GB1572002A - Apparatus for the production of curable resin foam - Google Patents

Description

(54) APPARATUS FOR THE PRODUCTION OF CURABLE RES1N FOAM (71) We. CIBA-GEIGY AG. a Swiss Body Corporate of Basle. Switzerland. do hereby declare the invention for which we pray that a patent may be granted to us and the method bv which it is to be performed to be particula;ly described in and bv the following statement: This invention relates to an apparatus for producing a foam of a curable resin. especially a urea-formaldehvde resin, and which is suitable for pnviding, especially repetitively. small quantities of foam. It further relates to a method of using such apparatus and to resin foams made using such an apparatus and by such a method.

Methods of producing foams of ureaformaldehvde resins are well known. the foam being used for insulating purposes.

especially for filling cavity walls of houses.

etc. The foam is usuallyproduced in sitlç by means of a foam gun. Conventionally. this gun comprises a tube packed with a material of large surface area. such as small glass beads or a series of grids. through which are passed air and a liquid mixture of a surfactant with either the resin or its hardener.

thus forming a foam. This foam is then mixed with that component (in liquid form) which was omitted earlier. li~.. either the hardener or the resin: the foam. which is now in the curable state. is ejected from the apparatus through a tube, which is generally flexible. into the area to be filled, where it rapidly cures to a rigid. self-supporting foam. This process. and apparatus for car rying it out. have been described in British Patent Specification Nos. 755173. 872851, 76l99. {8')tA:E6A, 9()7()36, and 933264. and in United States Patent No. 294190(1. In all of these disclosures the apparatus has valves, or like controls. on the inlets to the gun but none on the outlet In conventional foam guns. production of the foam is controlled by valves on each of the input lines to the gun of hardenersurfactant (or resin-surfactant) mixture.

compressed air, and resin (or hardener).

When these valves are turned off after use.

the resin-hardener mixture still in the outlet tube is allowed to run out under gravity to waste. The volume of this wasted mixture is usually small - in the region of 50 to 100 ml before foaming - and is negligible when the volume of foam produced in one discharge is large. However. when the volume of foam desired in one discharge is also small. the volume of wasted mixture can approach, or even exceed. that utilised.

A further disadvantage of such foam guns, when used for repeated small discharges of foam, is that. when the gun is turned off, there is a loss of pressure.

resulting in collapse of some of the foam alreadv made. When the gun is turned on, this collapsed foam mixes with the fresh foam produced and so increased its density.

Inconsistent or. worse. unsuitable, foam results. There is therefore a need for a special foam pun suitable for the repetitive discharge of small quantities of foam.

In United States Patent No. 3 181 839 there is described an apparatus for making plastics foams, particularly polyurethane foam. in which the components are mixed in a pressurised mixing tank and fed to a flow restricting device which automatically controls the discharge of the foam. The disadvantage of such an apparatus is that, if discharge of foam has to be stopped for an extended period, the whole apparatus has to be flushed to avoid the resin-hardener mixture solidifying in the apparatus and so blocking it. British Patent No. 1504044 describes a similar apparatus, but more suited to ureaformaldehvde foam.

We have now developed an apparatus which allows small quantities of curable resin foam. prepared by an aeration process as described above. to be discharged with very little waste. There is negligible loss of back-pressure in the gun. and so predetermined amounts of foam of substantiallv constant densitv mav be produced. Filling of small cavities. or the discharge of measured amounts, can be accuratelv and economically carried out. This apparatus can be stopped for extended periods without the need to flush all the resin-hardener mixture from the chambers and conduits.

According to the present invention there is provided a foam gun for the mixing and discharge of a foamed curable mixture of a liquid resin and a liquid hardener therefor.

which comprises (a) a foam producing chamber provided with an inlet pipe for a mixture of the resin and a surfactant, an inlet pipe for compressed air and outlet pipe for the resultant foamed resin. and (b) a discharge head connected to said outlet pipe, and which is provided with an inlet pipe for the liquid hardener, wherebv the foamed resin and liquid hardener are mixed within the dischaae head: each of said inlet pipes and said outlet pipe being provided with a valve for controlling the respective flows. the said four valves being linked to operate substantially simultaneously.

