CA1238738A - Process for forming native starch into shaped article using injection molding technique - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
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

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E~ACKCROU~ OF T~ INV~TION
A. FIELl:~ OF THE IN~TENIION
The present invention relates to a moldable starch composition for use in an injection molding device to produce capsules. The present invention utilizes starch made from corn wheat, potatoes, rice, tapioca and the ~like. Said types of starch have a usual molecular mass range of 10,000 to 20,000,000 Dalton.
The starch contains about 0 to 100% of a~ylose, and about 100 to 0% of amylo-pectin; preEerably 0 to 70% of amylose, and about 95 to 10%
of amylo-pectin and is most preferably potato starch and corn starch.
When in the following description the term "starch" is used, this also includes ~oams, modifications or derivatives of starch, and co~binations thereof with h~7drophilic polymer com~ositions whose properties are acceptable for the intended injection molded products, especially capsule materials.
Hyd m philic po]y~ers are polymers with ~olec~ula~ masses from approximately 103 to 107 Dalton carrying molecular groups in their backbone and/or in their side chains and capable of forming and/or Eeu~ticipating in hydrogen bridges. Such hydrophilic polymers exhibit in their water adsorption isotherm (in the temperature range between approximately 0 to 200 degrees C) and inflection point ciose to the water activity ~oint at 0.5.
Hydrophilic polymers are distin~uished from the group called hydrocolloids by their molecular dispersity of said hydrophilic polymers a fraction of water according to the working range of the present invention- of 5 to 30% by weight of said hydrophilic poly~ers must be included provided that the temperature of said hydrophilic polymers i.s in the working ranse between 80 degrees C and 240 deg~aes C of the present invention.

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It is a primary object of the present invention to utilize starch compositions in the production of injec-tion molded products, especially capsules.
REFERENCES TO COPENDING CANA I N_PATENT APPLICATIONS
Serial ~s. 424,561 and 424,566, filed March 25, 1983 and commonly assigned as the present application.

B. DESCRIPTION OF THE PRIOR ART
Capsule-making machines have been developed to utilize dip-molding technology. Such technology involves the dipping of capsule-shaped pins into a gelatin solution, removing the pins rom the solutiont drying of the gelatin upon the pins, stripping off the gelatin capsule parts from the pins, adjusting for length, cutting, joining and ejecting the capsules.
Prior art capsule-making machines have utilized the combination of mechanical and pneumatic elements to perform~these functions at speeds up to about 1,200 5 ize 0 capsules per minut~. While the above described apparatusses are in general suitable for the intended purposes, it is desirable to produce capsules by in-iection molding at considerably higher speed, while at the same time precisely controlling the properties of the starch in order to produce the capsules hyyenic-ally and with minimum dimensional deviations so that the capsules can be filled on high speed equipment.
A prerequisite for any material to be moldable by an injection process is its ability to pass a glass transition point at a temperature compatible with the thermal stability of the material and the technical possibilities of an injection molding device. A
pre-requisite of any material to deliver shaped products of high dimensional stability in an injection , , : :, - , ,:

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molding process i5 its minimUM elastic recovery after the mold is opened. This can be achieved by setting the dispersity of said material at the molecular level during the injection process.
Shirai et al. in US patent 4,216,240 describes an injection molding process to produce an oriented fi-brous protein product. The fibrous product obtained by this process differs fundamentally from the trans-parent glasslike material of the capsules obtained from the present invention. Furthermore to obtain a flowable mass for the molding process, the protein mixtures used by Shirai et al. have to be denatured and thus lose their capacity to undergo dissolution.
Nakatsu~a et al. in US Patent 4,076,846 uses binary mixtures of starch with salts of protein materials to obtain an edible shaped article by an injection molding process. With ~he present invention shaped articles can be produced with starch without admixture with salts of protein materials therewith.
eusdens et al. in U.S. Patent No. 3,911,159 dis-closes the formation of filamentous protein structures to obtain edible products of improved tenderness. With the present invention shaped articles are produced without a filamentous prot~in structure.
The use v~ an injection molding device for pro-ducing capsules with starch is new and has not been su~gested in the technical literature. Many useful products can be prepared b~ the ;njection molding of starch other than capsules with the necessity of high form stability and minimum dimensional deviations.
These products would include candies, packaging containers for food-stuffs, pharmaceuticals, chemicals, dyestuffs, spices, fertilizing combinations, seeds, cosmetics and agricultural products and matrices of various shapes and size of starch compositions containing substances and/or active ingredients including food stuffs, pharmaceuticals, chemicals, .
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dyestuffs, spices, fertilizin~ combinations, seeds, cosmetics and agricultural products, which are micro dispersed within the matrix and released from it through disintegration and/or dissolution and/or bioerrosion and/or diffusion depending on the solubility characteristics of the used starch composition. Some of these products may also result in a controlled release delivery system for the enclosed substance. Purthermore, medical and surgery products can be ptepared by injec~ion molding starch compositions. The biodegradable nature of starch makes it environmentally desirable over certain materials presently being used. In addition, the non-toxic mixture of the materials further enhances their desir-ability as a material to be used in the iniectionmolding industry. It is an object of this invention to encompass all injection molded produc~s that may be produced by the teachings of that invention. The present invention ~istinguishes from the known prior art described above, by the recognition that starch possesses a dissolution point within a temperature range usable for an injection molding process, provided the water content of the starch lies within a charac-teristic range, giving allowance to avoid any essential drying or humidification processes of the capsules.
Above the dissolution point the starch is in the state of molecular dispersity. Due to the present invention the starch during the injection molding process is for a considerable tim~ at a temperature which is higher than the temperature of the dissolution point. When materials, such as medicaments, food-stuffs, etc. are dispersed in the starch compositions, quantities can not be employed that will so effect the properties of the starch that it will no longer be injection moldable.
SUMMARY OF THE INVENTION
The present invention provi~es a process for forming ~ -: . . , . ~ - , ~
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native starch into a shaped article usiny an injection moulding technique, comprising: a) providing starch having a water content in the range of from 5 to 30 weight percent based on the combined weight of starch and water; b) plasti-cizing the starch at an elevated temperature; c) injection moulding the plasticized starch at an elevated ~emperature and pressure into a cooled mould; and d) ejecting the shaped article from the mould.
The present invention also provides products made by the above process.

