Coupling Agents and Surfactants for the Preparation of Aqueous Solutions of DOWANOL EPh Glycol Ether

Transcription

1 Coupling Agents and Surfactants for the Preparation of Aqueous Solutions of DOWANOL EPh Glycol Ether Introduction Challenge DOWANOL EPh glycol ether is an aromatic, slow-evaporating glycol ether with applications in household and specialty cleaners where the solvent acts as an oil and grease remover, and textile baths, where the solvent act as a plasticizer and allows water-based dyes to penetrate hydrophobic fibers. It is also effective in the formulation of homogeneous, stable metal working fluids. However, the limited solubility of this solvent in aqueous solutions often hinders its use in applications where water is the predominant media. In this technical data sheet we describe two ways to improve the solubility of DOWANOL EPh in aqueous media. One method relies on the use of surfactants and the other on the use of coupling agents. Materials Used Product Designation Description Abbreviation Supplier DOWANOL EPh Glycol Ether (ELP Grade) Assay-99.9% 2-phenoxyethanol EPh Dow Chemical TERGITOL 15-S-7 Surfactant Mixture of linear secondary alcohols 15-S-7 Dow Chemical TERGITOL 15-S-9 Surfactant Mixture of linear secondary alcohols 15-S-9 Dow Chemical TERGITOL 15-S-15 Surfactant Mixture of linear secondary alcohols 15-S-15 Dow Chemical TERGITOL 15-S-20 Surfactant Mixture of linear secondary alcohols 15-S-20 Dow Chemical TERGITOL 15-S-30 Surfactant Mixture of linear secondary alcohols 15-S-30 Dow Chemical TERGITOL TMN 6 Surfactant (90% aqueous) Nonionic Surfactant TMN 6 Dow Chemical TERGITOL TMN 10 Surfactant (90% aqueous) Nonionic Surfactant TMN 10 Dow Chemical Sodium Lauryl Sulfate Anionic Surfactant SLS Fisher Scientific DOWFAX C10L surfactant Anionic Surfactant C10L Dow Chemical Cetyltrimethylammonium chloride (25wt% aqueous) Cationic Surfactant cetyl Aldrich Butyl CELLOSOLVE Solvent Assay 99.9% 2-butoxyethanol BuCs Dow Chemical Methoxytriglycol Assay 99% triethylene glycol methyl ether MTG Dow Chemical Butyl CARBITOL Solvent Assay 99.9% diethylene glycol n-butyl ether BuCb Dow Chemical DOWANOL TPM Glycol Ether Assay 99% tripropylene glycol methyl ether TPM Dow Chemical Solubility and Compatibility in the Presence of Surfactants Aqueous surfactant solutions containing 0.5%, 1.0%, 2.5% and 5.0% surfactant were prepared. The solutions were mixed for 5 seconds. If bubbles formed during mixing, the solutions were allowed to sit until the bubbles dissipated. A burette was filled with the DOWANOL EPh and clamped in place. The surfactant solution was stirred at 2 rpm and the DOWANOL EPh was added drop wise to a cloudy end point that persisted after 5 minutes. The total weight of the solvent added was obtained by difference and recorded. It was then converted to weight %. All titrations were conducted at room temperature (25 C). To determine solubility of water in solvent, the same procedure was used except that the surfactants were dissolved in the solvent and the water was added as the titrant. Results can be found in Tables 1 and 2. Page 1 of 5 Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Form No

2 Table 1: Solubility of DOWANOL EPh in Water at Various Surfactant s Weight % Solvent 0.5% 1.0% 2.5% 5.0% Surfactant 15-S S S S S TMN TMN SLS C10L cetyl Note: The Solubility of neat EPh in water is 2.4% Effects of surfactants on the solubility of DOWANOL EPh glycol ether in water Effects of surfactants on the solubility of water in DOWANOL EPh glycol ether The addition of 1% by weight sodium lauryl sulfate (SLS) to the water doubled the solubility of the solvent in the water. The solvent solubility continued to increase with increasing SLS concentration and reached 10% by weight when the SLS concentration was adjusted to 5% by weight. DOWFAX C10 L was the second best performer doubling the solvent solubility when used at 2.5% by weight. Cetyltrimethylammonium chloride performed well at 2.5% by weight but did not enhance the solvent solubility further when used at higher concentration. Improved solvent solubility was also obtained with TERGITOL surfactants containing > 15 EO units, namely the 15-S-15, 15-S-20 and 15-S-30, which doubled the solvent solubility when used at 5% by weight. As shown by the data in Table 2, only TERGITOL 15-S-20 had a small, enhancing effect on the solubility of water in the solvent, increasing the solubility from 12% to about 16% at the 0.5% by weight surfactant concentration. Higher surfactant concentration did not improve the water solubility in the solvent. All other surfactants had a marginal effect at best or as in the case of DOWFAX C10L and cetyltrimethylammonium chloride actually decreased the water solubility in the solvent. Table 2: Solubility of Water in DOWANOL EPh at Various Surfactant s Weight % Water 0.5% 1.0% 2.5% 5.0% Surfactant 15-S S S S S TMN TMN SLS ** ** ** ** C10L cetyl Note: The Solubility of water in neat EPh is 12.6 %. **SLS is not soluble in DOWANOL EPh Page 2 of 5 Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Form No

