Isopentyldiol for Improved Sensory, Formulation and Manufacturing Benefits

Jan 13, 2014 | Contact Author | By: Luigi Rigano, PhD, and Nicola Lionetti; Rigano Industrial Consulting and Research, Milan, Italy
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Title: Isopentyldiol for Improved Sensory, Formulation and Manufacturing Benefits
hydrotropex wetting agentx fillersx swellingx sensory ingredientx
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Keywords: hydrotrope | wetting agent | fillers | swelling | sensory ingredient

Abstract: A novel safe hydrotrope and wetting agent with exceptional skin feel is evaluated here for its solvent power and versatility in cosmetic formulas. Key features examined are sensory properties, hair feel modification and improvement of foam performance in skin cleansers.

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L Rigano and N Lionetti, Isopentyldiol for improved sensory, formulation and manufacturing benefits, Cosm & Toil 128(12) 874-883 (Dec 2013)

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Small molecular weight solvents are sought in cosmetics, as it is challenging to find molecules that are efficient, safe for the skin and eyes, scarcely flammable, versatile, sensorially acceptable and compatible with most common cosmetic ingredients, all at the same time. This is why water, ethanol, glycerin and propylene glycols have been used for decades in most cosmetic formulas. Cosmetically acceptable lipophilic solvents are even rarer. In relation, one category of solvents with good potential for cosmetic applications is amphiphilic polyols. Polyols are alcohols containing multiple hydroxyl groups in their structure; these occur naturally in plants and animals, and also are produced synthetically.

The most active industries producing new low molecular weight molecules are those working with isoprene and terpenoid structures. In nature, isoprene moieties are the building blocks for many complex molecules like terpenes and natural rubber. For industrial applications like pharmaceutical intermediates, as well as solvent blends and paints, extensive investigations on the human and environmental safety of new small size molecules have been conducted.

Of these molecules, isopentyldiol (IPD) has survived scrutiny for potential skin sensitization and irritation, eye irritation, genotoxicity and toxicity to fish, Daphnia and aquatic plants. Being subject to Japanese standards for quasi-drug ingredients, it also has been rated highly in terms of safety. Its safety profile together with interesting sensory properties make it a novel candidate for the personal care industry. Here, the authors investigate its properties for cosmetics and personal care applications via tactile evaluations; tests, in combination with sorbitol, to restore smoothness in damaged hair; and a skin moisturization evaluation for its capability to increase skin moisture levels.

Isopentyldiol Structure

A unique one-step synthesis technology was used to prepare isoprene from the C4 fraction of naphtha cracking, which was then put through stringent purification processes to eliminate volatile odorous fractions, yielding an original hydrophilic polyol. IPD has an isoprene diol structure. Specifically, it is a branched chain bi-alcohol with a five carbon atom backbone, described by the formula: 3-methyl-1,3-butanediol. Due to its amphiphilic molecular structure, relatively small molecular size and the presence of two strategically positioned hydroxyl groups, it can form both intra-molecular and extended intermolecular hydrogen bonds, depending on the surrounding vehicle. It also has superior affinity to the skin and acts as a skin humectant and hydrotrope, as will be shown.

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Table 1. Oils evaluated and resulting miscibility with IPD

Table 1. Oils evaluated and resulting miscibility with IPD

The materials used were characterized by chemical structures of increasing polarity—from hydrocarbons to silicones, ethers, esters, vegetal triglycerides and fatty alcohols—and chosen for their ease of handling; the selected oils and the observed results are reported here.

Table 2. Sensory evaluations

Table 2. Sensory evaluations

Generally, IPD increased spreading time and improved emollient feel and shine effects.

Table 3. Active principles tested and their solubility in IPD

Table 3. Active principles tested and their solubility in IPD

The selected active principles and solubility results are expressed in % w/w here.

Table 4. Maximum amount of water and oil added to transparency

Table 4. Maximum amount of water and oil added to transparency

Maximum amount of water and oil added to blends of active principles and IPD, leading to transparent solution

Table 5. Dispersant/solubilizing properties for silica powders of IPD, glycerin sorbitol

Table 5. Dispersant/solubilizing properties for silica powders of IPD, glycerin sorbitol

These results suggest IPD could be suitable for use in toothpastes, both transparent and traditional, due to its good wetting properties for silica powders and its aforementioned solubilizing capacity of aromas and fragrances.

