CA1142314A - Process and apparatus for continuous production of polyurethane foam - Google Patents

Abstract

ABSTRACT

A process and apparatus are disclosed for the continuous production of polyurethane foam. The invention is directed to the use of a laterally translating mold, the first portion of which has divergent side walls, including a "V"-shaped mold having divergent straight vertical side walls. A polyurethane reaction mixture is deposited at or near the apex of that mold. The deposited mixture can be a partially-expanded preformed fluid mixture formed, for example, by a centrifugal mixing means. Typically, the mixture is permitted to substantially complete its rise after being conveyed past the extremeties of the divergent side walls of the first mold portion. The invention con-templates use of a ratio of conveyor velocity to foam product height lower than those of the prior art. Both rectangular and circular cross sectional products can be produced.

Description

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PROCESS AND APPARATUS FOR CO~ITI~I[JOUS
PRODUCTION OF POLYURETHANE FOAM

T~CHNICAL FIELD
5 The present invention relates to the eontinuous produetion of east polyurethane fo~ms, sueh as rigid, semirigld and flexible polyurethane foams.

BACXGROUND ART
1O Polyurethane Eoams are widely used as materials from whieh artieles sueh as mattresses, seat eushions, and thermal insulators are fabrieated. Sueh polymerie foam materials are ordinarily manufaetured by a easting pro-eess in whieh a mixture of liquid polyurethane-foam-generating reaetants are deposited in a mold~ As used herein, the term "mold" ineludes both stationary molds for bateh eastinc3 and translating or otherwise movahle m~lds for eontinuous easting. Evolution o~ a gas eauses the reaetants to foa~. For some ~oam formulations, the reaetants themsel~es reaet to evolvè sufficlent gas;
in others a blowing agent is mixed with the reaetants to provide gas evolution. Continued gas evolution causes the foam to e~pand to fill the mold. The foam, initially a partially expanded fluid mi~ture, becomes increasin~ly viscous as the reaetants polymerize, ulti~ately curing into a polyurethane foam casting silaped by the mold.

Slabs of polyure~ilane foam appro~imately rectangular or eircular in eross seetion are conventionally east in a translatincJ channel-shaped mold. Such molds typically include a belt eonveyor forming the bottom of the mold ancl a pair of spacecl-apart, opposincJ-side walls, which can be fi:;ecl or translat.lble at the speed of tlle eon-veyor. The mold sides and bottom are ~enerally lined witll one or more sheets of fle~ible-web such as kraft paE~er or polyetllylene film. The sheets of mol~ liner ~re ~'f ~

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ordinarily withdrawn from rolls and continuously translated along the mold channel at the same speed as the belt of the conveyor.
Liquid-foam-generating reactants are deposited on the mold bottom in a zig-zag pattern from a pouring nozzle positioned above the mold which is reciprocated back and forth across the width oE the mold. Typically, after the reactants flow together, they expand and form a uniform slab of foam. Conventional production of foam products having rectangular and circular cross sections is taught in U.S. Patent No. 3,325/823 to Boon and U.S. Patent No. 3,325,573 to Boon et al., respectively.

If fresh reactant mixture is deposited on top of foam generated from previously deposited reactants, the resulting cured foam will have an uneven surface and non-uniform density, which is un-desirable for most applications. By continuously translating the mold liner, the reactant mixture is continuously carried away from the pouring area below the pouring noz~le, which reduces the tend-ency for fresh reactant mixture to cover that previously deposi-ted.

Propitious selection of conveyor velocity can prevent production of undesirable foam products. ~ range of ve]ocities can be established for a particular reactant mixture formulation.
Minimum velocity is achieved when liquid reactant mixture is evenly distributed on the bottom of the mold and does not flow in a direction opposite to that of the mold and conveyor.
Maximum velocity is achieved when the deposited liquid mixture begins to flow in the same direction as the conveyor.

Selection of a velocity within the mentioned range requires consideration of the chemical reaction occuring subsequent to the depositing of liquid mixture in the mold. During ,i,~,,_,, f .
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residence in the mold, liquid mixture foams and curès.
The height of the foam is affecte~ bv conveyor velocity.
Because economy necessitates maximum product height, lower velocities are preferred during the foaming portion of the 5 reaction to attain such heights. The ratio of eonveyor velocity to product height is a useful criterion for evaluating proeess efficiency, i.e. the lower the ratio, the more efficient the process. According to the process of this invention, that ratio can be reduced to the ranse 10 of about l to about 3.

