CA1146164A - Opposed piston-cylinders operating a combined throttling-mixing and injection valve - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method is disclosed for intimately blend-ing two liquid phases, such as is required for example in the plastics materials industry, the me-thod causing the two liquids to flow under throttled conditions through a nozzle after having been pressurized. The admixture is intimate and is obtained quickly, pressure cross-linking and incrustation formation being thus effectively pre-vented. An apparatus for performing the method is also disclosed, which is constructionally simple and efficient.

Description

The present invention relates to a method for admix-ing at least two liquids and feeding them to a shaping mould and a device for use in said method.
In the transformation of materials which starts from mixtures of liquids, including viscous liquids, which are then injected ox cast into hollow moulding spaces wherein they harden under certain conditions of cross-linking, in particu-lar mixtures of monomers, cross-linking agents, plasticizers, catalysts active and inert fillers and dyestuffs, there are two discrete processirlg stages, viz. the intimate admixtllre of the components and the injection or casting operation, which generally take place in two separate locations in the installation.
The circumstance that these processing stages are carried out in two separate locations of the plant has a number of shortcomings.
In the first place, the processing times are too ~` long, then the machinery is very bulky, lntricate and thus expensive, not only as regards the initial costs, but also the running and the upkeep costs.
Another serious defect of the conventional blending systems is that they use blenders of the dynamic type such as ~` mills, which are not always in a position to provide that satisfactory intimate admixture of the components which is required to shape certain compounds adequately in order that products exhihiting preselected properties may be obtained.
An object of the present inventlon is to redress ' certain shortcomings as outlined above by providing a method ..~
for admixing substance of a liquid nature and for feeding the thusly obtained admixture into a shaping mould, said method being capable of being carxied out in the same part of an installation and in sequential processing order without lag tin~s.

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~ nother ob]ect of the present invention is to pro-vide such a method capable of bringing about an intimate ad-mixture of the components such as cannot be obtained conven-tionally.
According to the present invention, there is provid-ed a method ~or admixing at least two liquids and for feeding them into a shaping mould, said method being characterized in that it comprises the steps of:
a) Causing a first liquid to flow under pressure within a closed loop b~ having the liquid flowing repeatedly through at least a throttling site for impressing to the liquid a laminar ~ flow motion, and :` ~ b) Causing a flow in said closed loop a second liquicl under pressure, together with said first liquid, causing both to pass repeatedly through said throttli.ng side, and c) Feedlng the mixture obtained in said loop directly into a shaping mould sltuated downstream of sai~ closed loop.
The present invention~also proviaes:a device capable of appropriately pe~rforming the stages of the method~outlined

2:0 above.
To~this purpose, according to the invention, the device comprises: a cylindrical chamber for mixing said two : liquids together and feeding them admixed to said mould, two .: counteracting pistons driven to slide within said chamber, a :
partition diaphragm inserted between said pistons so as to :~ , . ;
~, ~ 30 : ~i ~ 2 -split the chamber into two compartments which communicate through at least one passageway through said diaphragm, feed-ing ducts for said liquids which o~en into said chamber, and a valve-controlled discharge nozzle for the liquid mixture.
The features of the invention will become still more clearly apparent from the ensuing detailed description o~ an exemplary embodiment of the installation adopted to carry out said method, the installation being illustrated in the accom- ;
panying drawings, wherein:
: 10 Figure 1 is a schematic of the operational layout ~:: of the installation;
: Fi~ure 2 is a longitudinal cross-sectional view show-ing:the actual admixing device, the cross-sectional view being i~ taken along the line II-II of Figure l; and , ~
Figure 3 is a cross-sectional view taken along the ~ ~
line III-III of Figure 2. ~:.
Figure 1 is a schematic illustrating the principle of the processing installation, starting for example from the two components, A and B, as prepared in the storage tanks 3 and 4, wherefro~, by means of the dry air pressure from llnes :: I and 2,:they separately pass into the loading cylinders 11 and 12, via the lines 5 and 6, and through the nonreturn valves 7 and 8.

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By displacing the pistons in the loading cylinders 11 and 12 by means of the hydraulic system comprising a central unit 14 and the cylinder 13, the chambers 20 and 21 of the injector-mixer of the present invention are filled.
The two charges A and B flow through the nonreturn valves 9 and 10.
The injector-mixer essentially comprises the chambers 20 and 21 and by a separation-admixture diaphragm 19, diagram-matically shown in Figure 2.
; 10 The reciprocation of the pistons 22 and 23 in the same direction causes the ma~erials of the batches to be blend-ed and become intimately interdispersed. The pistons 22 and 23 are actuated by counterpistons in compressed air cylinders 17 and 18. Due to the actuation of the pistons 22 and 23 the batches flow through the communication passageway 24 between the two chambers, in such a mode of flow as to have high values i ( of the sIiding velocity gradient.
The shear stress at the wall will thus become the :: greater, the higher the viscosities of the batches and of the mixture will be. Preferably, to this purpose, the passageway 24 comprises two branches 26, 27 which converge into a mixture discharge nozzle 28.
In comparison with other static mixers, it has sur- ;
; prisingly been found that there is no necessity of splitting the streams i.nto a number of fillets duxing the flow of the materials, but that it is sufficient to work under conditions of high shear stresses in order that a satisfactory copenetra-. tion of the batches to be mixed may be ... .