Table 6. Height and stability of foam of surfactants with or without IPD

Table 6. Height and stability of foam of surfactants with or without IPD

The behavior of IPD in combination with common cosmetic surfactants also was teste, as shown here.

Table 7. All evaluated stability parameters, STD vs IPD 5%

Table 7. All evaluated stability parameters, STD vs IPD 5%

When added to the water phase, IPD produced smaller-diameter oil droplets, with better homogeneity of the system, compared with the same standard emulsion without IPD, subsequently improving its stability.

Table 8. Results of the drop test

Table 8. Results of the drop test

Results of the drop test (from 30 cm) of three samples compacted at 50 bar

Figure 1. Structure of IPD

Figure 1. Structure of IPD

IPD has an isoprene diol structure; specifically, it is a branched chain bi-alcohol with a five carbon atom backbone, described by the formula: 3-methyl-1,3-butanediol.

Figure 2. Microscope analysis of emulsion with and without IPD

Figure 2. Microscope analysis of emulsion with and without IPD

Microscope analysis of an o/w emulsion with 5% IPD in the water phase (left) and without IPD (right)

Figure 3. Moisturizing effect on skin of IPD and its combination with sorbitol

Figure 3. Moisturizing effect on skin of IPD and its combination with sorbitol

Moisturizing effect on skin of IPD and its combination with sorbitol in comparison to sodium hyaluronate and the basic cream without active principles (n = 5); statistical analysis on average values

Figure 4. Depiction of method to evaluate smoothness of hair

Figure 4. Depiction of method to evaluate smoothness of hair

The angle of the plate required for a 50-g weight to drop in 3 sec is determined; the higher the sliding angle, the more damage to the lock.

Figure 5. Drop height results of IPD and sorbitol

Figure 5. Drop height results of IPD and sorbitol

Drop height results of IPD and sorbitol compared to dipropylene glycol (DPG), butylene glycol (BG), propylene glycol (PG) and hydrolyzed proteins on Caucasian hair

Figure 6. Static friction results of IPD and sorbitol

Figure 6. Static friction results of IPD and sorbitol

Static friction results of IPD and sorbitol compared with dipropylene glycol (DPG), butylene glycol (BG), propylene glycol (PG) and hydrolyzed proteins on Caucasian hair

Figure 7. SEM images of repair effect of IPD and sorbitol

Figure 7. SEM images of repair effect of IPD and sorbitol

IPD showed a synergistic effect with sorbitol (ratio 1:1) in the treatment of damaged hair.

Footnotes [Rigano 128(12)]

a The described isopentyldiol is manufactured by Kuraray, www.kuraray.eu.

b MT 700B (INCI: Titanium Dioxide) is a product of Tayca, www.tayca.co.jp/english.

c A 407 Tudor Willow (INCI: Iron Oxide) is a product of Kingfisher, www.kumkangtr.com/kingfisher.htm.

d Tixosil 43 and 73 (INCI: Hydrated Silica) are products of Rhodia, www.rhodia.com.

e Aerosil 200 (INCI: Hydrophilic Fumed Silica) is a product of Evonik, www.evonik.com.

Formula 1. O/W emulsion to verify IPD influence on particle size

Water (aqua) 73.50% w/w
Hydrogenated Polydecene 20.00
Steareth-2 3.00
Steareth-21 1.00
Cetearyl Alcohol 1.50
Propylene Glycol (and) Diazolidinyl Urea (and) Methylparaben (and) Propylparaben 1.00
  100.00

 

     

Formula 2. Base moisturizing cream

Water (aqua) qs to 100.00% w/w
Carbomer 0.15
Glyceryl Stearate (and) PEG 100 Stearate 3.00
Cetyl Alcohol 1.00
Paraffinum Liquidum 3.00
Triethanolamine 0.60

Preservative

qs

Formula 3. Compact powder

CI 77492 2.00% w/w
CI 77491 0.30
CI 77491 (and) CI 77499 0.50
CI 77499 0.20
Talc 23.50
Mica 50.00
CI 77891 13.00
Magnesium Stearate 2.00
IPD 7.00
Cera Alba 0.50
Phenoxyethanol 0.80
Fragrance (parfum) 0.20
  100.00

 

      

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