JPH09216273A - Method for producing thermoplastic resin foam sheet having skin layer - Google Patents

Abstract

(57) Abstract: A method for producing a foamed thermoplastic resin sheet having a skin layer by using an extrusion molding device having a simple structure is provided. SOLUTION: An expandable thermoplastic resin is extruded from a die, and a thermoplastic resin foam sheet having a skin layer for cooling and shaping by using a cooling plate having two upper and lower cooling surfaces attached to the tip of the die is produced. A method, wherein the upper and lower two cooling surfaces of the cooling plate are opened forward at an opening angle of 5 to 35 °, and the temperature of the cooling plate cooling surface is 20 to 100 ° C.
And a method for producing a thermoplastic resin foam sheet having a skin layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a thermoplastic resin foam sheet having skin layers on both surfaces.
Specifically, when an expandable thermoplastic resin is extrusion-molded to form a foamed sheet, a cooling plate having a simple structure is attached to the tip of the die, and a single molding device is used to heat the skin layer on both surfaces. The present invention relates to a method for producing a plastic resin foam sheet.

[0002]

2. Description of the Related Art A method for producing a foamed resin sheet having a skin layer is disclosed in, for example, JP-B-45-29919 and JP-B-48-12423, and is already known. However, the method disclosed therein is a method using a die, a molding tool, or the like having a complicated structure in which a mandrel is mounted. Also, when manufacturing a wide variety of products,
It is necessary to provide various types of dies, molding tools, etc. according to the shape of the product, and in the case of producing a large number of products in small quantities, the equipment cost will increase and the cost will increase.

Further, Japanese Patent Laid-Open No. 50-107067,
Japanese Patent Laid-Open No. 51-578 discloses a method for producing a foamed resin sheet having a skin layer. However, the methods disclosed in these are methods in which two or more extruders are used, a foam layer is formed by one extruder, a skin layer is formed by the other extruder, and then both are laminated. . Therefore, the process becomes complicated and, as a result, the manufacturing cost increases.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to use an extrusion molding apparatus having a simple structure and to provide a heat treatment having a skin layer. It is an object of the present invention to provide a method capable of producing a foamed plastic resin sheet.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention mounted a cooling plate of a specific shape on the tip of a die and inflated the thermoplastic resin discharged from the die. By cooling under certain conditions,
The present inventors have found that a thermoplastic resin foam sheet having thick skin layers on both sides can be easily manufactured, and completed the present invention.

That is, according to the present invention, an expandable thermoplastic resin is extruded from a die, and a thermoplastic resin having a skin layer for cooling and shaping using a cooling plate having two upper and lower cooling surfaces mounted on the tip of the die is used. A method for producing a resin foam sheet, characterized in that the upper and lower two cooling surfaces of the cooling plate are opened forward at an opening angle of 5 to 35 °, and the temperature of the cooling plate cooling surface is 20 to 100 ° C. A method for producing a thermoplastic resin foam sheet having a skin layer is provided.

A feature of the present invention is that a cooling plate having upper and lower two cooling surfaces is attached to the tip of the die and the expandable thermoplastic resin discharged from the die is cooled to form a skin layer. The cooling plate used in the present invention has an extremely simple structure and has an advantage that it can be installed inexpensively. Further, by adjusting the surface distance of the cooling roll in the next step, by adjusting the take-up speed of the foamed sheet, the thickness of the foamed sheet can be appropriately adjusted, which is extremely useful as a method for producing a small amount of a variety of thermoplastic resin foamed sheets. Is. still,
In the present invention, the expandable thermoplastic resin, heating and kneading the thermoplastic resin and the foaming agent in a molding machine such as an extruder,
It means a molten thermoplastic resin containing a foaming agent and / or a foaming gas, which is formed by melting.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The expandable thermoplastic resin used in the present invention is obtained by adding a foaming agent to a thermoplastic resin, mixing it, and heating, kneading, and melting in a molding machine such as an extruder. The expandable thermoplastic resin is extruded into a sheet form from a die lip at the tip of a molding machine such as an extruder, and the surface of the sheet is cooled by a cooling surface of a cooling plate attached to the tip of the die to form a skin layer. . The inside of the sheet that is not cooled by the cooling plate foams to form a foamed layer.
The obtained foamed sheet is preferably further cooled by a chill roll and taken off to be a product. Hereinafter, the present invention will be described in detail.

As the thermoplastic resin used in the present invention, polypropylene and propylene-other olefin copolymers,
High density polyethylene, low density polyethylene, ethylene-
Other examples include polyolefins such as olefin copolymers, polystyrene, polyvinyl chloride, polyamide, polyethylene terephthalate, polymethylmethacrylate, and polycarbonate. Of these, polyolefin is preferably used.

