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(11) | EP 0 632 155 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method for continuous mercerization of polyester fibres and relative apparatus |
| (57) Continuous mercerisation method which is suitable to carry out mercerisation treatment
of a plurality of threads (11) of polyester fibres being unwound independently, continuously
and parallel to each other from one (12) or more (112-212) feeder beams, the plurality
of threads (11) undergoing the following operational steps in succession: impregnation
(13) by immersion in at least one tank (22) containing heated caustic soda lye; first
drying (14) in an oven (31a) with a circulation of hot air; steam treatment (15);
neutralisation with hot washing, the neutralisation comprising a first stage of washing
in hot water (16) by immersion in at least one tank (22) containing a bath of hot
water, a second stage of actual neutralisation (17) by immersion in at least one tank
(22) containing acid liquor and a third stage of rinsing (18) by immersion in at least
one tank (22) containing cold water; a second and final drying (19) in an oven (31b)
with a circulation of hot air; the threads (11) leaving the second and final drying
(19) being wound on at least one take-up beam (39). Continuous mercerisation plant which is suitable to carry out mercerisation treatment of a plurality of threads (11) of polyester fibres being unwound continuously and parallel to each other from one (12) or more (112-212) feeder beams, the plant (20) employing the above method (10) and comprising the following operational assemblies positioned in succession: an impregnation assembly (29) comprising at least one tank (22); a first drying assembly (30) comprising an oven (31a) working with hot air; a steaming assembly (34); a hot water washing assembly (35) comprising at least one tank (22); a neutralisation assembly (36) comprising at least one tank (22); a cold water rinsing assembly (37) comprising at least one tank (22); a second and final drying assembly (38) comprising an oven (31b) working with hot air; and a thread (11) take-up assembly comprising at least one take-up beam (39). |
[0001] This invention concerns a method for the continuous mercerisation of polyester fibres, as set forth in the main claim.
[0002] To be more exact, the invention concerns a method suitable to carry out mercerisation treatment of a plurality of polyester fibres being unwound parallel and continuously from at least one feeder beam.
[0004] The state of the art covers a plurality of methods and devices for mercerisation of woven fabrics and threads, especially consisting of cotton.
[0005] It is known that mercerisation is a treatment with caustic soda applied, for instance, to threads, and the description that follows will refer to threads, which are subjected to a suitable tension to ensure that they acquire a lustre like that of silk.
[0006] In general, the threads to be used, above all, for knitwear made by hand or machine, for shirts, embroidery and sewing threads undergo mercerisation.
[0007] The principle on which mercerisation is based has been known for a long time; the action of the caustic soda causes a great shrinkage of the cotton which, when brought back to its original length, possesses a silky lustre.
[0008] The same result is achieved by preventing shrinkage of the cotton by applying a suitable tension.
[0009] Polyester fibres, instead, are very shiny and smooth and therefore sometimes have to be dulled. Moreover, where the same dye is used, mercerised fibres are coloured much more intensely than non-mercerised fibres, and this leads to a smaller consumption of dyestuffs in the dyehouse.
[0010] Mercerisation increases also the mechanical strength of polyester fibres although the properties of resilience suffer.
[0011] Methods have now been disclosed whereby polyester fibre fabrics are subjected to a caustic soda bath which makes the fabrics more opaque.
[0012] This method, besides being of a discontinuous type, entails the problem that all the fibres forming the fabric undergo that bath of caustic soda.
[0013] This fact does not allow mixed fabrics to be produced with mercerised polyester fibres and non-mercerised polyester fibres so as to achieve particular required aesthetic effects.
[0014] The present applicants are not aware of methods or relative plants for the continuous mercerisation of polyester fibres in the form of threads.
[0015] The present applicants have investigated, tested and obtained this invention to overcome the shortcomings of the state of the art and to achieve further advantages.
[0016] The invention is set forth and characterised in the respective main claims, while the dependent claims describe variants of the idea of the main embodiment.
[0017] The purpose of the invention is to provide a method for the continuous mercerisation of polyester fibres on an industrial scale with limited costs and with technological results of a high quality.
[0018] The method according to the invention arranges to process continuously a plurality of independent threads consisting of polyester fibres and being unwound parallel to one another from at least one feeder beam.
[0019] The plurality of polyester threads undergoes substantially six steps of mercerisation treatment:
- immersion in a caustic soda solution at about 32° Baumé;
- a first drying with hot air;
- steaming at 100°C;
- washing in hot water at about 70-80°C;
- neutralisation in acetic acid at 20°C;
- rinsing in cold water at about 20°C;
- second and final drying with hot air.
