WO2018004478A1

WO2018004478A1 - An improved method of soft nonwoven fabric production

Info

Publication number: WO2018004478A1
Application number: PCT/TR2016/050202
Authority: WO
Inventors: Mehmet Fatih ERGÜNEY; Sebnem KEMALOGLU DOGAN; Eylem CANBOLAT
Original assignee: Hayat Kimya San. A. Ş.
Priority date: 2016-06-29
Filing date: 2016-06-29
Publication date: 2018-01-04

Abstract

A method is provided to produce a nonwoven fabric with improved softness and tensile strength. The present invention relates to a nonwoven fabric comprising polypropylene based polymer mixture and glycerol monostearate as an additive that helps to transfer heat applied on the nonwoven surface. The present invention further relates to a method of web bonding under decreased temperature and pressure to obtain nonwoven products having improved softness, pilling resistance and tensile strength.

Description

AN IMPROVED METHOD OF SOFT NONWOVEN FABRIC PRODUCTION

TECHNICAL FIELD

The present invention relates to a nonwoven fabric, having improved softness.

The present invention relates to a process to produce a nonwoven fabric having improved softness.

The present invention further relates to the composition of a nonwoven fabric.

The present invention relates to the embossment of a nonwoven fabric. BACKGROUND ART

Nonwoven webs or fabrics are one of the oldest and simplest textile fabrics that are desirable for use in a variety of products such as garments, disposable diapers, and other personal hygiene products, including wet wipes. Nonwoven webs having high level of strength, softness, and abrasion resistance are desirable for disposable absorbent products, such as diapers, incontinence pads, training pants, feminine hygiene products, and the like. Especially, in a disposable diaper, it is highly desirable to have soft, strong, nonwoven components, such as topsheets or backsheets. Topsheets as, body- contacting portion of a diaper which makes softness highly beneficial. Backsheets benefit from the appearance of being cloth-like, and softness adds to the cloth- like perception consumers prefer. But in the conditions preferred to obtain softer surfaces there can be pilling as small bundles of fibers on the surface of the nonwoven web. Pilling can result highly undesirable conditions for consumers using disposable absorbent articles. Especially for disposable diapers, babies can swallow those bundles of fibers. The present invention aims to produce nonwoven fabrics having improved softness besides, resistant to pilling and improved mechanical strength.

Nonwoven fabrics can be produced by a variety of known processes other than weaving or knitting. The nonwoven fabric properties depend on following aspects to a great extent,

- The nature of fibers

- Technology which determines how the fibers are to be arranged

- The bonding process and the bonding agents Emboss roll conditions that applied on web surface for thermal bonding and embossing

Fabric properties of nonwovens range from crisp to soft touch, impossible to tear to extremely weak.

The softness of a nonwoven web is an important factor in applications, such as disposable diapers, in which a nonwoven web is in contact with a wearer for an extended period of time. Various methods of increasing the softness of a nonwoven web are known in the art. These methods include wash softening, mechanical stretching, and topical treatment of the web with softening chemicals.

The technique of wash softening of the nonwoven web is time consuming, and does not fit to the requirements of industrial production. Additionally, large volumes of water from the washing process must be handled, either by recycling or disposal.

Softness can be improved by mechanically post treating a nonwoven. For example, by incrementally stretching the nonwoven web can be made soft and extensible, while retaining sufficient strength for use in disposable absorbent articles. However, if is believed that such mechanical methods would negatively affect the pilling resistance.

Besides, mechanical softening alone by stretching does not provide the degree of softness being favorable for some applications. Topical treatments alone also do not provide the degree of softness proper for some applications and have manufacturing constraints in addition.

In current technology it is possible to produce soft touch nonwoven fabrics by another method such as, following bico technology by using polyethylene coating on polypropylene web or by using large weight of webs. But this method is very expensive and involves time consuming process. Additionally the process is not recycle able because of mixing two or more different kinds of polymers such as polypropylene and polyethylene. These kinds of fabrics are obtained at higher weight to not to lose mechanical performance while getting softer surfaces that makes them very expensive. During this process pilling occurs on the surface of nonwoven fabric which is caused by used polyethylene for coating the polypropylene core to obtain softer surfaces as an unwanted result. Bond patterns have also been utilized to improve strength and pilling resistance in nonwovens while maintaining or even improving softness. Various bond patterns have been developed to achieve improved abrasion resistance without too negatively affecting softness.