As the blowing agent, nitrogen, carbon dioxide, ethane, propane, butane, pentane, hexane, heptane, ethylene, propylene, water, petroleum ether, methyl chloride, monochlorotrifluoromethane, dichlorodifluoromethane, dichlorotetra Fluorethane, sodium bicarbonate, ammonium bicarbonate, sodium borohydride, azodicarbonamide, N, N-dinitrosopentamethylenetetramine, p, p-oxybis (benzenesulfonylhydrazide) azobisisobutyronitrile,
Paratoluene sulfonyl hydrazide etc. are mentioned.

There is no particular limitation on the amount of the foaming agent added, and normally, the amount used in the production of the foamed resin sheet may be used. The amount of the foaming agent added varies depending on the expansion ratio of the sheet, but is usually 0.
It is about 1 to 5 parts by weight. In addition to the foaming agent, other additives such as a lubricant, an ultraviolet absorber, a heat stabilizer, a pigment and a dye may be added to the thermoplastic resin, if necessary.

Next, an example of the cooling plate used in the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a cooling plate mounted on the tip of a T-die. The cooling plates 2 and 2'are attached to the tip of the T die 1 attached to the tip of the extruder. A flat resin flow passage is formed inside the T-die 1 from the inlet toward the lip 4, and the flow passage communicates with the lips 4 and 4 ′ through the manifold 3. The cooling plates 2, 2 ′ have an upper cooling surface 5 and a lower cooling surface 6. The cooling plate 2 has one end of its upper cooling surface 5 flush with the inner surface of the lip 4, and the cooling plate 2 ′ has one end of its lower cooling surface 6 flush with the inner surface of the lip 4 ′. Each of them is attached so as to be a horizontal surface, and attached to the T-die 1 with bolts 7 and 7 '. Inside the cooling plates 2, 2 ', a passage 8 for a temperature control medium,
8'is provided. It is preferable that the heat insulating materials 9 and 9 ′ are sandwiched between the mounting surfaces of the T die 1 and the cooling plates 2 and 2 ′.

The present invention is characterized in that the angle θ between the upper cooling surface 5 and the lower cooling surface 6 of the cooling plates 2 and 2 '(the angle that opens in the resin flow direction) is limited to a specific range. . In order to achieve the object of the present invention, the angle θ is 5 to 3
It is preferably in the range of 5 °. More preferably 8
３０30 °. The angle θ affects the thickness of the skin layer of the resulting thermoplastic resin foam sheet, the surface state of the skin layer, the extrusion moldability, and the like. If the angle θ becomes too large, the expandable thermoplastic resin discharged from the lips 4, 4 ′ becomes difficult to adhere to the upper cooling surface 5 and the lower cooling surface 6 of the cooling plates 2, 2 ′, and a thick skin layer is formed. It will be difficult. vice versa,
If it is too small, the fluidity of the expandable thermoplastic resin passing through the cooling plates 2 and 2'is lowered, and it becomes difficult to obtain a foamed sheet having a good surface condition. From this viewpoint, the angle θ is preferably in the above range.

The length of the cooling plates 2, 2 '(horizontal length, the same applies hereinafter) is preferably such that the pressure loss of the resin flow does not become too large. On the other hand, if it is too short, it becomes difficult to process the passage 9 for the temperature control medium and the like inside. Considering this point, the length of the cooling plates 2 and 2'is 10
It is preferably about 50 mm. The left and right side surfaces of the space formed by the upper cooling surface 5 and the lower cooling surface 6 of the cooling plates 2 and 2'may be left open, or a metal plate or the like may be attached and sealed.

The thermoplastic resin containing the foaming agent heated, kneaded and melted in the extruder becomes an expandable thermoplastic resin and is discharged from the lips 4, 4'through the manifold 3 of the T die 1, and then, Upper cooling surface 5 of cooling plates 2 and 2 '
Both surfaces are cooled by the lower cooling surface 6, and skin layers are formed on both surfaces of the sheet. The expandable thermoplastic resin having the skin layer formed therein expands to form a foam layer. The temperature at which the thermoplastic resin containing the foaming agent is kneaded and melted in the extruder varies depending on the type of resin, but is usually about 120 to 250 ° C.

The temperature of the cooling plate depends on the thickness of the skin layer,
Affects the surface condition of the skin layer. When the temperature is high,
The surface condition of the skin layer is good, but the skin layer becomes thin, and when the temperature is low, the surface condition of the skin layer deteriorates. Considering these, it is preferable to control the temperature of the cooling plate so that the temperatures of the upper cooling surface 5 and the lower cooling surface 6 are 20 to 100 ° C. More preferably, it is 50-80 degreeC. By controlling the angle θ and the temperature of the cooling plate within the above ranges, a skin layer having a thickness of 0.3 to 2 mm is formed on both surfaces of the sheet.

The thermoplastic resin foam sheet, which has been cooled by the cooling plate and has the skin layers formed on both surfaces, expands internally, so that a temperature near room temperature is obtained by using a cooling roll such as a pair of small rolls. It can be cooled to a predetermined thickness. In this case, the thickness adjustment of the foam sheet is
This can be done by adjusting the surface gap and the take-up speed of at least one pair of cooling rolls forming a pair. The upper limit of the number of pairs of cooling roll groups is not particularly limited, but may be about 10 pairs.

Thickness of thermoplastic resin foam sheet that can be produced by applying the present invention (total of front and back skin layers and internal foam layer)
Is usually 5 depending on the shape of the cooling plate.
It is about 50 mm. It is preferable to apply a thick foamed sheet having a large angle θ shown in FIG. 1 and a thin foamed sheet having a small angle θ. For example,
When a cooling plate having an angle θ of 17 degrees is used, a foamed sheet having a thickness of 8 to 20 mm can be easily manufactured.

By adjusting the surface gap and the take-up speed of the pair of cooling rolls, a foamed sheet having a skin layer of a wide range of thickness can be manufactured by the same manufacturing facility (cooling plate). In the present invention, the surface gap of the cooling roll is 5 to 50 mm, and the take-up speed is 10 to 500 mm / m.
in. Examples of the method for collecting the foamed sheet include a method using a rubber roll, a caterpillar, or the like.

The thermoplastic resin foam sheet having the skin layer manufactured as described above is cut into a predetermined width and length to obtain a product. Usually the width is 20-2000
mm, the length is about 0.2 to 5 m.

It is preferable to provide heat insulation between the cooling plate and the die so that the die is not cooled. As a method of heat insulation, there is a method of interposing an object having a small thermal conductivity such as PES or PEEK between the die and the cooling plate, and a method of cutting the die or the cooling plate into a recess to reduce the contact area between the die and the cooling plate. Can be mentioned. Moreover, it is preferable that the upper and lower cooling surfaces of the cooling plate have a slipperiness of the foamed resin by Teflon processing or the like.

Since the thermoplastic resin foam sheet having a skin layer produced by applying the present invention has appropriate rigidity and is lightweight, furniture such as shelves and tables can be used as a substitute for wooden boards. It can be used in various fields such as office supplies, building materials, and stationery materials.

[0023]

The present invention will be described in detail below with reference to examples. Example 1 Polypropylene (manufactured by Mitsui Toatsu Chemicals, Inc., trade name: BJ)
HH-2283) 100 parts by weight, azodicarbonamide (hereinafter referred to as ADCA) type foaming agent 0.7 parts by weight and liquid paraffin 0.2 parts by weight were mixed with a Henschel mixer to obtain a resin composition. Extruder (Cylinder diameter: 40m
m, L / D: 28) T-die at the tip of the cylinder (width of lip opening: 150 mm, lip opening: 0.7 m
m) is attached, and a cooling plate (θ: 17 degrees, horizontal length: 20 mm, side surface: open type) of the same shape as that shown in FIG. Put a sheet made of ether ether ketone between them,
Hot water was circulated inside the cooling plate to control the cooling surface temperature of the cooling plate to 80 ° C. Further, after the cooling plate, 6 pairs of pairs of small rolls (diameter: 80 mm, surface gap between rolls: 10 mm) were attached. Using the above molding equipment, extruder cylinder temperature 180 ° C, die temperature 1
Under conditions of 90 ° C., the obtained resin composition is heated, kneaded, melted and extruded from a T die, and both surfaces of the molten sheet are cooled by a cooling plate having a cooling surface temperature of 80 ° C.
Speed of 25 mm while cooling to room temperature with 6 pairs of small rolls
/ Min to produce a polypropylene foam sheet having skin layers on both sides. The obtained foamed sheet had a thickness of 10 mm, an apparent density of 0.3 g / cm ³ , and the skin layers had a thickness of 0.5 mm for both front and back sides. Main molding conditions, the thickness of the obtained foam sheet, the thickness of each skin layer,
The apparent density of the foamed sheet is shown in [Table 1].

Examples 2 to 7 Skin layers were formed on both sides in the same manner as in Example 1 except that the cooling surface temperature of the cooling plate, the cooling roll surface gap, and the take-up speed were changed to the conditions shown in [Table 1]. A polypropylene foam sheet having the above was produced. Table 1 shows the main molding conditions, the thickness of the obtained foamed sheet, the thickness of each skin layer, and the apparent density of the foamed sheet.

