CN101092458A - Starch pretreatment method doe raising graft efficiency for grafting starch slurry - Google Patents

Abstract

A starch pretreatment method for improving grafting efficiency of grafted modified starch sizing belongs to the technical field of modified starch sizing used in textile warp yarn sizing. The invention comprises two steps of starch allyl etherification pretreatment and radical graft copolymerization. Through the etherification pretreatment of the starch raw material, the allyl atomic group containing the carbon-carbon double bond is introduced into the starch macromolecule, and then the etherified starch and the vinyl monomer are grafted and copolymerized under the action of the initiator. The grafted branch chain is introduced to prepare the grafted starch slurry with high grafting efficiency. The present invention introduces an allyl side group containing a carbon-carbon double bond on the starch macromolecule, so that the homopolymerization reaction is partially converted into a graft copolymerization reaction in the subsequent starch graft copolymerization reaction process, reducing The amount of homopolymer generated can significantly increase the content of graft copolymer in the grafted starch slurry, effectively improve the graft efficiency of graft copolymerization reaction, and reduce monomer consumption and production cost.

Description

A starch pretreatment method for improving the grafting efficiency of grafted starch slurry

technical field

The invention discloses a starch pretreatment method for improving the grafting efficiency of grafted starch sizing, and prepares the grafted starch sizing with high grafting efficiency by the method, which belongs to the technical field of modified starch sizing used in textile warp yarn sizing.

Background technique

Sizing is an important process in warp preparation engineering. The purpose of sizing is to endow the warp with the ability to resist complex mechanical external forces, improve the weavability of the warp, and ensure the smooth progress of the weaving process. During the weaving process, the warp yarn is not only subjected to repeated friction of warp wires, healds and reeds, but also subjected to stretching, impact and twists caused by shedding and beating-up. Unsized yarn has more hairiness on the surface, poor cohesion between fibers, and is difficult to withstand repeated stretching, friction, impact and twists and turns during the weaving process. The warp structure will gradually loosen and hairiness will increase, resulting in unclear openings and warp breaks head and cannot weave. Therefore, both single yarn and general strands need to be sized before weaving.

According to the role played in the slurry, the composition of the slurry can be divided into two categories, one is the adhesive, and the other is the auxiliary agent. Adhesive is an adhesive material, mainly including starch, PVA and acrylic copolymer. Among them, starch is the most commonly used adhesive in sizing production. It has good adhesion to natural fibers. It is rich in sources, low in price, and friendly to the environment, but there are also some shortcomings, such as brittleness and hardness of the size film, High viscosity, poor viscosity stability, etc. Therefore, improving the performance of starch size is of great significance for reducing costs, improving production efficiency, and improving the quality of sizing and cloth.

To modify the defects of native starch has become an effective way to improve the sizing performance of starch size. Grafted starch size is a new type of modified starch size. Due to the introduction of grafted branch chains, it not only retains the characteristics of starch itself, but also has the characteristics of synthetic polymers. When the amount of grafted monomers is the same, increasing the grafting efficiency can increase the grafting rate and reduce the content of homopolymer in the product. Although the homopolymer also has a certain sizing performance, it is far less than that of grafted branched chains in starch. Sizing performance, so increasing the grafting efficiency can improve the sizing performance of the grafted starch size. On the other hand, under the premise of a given product performance index, improving the grafting efficiency can reduce the monomer consumption and reduce the cost. For this reason, improving grafting efficiency has become an important measure to obtain high-performance grafted starch size and reduce costs. However, due to the inevitable chain transfer phenomenon of vinyl monomers in the free radical polymerization reaction, the existence of homopolymers in the product is inevitable, and the grafting efficiency is usually not high enough. Therefore, in order to improve the grafting efficiency of the grafted starch slurry, it is necessary to carry out pretreatment for the purpose of improving the grafting efficiency to the starch raw material.

Contents of the invention

The purpose of the present invention is to provide a kind of starch pretreatment method that can improve the grafting efficiency of grafted starch slurry. The grafted starch size prepared by the method of the invention has relatively high grafting efficiency, improves the use performance of the grafted starch size, and reduces the cost of raw materials.

