The present invention concerns cellulosic fibres with hydrophobic properties showing more softness and bulk and a process for production thereof.

Cellulosic Man Made Fibres are known for their hydrophilic, water absorbing attributes. In contrast synthetic fibres such as polyester, polyethylene and polypropylene are inherently hydrophobic which means that they do not absorb water into their interior structure.

Some natural grown fibres like cotton possess natural waxes which protect the plants in nature and make the raw fibre hydrophobic. Usually these waxes are removed to achieve an absorbent, soft cotton fibre for textile and nonwoven processing.

Cellulosic fibres of the viscose type and modal type are produced according to the viscose process. Such fibres have been given the generic names, Viscose and Modal by BISFA (The International Bureau for the Standardisation of man made Fibres)

In recent years the "amine-oxide-process" or "Lyocell process" has been established as an alternative to the viscose process, wherein cellulose, without forming a derivative, is dissolved in an organic solvent of an amine-oxide, in particular N-Methylmorpholine-N-oxide (NMMO). Cellulosic fibres produced from such solutions are called "solvent-spun" fibres and have been given the generic name Lyocell by BISFA (The International Bureau for the Standardisation of man made Fibres).

Other man-made cellulose fibres can be made using chemical processes (e.g. the cuproammonium process) or using other direct solvents such as ionic liquids.

For hygiene applications, synthetic fibres such as polyester are widely used as they enhance bulk, opacity and softness in nonwoven and textile applications.

For ecological reasons, cellulosic fibres and especially man-made cellulosic fibres continue to gain importance as they are made from a renewable raw material and are biodegradable. As a result, there is a growing demand for cellulosic fibres which are soft, hydrophobic, give higher bulkiness and are biodegradable.

The object of the invention is to provide hydrophobic cellulose fibres which are biodegradable and water repellent. Said fibres are extra soft and show higher bulk in nonwoven fabrics. Said object is achieved by means of a cellulosic fibre comprising a hydrophobic surface agent and the fibre is characterised in that the softness of the fibre according to the sledge test is at least 1.3 times higher than the softness of a cellulosic man-made fibre of an untreated fibre of the same type.

The cellulosic fibres can be natural grown like cotton, or be a man-made cellulosic fibre, such as viscose, modal or lyocell.

The cellulosic man-made fibres can also

a) be physically modified for example, in shape (triloba!, multilobal) or length (flock, short cut to continuous filament)

b) have incorporated materials , such as colour pigments, flame retardants, ion

exchange resins, carbon blacks.

c) be chemically modified, for example as is the case with Modal or cross linked fibres.

In the context of the invention, the term "untreated fibre" refers to a fibre where the surface of the fibre is non-modified. In case of a freshly spun fibre, i.e. a never-dried fibre, the surface is non-modified initially. Commercially available fibres usually contain a soft finish which has to be completely removed to get a non-modified surface before the hydrophobic treatment.

The term "same type" means a fibre of the same nature, titer and length.

As hydrophobising agents Alkyl or Alkenyl Ketene Dimer (AKD) is used, which is shown in formula (1) , where R1 and R2 are hydrocarbon groups with between 8 and 40 carbon atoms and which can be both, saturated or unsaturated, straight- chained or branched.

(1) R1-CH =C-CH— R2

O C=0

Formulations which have similar effects are substituted cyclic dicarboxylic acid anhydrides like substituted succinic or glutaric acid anhydrides and similar.

The preferred Alkyl Ketene Dimers are prepared from acid chlorides by e.g. the method described by R. Adams, Org. Reactions Vol. Ill, p 129 John Wiley & Sons Inc. NY 1946 or J.C. Saner; Journal of the American Chemical Society, Vol. 69, p. 2444 (1947). Alkyl Ketene Dimer (AKD) is well known in the paper industry to enhance the water repellence of surfaces e.g. used in food packaging. The use of AKD is known for sizing papers as known from GB 2 252 984 A and EP 0 228 576 B1. The joint use of AKD and ASA (alkyl succinic acid) is described in W099/37859. AKD is usually used at the wet end of the paper machine.

In a process for producing a cellulosic fibre with hydrophobic properties the process is characterised by the steps

a) providing a cellulosic fibre with a non-modified surface

b) treating the cellulosic fibre with a hydrophobic agent

The hydrophobic agent can be applied during man made fibre production - this means after the fibre is already formed and washed but before drying, i.e. never-dried fibres. In this case the surface is non-modified.

If commercial available cellulosic fibres, comprising a finish, are used, this finish has to be removed.

The hydrophobic agents, such as AKD formulations are commercially available (for example Hydrores© compounds sold by Kemira). The most common are formulations with around 5 - 25% of active compound. In the case of the examples, Formulation A is an acidic solution with around 10 - 12% of active material while Formulation B is an acidic emulsion with an active compound of around 20 - 22%.

