Graft-modified starch, process for its preparation and low-temperature sizing applications

Abstract

The application provides a grafted modified starch, a preparation method thereof and a low-temperature sizing application. The acid hydrolysis starch is used as a raw material, the acid hydrolysis starch has a lower molecular weight, a relatively less hydrogen bond structure in the molecule, a relatively increased porosity of the system, and small molecules are more easily entered into the interior of the starch; the acid hydrolysis starch is modified by using acrylic acid and vinyl acetate, so that the grafted starch has more carboxyl and hydroxyl groups on the molecular structure, the hydrophilicity of the modified starch can be further increased, the starch can be low-temperature gelatinized, the purpose of low-temperature sizing is achieved; then the carboxyl-hydroxyl starch is esterified, and ester groups are introduced, so as to adjust the hydrophilicity and hydrophobicity of the modified starch, the introduction of the hydrophobic groups can reduce the viscosity of the sizing material and improve the fluidity of the sizing material, meanwhile, the introduction of the specific ester groups can also increase the affinity of the gelatinized sizing material to fibers, improve the applicability to various textile fabrics, and solve the problems that the adhesion of the original starch sizing material to the yarn is not strong, and the sizing film is hard and brittle.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of textile sizing materials, and particularly relates to a grafted modified starch, a preparation method thereof and low-temperature sizing application. BACKGROUND

[0002] There are a large number of exposed hairs on the surface of the original yarn, which will rub against the machine during weaving, causing irregular entanglement between warp yarns, poor orientation, weakened cohesion between yarns, poor wear resistance of the woven yarn, and easy occurrence of broken yarn phenomenon, which seriously reduces the weaving efficiency. The warp yarns are treated by using the penetration, coagulation and deposition film-forming properties of the polymer sizing material to form a network porous cross-linked system inside the warp yarns, and a protective film is deposited on the surface of the warp yarns. The protective film can bind a large number of exposed hairs on the surface of the original yarn to the surface of the original yarn, reduce the cohesion reduction effect caused by the irregularity of the hairs, improve the orientation of the original yarn, and the developed network porous cross-linked system inside the warp yarns enhances the interaction between the original yarns and improves the strength of the yarns. The warp sizing method can increase the wear resistance of the yarns and reduce the broken yarn phenomenon, thereby being beneficial to improving the weaving efficiency.

[0003] The traditional high-temperature warp sizing process is to use the polymer sizing material to cause a certain degree of damage to its own structure at high temperature, reduce the crystallinity, increase the chain segment mobility, and swell the system, thereby improving the solubility to complete the high-temperature sizing process of the sizing material and the high-temperature sizing of the sizing solution. The traditional high-temperature sizing method has many drawbacks, such as dependence on high temperature, instability of the system, limitations of application, complexity of application, and economy of energy, and some other problems, which restrict the development of the textile field.

[0004] Low-temperature sizing can make up for the drawbacks of the traditional sizing process, but the low-temperature sizing process also faces some key problems. How to make the polymer sizing material into sizing at low temperature and then deposit on the surface of the yarn is a bottleneck problem restricting the low-temperature sizing process. Common starch sizing material is difficult to size because its molecular chains are arranged in parallel, the orientation is high, the order is increased, the molecular motion is weakened, it is difficult to flow, it is difficult to size into liquid, and it is extremely difficult to size. At the same time, due to the high molecular weight, multiple hydroxyl groups and planarity of the glucose ring of the starch itself, hydrogen bonds are easily formed between the starch molecular chains, association occurs, the bonding force is strong, water molecules are not easy to enter the starch molecules, swelling is difficult, and sizing is difficult. Even if the sizing is successful, the adhesion of the sizing film formed to the fiber is not strong, the sizing film is hard and brittle, and it cannot meet the actual demand. Therefore, if low-temperature sizing is to be realized, the conditions of low molecular weight, multiple hydrophilic groups, good chain segment linearity, good permeability, good affinity with fibers and the like need to be met.

[0005] At present, there are literatures reported that acetic acid ester starch is grafted with PVA to improve the sizing effect of the sizing material, although the sizing effect is obviously improved, but it still has the following problems: the molecular weight of acetic acid ester starch is larger, and a higher temperature is needed than ordinary starch for sizing; the grafted modified PVA with high molecular weight forms a complex system with larger molecular weight, and after sizing, the viscosity of the sizing film is large, the penetration and diffusion of the sizing material on the warp yarn are reduced, it is difficult to form a stable network porous system in the yarn, the strength of the yarn is reduced, and the desizing is difficult, which affects the subsequent process. Therefore, it is necessary to provide a new sizing material suitable for low-temperature sizing and having strong affinity with the warp yarn, which is beneficial to improve the strength and wear resistance of the yarn. SUMMARY

[0006] In view of the problems that the existing sizing material cannot realize low-temperature sizing, and the sizing will affect the strength of the yarn and the subsequent desizing process, the application provides a grafted modified starch, a preparation method thereof and low-temperature sizing application.

