JPH08183054A - Polycarbonate resin-extruded foam sheet - Google Patents

Abstract

PURPOSE: To provide a polycarbonate resin-extruded foam sheet having a high expansion ratio, excellent in thermoformability such as vacuum forming, etc., mold duplicativity and deep drawing properties, and, further, excellent in cushioning properties and flexibility. CONSTITUTION: A polycarbonate resin-extruded foam sheet has a skin layer on at least one face of a foam layer and has 0.5-10mm in thickness and a density of 0.03-0.6g/m<3> (preferably, less than 75% of a closed cell content). The relation between the thickness (T) of the skin layer and the thickness (t) of a cell membrane forming the foam layer satisfies the condition of T/t>=2.

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 specifically, a heat insulating container material excellent in thermoformability such as vacuum forming, heat insulating property, rigidity and toughness and enduring microwave oven heating, The present invention relates to a polycarbonate resin extruded foam sheet which is suitable as an interior heat insulating material for construction.

[0002]

2. Description of the Related Art Polycarbonate resin foams have high heat resistance, aging resistance, water resistance and the like, and also have excellent electrical and mechanical properties. Therefore, they are interior materials for automobiles and constructions, packaging materials, various containers. It is expected to be used for other purposes. Also,
It is especially promising as a container material for microwave ovens and retort foods that require heat resistance. Although there are many advantages as described above, the flow starting point of the polycarbonate resin is much 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, the solubility coefficient is 6.
A method in which 5 or more organic substances are used as a foaming agent (JP-A-2-261).
No. 836), a method in which isoparaffin having a boiling point of 50 to 150 ° C. is used as a foaming agent (Japanese Patent Publication No. 47-43183).
Etc. have been proposed. However, when a polycarbonate resin foamed sheet is produced by a foaming method using these foaming agents, a foamed sheet having a closed cell structure, which is considered to be good in a resin foamed sheet such as polyolefin or polystyrene, has a sheet width sandwiching member or Only the one with insufficient thickness and magnification is obtained, which is not practically usable, and there is a drawback that the heat insulating property as a foam is deteriorated due to insufficient magnification and thickness. Further, since polycarbonate has a low melt tension, when the foamed sheet discharged from the die slip port is picked up and hung on a mandrel, cracks or the like occur, so that the obtained extruded foamed sheet has a drawback that the surface condition is poor.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides vacuum forming with a high expansion ratio, which has an excellent surface appearance, excellent heat insulating properties, toughness, and rigidity, and has good thermoformability. It is an object of the present invention to stably provide a polycarbonate resin extruded foam sheet having a sheet width and physical properties suitable for practical use.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have found that the polycarbonate resin foam sheet obtained by extrusion foaming has a poor surface appearance, and is a polycarbonate resin foam, but lacks the heat insulating property and thermoformability of the sheet. The present invention has been completed by discovering that these are related to the thickness of the foam, the density, the thickness of the skin layer of the foam sheet and the thickness of the foam film constituting the foam layer. .

That is, according to the present invention, there is provided a polycarbonate resin extruded foam sheet having a thickness of 0.5 to 10 mm and a density of 0.03 to 0.6 g / cm ³ , which has a skin layer on at least one side of the foam layer. The relationship between the layer thickness (T) and the thickness (t) of the foam layer constituting the foam layer is T / t ≧ 2
2. A polycarbonate resin extruded foamed sheet, characterized by satisfying the condition (1), and in particular, the extruded foamed sheet of polycarbonate resin according to claim 1, characterized in that the closed cell ratio of the extruded foamed sheet is less than 75%. Seats are provided.

In order to explain the characteristics of the polycarbonate resin extruded foam sheet according to the present invention, a general method for producing an expanded foam sheet by extrusion foaming will be described below. Charge the resin and additives such as bubble regulator in the extruder,
Step of heating / melting / kneading in the machine Step of pressing a desired amount of foaming agent into the kneaded product and kneading the foaming agent into the kneaded material The process of extruding from the circular die to the low pressure part, taking it off on the side of the cylinder of the cylindrical resin cooling device (mandrel) to form a cylindrical foam, and then cutting in the extrusion direction to form a sheet foam. It is manufactured by passing through.

Further, a general sheet thermoforming method will be described below. 1. 1. Preheat the foam sheet until it softens and position it in the mold. 2. A step of bringing the pre-ripened sheet into close contact with the mold surface by evacuation. 3. Step of cooling the shaped foamed sheet 4. Molded by going through the process of taking out the molded product from the mold cavity.

The above 2. As a concrete example of the vacuum forming shown in the step of, and further the pneumatic forming, straight forming, drape forming, reverse draw forming, air slip forming,
Air blow molding by chamber blow method, plug assist molding, drape and plug assist molding, plug assist reverse draw molding, air cushion molding,
Examples include plug-assisted air slip molding, contact heating type pressure molding, and press molding.

