JP2013209577A - Polyethylene resin foam sheet and laminated foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an antistatic effect while reducing a usage of a polymeric antistatic agent in a polyethylene resin foam sheet or laminated foam sheet.SOLUTION: A polyethylene resin foam sheet includes a polymeric antistatic agent containing lithium ion.

Description

  The present invention relates to a polyethylene resin foam sheet containing a polymer antistatic agent, and a laminated foam sheet in which a polyethylene resin film is laminated on one side of a polyethylene resin foam sheet.

The polyethylene resin foam sheet is not only relatively inexpensive but also has a low manufacturing cost as well as a lightweight, soft feel and excellent workability such as cutting properties. It is widely used.
Moreover, the polyethylene-type resin foam sheet is used also as a raw material for bonding a polyethylene-type resin film and forming a laminated foam sheet.
The laminated foam sheet is used in various applications as a cushioning material because it is superior in surface smoothness and mechanical strength as compared with a polyethylene resin foam sheet.
However, the polyethylene-based resin foam sheet and the laminated foam sheet are easily charged by static electricity, and have a problem that dust or the like adheres to them during storage.
For this reason, when used for applications related to electrical / electronic components, static electricity may adversely affect them.

It is known that such problems due to charging of the polyethylene resin foam sheet can be prevented by lowering the value of the surface resistivity. For example, in the case of a general polystyrene resin, the surface of a film of a single resin The resistivity value is usually over 10 ¹⁵ (Ω / □) order, but it is reduced to 10 ¹³ (Ω / □) order or less to prevent the above problems. It is known that it can be done.

As a method of reducing the surface resistivity, a method of incorporating a component called an antistatic agent in a resin composition used for forming a polyethylene-based resin foam sheet has been employed. Conventionally, a component such as a surfactant is used. Is contained in the raw material.
This surfactant usually has a molecular weight of about 1000 or less and is also referred to as a “low molecular weight antistatic agent”. The low molecular weight antistatic agent is a polymer that is effective for antistatic properties. Since the diffusion rate in the inside is high, there is a possibility that a problem of so-called “bleed out” occurs due to oozing on the surface of the polystyrene resin film over time.

In recent years, instead of a low molecular weight antistatic agent, a so-called “polymeric antistatic agent” that is effective in antistatic with a high molecular weight substance having a molecular weight exceeding 1000 and reaching several tens of thousands. Use has been studied (see Patent Document 1 below).
As this type of polymer antistatic agent, a material mainly composed of a copolymer having a polar block containing an ether bond or an ester bond and a nonpolar block made of alkyl or the like is known. Since the polymer type antistatic agent has a low migration property in the polymer, problems such as bleeding out can be suppressed.
On the other hand, polymer antistatic agents are not effective unless they are mixed in a relatively large amount, and are much more expensive than polyethylene resins, which increases the material cost of polyethylene resin foam sheets. Therefore, the versatility may be reduced.

  In order to prevent such a situation, studies have been widely conducted to effectively act a polymer type antistatic agent in a small amount, but the method has not been established.

JP 2008-7670 A

  The present invention relates to a polymer type electrification sheet in a polyethylene type resin foam sheet containing a polymer type antistatic agent, a laminated foam sheet in which a polyethylene resin film is laminated on one side of such a polyethylene resin foam sheet, and the like. An object is to prevent charging while reducing the amount of the inhibitor used.

  As a result of intensive studies by the present inventors to solve the above-mentioned problems, a polymer type antistatic agent containing lithium ions is more polyethylene-based than a polymer type antistatic agent containing substantially no lithium ions. The antistatic effect on the resin foam sheet is particularly excellent, and the present invention has been completed by finding that a sufficient antistatic effect is exhibited only by adding a small amount to the polyethylene resin foam sheet.

  The present invention relating to a polyethylene resin foam sheet for solving the above-mentioned problems is characterized by containing a polymer type antistatic agent containing lithium ions.

  Further, the present invention relating to a laminated foam sheet for solving the above problems is a laminated foam sheet in which a polyethylene resin film is laminated on one side of a polyethylene resin foam sheet, and the polyethylene resin foam sheet includes It is characterized by containing a polymer type antistatic agent containing lithium ions.

