Cellulose substrate with anti-flame properties and relative production method

Abstract

Method for sulphation and phosphorylation of a cellulose substrate for imparting anti-flame properties to the substrate in which at least one phosphonic acid of formula (I):
PO(OH).sub.2—R—PO(OH).sub.2,   (I)
is used as a catalyst of sulphation and a phosphorylating agent and relative substrate.

Claims

1. A method for sulphation and phosphorylation of a cellulose substrate to impart anti-flame properties to the cellulose substrate comprising the following operations: i) provide a cellulose substrate; ii) prepare a sulphation and phosphorylation solution, the sulphation and phosphorylation solution comprising water, ammonium sulphamate, urea and at least one compound of formula (I):
PO(OH).sub.2—R—PO(OH).sub.2  (I) wherein R represents a linear or branched, substituted or unsubstituted C.sub.1-10 alkyl group; a N(R.sub.1) group; a R.sub.2N(R.sub.3)R.sub.4 group; R.sub.1 represents H, a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; R.sub.2 and R.sub.4 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; R.sub.3 represents a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; a R.sub.5N(R.sub.6)R.sub.7 group; R.sub.5 and R.sub.7 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; R.sub.6 represents a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; a R.sub.8N(R.sub.9)R.sub.10 group; R.sub.8, R.sub.9 and R.sub.10 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; with the proviso that the number of —PO(OH).sub.2 groups in the general formula (I) is not greater than 5; iii) immerse the cellulose substrate in the sulphation and phosphorylation solution; iv) extract the cellulose substrate from the sulphation and phosphorylation solution; v) maintain the cellulose substrate at a temperature comprised between 110° and 175° C. for a period of time comprised between 1 minute and 3 hours, obtaining at the end a sulphated and phosphorylated cellulose substrate with anti-flame properties.

2. The method for sulphation and phosphorylation according to claim 1, wherein before operation v) the substrate extracted from the sulphation and phosphorylation solution is subjected to a centrifugation and heat drying operation.

3. The method for sulphation and phosphorylation according to claim 1, wherein at the end of the operation v) the substrate is subjected to a washing operation and heat drying.

4. The method for sulphation and phosphorylation according to claim 1, wherein the sulphation and phosphorylation solution is prepared by mixing in the following order water, urea, at least one compound of formula (I) and ammonium sulphamate.

5. The method for sulphation and phosphorylation according to claim 1, wherein the sulphation and phosphorylation solution contains: water in a quantity between 80 and 25% w/w, urea in an amount between 10 and 30% w/w, at least one compound of formula (I) in an amount between 5 and 30% w/w, and ammonium sulphamate in an amount between 5 and 30% w/w.

6. The method of sulphation and phosphorylation according to claim 1, wherein when any one of the groups R, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, if present, represents a substituted alkyl group, the one or more substituents are selected independently from —OH, —COOH, —PO(OH).sub.2, —NH.sub.2, —NHR.sub.11, —NR.sub.12R.sub.13, —Cl, —Br, —F, wherein R.sub.11, R.sub.12 and R.sub.13 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group.

7. The method for sulphation and phosphorylation according to claim 6, wherein when any one of the groups R.sub.11, R.sub.12 and R.sub.13 of the general formula (I), if present, represents a substituted alkyl group, the one or more substituents are represented by the —PO(OH).sub.2 group.

8. The method for sulphation and phosphorylation according to claim 1, wherein the groups R.sub.2, R.sub.4, R.sub.5 and R.sub.8, if present, represent independently an unsubstituted alkyl group.

9. The method for sulphation and phosphorylation according to claim 1, wherein when the groups R.sub.3, R.sub.6, R.sub.7, R.sub.9 and R.sub.10, if present, represent independently a substituted alkyl group, the one or more substituents are represented by the —PO(OH).sub.2 group.

