Starch has a long history as the main sizing agent for warp sizing. China's Yuan Dynasty (about AD 1300) used wheat flour as the slurry. 1890 Shanghai Woven Layout (the first textile mill in China) also uses fermented wheat flour as warp sizing agent. 182 1 year, dextrin was used as sizing agent abroad, and starch manufacturing industry appeared at the same time. At first, wheat starch was the main starch, and soon, other starches were also produced and applied.
Although there are a large number of starch-containing varieties in the plant world, there are not many varieties that can be used in industry. Mainly corn, potatoes, wheat, sweet potatoes, cassava and so on. Corn has high yield, wide planting area, high starch content, many kinds of by-products, high economic value, easy transportation and storage, and can be produced by processing plants all year round, regardless of seasons and regions, and has many excellent characteristics (stable viscosity, etc. Therefore, in the world starch production, corn starch accounts for more than 70%. In the United States, more than 95% of starch comes from corn, while in Europe, potato is the main starch. In Thailand, Brazil and other countries, cassava starch is also developing rapidly in southern China. Wheat starch was widely used in the past, but it declined in the first 20 years. However, in recent years, the amount of wheat starch has increased, which is mainly used to develop new uses of carbonless copy paper. The output of starch and modified starch in the world and several major countries in recent years is shown in table 1. As can be seen from the table, the scale of China's starch industry is still very small, especially the output of modified starch is too low.
Table 1 Overview of Starch Production (2000) National Raw Starch Output
Output of modified starch (ten thousand tons)
(ten thousand tons)
Global 4700 700
China 550 35
USA 1600 260
450 100 euro
Japan 200
Starch is a natural polymer compound, belonging to polysaccharide, which exists in seeds, tubers, tubers or fruits of some plants. Starch extracted from plant tubers and tubers is called root starch, such as potato starch, sweet potato starch and cassava starch. Starch extracted from plant seeds or fruits is called seed starch, such as wheat starch, corn starch and acorn starch.
Starch has good adhesion to hydrophilic natural fibers and certain film-forming ability, which can basically meet the sizing requirements of these fibers. Starch is rich in resources and low in price, and has accumulated rich experience in the application of textile warp sizing. However, its sizing performance is not ideal, and it is often necessary to make up for it with various auxiliary sizes. Modifying starch by physical or chemical methods or mixing it with other sizes can improve the sizing effect of starch and expand its application scope. The pollution of starch pulp desizing sewage to the environment is lower than that of other chemical pulps. Therefore, at present, starch and modified starch still account for the largest proportion (65% ~ 70%) in all kinds of pulp.
Total capacity of modified starch equipment in China: 700,000 tons/year (actual output of 200 1 year is 350,000 tons). According to production mode: output of chemically modified starch: 230,000 tons/year; Pre-gelatinization yield: 654.38+10,000 tons/year; Other modes of production: 20,000 tons/year. 1996 actual sales of modified starch in China: 2 10000 tons; In 2000, it was 350,000 tons, which was mainly used in the following industrial sectors (Table 2). Generally speaking, China's modified starch is still in the primary stage of development and has broad prospects. It is predicted that it will exceed10 million tons by 20 10, and the production of modified starch will become the main pillar of starch industry and fine chemical industry.
Table 2 Application of China Modified Starch
Actual sales volume of industrial sector 1996
Demand in 2002 (10,000 tons)
(ten thousand tons)
Paper industry 8.0 20 ~ 30
Textile industry 5.5 10 ~ 13
Feed industry 4.08 ~ 10
Food industry 0.5 14 ~ 16
Pharmaceutical industry 2 ~ 4
Foundry industry 3 ~ 4
Starch plastic 10 ~ 12
Other industries 3.05 ~ 8
Total 2 1 72 ~ 100
Second, the structural characteristics and denaturation principle of starch macromolecules
First, the structural characteristics of starch:
Starch is a high molecular compound condensed from α -glucose and a kind of high glycan. The glycosidic bonds in the macromolecular structure of starch and the hydroxyl groups contained in it are the internal factors for the possibility of preparing various modified starches. The break of glycosidic bond decomposes macromolecules, reduces the degree of polymerization, and mainly changes the physical properties of starch. A series of chemical reactions have taken place between the hydroxyl groups on the sixth carbon atom (primary carbon atom) and the second and third carbon atoms (secondary carbon) of glucose residue-oxidation, etherification, esterification, amination and graft polymerization. , can produce a series of modified starch. The structure of starch macromolecules can also be changed by heating or high-energy radiation to prepare pregelatinized starch and degraded starch. Modified starch can also be prepared by special biological enzymes.