Among the polymer antistatic agents, the polymer antistatic agents containing lithium ions are excellent in the antistatic effect on the polyethylene resin foam sheet.
Therefore, by using a polymer-type antistatic agent containing lithium ions, the required antistatic effect can be exerted on polyethylene-based resin foam sheets and laminated foam sheets while reducing the amount of polymer-type antistatic agent used. sell.

With respect to the embodiment of the present invention, a polyethylene-based resin foam sheet (hereinafter also simply referred to as “foam sheet”) formed by a general extrusion foaming method is used between these glass plates for the purpose of protecting them. A description will be given while exemplifying a mode suitable for a slip sheet to be inserted.
The foam sheet of this embodiment contains a polyethylene-based resin (A) and a polymer type antistatic agent (B) containing lithium ions as essential components. In this embodiment, the HLB by the Davis method is further used. It is preferable to contain an anionic surfactant (C) having a value of 20 or more.

(A) Polyethylene resin The polyethylene resin is not particularly limited, but has a melt mass flow rate (hereinafter also referred to as “MFR”) of 2 to 6 g / 10 min, and a resin density of 925 kg / m ³ or more. It is preferable to use a low density polyethylene resin of 935 kg / m ³ or less.
The low density polyethylene resin exhibiting the MFR value as described above is preferable. When the MFR is less than 2 g / 10 min, a problem occurs in the kneadability with the polymer type antistatic agent in the extruder and the antistatic performance is lowered. This is because there is a possibility that it may be difficult to obtain a good foamed sheet by causing foam breakage during extrusion foaming.
Moreover, it is preferable that MFR is 6 g / 10min or less, when MFR exceeds 6 g / 10min, melt tension will become low too much and it will become difficult to obtain a low-density foam sheet.
In addition, if the MFR exceeds 6 g / 10 min, there is a possibility that a deposit in the form of a spear tends to occur at the tip of the die during extrusion foaming.

  In the present specification, the melt mass flow rate of JIS K 7210: 1999 “Plastic-thermoplastic melt mass flow” is also used for the MFR of the polymer type antistatic agent described below, unless otherwise specified. The value measured by the method described in Method B (however, the test temperature is 190 ° C. and the load is 21.18 N) is intended. “Rate (MFR)” and “Melt Volume Flow Rate (MVR) Test Method”

The polyethylene-based resin constituting the foamed sheet of the present embodiment preferably has the above-described density. When the resin density is less than 925 kg / m ³ , the foaming agent from the foamed sheet after extrusion is used. The resin itself has a low rigidity and the rigidity of the resin itself is small, and the shrinkage may not be suppressed. On the other hand, if the resin density exceeds 935 kg / m ³ , the rigidity of the resin itself is too large and the foam sheet becomes a packaging material. This is because there is a risk of losing cushioning properties.

(B) Polymeric antistatic agent As the polymeric antistatic agent (B), it is important to use one containing lithium ions, and in particular, a block of a polyolefin block and a polyether block. A copolymer having a ionic conductivity of the polyether block improved by lithium ions is preferred.
Since lithium ions have the smallest ion radius and the highest degree of freedom of ion movement among alkali metals, it is considered that static ions can be quickly dissipated by ion conduction and the charged voltage can be attenuated.
That is, the presence of lithium ions in the polyethylene resin by the polymer type antistatic agent provides excellent and stable antistatic performance.
Specifically, lithium ions can be contained in the polymer antistatic agent in the form of a lithium salt. Examples of the lithium salt include lithium chloride, lithium fluoride, lithium bromide, lithium iodide, Lithium perchlorate, lithium acetate, lithium fluorosulfonate, lithium methanesulfonate, lithium trifluoromethanesulfonate, lithium pentafluoroethanesulfonate, lithium nonafluorobutanesulfonate, lithium undecafluoropentanesulfonate, tridecafluorohexane Lithium sulfonate is mentioned, Among these, lithium chloride, lithium perchlorate, and lithium trifluoromethanesulfonate are preferable.

Note that whether or not the polymer type antistatic agent contains lithium ions can be determined by measuring the amount of metal elements.
More specifically, it can be determined by confirming the presence of 50 μg / g or more of lithium when the eluted metal element is measured by performing the following measurement.

