KR20100107410A - Multi-layered polystyrene resin foamed sheet - Google Patents

Abstract

PURPOSE: A laminate polyethylene resin foamed sheet is provided to prevent dust from being attached to a sheet. CONSTITUTION: A polyethylene resin layer with a polymer type charge inhibitor is attached to at least one side of a polyethylene resin foamed sheet several times to make a laminate sheet. The laminate sheet satisfy the following conditions. A formed film thickness of a formed sheet is 6 ~ 100 micro meter. The number of forms is smaller than 2 in a thickness direction.

Description

Laminated Polyethylene Resin Foam Sheet {MULTI-LAYERED POLYSTYRENE RESIN FOAMED SHEET}

The present invention relates to a laminated polyethylene resin foam sheet.

In order to prevent the occurrence of damage and scratches of the glass substrate for display used in the recent thin television, the polyethylene resin extruded foam sheet rich in flexibility and buffering has come to be used as the packaging material. Since a very high level of surface cleanliness is required for this display glass substrate, the polyethylene resin extrusion foam sheet containing a polymeric antistatic agent is used as a packaging material. As such a foam sheet, there exists the slip paper for glass substrates of patent document 1, for example.

However, the foam sheet as a cushioning material and packaging material of the electronic precision apparatus used conventionally, including the interlayer paper for glass substrates of patent document 1, contained the expensive polymeric antistatic agent in the whole foam sheet. Although the foam sheet has been studied to some extent so that antistatic property can be expressed by a small amount of addition, the foam sheet is expensive and leaves room for improvement.

MEANS TO SOLVE THE PROBLEM In order to solve this problem, the present inventors developed the laminated polyethylene resin foam sheet which laminated | stacked the unfoamed polyethylene resin layer on the surface of a foam sheet, and added the polymeric antistatic agent only to this resin layer. However, this laminated foam sheet exhibited good antistatic properties, but had a problem of poor slipperiness. Specifically, when the foam sheets are laminated and stored, the foam sheets adhere to each other and are difficult to be peeled off, or are easily adhered to a packaged object such as a glass substrate, and are difficult to peel off, or the package is stored in the foam sheet. Since foam seat | seet does not slip well at the time of a covering operation | work, there existed a case where wrinkled or a workability | operativity was reduced to foam seat | seet. Moreover, when a to-be-packed object avoids static electricity like a glass substrate, there existed a subject which peeling charging generate | occur | produces when peeling the foam sheet from a glass substrate. Moreover, when this foam sheet is used as a packaging material, although it is excellent in bufferability, there also exists a subject also in the visibility of a to-be-packed object.

Japanese Laid-Open Patent Publication 2005-194433

In view of the above problems, the present invention can prevent adhesion between foam sheets and adhesion to a packaged object such as a glass substrate, which is excellent in packing workability of the packaged material, and prevents peeling charging to prevent An object of the present invention is to provide a laminated polyethylene resin foam sheet that can prevent dust and dirt from adhering to the package.

According to this invention, the laminated polyethylene resin foam sheet shown below is provided.

[1] In a laminated sheet having a thickness of 0.2 to 2.0 mm and an apparent density of 0.02 to 0.1 g / cm 3, obtained by laminating and bonding a polyethylene resin layer containing a polymer type antistatic agent to at least one side of the polyethylene resin foam sheet.

The laminated sheet satisfies at least any one of the following conditions (i), (ii) and (iii).

(Iii) The basis weight of a polyethylene resin layer is 8 g / m <2> or less, the bubble film thickness of foam seat | seet is 6-100 micrometers, and the average number of bubbles in a thickness direction is two or less.

(Ii) The polyethylene resin layer is 30-90 weight% of melting | fusing point 115 degreeC or less and 128 degrees C or less and density 0.910-0.970 g / cm <3> of polyethylene resin (a), 0-60 weight% of melting | fusing point 115 degreeC or less and density 0.890- It is comprised by 0.930 g / cm <3> of polyethylene resin (b) and 10-50 weight% of polymeric antistatic agent (c) ((a) + (b) + (c) = 100 weight%).

(Iii) polyethylene resin foam sheet having a melting point of more than 10 to 50% by weight of more than 115 ° C and 125 ° C or less, and a polyethylene resin (d) having a density of 0.910 to 0.940 g / cm 3 and a melting point of 50 to 90% by weight of 115 ° C or less and a density of 0.890. It is comprised by the polyethylene resin (b) (however, (d) + (b) = 100 weight%) of -0.930 g / cm <3>.

[2] The laminated polyethylene resin foam sheet according to the above 1, wherein the condition (i) and at least one condition selected from the condition (ii) and the condition (i) are satisfied at the same time.

[3] The laminated polyethylene resin foam sheet according to the above 1 or 2, wherein the applied voltage half life of the laminated foam sheet after washing with water is 10 seconds or less.

The laminated polyethylene resin foam sheet of the present invention (hereinafter also referred to as a laminated foam sheet or laminated sheet) has excellent surface protection property of the packaged object and adheres to dust and dust because the polyethylene resin layer contains a polymer antistatic agent. It is excellent in prevention property and is suitable as a packaging material of electronic precision instruments, such as a glass substrate for a display.

In addition, although the polyethylene resin layer contains a polymer type antistatic agent, since the polyethylene resin foam sheet does not need to contain a polymer type antistatic agent substantially, since the content of the polymer type antistatic agent of the laminated foam sheet as a whole becomes at least, it is manufactured at low cost. can do.

In addition, the laminated foam sheet of the present invention satisfies at least one of the conditions (iii), (ii) and (iii) so that the laminated foam sheets do not adhere well to each other or to the packaged body and are excellent in slipperiness. Therefore, peeling electrification is unlikely to occur and the packing work efficiency is excellent.

Moreover, the laminated foam sheet of this invention can have the effect of improving the visibility of the to-be-packaged object at the time of packing the to-be-packed object by satisfying the said conditions (i).

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the DSC curve which a protrusion part (shoulder) appears in the area | region high temperature side and 110 degreeC or more than the peak temperature of a main melting peak.
FIG. 2 is a diagram showing an example of a DSC curve in which different melting peaks appear on the high temperature side and 110 ° C or higher region than the peak temperature of the main melting peak.
FIG. 3A is a cross-sectional view of the extrusion direction MD of the laminated foam sheet obtained in Example 1. FIG. FIG.3 (b) is sectional drawing of the width direction TD of the said laminated foam sheet.
4 (a) is a cross-sectional view of the MD of the laminated foam sheet obtained in Example 8. FIG. 4B is a cross-sectional view of the TD of the laminated foam sheet.
FIG. 5A is a cross-sectional view of MD of the laminated foam sheet obtained in Comparative Example 1. FIG. 5B is a cross-sectional view of the TD of the laminated foam sheet.
It is explanatory drawing which shows an example of the manufacturing method of a laminated foam sheet.