The foamed layer of the extruded polycarbonate resin foam sheet of the present invention may be either closed cells or open cells, that is, the closed cell ratio may be high, low or intermediate. In ordinary extrusion foaming, a foaming agent and a resin are melt-kneaded in an extruder, the temperature of the kneaded product is gradually lowered in the extruder, and the melt tension such that each cell of the foam becomes independent cells. By cooling to a temperature in which the viscosity and the viscosity are balanced and extruding into a low pressure region at the die outlet, and foaming, a foam having a high closed cell rate can be obtained. Further, the extrusion temperature is extruded at a temperature higher than the normal extrusion temperature mentioned above, so that the melt tension and viscosity of the extruded resin are lowered and the cell cannot withstand the expansive force of the foaming agent, and a part of the cell membrane is It is destroyed and communicates with adjacent cells, and has a low independent foaming rate, that is,
An open cell foam is obtained. In the present invention, the extrusion temperature of the foamed polycarbonate resin sheet is in the range of 190 ° C. to 200 ° C. in order to obtain a foamed sheet having a high closed cell rate, but 210 ° C. in order to obtain a foamed sheet having a high open cell rate. The range of ~ 230 ° C is preferred. Furthermore, by lowering the molecular weight of the resin, the melt tension can be reduced, the shape retention of the cell can be reduced, and a foamed layer of open cells can be easily obtained, and extrusion foaming can be performed under the condition that a foamed sheet with a high closed cell rate is obtained. Even if the above step is performed, if the foamed sheet immediately after extrusion is not sufficiently cooled, open cells can be obtained.

As described above, in addition to the difference in the extrusion conditions between the closed cell structure and the continuous cell structure, the selection of the polycarbonate resin itself is an important factor in obtaining the closed cell structure. For example, in the case of obtaining a closed cell polycarbonate resin foam, the viscosity average molecular weight of the polycarbonate resin is preferably 29000 or more, while in the case of aiming for open cells, the viscosity average molecular weight of the resin is
It is preferably 20,000 to 29000, and if it is 20,000 or less, it is difficult to form cells themselves and it is difficult to obtain a foam.

When obtaining a polycarbonate resin foam sheet, it is much more difficult to obtain a foamed sheet having a closed cell structure than that having an open cell structure. Since it affects the width and density, the industrially manufacturable range of thickness, width, density, etc. tends to be narrower than that of open cells.

The extruded foamed polycarbonate resin sheet of the present invention is such that a skin layer is provided on at least one surface of the foamed layer which is such a core layer. A foamed sheet consisting only of the foamed layer of the core layer, when the closed cell ratio is high, hardly allows gas to pass therethrough momentarily and is excellent in thermoformability of the foamed sheet. By providing
Its thermoformability, impact resistance and rigidity are remarkably improved, and the surface characteristics are also excellent. In particular, the physical properties showing the bending strength of the sheet (hereinafter referred to as the stiffness) and the bending elastic modulus are significantly improved. The foamed sheet of the present invention has a thickness of 0.5 to 10 mm, preferably 1 to 5 mm,
The density is 0.03 to 0.6 g / cm ³ .
The thickness and density of the sheet greatly affect the stiffness of the sheet,
The thicker the sheet and the higher the density, the stronger the stiffness tends to be. However, since the foamed sheet of the present invention has the skin layer having a thickness twice or more the thickness of the cell membrane constituting the foamed layer, the influence thereof is small, and for example, the bending elastic modulus is 3
It is relatively easy to obtain a material having a thickness of 000 kg / cm ² or more, even if it has a small thickness or a small density.

A foamed sheet consisting of only the foamed layer of the core layer has a low closed cell ratio, but the thermoformability of the foamed sheet is extremely poor due to the free passage of gas, but a skin layer is provided on the foamed layer. As a result, the thermoformability becomes extremely excellent and the surface characteristics become excellent. The skin layer, which is a constituent element of the present invention, does not substantially have holes, and hardly allows gas to pass through instantaneously during thermoforming by vacuum forming and / or pressure forming.

In the present invention, in order to prepare a variety of foam sheets having various thickness, width and density ranges, it is advantageous that the foam sheets have a high degree of open cells. A method of indicating the degree of open cells in a foam sheet,
That is, in the present invention, as a method of measuring the closed cell ratio, an air comparison type hydrometer [Type 930 manufactured by Toshiba Beckman Co., Ltd.]
In accordance with ASTM D2856, and was defined by the value obtained by adopting the following measurement conditions. Conditions Sample size: The foamed sheets are cut into 25 mm squares and stacked to have a size of about 30 mm. Apparent volume: The above sample is measured with a caliper to a unit of 10 μm to determine the volume.

In the foamed sheet having the skin of the present invention, when the closed cell ratio is 75% or more, the thermoformability is remarkably improved and the physical properties such as impact resistance and rigidity are excellent. On the other hand, the closed cell ratio is less than 75%, preferably 10
Even when the content is at least 70% and less than 70%, the thermoformability becomes excellent as described above, and a molded product can be obtained in the same manner as when the closed cell ratio is at least 75%.

