Method for degumming of silk gauze fabric by alkali gel

Abstract

The present application relates to printing and dyeing process technical field, specifically to a kind of silk gauze alkali gel degumming method, comprising the following steps: S1. A small amount of food-grade sodium polyacrylate is added to sodium hydroxide solution at a constant speed, and an electric mixer is used to continuously stir thoroughly, so that sodium polyacrylate is stirred uniformly, and an alkali gel with a certain amount of alkali agent is prepared;S2. The fabric is weighed and fixed on the printing table version, and the prepared alkali gel is single-sidedly scraped with a printing screen to form a large square pattern. Then, the fabric with scraped gel is clamped between two layers of cotton cloth and placed in a hot press flatbed machine for degumming at a set temperature and time. After degumming, repeatedly wash with cold running water until the sizing is washed clean and the washing water is neutral. Then, dry in a 95℃ oven for 2 hours, weigh and store after overnight equilibration, and repeat the operation 3 times to complete degumming. The alkali gel can form a relatively stable alkali environment on the surface of the fabric, allowing the alkali agent to fully contact and react with sericin, thereby improving the degumming effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of printing and dyeing process, in particular to a silk gauze fabric alkali gel degumming method. BACKGROUND

[0002] Silk gauze fabric is a gauze with silk as warp and weft, also known as plain gauze. Silk gauze is made of 100% mulberry silk, which is a natural protein fiber with excellent moisture absorption, air permeability and gloss. The main component of silk gauze is protein fiber, and alkali has a certain dissolving and swelling effect on it. By taking advantage of this property of silk gauze fiber, alkali is printed on silk gauze fabric by printing, so that the fiber in the alkali printed part changes physically and chemically, thereby forming different colors, patterns or special texture effects on the fabric.

[0003] In the traditional alkali degumming process, improper control of parameters such as alkali concentration, temperature and treatment time can easily cause great damage to silk gauze fabric, affecting the hand feeling, strength and gloss of the fabric; and the silk gauze fabric degumming process may need to use complex equipment and chemical reagents, the operation process is cumbersome, and the cost is high. SUMMARY

[0004] In view of the shortcomings of the prior art, the present application provides a silk gauze fabric alkali gel degumming method, which solves the problems of easy damage to silk gauze fabric and high cost of existing alkali degumming.

[0005] To achieve the above purpose, the present application is realized by the following technical scheme: a silk gauze fabric alkali gel degumming method, comprising the following steps:

[0006] S1. Alkaline water preparation

[0007] A certain amount of slaked lime is dissolved in distilled water at room temperature, 0.2g of slaked lime is added per 100mL of distilled water, and after fully stirring and dissolving, it is left overnight. When the insoluble lime precipitate appears at the bottom of the solution, take the supernatant to prepare saturated lime water;

[0008] S2. Alkali paste preparation

[0009] Take 5% urea and 20% wheat starch by weight, dissolve in lime water of a fixed mass fraction, heat to near boiling without water, and cook for 5min, stirring continuously during the process, to prepare a uniform, particle-free translucent paste system of alkali printing paste for standby;

[0010] S3. Alkali gel preparation

[0011] Take 4g of food-grade sodium polyacrylate, add it to a fixed mass fraction of 100mL sodium hydroxide solution at a uniform speed, continuously stir with an electric mixer during the addition process to ensure uniform stirring of the sodium polyacrylate, and let it stand overnight to fully integrate, preparing a certain amount of alkali gel for use;

[0012] S4. Alkali gel degumming

[0013] The fabric is weighed and recorded and fixed on the printing table, a 150-mesh flat net single-wire diameter of 106μm is selected, and a large block square pattern of 10cm×10cm is scraped with the prepared alkali gel on one side; the fabric with the scraped gel is placed between two layers of cotton cloth and placed in a hot pressing flat machine for degumming treatment according to the set temperature and time; after degumming, the fabric is washed repeatedly with cold running water until the sizing agent is removed and the washing water is neutral; the washed fabric is dried in a 95℃ oven for 2h, weighed and saved after overnight equilibration, and the above operation is repeated 3 times to complete the degumming.

[0014] Preferably, the S3 step can also be degummed by alkali steaming, and the specific process is as follows:

[0015] The fabric is weighed and recorded and fixed on the printing table, a 150-mesh flat net single-wire diameter of 106μm is selected, and a large block square pattern of 10cm×10cm is scraped with the prepared alkali gel on one side; the fabric with the scraped gel is placed between two layers of cotton cloth and placed in a hot pressing flat machine for degumming treatment according to the set temperature and time; after degumming, the fabric is washed repeatedly with cold running water until the sizing agent is removed and the washing water is neutral; the washed fabric is dried in a 95℃ oven for 2h, weighed and saved after overnight equilibration, and the above operation is repeated 3 times to complete the degumming.

