包装盒专业英语3.ppt

1、 UNIT TWO PACKAGING MATERIALS AND CONTAINER 第二单元第二单元 包装材料和容器包装材料和容器 Lesson 3 Paper and Paperboard 第第3课课 纸与纸板纸与纸板 Introduction Definition of paper:Paper is defined as a matted or felted sheet usually composed of plant fiber.Paper has been commercially made from such fiber sources as rags(linen),bagas

2、se(sugar cane),cotton,and straw.Modern paper is made almost exclusively from cellulose fiber derived from wood.Although the word“paper”is derived from the Egyptian term,“papyrus”was not a true paper in the modern sense.-Invention of paperThe invention of paper by blending cellulose fibers didnt occu

3、r until the beginning of the second century A.D.Introduction Tsai Lun,a member of the court of the later Han Dynasty,is generally credited with developing the first real papermaking process in 105 A.D.The“Fourdrinier machine”was the first on the market and produced a homogenous(single-ply)sheet of b

4、oxboard in various thicknesses.It was soon joined by the“Cylinder machine”which formed a multi-layered(multi-ply)type of paperboard.These machines were first installed in the United States around 1830.Introduction Paper and paperboard Paperboard,boxboard,cardboard,and cartonboard are all terms used

5、to describe heavier paper stock.The International Organization for Standardization(ISO)states that material weighing more than 250 grams per square metre(511b per 1,000 sq.ft.)shall be known as paperboard.U.S.practice calls material that is more than 300(0.012 in.)thick paperboard.Representative Pap

6、ermaking Machines Fourdrinier Machines Fourdrinier machines(Figure 3.1)pump furnish from a headbox directly onto a moving wire screen through which the water is continuously drained.Fourdrinier machines may have a second headbox(Figure 3.2)situated downstream of the first headbox to add further quan

7、tities of furnish onto the partially dewatered initial lay-down.Representative Papermaking Machines Figure 3.1 Furnish pours out of the headbox of a fourdrinier machine and onto an endless wire or screen where excess water can be drained.The fibers remain trapped on the screen Representative Paperma

8、king Machines Figure 3.2 Paper is dewatered at the wet end of a fourdrinier machine Representative Papermaking Machines Cylinder Machines A cylinder machine(Figure 3.3)rotates a screen drum in a vat of furnish.(The paper is sometimes called vat paper.)As the water pours through the screen,fiber accu

9、mulates on the outside of the screen.This thin layer of matted fiber is transferred onto a moving felt belt that passes sequentially over further rotating cylinders,each of which deposits another fiber layer.Representative Papermaking Machines Figure 3.3 A single cylinder station on a cylinder-type

10、machine Representative Papermaking Machines Cylinder machines dewater furnish at the cylinder and paste a thin layer of fiber against the felt.(Figure 3.4.)Figure 3.4 A cylinder machine with six cylinders at which a paper layer can be formed Representative Papermaking Machines The fibers of subseque

11、nt layers do not intermingle,and therefore the bond between the layers is weak.The dry end is similar to that of the fourdrinier machine.Cylinder machines do not have the fourdrinier machines limitation on the number of stations,and six-or seven-station machines are common.Higher-caliper boards for

12、folding and setup cartons are usually cylinder boards.Generally,papers are made on fourdrinier or twin-wire formers,whereas heavier paperboard products are made on cylinder-type machines.Extremely heavy boards are made by laminating several thinner sheets.A typical cylinder board construction(Figure

13、 3.5):Representative Papermaking Machines Figure 3.5 Cylinder boards are multiply boards.An advantage is that the plies can all be different Representative Papermaking Machines Twin-Wire Machines Vertiformers and twin-wire formers(Figure 3.6)inject the furnish between two moving wire screens.The adv

14、antage is that dewatering takes place on both sides of the paper and is therefore fast.These machines can produce single and multi-ply sheets with identical formation at both faces.Machine Direction and Cross Direction Depositing a fiber-and-water slurry onto a moving wire belt tends to align fibers

15、 in the direction of travel,known as the machine direction(MD).The direction across the apermaking machine and across the fiber alignment is the cross direction(CD)(Figure 3.7).Because of this fiber alignment,paper is an anisotropic material;measured properties differ depending on the direction in w

16、hich the property is measured.Representative Papermaking Machines Figure 3.6 Water can be simultaneously removed from both sides of the paper on a twin-wire paper former Representative Papermaking Machines Figure 3.7 Fibers in a manufactured paper sheet tend to align themselves in the machine direction Representative Papermaking Machines Figure 3.8 shows the relationship of tear,stiffness,and fold endurance to machine direction.Paper specification sheets normally show physical values measured in