Further, in the extruded polycarbonate resin foam sheet of the present invention, the relationship between the thickness (T) of the skin layer and the thickness (t) of the foam layer constituting the foam layer satisfies the condition of T / t ≧ 2. Is characterized by. FIG. 1 shows the relationship between the thickness (T) of the skin layer of the polycarbonate extruded foam sheet of the present invention and the thickness (t) of the cell layer constituting the foam layer. A sectional view of a conventional polycarbonate extruded foam sheet is shown in FIG. By satisfying the condition of T / t ≧ 2, the physical properties such as impact resistance, rigidity, and heat insulating property are remarkably excellent without being restricted by the closed cell ratio of the foamed layer, and further, the polycarbonate resin having a high closed cell ratio. It exhibits deep drawing formability by vacuum forming, pressure forming, etc., which is far better than the foam sheet alone.

In general, in the case of a polycarbonate resin foam sheet alone, the closed cell ratio, which tends to change the thickness, density, width, etc., fluctuates greatly, and the impact resistance and rigidity are improved and the density is reduced by increasing the thickness. The improvement of heat insulation by
There is a problem that those effects cannot be achieved as expected. The present invention has these problems, by providing a thick skin layer on at least one side of the foam layer, the thickness, density, and width can be changed relatively freely without being bound by the fluctuation of the closed cell ratio, and the desired application can be achieved. It is possible and possible to obtain a foamed sheet having excellent desired properties exceeding the foamed sheet alone having a corresponding closed cell structure.

Further, the thickness of the foamed sheet of the present invention is, as described above, in the range of 0.5 mm to 10 mm, preferably in the range of 1 mm to 5 mm. The thickness of the sheet is 0.
If it is thinner than 5 mm, the molded product has no strength, and if it exceeds 10 mm, the heating during molding cannot evenly heat the inside of the sheet, and a good molded product cannot be obtained.

Further, when a general resin foam sheet such as a polystyrene foam sheet is produced, the cylindrical tubular foam is taken off at a speed slightly higher than the resin extrusion speed. Bubbles in the extrusion direction cross section in the body 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 with good shape without heating unevenness can be obtained, and bending strength and mechanical strength are also improved.

On the other hand, in an ordinary 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 higher than the speed at which the resin is extruded from the die.
So, in reality, the cylindrical tubular foam is taken over on the side of the cylinder of the mandrel with a small diameter, with a little fluffing.
Since the cylindrical tubular foam body is bulged near the die outlet where bubbles are formed, the bubbles formed are formed into a spherical shape that is slightly elongated in the thickness direction. Since the bubbles are formed in this manner, when the foamed sheet is heated and softened in the molding machine to be molded, the bubbles tend to be spherical at the softening temperature, and the foamed sheet expands. However, since the edge of the sheet is pressed inside the molding machine, there is no escape area for the stretched sheet, and the sheet is wavy in the molding machine and uneven heating occurs, and pucking or tearing occurs when molding such a sheet. However, the quality of the molded product deteriorates. The naki mentioned above means that the skin layer formed on the surface of the foamed sheet has cracks.

In addition to the above, one of the drawbacks of the conventional extruded foamed polycarbonate resin sheet is that it is difficult to manufacture a foamed sheet having a closed cell structure exceeding a sheet width of 500 mm. This is a problem that occurs because it is difficult to smoothly take out the extruded cylindrical foam with a mandrel having a diameter that is 250% or more larger than the circular die diameter due to the small elongation of the tubular foam. . And
If the sheet width is narrow, the work efficiency is poor for building materials, and it becomes difficult to manufacture large molded products. In general, a continuous heat molding machine for packaging containers is at least 50 in terms of work efficiency.
Since it is designed to use a sheet having a width of more than 0 mm, the type of molding machine that can be used is limited for a sheet having a width of 500 mm or less. In order to solve these problems, for example, even if a method of forcibly pulling out the cylindrical foam with a mandrel having a large diameter is adopted, the sheet will be torn or the sheet thickness will become thin, or the surface condition will deteriorate, etc. However, a high quality foamed sheet cannot be obtained.
Therefore, it was tried 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 of the foamed sheet obtained by the foaming phenomenon, such as the surface condition and mechanical properties, deteriorates.

In the polycarbonate resin extruded foamed sheet of the present invention, it is possible to control the thickness, density, etc. by using, for example, 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. It is preferable above. 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-1000 [viscosity average molecular weight 32
000, 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.

Since the foamed layer constituting the foamed polycarbonate resin extruded foamed sheet of the present invention does not need to take into consideration the closed cell ratio in particular, it is possible to control the temperature of the resin discharged from the extruder, or to take out the cylindrical foamed material. The thickness, density and sheet width can be adjusted. For example, a cylindrical tubular foam extruded from the die tip of an extruder to a low pressure region formed a balloon (a portion where the diameter of the cylindrical foam is expanded from the die diameter to the mandrel diameter) while being inflated by air from the inside. Later, it is taken up on the cylindrical side of the mandrel. At that time, increase the lip clearance at the tip of the die,
A thick sheet can be obtained by reducing the sheet take-up speed, and a thin sheet can be obtained by narrowing the clearance and increasing the take-up rate. The range of the good clearance varies depending on the amount of the foaming agent added, the resin temperature, the molecular weight of the resin, etc., but is 0.3 mm to 1.5 mm, preferably 0.
5 to 1.2 mm is good. However, the lip clearance is 1.
If it is larger than 5 mm, the pressure near the tip of the die is reduced as described above, the foaming agent is vaporized inside the die, and internal foaming may occur, resulting in a poor surface appearance of the sheet. On the other hand, if the width is less than 0.3 mm, the pressure at the tip of the die rises too much, the resin heats up, and the temperature deviates from the temperature suitable for foaming, making it difficult to obtain a good sheet.

The density (expansion ratio) of the obtained sheet can be changed by changing the addition amount of the foaming agent.
At that time, it is necessary to increase or decrease the addition amount of talc, silica, mica, mica, or other inorganic powder used as a bubble control agent. When increasing the density of the sheet, the bubbles are less likely to become finer, and it is necessary to add a large amount of a bubble control agent. Conversely, when decreasing the density, the addition amount must be reduced.

The width of the obtained sheet can be changed by changing the diameter of the die and the diameter of the mandrel. As a matter of course, if the diameter of the mandrel for finally cooling and solidifying the sheet is increased, the width of the obtained sheet becomes wider. Depending on the molecular weight of the resin, temperature, etc., the circumference of the resin discharged from the die can be expanded well depending on the amount of foaming agent added, and the ratio of the die diameter to the mandrel diameter (blow-up ratio) If they are not combined, a good sheet having a high closed cell rate cannot be obtained.

As for the skin layer, when the resin comes out from the lip at the tip of the die and is foamed, air is blown onto the surface of the die to cool it, and the resin on the sheet surface is suppressed to form a thick non-foamed skin layer. (See FIG. 3A). The temperature of the air is preferably 10 ° C to 120 ° C. At this time, the thickness of the skin layer can be changed by changing the temperature of the air, and the lower the temperature, the thicker the skin layer can be. The temperature is preferably around 30 ° C. Further, the lower the temperature of air, the more easily the skin layer is stretched. However, if the take-up speed is slow, the stretching is not sufficient,
Problems such as cracking and drawdown occur during thermoforming of the sheet. Therefore, it is desirable that the take-up speed be faster than the speed obtained by the following formula.

[Equation 1]

The skin layer can be formed by a method other than the above method. For example, the obtained sheet is brought into contact with a heated roll to melt the surface and further cooled to form a smooth skin layer (see FIG. 3 (b)). At this time, the roll temperature is preferably 200 ° C. to 300 ° C., and the line speed is preferably 0.5 m / min to 10 m / min, more preferably 1 m / min to 5 m / min. As for the method of forming the skin layer, the latter can make the surface smoother and the thickness of the skin layer can be made thicker, but it is difficult to stretch the skin layer.

The foamed sheet of the present invention is preferably stretched. The degree of stretching can be expressed by the change in heating dimension. For example, the dimensional change when heated at 170 ° C. for 30 seconds is in the range of −30 to 0% in the resin extrusion direction, particularly preferably in the range of −30 to −3%, and it shrinks somewhat during heat molding. It is possible to obtain a molded product with good shape without heating unevenness. In addition, the dimensional change in the width direction under the above heating conditions is preferably in the range of -10 to -1%, particularly -7 to -3% from the viewpoint of preventing heating unevenness. The measurement of the change in heating dimension is obtained as follows. A 170 × 170 mm test piece is prepared, and a straight line having a length of 100 mm is drawn in a cross shape in the central portion along the flow direction (MD) and the width direction (TD). This test piece is
After heat treatment for 30 seconds in an oven of 0 ± 2 ° C., the length of the straight line is measured, and the change in heating dimension is obtained 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.

In the present invention, the closed cell ratio is basically adjusted by selecting the extrusion temperature in consideration of the balance between melt tension and viscosity, adjusting the temperature by heating or cooling the foamed sheet after extrusion, and adjusting the molecular weight of the polycarbonate resin. It can be performed by adjustment or the like. For example, in the present invention, in order to obtain a foam having a high closed cell rate (closed cell rate of 75% or more), the viscosity average molecular weight of the polycarbonate resin extruded foam sheet is preferably 29000 or more. Furthermore extrusion temperature be in the range density of less than 0.03g / cm ³ ~0.06g / cm ³ foam is preferably 190 ° C. to 195 ° C., the density of the foam is 0.06g / cm ³ ~0. In the range of 6 g / cm ³ , 195 ° C to 200 ° C is preferable. On the other hand, when a foam having a low closed cell rate (closed cell rate of less than 75%), that is, an open cell foam is to be obtained, the viscosity average molecular weight of the resin is preferably 20,000 to 290,000. Furthermore extrusion temperature as long as the density of the foam is in the range of 0.03g / cm ³ ~0.06g / cm ³ is preferably 210 ° C. to 220 ° C., the foam density is 0.06g / cm ³ ~0.6g The extrusion temperature is preferably 220 ° C to 230 ° C in the range of / cm ³ .

