US 2102255 A
Description (OCR text may contain errors)
Dec. 14, 1937. c, H, CAMPBELL 2,102,255
PROCESS FOR THE MANUFACTURE OF COMPOSITE GLUE PRODUCTS Filed Nov. 6, 1935 ENTOR. iffy 2 4 INV CHARLES H. CAMPBELL.
Patented Dec. 14, 1937 UNETEE STATES twili ht? @FFIQE PROCESS FOR THE MANUFACTURE OF C(HVIPOSITE GLUE PRUBUUES 8 Claims.
This invention relates to processes for the manufacture of a composite glue product comprising an inert, finely divided base which is covered with a glue film, and is particularly di- 6 rected to processes for the production of a pulverulent product by spraying a glue solution upon a moving mass of heated, inert powder.
It has heretofore been the practice to make composite glue products by incorporating a powdered base material into a glue solution and then drying the mixture. According to one procedure, such a mixture was dried in trays and the dry material ground. This mode of operation was found quite unsatisfactory because the base material separated from the glue, settling to the bottom of the trays. When the material was subsequently ground, the composite product contained a large amount of glue unassociated with the base.
To obviate the difficulties encountered by reason of a separation of glue and base material, another procedure was developed according to which a mixture of glue with base was agitated during the drying period. While the composite product produced employing this method has a relatively uniform distribution of base in the glue, it has many hard lumps of base particles agglomerated with glue.
These processes for the production of composite glue products require that the mixture of glue and base be heated for a considerable time at a relatively high temperature so that a dry product is produced. Heating the glue in this manner impairs its quality, and the glue used for the production of such composite products loses from twenty-five to about thirty-five per cent of its strength.
Composite products'produced according to the foregoing processes, moreover, are very difficult to grind to the fineness necessary in order that the glue in the finished product will be soluble without an undue delay in soaking, swelling, gelling, and dissolving. To grind the products, it is necessary that they be dried to a friable condition. After a short period of grinding, the, hygroscopic products, resulting from hydrolysis of the glue on heating, absorb moisture from the air, and it is necessary to redry the product before the grinding can be continued. A considerable loss of glue strength results both from the heating incident to the grinding operation and from the heating required to redry the product. The grinding of the product, moreover, tends to separate the glue from the inert base.
A mixture of glue solution and base may be flash dried without substantial loss of glue strength according to the processes of my prior Patent 1,940386 issued December 19, 1933, and the composite products thus produced are readily soluble.
While the products of my patent aforesaid are of excellent character, the equipment required for entirely satisfactory flash drying procedures involves a greater capital expenditure than the apparatus heretofore employed. The handling of the glue-base magma also requires that the best equipment be used because the magma exercises a considerable abrasive action, and the nozzles and similar devices are subject to considerable wear.
I have found that the difficulties heretofore encountered can be avoided and a product of excellent character produced by spraying a glue solution upon a moving body of finely powdered, inert material. Unlike prior procedures, this does not involve handling of a glue-base magma.
By spraying a glue solution upon an agitated mass of finely divided material, the particles of the base material can be uniformly coated with glue, and a readily soluble, pulverulent, composite glue product of uniform character can readily be produced. This product does not require grinding, of course, and a considerable amount of labor and expense is thus avoided.
The glue solution loses a large amountof its water content during the spraying operation, and very little additional drying is required. If the finely divided base be heated, it supplies the additional heat required to complete the drying of the glue. Accordingly, as soon as the required amount of glue has been applied to the base, the product requires no additional heating to complete its manufacture.
The relatively short time during which th glue is heated does not greatly reduce its strength. The glue in products produced according to this invention ordinarily has a glue strength within about six to eight per cent of the strength of the original glue. While the loss of strength is greater than that produced by the processes of my prior patent aforesaid, it is much smaller than the loss ordinarily produced by other prior art processes, which loss may amount to thirty-five per cent of the original glue strength.
The processes, of this invention permit the production of composite glue products of diverse character. This flexibility of operation results from the fact that almost every factor determinative of the product characteristics can easily be controlled at will. The temperature of the base material, the character of the glue spray,
, and the distance of the spray nozzle from the Figure 3 shows a modified form of apparatus i suitable for use with continuous processes.
Referring to Figure 1 in more detail, I designates a mixer' which is employed to'agitate a mass of finely, divided inert base material. This mixer is of a conventional type, and is of the same design as mixers heretofore used for mixing and kneading dough, tar,'and the like.
