CA1136805A - Process and installation for the continuous manufacture of starch adhesives - Google Patents
Process and installation for the continuous manufacture of starch adhesivesInfo
- Publication number
- CA1136805A CA1136805A CA000346037A CA346037A CA1136805A CA 1136805 A CA1136805 A CA 1136805A CA 000346037 A CA000346037 A CA 000346037A CA 346037 A CA346037 A CA 346037A CA 1136805 A CA1136805 A CA 1136805A
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- CA
- Canada
- Prior art keywords
- starch
- paste
- outlet
- pump
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J103/00—Adhesives based on starch, amylose or amylopectin or on their derivatives or degradation products
- C09J103/02—Starch; Degradation products thereof, e.g. dextrin
Abstract
Abstract of the Disclosure A process for the continuous production of starch corrugating pastes which comprises the steps of slurrying natural or non-gelatinised starch in water to provide a starch suspension, continuously gelatinising a first portion of said starch suspension by contacting with excess alkaline agent, continuously mixing the gelatinised first starch portion with a second portion of said starch suspension, and continuously neutralizing a portion of the excess alkali present in the gelatinised starch with boric acid.
The process obviates disadvantages in prior art processes, in-cluding high viscosity in primary pastes, difficulty in adapting to continuous production, lack of flexibility in the choice of paste formulations and lack of stability in the pastes resulting in change in viscosity and imperfect pasting of the cardboard.
The process obviates disadvantages in prior art processes, in-cluding high viscosity in primary pastes, difficulty in adapting to continuous production, lack of flexibility in the choice of paste formulations and lack of stability in the pastes resulting in change in viscosity and imperfect pasting of the cardboard.
Description
1~3~i~0S
Field of the Invention The present invention relates to a process for producing starch pastes intended in particular for the manufacture of corrugated paper and cardboard. The invention also includes a system for the automatic and continuous implementation of the above process.
Background of the Invention .
At the present time starch-based pastes, in particular those intended for the production of corrugated paper, are generally prepaxed by the following processes:
1) Stein-Hall process, the oldest and most com-mon process, according to which some of the starch in aqueous suspension is gelatinized at a high temperature in the presence of an alkaline agent, generally caustic soda, and constitutes a primary paste acting as a support or "carrier" for further starch added to the mixture as a powder or in the form of an aqueous suspension. The caus-tic soda is added only to the carrier portion or together with the carrier portion and the crude starch portion, which should then be in the form of a "milk", but in both cases the total amount of caustic soda should be such that it does not produce any swelling of the crude starch in the final paste, which would indicate instability. After the carrier portion has been boiled it is at a fairly high temperature, generally above 60C, and it is necessary to reduce this temperature to a maximum value of 45C before adding the crude starch if one is to avoid the risk of ; swelling the latter. This objective is achieved in prac-tice by adding cold water to the primary paste.
It is thus necessary in the whole preparation procedure to keep a sufficient amount of cold water for this operation, which means that the primary paste of the carrier is relatively highly concentrated before dilution, 113~
that is to say contains of the order of 10% of starch, and is consequently very viscous. This high viscosity is a serious drawback as regards the design of an automatic and continuous boiling apparatus.
Field of the Invention The present invention relates to a process for producing starch pastes intended in particular for the manufacture of corrugated paper and cardboard. The invention also includes a system for the automatic and continuous implementation of the above process.
Background of the Invention .
At the present time starch-based pastes, in particular those intended for the production of corrugated paper, are generally prepaxed by the following processes:
1) Stein-Hall process, the oldest and most com-mon process, according to which some of the starch in aqueous suspension is gelatinized at a high temperature in the presence of an alkaline agent, generally caustic soda, and constitutes a primary paste acting as a support or "carrier" for further starch added to the mixture as a powder or in the form of an aqueous suspension. The caus-tic soda is added only to the carrier portion or together with the carrier portion and the crude starch portion, which should then be in the form of a "milk", but in both cases the total amount of caustic soda should be such that it does not produce any swelling of the crude starch in the final paste, which would indicate instability. After the carrier portion has been boiled it is at a fairly high temperature, generally above 60C, and it is necessary to reduce this temperature to a maximum value of 45C before adding the crude starch if one is to avoid the risk of ; swelling the latter. This objective is achieved in prac-tice by adding cold water to the primary paste.
It is thus necessary in the whole preparation procedure to keep a sufficient amount of cold water for this operation, which means that the primary paste of the carrier is relatively highly concentrated before dilution, 113~
that is to say contains of the order of 10% of starch, and is consequently very viscous. This high viscosity is a serious drawback as regards the design of an automatic and continuous boiling apparatus.
2) The so-called "no carrier" process, according to which all the starch is partially swelled under the action of the alkaline conditions and temperature. The degree of gelatinization o~ the starch is monitored by measuring the viscosity, and the reaction is stopped at the desired point by adding an acidic compound, for example aluminium sulphate. A process of this type is difficult to adapt to continuous production.
3) Cold processes are known which use a complete mixture containing crude starch~ pre-gelatinized starch and chemical additives. The paste is obtained by simply dis-persing the pre-gelatinized starch powder in water to form the carrier. The process can be adapted to automatic and continuous production, but there is the disadvantage of the high cost of the pre-gelatinized starch and mixtures, and the lack of flexibility in the choice of paste formula-tions.
4) The so~called "Cold Burst" process, according to which a modified or unmodified starch in granular form is gelatinized in an aqueous medium by an alkaline agent, - generally caustic soda, and not by raising the temperature.
This process has a certain number of advantages, including the fact that boiling at high temperatures or the need for costly pre-gelatinized starch are avoided, and the length of preparation of the paste is reduced and the temperature monitoring procedures are simplified, and consequently the labour costs are reduced.
This last method of preparation appears to be most capable of implementation by means of an automatic 113~0S
and continuous arrangement, since the primary paste or carrier does not have to be cooled and may be prepared in a relatively low concentration, namely of the order of 5%
of starch, and thus forms a not very viscous solution that can easily be poured.
