CA1108825A - Foaming apparatus - Google Patents
Foaming apparatusInfo
- Publication number
- CA1108825A CA1108825A CA288,406A CA288406A CA1108825A CA 1108825 A CA1108825 A CA 1108825A CA 288406 A CA288406 A CA 288406A CA 1108825 A CA1108825 A CA 1108825A
- Authority
- CA
- Canada
- Prior art keywords
- impeller
- inlet
- hardener
- resin
- casing
- 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.)
- Expired
Links
Landscapes
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
Abstract of Disclosure Apparatus for manufacturing low density, cured urea/formaldehyde resin foams includes a centrifugal mixing head comprising a casing and an impeller rotatably mounted therein, the casing having an inlet directed generally axially with respect to the axis of rotation of the impeller and an outlet directed generally tangentially relative to said axis.
Description
-The present invention relates to apparatus for the production oi lo~ density self-sustaining foams of cured urea/formaldehyde resin material. Such ~oams can be used, for example, in the building industry for thermal insulation purposes.
Low density in the present context means a dry density of less than 20 kg/m in the absence o~ any inert ~iller, corresponding to a resin solids content of less than 20 kg/m3. Such foams are made by forming a ~et f oam containing an intimate mixture o~ a resin and a hardener for the resin, both being initially in aqueous solution.
The wet foam can be injected, for example, into a cavity wall and allowed to cure/clry in situ.
Conventional apparatus ~or producing low-denslty urea/
~ormaldehyde resin ~oams su~ers ~rom a variety oi de~ects which result in optimum processing conditions being di~ficult to achieve, mainly due to the many variables involved.
It is an object of the present invention to provide apparatus in which the effects of at least some of these variables can be minimised.
~ccording to the present invention apparatus ~or making lo~v density cured urea/~ormaldehyde resin ~oams includes a centri~ugal mixing head as hereina~ter defined. A
centri~ugal mixing head in this specification means a casing and an impeller rotatably mounted therein, the casing having an inlet directed generally a~ially with respect to the axis ~ rotation o~ the impeller and an outlet directed generally tangentially relative to said axisO
Preierably the impeller is constituted by at least one paddle projecting radially ~rom a central drive shaft.
.~
~ , , , .
Advantageously, the paddle is per~orated to improve the mi~ing action. Preferably the impeller has ~wo paddles located on opposite sides of the sha~t in dynamically balanced relation thereto, although more than two paddles can be used, if desired. The paddles may also take the form o~ a set of rods or bars extending radially fron the central drive shaft.
The paddles pre~erably extend ~rom a central boss on the drive sha~t, the boss having a conical portion directed towards the inlet. The inlet to the casing may be offset with respect to the axis of the drive sha~t so as to provide a maximum duration ~or the mixing action.
The apparatus preferably includes feed means for supplying resin and hardener to the inlet o~ the centri~ugal mixing h~ad; the ~eed means ~re~erably includes ~oam generating ~eans operable to ~oc~m the resin or the hardener or both prior to supplying them to the inlet. Advantageously, the centrifugal mixing head is located immediately downstream o~ the ~oam generating ~eans and where either the resin or the hardener is unfoamed, the apparatus preferably includes a nozzle ~or supplying the unioamed component to the inlet. Preferably the nozzle is located in the inlet and is directed towards the impeller.
Whilst it is normally more convenient to ~oam the hardener solution prior to mixing in the resin, the apparatus may also be used ~or the converse route, wherein a ~oam o~ resin solution is mixed with an unfoamed hardener solution. For practical purposes, however, it is normally easier to ~oam the hardener solution - which usually contains a surfactant - than the resin solution which is viscous, espec~ally when relatively undiluted~ The ,: ,.
z~
~4-resin solution normally also contains a surfactant, but because it is viscous, considerable difficulty may be ex~
perienced in mixing it with the foamed hardener solution to obtain a homogeneous wet foam. In conventional foam making appara-tus it is necessary to inject the resin solu-tion into the hardener foam by means of an atomising jet and it is this that has hitherto effectively limited the surfactant content of the hardener foam. Too much surfac-tant in the hardener used in conventional apparatus results in a fine foam which is very stable, but which also tends to restrict the rate of dispersion of atomised resin and give a badly mixed product.
This particular problem is more acute in hot weather but attempts to remedy it by reducing hardener surfactant con-tent can result in coarse-celled foams of inadequate sta-bility.
By using the centrifugal mixing head of the present invention the above-mentioned problems can be to a large extent overcome, since the mixing operation is positive. It is no longer necessary to atomise the resin, so the surfac-tant content of the hardener foam is not critical and it can be increased beyond conventional levels to give fine, stable homogeneous foams, which allow formulations having a relatively long gel time to be used, without encountering the bad mixing problems frequently experienced when using conventional apparatus.