10. The method for sulphation and phosphorylation according to claim 1, wherein the at least one phosphonic compound of formula (I) is selected from: 1-hydroxyethan-1,1-diphosphonic acid, hydroxyethyl-imino-bis-(methylene-phosphonic) acid, amino-tris-(methylene phosphonic) acid, ethylenediamine tetra-(methylene phosphonic) acid, diethylentriamine-penta-(methylene phosphonic) acid, (1-aminoethylidene) bisphosphonic acid, oxidronic acid, pamidronic acid, alendronic acid, (1-hydroxy-2-methyl-1-phosphonopropyl) phosphonic acid, (aminomethylene) bisphosphonic acid, 1-hydroxypentane-1,1-bisphosphonic acid, [(2-hydroxypropan-1,3-diyl) bis(nitrilodimethane-diyl)] tetrakis-phosphonic acid, clodronic acid, (difluoromethylene) bisphosphonic acid, (dibromomethylene) bisphosphonic acid, (hydroxymethan) bisphosphonic acid.

11. The method for sulphation and phosphorylation according to claim 1, wherein the cellulose substrate comprises cellulose fibres of natural or artificial origin, or mixtures thereof.

12. The method for sulphation and phosphorylation according to claim 1, wherein the sulphated and phosphorylated cellulose substrate has a Limiting Oxygen Index (L.O.I.) between 25 and 35.

13. The method for sulphation and phosphorylation according to claim 1, wherein the sulphated and phosphorylated cellulose substrate has a tensile strength, abrasion resistance and a hand substantially equal to those of an untreated substrate.

14. A cellulose substrate with anti-flame properties obtained by implementing the method according to claim 1.

15. The method for sulphation and phosphorylation according to claim 1, wherein the sulphation and phosphorylation solution is prepared under a heated condition.

16. The method for sulphation and phosphorylation according to claim 1, wherein R represents a linear or branched, substituted or unsubstituted C.sub.1-5 alkyl group; a N(R.sub.1) group; a R.sub.2N(R.sub.3)R.sub.4 group; R.sub.1 represents H, a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group; R.sub.2 and R.sub.4 represent independently a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group; R.sub.3 represents a linear or a branched, substituted or unsubstituted C.sub.1-3 alkyl group; a R.sub.5N(R.sub.6)R.sub.7 group; R.sub.5 and R.sub.7 represent independently a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group; R.sub.6 represents a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group; a R.sub.8N(R.sub.9)R.sub.10 group; R.sub.8, R.sub.9 and R.sub.10 represent independently a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group.

17. The method for sulphation and phosphorylation according to claim 2, wherein the heat drying operation occurs at a temperature between 70 and 90° C.

18. The method for sulphation and phosphorylation according to claim 3, wherein the washing operation occurs under a heated condition.

19. The method for sulphation and phosphorylation according to claim 3, wherein the substrate is subjected to the washing operation, under a heated condition, and heat drying, at a temperature between 70 and 90° C.

20. The method for sulphation and phosphorylation according to claim 5, wherein the sulphation and phosphorylation solution contains: water in a quantity between 50 and 60% w/w, urea in an amount between 10 and 20% w/w, at least one compound of formula (I) in an amount between 10 and 20% w/w, and ammonium sulphamate in an amount between 8 and 15% w/w.

21. The method of sulphation and phosphorylation according to claim 6, wherein R.sub.11, R.sub.12 and R.sub.13 represent independently a linear or branched, substituted or unsubstituted C.sub.1-3 alkyl group.

22. The method for sulphation and phosphorylation according to claim 12, wherein the sulphated and phosphorylated cellulose substrate has a Limiting Oxygen Index (L.O.I) between 28 and 32.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will now be described in detail, by way of non-limiting example, with reference to the attached figures, in which:

(2) FIG. 1: shows the chemical structure of cellulose substrates.

(3) FIG. 2: shows the chemical structure of cellulose microfibrils.

(4) FIG. 3: shows the reaction of thermal decomposition of cellulose.

(5) FIG. 4: shows the chemical structure of cellulose phosphorylated according to the known technique.

