Analysis of common quality problems in airlaid paper products

Update:08 Aug 2020

Airlaid paper thickness and bulkiness index. Airlaid pa […]

Airlaid paper thickness and bulkiness index. Airlaid paper is also called dust-free paper sometimes.

These two indexes are basically the same. Under the same quantitative conditions, the greater the thickness, the greater the volume. In the field of sanitary materials, such as the manufacture of panty pads and sanitary napkins. , The thickness requirement is usually put forward, because the greater the thickness of the same basis weight, the unit cost of the product will be greatly reduced.

For glued dust-free paper, the main influencing factors are:
(1) Fluff pulp factor: The longer the fluff pulp fiber, the higher the roughness, and the better the bulkiness of the paper; Kraft pulp has better bulkiness than Kraft pulp. Softwood pulp has better bulkiness than hardwood pulp. The bulkiness of untreated pulp is better than that of treated pulp;
(2) The higher the temperature and pressure of the press and embossing machine, the tighter the paper will be, the larger the volume and the smaller the thickness;
(3) It is related to the retention rate of fine fibers in the forming part: In the production process, 80 mesh carbon mesh is generally used, and fine fibers below 1.0 mm account for 5% of the total u5DE6. If the degree of vacuum in the forming part is controlled to reduce the loss of fine fibers or to recycle them, the bulkiness of the paper can be improved;    

(4) Related to the texture of the transfer net (embossed net), the bulkiness of the paper produced by the plain net is better than other large nets;
(5) The bulkiness of high basis weight paper is better than that of low basis weight paper. On the one hand, it is because of the high retention rate of fine fibers when forming high basis weight paper. On the other hand, the unit amount of glue used for high basis weight paper Much lower. . For heat-sealed dust-free paper, in addition to the above factors, the main factor affecting the volume and thickness index is the oven temperature. Within the process allowable range, the higher the temperature, the better the hot-melt bonding conditions, and the higher the volume and thickness. Of course, some users may require the thickness when ordering, so it must be adjusted according to the production process.
Softness index
The softness mainly depends on two factors: the hardness of the paper and the friction of the paper surface. 

For glued clean paper, the main factors affecting the softness index are:

(1) Fluff pulp factor: The greater the roughness of the fluff pulp fibers, the greater the rigidity, the greater the surface friction of the paper, and the worse the softness of the paper; through the comparison of different fluff pulps, the overall situation is sulfite pulp Its softness is better than that of kraft pulp. The softness of treated fluff pulp (including semi-treated and fully treated) is better than untreated fluff pulp;

(2) It is also related to the retention rate of fine fibers during the forming process. When more fine fibers are retained, the paper will become larger and feel softer;
(3) When the heat pressure is high, the paper is tight and the softness is poor;
(4) Adhesive factors: First of all, the type of adhesive must be special latex for dust-free paper, which has a good feel. After some domestic VAF latex is dried, the surface of the paper becomes hard and the softness is very poor. The second is the amount of adhesive. Under the condition of ensuring the strength, the less the amount of latex, the better, which not only improves the flexibility, but also reduces the cost. The third is the distribution of the adhesive in the paper. For example, the adhesive is evenly distributed on the inner and outer layers of the paper when spraying glue, with good flexibility; when the adhesive is more distributed on the two surfaces, the surface of the paper will change. It is rough and hard, and the softness will drop sharply.
For heat-sealed dust-free paper, because it contains a small amount of latex and the hot-melt fiber itself is quite soft and elastic, the entire paper structure is loose, and its softness is generally better than that of glued dust-free paper. The main influencing factor is the influence of hot melt fiber, except fluff pulp. First of all, the softness of the hot melt fiber itself;  . The second is the thermal melting temperature. In the process range, when the oven temperature is low and the hot-melt bonding points are appropriately small, the upper part of the outer layer of the hot-melt fiber is melted, the inner layer structure is intact, its own performance can still be maintained, and the softness is good. When the oven temperature is higher, especially when the temperature exceeds the melting point of the outer layer, as the melting point and bonding point of the outer layer increase, the paper gradually thickens, the hardness increases, and the softness decreases.

In addition, whether it is glued paper or heat-sealed paper, after proper calendering and humidification in the finishing process of roll paper, the softness will be improved to varying degrees.

Generally speaking, it includes two aspects: lateral water absorption speed and saturated water absorption capacity. The lateral water absorption speed refers to the height of the liquid spreading along the paper in a certain period of time. Saturated water absorption capacity refers to the multiple of liquid that can be absorbed per unit mass of paper. As a highly absorbent product, dust-free paper is widely used in the field of hygienic absorbent materials, such as the absorbent core layer of sanitary napkins, watch pads, sanitary napkins, and baby diapers. Therefore, the liquid absorption capacity of the product has attracted great attention. As for the saturated water absorption capacity, the current adhesive paper can reach 7-9 times, and the heat-sealing paper can reach 15 times, without SAP.

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