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Title:
USE OF A CELLULOSIC FIBRE IN FILLINGS
Document Type and Number:
WIPO Patent Application WO/2008/019412
Kind Code:
A3
Abstract:
Use of a cellulosic fibre having had no flame retardant treatment for the manufacture of fillings having flame retardant self-extinguishing properties, and a filled product having flame retardant properties comprising a fabric cover and a filling including a cellulosic fibre as set above.

Inventors:
BURROW THOMAS RICHARD (GB)
RUEF HARTMUT (AT)
FIRGO HEINRICH (AT)
Application Number:
PCT/AT2007/000378
Publication Date:
April 10, 2008
Filing Date:
August 06, 2007
Export Citation:
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Assignee:
CHEMIEFASER LENZING AG (AT)
BURROW THOMAS RICHARD (GB)
RUEF HARTMUT (AT)
FIRGO HEINRICH (AT)
International Classes:
A47C27/12; B68G1/00
Domestic Patent References:
WO2006060835A12006-06-15
WO2004023943A12004-03-25
WO2005007945A12005-01-27
Foreign References:
EP1203546A22002-05-08
Attorney, Agent or Firm:
NEMEC, Harald et al. (Wien, AT)
Download PDF:
Claims:
CLAIMS

I . Use of a cellulosic fibre having had no flame retardant treatment for the manufacture of fillings having flame self-extinguishing properties. 2. Use of a cellulosic fibre as claimed in Claim 1 in which the cellulosic fibre is a natural cellulosic material selected from the group cotton, a bast fibre such as sisal, coir, linen, hemp or flax or a cellulosic fibre formed directly from wood pulp.

3. Use of a cellulosic fibre as claimed in Claim 1 in which the cellulosic fibre is a man-made cellulosic fibre.

4. Use of a cellulosic fibre as claimed in Claim 3 in which the cellulosic fibre is selected from the group of viscose fibres and lyocell fibres.

5. Use of a cellulosic fibre as claimed in Claim 4 in which the viscose fibre is selected from the group modal fibre and regular viscose fibre. 6. Use of a cellulosic fibre as claimed in Claim 5 in which the regular viscose or the modal fibre has a plurality of limbs, preferably 3 limbs, in cross- sectional shape.

7. Use of a cellulosic fibre as claimed in any one of Claims 1 to 6 in which the decitex of the fibre is in the range 1.3 decitex to 17 decitex, preferably in the range 5 to 8 decitex.

8. Use of a cellulosic fibre as claimed in any one of Claims 1 to 7 in which the cellulosic fibre is mixed with at least one non-cellulosic man-made fibre.

9. Use of a cellulosic fibre as claimed in Claim 8 in which the at least one man-made fibre is a thermoplastic fibre. 10. Use of a cellulosic fibre as claimed in any one of claims 1 to 9 I which the LOl of the cellulosic fibre is 20 or less.

I 1. Use of a cellulosic fibre as claimed in claim 10 in which the LOI of the cellulosic fibre is in the range 18 to 20.

12. Use of a cellulosic fibre as claimed in any one of Claims 1-11 in which the cellulosic fibre is mixed with at least one further fibre which incorporates a

flame retardant material, said flame retardant material in the case of a cellulosic man-made fibre not being an unmodified hectorite clay or a hydrophobically modified hectorite clay.

13. Use of a cellulosic fibre as claimed in claim 12 in which the at least one further fibre is also a cellulosic fibre.

14. Use of a cellulosic fibre as claimed in Claim 13 in which the flame retardant for the at least one further fibre is selected from the group consisting of a phosphorous containing substance and a nano clay, other than unmodified hectorite clay or a hydrophobically modified hectorite clay where the cellulosic fibre is a man-made fibre.

15. Use of a cellulosic fibre as claimed in any one of Claims 1 to 14 in which the fillings are self-extinguishing when tested in accordance with the draft proceeding shown in the California Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulation TB604 dated October 1 , 2004.

