ECOLOGICAL NONWOVEN TEXTILES FOR TECHNICAL APPLICATIONS

Transcription

1 BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică Gheorghe Asachi din Iaşi Tomul LVI (LX), Fasc. 1, 2010 SecŃia TEXTILE. PIELĂRIE ECOLOGICAL NONWOVEN TEXTILES FOR TECHNICAL APPLICATIONS BY FLORENTINA-FLORI COSTACHE* and MARIA ZAMFIR** Abstract. The paper is presenting researches on structures of nonwovens for technical applications, with a very high liquid absorption capacity, used even for the wide range of emergency cases when such property is a requirement, as examples being the medical products. The nonwovens made from biodegradable fibre raw materials are evaluated by point of view of functional characteristics. Key words: nonwoven, ecological textiles, structure, absorption, technical application. 1. Introduction The paper is presenting researches on medical products made by nonwovens technologies with a high absorption capacity need in emergency cases on battlefield or other types of disasters. The nonwoven technology has the fastest growing of more 10% yearly within the textile industry [10]. The nonwoven products are realized from cotton fibres treated by alkaline boiling and bleaching processes to improve the characteristic performance of products. Products of 200 g/m 2 to 300 g/m 2 average basic weight, with high liquid absorption capacity can replace the woven gauze medical products. The new products are obtained by thermally or needlepunching process. The end-uses of products are for absorbent pads, bandages, bed linen, blankets for hospitals, burn dressings, cast liners, swabs, puffs, absorbent puffs, component of face masks, finger bandages, heat packs, incubator mattress, medical filters, procedure packs, medical equipment, wound dressings, etc. The pulp fibres have been also used to diversify the nonwoven products for very special medical end-uses with a very high liquid absorption capacity [10], [11]. As an innovative technology to obtain ecological products, the cellulose

2 56 Florentina-Flori Costache and Maria Zamfir fibres nonwoven technology is more widely used to obtain environmentally friendly products [3], [4], and [10]. From the cellulose fibres category, the fibres of cotton are the most customary fibres for nonwoven products for a very large area of end-uses including the medical products. The production of nonwoven based medical products is based on the following criteria: No indigene nonwovens for medical applications; The lower production cost for medical nonwovens due to less process steps (by number and by length) compared to the classical woven gauze process steps, as well as less raw materials, energy and labour; The highest absorption capacity compared to the classical products; The nonwoven equipments are of higher outputs. The most consumers perceive that the cotton is a superior fibre. The general cotton fibre characteristics [5] that could determine the enduses of nonwovens and cotton processing are shown in Table 1. Table 1 The Cotton Fibre Characteristics Property Value Fineness, [µm] Length, [mm] Moisture regain at 65% r.h., 20 C, [%] 7 8 Dry tenacity, [cn/denier] cotton is 20% stronger when wet Wet tenacity, [cn/den] Breaking extension, [%] 6.8 Absorbency, [%] 8 11 at standard conditions Coefficient of friction 0.25 for raw dry cotton, strongly changes for treated and/or wet fibre The main general characteristics which can influence the applications of the cotton fibres for technical nonwovens are the soft hand, the good absorbency, the good strength and abrasion resistance. The main chemical properties that could determine the end-use of cotton nonwovens are: cotton swells in a high humidity environment, in water, in concentrated solutions of certain acids, salts and bases; cotton is attacked by hot dilute or cold concentrated acid solutions; cold weak acids do not affect cotton; cotton degradation is usually attributed to oxidation, hydrolysis or both; cotton is extremely susceptible to the biological degradation (micro organisms, fungi, etc.) [3], [4], [5]. The trash content is highly correlated to leaf grade of the sample. High trash content is not desirable for medical nonwovens. The neps sometime detract the visual appearance. For some end-uses of