This invention also includes within its scope a method of discharging a foamed curable mixture of a liquid resin and a liquid hardener therefor. utilising a foam gun of this invention. which comprises opening substantiallv simultaneouslv in the foam gun the said valves for the mixture of liquid curable resin and surfactant and for compressed air on the inlet to. and the said foamed resin outlet valve on the conduit from. the foaming chamber. and the said valve for the harciener on the inlet to the discharge head and. when a required quanti Iv of the foamed curable mixture of resin and hardener has been discharged. closing the said four valves substantially simul taneouslv.

The valves used in the apparatus of the present invention mav be operated mechanicallv. pneumaticallv. or electricallv. and the mechanism which links their operation.

comprising a linkage and a control unit. mav be likewise mechanical. pneumatic. or electrical. following standard practices.

The invention is illustrated bv way of Example in the drawings accompanying the Provisionill Specification in which Figure 1 shows a schematic cross-sectional view of a foam gun of this invention. Figure 2 shows a cross-sectional view of a preferred type of dischlrge head used in the new foam guns.

and Figure 2A shows a cut-awav perspective view of the same tvpe of discharge head as shown in Figure 2. Figures 3 and 4 show a schematic cross-sectional view and a cut awav perspective view. respectively, of a modification of a foam gun of this invention in which the hardener is mixed with air before it contacts the foamed resin.

In Figure 1, conduit 1 is attached to a source (not shown) of a mixture of a liquid resin and a surfactant, and conduit 2 is connected to a source (not shown) of compressed air. Passage of the resinsurfactant mixture and air is controlled by valves 3 and 4. The foaming chamber 5.

which is typically 30 to 5() cm in length and 4 to 6 cm in diameter, is packed with a filling material, the presence of which ensures thorough mixing of the air and the resinsurfactant mixture. a foam being formed.

Small glass beads (ballotini) are especially suitable as this filling material. On leaving the foaming chamber 5, the foam passes through conduit 6. where its flow is controlled by valve 7. and into the discharge head 8. A liquid hardener for the resin flows from a source (not shown) through conduit 9 to the discharge head 8. The flow of hardener is controlled bv valve 10. In the discharge head the hardener is sprayed into the foam which is immediatelv discharged. Operation of valves 3. 4. 7. and 10 is controlled by a control unit 11 through linkages 12. 13. and 14. arranged so that the valves operate substantiallv simultaneously.

As may be seen. the only part of the apparatus which contains a resin-hardener mixture is the discharge head. If the apparatus is stopped for an extended period. the verv small volume of setting foam in the head will either run out under gravitv or mav be verv easilv removed by physical methods before or after it has hardened, without necessitatilig a dismantling of the whole assembly or complete flushing with a solvent.

The nature of the linkages may correspond to the nature of the actuating mechanism for the valves. Thus. where electricallyoperated valves are fitted. the linkages 12, 13. and 14 mav be electrical wire and the control unit mav be an on/off switch. Where the valves are operated bv fluid pressure, the linkages 12, 13. and 14 mav be fluidfilled and the control unit it may be a source of fluid pressure. Similarly. with mechanicallv-operated vales. the linkages 12. 13. and 14 mav be mechanical and the control unit 11 may be a source of mechanical movement.