BRIEF DESCRIPTIO~ OF THE DRAWINGS
The invention both as to its organization and method of operation together with further objects and advantages thereof will best be understood by ref~rence to the following specifications and taken in conjunction with the accompanying drawings.
- Fig. 1 is a schematic layout of a reciprocating screw injection molding device for making capsule parts;
Fig. 2 is a schematic of an injection molding ,~

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work cycle for making capsule parts;
Fig. 3 is a schematic of an embodiment of a combined injection molding device-microprocessor apparatus for c2p5ul~ parts;
Fig. 4 is an expanded schematic o~ the exit end of the injection molding device;
Fig. 5 is ~he diagram of dependence of shear viscosity of starch within the pertinent ranges of the - shear rate in the present invention;
Fig. 6 is the diagram of molding area for starch within the ranges of temperature and pressure of starch for the present invention;
Fiy. 7 is the diagram of dependence of glass trans-ition temperature range and melting temperature range fox ~he pertinent water content ranges of starch;
Fig. 3 is the diagram of dependence of differen-tial calorimeter scan in which the heat consumption - rate of the starch is plotted for the pertinent temperature range of the present invention; and Fig. 9 i5 a diagram of dependence of equilibrium water content of the starch in the water activity program.
DETAILED DESCRIPT-~M OF THE PREFERRED ~MBODI~IENT
Referring now to Fig. 1 the injection molding device 27 generally consists of three units: a hopper unit 5, an injection unit l and a molding unit 2.
The function of the hopper unit 5 is receiving, storing, maintaining and feeding starch 4 at a constant temperature and a~ a constant water content. The hopper unit 5 comprises a vertical cylinder 30 having a closed top 31 with an inlet 32 therein to receive starch 4. At the bottom of the vertical cylinder 30 is a closed conical ~unnel 33 and a discharge outlet 34 to feed starch 4 into an inlet 34 of the injection unit 1.
There is an air duct 35 communicating between the closed top 31 and the conical funnel 33 wherein air is ' :' . ' .' "-' . " '' ' .
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circulated by a blower 36, the air temperature is maintained by a thyristor 37 and the air relative humidity is maintained by a steam injector 38.
The function of the injection unit 1 is melting, dissolving in water, and plasticizing in the extruder barrel 17 the starch 4 fed from the hopper unit 5 into the extruder inlet 54 and injecting the plasticized starch 14 into the molding unit 2.
The function of the molding unit 2 is auto-matically holding, opening and closing the mold 6having capsule shaped cavities 19 therein, and ejecting the capsule parts 7 therefrom~
: Within the injection unit 1 the screw 8 ~oth ; rotates and undergoes axial reciprocal motion. When the screw 8 rotates, i performs the functions of mel~ing, dissolving in water, and plasticizing the ~: starch 4. When the screw 8 moves axially, it performs ; the function of injecting by transporting and ramming : the plasticized starch 14 into the mold 6. The screw 8 is rotated by a variable-speed hydraulic motor 9 and drive 10, and its axial motion is reciprocated by a duplex hydraulic cylinder 11.
Compressiorl Gf the plasticized starch 14 in fron~
of the rotating screw 8 forces back the screw assembly 20 containing the screw 8, the drive 10 and the motor 9. When the screw assembly 20 reaches a preset back position a limit switch 12 is contacted. When a defined time has elapsed during which the starch 4 becomes fully plasticized starch 14 the hydraulic cylinder 11 brings the screw assembly 20 forward and uses the screw 8 as a ram for the plasticized starch 14 to be injected through a valve body assembly 5a including a one-way valve 15, a needle valve 23, nozzle 22 and an outlet port 21 into the molding unit 2. The one-way valve 15 prevents the plasticized starch 14 from going back over the helical flutes 16 of the screw ' . ~ ' ', ' . ' ~`

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8. The extruder harrel 17 has h~atiny coils 18 to heat the starch 4 while i~ is being compressed by the screw 8 into plasticized starch 14. It is desirable for the plasticized starch 14 to be heated at the lowes~
possible temperature and to be transported with the lowest possible speed of the screw ~. The speed of the screw 8 and the heating of the plasticized starch 14 within the ex~ruder barrel 17 by the steam heating coils 13 control the quality and the output rate of the : 10 plasticized starch 14 injected into the molding unit ~. The m~lding unit 2 holds the mold 6 having capsule shaped cavities 19 into which the plasticized starch 14 is injec~ed and maintained under pressure~ Refrigerant cooling conduits 24 encircle the mold 6 so that when lS the plasticized starch 14 in ~he mold 6 has cooled and sufficiently solidified, the molding unit 2 opens, the mold 6 separates and the capsule parts 7 are ejected.
Referring now to Fig. 1 and also to Fig. 2 which depicts ~e injection molding work cycle for starch 4 containin~ approximately 20% water7 by weight~ In general the work cycle of starch 4 is as follows in the injection molding device 27 o the present invention:
a. starch 4 is fed into the hopper unit 5 where it is xeceived, stored and maintained under conditions of temperature rang;ng Erom ambient to 100C, pressure ranying from 1-5 x 105 Newtons per s~uare meter (N x m~2) and water content ranging from 5 to 30% by weight of starch b. the stored starch 4 is melted under controlled condition of temperature ranging from 80 to 240C, water content ranging from 5 to 30~ by weight of starch and pressure ranging from 600 to 3000 x 105 N x m~2, c. the molten starch 4 is dissolved in water under controlled conditions of temperature ranging from 80 to 240C pressures ranging from 600 to 3000 x 105 N x ' ' :
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m~2 and water con~ent ranging from 5 ~o 30% by weight o~ starch.
d. the dissolved starch 4 is plasticized under controlled conditions o~ temperature ranging from 80 to 24VC, pressure ranging from 600 to 3000 x 105 N x m~2 and water content ranging from 5 to 30% by weight of starch.
e. the plasticized starch 14 is injected into the mold 6 under controlled conditions of temperature above 80C, injection pressure ranging from 600 to 3000 x 105 N x ~-2 and a clamping force of the mold 6..with a range of approximately 100 to 10,000 Kilo Newton, and ~ the capsule-shaped parts 7 are ejected from the plasticized starch 14 within the mold 6.
Beginning at point A of Fig. 2 the screw 8 moves forward and fills the mold 6 with plasticized starch 14 un~il Point B and maintains the injected plasticized starch 14 under high pressure, during what is called the hold time from point B until Point C of Fig. 2. At Point A the one-way valve 15 at the end of the screw 8 prevents the plasticized starch 14 from flowing back ~rom the cylindrical space in front of the screw 8 into th~ helical flutes of screw 8. Duriny hold time, additional plasticized starch 14 is injected, off-