[0016] Preferably, the S4 step can also be degummed by alkali cooking, and the specific process is as follows:

[0017] The silk gauze fabric is cut into a size of 20cm×20cm and weighed and recorded with an electronic balance, then folded 4 layers and clamped in 2 pieces of 5cm×5cm high-strength resin clamps, and fixed with a constant clamping force using a G clamp, and the clamped fabric is immersed in alkali water for alkali cooking degumming at a bath ratio of 1:80, and after treatment at a certain temperature for a period of time, it is washed repeatedly with distilled water until the washing solution is neutral; finally, the degummed fabric is dried in a 95℃ oven for 2h, weighed and saved after overnight equilibration, and the above operation is repeated 3 times to complete the degumming.

[0018] Preferably, the temperature of the alkali cooking degumming is 60-100℃, and the treatment time is 15-150min.

[0019] Preferably, the treatment temperature of the alkali degumming by boiling is 60-100℃, and the treatment time is 15-150min.

[0020] Preferably, the treatment temperature of the alkali degumming by boiling is 60-100℃, and the treatment time is 15-150min.

[0021] The application provides an alkali degumming method for silk gauze fabric.

[0022] 1. The alkali degumming method can make the fabric be uniformly affected by the alkali liquor during the alkali boiling process, thereby improving the uniformity and completeness of the degumming.

[0023] 2. The alkali degumming method uses low-cost raw materials, and the raw materials are widely available and less pollute the environment. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Figure 1 is a diagram showing the influence of the hot-pressing temperature on the degumming rate of the silk gauze according to the application;

[0025] Figure 2 Figure 2 is a diagram showing the influence of the hot-pressing time on the degumming rate of the silk gauze according to the application;

[0026] Figure 3 Figure 3 is a diagram showing the surface morphology of the silk gauze under different hot-pressing times according to the application, wherein Figure 3 (a) is the hot-pressing time of 10s, Figure 3 (b) is the hot-pressing time of 50s, Figure 3 (c) is the hot-pressing time of 90s;

[0027] Figure 4 Figure 4 is a diagram showing the surface morphology of the silk gauze and its fabric under different alkali degumming processes according to the application, wherein Figure 4 (a) is the silk gauze without degumming, Figure 4 (b) is the silk gauze degummed by boiling, Figure 4 (c) is the silk gauze degummed by boiling and steaming, Figure 4 (d) is the silk gauze degummed by alkali gel;

[0028] Figure 5Infrared spectra of different alkali degumming processes of the silk gauze of the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. EMBODIMENT

[0030] The embodiment of the present application provides a silk gauze fabric alkali gel degumming method, comprising the following steps:

[0031] S1. Alkaline water preparation

[0032] A certain amount of slaked lime is dissolved in distilled water at room temperature, 0.2 g of slaked lime is added per 100 mL of distilled water, and after fully stirring and dissolving, it is left overnight. When insoluble lime precipitate appears at the bottom of the solution, the supernatant is taken, and saturated lime water is prepared;

[0033] S2. Alkali degumming

[0034] The silk gauze fabric is cut into multiple pieces of 20 cm x 20 cm size, weighed and recorded using an electronic balance, then folded 4 layers each and clamped in 2 pieces of 5 cm x 5 cm high-strength resin clamps, and fixed by applying a constant clamping force using a G clamp. The clamped fabric is immersed in alkaline water for alkali degumming at a bath ratio of 1:80, and each is treated at an environmental temperature of 60℃, 70℃, 80℃, 85℃, 90℃, 95℃, 100℃ for 15min, 30min, 45min, 60min, 75min, 90min, 120min, 150min, and repeatedly washed with distilled water until the washing solution is neutral in acidity and alkalinity. Finally, the degummed fabric is dried in a 95℃ oven for 2h, weighed and stored after equilibration overnight, and the degumming is completed after repeating the above operation 3 times. EMBODIMENT

[0035] The embodiment of the present application provides a silk gauze fabric alkali gel degumming method, comprising the following steps:

[0036] S1. Alkaline paste preparation

[0037] 5% urea and 20% wheat starch are weighed and dissolved in lime water of a fixed mass fraction, and then heated to near boiling for 5min with constant stirring to prepare an alkali steaming printing paste in a uniform, non-granular, translucent paste system for standby;

