GB2210069A

GB2210069A - Electrically conductive cellulosic fibres

Info

Publication number: GB2210069A
Application number: GB8721891A
Authority: GB
Inventors: Alexander James Heald
Original assignee: Courtaulds PLC
Current assignee: Akzo Nobel UK PLC
Priority date: 1987-09-17
Filing date: 1987-09-17
Publication date: 1989-06-01
Also published as: EP0308234B1; DE3866837D1; EP0308234A1; JPH01144503A; GB8721891D0

Description

Electrically Conductive Fibre 2 c " 1 C), 0 6 /2 This invention relates to

electrically conductive ce llulos ic -based fibres and to methods for making such f ibres.

Electrically conductive acrylic fibres are used to provide antistatic properties in textile products such as carpets and clothing. The acrylic fibres are made conductive by impregnation with copper sulphide. One method for making those fibres is described in European Patent 35 406 in which acrylic fibre is treated with a copper compound such as copper sulphate and a reducing agent to adsorb copper ions onto the fibre, 'followed by treatment with a sulphur- containing compound which c onverts the copper ions to copper sulphide, thus producing an electrically conductive acry-lic fibre.

is A similar method is described in GB Patent 1372656, except that the synthetic fibre, such as acrylic fibre, _Js treated firstly with a sulphur-containing compound, namely hydrogen sulphide, thioacetamide or thiourea, and secondly with a metal salt solution, for example aqueous copper sulphate.

Attempts have been made to adapt those methods for the production of a conductive cellulosic fibre. In US Patent 4378226 cotton and rayon fibres are pretreated with acrylonitrile or dicyandiamide to introduce cyanic groups into the fibres before they are treated with the copper and sulphide compounds as described above. That method has the disadvantage that acrylonitrile and dicyandiamide are toxic and therefore hazardous to use. To our knowledge cellulosic fibres are not produced commercially by that method.

L Japanese Patent Application Kokai 61-32305 describes a conductive regenerated cellulosic fibre in which the n 1 1 j i 2 - regenerated cellulose is impregnated with copper sulphide without first being pretreated. We have not been able to produce a viscose fibre having adequate electrical conductivity by using the method exemplified in that patent application.

The present invention provides an electricaliv conductive fibre comprising'a cellulosic fibre modified reaction with Compound A (as hereinafter defined), and impregnated with a metal sulphide selected from copper, iron, silver, tin and lead sulphide. By Compound A we mean the reaction product of a mono- or polyfunctional amine having one or more primary and/or secondary and/or tertiary amino groups with cyanamide, dicyard- Lamide, guanidine or bisguanidine, or a salt thereof.

The cellulosic-based fibre according to the invention can be produced by:

(a) treating a cellulosic fibre with an aqueous solution of Compound A to form a modified cellulosic f ibre; and (b) treating the modified fibre with an aaueou., solution of a water-soluble salt of a metal selected from copper, iron, silver, tin and lead, a reducing agent,and a sulphur -containing compound capable of reacting with the metal salt to form a metal sulphide which is adsorbed onto the modified fibre.

By pretreating the fibre with Compound A, a ce llulos ic -based fibre with good electrical conductivity is obtained. Because compound A is relatively non-toxic the process according to the invention has the advantage that it is non-hazardous. Furthermore the level of conductivity is not substantially impaired by washing.

1 By Icellulosic fibre' is meant a fibre consisting cf. either natural cellulose such as cotton or regenerated cellulose such as viscose or rayon, or a blend thereof.

The compounds comprising the group "Compound A" are known and may be prepared by the methods described for example in GB Patent 657753 and US Patents 2649354 and 4410652. Suitably the amine, in free base or salt form, is reacted with the other material in the absence of water at elevated temperatures. optionally in the presence of a 10 non-aqueous solvent. Preferablv the reaction is carried out in the absence of solvent and at a temperature of 140-1600C, and, for most combinations of reagents, arLmonia is evolved. The reagents are preferably reacted in a molar ratio of 0.1 to 1 mole of cyanamide, dicyandiamide, 'dine or bisguanidine per mole of reactive ar-nine quan, groups, and when dicyandiamide s reacted with a polvalkylene polyamine, the molar ratio of the react-ants is more preferably from 2:1 to 1:2, particularly about 1:1.