EMBODIMENT OF THE INVENTION Hereinafter, the laminated polyethylene resin foam sheet of this invention is demonstrated in detail.

The laminated foam sheet of the present invention is formed by laminating a polyethylene resin layer (hereinafter also referred to simply as a resin layer) containing a polymer type antistatic agent on at least one side of a polyethylene resin foam sheet (hereinafter, simply referred to as a foam sheet). It is a laminated sheet.

Since the laminated foam sheet of this invention is excellent in antistatic property, slipperiness | lubricacy, peeling property, etc., it is suitable as a packaging material of the glass substrate for display used for a thin type television, In addition, it is an electronic product, a precision instrument, a circuit base, a silicon wafer, etc. It can be used suitably as a packaging material of electronic precision instruments of the present invention.

The foamed sheet and the resin layer laminated and bonded to the foamed sheet constituting the laminated foam sheet of the present invention all have polyethylene resin as the main component of the base resin. The polyethylene resin is a thermoplastic resin having low surface hardness and excellent flexibility and suitable for protecting the surface of a package. In addition, making the polyethylene resin in this specification the main component of a base resin means that it contains 50 weight% or more, Preferably it is 70 weight% or more, More preferably, 80 weight% or more in a base resin.

-올레핀의 에틸렌계 공중합체, 추가로 이들의 2 종 이상의 혼합물 등을 포함하는 것이다.The polyethylene resin in this specification is an ethylene homopolymer, such as a branched low density polyethylene, a linear low density polyethylene, a linear ultra low density polyethylene, a linear high density polyethylene, and a long-chain branched high density polyethylene, and has 3-10 carbon atoms.

-Ethylenic copolymers of olefins, mixtures of two or more thereof, and the like.

In addition, the structure of the polyethylene resin used for a foam seat | seet and a resin layer does not need to be the same, A different structure can be employ | adopted in order to exhibit each characteristic of both as mentioned later.

Melting | fusing point of the polyethylene resin in this specification can be measured by the method based on JISK71121-1987. That is, pretreatment is performed by the conditions (but cooling rate is 10 degree-C / min) of the state control (2) of the test piece in JISK 7121-1987, and a melting peak is raised by heating up at 10 degree-C / min. Get And the peak temperature of the obtained melting peak is made into melting | fusing point. In addition, when two or more melting peaks appear, it is set as the peak temperature of a main melting peak (peak with the largest area). However, when there is another peak having a peak area of 80% or more with respect to the peak area of the peak having the largest area, the average value of the peak of the peak temperature of the peak and the peak temperature of the peak having the largest area Is employed as the melting point.

In the base resin which comprises the foaming sheet and resin layer in this invention, in addition to the polyethylene resin which is a main component, an ethylene-vinyl acetate copolymer, a polypropylene, and a propylene ethylene copolymer in the range which does not impair the objective and effect of this invention. Ethylene resins, such as propylene resins, styrene resins, such as polystyrene, and ethylene propylene rubber, etc. may be mix | blended. Moreover, content of the said resin is 50 weight% or less in base resin, Preferably it is 30 weight% or less, More preferably, it is 20 weight% or less.

Moreover, in the said base resin, functional additives, such as a bubble modifier, a nucleating agent, antioxidant, a heat stabilizer, a weathering agent, a ultraviolet absorber, a flame retardant, an antibacterial agent, an antishrinkage agent, in the range which does not impair the objective effect of this invention, for example. And additives such as inorganic fillers.

The resin layer which comprises the laminated foam sheet of this invention contains a polymer type antistatic agent with polyethylene resin, and is excellent in antistatic performance and antistatic agent migration to a to-be packaged body.

The number average molecular weight of this antistatic agent is 2000 or more, Preferably it is 2000-100000, More preferably, it is 5000-60000, Especially preferably, it is 8000-400000. Therefore, the antistatic agent is a polymer type antistatic agent which is distinguished from the antistatic agent which contains surfactant as a main component.

In addition, the said number average molecular weight is calculated | required using high temperature gel permeation chromatography. For example, when the polymer type antistatic agent is a hydrophilic resin containing polyether esteramide or polyether as a main component, orthodichlorobenzene is used as a solvent, the sample concentration is 3 mg / ml, and the polystyrene is used as the reference material. It is a value measured on 135 degreeC conditions. In addition, the kind of said solvent and column temperature change suitably according to the kind of polymeric antistatic agent.

Polymer type antistatic agent used in the present invention, the volume resistivity and the like 10 ⁵ ~ 10 ¹¹ Ω ㎝ and a copolymer of a hydrophilic resin and a polyolefin.

Examples of the hydrophilic resin include polyether diols, polyether diamines, and polyethers such as modified substances thereof, polyether esteramides having segments of polyetherdiol as polyether segment forming components, and polyetherdiol as polyether segment forming components. Polyetheramideimide having a segment of polyetheramideimide, polyetherester having a segment of polyetherdiol as a polyether segment forming component, polyetheramide having a segment of polyetherdiamine as a polyether segment forming component, poly as a polyether segment forming component A polyether-containing hydrophilic resin such as polyetherurethane having a segment of etherdiol or polyetherdiamine, a car having 2 to 80, preferably 3 to 60, cationic groups partitioned by a nonionic molecular chain Anionic polymers having a ionic polymer and a dicarboxylic acid having a sulfonyl group and a diol or a polyether as essential structural units and having 2 to 80, preferably 3 to 60 sulfonyl groups in the molecule can be used. .

In addition, the polymer type antistatic agent has the same kind or compatibility as the polyethylene resin in order to improve the compatibility with the polyethylene resin, to give an excellent antistatic effect, and to obtain the effect of suppressing the decrease in physical properties caused by the addition of the antistatic agent. It preferred that the block copolymer a high resin, for example, block, and the volume resistivity of the polyolefin is 10 ⁵ ~ 10 ¹¹ Ω and ㎝ a number having a structure coupled to the shift block is repeated in the hydrophilic resin average molecular weight (Mn ) Is a block copolymer of 2000 to 60000. Among these, since the block copolymer of polyether and polyolefin is excellent in the said compatibility, it is preferable.

In addition, the block copolymer has a structure in which blocks of polyolefins and blocks of hydrophilic resins are alternately bonded repeatedly through at least one bond selected from ester bonds, amide bonds, ether bonds, urethane bonds, and imide bonds. .

