Process for Dyeing Ramie Sliver and Method for Preparing Yarn

Abstract

A process for dyeing ramie sliver, comprising: 1.) pretreatment: cooking the ramie sliver for 8-12 minutes in a cooking reagent in a bath ratio of 1:4-10, the cooking reagent is a 1-3 g/L aqueous solution of a penetrating agent; and 2.) dyeing: dyeing the cooked ramie sliver in an active dye in a bath ratio of 1:4-10. Also disclosed is a method for preparing ramie yarn. The ramie sliver dyed according to the present invention improves the properties of ramie fibers, such that the ramie fibers are less likely to break; and the ramie fibers are less likely to harden, avoiding poor drawing, needle breakage and missing stitches during carding and coalescing in post-procedures, thus achieving the purpose of smooth yarn spinning. Also disclosed is a method for preparing ramie colored-spun yarn.

Description

The present application claimed priority based on the patent application entitled by “Process for dyeing ramie sliver and method for preparing yarn” filed with the Chinese Patent Office (No. 201110179694.6) on Jun. 29, 2011, all contents of which are combined in the present application by reference.

FIELD OF INVENTION

The present invention relates to cloth dyeing technical field, in particular, a process for dyeing ramie slivers.

BACKGROUND OF THE INVENTION

Ramie is a fiber crop having good quality, high yield and characteristic of China, and the gross output of ramie in China occupies 90% of that of the world. Ramie fiber has the advantageous features of strong hydroscopicity, fast heat dissipation, corrosion resistance and bacterial inhibition, soft luster, recyclability, environmental friendliness and the like, as well as excellent wearability.

As production technology develops and people's living standard raises, ramie is used more and more, mainly for manufacturing ramie cloth, such as Chinese linen. Now, dyeing of ramie mainly lies in ramie yarn dyeing and stock (refined dry flax) dyeing, both of which have succeeded. However, the style of the colored fabric weaved with the dyed ramie yarns is relatively fixed, and dyeing of refined dry flax has a low yield, resulting in severe waste. Although dyeing of ramie slivers exists currently, and it greatly increase yield and achieve a varying colorful effect, which is difficult to be achieved by yarn dyeing, by coalescing ramie slivers having different colors and blend spinning into yarns, the existing ramie sliver dyeing technology generally uses the top dyeing technique conventional in wool or cotton spinning industry; moreover, the dyed fiber slivers are likely to break in coalescing and drawing, and the fibers are likely to harden due to no curling and poor cohesion of ramie fibers, readily leading to poor drawing, needle breakage and missing stitches during carding and coalescing in post-procedures, thus it is difficult to spin smoothly.

SUMMARY OF THE INVENTION

Directing to these disadvantages, the present invention provides a process for dyeing ramie slivers, by which the ramie slivers dyed is not liable to break and harden and enables smooth yarn spinning.

In order to achieve the above purpose, the invention provides the following technical solution: a process for dyeing ramie slivers, comprising

1) pretreatment: steaming ramie slivers for 8-12 min at a bath ratio of 1:4-10 with a 1-3 g/L aqueous solution of a penetrant as a steaming agent;

2) dyeing: dyeing the steamed ramie slivers in an active dye at a bath ratio of 1:4-10.

Preferably, the dyeing in step 2) comprises the following process: adding ramie slivers to a dissolved active dye at atmospheric temperature, stirring for 5-10 min; adding a salt solution, increasing temperature to 60° C.-70° C., running for 5-8 min, adding sodium carbonate solution, and running for 40-60 min while holding the temperature; taking the ramie slivers out, and sequentially performing washing with clear water, neutralizing with diluted acid, soaping, and washing with cold water.

Preferably, the dyeing process further comprises 3) post-treatment: subjecting the dyed ramie slivers to color fixing and oiling.

Said color fixing is carried out by immersing ramie slivers in an aqueous solution containing 2-4% (o.w.f) of a color fixing agent and 2-5% (o.w.f) of a softener at 35° C.-50° C. for 10-20 min;

Said oiling is carried out by immersing the color-fixed ramie slivers in an aqueous solution containing 2-3 g/L of an oil agent at 60° C.-70° C. for 20-30 min.

Preferably, said soaping is carried out by washing the ramie slivers in a solution of 1-2 g/L of detergent at 90° C.-100° C. for 10-15 min.

Preferably, the ramie slivers in step 1) are set to have a coiler shape.