Preferably Compound A is the reaction product of dicyandiamide with a polyalkylene polyamine,especially diethylenetriamine.

Suitable methods for treating the cellulosic fibre with Compound A are described in European Patent Application Publication No. 151370A and in GB Patent Application 8708192, the disclosures of which are incorporated herein by reference. Conventional techniques, for example an exhaustion or padding process, can be used to apply Compound A to the fibre.

As described in EP 151370A, Compound A can be applied using an exhaustion process by immersing the fibre in a bath containing an aqueous solution, which may be weakly acidic, of Compound A. The bath is then heated to 0 4 - between 50 and 1001C and an alkali such as sod-Ll-T, carbonate added to bring the pH value of the solutJon tbetween pH 9 and 11. The fibre is immersed in the batL1-1 for a time sufficient to fix compound A onto the fibre, usually between 10 and 30 minutes. The fibre is then.

washed in water.

A similar method is described in GB Application 8708192 except that the solution of Compound A is made more strongly alkaline, pH above 11, by the addition of a strong alkali such as sodium hydrox,4Lde rather than sodium carbonatel and the solution is maintained at a temperature below 501C. ithas been found that at tem,,=-ratures in excess cJ-5' SO'C the alkaliadversely affects the ability of Compound A to subsequently adsorb the metal ions which prov'de the electrical conduct 1v i ty- of the fibre. it is thought. that this is probably due to the formation c.' cross-links in ComDound A.

The concentration O.L the aqueous solution of Compound A with which the cellulosic fibre is treated depends upon the desired level of Compound A to be fixed, to the fibre. Preferably the level of fixation is between 0.2 and 5.0%, more preferably between 0.6 and 3.0% Compound A w/wf (weight/weight of fibre). The nature of the fixation is not fully understood, although it is thought to involve chemical bonding to the available hydroxyl groups in the cellulose, but the fixed compound is not removed by repeated washing. In general the method of EP 151370A is used to apply lower levels of Compound A, in the region of 0.2 to 1.0% w/wf, and the mdthod of GB Application 8708192 is used to apply levels above 1.0% w/wf, although lower levels can also be applied using the latter method.

The concentration of the solution is calculated 4 1 1 v according to the desired level of fixation of Compound A, taking into account that the percentage exhaustion is usually less than 100%, and commonly between 70 and 800P.. In addition it is preferred to treat the fibre with an excess of Compound A in order to achieve even take-up of the compound on the fibre. Any unfixed compound can be subsequently removed bv washing. Usuallv the concentration of the solution is between 0.5 and 20% Compound A w/wf, and preferably between 1.5 and 10c-ow/w-jr7.

After being impregnated with Compound A and washed, the resulting modified cellulosic fibre can be dried before being treated with the metal salt, reducing agent and sulphur-containing compound. However, it is preferred to treat the modified fibre with these compounds without first drying the fibre so that the electrically conductive fibre is produced in one centinuous process.

The modified fibre may be treated with the metal salt, reducing agent and sulphur-containing compound simultaneously, or the treatment with the sulphurcontaining compound can be a separate step from the treatment with the metal salt and reducing agent.

By choosing a sulphur -containing compound that is also a reducing agent, a separate reducing agent may be dispensed with.

Where the treatments are simultaneous, the modified fibre is immersed in an aqueous solution containing a metal salt of copper, silver, tin, lead or iron, a reducing agent and a sulphur -containing compound, and the bath is preferably heated to between 50 and 1000C, although higher temperatures can be employed. Treatment times can be from 10 to 90 minutes, although it is not. usually necessary to immerse the fibre in the bath for 6 longer than 1 hour. The resulting fibre, which is imprea-nated with the metal sulphide, is then washed in water and dried.