Hardener foam can be produced by passing the hardener solution through a foam generating column in such a way as to produce an extremely fine foam. However, this feature 30 is particularly appropriate to the manufac-ture of specific .
low shrinkage foams, whereas the centrifugal mixing head according to the present invention is equally applicable to production of conventional foams.
';
~, .~.
As mentioned above, the apparatus of the present invention can also be used to mix a resin foam with a hardener foam.
This particular method of producing urea/formaldehyde resin foams by mixing the resin and hardener as two foams is the S subject of our British Patent No. 1313103.
In order that the apparatus of the invention be better understood a preferred embodiment of :it will now be des-cribed by way of example with reEerence to the accompanying diagrammatic drawing in which:-Figure 1 is a schematic cross-sectional side view through a foam generating apparatus, including a centrifugal mixing head, in accordance with the invention;
Figure 2 is a cross-sectional side view through the mixing head of Figure l; and Figure 3 is a sectional view through the mixiny head oE
Figure 2 on line A-A thereof.
In Figure 1, a foam generating column ~ has a feed pipe 5 to which hardener solution and compressed air are supplied.
The column is packed with glass beads 6 and discharges into a coupling pipe 7 which connects it to the inlet 8 of a centrifugal mixing head, generally designated 9, and which has an outlet pipe 11. A resin feed pipe 16 is also provided at the inlet of the mixing head. Referring to all three figures, the mixing head 9 comprises a cylindrical (in plan) casing 10 containing an impeller 12 rotatably mounted in a bearing assembly 15 and driven by an air motor 13 through a shaEt 14. The casing is divisible (not shown) along a line parallel to line A-A to facilitate cleaning and/or servicing. The impeller has four blades 17, each set in a central boss 18. The blades are perforated to improve the mixing action and the assembly is dynamically balanced about the shaft 1~.
.....
t ~ ~
In the example described later, the blades were each about 30mm long, 20mm deep and had 5mm holes drilled in them. The inlet 8 is essentially directed onto the conical head o~ the boss 18) since this has been observed to enhance the mixing ef~iciency.
Re~erring now to Figure 2, the driYe s~ha~t 14 passing through the base of the mixing head is of course a potential source of leakage and in view o~ the corrosive nature o~ the acid hardeners normally used, a simple sleeve bearing is not satisfactory. Accordingly, the bearing assembly includes pair of garter seals 19 in a housing 20. Spring rings 21 urge the seals into contact with the shaft 14. The garter seals are disposed i~ bac~-to-back relation and the housing is supplied with grease 22 from a conventional spring loaded pressure lubricator 23, the grease forcing the seals apart and against the housing, whilst ~t the same time both lubricating the sha~t-to-seal contact area and repelling fluid leaking down the shaft. It has been follnd that apparatus constructed in this way is both reliable and reasonably robust, despite the corrosiYe nature of the hardener used.
As mentioned earlier, the inlet may be offset with respect to the axis oP the shaft 14 and the outlet, as indicated in Figure 3 by dotted lines 24. This provides for a ;~
maximum duration of the mixing action.
~xample ~_.
In a specific operation, an acid hardener solution containing 1.4% by weight of a sur~actant was fed to the column 4 at a rate of 2 litres/minute. The feed pipe S was also supplied with air at 40 KN/m and in the coupling pipe 7, a low density hardener foam resulted. The column was in this case 360mm long, 45~m in diameter and packed with 6mm glass beads.
.
.
An aqueous urea/~ormaldehyde resin solution containing 45 ~ 0 reactive resin solids was supplied via pipe 16 at a rate o~ 2~ litres/minute and mixeld with the foam in the ~ixer 9, the impeller being rotated at 900 r.p.m.
The resin was in this case "BEETLE" BU700 and the hardener was "B~ETLE" FH100, an acidic solution containing an anionic sur~actant. "BEETLE" is a Registered Trade MarL of British Industrial Plastics Limited.
The product ~rom the outlet pipe 11 was a homogeneous ~et ioam which on curing/drying had .a ~inal dry density o~ 14 kg/m.
~ ,. `
Low density in the present context means a dry density of less than 20 kg/m in the absence o~ any inert ~iller, corresponding to a resin solids content of less than 20 kg/m3. Such foams are made by forming a ~et f oam containing an intimate mixture o~ a resin and a hardener for the resin, both being initially in aqueous solution.
The wet foam can be injected, for example, into a cavity wall and allowed to cure/clry in situ.
Conventional apparatus ~or producing low-denslty urea/
~ormaldehyde resin ~oams su~ers ~rom a variety oi de~ects which result in optimum processing conditions being di~ficult to achieve, mainly due to the many variables involved.
It is an object of the present invention to provide apparatus in which the effects of at least some of these variables can be minimised.
~ccording to the present invention apparatus ~or making lo~v density cured urea/~ormaldehyde resin ~oams includes a centri~ugal mixing head as hereina~ter defined. A
centri~ugal mixing head in this specification means a casing and an impeller rotatably mounted therein, the casing having an inlet directed generally a~ially with respect to the axis ~ rotation o~ the impeller and an outlet directed generally tangentially relative to said axisO
Preierably the impeller is constituted by at least one paddle projecting radially ~rom a central drive shaft.
.~
~ , , , .
Advantageously, the paddle is per~orated to improve the mi~ing action. Preferably the impeller has ~wo paddles located on opposite sides of the sha~t in dynamically balanced relation thereto, although more than two paddles can be used, if desired. The paddles may also take the form o~ a set of rods or bars extending radially fron the central drive shaft.
The paddles pre~erably extend ~rom a central boss on the drive sha~t, the boss having a conical portion directed towards the inlet. The inlet to the casing may be offset with respect to the axis of the drive sha~t so as to provide a maximum duration ~or the mixing action.
The apparatus preferably includes feed means for supplying resin and hardener to the inlet o~ the centri~ugal mixing h~ad; the ~eed means ~re~erably includes ~oam generating ~eans operable to ~oc~m the resin or the hardener or both prior to supplying them to the inlet. Advantageously, the centrifugal mixing head is located immediately downstream o~ the ~oam generating ~eans and where either the resin or the hardener is unfoamed, the apparatus preferably includes a nozzle ~or supplying the unioamed component to the inlet. Preferably the nozzle is located in the inlet and is directed towards the impeller.
Whilst it is normally more convenient to ~oam the hardener solution prior to mixing in the resin, the apparatus may also be used ~or the converse route, wherein a ~oam o~ resin solution is mixed with an unfoamed hardener solution. For practical purposes, however, it is normally easier to ~oam the hardener solution - which usually contains a surfactant - than the resin solution which is viscous, espec~ally when relatively undiluted~ The ,: ,.
z~
~4-resin solution normally also contains a surfactant, but because it is viscous, considerable difficulty may be ex~
perienced in mixing it with the foamed hardener solution to obtain a homogeneous wet foam. In conventional foam making appara-tus it is necessary to inject the resin solu-tion into the hardener foam by means of an atomising jet and it is this that has hitherto effectively limited the surfactant content of the hardener foam. Too much surfac-tant in the hardener used in conventional apparatus results in a fine foam which is very stable, but which also tends to restrict the rate of dispersion of atomised resin and give a badly mixed product.
This particular problem is more acute in hot weather but attempts to remedy it by reducing hardener surfactant con-tent can result in coarse-celled foams of inadequate sta-bility.
By using the centrifugal mixing head of the present invention the above-mentioned problems can be to a large extent overcome, since the mixing operation is positive. It is no longer necessary to atomise the resin, so the surfac-tant content of the hardener foam is not critical and it can be increased beyond conventional levels to give fine, stable homogeneous foams, which allow formulations having a relatively long gel time to be used, without encountering the bad mixing problems frequently experienced when using conventional apparatus.
Hardener foam can be produced by passing the hardener solution through a foam generating column in such a way as to produce an extremely fine foam. However, this feature 30 is particularly appropriate to the manufac-ture of specific .
low shrinkage foams, whereas the centrifugal mixing head according to the present invention is equally applicable to production of conventional foams.
';
~, .~.
As mentioned above, the apparatus of the present invention can also be used to mix a resin foam with a hardener foam.
This particular method of producing urea/formaldehyde resin foams by mixing the resin and hardener as two foams is the S subject of our British Patent No. 1313103.
In order that the apparatus of the invention be better understood a preferred embodiment of :it will now be des-cribed by way of example with reEerence to the accompanying diagrammatic drawing in which:-Figure 1 is a schematic cross-sectional side view through a foam generating apparatus, including a centrifugal mixing head, in accordance with the invention;
Figure 2 is a cross-sectional side view through the mixing head of Figure l; and Figure 3 is a sectional view through the mixiny head oE
Figure 2 on line A-A thereof.
In Figure 1, a foam generating column ~ has a feed pipe 5 to which hardener solution and compressed air are supplied.
The column is packed with glass beads 6 and discharges into a coupling pipe 7 which connects it to the inlet 8 of a centrifugal mixing head, generally designated 9, and which has an outlet pipe 11. A resin feed pipe 16 is also provided at the inlet of the mixing head. Referring to all three figures, the mixing head 9 comprises a cylindrical (in plan) casing 10 containing an impeller 12 rotatably mounted in a bearing assembly 15 and driven by an air motor 13 through a shaEt 14. The casing is divisible (not shown) along a line parallel to line A-A to facilitate cleaning and/or servicing. The impeller has four blades 17, each set in a central boss 18. The blades are perforated to improve the mixing action and the assembly is dynamically balanced about the shaft 1~.
.....
t ~ ~
In the example described later, the blades were each about 30mm long, 20mm deep and had 5mm holes drilled in them. The inlet 8 is essentially directed onto the conical head o~ the boss 18) since this has been observed to enhance the mixing ef~iciency.
Re~erring now to Figure 2, the driYe s~ha~t 14 passing through the base of the mixing head is of course a potential source of leakage and in view o~ the corrosive nature o~ the acid hardeners normally used, a simple sleeve bearing is not satisfactory. Accordingly, the bearing assembly includes pair of garter seals 19 in a housing 20. Spring rings 21 urge the seals into contact with the shaft 14. The garter seals are disposed i~ bac~-to-back relation and the housing is supplied with grease 22 from a conventional spring loaded pressure lubricator 23, the grease forcing the seals apart and against the housing, whilst ~t the same time both lubricating the sha~t-to-seal contact area and repelling fluid leaking down the shaft. It has been follnd that apparatus constructed in this way is both reliable and reasonably robust, despite the corrosiYe nature of the hardener used.
As mentioned earlier, the inlet may be offset with respect to the axis oP the shaft 14 and the outlet, as indicated in Figure 3 by dotted lines 24. This provides for a ;~
maximum duration of the mixing action.
~xample ~_.
In a specific operation, an acid hardener solution containing 1.4% by weight of a sur~actant was fed to the column 4 at a rate of 2 litres/minute. The feed pipe S was also supplied with air at 40 KN/m and in the coupling pipe 7, a low density hardener foam resulted. The column was in this case 360mm long, 45~m in diameter and packed with 6mm glass beads.
.
.
An aqueous urea/~ormaldehyde resin solution containing 45 ~ 0 reactive resin solids was supplied via pipe 16 at a rate o~ 2~ litres/minute and mixeld with the foam in the ~ixer 9, the impeller being rotated at 900 r.p.m.
The resin was in this case "BEETLE" BU700 and the hardener was "B~ETLE" FH100, an acidic solution containing an anionic sur~actant. "BEETLE" is a Registered Trade MarL of British Industrial Plastics Limited.
The product ~rom the outlet pipe 11 was a homogeneous ~et ioam which on curing/drying had .a ~inal dry density o~ 14 kg/m.
~ ,. `
Claims (10)
1. Apparatus for the production of low density, self-sustaining foams of cured urea/formaldehyde resin material, said apparatus including a centrifugal mixing head comprising a casing and an impeller rotatably mounted therein, the casing having an inlet directed generally axially with respect to the axis of rotation of the impeller and an outlet directed generally tangentially relative to said axis, the impeller being constituted by at least one paddle projecting radially from a central drive shaft and wherein the paddle is perforated or is in the form of rods or bars extending radially from the central drive shaft to improve the mixing action.
2. Apparatus according to Claim 1 wherein the impeller has at least two paddles located on opposite sides of the shaft in dynamically balanced relation thereto.
3. Apparatus according to Claim 1 wherein the impeller includes a central boss having a conical portion directed towards the inlet.
4. Apparatus according to any preceding Claim 1 including feed means for supplying resin and hardener to the inlet.
5. Apparatus according to Claim 4 wherein the feed means includes foam generating means operable to foam the resin or the hardener or both prior to supplying them to the inlet.
6. Apparatus according to Claim 5 wherein the cen-trifugal mixing head inlet is located downstream of the foam generating means and where either the resin or the hardener is unfoamed, the apparatus includes a nozzle for supplying the unfoamed component to the inlet.
7. Apparatus according to Claim 6 wherein the nozzle is located in the inlet and is directed towards the impeller.
8. Apparatus according to Claim 1 wherein the inlet is disposed in the casing eccentrically with respect to the axis of rotation of the impeller so as to a maximum duration for the mixing action.
9. Apparatus according to Claim 1 wherein the impeller is driven by means external to the casing through a shaft and including sealing means to minimize fluid loss along said shaft.
10. Apparatus according to Claim 9 wherein the sealing means includes a pair of back-to-back sealing rings on the shaft, together with means for supplying a lubricant under pressure between said rings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA288,406A CA1108825A (en) | 1977-10-11 | 1977-10-11 | Foaming apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA288,406A CA1108825A (en) | 1977-10-11 | 1977-10-11 | Foaming apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1108825A true CA1108825A (en) | 1981-09-15 |
Family
ID=4109724
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA288,406A Expired CA1108825A (en) | 1977-10-11 | 1977-10-11 | Foaming apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1108825A (en) |
-
1977
- 1977-10-11 CA CA288,406A patent/CA1108825A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |