Corrugated cardboard also often hit "immunity prevention needle"

Dry climate in autumn and winter season, corrugated cardboard loss of water often appear pressure line breakage, broken corrugated, molding difficulties and other undesirable phenomena; spring and summer rainy corrugated board will absorb excess water in the air, resulting in softening, compressive strength and other ills . With the change of seasons, corrugated board is also changing, because we ignore these changes, or did not cause our attention at all, let it attack, resulting in the spring and summer corrugated board soft, fall and winter season corrugated board fracture and other quality accidents Frequent occurrences. The lighter was complained by the customer and the return was severe.

According to the author's investigation, the probability of this phenomenon is more than 90%, and most of them are in the season when the season is replaced, and they occur every year. Therefore, the losses caused to the producers account for 30-50% of the total mass loss. According to common sense, this year has happened and preventive measures will be taken next year, but otherwise! The purpose of the author's writing this article is to remind his friends in the industry that they should often use the “immunity prevention needle” for corrugated cardboard to avoid similar recurring mistakes. The author will introduce the following factors in the corrugated board "outbreak":

First, the impact of the storage environment

The storage environment is mainly reflected in temperature and humidity. Corrugated board is sensitive to temperature and humidity. We all know that according to the GB/T6544-2008 standard, the delivery of corrugated board should be no more than 14%. In fact, the water content of corrugated board produced is mostly between 8-10%, because the water content of the used linerboard is At about 8%, the moisture content of corrugated paper is about 11%. When the preheater, corrugating machine, dryer, etc., heat many times to volatilize a lot of water, although a certain amount of water is added during the coating process, When the dryer is set, it consumes more than half. When the humidity of the storage environment is greater than the moisture content of the paperboard, the corrugated board absorbs the moisture in the air until it is in equilibrium with the moisture in the air, so that the corrugated board is softened; otherwise, the dry air absorbs the moisture of the corrugated board, so the corrugated board Cardboard is severely dehydrated and loses its toughness. It breaks, breaks, and warps in the later carton forming process. The effects of high temperature, high humidity, and high temperature drying (low temperature drying) are even greater.

Let's take a look at the following experiment:

The materials used are: face paper 150g homemade B grade kraft paper, liner paper 120g made in domestic B grade linerboard, corrugated paper and sandwich paper are 110g high strength tile, 1000x600 AB Tray five layer corrugated cardboard 3000 pieces, "GB/T2828-2003 count sampling inspection procedures" sampling, and then according to "GB/T450-2002 paper and cardboard samples taken" sampling, using "GB/T462-2003 paper and board moisture determination", "GB/T6545 -1998 corrugated board burst strength measurement method, "GB/T6546 corrugated board side pressure strength determination method" measured 12% moisture, burst resistance 1350kPa, side pressure strength of 7.20kN/m. Then after the test data is recorded, 3000 tablets are divided into three groups. Each group of 1000 tablets is placed in the normal temperature, low temperature, and high temperature laboratory stacking, sampling, sampling, and testing.

1, at room temperature 0-30 °C, from low to high storage for 6 hours, still according to "GB/T2828-2003 count sampling inspection procedures" sampling, using "GB/T450-2002 paper and cardboard samples taken" sampling, Using "GB/T462-2003 paper and paperboard moisture determination", "GB/T6545-1998 corrugated board rupture strength determination method", "GB/T6546 corrugated board side pressure strength determination method" determination. When the laboratory humidity is between 55-65%, the experimental corrugated board moisture is 11.65%, the bursting resistance is 1345kPa, the side pressure strength is 7.00kN/m; when the laboratory humidity is between 70-80%, the experimental corrugated board moisture 13.65%, burst strength 1325kPa, side pressure strength 6.5kN/m.

2, in the low temperature -10--1 °C, from low to high storage for 6 hours, still according to "GB/T2828-2003 count sampling inspection procedures" sampling, using "GB/T450-2002 paper and cardboard samples taken" Sampling, using "GB/T462-2003 paper and paperboard moisture determination", "GB/T6545-1998 corrugated board rupture strength determination method", "GB/T6546 corrugated board side pressure strength determination method" determination. When the laboratory humidity is between 55-65%, the experimental corrugated board moisture is 9.65%, the burst strength is 1140kPa, the side pressure strength is 6.00kN/m; when the laboratory humidity is between 70-80%, the experimental corrugated board moisture 11.0%, burst resistance 985kPa, side pressure strength 5.5kN/m.