B, modified starch manufacturing methods mainly include:
Chemical denaturation: a product obtained by a chemical reaction with a chemical reagent. Such as: acid-hydrolyzed starch, oxidized starch, esterified starch, etherified starch, cross-linked starch, cationic starch, grafted starch, etc.
Physical modification: such as pregelatinized starch, starch treated by electron radiation, starch degraded by heat, etc.
Biological denaturation: such as enzymatic conversion of starch.
It must be pointed out that starch is an organic polymer compound, and its denaturation reaction must meet certain conditions (initiator, temperature, time and so on). ); It can't happen instantaneously like the acid-base neutralization reaction of inorganic compounds. The latter is a chemical reaction of ion exchange, and the reaction between starch and various denaturants can only occur after intermolecular collision and contact.
C, some factors affecting the sizing performance of modified starch size:
Because the raw material of modified starch is natural starch, the final performance and quality stability of the product are affected by many factors, including some natural factors. It can be said that the performance of modified starch often depends on the following factors:
1. Plant source: variety, soil, climate, season, etc.
2. Physical form: granular and pregelatinized;
3. Proportion and content of amylose and amylopectin;
4. Molecular weight distribution range (viscosity description commonly used in industry);
5. Impurities and related components (protein, fatty acids, phosphorus-containing compounds), or natural substitutes;
6. Pretreatment history: acid hydrolysis, oxidation, enzymatic degradation or dextrinization, etc.
7. Types of denaturation: esterification, etherification, oxidation, amination, grafting, etc.
8. Properties of substituents: acetyl, carboxymethyl, hydroxypropyl, amino, etc.
9. Degree of substitution and so on.
Recently, I encountered a problem: which kind of raw starch has better sizing performance? Because some brands on the market are modified starch pulp made of potato starch, which looks better than corn starch. From our decades of experience in the production and use of textile size, compared with the sizing performance of various raw starch, it should be:
Corn starch has the best sizing performance, the highest adhesion to natural fibers, and the most stable viscosity.
So in the past, when raw starch was used for sizing, corn starch was the first choice.
Followed by wheat starch, its adhesiveness is slightly worse than corn starch, but its fluidity is better than corn starch.
The third place is potato starch, which has poor adhesion to natural fiber but contains a small amount.
Natural phosphate has good fluidity and uniform particle size.
Followed by: cassava starch, sweet potato starch and so on.
3. Types of modified starch:
According to the above macromolecular structure and denaturation principle of starch, according to the development of many years, the commonly used modified starch size in warp sizing can be summarized as follows:
Decomposed starch (also known as the first generation modified starch)
Acid treated starch: acid hydrolyzed starch, soluble starch and low regulated starch.
Baked dextrin: white dextrin, yellow dextrin, printing and dyeing glue.
Oxidized starch: dialdehyde starch and hypochlorous acid oxidized starch.
Starch derivatives (second generation modified starch)
Starch ether methyl starch (MS)
carboxymethyl starch
hydroxyethyl starch
Hydroxypropyl starch (HPS)
Propylene starch
Cationic starch
Amide starch (also known as carbamate starch)
Starch acetate
Starch phosphate
Starch succinate enzyme
Starch xanthate
Starch carbamate (also known as amide starch)
Cross-linked starch formaldehyde cross-linked starch
Epichlorous acid cross-linked starch
Phosphate crosslinked starch
Acrylic cross-linked starch
Grafted starch (third generation modified starch)
Acrylamide grafted starch
Acrylate grafted starch
Vinyl acetate grafted starch
Physically treated modified starch
Radiation treatment: α, β, γ and neutron treatment of starch.
