JPH08281683A - Propylene resin plate-shaped foam and production thereof - Google Patents

Abstract

PURPOSE: To obtain plate-shaped foam extremely reduced in warpage and excellent in flatness by pressing cylindrical foam obtained by foaming a non- crosslinked propylene resin with drawdown properties of a specific value or less to form the same into a plate shape and holding the pressed foam between conveyor belts to transfer the same under cooling. CONSTITUTION: A non-crosslinked propylene resin with drawdown properties of 60m/min or less is melted in an extruder 1 and kneaded along with a foaming agent at high temp. under high pressure to form a foamable resin compsn. which is, in turn, extruded from the annular die 2 provided to the leading end of the extruder 1 under pressure lower than the pressure in the extruder to be foamed in a cylindrical form and this cylindrical foam 3 is pressed to fuse the inner surface thereof to obtain plate-shaped foam with a thickness of 2-15mm and density of 0.06-0.3g/cm<3> Next, the plate-shaped foam 4 is held between conveyor belts 5 and transferred to be cooled. As a result, the warpage of the plate-shaped foam can be set to 10mm or less. The cylindrical foam 3 is formed into a plate shape by pressing the foam 3 by pinch rolls 7 set to a temp. of 50-150 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a propylene-based resin plate foam and a method for producing the same.

[0002]

2. Description of the Related Art Various methods are known in which a melt-kneaded product of a thermoplastic resin and a foaming agent is extruded and foamed in a cylindrical shape from an annular die to form a plate-shaped (sheet-shaped) foamed body. The following two types are typical of this type of method. A cutter is provided on the mandrel that cools the tubular foam extruded and foamed from the annular die, and this cutter cuts the tubular foam from one end in the extrusion direction along the extrusion direction to form a plate-shaped (sheet-shaped) foam. How to get. A method for obtaining a plate-shaped (sheet-shaped) foam by pressing a tubular foam extruded and foamed from an annular die and fusing the inside of the pressed foam using the heat of the foam immediately after extrusion.

The foam obtained by the above method still has a force to return to the state (cylindrical) before being cut open. Therefore, when the external force is removed, the foam is greatly curled. Further, the inner surface side of the tubular foam extruded and foamed from the annular die is rapidly cooled by contacting the mandrel, but the outer surface side is only air-cooled, so the degree of cooling on the inner and outer surfaces of the tubular foam,
The cooling method is different, and as a result, the surface state of the obtained plate-shaped (sheet-shaped) foam differs from that of the back side. The curl of the plate-like (sheet-like) foam and the difference in the front and back surfaces are very problematic in the following fields (1) to (3). (1) If necessary, after being cut into a desired size, it is used in a flat plate shape (for example, panel, display material,
Various core materials, etc.) field. (2) Fields in which flat plates are punched and used (for example, partition materials). (3) Field of containers (so-called box-shaped containers) in which flat plates are cut into a container-deployed shape and then parts corresponding to the side walls of the container are erected and adjacent side walls are assembled by heat fusion or fastening. .

Therefore, in the fields (1) to (3) above, it is preferable to use the plate-like (sheet-like) foam obtained by the above method. By the way, conventionally, polystyrene and polyethylene have been widely used in the above method. However, the polystyrene plate-like foam has the advantage that it has high mechanical strength even at low density, but on the other hand, it has a problem that it tends to crack or break when bent, and that a large amount of black smoke is generated when incinerated. . On the other hand, in the case of the polyethylene plate-like foam, the problem as in the above polystyrene plate-like foam does not occur, but in order to have sufficient mechanical strength, the density must be increased (low foaming), Forced to increase weight.

Therefore, it has been desired to develop a polypropylene resin plate-like foam which is considered to have the advantages of both the polystyrene plate-like foam and the polyethylene plate-like foam. However, since polypropylene resins have a high degree of crystallinity, the range of appropriate foaming temperatures is extremely narrow, and it has conventionally been technically extremely difficult to obtain foams having a wide range of densities by the extrusion foaming method.

As a result of diligent research, the present applicant has found that by using a specific non-crosslinked polypropylene-based resin, a good extruded foam can be obtained in a wide density range, and such a non-crosslinked polypropylene-based resin is used. We filed an application for the used foam and its manufacturing method (Japanese Unexamined Patent Publication No. Heisei 4-
JP-A-363227, JP-A-5-98058, JP-A-5-124125, and JP-A-5-230255.
Issue).

