DESC: FIELD OF THE INVENTION:-
The invention relates to the acid resistance capsule. More particularly a composition for acid resistance capsules and process for making same.

BACKGROUND OF THE INVENTION:-
The object of present invention is to develop hard capsule shell which will provide acid resistance to the active pharmaceutical ingredient, food supplements and other nutritional products which undergo degradation in presence of acid.
Natural or synthetic substances which are acid unstable undergo chemical degradation in acidic environment present in stomach. Pharmaceutical drugs or compositions intended for oral consumption for human or animal, which releases in stomach are associated to gastric side effects such as gastric reflux or impairment of physiological and/or structural integrity of gastric mucosa. Such substances need complete protection or atleast some long time protection from gastric pH particularly for treatment of healthy human.
One such form to administer the substance is capsule. Capsules are being produced for centuries and most popular polymer is Gelatin. People tried to coat the filled gelatin capsule with solvent based acid resistance compositions. However could not produce high quality reproducible results due to poor adhesion on gelatin surface.
HPMC capsules were found to be better. There were 2 different technologies for manufacturing hard HPMC capsules. In first stainless steel pins are dipped in HPMC solution or slurry optionally having some gelling agent such as carrageenan or Gellan gum or pectin. Co gelling aid suitable for that gelling agent is also added. The capsules are then removed from dipping dish and dried at cold atmosphere with lower RH so that the gelling agent supports formation and drying takes place due to low RH of surrounding air. This is described in various patents such as US5264223, US5431917, US5756123, US6410050, EP1057862, WO2007020529. Another technology is to pre heat the stainless pins and dip in cold HPMC solution. The pin temperature gels the HPMC solution surrounding pin and gets picked up while removing pins from the dipping dish. The wet gel is than supplemented with additional heat so that the gel remains in same form and drying takes place. This process is also known as Thermo gelling process. The polymers that do not have thermo gelling behavior can be supported by thermo gelling agents commercially available. This is also described in various patents such as WO2008050209, US2014088202.
However making HPMC capsules first and then coating with acid resistant polymer adds one more process step. Hence objective of present invention is to manufacture hard capsule shell which will have acid resistant property.
The variety of acid resistant polymers are commercially available such as polymethacrylate (co polymer of methacrylic acid either methylmethacrylate or ethyl acrylate), cellulose base polymers such as Cellulose acetate Phthalate (CAP). HPMC phthalate (HPMC-P), HPMC Acetate succinate (HPMC-AS), polyvinyl acetate phthalate. Largely they are soluble and used in solvent.
More suitable form of composition for capsule manufacturing is making aqueous base composition.

OBJECT OF THE INVENTION:-
Object of the present is invention is to develop the acid resistance capsules and process for making the same.
It is also the object of the present invention is to manufacture hard capsule shell having varying acid resistance property.
Yet another object of the present invention is to manufacture hard capsule shell with HPMC-AS.
Yet another object of invention is to develop process to make aqueous composition of HPMC-AS
It is also object of the present invention to identify suitable supporting film forming agent to manufacture capsule.
It is also object of the present invention to manufacture hard capsule with using thermo gelling technology.
Yet another object of the present invention is to find suitable alkali to make aqueous composition of HPMC-AS.
It is also the object of the present invention to eliminate the drawbacks and / or shortfalls of the prior art.

