Comparatively Speaking: Complex Esters from Neopentyl Glycol vs. Trimethylol Propane vs. Pentaerythritol

May 20, 2009 | Contact Author | By: Anthony J. O'Lenick, Jr., Siltech LLC
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Title: Comparatively Speaking: Complex Esters from Neopentyl Glycol vs. Trimethylol Propane vs. Pentaerythritol
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Complex esters are an important class of compounds in the personal care market. These include fatty derivatives of neopentyl glycol (NPG), trimethylol propane (TMP) and pentaerythritol (PE). Their structures are given in Figure 1, Figure 2 and Figure 3, respectively. These materials are made from mono-substituted fatty acids and di-, tri- or tetra-functional hydroxyl compounds. They are not polyesters.

Polyesters are made with multifunctional acids and hydroxyl compounds. They offer the cosmetic formulator the potential to make products with a wide range of cushion and playtime. This, in turn, results in many cosmetically elegant formulations.

One of the major uses of complex esters is for low viscosity, cosmetically elegant oil phases. The PE esters have the most cushion and playtime while the NPG has the least cushion and is a dry oil.

The low viscosity is obtained using branched, monounsaturated or iso fatty acids. Table 1, Table 2, Table 3 and Table 4 compare oleate esters, eructate esters, C-20 guerbet acid esters and isostearate esters.

The guerbet C-20 esters have the lowest iodine value, meaning they have the best oxidative stability. Iodine value increases in the following order: guerbet C-20 esters, isostearate esters and euruic esters and oleate esters are about equal. Fragrance interactions also need to be considered when using esters with high iodine values.

 

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Table 1. Oleate esters

Properties NPG oleate TMP oleate PE oleate
Appearance at 25°C clear liquid clear liquid clear liquid
Odor bland bland bland
Color, Gardner 4 4 2
Refractive index at 25°C 1.463 1.469 1.472
Viscosity at 40°C, cst 24 48 64
Iodine value 80 85 87
Pour point, C -35 -20 -25

 

Table 2. Eructates esters

Properties NPG erucate TMP erucate PE erucate
Appearance at 25°C clear liquid clear liquid clear liquid
Odor bland bland bland
Color, Gardner 5 4 3
Refractive index at 25°C 1.466 1.472 1.475
Viscosity at 40°C, cst 32 65 90
Iodine value 93 87 85
Pour point, C -25 -5 -9

 

Table 3. C-20 guerbet acid esters

Properties NPG guerbet C-20 TMP guerbet C-20 PE guerbet C-20
Appearance at 25°C clear liquid clear liquid clear liquid
Odor mild mild mild
Color, Gardner 4 4 5
Refractive index at 25°C 1.453 1.459 1.461
Viscosity at 40°C, cst 36 73 90
Iodine value 0.3 0.3 0.4
Pour point, C <-40 -18 -35

 

Table 4. Isostearate esters

Properties TMP isostearate PE isostearate NPG isostearate
Appearance at 25°C clear liquid clear liquid clear liquid
Odor mild mild mild
Color, Gardner 3 2 2
Specific gravity at 25°C 0.91 0.91 0.91
Viscosity at 40°C, cst 105 167 45
Iodine value 3.3 3.0 3.2
Pour point, C -26 -18 -35

 

Figure 1. Neopentyl glycol

Neopentyl glycol

Neopentyl glycol

Figure 2. Trimethylol propane

Trimethylol propane

Figure 2. Trimethylol propane

Figure 3. Pentaerythritol

Pentaerythritol

Pentaerythritol

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