[0007]

According to the applicant's earlier application, a non-crosslinked polypropylene resin plate-like (sheet-like) foam having excellent properties over a wide density range can be obtained.
Further, the obtained foam has a characteristic of being excellent in thermoformability, but since these plate-like foams are obtained by the method described above, the above-mentioned (1) to (3) It is not suitable for use in such fields. Then, the present inventors tried to manufacture the plate-shaped foam for which the present applicant applied earlier by the above method, but it was found that the obtained plate-shaped foam had a large warp. When a plate-like foam with such a large warp is used in the fields of (1) to (3) above, the processing accuracy of the processing part during cutting (cutting) and punching may deteriorate. When the plate-like foams are conveyed to the continuous processing device, there is a risk that two plate-like foams may be conveyed at the same time in a state of being overlapped with each other, or no one may be conveyed. Further, when used in the field of (3), there is a possibility that a box-shaped container having a distortion may be obtained.

The inventors of the present invention have conducted extensive studies to find out the cause of the large warpage of the polypropylene resin plate-like foam produced by the above method, and as a result, found that the cooling inside the plate-like foam is insufficient. Was found to be the cause. In general, in a method of obtaining a plate-like foam by sandwiching the tubular foam and fusing the inner surface side, in the case of polystyrene or polyethylene, the tubular foam is formed immediately after extrusion by the expansion of the foaming agent or the expansion of the resin. After being cooled to some extent, the tubular foam is pressed at that temperature and the inner surface is fused. However,
When a highly crystalline polypropylene resin is used as a base material, crystallization occurs during cooling, and a large amount of crystallization heat associated with crystallization is generated from the tubular foam, which impedes cooling.
Therefore, although the surface side of the plate-like foam is cooled to some extent, the inside thereof is not sufficiently cooled, and this difference in cooling causes warpage. As a result of further intensive studies by the present inventors in order to solve such a problem, as a result of pressing the tubular foam into a plate shape, sandwiching both sides with a conveyor belt and transferring while cooling, The inventors have found that the above problem can be solved and completed the present invention.

[0009]

[Means for Solving the Problems] That is, the propylene-based resin plate-like foam of the present invention is obtained by melting a non-cross-linked propylene-based resin having a drawdown property of 60 m / min or less in an extruder,
A foamable resin composition formed by kneading with a foaming agent under high temperature and high pressure is extruded at a lower pressure than in the extruder through an annular die provided at the tip of the extruder to foam into a tubular shape, and the tubular foamed body is obtained. 2 to 1 made by sandwiching and fusing the inner surface
It is a plate-like foam having a density of 5 mm and a density of 0.06 to 0.3 g / cm ³ , and the warp of the plate-like foam is 10 mm or less.

Further, in the method for producing a propylene-based resin plate-shaped foam of the present invention, a non-crosslinked propylene-based resin having a drawdown property of 60 m / min or less is melted in an extruder and kneaded with a foaming agent under high temperature and high pressure. The foamable resin composition formed as described above is extruded under a lower pressure than in the extruder through an annular die provided at the tip of the extruder to foam in a tubular shape, and the tubular foam is pressed into a plate shape, and then It is characterized in that both sides of the plate-like foam are sandwiched by conveyor belts and cooled while being transferred.

In the method of the present invention, as a method of forming the tubular foam into a plate shape, a method of pinching with pinch rolls at a temperature of 50 to 150 ° C. is preferable.

The non-crosslinked propylene resin used in the present invention has good extrusion foamability in a wide density range, that is, has a drawdown property of 60 m / min or less. Is preferably 30 m / min or less, and more preferably 15 m / min or less. Further, a non-crosslinked propylene-based resin having a long-chain branch in the main chain is preferable because it is easy to adjust the drawdown property to the above range.

In the present invention, the drawdown property means that molten propylene resin heated to 230 ° C. is extruded from a nozzle (diameter 2.095 mm, length 8 mm) at a constant speed of 10 mm / min into a cord shape. Then, the string-like material is passed through a feed roll located above the tension detecting pulley located below the nozzle and then wound up by a winding roll, while the winding speed of the winding roll is gradually increased. The string-like material is cut, and the winding speed of the string-like material at the time of cutting is referred to.

The non-crosslinked propylene resin may be a homopolymer, a block copolymer or a random copolymer. In the case of a copolymer, an olefin other than propylene is used in the copolymer. Is preferably contained in an amount of 0.5 to 30% by weight, particularly 1 to 10% by weight. In this case, the olefin may be ethylene or a carbon number of 4
The α-olefins of 10 to 10 can be mentioned, and these can be used alone or in combination of two or more.

Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene or 3-methyl-1
-Hexene and the like can be mentioned.

The drawdown property used in the present invention is 60 m.
/ Min or less of the non-crosslinked propylene-based resin is an ordinary crystalline linear propylene-based resin (usually a weight average molecular weight of 100,
000 or more), and a resin containing an atactic component and / or an isotactic but not crystallized component therein (hereinafter, this resin is referred to as "propylene resin used in the present invention in order to be distinguished from the propylene resin used in the present invention. When referred to as "ordinary propylene-based resin" and simply referred to as "propylene-based resin", it means the propylene-based resin used in the present invention.
(120 ° C.) and heated to a temperature of 120 ° C. or lower to react with each other to bond an atactic or / and non-crystalline isotactic component as a branched chain to the main chain of the usual propylene resin. Can get
It is considered to have a branched structure mainly having long chain branches at the ends.

Examples of the low temperature decomposition type peroxide include di (s-butyl) peroxydicarbonate and bis (2-
Ethoxy) peroxydicarbonate, dicyclohexyl peroxydicarbonate, di-n-propylperoxydicarbonate, di-n-butylperoxydicarbonate, diisopropylperoxydicarbonate,
Examples thereof include t-butyl peroxy neodecanoate, t-amyl peroxy neodecanoate and t-butyl peroxypivalate.

The propylene-based resin in the present invention is a conventional propylene-based resin which is stirred in a reactor equipped with a stirrer while the inside of the reaction vessel is replaced with an inert gas such as argon,
Then, the above-mentioned peroxide is usually added in an amount of 5 to 50 mmol per 1 kg of the resin, and the mixture is heated to about 120 ° C., preferably about 70 to 105 ° C. while continuing stirring to react (usually 30 to 120 minutes), and thereafter, , Can be obtained by stopping the reaction. When stopping the reaction, a reaction stopper such as methyl mercaptan is introduced into the reaction vessel, or the reaction product is heated to about 130 to 150 ° C.
A method of heating for 0 to 40 minutes or the like is adopted.

The drawdown property can be adjusted by the number and length of the long chain branches. Generally, the larger the number of long chain branches and the longer the branch length, this value is It tends to decrease (numerical value decreases). Therefore, in order to obtain a polymer having a desired drawdown property, it is necessary to set the reaction conditions in consideration of these things.

Generally, in the case of having no long-chain branch, or having branch even if it is too short, or the number of branches is small, or in the case of ordinary propylene resin, etc.,
The drawdown property exceeds 60 m / min, and extrusion foaming is performed using such a material, and the density is 0.06 to
When trying to obtain a plate-like foam of 0.3 g / cm ³ , the resulting foam has many surface irregularities, which makes it unattractive as a product, and the smoothness of the plate-like foam is impaired, which results in secondary processing. It also becomes a cause to impede sex and the commercial value is low.

Further, the propylene-based resin used in the present invention preferably has a semi-crystallization time at the crystallization temperature + 15 ° C. of 800 seconds or longer, and particularly preferably 1000 seconds or longer. For the measurement of the half-crystallization time, a crystallization rate measuring device can be used.

In order to measure the semi-crystallization rate, first, the support holding the film-like sample is placed in the air bath of the crystallization rate measuring instrument to completely melt the sample, and then the molten sample is put together with the support. Immersion in an oil bath maintained at the crystallization temperature of the sample + 15 ° C so as to block the optical path between the light source and the optical sensor, and always keep constant at the optical sensor until the melted sample solidifies again. A voltage-time curve is obtained by adjusting the voltage of the light source so that the amount of light is detected. When the voltage on this curve is constant: L is V ₀ , the time until the voltage becomes 1/2 V ₀ is the half-crystallization time.

In the present invention, not only the above-mentioned propylene-based resin may be used alone, but also other resins may be mixed and used if necessary. Examples of the resin to be mixed and used are propylene-based resins other than the above, or high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-butene copolymer, ethylene-anhydrous. Examples thereof include ethylene resins such as maleic acid copolymers; butene resins; vinyl chloride resins such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymers; styrene resins.

When another resin is mixed and used, the amount of the resin to be mixed is limited to 40% by weight of the total weight of the polymer after mixing, and needless to say, the drawdown property of the mixture is 6%.
It should not exceed 0 m / min.

Examples of the foaming agent used in the method of the present invention include inorganic foaming agents, volatile foaming agents, decomposable foaming agents and the like. Examples of the inorganic foaming agent include carbon dioxide, air and nitrogen.