However, the cold process when carried out using natural starches has serious disadvantages, which include a lack of stability of the pastes under the action of shear forces that inevitably arise in a production unit for cor-rugated paper, when the paste circulates between thepasting machine and the paste reservoir under the action of circulation pumps; the modification of the paste is further accentuated by the rise in temperature, to 35-38C, when the paste passes over the pasting rollers. The result is a fall in viscosity of the paste and consequently a change in the thickness of the paste film deposited on the cardboard, or an imperfect pasting of the latter.
In order to obviate this defect it is not suffi-cient to subject the paste or even the carrier portion, the most sensitive part of the paste, after gelatinization in a conventional alkaline medium, to a mechanical action, even to a very intensive mechanical action, such as can be obtained with a powerful stirrer in an enclosure having the smallest volume compatible with the desired flow rate, and instead it is necessary to employ a starch whose resis-tance has been strengthened by a structural modification, namely either a fluidification or a cross-linking produced by a polyfunctional compound such as epichlorhydrin, phos-phorus oxychloride, sodium -trimetaphosphate, etc., this cross-linking being able to be produced in situ by employing the alkaline medium which catalyses the reaction. The use of a modified starch however results in a large increase in ` the cost of the paste.
, .
113~Q~i It is known, moreover, that starch pastes may contain a certain proportion of borax, in particular when used to manufacture corrugated paper.
The present invention is thus directed to a process for producing starch paste which obviates the aforementioned disadvantages while providing a product having the desired properties and which can be produced economically and continuously.
- Summar~
This invention relates to a process for the con-tinuous production of starch corrugating pastes which comprises the steps of:
a) slurrying natural or non-gelatinized starch in water to provide a starch suspensioni b) continuously gelatinizing a first portion of said starch suspension by contacting with excess alka-line agenti c) continuously mixing the gelatinized first starch portion with a second portion of said starch suspen-sion; and d) continuously neutralizing a portion of theexcess alkali present in the gelatinized starch with boric acid.
The process according to the invention, which is of the type comprising the stage of producing cold a pri-mary paste from a gelatinized starch in the presence of an alkaline agent, is essentially characterized by the fact that the primary paste is produced from a first portion of an aqueous starch suspension which is subjected to the action of an alkaline agent in excess, that the primary paste is mixed with a second portion of the said suspension, and that at least part of the alkaline agent present in excess is neutralized by means of boric acid.
~13~0S
According to other characteristic features, the contact time between the gelatinized starch and the second portion of starch suspension is prolonged, and the final paste obtained may be diluted and completely neutralized as desired.
Advantageously the process starts from water heated to a temperature between about 38 and 42C and a concentrated solution of alkaline agent is prepared, the hot water being used both for diluting the solution of alkaline agent to the desired concentration, for preparing the starch suspension, and, if necessary, for diluting the final paste.
In order to implement the above process, the system according to this invention comprises a reservoir of water heated to a constant regulable temperature, an assembly of three metering pumps for producing the primary paste from a first portion of aqueous starch suspension, a first pump connected to the outlet of a reservoir of con-centrated alkaline agent, a second pump connected to the water reservoir, a third pump connected to the outlet of a tank for preparing the aqueous starch suspension, situated . .
opposite a feed hopper, the outlet of the three metering pumps being connected to a means for bringing the consti-tuents of the primary paste in contact with one another, a fourth pump connected to the said tank and whose outlet is connected to a mixer for the primary paste and the second portion of aqueous suspension, the outlet of the said mixer being itself connected to a storage tank provided with a boric acid metering device and whose outlet is connected to at least one final paste vat provided wi-th level probes connected to the control means for the outlet of the four metering pumps.
According to other characteristic features, the
This process has a certain number of advantages, including the fact that boiling at high temperatures or the need for costly pre-gelatinized starch are avoided, and the length of preparation of the paste is reduced and the temperature monitoring procedures are simplified, and consequently the labour costs are reduced.
This last method of preparation appears to be most capable of implementation by means of an automatic 113~0S
and continuous arrangement, since the primary paste or carrier does not have to be cooled and may be prepared in a relatively low concentration, namely of the order of 5%
of starch, and thus forms a not very viscous solution that can easily be poured.
However, the cold process when carried out using natural starches has serious disadvantages, which include a lack of stability of the pastes under the action of shear forces that inevitably arise in a production unit for cor-rugated paper, when the paste circulates between thepasting machine and the paste reservoir under the action of circulation pumps; the modification of the paste is further accentuated by the rise in temperature, to 35-38C, when the paste passes over the pasting rollers. The result is a fall in viscosity of the paste and consequently a change in the thickness of the paste film deposited on the cardboard, or an imperfect pasting of the latter.
In order to obviate this defect it is not suffi-cient to subject the paste or even the carrier portion, the most sensitive part of the paste, after gelatinization in a conventional alkaline medium, to a mechanical action, even to a very intensive mechanical action, such as can be obtained with a powerful stirrer in an enclosure having the smallest volume compatible with the desired flow rate, and instead it is necessary to employ a starch whose resis-tance has been strengthened by a structural modification, namely either a fluidification or a cross-linking produced by a polyfunctional compound such as epichlorhydrin, phos-phorus oxychloride, sodium -trimetaphosphate, etc., this cross-linking being able to be produced in situ by employing the alkaline medium which catalyses the reaction. The use of a modified starch however results in a large increase in ` the cost of the paste.
, .
113~Q~i It is known, moreover, that starch pastes may contain a certain proportion of borax, in particular when used to manufacture corrugated paper.
The present invention is thus directed to a process for producing starch paste which obviates the aforementioned disadvantages while providing a product having the desired properties and which can be produced economically and continuously.
- Summar~
This invention relates to a process for the con-tinuous production of starch corrugating pastes which comprises the steps of:
a) slurrying natural or non-gelatinized starch in water to provide a starch suspensioni b) continuously gelatinizing a first portion of said starch suspension by contacting with excess alka-line agenti c) continuously mixing the gelatinized first starch portion with a second portion of said starch suspen-sion; and d) continuously neutralizing a portion of theexcess alkali present in the gelatinized starch with boric acid.
The process according to the invention, which is of the type comprising the stage of producing cold a pri-mary paste from a gelatinized starch in the presence of an alkaline agent, is essentially characterized by the fact that the primary paste is produced from a first portion of an aqueous starch suspension which is subjected to the action of an alkaline agent in excess, that the primary paste is mixed with a second portion of the said suspension, and that at least part of the alkaline agent present in excess is neutralized by means of boric acid.
