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Comparison of hydroxypropyl methylcellulose and carboxymethylcellulose

Views: 2     Author: Site Editor     Publish Time: 2022-11-29      Origin: Site

Let me explain from the application, properties, traits, price and other aspects of hydroxypropyl methylcellulose and carboxymethyl cellulose.

Carboxymethyl cellulose and hydroxypropyl methyl cellulose have similar uses but are much different in price?

1. The uses of carboxymethyl cellulose and hydroxypropyl methyl cellulose are only similar, but their functions are very different, and the technical indicators of the two are far apart.

2. The main raw materials of the two are the same refined cotton, but their auxiliary materials, production equipment, and process flow are different. The production equipment and process of hydroxypropyl methylcellulose are much more complicated.

3. Carboxymethyl cellulose has been developed in China for decades, and the technology, equipment, and processes are very mature, so the cost is also low.

Carboxymethyl cellulose and hypromellose are also processed from refined cotton as the main raw material. The two are not a kind of production process at all, and other accessories are also different, so the uses are also different. If it is used as a putty additive, CMC cannot be added to the putty with gray calcium and white cement. To use HPMC as the water retaining agent and improve their workability, HPMC is widely used in the field of putty, while CMC is only suitable for ordinary putty, such as large white putty, 821 putty, etc.

The first is the introduction of hydroxypropyl methylcellulose: hydroxypropyl methylcellulose HPMC where n is the degree of polymerization, R is H, -CH3 or -CH2CHCH3OH

Product performance and application of hydroxypropyl methylcellulose HPMC:

Hydroxypropyl methylcellulose is a non-ionic water-soluble cellulose ether polymer, odorless, tasteless, non-toxic, white or off-white powder, can be used in food, medicine, daily chemicals, coatings, polymerization reactions and construction etc. With the decrease of methoxyl content, the gel point of HPMC increases, the water solubility decreases, and the surface activity also decreases.

1. Water solubility: It can be dissolved in water in any proportion, and its concentration depends on the viscosity.

2. No ionic charge: It is non-ionic and will not combine with metal salts and ionic organics to form insoluble precipitates.

3. Organic solubility: Depending on the degree of substitution, it can be dissolved in a series of solvent systems composed of two organic substances and a solvent system of organic substances and water, making it uniquely compatible with water and organic substances.

4. Thermal gelation: When their aqueous solutions are heated to a certain temperature, they form a gel, and the formed gel turns into a solution again after cooling.

5. Surface activation: Provide surface activity in the solution to achieve the required emulsification and protective colloid, as well as phase stabilization.

6. Suspension: It can prevent the precipitation of solid particles, thus inhibiting the formation of sediment.

7. Protective colloid: it can prevent droplets and pellets from coalescing or coagulating.

8. Bonding: It can be used as an adhesive for pigments, tobacco products, and paper. It has excellent performance and can also be used in paints.

9. Metabolic inertia: Used as food and drug additives, they will not be metabolized and will not provide calories in food.

10. Enzyme resistance: It has good enzyme resistance and good viscosity stability during long-term storage.

11. PH stability: it has a wide range of PH value, PH3.0—11.0

12. Water retention: When used on porous surfaces such as walls, cement boards, and bricks, it can retain water.

13. Thickening: Its aqueous solution has thickening properties, and the thickening degree is related to the viscosity of the product used and the type of compound.

14. Film formation: It can be made into a transparent, tough and soft film with good oil resistance.

15. Lubrication: It can be used in rubber, asbestos, cement and ceramic products to reduce friction and improve concrete pumpability.

16. Emulsification: It can stabilize the emulsion by reducing the interface and surface tension and thickening the water phase.

Followed by the introduction of sodium carboxymethyl cellulose:

Properties of carboxymethyl cellulose:

1. CMC is a cellulose ether. Pure white or yellowish fibrous powder or granule, odorless, tasteless, non-toxic, but general industrial products contain sodium hydroxide, sodium oxide and sodium glycolate and other impurities, so they are slightly yellow and taste salty, and the CMC usually used is insoluble In acid and organic solvents such as methanol, ether, acetone, chloroform, stupid, etc., it is easily soluble in water and forms a colloidal solution. The degree of substitution is an important factor for its water solubility, and the viscosity has a great influence on water solubility. Usually, the viscosity is between About 250-500 centipoise, the degree of substitution is about 0.3, and gradually becomes alkali-soluble, and the degree of substitution is greater than 0.4, which means water-soluble. As the degree of substitution increases, the transparency of the solution also improves accordingly. CMC has the same properties as other ionic electrolytes, and it will first swell when it dissolves. Therefore, when preparing the solution, if the particles are uniformly wetted, they can be dissolved quickly, otherwise CMC will swell in water. Particles adhere to each other to form a strong film or stick to micelles, so that it is difficult to disperse and dissolve.

