AU670786B2 - A method of carbonizing textile material containing animal fibres - Google Patents

Description

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AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT

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.4 4 4k V Application Number: Lodged: Invention Title: A METHOD OF CARBONIZING TEXTILE MATERIAL CONTAINING ANIMAL FIBRES The following statement is a full description of this invention, including the best method of performing it known to :-US THIS INVENTION relates to a method of carbonizing textile material containing animal fibres, such as wool, in any form e.g. loose fibres, slivers and fabric, which textile material in case of slivers and fabric includes blends of the animal fibres with synthetic fibres, such as acrylic, polyester or polyamide fibres (hereinafter referred to generally as "textile material).

The invention relates also to an installation for carbonizing the aforementioned textile material.

In this specification, the expression "carbonizing textile material containing animal fibres" indicates a multi-stage process whereby unwanted vegetable matter which is present in the textile material, is carbonized and then removed from the textile material.

Conventional technology for carbonizing wool fibres so as to remove burr from the wool, known to the Applicants, involves immersion of the wool and burr in a 4,5 6,5% by mass aqueous solution of sulphuric acid containing a non-ionic surfactant, followed by hydro-extraction of thc S"wool, drying of the wool and burr by convectional heating at 700 C, and then baking of the burr by convectional heating at 1200 130'C until the vegetable matter has been carbonized. The disadvantages of this method are a relatively low degree of damage to the burr, and a deterioration in the mechanical properties of the wool fibres. Henceforth, all references in this specification to percentage concentrations of sulphuric acid in acid solution are to be understood as percent by mass of sulphuric acid of the total mass of the solution.

.oeo A further known technology is that of "rapid carbonizing".

This involves immersion of wool and burr in a 7,0 8,0% aqueous solution of sulphuric acid containing a non-ionic surfactant, for 30 60 seconds, followed by hydro-extraction of the wool and burr, exposure thereof at room temperature for 10 minutes (delay time), drying of the wool and burr by convectional heating at 700C, and then baking of the burr by convectional heating at 1300C 1500C until the vegetable matter has been carbonised. The disadvantages of this method are a relatively low degree of damage to large burr, such as Xanthium strumarium burr (cockle burr), and the long duration process. This method is conventionally used only for carbonising small size burr, such as Medicago polymorpha burr (spiral burr).

Various methods of carbonising wool, by treating the fibres with different carbonising reagents in inert organic solutions, have also been described in the literature. Thionyl chloride, sulphuryl chloride, anhydrous silicon tetrachloride or boron trichloride, and anhydrous acids have been used as carbonising reagents. However, these carbonising reagents are objectionable due to their toxicity, and their ability to hydrolysed in the presence of water. Organic solvents are volatile and toxic liquids, and some of them are dangerously explosive. These methods are therefore not used in practice.

It is an object of this invention to provide a method of carbonising textile material containing animal fibres, e.g. wool, whoreby the degree of damage to o the vegetable matter, e.g. burr, which is present in the fibres, is increased, while substantially preserving the mechanical properties of the animal fibres and shortening the duration of the process.

According to one aspect of the invention, broadly, there is provided a method of removing unwanted vegetable matter from textile material containing animal fibres and the unwanted vegetable matter, which includes the steps of S° pre-treating the textile material and vegetable matter by acidizing the Stextile material and vegetable matter in an aqueous acid solution until the moisture content of the vegetable matter is from about 2% to about 35% by weight of the dry vegetable matter; and baking the vegetable matter by heating it by means of at least one of a radio frequency and microwave electromagnetic field for a predetermined duration until the vegetable matter has been carbonised.

Henceforth, all references in this specification to percentage moisture content are to be understood as percentage by weight of the dry vegetable matter, or dry textile material as the case may be.

The vegetable matter may be large burr such as cockle burr, in which case the desired moisture content of the burr may be from about 2% to about 12% weight of the dry burr and the duration of the heating may be from about 0,25 minutes to about 4,0 minutes. Preferably, the moisture of the burr may be from about 4% to about 10% by weight of the dry burr and the duration of the heating may be from about 0,5 minutes to about 3 minutes. Most preferable, the moisture content of the burr may be from about 6% to about ideaily not more than about by weight of the dry burr and the duration of the heating may be about 1 minute to about 2 minutes.