The present invention further provides a preparation method of ramie spun yarn, and the technical solution thereof is as follows: a method for preparing ramie colored-spun yarn, comprising the following steps:

(1) preparing ramie fibers into ramie balls having a coiler shape;

(2) steaming ramie balls for 8-12 min at a bath ratio of 1:4-10 with a 1-3 g/L aqueous solution of a penetrant as a steaming agent;

(3) dyeing the ramie balls steamed in step (2) in an active dye at a bath ratio of 1:4-10;

(4) subjecting the ramie slivers dyed in step (3) to color fixing and oiling;

(5) dewatering and drying the ramie slivers from step (4); standing for more than 24 h;

(6) coalescing, drawing and combing the ramie slivers after standing in step (5); coalescing and drawing the combed ramie slivers; and

(7) spinning the ramie slivers from step (6) into yarns at 20-30° C. and relative humidity of 70-90%.

20-30° C. and relative humidity of 70-90%.

Preferably, drying in step (5) is required to achieve a moisture regain of 7-10% and an oil content of 0.5-1.5%.

Preferably, the ramie sliver used for spinning yarn in step (7) has at least one color.

In the present invention, ramie fibers are firstly made into ramie balls having a coiler shape and certain weight, subsequently bagged, caged and hoisted to a yarn dyeing machine for dyeing. The dyeing process involves steaming ramie balls with a steaming liquor containing a penetrant and then dyeing. In order to guarantee the subsequent spinnability of the ramie fibers, it is further needed to perform oiling treatment for improving spinnability to the dyed ramie fibers, followed by dewatering and drying, thereby preparing colored ramie fiber slivers meeting the requirements of spinning process. The colored ramie fiber slivers are then subjected to fiber loosening, coalescing and drawing, and spun after combing. The colored ramie fiber slivers can be spun solely or blend-spun with other weaving fibers to obtain ramie or its blend yarns having different characteristics and different colors.

The dyed ramie slivers in the present invention improves the properties of ramie fibers, such that the ramie fibers are not liable to break in coalescing and drawing; and the ramie fibers are not liable to harden, avoiding poor drawing, needle breakage and missing stitches during carding and coalescing in post-procedures, thus achieving the purpose of smooth yarn spinning.

The preparation method of ramie spun yarn according to the present invention effectively solves the technical problem in production of ramie sliver colored-spun yarn, and facilitates diversity of product and increase of added value or ramie product to thereby obtain higher economic benefit. Colorful ramie products having different elements can be prepared by the preparation process and method according to the present invention.

DETAILED EMBODIMENTS

A preparation method of ramie spun yarn, comprising the following steps:

1. preparing ramie fibers into ramie balls having a coiler shape and a weight of 4-5 kg/ball

	main process parameters	sliver weight 10-20 g/m
	thickness of the shaped ramie balls	200-250	mm
	central hole of the shaped ramie balls	Φ80-90	mm

2. loading the ramie balls into a nylon net bag, relatively fixing the ramie fiber slivers along axial direction with a proper tightness to prevent tangle thereof:

3. loading the ramie balls fixed as required to a suspended cage;

4. placing the suspended cage containing the ramie fiber slivers into a yarn dyeing pot;

5. dyeing the ramie fiber slivers in a yarn dyeing pot (model A11WIN-55, produced by Fong's National Engineering Co., Ltd, Hong Kong).

A suspended cage capable of holding ramie balls is designed taking the advantages of AUwin series dyeing vessels produced by Fong's National Engineering Co., Ltd., and placed into the dyeing vessel for dyeing. The AUwin series dyeing vessels produced by Fong's National Engineering Co., Ltd. have the advantages of energy saving, high efficiency, ability of pressure dewatering, and possession of AIR advanced intelligent washing system.

The ramie sliver dyeing process comprises the following process flow: pretreatment->dyeing->post-treatment;

Dyeing aid:
Penetrant JFC           produced by Hubei Jianli Chemical Industry
                        Co., Ltd.
Detergent 805           produced by Hubei Jianli Chemical Industry
                        Co., Ltd.
Color fixing agent      produced by Shenyang Chemical industry
                        Co., Ltd.
Dye                     produced by Yorkshire Chemicals Holdings
                        Ltd., active dye
Salt sodium chloride    produced by Hunan salt industry Co., LTD.
Alkali sodium carbonate produced by Zhuzhou Zhicheng Chemical
                        Industry Co., Ltd.
Softener                produced by Clariant Chemicals Ltd.
Ramie oiling agent      produced by Beijing CTA-Tex Chemicals Co.,
FD-ZY06A, FD-ZY06B      Ltd

1) Pretreatment

The pretreatment is for the purpose of removing the small quantity of oil and other aids attached on the ramie slivers, which is beneficial to fiber coloring and capable of guaranteeing the dyeing performance of the fibers.

