Nakajima Advanced Fiber Spinning Technology

1. Auflage 1994
ISBN: 978-1-84569-321-3
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 256 Seiten

Translated from Japanese, this book details some of the most interesting developments of the last few decades in the field of fibre manufacture. Many of these have been the result of intensive study in industry and research institutes in Japan - the country at the forefront of research in fibre spinning technology.

Autoren/Hrsg.

Nakajima, T.

Inhaltsverzeichnis

1;Front Cover;1
2;Advanced Fiber Spinning Technology;2
3;Copyright Page;3
4;Table of Contents;4
5;Contributors;8
6;Preface;12
7;Introduction;14
8;Japanese Patents: explanatory note;15
9;Chapter 1. Fundamentals of spinning;16
9.1;1.1 Introduction;16
9.2;1.2 Technological analysis of spinning;18
9.3;1.3 Structural formation during spinning;24
9.4;1.4 Fiber structure;28
9.5;1.5 Simulation of high-speed spinning;33
9.6;1.6 Concluding remarks;37
9.7;References;38
10;Chapter 2. Melt spinning;40
10.1;2.1 Introduction;40
10.2;2.2 Mechanical properties and structure of high-speed spun yarn;41
10.3;2.3 Structure formation in the high-speed spinning process;56
10.4;2.4 Applications of high-speed spinning;69
10.5;2.5 Present state of high-speed spinning operations;76
10.6;2.6 Conclusion;78
10.7;References;78
11;Chapter 3. Solution spinning;80
11.1;3.1 Introduction;80
11.2;3.2 Spinning technology of an acrylic filament yarn;81
11.3;3.3 Spinning technology of Bemberg rayon;93
11.4;3.4 Spinning technology of spandex fibers;112
11.5;References;119
12;Chapter 4. Spinning for nonwovens;120
12.1;4.1 Introduction;120
12.2;4.2 Spunbonded process;121
12.3;4.3 Meltblown process;125
12.4;4.4 Conclusions;129
12.5;References;129
13;Chapter 5. The spinning of highly aesthetic fibers;130
13.1;5.1 The evolution of aesthetic fibers;130
13.2;5.2 Specialized non-circular cross-section;132
13.3;5.3 Blended yarns of different shrinkage;136
13.4;5.4 Mixed-spinning, conjugate spinning and surface treatment;138
13.5;5.5 Splitting of conjugate fibers and super-fine fibers;141
13.6;5.6 Funny fibers;144
13.7;References;144
14;Chapter 6. Fiber spinning of anisotropic polymers;145
14.1;6.1 Anisotropic polymers;145
14.2;6.2 Lyotropic polymers;153
14.3;6.3 Thermotropic polymers;163
14.4;6.4 Summary;172
14.5;References;173
15;Chapter 7. Spinning of Thermotropic Liquid Crystal Polymers;175
15.1;7.1 Introduction;175
15.2;7.2 Thermotropic liquid-crystal polymers;176
15.3;7.3 Spinning of thermotropic liquid-crystal polymers;177
15.4;7.4 Heat treatment;178
15.5;7.5 Fiber formation and fiber characteristics;178
15.6;7.6 Fiber structure;183
15.7;7.7 Conclusion;185
15.8;References;185
16;Chapter 8. Gel spinning processes;187
16.1;8.1 Introduction;187
16.2;8.2 Spinning technology of ultra-high strength polyethylene fiber;187
16.3;8.3 Gel spinning - other flexible polymers;198
16.4;8.4 Conclusion;200
16.5;References;200
17;Chapter 9. Spinning of ultra-fine fibers;202
17.1;9.1 Introduction;202
17.2;9.2 Outline of ultra-fine fiber products and processes;203
17.3;9.3 Spinning of the continuous·filament type;205
17.4;9.4 Random·type spinning;215
17.5;9.5 Conclusion;219
17.6;References;221
18;Chapter 10. Spinning of optical fibers;223
18.1;10.1 Introduction;223
18.2;10.2 Structure of plastic optical fiber;224
18.3;10.3 Material of plastic optical fibre;225
18.4;10.4 Causes of transmission loss of plastic optical fiber;225
18.5;10.5 Process for manufacturing plastic optical fiber using PMMA as core material;226
18.6;10.6 Spinning technique for plastic optical fiber using PMMA as core material;230
18.7;10.7 Other processes for manufacturing plastic optical fiber;233
18.8;10.8 Multi-picture element plastic optical fiber;235
18.9;References;239
19;Appendix: Microscopic views of Shingosen;240
20;Index;269

Leseproben

1

Fundamentals of spinning

Ken-ichi Katayama    Takuma National College of Technology, Takuma-cho, Japan

Masaki Tsuji    Institute for Chemical Research, Kyoto University, Japan

There are a great many subjects covered by the heading ‘Fundamentals of spinning’. In this chapter, however, we confine ourselves to a description of the fundamentals of mathematical simulation for spinning and of new findings on structural formation during spinning and fiber structure. This description should be undertaken for each of the three types of spinning: melt spinning, dry spinning and wet spinning. However, we are concerned here mainly with melt spinning because it is the easiest for us to formulate and accordingly its theory is the most sophisticated of the three. The others are described only briefly with literature references to the details. Nevertheless, the authors hope that this short treatise will help the readers to understand other parts of this book.

1.1 Introduction

The viscose rayon method was developed towards the end of the last century and the melt spinning method for synthetic fibers was established in the early part of the 1930s. In the beginning of the history of spinning, progress in spinning technique was mainly made by accumulating empirical facts; that is to say, by repeating a set of procedures such as setting a spinning condition and measuring the resultant properties and structures of the spun fibers. There were few studies on physiochemical changes and on structural formation in the spun fibers between the spinneret and the take-up device. With the rapid advance of the synthetic fiber industry in the 1940s, a strong need arose to understand the basics of the spinning process in order to improve the productivity and quality control of the fibers. Consequently, towards the end of the 1950s, Ziabicki published a series of papers concerning melt spinning in which the spinning process was analyzed mathematically as an engineering problem: the papers served as a powerful incentive to researchers in this field of study. About the middle of the 1960s, Kase and Matsuo1,2 established a method for the quantitative description of the melt spinning process based on hydrodynamics, rheology and the theory of thermal conduction. Subsequently, Katayama et al3 studied structural formation and crystallization during a melt spinning process by using a special model spinning apparatus. From then on, studies in this field have been extensively carried out in Japan and elsewhere and most of the results are to be found in several references.4-9

In melt spinning, we can predict the diameter and temperature and the tension in a running filament if the spinning conditions and the rheological properties of a polymer used in the spinning process are given; the predicted values are, of course, in good agreement with the experimental results. Such a prediction, however, can be made only when no significant crystallization occurs during the spinning process. If crystallization must be taken into consideration, it becomes increasingly difficult for us to carry out mathematical simulation of the quantities mentioned above.

In this case, full quantitative knowledge of the following four points is needed for performing a mathematical simulation of melt spinning:

1 Molecular orientation caused by elongational melt flow.

2 Influence of molecular orientation on crystallization kinetics.

3 Changes in the rheological properties of the polymer caused by molecular orientation and crystallization.

4 Kinetics of non-isothermal crystallization.

The correlation between the above points is shown in Fig. 1.1. In this figure, an arrow indicates that an item from which the arrow starts influences another item to which the arrow is pointing.

1.1 Correlation between factors governing the melt spinning process

In the theory of Kase and Matsuo, mean values of temperature and of stress over the whole area of a transverse section of the filament were used. In the process of high speed spinning, however, the variables such as temperature, stress, orientation and crystallinity must be expressed as functions of the radial distance from the central axis of the filament as well as the distance from the spinneret. For example, consideration of the radial distribution of these variables is inevitable in discussing inhomogenous structures such as skin–core structure. In order to understand the spinning process, it is indispensable for us to know how structure will be formed during the process as well as to carry out the detailed technological analysis of the process. In the following part of this chapter, the fundamental equations describing the melt spinning process accompanied by crystallization will be developed. After this the oriented crystallization, which is closely related to the structure formation during the spinning process, will be discussed and the differences between oriented and unoriented crystallization will be highlighted. Then the importance of gelation in the process of solution spinning and of phase separation will be mentioned. Finally, examples of mathematical simulation of high speed melt spinning will be demonstrated.

1.2 Technological analysis of spinning

For the technological analysis of spinning, three fundamental equations are derived from the conversion of energy, the conversion of momentum and the conversion of matter, respectively. Here, for simplification, the two differential operators are defined as follows:

=i??x+j??y+k??z

  [1.1]

Dt=??t+Vx??x+Vy??y+Vz??z

  [1.2]

where t is the time, (x,y,z) the spatial co-ordinates, V(Vx,Vy,Vz) the velocity of polymer, and i, j and k are the unit vectors in the x, y, and z directions, respectively.

1.2.1 Fundamental equations (melt spinning)10

1.2.1.1 Conversion of energy

Consider an arbitrary small-volume element dv fixed in space along the spinning path (Fig. 1.2) and an enthalpy change in the element. The fundamental equation for conservation of energy can then be derived.

1.2 Volume element

1.2.1.2 Inflow of heat through conduction

We assume that the thermal conductivity of the polymer Kc, is independent of temperature T. The net inflow of heat in unit time conducted through the xy-plane into the element, the centre of which is located at (x,y,z), is expressed as

c?T?zz+dz/2-Kc?T?zz-dz/2dxdy=Kc?2T?x2dxdydz

  [1.3]

Accordingly, by summing such quantities for all the three directions, heat transferred into the element in unit time is

c?2Tdv?2:Laplacian

  [1.4]

1.2.13 Inflow of heat accompanying transfer of matter

For the polymer, the specific heat at constant pressure, the heat of crystallization, the crystallinity and the density are expressed as Cp, ? H, X and p respectively. We assume that Cp, and ? H are independent of T and that the enthalpy per unit mass (H) is a function of T and X.

The net enthalpy in unit time which flows into the volume element dv through the xy plane is

?HVz|z+dz/2+?HVz|z-dz/2dxdy=-??HVzdzdv

  [1.5]

Accordingly, by summation of such quantities for all the three directions,

?.?HVdv

  [1.6]

Using the equation of continuity ??/?t = – ?. (?V) (modified equation 1.4),

?.?HVdv=H?p?t-?V.?H

  [1.7]

1.2.1.4 Conservation of enthalpy

Here, we direct our attention to the conservation of enthalpy within dv

?H?t=Kc?2T+H???t=?V.?H

  [1.8]

Since ?H/?T = Cp and ?H/?X = –?H,

H=Cp?T-?H.?X

  [1.9]

Substitution of this relation into equation 1.8 gives

?H?t=Kc?2T-Cp?V.?T-??HV.?X

  [1.10]

For the steady state, equation 1.10 becomes

.?T-??2T=?HCpV.?X

  [1.11]

where ? = Kc / (? Cp) is the thermal...