[0038] S2. Alkali degumming

[0039] Weigh and record the fabric and fix it on the printing table. Use a 150-mesh flat screen with a monofilament diameter of 106μm. Use the prepared alkaline printing paste to smear a large square pattern of 10cm×10cm on one side. Place the printed fabric with the alkali paste in a high-temperature steam oven and treat it at ambient temperatures of 60℃, 70℃, 80℃, 85℃, 90℃, 95℃, and 100℃ for 15min, 30min, 45min, 60min, 75min, 90min, 120min, and 150min, respectively. Then wash it with 55℃ warm water and then wash it repeatedly with cold running water until the paste is removed and the washing liquid is neutral. Finally, dry the fabric in a 95℃ oven for 2 hours, weigh it after equilibration overnight, and store it. Repeat the above operation 3 times to complete the degumming. Example

[0040] This invention provides a method for degumming silk fabrics using alkaline gel, comprising the following steps:

[0041] S1. Preparation of alkaline gel

[0042] Weigh 4g of food-grade sodium polyacrylate and add it in small, uniform amounts to 100mL of sodium hydroxide solution with a fixed mass fraction. During the addition process, use an electric stirrer to continuously and thoroughly stir the sodium polyacrylate until it is evenly mixed. Let it stand overnight to fully integrate and prepare an alkaline gel with a certain amount of alkali.

[0043] S2. Alkali gel degumming

[0044] The fabric was weighed, recorded, and fixed onto the printing plate. A 150-mesh flat screen with a monofilament diameter of 106μm was used for printing. A large square pattern of 10cm×10cm was printed on one side using the prepared alkaline gel. The gel-coated fabric was placed between two layers of cotton fabric and placed in a hot press. It was treated at ambient temperatures of 40℃, 50℃, 60℃, 70℃, 80℃, 85℃, 90℃, 95℃, 100℃, 110℃, 120℃, and 130℃ for 10s, 30s, 50s, 70s, 90s, 110s, 130s, and 150s respectively for degumming. After degumming, the fabric was repeatedly washed with cold running water until the sizing agent was removed and the washing water was neutral. The washed fabric was dried in a 95℃ oven for 2 hours, equilibrated overnight, weighed, and stored. This process was repeated 3 times to complete the degumming.

[0045] The effect of different hot-pressing temperatures on the degumming rate of silk yarn in Examples 1 to 3, such as Figure 1 And as shown in Table 1 below:

[0046] Table 1. Effect of hot pressing temperature on degumming rate of silk yarn

[0047] Hot-pressing temperature / °C Alkali boiling degumming rate / % Alkali steaming degumming rate / % Alkali gel degumming rate / % 40 \ \ 7.4±0.39 50 \ \ 11.88±0.68 60 20.28±0.24 2.82±2.11 16.56±0.26 70 24.54±0.11 3.01±1.17 23.65±0.39 80 27.12±0.35 6.21±1.46 23.96±0.64 85 31.47±0.16 10.61±2.62 23.98±0.32 90 34.01±0.38 12.88±1.31 22.5 ±0.26 95 38.35±0.52 18.79±1.05 22.13±0.45 100 42.14±0.85 25.15±0.26 21.77±0.53 110 \ \ 21.35±0.82 120 \ \ 21.25±0.88 130 \ \ 20.62±0.68

[0048] From Table 1, it can be seen that the degumming rate increases with the increase of temperature in both alkali boiling and alkali steaming degumming, while in the alkali gel degumming process, the degumming rate of silk gauze decreases when the hot-pressing temperature exceeds 90°C, which is quite different from the alkali boiling and alkali steaming degumming. In alkali steaming, the water molecules in the steam slowly release the alkali agent in the paste to act on the sericin, and the amount of steam is limited when the water does not reach the boiling point, so the degumming rate increases slowly and is always less than 20%. Under the condition of alkali steaming at 100°C, the degumming rate is maintained at about 25%. In alkali boiling degumming, the sericin on the surface of the silk can be better surrounded and degummed by the alkali aqueous solution, which makes the alkali boiling degumming rapid and effective. The degumming rate is about 27% under the condition of alkali boiling at 80°C, which is significantly higher than that of alkali steaming. In the alkali steaming degumming process, the water in the alkali gel evaporates slowly at low temperature, and the alkali agent acts on the fabric for continuous and stable degumming. With the continuous increase of temperature, the water in the gel evaporates rapidly, and when the gel is completely dehydrated and dried, the degumming of silk no longer occurs. Therefore, in the alkali gel degumming process, the temperature should be avoided to be too high to affect the evaporation of water in the gel.