(6) FIG. 5: shows the chemical structure of a phosphorylating agent according to the present description containing at least one primary hydroxyl free to react with ammonium sulphamate.

(7) FIG. 6: shows the chemical structure of cellulose subjected to a sulphation and phosphorylation method according to the present description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) The invention will now be described in detail, by way of non-limiting example, with reference to a cellulose substrate with improved anti-flame properties essentially consisting of cotton.

(9) It is clear that the scope of this description is in no way limited to a cotton substrate; the procedure described herein is applicable to cellulose substrates of natural or artificial origin, such as flax, jute, hemp, coconut, ramie, bamboo, raffia, esparto, manila, sisal, nettle, kapok, cellulose, preferably pure cellulose, cellulose acetate, cellulose triacetate, viscose, modal, lyocell, cupra rayon, rubber (natural rubber) and alginate or mixtures thereof.

(10) Furthermore, while the experimental data provided below refer to a cellulose substrate essentially consisting of cotton in the form of yarn, the method of the present description is applicable to cellulose substrates in the form of fibres, ribbons, cords, threads, fabrics and non-woven fabrics.

(11) In the following description, numerous specific details are presented to provide a complete understanding of the embodiments. The embodiments may be practiced without one or more of the specific details, or with other processes, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects of the embodiments.

(12) Throughout the present specification, reference to “one embodiment” or “an embodiment” means that a particular configuration, structure, or feature described in connection with the embodiment is included in at least one embodiment. So, the appearance of the phrases “in one embodiment” or “in a certain embodiment” in various places throughout the present specification does not necessarily refer to the same embodiment. Furthermore, particular configurations, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

(13) The headings presented herein are merely for convenience and do not interpret the scope or meaning of the embodiments.

(14) An embodiment of the present description relates to a cellulose substrate subjected to chemical treatment to impart anti-flame properties to the substrate, in which the treated substrate has a L.O.I. comprised between 25 and 35, more preferably between 28 and 32, and has tensile strength, abrasion resistance and hand that are substantially equal to those of an untreated cellulose substrate.

(15) An embodiment of the present description relates to a method of sulphation and phosphorylation of a cellulose substrate for imparting anti-flame properties to the substrate characterized by the use of at least one phosphonic acid that functions as a sulphation catalyst and a phosphorylating agent capable of reacting with any cellulose substrate having reactive hydroxyl groups.

(16) The phosphonic acids used in the procedure described herein are organic compounds that contain 2 to 5 phosphonic groups.

(17) In one embodiment, the phosphonic acids used in the procedure described herein are represented by the general formula (I):
PO(OH).sub.2—R—PO(OH).sub.2  (I)

(18) wherein

(19) R represents a linear or branched, substituted or unsubstituted C.sub.1-10, preferably C.sub.1-5, alkyl group; a N(R.sub.1) group; a R.sub.2N(R.sub.3)R.sub.4 group;

(20) R.sub.1 represents H, a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group;

(21) R.sub.2 and R.sub.4 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group;

(22) R.sub.3 represents a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group; a R.sub.5N(R.sub.6)R.sub.7 group;

(23) R.sub.5 and R.sub.7 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group;

(24) R.sub.6 represents a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group; a R.sub.8N(R.sub.9)R.sub.10 group;

(25) R.sub.8, R.sub.9 and R.sub.10 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group;

(26) with the proviso that the number of —PO(OH).sub.2 groups in the general formula (I) is not greater than 5.

(27) In one embodiment, when any one of the groups R, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7, R.sub.8, R.sub.9, R.sub.10, if present, is a substituted alkyl group, the one or more substituents are selected independently from —OH, —COOH, —PO(OH).sub.2, NH.sub.2, —NHR.sub.11, —NR.sub.12R.sub.13, —Cl, —Br, —F,

(28) wherein

(29) R.sub.11, R.sub.12 and R.sub.13 represent independently a linear or branched, substituted or unsubstituted C.sub.1-5, preferably C.sub.1-3, alkyl group;

(30) with the proviso that the number of —PO(OH).sub.2 groups in the general formula (I) is not greater than 5.