16. A filled product having flame retardant properties comprising a fabric cover and a filling including a cellulosic fibre as claimed in any one of claims 1 to 15.

17. A filled product as claimed in Claim 16 in which the fabric cover is a woven fabric.

18. A filled product as claimed in Claim 17 in which the woven fabric is formed from yarns having a mixture of a cellulosic fibre and a polyester fibre.

19. A filled product as claimed in Claim 18 in which the cellulosic fibre of the woven cover is cotton. 20. A filled product as claimed in any one of Claims 16 to 19 in which the filled product is selected from the group including the inner stuffing of mattresses and upholstered chairs, mattress pads, fibre batting, and top-of-the-bed- products such as sleeping pads, comforters, duvets, pillows, bedspreads and quilts.

21. A filled product as claimed in any one of claims 16 to 20 in which the density of the filling is within the range 0.01 to 0.25 grams per cc, preferably 0.02 to 0.1 gram per cc, further preferably 0.025 to 0.075 grams per cc, further preferably 0.05 grams per cc.

Description:

LvoceH Fillings

This invention relates to uses of cellulosic fibre and has particular reference to such uses in the manufacture of fillings that have flame self extinguishing properties.

There is increasing commercial pressure to produce products which are safer in the home. For example, in California, USA, there is a proposed flammability test procedure which may be used as the basis for standards for filled bed clothing or top-of-the-bed items such as comforters, quilted duvets covers, quilted bed pads, duvets, bedspreads, bed pillows, bed rest cushions, mattress pads, quilted bed shams, quilted pillowcases, padded headboards and foam topper pads.

Many of these products are manufactured utilising polyester fibre as the filling, often with a polyester/cotton cover. If such filled products are set on fire, it is observed that, after ignition with a small flame for 20 seconds, both the cover and the filling burn readily. Within 3 or 4 minutes the whole product has been burnt leaving only a small pool of molten polyester. This pool continues to burn locally where small pieces of cotton act as a wick to conduct the molten polyester into a flame zone. For an item the size of a small pillow, the whole process is virtually complete in 2 minutes leaving only a small flame burning as the remains of the molten polyester is consumed. In California, the California Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulation has published a draft technical bulletin commonly referred to as TB604 which describes the test method. In this specification, the draft dated October 1 2004 is herein referred to as the draft TB604 procedure.

The final version of TB604 has yet to be determined, but many companies and individuals are currently working in an attempt to produce designs and

products which will meet what those companies and individuals consider is likely to be the final version of TB604.

There have been many attempts in the prior art to modify cellulose moulded bodies, such as fibres, in order to impart thereon flame-retardant properties.

The term "Flame Retardant" (FR) is sometimes used by different people with different meanings. In this specification the terms FR and RF will be used as follows. FR is used to mean flame retardant, and RF is used to mean reduced flammability. FR materials can be those which are inherently flame retardant as well as those which have been treated to give flame retardant properties. For example, FR viscose available from Lenzing AG fully meets the requirements of the vertical flame test as set out in ISO 15025. This is a case where a naturally flame supporting material, viscose rayon, has been given a treatment to make it flame retardant. In contrast, a polyararnid fibre, such as Nomex® from Du Pont, is an inherently flame retardant fibre not requiring a treatment to give it FR properties.

However there are fibres which can be made to have reduced flammability properties, even if the fibres cannot be made into materials which will fully pass ISO 15025 and be considered as FR fibres. These fibres are those which have been given a treatment to reduce the flammability of the fibre without necessarily making it fully an FR fibre. As an example, lyocell fibres can be treated with certain clays to give the fibre reduced flammability properties without necessarily enabling it to meet the ISO 15025 test. Clearly the terms FR and RF can overlap. An inherently FR fibre could be treated to further reduce its flammability, making it both an FR and an RF fibre.

Alternatively, a normally flammable fibre could be treated with a flame retardant at a level such that it becomes an FR fibre, or the fibre could be treated

with the same treatment at a Sower level (or a different treatment) so that it does not attain full FR status, but it has become, by definition become an RF fibre.