[0007] To solve the above technical problems, the technical scheme provided by the application is:

[0008] A preparation method of a grafted modified starch, comprising the following steps:

[0009] Step a, adding acid hydrolysis starch into water, uniformly dispersing, heating and gelatinizing to obtain acid hydrolysis starch slurry;

[0010] Step b, adding acrylic acid, vinyl acetate and initiator into the acid hydrolysis starch slurry, reacting for a first preset time, adding catalyst, reacting for a second preset time, cooling, neutralizing, solid-liquid separation, washing, drying to obtain carboxyl-hydroxyl starch;

[0011] Step c, adding the carboxyl-hydroxyl starch into water, heating and dissolving, then adding lactic acid, heating and reacting for a third preset time, solid-liquid separation, washing, drying to obtain grafted modified starch.

[0012] Compared with the prior art, the acid hydrolyzed starch is used as a modified raw material, the acid hydrolyzed starch has a lower molecular weight, a relatively less hydrogen bond structure in the molecule, and a relatively increased porosity of the system, and small molecules are more easily entered into the interior of the starch; on this basis, the acid hydrolyzed starch is modified by using acrylic acid and vinyl acetate, so that the starch molecule structure after grafting has more carboxyl and hydroxyl groups, the hydrophilicity of the modified starch can be further increased, the starch can be gelatinized at a low temperature, and the purpose of low-temperature sizing is achieved; however, the introduction of the carboxyl and hydroxyl hydrophilic groups increases the viscosity of the sizing after the modified starch is gelatinized, and the sizing fluidity is poor, therefore, the carboxyl-hydroxyl starch is further esterified in the application, an ester group is introduced, the hydrophilicity and hydrophobicity of the modified starch are adjusted, the introduction of the hydrophobic group can reduce the viscosity of the sizing and improve the sizing fluidity, meanwhile, the introduction of the specific ester group can also increase the affinity of the gelatinized sizing to fibers, improve the applicability to various textiles, and solve the problems of the original starch sizing, such as poor adhesion to yarns and hard and brittle sizing film.

[0013] The grafted modified starch has a higher solubility, can realize low-temperature sizing, and has certain spatial volume of the carboxyl, hydroxyl and ester groups on the grafted modified starch; meanwhile, the long-chain structure introduced by the polymerization of the acrylic acid, the vinyl acetate and the lactic acid significantly increases the contact area of the grafted modified starch and the yarn, so that the grafted modified starch is more easily interacted with the yarn and has higher affinity to the yarn; the introduced hydrophilic and hydrophobic groups not only can improve the water binding capacity of the sizing after gelatinization and enhance the stability of the sizing, but also can appropriately reduce the viscosity of the sizing and increase the fluidity of the sizing, so that the sizing can be uniformly deposited on the surface of the yarn to form a stable and uniform protective film, and the problems of the original starch sizing, such as poor adhesion to yarns and hard and brittle sizing film, are solved; and the grafted modified starch is more easily penetrated into the interior of the yarn to form a crosslinked three-dimensional network structure in the interior of the yarn, so that the binding force between the yarns is improved, the strength and wear resistance of the yarn are increased, the yarn breakage phenomenon is reduced, the weaving efficiency is improved, and the grafted modified starch has a higher popularization and application value.

[0014] Further, in step a, the preparation method of the acid hydrolyzed starch comprises the following steps:

[0015] S1, starch is added into an alcohol water solution to obtain a starch emulsion;

[0016] S2, the starch emulsion is heated to 60-70 DEG C and stirred for 1-2 hours, then solid-liquid separation, washing and drying are performed to obtain refined starch;

[0017] S3, the refined starch is added into water and uniformly dispersed to obtain a refined starch dispersion; an acid solution is added into the refined starch dispersion, and acid hydrolysis is performed by heating to 60-70 DEG C, then neutralization, solid-liquid separation, washing and drying are performed to obtain acid hydrolyzed starch.