(31) In one embodiment, when any of the groups R.sub.11, R.sub.12 and R.sub.13, if present, represent a substituted alkyl group, the one or more substituents are represented by the —PO(OH).sub.2 group with the proviso that the number of —PO(OH).sub.2 groups in the general formula (I) is not more than 5.

(32) In one embodiment, the groups R.sub.2, R.sub.4, R.sub.5 and R.sub.8, if present, represent independently an unsubstituted alkyl group.

(33) In one embodiment, when the groups R.sub.3, R.sub.6, R.sub.7, R.sub.9 and R.sub.10, if present, represent independently a substituted alkyl group, the one or more substituents are represented by —PO(OH).sub.2 group, provided that the number of PO(OH).sub.2 groups in the general formula (I) is not more than 5.

(34) In one embodiment, the phosphonic compounds of formula (I) used in the method described herein are: 1-hydroxyethan-1,1-diphosphonic acid, hydroxyethyl-imino-bis-(methylene-phosphonic) acid, amino-tris-(methylene phosphonic) acid, ethylenediamine tetra-(methylene phosphonic) acid, diethylentriamine-penta-(methylene phosphonic) acid, (1-aminoethylidene) bisphosphonic acid, oxidronic acid, pamidronic acid, alendronic acid, (1-hydroxy-2-methyl-1-phosphonopropyl) phosphonic acid, (aminomethylene) bisphosphonic acid, 1-hydroxypentane-1,1-bisphosphonic acid, [(2-hydroxypropan-1,3-diyl) bis(nitrilodimethane-diyl)] tetrakis-phosphonic acid, clodronic acid, (difluoromethylene) bisphosphonic acid, (dibromomethylene) bisphosphonic acid, (hydroxymethan) bisphosphonic acid.

(35) In one embodiment, the method of sulphation and phosphorylation of a cellulosic substrate provides the following steps:

(36) i) provide a cellulose substrate;

(37) ii) prepare a sulphation and phosphorylation solution, preferably under heated condition, the sulphation and phosphorylation solution comprising water, ammonium sulphamate, urea and at least one compound of formula (I) as described above;

(38) iii) immerse the cellulose substrate in the sulphation and phosphorylation solution;

(39) iv) extract the cellulose substrate from the sulphation and phosphorylation solution;

(40) v) maintain the cellulose substrate at a temperature comprised between 110° and 175° C. for a period of time comprised between 1 minute and 3 hours, obtaining at the end a sulphated and phosphorylated cellulose substrate with anti-flame properties.

(41) In one embodiment, before operation v) the substrate extracted from the sulphation and phosphorylation solution is subjected to a centrifugation and heat drying operation, preferably at a temperature between 70 and 90° C.

(42) In one embodiment, at the end of the operation v) the substrate is subjected to a washing operation, preferably under heated condition, and heat drying, preferably at a temperature between 70 and 90° C.

(43) In one embodiment, the sulphation and phosphorylation solution is prepared by mixing in the following order water, urea, at least one phosphonic acid of formula (I) and ammonium sulphamate.

(44) In one embodiment, the sulphation and phosphorylation solution contains: water in a quantity comprised between 80 and 25% w/w, preferably 50 and 60% w/w, urea in an amount comprised between 10 and 30% w/w, preferably 10 and 20% w/w, at least one phosphonic acid of formula (I) in an amount comprised between 5 and 30% w/w, preferably 10 and 20% w/w, and ammonium sulphamate in an amount comprised between 5 and 30% w/w, preferably 8 and 15% w/w.

(45) Without wishing to be bound to any one theory in that regard, the inventors have reason to believe that the reactions of sulphation and phosphorylation of a cellulose substrate according to the present description can be illustrated as shown in diagram I.