STATEMENT OF INVENTION:
Accordingly (claim 1) invention provides an acid resistance HPMC capsules comprises 20 to 49% of acid resistant polymer and is hard shell made by mixer of an acid resistance polymer HPMC-AS , reacted with alkali to make aqueous composition solution and a second a film forming polymer is HPMC dispersed first in hot water to make aqueous solution and thereafter cooled such that ratio of the dry basis HPMC-AS to HPMC will be between 20:80 to 49:51; further processing aids such as colourants, plasticizers, surfactants like added during mixing of the said solutions.
Accordingly (claim 6), the invention also provides a process for making the acid resistance HPMC capsule comprises steps
(i) making aqueous composition of polymer HPMC-AS (hydroxypropyl methyl cellulose acetate succinate) by adding alkali in water thereby reacting polymer at low temperature;
(ii) making aqueous composition of polymer HPMC by dispersing HPMC in hot water and cooling the said solution thereafter;
(iii) mixing the said aqueous solution of HPMC-AS of step (i) and HPMC of step (ii) in a fixed dry basis ratio between 20:80 to 49:51;
(iv) adding processing aid such as colouring agents, plasticizers, surfactants to the said solution of step (iii) to maximum of 10% on dry polymer composition;
(v) pouring the said solution of step (iv) in dipping dish;
(vi) preheating the stainless steel pins to temperatures between 80 to 120 deg C prior to dipping;
(vii) dipping the said pins in the said solution of step (v) maintained at temperature between 15 to 25 deg C;
(viii) withdrawing the said pins at a predefined sequence of velocity and time;
(ix) distributing and transferring the picked wet mass by the said pin to oven type of tunnel having temperature between 120 to 60 deg C to bring down water content of wet shell formation;
(x) subjecting the said pins at lower temperature once the said wet shell water content reaches below 50% and air blasting between 30 to 40 deg C till the shell moisture reaches below 8 %;
(xi) Removing the said shells of step (ix) from pins, cutting to required length and then joining together to form capsule.

SUMMARY OF THE PRESENT INVENTION:-
According to present invention, hard capsules can be produced having acid resistance property. The acid resistance polymer is HPMC-AS and another film forming polymer is HPMC. HPMC-AS is first reacted with alkali to make aqueous composition. HPMC is also dispersed first in hot water and then on cooling complete solution is prepared. Both the solutions are then mixed in such a ratio that the dry basis ratio of HPMC-AS to HPMC will be between 20:80 to 49:51. To this processing aids are added such as colourants, plasticizers, surfactants etc. The capsules are produced as follows
(i) Aqueous composition of HPMC-AS is made by adding alkali in water then reacting polymer at low temperature.
(ii) Aqueous composition of HPMC is made by dispersing HPMC in hot water and then cooling the same.
(iii) Both the above are mixed at a fixed dry basis ratio between 20:80 to 49:51
(iv) Processing aid such as colouring agents, plasticizers, surfactants are added to maximum of 10% on dry polymer composition.
(v) The solution is then poured in dipping dish.
(vi) Stainless steel pins are pre heated to temperatures between 80 to 120 deg C prior to dipping.
(vii) Pins are dipped in solution of temperature between 15 to 25 deg C
(viii) Pins are withdrawn at a predefined sequence of velocity and time.
(ix) The picked wet mass is then distributed and transferred to oven type of tunnel. The temperature is subjected between 120 to 60 deg C
(x) Once the wet shell water content reaches below 50 % the pins are subjected to low temperature air blast between 30 to 40 deg C till the shell moisture reaches below 8 %
(xi) The shells are then removed from pins, cut to required length and then joined together to form capsule.

DETAILED DESCRIPTION OF THE INVENTION:-
Capsule manufacturing is mainly dependent on polymers rheological behavior. Mainly its viscosity at the temperature of dipping, maximum viscosity it can attain while setting and whether it has gelling ability or not.
In thermo gelling technology all these values are to be evaluated by gradually increasing the temperature. Viscosity at dipping temperature is evaluated by subjecting polymer solution in small cylinder of Brookefield viscometer LV DV II+pro viscometer with spindle no S-31 and at 100 rpm. Maximum viscosity is measured on Anton Paar rheometer model- MCR51 and by rotational method with 0.5 sec-1 shear rate. The temperature is gradually increased and viscosity constantly measured. We get onset of Gelation and highest viscosity at certain temperature. Gelling ability is measured by measuring polymer solutions storage modulus (G’) and loss modulus (G”). Initially loss modulus ia high and storage modulus is low. As the temperature increases the storage modulus increases. The point at which both cross, is known as gel point. This is also measured on Anton Paar rheometer model – MCR51 and in Oscillation mode. The strain maintained at 20% and angular frequency maintained at 10 rad/sec.
All the above measurements decide the suitable alkali to be used and also suitable substitution type of HPMC to be used.
According to present invention the acid resistant polymer is HPMC Acetate Succinate (HPMC-AS) and film forming polymer is HPMC.
HPMC-AS means polymer hydroxypropyl methyl cellulose acetate succinate. HPMC-AS is commonly known in the field of polymers with the additional alternative nomenclature: Hypromelose acetate succinate. Cellulose,2-hydroxypropylmethyl ether, acetate, hydrogen butanedioate. Its CAS registry number is 71138-97-1.
Commercially available HPMC-AS is AffinisolTM HPMCAS from DOW, AQOAT from Shinetsu and Aquasolve AS from Ashland. Shinetsu has different grades corresponding to its succinoyl group and acetyl group range. “L” grade has acetyl group 5-9% and Succinoyl group 14-18%. “M” grade has acetyl group 7-11% and Succinoyl group 10-14%.“H” grade has acetyl group10-14% and Succinoyl group 4-8%. The varying substitution combination decides the pH at which the polymer will began to dissolve. It also has the powder in micronized grade ( F) and granular grade (G). “F” grade has average particle size as 1 micron where as “G” grade has average particle size as 5 microns.
In another embodiment the HPMC -AS is of low pH grade
In another embodiment the HPMC-AS is granular grade
In another embodiment the preferred HPMC is 2208 or 2906 or 2910 chemistry. More preferred is 2906 chemistry.
In another embodiment the preferred viscosity grade of HPMC is 3 to 15 cps more preferably between 4 to 6 cps.
The preferred ration of HPMC-AS to HPMC is between 20:80 and 49:51
To make clear solution HPMC-AS needs to be neutralized. Neutralization means succinis acid groups present in the HPMC-AS polymer is neutralized or converted from the protonated to anionic form by addition of an alkaline material.
The preferred alkali selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), ammonium hydroxide (NH4OH),
The composition of present invention may further comprise plasticizers, surfactants, anti microbial agents, coloring agents and so on.
The coloring agents and opacifiers are selected from permitted colorant and dyes as listed in Rule 27 of Drugs and Cosmetics Act and Rule ( India) and permissible under the regulatory requirements of the country of use. They comply with the Bureau of Indian Standards (BIS) and / or Code of Federal Regulations (CFR) and / or EEC directives.
In an embodiment, the coloring agent may be a color selected from the group comprising annatto, carotene, chlorophyll, cochineal, curcumin, caramel, riboflavin, red iron oxide, yellow iron oxide, titanium di-oxide, black iron oxide and mixtures thereof.
In yet another embodiment, the coloring agent may be selected from quinazarine green, alizarin cyanine green, fast green, tartrazine, sunset yellow, quinoline yellow, erythrosine, eosin YS, toney red, ponceau 4R, carmoisine, indigo carmine, brilliant blue, orange G, resorcin brown, naphthol blue black, allura red, and combinations thereof.
In another embodiment, the coloring agent may be lake salts (example aluminum) any of the above listed water soluble coloring agents and combinations thereof.
The coloring agent is preferably used in an amount of from 0.01 to about 8% w/w of dry polymer.
The plasticizers and surfactants are selected from glyceryl esters, glycol esters, sorbitan monoesters, sorbitan polyoxyethylene esters, polyoxyethylene ethers, glycerols, polyethylene glycols, polyols, fatty acid esters, glycerol polyethylene, glycol ricinoleate, macrogolglycerides, SLS, Tryethyl citrate (TEC), Actyl Tryethyl citrate (ATEC), triacetine and mixture thereof.
The plasticizers and surfactants are preferably used in an amount of from 0.01 to about 5% w/w of acid resistant polymer.