The skilled reader will be aware of these factors and be able easily to interpret the requirements for the fibres as set out herein.

References to certain prior art treatments to develop an FR cellulosic fibre are set out below:

As regards moulded bodies produced according to the amine-oxide process, such as Lyocell fibres, WO 93/12173 discloses triazine compounds containing phosphorus and their use, including use in cellulose solutions in tertiary amine oxides.

WO 94/21724 describes flame retardants containing phosphorus. The use thereof for Lyocell fibres is also mentioned.

WO 94/26962 discloses a process for the manufacture of a flame retardant Lyocell fibre. In this process, a flame retardant is added during the manufacturing process of the fibres, before drying of the fibres.

According to WO 96/05356, textile materials containing Lyocell fibres are treated with compounds containing phosphorus and nitrogen.

WO 97/02315 discloses the manufacture of a flame-retardant Lyocell fibre, whereby a cyclic phosphine-oxide is added to the spinning dope.

DE 44 26 966 generally mentions the addition of filling compounds to Lyocell fibres, whereby the filling compounds are added in high amounts.

WO 96/27638 quite generally mentions silicates as flame retardant agents, which can be added to a Lyocell dope.

WO 04/081267 discloses modified fibres, which have been produced according to the amine-oxide process and to which ceramic oxides, preferably silicon dioxide, are added.

In addition, certain other treatments to produce an RF fibre utilising nano- composites of clay are known and are described in the following references:

US-A- 6,893,492 describes methods of improving the thermal stability of nanocomposites made from cellulosic materials in combination with clays such as smectic clays, hectorites and synthetic clays to produce materials that have a raised temperature at which degradation occurs and enhanced char yields. See also the paper published in Polymer Preprints 2002, 43(2), 1279 by Leslie A. White and Noelie R. Bertoniere of the Cotton Textile Chemical Research Unit, South Regional Research Center and entitled "Preparation of Cotton/Clay Nanocomposites".

In the case of the addition of nano-clays to the fibres, the use of an unmodified or hydrophobically modified clay normally gives an RF fibre, but certain chemical modifications may enable the production of FR fibres.

The above processes have several disadvantages: Some of the known processes are expensive or use substances which are questionable from an ecological viewpoint. Many of the processes published up to now are not compatible with the requirements of a continuous fibre production process. For this reason, up to now none of the above proposals has reached the stage of production in large scale.

The present invention has emerged as a result of an amazing observation made by the inventors. This observation, which forms the basis of much of the present invention, can be summarised quite succinctly. Whereas a 100% . polyester fibre filled pillow which has a 50% polyester/50% cotton cover burns rapidly, as noted above, it has been observed that if a 50/50 polyester/cotton cover is filled with a mixture of 50% polyester fibres 50% lyocell fibres of about 6 decitex a totally different result is obtained. When such a product is tested in

accordance with the draft TB604 testing standard a completely unexpected effect is observed. The cover, which is a woven material made of 50/50 polyester/cellulosic fibre (the cellulosic fibre being cotton) burns away, but the filling does not burn away. And yet the filling is also a 50/50 polyester/cellulosic fibre mixture but this time the cellulosic fibre being a lyocell fibre is in a loose blend with the polyester and yet it does not burn away. It forms a self extinguishing char coated structure essentially unchanged in shape and volume and which is self-extinguishing. Thus the denser woven polyester cellulosic fibre fabric burns away and yet the looser and air filled blend of the polyester and cellulosic fibres in the filling does not.