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achieYedO
Of course, the motion of reciprocation of the two pistons in the injection and a~lixture chamber takes place with the val~es 9~ lO a~l 25 shut.
For the injection or cast:ing of the admixed mate-rials~ the valve 25 is opened and the two pistons 22 and 23 are actuated either singly or together ~consi-stently with the amount of mat~rial to be injected), so as to feed the mixture~ through the noz~Ie 28~ into the mould~ which has been diagrammatically shown at~S.
When charges subsequent to the first are carried out ith unblended material~ the latter acts as a diluent of possible incrusta~ions due to premature cross-linking and/or stagnation of material~ so that the succession of the charges permits to consider the system as self-clean-ing~ with apparent technical and economical a~an~age.
In this connection~ it is ~referred to feed and to ~; ~ subject to laminar flow through~the~passageway 24 the first batch, then to feed in the second batch~and subject-.
ing them to laminar flow together.
With the apparatus shown in FIGURES 1~ 2 and 3~
~ ;r~ C there have been carried out process runs of~ =
; ~ ~ and the results are tabula-ted in the ensuing Examples.
EXAMPLE
~; 25 Batch A is a polyurethan elastomer based on isocya-nates oP the kind of ADIPRENE L lO0 (Reg. Trade Mark) of the ~uPont Company~ having the Pollowing properties :
Specific gravity at 25C 1.06 Brookfield viscosity at 30~C 18.000 cps Average isocyanate contents 4.1~
Batch B ls a mixturc of pl~sticl~er, cross-linking ~' ~
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agent and catalyst.
The plasticizer is DOP ~lioctyl phthalate)~ the cross~linking agcnt is MOCA ~Reg Trade Mark) of D~Pont ~4~41-methylene-bi~-2-chlorvaliiline) and the catalyst is adipic acid The operative varîable w~s taken as the increasing number of reciprocations of the pistons 2~ and 23 in the opposite directions. While accepting the principle that ~- ~ the final characteristics are~ as an average~ those obtain-~;~ 10 able as ma~ima with the relative compounds, there have bee `~ ~tatistically evaluated the co~Eficlents of variation for - tests repeated 20 times on the sam~ sample, ~y detecting the decrease as a function oE the number of reciproca-- ~ tions of the pistons and the constancy after the second .~
15 movement. The values of the coefficients of variation have a magnitude which virtually corresponds to the errors of the measuring methods. Thi~ r~act means that by actua-' ting the pistons 22, 23 only t~ice prior to the effecting , .
the casting or the injection into the mould, a perfect ~- zo homogeneization of the blend lS achieved.
;~ The compound formulae and the resul-ts are tabulated hereun~l~r.
Adipr~,ne L 100~ ) 100 100 lOO 100 Moca ~ J 12.5 12.5 12.5 12.5 ~5 DOP 40 4a 4o 4o Adipic acid 0.15 0.15 0.15 0.15 N reciprocations 1 2 3 10 Admixing temperature, C 100 100 100 100 Cross-linking time, hrs 3 3 3 3 30 Temperature of cross-lin~ing C 100 100 100 100 Post-cross-linking~hrs 160 160 160 160 :

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Xost-cross linking teMpt.C24 24 24 ~4 Hardness~ Shore A 81 82 81 81 Modulus at 100% el.,kg/cm2 37 37 38 37 ~odulus at 300~ el.,kg/cm2 60 62 61 60 Tensile strength,kg/cm~~05 210212 210 Elong.a-t break, % 600 610 620615 Compression set,% 40 41 39 40 ~22 hrs at 70C) - Resilience,% (Bashore) 51 5 51 51 ARIATION COEFFICIENTS in %
Hardness 14 8 7 8 Tenslle strength 16 10 8 9 Resilience 10 l7 8 7 ; EXAMP1E
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The same procedure of E~ample l has been adopted but a dyestuff has been added to the formulation (for example, in an epoxy base paste~. -There have been obtai~ed the same results as forExample 1.
The dyestuff has been a~mixed as a component of batch B and the microscopical ~nalysis has shown that it had been finely dispersed.

