Process for producing soap bars

Details Process for producing soap bars Process for producing soap bars

1998-08-20

2001-06-05

Ogden, Necholus (Department: 1751)

Cleaning compositions for solid surfaces, auxiliary compositions

Cleaning compositions or processes of preparing

For cleaning a specific substrate or removing a specific...

C510S152000, C510S155000

Reexamination Certificate

active

06242398

ABSTRACT:

The invention relates generally to soap bars, and in particular to a process for producing soap bars comprising a benefit agent.
Toilet soap is the major product used for personal washing world-wide. Although the fat charge used to make such products varies enormously, the in-use properties vary little, apart from the amount of lather.
The bar sensory properties, i.e. lather quality and after-wash wet-skin feel, are totally unaffected by the fat charge. One of the main aims in recent years has been to find routes to modify bar sensory properties, especially the interaction of the product with skin. This aim is linked directly to consumer requirements for novel experiences from a bar product.
Early attempts in this direction relied upon addition of fatty acids to soaps which led to a modified lather creaminess, but provided no affect on the after-wash wet-skin feel. More recently some success has been had by addition of synthetic actives which because of their lime-soap dispersant action tend to modify the interaction of precipitated calcium and magnesium soaps with skin, and thereby modify the wet-skin feel of the product. This approach, although successful, does impose significant changes on fat charge in order to maintain acceptable bar processing and properties in the presence of high solubility synthetic actives.
A break-though in sensory delivery from toilet soaps would be one or more additives which could be incorporated into existing toilet soaps formulations using existing equipment, without the need for any modification in fat charge. This would enable such products to be processed at similar through-puts to conventional toilet soaps and, because of the use of identical fat charge, no disruption in wet soap manufacture in factories. Changing fat charge is a major issue in continuous soap manufacture, due to the fact that process control is extremely fat charge sensitive.
One approach which has been intensely studied by a number of workers is to incorporate an oil into the soap base. This has led to claims of a modicum of success but does have several drawbacks, i.e.—
i. the soap mass becomes sticky and difficult to process due to oil coating soap and equipment; typical problems include poor feed into mills, low extrusion rates and die block.
ii. the finished product has a sticky feel and requires additional packaging to avoid contamination/leakage of oil into pack.
iii. the size of oil droplets in the product is extremely process sensitive, hence manufacture must be carefully controlled, i.e. reduced throughput is often necessary.
In general, this type of product can deliver sensory benefits but because of the aforementioned problems, it has not been commercially feasible.
It is an object of the invention to provide an improved process for making soap bars which overcomes at least some of the above problems.
We have discovered that incorporation of specific benefit agents into water soluble carriers can substantially correct or improve on all of the aforementioned process problems, and can lead to the production of bars at similar throughputs to conventional toilet soaps which have finishes comparable to conventional toilet soaps. In addition these products deliver modified lather and wet-skin feel sensory properties without any detrimental effects on general bar in-use properties such as amount of lather, wear-rate and mush.
The basis of this invention is that the benefit agent is first pre-blended into a solid carrier matrix so that its domain size is fixed, and constant throughout the process regime. This ensures that process effects on oil-droplet size are minimised, and hence ensures consistent delivery of sensory properties independent of process variation. Additionally, for benefit agents which can be solubilised by soap, (e.g. vegetable oils) the carrier effectively removes oil-migration through the product, and hence removes the risk of oil-solubilisation, since the oil is prevented from mixing with liquid material in the bar.
The carrier is selected from materials which are water soluble, and so dissolve to release the benefit agent during the washing process. We have also found that the delivery of sensory effects on wet-skin feel are significantly enhanced if the carrier dissolves via a viscous solution state, i.e. the carrier dissolves producing an initial substantial increase in viscosity (e.g. initial stages of polymer hydration). This viscous state during which benefit agent is released is key to delivery of a sensory effect to modify after-wash wet-skin feel. Typically carriers which meet this criteria have viscosities of a 60% carrier/water solution in excess of 1000 cps measured at a shear rate of 10s
−1
at 20 degrees Celsius.
The soap of the current invention is typically comprised of non-lauric oils and lauric oils, ideally in a blend ratio of 95/5 to 10/90. Typical non-lauric oils include tallow, palm, tallow stearines, palm stearines, partially hardened vegetable oils and mixtures of these with partially or fully hardened oils. Typical lauric oils include coconut, palm kernel, and babassu oils. The soap base is generally produced by saponification of the oil blend using an appropriate alkali such as sodium, potassium, calcium and magnesium alkalis or combinations thereof. The soap base so made is ideally dried to a moisture content in the range 5-25% prior to addition of carrier-benefit-agent premix, or alternatively the carrier-benefit agent premix can be added to the neat soap prior to drying.
The carrier ideally exists as a solid at ambient and process conditions, hence its melting point preferably exceeds 80° C. The carrier is ideally wholly water soluble, and will ideally dissolve in water via a viscous liquid, where the viscosity of a 60% carrier/water solution is in excess of 1000 cps at a shear rate of 10s
−1
at 20 Celsius. The viscous liquid state can be achieved by for example formation of liquid crystals or by molecular entanglement of long molecules, (e.g. polymers).
Examples of carriers which meet these requirements are maltodextrins, starches, modified starches, PVP's, PVA's, and cellulosic polymers, however other carriers which meet the above mentioned physical requirements are envisaged.
Preferred properties of the benefit agents are as follows. Firstly they should preferably be liquids at typical ambient wash temperatures and process temperatures, i.e. they should have a freezing point less than 30° C. Secondly, they should be essentially free of water to avoid dissolution of the carrier in the bar product, prior to washing with the product. Thirdly they should have a low viscosity, i.e. less than 60,000 cps, more preferably less than 30,000 cps. Fourthly they should ideally be immiscible with water.
Examples of benefit agents which meet these requirements are low viscosity silicone oils, vegetable oils, mineral oils, synthetic oils, (e.g. IPM, IPP), and mixtures thereof.
The benefit agent can be an “emollient oil”, by which is meant a substance which softens the skin (stratum corneum) by increasing its water content, and keeping it soft by retarding decrease of water content.
Preferred emollients include:
(a) silicone oils, gums and modifications thereof such as linear and cyclic polydimethylsiloxanes; amino, alkyl alkylaryl and aryl silicone oils;
(b) fats and oils including natural fats and oils such as jojoba, soybean, rice bran, avocado, almond, olive, sesame, persic, castor, coconut, mink oils; cacao fat; lard; partially hardened oils obtained by hydrogenating the aforementioned oils; and synthetic mono, di and triglycerides such as myristic acid glyceride and 2-ethylhexanoic acid glyceride;
(c) waxes such as carnauba, spermaceti, lanolin and derivatives thereof;
(d) hydrophobic plant extracts;
(e) hydrocarbons such as liquid paraffins, Vaseline (trade mark), microcrystalline wax, ceresin, squalene, pristan and mineral oil;
(f) higher fatty acids such as oleic, linoleic, linolenic, lanolic, isostearic and poly unsaturated fatty acids (PUFA);
(g) higher alcohols such as lauryl, oleyl, cholesterol an

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