The technical solution of the present invention: the preparation process of the grafted starch slurry with high grafting efficiency includes two steps of starch allyl etherification pretreatment and free radical graft copolymerization. By carrying out etherification pretreatment on the starch raw material, an allyl atom group containing a carbon-carbon double bond is introduced on the starch macromolecule, and then the etherification pretreated starch containing a carbon-carbon double bond substituent is combined with a vinyl monomer The graft copolymerization reaction is carried out under the action of the initiator, and the grafted branch chain is introduced on the starch macromolecule to obtain the grafted starch slurry with high grafting efficiency. The preparation process is as follows:

(1) Starch etherification pretreatment: use an organic solvent or a mixed system of organic solvent-water as the reaction medium, the mass fraction of the organic solvent is 0-50%, and the starch is made into a starch with a mass percentage of 5%-45% Suspension, add sodium hydroxide aqueous solution dropwise, stir and alkalinize for 30min, then add allyl halide dropwise to carry out allyl etherification reaction, control the dropping speed, make it complete within 15min-30min, sodium hydroxide and allyl The molar ratio of halides is 1:1-5:1, stirred and reacted at 10°C-60°C for 1-36 hours, filtered, washed and dried to obtain allyl etherified starch; the etherifying agent used is Allyl halide, the amount of etherification agent to starch is 0.1%-20% (w/w), and the degree of substitution of etherified starch is 0.001-0.20;

(2) Preparation of grafted starch slurry: add water to make the etherified starch into a suspension with a mass percentage of 5%-45%, drop vinyl monomers and initiators under the protection of nitrogen to carry out graft copolymerization, The molar ratio of vinyl monomer to etherified starch is 0.01:1~1:1, with H ₂ O ₂ and FeSO ₄ ·(NH ₄ ) ₂ SO ₄ as initiators, H ₂ O ₂ and FeSO ₄ ·(NH ₄ ) The amount of ₂ SO ₄ is 0.1%-5% and 0.01%-2% of the starch mass respectively, stirred and reacted at 5-75°C for 1-15 hours, filtered, washed and dried to obtain grafted starch slurry .

The starch raw material is selected from corn starch, wheat starch, sweet potato starch, tapioca starch or potato starch.

The graft copolymerization reaction is carried out according to the mechanism of free radical initiation. The chemical initiators used include thermal decomposition type and redox type. When H ₂ O ₂ and FeSO ₄ ·(NH ₄ ) ₂ SO ₄ are used as initiators, The dosages of the two are respectively 0.1%-5% and 0.01%-2% of the starch mass.

Starch always maintains a granular state during the above-mentioned allyl etherification reaction and graft copolymerization reaction, as well as in the finished product. The starch pretreatment method involved in the present invention can increase the grafting efficiency of the grafted starch slurry by 10%-20% compared with the existing grafting efficiency within the range of the starch allyl etherification substitution degree of 0.01-0.1.

Beneficial effects of the present invention: the present invention finds that before the graft copolymerization reaction, by introducing the pretreatment method of the allyl atomic group containing carbon-carbon double bond in the starch macromolecule, the grafted starch slurry can be greatly improved. material grafting efficiency.

Compared with the conventional grafted starch sizing, the grafted starch sizing prepared by the method of the present invention has a remarkable feature of higher grafting efficiency, which can obviously improve the use performance of the sizing and reduce the production cost. Therefore, the present invention effectively solves a long-standing problem of grafted starch sizing in the early stage, that is, the problem of low grafting efficiency.

The high-efficiency grafted starch size prepared by the invention is used for weaving warp yarn sizing. Starch always maintains a granular state during the process of allyletherification and graft copolymerization, as well as in the finished product, which is convenient for use.

Detailed ways

Example 1

Disperse the acid-thinned starch with a dry weight of 235g in 550g isopropanol solvent, prepare a starch emulsion suspension with a mass concentration of 30%, then move it into a 1000mL three-necked flask equipped with a mechanical stirrer, a thermometer and a dropping funnel, drop Add sodium hydroxide solution (the molar ratio of sodium hydroxide to allyl chloride is 1.5:1), stir and basify at 30°C for 30 minutes, and then add dropwise allyl chloride solution (allyl chloride tested in 2# to 6# The molar ratio of chlorine to starch is: 0.005, 0.01, 0.02, 0.04 and 0.1), control the speed of dripping so that it is completed within 20min~30min, after reacting at 30°C for 24h, filter the product and redisperse it in 700mL distilled water - in ethanol solution (18:82, volume ratio), neutralized to pH7 with dilute hydrochloric acid (4mol/L), and then washed twice with 500 ml of the above-mentioned distilled water-ethanol solution after suction filtration, then dried at 50°C, pulverized and sieve.