More specifically, as the polymer type antistatic agent preferably used in the present invention, the compositions described in JP-A-103466 and JP-A-2001-278985 can be mentioned. The composition described in JP-A-103466 is a block copolymer containing (I) a thermoplastic resin, (II) polyethylene oxide or a polyethylene oxide block component of 50% by weight or more, and (III) the polyethylene in (II). The oxide block component, the metal salt to be dissolved, and these (I) to (III) are main components. In the composition described in JP 2001-278985 A, a block of polyolefin (a) and a block of hydrophilic resin (b) having a volume resistivity of 1 × 10 ⁵ to 1 × 10 ¹¹ Ω · cm are alternately bonded. It is a block copolymer whose number average molecular weight (Mn) which has a structure is 2000-60000. The blocks of (a) and (b) have a structure in which they are alternately bonded through at least one bond selected from an ester bond, an amide bond, an ether bond, a urethane bond, and an imide bond. As a specific example of such a polymer type antistatic agent, what is marketed under brand names, such as "SD100" by Mitsui Dupont Polychemical Co., Ltd. and "Peresart 300" by Sanyo Chemical Co., Ltd., is mentioned, for example.

Although the said polymeric antistatic agent can be used individually, respectively, you may use combining multiple.

In addition, the melting point of the polymer type antistatic agent is preferably 70 to 270 ° C, more preferably 80 to 230 ° C, and particularly preferably 80 to 200 ° C from the viewpoint of antistatic function expression.

Melting | fusing point of the said polymeric antistatic agent is a value measured based on JISK71121-1987 like the melting point measuring method of the polyethylene resin mentioned above.

Content of the polymeric antistatic agent in the resin layer of this invention becomes like this. Preferably it is 10-50 weight% of the whole resin layer, More preferably, it is 15-40 weight%, Especially preferably, it is 20-35 weight%. . If the content is too small, there is a possibility that the antistatic properties required for the packaging material of the electronic precision apparatus cannot be exhibited. On the other hand, even if the content is too large, there is no problem in the antistatic performance, but the antistatic performance reaches a limit and the cost performance is deteriorated.

Although the said polymeric type antistatic agent does not need to be added to the foam sheet in this invention, When a polymeric type antistatic agent is added by using the collect | recovery raw material of a laminated foam sheet as a raw material for foam sheets, a foam sheet is a polymer type | mold. It will contain an antistatic agent. Also in this case, in order not to inhibit the foamability of a foam sheet, it is preferable to make content of a polymeric antistatic agent into the ratio of 15 weight part or less with respect to 100 weight part of base resin which comprises a foam sheet. Moreover, in order to maintain the mechanical strength of a laminated foam sheet, 8 weight part or less is preferable with respect to 100 weight part of base resin which comprises a foam sheet, More preferably, it is 5 weight part or less. Moreover, further improvement of antistatic effect can also be anticipated by adding an antistatic agent to foam seat | seet.

The thickness of the laminated foam sheet of this invention is 0.2-2.0 mm. If the thickness is too thin, the buffering property and the surface protection against the packaged object such as an electronic precision instrument become insufficient, and if the thickness is too thick, the volume of the laminated foam sheet increases during packaging or disposal of the laminated foam sheet. This can lead to problems or disadvantages in the cost of transporting the package. From such a viewpoint, the thickness of the laminated foam sheet is more preferably 0.3 to 1.5 mm, particularly preferably 0.4 to 1.3 mm, most preferably 0.5 to 1.2 mm.

The apparent density of the laminated foam sheet of the present invention is 0.02 to 0.1 g / cm 3. When the apparent density is too big | large, there exists a possibility that surface protection property may fall. On the other hand, when the apparent density is too small, mechanical strength such as shape retention or compressive strength desired for the laminated foam sheet is lowered, and the waist portion is weak, which may cause sagging of the laminated foam sheet. From such a viewpoint, the apparent density is preferably from 0.025 to 0.095 g / cm 3, more preferably from 0.03 to 0.09 g / cm 3.

It is preferable that the resin layer in this invention is small in basis weight and thin in thickness. For example, when the basis weight is small and the thickness is small, in the structure described later, irregularities on the surface of the foam sheet having a sparse bubble appear in the resin layer, thereby making it difficult to adhere to the package.

From this viewpoint, the basis weight is preferably 8 g / m 2 or less, more preferably 1 to 6 g / m 2, and particularly preferably 1.5 to 5 g / m 2. If the basis weight is in the above range than necessary, the surface becomes excessively smooth or the resin layer expressing antistatic property is prevented from becoming too thin, and the anti-sticking property and the stable antistatic property of the laminated foam sheet to the packaged object are prevented. It is preferable from a viewpoint. Moreover, as long as it exists in the range which achieves the objective and effect of this invention, a resin layer may have some thickness nonuniformity.

The thickness of the whole laminated foam sheet in this invention is an arithmetic mean value of the thickness (mm) measured at intervals of 1 cm in the width direction over the entire width of the laminated foam sheet.

The apparent density (g / cm 3) of the laminated foam sheet in the present invention is a value obtained by dividing the weight (g) of the test piece cut out from the laminated foam sheet by the volume (cm 3) of the test piece.

In addition, the apparent density (g / cm <3>) of the foam sheet which comprises a laminated foam sheet subtracts the weight (g) of the resin layer of the test piece mentioned later from the weight (g) of a test piece, and calculate | requires the weight of the foam sheet of a test piece, and laminate | stacks The thickness of the foam sheet is obtained by subtracting the average thickness of the resin layer of the test piece described later from the thickness of the foam sheet, and the weight of the foam sheet is divided by the volume (cm 3) obtained from the outer dimensions of the foam sheet.

In the present invention, the basis weight of the resin layer can be obtained by the following method.

The vertical cross section of the laminated foam sheet in the width direction is appropriately enlarged with a microscope or the like, and the thickness of the resin layer is measured at ten points in the width direction at equal intervals, and the arithmetic mean value of the obtained value is made the average thickness of the resin layer, The basis weight [g / m <2>] of a resin layer can be calculated by multiplying the density of the base resin which comprises a resin layer, and converting in units. However, this method is limited to the case where the interface of a resin layer and foam sheet is clear.

In addition, the density (g / cm <3>) of the base resin of a resin layer can be calculated | required as the sum total of the value computed by multiplying the density of each resin which comprises a base resin by the content weight ratio of each resin.

In addition, when it is difficult to measure basis weight by the said method, in the laminated foam sheet manufactured by co-extrusion, the discharge amount X [kg / hour] of the resin layer and the width W of the laminated foam sheet obtained in extrusion foaming conditions. From [m] and sheet length L [m / hour] extruded per unit time of laminated foam sheet, the basis weight [g / m <2>] of a resin layer can be calculated | required by the following (1) formula. Moreover, when laminating | stacking a resin layer on both surfaces of a foam sheet by an extrusion laminating method, basis weight of each resin layer can be calculated | required based on the discharge amount of each resin layer.

