造纸专业英语6

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,*,Reading material: wet-chemistry theory,Wet strength of paper is often referred to as relative wet-strength, the ratio between wet strength and dry strength. Normally, 10 to 15% is considered as a wet-strength paper.,In contrast to dry strength, the origins in the,hydrogen bonds,present in natural cellulose, wet strength requires water stable (,covalent,),bonds,. Naturally, cellulose contains few covalent bonds, and therefore wet-strength chemicals are necessary.,hydrogen bond,氢键,covalent bond,共价键,-,valent,.,价的,co-,共同，一起,Reading material: wet-chemistry theory,Polymer resins are often used to increase wet strength. Two different wet-strength,mechanism,s exist, the protection mechanism and the reinforcement mechanism. The protection mechanism involves,diffusion,of the wet-strength polymer to the,fibre,surface where it,cross-link,s through and around the,fibres,. Such cross-linked networks prevent,fibre,swelling and helps to preserve covalent bonds when the paper is exposed to water. In contrast, the reinforcement mechanism means that new bonds between the wet-strength polymer and the,fibres,are formed.,mechanism,机理,diffusion,扩散,cross-link,交联,Reading material: wet-chemistry theory,Fiber,charge,is an important factor that influences the papermaking process as well as the paper properties. Cellulose,fibres,contain various,ionisable,group,s:,carboxyl,-,sulfonic,acid-,phenolic,- and,hydroxyl,groups and are therefore negatively charged at all pH values.,charge n.,电荷,v.,使充电,ionisable,可离子化的,group,基团,carboxyl,羧基,sulfonic,acid,磺酸,phenolic,酚的,hydroxyl,羟基,Reading material: wet-chemistry theory,Under normal papermaking conditions, the negative,fibre,charge is due to carboxyl and,sulfonic,acid groups. These charged groups are located either on the fiber surfaces or inside the,cell wall,; hence they are referred to as surface- and,bulk,charges,respectively,. Surface charges are important for,fibre,- and paper strength.,cell wall,细胞壁,bulk,大小,体积,大批,respective,分别的,Reading material: wet-chemistry theory,Adsorption,of polymers is used in many applications. The driving force is a strong polymer-surface interaction. If the,solvent,is poor, then adsorption is more favourable than the polymer-solvent interaction. A condition for most cationic additives is the ability to adsorb to the,fibre,surface. That is why polymer additives used in papermaking often are cationic.,adsorption n.,吸附,adsorbent,吸附剂,absorbent,吸收剂,Solvent n.,溶剂,poor solvent,不良溶剂,Reading material: wet-chemistry theory,The,density,and,distribution,of charges are also very important. Other factors that affect the adsorption are,molecular weight,of the polymer and the presence of,fibre,segment,s called “,fine,s”. Fines have large,specific area,and their capacity to adsorb polymers is therefore higher than for whole,fibres,.,density n.,密度,distribution n.,分布,molecular weight,分子量,segment,片断,fine,细小纤维,specific area,比表面积,specific,比的,Reading material: wet-chemistry theory,Polymer adsorption is often,reversible,and there is a probability that they will,detach,from the surface. This probability is generally low since all segments have to detach at the same time. However, changes in pH,ionic strength,etc. might cause,desorption,of polymers from the,fibre,surface.,reversible adj.,可逆的,ionic strength,离子强度,desorption,n.,解吸,Reading material: wet-chemistry theory,The natural,biopolymer,：,A natural biopolymer is generally,characterize,d in terms of its:,quality,(,heavy metal/protein content,pyrogenicity, clarity,etc),intrinsic properties,(molecular weight,viscosity, degree of,deacetylation, stability) and physical form (size etc).,biopolymer,生物聚合物,characterize,表现,特色,in term of,依照,heavy metal,重金属,protein,蛋白质,content,含量,pyrogenicity,致热性,clarity,透明度,intrinsic property,固有特性,viscosity,黏度,deacetylation,脱乙酰作用,Reading material: wet-chemistry theory,The commercial prospect of the actual biopolymer is good since its natural resources are abundant. The natural biopolymer has the following properties:,availability and ability to be used in varying form: powder, solution and,gel,s.,Non-toxicity,Biocompatibility,Good absorption capacity,Non-water,solubility,gel,凝胶,Biocompatibility,生物适应性,Reading