Title:  Aqueous film coating with improved properties

United States Patent:  6,468,561

Issued:  October 22, 2002

Inventors:  Grillo; Susan M. (Quakertown, PA); Steffenino; Rita M. (Harleysville, PA); Porter; Stuart C. (Hatfield, PA); Woznicki; Edward J. (Douglassville, PA); Isganitis; David K. (East Greensville, PA)

Assignee:  BPSI Holdings, Inc. (Wilmington, DE)

Appl. No.:  886731

Filed:  June 30, 1997

Providing a film coating on solid forms such as pharmaceutical tablets, foods, confectionery forms, seeds for agriculture, and the like by coating them with polydextrose, or a combination of polydextrose and another polymer, or a layer of polydextrose overcoated by a layer of another polymer.

SUMMARY OF THE INVENTION

Aqueous film coatings based on the polymer polydextrose provide the solution to both the pharmaceutical, and the food and confectionery problems described. Used alone, or in combination with other polymers, polydextrose produces pharmaceutical film coatings that exhibit excellent adhesive qualities, while when used in food and confectionery applications, it can produce coatings with good organoleptic properties that are low calorie and non-cariogenic in nature.

Aqueous film coatings based on the polymer polydextrose are useful on various grains and seeds since such coatings facilitate handling of the grains and seeds. For example, some automatic planting machines do not effectively manipulate seeds that are tiny in size, and coating such seeds with the inventive coating creates a larger volume that is more easily handled by the automatic planting machines. Further, the inventive coating maintains the germinative properties of the seeds.

One characteristic of polydextrose, however, is that it has an extremely low average molecular weight value (for example, peak molecular weight, M_p, is approximately 1230). It is well known that low molecular weight polymers produce extremely weak films. Rowe ("Molecular Weight Studies on Hydroxypropyl Methylcellulose Phthalate" Acta-Pharm. Technologica 28 (2), p. 129 1982) has stated that for the purposes of film coating, there exists a CRITICAL MOLECULAR WEIGHT value for polymers such as hydroxypropyl methylcellulose (H.P.M.C.), below which there is a great risk of the coating cracking. For H.P.M.C., he stated that the M_p value, which is indicative of the molecular weight of the main component, is approximately 8.0.times.10⁴.

This value for HPMC is significantly greater than the M_p value for polydextrose, which would thus not be expected to produce satisfactory film coatings.

Additionally, Osterwald ("Properties of Film-Formers and Their Use in Aqueous Systems", Pharm. Res., 1985, p. 15) has stated that for film coating, polymers producing solutions (containing 2% w/w of the polymer in water) having viscosities in the range of 3-15 mPas (milli Pascal seconds) (same as centipoise numerically) ought to be used, and that below this range, the polymer chains shorten to such an extent that the stability of the film is affected (i.e. film strength decreases too much). Two percent aqueous solutions of polydextrose have a viscosity of less than 2 mPas (in fact the value is too low to be differentiated from that of plain water).

Consequently, to those skilled in the art, polydextrose would be considered to produce film coatings that are entirely unsuitable for modern film coating processes; yet we have found it can produce excellent film coatings that in some cases have superior properties to those obtained from more traditional polymers.

Finally, polydextrose can be formulated into a dry-edible film coating composition, shipped to the user and mixed easily into water to form an aqueous coating suspension.

The polydextrose aqueous coating suspension comprises an effective amount of polydextrose, plasticizer, detackifier, and a secondary film former, mixed into water to form an aqueous coating suspension which may be applied to the forms to be coated, as by spraying. Optionally, a colorant may be added to the aqueous coating suspension before the coating step. Also, other polymers, such as maltodextrin and cellulosic, vinylic, and acrylic polymers, may be used in combination with polydextrose. For example, a cellulosic polymer, such as hydroxypropyl methylcellulose, may be substituted for the secondary film former, and the resulting formula is particularly adapted for coating waxy matrix tablets, which are particularly difficult to coat. All ingredients of the coating suspension are edible and suitable for ingestion.

The film former of the coating is polydextrose, or a mixture of polydextrose and one or more other polymers, such as a cellulosic polymer film former.

Also, it may be advantageous to coat with a layer of polydextrose aqueous coating suspension, and then overcoat with a layer of another polymer coating suspension such as a cellulosic film polymer coating suspension.

Other polymers that may be used with polydextrose may be maltodextrin, vinylic polymers, acrylic polymers and cellulosic polymers. The acrylic polymer may be an acrylic latex. The cellulosic film polymer may be hydroxypropyl methylcellulose, hydroxypropyl cellulose, pseudolatex ethylcellulose, or water-soluble cellulose acetate.

The plasticizer may be polyethylene glycol, triacetin, propylene glycol, acetyltriethyl citrate, dibutyl sebacate, or glycerine.

The colorants may be FD&C lakes, D&C lakes, titanium dioxide, or dyes approved for ingestion by the U.S. Federal Drug Administration. Examples of such pigments are listed in Colorcon U.S. Pat. No. 4,543,370 issued Sep. 24, 1985, and incorporated herein by reference.

The detackifier may be lecithin or mineral oil.

The secondary film former may be sodium alginate or propylene glycol alginate.

With some polymer coatings, such as polydextrose/EUDRAGIT formula coatings, an antifoaming agent (such as AEROSOL OT, 75%) and a lubricating aid (such as magnesium stearate) may be added to the formula.

The polydextrose based coating is especially effective in coating tablets and the like having debossed or intaglio logos, trademarks, designs or words thereon since it adheres to the tablet surfaces without bridging and obscuring the debossed or intaglio printing.

Claim 1 of 55 Claims

What is claimed is:

1. A method of film coating solid forms such as pharmaceutical tablets, food, confectionery forms, seeds for agriculture, and the like with a protective film comprising the steps of

mixing an effective amount of film forming polydextrose, an effective amount of plasticizer, an effective amount of detackifier, and an effective amount of secondary film former into water to form an aqueous coating suspension,

forming a film coating on the solid forms by applying an effective amount of said coating suspension onto said solid forms to form a film coating thereon, and

drying the film coating on said solid forms.
 

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