A body of base material in the mixer may be agitated by the arms 2 and 3. 7 These arms 2 and 3 are rotated in opposite directions by con ventional gears and a motor, not shown.
In order to control the temperature of the mass of finely divided material, the mixer is provided with a'steam-jacket 4. V Y
As is indicated in the drawing a glue solution is sprayed upon the agitated mass of base material by means of a, nozzle 5. The construction of a suitable nozzle is more fully illustratedin Figure 2.
I have found that it is necessary to employ a special type of-nozzle if the best results are to be obtained. Nozzles of conventional design operate satisfactorily for a time, but, after a short period of operation, they become clogged.
This clogging of the nozzles is attributable to the cooling effect of the evaporationof glue solution near the nozzles. The cool zone at the nozzle outlet causes'glue to deposit as a heavy glue 'jelly which, in a short time, seals the small nozzle orifice. When the nozzle becomes clogged, it is necessary to clean it as by dissolving the glue in hot water; a p
Atypical nozzle which will operate continuously is shown in Figure 2. The nozzle 5 is provided with a tube 6 which terminates in a spraying orifice. The pipe 8 carries glue solution, and discharges it in anebular spray upon the inert base material. The outer casing of the nozzle 5 forms a passage I around the pipe 6. Steam, hot air, or hot products of combustion are forced thru the passage 1. I
By surrounding the glue spray with a stream of hot gases, cooling of the nozzle orifice is avoid ed'and clogging of the nozzle is prevented. The hot gases, moreover, aid in drying the glue solution, and, by control of the gas temperature and velocity, one may effect a'desired-rate and manner. of drying. More will be said hereinafter regarding thistype of control. I 7 I While the type of nozzle'abo've described is very satisfactory, it will be understood thatI do not intend to belimited thereto. Instead of supplying hot gases to thenozzle, onemay blow atmospheric air thru the passage 1 and heat it electrically by means of a suitably insulated coil of resistance wire secured to the nozzle casing. Other means of providing a heatedfiow of gas around a glue spray will readily occur to those skilled in the art. It will also be understood that the processes of my invention may 'even be operated for at least a short period with a conventional, unheated nozzle.
Whatever type of nozzle isemployed, it is important that a nebular spray be obtained. the glue solution be discharged upon the base material as large droplets, the glue will not satisfactorily coat the inert powder; The droplets of glue would be present in the final product as f difiicultly soluble. particles. The glue, then,
. should be atomized to form what is ordinarily termed a nebular spray, arid I prefer to use as fine a spray as may economically be maintained.
The sprayed glue particles tend to fiatte'n'and to assume a film-like or plate-like form as they move towards the inert base material. After such a plate of glue strikes the inert particles of base material, it is broken and cut up by the particles, thus coating them with glue. When a weak'glue isused, even fairly large drops will flatten out enough to result in a pulverulent, com
posite product. When-a stronger or more concentrated glue is used, smaller droplets should be formed as the more coherent solution does not flatten out to so great an extent.
The orifice of the pipe 6 should be of a more or less rectangular cross-section so that an even distribution of glue may be obtained. The crosssection of the glue. spray may also be controlled to some extent, if desired, by the cross-section of the hot gas stream surrounding it. It willbe understood, however, that while it isdesirable to employ a glue spray more or less rectangular in cross-section, this refinement is not essential per minute.
Hot combustion gases at about 250 F.jwere admitted thru the passage 1. A glue solution containing one part of high grade, hide glue in three parts of water was admitted to the pipe 6- at a pressure of about one hundred pounds per square inch, and was sprayed upon the agitated mass of Whiting.
The'nozzle was set at an angle of about 40 to the horizontal, and it was located about eighteen inches from the base material being sprayed.
This location of the nozzle had previously been determined by experiment.
'After an amount of glue solution equivalent to aboutone part of dry glue for eachtwo parts of whiting had been sprayed upon the base, the
At this time the mixer 'arms'were rotating at about twenty revolutions to the operation of the processes of my invenspraying of the glue solution was discontinued, 7
and thejpulverulent product was ,dumpedfrom the mixer. The product thus (obtained was in finely divided form,and the whiting was rather uniformly coated with glue. This product is very satisfactory as an ingredient of distemper paints and calcimine's. V
It will readily be understood that while the specific conditions given above are about optimum for the operation set forth, they may be widely varied without departing from the spirit of my invention.