3 Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 1, cotton nonwovens, such as very high absorbent products, the neps seems not to be very negativist characteristics. The scouring is accomplished by saturating the cotton fibre with a caustic soda (sodium hydroxide) solution. In nonwovens, the cotton fibres are generally used in their bleached form. The cotton fibres are used in the manufacture of nonwovens either alone or in a blend. The various processes for nonwoven production are carding, carding-lapping for fibrous web forming and then hydroentangling, needlepunching or thermally processes to bond the fibrous webs. The hydroentangling process gives high strength without interfering with the absorbency, tensile strength and comfort properties of cotton, and without using any chemical. The hydroentangling process, known as Spunlaced, is highly attractive with cotton because it preserves the pure fibre condition which is conducive to obtain products with high absorbency. The Spunlaced nonwovens have many characteristics that are similar to woven cotton fabrics and many more related to the high purity because of fibres cleaning by the high pressure water jets which intimately are penetrating into fibrous web structure. The needlepunched cotton nonwovens provide highly efficient filter media based on the irregular fibre shape and absorption properties. The increasing of the tenacity in the wet condition can be an important advantage for cotton filters. The regular length staple cotton should be considered for needlepunching since longer lengths perform better. Even though cotton staple has random length distribution, an enough long fibre must be in a regular staple to form strong fabrics. The fibre finishing operation is critically in during the needlepunching process. A good lubrication is needed to prevent bleached cotton fibre damage and needle breakage. The special needles (Foster Needle, Groz- Beckert or Singer types) are recommended for the needlepunching process. The thermoplastic fibres used for cotton fibre web bonding are the polyester and polypropylene. The polypropylene fibres are preferred because of economics, density and low melting temperature considerations. Generally, an engraved calendering roll with at least 30% bonding area is needed when the blends of cotton and polypropylene fibrous web are bonded. The unbleached cotton cannot be effectively bonded in the typical low-melt synthetic fibre blends due to the natural waxes, on raw fibres, which interfere with the adhesion expected of thermal bonding [4], [5]. The proportion of cotton in the cotton-surfaced and cotton-core products, for nonwoven composites, can be adjusted to meet consumer needs and improve durability and usefulness of products developed by this method [6], [7]. The cotton characteristics need in nonwoven products to be considered are excellent absorbency and feels comfortable against the skin, good strength both wet and dry, and moderate dimensional stability and elastic recovery. The cotton nonwoven advantages are: Cotton nonwovens can be recycled, re-used or disposed off by natural degradation conditions;

4 58 Florentina-Flori Costache and Maria Zamfir Cotton is a readily renewable resource with long-term supply assurance; The purity and absorbency of bleached cotton are utilized in growing medical and healthcare applications produced especially by the Spunlacing process. The cotton nonwoven disadvantages are: Bleached cotton fibre for nonwoven application is a relatively new fibre. It is a comparatively expensive fibre. Cotton use is still restricted to specialized applications. This situation is likely to change in the future as the price is further reduced and availability increased. 2. Experiments 2.1. Cellulose Nonwovens Obtained by Thermally Bonding Two experiments to obtain the thermally bonded and needlepunched nonwovens have been carried out. By the 1 st experiment, products based treated cotton by alkaline boiling in mixture with the bi-component polyester/polyethylene fibres of 0.44 tex finesse, 110ºC value of transition temperature, have been obtained by carding and thermally processes [6], [7], [8], [9]. The characteristics of raw cotton are: dtex finesse, 30 mm length, 11.9% short fibres, 554 neps, and 0.90 maturity degree. Table 2 presents the variants obtained by raw materials. The variants 1, 2 and 3 were bonded by thermally calendering at N/cm 2 pressure and 15 m/min speed, and the variants 4, 5 and 6 bonded by through oven heating. Table 2 Variants of Products by Component Fibre Types Var. Raw materials Basic weight [g/m 2 ] Density, [kg/m 3 ] 1 50% raw cotton + 50% PET/PE % raw cotton + 30% PET/PE % treated cotton + 30% PET/PE % treated cotton + 50% PET/PE % raw cotton + 30% PET/PE % treated cotton + 30% PET/PE Generally, an engraved calendering roll with at least 30% bonding area is needed. Increasing the cotton content of thermal bonded fabrics decreases the number of bonding points, therefore reducing the fabric strength. The breaking force is between 2.15 dan and 4.73 dan for variants 1, 2 and 3. No tensional characteristics were determined for 4, 5 and 6 variants because they are bulky structures due to the bonding process. For comparing, two other Dan-Web product types, with and without super-absorbent polymer powder having the pulp fibres as main component have been evaluated and data are presented in Table 3. The Dan-Web company is a through air-forming pulp web equipment type manufacturer [1].