The cellulosic fibres are preferably treated with the AKD formulation in a concentration range of 0.0001 % to 10 %, preferably of 0.001% to 5 %, and most preferred of 0.001% to 3 % on cellulosic fibre.

The invention is shown by the following examples General procedure

Trials were made using Lenzing Viscose, Lenzing Tencel or Cotton. Table 1 shows the main fibre types which have been used. As hydrophobic agents, an AKD-formulation such as Hydrores® from Kemira was used. The commercial available formulations where diluted with water to get the concentrations shown in the examples: AKD 1 means the AKD solution used for the treatment has been prepared from Formulation A, AKD 2 means the AKD solution used for the treatment has been prepared from Formulation B. Example A Viscose (sample 6)

7g of bone dry viscose fibres, where the soft finish has been removed with alcohol, are soaked in 100ml of an aqueous Hydrores© solution containing 0.07g of AKD (1 % AKD on cellulose) at room temperature (liquor ratio 1 :15). After 30 min stirring, fibres were centrifuged until they had a moisture content of 50%, dried at 70°C in a desiccator's cabinet to a moisture content of 6%. The resulting fibres are bulky, soft and show hydrophobic characteristics.

Example B Viscose (sample 4 and 5)

1 g of viscose fibres from the viscose process before aftertreatment, were pressed to a moisture content of 50% (never dried Viscose) and put into a basin containing an aqueous solution of 100ml Hydrores© containing 0.035g of AKD (0.5 % AKD on cellulose) at room temperature (approximate liquor ratio of1.15) After 30 min stirring, fibres were centrifuged to a moisture content of 50% and dried at 70 °C in a desiccator's cabinet to a moisture content of 6%. The resulting fibres are bulky, soft and show hydrophobic characteristics.

Example C Tencel (sample 12)

7g of bone dry Tencel fibres, where the soft finish has been removed with alcohol, were soaked in 100ml of an aqueous solution of Hydrores© containing 0.07g of AKD (1 % AKD on cellulose) at room temperature (liquor ratio 1 :15). After 30 min stirring, the fibres were centrifuged to a moisture content of 50% and dried at 70 °C in a desiccator's cabinet to a moisture content of 6%. The resulting fibres are bulky, soft and show hydrophobic

characteristics.

Example D Tencel (sample 10 and 1 1 )

1 g of never dried Tencel fibres, taken wet from the lyocell production before aftertreatment were pressed to a moisture content of 50% and soaked in an aqueous solution of Hydrores© containing 0.035g of AKD (0.5% of AKD on cellulose) at room temperature (approximate liquor ratio of 1 :15)). After 30 min stirring, the fibres were centrifuged to a moisture content of 50% and dried at 70°C in a desiccator's cabinet to a moisture content of 6%. The resulting fibres are bulky, soft and show hydrophobic attributes.

Example E Cotton (sample 14 and 5)

7g of bone dry bleached cotton fibres, where any soft finish has been previously removed with alcohol, were soaked in an aqueous solution containing 0.035g of AKD (0.5% of AKD on. cellulose) at room temperature (liquor ratio 1 :15). After 30 min stirring, the fibres were centrifuged to a moisture content of 50% and dried at 70°C in a dessicator overnight. The resulting cotton fibres are water repellent and very soft.

Table 1 shows an overview of the fibre samples according to examples A to E

Table 1 : Overview of Fibre samples

Sledge Test:

The softness of the fibre was determined by the Sledge test which is described in EN 1202 PPS. The key elements of this test are:

5g Fibre samples are collected and carded twice using e.g. MTDA-3 Rotorring equipment. Fibres are conditioned according to EDANA instructions (ERT 60.2-99) for at least 24 hours and cut into pieces using a master plate. The material is put into the test machine and a sledge (carrying a weight of 2000g) is mounted and laid on the sample. The test is started and a measurement of the power required to drag the sledge is taken after 10 seconds.

The softer the fibre surface, the less power is needed to pull the sledge forward. To compare the softness of the various samples, a ratio of the power to drag a treated fibre sample compared to the power to drag either a similar commercial sample or a similar commercial sample with soft finish removed has been calculated. For example, in table 2 it can be seen that the softness of the viscose fibre treated with the hydrophobic agent is 2.23 times higher than the equivalent commercially available product.

Table 2: Sledge Test results on typical commercial fibres

In a second test series, never dried cellulosic fibres have been treated with lower concentrations of AKD (table 3):

Table 3: Sledge Test results at lower concentrations of AKD

The test results show that cellulosic fibres treated even with low levels of the hydrophobic agents have a softness which is around 2 to 2.5 times greater than an untreated, unfinished man made cellulosic fibre and around 1.7 to 2 times greater than the equivalent commercial man made cellulosic fibres. The results in table 4 show that treatment with the hydrophobic agent is equally effective on bright or dull fibres, on fibres with different linear densities and on fibres with multilobal cross sections.

