METHYLAL IN COSMETIC

Methylal is the INCI name of dimethoxymethane. It is used in many formulae in which a solvent is needed.

1. Aerosol and pump sprays :
   • hair sprays,
   • deodorants,
   • dry shampoos, etc.
     
     
2. Nail varnishes.
   Nail varnish removers.
   
   
3. Shaving gels.
   After shave lotions.
   
   
4. Hand cleaners, gels, ...

Why is methylal used ?

for	its proven extremely low toxicity, its high solvent power, its low viscosity, its water miscibility, its quick drying time,

and also because methylal has an amphiphilic character not perturbing the equilibrium of emulsions

ADVANTAGES OF METHYLAL IN COSMETIC

I - AEROSOL AND PUMP SPRAYS

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Methylal can be used in hair sprays, deodorants, dry shampoos, etc.

The advantages of methylal in aerosol and pump sprays are :

• solvency,
• small particle size,
• shorter drying time,
• synergy with " New Aerosol Systems ".

A - Solvency
Methylal is useful for achieving a real solution of active ingredients (hair spray resins, silicones, ...).

The liquified gasses participate in the solvency of the liquid blend in the aerosol and decrease the solvent power of the mixture.
In order to solubilize the active ingredients, you need to increase the solvent power and therefore you have to incorporate in the blend a powerful solvent such as methylal.

Comparison of Kauri-Butanol values :

methylal : methylene chloride : dimethylether : propane : isobutane :

164 115 91 15 17

B - Methylal improves the spray quality and reduces the particle size
Hair spray example :

We have filled various classic formulae, starting

from B

to A

HS 24 B % WEIGHT		HS 24 A % WEIGHT
6.02 0.07 0.07 63.84 0	luviskol va 37 hm dow fluid 344 freshlon fragrance ethyl alcohol methylal cosmetic grade	6.02 0.07 0.07 31.92 31.92
30.00	propane-butane 3.2 bar	30.00
100.00		100.00

and compared the particle size :


This phenomenon is also verified with DME and water (average particle size measurement without resin).


and is always true with pumps (reduction of particle size) :

SAMPLE N°	1	2	3	4
ADVANTAGE CP AMP 100 SURFADONE LP 300 PERFUME METHYLAL ETHANOL WATER	10 0,21 0,1 0,2 0 74,8 14,69	10 0,21 0,1 0,2 10 64,8 14,69	10 0,21 0,1 0,2 20 54,8 14,69	10 0,21 0,1 0,2 30 44,8 14,69

C - Methylal shortens the drying time
A practical test* with hair spray HS 24 B and A (ethanol- and methylal-based) shows the following :
*Half head study of Hazel Pool UK of June 1996

This reduction of drying time is much more evident with water-based formulations with DME.

The drying time of a solvents/propellant blend sprayed on paper is drastically reduced by the incorporation of methylal :



Results :
Better performances of the hair spray, thanks to a shorter drying time:

• initial hold is better,
• beading is reduced.

D - Synergy with "New Aerosol Systems"

• CO₂ - N₂O propellants
  
  
  • extremely high solubilization of CO₂ and N₂O in methylal:

    Bunsen coefficient CO2 :

    9.5 in methylal 2.9 in ethanol

• N₂- compressed air-bag systems
  
  The challenge for those spray devices is to reach
  
  
  • fine pulverization,
  • good drying time.
  Methylal is an outstanding solvent to reach these goals, thanks to its
  
  • low viscosity,
  • quick evaporation.

II - NAIL VARNISHES

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Methylal presents many advantages in the formulation of nail varnishes :

• high solvency towards nitrocellulose and cellulose acetates,
• quick drying,
• weaker smell compared to acetone.

Moreover, the use of toluene is avoided. NAIL VARNISH REMOVERS Thanks to the solvency characteristics of methylal, water-based nail varnish removers can be prepared with :

• an extremely low irritation level and
• a very high efficiency.
  

III - SHAVING GELS

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Methylal shows an excellent miscibility with butane and water, which makes it possible to substitute isopentane as foaming agent (foam promotor) by a mixture of methylal and butane.

The advantage is a better water miscibility. The gel has as a consequence a better transparency.

There is also an additional advantage of using methylal : possible foam generation regulation through adjustment of the methylal/butane balance. AFTER SHAVE LOTIONS The fast evaporation of methylal gives a nice refreshing effect.

IV - HAND CLEANERS - GELS

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Methylal has a strong degreasing power as well as water miscibility.

This is a unique combination making it possible to formulate transparent hand cleaning gels (cold processed).

SPECIFICATIONS OF METHYNAL

	Cosmetic grade	Anhydrous grade	Pure grade	Technical grade
Methylal	99.5 % min.	99.9 % min.	99.5 % min.	93 % min.
Methanol	< 1 ppm	< 0.05 %	< 0.05 %	6.5 % max
Formaldehyde	< 1 ppm	< 0.005 %	< 0.0005 %	< 0.02 %
Water	< 0.5 %	< 0.03 %	< 0.5 %	< 0.25 %

ATMOSPFERIC CHEMISTRY OF METHYLAL

VOC	The degradation of methylal in the atmosphere happens through its reaction with the hydroxyl radical because methylal does not photolyse. The formation of ozone needs several reactional steps and the velocity of the degradations during the added steps is extremely low. Therefore the contribution of methylal to the formation of tropospheric ozone should be low.
GWP	Methylal has an atmospheric lifetime of 58 hours, which indicates that the global warming potential of methylal is negligible.
ODP	Due to the absence of a halogenated atom, the Ozone Depletion Potential of methylal is zero.

FORMULATION GUIDELINES

Hairsprays

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HS 1 HS 2 HS 4 HS 5 HS 24 A+B HS 25 HS 26 HS 27 HS 30+31 HS 30 HS 33

HAIR SPRAY 80% VOC HAIR SPRAY CO2 PROPELLED PUMP HAIR SPRAY 80 % VOC PUMP HAIR SPRAY 80 % VOC HAIR SPRAY 100% VOC HAIR SPRAY WITH PUMP HAIR SPRAY WITH PUMP HAIR SPRAY WITH PUMP HAIR SPRAY 100 % VOC HAIR SPRAY HAIR SPRAY

Dry Shampoo

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DSH 1

DRY SHAMPOO - AEROSOL - ALCOHOL FREE

Body Deodorants

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BD 5 BD 6 BD 7 BD 8 BD 9

BODY DEODORANT - ALCOHOL FREE BODY DEODORANT - CO2 PROPELLED PERFUME DEODORANT - WITH PUMP BODY DEODORANT - WITH PUMP BODY DEODORANT - WITH PUMP - ALCOHOL FREE

Miscellaneous

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RS 3	MUSCLE DECONTRACTING SPRAY