EP0016194A1

EP0016194A1 - Fibrous products and their manufacture

Info

Publication number: EP0016194A1
Application number: EP19790901012
Authority: EP
Inventors: Frederick R.W. Sloan
Original assignee: Lintrend Developments (ni) Ltd
Current assignee: Lintrend Developments (ni) Ltd
Priority date: 1978-08-15
Filing date: 1980-03-25
Publication date: 1980-10-01
Also published as: WO1980000463A1; IN153074B

Abstract

Des fibres de lin de ramie ou de coton sont mises en contact avec un alcali fort lorsqu'elles sont exemptes de resine ou d'agent de reticulation. Ce traitement est en general effectue sur le lin ou la ramie dans des conditions permettant d'obtenir, par exemple, un retrecissement de 20%. Une structure fibreuse de lin ou de ramie est obtenue dans laquelle les fibres sont substantiellement exemptes de noeuds. Le produit fibreux qui a ete mis en contact avec l'alcali peut etre fixe dans sa configuration resultante, generalement avec un agent de reticulation. Le produit peut etre un tissu de lin ou de ramie ayant une resistance aux faux plis sous humidification. Des tissus de coton extensible ou d'autres tissus ainsi que des tissus en lin a tissage ouvert ayant une resistance aux faux plis a sec ou sous humidification peuvent egalement etre obtenus. Des melanges de fibres de lin avec d'autres fibres peuvent etre prepares par traitement chimique du lin suivi d'un cardage et la combinaison du lin carde avec les autres fibres et l'etirage et le filage du melange.Ramie or cotton flax fibers are contacted with a strong alkali when they are free of resin or crosslinking agent. This treatment is generally carried out on flax or ramie under conditions allowing to obtain, for example, a shrinkage of 20%. A fibrous structure of flax or ramie is obtained in which the fibers are substantially free from knots. The fibrous product which has been brought into contact with the alkali can be fixed in its resulting configuration, generally with a crosslinking agent. The product can be a linen or ramie fabric having a resistance to wrinkles under humidification. Stretch cotton fabrics or other fabrics as well as open woven linen fabrics having resistance to wrinkles when dry or under humidification can also be obtained. Mixtures of flax fibers with other fibers can be prepared by chemical treatment of flax followed by carding and the combination of carded flax with the other fibers and the drawing and spinning of the mixture.

Description

FIBROUS PRODUCTS AND THEIR MANUFACTURE Processes are now well established for imparting easy care properties such as wet crease resistance and/or dry crease or crush resistance to a wide variety of fibres, notably cotton. Such processes generally involve treatment of the fibre with a true resin, such as a ureaformaldehyde precurser resin, followed by completing the formation of the resin by polymerising the resin in the fibres, or treatment with one of the so-called textile resins, more properly known as cross-linking agents. These cross-linking agents react with gτoups in the cellulosic molecule to cross-link adjacent molecules. By appropriate choice of treatments wet or dry crease resistance can be obtained with cotton, although it would be desirable to improve the properties of cotton fabrics further, for instance by making the fabrics more springy, so as to improve crush resistance.

Linen and ramie fibres are, like cotton, cellulosic but they have a very different physical structure from cotton fibres. Dry crease resistance has been imparted to medium and heavy linen fabrics on a wide scale by treatment with a resin but the treatment is unsatisfactory on lightweight fabrics because the process causes embrittlement and there has been no satisfactory way of imparting to linen or ramie products wet crease resistance without serious embrittlement. Accordingly drip-dry or minimum iron linen fabrics have not been available and so linen has in practice been unable to compete in many of the garment and other easy care markets, notably men's apparel.

In simplified terms, one essential difference between cotton and linen or ramie fibres is that cotton has essentially the same physical structure throughout its length but linen and ramie fibres consist of elongated substantially rigid portions connected together by short flexible portions of fibrils, these short portions conveniently being termed the nodes. For instance the nodes in flax are about 0.3 mm apart. It seems that most if not all known chemical treatments of linen and ramie fibres have little effect on the rigid portions and instead act mainly or entirely on the nodes. Microscopic examination of the nodes reveals that the nodes in raw linen and ramie fibres have a fold in them. That is to say there is a band around the diameter of the node in which there is a sharp change in direction of the fibrils. Linen or ramie fibre that has been treated by the various known methods involving, for instance, resin and .alkali treatment still has this significant change in direction in the fibrils in the node portion but the change is less abrupt than in the raw fibre. It is an object of the invention to achieve desirable modifications in cotton, linen or ramie fibres such that the products containing them have improved properties, and in particular in linen or ramie fibres, especially so that fabrics made of the fibres have improved wet crease resistance.