To reduce further the tendency of the liquid reaetants to flow back under the pouring no~zle and-to assist the "zig-zags" of reacta~t mixture to merge uniformly, it is customary to ine~ine a pouring board, the surface under the nozzle, fro~ horizontal so that the bottom liner slopes downward in the direction oE translation. Ho~ever, the angle of inclination of the pouring board cannot be c3reater than about ~.5 from horlzontal for typical fle~-ible polyether polyurethane-foam formulations without causing the reactant mixture to flow forward under previously deposited miYture, which leads to undesirable nonuni~urm foam. The angle af incli~ation is different for different foam formulations, such as poly-ester yolyurethane foams~

~'roblcms arise if the mold bottom slopes do-~nward along its entire length. Conventional continuous sl~b molds are cluite long, typically in eYcess of G0 feet, to provide for thc long curing time of the fo~m. Building a translata~le mold of this length inclined from hori-ontal is significantly more e.Ypensive than building a translatablc mold of the same length which is horizontal, because, for e~ample, the buildincJ housin~ the inclined mold ~Jould be requirecl to have higher than normal ccilings.

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~1oreover, it is e~pensive to change the angle of inclina-tion of the entire mold to compensate for differing vis-cosities a~ong various foam formulations. Thus, some continuous slab molds have horizontal belt conveyors for 5 most of the length of the mold bottom, but have relatively short inclined pouring boards located beneath the pouring nozzles. The expansion and rise of the foam generally takes place on the sloping pouring board.

A s~cond reason for providing a pouring board which makes an angle with respect to the belt conveyor relates to the cross-sectional shape of the slab cast in the mold. ~s the foam expands and rises in the mold, it encounters the sides of the mold. If the mold-side liners are being translated substantially parallel to the ~old bottom, the e~cpandinc~ foam experiences a shear force which resists its rise along the sides. This shear force results in a round-ing of the top of the slab to form a crown or crest of convex shape, much like a loaf of bread. For most appli-cations, such rounded portions are unusable and must `oediscarded as scrap. Thus, the more nearly rectangular the cross section of the slab, i~e., the Elatter the top, the ~ore economical is the castin~ process.

If, over the length the foam e~pands, the mold bottom lincr and the two mold side liners are translated at an anc~Le with respect to one another, the mold side liner can have a velocity component relative to the mold bottom in thc direction of the e~pansion of thc foaln. This velocity component can cor1E~ensate for the shear forcA
~hich resists the rise of the foam. Guidir.cJ the mold bottom lincr across an inclined pourincJ board, which intcrsects an inclincd Mold-bottom conveyor can provide such a compensatinc~ velocity componcnt when foa~ e~pansio occurs over the lenc~th o~ the pourin~ board ancl wl1en mold-. . .

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side liners are -transla-ted parallel to the mold-bottom conveyor. The angle of intersection, which ordinarily leads to polyurethane foam slabs having the most nearly rectangular cross sections, is about 10 for typical foam formulations and production conditions. Unfortu-nately, if the pouring board is sloped 10 from horizontal freshly deposited reactant mixture tends to flow forward, as discussed above, leading to foam slabs of non-uniform density or other imperfections.
Although it is possible to construct a continuous slab mold with a pouring board inclined from horizontal by an angle of 4.5 and intersecting the belt conveyor at 10, the bel~ conveyor in such a case must be inclined upward ~5 by an angle of 5.5. See, for example, the apparatus of patent '823. As noted above, however, inclined trans-latable molds are more expensive than comparable hori-zontal molds.

United States Patent No. 3,786,122 discloses a process for producing polyurethane foam slabs which employs a horizontal, channel-chaped mold having at its forward end in inclined "fall plate" which makes an angie of signi-ficantly grea-ter than 4.5 from horizontal. The problem of reactant mixture flowing down the inclined fall plate is obviated by prereacting the reactant mixture prior to introducing it onto the fall plate. The prereacting step is carried out in a trough which opens onto the upper edge of the fall plate. Liquid foam reactants are introduced onto the 'bottom of the trough and the foam which is generated is allowed to expand upwards in the trough and spill over onto the fall plate. The faom contir)ues to expand as it is carried down along the fall plate by a translating bottom sheet. Because the prefoamed reactant mixture exiting the trou~h is more viscous than ;

the initial liquid reactant ~ixture, the fall plate can be inclined at a grea-ter angle from horizontal than a pouring board in a conventional polyurethane foam slab mold.

5 An additional result of introducing prefoamed reactant mi~ture into the mold is that relativel~ high foam slabs can be produced as co~pared with conventional processes.
Econo~ies result from producing high slabs because, the thic~er the foam slab, the less is the loss from discarding rind which generally coats polyurethane foam castinc;s.
With a conventional slab mold, if the rate of introduction of reactant mixture is ~ept constant and the rate of translation of the mold liner is reduced, the height of the foam slab -tends to increase because more foam~generating reactant is deposited per unit length. EIowever, if the rate of translation is slowed sufficiently, the expanding foam, particularly the youngest and most fluid portion, beco~es unstable and tends to slip and shit, which results in cracks and other imperfections in the cured foam.

