造纸专业英语7.ppt

1、,Lesson 16 Dry and wet strength additives,A number of natural and synthetic polymeric substances may be admixed with the stock at the wet end to improve the physical properties of the dry sheet. Their action is to reinforce fiber-to-fiber bonds and thereby improve the burst and tensile strength, pro

2、vide greater resistance to erasure, reduce “fuzz” or lint on the paper surface, reduce the rate of water penetration.,additive 添加剂 synthetic 合成的 polymeric 聚合物的 stock 坯料，材料，原料 bond 键 burst 耐破度,tensile strength 抗张强度 fuzz 细毛, 绒毛 lint 棉绒 penetration 浸透 erasure 抹掉，消除,Lesson 16 Dry and wet strength additi

3、ves,The traditional internal strength additives are natural and modified starches and gums. Both are usually cooked at low concentration prior to use to promote swelling and dispersion. The trend today is toward increased use of such synthetic polymers as latexes and polyacrylamides either alone or

4、in combination with starches and gums.,starch 淀粉 gum 树胶 concentration 浓度 swell 润胀 dispersion 分散 latex 胶乳 polyacrylamide 聚丙烯酰胺 acryl 丙烯（醛基）,Lesson 16 Dry and wet strength additives,resin 树脂,The action of wet-strength resins is to tie fibers and fines together with additional bonds that are not taken

5、apart by water. Wet-strength paper is defined as such if it retains more than 15% of its tensile strength when wet.,Lesson 16 Dry and wet strength additives,agent 药剂 urea 尿素 formaldehyde 甲醛 melamine 三聚氰胺 polyamide 聚酰胺 water-soluble 水溶性的 anionic 阴离子的 cationic 阳离子的 degree of polymerization 聚合度 cure 熟化

6、，固化,The most common wet-strength agents are urea-formaldehyde, melamine-formaldehyde, and polyamide resins; they are water-soluble and available in both anionic and cationic forms. These agents are applied at an intermediate degree of polymerization, so that the final “cure” is obtained in the dryer

7、s.,Lesson 17 Internal sizing and alkaline papermaking,The purpose of sizing is to enable paper products to resist penetration by fluids. Sizing can be achieved either by using wet-end additives (“internal sizing”) or by applying a suitable coating to the surface of the dried paper (“surface sizing”)

8、. Internal sizing is accomplished by adding materials to the stock before the headbox to retard water penetration into the final paper.,size n.胶料 v. 上胶 sizing 上胶，施胶 coat v. 外面覆盖 fluid 流体 headbox 流浆箱,Lesson 17 Internal sizing and alkaline papermaking,Water penetration is retarded by the nonpolar port

9、ions of the size molecule. A reactive portion of the size molecule anchors it to the surface of the fiber. Surface sizing works by different mechanism and occur at the size press where an application of starch (or other material) fills the capillaries of paper, making water penetration much more dif

10、ficult. Starch is not hydrophobic as are internal sizing agents.,nonpolar 非极性的 anchor v. 抛锚停泊，使固定 capillary 毛细管 hydrophobic 憎水的,Lesson 17 Internal sizing and alkaline papermaking,There are two common methods used in internal sizing: rosin sizing, which must be carried out at pH46 and alkaline sizing

11、, which is carried out at pH8 or higher with alkyl ketene dimer (AKD) and alkyl succinic anhydride (ASA). Paper may be hard-sized (high resistance to liquid penetration such as printing and packaging papers), slack-sized (low penetration such as newsprint), or no-sized paper (toweling and sanitary p

12、apers).,rosin 松香 alkaline 碱性的 alkyl ketene dimer 烷基烯酮二聚体 succinic 丁二酸的 alkyl succinic anhydride 烯基琥珀酸酐 anhydride 酸酐,Lesson 17 Internal sizing and alkaline papermaking,For rosin sizing with alum, the rosin is precipitated onto the fibers by the action of alum as an oriented monolayer of aluminum resi

13、nate molecules.,alum 明矾 precipitate v. 沉淀 monolayer 单层 resinate 树脂酸盐,Lesson 17 Internal sizing and alkaline papermaking,Rosin may be used in the salt form as a solution at pH 10-11 (soap size), the salt form with 20%-30% water (paste rosin size) or in the free acid form as an emulsion (emulsion size

14、), which is effective at slightly higher headbox pH than the others. Normally the rosin is added before the alum. If alum is added before alum, the process is called reverse sizing, which is useful in water containg high amounts of calcium.,soap size 皂化物胶料 paste rosin size 糊状松香胶料 emulsion size 乳液状胶料

15、 calcium 钙,Lesson 17 Internal sizing and alkaline papermaking,For alkaline sizing, synthetic sizing agents react chemically with the cellulose hydroxyl groups to form stable ester linkages to give sizing effects. These agents are not water soluble and must be used as emulsions. Cationic starch is us

16、ed to stabilize these emulsions.,ester 酯 linkage 键; 键合,Lesson 17 Internal sizing and alkaline papermaking,With most internal sizing methods, hardwood pulps are much easier to size than softwood pulps; sulfate pulps are easier to size than sulfite pulps, which are both easier to size than thermomecha

17、nical pulps. The explanation centers around the number of carboxylate groups as anchor points in sizing.,thermomechanical 热机的 carboxylate 羧酸盐,Lesson 17 Internal sizing and alkaline papermaking,There are several important advantages to alkaline papermaking. The papers have longevity; calcium carbonat

18、e (inexpensive and bright filler) can be used; paper is stronger and less brittle; there is less corrosion on the paper machine; and there are few problems using recycling fiber containing calcium carbonate filler.,longevity n.长命, 寿命,与(hydro-，hydr)有关的词,Hydrogen Hydrate Hydration Hydric Hydride Hydrolysis Hydrophobic Hydrophilic Hydrosulphate Hydrosulphide Hydroxide Hydroxyl,氢 水合物， 水合作用 含氢的 氢化物 水解 憎水的 亲水的 硫酸氢盐 硫氢化物 氢氧化物 羟基,与硫sulph(o)-有关的词,Sulphur Sulphide Sulphite