CA2181514A1 - Process to make polyurethane foam products - Google Patents
Process to make polyurethane foam productsInfo
- Publication number
- CA2181514A1 CA2181514A1 CA 2181514 CA2181514A CA2181514A1 CA 2181514 A1 CA2181514 A1 CA 2181514A1 CA 2181514 CA2181514 CA 2181514 CA 2181514 A CA2181514 A CA 2181514A CA 2181514 A1 CA2181514 A1 CA 2181514A1
- Authority
- CA
- Canada
- Prior art keywords
- area
- storage means
- polyol
- isocyanate
- foaming agent
- 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.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/36—Feeding the material to be shaped
- B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
- B29C44/388—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length into moving moulds
Landscapes
- Polyurethanes Or Polyureas (AREA)
Abstract
A method for making polyurethane foam products from isocyanate, a polyol and a foaming agent comprising:
a. producing a plurality of mixtures of the polyol and the foaming agent in a first area;
b. circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molds in a second area;
c. providing the isocyanate to said plurality of molds positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molds in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
a. producing a plurality of mixtures of the polyol and the foaming agent in a first area;
b. circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molds in a second area;
c. providing the isocyanate to said plurality of molds positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molds in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
Description
i 2181514 Title: Process to Make Polyurethane Foam Products FIELD OF THE INVENTION
The present invention relates to a process of making a polyurethane foam, and more particularly, to a process of making a polyurethane foam in which the foaming agent comprises a lower alkane such as pentane.
Polyurethane foams are typically made by reacting an isocyanate together with a polyol and a foaming agent. Historically, chlorofluorocarbons ("CFCs") were commonly used as foaming agents to foam or "blow" the polymer in a reaction mold. Typical examples of CFCs used in the process of foaming polyurethane were trichlorofluoromethane (R-11), dichlorodifluormethane (R-12), and trichlorotrifluorethane (R-113).
In operation, typically the reactants are stored and agitated in tanks positioned adjacent to the molding machine. Each time it is 2 0 desired to make a different coloured foam product, typically one of the feed tanks must be drained and cleaned before producing a differently coloured foam from the same reaction mold. This results in a period of down time while the tank is drained and cleaned.
With the discovery that CFCs have a deleterious effect on 2 5 the ozone layer in the atmosphere, the use of CFC's has been banned in many countries around the world. As a result, other foaming agents which do not contain CFCs have been developed, and are currently in commercial use.
One alternate foaming agent which has been identified is 3 0 water (eg. see U.S. Patent No. 5,223,549 to Wiedermann et al). Water is a readily available and safe alternate foaming agent. Polyurethane foams produced using water as a foaming agent do not form a skin.
Accordingly, if additional strength is required or if the molded product forms part of an exterior surface (eg. a steering wheel for a car or an arm for a chair), then the molded product must be subjected to a second process or in-mold coating to form a skin.
A further alternate foaming agent which has been identified are the lower alkanes (C3-C6) and in particular, n-pentane and its isomers (isopentane, neopentane and cyclopentane). These foaming agents may be used either alone or in combination with other foaming agents to produce a foamed product having an integral skin.
For example, see U.S. Patent No. 5,182,309 to Hutzen, U.S. Patent No.
5,283,003 to Chen, U.S. Patent No. 5,387,618 to Smits and U.S. Patent 1 0 No. 5,444,101 to De Vos et al.
One major drawback to the use of pentane as a foaming agent is that, when its vapour is mixed with oxygen, it may form an explosive mixture. Thus, if pentane is used, the area in which an explosive mixture of pentane may be formed should be explosion 1 5 proof. This is typically very expensive and commercially undesirable.
Accordingly, despite the benefits of using pentane, the use of pentane as a blowing agent has generally had only limited penetration into the marketplace.
In accordance with the present invention there is provided a method for making polyurethane foam products from isocyanate, a polyol and a foaming agent comprising:
(a) producing a plurality of mixtures of the polyol and 2 5 the foaming agent in a first area;
(b) circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molding means in a second area;
(c) providing the isocyanate to the plurality of molding 3 0 means positioned in the second area whereby a number of different polyurethane foam products of -differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to the molding means in the second area and allowing the isocyanate, polyol and foaming agent to react therein.
According to a further embodiment, a method for making polyurethane foam products from isocyanate, a polyol and a lower alkane foaming agent comprises:
(a) passing the polyol and the foaming agent through pump means to produce a mixture of the polyol and the foaming agent and introducing the mixture into a plurality of first storage means, the plurality of first storage means being positioned in a first area;
(b) combining at least one additive with each of the mixtures;
(c) circulating each of the mixtures from the first area to a plurality of molding means in a second area;
(d) providing the isocyanate to the plurality of molding means positioned in the second area whereby a number of different polyurethane foam products of 2 0 differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to the molding means in the second area and allowing the isocyanate, polyol and foaming agent to react therein.
In one embodiment the foaming agent is a lower alkane, 2 5 preferably comprising pentane, and the first area is of explosion proof construction. Further, each of the mixtures of the polyol and the foaming agent may be individually stored in the first area in a second storage means and at least one additive is combined with each of the mixtures in the second storage means. Each of the second storage 3 0 means may include mixing means to maintain a uniform mixture of the polyol, the foaming agent and the at least one additive (which may be a colorant).
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages of the present invention will 5 be more fully and completely understood through a consideration of the following description taken together with the accompanying drawing of a preferred embodiment of the invention in which:
Figure 1 is a diagrammatic view of a tank farm used in an apparatus made in accordance with a preferred embodiment of the 1 0 present invention; and Figure 2 is a diagrammatic view of a reaction area used in an apparatus made in accordance with a preferred embodiment of the present invention.
Referring to Figures 1 and 2, there is shown a diagrammatic view of an apparatus 10 made in accordance with the present invention. Apparatus 10 comprises tank farm 15 (Figure 1), and reaction area 20 (Figure 2).
2 0 Referring to Figure 1, tank farm 15 comprises means for storing the reactants. For example, tank farm 15 may comprise storage tanks 40 and 45 for storing the reactants prior to reaction in a mold.
Storage tank 40 may be used to store the isocyanate and storage tank 45 may be used to store a polyol/foaming agent mixture.
2 5 Storage tanks 40 and 45 may be fed from feed tanks 25, 30 and 35. Feed tank 25 may be used to store the isocyanate, feed tank 30 may be used to store the polyol, and feed tank 35 may be used to store the foaming agent (eg. pentane). Tanks 25, 30, 35, 40 and 45 may be made of any appropriate materials known in the art and are sized to 3 0 provide a continuous flow of reactants to the process. The feed tanks 25, 30 and 35 may, for example, be bulk containers in which the 218151~
isocyanate, polyol and foaming agent are received from the supplier.
The isocyanate is transferred to storage tank 40 from the feed tank 25 by means of pump 65 through pipeline 70. Pump 65 may be any suitable pump to handle isocyanate, and may be a positive 5 displacement pump. Pipeline 70 may be of any appropriate size and material. Pipeline 70 preferably has shut off valves 75a and b located on either side of pump 65 to shut off the flow of isocyanate from feed tank 25 to storage tank 40.
The isocyanate may be transferred into storage tank 40 10 from the top thereof such as at inlet 80. In order to reduce unnecessary foaming and frothing of the isocyanate in the primary storage tank, inlet 80 is preferably designed so that the isocyanate flowing into storage tank 40 flows down the inner side wall of the tank, rather than falling directly into the isocyanate already in the tank. For example, 15 inlet 80 may be angled so that the isocyanate travels to the wall of storage tank 40 and then flows down the wall (not shown).