This proble~ of instability of rising foam is reduced in the process of the '122 patent by introducing into the translating mold prefoamed reactant rni.~ture which is sufficiently viscous as to be able to sustain a relatively steep slope of the pouring boarcl as it cormpletes its e:~pansion. Thus, the hei~ht of the foam can be increased.
In addition to permitting higher foam slabs to be cast by reducin~ the translation speed of the mold liner, this process permits the use oE sla~ molds shorter than thos2 o conventional processes, because the slab moves a shorter distance durincl tlle curing time.

Certain pro~lems attend the use of the open trou~'l oE the '122 patent. For e~ampl2, c~langincJ the width of the trough is difficult because foam deposits interfere with 3~

re-establishing fluid--tight seals. Moreover, the trough opening is subject to partial blockage by deposits of cured foam along the back and sides where the flow of prefoamed reactant mi~ture stagnates. Such deposits 5 break free from time to time and are swept over the weir into the rising foarlr thereby causing objectionable non-uinformities in the ~oam slab. A urther difficulty is encountered when air bubbles are introduced into the bottom of the trough with the liquid reactants. These 10 air bubbles generally remain entrained in the foam, leading to voids and other defects in the cured material.

United States Patent No. 3,870,441 discloses an apparatus for producing polyurethane foam slabs which uses a 15 horizontal, channel-shaped mold similar to the ayparatus disclosed in the '122 patent. Li~ewise, liquid foam re~ctants are introduced into the bottom of the trough and allowed to expand upward eventually spilling over onto a fall plate. The e~panding foam moves across the 20 fall plate to a conveyor via a translating bottom sheet.
The improvement of the '~41 patent is directed to a means for assisting the expanded foam in spilling over the fall plate. That flow assisting means comprises translating sheets, substantially ~erpcndicular to the bottom shee-t, 25 which continuously move around the ~eripllery of the channel-shaped mold including the periphery of the trough. }~owever, that improvement to the '122 pa-tent does not alleviate all of the drawbacks noted above for the '122 patent.

DISCLOSUR~ OF INV~.NTION
The prcsent invention is directed to a proccss and apparatus Eor the production of pol~urcthane foam products.
Thc invention contem~latcs the use of a uniquc l~terally translating mold arrangement having the ability to achieve 35 high block heights or grcater diameter round bloc~ foams.

Specifically, that mold arrangement contains a first mold portion with diverging side walls, particularly a "V"-shaped mold portion with diverging straight vertical side ~alls.
The angle of the diverging side walls is not critical, but should be less than about 120, preferably within the range of 10 to 90. The angle referred to is defined by imaginery lines from the apex of the first mold portion to the point of intersection of the diverging side walls with the parallel second side wall portions of the mold.
Reaction mi~ture is deposited at the apex of the "V" and substantially co~pletes its expansion shortly ~ast the extremeties of the "V" which join parallel side walls of a conventional mold arrangement. A centrifuge,as described in U.S. patent No. 4,158,132 issued on June 12, 1979, can advantageously be employed to deposit a partially-expanded prefoamed mi~ture of reactants. The mixture can be deposited on a seg~ented pouring board. Use o~ the present invention results in low ratios of conveyor velocity to product height as compared with substantially higher ratios used in prior art processes and apparatus.

BRIEF DESCRIP~ION OF DR~INGS
Several preferred embodiments of the invention are described below with reference to the accompanying5 drawings, in which:
Figure 1 is a plan view of an apparatus OL the present invention used for producing polymeric foam proclucts utili~ing a mold having a "V"
sh~pe;
Figure 2 is an elcvation and partial scc~ion of the embodiment of Figure 1 whercin a conventional mi~ing hcad is used to deposit polyurcthane reactants on a pouring board inclined at an anglc a from horizontal near the apex of the "V" portion of thc mold;