As the volatile foaming agent, propane, n
-Butane, i-butane, a mixture of n-butane and i-butane, aliphatic hydrocarbons such as pentane and hexane; cycloaliphatic hydrocarbons such as cyclobutane and cyclopentane; trichlorofluoromethane, dichlorodifluoromethane, 1,1-dichloro-1,1,1,2-tetrafluoroethane, 1,1-difluoro-1
Examples include halogenated hydrocarbons such as chloroethane, 1,1,1,2-tetrafluoroethane, methyl chloride, ethyl chloride and methylene chloride.

Further, examples of the decomposition type foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate and the like. These foaming agents can be appropriately mixed and used.

The amount of the foaming agent used depends on the kind of the foaming agent, the desired expansion ratio, and the like. Density 0.06-0.3
The standard of the amount of the foaming agent used for obtaining the g / cm ³ foam is 0.5 to 100 parts by weight of the volatile foaming agent per 100 parts by weight of the resin.
8.0 parts by weight (butane equivalent), 0.2 with inorganic blowing agent
It is about 5.0 parts by weight (converted to carbon dioxide) and about 0.1 to 15 parts by weight of the decomposing type foaming agent.

The resin and the foaming agent are melt-kneaded in the extruder to form a foamable composition in the extruder. A foam regulator is added to the foamable composition as needed. be able to. Examples of the cell regulator include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, and reaction mixtures of polycarboxylic acids with sodium carbonate or sodium bicarbonate. Resin 10
It is preferable to add about 13 parts by weight or less per 0 part by weight (except when a large amount of inorganic filler is contained in the resin). Further, if necessary, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant and a colorant may be added.

Further, the resin may contain an inorganic filler in advance in an amount of 40% by weight based on the total weight. Examples of the inorganic filler include talc, silica, calcium carbonate, clay, zeolite, alumina, barium sulfate and the like. The average particle size of these is preferably 1 to 70 μm. When a large amount of such an inorganic substance is contained, the resulting plate-like foam has improved heat resistance and can reduce the calories burned during incineration.

The present invention will be described below with reference to the drawings. FIG.
In the above, 1 is an extruder, in which a foaming agent and various additives as required are added to the resin in the extruder 1, and these are melt-kneaded under high temperature and high pressure to form a foamable composition.
When the foamable composition is extruded into a tubular shape from the annular die 2 at the tip of the extruder under a lower pressure than in the extruder, the foamable composition foams to form a tubular foam 3.

The tubular foam 3 is pinched by pinch rolls or the like to form a plate-like foam 4 having an inner surface fused and then cooled while sandwiching it from both sides of the plate-like foam 4 by using a conveyor belt 5. It When the plate-shaped foam 4 is cooled using the cooling roll, the cooling roll and the plate-shaped foam 4 are merely in line contact with each other, so that the inside of the plate-shaped foam 4 is sufficiently cooled. You cannot do it. As a result, the plate-shaped foam 4 is likely to be largely warped. Further, it is possible to increase the cooling effect by arranging a large number of cooling rolls in parallel, but the length of the production line must be considerably lengthened (20 m or more). In that respect, the conveyor belt 5 used for cooling in the method of the present invention can easily come into surface contact with the plate-like foam 4 in a large area, and as a result, the inside of the plate-like foam 4 can be sufficiently filled in a short time. It becomes possible to cool, and it is possible to prevent the plate-shaped foam body 4 from being largely warped. In addition, the length of the entire production line can be the same as the conventional one or slightly extended.

In order to sufficiently cool the plate-shaped foam 4 by using the conveyor belt 5, the interval between the belts 5 is adjusted so that the conveyor belts 5 are in close contact with both surfaces of the plate-shaped foam 4. The spacing between the conveyor belts 5 can be easily adjusted by providing a spacing roll 10 on the side of the conveyor belt 5 that is in contact with the plate-shaped foam 4 opposite to the plate-shaped foam 4 side.

Examples of the material of the conveyor belt 5 include rubber, steel, etc. The conveyor belt 5 is immersed in a water tank 6 provided separately during the endless running and cooled to cool the plate-shaped foam 4. Can always be cooled well. In this case, the water temperature in the water tank 6 for cooling the conveyor belt 5 is preferably 5 to 40 ° C. Further, the conveyor belt 5 is preferably configured so that the length in contact with the plate-shaped foam 4 is 1000 mm to 5000 mm.