Where the treatments are separate, the modified fibre may be first immersed in an aqueous bath containing metal salt of copper, silver, tin, lead or iron and reducing agent and the bath preferably heated to between 50 and 1OCC, to absorb metal ions onto the fibre. Treatment times can be from 10 to 90 minutes, although they are not usually more than 1 hour. Following this the fibre is immersed in a second bath, optioniilly with intermed-iate washing, containing a sulphur -containing cc.-n-nound to convert the adsorbed metal ions to the corres.. Do-.d--zng metal sulphide. Treatment temperatures and times are withi.n. the ranges given for the treatment: with the metal salt and' reducing agent. The resulting fibre is then washed water and dried.

In both the simultaneous and the separat-e treatments, the concentration of metal salt in the solut-lon is preferably between 6 and 300 g/1, and the concenz--a-L-Jcn of: sulDhur- containing compound between 35 and 250 a/1.

The metal salt is preferably a copmer(II) examDles of suitable commounds include copper (II) sulphate, copper (II) chloride, copper (II) nitrate, copper (II) acetate and the like.

Suitable sulphur-containing compounds include sodium sulphide, sodium thiosulphate, sodium metabisulphite, sodium hydrosulphite, sulphurous acid and dithionous acid, or a mixture thereof. When sulphur -c ontai ning compounds such as sodium thicsulphate or sodium metabisulphite are employed, then these compounds also act as a reducing agent so that a separate reducing agent is not necessarily reauired. Examples of other reducing agents include i 1 1 metallic copper, glucose, formaldehyde, ferrous sulphate and the like.

As an alternative method, the modified fibre may be treated with another sulphur-containing compound such as thicurea, thioacetamide, Rongalite Z (ZnSO 2 CH 2 O.H 2 0) or Formosul (Na 2 so 2 CH 2 O.H 2 0) prior to being treated wiL-h the metal salt. It has been found that this pretreatment enhances the electrical conductivity of the resulting fibre in some instances. The subsequent treatment with the sulphur -conta in ing compound may then be cm,-4,,--ted, but it is preferred to include it so that the pretreatment is in addition to the above-mentioned steps.

In general the greater the amount of metal sulphide impregnated in the cellulosic fibre, the higher its conductivity, although too a high level of metal sulphide can reduce the fibre's physical properties, such as fibre strength. Preferably the modified fibre is impregnatedwith between 1 and 30% metal sulphide w/wil, more preferably between 10 and 25% w/wf.

Although the exact form of the metal sulphide adsorbed onto the fibre is not known, when copper sulphide is adsorbed the green and dark green/black colours of the resulting conductive fibre indicate that both copper(I) sulphide and copper(II) sulphide are present in the fibre.

The cellulosic fibre which is to be heated with Compound A and impregnated with the metal sulphide may be in loose f ibre f orm, or as a yarn or f abric or any other suitable form. In addition, the cellulosic fibre may be treated with Compound A in, for example, loose fibre form, and then made up into a yarn or f abric prior to being impregnated with the metal sulphide.

Products made from the conductive fibre according to the invention may comprise solely the conductive ( -k) 1 cellulosic-based fibre or may be blended with other fJ-bres or yarns, for example non-conductive ceijulosic fibre such as cotton or viscose fibre, wool, acrylic, polyester, polypropylene, nylon and other synthetic or natural fibres. The fibre can also be blended with other conductive fibres, for example carbon or metal fibres.

The conductive fibre.of the invention has numerous applications in a variety of fields. It is particularly useful in providing anti-stazic properties in textile products, for example carpets both in the carpet tufts and in carpet backings, upholsterr includ-ng automotive upholstery fabrics, and clothing. For anti-static applications, the conductive fibre is usual!,; blended with other textile fibres, or yarns formed from the con--'uctive fibre are woven or knitted with textile yarns. The proportion of conductive fibre is generally in the range of 0.1 to 20% conductive fibre. by weight based. cn the total fibre weight of the product, although higher proDort-Lons can be employed if desired.

The conductive fibre has electro-thermal properties which can be utilised in a variety of applications, for example electric blankets, floor heating, electrically heated clothing, pipeline heating, thermal cover. ngs, thermal shieldings and the like. It has been f ound that the fibre according to the invention increases in temDerature with increasing power up to a specific temperature, which when the fibre is impregnated with copper sulphide is in the region of 600C, after which no appreciable increase in temperature occurs with further increase in power. Thus the conductive fibre is especially useful in applications which require automatic thermo-static control.

