JPH0866953A - Polycarbonate resin extrusion foamed sheet - Google Patents

Abstract

PURPOSE: To manufacture a molded piece of excellent quality with a good yield by a foamed sheet whose dimensional stability at molding with heat is excellent so that the foamed sheet is not torn nor corrugated in manufacturing a molded piece. CONSTITUTION: A foamed sheet is formed by melting and kneading a polycarbonate resin and a foaming agent with an extruder and extruding the kneaded matter from a die at the tip of the extruder to a low pressure area. When an average cell diameter and a cell shape of the foamed sheet satisfy the following conditional expressions 1<X/Z<=3, 1<Y/Z<=5, (X+Y+Z)/3>=0.1mm, wherein X represents an average cell diameter (m) in a direction crossing a sectional thickness direction of a sheet width direction, Y represents an average cell diameter (mm) in a direction crossing a sectional thickness direction of a sheet extruding direction, and Z represents an average cell diameter (mm) in a thickness direction of the sheet cross section, a polycarbonate resin extrusion foamed sheet can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate resin extruded foam sheet, and more particularly to a polycarbonate resin extruded foam sheet having good heat moldability.

[0002]

2. Description of the Related Art Polycarbonate resin foams have high heat resistance, aging resistance, water resistance and the like, and have good electrical and mechanical properties. Therefore, polycarbonate resin foams can be used for interior materials of automobiles and constructions, packaging materials, various containers, etc. Applications are expected to expand. Further, it is particularly promising as a container material for microwave ovens and retort foods, which requires heat resistance. Although there are many advantages as described above, the flow starting point of the polycarbonate resin is significantly higher than that of polystyrene and the like, and since the melt viscosity is low and the elongation of the heating sheet is small, the desired foamed sheet can be obtained by the usual extrusion foaming method. It is difficult. Therefore, a method of using an organic substance having a solubility coefficient of 6.5 or more as a foaming agent (JP-A-2-261836), a method of using isoparaffin having a boiling point of 50 to 150° C. as a foaming agent (JP-B-47-43183) and the like are available. Proposed. However, even if these foaming agents are used, a foamed sheet having good dimensional stability cannot be obtained during the heat-molding process, so that there is a problem that the sheet is torn or corrugated during the process.
In addition to the above-described extrusion foaming method, a method of impregnating a sheet-shaped polycarbonate with a foaming agent to heat-foam it, and a method of heating foaming a polycarbonate gelled with a lower alkylbenzene and a low boiling point solvent (Japanese Patent Publication No. 46-31468).
Japanese Patent Publication) is also proposed. However, since the foamed sheet produced by these methods is more expensive than the extruded foamed sheet and does not improve the dimensional stability at the time of heat molding processing, it is considered as an advantageous foamed sheet except in special cases. I can't say.

[0003]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a polycarbonate resin foam sheet which can be manufactured by a cost-effective extrusion foaming method and has good dimensional stability when heated and molded. It is an issue.

[0004]

[However, X is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the sheet width direction cross section, Y is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the sheet extrusion direction section, and Z is the sheet Shows the average bubble diameter (mm) in the thickness direction of the cross section]

In order to explain the features of the polycarbonate resin extruded foam sheet according to the present invention, a general method for producing an expanded sheet by extrusion foaming will be described below. A resin and an additive such as a bubble control agent are charged in an extruder and heated, melted and kneaded in the extruder. A desired amount of foaming agent is pressed into the kneaded product and the foaming agent is kneaded into the kneaded product. The kneaded material in which the foaming agent is kneaded is extruded at a predetermined temperature from the circular die at the tip of the extruder to the low pressure part, and this is drawn onto the cylindrical side surface of the cylindrical resin cooling device (mandrel) to form a tubular foam. After being formed, it is cut open in the extrusion direction to obtain a sheet-like foam. In the case of producing a foamed sheet by the above method, when a general resin foamed sheet such as a polystyrene foamed sheet is produced, the tubular foam is taken off at a speed slightly higher than the resin extrusion speed, so that the tension in the take-up direction is applied to the tubular foam. As a result, bubbles having a cross section in the extrusion direction in the foam are formed flat. Then, when the sheet is heated and softened in a molding machine to form the sheet, the sheet shrinks as the bubbles in the sheet try to change from a flat shape to a spherical shape, resulting in a taut state. As a result, it is considered that a molded product having a good shape without heating unevenness can be obtained, and bending strength and mechanical strength are also improved.

On the other hand, in a polycarbonate resin extruded foamed sheet, since the resin extruded from the die outlet has a very small elongation, it is difficult to draw the resin into the mandrel at a speed faster than the speed of extruding the resin from the die.
Therefore, in reality, the tubular foam is taken up by the mandrel while being slightly blunted, and since the tubular foam is blunted near the die exit where bubbles are formed, the bubbles that are formed are slightly vertical in the thickness direction. Becomes spherical. Since the bubbles are formed in this way, when the foamed sheet is heated and softened in the molding machine to be molded, the bubbles tend to become spherical at the softening temperature, and the foamed sheet expands. However, since the edges of the sheet are pressed in the molding machine, there is no escape area for the stretched sheet, and in the molding machine, the sheet is wavy and unfolded, causing uneven heating, and pucking or tearing occurs when molding such a sheet. However, the quality of the molded product deteriorates due to such problems. The naki mentioned above means that the skin layer formed on the surface of the foamed sheet has cracks.

In addition to the above, in the conventional production of a polycarbonate resin extruded foam sheet, one of the drawbacks is that it is difficult to produce a foam sheet having a sheet width exceeding 500 mm. This is a problem that occurs because it is difficult to smoothly take out the extruded tubular foam with a mandrel having a diameter that is 250% or more larger than the circular die diameter because the tubular foam has a small elongation. If the sheet width is narrow, work efficiency is poor for building materials, and it becomes difficult to manufacture a large molded product. Further, in general, a continuous thermoforming machine such as a packaging container is designed to use a sheet having a width of at least 500 mm from the viewpoint of work efficiency.
For a sheet having a width of mm or less, the type of molding machine that can be used is limited. In order to solve these, for example, even if a method of forcibly pulling the tubular foam with a large-diameter mandrel is adopted, in this method the sheet is torn or the sheet thickness becomes thin or the surface condition becomes poor, etc. Problems occur and high quality foamed sheets cannot be obtained. Therefore, it was attempted to increase the diameter of the circular die to obtain a wide sheet, but in this case it is difficult to maintain the die pressure at the tip of the extruder because the circular die diameter is large, and for that reason, inside the die. The quality such as the surface condition and mechanical properties of the foamed sheet obtained by the foaming phenomenon deteriorates.

The polycarbonate resin extruded foamed sheet of the present invention is a foamed sheet which has good dimensional stability during molding under heating and therefore does not break or wavy and can be manufactured into high quality molded articles with good yield. .. Also, width 5
It is an excellent foamed sheet exceeding 00 mm. And X
Is the average bubble diameter (mm) in the direction orthogonal to the thickness direction of the sheet width direction cross section, Y is the average bubble diameter (mm) in the direction orthogonal to the thickness direction of the sheet extrusion direction cross section, and Z is the average in the thickness direction of the sheet cross section. Assuming the bubble diameter (mm), 1<X/
Z≦3, preferably 1.5<X/Z≦3, and 1<Y/Z
A foamed foam sheet having a shape of ≦5, preferably 1.5<Y/Z≦5. The size of the bubble is (X+Y+Z)/
It is a foamed sheet having an average diameter of 0.1 mm or more, preferably 0.2 to 0.5 mm, as can be seen from 3≧0.1 mm. This extruded foam sheet is shown in FIG. 1, where (a) of FIG. 1 is a perspective view of the foam sheet, (b) is an enlarged sectional view of the portion indicated by A in (a), and (c) is (a). It is an expanded sectional view of the portion shown by B of FIG. Also,
X, Y, and Z in FIG. 1 represent the sheet width direction, sheet extrusion direction, and sheet thickness direction, respectively, and are X ₁ , X ₂ , Y ₁ , and
Y ₂ , Z ₁ , and Z ₂ represent the diameter of each bubble in each direction.

Since this foamed sheet is formed of bubbles having the above-mentioned shape, the dimensional change when heated at 170° C. for 30 seconds is 0 to -30%, particularly preferably -3 to -30% in the resin extrusion direction. Since it is in the range of 1, and shrinks a little during heat molding, it is possible to obtain a molded article with good shape without heating unevenness as in the case of molding a polystyrene foam sheet or the like. In addition, the dimensional change in the width direction under the above heating conditions is -1 to
It is preferably −10%, particularly preferably −3 to −7% from the viewpoint of preventing uneven heating. In addition, the measurement of the heating dimension change is obtained as follows. A 170×170 mm test piece was prepared, and the flow direction (MD) and width direction (T
Draw a straight line with a length of 100 mm along D) in a cross shape. The test piece is heat-treated in an oven at 170±2° C. for 30 seconds, the length of the straight line is measured, and the change in heating dimension is determined by the following formula. Change in heating dimension = [(length after heating mm-100 mm)/
100 mm]×100 This test is performed 3 times and the average value is taken as the change in the heating dimension in the MD direction and the TD direction.

The polycarbonate resin extruded foam sheet of the present invention described in detail above can be manufactured by various methods. For example, it can be achieved by using a raw material polycarbonate having a viscosity average molecular weight of 25,000 or more and a melt tension at 250° C. of 2.3 g or more. As such a polycarbonate, Iupilon S-1000 manufactured by Mitsubishi Gas Chemical Co., Inc. [viscosity average molecular weight 26000,
Melt tension 2.4 g (250° C.)], Iupilon E-10
00 [viscosity average molecular weight 32000, melt tension 6.4 g
(250° C.)], Iupilon E-2000 [viscosity average molecular weight 29000, melt tension 2.6 g (250° C.)] and the like. In addition, it may be achievable by combining a polycarbonate other than the above with a specific foaming agent. In addition to the above, the foamed sheet of the present invention can be obtained by controlling the temperature of the resin discharged from the extruder or improving the method for taking up the tubular foam. That is, it is as follows.

Generally, the tubular foam extruded from the tip of the die of the extruder into the low pressure region forms a balloon (a portion where the diameter of the tubular foam is expanded from the die diameter to the mandrel diameter) while being inflated by air from the inside. Later it is pulled onto the cylindrical side of the mandrel. And
When a polystyrene resin foam or a polyethylene resin foam is produced, air from a compressor at room temperature may be used as the air, but the base resin of the foam sheet of the present invention is a polycarbonate resin and has a glass transition point of 150.
Since the temperature is as high as ℃, the tubular foam solidifies immediately in the air of the compressor at room temperature, which makes the take-up operation difficult. However, if the temperature of the air is adjusted within the range of 51 to 200° C., the take-up operation can be facilitated. Further, if the take-up speed is slow during the take-up operation, the orientation of the bubbles constituting the foamed sheet in the extrusion direction will be insufficient, so the take-up speed is preferably higher than the speed obtained by the following formula. By this method, a good polycarbonate resin extruded foam sheet for the purpose of the present application can be obtained.

As described above, the raw material and the foaming agent for producing the polycarbonate resin extruded foam sheet of the present invention may be limited, but the range of the raw material and the foaming agent which can be used is as follows. Is. Polycarbonate used as a foam sheet material of the present invention,
It is a polyester formed from carbonic acid and glycol or bisphenol. An aromatic polycarbonate having diphenylalkane in its molecular chain is preferable because it has high crystallinity, a high melting point, and excellent heat resistance, weather resistance, and acid resistance. As such a polycarbonate,
2,2-bis(4-oxyphenyl)propane (also known as bisphenol A), 2,2-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)cyclohexane, 1,1-bis( Examples include polycarbonates derived from bisphenols such as 4-oxyphenyl)isobutane and 1,1-bis(4-oxyphenyl)ethane.

As the foaming agent used in the production of the foamed sheet of the present invention, any of an inorganic foaming agent, a volatile foaming agent and a decomposition type foaming agent can be used. In the case of the extrusion foaming method, the decomposition type foaming agent is used. It is preferable to use an inorganic foaming agent or a volatile foaming agent since a foam having a high expansion ratio cannot be obtained. As the inorganic foaming agent, carbon dioxide, air, nitrogen and the like are preferably used. Examples of the volatile blowing agent include propane, n-butane, i-butane, n-pentane, i-
Lower aliphatic hydrocarbons such as pentane and hexane; Lower alicyclic hydrocarbons such as cyclobutane and cyclopentane; Lower aromatic hydrocarbons such as benzene, toluene and xylene; Aliphatic lower monohydric alcohols such as methanol and ethanol; Acetone , Lower aliphatic ketones such as methyl ethyl ketone; 1
-Chloro-1,1-difluoroethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, 1,
Low boiling halogenated hydrocarbons such as 1-difluoroethane;
Etc. are illustrated.