Basis weight [g / m 2] = [1000 × / (L × W)]. (One)

The laminated foam sheet of this invention is excellent in antistatic property since a resin layer contains a polymeric antistatic agent as mentioned above. Specifically, the applied voltage half life after washing with water is preferably 10 seconds or less, more preferably 7 seconds or less, and still more preferably 5 seconds or less. If the applied voltage half-life is 10 seconds or less, adhesion of dust to an electronic precision apparatus can be prevented by using a laminated foam sheet as a buffer material and packaging material of electronic precision instruments, such as a glass substrate for a display. In addition, the laminated foam sheet hardly decreases the applied voltage half-life even after washing with water, thereby exhibiting sufficient antistatic properties, and thus, antistatic properties that are stable over a long period of time, unlike packaging materials exhibiting antistatic properties with conventional surfactants. Can be expressed. The lower limit of the applied voltage half-life is preferably smaller. The lower limit of the applied voltage half life is approximately 0.5 seconds.

The measurement of the applied voltage half life in this specification is a value measured based on JISL1094 (1988) A method using the laminated foam sheet after water washing as a measurement sample. Specifically, a test piece (40 mm × 40 mm × thickness: measured object thickness) cut out from the laminated foam sheet was placed in a beaker with 300 ml of 40 ° C water, washed with stirring for 10 minutes, and then the test piece was taken out of warm water. After adjusting the state of the test piece by leaving it for 36 hours in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50%, a turntable rotational speed of 1300 rpm and an applied voltage (+) of 10 kW for 30 seconds by JIS L 1094 (1988) A method Obtain the applied voltage half-life under the application condition of.

The laminated sheet of the present invention satisfies at least one of the following conditions (i), (ii) and (iii).

(Iii) The basis weight of a polyethylene resin layer is 8 g / m <2> or less, the bubble film thickness of foam seat | seet is 6-100 micrometers, and the average number of bubbles in a thickness direction is two or less.

(Ii) The polyethylene resin layer is 30-90 weight% of melting | fusing point 115 degreeC or less and 128 degrees C or less and density 0.910-0.970 g / cm <3> of polyethylene resin (a), 0-60 weight% of melting | fusing point 115 degreeC or less and density 0.890- It is comprised by 0.930 g / cm <3> of polyethylene resin (b) and 10-50 weight% of polymeric antistatic agent (c) ((a) + (b) + (c) = 100 weight%).

(Iii) polyethylene resin foam sheet having a melting point of more than 10 to 50% by weight of more than 115 ° C and 125 ° C or less, and a polyethylene resin (d) having a density of 0.910 to 0.940 g / cm 3 and a melting point of 50 to 90% by weight of 115 ° C or less and a density of 0.890. It is comprised by the polyethylene resin (b) (however, (d) + (b) = 100 weight%) of -0.930 g / cm <3>.

The laminated foam sheet which satisfies the above (i) is a foam sheet having a larger bubble film thickness than usual and having a smaller number of bubbles in the thickness direction, that is, mainly composed of coarse bubbles. In the laminated foam sheet in which a resin layer having a thin basis weight of 8 g / m 2 or less is laminated on the foam sheet satisfying the above (i), the unevenness of the coarse bubbles appears on the surface of the resin layer, and thus the contact with the package body. The area is small, and the rigidity against bubble compression is also high. Therefore, in the laminated foam sheet of the present invention, the laminated foam sheet itself is difficult to adhere to the package even though a resin layer containing a relatively large polymer antistatic agent is laminated on the surface. 6-70 micrometers is preferable, as for the bubble film thickness from the said viewpoint, 7-50 micrometers is more preferable, 10-35 micrometers is especially preferable, The number of bubbles is preferably 1.7 or less, and further 1.5 or less desirable. In addition, the laminated foam sheet which satisfies the above (i) has a larger bubble diameter and a smaller number of bubbles in the thickness direction, so that the transmittance of light is high so that it is possible to confirm what is to be packaged when used as a packaging material. Can improve the visibility.

In this invention, average bubble film thickness th (micrometer) can be calculated | required by the following formula.

th (μm) = (0.46 / ρp) ρf

However, D is the average bubble diameter (micrometer) of a foam sheet, (p) is the density (g / cm <3>) of the base resin of a foam sheet, and (p) is the apparent density (g / cm <3>) of a foam sheet.

In addition, the average bubble diameter D of a foam sheet is a value computed by following Formula based on ASTMD3576-77.

D = arithmetic mean value (μm) of the average bubble field in three directions (thickness direction, width direction and extrusion direction) /0.616

The density ρp (g / cm 3) of the base resin of the foam sheet was obtained by cutting out the foam sheet so as not to include the resin layer from the laminated foam sheet, and defoaming the cut foam sheet with a heat press apparatus to solidify the density. It can obtain | require by measuring. Moreover, the density (g / cm <3>) of each resin which comprises the base resin of a foam sheet can also be calculated | required as the sum total of the value computed by multiplying the density of each resin which comprises a base resin by the content weight ratio of each resin.

The density p p (g / cm 3) of the base resin of the foam sheet can be calculated based on the apparent density of the laminated foam sheet, the thickness of the foam sheet, and the density and thickness of the resin layer of the laminated foam sheet.

In addition, the apparent density ρf (g / cm 3) of the foam sheet is determined based on the basis weight of the laminated foam sheet obtained by multiplying the density of the laminated foam sheet by the unit of the density of the sample obtained by defoaming and solidifying the laminated foam sheet by a heat press apparatus. The thickness of the foam sheet obtained by subtracting the basis weight of the resin layer obtained by multiplying the density of the resin layer by the thickness of the resin layer and converting the unit to calculate the basis weight of the foam sheet, and then subtracting the thickness of the resin layer from the thickness of the laminated foam sheet. It can obtain | require by dividing the basis weight of foam seat | seat by unit conversion.

The average bubble film thickness can be adjusted with the apparent density of a foam sheet, and the average bubble diameter of a foam sheet. The change of the apparent density of a foam sheet can be adjusted with the addition amount of a foaming agent.

In addition, the average bubble diameter of foam seat | seet can be adjusted with the kind and addition amount of a foaming agent and a bubble regulator, the pressure conditions in the die at the time of extrusion foaming, etc. For example, when the kind and addition amount of a blowing agent are made constant, an average bubble diameter can be adjusted with the pressure in the die at the time of extrusion foaming, and the addition amount of a bubble regulator. Specifically, the average bubble diameter of the foam sheet can be made smaller as the pressure in the die is increased and / or the amount of the bubble adjuster is increased under the condition that the type and amount of the blowing agent are constant.

