthly profit can reach 2.5-30 thousand yuan, while the price of silicate (water glass) in the south is 700-750 yuan / ton, and the coating amount is double that of corn starch adhesive, especially in case of Rainy weather, carton easy to yellow, moisture absorption, cartons become soft and even degumming quality problems, so the application of corn starch adhesive has a certain degree of economic and social benefits.