Main Process Parameters:

	Penetrant JFC	1	g/L
	Bath ratio	1:4-10
	Temperature	100°	C.
	Time	10	min
	Circulation	completely internal flow

Key points: completely-internal-flow is adopted in the circulation for temperature increase, where the rate of temperature increase is set to be the fastest, and the pump speed is 90%. After pretreatment is finished, washing with cold water is conducted once for 5 min, and the tank is opened for checking.

2) Dyeing

Dye: active dye, the amount thereof varies according to colors

Bath ratio: 1:410

Dissolved dye is added at atmospheric temperature, followed by running for 5 min; dissolved salt is added and then temperature is increased to 60° C., followed by running for 5 min; dissolved sodium carbonate is added, followed by running for 40-60 min while holding the temperature at 60° C., and then a sample is taken. The color is checked. If the color is correct, water is discharged, and washing with clear water is conducted once for 5 min; subsequently, glacial acetic acid is added for neutralization (HAC 2-4 g/l), and water is discharged after running at atmospheric temperature for 5 min. Soaping is performed once (detergent 1-2 g/l, temperature 90-100° C., time 10 min), then water washing and overflow water washing are carried out sequentially, followed by washing with 80° C. water once for 5 min (washing with hot water is performed again if the color is very deep) and washing with cold water for 1-2 times each for 5 min. Lubrication treatment is carried out (color fixing agent is added if the color is deep) at 40° C. for 10 min, and then water is discharged out of the cage.

In the steps in which the ramie balls are disposed in the dyeing vessel, the rates of temperature increase and decrease are set to be the fastest, expect for that the rate of temperature increase in dyeing is controlled at 2° C./min, so that the retention time of the ramie balls in the dyeing vessels is shortened as much as possible, and the impact of liquid flow on the ramie balls is reduced, thereby avoiding tangle.

Key points of dyeing: the dyes having low substantivity and better migrating property (especially dyes of medium and light color) should be used. The dyes and aids should be substantially dissolved before addition. Feed speed should be controlled severely, and dye is fed at a speed of 50% for 10 min; and the aids are fed at a speed of 70% for 5 min. Dyeing is performed for 40-60 min with rate of temperature increase controlled at 2° C./min. Bidirectional circulation is adopted in dyeing, comprising external flow at a pump speed of 60% for 2 min and internal flow at a pump speed of 90% for 4 min, and internal-flow starting is adopted.

3) Post-Treatment

The purpose of post-treatment is to fix color for improving color fastness of dyeing and to oil for enabling smooth carding. Post-treatment is performed under the environment bidirectional flow comprising internal flow at a pump speed of 80% for 4 min and external flow at a pump speed of 40% for 1 min.

Main Process Parameters for Color Fixing:

	Temperature	40°	C.
	Time	10	min
	Color fixing agent	2-4%
	Softener	2-5%

Main Process Parameters for Oiling:

	Temperature	60°	C.
	Time	20	min
	Oiling concentration	2-3	g/l

6. Dewatering the dyed ramie fiber slivers which have been subjected to color fixation and oiling.

7. Dying the dyed and dewatered ramie fiber slivers (radiofrequency dryer)

A moisture regain of 7-10% is required after drying;

An oil content of 0.5-1.5% is required after drying.

8. Standing and incubating the treated ramie fiber slivers for more than 24 h to eliminate partial internal stress of fibers and keep internal-external equilibrium of the regain.

9. Coalescing and drawing the dyed ramie fiber slivers subjected to standing and incubating on a double-apron drawing frame by using a low-speed, light-weight and small draft process, to achieve the purpose of reducing fiber hardening and loosening the fibers, so as to benefit the yarn spinning process.

10. Coalescing and drawing the dyed ramie fiber slivers treated with the double-apron drawing frame again on a needle-plate drawing frame to improve the evenness of the ramie slivers.

11. Removing part of flaws and short fibers from the coalesced dyed ramie Fiber slivers on a ramie comber by using a process of “low speed, fine combing and light weight”, so as to satisfy the requirement of high-quality yarn. A smooth roll is used instead of a grooved roll at the sliver outlet to improve cohesion of fibers and thereby facilitate the subsequent production. Different process schemes may be made based on different raw materials, for example, this procedure may be canceled to meet any requirements for the style and the like of product.