[0049] The influence of different hot-pressing treatment times of Examples 1 to 3 on the degumming rate of silk gauze is shown in Table 2 as follows: Figure 2

[0050] Table 2 Influence of hot-pressing time on the degumming rate of silk gauze

[0051] Hot-pressing time Alkali water degumming rate / % Alkali paste degumming rate / % Alkali gel degumming rate / % 10s \ \ 14.79±0.82 30s \ \ 22.81±0.26 50s \ \ 26.88±0.26 70s \ \ 25.52±0.39 90s \ \ 22.92±0.39 110s \ \ 21.46±0.15 130s \ \ 21.15±0.97 150s \ \ 21.25±0.51 15 min 25.34±0.56 16.54±2.60 \ 30 min 27.12±0.35 20.00±0.94 \ 45 min 31.24±0.81 21.43±0.51 \ 60 min 35.14±0.62 22.53±1.20 \ 75 min 39.32±1.17 23.72±0.89 \ 90 min 43.16±0.62 24.41±0.52 \ 120 min 52.37±0.54 25.27±0.54 \ 150 min 60.31±0.78 25.54±1.31 \

[0052] From Table 2, it can be seen that the alkali gel degumming rate gradually increases from 14.79% at 10s of hot-pressing to 26.88% at 50s of hot-pressing, and then continuously decreases to about 21% with the increase of hot-pressing time. This trend of first increasing to a certain highest point and then decreasing is quite different from the alkali boiling and alkali steaming degumming. In the alkali boiling degumming process, the degumming rate reaches 25.34% at 15min of alkali boiling, and reaches 27.12% at 30min of alkali boiling, which is already completely degummed. When the time continues to increase to 2 hours, the fabric weight decreases by more than 50%, and the silk fibroin is damaged. In the alkali steaming degumming process, the degumming rate is about 25% at 2 hours of alkali steaming, although it shows a slow growth trend with the increase of time, but there is no case of degumming rate decrease, which is due to the change of water in the degumming process.

[0053] ​The alkali gel provides the required alkali, water and heat for the degumming of silk in the local printing process. When the degumming starts, the three conditions are met at the same time, the sericin starts to swell and separate from the fibroin, at this time the heating is stopped, the sericin is easily washed away by the clean water, showing a continuous increase in the degumming rate. However, as time increases, the water in the alkali gel gradually decreases, the swelled sericin starts to dry and shrink, and re-adhere to the fibroin, which makes the degumming rate show a decreasing trend. As shown in Figure 3 , Figure 3 The amount of sodium hydroxide is 8g / L -1 , the hot-pressing temperature is 80℃, and the surface morphology and fiber morphology of the silk gauze fabric under different degumming time conditions. As can be seen from Figure 3 (a), when the hot-pressing degumming time is 10s, part of the silk surface is degummed, but the silk gauze yarn basically maintains the fiber bundle state; when the hot-pressing degumming time is 50s, the yarn fiber bundle is fluffy, and the silk surface is completely degummed, as shown in Figure 3 (b); but as the degumming time continues to increase, the alkali gel dries, and the separated sericin also re-adheres to the silk surface, as shown in Figure 3 (c), which makes the degumming rate of silk gauze decrease with time. Therefore, during the alkali gel degumming process, the degumming and cleaning should be carried out before the gel is completely dried, so as to prevent the sericin from re-adhering.

[0054] In order to further observe the differences in the degumming effect of silk gauze surface under different alkali degumming processes and whether it has an impact on the fiber structure, SEM scanning electron microscope and infrared spectrometer are used for comparative analysis.

[0055] Experiment one: comparison of surface morphology of silk gauze after different alkali degumming

[0056] The surface morphology and structure of silk gauze under different process conditions are further observed by SEM scanning electron microscope. As shown in Figure 4 , Figure 4 (a) is the silk gauze without degumming, it can be seen that the surface of the original silk fiber is rough, the sericin tightly adheres to the multiple fibroin, and there is a large gap between the warp and weft yarns of silk gauze; Figure 4 (b) is the surface morphology of silk gauze under the condition of high-temperature alkali cooking treatment (saturated lime water, bath ratio 1:80, temperature 80℃, time 30min, complete degumming condition); Figure 4 (c) is the surface morphology of silk gauze under the condition of lime alkali paste-steam synergistic treatment (saturated lime water alkali paste, steam temperature 100℃, steam time 120min). Figure 4 (d) is the surface morphology of silk gauze under the condition of alkali gel degumming treatment (the amount of sodium hydroxide is 8g / L -1The surface morphology of silk gauze under the condition of hot-pressing temperature 80℃ and hot-pressing time 50s) can be seen that under the three degumming ways, the surface morphology of silk gauze has no obvious difference, and the silk fibers all achieve good degumming, the fibrillar structure of silk fibroin presents fine longitudinal stripes, the fiber surface is smooth and no sericin is attached, and the fabric structure is fluffy.