It is also possible. of course. to control valves of one type. say. mechanicallyoperated valves, by a control mechanism of another type. such as pneumaticallycontrolled pistons. While such a combination is not ideal from an enlarging viewpoint. it is often convenient to convert a commerciallv-available foam gun having three mechanically-operated inlet valves into a gun of the present invention by fitting a mechanically-operated outlet valve. feeding the hardener supply from its valve.

through a conduit. to the discharge head, and operating all four valves by a pneumatically-operated mechanism comprising a fluid-filled tube and a source of fluid pressure. Such pneumatically-operated mechanisms are commercially available Figure 1 shows the gun as having a single outlet from the discharge head. It is. howev er. preferred to have multiple outlets from the discharge head. and one such multiple outlet discharge head is shown in cross scction in Figure 7 and in cut-away perspective view in Figure 2A. Foamed resin passes through conduit 15 into a series of narrower conduits 16. Hardener for the resin passes through conduit 17 into a series of conduits 18 which pass into foam conduits 16. Spray nozzles 19 on the outlets of the hardener conduits ensure effective contact between the hardener and the foamed resin. These spray nozzles mav be of any conventional design which breaks the stream of hardener into a series of fine droplets.

In order to increase the effectiveness of the spray nozzles for the hardener it is sometimes found advantageous to inject air into the hardencr stream. For this purpose the conduit for liquid hardener is further connected to a source of compressed air. the conduits for liquid hardener and compressed air optionallv being fitted with nonreturn valves. If the air is injected con tinuousl. i.e.. whether or not the resin and hardener are being ejected. it serves to prevent the hardener sprav nozzle from becoming blocked. This modification of the apparatus is shown in Figures 3 and 4.

In Figure 3. components 1 to 14 have exactlv the same significance as in Figure 1.

A conduit 2() is attached to a source (not shown). of compressed air. Non-return valves 21 and 22 are optionally inserted into conduits 9 and 30 to prevent hardener or air from being forced back along conduits 20 and 9 respectively. The apparatus will work successfully without valves 21 and 22, but obviously the pressure in conduits 9 and 20 must then be carefullv balanced.

Air may also be injected into the hardener stream on a multiple outlet mixing head, and an apparatus for this is shown in Figure 4. Conduit '3 is connected to a source (not shown). of compressed air and conduit 24 to a source (not shown). of the hardener. these connections optionally being made via nonreturn valves (not shown). Branches 25 and '( from conduits 23 and 24 lead into conduits 27 which pass into the branches 28 of discharge tube 29 which is itself connected to a source (not shown) of foamed resin. Sprav heads 3U at the outlet of conduits '7 atomise the hardener. this atom isition being aided by the passage of compressed air. Alternatively. to improve atomisation. compressed air may be introduced concentrically with the hardener solution at the spray heads 30.

Use of the apparatus of the present invention is, as already stated. particularly indicated where the wastage from a conventional foam gun would constitute a considerable proportion of the resin and hardener used. Typical applications include foaming in agricultural locations. such as for the protection of crops from frost damage, production of small castings or discrete particles of foam. and especially filling of cavities in bricks or other building blocks to increase their thermal insulating properties.

WHAT WE CLAIM IS: 1. A foam gun for the mixing and discharge for a foamed curable mixture of a liquid resin and a liquid hardener therefor, which comprises ( a) a foam producing chamber provided with an inlet pipe for a mixture of the resin and a surfactant, an inlet pipe for compressed air and an outlet pipe for the resultant foamed resin. and (b) a discharge head connected to said outlet pipe, and which is provided with an inlet pipe for the liquid hardener, wherebv the foamed resin and liquid hardener are mixed within the discharge head; each of said inlet pipes and said outlet pipe being provided with a valve for controlling the respective flows, the said four valves being linked to operate substantially simultaneously.

2. A foam gun according to claim I, in which the valves are operated mechanically, pneumatically, or electrically.

3. A foam gun according to claim 1 or 2, in which all the said valves are linked to operate substantially simultaneously by a mechanical. pneumatic, or electrical mechanism.

4. A foam gun according to claim 3, in which the mechanical, pneumatic, or electrical mechanism comprises a linkage and a control unit.