[0018] The force between adjacent molecular chains of the acidolysed starch is weakened, the multidirectional crosslinking system generated by the secondary bond is partially destroyed, more groups are exposed, grafting modification is easier, grafting rate is improved, and modification effect is improved; and the molecular weight of the acidolysed starch is lower than that of the original starch, and the intramolecular hydrogen bond structure is relatively less, so that the water solubility is higher, and low-temperature sizing is easier to achieve. However, the molecular weight of the acidolysed starch is relatively low, which affects the paste-forming property and adhesion of the starch, therefore, the acidolysed starch is grafted with acrylic acid, vinyl acetate and lactic acid in the application, so as to make up for the problem of low molecular weight of the acidolysed starch, and the affinity between the grafted modified starch and the yarn is further improved by introducing carboxyl, hydroxyl, ester and long-chain hydrophobic structure, the fluidity and adhesion of the paste sizing are improved, so that the strength and wear resistance of the yarn are improved, and the subsequent desizing process is not affected.

[0019] In combination with the above, preferably, in S1, the mass concentration of the starch emulsion is 37% to 47%.

[0020] In combination with the above, preferably, in S1, the alcohol aqueous solution is a mixed solution of methanol and distilled water with a volume ratio of 3:1 to 5:1.

[0021] In combination with the above, preferably, in S3, the mass concentration of the refined starch dispersion liquid is 33% to 45%.

[0022] The preferred starch refining process can effectively remove keratin and other impurities in the starch, improve the quality of the starch, and reduce the subsequent phenomena of sizing aggregation, sizing foaming and the like.

[0023] Specifically, the starch in the application can be conventional starch in the art, such as corn starch, wheat starch and the like.

[0024] In combination with the above, preferably, in S3, the acid solution is a hydrochloric acid solution with a mass concentration of 1.5 mol / L to 2.5 mol / L, and the volume-mass ratio of the acid solution to the refined starch is 1L:10kg to 1L:12kg.

[0025] In combination with the above, preferably, in S3, the acidolysis time is 3.5h to 4.5h.

[0026] Due to a large number of hydroxyl groups in the molecular chain of the original starch, secondary bonds (hydrogen bonds) are easily formed between adjacent molecules, the molecular chain bonding is significant, a multidirectional crosslinking system is easily formed, and the reactive groups in the molecular chain are easily wrapped and cannot be exposed, resulting in a low grafting rate. The preferred acidolysis condition in the application can partially destroy the multidirectional crosslinking system generated by the secondary bond bonding in the starch, so that the reactive groups in the starch are fully exposed, and the grafting rate is improved.

[0027] Preferably, in step a, the mass concentration of the acid hydrolysis starch slurry is 40% to 50%.

[0028] Preferably, in step a, the temperature of the temperature-raising gelatinization is 85°C to 95°C, and the gelatinization time is 0.5h to 1.5h.

[0029] Preferably, in step b, the mass ratio of the acid hydrolysis starch, acrylic acid, vinyl acetate and initiator is 1.5 to 2.0:0.4 to 0.6:0.5 to 1.0:0.01 to 0.03.

[0030] Preferably, in step b, the initiator is dimethyl 2,2'-azobis(2-methylpropionate).

[0031] Preferably, in step b, the catalyst is a cerium ammonium nitrate solution with a concentration of 1.5mol / L to 3.0mol / L, and the volume-mass ratio of the catalyst to the acid hydrolysis starch is 1L:10kg to 1L:12kg.

[0032] Preferably, in step b, the temperature of the reaction is 60°C to 70°C.

[0033] Preferably, in step b, the first preset time is 0.5h to 1h.

[0034] Preferably, in step b, the second preset time is 2h to 3h.

[0035] Preferably, the reaction conditions are conducive to the full reaction of the acrylic acid, the vinyl acetate and the acid hydrolysis starch, and the improvement of the grafting rate of the acrylic acid and the vinyl acetate.

[0036] Preferably, in step c, the temperature of the temperature-raising dissolution is 90°C to 95°C.

[0037] Preferably, in step c, the mass concentration of the dispersion liquid obtained after the carboxy-hydroxylated starch is added with water is 40% to 50%.

[0038] Preferably, in step c, the lactic acid is added in 4 to 6 batches, each batch is added with an interval of 30min to 40min, and the last batch of lactic acid is added with an interval of 60min to 70min.

[0039] Preferably, in step c, the mass-volume ratio of the carboxy-hydroxylated starch to the lactic acid is 1.8kg:0.76L to 1.8kg:0.42L.

[0040] Preferably, in step c, the temperature-raising reaction time is 85°C to 95°C.

[0041] The application also provides a grafted modified starch prepared by any one of the above preparation methods.

[0042] Compared with the prior art, the grafted modified starch provided by the application has the following beneficial effects:

[0043] (1) The acid hydrolyzed starch is used as the raw material of the grafted modified starch, so that the interaction force in the modified starch molecule can be reduced, the solubility of the modified starch is improved, and low-temperature sizing is facilitated; meanwhile, a large number of hydroxyl groups and carboxyl groups are introduced into the acid hydrolyzed starch molecule, the number of hydrophilic groups of the modified starch is increased, and the low-temperature swelling effect is enhanced.

