Introduction of Low Viscosity Hydroxypropyl Methyl Cellulose HPMC

Low-viscosity hydroxypropyl methyl cellulose HPMC has good water solubility, high transparency, good gel properties, strong fluidity, and surface activity. It is widely used in medicine and food, petrochemical, construction, textile and electronics industries. Industrial products such as films prepared from cellulose ether have high mechanical strength, flexibility, heat resistance and cold resistance, and have good compatibility with various resins and plasticizers, making them a good coating material .

However, the low-viscosity hydroxypropyl methylcellulose aqueous solution has a thermal gel behavior, which is soluble in cold water, and can form a gel when heated, and then dissolve again after cooling. This is significantly different from the general natural polymer materials (such as starch) that form gels under cooling conditions. In the process of thermal gel change, the viscosity of the hydroxypropyl methyl cellulose solution changes greatly.

Viscosity behavior is affected by many factors. The author investigated the law of the viscosity change of low-viscosity hydroxypropyl methylcellulose under the changing conditions of temperature, pH, concentration, tackifier, salt, etc., in order to provide reference for using its viscosity characteristics to serve the production field.

Preparation of cotton for hydroxypropyl methylcellulose

The term hydroxypropyl methyl cellulose is not only a bit awkward to pronounce, but it is hard to understand its composition and use as mortar. About how it is formed, today, we will give you a lesson in popular language. explain.

Hydroxypropyl methyl cellulose is actually made of cotton. Of course, not just any cotton can be refined. Good cotton is needed. The production process is to first treat the cotton in lye and then It is pulverized, and then it is aged at 35 degrees, and then it is put into propylene oxide and methyl chloride and then processed. The first step is dehydration and crushing. Although this process seems more complicated, as long as you are proficient in the operation, you will not have this idea.

Regarding how to identify the quality of hydroxypropyl methylcellulose, in fact, the country does not yet have a hard indicator, because its product uses and auxiliary materials and additives are different, so the quality is not easy to check.

Cellulose ether was reported in 1905. It was prepared by Suida reacting alkali-swollen cellulose with dimethyl sulfate, but no isolated cellulose ether could be obtained at that time. In 1912, a patent for the preparation of cellulose ethers appeared. ; In 1927, the synthesis and separation of hydroxypropyl methyl cellulose were successful; in 1938, Dow Chem. realized the industrial production of methyl cellulose and “Methocel”; in 1948, large-scale hydroxypropyl methyl cellulose was carried out in the United States. Industrial production, and the production process reached maturity in 1960 to 1970.

The HPMC production companies currently compared in the world mainly include Dow Chemical Co., Hercules Co., and Clariant Co. in Germany. Japan’s Shin-Etsu Chemical Co. and South Korea’s Samsung Fine Chemical Co. (Samsung Fine Chemical Co.) have introduced technology and equipment from Dow Chemical Co. and German Loedige Co., respectively.

The production methods of hydroxypropyl methylcellulose can be divided into two categories: gas phase method and liquid phase method. At present, developed countries such as Europe, America and Japan adopt the gas phase process, using wood pulp as the raw material (cotton pulp is used in the production of high-viscosity products). The alkalization and etherification are carried out in the same reaction equipment. The main reaction is a horizontal reactor. The central horizontal stirring shaft and side rotating flying knife designed for the production of cellulose ether can obtain a good mixing effect. The reaction process adopts automatic control means, which can control temperature and pressure. After the reaction is completed, the excess methyl chloride and the by-product dimethyl ether enter the recovery system in gaseous form, and are recycled and reused separately. The purification treatment is carried out in a continuous rotary filter press. The crushing is carried out in the finished product crusher while drying to remove excess water. Auxiliary processes such as mixing and packaging are also completed under the automatic control system.

The gas-phase process has the following advantages: compact equipment, high single-batch output; lower reaction temperature than liquid-phase method, shorter reaction time than liquid-phase method; more accurate reaction control than liquid-phase method; no need for complex solvent recovery system; low labor cost , The labor intensity is small.

However, this process also has the following shortcomings: large investment in equipment and automatic control, high technical content, and large investment and construction costs; due to the high degree of automation, the requirements for the quality of the operators are high, and once a failure occurs, major accidents are prone to occur. If something goes wrong, the whole line will stop production.

