JPS60192606A - Peeling method of plastic molded article from glass mold - Google Patents

Abstract

PURPOSE:To peel a plastic molded article efficiently from a glass mold by dipping it alternately into a plurality of kinds of liquid flon having different boiling points and giving adhesive agent a temperature change. CONSTITUTION:Adhesive agent between a plastic molded article obtained by injecting liquid plastic material into a glass mold and hardening it there and the glass mold is dipped alternately into a plurality of kinds of liquid flon maintained in the respective different boiling points in the interval between the lowermost and the uppermost boiling point -30 deg.C and 50 deg.C to give the adhesive agent temperature change. Thus, the plastic molded article can be peeled efficiently from the glass mold. Further, flon is noncombustible and very low in toxicity. Therefore, working circumference is improved remarkably in comparison with the case where chlorinated solvent such as trichlorethylene, tetrachloroethylene or carbon tetrachloride, etc. is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objects and Prior Art) The present invention relates to a method for peeling a plastic molded article molded (cast polymerized) by injecting and curing a liquid plastic raw material into a glass mold from a glass mold.

Conventionally, when molding plastic lenses etc. using the cast polymerization method, a precisely polished glass mold is used, but after curing the molded product adheres tightly to the glass mold.
For example, if an attempt is made to separate the glass mold and the molded article by driving a wedge into the gap between them, the glass mold and the molded article often break. For this reason, various methods have been devised to separate the glass mold and molded product without causing damage.
For example, a plurality of chlorinated hydrocarbon solvents having a temperature difference (Japanese Patent Publication No. 57-46735)
A method of peeling by passing through a water tank (Special Publication No. 57-46732) and repeatedly cooling and heating, using heat shock.
Also, methods have been proposed in which ultrasonic irradiation is used in conjunction with ultrasonic irradiation to promote peeling during passage through these liquid tanks (Japanese Patent Publication No. 57-46733).

However, when using chlorinated solvents such as trichlorethylene, tetrachlorethylene, carbon tetrachloride, etc., the working environment deteriorates due to the high toxicity of these solvents.
Also, these solvents have high dissolving power, and what's more? O-130
Since a high-temperature solvent of "C" is used, there are problems such as corrosion by the solvent depending on the material of the plastic.In addition, in the method using the water tank described above, the temperature of the cooling tank is 110 to 10 °C.
A water tank of grade C is used, but care must be taken to control the temperature to prevent freezing. Furthermore, in order to dry the glass mold and molded product after immersion in a water tank and peeling off, separate equipment such as a fluorocarbon dehydrator and dryer is required, resulting in problems such as low workability.

The present invention aims to solve the problems of the conventional L method.

(Structure of the Invention) That is, the present invention provides a bond between a plastic molded product obtained by injecting a liquid plastic raw material into a glass mold and curing the mold, and a glass mold having a boiling point of 130°C or higher and 50°C.
A plastic molded article is peeled from a glass mold by alternately immersing it in a plurality of types of fluorocarbon liquids having different boiling points maintained at each boiling point within the following range and applying a temperature change to the adhered article. It's a method.

In the present invention, a plurality of types of fluorocarbons are used, all of which have a boiling point of -30°C or higher and 50°C or lower. It is not preferable to use fluorocarbons having a boiling point lower than 130° C., since heat shock will be excessive and the glass mold or molded product will be easily damaged. Also, the boiling point is 50°C
The use of fluorocarbons in excess of this amount is not only economically disadvantageous due to the large energy consumption required for heating, but also is undesirable because it may cause deterioration depending on the type of plastic. Examples of suitable fluorocarbons having a boiling point within the above range include base methane and base ethane such as trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, and dichlorotetrafluoroethane. According to the present invention, a close contact between a glass mold and a plastic molded article is placed in a liquid in which multiple types of fluorocarbons selected from the above boiling point range, that is, fluorocarbons on the low boiling point side and fluorocarbons on the high boiling point side, are both in a boiling state. By alternately immersing the glass mold and plastic molded article in water and repeating the operation of cooling→heating or heating→cooling one or more times, both the glass mold and the plastic molded article can be peeled off in a short time without damaging both.

It is generally preferable to set the boiling point difference between the low boiling point side fluorocarbon for cooling and the high boiling point side FC for heating to be in the range of 20 to 80°C. Preferred low boiling point fluorocarbons are dichlorodifluoromethane (boiling point -29.8°C) and dichlorotetrafluoroethane (boiling point 3.8°C), and high boiling point fluorocarbons are preferably trichlorofluoromethane (boiling point -29.8°C) and dichlorotetrafluoroethane (boiling point 3.8°C). These include trichlorotrifluoroethane (boiling point 47.6°C) and trichlorotrifluoroethane (boiling point 47.6°C).