The invention will now be illustrated by the following Examples. Unless otherwise stated all parts and i:

-X 1 percentages are by weight and, when based on the fibre weight, are based on the total dry weight of the fibre.

F-xamDle 1 In this Example viscose fibre is modified by reaction with the sulphate salt of the reaction product C.L dicyandiamide and diethylenetriamine. In this and subsequent Examples this sulphate salt is referred to as "Compound AI". A method for its preparation is given in EP 151370A mentioned above, on page 19, Example 1.

1.7 decitex, 5Orr.m staple viscose fibre was immersed in a bath containing an aqueous solution of Cc.mpound AI. The liquor to goods ratio was 30:1 and the concentration of Compound AI was 1.65% w/wf. The temiDerature c.-Lc the bath was raised from room temperature to 700(2 and sodium carbonate added to increase the pH of the solution to pH 1.0 - 9.5. The viscose fibre was immersed in the bath for minutes with agitation, after which the fibre was -cooled and washed thoroughly with water.

The resulting modified viscose fibre was then immersed in a second bath containing an aqueous solution of 12.5 g/1 copper (II) sulphate and 112 9/1 sodium thiosulphate. The liquour to goods ratio was 30:1. The bath was heated at a rate of 20C/minute to raise the temperature of the solution from room temperature to 850C.

The fibre was treated with the solution for 30 minutes at _85C, after which it was cooled. washed with warm water and then cold water, hydroextracted and dried.

The resulting fibre contained 0.72% Compound A1 as determined by Kjeldhal Nitrogen Analysis. The fibre was dark green/black in colour and had an electrical resistivity of 20 ohm cm.

9 - 10 Example 2

1.7 decitex, SOnL-n staple viscose fibre was immersed in a bath containing an aqueous solution of 1.65% CompounC A1 at a liquour to goods ratio of 20:1. After 5 minutes 1 g/1 of sodium hydroxide was added and the temperature of the bath raised to 40'C. Treatment was continued for 10 minutes after which the bath was cooled and the fibre washed thoroughly with cold water.

The resulting modified f-Jb-re was then treated with copper (II) sulphate and sodium thiosulphate as desc-ribed in ExamDle 1.

The resulting fibre contained 0.64% Compcund Al. The fibre was dark green in colour and had a res-is---iv-J-%-vof 50 ohm cm.

ExamDle 3 1.7 decitex, 37 mm staple viscose filD-re was t-reated with Compound A1 as described in Example 2.

The resulting modified fibre was then immersed in a second bath containing an aqueous solution of 300 g/1 copper (=) sulphate and 100 g/1 sodium thiosulphate. The temperature of the bath was raised to 850C and the fibre was immersed in' the solution for a further 45 minutes, after which the bath was cooled and the fibre washed thoroughly with water.

The resulting fibre was black in colour and had a resistivity of 16 ohm cm.

F-xample 4 A wound yarn package of 16s cotton count 100% cotton yarn was immersed in a bath containing an aqueous solution tr f -t I of 5.5% Compound A1 at a 20:1 licour to goods ratio. The bath was initially at room temperature and after the package had beer. immersed for 5 minutes 3 c/1 of sodium hydroxide was added. The bath temperature was then raised to 400C and the treatment continued for a further 10 minutes after which the bath was cooled and the fibre washed with water.

The resulting modified cotton package was immersed in a second bath containing an aqueous solution of 25 g/1 copper (II) sulphate and 224 g/1 sodium thiosulphate. The temperature of the bath was raised from room temperature to 850C and the treatment continued for 1 hour. The bath was then cooled and the package washed thoroughly with water.

The resulting yarn package was black in colour and had a resistivity of less than 10 ohm cm.

Example 5

A weft knit 100% cotton interlock fabric was immersed in a bath containing an aqueous solution of 1.650-0 Compound A1 at a 20:1 liquour to goods ratio. The temperature of the bath was raised to 70C and sodium carbonate added to increase to pH value of the solution to pH 9.0-9.5. Treatment was continued for 20 minutes and then the bath cooled and the fabric washed with water.

