JP2003201359A - Crosslink-free polyolefine foam sheet and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crosslink-free polyolefine form sheet which has the front and back sides having same excellent antistatic properties and is excellent in recyclability. <P>SOLUTION: The crosslink-free polyolefine form sheet comprises 100 pts.wt. of a polyolefine resin and 0.2-5 pts.wt. of a nonionic surfactant type antistatic agent, wherein the polyolefine resin is composed of 70-98 wt.% of a polypropylene resin and 2-30 wt.% of an ethylene-α-olefin copolymer, so that the nonionic surfactant type antistatic agent may be bled out smoothly and securely from the low crystallized ethylene-α-olefin copolymer component on the front and back sides of the crosslink-free polyolefine foam sheet. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyolefin resin foam sheet having a small difference in antistatic property between front and back surfaces and having excellent antistatic property.

[0002]

2. Description of the Related Art Conventionally, non-crosslinked polyolefin resin foamed sheets have been widely used, for example, as packaging materials for electronic parts because of their excellent workability and low cost. Then, the non-crosslinked polyolefin resin foam sheet, the polyolefin resin is supplied to the extruder, melt-kneaded and extruded into a cylindrical shape, and the cylindrical foam body is cooled by a cooling mandrel and then cut into a sheet shape. It is manufactured by

Further, since the polyolefin resin is an electrical insulator, it is necessary to impart antistatic property when it is used as a packaging material for electronic parts, and as a method therefor, a non-crosslinked polyolefin resin foam sheet is electrically charged. There is a method of kneading the anti-static agent. In this case, the anti-static property is imparted to the foamed sheet by bleeding out the anti-static agent to the surface of the non-crosslinked polyolefin resin foam sheet.

However, the bleed-out of the antistatic agent is greatly affected by the crystal structure such as the crystal orientation and the crystallinity of the resin, and the more the crystal portion is, the more difficult the antistatic agent is to bleed out.

In the above-mentioned method for producing a non-crosslinked polyolefin resin foam sheet, a difference in atmospheric temperature is generated between the inner and outer surfaces of the cylindrical foam between the cylindrical die of the extruder and the cooling mandrel, and further cooling is performed. Since the degree of cooling is different between the outer surface of the cylindrical foam that contacts the mandrel and the outer surface of the cylindrical foam that does not contact the cooling mandrel, these affect the crystal structure of the resin and bleed out the antistatic agent. There is a problem in that the degree of the difference between the front and back surfaces of the sheet is different, and the antistatic property of the obtained non-crosslinked polyolefin resin foam sheet is different between the front and back surfaces.

As the polyolefin resin foamed sheet, there is also provided a low density crosslinked polyolefin resin foamed sheet having a foaming ratio of 10 times or more by introducing a crosslinked structure into the polyolefin resin.

As a method for producing the crosslinked polyolefin resin foam sheet, for example, a polyolefin resin, a thermal decomposition type foaming agent, a crosslinking agent and a crosslinking auxiliary agent are supplied to an extruder, melt-kneaded and extruded into a sheet. After obtaining the foamable resin sheet, the foamable resin sheet is irradiated with ionizing radiation such as an electron beam to introduce a crosslinked structure into the foamable resin sheet, and then heated and foamed. A manufacturing method may be mentioned.

However, the method for producing the crosslinked polyolefin resin foamed sheet has a problem in that the cost is high due to the large number of steps, and the recyclability is low because the crosslinked structure is introduced into the polyolefin resin. .

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a non-crosslinked polyolefin resin foam sheet having excellent antistatic properties on the front and back surfaces and no difference in antistatic properties on the front and back surfaces, and having excellent recyclability. To do.

[0010]

The non-crosslinked polyolefin resin foam sheet of the present invention comprises a polypropylene resin 70.
To 98% by weight and ethylene-α-olefin copolymer 2
It is characterized by containing 100 parts by weight of a polyolefin resin consisting of ˜30% by weight and 0.2 to 5 parts by weight of a nonionic surfactant type antistatic agent.