(46) ##STR00001##

(47) In one embodiment, when the compound of formula (I) contains an alkyl group substituted with a primary hydroxyl, the inventors have reason to believe that this hydroxyl group is able to react with the ammonium sulphamate compound.

(48) By way of example, when the R group represents an alkyl group substituted with a primary hydroxyl group, the inventors have reason to believe that the sulphation and phosphorylation reactions of a cellulose substrate according to the present description can be illustrated as shown in diagram II.

(49) ##STR00002##

(50) The method of the present description overcomes the disadvantages of the traditional method of sulphation and phosphorylation of a cellulose substrate.

(51) First the procedure described herein does not determine a loss of resistance of the cellulose substrate, as it does not cause degradation of the 1,4 glucosidic bonds of the cellulose.

(52) The phosphonic acids of formula (I) as catalysts in the sulphation reaction and as phosphorylating agents produce a weakly acidic reaction unable to break the 1,4 glucosidic bonds of the cellulose.

(53) Moreover, the phosphonic acids of formula (I) contain from 2 to 5 free phosphonic groups capable of reacting with all or part of the free hydroxyl groups of cellulose, which results in a high capacity of these compounds to bind to cellulose.

(54) The anti-flame properties of the substrate subjected to the method of sulphation and phosphorylation according to the present description are improved compared to what is obtainable with known methods, in that it produces a massive synergistic accumulation of sulphur, nitrogen and phosphorus bound to the cellulose substrate, without weakening it.

(55) In an unexpected way, the use of phosphonic acids of formula (I) allows the sulphation and phosphorylation reactions to be carried out simultaneously. The reaction kinetics are relatively fast.

(56) An excellent degree of sulphation, nearly double that of the classical method, is achieved already in the first minutes of reaction and starting at a temperature of 110° C.

(57) Without wishing to be bound to any one theory in this regard, the inventors have reason to believe that the aqueous solution based on phosphonic acids, urea and ammonium sulphamate with heating determines, in addition to partial evaporation of the water, the formation of an oily liquid mass with a pH approximately equal to 2 that, by penetrating inside of the cellulose fibrils, creates ideal acidic conditions for the solid-liquid sulphation and phosphorylation reactions of the cellulose at temperatures in the order of 100-110° C.

(58) In particular, the inventors have reason to believe that urea is able to create complexes with phosphonic acids, wherein such complexes are more soluble in an aqueous environment than the phosphonic acids alone, thus allowing a nearly quantitative reaction of these compounds with the cellulose itself.

(59) The sulphation and phosphorylation method according to the known technique, namely by employing phosphoric acid in quantities less than 1% (as a larger quantity would lead to the dissolution of the cellulose substrate itself), involves recrystallisation of the reagents on the fibre at temperatures below 140-150° C.; only at temperatures above 140-150° C. is urea able to act as a reaction solvent to facilitate the sulphation and phosphorylation reactions.

(60) It is important to note that in the absence of at least one phosphonic acid of formula (I) a method of sulphation and phosphorylation shows no sign of cellulose sulphation at temperatures from 110° C. to 140° C.

(61) Without wishing to be bound to any one theory in that regard, the inventors have reason to believe that sulphation starts first on the phosphorylating agent, if it contains a reactive primary alcohol.sup.1,3,8 (obtaining a compound as shown in FIG. 5) and only successively on the solid cellulose substrate, which usually reacts at minimal temperatures from 150° C. to 200° C.

(62) The phosphorylation reaction conducted with at least one compound of general formula (I) is also almost quantitative, substantially reducing the number of free hydroxyl groups capable of coordinating to calcium and magnesium ions (as shown schematically in FIG. 6).

(63) In fact, the anti-flame cellulose substrates produced by the method of the present description have excellent resistance to washing in water.

(64) Moreover, there are no problems related to the use of highly toxic compounds: the phosphonic acids used have a low toxicity level, low volatility and high thermal stability, the latter being an important feature for reactions performed at elevated temperatures.