By increasing the size of the bond sites; or by decreasing the distance between bond sites, more fibers are bonded, and pilling resistance can be increased. However, the corresponding increase in bond area of the nonwoven also increases the rigidity of the nonwoven which increases the stiffness whereas the softness decreases.

In the prior art, there exist trials to obtain softer nonwoven products. But these trials have ended with decreased mechanical resistant. Among these processes different additives were used in the masterbatch to obtain nonwoven fabrics with specified features. US6740609 discloses a melt extruded nonwoven fabric in which the polypropylene fibers are incorporating fatty acid amides that improves the softness of the fabric. Stearamide and erucamide is used in the masterbatch in specified amounts for this purpose as well. But said process did not lead to an improvement. Considering the used additives the process is not economically feasible.

WO2004005601 discloses a method for producing softer fiber which comprises thermoplastic polymer and additives such as; olefinic elastomers or amides. Glycerol monostearate is used in this process as an antistatic agent. There still exists a need of obtaining softer nonwoven products without losing the strength of nonwoven fabrics under cost consideration of production.

SUMMARY OF INVENTION

The present invention overcomes said problems. In the present invention mechanically and physically improved nonwoven fabrics are produced. Softer surfaces are obtained without losing strength of the nonwoven fabric by bonding fibers together with emboss roll calendar (18) that is set in decreased temperatures comparing to known techniques. The present invention provides an improved process for producing soft nonwoven webs formed by a mixture of a thermoplastic polymer and additives selected from heat transfer agents such as; glycerol monostearate. The present invention provides a method of obtaining soft nonwoven fabric formed of continuous thermoplastic filaments. Particulary polymer based masterbatch including glycerol monostearate as heat transfer agents provided. According to the present invention the fiber filaments are thermally bonded together by using embossing roll calender (18) having reduced application temperature that is providing softness, bulk and improved strength while retaining other properties such as strength and pilling resistance.

In the present invention, said embossing roll calender (18) have specified structure of engravings. These structures of calender engravings can be round, oval, oblong, eklips, polygonal or angular shaped.

The materials of the invention can be used for disposable products such as diapers, sanitary napkins or any kinds of hygiene products.

The present invention relates to a method of using embossing roll calenders (18) having reduced temperatures. With the improved method, there is provided a nonwoven fabric with improved softness and tensile strength.

The process steps of the present invention comprises;

- extruding (8) polymer and additives as masterbatch,

- spinning of fibers,

- web formation (16) and

- thermo bonding of fiber filaments by emboss roll calenders (18) having reduced application temperature. The selection of raw material which is used in formation of nonwoven fibers affects the performance of web structures. Many kinds of polymers have been known are used as fiber forming materials in the prior art.

It has also been known that, some physical and mechanical properties of nonwoven fabrics can be improved by embossing the web hereby deforming the web structure. Applying best method with suitable raw material is the critical goal of obtaining soft and strong webs without pilling. Furthermore, cost effectiveness must be considered as an important factor of manufacturing process. Obtaining the best nonwoven product having enhanced softness and strength can cause high production costs.

Nonwoven fabrics, typified by spunbond or melt blown nonwoven fabrics are usually partially thermobonded via an embossing roll (18) in order to prevent the falling-off of fibers which form the nonwoven fabric and by this way to improve the strength of the fabric.

In the present invention spun bonded or melt blown webs are bonded by thermal bonding with application of embossing roll calender (18) having reduced temperatures in contrast with the known technologies. Emboss roll calendar (18) is a thermal bonding calender that has specific design pattern to get embossed patterns on nonwoven web to obtain nonwoven fabric.

In the present invention themoplastic polymer structures are used with glycerol monostearate as an additive having high heat transfer feature that help to transmit heat in deeper points of nonwoven structure in a short time period.

In the present invention glycerol monostearate is used as an additive to transfer heat into deeper points during the thermal calendering process that will help to obtain soft nonwoven products having strong mechanical and physical properties. In the present invention there are embossed portions that are responsible of improving mechanical and pilling resistance properties of nonwoven fabric.

