Opaque shower gel - Chemists Corner

Formulating

Opaque shower gel

Posted by Tyss on July 28, 2021 at 12:42 pm

Dear all,

I need your help in solving a problem with the clouding of the opacifier in a shower gel formula.

Indeed, I use in my shower gel formula 0.2% opacifying (styrene acrylate copolymer) diluted with a coefficient: 1: 4

My formula contains:

Aqua: QSP100

Sodium laureth sulfate 70%: 10%

Coacamidopropyl betaine 30%: 5%

Cocamide DEA: 2%

emollient: 0.4%

fragrance: 1%

citric acid: 0.1

Conservative: MCIT & MIT: 0.1%

Dye

EDTA: 0.05%

Decyl glucoside: 1%

Sodium chloride: 1.7%

After a certain time at room temperature (1 month and more), we notice a phenomenon of non-stability of the opacifier: a transparent layer at the bottom or a white layer at the bottom of the bottle.

I didn’t really understand what happened.

Can you guide me to solve this problem

Best regards

chemicalmatt replied 3 years, 7 months ago 4 Members · 8 Replies
8 Replies

ketchito

Member
July 28, 2021 at 3:38 pm

@Tyss Styrene acrylate copolymer is sensitive to electrolytes, so that might be the problem. You could try to either increase the amount of SLES (this would increase viscosity a bit and help dissolve some structures that might give you the hazy appearance), or increase either the Betaine or CDEA…all of this, along with a reduction of Sodium chloride. You could even add a rheology modifier (Crothix is a nice choice).
Bax65

Member
July 29, 2021 at 11:34 am

@ketchito - the electrolyte content of this formlulation should not be critical for a Styrene Acrylates Copolymer.
@Tyss - I can imagine that the incorporation of the opacifyer might have not been homogeneous enough.
If it shall not be dispersed evenly enough particles may stick together (conglomerates) which than behave like a bigger particle - making them more prone to separate.
Maybe you can work with a Styrene/Acrylates Copolymer (SAC) that is delivered combined with a surfactant. This makes incorporation easier and more homogeneous compared to the products which only contain the polymer.
I am only aware of Euperlan PCO as such mixture (Styrene/Acrylates Copolymer with Coco-Glucoside). But maybe there is another one in the market.
ketchito

Member
July 29, 2021 at 1:25 pm

@Bax65 Electrolyte content is a critical parameter when using Styrene acryate copolymer opacifiers, especially in a SLES-CAPB-NaCl system. You can check this info from Dow: https://chemical-centre.com/f/pcopac.pdf. 

@Tyss There are different types of styrene acrylate copolymer opacifiers, ones more sensitive to others to electrolytes, but 1.7% NaCl is indeed high for your system. I’d advise you to switch from NaCl to Crothix Liquid, just to check if the level of NaCl is indeed messing with your formula.
Bax65

Member
July 29, 2021 at 1:41 pm

@ketchito - thanks for sharing the link. Interesting information!
I have mainly experience with the mentioned Euperlan PCO and there I used it with similar electrolyte concentartions without any issue - even with benzoic acid preservation at pH 4.5 - 5.5.
But generally reducing NaCl level is a good idea.
The PEG-150 Pentaerythrityl Tetrastearate is surely a quite powerful thickener for various surfactant systems.
ketchito

Member
July 29, 2021 at 1:44 pm

@Bax65 Indeed!…I actually had the same issue with that opacifier few months ago, and had nightmares for weeks, before finding that life-saving info from Dow.
Tyss

Member
July 30, 2021 at 10:47 am

Dear all,

Thanks for your collaboration.

I use the opacifier of INNOSPEC (in PJ TDS)

If I understand correctly, I must reduce the percentage of salt to 1.5% max and increase the viscosity by another component to ensure the stability of my shower gel.

The quality of the opacifier can affect the stability of the product?

Which is the most stable opacifier: the one mixed with a nonionic surfactant or alone.

Best regards.
Bax65

Member
July 30, 2021 at 11:08 am

@Tyss - correct. Try to lower your total salt content.
This will very likely result in a reduced viscosity of your formulation.
To compensate this viscosity loss you shall use another, salt free thickener - e.g. the mentioned Crothix Liquid. Alternatively you can try to increase the Cocamide DEA to 3%. This normally also helps to thicken.

Regarding the opacifier: If you can get a sample of the Euperlan PCO I would give it a try. From my experience it is giving a more homogene distribution, which is an advantage when incorporated but also in stability.
chemicalmatt

Member
July 30, 2021 at 8:41 pm

I will second @ketchito on that electrolyte issue. When using latex opacifiers, best to leave the salt out completely. Likewise with most amphoterics (CAPB has 5% NaCl remember) though you don’t have a lot in there. There is another equally important factor: order of addition. Always add/disperse the opacifier to the initial water first, before any other ingredient. They ppt out often when added later. This formula can also be easily thickened using an acrylates copolymer, very compatible with the anionic latex opacifiers you are using, and you’ll never see any separation again since these add yield value to the mix. Synthalen W600 (3V Sigma) or Carbopol Aqua SF-1 (Lubrizol), depending on how much you are willing to spend.