~13~0S
According to other characteristic features, the contact time between the gelatinized starch and the second portion of starch suspension is prolonged, and the final paste obtained may be diluted and completely neutralized as desired.
Advantageously the process starts from water heated to a temperature between about 38 and 42C and a concentrated solution of alkaline agent is prepared, the hot water being used both for diluting the solution of alkaline agent to the desired concentration, for preparing the starch suspension, and, if necessary, for diluting the final paste.
In order to implement the above process, the system according to this invention comprises a reservoir of water heated to a constant regulable temperature, an assembly of three metering pumps for producing the primary paste from a first portion of aqueous starch suspension, a first pump connected to the outlet of a reservoir of con-centrated alkaline agent, a second pump connected to the water reservoir, a third pump connected to the outlet of a tank for preparing the aqueous starch suspension, situated . .
opposite a feed hopper, the outlet of the three metering pumps being connected to a means for bringing the consti-tuents of the primary paste in contact with one another, a fourth pump connected to the said tank and whose outlet is connected to a mixer for the primary paste and the second portion of aqueous suspension, the outlet of the said mixer being itself connected to a storage tank provided with a boric acid metering device and whose outlet is connected to at least one final paste vat provided wi-th level probes connected to the control means for the outlet of the four metering pumps.
According to other characteristic features, the
-5-1~3~ 5 assemblies of metering pumps are prcvided with three-way valves for returning the flow to the respective reservoirs;
the mixers are preferably of the static type; the reser-voirs and tanks are provided with constant level control means; the assembly of the liquid circulation means are controlled automatically by means of level probes placed in the final paste vats.
Other characteristic features and advantages of the present invention will be more readily understood on reading the following description, in conjunction with the attached drawing which diagrammatically represents the plant and illustrates the process according to the inven-tion.
Description of Preferred Embodiments In accordance with the invention, the primary paste or carrier is made from a natural starch, gelatinized in the presence of an amount of caustic soda or other al-kaline agent in excess with respect to the amount contained in a normal paste for corrugated paper or cardboard. The excess caustic soda is then neutralized and this operation is profitably employed to reform borax, which is always present in this type of paste, from the boric acid added during the mixing or immediately after the mixing of the gelatinized starch and crude starch. The amount of borax may be modified as desired as a function of the excess caustic soda. Under these conditions, during the course of the gelatinization of the carrier portion in a static mixer and in the storage enclosure connected thereafter, the starch is sufficiently degraded to reach the resistance point, which enables it to retain a stable viscosity during the various actions to which the paste is subjected.
The water reservoir preferably is kept at a con-stant temperature of the order of 38C to 42C, and is used:
- on the one hand to prepare, in a feed vat, an aqueous starch suspension of constant concentration pre-ferably fixed at a value of 30 to 436 of dry matter which can be regulated as desired within this range;
- on the other hand to dilute caustic soda to a preferred concentration of about 400 g/litre to a concen-tration of about 10 g to 20 g/litre.
The assemblies of metering pumps consist of a four-head metering pump which ensures a perfect synchroni-zation and enables a constant relationship between theflow rates of the various constituents of the paste to be maintained, or, by way of variation, consists of an assembly of four variable flow metering pumps operating continuously, the liquids being recycled automatically outside the pro-duction. The following simultaneous operations may accord-ingly be realized:
1) Metering of the solution of concentrated caustic soda;
2) Metering of the water of dilution for the caustic soda, the mixing being effected in a pipe arrange-ment by means of a T or, better, by means of a static mixer;
3) Metering of the amount of starch suspension necessary to produce the carrier part or primary paste;
4) Metering of the amount of starch suspension necessary to form the crude starch part of the paste. This secondary starch suspension is mixed with the carrier paste in a second static mixer; homogenization is completed by passing the suspension through a pump connected in series and operating in counter-current, as will be explained in detail hereinafter.
The flow rate of the secondary starch suspension to the static mixer is controlled by a probe located in the outlet of the storage vessel in which the gelatinization of ~3~05 the primary starch takes place; the supply of crude starch may also be effected by means of a timing system.
The final mixture of primary starch and secondary starch is then passed to a storage vat where it remains for a specific duration determined by means of an overflow level device.
The storage tank located at the end of the circuit results in a good homogenization of the paste and brings it to its final equilibrium state. A11 the desired additives, for example resins intended to make the paste resistant to moisture, can easily be added to this tank.
With reference to the accompanying drawing, the starch is distributed from a hopper or silo 1 and, via a volumetric metering device 2, to the starch milk prepara tion vat 3. This vat is provided with a high speed stirrer 4 and is connected via a line 5 to the water reservoir 6 maintained at the desired temperature by means of, for example, a steam coil 7. The vat 3 constitutes the device for preparing the starch milk, and i5 able to deliver con-tinuously an aqueous suspension within a wide range of con-stant and regulable concentration, of the order of 30 to 43~ by weight of dry matter.
The water reservoir 6 provides depending on requirements, and via automatic stopcocks (not shown), water at a fixed chosen temperature, generally of the or-der of 38 to 42C, using a thermostatic regulation of the heating by means of the steam coil 7. The temperature of the water is adjusted so as to obtain a final mixture which arrives at a temperature of about 38C at the storage tank 8.
A reservoir 9 for caustic soda having a concen-tration of about 400 g/l is connected via a line 10 to a meteri.ng pump Pl, forming part of an assemhly Pl, P2, P3, ~136~305 P4, described hereinafter.
This assembly may consist of a single four-head metering pump or of four metering pumps each driven by a variable transmission motor, having the general reference numeral 11, and it enables the flow rate for each liquid to be chosen within a defined range, the flow rate being read on a flow meter in a manner known per se. The pumps operate continuously, and the liquids are recycled, outside production, to their respective vats or reservoirs by a set of automatic three-way valves, namely the valve 12 con-nected to the concentrated caustic soda reservoir 9 via the line 13, the valve 14 connected to the water reservoir 6 via the line 15, and the valves 16 and 17 connected to the vat 3 via the lines 18 and 19 respectively.