In the invention the properties of a fibrous product comprising linen, ramie or cotton fibres are improved by contacting the fibrous product, while it is substantially free of resin or textile cross-linking agent, with strong alkali under conditions such that the fibres can shrink by at least 10% in length, andthereby shrinking the product by at least 10%. In order to obtain optimum improvement in properties the potential and actual shrinkage often should be at least 15 and often at least about 20%. It is generally unnecessary to achieve shrinkage of more than 25 or 30%. If the fibrous product is woven, it is satisfactory if only one direction (generally the weft) shrinks as described. The treatment modifies the cotton, linen or ramie fibres such that when, as is preferred, the fibres are then fixed substantially in their shrunk configuration by some subsequent treatment the resultant fibre product has improved properties. The treatment has particularly significant effect on the properties and the visual appearance of linen or ramie fibres. Thus whereas when such fibres are viewed under 125 magnification mounted in oil before the treatment the nodes mentioned above are readily visible the fibres viewed under the same conditions after the treatment appear substantially free of nodes. Thus each of the nodes which is readily apparent before treatment disappears completely or at least so that it is difficult to observe its presence, as a result of the treatment, and, so far as we are aware this is a previously unknown structure. It appears that, in respect of linen and ramie, it is this structure rather than the specific process steps by which it is obtained, that results in the fibres having the desirable properties described below, especially after fixing the structure chemically. The invention also includes a fibrous product comprising linen or ramie fibres which, when mounted in oil and observed at 125 magnification, appear substantially free of nodes. The fibrous product may be in the form of free fibres or a sliver but more usually is in the form of yarn or a fabric. The product may be chemically fixed, as described below. The product is preferably made by shrinkage in alkali while free of resin or cross-linking agent but any other treatment that results in the substantial disappearance of thenodes, can be used.

This aspect of the invention is illustrated in the accompying figures which are photomicrographs of linen fibres mounted in liquid paraffin and viewed at 125 magnification.

The fibres 1 shown in Figure 1 are bleached flax fibres. The traditional linen structure is readily visible, consisting of recurring elongated relatively rigid portions 2 separated by nodes 3. As is just visible, these nodes tend to have a larger diameter than the portions 2. The fibres shown in Figure 2 are the corresponding bleached fibres after they have been contacted with strong alkali while relaxed and allowed to shrink by at least 10%, generally about 20%. As is readily apparent the fibres 1 are now substantially free of nodes. Thus substantially nowhere are there any clearly visible nodes. There are some markings 5 which probably indicated the remnants of nodes but these markings are, at this, magnification, so indistinct that it is difficult to be certain. There are also significant lengths, 4, that appear totally free of remnants of nodes.

Known treatments of linen and ramie fibres have tended to lessen the effect of nodes but none have substantially eliminated them, for instance as illustrated in these Figures. On greater magnification it can be seen that whereas in the initial fibres there are folds in the fibrils in the region of the nodes with a sudden change in direction of the fibrils within the nodes, in the novel fibres the fibrils no longer have this sudden change in direction but instead tend to follow a gently curved or linear path throughout the length of where the node used to be.

The method of the invention is, however, not limited to being conducted under conditions that give a readily visible change in the structure of the fibres and instead the method involves any treatment under strong alkali that gives at least 10% shrinkage of the fibres and which is conducted while the fibres are substantially free of resins or textile cross-linking agents. It is essential that they are free of these materials. If they are not, it will be much more difficult, and will probably be impossible, to achieve the desired high degree of shrinking and to fix the fibres substantially in their shrunk configuration.

Linen or ramie fibres, and often also cotton fibres, will generally have been bleached before treatment and generally also scoured so as to make them more wettable. The scouring may be conducted by boiling yarn or fabric with soda ash (sodium carbonate) or other alkali that will remove waxes and pectins but the process preferably is not such as to remove any significant amount of hemicellulose. Thus whereas it is common when, for instance, treating linen or ramie fibres deliberately to remove hemicellulose the fibres treated in accordance with the invention, and the novel fibres of the invention, are preferably treated under conditions such that they substantially maintain their original hemicellulose content and will thus generally contain more than 10% and preferably morethan 15% hemicellulose.