3, in high temperature 31-45 °C, from low to high storage for 6 hours, still according to "GB/T2828-2003 count sampling inspection procedures" sampling, using "GB/T450-2002 paper and cardboard samples taken" sampling, Using "GB/T462-2003 paper and paperboard moisture determination", "GB/T6545-1998 corrugated board rupture strength determination method", "GB/T6546 corrugated board side pressure strength determination method" determination. When the laboratory humidity is between 55-65%, the experimental corrugated board moisture is 8.0%, the burst strength is 1135kPa, and the side pressure strength is 6.3kN/m; when the laboratory humidity is between 70-80%, the experimental corrugated board moisture is 18 %, burst resistance 960 kPa, side pressure strength 3.0 kN/m.

According to the experimental results, it is easy to see that the storage environment of corrugated cardboard is suitable for air humidity of 55-65%, and the temperature is 0-28°C. The temperature has little effect on the side pressure strength of the corrugated board, which has an impact on the bursting resistance. The rupture strength below −1° C. drops by about 25%. The effect of humidity on the corrugated paperboard is very obvious. With the increase of temperature and humidity, the side pressure strength of corrugated paperboard showed a significant downward trend, and it began to drop sharply at a temperature of 30°C and a humidity of 80%, and the decline rate was more than 50%.

Second, the influence factors of transport vehicles

When centralized board making and decentralized box making, most of the transportation tools for corrugated board are automobile transportation, and the automobile transportation is divided into open transportation (convertible van) and enclosed transportation (box truck). Open car transportation has high temperatures and high air humidity. When the air temperature is low and the air humidity is low, the cardboard is prone to dehydration, causing warpage and fracture, and cracking often occurs when entering the next process. Now most corrugated board processing companies have already adopted van trucking.

Third, the storage time of the factors

Corrugated board is the most suitable for entering the next process 4-6 hours after it goes offline. Because the board is completely set, the physical properties will not change during the process of printing and stamping. In other words, the quality of the corrugated board at this time is the most stable. After several hours of “internal adjustment”, the adhesive strength, bursting strength, side pressure strength, thickness, and other indicators are restored to the extreme, and the moisture is also balanced with the best storage environment. Now. Of course, the storage time depends on the materials used in the corrugated paperboard. If the paper fiber inside is short and the toughness is poor, it is necessary to enter the next process as soon as possible within the shortest time of the offline process. Otherwise, there will be quality problems such as pressure line breakage and folding fracture. . In the spring and autumn season where the climate is dry, we must pay particular attention to that if the storage time exceeds 6 hours or more, the cardboard will be severely dehydrated and cause quality accidents when it enters the molding process. In summer, the high-temperature and rainy cardboard absorbs the moisture in the air to achieve the moisture balance with the environment. The cardboard becomes soft and the compressive strength drops dramatically.

We conducted an experiment in September. The temperature was 23-28°C and the humidity was 60-65%. 1500 pieces of corrugated cardboard were sampled. The material, type, specifications, technology, equipment, and time of the next line were the same. The sample was measured for moisture. 12%, burst strength 1386kPa, side pressure strength 6.6kN/m. They were divided into 3 groups according to 500 tablets and stored for 6 hours, 24 hours and 240 hours respectively. The test data obtained from the experiment are as follows:

6 hours result: moisture 11.5%; burst strength 1450 kPa; side pressure strength 6.8kN/m

Results for 24 hours: moisture 10.5%; burst strength 1290 kPa; side pressure strength 6.3 kN/m

240 hours of results: moisture 7.5%; burst strength 950 kPa; side pressure strength 5.1kN/m

Corrugated board storage time of 6 hours burst strength and side pressure strength not only did not reduce, but increased. With the prolongation of the storage time, the moisture, bursting strength, and side pressure strength all decreased to varying degrees, but the most significant drop was the burst strength. This shows that the storage time is closely related to the quality of corrugated board.