Method for improving washing size change rate of pure cotton knitted fabric

Abstract

The invention discloses a method for improving the washing size change rate of a pure cotton knitted fabric, and relates to the technical field of textile printing and dyeing. In the liquid ammonia finishing process, after fabric feeding, pre-drying, air cooling and liquid ammonia padding are conducted on the fabric, the weft-direction fabric edge of the fabric is fixed to a needle plate to be expanded, overfeeding is conducted on the fabric in the warp direction, ammonia is removed in a hot air drying mode while expanding and overfeeding are conducted, and finally steam deodorization and cropping are conducted. According to the method, the washing size change rate of the pure cotton knitted fabric is improved by expanding the fabric padded with liquid ammonia in the weft direction / transverse direction and overfeeding in the warp direction / longitudinal direction in combination with continuous needle plate fixation in the hot air ammonia removal process, and specifically, the washing size change rates of the pure cotton knitted fabric prepared by the method in the warp direction and the weft direction are + 0.2% and-2.2% respectively.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of textile printing and dyeing technology, and particularly relates to a method for improving the water washing size change rate of pure cotton knitted fabric. BACKGROUND

[0002] Liquid ammonia is prepared by cooling ammonia gas at room temperature to -33.4 DEG C, and has the characteristics of small molecular weight, low viscosity and surface tension. Liquid ammonia is easy to flow and has excellent penetration, and can easily penetrate into fibers to cause changes in fiber crystallinity. The cotton fabric after liquid ammonia finishing has soft hand feeling, soft luster and stable size, and can effectively improve the wearability of the fabric, so that it can be widely used in the printing and dyeing industry.

[0003] At present, the non-expanding type (roller type) liquid ammonia finishing method is adopted, that is, the fabric is immersed in liquid ammonia and then the weft / horizontal free shrinkage method is used to finish the fabric. During the liquid ammonia treatment process, ammonia gas can penetrate into the interior of cotton fibers in a very short time, break the hydrogen bond of fiber molecules, and make the cotton fibers in a certain plastic state. The pore size distribution of the cotton fibers treated by liquid ammonia is more uniform. However, after the fabric is immersed in liquid ammonia, the weft / horizontal direction will shrink sharply, resulting in a narrow width of the fabric. Since liquid ammonia has a certain setting effect on cotton fibers, the fabric will be stretched to the designed width in the finishing process, but this will result in a large shrinkage of the finished fabric in the weft / horizontal direction. In view of the problem of the sharp shrinkage of the fabric after immersion in liquid ammonia, some dyeing plants add a stretching process before liquid ammonia finishing to stretch the fabric width to the width of the gray fabric before liquid ammonia finishing, which will increase the production cost.

[0004] In the prior art, CN114960184A discloses a kind of ironing-free shrinkage-resistant knitted fabric and its preparation method, which realizes the effect of preventing shrinkage by using non-expanding liquid ammonia treatment and moisture crosslinking combination. Among them, moisture crosslinking treatment can realize the covalent crosslinking between molecular chains to limit the relative displacement of fibers, thereby making the prepared fabric have certain shrinkage resistance. In this patent, non-expanding liquid ammonia finishing method is adopted, and moisture crosslinking is used to improve the problem of severe shrinkage in weft direction / width direction caused by liquid ammonia finishing method, but the acidic catalyst used in the process of moisture crosslinking will damage the fiber strength, and the crosslinking after the hardening effect will affect the soft and fluffy hand feeling of the fabric. CN118292167A discloses the processing technology of hemp four-way stretch fabric, which adopts non-expanding liquid ammonia finishing method and fabric component improvement to improve fabric shrinkage, thereby reducing the water washing size change rate of the fabric. The above-mentioned patent is also a non-expanding liquid ammonia finishing method, which improves the problem of severe shrinkage in weft direction / width direction after liquid ammonia finishing treatment by improving the fabric components. CN104441805A discloses a water-soluble adhesive lining with a warp and weft size change rate of-0.6% to 0.5%, which realizes shrinkage-resistant finishing after liquid ammonia finishing by using two-dip-two-nip shrink-resistant finishing liquid, 80-100℃ loose drying, super feeding upper needle plate, eight grid 170-175℃ hot air baking. This patent uses shrink-resistant finishing liquid and super feeding to control the shrinkage of the fabric, rather than through the way of liquid ammonia. Among them, the use of shrink-resistant finishing liquid not only increases the wastewater treatment cost, but also causes chemical residues, which may even affect the hand feeling of cotton knitted fabric. In addition, in the subsequent super feeding and hot air baking stage, the fiber is in a dry state, and its setting effect is far inferior to that of the fiber directly stretched in a swollen state after liquid ammonia treatment.