The treatment with strong alkali must be under conditions such that the desired shrinkage can and does occur. These conditions require a choice both of chemical conditions and physical conditions.

As the chemical conditions, known mercerising reagents and temperatures may be used. Suitable reagents are strong ammonia, cuprammonium solutions and caustic soda, the latter being preferred. Typical concentrations of caustic soda are 10 to 40%, especially 20 to 30%, by weight giving about 60ºTw. Treatment preferably comprises impregnation e.g. by immersion in a 3 bowl trough mangle, at a temperature below 30ºC, preferably 0 to 10ºC, followed by soaking for an adequate period, normally at least 5 or 10 minutes, but usually less than 60 minutes. Impregnation of caustic soda between

0-10ºC is the preferred method. This is obtained by refrigerating the caustic soda and circulating the liquor in the trough of the impregnating mangle.

As the physical conditions, the fibres that are to shrink must not be under tension or other forces such as seriously to inhibit the shrinkage. If the fibrous product is a sliver then the sliver must not be under tension. Generally it is desirable to impress a crimp on the sliver in known manner so as to give it improved physical integrity. If the fibrous product is in the form of yarn then the yam must be held during the treatment in the relaxed state. For instance the yarn can be treated as a skein but it would not be satisfactory to treat it while it was on a tightly wound bobbin since the yarn in a bobbin is not sufficiently relaxed to permit free shrinkage. Normally, however, the yarn is converted into a fabric before it is treated in which event scouring and bleaching can be conducted either on the yarn or on the fabric.

Fabric that is being treated must be sufficiently relaxed to permit substantial shrinkage of it, preferably to permit the maximum amount of shrinkage attainable in the mercerisation step. Accordingly it should be held in a J-box or other equipment that will allow free shrinkage for the chosen period usually 5 to 15 minutes. The shrinkage may be more then desired, in which event it may then be brought back to the desired shrunk width on a stenter frame. Fabric can be held on a stenter frame during shrinkage but only if the tension applied by the stenter is so low as to' permit the desired high shrinkage. Alternatively, treatment can take place on a batch. That is to say, the fabric is impregnated with caustic soda and rolled on to a batch. Under these circumstances there will be minimum warp tension but maximum width shrinkage. The forces of tension in the warp are not so high as those that would be present during, for instance, passage down a mercerising range.

The fibrous product is generally a woven fabric and the weave may also affect the degree of shrinkage. Thus if there is a tight weave, with little or no space between adjacent threads, there will be less room for shrinkage. We have surprisingly found that provided the warp or the weft are highly shrunk it is less important whether or not the other is shrunk and, if shrunk, whether the shrunk configuration is fixed. When handling the fabric, e.g. prior to and during the fixing step, there is a natural tendency to lose or reduce any shrinkage in the warp and it has been found satisfactory to concentrate on achieving high shrinkage in the weft. Accordingly the weave of the fabric is preferably such that the spacing between the warp threads is sufficient to permit shrinkage of the weft by at least 10%, and usually 15 or 20%, and preferably there are less warp than weft threads, for instance so that after achieving the high shrinkage in the weft and little or no shrinkage in the warp the fabric is substantially square woven with equal numbers of warp and weft threads. The initial weave may in fact be such as to restrict warp shrinkage.

During the shrinkage while relaxed warp shrinkage may be from 2 to 10% while weft shrinkage may be 15 to 30%, for instance 21%.

Desirable modifications in the properties of textile fibres are achievable if the shrinkage results in the fibres and yarn spun from them still being substantially linear. However if the yarn is a fine tightly spun yarn it is possible readily to achieve both shrinkage of the individual fibres within the yarn and also crimping of the fibres and the yarn.