2. CMC is hygroscopic. The equilibrium moisture of CMC increases with the increase of air humidity and decreases with the increase of temperature. When the room temperature and average temperature are 80-85%, the equilibrium moisture is above 26%, and the product moisture is about 7%. Low balance moisture. Even if its shape contains about 15% water, there is almost no difference in appearance, but when the water content is above 20%, it can be seen that some stickies adhere to each other, especially those with high viscosity.

3. The important characteristic of CMC is that it can form a high viscosity colloidal solution. The main factors that can affect its viscosity are: concentration, pH, temperature, degree of substitution and salts.

(1) The effect of concentration on viscosity: Whether it is low, medium or high viscosity CMC, its viscosity curve rises approximately linearly with the increase of concentration, especially for high viscosity.

(2) The influence of pH value on viscosity: when the CMC solution is at pH6.5-9.0, its viscosity is high and stable. Generally, the viscosity does not change too much in the range of PH6.0-11.0. When the pH of medium viscosity and high viscosity is greater than 11.5, it will drop sharply, and the effect of low viscosity is less.

4. Calcium salts and magnesium salts cannot cause the CMC solution to precipitate, but can reduce its viscosity (crude CMC containing impurities such as sodium hydrochloride, sodium carbonate, sodium sulfate, etc., its impurities will meet with calcium salts, magnesium salts will produce precipitation).

5. The stability of CMC is better, and the one with high substitution degree is more stable. However, the viscosity of the CMC solution will decrease during storage, and the rate of decrease will vary with the product, so it is not suitable for long-term storage after being formulated into a solution.

6. Viscosity. Viscosity is an important physical and chemical index of carboxymethyl cellulose (referring to the viscosity of its aqueous solution). Since it is mostly formulated into a colloidal solution when used, the viscosity is the decisive factor for the colloidal solution. The viscosity is directly related to the degree of polymerization. The viscosity of methyl cellulose is essentially a concrete manifestation of the degree of polymerization of cellulose. It is worth noting that the aqueous solution of carboxymethyl cellulose is non-Newtonian (Non-Newtonian), which is manifested in two aspects of pseudoplasticity (Pseudo Plasicity) and thixotropy (Thixatsopy). Pseudoplasticity is because the carboxymethyl group is not evenly substituted into the cellulose molecular chain, so when measuring the viscosity, although the same solution uses a relatively large shear stress to cause a high flow rate, the resulting viscosity is smaller than that of a smaller shear stress that causes the occurrence As a result of slower flow rate, the phenomenon of thixotropy is that when the carboxymethyl cellulose solution is left to stand for a certain period of time, the viscosity of the solution with small thixotropy will increase slightly, and the solution with large thixotropy will even condense into a jelly-like state. Vigorous stirring destroys the jelly structure, and then proper stirring can restore the original viscosity. There are many factors affecting viscosity, such as pH, temperature, heating time, storage time, etc., among which the main factor is the solution storage time. Therefore, the method of measuring viscosity must be consistent in order to obtain consistent results and repeatability.

Carboxymethyl Cellulose Uses:

CMC has a wide range of uses, non-toxic, non-corrosive, harmless to the human body, does not pollute the environment, has strong cohesive force, does not mildew, and does not grow insects. It can be used as an emulsifier, thickener, stabilizer, sizing agent, and Membranes, adhesives, etc.

1. Application of cellulose CMC for tobacco flakes: The cellulose for tobacco flakes modified by CMC is non-toxic, odorless, white in appearance, flocculent powder, and its aqueous solution is a neutral transparent viscous liquid.

2. Application of architectural decoration: spraying on large white, spraying lime slurry, gypsum putty, cement putty, talcum powder putty, 821 putty powder, imitation porcelain putty, paint spraying, rolling coating, bullet coating, brushing, art decoration Surface, plastering, wallpaper, wall covering, floor tiles, ceramic tiles, ceramic mosaic tiles, etc.

3. Application in synthetic detergent and soap industry: CMC is a good active agent for synthetic detergent. It is mainly used in detergents to make use of its emulsifying and protective colloidal properties. During the washing process, it produces anions that can simultaneously make the surface of the object to be washed and the dirt particles negatively charged, so that the dirt particles have phase separation in the water phase, and are compatible with The surface of the solid-phase object to be washed has repellency, so it can prevent dirt from re-depositing on the object to be washed, and can keep white fabrics white, and colored fabrics are bright in color. After adding 2% HLO5 type CMC to the detergent, the detergent The whiteness of white fabric can be kept above 90%.

The above is the properties and uses of hydroxypropyl methylcellulose and carboxymethyl cellulose, so it can be seen that HPMC and CMC are two different substances with different uses and properties.