As described above, the raw material and the foaming agent for producing the extruded polycarbonate resin foam sheet of the present invention may be limited, but the range of usable raw materials and the foaming agent is as follows. Is. The polycarbonate used as the foamed sheet material of the present invention 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-bis (4-oxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-oxyphenyl) butane, 1,1-bis (4-oxyphenyl) cyclohexane, 1,1-bis (4- Examples include polycarbonates derived from bisphenols such as 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. Since it is difficult to obtain a foam having a high expansion ratio by using only this, it is preferable to use an inorganic foaming agent or a volatile foaming agent. Volatile blowing agents include propane, n-butane, i
-Lower aliphatic hydrocarbons such as butane, n-pentane, i-pentane and hexane; lower alicyclic hydrocarbons such as cyclobutane and cyclopentane; lower aromatic hydrocarbons such as benzene, toluene and xylene; methanol, ethanol and the like Lower aliphatic monohydric alcohols; lower aliphatic ketones such as acetone and methyl ethyl ketone; 1-chloro-1,1-difluoroethane, pentafluoroethane, 1,1,1,2
-Low-boiling halogenated hydrocarbons such as tetrafluoroethane and 1,1-difluoroethane; and the like, and examples of the inorganic foaming agent include inorganic gases such as carbon dioxide gas and nitrogen gas. The foaming agents described in detail above can be used alone or as a mixture of two or more kinds. For example, different types of foaming agents such as an inorganic foaming agent and a volatile foaming agent can be used together. In addition, a decomposable foaming agent may be used in combination for controlling the bubble diameter.

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, the amount of the foaming agent used is mainly determined by the desired density of the foamed sheet. Can say The density of the foamed sheet of the present invention is preferably 0.03 to 0.6 g / cm ³ , particularly preferably 0.06 to 0.24 g / cm ³ , and a foaming agent may be used so as to fall within this range. . In addition,
When the density of the foamed sheet of the present invention is less than 0.03 g / cm ³ , the strength of the molded product is too small and the density is 0.6 g / cm ^3.
If it exceeds, the insulation cost will decrease and the weight will increase, and the manufacturing cost will increase. The density of the foam sheet is 0.06 to
0.24 g / cm ³ is preferable, and the amount of the foaming agent necessary for that is 0.5 to 10 parts by weight (when butane is used) for the volatile foaming agent and 0 for the inorganic foaming agent per 100 parts by weight of the resin. 2 to 3.0 parts by weight (when carbon dioxide is used). The density of the foamed sheet in the present invention means not only the density of the foamed layer but also the density of the entire foamed sheet including the skin layer.

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 an inorganic powder such as talc, silica, mica or mica. These cell regulators may be used alone or in combination of two or more. The addition amount is 0.01 to 5 per 100 parts by weight of resin.
The amount is preferably 0.05 to 0.5 part by weight. If the amount is less than 0.01 parts by weight, it becomes difficult to actually foam the polycarbonate resin, while if the amount is more than 5 parts by weight, the physical properties of the foamed molded product obtained are deteriorated.

Further, the foamed sheet of the present invention may contain known additives such as a flame retardant, a heat stabilizer, a weather resistance improver and a colorant, which are commonly added to ordinary foamed sheets.

Since the extruded polycarbonate resin foamed sheet of the present invention obtained as described above has a skin layer, it is extremely excellent in moldability, particularly in vacuum moldability and / or pressure air moldability, and in addition, it is a polycarbonate resin. It is a foamed sheet with the original characteristics. The polycarbonate resin originally has high rigidity, and if the closed cell rate of the sheet is 75% or more, the rigidity tends to be too high as a foamed sheet. For example, when a molded product is obtained by using a polycarbonate foam sheet as a cushioning material such as an industrial member, it is preferable to select one having a closed cell ratio of less than 75%. When the closed cell content of the foamed layer is less than 75%, the foamed sheet has both the original physical properties of the polycarbonate resin (heat resistance, aging resistance, water resistance, and impact resistance) and further cushioning properties. Control of sheet thickness, density, sheet width, etc. becomes relatively easy,
The range of choices such as the size and physical properties of the foamed sheet expands according to the application.

[0036]

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 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was fed to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 197 ° C., and the inside of the tubular foam was inflated with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.7 mm. The discharge rate of tubular foam is 5
0 kg / hr, the take-up speed of the foam is 6.1 m / min
And This foamed sheet had a closed cell rate of 80%, a density of 0.12 g / cm ² , a sheet thickness of 2.0 mm, a sheet width of 640 mm, and a bubble film thickness of 40 μm, and a skin layer having a thickness of 100 μm on both sides of this sheet. Was set up.
The skin layer was formed by blowing air from the outside and inside of the sheet near the die slip outlet. At this time, the temperature of the air is 50 ° C and the air flow rate is 0.
It is 8 m ³ / min. This sheet bending elastic modulus and heating dimensional change rate were measured, and the upper surface diameter was 150 mm and the lower surface diameter was 110 m using a thermoforming machine for taking multiple sheets.
Vacuum molding was performed on a bowl-shaped molded product having a depth of 90 mm and a depth of 90 mm, and the exposure of the sheet during molding and heating, the deep-drawing moldability, and the mold reproducibility were evaluated. The results are shown in Table 1.

Example 2 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin made of bisphenol A (viscosity average molecular weight 29000) was fed to the extruder and heated in the extruder. After melting and kneading, 0.53 mol of isopentane per 1 kg of resin as a foaming agent was pressed into the extruder and extruded at a resin temperature of 196 ° C., and the inside of the tubular foam was inflated with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.7 mm. The discharge rate of tubular foam is 5
1 kg / hr, the take-up speed of the foam is 6.2 m / min
And This foamed sheet had a closed cell rate of 80%, a density of 0.10 g / cm ² , a sheet thickness of 3.0 mm, a sheet width of 640 mm, and a bubble film thickness of 20 μm, and a skin layer having a thickness of 50 μm on both sides of this sheet. Was set up. The skin layer is formed by a method of bringing the sheet into contact with a heated roll off-line, and the temperature of the roll is 210 ° C. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin made of bisphenol A (viscosity average molecular weight 29000) was fed to the extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 196 ° C., and the inside of the tubular foam was inflated with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.8 mm. The discharge rate of tubular foam is 5
0 kg / hr, the take-up speed of the foam is 3.5 m / min
And This foamed sheet had a closed cell rate of 80%, a density of 0.10 g / cm ² , a sheet thickness of 5.0 mm, a sheet width of 640 mm, and a bubble film thickness of 50 μm, and a skin layer having a thickness of 120 μm on both sides of this sheet. Was set up.
The skin layer is formed by a method of bringing the sheet into contact with a heated roll offline, and the temperature of the roll is 210 ° C.
Is. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was fed to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 221 ° C. to inflate the inside of the tubular foam with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.8 mm. The discharge rate of tubular foam is 5
2 kg / hr, the take-up speed of the foam is 6.2 m / min
And This foamed sheet had a closed cell rate of 60%, a density of 0.13 g / cm ² , a sheet thickness of 4.0 mm, a sheet width of 640 mm, and a cell membrane thickness of 50 μm, and a skin layer having a thickness of 120 μm on both sides of this sheet. Was set up.
The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet.
At this time, the air temperature is 50 ° C and the air flow rate is 1.0 m.
³ / min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 5 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was fed to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into the extruder and extruded at a resin temperature of 215 ° C., and the inside of the tubular foam was inflated with room temperature air to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.5 mm. The discharge rate of tubular foam is 4
9 kg / hr, the take-up speed of the foam is 7.0 m / min
And This foamed sheet had a closed cell rate of 45%, a density of 0.48 g / cm ² , a sheet thickness of 2.0 mm, a sheet width of 640 mm, and a bubble film thickness of 10 μm, and a skin layer having a thickness of 30 μm on both sides of this sheet. Was set up. The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet. At this time, the air temperature is 60 ° C and the air flow rate is 0.8 m ^3.
/ Min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 6 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 22000) made of bisphenol A was supplied to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 224 ° C., and the inside of the tubular foam was inflated with room temperature air to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.7 mm. The discharge rate of tubular foam is 5
0 kg / hr, the take-up speed of the foam is 6.1 m / min
And This foamed sheet had a closed cell rate of 15%, a density of 0.12 g / cm ² , a sheet thickness of 3.0 mm, a sheet width of 640 mm, and a bubble film thickness of 50 μm, and a skin layer having a thickness of 100 μm on both sides of this sheet. Was set up.
The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet.
At this time, the air temperature is 60 ° C and the air flow rate is 0.8m.
³ / min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 7 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was supplied to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 221 ° C. to inflate the inside of the tubular foam with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.8 mm. The discharge rate of tubular foam is 5
2 kg / hr, the take-up speed of the foam is 6.2 m / min
And This foamed sheet had a closed cell rate of 60%, a density of 0.13 g / cm ² , a sheet thickness of 4.0 mm, a sheet width of 640 mm, and a cell membrane thickness of 50 μm, and a skin layer having a thickness of 120 μm on both sides of this sheet. Was set up.
The skin layer is formed by a method of bringing the sheet into contact with a heated roll offline, and the temperature of the roll is 210 ° C.
Is. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 8 To 100 parts by weight of a polycarbonate resin made of bisphenol A (viscosity average molecular weight of 29000), 0.05 parts by weight of talc as a nucleating agent was added to a raw material resin, which was heated in the extruder. After melting and kneading, 1.1 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 223 ° C. to inflate the inside of the tubular foam with normal temperature air to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 318 mm and then cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 100 mm, and the die clear is 1.0 mm. The discharge rate of the tubular foam was 49 kg / hr, and the take-up speed of the foam was 1.5 m / mi.
It was set to n. This foamed sheet had a closed cell rate of 45%, a density of 0.047 g / cm ² , a sheet thickness of 6.0 mm, a sheet width of 1000 mm, and a bubble film thickness of 15 μm, and a skin layer having a thickness of 40 μm on both sides of this sheet. Was set up. The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet. At this time, the temperature of the air is 60 ° C and the air flow rate is 0.
It is 8 m ³ / min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 9 To 100 parts by weight of a polycarbonate resin composed of bisphenol A (viscosity average molecular weight 22000), 0.05 parts by weight of talc as a nucleating agent was added, and the starting resin was fed to the extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 221 ° C. to inflate the inside of the tubular foam with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 318 mm and then cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 100 mm, and the die clear is 1.2 mm. The discharge rate of the tubular foam was 51 kg / hr, and the take-up speed of the foam was 1.2 m / mi.
It was set to n. This foamed sheet had a closed cell rate of 60%, a density of 0.13 g / cm ² , a sheet thickness of 6.0 mm, a sheet width of 1000 mm, and a bubble film thickness of 20 μm, and a skin layer having a thickness of 50 μm on both sides of this sheet. Was set up.
The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet.
At this time, the air temperature is 60 ° C and the air flow rate is 0.8m.
³ / min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Example 10 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was supplied to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into the extruder and extruded at a resin temperature of 220 ° C., the inside of the tubular foam was inflated with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 415 mm and then cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 134 mm, and the die clear is 0.7 mm. The discharge rate of the tubular foam was 51 kg / hr, and the take-up speed of the foam was 4.5 m / mi.
It was set to n. This foamed sheet has a closed cell rate of 40%, a density of 0.10 g / cm ² , a sheet thickness of 1 mm, and a sheet width of 13
The skin layer had a thickness of 00 mm and a bubble film thickness of 20 μm, and both surfaces of this sheet were provided with a skin layer having a thickness of 50 μm. The skin layer was formed near the die slip by blowing air from the outside and inside of the sheet. At this time, the air temperature is 60 ° C and the air flow rate is 0.8 m ³ /
It is min. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin (viscosity average molecular weight 29000) made of bisphenol A was heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 196 ° C., and the inside of the tubular foam was inflated with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.7 mm. The discharge rate of tubular foam is 5
0 kg / hr, the take-up speed of the foam is 5.9 m / min
And This foamed sheet had a closed cell rate of 80%, a density of 0.12 g / cm ² , a sheet thickness of 4.0 mm, a sheet width of 640 mm, a bubble film thickness of 40 μm, and a skin layer of 40 μm.
It was. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 A raw material resin prepared by adding 0.05 part by weight of talc as a nucleating agent to 100 parts by weight of a polycarbonate resin made of bisphenol A (viscosity average molecular weight 29000) was fed to an extruder and heated in the extruder. After melting and kneading, 0.5 mol of isopentane per 1 kg of resin as a foaming agent was pressed into an extruder and extruded at a resin temperature of 221 ° C. to inflate the inside of the tubular foam with air at room temperature to form a balloon. After being formed, this was taken up by a mandrel having a diameter of 200 mm and cut open along the extrusion direction to obtain a sheet-shaped foam. The circular die diameter is 65 mm, and the die clear is 0.7 mm. The discharge rate of tubular foam is 5
0 kg / hr, the take-up speed of the foam is 6.6 m / min
And This foamed sheet had a closed cell rate of 30%, a density of 0.08 g / cm ² , a sheet thickness of 5.0 mm, a sheet width of 640 mm, a bubble film thickness of 20 μm, and a skin layer of 18 μm.
It was. The obtained sheet was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Molding evaluation and physical property measurement of each foamed sheet of Examples and Comparative Examples were carried out according to the following criteria. [Evaluation Criteria] -Sheet bleaching during molding heating ◎ Good ○ No bleaching but drawdown △ Some slight bleaching × Large blasting ・ Deep drawing formability ○ Good △ Naki occurs × Tear occurs ・ Gold Mold reproducibility ○ Good △ Corner of molded product is not molded sharply × Mold shape is not reproduced