Additives which are desired to be incorporated into the resultant foam may be either incorporated into the isocyanate feedstock from the supplier, or mixed with the isocyanate in storage 2 0 tank 40. Additives which are commonly incorporated into polyurethane foam include crosslinking agents (such as low molecular weight polyols, for example triethanolamine), foam stabilizers (such as siloxane-oxyalkylene copolymers), and fire retardants (such as halogenated alkyl phosphates such as chloropropyl phosphate). Other 2 5 additives may also be added to the isocyanate for incorporation in the resultant foam product.
Storage tank 40 may have mixing means to disperse the additives in the isocyanate. As shown in Figure 1, the mixing means may be a variable speed mixer 55 having with blades 60 located at one 3 0 end and a motor 62 at a position external to storage tank 40. Mixer 55 is preferably continuously operated so that the additives are uniformly dispersed throughout the isocyanate at all times.
To prevent undesirable foaming and frothing of the isocyanate and additives, the level of the isocyanate and additives in storage tank 40 is preferably maintained at a level higher than blades 5 60 of the mixer 55. To this end, storage tank 40 may have a level indicator 85 through which the level of isocyanate and additives in the tank may be viewed. Level indicator 85 has a top 90, a bottom 95 and may be any known type, such as a transparent tube made from glass or another suitable substance. Such level indicators are commonly 1 0 known in the art. The level indicator is connected to storage tank 40, and may have shut off valves 100a and b as shown.
According to the preferred embodiment, the polyol and foaming agent are transferred to storage tank 45 from their respective feed tanks 30 and 35 by means of a pump 115 through pipelines 120 1 5 and 131. Pump 115 may be any pump generally known in the art which will act to disperse and mix the foaming agent with the polyol.
Preferably pump 115 produces considerable turbulence to achieve such mixing. Pump 115 may, for example, be a gear pump or a rotary positive displacement pump. Pipelines 120 and 131 may be of any appropriate size and material. Pipeline 120 preferably has shut off valves 125a and b located on either side of the pump 115 to shut off the flow of polyol from the feed tank 30 to the primary storage tank 45.
Pipeline 131 preferably has shut off valve 132 to shut off the flow of foaming agent to primary storage tank 45.
The polyol and pentane may be transferred via pipeline 120 into storage tank 45 from the top thereof such as at inlet 130.
Again, in order to reduce unnecessary foaming and frothing of the polyol/foaming agent mixture in storage tank 45, inlet 130 is preferably designed so that the polyol flowing into storage tank 45 flows down the inner side wall of the tank, rather than falling directly into the mixture already in the tank.
The foaming agent may be any whose vapour may form an explosive mixture with air. The foaming agent may be a lower alkane, and preferably comprises pentane. Hereinafter, reference will be made to pentane as the foaming agent, although it will be 5 appreciated that other foaming agents may be used in the place of pentane.
The pentane is transferred to storage tank 45 from feed tank 35. As shown in Figure 1, pentane feed tank 35 is connected to pipeline 120 by means of pipe 131 which is positioned upstream to 1 0 pump 115. Shut off valve 132 is preferably provided adjacent to feed tank 35 to control the flow of pentane from the feed tank 35 into storage tank 45. Metering means, such as meter 134, is provided to measure the amount of pentane which is drawn from pentane feed tank 35. In the preferred embodiment, meter 134 is in the form of 1 5 weigh scale 136. Accordingly, pentane feed tank 35 rests on weigh scale 136 and the amount of pentane delivered from the pentane feed tank may be measured by the drop in weight of the pentane feed tank 35.
In use, while a predetermined amount of polyol is being transferred from feed tank 30 to storage tank 45, shut off valve 132 is 20 opened and pump 115 draws pentane from the pentane feed tank 35 through pipeline 131 and into pipeline 120 simultaneously with the polyol being drawn from polyol feed tank 35. As the pentane and the polyol are drawn together through pump 115 and pipeline 120, the pentane is dispersed within the polyol through the mixing action 2 5 created by pump 115. Thus, the pentane and the polyol may be mixed prior to their entry into tank 45, eliminating the need for expensive high intensity mixing equipment in tank 45.
Storage tank 45 preferably has mixing means such as a variable speed mixer 105, with blades 110 located at one end, and a 30 motor 112 at a position external to storage tank 45. Mixer 105 is preferably provided to maintain the dispersion of the pentane in the polyol while the mixture is stored in the tank. Because the pentane is dispersed in the polyol as it passes through pump 115 and pipeline 120, high intensity mixers are not required, and the mixer 105 may be an inexpensive low intensity mixer.
To prevent undesirable foaming and frothing of the polyol/pentane mixture, the level of the polyol/pentane mixture in storage tank 45 is preferably maintained at a level higher than blades 110 of the mixer 105. To this end, storage tank 45 may have a level indicator through which the level of the polyol/pentane mixture in 1 0 the tank may be viewed, similar to that for storage tank 40.
The present invention also contemplates that it may be desirable to have the capability to produce a variety of foam products, each of which contains different additives, from the same base feed material. An example of such is differently coloured foam products.
1 5 Therefore, tank farm 15 comprises a plurality of secondary storage tanks. Three such tanks, denoted 135a, b, c, are shown in Figure 1. Each storage tank 135a, b, c has a respective inlet 152a, b, c and a respective shut off valve 160a, b, c. The inlets 152a, b, c are preferably located at the top of the respective secondary storage tanks 135a, b, c and are 20 preferably designed so that the polyol flows into the tank along the inner wall of the tank, thereby avoiding undesirable splashing, foaming and frothing.
As shown, the polyol is transported from the primary storage tank 45 to one of the secondary storage tanks 135a, b, c by 2 5 pipeline system 140, where any desired additives, such as colorants, may be added to the polyol. As will be appreciated, pipeline system 140 may be connected to any number of desired tanks 135, thereby allowing the production of any number of different foams (eg. differently coloured foam products).
Feed means is provided to systematically supply each storage tank 135 with its own mixture of foaming agent, polyol and 218151~
additive. As shown, pipeline system 140 is connected at one end 145 to outlet 147 of polyol storage tank 45. Outlet 147 is preferably located at the lower end of storage tank 45. Pump 150 is provided to pump the polyol/pentane mixture from the primary storage tank 45 to storage 5 tanks 135a, b, c. Pump 150 may be any suitable pump, and in the preferred embodiment, pump 150 is a positive displacement pump.
Pipeline system 140 is also connected to each inlet 152a, b, c. Shut off valve 155 is provided at the outlet 147 of storage tank 45 to shut off the flow of the polyol/pentane mixture when desired (for example, during 1 0 maintenance or when tanks 135 are in use). Shut off valves 160a, b, c control the flow of polyol into the respective tank 135 as desired. It will be appreciated that, in an alternate embodiment, the pentane is mixed with the polyol as the polyol is transferred from storage tank 45 to tank 135. In such an embodiment, pump 150 is of the same type as discussed 1 5 for pump 115.
Each of tanks 135a, b, c preferably has a variable speed mixer 170a, b, c with blades 175a, b, c and a motor 180a, b, c, and a level indicator 185a, b, c which may be similar to those hereinbefore described. As with storage tank 45, it is desirable to maintain a level of 2 0 polyol/pentane mixture higher than that of the blades 175a, b, c of the mixer 170a, b, c in order to reduce foaming and frothing.
A plurality of additive dispensers 190a, b, c are provided for each of secondary storage tanks 135a, b, c. The additive dispensers are used to add the required amount of the preselected additives to 2 5 each tank 135 in order to obtain a foam having the desired properties.
Additive dispensers 190a, b, c are preferably located at the top of the secondary storage tanks 135a, b, c. Additive dispensers 190a, b, c are connected to the secondary storage tanks 135a, b, c by a respective pipeline 205a, b, c. A series of shut off valves 207a, b, c are provided so 3 0 that additives may be held within the container prior to feeding into the storage tanks 135.
218151 l In the preferred embodiment, the additive dispensers 190 are used to add a preselected colour dye to the polyol/pentane mixture in storage tanks 135. Thus a plurality of secondary storage tanks 135a, b, c each containing a differently coloured polyol/pentane mixture can be 5 provided, with each secondary storage tank 135a, b, c being supplied from a single common polyol/pentane storage tank 45. In addition, other additives may be added into the secondary storage tanks 135 through the dispensers 190. Any additives which are desired to be incorporated into only selected polyurethane foam products are added 1 0 into a selected secondary storage tank 135 rather than to the isocyanate primary storage tank 25 which delivers the additives to every mold (as discussed hereinafter).
In operation, a predetermined amount of polyol/pentane mixture is transferred from the storage tank 45 to a selected secondary 1 5 storage tank 135 through pipeline 140 by opening shut off valve 155 and switching on pump 150. Metering means, such as meter 220, is provided, such as on pipeline 140, to measure the quantity of polyol/pentane mixture which is transferred from storage tank 45 to the selected secondary storage tank 135. A bypass line 221 with a shut 2 0 off valve 222 may be incorporated around the meter 220. In such case, two shut off valves 223 and 224 are provided on each side of the meter 220.
In the preferred embodiment, each of the tanks is connected to an inert gas (eg nitrogen) source, and is maintained at 2 5 constant positive pressure. This serves several purposes. First, pentane when mixed with oxygen in appropriate concentrations is highly explosive. By maintaining the tanks under a positive pressure of nitrogen, a nitrogen blanket fills any void space in the tanks, and the risk of explosion is greatly reduced as air, which contains oxygen, is 30 prevented from entering the system. In addition, maintaining of all the tanks under nitrogen from the same source ensures that the -- 218151'~
ambient pressure in the entire system is equalized.
To this end, as shown in Figure 1, isocyanate storage tank 40, each of the polyol/pentane storage tanks 45 and 135a, b, c, and each of the additive dispensers 190 are connected to a source of an inert gas 5 (eg. nitrogen) through pipeline 235. The tanks may be maintained by the nitrogen at a pressure slightly greater than the ambient pressure, for example between about 2 psi and 3 psi above the ambient pressure.
The nitrogen is delivered from nitrogen source 240, which may be a standard gas cylinder as is commonly known. Preferably, a pressure 1 0 reducer valve 237 is provided to reduce the pressure from that in the gas cylinder to about 2 psi to 3 psi above the ambient pressure. A series of connecting pipes 242 are provided to connect each tank and each additive dispenser to the main nitrogen pipeline 235. Preferably, each of the connecting pipes 242 has a shut off valve 245, so that the flow of 1 5 nitrogen to any individual tank or additive dispenser may be closed. In addition, there is preferably a shut off valve 247 located adjacent to nitrogen source 240, so that the flow of nitrogen to the entire system may easily be turned on and off. As will be appreciated, by connecting the main nitrogen pipeline 235 to each tank and additive disperser in 2 0 the system, the entire tank system will be maintained under a common, preselected positive pressure of an inert gas.
Referring to Figure 2, reaction area 20 comprises one or more molds 250 in which the isocyanate and the polyol/pentane mixture produce polyurethane foam products of desired shape.
2 5 Reaction area 20 further comprises a plurality of polyurethane dispensing means, for example dispensing machines 281, to which the isocyanate and polyol/pentane mixture are separately circulated prior to being dispensed by dispensing heads 300 dispensing into the molds 250. The molds, dispensing machines and dispensing heads will not be 3 0 described in detail herein, as they may be any standard device known in the field.
The reactants (ie. the isocyanate, and the polyol/pentane mixture) are transported from tank farm 15 to reaction area 20 through a distribution system 255. Distribution system 255 generally comprises a plurality of pipelines 260 and 265a, b, c. Pipeline 260 transports the 5 isocyanate from isocyanate storage tank 40 to reaction area 20, while the pipelines 265a, b, c transport the polyol/pentane mixtures from secondary storage tanks 135a, b, c respectively to reaction area 20.
In the preferred embodiment, pipeline 260 forms a continuous circuit, starting at an outlet 267 at lower most portion 270 1 0 of isocyanate storage tank 40, running to the reaction area 20, and returning to isocyanate storage tank 40 via return inlet 272 located, eg., at the upper portion of isocyanate storage tank 40. The isocyanate is transported through pipeline 260 by means of a pump 280 suitable for pumping isocyanate, eg a positive displacement pump, which is 1 5 preferably located near isocyanate storage tank 40. Shut off valve 275 may be provided in pipeline 260 adjacent to outlet 267 in order to stop the flow of the isocyanate through pipeline 260. When the apparatus is in use, the isocyanate is continuously circulated throughout pipeline 260 so that it is available to be supplied to any one or more of the 2 0 polyurethane dispensing machines at any given time.
Pipeline 260 is sized to supply the isocyanate to a preselected number of dispensing machines 281. For example, if it is desired to be able to supply three different dispensing machines at any given time, a larger diameter pipe will be required than if only one 2 5 dispensing machine will be used at any given time.
In the preferred embodiment, each of pipelines 265a, b, c also forms a continuous loop. As shown, pipelines 265a, b, c are connected to a respective outlet 285a, b, c provided preferably in the lower portion a respective secondary storage tank 135a, b, c. Pipelines 30 265a, b, c extend to reaction area 20, and return to a respective inlet 290a, b, c located, eg., at the upper portion of the respective secondary - 218151 l storage tank 135a, b, c.
The polyol/pentane mixture is delivered through pipelines 265a, b, c by pump means, eg. positive displacement pumps 295a, b, c, which are preferably located near secondary storage tanks 5 135a, b, c. As with pipeline 260, each pipeline 265a, b, c has a respective shut off valve 292a, b, c located adjacent to the outlets 285a, b, c on secondary storage tanks 135a, b, c so that the flow of the pentane/polyol mixture through one or more of pipelines 265a, b, c may be stopped if desired. When the apparatus is in use, the pentane/polyol mixture is 1 0 continuously circulated through pipelines 265a, b, c so that the mixture is available to be supplied to any one or more of the dispensing machines 281 at any desired time.
Pipelines 265a, b, c are each sized to supply the polyol/pentane mixture to a preselected number of polyurethane 1 5 dispensing machines 281. Typically, however, supply to a single polyurethane dispensing machine will be sufficient, as each dispensing machine may be connected with any number of molds 250, as will be discussed.
Each of the dispensing machines 281 is connected to 2 0 pipeline 260 (which circulates the isocyanate) by a pipe 282 having a shut off valve 283, and to one of the pipelines 265a, b, or c (which circulates the desired coloured pentane/polyol mixture) by a coupling 305. Each coupling 305 may comprise a flexible hose which may be releasably connectable with any of the pipelines 265. In this manner, it 25 is easy to change the source of polyol/pentane mixture which is provided to a dispensing machine 281 simply by disconnecting the flexible hose from one pipeline 265 and connecting it to a different pipeline 265. The manner in which the flexible hose is connected to the desired pipeline 265 may be any means known in the art.
3 0 Each coupling 305 may have a shut off valve 307 or other means to selectively control the flow of the isocyanate and the - 21815t~
preselected coloured polyol/pentane mixture into the dispensing machine 281. The dispensing machine 281 may be any standard machine known in the art. Each dispensing machine 281 is connected with an associated dispensing head 300 in which the reactants are 5 mixed in predetermined ratios and dispensed in to a mold 260 in which a foam article is produced, as is commonly known.
The operation of the system will now be described.
Isocyanate storage tank 40 is filled and the isocyanate is circulated through pipeline 260. Polyol storage tanks 135 are filled with a 1 0 polyol/pentane mixture and the selected additives (eg. colorants) are added to each tank 135. These mixtures are circulated through pipelines 265. Each plant may make parts in one of a series of standard colours. Thus, a tank 135 may be provided for each such colour.
Next, a dispensing machine 281 is selected. The 1 5 dispensing machine will generally be selected depending upon the molds with which it is associated and the parts which are to be produced. It will be appreciated that as each dispensing machine 281 is connected to a different pipeline 265, any selected mold 250 may be used to manufacture parts of any desired colour, simply by associating 2 0 the mold with the appropriate dispensing machine 281. If parts made of one colour have been made in one particular mold 250, and it is now desired to make the same parts but in a different colour in the same mold 250, then this change may be performed relatively easily by flushing out the mold 250, and associating it with a different 25 dispensing machine. Thus, the actual down time of any particular mold 250 may be minimized. Further, if it is desired to change the colour of foam which is produced by any particular dispensing machine 281, then the dispensing machine 281 and the coupling 305 are flushed, and coupling 305 is connected with a different pipeline 3 0 265.
When a dispensing machine 281 has been selected, and cleaned if required, the respective shut off valves 307 and 283 are opened and the isocyanate and the selected polyol/pentane mixture flow into the dispensing machine 281 where they may circulate out of contact with each other. The isocyanate and polyol/pentane mixtures 5 are then delivered to the dispensing head 300 associated with the dispensing machine 281 in a predetermined ratio.
The isocyanate and polyol/pentane mixtures come into contact while being discharged from the dispensing head in a predetermined ratio and quantity. These mixtures are immediately 1 0 thereafter dispensed into a mold 250 where foaming takes place, as shown by arrows A in Figure 2.
The dispensing head may then be moved so as to be associated with a different mold 250, where the procedure is repeated.
This can be accomplished by either maintaining the molds in a 1 5 stationary position and moving the dispensing head, or by maintaining the dispensing head in a stationary position and moving the molds into position one after another (for example on a carousel).
Each of these methods is well known.
By this method, any number of different molds may be 20 connected in circuit to simultaneously make the same or different articles of polyurethane foam in the same or different colours, simply be associating the mold with the appropriate dispensing machine and dispensing head. This method also allows great flexibility in manufacturing. For example, if one mold requires service, then the remaining molds may still be used to make parts. If necessary, the mold requiring service may be removed from the apparatus and replaced with a different mold. This switch over may be made with only minimal cleaning if the mold had been used to make different coloured parts.
As well, it is possible to use the same mold to make products of differing colours, simply by disassociating the mold with one dispensing machine and associating it with a different dispensing machine after flushing.
A further advantage of the system is that the polyol/pentane mixing equipment for an entire plant may be 5 contained within a single explosion proof room while allowing the production of a number of different polyurethane foam products simultaneously. Thus, construction costs may be minimized. The room should be constructed to prevent the possibility of an explosion.
In addition, the room should be designed so that, in the event of an 10 explosion, damage to the area will be minimized. Each of these construction techniques are well known in the art.
It will be obvious, however, that the isocyanate tanks 25 and 40 need not be located in an explosion proof surrounding, as the isocyanate and additives are typically not explosive. Under normal 15 circumstances, if desired, the tanks 25 and 40 may be located in a separate, non-explosion proof room.
The polyol/pentane mixture in tanks 135 is preferably maintained at a temperature between about 15~C and about 22~C, and more preferably at about room temperature (between about 17~C and 2 0 about 20 ~C). If the temperature is maintained lower than about 15~C
then the polyol difficult to pump because of its increased viscosity.
Therefore, it is desirable to cool the polyol/pentane mixtures during warm seasons.
The system may be cooled in any known manner, such as 25 tanks encased in cooling jackets, heat exchangers on the pipes to remove excess heat during circulation, cooling means in the storage tanks, or through air conditioning the entire room in which the mixing and storage tanks are located (ie. the tank farm). Preferably, the system is cooled by air conditioning the room in which tanks 135 are 3 0 housed. Preferably, this room is maintained at a temperature between about 15~C and about 22~C and more preferably between about 17~C
218151~
.
and about 20 ~C.
It will be appreciated that various changes may be made within the spirit of the described invention, and all such changes are within the scope of the invention. The method may be used in 5 association with any molding machines known in the art and the reactants may be mixed together at the molding machine in manner known in the art.
The present invention relates to a process of making a polyurethane foam, and more particularly, to a process of making a polyurethane foam in which the foaming agent comprises a lower alkane such as pentane.
Polyurethane foams are typically made by reacting an isocyanate together with a polyol and a foaming agent. Historically, chlorofluorocarbons ("CFCs") were commonly used as foaming agents to foam or "blow" the polymer in a reaction mold. Typical examples of CFCs used in the process of foaming polyurethane were trichlorofluoromethane (R-11), dichlorodifluormethane (R-12), and trichlorotrifluorethane (R-113).
In operation, typically the reactants are stored and agitated in tanks positioned adjacent to the molding machine. Each time it is 2 0 desired to make a different coloured foam product, typically one of the feed tanks must be drained and cleaned before producing a differently coloured foam from the same reaction mold. This results in a period of down time while the tank is drained and cleaned.
With the discovery that CFCs have a deleterious effect on 2 5 the ozone layer in the atmosphere, the use of CFC's has been banned in many countries around the world. As a result, other foaming agents which do not contain CFCs have been developed, and are currently in commercial use.
One alternate foaming agent which has been identified is 3 0 water (eg. see U.S. Patent No. 5,223,549 to Wiedermann et al). Water is a readily available and safe alternate foaming agent. Polyurethane foams produced using water as a foaming agent do not form a skin.
Accordingly, if additional strength is required or if the molded product forms part of an exterior surface (eg. a steering wheel for a car or an arm for a chair), then the molded product must be subjected to a second process or in-mold coating to form a skin.
A further alternate foaming agent which has been identified are the lower alkanes (C3-C6) and in particular, n-pentane and its isomers (isopentane, neopentane and cyclopentane). These foaming agents may be used either alone or in combination with other foaming agents to produce a foamed product having an integral skin.
For example, see U.S. Patent No. 5,182,309 to Hutzen, U.S. Patent No.
5,283,003 to Chen, U.S. Patent No. 5,387,618 to Smits and U.S. Patent 1 0 No. 5,444,101 to De Vos et al.
One major drawback to the use of pentane as a foaming agent is that, when its vapour is mixed with oxygen, it may form an explosive mixture. Thus, if pentane is used, the area in which an explosive mixture of pentane may be formed should be explosion 1 5 proof. This is typically very expensive and commercially undesirable.
Accordingly, despite the benefits of using pentane, the use of pentane as a blowing agent has generally had only limited penetration into the marketplace.
In accordance with the present invention there is provided a method for making polyurethane foam products from isocyanate, a polyol and a foaming agent comprising:
(a) producing a plurality of mixtures of the polyol and 2 5 the foaming agent in a first area;
(b) circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molding means in a second area;
(c) providing the isocyanate to the plurality of molding 3 0 means positioned in the second area whereby a number of different polyurethane foam products of -differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to the molding means in the second area and allowing the isocyanate, polyol and foaming agent to react therein.
According to a further embodiment, a method for making polyurethane foam products from isocyanate, a polyol and a lower alkane foaming agent comprises:
(a) passing the polyol and the foaming agent through pump means to produce a mixture of the polyol and the foaming agent and introducing the mixture into a plurality of first storage means, the plurality of first storage means being positioned in a first area;
(b) combining at least one additive with each of the mixtures;
(c) circulating each of the mixtures from the first area to a plurality of molding means in a second area;
(d) providing the isocyanate to the plurality of molding means positioned in the second area whereby a number of different polyurethane foam products of 2 0 differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to the molding means in the second area and allowing the isocyanate, polyol and foaming agent to react therein.
In one embodiment the foaming agent is a lower alkane, 2 5 preferably comprising pentane, and the first area is of explosion proof construction. Further, each of the mixtures of the polyol and the foaming agent may be individually stored in the first area in a second storage means and at least one additive is combined with each of the mixtures in the second storage means. Each of the second storage 3 0 means may include mixing means to maintain a uniform mixture of the polyol, the foaming agent and the at least one additive (which may be a colorant).
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages of the present invention will 5 be more fully and completely understood through a consideration of the following description taken together with the accompanying drawing of a preferred embodiment of the invention in which:
Figure 1 is a diagrammatic view of a tank farm used in an apparatus made in accordance with a preferred embodiment of the 1 0 present invention; and Figure 2 is a diagrammatic view of a reaction area used in an apparatus made in accordance with a preferred embodiment of the present invention.
Referring to Figures 1 and 2, there is shown a diagrammatic view of an apparatus 10 made in accordance with the present invention. Apparatus 10 comprises tank farm 15 (Figure 1), and reaction area 20 (Figure 2).
2 0 Referring to Figure 1, tank farm 15 comprises means for storing the reactants. For example, tank farm 15 may comprise storage tanks 40 and 45 for storing the reactants prior to reaction in a mold.
Storage tank 40 may be used to store the isocyanate and storage tank 45 may be used to store a polyol/foaming agent mixture.
2 5 Storage tanks 40 and 45 may be fed from feed tanks 25, 30 and 35. Feed tank 25 may be used to store the isocyanate, feed tank 30 may be used to store the polyol, and feed tank 35 may be used to store the foaming agent (eg. pentane). Tanks 25, 30, 35, 40 and 45 may be made of any appropriate materials known in the art and are sized to 3 0 provide a continuous flow of reactants to the process. The feed tanks 25, 30 and 35 may, for example, be bulk containers in which the 218151~
isocyanate, polyol and foaming agent are received from the supplier.
The isocyanate is transferred to storage tank 40 from the feed tank 25 by means of pump 65 through pipeline 70. Pump 65 may be any suitable pump to handle isocyanate, and may be a positive 5 displacement pump. Pipeline 70 may be of any appropriate size and material. Pipeline 70 preferably has shut off valves 75a and b located on either side of pump 65 to shut off the flow of isocyanate from feed tank 25 to storage tank 40.
The isocyanate may be transferred into storage tank 40 10 from the top thereof such as at inlet 80. In order to reduce unnecessary foaming and frothing of the isocyanate in the primary storage tank, inlet 80 is preferably designed so that the isocyanate flowing into storage tank 40 flows down the inner side wall of the tank, rather than falling directly into the isocyanate already in the tank. For example, 15 inlet 80 may be angled so that the isocyanate travels to the wall of storage tank 40 and then flows down the wall (not shown).
Additives which are desired to be incorporated into the resultant foam may be either incorporated into the isocyanate feedstock from the supplier, or mixed with the isocyanate in storage 2 0 tank 40. Additives which are commonly incorporated into polyurethane foam include crosslinking agents (such as low molecular weight polyols, for example triethanolamine), foam stabilizers (such as siloxane-oxyalkylene copolymers), and fire retardants (such as halogenated alkyl phosphates such as chloropropyl phosphate). Other 2 5 additives may also be added to the isocyanate for incorporation in the resultant foam product.
Storage tank 40 may have mixing means to disperse the additives in the isocyanate. As shown in Figure 1, the mixing means may be a variable speed mixer 55 having with blades 60 located at one 3 0 end and a motor 62 at a position external to storage tank 40. Mixer 55 is preferably continuously operated so that the additives are uniformly dispersed throughout the isocyanate at all times.
To prevent undesirable foaming and frothing of the isocyanate and additives, the level of the isocyanate and additives in storage tank 40 is preferably maintained at a level higher than blades 5 60 of the mixer 55. To this end, storage tank 40 may have a level indicator 85 through which the level of isocyanate and additives in the tank may be viewed. Level indicator 85 has a top 90, a bottom 95 and may be any known type, such as a transparent tube made from glass or another suitable substance. Such level indicators are commonly 1 0 known in the art. The level indicator is connected to storage tank 40, and may have shut off valves 100a and b as shown.
According to the preferred embodiment, the polyol and foaming agent are transferred to storage tank 45 from their respective feed tanks 30 and 35 by means of a pump 115 through pipelines 120 1 5 and 131. Pump 115 may be any pump generally known in the art which will act to disperse and mix the foaming agent with the polyol.
Preferably pump 115 produces considerable turbulence to achieve such mixing. Pump 115 may, for example, be a gear pump or a rotary positive displacement pump. Pipelines 120 and 131 may be of any appropriate size and material. Pipeline 120 preferably has shut off valves 125a and b located on either side of the pump 115 to shut off the flow of polyol from the feed tank 30 to the primary storage tank 45.
Pipeline 131 preferably has shut off valve 132 to shut off the flow of foaming agent to primary storage tank 45.
The polyol and pentane may be transferred via pipeline 120 into storage tank 45 from the top thereof such as at inlet 130.
Again, in order to reduce unnecessary foaming and frothing of the polyol/foaming agent mixture in storage tank 45, inlet 130 is preferably designed so that the polyol flowing into storage tank 45 flows down the inner side wall of the tank, rather than falling directly into the mixture already in the tank.
The foaming agent may be any whose vapour may form an explosive mixture with air. The foaming agent may be a lower alkane, and preferably comprises pentane. Hereinafter, reference will be made to pentane as the foaming agent, although it will be 5 appreciated that other foaming agents may be used in the place of pentane.
The pentane is transferred to storage tank 45 from feed tank 35. As shown in Figure 1, pentane feed tank 35 is connected to pipeline 120 by means of pipe 131 which is positioned upstream to 1 0 pump 115. Shut off valve 132 is preferably provided adjacent to feed tank 35 to control the flow of pentane from the feed tank 35 into storage tank 45. Metering means, such as meter 134, is provided to measure the amount of pentane which is drawn from pentane feed tank 35. In the preferred embodiment, meter 134 is in the form of 1 5 weigh scale 136. Accordingly, pentane feed tank 35 rests on weigh scale 136 and the amount of pentane delivered from the pentane feed tank may be measured by the drop in weight of the pentane feed tank 35.
In use, while a predetermined amount of polyol is being transferred from feed tank 30 to storage tank 45, shut off valve 132 is 20 opened and pump 115 draws pentane from the pentane feed tank 35 through pipeline 131 and into pipeline 120 simultaneously with the polyol being drawn from polyol feed tank 35. As the pentane and the polyol are drawn together through pump 115 and pipeline 120, the pentane is dispersed within the polyol through the mixing action 2 5 created by pump 115. Thus, the pentane and the polyol may be mixed prior to their entry into tank 45, eliminating the need for expensive high intensity mixing equipment in tank 45.
Storage tank 45 preferably has mixing means such as a variable speed mixer 105, with blades 110 located at one end, and a 30 motor 112 at a position external to storage tank 45. Mixer 105 is preferably provided to maintain the dispersion of the pentane in the polyol while the mixture is stored in the tank. Because the pentane is dispersed in the polyol as it passes through pump 115 and pipeline 120, high intensity mixers are not required, and the mixer 105 may be an inexpensive low intensity mixer.
To prevent undesirable foaming and frothing of the polyol/pentane mixture, the level of the polyol/pentane mixture in storage tank 45 is preferably maintained at a level higher than blades 110 of the mixer 105. To this end, storage tank 45 may have a level indicator through which the level of the polyol/pentane mixture in 1 0 the tank may be viewed, similar to that for storage tank 40.
The present invention also contemplates that it may be desirable to have the capability to produce a variety of foam products, each of which contains different additives, from the same base feed material. An example of such is differently coloured foam products.
1 5 Therefore, tank farm 15 comprises a plurality of secondary storage tanks. Three such tanks, denoted 135a, b, c, are shown in Figure 1. Each storage tank 135a, b, c has a respective inlet 152a, b, c and a respective shut off valve 160a, b, c. The inlets 152a, b, c are preferably located at the top of the respective secondary storage tanks 135a, b, c and are 20 preferably designed so that the polyol flows into the tank along the inner wall of the tank, thereby avoiding undesirable splashing, foaming and frothing.
As shown, the polyol is transported from the primary storage tank 45 to one of the secondary storage tanks 135a, b, c by 2 5 pipeline system 140, where any desired additives, such as colorants, may be added to the polyol. As will be appreciated, pipeline system 140 may be connected to any number of desired tanks 135, thereby allowing the production of any number of different foams (eg. differently coloured foam products).
Feed means is provided to systematically supply each storage tank 135 with its own mixture of foaming agent, polyol and 218151~
additive. As shown, pipeline system 140 is connected at one end 145 to outlet 147 of polyol storage tank 45. Outlet 147 is preferably located at the lower end of storage tank 45. Pump 150 is provided to pump the polyol/pentane mixture from the primary storage tank 45 to storage 5 tanks 135a, b, c. Pump 150 may be any suitable pump, and in the preferred embodiment, pump 150 is a positive displacement pump.
Pipeline system 140 is also connected to each inlet 152a, b, c. Shut off valve 155 is provided at the outlet 147 of storage tank 45 to shut off the flow of the polyol/pentane mixture when desired (for example, during 1 0 maintenance or when tanks 135 are in use). Shut off valves 160a, b, c control the flow of polyol into the respective tank 135 as desired. It will be appreciated that, in an alternate embodiment, the pentane is mixed with the polyol as the polyol is transferred from storage tank 45 to tank 135. In such an embodiment, pump 150 is of the same type as discussed 1 5 for pump 115.
Each of tanks 135a, b, c preferably has a variable speed mixer 170a, b, c with blades 175a, b, c and a motor 180a, b, c, and a level indicator 185a, b, c which may be similar to those hereinbefore described. As with storage tank 45, it is desirable to maintain a level of 2 0 polyol/pentane mixture higher than that of the blades 175a, b, c of the mixer 170a, b, c in order to reduce foaming and frothing.
A plurality of additive dispensers 190a, b, c are provided for each of secondary storage tanks 135a, b, c. The additive dispensers are used to add the required amount of the preselected additives to 2 5 each tank 135 in order to obtain a foam having the desired properties.
Additive dispensers 190a, b, c are preferably located at the top of the secondary storage tanks 135a, b, c. Additive dispensers 190a, b, c are connected to the secondary storage tanks 135a, b, c by a respective pipeline 205a, b, c. A series of shut off valves 207a, b, c are provided so 3 0 that additives may be held within the container prior to feeding into the storage tanks 135.
218151 l In the preferred embodiment, the additive dispensers 190 are used to add a preselected colour dye to the polyol/pentane mixture in storage tanks 135. Thus a plurality of secondary storage tanks 135a, b, c each containing a differently coloured polyol/pentane mixture can be 5 provided, with each secondary storage tank 135a, b, c being supplied from a single common polyol/pentane storage tank 45. In addition, other additives may be added into the secondary storage tanks 135 through the dispensers 190. Any additives which are desired to be incorporated into only selected polyurethane foam products are added 1 0 into a selected secondary storage tank 135 rather than to the isocyanate primary storage tank 25 which delivers the additives to every mold (as discussed hereinafter).
In operation, a predetermined amount of polyol/pentane mixture is transferred from the storage tank 45 to a selected secondary 1 5 storage tank 135 through pipeline 140 by opening shut off valve 155 and switching on pump 150. Metering means, such as meter 220, is provided, such as on pipeline 140, to measure the quantity of polyol/pentane mixture which is transferred from storage tank 45 to the selected secondary storage tank 135. A bypass line 221 with a shut 2 0 off valve 222 may be incorporated around the meter 220. In such case, two shut off valves 223 and 224 are provided on each side of the meter 220.
In the preferred embodiment, each of the tanks is connected to an inert gas (eg nitrogen) source, and is maintained at 2 5 constant positive pressure. This serves several purposes. First, pentane when mixed with oxygen in appropriate concentrations is highly explosive. By maintaining the tanks under a positive pressure of nitrogen, a nitrogen blanket fills any void space in the tanks, and the risk of explosion is greatly reduced as air, which contains oxygen, is 30 prevented from entering the system. In addition, maintaining of all the tanks under nitrogen from the same source ensures that the -- 218151'~
ambient pressure in the entire system is equalized.
To this end, as shown in Figure 1, isocyanate storage tank 40, each of the polyol/pentane storage tanks 45 and 135a, b, c, and each of the additive dispensers 190 are connected to a source of an inert gas 5 (eg. nitrogen) through pipeline 235. The tanks may be maintained by the nitrogen at a pressure slightly greater than the ambient pressure, for example between about 2 psi and 3 psi above the ambient pressure.
The nitrogen is delivered from nitrogen source 240, which may be a standard gas cylinder as is commonly known. Preferably, a pressure 1 0 reducer valve 237 is provided to reduce the pressure from that in the gas cylinder to about 2 psi to 3 psi above the ambient pressure. A series of connecting pipes 242 are provided to connect each tank and each additive dispenser to the main nitrogen pipeline 235. Preferably, each of the connecting pipes 242 has a shut off valve 245, so that the flow of 1 5 nitrogen to any individual tank or additive dispenser may be closed. In addition, there is preferably a shut off valve 247 located adjacent to nitrogen source 240, so that the flow of nitrogen to the entire system may easily be turned on and off. As will be appreciated, by connecting the main nitrogen pipeline 235 to each tank and additive disperser in 2 0 the system, the entire tank system will be maintained under a common, preselected positive pressure of an inert gas.
Referring to Figure 2, reaction area 20 comprises one or more molds 250 in which the isocyanate and the polyol/pentane mixture produce polyurethane foam products of desired shape.
2 5 Reaction area 20 further comprises a plurality of polyurethane dispensing means, for example dispensing machines 281, to which the isocyanate and polyol/pentane mixture are separately circulated prior to being dispensed by dispensing heads 300 dispensing into the molds 250. The molds, dispensing machines and dispensing heads will not be 3 0 described in detail herein, as they may be any standard device known in the field.
The reactants (ie. the isocyanate, and the polyol/pentane mixture) are transported from tank farm 15 to reaction area 20 through a distribution system 255. Distribution system 255 generally comprises a plurality of pipelines 260 and 265a, b, c. Pipeline 260 transports the 5 isocyanate from isocyanate storage tank 40 to reaction area 20, while the pipelines 265a, b, c transport the polyol/pentane mixtures from secondary storage tanks 135a, b, c respectively to reaction area 20.
In the preferred embodiment, pipeline 260 forms a continuous circuit, starting at an outlet 267 at lower most portion 270 1 0 of isocyanate storage tank 40, running to the reaction area 20, and returning to isocyanate storage tank 40 via return inlet 272 located, eg., at the upper portion of isocyanate storage tank 40. The isocyanate is transported through pipeline 260 by means of a pump 280 suitable for pumping isocyanate, eg a positive displacement pump, which is 1 5 preferably located near isocyanate storage tank 40. Shut off valve 275 may be provided in pipeline 260 adjacent to outlet 267 in order to stop the flow of the isocyanate through pipeline 260. When the apparatus is in use, the isocyanate is continuously circulated throughout pipeline 260 so that it is available to be supplied to any one or more of the 2 0 polyurethane dispensing machines at any given time.
Pipeline 260 is sized to supply the isocyanate to a preselected number of dispensing machines 281. For example, if it is desired to be able to supply three different dispensing machines at any given time, a larger diameter pipe will be required than if only one 2 5 dispensing machine will be used at any given time.
In the preferred embodiment, each of pipelines 265a, b, c also forms a continuous loop. As shown, pipelines 265a, b, c are connected to a respective outlet 285a, b, c provided preferably in the lower portion a respective secondary storage tank 135a, b, c. Pipelines 30 265a, b, c extend to reaction area 20, and return to a respective inlet 290a, b, c located, eg., at the upper portion of the respective secondary - 218151 l storage tank 135a, b, c.
The polyol/pentane mixture is delivered through pipelines 265a, b, c by pump means, eg. positive displacement pumps 295a, b, c, which are preferably located near secondary storage tanks 5 135a, b, c. As with pipeline 260, each pipeline 265a, b, c has a respective shut off valve 292a, b, c located adjacent to the outlets 285a, b, c on secondary storage tanks 135a, b, c so that the flow of the pentane/polyol mixture through one or more of pipelines 265a, b, c may be stopped if desired. When the apparatus is in use, the pentane/polyol mixture is 1 0 continuously circulated through pipelines 265a, b, c so that the mixture is available to be supplied to any one or more of the dispensing machines 281 at any desired time.
Pipelines 265a, b, c are each sized to supply the polyol/pentane mixture to a preselected number of polyurethane 1 5 dispensing machines 281. Typically, however, supply to a single polyurethane dispensing machine will be sufficient, as each dispensing machine may be connected with any number of molds 250, as will be discussed.
Each of the dispensing machines 281 is connected to 2 0 pipeline 260 (which circulates the isocyanate) by a pipe 282 having a shut off valve 283, and to one of the pipelines 265a, b, or c (which circulates the desired coloured pentane/polyol mixture) by a coupling 305. Each coupling 305 may comprise a flexible hose which may be releasably connectable with any of the pipelines 265. In this manner, it 25 is easy to change the source of polyol/pentane mixture which is provided to a dispensing machine 281 simply by disconnecting the flexible hose from one pipeline 265 and connecting it to a different pipeline 265. The manner in which the flexible hose is connected to the desired pipeline 265 may be any means known in the art.
3 0 Each coupling 305 may have a shut off valve 307 or other means to selectively control the flow of the isocyanate and the - 21815t~
preselected coloured polyol/pentane mixture into the dispensing machine 281. The dispensing machine 281 may be any standard machine known in the art. Each dispensing machine 281 is connected with an associated dispensing head 300 in which the reactants are 5 mixed in predetermined ratios and dispensed in to a mold 260 in which a foam article is produced, as is commonly known.
The operation of the system will now be described.
Isocyanate storage tank 40 is filled and the isocyanate is circulated through pipeline 260. Polyol storage tanks 135 are filled with a 1 0 polyol/pentane mixture and the selected additives (eg. colorants) are added to each tank 135. These mixtures are circulated through pipelines 265. Each plant may make parts in one of a series of standard colours. Thus, a tank 135 may be provided for each such colour.
Next, a dispensing machine 281 is selected. The 1 5 dispensing machine will generally be selected depending upon the molds with which it is associated and the parts which are to be produced. It will be appreciated that as each dispensing machine 281 is connected to a different pipeline 265, any selected mold 250 may be used to manufacture parts of any desired colour, simply by associating 2 0 the mold with the appropriate dispensing machine 281. If parts made of one colour have been made in one particular mold 250, and it is now desired to make the same parts but in a different colour in the same mold 250, then this change may be performed relatively easily by flushing out the mold 250, and associating it with a different 25 dispensing machine. Thus, the actual down time of any particular mold 250 may be minimized. Further, if it is desired to change the colour of foam which is produced by any particular dispensing machine 281, then the dispensing machine 281 and the coupling 305 are flushed, and coupling 305 is connected with a different pipeline 3 0 265.
When a dispensing machine 281 has been selected, and cleaned if required, the respective shut off valves 307 and 283 are opened and the isocyanate and the selected polyol/pentane mixture flow into the dispensing machine 281 where they may circulate out of contact with each other. The isocyanate and polyol/pentane mixtures 5 are then delivered to the dispensing head 300 associated with the dispensing machine 281 in a predetermined ratio.
The isocyanate and polyol/pentane mixtures come into contact while being discharged from the dispensing head in a predetermined ratio and quantity. These mixtures are immediately 1 0 thereafter dispensed into a mold 250 where foaming takes place, as shown by arrows A in Figure 2.
The dispensing head may then be moved so as to be associated with a different mold 250, where the procedure is repeated.
This can be accomplished by either maintaining the molds in a 1 5 stationary position and moving the dispensing head, or by maintaining the dispensing head in a stationary position and moving the molds into position one after another (for example on a carousel).
Each of these methods is well known.
By this method, any number of different molds may be 20 connected in circuit to simultaneously make the same or different articles of polyurethane foam in the same or different colours, simply be associating the mold with the appropriate dispensing machine and dispensing head. This method also allows great flexibility in manufacturing. For example, if one mold requires service, then the remaining molds may still be used to make parts. If necessary, the mold requiring service may be removed from the apparatus and replaced with a different mold. This switch over may be made with only minimal cleaning if the mold had been used to make different coloured parts.
As well, it is possible to use the same mold to make products of differing colours, simply by disassociating the mold with one dispensing machine and associating it with a different dispensing machine after flushing.
A further advantage of the system is that the polyol/pentane mixing equipment for an entire plant may be 5 contained within a single explosion proof room while allowing the production of a number of different polyurethane foam products simultaneously. Thus, construction costs may be minimized. The room should be constructed to prevent the possibility of an explosion.
In addition, the room should be designed so that, in the event of an 10 explosion, damage to the area will be minimized. Each of these construction techniques are well known in the art.