The detailed manufacturing process for preparation of improved acid resistance capsule shell comprises the following steps:
(i) Aqueous composition of HPMC-AS is made by adding alkali in water then reacting polymer at low temperature.
(ii) Aqueous composition of HPMC is made by dispersing HPMC in hot water and then cooling the same.
(iii) Both the above are mixed at a fixed dry basis ratio between 20:80 to49:51
(iv) Processing aid such as colouring agents, plasticizers, surfactants are added to maximum of 10% on dry polymer composition.
(v) The solution is then poured in dipping dish.
(vi) Stainless steel pins are pre heated to temperatures between 80 to 120 deg C prior to dipping.
(vii) Pins are dipped in solution of temperature between 15 to 25 deg C
(viii) Pins are withdrawn at a predefined sequence of velocity and time.
(ix) The picked wet mass is then distributed and transferred to oven type of tunnel. The temperature is subjected between 120 to 60 deg C
(x) Once the wet shell water content reaches below 50 % the pins are subjected to low temperature air blast between 30 to 40 deg C till the shell moisture reaches below 8 %
(xi) The shells are then removed from pins, cut to required length and then joined together to form capsule.
The present invention will now be described with reference to the examples below:
Example – 1
S-1) Preparation of 1kg Aqueous composition of HPMC-AS with NaOH
Take 200 gm of HPMC AS of shinetsu LG grade. Disperse it in 740 gm cold water of 10 deg C under constant stirring. Also take 12 gm of NaOH and dissolve it in 48 gm of water. Slowly add the caustic solution in the dispersion under stirring of HPMC-AS and water. The reaction starts and aqueous solution of HPMC-AS get ready. Hold it for some time to eliminate foam and bubbles.
S-2) Preparation of 1kg Aqueous composition of HPMC-AS with KOH
Take 200 gm of HPMC AS of shinetsu LG grade. Disperse it in 720 gm cold water of 10 deg C under constant stirring. Also take 16 gm of KOH and dissolve it in 64 gm of water. Slowly add the KOH solution in the dispersion under stirring of HPMC-AS and water. The reaction starts and aqueous solution of HPMC-AS get ready. Hold it for some time to eliminate foam and bubbles.
S-3) Preparation of 1kg Aqueous composition of HPMC-AS with NH4OH
Take 140 gm of HPMC AS of shinetsu LG grade. Disperse it in 848 gm cold water of 10 deg C under constant stirring. Slowly add 12.3 gm Ammonia solution (30%) in the dispersion under stirring of HPMC-AS and water. The reaction starts and aqueous solution of HPMC-AS get ready. Hold it for some time to eliminate foam and bubbles.
S-4) Preparation of 1kg Aqueous composition of HPMC (2910 chemistry HP above 8.5%)
Take 200 gm of HPMC of 2910 chemistry. Disperse it in 800 gm hot water of 80 deg C under constant stirring. Cool the solution to 10 deg C. Aqueous solution of HPMC will get ready. Hold it for some time to eliminate foam and bubbles.
S-5) Preparation of 1kg Aqueous composition of HPMC (2906 chemistry)
Take 200 gm of HPMC of 2906 chemistry. Disperse it in 800 gm hot water of 80 deg C under constant stirring. Cool the solution to 10 deg C. Aqueous solution of HPMC will get ready. Hold it for some time to eliminate foam and bubbles.
Example – 2
Preparation of compositions and measurement of rheological behaviors.
Prepare compositions as per table below.
Measure following parameters
1- Measurement of viscosity at 25 deg C
Take small sample in sample holder of Brooke field LVDV II+pro viscometer. Use spindle no S-31 and measure viscosity at 25 deg C at 100 rpm.
2- Measurement of gel point
Take small sample in sample holder of Anton Paar MCR51 rheometer. By using oscillation mode measure storage modulus (G’) and loss modulus (G”). Set the strain as 20% and angular frequency as 10 rad/sec. Measure the values by gradually increasing temperature from 20 to 80 deg C. The point of intersection is gel point.
3- Measurement of peak viscosity
Take small sample in sample holder of Anton Paar MCR51 rheometer. Measure viscosity by using rotational mode. Set the shear rate as 0.5 sec-1. Measure the values by gradually increasing temperature from 20 to 80 deg C. The viscosity will start increasing at some temperature and reach to peak value. It will then drop. Note peak viscosity value.
Trial code Solution as S-1 Solution as S-2 Solution as S-3 Solution as S-4 Solution as S-5 TEC
T1 200 gm 800 gm - 0.2 gm
T2 300 gm 700 gm - 0.3 gm
T3 400 gm 600 gm - 0.4 gm
T4 490 gm 510 gm - 0.5 gm
T5 200 gm - 800 gm 0.2 gm
T6 300 gm - 700 gm 0.3 gm
T7 400 gm - 600 gm 0.4 gm
T8 490 gm - 510 gm 0.5 gm
T9 200 gm 800 gm - 0.2 gm
T10 300 gm 700 gm - 0.3 gm
T11 400 gm 600 gm - 0.4 gm
T12 490 gm 510 gm - 0.5 gm
T13 200 gm - 800 gm 0.2 gm
T14 300 gm - 700 gm 0.3 gm
T15 400 gm - 600 gm 0.4 gm
T16 490 gm - 510 gm 0.5 gm
T17 57 gm 160 - 0.24 gm
T18 85 gm 140 - 0.36 gm
T19 114 gm 120 - 0.48 gm
T20 143 gm 100 - 0.6 gm
T21 57 gm - 160 0.24 gm
T22 85 gm - 140 0.36 gm
T23 114 gm - 120 0.48 gm
T24 143 gm - 100 0.6 gm