[0044] (2) The large number of hydroxyl groups, carboxyl groups and ester groups introduced into the acid hydrolyzed starch molecule can destroy the hydrogen bond interaction in the starch molecule, reduce the orientation degree and regularity of the molecular chain, make the modified starch molecular chain in a random loose state, and make water molecules more easily enter the inside of the modified starch molecule, so that the swelling of the modified starch at low temperature is facilitated.

[0045] (3) The cross arrangement of the hydroxyl groups, carboxyl groups and ester groups introduced into the acid hydrolyzed starch molecule produces a steric hindrance effect, increases the volume of the molecular chain, reduces the interaction force between the molecules, and improves the movement possibility of the molecular chain, so that the flowability of the sizing agent is improved, and a strong and tough film can be formed on the surface of the yarn; and the introduced carboxyl groups, hydroxyl groups and ester groups have high affinity for fibers, penetrate into the inside of the fibers after sizing, and form a reticular porous system in the inside of the fibers by crosslinking, so that the interaction force between the fibers is enhanced, the fiber strength and wear resistance are enhanced, and the yarn breakage phenomenon is reduced.

[0046] The application further provides application of the grafted modified starch in sizing of textile warp yarns, and the sizing temperature is 60-70 DEG C.

[0047] The grafted modified starch provided by the application is suitable for sizing of cotton and polyester-cotton blended yarns, and is also suitable for sizing of other yarns, and can effectively improve the sizing problem of some yarns such as hemp, soybean protein fiber and bamboo pulp fiber which are not resistant to heat and humidity and are difficult to size at low temperature.

[0048] The application further provides a textile warp yarn sizing agent, which comprises the grafted modified starch.

[0049] The application further provides a warp yarn sizing method, which at least comprises the following steps:

[0050] The textile warp yarn sizing agent is added into water, heated to 60-70 DEG C, and stirred and gelatinized to obtain a sizing agent;

[0051] The sizing agent is used for sizing treatment of the warp yarn.

[0052] Preferably, the mass concentration of the sizing agent is 40-50%.

[0053] Preferably, the sizing speed of the sizing treatment is 18-22 m / min, and the tension of the warp yarn is 1.5-1.7 N.

[0054] The grafted modified starch provided by the application can meet the demand for low-temperature (60-70 DEG C) sizing, and the sizing liquid formed is uniform, has good fluidity and permeability, and is beneficial to the smooth progress of the sizing process, and has good affinity and adhesion to fibers, can form a uniform and stable sizing film on the surface of the yarn, and form a three-dimensional network crosslinked structure in the interior of the fiber, so that the mechanical properties of the sized yarn obtained after sizing are significantly improved; in addition, the warp yarn obtained after sizing is beneficial to desizing before subsequent printing and dyeing, and can effectively improve the weaving efficiency; furthermore, low-temperature sizing can also reduce the temperature of the sizing workshop, create a relatively comfortable working environment, and meet the current development requirements of energy saving and consumption reduction, and has high popularization and application value. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the application more clear, the application will be further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0056] Example 1

[0057] The embodiment of the application provides a preparation method of grafted modified starch, comprising the following steps:

[0058] In step a, 80 kg of wheat starch is poured into a sizing tank, 130 L of a methanol water (V1 / V2=80 / 20) solution is added, and the mixture is uniformly mixed to obtain a starch emulsion; the temperature of the sizing tank is increased to 60 DEG C, and stirring is performed for 2 h, then the solution is discharged, the solid is washed with a methanol water (V1 / V2=80 / 20) solution for 3 times, and the solid is dried at 50 DEG C, crushed, ground, and sieved to obtain refined starch.

[0059] In step b, 40 kg of the refined starch is poured into a sizing tank, 65 L of water is added, and the mixture is uniformly mixed to obtain a refined starch dispersion; the temperature is increased to 60 DEG C, 3.7 L of a 2 mol / L dilute hydrochloric acid solution is added to the refined starch dispersion, stirring is performed for 4.5 h, then a 1 mol / L sodium carbonate solution is added to adjust the pH to 7.0, the mixture is left to stand for 1 h, the solution is discharged, the obtained solid is washed with an ethanol water (V1 / V2=85 / 15) solution for 5 times, the solid is dried at 50 DEG C, crushed, ground, and sieved to obtain acid hydrolyzed starch.