(65) Finally, the sulphation and phosphorylation method described herein does not give rise to hazardous gaseous components such as ammonia or urea.

(66) In particular the use of urea in non-stoichiometric quantities with respect to the phosphonic acid groups of the compound of formula (I) allows binding of the ammonia that forms during sulphation and of the urea itself during its passage to the liquid state, due to the formation of complexes with phosphonic groups.

(67) The method of the present description provides a cellulose substrate having improved anti-flame properties and with physical characteristics substantially similar to those of the untreated substrate, unlike the substrates obtained with procedures known in the art.

(68) In particular, the presence of chemical groups based on nitrogen, phosphorus and sulphur provides improved anti-flame properties.

(69) Sulphur releases sulphuric acid allowing the cellulose material to degrade at temperatures below the ignition temperature, nitrogen forms non-combustible gases that inhibit flames and finally phosphorus inhibits the formation of levoglucosan during heating and also forms the compound P.sub.2O.sub.5, which provides a barrier effect and prevents the flame from crossing it.

(70) A non-limiting example of an embodiment of the method of sulphation and phosphorylation of a cellulose substrate according to the present description is provided below.

(71) A) Preparation of Cotton Yarn Nm 2/8000.

(72) Cotton is a raw material of plant origin that—in the raw state—is in the form of fibre filaments grouped into bolls with a chemical composition shown in Table 2.

(73) TABLE-US-00002 TABLE 2 Quantity Compound (%) Cellulose 83.5 Fats and waxes 0.8 Pectin and lignin 6.3 Minerals and organic acids 2.0 Hemicellulose and sugars 0.5 Various 0.4 Water 6.5

(74) The percentages of impurities in cotton fibres (such as fats and waxes, pectin and lignin, mineral substances and organic acids) are very high, and impart a lipophilic character to the fibre, which is removed through chemical processes of washing and sterilization known in the textile sector.

(75) The cotton yarn is then treated in autoclaves at 100° C. at a pressure of 3.5 bar for one hour as follows:

(76) i) Washing with a solution having a substrate:bath ratio equal to about 1:10 weight/weight, where the composition of the solution is illustrated in Table 3.

(77) TABLE-US-00003 TABLE 3 Quantity Compound (% w/w) Deionized water 95.2% Lauryl ether sulphate 27% w/w  0.2% Sodium polyacrylate MW/4500  0.2% Caustic Soda 30% w/w   1%

(78) ii) Rinsing with water in 3 cycles:

(79) Time=10 min; Temperature=40° C.; Pressure=3.5 bar.

(80) The resulting product is a white yarn with hydrophilic properties able to receive the subsequent sulphation and phosphorylation reactions.

(81) B) Preparation of the Solution for the Sulphation and Phosphorylation Method:

(82) The sulphation-phosphorylation solution is prepared by mixing the following in the order given and under heated condition (approximately 50° C.): water at 55% w/w, urea at 17% w/w, hydroxyethyl-imino-bis (methylene-phosphonic) acid at 20% w/w and ammonium sulphamate at 8% w/w.

(83) C) Preparation of Cotton Yarn by Immersion and Centrifugation.

(84) 200 grams of yarn are immersed in the sulphation-phosphorylation solution and subsequently centrifuged.

(85) After centrifugation, the cotton yarn retains approximately 80% of the sulphation-phosphorylation solution.

(86) D) Reaction with Heating and Rinsing.

(87) The yarn obtained after centrifugation is dried with forced air for thirty minutes at 80° C. and maintained at a temperature of about 115° C. for 2 hours to obtain sulphation and phosphorylation of the cellulose.

(88) The resulting yarn is then washed at 50° C. with detergent and water and dried again at 80° C. with forced air.

(89) E) Assessment of Physical Parameters

(90) The physical parameters of a yarn are the tensile strength and the tensile elongation.

(91) These parameters were tested with an Uster® Tensorapid 4 from Uster Technologies AG using the technical standard UNI EN ISO 2062:2010.