The measurement of the number of bubbles in the thickness direction determines the measurement points at intervals of 1 cm in the width direction over the entire width of the foam sheet, and determines the thickness (mm) of the determined measurement points and the number of bubbles in the thickness direction of the measurement points. The arithmetic mean value of the number of bubbles in the thickness direction of each measurement point was obtained by dividing the number of bubbles in the thickness direction of each measuring point (piece) by the thickness (mm) of the measuring points, and the number of bubbles in the thickness direction in the present invention. Let it be (piece / mm). The number of bubbles in the thickness direction of each measuring point is a value obtained by drawing a straight line in the thickness direction of the measuring point and counting the number of bubbles intersecting the straight line.

The laminated foam sheet which satisfies the above (ii) has a polyethylene resin (a) having a resin layer of more than 30 to 90% by weight of melting point of 115 ° C or more and 128 ° C or less and a density of 0.910 to 0.970 g / cm 3, and 0 to 60% by weight. Polyethylene resin (b) having a density of 0.890 to 0.930 g / cm 3 and a melting point of 115 ° C. or less, and a polymer antistatic agent of 10 to 50% by weight (c), provided that (a) + (b) + (c) = 100 weight %).

Since the polyethylene resin (a) is excellent in rigidity, the resin layer containing such polyethylene resin (a) is rich in rigidity and heat resistance. Therefore, since the laminated foam sheet which satisfy | fills (ii) is excellent in antistatic property and has sufficient rigidity as a whole, it is easy to apply | coat to a to-be-packed object, and to remove | detach. Moreover, the laminated foam sheet which satisfy | fills (ii) improves heat resistance as a whole.

In addition, since the laminated foam sheet satisfies the conditions of specific apparent density and thickness, the resin composition of the entire laminated sheet is a small amount of polyethylene resin (a) due to the polyethylene resin (a) contained in the resin layer in the entire polyethylene resin ( It contains a).

Therefore, in the laminated foam sheet which satisfy | fills said (ii), in the DSC curve obtained by the heat flux differential scanning calorimetry of the heat of fusion after performing the constant heat processing based on JISK7122-1987 which makes a laminated sheet a sample, As shown in Fig. 1, protrusions derived from the polyethylene resin (a) appear in the main melting peak region at a temperature higher than the peak temperature of the main melting peak and 110 ° C or more. In addition, the presence of the protrusion observed in FIG. 1 can be determined by confirming the existence of an inflection point by differentiating the DSC curve by a second system with a soft or the like attached to the DSC measuring apparatus.

In addition, when polyethylene resin (a) is contained also in the polyethylene resin which comprises a foaming sheet, a melting peak appears by covering the protrusion part which exists in the area | region high temperature side and 110 degreeC or more above the peak temperature of the main melting peak in the said DSC curve. In some cases.

As said polyethylene resin (a), the polyethylene resin of more than 115 degreeC of melting | fusing point 125 degreeC or less and a density of 0.910-0.940 g / cm <3> is more preferable.

As said polyethylene resin (a), what is called a linear low density polyethylene and a high density polyethylene is illustrated.

From a viewpoint of having desired rigidity, 40-90 weight% is preferable and, as for content of a polyethylene resin (a), 45-85 weight% is more preferable.

When there is too much content of the said polyethylene resin (b), since content of a polyethylene resin (a) will become small, the rigidity of a resin layer will run out, and the workability of covering a laminated foam sheet to a to-be-packed body, and the operation | work which peels off will be improved. You cannot expect it. From such a viewpoint, 0-45 weight% is preferable and, as for content of a polyethylene resin (b), 0-30 weight% is more preferable.

As said polyethylene resin (b), what is called a branched low density polyethylene is illustrated.

When there is too little content of the said polymeric antistatic agent (c), there exists a possibility that the antistatic property calculated | required by the packaging material of an electronic precision instrument may not be exhibited. On the other hand, even if the content is too large, there is no problem in terms of antistatic performance. However, since the antistatic performance reaches a limit, there is a concern that the cost performance may be lowered. From this viewpoint, 15-40 weight% is preferable and, as for content of a polymeric antistatic agent (c), 20-35 weight% is more preferable.

The laminated foam sheet which satisfies the above (i) has a foamed sheet having a melting point of 10 to 50% by weight over 115 ° C and 125 ° C or less and a polyethylene resin (d) having a density of 0.910 to 0.940 g / cm 3 and 50 to 90% by weight. It is comprised from the polyethylene resin (b) (however, (d) + (b) = 100 weight%) of density 0.890-0.930 g / cm <3> and melting | fusing point 115 degrees C or less.

The laminated foam sheet which satisfies the above (i) is a foam sheet containing a polyethylene resin (d) having a melting point of more than 115 ° C and 125 ° C or less and a density of 0.910 to 0.940 g / cm 3. And the resin composition of the whole laminated foam sheet contains a comparatively large quantity of polyethylene resin (d) by the polyethylene resin (d) contained in a foam sheet.

Since the polyethylene resin (d) is excellent in rigidity, the foam sheet containing the polyethylene resin (d) is rich in rigidity. Therefore, since the laminated foam sheet which satisfies the above-mentioned (i) has sufficient rigidity as a whole, it is easy to apply to the package and to remove it, so that a good foam sheet can be produced.

From said viewpoint, 20-50 weight% is preferable, as for content of a polyethylene resin (d), 25-45 weight% is more preferable, 50-80 weight% is preferable, and, as for content of a polyethylene resin (b), 55- 75 weight% is more preferable.

As said polyethylene resin (d), what is called a linear low density polyethylene is illustrated.

In the laminated foam sheet which satisfies the above (i), since the polyethylene resin foam sheet contains polyethylene resin (d) having a melting point of more than 115 ° C and 125 ° C or less and a density of 0.910 to 0.940 g / cm 3, JIS is used as the sample for the laminated sheet. In the DSC curve obtained by heat flux differential scanning calorimetry of heat of fusion after constant heat treatment based on K 7122-1987, as shown in FIG. Another melting peak resulting from the resin (d) appears. In addition, the presence of the 2nd peak observed in FIG. 2 can visually confirm the DSC curve.

It is preferable that the laminated foam sheet of this invention satisfy | fills said condition (iii) and said condition (ii) simultaneously. This consists of a foam sheet comprised of a rigid resin layer and mainly coarse bubbles. Therefore, it is a laminated foam sheet having a small contact area with the package to be difficult to adhere to the package, having sufficient rigidity, easy to apply to the package, peel off, etc., and excellent in antistatic property. .