Instead, the vegetable matter may be small burr such as spiral burr, and the desired moisture content of the burr may be from about 6% to about 35% by weight of the dry burr and the duration of the heating may be from about 0,25 minutes to about 4,0 minutes. Preferably, the moisture content of the burr may be from about 10% to about 30% by weight of the dry burr and the duration fo the heating my be from about 0,25 minutes to about 4,0 minutes. Preferably, the 0 moisture content of the burr may bc from about 10% to about 30% by weight of the dry burr and the duration of the heating may be from about 0,5 minutes to about 3 minutes. Most preferably, the desired moisture content fo the burr may be from about 15% to about 25%, by weight of the dry burr ideally not more than about 25%, and the duration of the heating may be about 1 minute to about 2 minutes.

Pre-treating the textile material and vegetable matter may inolude the steps of acidizing the textile material and vegetable matter in an aqueous acid solution; hydro-extracting the acidized textile material and vegetable matter; and drying the hydro-extracted textile material and vegetable matter to the desired moisture content of the vegetable matter.

When the textile material is in the form of loose wool fibres, acidizing the fibres and vegetable matter may be effected by soaking them in a 4 10% aqueous sulphuric acid solution. The aqueous sulphuric acid solution may include at least one oxidizing agent selected from the group consisting in sodium perchlorate, hydrogen peroxide and perchloric acid, in the manner described by Broderick, et al, Proc. 8th Int. Wool Res.

Conf., Christchurch, Volume II, 175 (1990), the contents of which are included herein by reference; and a non-ionic surfactant.

Instead, acidizing the fibres and vegetable matter may be effected by soaking them in a 4 10% aqueous solution of aluminium fluoride and hydrochloric acid, in the manner described by Van Hornuff, G., Melliand Textilber., 41, 474 (1960); Frieser, Textil Praxis, 17, 1021 (1962); Haly, and Hafey, Proc. 5th Int. Wool Res. Conf., Aachen, Volume IV. 115 (1976), the contents of which are included herein by reference.

When the textile material is in the form of fabric, acidizing the fabric and vegetable matter may be effected by immersion in an aqueous sulphuric acid solution. Instead, acidizing the fabric and vegetable matter may be effected by immersion in an aqueous solution of aluminium chloride; or by treating the fabric with hydrogen chloride gas; or by immersion in an organic solvent, such as perchloroethylene, followed by immersion in an aqueous sulphuric acid solution in the manner described by Rouette, H-K and Kittan, Wool Fabric Finishing P50, 1991, the contents of which are included herein by reference.

Hydro-extracting the textile material and vegetable matter may be effected by passing them through squeeze-rollers.

Drying the hydro-extracted textile material and vegetable matter may be effected by means of at least one of convectional heating, a radio frequency electromagnetic field and a microwave electromagnetic field.

Heating the textile material and vegetable matter by means of a radio frequency or microwave electromagnetic field may be effected by passing the textile material and the vegetable matter through a radio frequency or microwave heating zone in which the electromagnetic field is generated.

Passing the textile material and the vegetable matter through the radio frequency or microwave heating zone may be effected by conveyor means which intersects the heating zone, and on which the textile material and vegetable matter are placed.

The method may include the step of extracting the carbonized vegetable matter from the textile material. When the method is applied to carbonizing loose fibres, this may be effected by crushing the carboni-rd vegetable matter and removing the crushed carbonized vegetable matter from the loose fibres.

Crushing and removing the carbonized vegetable matter may be effected by passing the loose fibres and the vegetable matter through a conventional crushing and dedusting apparatus.

7 Instead, when the method is applied to carbonizing fabric, extracting the carbonized vegetable matter may be effected by beating the fabric and removing the carbonized vegetable matter from the fabric.

Beating the fabric and removing the carbonized vegetable matter from the fabric may be effected by passing the fabric through any conventional beating machine suitable for fabrics.

The method may include the step of, after extracting the carbonized vegetable matter from the loose fibres, neutralizing the loose fibres. Neutralizing the loose fibres may be effected by washing, followed by treatment with a base solution, followed by washing and drying the loose fibres. The loose fibres may be loose wool fibres.

Instead, when the method is applied to fabric, neutralizing the fabric may be effected by rinsing the fabric in running water, followed by treatment with a base solution, followed by rinsing in water and then drying the fabric.

*The specific parameters employed in the method of the invention will depend on the kind of burr present in the wool. However, if the wool contains large burr, such as Xanthium Strumarium (cockle burr), then the method of the invention may in general terms comprise acidizing the wool and burr by soaking them in a 4% preferably 5% most preferably aqueous solution of sulphuric acid containing 0,02% 0,2% non-ionic surfactant for 5 minutes; S.hydro-extracting the wool and burr by means of squeeze rollers, and drying by convectional heating at 50 700C, or by a combination of convectional heating and radio frequency or microwave heating, to a burr moisture content of 2% 12%, preferably 4% 10%, most preferably 6% and ideally not more than about and baking the burr by heating them by means of radio frequency or microwave electromagnetic radiation for 0,25 4,0 minutes, preferably 0,5 minutes, most preferably 1,0 2,0 minutes. After this, the wool may pass through the crushing and dedusting and neutralising steps.