The polyolefin resin constituting the non-crosslinked polyolefin resin foam sheet comprises 70 to 98% by weight of polypropylene resin and 2 to 30% by weight of ethylene-α-olefin copolymer.

The polypropylene-based resin is not particularly limited as long as it has been conventionally used for foams, and examples thereof include homopolypropylene and block copolymerization of propylene and a monomer copolymerizable therewith. Examples thereof include coalesce and random copolymers.

Examples of the monomer copolymerizable with propylene include ethylene, 1-butene, isobutene,
Α-olefins such as 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and 1-decene, cyclic olefins such as cyclopentene and norbornene, 1 , 4-hexadiene, 5-methyl-1,4-hexadiene, 7-methyl-1,6-octadiene and other dienes, vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, acrylic acid Methyl,
Non-crosslinked polyolefin system obtained include vinyl monomers such as ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, maleic anhydride, styrene, methylstyrene, vinyltoluene and divinylbenzene. Ethylene is preferred because the resin foam sheet has excellent impact resistance and foaming properties.

If the propylene component in the block copolymer or random copolymer of propylene and a monomer copolymerizable therewith is small, the resulting non-crosslinked polyolefin resin foam sheet has heat resistance, rigidity, and
Since the chemical resistance may decrease, it is preferably 80% by weight or more, more preferably 90% by weight or more.

Further, by using a polypropylene resin having a free-end long-chain branch in the molecule as the polypropylene resin, the foamability can be improved.
A polypropylene resin having a free long-chain branch in such a molecule is, for example, a product name “Pro-fax PF-814” or “Pro-fax S” from Sun Aroma Co.
It is sold under the name of "D-632".

Further, if the melt tension of the polypropylene resin is high, the extrusion processability at the time of production may be lowered and the productivity may be lowered, and if it is low, a good non-crosslinked polyolefin resin foam sheet may be obtained. Therefore, 0.01 to 40 g is preferable, and
30 g is more preferable.

The melt tension of the polypropylene resin is measured according to the following procedure. That is,
Using a melt tension measuring device, polypropylene resin is heated to 230 ° C., and the melted polypropylene resin is 2.095 m in diameter with a piston extrusion type plastometer.
Piston descending speed of 10 from a nozzle of m and 8 mm in length
The cord was extruded into a string at a constant speed of mm / minute, and then the string was passed through a tension detection pulley which was kept 35 cm below the nozzle, and the string was wound by a winding roll at about 66 m / min ^2. The tension of the string-like material when it was cut was taken as the melt tension of the polypropylene-based resin. As the melt tension measuring device, a commercially available product from Toyo Seiki Seisakusho under the trade name "Capirograph PMD-C" can be used.

The α-olefin of the ethylene-α-olefin copolymer is, for example, propylene or 1
-Butene, isobutene, 1-pentene, 3-methyl-1
-Butene, 1-hexene, 4-methyl-1-pentene,
1-heptene, 1-octene, 1-decene and the like can be mentioned.

If the above-mentioned α-olefin has a large number of carbon atoms, the cost becomes high, and if the number of carbon atoms is small, the bleed-out of the antistatic agent to the surface of the non-crosslinked polyolefin resin foam sheet obtained is bleed out. Since the antistatic property of the foamed sheet may be insufficient and a large difference may occur in the surface specific resistance between the front and back surfaces of the foamed sheet, α-olefin having 4 to 8 carbon atoms is preferable, 1-
Butene, 1-hexene and 1-octene are more preferable,
1-hexene is particularly preferred.

Examples of copolymers of ethylene and α-olefins having 4 to 8 carbon atoms include, for example, Sumitomo Chemical Co., Ltd., trade name "Esprene NO416" (ethylene-1-butene copolymer), Nippon Polychem. Trade name "KANER KS240" (ethylene-1-hexene copolymer) from Dow Chemical Co., Ltd., trade name "ENGAGE EG8100" from Dow Chemical Co.
(Ethylene-1-octene copolymer).