For instance if tightly spun yarn forms the weft of the fabric having adequate spaces between adjacent warp threads to permit crimping the treatment of the invention can readily be conducted to provide even greater shrinkage in the weft, for instance 15 to 40%, generally around 30%, and in particular to produce crimped weft with the result that the fabric is stretchable in the weft direction. Generally the weave is such that there are initially less warp than weft but that after the treatment of the invention there are substantially equal numbers of warp and weft. Thus by the invention it is possible to produce stretchable cotton or linen fabrics. The degree of stretch may be 5 to 20% or more. If the yarn is a less tightly spun yarn and a fabric is woven from that with an open weave,weft stretching of 10 to 30%, generally about 20%, is achieved, substantially without crimping occurring, and the final product after fixing has good crush and wet and dry crease resistance. This is a particular advantage for linen fabrics where these properties have not hitherto been available. In such products it is desirable before shrinking, and often after the shrinking as well, for there to be slightly more warp threads than weft.

After the alkali shrinkage while relaxed the fibre product is generally rinsed and dried and may be dyed before the shrunk configuration is fixed. The purpose of the fixing is to hold the shrunk fibres substantially in the configuration obtained by the alkali treatment, e.g. their de-noded structure if the fibres are of linen that has been de-noded by the alkali treatment. Polymerisable resins can be used for the fixing, such as polymerisable ureaformaldehyde resins e.g. dimetholyl urea and dimethylol melamine and in some instances, for instance when the fibres are cotton fibres, these are entirely satisfactory. However in some fabrics, especially linen, although they improve dry crease resistance they may cause some embrittlement. This embrittlement can be reduced by subjecting the fabric after polymerisation of the resin to an after treatment such as mercerisation, e.g. using the strong alkali conditions discussed above. Normally this mercerisation is conducted under tension. The traditional method of reducing embrittlement, namely mercerising the fabric containing the polymerised resins while relaxed, so as to achieve shrinkage, is not very effective since the fabric is generally fully shrunk already. To compensate for this difficulty it is possible to conduct the treatment while relaxed under conditions such that full shrinkage does not occur, then to apply and polymerise the resin, and then to mercerise again while relaxed, so as to achieve further shrinkage.

Preferably the shrunk and/or de-noded fibres are fixed by being chemically cross-linked in their new configuration. Such cross-linked products form an important aspect of the invention since they can have good wet crease properties without suffering from embrittlement. While this is useful with cotton it is of particular value for linen and ramie since the invention thus permits, for the first time the manufacture of lightweight, minimum iron, easy care linen fabrics.

The cross-linking is caused by treatment with a cellulose cross-linking agent, generally in the presence of a catalyst. This cross-linking agent is a bi- or poly-functional reagent that will react with, and thus bridge and cross-link, hydroxy groups in the cellulose.

Typical bi- or polyfunctional compounds that serve as cross-linking agents are alcohols, aldehydes such as glyoxal, and methylol urea derivatives that will react with cellulose in preference to undergoing self polymerisation, such as dimethylol cyclic methylene or ethylene urea.

Catalysts suitable for such cross-linking materials are well known and are generally acidic, for instance inorganic or organic acids such as citric or succinic acid or acidic salts such as magnesium chloride. Preferably, instead of using phase separation catalysts such as these , non-phase separation catalysts (for instance a triethylene glycol citric acid or other citric acid water soluble polyester)are used. The cross-linking agent and catalyst are generally applied from an aqueous solution containing, for instance, 10 to 30% of the cross-linking agent and 0.5 to 5% of the catalyst. The pick up may be, for example, 50 to 80% by weight of the solution and curing of the catalyst may be achieved by, for instance, heating at 120 to 220°C for 0.5 to 5 minutes.

Some cross-linked fabrics, especially tightly woven fabrics containing linen or ramie fibres, benefit from being subjected to brief treatment with typical mercerising reagents, such as the strong alkalies discussed above, normally while under tension although in many cases the alkali need not be as strong as that normally used in the prior art, and can be for example 35°Tw. This treatment may improve extensibility and therefore the resistance to tear and abrasion of the fabrics.

The method of the invention can be conducted on a variety of fibrous products ranging from slivers, generally crimped slivers, of free fibres, to yarns spun from the fibres and fabrics formed from the fibres, generally by weaving. If it is conducted on slivers or yarns these are generally converted to fabrics after the fixing of the shrinkage. The fibrous product may consist solely of linen, ramie or cotton fibres or may comprise a mixtureof different fibre types. For instance the warp may be of one fibre type and the weft of another. Often a homogeneous blend of cotton, ramie or linen with another fibre type is used. This second fibre type may be a natural fibre, for example cotton, linen or ramie or viscose, or modified viscose or a synthetic fibre such as polyester, acrylic or nylon. There may be from 20 to 85%, preferably 40 to 80%, by weight of these second fibres. Preferred are blends of, as the first fibre, cotton, linen or ramie with, as the second fibre, cotton,linen, ramie, viscose or modified viscose. Preferred blends are of linen with cotton, linen with viscose and cotton with viscose.