(Pretreatment of measurement sample)
First, a 50 ml plastic container is filled with distilled water and then heated and washed at 70 ° C. for 2 hours.
1 g of a sample is precisely weighed into an empty 50 ml plastic container that has been heated and washed, 50 ml of distilled water is added, the container is covered, and the container is sealed.
The sealed container is placed in a dryer set at a temperature of 60 ° C., heated for 20 minutes, shaken well by hand, and further heated for 20 minutes.
And after heating for a total of 40 minutes, it shakes well again by hand, a liquid supernatant liquid is extract | collected and it is set as a measurement sample.

(Measurement)
The metal element amount can be measured using a multi-type ICP emission spectroscopic analyzer (manufactured by Shimadzu Corporation: ICPE-9000).
A standard solution for preparing a calibration curve for use in quantification is obtained from XSTC-13 manufactured by SPEX (31 element general-purpose mixed standard solution each 10 ppm) and XSTC-8 manufactured by SPEX (10 element each general-purpose mixed standard solution 10 ppm).
These mixed standard solutions are diluted and prepared stepwise with distilled water to prepare 0 ppm (BK), 0.2 ppm, 1 ppm, 2.5 ppm, and 5 ppm standard solutions.
The standard solution of each concentration is measured under the following conditions to obtain the peak intensity of the wavelength of each element.
Concentrations and peak intensities are plotted to obtain an approximate curve (straight line or quadratic curve) by the least square method.

(Measurement condition)
Observation direction: axial direction, exposure time: 30 seconds High frequency output: 1.20 kW
Carrier plasma auxiliary flow rate: 0.7-10.0-0.6 L / min

The polymer antistatic agent is preferably a polymer antistatic agent having a crystallization temperature of less than 90 ° C. and an MFR of 5 to 40 g / 10 min.
The crystallization temperature of the polymer antistatic agent is preferably less than 90 ° C. If the crystallization temperature is 90 ° C or higher, crystallization proceeds in the extruder and dispersion becomes worse. When the foam film is stretched during extrusion foaming, the polymer antistatic agent does not deform and becomes a lump, increasing the distance between dispersed particles of the antistatic agent, making it difficult to develop an antistatic function commensurate with the amount added. This is because

In addition, it is preferable that the MFR of the polymer antistatic agent is within the above-described range. If the MFR of the polymer antistatic agent is less than 5 g / 10 min, the polyethylene resin in the extruder or in the die is used. This is because the dispersion is uneven and the surface resistivity is excellent, but the static electricity decay rate tends to deteriorate.
Moreover, it is preferable that MFR is in the above range. If MFR exceeds 40 g / 10 min, the dispersibility with polyethylene resin is lowered and the melt tension of the polyethylene resin composition is lowered. For this reason, a low-density foam sheet cannot be obtained, or there is a possibility of generating coarse bubbles that are communicated.

In the present specification, the crystallization temperature is intended to be a value measured according to the method described in JIS K7122 “Method for measuring transition temperature of plastic” unless otherwise specified.
Specifically, using a differential scanning calorimeter (for example, “DSC 6220” manufactured by SII Nano Technology Co., Ltd.), about 6.5 mg of a sample is filled in a measurement container, and the nitrogen gas flow rate is 30 ml / min. The temperature can be raised and cooled between 30 ° C. and 200 ° C. at a heating / cooling rate of ° C./min, and the exothermic peak temperature during cooling can be measured as the crystallization temperature.
In addition, when two or more exothermic peaks appear, the temperature of the peak of the highest temperature peak among the area peaks having 5% or more of the total peak area is defined as the crystallization temperature.

The polymer type antistatic agent (B) containing lithium ions is preferably contained in the foamed sheet so as to be 3 to 15 parts by mass with respect to 100 parts by mass of the polyethylene resin (A).
It is preferable that the polymer type antistatic agent is contained in the foamed sheet in such a ratio. By setting the content to 3% by mass or more, the antistatic performance is more reliably exhibited with respect to the foamed sheet. This is because not only it becomes easy to obtain a low-density foam sheet having good foamability but also the material cost of the foam sheet is suppressed from being excessive. Because it can.

(C) Surfactant The surfactant contained in the foamed sheet together with the polymer type antistatic agent is preferably a so-called low molecular weight antistatic agent that functions for antistatic, and in this embodiment, the interface It is preferable to employ an anionic surfactant having an HLB value by the Davis method of 20 or more (the upper limit is usually 50) as the activator.
The Davis method is a method in which a surfactant molecule is divided into atomic groups (or functional groups), a specific number of groups is given to each atomic group, and an HLB value is obtained by calculation. For example, Sanyo Chemical Industries, Ltd. It can be calculated based on the method specifically described in the book name “Introduction to Surfactant” issued by the company.
In the following description, “HLB value” means “HLB value by Davis method” unless otherwise specified.

This type of surfactant quickly bleeds out to the surface of the foam sheet, and adheres to the surface of the glass plate quickly, for example, when the foam sheet of this embodiment is used as a slip sheet sandwiched between the glass plates.
Furthermore, deformation of the polymer antistatic agent is promoted when the cell membrane is stretched during extrusion foaming, and variation in expression can be suppressed even with a smaller amount.
However, since it has a high HLB value as described above, it can be easily removed by water washing or the like.
In addition, since it is possible to prevent deposits other than this surfactant from adhering to the mating material such as a glass plate, these surfactants are difficult to remove by washing or the like. It is possible to expect the effect of preventing the above.

  Examples of the anionic surfactant include dialkyl sulfosuccinate, alkyl sulfonate, alpha olefin sulfonate, linear alkyl benzene sulfonate, naphthalene sulfonate-formaldehyde condensate, alkyl naphthalene sulfonate, N -Sulfonate surfactants such as methyl-N-acyl taurine salts; carboxylates such as aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, N-acyl sarcosine salts, N-acyl glutamates Surfactants; sulfates such as alkyl sulfates, polyoxyethylene alkyl ether sulfates, and oil sulfates; alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyls Phenyl A It can be employed as phosphate salt-based surfactants such as Berlin salt.

When the content of the anionic surfactant in the foam sheet is too small, it is difficult to expect an effect of preventing substances other than the anionic surfactant from adhering to the surface of the counterpart material. At the same time, it becomes difficult to impart a sufficient antistatic effect to the foam sheet.
On the other hand, since there is a limit to the improvement of the antistatic effect and the suppression effect of deposits other than the anionic surfactant, even if the anionic surfactant is contained in the foam sheet more than necessary, the foam sheet is simply It just makes it difficult to manufacture.
For this reason, the anionic surfactant (C) is preferably contained in the foamed sheet so that the ratio with respect to 100 parts by mass of the polyethylene resin (A) is 0.1 to 1.0 part by mass. .

  Among those exemplified above, the anionic surfactant to be contained in the foam sheet in the present embodiment is preferably a sulfonate surfactant in that it can be easily washed and removed from the surface of the contacted object. Among the sulfonate surfactants, it is preferable to use any one of dialkyl sulfosuccinate, linear alkylbenzene sulfonate, and alkyl sulfonate.

  In addition, it is not necessary to use said anionic surfactant individually by 1 type, You may mix and use 2 or more types.

In addition, in order to produce this foamed sheet by extrusion foaming, the foamed sheet of this embodiment can further contain components necessary for foaming in addition to the above components.
Examples of the foaming component include a foaming agent and a bubble regulator. In addition to these, additives such as a heat stabilizer, an ultraviolet absorber, an antioxidant, and a colorant may be added as necessary. It can also be contained in a foam sheet.

Examples of the blowing agent include hydrocarbons such as isobutane, normal butane, propane, pentane, hexane, cyclobutane, and cyclopentane, and inorganic gases such as carbon dioxide and nitrogen.
Especially, as said foaming agent, the mixed butane of isobutane and normal butane is preferable.

  When isobutane / normal butane mixed butane is used in this manner, isobutane suppresses rapid dissipation of the foaming agent in the extrusion foaming process, while normal butane having excellent compatibility with the polyethylene-based resin is open-celled. Since the increase in the rate is suppressed, it is possible to obtain a foam sheet that is excellent in cushioning properties with little shrinkage and low open cell rate.

The amount of the foaming agent used for extrusion foaming depends on the desired degree of foaming, but is usually 5 parts by mass or more and 25 parts by mass with respect to a total of 100 parts by mass of the polyethylene resin and the polymer antistatic agent. It is as follows.
Usually, the addition ratio of the foaming agent is within such a range that if the foaming agent is less than 5 parts by mass, it is difficult to obtain sufficient foaming, and if it exceeds 25 parts by mass, the foam film is broken and a good foamed sheet It is because there exists a possibility that it may become impossible to obtain.