[Bending Elastic Modulus Measuring Method] A stress-strain is obtained by performing a three-point bending test under the following test pieces and test conditions. Specimen size Length (l): 15 cm Width (b): 2.5 cm Thickness (t): Sheet thickness cm Bending fulcrum distance (L): 10 cm Radius of support base tip: 0.5 cm Pressing wedge tip Radius: 0.5 cm Test speed: 1 cm / min or less The flexural modulus [kg / cm ² ] is calculated according to the following formula. Flexural modulus [kg / cm ^{2] = pL 3 / 4bt 3 r p} (kg): Stress - strain curve of the linear portion load r (cm): stress in load p - straight portions strain strain curve

[Measurement of Change in Heating Dimension] A test piece having a length of 170 mm and a width of 170 mm is prepared, and a straight line having a length of 100 mm is drawn in a cross shape in the central portion along the flow direction (MD) and the width direction (TD). Place the test piece in an oven at 170 ° C for 3
After heating for 0 seconds, the length of the straight line is measured, and the change in heating dimension is obtained by the following formula. Heating dimensional change (%) = [(length after heating mm-100m
m) / 100 m] × 100 This test is repeated three times for MD and TD, and the average value is taken as the change in heating dimension in the MD and TD directions.

[Measurement of closed cell ratio] Length 25 mm x width 25
Vx is determined by an air pycnometer method according to ASTM D2856 by stacking 0 mm test pieces and using a number of measurement samples having a thickness of about 30 mm. Hereinafter, the closed cell rate Fc (%) is calculated according to the following equation. Fo = [(Va-Vx) / Va] × 100 Fc = 100-Fo Fo (%) = Open cell ratio Va (cm ³ ): Apparent volume determined from the outer dimensions of the measurement sample Vx (cm ³ ): Measurement sample Real volume of

[Measuring Method of Sheet Skin Layer Thickness] The center of the sheet is the intersection of the longitudinal and lateral centerlines, and one side is 10
Cut a square sample to 0 mm. One side of the square sample at that time is parallel to the longitudinal direction of the sheet (however, when the sheet is not a square, the square sample is cut out from the central portion by inferring the longitudinal direction and the lateral direction from the cross-sectional shape of bubbles, etc.). . Next, the thicker skin layer of the cut out square sample is used as the upper surface (however, if the skin layer of the square sample has the same thickness on both sides, either side may be used, and if only one side has a skin layer, that surface is The upper surface of the sample), and the side cross section of the sample is magnified 50 times with a microscope, and the thickness from the outermost surface of the upper surface to the bubbles on the outermost surface (see T ₁ , _2, ... In FIG. 1) of the sample is measured. 20 points are measured at 2 mm intervals to the left and right from the center of the side, and 40 points per side and 4 sides are measured, and the average value at 160 points in total is taken as the surface layer thickness. The value is obtained by rounding off the unit of 0.1 μm. When measuring the thickness T of the skin layer at intervals of 2 mm as described above, if the measurement points coincide between the bubbles as shown in TA shown in FIG. 1, that value is not adopted and the average value is calculated. The number of measurement points that were not used is also reduced in obtaining the parameter.

[Method for measuring bubble film thickness] Using the square sample used in the measurement of the sheet skin layer thickness, the top, bottom, left, and right are found in the area (20 mm × thickness) 10 mm to the left and right from the center of the side of the sample. Measure all of the shortest distances between adjacent bubbles (see T ₁ , _2, ... in Fig. 1),
The average value of the total number of measurement points on four surfaces is taken as the bubble film thickness. The value is obtained by rounding off the unit of 0.1 μm. A continuous bubble on the sample cross section is regarded as one bubble. In addition, it is assumed that the measurement is performed once for adjacent bubbles, and the shortest distance between the bubbles and the four bubbles existing at the closest top, bottom, left, and right positions with respect to one bubble is measured.

[0055]

[Table 1]

[0056]

EFFECTS OF THE INVENTION The extruded polycarbonate resin foam sheet of the present invention has a skin layer having a specific relationship with the thickness of the foam film of the foam layer on the surface thereof. The drawability is remarkably good, and the thermoformability such as vacuum forming and the mold reproducibility are excellent even when the closed cell ratio is low. Moreover, even if the closed cell content of the foam layer is low, or even if the open cell content is high, it is superior in physical properties to the conventional polycarbonate resin foam sheet, such as flexural modulus, and When the open cell ratio of the foamed layer is high, that is, when the closed cell ratio is low, it is possible to obtain a thicker or wider one than the conventional one relatively easily because it does not have to be restricted to a bubble forming state. Moreover, as described above, no deterioration in physical properties is observed, so there is a wide range of products that can be selected depending on the application, such as heat-insulating containers, interior materials for construction, interior materials for automobiles, light-quantity adjusting construction materials such as carports and agricultural simple houses. Can be expanded.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional partial view for explaining a skin layer and a foam layer of a polycarbonate resin extruded foam sheet of the present invention.

FIG. 2 is an enlarged sectional view of a conventional extruded polycarbonate resin foam sheet.

FIG. 3 is a schematic process drawing for providing a skin layer on an extruded foam sheet.

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Claims (2)

[Claims] 1. A foamed layer having a skin layer on at least one surface, a thickness of 0.5 to 10 mm, and a density of 0.03 to 0.6 g / c.
A polycarbonate resin extruded foam sheet of m ^3,
A polycarbonate resin extruded foam sheet, characterized in that the relationship between the thickness (T) of the skin layer and the thickness (t) of the foam layer constituting the foam layer satisfies the condition of T / t ≧ 2. 2. The extruded polycarbonate resin foam sheet according to claim 1, wherein the extruded foam sheet has a closed cell ratio of less than 75%.