Hypromellose (

INN Inns are generally establishments or buildings where travelers can seek lodging, and usually, food and drink. Inns are typically located in the country or along a highway. Before the advent of motorized transportation, they also provided accomm ...

), short for hydroxypropyl methylcellulose (HPMC), is a

semisynthetic Semisynthesis, or partial chemical synthesis, is a type of chemical synthesis that uses chemical compounds isolated from natural sources (such as microbial cell cultures or plant material) as the starting materials to produce novel compounds with ...

, inert, viscoelastic

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

used in eye drops, as well as an

excipient An excipient is a substance formulated alongside the active ingredient of a medication. They may be used to enhance the active ingredient’s therapeutic properties; to facilitate drug absorption; to reduce viscosity; to enhance solubility; to i ...

and controlled-delivery component in oral medicaments, found in a variety of commercial products. As a

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...

, hypromellose is an

emulsifier An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althou ...

thickening A thickening agent or thickener is a substance which can increase the viscosity of a liquid without substantially changing its other properties. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering their ...

and suspending agent, and an alternative to animal gelatin. Its

Codex Alimentarius The is a collection of internationally recognized standards, codes of practice, guidelines, and other recommendations published by the Food and Agriculture Organization (FAO) and World Health Organization (WHO) of the United Nations relating to f ...

code (

E number E numbers, short for Europe numbers, are codes for substances used as food additives, including those found naturally in many foods, such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly ...

) is E464.

Chemistry

Hypromellose is a solid, and is a slightly off-white to beige powder in appearance and may be formed into granules. The compound forms

colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exte ...

s when dissolved in water. This non-toxic ingredient is combustible and can react vigorously with

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ''electron donor''). In ot ...

s. Hypromellose in an aqueous solution, like

methylcellulose Methyl cellulose (or methylcellulose) is a compound derived from cellulose. It is sold under a variety of trade names and is used as a thickener and emulsifier in various food and cosmetic products, and also as a bulk-forming laxative. Like cell ...

, exhibits a thermal gelation property. That is, when the solution heats up to a

critical temperature Critical or Critically may refer to: *Critical, or critical but stable, medical states **Critical, or intensive care medicine *Critical juncture, a discontinuous change studied in the social sciences. *Critical Software, a company specializing in ...

, the solution congeals into a non-flowable but semi-flexible mass. Typically, this critical (congealing) temperature is inversely related to both the solution concentration of HPMC and the concentration of the methoxy group within the HPMC molecule (which in turn depends on both the degree of substitution of the methoxy group and the molar substitution). That is, the higher the concentration of the methoxy group, the lower the critical temperature. The inflexibility/viscosity of the resulting mass, however, is directly related to the concentration of the methoxy group (the higher the concentration is, the more viscous or less flexible the resulting mass is).

Uses

There are many fields of application for hypromellose, including: * Tile adhesives * Cement renders * Gypsum products * Pharmaceutical * Paints and coatings * Food * Cosmetics * Detergents and cleaners * Eye drops * Contact lenses * Polyvinyl Chloride (PVC)

Use in whole grain breads

Agricultural Research Service The Agricultural Research Service (ARS) is the principal in-house research agency of the United States Department of Agriculture (USDA). ARS is one of four agencies in USDA's Research, Education and Economics mission area. ARS is charged with ext ...

scientists are investigating using the plant-derived HPMC as a substitute for

gluten Gluten is a structural protein naturally found in certain Cereal, cereal grains. The term ''gluten'' usually refers to the elastic network of a wheat grain's proteins, gliadin and glutenin primarily, that forms readily with the addition of water ...

in making all-oat and other grain breads. Gluten, which is present in wheat, rye, and barley, is absent (or present only in trace quantities) in oat and other grains. Like gluten, HPMC can trap air bubbles formed by the yeast in bread dough, causing the bread to rise.

Use in construction materials

HPMC is used primarily in construction materials like tile adhesives and renders where it is used as a

rheology Rheology (; ) is the study of the flow of matter, primarily in a fluid (liquid or gas) state but also as "soft solids" or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applie ...

modifier and water retention agent. Functionally HPMC is very similar to HEMC (hydroxy ethyl methyl cellulose) Trade names include Methocel and Walocel. The global leading producer is now DuPont, formerly manufactured under Dow Wolff Cellulosics GmbH.