5. A foam gun according to claim 4, in which the valves are electrically operated and the linkage comprises an electrical wire and the control unit comprises an on/off switch.

6. A foam gun according to claim 4, in which the valves are operated by fluid pressure and the linkage comprises a fluidfilled tube and the control unit comprises a source of fluid pressure.

7. A foam gun according to claim 4, in which the valves are mechanically operated and the linkage comprises a mechanical link and the control unit comprises a source of mechanical movement.

8. A foam gun according to claim 4, in which the valves are mechanically operated and the linkage comprises a fluid-filled tube and the control unit comprises a source of fluid pressure.

9. A foam gun according to any of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (1)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   through a conduit. to the discharge head, and operating all four valves by a pneumatically-operated mechanism comprising a fluid-filled tube and a source of fluid pressure. Such pneumatically-operated mechanisms are commercially available Figure 1 shows the gun as having a single outlet from the discharge head. It is. howev er. preferred to have multiple outlets from the discharge head. and one such multiple outlet discharge head is shown in cross scction in Figure 7 and in cut-away perspective view in Figure 2A. Foamed resin passes through conduit 15 into a series of narrower conduits 16. Hardener for the resin passes through conduit 17 into a series of conduits 18 which pass into foam conduits 16. Spray nozzles 19 on the outlets of the hardener conduits ensure effective contact between the hardener and the foamed resin. These spray nozzles mav be of any conventional design which breaks the stream of hardener into a series of fine droplets.

   In order to increase the effectiveness of the spray nozzles for the hardener it is sometimes found advantageous to inject air into the hardencr stream. For this purpose the conduit for liquid hardener is further connected to a source of compressed air. the conduits for liquid hardener and compressed air optionallv being fitted with nonreturn valves. If the air is injected con tinuousl. i.e.. whether or not the resin and hardener are being ejected. it serves to prevent the hardener sprav nozzle from becoming blocked. This modification of the apparatus is shown in Figures 3 and 4.

   In Figure 3. components 1 to 14 have exactlv the same significance as in Figure 1.

   A conduit 2() is attached to a source (not shown). of compressed air. Non-return valves 21 and 22 are optionally inserted into conduits 9 and 30 to prevent hardener or air from being forced back along conduits 20 and 9 respectively. The apparatus will work successfully without valves 21 and 22, but obviously the pressure in conduits 9 and 20 must then be carefullv balanced.

   Air may also be injected into the hardener stream on a multiple outlet mixing head, and an apparatus for this is shown in Figure 4. Conduit '3 is connected to a source (not shown). of compressed air and conduit 24 to a source (not shown). of the hardener. these connections optionally being made via nonreturn valves (not shown). Branches 25 and '( from conduits 23 and 24 lead into conduits 27 which pass into the branches 28 of discharge tube 29 which is itself connected to a source (not shown) of foamed resin. Sprav heads 3U at the outlet of conduits '7 atomise the hardener. this atom isition being aided by the passage of compressed air. Alternatively. to improve atomisation. compressed air may be introduced concentrically with the hardener solution at the spray heads 30.

   Use of the apparatus of the present invention is, as already stated. particularly indicated where the wastage from a conventional foam gun would constitute a considerable proportion of the resin and hardener used. Typical applications include foaming in agricultural locations. such as for the protection of crops from frost damage, production of small castings or discrete particles of foam. and especially filling of cavities in bricks or other building blocks to increase their thermal insulating properties.

   WHAT WE CLAIM IS:

   1. A foam gun for the mixing and discharge for a foamed curable mixture of a liquid resin and a liquid hardener therefor, which comprises ( a) a foam producing chamber provided with an inlet pipe for a mixture of the resin and a surfactant, an inlet pipe for compressed air and an outlet pipe for the resultant foamed resin. and (b) a discharge head connected to said outlet pipe, and which is provided with an inlet pipe for the liquid hardener, wherebv the foamed resin and liquid hardener are mixed within the discharge head; each of said inlet pipes and said outlet pipe being provided with a valve for controlling the respective flows, the said four valves being linked to operate substantially simultaneously.