The inlet of the pump P2 is connected to the out-let 20 of the water reservoir 6 via the line 21, and the inlets of the pumps P3 and P4 are connected to the outlet of the vat 3 via the line 22.
The pumps Pl and P2 inject their liquid flows through the lines 23 and 24 respectively to a first point A, and then the pump P3 injects a first portion of starch suspension through the line 25 to a second point B up-stream of a first static mixer 26 intended to homogenize the various constituents and gelatinize the starch. This gelatinization is prolonged and completed by contact with a coil 27 connected to the outlet of the static mixer 26 via a line 28 whose dimensions are such that the storage time is at least one minute.
The pump P4 injects the second portion of starch suspension into the primary paste at a third point C, via the line 29, just upstream of a second static mixer 30, and at the outlet of the coil 27~ The simultaneous arrival of the two flows at the point C is regulated by a probe _g_ 1~3~05 (not shown) located at the outlet of the coil 27 or, more simply, by a suitable timing device. The static mixer 30 homogenizes the primary paste/crude starch mixture, this homogenization being completed for example by an in-line pump 31 operating in a counter-current manner.
The final mixture flows via the line 32 from the outlet of the pump 31 to the storage tank of vat 8 provided with an efficient stirrer 33. This vat 8 is furthermore provided with an automatic volumetric metering device 34 for metering the boric acid in the desired amount, as well as with an overflow level device 35 intended to allow the paste to remain in the vat 8 for 30 to 40 minutes, while being stirred, before the paste is distributed.
To this end the outlet of the vat 8 is connected via a line 36 containing a suitable circulation pump 37 to at least two storage vats 38 and 39. These vats are fed with fresh paste under instructions from a probe S situated at a low level and which initiates the production procedure, a three-way valve 40 arranged in the line 36 directing the distribution by a rocking or tilting action to the required position.
Advantageously, and particularly in the case where the starch paste is produced for corrugated paper, the vat 38 receives directly the final starch, which has the characteristics of so-called "double face" paste. The vat 39 may be allocated for the so-called "simple face"
paste and, in this case, its feed inlet 41 is connected to the valve 40 via a line 42 comprising an inlet 43 for water of dilution, which may be connected to the reservoir 6 and, if necessary, an inlet 44 for the addition of an acid such as hydrochloric acid, these additives being mixed by means of a third static mixer 45 whose outlet forms the feed 41 for the vat 39, the hydrochloric acid being contained in a ~t~80S
vat 46.
Suitable probes 47 and 48 placed at a high level in the vats 38 and 39 respectively are intended to stop the distribution and interrupt the whole production cycle, the assembly of pumps Pl to P4 then being in the recycling position via the valves 12, 14, 16 and 17, until produc-tion is restarted by one of the low level probes S~
The following examples, which are given by way of illustration and are in no way meant to be limiting, will provide a better understanding of the scope and value of the invention. In these examples all the percentages are given by weight unless otherwise indicated.
Example 1 Preparation of a paste for corrugated paper, having a starch_concentration of 20%
This test is carried out using a natural maize starch containing 12.5% moisture. The temperature of the water in the reservoir is maintained at 40C and the starch milk is prepared in a concentration of 40% of commercial starch, i.e. 35% of dry matter.
The afore-described system is used, in conjunc-tion with the following regulation of the pumps:
The pump Pl delivers a solution of caustic soda in a concentration of 420 g/litre at a rate of 36 litres/
hour.
The pump P2 delivers water from the reservoir at a rate of 1200 litres/hour.
The pump P3 feeds the circuit with starch milk for the formation of the carrier, at a rate of 140 litres/
hour.
The pump P4 provides the crude starch or secon-dary starch at a rate of 940 litres/hour.
The boric acid is fed to the paste arriving at the storage tank at a rate of 5 kg/hour.
The characteristics of the components employed are as follows:
Concentration of dry matter in the starch of the carrier paste= 4.05%;
Ratio of carrier starch to total starch = 13%;
Concentration of the caustic soda after dilution = 12.2 grams/litre.
The flow rate of final, undiluted paste is 2320 litres/hour and the characteristics of this paste on arri-val at the storage vat for the double face paste are as follows:
Concentration of starch = 20.1%
Temperature = 38C
Stein-Hall viscosity at 35C = 50 s Brookfield viscosity at 35C
(20 revs./min.) = 3000 mPas Alkalinity in % NaOH/starch = 2.70 Borax as % Na2B407, 10 H2O/starch = 1-5 Stability of the paste: no notable change in viscosity at 35C after shear forces produced by a turbine blade rotating at 600 revs./minute for 4 hours. On settling at ambient temperature for 96 hours, the Stein-Hall viscosity normally increases to a value of the order of 70 s, but re-adopts its initial value after stirring and adjusting the temperature to 35C.
Gelatinization temperature of the paste = 58C.
The simple face paste is obtained by dilution wi~h cold water at a flow rate of 280 litres of water per 0 hour, and has the following characteristics:
Flow rate = 2600 litres/hour Concentration of starch = 18%
Temperature = 35~C
~3~i805 Stein-Hall viscosity at 35C = 36 s ~ alkalinity/starch = 2.7 Borax in % Na2B4O7, 10 H2O/starCh = 1.5 Gelatinization temperature = 60C
Stability of the paste: same remarks as for the double face paste.
Example 2 -Pre~aration of a paste for corrugated paper, having a starch concentration of 25%
The test is carried out as previously, using natural maize starch containing 12.5% moisture.
The temperature of the water in the reservoir is maintained at 39C and the starch milk is prepared having a concentration of 40% of commercial starch, i.e. 35% of dry matter.
The pump Pl delivers a solution of caustic soda in a concentration of 415 g/litre, at a rate of 43 litres/
hour.
The pump P2 delivers water at a rate of 940 litres/hour.
The pump P3 feeds starch milk for the carrier at a rate of 156 litres/hour.
The pump P4 feeds crude starch milk at a rate of 1260 litres/hour.
The boric acid is added to the storage tank at a rate of 6.55 kg/hour.
Concentration of dry starch matter in the carrier paste = 5.4%.
