University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange

Masters Theses Graduate School

8-2002

Fiber Splitting of Bicomponet Melt Blown Microfiber Nonwovens by Chemical and Water Treatment

Hua Song University of Tennessee - Knoxville

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Recommended Citation Song, Hua, "Fiber Splitting of Bicomponet Melt Blown Microfiber Nonwovens by Chemical and Water Treatment. " Master's Thesis, University of Tennessee, 2002. https://trace.tennessee.edu/utk_gradthes/2176

This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council:

I am submitting herewith a thesis written by Hua Song entitled "Fiber Splitting of Bicomponet Melt Blown Microfiber Nonwovens by Chemical and Water Treatment." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in .

Dong Zhang, Major Professor

We have read this thesis and recommend its acceptance:

Kermit Duckett, Christine (Qin) Sun, Paula Carney

Accepted for the Council: Carolyn R. Hodges

Vice Provost and Dean of the Graduate School

(Original signatures are on file with official studentecor r ds.) To the Graduate Council:

I am submitting herewith a thesis written by Hua Song entitled “FIBER SPLITTING OF BICOMPONENT MELT BLOWN MICROFIBER NONWOVENS BY CHEMICAL AND WATER TREATMENT”. I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Textiles, Retailing and Consumer Sciences.

Dong Zhang Major Professor

We have read this thesis and recommend its acceptance:

Kermit Duckett

Christine (Qin) Sun

Paula Carney

Accepted for the Council:

Dr. Anne Mayhew Vice Provost and Dean of Graduate Studies

(Original signatures are on file with official student records.)

FIBER SPLITTING OF BICOMPONENT MELT BLOWN MICROFIBER NONWOVENS BY CHEMICAL AND WATER TREATMENT

A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville

Hua Song August 2002

ACKNOWLEDGMENTS

I would like to thank all those who helped me in completing Master of Science in Textile Science. I thank people in the textile program and in Textiles and Nonwovens Development Center (TANDEC).

I am very thankful to the following TANDEC faculties and engineers for their precious guidance and suggestions, Dr. Dong Zhang, Dr. Christine (Qin) Sun, Dr. Kermit Duckett, and Mr. Van Brantley.

I thank my family and friends, whose suggestions and encouragement made this work possible.

ii ABSTRACT

The melt blowning process is unique because it is used almost exclusively to produce microfibers rather than fibers the size of normal textile fibers. With bicomponent meltblown bicomponent fabrics, PLA/PP and PLA/PTT, an alkaline treatment was applied to the fabrics, causing the dissolvable part (PLA) removed from the bicomponent fibers.

Alternatively, water treatment is preferred compared to alkaline treatment. Water dispersive Eastman AQ polymers were introduced to melt blown processing for the first time. After the water dispersive AQ polymer was determined to be able to be processed into a nonwoven fabric using the melt blowing processing line, the feasibility of processing bicomponent nonwoven with that polymer was proved. Then, AQ/PP bicomponent melt blown fabrics were produced with TANDEC Reicofil® Bicomponent Meltblown Line successfully. Water treatment was performed on the bicomponent webs, causing the dispersive part, AQ polymer, dispersed in soft water.

The effects of alkaline and water treatment on the properties of bicomponent melt blown webs were studied. After both treatments, bicomponent melt blown fabrics tended to decrease in fiber size, basis weight, thickness, tenacity and stiffness. Air permeability appeared to decrease for high PLA or AQ composition samples, and hydrostatic pressure as well as derived filtration efficiency increased for those samples. Elongation increased notably for most samples with different bicomponent ratios after water treatment.

The relationship between polymer ratio in a bicomponent fiber and the fiber cross- section geometry was mathematically investigated, as well as specific surface area change of a fiber after fiber size reduction treatments.

A preliminary experimental study was done to give some general optimized water treatment conditions for AQ/PP bicomponent melt blown fabrics. Also, an empirical rule was summarized about the treatment time of complete AQ polymer dispersion. Some DSC scans of AQ resins and AQ polymer nonwoven products indicated the possibility of recycling AQ polymer after the water treatment.

iii TABLE OF CONTENTS Chapter Page

I. INTRODUCTION...... 1 Background and Literature Review...... 1 Melt Blown Nonwovens ...... 1 Bicomponent Fibers...... 2 Microfiber Processing...... 4 Biodegradable and Water Soluble Polymers ...... 5 Objective of This Research ...... 7

II. EXPERIMENTS ...... 9 Alkaline Solution Treatment ...... 9 Polymer Materials...... 9 Chemicals...... 9 Chemical Treatment...... 9 Testing...... 9 Preliminary Study Eastman AQ Polymer...... 10 Eastman AQ Resin...... 10 Eastman AQ Polymers Melt Blown Nonwoven fabrics Testing ...... 10 Water Treatment...... 11 Polymer Materials...... 11 Processing ...... 11 Water Treatment ...... 11

III. RESULTS AND ANALYSIS ...... 16 Chemical Treatment ...... 16 Eastman AQ Polymer Preliminary Study...... 18 Eastman AQ resins...... 18 Eastman AQ polymers melt blown fabrics ...... 18 Water Treatment...... 19 AQ Polymer Solution Process ...... 19 Incomplete Dispersion of AQ/PP Bicomponent Nonwoven Web...... 19 Complete Dispersion of AQ/PP Bicomponent Nonwoven Web ...... 20 SEM images analysis ...... 20 Physical Properties Analysis...... 23 Differential Scanning Calorimetry Analysis...... 40 AQ Bico Distilled Water Treatment Optimization ...... 46

IV. CONCLUSION AND RECOMMENDATION ...... 49

LIST OF REFERENCES...... 51 VITA...... 54

iv LIST OF FIGURES Figure Page

Figure 1. Schematic of a melt blowing process ...... 2 Figure 2. Cross sections of bicomponent fibers...... 3 Figure 3. Branched Water Dispersible Structure ...... 8 Figure 4. Sodiosulfoisophthalic Acid ...... 8 Figure 5. SEM microphotographs of bicomponent melt blown web (PLA/PP 75/25)..... 17 Figure 6. SEM microphotograph of #10, 75/25 AQ/PP melt blown nonwoven before water treatment...... 21 Figure 7. SEM microphotograph of #10, 75/25 AQ/PP melt blown nonwoven after water treatment...... 21 Figure 8. Cross section SEM microphotograph of #10, 75/25 AQ/PP melt blown nonwoven after water treatment...... 22 Figure 9. Cross section SEM microphotograph of #9, 50/50 AQ/PP melt blown nonwoven after water treatment...... 22 Figure 10. More cross section SEM microphotograph of #9, 50/50 AQ/PP melt blown nonwoven after water treatment...... 23 Figure 11. Physical tests on AQ/PP bicomponent nonwoven webs ...... 25 Figure 12. Fiber diameter distribution of #7 (25/75 AQ/PP) melt blown webs before and after water treatment, determined from OM and SEM images...... 29 Figure 13. Fiber diameter distribution of #10 (75/25AQ/PP) melt blown webs before and after water treatment, determined from images...... 30 Figure 14. Ideal cross section diagram of a side-by-side bicomponent fiber...... 31 Figure 15. Fiber diameter distribution of #9 (50/50 AQ/PP) melt blown webs before and after water treatment, determined from images...... 32 Figure 16. AQ polymer weight percentage in a bicomponent fiber verses its relative position in the fiber’s cross-section...... 35 Figure 17. Polymer components’ arrangement in a bicomponent fiber (cross section). .. 37 Figure 18. Specific area S/V verses height of the left part in a bicomponent fiber after treatment ...... 39 Figure 19. DSC scans of Eastman AQ35S and AQ55S pellets...... 41 Figure 20. DSC scans of Eastman AQ35S and AQ55S melt blown nonwoven webs...... 41 Figure 21. More DSC scans of Eastman AQ35S and AQ55S melt blown nonwoven webs ...... 42 Figure 22. DSC scans of Eastman AQ35S/PP bicomponent melt blown nonwoven webs: #7, 25/75 AQ/PP; #9, 50/50 AQ/PP; #10, 75/25 AQ/PP...... 42 Figure 23. DSC scans of Eastman AQ35S/PP bicomponent melt blown nonwoven webs after complete water treatment : #10, 75/25 AQ/PP; #9, 50/50 AQ/PP; #7, 25/75 AQ/PP...... 43 Figure 24. Two DSC scans of film extracted from #7 25/75 AQ35S/PP water treatment solution by natural evaporation...... 45 Figure 25. DSC scans of solution extractants from #10, 75/25 AQ35S/PP nonwoven web and Eastman AQ35S pellets by heating up solution...... 45