[0005] Therefore, in view of the problem of excessive shrinkage in weft direction / width direction of pure cotton knitted fabric after liquid ammonia treatment, it is particularly necessary to develop a method for improving the water washing size stability of pure cotton knitted fabric. SUMMARY

[0006] In view of the above-mentioned prior art, the purpose of the present application is to provide a method for improving the water washing size change rate of pure cotton knitted fabric. Specifically, during the liquid ammonia finishing process, after the fabric is fed, it is pre-dried, air-cooled, and then immersed and padded with liquid ammonia. The weft edges of the fabric are fixed on the needle plate for expansion, and the warp direction is super fed. At the same time, hot air drying is used to remove ammonia. Finally, steam deodorization is carried out, and the fabric can be dropped. In this application, during the ammonia removal process by hot air, the weft / warp of the fabric after immersion and padding with liquid ammonia is fixed on the needle plate for expansion, at the same time, the warp / length is super fed, and the needle plate is kept fixed until the ammonia removal is completed, so as to improve the water washing size change rate of pure cotton knitted fabric. Specifically, the pure cotton knitted fabric prepared by the method of the present application has a warp and weft water washing size change rate of +0.2% and-2.2%, respectively.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] The present application provides a method for improving the water washing size change rate of pure cotton knitted fabric, comprising the following steps:

[0009] In the liquid ammonia finishing process, the pure cotton knitted fabric is pre-dried, air-cooled and sealed after feeding, then immersed in liquid ammonia for padding treatment; after the padding is completed, the weft selvedge of the fabric is fixed on the needle plate for expansion treatment, and the warp direction of the fabric is overfed, hot air ammonia removal is carried out at the same time, and finally the fabric after hot air ammonia removal is taken out, and steam ammonia removal is carried out under sealed conditions, and then the fabric is dropped.

[0010] Preferably, the steam pressure in the pre-drying process is 1.3-1.7KG.

[0011] Preferably, the air cooling process is carried out at a cold air temperature of 8-12℃.

[0012] Preferably, in the padding process, the temperature of the liquid ammonia is-33~-34℃, the dipping time is 3-6s, the press of the padder is 5.0-6.0KG, and the speed is 10-30m / min.

[0013] Preferably, after the padding is completed, the liquid retention rate of the fabric is 45-55%.

[0014] Preferably, the overfeed amount is +3% to +8%.

[0015] Preferably, in the hot air ammonia removal process, the hot air temperature is 130±5℃.

[0016] Preferably, in the steam ammonia removal process, the steam pressure is 2-4KG.

[0017] The present application has the following advantages:

[0018] The present application immerses the pure cotton knitted fabric in liquid ammonia, fixes the weft / horizontal direction of the fabric on the needle plate for expansion treatment, overfeeds the warp / vertical direction of the fabric, and removes ammonia by hot air drying at the same time, and ensures that the fabric is fixed on the needle plate during the hot air ammonia removal process. This method can avoid the shrinkage of the weft / horizontal direction of the fabric during the ammonia removal process. The present application fixes the weft / horizontal direction of the fabric on the needle plate for expansion after immersing in liquid ammonia, overfeeds the warp / vertical direction at the same time, and keeps the needle plate fixed until the ammonia removal is completed, so as to improve the water washing size change rate of the pure cotton knitted fabric. DETAILED DESCRIPTION

[0019] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0020] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0021] During the liquid ammonia treatment process, liquid ammonia penetrates into the amorphous region of the cotton fiber, breaking the hydrogen bonds between the molecular chains, causing the fiber to change from a rigid state to a plastic state. At this time, the cellulose molecular chains can move freely, and the fiber swells. The radial swelling of the fiber is much higher than the axial swelling. Due to the high radial swelling of the fiber and the high flexural wave shape of the weft yarn in the natural state, the weft direction / transverse direction is prone to severe contraction, resulting in a narrow width of the fabric. In the prior art, the liquid ammonia finishing method is a non-expanding (drum) type liquid ammonia finishing method. In order to improve the problem of severe shrinkage of the fabric after liquid ammonia immersion, some dyeing plants perform tentering on the fabric before liquid ammonia finishing. Although this operation can improve the water washing size change rate of pure cotton knitted fabric, it increases the production cost.