Ratio of carrier starch/total starch = 11%
Concentration of caustic soda after dilution =
18.16 g/l The flow rate of undiluted final paste is 2400 l/h Characteristics of the double face paste:
~13ti~5 Starch concentration = 25%
Temperature = 38C
Stein-Hall viscosity at 35C = 52 s Alkalinity in % NaOH/starch = 2.4 sorax in % Na2B407, 10 H2O/starch = 1-5 Gelatinization temperature of the paste = 58C
Stability of the paste: no notable change in the viscosity at 35C after the action of shear forces produced for 4 hours or after settling at ambient tempera-ture for 2 to 4 days.
Simple face paste: obtained by dilution with cold water at a rate of 290 litres/hour and by adding hy-drochloric acid, density 1.16 (content of pure acid equal to 370 g/l) at a flow rate of 6.46 litres/hour.
The characteristics of this simple face paste are as follows:
Flow rate = 2690 litres/hour Starch concentration = 22.5%
Temperature = 34C
Stein-Hall viscosity at 35C = 33 5 % alkalinity/starch = 2.0%
Borax in % Na2B407, 10 H20/starch = 1.5 Gelatinization temperature = 64C
Stability of the paste: identical to that of the double face paste during exposure to shear forces at 35C, and is even improved as regards the viscosity behaviour when the paste is allowed to settle at ambient temperature.
The process and plant according to the invention provide a really continuous and automatic production of starch pastes, and permit a considerable reduction in the storage capacity.
The plant is simple and reliable, and the constant -13a-1~3~i8~S
relationship between the flow rates of the various consti-tuents of the paste ensures a constancy of the characteris-tics of the pastes obtained from a given starch. It is not necessary to subject the operation of the plant to control by a device comprising a viscosimeter.
The various operating parameters can be regulated precisely and rapidly.
The gelatinization of the carrier in the cold constitutes an economy in the use of steam and requires only expanded steam to maintain the water at a temperature of about 40C. It also enables a carrier with a low starch concentration and which is thus not very viscous and can flow easily, to be obtained.
The system according to the invention is highly flexible in operation, and is capable of producing pastes having regulable starch concentrations of between 18 and 30% by varying the alkalinity as desired. The hydrochloric acid neutralization device enables the alkalinity of the simple face paste to be adjusted independently of that of the double face paste.
The replacement of borax by boric acid also has several advantages, and represents a device for increasing _ _ _ . , _ _ . . . . . . . .. . . _ ~L~3~i~05 the de~ree of degradation of the c2rrier starch in orcer to reach its resistan_e poin~, by using an amount of âdditioncl caustic sodc e~uivalent to the caustic SOdâ necessary to reform the borax. It is easier to meter dry th~n borax, ~ince the flow behaviour of the powder is better and, above allJ it dissolves more rapidly in the st2rch paste.
The storage tank located at the end of the cir-cuit enables the paste to be well homogenised and brings the latter to its final equilibrium state. All the desirable additives, for example resins intended to make the p2ste resistant to moisture, can easily be added to this tank., ~s regards the properties of the paste, the pro- --cess accordirg to the invention enables the followinG fe~-tures in particular to be obtained:
- a constant viscosity at the desired level;
- a good stability with regârd to temperature and shear forces;
- a good stability over time, without any no-ticeable change between 35C and ambient te~perature, for a storage period as long as 96 hours; no irreversible retro-de&radation - good water retention, and no separation on storage or settling. --It should of course be understood that the present invention has been described and illustrated only by wcy of example, which is in no way limiting, and any modifications -~
within the field of technical e~uivalence may be madè to the invention without goinG beyond its scope.
the mixers are preferably of the static type; the reser-voirs and tanks are provided with constant level control means; the assembly of the liquid circulation means are controlled automatically by means of level probes placed in the final paste vats.
Other characteristic features and advantages of the present invention will be more readily understood on reading the following description, in conjunction with the attached drawing which diagrammatically represents the plant and illustrates the process according to the inven-tion.
Description of Preferred Embodiments In accordance with the invention, the primary paste or carrier is made from a natural starch, gelatinized in the presence of an amount of caustic soda or other al-kaline agent in excess with respect to the amount contained in a normal paste for corrugated paper or cardboard. The excess caustic soda is then neutralized and this operation is profitably employed to reform borax, which is always present in this type of paste, from the boric acid added during the mixing or immediately after the mixing of the gelatinized starch and crude starch. The amount of borax may be modified as desired as a function of the excess caustic soda. Under these conditions, during the course of the gelatinization of the carrier portion in a static mixer and in the storage enclosure connected thereafter, the starch is sufficiently degraded to reach the resistance point, which enables it to retain a stable viscosity during the various actions to which the paste is subjected.
The water reservoir preferably is kept at a con-stant temperature of the order of 38C to 42C, and is used:
- on the one hand to prepare, in a feed vat, an aqueous starch suspension of constant concentration pre-ferably fixed at a value of 30 to 436 of dry matter which can be regulated as desired within this range;
- on the other hand to dilute caustic soda to a preferred concentration of about 400 g/litre to a concen-tration of about 10 g to 20 g/litre.
The assemblies of metering pumps consist of a four-head metering pump which ensures a perfect synchroni-zation and enables a constant relationship between theflow rates of the various constituents of the paste to be maintained, or, by way of variation, consists of an assembly of four variable flow metering pumps operating continuously, the liquids being recycled automatically outside the pro-duction. The following simultaneous operations may accord-ingly be realized:
1) Metering of the solution of concentrated caustic soda;
2) Metering of the water of dilution for the caustic soda, the mixing being effected in a pipe arrange-ment by means of a T or, better, by means of a static mixer;
3) Metering of the amount of starch suspension necessary to produce the carrier part or primary paste;
4) Metering of the amount of starch suspension necessary to form the crude starch part of the paste. This secondary starch suspension is mixed with the carrier paste in a second static mixer; homogenization is completed by passing the suspension through a pump connected in series and operating in counter-current, as will be explained in detail hereinafter.
The flow rate of the secondary starch suspension to the static mixer is controlled by a probe located in the outlet of the storage vessel in which the gelatinization of ~3~05 the primary starch takes place; the supply of crude starch may also be effected by means of a timing system.
The final mixture of primary starch and secondary starch is then passed to a storage vat where it remains for a specific duration determined by means of an overflow level device.