12. Coalescing and drawing the combed dyed ramie fiber slivers on a drawing frame for 3-5 times. The coalescing process is performed at a low speed and a light weight by using a trumpet with a perfect pressurizing automatic stopper, smooth passage and small diameter, to improve the evenness and smoothness of the fiber slivers, to ensure uniform mixing and to enable the slivers to shape well.

13. Treating roving according to a process principle of low speed, light weight and appropriate twist factor.

14. Treating spun yarn at a low speed and an appropriate pressure with a small draft and appropriate setting and tension, to reduce hairiness and broken ends and improve evenness of the slivers.

15. Keeping, a relatively high environment temperature and humidity during the yarn spinning process.

Temperature       20-30° C.
Relative humidity 70-90%

16. carrying out color mixing of dyed ramie fiber slivers by means of sliver mixing as well as other means.

The invention is described in detail in combination with the following examples, and such description is merely for demonstration and explanation, without any intention of limitation to the protection scope of the invention.

Example 1

Production of 24 Nm Coffee-Colored Ramie Knitting yarn

1. Ramie fiber slivers were made into ramie balls having a coiler shape

Weight of ramie fiber slivers: 10±1 g/m

Shaping height of the ramie balls: 200-250 mm

Shaping weight of the ramie balls: 4500-5000 g/ball

The central hole diameter of the shaped ramie balls: Φ80-90 mm

2. The ramie balls were loaded into a nylon net bag, the ramie fiber slivers were fixed along the axial central hole from the external with a proper tightness to prevent tangle thereof.

3. The fixed ramie balls were loaded to a suspended cage;

4. The suspended cage containing the ramie fiber balls were placed into a yarn dyeing machine;

5. The ramie fiber slivers were dyed.

Dyeing process flow: pretreatment->dyeing->post-treatment

(1) Pretreatment

pretreatment aids:

penetrant JFC: 1 g/L

bath ratio: 1:4

temperature: 100° C.

time: 10 min

circulation: entire internal and external flow

pretreatment pump power: 90% for internal flow, 40% for external flow

time: 5 min for internal flow, 3 min for external flow

• • Circulation was carried out in such manner that even dyeing is ensured and tangle of fiber slivers is prevented.

(2) Dyeing

dye: active dye (coffee-colored) 3BE-N 0.63%, 3BF-N 0.51%, B: 23%.

Bath ratio: 1:4

Dissolved dye was added at atmospheric temperature, followed by running for 5 min; dissolved salt was added and then temperature was increased to 60° C., followed by running for 5 min; dissolved sodium carbonate was added, followed by running for 40-60 min while holding the temperature at 60° C. The color is checked, if the color was correct, water was discharged, and washing with clear water was conducted once for 5 min; subsequently, glacial acetic acid was added for neutralization (HAC 2-40), and water was discharged after running at atmospheric temperature for 5 min. Soaping was performed once (detergent 1-2 g/l, temperature 90-100° C., time 10 min), then water washing and overflow water washing were carried out sequentially, followed by washing with 80° C. water once for 5 min (washing with hot water was performed again if the color was very deep) and washing with cold water for 1-2 times each for 5 min. Lubrication treatment was carried out (color fixing agent was added if the color was deep) at 40° C. for 10 min, and then water was discharged out of the cage.

Dyeing pump power: internal 90%, external 80%

Circulation time: internal 4 min, external 2 min

(3) Post-Treatment

acid washing: HAC 2-4 g/L 10 min

color fixing: 10° C. 10 min

color fixing agent: 2%

softener: 5%

• • 6. The dyed ramie fiber slivers subjected to color fixing and washing was immersed in oil to ensure the spinnability of the fibers.

Main Process Parameters for Oiling

Ramie oiling agent: FD-ZY06A, FD-ZY06B 2.5 g/L

Bath ratio: 1:7

Time: 6 h

Temperature: 55° C.

pH value: 8.5

• • 7. The oiled dyed ramie fiber slivers was dewatered with a centrifugal dewatering machine, and the dyed ramie fiber balls were parallely placed into a dewatering machine one by one for dewatering.

Required moisture content after dewatering: 45-55%

• • 8. drying

Using a radiofrequency dryer: model FTDW85, produced by

Fong's National Engineering Co., Ltd.