[0060] Step c, put the above acid hydrolysis starch 20 kg into a reaction kettle, add 30 L of water, adjust the temperature of the reaction kettle to 90℃, high-temperature stirring gelatinization for 60 min, then cool the reaction kettle to 70℃, add 5 kg of acrylic acid, 6.25 kg of vinyl acetate and 0.125 kg of dimethyl azobis isobutyrate, and keep the reaction for 30 min, then add 2 L of 2 mol / L cerium nitrate solution, continue to keep the reaction for 2 h, cool down, add sodium hydroxide solution to adjust the pH to 6.5, stand for 1 h, discharge the solution, wash the obtained solid with water for 3 times, dry at 50℃, crush, grind, sieve, and obtain carboxyl-hydroxyl starch;

[0061] Step d, put the above carboxyl-hydroxyl starch 20 kg into a reaction kettle, add 30 L of water, adjust the temperature of the reaction kettle to 95℃, stir for 20 min, add 6.1 L of lactic acid in 4 times with an interval of 40 min, keep the reaction for 1 h after adding, cool down, add 40 L of acetone to the reaction kettle, stir for 20 min, stand for 1 h, discharge the solution, wash the obtained solid with water for 3 times, dry at 50℃, crush, grind, sieve, and obtain graft-modified starch.

[0062] Example 2

[0063] The embodiment of the present application provides a preparation method of graft-modified starch, which comprises the following steps:

[0064] Step a, pour 80 kg of wheat starch into a mixing tank, add 160 L of methanol water (V1 / V2=75 / 25) solution, mix uniformly, and obtain starch emulsion; increase the temperature of the mixing tank to 65℃, stir for 1.5 h, stand, discharge the solution, rinse the solid with methanol water (V1 / V2=80 / 20) solution for 3 times, dry at 50℃, crush, grind, sieve, and obtain refined starch;

[0065] Step b, pour the above refined starch 40 kg into a mixing tank, add 75 L of water, mix uniformly, and obtain refined starch dispersion; increase the temperature to 65℃, add 4.0 L of 1.5 mol / L dilute hydrochloric acid solution to the refined starch dispersion, stir for 4 h, then add 1 mol / L sodium carbonate solution to adjust the pH to 6.8, stand for 1 h, discharge the solution, wash the obtained solid with ethanol water (V1 / V2=85 / 15) solution for 5 times, dry at 50℃, crush, grind, sieve, and obtain acid hydrolysis starch;

[0066] Step c, put the above acid hydrolysis starch 20 kg into a reaction kettle, add 25 L of water, adjust the temperature of the reaction kettle to 85℃, high-temperature stirring gelatinization for 90 min, then cool the reaction kettle to 65℃, add 4.2 kg of acrylic acid, 5.2 kg of vinyl acetate and 0.11 kg of dimethyl azobis isobutyrate, and keep the reaction for 45 min, then add 1.7 L of 3 mol / L cerium nitrate solution, continue to keep the reaction for 2.5 h, cool down, add sodium hydroxide solution to adjust the pH to 6.8, stand for 1 h, discharge the solution, wash the obtained solid with water for 3 times, dry at 50℃, crush, grind, sieve, and obtain carboxyl-hydroxyl starch;

[0067] Step d, put the above carboxyl-hydroxyl starch 20 kg into a reaction kettle, add 25 L of water, adjust the temperature of the reaction kettle to 93℃, stir for 30 min, add 8.5 L of lactic acid in 6 times with an interval of 30 min, after adding, keep the reaction for 1 h, cool down, add 40 L of acetone into the reaction kettle, stir for 20 min, stand for 1 h, discharge the solution, wash the obtained solid with water for 3 times, dry at 50℃, crush, grind, sieve, and obtain graft-modified starch.

[0068] Example 3

[0069] The embodiment of the present application provides a preparation method of graft-modified starch, which comprises the following steps:

[0070] Step a, pour 80 kg of wheat starch into a mixing tank, add 110 L of methanol water (V1 / V2=82 / 18) solution, mix uniformly, and obtain starch emulsion; increase the temperature of the mixing tank to 70℃, stir for 1 h, stand, discharge the solution, rinse the solid with methanol water (V1 / V2=80 / 20) solution for 3 times, dry at 50℃, crush, grind, sieve, and obtain refined starch;

[0071] Step b, pour the above refined starch 40 kg into a mixing tank, add 52 L of water, mix uniformly, and obtain refined starch dispersion; increase the temperature to 70℃, add 3.4 L of 2.5 mol / L dilute hydrochloric acid solution into the refined starch dispersion, stir for 3.5 h, then add 1 mol / L sodium carbonate solution to adjust the pH to 6.7, stand for 1 h, discharge the solution, wash the obtained solid with ethanol water (V1 / V2=85 / 15) solution for 5 times, dry at 50℃, crush, grind, sieve, and obtain acid hydrolysis starch;