[0057] Experiment two: infrared comparison of silk gauze after degumming by different alkali agents

[0058] The differences in light transmittance and absorption peaks of silk gauze under different degumming processes are mainly due to the influence of the degumming process on the molecular structure of silk. Silk-I crystal structure is a metastable structure formed by the accumulation of silk fibroin segments with α-type molecular conformation. Silk-I (α-helix) can be converted to Silk-II (β-fold) after treatment such as wet heat and stress. The degumming rates obtained by the three degumming methods under different process conditions are slightly different, as shown in Table 1. Figure 5 Figure 5 Among them, (a) is not degummed, (b) is degummed by alkali boiling, (c) is degummed by alkali steaming, and (d) is degummed by alkali gelatinization. As can be seen from Figure 2, Figure 5 Compared with the non-degummed sample (a), the three samples all have an absorption peak at 3275 cm -1 , which corresponds to the stretching vibration of N—H bond, and all have absorption peaks of amide I, II and III stretching vibration in β-fold structure at 1615, 1509 and 1221 cm -1 , respectively. Compared with the four samples, there is no obvious shift in the absorption peaks, and no new peaks appear or decrease, which indicates that the three degumming processes have no obvious effect on the main chemical structure of silk gauze fabric, and no new molecular structure or new functional group is produced. Compared with the non-degummed sample (a), the stretching vibration absorption peak intensity of the samples by the three degumming methods at 1615 cm -1 (amide I region), 1509 cm -1 (amide II region) and 1221 cm -1 (amide III region) increases with the increase of degumming rate. This is because in silk, sericin is mainly amorphous structure, while silk fibroin has both amorphous structure and β-fold structure. With the increase of degumming rate, the amorphous Silk-I (α-helix) structure is reduced with the removal of sericin because of its water solubility and instability, while the proportion of Silk-II (β-fold) increases because of its stability and water insolubility.

[0059] Alkali degumming of silk gauze fabric was carried out by alkali boiling, alkali steaming and alkali gelatinization, respectively, and the degumming mechanism, surface morphology and infrared of the degummed silk gauze were compared, and the following conclusions were drawn:

[0060] ​The alkali degumming process of silk gauze fabric cannot be separated from the combined action of alkali, water and heat. The strong alkali effect of sodium hydroxide is used to neutralize the carboxyl group on the polyacrylic acid sodium molecule, and the carboxylate negative ion is produced by ionization, so that the viscosity increases sharply to form alkali gel. In the local degumming microsystem, alkali gel meets the conditions of alkali, water and heat required for fine degumming of silk gauze, combines the dual effects of alkali boiling and alkali steaming, and can achieve rapid degumming at a hot-pressing temperature of 80 °C and a hot-pressing time of 50 s. The effects of alkali boiling, alkali steaming and alkali gel degumming processes on the degumming effect of silk gauze under the conditions of hot-pressing temperature and hot-pressing time were compared, and the surface morphology and infrared of silk gauze after degumming by the three processes were compared. The results show that under the three degumming methods, the surface morphology of silk gauze has no obvious difference, the surface of silk fiber is smooth without silk gum adhesion, and the main chemical structure has no obvious influence. The fine degumming of silk gauze by alkali gel process has important significance for expanding the artistic expression and application of traditional alkali printing process in modern silk degumming and printing.

[0061] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for alkaline gel degumming of silk fabrics, characterized in that: Includes the following steps: S1. Preparation of alkaline gel Weigh 4g of food-grade sodium polyacrylate and add it in small, uniform amounts to 100mL of sodium hydroxide solution with a fixed mass fraction. During the addition process, use an electric stirrer to continuously and thoroughly stir the sodium polyacrylate until it is evenly mixed. Let it stand overnight to fully integrate and prepare an alkaline gel with a certain amount of alkali. S2. Alkali gel degumming Weigh and record the fabric weight, then fix it onto the printing plate. Use a 150-mesh flat screen with a monofilament diameter of 106μm. Use the prepared alkaline gel to squeegee a large square pattern of 10cm×10cm on one side. Place the gel-coated fabric between two layers of cotton fabric and put it in a hot press. Degumme it at a temperature of 40-130℃ for 10-150 seconds. After degumming, wash the fabric repeatedly with cold running water until the sizing is removed and the washing water is neutral. Dry the washed fabric in a 95℃ oven for 2 hours, equilibrate overnight, weigh and store it. Repeat this process 3 times to complete the degumming.

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