(92) The yarns are tested 20 times per sample, and the results expressed as mean values, with standard deviation less than 0.25.

(93) In Table 4 the values obtained for the yarn before being subjected to the sulphation and phosphorylation method according to the present description (untreated yarn) are reported, the values obtained for a cotton yarn subjected to a sulphation and phosphorylation method according to the present description (treated yarn), and the values obtained for a yarn subjected to sulphation and phosphorylation according to the known art (yarn treated according to the prior art), that is, using a sulphation and phosphorylation solution containing ammonium sulphamate to 10%, urea 20% and 1% phosphoric acid as the catalyst.

(94) TABLE-US-00004 TABLE 4 % loss of % loss of elongation resistance Elongation compared to Resistance compared to Compound (%) untreated (Kgf) untreated Untreated 18.707 — 2.736 — yarn Treated 9.100 51.3 2.589 5.3 yarn Yarn 2.210 88.3 1.158 57.7 treated according to the known art

(95) Three warp-weft fabrics with a weight of about 480 g/m.sup.2 were woven using a laboratory loom in order to assess the abrasion resistance of a fabric made with the cotton yarn treated according to the method object of the present description.

(96) Abrasion resistance was determined according to the UNI EN ISO 12947-2:2000 using a Martindale apparatus. The results are reported in table 5.

(97) TABLE-US-00005 TABLE 5 Breaking at cycle Compound (N) Fabric from untreated yarn 21,000 Fabric from treated yarn 20,000 Fabric from yarn treated according to 4,000 the prior art

(98) From Tables 4 and 5, the inventors have reason to believe that yarn treated according to the method object of the present description does not undergo any change of physical properties (such as tensile strength and abrasion resistance). These characteristics are fundamental to the marketability of a textile article.

(99) The loss of resistance for the treated yarn compared to the untreated yarn is 5%; whereas, the loss of resistance found with the yarn treated according to the sulphation and phosphorylation method of the prior art is much higher, with a loss equal to 57%.

(100) The loss of abrasion resistance of the fabric made with yarn treated according to the present description is minimal compared to the fabric from untreated yarn: the test results show values respectively of 20,000 and 21,000 cycles, virtually equal if compared with the loss of abrasion resistance of a fabric from yarn treated according to the prior art, which has a rupture value of 4,000 cycles.

(101) Resistance values of lower than 30% compared to an untreated fabric significantly impair the workability of a yarn in the various production processes for making a fabric.

(102) The value of abrasion resistance of a fabric is also a fundamental characteristic: it is unlikely that a fabric with average abrasion resistance values of less than 10,000 cycles is marketable.

(103) F) Assessment of Chemical Parameters

(104) Volatile or releasable components present in the substrate subjected to the sulphation and phosphorylation method as described above were measured with gas-chromatography coupled to mass spectrometry performed using the head space technique.

(105) A sample of treated yarn was tightly closed in a suitable container, brought to the desired temperature using a thermostatic bath and maintained under these conditions for a certain period of time to allow equilibration between the volatile compounds present in the sample and those released from the sample in the vapour phase. A predetermined volume of the head space (250 μl) was sampled with a gas tight syringe and injected into a gas chromatograph.

(106) A Hewlett-Packard 5890 gas chromatograph equipped with a 5970 Mass Selective Detector (MSD) was used; the column was a 30 m Supelco SPB-1.

(107) The initial column temperature was set at about 40° C. and maintained for 5 minutes; the temperature was raised from 40 to 250° C. with a heating ramp programmed at 20° C./min. The temperature was maintained at 250° C. for 19 minutes. The injector temperature was 220° C.

(108) The samples obtained from step C conducted at 25° C., 110° C. and 130° C. for 1 hour were analyzed.

(109) The analysis did not provide any appreciable results; in fact, the chromatogram of the sample is perfectly comparable to the blank: the sample does not release any volatile substances, such as ammonia or urea; in contrast to what is described in the known art methods.sup.4,5,7.