[0072] Step c, the above acid hydrolysis starch 20 kg is placed in a reaction kettle, 20 L of water is added, the temperature of the reaction kettle is adjusted to 95℃, high temperature stirring gelatinization is carried out for 30 min, then the reaction kettle is cooled to 60℃, 7 kg of acrylic acid, 12 kg of vinyl acetate and 0.36 kg of dimethyl azobisisobutyrate are added, and the reaction is kept for 60 min, then 1.8 L of 1.5 mol / L cerium nitrate solution is added, and the reaction is kept for 3 h, the temperature is lowered, sodium hydroxide solution is added to adjust the pH to 6.7, and the solution is discharged after standing for 1 h, the obtained solid is washed with water for 3 times, dried at 50℃, crushed, ground, and sieved to obtain carboxyl-hydroxyl starch;

[0073] Step d, the above carboxyl-hydroxyl starch 20 kg is placed in a reaction kettle, 20 L of water is added, the temperature of the reaction kettle is adjusted to 90℃, stirring is carried out for 20 min, 5 L of lactic acid is added in 5 times with an interval of 30 min, and the reaction is kept for 1 h after the addition is completed, the temperature is lowered, 40 L of acetone is added to the reaction kettle, stirring is carried out for 20 min, and the solution is discharged after standing for 1 h, the obtained solid is washed with water for 3 times, dried at 50℃, crushed, ground, and sieved to obtain grafted modified starch.

[0074] Comparative example 1

[0075] The present comparative example provides a preparation method of grafted modified starch, which is different from example 1 only in that wheat raw starch is used instead of acid hydrolysis starch for graft modification, and the wheat raw starch manufacturer is Suzhou Lanli Chemical Technology Co., Ltd., and the specific steps are as follows:

[0076] Step a, the above raw starch 20 kg is placed in a reaction kettle, 30 L of water is added, the temperature of the reaction kettle is adjusted to 90℃, high temperature stirring gelatinization is carried out for 60 min, then the reaction kettle is cooled to 70℃, 5 kg of acrylic acid, 6.25 kg of vinyl acetate and 0.125 kg of dimethyl azobisisobutyrate are added, and the reaction is kept for 30 min, then 2 L of 2 mol / L cerium nitrate solution is added, and the reaction is kept for 2 h, the temperature is lowered, sodium hydroxide solution is added to adjust the pH to 6.5, and the solution is discharged after standing for 1 h, the obtained solid is washed with water for 3 times, dried at 50℃, crushed, ground, and sieved to obtain carboxyl-hydroxyl starch;

[0077] Step b, the above carboxyl-hydroxyl starch 20 kg is placed in a reaction kettle, 30 L of water is added, the temperature of the reaction kettle is adjusted to 95℃, stirring is carried out for 20 min, 6.1 L of lactic acid is added in 4 times with an interval of 40 min, and the reaction is kept for 1 h after the addition is completed, the temperature is lowered, 40 L of acetone is added to the reaction kettle, stirring is carried out for 20 min, and the solution is discharged after standing for 1 h, the obtained solid is washed with water for 3 times, dried at 50℃, crushed, ground, and sieved to obtain grafted modified starch.

[0078] Comparative example 2

[0079] The comparative example provides a preparation method of graft-modified starch, which is different from example 1 only in that esterified starch is used instead of acid hydrolyzed starch for graft modification, and the production factory of the esterified starch is Foshan Guonong Starch Co., Ltd. The specific steps are as follows:

[0080] In step a, 20 kg of the above esterified starch is placed in a reaction kettle, 30 L of water is added, the temperature of the reaction kettle is adjusted to 90°C, high-temperature stirring gelatinization is carried out for 60 min, then the reaction kettle is cooled to 70°C, 5 kg of acrylic acid, 6.25 kg of vinyl acetate and 0.125 kg of dimethyl azobisisobutyrate are added, the reaction is kept for 30 min, 2 L of 2 mol / L cerium nitrate solution is then added, the reaction is kept for 2 h, the temperature is lowered, sodium hydroxide solution is added to adjust the pH to 6.5, it is left to stand for 1 h, the solution is discharged, the obtained solid is washed with water for 3 times, dried at 50°C, crushed, ground, sieved, and carboxyl-hydroxyl starch is obtained;

[0081] In step b, 20 kg of the above carboxyl-hydroxyl starch is placed in a reaction kettle, 30 L of water is added, the temperature of the reaction kettle is adjusted to 95°C, stirring is carried out for 20 min, 6.1 L of lactic acid is added in 4 times with an interval of 40 min, after the addition is completed, the reaction is kept for 1 h, the temperature is lowered, 40 L of acetone is added to the reaction kettle, stirring is carried out for 20 min, it is left to stand for 1 h, the solution is discharged, the obtained solid is washed with water for 3 times, dried at 50°C, crushed, ground, sieved, and graft-modified starch is obtained.