The above-mentioned foaming agents can be used alone or as a mixture of two or more kinds, and it is also possible to use together different types of foaming agents such as an inorganic foaming agent and a volatile foaming agent. The amount of the foaming agent used varies depending on the type of the foaming agent and the desired expansion ratio, and the density of the foamed sheet is determined by the expansion ratio. Therefore, it can be said that the amount of the foaming agent used is mainly determined by the desired density of the foamed sheet. And the foamed sheet of the present invention has a density of 0.04 to 0.4 g/cm ³ , and preferably a density of 0.04 to 0.4 g/cm ³ .
Since it is desirable that the amount be in the range of 06 to 0.24 g/cm ³ , the foaming agent may be used so as to fall within this range. When the density of the foamed sheet of the present invention is less than 0.04 g/cm ³ , the strength of the molded product is too small, and when the density exceeds 0.4 g/cm ³ , the heat insulation property is decreased and the weight is increased and the manufacturing cost is also increased. To do.
The density of the foamed sheet is preferably 0.06 to 0.24 g/cm ^3, and the amount of the foaming agent required for that purpose is 10
0.5 to 10 parts by weight of volatile foaming agent (when butane is used) and 0.2 to 3.0 parts of inorganic blowing agent per 0 parts by weight.
It is about part by weight (when carbon dioxide is used).

In the foamed sheet of the present invention, in order to smoothly foam the polycarbonate resin, a cell regulator may be added to the melt-kneaded product of the resin and the foaming agent, if necessary. In this case, the air bubble modifier is preferably inorganic powder such as talc or silica, an acid salt of polyvalent carboxylic acid, a mixture of polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate, and the like. The amount added is 0.01 to 1.0 part by weight, preferably 0.05 to 0.5, per 100 parts by weight of the resin.
It is good to use parts by weight. To the foamed sheet of the present invention, known additives such as a flame retardant, a heat stabilizer, a weather resistance improver, and a colorant, which are commonly added to foamed sheets, can be added. The foamed sheet of the present invention is preferably a foamed sheet having an oxygen permeation amount of 6500 cm ³ /m ² or less per 24 hours in the standard state because the bubbles are formed of the polycarbonate resin film. Since the amount of oxygen permeation is small, the foamed sheet has good heat insulating properties, a small decrease in compressive strength, and a small permanent set.

The oxygen permeation amount of the bubbles in the foamed sheet varies depending on the difference in the skin layer and the bubble structure of the foamed sheet. And, it is self-evident that the amount of oxygen permeation increases when continuous cells are formed, but even a foam that does not have pores in the skin layer and appears to be mainly composed of closed cells,
When the bubbles inside form continuous bubbles, the amount of oxygen permeation increases. Therefore, in the foamed sheet of the present invention, the amount of oxygen permeation is small, which means that there are few pores in the skin layer and a cell structure, particularly even in a portion where continuous cells are likely to be formed, such as the central portion in the thickness direction, It is meant to consist mostly of closed cells. Besides, it is easily estimated that the bubble diameter and the bubble film thickness also affect the oxygen permeation amount, but as can be seen from the fact that when the bubble film thickness is large, the oxygen permeation amount is small and the compressive strength increases, It has been confirmed that the physical properties of the foamed sheet are improved when the various elements described above tend to make oxygen permeation difficult. That is, physical properties such as heat insulating property, compressive strength, and permanent strain can be estimated using the oxygen permeability as an index.

The oxygen permeation amount can be measured as follows. After covering the opening surface of the container through which gas is impermeable with a foam sheet for measurement having the same dimensions as the opening surface, the foam sheet and the opening surface are bonded with an epoxy adhesive and the cut surface of the foam sheet is cut. Seal well. Since two copper pipes for gas replacement are connected to this container, nitrogen is supplied from one copper pipe at a rate of 20 ml/min after the inside of the container is sufficiently replaced with nitrogen, and the other copper pipe is supplied. Discharge the gas in the container from. The oxygen content in the exhaust gas obtained in this way was changed to MODERN CONTROLS.
Detected with an oxygen detector such as OX-TRAN100 manufactured by
Oxygen detection amount per 24 hours x [cm ³ /24 hr] (2
5° C., 1 atm). From this value, the oxygen mole fraction in the air, and the measurement foamed sheet area S [m ² ] corresponding to the container opening area, the oxygen permeation amount X [cm ³ /m ² /24h]
r] is calculated by the following formula. X [(STP) cm ³ /m ² ·24 hr] = (100 ·
x)/(21S)