It has surprisingly been found that if yarn or fabric woven from yarn formed of a blend of viscose with linen, cotton or ramie fibres is subjected to the strong alkali treatment of the invention the viscose does not dissolve in the alkali. Further, the products produced, especially from linen viscose blends, have extremely desirable physical properties.

The use of cotton as part or all of the fibre blend tends to give improved handle and other properties compared to linen alone, but the use of an intimate blend of linen or ramie with cotton, viscose or modified viscose, and in particular a blend of linen or ramie with cotton, permits the production of a better combination of handle, crease recovery, moisture retention, permeability, general easy care properties and cost than is attainable with either fibre alone. Preferred blends contain 15 to 60%, preferably 20 to 50% linen or ramie with the balance other fibres, for example 30 to 50% linen and 70 to 50% cotton.

Homogeneous blends of fibres may be obtained by known methods, but such methods tend to be rather unsatisfactory when one component of the blend is to be linen or ramie s ince natural linen or ramie fibres have fibre lengths and diameter greater than the fibre length and diameter that is normal for fibres such as cotton, viscose or modified viscose. Preferably therefore a homogeneous fibre blend of linen or ramie fibres with other fibres is made by a process comprising chemically treating the linen fibre bundles to release at least partially the individual linen fibres.

The chemical treatment should be such as to bleach and crack the pectin that holds the fibres together in the bundles, so as to tend to release the individual fibres during subsequent mechanical working, such as spinning. Suitable treatment comprises contacting the fibres with hypochlorite and/or chlorite solution, preferably as alkali metal salt solutions, generally sodium hypochlorite and/or sodium chlorite. For example the method may comprise soaking the linen fibres with aqueous sodium hypochlorite at ambient temperature using a concentration of 15% by weight on the fibre of 5% solution (or equivalent amounts of other concentrations) for sufficient time, which is generally about 40 minutes, until the concentration of hypochlorite has reduced to about 1.5 grams per litre. The hypochlorite solution is then drained off and the resultant linen fibres are then soaked in sodium chlorite solution, generally about a 2.5% by volume of 26% solution (or equivalent amounts of other concentrations) at about 80ºC for about one hour. Other conditions can be used, e.g. periods of 15 minutes to 3 hours, 10 to 20% of sodium hypochlorite and 1 to 5% of sodium chlorite and the temperature of a hypochlorite treatment may be 5 to 40°C and for the chlorite treatment 50 to 90°C. The chemical treatment should be accompanied or followed by sufficient mechanical working to facilitate release of the individual fibrils but generally the conventional treatment to which the fibres will inevitably be subjected, such as the conventional drawing, pin and spinning treatments, may make it unnecessary to subject the fibres to a deliberate additional friction stage. Although the chemically treated linen fibres can be combined in the loose state with the other fibres before or during carding into a sliver an important feature is the formation of a carded sliver of the chemically treated fibres, e.g. by carding after the chemical treatment, and the separate, carding of the second fibres into a second sliver, and then combining these slivers to form a homogeneous fibre blend. This combination may be conducted by carding the slivers together. The fibre blend may be drawn and spun in conventional manner. In one method the sliver of linen may be cut, e.g. to 3 to 7 cm, reformed into a sliver and blended with cotton or viscose for short staple spinning. We thus provide also a novel method for making a homogeneous blend of linen fibres with other fibres comprising forming a carded sliver of linen fibres chemically treated to release at least partially the individual fibrils, separately carding the other fibres and combining the slivers. The resultant blend may be used in any textile where a blend of linen or ramie and other fibres is desired but preferably is subjected to treatment with strong alkali while relaxed and further processing, all as described above. The described method of making a homogeneous fibre blend is advantageous since the carding conditions for each fibre can be selected to be the optimum for that fibre without regard to the other fibre, and in particular optimum breakdown of fibre bundles of the chemically treated linen or ramie fibres can be achieved during spinning.

The following are examples of the invention. Example 1 A linen fabric is woven from 60 s lea yarn in both warp and weft (bleached yarn), having 22.6 threads per cm in the warp and 26.5 threads per cm in the weft. The width is 145 cm.