Embossed portions depth on nonwoven fabric is directly related with the mechanical performance of the fabric. If the fiber filaments are bonded together with high temperatures the applied heat goes deeper and the width of the embossed portions increases which will end as strong nonwoven fabric structures. On the contrary, applying high temperature on nonwoven surface dicreases softness of fabric that is an unwanted phenomena by users. Usually the application ends with the products deformed in several parts of them. In the present invention by using glycerol monostearate, applied heat to bond fibers is decreased, but it is transmitted to deeper points of the nonwoven surface by heat transfer agent. As a result of the application, two important improvement is observed;

1- The softness of nonwoven surface is increased, because of applying decreased amount of heat,

2- The mechanical performance of the nonwoven is increased by strong bonding of the fibers despite of applying decreased amount of heat. With the help of the heat transfer agent, heat applied on the surface could proceed in deeper points of nonwoven and there exists no need to apply high pressures on web. By this way; soft and strong webs are obtained without deforming the web structure.

In the present invention there are non-embossed portions that are responsible of improved softness of nonwoven fabric. In the present invention an emboss roll thermobonding calendar (18) is used to bond fibers to form nonwoven fabric. Said emboss roll calendar (18) has reduced temperatures in contrast with the calender temperatures used in known techniques.

In known techniques polyethylene coating can be applied on polypropylene webs to obtain improved softness but it causes pilling and lack of strength, so there can be a need of using high weight fibers. Nonwoven fabrics in which polypropylene is used as fiber former prevents pilling of fibers comparing to polyethylene coated fibers.

In the present invention, using thermobonded polypropylene fiber with an embossing roll calender (18) under reduced temperatures allows obtaining nonwoven fabrics having superior softness properties in comparison to other nonwoven fabrics bonded under high temperature embossing roll calenders (18). Furthermore, it is seen that, the strength of nonwoven fabric is increased and the pilling resistance is maintained. BRIEF DESCRIPTION OF DRAWINGS

FIG. 1. Scheme of bonding process of fibers with emboss roll calendar (18)

FIG. 2. Embossed nonwoven fabric structure that is used in Example 1 and Comparative

Example 1

FIG. 3. Embossed nonwoven fabric structure that is used in Example 2 and Comparative Example 2 FIG. 4. Embossed nonwoven fabric structure that is used in Example 3 and Comparative Example 3.

Wherein;

2. Polymer Addition

4. Additive Addition

6. Polymer Feed

8. Extruder

10. Quenching

12. Drawing

14. Conveyor Belt

16. Web Formation

18. Emboss Roll Calenders

20. Winding

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention relates to method of production of nonwoven fabric comprising thermoplastic polymer based fibers and glycerol monostearate as heat transfer agent. In the present invention method, decreased amount of heat is applied to bond fibers with the help of good heat transfer feature of glycerol monostearate.

The present invention provides improvements in continuous fibers bonded thermoplastic webs, concerning softness of the nonwoven product by decreasing the amount of heat applied in bonding process.

The term of nonwoven fabric states that in the present invention, fibers are held together by a process of bonding to form a fabric.

Fiber refers to structures which are used to form nonwoven fabric.

Fabric refers to web of fibers, that is finished by embossing with bonding techniques such as hot calendering.

The application temperature refers to the temperature of the calendar roll by touching on the nonwoven web surface. Emboss roll application temperature refers to the calender temperature that is applied directly on nonwoven web surface. The nonwoven fabric properties depend on different criteria such as; type of fiber that is used as raw material, the technology to arrange the fibers, bonding processes that allow holding fibers together, emboss structure of pattern that is applied on nonwoven web structure with the help of heat and pressure. Choosing the right fiber to process the fabric is one of the most important parts of nonwoven manufacturing. Cost effectiveness, easy to use and process according to special properties of the fiber, and further processing are taken into consideration.

Non-limiting examples of polymer materials suitable for forming nonwoven fiber such as; rayon, nylon, wool or cotton can be used as natural fabrics and polyesters or acrylics can be used as synthetic fibers. Especially synthetic fibers such as polypropylene, polyethylene, polyester, or polyurethane are used for cheaper, ease of processing conditions and for new and more exacting applications. Nonwoven webs can be produced by different methods of production such as; wet bonded, dry bonded, filament formation spun bonded, or melt blown techniques.

In the present invention; using one method or combination of different methods are also possible in production of multi layer nonwoven webs such as; SSS, SMS, SM MS or SSMS but the most preferred method is by production of SSS process, whereby S for spunbond and M for melt blown layer stands.

Nonwoven webs that are produced by different known methods can be bonded by using different techniques of bonding process and the bonding agents to avoid falling off the fibers and holding them together. Non-limiting examples can be applied on bonding of web such as; mechanical bonding, chemical bonding or thermal bonding.