Where the wool contains small size burr, such as Medicago polymorpha (spiral burr), the method of the invention may in general terms comprise acidizing the wool and the burr by soaking them in 4% preferable 5% most preferably 5% aqueous solution of sulphuric acid containing 0,02 0,2% non-ionic surfactant, for 1 minute; hydro-extracting the wool and burr by means of squeeze rollers, and drying by convectional heating at 50 -701C, or by a combination of convectional heating and radio frequency or microwave heating, to a burr moisture content of 6% 35%, preferably 10%-30%, most preferably 15% 25%, and ideally not more than about 25% arid baking the burr by heating them by means of radio frequency or microwave electromagnetic radiation for 0,025 4,0 minutes, preferab'v 0,5 minutes, most preferably 1,0 -2,0 minutes. After this, the wool may pass through the crushing opening and dedusting and neutralising steps.

The invention extends to an installation for removing unwanted vegetable matter from textile material containing animal fibres and the unwanted vegetable matter, which includes acidizing means for acidizing the fibres and vegetable matter to achieve a desired moisture content in the vegetable matter hydro-extracting means downstream of the acidizing means; at least one of a radio frequency and microwave heating apparatus for baking the vegetable matter until it has bee carbonised; extraction means downstream of the heating apparatus, for extracting the

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carbonised vegetable matter from the textile material; S- neutralising means downstrceam of the extraction means, for neutralising the textile fibres; and automatic conveyor means for downstream conveying of the fibres and Svegetable matter.

The radio frequency or microwave heating apparatus may include a radio wave or microwave-impervious housing which defines a chamber Shaving an entrance and an exit; 9 a generator for generating at least one of a radio frequency and microwave electromagnetic field; electromagnetic field concentration means mounted within the chamber intermediate its entrance and its exit and connected to the generator, for concentrating the electromagnetic radiation in the radio frequency or microwave heating zone; and conveyor means which intersects the radio frequency or microwave heating zone, for conveying the textile material and the vegetable matter into the chamber through the entrance to the chamber, through the heating zone and out of the chamber.

The radio wave or microwave impervious housing may be made from any suitable acid-resistant material such as stainless steel.

The generitor may be a radio frequency generator for generating a radio frequency electromagnetic field; or a magnetron, Klystron, triode or the like type of electronic device for generating a microwave electromagnetic field.

In the embodiment of the apparatus in which the generator is a radio frequency generator, the electromagnetic field concentration means may include an electrode assembly comprising a pair of mutdA 4 ly spaced electrodes mounted within the chamber and connected to the generator, the heating zone being defined by the space between the electrodes.

The electrodes of the electrode assembly may be substantially planar electrodes which are mounted in mutually vertically spaced .Z relationship within the chamber, and the conveyor means a continuous Sconveyor belt which passes through the entrance to the chamber, through the radio frequency heating zone between the electrodes and through the exit of the chamber.

Instead, in the embodiment of the apparatus in which the generator is a microwave generator, the electromagnetic field concent-rtion means may include a waveguide connected to the microwave generator, the microwave heating zone being defined by the waveguide.

The heating apparatus may include moisture extraction means mounted on the housing for extracting moisture generated during the operation of the apparatus, from the chamber.

The installation may include acidizing means upstream of the heating apparatus, for acidizing the fibres and vegetable matter.

When the textile material is in the form of loose fibres or fabric, the acidizing means may be conventional acidizing baths, che installation including hydro-extracting means downstream of the acidizing baths.

The hydro-extracting means may be in the form of squeeze rollers or a centrifuge.

The installation may include neutralizing means downstream of the extraction means, for neutralizing the textile material.

S• When the textile material is in the form of loose fibres, the extraction means may be a conventional crushing and dedusting apparatus.

28. Instead, when the textile material is in the form of fabric, the extraction means may be any conventional beating machine suitable for fabric.

The installation may include automatic conveyor means for downstream conveying of the fibres and vegetable matter.

11 When the textile material is in the form of loose fibres, the automatic conveyor means may be in the form of an automatic conveyor belt.

Instead, when the textile material is in the form of fabric, the automatic conveyor means may be in the form of guide rollers.

The installation of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, and dhe method of the invention with reference to the following non-limiting examples.

