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How do surface sizing agents work?
Source: | Author:kesikeen | Published time: 720 days ago | 364 Views | Share:
The paper sheet is coated with a layer of starch on the surface of the paper sheet through surface sizing. After drying, a continuous adhesive film is formed on the surface of the paper sheet, but because starch is hydrophilic.

The paper sheet is coated with a layer of starch on the surface of the paper sheet through surface sizing. After drying, a continuous adhesive film is formed on the surface of the paper sheet, but because starch is hydrophilic. Therefore, it does not reduce the water absorption of the paper like other sizing agents, but because the amount of sizing is small, it does not have much effect on the water absorption value.

How starch works

The paper sheet is coated with a layer of starch on the surface of the paper sheet through surface sizing. After drying, a continuous adhesive film is formed on the surface of the paper sheet, but because starch is hydrophilic. Therefore, it does not reduce the water absorption of the paper like other sizing agents, but because the amount of sizing is small, it does not have much effect on the water absorption value.

The main function of starch surface sizing of paper sheets is to improve the bonding strength between the fibers of the paper sheets, so as to achieve the purpose of improving the surface strength of the paper sheets; at the same time, it also improves the stiffness of the paper sheets. In particular, the current product market is sluggish. In order to reduce production costs, many papermaking enterprises want to achieve their goals by increasing the ash content of finished paper. However, the increase in ash content will inevitably lead to hair loss and powder loss during the printing process. And the stiffness of the paper will inevitably decline. Therefore, increasing the surface sizing amount of the paper sheet can effectively improve the surface strength and stiffness of the paper. Improve printing performance and use effect.

How AKD works

The AKD sizing is changed from the pulp to the surface (the AKD synergist that is compatible with it needs to be used when AKD surface sizing, otherwise it will be hydrolyzed seriously and the aging will be slow) or partially changed to the surface, which not only improves the degree of AKD curing, but also eliminates AKD hydrolysis. Contamination of the wet end system by product.

AKD surface sizing mainly involves covalent bonding between AKD and cellulose to fix it on the fiber. AKD has a reactive group, which can directly react with the hydroxyl group of cellulose to form a covalent bond and form a stable film on the surface of the fiber. Change the fiber from hydrophilic to hydrophobic.

But the effect of AKD and fiber is slow. A certain drying temperature and curing time are required, so when using AKD surface sizing, an additive that accelerates AKD curing must be used to achieve AKD surface sizing.

Under normal circumstances, AKD synergists mainly include polyamide polyamine epichlorohydrin resin (PAE), polyacrylamide (PAM), or the simultaneous use of PAE and PAM. For example, when PAE is used as a synergist for AKD, when the paper is heated and dried, the epoxy group in the PAE molecule will open the ring to cause the secondary amino group to be alkylated. At this time, the PAE resin becomes a nucleophile, which attacks the lactone ring of AKD, prompts it to open, and is fixed on the macromolecular chain of the PAE resin. PAE resin has strong bridging ability and is irreversibly fixed on the fiber surface, so that AKD is irreversibly bound to the fiber surface through the intermediate reaction with PAE resin.

The working principle of styrene-acrylic copolymer emulsion

The surface sizing agent of styrene-acrylic acid copolymer emulsion is used for surface sizing together with surface sizing starch, which is to coat a layer of sizing agent on the surface of paper. After drying, a continuous adhesive film is formed on the surface of the paper sheet to prevent the penetration of liquid and obtain better surface properties. As well as improving the physical properties of the paper sheet, at the same time, the carboxylic acid group in the surface sizing solution dissociates and interacts with the anionic components in the paper layer to penetrate into the fiber gap of the paper sheet, thereby improving the bonding strength between the paper fibers. The purpose of improving the surface strength of the paper sheet.