In the present invention various bonding techniques can be applied but the most preferred bonding technique is thermal bonding by applying heat and pressure with hot calenders. In this way, using decorative emboss rolls area bonding, point bonding or embossing can be performed. Especially continuous filament webs are bonded by thermal bonding using hot calendering emboss roll. There are important criterias that affect the strength and softness of nonwoven web structures. The important parameters are calender pattern, temperature and pressure of rollers that are related with emboss roll.

Embossing nonwoven web structure is one of the other critical goal for evaluating performance of nonwoven fabric.

Embossing process is the final step in nonwoven fabric production process since it enables to produce a product which is soft, aesthetically decorated and high in bulk. Depending on the emboss roll calendar (18) temperature and pressure, the physical and mechanical properties of the nonwoven fabrics are changing.

The spun bond process is widely used to produce nonwoven fabrics. Typical spun bond process components are polymer addition (2), additive addition (4), polymer feed (6), extruder (8), quenching system (10), drawing and deposition system (12), conveyor belt

(14), web formation (16), embossing calenders (18) for bonding and winding (20). In general spun bonded production process requires the steps;

1- Formation of continues filament synthetic fibers,

2- Formation of continues filament webs,

3- Lying the continuous filament webs on conveyor belt (14),

4- Mechanical, chemical or thermal bonding of webs with emboss roll calendar (18) and,

5- Finishing and winding (20).

In the present invention, a melt solution of a fiber forming polymer or a mixture of polymers is extruded through a system requiring spinnerets in a high velocity current of air. Said formed fibers are deposited on to conveyor belt (14) to form a web. The belt than carries the web to a bonding stage where consolidation of web occurs to form nonwoven fabric.

Spun bonded fabrics tend to have low bulk and high strength that allows to be used in many industrial applications. In the present invention, fabrics have strong webs, low elongation and filament diameter in the range of 1 -3 denier and more specifically 1 ,5-2 denier. Small denier is preferred because, homogeny distribution of filaments are required to form web structures which is preferred to be used at top sheet or other water and air pervious layers of hygiene articles.

The melt blown process is one of the widely used processes to produce nonwoven fabrics in which the production steps are in the same manner as spun bonded webs. Extruded polymers pass through the holes in a spinneret into a high velocity current of air.

The difference of melt blown method from spunbond method is an increased force used by the air current which breaks the filaments rather than just drawing them to produce fibers of varying lengths. Melt blown fibers have smaller diameters so that the fiber size is influenced by, process air volume, throughput, temperature, number of holes of spinneret and type of polymer resin. By applying higher process air temperature then melting temperature of the used polymer endless filaments can be obtained by melt blown process.

Melt blown fabrics have, filament diameter in the range of 1 -3 denier, more specifically 1 - 1 ,5 denier. Melt blown filament denier is smaller that allows producing hydrophobic and liquid and air impervious web structure. Such materials are preferably used at back sheet or cuffs of diapers or hygiene articles.

Thermal bonding, in which the fibers bond together when heated under pressure, subjected to heat a bonding agent and pressure.

The processing steps of thermal bonding succeeds in the present invention as below;

- Heating up of the laid down fibers formed as web structure,

- Welding of the webs into very small film spots, by applying decreased temperature and pressure of the rolls,

Rapid cooling down of the web to avoid neck in and,

- Achievement of uniformly strengthened embossed fabric.

The nonwoven products produced by using spunbond or meltblown processes are used in various applications. Nonwoven products are widely used in medical, hygiene and technical fields such as; medical applications, masks, hygenic products, diapers, incontinence peds, feminine hygiene articles or nappies, bedding, filtration or clothing. Bicomponent multilayer fibers can be used to produce a bonded fabric with one of the components being thepmoplastic to facilitate heat bonding and the other component having property that will enhance the quality of final fabric area density in the process which is controlled by the speed of conveyor belt (14).

If the webs are bonded under high temperature and pressure, the created product is relatively stiff, dense and occasionally deformed which is not wanted to be used in hygiene articles or clothing. There is a need to have softer products which are strong enough.

If the webs are bonded under mild conditions like decreased temperature and pressure; the obtained product is softer, but at that time the mechanical performance or strength of the web can not have the desired performance. The non limiting embodiments are given below to understand the invention clearly;

In one embodiment, a fiber which forms the nonwoven fabric is selected from natural or sythetic fibers; specifically cotton as natural fiber and thermoplastic polymers as synthetic fibers are prefered as raw material, more specifically polypropylene based polymer mixture having 25 to 27 g/10 min melt flow index (MFI) at 230 °C, is selected for the production of nonwoven fabric in the present invention.