Further, if the density of the ethylene-α-olefin copolymer is high, the bleed-out of the antistatic agent to the surface of the obtained non-crosslinked polyolefin resin foam sheet will be insufficient and the foam sheet will be prevented from being charged. Property may decrease, or a large difference may occur in the surface resistivity between the front and back surfaces of the foamed sheet. If the difference is small, the mechanical strength and rigidity at high temperature of the obtained polyolefin resin foamed sheet may decrease. Sometimes 0.85 to 0.91 g / cm
³ is preferable, and 0.86 to 0.88 g / cm ³ is more preferable.

When the content of the ethylene-α-olefin copolymer is high, the open cell ratio of the non-crosslinked polyolefin resin foam sheet obtained is increased, and when the content is small, the non-crosslinked polyolefin resin obtained is obtained. Bleedout of the antistatic agent to the surface of the resin foam sheet becomes insufficient and the antistatic property of the foam sheet decreases, and there is a large difference in the surface resistivity between the front and back surfaces of the foam sheet. The content of the polyolefin-based resin comprising ethylene-α-olefin copolymer is limited to 2 to 30% by weight, preferably 5 to 15% by weight. Further, for the same reason, the content of the polypropylene resin in the polyolefin resin composed of the polypropylene resin and the ethylene-α-olefin copolymer is limited to 70 to 98% by weight, and preferably 85 to 95% by weight. .

Examples of the nonionic surface active antistatic agent include alcohol antistatic agents such as polyethylene glycol, polyoxyethylene alkyl ethers,
Ether antistatic agent such as polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, ester antistatic agent such as glycerin fatty acid ester, amine such as polyoxyethylene alkylamine Antistatic agents, glycerin antistatic agents such as polyoxyethylene glyceride, amide antistatic agents such as alkylalkanolamides,
Alcohol-based antistatic agents and amine-based antistatic agents are preferable, polyethylene glycol and polyoxyethylene alkylamines are more preferable, and polyoxyethylene alkylamines are particularly preferable, because the bleed-out rate is high. The nonionic surfactant type antistatic agent may be used alone or in combination.

When the content of the nonionic surface active antistatic agent in the non-crosslinked polyolefin resin foam sheet is large, the obtained non-crosslinked polyolefin resin foam sheet surface is sticky, and when it is small, Since the antistatic property of the obtained polyolefin resin foamed sheet is lowered, it is limited to 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin.

Further, JIS K6911 5.13 on the front and back surfaces of the non-crosslinked polyolefin resin foam sheet
When the surface specific resistance at a temperature of 22 ° C. and a humidity of 65% in accordance with the above is high, the antistatic property of the non-crosslinked polyolefin resin foamed sheet may be lowered, so that it is preferably less than 1 × 10 ¹³ Ω. More preferably, it is not less than 10 ⁸ Ω and less than 1 10 ¹³ Ω.

Then, a higher temperature of 22 ° C. on the front and back surfaces of the non-crosslinked polyolefin resin foam sheet, a surface specific resistivity A at a humidity of 65%, and a lower temperature of 22 ° C.,
The ratio (A / B) to the surface resistivity B at a humidity of 65% is
If it is large, the antistatic property of the non-crosslinked polyolefin resin foamed sheet may become nonuniform, so less than 100 is preferable.

Further, JISK6911 5.13 on the front and back surfaces of the above non-crosslinked polyolefin resin foam sheet.
When the surface specific resistance at a temperature of 22 ° C. and a humidity of 40% in accordance with the above is high, the antistatic property of the non-crosslinked polyolefin-based resin foam sheet is deteriorated, so less than 1 × 10 ¹⁴ Ω is preferable, and 1 × 10 ⁸ is preferable. More preferably, it is Ω or more and less than 1 × 10 ¹⁴ Ω.

