The use of alkenyl succinic anhydride (ASA) materials in internal paper sizing is well established, and the volume of these types of products used worldwide is very large. ASA materials are used to impart a degree of hydrophobicity to the paper fibers during production, and an overall resistance to liquid absorption to the finished paper product.
ASA is most commonly produced by the high temperature reaction of maleic anhydride (MA) and a long chain internal olefin. The olefin to MA mole ratio is usually greater than 1.0. The type of olefin used to produce the ASA can have a significant impact on product performance. The olefins employed in commercial ASA sizes typically contain a carbon chain length of 16-18.
It is also known that the degree of linearity of the olefin and the position of the double bond in the olefin can impact performance. For example, in general ‘isomerized’ olefins are used over alpha olefins. The isomerized olefins are generated by heating an alpha olefin in the presence of a suitable catalyst to move the double bond from the terminal position of the olefin to an internal position. Typically, the isomerization process creates a complex mixture of various olefin isomers. The main reason that isomerized olefins are used is the observed increase in ASA performance, and the creation of a liquid form of ASA (as opposed to a more crystalline or solid product).
ASA compounds prepared from maleic anhydride and various internal olefins are disclosed in U.S. Pat. No. 3,821,069. ASA compounds prepared from maleic anhydride and mixtures of olefins, including internal olefins, are disclosed in U.S. Pat. No. 6,348,132. The preparation of internal olefins by a metathesis reaction and a utility of the metathesized olefins in the preparation of ASA compounds are disclosed in U.S. Patent Application No. 2003/0224945 A1. A purported relationship between double bond position and carbon chain length in olefins used to prepare ASA compounds is discussed in Smith, D., “ASA Components: Their Synthesis and Relative Sizing Performance” in Proceedings of Scientific & Technical Advances in the Internal & Surface Sizing of Paper & Board, Florence, Italy, Pira International (1999).
Commercial ASA compounds are typically prepared from maleic anhydride and C16 internal olefins, C18 internal olefins and mixtures of C16 and C18 internal olefins. However, as discussed herein, these ASA compounds are often unsuitable for sizing paper products that require resistance to aggressive liquids. Accordingly, there is an ongoing need for improved sizing products for this application, particularly for sizing products that do not require co-administration of additional products such as alkyl ketene dimer (AKD) or rosin sizes.
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