In an embodiment the polymer can be used singly or in combination of one or more species. It can include antistatic agent, flame retardant, synthetic oil, coloring inhibitor, lubricant, dye, heat transfer agent, plasticizer or pigment. In the present invention glycerol monostearate in the range of 0,5-5 % can be used as heat transfer agent in polymer masterbatch to decrease the emboss roll application temperature. Specifically, heat transfer agent used in polymer masterbatch is in the range of 1 -3 % and more specifically the used amount of heat transfer agent is around 1 ,5 %.

In another embodiment, any known technology can be applied to form nonwoven fibers, such as wet bonded, dry bonded, spun bonded or melt blown. In the present invention, more specifically spun bonded or melt blown technology is applied to obtain fibers. In a further embodiment, the present invention is specifically including a multi-layer nonwoven fabric, consisting at least three layers which are stacked together with known techniques, wherein each of two outer nonwoven fiber layers of multi-layer nonwoven fabric are formed of a spunbond nonwoven fibers and one middle layer can be formed of a melt blown nonwoven fiber or spun bonded fiber, that can be more specifically spunbond (SSS) formed nonwoven fabric.

In one embodiment, formed spunbond nonwoven fibers have the diameter of fiber forming the nonwoven fabric is in the range of 1 -3 denier by adjusting the line speed in the range of 700 to 750 m/min. When the line speed is more than 750 m/min low weighted webs are obtained and when the speed is less than 700 m/min high weighted webs are obtained which will affect softness negatively and will not be cost effective. The line speed is adjusted to 720 m/min more specifically, that allows obtaining lighter web structures having improved properties.

In the present invention, according to the improved method, decreased temperature and pressure on bonding of fibers are applied. The web structure is not deformed under these mild conditions. Therefore there is no need to form high weighted webs to obtain mechanically strong web structures. In the light of the present invention, formed lighter web structures have improved softness and mechanical strength properties. In a further embodiment, nonwoven fibers can be bonded with methods of thermal bonding, mechanical or chemical bonding. In the present invention, fibers are more specifically thermally bonded by adjusting the temperature and pressure during embossing. The applied temperature on the web is in the range of 100-180 °C and more preferably it is in the range of 120-150 °C and much more preferably it is in the range of 130-135 °C. The pressure applied by emboss roll on the web structure is in the range of 70-100 N/mm² and more preferably it is in the range of 80-85 N/mm².

In the case where the nonwoven fabric is formed by afore mentioned emboss roll conditions, when the embossing temperature is higher than 180 °C, formed fibers are fused together and impossible to separate.

In the case of the applied embossing pressure is higher than 100 N/ mm² formed web structures can be deformed and have unwanted holes on it, that can not be used efficiently. In a further embodiment a nonwoven fabric has embossed and non embossed portions that creates bonding and nonbonding areas which effect the softness and strength of nonwoven fabric. In a further embodiment, a nonwoven fabric having embossed structures which can be in the range of 10-50 figures/cm² more specifically 15-30 figures/cm². This enhances softness of nonwoven fabric and provides an excellent feel to the touch.

As shown in FIG. 2, 3, and 4 the nonwoven fabric having different embossed patterns used as emboss structures in examples and comparative examples.

[EXAMPLES

Example 1 : Process of preparing nonwoven fabric with the method of the present invention referring to a pattern as shown at FIG. 2

Nonwoven fabric sample bonded with an embossing calender having decreased temperature and pressure having emboss pattern of FIG. 2 is prepared by following the steps;

a) Cylindric granulate polypropylene having 0,90 g/cm³ density is used as raw material in masterbatch.

b) Glycerol monostearate in amount of 1 ,5 % by weight is added in the polypropylene based polymer masterbatch,

c) Prepared polymer mixture in step a and b, is melted and extruded in the line of extruder (8).

d) Melt polymer is sent to spinnerets to form fibers having linear mass density of

1 ,5 denier.

e) Spinned fibers are sent to the conveyor belt (14) to lay down with the help of vacuum air and line speed is set at 720 m/min,

f) Formed webs at step e are bonded with hot embossing calender roll that have the application temperature of 130-135 °C and 80-85 N/mm² pressure.