Figure 3 is also an elevation and partial section of a modificatlon of Figure l wherein the segmented pouring board is depic~ed having a first horizontal segment followed by a second se~ment .inclined at an angle c~ ~rom horizontal;
Figure 4 is also an elevation and par-tial section of a modification of Figure l wherein the polyure-thane foam reactants are passed from a conventional mi~ing head into a prefoaming means and then 10 . deposited on a device depicted in ~reat det,~il in Figure 4A, which device is suspended below the ~ixing head and above the pouring board as a partially-expanded prefoa~ed ~ixture of reactants;
Figure 4A is a frontal view of the device in Figure 4 on which the partially-expanded prefoamed mixtuxe of reactants is deposited;
Figure 5 is also an elevation and partial section of a modi~ication of Figure ~ ~herein a se~mented pouring board is depicted having a irst and 20 second segment inclined at angles al and ~2 from horizontal, respectively;
Figure 6 is a frontal view of the modification of Figure l, wherein the polyurethane foam-forming reactants are ~assed into a cone-shaped bottom 25 pre~oaming m~ans and then deposited on the pouring board by flowing out of the cone-sllaped prefoaminc3 means as a partially-e~panded prefoamed mi~;ture of reactants; and Figure 6A is a frontal view o the cone-shaped 30 prefoamin~ means utili~ed in the apparatus de~icted in Fic3ure 6 used in conjunction with an upstream or bottom ccntrifucJe.

BEST ~OD~ FOR CARRYIN~, OUT TIIE I;IVr.NTION
Referring now to Figure l, and apparatus l0 for producing 3:~

products of free-rising polyurethane foam is illustrated.
The foam product will have a substantially reetangular cross sec~ion (See Patent '823 to Boon); however, this apparatus eould be modified to make a foam produet with 5 a substantially eircular cross seetion aecording to the teachings of the '573 patent to Boon et al. Such apparatus is suitable for use with the process of the present inven-tion. The apparatus ineludes a eonduit 11, which ean be stationar~ or ean reeiprocate, depending upon the neees-10 sity for distxibuting the premi~ed reactants near the apexof the "V" shaped first portion 12 of a eontinuously translating mold 13. The latter seeond portion of mold 13 includes a eonventional arrangement for produeing a product having the desired shape with a eonventional ~ottom convev-or means to translate the e~panding and curir~g polyurethane foam and parallel side walls whieh ean be either mo~ing or stationary. The "V"-shaped portion ineludes the first mold portion side walls 1~ which diverge and cannot be parallel or eonvergent. Those first mold portion side

2~ walls of the "V"-shaped portion join at their e~ctremeties the second mold portior, parallel side walls 15 comprising the latter second portion of the r~old 13.

Fig 2 shows conduits 16 and 17 which simultaneously eon~ev a mixture of polyurethane foam forming reactants to a conventional mi~ing head 18 eonnected to conduit 11 for depositincJ premi~ed reactants on pouring board 19.
mold bottom liner 20 made of a fle~cible-wcb, such as ~Craft paper, is supplied from a roll shown in the drawinc3 and is cJuided o~;er pouring board 19 onto a mold bottom surfac, 21 of a bottom belt conveyor 22.
.
First and second side mold-side liners 23 and 23.~, also made of a fle~cible-web, such as i~raft papcr, are g~lided past opposincJ guide mcans 2-l and then trallsl~te across ~23~

the first portion mold side-walls 14 of the "V" shaped first mold portion 12 and then past second ~old portion side walls 15 of r~old 13. Mold side liners 23 are posi-tioned flat against mold side walls 14 and 15 by the pressure of the expanding, premixed polyurethane foam forming reactants. The mold side liners and mold bottom liner define a channel-shaped mold or casting foam products, which can have subs~antially rectangular or substantially circular cross sections. Means are provided for guiding and translating the side liners and bottom liner in a parallel relationship. Of course, the rate of translation of the three liners should be substantially equal to the rate of txanslation of belt conveyor 22.
Pouring board 19 can be substantially ~lat or curved and makes an angle a from the horizontal. The angle of inclination a can be adjusted to accor~modate varia-tions in the viscosity of the mi~ture being deposited thereon.

Although a one angle pouring board 19 is illustr~ted in Fi~ures 1 and 2, in certain applications it can be advantageous to er~ploy pouring boards havincJ more than onc segment such as that shown in Flgure 3, each segment being inclined at a different ancJle from horizontal, or, as in Figure 3 with a first secJment horizontally arranged. Figurc 3 shows a pourincJ board consisting of two secJmcnts, a first horizontal segment 25 locatcd adjaccnt conduit 11 and a second inclined secJr~lcnt 2G
abutting first secJment 25 and adjacent to bclt conveyor 22 inclincd at an angle a from horizontal. Such a pouring ~oard arra.lc3ernent ~as been used to r~a~e foam products of substantially rectang-llar and substantially circular cross sections. Ot~er scgmented pouring boards , ': .

are of course within the bounds of the instan-t invention.