Moreover, it is preferable that the laminated foam sheet of this invention satisfy | fills the said condition (i) and the said condition (i) simultaneously. In addition, satisfying the said condition (iii) and said condition (iii) simultaneously also includes satisfying the said condition (iii), said condition (ii), and the said condition (iii) simultaneously. Satisfying the above condition (iii) and the above condition (iii) at the same time includes the configuration of a resin layer excellent in antistatic properties and a foam sheet having a rigidity and a sparse bubble. Therefore, it is a laminated foam sheet having a small contact area with the package to be difficult to adhere to the package, having sufficient rigidity, easy to apply to the package, peel off, etc., and excellent in antistatic property. .

Moreover, the resin layer formed in the foam sheet which satisfies condition (i) preferably satisfies the condition (i).

Next, the manufacturing method of the laminated polyethylene resin foam sheet of this invention is demonstrated.

As a manufacturing method of the laminated foam sheet of this invention, the co-extrusion foaming method which laminate-merges and fuses the molten resin which forms a resin layer and the molten resin which forms a foam sheet in an die is employ | adopted preferably. This coextrusion foaming method is preferable because the thickness of the resin layer can be reduced, and a laminated foam sheet having a high adhesive strength between the resin layer and the foam sheet can be obtained. However, in this invention, a conventionally well-known method, such as manufacturing a foam sheet by extrusion foaming and laminating | stacking a resin layer on a foam sheet by extrusion lamination, can also be applied.

The method for producing a sheet-shaped laminated foam sheet by the coextrusion foaming method includes a method of coextrusion foaming into a sheet shape using a flat die for coextrusion to form a sheet-shaped laminated foam sheet, and an annular die for coextrusion. And co-extrusion foaming into a tubular shape to obtain a tubular laminated foam, and then the cylindrical foam is cut to form a sheet-shaped laminated foam sheet. In these, the method of using a co-extrusion annular die is a preferable method, since the wide laminated foam sheet whose width | variety is 1000 mm or more can be manufactured easily.

The case of coextrusion using the said cyclic die is demonstrated in detail below.

First, as shown in FIG. 6, the polyethylene resin containing a polyethylene resin (a), a polyethylene resin (b), etc., and a polymeric antistatic agent (C) are supplied to the resin layer formation extruder 11, and it heat-melts After kneading and kneading, a volatile plasticizer (E1) is added as necessary, followed by melt kneading to obtain a resin melt (F1) for forming a polyethylene resin layer. At the same time, a polyethylene resin comprising a polyethylene resin (b), a linear polyethylene resin (d), and the like, and an additive (G) such as a bubble regulator added as necessary, are supplied to the extruder 12 for foam sheet formation, followed by heating and melting. And kneading, the physical foaming agent (E2) is press-fitted and kneaded again to obtain a resin melt (F2) for forming a polyethylene resin foam sheet.

In the coextrusion method, if the resin melt for forming the resin layer (F1) and the resin melt for forming the foam sheet (F2) can be laminated in the annular die, the extruded melts may be laminated outside the outlet of the die. have.

The volatile plasticizer (E1) added to the resin melt for forming the resin layer (F1) has a function of lowering the melt viscosity of the resin melt (F1), and the polyethylene resin layer after formation of the polyethylene resin layer (J). What volatilizes from and does not exist in a resin layer is used. By adding the volatile plasticizer (E1) to the resin melt, the extrusion temperature of the resin melt for forming the resin layer (F1) can be brought close to the extrusion temperature of the resin melt for forming the foam sheet (F2) when the laminated foam sheet is coextruded. Along with this, the melt elongation of the resin layer J in the softened state can be significantly improved. Then, since the bubble of foam seat | seet (I) becomes difficult to be destroyed by the heat of a resin layer at the time of foaming, and the elongation of the resin layer (J) is harvested by the elongation at the time of foaming of foam seat (I), a resin layer Crack generation due to insufficient elongation of (J) is prevented.

As the volatile plasticizer (E1), one or two or more selected from aliphatic hydrocarbons and alicyclic hydrocarbons having 3 to 7 carbon atoms, aliphatic alcohols having 1 to 4 carbon atoms, or aliphatic ethers having 2 to 8 carbon atoms are preferably used. When a low volatility like a lubricant is used instead of the volatile plasticizer (E1), the lubricant may remain in the resin layer (J) to contaminate the surface of the package. On the other hand, a volatile plasticizer (E1) is preferable at the point that a volatile plasticizer itself hardly remains in the resin layer (J) obtained by plasticizing resin of the resin layer (J) efficiently.

As said C3-C7 aliphatic hydrocarbon or alicyclic hydrocarbon, propane, normal butane, isobutane, normal pentane, isopentane, neopentane, cyclopentane, normal hexane, isohexane, cyclohexane, normal heptane etc. Can be mentioned.

As said C1-C4 aliphatic alcohol, methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, normal butyl alcohol, sec-butyl alcohol, tert- butyl alcohol is mentioned, for example.

As said C2-C8 aliphatic ether, For example, dimethyl ether, diethyl ether, propyl ether, isopropyl ether, methyl ethyl ether, methyl propyl ether, methyl isopropyl ether, methyl butyl ether, methyl isobutyl ether, Methyl amyl ether, methyl iso amyl ether, ethyl propyl ether, ethyl isopropyl ether, ethyl butyl ether, ethyl isobutyl ether, ethyl amyl ether, ethyl iso amyl ether, vinyl ether, allyl ether, methyl vinyl ether, methyl allyl Ether, ethyl vinyl ether, and ethyl allyl ether.

The boiling point of the volatile plasticizer (E1) is preferably 120 ° C. or less, more preferably 80 ° C. or less, from the point of volatilization from the resin layer (J). If the boiling point of the volatile plasticizer (E1) is within the above range, and the obtained laminated foam sheet (H) is left after the coextrusion, the volatile plasticizer (E1) may be caused by heat immediately after coextrusion or gas permeation at room temperature thereafter. Is naturally volatilized and removed from the resin layer (J) of a laminated foam sheet. The lower limit of the boiling point of this volatile plasticizer (E1) is -50 degreeC in general.

It is preferable that the addition amount of a volatile plasticizer (E1) is 5 weight part-50 weight part mainly with respect to 100 weight part of base resin which is a kneaded material of a polyethylene resin and a polymeric antistatic agent (C). When the amount of the volatile plasticizer (E1) added is 5 parts by weight or more, heat generation due to shearing at the time of kneading such as polyethylene resin constituting the resin layer (J) is suppressed, so that the resin layer (J) is laminated. An increase in the resin temperature of the resin melt F2 is suppressed (temperature lowering effect). Therefore, at the time of co-extrusion foaming with the resin melt for resin layer formation, when foaming resin melt (F2) for foam sheet formation is foamed, damages such as foaming of bubbles are prevented. In addition, the resin melt (F2) for foam sheet formation is extruded from the die under normal pressure to form foam sheet (I).