(110) G) Assessment of Anti-flame Parameters

(111) A sample of yarn treated according to the present description was tested for burning behaviour using the oxygen index at room temperature through technical standard UNI EN ISO 4589-2:2008.

(112) The sample had an L.O.I. value of 29.

(113) The fire behaviour of a fabric made using a cotton yarn treated according to the present description was also determined.

(114) The fabric made according to the parameters described in step E was tested according to the UNI EN ISO 15025 method A in order to determine the conformity of articles intended for protective garments.

(115) The test uses a rectangular specimen of fabric subjected to igniting of a flame that is placed perpendicular to it for a given period of time.

(116) The test assesses and verifies flame spreading behaviour according to the criteria below: no specimen shall catch fire at the top or at the side edge (respectively wales and ranks of the fabric); no specimen shall undergo the formation of a hole; no specimen shall melt, ignite or produce molten debris; the average value of the residual flame after ignition must be less than or equal to 2 seconds; the average residual glow time of the debris after the ignition must be less than or equal to 2 seconds.

(117) The test results are shown below in tables 6 and 7.

(118) TABLE-US-00006 TABLE 6 Minimum Treated article Parameters Requirements wales ranks Post combustion <=2 0 0 0 0 Post incandescence <=2 0 0 0 0 Combustion up to No No No No No the vertical edges Combustion up to No No No No No the top edge Formation of holes No No No No No Debris burning No No No No No ISO 11612 Classification Meets the requirements

(119) TABLE-US-00007 TABLE 7 Treated article subjected Minimum to 10 washes in water Parameters Requirements wales ranks Post combustion <=2 0 0 0 0 Post incandescence <=2 0 0 0 0 Combustion up to No No No No No the vertical edges Combustion up to No No No No No the top edge Formation of holes No No No No No Debris burning No No No No No ISO 11612 Classification Meets the requirements

(120) As can be seen from the values in tables 6 and 7, the fabric sample treated according to the sulphation and phosphorylation method with at least one phosphonic acid of formula (I) according to the present description fully satisfies the criteria of the UNI EN ISO 11612 standard.

(121) The same fabric had positive results when assessed with the following tests used for furnishings: Uni 9175:2010, Din 4102 B1, BS 5852 part 1, BS 5852, BS7176:95, BS 5867 part 2.

BIBLIOGRAPHIC REFERENCES

(122) 1. Lewin M.; Isaacs P. K. “Imparting flame resistance to materials comprising or impregnated with hydroxy group-containing polymers” From Ger. Offen. (1971), Database: CAPLUS 2. Cotton fibres. International Fibre Science and Technology Series (2007) 3. Lewin M.; Brozek J.; Martens M. M. “The system polyamide/sulfamate/dipentaerythritol: flame retardancy and chemical reactions” Polymers for Advanced Technologies (2002) Editor: Dr Abraham Domb. 4. Lewin M. “Flame retarding of polymers with sulfamates” Recent Advances in Flame Retardancy of Polymeric Materials (1997) 19th Annual BCC Conference on Flame Retardancy, Stamford, Conn., 2008. 11. 5. Lewin M. “Flame retarding of polymers with sulfamates. I. Sulphation of cotton and wool” J. Fire Sciences, 1997; 15: Technomic, 263-27 6. “Cotton fibres” International Fibre Science and Technology Series (1998), 15 (Handbook of Fibre Chemistry (2nd Edition)), 577-724. 7. “Reactions of ammonium sulfamate with amides and ureas, generation of volatile by-products” Canadian Journal of Chemistry (1956), 34, 1662-70. 8. Lewin M.; Brozek J.; Martens M. M. “A novel system for flame retarding polyamides” From Recent Advances in Flame Retardancy of Polymeric Materials (2001) 9. Blanchard E. J.; Graves E. E. “Phosphorylation of cellulose with some phosphonic acid derivatives” Textile Research Journal (2003)