Comparative Example 1 : Process of preparing nonwoven fabric with the known methods of referring to pattern as shown at FIG. 2 (Lack of heat transfer agent, increased temperature and pressure) Nonwoven fabric sample bonded with a embossing calender having increased temperature and pressure having emboss pattern of FIG. 2 is prepared by following the steps;

a) Cylindrical granulate polypropylene having 0,90 g/cm³ density is used as raw material in masterbatch.

b) Prepared polymer mixture in step a, is melted and extruded in the line of extruder (8).

e) c) Melt polymer is sent to spinnerets to form fibers having linear mass density of 1 ,5 denier.

f) Spinned fibers are sent to the conveyor belt (14) to laydown with the help of vacuum air and line speed is set at 720 m/min,

e) Formed webs at step d are bonded with hot embossing calender roll that have the application temperature of 140-145 °C and 90-95 N/mm² pressure. Example 2: Process of preparing nonwoven fabric with the method of the present invention referring to a pattern as shown at FIG.3

The procedure of Example 1 is repeated to produce nonwoven fabric sample bonded with a embossing calender having decreased temperature and having emboss pattern of FIG. 3

Comparative Example 2: Process of preparing nonwoven fabric with the known methods of referring to pattern as shown at FIG. 3

The procedure of Comparative Example 1 is repeated to obtain nonwoven fabric sample bonded with a embossing calender having increased temperature and pressure having emboss pattern of FIG. 3.

Example 3: Process for preparing nonwoven fabric with the method of the present invention referring to a pattern as shown at FIG.4

The procedure of Example 1 is repeated to produce nonwoven fabric sample bonded with a embossing calender having decreased temperature and pressure and having emboss pattern of FIG. 4 Comparative Example 3: Process for preparing nonwoven fabric with the known methods of referring to pattern as shown at FIG. 4

The procedure of Comparative Example 1 is repeated to obtain nonwoven fabric sample bonded with a embossing calender having increased temperature and pressure having emboss pattern of FIG. 4.

Examples of 1 , 2 and 3 having different emboss structures are obtained by following the method in the present invention. The comparative examples of them are obtained by the method known in the prior art.

The test results and comparements of the test results of examples are shown in Table 1. TEST METHODS EVALUATION OF SOFTNESS

For evaluation of the softness of nonwoven fabric two methods are applied as explained below;

1. Tissue Softness Analyzer (TSA) used as softness measurement equipment.

TSA is generally used for the measurements of paper softness. A new method is applied to observe the softness of nonwoven fabric by using Emtec Tissue Softness Analyzer.

According to TSA measurement, 3 results are observed which are;

surface softness (TS7),

- bulk softness (TS750) and,

overall softness (HF) of fabric layer.

Nonwoven softness analysis is performed by using TSA as following;

1- The nonwoven sample is attached on the clamping ring of TSA equipment and fastened with screws,

2- Measuring head with rotor and engine is put on the sample,

3- Measuring head with ceramic rotor rotates under touching on the surface of the sample and for 45 seconds,

4- The measuring cell measures the force applied on the surface, 5- Obtained softness results are calculated as overall softness and given as a report.

Whereby, 200 mN force is applied on the surface of the nonwoven fabric at 45 seconds and, 3 results are observed as; surface softness (TS7), bulk softness (TS750) and overall softness (HF). HF result is taken as overall softness which is calculated by the software, by using the results of TS7 and TS750.

5 single measurements of the same sample are performed successively and the average of the measurements is taken as the final result.

2. Improved softness felt by hand feel observation.

It is a feel to the touch measurement depending on hand feel as a subjective measurement. According to this measurement the surface softness is graded on the following criteria;

1 point: limited amount of softness feeling

2 points: feeling of improved softness

3 points: recognizable feeling of softness

4 points: very good softness feeling

ASSESSMENT OF SOFTNESS TEST RESULTS

According to obtained results of TSA and hand feel observations shown at table 1 ;

It can be seen that the softness value of example 1 , having emboss structure of FIG. 2, is greater than comparative example 1.

It can be seen that the softness value of example 2, having emboss structure of FIG. 3, is greater than comparative example 2. It can be seen that the softness value of example 3, having emboss structure of FIG. 4, is greater than comparative example 3.

Comparing the results of the overall softness value of example 1 (103,4) is greater than comparative example 1 (102,1 ); the overall softness value of example 2 (103,2) is greater than comparative example 2 (101 ,7) and; the overall softness value of example 3 (101 ,8) is greater than comparative example 3 (101 ,2).

It can be seen that, the web structures of example 1 , 2 and 3 that are produced by the improved method of the invention and having different emboss designs have better softness values than comparative examples that are produced under increased temperature and pressure as known method in the prior art.