[0082] Comparative example 3

[0083] The comparative example provides a preparation method of graft-modified starch, which is different from example 1 only in that esterified starch is used instead of acid hydrolyzed starch for graft modification, and the production factory of the esterified starch is Foshan Guonong Starch Co., Ltd. The specific steps are as follows:

[0084] In step a, 20 kg of the above esterified starch is placed in a reaction kettle, 30 L of water is added, the temperature of the reaction kettle is adjusted to 90°C, high-temperature stirring gelatinization is carried out for 60 min, then the reaction kettle is cooled to 70°C, 5 kg of acrylic acid, 6.25 kg of vinyl acetate and 0.125 kg of dimethyl azobisisobutyrate are added, the reaction is kept for 30 min, 2 L of 2 mol / L cerium nitrate solution is then added, the reaction is kept for 2 h, the temperature is lowered, sodium hydroxide solution is added to adjust the pH to 6.5, it is left to stand for 1 h, the solution is discharged, the obtained solid is washed with water for 3 times, dried at 50°C, crushed, ground, sieved, and carboxyl-hydroxyl starch is obtained;

[0085] Step b, the carboxyl-hydroxyl starch 20 kg was placed in a reaction kettle, 30 L water was added, the temperature of the reaction kettle was adjusted to 95℃, stirred for 20 min, 6.1 L lactic acid was added in 4 times with 40 min interval, after the addition was completed, the reaction was kept for 1 h, the temperature was lowered, 40 L acetone was added into the reaction kettle, stirred for 20 min, stood for 1 h, the solution was discharged, the obtained solid was washed with water for 3 times, dried at 50℃, crushed, ground, and sieved to obtain the grafted modified starch.

[0086] Grafting rate test

[0087] The acid hydrolyzed starch to be reacted and the grafted modified starch product finally prepared were dried to constant weight, and their masses were respectively weighed by an electronic balance, and were recorded as m1 and m2. The grafting rates of each example and the comparative example were respectively calculated according to the following formula.

[0088] Grafting rate

[0089] In the formula, m1 is the mass of the acid hydrolyzed starch to be reacted, kg;

[0090] m2 is the mass of the grafted modified starch prepared by reaction, kg.

[0091] The results of the grafting rate are shown in Table 1.

[0092] Table 1

[0093] Grafting ratio Example 1 42.52％ Example 2 31.45％ Example 3 35.97％ Comparative Example 1 5.73％ Comparative Example 2 9.74％ Comparative Example 3 21.15％

[0094] Application example

[0095] The grafted modified starch prepared in Examples 1-3 and Comparative Examples 1-3 was respectively subjected to sizing test according to the following method:

[0096] A GA392 type electronic single yarn sizing machine was used for the sizing test. The yarn sizing machine was preheated for 30 min, the temperature of the sizing tank was set to 70℃, the prepared grafted modified starch was added into water to prepare a sizing liquid with a mass concentration of 45%, and mechanical stirring was carried out for 1 h to completely gelatinize the sizing liquid. The polyester-cotton blended yarn (65:35) was wound on the sizing machine for sizing treatment. The sizing speed was 20 m / min, and the sizing tension was 1.6 N. After the sizing was completed, the yarn cylinder was taken out, pressed, and dried.

[0097] Sizing yarn performance test:

[0098] A YG023A type full-automatic single yarn strength tester was used to test the strengthening rate and elongation reduction rate of the sized yarn. The test conditions were as follows: initial tension 12.5 cN, clamp distance 500 mm, and tensile speed 500 mm / min.

[0099] The wear resistance of the sized yarn is tested by using a LFY-109B computer yarn wear tester, and the test is performed according to the standard FZ / T01058-1999 "Yarn Wear Resistance Test Method Reciprocating Roller Method". The test results are shown in Table 2.

[0100]

[0101]

[0102]

[0103] Table 2

[0104]

[0105] In summary, the grafted modified starch prepared in the embodiment of the present application can be used for sizing at a low temperature of 60-70 ℃, and can form a uniform and stable size film on the surface of the yarn, and can effectively improve the strength and wear resistance of the yarn, and does not affect the subsequent desizing process, is conducive to improving the weaving efficiency, and meets the current development trend of energy saving and consumption reduction, and has high practical value.

