Haze-free cellulose ether capsules and process for making

Details Haze-free cellulose ether capsules and process for making Haze-free cellulose ether capsules and process for making

1999-04-21

2001-09-25

Brunsman, David (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Carbohydrate or derivative containing

C106S198100, C536S085000, C536S086000, C536S088000, C536S089000, C264S301000

Reexamination Certificate

active

06294008

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to haze-free cellulose ether capsules and a process for making. The capsules are useful in pharmaceutical applications.
BACKGROUND OF THE INVENTION
Cellulose ethers are commonly employed commercially to form capsules which are adapted to contain and orally deliver pharmaceutical agents and medicaments. Preferred cellulose ethers for such applications are methylcellulose and hydroxypropylmethylcellulose.
Cellulose ether capsules are typically manufactured by dipping hot pins in a cold, aqueous cellulose ether dip coating solution. The solution gels on the pins and water evaporates during a drying step to form thin film layers of dried cellulose ether around the hot pins. The thin films take the form of caps and bodies, which are then removed from the pins. Caps are mated with bodies to form capsules. Analogous processes exist wherein cold pins are dipped in a hot, aqueous cellulose ether solution. Processes for making capsules are seen in U.S. Pat. Nos. 3,617,588;4,001,211;4,917,885; and 5,756,036, which are incorporated herein by reference.
A problem commonly encountered in manufacturing cellulose ether capsules is haze formation at their inner surfaces. Haze formation is most noticeable in transparent capsules.
Haze causes cellulose ether capsules to exhibit less luster and gloss than they would otherwise. Due to haze, cellulose ether capsules typically do not have the same level of luster as gelatin capsules. This difference in appearance is discussed in “HPMC Capsules—An Alternative to Gelatin,”
Pharmaceutical Technology Europe
10(11) (1998).
It would be desirable to have cellulose ether capsules which are substantially free of haze formation at their interior surfaces and a process for making such capsules. It would also be desirable to have a process for making a cellulose ether composition useful in such capsules.
SUMMARY OF THE INVENTION
According to the present invention, there is a cellulose ether composition comprising a low molecular weight cellulose ether. The composition has a sodium chloride content of about 0.3 weight percent or less based upon the weight of the cellulose ether. The composition exhibits significantly reduced haze formation when in capsule form. Useful embodiments also include aqueous and capsule forms of the composition.
Further according to the present invention, there is a process for making a cellulose ether composition. The process comprises a) alkalyzing a cellulose pulp by contacting it with sodium hydroxide; b) etherifying the cellulose pulp to form a cellulose ether; c) washing the cellulose ether to reduce sodium chloride content; d) drying the cellulose ether to a reduced moisture content; e) milling the cellulose ether to a particulate form; f) contacting the particulate cellulose ether with an amount of hydrogen chloride sufficient to partially depolymerize it such that a two percent aqueous solution of it has a viscosity of 200 cP or less at 20° C.; g) partially or substantially neutralizing the acid by contacting with a sodium compound. The cellulose ether is washed to a sufficient extent and the amount of hydrogen chloride employed is adjusted to a sufficient extent to limit the sodium chloride content of the depolymerized cellulose ether to about 0.3 weight percent or less based upon the weight of the depolymerized cellulose ether.
Further according to the present invention, there is a process for making cellulose ether capsules from the cellulose ether composition having low sodium chloride content. The cellulose ether is dissolved in water to form a dip coating solution. Metal pins are dipped into the coating solution. The solution is allowed to gel and subsequently dry on the pins to form thin films of dried cellulose ether around the pins. The thin films takes the form of caps and/or bodies which are then removed from the pins. The caps and/or bodies can subsequently be mated to form whole capsules. Both hot pin/cold solution and cold pin/hot solution processes are contemplated.


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