material: wet-chemistry theory,Its largest use is as,flocculent,and,chelator,of toxic and,radioactive,metals but some other important applications can be cited: as a,component,in wound,dressing,s and drug delivery systems thanks to its biocompatibility, non-toxicity and wound-healing effect. The natural biopolymer is also an excellent,moisturizer,and is therefore used in hair- and skin care products.,flocculent,絮凝剂,chelator,螯合剂,chelate,螯合物，使螯合,radioactive,放射性的,dressing,敷料,component,成分,moisturizer,润湿剂,Reading material: wet-chemistry theory,The actual biopolymer has, like cellulose, a,linear,structure but instead of the hydroxyl group there is another,reactive group,. At,acidic,pH these groups become positively charged groups with high,reactivity,. Thus, they are very efficient in,neutralizing,the negatively charged,fibres,.,linear,线型的,reactive group,活性基团,reactivity neutralize,使中和,Reading material: wet-chemistry theory,The possibility of the natural biopolymer to be used as wet-strength additive lies within its structure, which is very similar to that of cellulose or CMC (,carboxyl methylcellulose,); the,glucose,units are linked together by -1,4,glycoside,bonds. The close similarity to cellulose probably makes it possible for the natural biopolymer to form strong hydrogen bonds to cellulose. By studying the irreversible adsorption of CMC to cellulose some general wet-strength mechanisms can be understood.,carboxyl methylcellulose,羧甲基纤维素,glucose,葡萄糖,glycoside ,葡萄,糖甙,甙,配糖体,Reading material: wet-chemistry theory,Irreversible adsorption of CMC,：,CMC is the most widely used water-soluble,derivate,of cellulose. It is produced by reacting cellulose with,monochloracetate,.,derivate,衍生物,= derivative,monochloracetate,一氯醋酸,Reading material: wet-chemistry theory,Irreversible adsorption of CMC is an alternative to improve paper strength. CMC can be irreversibly attached to cellulose at high temperature and in presence of an,electrolyte,. A salt is used to shield the,repulsion,between negatively charged,fibres,and CMC, making it possible for CMC to approach the,fibre,surface and attach. The irreversible adsorption is believed to be a matter of,co-,crystalisation,mechanisms. An irreversible adsorption is,thermodynamically,stable and cannot be washed away.,electrolyte,电解质,repulsion,排斥力,co-,crystalisation,共结晶作用,thermodynamical,热力学的,Reading material: wet-chemistry theory,A common technique for wet-strength development of paper is to add CMC together with,PAC,to the pulp. Cationic,PAE,helps to retain the anionic CMC to the,fibre,surface. Both dry and wet strength are improved. The surface,conformation,and properties of such,fibres,will be different compared to when only CMC is added.,polyaluminum,chlorides,聚合氯化铝,PAC,polyaminoamide,-,epichlorohydrin,聚酰胺多胺环氧氯丙烷,(PAE),amino,氨基的,amide,酰胺,amine,胺,imine,亚胺,conformation,构造,Reading material: wet-chemistry theory,Temperature has strong effect on CMC adsorption. The adsorption increases rapidly with temperature up to 120,C.,High electrolyte concentration also promotes the adsorption. At low electrolyte concentration no CMC is attached between pH6 and 11 whereas high electrolyte concentration makes the adsorption less pH dependent. Acidic conditions are more,favourable,and the adsorption increases when a,divalent-,instead of a,monovalent,ion is used.,C,Dcgrees,Centigrade,摄氏度,Fahrenheit,华氏,divalent,二价的,trivalent,三价的,monovalent,单价的,Reading material: wet-chemistry theory,Another factor is pulp,consistency,; high consistency promotes the attachment when divalent ions are used. The attachment also depends on the DS (,degree of substitution,); namely, it decreases for higher DS, due to the charge repulsion between CMC and,fibres,. Co-,crystallisation,mechanisms are also more efficient with purer cellulose,fibres,than if lignin and hemicelluloses are present.,consistency,稠度，浓度,DS degree of substitution,取代度,Reading material: wet-chemistry theory,The great advantage of CMC is that it can improve wet strength without beating of the,fibres,. This is very useful for the production of,tissue paper,that requires softness and good adsorption since beating gives stiffer paper with less,porosity,.,tissue paper,棉纸，卫生纸,porosity,多孔性,有孔性,