[0022] Based on this, the present application provides a method for improving the water washing size change rate of pure cotton knitted fabric. Specifically, the fabric of the pure cotton knitted fabric is subjected to pre-drying, air cooling and sealing treatment, and then immersed in liquid ammonia for padding treatment. After the padding treatment is completed, the weft selvedge of the fabric is fixed on the needle plate for expanding treatment, and the warp direction of the fabric is subjected to overfeed treatment. The hot air ammonia removal is carried out at the same time as the expanding treatment and overfeed treatment, and the weft selvedge of the fabric is always fixed on the needle plate during the hot air ammonia removal process. Finally, the fabric after hot air ammonia removal is subjected to sealing treatment, and then steam ammonia removal is carried out, and the fabric is dropped.

[0023] Due to the breaking of hydrogen bonds in the fiber after liquid ammonia padding, the fiber is in a plastic state. At this time, the weft direction / transverse direction of the fabric is fixed on the needle plate for expanding, which is equivalent to applying a continuous mechanical stress to the weft direction / transverse direction of the fabric, so that the molecular chains of the fiber can be oriented along the stretching direction. Combined with the subsequent hot air ammonia removal operation, the fabric can rebuild hydrogen bonds in the stretching state during the hot air ammonia removal process, and the stretching state can be locked by rebuilding the hydrogen bond network, thereby improving the problem of shrinkage of the weft direction / transverse direction of the fabric during the ammonia removal process. In addition, the warp direction / longitudinal direction of the fabric after liquid ammonia padding is subjected to overfeed, so that the warp yarn is in a wave-shaped relaxed state, so that the axial shrinkage of the plastic state fiber can be fully released, and the radial tension of the fiber is eliminated, avoiding the shrinkage due to internal stress after drying.

[0024] The application improves the existing non-broadening liquid ammonia finishing method, and the method can improve the water washing size change rate of pure cotton knitted fabric after the warp / wale of the fabric is super-fed, the weft / cross is broadened, and the hot air ammonia removal process is combined with the continuous pin plate fixation method. Specifically, the water washing change rate of the pure cotton knitted fabric is: warp / wale +0.2%, weft / cross -2.2%.

[0025] The experimental materials used in the embodiments of the application are conventional experimental materials in the art and can be purchased through commercial channels.

[0026] The padder pressure and steam pressure KG in the application refer to kilogram force per square centimeter, i.e., KGf / cm 2 .

[0027] Example 1

[0028] A pure cotton knitted fabric is obtained by adopting 60S / 1 pure cotton combed compact spinning, in-drum pretreatment, dehydration, opening, drying, liquid ammonia finishing, edge sewing, dyeing, opening, drying, and auxiliary finishing. The designed width of the obtained pure cotton knitted fabric is 165 cm, and the designed finished product gram weight is 160 g / m 2 .

[0029] The liquid ammonia finishing process is as follows: after the pure cotton knitted fabric is fed, it is placed in a steam pressure of 1.5 KG for pre-drying to realize fabric heating and dehumidification; after heat exchange is performed by using salt water refrigerant to control the cold air temperature to 10℃ for cooling, pre-dynamic sealing is performed to avoid ammonia gas volatilization to the outside of the equipment; then the fabric is placed in liquid ammonia at-34℃ for padding treatment, during the padding process, the padder pressure is 5.5 KG, the speed is 15 m / min, and the immersion time of the fabric in the liquid ammonia is 4 s; after the padding is completed, the weft selvedge of the fabric is fixed on the pin plate for broadening treatment, +5% super feeding is applied to the warp of the fabric, and hot air temperature of 130℃ is controlled for hot air ammonia removal during broadening and super feeding; finally, the fabric after hot air ammonia removal is taken out for post-dynamic sealing to avoid ammonia gas volatilization to the outside of the equipment, the steam pressure is controlled to 3 KG for steam deodorization, and water vapor is used to further remove the residual ammonia molecules on the fabric.

