JPH028565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The disclosed technology belongs to the technical field of a method for adding a colorant that is added when molding a resin product.

<Explanation of the gist> Therefore, the present invention supplies a fixed amount of coloring agent to the resin that is supplied to the cylinder of an injection molding machine and injected into the cavity by a screw, and produces a predetermined product such as a colored resin part for a vehicle. This is a method of adding other coloring agents when molding other products of different colors in the same molding machine after several moldings, and after cleaning the cylinder by free-shotting, etc. This invention relates to a method of adding a coloring agent to injection molding in which other products are molded by adding a coloring agent, and in particular, the invention relates to a method of adding a coloring agent to injection molding to mold other products. The inside of the cylinder is cleaned by free-shotting with a resin mixed with a coloring agent, and during the free-shotting, the amount of other coloring agents added is increased according to the amount of resin necessary for cleaning, such as the internal volume of the cylinder, and restored in the molding process. This invention relates to an addition method that changes the

<Conventional technology> In general, injection molding of molded products is a molding technology in which a molding material such as a resin is heated to melt and fluidize, then injected into a cavity with a screw, and then cooled and solidified to form a product. It is mainly effective in molding resin products, and is widely used in various industries because it is highly mass-producible.

By the way, when injection molding colored resin products, various colorants containing pigments are added to the molding material, and the resin is plasticized together with these colorants and injected into the cavity in the mold. It's like that.

Therefore, the state of addition of the colorant determines the quality of the product, and the hiding rate of the product in particular plays a large role in determining the value of the product itself (this is particularly important in the case of interior and exterior parts of vehicles). Therefore, quantitative feeders and the like are used to stably supply the colorant.

As is well known, conventionally, for example, when two different colored products are manufactured individually and continuously,
A common method was to temporarily stop the supply of one colorant, supply only resin, perform a free shot to clean the cylinder, and then supply another colorant to mold other products with different colors.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional method of adding colorants, a larger amount of resin is required during the free shot during cleaning than during molding, resulting in the problem that the product is not produced and there is a lot of loss. It was hot.

To deal with this problem, after stopping the supply of one colorant, switching to another colorant and running the molding operation, a product with mixed colors of two colors is produced, and then repeating the process multiple times in that state. There was also a method of free-shotting, but when free-shotting the resin, the amount of resin flowing through the screw in the cylinder increases as described above, so the content of colorant relative to the amount of resin becomes relatively small. Even if the previously used colorant no longer mixes with the product, the hiding rate of the product will decrease, resulting in a product with a lighter color.
The problem was that this could occur several times in a row after the free shot.

Therefore, in order to secure a predetermined colorant content, it is necessary to continue molding and discharge the material with a low colorant content from the cylinder by the molding operation rather than by free shot, which has the disadvantage of increasing costs. It was hot.

<Objective of the invention> The object of the invention is to solve the problem of adding a coloring agent in resin molding based on the above-mentioned conventional technology, and to solve the problem of adding a coloring agent to the resin. The purpose of the present invention is to provide an excellent method for adding colorants in injection molding, which not only ensures that product properties are not deteriorated, but also ensures cleaning inside the cylinder, and that is beneficial to fields in which resin molding technology is used in various industries. It is.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims and in accordance with the above-mentioned objects, is to inject a resin to which a coloring agent is added into a cavity through a screw. After molding the product, add other coloring agents, and if color mixing occurs in the molded product, remove the nozzle head from the cavity, clean it with a free shot while discharging it with a screw, and remove the previous coloring from the product. After confirming that the agent is no longer mixed in, the nozzle head is brought into close contact with the cavity again and molding is resumed. At this time, the measuring time of the injection molding machine differs between molding and free shot (the measuring time is short during free shot), and the amount of colorant supplied is determined by the rotation speed of the feeder and the measuring time, so the color The color density of the resin in the cylinder after replacement is completed will decrease due to the shortened measurement time, so when cleaning with a free shot, the amount of other colorants added should be changed in accordance with the amount of resin required for cleaning. A technical measure is taken in which the amount is increased in accordance with the increased amount of resin during cleaning, and decreased in accordance with the amount of resin supplied during molding operation.

<Example> Next, an example of the present invention will be described below with reference to the drawings.

First, as shown in FIGS. 1 and 2, the resin 3 supplied to the cylinder 1 via the hopper 2 is
When the screw 5 is rotated in the direction of the arrow and retreated to the right in the drawing, the cylinder 1 is heated and melted by a heater (not shown) together with the coloring agent A from the metering pump 4 attached to the hopper 2. (Fig. 2).

Then, as shown in FIG. 3, the rotation of the screw 5 is stopped, and the screw 5 is inserted through the nozzle head 6 to fill a cavity (not shown) with molten resin, thereby molding a product colored with the coloring agent A.

By repeating this process, products of the same color of colorant A can be molded.

Therefore, when changing the color to another colorant B, first, as shown in FIG.
is filled with colorant B and supplied into the base of the hopper 2, while the screw 5 in the cylinder 1 is
Rotate in the direction of the arrow around the position of the tip 7 of
The coloring agent A inside the cylinder 1 is cleaned by performing a so-called free shot.

In this case, when the screw 5 performs a free shot, the nozzle head 6 becomes free, so
The resistance to resin filling is reduced, and as described above, the resin 3 is supplied from the hopper 2 to the cylinder 1 at a faster rate than during the molding operation.