The resulting modified fabric was immersed in a second bath containing an aqueous solution of 6.25 g/1 copper (II) sulphate and 38 9/1 sodium thiosulphate at a liqour to goods ratio of 30:1. The bath temperature was raised to 8SIC and the fabric was immersed for 30 minutes, 30 followed by cooling and washing with water.

k - 12 The resulting fabric was dark green in cc-Icur an(S had a resistivity of 210 ohm cm.

Example 6

A wef:t knit 100% cotton interlock fab-4Lc was treated with Compound A1 as described in Example 5 and then treated with copper (II) sulphate and sodium thiosulphate as described in Example 3. The resulting fabric was black and had a resistivity of less than 10 ohm cm.

Exam-ple 7 A weft knit 100% cotton interlock fabric was treated with ComDound A! as described in Example 3.

The resulting modified fabric was then inmiersed- in a second bath containing an aqueous solution of 8.0% Formosul for 1 hour at room temperature, after which the fabric was hydroextracted.

Following the Formosul treatment, the fabricwas immersed in a third bath containing an aqueous sclution of 300 g/! copper (II) sulphate and 100 g/1 sodium thiosulphate for 1 hour at SOOC. The bath was then cooled and the fabric washed with water.

The resulting fabric was black and had a resistivity of 21 ohm cm.

0 1

Claims

1 An electrically conductive fibre comprising a cellulosic fibre modified by reaction with the reaction product of a mono- or polyfunctional amine having one or more primary and/or secondary and/or tertiary amino groups with cyanamide, dicyandiamide, guanidine or bisguanidine, cr a salt thereof, and impregnated with a metal sulphide selected from copper, iron, silver, tin and lead sulphide.

2. A f ibre as claimed in Claim 1 wherein the amount of the said reaction product incorporated in the f -ibre is between 0.2 and 5.0% w/wf, preferably between 0.6 and 3.0 W/Wf.

3. A f ibre as claimed in Claim 1 or 2 wherein the said reaction product is the product of dicyandiamide and diethylenetriamine.

4. A fibre as claimed in Claim 1,2 or 3 wherein the amount of metal sulphide impregnated in the fibre is between 1 and 30% w/wf, preferably between 10 and 25% w/w.-7.

5. A fibre as claimed in any preceding claim wherein the metal sulphide is copper sulphide.

6. A method for the production of an electrically conductive cellulosic-based fibre which comprises:- (a) treating a cellulosic fibre with an aqueous solution of the reaction product of a mono or polyfunctional amine having one or more primary and/or secondary and/or tertiary amino groups with cyanamide, dicyandiamide, guanidine or bisguanidine, or a salt thereof, to form a modified cellulosic fibre; and (b) treating the modified fibre with an aqueous solution of a water soluble metal salt of copper, iron, 30 silver, tin or lead, a reducing agent and a sulphur- to4 containing compound capable of reacting with the metal salt to form metal sulphide which is absorbed onto the modified f ibre.

7. A method as claimed in Claim 6 wherein the said reaction product is the product of dicyandiamide and diethylenetriamine.

8. A method as claimed in Claim 6 or 7 wherein tI-c metal salt is a copper (II) salt, preferably copper sulphate.

9. A method as claimed in any of Cialms 6 to 8 wherein the sulphur-containing compound is also the reducing agent.

10. A method as claimed in any of Claims 6 to 9 wherein the sulphur-containing compound is sodium thiosulphate or sodium metabisulphite.

11. A method as claimed in any of Claims 6 to 10 wherein the modified fibre is treated simultaneously with the metal salt, reducing agent and sulphur-containing compound.

12. A method as claimed in any of Claims 6 to 11 wherein between steDs (a) and (b) the modified fibre is treated with thiourea, thioacetamide, Ronaalite Z or Formosul.

Pub'Is' ed 1986 a' n':e Pa-en- OfIC5 Siate House 66 71 London WC1R 4TP llirzhe: czpies r.nkv be obtamed frc= The Patent Ofice Sales Branch, St Ma-,7 Cray. Orping=. Kent BM 3RD- Printed by MultPlex tecluuques ltd. St Ma--y Crky. Kent Con. 167