Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Tablets – lozenges – or pills
Patent
1995-02-17
1999-01-12
Page, Thurman K.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Tablets, lozenges, or pills
424464, 424489, A61K 916, A61K 920
Patent
active
058584064
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB93/00965 filed May 10, 1993.
The present invention relates to carboxylic acid polymer compositions and particularly relates to concentrates of acrylic acid polymers and their use to prepare gels of diluted and neutralized polymer.
The polymers to which the invention relates include cross-linked polymers of acrylic acids which are widely used as thickeners, stabilizers and emulsifiers in many industries. Said cross-linked polyacrylic acids are produced and sold under a number of trade names for example Carbopol (B F Goodrich), Acrisint (Sigma), Pemulen (B F Goodrich) Junlon (Nihon Kogakyu), etc. They are however most often referred to by either of the generic terms carbomer or cross-polyacrylate, (developed by the Cosmetics, Toiletries and Fragrances Association). The polymer products are referred to by these names in this application.
Said products so described are supplied in the form of very fine powders with poor flow properties, and handling of these products is not easy. However, it has always been considered that the products must be in the form of very fine powder if complete wetting and reasonably rapid hydration of each particle is to take place when the products are added to a liquid medium, such as water, to form a gel from which products such as liquid detergents, cosmetics, toiletries or pharmaceutical products can be made. A consequence of the products being in the form of a very fine powder is that they have a pronounced tendency to dust and fly about the work place even when care is taken to minimise this.
It is conventionally regarded therefore that, despite the handling difficulties, the products must be supplied in the form of fine powders since, when they are to be converted to a gel, and in the initial stage of hydration for this conversion, i.e., wetting of the powders, the formation of a very stiff gel on the outside of the powder particles occurs which delays and restricts the entry of further water to hydrate the remainder of the particle. The stiff gel on the outside of the particle therefore tends to prevent further water ingress into the particle, thereby retarding the formation of a smooth gel. In addition, agglomerates of the powder particles form lumps which increases the problem of wetting out and dispersion.
Furthermore, when disturbed, the dry powder tends to develop strong electrostatic charges which impairs further the ability of the powder to flow in the required direction and, in the extreme, causes small agglomerates to fly about which results in loss of material. This makes the automatic measuring out of the carbomers virtually impossible.
As a result of these problems, manufacturers of the products always advise that the said product be carefully sifted into the water in an attempt to break up the dry agglomerates which tend to form during storage. Furthermore, these carbomers, when fully swollen and hydrated, have the property of suspending insoluble gases, liquids and solids. This property, although very desirable in most instances, can make the removal of air bubbles from the mixture very difficult, if not impossible, within a reasonable period of time.
In an attempt to overcome this problem it has been proposed to prepare concentrated dispersions of resins in water. However, due to the high viscosity of said resins, they are extremely difficult or impossible to handle. A further initiative, as described in co-pending application No 9114095.4 provides, by incorporating small proportions of salts of multi-valent cations in these dispersions either by dry blending the polymer and salt together before adding them to the water; or by mixing the salt, carbomer, and water in any order, a concentrate which has been found to be extremely effective and to have gained acceptance as a workable alternative.
The provision of said multi-valent cations in the blend has been found to be acceptable but further research has shown that the important factor of handling difficulties of the powdered carbomer in a dry state is not properly addressed.
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Minister Peter E.
Stead Stanley Gordon
Monsanto Raphael A.
Page Thurman K.
Rohm Benita J.
Spear James M.
Surfachem Group PLC
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