JPH052720B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention provides a method for removing mold deposits that adhere to the surface of a mold by molding a thermoplastic resin composition, which can be removed very easily. The present invention relates to a cleaning liquid and a method for removing deposits using the cleaning liquid. [Prior art and its problems] Thermoplastic resin compositions are usually formed by injection molding or extrusion molding. However, when molding is performed, development occurs in which gases generated during molding solidify or compounds contained in the composition precipitate and adhere to the surface of the mold used for molding. . There is a problem that this is transferred to the surface of the molded product, impairing the appearance and dimensional accuracy of the product, or causing defective mold release, and various studies have been conducted on methods for removing such mold deposits. However, no satisfactory method has been found yet. In other words, currently common methods include applying a cleaning solution to the mold and then wiping off the deposits using a cloth or absorbent cotton, or applying the cleaning solution and then molding under normal molding conditions to remove the deposits. However, the cleaning liquid itself has poor cleaning properties, and is particularly ineffective against deposits such as paraformalbite when molding polyacetal resin compositions, and wiping them off requires a great deal of effort. Regarding wiping, it is difficult to completely remove deposits down to the smallest detail in complex molds used for precision molding of gears, etc., and the mold may be damaged during wiping. Additionally, with solvents containing strongly alkaline, acidic, or oxidizing components, it may be possible to remove deposits relatively easily, but they may cause corrosion of the mold surface,
It is unsuitable as it may cause damage. As a method for efficiently performing such general mold cleaning, the present inventor has discovered a method for efficiently performing mold cleaning using a general organic solvent, especially by using ultrasonic waves, and has developed this method. A patent application has already been filed for this (Japanese Patent Application Laid-open No. 59-202298).
However, this method requires expensive equipment such as an ultrasonic oscillator, which increases the installation cost of the equipment, and requires complicated operations such as setting the ultrasonic oscillator during cleaning. In some respects, this was not a satisfactory method. [Means for Solving the Problems] Therefore, the present inventors have made intensive studies to obtain a cleaning liquid that does not have such drawbacks and can effectively remove mold deposits, and as a result, the present invention has been developed. It was reached. That is, the present invention provides a method for removing mold deposits that adhere to the surface of a mold during molding of a thermoplastic resin composition, such as a polyacetal resin composition, in particular, using a mixture containing lactone releaser and alcohol. The present invention relates to a method for removing mold deposits, which is characterized by using an organic cleaning liquid. One of the essential components of the cleaning liquid used in the present invention
Lactones are the functional groups of esters.
Cyclic esters containing CO-O- in the ring and their derivatives with 4 to 6 atoms constituting the main ring containing the ester group, i.e. β-lactone (4-membered ring), γ
-lactone (5-membered ring), δ-lactone (6-membered ring)
and derivatives thereof. Examples of these include β-propiolactone, γ-butyrolactone, γ-valerolactone, γ-caprolactone,
γ-Capryrolactone, γ-Laurolactone, γ
- palmitolactone, γ-stearolactone, crotolactone, α-angelicalactone, β-angelicalactone, δ-valerolactone, δ-caprolactone, etc. The amount of lactones used in the present invention is
The amount is at least 5% by weight, preferably 10 to 50% by weight, based on the total amount of the cleaning liquid. Next, alcohols, which are other essential components used in the present invention, include aliphatic and aromatic hydrocarbons, saturated and unsaturated monohydric alcohols and dihydric alcohols such as alicyclic compounds, Polyhydric alcohols, etc. The alkyl group of the preferred saturated aliphatic monohydric and dihydric alcohol has 1 to 6 carbon atoms, especially 1
-4 is suitable. Examples of these are methanol, ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-
Butyl alcohol, ethylene glycol, propylene glycol, trimethylene glycol, 1,
2-butanediol, 1,3-butanediol,
These include 1,4-butanediol, 2,3-butanediol, isobutylene glycol, and the like. Examples of aromatic alcohols include benzyl alcohol and cinnamyl alcohol. Examples of alicyclic alcohols include cyclopentanol and cyclohexanol. In the present invention, alcohol is added at 5% of the total amount of cleaning liquid.
The content is preferably from 50 to 90% by weight, particularly from 50 to 90% by weight. Further, as other solvents, a mixed solution containing one or more of water, ethers, ketones, other esters, aromatic hydrocarbons, or other halogen derivatives can be used. A method for removing mold deposits using the cleaning liquid of the present invention can be performed by a conventionally known general method, for example, by impregnating a piece of cloth, a piece of paper, etc. with the cleaning liquid of the present invention. wiping off the deposits on the mold surface (at this time, you may also use an appropriate polishing powder),
There is also a method of applying a cleaning liquid to the surface of the mold on which deposits have adhered by an appropriate method, and then repeating molding to transfer the deposits to the molded product and removing them from the mold surface, or a method of removing the deposits from the mold surface. Any method may be used, such as a method of using them together. Further, the use of the cleaning liquid of the present invention is also effective in other methods. [Effects of the Invention] The method for removing mold deposits using the mixed organic cleaning solution containing lactones and alcohols according to the present invention does not corrode or damage the mold, and can be used with general organic solvents such as alcohols. Compared to methods that use , ethers, ketones, other esters, water, or a mixture of two or more of these, it is easier to remove deposits, and special means such as ultrasound can be used in combination. For example, the number of times of wiping required to restore the original clean surface by applying cleaning liquid to a piece of cloth and wiping off the deposits on the mold surface, or applying it to the mold deposits to remove adhesion during molding. number of times,
The required time etc. can be shortened. Additionally, in general, the higher the mold temperature, the easier it is to remove mold deposits using the above method, but raising the mold temperature increases the time required to interrupt a series of molding operations, which reduces production efficiency. inhibited. However, according to the method using the cleaning liquid of the present invention, deposits can be removed even when the mold is at a relatively low temperature, which is also advantageous in terms of production efficiency. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 5, Comparative Examples 1 to 12 A circular (50 mmφ x 3 mm) molded product was made by injection molding at a resin temperature of 200°C and a mold temperature of 60°C using Diuracon M9002 manufactured by Polyplastics Co., Ltd. as a polyacetal resin. When 10,000 shots of the material were molded, white mold deposits adhered to the nest inside the mold. Then remove the nest and
A 5 cm square piece of cloth (flannel) was soaked uniformly in the cleaning solution shown in Table 1 without any particular heating, and then a cloth (flannel) was folded into four and a wiping operation was attempted. In addition, each wiping operation should be performed under the same conditions as much as possible (wipe the mold surface twice with the same piece of cloth - count this as one time - change the cloth and repeat), so that the mold surface is The number of times of wiping required to restore the original clean state in terms of gloss etc. was compared (Method A). The results are shown in the column of Method A in Table 1. On the other hand, molding was carried out under exactly the same conditions as above, and the cleaning solution shown in Table 1 was applied to the mold with the same deposits without removing the insert or heating it. It was applied to the deposits on the mold, and after about 1 minute, the molding operation was repeated until the mold surface was restored to its original clean state in terms of gloss and the like. At this time, a new cleaning solution was applied every 5 shots (Method B). The results are shown in the column of Method B in Table 1.

