JP7526106B2 - Mixing device and method for producing foam - Google Patents

Description

The present invention relates to a mixing device for mixing a blowing agent into a liquid, and a method for producing a foam by mixing a blowing agent into a liquid.

Conventionally, a widely known construction method is to mix polyol and isocyanate on-site onto the roof, wall, floor, etc. of a building or structure, and spray the mixture to foam, thereby forming polyurethane foam. The froth method is a widely known method of constructing polyurethane foam. In the froth method, for example, a blowing agent flow path connected to a liquid flow path for supplying polyol is provided, and a mixing device is generally used that mixes a blowing agent such as carbon dioxide from a tank or the like into the polyol in the liquid flow path via the blowing agent flow path. The polyol mixed with a blowing agent such as carbon dioxide in the mixing device is further mixed with isocyanate and then sprayed outside.

In general, the polyol is supplied under pressure to the liquid flow path of the mixing device, and the foaming agent can be stably mixed with the polyol by supplying the foaming agent to the liquid flow path after being pressurized to a pressure higher than that of the polyol in the liquid flow path.
Patent Document 1 shows a mixing device for mixing a foaming agent with a liquid such as polyol, which has a foaming agent pump connected to a foaming agent flow path and an on-off valve provided in the foaming agent flow path. In Patent Document 1, the discharge amount of the foaming agent pump is controlled to a predetermined value so that the pressure in the foaming agent flow path is higher than the pressure in the liquid flow path, and the on-off valve is opened when the pressure in the foaming agent flow path is higher than the pressure in the liquid flow path. Therefore, the pressure on the foaming agent flow path side decreases when the valve is opened, but the pressure decrease is prevented by the discharge of the foaming agent from the foaming agent pump. Therefore, even if a liquid such as polyol is supplied to the liquid flow path by a pulsating pump and a pressure change occurs due to pulsation, the foaming agent can be stably supplied to the liquid flow path.

JP 2016-78304 A

The pressure of the liquid in the liquid flow path of the foaming device may fluctuate due to external factors other than pulsation, such as the ambient temperature and spray conditions. However, the mixing device of Patent Document 1 may not be able to respond to pressure fluctuations other than pulsation and may not be able to stably supply the foaming agent to the liquid flow path. Furthermore, in order to stably supply the foaming agent, the mixing device of Patent Document 1 needs to be provided with a foaming agent pump and the discharge volume of the foaming agent pump needs to be controlled to a predetermined value, which makes the configuration of the mixing device complex.

Therefore, an object of the present invention is to provide a mixing device and a method for producing a foam that can stably supply a foaming agent to a liquid flowing through a liquid flow path with a simple device configuration, even if the pressure in the liquid flow path fluctuates due to external factors such as temperature and spraying conditions.
Another object of the present invention is to provide a mixing device and a method for producing a foam that are capable of supplying a foaming agent to a liquid flowing through a liquid flow passage without using a foaming agent pump.

The present invention relates to the following items [1] to [9].
[1] A mixing device for mixing a foaming agent with a liquid flowing through a liquid flow path, comprising:
a foaming agent container for containing the foaming agent;
a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows and supplies the foaming agent to a liquid flow path;
a pressure adjusting device provided in the foaming agent flow path and configured to adjust a supply pressure of the foaming agent to the liquid flow path;
and a pressure control means for controlling the pressure adjusting device based on the pressure detected in the liquid flow path so that the supply pressure is higher than the pressure in the liquid flow path.
[2] The mixing device according to the above [1], further comprising at least one heater selected from the group consisting of a foaming agent container heater for heating the foaming agent container and a flow path heater for heating the foaming agent flow path.
[3] The mixing device according to any one of the above [1] or [2], wherein the control means controls the pressure regulating device so that the supply pressure of the foaming agent is 0.4 MPa or more higher than the pressure in the liquid flow path.
[4] A mixing device for mixing a foaming agent with a liquid flowing through a liquid flow path, comprising:
a foaming agent container for containing the foaming agent;
a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows and supplies the foaming agent to a liquid flow path;
a foaming agent container heater for heating the foaming agent container;
The mixing device is configured to heat a foaming agent by the heater and supply the foaming agent in a pressurized state to the liquid flow path.
[5] The mixing device according to the above [4], wherein the supply pressure of the foaming agent to the liquid flow path is higher than the pressure within the liquid flow path.
[6] The mixing apparatus according to any one of the above [1] to [5], wherein the foaming agent is carbon dioxide.
[7] The mixing device according to any one of the above [1] to [6], further comprising a supply amount adjustment means provided in the foaming agent flow path and adjusting the amount of the foaming agent supplied to the liquid flow path.
[8] A method for producing a foam by mixing a foaming agent with a liquid flowing through a liquid flow path, comprising the steps of:
supplying the foaming agent from a foaming agent container containing the foaming agent to the liquid flow path through a foaming agent flow path;
a pressure adjusting device provided in the foaming agent flow path that adjusts the supply pressure of the foaming agent to the liquid flow path, and based on the pressure detected in the liquid flow path, the pressure adjusting device is controlled so that the supply pressure is higher than the pressure in the liquid flow path.
[9] A method for producing a foam by mixing a foaming agent with a liquid flowing through a liquid flow path, comprising the steps of:
A method for producing a foam, comprising heating and pressurizing the foaming agent supplied to the liquid flow path, and adjusting the supply pressure of the foaming agent to the liquid flow path so that it is higher than the pressure within the liquid flow path.