5 Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 1, Table 3 Dan-Web Product Types as Example Characteristic Variant A Variant B Fibre content 15.7% PET 62.9% fluff pulp fibre 21.4% superabsorbent polymer 15.7% PET 84.3% fluff pulp fibre Surface weight, [g/m 2 ] Breaking force, N/50 mm: MD direction CD direction Salted 0.9% water absorption capacity, [g/g] Absorption capacity under pressure of 10 g/cm 2, [g/g] From Table 3 is resulting that the variants of Dan-Web products with fluff pulp fibre content have the breaking resistance less than of the products obtained by the experiments presented in this research. The variation of liquid absorption height by time is presented in the Fig. 1, and the variation of liquid absorption speed by time is presented in the Fig. 2. It is resulting that the variants with treated cotton have higher values for liquid absorption height and speed. The percent of bi-component fibres are influencing the tensional characteristics. The variant 3 with 70% treated cotton and 30% bi-component fibres, was selected because of its absorbency characteristics. 1,2000 h [cm] 5,00 4,50 4,00 3,50 3,00 t1=3min t2=6min t3=9min t4=12min V [cm/min] 1,0000 0,8000 0,6000 t4=12min t3=9min t2=6min t1=3min 2,50 2,00 t [min] 0,4000 1,50 1,00 0,50 0, A t4=12min t3=9min t2=6min t1=3min B nr variantă 0,2000 0, A B t1=3min t2=6min t3=9min t4=12min nr variantă t [min] Fig. 1 The absorption height by time. Fig. 2 The absorption speed by time Cellulose Nonwovens Obtained by Needlepunching Bonding Process The raw materials for the 2 nd experiment have been the following: Cotton fibres of 23.8 mm the medium length, treated by alkaline boiling process and blenching alkaline boiling process. Pulp fibres to diversify and to obtain composite structures with high absorption capacity, low cost and bulky size.

6 60 Florentina-Flori Costache and Maria Zamfir Woven gauze made from cotton to encapsulate the absorbent cotton nonwovens to increase the consumer s confidence. The medical nonwoven products have been obtained as simple and as composite nonwoven structures. To increase the absorption capacity, the degree of white, and the purity, the cotton fibres must be cleaned-up by alkaline boiling including bleaching by a continuously process or in autoclave. By alkaline boiling process and simultaneously bleaching process, the cotton fibres result in 100% purely cellulose state. The process of alkaline boiling including the bleaching was done by including in recipe the hydroxide of sodium NaOH, peroxide (H 2 O 2 ), stabilizer for peroxide, as well a warmly and cold washing. The nonwovens were produced using carding-lapping and needlepunching, pulp fibres being added to the web. For needlepunching process, the 15 x 16 x 36 x 3 ½ R221 G Groz-Beckert needle have been chosen to needlepunch the fibrous webs [11]. The characteristic considered to be evaluated is the capacity of liquids absorption. It must be mentioned that the classical woven gauze has an absorption capacity around 800%. The absorbent product characteristics are presented in Table 4. Table 4 The Characteristics of the Needlepunched Absorbent Products Characteristic Product / Value II-C * II-D ** II-E *** Average surface weight, [g/m 2 ] Thickness, mm Apparently density, [kg/m 3 ] Absorption capacity of liquid - water, [%] Strength & compactness in wet state Low Very high Very high * raw cotton; ** alkaline boiled cotton; *** bleached alkaline boiled cotton. Variants of absorbent sponges, obtained by encapsulating into woven gauzes or by including the pulp fibres and then encapsulating into woven gauzes, are presented in Table 5. It may be noticed that the average surface weight of products is adaptable to beneficiary requirements. The obtained nonwoven products prove an instantaneously sinking capacity into liquid, sufficient softness and enough pleasing touch to be used as absorbent products into contact with body skin or even a wound.

7 Bul. Inst. Polit. Iaşi, t. LVI (LX), f. 1, Table 5 The Characteristics of the Absorbent Product Variants Characteristic Product & Value II-D1 II-D-p II-E1 II-E-p Average surface weight, [g/m 2 ] Thickness, [mm] Absorption capacity (water), [%] Strength & compactness in wet state Very high Very high Very high Very high II-D1 alkaline boiled cotton product & encapsulated into woven gauze; II-D-p alkaline boiled cotton product including pulp fibres by a simple stratification, and encapsulated into woven gauze; II-E1 leached alkaline boiled cotton product and encapsulated into woven gauze; II-E-p bleached alkaline boiled cotton product including pulp fibres by a simple stratification, and encapsulated into woven gauze. 3. Conclusions The points to be considered in the production of absorbent sponges are: The changing in cotton fibre characteristics by ecological treatments of alkaline boiling / bleaching alkaline boiling. For cotton medical nonwovens, the treatments definitely are contributing to the increasing of absorption capacity performances. All treatments and processes must be set-up to ensure minimum damages on cotton fibres in terms of surface changes and its processability. The addition of pulp fibres into nonwoven structures for medical products increases the absorbency characteristics. The treated cotton nonwovens encapsulated into the woven gauze are also increasing the confidence of the medical staff and/or patients to be usefully for medical sector. The obtained thermally bonded nonwovens can be considered environmentally safe due to their high content of cellulose fibres as well as the short duration and low power required for thermal bonding. The products obtained in this research can be also considered environmentally safe because of their high biodegradability. The high absorbent nonwoven medical products can be used in emergency cases or any disaster. Received: September 22, 2009 * Anghel Saligny College of Roşiorii de Vede costache_florentina_flori@yahoo.com ** Gheorghe Asachi Technical University of Iaşi, Department of Technology and Design of Textile Products mzamfi@tex.tuiasi.ro

8 62 Florentina-Flori Costache and Maria Zamfir R E F E R E N C E S 1. * * * Dan-Web Company prospectus, Holland. 2. * * * Guide to Fibres for Nonwovens. Nonwovens Industry, June, 1996, Allen H.Ch., Cotton in Absorbent Cores. Nonwovens World, August-September, * * * A Guide to Fibres for Nonwovens. Nonwoven Industry, June, * * * Natural Cotton Fibre. Nonwoven Industry, January, 1999, McLean E.C., Wadsworth L.C., Christine (Qin) Sun C.Q., Zhang D., Shaker G., Development of Highly Absorbent Cotton-Core Nonwovens. INTC 2001 Nonwovens Conference, Baltimore, September 5-7, McLean E.C., Wadsworth L.C., Gosavi N., Cotton Core Nonwovens. Nonwovens World A Journal for Management, Vol. 10, 5, 2001, Sun Q., Zhang D., Wadsworth L.C., Allen Jr. H.C., Processing and Properties of Stretchable Cotton-Surfaced Nonwovens. Book of Papers, INDA-Tec 99, , Atlanta, GA, September 21-23, Wadsworth L.C., Suh H.S., Cotton-Surfaced Nonwovens for Short-Wear-Cycle Apparel. International Nonwovens Journal, 9, 2, 13 17, Zamfir M., Textile neńesute Textile funcńionale. Edit. Performantica, Iaşi, Zamfir M., Van Langenhove L., Kiekens P., Textile tehnice din materiale neńesute interńesute. Edit. Cermi, Iaşi, TEXTILE NEłESUTE ECOLOGICE PENTRU APLICAłII TEHNICE (Rezumat) Lucrarea prezintă cercetări privind realizarea unor structuri textile neńesute pentru aplicańii tehnice, cu o capacitate mare de absorpńie a lichidelor, utilizate chiar şi pentru cazuri de urgenńă când o astfel de proprietate este o cerinńă prioritară, de exemplu produse medicale. Textilele neńesute obńinute din materii prime sub formă de fibre biodegradabile sunt evaluate din punct de vedere al caracteristicilor funcńionale.