The'rate of rotation of the arms may be widely varied according to the temperatures selected and the rate at which the glue solution is sprayed. The base material must be moved rapidly enough so that no more than enough glue is applied to a given surface layer of particles. The best speed for the mixer arms can readily be determined for a particular installation by experiment.
It has already been noted that the mixer arms rotate in opposite directions, and, in the above procedure, the arms were rotated so that they came up at the outside of the mixer and went down at the center. This is the manner in which these arms are ordinarily rotated, but they may advantageously be rotated in the opposite directions. It will also be understood that conven tional mixers in which one set of arms rotates more rapidly than the other may be used, but this is not particularly desirable. Devices of various types which are provided with means capable of moving a body of finely divided material may obviously be used.
The glue solution used can be made with any grade of hide glue, or bone glue, or mixtures of the same at the option of the user. Or if desired, it is possible to employ a glue liquor that has been passed thru evaporators but has not yet been chilled and. dried.
About one part of medium grade glue should be present for each two parts of water, but it may be desired to use more dilute or more concentrated solutions particularly with various grades of glue. Too concentrated a solution should not be used because it is diflicult satisfactorily to spray and because it may lose its water too quickly. Too dilute a solution, similarly, is not satisfactory because too large an amount of heat will be required to evaporate the excessive amount of water. As will be noted hereinafter, the concentration of the glue solution should be selected with reference to the character of the glue, the operating temperatures, and the operating conditions. Generally, about one part of glue should be used with each two to five parts of water.
The pressure under which the glue solution is supplied to the nozzle will depend upon the nozzle design, the solution concentration, and the character of the glue. Generally, a pressure of the order of one hundred pounds per square inch is required to obtain a suitable nebular spray as above described.
The amount of glue sprayed upon the inert mass can, of course, beselected at will. For the production of a composite product suitable for use in calcimines, it is ordinarily desirable to spray an amount of solution equivalent to about one part of glue to each two to eight parts of whiting or gypsum. These proportions may "obviously be varied according to the proposed use of the composite glue product.
To produce a composite product suitable for use in calcimines and the like, other finely divided inert materials such as gypsum, clay, talc, and the like may be used as a base. It may also be found desirable to apply a glue solution-to a mixture of inert materials. For instance, I may apply a glue spray according to the processes of my invention to a mixture of finely divided calcimine materials as whiting, gypsum, clay, and a suitable dry aniline color.
The temperature of the body of base material is an important factor in the operation of the process above described. It will be evident that the steam temperature and pressure applied to the jacket 4 will be governed by the temperature which it is desired to maintain for the inert material. To shorten the time that a batch is in a mixer, it will ordinarily be found desirable to preheat the inert material before charging it into the mixer. In this way, the inert base can be more quickly and economically heated, and the output of a mixer will be greater.
The temperature of the gas supplied around the glue conduit 6 is also an important factor, and one which must be correlated with the temperature of the inert base. The position of the nozzle must also be selected with reference to the temperatures. It is to be noted that combustion gases were used in the above process because the glue loses less strength if dried in an inert atmosphere. It is preferred, accordingly, to employ an inert gas when convenient.
The heat supplied by the gases in direct heat exchange relation thereto effects a partial drying of the glue solution, and the gas temperature and volume should be selected with reference to the extent of drying desired.
In the process described above, the gas was at a temperature of 250 F. In the distance between the nozzle and the base material, about eighteen inches, the glue solution lost about sixty per cent of its water. If a higher gas temperature were used, the glue would be dried too much unless a more dilute solution were used or unless the nozzle were positioned nearer to the base material. Similarly, if a lower gas temperature were used, the glue solution would not be adequately dried unless the nozzle were positioned further from the base material, or unless a more concentrated solution were used.
It will be evident, then, that the solution concentration, the nozzle position, and the gas temperature must be correlated to obtain a given amount of drying of the solution prior to its contact with the base material. It has already been indicated that the solution concentration is preferably varied within limits, and it will be understood that the solution must be dilute enough to spray, but must not be so dilute as to require excessive heat to remove the moisture. The nozzle position, similarly, can only be varied within limits because if it is too close, the glue solution would not cover a large enough area of base material, and if it is too far the glue particles would lose their velocity and direction.
The gas temperature should generally be between about two-hundred-and-twenty and twohundred-and-sixty degrees F. for most operations, the a much wider range of temperatures may be used by suitable adjustment of other factors. The gas temperature, obviously, should be high enough to prevent clogging of the nozzle.
