JPS634502B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing foam from polycarbonate moldings.

Polycarbonate foam has excellent properties,
For example, due to its good electrical properties, high heat resistance, good mechanical properties, high aging resistance, good water resistance, etc., it is suitably used for various purposes such as heat insulating materials, building materials, etc.

Conventionally, polycarbonate foams, like other thermoplastic resin foams, have been produced by using a pyrolytic blowing agent or a volatile organic solvent as a blowing agent.

However, thermally decomposable blowing agents have the disadvantage that when they decompose, compounds containing nitrogen-containing groups such as amino groups and nitrile groups remain, resulting in the decomposition of polycarbonate, whereas volatile organic solvents do not have the above disadvantages. However, since foaming is carried out by heating a material impregnated with an organic solvent to evaporate and swell the organic solvent, it has the disadvantage that only a foam with a low magnification can be obtained.

SUMMARY OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a method for producing a foam with a high magnification by using an organic solvent as a blowing agent. Another object of the present invention is to provide a method for producing a foam having a skin layer and having high strength.

That is, the gist of the present invention is as follows: 1. A polycarbonate molded body is impregnated with an organic solvent having a boiling point lower than the glass transition temperature of the polycarbonate, and the impregnated polycarbonate molded body is supplied to a mold, and is heated to a temperature higher than the melting point of the polycarbonate while being pressurized in the mold. After heating, the polycarbonate foam is cooled to a temperature range from the glass transition temperature to the melting point of the polycarbonate, and then decompressed and foamed in a substantially closed mold. The polycarbonate is impregnated with an organic solvent having a boiling point lower than the glass transition temperature of the polycarbonate, supplied to a mold, and heated in the mold to a temperature higher than the melting point of the polycarbonate while being pressurized. The method of producing polycarbonate is characterized in that it is rapidly cooled to a temperature range, then a mold is expanded in one direction, and foaming is performed in the expanded and substantially sealed mold.

The polycarbonate used in the present invention is a polyester of carbonic acid and glycol or bisphenol, and the aromatic polycarbonate having diphenyl alkane in the molecular chain has good crystallinity, a high melting point, heat resistance, weather resistance, It is preferred because it has excellent acid resistance. Examples of the aromatic polycarbonates include 2,2-bis(4-oxyphenyl)propane, 2,2-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)cyclohexane, and 1,1-bis(4-oxyphenyl)butane. 4
-oxyphenyl)butane, 1,1-bis(4-
oxyphenyl)isobutane, 1,1-bis(4
Polycarbonates from bisphenols such as -oxyphenyl)ethane may be mentioned.

In the present invention, the polycarbonate is formed into a molded article, and any conventionally known method may be employed as the molding method, such as extrusion molding, injection molding, compression molding, etc.

The organic solvent used in the present invention is one that can be impregnated into the polycarbonate and has a boiling point lower than the glass transition temperature of the polycarbonate, and preferably has a boiling point of 0°C or higher, such as pentane, isopentane, hexane, etc. , aliphatic hydrocarbons such as isohexane, heptane, octane, cyclohexane, trichlorotrifluoroethane, dichlorotetrafluoroethane,
Examples include fluorinated aliphatic hydrocarbons such as tetrachlorodifluoroethane, aromatic hydrocarbons such as benzene, toluene, and xylene, alcohols such as butyl alcohol and propyl alcohol, and ethers. Preferably, the material does not whiten or react with the polycarbonate when impregnated with the polycarbonate, and pentane, isopentane, heptane, isoheptane, cyclohexane, and trichlorotrifluoroethane are preferred, and cyclohexane and trichlorotrifluoroethane are more preferred. .

In the present invention, the polycarbonate molded body is impregnated with the organic solvent, and any known impregnation method may be adopted. For example, the polycarbonate molded body, an organic solvent and, if necessary, nitrogen are placed in a pressure vessel. A method is adopted in which an inert gas such as gas or carbon dioxide is supplied, and the organic solvent is heated to a temperature higher than the boiling point and pressurized.