Weigh 120 g of the allyl starch prepared by the above reaction and add it into 280 g of distilled water to form a starch emulsion suspension with a mass concentration of 30%. Adjust the pH value of the reaction medium to 3 to 4 with dilute hydrochloric acid solution, and transfer it into a 500 ml four-port inside the flask. Put the flask into a constant temperature water bath with a temperature of 30°C, install a stirrer, a thermometer, a dropping funnel and a nitrogen tube, feed nitrogen and stir to eliminate the oxygen present in the four-necked flask. Make H ₂ O ₂ and FeSO ₄ ·(NH ₄ ) ₂ SO ₄ into a solution with a mass fraction of 0.5% to 1.0%, H ₂ O ₂ /FeSO ₄ ·(NH ₄ ) ₂ SO ₄ /starch glucose residue mole The ratio is 20/1/1000. After 30 minutes, use the dropping funnel to drop methyl acrylate monomer (the monomer mass is 10% of the dry weight of starch), FeSO ₄ ·(NH ₄ ) ₂ SO ₄ aqueous solution and H ₂ O ₂ Aqueous solution, control the speed of dripping, so that it is completed within 15min to 20min, the whole polymerization reaction is stirred for 3h under the protection of nitrogen, add 3.25mL of 2% hydroquinone solution, and then adjust the pH value of the grafted starch milk 6-7, terminate the reaction, filter, wash and dry to obtain the product. See attached table 1 for the grafting efficiency, grafting rate and polymerization reaction yield of methyl acrylate grafted starch size.

Table 1 Grafting parameters of methyl acrylate grafted etherified starch

Degree of substitution Polymerization yield (%) Grafting efficiency (%) Grafting rate (%) 1# DS=0 96.0 51.6 4.95 2# DS=0.0054 93.8 60.2 5.65 3# DS=0.011 93.9 65.5 6.15 4# DS=0.023 95.0 70.5 6.69 5# DS=0.043 96.8 71.4 6.92 6# DS=0.068 94.0 72.8 6.84

Even if the test conditions are changed, as long as the degree of substitution of etherified starch is controlled to a corresponding value, the corresponding grafting efficiency can be basically achieved.

Example 2

Using the method and steps of Example 1, only the type of grafted monomers was changed. See attached table 2 for the grafting efficiency, grafting rate and monomer conversion rate of the acrylic acid grafted starch size.

Table 2 Grafting parameters of acrylic acid grafted etherified starch

Degree of substitution Monomer conversion rate (%) Grafting efficiency (%) Grafting rate (%) 1# DS=0 98.0 53.2 5.21 2# DS=0.0046 98.7 62.7 6.19 3# DS=0.011 99.2 64.3 6.38 4# DS=0.025 95.7 68.3 6.53 5# DS=0.037 97.4 73.7 7.18 6# DS=0.10 95.1 74.0 7.04

Claims (3)

1, a kind of pretreatment method of starch that improves the grafting starch grafting efficiency, it is characterized in that by starch material is carried out the allyl etherization pre-treatment, on starch polymer, introduce the allyl group atomic group that contains carbon-to-carbon double bond, to contain substituent etherificate pretreated starch of carbon-to-carbon double bond and vinyl monomer then and under the initiator effect, carry out graft copolymerization, on starch polymer, introduce grafted branches, make the grafting starch of high grafting efficiency, preparation technology is:

(1) starch etherificate pre-treatment: with organic solvent or with the mixed system of organic solvent-water as reaction medium, the massfraction of organic solvent is 0-50%, starch is made into the starch suspension that mass percent is 5%-45%, the dropping sodium aqueous solution, stir alkalization 30min, drip allyl halide then and carry out the allyl etherization reaction, the control rate of addition, make it in 15min-30min, to finish, the mol ratio of sodium hydroxide and allyl halide is 1: 1-5: 1, at 10 ℃ of-60 ℃ of following stirring reaction 1-36 hours, filter, make allyl etherization starch after washing and the drying; Used etherifying agent is an allyl halide, and etherifying agent is 0.1%-20% (w/w) to the consumption of starch, and the substitution value of etherification starch is 0.001-0.20;

(2) preparation grafting starch: add water etherification starch is made into the suspension that mass percent is 5%-45%; dropping vinyl monomer and initiator carry out graft copolymerization under protection of nitrogen gas; the mol ratio of vinyl monomer and etherification starch is 0.01: 1～1: 1, with H ₂O ₂And FeSO ₄(NH ₄) ₂SO ₄Be initiator, H ₂O ₂And FeSO ₄(NH ₄) ₂SO ₄Consumption be respectively the 0.1%-5% and the 0.01%-2% of starch quality, at 5-75 ℃ of following stirring reaction 1-15 hour, make grafting starch after filtration, washing and the drying.

2, preparation method according to claim 1 is characterized in that starch material is selected from W-Gum, wheat starch, sweet potato starch, tapioca (flour) or yam starch.

3, preparation method according to claim 1 is characterized in that starch in above-mentioned allyl etherization reaction and graft copolymerization process, and remain graininess in finished product.