The surface specific resistivities of the front and back surfaces of the non-crosslinked polyolefin resin foam sheet are determined by JIS.
It is measured in accordance with K6911 5.13, but specifically, a test piece having a flat square shape of 10 cm on each side, which has been passed for 20 days or more after production, under a measurement atmosphere, that is, at a temperature of 22 ° C. and a humidity of 65%, Alternatively, it means the surface specific resistance after 1 minute has passed after applying a voltage of 500 V to this test piece after leaving it in an atmosphere of a temperature of 22 ° C. and a humidity of 40% for 24 hours.

Here, the reason why the test piece 20 days or more after the manufacture is used for measuring the surface resistivity is as follows. That is, the nonionic surfactant type antistatic agent in the non-crosslinked polyolefin resin foam sheet gradually bleeds out to the sheet surface immediately after the production of the foam sheet, but after 20 days or more after the production, This is because the bleedout of the ionic surfactant type antistatic agent to the surface of the foamed sheet is in an equilibrium state, and the surface resistivity of the foamed sheet hardly changes.

Therefore, the test piece for measuring the surface resistivity of the front and back surfaces of the non-crosslinked polyolefin resin foam sheet may be at least 20 days after production, for example, one month or more. It does not matter even if it was done.

Further, if the density of the non-crosslinked polyolefin resin foamed sheet is high, the cushioning property and the lightness of the obtained non-crosslinked polyolefin resin foamed sheet may be lowered, and if it is small, the non-crosslinked polyolefin resin foamed sheet is not obtained. Since the open cell ratio of the crosslinked polyolefin resin foamed sheet may increase and the mechanical strength may decrease, 0.10 to 0.60 g / cm.
³ is preferable, and 0.18 to 0.45 g / cm ³ is more preferable.

Further, if the thickness of the non-crosslinked polyolefin resin foamed sheet is large, it may be difficult to wind it into a roll and the workability may be deteriorated. Since the mechanical strength of the molded product obtained by molding is sometimes 0.5 to 4.0 mm, more preferably 1.0 to 3 mm.

Next, a method for manufacturing the above polyolefin resin foam sheet will be described. The method for producing the polyolefin resin foam sheet is not particularly limited,
For example, a predetermined amount of polypropylene resin and ethylene-
Polyolefin resin consisting of α-olefin copolymer, nonionic surfactant type antistatic agent and foaming agent are supplied to an extruder, melt-kneaded, extruded and foamed into a cylindrical shape from a die of the extruder, and this cylinder A method for producing a non-crosslinked polyolefin-based resin foam sheet is described, in which the foamed body is cooled by a cooling mandrel having a diameter larger than that of the cylindrical foamed body, and then cut into a sheet shape.

When the ratio of the diameter of the cooling mandrel to the diameter of the die of the extruder is large, cracks may occur in the cylindrical foam, and when the ratio is small, the ethylene-α-olefin copolymer is extruded. Direction is not sufficiently stretched, and the ethylene-α-olefin copolymer is not uniformly and densely dispersed in the polypropylene-based resin serving as the matrix, and the non-ionic interface to the surface of the resulting non-crosslinked polyolefin-based resin foam sheet is obtained. Since the bleed-out of the activator type antistatic agent becomes insufficient, the antistatic property of the non-crosslinked polyolefin resin foamed sheet may decrease, or a large difference may occur in the antistatic performance between the front and back surfaces. 2 or more is preferable,
2.5 to 3.5 are more preferable.

The foaming agent is not particularly limited as long as it is a foaming agent which has been conventionally used for extrusion foaming, and examples thereof include inert gases such as nitrogen, carbon dioxide and helium, propane, butane, pentane and hexane. And the like, alicyclic hydrocarbons such as cyclopentane and cyclohexane, halogenated hydrocarbons such as chlorodifluoromethane and trifluoromethane, ethers such as methyl-t-butyl ether and dimethyl ether Examples of the physical foaming agents, azodicarbonamide, bicarbonates such as sodium bicarbonate, organic acids such as citric acid or salts thereof, and the like may be used alone or in combination.

The amount of the foaming agent added may be appropriately adjusted depending on the expansion ratio of the non-crosslinked polyolefin resin foam sheet, but is preferably 0.4 to 10 parts by weight with respect to 100 parts by weight of the polyolefin resin.

Further, in order to adjust the cell diameter of the non-crosslinked polyolefin resin foam sheet, if necessary, a sodium bicarbonate-citric acid cell nucleating agent, talc, a cell nucleating agent such as polytetrafluoroethylene powder, etc. May be added.

[0038]

The non-crosslinked polyolefin resin foamed sheet of the present invention comprises 100 parts by weight of a polyolefin resin composed of 70 to 98% by weight of a polypropylene resin and 2 to 30% by weight of an ethylene-α-olefin copolymer and a nonionic interface. Since it contains 0.2 to 5 parts by weight of the activator type antistatic agent, the nonionic surfactant type antistatic agent is added to the non-crosslinked polyolefin resin foam from the ethylene-α-olefin copolymer part having low crystallinity. The sheet surface can be smoothly and surely bleeded out, and the non-crosslinked polyolefin resin foam sheet can be made to have excellent antistatic properties with almost no difference in antistatic properties between the front and back surfaces.

Further, a predetermined amount of a polypropylene resin and a polyolefin resin composed of an ethylene-α-olefin copolymer, a nonionic surfactant type antistatic agent and a foaming agent are supplied to an extruder and melt-kneaded to form a cylinder. When extruded and foamed into a shape, the cylindrical foam is cooled by a cooling mandrel having a diameter larger than that of the cylindrical foam, and when a non-crosslinked polyolefin resin foam sheet is produced by cutting into a sheet, The ethylene-α-olefin copolymer in the non-crosslinked polyolefin-based resin foam sheet has a spindle shape in the extrusion direction due to the extension force applied in the extrusion direction, and the ethylene-α-olefin copolymer having the spindle shape is formed. The polymer has a structure in which it is dispersed like islands in a dense state in a polypropylene resin that serves as a matrix.

Therefore, a nonionic surfactant type antistatic agent is more smoothly and surely formed on the surface of the non-crosslinked polyolefin resin foam sheet from the ethylene-α-olefin copolymer densely dispersed in the polypropylene resin. Therefore, the non-crosslinked polyolefin resin foam sheet has excellent antistatic properties with almost no difference in antistatic properties between the front and back surfaces.

[0041]

Examples (Example 1) Propylene-ethylene block copolymer having free-end long-chain branch in the molecule (trade name "Pro-fax SD-632" manufactured by San Aroma Co., Ltd.,
Melt index: 3.0 g / 10 minutes, melt tension: 21.9 g) 90% by weight and ethylene-1-hexene copolymer (manufactured by Nippon Polychem Co., Ltd., trade name "Karnell K"
S240 ", density 0.88 g / cm ³ ) 100 wt% of a polyolefin resin consisting of 10 wt%, polyoxyethylene alkylamine (Kao Corporation trade name" TS-2
B ") 3 parts by weight and sodium bicarbonate-citric acid-based cell nucleating agent (trade name" Hydrocelol H "manufactured by Clariant
K-70 ") 0.2 part by weight of the resin composition is fed to the first single-screw extruder of the tandem type extruder and melt-kneaded at 200 ° C., and at the same time, 4 parts by weight per 100 parts by weight of the polyolefin resin. 35 parts by weight of isobutane
And a blowing agent consisting of 65% by weight of normal butane was pressed into the first extruder. In addition, the tandem type extruder described above has a caliber of 1 mm via a connecting pipe to a first single-screw extruder having a caliber of 90 mmφ.
A product obtained by connecting a second single-screw extruder having a diameter of 15 mm was used.

Then, the resin composition melt-kneaded by the first single-screw extruder is continuously supplied into the second single-screw extruder through a connection pipe maintained at 195 ° C., and the second single-screw extruder is used. Melt kneading while gradually lowering the temperature in the cylinder from 185 ° C to 155 ° C, and discharge amount 1 from a circular die with a diameter of 140 mmφ connected to the tip of the second single-screw extruder.
It was extruded into a cylindrical shape in the air at a rate of 00 kg / h.