The advantages of hydroxyethyl cellulose HEC as a thickener in coatings

Hydroxyethyl cellulose HEC is the hydroxyethyl ether of cellulose. The product is a odorless, non-toxic white or light yellow powder of cellulose, with various specifications and brands due to different manufacturing methods and manufacturing processes. In recent years, there have been new developments. Different types of hydroxyethyl cellulose products such as anti-enzyme type and associative type have come out.
Hydroxyethyl cellulose HEC is a commonly used thickener in coatings and has the following advantages:
(1) Strong versatility. Hydroxyethyl cellulose HEC is a non-ionic water-soluble polymer, which can be used in a wide pH range (2-12). It can be mixed with common paint components (such as pigments, additives, soluble salts and electrolytes) without abnormal phenomena.
(2) The paint thickened with hydroxyethyl cellulose HEC has pseudoplasticity, so it can be applied by brushing, spraying, roller coating and other construction methods, which is labor-saving and easy to hang, not easy to splash, not easy to drip and sag, etc. Advantages, leveling is also better.
(3) There is no bad effect on the coating film. Due to the insignificant water surface tension characteristics of the HEC aqueous solution, it is not easy to foam during construction and production, and there is less tendency to produce volcanic holes.
(4) Good color development. Hydroxyethyl cellulose HEC has excellent miscibility to most binders and coloring agents, so that the formulated paint has good color stability and consistency.
(5) Good storage stability. During the storage process of the paint, the suspension and dispersion of the pigment can be maintained, and there is no floating or blooming disease. There is less water layer on the surface of the paint. When the storage temperature changes, the viscosity remains More stable.

The difference between hydroxypropyl starch ether HPS and cellulose ether

The difference between hydroxypropyl starch ether and cellulose ether and its role in mortar

1. Starch ether can effectively improve the anti-sagging and anti-slip properties of the mortar. However, cellulose ethers usually can only increase the viscosity and water retention of the system, but cannot improve the anti-sagging and anti-slip properties.

2. Thickening and viscosity. Generally, the viscosity of cellulose ether is about tens of thousands, while the viscosity of starch ether is several hundred to several thousand, but this does not mean that starch ether is not as thick as cellulose ether in thickening mortar. The thickening mechanism of the two is different.

3. Compared with cellulose ether, starch ether can significantly increase the initial yield value of tile adhesive, thereby improving its anti-slip performance.

4. Air-entraining. Cellulose ether has strong air-entraining properties, while starch ether has no air-entraining properties.

5. Molecular structure of cellulose ether. Although both starch and cellulose are composed of glucose molecules, their composition is different. The orientation of all glucose molecules in starch is the same, while cellulose is just the opposite. The orientation of each adjacent glucose molecule is more common and commonly used are potato starch, tapioca starch, corn starch, wheat starch, etc. Compared with cereal starches with higher fat and protein content, the starches of root crops such as potato and tapioca starch are more pure.

Starch is a polysaccharide polymer compound composed of glucose. There are two kinds of molecules, linear and branched, called amylose (content about 20%) and amylopectin (content about 80%). To improve the use of starch in building materials

Etherification synthesis principle of hydroxypropyl methyl cellulose (HPMC)

Hydroxypropyl methyl cellulose ((HPMC), the raw material cellulose, can be refined cotton or wood pulp. It is necessary to crush it before or during the alkalization process. The crushing is done by mechanical energy. Destroy the aggregated structure of cellulose raw materials to reduce crystallinity and degree of polymerization, increase its surface area, thereby improving the accessibility and chemical reaction ability of the reagents to the three hydroxyl groups on the cellulose macromolecular glucose ring base.

Hydroxypropyl methyl cellulose (HPMC) is used as the raw material substrate to produce oil, which can realize the utilization of whole sugar, improve the utilization rate of raw materials, reduce the residual amount of substrate in the fermentation broth, and reduce the cost of wastewater treatment. The characteristics of methyl cellulose facilitate the optimization of batch, fed-batch and continuous fermentation processes, avoiding a series of problems such as controlling the medium composition and dilution rate; at the same time, it is also conducive to the regulation of the fermentation process. Because the properties of hydroxypropyl methyl cellulose (HPMC) are similar to other water-soluble ethers, it can be used as a film-forming agent, thickener, emulsifier and stabilizer in latex coatings and water-soluble resin coating components, so that The film has good abrasion resistance, leveling and adhesion, and has improved surface tension, stability to acid and alkali, and compatibility with metallic pigments.

Hydroxypropyl methylcellulose (HPMC) has a good effect as a thickener for white water-based polyvinyl acetate paint. The degree of substitution of cellulose ether is increased, and the resistance to bacteria and erosion is also enhanced.

Although the principle of the etherification synthesis of hydroxypropyl methylcellulose (HPMC) is not complicated, it is alkalization, raw material crushing, and alkalization. The various environments of etherification, solvent recovery, centrifugal separation, washing and drying involve a large number of key technologies and rich knowledge.

For different types of products, each environment has the latest control conditions, such as temperature, time, pressure and material flow control. Auxiliary equipment and control instruments are a reliable and beneficial guarantee for stable product quality and reliable production system.