The present invention is characterized in that the fluorocarbon used for cooling or heating the adhered material is maintained in a boiling state. In this way, the temperature of the cooling tank and heating tank is always kept constant without the need for special control, so there is a risk that heat shock will become too large or too small due to inappropriate temperature control. There is no problem, and process control is extremely easy. Furthermore, when the above-mentioned adhered object is immersed in a low-boiling-point chlorofluorocarbon for cooling, the latent heat of vaporization of the fluorocarbon causes rapid cooling, so it is effective at a lower heating temperature of 50°C or less than when using a chlorinated solvent. Furthermore, when the cooling or heating Freon boils, the impact force applied to the adhered material has the effect of promoting peeling.

Usually, one Freon bath for cooling and one for heating are provided, and by immersing the adherent material in the order of cooling bath → heating bath, or heating bath → cooling bath, it is possible to apply a heat shock and peel off the adhered material. If necessary, peeling can be promoted by alternately repeating the immersion in the various types described above two or more times. Furthermore, by providing three or more fluorocarbon baths and immersing them in sequence, it is also possible to carry out cooling→heating or heating→cooling operations. The time for immersing the adhered object in the Freon tank for cooling and heating varies depending on the size of the molded object and the glass mold, but for example, in the case of plastic lenses, it is usually 5 to 50 minutes.
It takes about 60 seconds.

The form of the fluorocarbon tank used to carry out the present invention is not particularly limited, and the low-boiling fluorocarbon tank for cooling may be a cold storage tank, and the high-boiling fluorocarbon tank for heating may be a conventionally known fluorocarbon steam cleaning machine, etc. can be used.

In the present invention, since the surface tension of fluorocarbons is significantly lower than that of water or chlorinated solvents, fluorocarbons easily penetrate into the gap between the glass mold and the plastic molded product, and have the effect of promoting the separation of the two. Since the surfaces of both plastics are thoroughly wetted, the process of immersing the plastic in Freon and peeling it off also provides a cleaning effect on both surfaces, and there is an advantage that there is no need to provide a separate cleaning tank. When particularly precise cleaning is required,
For example, the peeled glass mold and plastic molded article taken up from the low-boiling point Freon tank are held in a vapor zone above the boiling Freon liquid in the high-boiling point Freon tank, and the Freon vapor is condensed on the surfaces of the glass mold and the molded article. The process can also be completed by steam cleaning.

Furthermore, since the evaporation rate of Freon is extremely fast compared to water, chlorinated solvents, etc., there is no need to provide a separate drying process after the stripping process, which streamlines the process.

According to the present invention, in addition to the above effects, the following advantages can be obtained compared to conventional peeling methods.

(1) Since fluorocarbons are nonflammable and have extremely low toxicity, the working environment is significantly improved compared to when chlorinated solvents such as trichlorethylene, tetrachlorethylene, or carbon tetrachloride are used.

(2) Due to the selective solubility of fluorocarbons and the low heating temperature of 50°C or less for imparting heat shock, there is no risk of attack on plastic moldings as in the case of using the above-mentioned chlorinated solvents; Applicable to a wide variety of plastic molded products.

Example 1 After casting and curing, an electrodeposited material of an allyl diglycol carbonate polymer lens and a crow shape was placed in a dichlorodifluoromethane solution maintained at a boiling state (-29.8°C) in a cold storage tank. 17 for 20 seconds, and then immersed for 20 seconds in a trichlorotrifluoroethane solution maintained at a boiling state (47.6°C) in a nine-air washer, and the lens and glass mold were separated in the solution. was observed. When the separated lens and glass mold were lifted from the trichlorotrifluoroethane solution into a trichlorotrifluoroethane steam tank in a steam cleaning machine, the trichlorotrifluoroethane solution that had adhered to the surfaces of the lens and glass mold was removed. It evaporated quickly and dried. Both the lens and the crow mold after drying were clean and no scratches were observed.

Patent Applicant: Mitsui Fluorochemical Co., Ltd. Patent Attorney: Shoji Ao Asa

Claims (1)

[Claims] A plastic molded product obtained by injecting a liquid plastic raw material into a glass mold and curing it and a product in close contact with the glass mold are heated to a boiling point of 130°C or more and 5000°C or less
A method for peeling a plastic molded article from a glass mold, which comprises alternately immersing the adhered article in a plurality of types of fluorocarbon liquids having different boiling points, each maintained at a different boiling point, and applying a temperature change to the adhered article.