High frequency treatment of starch
Wet-heat treated starch
Microwave treatment of starch
Four, the basic characteristics of commonly used modified starch size
1. Acid-hydrolyzed starch:
Acid hydrolyzed starch is also called acidified starch. There are also many names in the world: acid-converted starch or acid-modified starch, but it is often called thin boiled starch in industry. Acid hydrolysis of starch has a long history. As early as 1886, natural starch was treated with hydrochloric acid. It is mainly the product of starch macromolecules decomposed by acid. At present, there are various acid-modified starches in industry, which are used in many industries. 70% of modified starch consumption in the United States is acid-hydrolyzed starch.
There are two main purposes to study and explore this kind of modified starch: (1) reducing viscosity to increase the concentration range that can be applied in industry; (2) Changing rheological properties to expand the functionality of starch in industrial applications, such as converting fructose and syrup, so as to prepare chewing gum raw materials with appropriate gel hardness and gel rupture strength.
oxidized starch
Oxidized starch is one of the most common modified starches. Compared with natural starch, it is white, easy to gelatinize, wide in viscosity adjustment range, high in viscosity stability, strong in transparency, film forming and adhesion, and low in cost. It has been widely used in papermaking, textile, food and other industries.
Hydroxyl groups and glycosidic bonds in starch macromolecules are the main internal causes of oxidation. According to the action form of oxidant on starch, it can be divided into two types: specific oxidant and random oxidant. Specific oxidants can only oxidize specific parts of starch macromolecules. For example, periodic acid can only oxidize the secondary alcohol groups on C2 and C3, and the product is called dialdehyde starch. Random oxidants can randomly oxidize the relevant parts of starch macromolecules, such as hypophosphite and hydrogen peroxide.
Sodium hypochlorite or calcium hypochlorite is commonly used as oxidant in industry, and sodium hypochlorite is mainly used in textile industry. Sodium hypochlorite is prepared by slowly introducing chlorine into a cold aqueous solution of sodium hydroxide. When the temperature is too high (above 30℃), hypochlorite will be converted into chloride, and the oxidation efficiency will be lost.
0. 1, it began to show partial water solubility. The higher the degree of substitution; The greater the solubility, the faster the dissolution rate. When the degree of substitution is ≥0.5, it has been dissolved in cold water. The aqueous solution is clear, transparent and viscous. Solubility and dissolution rate are also related to the particle structure and polymerization degree of natural starch. The substitution degree of carboxymethyl starch for industrial use is generally below 0.9.
Carboxymethyl starch is also a kind of polymer dielectric, which is an anion and formed by introducing groups. It can form a salt with alkali metal, which improves the water absorption and water solubility of the product. In the case of bivalent or above heavy metal salts, the slurry flocculates and even appears insoluble precipitation. Cationic dyes (methyl blue dyes) can be used for dyeing, and cationic auxiliary materials, such as cationic surfactants, should be avoided in slurry preparation.
Commercial carboxymethyl starch often contains a certain amount of salt (mainly sodium chloride), which is closely related to the performance of carboxymethyl starch, so it has always been regarded as one of the main quality indexes of this kind of products. Carboxymethyl starch with high salt content not only greatly improves the water absorption, but even makes the slurry sticky again; More seriously, it will corrode the parts of sizing and mixing equipment.
In the textile industry, it is mainly used as an auxiliary adhesive size for warp sizing. It has good adhesion to natural fibers and can be used for sizing medium and fine count cotton yarn, ramie yarn yarn and linen yarn. Because of its water solubility, it is also suitable for sizing viscose yarn and combed wool yarn; It has good miscibility with water-soluble polymer compound polyacrylic acid, so sometimes this mixed pulp is used for sizing polyester-cotton blended yarn, and the mixing ratio is generally 10% ~ 30%. However, due to its high price, it is usually used as a substitute for carboxymethyl cellulose (CMC) to promote the miscibility of other pulp components.