Amazingly therefore, it has been found that although both the cover and the filling are each 50% polyester 50% cellulosic fibre, the cover burns away and the filling simply chars and does not support flames. This was a quite unexpected observation. Given that a 100% polyester filled product burns out in 2 or 3 minutes, and given that it is well known that cellulosic fibres are highly flammable, this is a quite remarkable result. For very many years a great deal of work has been carried out to give cellulosic fibres flame retardant properties and to increase the Limiting Oxygen Index (LOI) - see above. Now it has been discovered that, in the special case of a filling material, cellulosic fibres having had no flame retardant treatment can be used and get good results. Such untreated fibres are less likely to give any adverse reactions to their users and are by definition less expensive to produce than the same fibres which have had an additional treatment. Of course the invention further contemplates the additional use of flame retardant treated fibres in blends with untreated cellulosic fibres, as well as the untreated cellulosic fibres being used in a blend with other fibres such as polyester fibres.

Cellulosic fibres are given many treatments during processing, such as the application of finishes and dyes. Many of these finishes may slightly affect the LOI

of the underlying fibre. However flame retardant treatments as such can be thought of as falling within several main types:

Organic and inorganic salt finishes, typically based on boric acid, sulphamic acid or phosphoric acid, ammoniates, salts of organic amines, metallic salts, ammonium phosphates, and ammonium sulphamates.

Products based on metal oxides and chlorinated binding agents, often not wash resistant and based on antimony oxide, with a chloroparaffin or PVC Phosphorous and nitrogen containing products, often used with resins

Organic phosphorous-nitrogen compounds.

Clay containing products, particularly nano-clay containing products.

Such flame retardant products are applied for the express purpose of increasing the LOI of the cellulosic fibre from its LOI of about 18-20 in the untreated state to an LOI figure of greater than 25, preferably greater than 27. For the purposes of the present invention, a treatment is considered to be a flame retardant treatment if it is one specifically applied to increase the LOI of the fibre as an objective of the treatment. An increase of an LOI figure to above an LOI of 21 , or above 22 or further above 25, is considered to be a flame retardant treatment.

Treatments such as the application of a silicone finish which may, as an irrelevancy to the purpose of the application of the finish, result in a slight increase of the LOI of the fibre are not, for the purposes of this invention, deemed to be flame retardant treatments.

The present invention therefore provides for the use of a cellulosic fibre having had no flame retardant treatment for the manufacture of fillings having flame self-extinguishing properties.

The cellulosic fibre may be a natural cellulosic material selected from the group cotton, a bast fibre such as linen, sisal, coir hemp or flax or a cellulosic fibre formed directly from wood pulp or may be a man made cellulosic fibre.

The man-made cellulosic fibre may be selected from the group of viscose fibres and lyocell fibres. The viscose fibre may be selected from the group modal fibre and regular viscose fibre. The regular viscose or the modal fibre may have a plurality of limbs, preferably 3 limbs, in cross-sectional shape.

The cellulosic fibre may have a decitex in the range 1.3 decitex to 17 decitex, preferably in the range 5 to 8 decitex.

The cellulosic fibre may be mixed with a non-cellulosic man-made fibre, which may be a thermoplastic fibre, preferably a polyester fibre.

The cellulosic fibre preferably has an LOI at or below 20, further preferably in the range 18 to 20.

The cellulosic fibre may be mixed with a further fibre which incorporates a flame retardant material, said flame retardant material, not being unmodified hectorite clay or a hydrophobically modified hectorite clay in the case of a man- made cellulosic fibre. The further fibre may also be a cellulosic fibre which may be treated with a flame retardant selected from the group consisting of phosphorous containing substance and nano-clays other than unmodified hectorite clay or a hydrophobically modified hectorite clay where the further fibre is a man made fibre.

The present invention provides for the use of a cellulosic fibre as set out above in which the fillings are self-extinguishing when tested in accordance with the draft proceeding shown in the California Department of Consumer Affairs, Bureau of Home Furnishings and Thermal Insulation TB604 dated October 1 , 2004.

The present invention yet further provides for a filled product having flame retardant properties comprising a fabric cover and a filling including a cellulosic fibre as set out above.

The fabric cover may be a woven fabric. The woven fabric may be formed from yarns having a mixture of a cellulosic fibre and a polyester fibre. The cellulosic fibre of the woven cover may be cotton.

The filled product may be selected from the group including the inner stuffing of mattresses and upholstered chairs, mattress pads, fibre batting, and top-of-the-bed-products such as sleeping pads, comforters, duvets, pillows, bedspreads and quilts.

The filled product may have a filling with a density within the range 0.01 to 0.25 grams per cc, preferably 0.02 to 0.1 gram per cc, further preferably 0.025 to 0.075 grams per cc, further preferably 0.05 grams per cc.

Flame retardant cellulosic fibre may contain clays and in accordance with the content of co-pending Austrian Application No AT-A 2028/2005 the clays may be unmodified hectorite clay or hydrophobically modified hectorite clay when the fibre is a man-made cellulosic fibre (referred to in the application as a cellulosic moulded body). No claim is made in this application to a filling material of a filled object in which the filling comprises a blend of a cellulosic fibre having had no

flame retardant treatment and a man made fibre or cellulosic moulded body in which the flame retardant is selected from the group consisting of unmodified hectorite clay or a hydrophobically modified hectorite clay

The filling may be formed by carding and cross folding the cellulosic fibre optionally with a polyester fibre. Instead of carding the fluffy mass of fibre may be created by an opener such as a garnet.

Whereas it is known that lyocell fibre may be mixed with polyester fibre for use in duvets prior to the making of the present invention, it has not been appreciated that cellulosic fibres in the untreated state, as far as flame retardancy was concerned, could be used for the manufacture of fillings having flame self extinguishing properties.

This is all the more surprising given the fact that when such fillings are placed in a polyester/cotton cover, the cover burns but not the filling. It would have been expected that the cellulosic fibre when used on its own would simply burn through and the filling would burn away rapidly. Quite why this does not happen is at the moment unclear to the present inventors. Given that the cellulosic fibres present in a polyester/cotton covered 100% polyester filled product act as wicks, once the main cover has burnt away, and the remaining polyester from the filling has burnt to a molten pool, it would be expected that the same would happen with a filling comprising a 50/50 mixture of cellulosic fibre and a polyester fibre. Again, it is not clear why the filling does not burn. However, repeated observations by the inventors as set out below have found this to be the case and this remarkable observation forms the basis of the present application.

Examples

Sample cushions or pillows were made to enable a series of tests to be carried out. In each case the covering for the cushion was a woven fabric having a weight of 8Og per square metre.

The samples were made up and tested in accordance with the test method as set out in the draft TB604 procedure. Multiple layers of carded and, where relevant, blended filling fibre material were cut to 305mm by 305mm. Several layers were stacked so that their height was 89mm. The weight of the filling depended on the material of the fibre. For 100% polyester the weight was 85g. For RF lyocell incorporating a nano-clay as set out in co-pending Austrian Application No AT-A 2028/2005, the weight was 145g. The density of the 100% polyester filling was therefore 10.3 kg/m 3 , and for the RF lyocell it was 17.5 kg/m 3 .

The filling was inserted into a cover having an original flat size of 381 mm by 381 mm so that after the filling was inserted the cushion was about 350mm by 350mm.

Ignition is initiated by the application of a small flame to the side of the pillow for 20 seconds. The pillow is located on a metal scale and the weight loss is observed during the test. The weight loss is noted after 3 minutes and 6 minutes. To pass the draft test, the average weight loss for three samples has to be less than 25g after three minutes and 30% after 6 minutes with no sample loosing more than 35% of its weight within 6 minutes. To some extent the weight loss is dependant on the weight loss of the cover fabric, not of the filling.

The first test was of a series of products not in accordance with the invention. These were cushions of a 50/50 cotton/polyester covering fabric filled

with 100% polyester filling. Three different polyester fibres were used. The first was a polyester of an unknown origin. The second was a fibre sourced from Wellman and the third a Trevira® fibre from Reliance Industries. These three samples all burnt out completely in about 2 minutes, leaving a pool of molten polyester with strands of cotton form the cover acting as wicks and continuing to burn for several minutes. The test was terminated before either the 3 minute or the 6 minute time had elapsed. The actual weight losses at the end of the two minute periods were 43%, 25% and 24%.