Examples 8 to 10 The amount of ADCA-based blowing agent added was changed to 0.4 parts by weight, the opening angle of the cooling plate was changed to 8 degrees, the cooling surface temperature of the cooling plate, the cooling roll surface gap, and the take-up speed. A polypropylene foam sheet having skin layers on both sides was produced in the same manner as in Example 1 except that was changed to the conditions shown in [Table 1]. Table 1 shows the main molding conditions, the thickness of the obtained foamed sheet, the thickness of each skin layer, and the apparent density of the foamed sheet.

Examples 11 to 13 Using 2.0 parts by weight of a sodium hydrogencarbonate type foaming agent,
The same procedure was performed as in Example 1 except that the opening angle of the cooling plate was changed to 30 degrees and the cooling surface temperature, the cooling roll surface gap, and the take-up speed of the cooling plate were changed to those shown in [Table 1]. A polypropylene foam sheet having a skin layer was produced. Table 1 shows the main molding conditions, the thickness of the obtained foamed sheet, the thickness of each skin layer, and the apparent density of the foamed sheet.

Comparative Example 1 A polypropylene foam sheet having skin layers on both sides was produced in the same manner as in Example 1 except that the cooling surface temperature of the cooling plate was changed to 10 ° C. The thickness of the skin layer is 2.5 mm
However, the surface was rough and the surface condition was poor. Table 1 shows the main molding conditions, the thickness of the obtained foamed sheet, the thickness of each skin layer, and the apparent density of the foamed sheet.

Comparative Example 2 A polypropylene foam sheet having skin layers on both sides was produced in the same manner as in Example 4 except that a cooling plate having an opening angle of 3 degrees was used. However, the foamed resin was only extruded from the central portion between the cooling plates, and a foamed sheet having a good skin layer could not be obtained.

Comparative Example 3 An attempt was made to manufacture a polypropylene foam sheet having skin layers on both sides in the same manner as in Example 1 except that a cooling plate having an opening angle of 40 degrees was used. However, the foamed resin extruded from the die hardly contacted the cooling surface of the cooling plate, and the surface was wavy, and a good skin layer was not formed.

[0030]

[Table 1]

[0031]

According to the present invention, a thermoplastic resin foam sheet having a thick skin layer can be manufactured by mounting a cooling plate having a simple structure on the tip of a die and cooling it at a specific temperature. . In addition, the same cooling plate can be used to manufacture foamed sheets having different thicknesses, and the thickness of the skin layer can be easily adjusted. Therefore, a foamed sheet having skin layers on both sides can be manufactured at a cost substantially equal to that of a foamed sheet having no skin layer,
Very useful in industry.

[Brief description of drawings]

FIG. 1 is a side sectional view of a cooling plate mounted on the tip of a die.

[Explanation of symbols]

 1 T-die 2, 2'cooling plate 3 manifold 4, 4'lip 5 upper cooling surface 6 lower cooling surface 7, 7'bolt 8, 8'passage for temperature control medium 9, 9'insulating material θ upper cooling surface Angle formed by lower cooling surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B29L 7:00 C08L 23:02

Claims (5)

[Claims] 1. A foamed thermoplastic resin sheet having a skin layer formed by extruding an expandable thermoplastic resin from a die and cooling and shaping using a cooling plate having two upper and lower cooling surfaces attached to the tip of the die. In the manufacturing method, the upper and lower two cooling surfaces of the cooling plate are opened forward at an opening angle of 5 to 35 °, and the temperature of the cooling plate cooling surface is 20 to 100 ° C.
And a method for producing a thermoplastic resin foam sheet having a skin layer. 2. The method for producing a foamed thermoplastic resin sheet having a skin layer according to claim 1, wherein the expandable thermoplastic resin is a polyolefin resin containing a foaming agent and / or a foaming gas. 3. The method for producing a thermoplastic resin foam sheet having a skin layer according to claim 1, wherein the cooling plate has a length of 10 to 50 mm. 4. The front and back skin layers have a thickness of 0.3 to 2 m.
m, the total thickness of the foamed sheet is 5 to 50 mm, and the method for producing a thermoplastic resin foamed sheet having a skin layer according to claim 1. 5. After cooling with a cooling plate, a speed of 10 to 10 is obtained while cooling to a temperature near room temperature using at least one pair of cooling rolls having a surface interval of rolls of 5 to 50 mm.
The pick-up is performed at 500 mm / min.
5. A method for producing a thermoplastic resin foam sheet having the skin layer according to any one of 4 to 4.