In the foamed sheet of the present invention, since the relationship between the melt viscosity of the raw material resin and the viscosity average molecular weight and the method of collecting the extruded tubular foamed body are taken into consideration, the diameter of the circular die is 250% or more. Furthermore, the tubular foam can be drawn onto a mandrel having a diameter of 300-350%. Then, even if the tubular resin is taken into a mandrel having a diameter larger than the circular die diameter by 250% or more, the sheet thickness does not become thin partially or entirely, and the sheet thickness is 0.5 to 10 mm, particularly 1 A uniform thickness of ~5 mm can be achieved. If the thickness of the foamed sheet is less than 0.5 mm, the strength of the molded product formed from the sheet is small, and if the thickness exceeds 10 mm, the temperature of the sheet surface and the inner surface becomes non-uniform during heat molding, which results in defective molding. Often becomes. As described above, the foamed sheet of the present invention is obtained as a sheet having a uniform thickness, but in order to make the thickness more uniform, the resin flow channel width near the opening of the circular die is narrowed; extruded from the circular die. When the tubular foam is taken up by the mandrel and cooled, the cooling air is blown from the surface of the mandrel and the outside to the inner surface and the outer surface of the tubular foam; one or more methods may be used.

The polycarbonate resin foamed sheet obtained as described above is a foamed sheet having good moldability and having the original characteristics of the polycarbonate resin, and a molded product can be produced as it is. However, when it is necessary to further increase the mechanical strength of the foamed sheet, it is preferable to laminate a thermoplastic resin on both sides or one side of the foamed sheet. Then, as the thermoplastic resin in this case, it is preferable to use a polycarbonate resin having good adhesiveness to the foamed sheet, and a recovered resin can be used for the polycarbonate resin. That is, in this case, the strength of the molded product hardly changes regardless of whether the new resin or the recovered resin is used as the laminated resin. It is self-evident that the laminated material composed of an unsaturated polyester resin reinforced with glass fiber, carbon fiber or the like, a thermoplastic resin or a thermosetting resin, and a polycarbonate resin foam sheet of the present invention are laminated. You can also

[0020]

EXAMPLES Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

Example 1 Viscosity average molecular weight 250 derived from bisphenol A
00, density 1.2 g/cm ³ , melt tension at 250° C., 100 g by weight of a polycarbonate resin, 0.02 part by weight of talc as a cell adjuster, and heating, melting and mixing in an extruder. Then, n-pentane was press-fitted into the extruder at 0.53 mol/kg resin, and the tubular resin impregnated with the foaming agent was extruded from the circular die at the tip of the extruder at a resin temperature of 200° C. to form a tubular foam. A balloon was formed while heating the inside and the outside with hot air of 80° C., the balloon was taken up by a mandrel having a diameter of 200 mm, and then cut open along the extrusion direction to obtain a sheet-like foam. The circular die diameter is 65m
m and die clear are 0.7 mm. The discharge rate of the tubular foam was 50 kg/hr and the take-up speed of the resin was 6.5 m/min. Table 1 shows the density, thickness, width, shape and size of bubbles, and dimensional change of the obtained foamed sheet when heated to 170° C. for 30 seconds. Note that X, Y, and Z shown in this table are X, Y, and Z described above for explaining the shape of the bubbles, MD is the longitudinal direction (extrusion direction) of the sheet, and TD is the sheet's The width direction is shown.

Example 2 The amount of n-pentane added was 0.97 mol/kg resin,
Except that the take-up speed of the tubular foam was 8.0 m/min,
A foamed sheet was prepared in the same manner as in Example 1. Table 1 shows the density, thickness, width, shape and size of bubbles, and dimensional change during heating, which were measured in the same manner as in Example 1 of the obtained foamed sheet.

Example 3 The amount of n-pentane added was 1.33 mol/kg resin,
A foam sheet was produced in the same manner as in Example 1 except that the mandrel diameter was 350 mm and the tubular foam take-up speed was 11.0 m/min. Table 1 shows the density, thickness, width, shape and size of bubbles, and dimensional change during heating, which were measured in the same manner as in Example 1 of the obtained foamed sheet.