[0020] Downstream of the second and final drying operation the threads are taken up advantageously in separate groups on at least one take-up beam but advantageously on a plurality of take-up beams of smaller sizes than the feeder beam or beams.
[0021] The above mercerisation steps are carried out in a plurality of tanks which can be moved advantageously to assist the operations of cleaning, maintenance and replacement.
[0022] Moreover, the tanks include means to facilitate the passage and insertion of the threads in the operational assemblies arranged within the tanks themselves.
[0023] According to the invention each group of tanks or, rather, each tank is equipped with its own drive and control means, which are governed by a central data processing unit that sets the various processing parameters from time to time.
[0024] According to a variant the plant is equipped with a system to monitor all the physical magnitudes involved in the treatment, which are fed to the central data processing unit so as to optimise each operational step, especially from the technological and energy point of view.
[0025] Next, the invention includes modular elements which enable the fabrication costs to be reduced and the plant to be personalised to suit customers' requirements.
[0026] According to the invention the threads can be tied together crosswise to their direction of feed in the plant at pre-set intervals; this solution ensures that each thread is fed along the whole path of the treatment even if there are any breakages. The connections can be removed before the threads are wound on the take-up beams.
The attached figures are given as a non-restrictive example and show a preferred embodiment of the invention as follows:-
- Fig.1
- shows the method according to the invention in a block diagram;
- Fig.2
- is a diagrammatic lengthwise view of the mercerisation plant according to the invention;
- Fig.3
- is a plan view of the plant of Fug.2;
- Fig.4
- is a side view of a tank of the type disclosed in EP-A-90123294.2 and used in the plant according to the invention.
[0027] The reference number 10 denotes generally a method for the continuous mercerisation of threads of polyester fibres being unwound from at least one feeder beam 12.
[0028] The method 10 according to the invention arranges that the threads 11 being unwound at a speed of about 75 metres per minute undergo the following operational steps in succession:
- impregnation 13 in a caustic soda solution at 32° Baumé and at a temperature of about 70-75°C for about 6 seconds;
- a first drying 14 in an oven with hot air;
- steaming 15 at 100°C;
- washing in hot water 16 at about 70-80°C;
- neutralisation in acetic acid 17 at about 20°C;
- rinsing in cold water 18 at about 20°C;
- second and final drying 19 with hot air.
[0029] In the cycle according to the invention particular importance belongs to the first drying step 14, which performs a task of improving the mercerisation action as compared to all the prior art.
[0030] Figs.2 and 3 show diagrammatically the lay-out of a plant 20 for the continuous mercerisation of threads 11 of polyester fibres according to the invention.
[0031] The plant 20 is fed by a plurality of threads 11 being unwound from at least one beam 12. In the embodiment shown as an example the feed consists of two beams 112 and 212 to feed separately two plants 120-220 having an identical lay-out and facing each other.
[0032] In the description that follows we shall refer in the same way to a path of treatment of the threads 11 whereby those threads 11 are unwound from one single beam 12 or from a plurality of beams 112-212.
[0033] With a lay-out such as that shown in Figs.2 and 3 the present applicants have found that the speed of unwinding of the threads 11 from the beam 12, this speed being the same for the whole mercerisation process, can be 75 metres per minute or more whilst ensuring at the same time the required level of quality of the product processed. The threads 11 unwound from the beam 12 are fed by a feeder assembly 21 consisting of two beams 112-212 placed side by side in this case.
[0034] The threads 11 are delivered by the feeder assembly 21 to an assembly 29 which in this case consists of two tanks 22 for impregnation of the threads 11 in a caustic soda solution at 32° Baumé.
[0035] A plurality of tanks 22 positioned also in assemblies downstream of the feeder assembly 21 is employed in the mercerisation plant 20. These tanks 22 are advantageously of the type disclosed in EP-A-90123294.2, and a tank 22 of this type is shown as an example in Fig.4.
[0036] When in the description that follows we speak of tanks 22 included in other assemblies for treatment of the threads 11, we shall be referring to the same type of tank 22 as that employed in the impregnation assembly 29.
[0037] The tank 22 in this case includes a container 23 to hold the treatment liquid, an upper transverse intake roll 24 and an upper transverse output roll 24, a pair of lower transverse rolls 25 positioned at the bottom of the container 23 and an intermediate transmission roll 26.
[0038] Pressure means 27 may be included to apply pressure on the threads 11 at least on the upper rolls 24.
