Hydroxypropyl Methyl Cellulose (HPMC)
In recent years, the production and usage of Hydroxypropyl Methyl Cellulose (HPMC) have been increasing rapidly. Hydroxypropyl methyl cellulose is a non-ionic cellulose mixed ether made from refined cotton by alkalization treatment, using propylene oxide and chloromethane as etherizers, through various chemical reactions. The substitution degree of hydroxypropyl methylcellulose is generally 1.2~2.0, and its properties are different by the ratio of methoxy content and hydroxypropyl content. Specifically, you can learn about the 'Effect of methoxy content and hydroxypropoxy content on HPMC'.
1. Hydroxypropyl methyl cellulose is easily soluble in cold water, and will encounter difficulties when dissolved in hot water. Its gelation temperature in hot water is significantly higher than that of methyl cellulose. The dissolution in cold water is also greatly improved compared to methyl cellulose.
2. The viscosity of hydroxypropyl methyl cellulose is related to its molecular weight, large molecular weight is high viscosity. Temperature also affects its viscosity, and the viscosity decreases when the temperature rises. However, its viscosity is less affected by temperature than that of methyl cellulose. Its solution is stable when stored at room temperature.
3. The water retention of hydroxypropyl methyl cellulose depends on its additive amount, viscosity, etc., and the water retention rate is higher than that of methyl cellulose under the same additive amount.
4. Hydroxypropyl methyl cellulose is stable to acid and alkali, and its aqueous solution is very stable in the range of pH=2~12. Caustic soda and lime water do not have much effect on its performance, but alkali can accelerate its dissolution rate. Hydroxypropyl methyl cellulose has stability to general salts, but when the concentration of salt solution is high, the viscosity of hydroxypropyl methyl cellulose solution will have a tendency to increase.
5. Hydroxypropyl methyl cellulose can be mixed with water-soluble polymer compounds to become uniform, higher viscosity solution. Such as polyvinyl alcohol, vegetable gum, etc.
6. Hydroxypropyl methyl cellulose has better enzyme resistance than methyl cellulose, and the possibility of enzymatic degradation of its solution is lower than that of methyl cellulose. Hydroxypropyl methyl cellulose adhesion to mortar construction is higher than methyl cellulose.
Methyl cellulose (MC)
Methyl cellulose is refined cotton treated with alkali and then made into cellulose ether through a series of reactions using methylene chloride as the etherifying agent. The general degree of substitution is 1.6~2.0, and the solubility varies with the degree of substitution. It belongs to non-ionic cellulose ether.
1. Methyl cellulose is soluble in cold water, hot water solubility will encounter difficulties, and its aqueous solution is very stable in the range of pH=3~12. It is compatible with starch, guanidinium gum, etc. and many surfactants. When the temperature reaches the gelation temperature, gelation will occur.
2. The water retention of methyl cellulose depends on its addition amount, viscosity, particle fineness and dissolution speed. Generally the larger the addition amount, the smaller the fineness and the larger the viscosity, the higher the water retention rate. The viscosity is not directly proportional to the water retention rate. The dissolution rate mainly depends on the degree of surface modification of cellulose particles and particle fineness. Among the several cellulose ethers introduced in this paper, methyl cellulose and hydroxypropyl methyl cellulose have higher water retention rates.
3. Changes in temperature can seriously affect the water retention of methyl cellulose. Generally the higher the temperature, the worse the water retention. If the mortar temperature exceeds 40 ', the water retention of methyl cellulose will be significantly worse, seriously affecting the constructability of mortar.
4. Methyl cellulose has a significant impact on the construction and adhesion of mortar. The 'adhesion' refers to the adhesion between the applicator and the wall substrate, i.e. the shear resistance of the mortar. Adhesion is large, the shear resistance of the mortar is large, the force required by the workers in the process of application is also large, and the constructability of the mortar is poor. In the cellulose ether products methyl cellulose adhesion is at a medium level.
Hydroxyethyl cellulose (HEC)
Hydroxyethyl cellulose is made from refined cotton treated with alkali and reacted in the presence of acetone with ethylene oxide as the etherifying agent. Its substitution degree is generally 1.5~2.0. It has strong hydrophilicity and is easy to absorb moisture.
1. Hydroxyethyl cellulose can be dissolved in cold water, hot water is more difficult to dissolve. Its solution is stable at high temperature and does not have gelation. It can be used for a longer time in mortar under high temperatures, but the water retention is lower than methyl cellulose.
2. hydroxyethyl cellulose has the stability to general acid and alkali, alkali can accelerate its dissolution, and can slightly increase viscosity, its dispersion in water than methyl cellulose and hydroxypropyl methyl cellulose is slightly worse.
3. Hydroxyethyl cellulose has good performance on mortar anti-hanging, but the retardation time of cement is longer.
4. The performance of hydroxyethyl cellulose produced by some Chinese enterprises is significantly lower than that of methyl cellulose due to high water content and high ash content.
Carboxymethyl cellulose (CMC)
Carboxymethyl cellulose is made from natural fiber (cotton, etc.) after alkali treatment, with sodium monochloroacetate as the etherifying agent, after a series of reaction processing and made of ionic cellulose ether. Its substitution degree is generally 0.4~1.4, and the performance is greatly affected by the substitution degree.
1. Carboxymethyl cellulose is more hygroscopic and will contain more water when stored in general conditions.
2. Carboxymethyl cellulose aqueous solution will not produce gel, with the increase in temperature and viscosity decline, the temperature exceeds 50 ', the viscosity will be irreversible.