[0030] Example 2

[0031] The difference between this embodiment and Embodiment 1 is as follows: During the liquid ammonia finishing process, after the pure cotton knitted fabric is fed into the machine, it is pre-dried under a steam pressure of 1.3KG to achieve heating and dehumidification of the fabric; a brine refrigerant is used for heat exchange, and the cold air temperature is controlled at 8℃ for cooling, followed by a pre-dynamic seal to prevent ammonia from evaporating to the outside of the equipment; then the fabric is immersed in liquid ammonia at -33℃ for padding treatment. During padding, the padding pressure is 5.0KG, the speed is 10m / min, and the immersion time of the fabric in liquid ammonia is 5s; after padding, the weft edge of the fabric is fixed to the needle plate for expansion treatment, and +3% overfeed is applied to the warp direction of the fabric. While expanding and overfeeding, the hot air temperature is controlled at 125℃ for hot air ammonia removal; finally, the fabric after hot air ammonia removal is removed and a post-dynamic seal is performed to prevent ammonia from evaporating to the outside of the equipment. The steam pressure is controlled at 2KG for steam deodorization, and water vapor is used to further remove residual ammonia molecules on the fabric before the fabric is removed.

[0032] Example 3:

[0033] The difference between this embodiment and Embodiment 1 is as follows: During the liquid ammonia finishing process, after the pure cotton knitted fabric is fed into the machine, it is pre-dried under a steam pressure of 1.7KG to achieve heating and dehumidification of the fabric; a brine refrigerant is used for heat exchange, and the cold air temperature is controlled at 12℃ for cooling, followed by a pre-dynamic seal to prevent ammonia from evaporating to the outside of the equipment; then the fabric is immersed in liquid ammonia at -35℃ for padding treatment. During padding, the padding pressure is 6.0KG, the speed is 30m / min, and the immersion time of the fabric in liquid ammonia is 3s; after padding, the weft edge of the fabric is fixed to the needle plate for expansion treatment, and +8% overfeed is applied to the warp direction of the fabric. While expanding and overfeeding, the hot air temperature is controlled at 135℃ for hot air ammonia removal; finally, the fabric after hot air ammonia removal is removed and a post-dynamic seal is performed to prevent ammonia from evaporating to the outside of the equipment. The steam pressure is controlled at 4KG for steam deodorization, and water vapor is used to further remove residual ammonia molecules on the fabric before the fabric is removed.

[0034] Comparative Example 1:

[0035] The difference between this comparative example and Example 1 is that: after impregnation, the weft direction of the fabric was not widened, nor was the warp direction overfed. Specifically:

[0036] The liquid ammonia finishing process is as follows: after the pure cotton knitted fabric is fed into the fabric, it is pre-dried, air-cooled and impregnated with liquid ammonia. After the impregnation is completed, the hot air temperature is controlled at 130℃ to remove ammonia. Finally, the fabric after hot air ammonia removal is removed and dynamically sealed to prevent ammonia from evaporating to the outside of the equipment. The steam pressure is controlled at 3KG to deodorize the steam. Water vapor is used to further remove the residual ammonia molecules on the fabric before the fabric is removed.

[0037] Comparative Example 2:

[0038] The difference between the comparative example and Example 1 is that after padding, the weft of the fabric is not expanded, and only the warp of the fabric is super-fed. The specific process is as follows:

[0039] The liquid ammonia finishing process is as follows: after the pure cotton knitted fabric is fed, pre-drying, air cooling and liquid ammonia padding are carried out, after the padding is completed, +5% super feeding is applied to the warp of the fabric, and hot air ammonia removal is carried out at the same time by controlling the hot air temperature to be 130°C; finally, the fabric after hot air ammonia removal is taken out and post-dynamic sealing is carried out to avoid ammonia volatilization to the outside of the equipment, steam deodorization is carried out by controlling the steam pressure to be 3KG, and water vapor is used to further remove the residual ammonia molecules on the fabric, and the fabric is dropped.

[0040] Comparative Example 3:

[0041] The difference between the comparative example and Example 1 is that after padding, the weft of the fabric is not expanded, and only the warp of the fabric is super-fed. The specific process is as follows:

[0042] The liquid ammonia finishing process is as follows: after the pure cotton knitted fabric is fed, pre-drying, air cooling and liquid ammonia padding are carried out, after the padding is completed, +5% super feeding is applied to the warp of the fabric, and hot air ammonia removal is carried out at the same time by controlling the hot air temperature to be 130°C; finally, the fabric after hot air ammonia removal is taken out and post-dynamic sealing is carried out to avoid ammonia volatilization to the outside of the equipment, steam deodorization is carried out by controlling the steam pressure to be 3KG, and water vapor is used to further remove the residual ammonia molecules on the fabric, and the fabric is dropped.