[0039] Actuation means 28 to drive the rolls are positioned above the tank 22 and may cooperate with one single tank 22 or with assemblies of tanks.
[0040] The intermediate transmission roll 26 is equipped advantageously with its own motor able to move the transmission roll 26 crosswise to the direction of feed of the threads 11; the purpose of this is to be able to ensure correct positioning of the plurality of threads 11 along their feed path through the plant 30, such positioning of the threads 11 being checked by control means such as photoelectric cells cooperating with the motor of the intermediate transmission roll 26.
[0041] All the rolls, whether upper 24, lower 25 or intermediate 26, performing the supporting and drafting are fitted as cantilevers so as to facilitate the alignment of the plant 20 by hand.
[0042] Each tank 22 is arranged in the plant 20 with the ability to displace the container 23 so as to free the rolls 24-25-26 and make possible a ready insertion and passage of the threads 11 during operations to change batches or for other necessary actions.
[0044] The temperature of the impregnation bath is kept at about 70-75°C, while the metering and heating of the caustic soda can be carried out and controlled in a supplementary container.
[0045] The quantity and temperature of the caustic soda solution and also the metering of the caustic soda can be controlled advantageously by suitable sensors placed in the tanks; these sensors are connected to centralised control means which manage the operations automatically. This feature forms part of every other operational assembly described hereinafter.
[0046] The solution for topping up the tanks 22 of the impregnation assembly 29 can be prepared in a separate tank and heated by heat exchangers independently or with conservation of heat.
[0047] As an indication and with a mercerisation speed of about 75 metres per minute, the threads 11 in the lay-out shown take about 6 seconds to pass through the whole impregnation assembly 29 according to trials conducted by the present applicants.
[0048] The threads 11 are fed from the impregnation assembly 29 into a first drying assembly 30 consisting of a first oven 31a, in which the threads 11 undergo a series of passes between upper rolls 32 and lower rolls 33. The drying may be substantially complete or be partial.
[0049] The first oven 31a will advantageously be of a type with a forced circulation of air heated with a submerged combustion system or another known heating system. In the above conditions the first drying step 14 will last for about 48 seconds.
[0050] The first drying step 14 is especially important for the results of the mercerisation method according to the invention.
[0051] The threads 11 leaving the first drying assembly 30 are fed to a steaming assembly 34, in which the threads 11 undergo a series of passes between upper rolls 32 and lower rolls 33 and are subjected to a current of steam at a temperature of about 100°C.
[0053] The threads 11 leaving the steaming assembly 34 are fed into a hot-water washing assembly 35 consisting of two tanks 22 of the type described above in this case.
[0054] The water in the hot-water washing assembly 35 is kept at a temperature of about 70-80°C and the hot-water washing step 16 lasts for about 6 seconds.
[0055] So as to neutralise the pH of the threads 11, the threads 11 then undergo a neutralisation step 17 performed in a neutralisation assembly 36 consisting of two tanks 22 holding acetic acid at a temperature of about 20°C. This step of neutralising 17 the threads 11 lasts for about 6 seconds in this case.
[0056] Thereafter the threads 11 are fed to a cold water rinsing assembly 37 consisting of two groups, each of two tanks 22, containing water at a temperature of about 20°C.
[0058] The tanks 22 of the hot-water washing assembly 35 and cold-water rinsing assembly 37 are equipped with inlets and outlets for water, which can be delivered continuously in the opposite direction to the feed of the threads 11 to be processed.
[0059] The water flows advantageously into each of the washing and rinsing assemblies 35-37 from one tank into another through overflow pipes.
[0060] The water collected at the outlets of the washing and rinsing assemblies 35-37 can be treated to recover caustic soda by evaporation of the water.
[0061] The thermal energy made available in the treatment can be employed to heat water used in the preceding steps.
[0062] The threads 11 are fed from the cold water rinsing assembly 37 to a second and final drying assembly 38, which consists of a second oven 31b in which the threads 11 undergo a series of passes between upper rolls 32 and lower rolls 33.
[0063] The second oven 31b may advantageously be of the same type as the first oven 31a or be replaced by other known heating systems.
[0064] The threads 11 in the second and final drying step 19 are subjected to a current of hot air for about 48 seconds.