In addition, as the bubble adjusting agent for adjusting bubbles formed by the foaming agent, polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate (sodium bicarbonate) used as inorganic powders such as talc and silica, or as a decomposable foaming agent And azodicarboxylic acid amide.
These may be used alone or in combination. The addition amount is preferably 0.5 parts by mass or less per 100 parts by mass of the polyethylene resin.

The density (apparent density) of the foam sheet is not particularly limited, and may be a density that can provide cushioning properties that are generally required as a slip sheet for a glass substrate, and may be 10 kg / m ³ or more and 70 kg. / M ³ is preferable, and 15 kg / m ³ or more and 60 kg / m ³ or less is particularly preferable.
The density in such a range is selected as a preferable value because when the density is 70 kg / m ³ or more, there is a possibility that the foam sheet is insufficient in flexibility and has a low cushioning property. This is because if the density is too small, the strength of the foamed sheet is not sufficient, and as a result, the buffering property may be low.
Furthermore, if the thickness of the cell membrane is too thin, the shrinkage increases, and as a result, when a long foam sheet is produced, it is difficult to wind it as a roll.
Accordingly, the density is preferably 10 kg / m ³ or more, and more preferably 15 kg / m ³ or more.

  The foamed sheet according to the present embodiment can be produced in the same manner as a general extruded foamed sheet. For example, an extruded foaming process for producing an extruded foamed sheet by extrusion foaming the polyethylene resin composition. A roll-up process in which an extruded sheet is wound up by a winder, an aging process in which the wound-up roll roll is aged for a certain period, and the roll roll is used for a product roll. It can be manufactured by performing a rewinding cosmetic winding process.

In addition, the foam sheet of this embodiment is suitable also for laminating | stacking a polyethylene-type resin film and using it as a laminated foam sheet.
For example, a polyethylene resin film made of a polyethylene resin that is the same as or different from that used for a foam sheet and a foam sheet are overlaid, and these are heat-sealed by passing through a heat roll to integrate the layers. Laminated foam sheet that is made by laminating and integrating the foam sheet and polyethylene resin film by coextrusion, or laminated foam that is made by extruding polyethylene resin on the surface of the foam sheet in the form of a film and integrating them The sheet has a state in which one surface layer portion is composed of a polyethylene resin foam sheet and the other surface layer portion is composed of a polyethylene resin film, which is excellent in cushioning properties and surface strength, and forms one surface. Excellent antistatic effect can be exhibited by the foamed sheet.

In addition, when the antistatic effect excellent in both surfaces of such a laminated foam sheet is calculated | required, the polymer type antistatic agent which contains lithium ion also in the polyethylene-type resin film side, and the HLB value by a Davis method May contain 20 or more anionic surfactants.
In that case, the polymer type antistatic agent or anionic surfactant to be contained in the foam sheet and the polymer type antistatic agent or anionic surfactant to be contained on the polyethylene resin film side are classified as follows. You may make it common and may make these differ.

The laminated foam sheet is not limited to such a two-layer structure. For example, a laminated sheet of foam sheet / foam sheet / polyethylene resin film formed by co-extrusion of three layers is also a glass plate. It can be used as a slip paper.
In such a case, it is not necessary for the foam sheet constituting the intermediate layer to contain an antistatic agent or an anionic surfactant, and lithium ions are contained only in the foam sheet constituting the surface layer portion. What is necessary is just to contain the polymeric antistatic agent to contain.
Although no further details will be given here, various modifications other than such examples can be adopted in the present invention.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Combination agent)
Table 1 below shows the abbreviations of the compounding agents used for the production of the polyethylene resin foam sheet and the details thereof.

