CS252813B2 - Method of shaped products injection moulding - Google Patents

Abstract

Capsules and other shaped products formed from a moldable starch composition in an injection molding device is disclosed in the present invention. The composition comprising starch having a molecular mass range of 10,000 to 20,000,000 Dalton, and a water content range from 5 to 30% by weight. The starch contains about 0 to 100% of amylose, and about 100 to 0% of amylo-pectin.

Description

252813 2

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for injection molding native starch articles with feed. Starch obtained from wheat, potato, corn, rice, tapioca and the like is used. These starch types typically have a molecular weight range of 10,000 to 20,000,000 (Daltons). Starch contains about 0 to 100% amylose and about 100 to 0% amylopectin, preferably 0 to 70% amylose and about 95 to 10% amylopectin.

The term " starch " as used herein also includes foams, modifications, or starch derivatives or combinations thereof with hydrophilic polymer compositions whose properties are acceptable for the desired injection molded articles, especially capsules. 3 7

Hydrophilic polymers are polymers with a molecular weight of about 10 to 10 (Daltons) and with molecular groups in the main and / or side chains that are capable of forming and / or participating in hydrogen bonds. These hydrophilic polymers have an infectious point near the wateractivity point at 0.5 at the water isothermal absorption (in the temperature range of about 0 to 200 ° C).

The hydrophilic polymers of the present invention differ from the group of so-called hydrocolloids with their molecular dispersions - they must contain 5 to 30% by weight in the working range of the invention when the temperature of the hydrophilic polymer is in the working range of 80 to 240 ° C according to the invention.

The capsule manufacturing device has so far been developed for dipping technology. Tatotechnology is that the capsule-shaped mandrels are dipped in gelatin solution, then the solution is removed, the gelatin on the mandrels is dried, the gelatinous parts of the capsule are wiped off the thorns, adjusted their length, cut, joined and discarded. The capsule manufacturing apparatus has yet to realize these functions using a combination of mechanical and pneumatic elements and reaches a production rate of up to 1200 pieces of min. Capsule size. Although the device described is generally suitable for its intended purpose, a considerably higher velocity is required at the same time to produce accurate capsules. by controlling the properties of the starch for the hygienic manufacture of the capsules with minimal dimensional variations that can be filled on a device operating at high speed. A preliminary requirement for the material to be injected is the ability of the glass transition at a temperature compatible with the thermal stability of the material and the technical possibilities of the injection device. A prerequisite for the material from which molded products with high dimensional stability are to be produced is its minimal elastic relaxation upon opening the mold. This can be achieved by adjusting the dispersion of the material to the molecular level during injection.

Shirai et al., U.S. Pat. No. 4,216,240, describes injection molding to form an oriented fiber protein product. The fibrous product obtained in this way differs fundamentally from the transparent glassy material to the capsules of our invention. Furthermore, in order to obtain a liquid mass for injection, the Shirai and d. Protein blends must be denatured and thus lose the ability to undergo dissolution.

U.S. Pat. No. 4,076,846, Nakatsuka, et al., Uses binary starch mixtures with proteinaceous salts to obtain an edible molded article. According to our invention, it is possible to obtain molded starch products without the addition of proteinaceous salts.

Heusdens et al., U.S. Patent No. 3,911,159 discloses the formation of fibrous protein structures "to produce edible products with improved softness. According to our invention, shaped products are produced without fibrous protein structure.

The use of an injection molding machine for the production of starch capsules is new and has not been described in the technical literature. Many useful products can be produced from the starch by injection molding, requiring "low dimensional stability and minimum dimensional variations".

These include, for example, confectionery, food packaging, pharmaceutical products, chemicals, dyes, spices, fertilizer compositions, seeds, cosmetic products, agricultural products and matrixes of starch compositions of various shapes and sizes, containing substances and / or active ingredients, including foodstuffs, pharmaceuticals, chemicals, dyes, spices, fertilizer compositions, seeds, cosmetic products and agricultural products, which are dispersed in the matrix and released from it by disintegration and / or dissolution and / or bioerose / or diffuse the starch used, depending on the dissolution characteristics Some of these products may also be in a controlled release system of the formulation. Further, medical and medical products can be obtained by injecting starch compositions. Starch biodegradability makes it more convenient to use non-currently used substances in terms of environmental protection. The nontoxicity of the composition further enhances its suitability for injection molding material. The subject matter of our invention differs from the above-described prior art in that starch lubrication temperature intervals lie within a temperature range suitable for injection when the starch water content lies within a characteristic range that makes it possible to dispense with no further drying or wetting of the capsules. Above the lubricating temperature, the starch is in a state of molecular dispersity. During the injection process according to the invention, the starch is for a considerable time higher than the lubricating temperature. When drugs, foods and other substances are dispersed in starch compositions, it is not possible to use such amounts that would affect the properties of the starch so that it would no longer be injectable. SUMMARY OF THE INVENTION The present invention relates to a method for injecting molded articles, wherein the native starch having a water content of 5 to 30% by weight is plasticized at a temperature of 80 to 240 ° C and injected at a temperature of 80 to 240 ° C and a pressure of 600 to 10,000. the cooled mold and the solid product is discarded. The starch composition has a water content in the range of about 5 to 30% by weight. It contains about 0 to 100% amylose and about 100 to about 0 amylopectin. The starch composition of the invention is suitable for injection molding without the aforementioned disadvantageous prior art.

From the starch composition according to the invention, capsules with high speed and precision can be produced by injection molding and can then be used in high speed filling equipment.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by the drawings for better understanding thereof.

FIG. 1 presents a schematic sketch of a reciprocating worm injection machine for producing capsule parts.

Fig. 2 is a schematic diagram of the operating cycle of the capsule parts.

FIG. 3 is a schematic diagram of an embodiment of a combined microprocessor injection molding apparatus for capsule components.

Fig. 4 is an enlarged diagram of the outlet portion of the injection device.

FIG. 5 shows a diagram of the dependence of the starch shear viscosity in the shear rate range corresponding to the present invention.

FIG. 6 shows a diagram of a starch forming region in the temperature and pressure range of a starch according to the invention.

Fig. 7 is a plot of the glass transition temperature range and temperature range within the starch water content of the invention. 252813 4

FIG. 8 is a plot of differential calorimeter recording where the starch consumable is plotted against the temperature range of the invention.

Fig. 9 is a plot of the equilibrium water content of starch in a water activity program. The following symbols are used in the text:

Table II symbol unit description T, Pa and ° C, Pa H (T, P) kJkg K (T, P) N_1m2 (T, P) (θοΓ1 V (g, T, P) kgs l

Ambient temperature and pressure.

Enthalpy of starch-water system at a given temperature.

Compressibility of starch at a given temperature and pressure. Its numerical value corresponds to the relative change in volume due to a change in pressure on the unit. TM1 TM2 T.

M T (t)

Tt (t)

Pa

Volume thermal expansion coefficient of starch for a given temperature and pressure. Its numerical value corresponds to the relative change in volume due to the change in temperature per unit of quantity.

The rate of flow of starch at a given temperature, velocity shear deformation (s - "*), and pressure. Its numerical value corresponds to the volume of the melt leaving the outlet cross section of the injection device due to the shear rate used.

Starch glass transition temperature range.

Melting range of partially crystalline starch.

Melting temperature.

The temperature of the starch in the nozzle area of the injection unit.

Starch temperature in the mold.

Starch pressure in the mold.

Starch pressure in the nozzle area.

Water content of starch, expressed as weight of water-starch system. 5 252813

For control and regulation. The injection process (IMP) requires 1) heat consumption in the melting process: H (T, P) to H (T, P) 'n' a 'and 2) the rate of starch heating in the injection device. To calculate these values, the heat conduction value of starch and the heat transfer value between starch and the structural material of the roller in contact with the starch are required. The heating rate and heat consumption of the starch provide the minimum time interval necessary to prepare the starch for injection, and the necessary heating value of the injection device. 3) Tn depends on X in the starch. If the starch water content is too low, it is too high to cause degradation. A minimum water content of 5% by weight is required to maintain below 240 ° C. 4) The flow rate V (g, T, P) is also strongly dependent on the water content of the starch. To accelerate the IMP, a high flow rate V (g, T, P) is required, which can be achieved by a higher water content

The upper limit of the water content is defined by the adhesion and mechanical deformation of the capsules? usually not exceeding a water content of 0.30. Starch in the mold reduces its volume due to temperature changes T to T. This would result in empty volumes and reduced capsule sizes, which would have unacceptable quality. It is an important requirement in the manufacture of capsules that dimensional variations are less than 1%. To compensate for precipitation when temperature changes, the mold should be filled at a precise pressure of Pfi. This filling pressure is determined by the sizes (T, P) and K (T, P). The injection pressure (P1) again depends on T, which, as already mentioned, is strongly dependent on X.

Fig. 5 shows the dependence of the starch shear viscosity at 130 ° C on the velocity shear deformation for starch with a water content of X 0,2 0.2.

Fig. 6 is a diagram of a starch forming region with a water content of 0.24. During injection, the plasticized starch is discontinuously extruded and immediately cooled in a mold having the desired portion of the capsule. Formability depends on the properties of the starch and the process conditions, the most important of which are the thermomechanical properties of the starch, as well as the geometry and temperature and pressure conditions of the mold. On the forming diagram in Fig. 6, the pressure and temperature limits for the processing of starch by injection are shown in combination with a microprocessor. The maximum temperature of 240 ° C is determined by the visible starch degradation over which it occurs. The lower limit of 80 ° C was determined by the development of too high a viscosity and melt elasticity in a preferred range of water content of X = 0.05 to 0.30. The upper pressure limits of 3.10 Pa are given by the onset of overflows when the starch melt flows into the gap between the nozzles of of different metals forming the mold, while forming thin strips adhering to the finished capsule components in place of the dividing lines. The lower intermediate pressure of about 6.10 Pa is due to the formation of reject sprays, when the mold cannot be completely filled with starch. Table III lists the operating parameters of the injection molding process using the inventive starch composition.

Table III

Working parameters of injection molding process

Density 1.5.10 ^ kgm

Crystallinity 20 to 70% H (Tn, Pn) to H (Ta, Pa) 63 kJkg-1 252813 6 Net calorific value for 10 kg melt / h (corresponding to 10 °

capsules / h) 6.3.102 kJ (Ta, Pa) 3.1.10-4 <° C) -1

Contraction due to crystallization negligible

The critical shear rate of deformation 10 to 10 with the starch composition of the present invention is extruded and molded as follows.

Fig. 7 shows the glass transition temperature range and the melting point range as a function of the starch-water system composition. The melting range of over 100 ° C is very wide compared to, for example, the melting point of gelatin, which is about 20 ° C. At temperatures below the glass transition range, ordinary starch, commercially available, is a semi-crystalline polymer containing about 30-100% amorphous by volume and 0 to 70% by volume of the crystalline fraction. When the starch temperature rises at a precise water content, the starch passes through a glass transition range. Referring to Fig. 1, this process of starch heating takes place in the extrusion cylinder 17. In Fig. 2, the process of heating the starch corresponds to the time of the entire injection cycle. The area in Fig. 7 between the glass transition range and the melting range is called the area II. In region II, we find crystalline starch and starch melt. The glass transition is not a thermodymic transition of any order, but is characterized by a change in molecular starch molecular motion and a few orders of magnitude of the amorphous starch's elastic modulus. By switching from region II to region I in Fig. 7, the translational movement of molecular starch or large portions thereof freezes within the glass transition temperature range, and this is reflected in the change in specific heat (c ^) and the thermal coefficient of expansion () in this range. By moving from area II to zone III, the spiraling portion of starch melts due to the transition of the crystalline starch melting range. Referring to Figure 1, this starch heating process takes place in an extrusion cylinder 17. In Figure 2, this starch heating process takes place throughout the entire injection cycle. This spiral-coil transition is a true first order thermodynamic transition and is an endothermic process. It can be detected by calorimetry or by measuring the change in the linear volume viscoelastic modulus due to temperature changes. A typical temperature difference record of the differential calorimeter is shown in Figure 8. On the vertical axis, the heat consumption rate of the sample in relation to the reference sample (empty sample holder) is plotted. The rate of heat consumption by the sample depends on the temperature of the starch sample that is carried on the horizontal axis in degrees Celsius. The baseline offset corresponds to the glass transition and the top of the match or spiral coil transition. The linear volume viscoelastic modulus E can be measured at low sinusoidal shear deformations of the starch sample. Referring to FIG. 1, starch heating is even higher than TM in the front pressurizing roller 17. This heating is not only due to the heating coils 28, but to a large extent also to the internal friction during the rotation of the screw and injection due to high deformations. the elastic deformation of the injected starch 14 upon opening the mold is negligible if the temperature of the plasticized starch 14 during injection is higher than the TM; otherwise, the forming sequence is reduced by at least one order. Referring to FIG. 2, the required time of cooling of the plasticized starch in the mold - in order to avoid reversible elastic deformation of the starch - is located between the duty cycle points B and E.

Reducing the forming sequence associated with long starch dwelling in the mold is undesirable for two reasons: low product yield and loss of water contained in the starch in the extruder. At an elevated injection temperature, water is always transferred from the hot cylinder to the cold starch in the extrusion cylinder. This water transport can be compensated for by the transport of starch in the opposite direction. Referring to FIG. 1, starch is transported by the action of a screw with respect to FIG. 2, the starch is transported between C and D points of the duty cycle. In order to create a stationary water content in the starch in the melting region of the extrusion cylinder, it is necessary to work with a short sequence of injection. In order to create a constant sufficiently high water content in the starch in the extruder, it is necessary to use starch with the appropriate sorption isotherm shape (Fig. 9). The constant water content of starch in the extruder is necessary to maintain constant production conditions. condition X is greater than 0.05, otherwise T1 is greater than 240 ° C, undesirable for starch degradation In the branching and crosslinking process, it is important to add crosslinking agents, especially, crosslinking agents, shortly before the molten starch is injected. Referring to FIG. 1, an aqueous solution of crosslinking agents is injected prior to the mixing assembly positioned between the extrusion roller 17 and the nozzle 15. Referring to FIG. 4, this is integrated in the valve body 50. For example, the crosslinking reaction takes place during the injection cycle and the time after the capsule is ejected. . In the above E-described technology, branching does not occur when a change thermomechanických sítováník disadvantageous properties of the starch polymers during the melting and dissolution. Starch compositions are extruded and injected under the conditions shown in Table IV.

Table IV

Injection Unit

Screw diameter mm 24 _ 28 32 18 Injection pressure Pa 2, 2.-108 1.6.108 1.108 Injection volume 3 cm 38 51.7 67.0 21.3 Effective screw length L: D 18.8 16.1 13.0 18 Plasticizing capacity (PS) kg / h (max) la) 13.5 21.2 21.0 11a) 9.2 14.5 15 lb) 23.6 34 36 11b) 17.5 27 27.0 Screw augmentation mm (max) 84 84 84 84 Injection Capacity kW 30 30 30 Injection Speed mm / s (max) 2,000 2,000 2,000 2,000 Touch Force Nozzle kN 42.2 41.2 41.2 41.2 Rotational Speed Screw. -1mm la) 20 to 80 11a) 20 to 17 lb) 20 to 60 11b) 20 to 40 6 252813 8

Number of heating zones 55 55

Installed heating power kW 6.1 6.1 6.0

Forming Unit Clamping Force kN 60

In addition to capsule injection, one skilled in the art can also use the described process to produce capsule profile extrusion, molding, vacuum forming, thermoforming, extrusion, casting, and vacuum molding. The term "forming" is therefore chosen to include all of the above methods; however, injection molding is most preferred. A preferred embodiment of the invention consists in injecting starch capsules from different types of starch, but it has been found that high quality capsules can also be produced according to the present invention using starch modified by a) crosslinking agents, for example: epichlorohydrin, dicarboxylic anhydride, formaldehyde, phosphorus oxychloride, metaphosphate, acrolein, organic divinylsulfones and the like, b) crosslinking the starch with microwaves and the like, c) pretreatment, such as with acids and / or enzymes, to obtain dextrins and / or pregelatinization and / or ultrasonic treatment and / or; gamma irradiation, d) chemical modification such as oxidized starch, starch monophosphate, starch diphosphate, starch acetate, starch sulphate, starch hydroxyethyl ether, carboxymethyl starch, ether starch, 2-hydroxypropyl starch, alpha starch, starch xanthide, starch-chloroacetic acid, starch ester, formaldehyde starch, sodium starch glycolate, and e) using mixtures or a combination of such modified starches, respectively. procedures a) to d) for modifying starches. Furthermore, it has been found that high-quality capsules of different types of starch and / or modified starches a), b), c), d) and e) combined with extenders such as sunflower proteins, soy proteins can be produced on the injection device of the invention. ; , polyvinyl acetate phthalate, gelatin, phthalate gelatin, succinated gelatin, crotonic acid, monosaccharides, oligosaccharides such as lactose, polysaccharides such as agar-agar, acacia, guar, dextran and the like, and / or with extender in an amount of 1 to 60% by weight, such as cross-linked gelatin, poly-saccharides such as cellulose, me thylcellulose, chitin, polymaltose, polyfructose and the like, pectin, silicates, carbonates and bicarbonates. The amount of extender is limited so as not to affect starch injectability. In the manufacture of capsules of different types of starch and / or modified starches and / or scraps as described above, the use of plasticizers, dye lubricants, especially pharmaceutical grade cleaners, results in optimum product properties.

Pharmacologically acceptable emollients such as polyethylene glycol or preferably low molecular weight organic plasticizers such as glycerin, sorbitol, dioctyl sodium sulfosuccinate, triethyl citrate, tributyl nitrate, 1,2-propylene glycol, mono-, di-, triacetates of glycerin and the like have been used at various concentrations from about 0.5 to 40, preferably 0.5 to 10 t, based on the weight of the starch composition. 9 252813

Pharmacologically acceptable lubricants such as lipids, i.e. glycerides (oils and fats), waxes phospholipids, such as unsaturated and saturated vegetable fatty acids and their salts, such as aluminum, calcium, magnesium and tin stearates, as well as talc, silicones, etc. using concentrations of about 0.001 to 10% by weight of the starch composition.

Pharmaceutically acceptable dyes, such as azo dyes and other dyes and pigments, for example iron oxides, titanium dioxides, natural dyes, etc., are used in a concentration of 0.001 to 10, preferably 0.001 to 5%, by weight of the starch composition. Examples

In order to verify the above-described method and apparatus of the present invention, commercially available native starch with different water contents and extenders are prepared, conditioned and then tested in an injection molding machine under various working conditions.

The individual cycle times of FIG. 2 on the microprocessor injection molding apparatus are used tactically

Cycle points

Time

A-B

B-C

CD

D-E

E-A 1 s, variable, depending on temperature1 s1 s variable depending on temperature1 s

Nozzle pressure: 2.10 ® Pa

Temperature at different points of the screw: (variable, see examples below) The following abbreviations are used in the following examples: Τ ^ temperature at the beginning of the screw (° C) temperature at the center of the screw (° C) Τθ temperature at the end of the screw (° C)

Tn nozzle temperature (° C) LFV linear flow rate (mm / s) L flow length (cm) D film thickness (cm)

Satisfactory starch capsules were made from the starch formulations listed below and under the following operating conditions: Example 1: Starch composition:

Wheat Starch 8.2% by weight, gelatin 73.8% by weight, water 18% by weight, titre Th Tm in iFV 765 125 130 140 140 66 1 000 252813 10

LFV i Example 2 ‘Starch composition: Wheat starch 41% by weight, gelatin 41 ΐ by weight, water 18. By weight.

Working conditions:

T T T b m θ n 126S 125 135 140 140 Example 3 Starch composition: Wheat starch 67.6% by weight, gelatin 24.6% by weight, water 15.8% by weight.

Working conditions: 66 820 Tb number Tra Te Tn 298S 125 135 140 140 Example 4 Starch composition: Wheat starch 79.4% by weight, water 20.6% by weight.

Working Conditions: 66

LFV 1200

T. T T T b m e 305S 115 130 140 140 Example 5 Starch Composition:

D 66 820 Wheat starch 78.32% by weight, water 21.6% by weight, erythrosine 0.007 8% by weight.

Working conditions: number

349S b 110 125 135 135 66

LFV 1000 Example 6 Starch Compound: Wheat Starch 9.2% by weight, HPCMP 74.1% by weight, lubricant + plasticizer 5.1 8% by weight, water 7.5% by weight. 11 252813

Working conditions: number

349S b 110 125 135 135

LFV 1000 An intracellular capsule was obtained from this starch composition. Example 7 Starch composition: Wheat starch 78.5% by weight, water 21.5% by weight.

Working conditions: number τ. τ τ τ

400S

404S 130 110 150 115 160 125 160 125 66 66

LFV 820 820 Example 8 Starch composition: Wheat starch 87.3% by weight, water 12.7% by weight.