In the present invention, by providing the mixing device with a predetermined pressure regulating device and pressure control means, even if the pressure in the liquid flow path fluctuates due to external factors such as temperature and spraying conditions, the foaming agent can be stably supplied to the liquid flowing through the liquid flow path with a simple device configuration.
In another aspect of the present invention, a heater is provided in the mixing device to heat and pressurize the foaming agent, making it possible to supply the foaming agent to the liquid flowing through the liquid flow path without using a foaming agent pump.

FIG. 1 is a schematic diagram showing a mixing device according to one embodiment of the present invention. FIG. 1 is a schematic diagram showing a foaming device according to one embodiment of the present invention. 10 is a flowchart showing the procedure of a preparation step before a foaming agent is caused to flow into a liquid flow path. 5 is a flowchart showing a pressure control routine executed by the pressure control means when a foaming agent is mixed into a liquid. FIG. 13 is a schematic diagram showing a modified example of a mixing device according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
1 shows a mixing device 10 according to one embodiment of the present invention. The mixing device 10 is a device for mixing a blowing agent E into a liquid L1.

(liquid)
The liquid L1 is not particularly limited, but is preferably a foam raw material that is a raw material for a foam. The mixing device 10 can produce a foam by mixing the foam raw material liquid L1 with a blowing agent E. Examples of the foam include polyurethane foam, phenol foam, and polystyrene foam. Therefore, the liquid L1 may be any material that can be used as a raw material for these foams. Among the above-mentioned foams, polyurethane foam is preferable from the viewpoints of ease of production, curing speed, and foamability. Furthermore, it is more preferable that the polyurethane foam is a rigid polyurethane foam. By using a rigid polyurethane foam, the self-adhesiveness, heat insulation, mechanical strength, and the like are likely to be good.

A urethane resin composition for forming a polyurethane foam is generally prepared by mixing a first liquid containing a polyol and a second liquid containing a polyisocyanate. The urethane resin composition is foamed and cured by a blowing agent E mixed into the composition to form a polyurethane foam. The blowing agent E may be mixed into either the first liquid or the second liquid, but is preferably mixed into the first liquid from the viewpoint of stability and the like. That is, the mixing device 10 preferably mixes a gaseous blowing agent E into a liquid (first liquid or second liquid) containing either a polyol or a polyisocyanate, but more preferably mixes the blowing agent E into a liquid (first liquid) containing a polyol.
The liquid (first liquid) containing a polyol is preferably a polyol composition containing a curing catalyst and a foam stabilizer in addition to the polyol, and generally further contains a foaming agent. The foaming agent previously contained in the first liquid (polyol composition) in this way is also called an "internal foaming agent" to distinguish it from the above-mentioned foaming agent E.
In addition to the curing catalyst, foam stabilizer, and water, the polyol composition may contain various additives such as a flame retardant (a solid flame retardant, a liquid flame retardant), an antioxidant, a heat stabilizer, a metal damage inhibitor, an antistatic agent, a crosslinking agent, a lubricant, a softener, and a pigment.

(Foaming Agent)
The internal blowing agent is not particularly limited, and hydrofluoroolefins (HFO), hydrofluorocarbons (HFC), hydrocarbons, diethyl ether, etc. can be used. Examples of the hydrofluoroolefins (HFOs) used as the internal blowing agent include fluoroalkenes having about 3 to 6 carbon atoms, preferably 3 or 4 carbon atoms, and more preferably 3 carbon atoms. The hydrofluoroolefins may be hydrochlorofluoroolefins having chlorine atoms. Examples of the hydrofluorocarbons (HFCs) include hydrofluorocarbons having about 1 to 4 carbon atoms, and the hydrofluorocarbons may have chlorine atoms. Examples of the hydrocarbons include hydrocarbons having 2 to 5 carbon atoms. As the hydrocarbons having 2 to 5 carbon atoms, hydrocarbons having 3 or 4 carbon atoms are preferable, and LPG mainly composed of propane and butanes can also be used.

On the other hand, the foaming agent E may be any foaming agent that can be used for foaming by the froth method, and may be a foaming agent that becomes a gas at room temperature (23°C) and normal pressure (1 atm), and preferably has a boiling point of less than 0°C at normal pressure. The foaming agent E is not particularly limited, but examples thereof include hydrofluoroolefin (HFO) and carbon dioxide. In the froth method, foaming agent E, which becomes a gas at room temperature and normal pressure, is mixed with a foam raw material such as a liquid (one-liquid) containing polyol to foam the mixture. In addition, the liquid containing polyol generally contains a foaming agent (internal foaming agent) in advance, and in such a case, foaming agent E functions as a foaming assistant to improve foaming properties and workability.