v LIST OF TABLES Table Page

Table 1. Typical Properties of Eastman AQ35S and AQ55S polymers ...... 8 Table 2. Eastman AQ melt blown nonwovens production conditions...... 11 Table 3. Samples for water treatment ...... 12 Table 4. Melting flow rate testing results ...... 18 Table 5. AQ content in AQ/PP bicomponent fibers and corresponding geometrical features. R is the radius of the fiber; S stands for the surface area of a whole fiber, and V is its volume, S/V gives the specific area of a fiber...... 36 Table 6. Normalized heat of flow of PP melt peak in bicomponent melt blown webs before and after water treatment...... 43 Table 7. Basis weight percent change at different treatment time and temperature...... 48 Table 8. Recommended treatment conditions at 0.05% solids concentration: ...... 48

vi CHAPTER I INTRODUCTION

Background and Literature Review

Melt Blown Nonwovens

The definitions of the nonwovens most commonly used nowadays are those by the Association of the Nonwovens Fabrics Industry (INDA) and the European Disposables and Nonwoven Association (EDANA).

EDANA definition: Nonwovens are a manufactured sheet, web or batt of directionally or randomly oriented fibers, bonded by friction, and/or cohesion and/or adhesion, excluding paper or products which are woven, knitted, tufted stitchbonded incorporating binding yarns or filaments, or felted by wetmilling, whether or not additionally needled. The fibers may be of natural or man-made origin. They may be staple or continuous or be formed in situ [EDANA, 1988].

Melt blowing is one of the most popular processes to make super fine fibers on the micron or sub-micron scale. It is a “one-step process in which high velocity fluid, normally air blows molten thermoplastic resin from an extruder die tip to a conveyor, or take-up screen, or substrate to form a fine fibered, self-bonded web” [Staff report, 1989]. The melt blown process converts resins to nonwoven fabrics in a single integrated process. The schematic of the melt blowing process is shown in Figure 1. A typical melt blowing process consists of the following elements: extruder, metering pumps, die assembly, web formation, and winding.

The concept of melt blowing thermoplastics was first introduced to the public in 1954 through a Naval Research Laboratory project initiated by Wente [Haynee, 1991]. Since then, the melt blowing process and a variety of melt blown products have been recognized, developed, and commercialized. Over 320 US patents have been granted to the technologies and products related to melt blowing in the past 50 years. It is clear that the melt blown technology is finding its application in more and more fields.

This melt blown process is unique because it is used almost exclusively to produce microfibers rather than fibers the size of normal textile fibers, generating fine fibers not available to the other nonwoven processes. Melt blown microfibers generally have diameters in the range of 2 to 5 µm, although they may be as small as 0.1µm and as large as 10 to 15 µm. Differences between melt-blown nonwoven fabrics and other nonwoven fabrics, such as degree of softness, cover or opacity and porosity can generally be traced to differences in filament size. The average fiber diameter can be controlled by the specific resin employed and the processing conditions selected. With such fiber fineness,

1

Figure 1. Schematic of a melt blowing process the number of fibers per unit weight is greatly increased. Further, the amount of fiber surface exposed is also substantially greater than that exposed in conventional webs. As a consequence, these characteristics can have a significant impact in a variety of product applications. At the present time, filtration media, medical fabrics, sanitary products, oil adsorbents, apparel, hot-melt adhesives, electronic specialties and other miscellaneous applications, such as the tents and elastomeric nonwoven fabrics are successfully served by melt-blown products.

Bicomponent Fibers

Bicomponent fibers are not new. Thus, wool is a naturally occurring bicomponent fiber, and glass bicomponent fibers were produced in the latter part of the nineteenth century. Bicomponent, side-by-side viscose fibers were patented in 1937 [Porter, 1984]. In the 1960s, bicomponent fibers were introduced for use in hosiery and in nonwoven products.

One of the first producers of bicomponent fibers was the Du Pont Company, with its self-crimping Cantrece, a bicomponent nylon monofilament used in hosiery [Davies, 1991]. In recent years, the Japanese have developed the market for the sheath/core bicomponent fiber, which is mainly used in nonwoven fabrics. In these fibers, the sheath is the lower melting component used to thermally bond fiber to fiber in nonwoven fabrics.

Bicomponent fibers may be classified as sheath/core, side-by-side, eccentric, islands-in-the-sea, and citrus, as shown by the cross sections of these fibers given in

2

Figure 2. Cross sections of bicomponent fibers

Figure 2. The islands-in-the-sea and citrus bicomponent fibers are used chiefly to make microfibers; microfibers have no universally accepted definition but are usually considered to be those with a decitex per filament of less than 1. With bicomponent fibers, one of the fiber components is removed by the use of heat, a solvent, or a chemical or the two component fibers can be physically split apart. The Japanese have produced microfibers from PET and other polymers that imitate silk in some properties. Today, many companies, especially in Europe and the Unite States, have learned how to control the spinning of microfibers directly without making precursor bicomponent fibers. These mircrofibers have grown rapidly in volume.

