Methylcellulose

Methyl cellulose is a white or off-white fibrous or granular powder; odorless and tasteless. Widely used in building construction, building materials, dispersive coatings, wallpaper pastes, polymerization aids, paint removers, leather, inks, papermaking, etc.Used as thickeners, adhesives, water-retaining agents, film-forming agents, forming Agent.

Methyl cellulose-basic information

Molecular composition and structural formula:

Quality standard: Q / SHD005-2002

English name: Methyl cellulose

Chinese alias: cellulose methyl ether

Based on the dry product, the methoxy group (—OCH3) should be 27.0% to 32.0%.

Properties: white or almost white fibrous or granular powder; odorless and tasteless. Swells into a clear or slightly cloudy colloidal solution in water; insoluble in absolute ethanol, chloroform or ether.

Storage and shelf life: sealed and stored in a dry place.

Category: Pharmaceutical Excipients.

Methyl cellulose-physical and chemical properties

Exterior

   MC is white or off-white fibrous or granular powder, odorless. The average molecular weight is 186.86n (n is the degree of polymerization), about 18,000 to 200,000.

Character

   MC is almost insoluble in absolute ethanol, ether, and acetone. It rapidly disperses and swells in hot water at 80 ~ 90> ℃, and dissolves quickly after cooling down. The aqueous solution is quite stable at normal temperature, can gel at high temperature, and the gel can change with the solution with the temperature. It has excellent wetting, dispersing, adhesive, thickening, emulsifying, water-holding and film-forming properties, and impermeability to oils and fats. The formed film has excellent toughness, flexibility and transparency. Because it is non-ionic, it can be compatible with other emulsifiers, but it is easy to salt out and the solution is stable in the range of PH2-12.

Apparent density: 0.30-0.70g / cm3, density is about 1.3g / cm3.

The theoretical substitution degree DS of methyl cellulose in industry is 1.5 ~ 2.0, and the bulk density is 0.35 ~ 0.55g / cm3.

Methyl cellulose-quality index

Appearance: off-white fibrous to powdery rice

Gel temperature (2% aqueous solution): 50 ～ 55 ℃

Methoxy content: 26% ～ 33%

Water insoluble matter ≤2.0%

Degree of substitution (DS) 1.3 ～ 2.0

Moisture ≤5.0%

Viscosity (20 ℃, 2% aqueous solution) 15 ～ 4000mPa.s

Methyl cellulose-identification

(1) Take an appropriate amount of 1% aqueous solution of this product, and place it in a test tube, slowly add 2ml of 0.0355% anthrone sulfuric acid solution along the tube wall, place it, and show a blue-green ring at the interface between the two liquids. (2) Take 10ml of 1% aqueous solution of this product and heat it to produce a mist or flake precipitate. After cooling, the precipitate dissolves. (3) Take an appropriate amount of 1% aqueous solution of this product and pour it on a glass plate. After the water evaporates, a layer of tough film is formed.

Methyl cellulose-check

Methylcellulose

PH: Take 1.0g of this product, add 100ml of water to dissolve it, and measure it according to law (Appendix VI H). The pH value should be 4.0 ～ 8.0. Viscosity, take an appropriate amount of this product, calculate it as dry product, add water at 90 ° C to make a 2.0% (g / g) solution, and stir well for about 10 minutes. Cool in an ice bath. Continue stirring during the cooling process, keep it for another 40 minutes, adjust the weight, and stir well. Measure at 20 ° C ± 0.1 ° C with a rotary viscometer (Appendix VI G Second Method), and indicate the viscosity is less than or equal For 100mPa.s, the viscosity should be 80.0% to 120.0% of the marked viscosity, and for those with a viscosity greater than 100mPa.s, the viscosity should be 75.0% to 140.0% of the marked viscosity. Loss on drying Take this product and dry it at 105 ℃ for 2 hours. The weight loss should not exceed 5.0% (Appendix Ⅷ L). Ignition residue Take 1.0g of this product and inspect it according to law (Appendix Ⅷ N). The residual residue shall not exceed 1.0%. Heavy metal Residues left under the item of burning residue shall be inspected according to law (Appendix ⅧH second method), and the content of heavy metals shall not exceed 20 parts per million. For arsenic salt, take 1.0g of this product, add 1.0g of calcium hydroxide, mix, add water and stir well. After drying, first burn with a low fire to carbonize, and then burn at 500-600 ℃ to completely ash, let cool, add 8ml of hydrochloric acid and 23ml of water shall be inspected according to law (Appendix Ⅷ J First Law) and shall meet the requirements (0.0002%).

Methyl cellulose-determination

Take this product, weigh it accurately, and measure it according to methoxy method.

Methyl cellulose-dissolution method

Methylcellulose

   MC> The product is directly added to the water, which will cause agglomeration, and then dissolve, but the dissolution is very slow and difficult. Three methods of dissolution are suggested below, and users can choose the most convenient method according to the use situation:

    I. Hot water method: Because MC is not dissolved in hot water, MC can be evenly dispersed in hot water at the initial stage. When cooling, the two typical methods are described as follows:

   1. Put the required amount of hot water in the container and heat it to about 70 ° C. MC was gradually added with slow stirring, MC began to float on the surface of water, and then gradually formed a slurry, and the slurry was cooled with stirring.

   2. Add the required amount of 1/3 or 2/3 of water to the container and heat to 70 ° C. Disperse the MC according to 1) to prepare a hot water slurry; then add the remaining amount of cold or ice water to In a hot water slurry, the mixture was cooled after stirring.

Powder mixing method: MC powder particles and equivalent or larger amounts of other powdery ingredients are fully dispersed by dry mixing, and then dissolved by adding water, then MC can be dissolved without agglomeration.

   3. Organic solvent wetting method: Disperse or wet MC with an organic solvent such as ethanol, ethylene glycol or oil before dissolving it with water. At this time, MC can also be dissolved smoothly.

Methyl cellulose-uses

   Used as a thickener for water-soluble adhesives, such as thickeners for neoprene latex.

   It can also be used as dispersant, emulsifier and stabilizer for vinyl chloride and styrene suspension polymerization. MC with DS = 2.4 ～ 2.7 is soluble in polar organic solvents, which can prevent the solvent (dichloromethane-ethanol mixture) from volatilizing.

   It is also widely used in building construction, building materials, dispersive coatings, wallpaper pastes, polymerization assistants, paint removers, leather, inks, papermaking, etc., respectively as thickeners, adhesives, water-retaining agents, film-forming agents, and coatings. Shape agent and so on. For example, it is used as a binder, thickener and water-retaining agent in building materials, as a film-forming agent and thickener in the coating industry, and it is also widely used in petroleum drilling and daily chemical industries.