Figure 4 depicts a further modification of ~igure 1 em?loy-ing a prefoaming means 27 used in making a partially e~panded prefoamed mixture of polyurethane foam forming reactants to be deposited on pouring board 19. Prefoam-ing means 27 is illustrated as a top centrifuge such as those described in ~T.S. patent No. 4,158,132 issued on ~une 12, 1979. Other prefoaming means useful in the practice of the present invention are the cone-shaped prefoaming means alone or in conjunction with the botto~
centrifuge depicted in Figures 6 and 6A; in this regard rererence is made again to U.S. ~atent No. 4,158,132.
As previously described, conduits 16 and 17 simultaneously transport polyurethane foa~ reactants into mi~cing head 18. Premi~ced reactants e~cit mixing head 18 through conduit 11 which comprises the inlet for pre-oal~ing means 27, which is illustrated in this instance as a top centrifuc~e.

~Jhen prefoaming means 27 includes a top centri~uc3e, a variable speed electric motor 28 is used to rotate container 29 by way of a pully drive 30. A motor speed control 31 varies the speed of motor 28. Accordingly, mi:ced reactants enter through inlet tube 11 to rotatinc~
pressurized container 29 to form a partially-e~panded polymeric mi~.ture 32.

~ gas atmosphcre can be maintained ovcr mi~ture 32.
Thc pressure of that atmosphere is controlled at a pre-determincd value by a convelltional gas pressure controller 33 ~hich is conncctcd to containcr 29 by concluit 3l.
That prcssure propcls the partially-ecpanclccl mi:;turc through fle~iblc conduit 35 to a dispcnsing nozzle 3G.

Fle~i~le conduit 35 d.irects the partially-expanded mi:~ture from the interior of the eontainer 29 to the apex of the "V"-shaped portion 12 of mold 13. Nozzle 36 is positioned above pouring board 19 near the apex of the "V"-shaped 5 portion of the mold. Advantageously, a eireular reservoir 37 and a weir 38 cor,nbination is positioned below nozzle 36; this eor~ination is depicted in greater detail by Figure 4A. The nozzle ean be stationary or be reciprocated eross-wise of mold 13 aeross the width of the apex of the "V"-shaped portion 12 by eonventional reei~rocation means. An edge of the pouring board 19 abuts a surface of a eonventional belt eonveyor 22 r which is used to form a mold bottom surface 21. That surface is ~referably substantially horizontal. Other-wise, the apparatus operates in a manner previouslydescribed with regard to Figure 1.

The circular reservoir 37 and weir 38 cor~bination depicted by Figure 4A is employed to further control the spread of the partially-expanded prefoamed mi~ture of reactants onto the pour board 19. That cornbination also contains a lip 3~ over which the partially-e~panded prefoamed mi~ture of reactants ~asses before running onto the ~our board 19.

Althouqh a one secJnent pouring board 19 is depicted in Figure 4, in certain applications it can be advanta~eous to emnloy a multi-segmented pouring board such as that shown in Fic~ure 5, each segment being inclined at a different ~ngle from hori70ntal. Figure 5 sho~s a pouring boatd consistincJ of t~o segmellts, a first seg-ment ~0 located adjaccnt to pouring no~zle and llaVinCJ
an anqle al ~ro~ horizontal and a second sec~ment 41 abutting fi.rst segment 40 and adjacent belt conveyor 22, having an angle a2 Erom horizolltal. ~gain, further ._ _ ... _ _. __ _ .. . .. . . .. . . .. _ . . . . _ . .. __ .. . . . . , _. ._ . .... .

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multiplo-secJmented pouring boarcls are within the scope of the instant invention.

Fi~ure 6 shows a frontal ~Jiew of the modification of the apparatus depicted by Figure 1, wherein a cone-shaped bottom prefoaming means 42 is e~ployed to deposit the partially-expanded prefoamed mixture of reactants onto the pouring board 19. In that cone-shaped bottom prefoaming means (depicted separably by Figure 6A), the partially-e~panded prefoamed mi~ture of reactants is introduced from below the pouring board 19 through conduit 43; thereafter the mixture exits from the opening 44 and flo~s into the reservoir 45 formed by the back and side wall 46 and the front weir 47. Thereaftex the partially-e~panded prefoamed mi~ture of reactants moves onto pouring boarcl 19, above which a mold bottom liner 20 made of a fle~ible web, such as KraEt paper, passes.
The first and second side wall liners 23 and 23a, also made of a flexible weh such as ~raft paper, are guided past OppOSincJ guide means 24 and 24a. The bottom mold liner 20 and first and second side wall liners 23 and 23a thereafter pass over the surface 21 of the bottom belt conveyor 22.

Figure 6A depicts separably the cone-s~laped bottom prefoamincJ means employed in FicJure 6. Figure 6A also contains reference to a bottom centrifucJe 48 which has been employed advantageously in combination ther~with.