2~ setting contraction due to cooling and solidificationof the plasticized starch 14. Later, the outlet port 21, which is a narrow entrance to the molding unit 2 closes, thus isolating the molding unit 2 from the injection unit 1. The plasticized starch 14 within the mold 6 is still at high pressure. As the plasticized starch 14 cools and solidifies, prsssure drops to a level that is high enough to ensure the absence of sinkmarks, but not so high tha~ it becomes difficult to remove the capsule parts 7 from the capsule-shaped cavities 19 within the mold 6. After the outlet port 21 closes, at Point C, screw 8 rotation commences. ~he ' . . .

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plasticized starch 14 is accommodated in the increased cylindrical space in front of the screw 8 created by its backward axial motion until Point D. The flow rate of the plasticized starch 14 is controlled by the speed of the screw 8 and the pressure is controlled by the back pressure (i.e., the hydraulic pressure exerted on the screw assemb]y 20) which in turn determines the pressure in the plasticized starch 14 in f~-ont of the screw 8. After plasticized starch 14 generation for the nex~ shot into the mold 6, the screw 8 rotation ceases at Point D~ The starch 4 on the stationary screw 8 is held at melt temperature from Points D to E by heat conduction from the heating coils 18 on the ex~ruder barrel 17. Meanwhile, the solidified capsule parts 7 are ejected from the mold 6. Thereafter, the mold 6 closes to accept the next shot of plasticiæed starch 14. All of these operations are automated and controlled by a microprocessor as hereinafter described~
~eferring now to Fig. 2 and and also to Fig. 3.
The injection molding work cycle of Fig. 2 is accomp-l;shed on the injection molding device 27 of Fig. 3 by hydraulic and electrical components and the correspond-ing circuits controlled by the microprocessor 28 of Fig.

3.
Through the use of solid-state circuitry and of speed, temperature, limit and pressure switches for the electric and hydraulic systems, the microprocessor 28 of the present invention utili~ed command signals in its memory 51 for the parameters of time, temperature and pressure conditions of Table l below for the in-jection molding work cycle of Fig. 2 to be accomplished by the injection molding device of Fig. 3 for producing capsule parts 7.

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anges of Iime, Temperature_and Pressure at the top of the Screw for the Iniection Molding Work Cy~le of Fig.2:
POINTS
S A B C D E
-2 ~2 -2 -2 -2 T~ 10 -1 10 -1 10 -1 10 -1 10 -1 (seconds) Temperature ~mbient-100 80-240 80-190 80-240 80-240 10 ~C~lsius~
Pressure A - B B - C C - D D - E
(195 X N x m~2) 600-3000 600-3000 10-1000 10-1000 .
(~ewtons per square meter) ~eferring now to Fig. 3 illustrating the combined injection molding device 27 and microprocessor 28 utilizing the method of present invention.
The combined injection molding device 27 and microprocessor 28 comprises six control circuits of which five are closed-loop, fully analog, and one is on-off. Starting a~ molding cycle Point A in Fig. 2, the injection molding work cycle operates as follows:
When sufficient plasticiz~d starch 14 has accumu-lated in front of the screw 8 (microprocessor limit switch controlled) and also when the screw assembly 20 carrying the screw 8, drive 9 and hydraulic motor 11 has been pushed far enough backwards against a constant back-pressure as controlled by control circuit 2, limit ~witch 12 will be actuated by position sensing circuit ~ 30 I4. The two conditions for actuating cylinder 11 ; ~barrel unit forward) are. 1) clamping force of the mold is built-up, and 2) limit switch 12 is activated.
~his rams the barrel 17 together with the nozzle 1 with screw assembly 20 forward, thus for sealing 3~ purposes. Sufficien~ pressure is controlled by control circuit 2 with means of pressure sensor I2. Under ;` :

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these conditions hydraulic piston 9 rams the screw assembly 20 forward~ thus injecting the plasticized starch 14 into the mold 6 when molding cycle Point B of Fig~ 2 is reachedy and, as controlled by the microprocessor 28, the screw 8 remains for a certain period of time until Point C stationary in this forward position under high pressure.
From molding cycle Point B of Fig. 2 onwards the plasticized starch 14 cools down in the mold 6 and the port 21 closes at molding cycle Point C of Fig. 2.
At molding cycle Point C of ~igO 2 the screw 8 starts to rotate again and the hydraulic pressure reduces from holding presure to back pressure in the hydraulic cylinder 11. This pressure set is less than the holding pressure at Point C.
The barrel 17 is kept under constant pressure towards the mold 6 by the pressure in the back position of the hydraulic cylinder 11. This is achieved by means of the control circuit 2 where a proportional hydraulic valve is controlled by a pressure sensor circui~
As the screw 8 rotates a recharge of starch 4 is made from tne hopper S. During a cartain time period and at a defined rotating speed of the screw 8, controlled by control circuit 3, a precise amount of starch 4 is fed into the extruder barrel 17. Control circuit 3 is actuated by speed sensor circuit 13, measuring the rotating speed of the screw 8 and sensing hack to a hydraulic proportional flow control valve 03 controlled by control circui~ 3, thus assuring a constant rotating speed of the hydraulic motor 10, - irrespective of the changing torque resulting ~rom introduction of the starch 4 recharge.
When the load time is completed, the screw 8 rotation is stopped and molding cycle Point D of Fig. 2 is reach~d. The time ~rom molding cycle Points D to A