Subsequently, the cylindrical foam was expanded at a diameter of 3.2 m / min while being drawn, and then supplied to a cooling mandrel having a diameter of 414 mmφ and a length of 500 mm, and the inner surface of the cylindrical foam was cooled by a cooling mandrel. While contacting the outer peripheral surface of the cylindrical foam from the inner peripheral surface side,
Air at 30 ° C. is blown onto the outer peripheral surface of the cylindrical foam from a ring-shaped cooler arranged on the outer peripheral side of the cooling mandrel so as to surround the cooling mandrel, so that the cylindrical foam is also covered from the outer peripheral surface side. Cooled.

Next, the cylindrical foam discharged from the cooling mandrel is continuously cut in the extruding direction at two locations having a phase difference of 180 ° C. in the circumferential direction to form a sheet-like non-crosslinked polyolefin. A resin-based foamed sheet was continuously produced.

The non-crosslinked polyolefin resin foamed sheet had excellent antistatic properties with almost no difference in surface specific resistance between the front and back surfaces. Also, when the above non-crosslinked polyolefin resin foamed sheet was heated to form a tray, which was used as a packaging tray for electronic parts, the surface of the obtained packaging tray was not damaged, its appearance was beautiful and its mechanical strength was good. Was also excellent.

(Example 2) As a polyolefin resin, a propylene-ethylene block copolymer (a sun aroma resin) was used.
Brand name "Pro-fax SD-632" manufactured by the company is 8
0% by weight and 20% by weight of ethylene-1-hexene copolymer (trade name "Kanel KS240" manufactured by Nippon Polychem Co., Ltd.) were used, and polyoxyethylene alkylamine was 1.5 parts by weight. A non-crosslinked polyolefin resin foam sheet was manufactured in the same manner as in Example 1 except for the above.

The non-crosslinked polyolefin resin foam sheet had excellent antistatic properties with almost no difference in surface specific resistance between the front and back surfaces. Also, when the above non-crosslinked polyolefin resin foamed sheet was heated to form a tray, which was used as a packaging tray for electronic parts, the surface of the obtained packaging tray was not damaged, its appearance was beautiful and its mechanical strength was good. Was also excellent.

(Example 3) Ethylene-1-hexene copolymer (trade name "KANER KS24 manufactured by Nippon Polychem Co., Ltd."
0 "), an ethylene-1-octene copolymer (trade name" ENGAGE EG810 "manufactured by Dow Chemical Co., Ltd.
0 ", density: 0.87 g / cm ³ ) except that the non-crosslinked polyolefin resin foam sheet was continuously produced in the same manner as in Example 1.

The non-crosslinked polyolefin resin foam sheet had excellent antistatic properties with almost no difference in surface specific resistance between the front and back surfaces. Also, when the above non-crosslinked polyolefin resin foamed sheet was heated to form a tray, which was used as a packaging tray for electronic parts, the surface of the obtained packaging tray was not damaged, its appearance was beautiful and its mechanical strength was good. Was also excellent.

Example 4 Ethylene-1-hexene copolymer (trade name "KANER KS24, manufactured by Nippon Polychem Co., Ltd."
0 ") was replaced with an ethylene-1-hexene copolymer (trade name" Kanel KF380 "manufactured by Japan Polychem, density: 0.918 g / cm ³ ) in the same manner as in Example 1. To continuously produce a non-crosslinked polyolefin resin foam sheet.

The non-crosslinked polyolefin resin foamed sheet had excellent antistatic properties with almost no difference in surface specific resistance between the front and back surfaces. Also, when the above non-crosslinked polyolefin resin foamed sheet was heated to form a tray, which was used as a packaging tray for electronic parts, the surface of the obtained packaging tray was not damaged, its appearance was beautiful and its mechanical strength was good. Was also excellent.

(Comparative Example 1) As a polyolefin resin, a propylene-ethylene block copolymer (Sun Aroma-
A non-crosslinked polyolefin resin foam sheet was continuously manufactured in the same manner as in Example 1 except that only the trade name "Pro-fax SD-632" manufactured by the company) was used.

