JPH0410914A - Method for mixing foamable agent into resin material - Google Patents

Abstract

PURPOSE:To effect mixing efficiently, while the vaporization of a foaming agent is being restrained, by mixing a foamable agent, which is injected into a return pipe of a resin material circulation line, in said return pipe and in a resin material storage vessel in succession. CONSTITUTION:In a circulation line for circulating resin material 4 between a resin material storage vessel 3 and a resin material reaction injection molding device 20, a foamable agent is injected, from a cylinder 2, into a return pipe, through which the material 4 is returned to the vessel 3 from the device 20, so that the material 4 and the agent are primarily mixed by means of a first mixer 8 provided in the return pipe 1. Further, the material thus mixed is fed into the resin material in the vessel 3 to be secondarily mixed therein by mean of a second mixer 12. As a result, vaporization of the foamable agent is restrained, resulting in efficient mixing of the resin material and foamable agent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of mixing a blowing agent into a synthetic resin raw material and molding the mixture by reaction injection molding or the like.

(Prior Art) Conventionally, when foaming and molding synthetic resin raw materials such as polyurethane (hereinafter referred to as PU raw materials), Froncas is used as a foaming agent. Currently, the depletion of the ozone layer by FFCs and its negative effects on health have become a major issue internationally, and UNEP (United Nations Environment Program) organized the CC0L (Ozone Interchange Coordination Committee) and announced in March 1985 that In September 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was adopted. In accordance with the above two treaties, the Japanese government also
In May 1988, the ``Freon Control Law'' was enacted to regulate the production and use of fluorocarbons. The target Froncas are 5 types of Freon-1112113114115, and 19
Taking production and usage fees in 1986 as 100, in 1989 it was less than l 009, and in 1993 it was less than 80%,
It is scheduled to be reduced to less than 50% in 1998.

The main uses of Froncus are (1) for refrigerants, (2) for aerosols, (3) for foaming, and (4) for cleaning.
Regarding foaming, the objects to be used can be classified into (a) urethane foam and tb+ foamed polystyrene/foamed polyolefin.
12,114 are mainly used.

As a candidate for a substitute with a lower ozone depletion coefficient than these CFCs, ozone-22 is a promising candidate9.For example, in the case of ozone-22, (1) Ozone depletion when the ozone depletion power of CFC-11 is set to 1. The coefficient is 0.05 (2) Since the foaming efficiency is good, the usage fee is 17 of Freon-11.
3 is fine.

(3) Improve the appearance of foamed products.

There is an advantage.

Conventionally, when mixing and blending fluorocarbon gas as a blowing agent into synthetic resin raw materials such as polyurethane, as shown in FIG. It is blended by stirring and dissolving.

(Problem to be Solved by the Invention) However, in the above method, the introduced freon gas vaporizes as bubbles to the outside of the liquid 13 of the PtJ raw material 4, and is not sufficiently mixed and dissolved, so that it cannot be used as a blowing agent. It is difficult to blend Freon (especially Freon-22).

Most of the above-mentioned FFC substitutes have a low boiling point, so there is a lot of volatilization loss when mixed into synthetic resin raw materials, and the mixing efficiency is poor.
1'C, Freon-13 is -81'C, Freon-12Bl
has a boiling point of -4°C, and 7 o 7-142B has a boiling point of -10°C.

On the other hand, in urethane RIM molding (reaction injection molding) and the like, a method is adopted in which the raw material is constantly circulated between a storage tank and an injection device in order to prevent fluctuations in the temperature, viscosity, etc. of the foamed raw material. This circulation is carried out in a closed circuit that is not open to the outside air, so the Freon-22 is injected into the return path in this circuit, mixed by a mixer in the closed space of the path, and merged into the raw material circulation route. It is best to efficiently mix the blowing agent into the raw material by performing secondary stirring in the storage tank.The raw material immediately after the addition of Freon-22 has a high concentration of Freon, is unstable, and easily separates, so it should be mixed immediately into the storage tank. It is necessary to introduce the chlorofluorocarbon into a large amount of raw materials and perform secondary stirring to reduce the concentration of chlorofluorocarbons and stabilize the mixed state. Therefore, it is not appropriate to mix Freon-22 into the first half of the circulation circuit, that is, the circuit from the storage tank to the injection device. It is easy to separate inside the metering pump of the injection device and cause problems.

In view of the above-mentioned problems with the conventional method of mixing a blowing agent into a resin raw material, an object of the present invention is to provide a method that can suppress vaporization of the blowing agent and efficiently mix the blowing agent into a resin raw material. do.

(Means for solving the problem) In order to achieve the above object, the method of mixing a blowing agent into a resin raw material of the present invention circulates a resin raw material between a resin raw material storage container and a resin raw material reaction injection molding device. In the circulation circuit for this purpose, a foaming agent is injected into the return pipe that returns the resin raw material from the resin raw material reaction injection molding device to the resin raw material storage container, and the resin raw material and foam are foamed by the first mixer placed in the return pipe. This mixed raw material is introduced into the resin raw material in the resin raw material storage container, and is mixed secondarily in the resin raw material storage container by a second mixer.

(Function) According to the method of the present invention configured as described above, the blowing agent injected into the return pipe in the resin raw material circulation circuit is stirred and mixed in two stages: in the return pipe and in the resin raw material storage container. As a result, vaporization of the blowing agent is suppressed, and mixing of the blowing agent into the WJ fat raw material is performed efficiently.

(Example) Hereinafter, with reference to the drawings, an example of the method of foaming and mixing into a resin raw material of the present invention will be described.

Figure 1 shows an example of the configuration of an apparatus for carrying out the method of the present invention.
The PU raw material circulation return piping 1 of the equipment (1!! Fat raw material reaction injection molding apparatus) 20 is configured to carry out the process, and the fluorocarbon cylinder 2 is directly connected to the return piping 1.

A tank (resin raw material storage container) 3 is charged with a PU raw material 4 in which raw materials other than fluorocarbon, such as a polyol, a crosslinking agent, a catalyst, a foam stabilizer, etc. are already mixed. On this occasion,
The amount of PU raw material 4 is relative to the capacity of tank 3 - the more the better.
If possible, keep it full and pressurize the tank at least 1.5k.
g/al or more, for example, the raw material liquid temperature (usually 20 to 30
℃), the vapor pressure of Freon-22 in this example is 2
It is desirable to pressurize up to 7 kg/a# at 0°C. By doing this, vaporization of the introduced Freon can be prevented to some extent, and dissolution is ensured.

The amount of fluorocarbon is measured by the remaining amount in the fluorocarbon cylinder 2 or by the flowmeter 5. 14 is a scale for weighing the fluorocarbon cylinder 2. Freon is mixed in by opening and closing a valve 6 in the piping. The fluorocarbons that have passed through the valve 6 pass through the check valve 7 and are sent to the PU raw material circulation return pipe 1 at approximately 5 to 50 kz.
/al! The mixture is injected at a pressure of 1, and is immediately introduced into the tank 3 through a static mixer (first mixer) 8.

As shown in the cross section of FIG. 2, the static mixer 8 has a plurality of ah-shaped elements 9 arranged in a vibrator-like body, which are alternately twisted to the right and twisted in the opposite direction. In this static mixer 8, the PU raw material 4 and the fluorocarbon are rotated and flowed according to the element 9 and mixed. Figure 3 shows the state of this rotational flow.
11 indicates rotation in the right and left elements, respectively, and 11 indicates rotation in two elements. By passing through the static mixer 8, the PtJ raw material 4 and Freon are efficiently mixed and dissolved. The injection pressure of Freon is determined to be the optimum value depending on the viscosity of the PU raw material and the liquid temperature, but it is usually 5 to 1
50 kg/d is desirable, and the mixing ratio of Freon to the PU raw material at this time is 0.5 kg/d.
It is preferable to inject the chlorofluorocarbons at a ratio of 0.05 to 0.50, and it is more efficient to mix in a ratio larger than the target mixing ratio of chlorofluorocarbons (usually 3 to 20%).