Table 4: Sledge test results on a variety of man made cellulose fibres

In a third test series, the effects of the hydrophobic agents on cotton were evaluated (table 5):

Table 5: Sledge test results on treated cotton

Although commercial bleached cotton with an added soft finish is softer than the natural, unbleached equivalent, this is achieved at the expense of losing its hydrophobic character. The use of the hydrophobic agents, allow this hydrophobic attribute to be maintained while also producing a fibre which is 1.4 times softer than the naturally occurring product and similar to the bleached and finished commercial product.

The material can be processed with all state of the art nonwoven techniques, including for example, needle punching, spunlacing and air laying. Conventional textile processing routes are also possible.

The inventive fibre can be use in different applications, especially in nonwovens, for example in wipes for biodegradable wipes with high softness and bulk or household wipes with improved static properties,

in tampons, especially for tampon cover stock with high softness and low friction or for string applications

in the medical sector, for example for blood and liquid repellent cover sheets and drapes or gowns and face masks applications,

in the technical sector, for example for car interior, hydrophobic layers in car seats, geo textiles and agricultural textiles, for filtration, particularly for oil, or fat removal, in flock, paint dispersions, and as reinforcement fibres

in textile applications in home textiles, e.g. fillings, padding and beddings, duvets, comforters, pillows, mattresses, single use blankets, in sports sector, as wool types, especially for double facing with extreme softness), animal clothing and bedding.

Nonwoven fabrics

A further object of the invention is to provide nonwoven fabrics which show lower bulk density and higher softness which are desirable in many applications. The treated fibres can be processed using most state of the art nonwoven techniques, e.g. Needle punch, spun lace and air laid. In particular, because the chemical bonding between AKD and regenerated cellulosic fibres is so strong, treated fibres can withstand the relatively severe spunlacing process conditions.

Nonwoven webs and fabrics according to the invention are characterised in that they contain hydrophobic cellulosic fibres according to the invention. The fabric can be made from hydrophobic cellulosic fibres alone or also in blends with rayon, Tencel, polyester or any other fibre used in nonwoven production.

To demonstrate the benefits of the invention in terms of fabric properties, a range of samples were produced using both needlepunched and spunlaced technologies and these were tested for softness and flexibility using flexural rigidity and Handle-o-meter tests and for bulk density. Needlepunched fabrics were produced on a pilot line built by Tec Tex (Italy) and made to 60 gsm (grams per square metre) or 120 gsm fabrics, needled from both sides in a range from 100 to 200 needle punches per unit and with the needle depth between 16 and 18 mm. Spunlaced fabrics were produced on a pilot plant at NIRI to a basis weight of 55 gsm.

Flexural rigidity was tested according to EDANA WSP 90.5 (05) for bending length. In this test, a strip of fabric is fixed at one end, free at the other end and supported on a horizontal platform. The strip of fabric is advanced over the edge of the platform until the leading edge of the test specimen has reached a plane passing through the edge of the platform and inclined at an angle of 41.5° below the horizontal At this point, the overhanging length equals twice the bending length of the test specimen, and thus the bending length can be calculated. Flexural rigidity was measured according to the WSP method in four ways - MD (machine direction) and CD (cross direction), for both the front and back sides of the fabric. The values were averaged and compared to fabrics of comparable weight which were made from untreated fibres.

Handle- O -Meter testing was carried out according to WSP 90.3.0 (05). In this test, the nonwoven to be tested is deformed through a restricted opening by a plunger and the required force is recorded. A lower required force equates to a softer, more flexible fabric. Bulk density was calculated from area weight [WSP 130.1 (05)] and thickness [WSP

120.6(05)], according to EDANA methods.

For all tests, results were normalised to the relevant control for fabrics made from untreated fibres and then expressed as a percentage. For all tests, a percentage result lower than 100 shows an improvement in that property, like lower bending length, lower flexural rigidity, lower force required in the Handle-O-Meter test or lower bulk density, and hence thicker fabrics for the same basis weight. Results can be found in tables 6,7 and 8.

Examples of needle punched fabrics .

Example F:

Never dried Viscose fibres 1.7dtex/40mm were treated with 0.5% AKD solution according to Example B. The dried fibre was processed to form fabrics with basis weights of nominally 60gsm and 120gsm .

Example G:

Never dried Tencel fibres 1.7dtex/38mm were treated with 0.5% AKD solution according to Example D. The dried fibre was processed in a needle punch pilot plant to form fabrics with basis weights of nominally 60gsm and 120gsm.