Time 5 m/h

Regain after drying: 7-10%

Oil content: 0.5-1.0%

• • 9. operation essentials
  • (1) Ramie slivers should be placed in parallel in the production process and should not be disordered.
  • (2) After pretreatment was finished, the vessel should be opened, and the fastening screws should be readjusted.
  • (3) Internal and external circulation time and pressure of the circulation pump should be adjusted well in the dyeing process to decrease hairiness as mush as possible.
  • 10. The dyed ramie fiber slivers were allowed to stand and be incubated for more than 24 h under natural conditions.
  • 11. The dyed ramie fiber slivers were coalesced and drawn to reduce hardening of fiber and loose the fiber.

Machine model: BR221 apron drafting machine

Coalescing number: 6-8

Draft: 6-9

Feed weight: 10-15 g/m

Front roller speed: 50-120 m/min

Setting for drawing: front roller-middle roller 170 mm

• • middle roller-rear roller 240 mm
  • 12. The dyed ramie fiber slivers treated with a double-apron drawing frame were coalesced and drawn again to improve evenness of the ramie slivers.

Model CZ304A gill faller

Coalescing number: 6-8

Draft: 6-9

Feed weight: 10-15 g/m

Sliver discharge weight: 10-12 g/m

Front roller speed: 35/55 m/min

Needle plate beats: 800-1000/min

Needle plate density: 7-10 needles/inch

Setting in drawing: 45-55 mm

• • 13. The coalesced dyed ramie fiber slivers were combed to remove part of short fibers and impurities and improve quality of the fiber.

Machine model: B311 comber

Pulling setting: 30-45 mm

Combing setting: 1 mm

Feeding: 15-19 T

Cylinder: 90-100/min

Sliver discharge weight: 45-55 g/5 m

• • 14. The combed dyed ramie fiber slivers were subjected to coalescing and drawing for 3-4 times to obtain even final coalesced slivers meeting the requirements of spinning process.

Machine model: gill faller

Main Process Parameters:

Setting in drawing: 40-55 mm

Needle plate density: 10-18 needles/inch

Needle plate beats: 390-800/min

Draft: 6-9

Coalescing number: 6-10

Sliver discharge weight: 8-15 g/m

• • 15. The dyed ramie fiber slivers were spun into slubbing

Main Process Parameter

Front roller speed: 100-200 r/min

Spindle speed: 200-350 r/min

Draft: 5-10

Twist factor: 18-22

Count of delivery: 1-2 Nm

• • 16. The slubbing was spun into roving

Main Process Parameters

Front roller speed: 55-90 r/min

Spindle speed: 200-450 r/min

Draft: 5-10

Twist factor: 18-22

Count of delivery: 2-4.5 Nm

• • 17. Yarns were spun

Main process parameters

Front roller speed: 80-110 r/min

Spindle speed: 500-7000 r/min

Draft: 10-20

Twist factor: 90

Count of delivery: 24 Nm

• • 18. drum (equipped with an electronic yarn clearer)

Drum speed: 300-400 m/min

Main parameters of the electronic yarn clearer

D: 2.0

DL: 2.5 cm

• • The finally produced ramie yarns were detected. The yarns have the features of soft luster, cleanness, less hairiness, etc., and are suitable for use in woven or knitted ramie products.

Example 2

Production of 60 Nm Ramie-Viscose Gray Spun Yarn (30% ramie/70% viscose)

• • 1. Ramie fiber slivers were dyed into black according to steps 1-10 of Example 1.
  • 2. Combed black ramie fiber slivers were produced according to steps 11-13 of Example 1.
  • 3. The Combed black ramie fiber slivers were coalesced and drawn to form even semi-finished product satisfying process requirements.

Main Process Conditions:

Needle plate beats: 600-800/min

Needle plate specification: 10-14 needles/inch

Draft: 5-9

Sliver discharge weight: 9-10 g/m (dry weight)

• • 4. inherently white ramie fiber slivers were pre-coalesced and drawn to form even semi-finished product satisfying process requirements, in which the main process conditions were identical with those provided in step 3.
  • 5. Inherently white viscose fiber slivers were pre-coalesced, coalesced, and drawn to form even semi-finished product satisfying process requirements, in which the main process conditions were identical with those provided in step 3.
  • 6. Process flow for production of colorful fiber slivers:

Pre-coalescing of inherently white ramie fiber slivers
Pre-coalescing of black ramie fiber slivers {close oversize brace}
Pre-coalescing of inherently white viscose fiber slivers
−> primary coalescing−> secondary coalescing−> and coalescing
for the third time−> final coalescing−> slubbing−> roving−>
yarn−> drum

• • 7. Colorful fiber slivers satisfying process requirements were produced according to step 14 as sated in example 1.
  • 8. Slubbing is spun according to step 15 as stated in example 1.
  • 9. Roving is spun according to step 16 as stated in example 1.
  • 10. Yarns were spun according to step 17 as stated in example 1.
  • 11. Cheeses were produced according to step 18 as sated in example 1.