In the drawings, Figure 1 shows a schematic representation of an installation according to one aspect of the invention for carbonizing loose fibres; Figure 2 shows a sectional side view of an embodiment of the radio frequency heating apparatus of the installation of Figure 1 for carbonizing loose fibres; and Figure 3 shows a sectional side view of a microwave heating 2apparatus of the installation of Figure 1 for carbonizing loose fibres.

Referring to Figure 1 of the drawings, reference numeral generally indicates an installation for carbonizing wool according to one 1o: aspect of the invention. The installation 10 comprises automatic feeders 11, and conventional acidizing baths 12 for acidizing the wool shown in the form of loose wool fibres 31 and burr 33 (Figures 2 and by soaking them in an aqueous solution of sulphuric acid and a non-ionic surfactant, or any other conventional system for treating the wool and burr with sulphuric acid.

.2 When the textile material is in the form of fabric, acidizing the fabric will "be effected by soaking them in an aqueous solution of sulphuric acid and a non-ionic surfactant, or any other conventional system for treating the wool and burr with sulphuric acid or other reagents. Squeeze rollers 14 are 12 provided downstream of the b i2, for hydroextracting the wool and burr, wvhich are conveyed downstream by means of an automatic conveyor belt 16.

A conventional drying oven 18 is provided downstream of the squeeze rollers 14, for drying the wool and burr until the burr reaches the desired moisture content. Radio frequency or microwave heating apparatus 20 or of the kind described below with reference to Figures 2 and 3 is provided downstream of the convectional oven 18, for baking and carbonizing the burr. A conventional crushing and dedusting apparatus 22, is provided downstream of the heating atparatus 20, 50, for crushing and removing the carbonized burr from the wool. The installation 10 further comprises a neutralizing apparatus, generally designated by reference numeral 24, downstream of the crusher 22, for washing and neutralizing the wool. The neutralizing apparatus includes bowls (not shown) for washing the wool and treating the wool with a base solution, and a drying oven (not shown) for drying the wool.

Referring to Figure 2 of the drawings, the radio frequency heating apparatus 20 includes a housing 26 which is of stainless steel and is therefore acid resistant and radio wave impervious. The housing 26 define6 a chamber 28 which has an entrance 30 and an exit 32. A radio frequency generator 34 is provided. An electrode assembly 36 comprises a pair of planar electrodes 38 and 40 which are mounted in mutually vertically spaced relationship within the chamber 28, a radio frequency heating zone 42 being defined by the space between the electrodes 38 and 40. The electrodes 38 and 40 are comnnected to the radio frequency generator 34. A continuous o 2S conveyor belt 16 continuously driven by di ive assemblies (not shown) passes through the entrance 30 to the chamber, through the heating zone 42 -oo between the electrodes 38 and 40, and through the exit 32 of the chamber 28. Moisture extraction means in the form of an extractor fan 44 is 00 provided for extracting moisture which is generated during the operation of the apparatus 20, from the chamber 28.

In use, a radio frequency electromagnetic field is generated by the generator 34 and concentrated in the radio frequency heating zone 42 between the electrodes 38 and 40. Wool fibres 31 in which burr 33 is present, and which burr 33 has been treated to reach a desired moisture content according to the method described in more detail hereinbelow, is passed by the conveyor belt 16 through the radio frequency heating zone 42.

The burr is heated by means of radio frequency electromagnetic field for a predetermined period of time, such that the burr 33 is baked and carbonized in the radio frequency heating zone 42.

Referring to Figure 3 of the drawings, reference numeral generally indicates a microwave heating apparatus for an installation of the invention. Like numerals denote similar features to those indicated in Figure 2. The apparatus 50 is of the kind described by D.G. Evans and J.K.

Skelly in J. of the Soc. of Dyers and Colourists, 1972, v.88, N12, pp. 429-433, the contents of which are included herein by reference. The apparatus includes a microwave generator 52 which is connected to a waveguide 54 which extends through the chamber 28. A terminating load 56 is provided for the microwave generator 52. The chamber 28 has chokes 28.1 at or near the entrance 30 and exit 32 thereof. A glass tube 58 extends through the chamber 28, between the entrance 30 and the exit 32 thereof, through which tube 58 the conveyor belt 16 runs.

In use, a microwave electromagnetic field is generated by the generator 52 and concentrated in the microwave heating zone defined by the waveguide 54. Wool fibres 31 in which burr 33 is present, and which burr 33 has been treated to reach a desired moisture content according to the method described in more detail hereinbelow, is passed by the conveyor belt 16 through the microwave heating zone defined by the waveguide 54.