The amount of water to be removed from the glue by the time that it reaches the base material is subject to considerable variation. The glue must not be too dry when it reaches the base material, or it will not be soft enough properly to coat the base particles.
The base material should ordinarily be at a temperature such as will complete the drying of the glue. If a large volume of hot gas is admitted at 1, very little heating of the particles of base material will be required because the hot gases passing over the surface of the base material will dry the glue even after it is on the particles. 7 i
The base material should not be heated above about 212 to 220 F. because much higher tem- Deratures may result in a loss of glue strength.
As soon as the glue has coated the base material and is dry, further heating at a moderate temperature efiects only asmall loss of glue strength.
' nates a rotatable drum of a' type frequently used an unpufied condition.
For this reason, the relatively short period of heating to which the material is subjected in the course of its production does not result in an excessive loss of glue strength. I
It will be understood that, preferably, the conditions will be such as to dry the glue enough to prevent agglomeration before substantial agglomeration occurs. Following the teachings of .my invention, one skilled in the artwill experience little diflicultyl in adjusting the variables above discussed to produce a pulverulent, composite product. It is important, however, that it be understood that the factors must be correlated.
When glue is flash dried according to theprocesses of my prior patent aforesaid, the high temperatures cause a pufiing' of the glue. This pufiing is probably attributable to the escape of water as steam. Glue which has been puffed in this manner is somewhat sponge-like in structure and, as so great a surface is accessible to water, it is very easily water-soluble. 7 'While the products as produced above are readily water-soluble, it may be desirable to puiit' them; This can readily be accomplished by raising the base material to a pufling temperature, but a slight loss of glue strength may result if' such temperatures be maintained for too long a period. Alternatively, the gas admitted at 1 can be raised to a pufiing temperature, and the high temperatures will prevail only on the surface of the body of inert material. To avoid overheating of the liquid glue, a separate, high temperature gas nozzle may be provided to supply hot gas to the surface of the body of inert material.
In Figure 3 there is illustrated an apparatus by means of which a composite glue product may continuously be produced in either a puffed or In Figure 3, the reference character 8 desigas a drier. The drum 8 is provided with circumferential bearings 9 which rest upon suitable rollers I0. Thrust rollers, not shown, are provided in conventional manner to prevent endwise movement of the'drum. The drum is caused to rotate'by a girth gear H, driven by a'pinion 12. A finely divided inert'material is fed from hopper ill by a conveyor screw l4, and the material is steadily and continuously fed to the upper end of drum 8 thru the axial pipe I5.
The inert base material moves towards the lower end of the drum, and, as it moves, it is sprayed with glue by means of a nozzle I6. A
hot gas admitted at I! acts to dry the glue, and the flow of hot gas to the upper. end of the drum, countercurrent to its flow, preheats the base material. I
The upper end of the drum 8 may-be provided with an opening of variable'size for the escape of hot gas. 'By varying the sizeof the opening, the rate of gas flow may, in some measure, be controlled. v V
The composite glue product discharged" at the lower end of the drum falls 'upon a conveyor I8 and is carried to a receptacle l9. A scraper 2ll may'be provided to remove any of the product process.
flow of hot gas; Under some conditions of oper ation, the hot gas from I! will keep the nozzle I6 warm enough to prevent clogging, but it is preferable to provide means to heat the'nozzle.
The nozzle may be heated by means of an electric resistance secured thereto, or by a steam jacket, or by other indirect heat exchangemeanso It is to be noted that in using the'device of Figure perature, say 400 F. The coated product upon which the gas from I! is directed .would be sub.-
jected to a high temperature for only a short period. The gas would then' pass on to a directheat exchange with the glue spray wherei'it If it is desired to produce a puffed prod- 4 would be considerably cooled. The somewhat:
preheat the base material.
If convenient, theho't gas admitted'at' I! should be inert. If hot combustion gases are used, for instance,the drying of the 'gluewill be accomplished in an inert atmosphere. 7 I
Instead of using separate nozzles l6 and I1,
cooled gas would then continue upwardly and a nozzle such as that shown in Figure 2 maybe 1 used. V
It will be understood that various types of drums may be used in the practice of the above For instance, one may employa drum of known type which has an outer shell serving as an indirect heat exchange means.
