Effects of aqueous suspension properties on the atomization and dispersibility of spray dried cellulose nanocrystallite granules

加拿大是全球主要的森林产品国家，在下一代高附加值木材衍生产品：纤维素纳米晶(CNC)和纤维素纳米纤维(CNF)的商业化方面处于领先地位。为了加快木基纳米纤维的商业化进程，并保持全球领先地位，加拿大森工行业领先的研究机构FP Innovation确定了需要解决的六(6)个主要挑战。其中之一是纤维素纳米晶在水介质中的分散，这在本提案中得到了解决。CnC通常首先通过碾磨，然后通过硫酸盐纸浆纤维素的酸解来生产。采用浓硫酸(65%)去除无定形区域，释放出均匀的、无缺陷的纤维素纳米晶(Cnc)。生产的浆料首先经过离心、过滤，然后再进行喷雾干燥。因此，纳米颗粒以自由流动的干燥颗粒状物质的形式被回收。在喷雾干燥过程中，水的蒸发往往会导致纳米颗粒的不可逆聚集。粉末状的CNC必须重新分散在水溶液中，才能准确地应用到最终产品中。因此，需要对干燥过程中的团聚进行适当的控制，以保持再分散过程后单个纳米颗粒的尺寸和表面性质。本文讨论了在喷雾干燥操作中，电解质、表面活性剂和聚合物对干燥的纳米颗粒的液滴形成和形貌以及它们在水介质中的分散性的影响。本研究的目的是了解过滤后的CNC悬浮液的性质对喷雾干燥和干燥的CNC颗粒的形态有何影响。这反过来又有助于形成聚集体和纳米颗粒在水中的再分散。在不同的CNC悬浮液浓度、电解液(NaC L)、表面活性剂(含12-14个碳链的非离子线性二次醇)和脱絮剂(聚丙烯酸铵)存在下进行喷雾干燥，并在不同的喷雾干燥器操作条件下运行。

Canada is a major global forest products country and leads the commercialization of next generation high-value added wood derived products:cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF). To accelerate the commercialization process of wood based nanofibers and maintain global leadership, Canadian forest industries leading research organization, FPInnovations identified six (6) main challenges to be solved. One of them is the dispersion of cellulose nanocrystals in aqueous media which is addressed in this proposal. CNC is typically produced first by milling and then acid hydrolyzing of kraft pulp cellulose. Employing concentrated (65%) sulfuric acid removes the amorphous regions and releases homogenous and defect free cellulose nanocrystals (CNC). The produced slurry is first centrifuged, filtrated and then CNC dispersion slurry is spray dried. Thus, CNC particles are recovered in the form of free flowing dry granular material. In spray drying, evaporation of water often causes an irreversible aggregation of CNC particles. CNC in powder state must be redispersed in aqueous solutions for accurate end product applications. Hence, proper control of aggregation during drying is needed to preserve individual particles sizes and surface properties of CNC particles after the redispersion processes.This proposal deals with how electrolytes, surfactants and polymers in aqueous CNC suspensions influence the droplet formation and the morphology of dried CNC granules during the spray drier operations and their dispersibility in aqueous media. The objective of this research is to understand how CNC suspension properties after filtration influences the spray drying and morphologies of dried CNC granules. This in turn contributes to the formation of aggregates and redispersion of CNC granules in water. Spray drying of CNC suspensions will be carried out at various CNC suspension concentrations, electrolyte (NaCl), surfactant (non-ionic linear secondary alcohol with 12-14 carbon chain), and deflocculant (ammonium polyacrylate) presence and operating at different spray dryer operating conditions.