In the present invention, it is preferable to use carbon dioxide as the foaming agent E. Carbon dioxide can be put into a supercritical or subcritical state at relatively low pressure and temperature, as described below. Therefore, foaming agent E can be easily mixed into liquid L1 in a supercritical or subcritical state by pressurizing and heating as described below, thereby improving the mixability with liquid L1. In addition, the use of carbon dioxide reduces the environmental impact.

(Liquid flow path)
A liquid pump 40 is connected to the liquid flow path 30, and the liquid L1 is caused to flow through the liquid flow path 30 by the liquid pump 40. The liquid L1 caused to flow through the liquid flow path 30 is caused to flow in a state pressurized to the discharge pressure. A liquid flow path pressure gauge 31 is connected to the liquid flow path 30, and the pressure inside the liquid flow path 30 is detected by the liquid flow path pressure gauge 31.

The liquid pump 40 may be either a pulsating pump or a non-pulsating pump. It is preferable that the liquid pump 40 is a fixed-volume pump that delivers a fixed amount of liquid L1. When a pulsating pump is used as the liquid pump 40, the pressure in the liquid flow path 30 fluctuates periodically in accordance with the pulsation.

[Mixing device]
The mixing device will now be described in more detail.
The mixing device 10 comprises a foaming agent container 11 that contains a foaming agent E, a foaming agent flow path 12 that flows the foaming agent E supplied from the foaming agent container 11 and supplies the foaming agent E to a liquid flow path 30, a pressure adjustment device 13 that is provided in the foaming agent flow path 12 and adjusts the supply pressure of the foaming agent E to the liquid flow path 30, and a pressure control means 14 that controls the pressure adjustment device 13.
The mixing device 10 also includes heaters such as a foaming agent container heater 21 and a flow path heater 22. The mixing device 10 pressurizes the foaming agent E by heating it with the heaters, and thereby supplies the foaming agent E in a pressurized state to the liquid flow path 30.

A pressure-resistant container is used as the foaming agent container 11, and for example, a known gas cylinder may be used. It is preferable to use a foaming agent container 11 that does not have a siphon tube. By using a container without a siphon tube, when the foaming agent E is carbon dioxide, the foaming agent E is easily discharged from the foaming agent container 11 in a gaseous state or in a subcritical or supercritical state.

The foaming agent container 11 may store the foaming agent E in a pressurized state. The mixing device 10 also includes a foaming agent container heater 21 for heating the foaming agent container 11, and the foaming agent container 11 is heated by the foaming agent container heater 21. The internal pressure of the foaming agent container 11 increases when it is heated.

A container pressure regulator 28 capable of adjusting the primary pressure is provided at the supply port of the foaming agent container 11. The container pressure regulator 28 is, for example, a pressure adjustment valve. The primary pressure is the pressure of the foaming agent E supplied from the foaming agent container 11 to the foaming agent flow path 12, and is also the pressure inside the upstream flow path 12A described below.

As described above, the foaming agent flow path 12 is a path that supplies the foaming agent E from the foaming agent container 11 to the liquid flow path 30. A pressure adjustment device 13 is provided midway along the foaming agent flow path 12. In this embodiment, an on-off valve 23 is provided upstream of the pressure adjustment device 13 in the foaming agent flow path 12. When the on-off valve 23 is opened, the foaming agent E is supplied from the foaming agent container 11 to the liquid flow path 30 via the foaming agent flow path 12.

The pressure regulator 13 regulates the pressure of the downstream flow path 12B (also referred to as "secondary pressure"). The downstream flow path 12B means the flow path downstream of the pressure regulator 13 (on the liquid flow path 30 side) of the foaming agent flow path 12. The downstream flow path 12B is connected to the liquid flow path 30. Therefore, the supply pressure of the foaming agent E to the liquid flow path 30 is regulated by regulating the secondary pressure of the downstream flow path 12B. The pressure regulator 13 is, for example, a pressure regulation valve. The pressure regulation valve can regulate the secondary pressure of the downstream flow path 12B by adjusting its opening degree. The pressure regulator 13 can lower the pressure (secondary pressure) of the downstream flow path 12B to be lower than the pressure (primary pressure) of the upstream flow path 12A. The upstream flow path 12A means the flow path upstream of the pressure regulator 13 (on the foaming agent container 11 side) of the foaming agent flow path 12. The secondary pressure is higher than the pressure inside the liquid flow path 30.
Here, since the downstream flow path 12B is connected to the liquid flow path 30 as described above, the internal pressure is likely to fluctuate due to pressure fluctuations in the liquid flow path 30. However, by adjusting the secondary pressure using the pressure adjustment device 13, the pressure fluctuations can be minimized.

The pressure control means 14 receives the pressure (detected pressure) inside the liquid flow path 30 detected by the liquid flow path pressure gauge 31. The pressure control means 14 controls the pressure adjustment device 13 based on the input detected pressure to adjust the supply pressure to a control target value. Specifically, the pressure adjustment device 13 is controlled so that the supply pressure is higher than the pressure (detected pressure) inside the liquid flow path 30. Note that the pressure (secondary pressure) in the downstream flow path 12B is substantially constant, and the supply pressure is adjusted by the control of the pressure adjustment device 13.
In this embodiment, the supply pressure is made higher than the pressure of the liquid L1 flowing through the liquid flow path 30, so that the foaming agent E can be mixed stably with the liquid L1 flowing through the liquid flow path 30.