In the production method described above, ramie fiber slivers were dyed and then prepared into blend colored-spun yarns having unique style by using a ramie spinning apparatus. The obtained yarns have unique style and good luster, and can lead the fashion trend of ramie textiles; meanwhile, they enable enrichment of ramie textile products and added value increase of the products.

The above is merely preferred embodiments of the present invention. It should be indicated that, those skilled in the art may make some improvement and retouch on the premise of not deviating from the principle of the present invention, and such improvement and retouch should be considered within the protection scope covered by the invention.

Claims

1. A ramie sliver dyeing process, comprising

(1) pretreatment: steaming ramie slivers for 8-12 min at a bath ratio of 1:4-10 with a 1-3 g/L aqueous solution of a penetrant as a steaming agent;

(2) dyeing: dyeing the steamed ramie slivers in an active dye at a bath ratio of 1:4-10.

2. The ramie sliver dyeing process according to claim 1, characterized in step (2) dyeing comprising the following procedures: adding ramie slivers to a dissolved active dye at atmospheric temperature, stirring for 5-10 min; adding a salt solution, increasing temperature to 60° C.-70° C., running for 5-8 min, adding sodium carbonate solution, and running for 40-60 min while holding the temperature; taking the ramie slivers out, and sequentially performing washing with clear water, neutralizing with diluted acid, soaping, and washing with cold water.

3. The ramie sliver dyeing process according to claim 1 characterized in further comprising (3) post-treatment: subjecting the dyed ramie slivers to color fixing and oiling,

said color fixing is carried out by immersing ramie slivers in an aqueous solution containing 2-4% (o.w.f) of a color fixing agent and 2-5% (o.w.f) of a softener at 35° C.-50° C. for 10-20 min,

said oiling is carried out by immersing the color-fixed ramie slivers in an aqueous solution containing 2-3 g/L of an oil agent at 60° C.-70° C. for 20-30 min.

4. The ramie sliver dyeing process according to claim 2, characterized in that said soaping is carried out by washing the ramie slivers in a 1-2 g/L of detergent at 90° C.-100° C. for 10-15 min.

5. The dyeing process according to claim 1, characterized in that the ramie slivers in step (1) are set to have a coiler shape.

6. A method for preparing ramie colored-spun yarn, comprising the following steps:

(1) preparing ramie fibers into ramie balls having a coiler shape;

(2) steaming ramie balls for 8-12 min at a bath ratio of 1:4-10 with a 1-3 g/L aqueous solution of a penetrant as a steaming agent;

(3) dyeing the ramie balls steamed in step (2) in an active dye at a bath ratio of 1:4-10;

(4) subjecting the ramie slivers dyed in step (3) to color fixing and oiling;

(5) dewatering and drying the ramie slivers from step (4); standing for more than 24 h;

(6) coalescing, drawing and combing the ramie slivers after standing in step (5); coalescing and drawing the combed ramie slivers; and

(7) spinning the ramie slivers' from step (6) into yarns at 20-30° C. and relative humidity of 70-90%.

7. A method for preparing ramie colored-spun yarn according to claim 6, characterized in that the drying in step (5) is required to achieve a moisture regain of 7-10% and an oil content of 0.5-1.5%.

8. A method for preparing ramie colored-spun yarn according to claim 6, characterized in that the ramie sliver used for spinning yarn in step (7) has at least one color.

9. The ramie sliver dyeing process according to claim 2, characterized in further comprising (3) post-treatment: subjecting the dyed ramie slivers to color fixing and oiling,

said color fixing is carried out by immersing ramie slivers in an aqueous solution containing 2-4% (o.w.f) of a color fixing agent and 2-5% (o.w.f) of a softener at 35° C.-50° C. for 10-20 min,

said oiling is carried out by immersing the color-fixed ramie slivers in an aqueous solution containing 2-3 g/L of an oil agent at 60° C.-70° C. for 20-30 min.