To form the tubular foam 3 into the plate foam 4,
Examples include a method of pinching with a conveyor belt and a method of pinching with a pinch roll 7 as shown in FIG.
When the pressing of the tubular foam 3 is performed by a conveyor belt, it is preferable to use a conveyor belt different from the above-mentioned conveyor belt 5. This is because when the tubular foam 3 is rapidly cooled while being pressed, the temperature of the surface portion is drastically reduced as compared with the inner layer portion of the plate foam, and a large temperature difference is generated inside and outside the plate foam, causing surface wrinkles. Is more likely to occur.

As described above, it is preferable that the plate-shaped foam 4 is not rapidly cooled when the cylindrical foam 3 is pressed, and therefore the pressing means has a temperature that does not rapidly cool the plate-shaped foam 4. It is preferable to control In terms of such ease of temperature control, the pinch roll 7 is preferable as the pinching means. When pinching the tubular foam 3 with the pinch roll 7, the temperature of the pinch roll 7 is preferably 50 to 150 ° C. When the temperature of the pinch roll 7 is less than 50 ° C, wrinkles are likely to occur on the surface of the plate-shaped foam 4, and when the temperature of the pinch roll 7 exceeds 150 ° C, the foam is easily fused to the pinch roll 7. It becomes difficult to stably obtain a plate-shaped foam.

The transfer speed of the plate-shaped foam 4 by the conveyor belt 5 is made slightly higher than the transfer speed of the plate-shaped foam 4 by the pinch roll 7 so that the pinch roll 7 and the conveyor belt are attached to the plate-shaped foam 4. When a tension is applied between the plate-like foam and the plate-like foam, a plate-like foam having even better surface flatness can be obtained.

In the method of the present invention, the tubular foam body 3 extruded and foamed from the annular die 2 may be cooled by blowing air on its outer surface. However, in this case, it is necessary to cool the surface so that wrinkles do not occur. In the figure, 4a is a plate-like foam as a final product, 8
Is a plate-shaped foam take-up roll, and 9 is a cutter for cutting the plate-shaped foam.

The method of the present invention has a thickness of 2 to 15 mm, especially 2
It is suitable for producing a plate-shaped foam having a thickness of 10 mm. According to the method of the present invention, a plate-like foam having a thickness of less than 2 mm or a thickness of 15 mm
It is possible to produce a plate-shaped foam having a thickness of less than 2 mm, but if the thickness is less than 2 mm, the rigidity of the plate-shaped foam is insufficient. It becomes difficult to sufficiently cool the layer portion, and it is easy to obtain a foam having large warpage and corrugated irregularities. Further, the method of the present invention is a method suitable for producing a plate-like foam having a density of 0.06 to 0.3 g / cm ³ , particularly 0.09 to 0.3 gcm ³ . It is also applicable to the production of a plate-like foam having a density of less than 0.06 g / cm ^{3 and} a plate-like foam having a density of more than 0.3 g / cm ³ , but having a density of 0.06 g / cm 3.
^If it is less than ^3, the flatness of the surface of the plate-like foam tends to decrease,
Further, if the density is more than 0.3 g / cm ³ , the flexibility and the heat insulating property are low and the weight becomes large. According to the method of the present invention, when a plate-like foam having the above-mentioned thickness and density is produced, a plate-like foam having excellent flatness is obtained, and the plate-like foam has an excellent warp of 10 mm or less. Is.

The warp of the plate-shaped foam in the present invention is cut from the plate-shaped foam into a rectangular shape of 1000 mm ± 30 mm in the extrusion direction and 630 mm ± 30 mm in the direction orthogonal to the extrusion direction (the thickness is unchanged). The sample end in the state where a sample for measurement is prepared and the sample is allowed to stand still on a plate-shaped member having a horizontal plane portion having a larger area than the sample (a force other than its own weight is not applied). Means the maximum value (mm) of the gap generated between the plate and the horizontal surface of the plate member. The maximum value means the maximum value of not only one surface of the sample but also the other surface measured.

The plate-like foam of the present invention has a high level of warpage measured as described above of 10 mm or less. Needless to say, the smaller this value is, the higher level of warpage is 5 mm or less. Preferably there is.

The plate-like foam obtained by the method of the present invention is suitable as a raw material for various core materials, partition materials, box-shaped containers and the like. It is also possible to carry out molding such as vacuum molding and pressure molding.

Hereinafter, the present invention will be described in more detail with reference to examples.

