JPS596220B2 - Injection molding machine cleaning method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for cleaning an injection molding machine.

More specifically, the present invention relates to a method for cleaning an injection molding machine using a mixture of a styrenic resin and a crystalline linear polyester resin having a melting point higher than the molding temperature of the styrenic resin.

Generally, injection molding is often used as one of the methods for molding molded resins.

When a molded resin is injection molded using an injection molding machine, the resin remains inside the injection molding machine, that is, inside the cylinder after the injection molding is completed.

Therefore, when injection molding another resin or a resin of a different color next time, it is necessary to completely remove the molding resin remaining in the injection molding machine.

Conventionally, this removal work requires a large amount of cleaning resin, and especially when injection molding a white or light color after injection molding a black product, an extremely large amount of resin is required and there is a large loss. was inviting.

On the other hand, if the next resin is injection molded while the residual resin has not been completely removed by this cleaning process, stains may appear on the surface of the molded product with the hue of the residual resin, or they may overlap with each other. If the compatibility is poor, delamination may occur, resulting in a defective product.

From these points, when removing styrene resin that remains inside the injection molding machine, especially when styrene resin is injected using a large molding machine, we need a method that uses as little resin as possible and can completely remove it. is needed.

Conventionally, methods using various cleaning resins have been devised as methods for removing molding resin remaining in these injection molding machines, and some of them are commercially available as cleaning resins.

However, none of these methods is necessarily satisfactory because they have poor cleaning effects, deteriorate the physical properties of the molded resin, or are extremely expensive and therefore impractical.

The inventors of the present invention have arrived at the present invention as a result of intensive study on a method for cleaning an injection molding machine that solves the above-mentioned conventional problems.

That is, the gist of the present invention is that when cleaning and removing styrene resin remaining in an injection molding machine, a styrene resin and a crystalline linear polyester resin having a melting point higher than the melting start temperature of the styrenic resin are used. The mixture is injected in the first stage at a temperature higher than the melting start temperature of the styrenic resin and lower than the melting point of the crystalline linear polyester resin, and in the second stage at a temperature higher than the melting point of the crystalline linear polyester resin. The present invention relates to an injection molding machine cleaning method characterized by:

According to the present invention, when removing molding resin (styrenic resin) that remains in an injection molding machine, it is possible to completely remove it using a much smaller amount of resin than in conventional methods.

The styrenic resin in the present invention includes polymers such as styrene, α-monosubstituted styrene (e.g., α-methylstyrene), and nuclear-substituted styrene (e.g., chlorostyrene), copolymers thereof, and monomers thereof. Copolymers obtained from copolymerizable vinyl compounds (for example, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, acrylic esters, methacrylic esters, etc.), and rubber-like polymers with these (for example, butadiene rubber, These include resin compositions obtained from acrylic rubber, ethylene-propylene rubber, etc.).

The crystalline linear polyester resin having a melting point higher than the molding temperature of the styrene resin used in the present invention is, for example, an aromatic dibasic acid such as terephthalic acid or isophthalic acid,
A polyester resin obtained from an aliphatic dibasic acid such as adipic acid or a lower alkyl ester thereof and a dihydric alcohol such as ethylene glycol is used, and polyethylene terephthalate (PET), polybutylene terephthalate, etc. are particularly preferred.

Moreover, these polyester resins are used in large quantities for films, and inexpensive scrap products obtained from these films can be used.

The mixing ratio of the styrene resin and the crystalline linear polyester resin used in the present invention is as follows:
It is preferable to use 90 to 30 parts by weight of the crystalline linear polyester resin (II) to 10 to 70 parts by weight of I).

When the weight ratio (I)/(If) is less than 10,790, fluidity tends to decrease, and when it exceeds 70/30, the cleaning effect tends to decrease.

In the present invention, the temperature in the step of filling the resin mixture into the injection molding machine and injecting it out of the system is at least the molding temperature of the styrene resin and below the melting point of the crystalline linear polyester resin in the first step; In the second stage, the temperature is preferably higher than the melting point of the crystalline linear polyester resin.

It is preferable to wash until the hue of the resin remaining at each stage disappears.

For example, when using a mixture of AAS (acrylate-acrylic rubber-styrene copolymer) and PET, the first stage is 190-230°C, and the second stage is 24°C.
A temperature range of 0 to 280°C is preferred.

In this case, if the temperature is lower than 190°C in the first stage, the fluidity of the resin will decrease significantly, making molding difficult;
If the temperature exceeds 230°C, the effect of removing the retained resin tends to decrease.

In the second stage, if the temperature is less than 240°C, PET will not melt,
If the temperature exceeds 280°C, there is a possibility that AAS will partially decompose.

In the present invention, the styrenic resin and the crystalline linear polyester resin may be mixed by any conventional method.

For example, both powder and pellet forms can be easily mixed using a blender or mixer.

However, the size of the crystalline linear polyester resin is preferably smaller than the nozzle diameter of the injection molding machine.