   2. A foam gun according to claim I, in which the valves are operated mechanically, pneumatically, or electrically.

   3. A foam gun according to claim 1 or 2, in which all the said valves are linked to operate substantially simultaneously by a mechanical. pneumatic, or electrical mechanism.

   4. A foam gun according to claim 3, in which the mechanical, pneumatic, or electrical mechanism comprises a linkage and a control unit.

   5. A foam gun according to claim 4, in which the valves are electrically operated and the linkage comprises an electrical wire and the control unit comprises an on/off switch.

   6. A foam gun according to claim 4, in which the valves are operated by fluid pressure and the linkage comprises a fluidfilled tube and the control unit comprises a source of fluid pressure.

   7. A foam gun according to claim 4, in which the valves are mechanically operated and the linkage comprises a mechanical link and the control unit comprises a source of mechanical movement.

   8. A foam gun according to claim 4, in which the valves are mechanically operated and the linkage comprises a fluid-filled tube and the control unit comprises a source of fluid pressure.

   9. A foam gun according to any of

   claims 1 to 8, having a single outlet from the discharge head.

   1(). A foam gun according to any of claims I to 8. having a multiple outlet from the discharge head.

   11. A foam gun according to any of claims I to 1(). in which the conduit for liquid hardener is further connected to a source of compressed air.

   12. A foam gun according to claim 11, in which the conduit for liquid hardener and the conduit for compressed air are fitted with non-return valves.

   13. A foam gun according to claim 1.

   substantiallv as described herein.

   14. A foam gun according to claim 13, substantially as described in the drawings accompanying the Provisional Specifications.

   15. A foam gun according to claim 13, substantially as described in Figures 1 and 2 of the drawings accompanying the Provisional Specifications.

   16. A method of discharging a foamed curable mixture of a liquid resin and a liquid hardener therefor, utilising a foam gun as claimed in any of claims 1 to 1() and 15.

   which comprises opening substantially simultaneously in the foam gun the said valves for the mixture of liquid curable resin and surfactant and for compressed air on the inlet to. and the said foamed resin outlet valve on the conduit from. the foaming chamber. and the said valve for the hardener on the inlet to the discharge head and, when a required quantitv of the foamed curable mixture of resin and hardener has been discharged. closing the said four valves substantiallv simultaneously.

   17. A method of discharging a foamed curable mixture of a liquid resin and a liquid hardener therefor. utilising a foam gun as claimed in any of claims 11 to 14. which comprises opening substantiallv simul taneously in the foam gun the said valves for the mixture of liquid curable resin and surfactant and for compressed air on the inlet to. and the said foamed resin outlet valve on the conduit form. the foaming chamber. and the said valve for the hardener on the inlet to the discharge head and, when a required quantitv of the foamed curable mixture of resin and hardener has been discharged. closing substantially simul taneouslv the said valves for the mixture of liquid curable resin and surfactant and for compressed air on the inlet to. and the said formed resin outlet valve on the conduit from. the foaming chamber. and the said valve for the hardener on the inlet to the discharge head.

   18. A method according to claim 16. in which the liquid crumble resin is a urea formaldehvde resin.

   1C). A method according to claim 17. in which the liquid curable resin is a ureaformaldehyde resin.

   20. A method according to claim 16.

   substantially as described herein.

   21. A method according to claim 17, substantiallv as described herein.

   22. Resin foam discharged by means of a foam gun as claimed in any ofclaims 1 to 10 and 15.

   23. Resin foam discharged by means of a foam gun as claimed in any of claims II to 14.

   24. Resin foam discharged bv means of a method as claimed in any of claims 16. 18, and 20.

   25. Resin foam discharged by means of a method as claimed in any of claims 17. 19, and 21.