The pressure control means 14 may be configured as a known control device equipped with a CPU (microprocessor), memory, input ports, output ports, etc., and may be configured as a personal computer, etc.

In this embodiment, the supply pressure (i.e., the secondary pressure) is higher than the pressure in the liquid flow path 30, and the pressure adjustment device 13 is preferably controlled so that the difference is 0.4 MPa or more. When the supply pressure is 0.4 MPa or more higher than the pressure in the liquid flow path 30, the foaming agent E in a high-pressure gas state or in a subcritical or supercritical state as described below can be appropriately mixed with the liquid L1 flowing in the liquid flow path 30. Furthermore, even if the pressure of the liquid L1 flowing in the liquid flow path 30 fluctuates, the supply pressure is reliably higher than the pressure in the liquid flow path 30, and stable mixing can be performed.
From the above viewpoint, it is more preferable that the difference between the supply pressure and the pressure inside the liquid flow path 30 is controlled to be 0.8 MPa or more.

The difference between the supply pressure and the pressure in the liquid flow path 30 is preferably controlled to 2.5 MPa or less, and more preferably to 2.0 MPa or less. In this way, by not making the supply pressure higher than necessary compared to the pressure in the liquid flow path 30, it is possible to prevent the pressure in the foaming agent flow path 12 from becoming too high.

The pressure within the liquid flow path 30 may fluctuate periodically in accordance with the pulsation of the liquid pump 40, but the supply pressure only needs to be greater than the maximum pressure caused by the pulsation, and the difference from that maximum pressure needs to be within the above-mentioned range.
That is, when the pressure detected by the liquid flow path pressure gauge 31 changes periodically, the detected pressure referred to by the pressure control means 14 is preferably a maximum value, or may be an average value of two or more maximum values. Of course, even when the pressure detected by the liquid flow path pressure gauge 31 does not change periodically, the detected pressure referred to by the pressure control means 14 may be an average value of two or more measured pressures.

The primary pressure in the upstream flow path 12A is higher than the internal pressure of the downstream flow path 12B. The primary pressure of the upstream flow path 12A is not particularly limited, but is preferably 0.4 MPa or more higher than the supply pressure (secondary pressure), and more preferably 0.8 MPa or more higher. In this way, the pressure (primary pressure) of the upstream flow path 12A is sufficiently higher than the pressure (secondary pressure) of the downstream flow path 12B, making it easier to adjust the secondary pressure (i.e., supply pressure) to a desired value.

The mixing device 10 is equipped with a flow path heater 22 that heats the foaming agent flow path 12, and the foaming agent flow path 12 is heated by the flow path heater 22. By being heated by the flow path heater 22, the foaming agent E inside the foaming agent flow path 12 is prevented from being cooled by heat loss from the outside, and the temperature inside the foaming agent flow path 12, as well as the primary pressure and secondary pressure, are maintained within a predetermined range.

The foaming agent E in the foaming agent flow path 12 is heated and pressurized, and flows in a high-pressure gas state (i.e., a state in which the pressure is higher than the pressure in the liquid flow path 30 by a predetermined amount or more) or in a subcritical or supercritical state through the foaming agent flow path 12. In this way, the foaming agent E in a high-pressure gas state or in a subcritical or supercritical state is easily mixed with the liquid L1 in the liquid flow path 30.
However, from the viewpoint of mixability with the liquid L1, the foaming agent E is preferably in a subcritical or supercritical state when mixed with the liquid L1. Therefore, the foaming agent E1 is preferably in a subcritical or supercritical state in both the upstream flow path 12A and the downstream flow path 12B of the foaming agent flow path 12.

The foaming agent E inside the foaming agent flow path 12 may be heated so that both the upstream flow path 12A and the downstream flow path 12B have a temperature within a predetermined temperature range, and more specifically, may be heated so that the temperature remains within a predetermined temperature range after being discharged from the foaming agent container 11 until it is mixed into the liquid flow path 30.
Therefore, it is preferable that the flow path heater 22 heats both the upstream flow path 12 A and the downstream flow path 12 B. Moreover, the flow path heater 22 may be disposed, for example, so as to surround the pipes constituting each of the upstream flow path 12 A and the downstream flow path 12 B, and is preferably disposed so as to heat the entire foaming agent flow path 12 (the upstream flow path 12 A and the downstream flow path 12 B).
The flow path heater 22 is not particularly limited, and may be configured with a thermocouple or the like, or may be configured with a heat medium type heater that performs heating by circulating a heat medium inside.

The foaming agent flow path 12 is further provided with a supply amount adjustment means 15 for adjusting the supply amount of the foaming agent E to the liquid flow path 30. For example, a mass flow controller is used as the supply amount adjustment means 15. The supply amount adjustment means 15 is provided downstream of the pressure adjustment device 13 (i.e., the downstream flow path 12B). The supply amount adjustment means 15 measures the mass per unit time of the foaming agent E passing through the foaming agent flow path 12, and adjusts the mass per unit time of the foaming agent E passing through the foaming agent flow path 12 based on the measured value, so that the mass per unit time of the foaming agent E passing through the foaming agent flow path 12 becomes a predetermined amount (control target value). The supply amount adjustment means 15 adjusts the mass per unit time of the foaming agent E passing through the supply amount adjustment means 15, for example, by adjusting the opening degree.
The control target value may be set according to the set supply amount of liquid L1 of liquid pump 40, and may be input manually or the like to supply amount adjustment means 15. In addition, with respect to downstream flow path 12B, the portion upstream of supply amount adjustment means 15 may be referred to as flow path 12C, and the portion downstream of supply amount adjustment means 15 may be referred to as flow path 12D.