It will be obvious, however, that the isocyanate tanks 25 and 40 need not be located in an explosion proof surrounding, as the isocyanate and additives are typically not explosive. Under normal 15 circumstances, if desired, the tanks 25 and 40 may be located in a separate, non-explosion proof room.
The polyol/pentane mixture in tanks 135 is preferably maintained at a temperature between about 15~C and about 22~C, and more preferably at about room temperature (between about 17~C and 2 0 about 20 ~C). If the temperature is maintained lower than about 15~C
then the polyol difficult to pump because of its increased viscosity.
Therefore, it is desirable to cool the polyol/pentane mixtures during warm seasons.
The system may be cooled in any known manner, such as 25 tanks encased in cooling jackets, heat exchangers on the pipes to remove excess heat during circulation, cooling means in the storage tanks, or through air conditioning the entire room in which the mixing and storage tanks are located (ie. the tank farm). Preferably, the system is cooled by air conditioning the room in which tanks 135 are 3 0 housed. Preferably, this room is maintained at a temperature between about 15~C and about 22~C and more preferably between about 17~C
218151~
.
and about 20 ~C.
It will be appreciated that various changes may be made within the spirit of the described invention, and all such changes are within the scope of the invention. The method may be used in 5 association with any molding machines known in the art and the reactants may be mixed together at the molding machine in manner known in the art.
Claims (23)
1. A method for making polyurethane foam products from isocyanate, a polyol and a foaming agent comprising:
a. producing a plurality of mixtures of the polyol and the foaming agent in a first area;
b. circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molding means in a second area;
c. providing the isocyanate to said plurality of molding means positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molding means in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
a. producing a plurality of mixtures of the polyol and the foaming agent in a first area;
b. circulating each of the mixtures of the polyol and the foaming agent from the first area to a plurality of molding means in a second area;
c. providing the isocyanate to said plurality of molding means positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molding means in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
2. The method as claimed in claim 1 wherein said isocyanate is stored in a first storage means located in said first area and said isocyanate is circulated from said storage means to said molding means.
3. The method as claimed in claim 1 wherein said foaming agent is a lower alkane and said first area is constructed to withstand an explosion.
4. The method as claimed in claim 1 wherein each of said mixtures of the polyol and the foaming agent are individually stored in said first area in a second storage means and at least one additive is combined with each of said mixtures in said second storage means.
5. The method as claimed in claim 4 wherein each of said second storage means includes mixing means to maintain a uniform mixture of the polyol, the foaming agent and the at least one additive.
6. The method as claimed in claim 5 wherein said additives comprise colorants.
7. The method as claimed in claim 1 wherein each of said mixtures is individually circulated between said first area and said second area by pipe means, each of said pipe means defining a continuous circuit.
8. The method as claimed in claim 4 wherein each of said mixtures is individually circulated between said second storage means and said second area by pipe means extending in a continuous circuit from said second storage means to said second area and back to said second storage means.
9. The method as claimed in claim 4 wherein said isocyanate is stored in a first storage means located in said first area and said isocyanate is individually circulated between said first storage means and said second area by first pipe means extending in a continuous circuit from said first storage means to said second area and back to said first storage means and each of said mixtures is individually circulated between said second storage means and said second area by second pipe means extending in a continuous circuit from said second storage means to said second area and back to said second storage means.
10. The method as claimed in claim 1 wherein the temperature of said second mixtures is maintained below about 22°C
by cooling.
by cooling.
11. The method as claimed in claim 10 wherein the temperature of the ambient air in said first area is maintained at about room temperature.
12. The method as claimed in claim 11 wherein said ambient air is maintained by air conditioning means.
13. A method for making polyurethane foam products from isocyanate, a polyol and a lower alkane foaming agent comprising:
a. passing the polyol and the foaming agent through pump means to produce a mixture of the polyol and the foaming agent and introducing said mixture into a plurality of first storage means, said plurality of first storage means being positioned in a first area;
b. combining at least one additive with each of said mixtures;
c. circulating each of said mixtures from the first area to a plurality of molding means in a second area;
d. providing the isocyanate to said plurality of molding means positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molding means in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
a. passing the polyol and the foaming agent through pump means to produce a mixture of the polyol and the foaming agent and introducing said mixture into a plurality of first storage means, said plurality of first storage means being positioned in a first area;
b. combining at least one additive with each of said mixtures;
c. circulating each of said mixtures from the first area to a plurality of molding means in a second area;
d. providing the isocyanate to said plurality of molding means positioned in a second area whereby a number of different polyurethane foam products of differing characteristics may be produced simultaneously by delivering the isocyanate, polyol and the foaming agent to said molding means in a second area and allowing the isocyanate, polyol and foaming agent to react therein.
14. The method as claimed in claim 13 wherein said isocyanate is stored in a second storage means located in said first area and said isocyanate is circulated from said second storage means to said molding means.
15. The method as claimed in claim 13 wherein said first area is constructed to explosion proof engineering standards.
16. The method as claimed in claim 13 wherein each of said mixtures of the polyol, the foaming agent and said at least one additive are individually stored in said first area in a first storage means and each of said first storage means includes mixing means to maintain a uniform mixture of the polyol, the foaming agent and said at least one additive.
17. The method as claimed in claim 16 wherein said additives comprise colorants.
18. The method as claimed in claim 16 wherein each of said mixtures is individually circulated between said first storage means and said second area by pipe means extending in a continuous circuit from said first storage means to said second area and back to said first storage means.
19. The method as claimed in claim 16 wherein said isocyanate is stored in a second storage means located in said first area and said isocyanate is individually circulated between said second storage means and said second area by first pipe means extending in a continuous circuit from said second storage means to said second area and back to said second storage means and each of said mixtures is individually circulated between said first storage means and said second area by second pipe means extending in a continuous circuit from said first storage means to said second area and back to said first storage means.
20. The method as claimed in claim 13 wherein the temperature of said second mixtures is maintained below about 22°C
by cooling.
by cooling.
21. The method as claimed in claim 13 wherein the temperature of the ambient air in said first area is maintained at about room temperature.
22. The method as claimed in claim 21 wherein said ambient air is maintained by air conditioning means.
23. The method as claimed in claim 13 wherein said first storage means are connected to a source of inert gas to maintain an inert atmosphere in said first storage means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2181514 CA2181514A1 (en) | 1996-07-18 | 1996-07-18 | Process to make polyurethane foam products |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2181514 CA2181514A1 (en) | 1996-07-18 | 1996-07-18 | Process to make polyurethane foam products |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2181514A1 true CA2181514A1 (en) | 1998-01-19 |
Family
ID=4158632
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2181514 Abandoned CA2181514A1 (en) | 1996-07-18 | 1996-07-18 | Process to make polyurethane foam products |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2181514A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102558831A (en) * | 2011-10-22 | 2012-07-11 | 上海华篷防爆科技有限公司 | Organic barrier and explosion-proof material and preparation method for same |
| CN106738416A (en) * | 2016-12-30 | 2017-05-31 | 武汉正为机械有限公司 | Polyurathamc raw material is from dispensing mixing arrangement and mixed method |
-
1996
- 1996-07-18 CA CA 2181514 patent/CA2181514A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102558831A (en) * | 2011-10-22 | 2012-07-11 | 上海华篷防爆科技有限公司 | Organic barrier and explosion-proof material and preparation method for same |
| CN106738416A (en) * | 2016-12-30 | 2017-05-31 | 武汉正为机械有限公司 | Polyurathamc raw material is from dispensing mixing arrangement and mixed method |
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