The burr 33 is heated by means of the microwave electromagnetic field for a predetermined period of time, such that the burr 33 is baked and carbonized in the microwave heating zone.

The method of the invention will now be described with reference to the following non-limiting examples: Example 1 Conditioned 26p.m scoured Merino wool containing Xanthium Chinense burr was treated by immersion in a 6,0% aqueous solution of sulphuric acid containing 0,2% of a non-ionic surfactant available in the former USSR under the trade name "Nekal", for 5 minutes at 20* C. The wool and burr were hydro-extracted by squeeze rollers and dried in a circulating oven at 70 C mutil the burr reached a moisture content of The dried wool and burr were heated by means of a radio frequency electromagnetic field at a frequency of 13,56 MHz and an intensity of 500 V/cm, for 2 minutes.

The wool was then washed in water at 20 C, neutralised in a neutralising bath containing a 0,1% aqueous ammonia solution for 3 minutes, and then washed in water at 20" C. Finally the wool was dried for 10 minutes at 85 90 C.

below.

ThS mechanical characteristics of the wool fibres, are represented in Table 1 below.

to TABLE I Xanthium Chinense Burr Damage and Mechanical Characteristics of Wool Fibres Duration Breaking Concentration of radio Tensile Elongation of Sulphuric frequency Burr Strength of of wool Acid Solution heating Damage wool fibres fibres (Min) (cN) 1,0 23,5 10,2 47 2,0 40,0 10,2 4,0 48,2 10,3 47 1,0 26,2 10,0 2,0 50,6 9,8 47 4,0 57,1 10,1 1,0 29,6 9,9 44 2,0 61,0 9,9 44 4,0 66,8 9,7 44 10,0 0,25 20,3 9.9 10,0 1,0 32,0 10,2 46 10,0 2,0 68,6 9,9 10,0 4,0 69,6 10,2 47 Conventional Technology 12,2 9,3 44 Example 2 Conditioned 26 pm scoured Merino wool and Xanthium strumarium burr were treated according to the method of the invention in the same manner as described in Example 1, except that a surfactant available in Germany under the trade name "Triton X100" was used at a concentration of 0,02%, and the frequency of the electromagnetic field was 27,12 MHz.

The results of this treatment at various sulphuric acid concentrations, electromagnetic field intensities and durations of radio frequency heating, in terms of burr damage and the temperature of the wool after heating, are represented in Table II below.

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16 TABLE H Xanthium Strumarium Burr Damage and Wool Temperature after heating at 27,12 MHz Concentration Electro- Duration of Sulphuric magnetic of radio Temperature Acid Solution field frequency of Wool after Burr Intensity heating Treatment Damage (V/cm) (Min) C) 410 4,0 60 21,4 330 1,0 35 19,3 330 2,0 38 20,9 330 3,0 37 30,4 410 1,0 40 25,2 410 2,0 43 29,8 410 3,0 47 37,5 6,0 500 1,0 43 31,2 500 2,0 47 48,7 330 3,0 40 27,8 410 1,0 39 39,6 410 2,0 42 40,1 8,0 410 3,0 47 40,8 Conventional Technology 17,9 Example 3 Conditioned 26p.m scoured Merino wool and Medicago polymorpha burr were treated according to the method of the invention in the same manner as described in Example 2, except that the immersion time in the acid solution was 1 minute.

The results of this treatment at various sulphuric acid concentrations, radio frequency heating time and electromagnetic field intensities, in terms of damage of the burr are represented in Table III below.

17 TABLE III Medicago Polymorpha Burr Damage after heating at 27,12 MHz go 25 .e '.j .2 Moisture Electro- Duration of Concentration Content of magnetic radio of Sulphuric Burr after field frequency Burr Acid Solution Drying Intensity heating Damage (V/cm) (Min) 10 410 4,0 77,1 12 410 1,0 79,6 12 410 1,5 81,9 12 410 2,0 87,4 12 500 0,5 78,2 12 410 1,0 78,1 12 410 1,5 80,7 12 410 2,0 88,4 16 410 1,0 79,2 8,0 16 410 1,5 83,6 16 410 2,0 85,3 8,0 76,8 Conventional "rapid carbonizing" technology Example 4 Conditioned 26tpm scoured Merino wool containing Xanthium Chinense and Medicago polymorpha burr were treated according to the method of the invention in the same manner as described in Example 1, except that the wool and burr were dried to achieve various moisture contents in the burr and the duration of the radio frequency heating was 4 minutes.

The results of this treatment for various burr species at various burr moisture contents before baking, are represented in Table IV.

