104

Original Research Paper

J. Jpn. Soc. Colour Mater., 96〔3〕，104–107（2023）

Oil-Gelling Ability of the Mixture of Plant-Derived Highly Purified Paraffin Waxand Botanical Waxes
Kirara Nagatsu＊, Chihiro Izawa＊ and Masashi Shibata＊,†＊School of Bioscience and Biotechnology, Tokyo University of Technology, 1404-1 Katakura-machi, Hachioji-shi, Tokyo 192-0982, Japan†Corresponding Author, E-mail: mshibata@stf.teu.ac.jp(Received November 30, 2022; Accepted January 25, 2023 )Abstract
Oil gels composed of oils and waxes are used in stick cosmetics. Recently, modification of petroleum-derived waxes to botanical waxes hasbecome desirable; however, the gel hardness of these gels is insufficient. Therefore, to improve the gel hardness of rice paraffin wax (RP-wax),
a highly purified botanical wax, the mixing effect with other botanical waxes, namely carnauba wax and rice bran wax, was investigated.
RP-wax has a lower gel hardness than petroleum-derived paraffin waxes because of the formation of large plate crystals in the gel. The gelhardness of carnauba wax is very low owing to the existence of spherical clusters composed of small crystallites in the gel. However, whenRP-wax was mixed with 20% carnauba wax, its gel hardness significantly improved. This was due to the size reduction of plate crystals in
the gel and the disappearance of the spherical clusters derived from carnauba wax. However, rice bran wax did not produce a similar effect.
Key-words: Rice paraffin wax, Carnauba wax, Oil gel, Gel hardness, Wax crystal

1．Introduction
Oil gels are obtained by heating and mixing oils andsolid waxes, followed by cooling. They are mainly usedin stick cosmetics, such as lipsticks, foundations, andantiperspirants1). Hydrocarbon waxes, such as paraffin waxes
and synthetic waxes, are mainly used as gelling agents foroil gels 2,3 ). However, the replacement of hydrocarbon waxes
by botanical waxes from the point of view of substitution by
renewable resources and regulation of petroleum- or mineralderived ingredients in the cosmetic industry is desired.
However, the oil gel hardness of botanical waxes (such as
rice bran wax, carnauba wax, and candelilla wax) is much
lower than that of petroleum-derived waxes 4 ). Many studies
have been conducted to improve the gel hardness of botanicalwax. Mixing different types of waxes sometimes causes gel
hardness to vary. For example, a mixture of higher alcohols
and fatty acids 5 ), a mixture of candelilla wax and carnauba
wax 4 ), the addition of high-purity esters to candelilla wax 6 ),and the addition of high-melting-point alcohols to rice bran
wax 7 ), can improve gel hardness.
Gel hardness can be increased by removing impurities
from the botanical waxes and obtaining only the maincomponent. Currently, highly purified botanical waxes, suchas hydrocarbon and ester mixture extracted from candelillawax, and hydrocarbon extracted from rice bran wax arecommercially available. However, the gel hardness of thesehighly purified waxes is still lower than that of commercial
hydrocarbon waxes.
© 2023 Journal of the Japan Society of Colour Material

In this study, we investigated the effect of rice paraffin
wax, a highly purified botanical wax, on gel hardness whenmixed with other botanical waxes. Rice paraffin wax is asolid hydrocarbon obtained from the portion discarded during
rice oil production by using liquid-phase chromatography.

2．Materials and Methods
Rice paraffin wax (Phytochemical Products Inc., RPwax) was used as the highly purified wax. Rice bran wax(Rice bran wax S-110, Yokozeki Oil & Fat Industries Co.,
Ltd.) and carnauba wax (TOWAX-1F3, Cerarika Noda Co.,
Ltd.) were used as the typical botanical waxes. Paraffin wax(HNP-9, Nippon Seiro Co., Ltd.) was used for comparison.
Caprylic/capric triglyceride (O.D.O, The Nisshin Oillio
Group, Ltd.) was used as a plant-derived oil. The wax and oil
were mixed at a weight ratio of 15/85.
Wax ( 1.5 g) and 8.5 g of oil were placed in a 100 mL
glass beaker and stirred on a hot plate at 90 °C for 30 min.
The mixture was poured into a polycarbonate cylindricalcontainer with a diameter of 3 cm and a height of 1 cm andallowed to stand at 25 ℃ for 24 h.
The hardness of the obtained oil wax gel was measured
using a gel hardness meter (Rheotex SD 700, Sun ScientificCo., Ltd.) equipped with a spherical plunger of 5 mm indiameter. The plunger was inserted 2.5 mm into the gelwith a speed of 30 mm/min, and the maximum stress wasmeasured.
The wax crystals in the gel were observed by scanningelectron microscopy ( SEM, JSM- 6060 LV, JEOL Ltd. )－10－