It has been shown that, the improved method in the present invention can be used in different emboss structures and ends up with high softness and strength results.

The softness results of hand feel observations are also supporting TSA softness test results. Comparing the result of example 1 , 2 and 3 with the comparative examples of 1 , 2 and 3 it can be seen that, examples 1 , 2 and 3 have very good softness which has the softness value of 4. However comparative examples 1 , 2 and 3 have recognizable feeling of softness has the softness value of 3. It can be said that the best overall softness is observed in example 1 product produced with the method of invention.

EVALUATION OF PILLING RESISTANCE

Martindale pilling test equipment is used to measure the pilling resistance of nonwoven samples. The equipment is calibrated under IS012947 standard. The equipment has two parts of standard felts that are upper and lower felts. Measurement conditions are followed by using IS0139 standards. According to standards the place that is used to measure the pilling resistance of the samples is set at 20(±2)°C and %65(±2) humidity. The test is performed under TS EN ISO 12945 standards.

For the measurement of the pilling resistance of nonwoven the following procedure is applied;

1- Nonwoven sample is prepared with 140 (±5) mm diameter,

2- The nonwoven sample is attached on the upper felt, that has 90 mm diameter,

3- Nonwoven sample is prepared with 190 (±5) mm diameter, 4- The nonwoven sample is attached on the lower felt, that has 140 mm diameter,

5- The lower felt is closed on the upper felt,

6- The upper and lower felts are rubbed 1000 times against each other,

7 3 single measurements are applied for each sample and average of them is taken as the result,

8 The test sample results and the samples which are not tested under pilling equipment are compared with each other.

To evaluate the test results of the pilling resistance of nonwoven fabric visual observation is applied.

According to this measurement the surface pilling is graded on the following criteria;

1 point: there is no pilling

2 points: small amount of pilling started to form

3 points: recognizable pilling started to form

4 points: fibers are considerably turned off

5 points: fibers are totally turned off ASSESSMENT OF PILLING RESISTANCE TEST RESULTS

According to pilling resistance test results of nonwoven fabrics with different embossing designs as shown at table 1 ; it can be seen that the best results are observed from example 1 , 2 and 3 products which are produced with the method of the present invention. Example 1 , 2 and 3 have superior pilling resistance properties compared to comparative examples 1 , 2 and 3.

By application of pilling test process on the surface of example 1 product, no pilling is observed. By comparative example 1 product, it is seen that recognizable pilling has started to form.

Example 2 product is compared with comparative example 2 product and it is observed that, the pilling resistance of example 2 is better than comparative example 2 again. Example 3 product has recognizable pilling resistance than comparative example 3 product again. The results show that, by example 3 product small amount of pilling has started but in comparative example 3, the fibers are considerably turned off. It can be said that, the best resistance of pilling is observed with the product of example 1.

EVALUATION OF STRENGTH

Tensile measurement test is applied by using Zwick strength equipment to evaluate the strength of nonwoven samples.

Tensile measurements at maximum force (N/5 cm) are measured with test stripe having 50mm x 250 mm dimensions, 100 mm clamp distance and 100 mm/min testing speed. The results are shown as average values of four single measurements.

The test is performed under ASTM D882-10 standard as;

1- Nonwoven test sample is prepared having 50 mm of machine direction (MD) and 250 mm of cross machine direction (CD),

9- The upper and lower parts of the sample is attached to the draw part of the machine and,

10- Tensile strength (F_max ) of the sample is measured.

ASSESSMENT OF TENSILE STRENGTH TEST RESULTS

According to tensile strength test results of both in the machine direction (M D) and in the cross machine direction (CD) as shown at Table 1 , it is seen that, M D and CD tensile strength values of examples 1 , 2 and 3 products are superior to comparative example 1 , 2 and 3 product's values. The most significant changes can be seen in examples 1 and 2.

When the result of example 1 product is compared with the comparative example 1 product; it can be said that a recognizable increase in MD and CD strength is observed. MD tensile strength of example 1 product is 31 ,9, and CD tensile strength is 16,7. In contrast, MD tensile strength of comparative example 1 product is 26,0 and CD tensile strength is 12,0. It has a positive effect on mechanical properties of nonwoven fabric used in industrial applications.