Therefore, since the content of colorant B in the resin discharged from the cylinder 1 decreases, the colorant B supplied by the hopper 2 is transferred to the constant supply pump 4 in response to the increased amount required by the resin 3. Add and increase.

The determination of the amount of change by the quantitative supply pump 4 will be described later.

Therefore, the resin 3 discharged from the cylinder 1
When the contamination of colorant A decreases over time and is finally no longer visible, the cylinder 1 will be filled with resin 3 having an appropriate content of colorant B. As shown in the figure, by retracting the screw 5 and performing the same molding operation as described above, a product with appropriate opacity can be obtained, and efficient molding can be achieved by minimizing loss of resin 3 and colorant B. I can do it.

Incidentally, when the molding operation is restarted, the amount of colorant B added is decreased and restored in accordance with the amount of resin supplied.

Next, Experimental Example 1 based on the prior art and Experimental Example 2 based on the above embodiment will be described.

In this case, () Molded product: Vehicle console box, Weight: 800g () Resin: ABS heat-resistant grade () Colorant A: Liquid color (blue type), Specific gravity 1.3, Addition amount 1.2 parts Colorant B: Liquid color ( Gray type), Specific gravity: 1.8, Addition amount: 1.8 parts, () Metering pump: Gear pump 2.4 cc/rotation () Time required to measure the resin during molding operation (hereinafter referred to as measuring time): 20 seconds during molding operation, 15 seconds when free shot , if the amount Q of colorant to color one shot is constant, the supply of a predetermined amount of colorant can be achieved by selectively or automatically adjusting the rotation speed R in response to variations in the metering time t. It becomes possible.

Experimental example 1 The rotation speed of metering pump 4 during molding operation
Specified amount of colorant A at 10 rpm (800g x 0.013 = 10.4
g) was fed in 20 seconds.

Next, when switching to colorant B and changing the rotation speed of metered supply pump 4 to 6.7rpm and continuing to supply a predetermined amount (800g x 0.012 = 9.6g) of colorant B for 20 seconds, screw 5 was applied 6 times. A mixed molded product of colorants A and B was obtained in the round trip (6 shots).

At this point, the system was switched to free shot and the rotational speed of the metering pump 4 was kept at 6.7 rpm, and about 5 kg of resin was lost even though it was completely converted to colorant B.

Subsequently, the molding operation was switched to, but the 5th shot was a molded product with a light color, that is, a molded product with a low colorant content.

Experimental Example 2 On the other hand, in Experimental Example 1 described above, at the time of switching to the free shot, the rotation speed of the metering pump 4 was increased in accordance with the metering time reduction of 15 seconds/20 seconds = 3/4, and the rotation speed was increased to 6.7 rpm ÷ When setting 3/4 = 8.9 rpm and increasing the amount of colorant B added, only about 4 kg of resin was lost to change the color, and the colorant returned to normal from the first shot after switching to molding operation. A product with the following content was obtained.

Therefore, compared to Experimental Example 1, which was based on the prior art, the loss of resin was suppressed by 1 kg, and the result was that there was no operational loss during the molding operation.

<Other Examples> The embodiments of the present invention are of course not limited to the above-mentioned embodiments. For example, the amount of colorant added may be automatically changed according to the concentration of colorant in the cylinder. Various embodiments can be adopted as the quantitative supply pump, such as a roller pump if the liquid is transported by rotation or the like.

<Effects of the Invention> As described above, according to the present invention, in the injection molding of resin products, basically various colorants are exchanged and used regularly or irregularly, so it is not necessary to perform color cleaning each time. Although it is not possible to completely avoid the loss of resin for cleaning, it is possible to minimize the loss and eliminate unnecessary operations as much as possible, improve yields, and improve production. The excellent effect of improving performance and reducing costs can be achieved.

In addition, the inside of the cylinder is cleaned by free-shotting the cylinder with resin until another product is molded with the colorant changed to another colorant, and at this time, the amount of the other colorant added is adjusted to the required amount for cleaning. By changing it in accordance with the amount of resin, the amount of resin lost during cleaning is reduced, and it is also possible to maintain the appropriate coloring density of the resin in the cylinder after starting molding operation, resulting in an appropriate density. There is no need to perform unnecessary molding operations during the process, and the excellent effect is that products with high properties and precision can be produced without reducing production efficiency.

In addition, there is an advantage that loss of resin, etc. can be suppressed, and costs can be substantially reduced.

[Brief explanation of drawings]

The drawings show examples of the present invention. Figures 1, 2, and 3 are cross-sectional views of the molded state when a coloring agent is added, and Figures 4 and 5 are cross-sectional views of the molded state when other colorants are added. FIG. 1... cylinder, 5... screw, 3... resin, A... coloring agent, B... other coloring agent.

Claims (1)

[Claims] 1 After adding a coloring agent to the resin that is supplied to the cylinder and injected into the cavity by a screw to mold the product, a free shot is performed to clean the cylinder, and then another colorant is added to mold other products. In the method of adding colorants in injection molding, the amount of other colorants added is increased during a free shot when cleaning the inside of the cylinder with the above colorant replaced with another colorant than during molding. A method for adding a colorant in injection molding, characterized by: