JPS6121813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reaction injection molding method,
In particular, it relates to reaction injection molding processes using runners in which the runners are provided with closed branches to prevent the initial flow of liquid components flowing through the runners from flowing into the mold.

Reaction Injection Molding
is a method used for molding synthetic resins formed from a plurality of liquid components that quickly react when mixed together, such as polyurethane. In the case of polyurethane, it usually consists of a liquid component mainly consisting of an isocyanate compound having at least two isocyanate groups and an active hydrogen compound having at least two active hydrogens, such as a polyether polyol or a polyester polyol. 2 with liquid component
Formed from ingredients. Reaction injection molding is performed using a device that mainly consists of a mixing injection machine that mixes and injects these multiple liquid components and a mold, and the runner that connects the mixing injection machine and the mold is usually a molding machine. It is provided integrally with the mold and on the separation surface of the mold. This is because when opening the mold and taking out the molded product, it is necessary to take out the cured material inside the runner at the same time.

A mixing injection machine normally collides and mixes a plurality of pressurized liquid components and sends the mixture to a mold. For this reason, it has a mechanism for opening and closing the flow of each liquid component and a mixing device for collision-mixing each liquid component. Specifically, for example, JP-A-49-21465 and JP-A-Sho.
There is a device described in Japanese Patent No. 53-9854. Also,
A specific example of the runner is one described in Japanese Patent Application Laid-Open No. 49-74758. This runner is provided with a post-mixing device, and this runner is provided with a separation surface that is identical to the separation surface of the mold;
The cured material inside the runner can be taken out by opening the runner.

In reaction injection molding, it is necessary that the plurality of components to be mixed be uniformly mixed in a desired ratio. If a plurality of components are not uniformly mixed in the desired proportions, the curing reaction and the time it takes to proceed will become uneven, which will not only adversely affect the physical properties of the molded product, but also likely cause insufficient filling and non-uniform appearance. The part where non-uniform mixing ratios are most likely to occur is when injection of multiple components is initiated. Injection of a plurality of components is performed by opening the respective injection ports, but it is likely that the opening times of the injection ports may be deviated and the injection start times of the plurality of components may not be exactly the same. Therefore, the mixing ratio of the mixture of a plurality of components at the start of injection differs from the subsequent mixing ratio. Further, even if the opening time of the injection port is exactly the same, the injection pressures of the plurality of components may be different, so that the mixing ratio may be different. For example, if one component has a higher viscosity than another component, the injection pressure at the start of injection may be lower than subsequent injection pressures. Furthermore, when a component injected from another injection port is further mixed into the mixture injected and mixed at the same time, it becomes even more difficult to adjust the timing of the injection. For example, when two components are injected into a mixing chamber and the resulting mixture flows through a runner and is sent to a mold, if an attempt is made to mix a third component into the mixture in the runner, the first two components will be injected. This is because the start of injection of the third component must be delayed until the third component is mixed in. Timing control of the injection of this third component is extremely difficult, and the initial portion of the mixture sent to the mold is likely to lack or have an excess of the third component.

The present inventor studied a method for preventing the mixing ratio of a plurality of components from occurring at a portion where the mixing ratio differs from the intended mixing ratio at the start of injection in reaction injection molding. However, timing control of the injection start of multiple components is not only difficult with mechanical and electrical control of a mixing injection machine, but also due to physical properties such as viscosity of multiple components and their mixtures. The problem was thought to be extremely difficult to solve due to the need for change. Therefore, the inventor of the present invention did not send the first part of the mixture flow (in extreme cases, it may consist of only one component) of the mixture in which multiple components are injected and mixed, and instead We attempted to solve this problem by sending the material to the mold. As a result, only the mixture having the desired mixing ratio can be sent to the mold, and there is no need to solve the above-mentioned problem of time adjustment. Therefore, the inventor of the present invention has developed a method using conventional reaction injection molding that uses at least two components and a third component that has a higher viscosity than each of those components, which has a greater problem in time control than the conventional reaction injection molding that uses at least two components. In reaction injection molding of all three components, a method was investigated in which the initial flow of the mixture of at least three components was not sent to the mold. As a result, a branch is provided in the runner part, and the branch runner into which the first flow of the mixture flows is made into a closed branch runner, and the molding mold is made so that the cured material cured within this branch runner can be taken out. It was discovered that a closed branch runner, as well as a branch runner that leads to a block, has a separation surface. The present invention relates to this reaction injection molding method, that is, a reaction injection method in which a plurality of components that can rapidly react and form a synthetic resin when mixed are mixed and injected into a mold to perform molding. In the molding method, at least three components are formed, consisting of at least two components that react more rapidly than when a plurality of components are mixed, and a third component that has a higher viscosity than any of the at least two components; providing at least one closed branch runner into which the mixture initially flows into a runner for conveying the mixture of ingredients into the interior space of the mold; and providing the closed branch runner with a longitudinal separation surface to form the runner; This is a reaction injection molding method characterized by making a runner into a separable runner.

FIGS. 1 and 2 show a mold using the method of the present invention, and FIGS. 3 to 6 show cross-sectional views of a mixing injection machine. FIG. 1 is a view showing the separation surface of the lower die of a mold having a runner in the present invention. Second
The figure shows a cross section of a closed mold. Lower mold 1
A runner 2 is provided on the separating surface of the runner, and the runner after the branch point 3 is divided into a closed branch runner (4) and a runner 6 communicating with the mold interior space 5. The mixing injection machine 7 is a mixing injection machine with a piston valve, the details of which are shown in FIGS. 3 to 6. As described later, the first component is the first component.
the second component from the second inlet pipe 9, and the third component from the two third inlet pipes 1.
0 and 11 into the mixing chamber 12 in the mixing injection machine 7. However, when each component is not injected,
The first component is returned to the respective containers through the first discharge pipe 13 and the second component is circulated through the second discharge pipe 14. However, the third component is not recycled.
FIG. 2 is a cross-section taken through the closed branch runner 4 of a mold in which the upper mold 15 and the lower mold 1 are closed together. Separation line 1 indicating the separation surface of the mold
6 passes through a runner provided integrally with the mold, making the entire runner separable.

FIG. 3 is a vertical cross-sectional view of the mixing injection machine 7 when each component is not injected, FIG. 4 is a vertical cross-sectional view when each component is injected, and FIG. 5 is a--a in FIG. 3.
The cross-sectional view at a′ and FIG.
FIG. The mixing injection machine 7 consists of a valve piston 17 and a cylinder 18, the valve piston 17 having a first groove 19 through which the first component flows.
and a second groove 20 through which the second component flows. When each component in Figure 3 is not injected, the first
The component is circulated from the first inlet pipe 8 through the first groove 19 and discharged from the first discharge pipe 13, and similarly, the second component is circulated through the second inlet pipe 9 and the second groove 20. and circulates through the second discharge pipe 14. The third component is not circulated as shown in FIGS.
0,11 are closed. When the piston valve 17 rises, a mixing chamber 12 is formed at the tip of the piston valve 17, and the three components are simultaneously introduced into the mixing chamber 1 from each introduction pipe.
2 and mixed. In the figure, the third component is 2
Although it is introduced through two introduction tubes, it may of course be introduced through one introduction tube. However, mixing performance is improved by dividing the third component into two parts and introducing them from the direction in which they collide with each other.

The three component mixture flows into runner 2 and then into runner 4, which is first closed, as shown in FIG. This blocked branch runner 4
Once filled with the mixture, the subsequent mixture flows into the mold interior space 5 through a runner 6 that opens into the mold interior space 5 . When the mold interior space 5 is filled with the mixture, the mixing injection machine 7 returns to the state shown in FIG. 3, and the mixing injection is completed. The mixture is then cured and finally the molding is removed from the mold. When the mold is opened, the runner provided integrally with the mold also opens, and the cured material is also taken out into the runner. A mixture having an inappropriate mixing ratio is hardened in the closed runner 4, but this is also taken out at the same time.

Other examples using the method of the present invention are shown in FIGS. 7 and 8. FIG. 7 is a view showing the separation plane of the lower mold similar to FIG. 1, and FIG. 8 is a view showing the c-c' cross section when the mold is closed. Upper mold 21 and lower mold 22
Two valve pistons are provided in the lower die 22 of a mold consisting of a first component, and the first valve piston 23 is a valve piston having a circulation structure as shown in FIGS. 3 to 6. and the second component. The second valve piston 24 is a valve piston for injecting only the third component and does not have a circulation structure. These two valve pistons are simultaneously driven by one piston 25, and when the piston 25 is pulled from the state in which each component is not injected, the three components flow into the runner 26 at the same time. This runner 26 branches into two, and the tips of the two branch runners 27 and 28 are closed runners 29 and 3.
It is 0. Two branch runners 27, 28
A plurality of channels leading to the runner 31 that communicates with the mold interior space are provided in the middle of the mold, and the mixture passing through these channels collides with each other and is remixed before flowing into the mold interior space. When the injection is completed, the mixture is cured, and the mold is opened, the cured material in each runner can be taken out together with the molded product.

Reaction injection molding is used to mold synthetic resin moldings from a plurality of components that, when mixed, cause a rapid reaction to form a synthetic resin. For example, polyurethane, unsaturated polyester resin,
It is used for molding epoxy resins, polyamides, etc., but is particularly suitable for molding polyurethane. For example, it is suitable for molding polyurethane elastomers, foams, hard resins, etc. In the case of polyurethane, the first component is a liquid component whose main component is an isocyanate compound, and the second component is a liquid component whose main component is an active hydrogen compound. Usually, these two components are used for molding, but the number of components is increased, and there is also molding using three or more components. On the other hand, when molding a filler-containing synthetic resin such as filler-containing polyurethane, conventionally the filler has been dispersed in at least two of these components. However, components containing fillers have a high viscosity, and these components are recycled, causing various disadvantages. Therefore, the filler is the third filler.
It was considered advantageous to inject the first and second components separately. Of course, the filler alone will not flow, so a liquid or the like is added to make it flowable, and it is used as a fluidizable solid such as a high viscosity slurry liquid or gel. The liquid added to the filler is suitably an isocyanate compound or an active hydrogen compound, with active hydrogen compounds such as polyols being particularly preferred. The proportion of filler in the third component is suitably at least 30% by weight, particularly at least 50% by weight. This third component, unlike the first and second components, is not recycled. Therefore, the disadvantageous problems associated with circulation, such as the high pressure required and the tendency to wear the inner surface of the container wall, are solved. As the filler, glass fiber milled fibers, chopped glass fiber strands, mica, and other fibrous or flat plate-like reinforcing fillers are preferred. Also, powder fillers such as calcium carbonate, aluminum hydroxide, barium sulfate, and others can be used.

[Brief explanation of the drawing]

1 and 2 are a plan view and a sectional view, respectively, of a mold using an example of the method of the present invention. Figures 3 and 4 are longitudinal sectional views of the mixing injection machine, and Figures 5 and 6 are A in Figure 3.
-A', BB' section cross-sectional view. 7 and 8 are a plan view and a sectional view, respectively, of a mold using another example of the method of the present invention. 1, 15, 21, 22...Mold, 2, 26...
...Runner, 4,29,30...Closed runner, 7...Mixing injection machine, 17,23,24...
valve piston.

Claims (1)

[Claims] 1. In a reaction injection molding method in which a plurality of components that can cause a rapid reaction to form a synthetic resin when mixed are mixed and molded by injection into a mold,
At least three components consisting of at least two components that cause a rapid reaction when mixed with a plurality of components and a third component that has a higher viscosity than either of the at least two components, a mixture of these at least three components Providing at least one closed branch runner through which the mixture first flows into the runner feeding into the interior space of the mold, and providing the closed branch runner with a longitudinal separation surface so that the runner can be divided. A reaction injection molding method characterized by forming a runner. 2. The method according to claim 1, comprising two components and a third component that cause a rapid reaction when a plurality of components are mixed, and the three components are mixed simultaneously. 3. The method according to claim 1, characterized in that a third component is mixed into a mixture of two components that causes a rapid reaction when a plurality of components are mixed. 4. The method according to claim 1, wherein the third component is a highly viscous liquid consisting of a filler and a liquid component or a fluidizable solid.