In the present invention, the polycarbonate molded body impregnated with an organic solvent is then fed into a mold and heated to a temperature above the melting point of the polycarbonate while being pressurized. The above pressurizing conditions are not particularly limited, but 100
It is preferable to press under conditions of ~20 kg/cm ² and heating conditions are preferably 10 to 40° C. higher than the melting point of polycarbonate.

In the present invention, after heating and pressurizing, the temperature is cooled to a temperature range from the glass transition temperature to the melting point, but any method may be used for cooling, such as water cooling,
Methods such as air cooling may be used, and the polycarbonate molded body is preferably cooled to a temperature where the surface temperature is 10 to 40°C higher than the glass transition temperature.

When the pressure is released, the polycarbonate molded article begins to foam, but in the present invention, foaming is performed in a mold that is sealed in a furnace. Any method may be used for the above foaming, such as a method in which the polycarbonate molded product is decompressed and then fed into a predetermined substantially closed mold to foam, or a method in which the polycarbonate molded product is heated and pressurized with a press, and after cooling, the press is expanded. , a method for foaming by installing a spacer around the press, etc.

Further, the polycarbonate molded body was heated and pressurized in a mold to a temperature above the melting point, and then rapidly cooled to a temperature range from the glass transition temperature to the melting point, and then the mold was expanded in one direction, and the mold was expanded and substantially sealed. When foamed in a mold, the periphery of the polycarbonate molded body is rapidly cooled, the interior is not cooled, and foaming occurs only in one direction, resulting in a foamed body with a skin and elongated cells in one direction.

In addition, when producing a polycarbonate molded article, plasticizers and lubricants commonly used in polycarbonate molding may be added, and calcium carbonate, talc, clay, mica powder, perlite, silica, kaolin, diatomaceous earth, etc. Foam control agents may also be added.

The structure of the present invention is as described above, and the polycarbonate molded body is impregnated with an organic solvent, heated and pressurized in a mold, and then cooled to a temperature range from the glass transition temperature to the melting point, decompressed, and almost sealed. Since it is foamed in the mold, the impregnated organic solvent does not vaporize and escape when heated and pressurized, and also does not escape into the atmosphere during foaming, resulting in a uniform foam with a high expansion ratio. is obtained. Furthermore, when the material is rapidly cooled and foamed in a substantially closed mold expanded in one direction, a foam with a high expansion ratio having a skin and elongated cells in one direction can be obtained. Furthermore, since the blowing agent used in the present invention is an organic solvent, there is no risk that the polycarbonate will decompose, and the properties of the polycarbonate such as electrical properties, mechanical properties, heat resistance, aging resistance, and water resistance will deteriorate. It is suitable for use in heat insulation materials, electrical insulation materials, building materials, etc.

Next, the manufacturing method of the present invention will be explained using examples.

Example 1 A spacer with a square inner shape of 120 x 120 mm and a thickness of 3 mm was placed on a press plate, and granular polycarbonate resin [manufactured by Teijin Chemicals, trade name: Panlite K-1300, 2] was placed inside the spacer. 2-bis(4-oxyphenyl)propane] was supplied and molded for 5 minutes at 280° C. and 150 kg/cm ² to obtain a polycarbonate plate.

The obtained polycarbonate plate and cyclohexane 3 were supplied to the pressure vessel No. 5, and heated in an oil bath maintained at 170° C. for 80 minutes to impregnate the polycarbonate plate with cyclohexane. After cooling the inside of the pressure vessel to room temperature, the polycarbonate plate was taken out and weighed, and it was found that cyclohexane was
It was impregnated with 19% by weight.

The polycarbonate plate impregnated with the above cyclohexane is supplied to the spacer, and is pressed in the press.
Heat and pressurize for 5 minutes at 240℃ and 150Kg/cm ² , turn off the power to the press while applying pressure, and cool to 160℃. Then, at the same time as releasing the pressure, pull up the press plate and place the spacer with an inner diameter of 360×. The spacer was replaced with a 360 mm square spacer 9 mm thick, pressed again and left to stand, yielding a polycarbonate foam measuring 360 x 360 x 9 mm. Expanded bubbles are approximately spherical,
It was uniformly dispersed, and the apparent specific gravity was 0.044.