0 o '2Q Example Conditional 26p.m scoured Merino wool and Medicago polymorpha burr were treated according to the method of the invention in the same manner as described in Example 1, except that the wool and burr were dried to a desired moisture content of the burr, and then the wool and burr were heated by means of a microwave electromagnetic field having a frequency of 2450 MHz for 4 minutes. This was done in a microwave oven available in the former USSR under the trade name "Electronica".

The results of this treatment for various burr moisture contents before baking are represented in Table V under Run Numbers 11 to 15. For Run number 15 in Table V, after baking the tensile strength of the wool fibres was found to be 10,0cN, and its breaking elongation 46%.

TABLE IV Dependence of Burr Damage on its Residual Moisture Content Sulphuric Acid Solution, immersion time 5 minutes; Radio frequency 13,56 MHz intensity 500 V/cm; heating time 4 minutes) Run Burr Species Type of Burr Burr No. heating Moisture Damage 1 Xanthium Chinense Radio 18,0 29,0 2 frequency 11,4 31,8 3 10,0 39,1 4 8,0 57,1 4,0 58,0 6 Medicago Polymorpha Radio 120 44,2 7 frequency 60 52,1 8 25 92,5 9 18 93,8 _10 98,0 19 TABLE V eeoc o e ee 25 *o Run Burr Species Type of Burr Burr No. heating Moisture Damage 11 Medicago Polymorpha Microwave 120 43,3 12 60 45,6 13 25 79,3 14 18 82,5 10 86,9 COMPARATIVE EXAMPLES In one comparative test run, conditioned 26pm scoured Merino wool and Xanthium burr were treated by means of the conventional technology.

Wool and burr were immersed in 6,0% aqueous solution of sulphuric acid containing 0,2% Nekal or 0,02% Triton X100, for 5 minutes at 20 C. The wool and burr were hydro-extracted by squeeze rollers and dried in a circulating oven at 70" C to a moisture content of the wool of 10%. The dried wool and burr were baked by convectional heating for 4 minutes at 120 The wool was neutralised according to the method described in Example 1.

In another comparative test run, the conditioned 26|pm scoured Merino wool and Medicago polymorpha burr were treated by means of the conventional "rapid carbonizing" technology. The wool and burr were immersed in 8% solution of sulphuric acid containing 0,02% Triton X100 for 1 minute at room temperature. The wool and burr were hydro-extracted by squeeze rollers and exposed for 10 minutes at room temperature (delay time).

Thereafter the wool and burr were dried in an air circulating oven at 70 C to a moisture content of the wool of 10% followed by baking by convectional heating for 5 minutes at 130* C. The wool was neutralised according to the method described in Example 1.

The degree of damage suffered by the burr was measured according to the principle of a method described by Kirkpatrick, A New Approach to Wool Carbonizing, Textile Res. 56, 67 71, (1986). The burr were passed through the rollers and crushed, and the residues were sifted through a 1mm sieve. The percent by mass that passes through the sieve provides a measure of the damage imparted to the burr. Tensile strength and breaking elongation of single wool fibres were determined on an Electronic Breaking Device FM-27.2 (Hungary). The breaking strength and elongation of wool fibres, in bundle form, were measured on a "Stelometer". For each .ample, three tests were performed and the results were averaged.

The dependence of the burr damage on its moisture content after drying has already been illustrated in Tables IV and V above.

A comparative analysis of the mechanical characteristics of wool treated by means of the conventional technology, wool treated by means of the method of the invention, and untreated wool, are given in Table VI below.

21 TABLE VI Bundle Breaking Strength and Elongation of Wool Fibres Run Concentration No. of Sulphuric Breaking Standard Elonga- Standard Acid Solution Strength Error tion Error (cN/tex) (cN/tex) 1 Conventional 12,52 1,09 24,1 4,3 technology 2 Conventional 14,18 2,72 20,4 "rapid carbonizing" technology 3* 6,0 14,06 0,92 20,2 3,2 4* 8,0 15,76 0,28 24,3 2,2 8,0 13,85 0,54 22,5 6 Untreated wool 14,36 0,52 21,6 3,4 r~^

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Employing the method described in Example 2.

Employing the method described in Example 3.

It can be concluded from the data shown in Tables IV and V that the drying of the Xanthium burr is to be continued until it reaches an optimum moisture content of not more than about 8% before baking, whereas in the case of the Medicago polymorpha burr, the optimum moisture content should be not more than about 25% before baking.