[Table] Examples 6-7, Comparative Examples 13-16 Injection using Tenatsuku-4010 manufactured by Asahi Kasei Industries, Ltd. as the polyacetal resin and changing the molding conditions (resin temperature 210°C, mold temperature 80°C) After molding, the same tests as in the above Examples and Comparative Examples were conducted using the cleaning liquid shown in Table 2. The results are shown in Table-2.

[Table] Example 8, Comparative Examples 17 to 19 Using Diuranetx 3370 manufactured by Polyplastics Co., Ltd. as a flame-retardant polyester resin, injection molding was performed at a resin temperature of 250°C and a mold temperature of 60°C to form a circular shape (50 mmφ ) When 20,000 shots of the molded product were molded, a white substance adhered to the mold and a slight tar-like substance adhered to the outside of the cavity. Wiping was attempted according to Method A of Examples 1 to 5 without particularly heating this mold. The results are shown in Table-3.

【table】

Claims (1)

[Claims] 1. In a method for removing mold deposits adhering to the surface of a mold used for molding a thermoplastic resin composition, a mixed organic cleaning liquid containing lactones and alcohols is used. A method for removing mold deposits, characterized by: 2. The method for removing mold deposits according to claim 1, wherein the thermoplastic resin is particularly a polyacetal resin.