Result –
Trial no Viscosity at 25 C - cps Gel point in C Peak viscosity-cps Trial no Viscosity at 25 C - cps Gel point in C Peak viscosity-cps
T1 3395 55 68600 T5 3890 45 172000
T2 3419 51 54500 T6 4250 46 142000
T3 3502 50 60400 T7 4769 47 137000
T4 3560 53 59200 T8 5016 50 140000
T9 4305 55 81400 T13 9200 52 121000
T10 4620 53 77500 T14 8400 54 110000
T11 4911 52 89200 T15 7500 52 109000
T12 5040 53 95700 T16 7198 55 109000
T17 3500 55 53000 T21 5100 47 160000
T18 3000 56 37000 T22 4500 48 108000
T19 2200 58 25000 T23 4000 50 84000
T20 2000 57 20000 T24 3800 52 73000

As can be seen that trials where S-5 solution was used gel points are lower temperature and also peak viscosity is high as compared to S-4 solution. Also combination of S-1 and S-5 gives low viscosity at 25 deg C and yet high peak viscosity. This is very critical for good formation of shells as well as manufacturing shells at high machine speeds.
Example – 3
Manufacturing capsules.
Solution were prepared as per few trial combination. The solution was poured in dipping dish and maintained at 22 deg C. Pins were pre heated between 90 to 125 deg C and then dipped in dipping solution. The picked wet mass is then distributed around pin and subjected to high temperature in oven type tunnel. The air temperature is varied between 120 to 65 deg C till the shell water content reduces to below 50 %. The pins with wet film is then exposed to cold air blast of temperature between 25 to 40 deg C. The dried shells were then removed from pin , cut to specified length and joined to form capsules. The capsules were then evaluated for appearance, defects, taste, brittleness strength etc.