The PU raw material circulation return pipe 1 is provided with a switching valve 15, and as shown in FIG.
The fluid is sent to the tank 3 through the flow control valve 15, and when no fluorocarbon is mixed in, the fluid is sent directly to the tank 3 through the switching valve 15. In addition, the tank 3 is equipped with a stirring agitator (second mixer) 12 driven by a motor, and by operating this stirring agitator 12 when Freon is mixed, further mixing and dissolution can be ensured. .

As another embodiment of the method of the present invention, in addition to the configuration of the above embodiment, a fifth blowing agent injection nozzle for injecting fluorocarbon is added.
By using such a blowing agent injection nozzle, a porous nozzle 16 as shown in the figure or a rotating nozzle 17 as shown in FIG. 6 may be inserted into the PU raw material ring return pipe 1. Mixing efficiency is further improved.

(Effect of Gyomei) As is clear from the above explanation, the method of mixing the blowing agent into the resin raw material of the present invention is based on the resin raw material storage container and the resin raw material container.
In the circulation circuit for circulating the resin raw material between the resin raw material reaction injection molding device and the resin raw material storage container, the foaming agent is injected into the return pipe where the resin raw material returns from the resin raw material reaction injection molding device to the resin raw material storage container. A resin raw material and a foaming agent are mixed together by a first mixer disposed inside the container, the mixed raw material is introduced into a resin raw material in a resin raw material storage container, and a second mixer is used in this resin raw material storage container to mix the resin raw material and a foaming agent. Since the blowing agent is configured to be mixed, the blowing agent is stirred and mixed in two stages in the return pipe and in the resin raw material storage container, and vaporization of the blowing agent is suppressed to efficiently mix the blowing agent with the resin raw material. can.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the configuration of an apparatus for implementing the method of mixing a blowing agent into resin raw materials of the present invention, Figure 2 (2) is a sectional view of a static mixer (first mixer), and Figure 2 (2) is a cross-sectional view of a static mixer (first mixer);
is a diagram showing the elements of the static mixer, FIG. 3 is an explanatory diagram showing the rotation of the raw material in the static mixer, and FIG. 4 is a diagram showing the flow of the raw material due to the operation of the switching valve.
a) is an explanatory diagram showing when fluorocarbons are mixed in, and (b) is an explanatory diagram showing when fluorocarbons are not mixed in. FIGS. 5 and 6 are perspective views showing a multi-hole nozzle and a rotating nozzle, respectively, in other embodiments of the present invention, and FIG. 7 1 is a diagram showing an example of the configuration of an apparatus for carrying out a conventional method of mixing a blowing agent into a tMk raw material. 1...PU raw material circulation return piping, 2...Freon cylinder, 3...tank (resin raw material storage container), 4...PU
Raw materials, 8... Static mixer (first mixer), 12
... Stirring agitator (second mixer), 20...
RIM equipment (resin raw material reaction injection molding equipment) Figure Figure Figure 3° tampf (lit 100% volume%) 20: RIM equipment S (#n dazzling repulsion/injection octavo equipment) procedure correction Letter (method) August 7, 1990

Claims (1)

[Claims] Of the circulation circuit for circulating the resin raw material between the resin raw material storage container and the resin raw material reaction injection molding device, a blowing agent is installed in the return pipe where the resin raw material returns from the resin raw material reaction injection molding device to the resin raw material storage container. is injected, the resin raw material and the blowing agent are mixed together by the first mixer disposed in the return pipe, the mixed raw material is introduced into the resin raw material in the resin raw material storage container, and the resin raw material is introduced into the resin raw material storage container. A method for mixing a blowing agent into a resin raw material, characterized in that secondary mixing is performed by a second mixer.