【Example】

Examples 1-5, Comparative Examples 1-2 In the extruder, the non-crosslinked propylene resin 100 shown in Table 1 was used.
After adding butane (foaming agent) at a ratio shown in Table 1 to parts by weight and melt-kneading, the meltable foamable composition was heated at a temperature (foaming temperature) shown in Table 1 through a 200 mm diameter circular die. Was extruded to form a tubular foam, and the tubular foam was pinched by pinch rolls at the temperatures shown in Table 1 to obtain a plate-like foam having an inner surface fused. In each example, both sides of the plate-shaped foamed body after sandwiching are sandwiched by conveyor belts arranged above and below to be cooled while being conveyed, and then cut by a cutter to be 1000 mm (length in extrusion direction) × 650 mm ( A rectangular plate-shaped foam (having a length in the direction orthogonal to the extrusion direction) was obtained (hereinafter, this plate-shaped foam is referred to as a rectangular foam in order to distinguish it from the plate-shaped foam before cutting). The conveyor belt is immersed in a water tank during its rotation (the water temperature is shown in Table 1), and then is brought out of the water tank and comes into contact with the plate-like foam (see FIG. 1). . At this time, the contact length between the plate foam and the conveyor belt is 3000 mm.
And In each comparative example, the conveyance and cooling by the conveyor belt were not performed. Table 1 also shows the properties of the rectangular foams obtained in Examples and Comparative Examples.

[0045]

[Table 1]

Resin A and resin B in the column of resin type in Table 1 are shown in Table 2. The meltdown tester type II manufactured by Toyo Seiki Seisakusho Co., Ltd. was used for measuring the drawdown property in Table 2, and the crystallization rate measuring device manufactured by Kotaki Corporation was used for measuring the half crystallization time. MK-801 type was used.

[0047]

[Table 2]

[0048]

As described above, the plate-like foam of the present invention has an extremely small warp and an excellent flatness. When the plate-like foam is cut (cut) or punched, The processing accuracy can be improved, and even if these processes are performed by a continuous processing device, when the plate-shaped foam is transferred to the processing device, it will be transferred in a state where two sheets are overlapped at the same time, or even one sheet is transferred. The incidence of troubles such as not being transported is greatly reduced. Further, the container-shaped shaped plate cut from the plate-shaped foam of the present invention, the box-shaped container assembled by bending, can be maintained at an extremely small level even if there is no distortion, and it has high commercial value. Become. Further, according to the production method of the present invention, there is an advantage that the above-mentioned excellent plate-like foam can be obtained without greatly extending the production line length. In addition, the method of the present invention can prevent not only the warp of the plate-shaped foam but also the generation of corrugated irregularities that are likely to occur after the pressing. Further, by pinching the tubular foam with a pinch roll at 50 to 150 ° C.,
It is possible to effectively prevent wrinkles that are likely to occur on the surface of the plate-shaped foam. As a result, a plate-shaped foam having a high commercial value can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus showing an outline of the method of the present invention.

[Explanation of symbols]

 1 Extruder 2 Annular Die 3 Cylindrical Foam 4 Plate Foam 5 Conveyor Belt 7 Pinch Roll

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location C08L 23:10 (72) Inventor Takashi Muroi 1-73 Yonishicho, Utsunomiya City, Tochigi Prefecture

Claims (3)

[Claims] 1. A foamable resin composition formed by melting a non-crosslinked propylene resin having a drawdown property of 60 m / min or less in an extruder and kneading the foaming agent under high temperature and high pressure.
Through an annular die provided at the tip of the extruder, the resin is extruded under a lower pressure than in the extruder to foam in a tubular shape, and the tubular foam is pinched to fuse the inner surface to a thickness of 2 to 15 mm,
A propylene-based resin plate-like foam, which is a plate-like foam having a density of 0.06 to 0.3 g / cm ³ , and the warp of the plate-like foam is 10 mm or less. 2. A foamable resin composition formed by melting an uncrosslinked propylene-based resin having a drawdown property of 60 m / min or less in an extruder and kneading the foaming agent under high temperature and high pressure at the tip of the extruder. It is extruded under a lower pressure than in the extruder through an annular die provided to foam into a tubular shape, and the tubular foam is pressed into a plate shape, and then both sides of this plate foam are sandwiched by a conveyor belt and transferred. A method for producing a propylene-based resin plate-shaped foam, which comprises cooling while cooling. 3. The clamping force of the tubular foam is controlled at a temperature of 50 to 15
The method for producing a propylene-based resin plate-like foam according to claim 2, which is carried out by pinch roll at 0 ° C.