Example 4 Carbon dioxide gas was used as a foaming agent, and the amount of the carbon dioxide gas added was 0.52 mol/kg of resin, and the take-up speed of the tubular foam was 6.2 m.
A foamed sheet was produced in the same manner as in Example 1 except that it was set to /minute. Density, thickness of the obtained foam sheet,
Table 1 shows the width, the shape and size of the bubbles, and the dimensional changes during heating, which were measured in the same manner as in Example 1.

Comparative Example 1 Methyl chloride was used as a foaming agent, the amount of the resin was 0.97 mol/kg, and the tubular foam was collected by a mandrel having a diameter of 150 mm at a speed of 3.5 m/min. A foamed sheet was produced in the same manner as in Example 1. Table 1 shows the density, thickness, width, shape and size of bubbles, and dimensional change during heating, which were measured in the same manner as in Example 1 of the obtained sheet.

Comparative Example 2 An attempt was made to prepare a foamed sheet in the same manner as in Comparative Example 1 except that the mandrel used had a diameter of 200 mm, but the elongation of the resin at the outlet of the circular die was not sufficient. The sheet could not be formed.

Comparative Example 3 A foamed sheet was prepared in the same manner as in Example 1 except that the take-up speed of the tubular foam was 3.5 m/min, and the density, thickness, width and bubbles shown in Table 1 were obtained. Shape and size and dimensional change during heating (measured in the same manner as in Example 1)
A foamed sheet having Since the foamed sheet had a dimensional change of +8.5% when heated in the longitudinal direction, it was severely corrugated due to waviness in the molding machine during heat molding, and a good molded body could not be obtained.

Comparative Example 4 An attempt was made to produce a foamed sheet in the same manner as in Example 1 except that chlorodifluoromethane was used as the foaming agent and the amount added was 0.56 mol/kg resin. A sheet could not be produced because the resin at the outlet of the circular die was insufficiently stretched.

[0029]

[Table 1]

[0030]

EFFECT OF THE INVENTION The polycarbonate resin extruded foamed sheet of the present invention has good dimensional stability when heated and molded because the foamed cells are formed in a flat shape, and therefore the foamed sheet breaks during molding. It is a foamed sheet which is less likely to wavy or wavy, and which allows a high-quality molded product to be obtained with good yield. Further, the polycarbonate resin extruded foam sheet of the present invention has an oxygen transmission amount of 6500 (S
In the case of TP) cm ³ /m ² ·24 hr or less, the foamed sheet is lightweight and has a high heat insulating property and also has a large mechanical strength such as compression strength of the molded product. Furthermore, the polycarbonate resin extruded foam sheet of the present invention has a density of 0.04 to 0.4.
Since it is possible to produce a foamed sheet having a g/cm ³ , a thickness of 0.5 to 10 mm, and a width of 500 mm or more orthogonal to the sheet extrusion direction, it is suitable as a foamed sheet for the production of large-sized molded articles and building materials. Above is a foam sheet that can be used on all types of continuous thermoforming machines currently in use.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a bubble shape in a foam sheet of the present invention.

[Explanation of symbols]

X sheet width direction Y sheet extrusion direction Z sheet thickness direction

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C08L 69:00

Claims (4)

[Claims] 1. A foamed sheet obtained by melt-kneading a polycarbonate resin and a foaming agent with an extruder and then extruding the melt-kneaded product from a die at the tip of the extruder to a low pressure region, wherein the average diameter and shape of bubbles in the foamed sheet. Satisfies the following conditional expression: A polycarbonate resin extruded foam sheet. 1<X/Z≦3 1<Y/Z≦5 (X+Y+Z)/3≧0.1 mm [where X is the average cell diameter (mm) in the direction orthogonal to the thickness direction of the sheet width direction cross section, and Y is The average cell diameter (mm) in the direction orthogonal to the thickness direction of the sheet extrusion direction cross section is
Z represents the average cell diameter (mm) in the thickness direction of the sheet cross section] 2. The oxygen permeation amount is 6 per 24 hours in a standard state.
^{2. The} pressure is 500 cm ³ /m ² or less.
The polycarbonate resin extruded foam sheet described in 1. 3. The method according to claim 1 or 2, wherein the density is 0.04 to 0.4 g/cm ³ , the thickness is 0.5 to 10 mm, and the width orthogonal to the sheet extrusion direction is more than 500 mm. Polycarbonate resin extruded foam sheet. 4. The polycarbonate resin extruded foam according to claim 1, wherein the dimensional change when heated at 170° C. for 30 seconds is in the range of 0 to −30% in the extruding direction. Sheet.