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of Fig. 2 allows for the starch 4 to plasticize completely under controlled temperature conditions as controlled by control circuit 1.
A temperature sensor circuit Il senses a ~hyristor heat regulator l heating the extruder barrel 17 as directed by control circuit 1.
During the time interval from molding cycle Points B to E on Fig. 2, the mold 6 has cooled down su~-ficiently so that the finished capsule parts 7 can be ejected from the mold ~
After ejection of the capsule parts 7, the work cycle returns to Point A of Fig. 2 where a certain volume of plasticized starch 14 ha~ accumulated in front of the screw 8 (sensing circuit I~ is actuated and time has elapsed) so that the work cycle of Fig. 2 can be repeated.
I~ is important to note the temperature and hu-midity control loops 5 and 6, for the maintenance of precise water content of the starch 4 in the hopper 5, which is essential for proper operation at the desired speeds~
The microprocessor 28 includes a memory section 51 to store th ~esired operating ~arameters; a sensing and signaling section 52 to receive the sensing siynals of actual operating conditions, to deteet the deviation between the desired and ac~ual operating conditions, and to send signals for adjustment through the actuating section 53 to the thyristors and valves.
~eferring now to Fig. 4 there is shown the valve assembly 50 including the outlet port 21, the nozzle 22, the needle valve 23, and the bearing 15. These elements operate as follows:
At Point A in Fig. 2 the needle valve 23,is ~ h~e ~5 retracted from the outlet port 21 when ~ pressure in the starch 14 while the bearing 15 is pressed against the valve body so as ~o form an inlet opening ' :: ' ' :'- ' ~ :' ' ' '.' :

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5S for plasticized sta~ch 14 into the nozzle 22 which defines a charging chamber for plas~icized starch 14.
-The plasticized starch 14 is injected through nozzle 22 and înto the mold ~ during the mold-filling time S between Points A and B in Fig. 2. At Point C in Fig. 2 the needle valve 23 is pushed forward so as to close the outlet port 21 during which time between Point C
and E in Fig. ~, the inlet of mold 6 is closed and the . capsule part 7 in the mold 6 is cooling. The needle valve 23 remains closed between Point E and A in Fig. 2 during which time the capsule part 7 is ejected from the mold 6~
The one-way valve 15 and the needle valve 23 are actuate~ by a spring~tensioned lever 25 which normally closes both the outlet port 21 and the nozzle 2~ until the lever 2~ is cam-actuated pursuant to siynals from the microprocessor 28.
The thermomechanical properties of starch, i.e.
storage and loss shear modules at different temperatures, 20 are strongly dspendent on i~s water content. The capsule molding process o~ the present invention can be used for starch w;th a water content preferably within - a range of S to 30~. Ihe lower limit is deined by the maximum processing temperature of 240C, which in turn 2~ cannot be exceeded in order to avoid degradation. The upper limit is determined by the stickiness and distor-tion o~ the ~inished capsules. ~t sho~d a~so be note~ that pla.sticiz.ing i5 caused by heat a~d pressure when dealing with t~ermoplactic material, however, w~ith starch it is .30 necessary to also have strong shearing forces. The abbreviations in Table 2 below will be used hereina~ter :~ in this application:

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Tahle 2 Abbreviations for Physical Parameters ABBREVIATION UNIT DESCRIPTION
Ta,Pa Degree C, N x m 2 Ambient temper-S ature and pressure.
H(T,P~ KJoule x Kg-2 Enthalpy of starch-water system at a temperature O
K(TrP) N-l x m2 Compressibility of the starch at a given temperature and pres sure. Its numerical value is the relative volume change due to change of pressure by a unit amount.
(T,P~ ~Degree C)-l Volumetric thermal expansion coefficient of the starch at a given temperature and pressure. Its numerical value is the relative volume change due to change 2S of temperature by a unit amount.
V( g,T,P) Kg x sec~l is the flow rate o~
the starch at a given temperature and shear deformation rate [sec. -1] and pressure.
Its numerical value is the volume of a melt leaving the exit cross-sec~ional area of an injection molding :, . ' ' .:' :
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device in unit time due to the applied shear deformation rate.
TGl; TG~ Deg C The temperature range of the glass-transition of the starch.
TMl; TM2 Deg C The temperature range of the melting of the partially crystalline starch.
TM Melting temperature Tn~t) Deg C The temperature of the starch in the nozzle area of the injection unit.
Tt~t) Deg C The temperature of the starch in the mold.
Pt N x m~2 - The pressure of the starch in the mold.
20 Pn ~ x m~2 ~he pressure in the nozzle area of the starch.
X The water content of the starch, expressed 2S as the weight fraction of the water - starch system, For the control and regulation of the injection molding process (IMP) we need knowledge of the ~0 ~1) heat consumption of the melting process:
H(Tn, Pn) ~ H(Ta~ Pa~
t2~ the heating rates of the starch in the injection molding device. To calculate this we need the heat conduction number of the starch and the heat transfer number of the starch and the specific material of construction of the bartel which is in contact with the starch.
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The heating rate and the heat consumption of the starch yive the minimum time interval necessary to make the starch ready to inject and the necessary heating power of the injection molding device.
(3~ the Tn depends on X of the starch. If the water conten~ of the starch in the mold is too low, the resulting Tn will be too high and cause degradation.
A minimum water content of 5% by weight is required to keep Tn below 240C.

