Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Particulate form
Reexamination Certificate
2000-02-22
2001-07-03
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Particulate form
C424S489000, C424S488000, C514S772400
Reexamination Certificate
active
06254892
ABSTRACT:
The present invention relates to improved chemical compositions in pellet form which disintegrate quickly and efficiently in aqueous media. By “pellet”, we mean any solid formulation, including, but not limited to, tablets, bricks, bars, granules, balls, or blocks, also agglomerated materials such as those which form as a result of material sticking together during storage, especially under high humidity conditions.
It is well known to use chemical compositions in pellet form, for example, in the field of medicine and agriculture and more recently other areas such as in detergent applications. Pellets offer certain advantages over granular compositions; they are non-dusting, do not require measuring, take less space because they are compressed and the ingredients do not segregate during transit and storage. However, problems are experienced regarding the dissolution or disintegration of the pellets in use. In the manufacturing process, a balance must be kept between a pellet pressure which is, on the one hand, high enough to ensure that the pellets are well formed and resistant to handling, and a pellet pressure which is, on the other hand, low enough to achieve an appropriate solubility/dispersibility profile. To combat this problem, it is known to be helpful to use a processing additive either to improve pellet cohesion without the use of high pelleting pressure or to improve tablet dispersibility.
Looking specifically at additives which improve dispersibility, Journal of Pharmaceutical Sciences Vol. 61, No., 11, 1972, pp 1695-1711 reviews the various classes of known disintegrants; for example, materials which, (i) cause disintegration by evolving gas, such as sodium bicarbonate in the presence of citric or tartaric acid; (ii) those which promote water absorption, such as starch, colloidal silicon dioxide, carboxymethyl cellulose and rice starch; (iii) those which swell, for example, crosslinked polyacrylic acids, crosslinked gum arabic, carboxymethyl cellulose; (iv) those which increase porosity such as potato and corn starch and finally (v) those which undergo physicochemical bonding, such as micro crystalline cellulose and kaolin.
There are also many prior art patent documents directed to detergent tablets which contain disintegration agents. Examples of these include: EP-A-0799886 which discloses the use of starch derivatives, cellulose compounds, polyvinyl pyrrolidone compounds, bentonite compounds, alginates, gelatine and pectines as disintegrants and EP-A-0522766 which lists corn, maize, rice and potato starches, and starch derivatives, cellulose and cellulose derivatives and various synthetic organic polymers such as polyethylene glycol, crosslinked polyvinyl pyrrolidone and inorganic materials which swell such as bentonite clay, as disintegrants.
EP-A-0481547 teaches multilayer machine dishwashing detergent tablets which contain an outer layer, a barrier layer and an inner layer. The tablets release the detergent ingredients sequentially, first from the outer layer and then from the inner layer and the time delay between the two dissolutions is controlled by the thickness and choice of ingredients in the barrier layer separating the outer and inner layers. One of the ingredients in this barrier layer is a disintegrant which preferably includes one of a maleic acid/acrylic acid copolymer or a salt thereof, ethylene maleic anhydride crosslinked polymer and polyethylene glycol.
EP-A-0238341 identifies sequestering agents, for instance, nitrilo triacetic acid or diethylene diamine tetra acetic acid or a low molecular weight anionic polymer formed from ethylenically unsaturated monomers, e.g., unsaturated carboxylic acid, sulphonic acid or phosphonic acid monomers, as disintegrants. Further, this document mentions, when discussing the teaching of background art documents EP-A-0075818 and EP-A-0037026, that the conventional insoluble water swellable disintegration aids disclosed therein, such as high molecular carbohydrates like starch, pulverised cellulose such as ground wood, or polyvinyl pyrrolidone and so on, either do not lead to satisfactory disintegration or the disintegration is very slow at low temperatures. Another disadvantage observed through the use of cellulose and cellulose derivatives is that at use levels which are effective to promote disintegration, for example around 5% by weight of the tablet, the tablets are friable and break easily. This problem can be overcome by the addition of processing aids, for example binders which “glue” the tablet particles together, but this adds cost and reduces the volume of the tablet which is available for active ingredients.
The dissolution or disintegration of tablets for use in detergent compositions for automatic dishwashing is usually controlled to ensure dissolution which is regular but not too quick so as to avoid too much of the detergent composition being consumed in the pre-wash. However, during the main dishwash cycle it is advantageous for the remainder of the tablet to dissolve quickly so that residual tablet solids are not a problem on the dishware. By contrast, a key requirement in detergent compositions for laundry applications is to deliver as much of the detergent composition as possible so that it is available in the initial step of the wash. This will also be the case if the dishwashing machine has no pre-wash cycle. Since calcium and magnesium hardness ions in the wash water are already present at the beginning of the wash cycle, there is a high risk that sequestering ingredients are at too low a concentration and these will precipitate together with these hardness ions. This will result in insoluble scale being formed on the garments being laundered and a reduced amount of active material in the detergent composition being available for cleaning. With certain builders in detergent compositions, for example, sodium tripolyphosphate (STPP), this problem is critical since Ca/STPP precipitates can form scale which is very difficult to remove. The size of the tablets and the application conditions will also affect the tablet dispersability profile; for example, tablets for use in laundry applications are typically considerably larger than those used in automatic dishwashing machines or in water softening; 40 gram (g) up to 55 g tablets for laundry versus 20-25 g tablets for dishwashing and water softening. This fact, coupled with the tendency for the laundry tablet to be buried in the garments being washed means that the solubility requirements are particularly difficult to meet for tablets used in laundry applications as compared to other applications.
The applicants have previously disclosed, in French patent application 9807643, pellet formulations which disintegrate or dissolve very quickly on contact with water, making them suitable for use in applications which require the active ingredients to be delivered quickly. These pellets comprise: (a) at least one constituent with pharmaceutical, agrochemical, water treatment, water softening, fabric softening or detergency activity; and (b) at least one disintegration agent comprising one or more crosslinked polyacrylate water absorbent polymers with a gel-formation time of 30 seconds or less.
Such pellets have sufficient strength so that they do not crumble or break whilst being stored, transported or handled and are able to be stored under various climatic conditions involving fluctuating temperatures and humidities. It is particularly desirable that the pellets are sensitive to water but not to moisture. They must also have good activity, which requires a high content of active ingredients, and be able to exert this good activity at different temperatures and over a wide spectrum of application conditions, for example over a range of degrees of water hardness in the case of detergents.
The applicants have now found that these pellets can be even further optimised. It has been observed by the applicants that the rate of tablet disintegration is increased with increasing levels of disintegration agent present in the tablet, however, when the tablet c
Duccini Yves
Gauthier Francois
Tatin Johan
Fubara Blessing
Howell Thomas J.
Page Thurman K.
Rohm and Haas Company
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