[0106] The above only describes the preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a graft-modified starch, characterized by, The method comprises the following steps: Step a, adding acid hydrolysis starch into water, uniformly dispersing, heating and gelatinizing to obtain acid hydrolysis starch slurry; Step b, adding acrylic acid, vinyl acetate and initiator into the acid hydrolysis starch slurry, reacting for a first preset time, adding catalyst, reacting for a second preset time, cooling, neutralizing, solid-liquid separation, washing, drying to obtain carboxyl-hydroxyl starch; Step c, adding the carboxyl-hydroxyl starch into water, heating and dissolving, then adding lactic acid, heating and reacting for a third preset time, solid-liquid separation, washing, drying to obtain graft-modified starch.

2. The method of preparing a graft modified starch according to claim 1, wherein, In step a, the preparation method of the acid hydrolysis starch comprises the following steps: S1, adding starch into alcohol aqueous solution to obtain starch emulsion; S2, heating the starch emulsion to 60-70 DEG C and stirring for 1-2 h, then solid-liquid separation, washing, drying to obtain refined starch; S3, adding the refined starch into water, uniformly dispersing to obtain refined starch dispersion, adding acid solution into the refined starch dispersion, heating to 60-70 DEG C for acid hydrolysis, neutralizing, solid-liquid separation, washing, drying to obtain acid hydrolysis starch.

3. The method of preparing a graft modified starch according to claim 2, wherein the starch is a starch selected from the group consisting of corn starch, wheat starch, rice starch, potato starch, tapioca starch, and a mixture thereof. In S1, the mass concentration of the starch emulsion is 37-47%; and / or In S1, the alcohol aqueous solution is a mixed solution of methanol and distilled water with a volume ratio of 3:1-5:1; and / or In S3, the mass concentration of the refined starch dispersion is 33-45%; and / or In S3, the acid solution is a hydrochloric acid solution with a mass concentration of 1.5-2.5 mol / L, and the volume-mass ratio of the acid solution to the refined starch is 1 L:10 kg-1 L:12 kg; and / or In S3, the acid hydrolysis time is 3.5-4.5 h.

4. The method of preparing a graft modified starch according to claim 1, wherein In step a, the mass concentration of the acid hydrolysis starch slurry is 40-50%; and / or In step a, the heating and gelatinizing temperature is 85-95 DEG C, and the gelatinizing time is 0.5-1.5 h.

5. The method of preparing a graft modified starch according to claim 1, wherein the starch is a starch selected from the group consisting of corn starch, wheat starch, rice starch, potato starch, tapioca starch, and combinations thereof. In step b, the mass ratio of the acid hydrolysis starch, acrylic acid, vinyl acetate and initiator is 1.5-2.0:0.4-0.6:0.5-1.0:0.01-0.03; and / or In step b, the initiator is dimethyl 2,2'-azobis(2-methylpropionate); and / or In step b, the catalyst is cerium ammonium nitrate solution with a concentration of 1.5-3.0 mol / L, and the volume-mass ratio of the catalyst to the acid hydrolysis starch is 1 L:10 kg-1 L:12 kg; and / or In step b, the reaction temperature is 60-70 DEG C; and / or In step b, the first preset time is 0.5-1 h; and / or In step b, the second preset time is 2-3 h.

6. The method of preparing a graft modified starch according to claim 1, wherein the starch is a starch selected from the group consisting of corn starch, wheat starch, rice starch, potato starch, tapioca starch, and combinations thereof. In step c, the heating and dissolving temperature is 90-95 DEG C; and / or In step c, the mass concentration of the dispersion obtained after adding the carboxyl-hydroxyl starch into water is 40-50%; and / or In step c, the lactic acid is added in 4-6 batches, and each batch is added after an interval of 30-40 min, and the last batch of lactic acid is added after reacting for 60-70 min; and / or In step c, the mass-volume ratio of the carboxy-hydroxylated starch to lactic acid is 1.8 kg:0.76 L to 1.8 kg:0.42 L; and / or In step c, the time of the temperature rising reaction is 85℃ to 95℃.

7. A graft-modified starch characterized in that, The graft-modified starch is prepared by the method of any one of claims 1 to 6.

8. Use of the graft-modified starch according to claim 7 for the sizing of textile warp threads, characterized in that, The temperature of the sizing is 60℃ to 70℃.

9. A textile warp sizing size, characterized in that, The graft-modified starch of claim 7.

10. A warp sizing method characterized by comprising: At least comprising the following steps: The sizing paste of claim 9 is added into water, heated to 60℃ to 70℃, and stirred and gelatinized to obtain a sizing solution; The sizing solution is used to size the warp yarns.

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