(4) the flow rate V(g,T,P) is as well strongly dependent on the water content of the starch. To speed up the IMP we need a high flow rate V(g,T,P) which can be achieved by a higher water contentO
The upper limit of the water content is defined by the stickiness and mechanical failure of the capsules;
a water content of 0.30 cannot be generally exceeded.
The starch in the mold will reduce its volume due to the temperature change Tt-Ta. This would result in voids and diminution of size of the capsule, which therefore would be of unacceptable quality. It is an important re~uirement in capsule making that the dimensional deviations are less than 1~. To compensate for shrinking by the ~em~erature chance, the mold ml~st be filled at a distinct pressure Pn. This filling pressure is determined by the quantities (T,P) and K(T,P~. The injection pressure (Pn) depends again on Tn~ which as was shown already is in turn strongly dependent on X.
Referring no~A~ to Fig~ 5, the shear rate dependent shear viscosit~ of starch at 130 degrees C is shown for starch with a water content X of 0.2.
Referring now to Fig. 6, the molding area diagram for starch with water content of ~.24. During injection ' , ~ . , ~L23~

molding tlle plasticized starch is discontinuously extruded and immediately cooled in a mold of the desired sha~ of the capsule part. Moldability depends on the starch properties and the process conditions, of which the thermomechanical properties of the starch as well as the geometry and the temperature and pressure condi~ions of the mold are the most important.
In the molding area diagram o~ Fig. 6 the limits of pressure and temperature are indicated for the processing of starch in the combined injection molder-microprocessor of the pr~sent invention. The maximum tempera~ure of 240C is determined by visible degradation of the starch above that limit~ The lower temperature limit of 80C was deterrnined by the lS development of too high viscosity and melt elasticity in the preferred water content range Xo 0 05 to 0.30.
The higher pressure limits of 3X108 N x m~2 are given by the start of flashing when the melted starch flows in a gap between the various metal dies which make up the molds, thus creating thin webs a~tached to the molded starch capsule parts at the separating lines. The lower pressure limits of about 6x107 N x m~~ are de~ermined by short shocs, when the mo~
cannot be completely filled by ~he starch. Shown below in Table 3 are the working pararneters for the injection molding process using the starch composition of the present invention.

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Table 3 ~ORKING PARAMETERS FOR INJECTION MOLDING PROCESS
Density - 1.5 - x 1~3kg x m~3 Cristallinity 2U to 70

5 H~Tn,Pn) - H(Ta~Pa) 63 KJoule x kg~
Net heating performance 6.3x102 KJoule for 10 kgsO melt/h (corresponding to 1~6 capsules/h) (Ta,Pa) 3.1x10-4 (Degree C)-l Contraction due to negligible crystallization Critical shear 104 - 1o6 sec -1 deformation rate ~he starch compositlons of the present invention are extruded and molded as described below:
~ eferring now to Fig. 7 the glass transition range and the melting temperature range is shown as a function of the composition of the starch-water system. The melting range is very broad with over 100C in compari-son with the melting range of e.g. gelatin, which comes to about 20C. At temperatures below the glass transi-tion range, ordinary starch, as available comm~rcially, is a partially cr~stalline polymer containing approxi-mately 30-100% amorphous and approximately 0-70 crystalline parts by volume.
By raising the temperature of said starch at a distinct water content the starch passes through the glass transition range~
Referring again to Fig. 1 said heating process of the- starch will take place within the extruder barrel 17. Referring again to Fig. 2 said heating process of the starch will take place during the entire injection moldin~ work cycle. The area in Fig. 7 between the , ,, ,' ' ' . ' - . . : , . .

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glass transition range and the melting rang0 is called area II. In area II we find crystalline starch and a starch melt. The glass-transition is not a thermodynamic transit;on range of any ord~r but is characterized by a change of the molecular movement of the starch molecules and by a change of the bulk storage module of the amorphous starch by several orders of magnitude. By passing from area II to area I
in Fig. 7 the translational movements of the starch molecules or those of large parts of said molecules will be frozen in the glass transition ~emperature range and this is reflected by a change in the specific heat (cp~ and the volumetric thermal expansion coefficient ( ~ in said temperature range. By passing from area II to area III due to crossing the melting - range of $he crystalline starch the helically ordered part of the starch will melt. Referring to Fig. l said hea~ing process of the starch will take place within the extruder barrel 17. Referring again to Fig~
2, said heating process of the starch will take place during the entire injection molding work cycle~ Said helix-coil transition is a true thermodynamic transition of the first order and is an endothermic process. Said transitions can be detected by scanning calorimetry or by measurement of the change of the linear viscoelastic bulk storage module due to change of the temperature. A typical plot of a temperature scan with a differential calorimeter is shown in Fig.
8. On the ordinate is plotted the velocity of the heat consumed by the sample relative to a reference (empty sample holder~. The velocity of heat consumption of the sample is due to the change of the temperature of the starch sample, and said temperature is plotted on the abscissa as degrees of Celsius. The base line shift on said plot is corresponding to the glass transition and the peak to the melting or to the helix~coil transition. The linear viscoelastic bulk storage . . . . : . : . -,. - , :. . ,. : .
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module E can be measured at srnall sinusoidal shear deforma~ions of the starch sample.
Referring again to Fig. 1 the heating of the starch 4 to a temperature higher than TM takes place 5 in ~he forward part of the extruder barrel 17. Said heating process will be maintained not only by the heating coils 18 but to an important proportion by the internal friction during the screw ro~ation and the injection process due to the high deformational rates.
It was found that the reversible elastic deformation of the injection molded starch 14 after opening the mold 6 is negligible if the temperature of the plastici~ed starch 14 during the injection process is higher than TM, otherwise the molding sequence would drop by at 1~ least an order of magnitude.
~ eferring again to Fig. 2 the necessary cooling period for the plasticized starch in the molds - to p~event any reversible elastic deformation of said starch will take place between points B and E of the working cycle. A restriction of the molding sequence to low speed coupled with long keeping of the starch in the ~old is undesirable because of two reasons: low output of the product and loss of water content of the statch in the extruder. At the elevated injection temperature ~here is always a transport of water from the hot to the cold starch in the extruder barrel.
Said water transport can be compensated due to the transport of the starch by the screw in the opposite direction.
Referring again to Fig. 1 said transport of starch 4 will be maintained by screw 8. Referring again to Fig. 2 said transport of starch will take place between the points C and D of the workin~ cycle.
To build up a stationary water content of the starch in the melting area of the extruder barrel, it is necessary to work at an injection sequence which is ' ' ,' , ~ :
. - .

