| In this paper, a new nano cellulose product——microfribillated cellulose(MFC) is introduced, its preparation and properties of it were also studies. Microfibrilliated cellulose (MFC) is moderately degraded and greatly expanded in surface area, and obtained by a homogenization process again and again on the basis of saving original degree of polymerization of natural cellulose, it is a new cellulose product of greatly expanding. What’s more, some common preparation methods of microfibrillated cellulose is introduced at the same time, such as mechanical method, chemical method, biological method, chenmical and mechanical method, etc.As a new type of nano-material, microfibrillated cellulose (MFC) has a very attractive business prospects and potential application, it can be used as coating agents, stabilizer, adhesives, thickeners, sizing agents, drug vehicles and so on, so microfibrilliated cellulose (MFC) has a very broad application prospects in food, pharmaceutical, coatings, cosmetics, electronic products, and others fields. Penetration point of this study was to use microfibrillated cellulose (MFC) as a coating agent for paper coating. In addition, because of its safety, environmental protection and pollution-free, while its fibers winding with paper fibers forming strong hydrogen bonding, MFC can be firmly attached to the surface of papers as a coating agent. So MFC could be used for coated paper in some food packaging materials to achieve the goal of green packaging materials.In this study, the bleached kraft hardwood pulp was used as the raw material. PFI mill first was used for prior pulp defibrination pretreatment; then the advantages and disadvantages of several pretreatment methods were summarized to select an optimal chemical oxidation pretreatment method——TEMPO/NaBr/NaClO oxidation system and finally oxidation pulps were treated with high pressure homogenizer to gain the final product microfibrillated cellulose (MFC). After this, the performances of MFC were characterized by scanning electron microscopy, infrared spectroscopy equipment and other instruments. And the influence of chemical oxidizing conditions, homogenizing conditions exerted on particle size, water retention value of MFC and related properties of MFC coated papers. Research results showed that5000rpm for grinding slurry handing by MFI mill; chemical oxidation condition adjusted to:TEMPO:NaBr=1:10, TEMPO for0.75%, NaBr for7.5%, NaClO for60%, NaOH for3%; homogenizing pressure adjusting to range of50～60MPa, homogenizing times for20, comprehensive performances of gained MFC could achieve more desirable target. With this optimal process, the particle size of MFC was about40nm, its surface charge density was about1689μeq/g, and its water retention value reached1700%; the intensity index and gas-barrier properties of MFC coated paper were also improved obviously:tensile index improving about18.4%, bursting index about401%, folding endurance about106.9%, and air permeability of the coated paper reducing about three orders of magnitude (from5.316um/Pa· s of original paper to0.0075umPa·s). In addition, the enhancement of performances of MFC and shellac compound used in paper coating was studied in this paper. Results showed that mixture of MFC and shellac on the surface of paper (MFC as bottom, and shellac as top layer)gained better moisture resistance than MFC single coating:air permeability was reduced to0.0002um/Pa· s of coated paper from5.95um/Pa·s of original paper(reducing about four orders of magnitude), WVT also reduced from1752g/m2·24h to74g/m2·24h(reducing about two orders of magnitude);and its intensity performances also gained increase of different degree. |
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