The second test series was also of products not in accordance with the invention (although meeting the requirements of the TB604 test). These were cushions filled with 50% polyester and a 50% RF lyocell fibre. Again three cushions were tested each with a different combination of cover and filling.

(i) Filling 50% RF lyocell of 6.7 dtex and 60 mm staple length 50% of the first type of polyester, with a cover of 50%cotton/ 50% polyester fabric.

(ii) Filling 50% RF lyocell of 6.7 dtex and 60 mm staple length 50% of the second type of polyester, with a cover of 100% 0.9 Decitex lyocell fabric. (iii) Filling 50% RF lyocell of 6.7 dtex and 60 mm staple length 50% of the third type of polyester, with a cover of 100% 0.9 Decitex lyocell fabric.

In the tests, there was a weight loss after 3 minutes of 30% for the first cushion, 26% for the second and 25% for the third.

The third series of tests were of products in accordance with the invention. In all cases the filling was of 50% bright lyocell of 6.7 decitex and having a staple length of 60mm. Three samples were made up and tested.

(i) The filling polyester was of the second type and the cover was a

50/50 cotton /polyester fabric (ii) The filling polyester was of the third type and the cover again was a 50/50 cotton /polyester. (iii) The filling was of the third polyester type and the cover was a 100

0.9 decitex lyocell fabric.

The results of these tests were that after 3 minutes the weight losses were 40% for the first sample, 42% for the second sample and 48% for the third sample. However, although the covers burned, the cores remained as a charred, but substantially unaltered, structures. The flames went out after 5 minutes and 20 seconds in each test.

The final tests were also of products in accordance with the invention. These were of cushions filled with 100% standard bright lyocell fibre of 6.7 decitex and with a staple fibre length of 60 mm. Two different samples were tested, (i) with a cover of 50%cotton/50% polyester (ii) with a cover of 100% 0.9 decitex lyocell fabric

The results after 3 minutes were that the first sample had lost 40% of its weight and the second sample had lost 28% of its weight. The covers were still burning on the side opposite the ignition point after 3 minutes.

It will be seen that most of these products do not pass the draft TB604 test as currently written. To some extent this is because of the fact that the covers are such a large percentage of the weight of the total cushion. However, it has been observed that the products in accordance with the invention have properties which are sufficiently valuable to have usage whatever the final form of the TB 604 regulation. The properties have been unexpectedly discovered as a result of work

carried out to find products which meet the wording of the current draft. They have, in effect been inspired by the demands of the draft standard.

The denier of the filling would normally be chosen to match the mechanical requirements of the product. Normally a high denier cellulosic fibre such as a 6 or 7 decitex fibre would be used for products such as quilts or comforters as such fibre has a stiffness which gives the required feel for the product. Other products may best be suited to other decitex material.

Normally staple cellulosic fibre is preferred as a filling material, but filamentary fibre could be used if required.

The density of the fillings used can vary widely within the range 0.01 to 0.25 grams per cc, preferably 0.02 to 0.1 gram per cc, further preferably 0.025 to 0.075 grams per cc, further preferably 0.05 grams per cc. However, the filling density range may be selected by the user depending on application.

The cover fabric may be formed of any suitable material. Standard cover fabrics are formed from 50/50 polyester /cotton. Other cellulosic fibres can be used in place of cotton. However it is contemplated as part of the invention that either or both of the polyester or the cellulosic fibre component of the cover may be formed of a flame retardant or reduced flammability fibre. Thus the cover may be formed from polyester and FR or RF lyocell or an FR or RF polyester and lyocell or a FR or RF polyester and an FR or RF lyocell. For lyocell and FR or RF lyocell, other FR or RF cellulosics may be used, such as cotton or a viscose rayon fibre including modal fibre.