Among the companies that have developed non-paraben preservatives is Schülke, which has U.S. offices in Mt. Arlington, NJ. Several of the company’s mixtures are effective against bacteria, yeast and molds.
Euxyl K 700 (INCI: Phenoxy- ethanol (and) benzyl alcohol (and) potassium sorbate (and) tocopherol) is a liquid with a pH of 5.5 that can be used in a leave on or rinse off formulation. The company’s recommended concentration for either rinse off or leave on is 0.5-1.5%. Below is a list of minimum inhibitory concentrations (MIC) of Euxyl K 700 against various organisms. A repeated challenge test was used to determine the efficacy of the preservative. After growing the organisms in a soya agar or Sabouraud-dextrose media, the preservative is streaked on it at various time intervals.
Euxyl K 700 can be used in anionic, cationic or nonionic systems, butis not effective in a formula pH above 5.5. It does not foam and about 2 grams of K 700 will dissolve in 100 grams of water at 20°C.It is readily soluble in propylene glycol, propanol or acetone.
Another choice is Euxyl K 701 (INCI: Phenoxyethanol (and) benzoic acid (and) dehydroacetic acid (and) ethylhexylglycerin).This clear yellow liquid has a water solubility of 10 grams per liter at 20°C.Suggested use level for leave-on or rinse-off products is 0.4 to 1.2%.It should be added during the cooling phase at 40°C, and the pH should not be above 6.0.
In Europe, dehydroacetic acid cannot be used in aerosols, therefore, K 701 is also prohibited.
Euxyl K 702 (INCI: Phenoxy- ethanol (and) benzoic acid (and) dehydroacetic acid (and) ethylhexylglycerin (and) polyaminopropyl biguanide) is another preservative that is effective when used between 0.2-1.0%.The challenge test described above showed that K 702 prevented growth even after three months storage at 40°C.The K 702 should also be added while cooling at 40°C, and it is stable up to pH 6.0.Yellow discolorations will occur in the presence of iron ions. It is 1% soluble in water at 20°C.
A formula showing its use follows:
W/O Moisturizing Cream
Polyglyceryl-4 isostearate (and) 5.0
(and) hexyl laurate
Euxyl K 7020.6
Perfume and colorq.s.
No heating necessary.Add silica to the oils in phase A with adequate agitation. Dissolve the cellulose in the vortex while mixing phase B.Add the salt after the cellulose is fully hydrated. Add phase B to phase A while mixing. Homogenize. Add phase C in order listed.