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~;~The batch A is ADIPREN~ L 100 (Reg.Trade Mark), the batch B is a mixture of DOP and methylene dianiline.
25 The blending has been obtained ~ith 1 and 3 reciproca-tions of the pistons.
~- ADIPRENE L 100~(~ r~ irk )100 100 lethy1ene dianiline 9.6 9.6 Admixture tempera-ture,C 66 66 ~ - Time of remo~al from mo~lds,mins. 3 3 ,~'~` ~ : : :

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Cross-linking time at 100 C, hrs Conditioniny time UR 50%) at 24C, hrs 160 160 Piston reciprocations, N 1 3 Modulus at 100% el.kg/cm 40 39 Modulus at 300~ el.kg/cm2 55 56 Tensile strength, kg/cm 190 200 Elong. at break, % 600 630 Hardness, Shore A 73 73 Compress.set(B),%,22hrs at 70 C 25 27 10 Resilience (bashore), % 53 52 COEFFICIENTS OF VARIATION,~
Tensile strength 20 10 Elongation at break 15 9 ~ardness 20 8 Batch A is ADIPRENE L 100 (Reg. Trade Mark) supple-mented by ferric acetylacetonate as the catalyst.
Batch B is composed by ADIPRENE L 100 (Rey. Trade Mark) and polyols as cross-linking agents (1,4-butanediol and trimethylol propane).
The number of reciprocations of the pistons 22, 23 has been varied and the coefficients of variation has been calculated as for Example 1. The formulations and the results which have been obtained are tabulated hereunder:
ADIPRENE L 100 (a trademark) 100 100 100 100 . , 1,4-butanediol 3.53.5 3 5 3.5 Trimethylolpropane 0.80.8 0.8 0.8 Ferric acetylacetonate 0.010.01 0.01 0.01 Cross-linking, hrs/ C 6 at 1006 at 1006 at 100 6 at 100 Post cross-linking, hrs 160160 160 160 (U.R~ 5D~ at 24 :

~iston reciprocati.ons~N 1 2 3 10 Modulus at 100% el.kg/cm~ 19 ~0 18 19 Modulus at 300% el.kg/cm2 33 30 35 34 ~ Tensile strength,kg/cm~ 137 14~ 136 138 .~ 5 Elong~at break,% 500 480 510 500 Shore A Hardness 58 57 58 5S
COEFFICIENTS OF ~ARIATION IN ~0:
Tensile strength 2~ 12 11 9 : : Elongation at break 18 8 9 8 Har~ness 16 ~0 12 10 : Thusg according to the invention~ the a~mixture - is ef~ected by a statlc blender base-l on the flow of the . materials -through appropr1ate ports, under such condi-: tions of flow as to provide a complete interpenetration of the components by virtue of the shearing stresses . which are thus generated. The absence of mechanica1 : component parts in movemerlt in tt~e interior of the mass of the ingredients of the admi.~xture prevents the forma~
. tion of incrustations which would be caused by the perma:--, -nence of materiaIs around such parts as shafts, helices - or otherwise. Such incrustations are often due to pre-: mature polymerizations or premature cross-linking as ge~
nerated by diffeteNtial stresses around moving shafts ~; and by the stirring time as required in a usual dynamic :~ 25 blender to effect the admixture in question~
In the case in point the times which are required ~: for effecting blending may be reduced to a few seconds,; to that hardening phenomena are minimized prior to in-jection and it becomes possible to work at temperatures which are sufficiently high to .ninimize also -the cro3s-~:: linkin~ cycles.

Claims (2)

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

1. A method for admixing at least two liquids and feeding them into a mould via first and second branched, con-verging throttling passageways formed in a nozzle block leading to a discharge passage and defining a first and second chamber which comprises the steps of: feeding a first liquid through a first inlet passage into said first chamber; circulating the first liquid under pressure between the first and second chambers through the throttling passageways to clean the chambers and passageways; converging the first liquid through the first and second branched, converging passageways in the nozzle block for impressing on the liquid a laminar flow motion; thereafter feeding a second liquid through a second inlet passage into said second chamber separated from the first chamber by said nozzle block; circulating the first and second liquids back and forth under laminar flow from one to ten times in a closed loop between the first and second chambers; converging the first and second liquids through the first and second branched, converging passageways in the nozzle block to thoroughly admix the first and second liquids and to generate a desirable sliding velocity gradient; and feeding the admixed liquids through said discharge passage in the nozzle block directly into said mould, thus preventing incrustations of the liquids in the first and second chambers and nozzle block.

2. A device for use in admixing at least two liquids and feeding the mixture so obtained directly to a moulding space, which device comprises a cylindrical chamber for admixing said two liquids together and for feeding the thusly obtained mixture directly into said moulding space, two counteracting pistons drivable so as to slide within said chamber, a partition diaphragm disposed between said pistons so as to partition said chamber into two compartments which communicate with one an-other through at least one throttling passageway formed through said diaphragm, and in each of which compartments one of said pistons is slidable to cause the liquids to circulate back and forth between said compartments, feeding ducts for said liquids which open into each of said compartments of said chamber and a discharge nozzle for said mixture controlled by a valve means, said ducts and said nozzle being formed through said diaphragm, said passageway comprising two branches which con-verge into said nozzle.