3. The stability of carboxymethyl cellulose is greatly affected by pH. Generally it can be used in gypsum-based mortar, not in cement-based mortar. At high alkalinity, it will lose viscosity.
4. The water retention of carboxymethyl cellulose is much lower than methyl cellulose. It has retardation effect on gypsum-based mortar and reduces its strength. However, the price of carboxymethyl cellulose is significantly lower than methyl cellulose.
Hydroxypropyl Methylcellulose (HPMC) and its derivatives, including Methylcellulose (MC), Hydroxyethyl Cellulose (HEC), and Carboxymethyl Cellulose (CMC), are widely used in various industries for their unique properties and functionalities.Understanding the differences between these compounds is crucial for optimizing their utilization in different sectors, ranging from pharmaceuticals and food to construction and personal care.
Cellulose derivatives are indispensable in numerous industries due to their versatile properties and applications. Among these derivatives, Hydroxypropyl Methylcellulose (HPMC), Methylcellulose (MC), Hydroxyethyl Cellulose (HEC), and Carboxymethyl Cellulose (CMC) stand out for their widespread use and distinct characteristics.
1.Chemical Structures:
Hydroxypropyl Methylcellulose (HPMC):
HPMC is synthesized from cellulose through chemical modification involving the substitution of hydroxyl groups with methyl and hydroxypropyl groups. The degree of substitution (DS) determines its properties, including viscosity and solubility. HPMC's chemical structure imparts good film-forming properties and water retention capabilities, making it suitable for various applications.
Methylcellulose (MC):
MC is derived from cellulose by substituting hydroxyl groups with methyl groups. Unlike HPMC, MC lacks hydroxypropyl groups. Its properties are influenced by factors such as degree of substitution and molecular weight. MC exhibits excellent water retention and thickening properties, making it valuable in industries like pharmaceuticals and food.
Hydroxyethyl Cellulose (HEC):
HEC is synthesized by etherification of cellulose with ethylene oxide. The introduction of hydroxyethyl groups imparts unique properties such as high thickening efficiency and pseudoplasticity. HEC is widely used in personal care products, paints, and adhesives due to its rheological control and film-forming capabilities.
Carboxymethyl Cellulose (CMC):
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CMC is produced by reacting cellulose with chloroacetic acid or its sodium salt. Carboxymethyl groups are introduced, enhancing properties such as water solubility, viscosity, and stability. CMC finds applications in food, pharmaceuticals, and oil drilling due to its thickening, stabilizing, and binding properties.
2.Properties:
Viscosity:
HPMC, MC, HEC, and CMC exhibit varying viscosity levels depending on factors like degree of substitution, molecular weight, and concentration. Generally, HPMC and MC offer superior viscosity control compared to HEC and CMC, with HEC providing high thickening efficiency at lower concentrations.
Water Retention:
HPMC and MC possess excellent water retention capabilities, crucial for applications requiring moisture retention and prolonged release. HEC also exhibits good water retention properties, while CMC offers moderate water retention due to its high solubility.
Film Formation:
HPMC and HEC are known for their film-forming abilities, enabling the development of coherent and flexible films. MC, although capable of forming films, may exhibit brittleness compared to HPMC and HEC. CMC, primarily used as a thickening and stabilizing agent, has limited film-forming properties.
Solubility:
All four cellulose derivatives are water-soluble to varying extents. HPMC, MC, and CMC dissolve readily in water, while HEC exhibits lower solubility, requiring higher temperatures for dissolution. Additionally, the degree of substitution influences the solubility of these derivatives.
3.Applications:
Pharmaceuticals:
HPMC and MC are extensively used in pharmaceutical formulations as binders, disintegrants, and controlled-release agents due to their biocompatibility and sustained release properties. HEC finds applications in ophthalmic solutions and topical formulations owing to its clarity and viscosity control. CMC is employed in oral suspensions and tablets for its thickening and stabilizing effects.
Food Industry:
CMC plays a crucial role in the food industry as a thickener, stabilizer, and fat replacer in products like ice cream, sauces, and bakery items. HPMC and MC are utilized in food formulations for their thickening, gelling, and water-binding properties. HEC is less common but may be used in specialized applications such as low-calorie foods and beverages.
Construction:
HPMC is widely employed in construction materials such as cementitious mortars, tile adhesives, and gypsum-based products due to its water retention, workability enhancement, and adhesive properties. MC is also utilized in similar applications, contributing to improved consistency and cohesion. HEC finds limited use in construction due to its higher cost compared to HPMC and MC.
Personal Care Products:
HEC and HPMC are prevalent in personal care products like shampoos, lotions, and creams as thickening agents, stabilizers, and film formers. Their compatibility with a wide range of cosmetic ingredients and their ability to enhance product performance make them indispensable in formulations. CMC may be used in niche applications within the personal care industry due to its stabilizing and thickening properties.
4.Industrial Significance:
The significance of HPMC and its derivatives lies in their multifunctionality and adaptability across various industries. These cellulose derivatives serve as vital components in formulations, contributing to product quality, performance, and functionality. Their diverse properties make them indispensable in sectors such as pharmaceuticals, food, construction, and personal care, driving innovation and market growth.
Hydroxypropyl Methylcellulose (HPMC) and its derivatives, including Methylcellulose (MC), Hydroxyethyl Cellulose (HEC), and Carboxymethyl Cellulose (CMC), offer unique properties and functionalities suited to a wide range of applications. While these cellulose derivatives share commonalities in terms of chemical origin and water solubility, they exhibit distinct characteristics in terms of viscosity, water retention, film formation, and solubility. Understanding these differences is essential for optimizing their utilization across industries, fostering innovation, and driving economic growth.
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