3~

short. To establish a constant and high enough water content oE the starch in the extruder barrel, it is further necessary to use starch with the proper shape of the sorption isotherm. (See Fig. 9.) The constant water content of the starch in the extruder barrel is necessary due to the maintenance of constant production conditions. The water content of the starch during the injection must fulfill the condition: X higher than 0.05 otherwise T~ is also higher than 240C and this is undesirable due to degradation of the starch.
In the procedure of branching and crosslinking of starch, it is important to add crosslinking agents, especially the covalent crosslinking agents, shortly before injec~ion of the molten starch.
Referring again to Fig. 1, an aqueous solution of crosslinking agents is injected in front of a mixing systern being placed between barrel 17 and nozzle 150 ~eferring now to Fig. 4, this device is integrated in the valve body 50. For example, the crosslinking reaction mainly occurs during the injection cycle and the time after ejection oE the capsule. By the abcve described technology on branching and crosslinking there is no disadvantage oE changing the therm~-mechanical properties oE the starch polymers during the melting and solution process.

. ~.-. - --.
' ~ ..' .' . .

~3~ 3~
2~ ~
l'he s~arch compositions are ex~ruded and injected under the followillg c~nditions given in Table 4 below:
Table 4 Injection and Molding Conditions for Starch 5 Iniection Unit Screw diameter mm 24 28 3~ 18 . . _ . . . . .
Injection pressure N x m~2 2.2xlOB 1.6x108 l.x108 Calcuted in;ection cm3 38 51.7 67. 21.3 Effecti~e screw lenath L:D 18.8 16,1 13. 18 _ _ .. .. _ 10 -- Plasticising capacity (PS) kg/h(l~x.) la) 13.5 21.2 21.
lla) 9.2 14.5 15 - lb) ~3.6 3~ 36 llb) 17. 5 27 27 ~ . _ . . _ . _, . . .
Screw stroke mm (n~x.) 84 84 84 84 . . . _ . . .
Iniecti~n caDacitY kW ` 30 30 30 Iniection velocitv mm/s(max.) 2000 2000 2000 2000 Nbzzle contact force kN - 41.2 41.2 41~2 ~1.2 .. . . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Screw rotating speed m~n~lVar. la) 20 - 80 - - lla) ~0 - 17 Var. lb) 20 - 60 llb) 20 - 4U
. . _ . . _ _ _ .
Number of heatina zones 5 5 5 5 . ~ . _ _ _ _ _ . _ . . . . _ _ .. _ Insta~led heatin~ ~Eacity kW _ 6.1 6 1 6 ~ldina unit . . _ _~_ . _ , . _ . _ _ .
25 ClamDina force kN 60 ._ . _ . _ __ ~ . . _ . .. .. _ .. ..
~ qhi~e the pre~erred embodi~ent of the injection mo~ding apparatus is for the met~od of producing starch capsules ~rom vaxious types of starch, it has been found that quality capsules may also be manufactured utilizing , ~ ' 1;~38 ~8 the present invention with starch modiied by a) crosslinking ayents as:
epichlorohydrin, anhydride of dicarboxylic acid, formald~hyde, phosphorous oxyehlorine, metaphosphate, acrolein, organic divinylsulfons and the like.
b~ crosslînking the starch with mi~rowaves and the like.
e~ prior p;-ocessing like treatment with acids and~or enzymes in order to yield dextrines .
andJor pregelatinizing and/or treatment with ultrasonic andJor treatment with gamma radiation.
d) Chemieal derivations as:
lS ox~-dized starch~ starch monophosphate, stareh diphospha~e, starch acetate, stareh sulfate,-starch hydroxyethylether; carboxymethyl stareh, starch etherr 2-hydroxypropyl starch, alphatized starch, starch xanthide, starch ehloroaeetie acid, starch ester, formaldehyde stareh, sodium carboxymethyl stareh; and e ~ mixtures or combinations of these modified starehes and stareh modifieation proeedures a) to d) respeetively.
I~ addition it has been found tha~ the injection molding apparatus of the present invention can produce quali~y eapsules with various types of starch and/or with the aboye mentioned modified starches ~1, B), C), D) and E) combined with extanders such as sunflower proteins, soybean prot~ins, cotton seed ~roteins, peanut proteins, blood proteins, egg proteins, ra~e seed proteins and acetylated derivatives thereof, gelatin, crosslinked gelatin, vinylacetate, poly saccharides as cellulose, methylcellulose, hydroxypropyl cellulose, hydroxypropyl-methylcellulose, hydroxymet~ylce~lulose, hydroxyethy-cellulose, sodium carboxy methylcellulose, polyvinyl-pyrrolidone, bentonite, agar-agar, gum arabic, guar, dextran, chitin, polymaltose, polyfructose, pectin, alginates, alginic acids and the like, monosaccharides as flucose, fructose, saccharose and the like, oligosaccharides as lac-tose .' .,, ~, - : . :' -- . . .
:. . . . .
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and the lik~, silicates, carbona-tes and bicarbonates, the quan-tity of extender is controlled so as not to effect the ability of the starch to be injection molded.
In addition it has been found that the injection molding apparatus o~ the present invention can produce capsules having enteric properties ~2 hours resistance in gastric ]uice, well soluble within 30 nunutes in intestinal juice according to USP XX) with various types of starch and/or with the above mentioned modified starches A), B), C), D) and E~ c~bined with enteric polymers as hydroxypropyl-methylcellulose phtalate (HPMCP), cellulose acetylphtalate (C~P~, acrylates and methacrylates, polyvinyl-acetate-phtalate (PVAP), phtalated gelatin, succinated gelatin, crotonic acid, shellac and the like. The quantity of extender is controlled so as not to effect the ability of the starch ~o be in~ection molded.
Ebr the manufacturing of capsules with different types of starches and/or mK~ified starches and/or extended starches as mentioned a~ove, the utilization of plasticizers, lubxicants and coloring agents specifically of pharmaceutical grades lèads to optimal product qualities:
Pharmacologically acceptable plasticizers, such as polyethylene glycol or preferably low-molecular weight organic plasticizers, l~ke glycerol, sorbitol, dioctyl-sodium sulfosuccinate, triethyl citrat~, tributyl citrate, ~,2-propylenglycol, mcno-,di-, tri-acetates of glycerol etc. are utilized at various concentrations of about 0.5 - 40~ preferably ~t 0.5~10% based upon the weight of the starch composition.
Pharmacologically acceptable lubricants, such as lipids, i.e. glycerides (oils and fats), wax and phospholipids, such as unsaturated and saturated plant fatty acids and salts thereof, such as th~ stearates of aluminum, calcium, magnesium and tin; as well as talc, silicones, etc. are to be used at concentrations of about 0.001 - 10 based upon the weight of the starch composition.
~larmaceutically acceptable coloring agents, such as azo-dyes and other dyestuffs and pigments as iron oxides, titanium dioxides, natural dyes etc. are used at concentrations of about 0.001-10~ preferably at cr/;

.