By comparing the results of example 2 product with the comparative example 2 product; a recognizable increase in M D and CD strength can be seen. M D tensile strength of example 2 product is 35,5, and CD tensile strength is 18,8. In contrast, MD tensile strength of comparative example 2 product is 25,7 and CD tensile strength is 1 1 ,7.

Comparing the M D and CD tensile strength test results of example 3 product with comparative example 3 product, it is seen that the MD strength of example 3 product is 26,7 and CD strength is 13,4 wherein MD strength of comparative example 3 product is 25,1 and CD strength of it is 12,0. There is a slight increase in tensile strength of example 3 product. As a result by improving softness and pilling resistance of the nonwoven, strength of the nonwoven fabric is also improved this has considerable effect on the nonwoven fabric.

As a result of the present invention, the polypropylene spun bonded nonwoven fabric, having light weight is exhibiting excellent feeling to the touch and high softness. Additionally it is observed that the nonwoven fabric of the present invention shows the best resistance to pilling and it has also improved mechanical strength comparing to the products produced with known methods.

The nonwoven fabrics produced with the method of invention are particularly employed as a material for hygiene products such as diapers, femcare products or nappies as a part of top sheet, back sheet, panels, cuff, waist parts or ears of baby diapers, adult diapers, incontinence diapers, pant like diapers or feminine hygiene article ears.

It can be seen that, the method of invention can be applied on web bondings having different emboss structures. According to the test results, shown in table 1 , examples 1 , 2 and 3 having different emboss structures have improved properties.

Following table 1 is showing the specific properties of nonwoven fabrics have different embossed patterns, production conditions of nonwoven fabrics and the test results of different embossed patterns shown in examples. TABLE 1

Test Results of Examples and Comparative Examples

Claims

1- A method of producing a nonwoven fabric having improved softness, comprising polymer filaments and polymer based carrier filaments incorporating glycerol monostearate as heat transfer agent in an amount of at least % 0,5, is characterized in that;

said filaments are bonded by thermal heat transfer with embossing roll calender (18) wherein the applied temperature of the embossing roll on nonwoven surface is between 100-180 °C and, applied pressure of the embossing roll on nonwoven surface is between 70-100 N/ mm².

2- A method of producing a nonwoven fabric according to claim 1 , wherein said polymer filaments and polymer based carrier filaments comprise thermoplastic polymer, preferably polypropylene, polyethylene or mixtures thereof.

3- A method of producing a nonwoven fabric according to claim 1 , wherein said polymer based carrier filament incorporate glycerol monostearate as heat transfer agent, in the range of 0,5- 5%, preferably in the range of 1 - 3%, and more preferably around 1 ,5% by weight.

4- A method of producing a nonwoven fabric according to claim 1 , wherein the temperature of the embossing roll calender applied on nonwoven surface to bond the filaments is between 120-150 °C and more preferably between 130-135 °C.

5- A method of producing a nonwoven fabric according to claim 1 , wherein the pressure of embossing roll calender applied on nonwoven surface to bond the filaments is between 70-100 N/ mm² preferably, 80-85 N/ mm².

6- A method of producing a nonwoven fabric according to preceding claims, wherein said emboss roll calender (18) engravings can be round, oval, oblong, eklips, polygonal or angular shaped.

7- A method of producing a nonwoven fabric according to preceding claims, wherein said nonwoven fabric comprise at least three layers of filaments which are stacked together, wherein each of two outer nonwoven fabric layers are spunbond nonwoven layers. 8- A method of producing a nonwoven fabric according to claim 7, wherein said spunbond nonwoven fabric has the diameter of fiber filament in the range of 1 -3 denier.

9- A method of producing a nonwoven fabric according to claim 1 , comprising the steps;

a) addition of glycerol monostearate in an amount of 1 ,5 % in the masterbatch of polypropylene based polymer mixture,

b) extrusion of the mixture polymer to melt,

c) spinning the melt polymer filaments through 1 ,5 denier diameter spinnerets, d) cooling the filaments,

e) stretching the filaments through conveyor belt (14) and lay down with air and vacuum,

f) formation of nonwoven webs,

g) thermal bonding of webs with embossing roll calendar at 130 °C and 80 N/ mm² pressure on the nonwoven web surface,

h) finishing and winding (20) the nonwoven fabric.

10- A method of producing nonwoven fabric according to preceding claims, wherein the formed nonwoven fabric can be used in hygiene products such as diapers, femcare products, nappies, adult diapers, incontinence diapers, pant like diapers and feminine hygiene article; as a part of top sheet, back sheet, panels, cuff, waist parts or ears.