In accordance with thc proc~ss of the subject invention, a first component A and a second component B ~nter mi:~in-~ hcad 18 simultaneously. These compollcnts are preml~ed usin~ a conventional mi:;in~ heacl and can either be deposited directly on pOurincJ boar~ 19 by conduit 11 or c~n entcr preEoamin~ means 27 where a partially-. _ . . _ _ . .. . . _ _ . . _ _, . _ .. ... . . _ . . . . . .. _ . _ . .

3~a expanded prefoamed mixture 32 is formed and then be sub-se~uently deposited via nozzle 36 on the pouring board.
Conduit 11 and nozzle 36 can either be stationary or be reciprocated. The mixture is normally deposited at a 5 constant rate near the apex of the "V" shaped portion 12 of mold 13. The components of the mixture continue to react~ expand and cure to for~ a polyurethane foam product.
The deposited mixture continuously translates along with the mold liners and the conveyor~ The conveyor normally 10 translates at a constant velocity. Typical foam Eormula-tions used in the subject invention are exe~plified hereinafter.

E~AMP~ES
15 The following examples are illustrative of the ease with which polyurethane oam products can be produced in accordance with the process of the presen-t invention.

E~IPLE I
20 A slab of polyurethane foam was cast continuously using a conventional mixing head illustrated in Figure 1. The following formulation was mixed in the head and deposited near the apex of the "V"-shaped po~tion oE the mold:

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EXP~IPLE I
Component A weight % wei~ht % ~/min Dow Polyol CP 3140 (3700 MV65.0565.05 3,470 copolymer of ethylene oxide and propylene oxide, made by 5 Dow Chemical Company) Master Batch I:
Dow Polyol CP 314032.45 BF 2370 tSilicone surfactant made by Goldschmidt Chemical Company) 0-75 10 Water 4.00 A-l (70~ solution of bis (di methyleminoethyl) ether in di propylene glycol, ~ade by Union Carbide Company) 0.10 37.30 37.30 1,990 - ~aster Batch II:
15 Dow Pol~ol CP 31402.50 C-6 (33-1/3% T-9) ~33-1/3%
solution of stannous octaote ;n ~ioctyl Phth~l~te made by W~tco Chemical Company) 0O75 3.25 3.25 173 Component B
20 TD-80 (Toluene diisocyanate 80/20 2,4/2,6 isolner ratio, made by Mobay Chemical) 50.00 50.00 2,667 155.60 8,30~
(18.26 lb/min) The ingredients of component A, co~prising the polvmer componcnt, were premixed and pumped by a sin~le stream ; into thc mi~ing head. Component B, comprisin~ the toluene diisocyanate componen~, was separately and simultaneously pumped into the head. The two components were mi~ed at a~Dient tem~erature. The feed rate of the blended components was 8,300 grams/~,linute or 18 26 pounds/minute.
The resulting mi~;ture was deposited ~t a constant rate ncar the ape~: of thc "V"-shape~ portion of the mold. The first mold side walls of the "V"-shaped portion were 44 inches in length and were spaced apart 25 inches at the ~ .
.: .

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point where they joined second mold side walls. The angle bett~een the divergen~ side walls in this ins-tance is therefore about 33. The e~panded ~i~ture moved down a segmented pouring board similar to that depicted in 5 Figure 3. The first segment of the pouring board was inclined at an angle 0 from the horizontal while the second segment was inclined at an angle 17 from the horizontal. The segmented pouring board abutted a conveyor inclined upwardly at an angle 3 from the horizontal.
10 The constant velocity of the conveyor was 4.29 ft/min.
Consonant with Figure 3, the mold was channel-shaped with parallel side ~alls lined with Xraft paper which paper mo~-ed at the same velocity as the conveyor. A substan-tially rectangular polyurethane foam product was producedhaving a density of 1.65 poundstcubic Eoot and having a height of 19.2 inches. The ratio of conveyor velocity to product height was about 2.7.

EXA~IPLE II
20 E~ample I was repeated using a lower feed rate and a different reactant formulation:
Component A weight % weigh-t ~ g/min Dow Pol~ol CP 314077.1377.13 3,470 ~laster Batch I:
25 Dow Pol'~ol CP 314020.37 BF-2370 0.7S
~ater 4.00 7~-1 0.10 25.22 25.22 1l13S
~l~ster BAtcll II:
Do~./ Pol~ol CP 31402.50 30 C-6 (33-1/3~ T-9) 0.75 3.25 3.%5 l~G
ComDoncnt: B
TD-~0 50.00 50.00 2,249 155.G0 7,000 (15.~
lb/~in) The feed rate of the reactants was 15.4 pounds/minute, and the velocity of the conveyor was 3.41 feet/minute. A
qualit~ foam pxoduct was produced ha~ing a rectangular cross section and having a height of 15.9 inches. The ratio of conveyor velocity to product height was about 2.6.