The fabric is given a light preparation in the normal way, i.e. it is singed to remove surface hair, and the fabric at width is passed through enzyme solution to remove the starch used in sizing the warp. The fabric is plaited down, and after 6 hours washed off through hot water, and given a mild scour with 1% w/v solution of soda ash, to which a detergent or scouring assistant may be added. This treatment may be carried out at width on a roll, or in rope form on a winch. The former method is preferred. The fabric is dried and stentered to width say 152 cm. The fibres still contain more than 10% hemicellulose.

The fabric is then treated with strong causticsoda solution, about specific gravity of 60°Tw. This is conveniently done on a three bowl pad mangle. The fabric passed through the caustic soda in the first trough is squeezed between the bottom rollers, and is then immersed in the second bath and squeezed again. The pick up will be around 60%. The fabric saturated with caustic soda is then delayed in a J-box for at least 15 minutes, during which period it will shrink about 10% in the warp and about 21% in the weft, i.e. to 112 cm. The fabric is then washed off on the stenter and neutralised in the normal way and the width brought to 120 cm. It is then dried and may be dyed in the normal way to any shade chosen.

After dyeing the fabric is impregnated while held at 120 cm width on a stenter, with a 20% w/v solution of dimethylol cyclic ethylene urea activated with 2% w/v citric acid or 1.5% magnesium chloride. The wet pick-up is around 70%. This will of course vary with the weight of the fabric treated. The fabric is then dried on the stenter and after drying subjected to at least 180ºC for 2 minutes which affects the reaction between the hydroxyl groups of the cellulose and those of the urea derivative. The fabric is then washed off. At this stage it may be dried, or while held on a stenter it may be treated in the wet state with strong caustic soda solution of about 60ºTw. and then washed off at width on the stenter and subsequently dried. The width may be allowed to come in from 120 cm to 115 cm.

The fabric may then be finished in the normal way, i.e. passed through a Regmel or Sanforizing machine to give warp shrinkage of about 2%. The final fabric will have shrunk about 10% in the warp and about 21% in the weft and has a wet crease recovery angle of about 130°.

Many variations on processing sequence are possible, but all of them will cause the nodes to be swollen so that they become invisible under the microscope, as in Figure 2. Example 2

A linen fabric is woven with 8.5 threads per cm in the weft and 8.8 threads per cm in the warp. The warp is 1/16s lea bleached yarn and the weft 20s lea bleached yarn. In both cases yarns are spun on the wet system. The width of the fabric is 147.3cm. The fabric is first singed to remove surface hair, and then passed through enzyme solution to de-size the warp in the event that a starch-type product has been used. Alternatively hot water with a wetting agent will suffice if a polyvinylalcohol type of sizing agent has been used. The fabric is plaited down, or batched for about 6 hours, after which it is washed off. Subsequently it is given a mild scour with a 1% w/v solution of soda ash. This treatment may be carried out at width, or in rope form, but preferably at width to avoid distortion of the threads as might occur in such an open mesh type construction. The fabric is then dried and stentered to width, say 144.8 cm. The fabric is then treated with strong caustic soda solution of specific gravity of about 60ºTw and preferably cooled to a temperature of about 10ºC. In this case, in order to minimise distortion of the weft threads, a single passage only between the rollers is given during the impregnation with the caustic. In other words, the fabric is passed between the bottom two rollers only of a 3 bowl pad mangle. The fabric, saturated with caustic soda is then plaited down in a J-box, where it is allowed to remain for 15 minutes. It will have shrunk to about 109.2 cm wide and about 10% in length. It is then washed off on the range and stentered to a width of 114.3 cm. It may then be dried and dyed in the normal way to any suitable shade.

After dyeing, the fabric is impregnated with a 15% w/v solution of di-hydroxy di-methylol cyclic ethylene urea activated with a 2% w/v solution of citric acid. The wet pick-up is around 80%. The fabric is then dried on the stenter to a width of 114.3 cm and after drying, subjected to a heat treatment of 160°C for 1 ½ mins.