The storage tank located at the end of the circuit results in a good homogenization of the paste and brings it to its final equilibrium state. A11 the desired additives, for example resins intended to make the paste resistant to moisture, can easily be added to this tank.
With reference to the accompanying drawing, the starch is distributed from a hopper or silo 1 and, via a volumetric metering device 2, to the starch milk prepara tion vat 3. This vat is provided with a high speed stirrer 4 and is connected via a line 5 to the water reservoir 6 maintained at the desired temperature by means of, for example, a steam coil 7. The vat 3 constitutes the device for preparing the starch milk, and i5 able to deliver con-tinuously an aqueous suspension within a wide range of con-stant and regulable concentration, of the order of 30 to 43~ by weight of dry matter.
The water reservoir 6 provides depending on requirements, and via automatic stopcocks (not shown), water at a fixed chosen temperature, generally of the or-der of 38 to 42C, using a thermostatic regulation of the heating by means of the steam coil 7. The temperature of the water is adjusted so as to obtain a final mixture which arrives at a temperature of about 38C at the storage tank 8.
A reservoir 9 for caustic soda having a concen-tration of about 400 g/l is connected via a line 10 to a meteri.ng pump Pl, forming part of an assemhly Pl, P2, P3, ~136~305 P4, described hereinafter.
This assembly may consist of a single four-head metering pump or of four metering pumps each driven by a variable transmission motor, having the general reference numeral 11, and it enables the flow rate for each liquid to be chosen within a defined range, the flow rate being read on a flow meter in a manner known per se. The pumps operate continuously, and the liquids are recycled, outside production, to their respective vats or reservoirs by a set of automatic three-way valves, namely the valve 12 con-nected to the concentrated caustic soda reservoir 9 via the line 13, the valve 14 connected to the water reservoir 6 via the line 15, and the valves 16 and 17 connected to the vat 3 via the lines 18 and 19 respectively.
The inlet of the pump P2 is connected to the out-let 20 of the water reservoir 6 via the line 21, and the inlets of the pumps P3 and P4 are connected to the outlet of the vat 3 via the line 22.
The pumps Pl and P2 inject their liquid flows through the lines 23 and 24 respectively to a first point A, and then the pump P3 injects a first portion of starch suspension through the line 25 to a second point B up-stream of a first static mixer 26 intended to homogenize the various constituents and gelatinize the starch. This gelatinization is prolonged and completed by contact with a coil 27 connected to the outlet of the static mixer 26 via a line 28 whose dimensions are such that the storage time is at least one minute.
The pump P4 injects the second portion of starch suspension into the primary paste at a third point C, via the line 29, just upstream of a second static mixer 30, and at the outlet of the coil 27~ The simultaneous arrival of the two flows at the point C is regulated by a probe _g_ 1~3~05 (not shown) located at the outlet of the coil 27 or, more simply, by a suitable timing device. The static mixer 30 homogenizes the primary paste/crude starch mixture, this homogenization being completed for example by an in-line pump 31 operating in a counter-current manner.
The final mixture flows via the line 32 from the outlet of the pump 31 to the storage tank of vat 8 provided with an efficient stirrer 33. This vat 8 is furthermore provided with an automatic volumetric metering device 34 for metering the boric acid in the desired amount, as well as with an overflow level device 35 intended to allow the paste to remain in the vat 8 for 30 to 40 minutes, while being stirred, before the paste is distributed.
To this end the outlet of the vat 8 is connected via a line 36 containing a suitable circulation pump 37 to at least two storage vats 38 and 39. These vats are fed with fresh paste under instructions from a probe S situated at a low level and which initiates the production procedure, a three-way valve 40 arranged in the line 36 directing the distribution by a rocking or tilting action to the required position.
Advantageously, and particularly in the case where the starch paste is produced for corrugated paper, the vat 38 receives directly the final starch, which has the characteristics of so-called "double face" paste. The vat 39 may be allocated for the so-called "simple face"
paste and, in this case, its feed inlet 41 is connected to the valve 40 via a line 42 comprising an inlet 43 for water of dilution, which may be connected to the reservoir 6 and, if necessary, an inlet 44 for the addition of an acid such as hydrochloric acid, these additives being mixed by means of a third static mixer 45 whose outlet forms the feed 41 for the vat 39, the hydrochloric acid being contained in a ~t~80S
vat 46.
Suitable probes 47 and 48 placed at a high level in the vats 38 and 39 respectively are intended to stop the distribution and interrupt the whole production cycle, the assembly of pumps Pl to P4 then being in the recycling position via the valves 12, 14, 16 and 17, until produc-tion is restarted by one of the low level probes S~
The following examples, which are given by way of illustration and are in no way meant to be limiting, will provide a better understanding of the scope and value of the invention. In these examples all the percentages are given by weight unless otherwise indicated.
Example 1 Preparation of a paste for corrugated paper, having a starch_concentration of 20%
This test is carried out using a natural maize starch containing 12.5% moisture. The temperature of the water in the reservoir is maintained at 40C and the starch milk is prepared in a concentration of 40% of commercial starch, i.e. 35% of dry matter.
The afore-described system is used, in conjunc-tion with the following regulation of the pumps:
The pump Pl delivers a solution of caustic soda in a concentration of 420 g/litre at a rate of 36 litres/
hour.
The pump P2 delivers water from the reservoir at a rate of 1200 litres/hour.
The pump P3 feeds the circuit with starch milk for the formation of the carrier, at a rate of 140 litres/
hour.
The pump P4 provides the crude starch or secon-dary starch at a rate of 940 litres/hour.
The boric acid is fed to the paste arriving at the storage tank at a rate of 5 kg/hour.
The characteristics of the components employed are as follows:
Concentration of dry matter in the starch of the carrier paste= 4.05%;
Ratio of carrier starch to total starch = 13%;
Concentration of the caustic soda after dilution = 12.2 grams/litre.