At these moisture contents, a high degree of carbonizing of the burr was achieved. All the burr observed were characterised by intensive and uniform charring. The radio frequency and microwave heating allows the degree of damage of the Xanthium burr to be increased by about 3 times, and that of the Medicago polymorpha burr by about 16%, in comparison with the conventional technology (Tables I The duration 22 of the heating time, when compared to the duration in the conventional methods, can be shortened to two minutes for Xanthium burr and to about 1,0 minutes for the Medicago polymorpha burr (Tables I III). This results in a higher productivity of the method of the invention when compared to the conventional carbonizing methods, and a corresponding cost saving.

During the heating by means of the method of the invention, the temperature of the wool did not exceed 60°C (Table II). The wool was therefore not overdried and had a moisture content of 13 18% after the heating. Consequently the mechanical properties of the wool were substantially preserved (Tables I and V).

The radio frequency and microwave heating results in the differential o* heating of the wool and burr due to their different dielectric and thermal characteristics. This enables higher temperatures to be achieved for the vegetable matter (burr) whereas the temperatures reached by the wool during the process remain relatively low.

It will thus be appreciated that tbh method of the invention results in heating the burr to charring temperature with only slight heating of the wool fibres. As a result, the mechanical properties of the wool fibres are 32U: preserved while the burr is turned into a brittle product it is carbonized) which is easily removable by mechanical action.

Heating with radio frequency or microwave electromagnetic fields is particularly advantageous when carbonizing large burr, such as Xanthium.

In such cases an extremely low effectiveness is inherent in the conventional technology where thermal energy is transferred to the burr from outside by convection. Under these conditions, the inner layers of the burr are not heated up to the necessary temperature and remain practically undamaged.

The internal nature of the heating by microwave and radio frequency field 23 allows a rapid and homogeneous heating across the entire cross-section of the burr to be achieved. This increases the damage to the burr and therefore also increases the efficiency of the process.

In the case of the carbonizing of spiral burr, the method of the invention enables the delay time before drying to be avoided, and decreases the duration of the whole process by about half. It also allows less colncentrated solutions of sulphuric acid to be used.

Using conventional technology, after the baking step, the wool fibres have an extremely low moisture content, about 3 and are therefore brittle.

The method of the invention allows overdrying of the wool fibres to be avoided due to only a slight heating of the wool taking place during heating.

This preserves the wool during subsequent mechanical treatments which it undergoes.

S. The Applicants therefore believe that it is an advantage of the S '15: method of the invention that it improves the efficiency with which the S• vegetable matter is damaged or carbonized, reduces the processing time of the fibres and reduces damage to the fibres during the carbonizing of the vegetable matter.

It ,vil be appreciated that ihe method and installation of the invention can be applied to carbonizing textile material containing animal fibres other than wool, e.g. mohair, in any form e.g. loose fibres, slivers and fabric.

Claims (20)

1. A method of removing unwanted vegetable matter from textile material containing animal fibres and the unwanted vegetable matter, which includes the steps of pre-treating the textile material and vegetable matter by acidising the textile material and vegetable matter in an aqueous acid solution until the moisture content of the vegetable matter is from 2% to 35% by weight of the dry vegetable matter; and baking the vegetable matter by heating it by nm-,ns of at least one cG a radio frequency and microwave electromagr"., field for a predetermined duration until the vegetable matter has been carronised. o

2. A me'hod as claim in claim wherein acidising the textile material and vegetable matter is effected by soaking them in an aqueous acid solution 0 e selected from the group consisting in a 4-10% aqueous sulphuric acid solution and an aqueous solution of aluminium fluoride and hydrochloric acid. 0 0

3. A method as claimed in claim 2, wherein the aqueous sulphuric acid solution includes at least one oxidising agent selected from the group consisting in sodium perchlorate, hydrogen peroxide and perchloric acid; and a non-ionic surfactant.

4. A method as claimed in any one of claims 1 to 3 inclusive, wherein the duration of the heating is from 0.25 minutes to 4 minutes. A method as claimed in claim 4 wherein the vegetable matter is large burr and the moisture content of the burr is from 2% to 12% by weight of the dry burr.

6. A method as claimed in claim 5 wherein the moisture content of the burr is from 4% to 10% by weight of the dry burr and the duration of the heating is minutes to 3 minutes.

7. A method as claimed in claim 5 wherein the moisture content of the burr is from 6% to 8% by weight of the dry burr and the duration of the heating is 1 minute to 2 minutes.

8. A method as claimed in claim 4 wherein the vegetable matter is small burr and the moisture content of the burr is from 6% to 35% by weight of the dry burr.

9. A method as claimed in clai;n 8 wherein the moisture content of the burr is from 10% to 30% by weight of the dry burr and the duration of the heating is minutes to 3 minutes, A method as claimed in claim 9 wherein the moisture content of the burr is from 15% to 25% by weight of the dry burr Lnd the duration of the heating is 1 minute to 2 minutes.

11. A method as claimed in any one of the preceding claims wherein heating the textile material and vegetable matter is effected by passing the textile material and the vegetable matter through a radio frequency or microwave heating zone in which the electromagnetic field is generated, by conveyor means I 4 which intersects the heating zone and on which the textile material and vegetable matter are placed.

12. A method as claimed in any of the preceding claims which includes the steps of, after pre-treating the textile material and vegetable matter, hydro-extracting the acidized textile material and vegetable matter; and drying the hydro-extracted textile material and vegetable matter to the desired moisture content of the vegetable matter.

13. A method as claimed in claim 12, wherein hydro-extracting the textile material and vegetable matter is effected by passing them through squeeze- rollers or through a centrifuge.

14. A method as claimed in claim 13, wherein drying the hydro-extracted textile material and vegetable matter is effected by at least one of convectional heating, a radio frequency electromagnetic field and a microwave electromagnetic field. A method as claimed in any one of the preceding claims, which includes the step of extracting the carbonized vegetable matter from the textile material. S16. A method as claimed in claim 15, which oooe .12U. includes the step of, after extracting the carbonized :'.-.vegetable matter from the textile material, neutralizing the textile material.

17. A method as claimed in any one of the S"preceding claims, wherein the textile material is loose wool fibres. 27

18. An installation for removing unwanted vegetable matter from textile material containing animal fibres and the unwanted vegetable matter, which includes acidising means for acidising the fibres and vegetable matter to achieve a desired moisture content in the vegetable matter; hydro-extracting means downstream of the acidising means; at least one of a radio frequency and microwave heating apparatus downstream of the hydro-extracting means for baking the vegetable matter until it has been carbonised; extraction means downstream of the heating apparatus, for extracting the carbonised vegetable matter from the textile material; neutralising means downstream of the extraction means, for neutralising the textile fibres; and automatic conveyor means commencing at the acidising means and continuing through the installation to the neutralising means for downstream conveying of the fibres and vegetable matter.

19. An installation as claimed in claim 18, in which the radio frequency or microwave heating apparatus includes a radio wave or microwave-impervious housing which defines a chamber having an entrance and an exit; a generator for generating a radio frequency or microwave electromagnetic field; an electromagnetic field concentration means mounted within the chamber intermediate its entrance and its exit and connected to the generator, for concentrating the electromagnetic radiation in the radio frequency or microwave heating zone; and conveyor means which intersects the radio frequency or microwave heating zone, for conveying the textile material and the vegetable matter into the chamber through the entrance to the chamber, through the heating zone and out of the chamber. An installation as claimed in claim 19, wherein the generator is a radio frequency generator, and the electromagnetic field concentration means includes an electrode assembly comprising a pair of mutually spaced electrodes mounted within the chamber and connected to the generator, the heating zone being defined by the space between the electrodes.

21. An installation as claimed in claim wherein the electrodes are substantially planar electrodes mounted in mutually vertically spaced relationship within the chamber, and the conveyor means is a continuous conveyor belt which passes through the entrance to the chamber through the radio frequency heating zone between the electrodes and through the exit of the chamber.

22. An installation as claimed in claim 19, wherein the generator is a microwave generator, and the electromagnetic field concentration means includes a waveguide connected to the microwave generator, the microwave heating zone being defined by the waveguide.

23. An installation as claimed in claim 18, :wherein the extraction means includes a conventional crushing and dedusting apparatus.

24. A nw method of carbonizing textile material containing animal fibres, substantially as herein described and illustrated.

25. A new installation for carbonizing textile material containing animal fibres, substantially as herein described and illustrated. DATED: This 7th day of March 1996 CSIR RIGA TECHNICAL UNIVERSITY WATERMARK PATENT TRADEMARK ATTORNEYS LEVEL 4 AMORY GARDENS R 4 2 CAVILL AVENUE ASHFIELD NSW 2131 (3^ AUSTRALIA ABSTRACT The invention provides a method of carbonizing textile material containing animal fibres, which includes the steps of pre-treating the textile material and vegetable matter until the vegetable matter reaches a desired moisture content; and baking the vegetable matter by heating it by means of at least one of a radio frequency and microwave electromagnetic field for a predetermined duration until the vegetable matter has been carbonized. S o S *S 6 o *of