Example 2 A spacer with a square inner diameter of 160 x 160 mm and a thickness of 1 mm was placed on a press plate, and granular polycarbonate resin [manufactured by Teijin Kasei Co., Ltd., trade name: Panlite L-1250, 2] was placed inside the spacer. [Polycarbonate from 2-bis(4-oxyphenyl)propane] was supplied and press-molded for 5 minutes at 280° C. and 180 kg/cm ² to obtain a polycarbonate plate.

Example 1 using the obtained polycarbonate plate
When impregnated with cyclohexane in the same manner as in step 1, the impregnation amount was 15.8% by weight.

The above cyclohexane-impregnated polycarbonate plate was fed into a female mold with an inner diameter of 160 x 160 x 30 (depth) mm, and heated and pressurized in a male mold at 240°C and 150 kg/cm ² for 5 minutes. While still under pressure, the inner surface of the mold was rapidly cooled with water to 180℃, then the pressure was released, and the male mold was pulled up and fixed so that the gap between the male mold and the female mold was 25 mm. , 160×160×
A 25 mm polycarbonate foam was obtained.

The obtained foam had a surface layer of about 1 mm, elongated cells were uniformly dispersed in the thickness direction, and the expansion ratio was 24.3 times.

Example 3 The press plate has a square inner shape of 160 x 160 mm,
Place a spacer with a thickness of 0.5 mm, and supply granular polycarbonate resin [manufactured by Teijin Chemicals, product name Panlite L-1250W, polycarbonate made from 2,2-bis(4-oxyphenyl)propane] into the spacer. Then, press molding was performed for 5 minutes at 280° C. and 180 kg/cm ² to obtain a polycarbonate plate.

The obtained polycarbonate plate and trichlorotrifluoroethane 3 were supplied to the pressure vessel of 5,
The polycarbonate plate was impregnated with trichlorotrifluoroethane by heating in an oil bath maintained at 170°C for 3 hours. After cooling the inside of the pressure vessel to room temperature, the polycarbonate plate was taken out and weighed, and it was found that trichlorotrifluoroethane was present.
It was impregnated with 16.5% by weight.

The above trichlorotrifluoroethane-impregnated polycarbonate plate was supplied to the female mold used in Example 2, and the male mold was heated at 240°C and 130 kg/cm ² for 10 min.
Heat and pressurize for a minute, then water the inside of the mold while keeping the pressure applied.
When the mold was rapidly cooled to 180°, the pressure was released, and the male mold was pulled up and fixed so that the gap between the male and female molds was 20 mm, a foam of 160 x 160 x 20 mm was obtained.

The resulting foam has a surface of approximately 0.8 mm;
Elongated air bubbles were uniformly dispersed in the thickness direction, and the expansion ratio was 38.8 times.

Claims (1)

[Claims] 1. A polycarbonate molded body is impregnated with an organic solvent having a boiling point lower than the glass transition temperature of the polycarbonate, supplied to a mold, and heated to a temperature higher than the melting point of the polycarbonate while being pressurized within the mold. After that, the polycarbonate foam is cooled to a temperature range from the glass transition temperature to the melting point of the polycarbonate, and then depressurized and foamed in a substantially closed mold. 2. The manufacturing method according to claim 1, wherein the polycarbonate is an aromatic polycarbonate. 3. The manufacturing method according to claim 1 or 2, wherein the organic solvent has a boiling point of 0° C. or higher. 4 A polycarbonate molded body is impregnated with an organic solvent having a boiling point lower than the glass transition temperature of the polycarbonate, supplied to a mold, and heated in the mold to a temperature higher than the melting point of the polycarbonate while being pressurized. A method for producing polycarbonate, which comprises rapidly cooling the polycarbonate to a temperature range from the glass transition temperature to the melting point, then expanding a mold in one direction, and foaming in the expanded and substantially sealed mold. 5. The manufacturing method according to claim 4, wherein polycarbonate or aromatic polycarbonate is used. 6. The manufacturing method according to claim 4 or 5, wherein the organic solvent has a boiling point of 0° C. or higher.