3 Solubility in Presence of Coupling Agents Four glycol ethers previously established as excellent coupling agents for hydrophobic solvent-water systems were evaluated as coupling agents for the phenolic glycol ether-water system. Samples containing different weight ratios of DOWANOL EPh and water were mixed and titrated to a clear end point with the coupling agent under evaluation. Ternary phase diagrams prepared from the data collected can be found in Figures 1-4. In these diagrams, solvent compositions falling under the area of the curve represent a 2-phase system and those above the curve are single phase systems. Figure 1: Phase Diagram for DOWANOL EPh, Water and DOWANOL TPM Ternary System Wt % TPM Wt % EPh Wt % Water Figure 2: Phase Diagram for DOWANOL EPh, Water and Methoxytriglycol Ternary System Wt % MTG Wt % EPh Wt % Water Page 3 of 5 Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Form No

4 Figure 3: Phase Diagram for DOWANOL EPh, Water and Butyl CARBITOL Ternary System Wt % BuCb Wt % EPh Wt % Water Figure 4: Phase Diagram for DOWANOL EPh, Water and Butyl CELLOSOLVE Ternary System Wt % BuCs Wt % EPh Wt % Water Page 4 of 5 Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Form No

5 Summary In general, the solubility of phenolic glycol ethers in water can be improved by adding surfactants to the water. The addition of 1% by weight sodium lauryl sulfate (SLS) to the water doubled the solubility of DOWANOL EPh in the water (5.8% vs. 2.4% in the absence of surfactant. The solvent solubility increased with increasing SLS concentration and reached 10% by weight when the SLS concentration was adjusted to 5% by weight. DOWFAX C10L doubled the DOWANOL EPh solubility when used at 2.5% by weight. Increasing the DOWFAX C10L concentration to 5% by weight enhanced the solvent solubility further but not to the levels observed with the SLS. Cetyltrimethylammonium chloride performed well at 2.5% by weight but did not enhance the DOWANOL EPh solubility further when used at higher concentration. Improved DOWANOL EPh solubility in water was obtained with TERGITOL surfactants containing >15 EO units, namely the 15-S-15, 15-S-20 and 15-S-30, which doubled the solvent solubility when used at 5% by weight. The rest of the surfactants evaluated did not increase the solvent solubility in water, and in some cases decreased the solubility. In general, the solubility of water in DOWANOL EPh glycol ether is not improved by the addition of surfactants tested. Only TERGITOL 15-S-20 had a small, enhancing effect on the solubility of water in the solvent, increasing the solubility from 12% to about 16% at the 0.5% by weight surfactant concentration. Higher surfactant concentration did not improve the water solubility in the solvent. All other surfactants had a marginal effect at best or as in the case of DOWFAX C10L and cetyltrimethylammonium chloride actually decreased the water solubility in the solvent. The best overall coupling agent for the DOWANOL EPh/water system was methoxytriglycol (MTG) which coupled 10% DOWANOL EPh into the water at a concentration of 28% by weight, and equal amounts (38%) solvent and water at a concentration of 24% by weight. Contact information: North America: Europe: (+32) Asia/Pacific: (+852) Other areas: NOTICE: No freedom from any patent owned by Seller or others is to be inferred. Because use conditions and applicable laws may differ from one location to another and may change with time, Customer is responsible for determining whether products and the information in this document are appropriate for Customer s use and for ensuring that Customer s workplace and disposal practices are in compliance with applicable laws and other governmental enactments. Seller assumes no obligation or liability for the information in this document. NO WARRANTIES ARE GIVEN; ALL IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE ARE EXPRESSLY EXCLUDED. Page 5 of 5 Trademark of The Dow Chemical Company ( Dow ) or an affiliated company of Dow Form No