Cellulose ether- thickening mechanism.pdf - TECHNICAL...

TECHNICAL INFORMATION
Hercules does not recommend any use of its products that would violate any patent or other rights.
Aqualon, a Division of Hercules Incorporated
Widnes/Uk, Rijswijk/NL, Düsseldorf/D, Le Pecq/F,
Castelmaggiore (BO)/I, Tarragona/E, Warsaw/PL
62.050-E1
Reprint SÖFW 15/1994 page 1 of 6
Lecture J.J. de Bruin* at the IN-Cosmetics 1994 1994
Barcelona - Spain
Hydrophobically modified Cellulose Ether for Personal Care
Introduction
Cellulose ethers are well known for their thickening and rheology modifying properties. These are in fact
only a few of the many functions of this versatile raw material. Examples thereof are found in various toiletry
articles (Fig. 1). Besides as thickener, the cellulosics can act herein as foam booster, or have lubricating
properties that give the formulation a silky feel. Another example is the thermoplastic property of
hydroxypropylcellulose in combination with its film forming ability. These properties can be useful in styling
formulations. In combination with synthetic resins it will render high hold styling products with a soft, non
tacky feel due to the flexible film that Klucel forms
(1)
.
In the rapid changing personal care market, mildness and ecotoxicological aspects are becoming important
criteria when it comes to the selection of raw materials. Cellulosics are meeting these criteria as they are
made from renewable resources. As a result of a long experience in personal care applications they have
been reviewed as a safe cosmetic ingredients in the present practice of use and concentration
(2)
.
In this paper information will be given on hydrophobically modified hydroxyethylcellulose, Natrosol

Plus
grade 330 CS, one of the latest new cellulose derivatives. A product with some unique properties which
cannot be matched by other cellulosics. It is good to know that ACT (associative cellulosic thickener), AT
(associative thickener) and HMHEC (hydrophobically modified hydroxyethylcellulose) are frequently used
abbreviations in literature. Both the Aqualon trade name and the latter term will be used in the rest of this
paper.
Chemistry
The starting material cellulose itself is insoluble in water. This is the result of the tight connection of the
paired cellulose chains via hydrogen bridges (Fig. 2). By etherification these bonds can be disrupted,
rendering soluble material. Prior to the etherification, the cellulose has to be made accessible to the reagent.
This can be done by swelling in alkali. In a second step this alkalicellulose reacts with ethyleneoxide. The
starting material for the HMHEC is a hydroxyethylcellulose (HEC) with a molecular weight of approximately
300 000 D. The hydroxyethyl molecular substitution, the average mole of substituents per anhydroglucose
unit, ranges from 3.0 to 3.7.
In a following step the hydrophobe is substituted onto this HEC backbone. The hydrophobe groups can be
C
8
to C
22
however, as implied by the CTFA nomenclature, they merely consist of cetyl groups.