3~i OoOOl - 5% based upon the weight of the starch composition.

To test the method and appratus as decribed beEore according to the present invention, batches of commer-cially available native starch with different water contents and extenders were prepared and conditioned and then tested in an iniection molding machine at different working conditions.
~eferring to Fig. 2 the cycle times of the injection molding-microprocessor apparatus are as follo~s:

Cycle Points Times A-B 1 s cond, variable, depending on temperature B-C 1 second C-D 1 second ~-E Variable depending on temperature E-~ 1 second Pressure in the no~zle: 2x108N x m~2 Temperatures at different points of screw: (variable, see Examples below.3 In the following Examples the abbreviations mean:
Tb temperature at beginning of screw (C) Tm temperature at middle of screw (C~
Te temperature at end of screw (C) Tn temperature at nozzle (~C) LFV linear flow velocity (mm/second) L flow length ~cm~) D film thickness (cm.) :
:

~ ;~3~3~7~a Acceptable starch capsules were processed according to the starch compositions and to the working conditions tabulated in the Examples below:
Example 1 Starch composition:
Wheat starch, gelatin 150B, water: 8.2% bw, 73.8 bw, 18bw, Working c~ndition:
number Tb Tm Te Tn L LFV

765 1:~5 13~ 140 140 66 1000 Example 2 .
Starch composition:
Wheat sta~ch, gelatin 150B, water: 41% bw, 41% bw/ 18% bw Working co~ditions:
number Tb Tm Te Tn L LFV

_ Example 3 Starch co~position:
Wheat starch, gelatin 150B, water: 67.6~ bw, 24.6% bw, 15.8~ bw Working conditions:
number T~ Tm Te Tn L LFV

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Example 4 Starch composition:
Wheat starch, water: 79.4% bw, 20.6~ bw Working conditions:
5 number Tb Tm Te Tn L LFV
_ Example 5 Starch composition:
Wheat starch, water, erythrosine: 78.32% bw, 21~6% bw, 0.0078~ bw Working conditions:
number Tb Tm Te Tn L LFV
D

349S 110 125 ~35 135 66 1000 :
Example 6 Starch composition:
~heat starch, HPCMP, lubricants + plas~icizers, water:
9~.2% hw, 74.1% bwt 5.1% bw, 7..S~ bw ~Working conditions:
number Tb Tm Te Tn L LFV

~0 3~9S 110 125 135 135 66 1000 This starch composition yielded an enteric cap~ule.

. .
' ' ' ' , . , ~. ~: ' :
: .. . . . . . .
. . . .

: ' ,'~ .' : ' 7~8 Starch composition:
Wheat starch, water: 78.5% bw, 21.5% bw Working conditions~
5 number Tb Tm Te Tn L LFV
D

~04S 110 115 125 12~ 66 820 .
Example 8 S~arch composition:
Wheat starch, water: 87.3% bw, 12.7% bw Working conditions:
numberTb Tm Te Tn L LFV
D

- ~05S 150 160 170 170 66 820 _ _ _ _ _ _ Example g Starch compvsit on:
; 15 Wheat starch, Calcium-stearate, water: 76.8~ bw, 3% bw, 70~2% bw Working conditions:
numberTb . Tm Te Tn L LFV
.

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.

~3~37~

E~ample 10 Starch composition:
Whea~ starch, glycerin, water: 77.2% bw, 3g bw, 19.8% bw Working conditions:
S number Tb Tm Te Tn L LFV
D

Example 11 Starch composition:
Wheat s'carch, Polyethylene-glycol ~10,000 m.w.), water, 10 talcumO 7205% i:w, 3% bw, 22.5% bw, 2% bw Working conditions:
number Tb Tm Te Tn L LFV

- -~15S 130 1~0 160 160 66 ~40 .
Example 12 Starch composition:
Potato starch, water: 80.7~ bw, 19.3% bw Working conditions:
number Tb Tm Te Tn L LFV
.

20 ~17S 100 110 1~0 130 66 840 ..
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Example ]3 This example demonstrated the dependence of the capsules disintegration properties on the content of amylose. For these tests, the capsules were filled with lactose.

.
starch ¦ working conditions ¦ disintegration cc~position l (C) ¦ prcperky of I Tb, Tm~ Te~ Tnr _ LFV ¦ the capsules ~ D
maize starch ~ 110, 1~0, 140, 140, 66, ¦ floculation in (about 20% ~ 840 ¦ water of 369C, a~ylose~ ¦ ¦ disintegration ~ _ ¦ within 30 minutes .. .. . .
15 maize starch ¦ 110, 120, 140, 140, 66, ¦ no opening in (65~ amylo~e) 1 840 ¦ water of 36~ C
80% b.w., ¦ i within 30 minutes water 20% b.w.
maize starch ¦ 110, 120, 140, 140, 66, ¦ disintegration in 20 (0% amylose, 1 836 ¦ water of 36C, 100% amylopectin) ¦ disintegration 79.2 b.w., i ¦ within 30 minutes water ~0.8% b.w.¦ I _ This invention has been described in terms of specific ~S embodiments set forth in detail, but it should be under-stood that these are by way of illustration only and that the invention is not necessarily limited thereto. Modifi-cations and variations will be apparent from this disclo-sure and may be resor~ed to without departing from the spirit of this invention, as those skilled in the art will readily understand. Accordingly, such variations and modifications of the disclosed invention are considered to be within the purview and scope of this invention and the following claims.