Working conditions:

number Τ, Τ T T

405S 150 160 170 170 66 Example 9 Starch composition: Wheat starch 76.8%, calcium stearate 3%, water 20.2

Working conditions: number

411S

413S 100 130 110, 140 135 160 135 160 66 66

LFV 820% by weight

LFV 880 820 Example 10 Starch Compound: Wheat Cane 77.2% by weight, glycerin 3% by weight, science 19.8% by weight. 252813 12

Working conditions:

T, T bm 410S 100 110 414s 130 140 Example 11 T e n LD LFV 130 130 66 860 160 160 66 840 Starch Compound: Wheat Starch 72.5% by weight, polyethylene glycol (10,000 MW) 3% by weight water 22.5 wt%, talc 2 wt%.

Working conditions: Number Tb T m Tn L D LFV 412S 100 110 130 130 66 840 415S 130 140 160 160 66 840 Example 12 Starch composition:

Potato starch 80.7% by weight

Working conditions:

T, T b m 417S 1000 110 water 19.3% by weight 130-130

LFV 66 840 Example 13

This example demonstrates the capsule filled with lactose. dependence of disintegration of capsules on amylose content. In the tests of the screw composition, working conditions (° C) corn starch (about 110, 120, 20% amylose) corn starch 110, 120, 20% amylose) corn starch 110, 120, (65% amylose) 80% wt. water 20% wt. corn starch 110, 120, (0% amylose, 100% amylopectin) 79.2 wt%, water 20.8 wt%; 140, 140, 66, 840 140, 140, 66, 840 140, 140, 66, 840 140, 140, 66, 836 Characteristics of disintegration of flocculation capsules in water at 36 ° C, disintegration in 30 min at 36 ° C, disintegration during 30 min in water at 36 ° C during 30 min no holes disintegration in water at 36 ° C, disintegration in 30 min

It should be noted that the specific embodiments of the invention described above serve only to illustrate and the invention is not limited thereto. 2 of the description, various variations and variations of ", H 1 Vpr-", n <1, <1, zřejmé,,,

Claims (8)

13 252813 OBJECT OF THE INVENTION CLAIMS 1. A process for the injection of molded articles made from native starch and water and optionally containing other ingredients, characterized in that the starch with a water content of 5 to 30% by weight, based on the total weight of all components, is plasticized at 80 to 240 ° C and injected at a temperature of 80 to 240 ° C and a pressure of 600 to 10000 mbar into the cooled form and the solid product is discarded. 2. The process of claim 1 wherein the water content of the starch is about 15.8; 18; 19.8; 20; 20.2; 20.5; 20.8; 21.5; 21.6 or 22.5% by weight, based on the weight of the components present. 3. Process according to claim 1 or 2, characterized in that the starch is wholly or partly made from corn, wheat, potato, rice or tapioca starch or mixtures thereof. 4. A process according to any one of claims 1 to 3, wherein the starch / water composition comprises one or more softening agents and / or one or more plasticizers and / or one or more lubricants and / or one or more coloring agents. 5. The process of claim 4 wherein the extender is selected from the group consisting of sunflower proteins, soy proteins, cotton proteins, peanut proteins, blood proteins, egg proteins, rapeseed proteins and their acetylated derivatives, gelatin, cross-linked gelatin, vinyl acetate polysaccharides such as cellulose, methylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, sodium carboxymethylcellulose, polyvinylpyrrolidone, agar-agar, acacia, guar, dextran, chitin, polymaltose, polyfructose, pectin, alginates, alginic acids, monosaccharides, preferred glucose , fructose, sucrose, oligosaccharides, preferably lactose, silicates, bentonite, silicates, carbonates and bicarbonates. 6. Process according to claim 4 or 5, characterized in that the plasticizer is selected from the group consisting of polyethylene glycol and low molecular weight organic plasticizers, for example glycerol, sorbitol, dioctyl sodium sulfosuccinate, triethyl citrate, tributyl citrate, 1,2-propylene glycol, mono-, di-glycerol triacetates. . 7. A process according to any one of claims 4 to 6 wherein the lubricant is selected from the group consisting of lipids, unsaturated and saturated vegetable fatty acids and salts thereof, aluminum, calcium, magnesium and tin stearates, talc and silicones. C. The process of claim 7 wherein the lubricant is a glyceride, a phospholipid or a mixture thereof at a concentration of 0.001 to 10% by weight. 9. A process according to claim 1, wherein the starch / water composition comprises one or more enteric polymers selected from the group consisting of hydroxypropyl methylcellulose phthalate, cellulose acetyl phthalate, acrylates and methacrylates, polyvinyl acetate phthalate, phthalate gelatin, succinated gelatin, acid. croton, shellac, and the like