(Formulation example 1)
Low-density polyethylene resin (trade name: “LF580”, density: 928 kg / m ³ , MFR = 4.0 g / 10 min) manufactured by Nippon Polyethylene Co., Ltd., 100 parts by mass, polymer type charging manufactured by Sanyo Chemical Co., Ltd. 4 parts by weight of an inhibitor (polyether-polypropylene block copolymer, trade name: “Peletron HS”, MFR = 6 g / 10 min), an anionic surfactant (alkyl having 12 to 16 carbon atoms) manufactured by Sanyo Chemical Co., Ltd. Containing 90% by mass or more of sulfonate, 0.5 part by mass of trade name “Chemist 3033”, softening point 70 ° C., HLB value 40), and a cell conditioner masterbatch made by Sankyo Kasei Co., Ltd. (containing azodicarbonamide) Master batch: A blend containing a trade name “Cermic MB1023”) at a ratio of 0.05 part by mass is a first press of a tandem extruder. Machine (cylinder diameter: 90 mm) was supplied to the maximum reachable temperature at the extrusion machine was melt-kneaded such that the 210 ° C..
Also, mixed butane (isobutane / normal butane = 50/50 (molar ratio)) as a foaming agent was pressed in from the middle of the first extruder so that the ratio to 100 parts by mass of the low-density polyethylene resin was 13 parts by mass. Further, melt kneading was performed.
After melt-kneading in this first extruder, it is cooled to a temperature range (111 ° C.) suitable for foaming with a second extruder (cylinder diameter: φ150 mm) connected to the first extruder, and the outlet diameter is 222 mm ( It was extruded and foamed into the atmosphere from a circular die having a slit of 0.31 mm.
The extruded foam is cooled by blowing air, then cooled along a cooling mandrel having a diameter of 770 mm and a length of 650 mm, and extruded with a cutter provided behind the cooling mandrel. The cylindrical foam was continuously cut along the direction to obtain a long band foam sheet.

When the thickness of the obtained foamed sheet was measured using a constant pressure thickness measuring machine (Model PG- (special) S-37387 ("SCM-627") manufactured by Teclock), the thickness (apparent density) was 0.51 mm. Was 52 kg / m ³ when measured based on JIS K 7222: 2005 “Foamed Plastics and Rubbers—How to Obtain Apparent Density”.

Moreover, the value of surface resistivity was measured with respect to the obtained polyethylene-type resin foam sheet by the method described in JIS K 6911: 1995 “Thermosetting Plastics—General Test Method”.
Specifically, after a flat square test piece having a side of 10 cm is left in an atmosphere of a temperature of 22 ° C. and a humidity of 60% for 24 hours, a test apparatus (manufactured by Advantest Corporation) under an environment of a temperature of 22 ° C. and a humidity of 60% is used. Using a digital ultra-high resistance / microammeter R8340 and a resiliency chamber R12702A), an electrode is crimped to a test piece with a load of about 30 N, a voltage of 500 V is applied, and a resistance value after one minute has elapsed. Measured and calculated by the following formula.
ρs = π (D + d) / (D−d) × Rs
However,
ρs: Surface resistivity (Ω / □)
D: Inner diameter (cm) of the annular electrode on the surface (7 cm for the resiliency chamber R12702A)
d: outer diameter (cm) of inner circle of surface electrode (5 cm for resiliency chamber R12702A)
Rs: Surface resistance (Ω)
Moreover, measurement was implemented 3 times and each arithmetic mean value was calculated | required.

(Formulation Examples 2 to 16)
The same evaluation as in Formulation Example 1 was performed except that the type and blending amount of the polymeric antistatic agent to be blended in the production of the foamed sheet were changed as shown in Tables 2 and 3.
The results are shown in Tables 2 and 3 below.

  From the results shown in this table, it can be seen that the polymer type antistatic agent containing lithium ions exhibits an excellent antistatic effect in a small amount with respect to the polyethylene resin foam sheet.

Claims (4)

  A polyethylene-based resin foam sheet comprising a polymer-type antistatic agent containing lithium ions.   A polyethylene-based resin (A), the polymer-type antistatic agent (B) containing lithium ions, and an anionic surfactant (C) having an HLB value of 20 or more by the Davis method, A) The content of the polymer antistatic agent (B) is 3 to 15 parts by mass with respect to 100 parts by mass, and the content of the anionic surfactant (C) is 0.1 to 1 part by mass. The polyethylene-based resin foam sheet according to claim 1. A laminated foam sheet in which a polyethylene resin film is laminated on one side of a polyethylene resin foam sheet,
A laminated foam sheet, wherein the polyethylene resin foam sheet contains a polymer type antistatic agent containing lithium ions.   The laminated foam sheet according to claim 3, wherein the polyethylene-based resin film also contains a polymer type antistatic agent containing lithium ions.