The reaction between the hydroxyl groups of the cellulose and those of the urea derivative are now complete. It is then washed off and will have a satisfactory dry crease recovery angle, together with a high wet crease recovery angle and satisfactory abrasion resistance for apparel for women. If the end use is to be menswear, e.g. safari type shirts or sportswear, then it is an advantage to subject the fabric to an after-mercerising treatment. The fabric, after curing, is impregnated with caustic soda solution 35°Tw and immediately, without delay, washed off and brought to width. It will be found that the fabric will shrink slightly and it brought to the width of 110.5 cm.

It is then dried on a stenter and passed through a Sanforiser or Rigmel machine to give a soft and lustrous finish.

The resultant fabric has excellent resistance to dry hand crushing in addition to high wet crease recovery. Example 3 A fabric is constructed having 21.3 threads per cm in the weft and 17.7 threads per cm in the warp. The yarn is a 60s lea wet-spun grey flax in both cases. The width of the fabric is 121.3 cm.

It is first singed to remove surface hairs and then passed through an enzyme solution in order to de-size the warp. Then it is given a scouring and bleaching treatment in rope form. This treatment is a standard one normally given to grey linen. After this it is dried on cylinders, and the width will be approximately 991. cm.

The fabric is then treated with strong caustic soda solution of specific gravity 60°Tw. This is done preferably on a 3 bowl pad mangle or alternatively two double bowl mangles in tandem. Saturated v/ith caustic soda, it is then delayed in a J-box for 10-15 mins during which period it will shrink about 7% in the warp and toabout 83.8 cm width. It is then washed off on the stenter and neutralised in the normal way, followed by drying and dyeing to any suitable shade using either Yat or Reactive dyestuffs.

After dyeing the fabric is impregnated with a 20% w/v solution of di-hydroxy di-methylol cyclic ethylene urea activated with 2% w/v triethylene glycol citric acid polyester. The acid value of such a polyester should be about 190, the pH of the impregnating solution will be at least 3.2. The wet pick-up is around 70%. The fabric is then dried on the stenter and after drying, subjected to a temperature of 170°C for 2 mins. It is then washed off and dried.

It is then given a treatment with strong caustic soda solution of about 60°Tw and in this case there is no delay or dwell period in the caustic solution. It is simply run down the merceriser range, washed off and dried. The width will now be 78.7 cm. It is then finished off through a Rigmel machine with a rubber belt and the resultant finish will be soft and lustrous. It has a weft stretch of about 16%. Example 4

A fabric is constructed from 100% cotton yarn, having 21.3 threads per cm in the weft and 17.7 in the warp. The warp is composed of 1/20s c.c. Egyptian combed cotton, and the weft 1/30s c.c. also Egyptian combed cotton yarn. The width of the fabric is 121 .9 cm. The processing details are those given in Example 3 above. The final product is a cotton fabric having weft stretch of about 15% with good wet crease recovery and useful dry crease recovery with crush resistant properties. Example 5

Linen fibres are soaked in a 15% by weight of the fibres of a 5% aqueous sodium hypochlorite solution at ambient temperature for about 407 mins, and in particular until the concentration of hypochlorite in the solution has fallen to 1,5 gms. per litre. The solution is then drained off and the resultant fibres are soaked in 2.5% by volume of a 26% sodium chlorite solution at about 80°C for approximately 1 hour. The solution is then drained off and the fibres washed and dried. They are then carded into a sliver using a conventional flax type card. The sliver is then crimped by mechanical means, e.g. a stuffing box, and cut into lengths of approximately 5 cms. The stapled fibre is then carded on the cotton carding machine, or a modified woollen card to produce a continuous sliver which is then combined with a conventional cotton sliver, and both are then drawn and spun by conventional cotton or woollen spinning techniques to produce a blended yarn of 33% by weight of linen and 66% by weight of cotton.

A fabric is then constructed in a manner as described in Example 1, and finished according to the details given in that example.

Instead of carrying out the chemical treatment described above, fibre that is commercially available under the Trade Name "Linron" and that has been stapled to about 5 cms in length may be fed directly on to a cotton type card, the resultant sliver being then blended with cotton and spun to a count of 20s c.c.

A fabric is constructed having 20.9 threads per cm in the weft and 18.1 threads per cm in the warp. The width is 147.3cm. It is processed exactly as in Example 1 and has a finished width of 114-117 cm.