In addition, the volatile plasticizer (E1) improves the extensibility to harvest to the foam sheet at the time of forming the resin layer of the laminated foam sheet of the resin melt for forming the resin layer (F1) (extension improvement effect), and the resin layer ( It also has the effect of forming the thickness of J) uniformly thin. From this viewpoint, 7 weight part or more is preferable and, as for the addition amount of a volatile plasticizer (E1), 10 weight part or more is more preferable.

On the other hand, when there is too much addition amount of a volatile plasticizer (E1), there exists a possibility that the physical property fall of the resin layer (J) itself may occur, but volatile plasticizer (E1) does not melt | dissolve sufficiently in the resin melt (F1) for resin layer formation, and die The volatile plasticizer may be ejected from the lip, or a hole may be formed in the resin layer (J), or the thickness and thickness of the resin layer may be too large. From this viewpoint, 40 weight part or less is preferable, as for the addition amount of a volatile plasticizer (E1), 30 weight part or less is more preferable, 25 weight part or less is further more preferable. By making the addition amount of a volatile plasticizer (E1) into the said range, the sufficient temperature fall effect and the elongation improvement effect of the resin melt for resin layer formation at the time of co-extrusion are ensured.

Moreover, you may add various additives to resin which forms the melt F1 in the resin melt for formation of resin layer F1 in the range which does not impair the objective of this invention. As various additives, antioxidant, a heat stabilizer, a weathering agent, a ultraviolet absorber, a flame retardant, a filler, an antibacterial agent, etc. are mentioned, for example. Although the addition amount in that case is suitably determined according to the objective and effect of an additive, 10 weight part or less is preferable with respect to 100 weight part of base resin, respectively, 5 weight part or less is more preferable, 3 weight part or less is especially preferable.

As a physical blowing agent (E2) added to the said resin melt for foam sheet formation (F2), For example, aliphatic hydrocarbons, such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, isohexane, cyclopentane, Organic physical blowing agents such as alicyclic hydrocarbons such as cyclohexane, hydrocarbon chlorides such as methyl chloride and ethyl chloride, fluorinated hydrocarbons such as 1,1,1,2-tetrafluoroethane and 1,1-difluoroethane and nitrogen And inorganic physical blowing agents such as carbon dioxide, air, and water. In some cases, decomposition type blowing agents such as azodicarbonamide may be used. Said physical blowing agent can mix and use 2 or more types. Among these, organic physical blowing agents are preferred from the viewpoint of compatibility with polyethylene resins and foaming properties, and among them, it is preferable to have normal butane, isobutane or a mixture thereof as a main component.

The addition amount of a physical blowing agent (E2) is adjusted according to the kind of blowing agent and the apparent density aimed at. In addition, the addition amount of a bubble adjuster is adjusted according to the target bubble diameter. For example, in order to obtain the laminated foam sheet of the said density range using the butane mixture of 30 weight% of isobutane and 70 weight% of normal butanes as a foaming agent, the addition amount of a butane mixture is 3-30 weight part per 100 weight part of base resin, Preferably it is 4-20 weight part, More preferably, it is 6-18 weight part.

As a main thing of the additive (G) added to the said resin melt for foam seat formation (F2), a bubble adjuster is normally added. As a bubble adjuster, both an organic type and an inorganic type can be used. Examples of the inorganic bubble regulators include metal borates such as zinc borate, magnesium borate, and borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, sodium hydrogencarbonate, and the like. Examples of the organic bubble regulator include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl) sodium, sodium benzoate, calcium benzoate, aluminum benzoate, sodium stearate and the like. Moreover, the thing which combined citric acid, sodium hydrogencarbonate, the alkali salt of citric acid, sodium hydrogencarbonate, etc. can also be used as a bubble regulator. These bubble adjusters can also mix and use 2 or more types.

In addition, the addition amount of a bubble regulator is 0.01-3 weight part per 100 weight part of base resins, Preferably it is 0.03-1 weight part. In order to obtain the laminated foam sheet which satisfies the above (i), for example, the average bubble diameter and the average number of bubbles in the thickness direction are determined while adjusting the basis weight of the resin layer and taking into account the thickness, apparent density and the like of the foam sheet. What is necessary is just to adjust the addition amount of a bubble adjuster so that (iii) may be satisfied.

Into the resin melt (F2) for forming a polyethylene resin foam sheet, other resins such as styrene resins and elastomers, and additives such as heat stabilizers can be blended within the range of not impairing the object and effect of the present invention as described above.

As mentioned above, when manufacturing a laminated foam sheet by coextrusion, the resin melt for forming a resin layer (F1) is formed using the extruder 11, and the resin for forming a foam sheet using the extruder 12 is used. The melt F2 is formed, adjusted to a temperature at which the resin melt F2 can be foamed in the extruder 12, and adjusted to a temperature at which the resin melt F1 can be coextruded in the extruder 11, and Then, the resin melt for forming the resin layer (F1) and the resin melt for forming the foam sheet (F2) are introduced into the co-extruded annular die 13, and both of them are laminated. The foamed melt (F2) is formed to form a cylindrical laminated foam in which a resin layer is laminated on the foam, and the inner surface of the cylindrical laminated foam is cut along with a circumferential cooling device while being cut while being cut while being cut to form a laminated foam. A sheet can be obtained. However, if the resin melt for forming the resin layer (F1) and the resin melt for forming the foam sheet (F2) can be laminated inside the annular die as described above, they may be laminated near the outlet or outside the die. . The annular die, the extruder, the cylindrical cooling device, the device for cutting the cylindrical laminated foam, and the like can be used a known one conventionally used in the extrusion foaming field.

Moreover, in order to make small the value of the average bubble number of the thickness direction in the said condition (iii) of this invention, the addition amount of a bubble adjuster is adjusted little, the rib which has a parallel land at the tip of a cyclic die is formed, and foam sheet formation Extrusion can be adjusted by suppressing expansion (swell) in the thickness direction in the thickness direction of the molten resin melt while preventing generation of corrugated gates, and by adjusting the shearing heat generation of the resin melt for foam sheet formation in parallel lands to achieve bonding between the bubbles.

Example

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail based on an Example. However, this invention is not limited by the Example.

As a bubble adjuster, the bubble adjuster masterbatch which mixes 20 weight% of talc (Matsumura Industries Co., Ltd. make, brand name "high filler # 12") with respect to 80 weight% of low density polyethylene resins was used.

Table 1 shows the types, manufacturers, densities, melting points, MFIs (190 ° C, and loads of 21.18 N) of polyethylene resins used for resin layer formation and foam sheet formation.

As a polymer type antistatic agent, "Peresart 300" (The melting point 136 degreeC, number average molecular weight 14000, density 990 g / L) which has the polyether polypropylene block copolymer by Sanyo Chemical Co., Ltd. as a main component was used.