The non-crosslinked polyolefin resin foamed sheet had a large difference in surface specific resistance between the front and back surfaces, and was inferior in antistatic property. Also, when the above non-crosslinked polyolefin resin foamed sheet was heated to form a tray, which was used as a packaging tray for electronic parts, the surface of the obtained packaging tray was not damaged, its appearance was beautiful and its mechanical strength was good. Was also excellent.

(Comparative Example 2) A propylene-ethylene block copolymer (san aroma
Company name "Pro-fax SD-632") 6
A non-crosslinked polyolefin-based resin was prepared in the same manner as in Example 1 except that 5% by weight and 35% by weight of an ethylene-1-hexene copolymer (trade name "Kanel KS240" manufactured by Nippon Polychem Co., Ltd.) were used. A resin foam sheet was continuously produced.

The above-mentioned non-crosslinked polyolefin resin foam sheet had a large bubble diameter on the surface portion and had rough front and back surfaces. Furthermore, when the above-mentioned non-crosslinked polyolefin resin foamed sheet is heated and molded into a tray shape to form a packaging tray for electronic parts, the molding elongation is poor in the non-crosslinked polyolefinic resin foamed sheet, and the obtained packaging tray surface Was inferior in mechanical strength.

JIS K6911 in the non-crosslinked polyolefin resin foam sheet obtained as described above
The surface specific resistance of the front and back surfaces at a temperature of 22 ° C. and a humidity of 65% according to 5.13 and the surface specific resistance of the front and back surfaces at a temperature of 22 ° C. and a humidity of 40%, and the open cell ratio are shown below. The measurement was performed by the method and the results are shown in Table 1.

(Surface specific resistivity) Temperature 22 ° C., humidity 65
The surface specific resistance of the front and back surfaces of the non-crosslinked polyolefin resin foam sheet in% is measured by the surface specific resistance measuring device (ADV
Product name "ULTRA HIGH R" manufactured by ANTEST
JIS K using ESISTANCE METER)
Measured according to 6911 5.13. In particular,
A square test piece with a side of 10 cm was heated at a temperature of 22 ° C.
After standing for 24 hours in an atmosphere with a humidity of 65%, the test piece was set in a surface resistivity measuring device, a voltage of 500 V was applied to the test piece, and the surface resistivity after 1 minute was measured. As test pieces, four test pieces that had been produced for 20 days were prepared, and the average value of the surface specific resistances was taken as the surface specific resistance.

The surface specific resistivities of the front and back surfaces of the non-crosslinked polyolefin resin foam sheet at a temperature of 22 ° C. and a humidity of 40% are the same as those of the above temperature 22 except that the atmosphere is left at 22 ° C. and the humidity is 40%. It was measured by the same method as the method for measuring the surface specific resistance of the front and back surfaces of the non-crosslinked polyolefin resin foam sheet at a temperature of 65 ° C. and a humidity of 65%.

Since the surface of the non-crosslinked polyolefin resin foam sheet of Comparative Example 2 was rough and rough, the surface resistivity of the front and back surfaces could not be measured.

In Table 1, the surface of the non-crosslinked polyolefin resin foam sheet means the surface corresponding to the outer peripheral surface of the cylindrical foam, and the back surface of the noncrosslinked polyolefin resin foam sheet means the cylindrical foam. The surface corresponding to the inner peripheral surface.

(Open cell ratio) The open cell ratio of the non-crosslinked polyolefin resin foam sheet was measured using an air-comparison hydrometer (trade name "1000" manufactured by Tokyo Science Co., Ltd.).
It measured based on the 1 / 2-1 atmospheric pressure method. As the test piece, a laminated body was used in which a plurality of non-crosslinked polyolefin resin foamed sheets cut out in a flat square shape with one side of 25 mm were laminated in the thickness direction so that the total thickness was about 25 mm. Five bodies were made, and the average value of the open cell rates in the five laminated bodies was defined as the open cell rate.