Results –
Trial no Appearance Defects
Taste Brittleness
Strength
T4 Thin capsule Low dome Neutral No brittle weak
T6 Good capsule No defect Neutral No brittle Good
T8 Good capsule No defect Neutral No brittle Good
T10 Thin capsule Low dome Neutral No brittle weak
T12 OK capsule No defect Neutral No brittle Good
T15 Good capsule No defect Neutral No brittle Good
T19 No capsule - - - -
T22 OK capsule Cutting defects Bitter Slightly brittle OK
T24 OK capsule Cutting defects Bitter Slightly brittle OK

As can be seen, good capsules can be formed by skill known to operators with nearly all combinations. However with solution S-1 with S-5 the capsule formation and other aspects are much better as compared to others.
Example – 4
In vitro acid solubility and drug release test.
Capsules were manufactured with trial no T5, T6, T7, T8. The capsules were filled with 325 mg Acetaminophen. The capsules were subjected to dissolution test in 0.1 N HCL media and as per Acetaminophen monograph described in USP. Drug release was estimated by taking periodic samples at regular interval.
Results –
Time T5 capsules T6 capsules T7 capsules T8 capsules
0 min 0 % 0 % 0 % 0 %
20 min 6 % 3 % 2 % 0 %
40 min 15 % 8 % 6 % 4 %
60 min 20 % 12 % 11 % 5 %
80 min 32 % 21 % 16 % 6 %
100 min 45 % 30 % 20 % 8 %
120 min 70 % 48 % 30% 10 %

As can be seen, based on the requirement capsules with different release pattern and having acid resistance can be manufactured.
DETAILS OF INVENTION:
• An aqueous composition for making hard capsule shell comprising,
a. An aqueous solution made of acid resistant polymer
b. An suitable alkali to neutralize acid resistant polymer
c. An aqueous solution made of film forming polymer
d. Processing aid
e. Water.

The acid resistant polymer is HPMC acetate succinate and is having acetyl group 5-9% and Succinoyl group 14-18% and of granular grade.
The alkali is selected from sodium hydroxide, potassium hydroxide, ammonia and/or mixture thereof to neutralize the acid resistant polymer. The film forming polymer is HPMC is of HP content between 5 to 8.5 % preferably 2906 chemistry and having viscosity of 4 to 6 cps measured at 20 deg C at 2% concentration. The ratio of acid resistant polymer to film forming polymer is selected between 20: 80 to 49:51. At least one processing aid is plasticizer present in an amount ranging from 0.1% to 5 % by weight of acid resistant polymer present in the composition. The plasticizer is selected from glyceryl esters, glycol esters, sorbitan monoesters, sorbitan polyoxyethylene esters, polyoxyethylene ethers, glycerols, polyethylene glycols, polyols, fatty acid esters, glycerol polyethylene, glycol ricinoleate, macrogolglycerides, SLS, Tryethyl citrate (TEC), Actyl Tryethyl citrate (ATEC), triacetine and mixture thereof. At least one processing aid is colouring agent present in an amount ranging from 0.1% to 10 % by weight of total polymer present in the composition. The colouring agent is selected from permitted colorant and dyes as listed in Rule 27 of Drugs and Cosmetics Act and Rule ( India) and permissible under the regulatory requirements of the country of use. They comply with the Bureau of Indian Standards (BIS) and / or Code of Federal Regulations (CFR) and / or EEC directives.
The colouring agent is selected from the group comprising annatto, carotene, chlorophyll, cochineal, curcumin, caramel, riboflavin, red iron oxide, yellow iron oxide, titanium di-oxide, black iron oxide and mixtures thereof.
The colouring agent is selected from quinazarine green, alizarin cyanine green, fast green, tartrazine, sunset yellow, quinoline yellow, erythrosine, eosin YS, toney red, ponceau 4R, carmoisine, indigo carmine, brilliant blue, orange G, resorcin brown, naphthol blue black, allura red, and combinations thereof.
The colouring agent is selected from lake salts (example aluminum ) any of the above listed water soluble coloring agents and combinations thereof.

• A capsule shell comprising of 20 to 49% of acid resistant polymer and is hard shell.

