Ethyl Cellulose

Ethylcellulose (EC) is a cellulose derivative that is insoluble in water but soluble in organic solvents.It is commonly used in pharmaceuticals as a binder for tablets and granules, increasing tablet hardness and reducing brittleness.

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Ethyl cellulose (EC)

EC (Ethyl cellulose)

EC is white to off-white granules or powder, odorless, tasteless, caloric, metabolically inert, and a 5% suspension of this product is neutral to litmus paper.
The unique properties of various ethyl celluloses are determined by the number of anhydroglucose units n in the polymer chain and the degree of ethoxy substitution DS, which is usually 2.4-2.6.

Product Parameters

Item	Index
	K series	N series	T series
Ethoxy Wt%	45.5 - 46.8	47.5 - 49.5	49.5 or more
Drying weight loss Wt%	≤3.0
Burning residue Wt%	≤0.4
Heavy metal ppm	≤10
Arsenic Ppm	≤3
Ammoniates Wt%	≤0.1
Acetaldehyde Wt%	≤0.01

Complies with the 2020 edition of the Chinese Pharmacopoeia (Part 4); Registration Number: F20170000436/F20209990406

Viscosity classification

Viscosity measurement conditions: 20±0.1°C, Pinnacle capillary assay: Solvent concentration 5%

Solvent: Toluene : Ethanol = 80 : 20 mixture (weight ratio)

Typical grade	Viscosity( mPa.s, 5%)
TZN5	3-7
TZN7	6-9
TZN10	9-11
TZN20	18-22
TZN50	45-55
TZN100	90-110
TZN200	180-220

Note: Special specifications should comply with the marked viscosity ≥10 mpa.s, the viscosity should be 90.0-110.0% of the marked value; the marked viscosity between 6 - 10mpa.s, the viscosity should be 80.0-120.0% of the marked value; the marked viscosity ≤ 6mpa.s, the viscosity should be 75.0-140% of the marked viscosity.

Solubility and dissolution method of organic solvents

This product is slightly soluble in ethyl acetate, insoluble in water, glycerol, and propylene glycol; it can be dissolved in various organic solvents, such as dichloromethane, fatty alcohols (ethanol, isopropanol), other alcohols, ketones, aromatic hydrocarbons, etc.

Common solvents (volume ratio):

1.Dichloromethane: ethanol = 1:4 (or 1:1; 4:1)

2.Ethanol

3.Acetone: isopropanone = 65:35

4.Toluene: isopropanol = 4:1

5.Methyl acetate: methanol = 85:15

The viscosity in the mixture of alcohol and aromatic hydrocarbons decreases with the increase of alcohol content. When the alcohol accounts for 30-35%, the viscosity is the lowest.

Dissolution method: Slowly add EC into the container containing the solvent under stirring until it is completely wetted and dissolved.

Product Physicochemical characteristics

The pseudo specific gravity is 0.3-0.4g/cm³, the relative density is 1.07-1.18g/cm³, the softening point is 135-155°℃, it is insoluble in water but soluble in a variety of organic solvents, and forms a strong and tough film at low concentrations.
It is acid and alkali resistant, has excellent stability within the range of PH 3-11, and does not deteriorate after long-term storage.

It has good thermoplasticity and is compatible with many resins and plasticizers.

Membrane Properties

EC films are hard and insoluble in water. The properties depend on the viscosity, solvent, and type and amount of plasticizer.Generally, as the viscosity increases, the toughness of the film increases.

Effect of solvent: (temperature 25°C, 100ml solvent plus 20g plasticizer)

Solvents	Viscosity (mpa.s)	Tensile strength (MPa)
70 acetone/30 isopropyl ketone	671	42.7
65 acetone/35 isopropyl ketone	1066.7	41.2
80 methyl acetate/20 isopropyl ketone	785.6	36.1
50 methylene chloride/50 ethanol	1092.0	28.0

Application

Ethyl cellulose is insoluble in water but soluble in a variety of organic solvents, so it is often used as a binder for tablets and granules. It can increase the hardness of tablets and reduce their brittleness, while the film on the surface of the tablet is only thickened by 10-30um. It can also be used as a film-forming agent for coating materials to improve the appearance of tablets, isolate the taste, avoid the effectiveness of water-sensitive drugs, prevent the drugs from becoming damp and deteriorating, and enhance the safe storage of tablets. It can also be used as a skeleton material for skeleton sustained-release tablets, sustained-release pills, sustained-release microcapsules, etc., to play a release retardation role.

Product specifications and applications

Typical grade	Reference dosage	Application
TZN7	3%-20%	The sustained-release coating provides good diffusioncontroland can also be mixed with water-solubleHPMC to adiust the diffusion rate.
TZN10
TZN20
TZN50	10%-20%	Microcapsules
TZN20
TZN100
TZN7	1%-5%	Tablet floating layer, used as organic solvent coating to form a firm film with good adhesion, which can mask the taste of the drug. It is often used in combination with HPMC.
TZN10
TZN20
TZN10	2%-6%	Tablet granulation binder, used as solventgranulation for water-sensitive componentsproducing firm tablets with good dissolutionproperties.lts thermoplasticity facilitates extrusiongranulation.
TZN20

Production Process

The preparation method mainly includes two key steps: alkalization reaction and etherification reaction, as follows:

1. Alkalization reaction

‌Raw material treatment:Soak cellulose (such as cotton pulp or bleached wood pulp) in a NaOH solution with a concentration of 18%~25% to fully expand it to form alkali cellulose. The treatment temperature is usually 24~40℃ and the time is 3~3.5 hours.

‌Alkalization conditions‌: In a nitrogen atmosphere, cellulose is mixed with an inert solvent, a concentrated alkali solution and a solid alkali, and heated and stirred under sealing to obtain alkali cellulose.

2. Etherification reaction

‌Reaction process‌: Alkali cellulose is reacted with ethyl chloride in an autoclave. The reaction temperature gradually rises to 120~140℃, the pressure is maintained at 14.5 atmospheres, and the reaction time is 10~12 hours.

‌Control parameters‌: The etherification degree and viscosity of ethyl cellulose can be controlled by adjusting the amount of ethyl chloride, the reaction temperature and time.

3. Product extraction

Neutralization and washing: After the reaction is completed, cool to room temperature, add acid for neutralization, and wash the product with hot water to remove impurities.

Drying and molding: Dry the washed product to obtain white amorphous powdered ethyl cellulose.

4. Preparation of high-substituted ethyl cellulose

Optimization method: Use inert solvents and solid alkali to improve the utilization rate of etherification reagents, reduce side reactions, and obtain ethyl cellulose with high degree of substitution and uniform distribution of substituents.