As the physical blowing agent, mixed butane consisting of 70% by weight of normal butane and 30% by weight of isobutane was used.

Examples 1-11, Comparative Examples 1-3

As the extruder 12 for forming a polyethylene resin foam sheet, a tandem extruder composed of a first extruder having a diameter of 90 mm and a second extruder having a diameter of 120 mm was used, and a diameter of 50 mm and L was used as the extruder 11 for forming a polyethylene resin layer. A third extruder of / D = 50 was used. In addition, the outlets of the second extruder and the third extruder were connected to the annular die for co-extrusion, so that each molten resin could be laminated in the annular die.

The polyethylene resin of the formulation shown in Table 2 and a polymeric antistatic agent are supplied to a 3rd extruder, and it heat-kneaks, pressurizes the said mixed butane of the quantity shown in Table 2 as a volatile plasticizer, and kneads again, and the extrusion resin shown in Table 2 The resin melt for forming a resin layer is adjusted to a temperature, and the resin melt for forming a resin layer is introduced into a co-extruded annular die at a discharge amount that is the basis weight of the "resin layer / foam sheet / resin layer" shown in Table 2. It was.

At the same time, the polyethylene resin of the mixing | blending shown in Table 2 and the bubble regulator masterbatch were supplied to the raw material inlet of the 1st extruder of a tandem extruder, and it knead | mixed by heat, and it was set as the molten resin mixture adjusted to about 200 degreeC. Next, the physical blowing agent of the quantity shown in Table 2 is press-inserted into this molten resin mixture, it is then supplied to the 2nd extruder connected downstream of the said 1st extruder, temperature is adjusted to the extrusion resin temperature shown in Table 2, and foaming is carried out. The resin melt for sheet formation was used, and the resin melt for foam sheet formation was introduced into the annular die for co-extrusion at a discharge amount that constitutes the basis weight of the "resin layer / foam sheet / resin layer" shown in Table 2.

The resin melt for forming the resin layer introduced into the co-extruded annular die is laminated and joined to the outside and inside of the foam melt for forming the foam sheet which is introduced into the co-extruded annular die and flows through the resin flow path in the die. The laminate was extruded from the die into the atmosphere to form a tubular laminated foam having a three-layer configuration consisting of a resin layer / foam / resin layer. The extruded cylindrical laminated foam was cut along with the cooled columnar cooling device (mandrel) and taken out, and the laminated foam sheet was obtained.

Table 3 shows various physical properties of the laminated foam sheets obtained in Examples and Comparative Examples.

Measurement of the average bubble diameter in Table 3, the average number of bubbles in the thickness direction, the bubble film thickness, and the applied voltage were carried out at each of five points with respect to each laminated foam sheet by the above-described method, and the arithmetic mean value of the measured value was It was set as the measurement result.

The measurement of peeling strength in Table 3 was performed as follows.

The foam sheet was cut out to a size of 40 mm in width x 76 mm in length. Then, the cut foam sheet and plate glass were crimped | bonded for 18 hours by the load of 130 g / cm <2> in the atmosphere of temperature 60 degreeC, and 50% RH humidity. The load at the time of peeling the foam sheet crimped | bonded to the plate glass on the said conditions by the 90 degree peeling test at the speed of 100 mm / min was measured. The measurement was performed at 6 points about each laminated foam sheet, and the arithmetic mean value of the measured value was made into peeling strength (gf / 40mm).

The measurement result of peeling strength was evaluated by the criteria shown below.

◎ ： Less than 0.7gf / 40mm

○: 0.7 gf / 40 mm or more, less than 1.3 gf / 40 mm

△: 1.3 gf / 40 mm or more, less than 1.9 gf / 40 mm

× ： 1.9 gf / 40 mm or more

The static friction coefficient in Table 3 is the value measured based on JISK7125-1999. First, the sliding piece was cut out from the laminated foam sheet by the size of width 100mm x length 100mm. Moreover, the test piece was cut out to the size of width 130mm x length 200mm from the foam seat | seet same as a sliding piece. Friction was generated when a square sliding piece having a contact area of 100 cm 2 (one side length 100 mm) moved horizontally on the test piece. The load of the sliding piece was adjusted to 125 g ± 1.2 g, and the moving speed of the test piece causing friction was measured at 500 mm / min. The test was carried out by matching the test piece, the sliding piece, and the sliding direction with the length (length) direction of the sheet. The friction coefficient was measured according to the above measurement procedure, and the value obtained by dividing the maximum load at the start of the frictional motion by the load of the sliding piece was defined as the value of the static friction coefficient. In addition, the said measurement was performed at each 5 points | pieces between the surface and back surfaces of a laminated foam sheet, and the average value of the static friction coefficient of 10 points calculated | required was made into the measured value.

The measurement result of the static friction coefficient was evaluated based on the criteria shown below.

◎: Less than 0.7

○: 0.7 or more, less than 1.2

× ： 1.2 or more

Claims (3)

In a laminated sheet having a thickness of 0.2 to 2.0 mm and an apparent density of 0.02 to 0.1 g / cm 3, by laminating and bonding a polyethylene resin layer containing a polymer type antistatic agent to at least one side of the polyethylene resin foam sheet,
The laminated sheet satisfies at least any one of the following conditions (i), (ii) and (iii).
(Iii) The basis weight of a polyethylene resin layer is 8 g / m <2> or less, the bubble film thickness of foam seat | seet is 6-100 micrometers, and the average number of bubbles in a thickness direction is two or less.
(Ii) The polyethylene resin layer is 30-90 weight% of melting | fusing point 115 degreeC or less and 128 degrees C or less and density 0.910-0.970 g / cm <3> of polyethylene resin (a), 0-60 weight% of melting | fusing point 115 degreeC or less and density 0.890- It is comprised by 0.930 g / cm <3> of polyethylene resin (b) and 10-50 weight% of polymeric antistatic agent (c) ((a) + (b) + (c) = 100 weight%).
(Iii) polyethylene resin foam sheet having a melting point of more than 10 to 50% by weight of more than 115 ° C and 125 ° C or less, and a polyethylene resin (d) having a density of 0.910 to 0.940 g / cm 3 and a melting point of 50 to 90% by weight of 115 ° C or less and a density of 0.890. It is comprised by the polyethylene resin (b) (however, (d) + (b) = 100 weight%) of -0.930 g / cm <3>. The method of claim 1,
The laminated polyethylene resin foam sheet which satisfy | fills the said condition (iii) and at least 1 condition chosen from the said condition (ii) and the said condition (iii) simultaneously. The method according to claim 1 or 2,
The applied voltage half-life of the laminated foam sheet after washing with water is 10 seconds or less, characterized in that the laminated polyethylene resin foam sheet.

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