AQUEOUS ETHYLCELLULOSE DISPERSIONS With polymeric additive

Abstract

Provided is an aqueous composition having pH of 8 or higher and comprising (a) a solid phase comprising dispersed particles that comprise an amount of ethylcellulose polymer, (b) an amount of one or more polymeric dispersants, wherein said polymeric dispersant has a weight-average molecular weight of 5,000 daltons or higher, and wherein said polymeric dispersant has an acid value of 60 to 190 mg KOH/g of polymer. Also provided is a method of making such a composition using an extruder. Also provided is a film made by removing water from such a composition.

Claims

1. An aqueous composition having pH of 8 or higher and comprising (a) a solid phase comprising dispersed particles that comprise an amount of ethylcellulose polymer, (b) an amount of one or more polymeric dispersants, wherein said polymeric dispersant has a weight-average molecular weight of 5,000 daltons or higher, and wherein said polymeric dispersant has an acid value of 60 to 190 mg KOH/g of polymer.

2. The aqueous composition of claim 1 wherein said composition comprises monomeric dispersant in an amount of 0 to 0.01% by weight based on the weight of said composition.

3. The aqueous composition of claim 1 wherein said polymeric dispersant comprises one or more olefin copolymers, one or more monoester derivatives of cellulose, or a mixture thereof.

4. A method of making the aqueous composition of claim 1, wherein said method comprises (i) feeding the ethylcellulose polymer and the polymeric dispersant into a melt and mix zone of an extruder wherein the ethylcellulose polymer and the polymeric dispersant are heated and mixed together to form a melt; (ii) conveying the melt to an emulsification zone of the extruder in which the temperature and pressure are controlled; (iii) feeding a base and water into the emulsification zone wherein the melt is dispersed to form an emulsion having 60% to 72% solids by volume; (iv) conveying the emulsion to a dilution and cooling zone of the extruder; and feeding water into the dilution and cooling zone to dilute the high internal phase emulsion thereby forming the aqueous composition.

5. The method of claim 3, wherein said base is a fugitive base.

6. A film made by a process comprising removing water from the aqueous composition of claim 1.

7. The film of claim 5 wherein said film is on the surface of or encapsulating or enveloping a multiparticulate.

8. The film of claim 5 wherein said film is on the surface of a pharmaceutical tablet or pharmaceutical capsule.

Description

EXAMPLE 1

Aqueous Dispersion of EC with PD

[0071] Using a Berstorff extruder (ratio of length to diameter of 36, diameter of 25 mm), EC was delivered using a Schenck Accurate volumetric solids feeder equipped with a large tube and large open helix, and PD was delivered by a second Schenck Accurate volumetric solids feeder equipped with a large tube and large helix. EC and PD were delivered to a heated melt and mix zone to produce a melt. The melt was conveyed to an emulsification zone and mixed with water and ammonia to produce an emulsion. The barrels were set to 170° C. The front end heaters (3-way valve, back pressure regulator) remained on during the run and set to 180° C. The initial water feed heater (“IA heater”) was turned on to deliver at ˜160° C. The dilution water heater was set to 120° C. Extruder exit temperature was 165° C.

[0072] The weight ratio of EC to PD was 70:30. The mole ratio of ammonia to carboxyl groups on the PD was 1.4:1. The solids content of the emulsion was 70% by weight.

[0073] Resulting dispersion: pH was 9.27; solids was 26.95% by weight; viscosity (Brookfield RV2, 50 rpm, 25° C.) was 22 mPa-s; volume-average particle diameter was 0.552 μm.

COMPARATIVE EXAMPLE A

EC, DBS, and Oleic Acid

[0074] Using the same extruder as Example 1, EC was delivered using a Schenck Accurate volumetric solids feeder equipped with a large tube and large open helix. The DBS and oleic acid were blended at a 16.25/8.75 weight ratio and delivered using an ISCO syringe pump that was plumbed into the melt zone. The melt zone was set to 135° C., the emulsion zone was set to 125° C., and the exit zones were set to 145° C. Water and ammonia were introduced into the emulsion zone. The front end heaters (3-way valve, BPR) remained on during the run and set to 180° C. The IA heater was turned on to 150° C. to ensure that it was delivering at least at 130° C. The dilution heater was set to 120° C. Extruder exit temperature was 140° C.

[0075] Weight ratios of EC/DBS/Oleic acid were 74/17/9. The mole ratio of ammonia to oleic acid was 1.4:1. The solids content of the emulsion was 82% by weight.

[0076] The properties of the resulting dispersion: pH was 9.02; solids level was 27.02% by weight; viscosity (Brookfield RV2, 50 rpm, 25° C.) was 117 mPa-s; volume-average particle size was 0.203 um.

EXAMPLE 2

Composition with DBS

[0077] The dispersion of Example 1 was mixed with DBS. The amount of DBS was 27% by weight based on the total weight of solids in the dispersion. The liquid DBS was added to the aqueous dispersion and combined with a impeller spinning at 200 rpm for 2 minutes.

EXAMPLE 3

Tensile Testing of Films

[0078] Films were cast as follows: Films were cast at thickness of 0.5 mm (20 mil) wet onto a pre-cleaned glass plate using a BYK four-sided draw-down bar. Films were covered and transferred to an oven set to 60° C. to cure for 2 hr. Films were then taken to a controlled humidity room (55% relative humidity, 22° C.) for at least 12 hrs for the moisture content of the films to equilibrate.

[0079] Tensile measurements were taken using an Instron™ frame 4201 tensile tester using a 50N static load cell (11 lb) equipped with smooth rubber grips. Prior to analysis, the films were held in a controlled humidity room (22° C., 50% RH) and allowed to equilibrate for a minimum of 12 hrs Immediately prior to analysis, the films were removed from the glass substrates using a straight blade to lift and peel the films away from the surface of the glass plate. The films were punched using a pneumatic press using the ASTM D638 type V (dog bone) die. Each type of film was analyzed using ten samples cut from at least three different films. The thickness was determined by measuring along three points of the center of the film strips using a Mitutoya Digimatic™ Indicator and taking the average thickness. The strips were pulled at 0.508 cm/min (0.2 in/min). The Young's modulus was measured by fitting the points in the linear area of the stress/strain curve. The maximum stress (reported as Tensile Strength) and strain at break (reported as % Elongation) were manually determined by reading the values from the stress/strain curve.

[0080] Results were as follows:

TABLE-US-00001 Young's Modulus Elongation Tensile Strength Sample (MPa) (%) (MPa) Comparative Example 23.1 39.0 1.3 A Example 2 32.6 35.6 2.1
Example 3 had comparable elongation to Comparative Example A, and Example 3 had improved Young's Modulus and Tensile Strength over Comparative Example A.

COMPARATIVE EXAMPLE B

Attempts to use PVOH

[0081] A procedure using an extruder as in Example 1 was attempted. The ingredients fed to the extruder were EC, vegetable oil plasticizer (VEG-P), and PVOH (MOWIOL™ 18-88 polyvinyl alcohol, 87% hydrolyzed, from Clariant GmbH). No base was fed to the extruder. Feed rates were as follows:

TABLE-US-00002 Feed Rates (grams/minute) EC VEG-P PVOH Initial Aqueous Dilution Water 41.2 11.4 4.2 10.0 115 41.2 11.4 4.2 15.1 115 41.2 11.4 4.2 18.9 115 41.2 11.4 4.2 22.1 115 41.2 11.4 4.2 30.9 115
In all attempts, no dispersion of EC resulted.