• A method of manufacturing hard shell according to the present invention consists of the following steps:
a. Aqueous composition of HPMC-AS is made by adding alkali in water then reacting polymer at low temperature.
b. Aqueous composition of HPMC is made by dispersing HPMC in hot water and then cooling the same.
c. Both the above are mixed at a fixed dry basis ratio between 20:80 to49:51
d. Processing aid such as colouring agents, plasticizers, surfactants are added to maximum of 10% on dry polymer composition.
e. The solution is then poured in dipping dish.
f. Stainless steel pins are pre heated to temperatures between 80 to 120 deg C prior to dipping.
g. Pins are dipped in solution of temperature between 15 to 25 deg C
h. Pins are withdrawn at a predefined sequence of velocity and time.
i. The picked wet mass is then distributed and transferred to oven type of tunnel. The temperature is subjected between 120 to 60 deg C
j. Once the wet shell water content reaches below 50 % the pins are subjected to low temperature air blast between 30 to 40 deg C till the shell moisture reaches below 8 %
k. The shells are then removed from pins, cut to required length and then joined together to form capsule.
,CLAIMS:1. An acid resistance HPMC capsules, comprises 20 to 49% of acid resistant polymer, a hard shell made by mixer of an acid resistance polymer HPMC-AS , reacted with alkali to make aqueous composition solution and a second a film forming polymer is HPMC dispersed first in hot water to make aqueous solution and thereafter cooled such that ratio of the dry basis HPMC-AS to HPMC will be between 20:80 to 49:51; further processing aids such as colourants, plasticizers, surfactants and the like added during mixing of the said solutions.
2. The acid resistance HPMC capsules as claimed in claim 1 wherein the said HPMC-AS is of low pH grade.
3. The acid resistance HPMC capsules as claimed in claims 1 and 2 wherein the said HPMC-AS is of granular grade.
4. The acid resistance HPMC capsules as claimed in claims 1 to 3 wherein the said HPMC is 2208 or 2906 or 2210 chemistry and preferably 2906 chemistry.
5. The acid resistance HPMC capsules as claimed claims 1 to 4 wherein the said HPMC having viscosity in the range of 3 to 15 cps and preferably viscosity in the range of 3 to 6 cps.
6. A process for making the acid resistance HPMC capsule comprising the steps of:
(i) making aqueous composition of polymer HPMC-AS (hydroxypropyl methyl cellulose acetate succinate) by adding alkali in water thereby reacting polymer at low temperature;
(ii) making aqueous composition of polymer HPMC by dispersing HPMC in hot water and cooling the said solution thereafter;
(iii) mixing the said aqueous solution of HPMC-AS of step (i) and HPMC of step (ii) in a fixed dry basis ratio between 20:80 to 49:51;
(iv) adding processing aid such as colouring agents, plasticizers, surfactants to the said solution of step (iii) to maximum of 10% on dry polymer composition;
(v) pouring the said solution of step (iv) in dipping dish;
(vi) preheating the stainless steel pins to temperatures between 80 to 120 deg C prior to dipping;
(vii) dipping the said pins in the said solution of step (v) maintained at temperature between 15 to 25 deg C;
(viii) withdrawing the said pins at a predefined sequence of velocity and time;
(ix) distributing and transferring the picked wet mass by the said pin to oven type of tunnel having temperature between 120 to 60 deg C to bring down water content of wet shell formation;
(x) subjecting the said pins at lower temperature once the said wet shell water content reaches below 50% and air blasting between 30 to 40 deg C till the shell moisture reaches below 8 %;
(xi) removing the said shells of step (ix) from pins, cutting to required length and then joining together to form capsule.
7. The process as claimed in claim 6 wherein the said HPMC-AS is of low pH grade.
8. The process as claimed in claim 6 and 7 wherein the said HPMC is of granular grade.
9. The process as claimed in claim 6 and 8 wherein the said HPMC is 2208 or 2906 or 2210 chemistry and preferably 2906 chemistry.
10. The process as claimed in claims 6 to 9 wherein the said HPMC having viscosity 3 to 15 cps and preferably viscosity 3 to 6 cps.