If it is significantly larger than the nozzle diameter, the nozzle etc. may be clogged with crystalline polyester and the cleaning speed may be reduced.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Sixty shots of a black colored AAS resin (pellets made by adding 2% carbon black to Byfux V6100A (melting start temperature 200°C) manufactured by Hitachi Chemical Co., Ltd.) were injection molded under the following molding conditions.

[Injection molding conditions]

Molding machine: ■Nippon Steel's new V36A-150 type screw complete automatic injection molding machine Cylinder temperature 201220°C C2230°C 0230°C Nozzle 2/30°C Injection pressure crab 6ooKF! /crtt Screw rotation speed: 60 rpm After injection molding, a part of the cylinder is moved back, and 40 parts of AAS resin Pitax V6100A and 60 parts of polyethylene terephthalate (PET melting point 250°C) are mixed, and the cylinder temperature is set to C1210. °C1C2210℃
, 03210°C, nozzle 210°C, other conditions being the same, continue filling the cylinder and injecting it out of the system from the nozzle until the black color disappears, then set the cylinder temperature to 1240°C, 02250°C. °C, 03250 °C
, the nozzle was set at 250° C., and the same operation was continued until the color completely changed to a natural color.

The amount of resin required to completely wash away the retained black AAS resin was measured.

The results are shown in Table 1. Comparative Example 1 In Example 1, after AAS resin was injection molded, a part of the cylinder was moved back and natural colored AAS resin was injected from the nozzle to the outside of the system while being filled into the cylinder under the same injection molding conditions. This process was repeated until the black AAS resin was completely washed away.

The amount of resin required at this time was measured and shown in Table 1.

From the results in Table 1, it can be seen that by using the mixture of AAS resin and PET, the amount of resin required to completely clean the AAS resin accumulated in the cylinder is significantly reduced.

Examples 2 to 4 and Comparative Example 2 Tests were conducted in the same manner as in Example 1, except that the cleaning mixture was as shown below and the cylinder temperature was as shown in Table 2.

The results are shown in Table 2. 0! Mf”’ke=:5 wealth:::= ○Example 3 (Ω life: (V6100A) :::
O Example 4 [Public base (V6100A) Ho: 0 Comparative example 2 AAS (V6100A) 50 copies LPET
A from the results of 50 parts table 2
The AS/PET mixture was heated at 210°C in the first stage, and at 210°C in the second stage.
All methods of cleaning by changing the cylinder temperature of 50°C yielded good results, and the accumulated AA was removed.
It is found that this method is very effective in removing S resin.

Example 5 and Comparative Example 3 Using the injection molding machine shown in Example 1, 60 shots of pellets prepared by adding 2% carbon black to ABS resin Tuflex 210 manufactured by Mitsubishi Monsanto ■ were injection molded under the same molding conditions.

After injection molding, the inside of the injection molding machine was cleaned by repeatedly filling the cylinder with a natural product and injecting it out of the system (so far, Example 3).

Next, after injection molding 60 shots of black Toughflex 210 pellets, the cylinder temperature was set to 01210°C, C2
Setting the temperature to 10℃, C3210℃, nozzle 210℃, Tuflex 21040 parts, PET (melting point 250℃) 60
The inside of the injection molding machine was cleaned using the mixture.

Next, the cylinder temperature was set to C1240℃ and C2250℃.
Set C1C3250℃, nozzle 250℃ (PET
The components were melted) and further washed (so far Example 5).
).

The amount of resin required for cleaning until the color completely changed from black to natural was measured.

The results are shown in Table 3.

Examples 6 to 8 and Comparative Examples 4 to 5 AAS resin (Pitax V6101AH) colored black with 2% carbon black was molded under the following injection molding conditions.
0 shot injection molding.

[Injection molding conditions]

Molding machine: Matsuyama Seisakusho 5I-50 type inline screw complete injection molding machine Cylinder temperature: C, 230℃, C2230℃, nozzle 230℃ Injection pressure 700Kp/ffl Screw revolution speed: 50 rpm After injection molding is completed , using a mixture of the same AAS resin and PET (melting point 250° C.) as the above AAS resin shown in Table 4, and setting the cylinder temperature shown in Table 4 to Example 1.
In the same way, the inside of the injection molding machine was cleaned until the color completely changed from black to natural.

When the amount of resin required for cleaning was measured, the results shown in Table 4 were obtained.

As is clear from the above, according to the present invention, an injection molding machine can be effectively cleaned with a small amount of cleaning resin used.

Claims (1)

[Claims] 1. In order to wash and remove the styrenic resin remaining in the injection molding machine, in the first step, a mixture of a styrenic resin and a crystalline linear polyester resin having a melting point higher than the melting start temperature of the styrenic resin is A method for cleaning an injection molding machine characterized by injecting at a temperature higher than the melting start temperature of the styrene resin and lower than the melting point of the crystalline linear polyester resin, and in a second step at a temperature higher than the melting point of the crystalline linear polyester resin. .