1. Continuous mercerisation method which is suitable to carry out mercerisation treatment
of a plurality of threads (11) of polyester fibres being unwound independently, continuously
and parallel to each other from one (12) or more (112-212) feeder beams, the method
being characterised in that the plurality of threads (11) undergoes the following
operational steps in succession:
- impregnation (13) by immersion in at least one tank (22) containing heated caustic soda lye;
- first drying (14) in an oven (31a) with a circulation of hot air;
- steam treatment (15);
- neutralisation with hot washing, the neutralisation comprising a first stage of washing in hot water (16) by immersion in at least one tank (22) containing a bath of hot water, a second stage of actual neutralisation (17) by immersion in at least one tank (22) containing acid liquor and a third stage of rinsing (18) by immersion in at least one tank (22) containing cold water;
- a second and final drying (19) in an oven (31b) with a circulation of hot air;
the threads (11) leaving the second and final drying (19) being wound on at least one take-up beam (39).2. Method as in Claim 1, in which the temperature of the bath in the step of impregnation
(13) in caustic soda is about 70-75°C.
3. Method as in Claim 1 or 2, in which the temperature of the bath in the hot-water washing
step (16) is about 70-80°C.
4. Method as in any claim hereinbefore, in which the temperature of the bath in the neutralisation
step (17) is about 20°C.
5. Method as in any claim hereinbefore, in which the temperature of the bath in the cold-water
rinsing step (18) is about 20°C.
6. Method as in any claim hereinbefore, in which the bath of the neutralisation assembly
(36) contains acetic acid.
7. Method as in any claim hereinbefore, in which the threads (11) are washed in a current
flowing in the opposite direction to their direction of feed in the washing and rinsing
(16-18) and neutralisation (17) steps.
8. Method as in any claim hereinbefore, in which the wash water leaving the washing and
rinsing steps (16-18) is treated to recover caustic soda.
9. Method as in any claim hereinbefore, in which the thermal energy made available by
the recovery of caustic soda is used in one or more steps of the method itself.
10. Method as in any claim hereinbefore, in which the air temperature is kept in the range
of 90 to 120°C during the first and second drying steps (14-19).
11. Method as in any claim hereinbefore, in which the mercerisation speed is at least
75 metres per minute.
12. Method as in any claim hereinbefore, in which the threads (11) being unwound from
the feeder beam (12) or beams (112-212) are connected together crosswise at pre-set
intervals.
13. Method as in any claim hereinbefore, in which each step of the mercerisation method
(10) is governed by a central data processing unit controlling and regulating the
processing parameters.
14. Method as in any claim hereinbefore, which comprises a monitoring system to check
all the physical magnitudes of the treatment.
15. Continuous mercerisation plant which is suitable to carry out mercerisation treatment
of a plurality of threads (11) of polyester fibres being unwound continuously and
parallel to each other from one (12) or more (112-212) feeder beams, the plant (20)
employing the method (10) of the claims hereinbefore and being characterised in that
it comprises the following operational assemblies positioned in succession:
- an impregnation assembly (29) comprising at least one tank (22);
- a first drying assembly (30) comprising an oven (31a) working with hot air;
- a steaming assembly (34);
- a hot water washing assembly (35) comprising at least one tank (22);
- a neutralisation assembly (36) comprising at least one tank (22);
- a cold water rinsing assembly (37) comprising at least one tank (22);
- a second and final drying assembly (38) comprising an oven (31b) working with hot air; and
- a thread (11) take-up assembly comprising at least one take-up beam (39).
16. Plant (20) as in Claim 15, in which the impregnation assembly (29) comprises two tanks
(22), one placed downstream of the other.
17. Plant (20) as in Claim 15 or 16, in which the hot water washing assembly (35) comprises
two tanks (22), one placed downstream of the other.
18. Plant (20) as in any of Claims 15 to 17 inclusive, in which the neutralisation assembly
(36) comprises two tanks (22), one placed downstream of the other.
19. Plant (20) as in any of Claims 15 to 18 inclusive, in which the cold water rinsing
assembly (37) comprises two tanks (22), one placed downstream of the other.
20. Plant (20) as in any of Claims 15 to 19 inclusive, in which the upper (24), lower
(25) and intermediate transmission (26) transverse rolls respectively feeding the
bundle of threads (11) and positioned in the tanks (22) are supported as cantilevers.
21. Plant (20) as in any of Claims 15 to 20, inclusive, in which the upper rolls (24)
of the tanks (22) cooperate with means (27) applying pressure to the threads (11).
22. Plant (20) as in any of Claims 15 to 21, inclusive, in which the impregnation assembly
(29) is connected to a supplementary means that heats the caustic soda.
23. Plant (20) as in any of Claims 15 to 22, inclusive, which is connected to a central
data processing system.