Side-by-side bicomponent fibers are produced, as the name implies, by spinning two fiber components together so that they are joined longitudinally. One of reasons for manufacturing these fibers is to provide helical crimp, caused by differences in the expansion or shrinkage of the two components of the fibers. The two components may differ in chemical composition or differ in some property such as molecular weight or degree of crystallization, which provides differential expansion or shrinkage. Sometimes the polymer components may differ in degree of hydrophilicity; for example, both polymers may be copolymers of polyacrylonitrile but contain different amounts of sulfonic acid groups. Bicomponent side-by-side inorganic fibers with crimp have also been produced.

Side-by-side bicomponent fabrics made with side-by-side bicomponent fibers have high bulk and resiliency. However, they may not have the strength of nonwoven fabrics made with sheath/core bicomponent fibers. Bouchillon [1992] points out that with these side-by-side fibers, “the bulk, resiliency, and stretch/recovery properties are desirable for many nonwoven applications, including: shoe components, apparel, toys, sleeping bags, pillows, furniture, and automotive.” Additives can also be used to impart various properties to fabrics made from side-by-side fibers.

3 Microfiber Processing

As mentioned above, microfibers have no universally accepted definition but are usually considered to be those with a decitex per filament of less than 1.

Most microfiber is made of polyester; however, other polymers are used, including nylon, polyacrylonitrile, , cellulose acetate, and rayon. Mixtures of polymers such as polyester-nylon and polyester-polypropylene are also used. Microfibers are manufactured in both staple and filament forms. Microfibers are chiefly made in three different ways: (1) chemical dissolution of one of the components in a bicomponent fiber, (2) physical splitting of a bicomponent fiber, and (3) direct spinning of the microfiber. Methods 1 and 2 can be accomplished in the fabric finishing process.

The production of polyester microfibers started in Japan in the 1970s by size reduction of the fibers in polyester fabrics, using hot alkaline treatment to dissolve their surface polymer. Polyester fabric was subjected to hot alkaline treatment to remove up to 40-50%, usually 20-30%, of the fabric weight. The treatment resulted in smaller diameter fibers and a fabric “with an increased liveliness, drape, and covering power, plus a warm, dry, silk-like hand with increased scroop”. In the Unites States similar treatment of polyester fabric is carried out with lower weight loss, typically 8-15% (Goldstein, 1993). Rame [1992] has studies the loss in weight of polyester fibers in alkali and found that it is linear from 15 to 95°C at 10% concentration of alkali. He found that silk like properties can be imparted to polyester with a weight reduction of 8 to 12%.

Microfiber can be produced from a bicomponent fiber by dissolving one component. The bicomponent fiber may be splittable, resulting in microfibers that are a mixture of both components. Microfibers can be made from bicomponent fibers of various configurations, including islands-in-the-sea and citrus structures. The microfiber made by Kanebo in Janpan [Murata, 1993] is split by a chemical treatment. Fabrics made from a resulting polyester/nylon microfiber have a hand similar to silk.

A 1992 U.S. patent to Chisso Corp. in Japan describes the preparation of microfibers from islands-in-the-sea or side-by-side multicomponent fibers [Kawano, 1992]. For the islands-in-the-sea fibers, the sea component is dissolved, leaving the island component as a very small microfiber less than 0.1 dtex in size. An example of a side-by-side fiber is given in which one side of the fiber is an islands-in-the-sea with a sea component of saponifiable polyvinyl alcohol and an island component of polypropylene. The other side of the fiber is . The polyvinyl alcohol is extracted with water or an alkaline solution. What remains are very fine microfibers (less than 0.1 denier) of polypropylene mixed with larger (5.5 denier) polyethylene fibers. An example is also given of a sheath/core fiber in which the sheath component contains saponified polyvinyl alcohol as the sea component and polypropylene as the island component. The core component is polyethylene. After extraction of the saponified polyvinyl alcohol with water or alkaline solution, the very fine microfibers are polypropylene of less than 0.1 denier and the core

4 component contains large (2.4 denier) polyethylene fibers. The patent also describes nonwoven fabrics made from a mixture of very fine polypropylene fibers and the larger polyethylene fibers. The polyethylene fiber becomes the binder fiber in the nonwoven fabric. The water or alkaline solution extraction may be carried out after the fabric is prepared.

Microfibers