The flow rate of final, undiluted paste is 2320 litres/hour and the characteristics of this paste on arri-val at the storage vat for the double face paste are as follows:
Concentration of starch = 20.1%
Temperature = 38C
Stein-Hall viscosity at 35C = 50 s Brookfield viscosity at 35C
(20 revs./min.) = 3000 mPas Alkalinity in % NaOH/starch = 2.70 Borax as % Na2B407, 10 H2O/starch = 1-5 Stability of the paste: no notable change in viscosity at 35C after shear forces produced by a turbine blade rotating at 600 revs./minute for 4 hours. On settling at ambient temperature for 96 hours, the Stein-Hall viscosity normally increases to a value of the order of 70 s, but re-adopts its initial value after stirring and adjusting the temperature to 35C.
Gelatinization temperature of the paste = 58C.
The simple face paste is obtained by dilution wi~h cold water at a flow rate of 280 litres of water per 0 hour, and has the following characteristics:
Flow rate = 2600 litres/hour Concentration of starch = 18%
Temperature = 35~C
~3~i805 Stein-Hall viscosity at 35C = 36 s ~ alkalinity/starch = 2.7 Borax in % Na2B4O7, 10 H2O/starCh = 1.5 Gelatinization temperature = 60C
Stability of the paste: same remarks as for the double face paste.
Example 2 -Pre~aration of a paste for corrugated paper, having a starch concentration of 25%
The test is carried out as previously, using natural maize starch containing 12.5% moisture.
The temperature of the water in the reservoir is maintained at 39C and the starch milk is prepared having a concentration of 40% of commercial starch, i.e. 35% of dry matter.
The pump Pl delivers a solution of caustic soda in a concentration of 415 g/litre, at a rate of 43 litres/
hour.
The pump P2 delivers water at a rate of 940 litres/hour.
The pump P3 feeds starch milk for the carrier at a rate of 156 litres/hour.
The pump P4 feeds crude starch milk at a rate of 1260 litres/hour.
The boric acid is added to the storage tank at a rate of 6.55 kg/hour.
Concentration of dry starch matter in the carrier paste = 5.4%.
Ratio of carrier starch/total starch = 11%
Concentration of caustic soda after dilution =
18.16 g/l The flow rate of undiluted final paste is 2400 l/h Characteristics of the double face paste:
~13ti~5 Starch concentration = 25%
Temperature = 38C
Stein-Hall viscosity at 35C = 52 s Alkalinity in % NaOH/starch = 2.4 sorax in % Na2B407, 10 H2O/starch = 1-5 Gelatinization temperature of the paste = 58C
Stability of the paste: no notable change in the viscosity at 35C after the action of shear forces produced for 4 hours or after settling at ambient tempera-ture for 2 to 4 days.
Simple face paste: obtained by dilution with cold water at a rate of 290 litres/hour and by adding hy-drochloric acid, density 1.16 (content of pure acid equal to 370 g/l) at a flow rate of 6.46 litres/hour.
The characteristics of this simple face paste are as follows:
Flow rate = 2690 litres/hour Starch concentration = 22.5%
Temperature = 34C
Stein-Hall viscosity at 35C = 33 5 % alkalinity/starch = 2.0%
Borax in % Na2B407, 10 H20/starch = 1.5 Gelatinization temperature = 64C
Stability of the paste: identical to that of the double face paste during exposure to shear forces at 35C, and is even improved as regards the viscosity behaviour when the paste is allowed to settle at ambient temperature.
The process and plant according to the invention provide a really continuous and automatic production of starch pastes, and permit a considerable reduction in the storage capacity.
The plant is simple and reliable, and the constant -13a-1~3~i8~S
relationship between the flow rates of the various consti-tuents of the paste ensures a constancy of the characteris-tics of the pastes obtained from a given starch. It is not necessary to subject the operation of the plant to control by a device comprising a viscosimeter.
The various operating parameters can be regulated precisely and rapidly.
The gelatinization of the carrier in the cold constitutes an economy in the use of steam and requires only expanded steam to maintain the water at a temperature of about 40C. It also enables a carrier with a low starch concentration and which is thus not very viscous and can flow easily, to be obtained.
The system according to the invention is highly flexible in operation, and is capable of producing pastes having regulable starch concentrations of between 18 and 30% by varying the alkalinity as desired. The hydrochloric acid neutralization device enables the alkalinity of the simple face paste to be adjusted independently of that of the double face paste.
The replacement of borax by boric acid also has several advantages, and represents a device for increasing _ _ _ . , _ _ . . . . . . . .. . . _ ~L~3~i~05 the de~ree of degradation of the c2rrier starch in orcer to reach its resistan_e poin~, by using an amount of âdditioncl caustic sodc e~uivalent to the caustic SOdâ necessary to reform the borax. It is easier to meter dry th~n borax, ~ince the flow behaviour of the powder is better and, above allJ it dissolves more rapidly in the st2rch paste.
The storage tank located at the end of the cir-cuit enables the paste to be well homogenised and brings the latter to its final equilibrium state. All the desirable additives, for example resins intended to make the p2ste resistant to moisture, can easily be added to this tank., ~s regards the properties of the paste, the pro- --cess accordirg to the invention enables the followinG fe~-tures in particular to be obtained:
- a constant viscosity at the desired level;
- a good stability with regârd to temperature and shear forces;
- a good stability over time, without any no-ticeable change between 35C and ambient te~perature, for a storage period as long as 96 hours; no irreversible retro-de&radation - good water retention, and no separation on storage or settling. --It should of course be understood that the present invention has been described and illustrated only by wcy of example, which is in no way limiting, and any modifications -~
within the field of technical e~uivalence may be madè to the invention without goinG beyond its scope.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A system for producing starch paste continuously and auto-matically, which comprises: a reservoir of water heated to a constant regulable temperature; an assembly of three metering pumps for producing a primary paste from a first portion of aqueous starch suspension, characterized in that the first pump is connected to the outlet of a reservoir of concentrated alkaline agent, the second pump is connected to said water reservoir, the third pump is connected to the outlet of a tank for preparing the aqueous starch suspension situated opposite a feed hopper, wherein the outlets of the three metering pumps are connected to a combining means for bringing the keenest-tuents of the primary paste in contact with one another; a fourth pump connected to the said starch suspension tank and whose outlet is connected to a mixer for mixing the primary starch paste from said combining means with a second portion of starch suspension, wherein the outlet of the said mixer is connected to a storage tank provided with a boric acid meter-ing device and the storage tank outlet is connected to at least one final paste vat provided with level probes for con-trolling the output of the four metering pumps.
