JPH02261836A - Foamed sheet-like polycarbonate with improved surface properties and preparation thereof - Google Patents

Abstract

PURPOSE:To improve heat-insulating properties and surface characteristics by forcing a specified foaming agent into a polycarbonate resin heat-melted with an extruder and extrusion-molding the mixture. CONSTITUTION:After a polycarbonate resin wherein a plasticizer, a lubricant, a nucleating agent (e.g. talc) are incorporated is fed in an extruder and heat- melted, a foaming agent with a solubility parameter of 6.5 or larger (e.g. methylene chloride) is forced thereinto so as to obtain a ratio of 0.11 to 1.1mol/kg resin and the mixture is extruded into a sheet to obtain a foamed polycarbonate sheet with a foaming ratio 2 to 20, a mean cell diameter of 0.2mm or larger and a thickness of 5mm or less.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a polycarbonate foam plate with improved surface properties and a method for producing the same, and more particularly, to fields that require particularly heat resistance, such as architecture. The present invention relates to a polycarbonate foam plate suitable as a material for interior materials and food packaging containers, particularly microwave oven containers and retort food containers that require heat resistance and a beautiful appearance, and a method for producing the same.

[Prior art and problems]

Conventionally, in extrusion foaming of polycarbonate resin, the current situation is that foams having closed cells have only been obtained with a foaming ratio of 20 times or more.

In this case, since a large amount of blowing agent is used, the solubility of the blowing agent in the resin is insufficient, and the blowing agent is likely to be liberated and unevenly dispersed inside the extruder, resulting in unevenness on the surface of the foam after extrusion. For example, Japanese Patent Laid-Open No. 58-67423 discloses a method for producing a high-density foam made of polycarbonate resin.

However, in this method, in order to assist the dispersibility of a large amount of blowing agent, the resin is impregnated with the blowing agent before being introduced into the extruder. If extrusion foaming is carried out, the foaming agent will be liberated inside the extruder, causing fluctuations in the load and pressure of the extruder, fluctuations in the discharge amount, etc., making it impossible to obtain a homogeneous foam, and sheet extrusion. In this case, it is not possible to obtain a foamed sheet with commercial value due to deterioration of the sheet surface due to drifting due to poor sealing at the die part or foaming inside the goo.

Furthermore, in the production of foams at relatively high temperatures such as injection molding, the expansion ratio is limited to a low expansion ratio of 2 times or less. This is because the injection viscosity is too low for foaming, and when the amount of blowing agent is increased to increase the expansion ratio to 2 times or more, problems such as coalescence of cells and formation of open cells cannot be avoided.

[Means for solving problems]

In view of these circumstances, the inventors of the present invention have conducted extensive research to solve the above-mentioned problems. By adjusting the expansion ratio, average cell diameter, and thickness, the inventors of the present invention have achieved improved surface properties and excellent heat insulation properties. It was discovered that a polycarbonate foam can be obtained, and based on this knowledge, the present invention was completed.

That is, the first aspect of the present invention is to produce a polycarbonate foam plate having an expansion ratio of 2 to 20 times, an average cell diameter of 0.2 rum or more, and a thickness of 5M or less; 0.11-1.1 m of a blowing agent having a solubility parameter (sp value) of 6.5 or more is supplied and melted by heating.

Polycarbonate foam with improved surface properties, characterized by obtaining a polycarbonate foam plate with an expansion ratio of 2 to 20 times, an average cell diameter of 0.2 or more, and a thickness of 5 or less by press-fitting 1/kg resin. Each content includes a method for manufacturing a plate-shaped body.

Characteristics of polycarbonate crystalline resin include large viscosity changes due to temperature, fluidity close to Newtonian, and high shear heat generation.
In sheet extrusion using a die or the like, the resin temperature cannot be lowered due to overload of the extruder and shear heat generation within the die.

By the way, the resin temperature at which stable extrusion can be achieved is much higher than the temperature required for foaming, and if left as it is, the bubbles will become interconnected.
A sufficient foam sheet could not be obtained, so we investigated a method of cooling the foam immediately after it was extruded from the die, and as a result, we increased the heat transfer coefficient of the sheet. That is, it has been found that it is possible to form a sheet by controlling the average cell diameter and sheet thickness.

The polycarbonate foam plate of the present invention has a foaming ratio of 2 to
20 times, preferably 5 to 10 times, average cell diameter of 0.29 or more, preferably 0.5 to lam, and thickness of 5 cm or less, preferably 5 to IIIffl.

If the foaming ratio is less than 2 times, the insulation performance will decrease;
If it is larger than 20 times, it will not be possible to obtain a surface with good surface properties.

When the average cell diameter is smaller than 0.2, only the surface of the sheet is cooled, and a sheet with excellent heat insulation properties of closed cells cannot be obtained.

The polycarbonate foam plate of the present invention uses a blowing agent with a solubility parameter of 6.5 or more, preferably 7.0 to 9°8, and a blowing agent of 0.11 to 1.1 mol/kg.
It can be obtained by press-fitting a range of resin into a molten resin in an extruder.

Examples of blowing agents with a solubility parameter of 6.5 or higher include C3 or higher hydrocarbons such as pentane, hexane, and octane, halogenated hydrocarbons such as methyl chloride, methylene chloride, dichloromonofluoromethane, and monochlorodifluoroethane, and cyclohexane. It will be done. These may be used alone or in combination of two or more, and other blowing agents may also be added in small amounts.