In this embodiment, by using a mass flow controller (supply amount adjustment means 15) in addition to the pressure adjustment device 13, the foaming agent E supplied from the foaming agent container 11 is supplied to the liquid L1 flowing through the liquid flow path 30 after the pressure and mass per unit time are adjusted to predetermined values, so that the foaming agent E is mixed into the liquid L1 in a stable and accurate supply amount.
The amount of foaming agent E supplied to the liquid flow path 30 per unit time is preferably 0.05 to 1.5%, more preferably 0.08 to 1.0%, and even more preferably 0.10 to 0.50%, by mass relative to the amount of liquid L1 flowing through the liquid flow path 30 supplied per unit time. By keeping the amount of foaming agent E supplied within the above range, it becomes possible to include an appropriate amount of foaming agent in the polyol or the like, and the polyurethane foam can be appropriately foamed.

Further, a foaming agent supply valve 29 is provided in the downstream flow path 12B. The foaming agent supply valve 29 is a valve that controls the supply of the foaming agent E from the foaming agent flow path 12 to the liquid flow path 30. When opened, the foaming agent supply valve 29 supplies the foaming agent E from the foaming agent flow path 12 to the liquid flow path 30, and when closed, stops the supply of the foaming agent E to the liquid flow path 30. The foaming agent supply valve 29 is configured, for example, with a solenoid valve. The foaming agent supply valve 29 is opened in conjunction with the supply of the liquid L1 from the liquid pump 40, whereby the foaming agent E is appropriately mixed into the liquid L1.
When the liquid pump 40 is a pulsating pump, the foaming agent supply valve 29 is preferably opened and closed in accordance with the timing of the suction and discharge of the liquid.

The mixing device 10 further includes a foaming agent flow path pressure gauge for measuring the pressure in the foaming agent flow path 12. In this embodiment, an upstream flow path pressure gauge 25A and a downstream flow path pressure gauge 25B are provided in the upstream flow path 12A and the downstream flow path 12B, respectively. By providing the upstream flow path pressure gauge 25A and the downstream flow path pressure gauge 25B, it can be confirmed whether the primary pressure and the secondary pressure (supply pressure) in the foaming agent flow path 12 are controlled to the set pressures.
In the mixing device 10, the pressure detected by the downstream flow path pressure gauge 25B (detected pressure) is input to the pressure control means 14. The pressure control means 14 controls the pressure adjustment device 13 based on the input detected pressure so that the supply pressure becomes a control target value.

In addition, a safety valve may be attached to the foaming agent flow path 12. For example, first and second safety valves 26A, 26B may be attached to the upstream flow path 12A and the downstream flow path 12B, respectively. The first and second safety valves 26A, 26B are, for example, open valves that open when the pressure inside the upstream flow path 12A and the downstream flow path 12B exceeds a certain value, thereby preventing the pressure inside the upstream flow path 12A and the downstream flow path 12B from exceeding a certain value. This prevents the mixing device 10 from being damaged due to an abnormality occurring in the mixing device 10 causing the inside of the foaming agent flow path 12 to be overpressurized beyond the design pressure.

Furthermore, a check valve 27 may be provided in the flow path 12D. The check valve 27 is disposed near the junction of the flow path 12D with the liquid flow path 30. The check valve 27 is a valve that allows the foaming agent E to flow from the foaming agent flow path 12 side to the liquid flow path 30 side, but prevents the flow of fluid in the opposite direction. The check valve 27 may be a valve that opens when the pressure on the upstream side in the flow path 12D is equal to or greater than the pressure on the liquid flow path 30 side, and closes when the pressure on the upstream side is lower than the pressure on the liquid flow path 30 side. The check valve 27 prevents the liquid L1 flowing through the liquid flow path 30 from flowing back into the foaming agent flow path 12.

(Foaming device)
2 shows an embodiment of a foaming device including the above-mentioned mixing device 10. The foaming device 50 in this embodiment is a device for forming polyurethane foam. As described above, the polyurethane foam is preferably a rigid polyurethane foam. The foaming device 50 is an on-site foaming device that is brought to a construction site where the polyurethane foam is to be constructed, and is a device for forming the polyurethane foam at the construction site.

In addition to the mixing device 10, the foaming device 50 further includes the above-mentioned liquid flow path 30 (hereinafter also referred to as the first liquid flow path 30) and liquid pump 40 (hereinafter also referred to as the first liquid pump 40). The foaming device 50 also includes a second liquid flow path 35 through which liquid L2 separate from the above-mentioned liquid L1 flows, and a second liquid pump 45 that delivers liquid L2 to the second liquid flow path 35. The first and second liquid pumps 40, 45 are connected to a liquid container such as a drum (not shown), and deliver the liquids L1, L2 sucked from the liquid container to the first and second liquid flow paths 30, 35, respectively.

As described above, polyurethane foam can be formed by mixing a first liquid containing a polyol and a second liquid containing a polyisocyanate, and foaming and curing the mixture. The liquid L1 flowed through the first liquid flow path 30 is one of the first liquid or the second liquid, and the liquid L2 flowed through the second liquid flow path 35 is the other of the first liquid or the second liquid. It is preferable that the liquid L1 is a first liquid containing a polyol and the liquid L2 is a second liquid containing a polyisocyanate.

The foaming device 50 includes a spray gun 51. The spray gun 51 includes a discharge section 51A and a mixing section 51B. In the mixing section 51B, the first and second liquid flow paths 30, 35 are joined. The first and second liquids flowing through the first and second liquid flow paths 30, 35 are mixed in the mixing section 51B, and the mixture (urethane resin composition) is sprayed from the discharge section 51A. At this time, the urethane resin composition may be sprayed onto the target surface such as the roof, wall, or floor of a building or structure. The sprayed urethane resin composition foams and hardens to become polyurethane foam. The polyurethane foam is used, for example, as a heat insulating material.

In the foaming device 50 described above, liquid L1, which is appropriately mixed with foaming agent E using the mixer 10, is used as the raw material for polyurethane foam, so polyurethane foam with good foaming and spraying properties can be formed.

Next, with reference to Figures 3 and 4, the method of mixing the foaming agent into the liquid in the mixing device of this embodiment will be described in more detail. Figure 3 is a flow chart showing the operating procedure of the preparation step before the foaming agent E is caused to flow into the liquid flow path 30. Below, the preparation step before the foaming agent E is caused to flow into the liquid flow path 30 will be described in detail, first with reference to Figure 3. Note that below, the pressure, temperature, etc. will be described using a specific example in which the foaming agent E is carbon dioxide, but if the foaming agent E is another substance, the pressure, temperature, etc. can be set according to the properties of that substance.

(Preparation process)
First, in the preparation step, the on-off valve 23 is closed, and the foaming agent container heater 21 and the flow path heater 22 are heated in step S1 to raise the internal temperature of the foaming agent container 11 and the internal temperature of the foaming agent flow path 12 to preferably 28 to 40° C. The internal pressure of the foaming agent container 11 increases as it is heated, and is preferably 7.5 to 14 MPa. By keeping the internal pressure of the foaming agent container 11 at 14 MPa or less and 40° C. or less, it is possible to prevent the safety plate of the gas cylinder from bursting due to overheating, causing the foaming agent E to be released to the outside of the container 11, thereby improving safety.
From these viewpoints, the internal pressure of the heated foaming agent container 11 is more preferably 8 to 12 MPa, and the temperature of the foaming agent E contained inside the foaming agent container 11 is more preferably 30 to 40°C.
Next, in step S2, the set pressure of the liquid pump 40 and the supply amount of the liquid L1 are determined, and the settings of the liquid pump 40 are changed to achieve the set pressure and supply amount. At this time, the set pressure of the liquid pump 40 is set so that the liquid L1 flows through the liquid flow path 30 at, for example, 5 to 9 MPa, preferably 5.5 to 7.5 MPa.

Then, in step S3, a control target value is set in the supply amount adjustment means 15. The control target value may be set, for example, manually. The control target value is a control target value related to the mass per unit time of the foaming agent E passing through the foaming agent flow path 12. As described above, the control target value is set to be, in mass proportion, preferably 0.05 to 1.5%, more preferably 0.08 to 1.0%, and even more preferably 0.10 to 0.50% of the supply amount per unit time of the liquid L1 flowing through the liquid flow path 30.

Next, in step S4, the pressure (primary pressure) of the foaming agent E supplied from the foaming agent container 11 to the foaming agent flow path 12 is adjusted to a predetermined pressure. Specifically, the pressure upstream of the on-off valve 23 is appropriately adjusted so that the primary pressure is preferably 7.5 to 14 MPa, more preferably 8 to 12 MPa, when the on-off valve 23 is opened. Usually, the container pressure adjusting device 28 is appropriately operated, and the foaming agent container 11 is heated, or the like, to adjust the pressure.
The preparation process is completed by carrying out the above steps S1 to S4. In the above description, steps S1 to S4 are carried out in sequence, but they do not have to be carried out in the above order and may be carried out in any order, or two or more steps may be carried out in parallel. For example, since it takes time to heat the foaming agent passage 12 and the foaming agent container 11, another step may be carried out while these are being heated.

After the above preparation steps, the foaming agent E is mixed into the liquid L1. Specifically, the on-off valve 23 is opened to supply the foaming agent E to the liquid flow path 30 through the foaming agent flow path 12, and the liquid pump 40 is driven to flow the liquid L1 into the liquid flow path. As described above, the pressure of the foaming agent E is adjusted by the pressure adjustment device 13 controlled by the pressure control means 14, and the mass per unit time of the foaming agent E passing through the foaming agent flow path 12 is adjusted by the supply amount adjustment means 15, before it is supplied to the liquid flow path 30.

(Pressure Control Routine)
A pressure control routine executed by the pressure control means 14 when the foaming agent E is mixed into the liquid L1 is shown in Fig. 4. Hereinafter, the pressure control method executed by the pressure control means 14 will be described in detail with reference to Fig. 4.
In this routine, first, in step S11, the pressure (detected pressure) of the liquid flow path 30 detected by the liquid flow path pressure gauge 31 is input, and then, in step S12, a control target value of the pressure adjustment device 13 is calculated based on the input detected pressure. Here, the control target value is set to a pressure higher than the detected pressure, and as described above, is set to be preferably 0.4 MPa to 2.5 MPa higher than the detected pressure, and more preferably 0.8 MPa to 1.5 MPa higher. Specifically, the control target value of the supply pressure of the foaming agent E to the liquid flow path 30 is preferably 5.5 to 10 MPa, and more preferably 6.5 to 8.5 MPa.
Next, in step S13, the opening degree of the pressure regulator 13 is adjusted to control the pressure regulator 13 so that the supply pressure (i.e., the secondary pressure downstream of the pressure regulator 13) becomes the above-mentioned control target value.

Then, in step S14, the pressure (secondary pressure) of the downstream flow path 12B detected by the downstream flow path pressure gauge 25B is input. In step S15, it is determined whether the detected secondary pressure matches the control target value, and if it is determined that it matches, it is assumed that the secondary pressure has been adjusted to the control target value and this routine is terminated. If it is determined in step S15 that it does not match the control target value, the process returns to step S13, and steps S13 to S15 are repeated until the secondary pressure is adjusted to the control target value.

The pressure control routine shown in FIG. 4 may be repeated as long as liquid L1 continues to be supplied from the liquid pump 40. In this way, by repeating this routine, the supply pressure can be adjusted to an appropriate value even if pressure fluctuations occur in the liquid flow path.

As described above, in this embodiment, by providing the pressure regulator 13 in the foaming agent flow path 12, the supply pressure can be adjusted while suppressing fluctuations in the supply pressure. Furthermore, the pressure regulator 13 is controlled by feedback control in the pressure control means 14 so that the supply pressure is higher than the pressure of the liquid flowing in the liquid flow path 30. Therefore, even if the pressure in the liquid flow path 30 fluctuates due to external factors, the foaming agent E can be stably supplied to the liquid L1. Furthermore, even if the foaming agent E is mixed with the liquid L1 as a high-pressure gas or in a subcritical or supercritical state, the foaming agent E can be appropriately mixed with the liquid L1.
The foaming agent flow path 12 and the foaming agent container 11 are heated by a heater. The foaming agent E supplied to the liquid flow path 30 is pressurized by being heated, and the pressure is increased or maintained at a certain pressure or higher, so that, as described above, the supply pressure of the foaming agent E to the liquid flow path 30 becomes higher than the pressure inside the liquid flow path 30. For example, when the foaming agent E is carbon dioxide or the like, the foaming agent can be easily mixed with the liquid L1 as a high-pressure gas or in a subcritical or supercritical state.
Furthermore, by providing a supply amount adjustment means 15 consisting of a mass flow controller or the like, not only the pressure but also the supply amount (mass per unit time) of the foaming agent E can be accurately adjusted before supplying the foaming agent E to the liquid L1, thereby enabling precise control of the amount of foaming agent E mixed with the liquid L1.
In addition, in the mixing device 10, a foaming agent pump for supplying the foaming agent E is not provided, and the supply of the foaming agent E is controlled by pressure control, so that the foaming agent E can be appropriately mixed into the liquid L1 with a simple configuration.

[Modification]
The embodiment described above is merely an example of the present invention, and various improvements and modifications are possible as long as the effects of the present invention are achieved.
For example, the mixing device 10 is provided with a supply amount adjustment means 15 configured with a mass flow controller, but in cases where there is no need to accurately control the amount of foaming agent to be mixed with the liquid L1, the supply amount adjustment means 15 may be omitted, or a supply amount adjustment means 15 configured with a device other than a mass flow controller may be provided.
In addition, in the above embodiment, the foaming agent E is supplied from the foaming agent container 11 to the foaming agent flow path 12 and further to the liquid flow path 30 without using a foaming agent pump, but the foaming agent E in the foaming agent container 11 may be supplied to the foaming agent flow path 12 and further to the liquid flow path 30 by increasing the pressure of the foaming agent E using a foaming agent pump.

Also, the foaming agent flow path pressure gauge (at least one of the upstream flow path pressure gauge 25A and the downstream flow path pressure gauge 25B) for measuring the pressure in the foaming agent flow path 12 may be omitted as appropriate. When the downstream flow path pressure gauge 25B is omitted, steps S14 and S15 are omitted in the pressure control routine shown in Fig. 4. That is, the pressure control in the pressure adjustment device 13 is performed without referring to the pressure detected by the downstream flow path pressure gauge 25B, but the supply pressure can be adjusted with a certain degree of accuracy.
Also, for example, in cases where the foaming agent E is other than carbon dioxide and there is no need to heat the foaming agent E, one or both of the container heater 21 and the flow path heater 22 may be omitted as appropriate. Furthermore, the on-off valve 23, the first and second safety valves 26A and 26B, the check valve 27, the container pressure adjusting device 28, the foaming agent supply valve 29, and the like may also be omitted as appropriate depending on the purpose.