2. A system according to claim 1, characterized by the fact that the outlets of the four metering pumps contain three-way valves, for recycling outside production-to the respective reservoirs, and controlled by the level probes.
3. A system according to claim 1, characterized by the fact that combining means consists of a static mixer followed by a coil designed to ensure a contact time of at least one minute.
4. A system according to claim 1, 2 or 3, characterized by the fact that the storage tank outlet is connected via a three-way valve to a storage vat provided with a feed line for feeding a neutralising agent such as hydrochloric acid, an inlet for water of dilution, and a stirrer.
5. A system according to claim 1, 2 or 3, characterized by the fact that the storage tank for the final paste includes a timing device for ensuring a contact time of about 40 minutes.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7904275A FR2449717A1 (en) | 1979-02-20 | 1979-02-20 | PROCESS AND PLANT FOR THE CONTINUOUS MANUFACTURE OF AMYLACEOUS ADHESIVES |
| FR79-04275 | 1979-02-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1136805A true CA1136805A (en) | 1982-12-07 |
Family
ID=9222195
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000346037A Expired CA1136805A (en) | 1979-02-20 | 1980-02-20 | Process and installation for the continuous manufacture of starch adhesives |
Country Status (19)
| Country | Link |
|---|---|
| JP (1) | JPS55129466A (en) |
| AR (1) | AR221407A1 (en) |
| AU (1) | AU534677B2 (en) |
| BE (1) | BE881782A (en) |
| BR (1) | BR8000939A (en) |
| CA (1) | CA1136805A (en) |
| DE (1) | DE3005197A1 (en) |
| DK (1) | DK154655C (en) |
| ES (2) | ES488701A1 (en) |
| FI (1) | FI71760C (en) |
| FR (1) | FR2449717A1 (en) |
| GB (1) | GB2045792B (en) |
| IN (1) | IN153679B (en) |
| IT (1) | IT1147318B (en) |
| MX (1) | MX153167A (en) |
| MY (1) | MY8400213A (en) |
| NL (1) | NL8000997A (en) |
| NZ (1) | NZ192751A (en) |
| SE (1) | SE447264B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5840108A (en) * | 1996-07-26 | 1998-11-24 | Karras; George C. | Method and apparatus for continuous preparation of corrugating adhesive |
| EP1352939A1 (en) * | 2002-04-12 | 2003-10-15 | Remy Industries N.V. | Starch-based glue paste compositions |
| CN114082379A (en) * | 2021-11-20 | 2022-02-25 | 枣庄市金科化工有限公司 | Processing technology of environment-friendly starch adhesive |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2346644A (en) * | 1940-03-18 | 1944-04-18 | Stein Hall Mfg Co | Method of bonding |
| FR2184455B1 (en) * | 1972-05-17 | 1977-01-28 | Roquette Freres |
-
1979
- 1979-02-20 FR FR7904275A patent/FR2449717A1/en active Granted
-
1980
- 1980-01-19 AR AR279996A patent/AR221407A1/en active
- 1980-01-29 NZ NZ192751A patent/NZ192751A/en unknown
- 1980-01-29 IN IN55/DEL/80A patent/IN153679B/en unknown
- 1980-02-04 AU AU55197/80A patent/AU534677B2/en not_active Expired
- 1980-02-07 GB GB8004121A patent/GB2045792B/en not_active Expired
- 1980-02-12 DE DE19803005197 patent/DE3005197A1/en not_active Withdrawn
- 1980-02-14 BR BR8000939A patent/BR8000939A/en not_active IP Right Cessation
- 1980-02-15 FI FI800459A patent/FI71760C/en not_active IP Right Cessation
- 1980-02-18 ES ES488701A patent/ES488701A1/en not_active Expired
- 1980-02-18 ES ES488713A patent/ES488713A1/en not_active Expired
- 1980-02-19 NL NL8000997A patent/NL8000997A/en not_active Application Discontinuation
- 1980-02-19 IT IT20026/80A patent/IT1147318B/en active
- 1980-02-19 SE SE8001291A patent/SE447264B/en not_active IP Right Cessation
- 1980-02-19 MX MX181231A patent/MX153167A/en unknown
- 1980-02-19 BE BE2/58412A patent/BE881782A/en not_active IP Right Cessation
- 1980-02-19 DK DK071380A patent/DK154655C/en not_active IP Right Cessation
- 1980-02-20 JP JP1926280A patent/JPS55129466A/en active Pending
- 1980-02-20 CA CA000346037A patent/CA1136805A/en not_active Expired
-
1984
- 1984-12-30 MY MY213/84A patent/MY8400213A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| ES488713A1 (en) | 1980-09-16 |
| FI71760C (en) | 1987-02-09 |
| SE447264B (en) | 1986-11-03 |
| AU534677B2 (en) | 1984-02-09 |
| NZ192751A (en) | 1982-08-17 |
| JPS55129466A (en) | 1980-10-07 |
| GB2045792B (en) | 1983-03-09 |
| AU5519780A (en) | 1980-08-28 |
| GB2045792A (en) | 1980-11-05 |
| AR221407A1 (en) | 1981-01-30 |
| DE3005197A1 (en) | 1980-09-04 |
| DK154655C (en) | 1989-05-22 |
| BE881782A (en) | 1980-08-19 |
| IN153679B (en) | 1984-08-04 |
| DK71380A (en) | 1980-08-21 |
| MX153167A (en) | 1986-08-15 |
| FR2449717A1 (en) | 1980-09-19 |
| SE8001291L (en) | 1980-08-21 |
| BR8000939A (en) | 1981-08-25 |
| FR2449717B1 (en) | 1982-06-04 |
| IT1147318B (en) | 1986-11-19 |
| DK154655B (en) | 1988-12-05 |
| IT8020026A0 (en) | 1980-02-19 |
| FI800459A (en) | 1980-08-21 |
| NL8000997A (en) | 1980-08-22 |
| MY8400213A (en) | 1984-12-31 |
| ES488701A1 (en) | 1980-09-16 |
| FI71760B (en) | 1986-10-31 |
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