Студопедия
Случайная страница | ТОМ-1 | ТОМ-2 | ТОМ-3
АвтомобилиАстрономияБиологияГеографияДом и садДругие языкиДругоеИнформатика
ИсторияКультураЛитератураЛогикаМатематикаМедицинаМеталлургияМеханика
ОбразованиеОхрана трудаПедагогикаПолитикаПравоПсихологияРелигияРиторика
СоциологияСпортСтроительствоТехнологияТуризмФизикаФилософияФинансы
ХимияЧерчениеЭкологияЭкономикаЭлектроника

As resins or inorganic compounds can adversely affect the filterability of viscose,

Читайте также:
  1. As minor streams are neglected, such as dust, sulfur dioxide, reduced sulfur compounds
  2. Extractives, resins
  3. Formation of Organochlorine Compounds
  4. Increase equally affects purification, as would a decrease in NaOH concentration
  5. Inorganic Side Reactions during Chlorine Dioxide Bleaching of Wood Pulps
  6. Steam side of the heating element and adversely affect heat transfer by reducing

And some residual noncellulosic carbohydrates can promote yellowing of cellulose

Acetate spinning dope. Since the (almost) complete removal of noncellulosic impurities

Would be very expensive and,moreover environmentally harmful (high yield loss,

High chemical charges, additional equipment, etc.), the main emphasis is placed on

Adjusting the refining processes on the demands of each cellulose product.

The suitability of dissolving pulps can be adequately determined only by simulating

The conversion processes to the final products (e.g., to regenerated fibers or

Cellulose derivatives) on a small scale. Sometimes, even pilot plant or mill-scale

Tests are needed to approve the dissolving pulp for further processing. This is particularly

True in the case of new applications such as the Lyocell process. Since the

Early days of cellulose research, much effort has been undertaken to develop analytical

Methods that provide rapid and reliable assessment of the quality of dissolving

pulp. There are many established methods for evaluating pulp quality [1–3],

but they are insufficient to provide a full picture of the dissolving pulps′ properties.

The relationships between structure, chemical composition and behavior

With regard to topochemical reactions are too complex. The difficulty of reliable

Cellulose characterization has been expressed appropriately by L.E. Wise, an

Important pioneer of cellulose chemistry and technology, by the statement that

“Cellulose is a system, not a pure individual” [1].

Dissolving Grade Pulp

The processability of a dissolving pulp is often characterized as its reactivity

Towards derivatizing chemicals or solvents. Reactivity is related to the accessibility

Of chemicals to the cellulose, which virtually means the relative ease by which the

Hydroxyl groups can be reached by the reactants. The structure and morphology

Of cellulose is responsible for the homogeneity of the conversion process and the

Final product quality. A reliable analysis of the property profile of dissolving pulps

Involves the extensive characterization of the cellulose structure at three different

levels: (a) the molecular level of the single macromolecule; (b) the supramolecular

Level of aggregation of macromolecules to highly ordered structural entities; and

(c) the morphological level comprising the architecture of well-organized fibrillar

elements [4]. Moreover, the pore system providing access to the molecular structure


Дата добавления: 2015-10-21; просмотров: 147 | Нарушение авторских прав


Читайте в этой же книге: To applications such as newsprint, toilet tissues, and paperboard as they tend to | Be transferred to paper-grade pulps. The papermaking properties of pulp are | Acid side chains. The glycosidic bond between uronic acid and the xylan backbone | High LODP, the high modulus in the stress-strain curve, the excellent swelling | Of chemical paper pulps, including TCF and ECF variants for both softwood | Be expected when high dosages of, for example, ozone, or other bleaching chemicals | Is rather unstable in acid sulfite pulping, and this results in a low (hemicellulose) | Groups, depending on the amount and their distribution along the polysaccharide | Beech Sulfite Beech Kraft Eucalyptus Kraft | From rather high molecular-weight cellulose and very low molecular-weight hemicellulose |
<== предыдущая страница | следующая страница ==>
Fiber length below 0.2 mm, indicating the presence of large amounts of fines derived| Is an important characteristic of dissolving pulps. Finally, the qualitative and

mybiblioteka.su - 2015-2024 год. (0.005 сек.)