Table 6 shows the softness / flexibility.results for needlepunch fabrics according examples F and G. In all cases, the use of treated fibres results in fabrics which are softer / more flexible and by between 17 and 61% compared to fabrics made from standard, untreated fibres. There is good correlation between the flexural rigidity and Handle-O-Meter tests.

Table 6: Softness / flexibility results for needlepunch fabrics

Examples of spunlace fabrics:

Fibres made according to sample B and D were converted on a spunlace pilot plant and processed to form fabrics with a basis weight of nominally 55gsm. Fabrics in both 100% and blends with commercially available Viscose and Tencel were made. Tables 7 and 8 show the effects on fabric softness as measured by the Handle-O-Meter. The use of treated fibre has a very significant effect on fabric softness and flexibility as measured by the Handle-O-Meter with 100% treated fibre giving over a 50% improvement in softness.

Table 7: Softness / flexibility results for 55 gsm viscose spunlaced fabrics

Fabric sample Handle-O-Meter %

100% Viscose 1.7dtex/40mm dull standard 100

100% Viscose 1.7/40 dull + 0.5% AKD 2 48 The addition of even small blend percentages of treated fibre also have a very significant effect on fabric softness as measured by the Handle-O-Meter with softness increasing as the blend percentage is increased (table 8):

Fabrics made from treated fibres show lower bulk densities than fabrics made from the same untreated fibres and would typically allow a 10% reduction in basis weight to give the same thickness in a needle punched fabric (table 9).

Table 9: Bulk density of needle punched fabrics:

When treated fibres are used as a 00% substitute for the same untreated fibres, bulk density is reduced by over 25% (table 10):

Table 10: Bulk density of 55 gsm spunlaced fabrics

Low blends of treated fibre down to 5% reduce the bulk density of the fabrics (table 11): Table 11 : Effect of minor blends of treated fibres on bulk density of 55 gsm Tencel spunlaced fabrics

Overall, Nonwoven fabrics according to the invention show increased softness and are characterised in that the flexural rigidity (stiffness) of the nonwoven is at least 15 % but up to 49% lower than the stiffness of a nonwoven consisting of comparable untreated fibres.

It was also found that nonwovens according to the invention show lower bulk density compared with untreated fibres under the same conditions with up to a 25% reduction in bulk density for fabrics made from 100% treated fibres.

Cellulosic webs or fabrics treated with the hydrophobic agents

It is also possible to treat cellulosic fabrics made from standard man made cellulose fibre or bleached cotton with the hydrophobic agent provided that any soft finish on the fabric is first removed. In the case of a spunlaced fabric, soft finish removal may be achieved by the spunlacing process itself or subsequently in a separate removal step. This process is useful if a totally hydrophobic fabric is required.

Example H:

Spun laced fabric samples produced from standard commercial Tencel or from standard commercial viscose samples were put into 0.1% AKD 2 solution and stirred. After 5 min the samples were taken out, squeezed and put into a desiccators' cabinet at 70°C to dry. The resulting fabrics were completely water repellent and soft. Softness was measured relative to untreated fabrics using the Handle-O-Meter method described previously and the results are shown in tables 12 and 13. The softness of fabrics treated with the hydrophobic agent are around 50% of that for standard untreated spunlaced fabrics.

Table 12: Handle - O- Meter: Spunlaced Viscose fabric treated with the hydrophobic agent

Table 13: Handle - O- Meter: Spunlaced Tencel fabrics treated with the hydrophobic agent

Biodegradabilitv / Compostabilitv:

Needle punched fabrics (chosen from those used to assess softness and bulk density - see tables 6 and 9) made from fibres treated with the hydrophobic agent were cut into pieces of around 3 x 4cm, weighed and then buried in soil. Samples were taken after 2 weeks, 1 month and 2 months and weighed to check the level of biodegradation. All samples had completely degraded after two months. Results are given in table 14.

Tests according to ASTM D 6400 (or DIN EN ISO 14855 or DIN EN 14046) say that a material is biogedradable if all organic compounds are decomposed in different chemical structures which are also naturally metabolites. This must happen during organic composting. Nonwoven consisting of Viscose and Lyocell fibres (commercially available and treated with AKD 2) are fulfilling these parameters.

Table 14: Weight reduction of samples vs. soil burial time

Fabric sample Test l Test 2

2 weeks 1 month 2 month 2 weeks 1 month 2 month

[%] [%] [%] [%] [%] [%]

60 gsm needlepunched

Viscose with 0.5% AKD 2 85,3 100,0 100,0 85,0 100,0 100,0

120 gsm needlepunched

Viscose with 0.5% AKD 2 54,8 100,0 100,0 46,8 100,0 100,0

60gsm needlepunched

Tencel with 0.5% AKD 2 27,5 81 ,8 100,0 24,1 72,4 100,0

120 gsm Tencel with 0.5%

AKD 2 17,2 62,3 100,0 15,9 65,0 100,0