Starch acetate
Starch acetate is also called starch acetate. Its reaction principle was known as early as 100 years ago. After that, we are interested in highly acetylated starch esters and other starch esters with substitution degree of 2 ~ 3 in order to replace cellulose acetate. They are soluble in solvents (acetone, chloroform, etc. ) and thermoplastics. Starch acetate plays an important role in the exploration of physical properties of starch and the study of amylose "fiber" and film. Because they can't compete with similar cellulose derivatives in strength and price, they can't make a breakthrough in business. However, starch acetate with a degree of substitution lower than 1.0 basically belongs to hydrophilic substances and has been produced on an industrial scale. At present, some countries in Europe, America and Japan mainly produce products with low degree of substitution (DS < 0.2), which have been used in some industrial sectors.
The esterification reagents studied earlier and used recently include acetic anhydride, acetic anhydride-pyridine, acetic anhydride-acetic acid mixture, ketene, vinyl acetate or acetic acid. Commercially applicable products are derivatives with a low degree of substitution of 0.0 1 to 0.2.
Because of its film-forming ability and good adhesion to cellulose, it has been used as a surface sizing agent in paper industry. In this application, it is more competitive than hydroxyalkyl starch ether, oxidized starch or starch converted by enzyme and heat.
In the application of preparing adhesive such as adhesive tape, the obvious advantages of acidolysis waxy corn starch acetate are luster, viscosity and rewetting ability. The adhesive tape made of oxidized waxy corn acetate with carboxyl content of 0.3% ~ 0.5% and acetyl content of 1.5% ~ 2% has the properties of animal glue products.
Warp sizing in textile industry is the main market of starch products. The properties of corn starch and corn acetate starch used for sizing polyester cotton yarn were compared. As can be seen from the table, due to the good affinity of acetate starch, polyester-cotton sizing yarn shows good wear resistance, and the hairiness of sizing yarn is also obviously reduced, which is conducive to the improvement of weaving efficiency.
Performance Comparison of Surface Sized Yarn
Performance value of natural starch
Acetate starch sizing
(medium viscosity) acetate starch sizing yarn
(low viscosity) raw yarn
Wear resistance (times) 39.9 4 1.2 59.5 18.4
Fracture strength (N) 2.6 1 2.74 2.79 2.56
Elongation (%) 5.62 5.37 5. 10 8.86
The fracture work (n·cm) is 4.71.42 4.1.26.57.
Specific adhesion (n/%) 0.26-0.28-
> > 2mm hairiness (root/10m) 53 42 57 74
> > 3mm hairiness (root/10m)1811924.
> > 5mm hairiness (root/10m) 7-2 15
The desizing rate (%) is 8.0311.6910.86-
Starch acetate is mainly used for sizing natural fiber yarn and polyester-cotton blended yarn. Acetate starch can be used as the main sizing agent for fine count high density cotton fabric and ramie yarn. Because its size film has high strength, flexibility and high adhesion to this kind of fiber, it has good weaving performance. It can also be used for polyester/viscose and polyester/wool blended yarn as one of the components of mixed size. It has good miscibility with common synthetic slurry and can be mixed in any proportion. Generally, the mixing ratio with synthetic slurry is between 10%-30%. If the quality of acetate starch is good, combined with reasonable sizing technology and strict operation management, its proportion can reach 50%.
This starch ester is easy to desize in the desizing process because of its good dispersibility and solubility.
It can also be used as sizing agent for glass fiber yarn. It is also an ideal sizing agent for wool yarn and viscose yarn.
Due to the weak gel tendency, sizing can be carried out at a lower temperature to prevent high temperature from damaging the properties of this fiber.
The preparation of cassava starch acetate and its application in sizing polyester-cotton blended yarn were systematically studied, and the comparative test and production application were carried out in the production workshop.
Starch carbamate
Starch carbamate is also called "amide starch". The reagent used in this modified starch is urea, so it is more called "urea starch" in business. In fact, these three names are the same product.
Urea is a nitrogen-containing organic compound, which can promote starch swelling. If a large amount of urea (3 ~ 6 ∶ L of the weight of starch) is added, starch can be gelatinized into slurry at room temperature. Some people also use this cold gelatinized starch size to size 20 ~ 30 tex cotton yarn, which has a certain weaving effect. This cold gelatinization phenomenon is not chemical denaturation, but physical action. The hydrophilicity and hygroscopicity of urea break the hydrogen bond between starch molecules and promote the penetration of water. Many studies show that the denaturation mechanism of urea on starch mainly occurs at high temperature.