Use of 1,3-selective lipases for pitch control in pulp and paper processes

Abstract

Formulations for pitch control, and methods of making and using thereof, are described herein. The formulations contains one or more 1,3-selective lipases. 1,3-selective lipases catalyze the hydrolysis of the terminal ester groups in triglycerides leaving the internal ester group intact. The enzyme formulations can contain one or more additives, such as dispersants, metal ions, absorbents, adsorbents, cationic polymers, and combinations thereof. The enzyme formulation is typically applied as a solution to the pulp stock. The enzyme formulations can be applied at any of one or more various points during the pulping and paper manufacturing processes. The use of selective lipase(s) decreases the total concentration of fatty acids in the system, and catalyzes the formation of monoglycerides, which are more effective at dispersing fatty acids than glycerol, the product of non-selective lipases, thereby improving pulp and paper machine runnability and pulp and paper quality.

Description

FIELD OF THE INVENTION[0001]The present invention is generally in the field of treating pulp stocks with enzyme formulations in order to reduce pitch deposition, particularly enzyme formulations containing 1,3-selective lipases.BACKGROUND OF THE INVENTION[0002]Wood resin is composed of fatty acids and resin acids, triglycerides, steryl esters, and sterols. Wood resins, as well as other extractives such as lignans, pectins, and phenols, are the major components of pitch deposits. During pulping, such as mechanical pulping and / or thermomechanical pulping, the encapsulated resin is liberated from ray parenchyma cells and resin canals. Some of the dispersed resin droplets precipitate onto fiber surfaces impairing fiber to fiber bonding and thereby negatively affect the physical properties of the pulp. Dispersed resin which precipitates later in the pulping and papermaking processes can affect machine runnability and reduce paper quality which can result in increased manufacturing costs....

AI Technical Summary

Benefits of technology

[0013]The final formulations can be produced in the form of a liquid, gel, or solid. The enzymes can also be immobilized in a solid or gel substrate to increase the stability of the enzyme and / or to increase the number of cycles of use. In one embodiment, the enzyme formulation is applied as a solution to the pulp stock.

[0018]A further advantage of the use of 1,3-selective lipases is the production of monoglycerides. Monoglycerides are strong dispersants and emulsifiers for fatty acids and soaps, reducing the amount of fatty acid soap deposition on pulp and paper making machinery. Therefore, the use of selective lipase(s) not only decreases the total concentration of fatty acids in the system, but forms monoglycerides, which are more effective at dispersing fatty acids than glycerol, the product of non-selective lipases.

[0019]The Examples show that non-selective lipase products, such as EnzOx® PC, produce a much higher amount of pitch deposition than formulations containing 1,3-selective lipases. Extensive studies were conducted to analyze the chemical composition of the deposits produced in the lab tests and at various paper mills that had applied the non-selective enzyme treatments. It was found that the deposits contain mostly aluminum and calcium soaps of fatty acids, produced from reactions between aluminum and calcium ions and fatty acids generated from the hydrolysis of triglycerides by non-selective lipolytic enzymes. In comparison, the formulation containing 1,3-selective lipase(s) produced much less deposits, even lower than the control (i.e., without an enzyme treatment). The use of selective lipase(s) decreases the total concentration of fatty acids in the system due to the selective hydrolysis of triglycerides and converts triglycerides to monoglycerides which effectively disperses pitch, and thus prevents the deposition of fatty acids and their metal soaps.

Problems solved by technology

Some of the dispersed resin droplets precipitate onto fiber surfaces impairing fiber to fiber bonding and thereby negatively affect the physical properties of the pulp.

Dispersed resin which precipitates later in the pulping and papermaking processes can affect machine runnability and reduce paper quality which can result in increased manufacturing costs.

However, the use of such fixing agents has its limitations, particularly when used with recycled paper.

The above treatments, however, can result in increased concentrations of fatty acids, which may affect pulp and paper machine runnability and pulp and paper quality.

For example, large concentrations of fatty acids can react with aluminum, calcium, and other metal ions in the pulping process to form fatty acid soap deposits, known as “butter beans” or “sunflower seeds”, which can create deposition problems more serious than triglycerides and adversely affect pulp and paper machine runnability and pulp and paper quality.

Fatty soap deposits are known to create small holes in the finished paper in mills that have used non-selective lipase treatments.

When the fatty acids (generated from the enzymatic conversion of triglycerides) are not precipitated by alum or fixed by cationic coagulants, they agglomerate into small particles and create fatty acid spots (that are translucent or semi-translucent) on the finished paper, adversely affecting paper quality.

Images