In addition, as another aspect of the present invention, as shown in the above embodiment, the foaming agent E is heated and pressurized by a heater such as the foaming agent container heater 21 or the flow path heater 22, and the supply pressure of the foaming agent E to the liquid flow path 30 is adjusted to be higher than the pressure within the liquid flow path 30.
In another aspect, the pressure control means 14 and the pressure adjustment device 13 may be omitted. If these are omitted, the supply pressure of the foaming agent E cannot be controlled based on the pressure detected in the liquid flow path 30, but in cases where the pressure fluctuation in the pressurized liquid flow path 30 is small, the supply pressure of the foaming agent E can be increased to a predetermined pressure by heating the heater, and the supply pressure of the foaming agent E can be maintained at or above the predetermined pressure, thereby generally stabilizing the supply of the foaming agent E to the liquid flow path 30. In addition, the mixing device 10 may omit the pressure control means 14 and have the pressure adjustment device 13. If the pressure control means 14 is omitted, the supply pressure of the foaming agent E cannot be controlled based on the pressure detected in the fluid flow path 30, but the supply pressure of the foaming agent E can be adjusted, for example, by manually operating the pressure adjustment device 13.

Furthermore, in the above-mentioned another aspect, as long as the foaming agent E is heated by a heater and put into a pressurized state, so that the supply pressure of the foaming agent E to the liquid flow path 30 is made higher than the pressure within the liquid flow path 30, either the foaming agent container heater 21 or the flow path heater 22 may be omitted.
For example, even if the foaming agent container heater 21 is omitted, the foaming agent E can be pressurized inside the foaming agent flow path 12 by heating the foaming agent E using the flow path heater 22, thereby making the supply pressure of the foaming agent E to the liquid flow path 30 higher than the pressure inside the liquid flow path 30.
Similarly, even if the flow path heater 22 is omitted, the supply pressure of the foaming agent E to the liquid flow path 30 may be made higher than the pressure inside the liquid flow path 30 by sufficiently heating and pressurizing the foaming agent E with the foaming agent container heater 21. Furthermore, the flow path heater 22 may also be omitted when the outside air temperature is high.

Furthermore, as a modification of the above embodiment, the present invention may include a needle valve 32 between the foaming agent supply valve 29 and the check valve 27, as shown in FIG. 5. The pressure control routine described above has a time lag. It is desirable to have a flow rate restriction at the moment the foaming agent supply valve 29 is opened. By providing the needle valve 32, it is possible to prevent a pressure drop and ensure a stable supply of foaming agent E.

REFERENCE SIGNS LIST 10 Mixing device 11 Foaming agent container 12 Foaming agent flow path 12A Upstream flow path 12B Downstream flow path 13 Pressure adjustment device 14 Pressure control means 15 Supply amount adjustment means 21 Foaming agent container heater 22 Flow path heater 23 Opening/closing valve 25A Upstream flow path pressure gauge 25B Downstream flow path pressure gauge 26A, 26B First and second safety valves 27 Check valve 28 Container pressure adjustment device 29 Foaming agent supply valve 30 Liquid flow path (first liquid flow path)
31 Liquid flow path pressure gauge 32 Needle valve 35 Second liquid flow path 40 Liquid pump (first liquid pump)
45 Second liquid pump 50 Foaming device 51 Spray gun 51A Discharge section 51B Mixing section E Foaming agent L1, L2 Liquid

Claims (3)

A mixing device for mixing a foaming agent with a liquid flowing through a liquid flow path, comprising:
a foaming agent container for containing the foaming agent;
a foaming agent flow path through which the foaming agent supplied from the foaming agent container flows and supplies the foaming agent to a liquid flow path;
a container pressure adjusting device for adjusting the pressure of the foaming agent supplied from the foaming agent container to the foaming agent flow path;
a pressure adjusting device provided in the foaming agent flow path and configured to adjust a supply pressure of the foaming agent to the liquid flow path;
a supply amount adjusting means provided on a downstream side of the pressure adjusting device in the foaming agent flow path and adjusting the amount of the foaming agent supplied to the liquid flow path;
At least one of a foaming agent container heater for heating the foaming agent container and a flow path heater for heating the foaming agent flow path;
a foaming agent supply valve provided downstream of the supply amount adjustment means in the foaming agent flow path and configured to control the supply of the foaming agent from the foaming agent flow path to the liquid flow path,
the pressure regulating device is a pressure regulating valve,
The mixing device further comprises a pressure control means for controlling a pressure adjusting device based on the pressure detected in the liquid flow path so that the supply pressure becomes higher than the pressure in the liquid flow path. 2. The mixing device according to claim 1 , wherein the control means controls the pressure adjusting device so that the supply pressure of the foaming agent is at least 0.4 MPa higher than the pressure in the liquid flow path. 3. The mixing device according to claim 1 or 2, wherein the blowing agent is carbon dioxide.