[0043] Test Example 1: Detection of water washing dimensional change rate

[0044] The pure cotton knitted fabrics prepared in Example 1 and Comparative Examples 1-3 are subjected to water washing experiment according to AATCC135-2015(3)IIIA(iii)3X, and the water washing dimensional change rate of the pure cotton knitted fabric is detected, and the results are shown in Table 1.

[0045] Table 1 Water washing dimensional change rate of pure cotton knitted fabric prepared in Example 1 and Comparative Examples 1-3

[0046] Group Washing dimensional change in the warp direction Washing dimensional change in the weft direction Example 1 +0.2％ -2.2％ Comparative Example 1 -0.4％ -5.8％ Comparative Example 2 -0.1％ -5.0％ Comparative Example 3 -0.3％ -3.6％

[0047] As can be seen from Table 1, by expanding the weft / cross direction of the fabric after immersion in the liquid ammonia and combining the process of continuous needle plate fixation in the hot air ammonia removal process, and overfeeding the warp / length direction, the size change rate of the pure cotton knitted fabric in the warp and weft directions after washing is +0.2% and -2.2%, respectively. Compared with Comparative Example 1 (control group), the size change rate of the pure cotton knitted fabric in the warp and weft directions in Example 1 is increased by 0.6% and 3.6%, respectively; in Comparative Example 2, only the warp / length direction of the fabric after immersion in the liquid ammonia is overfed, and the weft / cross direction is not expanded, and the size change rate of the pure cotton knitted fabric in the warp and weft directions is increased by 0.3% and 0.8%, respectively; in Comparative Example 3, only the weft / cross direction of the fabric after immersion in the liquid ammonia is expanded and combined with the process of continuous needle plate fixation in the hot air ammonia removal process, and the warp / length direction is not overfed, and the size change rate of the pure cotton knitted fabric in the warp and weft directions is increased by 0.1% and 2.2%, respectively. Therefore, expanding the weft / cross direction of the fabric after immersion in the liquid ammonia and combining the process of continuous needle plate fixation in the hot air ammonia removal process, and overfeeding the warp / length direction has a synergistic effect on improving the size change rate of the pure cotton knitted fabric after washing.

[0048] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for improving the wash size change of pure cotton knits, characterized by, The process comprises the following steps: In the liquid ammonia finishing process, the pure cotton knitted fabric is pre-dried, air-cooled and sealed after being fed, and then is immersed in liquid ammonia for padding treatment. After the padding treatment is completed, the weft selvedge of the fabric is fixed on the needle plate for spreading treatment, the warp of the fabric is overfed, and hot air is used to remove ammonia at the same time. Finally, the fabric after the hot air ammonia removal is taken out, and steam is used to remove ammonia under sealed conditions, and then the fabric is dropped.

2. The method of improving the wash size change of pure cotton knits of claim 1, wherein, During the pre-drying process, the steam pressure is 1.3-1.7KG.

3. The method of improving the wash size change of pure cotton knits of claim 1, wherein, During the air-cooling process, the cold air temperature is 8-12℃.

4. The method of improving the wash size change of pure cotton knits of claim 1, wherein, During the padding process, the temperature of the liquid ammonia is-33~-34℃, the immersion time is 3-6s, the press of the pad is 5.0-6.0KG, and the speed is 10-30m / min.

5. The method of improving the wash size change of pure cotton knits of claim 1, wherein, After the padding process is completed, the liquid retention rate of the fabric is 45-55%.

6. The method of improving the wash size change of pure cotton knits of claim 1, wherein, During the overfeeding of the warp of the fabric, the overfeeding amount is +3%~+8%.

7. The method of improving the wash size change of pure cotton knit fabric according to claim 1, wherein, During the hot air ammonia removal process, the hot air temperature is 130±5℃.

8. The method of improving the wash size change of pure cotton knit fabric according to claim 1, wherein, During the steam ammonia removal process, the steam pressure is 2-4KG.