If a blowing agent with a solubility parameter of less than 6.5 is used, the compatibility with the polycarbonate resin will be poor, and uniform dispersion and dissolution within the extruder will not be achieved, making it difficult to ensure the stability of the extruder load. becomes impossible. Furthermore, even if the expansion ratio is 20 times or less, the surface properties of the foam sheet deteriorate and voids occur. Also, the amount of blowing agent injected is 0.
If it is less than 11 mol/kg resin, the foaming ratio will be 2.
It becomes smaller than twice as much, and sufficient insulation cannot be obtained; on the other hand, 1
．． If the amount exceeds 1 mol/resin, the blowing agent will not be sufficiently dissolved in the polycarbonate resin, and the release of the blowing agent will cause unevenness on the sheet surface and voids due to non-uniform dispersion.

Examples of the polycarbonate resin used in the present invention include 2.2-bis(4-oxyphenyl)propane, 2.
．． 2-bis(4-oxyphenyl)butane, 1.1-bis(4-oxyphenyl)cyclohexane, 1.1-bis(4-oxyphenyl)butane, 1.1-bis(4-
Aromatic polycarbonates such as oxyphenyl)isobutane and 1,1-bis(4-oxyphenyl)ethane are preferred because they have excellent heat resistance.

It is also possible to use various additives commonly used for molding polycarbonate resins. Examples of these additives include plasticizers, lubricants, and nucleating agents such as talc, clay, silica, kaolin, and calcium carbonate.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by these in any way.

Example 1 A raw material resin prepared by adding 0.02 parts by weight of talc as a nucleating agent to 100 parts by weight of polycarbonate resin made of bisphenol A (average molecular weight 125,000) was supplied to an extruder, and heated and melted and kneaded in the extruder. After that, the SP value is 9.7
of methyl chloride for 0.97 s.

1/kg of resin was press-fitted and extruded into a sheet form from the tip of an extruder at an extrusion temperature of 200°C, and the take-up speed was adjusted to obtain a foamed sheet with a thickness of 3.0 am.

The obtained foam sheet was as shown in Table 1 (with a foaming ratio of 15
．． A foamed sheet with a beautiful surface and an average cell diameter of 0.3 nm was stably obtained.

Example 2 0.56 mo of Freon 22 with an SP value of 6.6 as a blowing agent
Extrusion molding was carried out in the same manner as in Example 1 except that the resin pressure was increased by 1/kg.

As shown in Table 1, the obtained foam sheet had a foaming ratio of 9.
A foamed sheet with a beautiful surface was stably obtained with an average cell diameter of 8 times and an average cell diameter of 0.3 wa.

Comparative Example 1 Extrusion molding was carried out in the same manner as in Example 1, except that 1.7 mol/kg of methyl chloride was press-injected into the resin as a blowing agent and the extrusion temperature was 175°C.

As shown in Table 1, the obtained foam sheet had a foaming ratio of 31.
．． Although it was highly foamed and highly closed cells with a closed cell ratio of 83.4%, it had a non-uniform cell structure containing voids and had a severely uneven surface.

Furthermore, hunting occurred in the motor load of the extruder, making stable extrusion impossible.

Comparative example 2 0.7 m of Freon 12 with an sp value of 5.5 as a foaming agent.

Extrusion molding was carried out in the same manner as in Example 1 except that 1/kg resin was press-fitted.

As shown in Table 1, the obtained foamed sheet had a non-uniform cell structure containing voids, had severe surface irregularities, and had a poor closed cell ratio of 16.3%. Furthermore, the motor load on the extruder and the pressure hunting inside the extruder were severe, making stable extrusion impossible.

Comparative Example 3 Extrusion molding was carried out in the same manner as in Example 1, except that the amount of talc as a nucleating agent was increased from 0.02 parts by weight to 0.1 parts by weight.

As a result, a foamed sheet containing fine cells with an average cell diameter of 0.15 am was stably obtained, but the closed cell ratio of the sheet was as low as 7.2%.

Comparative Example 4 Extrusion molding was carried out in the same manner as in Example 1, except that the take-up speed of the sheet immediately after extrusion was set to i71, and the sheet thickness was set to 5.3 mm.

As a result, a foamed sheet with an average cell diameter of 0.3 trrts and good surface properties was stably obtained, but the closed cell ratio was as low as 30.3%.

[Action/Effect]

As described above, according to the present invention, it is possible to obtain a polycarbonate foam plate having excellent heat insulation properties and good surface properties.

Claims (1)

[Scope of Claims] 1. A polycarbonate foam plate having a foaming ratio of 2 to 20 times, an average cell diameter of 0.2 mm or more, and a thickness of 5 mm or less. 2. Supply the polycarbonate resin to an extruder and heat it to melt it, and add a blowing agent with a solubility parameter of 6.5 or more to 0.
．． By press-fitting 11 to 1.1 mol/kg resin,
A method for producing a polycarbonate foam plate with improved surface properties, characterized by obtaining a polycarbonate foam plate with an expansion ratio of 2 to 20 times, an average cell diameter of 0.2 mm or more, and a thickness of 5 mm or less.