EXP~IPLE III
A slab of polyurethane foam was cast continuously using a centrifugal prefoa~ing means similar to that illustrated in Figure 4. The following formulation was mixed in the prefoaming means:
Component A weight % weight % g/min ~ow Polyol CP 3140 75.00 75.00 7,160 ~laster Batch I:
15 Dow Polyol CP-3140 22.50 BF 2370 0.80 ~ater ~.oo A-5 ( Terti~ry ~mlne C~t~lyst) 0.03 27~33 27.33 2,609 ~laster Batch II:
Do~l Polyol CP-3140 2.50 C-6 ( 33-1/30D T-9) 0 .57 3.07 . 3.~7 293 Component B
25 TD-80 50 00 50.00 4,773 155.~0 14,835 ~32.6 lb/min) Thc ingredients of component A, comprising the pol~ol componcnt, were premixed and pumped as a single stream into a conventional mi~ing head. Component B, comprising the tolucne diisocyanate component, ~as separatcly and simultaneously pumped into tha~ head. Then the two components werc mi:;ed at am~ient tcmperature. Tl-e mi~ed components were then fed into a centrifu~al prefoa~ing means to form a partially-e~pandcd ~olyurethane foam ~Z3~

mi~ture. That mi~ture was deposited near the apex of the "V"-shaped portlon of the mold a-t a constant feed rate of 14,835 grams/minute. First mold side walls of the "V" were 60 inches in length and were spaced 46 inches apart; the 5 angle bet~een the side portions of the "V"-shaped mold is, therefore, abou-t 45. The pouring board, upon which the partially-expanded mixture was deposited, contained 3 segments: a first segment inclined at 15, a second segment inclined at Q and a third segment inclined at 13. The pouring board abutted a convevor which was upwardly inclined at an angle of 3. The latter portion of the mold was channel-shaped with parallel side walls spaced apart about 46 inches. The mold was lined with Kraft paper which translated at a constant velocity.
Utilizing the formulation and feed rate mentioned above, a number of experiments were conducted wherein the velocity of the conveyor was varied. The results are tabulated below:

TABLE
Experiment Conveyor Velocity (V Product Height (~i) Ratio Number ft/min c) inches 12)/~
1 2.75 17 2 1.92 2 2.93 16.15 2.18 25 3 3.02 16.65 2.1S

4 3.02 16.10 2. 5 3.34 16.5 2.43 G 3.34 16.95 2.36 7 3.34 16.15 2.~3 8 3.61 lG.55 2.62 9 ~.10 17.6 2.79 -4.3~ 2.9 The ratio varied from abou~ 1.9 to about 2.9.

, h~
o EXA~IPLE IV
E~periment I was repeated using a similar polyurethane fo~r~ulation with an increased eed rate of 32.6 pounds per minute:
Co~?onent A weight ~ weight ~ g/min Dow Polyol CP 314075.00 75.00 7,160 Master Batch I:
Dow Polyol CP-3140 22.50 BF 2370 0.80 ~ater 4 00 A-S 0.07 27.37 27.37 2,613 ~laster Batch II:
Dow Polyol CP-3140 2.50 C-6 (33-1/3~ T~9~0 57 3.07 3.07 299 Com?onent B
TD-80 50 00 S0 00 4,773 155.44 14,845 (32.6 1~/
min) Fi~st r~old side walls of the "V"-shapecl portion of the ~ ~.old ~vere 60 inches in length and spaced apart 46 inches at the point where the~ joined the latter portion of the mold (i.e. a = about 45). Tne e~panded mi~ture moved down a segmented pouring board: a first secJment inclined at 15, a second segment inclined at 0, a third segment inclined at 3, and a fourth segment inclincd at 1~. The segmcnted pourincJ board ~butted a conveyor inclined upwardly at an an~le of 3. The velocitv of thc conveyor ~as 4.0 fee t/minute, and the heicJht of the rectanc3ular foam slab was 15.5 inches, ~ \~hich resultcd in a ratio oE the conveyor velocity to thc pro~uct hcig11t o~ abou, 3.2.

E~ lPLr; V
- E.:;amplc III was repcated for round block production using a tunnel-sha~cd portion for the latter portion of the mold.

, . .

The following polyether formulation was ~i~.ed in the prefoaming means:
ComDonent A weight ~ weiaht ~ g/min , Dow polyol CP-314064.96864.9683,470

5 ~5aster Batch I:
Do~ Polyol CP-314032.522 BF 2370 0.800 llater 4.000 A-5 0.030 37.35237.3521,995 Master Batch II:
Dow Polyol C0-3140 2.50 C-6 (33-1/3% T~9) 0 57 3.0703.070 164 Component B
TD-80 50.Q0050.0002,671 155.3908,300 (16.26 lb/min) First mold side walls had length of 44 inches ancl were spaced 23 inches apart. l~he pouring board was segmented ' having a first seg~ent inclined at 6, and a second segment inclined at 15. The pouring board abutted the conveyor which was inclined upwardly at an an~le of 3.
' Circular foa~ products were obtained having a diameter of 22 inches. The velocity of the conveyor varied from 2.13 feet/~inute to 4.19 feet/minute with attendant ratios of about 1.1 and about 2.2, respectively.

Over~ll, it should be noted that certain free-risiny polyester-derived polyurethane foam formulations may be too sensitive to mechanical stresses to be employed in the present invention.

It is not intcnded to limi~ tlle present invention to ;; the speciEic embodiments dcscri~ed above. Other cllan~es may be mad2 in the process and apparatus specifically described herein without de?arting from the scope and tcachings of the instant invention, and it is intended .

, ., to encompass all other embodiments, alternatives an'd modifications consistant with the present invention.

Claims (18)

Claims: `

1. In a process for continuously molding free-rising polyurethane foam in a continuous, laterally translating open top mold at a given bottom conveyor velocity by depositing a polyurethane foam forming mixture of reac-tants at a given feed rate on a pouring board, the im-provement comprising increasing the height of the molded flexible polyurethane foam product obtained by (i) depo-siting said polyurethane foam forming mixture of reac-tants near the apex of a first mold portion of the later-ally translating mold, which first portion of said later-ally translating mold has divergent first side walls which form an angle therebetween of more than about 10°
and less than about 120° and which join, at their extre-meties, the parallel second side walls of a second portion of said translating mold, and (ii) allowing said polyure-thane foam forming mixture of reactants to substantially complete its rise after traversing past said first portion of the translating mold.

2. The process of claim 1 therein the ratio of the con-veyor velocity to the foam product height is from about 1 to about 3.

3. The process of claim 1 wherein said polyurethane foam forming mixture of reactants is deposited in partially-expanded, prefoamed form between the divergent vertical side walls of the first mold portion.

4. The process of claim 3 wherein said polyurethane foam forming mixture of reactants is deposited in a partially-expanded, prefoamed form from a centrifuge profoaming means.

5. The process of claim 3 wherein said polyially-foam forming mixture of reactants is deposited in a partially-expanded, profoamed form from a cone-shapcd prefoaming means.

6. The process of claim 1 wherein said polyurethane foam is a polyester-derived polyurethane foam.

7. The process of claim 1 wherein the deposited mixture of reactants translates across a segmented pouring board having a horizontal first segment.

8. The process of claim 1 or 7 wherein the deposited mixture of reactants translates across a pouring board having at least one segment downwardly inclined toward the second portion of the translating mold.

9. The process of claim 1 wherein a continuous slab is molded having a substantially rectangular cross section.

10. The process of claim 1 wherein a continuous slab is molded having a substantially circular cross section.

11. In an apparatus for producing free rising polyure-thane foam including:
(a) means for mixing liquid polyurethane foam generating reactants;
(b) means for depositing the mixed reactants in a laterally-translating mold; and (c) a continuous, open top mold, which includes:
(1) a bottom belt conveyor extending laterally for translating a foam product;
(2) a laterally translating mold whose bottom surface is adjacent the belt conveyor;
and (3) a pouring board disposed between side walls of the mold having an elevated edge adjacent said depositing means which extends to the mold bottom surface;
the improvement which consists essentially of employing a stationary depositing means to deposit the mixture of polyurethane foam forming reactants near the apex of a first open top mold portion having divergent first side walls which form an angle therebetween of more than about 10° and less than about 120° and which join, at their extremeties, the parallel second side walls of a second portion of said translating mold.

12. The improvement of claim 11 wherein a prefoaming means is employed in combination with the depositing means so that, when deposited, the mixture of polyurethane foam forming reactants is in the partially-expanded pre-foamed state.

13. The improvement of claim 12 wherein the prefoaming means is a centrifuge.

14. The improvement of claim 12 wherein the prefoaming means is a cone-shaped bottom prefoaming means.

15. The improvement of claim 11 wherein the pouring board is segmented.

16. The improvement of claim 15 wherein the pouring board has a first horizontal segment adjacent said depositing means followed by an inclined second segment.

17. The improvement of claim 11 wherein the second mold portion is rectangular.

18. The improvement of claim 11 wherein the second mold portion is circular.