[0062]

[Table 1]

[0063]

INDUSTRIAL APPLICABILITY The non-crosslinked polyolefin resin foam sheet of the present invention comprises 100 parts by weight of a polyolefin resin composed of 70 to 98% by weight of a polypropylene resin and 2 to 30% by weight of an ethylene-α-olefin copolymer and a nonionic resin. Since it contains 0.2 to 5 parts by weight of a surfactant type antistatic agent,
The non-ionic surfactant type antistatic agent can be smoothly and reliably bleeded out from the low crystallinity ethylene-α-olefin copolymer part to the front and back surfaces of the non-crosslinked polyolefin resin foam sheet. The non-crosslinked polyolefin resin foamed sheet has almost no difference in antistatic property between the front and back surfaces thereof and has superior antistatic property.

When the density of the ethylene-α-olefin copolymer is 0.85 to 0.91 g / cm ³ , the non-crosslinked polyolefin resin foam sheet has an antistatic property between its front and back surfaces. It has almost no difference and has an excellent antistatic property as well as an excellent mechanical strength.

Finally, polypropylene resin 98 to 70
% By weight and ethylene-α-olefin copolymer 2 to 30
100 parts by weight of a polyolefin resin consisting of 10% by weight, 0.2 to 5 parts by weight of a nonionic surfactant type antistatic agent, and 0.4 to 10 parts by weight of a foaming agent are supplied to an extruder and melt-kneaded to form a cylindrical shape. After extrusion foaming, the cylindrical foam is cooled by a cooling mandrel having a diameter larger than that of the cylindrical foam, and then cut into a sheet shape to produce a non-crosslinked polyolefin resin foam sheet. The ethylene-α-olefin copolymer in the polyolefin resin foamed sheet has a spindle shape in the extrusion direction due to the extension force applied in the extrusion direction, and the ethylene-
The α-olefin copolymer is dispersed like islands in a polypropylene resin serving as a matrix in a dense state with small gaps.

Therefore, on the surface of the non-crosslinked polyolefin resin foamed sheet, a nonionic surfactant type antistatic agent is introduced from the ethylene-α-olefin copolymer portion densely dispersed in the polypropylene resin as the matrix. Bleed-out can be performed more smoothly and reliably, and thus the obtained non-crosslinked polyolefin resin foam sheet has excellent antistatic properties with almost no difference in antistatic properties between the front and back surfaces.

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Claims (4)

[Claims] 1. Polypropylene resin 70 to 98% by weight
And ethylene-α-olefin copolymer 2 to 30% by weight
A non-crosslinked polyolefin-based resin foam sheet comprising 100 parts by weight of a polyolefin-based resin containing 0.2 to 5 parts by weight of a nonionic surfactant type antistatic agent. 2. The surface specific resistances A and B of the front and back surfaces at a temperature of 22 ° C. and a humidity of 65% according to JIS K6911 5.13 are less than 1 × 10 ¹³ Ω, and the higher surfaces of the front and back surfaces. The non-crosslinked polyolefin resin foam sheet according to claim 1, wherein the ratio (A / B) between the specific resistance A and the lower specific surface resistance B is less than 100. 3. The non-crosslinked polyolefin resin foam sheet according to claim 1 or 2, wherein the ethylene-α-olefin copolymer has a density of 0.85 to 0.91 g / cm ^3. . 4. Polypropylene resin 70 to 98% by weight
And ethylene-α-olefin copolymer 2 to 30% by weight
100 parts by weight of a polyolefin resin, 0.2 to 5 parts by weight of a nonionic surfactant type antistatic agent, and 0.4 to 10 parts by weight of a foaming agent are supplied to an extruder, melt-kneaded, and extruded into a cylindrical shape. A method for producing a non-crosslinked polyolefin resin foam sheet, which comprises foaming, continuously cooling the cylindrical foam with a cooling mandrel having a diameter larger than that of the cylindrical foam, and then cutting into a sheet shape.