Fabrics made according to this example have a better combination of handle, crease resistance, easycare properties and permeability than the products of Example 1 and may also be of reduced cost. Alternatively, products having substantially the same wet crease resistance as in Example 1 can be achieved using the blended fibres of this example in a process in which the shrinkage and/or cross-linking are less than in Example 1. Example 6 The process of Example 5 above is repeated, but instead of using cotton fibres, viscose is used. The resultant product will have very superior crease recovery and a much better dry crease resistance than is obtainable by any of the other examples.

Claims

1. A process for modifying the properties of a fibrous product comprising fibres selected from linen, ramie and cotton fibres, the process comprising contacting the product with strong alkali, characterised in that the contact with alkali is conducted while the product is substantially free of resin or textile cross-linking agent, and is conducted under conditions such that the fibres can shrink by at least 10% in length and that the product shrinks by at least 10%.

2. A process according to claim 1 in which the fibres are linen or ramie fibres.

3. A process according to claim 2 in which the contact with alkali results in the fibres, when mounted in oil and observed at 125 magnification, appearing substantially free of nodes.

4. A process according to any preceding claim in which the fibrous product is a woven fabric and the fibres are in the weft of the fabric, the spacing between the warp threads is sufficient to permit shrinking of the weft by at least 10%, and the contact with alkali is conducted while the, fabric is free of any transverse tension that restricts substantially the shrinkage of the weft.

5. A process according to any preceding claim in which the shrinkage is at least about 20%.

6. A process according to any preceding claimin which the contact with strong alkali comprises soaking the fibres for at least 5 minutes in a 20 to 30% by weight aqueous sodium hydroxide solution at 0 to 30°C,

7. A process according to any preceding claim in which the fibres have previously been bleached and/or scoured under conditions such that they substantially maintain their original hemicellulose content.

8. A process according to any preceding claim in which the fibres are fixed substantially in their shrunk configuration.

9. A process according to claim 8 in which the fixing of the fibres is conducted by cross-linking the shrunk fibres by reaction with a cellulose cross-linking agent.

10. A process according to any preceding claim in which, after the contact with alkali and before the fixing of the fibres, the fibrous product is rinsed, dried and dyed.

11. A process according to any of claims 8 to 10 in which, after fixing the fibres in their shrunk configuration, the product is mercerised.

12. A process according to claim 11 in which the mercerising is conducted under tension.

13. A process according to any preceding claim in which the fibrous produtt comprises a homogeneous blend of first and different, second. fibres, the first fibres being selected from cotton, linen or ramie and the second fibres being selected from cotton, linen, ramie, viscose or modified viscose.

14. A process according to claim 13 in which the homogeneous blend is a blend of linen and cotton, linen and viscose or cotton and viscose.

15. A process according to any preceding claim in which the fibτous product comprises a homogeneous blend of linen or ramie fibres with second fibres and the blend has been made by a method comprising chemically treating linen or ramie fibie bundles to release at least partially the individual linen or ramie fibres and forming a carded sliver of the linen or ramie fibres, separatelycarding the second fibres, and combining the slivers to form a homogeneous fibre blend.

16. A process according tc any of claims 1 to 15 in which the fibrous product that is contacted with the alkali comprises a woven fabric formed from coarse yarn containing linen fibres and which has an open weave, before and after the process, whereby the product after the process has crush resistance.

17. A process according to any of claims 1 to 15 in which the fibrous product comprises tightly spun yarn that is crimped by the shrinkage, whereby the product after the process is stretchable.

18. A process according to claim 17 in which the fibres are cotton fibres.

19. A process for modifying the properties of a fibrous product comprising linen or ramie fibres by fixing the fibres with a resin or cellulose cross-linking agent, characterised in that the fibres appear substantially free of nodes when mounted in oil and observed at 125 magnification.

20. A fibrous product comprising linen or ramie fibres characterised in that the fibres, when mounted in oil and observed at 125 magnification, appear substantially free of nodes.

21. A product according to claim 20 in which the fibres have been reacted with a cellulose cross-linking agent.

22. A process for making a yarn comprising a homogeneous fibre blend of linen or ramie fibres with second fibres by blending the fibres and drawing and spinning the blend characterised in that the linen or ramie fibre bundles are, before the blending, chemically treated to release at least partially the individual fibres and a carded sliver of the treated linen or ramie fibres is formed, the second fibres are separately carded into a sliver, and the blending is conducted by combining the slivers to form a homogeneous fibre blend.