Ophthalmic applications

Hypromellose solutions were patented as a semisynthetic substitute for tear-film. Its molecular structure is predicated upon a base celluloid compound that is highly water-soluble. Post-application, celluloid attributes of good water solubility reportedly aid in visual clarity. When applied, a hypromellose solution acts to swell and absorb water, thereby expanding the thickness of the tear-film. Hypromellose augmentation therefore results in extended lubricant time presence on the cornea, which theoretically results in decreased eye irritation, especially in dry climates, home, or work environments. On a molecular level, this polymer contains beta-linked D-glucose units that remain metabolically intact for days to weeks. On a manufacturing note, since hypromellose is a vegetarian substitute for gelatin, it is slightly more expensive to produce due to semisynthetic manufacturing processes. Aside from its widespread commercial and retail availability

over the counter Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...

in a variety of products, hypromellose 2% solution has been documented to be used during surgery to aid in corneal protection and during orbital surgery.

Excipient/tableting ingredient

In addition to its use in ophthalmic liquids, hypromellose has been used as an

in oral tablet and capsule formulations, where, depending on the grade, it functions as controlled release agent to delay the release of a medicinal compound into the digestive tract. It is also used as a

binder Binder may refer to: Businesses * Binder FBM, a former German jewelry manufactory * Binder Dijker Otte & Co., the expansion of "BDO" in BDO International Computing * Binder Project, package and share interactive, reproducible environments * Fil ...

and as a component of tablet

coatings A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings. Paints and ...

Test methods

Various benchmark tests are used to qualify hypromellose: *

Viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

* Degree of substitution (DS) * Molar substitution (MS) * Salt content * Moisture * Ash Content

Viscosity test methods

Because hypromellose solution is a non-newtonian solution and exhibits pseudoplastic, more specifically,

thixotropic Thixotropy is a time-dependent shear thinning property. Certain gels or fluids that are thick or viscous under static conditions will flow (become thinner, less viscous) over time when shaken, agitated, shear-stressed, or otherwise stressed ...

behavior, various test methods are available, and the results of different methods and viscosimeters do not necessarily correspond to each other. Also, due to viscometer acceptable ranges of error, viscosity is typically given as a mean, or as a range. Typical viscosity test will specify the following: *Solution concentration (1%, 2%, 1.9% bone dry, etc.) *Viscometer (RheoSense m-VROC and microVISC, Brookfield LV or RV, Höppler falling ball, Haake Rotovisco, etc.) *Viscometer spindle number (1 ~ 4 for Brookfield LV, 1 ~ 7 for Brookfield RV, etc.) *Solution Temperature (20 °C, 25 °C, etc.)

Degree of substitution

Degree of substitution is the average level of methoxy substitution on the cellulose chain. Since there are maximum three possible sites of substitution with each cellulose molecule, this average value is a real number between 0 and 3. However, degree of substitution is often expressed in percentages.

Molar substitution

Molar substitution is the average level of hydroxypropoxy substitution on the cellulose chain. Since hydroxypropoxy base can be attached to each other on side chains and does not each require a base substitution site on the cellulose molecule, this number can be higher than 3. However, molar substitution is also often expressed in percentages.

Moisture

Since all cellulose ethers are

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

, they will absorb moisture from surroundings if left exposed from original packaging. Thus, moisture must be tested and weight corrected to ensure adequate amount of dry active material are apportioned for usage. Moisture is tested by weighing a sample of X grams on an analytic scale, and drying the sample in an oven at 105 °C for 2 hours, then weighing the sample again on the same scale.

Ash Content

The content of active ingredients in HPMC is directly proportional to its cost-effectiveness, which means better performance at the same dosage. The active ingredient in HPMC is etherified cellulose, an organic substance. Its content can be measured by the ash content from calcined HPMC. Generally, a higher ash value indicates a lower content of active ingredients. Place the crucible with the dried HPMC sample into a furnace set to 550°C. During this process, the organic components of HPMC burn away, leaving behind only inorganic ash. Then you can calculate the ash content using the following formula: Content(%) = Weight of Ash(g) / Initial Sample Weight(g) x 100%

Top HPMC Manufacturers

Source: *Dow Inc - Materials Science & Chemical Manufacturing *Ashland Global - Ashland Inc. is an American chemical company headquartered in Wilmington, Delaware. *Lotte Fine Chemical - LOTTE Fine Chemical is a global specialty chemicals company, creating Lifetime Value. *Landu New Material co.,ltd - Committed to each gram *Shin-Etsu Chemical Co.- s the largest chemical company in Japan. *Landercoll - LANDERCOLL Precision for Tomorrow’s Industries *Nouryon

References

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External links

Methylcellulose & Hydroxypropyl Methyl Cellulose for building materials
Polysaccharides Edible thickening agents Cellulose Excipients Cellulose ethers E-number additives