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Claims (26)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for forming starch into a shaped article using an injection moulding technique, comprising:
(a) providing a starch composition comprising from about 5 to about 30 weight percent water based on the combined weight of starch and water;
(b) heating the composition of step (a) at a temperature in the range of from 80 to 240°C at a pressure of at least about 2 x 105 nt.m-2, the heating temperature being above the glass transition temperature and melting point of the composition;
(c) further heating and plasticizing the product of step (b) at a temperature in the range of from 80 to 240°C to an essentially molecularly dispersed form;
(d) injecting the product of step (c) into a mould cavity whilst maintaining its water content in the range of from 5 to 30 weight percent;
(e) cooling the mould cavity to a temperature below the glass transition temperature of the contents thereof, to form a moulded article in the mould cavity; and (f) ejecting the moulded article from the mould cavity.

2. A process according to claim 1, wherein the water content of the starch is selected from 15.8; 18, 19.8, 20, 20.2, 20.5, 20.8, 21.5, 21.6, and 22.5 weight percent.

3. A process according to claim 1, wherein the starch, at least in part, is selected from corn starch, wheat starch, potato starch, rice starch, tapioca starch and a mixture thereof.

4. A process according to claim 1, wherein the starch includes an additive.

5. A process according to claim 4, wherein the additive is selected from an extender, a plasticizer, a lubricant, a colouring agent and a mixture thereof, and the additive is mixed with the starch.

6. A process according to claim 5, wherein the plasticizer is present in an amount of from 0.5 to 40 weight percent based on the weight of the starch.

7. A process according to claim 6, wherein the plasticizer is selected from polyethylene glycol and a low-molecular-weight organic plasticizer.

8. A process according to claim 7, wherein the low-molecular-weight organic plasticizer is selected from glycerol, sorbitol dioctylsodium sulphosuccinate, triethyl citrate, tributyl citrate, 1,2-propyleneglycol, and mono-, di- and tri-glycerol acetate.

9. A process according to claim 5, wherein the lubricant is present in an amount of from 0.001 to 10 weight percent based on the weight of the starch.

10, A process according to claim 9, wherein the lubricant is selected from a saturated plant fatty acid and salt thereof, an unsaturated plant fatty acid and salt thereof, a stearate of Al, Ca, Mg and Sn, talc and a silicone.

11, A process according to claim 10, wherein the lubricant is selected from a glyceride, a phospholipid and a mixture thereof.

12. A process according to claim 5, 6 or 9 , wherein the colouring agent is present in an amount of from 0.001 to 10 weight percent based on the weight of the starch.

13 A process according to claim 5, 6 or 9, wherein the extender is selected from a sunflower protein, a soybean protein, a cotton seed protein, a peanut protein, a blood protein, an egg protein, a rape seed protein and an acetylated derivative thereof, a gelatin, a crosslinked gelatin, a vinylacetate, a polysaccharide, a monosaccharide, an oligosaccharide, a bentonite, a silicate, a carbonate and a bicarbonate.

14. A process according to claim 5, 6 or 9, wherein the extender is selected from a cellulose, a methyl-cellulose, a hydroxypropyl-cellulose, a hydroxypropyl-methyl-cellulose, a hydroxymethyl-cellulose, a hydroxy-ethyl-cellulose, a sodium carboxy methylcellulose, a polyvinyl-pyrrolidone, agar-agar, gum arabic, guar, dextran, chitin, a polymaltose, a polyfructose, pectin, an alginate, an alginic acid , glucose, fructose, saccharose and lactose.

A process according to claim 1, 2 or 3, wherein the starch is mixed with a polymer having enteric properties and selected from hydroxypropylmethyl-cellulose-phthalate (HPMCP), cellulose-acetylphthalate (CAP), an acrylate, a methacrylate, polyvinylacetatephthalate (PVAP), phthalated gelatin, succinated gelatin, crotonic acid and shellac.

16. An injection moulded article, comprising: starch having a water content in the range of from 5 to 30 weight percent based on the combined weight of starch and water, wherein the starch is plasticized at a temperature of from 80 to 240°C
before being injection moulded at a temperature of from 80 to 240°C and a pressure sufficient to fill the mould cavity into a cooled mould.

17. An article according to claim 16, wherein the article 18 a capsule.

18. An article according to claim 16, wherein the article is a candy.

19. An article according to claim 16, wherein the article is a packaging container for foods, pharmaceuticals, chemicals, deyes, spices, fertilizers, seeds, cosmetics or agricultural products.

20. An article according to claim 16, wherein the article is a matrix capable of variable shape and size, the matrix having microdispersed therein foods, pharmaceuticals, chemicals, deyes, apices, fertilizers, seeds, cosmetics or agricultural products, the dispersion being released through disintegration, dissolution, bioerrosion, diffusion or a mixture thereof depending on the solubility characteristics of the starch, to give a controlled release delivery system for the microdispersed substance.

21. An article according to claim 16, wherein the article is a medical or surgical product.

22. An article according to claim 16, wherein the starch includes an additive.

23. An article according to claim 16, with: (i) a glass transition temperature above the temperature of use, and (ii) a self-sustaining shape, wherein the starch-water composition of the article upon moulding exhibits a negligible reversible elastic deformation.

24. A starch-water composition for injection moulding at a temperature of from 80 to 240°C and a pressure sufficient to fill the mould cavity into a cooled mould, including 5 to 30 weight percent water based on the composition weight, which has been plasticized at a temperature of from 80 to 240°C, wherein the composition is a homogenous thermoplastic melt when held above its glass transition temperature and upon cooling exhibits negligible reversible elastic deformation.

25. An article made from the composition of claim 24, wherein the wall structure of the article is essentially amorphous.

26. A process, an article or a composition according to claim 1, 16 or 24, respectively, wherein the injection moulding pressure is in the range of from 6 x 107 to 3 x 108 nt.m-2.