While'the above processesoifer some advan tages, the processesemploying a device such as isshown in Figure .1 are preferred because; of
the smaller equipment costs and because of the positive mixing action. I
While the processes of my invention areparticularly advantageous in the production ofa composite product for use in calcimines, it will be understood that such composite glue products can be used in a number of other ways. 7 It will also be understood that while the preferred processes of this invention lead to a pulverulent product, the process conditions may be a modified so as to produce an agglomerated prod- J uct. Such processes which lead to an agglom erated product are superior to prior art processes leading to a similar product, but, as such'rnaterial must be ground, it is very desirable to produce directly a pulverulent, composite'glue prdduct. L
While I have shown a number of illustrative processes, conditions, and devices, I do not intend to be limite-d'thereby, the scope of my -lnvention appearing in the following claims.
Iclaim: r 1. Ina process for they production of a pulverulent, composite glue product, the steps comprising heating a finely divided, inertbase, agltating the base with the type of agitation accomplished by mixer arms, during the agitation directing a nebular spray of glue solutionupon the surface of the agitated base, and simultaneo usly directing a flow of hot gas around the glue spraypart'ially to dry the glue before it impacts upon the base material, thetotal heat being sufiicient to'dry the glue before substantial agglomeration of base particles occurs.
2.'In a process for the production of a pill-11,5
verulent, composite glue product, the steps comprising heating a finely divided, inert calcimine base, agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, during the agitation directing a spray of glue solution upon the surface of the agitated base, and simultaneously directing a flow of hot gas around the glue spray partially to dry the glue before it impacts upon the base material, the total heat being sufiicient to dry the glue before substantial agglomeration of base particles occurs.
3. In a process for the production of a pulverulent, composite glue product, the steps comprising heating a finely divided, inert calcimine base to a temperature not substantially higher than about 212 F., agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, directing a nebular spray of glue solution upon the surface of the agitated base, simultaneously directing a flow of hot gas around the glue spray partially to dry the glue before it impacts upon the base material, the total heat being sufficient to dry the glue before substantial agglomeration of base particles occurs.
4. In a process for the production of a pulverulent, composite glue product, the steps comprising heating a finely divided, inert calcimine base, agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, directing a spray of glue solution upon the surface of the agitated base,
and directing a flow of hot gas towards the base material, the hot gas partially drying the glue before it impacts upon and coats the particles of base material and the heat which the glue solution gm'ns from the gas plus the heat which it gains from the base material being adequate to dry the glue enough to prevent substantial agglomeration of base particles coated therewith.
5. In a process for the production of a pulverulent composite glue product, the steps comprising heating a finely divided, inert calcimine base, agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, heating a glue solution and directing a spray of the heated solution upon the surface of the agitated base, and directing a flow of hot gas towards the base material, the hot gas partially drying the glue before it impacts upon and coats the particles of base material and the heat which the glue solution has plus that which it gains from the gas plus that V which it gains from the base material being adequate to dry the glue enough to prevent substantial agglomeration of base particles coated therewith.
6. In a process for the production of a pulverulent, composite glue product the steps comprising heating a finely divided inert calcimine base by contacting it directly with a flow of hot gas, agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, directing a spray of glue solution upon the surface of the agitated base and directing a flow of hot gas towards the base material thus partially drying the glue before it impacts upon and coats the base material and the heat which the glue solution thus gains from the gas plus the heat which it gains from the base material being adequate to dry the glue enough to prevent substantial agglomeration of base particles coated therewith.
7. In a process for the production of a pulverulent, composite glue product the steps comprising heating a finely divided inert calcimine base by indirect heat exchange, agitating the base so that its particles are brought to the surface and then displaced in turn by other particles, directing a spray of glue solution upon the surface of the agitated base and directing a flow of hot gas towards the base material thus partially V drying the glue before it impacts upon and coats the base material and the heat which the glue solution thus gains from the gas plus the heat which it gains from. the base material being adequate to dry the glue enough to prevent substantial agglomeration of base particles coated therewith. I
8. In a process for the production of a pulverulent composite glue product, the steps comprising heating a finely divided inert calcimine base, agitating the base so that its parti'cles'are brought to the surface and then displaced in turn by other particles, directing a spray of glue solution upon the surface of the agitated base, partially drying the glue in its passage towards the base by contacting it directly with hot gas, the heat which is supplied to the glue solution before it impacts upon the base material plus the heat supplied to the glue by the base material being adequate to dry the glue enough to prevent substantial agglomeration of base particles coated therewith.
CHARLES H. CAMPBELL.-